Pretreatment solution, ink set, inkjet recording device, and inkjet recording method

Abstract

This technology provides the ability to form highly adhesive images on non-permeable media using water-based inks. [Solution] The pretreatment solution is used for pretreatment of non-penetrating media on which images are recorded using water-based ink. The polarity term of the surface free energy of the non-penetrating media is 10 mJ / m 2 The following applies: The above pretreatment solution contains 10% by mass or more of 2-ethylhexyl acrylate.

Description

Technical Field

[0001] The present invention relates to a pretreatment liquid, an ink set, an inkjet recording apparatus, and an inkjet recording method.

Background Art

[0002] Patent Documents 1 and 2 disclose aqueous inks for forming images on media by an inkjet recording apparatus. In such aqueous inks, when forming an image on a non-permeable medium with low water permeability, it is essential to have high adhesion to the non-permeable medium. On the other hand, in the aqueous ink described in Patent Document 2, fine particles of urethane resin are blended as a binder so as to obtain high adhesion to the non-permeable medium.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of aqueous inks, in applications where an image is formed on the surface exposed to the viewer side in a non-permeable medium, high abrasion resistance of the image formed on the non-permeable medium is required. In this regard, in an aqueous ink containing fine particles of urethane resin, the abrasion resistance of the image formed on the non-permeable medium tends to be insufficient. Also, in an aqueous ink containing a binder, there is a problem that it is difficult to obtain ejection stability.

[0005] In view of the above circumstances, an object of the present invention is to provide a technique capable of forming an image with high adhesion on a non-permeable medium using an aqueous ink.

Means for Solving the Problems

[0006] To achieve the above objective, a pretreatment solution according to one embodiment of the present invention is used for pretreatment of non-permeable media on which images are recorded using water-based ink. The polarity term of the surface free energy of the non-permeable media is 10 mJ / m 2 The following applies: The above pretreatment solution contains 10% by mass or more of 2-ethylhexyl acrylate.

[0007] This pretreatment solution uses 2-ethylhexyl acrylate as a binder, which has the effect of improving adhesion to low-polarity surfaces, thereby achieving high adhesion of images formed with water-based inks to low-polarity, non-permeable media.

[0008] An ink set according to one embodiment of the present invention comprises the above-mentioned pretreatment liquid and an aqueous ink. The above-mentioned water-based ink contains a pigment, polyurethane fine particles, a water-soluble solvent, and water. The polyurethane fine particles described above have a glass transition temperature of 40°C to 110°C, and a fracture elongation of 50% or less at 25°C. The above-mentioned water-soluble solvents have a boiling point of 200°C or higher and an SP value of 19.5 to 25.5. The content of the polyurethane fine particles in the above-mentioned water-based ink is 3% by mass or more and 8% by mass or less in terms of solid content. The content of the above-mentioned water-soluble solvent in the above-mentioned water-based ink is 0.5% by mass or more and less than 2% by mass.

[0009] In this water-based ink, hard polyurethane microparticles with a high glass transition temperature and a fracture elongation of 50% or less after film formation are used as a binder. This suppresses the binder's effect on improving image adhesion to non-permeable media while improving the scratch resistance of the image formed on the non-permeable media. In contrast, this water-based ink incorporates a water-soluble solvent with a boiling point of 200°C or higher and an SP value of 19.5 to 25.5. Furthermore, by pre-treating the non-permeable media with the aforementioned pre-treatment solution, high image adhesion to the non-permeable media can be obtained. Therefore, with this ink set, it is possible to form an image on non-permeable media that combines both adhesion and scratch resistance.

[0010] The D50 of the above polyurethane fine particles may be between 10 nm and 100 nm.

[0011] The above-mentioned water-based ink may further contain a silicone-based surfactant.

[0012] An inkjet recording apparatus according to one embodiment of the present invention records an image on the recording surface of a non-penetrating medium. The above-mentioned inkjet recording device comprises a pre-processing unit, a recording head, and a control unit. The above pre-treatment unit applies the above pre-treatment solution to the recording surface. The recording head ejects the water-based ink onto the recording surface. When the non-permeable media includes at least one of polypropylene and polyethylene, the control unit controls the recording head to eject the aqueous ink onto the recording surface after the pre-treatment unit has applied the pre-treatment liquid to the recording surface.

