Electrophotographic photoreceptor, process cartridge, and image forming apparatus
阅读说明：本技术 电子照相感光体、处理盒及图像形成装置 (Electrophotographic photoreceptor, process cartridge, and image forming apparatus ) 是由 藤井亮介 山田渉 岩崎真宏 草野佳祐 福井泰佑 冈崎有杜 于 2019-09-05 设计创作，主要内容包括：本发明提供一种抑制局部清洁性的降低的电子照相感光体、处理盒及图像形成装置。本发明的电子照相感光体包括：导电性基体、以及感光层,所述感光层设置在所述导电性基体上,且最表面层含有含氟树脂粒子及具有特定结构单元的氟系接枝聚合物。(The invention provides an electrophotographic photoreceptor, a process cartridge and an image forming apparatus, which can inhibit the reduction of local cleaning performance. The electrophotographic photoreceptor of the present invention comprises: the conductive substrate is provided with a conductive substrate, and a photosensitive layer, wherein the photosensitive layer is provided on the conductive substrate, and the outermost layer contains fluorine-containing resin particles and a fluorine-based graft polymer having a specific structural unit.)
1. An electrophotographic photoreceptor, comprising: a conductive base, and a photosensitive layer provided on the conductive base and having a predetermined thickness
The outermost layer contains fluorine-containing resin particles and a fluorine-containing graft polymer having a structural unit represented by the following general Formula (FA), a structural unit represented by the following general Formula (FB) and a structural unit represented by the following general Formula (FC),
in the general Formulae (FA), (FB) and (FC), RF1、RF2、RF3And RF4Each independently represents a hydrogen atom or an alkyl group; xF1Represents an alkylene chain, a halogen-substituted alkylene chain, -S-, -O-, -NH-or a single bond; y isF1Represents an alkylene chain, a halogen-substituted alkylene chain, - (C)fxH2fx-1(OH)) -or a single bond; qF1represents-O-or-NH-; fl, fm and fn each independently represent an integer of 1 or more; fp, fq, fr and fs each independently represents an integer of 0 or 1 or more; ft represents an integer of 1 or more and 7 or less; fx represents an integer of 1 or more; rF5And RF6Each independently represents a hydrogen atom or an alkyl group; fz represents an integer of 1 or more.
2. The electrophotographic photoreceptor according to claim 1, wherein the number of carboxyl groups in the fluorine-containing resin particles is 10 per 106The number of carbon atoms is 0 to 30, and the amount of the basic compound is 0ppm to 3 ppm.
3. The electrophotographic photoreceptor according to claim 2, wherein the number of carboxyl groups is 10 per unit6The number of carbon atoms is 0 to 20, and the amount of the basic compound is 0ppm to 1.5 ppm.
4. The electrophotographic photoreceptor according to claim 2, wherein the basic compound is an amine compound.
5. The electrophotographic photoreceptor according to claim 2, wherein the basic compound is a basic compound having a boiling point of 40 ℃ or more and 130 ℃ or less.
6. The electrophotographic photoreceptor according to claim 1, wherein the amount of perfluorooctanoic acid is 0ppb or more and 25ppb or less with respect to the fluorine-containing resin particles.
7. The electrophotographic photoreceptor according to claim 6, wherein the amount of perfluorooctanoic acid is 0ppb or more and 20ppb or less with respect to the fluorine-containing resin particles.
8. The electrophotographic photoreceptor according to claim 1, wherein the weight average molecular weight Mw of the fluorine-based graft polymer is 2 ten thousand or more and 20 ten thousand or less.
9. The electrophotographic photoreceptor according to claim 8, wherein the weight average molecular weight Mw of the fluorine-based graft polymer is 5 ten thousand or more and 20 ten thousand or less.
10. The electrophotographic photoreceptor according to claim 1, wherein the content of the fluorine-containing graft polymer is 0.5% by mass or more and 10% by mass or less with respect to the fluorine-containing resin particles.
11. The electrophotographic photoreceptor according to claim 1, wherein the fluorine-based graft polymer has a molecular weight distribution Mw/Mn of 1.5 or more and 5.0 or less, Mw representing a weight average molecular weight, and Mn representing a number average molecular weight.
12. A process cartridge comprising the electrophotographic photoreceptor according to any one of claims 1 to 11, and
the process cartridge is detachably provided in the image forming apparatus.
13. An image forming apparatus includes:
the electrophotographic photoreceptor according to any one of claims 1 to 11;
a charging mechanism for charging a surface of the electrophotographic photoreceptor;
an electrostatic latent image forming mechanism for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor;
a developing mechanism for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image; and
a transfer mechanism that transfers the toner image to a surface of a recording medium.
Technical Field
The invention relates to an electrophotographic photoreceptor, a process cartridge and an image forming apparatus.
Background
Conventionally, as an image forming apparatus of an electrophotographic system, an apparatus is widely known which uses an electrophotographic photoreceptor (hereinafter, sometimes referred to as "photoreceptor") to sequentially perform steps such as charging, electrostatic latent image formation, development, transfer, cleaning, and the like.
As electrophotographic photoreceptors, there are known: a function separation type photoreceptor in which a charge generation layer for generating charges and a charge transport layer for transporting charges are laminated on a substrate having conductivity such as aluminum, or a single layer type photoreceptor in which the same layer exhibits a function of generating charges and a function of transporting charges.
For example, patent document 1 discloses "an electrophotographic photoreceptor having at least a photosensitive layer on a conductive support, and a surface layer containing a binary fluorine-containing graft polymer and fluorine-containing resin particles, the binary fluorine-containing graft polymer containing two specific structural units, having a fluorine content of 10 mass% or more and 40 mass% or less, a weight average molecular weight Mw of 5 ten thousand or more and 20 ten thousand or less, a ratio [ Mw/Mn ] of the weight average molecular weight Mw to the number average molecular weight Mn of 1 or more and 8 or less, and a perfluoroalkyl group having 1 or more and 6 or less carbon atoms". Patent document 1 describes that the dispersibility of fluorine-based resin particles is improved by adding a binary fluorine-based graft polymer as a dispersing aid.
[ Prior art documents ]
[ patent document ]
[ patent document 1] Japanese patent laid-open publication No. 2011-
Disclosure of Invention
[ problems to be solved by the invention ]
Conventionally, fluorine-containing resin particles have been formulated in the surface layer of an electrophotographic photoreceptor for the purpose of improving the cleaning property. In order to improve the dispersibility of the fluorine-containing resin particles, a dispersant such as a fluorine-containing graft polymer is used.
However, even when a dispersant is blended with the fluororesin particles in a coating liquid for forming a surface layer of an electrophotographic photoreceptor to improve the dispersibility of the fluororesin particles, the dispersibility is lowered with time, and the fluororesin particles may be precipitated or re-coagulated.
Further, when the surface layer of the electrophotographic photoreceptor is formed from a coating liquid containing fluororesin particles having a reduced dispersibility, the local cleaning property may be reduced. After the coating liquid is applied, the dispersibility of the fluororesin particles may be lowered due to a change in the component concentration such as drying of the coating film, and the local cleaning property may be lowered.
Accordingly, an object of the present invention is to provide an electrophotographic photoreceptor in which a decrease in local cleaning property is suppressed as compared with a case where an electrophotographic photoreceptor contains fluorine-containing resin particles and a fluorine-containing graft polymer having a fluorinated alkyl group in an outermost layer, the fluorine-containing graft polymer having only a structural unit represented by the following general Formula (FA) and a structural unit represented by the following general Formula (FB).
[ means for solving problems ]
The above problems can be solved by the following means.
＜1＞
An electrophotographic photoreceptor, comprising: a conductive base, and a photosensitive layer provided on the conductive base and having a predetermined thickness
The outermost layer contains fluorine-containing resin particles and a fluorine-containing graft polymer having a structural unit represented by the following general Formula (FA), a structural unit represented by the following general Formula (FB), and a structural unit represented by the following general Formula (FC).
[ solution 1]
(in the general Formula (FA), the general Formula (FB) and the general Formula (FC), RF1、RF2、RF3And RF4Each independently represents a hydrogen atom or an alkyl group. XF1Represents an alkylene chain, a halogen-substituted alkylene chain, -S-, -O-, -NH-or a single bond. Y isF1Represents an alkylene chain, a halogen-substituted alkylene chain, - (C)fxH2fx-1(OH)) -, or a single bond. QF1represents-O-or-NH-. fl, fm and fn are each independentlyAnd (b) represents an integer of 1 or more. fp, fq, fr and fs each independently represent an integer of 0 or 1 or more. ft represents an integer of 1 or more and 7 or less. fx represents an integer of 1 or more. RF5And RF6Each independently represents a hydrogen atom or an alkyl group. fz represents an integer of 1 or more)
＜2＞
The electrophotographic photoreceptor according to < 1 > in which the number of carboxyl groups in the fluorine-containing resin particles is 10 per unit6The number of carbon atoms is 0 to 30, and the amount of the basic compound is 0ppm to 3 ppm.
＜3＞
The electrophotographic photoreceptor according to < 2 > wherein the number of carboxyl groups is 10 per unit6The number of carbon atoms is 0 to 20, and the amount of the basic compound is 0ppm to 1.5 ppm.
＜4＞
The electrophotographic photoreceptor according to < 2 > wherein the basic compound is an amine compound.
＜5＞
The electrophotographic photoreceptor of < 2 > wherein the basic compound is a basic compound having a boiling point of 40 ℃ or more and 130 ℃ or less.
＜6＞
The electrophotographic photoreceptor of < 1 > wherein the amount of perfluorooctanoic acid is 0ppb or more and 25ppb or less with respect to the fluorine-containing resin particles.
＜7＞
The electrophotographic photoreceptor of < 6 > in which the amount of perfluorooctanoic acid is 0ppb or more and 20ppb or less with respect to the fluorine-containing resin particles.
