JP7593040B2 - Ink-jet ink for textile printing, ink-jet ink set for textile printing, and image forming method - Google Patents

Description

The present invention relates to an inkjet ink for textile printing, an inkjet ink set for textile printing, and an image forming method.

The inkjet printing process involves a process in which ink is ejected from an inkjet head and made to land on the fabric, a process in which the fabric on which the ink has landed is heated or otherwise treated to fix the dye contained in the ink to the fibers of the fabric, and a process in which the fabric to which steam has been applied is washed to remove any dye that has not been fixed.

Inkjet printing may require various characteristics depending on the use of the printed fabric. For example, decorative fabrics may require printing that produces sufficient color on both sides so that the fabric looks good even when the back side is visible. For this reason, printing methods that can dye the back side sufficiently to reduce the density difference between the front and back sides are being investigated.

As such a method, Patent Document 1 describes a method in which ink-coated fabric is heated and pressed at 100°C or higher while only water vapor is applied to the fabric using newspaper or a gas-permeable sheet that is impermeable to liquid components but allows water vapor to pass through.

Patent document 2 describes a method in which a penetrating liquid that adjusts the penetration of the ink composition into the fabric is applied to the fabric together with the ink composition, and the ink composition and the penetrating liquid are heated simultaneously to allow the dye in the ink to fully penetrate to the back side.

JP 2003-293272 A JP 2016-138343 A

The techniques described in Patent Documents 1 and 2 both aim to dye the back side of the fabric thoroughly by increasing the permeability of the ink into the fabric. However, according to the knowledge of the inventors, there are cases where dyeing the back side of the fabric thoroughly results in a greater decrease in color density on the front side than would be expected from the increase in color density on the back side.

Furthermore, according to the inventors' findings, when attempting to dye the back side of the fabric thoroughly using these methods, the ink was prone to bleeding.

Furthermore, all of these methods require major changes to the configuration of the image forming device or the use of a penetrant liquid other than ink, making them difficult to put into practical use. In contrast, if the composition of the ink is changed so that the back side of the fabric is dyed sufficiently, it can be easily applied to conventional image forming devices and is highly practical.

In view of the above circumstances, the present invention aims to provide an inkjet ink for textile printing that can sufficiently color both the front and back sides of a fabric, reducing the density difference between the front and back sides of the fabric while suppressing a decrease in color density on the front side and the occurrence of bleeding, an inkjet ink set for textile printing that includes the inkjet ink for textile printing, and an image forming method that uses the inkjet ink for textile printing.

One embodiment of the present invention for solving the above problems relates to an ink-jet ink for textile printing, which contains a water-soluble dye, two or more types of organic solvents, and water, and satisfies all of the requirements (1) to (4).
(1) The ratio of the organic solvent having a boiling point of 240° C. or higher to the total mass of the inkjet ink for textile printing is 3% by mass or more and 10% by mass or less. (2) The total content of the two or more organic solvents on a mass basis is greater than the content of water. (3) The surface tension of the ink for textile printing at 25° C. is 38 mN/m or more and 55 mN/m or less. (4) The viscosity of the ink for textile printing at 25° C. is 10 mPa·s or more and 14 mPa·s or less.

Another embodiment of the present invention for solving the above problem relates to an inkjet ink set for textile printing that includes two or more of the above inkjet inks for textile printing that contain different types of water-soluble dyes.

Another embodiment of the present invention for solving the above problem relates to an image forming method including a step of ejecting the above inkjet ink for textile printing from an inkjet head and causing the ink to land on a fabric.

The present invention provides an inkjet ink for textile printing that can sufficiently color both the front and back sides of a fabric, reducing the density difference between the front and back sides of the fabric while suppressing a decrease in color density on the front side and the occurrence of bleeding, an inkjet ink set for textile printing that includes the inkjet ink for textile printing, and an image forming method that uses the inkjet ink for textile printing.

FIG. 1 is a partial schematic diagram showing an example of the configuration of an ink-jet textile printing apparatus.

1. Inkjet ink for textile printing One embodiment of the present invention relates to an inkjet ink for textile printing that contains a water-soluble dye, two or more types of organic solvents, and water, and satisfies all of the following (1) to (4).
(1) The ratio of the organic solvent having a boiling point of 240° C. or higher to the total mass of the inkjet ink for textile printing is 3% by mass or more and 10% by mass or less. (2) The total content of the two or more organic solvents by mass is greater than the water content. (3) The surface tension of the inkjet ink for textile printing at 25° C. is 38 mN/m or more and 55 mN/m or less. (4) The viscosity of the inkjet ink for textile printing at 25° C. is 10 mPa·s or more and 14 mPa·s or less.

According to the new findings of the inventors, when attempting to increase the permeability of the ink to the back side of the fabric, the ink that has permeated the inside of the fabric subsequently penetrates into areas that cannot be seen from the outside of the fabric, such as the fine interfaces between threads and the fine spaces inside the threads. Therefore, although it is possible to increase the color density of the back side of the fabric by making the ink reach the back side of the fabric sufficiently, it is thought that the loss of color density on the surface due to the ink penetrating into the above-mentioned invisible areas will also be large, and the color density on the front side will decrease more than expected. In addition, when attempting to increase the permeability of the ink to the back side of the fabric, the ink will spread toward the surface of the fabric over time after application to the fabric, and the ink that has permeated into the inside of the threads will diffuse inside the threads along the fiber orientation direction, making it more likely for the ink to bleed.

If you want to increase the ink's ability to penetrate the back side of the fabric by changing the ink composition, you can change the ink composition so that the surface tension of the ink is lower. However, even when the surface tension of the ink is lowered, loss of color density on the surface due to ink penetrating into the invisible areas mentioned above, and bleeding due to ink spreading toward the surface of the fabric or ink penetrating into the inside of the threads and diffusing inside the threads are likely to occur.

In this embodiment, the amount of organic solvent is increased to increase the diffusion speed of the ink into the interior of the fabric, making it easier for the ink to reach the back side of the fabric. In other words, an ink containing a large amount of organic solvent contains relatively less water and the organic solvent travels a shorter distance, so the organic solvent diffuses through the ink in a short time after being applied to the fabric. Organic solvents have a lower surface tension than water and function as surfactants, so that the surface tension after being applied to the fabric decreases in an extremely short time. As a result, the surface tension of the ink of this embodiment immediately after being applied to the fabric is lower than that of conventional inks. Therefore, the ink of this embodiment is likely to penetrate into the interior of the fabric immediately after being applied to the fabric, which is thought to allow it to fully reach the back side of the fabric and to fully color the back side of the fabric.

On the other hand, in this embodiment, the surface tension of the ink after the above-mentioned decrease is kept in a relatively high range. This is believed to suppress the ink that has penetrated into the interior of the fabric from penetrating into the invisible areas, and to suppress loss of color density on the surface. This is also believed to suppress bleeding of the ink caused by the ink spreading in the direction of the surface of the fabric after being applied to the fabric. Furthermore, this is believed to suppress bleeding of the ink caused by the ink that has penetrated into the interior of the thread diffusing inside the thread along the fiber orientation direction.

The ink of this embodiment is based on the above concept and satisfies all of the above (1) to (4), thereby minimizing the density difference between the front and back of the fabric while suppressing the decrease in color density on the front side and the occurrence of bleeding. Each of the requirements (1) to (4) will be explained in detail below.

