JP2024050444A - Ink, ink set, image forming method, and image forming apparatus - Google Patents

Abstract

[Problem] To provide an ink that has excellent storage stability and ejection stability and is capable of forming images with excellent image fastness. [Solution] The ink contains a colorant, a first urethane resin, a second urethane resin, and water, and is characterized in that the glass transition point (Tg) of the first urethane resin is 0° C. or lower, the solid content of the first urethane resin is 5% by mass or more and 15% by mass or less with respect to the total amount of the ink, and the glass transition point (Tg) of the second urethane resin is 40° C. or higher, and the solid content of the second urethane resin is 0.5% by mass or more and 3% by mass or less with respect to the total amount of the ink. [Selected Figure] None

Description

The present invention relates to an ink, an ink set, an image forming method, and an image forming device.

Many techniques for dyeing (printing) fabrics (woven fabrics, knitted fabrics, nonwoven fabrics, etc.) have been proposed. Conventionally, screen printing, roller printing, etc. have been used as methods for printing fabrics, but from the viewpoints of high-mix low-volume productivity and instantaneous printing, it is advantageous to apply an inkjet recording method. In recent years, the inkjet recording method has rapidly spread because it can easily record color images and has low running costs.
Various techniques have been considered, such as so-called pigment printing, in which a pigment and a fixing resin are blended into an ink composition and used to print on fabric. In the case of pigment printing, it is important to physically fix the pigment to the fibers of the fabric, etc.

For example, when printing on a dark-colored recording medium, a technology is known in which a white base layer is formed by applying a white ink to a recording medium to which a pretreatment liquid has been applied, and color inks are applied onto the white base layer to improve the color development of the image, as well as a technology in which an acrylic resin or urethane resin with a glass transition point (Tg) of -45°C or higher and 0°C or lower is used in the ink to improve washing fastness (see, for example, Patent Document 1).

The present invention aims to provide an ink that has excellent storage stability and ejection stability and is capable of forming images with excellent image robustness.

The ink of the present invention, as a means for solving the above problem, is an ink containing a colorant, a first urethane resin, a second urethane resin, and water, characterized in that the glass transition point (Tg) of the first urethane resin is 0°C or lower, the solid content of the first urethane resin is 5% by mass or more and 15% by mass or less with respect to the total amount of the ink, the glass transition point (Tg) of the second urethane resin is 40°C or higher, and the solid content of the second urethane resin is 0.5% by mass or more and 3% by mass or less with respect to the total amount of the ink.

The present invention provides an ink that has excellent storage stability and ejection stability and is capable of forming images with excellent image robustness.

FIG. 1 is a schematic perspective view showing an example of an image forming apparatus of the present invention. FIG. 2 is a schematic perspective view showing an example of a container in the image forming apparatus of the present invention. FIG. 3 is a schematic diagram showing another example of the image forming apparatus of the present invention. FIG. 4 is a schematic diagram showing an example of a chart printed by the image forming apparatus of the present invention.

When a large amount of low Tg resin particles is contained in the ink, as in the invention described in the above-mentioned Patent Document 1, there is a problem that the filter permeability (ejection stability) and the storage stability of the ink deteriorate. Although the cause of this problem is not clear, it is speculated as follows.
It is believed that when high pressure is applied to the ink when the ink is delivered by a delivery device such as a tubing pump, the low Tg resin particles and pigment dispersions in the ink are sheared and destroyed, and the resulting aggregates cause clogging inside the filter.

The inventors therefore conducted extensive research and discovered that by adding a small amount of a high Tg urethane resin to an ink containing a low Tg resin, the dispersion stability of the pigment dispersion and resin particles in the ink can be improved, resulting in an ink with excellent ejection stability and storage stability. They also discovered that by adding a low Tg urethane resin to the ink, an image with excellent image fastness (friction fastness) can be obtained.

In the present invention, the mechanism by which the dispersion stability of the ink is improved has not been clarified, but is speculated as follows.
When a high Tg urethane resin is added to an ink containing a low Tg resin, it is believed that the high Tg urethane resin acts as a dispersant or spacer, suppressing the formation of aggregates derived from the low Tg resin, even when high pressure is applied to the ink.

Therefore, in the present invention, an ink containing a colorant, a first urethane resin, a second urethane resin, and water, in which the glass transition point (Tg) of the first urethane resin is 0°C or lower, the solid content of the first urethane resin is 5% by mass or more and 15% by mass or less with respect to the total amount of the ink, the glass transition point (Tg) of the second urethane resin is 40°C or higher, and the solid content of the second urethane resin is 0.5% by mass or more and 3% by mass or less with respect to the total amount of the ink, can be provided, which has excellent storage stability and ejection stability and is capable of forming images with excellent image fastness.

The ink of the present invention is described in detail below.

(Inks and ink sets)
The ink of the present invention contains a colorant, a first urethane resin, a second urethane resin, and water, and may contain an organic solvent, a surfactant, and other components (A) as necessary.
In this specification, the "first urethane resin" may be referred to as "(1) urethane resin" and the "second urethane resin" may be referred to as "(2) urethane resin." The "first urethane resin" and the "second urethane resin" may be collectively referred to as "urethane resin."
The ink is preferably a white ink or a color ink.

In this specification, the term "white ink" refers to a liquid composition that forms a white image by being applied to a recording medium, which will be described later. Note that, although details will be described later, when the ink set of the present invention contains a pretreatment liquid, the "white ink" may be a liquid composition that forms a white image by being applied to an area of the recording medium to which the pretreatment liquid has been applied.
By forming a white image on a recording medium, the white ink functions, for example, as a base layer for a color image formed by the color inks that is applied to the area where the white ink is applied, thereby improving the color development of the color image.
In this specification, "white" refers to a color commonly referred to as white or white in society, and includes colors that are slightly colored.

The Hunter whiteness of the white image formed on the recording medium with the white ink is not particularly limited and may be appropriately selected depending on the purpose, but is preferably at least 75, more preferably at least 80, and particularly preferably at least 85. When the Hunter whiteness of the white image is at least 75, the color development of the color image can be improved.
The method for measuring the Hunter whiteness is not particularly limited and may be appropriately selected depending on the purpose, and may be calculated by the following calculation formula (1) by measuring color values L, a, and b of a white image formed on a recording medium using a spectrodensitometer (e.g., X-rite eXact, manufactured by X-Rite Corporation). Note that L, a, and b are a color indication method established by the International Commission on Illumination (CIE), and are also written as "L ^* ", "a ^* ", and "b ^* ".
Hunter brightness=100−sqr[(100−L) ² +(a ² +b ² )] (Formula 1)

In this specification, the term "color ink" refers to a liquid composition that forms a color image by being applied to a recording medium. When the color ink and the white ink are used in combination, the liquid composition may be a liquid composition that forms a color image by being applied to an area of the recording medium to which the white ink has been applied.
In this specification, the term "color" refers to colors not included in the above-mentioned "white," and includes, for example, black, cyan, magenta, and yellow.

The ink set of the present invention comprises the white ink and the color inks, and may contain a pretreatment liquid and other components as necessary.
The ink set may include one type of the white ink or two or more types thereof.The ink set may include one type of the color ink or two or more types thereof.

In this specification, the term "ink set" refers to a set in which the white ink and the color inks exist independently. For example, the ink set is not limited to a set in which the white ink storage means for storing the white ink and the color ink storage means for storing the color inks are manufactured, sold, etc., in an integrated state. For example, even if the white ink storage means and the color ink storage means are manufactured, sold, etc., independently, the ink set is included in the ink set of the present invention if it is premised on the use of the white ink and the color inks in combination, or if it substantially induces the use of the white ink and the color inks in combination.

<First urethane resin and second urethane resin>
As the urethane resin in the present invention, polyether-type urethane resins containing ether bonds in addition to urethane bonds in the main chain of the polymer forming the urethane resin, polyester-type urethane resins containing ester bonds, polycarbonate-type urethane resins containing carbonate bonds, etc. can be used. Among these, polycarbonate-type urethane resins and polyester-type urethane resins are preferred.
The urethane resin is not particularly limited as long as it has a urethane skeleton and is water-dispersible, and can be appropriately selected depending on the purpose. From the viewpoint of preventing adhesion to a general inkjet head (nozzle plate having a water-repellent film), however, it is preferable to use an anionic urethane resin (anionic resin having a urethane skeleton) having an anionic functional group such as a carboxy group, a sulfo group, or a hydroxy group.
Here, when the ink set of the present invention has a pretreatment liquid described later, it is preferable that at least one selected from the urethane resin and the coloring material described later is anionic. When the urethane resin and at least one selected from the coloring material described later are anionic, the ink can be coagulated or thickened when the ink comes into contact with a pretreatment liquid containing an aggregating agent or the like, and as a result, the adhesion of the ink to the surface of a recording medium can be enhanced, which is preferable.

The shape of the urethane resin is not particularly limited and can be appropriately selected depending on the purpose, and may be either a regular shape or an irregular shape. Among these, a regular shape is preferable. When the urethane resin has a regular shape, it is preferable that it is spherical. When the urethane resin has a spherical shape, it is preferable that it is in the form of particles.

The content of the (1) urethane resin (solid content) is 5% by mass or more and 15% by mass or less with respect to the total amount of the ink, and from the viewpoint of achieving a good balance between continuous ejection stability and friction fastness, it is preferably 9% by mass or more and 13% by mass or less. When the content of the (1) urethane resin (solid content) is 5% by mass or more with respect to the total amount of the ink, the friction fastness of the image obtained by the ink of the present invention can be improved, which is preferable. When the content of the (1) urethane resin (solid content) is 15% by mass or less with respect to the total amount of the ink, the ejection stability of the ink becomes good, which is preferable.

The content of the (2) urethane resin (solid content) is 0.5% by mass or more and 3% by mass or less with respect to the total amount of the ink, and from the viewpoint of achieving a good balance between the storage stability, filter permeability, and friction fastness of the ink, it is preferable that the content of the (2) urethane resin (solid content) is 0.5% by mass or more and 3% by mass or less with respect to the total amount of the ink, since this leads to good storage stability and ejection stability (filter permeability), which is preferable. Note that if the content of the (2) urethane resin (solid content) exceeds 3% by mass with respect to the total amount of the ink, the above effect may become saturated.

The glass transition point (Tg) of the urethane resin (1) is 0° C. or lower, and preferably is −45° C. or higher and 0° C. or lower. By adding the urethane resin (1) having a glass transition point in the above range to the ink, the abrasion resistance of the image obtained by the ink can be improved.

The glass transition point (Tg) of the urethane resin (2) is 40° C. or higher, and preferably 40° C. or higher and 80° C. or lower. By adding the urethane resin (2) having a glass transition point in the above range to the ink, the storage stability and ejection stability (filter permeability) of the ink can be improved.

The glass transition point (Tg) of the urethane resin can be measured, for example, using a DSC-60A Plus equipped with a cooling device manufactured by Shimadzu Corporation.

The volume average particle diameter of the (1) urethane resin is not particularly limited and can be set appropriately depending on the purpose, but is preferably 10 nm or more and 150 nm or less, and more preferably 35 nm or more and 100 nm or less. If the (1) urethane resin has a volume average particle diameter of 10 nm or more, it is preferable because it has good friction resistance. If the (1) urethane resin has a volume average particle diameter of 150 nm or less, it is preferable because it has good filter liquid permeability.

The volume average particle diameter of the (2) urethane resin is not particularly limited and can be set appropriately depending on the purpose, but is preferably 10 nm or more and 100 nm or less, and more preferably 10 nm or more and 35 nm or less. If the (2) urethane resin has a volume average particle diameter of 10 nm or more, it is preferable because it can act as a dispersion aid for the (1) urethane resin. If the (2) urethane resin has a volume average particle diameter of 35 nm or less, it is preferable because its function as a dispersion aid for the (1) urethane resin is less likely to be impaired.

The volume average particle size of the urethane resin can be measured, for example, using a Nanotrac particle size distribution measuring device (Nanotrac WaveII-UT151, manufactured by Microtrac Bell Co., Ltd.).

The urethane resin may be a self-emulsifying type in which a hydrophilic component necessary for stable dispersion in water is introduced, or may be a type that becomes water-dispersible by using an external emulsifier. The urethane resin may be appropriately synthesized or a commercially available product.

Examples of commercially available urethane resins (1) include the following:
・Ucoat UX-300 (Tg: -25°C, volume average particle size: 120 nm, manufactured by Sanyo Chemical Industries, Ltd.)
・Ucoat UX-310 (Tg: -25°C, volume average particle size: 120 nm, manufactured by Sanyo Chemical Industries, Ltd.)
・Ucoat UX-340 (Tg: -50°C, volume average particle size: 50 nm, manufactured by Sanyo Chemical Industries, Ltd.)
・Permarin UA-150 (Tg: -70°C, volume average particle size: 70 nm, manufactured by Sanyo Chemical Industries, Ltd.)
・Permarin UA-200 (Tg: -35°C, volume average particle size: 70 nm, manufactured by Sanyo Chemical Industries, Ltd.)
・Permarin UA-350 (Tg: -30°C, volume average particle size: 70 nm, manufactured by Sanyo Chemical Industries, Ltd.)
・Permarin UA-368 (Tg: -20°C, volume average particle size: 300 nm, manufactured by Sanyo Chemical Industries, Ltd.)
U-coat UWS-145 (Tg: -45°C, volume average particle size: 20 nm, manufactured by Sanyo Chemical Industries, Ltd.)
Euprene UXA-307 (Tg: -45°C, volume average particle size: 200 nm, manufactured by Sanyo Chemical Industries, Ltd.)
Superflex 300 (polyurethane dispersion, Tg: -42°C, volume average particle size: 70 nm, solid content 30% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Superflex 420 (polyurethane dispersion, Tg: -10°C, volume average particle size: 10 nm, solid content 32% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Superflex 420NS (Tg: -10°C, volume average particle size: 10 nm, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Superflex 460 (polyurethane dispersion, Tg: -21°C, volume average particle size: 40 nm, solid content 38% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Superflex 460S (Tg: -28°C, volume average particle size: 30 nm, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Superflex 470 (polyurethane dispersion, Tg: -31°C, volume average particle size: 50 nm, solid content 38% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Superflex 500M (polyurethane dispersion, Tg: -39°C, volume average particle size: 140 nm, solid content 45% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Superflex 740 (polyurethane dispersion, Tg: -34°C, volume average particle size: 200 nm, solid content 40% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Takelac (registered trademark) WS-6021 (polyurethane dispersion, Tg: -60°C, volume average particle size: 90 nm, solid content 30% by mass, manufactured by Mitsui Chemicals, Inc.)
Takelac W-6110 (polyurethane dispersion, Tg: -20°C, volume average particle size: 90 nm, solid content 32% by mass, manufactured by Mitsui Chemicals, Inc.)

