阅读说明：本技术 固化性聚合物、聚合液、导电性膜和有机发光元件 (Curable polymer, polymerization solution, conductive film, and organic light-emitting element ) 是由 佐野彰洋 吉成优规 于 2018-06-01 设计创作，主要内容包括：本发明的目的在于提高有机发光元件的耐用寿命。为了解决上述课题,本发明的固化性聚合物包含高分子,该高分子含有具有共轭性单体的主链(1)和具有交联基的侧链(2),在高分子中掺杂有空穴(3)。(The purpose of the present invention is to improve the durability of an organic light-emitting element. In order to solve the above problems, a curable polymer of the present invention includes a polymer having a main chain (1) having a conjugated monomer and a side chain (2) having a crosslinking group, and a hole (3) is doped in the polymer.)

1. A curable polymer characterized by:

the polymer contains a main chain having a conjugated monomer and a side chain having a crosslinking group, and is doped with a hole.

2. The curable polymer according to claim 1, wherein:

also contains anionic molecules.

3. The curable polymer according to claim 2, wherein:

and also contains a cationic molecule which is a cationic molecule,

the molar concentration of the cationic molecules is 0.1 times or less the molar concentration of the anionic molecules.

4. The curable polymer according to any one of claims 1 to 3, wherein:

the conjugated monomer is 1 of the following chemical formulas (1) to (3):

in the formula, R¹～R⁵Independently from each other, selected from the group consisting of hydrogen, halogen, cyano, nitro, a linear, branched or cyclic alkyl group having 1 to 22 carbon atoms, a linear, branched or cyclic alkenyl group having 2 to 22 carbon atoms, a linear, branched or cyclic alkynyl group having 2 to 22 carbon atoms, an aryl group having 6 to 21 carbon atoms, a heteroaryl group having 12 to 20 carbon atoms, an aralkyl group having 7 to 21 carbon atoms and a heteroarylalkyl group having 13 to 20 carbon atoms, R¹～R⁵Is unsubstituted or substituted by 1 or more halogens, and m1 and m2 are each independently an integer of 0 to 5.

5. A polymerization liquid, characterized by:

a curable polymer composition comprising the curable polymer according to any one of claims 1 to 4.

6. A polymerization fluid as set forth in claim 5, wherein:

also contains acetylacetone metal coordination compound.

7. A conductive film, characterized in that:

a curable polymer composition comprising the curable polymer according to any one of claims 1 to 4.

8. An organic light-emitting element characterized in that:

a hole transport layer comprising the curable polymer according to any one of claims 1 to 4.

Technical Field

The invention relates to a curable polymer, a polymerization solution, a conductive film and an organic light-emitting element.

Background

Organic light-emitting devices have attracted attention as devices for providing thin, lightweight, and flexible illumination or display by using organic solid materials having a thickness of several tens of nm. Further, since the light-emitting element is self-luminous, realizes a high viewing angle, and has a high response speed of the light-emitting element itself, it is suitable for high-speed moving image display, and therefore, it is expected as a next-generation flat panel display or sheet display. Further, since uniform light emission can be performed over a large area, attention is being paid to the light emitting element as a new generation of illumination.

In an organic light-emitting device, a voltage is applied to an organic film sandwiched between an anode and a cathode, holes are injected from the anode into an organic layered film, electrons are injected from the cathode into the organic layered film, and the electrons and the holes recombine in a light-emitting layer, thereby emitting light.

The organic light-emitting element includes an anode, a hole transport layer for transporting holes from the anode to the light-emitting layer, a light-emitting layer, an electron transport layer for transporting electrons from the cathode to the light-emitting layer, and a cathode. In order to efficiently inject electrons and holes into the light-emitting layer, a plurality of different films may be stacked as the hole transport layer and the electron transport layer. In an organic light-emitting element, not only a light-emitting layer but also a hole transport layer and an electron transport layer are stacked using an organic solid.