In the ink according to the present embodiment, (1) the ratio of an organic solvent having a boiling point of 240° C. or higher (hereinafter, simply referred to as a "high boiling point solvent") to the total mass of the inkjet ink for textile printing is 3% by mass or more and 10% by mass or less. The high boiling point solvent increases the ejection property of the ink and accelerates the rate at which the surface tension of the ink decreases, making it easier to fully color the back side of the fabric. In order to fully obtain these effects, the above ratio of the high boiling point solvent is set to 3% by mass or more. On the other hand, if the ratio of the high boiling point solvent is excessive, the drying property of the ink decreases, or the organic solvent remaining on the fabric after drying moves the dye, which tends to cause strike-through (excessive increase in color density on the back side), a decrease in color density on the front side, bleeding, etc. In order to suppress these, the above ratio of the high boiling point solvent is set to 10% by mass or less. From the viewpoint of balancing these, the ratio of the high boiling point solvent is preferably 3% by mass or more and 8% by mass or less, and more preferably 3% by mass or more and 5% by mass or less.

In addition, the ink according to this embodiment has (2) a total content of organic solvents based on mass that is greater than the content of water. As explained above, by increasing the relative amount of organic solvent to water, the surface tension of the ink immediately after application to the fabric is reduced, allowing the ink to fully penetrate to the back side of the fabric and to fully color the back side of the fabric. In addition, by controlling the surface tension to a certain range at a high speed, penetration into relatively large voids along the yarn surface is prioritized, and penetration into fine interfaces between yarns and fine spaces inside the yarn is suppressed, so that it is possible to suppress the loss of color density on the surface due to the ink penetrating into the invisible parts, and the occurrence of bleeding due to the ink spreading in the direction of the surface of the fabric over time after application to the fabric, or the ink penetrating into the inside of the yarn and diffusing inside the yarn. Water is an essential component from the viewpoint of making it easier to control the surface tension of the ink so as not to lower it too much, and the ratio of the total content of organic solvents to the content of water is preferably (organic solvent:water) = (95:5) to (51:49), and more preferably (70:30) to (55:45).

In addition, the ink according to this embodiment has (3) a surface tension at 25°C of 38 mN/m or more and 55 mN/m or less. If the surface tension is 38 mN/m or more, the ink is prevented from penetrating into the invisible areas and from spreading toward the surface of the fabric after application to the fabric, thereby preventing loss of color density on the surface and the occurrence of bleeding. If the surface tension is 55 mN/m or less, the ink is prevented from penetrating insufficiently due to the surface tension being too high immediately after application to the fabric, allowing the back side of the fabric to be sufficiently colored. From the viewpoint of achieving a balance between these factors, the surface tension of the ink is preferably 40 mN/m or more and 52 mN/m or less, and more preferably 43 mN/m or more and 50 mN/m or less.

The ink according to this embodiment has (4) a viscosity at 25°C of 10 mPa·s or more and 14 mPa·s or less. If the viscosity is 10 mPa·s or more, the occurrence of bleeding due to the ink spreading toward the surface of the fabric after application to the fabric or the ink penetrating into the inside of the thread and diffusing inside the thread can be suppressed. If the viscosity is 15 mPa·s or less, the ink can be sufficiently penetrating into the inside of the fabric, allowing sufficient color development to the back side of the fabric, and insufficient spreading of dots can be suppressed. From the viewpoint of achieving a balance between these, the viscosity of the ink is preferably 10 mPa·s or more and 13 mPa·s or less, and more preferably 11 mPa·s or more and 13 mPa·s or less.

The ink used in this embodiment is described in more detail below.

1-1. Water-soluble dyes Water-soluble dyes are dyes that are soluble in water. For example, the water-soluble dyes may be dyes that have a solubility in water of 1 g/L or more at 25° C. Examples of water-soluble dyes include reactive dyes, acid dyes, basic dyes, and direct dyes. Of these, reactive dyes, acid dyes, and direct dyes are preferred, and reactive dyes are more preferred.

Examples of yellow reactive dyes include C.I. Reactive Yellow 2, C.I. Reactive Yellow 3, C.I. Reactive Yellow 7, C.I. Reactive Yellow 15, C.I. Reactive Yellow 17, C.I. Reactive Yellow 18, C.I. Reactive Yellow 22, C.I. Reactive Yellow 23, C.I. Reactive Yellow 24, C.I. Reactive Yellow 25, C. I. Reactive Yellow 27, C. I. Reactive Yellow 37, C. I. Reactive Yellow 39, C. I. Reactive Yellow 42, C. I. Reactive Yellow 57, C. I. Reactive Yellow 69, C. I. Reactive Yellow 76, C. I. Reactive Yellow 81, C. I. Reactive Yellow 84, C. I. Reactive Yellow 85, C. I. Reactive Yellow 86, C. I. Reactive Yellow 87, C. I. Reactive Yellow 92, C. I. Reactive Yellow 95, C. I. Reactive Yellow 102, C. I. Reactive Yellow 105, C. I. Reactive Yellow 111, C. I. Reactive Yellow 125, C. I. Reactive Yellow 135, C. I. Reactive Yellow 136, C. I. Reactive Yellow 137, C. I. Reactive Yellow 142, C. I. Reactive Yellow 143, C. I. Reactive Yellow 145, C. I. Reactive Yellow 151, C. I. Reactive Yellow 160, C. I. Reactive Yellow 161, C. I. Reactive Yellow 165, C. I. These include C.I. Reactive Yellow 167, C.I. Reactive Yellow 168, C.I. Reactive Yellow 175, and C.I. Reactive Yellow 176.

Examples of orange reactive dyes include C.I. Reactive Orange 1, C.I. Reactive Orange 4, C.I. Reactive Orange 5, C.I. Reactive Orange 7, C.I. Reactive Orange 11, C.I. Reactive Orange 12, C.I. Reactive Orange 13, C.I. Reactive Orange 15, C.I. Reactive Orange 16, C.I. Reactive Orange 20, C. I. Reactive Orange 30, C. I. Reactive Orange 35, C. I. Reactive Orange 56, C. I. Reactive Orange 64, C. I. Reactive Orange 67, C. I. Reactive Orange 69, C. I. Reactive Orange 70, C. I. Reactive Orange 72, C. I. Reactive Orange 74, C. I. These include C.I. Reactive Orange 82, C.I. Reactive Orange 84, C.I. Reactive Orange 86, C.I. Reactive Orange 87, C.I. Reactive Orange 91, C.I. Reactive Orange 92, C.I. Reactive Orange 93, C.I. Reactive Orange 95, and C.I. Reactive Orange 107.

Examples of red reactive dyes include C.I. Reactive Red 2, C.I. Reactive Red 3, C.I. Reactive Red 3:1, C.I. Reactive Red 5, C.I. Reactive Red 8, C.I. Reactive Red 11, C.I. Reactive Red 21, C.I. Reactive Red 22, C.I. Reactive Red 23, C.I. Reactive Red 24, C.I. Reactive Red 28, C. I. Reactive Red 29, C. I. Reactive Red 31, C. I. Reactive Red 33, C. I. Reactive Red 35, C. I. Reactive Red 43, C. I. Reactive Red 45, C. I. Reactive Red 49, C. I. Reactive Red 55, C. I. Reactive Red 56, C. I. Reactive Red 58, C. I. Reactive Red 65, C. I. Reactive Red 66, C. I. Reactive Red 78, C. I. Reactive Red 83, C. I. Reactive Red 84, C. I. Reactive Red 106, C. I. Reactive Red 111, C. I. Reactive Red 112, C. I. Reactive Red 113, C. I. Reactive Red 114, C. I. Reactive Red 116, C. I. Reactive Red 120, C. I. Reactive Red 123, C. I. Reactive Red 124, C. I. Reactive Red 128, C. I. Reactive Red 130, C. I. Reactive Red 136, C. I. Reactive Red 141, C. I. Reactive Red 147, C. I. Reactive Red 158, C. I. Reactive Red 159, C. I. Reactive Red 171, C. I. Reactive Red 174, C. I. Reactive Red 180, C. I. Reactive Red 183, C. I. Reactive Red 184, C. I. Reactive Red 187, C. I. Reactive Red 190, C. I. Reactive Red 193, C. I. Reactive Red 194, C. I. Reactive Red 195, C. I. These include C.I. Reactive Red 198, C.I. Reactive Red 218, C.I. Reactive Red 220, C.I. Reactive Red 222, C.I. Reactive Red 223, C.I. Reactive Red 226, C.I. Reactive Red 228, and C.I. Reactive Red 235.

