JP2024046321A - Inkjet recording device and inkjet recording method - Google Patents

Abstract

To provide an inkjet recording device which suppresses deformation of a first ink image due to contact with a liquid absorption member having a porous body and enables formation of a more stable and high quality image even when images are repeatedly formed.SOLUTION: An inkjet recording device has: a reaction liquid imparting unit for imparting a reaction liquid onto a body to be recorded; an ink imparting unit for imparting ink onto the body to be recorded to which the reaction liquid is imparted; a heating unit for heating the reaction liquid and the ink to 60°C or higher, and thereby forming a first ink image; a cooling unit for cooling the formed first ink image to less than 60°C so that a fall temperature becomes 5°C or more without deformation; and a liquid removal unit for bringing a liquid absorption member having a porous body into contact with the body to be recorded on which the cooled first ink image is formed, and forming a second ink image from which at least a part of a liquid component contained in the first ink image is removed.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inkjet recording apparatus and an inkjet recording method.

When recording an image using an inkjet method, bleeding may occur, in which adjacently applied inks mix with each other, and beading, in which ink that lands first is attracted to ink that lands later, may occur. In contrast, prior to ink application, a reaction liquid (also called a processing liquid) that increases the viscosity of the ink image by coagulating the solid content in the ink is applied to suppress interference between ejected dots. Techniques for suppressing bleeding and beading are known. However, especially in the method of applying ink after applying the reaction liquid, since two liquid compositions are applied, the total amount of liquid components applied increases, which tends to cause curling and cockling. .

On the other hand, water-based inks, which contain water as the main liquid component, are used as environmentally friendly inks. In the case of water-based inks, it is generally necessary to add a high boiling point solvent to prevent nozzle clogging due to drying. However, in aqueous solutions containing these high boiling point solvents, the viscosity increases due to the high concentration caused by the evaporation of water, causing the ink layer to become sticky. As a result, there is a concern that when recorded recording media are stacked, blocking may occur, in which the ink sticks to the back surface of the recording media, or the recording media may curl due to insufficient drying of the ink layer.
In response to such problems, the present inventors have proposed a transfer type ink jet recording method according to Japanese Patent Laid-Open No. 2003-233696.

International Publication No. 2017/119049

In the transfer type inkjet recording method described in Patent Document 1, the following steps are repeated: A step of forming a first image by applying a reaction liquid and ink onto a transfer body. A liquid removal step of contacting a porous body with the transfer body on which the first image has been formed, and forming a second image from which the liquid components contained in the first image have been removed. A transfer step of heating the second image to a temperature equal to or higher than the minimum film-forming temperature of the second image and transferring it onto a recording medium. The recording method is characterized in that the minimum film-forming temperature of the second image is a temperature of 100°C or higher, and the first image does not receive a thermal history of a temperature equal to or higher than the boiling point of water between the step of forming the first image and the step of removing the liquid. According to the invention described in Patent Document 1, it is possible to form a high-quality image that suppresses the curling, cockling, blocking, etc., and further achieves both image transferability and robustness. However, when forming the second ink image, although it is rare, the first ink image that comes into contact with the porous body may be deformed.

The present invention provides inkjet recording that suppresses deformation of a first ink image due to contact with a liquid absorbing member having a porous body even when images are repeatedly formed, and can form more stable high-quality images. The purpose of the present invention is to provide an apparatus and an inkjet recording method.

According to one aspect of the present invention, there is provided a reaction liquid applying unit that applies a reaction liquid containing an ink viscosity increasing component onto a recording medium, and a reaction liquid applying unit that applies a reaction liquid containing an ink viscosity increasing component onto a recording medium; An ink applying unit that applies an ink containing a a heating unit that forms an ink image; a cooling unit that cools the formed first ink image to a temperature of less than 60° C. and a drop temperature of 5° C. or more without deforming the formed first ink image; A second ink from which at least a part of the liquid component contained in the first ink image is removed by bringing a liquid absorbing member having a porous body into contact with the recording medium on which the first ink image is formed. An inkjet recording device is provided that includes a liquid removal unit that forms an image.

According to another aspect of the present invention, there is provided an inkjet recording method including a reaction liquid application step of applying a reaction liquid containing an ink viscosity increasing component onto a recording medium, an ink application step of applying an ink containing water and a coloring material onto the recording medium to which the reaction liquid has been applied, a heating step of heating the reaction liquid and the ink applied onto the recording medium to 60°C or higher to form a first ink image in which the reaction liquid and the ink are mixed, a cooling step of cooling the formed first ink image to a temperature lower than 60°C and a drop temperature of 5°C or higher without deforming the formed first ink image, and a liquid removal step of contacting the recording medium on which the cooled first ink image has been formed with a liquid absorbing member having a porous body to form a second ink image in which at least a part of the liquid component contained in the first ink image has been removed.

According to the present invention, even when images are repeatedly formed, deformation of the first ink image due to contact with a liquid absorbing member having a porous body can be suppressed, and a more stable high-quality image can be formed. An inkjet recording device and an inkjet recording method can be provided.

FIG. 1 is a schematic diagram showing an example of the configuration of a direct writing type inkjet recording apparatus according to the present invention. 1 is a schematic diagram showing an example of the configuration of a transfer type inkjet recording apparatus according to the present invention. FIG. 3 is a block diagram showing a control system for the entire inkjet recording apparatus shown in FIGS. 1 and 2 . 2 is a block diagram of a printer control unit in the direct drawing type inkjet recording apparatus shown in FIG. 1 . 7 is a graph showing temperature changes in an ink image area and a non-ink image area with respect to wind speed when air is blown at room temperature to the first ink image. 1 is a graph showing the yield shear stress versus temperature of a first ink image (aggregate).

As a result of repeated studies by the present inventors, in order to further improve image stability, after forming a first ink image on a recording medium, a liquid absorbing member having a porous body is attached to the first ink image. It has become clear that it is important to lower the temperature of the first ink image before contacting it. In other words, the present inventors believe that by increasing the yield shear stress of the first ink image due to temperature reduction, deformation of the first and second ink images can be suppressed and a high-quality image can be obtained. I gained knowledge. The above findings were obtained both when the recording medium is a recording medium (direct writing type inkjet recording apparatus) and when the recording medium is a transfer body (transfer type inkjet recording apparatus).
Hereinafter, the present invention will be described in detail by citing preferred embodiments.

<Inkjet recording device>
The inkjet recording device according to the present invention includes a reaction liquid applying unit, an ink applying unit, a heating unit, a cooling unit, and a liquid removing unit. The reaction liquid applying unit applies a reaction liquid containing an ink viscosity increasing component onto a recording medium. The ink applying unit applies an ink containing water and a coloring material onto the recording medium to which the reaction liquid has been applied. The heating unit heats the reaction liquid and the ink applied onto the recording medium to 60° C. or higher to form a first ink image in which the reaction liquid and the ink are mixed. The cooling unit cools the formed first ink image to a temperature lower than 60° C. and a drop temperature of 5° C. or higher without deforming the formed first ink image. The liquid removing unit brings a liquid absorbing member having a porous body into contact with the recording medium on which the cooled first ink image has been formed, to form a second ink image from which at least a part of the liquid component contained in the first ink image has been removed.
Here, the first ink image in the present invention means an ink image before being subjected to a liquid absorption process by a liquid absorbing member having a porous body, i.e., before the removal of liquid components, and the second ink image in the present invention means an ink image after the removal of liquid components in which the content of liquid components has been reduced through the liquid absorption process.

The inkjet recording apparatus according to the present invention includes an inkjet recording apparatus that forms an image on a recording medium as a recording medium, and an inkjet recording apparatus that forms an image on a transfer body as a recording medium and transfers the image to the recording medium. An example is an inkjet recording device. In the present invention, the former inkjet recording apparatus is referred to as a "direct drawing type inkjet recording apparatus", and the latter inkjet recording apparatus is referred to as a "transfer type inkjet recording apparatus". In a direct drawing inkjet recording apparatus, an image is formed and various types of image processing are performed on a recording medium for forming printed matter, and a printed matter having a final image is formed. That is, the recording medium itself is a member constituting the printed matter. On the other hand, in a transfer-type inkjet recording device, an image as an ink image formed with ink or the like on a transfer body is transferred to a recording medium for forming printed matter through various processes on the transfer body, and a printed matter with the final image is transferred. is formed. Each inkjet recording device will be explained below.

[Direct-writing type inkjet recording device]
In a direct-writing inkjet recording apparatus, a recording medium is a recording medium on which an image is to be recorded, i.e., a recording medium for forming a desired final image, and a first ink image and a second ink image obtained by removing at least a part of the liquid component from the first ink image are formed on the recording medium.
1 is a schematic diagram showing an example of the configuration of a direct-writing inkjet recording apparatus of the present invention. The direct-writing inkjet recording apparatus 100 has, in order from the upstream side in the transport direction of a recording medium 11, a reaction liquid deposition unit 101, an ink deposition unit 102, a cooling unit 103, and a liquid removal unit 104. The inkjet recording apparatus 100 also includes a heating unit (heater) 16 on the inner side of a transport belt 15 from the viewpoint of promoting the reaction between the reaction liquid and the ink.