＜8＞
The electrophotographic photoreceptor of < 1 > in which the fluorine-based graft polymer has a weight average molecular weight Mw of 2 ten thousand or more and 20 ten thousand or less.
＜9＞
The electrophotographic photoreceptor of < 8 > in which the fluorine-based graft polymer has a weight average molecular weight Mw of 5 ten thousand or more and 20 ten thousand or less.
＜10＞
The electrophotographic photoreceptor according to < 1 > wherein the content of the fluorine-based graft polymer is 0.5% by mass or more and 10% by mass or less with respect to the fluorine-containing resin particles.
＜11＞
The electrophotographic photoreceptor according to < 1 > in which the molecular weight distribution Mw/Mn (weight average molecular weight Mw/number average molecular weight Mn) of the fluorine-based graft polymer is 1.5 or more and 5.0 or less.
＜12＞
A process cartridge comprising the electrophotographic photoreceptor according to any one of < 1 > to < 11 > and
the process cartridge is detachably provided in the image forming apparatus.
＜13＞
An image forming apparatus includes:
the electrophotographic photoreceptor according to any one of < 1 > to < 11 >;
a charging mechanism for charging a surface of the electrophotographic photoreceptor;
an electrostatic latent image forming mechanism for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor;
a developing mechanism for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image; and
a transfer mechanism that transfers the toner image to a surface of a recording medium.
[ Effect of the invention ]
According to the invention < 1 >, there is provided an electrophotographic photoreceptor in which a decrease in local cleaning property is suppressed as compared with a case where an electrophotographic photoreceptor having fluorine-containing resin particles and a fluorine-based graft polymer having a fluorinated alkyl group in an outermost layer thereof has only a structural unit represented by the following general Formula (FA) and a structural unit represented by the following general Formula (FB).
According to the invention of < 2 > or < 3 >, there is provided an electrophotographic photoreceptor in which a decrease in local cleaning property is suppressed as compared with a case where the number of carboxyl groups in the fluorine-containing resin particles exceeds 30 or the amount of the basic compound exceeds 3 ppm.
According to the invention of < 4 > or < 5 >, there is provided an electrophotographic photoreceptor in which a decrease in local cleaning property is suppressed as compared with a case where the amount of an amine compound or a basic compound having a boiling point of 40 ℃ or more and 130 ℃ or less exceeds 3ppm as a basic compound.
According to the invention of < 6 > or < 7 >, there is provided an electrophotographic photoreceptor in which a decrease in local cleaning property is suppressed as compared with the case where the amount of perfluorooctanoic acid in fluorine-containing resin particles exceeds 25 ppb.
According to the invention < 8 > or < 9 >, there is provided an electrophotographic photoreceptor in which a decrease in local cleaning property is suppressed as compared with the case where the weight average molecular weight Mw of the fluorine-based graft polymer is less than 2 ten thousand or more than 20 ten thousand.
According to the invention < 10 >, there is provided an electrophotographic photoreceptor in which a decrease in local cleaning property is suppressed as compared with the case where the content of the fluorine-based graft polymer is less than 0.5% by mass or exceeds 10% by mass.
According to the invention < 11 >, there is provided an electrophotographic photoreceptor in which a decrease in local cleaning property is suppressed as compared with the case where the molecular weight distribution Mw/Mn (weight average molecular weight Mw/number average molecular weight Mn) of the fluorine-based graft polymer is less than 1.5 or exceeds 5.0.
According to the invention of < 12 > or < 13 >, there is provided a process cartridge or an image forming apparatus including an electrophotographic photoreceptor in which an outermost layer contains fluorine-containing resin particles and a fluorine-based graft polymer having a fluorinated alkyl group, and the fluorine-based graft polymer has only a structural unit represented by the following general Formula (FA) and a structural unit represented by the following general Formula (FB), and a decrease in local cleanability is suppressed as compared with a case of an electrophotographic photoreceptor including an electrophotographic photoreceptor in which such an electrophotographic photoreceptor is applied.
Drawings
Fig. 1 is a schematic cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor of the present embodiment.
Fig. 2 is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment.
Fig. 3 is a schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment.
[ description of symbols ]
1: base coat
2: charge generation layer
3: charge transport layer
4: conductive substrate
7A, 7: electrophotographic photoreceptor
8: charging device
9: exposure device
11: developing device
13: cleaning device
14: lubricant agent
40: transfer printing device
50: intermediate transfer body
100: image forming apparatus with a toner supply device
120: image forming apparatus with a toner supply device
131: cleaning scraper
132: fibrous component (roller shape)
133: fibrous component (Flat brush shape)
300: processing box
Detailed Description
Hereinafter, embodiments as examples of the present invention will be described in detail.
(electrophotographic photoreceptor)
The electrophotographic photoreceptor of the present embodiment includes: the photosensitive layer is provided on the conductive substrate, and the outermost layer contains fluorine-containing resin particles and a fluorine-based graft polymer having a fluorinated alkyl group.
The fluorine-based graft polymer has a structural unit represented by the following general Formula (FA), a structural unit represented by the following general Formula (FB), and a structural unit represented by the following general Formula (FC). Namely, the fluorine-based graft polymer is a ternary fluorine-based graft polymer.
The photoreceptor of the present embodiment is configured as described above, and is suppressed in the reduction of local cleaning properties. The reason is presumed as follows.
Conventionally, fluorine-containing resin particles have been formulated in the surface layer of an electrophotographic photoreceptor for the purpose of improving the cleaning property. In order to improve the dispersibility of the fluorine-containing resin particles, a dispersant such as a fluorine-containing graft polymer is used.
However, even when a dispersant is blended with the fluororesin particles in a coating liquid for forming a surface layer of an electrophotographic photoreceptor to improve the dispersibility of the fluororesin particles, the dispersibility is lowered with time, and the fluororesin particles may be precipitated or re-coagulated.
When the surface layer of the electrophotographic photoreceptor is formed from the coating liquid in which the dispersibility of the fluorine-containing resin particles is reduced, the dispersibility of the fluorine-containing resin particles in the surface layer is reduced, and a partial cleaning failure may occur. After the coating liquid is applied, the dispersibility of the fluororesin particles may be lowered due to a change in the component concentration such as drying of the coating film, and the local cleaning property may be lowered.
The dispersion stabilization of the fluorine-containing resin particles by the fluorine-containing graft polymer is referred to as stabilization by steric hindrance, and is determined by a balance between affinity of the fluorine-containing graft polymer with the fluorine-containing resin particles and affinity of the fluorine-containing graft polymer with a vehicle (specifically, a binder resin and a solvent) of the coating liquid.
Specifically, in general, in the fluorine-based graft polymer, a constituent unit derived from a fluorine-based monomer (corresponding to a structural unit represented by the general Formula (FA)) contributes to affinity with fluorine-containing resin particles, and improves adhesion to the fluorine-containing resin particles. On the other hand, the constituent unit derived from the macromonomer (corresponding to the structural unit represented by the general Formula (FB)) contributes to the affinity with the vehicle of the coating liquid, and exerts stabilization of the fluorine-containing resin particles by steric hindrance.
If the affinity between the fluorine-containing resin particles and the fluorine-containing resin graft polymer is too high as compared with the affinity between the fluorine-containing resin graft polymer and the carrier (specifically, the binder resin and the solvent) of the coating liquid, the fluorine-containing resin graft polymer attached to the fluorine-containing resin particles does not dissolve and diffuse in the dispersion liquid, and stabilization of the fluorine-containing resin particles by the steric hindrance of the fluorine-containing resin graft polymer is likely to be reduced.
On the other hand, if the affinity between the fluorine-based graft polymer and the fluorine-containing resin particles is too low as compared with the affinity between the fluorine-based graft polymer and the carrier (specifically, the binder resin and the solvent) of the coating liquid, the fluorine-based graft polymer is less likely to adhere to the fluorine-containing resin particles, and the function as a dispersant is less likely to be exhibited.
In addition, for example, in the above state, the dispersibility of the fluorine-containing resin particles is lowered with the passage of time due to a mechanical load caused by the circulation of the surface layer forming coating liquid, a change in temperature at the time of storage of the coating liquid, a change in component concentration at the time of drying of the coating film of the coating liquid, and the like, and the sedimentation or the recondensation of the fluorine-containing resin particles is likely to occur.
As a result, the dispersibility of the fluorine-containing particles in the surface layer of the photoreceptor is reduced, the concentration of the fluorine-containing particles is not uniform in the surface layer of the photoreceptor, and local cleaning defects may occur in portions where the concentration of the fluorine-containing particles is low.
In contrast, in the photoreceptor of the present embodiment, a ternary fluorine-based graft polymer having a structural unit represented by the general Formula (FC) in addition to the structural unit represented by the general Formula (FA) having a high affinity with the fluorine-containing resin particles and the structural unit represented by the general Formula (FB) having a high affinity with the carrier of the coating liquid is used as the fluorine-based graft polymer.
The structural unit represented by the general Formula (FC) is a structural unit having a low molecular weight, in which a carboxyl group or an alkyl group is provided on a polymer side chain. Therefore, the ternary fluorine-based polymer having the constituent unit represented by the general Formula (FA), the general Formula (FB), and the general Formula (FC) can balance the affinity of the fluorine-based graft polymer with the fluorine-containing resin particles and the affinity of the fluorine-based graft polymer with the carrier (specifically, the binder resin and the solvent) of the coating liquid. By the balance, the adhesion of the fluorine-containing graft polymer to the fluorine-containing resin particles is ensured, and the affinity of the fluorine-containing graft polymer to the vehicle of the coating liquid is also ensured, and the fluorine-containing resin particles can be stabilized by the steric hindrance of the fluorine-containing graft polymer.