Examples of violet reactive dyes include C.I. Reactive Violet 1, C.I. Reactive Violet 2, C.I. Reactive Violet 4, C.I. Reactive Violet 5, C.I. Reactive Violet 6, C.I. Reactive Violet 22, C.I. Reactive Violet 23, C.I. Reactive Violet 33, C.I. Reactive Violet 36, and C.I. Reactive Violet 38.

Examples of blue reactive dyes include C.I. Reactive Blue 2, C.I. Reactive Blue 3, C.I. Reactive Blue 4, C.I. Reactive Blue 7, C.I. Reactive Blue 13, C.I. Reactive Blue 14, C.I. Reactive Blue 15, C.I. Reactive Blue 19, C.I. Reactive Blue 21, C.I. Reactive Blue 25, C.I. Reactive Blue 27, C. I. Reactive Blue 28, C. I. Reactive Blue 29, C. I. Reactive Blue 38, C. I. Reactive Blue 39, C. I. Reactive Blue 41, C. I. Reactive Blue 49, C. I. Reactive Blue 50, C. I. Reactive Blue 52, C. I. Reactive Blue 63, C. I. Reactive Blue 69, C. I. Reactive Blue 71, C. I. Reactive Blue 72, C. I. Reactive Blue 77, C. I. Reactive Blue 79, C. I. Reactive Blue 89, C. I. Reactive Blue 104, C. I. Reactive Blue 109, C. I. Reactive Blue 112, C. I. Reactive Blue 113, C. I. Reactive Blue 114, C. I. Reactive Blue 116, C. I. Reactive Blue 119, C. I. Reactive Blue 120, C. I. Reactive Blue 122, C. I. Reactive Blue 137, C. I. Reactive Blue 140, C. I. Reactive Blue 143, C. I. Reactive Blue 147, C. I. Reactive Blue 160, C. I. Reactive Blue 161, C. I. Reactive Blue 162, C. I. Reactive Blue 163, C. I. Reactive Blue 168, C. I. Reactive Blue 171, C. I. Reactive Blue 176, C. I. Reactive Blue 182, C. I. Reactive Blue 184, C. I. Reactive Blue 191, C. I. Reactive Blue 194, C. I. Reactive Blue 195, C. I. Reactive Blue 198, C. I. Reactive Blue 203, C. I. Reactive Blue 204, C. I. Reactive Blue 207, C. I. Reactive Blue 209, C. I. Reactive Blue 211, C. I. Reactive Blue 214, C. I. Reactive Blue 220, C. I. Reactive Blue 221, C. I. These include C.I. Reactive Blue 222, C.I. Reactive Blue 231, C.I. Reactive Blue 235, and C.I. Reactive Blue 236.

Examples of green reactive dyes include C.I. Reactive Green 8, C.I. Reactive Green 12, C.I. Reactive Green 15, C.I. Reactive Green 19, and C.I. Reactive Green 21.

Examples of brown reactive dyes include C.I. Reactive Brown 2, C.I. Reactive Brown 7, C.I. Reactive Brown 9, C.I. Reactive Brown 10, C.I. Reactive Brown 11, C.I. Reactive Brown 17, C.I. Reactive Brown 18, C.I. Reactive Brown 19, C.I. Reactive Brown 21, C.I. Reactive Brown 23, C.I. These include C.I. Reactive Brown 31, C.I. Reactive Brown 37, C.I. Reactive Brown 43, and C.I. Reactive Brown 46.

Examples of black reactive dyes include C.I. Reactive Black 5, C.I. Reactive Black 8, C.I. Reactive Black 13, C.I. Reactive Black 14, C.I. Reactive Black 31, C.I. Reactive Black 34, and C.I. Reactive Black 39.

Examples of yellow acid dyes include C.I. I. Acid Yellow 1, C. I. Acid Yellow 3, C. I. Acid Yellow 11, C. I. Acid Yellow 17, C. I. Acid Yellow 18, C. I. Acid Yellow 19, C. I. Acid Yellow 23, C. I. Acid Yellow 25, C. I. Acid Yellow 36, C. I. Acid Yellow 38, C. I. Acid Yellow 40, C. I. Acid Yellow 42, C. I. Acid Yellow 44, C. I. Acid Yellow 49, C. I. Acid Yellow 59, C. I. Acid Yellow 61, C. I. Acid Yellow 65, C. I. Acid Yellow 67, C. I. Acid Yellow 72, C. I. Acid Yellow 73, C. I. Acid Yellow 79, C. I. Acid Yellow 99, C. I. Acid Yellow 104, C. I. Acid Yellow 110, C. I. Acid Yellow 114, C. I. Acid Yellow 116, C. I. Acid Yellow 118, C. I. Acid Yellow 121, C. I. Acid Yellow 127, C. I. Acid Yellow 129, C. I. Acid Yellow 135, C. I. Acid Yellow 137, C. I. Acid Yellow 141, C. I. Acid Yellow 143, C. I. Acid Yellow 151, C. I. Acid Yellow 155, C. I. Acid Yellow 158, C. I. Acid Yellow 159, C. I. Acid Yellow 169, C. I. Acid Yellow 176, C. I. Acid Yellow 184, C. I. Acid Yellow 193, C. I. Acid Yellow 200, C. I. Acid Yellow 204, C. I. Acid Yellow 207, C. I. Acid Yellow 215, C.I. Acid Yellow 219, C.I. Acid Yellow 220, C.I. Acid Yellow 230, C.I. Acid Yellow 232, C.I. Acid Yellow 235, C.I. Acid Yellow 241, C.I. Acid Yellow 242, and C.I. Acid Yellow 246.

Examples of orange acid dyes include C.I. Acid Orange 3, C.I. Acid Orange 7, C.I. Acid Orange 8, C.I. Acid Orange 10, C.I. Acid Orange 19, C.I. Acid Orange 22, 24, C.I. Acid Orange 51, C.I. Acid Orange 56, C.I. Acid Orange 67, C.I. Acid Orange 74, C.I. Acid Orange 80, C.I. Acid Orange 86, C. I. Acid Orange 87, C. I. Acid Orange 88, C. I. Acid Orange 89, C. I. Acid Orange 94, C. I. Acid Orange 95, C. I. Acid Orange 107, C. I. Acid Orange 108, C. I. Acid Orange 116, C. I. Acid Orange 122, C. I. Acid Orange 127, C. I. Acid Orange 140, C. I. These include C.I. Acid Orange 142, C.I. Acid Orange 144, C.I. Acid Orange 149, C.I. Acid Orange 152, C.I. Acid Orange 156, C.I. Acid Orange 162, C.I. Acid Orange 166, C.I. Acid Orange 168, and C.I. Acid Orange.

Examples of red acid dyes include C.I. Acid Red 88, C.I. Acid Red 97, C.I. Acid Red 106, C.I. Acid Red 111, C.I. Acid Red 114, C.I. Acid Red 118, C.I. Acid Red 119, C.I. Acid Red 127, C.I. Acid Red 131, C.I. Acid Red 138, C.I. Acid Red 143, C.I. Acid Red 145, C.I. Acid Red 151, C. I. Acid Red 183, C. I. Acid Red 195, C. I. Acid Red 198, C. I. Acid Red 211, C. I. Acid Red 215, C. I. Acid Red 217, C. I. Acid Red 225, C. I. Acid Red 226, C. I. Acid Red 249, C. I. Acid Red 251, C. I. Acid Red 254, C. I. Acid Red 256, C. I. Acid Red 257, C. I. Acid Red 260, C. I. Acid Red 261, C. I. Acid Red 265, C. I. Acid Red 266, C. I. Acid Red 274, C. I. Acid Red 276, C. I. Acid Red 277, C. I. Acid Red 289, C. I. Acid Red 296, C. I. Acid Red 299, C. I. Acid Red 315, C. I. Acid Red 318, C. I. Acid Red 336, C. I. Acid Red 337, C. I. Acid Red 357, C. I. Acid Red 359, C. I. Acid Red 361, C. I. Acid Red 362, C. I. Acid Red 364, C. I. Acid Red 366, C. I. Acid Red 399, C. I. Acid Red 407, C. I. Acid Red 415, and C. I. These include Acid Red 447.