Examples of commercially available urethane resins (2) include the following:
Superflex 130 (Tg: 101° C., volume average particle size: 30 nm, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Superflex 150 (polyurethane dispersion, Tg: 40° C., volume average particle size: 30 nm, solid content 30% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Superflex 170 (polyurethane dispersion, Tg: 75° C., volume average particle size: 10 nm, solid content 33% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Superflex 210 (Tg: 41° C., volume average particle size: 40 nm, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Superflex 820 (polyurethane dispersion, Tg: 46° C., volume average particle size: 30 nm, solid content: 30% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Superflex 830HS (polyurethane dispersion, Tg: 68° C., volume average particle size: 10 nm, solid content 27% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Superflex 870 (polyurethane dispersion, Tg: 78° C., volume average particle size: 30 nm, solid content: 30% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Takelac W-5030 (Tg: 85°C, volume average particle size: 50 nm, manufactured by Mitsui Chemicals, Inc.)
Takelac W-5661 (polyurethane dispersion, Tg: 70° C., volume average particle size: 30 nm, solid content 35% by mass, manufactured by Mitsui Chemicals, Inc.)
Takelac WS-5984 (Tg: 70°C, volume average particle size: 80 nm, manufactured by Mitsui Chemicals, Inc.)
Takelac W-6010 (Tg: 90°C, volume average particle size: 60 nm, manufactured by Mitsui Chemicals, Inc.)
Takelac W-6020 (polyurethane dispersion, Tg: 90° C., volume average particle size: 80 nm, solid content 30% by mass, manufactured by Mitsui Chemicals, Inc.)
Takelac W-605 (Tg: 100°C, volume average particle size: 80 nm, manufactured by Mitsui Chemicals, Inc.)
Takelac W-635 (Tg: 70°C, volume average particle size: 150 nm, manufactured by Mitsui Chemicals, Inc.)

<Coloring material>
In the present invention, the white ink contains a white coloring material, and the color inks contain color coloring materials.
The coloring material is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include pigments. As the pigment, for example, inorganic pigments and organic pigments can be used. These may be used alone or in combination of two or more.
Examples of the pigment that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy pigments, and metallic pigments (gold, silver, etc.).

The inorganic pigment is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, carbon black, etc. Among these, titanium oxide is preferable as a white coloring material, and carbon black is preferable as a black coloring material.
The carbon black is not particularly limited and can be appropriately selected depending on the purpose. Examples of the carbon black include channel black, furnace black, gas black, and lamp black produced by known methods such as a contact method, a furnace method, and a thermal method.

The organic pigment is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, aniline black, etc. Among these, the organic pigment is preferably an azo pigment or a polycyclic pigment.
Examples of the azo pigment include azo lake, an insoluble azo pigment, a condensed azo pigment, and a chelate azo pigment.
Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments.
Examples of the dye chelate include a basic dye type chelate and an acid dye type chelate.

Specific examples of the organic pigment include C.I. Pigment Yellow 1, C.I. Pigment Yellow 3, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 17, C.I. Pigment Yellow 24, C.I. Pigment Yellow 34, C.I. Pigment Yellow 35, C.I. Pigment Yellow 37, C.I. Pigment Yellow 42 (yellow iron oxide), C.I. Pigment Yellow 53, C.I. Pigment Yellow 55, C.I. Pigment Yellow 74, C.I. Pigment Yellow 81, C.I. Pigment Yellow 83, C.I. Pigment Yellow 95, C.I. Pigment Yellow 97, C.I. Pigment Yellow 98, C.I. Pigment Yellow 100, C.I. Pigment Yellow 101, C.I. Pigment Yellow 104, C.I. Pigment Yellow 108, C.I. Pigment Yellow 109, C.I. Pigment Yellow 110, C.I. Pigment Yellow 117, C.I. Pigment Yellow 120, C.I. Pigment Yellow 128, C.I. Pigment Yellow 139, C.I. Pigment Yellow 150, C.I. Pigment Yellow 151, C.I. Pigment Yellow 155, C.I. Pigment Yellow 153, C.I. Pigment Yellow 180, C.I. Pigment Yellow 183, C.I. Pigment Yellow 185, C.I. Pigment Yellow 213; C.I. Pigment Orange 5, C.I. Pigment Orange 13, C.I. Pigment Orange 16, C.I. Pigment Orange 17, C.I. Pigment Orange 36, C.I. Pigment Orange 43, C.I. Pigment Orange 51; C.I. Pigment Red 1, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 17, C.I. Pigment Red 22, C.I. Pigment Red 23, C.I. Pigment Red 31, C.I. Pigment Red 38, C.I. Pigment Red 48:2 (Permanent Red 2B (Ca)), C.I. Pigment Red 48:3, C.I. Pigment Red 48:4, C.I. Pigment Red 49:1, C.I. Pigment Red 52:2, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1 (Brilliant Carmine 6B), C.I. Pigment Red 60:1, C.I. Pigment Red 63:1, C.I. Pigment Red 63:2, C.I. Pigment Red 64:1, C.I. Pigment Red 81, C.I. Pigment Red 83, C.I. Pigment Red 88, C.I. Pigment Red 101 (Red Flame), C.I. Pigment Red 104, C.I. Pigment Red 105, C.I. Pigment Red 106, C.I. Pigment Red 108 (Cadmium Red), C.I. Pigment Red 112, C.I. Pigment Red 114, C.I. Pigment Red 122 (Quinacridone Magenta), C.I. Pigment Red 123, C.I. Pigment Red 146, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 168, C.I. Pigment Red 170, C.I. Pigment Red 172, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 179, C.I. Pigment Red 185, C.I. Pigment Red 190, C.I. C.I. Pigment Red 193, C.I. Pigment Red 209, C.I. Pigment Red 219; C.I. Pigment Violet 1 (Rhodamine Lake), C.I. Pigment Violet 3, C.I. Pigment Violet 5:1, C.I. Pigment Violet 16, C.I. Pigment Violet 19, C.I. Pigment Violet 23, C.I. Pigment Violet 38; C.I. Pigment Blue 1, C.I. Pigment Blue 2, C.I. Pigment Blue 15 (Phthalocyanine Blue), C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3 (Phthalocyanine Blue), C.I. Pigment Blue 15:4, C.I. Pigment Blue 16, C.I. Pigment Blue 17:1, C.I. Pigment Blue 56, C.I. Pigment Blue 60, C.I. Pigment Blue 63; C.I. Pigment Green 1, C.I. Pigment Green 4, C.I. Pigment Green 7, C.I. Pigment Green 8, C.I. Pigment Green 10, C.I. Pigment Green 17, C.I. Pigment Green 18, C.I. Pigment Green 36, etc.

The BET specific surface area of the pigment is not particularly limited and can be appropriately selected depending on the purpose, but is preferably from 10 m ² /g to 1,500 m ² /g, more preferably from 20 m ² /g to 600 m ² /g, and even more preferably from 50 m ² /g to 300 m ² /g.
A pigment having a desired BET specific surface area can be obtained by carrying out a general size reduction or pulverization treatment. The size reduction or pulverization treatment is not particularly limited and can be appropriately selected from known methods, such as ball mill pulverization, jet mill pulverization, ultrasonic treatment, etc. The pigment may be subjected to one type of treatment alone or two or more types of treatments in combination.

The cumulative 50% volume particle diameter D50 of the pigment is not particularly limited and can be selected appropriately depending on the purpose, but it is preferably 50 nm or more and 350 nm or less in the ink.

The pigment content (solid content) is not particularly limited and can be set appropriately depending on the purpose, but is preferably 1.0% by mass or more and 15.0% by mass or less, and more preferably 1.5% by mass or more and 10.0% by mass or less, relative to the total amount of the ink. When the pigment content (solid content) is 1.0% by mass or more, relative to the total amount of the ink, the color development and image density of the ink are improved, which is preferable. When the pigment content (solid content) is 15.0% by mass or less, relative to the total amount of the ink, the ejection stability of the ink is improved, which is preferable.

As the pigment in the present invention, a composite pigment may be used.
As the composite pigment, from the viewpoint of small average primary particle diameter, preferred are silica/carbon black composite material (manufactured by Toda Kogyo Co., Ltd.), silica/phthalocyanine PB15:3 composite material (manufactured by Toda Kogyo Co., Ltd.), silica/disazo yellow composite material (manufactured by Toda Kogyo Co., Ltd.), and silica/quinacridone PR122 composite material (manufactured by Toda Kogyo Co., Ltd.).

For example, if an inorganic pigment particle with a primary particle diameter of 20 nm is coated with an equal amount of organic pigment, the primary particle diameter of this composite pigment will be approximately 25 nm. If this can be dispersed to the primary particle level using an appropriate dispersant, it is possible to produce a very fine composite pigment dispersion ink with a dispersed particle diameter of 25 nm. In this composite pigment, the organic pigment on the coating surface contributes to the dispersion, but the properties of the inorganic pigment in the center also appear through the thin layer of organic pigment about 2.5 nm thick, so it is also necessary to select a pigment dispersant that can simultaneously stabilize the dispersion of both.

As described above, when the ink set of the present invention includes a pretreatment liquid, it is preferable that at least one selected from the urethane resin and the coloring material is anionic. That is, it is preferable that the coloring material is anionic, and it is more preferable that the coloring material is an anionic pigment.
Examples of the anionic pigment include surfactant-dispersed pigments in which a pigment is dispersed in a surfactant, resin-dispersed pigments in which a pigment is dispersed in a resin, resin-coated pigments in which the surface of a pigment is coated with a resin, and self-dispersed pigments in which hydrophilic groups are provided on the pigment surface. In any of these dispersion forms, it is preferable that the pigments are water-dispersible.

When the anionic pigment is the resin-coated dispersed pigment or the self-dispersed pigment, it is preferable that the pigment has at least one hydrophilic group on the surface.
Examples of the hydrophilic group include -COOM, _{-SO3M , -PO3HM , -PO3M2} , -CONM2, _-SO3NM2 , -NH- _{C6H4 -} COOM _{, -NH} - _{C6H4 - SO3M ,} -NH _- C6H4 _- PO3HM, _-NH - _{C6H4- PO3M2} , -NH- _{C6H4 - CONM2} , and -NH- _{C6H4 - SO3NM2} . These hydrophilic groups can be introduced by known methods. In addition, "M" in the hydrophilic group represents a counter _ion .

The counter ion represented by "M" in the hydrophilic group is preferably a quaternary ammonium ion. Specific examples of the quaternary ammonium ion include tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, benzyltrimethylammonium ion, benzyltriethylammonium ion, and tetrahexylammonium ion. Among these, tetraethylammonium ion, tetrabutylammonium ion, and benzyltrimethylammonium ion are preferred, and tetrabutylammonium ion is more preferred.
Inks using such pigments have excellent storage stability over time and suppress an increase in viscosity when water evaporates. This is presumably because the pigment dispersion can be kept stable due to the hydrophilic group containing the quaternary ammonium ion, even when the water evaporates from the water-rich ink and the ink becomes organic solvent-rich.

As an anionic pigment other than a coloring material having a hydrophilic group on the surface, from the viewpoint of storage stability of the ink, a polymer emulsion in which the pigment is contained in polymer fine particles is preferred. In the polymer emulsion, the pigment may be encapsulated in the polymer fine particles or adsorbed on the surface of the polymer fine particles. In this case, it is not necessary for all the pigment to be encapsulated in the polymer fine particles or adsorbed on the surface of the polymer fine particles, and a part of the pigment may be dispersed in the emulsion.
Examples of the polymer for the polymer particles include vinyl-based polymers, polyester-based polymers, and polyurethane-based polymers, etc. Among these, vinyl-based polymers and polyester-based polymers are preferred.
These may be used alone or in combination of two or more.

The mass ratio of the coloring material to the organic solvent is preferably adjusted as appropriate, since it is related to the ink ejection stability and the prevention of waste ink adhesion in the maintenance mechanism of the image forming device. For example, when an ink containing a large amount of the coloring material but a small amount of the organic solvent is ejected from an inkjet head, the evaporation of water near the ink meniscus of the nozzle may cause ejection defects.

<Water>
The water is not particularly limited and can be appropriately selected depending on the purpose. Examples of the water include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, and ultrapure water.
These may be used alone or in combination of two or more.

The water content is not particularly limited and can be set appropriately depending on the purpose, but from the viewpoint of the drying property and ejection reliability of the ink, it is preferably 10.0% by mass or more and 90.0% by mass or less, and more preferably 20.0% by mass or more and 60.0% by mass or less, of the total amount of the ink.