Methods of laminating organic solid materials of organic light emitting elements are roughly classified into vacuum vapor deposition and wet process. Wet processes, such as printing and ink jet processes, are expected to be superior to vacuum deposition methods in terms of mass productivity, cost reduction in manufacturing processes, and large screen size. In the wet process, when an organic film is once stacked and a new layer is formed, there is a problem that the already formed layer is dissolved. As a countermeasure, there is a method of: a curable polymer containing an organic molecule having a curable crosslinking group added to the organic molecule is dissolved in a solvent, applied by a wet process, and then cured by heat or light treatment. Since the cured film has a property of being not easily soluble in a solvent, lamination of an organic film in a wet process becomes easy.

In conventional organic light emitting devices, the following techniques are available as techniques for curing organic molecules.

Patent document 1 suggests that a polymer having a specific structure in which an alkylene group (quaternary carbon) is present in the main chain and a crosslinkable group is laminated by a wet film formation method, and that the polymer has high singlet excitation level and triplet excitation level, high hole transport ability, and high electrochemical stability after being crosslinked and made insoluble in an organic solvent. In addition, the electron accepting compound having an oxidizing power and an ability to accept electrons from the hole transporting compound is contained in the hole injecting layer adjacent to the anode among the plurality of hole transporting layers, whereby the conductivity can be improved.

In patent document 2, it is considered that protons or other cationic molecular impurities present in a doped polymer that is electrically conductive with a bronsted acid or the like dope intrinsic holes. By providing at least 1 crosslinkable undoped polymer buffer layer between the conductive doped polymer and the organic semiconductor layer, durability life-time and the like characteristics can be improved.

Disclosure of Invention

Technical problem to be solved by the invention

In the polymer for improving the conductivity of the hole injection layer shown in patent document 1 or the doped polymer shown in patent document 2, the polymer contains an electron-accepting compound or a compound having an oxidizing power such as a bronsted acid, and holes are doped in the hole transport layer. However, as shown in patent document 2, when these compounds having oxidizing power remain in the film after film formation, the durability life is reduced. Patent document 2 suggests that the durability life can be improved by providing a buffer layer, but the presence of the buffer layer increases the thickness of the element, and the driving voltage of the organic light-emitting element increases.

Means for solving the problems

In order to solve the above problems, a curable polymer of the present invention includes a polymer having a main chain of a conjugated monomer and a side chain having a crosslinking group, and a hole is doped in the polymer.

Effects of the invention

The organic light-emitting element having a hole transport layer formed using the curable polymer of the present invention has improved durability and life characteristics as compared with conventional organic light-emitting elements.

Drawings

Fig. 1 is a first schematic view showing a polymer structure of a curable polymer according to the present embodiment.

Fig. 2 is a second schematic view showing a polymer structure of the curable polymer according to the present embodiment.

Fig. 3 is a cross-sectional view showing one embodiment of the organic light-emitting device of the present embodiment.

Fig. 4 is a third schematic view showing a polymer structure of the curable polymer according to the present embodiment.

FIG. 5 is a schematic view showing a single hole device and an impedance measuring system.

Detailed Description

The best mode for carrying out the present invention will be described below.

< definition of curable Polymer >

In the present embodiment, the "curable polymer" means: the term "molecule having an inter-polymer cross-linked or an intra-polymer cross-linked structure" refers to a curable polymer in a state before a curing reaction occurs, and is obtained by initiating a cross-linking reaction of a polymer having a cross-linking group bonded to a side chain thereof by a curing treatment such as heat or light after being applied to a substrate.

Fig. 1 is a first schematic view showing a polymer structure of a curable polymer according to the present embodiment. In fig. 1, the main chain of the polymer includes a repeating conjugated main chain 1 including a chain or branched conjugated monomer. In the polymer, a crosslinking group 2 such as an epoxy group, oxetane group, benzocyclobutene group, or styrene group is attached to a side chain. Further, in the polymer of the curable polymer of the present embodiment, the conjugated main chain 1 is chemically doped with the holes 3 by a method described later.