Examples of violet acid dyes include C.I. Acid Violet 17, C.I. Acid Violet 19, C.I. Acid Violet 21, C.I. Acid Violet 42, C.I. Acid Violet 43, C.I. Acid Violet 47, C.I. Acid Violet 48, C.I. Acid Violet 49, C.I. Acid Violet 54, C.I. Acid Violet 66, C.I. Acid Violet 78, C.I. Acid Violet 90, C.I. Acid Violet 97, C.I. These include C.I. Acid Violet 102, C.I. Acid Violet 109, and C.I. Acid Violet 126.

Examples of blue acid dyes include C.I. Acid Blue 1, C.I. Acid Blue 7, C.I. Acid Blue 9, C.I. Acid Blue 15, C.I. Acid Blue 23, C.I. Acid Blue 25, C.I. Acid Blue 40, C.I. Acid Blue 62, C.I. Acid Blue 72, C.I. Acid Blue 74, C.I. Acid Blue 80, C.I. Acid Blue 83, C.I. Acid Blue 90, C. I. Acid Blue 92, C. I. Acid Blue 103, C. I. Acid Blue 104, C. I. Acid Blue 112, C. I. Acid Blue 113, C. I. Acid Blue 114, C. I. Acid Blue 120, C. I. Acid Blue 127, C. I. Acid Blue 128, C. I. Acid Blue 129, C. I. Acid Blue 138, C. I. Acid Blue 140, C. I. Acid Blue 142, C. I. Acid Blue 156, C. I. Acid Blue 158, C. I. Acid Blue 171, C. I. Acid Blue 182, C. I. Acid Blue 185, C. I. Acid Blue 193, C. I. Acid Blue 199, C. I. Acid Blue 201, C. I. Acid Blue 203, C. I. Acid Blue 204, C. I. Acid Blue 205, C. I. Acid Blue 207, C. I. Acid Blue 209, C. I. Acid Blue 220, C. I. Acid Blue 221, C. I. Acid Blue 224, C. I. Acid Blue 225, C. I. Acid Blue 229, C. I. Acid Blue 230, C. I. Acid Blue 239, C. I. Acid Blue 249, C. I. Acid Blue 258, C. I. Acid Blue 260, C. I. Acid Blue 264, C. I. Acid Blue 278, C. I. Acid Blue 279, C. I. Acid Blue 280, C. I. Acid Blue 284, C. I. Acid Blue 290, C. I. Acid Blue 296, C. I. Acid Blue 298, C. I. Acid Blue 300, C. I. Acid Blue 317, C. I. Acid Blue 324, C. I. These include C.I. Acid Blue 333, C.I. Acid Blue 335, C.I. Acid Blue 338, C.I. Acid Blue 342, and C.I. Acid Blue 350.

Examples of green acid dyes include C.I. Acid Green 9, C.I. Acid Green 12, C.I. Acid Green 16, C.I. Acid Green 19, C.I. Acid Green 20, C.I. Acid Green 25, C.I. Acid Green 27, C.I. Acid Green 28, C.I. Acid Green 40, C.I. Acid Green 43, C.I. Acid Green 56, C.I. Acid Green 73, C.I. Acid Green 81, C. Examples include C.I. Acid Green 84, C.I. Acid Green 104, C.I. Acid Green 108, and C.I. Acid Green 109.

Examples of brown acid dyes include C.I. Acid Brown 2, C.I. Acid Brown 4, C.I. Acid Brown 13, C.I. Acid Brown 14, C.I. Acid Brown 19, C.I. Acid Brown 28, C.I. Acid Brown 44, C.I. Acid Brown 123, C.I. Acid Brown 224, C.I. Acid Brown 226, C.I. Acid Brown 227, C.I. Acid Brown 248, C.I. Acid Brown 282, C.I. Acid Brown 283, C.I. Acid Brown 289, C.I. Acid Brown 294, C.I. Acid Brown 297, C.I. Acid Brown 298, C.I. Acid Brown 301, C.I. Acid Brown 355, C.I. Acid Brown 357, and C.I. Acid Brown 413.

Examples of black acid dyes include C.I. Acid Black 1, C.I. Acid Black 2, C.I. Acid Black 3, C.I. Acid Black 24, C.I. Acid Black 26, C.I. Acid Black 31, C.I. Acid Black 50, C.I. Acid Black 52, C.I. Acid Black 52:1, C.I. Acid Black 58, C.I. Acid Black 60, C.I. Acid Black 63, C. I. Acid Black 107, C. I. Acid Black 109, C. I. Acid Black 112, C. I. Acid Black 119, C. I. Acid Black 132, C. I. Acid Black 140, C. I. Acid Black 155, C. I. Acid Black 172, C. I. Acid Black 187, C. I. Acid Black 188, C. I. These include C.I. Acid Black 194, C.I. Acid Black 207, and C.I. Acid Black 222.

Examples of yellow direct dyes include C.I. Direct Yellow 8, C.I. Direct Yellow 9, C.I. Direct Yellow 10, C.I. Direct Yellow 11, C.I. Direct Yellow 12, C.I. Direct Yellow 22, C.I. Direct Yellow 27, C.I. Direct Yellow 28, C.I. Direct Yellow 39, C.I. Direct Yellow 44, C.I. Direct Yellow 50, C.I. Direct Yellow 58, C. I. Direct Yellow 79, C. I. Direct Yellow 86, C. I. Direct Yellow 87, C. I. Direct Yellow 98, C. I. Direct Yellow 105, C. I. Direct Yellow 106, C. I. Direct Yellow 130, C. I. Direct Yellow 132, C. I. Direct Yellow 137, C. I. Direct Yellow 142, C. I. These include C.I. Direct Yellow 147, and C.I. Direct Yellow 153.

Examples of orange direct dyes include C.I. Direct Orange 6, C.I. Direct Orange 26, C.I. Direct Orange 27, C.I. Direct Orange 34, C.I. Direct Orange 39, C.I. Direct Orange 40, C.I. Direct Orange 46, C.I. Direct Orange 102, C.I. Direct Orange 105, C.I. Direct Orange 107, and C.I. Includes Direct Orange 118 and more.

Examples of red direct dyes include C.I. Direct Red 2, C.I. Direct Red 4, C.I. Direct Red 9, C.I. Direct Red 23, C.I. Direct Red 24, C.I. Direct Red 31, C.I. Direct Red 54, C.I. Direct Red 62, C.I. Direct Red 69, C.I. Direct Red 79, C.I. Direct Red 80, C.I. Direct Red 81, C.I. Direct Red 83, C. I. Direct Red 84, C. I. Direct Red 89, C. I. Direct Red 95, C. I. Direct Red 212, C. I. Direct Red 224, C. I. Direct Red 225, C. I. Direct Red 226, C. I. Direct Red 227, C. I. Direct Red 239, C. I. Direct Red 242, C. I. Direct Red 243, and C. I. Direct Red 254 and others are included.

Examples of violet direct dyes include C.I. Direct Violet 9, C.I. Direct Violet 35, C.I. Direct Violet 51, C.I. Direct Violet 66, C.I. Direct Violet 94, and C.I. Direct Violet 95.