The recording medium 11 is held by an endless conveyor belt 15 stretched between rollers 13 and 14 from a recording medium feed tray 12, and is conveyed in the direction of arrow A from left to right on the paper in FIG. 1. The method of conveying the recording medium 11 is not limited to the belt method shown in FIG. 1, and various methods can be applied, such as a method of conveying the recording medium by closely contacting it with the surface (circumferential surface) of a drum-shaped member.

[Reaction liquid application unit]
The inkjet recording device 100 of this embodiment has a reaction liquid application unit 101 that applies a reaction liquid onto a recording medium 11. The reaction liquid application unit 101 shown in FIG. 1 is provided with a reaction liquid storage section 17 that stores a reaction liquid, and a gravure offset roller having reaction liquid application members 18 and 19 that apply the reaction liquid in the reaction liquid storage section 17 onto the recording medium 11. The reaction liquid application unit 101 may use any device that can apply a reaction liquid onto the recording medium 11, and various conventionally known devices may be appropriately used. Specifically, in addition to a gravure offset roller, an inkjet head, a die coating device (die coater), and a blade coating device (blade coater) may be used. By applying the reaction liquid before applying the ink, bleeding and beading can be suppressed.

[Reaction solution]
The reaction liquid contains a component that increases the viscosity of the ink (ink viscosity increasing component). Here, increasing the viscosity of ink means that the components that make up the ink, such as coloring materials and resins, come into contact with the components that increase the viscosity of the ink, chemically react with them, or physically adsorb them. An increase in ink viscosity is observed. This increase in ink viscosity occurs not only when an increase in ink viscosity is observed, but also when a local increase in viscosity occurs due to aggregation of some of the components that make up the ink, such as coloring materials and resins. included. The ink viscosity increasing component has the effect of reducing the fluidity of the ink and/or some of the components constituting the ink on the recording medium, thereby suppressing bleeding and beading during the first ink image formation. has. In the present invention, increasing the viscosity of the ink is also referred to as "making the ink viscous."
As such components for increasing the viscosity of the ink, known components such as polyvalent metal ions, organic acids, cationic polymers, porous fine particles, etc. can be used. Among these, polyvalent metal ions and organic acids are preferred. Further, it is also suitable to contain a plurality of types of ink viscosity increasing components.
Examples of polyvalent metal ions include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg 2+ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ , Fe ^{3+ , Cr 3+ ,} Y ³⁺ , and Al ³⁺ . Examples include trivalent metal ions.
Examples of organic acids include oxalic acid, polyacrylic acid, formic acid, acetic acid, propionic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, levulinic acid, succinic acid, glutaric acid, glutamic acid, and fumaric acid. , citric acid, tartaric acid, lactic acid, pyrrolidonecarboxylic acid, pyronecarboxylic acid, pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumaric acid, thiophenecarboxylic acid, nicotinic acid, oxysuccinic acid, dioxysuccinic acid, and the like.
Note that the content of the ink viscosity increasing component in the reaction liquid is preferably 5% by mass or more based on the total mass of the reaction liquid.

The reaction liquid may contain an appropriate amount of water or a water-soluble organic solvent having a boiling point higher than that of water. In this case, the water used is preferably deionized by ion exchange or the like. In addition, the water-soluble organic solvent that can be used in the reaction liquid in this embodiment is not particularly limited, and any water-soluble organic solvent that can be used in the ink described below may be used.

Further, the reaction liquid can be used by adding a surfactant or a viscosity modifier to adjust its surface tension and viscosity as appropriate. The material used is not particularly limited as long as it can coexist with the ink viscosity increasing component. Specifically used surfactants include acetylene glycol ethylene oxide adduct (product name: FS3100, manufactured by CAPSTONE; product name: Acetylenol E100, manufactured by Kawaken Fine Chemical Co., Ltd.), perfluoroalkyl ethylene oxide adduct (product name: Mega Fac F-444, Mega Fac TF-2066 (manufactured by DIC Corporation), etc.

The amount of the reaction liquid applied may be an amount that can form a substantially uniform layer when the reaction liquid is applied to all areas on the recording medium that can be applied by the ink application unit. This can suppress a decrease in the circularity of the ink dots. Furthermore, application of an excessive amount of reaction liquid may promote excessive shrinkage during the aggregation process of the ink solids, which may impair the image quality. From this perspective, the amount of the reaction liquid applied in this embodiment is preferably 0.05 g/ ^m2 or more and 2 g/ ^m2 or less, and more preferably 0.1 g/ ^m2 or more and 1.3 g/ ^m2 or less.

[Ink application unit]
The inkjet recording apparatus 100 of this embodiment includes an ink applying unit 102 that applies ink to the recording medium 11 to which a reaction liquid has been applied. A first ink image is formed by mixing the reaction liquid and ink, and a liquid component is removed from the first ink image in the next liquid removal unit 104.
As the ink application unit 102, an inkjet head is used. Inkjet heads include, for example, a type that ejects ink by causing film boiling in the ink using an electro-thermal converter to form bubbles, a type that ejects ink using an electro-mechanical converter, and a type that ejects ink using static electricity. Examples include a form of discharging . In this embodiment, a known inkjet head can be used, but from the viewpoint of forming high-speed and high-density images, an inkjet head using an electro-thermal converter is preferably used. Drawing is performed by receiving an image signal and applying the necessary amount of ink to each position.
The amount of ink applied can be expressed by image density (duty) or ink thickness. In this embodiment, the average value obtained by multiplying the mass of each ink dot by the number of applied ink dots and dividing by the printing area is set as the ink applied amount (g/m ² ). Note that the maximum amount of ink applied in the image forming area refers to the amount of ink applied in an area of at least 5 mm ² or more in the area used as information on the recording medium, from the perspective of removing liquid components in the ink. show.

The inkjet recording apparatus of this embodiment may have a plurality of inkjet heads in order to apply ink of each color onto a recording medium. For example, when forming images of each color using yellow ink, magenta ink, cyan ink, and black ink, an inkjet recording apparatus has four inkjet heads that eject each of the four types of ink onto a recording medium. Further, the ink application unit may include an inkjet head that ejects ink (clear ink) that does not contain a coloring material.

〔ink〕
Each component of the ink applied to this embodiment will be described.

(color material)
As the coloring material contained in the ink applied to this embodiment, a pigment or a mixture of a dye and a pigment can be used.
The type of pigment that can be used as a coloring material is not particularly limited. Specific examples of pigments include inorganic pigments such as carbon black; organic pigments such as azo-based, phthalocyanine-based, quinacridone-based, isoindolinone-based, imidazolone-based, diketopyrrolopyrrole-based, and dioxazine-based pigments. These pigments can be used alone or in combination of two or more, if necessary.
The type of dye that can be used as a coloring material is not particularly limited. Specific examples of the dye include direct dyes, acid dyes, basic dyes, disperse dyes, and food dyes, and dyes having anionic groups can be used. More specifically, dyes having an azo skeleton, a triphenylmethane skeleton, a phthalocyanine skeleton, an azaphthalocyanine skeleton, a xanthene skeleton, an anthrapyridone skeleton, etc. can be mentioned.
The content of the coloring material in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, and 1.0% by mass or more and 10.0% by mass or less based on the total mass of the ink. is more preferable.

(dispersant)
As the dispersant for dispersing the pigment, known dispersants used in inkjet inks can be used. In this embodiment, it is preferable to use a water-soluble dispersant having both a hydrophilic part and a hydrophobic part in its structure. In particular, a pigment dispersant made of a resin copolymerized with monomers containing at least a hydrophilic monomer and a hydrophobic monomer is preferably used. There are no particular limitations on each monomer used here, and known monomers are preferably used. Specifically, examples of the hydrophobic monomer include styrene and other styrene derivatives, alkyl (meth)acrylate, benzyl (meth)acrylate, and the like. Further, examples of the hydrophilic monomer include acrylic acid, methacrylic acid, and maleic acid.
The acid value of the dispersant is preferably 50 mgKOH/g or more and 550 mgKOH/g or less. Further, the weight average molecular weight of the dispersant is preferably 1,000 or more and 50,000 or less. Note that the mass ratio of the pigment to the dispersant in the ink (pigment:dispersant) is preferably in the range of 1:0.1 to 1:3.
It is also suitable to use a so-called self-dispersing pigment, which is made dispersible by surface modification of the pigment itself, without using a dispersant.