[0013] The above-described inkjet recording apparatus may further include a determination unit for determining whether the non-permeable media contains at least one of polypropylene and polyethylene. In this case, when the determination unit determines that the non-permeable medium contains at least one of polypropylene and polyethylene, the control unit controls the recording head to eject the aqueous ink onto the recording surface after the pretreatment unit applies the pretreatment liquid onto the recording surface.

[0014] The recording head may be a circulation type line head.

[0015] The inkjet recording apparatus may be used for producing a printed matter in which the recording surface of the non-permeable medium faces upward and no processing for protecting the image is applied.

[0016] In the inkjet recording method according to one embodiment of the present invention, an image is recorded on a recording surface of a non-permeable medium. In the inkjet recording method, after applying the pretreatment liquid onto the recording surface, the aqueous ink is ejected onto the recording surface.

Advantages of the Invention

[0017] As described above, the present invention can provide a technique capable of forming an image with high adhesion to a non-permeable medium using an aqueous ink.

Brief Description of the Drawings

[0018] [Figure 1] It is a flowchart showing an inkjet recording method according to an embodiment of the present invention. [Figure 2] It is a block diagram showing a schematic configuration of an inkjet recording apparatus according to an embodiment of the present invention. [Figure 3] It is a diagram showing evaluation criteria for scratch resistance.

Modes for Carrying Out the Invention

[0019] Embodiments of the present invention will be described.

[0020] [Configuration of Ink Set] An ink set according to one embodiment of the present invention comprises a pretreatment liquid and a water-based ink (hereinafter also simply referred to as "ink"). The recording medium to which images are formed by the ink set according to this embodiment is a non-penetrating medium having a low-polarity recording surface in which ink penetration is low and ink adhesion is difficult to obtain. Specifically, in this non-penetrating medium, the polarity term of the surface free energy is 10 mJ / m 2 The following are examples of non-permeable media. Examples of such non-permeable media include polypropylene film and polyethylene film. A commercially available surface free energy measuring device can be used to measure the surface free energy of a non-permeable media, for example, the "Handy Contact Angle Meter MSA Flex" manufactured by Sanyo Trading Co., Ltd. can be used.

[0021] In this embodiment, the ink set is used to form an image on the recording surface of a non-permeable medium after applying a pretreatment solution. As will be described in detail later, the ink set according to this embodiment is configured to form an image on the non-permeable medium that combines adhesion and abrasion resistance. Therefore, even when the ink set according to this embodiment is used to form an image on the front surface of the non-permeable medium that is exposed to the viewer, for example, when used for front printing on a transparent non-permeable medium, the configuration allows for the formation of an image that combines adhesion and abrasion resistance, making it less likely for the image to peel or rub off without the need for protective treatment such as lamination. Accordingly, the ink set according to this embodiment is particularly suitable for producing printed materials in which the recording surface of the non-permeable medium is visible from the front and no protective treatment is applied to the image. However, the ink set according to this embodiment is not limited to the above use and may be used, for example, for back printing on a transparent non-permeable medium.

[0022] [Pretreatment solution] (Schematic configuration) The pretreatment solution according to this embodiment contains a binder X and water. The pretreatment solution according to this embodiment can be applied to the recording surface of a non-impermeable medium and dried to form a pretreatment layer on the non-impermeable medium.

[0023] (Binder X) The pretreatment solution according to this embodiment contains a binder X to improve the adhesion of the ink-formed image to the non-permeable media. In the pretreatment solution according to this embodiment, 2-ethylhexyl acrylate is used as the binder X. In the pretreatment solution according to this embodiment, by using 2-ethylhexyl acrylate, which has the effect of improving adhesion to low-polarity surfaces, the adhesion of the ink-formed image to the low-polarity non-permeable media can be enhanced.

[0024] Such effects of the pretreatment solution according to this embodiment are better obtained when combined with the ink of the ink set according to this embodiment. However, such effects of the pretreatment solution according to this embodiment can also be effectively obtained when combined with water-based inks other than the ink of the ink set according to this embodiment, rather than with the ink set according to this embodiment.