<Organic Solvent>
The organic solvent is not particularly limited and may be appropriately selected depending on the purpose, but it is preferable to use an organic solvent having an equilibrium moisture content of 30% by mass or more in an environment of a temperature of 23° C. and a relative humidity (RH) of 80% (hereinafter, sometimes referred to as a "humectant"). Among these, it is more preferable that the organic solvent has a boiling point (bp) of 245° C. to 290° C. and an equilibrium moisture content of 43% by mass to 49% by mass. The selection of such an organic solvent is related to the suppression of color bleeding and beading (in other words, the control of static surface tension and dynamic surface tension), but is also related to the improvement of ink ejection stability and the suppression of adhesion of waste ink in the maintenance mechanism of the image forming apparatus.

Here, the "equilibrium moisture content" is a value calculated by the following formula (2) after measuring the equilibrium moisture content by using a saturated aqueous solution of potassium chloride and sodium chloride mixed in a ratio of 6:4 (potassium chloride:sodium chloride, parts by mass) in a desiccator kept at a temperature of 23°C ± 1°C and a relative humidity of 80% ± 3%, and storing petri dishes containing 1 g of each organic solvent in the desiccator.
Equilibrium moisture content (mass%) = [amount of moisture absorbed by organic solvent/(amount of organic solvent + amount of moisture absorbed by organic solvent)] x 100...calculation formula (2)

Examples of the wetting agent include polyhydric alcohols having an equilibrium moisture content of 30% by mass or more in an environment at a temperature of 23° C. and a relative humidity of 80%. Specific examples of the polyhydric alcohol include diethylene glycol (bp 245°C, equilibrium water content 43% by mass), triethylene glycol (bp 285°C, equilibrium water content 39% by mass), tetraethylene glycol (bp 324°C to 330°C, equilibrium water content 37% by mass), 1,3-butanediol (bp 203°C to 204°C, equilibrium water content 35% by mass), glycerin (bp 290°C, equilibrium water content 49% by mass), diglycerin (bp 270°C/20hPa, equilibrium water content 38% by mass), 1,2,3-butanetriol (bp 175°C/33hPa, equilibrium water content 38% by mass), and 1,2,4-butanetriol (bp 190°C to 191°C/24hPa, equilibrium water content 41% by mass). Among these, glycerin and 1,3-butanediol are preferred.
These may be used alone or in combination of two or more.

Examples of wetting agents other than the polyhydric alcohols include 2-methyl-1,3-butanediol (bp 214), 3-methyl-1,3-butanediol (bp 203° C.), dipropylene glycol (bp 232° C.), 1,5-pentanediol (bp 242° C.), propylene glycol (bp 187° C.), 2-methyl-2,4-pentanediol (bp 197° C.), ethylene glycol (bp 196° C. to 198° C.), tripropylene glycol (bp 187° C.), ethylene glycol (bp 196° C. to 198° C.), and propylene glycol (bp 187° C.). Examples of the copolymer include ethylene glycol (bp 267° C.), hexylene glycol (bp 197° C.), polyethylene glycol (viscous liquid to solid), polypropylene glycol (bp 187° C.), 1,6-hexanediol (bp 253° C. to 260° C.), 1,2,6-hexanetriol (bp 178° C.), trimethylolethane (solid, melting point (mp) 199° C. to 201° C.), and trimethylolpropane (solid, (mp) 61° C.).
These may be used alone or in combination of two or more.

The content of the organic solvent is not particularly limited and can be appropriately set depending on the purpose, but is preferably from 10.0% by mass to 75.0% by mass, and more preferably from 15.0% by mass to 50.0% by mass, based on the total amount of the ink.
It is preferable that the content of the organic solvent is 10.0% by mass or more based on the total amount of the ink, since this provides a good moisturizing effect for the ink.
If the content of the organic solvent is 75.0% by mass or less with respect to the total amount of the ink, the drying properties of the ink on a recording medium, which will be described later, are improved, and this is preferable.

Furthermore, when the recording medium described later is non-permeable (lowly permeable), it is preferable to use an organic solvent having a solubility parameter (SP value) of 9.0 (cal/cm ³ ) ^1/2 or more and less than 11.8 (cal/cm ³ ) ^1/2 . Specific examples of organic solvents having an SP value within the above range include 3-ethyl-3-oxetanemethanol (SP value: 11.31 (cal/cm ³ ) ^1/2 ), 3-methyl-3-oxetanemethanol (SP value: 11.79 (cal/cm ³ ) ^1/2 ), β-methoxy-N,N-dimethylpropionamide (3-methoxy-N,N-dimethylpropionamide) (SP value: 9.19 (cal/cm ³ ) ^1/2 ), β-butoxy-N,N-dimethylpropionamide (3-butoxy-N,N-dimethylpropionamide) (SP value: 9.03 (cal/cm ³ ) ^1/2 ), 1,2-hexanediol (SP value: 11.8 (cal/cm ³ ) ^1/2 ), and 2-ethyl-1,3-hexanediol (SP value: 10.6 (cal/cm ³ ) 1/2 ). ) ^1/2 ), 2,2,4-trimethyl-1,3-pentanediol (SP value: 10.8 (cal/cm ³ ) ^1/2 ), diethylene glycol monoethyl ether (SP value: 10.14 (cal/cm ³ ) ^1/2 ), 3-methoxy-1-butanol (SP value: 9.64 (cal/cm ³ ) ^1/2 ), 3-methoxy-3-methyl-1-butanol (SP value: 9.64 (cal/cm ³ ) ^1/2 ), 3-methyl-1,5-pentanediol (SP value: 11.8 (cal/cm ³ ) ^1/2 ), methylpropylene triglyceride (SP value: 9.43 (cal/cm ³ ) ^1/2 ), diethylene glycol mono-n-butyl ether (SP value: 9.86 (cal/cm ³ ) ^1/2 ), diethylene glycol monomethyl ether (SP value: 10.34 (cal/cm ³ ) ^1/2 ), triethylene glycol monomethyl ether (SP value: 10.12 (cal/cm ³ ) ^1/2 ), propylene glycol monopropyl ether (SP value: 9.82 (cal/cm ³ ) ^1/2 ), propylene glycol monomethyl ether (SP value: 10.19 (cal/cm ³ ) ^1/2 ), propylene glycol monobutyl ether (SP value: 9.69 (cal/cm ³ ) ^1/2 ), 3-methoxy-1-butanol (SP value: 10.65 (cal/cm ³ ) ^1/2 ), 3-methoxy-1-propanol (SP value: 10.41 (cal/cm ³ ) ^1/2 ), dipropylene glycol monomethyl ether (SP value: 9.84 (cal/cm ³ ) ^1/2 ), and 3-methyl-1,5-pentanediol (SP value: 11.8 (cal/cm ³ ) ^1/2 ).

In addition, when the recording medium described later is non-permeable (low permeable), the content of the organic solvent having an SP value in the above range is not particularly limited and can be set appropriately depending on the purpose, but from the viewpoint of suppressing color bleeding and beading (in other words, controlling static surface tension and dynamic surface tension) and from the viewpoint of the color development of the ink, it is preferably 0.5% by mass or more and 5.0% by mass or less, and more preferably 1.0% by mass or more and 4.0% by mass or less, based on the total amount of the ink.

<Surfactant>
The ink of the present invention preferably contains a surfactant from the viewpoint of suppressing color bleeding and beading (in other words, controlling static surface tension and dynamic surface tension).
Examples of the surfactant include acetylene surfactants, silicone surfactants, and fluorosurfactants. Specific examples of the acetylene surfactant include acetylene glycol compounds and acetylene alcohol compounds. Specific examples of the silicone surfactant include polyether-modified siloxane compounds. Specific examples of the fluorosurfactant include fluorine compounds.
Among these, polyether-modified siloxane compounds are preferred from the viewpoint of improving filter liquid permeability and friction fastness.
These may be used alone or in combination of two or more.
By including a surfactant in the ink of the present invention, the ink is less likely to wet the ink-repellent film on the nozzle plate of the inkjet head, which makes it possible to suppress ejection defects caused by the ink adhering to the nozzle, thereby improving ejection stability, which is advantageous.

The polyether-modified siloxane compound is preferably one represented by the following general formulas (1) to (4).

In the general formula (1), _R1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m represents an integer of 0 to 23, n represents an integer of 1 to 10, a represents an integer of 1 to 23, and b represents an integer of 0 to 23.

In the general formula (2), R ₂ and R ₃ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m represents an integer of 1 to 8, and c and d each independently represent an integer of 1 to 10.

In the above general formula (3), R ₄ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and e represents an integer of 1 to 8.

In the above general formula (4), R ₅ represents a polyether group of the following general formula (5);

In the general formula (5), _R6 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, g represents an integer of 0 to 23, and h represents an integer of 0 to 23. However, there is no case where g and h are 0 at the same time.

Specific examples of the compound represented by the general formula (1) include compounds represented by the following structural formulas (1) to (8).

Specific examples of the compound represented by the general formula (2) include compounds represented by the following structural formula (9).

Specific examples of the compound represented by the general formula (3) include compounds represented by the following structural formula (10).

Specific examples of the compound represented by the general formula (4) include compounds represented by the following structural formulas (11) to (13).

The polyether-modified siloxane compound may be appropriately synthesized or may be a commercially available product. Commercially available polyether-modified siloxane compounds include, for example, KF-353, KF-640, KF-642, KF-643, and KF-644 (all manufactured by Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5051 (manufactured by Nippon Emulsion Co., Ltd.), BYK-345, BYK-347, BYK-348, BYK-375, and BYK-377 (all manufactured by BYK Japan KK), and Silface S. Examples include AG002, Silface SAG003, Silface SAG005, Silface SAG503A, Silface SAG008 (all manufactured by Nissin Chemical Industry Co., Ltd.), TEGO_Wet_KL245, TEGO_Wet_250, TEGO_Wet_260, TEGO_Wet_265, TEGO_Wet_270, and TEGO_Wet_280 (all manufactured by Evonik Japan Co., Ltd.). Among these, KF-353 (manufactured by Shin-Etsu Chemical Co., Ltd.) is preferred from the viewpoint of improving filter liquid permeability and friction fastness.

The acetylene glycol compound and the acetylene alcohol compound are not particularly limited and can be appropriately selected depending on the purpose.
The acetylene glycol compound and the acetylene alcohol compound may be appropriately synthesized or may be a commercially available product. Examples of commercially available products of the acetylene glycol compound and the acetylene alcohol compound include Surfynol 104E (2,4,7,9-tetramethyl-5-decyne-4,7-diol), Surfynol 420, Surfynol 440, Surfynol 465, Surfynol SE, Surfynol SE-F, Surfynol PSA-336, Surfynol DF110D, Surfynol DF58, Olfin E1004, Olfin E1010, Olfin E1020, Olfin PD-001, Olfin PD-002W, Olfin PD-004, Olfin PD-005, Olfin EXP.4001, Olfin EXP.4200, Olfin EXP.4123, and Olfin EXP. 4300 (both manufactured by Nissin Chemical Industry Co., Ltd.).

The fluorine compound is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of low foaming, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chains are preferred.

Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid and perfluoroalkylsulfonate salts.
Examples of the perfluoroalkyl carboxylic acid compound include perfluoroalkyl carboxylic acids and perfluoroalkyl carboxylates.
Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group on the side chain include sulfate ester salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain, and salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain.

The counter ion of the salt in the fluorine compound is not particularly limited and can be appropriately selected depending _on the purpose. Examples thereof include Li, _Na , K, _NH4 , _NH3CH2CH2OH , NH2 _{( CH2CH2OH} ) ₂ , and NH _{( CH2CH2OH} ) _{3 .}

The fluorine compounds may be synthesized as appropriate or commercially available products may be used. Commercially available products of the fluorine compound include, for example, Surflon S-242, Surflon S-243, Surflon S-420, and Surflon S-431 (all manufactured by AGC Seimi Chemical Co., Ltd.); Megafac F-251, Megafac F-430, Megafac F-444, Megafac F-477, Megafac F-552, Megafac F-553, and Megafac F-554 (all manufactured by DIC Corporation); CAPSTONE FS-10, CAPSTONE FS-30, CAPSTONE FS-31, CAPSTONE FS-34, CAPSTONE FS-35, CAPSTONE FS-51, CAPSTONE FS-60, CAPSTONE FS-61, CAPSTONE FS-63, CAPSTONE FS-64, CAPSTONE FS-66, CAPSTONE FS-68, CAPSTONE FS-69, CAPSTONE FS-70, CAPSTONE FS-71, CAPSTONE FS-72, CAPSTONE FS-73, CAPSTONE FS-74, CAPSTONE FS-75, CAPSTONE FS-76, CAPSTONE FS-77, CAPSTONE FS-78, CAPSTONE FS-79, CAPSTONE FS-80, CAPSTONE FS-81, CAPSTONE FS-82, CAPSTONE FS-83, CAPSTONE FS-84, CAPSTONE FS-85, CAPSTONE FS-86, CAPSTONE FS-87, CAPSTONE FS-88, CAPSTONE FS-89, CAPSTONE FS-90, CAPSTONE FS-91, CAPSTONE FS-92, CAPSTONE FS-93, CAP FS-64, CAPSTONE FS-65, CAPSTONE FS-3100 (all manufactured by Chemours Corporation); Ftergent 212M, Ftergent 215M, Ftergent 250, Ftergent 251, Ftergent 222F, Ftergent 245F (all manufactured by Neos Corporation); Polyfox PF-136A, PF-156A, PF-151N (all manufactured by Kitamura Chemical Industries Co., Ltd.). Among these, CAPSTONE FS-3100 and CAPSTONE FS-34 manufactured by DuPont, FTERGENT 250 and FTERGENT 251 manufactured by NEOS Co., Ltd., and Polyfox PF-151N manufactured by Kitamura Chemical Industries Co., Ltd. are preferred because they provide good print quality, particularly color development, and significantly improve paper penetration, wettability, and dye uniformity.