(Resin fine particles)
The ink used in this embodiment can contain various fine particles that do not contain a coloring material. Among these, resin fine particles are preferable because they may be effective in improving image quality and fixing properties. The material of the resin particles that can be used in this embodiment is not particularly limited, and any known resin can be used as appropriate. Specifically, homopolymers such as polyolefin, polystyrene, polyurethane, polyester, polyether, polyurea, polyamide, polyvinyl alcohol, poly(meth)acrylic acid and its salts, poly(meth)alkyl acrylate, polydiene, or , and copolymers obtained by polymerizing a combination of a plurality of monomers for producing these homopolymers.
The weight average molecular weight (Mw) of the resin is preferably in the range of 1,000 or more and 2,000,000 or less. Further, the amount of resin fine particles in the ink is preferably 1% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 40% by mass or less, based on the total mass of the ink.

Furthermore, in this embodiment, it is preferable to use a resin fine particle dispersion in which the resin fine particles are dispersed in a liquid as the resin fine particles. Although the method of dispersion is not particularly limited, a so-called self-dispersing resin fine particle dispersion, which is dispersed using a resin obtained by homopolymerizing or copolymerizing a plurality of monomers having a dissociable group, is suitable. Here, examples of the dissociative group include a carboxyl group, a sulfonic acid group, a phosphoric acid group, and the like, and examples of the monomer having the dissociative group include acrylic acid, methacrylic acid, and the like.
Furthermore, a so-called emulsion-dispersion type resin particle dispersion in which resin particles are dispersed with an emulsifier can also be suitably used in this embodiment. As the emulsifier mentioned here, any known surfactant can be used, regardless of whether it has a low molecular weight or a high molecular weight. The surfactant is preferably a nonionic surfactant or a surfactant having the same charge as the resin fine particles.

The resin fine particle dispersion used in this embodiment preferably has a dispersed particle size of 10 nm or more and 1000 nm or less, more preferably 100 nm or more and 500 nm or less.
Furthermore, when producing the resin fine particle dispersion used in this embodiment, it is also preferable to add various additives for stabilization. Examples of the additive include n-hexadecane, dodecyl methacrylate, stearyl methacrylate, chlorobenzene, dodecyl mercaptan, blue dye (bluing agent), and polymethyl methacrylate.

(Wax particles)
The ink according to the present embodiment preferably contains a film-forming component having a minimum film-forming temperature (MFT) of 100° C. or higher. As such a film-forming component, wax particles may be contained in addition to the above-mentioned resin fine particles. By containing wax particles in the ink, when the image is heated and the temperature reaches or exceeds the minimum film-forming temperature, film formation proceeds rapidly, and in the case of a transfer type inkjet device described below, it is presumed that the transferability of the second ink image to a recording medium is improved.
Examples of components of wax particles include natural waxes and synthetic waxes. Examples of natural waxes include petroleum waxes, vegetable waxes, and animal and vegetable waxes. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and petrolatum. Examples of vegetable waxes include carnauba wax, candelilla wax, rice wax, and Japan wax. Examples of animal and vegetable waxes include lanolin and beeswax. Examples of synthetic waxes include synthetic hydrocarbon waxes and modified waxes. Examples of synthetic hydrocarbon waxes include polyethylene wax and Fischer-Tropsch wax. Examples of modified waxes include paraffin wax derivatives, montan wax derivatives, and microcrystalline wax derivatives. These may be used alone or in combination of two or more.
The wax particles are preferably added to the ink in the form of a wax particle dispersion in which the wax particles are dispersed in a liquid. The wax particles are preferably formed by dispersing the wax component with a dispersant. The dispersant is not particularly limited, and for example, a known dispersant can be used. However, it is preferable to select a dispersant in consideration of the stability in the dispersed state in the ink.
Moreover, the average particle size (90% particle size based on number) of the wax particles is preferably 1 μm or less, taking into consideration the ejection properties of the ink using an inkjet method.

(Surfactant)
The ink that can be used in this embodiment may contain a surfactant. Specific examples of the surfactant include acetylene glycol ethylene oxide adduct (product name: Acetyleneol E100, manufactured by Kawaken Fine Chemical Co., Ltd.). The amount of the surfactant in the ink is preferably 0.01% by mass or more and 5.0% by mass or less with respect to the total mass of the ink.

(Water and water-soluble organic solvents)
The ink used in this embodiment contains water as a liquid medium (solvent or dispersion medium). The water is preferably deionized by ion exchange or the like. The content of water in the ink is preferably 30% by mass or more and 97% by mass or less, and more preferably 50% by mass or more and 95% by mass or less, based on the total mass of the ink.
The ink may also contain a water-soluble organic solvent. The type of water-soluble organic solvent is not particularly limited, and any known water-soluble organic solvent may be used. Specific examples of water-soluble organic solvents having a higher boiling point than water include glycerin, diethylene glycol, polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, thiodiglycol, hexylene glycol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and 2-pyrrolidone. The ink may also contain ethanol, methanol, or the like having a lower boiling point than water. Of course, two or more of these may be mixed together.
The content of the water-soluble organic solvent in the ink is preferably 3% by mass or more and 70% by mass or less with respect to the total mass of the ink. A water-soluble organic solvent having a boiling point higher than that of water is also called a "high-boiling water-soluble organic solvent".
In the present invention, water is preferably the main component of the liquid medium in the ink. By using water as the main component of the liquid medium in the ink, the ink can be suitably used in an inkjet head using an electrothermal converter, which is capable of high-speed, high-density printing.

(Other additives)
In addition to the above-mentioned components, the ink that can be used in this embodiment includes a pH adjuster, a rust preventive, a preservative, a fungicide, an antioxidant, an anti-reduction agent, a water-soluble resin, and the like, as necessary. It may contain various additives such as a neutralizing agent and a viscosity modifier.

The first ink image formed by mixing the reaction liquid and the ink contains a liquid component containing water and a water-soluble organic solvent having a boiling point higher than that of water, and a solid component insoluble in the liquid component formed by mixing the reaction liquid and the ink. Therefore, at least one of the reaction liquid and the ink contains a water-soluble organic solvent having a boiling point higher than that of water. The content of the water-soluble organic solvent having a boiling point higher than that of water in the first ink image is preferably 3% by mass or more of the entire first ink image, and water is contained in a larger amount than that.

[Heating unit]
The inkjet recording apparatus 100 includes a heater as a heating unit 16 on the inner side of the conveyor belt 15. The recording medium 11 is heated using the heater, thereby accelerating the reaction between the reaction liquid and the ink applied onto the recording medium 11. As the heater, for example, a flat plate heater such as a planar heating element heater can be used. As a heating method, a method of heating from the back side (the surface opposite to the image forming surface) of the recording medium 11 (backside heating method) is preferable. In the present invention, the reaction liquid and ink on the recording medium 11, i.e., the temperature of the first ink image to be formed, is heated to 60° C. or higher by the heating unit 16. On the other hand, the temperature of the first ink image to be formed is preferably 70° C. or lower, and more preferably 65° C. or lower. It is even more preferable that the temperature of the first ink image to be formed is 60° C. If the temperature of the first ink image is 70° C. or lower, it is possible to suppress a situation in which the moisture on the surface of the first ink image is excessively dried due to excessive heating of the first ink image, and the moisture inside the first ink image cannot be removed in the liquid removing step. The temperature of the first ink image means the surface temperature of the first ink image, and can be measured using, for example, a non-contact infrared thermometer.

[Cooling unit]
The cooling unit 103, which is a feature of the present invention, will be described. In this embodiment, after the formation of the first ink image in the heating unit 16, the temperature of the formed first ink image is lowered by the cooling unit 103 before the liquid component is removed in the liquid removal unit 104. More specifically, the reaction liquid and the ink are heated to 60° C. or higher by the heating unit (heater) to form the first ink image, and then the first ink image is cooled in the cooling unit so that the temperature is lower than 60° C. and the drop in temperature is 5° C. or higher without deforming the first ink image. It has been found that if the temperature of the heated first ink image is lowered by 5° C. or more to less than 60° C. without deforming the first ink image during the period from the formation of the first ink image to the removal of the liquid component in the liquid removal unit 104, the yield shear stress of the first ink image becomes high. The cooling unit is not particularly limited, but may be an air blower or the like. However, if the air blowing speed during cooling by the air blower is too fast, the first ink image may be deformed, which is not in accordance with the object of the present invention and should be avoided.

To explain in more detail, FIG. 5 shows the results of blowing air on the first ink image at room temperature (25°C) and measuring the temperature of the ink image area and non-ink image area with a non-contact infrared thermometer. This is a graph showing. Note that the ink image area means a part to which ink and a reaction liquid are applied, and the non-ink image part means a part to which only a reaction liquid is applied or a part to which nothing is applied. The ink capacity of the first ink image (the sum of the mass of the reaction liquid and the mass of the ink image) was equivalent to 1 g/m ² . The recording medium 11 was heated to about 60° C. by the back heater 16 in order to promote the aggregation reaction between the reaction liquid and the ink. According to this graph, the temperature of the non-ink image area to which no ink was applied did not change substantially due to room temperature air blowing (air blowing speed: 22 m/s), but the temperature of the ink image area decreased.