[0025] In the pretreatment solution according to this embodiment, the content of binder X is 10% by mass or more in terms of solid content in order to fully obtain the effect of binder X described above. Furthermore, in the pretreatment solution according to this embodiment, it is preferable that the content of binder X is 25% by mass or less in terms of solid content in order to avoid dispensing problems due to viscosity increase during drying.

[0026] (water) In the pretreatment solution according to this embodiment, for example, ion-exchanged water, purified water, or distilled water can be used as water. In the pretreatment solution according to this embodiment, it is preferable that the water content is 40% by mass or more and 80% by mass or less, from the viewpoint of drying properties and discharge reliability.

[0027] (Other ingredients) The pretreatment solution according to this embodiment may contain components other than those listed above, as needed. For example, the pretreatment solution according to this embodiment may contain a water-soluble organic solvent. The water-soluble organic solvent to be included in the pretreatment solution according to this embodiment is not particularly limited, as long as it is compatible with other components. In the pretreatment solution according to this embodiment, the drying properties of the pretreatment solution can be adjusted by the water-soluble organic solvent. Examples of water-soluble organic solvents that can be used in the pretreatment solution according to this embodiment include methanol, ethanol, 1-propanol, 2-propanol, propylene glycol, acetone, tetrahydrofuran, and acetonitrile.

[0028] Furthermore, a surfactant may be added to the pretreatment solution according to this embodiment. In the pretreatment solution according to this embodiment, the compatibility and dispersion stability of each component can be improved by the surfactant. In addition, in the pretreatment solution according to this embodiment, the wettability to the recording medium can be improved by the surfactant. A silicone-based surfactant is preferred as the surfactant to be added to the pretreatment solution according to this embodiment.

[0029] Furthermore, in addition to the water-soluble organic solvent and surfactant, the pretreatment solution according to this embodiment may also contain various additives as needed, such as dissolution stabilizers, drying inhibitors, antioxidants, viscosity modifiers, pH adjusters, and fungicides.

[0030] [Water-based ink] (Schematic configuration) The water-based ink according to this embodiment contains pigment a, binder b, water-soluble solvent c, and water. The ink according to this embodiment is ejected from the recording head of an inkjet recording device onto the recording surface of a non-penetrating media, thereby forming an image on the recording surface of the non-penetrating media. In the ink according to this embodiment, by using binder b with a specific configuration and water-soluble solvent c with a specific configuration in combination, it is possible to form an image on the non-penetrating media that possesses both adhesion and abrasion resistance. The details of each component of the ink according to this embodiment will be described below.

[0031] (Pigment a) The ink according to this embodiment contains pigment a as a coloring agent, from the viewpoint of improving the ability to prevent color mixing and the water resistance of images recorded on the recording medium. Pigment a may be either an inorganic pigment or an organic pigment. In addition, pigment a may be used in combination with an extender pigment as needed.

[0032] Specific examples of inorganic pigments usable in the ink according to this embodiment include, for example, carbon black and metal oxides, with carbon black being particularly preferred for black inks. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.

[0033] Specific examples of organic pigments that can be used in the ink according to this embodiment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.

[0034] In the ink according to this embodiment, the hue is not particularly limited, and any chromatic pigment such as yellow, magenta, cyan, blue, red, orange, and green can be used. Specific examples of preferred chromatic pigments include CI pigment yellow, CI pigment red, CI pigment orange, CI pigment violet, CI pigment blue, and CI pigment green. In the ink according to this embodiment, one or more selected from these chromatic pigments can be used as pigment a.

[0035] (Binder b) In the ink according to this embodiment, a binder b is incorporated to improve the adhesion of the image to the non-permeable media. In the ink according to this embodiment, polyurethane microparticles, which are fine particles formed of polyurethane, are used as the binder b. The polyurethane microparticles used as the binder b have a high glass transition temperature of 40°C to 110°C and are hard with a break elongation of 50% or less at 25°C after film formation. As a result, the ink according to this embodiment provides high scratch resistance for the image formed on the non-permeable media.

[0036] In the ink according to this embodiment, by using rigid polyurethane microparticles as binder b, the effect of binder b on improving the adhesion of the image to the non-permeable media is weakened compared to a configuration using general polyurethane microparticles. In contrast, in the ink according to this embodiment, sufficient adhesion of the image to the non-permeable media is obtained by supplementing the adhesion of the image to the non-permeable media with the water-soluble solvent c and by pre-treating the non-permeable media with the above-mentioned pre-treatment liquid.

