阅读说明：本技术 喷墨记录装置及喷墨记录方法 (Ink jet recording apparatus and ink jet recording method ) 是由 山崎聪一 内园骏介 粂田宏明 于 2019-07-05 设计创作，主要内容包括：本发明提供一种能够提高叠放性的喷墨记录装置及喷墨记录方法。本实施方式所涉及的喷墨记录装置其特征在于,具备行式头,在所述行式头中,在与被记录介质的输送方向交叉的交叉方向上形成的喷出墨水的喷嘴的区域覆盖所述被记录介质的印刷区域的所述交叉方向,所述喷墨记录装置还具备,干燥单元,对所述被记录介质进行干燥；输送单元,输送所述被记录介质；以及控制单元,所述墨水包含胶体二氧化硅,所述控制单元对所述干燥单元及所述输送单元进行控制,使得在所述墨水附着在所述被记录介质上之后于0.4秒以内开始墨水的干燥。(The invention provides an ink jet recording apparatus and an ink jet recording method capable of improving the stacking property. The inkjet recording apparatus according to the present embodiment is characterized by including a line head in which a region of a nozzle that ejects ink, which is formed in a crossing direction that crosses a transport direction of a recording medium, covers the crossing direction of a printing region of the recording medium, and a drying unit that dries the recording medium; a conveying unit that conveys the recording medium; and a control unit that controls the drying unit and the transport unit so that drying of the ink is started within 0.4 seconds after the ink is attached to the recording medium.)

1. An inkjet recording apparatus including a line head in which a region of a nozzle that ejects ink, which is formed in a cross direction that crosses a transport direction of a recording medium, covers the cross direction of a printing region of the recording medium, the inkjet recording apparatus further including:

a drying unit that dries the recording medium;

a conveying unit that conveys the recording medium; and

a control unit for controlling the operation of the display unit,

the ink comprises a colloidal silicon dioxide, and the ink comprises,

the control unit controls the drying unit and the transport unit so that the drying of the ink is started within 0.4 seconds after the ink is attached to the recording medium.

2. The inkjet recording apparatus according to claim 1,

the colloidal silica is spherical and has a volume average particle diameter of 10 to 70 nm.

3. The inkjet recording apparatus according to claim 1 or 2,

the drying unit is air-dried.

4. The inkjet recording apparatus according to claim 3,

the control unit controls the drying unit or the conveying unit so that air is blown to the printing surface of the recording medium for 0.5 seconds or more.

5. The inkjet recording apparatus according to claim 1,

the surface of the colloidal silica is treated with alumina.

6. The inkjet recording apparatus according to claim 1,

the control unit controls the transport unit so that the recording medium is transported at a speed of 0.5m/sec or more with respect to the line head.

7. An ink jet recording method comprising the steps of:

ejecting ink containing colloidal silica from a line head toward a recording medium, the line head being formed such that nozzles for ejecting ink formed in a cross direction crossing a transport direction of the recording medium cover the cross direction of a printing region of the recording medium; and

drying of the ink is started within 0.4 seconds after the ink is attached to the recording medium.

Technical Field

The present invention relates to an ink jet recording apparatus and an ink jet recording method.

Background

In recent years, the speed of ink jet recording apparatuses has been increased, image quality has been improved, and techniques for suppressing curl have been developed.

For example, patent literature describes an invention of an inkjet image recording method in which printing is performed using an inkjet ink having a surface tension of 25mN/m or more and 40mN/m or less and a viscosity of 1mPa · s or more and 50mPa · s or less, and infrared radiation is performed after the printing. The above patent document describes that an ink jet printer can be provided which can improve the surface drying property of ink and improve wrinkles or curls even when a large amount of ink is injected.

Patent document 1: japanese laid-open patent publication No. 2007-152769

However, the recording method described in the patent document has the following problems: since the wet friction of the printing surface is large, when printing is performed at high speed and with a high duty ratio, it is sometimes difficult to properly convey the recording paper, and since the curling and cockling of the recording paper are not completely suppressed, curling and cockling occur, and the recording paper cannot be accurately stacked. In particular, when high-speed paper conveyance of 0.5m/s or more is required as in line inkjet, the problem of paper stacking property is more prominent.

Disclosure of Invention

Accordingly, an aspect of the present invention provides an inkjet recording apparatus and an inkjet recording method capable of improving stackability.