Figure 6 is a graph showing the results of measuring the yield shear stress of the aggregate (components equivalent to the first ink image) formed by mixing the reaction liquid with the ink versus the temperature of the ink used, using a viscoelasticity tester EC TWIST 520 (trade name, manufactured by Anton Paar). The ink temperature specifically refers to the surface temperature of the aggregate formed by the aggregation components (pigment and resin) in the ink aggregated by the reaction liquid. From this result, it was found that the yield shear stress of the first ink image increases when the temperature of the first ink image (aggregate) decreases. It is speculated that this is because the first ink image is less likely to deform due to the pressure applied to it when the liquid components are absorbed by the liquid removal unit.

The temperature of the first ink image formed in a heated state (hereinafter also referred to as "initial temperature") is 60°C or higher, but in the cooling unit, the temperature is lower than 60°C. , the temperature is lowered to 5°C or higher. Preferably, the temperature of the first ink image is cooled to below 55°C. The temperature of the first ink image after cooling is not limited as long as the liquid can be removed in the next liquid removal unit. For example, in the case of air blowing at room temperature (25°C), it is theoretically possible to eventually lower the temperature to room temperature, but if the time required for cooling is taken into consideration, it is sufficient to cool the room to about 40°C. That is, the first ink image is preferably cooled to 45°C, more preferably to 48°C. When heating to 60°C, the temperature drop is preferably set to 15°C or lower, more preferably 12°C or lower.
Furthermore, it was found that the temperature reduction of the first ink image was dependent on the wind speed during cooling. The wind speed of the blower is preferably 5 m/sec or more and 50 m/sec or less, more preferably 5 m/sec or more and 40 m/sec or less. When the wind speed is 5 m/sec or more, the temperature of the first ink image can be sufficiently lowered, and the image stability effect due to the increase in yield shear stress can be sufficiently obtained. Further, if the wind speed is 50 m/sec or less, it is possible to suppress the first ink image from collapsing due to the influence of the wind.

[Liquid removal unit]
The liquid removal unit 104 has a liquid absorbing member 20 having a porous body, and a pressing member 21 for absorbing liquid, which presses the liquid absorbing member 20 against a first ink image on the recording medium 11. By pressing the liquid absorbing member 20 against the first ink image by the pressing member 21, the liquid components contained in the first ink image are absorbed into the liquid absorbing member 20. As a result, the liquid components are absorbed from the first ink image on the recording medium 11, and a second ink image with a reduced amount of liquid components is formed.
There is no particular limitation on the shapes of the liquid absorbing member 20 and the pressing member 21. For example, as shown in Fig. 1, the pressing member 21 may be cylindrical, the liquid absorbing member 20 may be belt-shaped, and the cylindrical pressing member 21 may press the belt-shaped liquid absorbing member 20 against the recording medium 11. Alternatively, the pressing member 21 may be cylindrical, the liquid absorbing member 20 may be cylindrical formed on the circumferential surface of the cylindrical pressing member 21, and the cylindrical pressing member 21 may press the cylindrical liquid absorbing member 20 against the recording medium 11.
In this embodiment, in consideration of space within the inkjet recording apparatus, the liquid absorbing member 20 is preferably in the form of a belt. The liquid removal unit 104 having such a belt-shaped liquid absorbing member 20 may have a tension member for tensioning the liquid absorbing member 20. In Fig. 1, 22, 23, and 24 are tension rollers serving as tension members. Note that, in Fig. 1, the pressing member 21 is also a roller member that rotates in the direction of the arrow B like the tension roller, but is not limited to this.
The recording medium 11 on which the second ink image has been formed through the liquid component removal process in the liquid removing unit 104 is discharged onto the recording medium discharge tray 25 .

When the removal of the liquid component is explained from a different perspective, it can also be expressed as concentrating the ink constituting the first ink image. Concentrating the ink means that the liquid component contained in the ink is reduced, and the content ratio of solids such as coloring materials and resins contained in the ink to the liquid component is increased. When the first ink image is formed by applying the ink after the reactive liquid is applied onto the recording medium, the reactive liquid may remain without reacting with the ink in the non-image area where the first ink image is not formed. In such a case, in the liquid removing unit, the liquid absorbing member contacts (presses) not only the first ink image but also the unreacted reactive liquid, and removes the liquid component of the reactive liquid as well. In the above explanation, it is expressed that the liquid absorbing member contacts the first ink image and removes the liquid component from the first ink image. However, this does not have a limited meaning of removing the liquid component only from the first ink image, but means that it is sufficient to remove the liquid component at least from the first ink image on the recording medium. That is, the liquid absorbing member having a porous body comes into contact with the area where the first ink image is formed (also referred to as the "image forming area"), including the first ink image and the non-image area, and removes liquid components from at least the first ink image. The liquid components are not particularly limited as long as they do not have a fixed shape, have fluidity, and have a substantially fixed volume. For example, water and water-soluble organic solvents contained in the ink and reaction liquid are examples of liquid components.
Various conditions and configurations of the liquid removing unit 104 will be described in detail below. First, the porous body used in the liquid absorbing member 20 used in the present invention will be described below.

(Porous body)
In the present invention, the porous body may be any material having a large number of holes, and for example, a material having a large number of holes formed by the intersection of fibers is also included in the porous body of the present invention. The porous body of the liquid absorbing member 20 according to this embodiment preferably has an average pore size on the first surface side that contacts the first ink image smaller than the average pore size on the second surface side that faces the first surface. In order to suppress adhesion of ink solids (solids formed by mixing the reaction liquid and the ink) to the porous body, it is preferable that the pore size of the porous body is small, and the average pore size of the porous body on at least the first surface side is preferably 10 μm or less. In this embodiment, the average pore size refers to the average diameter on the surface of the first surface or the second surface, and can be measured by known means, such as mercury porosimetry, nitrogen adsorption method, SEM image observation, etc.
In order to obtain uniformly high air permeability, it is preferable to make the thickness of the porous body thin. The air permeability can be expressed by the Gurley value defined in JIS P8117, and the Gurley value is preferably 10 seconds or less. However, if the porous body is made thin, it may not be possible to secure a sufficient capacity for absorbing liquid components, so it is possible to make the porous body multi-layered.

(Layer structure of porous body)
Next, an embodiment in which the porous body has a multi-layer structure will be described. Here, the first layer will be described as the side that contacts the first ink image, and the layer laminated on the side of the first layer opposite the contact surface with the first ink image will be described as the second layer. Even if the porous body is composed of three or more layers, the layers will be described in order of lamination starting from the first layer. In this specification, the first layer may be referred to as the "absorption layer" and the second and subsequent layers as the "support layers."

[First layer]
In this embodiment, the material of the first layer is not particularly limited, and either a hydrophilic material with a contact angle with water of less than 90° or a water-repellent material with a contact angle with water of 90° or more can be used. The hydrophilic material is preferably selected from a single material such as cellulose or polyacrylamide, or a composite material thereof. In addition, the surface of the water-repellent material described below can be hydrophilized before use. Examples of the hydrophilization treatment include sputter etching, irradiation with radiation or H ₂ O ions, and irradiation with excimer (ultraviolet) laser light. In the case of a hydrophilic material, the contact angle with water is preferably 60° or less. In the case of a hydrophilic material, there is an effect of sucking up liquid, particularly water, by capillary force.
On the other hand, from the viewpoint of suppressing colorant adhesion and improving cleaning property, the material of the first layer is preferably a water-repellent material with low surface free energy, particularly a fluororesin.Specific examples of the fluororesin include polytetrafluoroethylene (hereinafter referred to as PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), etc.These resins can be used alone or in combination as necessary, and the first layer may be configured to have a plurality of films laminated therein.

In the case of a water-repellent material, the effect of absorbing liquid by capillary force is almost zero, and it may take time for the material to absorb liquid when it first comes into contact with an image. For this reason, it is preferable to impregnate the first layer with a liquid that has a contact angle with the first layer of less than 90°.
The liquid that is allowed to soak into the first layer in place of the liquid in the first ink image is sometimes called a preliminary penetrant liquid. A reaction liquid may be used as the preliminary penetrant liquid. The preliminary penetrant liquid can be allowed to soak into the first layer by applying the preliminary penetrant liquid from the first surface of the liquid absorbing member. The preliminary penetrant liquid is preferably prepared by mixing the first liquid (water) with a surfactant or a liquid that has a low contact angle with the first layer.