[0037] In the ink according to this embodiment, the binder b content is 3% by mass or more in terms of solid content in order to fully obtain the effect of binder b described above. Furthermore, in the ink according to this embodiment, the binder b content is 8% by mass or less in terms of solid content in order to avoid contamination of the nozzle surface in the recording head and ejection failure due to viscosity increase. Moreover, in the ink according to this embodiment, in order to more effectively obtain the effect of binder b described above, it is preferable that the particle size (D50) of binder b is 10 nm or more and 100 nm or less.

[0038] (Water-soluble solvent c) In the ink according to this embodiment, the boiling point is 200°C or higher, and the SP value (solubility parameter) is 19.5 or higher and 25.5 or lower. As a result, the ink according to this embodiment has improved film formation uniformity, and high image adhesion to non-penetrating media can be obtained. Examples of water-soluble solvent c that can be used in the ink according to this embodiment include diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, tripropylene glycol, and 3-methyl-1,3-butanediol.

[0039] In the ink according to this embodiment, the content of the water-soluble solvent c is 0.5% by mass or more in order to fully obtain the effect of the water-soluble solvent c described above. Furthermore, in the ink according to this embodiment, since the water-soluble solvent c is a high-boiling point solvent, the content of the water-soluble solvent c is 2% by mass or less in order to ensure drying properties in non-penetrating media.

[0040] (water) In the ink according to this embodiment, for example, ion-exchanged water, purified water, or distilled water can be used as water. In the ink according to this embodiment, from the viewpoint of drying properties and ejection reliability, it is preferable that the water content is 40% by mass or more and 80% by mass or less.

[0041] (Other ingredients) The ink according to this embodiment may contain other components as needed. For example, it is preferable to include a surfactant in the ink according to this embodiment. A silicone-based surfactant is preferred as the surfactant to be included in the ink according to this embodiment. By including a silicone-based surfactant in the ink according to this embodiment, the wettability on the surface of the layer formed with the pretreatment solution on the non-penetrating media can be improved. A silicone-based surfactant is a surfactant that has a siloxane bond in its molecule. Examples of commercially available silicone-based surfactants include Silface® SAG002 and Silface SAG503A, manufactured by Nisshin Chemical Industry Co., Ltd.

[0042] Furthermore, the ink according to this embodiment may contain a dispersant that enhances the dispersibility of pigment a in a solvent. A pigment dispersion resin can be used as the dispersant. The pigment dispersion resin is a fine particle of resin that is water-soluble and adheres to the surface of pigment a, thereby suppressing the aggregation of pigment a. Examples of pigment dispersion resins include copolymers of at least one monomer from alkyl (meth)acrylate, styrene, and vinylnaphthalene, and at least one monomer from (meth)acrylic acid and maleic acid.

[0043] As the pigment dispersion resin, a resin having repeating units derived from (meth)acrylic acid ((meth)acrylic acid units), repeating units derived from (meth)acrylate alkyl ester ((meth)acrylate alkyl ester units), and styrene units is preferred. In this case, the proportion of (meth)acrylic acid units among the total repeating units of the pigment dispersion resin is preferably 4.5% by mass or more and 8.0% by mass or less. The proportion of (meth)acrylate alkyl ester units among the total repeating units of the pigment dispersion resin is preferably 35% by mass or more and 70% by mass or less. The proportion of styrene units among the total repeating units of the pigment dispersion resin is preferably 27% by mass or more and 60% by mass or less. As the pigment dispersion resin, a resin having repeating units derived from methacrylic acid, repeating units derived from methyl methacrylate, repeating units derived from butyl acrylate, and styrene units is more preferred.

[0044] In the ink according to this embodiment, the pigment dispersion resin content is preferably 0.5% by mass or more and 8.0% by mass or less, and more preferably 1.5% by mass or more and 4.0% by mass or less. By setting the pigment dispersion resin content to 0.5% by mass or more, aggregation of pigment a can be more effectively suppressed. By setting the pigment dispersion resin content to 8.0% by mass or less, nozzle clogging of the recording head can be suppressed.