Therefore, even if a mechanical load due to the circulation of the coating liquid for forming the surface layer, a temperature change during storage of the coating liquid, a change with time in the component of the coating liquid such as volatilization of the solvent, a change in the component concentration during drying of the coating film of the coating liquid, or the like occurs, it is possible to suppress a decrease in the dispersibility of the fluorine-containing resin particles with the passage of time, and it is difficult for the fluorine-containing resin particles to settle or re-aggregate.
As a result, the dispersibility of the fluorine-containing particles in the surface layer of the photoreceptor is improved, and the cleaning failure locally generated is suppressed.
From the above, it is presumed that the photoreceptor of the present embodiment suppresses the reduction of the local cleaning property.
In the photoreceptor of the present embodiment, the fluororesin particles are dispersed in a nearly uniform state in the surface layer, that is, the fluororesin particles are dispersed in a state in which coarse aggregates are not formed. When coarse aggregates of the fluorine-containing resin particles are present in the surface layer of the photoreceptor, a difference in charged potential occurs between the photoreceptor surface and the photoreceptor surface at a site where the coarse aggregates are present and a site where the coarse aggregates are absent. The graininess of the image is reduced by the charging potential difference.
However, in the photoreceptor of the present embodiment, since coarse aggregates of fluororesin-containing particles are less likely to be present in the surface layer, it is also estimated that the decrease in the graininess of the image is suppressed.
The photoreceptor of the present embodiment will be described in detail below.
In the photoreceptor of the present embodiment, the outermost layer contains: fluorine-containing resin particles and a fluorine-based graft polymer having a fluorinated alkyl group.
The outermost layer contains a charge transport layer, a protective layer, and a single-layer photosensitive layer, and the outermost layer contains components other than fluorine-containing resin particles and a fluorine-based graft polymer, depending on the type of the layer. The other components will be described together with the structure of each layer of the photoreceptor.
First, the fluororesin particles will be explained.
Examples of the fluorine-containing resin particles include: particles of a homopolymer of a fluoroolefin; particles of a copolymer of one or more fluoroolefins and a non-fluorine-based monomer (i.e., a monomer having no fluorine atom) as two or more copolymers.
Examples of the fluoroolefin include: perfluoroolefins such as Tetrafluoroethylene (TFE), perfluorovinyl ether, Hexafluoropropylene (HFP), Chlorotrifluoroethylene (CTFE); non-perfluoroolefins such as vinylidene fluoride (VdF), trifluoroethylene, and vinyl fluoride. Among these, VdF, TFE, CTFE, HFP, and the like are preferable.
On the other hand, examples of the non-fluorine-containing monomer include: hydrocarbon (hydrocarbon) olefins such as ethylene, propylene and butene; alkyl vinyl ethers such as cyclohexyl vinyl ether (CHVE), Ethyl Vinyl Ether (EVE), butyl vinyl ether, and methyl vinyl ether; alkyl vinyl ethers such as polyoxyethylene allyl ether (POEAE) and ethyl allyl ether; organosilicon compounds having reactive α, β -unsaturated groups such as Vinyltrimethoxysilane (VSi), vinyltriethoxysilane, and vinyltris (methoxyethoxy) silane; acrylic esters such as methyl acrylate and ethyl acrylate; methacrylates such as methyl methacrylate and ethyl methacrylate; vinyl esters such as vinyl acetate, vinyl benzoate, and "beiova" (trade name, vinyl ester manufactured by Shell (Shell)). Among these, alkyl vinyl ethers, allyl vinyl ethers, vinyl esters, and organosilicon compounds having reactive α, β -unsaturated groups are preferable.
Among these, the fluorine-containing resin particles are preferably particles having a high fluorination rate, more preferably particles of Polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and the like, and particularly preferably particles of PTFE, FEP, and PFA.
Examples of the fluorine-containing resin particles include particles obtained by irradiation with radiation (also referred to as "radiation-irradiated fluorine-containing resin particles" in the present specification), particles obtained by polymerization (also referred to as "polymerized fluorine-containing resin particles" in the present specification), and the like.
The radiation-irradiated fluororesin-containing particles (fluororesin-containing particles obtained by irradiation with radiation) mean fluororesin-containing particles that are granulated while being polymerized by radiation, and fluororesin particles that are reduced in molecular weight and micronized from the polymerized fluororesin due to decomposition by irradiation with radiation.
The radiation-irradiated fluorine-containing resin particles also contain a large amount of carboxyl groups because a large amount of carboxylic acids are generated by irradiation with radiation in the air.
On the other hand, the polymerizable fluororesin-containing particles (fluororesin-containing particles obtained by polymerization) mean fluororesin particles that have been polymerized and granulated by suspension polymerization, emulsion polymerization, or the like, and that have not been irradiated with radiation.
The polymerized fluororesin-containing particles are produced by polymerization in the presence of a basic compound, and therefore contain the basic compound as a residue.
Further, the production of the fluororesin particles by the suspension polymerization method is, for example, a method of suspending additives such as a polymerization initiator and a catalyst in a dispersion medium together with a monomer for forming the fluororesin and then granulating the polymer while polymerizing the monomer.
Further, the production of the fluororesin particles by the emulsion polymerization method is, for example, a method of emulsifying a monomer for forming the fluororesin with additives such as a polymerization initiator and a catalyst in a dispersion medium by a surfactant (i.e., an emulsifier), and then polymerizing the monomer to form polymer particles.
That is, conventional fluorine-containing resin particles contain a large amount of carboxyl groups or basic compounds.
If the fluorine-containing resin particles contain a large amount of carboxyl groups, they exhibit ion conductivity, and thus have a property of being difficult to be charged.
Therefore, when conventional fluorine-containing resin particles containing a large amount of carboxyl groups are contained in the outermost surface layer of an electrophotographic photoreceptor, the chargeability of the photoreceptor is reduced under a high-temperature and high-humidity environment, and a phenomenon (hereinafter, also referred to as "fog") in which toner adheres to non-image portions may occur.
In addition, if the fluorine-containing resin particles contain a large amount of carboxyl groups, the dispersibility tends to be lowered. This is because the affinity between the fluorine-containing resin particles and the structural units derived from the fluorine-containing monomer of the fluorine-grafted polymer is reduced.
Therefore, if conventional fluorine-containing resin particles containing a large amount of carboxyl groups are contained in the outermost surface layer of the electrophotographic photoreceptor, the local cleaning property tends to be lowered.
On the other hand, if the fluorine-containing resin particles contain a large amount of the basic compound, the basic compound tends to increase the cohesion of the fluorine-containing resin particles.
Therefore, if conventional fluorine-containing resin particles containing a large amount of a basic compound are contained in the outermost surface layer of an electrophotographic photoreceptor, local cleaning properties tend to be reduced.
Further, when the fluorine-containing resin particles contain a large amount of a basic compound, the basic compound exhibits hole trapping property, and sensitivity tends to be lowered.
Therefore, when conventional fluorine-containing resin particles containing a large amount of a basic compound are contained in the outermost surface layer of an electrophotographic photoreceptor, the residual potential increases with time, and the image density may decrease.
Accordingly, the number of carboxyl groups in the fluororesin particles is preferably 106The number of carbon atoms is 0 to 30, and the amount of the basic compound is 0ppm to 3 ppm. Further, ppm is a mass basis.
From the viewpoint of suppressing the reduction in local cleaning properties and the suppression of fogging, the amount of carboxyl groups in the fluorine-containing resin particles is preferably 0 or more and 20 or less.
Here, the carboxyl group of the fluorine-containing resin particle is, for example, a carboxyl group derived from a terminal carboxylic acid contained in the fluorine-containing resin particle.
As a method for reducing the amount of carboxyl groups in the fluorine-containing resin particles, there can be mentioned: 1) a method in which radiation is not irradiated during the production of particles; 2) a method in which the irradiation is performed under a condition where oxygen is not present or under a condition where the oxygen concentration is reduced.
The number of carboxyl groups in the fluorine-containing resin particles is measured as described in Japanese patent application laid-open No. 4-20507 or the like, as follows.
The fluororesin particles were preformed by a press to prepare a film having a thickness of about 0.1 mm. The infrared absorption spectrum of the produced film was measured. The infrared absorption spectrum of the carboxylic acid-terminated fully fluorinated fluororesin particles prepared by bringing the fluororesin particles into contact with a fluorine gas was also measured, and the difference spectrum was calculated from the following equation.
The number of terminal carboxyl groups (per 10)6Carbon number of ═ l × K/t
l: absorbance of the solution
K: correction factor
t: thickness of film (mm)
The absorption wave number of carboxyl group was 3560cm-1The correction coefficient is set to 440.
The amount of the basic compound in the fluorine-containing resin particles is preferably 0ppm or more and 1.5ppm or less, and more preferably 0ppm or more and 1.2ppm or less, from the viewpoint of suppressing a decrease in local cleaning properties and suppressing an increase in residual potential.
Here, the basic compound containing the fluororesin particles is, for example: 1) a basic compound derived from a polymerization initiator used when the fluorine-containing resin particles are polymerized and granulated; 2) a basic compound used in a step of aggregating the polymer after polymerization; and 3) a basic compound used as a dispersing aid for stabilizing the dispersion after polymerization.
Examples of the basic compound include amine compounds, hydroxides of alkali metals or alkaline earth metals, oxides of alkali metals or alkaline earth metals, and acetates (for example, amine compounds are particularly preferable).
The basic compound is, for example, a basic compound having a boiling point (boiling point at normal pressure (1 atm)) of 40 ℃ or higher and 130 ℃ or lower (preferably 50 ℃ or higher and 110 ℃ or lower, and more preferably 60 ℃ or higher and 90 ℃ or lower).
Examples of the amine compound include a primary amine compound, a secondary amine compound, and a tertiary amine compound.
As the primary amine compound, there can be mentioned: methylamine, ethylamine, propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, hexylamine, 2-ethylhexylamine, sec-butylamine, allylamine, methylhexylamine and the like.