In this embodiment, the thickness of the first layer is preferably 50 μm or less, and more preferably 30 μm or less. The thickness can be obtained by measuring the thickness at any 10 points using a linear micrometer OMV_25 (product name, manufactured by Mitutoyo Corporation) and calculating the average value.

The first layer can be manufactured by a known method for manufacturing a thin porous membrane. For example, a sheet-like material is obtained from a resin material by a method such as extrusion molding, and then stretched to a predetermined thickness. A porous membrane can also be obtained by adding a plasticizer such as paraffin to the material during extrusion molding, and removing the plasticizer by heating or the like during stretching. The pore size can be adjusted by appropriately adjusting the amount of plasticizer added, the stretching ratio, etc.

[Second Layer]
The second layer is preferably a breathable layer. The second layer may be a nonwoven fabric or a woven fabric of resin fibers. The material of the second layer is not particularly limited, but is preferably a material having a contact angle with the liquid component equal to or lower than that of the first layer so that the liquid component absorbed into the first layer does not flow back. Specifically, the material of the second layer is preferably selected from a single material such as polyolefin (polyethylene (PE), polypropylene (PP) etc.), polyurethane, polyamide such as nylon, polyester (polyethylene terephthalate (PET) etc.), polysulfone (PSF) or a composite material thereof. In addition, the second layer is preferably a layer having a larger pore size than the first layer.

[Third Layer]
The multi-layered porous body may be composed of three or more layers. From the viewpoint of rigidity, the third and subsequent layers are preferably made of nonwoven fabric. The materials used are the same as those of the second layer.

[Other materials]
In addition to the porous body having the laminated structure described above, the liquid absorbing member may include a reinforcing member that reinforces the side surface of the liquid absorbing member. Further, the liquid absorbing member may include a joining member for connecting longitudinal ends of the elongated sheet-shaped porous body to form a belt-like member. As such a material, a non-porous tape material or the like may be used, and the material may be placed at a position or periodically so as not to come into contact with the image.

(Method for producing porous body)
The method of laminating the first layer and the second layer to form the porous body is not particularly limited. The two layers may simply be superimposed, or may be bonded to each other using a method such as adhesive lamination or thermal lamination. From the viewpoint of breathability, in this embodiment, lamination by thermal lamination is preferable. Also, for example, a part of the first layer or the second layer may be melted by heating and laminated. Also, a fusion material such as hot melt powder may be interposed between the first layer and the second layer, and the layers may be laminated by heating. When laminating the third layer or more, the layers may be laminated at once or sequentially, and the order of lamination is appropriately selected. Heating is preferably performed by a lamination method in which the porous body is heated while being sandwiched between heated rollers and pressurized.
Next, the processing conditions and the configuration of the liquid removal unit using the porous body will be described.

(Preprocessing)
In this embodiment, before the liquid absorbing member 20 having a porous body is brought into contact with the first ink image, it is preferable to perform pretreatment using a pretreatment unit (not shown in Figures 1 and 2) that applies a wetting liquid to the liquid absorbing member 20. The wetting liquid used in the pretreatment preferably contains water and a water-soluble organic solvent. The water is preferably water that has been deionized by ion exchange or the like. In addition, the type of water-soluble organic solvent is not particularly limited, and any known organic solvent such as ethanol or isopropyl alcohol can be used. In the pretreatment of the liquid absorbing member, the method of applying the wetting liquid to the porous body is not particularly limited, but immersion or dripping is preferable.

(Pressure conditions)
If the pressure of the liquid absorbing member that presses against the first ink image on the recording medium is 2.9 N/cm ² (0.3 kgf/cm ² ) or more, the liquid component in the first ink image is further absorbed. This is preferable because solid-liquid separation can be performed in a short time and liquid components can be efficiently removed from the first ink image. Note that the pressure of the liquid absorbing member in this specification means the nip pressure between the recording medium 11 and the liquid absorbing member 20. The nip pressure is calculated by measuring the surface pressure with a surface pressure distribution measuring device (trade name: I-SCAN, manufactured by Nitta Co., Ltd.) and dividing the weight in the pressurized region by the area.

(action time)
The action time for bringing the liquid absorbing member 20 into contact with the first ink image on the recording medium is 50 msec (milliseconds) in order to further suppress the coloring material in the first ink image from adhering to the liquid absorbing member. ) or less is preferable. Note that the action time in this specification is calculated by dividing the pressure sensing width in the moving direction of the recording medium by the moving speed of the recording medium in the above-mentioned surface pressure measurement. Hereinafter, this action time will be referred to as liquid absorption nip time.

[Recording medium and recording medium transport unit]
In this embodiment, the recording medium 11 is not particularly limited, and any known recording medium can be used. Examples of the recording medium include a long material wound into a roll or a sheet material cut into a predetermined size. Examples of the material include paper, plastic film, wood board, cardboard, and metal film.
Further, in FIG. 1, a recording medium conveyance unit for conveying the recording medium 11 includes a recording medium feed tray 12, a recording medium discharge tray 25, and a group of paper feed/discharge rollers (not shown). However, the structure is not particularly limited to this, as long as it can transport the recording medium.

[Control system]
The direct writing inkjet recording apparatus in this embodiment has a control system that controls each unit. FIG. 3 is a block diagram showing the overall control system of the direct writing inkjet recording apparatus shown in FIG. 1. As shown in FIG. In FIG. 3, 301 is a recording data generation unit such as an external print server, and 302 is an operation control unit such as an operation panel. Further, 303 is a printer control unit for carrying out a recording process, 304 is a recording medium conveyance control unit for conveying a recording medium, and 305 is an inkjet device for printing.

Figure 4 is a block diagram of the printer control unit in the direct drawing type inkjet recording device of Figure 1. 401 is a CPU that controls the entire printer, 402 is a ROM for storing the control program of the CPU, and 403 is a RAM for executing the program. 404 is an application specific integrated circuit (ASIC). The ASIC has a network controller, a serial IF controller, a head data generation controller, a motor controller, etc. built in. 405 is a liquid absorbing member conveyance control unit for driving the liquid absorbing member conveyance motor 406, and is command-controlled from the ASIC of 404 via the serial IF. 407 is a recording medium conveyance drive control unit for driving the conveyance drive motor 408, and is similarly command-controlled from the ASIC of 404 via the serial IF. 409 is a head control unit that generates final ejection data and drive voltage for the inkjet device 305. Additionally, 410 is a temperature control unit that controls the temperature of the heating unit 411 and the cooling unit 412.

[Transfer-type inkjet recording device]
Next, a transfer type inkjet recording apparatus will be described. In the transfer type inkjet recording apparatus, the recording medium is a transfer body that temporarily holds a first ink image and a second ink image that has absorbed liquid components from the first ink image. The transfer type inkjet recording apparatus also includes a transfer unit equipped with a transfer pressing member that heats the second ink image to a temperature equal to or higher than the minimum film-forming temperature of the second ink image and transfers it onto a recording medium on which a final image is to be formed.
2 shows a transfer type inkjet recording apparatus 200 in which the conveyor belt 15 in FIG. 1 is replaced with a belt-shaped transfer body 15. The transfer type inkjet recording apparatus 200 has the transfer body 15 and a transfer unit 205 including a transfer pressing member 26 and an opposing roller 27 for transferring the second ink image formed on the transfer body 15 onto the recording medium 11. Specifically, the transfer type inkjet recording apparatus 200 has a reaction liquid application unit 201, an ink application unit 202, a heating unit 16, a cooling unit 203, a liquid removal unit 204, a transfer unit 205, and a cleaning unit 28. The cleaning unit 28 is a unit for cleaning the surface of the transfer body after the second ink image is transferred to the recording medium 11, and can be provided as necessary. In this way, the transfer type inkjet recording apparatus 200 further has the transfer body 15, the transfer pressing member 26, the opposing roller 27, and the cleaning unit 28 in addition to the direct drawing type inkjet recording apparatus 100 described above. 1 except that the first and second ink images are formed on the transfer body 15. Therefore, detailed explanations will be omitted for the reaction liquid deposition unit 201, the ink deposition unit 202, the heating unit 16, the cooling unit 203, and the liquid removal unit 204. However, the recording medium in the explanation of the direct printing inkjet recording apparatus described above should be read as the transfer body.

[Transfer unit]
The transfer unit 205 heats the transfer body 15 and the second ink image formed on the transfer body 15 to a temperature equal to or higher than the lowest film forming temperature of the second ink image, thereby forming a recording to form a final image. A pressing member 26 for transferring onto the medium 11 and a facing roller 27 are provided. The opposing roller 27 is a roller that presses the transfer member 15 against the transfer pressing member 26 side with the recording medium 11 interposed therebetween. The opposing roller 27 can also serve as a heating member, which will be described later. The transfer position is not limited to the position shown in FIG. 2, and the support member facing the heating member may be used as an opposing roller for transfer.