[0045] Furthermore, in addition to surfactants and pigment dispersion resins, the ink according to this embodiment may also contain various additives such as dissolution stabilizers, antioxidants, viscosity modifiers, pH adjusters, and neutralizing agents, as needed.

[0046] [Inkjet recording method] The inkjet recording method according to this embodiment uses the ink set according to this embodiment described above. Figure 1 is a flowchart of the inkjet recording method according to this embodiment. In step S01, the polarity term of the surface free energy is 10 mJ / m 2 The following non-penetrating media is set in a predetermined position. In step S02, a pre-treatment solution is applied to the recording surface of the set non-penetrating media. In step S03, an image is formed by ejecting ink onto the recording surface of the non-penetrating media to which the pre-treatment solution has been applied.

[0047] [Inkjet recording device] The inkjet recording apparatus 1 according to this embodiment is configured to implement the inkjet recording method according to this embodiment described above. Figure 2 is a block diagram showing the schematic configuration of the inkjet recording apparatus 1. The inkjet recording apparatus 1 includes a pre-processing unit 2, a recording head 3, a discrimination unit 4, and a control unit 5.

[0048] The pre-processing unit 2 performs pre-processing by applying a pre-processing solution to the recording surface of the non-permeable media. The pre-processing unit 2 may have a recording head different from the recording head 3, and may be configured to discharge the pre-processing solution to the position on the recording surface of the non-permeable media where the image is formed by the recording head. As described above, the discharge stability of the pre-processing solution according to this embodiment is high, so the pre-processing unit 2 can discharge the pre-processing solution to the precise position on the recording surface of the non-permeable media. The recording head that discharges the pre-processing solution is preferably a circulating line head. In a circulating line head, the pre-processing solution is constantly circulated to the vicinity of the nozzle surface, further reducing the likelihood of discharge defects due to viscosity increase caused by drying. Note that the pre-processing unit 2 does not necessarily have to use a recording head; for example, it may be configured to apply the pre-processing solution to the entire area of ​​the recording surface of the non-permeable media using a roller.

[0049] The recording head 3 forms an image by ejecting ink to the position on the recording surface of the non-penetrating media where the image is to be formed. As described above, the ink ejection stability of this embodiment is high, so the recording head 3 can eject ink to the precise position on the recording surface of the non-penetrating media. The recording head 3 is preferably a circulating line head. In a circulating line head, the ink is constantly circulated to the vicinity of the nozzle surface, further reducing the likelihood of ejection failures due to viscosity increase caused by drying.

[0050] The discrimination unit 4 determines whether or not a non-penetrating media requires pretreatment by applying a pretreatment solution. For example, if the polarity term of the surface free energy of the non-penetrating media is 10 mJ / m, the discrimination unit 4 determines whether or not it is a non-penetrating media that requires pretreatment. 2 The determination is made as follows: In other words, the determination unit 4 determines whether the polarity term of the surface free energy of the non-penetrating media is 10 mJ / m 2 If the following is determined, it is understood that the media is impermeable and requires pretreatment. In addition, the discrimination unit 4 determines that the polarity term of the surface free energy of the impermeable media is 10 mJ / m 2 If it is determined that it is not one of the following, it is understood to be a non-penetrating media that does not require pre-processing.

[0051] Furthermore, the discrimination unit 4 may determine whether the non-permeable media contains at least one of polypropylene and polyethylene. In other words, if the discrimination unit 4 determines that the non-permeable media contains at least one of polypropylene and polyethylene, it is determined that the non-permeable media requires pretreatment. Conversely, if the discrimination unit 4 determines that the non-permeable media does not contain either polypropylene or polyethylene, it is determined that the non-permeable media does not require pretreatment.

[0052] If the discrimination unit 4 determines that the non-impermeable media requires pre-treatment, the control unit 5 controls the pre-treatment unit 2 to apply pre-treatment liquid to the recording surface of the non-impermeable media, and then controls the recording head 3 to eject ink onto the recording surface on the non-impermeable media to which the pre-treatment liquid has been applied. On the other hand, if the discrimination unit 4 determines that the non-impermeable media does not require pre-treatment, the control unit 5 can control the recording head 3 to eject ink onto the recording surface on the non-impermeable media to which the pre-treatment liquid has been applied, without the pre-treatment unit 2 applying pre-treatment liquid to the recording surface of the non-impermeable media.