The content of the surfactant is not particularly limited and can be set appropriately depending on the purpose, but is preferably 0.001% by mass or more and 5.0% by mass or less, and more preferably 0.01% by mass or more and 3.0% by mass or less, based on the total amount of the ink. A surfactant content of 0.001% by mass or more based on the total amount of the ink is preferable because it is easy to obtain an effect of suppressing color bleeding and beading (in other words, control of static surface tension and dynamic surface tension). Note that if the surfactant content exceeds 5.0% by mass based on the total amount of the ink, the effect may become saturated.

<Other Components (A)>
The other component (A) is not particularly limited and can be appropriately selected depending on the purpose. Examples of the other component (A) include (1) a urethane resin and (2) a resin other than a urethane resin, an additive, and the like.
In this specification, "(1) urethane resin and (2) resin other than urethane resin" may be referred to as "other resin".

<<Other resins>>
The other resins are not particularly limited and can be appropriately selected depending on the purpose as long as they do not fall under (1) urethane resin and (2) urethane resin, but resins having excellent film-forming properties, solvent resistance, water resistance, and weather resistance are useful in image formation. Examples of such resins include condensation-based synthetic resins, addition-based synthetic resins, and natural polymer compounds.
These may be used alone or in combination of two or more.

Examples of the condensation synthetic resin include polyester resin, polyepoxy resin, polyamide resin, polyether resin, poly(meth)acrylic resin, acrylic-silicone resin, and fluororesin. In this specification, "(meth)acrylic" means acrylic or methacrylic.
Examples of the addition-type synthetic resin include polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl ester resins, polyacrylic acid resins, and unsaturated carboxylic acid resins.
Examples of the natural polymer compounds include celluloses, rosins, and natural rubber.

The content of the other resins is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately set depending on the purpose.
The other resins may be appropriately synthesized or may be commercially available products. Examples of commercially available products of the other resins include the following.
Superflex 150HS (polyurethane dispersion, Tg: 32° C., volume average particle size: 80 nm, solid content 38% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Takelac (registered trademark) W-6061 (polyurethane dispersion, Tg: 25°C, volume average particle size: 100 nm, solid content 30% by mass, manufactured by Mitsui Chemicals, Inc.)
Boncoat VF1060 (acrylic emulsion, Tg: -10°C, solid content 50% by mass, manufactured by DIC Corporation)

<<Additives>>
The additives are not particularly limited and can be appropriately selected depending on the purpose. Examples of the additives include foam inhibitors (defoamers), pH adjusters, antiseptics and antifungals, chelating agents, rust inhibitors, antioxidants, ultraviolet absorbers, oxygen absorbers, and light stabilizers.

- Foam suppressor (defoamer) -
The foam inhibitor is added in a small amount to the ink to suppress foaming of the ink.
Here, "bubbling" refers to a liquid that becomes a thin film and encloses air. The characteristics of the ink, such as the surface tension and viscosity, are involved in the generation of this bubble. That is, liquids with high surface tension, such as water, are less likely to bubble because of the force that tries to make the surface area of the liquid as small as possible. In contrast, inks with high viscosity and high permeability tend to bubble easily because of their low surface tension, and the generated bubbles tend to be maintained due to the viscosity of the solution, making them difficult to eliminate.
Typically, foam suppressors destroy bubbles by locally lowering the surface tension of the foam film, or by dotting the foam surface with foam suppressors that are insoluble in the foaming liquid.

When the ink of the present invention contains a polyether-modified siloxane compound as a surfactant, the foam inhibitor is preferably a foam inhibitor containing a compound represented by the following general formula (6):

In the general formula (6), R ₇ and R ₈ each independently represent an alkyl group having 3 to 6 carbon atoms, R ₉ and R ₁₀ each independently represent an alkyl group having 1 to 2 carbon atoms, and n represents an integer of 1 to 6.

The foam inhibitor containing the compound represented by the general formula (6) does not reduce surface tension as strongly as the polyether-modified siloxane compound, but it is highly compatible with the polyether-modified siloxane compound. Therefore, the foam inhibitor is efficiently incorporated into the foam film, and it is believed that the difference in surface tension between the polyether-modified siloxane compound and the foam inhibitor causes the surface of the foam film to become locally unbalanced, destroying the foam.

Examples of the compound represented by the general formula (6) include 2,4,7,9-tetramethyldecane-4,7-diol and 2,5,8,11-tetramethyldodecane-5,8-diol. Among these, 2,5,8,11-tetramethyldodecane-5,8-diol is preferred due to its anti-foaming effect and high compatibility with ink.

The content of the foam inhibitor is not particularly limited and may be appropriately selected depending on the purpose. However, the content is preferably 0.01% by mass or more and 10.0% by mass or less, and more preferably 0.1% by mass or more and 5.0% by mass or less, based on the total amount of the ink.
It is preferable that the content of the foam inhibitor is 0.01% by mass or more based on the total amount of the ink, since this provides a good foam-inhibiting effect.
When the content of the foam inhibitor is 10.0% by mass or less with respect to the total amount of the ink, it is possible to suppress the influence on the ink properties such as the particle size of the resin particles.

- pH adjuster -
The pH adjuster is not particularly limited as long as it can adjust the pH of the ink, and can be appropriately selected depending on the purpose, and examples thereof include alcohol amines, hydroxides of alkali metal elements, hydroxides of ammonium, phosphonium hydroxides, carbonates of alkali metals, etc. Among these, alcohol amines are preferable.
These may be used alone or in combination of two or more.

Examples of the alcohol amines include diethanolamine, triethanolamine, and 2-amino-2-ethyl-1,3-propanediol.
Examples of the hydroxides of the alkali metal elements include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the hydroxide of ammonium include ammonium hydroxide and quaternary ammonium hydroxide.
The phosphonium hydroxide may, for example, be a quaternary phosphonium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate.

The content of the pH adjuster is not particularly limited as long as it can adjust the ink to the desired pH, and can be set appropriately depending on the purpose.

- Antiseptic and fungicide -
The antiseptic and antifungal agent is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include 1,2-benzothiazolin-3-one, sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1-oxide sodium, sodium benzoate, and sodium pentachlorophenol.
These may be used alone or in combination of two or more.
The content of the antiseptic/antifungal agent is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately set depending on the purpose.
The antiseptic and fungicide may be a synthesized product or a commercially available product, such as PROXEL (registered trademark) GXL (antiseptic and fungicide containing 1,2-benzothiazolin-3-one as the main component, manufactured by Avecia, 20% component, containing dipropylene glycol).

- Chelating agents -
The chelating agent is not particularly limited and can be appropriately selected depending on the purpose. Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uramildiacetate.
These may be used alone or in combination of two or more.
The content of the chelating agent is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately set depending on the purpose.

-anti-rust-
The rust inhibitor is not particularly limited and can be appropriately selected depending on the purpose. Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.
These may be used alone or in combination of two or more.
The content of the rust inhibitor is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately set depending on the purpose.

-Antioxidant-
The antioxidant is not particularly limited and can be appropriately selected depending on the purpose. Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.
These may be used alone or in combination of two or more.
The content of the antioxidant is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately set depending on the purpose.

-Ultraviolet absorber-
The ultraviolet absorber is not particularly limited and can be appropriately selected depending on the purpose. Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and nickel complex salt-based ultraviolet absorbers.
These may be used alone or in combination of two or more.
The content of the ultraviolet absorbing agent is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately set depending on the purpose.

<Ink properties>
The physical properties of the ink in the present invention are not particularly limited and can be appropriately set depending on the purpose. For example, it is preferable that the viscosity, surface tension, pH, etc. are within the following ranges.

The viscosity of the ink at 25° C. is preferably 5 mPa·s or more and 25 mPa·s or less, and more preferably 6 mPa·s or more and 20 mPa·s or less. The viscosity of the ink at 25° C. is preferably 5 mPa·s or more, since it is possible to obtain an effect of improving image density and character quality. In addition, the viscosity of the ink at 25° C. is preferably 25 mPa·s or less, since it is possible to improve the ejection stability of the ink.
The viscosity can be measured using, for example, a rotational viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) The measurement conditions are 25° C., a standard cone rotor (1°34′×R24), a sample liquid amount of 1.2 mL, a rotation speed of 50 rpm, and 3 minutes.

The pH of the ink is preferably from 7 to 12 from the viewpoint of improving the ejection stability of the ink.
The pH can be measured at 25° C. using, for example, a pH meter (HM-30R type, manufactured by DKK-TOA Corporation).

<Ink manufacturing method>
The ink can be produced by stirring and mixing the above-mentioned materials, and this can be done using equipment such as a sand mill, a homogenizer, a ball mill, a paint shaker, or an ultrasonic disperser.

<Ink composition analysis method>
The composition of the ink of the present invention can be analyzed using a gas chromatograph mass spectrometer (GC-MS, manufactured by Shimadzu Corporation), a TG/DTA simultaneous measurement device, or the like.

<Pretreatment solution>
The pretreatment liquid contains water and a flocculant, and may contain a resin (pre), a wax, an organic solvent (pre), a surfactant (pre), and other components (B) as necessary.
The pretreatment liquid is a liquid composition that is applied to a recording medium before the white ink and the color ink are applied. By applying the pretreatment liquid to a recording medium before the ink is applied, the ink that is applied later can be coagulated and thickened, thereby improving adhesion.

<<Water>>
The water is not particularly limited and can be appropriately selected depending on the purpose. For example, pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, and ultrapure water can be used.

The water content is not particularly limited and can be set appropriately depending on the purpose, but from the viewpoint of the drying property of the pretreatment liquid, it is preferably 10.0% by mass or more and 90.0% by mass or less, and more preferably 20.0% by mass or more and 60.0% by mass or less, based on the total amount of the pretreatment liquid.

<<Flocculant>>
In this specification, the term "aggregating agent" refers to a component that aggregates or thickens the ink when the pretreatment liquid comes into contact with the ink. Specific examples include components that aggregate anionic compounds (e.g., coloring materials or urethane resins) contained in the ink. By using a pretreatment liquid containing such an aggregating agent, the ink that comes into contact with the pretreatment liquid can be aggregated or thickened, improving the adhesion of the ink to the surface of a recording medium.

The flocculant is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include cationic compounds, etc. The cationic compound is preferably any one selected from inorganic metal salts, organic acid metal salts, organic acid ammonium salts, and cationic polymers, and more preferably any one selected from inorganic metal salts and cationic polymers.
These may be used alone or in combination of two or more.

Examples of the inorganic metal salts include magnesium sulfate, aluminum sulfate, manganese sulfate, nickel sulfate, iron (II) sulfate, copper (II) sulfate, zinc sulfate, iron (II) nitrate, iron (III) nitrate, cobalt nitrate, strontium nitrate, copper (II) nitrate, nickel (II) nitrate, lead (II) nitrate, manganese (II) nitrate, nickel (II) chloride, calcium chloride, tin (II) chloride, strontium chloride, barium chloride, magnesium chloride, sodium sulfate, potassium sulfate, lithium sulfate, sodium hydrogen sulfate, potassium hydrogen sulfate, sodium nitrate, potassium nitrate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium chloride, and potassium chloride. Among these, magnesium sulfate and potassium chloride are preferred as the inorganic metal salts.

Examples of the organic acid metal salt include sodium L-aspartate, magnesium L-aspartate, calcium ascorbate, sodium L-ascorbate, sodium succinate, disodium succinate, aluminum citrate, potassium citrate, calcium citrate, tripotassium citrate, trisodium citrate, disodium citrate, zinc lactate, aluminum lactate, potassium lactate, calcium lactate, sodium lactate, magnesium lactate, calcium acetate, potassium tartrate, calcium tartrate, DL-sodium tartrate, and potassium sodium tartrate.

It is preferable that the inorganic metal salt and the organic acid metal salt are each selected from calcium salts, magnesium salts, nickel salts, and aluminum salts. By using these salts as the inorganic metal salt and the organic acid metal salt, the coagulation effect on the urethane resin contained in the ink is improved, and the occurrence of color bleeding and beading can be further suppressed, and the storage stability of the pretreatment liquid can be improved, which is preferable.

Examples of the organic acid ammonium salt include ammonium acetate, ammonium propionate, ammonium lactate, ammonium oxalate, ammonium tartrate, ammonium succinate (diammonium succinate), diammonium malonate, diammonium hydrogen citrate, triammonium citrate, and ammonium L-glutamate.

The cationic polymer is preferably a cationic polymer compound of a quaternary ammonium salt type, specifically, dialkylallyl ammonium chloride polymer, dialkylaminoethyl (meth)acrylate quaternary ammonium salt polymer, modified polyvinyl alcohol dialkyl ammonium salt polymer, dialkyl diallyl ammonium salt polymer, etc.
In addition to the above-mentioned examples, other cationic polymers that may be used include cationic specially modified polyamine compounds, cationic polyamide polyamine compounds, cationic urea-formalin resin compounds, cationic polyacrylamide compounds, cationic alkyl ketene dimers, cationic dicyandiamide compounds, cationic dicyandiamide-formalin condensation compounds, cationic dicyandiamide-polyamine condensation compounds, cationic polyvinyl formamide compounds, cationic polyvinyl pyridine compounds, cationic polyalkylene polyamine compounds, and cationic epoxy polyamide compounds.
Among these, the compounds represented by the following general formulas (7) to (10) are preferred.

In the general formula (7), R ₁₁ each independently represents a methyl group or an ethyl group, Y ⁻ represents a halogen ion, and n represents an integer.

In the general formula (8), Y ^{1 −} represents a halogen ion, a nitrate ion, a nitrite ion, or an acetate ion; R ₁₂ represents H or CH ₃ ; R ₁₃ , R ₁₄ , and R ₁₅ each independently represent H or an alkyl group; and n represents an integer.

In the general formula (9), R ₁₆ each independently represents a methyl group or an ethyl group, Y ⁻ represents a halogen ion, a nitrate ion, a nitrite ion, or an acetate ion, and n represents an integer.