Fig. 2 is a second schematic view showing a polymer structure of the curable polymer according to the present embodiment. As shown in fig. 2, the main chain of the polymer may be constituted by a linear conjugated main chain 1 containing a chain-like conjugated monomer, as long as curability of the resin after curing is not impaired. In the side chain of the polymer, a crosslinking group 2 is attached to the side chain. Holes 3 are chemically doped in the conjugated main chain 1 of the polymer. The polymer of the curable polymer may be a mixture of the polymer of fig. 1 and the polymer of fig. 2.

Fig. 3 shows a structural example of the organic light emitting element. The organic light-emitting element 301 has a structure in which a glass substrate 31, an anode 32, a hole transport layer 33, a light-emitting layer 34, an electron transport layer 35, a cathode 36, and a sealing glass plate 37 are stacked.

When the stacked structure is formed, if other organic layers are stacked on the base organic layer using a wet process, the base organic layer may be dissolved. In contrast, by applying a curing treatment with heat or light to the base organic layer, even if another organic layer is stacked on the base organic layer by a wet process, the dissolution of the base organic layer can be avoided. A plurality of hole transport layers 33 or a plurality of electron transport layers 35 may be provided. In many cases, a layer adjacent to the anode is referred to as a hole injection layer and a layer adjacent to the light-emitting layer is referred to as a hole transport layer, but in this embodiment, both layers are collectively referred to as a hole transport layer.

< main chain of polymer of curable polymer >

As the conjugated monomer contained in the main chain of the polymer of the curable polymer of the present embodiment, for example, a known monomer for producing a resin for forming a hole transport layer, a light emitting layer, and an electron transport layer of an organic light emitting device can be used. The conjugated monomer has charge transporting property or luminescence.

Examples of the conjugated monomer include monomers having a skeleton of aromatic amine, stilbene, hydrazone, carbazole, aniline, oxazole, oxadiazole, benzoxazole, benzoxadiazole, benzoquinone, quinoline, isoquinoline, quinoxaline, thiophene, benzothiophene, thiadiazoleBenzodiazole, benzothiadiazole, triazole, perylene, quinacridone, pyrazoline, anthracene, rubrene, coumarin, naphthalene, benzene, biphenyl, terphenyl, anthracene, tetracene, fluorene, phenanthrene, pyrene, perylene, and perylene,

Pyridine, pyrazine, acridine, phenanthroline, furan and pyrrole, and derivatives thereof.

More preferably, the conjugated monomer is any one of the following chemical formulas (1) to (3).

In the formula, R¹～R⁵Preferably independently from each other, hydrogen, halogen, cyano, nitro, a linear, branched or cyclic alkyl group having 1 to 22 carbon atoms, a linear, branched or cyclic alkenyl group having 2 to 22 carbon atoms, a linear, branched or cyclic alkynyl group having 2 to 22 carbon atoms, an aryl group having 6 to 21 carbon atoms, a heteroaryl group having 12 to 20 carbon atoms, an aralkyl group having 7 to 21 carbon atoms and a heteroarylalkyl group having 13 to 20 carbon atoms, more preferably from hydrogen, halogen, cyano, nitro, a linear, branched or cyclic alkyl group having 1 to 22 carbon atoms, an aryl group having 6 to 21 carbon atoms, a heteroaryl group having 12 to 20 carbon atoms and an aralkyl group having 7 to 21 carbon atoms, further preferably from hydrogen, halogen, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 10 carbon atoms, particularly preferably from hydrogen, alkyl, aryl, heteroaryl, and heteroaryl, Bromine, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and phenyl.

The above groups are preferably unsubstituted or substituted with 1 or more halogens, more preferably unsubstituted.

m1 and m2 are preferably integers of 0 to 5 independently of each other, and more preferably 0 or 1.

In the present embodiment, "aralkyl group" means a group in which 1 hydrogen atom of an alkyl group is substituted with an aryl group. Preferred aralkyl groups are not limited, and include, for example, benzyl, 1-phenylethyl and 2-phenylethyl.