As the secondary amine compound, there can be mentioned: dimethylamine, diethylamine, di-N-propylamine, diisopropylamine, di-N-butylamine, diisobutylamine, di-t-butylamine, dihexylamine, bis (2-ethylhexyl) amine, N-isopropyl-N-isobutylamine, di-sec-butylamine, diallylamine, N-methylhexylamine, 3-methylpiperidine (3-picoline), 4-methylpiperidine, 2, 4-dimethylpiperidine (2,4-lupetidine), 2, 6-dimethylpiperidine, 3, 5-dimethylpiperidine, morpholine, N-methylbenzylamine and the like.
As the tertiary amine compound, there can be mentioned: trimethylamine, triethylamine, tri-N-propylamine, triisopropylamine, tri-N-butylamine, triisobutylamine, tri-tert-butylamine, trihexylamine, tris (2-ethylhexyl) amine, N-methylmorpholine, N, N-dimethylallylamine, N-methyldiallylamine, triallylamine, N, N-dimethylallylamine, N, N, N ', N' -tetramethyl-1, 2-diaminoethane, N, N, N ', N' -tetramethyl-1, 3-diaminopropane, N, N, N ', N' -tetraallyl-1, 4-diaminobutane, N-methylpiperidine, pyridine, 4-ethylpyridine, N-propyldiallylamine, 3-dimethylaminopropanol, 2-ethylpyrazine, 2, 3-dimethylpyrazine, 2, 5-dimethylpyrazine, 2, 4-dimethylpyridine, 2, 5-dimethylpyridine, 3, 4-dimethylpyridine, 3, 5-dimethylpyridine, 2,4, 6-trimethylpyridine, 2-methyl-4-ethylpyridine, 2-methyl-5-ethylpyridine, N, N, N ', N' -tetramethylhexamethylenediamine, N-ethyl-3-hydroxypiperidine, 3-methyl-4-ethylpyridine, 3-ethyl-4-methylpyridine, 4- (5-nonyl) pyridine, imidazole, N-methylpiperazine and the like.
As hydrogen of alkali metals or alkaline earth metalsExamples of the oxide include: NaOH, KOH, Ca (OH)2、Mg(OH)2、Ba(OH)2And the like.
Examples of the oxide of an alkali metal or an alkaline earth metal include CaO and MgO.
Examples of the acetate include zinc acetate and sodium acetate.
As a method for reducing the amount of the basic compound of the fluorine-containing resin particles, there can be mentioned: 1) a method of washing the particles with water, an organic solvent (e.g., an alcohol such as methanol, ethanol, or isopropanol, or tetrahydrofuran) or the like after the production of the particles; 2) after the production of the particles, the particles are heated (for example, to 200 ℃ or higher and 250 ℃ or lower) to decompose or gasify the basic compound and remove it.
The amount of the basic compound in the fluorine-containing resin particles is measured as follows.
Pretreatment-
In the case of measuring the amount of the basic compound from the outermost layer containing fluorine-containing resin particles, the outermost layer is immersed in a solvent (e.g., methanol or tetrahydrofuran), the fluorine-containing resin particles and components other than those insoluble in the solvent are dissolved in the solvent (e.g., methanol or tetrahydrofuran), and then the solution is dropped into pure water and the precipitate is separated by filtration. The solution containing the basic compound obtained at this time was collected. The insoluble matter obtained by the filtration and separation again was dissolved in a solvent, and then, the solution was added dropwise to pure water to separate the precipitate by filtration. The above operation was repeated 5 times to obtain fluorine-containing resin particles as a measurement sample.
When the amount of the basic compound is measured from the fluorine-containing resin particles themselves, the fluorine-containing resin particles are subjected to the same treatment as in the case of the layered product, and the fluorine-containing resin particles as the measurement sample are obtained.
Determination of
On the other hand, a standard curve (standard curve from 0ppm to 100 ppm) was obtained from the values of the basic compound concentration and the peak area of the basic compound solution (methanol solvent) having a known concentration by gas chromatography using a basic compound solution (methanol solvent) having a known concentration.
Then, the measurement sample was measured by gas chromatography, and the amount of the basic compound containing the fluororesin particles was calculated from the obtained peak area and the standard curve. The measurement conditions are as follows.
Determination of conditions
Head space sampler (head space sampler): HP7694 (manufactured by HP)
The measuring machine: gas chromatograph (HP6890 series, manufactured by HP company)
The detector: hydrogen Flame Ionization Detector (FID)
Column: HP19091S-433 (manufactured by HP Co., Ltd.)
Sample heating time: for 10min
Split Ratio (Split Ratio): 300: 1
Flow rate: 1.0ml/min
Column temperature setting: 60 deg.C (3min), 60 deg.C/min, 200 deg.C (1min)
In the fluorine-containing resin particles, the amount of perfluorooctanoic acid (hereinafter also referred to as "PFOA") is preferably 0ppb or more and 25ppb or less, preferably 0ppb or more and 20ppb or less, more preferably 0ppb or more and 15ppb or less, relative to the fluorine-containing resin particles, from the viewpoint of suppressing a decrease in local cleansing properties. Further, "ppb" is a mass basis.
Here, since the fluorine-containing resin particles (particularly fluorine-containing resin particles such as polytetrafluoroethylene particles, modified polytetrafluoroethylene particles, perfluoroalkyl ether/tetrafluoroethylene copolymer particles, and the like) use PFOA in the production process thereof or generate PFOA as a by-product, the fluorine-containing resin particles contain a large amount of PFOA.
It is considered that when PFOA is present, the fluorine-containing graft polymer as a fluorine-containing dispersant is in a state of high dispersibility of the fluorine-containing resin particles in the state of the surface layer forming coating liquid, and on the other hand, when the state of the coating liquid is changed (specifically, when the concentration of components in the coating film is changed during drying of the coating film after the coating liquid is applied), the state of adhesion of the fluorine-containing graft polymer to the fluorine-containing resin particles is changed. Specifically, it is considered that a part of the fluorine-containing graft polymer is detached from the fluorine-containing resin particles by the PFOA. Therefore, the dispersibility of the fluorine-containing resin particles is lowered, resulting in the coagulation of the fluorine-containing resin particles. This tends to reduce the local cleaning performance.
Therefore, the amount of PFOA in the fluororesin particles is preferably 0ppb or more and 25ppb or less. That is, it is preferable that the PFOA is not contained or the content thereof is suppressed even if PFOA is contained. This can further suppress a decrease in local cleaning performance.
As a method for reducing the amount of PFOA, there may be mentioned: a method of sufficiently cleaning the fluorine-containing resin particles with pure water, alkaline water, alcohols (methanol, ethanol, isopropanol, etc.), ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), esters (ethyl acetate, etc.), other common organic solvents (toluene, tetrahydrofuran, etc.), and the like. The cleaning may be performed at room temperature, and the amount of PFOA may be efficiently reduced by performing under heating.
The amount of PFOA is a value measured by the following method.
Pretreatment of the sample
In the case of measuring the amount of PFOA from the outermost layer containing fluorine-containing resin particles, the outermost layer is immersed in a solvent (for example, tetrahydrofuran), the fluorine-containing resin particles and components other than those insoluble in the solvent are dissolved in the solvent (for example, tetrahydrofuran), and then the solution is dropped into pure water and the precipitate is separated by filtration. The PFOA-containing solution obtained at this time is collected. The insoluble matter obtained by the filtration and separation again was dissolved in a solvent, and then, the solution was added dropwise to pure water to separate the precipitate by filtration. The work of collecting the PFOA-containing solution obtained at this time was repeated 5 times, and the aqueous solution collected in all the works was taken as the aqueous solution after the pretreatment.
When the amount of PFOA is measured from the fluororesin particles themselves, the fluororesin particles are treated in the same manner as in the case of the layer-like product to obtain an aqueous solution after the pretreatment.
Determination of
The preparation and measurement of the sample liquid were carried out according to the method shown in "center for environmental insurance research in the area of analysis of perfluorooctanesulfonic acid (PFOS) perfluorooctanoic acid (PFOA) in environmental water, substrate, and organism".
The average particle diameter of the fluorine-containing resin particles of the present embodiment is not particularly limited, but is preferably 0.2 μm or more and 4.5 μm or less, and more preferably 0.2 μm or more and 4 μm or less. Fluororesin particles having an average particle diameter of 0.2 to 4.5 μm (particularly fluororesin particles such as PTFE particles) tend to contain a large amount of PFOA. Therefore, the fluororesin particles having an average particle diameter of 0.2 μm or more and 4.5 μm or less tend to be particularly low in dispersibility. However, by controlling the amount of PFOA to the above range, the dispersibility is improved even in the case of fluorine-containing resin particles having an average particle diameter of 0.2 μm or more and 4.5 μm or less.
The average particle diameter of the fluorine-containing resin particles is a value measured by the following method.
The maximum diameter of the fluorine-containing resin particles (secondary particles formed by aggregating primary particles) is measured by observation with a Scanning Electron Microscope (SEM) at a magnification of, for example, 5000 times or more, and the average value obtained by measuring the maximum diameter of 50 particles is defined as the average particle diameter of the fluorine-containing resin particles. Further, a secondary electron image at an acceleration voltage of 5kV was observed using JSM-6700F manufactured by Japan Electron as SEM.
From the viewpoint of dispersion stability, the fluororesin particles preferably have a specific surface area (Brunauer-Emmett-Teller, BET) of 5m2More than 15 m/g2A ratio of 7m or less per gram, more preferably2More than g and 13m2The ratio of the carbon atoms to the carbon atoms is less than g.
The specific surface area is a value measured by a nitrogen substitution method using a BET type specific surface area measuring instrument (florosorb II2300 manufactured by shimadzu corporation).