In the general formula (10), Y ⁻ represents a halogen ion, a nitrate ion, a nitrite ion, or an acetate ion; X represents a halogen atom; n represents an integer of 1 to 3; and m represents an integer of 1 to 3.

The content of the coagulant is not particularly limited and can be set appropriately depending on the purpose, but from the viewpoint of the solubility of the coagulant and from the viewpoint of suppressing the occurrence of color bleeding and beading, it is preferably 0.1% by mass or more and 30.0% by mass or less, and more preferably 1.0% by mass or more and 20.0% by mass or less, based on the total amount of the pretreatment liquid.

<<Resin (pre)>>
In this specification, the resin contained in the pretreatment liquid may be referred to as a “resin (pre).” Note that the resin (pre) is different from the urethane resin (the first urethane resin and the second urethane resin) contained in the ink.
When the pretreatment liquid contains a resin (pre), the adhesion of the ink to a recording medium can be improved.

From the viewpoint of long-term storage stability, the resin (pre) is preferably a nonionic resin dispersed by steric hindrance, not a commonly used charge repulsion type emulsion. The resin (pre) being a nonionic resin is preferable because it can solve the following problems.
When an anionic resin, which is a charge repulsion type emulsion, is used as the resin (pre), aggregation occurs between the inorganic metal salt, which is an example of an aggregating agent, and the anionic resin.
When an anionic resin, which is a charge repulsion type emulsion, is used as the resin (pre), instantaneous aggregation occurs between the anionic resin and a metal polyvalent salt that generates trivalent cations upon dissociation.
When a cationic resin is used as the resin (pre), it is sufficiently stable when left at room temperature, but when it is left standing under heating as an accelerated test for long-term stability, thickening occurs.

The nonionic resin is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include polyolefin resins, chlorinated polyolefin resins, polyvinyl acetate resins, polyvinyl chloride resins, polyester resins, polyurethane resins, acrylic resins, styrene-butadiene resins, and copolymers of polymerizable compounds used in the polymerization of these resins. Among these, ethylene-vinyl acetate copolymer resins, ethylene-vinyl acetate-vinyl chloride copolymer resins, ethylene-vinyl acetate-vinyl versatate copolymers, and chlorinated olefin resins are preferred. These resins can further improve the adhesion of the ink to a recording medium.
These may be used alone or in combination of two or more.

The method for determining whether the resin (pre) is a nonionic resin is not particularly limited, but may include, for example, isolating the solid content from the pretreatment liquid by centrifugation, and then using pyrolysis GC-MS (e.g., GCMS-QP2020NX, manufactured by Shimadzu Corporation) to confirm that no material containing acidic functional groups such as carboxyl groups and sulfoxyl groups, or basic functional groups such as amino groups, is detected.

The shape of the resin (pre) is not particularly limited and can be appropriately selected depending on the purpose. It may be either a regular shape or an irregular shape. Among these, a regular shape is preferable. When the resin (pre) is regular, it is preferable that it is spherical. When the resin (pre) is spherical, it is preferable that it is a particle.

The glass transition point (Tg) of the nonionic resin is not particularly limited and can be appropriately selected according to the purpose, but is preferably −30° C. or higher and 30° C. or lower, and more preferably −25° C. or higher and 25° C. or lower. When the glass transition point (Tg) of the nonionic resin is −30° C. or higher, the resin film becomes strong, and the layer formed by the pretreatment liquid becomes more robust. In addition, when the glass transition point (Tg) of the nonionic resin is 30° C. or lower, the film-forming property of the resin is improved and flexibility is also ensured, so that the adhesion of the ink to the recording medium can be further improved.
The glass transition point (Tg) of the nonionic resin can be measured, for example, using a DSC-60A Plus equipped with a cooling device manufactured by Shimadzu Corporation.

The volume average particle diameter of the nonionic resin is not particularly limited and may be appropriately selected depending on the purpose, but is preferably 50 nm or more and 1000 nm or less, and more preferably 100 nm or more and 1000 nm or less.
The volume average particle diameter of the nonionic resin can be measured, for example, by a Nanotrac particle size distribution measuring device (Nnotrac WaveII-UT151, manufactured by Microtrac Bell Co., Ltd.).

The content (solid content) of the resin (pre) is not particularly limited and can be appropriately set depending on the purpose, but is preferably 0.5% by mass or more and 20.0% by mass or less with respect to the total amount of the pretreatment liquid.
When the content (solid content) of the resin (pre) is 0.5% by mass or more and 20.0% by mass or less with respect to the total amount of the pretreatment liquid, the adhesion of the ink to a recording medium can be further improved.

＜＜Wax＞＞
The wax is not particularly limited and can be appropriately selected according to the purpose, and for example, water-dispersible wax can be used. Specific examples of the wax include plant or animal waxes such as carnauba wax, candelilla wax, beeswax, rice wax, and lanolin; petroleum waxes such as paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, and petrolatum; mineral waxes such as montan wax or ozokerite; synthetic waxes such as carbon wax, hoechst wax, polyethylene wax, and stearic acid amide. Among these, paraffin wax and polyethylene wax are preferred, and paraffin wax is more preferred, from the viewpoint of improving the adhesion of the ink to the recording medium and the viewpoint of dispersibility in the pretreatment liquid.
These may be used alone or in combination of two or more.

The melting point of the wax is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 50°C or higher and 130°C or lower, and more preferably 60°C or higher and 120°C or lower. If the melting point of the wax is 50°C or higher and 130°C or lower, the adhesion of the ink to the recording medium can be further improved.

The volume average particle diameter of the wax is not particularly limited and can be appropriately set depending on the purpose, but is preferably from 1 μm to 20 μm, and more preferably from 1 μm to 5 μm.
The volume average particle diameter of the wax can be measured, for example, by a Nanotrac particle size distribution measuring device (Nanotrac WaveII-UT151, manufactured by Microtrac Bell Co., Ltd.).

The wax content (solid content) is not particularly limited and can be set appropriately depending on the purpose, but is preferably 0.05% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 3.0% by mass or less, based on the total amount of the pretreatment liquid. By having the wax content (solid content) of 0.05% by mass or more and 5.0% by mass or less, based on the total amount of the pretreatment liquid, it becomes easier to keep the white ink near the recording medium surface, and the Hunter whiteness can be improved.

<<Organic solvent (pre)>>
In this specification, the organic solvent contained in the pretreatment liquid may be referred to as an “organic solvent (pre).” Note that the organic solvent (pre) is different from the organic solvent contained in the ink.
Specific examples of the water-soluble organic solvent (pre) include ethylene glycol, propylene glycol, diethylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, and 1,6-pentanediol. polyhydric alcohols such as diol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, or petriol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene polyhydric alcohol alkyl ethers such as ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate; and ethylene carbonate.

The organic solvent (pre) preferably has a boiling point of 250° C. or less, since it not only functions as a wetting agent but also has good drying properties.
Among these, propylene glycol, 1,3-butanediol, and 1,2-butanediol are preferred from the viewpoint of facilitating wetting of the surface of the recording medium.

The content of the organic solvent (pre) in the pretreatment liquid is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of the drying property and ejection reliability of the pretreatment liquid, however, it is preferably 5.0% by mass or more and 60.0% by mass or less, and more preferably 10.0% by mass or more and 30.0% by mass or less, based on the total amount of the pretreatment liquid.

<<Surfactant (pre)>>
In this specification, the surfactant contained in the pretreatment liquid may be referred to as a “surfactant (pre).” Note that the surfactant (pre) is different from the surfactant contained in the ink.
The surfactant (pre) is not particularly limited and can be appropriately selected depending on the purpose, and any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used. These can be used alone or in combination of two or more.

- Silicone surfactant -
The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable that the silicone surfactant does not decompose even at high pH (pH 11 to 14).
Examples of silicone surfactants that do not decompose even at high pH (pH 11 to 14) include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, side-chain both-end modified polydimethylsiloxane, etc. Among these, from the viewpoints of improving hydrophilicity and increasing solubility in water, those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are preferred.
Furthermore, a polyether-modified silicone surfactant can also be used as the silicone surfactant. Examples of the polyether-modified silicone surfactant include a compound in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane.

The fluorosurfactant is not particularly limited and can be selected appropriately depending on the purpose, but the same fluorosurfactant as the fluorosurfactant contained in the ink can be used, and the preferred embodiments are also the same.

The amphoteric surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples of the amphoteric surfactant include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.

The nonionic surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples of the nonionic surfactant include polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkylamide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and ethylene oxide adduct of acetylene alcohol.

The anionic surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, and polyoxyethylene alkyl ether sulfate.

<<Other Components (B)>>
The other component (B) is not particularly limited as long as it does not impair the effects of the present invention and can be appropriately selected depending on the purpose. Examples of the other component (B) include antifoaming agents, antiseptic and antifungal agents, and rust inhibitors.

- Defoaming agent -
The defoaming agent may be the same as the foam suppressor (defoamer) described in the above section <Other components (A)>. The defoaming agent is not particularly limited and may be appropriately selected depending on the purpose. Examples of the defoaming agent include silicone defoamers, polyether defoamers, and fatty acid ester defoamers. Among these, silicone defoamers are preferred because of their excellent foam breaking effect.
These may be used alone or in combination of two or more.

- Antiseptic and fungicide -
As the preservative and antifungal agent, the same preservative and antifungal agent as described in the above section <Other components (A)> can be used.

-anti-rust-
As the rust inhibitor, the same rust inhibitors as those described in the section "Other Components (A)" above can be used.

<Recording media>
The recording medium to which the ink and the pretreatment liquid are applied is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include plain paper, glossy paper, special paper, fabric, film, OHP sheet, and general-purpose printing paper. Among these, the recording medium is preferably a low-permeability recording medium such as commercial printing paper, a non-permeability recording medium for signage, or fabric, from the viewpoint that color bleeding and beading are likely to occur and the effect obtained by applying the ink set is remarkable. Note that the fabric is a recording medium that is likely to have a large amount of white ink and color ink applied thereto, and therefore is likely to have color bleeding and beading.

As an example of the recording medium, a fabric will be described below. In this specification, the term "fabric" refers to fibers in the form of woven fabric, knitted fabric, nonwoven fabric, or the like.
The fibers are preferably organic fibers such as synthetic fibers, semi-synthetic fibers, regenerated fibers, and natural fibers.

Examples of the synthetic fibers include fibers of polyester, polyamide, acrylic, polyolefin, polyvinyl alcohol, polyvinyl chloride, polyurethane, and polyimide.
The semi-synthetic fibers include, for example, acetate, diacetate, and triacetate fibers.
Examples of the regenerated fibers include polynosic, rayon, lyocell, and cupra.
Examples of the natural fibers include cotton, linen, silk, and wool.

Among the fibers that make up the fabric, synthetic fibers such as polyester are more susceptible to color bleeding and beading than natural fibers such as cotton, and it is also more difficult to keep the white ink on the surface. However, the ink set of the present invention is advantageous in that it acts favorably on such fabrics, suppresses color bleeding and beading, and also makes it possible to keep the white ink on the surface.

The fabric is preferably a dark color colored fabric in which the fibers used in the fabric have a coloring agent such as a pigment or dye chemically or physically held inside or on the surface. When the fabric is a dark color, a white base may be formed between the fabric and the color image in order to improve the color development of the color image formed on the fabric. In other words, it is preferable to use the ink set having the white ink and the color ink.

In this specification, the term "dark colored fabric" refers to a fabric that satisfies the range of 60>L* when the lightness (L ^* ) of the fabric is measured using a spectrophotometer (e.g., X-rite eXact, manufactured by X-Rite Corporation), and is preferably a fabric that satisfies the range of 50>L ^* , more preferably a fabric that satisfies the range of 40>L ^* , even more preferably a fabric that satisfies the range of 30>L ^* , and particularly preferably a fabric that satisfies the range of 20> ^{L* .}

<Ink cartridge>
The ink set of the present invention may be contained in an ink cartridge. The ink cartridge contains the ink set of the present invention and has the ink set and a container, and may further have other members as necessary.
The ink cartridge is advantageous in that there is no need to directly touch the ink when replacing the ink, and there is no need to worry about staining the hands or clothes, and the ink can be prevented from being contaminated by foreign matter such as dust.

The ink cartridge may contain the ink set as an integrated unit, or may contain the white ink and the color inks separately. In addition, when the ink set has a plurality of the white inks and the color inks, the ink cartridge may contain each of the white inks and the color inks as an integrated unit, or may contain each of the color inks separately.

There are no particular limitations on the container, and its shape, structure, size, material, etc. can be appropriately selected depending on the purpose. For example, a container having an ink bag formed from an aluminum laminate film, a resin film, etc. is preferable.

There are no particular limitations on the method for manufacturing the ink cartridge, and it can be manufactured using any known method.

The ink cartridge is preferably configured so that the ink set contained in the ink bag or other container is further contained in a cartridge case (e.g., a plastic case) and is removably attached to an image forming device for use. This simplifies the refilling and replacement of ink and improves operability.

(Image forming apparatus and image forming method)
The image forming apparatus of the present invention has a white ink applying means and a color ink applying means, and may also have a white ink storage means, a color ink storage means, and other means as necessary.
The image forming method of the present invention has a white ink applying step and a color ink applying step, and may have other steps as necessary.
The image forming method is suitably carried out by the image forming apparatus.

<White ink applying unit and white ink applying process>
The white ink applying unit is a unit that applies white ink to a recording medium.
The white ink applying step is a step of applying white ink to a recording medium.
The white ink applying step is suitably carried out by the white ink applying unit.
The recording medium is not particularly limited and can be appropriately selected depending on the purpose, but the recording mediums described in the above <Recording Medium> can be used, and the same applies to preferred embodiments.