The present inventors have found that the above problems can be solved by adding colloidal silica to an ink for inkjet recording and starting drying of the printed surface within 0.4 seconds after printing.

An inkjet recording apparatus according to an aspect of the present invention is an inkjet recording apparatus including a line head in which a region of a nozzle that ejects ink, which is formed in a crossing direction that crosses a transport direction of a recording medium, covers the crossing direction of a printing region of the recording medium, the inkjet recording apparatus further including: a drying unit that dries the recording medium; a conveying unit that conveys the recording medium; and a control unit that controls the drying unit and the transport unit so that drying of the ink is started within 0.4 seconds after the ink is attached to the recording medium.

In addition, an inkjet recording method according to an aspect of the present invention includes the steps of: ejecting ink containing colloidal silica from a line head toward a recording medium, the line head being formed such that nozzles for ejecting ink formed in a cross direction crossing a transport direction of the recording medium cover the cross direction of a printing region of the recording medium; and starting drying of the ink within 0.4 seconds after the ink is attached to the recording medium.

Drawings

Fig. 1 is a side sectional view showing the structure of an inkjet recording apparatus in the present embodiment.

Description of the reference numerals

10 a recording device; 11 a control device; 12 a feeding part; 14 a conveying part; 15 a drying unit; 16 belt conveying sections; 18 a recording section; a 20Fd discharge unit; 22Fd placing part; 24 a turnover path part; a 26Fu discharging part; a 28Fu placing part; 30 feeding the tray; 32 a feed roller; 34 a transport drive roller; 36 transport follower rollers; 38 a first roller; 40 a second roller; 42 an endless belt; 42a upper section of the endless belt; a support 44; 46 a carriage; 48 ink jet head; 50 a first branch portion; 52, reversing the path; 54 a second branch portion; 56 discharge roller pair; 64 discharge drive roller; 68 drive shaft; 76 a carrying surface; 78 a convex portion; 80 a first force applying member; 82 a second force application member; 84. 86 supporting the shaft; p is recorded on the medium.

Detailed Description

The following describes in detail embodiments for carrying out the present invention. Note that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

Ink for inkjet recording

In an inkjet recording apparatus and an inkjet recording method, an inkjet recording ink containing colloidal silica (hereinafter, simply referred to as "ink") is used.

Colloidal silicon dioxide

The colloidal silica is silicon oxide (SiO)₂) A colloidal solution in which particles are dispersed in water or an organic solvent. The colloidal silica is spherical in shape, stably dispersed in the ink jet ink by a specific acid/alkali, and found to have an effect of improving the paper stacking property by reducing wet friction of the printed surface and an effect of suppressing curling of paper by the hygroscopicity and the like of silica. Thereby high-speed paper conveyance becomes possible. That is, the effect of adding colloidal silica is as follows, and this has not been found so far. That is, even if the ink is not completely dried, the ink is not completely dried due to the addition of colloidal silica to the ink, and the ink is not completely dried due to SiO₂Since some particles are present on the surface, the wet friction resistance of the printed surface is also reduced, and the stacking property is improved. In addition, due to SiO₂Since the particles are hygroscopic like silica gel, they have a curl suppression effect due to a moisturizing effect.

The colloidal silica preferably has an average particle diameter (volume average particle diameter) of 10nm to 70 nm. By setting the average particle diameter to 70nm or less, precipitation is suppressed and dispersion can be stably maintained. Further, the effect of improving the sliding friction of the print surface is obtained by setting the average particle diameter to 10nm or more.

The average particle diameter of the colloidal silica can be measured by a particle size distribution measuring apparatus using a dynamic light scattering method as a measurement principle. Examples of such a particle size distribution measuring instrument include "zeta potential/particle size/molecular weight measuring system ELSZ2000 ZS" (trade name) manufactured by Otsuka electronics Co., Ltd., which employs a homodyne optical system as a frequency analysis method. Note that in the present specification, the term "average particle diameter" refers to a number-based average particle diameter unless otherwise specified.

The colloidal silica may also be surface treated with alumina. This can improve storage stability. That is, by performing surface treatment with alumina, the range of pH in which dispersion can be stabilized becomes large, and even if the ink is neutral, dispersion can be stabilized.

As the colloidal silica, commercially available ones can be used, and examples thereof include Snowtex 20, Snowtex 30, Snowtex 40, Snowtex O, Snowtex N, and Snowtex C (all of the above are made by Nissan chemical industries Co., Ltd.).