From the viewpoint of dispersion stability, the apparent density (apparent density) of the fluororesin-containing particles is preferably 0.2g/ml or more and 0.5g/ml or less, and more preferably 0.3g/ml or more and 0.45g/ml or less.
In addition, the apparent density is a value measured in accordance with Japanese Industrial Standards (JIS) K6891 (1995).
The melting temperature of the fluorine-containing resin particles is preferably 300 ℃ to 340 ℃, more preferably 325 ℃ to 335 ℃.
The melting temperature is a melting point measured according to JIS K6891 (1995).
The content of the fluorine-containing resin particles is preferably 1 mass% or more and 30 mass% or less, more preferably 3 mass% or more and 20 mass% or less, and further preferably 5 mass% or more and 15 mass% or less, with respect to the total solid content of the outermost layer.
Next, a fluorine-containing graft polymer as a fluorine-containing dispersant will be described.
The fluorine-based graft polymer is a ternary fluorine-based graft polymer having a structural unit represented by the following general Formula (FA), a structural unit represented by the following general Formula (FB), and a structural unit represented by the following general Formula (FC).
[ solution 1]
In the general Formulae (FA), (FB) and (FC), RF1、RF2、RF3And RF4Each independently represents a hydrogen atom or an alkyl group.
XF1Represents an alkylene chain, a halogen-substituted alkylene chain, -S-, -O-, -NH-or a single bond.
YF1Represents an alkylene chain, a halogen-substituted alkylene chain, - (C)fxH2fx-1(OH)) -, or a single bond.
QF1represents-O-or-NH-.
fl, fm and fn each independently represent an integer of 1 or more.
fp, fq, fr and fs each independently represent an integer of 0 or 1 or more. ft represents an integer of 1 or more and 7 or less.
fx represents an integer of 1 or more.
RF5And RF6Each independently represents a hydrogen atom or an alkyl group.
fz represents an integer of 1 or more.
In the general Formulae (FA), (FB) and (FC), R is representedF1、RF2、RF3And RF4The group (b) is preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, etc., more preferably a hydrogen atom, a methyl group, and even more preferably a methyl group.
In the general Formulae (FA), (FB) and (FC), X is representedF1And YF1The alkylene chain (unsubstituted alkylene chain, halogen-substituted alkylene chain) of (a) is preferably a linear or branched alkylene chain having 1 to 10 carbon atoms.
Represents YF1Of (C)fxH2fx-1Fx in (OH)) -preferably represents an integer of 1 or more and 10 or less.
fp, fq, fr, and fs preferably each independently represent 0 or an integer of 1 to 10.
fn is preferably 1 or more and 60 or less, for example.
In the general Formulae (FA), (FB) and (FC), R is representedF5And RF6The group (b) is preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, etc., more preferably a hydrogen atom, a methyl group, and even more preferably a methyl group.
Here, in the fluorine-based graft polymer, the ratio of the structural unit represented by the general Formula (FA) to the structural unit represented by the general Formula (FB), that is, fl: fm, preferably 50: 50 to 99: 1, more preferably 50: 50 to 95: 5 in the above range.
In the fluorine-based graft polymer, the content ratio of the structural unit represented by the general Formula (FC) is preferably 99: 1-60: 40, more preferably 95: 5-70: range of 30
The fluorine-based graft polymer can be obtained by copolymerizing, for example, a (meth) acrylate having a fluorinated alkyl group (corresponding to a monomer that becomes a structural unit represented by general Formula (FA)), a (meth) acrylate having no fluorinated alkyl group and having an ester group (-C (═ O) -O-) and an alkyl ether chain (corresponding to a macromonomer that becomes a structural unit represented by general Formula (FB)), a (meth) acrylic acid having no fluorinated alkyl group, or an alkyl (meth) acrylate (corresponding to a monomer that becomes a structural unit represented by general Formula (FC)).
Examples of the (meth) acrylate having a fluorinated alkyl group include: 2,2, 2-trifluoroethyl (meth) acrylate, 2,2,3,3, 3-pentafluoropropyl (meth) acrylate, 2-perfluoropropylethyl (meth) acrylate, 2-perfluorobutyl (meth) acrylate, 2-perfluorohexylethyl (meth) acrylate, and the like.
Examples of the (meth) acrylic acid ester having no fluorinated alkyl group and having an ester group (-C (═ O) -O-) and an alkyl ether chain include: methoxy polyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate.
As the alkyl (meth) acrylate having no fluorinated alkyl group, there can be mentioned: isobutyl (meth) acrylate, tert-butyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 2-ethoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, benzyl (meth) acrylate, ethyl carbitol (meth) acrylate.
The term (meth) acrylate refers to both acrylates and methacrylates.
From the viewpoint of improving the dispersibility of the fluorine-containing resin particles (i.e., from the viewpoint of suppressing a decrease in local cleaning performance), the weight average molecular weight Mw of the fluorine-containing graft polymer is preferably 2 to 20 ten thousand, more preferably 5 to 20 ten thousand, and still more preferably 5 to 15 ten thousand.
From the viewpoint of improving the dispersibility of the fluorine-containing resin particles (i.e., from the viewpoint of suppressing a decrease in local cleaning performance), the number average molecular weight Mn of the fluorine-containing graft polymer is preferably 2 to 20 ten thousand, more preferably 2 to 15 ten thousand, and still more preferably 2.5 to 10 ten thousand.
From the viewpoint of improving the dispersibility of the fluorine-containing resin particles (i.e., from the viewpoint of suppressing a decrease in local cleaning performance), the molecular weight distribution Mw/Mn (weight average molecular weight Mw/number average molecular weight Mn) of the fluorine-containing graft polymer is preferably 1.5 or more and 5.0 or less, more preferably 1.5 or more and 3.5 or less, and still more preferably 1.5 or more and 3.0 or less.
In order to set the molecular weight distribution Mw/Mn within the above range, for example, the fluorine-based graft polymer obtained by polymerization is subjected to reprecipitation purification. For example, the molecular weight distribution Mw/Mn of the resulting fluorine-based graft polymer is in the above-mentioned range by adding a poor solvent to a fluorine-based graft polymer solution dissolved in a good solvent and recovering the precipitate.
The weight average molecular weight and the number average molecular weight of the fluorine-based graft polymer are values measured by Gel Permeation Chromatography (GPC). For example, the molecular weight measurement by GPC was carried out in a tetrahydrofuran solvent using GPC/HLC-8120 manufactured by Tosoh as a measurement apparatus and TSKgel GMHHR-M + TSKgel GMHHR-M (7.8mmI.D.30cm) manufactured by Tosoh, and the molecular weight was calculated from the measurement results using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample.
The content of the fluorine-containing graft polymer is, for example, preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 7% by mass or less, relative to the fluorine-containing resin particles.
Further, the fluorine-containing graft polymer may be used singly or in combination of two or more.
Hereinafter, the electrophotographic photoreceptor of the present embodiment will be described with reference to the drawings.
The electrophotographic photoreceptor 7A shown in fig. 1 is, for example, a photoreceptor 7 having a structure in which a primer layer 1, a charge generation layer 2, and a charge transport layer 3 are sequentially laminated on a conductive substrate 4. The charge generation layer 2 and the charge transport layer 3 constitute a photosensitive layer 5.
The electrophotographic photoreceptor 7 may have a layer structure in which the undercoat layer 1 is not provided.
The electrophotographic photoreceptor 7 may be a photoreceptor having a single-layer photosensitive layer in which the functions of the charge generation layer 2 and the charge transport layer 3 are integrated. In the case of a photoreceptor having a monolayer type photosensitive layer, the monolayer type photosensitive layer constitutes the outermost layer.
In addition, the electrophotographic photoreceptor 7 may be a photoreceptor having a surface protective layer on the charge transport layer 3 or the single layer type photosensitive layer. In the case of a photoreceptor having a surface protective layer, the surface protective layer constitutes the outermost layer.
Hereinafter, each layer of the electrophotographic photoreceptor of the present embodiment will be described in detail. Note that the description is omitted.
(conductive substrate)
Examples of the conductive substrate include a metal plate, a metal drum, and a metal belt containing a metal (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, or the like) or an alloy (stainless steel or the like). Examples of the conductive substrate include paper, resin film, and tape obtained by coating, vapor-depositing, or laminating a conductive compound (e.g., a conductive polymer, indium oxide, or the like), a metal (e.g., aluminum, palladium, gold, or the like), or an alloy. Here, the term "conductivity" means a volume resistivity of less than 1013Ω·cm。
In the case where the electrophotographic photoreceptor is used in a laser printer, it is preferable to roughen the surface of the conductive substrate so that the center line average roughness Ra is 0.04 μm or more and 0.5 μm or less in order to suppress interference fringes generated when laser light is irradiated. Further, in the case where incoherent light is used for the light source, surface roughening for preventing interference fringes is not particularly required, but it is suitable for longer life because generation of defects due to surface irregularities of the conductive substrate is suppressed.
Examples of the method of roughening the surface include: wet honing (honing) performed by suspending a polishing agent in water and spraying it on a conductive substrate, centerless grinding in which a conductive substrate is pressed against a rotating grinding stone and grinding work is continuously performed, anodizing treatment, and the like.
As a method of surface roughening, the following methods can be cited: the surface of the conductive substrate is not roughened, but conductive or semiconductive powder is dispersed in a resin, a layer is formed on the surface of the conductive substrate, and surface roughening is performed by particles dispersed in the layer.
The surface roughening treatment by anodization is a treatment of forming an oxide film on the surface of a conductive substrate by anodizing the conductive substrate made of metal (for example, aluminum) in an electrolyte solution as an anode. Examples of the electrolyte solution include a sulfuric acid solution and an oxalic acid solution. However, the porous anodic oxide film formed by anodic oxidation is chemically active in a state as it is, and is easily contaminated, and the resistance change due to the environment is also large. Therefore, it is preferable to perform sealing treatment on the porous anodic oxide film: in pressurized steam or boiling water (metal salts such as nickel may be added), the micropores of the oxide film are blocked by volume expansion due to hydration reaction, and thus a more stable hydrated oxide is obtained.