The method of applying the white ink is not particularly limited and can be appropriately selected depending on the purpose, and examples include a discharge method and a coating method. Among these, the method of applying the white ink is preferably a discharge method, and more preferably an inkjet discharge method.

The ejection method is not particularly limited and can be appropriately selected depending on the purpose. Examples include a method using a piezoelectric actuator, a method using thermal energy, a method using an actuator that utilizes electrostatic force, or a method using a continuous-ejection charge-control type head.

The amount of the white ink applied to the recording medium varies greatly depending on the type of the recording medium, but from the viewpoint of improving image quality and drying properties, the amount is preferably 1 g/ ^m2 or more and 500 g/ ^m2 or less, and more preferably 5 g/ ^m2 or more and 400 g/ ^m2 or less.
Furthermore, when the fabric is used as the recording medium, the weight of the fabric is preferably 50 g/ ^m2 or more and 500 g/ ^m2 or less, more preferably 100 g/ ^m2 or more and 400 g/ ^m2 or less, and even more preferably 150 g/ ^m2 or more and 300 g/ ^m2 or less.

<Color ink application unit and color ink application process>
The color ink applying unit is a unit that applies color ink to the area of the recording medium to which the white ink has been applied.
The color ink applying step is a step of applying color ink to the area of the recording medium to which the white ink has been applied.
The color ink applying step is suitably carried out by the color ink applying unit.

The method of applying the color ink is not particularly limited and can be appropriately selected depending on the purpose. For example, the same method as the method of applying the white ink can be used, and the preferred embodiments are also the same.

The amount of the color ink applied to the recording medium varies greatly depending on the type of the recording medium, but from the viewpoint of improving image quality and drying properties, it is preferably 1 g/ ^m2 or more and 50 g/ ^m2 or less, and more preferably 5 g/ ^m2 or more and 30 g/ ^m2 or less.
When the fabric is used as the recording medium, the weight of the fabric is preferably 5 g/m ² or more and 50 g/m ² or less, and more preferably 10 g/m ² or more and 30 g/m ² or less.

<White ink storage means and color ink storage means>
The white ink containing means is a means for containing white ink.
The color ink containing means is a means for containing color inks.
The white ink containing means and the color ink containing means may be the ink cartridges.
The white ink contained in the white ink containing means is a white ink contained in the ink set of the present invention.
The color inks contained in the color ink containing means are the color inks contained in the ink set of the present invention.

In the image forming method, it is preferable from the viewpoint of productivity that the time from when the white ink is applied to the recording medium until the color ink is applied to the area of the recording medium to which the white ink has been applied (i.e., between the white ink application process and the color ink application process) is as short as possible. Note that "the time from when the white ink is applied to the recording medium until the color ink is applied to the area of the recording medium to which the white ink has been applied" refers to the time required for the white ink to dry (aggregate and thicken). In general image forming apparatuses (methods), some are provided with a heating means (process) for heating and drying the white ink in order to suppress color bleeding and beading caused by insufficient drying of the white ink. However, with the ink set of the present invention, even without the heating means (process), the color ink is applied to the area of the recording medium to which the white ink has been applied after the white ink has been applied, thereby suppressing color bleeding and beading.

<Other Means and Other Steps>
The other means are not particularly limited and may be appropriately selected depending on the purpose. Examples of the other means include a pretreatment liquid storage means, a pretreatment liquid application means, and a heating means.
The other steps are not particularly limited and can be appropriately selected depending on the purpose. Examples of the other steps include a pretreatment liquid application step and a heating step.

<<Pre-treatment liquid storage means>>
The pretreatment liquid containing means is a means for containing a pretreatment liquid.
The pretreatment liquid contained in the pretreatment liquid containing means is the pretreatment liquid contained in the ink set of the present invention.

<<Pre-treatment liquid application unit and pre-treatment liquid application step>>
The pretreatment liquid applying device applies the pretreatment liquid to an area of the recording medium to which the white ink is to be applied, before the white ink is applied.
The pretreatment liquid application step is a step of applying a pretreatment liquid to an area of the recording medium onto which the white ink is to be applied, prior to the white ink application step.
The pretreatment liquid application step is suitably carried out by the pretreatment liquid application unit.

When the image forming apparatus of the present invention has the pretreatment liquid storage means and the pretreatment liquid application means, the white ink application means can be rephrased as a means for applying the white ink to an area of the recording medium to which the pretreatment liquid has been applied.
Furthermore, in the case where the image forming method includes a pretreatment liquid applying step, the white ink applying step can be rephrased as a step of applying the white ink to an area of the recording medium to which the pretreatment liquid has been applied.

The method of applying the pretreatment liquid is not particularly limited and can be appropriately selected depending on the purpose. For example, the same method as the method of applying the white ink can be used, and the preferred embodiments are also the same.

The amount of the pretreatment liquid applied to the recording medium varies greatly depending on the type of the recording medium. From the viewpoint of improving image quality and drying properties, the amount is preferably 0.1 g/ ^m2 or more and 500 g/ ^m2 or less, and more preferably 1 g/ ^m2 or more and 400 g/ ^m2 or less.
Furthermore, when the fabric is used as the recording medium, the weight of the fabric is preferably 100 g/ ^m2 or more and 500 g/ ^m2 or less, more preferably 200 g/ ^m2 or more and 500 g/ ^m2 or less, and even more preferably 300 g/ ^m2 or more and 400 g/ ^m2 or less.

<<Heating means and heating process>>
The heating unit is a unit that heats various liquids, such as the white ink, the color ink, or the pretreatment liquid, that are applied to the recording medium.
The heating step is a step of heating various liquids, such as the white ink, the color ink, or the pretreatment liquid, that have been applied to the recording medium.
The heating step is preferably carried out by the heating means.

The heating means is not particularly limited and can be appropriately selected from known heating means, such as a roll heater, drum heater, hot air generator, heat press device, etc.

It is preferable that the image forming method does not include a heating step of heating the recording medium to which the white ink has been applied between the white ink application step and the color ink application step as described above.
Similarly, it is preferable that the image forming apparatus does not have a heating unit between the white ink applying unit and the color ink applying unit, for heating the recording medium onto which the white ink has been applied.

The image forming apparatus of the present invention will be described in detail below with reference to Figures 1 to 3, but the present invention is not limited to this.

Figure 1 is a schematic perspective view showing an example of an image forming apparatus of the present invention. Figure 2 is a schematic perspective view showing an example of a storage means in the image forming apparatus of the present invention.

The image forming apparatus 400 shown in FIG. 1 is an image forming apparatus having a serial type inkjet head. A mechanism section 420 is provided inside the exterior 401 of the image forming apparatus 400. The storage sections 411 in the pretreatment liquid storage means 410p for the pretreatment liquid, the white ink storage means 410w for the white ink, the black ink storage means 410k for the black ink, and the cyan ink storage means 410c for the cyan ink are formed of a packaging material such as an aluminum laminate film. The storage sections 411 are stored in a storage container case 414 made of plastic, for example. As a result, each storage means 410 is used as an ink cartridge.

On the other hand, a cartridge holder 404 is provided at the rear side of the opening when a cover 401c of the main body of the image forming apparatus 400 is opened. Each of the containers 410 (p, w, k, and c) is detachably attached to the cartridge holder 404. This allows the discharge port 413 of each of the containers 410 (p, w, k, and c) to communicate with the inkjet ejection head 434 via each supply tube 436, making it possible to eject the pretreatment liquid and each ink from the inkjet ejection head 434 onto a recording medium.
In the image forming apparatus 400 shown in FIG. 1, the pretreatment liquid is applied to the recording medium by an inkjet ejection method, but the method of applying the pretreatment liquid is not limited to this, and the above-mentioned application methods can be used.

The image forming apparatus 400 may have a heating means for heating various liquids such as white ink, color ink, or pretreatment liquid applied to the recording medium, but it is preferable that the image forming apparatus 400 does not have a heating means for heating the recording medium to which the white ink has been applied between the application of the white ink and the application of the color ink. Such a heating means is provided for the purpose of suppressing color bleeding and beading caused by insufficient drying of the white ink by heating and drying the white ink, but the ink set of the present invention can suppress color bleeding and beading even without a heating means.

The image forming apparatus 400 may have a liquid delivery device 435 that delivers ink therein. A known means may be used to deliver ink in the liquid delivery device, such as a tubing pump (also called a tube pump or roller pump), a diaphragm pump, a piston pump, or a gear pump.

Here, an example of the image forming apparatus of the present invention is shown using FIG. 3. FIG. 3 is a schematic diagram showing another example of the image forming apparatus of the present invention. Note that the ink application process (white ink application process and color ink application process) and the pretreatment liquid application process in the image forming method of the present invention may be performed by the same printing device, or may be performed by separate printing devices.

The printing apparatus 100 in FIG. 3 includes a pretreatment liquid applying unit 110, an ink applying unit 120, a posttreatment liquid applying unit 130, a drying unit 140, and a transport unit 150. The pretreatment liquid applying unit 110 applies the pretreatment liquid to the recording medium M.
It is to be noted that it is possible to omit the pre-treatment liquid application unit 110, the post-treatment liquid application unit 130, the drying unit 140, and the transport unit 150. In particular, in the case of the present invention, the drying unit 140 does not have to be provided.
The pre-treatment liquid application unit 110, the ink application unit 120, and the post-treatment liquid application unit 130 may include a pre-treatment liquid storage unit 110a, an ink storage unit 120a, and a post-treatment liquid storage unit 130a. Each storage unit stores the pre-treatment liquid, the ink, and the post-treatment liquid to be applied to the recording medium in the application unit.

The method for applying the pretreatment liquid is not particularly limited, but examples thereof include an inkjet method, a roller coating method, a blade coating method, a gravure coating method, a gravure offset coating method, a bar coating method, a roll coating method, a knife coating method, an air knife coating method, a comma coating method, a U comma coating method, an AKKU coating method, a smoothing coating method, a microgravure coating method, a reverse roll coating method, a four to five roll coating method, a dip coating method, a curtain coating method, a slide coating method, and a die coating method.
The pretreatment liquid application unit 110 may be omitted because printing may be performed using a printing device after the pretreatment liquid has been manually applied to the recording medium in advance by a bar coating method or the like.

The recording medium M used for recording is not particularly limited, but examples include plain paper, glossy paper, special paper, cardboard, cloth, film, overhead projector sheets, general-purpose printing paper, etc.

The ink applying unit 120 applies an inkjet ink to the surface of the recording medium M to which the pretreatment liquid has been applied. As the ink applying unit 120, for example, a known inkjet head can be used.
The ink application unit 120 may be a head that ejects ink of any color, and for example, as necessary, heads that eject inks of Y (yellow), M (magenta), C (cyan), K (black), W (white), etc. may be provided.

The post-treatment liquid application unit 130 only needs to be able to apply the post-treatment liquid to the area on the surface of the recording medium M to which the inkjet ink has been applied, and for example, in addition to an inkjet head, a spray, a roller, or the like can be used.
The post-treatment liquid application unit 130 may be omitted.

Methods for applying the post-treatment liquid are not particularly limited, but examples include inkjet method, roller coating method, blade coating method, gravure coating method, gravure offset coating method, bar coating method, roll coating method, knife coating method, air knife coating method, comma coating method, U comma coating method, AKKU coating method, smoothing coating method, microgravure coating method, reverse roll coating method, 4-5 roll coating method, dip coating method, curtain coating method, slide coating method, and die coating method.

The drying section 140 dries the recording medium M to which the post-treatment liquid has been applied. If there is no post-treatment liquid application section, the drying section 140 may be omitted.
The drying section 140 may heat and dry the recording medium M to which the post-treatment liquid has been applied using hot air, infrared rays, microwaves, a roll heater, a heat press, etc., or the recording medium M to which the post-treatment liquid has been applied may be allowed to dry naturally without operating the drying section 140.

The conveying section 150 conveys the recording medium M.
The conveying unit 150 is not particularly limited as long as it is capable of conveying the recording medium M, but examples of the conveying unit 150 include a conveying belt and a platen.

The printing device 100 may further include a fixing unit that heats and fixes the image formed on the recording medium M. The fixing unit is not particularly limited, but examples thereof include a fixing roller and a heat press.

When a desktop printer is used as a printing device, one aspect of the pre-treatment liquid application section and post-treatment liquid application section is to add a liquid storage section and a liquid ejection head that contain the pre-treatment liquid and the post-treatment liquid, as in the case of inks such as black (K), cyan (C), magenta (M), yellow (Y), and white (W), and eject the pre-treatment liquid and the post-treatment liquid by an inkjet recording method.

The ink and treatment liquid can be used in a wide variety of ways, not limited to inkjet recording. In addition to inkjet recording, other methods include blade coating, gravure coating, bar coating, roll coating, dip coating, curtain coating, slide coating, die coating, and spray coating.

The present invention will be specifically explained below with reference to preparation examples, manufacturing examples, examples, and comparative examples, but the present invention is not limited to these preparation examples, manufacturing examples, and examples.

<Preparation of pigment dispersion or pigment-containing polymer fine particle dispersion>
Pigment dispersions or pigment-containing polymer fine particle dispersions were prepared by the methods described in Preparation Examples 1 to 9 below.