(transcript)
The transfer body applied to the present invention has a surface layer including a surface having an image forming area. The image forming area is an area provided on the surface of the surface layer of the transfer body, and the first ink image may be formed by applying ink to the entire image forming area, or ink may be applied to a part of the image forming area. The first ink image may be formed by Various materials such as resins and ceramics can be used as appropriate for the surface layer member, but materials with high compressive elastic modulus are preferred from the viewpoint of durability and the like. Specific examples include condensates obtained by condensing acrylic resins, acrylic silicone resins, fluorine-containing resins, and hydrolyzable organosilicon compounds. In order to improve wettability, transferability, etc. of the reaction solution, the surface layer may be subjected to surface treatment. Examples of the surface treatment include flame treatment, corona treatment, plasma treatment, polishing treatment, roughening treatment, active energy ray irradiation treatment, ozone treatment, surfactant treatment, silane coupling treatment, and the like. A plurality of these surface treatments may be combined. Further, the surface layer can also be provided with an arbitrary surface shape.

The transfer body applied to the present invention preferably has a compression layer that has the function of absorbing pressure fluctuations. By providing the compression layer, the compression layer absorbs deformation and disperses local pressure fluctuations, making it possible to maintain good transferability even during high-speed printing. Examples of materials for the compression layer include acrylonitrile-butadiene rubber, acrylic rubber, chloroprene rubber, urethane rubber, and silicone rubber.
When molding the rubber material, it is preferable to compound a predetermined amount of vulcanizing agent, vulcanization accelerator, etc., and further compound a foaming agent, hollow fine particles, salt, or other filler as necessary to make the material porous. This causes the air bubbles to be compressed with volumetric changes in response to various pressure fluctuations, so that deformation in directions other than the compression direction is small, and more stable transferability and durability can be obtained. Porous rubber materials include those with a continuous pore structure in which the pores are connected to each other, and those with an independent pore structure in which the pores are independent of each other. In the present invention, the porous material may have either structure, or these two structures may be used in combination.

The transfer member applied to the present invention preferably has an elastic layer between the surface layer and the compressed layer. As the member of the elastic layer, various materials such as resin and ceramic can be used as appropriate. Various elastomer materials and rubber materials are preferably used in terms of processing characteristics and the like. Specifically, for example, fluorosilicone rubber, phenyl silicone rubber, fluororubber, chloroprene rubber, urethane rubber, nitrile rubber, ethylene propylene rubber, natural rubber, styrene rubber, isoprene rubber, butadiene rubber, ethylene/propylene/butadiene copolymer. , nitrile butadiene rubber, etc. In particular, silicone rubber, fluorosilicone rubber, and phenyl silicone rubber are preferable in terms of dimensional stability and durability because of their small compression set. Further, these rubbers have a small change in elastic modulus due to temperature and are preferable in terms of transferability.

In the present invention, various adhesives or double-sided tapes may be used between the surface layer, the elastic layer, and the compression layer to fix and hold them. A reinforcing layer with a high compressive elastic modulus may be provided to suppress lateral stretching when mounted on the device and to maintain stiffness. A woven fabric may be used as the reinforcing layer. The transfer body can be produced by arbitrarily combining the layers made of the above materials.
The size of the transfer body can be freely selected according to the size of the desired print image. The shape of the transfer body is not particularly limited, and specific examples include a sheet shape, a roller shape, a belt shape, and an endless web shape.

(Press member for transcription)
In the present invention, the second ink image on the transfer body 15 is pressed onto the recording medium 11 by the transfer pressing member 26 onto the recording medium 11 conveyed by the recording medium conveying unit. Transfer a second ink image to the second ink image. By removing the liquid component contained in the first ink image on the transfer body and transferring the second ink image to the recording medium, it is possible to obtain a recorded image that suppresses curling, cockling, etc. becomes. The pressure member for transfer is not limited to the pressure roller as shown in the drawings, and a pressure member other than the pressure roller may be used.
The transfer pressing member 26 is required to have a certain degree of structural strength from the viewpoint of recording medium conveyance accuracy and durability. As the material of the pressing member, metal, ceramic, resin, etc. are preferably used. Among them, aluminum, iron, stainless steel, acetal resin, epoxy resin, polyimide, and polyethylene are used to provide rigidity and dimensional accuracy that can withstand pressure during transfer, as well as to reduce inertia during operation and improve control responsiveness. , polyethylene terephthalate, nylon, polyurethane, silica ceramics, and alumina ceramics are preferably used. Moreover, you may use these in combination.

There is no particular restriction on the time for which the second ink image on the transfer body is pressed against the recording medium (pressing time), but it is necessary to ensure that the transfer is performed well and that the durability of the transfer body is not impaired. In particular, it is preferably 5 msec or more and 100 msec or less. Note that the pressing time refers to the time during which the recording medium and the transfer body are in contact, and the surface pressure was measured using a surface pressure distribution measuring device (product name: I-SCAN, manufactured by Nitta Co., Ltd.). The value is calculated by dividing the length of the pressurized area in the conveyance direction by the conveyance speed.
Further, there is no particular restriction on the pressure with which the image on the transfer body is pressed against the recording medium. However, in order to ensure good transfer and not impair the durability of the transfer body, the pressure must be 9.8 N/cm ² (1 kgf/cm ² ) or more, 294.2 N/cm ² (30 kgf/cm ² ) It is preferable that it is below. Note that this pressing pressure refers to the nip pressure between the recording medium and the transfer body, and the value is calculated by measuring the surface pressure with the above-mentioned surface pressure distribution measuring device and dividing the weight in the pressure area by the area. This is what I did.
The temperature at which the second ink image on the transfer body is pressed against the recording medium is not particularly limited as long as the desired transferability can be obtained.

(Heating the second ink image)
A second ink image formed by removing a part of the liquid component from the first ink image by the liquid absorbing member is heated in the transfer unit to a temperature equal to or higher than the minimum film forming temperature of the second ink image, and then the second ink image is heated to the recording medium. transferred on top.
By heating the second ink image on the transfer body, a part of the solid content in the second ink image (for example, fine resin particles or aggregates of fine resin particles) is softened, and the image is transferred to a recording medium such as paper. Transfer on top. At this time, the second ink image is formed at a temperature higher than the lowest film forming temperature of the second ink image, specifically, higher than the lowest film forming temperature of a film forming component such as resin fine particles contained in the second ink image. Heat to. It is presumed that this causes the resin particles to melt on the transfer body, contact and fuse with the low-temperature recording medium, improve adhesion, and ensure good transfer.
The second ink image can be heated using a known heating member such as irradiation with various lamps such as infrared rays or a hot air fan. Among these, it is preferable to use an infrared heater because of its high heating efficiency. Note that, as described above, the opposing roller 27 can also be used as a heating member.

(Cooling of transfer body)
In this embodiment, since the transfer type inkjet recording apparatus 200 repeatedly performs image formation, liquid removal, and transfer, it is preferable to include a cooling member that cools the transfer body after transfer. Examples of the cooling member include a cleaning unit with a cooling water circulation device added thereto.

[Recording medium transport unit]
2, the recording medium transport unit for transporting the recording medium is composed of a recording medium feed roller 29 and a recording medium take-up roller 30. However, as long as the recording medium can be transported, the configuration is not particularly limited to this.

[Cleaning unit]
In this embodiment, the transfer type inkjet recording device may have a cleaning unit 28 that cleans the image remaining on the transfer body after transfer and paper dust and the like transferred from the recording medium. For cleaning, a known method such as contacting a porous member, rubbing with a brush, or scraping with a blade can be appropriately used. The cleaning unit may have a known shape such as a roller shape or a web shape. It is also preferable to cool the cleaning unit so that the cleaning unit also serves as the cooling member.

[Control system]
The transfer type inkjet recording device according to the present invention has a control system that controls each image forming device. A block diagram showing the overall control system of the transfer type inkjet recording apparatus is as shown in FIG. 3, similar to the direct writing type inkjet recording apparatus shown in FIG.
The block diagram of the printer control unit in the transfer type inkjet recording apparatus shown in FIG. 2 is the block diagram of the printer control unit in the direct writing type inkjet recording apparatus shown in FIG. 4, except that it includes a transfer body drive control unit and a transfer body drive motor. is equivalent to

<Inkjet recording method>
The inkjet recording method according to the present invention is a recording method using the inkjet recording apparatus according to the present invention. That is, the inkjet recording method according to the present invention includes the following steps. A reaction liquid application step of applying a reaction liquid containing an ink viscosity increasing component onto the recording medium. an ink application step of applying ink containing water and a coloring material onto the recording medium to which the reaction liquid has been applied; a heating step of forming a first ink image in which the reaction liquid and the ink are mixed by heating the reaction liquid and the ink applied on the recording medium to 60° C. or higher; A cooling step of cooling the formed first ink image to a temperature lower than 60° C. and a temperature drop of 5° C. or higher without deforming the formed first ink image. A liquid absorbing member having a porous body is brought into contact with the recording medium on which the cooled first ink image is formed, and at least a part of the liquid component contained in the first ink image is removed. 2. Liquid removal step to form the ink image.

