JP-7855933-B2 - Image forming method and ink set

Inventors

• 中村 正樹
• 白石 雅晴

Assignees

• コニカミノルタ株式会社

Dates

Publication Date

20260511

Application Date

20220607

Claims (11)

1. A process of applying an ink containing pigment and resin particles onto a fabric using an inkjet method, The process includes applying a post-treatment solution containing a lubricant to the ink applied to the aforementioned fabric in a wet-on-wet manner. The glass transition temperature of the resin constituting the aforementioned resin particles is 20°C or lower . When the dissolution parameter of the resin constituting the resin particles is SP1 (cal/ cm³ ) 1/2 and the dissolution parameter of the lubricant is SP2 (cal/ cm³ ) 1/2 , the following conditions satisfy 0.3 ≤ SP1 - SP2 ≤ 0.8. Image forming method.
2. The aforementioned resin particles include a (meth)acrylic resin. The image forming method according to claim 1.
3. The (meth)acrylic resin further has crosslinkable groups, At least one of the ink and the post-treatment liquid further comprises a crosslinking agent that reacts with the crosslinkable group. The image forming method according to claim 2.
4. The amount of crosslinking agent contained in the ink is greater than the amount of crosslinking agent contained in the post-treatment solution. The image forming method according to claim 3.
5. The lubricant includes a silicone resin. The image forming method according to claim 1 or 2.
6. The aforementioned silicone resin is a silicone acrylic copolymer. The image forming method according to claim 5.
7. The surface tension of the ink and the post-treatment liquid at 25°C is 36 to 50 mN/m, respectively. The image forming method according to claim 1.
8. When the surface temperature of the fabric is 40°C or lower, the time between applying the ink and starting to apply the post-treatment solution is 0.1 to 5 seconds. The image forming method according to claim 1.
9. The aforementioned fabric includes hydrophobic fibers and hydrophilic fibers. The image forming method according to claim 1.
10. This is an ink set for inkjet printing. An ink containing pigment and resin particles, It includes a post-treatment liquid containing a lubricant, The glass transition temperature of the resin constituting the aforementioned resin particles is 20°C or lower . When the dissolution parameter of the resin constituting the resin particles is SP1 (cal/ cm³ ) 1/2 and the dissolution parameter of the lubricant is SP2 (cal/ cm³ ) 1/2 , the following conditions satisfy 0.3 ≤ SP1 - SP2 ≤ 0.8. Ink set.
11. The aforementioned resin particles include (meth)acrylic resin, The lubricant comprises a silicone acrylic copolymer. The ink set according to claim 10.

Description

This invention relates to an image forming method and an ink set. Traditionally, the dyeing method involved immersing the fabric in a dye bath, a process known as exhaust dyeing. However, this method was time-consuming and had low production efficiency. In recent years, inkjet printing, which allows for quick dyeing and high production efficiency, has become widely used. In inkjet textile printing, tiny droplets of ink are ejected from an inkjet recording head and deposited onto fabric to form an image. While dye-based inks are the mainstream for inkjet textile printing, the use of pigment-based inks, which eliminate the need for post-processing steps such as washing away undissolved or unreacted dyes, is being considered. Pigment inks exhibit high color development by retaining pigment particles on the surface of fabrics. However, compared to dye inks, they tend to have lower pigment particle fixation and inferior friction fastness. Therefore, research is being conducted to improve pigment particle fixation and friction fastness by adding binder resins (resin particles) to the ink or by applying a post-treatment solution to the ink. For example, Patent Document 1 discloses an inkjet printing method comprising the steps of: inkjet coating a fabric containing a first treatment agent containing a cationic substance with an ink composition; and coating the fabric with a second treatment agent containing resin particles and a lubricant. In the examples, an ink composition containing a pigment and a urethane resin, and a second treatment agent containing an acrylic resin and a silicone-based wax are disclosed. Patent Document 2 discloses an inkjet printing method comprising the steps of: applying a treatment solution containing a polyvalent metal salt to a fabric to obtain a treated fabric; applying a white ink composition to the treated fabric using an inkjet method to obtain a printed fabric; and drying the printed fabric. It is also disclosed that the white ink composition includes a resin having a silicone group as the first fixing resin, and a urethane resin, polyester resin, or acrylic resin as the second fixing resin. Patent Document 3 discloses an ink set comprising a color ink containing a colorant and an overcoat liquid containing a polyester resin and a lubricant, but without a colorant. The embodiment discloses inkjet printing using an ink containing a urethane resin or polyester resin, and an overcoat liquid containing a urethane resin or polyester resin and polyethylene wax. Japanese Patent Publication No. 2021-85128Japanese Patent Publication No. 2021-98796Japanese Patent Publication No. 2013-221141 As a result of diligent research into the above-mentioned problems, the inventors have found that by 1) applying the post-treatment solution in a wet-on-wet manner, and 2) appropriately increasing the affinity between the resin particles in the ink and the lubricant in the post-treatment solution, it is possible to maintain friction fastness over a long period of time without impairing the texture of the fabric. Regarding 1), applying the post-treatment solution wet-on-wet means applying the post-treatment solution before most of the previously applied ink droplets have completely dried. Specifically, this means that per unit area of the recording area, the ratio of (amount of ink remaining when the post-treatment solution is applied) / (amount of ink applied) is 0.40 to 1.0, preferably 0.50 to 1.0, more preferably 0.70 to 1.0, and even more preferably 0.80 to 1.0. Here, "amount of ink remaining when the post-treatment solution is applied" refers to the amount of liquid ink that remains without drying. This remaining amount can be adjusted by appropriately adjusting various conditions, such as the time between applying the ink and applying the post-treatment solution. Applying the post-treatment solution wet-on-wet reduces the formation of an interface between the ink and the post-treatment solution, allowing for a continuous change in composition in the thickness direction. This suppresses the peeling of the post-treatment layer due to friction. As a result, the lubricating effect of the lubricant is sustained, maintaining friction fastness over a long period. Furthermore, applying the post-treatment solution wet-on-wet allows the ink and the post-treatment solution to mix, relatively increasing the amount of liquid components such as water and solvents that easily penetrate the fabric. This reduces the penetration of resin particles between fibers, making them more likely to remain on the fiber surface. This prevents the fabric from becoming stiff and helps maintain a good texture. Regarding (2), when the dissolution parameter of the resin constituting the resin particles contained in the ink is SP1 (cal/ cm³ ) 1/2 , and the dissolution parameter of the lubricant contained in the post-treatment solution is SP2 (cal/ cm³ ) 1/2 , the resin particles and lubricant are selected such that 0.3 ≤ SP1 - SP2