In the present embodiment, "arylalkenyl" means a group in which 1 hydrogen atom of an alkenyl group is substituted with an aryl group. The preferred arylalkenyl group is not limited, and examples thereof include styryl group.

In this embodiment, "heteroaryl" means: and (c) a group in which 1 or more carbon atoms of the aryl group are each independently substituted with a hetero atom selected from a nitrogen atom (N), a sulfur atom (S), and an oxygen atom (O). For example, "heteroaryl having 12 to 20 carbon atoms" and "heteroaryl having (cyclic) 12 to 20 members" mean: a group in which 1 or more carbon atoms of an aromatic group having at least 12 and at most 20 carbon atoms are independently substituted with the above-mentioned hetero atom. In this case, the substitution of N or S comprises the substitution of an oxide or dioxide of N-oxide or S, respectively. Preferred heteroaryl groups are not limited, and include, for example: furyl, thienyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, thiazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiadiazolyl, isothiazolyl, pyridyl, pyridazinyl, pyrazinyl, pyrimidinyl, quinolinyl, isoquinolinyl, indolyl and the like.

In the present embodiment, "heteroarylalkyl" means: a group in which 1 hydrogen atom of the alkyl group is substituted with a heteroaryl group. In the present embodiment, "halogen" means fluorine, chlorine, bromine, or iodine.

Particularly preferably, the conjugated monomer is selected from compounds having, as a skeleton, triphenylamine, N- (4-butylphenyl) -N ', N "-diphenylamine, 9-dioctyl-9H-fluorene, N-phenyl-9H-carbazole, N ' -diphenyl-N, N ' -bis (3-methylphenyl) - [1,1 ' -biphenyl ] -4, 4 ' -diamine, and N, N ' -bis (3-methylphenyl) -N, N ' -bis (2-naphthyl) - [1,1 ' -biphenyl ] -4, 4 ' -diamine, and derivatives thereof.

By using a polymer composition containing a main chain of a conjugated monomer having the above-described skeleton as the hole transport layer, the ionization energy of the hole transport layer can be adjusted to an appropriate value according to the ionization energy of the light-emitting layer material. In general, a value between the work function of the anode and the ionization energy of the light-emitting layer, or a value larger than the ionization energy of the light-emitting layer is preferable.

< crosslinking group of curable Polymer >

As the crosslinking group contained in the side chain of the curable polymer of the present embodiment, a known crosslinking group can be used. For example, a cyclic ether group such as an epoxy group or an oxetane group or a crosslinking group which undergoes a diels-alder type crosslinking reaction may be used, and a plurality of these crosslinking groups may be combined. The crosslinking group that undergoes the diels-alder type crosslinking reaction is not limited, and examples thereof include crosslinking groups having thiophene, styrene, pyrrole, and benzocyclobutene as a skeleton.

< hole dopant >

A typical hole dopant for doping a hole in a curable polymer is a dopant having a function as an ionic polymerization initiator for crosslinking a crosslinking group by cationic molecular polymerization. The ionic polymerization initiator for crosslinking the crosslinking group by cationic molecular polymerization contains a combination of a positively charged cationic molecule and a negatively charged counter-anionic molecule (hereinafter, these ions include ions remaining in the cured resin after curing, and are referred to as an ionic polymerization initiator). The cationic molecules are treated by heating or light irradiation to activate the chemical reaction. The anionic molecule is a molecule added to keep the positive charge of the cationic molecule neutral, and is a molecule having a negative charge and a stable state. The activated cationic molecules cause a chemical reaction in which the macromolecules of the curable polymer accept an electron, and the macromolecules are chemically doped with a hole.