The thickness of the anodic oxide film is preferably 0.3 μm or more and 15 μm or less, for example. When the film thickness is within the above range, barrier properties against implantation tend to be exhibited, and increase in residual potential due to repeated use tends to be suppressed.
The conductive substrate may be subjected to a treatment with an acidic treatment liquid or a boehmite (boehmite) treatment.
The treatment with the acidic treatment liquid is performed, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The proportions of phosphoric acid, chromic acid and hydrofluoric acid to be mixed in the acidic treatment liquid are, for example, in the range of 10 to 11 mass% for phosphoric acid, 3 to 5 mass% for chromic acid, and 0.5 to 2 mass% for hydrofluoric acid, and the concentration of the whole of these acids is preferably in the range of 13.5 to 18 mass%. The treatment temperature is, for example, preferably 42 ℃ to 48 ℃. The film thickness of the coating is preferably 0.3 μm or more and 15 μm or less.
The boehmite treatment is performed, for example, by immersing the conductive substrate in pure water at 90 ℃ or higher and 100 ℃ or lower for 5 minutes to 60 minutes, or by contacting the conductive substrate with heated water vapor at 90 ℃ or higher and 120 ℃ or lower for 5 minutes to 60 minutes. The film thickness of the coating is preferably 0.1 μm or more and 5 μm or less. Further, the anodic oxidation treatment may be carried out by using an electrolyte solution having low film solubility such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate or citrate.
(undercoat layer)
The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.
The inorganic particles include, for example, powder resistance (volume resistivity) 102Omega cm or more and 1011Inorganic particles of not more than Ω · cm.
Among these, as the inorganic particles having the above-mentioned resistance value, for example, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, zirconium oxide particles and the like are preferable, and zinc oxide particles are particularly preferable.
The specific surface area of the inorganic particles obtained by the BET method is preferably, for example, 10m2More than g.
The volume average particle diameter of the inorganic particles is, for example, preferably 50nm or more and 2000nm or less (preferably 60nm or more and 1000nm or less).
The content of the inorganic particles is, for example, preferably 10 mass% or more and 80 mass% or less, and more preferably 40 mass% or more and 80 mass% or less, with respect to the binder resin.
The inorganic particles may also be surface treated. The inorganic particles may be used by mixing two or more kinds of the inorganic particles having different surface treatments or different particle diameters.
Examples of the surface treatment agent include: silane coupling agents, titanate coupling agents, aluminum coupling agents, surfactants, and the like. Particularly preferred is a silane coupling agent, and more preferred is a silane coupling agent having an amino group.
Examples of the silane coupling agent having an amino group include: 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, etc., but not limited thereto.
Two or more silane coupling agents may be used in combination. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of the other silane coupling agent include: vinyltrimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane and the like, but are not limited thereto.
The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.
The treatment amount of the surface treatment agent is preferably 0.5 mass% or more and 10 mass% or less with respect to the inorganic particles, for example.
Here, from the viewpoint of improving the long-term stability of the electrical characteristics and the carrier blocking property, the undercoat layer preferably contains inorganic particles and an electron accepting compound (acceptor compound).
Examples of the electron-accepting compound include: quinone compounds such as chloranil and bromoquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4, 7-trinitrofluorenone, 2,4,5, 7-tetranitro-9-fluorenone, etc.; oxadiazole-based compounds such as 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3, 4-oxadiazole, 2, 5-bis (4-naphthyl) -1,3, 4-oxadiazole, and 2, 5-bis (4-diethylaminophenyl) -1,3, 4-oxadiazole; a xanthone-based compound; a thiophene compound; diphenoquinone compounds such as 3,3',5,5' -tetra-tert-butyl diphenoquinone; and electron transporting materials.
In particular, the electron-accepting compound is preferably a compound having an anthraquinone structure. The compound having an anthraquinone structure is preferably, for example, a hydroxyanthraquinone compound, an aminoanthraquinone compound, an aminohydroxyanthraquinone compound, and the like, and specifically, for example, anthraquinone, alizarin (alizarin), quinizarin (quinazarin), anthropazine (anthraufin), purpurin (purpurin), and the like are preferable.
The electron accepting compound may be dispersed together with the inorganic particles and contained in the undercoat layer, or may be contained in the undercoat layer in a state of adhering to the surface of the inorganic particles.
Examples of the method for attaching the electron-accepting compound to the surface of the inorganic particle include a dry method and a wet method.
The dry method is, for example, the following method: the electron accepting compound is attached to the surface of the inorganic particles by directly dropping the electron accepting compound or dropping the electron accepting compound dissolved in an organic solvent while stirring the inorganic particles with a stirrer or the like having a large shearing force, and spraying the electron accepting compound with dry air or nitrogen gas. The dropping or spraying of the electron-accepting compound is preferably carried out at a temperature not higher than the boiling point of the solvent. The electron-accepting compound may be further baked at 100 ℃ or higher after dropping or spraying. The baking is not particularly limited as long as it is a temperature and a time at which electrophotographic characteristics can be obtained.
The wet method is, for example, the following method: the electron accepting compound is attached to the surface of the inorganic particles by dispersing the inorganic particles in a solvent by a stirrer, ultrasonic waves, a sand mill, an attritor (attritor), a ball mill, or the like, adding the electron accepting compound, stirring or dispersing, and then removing the solvent. As for the solvent removal method, the solvent is distilled off by, for example, filtration or distillation. After removing the solvent, baking can be further performed at 100 ℃ or higher. The baking is not particularly limited as long as it is at a temperature and for a time at which electrophotographic characteristics can be obtained. In the wet method, the moisture contained in the inorganic particles may be removed before the electron-accepting compound is added, and examples thereof include: a method of removing water while stirring and heating the inorganic particles in a solvent, and a method of removing water by azeotroping the inorganic particles with a solvent.
The electron accepting compound may be attached before or after the surface treatment with the surface treatment agent is performed on the inorganic particles, or the electron accepting compound may be attached and the surface treatment with the surface treatment agent may be performed simultaneously.
The content of the electron-accepting compound with respect to the inorganic particles is, for example, preferably 0.01 mass% to 20 mass%, and more preferably 0.01 mass% to 10 mass%.
Examples of the binder resin used for the undercoat layer include: known polymer compounds such as acetal resins (e.g., polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone-alkyd resins, urea resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; a zirconium chelate compound; a titanium chelate compound; an aluminum chelate compound; a titanium alkoxide compound; an organic titanium compound; and a known material such as a silane coupling agent.
As the binder resin for the undercoat layer, for example, there can be also mentioned: a charge-transporting resin having a charge-transporting group, a conductive resin (e.g., polyaniline), and the like.
Among these, as the binder resin used for the undercoat layer, resins insoluble in the coating solvent of the upper layer are suitable, and thermosetting resins such as urea resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins are particularly suitable; a resin obtained by the reaction of at least one resin selected from the group consisting of a polyamide resin, a polyester resin, a polyether resin, a methacrylic resin, an acrylic resin, a polyvinyl alcohol resin, and a polyvinyl acetal resin with a hardener.
When two or more of these binder resins are used in combination, the mixing ratio thereof is set as necessary.
Various additives may be included in the undercoat layer in order to improve electrical characteristics, environmental stability, and image quality.
Examples of additives include: electron-transporting pigments such as polycyclic condensed type and azo type pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organotitanium compounds, silane coupling agents, and the like. As described above, the silane coupling agent is used for the surface treatment of the inorganic particles, but may be further added as an additive to the undercoat layer.
Examples of the silane coupling agent as an additive include: vinyltrimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane and the like.
Examples of the zirconium chelate compound include: zirconium butoxide, zirconium ethylacetoacetate, zirconium triethanolamine, zirconium acetylacetonate, zirconium ethylacetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium methacrylate butoxide, zirconium stearate, zirconium isostearate butoxide, and the like.
Examples of the titanium chelate compound include: tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, titanium acetylacetonate, titanium polyacetylacetonate, titanium octylidene glycolate, titanium ammonium lactate, titanium ethyl lactate, titanium triethanolamine, titanium polyhydroxystearate, and the like.
Examples of the aluminum chelate compound include: aluminum isopropoxide, aluminum monobutoxide diisopropoxide, aluminum butoxide, aluminum diisopropoxide ethylacetoacetate, aluminum tris (ethylacetoacetate), and the like.
These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.
The Vickers hardness of the undercoat layer is preferably 35 or more.
In order to suppress the moire (moire) image, the surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to 1/(4n) (n is the refractive index of the upper layer) to 1/2 of the wavelength λ of the exposure laser used.
In order to adjust the surface roughness, resin particles or the like may be added to the undercoat layer. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. In addition, the surface of the primer layer may be polished to adjust the surface roughness. Examples of the polishing method include: buff (buff) grinding, sand blasting, wet honing, grinding, and the like.
The formation of the undercoat layer is not particularly limited, and can be carried out by a known formation method, for example, as follows: a coating film of a coating liquid for forming an undercoat layer obtained by adding the above components to a solvent is formed, and the coating film is dried and, if necessary, heated.
As the solvent used for preparing the coating liquid for forming the undercoat layer, known organic solvents can be cited, for example: alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone alcohol solvents, ether solvents, ester solvents, and the like.
Specifically, examples of such solvents include: and common organic solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, and toluene.
Examples of the method for dispersing the inorganic particles in the preparation of the coating liquid for forming an undercoat layer include: roll mills, ball mills, vibratory ball mills, attritors, sand mills, colloid mills, paint stirrers and the like.