The content of the colloidal silica may be appropriately determined in consideration of the kind and the effect of adding the colloidal silica, and is preferably about 0.1 to 15 wt%, and more preferably about 3 to 10 wt% of the ink composition.

Pigment (I)

The ink of the present embodiment may include a pigment as a coloring material. The pigment is not particularly limited as long as it is a substance generally used in an aqueous pigment ink for inkjet.

Examples of the pigment include organic pigments such as azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, and the like), polycyclic pigments (including phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, and the like), nitro pigments, nitroso pigments, and aniline black; inorganic pigments such as carbon black (e.g., furnace black, thermal cracking lamp black, acetylene black, channel black, etc.), metal oxides, metal sulfides, and metal chlorides; extender pigments such as silica, calcium carbonate and talc.

Specific examples of the pigment include c.i. pigment yellow 64, 74, 93, 109, 110, 128, 138, 139, 150, 151, 154, 155, 180, 185, c.i. pigment red 122, 202, 209, c.i. pigment violet 19, c.i. pigment blue 15:3, 15:4, 60, c.i. pigment green 7 (phthalocyanine green), 10 (green gold) 36, 37, c.i. pigment brown 3,5, 25, 26, c.i. pigment orange 1,2, 5, 7, 13, 14, 15, 16, 34, 36, 38, 64, 71 and the like.

The pigment is preferably added to the ink as a pigment dispersion liquid obtained by dispersing a dispersant in water, or as a pigment dispersion liquid obtained by dispersing a self-dispersible surface-treated pigment obtained by introducing a hydrophilic group to the surface of pigment particles by a chemical reaction in water, or as a pigment dispersion liquid obtained by dispersing a pigment covered with a polymer in water.

The pigment and the dispersant constituting the pigment dispersion liquid may be used singly or in combination of two or more.

In order to obtain the advantageous effect of forming a clear image on various recording media, the pigment dispersion liquid is preferably contained in an amount of 0.05 to 25% by mass, more preferably 0.1 to 20% by mass, in terms of solid content, relative to the total amount (100% by mass) of the ink composition.

The ink of the present embodiment preferably contains at least one acid or base of an amino acid, an unsaturated fatty acid, an alkali metal hydroxide, and an amine as a pH adjuster, and more preferably contains all of these four acids or bases as a pH adjuster. In order to effectively suppress the ink from eroding the constituent materials of the ink jet recording apparatus and ensure the clogging recovery, the pH is preferably adjusted within a range of 6 to 10. When the four pH adjusters of the present embodiment are combined, the pH buffering function having long-term stability can be exhibited, and the other functions can be sufficiently exhibited, respectively, and a synergistic effect can be exhibited.

Amino acids

The amino acid has an excellent pH adjusting function of both amino and carboxyl functional groups, and also has a function as a humectant or a curl inhibitor for a recording medium.

The amino acid is preferably a chemically stable tertiary amino acid or a quaternary amino acid. Among them, at least either of dimethylglycine and trimethylglycine is preferable because of its small molecular weight.

The amino acid may be used alone or in combination of two or more.

The content of the amino acid is preferably 1 to 30% by mass, and more preferably 4 to 20% by mass, based on the total mass (100% by mass) of the ink. When the content is within the above range, the composition has an excellent pH adjusting function as an ampholyte of an acid and an alkali in addition to a function as a humectant and a curl suppressing agent of a recording medium.

Acetylenic diols

Acetylenic diols are nonionic surfactants having an ethynyl group at the center and a bilaterally symmetric structure, and are used as water-based materials in various fields as wetting agents that are not likely to foam. The acetylene glycol has excellent functions of wetting, defoaming, dispersing and the like. The diol is a diol having a very stable molecular structure, has a small molecular weight, and has an effect of reducing the surface tension of water, and thus the permeability and bleeding of the ink into a recording medium can be appropriately controlled. In addition, it has an effect of being able to suppress the attachment.

Specific examples of the alkynediol include 2,4,7, 9-tetramethyl-5-decyne-4, 7-diol, 3, 6-dimethyl-4-octyne-3, 6-diol, and 3, 5-dimethyl-1-hexyn-3-ol.