In the recording method using a direct-drawing inkjet recording device, the recording medium is a recording medium for forming a final image, and at least one of the liquid components is removed from the first ink image on the recording medium. The second ink image is formed with portions removed. In the recording method using a transfer type inkjet recording device, the recording medium is a transfer body that temporarily holds the first ink image and the second ink image. Further, the recording method includes a transfer step of heating the second ink image to a temperature equal to or higher than the lowest film forming temperature of the second ink image and transferring it onto the recording medium. The details of each step are as described for the above inkjet recording apparatus, and the explanation will be omitted.

The inkjet recording method according to the present invention repeats the above-mentioned reaction liquid application process, ink application process, heating process, cooling process, liquid removal process, and, when a transfer type inkjet recording device is used, a transfer process on the recording medium. With this recording method, even when images are repeatedly formed, there is no risk of the first ink image being deformed, and a more stable, high-quality image can be formed.

The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples, so long as it does not deviate from the gist of the invention. In the following description of the examples, "parts" are by weight unless otherwise specified.

<Preparation of reaction solution>
A reaction liquid having the following composition was used as the reaction liquid applied by the reaction liquid application unit 101. The cloud point of the surfactant in the reaction liquid was 50° C. The cloud point of the surfactant was measured by heating a 1% by mass aqueous solution of the surfactant.
Malic acid: 54.0 parts Potassium hydroxide: 2.0 parts Glycerin: 5.0 parts Surfactant (product name: Megafac TF-2066, manufactured by DIC Corporation): 5.0 parts Ion-exchanged water: balance

<Preparation of ink>
The ink applied by the ink applying unit 102 was prepared as follows.
(Preparation of pigment dispersion)
10 parts of carbon black (trade name: Monak 1100, manufactured by Cabot), aqueous resin solution (styrene-ethyl acrylate-acrylic acid copolymer, acid value 150, weight average molecular weight (Mw) 8,000, resin content 20 0 mass % aqueous solution neutralized with an aqueous potassium hydroxide solution) and 75 parts of pure water were mixed and charged into a batch type vertical sand mill (manufactured by Imex). Next, 200 parts of zirconia beads with a diameter of 0.3 mm were filled, and a dispersion treatment was performed for 5 hours while cooling with water. The obtained dispersion liquid was centrifuged to remove coarse particles, and then a black pigment dispersion having a pigment content of 10.0% by mass was obtained.

(Preparation of resin fine particle dispersion)
18% by mass of ethyl methacrylate, 2% by mass of 2,2'-azobis-(2-methylbutyronitrile), and 2% by mass of n-hexadecane were mixed and stirred for 0.5 hours. The obtained mixture was dropped into a 6% by mass aqueous solution (mixture ratio to the mixture: 78% by mass) of NIKKOL BC15 (trade name, manufactured by Nikko Chemicals Co., Ltd.) as an emulsifier, and stirred for 0.5 hours. Next, the obtained mixture was irradiated with ultrasonic waves for 3 hours using an ultrasonic irradiation machine. Subsequently, a polymerization reaction was carried out at 80°C for 4 hours under a nitrogen atmosphere, and the mixture was cooled to room temperature and filtered to prepare a resin fine particle dispersion having a resin content of 25.0% by mass.

(Preparation of Ink)
The black pigment dispersion and the resin microparticle dispersion obtained above were mixed with the following components and thoroughly stirred to disperse them. Then, pressure filtration was performed using a microfilter (manufactured by Fujifilm Corporation) with a pore size of 3.0 μm to prepare an ink. The remainder of the ion-exchanged water means the amount of all the components constituting the ink that make up 100.0% by mass.
Pigment dispersion (colorant content: 10.0% by mass): 40.0% by mass
Resin fine particle dispersion (resin content: 25.0% by mass): 20.0% by mass
Glycerin: 7.0% by mass
Polyethylene glycol (number average molecular weight (Mn): 1,000): 3.0% by mass
Surfactant (product name: Acetylenol E100, manufactured by Kawaken Fine Chemicals Co., Ltd.): 0.5% by mass
- Ion-exchanged water: balance

[Example 1]
In this example, an image was formed using the direct-writing type inkjet recording apparatus shown in FIG.
As the recording medium 11, printing paper Aurora Coat (product name, manufactured by Oji Paper Co., Ltd.) was used. First, the prepared reaction liquid was applied onto the recording medium 11 by the reaction liquid application unit 101 (reaction liquid application process). The amount of the reaction liquid applied was 0.4 g/ ^m2 . Next, the prepared ink was applied onto the recording medium 11 to which the reaction liquid was applied by using an inkjet head as the ink application unit 102 at 1 g/ ^m2 (ink application process). At this time, the reaction liquid and ink applied onto the recording medium were heated to 60°C (initial temperature) by using a silicone sheet heating element heater as the heating unit 16 arranged on the back surface of the conveyor belt 15. As a result, a first ink image was formed on the recording medium 11 (heating process).
The formed first ink image was cooled by blowing air from the cooling unit 103 at room temperature (25° C.) at a wind speed of 5 m/sec. (cooling step). As a result, the temperature of the first ink image was reduced by 5° C. from the temperature at the time of image formation (initial temperature). A small air blower (turbo-type electric air blower, manufactured by Yodogawa Electric Works) was used as the cooling unit 103. The surface temperature of the first ink image was measured using a non-contact thermometer (fiber-type thermometer, manufactured by Chino).
Next, a multilayered porous body serving as a liquid absorbing member 20 was pressed by a pressing member 21 against the recording medium 11 on which the cooled first ink image was formed, and the liquid component was removed from the first ink image to form a second ink image (liquid removing step). The pressing force of the pressing member 21 was adjusted so that the average nip pressure between the recording medium 11 and the liquid absorbing member 20 was 50 N/ ^cm2 (5.1 kgf/ ^cm2 ). A roller-shaped pressing member with a roller diameter of φ50 mm was used as the pressing member 21.
The obtained image was a high-quality image without image deformation. Furthermore, even when the steps from the reaction liquid application step to the liquid removal step were repeated to form images repeatedly, no image deformation was observed.

[Comparative example 1]
Image formation was performed in the same manner as in Example 1, except that air was not blown by an air blower. At this time, the temperature of the first ink image remained at the initial temperature and did not decrease.
As a result, although a high-quality image was obtained, image deformation sometimes occurred when images were repeatedly formed.

[Example 2]
Image formation was performed in the same manner as in Example 1, except that the wind speed by the blower was 50 m/sec. The temperature of the first ink image after the cooling step was 12° C. lower than the initial temperature. The obtained image was a high-quality image with no image deformation, as in Example 1. Further, no image deformation was observed even when images were repeatedly formed.

[Comparative example 2]
Image formation was performed in the same manner as in Example 1, except that the wind speed by the blower was 55 m/sec. The temperature of the first ink image after the cooling step was 13° C. lower than the initial temperature. However, because the wind speed was too high, image deformation had already occurred in the first ink image, and image deformation was also observed in the final image.

[Example 3]
In Example 3, an image was formed using the transfer type ink jet recording apparatus shown in FIG.
A sheet-like silicone rubber prepared as follows was used as the transfer body 15. A mixture was obtained by mixing 98.0 parts of silicone rubber (product name: KE-12, manufactured by Shin-Etsu Silicones) and 2.0 parts of carbon black. The mixture obtained was applied to a thickness of 0.6 mm on a polyethylene terephthalate sheet having a thickness of 0.1 mm, which was the support of the transfer body, to obtain a sheet-like transfer body.
First, the reaction liquid prepared above was applied onto the transfer body 15 by the reaction liquid application unit 201 (reaction liquid application process). The amount of the reaction liquid applied was 0.4 g/ ^m2 . Next, the ink prepared above was applied at 1 g/ ^m2 onto the transfer body 15 to which the reaction liquid had been applied, using an inkjet head as the ink application unit 202 (ink application process). At this time, the reaction liquid and ink applied onto the recording medium were heated to 60°C (initial temperature) using a planar heating element heater as the heating unit 16. This formed a first ink image on the transfer body 15 (heating process).
The formed first ink image was cooled by blowing air from the cooling unit 203 at room temperature (25° C.) and at a wind speed of 5 m/sec (cooling step). As a result, the temperature of the first ink image was reduced by 5° C. from the temperature at the time of image formation (initial temperature). A small air blower (turbo-type electric air blower, manufactured by Yodogawa Electric Works) was used as the cooling unit 203.
Next, a multilayer porous body was pressed as the liquid absorbing member 20 by a pressing member 21 against the transfer body 15 on which the cooled first ink image was formed, and the liquid component was removed from the first ink image to form a second ink image (liquid removing step). The liquid absorbing member 20 was adjusted to move at a speed equivalent to the moving speed of the transfer body 15 by tension members 22, 23, and 24 which transport the liquid absorbing member while tensioning it. The pressing force of the pressing member 21 was adjusted so that the nip pressure between the transfer body 15 and the liquid absorbing member 20 was 50 N/cm ² (5.1 kgf/cm ² ) on average. A roller-shaped pressing member with a roller diameter of φ50 mm was used as the pressing member 21.
Next, the obtained second ink image was transferred to the recording medium 11 (transfer process). At this time, the pressing force of the transfer pressing member 26 was adjusted so that the nip pressure between the transfer body 15 and the transfer pressing member 26 was 10 N/cm ² (1.0 kgf/cm ² ) on average. The recording medium 11 was transported by the recording medium feed roller 29 and the recording medium take-up roller 30 so that the speed was the same as the moving speed of the transfer body 15. The recording medium 11 used was the same as that in Example 1.
The obtained image was a high-quality image without image deformation. Furthermore, even when the steps from the reaction liquid application step to the transfer step were repeated to form images, no image deformation was observed.