(Preparation Example 1: Preparation of Surface-Modified Black Pigment Dispersion)
100 g of BLACK PEARLS (registered trademark) 1000 (carbon black having a BET specific surface area of 343 ^m2 /g and a dibutyl phthalate absorption (DBPA) of 105 mL/100 g, manufactured by Cabot Corporation), 100 mmol of sulfanilic acid (manufactured by Hayashi Pure Chemical Industries, Ltd.), and 1 L of highly pure ion-exchanged water were mixed at room temperature (23°C ± 0.5°C) using a Silverson (registered trademark) mixer (laboratory mixer, manufactured by Silverson Nippon) at 6,000 rpm to obtain a slurry.
Next, 100 mmol of nitric acid (1.42, manufactured by Honeywell-Fluka) was added to the resulting slurry, and after a further 30 minutes, 100 mmol of sodium nitrite (manufactured by Hayashi Pure Chemical Industries, Ltd.) dissolved in 10 mL of ion-exchanged high-purity water was slowly added. The mixture was then heated to 60° C. with stirring and reacted for 1 hour to obtain a modified pigment in which sulfanilic acid was added to carbon black.
Next, the pH was adjusted to 9 with a 10% by mass tetrabutylammonium hydroxide methanol solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and after 30 minutes, a modified pigment dispersion was obtained. Next, this modified pigment dispersion and ion-exchanged highly pure water were used to perform ultrafiltration using a dialysis membrane, and further ultrasonic dispersion was performed to obtain a surface-modified black pigment dispersion containing 20% by mass of pigment solid content.
The surface treatment level of the pigment in the obtained surface-modified black pigment dispersion was 0.75 mmol/g, and the cumulative 50% volume particle diameter D50 was 120 nm as measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.).

(Preparation Example 2: Preparation of Surface-Modified Magenta Pigment Dispersion)
1 kg of a pigment dispersion SMART Magenta 3122BA (a surface-treated dispersion of C.I. Pigment Red 122, pigment solid content 14.5% by mass, manufactured by SENSIENT) was subjected to acid precipitation with a 0.1 N aqueous hydrochloric acid solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.).
Next, the pH was adjusted to 9 with a 10% by mass aqueous solution of tetraethylammonium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and after 30 minutes, a modified pigment dispersion containing a pigment bonded to at least one aminobenzoic acid group or tetraethylammonium aminobenzoate salt was obtained. The modified pigment dispersion containing a pigment bonded to at least one aminobenzoic acid group or tetraethylammonium aminobenzoate salt and ion-exchanged highly pure water were subjected to ultrafiltration using a dialysis membrane, and further subjected to ultrasonic dispersion to obtain a surface-modified magenta pigment dispersion containing 20% by mass of pigment solid content.
The resulting surface-modified magenta pigment dispersion was measured using a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to have a cumulative 50% volume particle diameter D50 of 104 nm.

(Preparation Example 3: Preparation of Surface-Modified Cyan Pigment Dispersion)
1 kg of a pigment dispersion SMART Cyan 3154BA (C.I. Pigment Blue 15:4 surface-treated dispersion, pigment solid content 14.5% by mass, manufactured by SENSIENT) was subjected to acid precipitation with a 0.1 N aqueous hydrochloric acid solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.).
Next, the pH was adjusted to 9 with a 40% by mass benzyltrimethylammonium hydroxide methanol solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and after 30 minutes, a modified pigment dispersion containing a pigment bonded to at least one aminobenzoic acid group or aminobenzoic acid benzyltrimethylammonium salt was obtained. The modified pigment dispersion containing a pigment bonded to at least one aminobenzoic acid group or aminobenzoic acid benzyltrimethylammonium salt and ion-exchanged high purity water were used to perform ultrafiltration using a dialysis membrane, and further ultrasonic dispersion was performed to obtain a surface-modified cyan pigment dispersion containing 20% by mass of pigment solid content.
The resulting surface-modified cyan pigment dispersion was measured using a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to have a cumulative 50% volume particle diameter D50 of 116 nm.

(Preparation Example 4: Preparation of Surface-Modified Yellow Pigment Dispersion)
1 kg of pigment dispersion SMART Yellow 3074BA (C.I. Pigment Yellow 74 surface-treated dispersion, pigment solid content 14.5% by mass, manufactured by SENSIENT) was adjusted to pH 9 with 10% by mass tetrabutylammonium hydroxide methanol solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and after 30 minutes, a modified pigment dispersion containing a pigment bonded to at least one aminobenzoic acid group or aminobenzoic acid tetrabutylammonium salt was obtained. The modified pigment dispersion containing a pigment bonded to at least one aminobenzoic acid group or aminobenzoic acid tetrabutylammonium salt and ion-exchanged high purity water were used to perform ultrafiltration using a dialysis membrane, and further ultrasonic dispersion was performed to obtain a surface-modified yellow pigment dispersion containing 20% pigment solid content.
The resulting surface-modified yellow pigment dispersion was measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to have a cumulative 50% volume particle diameter D50 of 145 nm.

(Preparation Example 5: Preparation of Magenta Pigment-Containing Polymer Microparticle Dispersion)
After thoroughly replacing the air in a 1 L flask equipped with a mechanical stirrer, a thermometer, a nitrogen gas inlet tube, a reflux tube, and a dropping funnel, 11.2 g of styrene monomer (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 2.8 g of acrylic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 12.0 g of lauryl methacrylate (manufactured by BASF Corporation), 4.0 g of polyethylene glycol dimethacrylate (manufactured by Sigma-Aldrich Japan Co., Ltd.), 4.0 g of styrene macromer (manufactured by Toagosei Co., Ltd.), and 0.4 g of mercaptoethanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) were mixed in the flask and the temperature was raised to 65° C. Next, a mixed solution of 100.8 g of styrene, 25.2 g of acrylic acid, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol dimethacrylate, 60.0 g of hydroxylethyl methacrylate (manufactured by Nippon Shokubai Co., Ltd.), 36.0 g of styrene macromer, 3.6 g of mercaptoethanol, 2.4 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (95%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 18 g of methyl ethyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dropped into the flask over 2.5 hours. After the dropwise addition, a mixed solution of 0.8 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (95%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After stirring at 65° C. for 1 hour, 0.8 g of 2,2′-azobis(2,4-dimethylvaleronitrile) was added and further stirred for 1 hour. After the reaction was completed, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of polymer solution A with a concentration of 50% by mass.
Next, 28 g of polymer solution A, 42 g of C.I. Pigment Red 122 (manufactured by BASF), 13.6 g of 1 mol/L potassium hydroxide aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 20 g of methyl ethyl ketone, and 13.6 g of ion-exchanged water were thoroughly stirred and then kneaded using a roll mill. The obtained paste (about 117 g) was added to 200 g of pure water, thoroughly stirred, and then methyl ethyl ketone and water were distilled off using an evaporator. In order to further remove coarse particles, this dispersion was pressure-filtered with a polyvinylidene fluoride membrane filter (manufactured by Sigma-Aldrich Japan Co., Ltd.) with an average pore size of 5.0 μm to obtain a magenta pigment-containing polymer microparticle dispersion containing 15% by mass of pigment solids and 20% by mass of total solids.
The obtained magenta pigment-containing polymer fine particle dispersion was measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to have a cumulative 50% volume particle diameter D50 of 127 nm.

(Preparation Example 6: Preparation of cyan pigment-containing polymer particle dispersion)
In Preparation Example 5, except that the pigment C.I. Pigment Red 122 was changed to a phthalocyanine pigment (C.I. Pigment Blue 15:3, manufactured by Dainichi Seika Chemicals Co., Ltd.), a cyan pigment-containing polymer microparticle dispersion containing 15% by mass of pigment solids and 20% by mass of total solids was prepared in the same manner as in Preparation Example 5.
The polymer fine particles in the obtained cyan pigment-containing polymer fine particle dispersion were measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to have a cumulative 50% volume particle diameter D50 of 93 nm.

(Preparation Example 7: Preparation of yellow pigment-containing polymer particle dispersion)
A yellow pigment-containing polymer microparticle dispersion containing 15% by mass of pigment solids and 20% by mass of total solids was prepared in the same manner as in Preparation Example 5, except that the pigment C.I. Pigment Red 122 in Preparation Example 5 was changed to a bisazo yellow pigment (C.I. Pigment Yellow 155, manufactured by DIC Corporation).
The polymer fine particles in the obtained yellow pigment-containing polymer fine particle dispersion were measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to have a cumulative 50% volume particle diameter D50 of 76 nm.

(Preparation Example 8: Preparation of black pigment-containing polymer particle dispersion)
A black pigment-containing polymer microparticle dispersion containing 15% by mass of pigment solids and 20% by mass of total solids was prepared in the same manner as in Preparation Example 5, except that the pigment C.I. Pigment Red 122 in Preparation Example 5 was changed to carbon black (FW100, manufactured by Degussa).
The polymer fine particles in the obtained black pigment-containing polymer fine particle dispersion were measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to have a cumulative 50% volume particle diameter D50 of 104 nm.

(Preparation Example 9: Preparation of polymer-dispersed white pigment dispersion)
55.6 g of DISPERBYK-2081 (manufactured by BYK Japan Co., Ltd.) copolymer solution, 517 g of titanium oxide (TITONE R-25, manufactured by Sakai Chemical Industry Co., Ltd.), 50 g of β-methoxy-N,N-dimethylpropionamide (KJCMPA (registered trademark)-100, manufactured by Kj Chemicals Co., Ltd.), and 377.4 g of ion-exchanged water were thoroughly stirred and then charged into a bead mill (Dyno Mill) and dispersed until the cumulative 50% volume particle diameter D50 was 300 nm or less. In order to further remove coarse particles, this dispersion was pressure-filtered with a polyvinylidene fluoride membrane filter (manufactured by Sigma-Aldrich Japan Co., Ltd.) having an average pore size of 5.0 μm to obtain a polymer-dispersed white pigment dispersion containing 50% by mass of white pigment solid content.
The pigment particles in the obtained polymer-dispersed white pigment dispersion were measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to have a cumulative 50% volume particle diameter D50 of 283 nm.

<Ink Production>
White inks and color inks were produced by the methods described in Production Examples 1 to 78 below.

(Production Example 1: Production of Ink 1)
A vessel equipped with a stirrer was charged with 0.20 parts by mass of 2-amino-2-ethyl-1,3-propanediol (97%, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 0.30 parts by mass of 2,5,8,11-tetramethyldodecane-5,8-diol, 2.00 parts by mass of 2-ethyl-1,3-hexanediol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 6.00 parts by mass of 1,2-hexanediol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 30.00 parts by mass of propylene glycol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and 0.10 parts by mass of Capstone FS-3100 (fluorosurfactant, manufactured by Chemours Corporation), and the mixture was mixed and stirred for 30 minutes. Next, 0.05 parts by mass of an antiseptic and antifungal agent (PROXEL (registered trademark) GXL) and 30.00 parts by mass of the surface-modified black pigment dispersion of Preparation Example 1 were added, and the mixture was mixed and stirred for 20 minutes. Next, 16.67 parts by mass of (1) Takelac WS-6021 as a urethane resin, 3.33 parts by mass of (2) Takelac W-6020 as a urethane resin, and highly pure water in an amount to make the total 100 parts by mass were added, and the mixture was mixed and stirred for 60 minutes. Next, the resulting mixture was pressure-filtered through a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust, thereby obtaining ink 1.

(Production Examples 2 to 78: Production of Inks 2 to 78)
Inks 2 to 78 were obtained in the same manner as in Production Example 1, except that the ink formulations in Production Example 1 were changed to the materials and amounts shown in Tables 1 to 16 below.
In Tables 1 to 16 below, the unit of content of each material is "mass %", and the content is indicated as total amount, not solid content or active ingredient amount.

Details of the various materials shown in Tables 1 to 16 below are as follows:

--Coloring material--
Polymer-dispersed white pigment dispersion: AC-AW62 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., pigment solid content 50% by mass)

--First urethane resin--
・Superflex 420: polyurethane dispersion, Tg; -10°C, volume average particle size; 10 nm, solid content 32% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 460: polyurethane dispersion, Tg; -21°C, volume average particle size; 40 nm, solid content 38% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 470: polyurethane dispersion, Tg; -31°C, volume average particle size; 50 nm, solid content 38% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 500M: polyurethane dispersion, Tg; -39°C, volume average particle size; 140 nm, solid content 45% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 740: polyurethane dispersion, Tg; -34°C, volume average particle size; 200 nm, solid content 40% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Takelac W-6110: polyurethane dispersion, Tg; -20°C, volume average particle size; 90 nm, solid content 32% by mass, manufactured by Mitsui Chemicals, Inc. Superflex 300: polyurethane dispersion, Tg; -42°C, volume average particle size; 70 nm, solid content 30% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. U-coat UWS-145: Tg; -45°C, volume average particle size; 20 nm, manufactured by Sanyo Chemical Industries, Ltd.
Takelac WS-6021: polyurethane dispersion, Tg; -60°C, volume average particle size; 90 nm, solid content 30% by mass, manufactured by Mitsui Chemicals, Inc.

--Second urethane resin--
・Superflex 150: polyurethane dispersion, Tg; 40°C, volume average particle size; 30 nm, solid content 30 mass%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 170: polyurethane dispersion, Tg; 75°C, volume average particle size; 10 nm, solid content 33 mass%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 830HS: polyurethane dispersion, Tg; 68°C, volume average particle size; 10 nm, solid content 27 mass%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 820: polyurethane dispersion, Tg; 46°C, volume average particle size; 30 nm, solid content 30 mass%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 870: polyurethane dispersion, Tg; 78°C, volume average particle size; 30 nm, solid content 30 mass%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Takelac W-5661: polyurethane dispersion, Tg; 70°C, volume average particle size; 30 nm, solid content 35 mass%, manufactured by Mitsui Chemicals, Inc. Takelac W-6020: polyurethane dispersion, Tg; 90° C., volume average particle size; 80 nm, solid content 30% by mass, manufactured by Mitsui Chemicals, Inc.