Fig. 4 is a third schematic view showing a polymer structure of the curable polymer according to the present embodiment. The ionic polymerization initiator before crosslinking contains cationic molecules and anionic molecules at a molar ratio of 100: 100. After crosslinking, the cationic molecules contributing to doping of the holes become cationic decomposed products, and the cationic molecules not contributing to doping of the holes remain as they are. If it is assumed that xmol of the cationic molecules contributing to doping of the cavity remains, the cationic molecules and the cationic decomposition products and the anionic molecules exist in a ratio of x: 100 (100-x): 100 by molar concentration. It is more preferable that unreacted ionic polymerization initiator is not contained, and therefore, the molar concentration of the cationic molecules after crosslinking is preferably 0.1 times or less of that of the anionic molecules.

In the following description, an ion polymerization initiator is used as the hole dopant, but the hole dopant of the present embodiment is not limited to these, and may be a compound having an oxidizing power such as a known electron-accepting compound or a bronsted acid. In the following examples, unless otherwise specified, the compound having an oxidizing power in the ionic polymerization initiator means a cationic molecule. Examples of the hole dopant of the ionic polymerization initiator include: iodonium salts, sulfonium salts and ferrocene derivatives.

Particularly preferably, the ionic polymerization initiator is selected from the compounds represented by the following chemical formulae (4) to (6).

< Polymer doped with voids >

The curable polymer of the present embodiment is a curable polymer before crosslinking, contains a polymer having a conjugated monomer in the main chain and a crosslinking group in the side chain, and is a curable polymer in which a hole is doped in the polymer. The polymer was produced by the following 2 steps.

< step 1. hole doping >

A plurality of hole dopants are added to a solution containing a polymer having a conjugated monomer in its main chain and a crosslinking group in its side chain (hereinafter, this step is referred to as "hole doping"). The hole dopant contains a compound having oxidizing power. Hole doping refers to a chemical reaction that occurs due to the oxidizing force described above. In hole doping, it is preferable that a crosslinking reaction such as ring opening of a crosslinking group is not performed.

< step 2. separation and removal of unreacted compound having oxidizing power >

In step 1, a plurality of hole dopants are added, but not all of the hole dopants contribute to hole doping, and a part of the hole dopants remain in an unreacted state. The curable polymer after hole doping is dissolved in a solvent (for example, toluene) to form a solution. In this solution, the compound component having oxidizing power contained in the hole dopant remaining in an unreacted state is removed. In the case of using an ionic polymerization initiator as the hole dopant, the compound component having an oxidizing power is a cationic molecule.

The method for removing the above-mentioned compound components is not particularly limited, and examples thereof include solvent extraction and centrifugation.

For example, a polymer material used for an organic light-emitting element is often soluble in a nonpolar organic solvent such as toluene. On the other hand, since the cationic molecules and anionic molecules of the ionic polymerization initiator have electric charges, they tend to be dissolved in a polar solvent such as acetone. In step 1, a solvent (for example, toluene) is volatilized from a solution containing a curable polymer subjected to a hole doping reaction. The residual components are redissolved in another solvent (e.g., acetone). The cationic molecules and the anionic molecules are dissolved in the solvent, and the hole-doped polymer and the hole-undoped polymer are precipitated together. In this case, anions having the same number of molecules as that of the positively charged polymer doped with holes are physically co-precipitated.

By repeating this process, unreacted compound components (cationic molecules) having oxidizing power can be separated and removed with high purity.

< crosslinking reaction >

As a method for increasing the reaction rate of the crosslinking reaction, when an ionic polymerization initiator is added, cationic molecules as unreacted compound components having oxidizing power may remain as they are. In the present embodiment, the curing treatment is preferably performed at a higher temperature. As another method for accelerating the reaction rate of the crosslinking reaction, there is a method using a neutral catalyst. For example, a method of using an acetylacetonato-based metal complex as a basic catalyst is mentioned. Since the catalyst is not a reactant which itself generates a decomposition product, the catalyst can suppress the influence on the service life even if it remains in the film.