[0053] The inkjet recording device 1 is not limited to the above configuration and can be modified as needed. For example, the inkjet recording device 1 does not need to have a discrimination unit 4. In this case, the inkjet recording device 1 may have an input operation unit for receiving user input regarding whether or not the media is non-penetrating and requires pretreatment by applying a pretreatment solution.

[0054] [Examples and Comparative Examples] As examples and comparative examples of the present invention, pretreatment solutions and inks were prepared and evaluated.

[0055] (Preparation of pretreatment solution) Pretreatment solutions p1 to p5, to be used in the examples and comparative examples, were prepared.

[0056] • Pretreatment solution p1 An aqueous emulsion containing 2-ethylhexyl acrylate as a dispersed phase was prepared. This aqueous emulsion was diluted to 20% by mass in solid content, 20% by mass of propylene glycol, 0.1% by mass of a silicone-based surfactant ("Sylface SAG503A" manufactured by Nisshin Chemical Industry Co., Ltd.), and the remainder was deionized water to prepare pretreatment solution p1.

[0057] • Pretreatment solution p2 An aqueous emulsion containing 2-ethylhexyl acrylate as a dispersed phase was prepared. This aqueous emulsion was diluted to 20% by mass in solid content, 10% by mass of ethanol, 10% by mass of propylene glycol, 0.1% by mass of a silicone-based surfactant ("Sylface SAG503A" manufactured by Nisshin Chemical Industry Co., Ltd.), and the remainder was deionized water to prepare pretreatment solution p2.

[0058] • Pretreatment solution p3 An aqueous emulsion containing 2-ethylhexyl acrylate as a dispersed phase was prepared. This aqueous emulsion was adjusted to 10% by mass in terms of solid content, 30% by mass of propylene glycol, 0.1% by mass of a silicone-based surfactant ("Sylface SAG503A" manufactured by Nisshin Chemical Industry Co., Ltd.), and the remainder was deionized water to prepare pretreatment solution p3.

[0059] • Pretreatment solution p4 A water-based emulsion containing urethane resin as a dispersed phase was prepared. This water-based emulsion was adjusted to 20% by mass in solid content, 20% by mass in propylene glycol, 0.1% by mass in a silicone-based surfactant ("Sylface SAG503A" manufactured by Nisshin Chemical Industry Co., Ltd.), and the remainder was deionized water to prepare pretreatment solution p4.

[0060] • Pretreatment solution p5 An aqueous emulsion containing 2-ethylhexyl acrylate as a dispersed phase was prepared. This aqueous emulsion was adjusted to 5.0% by mass in terms of solid content, 35% by mass of propylene glycol, 0.1% by mass of a silicone-based surfactant ("Sylface SAG503A" manufactured by Nisshin Chemical Industry Co., Ltd.), and the remainder was deionized water to prepare pretreatment solution p5.

[0061] (Ink preparation) First, a pigment dispersion was prepared by dispersing pigment a in water. The pigment dispersion was prepared by wet dispersion of pigment a, a pigment dispersion resin, and water using a media-type wet dispersion machine. In wet dispersion using a media-type wet dispersion machine, for example, small-particle beads (for example, beads with a D50 of 0.5 mm or more and 1.0 mm or less) can be used as the media. The material of the beads is not particularly limited, but hard materials (for example, glass and zirconia) are preferred.

[0062] In both the examples and comparative examples, carbon black was used as pigment a, styrene-acrylic resin as the pigment dispersion resin, and deionized water was used as the water. In addition, in both the examples and comparative examples, the pigment a content was 3% by mass, the pigment dispersion resin content was 1.5% by mass, and the remainder was water.

[0063] Next, inks for the Examples and Comparative Examples were prepared. For the inks for the Examples and Comparative Examples, one of binders b1, b2, or b3 shown in Table 1 was used as binder b, and one of water-soluble solvents c1, c2, c3, c4, or c5 shown in Table 2 was used as water-soluble solvent c. The inks for the Examples and Comparative Examples were prepared by blending binder b, water-soluble solvent c, pigment dispersion, propylene glycol, triethylene glycol monobutyl ether, Silface SAG503A, and water. In both the Examples and Comparative Examples, deionized water was used as the water.