[Comparative example 3]
Image formation was performed in the same manner as in Example 3, except that the wind speed by the blower was 4 m/sec. The temperature of the first ink image after the cooling step was 4° C. lower than the initial temperature.
As a result, although a high-quality image was obtained, image deformation sometimes occurred when images were repeatedly formed.

The results of image formation in the examples and comparative examples are shown in Table 1. The image deformation on each recording medium was evaluated based on the following evaluation criteria.
<Image Deformation Evaluation Criteria>
A: No image deformation was observed even when images were repeatedly formed.
B: When images were repeatedly formed, image deformation was observed.
C: Image deformation was already observed in the first ink image.

The present invention relates to an inkjet recording apparatus having the following configuration.
[Configuration 1]
a reaction liquid application unit that applies a reaction liquid containing an ink viscosity increasing component onto the recording medium;
an ink applying unit that applies ink containing water and a coloring material onto the recording medium to which the reaction liquid has been applied;
a heating unit that forms a first ink image in which the reaction liquid and the ink are mixed by heating the reaction liquid and the ink applied on the recording medium to 60° C. or higher;
a cooling unit that cools the formed first ink image to a temperature lower than 60° C. and a drop temperature of 5° C. or higher without deforming the formed first ink image;
A liquid absorbing member having a porous body is brought into contact with the recording medium on which the cooled first ink image is formed, and at least a part of the liquid component contained in the first ink image is removed. a liquid removal unit forming a second ink image;
An inkjet recording device comprising:
[Configuration 2]
The inkjet recording apparatus according to Configuration 1, wherein the cooling unit is a blower.
[Configuration 3]
The inkjet recording device according to configuration 2, wherein the wind speed of the blower is 5 m/sec or more and 50 m/sec or less.
[Configuration 4]
The recording medium is a recording medium for forming a final image, and the second ink image from which at least a part of the liquid component has been removed from the first ink image is formed on the recording medium. The inkjet recording apparatus according to any one of configurations 1 to 3.
[Configuration 5]
The recording medium is a transfer body that temporarily holds the first ink image and the second ink image, and the second ink image is transferred to the second ink image at a minimum film forming temperature of the second ink image. The inkjet recording apparatus according to any one of configurations 1 to 3, further comprising a transfer unit that transfers onto a recording medium by heating to the above temperature.

The present invention also relates to the following inkjet recording method.
[Method 1]
a reaction liquid applying step of applying a reaction liquid containing an ink viscosity increasing component onto the recording medium;
an ink applying step of applying ink containing water and a coloring material onto the recording medium to which the reaction liquid has been applied;
a heating step of forming a first ink image in which the reaction liquid and the ink are mixed by heating the reaction liquid and the ink applied on the recording medium to 60° C. or higher;
a cooling step of cooling the formed first ink image to a temperature lower than 60° C. and a drop temperature of 5° C. or higher without deforming the formed first ink image;
A liquid absorbing member having a porous body is brought into contact with the recording medium on which the cooled first ink image is formed, and at least a part of the liquid component contained in the first ink image is removed. a liquid removal step for forming a second ink image;
An inkjet recording method comprising:
[Method 2]
The inkjet recording method according to method 1, wherein the reaction liquid applying step, the ink applying step, the heating step, the cooling step, and the liquid removing step are repeatedly performed on the recording medium.
[Method 3]
The inkjet recording method according to method 1 or 2, wherein the cooling step is performed by blowing air from a blower.
[Method 4]
The inkjet recording method according to method 3, wherein the air blowing is carried out at a speed of 5 m/sec or more and 50 m/sec or less by the blower.
[Method 5]
The recording medium is a recording medium for forming a final image, and the second ink image from which at least a part of the liquid component has been removed from the first ink image is formed on the recording medium. The inkjet recording method according to any one of methods 1 to 4.
[Method 6]
The recording medium is a transfer body that temporarily holds the first ink image and the second ink image, and the second ink image is transferred to the second ink image at a minimum film forming temperature of the second ink image. The inkjet recording method according to any one of methods 1 to 4, which comprises a transfer step of transferring onto a recording medium by heating to the above temperature.

11 Recording medium 15 Transfer body 16 Heating unit 20 Liquid absorbing member 100, 200 Inkjet recording device 101, 202 Reaction liquid application unit 102, 202 Ink application unit 103, 203 Cooling unit 104, 204 Liquid removal unit

Claims (11)

a reaction liquid application unit that applies a reaction liquid containing an ink viscosity increasing component onto the recording medium;
an ink applying unit that applies ink containing water and a coloring material onto the recording medium to which the reaction liquid has been applied;
a heating unit that forms a first ink image in which the reaction liquid and the ink are mixed by heating the reaction liquid and the ink applied on the recording medium to 60° C. or higher;
a cooling unit that cools the formed first ink image to a temperature lower than 60° C. and a drop temperature of 5° C. or higher without deforming the formed first ink image;
A liquid absorbing member having a porous body is brought into contact with the recording medium on which the cooled first ink image is formed, and at least a part of the liquid component contained in the first ink image is removed. a liquid removal unit forming a second ink image;
An inkjet recording device comprising: The inkjet recording apparatus according to claim 1, wherein the cooling unit is a blower. The inkjet recording apparatus according to claim 2, wherein the wind speed of the blower is 5 m/sec or more and 50 m/sec or less. The recording medium is a recording medium for forming a final image, and the second ink image from which at least a part of the liquid component has been removed from the first ink image is formed on the recording medium. The inkjet recording device according to any one of claims 1 to 3, wherein the inkjet recording device is The inkjet recording device according to any one of claims 1 to 3, wherein the recording medium is a transfer medium that temporarily holds the first ink image and the second ink image, and the inkjet recording device has a transfer unit that heats the second ink image to a temperature equal to or higher than the minimum film-forming temperature of the second ink image and transfers the second ink image onto the recording medium. a reaction liquid applying step of applying a reaction liquid containing an ink viscosity increasing component onto a recording medium;
an ink applying step of applying an ink containing water and a coloring material onto the recording medium to which the reaction liquid has been applied;
a heating step of heating the reaction liquid and the ink applied onto the recording medium to 60° C. or higher to form a first ink image in which the reaction liquid and the ink are mixed;
a cooling step of cooling the formed first ink image to a temperature lower than 60° C. and a drop temperature of 5° C. or more without deforming the formed first ink image;
a liquid removing step of contacting a liquid absorbing member having a porous body with the cooled recording medium on which the first ink image has been formed, thereby forming a second ink image from which at least a part of the liquid component contained in the first ink image has been removed;
1. An ink jet recording method comprising the steps of: The inkjet recording method according to claim 6, wherein the reaction liquid applying step, the ink applying step, the heating step, the cooling step, and the liquid removing step are repeatedly performed on the recording medium. 7. The inkjet recording method according to claim 6, wherein the cooling step is performed by blowing air from a blower. The inkjet recording method according to claim 8, wherein the air is blown at a speed of 5 m/sec or more and 50 m/sec or less by the blower. The recording medium is a recording medium for forming a final image, and the second ink image from which at least a part of the liquid component has been removed from the first ink image is formed on the recording medium. The inkjet recording method according to any one of claims 6 to 9. The recording medium is a transfer body that temporarily holds the first ink image and the second ink image, and the second ink image is transferred to the second ink image at a minimum film forming temperature of the second ink image. The inkjet recording method according to any one of claims 6 to 9, comprising a transfer step of transferring onto a recording medium by heating to a higher level.

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