Examples of commercially available Products of alkynediols include Surfynol 104 (series), 420, 440, 465 and 485 (trade names of Air Products and Chemicals Inc.), Olfine STG, PD-001, SPC, E1004, E1010 (trade name of Nissin Chemical Industry Co., Ltd.), Acetylenol E00, E40, E100 and LH (trade name of Kawaken Fine Chemicals Co., Ltd.) and the like.

One kind of the acetylene glycol may be used alone, or two or more kinds may be used in combination.

The content of the alkynediol is preferably 0.1 to 3.0% by mass, and more preferably 0.3 to 2.0% by mass, based on the total mass (100% by mass) of the ink. When the content is within the above range, the glossy feeling and the permeability are good.

Unsaturated fatty acid

The unsaturated fatty acid can be used in combination with the acetylene glycol to obtain the following effects. Acetylenic diols are low molecular weight surfactants with three dimensional stereo structures. Therefore, the surfactant is inherently difficult to foam and has excellent wettability. Oleic acid is a linear surfactant of unsaturated fatty acids, and is a surfactant which is also used for soap and is easy to foam. However, when the two are combined, foaming is not easily generated remarkably as compared with the presence of each alone.

Therefore, the tail of the ejected ink becomes short, and the satellites decrease. The reason for this is presumed to be that the use of an unsaturated fatty acid-based surfactant having a structure greatly different from that of an acetylenic diol in combination with the acetylenic diol disturbs the arrangement of the surfactant molecules on the surface of the ejected ink by steric hindrance, thereby lowering the film strength.

Unsaturated fatty acids have a function as a surfactant, a lubricant, and a penetrant in addition to a pH adjusting function of the acids.

Among the unsaturated fatty acids, unsaturated fatty acids having one double bond are preferable. Examples of the monounsaturated fatty acid include crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, cis-9-eicosenoic acid, erucic acid, and nervonic acid, but are not limited thereto. This is because, in the case of having two or more carbon double bonds, methylene hydrogen sandwiched between the carbon double bonds is extracted and easily oxidized. Linoleic acid, linolenic acid are suitable for this. Unsaturated fatty acids having one carbon double bond are advantageous in that they are difficult to oxidize because they have no methylene hydrogen. Further, many saturated fatty acids stable to oxidation are solid at ordinary temperature, and many are not suitable for addition to ink. Oleic acid is a substance satisfying all of these characteristics.

In summary, it is preferable that the unsaturated fatty acid is oleic acid or linoleic acid.

The unsaturated fatty acid may be a purified one or a vegetable oil such as olive oil containing oleic acid as a main component.

The unsaturated fatty acid may be used alone or in combination of two or more.

The content of the unsaturated fatty acid is preferably 0.05 to 3% by mass, and more preferably 0.1 to 1% by mass, based on the total mass (100% by mass) of the ink. When the content is within the above range, it is excellent in both functional balance of the excellent surfactant and the pH adjustor (acidic side).

Amines as pesticides

The amine has the effect of suppressing the nozzle deletion. In addition, the amine functions as a weakly basic pH adjuster. Further, the amine is amphiphilic, and therefore, the ink is excellent in long-term stability, and therefore, an alkanolamine is preferable among the amines. Further, by using an alkanolamine having a high boiling point among alkanolamines, clogging can be prevented, and therefore trialkanolamine is more preferable, and at least either tripropanolamine or triethanolamine is further preferable.

It should be noted that amines have the disadvantage of easily forming precipitates with unsaturated fatty acids, and if only one amine is used as a base, the stability is poor. Therefore, the base includes, in addition to the amine, an alkali metal hydroxide described later and the like.

One kind of amine may be used alone, or two or more kinds may be used in combination.

The content of the amine is preferably 0.05 to 2% by mass, and more preferably 0.1 to 1% by mass, based on the total mass (100% by mass) of the ink. When the amine content is in the above range, the pH of the ink can be adjusted to an appropriate range.

Alkali metal hydroxides

The alkali metal hydroxide has the effect of suppressing the nozzle deletion. In addition, although an alkali metal hydroxide is an excellent base, metal ions are easily trapped by an organic solvent or a pigment like a complex, and the long-term stability is poor. The alkali metal ion has a property of being difficult to precipitate with the unsaturated fatty acid as compared with the amine. Therefore, the use of an amine and an alkali metal hydroxide as a base in combination makes it possible to compensate for the disadvantages of both, and only exerts its advantages.

The alkali metal hydroxide is preferably at least one selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH), and more preferably at least one of NaOH and KOH.

