US-12624240-B2 - Pre-coating agent, ink set for inkjet recording, and laminate

Abstract

The present invention provides a pre-coating agent capable of, without containing a polyvalent metal salt, preventing or reducing mottling and bleeding to improve the print image quality and preventing or reducing strike-through of an ink composition for inkjet recording during printing using the ink composition for inkjet recording, as well as being capable of preventing or reducing peeling and a decrease in hardness of an overcoat layer in the post-process (formation of the overcoat layer). Provided is a pre-coating agent for forming a precoat layer to receive an ink composition for inkjet recording, the pre-coating agent containing inorganic particles, an amine salt of an organic acid, a resin emulsion, and water, the inorganic particles having a particle size of 1 μm to 10 μm, the pre-coating agent being free from a polyvalent metal salt.

Inventors

• Hirohito Maeda
• Hiroyuki Konishi
• Yuya Watanabe
• Ryohei Miyake

Assignees

• SAKATA INX CORP.

Dates

Publication Date

20260512

Application Date

20220322

Priority Date

20210331

Claims (8)

1. 1 . A pre-coating agent for forming a precoat layer that receives an ink composition for inkjet recording, the pre-coating agent comprising: inorganic particles; an amine salt of an organic acid; a resin emulsion; and water, wherein the inorganic particles have a particle size in a range from 1 μm to 10 μm, the pre-coating agent is free from a polyvalent metal salt that forms metal ions having a valence of 2 or higher, and the resin emulsion comprises at least one emulsion selected from the group consisting of a styrene-acrylic emulsion and a vinyl acetate emulsion.
2. 2 . The pre-coating agent according to claim 1 , wherein the inorganic particles are porous silica particles.
3. 3 . The pre-coating agent according to claim 1 , wherein the amine salt of an organic acid is a salt obtained by neutralizing at least one acid selected from the group consisting of polyacrylic acid, formic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, and derivatives thereof, with an amine.
4. 4 . An ink set for inkjet recording, comprising: the pre-coating agent according to claim 1 ; and an ink composition for inkjet recording.
5. 5 . The ink set for inkjet recording according to claim 4 , wherein the ink composition for inkjet recording is an ink composition for aqueous inkjet recording.
6. 6 . The ink set for inkjet recording according to claim 5 , wherein the ink composition for aqueous inkjet recording comprises a pigment coated with an alkali-soluble resin, a basic compound, and a water-soluble organic solvent.
7. 7 . A laminate sequentially comprising, on a substrate, a print layer formed using the ink set for inkjet recording according to claim 4 , and an overcoat layer containing a resin.
8. 8 . The pre-coating agent according to claim 1 , wherein the pre-coating agent is free from a polyvalent metal salt.

Description

TECHNICAL FIELD The present invention relates to a pre-coating agent, an ink set for inkjet recording, and a laminate. BACKGROUND ART In known image forming methods, the image quality is improved by applying or ejecting a pre-coating agent (pretreatment liquid) to the surface of a substrate before an ink composition for inkjet recording is ejected and pigments are aggregated on the substrate. For example, Patent Literature 1 discloses an image forming method including: a pre-treatment step of applying a pre-treatment liquid to a recording medium including a support and a coat layer on the support; an image forming step of applying an inkjet ink containing a colorant, a water-soluble organic solvent, a surfactant, a penetrant, and water to the face with the pre-treatment liquid applied thereto to form an image; and a post-treatment step of applying a post-treatment liquid to the face with the inkjet ink applied thereto to form a protective layer. In the method, the amount of pure water transferred to the coat layer of the recording medium in the contact period of 100 ms, measured using a dynamic scanning liquid absorptiometer, is 1 to 10 mL/m2, and at least one of the pre-treatment liquid or the post-treatment liquid contains water and an aqueous resin and further contains one of colloidal silica, barium sulfate, and titanium oxide. Patent Literature 2 discloses a recording medium including a support and at least one ink-receiving layer on the support. In the recording medium, the ink-receiving layer contains inorganic fine particles, cationic organic fine particles, and a water-soluble polyvalent metal salt, and the cationic organic fine particles are contained in the ink-receiving layer containing the cationic organic fine particles in an amount of 0.1 to 25% by mass based on the dry mass of the ink-receiving layer. Conventional methods, however, have problems when printing is performed on a support (substrate) using an ink composition for inkjet recording, including occurrence of mottling (solid filling) or bleeding in areas with a high print rate, which lowers the image quality, and penetration of the ink composition for inkjet recording to the back side of the support (substrate), which causes strike-through of the ink composition for inkjet recording. In conventional methods, a pre-treatment liquid (pre-coating agent) containing a polyvalent metal salt is preferred from the standpoint of improving the fixation of pigments. However, the polyvalent metal salt in the pre-treatment liquid may react with an overcoat resin used in the post-process (formation of an overcoat layer), disadvantageously causing peeling or a decrease in hardness of the overcoat layer. CITATION LIST Patent Literature Patent Literature 1: JP 2014-073672 APatent Literature 2: JP 2004-255772 A SUMMARY OF INVENTION Technical Problem The present invention has been made in view of the above-described problems, and aims to provide a pre-coating agent capable of, without containing a polyvalent metal salt, preventing or reducing mottling and bleeding to improve the print image quality and preventing or reducing strike-through of an ink composition for inkjet recording during printing using the ink composition for inkjet recording, as well as being capable of preventing or reducing peeling and a decrease in hardness of an overcoat layer in the post-process (formation of the overcoat layer). Solution to Problem The present inventors have made intensive studies in view of the above-described problems, and found that when a pre-coating agent for forming a precoat layer to receive an ink composition for inkjet recording contains inorganic particles having a specific particle size, an amine salt of an organic acid, a resin emulsion, and water, the pre-coating agent can solve all the problems described above without using a polyvalent metal salt. Thus, the present invention was completed. Specifically, the present invention relates to a pre-coating agent for forming a precoat layer to receive an ink composition for inkjet recording, the pre-coating agent containing inorganic particles, an amine salt of an organic acid, a resin emulsion, and water, the inorganic particles having a particle size of 1 μm to 10 μm, the pre-coating agent being free from a polyvalent metal salt. Preferably, the inorganic particles in the pre-coating agent of the present invention are porous silica particles. Preferably, the amine salt of an organic acid is a salt obtained by neutralizing at least one selected from polyacrylic acid, formic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, and derivatives of these, with an amine. Preferably, the resin emulsion includes at least one of a styrene-acrylic emulsion or a vinyl acetate emulsion. The present invention also relates to an ink set for inkjet recording including the pre-coating agent and an ink composition fo