< hole density n₀Measurement of

The hole density of a layer formed using a curable polymer doped with holes can be measured, for example, by the following method. An element having a structure in which a hole transport layer is sandwiched between electrodes such as anode ITO and cathode Al is referred to as a single hole element. A region having a low hole density (referred to as a depletion layer) is generated at the interface between the hole transport layer and Al on the hole transport layer side, due to the difference between the work function of the hole transport layer (usually 5eV or more) and the work function of Al (4.2 eV). The thickness d' of the depletion layer is represented by the following equation (7).

Where Δ Φ is a difference in work function between the hole transport layer and Al, and V is a voltage applied to the anode and the cathode. Epsilon₀The dielectric constant in vacuum is defined as ε is the relative dielectric constant of the film-forming layer.

The capacitance C' in the depletion layer is represented by the following formula (8).

Wherein S is the area of the element. The hole density n can be obtained by applying a voltage to the anode and the cathode and measuring the electrostatic capacity₀。

FIG. 5 is a schematic view showing a single hole device and an impedance measuring system. The electrostatic capacity derived from the depletion layer can be separated by performing frequency-dependent measurement of the impedance of the hole-only element 401 using the LCR meter 402.

< organic light emitting element >

Fig. 3 is a cross-sectional view showing one embodiment of the organic light-emitting device of the present embodiment. The organic light-emitting element 301 of this embodiment includes: an anode 32; a cathode 36; a light-emitting layer 34 disposed between the anode 32 and the cathode 36; and a hole transport layer 33 (also referred to as a "hole injection layer" in some cases) disposed between the anode 32 and the light-emitting layer 34. The anode 32 is formed, for example, by patterning Indium Tin Oxide (ITO) on the glass substrate 31. For example, after the hole transport layer 33 and the light-emitting layer 34 are sequentially formed on the anode 32 of the ITO glass substrate 31, aluminum (Al) is evaporated on the light-emitting layer 34 to form the cathode 36. The organic light-emitting element 301 of this embodiment is preferably sealed by: the anode 32, the hole transport layer 33, the light emitting layer 34, the electron transport layer 35, and the cathode 36 are sandwiched between the glass substrate 31 and the sealing glass plate 37, and then the glass substrate 31 and the sealing glass plate 37 are bonded to each other using a cured resin such as a photocurable epoxy resin.

In the organic light-emitting element of the present embodiment, the hole transport layer is made of a resin formed from a crosslinkable polymer. The hole transport layer can be produced by a method conventionally used in the art. For example, the curable polymer of the present embodiment may be applied to an anode patterned on a glass substrate by a wet process such as a spin coating method, a printing method, or an ink jet method, and then a resin may be formed by the above-described curing treatment. The resin formed from the polymerization solution has high curability and excellent resistance to organic solvents. Therefore, for example, when a light-emitting layer is laminated on the surface of a hole transport layer made of the resin by the wet process, the hole transport layer can be prevented from being dissolved by an organic solvent contained in a coating solution for the light-emitting layer. For example, the residual film ratio of the hole transport layer obtained using the resin formed of the curable polymer of the present embodiment is usually in the range of 60 to 100%, and typically in the range of 80 to 99%. The resin having organic solvent resistance represented by the residual film ratio has high curability. Therefore, by using the resin of this embodiment mode for the hole transport layer, the productivity of the organic light emitting element by the wet process can be improved.

The evaluation of the residual film ratio can be performed by the following procedure, for example. On the anode of the ITO glass substrate, a hole transport layer was formed using a resin formed of the curable polymer of the present embodiment and an ionic polymerization initiator. The ITO glass substrate having the hole transport layer formed thereon is immersed in an organic solvent (e.g., toluene) at 20 to 250 ℃ for 10 to 60 seconds. Then, the ITO glass substrate was taken out from the organic solvent, and the absorbance of the film before and after immersion was measured. The residual ratio (residual film ratio) of the film was determined from the ratio of absorbance. Since the absorbance is proportional to the film thickness, the ratio of the absorbance (presence/absence of immersion) matches the residual film ratio (presence/absence of immersion) of the hole transport layer. The higher the residual film rate, the higher the organic solvent resistance.