One kind of alkali metal hydroxide may be used alone, or two or more kinds may be used in combination.

The content of the alkali metal hydroxide is preferably 0.01 to 1% by mass, and more preferably 0.03 to 0.5% by mass, based on the total mass (100% by mass) of the ink. By setting the content of the alkali metal hydroxide within the above range, the pH of the ink can be set within an appropriate range. Further, when the contents of the amine and the alkali metal hydroxide are within the above ranges, the contents interact with each other as an alkali component, and a synergistic effect such as pH adjustment and suppression of nozzle dropout is exhibited.

Here, the unsaturated fatty acid, the amino acid, the alkali metal hydroxide, and the amine may be contained in the ink as separate substances, or may be contained as an acid-base salt. In particular, when the ink contains an acid-base salt composed of at least either of an unsaturated fatty acid and an amino acid and at least either of an alkali metal hydroxide and an amine, the pH buffering effect described above can be further exhibited, and therefore, it is preferable. Examples of such acid-base salts include, but are not limited to, potassium oleate, sodium oleate, lithium oleate, tripropanolamine oleate, triethanolamine oleate, potassium amino acid, sodium amino acid, and lithium amino acid.

Among them, since the ink is excellent in solubility in ink and pH adjusting function and does not adversely affect a pigment or other ink materials, it is preferable to use at least one selected from the group consisting of potassium oleate, tripropanolamine oleate, triethanolamine oleate, and potassium amino acid.

Other additives

The ink of the present embodiment may include an additive other than the above-described additives. Examples of such additives are shown below.

Wetting agent

For the purpose of preventing clogging in the vicinity of the nozzles of the inkjet head, it is preferable to add a water-soluble organic solvent having a wetting effect to the ink of the present embodiment.

Examples of the humectant include glycerin, 1,2, 6-hexanetriol, trimethylolpropane, pentanediol, 1, 3-propanediol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, polyethylene glycol having a number average molecular weight of 2000 or less, polyhydric alcohols such as dipropylene glycol, tripropylene glycol, isobutylene glycol, 2-butene-1, 4-diol, 2-ethyl-1, 3-hexanediol, 2-methyl-2, 4-pentanediol, meso-erythritol, and pentaerythritol, and so-called solid humectants such as glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose, sugar alcohols, hyaluronic acid, and ureas, And alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, and isopropanol, and 2-pyrrolidone, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan, acetin, diacetin, triacetin, and sulfolane.

The wetting agent may be used alone or in combination of two or more.

The content of the wetting agent is preferably 10 to 50% by mass with respect to the total mass (100% by mass) of the ink. When the content is within the above range, appropriate physical properties (viscosity, etc.) of the ink can be secured, and recording quality and reliability can be secured.

Water (W)

The water contained in the ink of the present embodiment is a main solvent, and pure water or ultrapure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, or distilled water is preferably used. In particular, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide to prevent the generation of mold and bacteria and to enable long-term storage of the ink.

Penetrant

For the purpose of promoting the permeation of the aqueous solvent into the recording medium, it is preferable that the ink of the present embodiment further includes a penetrant. The aqueous solvent quickly permeates into the recording medium, and a recorded matter with less image bleeding can be obtained.

As such a penetrant, at least either one of alkyl ethers of polyhydric alcohols (also referred to as glycol ethers) and 1, 2-alkyldiols is preferably used. Examples of the alkyl ether of the polyhydric alcohol include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-tert-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-tert-butyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol monobutyl ether. Examples of the 1, 2-alkyldiol include 1, 2-pentanediol and 1, 2-hexanediol. In addition, dihydric alcohols of straight-chain hydrocarbons such as 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 7-heptanediol, and 1, 8-octanediol are also included.

The penetrant may be used alone or in combination of two or more.

The content of the penetrant is preferably 3 to 20% by mass based on the total mass (100% by mass) of the ink. When the content is within the above range, the ink can be made to have good permeability to a recording medium, bleeding can be prevented from occurring in an image recorded using the ink, and the viscosity of the ink can be made not to be excessively high.

As described above, according to the present embodiment, it is possible to provide ink capable of forming a high-quality image at high speed while suppressing the generation of satellites. Specifically, according to the present embodiment, an ink composition in which an acetylene glycol and an unsaturated fatty acid are combined as a surfactant and the unsaturated fatty acid itself, an amino acid, an amine, and an alkali metal hydroxide are combined as a pH adjuster in order to solve a problem when using them, can provide an ink which is excellent in long-term stability and can suppress the formation of an ink droplet when ejecting ink even when recording is performed at high speed.