Examples of the method of applying the coating liquid for forming an undercoat layer on the conductive substrate include: a general method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a droplet coating (bead coating) method, an air knife coating method, or a curtain coating method.
The thickness of the undercoat layer is set, for example, within a range of preferably 15 μm or more, more preferably 20 μm or more and 50 μm or less.
(intermediate layer)
Although not shown in the drawing, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer.
The intermediate layer is, for example, a layer containing a resin. Examples of the resin used for the intermediate layer include: high molecular weight compounds such as acetal resins (e.g., polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone-alkyd resins, phenol-formaldehyde resins, and melamine resins.
The intermediate layer may also be a layer comprising an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.
These compounds for the intermediate layer may be used alone, or may be used as a mixture or a polycondensate of a plurality of compounds.
Among these, the intermediate layer is preferably a layer containing an organometallic compound containing a zirconium atom or a silicon atom.
The formation of the intermediate layer is not particularly limited, and may be carried out by a known formation method, for example, as follows: a coating film of a coating liquid for forming an intermediate layer obtained by adding the components to a solvent is formed, and the coating film is dried and, if necessary, heated.
As a coating method for forming the intermediate layer, a general method such as a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating (coating) method, a curtain coating method, or the like can be used.
The thickness of the intermediate layer is preferably set in a range of 0.1 μm to 3 μm, for example. In addition, the intermediate layer may also be used as an undercoat layer.
(Charge generation layer)
The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. In addition, the charge generation layer may be a vapor deposition layer of a charge generation material. The deposition layer of the charge generating material is suitable for a case where a non-coherent Light source such as a Light Emitting Diode (LED) or an organic-Electroluminescence (EL) image array is used.
As the charge generating material, there can be mentioned: azo pigments such as disazo and trisazo pigments; fused ring aromatic pigments such as dibromoanthanthrone; perylene pigments; a pyrrolopyrrole pigment; phthalocyanine pigments; zinc oxide; trigonal selenium, and the like.
Among these, in order to cope with laser exposure in the near infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material. Specifically, for example, more preferred are: hydroxygallium phthalocyanine; chlorogallium phthalocyanine; dichlorotin phthalocyanine; oxytitanium phthalocyanine.
On the other hand, in order to cope with laser exposure in the near ultraviolet region, as the charge generating material, preferred are: fused ring aromatic pigments such as dibromoanthanthrone; a thioindigo-based pigment; a porphyrazine compound; zinc oxide; trigonal selenium; disazo pigments, and the like.
The charge generating material can be used when using a non-coherent light source such as an LED or an organic EL image array having a central wavelength of light emission of 450nm or more and 780nm or less, but in terms of resolution, when using a photosensitive layer in a thin film of 20 μm or less, the electric field intensity in the photosensitive layer increases, and an image defect called a so-called black spot, in which charging due to injection of charges from a substrate is reduced, is likely to occur. This is remarkable when a charge generating material which easily generates dark current in a p-type semiconductor, such as trigonal selenium or a phthalocyanine pigment, is used.
On the other hand, when an n-type semiconductor such as a fused aromatic pigment, a perylene pigment, and an azo pigment, which is a charge generating material, is used, dark current is less likely to be generated, and image defects called black spots can be suppressed even when the semiconductor is formed into a thin film.
The determination of n-type can be determined by the polarity of the flowing photocurrent by a generally used Time of Flight (Time of Flight) method, and an n-type is used for which electrons flow as carriers more easily than holes.
The binder resin used in the charge generating layer may be selected from a wide range of insulating resins, and the binder resin may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane.
Examples of the binder resin include: polyvinyl butyral resins, polyarylate resins (condensation polymers of bisphenols and aromatic dicarboxylic acids, and the like), polycarbonate resins, polyester resins, phenoxy resins, vinyl chloride-vinyl acetate copolymers, polyamide resins, acrylic resins, polyacrylamide resins, polyvinyl pyridine resins, cellulose resins, urethane resins, epoxy resins, casein, polyvinyl alcohol resins, polyvinylpyrrolidone resins, and the like. Here, the term "insulating property" means that the volume resistivity is 1013Omega cm or more.
These binder resins may be used singly or in combination of two or more.
In addition, the blending ratio of the charge generating material to the binder resin is preferably 10: 1 to 1: 10, in the range of 10.
In addition, well-known additives may also be included in the charge generation layer.
The formation of the charge generation layer is not particularly limited, and may be carried out by a known formation method, for example, by: a coating film of the charge generation layer forming coating liquid obtained by adding the components to a solvent is formed, and the coating film is dried and, if necessary, heated. The charge generation layer may be formed by vapor deposition of a charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a fused aromatic pigment or a perylene pigment is used as the charge generation material.
As the solvent used for preparing the coating liquid for forming the charge generation layer, there may be mentioned: methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, toluene, and the like. These solvents are used singly or in combination of two or more.
As a method of dispersing particles (for example, a charge generating material) in the charge generating layer forming coating liquid, for example, a media dispersing machine such as a ball mill, a vibration ball mill, an attritor, a sand mill, a horizontal sand mill, or the like; or a non-medium disperser such as a stirrer, an ultrasonic disperser, a roll mill, or a high-pressure homogenizer. Examples of the high-pressure homogenizer include: a collision system in which the dispersion is dispersed by liquid-liquid collision or liquid-wall collision in a high-pressure state, a penetration system in which the dispersion is dispersed by penetrating a fine flow path in a high-pressure state, or the like.
In addition, when the dispersion is performed, it is effective to set the average particle diameter of the charge generating material in the coating liquid for forming a charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.
Examples of the method of applying the coating liquid for forming a charge generation layer on the undercoat layer (or on the intermediate layer) include: a general method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a droplet coating method, an air knife coating method, a curtain coating method, or the like.
The film thickness of the charge generation layer is set, for example, in a range of preferably 0.1 μm or more and 5.0 μm or less, more preferably 0.2 μm or more and 2.0 μm or less.
(Charge transport layer)
The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may also be a layer comprising a polymeric charge transport material.
As the charge transport material, there can be mentioned: quinone compounds such as p-benzoquinone, chloranil, bromoquinone and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4, 7-trinitrofluorenone; a xanthone-based compound; a benzophenone-based compound; a cyanovinyl compound; electron-transporting compounds such as vinyl compounds. As the charge transport material, there can be also mentioned: hole-transporting compounds such as triarylamine compounds, biphenylamine compounds, arylalkane compounds, aryl-substituted vinyl compounds, stilbene compounds, anthracene compounds, hydrazone compounds, and the like. These charge transport materials may be used singly or in combination of two or more, but are not limited thereto.
As the charge transport material, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferable from the viewpoint of charge mobility.
[ solution 2]
In the structural formula (a-1), ArT1、ArT2And ArT3Each independently represents a substituted or unsubstituted aryl group, -C6H4-C(RT4)＝C(RT5)(RT6) or-C6H4-CH＝CH-CH＝C(RT7)(RT8)。RT4、RT5、RT6、RT7And RT8Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.
Examples of the substituent for each of the above groups include: a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Further, as the substituent of each group, there may be mentioned a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.
[ solution 3]
In the structural formula (a-2), RT91And RT92Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. RT101、RT102、RT111And RT112Each independently represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C (R)T12)＝C(RT13)(RT14) or-CH-C (R)T15)(RT16)，RT12、RT13、RT14、RT15And RT16Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less.
Examples of the substituent for each of the above groups include: a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Further, as the substituent of each group, there may be mentioned a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.
Here, among the triarylamine derivative represented by the structural formula (a-1) and the benzidine derivative represented by the structural formula (a-2), those having "— C" are particularly preferable from the viewpoint of charge mobility6H4-CH＝CH-CH＝C(RT7)(RT8) "and triarylamine derivatives having" -CH-CH ═ C (R)T15)(RT16) "a benzidine derivative.
As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane can be used. Particularly preferred are polyester-based polymeric charge transport materials. The polymer charge transport material may be used alone, or may be used in combination with a binder resin.
Examples of the binder resin for the charge transport layer include: polycarbonate resins, polyester resins, polyarylate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, polysilanes, and the like. Among these, the binder resin is preferably a polycarbonate resin or a polyarylate resin. These binder resins may be used singly or in combination of two or more.
In addition, the blending ratio of the charge transport material to the binder resin is preferably 10: 1 to 1: 5.
in addition, well-known additives may also be included in the charge transport layer.
The formation of the charge transport layer is not particularly limited, and may be carried out by a known formation method, for example, by: a coating film of a charge transport layer forming coating liquid obtained by adding the components to a solvent is formed, and the coating film is dried and, if necessary, heated.
As the solvent used for preparing the coating liquid for forming a charge transport layer, there can be mentioned: aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, dichloroethane and the like; and common organic solvents such as cyclic or linear ethers such as tetrahydrofuran and diethyl ether. These solvents are used alone or in combination of two or more.
Examples of the coating method for applying the coating liquid for forming a charge transport layer on the charge generating layer include: a general method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a droplet coating method, an air knife coating method, a curtain coating method, or the like.
The film thickness of the charge transport layer is set, for example, in a range of preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 30 μm or less.
(protective layer)
The protective layer is disposed on the photosensitive layer as required. The protective layer is provided, for example, for the purpose of preventing chemical changes of the photosensitive layer upon charging or further improving the mechanical strength of the photosensitive layer.
Therefore, the protective layer may apply a layer containing a hardened film (crosslinked film). Examples of such layers include the layers shown in 1) or 2) below.