Examples of blue direct dyes include C.I. Direct Blue 1, C.I. Direct Blue 15, C.I. Direct Blue 71, C.I. Direct Blue 76, C.I. Direct Blue 77, C.I. Direct Blue 78, C.I. Direct Blue 80, C.I. Direct Blue 86, C.I. Direct Blue 87, C.I. Direct Blue 90, C.I. Direct Blue 98, C.I. Direct Blue 106, C. I. Direct Blue 108, C. I. Direct Blue 160, C. I. Direct Blue 168, C. I. Direct Blue 189, C. I. Direct Blue 192, C. I. Direct Blue 193, C. I. Direct Blue 199, C. I. Direct Blue 200, C. I. Direct Blue 201, C. I. Direct Blue 202, C. I. Direct Blue 203, C. I. Direct Blue 218, C. I. Direct Blue 225, C. I. Direct Blue 229, C. I. Direct Blue 237, C. I. Direct Blue 244, C. I. Direct Blue 248, C. I. Direct Blue 251, C. I. Direct Blue 270, C. I. Direct Blue 273, C. I. Direct Blue 274, C. I. These include C.I. Direct Blue 290, and C.I. Direct Blue 291.

Examples of green direct dyes include C.I. Direct Green 26, C.I. Direct Green 28, C.I. Direct Green 59, C.I. Direct Green 80, and C.I. Direct Green 85.

Examples of brown direct dyes include C.I. Direct Brown 44, C.I. Direct Brown 106, C.I. Direct Brown 115, C.I. Direct Brown 195, C.I. Direct Brown 209, C.I. Direct Brown 210, C.I. Direct Brown 222, and C.I. Direct Brown 223.

Examples of black direct dyes include C.I. Direct Black 17, C.I. Direct Black 19, C.I. Direct Black 22, C.I. Direct Black 32, C.I. Direct Black 51, C.I. Direct Black 62, C.I. Direct Black 108, C.I. Direct Black 112, C.I. Direct Black 113, C.I. Direct Black 117, C.I. Direct Black 118, C.I. Direct Black 132, C.I. Direct Black 146, C.I. Direct Black 154, C.I. Direct Black 159, and C.I. Direct Black 169.

The content of these water-soluble dyes is preferably 1% by mass or more and 35% by mass or less based on the total mass of the ink. If it is 1% by mass or more, the color density of the image is easily increased, and if it is 35% by mass or less, the ejection stability of the ink is less likely to be impaired. It is more preferable that the content is 3% by mass or more and 30% by mass or less based on the total mass of the ink.

1-2. Organic Solvent The ink according to this embodiment contains two or more kinds of organic solvents. The organic solvents are preferably water-soluble organic solvents.

Examples of water-soluble organic solvents include monohydric alcohols including methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol and t-butanol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, glycols including 1,6-hexanediol, 1,5-pentanediol, 1,4-butanediol, 1,3-butanediol, thiodiglycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol and 1,2-heptanediol, other polyhydric alcohols including glycerin and 1,2,6-hexanetriol, ethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, ethyl ... amines including ethyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine and tetramethylpropylenediamine; amides including formamide, N,N-dimethylformamide and N,N-dimethylacetamide; heterocyclic compounds including 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone and 1,3-dimethyl-2-imidazolidinone; sulfoxides including dimethylsulfoxide; and glycol ethers including alkyl ethers of diethylene glycol, alkyl ethers of triethylene glycol and alkyl ethers of dipropylene glycol.

The ink of this embodiment contains, as the two or more types of organic solvents, an organic solvent with a boiling point of 240°C or higher (high boiling point solvent) and an organic solvent with a boiling point of less than 240°C.

High boiling point solvents improve the ejection properties of the ink and accelerate the rate at which the surface tension of the ink decreases, making it easier for the ink to fully color the back side of the fabric. Examples of high boiling point solvents include glycerin, diethylene glycol, triethylene glycol, tripropylene glycol, and diglycerin.

As described above, the ratio of the high boiling point solvent to the total mass of the inkjet ink for textile printing is 3% by mass or more and 10% by mass or less (requirement (1)). When the ratio is 3% by mass or more, the ink ejection property is improved and the color can be sufficiently developed even on the back side of the floating thin film. When the ratio is 10% by mass or less, the ink dries well and the organic solvent is unlikely to remain on the fabric after drying, so that strike-through, a decrease in the color density on the surface, bleeding, etc. are unlikely to occur. From the viewpoint of achieving a balance between these, the ratio of the high boiling point solvent is preferably 3% by mass or more and 8% by mass or less, and more preferably 3% by mass or more and 5% by mass or less.

The total content of the two or more organic solvents by mass is greater than the water content (requirement (2)). By making the organic solvent content greater than the water content, the surface tension of the ink immediately after application to the fabric can be reduced, allowing the ink to fully color all the way to the back side of the fabric. In addition, it is possible to suppress the loss of color density on the surface caused by the ink penetrating into unseen areas as described above, and the occurrence of bleeding caused by the ink spreading toward the surface of the fabric after application to the fabric or the ink penetrating into the interior of the threads and diffusing inside the threads.

Specifically, the total content of the two or more organic solvents can be 35% by mass or more and 60% by mass or less with respect to the total mass of the ink. By making the content of the organic solvent 35% by mass or more with respect to the total mass of the ink, the above-mentioned action of improving the color development on the back side of the fabric and suppressing the loss of color development density and the occurrence of bleeding can be fully achieved. In addition, by making the content of the organic solvent 60% by mass or less with respect to the total mass of the ink, the ink dries more quickly and the organic solvent is less likely to remain on the fabric after drying, so that strike-through, a decrease in the color development density on the surface, the occurrence of bleeding, and the like are less likely to occur. From the viewpoint of achieving a balance between these, the total content of the two or more organic solvents is preferably 38% by mass or more and 58% by mass or less with respect to the total mass of the ink, and more preferably 43% by mass or more and 53% by mass or less.

The water content is preferably 25% by mass or more and 55% by mass or less, more preferably 30% by mass or more and 50% by mass or less, and even more preferably 35% by mass or more and 45% by mass or less, based on the total mass of the ink.

In addition, among the two or more organic solvents, the organic solvent with the largest content by mass is preferably an organic solvent having a surface tension of 41 mN/m or more and 50 mN/m or less at 25°C (hereinafter, simply referred to as a "high surface tension solvent"). If the amount of such an organic solvent with a high surface tension is large, the surface tension of the ink after application to the fabric and the surface tension decrease can be further increased, and the loss of color density on the surface due to the ink penetrating into the invisible parts described above and the occurrence of bleeding due to the ink spreading toward the surface of the fabric after application to the fabric or the ink penetrating into the inside of the thread and diffusing inside the thread can be more effectively suppressed. This also makes it possible to further improve the drying property of the ink.

Examples of the high surface tension solvent include ethylene glycol, diethylene glycol, 1,6-hexanediol, 1,3-propanediol, 1,5-pentanediol, etc. Among these, glycols such as ethylene glycol, diethylene glycol, and 1,3-propanediol are preferred from the viewpoint of moisturizing the head nozzle surface and dye solubility.

The water content is preferably 3% by mass or more and less than 48% by mass, more preferably 5% by mass or more and less than 45% by mass, and even more preferably 10% by mass or more and less than 45% by mass.

1-3. Other Additives The ink may optionally contain a surfactant, a preservative, an antifungal agent, and the like.

Examples of the above surfactants include anionic surfactants including dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts, nonionic surfactants including polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers, cationic surfactants including alkylamine salts and quaternary ammonium salts, and silicone-based and fluorine-based surfactants.

Among these, anionic surfactants are preferred from the viewpoint of allowing the fluorescent acid dye to penetrate more easily into the nylon fiber structure and reducing the occurrence of uneven density due to poor fixation of the fluorescent acid dye. Examples of preferred anionic surfactants include sodium di-2-ethylhexyl sulfosuccinate, sodium polyoxyethylene dodecyl ether sulfate, and sodium polyoxyethylene lauryl ether sulfate.