[0064] [Table 1]

[0065] [Table 2]

[0066] (Evaluation of pretreatment solution and ink) For the examples and comparative examples, image adhesion, image scratch resistance, and ink ejection stability were evaluated.

[0067] • Method for evaluating image adhesion In evaluating image adhesion, a solid image was formed by first applying a pretreatment solution to a non-permeable medium and then ejecting ink. The non-permeable medium used was a corona-treated biaxially oriented polypropylene (OPP) film manufactured by Futamura Chemical Co., Ltd. (Surface free energy polarity term: 0.16 mJ / m²). 2 A solid image was formed on a non-penetrating medium. Tape (manufactured by Nichiban Co., Ltd., Cellotape®, 18 mm wide, CT-18S) was applied to the solid image, and the surface condition of the solid image after peeling it off was observed. The ratio of the area where the image was peeled off to the total area where the tape was applied in the solid image was measured. The obtained measured value was used as the evaluation value for image adhesion. The evaluation value for image adhesion was evaluated according to the following criteria A to C. For image adhesion, a solid image with an evaluation of A was considered acceptable, and solid images with evaluations of B and C were considered unacceptable. A: 0% B: Less than 50% C: 50% or more

[0068] • Method for evaluating the scratch resistance of images In evaluating the scratch resistance of the images, solid images with a wet film thickness of approximately 6 μm were first formed on non-penetrating media coated with each pretreatment solution using each ink with a bar coater (K303S Multi Coater, manufactured by Matsuo Sangyo Co., Ltd.) at bar number 1. The non-penetrating media used was corona-treated biaxially oriented polypropylene (OPP) film manufactured by Futamura Chemical Co., Ltd. (polarity term of surface free energy: 0.16 mJ / m²). 2A solid color image was formed on a non-penetrating medium. After drying the image at 100°C for 10 minutes and then leaving it to stand in the air for half a day, the abrasion resistance test of the solid color image was performed using a JSPS-type friction tester. The solid color image after the test was visually observed and evaluated according to the following criteria A to C. For abrasion resistance, a solid color image with an evaluation of A was considered acceptable, while solid color images with evaluations of B and C were considered unacceptable. A: No streaks or abrasions are observed. (See Photo A in Figure 3) B: Fewer than 10 streaks are observed. (See photo B in Figure 3) C: More than 10 streaks are observed. (See photograph C in Figure 3)

[0069] ·Discharge stability The ejection stability of the pretreatment liquid and ink was evaluated by the degree of waviness in the non-printed area. In other words, with pretreatment liquids and inks, the lower the ejection stability, the more likely the tail of the ejected droplet is to become wavy, which causes waviness in the non-printed area. Therefore, it can be seen that the greater the waviness in the non-printed area, the lower the ejection stability.

[0070] The degree of distortion in the non-printed area was evaluated under normal temperature and high humidity conditions (temperature 25°C and humidity 80%RH) to minimize the effect of drying of the line head nozzles. An inkjet recording device (prototype, 600dpi, manufactured by Kyocera Document Solutions Inc.) was used as the evaluation machine. For this evaluation machine, the pretreatment liquid or ink was purged from the line head and the line head was wiped (purge-wipe process). One minute after the purge-wipe process, a single horizontal line (a line along the main scanning direction) was formed on A4 glossy paper (Seiko Epson Corporation's "Super Fine Paper") using the evaluation machine. At this time, the line width of the horizontal line was set to 1 dot (equivalent to 1 drop of pretreatment liquid or ink). The volume of pretreatment liquid or ink ejected per dot (volume per drop) from each nozzle of the line head was set to 3 pL.

[0071] Next, the amount of misalignment of the aforementioned horizontal lines was determined using an optical microscope (Nikon Corporation "MM-800"). Specifically, the maximum distance (amount of misalignment) in the sub-scanning direction of each dot constituting the aforementioned horizontal lines was measured using the application software included with the optical microscope. A larger amount of misalignment indicates that distortion occurred in the aforementioned horizontal lines due to warping in the non-printed area. For ejection stability, the amount of misalignment obtained for each pretreatment solution or ink was used as the evaluation value. The evaluation value of the ejection stability of each pretreatment solution or ink was evaluated according to the following A and B criteria. For image density, a pretreatment solution or ink with an evaluation of A is considered acceptable, and a pretreatment solution or ink with an evaluation of B is considered unacceptable. A: 20μm or less B: More than 20μm

[0072] (Examples 1-9) Examples 1 to 9 used inks with the compositions shown in Table 3. Table 4 shows the pretreatment solutions used for Examples 1 to 9, as well as the evaluation results for image adhesion, image scratch resistance, and ink ejection stability. As shown in Table 4, all of Examples 1 to 9 passed the tests for image adhesion, image scratch resistance, and ink ejection stability.