Ink jet recording apparatus

An inkjet recording apparatus (hereinafter, simply referred to as "recording apparatus") according to an embodiment of the present invention will be described below with reference to fig. 1. In the X-Y-Z coordinate system shown in fig. 1, the X direction represents the longitudinal direction of the recording medium, the Y direction represents the width direction of the recording medium in the conveyance path within the recording apparatus, and the Z direction represents the apparatus height direction.

As an example, the recording apparatus 10 is a line inkjet printer capable of high-speed and high-density printing. The recording apparatus 10 includes a control unit 11 that controls operations of respective units, a feeding unit 12 that stores a recording medium P such as a sheet, a conveying unit (conveying unit) 14, a drying unit 15, a belt conveying unit 16, a recording unit 18, an Fd (face down) discharging unit 20 that is a "discharging unit", an Fd (face down) placing unit 22 that is a "placing unit", a reversing path unit 24 that is a "reversing and conveying mechanism", a Fu (face up) discharging unit 26, and a Fu (face up) placing unit 28.

The feeding unit 12 is disposed below the recording apparatus 10. The feeding unit 12 includes a feeding tray 30 that stores the recording medium P, and a feeding roller 32 that feeds the recording medium P stored in the feeding tray 30 to the conveying path 11.

The recording medium P accommodated in the feeding tray 30 is fed to the conveying portion 14 along the conveying path 11 by the feeding roller 32. The conveying unit 14 includes a conveying drive roller 34 and a conveying driven roller 36. The conveyance drive roller 34 is driven to rotate by a drive source not shown in the figure. In the transport section 14, the recording medium P is nipped (nipped) between the transport driving roller 34 and the transport driven roller 36, and transported toward the belt transport section 16 located on the downstream side of the transport path 11.

The belt conveying unit 16 includes a first roller 38 located on the upstream side in the conveying path 11, a second roller 40 located on the downstream side, an endless belt 42 rotatably mounted on the first roller 38 and the second roller 40, and a support 44 that supports an upper section 42a of the endless belt 42 between the first roller 38 and the second roller 40.

The endless belt 42 is driven to move from the + X direction to the-X direction at the upper section 42a by the first roller 38 or the second roller 40 driven by a drive source not shown in the figure. Therefore, the recording medium P conveyed from the conveying unit 14 is further conveyed downstream of the conveyance path 11 by the belt conveying unit 16.

The recording unit 18 includes a line-type inkjet head (line head) 48 having a length equal to or greater than the width of the recording medium P, and a head holder 46 for holding the inkjet head 48. The inkjet head 48 is disposed so as to face the upper section 42a of the endless belt 42 supported by the support 44. When the recording medium P is conveyed in the upper section 42a of the endless belt 42, the inkjet heads 48 discharge ink onto the recording medium P to perform recording. The recording medium P is conveyed to the downstream side of the conveyance path 11 by the belt conveying unit 16 while being recorded.

The "line-type inkjet head" is a head used in a recording apparatus in which a nozzle region formed in a direction intersecting the transport direction of the recording medium P is provided so as to cover the entire intersection direction of the printing region of the recording medium P, and one of the head and the recording medium P is fixed and the other is moved to form an image. In addition, the nozzle region of the line head in the cross direction may not cover the entire cross direction of all the recording media P corresponding to the recording apparatus.

Further, a first branch portion 50 is provided on the downstream side of the belt conveying portion 16 in the conveying path 11. The first branch portion 50 is configured to be able to switch between the transport path 11 for transporting the recording medium P to the Fd discharge portion 20 or the Fu discharge portion 26 and the reversing path 52 for reversing the recording surface of the recording medium P and transporting the recording medium P to the reversing path portion 24 of the recording portion 18 again. The recording medium P conveyed by switching to the reversing path 52 by the first branching portion 50 is reversed on the recording surface during conveyance in the reversing path 52, and is conveyed again to the recording portion 18 so that the surface opposite to the first recording surface faces the inkjet head 48.

A second branch portion 54 is further provided on the downstream side of the first branch portion 50 along the conveyance path 11. The second branching portion 54 is configured to be capable of switching the conveyance direction of the recording medium P so as to convey the recording medium P to the Fd discharge portion 20 or convey the recording medium P to the Fu discharge portion 26.