Examples of the above preservatives or antifungal agents include aromatic halogen compounds, methylene dithiocyanate, halogen-containing nitrogen-sulfur compounds, and 1,2-benzisothiazolin-3-one (e.g., Proxel GXL (manufactured by Arch Chemical Company, Proxel is a registered trademark of the company)).

1-4. Physical properties, etc. The ink has a surface tension (static surface tension) of 38 mN/m or more and 55 mN/m or less at 25°C (requirement (3)). If the surface tension is 38 mN/m or more, it is possible to suppress the loss of color density on the surface due to the ink penetrating into the invisible area described above, and the occurrence of bleeding due to the ink spreading toward the surface direction of the fabric after application to the fabric or the ink penetrating into the inside of the thread and diffusing inside the thread after application to the fabric. If the surface tension is 55 mN/m or less, it is possible to suppress insufficient ink penetration due to the surface tension being too high immediately after application to the fabric, and to sufficiently color the back side of the fabric. From the viewpoint of balancing these, the surface tension of the ink is preferably 40 mN/m or more and 52 mN/m or less, and more preferably 43 mN/m or more and 50 mN/m or less. The surface tension of the ink can be a value measured by the Du Noy method, and can be measured, for example, by using CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.

The above surface tension of the ink can be adjusted by the presence or absence of a surfactant and its amount, the combination of organic solvents, etc.

The ink also has a viscosity at 25°C of 10 mPa·s or more and 14 mPa·s or less (requirement (4)). By increasing the viscosity to 10 mPa·s or more, it is possible to suppress the occurrence of bleeding caused by the ink spreading toward the surface of the fabric after application to the fabric or the ink penetrating into the inside of the thread and diffusing inside the thread. If the viscosity is 14 mPa·s or less, the ink can be sufficiently penetrated into the inside of the fabric to sufficiently color the back side of the fabric, and the occurrence of bleeding caused by the ink that has not penetrated into the inside of the fabric diffusing on the surface of the fabric can be suppressed. From the viewpoint of balancing these, the viscosity of the ink is preferably 10 mPa·s or more and 13 mPa·s or less, and more preferably 11 mPa·s or more and 13 mPa·s or less. The ink viscosity can be measured using an E-type viscometer at 25°C and 20 rpm, for example, a V-25 manufactured by Toki Sangyo Co., Ltd.

1-5. Manufacturing Method The ink can be prepared, for example, by mixing water, the above-mentioned two or more organic solvents, a water-soluble dye, and other optional additives by a known method.

2. Ink Sets Another embodiment of the present invention relates to ink sets that include the inks described above.

The ink set includes two or more inks that, when applied to a fabric, exhibit different color tones. Specifically, the ink set includes two or more inks for textile printing that contain different types of water-soluble dyes. At least one of the two or more inks may be the ink described above, but it is preferable that two or more inks are the inks described above. Note that different types of water-soluble dyes may mean that the inks contain different water-soluble dyes, or that the inks contain the same type of dye but in different amounts.

The bleeding caused by the ink penetrating into the inside of the thread and diffusing inside the thread is particularly likely to occur when multiple colors are applied to the fabric in layers to produce a mixed color. However, if the mixed color is produced using a multiple-color ink set that includes the inks described above, the ink is less likely to penetrate into the inside of the thread, and the bleeding is also suppressed.

The ink set can be, for example, a set of inks of multiple colors including yellow, magenta, cyan, and black. The ink set can also include inks of other special colors.

3. Image Forming Method and Image Forming Apparatus 3-1. Image Forming Method Another embodiment of the present invention relates to an image forming method using the ink or the ink set described above. The image forming method includes a step of ejecting droplets of the ink from a recording head to form an image on a fabric, and a step of heating the fabric on which the image has been formed to fix the image.

Specifically, the image forming method according to this embodiment includes (1) a step of applying a pretreatment agent to a fabric (pretreatment step), (2) a step of ejecting ink droplets onto the fabric to which the pretreatment agent has been applied to form an image (ink application step), and (3) a step of fixing the dye that has landed on the fabric to the fibers (coloring step), and may further include, as necessary, (4) a step of drying the fabric after the ink application (pre-drying step), (5) a step of removing the dye and pretreatment agent that have not been able to be dyed into the fabric (washing step), and (6) a step of drying the washed fabric (drying step).

(Pretreatment process)
The pretreatment step is a step of applying a pretreatment agent to a fabric. Examples of the method of applying the pretreatment agent to a fabric include a pad method, a coating method, a spray method, an inkjet method, etc. The pretreatment agent can be applied to the fabric by these methods.

From the viewpoint of obtaining a uniform image, it is preferable to wash away natural impurities (oils, waxes, pectins, natural colorants, etc.) adhering to the fabric fibers, residues of chemicals used in the fabric manufacturing process (glues, etc.), or dirt adhering to the fabric before applying the pretreatment agent to the fabric. Cleaning agents for washing the fabric include alkaline agents such as sodium hydroxide or sodium carbonate, anionic or nonionic surfactants, enzymes, etc.

The pretreatment agent preferably contains a resin component, a hydrotropic agent, and an alkaline agent, and may further contain additives such as a reduction inhibitor, a preservative, and a chelating agent.

The resin component preferably contains a hydrophilic resin having a hydroxyl group. Examples of hydrophilic resins having a hydroxyl group include natural gums including guar and locust bean, starches, sodium alginate, seaweed such as funori, plant skins including pectic acid, cellulose derivatives including methylcellulose, ethylcellulose, hydroxyethylcellulose, and carboxymethylcellulose, processed starches including roasted starch, alpha starch, carboxymethyl starch, carboxyethyl starch, and hydroxyethyl starch, processed natural gums such as shiratsu gum and roasted bean gum, and synthetic glues including alginate derivatives, polyvinyl alcohol, and polyacrylic esters.

Examples of hydrotropic agents include urea, ethylene urea, dimethyl urea, thiourea, monomethyl thiourea, dimethyl thiourea, and other alkyl ureas. The addition of a hydrotropic agent improves image density.

Examples of alkaline agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, amines such as mono-, di-, and triethanolamine, alkali metal carbonates or bicarbonates such as sodium carbonate, potassium carbonate, and sodium bicarbonate (sodium hydrogen carbonate), organic acid metal salts such as calcium acetate and barium acetate, ammonia and ammonia compounds, and sodium trichloroacetate, which becomes an alkaline agent under steaming or dry heat. Among these, sodium carbonate and sodium hydrogen carbonate are preferred. The amount of the alkaline agent applied is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass, based on the total mass of the fabric. The presence of an appropriate amount of alkaline agent in the fabric allows the textile printing ink containing a reactive dye to be reliably dyed. For this reason, it is preferable to have the alkaline agent contained in the fabric beforehand.

The amount of pretreatment agent applied (squeezing rate) or the amount of resin component contained in the pretreatment agent is set appropriately depending on the type of fabric and its application.

The pretreatment agent may further contain a reduction inhibitor, a preservative, or a chelating agent as necessary. The reduction inhibitor may be sodium m-nitrobenzenesulfonate or the like. The preservative may be the same as or be one of the preservatives exemplified as the preservatives for the textile printing ink. The chelating agent may be ethylenediaminetetraacetate, nitrilotriacetate, hexametaphosphate, pyrophosphate, metaphosphate, or the like.

The pretreatment agent applied to the fabric can also be heated and dried using hot air, a hot plate, or a heat roller.