[0073] [Table 3]

[0074] [Table 4]

[0075] (Comparative Examples 1-7) Comparative Examples 1 to 7 used inks with the compositions shown in Table 5. Table 6 shows the pretreatment solutions used for Comparative Examples 1 to 7, as well as the evaluation results for image adhesion, image scratch resistance, and ink ejection stability.

[0076] As shown in Table 6, Comparative Examples 1 to 6, which used pretreatment solution p4 that did not contain 2-ethylhexyl acrylate as a binder, failed in both adhesion and abrasion resistance. Among these, Comparative Example 6, which had a break elongation of over 50% at 25°C, showed better adhesion than Comparative Examples 1 to 5, but failed in discharge stability. Comparative Example 7, which used pretreatment solution p5 with a low content of 2-ethylhexyl acrylate, also failed in both adhesion and abrasion resistance.

[0077] [Table 5]

[0078] [Table 6] [Explanation of Symbols]

[0079] 1… Inkjet recording device 2…Pre-treatment section 3…Recording head 4...Discrimination section 5…Control Unit

Claims

1. A pretreatment solution for non-penetrating media in which images are recorded using water-based inks, The polarity term of the surface free energy of the non-penetrating media is 10 mJ / m ２ The following: The aforementioned pretreatment solution contains 10% by mass or more of 2-ethylhexyl acrylate. Pretreatment solution.

2. The pretreatment solution described in claim 1 and the water-based ink are provided, The aforementioned water-based ink is Pigments and Polyurethane fine particles having a glass transition temperature of 40°C to 110°C and a fracture elongation of 50% or less at 25°C, A water-soluble solvent having a boiling point of 200°C or higher and an SP value of 19.5 or higher and 25.5 or lower, It contains water, The content of the polyurethane fine particles in the aqueous ink is 3% by mass or more and 8% by mass or less in terms of solid content. The content of the water-soluble solvent in the water-based ink is 0.5% by mass or more and less than 2% by mass. Ink set.

3. The ink set according to claim 2, The D50 of the polyurethane fine particles is 10 nm or more and 100 nm or less. Ink set.

4. An ink set according to claim 2 or 3, The aforementioned water-based ink further contains a silicone-based surfactant. Ink set.

5. An inkjet recording device that records an image on the recording surface of a non-penetrating media, A pre-treatment unit for applying the pre-treatment solution according to claim 1 to the recording surface, A recording head that ejects the aqueous ink according to claim 2 onto the recording surface, When the non-permeable media includes at least one of polypropylene and polyethylene, the control unit controls the recording head to discharge the aqueous ink onto the recording surface after the pre-treatment unit has applied the pre-treatment liquid to the recording surface, An inkjet recording device equipped with the following.

6. An inkjet recording apparatus according to claim 5, The device further comprises a determination unit for determining whether the non-permeable media contains at least one of polypropylene and polyethylene. When the discriminator determines that the non-permeable media contains at least one of polypropylene and polyethylene, the control unit controls the recording head to discharge the aqueous ink onto the recording surface after the pre-processing unit has applied the pre-treatment liquid to the recording surface. Inkjet recording device.

7. An inkjet recording apparatus according to claim 5 or 6, The recording head is a circulating line head. Inkjet recording device.

8. An inkjet recording apparatus according to claim 5 or 6, The recording surface of the non-penetrating media is visible from the front, and it is used in the production of printed materials in which no processing is applied to protect the image. Inkjet recording device.

9. An inkjet recording method for recording an image on the recording surface of a non-penetrating medium, After applying the pretreatment solution according to claim 1 to the recording surface, the aqueous ink according to claim 2 is dispensed onto the recording surface. Inkjet recording method.

Images