1) A layer of a cured film of a composition containing a charge transport material containing a reactive group having a reactive group and a charge transport skeleton in the same molecule (i.e., a layer containing a polymer or a crosslinked product of the charge transport material containing a reactive group)
2) A layer comprising a hardened film of a composition containing a non-reactive charge transporting material and a non-charge transporting material containing a reactive group and having no charge transporting skeleton but having a reactive group (i.e., a layer comprising a non-reactive charge transporting material, a polymer or a crosslinked product with the non-charge transporting material containing a reactive group)
As the reactive group of the charge transport material containing a reactive group, there can be mentioned: chain polymerizable group, epoxy group, -OH, -OR [ wherein R represents alkyl group]、-NH2、-SH、-COOH、-SiRQ1 3-Qn(ORQ2)Qn[ wherein RQ1Represents a hydrogen atom, an alkyl group or a substituted or unsubstituted aryl group, RQ2Represents a hydrogen atom, an alkyl group, or a trialkylsilyl group; qn represents an integer of 1 to 3]And the like known as reactive groups.
The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, and is, for example, a functional group having at least a group containing a carbon double bond. Specifically, examples thereof include a group containing at least one selected from a vinyl group, a vinyl ether group, a vinyl thioether group, a styryl group (vinylphenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof. Among them, in terms of excellent reactivity, the chain polymerizable group is preferably a group containing at least one selected from a vinyl group, a styryl group (vinylphenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof.
The charge-transporting skeleton of the charge-transporting material containing a reactive group is not particularly limited as long as it has a known structure in electrophotographic photoreceptors, and examples thereof include a skeleton derived from a nitrogen-containing hole-transporting compound such as a triarylamine-based compound, a biphenylamine-based compound, or a hydrazone-based compound, and a structure conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferable.
These reactive group-containing charge transport materials, non-reactive charge transport materials, and non-charge transport materials containing reactive groups, which have reactive groups and a charge transport skeleton, can be selected from well-known materials.
In addition, well-known additives may also be included in the protective layer.
The formation of the protective layer is not particularly limited, and may be carried out by a known formation method, for example, as follows: a coating film of a coating liquid for forming a protective layer obtained by adding the above-mentioned components to a solvent is formed, and the coating film is dried and, if necessary, subjected to a hardening treatment such as heating.
As the solvent used for preparing the coating liquid for forming the protective layer, there may be mentioned: aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; alcohol solvents such as isopropyl alcohol and butyl alcohol. These solvents may be used alone or in combination of two or more.
The coating liquid for forming the protective layer may be a solvent-free coating liquid.
As a method for applying the coating liquid for forming the protective layer on the photosensitive layer (for example, charge transport layer), there can be mentioned: a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a curtain coating method, and other common methods.
The film thickness of the protective layer is set, for example, in the range of preferably 1 μm or more and 20 μm or less, more preferably 2 μm or more and 10 μm or less.
(Single layer type photosensitive layer)
The single-layer type photosensitive layer (charge generating/charge transporting layer) is, for example, a layer containing a charge generating material and a charge transporting material, and, if necessary, a binder resin and other well-known additives. In addition, these materials are the same as those described in the charge generation layer and the charge transport layer.
In the monolayer type photosensitive layer, the content of the charge generating material is preferably 0.1 mass% or more and 10 mass% or less, and preferably 0.8 mass% or more and 5 mass% or less, with respect to the total solid content. In the monolayer type photosensitive layer, the content of the charge transport material is preferably 5 mass% or more and 50 mass% or less with respect to the total solid content.
The monolayer type photosensitive layer is formed in the same manner as the charge generation layer or the charge transport layer.
The thickness of the monolayer photosensitive layer is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less.
< image forming apparatus (and process cartridge) >
The image forming apparatus of the present embodiment includes: an electrophotographic photoreceptor; a charging mechanism for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming mechanism for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor; a developing mechanism for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image; and a transfer mechanism that transfers the toner image to a surface of the recording medium. Further, as the electrophotographic photoreceptor, the electrophotographic photoreceptor of the present embodiment described above can be applied.
As the image forming apparatus of the present embodiment, known image forming apparatuses such as: a device including a fixing mechanism that fixes the toner image transferred to the surface of the recording medium; a direct transfer type device for directly transferring a toner image formed on the surface of an electrophotographic photoreceptor to a recording medium; an intermediate transfer system device that primarily transfers the toner image formed on the surface of the electrophotographic photoreceptor to the surface of an intermediate transfer member, and secondarily transfers the toner image transferred to the surface of the intermediate transfer member to the surface of a recording medium; a device including a cleaning mechanism that cleans the surface of the electrophotographic photoreceptor before charging after transfer of the toner image; a device including a charge removing mechanism for irradiating a charge removing light to the surface of the electrophotographic photoreceptor to remove charges after the transfer of the toner image and before the charge; an apparatus includes an electrophotographic photoreceptor heating member for raising a temperature of an electrophotographic photoreceptor and reducing a relative temperature.
In the case of an intermediate transfer system apparatus, the transfer mechanism may be configured to include, for example: an intermediate transfer body having a surface to which the toner image is transferred; a primary transfer mechanism that primarily transfers a toner image formed on a surface of the electrophotographic photoreceptor to a surface of the intermediate transfer member; and a secondary transfer mechanism for secondary-transferring the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium.
The image forming apparatus according to the present embodiment may be either a dry development type image forming apparatus or a wet development type (development type using a liquid developer) image forming apparatus.
In the image forming apparatus of the present embodiment, for example, a portion including the electrophotographic photoreceptor may be a cartridge (cartridge) structure (process cartridge) detachably provided to the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photoreceptor of the present embodiment can be suitably used. Further, in addition to the electrophotographic photoreceptor, at least one selected from the group consisting of a charging mechanism, an electrostatic latent image forming mechanism, a developing mechanism, and a transfer mechanism, for example, may be included in the process cartridge.
An example of the image forming apparatus according to the present embodiment is described below, but the present invention is not limited to this. In addition, main portions shown in the drawings are described, and descriptions of other portions are omitted.
Fig. 2 is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment.
As shown in fig. 2, the image forming apparatus 100 of the present embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming mechanism), a transfer device 40 (a primary transfer device), and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where the electrophotographic photoreceptor 7 can be exposed from the opening of the process cartridge 300, the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 with the intermediate transfer member 50 interposed therebetween, and the intermediate transfer member 50 is disposed so that a part thereof is in contact with the electrophotographic photoreceptor 7. Although not shown, a secondary transfer device is also provided for transferring the toner image transferred to the intermediate transfer member 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (primary transfer device), and a secondary transfer device (not shown) correspond to an example of the transfer mechanism.
The process cartridge 300 in fig. 2 integrally supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging mechanism), a developing device 11 (an example of a developing mechanism), and a cleaning device 13 (an example of a cleaning mechanism) in a casing. The cleaning device 13 includes a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is disposed so as to contact the surface of the electrophotographic photoreceptor 7. The cleaning member is not in the form of the cleaning blade 131, but may be a conductive or insulating fibrous member, and the fibrous member may be used alone or in combination with the cleaning blade 131.
In fig. 2, an example is shown in which the image forming apparatus includes a fibrous member 132 (roller-shaped) for supplying the lubricant 14 to the surface of the electrophotographic photoreceptor 7 and a fibrous member 133 (flat brush-shaped) for assisting cleaning, and these may be arranged as necessary.
Hereinafter, each configuration of the image forming apparatus according to the present embodiment will be described.
-charging means
As the charging device 8, for example, a contact type charging device using a conductive or semiconductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging pipe, or the like can be used. Further, a known charger itself such as a non-contact type roller charger, a grid electrode type (scorotron) charger using corona discharge, a grid electrode free (corotron) charger, or the like may be used.
-exposure device
The exposure device 9 may be, for example, an optical system device that exposes the surface of the electrophotographic photoreceptor 7 to light such as semiconductor laser light, Light Emitting Diode (LED) light, and liquid crystal shutter light in a predetermined manner. The wavelength of the light source is set within the spectral sensitivity region of the electrophotographic photoreceptor. As the wavelength of the semiconductor laser, near infrared having an oscillation wavelength in the vicinity of 780nm is mainly used. However, the wavelength is not limited to the above, and a laser beam having an oscillation wavelength of about 600nm or more, or a laser beam having an oscillation wavelength of 400nm or more and 450nm or less as a blue laser beam may be used. In addition, a surface-emitting laser light source of a type that can output multiple beams for forming a color image is also effective.
Developing device
As the developing device 11, for example, a general developing device that performs development by bringing or not bringing a developer into contact is cited. The developing device 11 is not particularly limited as long as it has the above-described function, and may be selected according to the purpose. Examples of the developer include a known developer having the following functions: the one-component developer or the two-component developer is attached to the electrophotographic photoreceptor 7 using a brush, a roller, or the like. Among them, it is preferable to use a developing roller that holds the developer on the surface.
The developer used in the developing device 11 may be a one-component developer of a single toner or a two-component developer containing a toner and a carrier. The developer may be magnetic or non-magnetic. These developers can be used by those well known in the art.
Cleaning device
The cleaning device 13 may use a cleaning blade type device including the cleaning blade 131.
In addition, a brush cleaning method or a simultaneous development cleaning method may be used in addition to the cleaning blade method.
-transfer means
Examples of the transfer device 40 include: a contact type transfer belt using a belt, a roller, a film, a rubber blade, or the like, a grid electrode type transfer belt using corona discharge, a non-grid electrode type transfer belt, or the like.
An intermediate transfer body
As the intermediate transfer member 50, a belt-shaped member (intermediate transfer belt) containing a polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, or the like, to which semiconductivity is imparted, can be used. In addition, as the form of the intermediate transfer body, a roll-shaped one other than a belt-shaped one may be used.
Fig. 3 is a schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment.
The image forming apparatus 120 shown in fig. 3 is a tandem (tandem) multicolor image forming apparatus having four process cartridges 300 mounted thereon. Image forming apparatus 120 is configured as follows: the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, respectively, and one electrophotographic photoreceptor is used for one color. Image forming apparatus 120 has the same configuration as image forming apparatus 100, except for the tandem system.
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