The fiber material constituting the fabric is not particularly limited as long as a hydrophilic resin having a hydroxyl group (as a pretreatment agent) is applied, but in terms of enhancing dyeability, it is preferable to include fibers that can be dyed with reactive dyes; that is, fibers that have hydroxyl groups. Examples of fibers that have hydroxyl groups include cellulose fibers such as cotton and protein fibers such as silk. The fabric may be any form of woven fabric, nonwoven fabric, knitted fabric, etc., made from these fibers. In addition, the fabric that can be used in the present invention may be composed only of fibers that can be dyed with reactive dyes, but it may also be a blended woven fabric or blended nonwoven fabric with rayon, polyurethane, polyester, acrylic, etc. In addition, the thickness of the fibers constituting the fabric is preferably within the range of 10 to 100 d.

(Ink application process)
The ink application process is a process in which ink droplets are ejected from an inkjet head toward the fabric to form an image before color development. While the fabric is moved relative to a head carriage carrying multiple inkjet heads, droplets of the ink set are ejected and land on the fabric. The surface temperature of the fabric when the ink droplets land is not particularly limited, but it is preferable to heat the fabric to a temperature in the range of 35 to 70° C. from the viewpoint of suppressing bleeding of the image before color development. When applying multiple colors of ink in layers, multiple inks included in the above-mentioned ink set are applied to the same location on the fabric.

The above-mentioned ink can penetrate sufficiently to the back side of the fabric, even when the ink ejection speed is high, and can cause sufficient color development to occur to the back side of the fabric. Therefore, in this embodiment, even if the frequency at which the ink is ejected from the inkjet head is 30 kHz or higher, it is possible to cause sufficient color development to occur to the back side of the fabric. The frequency at which the ink is ejected is preferably 10 kHz or higher and 50 kHz or lower, and more preferably 20 kHz or higher and 45 kHz or lower.

(Pre-drying process)
The preliminary drying step is a step of drying the fabric after the ink has been applied. Although not particularly limited, the preliminary drying is preferably performed by drying the fabric at 150° C. or less for 0.5 to 30 minutes. Examples of the drying method include an air convection method, a direct application to a heated roll method, and an irradiation method. Specifically, the ink is applied to the fabric, and the fabric is dried under the above-mentioned conditions and method before the fabric is wound up.

(Color development process)
The color development process is a process in which the fabric after the ink is applied (or after the pre-drying process if a pre-drying process is included) is heated to cause the reactive dye that has not yet been sufficiently absorbed into the fabric to be absorbed into the fabric, thereby causing the original hue of the ink to appear.

The color-developing temperature (heating temperature) depends on the color-developing method (heating method), but from the viewpoint of strengthening the dyeing of the reactive dye into the fabric, it is preferably from 95°C to less than 220°C, more preferably from 95°C to 190°C, and even more preferably from 100°C to 180°C.

The coloring method (heating method) may be a conventionally known method and is appropriately selected depending on the printing ink, fabric, etc. Examples of coloring methods include steaming with steam, baking or thermosol with dry heat, and HT steamer with superheated steam. Of these, the method of fixing the reactive dye in the ink with high-temperature steam (steaming method) and the dry heat method (baking method) are preferred.

In the steaming method using high-temperature steam, if the heating temperature is too low, there will be a lot of liquid water, and the reactive dyes contained in the dark and light colored inks will tend to hydrogen bond with the liquid water in addition to the fabric, and will tend to be washed away with the water, which may result in insufficient dyeing. Therefore, from the viewpoint of strengthening the dyeing of the reactive dye into the fabric, the heating temperature is preferably 95°C or higher, and more preferably 100°C or higher.

In the dry heat baking method, from the viewpoint of easily obtaining sufficient dyeing ability and easily suppressing decomposition of the dye, the heating temperature is preferably 150°C or higher and lower than 220°C, more preferably 150°C or higher and 190°C or lower, and even more preferably 150°C or higher and 180°C or lower.

(Washing process)
The washing step is a step of removing reactive dyes and pretreatment agents that have not been absorbed into the fabric after the color development step. Reactive dyes that have not been absorbed into the fabric can be removed using a conventionally known washing method, which is appropriately selected depending on the printing ink, fabric, etc.

(Drying process)
The drying step is a step of drying the washed fabric after the washing step. The drying method is not particularly limited, but may be a method of wringing the washed fabric, hanging it to dry, or drying it using a dryer (heat roll, iron, etc.).

3-2. Inkjet Textile Printing Apparatus Another embodiment of the present invention relates to an image forming apparatus (inkjet textile printing apparatus) for carrying out the above-mentioned image forming method.

Figure 1 is a partial schematic diagram showing an example of the configuration of an inkjet textile printing device. The inkjet textile printing device has a transport means 2 for transporting fabric P, a head carriage 5 carrying multiple inkjet heads (not shown) that eject ink droplets onto the fabric P, and a hot air applying means 6 for applying hot air to the fabric P.

The conveying means 2 includes an adhesive belt 21, a support roller 22, a conveying roller 23, and a nip roller 24. The adhesive belt 21 is held by the support roller 22 and the conveying roller 23, and rotates between the support roller 22 and the conveying roller 23. The nip roller 24 is disposed opposite the conveying roller 23 via the adhesive belt 21.

The hot air applying means 6 and the head carriage 5 are disposed above the fabric P. The hot air applying means 6 is provided with a fan 6A for blowing air onto the fabric and a heating element 6B capable of controlling temperature. Meanwhile, the head carriage 5 is provided with an inkjet head. There is no particular restriction on the type of inkjet head, and it may be either a thermal type or a piezoelectric type. The nozzle diameter of the inkjet head is preferably 10 to 100 μm, and more preferably 10 to 50 μm. If the nozzle diameter is 10 μm or more, nozzle clogging due to insoluble matter is unlikely to occur, and if it is 100 μm or less, the sharpness of the formed image is unlikely to decrease. In addition, the droplet size of the ejected ink is preferably 4 to 150 pl, and more preferably 5 to 80 pl. If the ink droplet size is 4 pl or more, the ejected ink droplets are unlikely to be affected by air currents near the head, and if it is 150 pl or less, the graininess of the formed image is unlikely to be noticeable.

When the transport roller 23 is driven, the fabric P placed on the upper surface of the adhesive belt 21 is transported to the lower surface of the nip roller 24. The fabric P is pressed by the adhesive belt 21 and the nip roller 24 and fixed to the adhesive belt 21. The fabric P fixed to the adhesive belt 21 is transported below the head carriage 5. Multiple inkjet heads mounted on the head carriage 5 eject ink droplets and cause them to land on certain areas (landing areas) of the fabric to which the pretreatment agent has been applied, forming an image. Next, temperature-controlled air or hot air is blown from the hot air application means 6 to dry the image formed on the fabric P.

The present invention will be described in more detail below with reference to examples, but the scope of the present invention should not be construed as being limited by these examples.

1. Preparation of ink [dye]
The following dyes were prepared:
RY95: C. I. Reactive Yellow 95

[Ink preparation]
The purified dye and the following materials were mixed in the mass ratios shown in Table 1, stirred to mix uniformly, and then filtered through a 1 μm mesh filter to obtain inks 1 to 4. Note that a pH additive was added to each ink to adjust the pH to 7.

(Water-soluble organic solvent)
EG: Ethylene glycol PG: Propylene glycol DEG: Diethylene glycol 1,3-PGO: 1,3-propanediol 1,3-BGO: 1,3-butanediol Gly: Glycerin

(Surfactant)
Surfactant 1: Olfin E1010 manufactured by Nissin Chemical Industry Co., Ltd. (nonionic surfactant (polyoxyethylene acetylene glycol ether), "Olfin" is a registered trademark of the company)

(others)
Antifungal agent: Arch Chemical Company, product name Proxel GXL
Ion-exchanged water

The surface tension of the formed ink was measured by the Du Nuit method using a CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.

The viscosity of the ink formed was measured at 25°C and 20 rpm using an E-type viscometer (TV-25, manufactured by Toki Sangyo Co., Ltd.).