The recording medium P conveyed to the Fd discharge unit 20 by the second branch unit 54 is discharged from the Fd discharge unit 20 and placed on the Fd placement unit 22. At this time, the recording surface of the recording medium P is placed so as to face the Fd placement unit 22. The recording medium P conveyed to the Fu discharging unit 26 by the second branching unit 54 is discharged from the Fu discharging unit 26 and is placed on the Fu placing unit 28. At this time, the recording surface of the recording medium P is placed so as to face the opposite side of the Fu placing section 28.

The drying unit 15 is configured and controlled to dry the print surface of the recording medium P discharged from the Fu discharging unit 26. The drying unit 15 is air-dried and includes an air outlet for supplying air to the printing surface of the recording medium. The drying unit 15 is disposed close to the Fu discharging part 26 so that air drying can be performed immediately after the paper is discharged from the Fu discharging part 26.

In the present embodiment, the control unit 11 controls the drying unit 15 or the conveying unit 14 so that the drying of the ink is started within 0.4 seconds after the ink is attached to the recording medium P. Here, "drying of the ink starts within 0.4 seconds after the ink is attached to the recording medium P" means that the time from the attachment of the ink to the blowing of the wind from the drying unit 15 in the region where the ink is attached to the recording medium is within 0.4 seconds. In this way, the supply of the air from the drying unit 15 and the transport speed at which the transport unit 14 transports the recording medium P are controlled so that the print surface of the recording medium P is dried as quickly as possible. By rapidly starting the drying of the ink within 0.4 seconds after the ink is attached to the recording medium P, the ink can be dried without penetrating into the recording medium P, and the occurrence of curling can be suppressed.

In the recording apparatus including the line-type ink jet head, when it is necessary to carry paper at a high speed of 0.5m/s or more, a problem of stacking of paper in particular becomes prominent. If the wet frictional resistance of the ink jet printing surface is large, there is a problem that the sheets do not slip and obstruct when the image is full, or even if the sheets are substantially aligned, it is difficult to align the sheets in order, and the stapler (stapler binding) is misaligned. In high-speed printing, since the paper is overlapped before the ink is dried, stackability becomes more difficult. Further, in the face-down discharge in which the discharge is performed with the print face down, since drying of ink is difficult, there arises a problem that stackability becomes more difficult. Further, at the time of printing, since the printing surface expands, there is a problem that permanent curling (primary curling) in which the printing surface is raised immediately after printing occurs. As the drying advances, there is a problem that paper discharge curl (secondary curl) in which the printing surface is depressed within a ten-second to several minutes occurs because the printing surface shrinks.

In the present embodiment, in the recording apparatus including the line-type ink jet head, colloidal silica is added to the ink for ink jet recording, and drying of the printing surface is started within 0.4 seconds after printing, whereby the curling can be suppressed while reducing the wet frictional resistance of the printing surface, and the stacking property can be improved.

Preferably, the control unit 11 controls the drying unit 15 or the conveying section 14 so as to blow air to the printing surface of the recording medium P for 0.5 seconds or more. This makes it possible to sufficiently dry the printing surface of the recording medium P placed on the Fu placement unit 28.

Further, the control unit 11 preferably controls the conveying portion 14 so that the recording medium P is conveyed at a speed of 0.5m/sec or more with respect to the inkjet head 48. In the present embodiment, in particular, in the line-type inkjet which is transported at high speed, the stackability can be improved.

As described above, according to the present embodiment, it is possible to provide an ink jet recording apparatus capable of forming a high-quality image at high speed while improving stackability.

Ink jet recording method

An inkjet recording method according to an embodiment of the present invention includes: a step of ejecting ink containing colloidal silica from a line-type ink jet head to a recording medium; and a step of starting the drying of the ink within 0.4 seconds after the ink is attached to the recording medium.

As described above, according to the present embodiment, it is possible to provide an ink jet recording method capable of forming a high-quality image at high speed while suppressing generation of satellites while improving stackability.

The recording apparatus and the recording method according to the present embodiment can be used without being restricted by a recording medium (for example, plain paper, coated paper, plain paper double-sided printing, and the like), but the effect is remarkable when plain paper is used as the recording medium. As an example of plain paper, paper generally called fine paper/neutral paper/copy paper can be cited.