Table 1 shows the composition of each ink prepared (content in mass %).

2. Preparation of Pretreatment Agent The following materials were stirred and mixed to prepare a pretreatment agent.
Sodium alginate (resin component): 5 parts by weight Urea (hydrotropic agent): 10 parts by weight Sodium bicarbonate (alkaline agent): 5 parts by weight Ion-exchanged water: 80 parts by weight

3. Image formation 3-1. Pretreatment step A 100% cotton fabric (with cotton broadsill, manufactured by Irosen Co., Ltd.) was prepared, and the above pretreatment agent was applied to the fabric at a squeezing rate of 80%, followed by drying.

Each of the inks A-1 to A-22 was set in a Nassenger V (manufactured by Konica Minolta, Inc.) The frequency at the time of ejection from the inkjet head was set to 35 kHz, and a solid image was formed using the inks.

3-3. Color Development Step The fabric on which the image was formed was subjected to a steam treatment for 8 minutes under conditions of a relative humidity of 100% and a temperature of 103° C. to fix the dye and develop the color.

4. Evaluation 4-1. Surface density, back surface density, and density ratio The surface density and back surface density of the obtained solid image were measured using a Minolta spectrophotometer CM-2022. The obtained surface density and back surface density, as well as their ratio (surface density/back surface density x 100 (%)), were calculated. The closer the color density ratio of the front and back surfaces is to 100%, the smaller the difference in color density between the front and back surfaces is. A front and back surface density ratio of greater than 95% and less than 105% was deemed to be acceptable.

4-2. Line drawing quality In the ink application process, cyan ink was applied in a straight thin line shape (width 1 pixel, 720 dpi condition) over the obtained solid image, and then colored to form a green thin line. The line drawing quality was evaluated according to the following criteria based on whether the line width of the formed thin line was enlarged and whether whisker-like bleeding was observed at the edge of the thin line. An evaluation result of 3 or more was deemed to be acceptable. The above cyan inks were prepared by changing the dye from RY95 to C.I. Reactive Blue 72 (RB72) for the corresponding inks A-1 to A-22.
4. No bleeding was observed at the edges, and a good thin line was formed. 3. No bleeding was observed at the edges, but there were some areas where the line width was wider. 2. Bleeding was observed at the edges. 1. Bleeding was observed at the edges, and a straight thin line was not formed.

4-3. Drying property After drying the print with a solid image at 80°C for 1 minute (after the preliminary drying process), the presence or absence of color transfer when the print was placed over a cloth was visually observed. Evaluation was then performed based on the following criteria. A print with an evaluation result of △ or higher was deemed to have passed.
◯: No color transfer was observed at all △: Slight color transfer was observed, but at a level that does not pose a problem in practical use ×: Significant color transfer was observed, at a level that poses a problem in practical use

4-4. Ejectability Ink was ejected from the inkjet head for a certain period of time under conditions of 25°C and 50% RH. After leaving it for 30 minutes, the ink was ejected again, and the ejectability at that time was observed with a drop watcher. The re-ejectability after leaving it for 30 minutes was evaluated based on the following criteria. The evaluation result of ○ was deemed to be acceptable.
〇: Re-ejection was possible without any problems. ×: An injection failure occurred, and maintenance (manual cleaning of the nozzle surface) was required.

The results are shown in Table 5.

As is clear from Table 5, when an image is formed using an ink that satisfies all of requirements (1) to (4), both the front and back sides of the fabric are sufficiently colored, reducing the density difference between the front and back sides of the fabric while suppressing a decrease in color density on the front side and the occurrence of bleeding.

In contrast, inks A-3 and A-19 (which do not meet requirement (1)), which contain more than 10% by mass of high-boiling-point solvent, had poor drying properties and the color on the front side was less than the color on the back side. This is thought to be because the ink was difficult to dry due to the large amount of organic solvent with a high boiling point, and the organic solvent that did not dry and remained (large amount on the front side) caused the dye to move.

Ink A-5, which contains less than 3% by mass of high-boiling-point solvent (not satisfying requirement (1)), had poor ink ejection properties and showed little color development on the back side. This is thought to be because the ink contained a small amount of organic solvent with a high boiling point, so the surface tension of the ink was less likely to decrease immediately after application to the fabric, making it difficult for the ink to reach the back side.

Ink A-6 and ink A-7, which contain less organic solvent than water (not meeting requirement (2)), showed less coloring on the back side. This is thought to be because the surface tension of the ink was not easily reduced immediately after application to the fabric, making it difficult for the ink to reach the back side.

In addition, inks A-8, A-21 and A-22, which have a surface tension of less than 38 mN/m at 25°C (not satisfying requirement (3)), showed less coloring on the front side than on the back side and also showed a lot of bleeding. This is thought to be because the ink penetrated into the minute interfaces between the threads and the minute spaces inside the threads, causing a loss of color density on the surface and bleeding due to the ink diffusing inside the threads.

In addition, ink A-13, which has a surface tension of more than 55 mN/m at 25°C (not satisfying requirement (3)), showed insufficient color development on the back side. This is thought to be because the surface tension of the ink immediately after application to the fabric was too high, preventing the ink from penetrating the fabric sufficiently.

In addition, ink A-14, which has a viscosity of less than 10 mPa·s at 25°C (not satisfying requirement (4)), showed a lot of bleeding. This is thought to be because the ink was prone to seep into the tiny spaces inside the thread and spread inside the thread, causing bleeding.

Ink A-17, which has a viscosity of more than 15 mPa·s at 25°C (not satisfying requirement (4)), showed insufficient color development on the back side and a lot of bleeding occurred. This is thought to be because the high viscosity of the ink meant that the ink could not penetrate the fabric sufficiently, and the ink that did not penetrate into the fabric spread over the surface of the fabric.

The ink of the present invention can sufficiently color both the front and back of a fabric, reducing the density difference between the front and back of the fabric while suppressing a decrease in color density on the front side and the occurrence of bleeding. Therefore, it is expected that this will contribute to the further spread of inkjet printing in fields that require sufficient appearance even when the back side is visible, such as decorative fabrics.

P: Fabric 2: Conveying means 21: Adhesive belt 22: Support roller 23: Conveying roller 24: Nip roller 5: Head carriage 6: Hot air applying means 6A: Fan 6B: Heating element

Claims (6)

An ink-jet ink for textile printing, comprising a water-soluble dye, two or more organic solvents, and water,
An ink-jet ink for textile printing that satisfies all of requirements (1) to (4).
(1) The ratio of the organic solvent having a boiling point of 240° C. or higher to the total mass of the inkjet ink for textile printing is 3% by mass or more and 10% by mass or less. (2) The total content of the two or more organic solvents on a mass basis is greater than the water content. (3) The surface tension of the inkjet ink for textile printing at 25° C. is 38 mN/m or more and 55 mN/m or less. (4) The viscosity of the inkjet ink for textile printing at 25° C. is 10 mPa·s or more and 14 mPa·s or less. The inkjet ink for textile printing according to claim 1, wherein the organic solvent having the largest content by mass of the two or more organic solvents is an organic solvent having a surface tension of 41 mN/m or more and 50 mN/m or less at 25°C. The inkjet ink for textile printing according to claim 1 or 2, wherein the organic solvent having the largest content by mass of the two or more organic solvents is glycol. a water-soluble dye used in the ink-jet printing ink set including two or more kinds of ink-jet printing inks, each of which is different from the other in kind;
An ink-jet ink set for textile printing, comprising the ink-jet ink for textile printing according to any one of claims 1 to 3. An image forming method comprising a step of ejecting the inkjet ink for textile printing according to any one of claims 1 to 3 from an inkjet head and causing the ink to land on a fabric. The image forming method according to claim 5, wherein the frequency of ejection from the inkjet head is 30 kHz or more.

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