--Other resins--
Superflex 150HS: polyurethane dispersion, Tg; 32°C, volume average particle size; 80 nm, solid content 38% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Takelac W-6061: polyurethane dispersion, Tg; 25°C, volume average particle size; 100 nm, solid content 30% by mass, manufactured by Mitsui Chemicals, Inc. Boncoat VF1060: acrylic emulsion, Tg; -10°C, solid content 50% by mass, manufactured by DIC Corporation

--Organic solvent--
Glycerin: bp; 290°C/760mmHg, equilibrium moisture content 49wt%, Fujifilm Wako Pure Chemical Industries, Ltd. Diglycerin: bp; 265-270°C/15mmHg, equilibrium moisture content 38wt%, Sakamoto Yakuhin Kogyo Co., Ltd. 1,3-butanediol: bp; 207°C/760mmHg, equilibrium moisture content 35wt%, Fujifilm Wako Pure Chemical Industries, Ltd. Ethylene glycol: bp; 197.3°C/760mmHg, equilibrium moisture content 44wt%, Fujifilm Wako Pure Chemical Industries, Ltd. Propylene glycol: bp; 188°C/760mmHg, Fujifilm Wako Pure Chemical Industries, Ltd. 3-Methyl-1,3-butanediol: bp; 203°C/760mmHg, Fujifilm Wako Pure Chemical Industries, Ltd.・1,2-butanediol: bp; 193°C/760mmHg, manufactured by Tokyo Chemical Industry Co., Ltd. ・1,2-hexanediol: bp; 223°C/760mmHg, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. ・Diethylene glycol monoethyl ether: bp; 202°C/760mmHg, manufactured by Tokyo Chemical Industry Co., Ltd. ・Triethylene glycol monobutyl ether: bp; 278°C/760mmHg, manufactured by Tokyo Chemical Industry Co., Ltd. ・2-ethyl-1,3-hexanediol: bp; 249°C/760mmHg, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. ・2,2,4-trimethyl-1,3-pentanediol: bp; 232°C/760mmHg, manufactured by Tokyo Chemical Industry Co., Ltd.

--Surfactants--
TEGO (registered trademark) Wet 270: polyether-modified siloxane compound, manufactured by Evonik, 100% active ingredient
Silface SAG503A: Polyether modified siloxane compound, manufactured by Nissin Chemical Industry Co., Ltd., 100% active ingredient
Surfynol 104E: 2,4,7,9-tetramethyl-5-decyne-4,7-diol, manufactured by Nissin Chemical Industry Co., Ltd., active ingredient 50%
Capstone FS-3100: Polyoxyethylene perfluoroalkyl ether, manufactured by Chemours, 100% active ingredient
・Emulgen LS-106: Polyoxyalkylene alkyl ether, manufactured by Kao Corporation, 100% active ingredient
・KF-353: Polyether modified silicone oil, Shin-Etsu Chemical Co., Ltd.

--Anti-septic and anti-fungal agent--
PROXEL (registered trademark) GXL: Antiseptic and antifungal agent with 1,2-benzothiazolin-3-one as the main ingredient (manufactured by Avecia, contains 20% dipropylene glycol)

--pH adjuster--
2-Amino-2-ethyl-1,3-propanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

<Physical properties of white ink and color ink>
For Inks 1 to 78 obtained in Production Examples 1 to 78, various physical properties such as viscosity, pH, and static surface tension were measured as described below, and the ejection stability (continuous ejection, filter permeability) and storage stability were evaluated. The results are shown in Tables 17 to 18.

-viscosity-
The viscosities of inks 1 to 78 obtained in Production Examples 1 to 78 were measured at 25° C. using a viscometer (RE85L, manufactured by Toki Sangyo Co., Ltd.).

-pH-
The pH of each of the inks 1 to 78 obtained in Production Examples 1 to 78 was measured at 25° C. using a pH meter (HM-30R type, manufactured by DKK-TOA Corporation).

-Static surface tension-
The static surface tension at 25° C. of Inks 1 to 78 obtained in Production Examples 1 to 78 was measured by the plate method (Wilhelmy method) using an automatic surface tensiometer (DY-300, manufactured by Kyowa Interface Science Co., Ltd.).

-Continuous discharge-
In an environment of 23±1° C., 1 L of each of the inks 1 to 78 obtained in Production Examples 1 to 78 was passed from the ink cartridge of an inkjet printer (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) to the ejection head of each color. Immediately after, using the inkjet printer, 200 consecutive sheets of a chart in which 80% of the area of an A4 size paper sheet created using Microsoft Word 2000 was filled with a solid image were printed on MyPaper (manufactured by Ricoh Co., Ltd.). Furthermore, the nozzle check chart after printing was used to evaluate the ejection disturbance of each ejection nozzle according to the following evaluation criteria.
The print mode used was the driver that came with the printer, with the plain paper user settings changed from "plain paper - standard fast" to "no color correction." For practical purposes, an evaluation standard of "B" or higher is required.
〔Evaluation criteria〕
A: In the nozzle check chart, the area where discharge disturbances are occurring is less than 1% of the total. B: In the nozzle check chart, the area where discharge disturbances are occurring is 1% or more and less than 3% of the total. C: In the nozzle check chart, the area where discharge disturbances are occurring is 3% or more and less than 5% of the total, or the number of non-discharging nozzles is less than 1% of the total. D: In the nozzle check chart, the area where discharge disturbances are occurring is 5% or more of the total, or the number of non-discharging nozzles is 1% or more of the total.

- Filter permeability -
In an environment of 23±1° C., 1 L of inks 1 to 78 obtained in Production Examples 1 to 78 were passed through a filter in an inkjet printing device (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) with a filterability of 10 μm, while being pumped with a tubing pump (model number TP-1973D, manufactured by Asone Co., Ltd.). The initial ink flow rate was 0.167 g/sec. The mass per minute immediately after the start of this liquid permeability and the mass per minute immediately before the end of flowing 1 L were measured to determine the weight loss rate, which was then evaluated according to the following evaluation criteria. For practical purposes, an evaluation criterion of "C" or higher is required.
〔Evaluation criteria〕
A: The weight loss rate is less than 1%. B: The weight loss rate is 1% or more and less than 5%. C: The weight loss rate is 5% or more and less than 10%. D: The weight loss rate is 10% or more and less than 15%. E: The weight loss rate is 15% or more.

-Storage stability-
50 g of each of the inks 1 to 78 obtained in Production Examples 1 to 78 was weighed into a 50 ml polyethylene container and stored in a thermostatic chamber at 70° C. for 10 days. The ink viscosity change rate before and after storage was determined and evaluated according to the following evaluation criteria. For practical purposes, an evaluation criterion of "B" or higher is required.
〔Evaluation criteria〕
A: The rate of change is less than 3%. B: The rate of change is 3% or more and less than 5%. C: The rate of change is 5% or more and less than 10%. D: The rate of change is 10% or more.

<Preparation of pretreatment liquid>
Pretreatment solutions 1 to 12 were prepared by the method described below.

(Pretreatment Liquid Preparation Example 1: Production of Pretreatment Liquid 1)
12.50 parts by mass of magnesium sulfate (manufactured by Tokyo Chemical Industry Co., Ltd.) was weighed into a glass beaker, 50.00 parts by mass of highly pure water was added, and the mixture was stirred for 5 minutes. Next, 3.00 parts by mass of propylene glycol, 0.05 parts by mass of a preservative and antifungal agent (PROXEL (registered trademark) GXL), and 0.10 parts by mass of 1,2,3-benzotriazole (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and the mixture was mixed and stirred for 15 minutes. Furthermore, highly pure water was added to make a total of 100 parts by mass, and the mixture was mixed and stirred for 10 minutes. This mixture was pressure-filtered using a polyvinylidene fluoride membrane filter with an average pore size of 10.0 μm to remove insoluble matter and other debris, and a pretreatment liquid 1 was prepared.

(Pretreatment Liquid Preparation Examples 2 to 12: Production of Pretreatment Liquids 2 to 12)
Pre-treatment liquids 2 to 12 were prepared in the same manner as in Pre-treatment liquid Preparation Example 1, except that the formulation of the pre-treatment liquid was changed to the materials and contents shown in Tables 19 and 20 below.
In Tables 19 and 20 below, the unit of content of each material is "mass %", and the content is indicated as total amount, not solid content or active ingredient amount.

The details of the various materials shown in Tables 19 and 20 are as follows:

--Cationic polymer--
Sharol (registered trademark) DC-902P: polydimethyldiallylammonium chloride, solid content 51.0% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. DK6810: polyamine resin, solid content 55.0% by mass, manufactured by Seiko PMC Corporation

--Nonionic resin particles--
Takelac W-635: polyurethane emulsion, solid content 35% by mass, manufactured by Mitsui Chemicals, Inc. SUMIKAFLEX-850HQ: ethylene-vinyl acetate-vinyl chloride copolymer, solid content 50% by mass, manufactured by Sumitomo Chemical Co., Ltd. SUMIKAFLEX-951HQ: ethylene-vinyl acetate-vinyl versatate copolymer, solid content 55% by mass, manufactured by Sumitomo Chemical Co., Ltd.

--wax--
AQUACER 497: Paraffin wax, active ingredient 50% by mass, manufactured by BYK Japan Co., Ltd. AQUACER 539: Modified paraffin wax, active ingredient 35% by mass, manufactured by BYK Japan Co., Ltd. AQUACER 531: Modified polyethylene wax, active ingredient 45% by mass, manufactured by BYK Japan Co., Ltd.

--Anti-septic and anti-fungal agent--
・PROXEL GXL: Antiseptic and antifungal agent with 1,2-benzothiazolin-3-one as the main ingredient (manufactured by Avecia, contains 20% dipropylene glycol)

Image formation was performed using the ink set according to the methods described in the following Examples 1 to 17 and Comparative Examples 1 to 11.

(Examples 1 to 17 and Comparative Examples 1 to 11)
Under environmental conditions adjusted to 23° C.±0.5° C. and 50%±5% RH, an inkjet printing device (Direct to Garment Printer RICOH Ri 6000, manufactured by Ricoh Co., Ltd.) was used, and the driving voltage of the piezoelectric element was varied so as to uniformly eject the ink, and settings were made so that the same amount of ink was deposited on the recording medium.

First, as shown in Table 21 below, a specified pretreatment liquid was applied to a specified recording medium using a specified application method (coating method) to a specified adhesion amount. After that, if the recording medium was a dark color polyester T-shirt (00300-ACT), it was dried in an oven at 130°C for 90 seconds, and if the recording medium was a dark color cotton T-shirt (00085-CVT), it was dried in an oven at 165°C for 90 seconds.

Next, the white ink and color inks contained in the specified ink set shown in Table 21 below were filled into the inkjet printing device, and the white ink was applied in a specified application amount shown in Table 21 below to the area of the recording medium to which the pretreatment liquid had been applied, to form a solid image. 17 seconds after the application of the white ink, color inks were applied in a specified application amount shown in Table 21 below to the area of the recording medium to which the white ink had been applied, to form the chart shown in FIG.
The recording medium was not heated between the application of the white ink and the application of the color inks.

Next, when the recording medium on which the chart shown in FIG. 4 was formed was a dark-colored polyester T-shirt (00300-ACT), it was dried in an oven at 130° C. for 3 minutes, and when it was a light-colored or dark-colored cotton T-shirt (00085-CVT), it was dried in an oven at 165° C. for 2 minutes to obtain a sample image.
In addition, in Figure 4, "W" represents a white solid image area as a base, "Y" represents a yellow solid image area formed on the base W, "M" represents a red solid image area formed on the base W, "C" represents a cyan solid image area formed on the base W, "P" represents a magenta solid image area formed on the base W, "V" represents a blue solid image area formed on the base W, "G" represents a green solid image area formed on the base W, "K" represents a black solid image area formed on the base W, " _k1 " to " _k6 " represent the black letter "R" formed on the base W, and "y" represents the yellow letter "R" formed on the base W. The chart shown in FIG. 4 was created based on an image that was digitized without color correction using software Photoshop (registered trademark) (manufactured by Adobe (registered trademark)), and printed at 600 dpi x 600 dpi.

Details of the various recording media shown in Table 21 below are as follows.
00085-CVT White: White cotton T-shirt, Printstar (registered trademark) 00085-CVT White, manufactured by Toms Co., Ltd. 00085-CVT Black: Dark cotton T-shirt, Printstar 00085-CVT Black, manufactured by Toms Co., Ltd. 00300-ACT Black: Dark polyester T-shirt, glimmer 00300-ACT Black, manufactured by Toms Co., Ltd.

<Evaluation of sample images>
The Hunter whiteness and rub fastness of each sample image obtained in Examples 1 to 17 and Comparative Examples 1 to 11 were evaluated as follows. The results are shown in Table 21 below.

- Hunter Whiteness -
The color values L, a, and b of the image density in the white solid image portion of each sample image obtained in Examples 1 to 17 and Comparative Examples 1 to 11 were measured using a spectrodensitometer (X-Rite eXact, manufactured by X-Rite Corporation), and the Hunter whiteness was calculated using the following calculation formula (1) and evaluated based on the following evaluation criteria. For practical purposes, an evaluation criterion of "B" or higher is required.
The image density was measured by placing a sample image on five sheets of medium-weight colored wood-free black paper (manufactured by Hokuetsu Corporation).
Hunter brightness=100−sqr[(100−L) ² +(a ² +b ² )] (Formula 1)
[Evaluation criteria]
A+: Hunter whiteness is 85 or more. A: Hunter whiteness is 80 or more and less than 85. B: Hunter whiteness is 75 or more and less than 80. C: Hunter whiteness is 70 or more and less than 75. D: Hunter whiteness is less than 70.

-Friction resistance-
Tests were conducted using a friction tester I type (crock meter) method using a friction tester I type according to the method specified in JIS L 0849. "Dry friction" was tested according to the dry test specified in JIS L 0849, and "wet friction" was tested according to the wet test specified in JIS L 0849, and evaluated based on the following evaluation criteria. For practical purposes, an evaluation criterion of "C" or higher is required.
[Evaluation criteria]
A: Color chart is 4-5 grade or higher B: Color chart is 3-4 grade or higher and 4 grade or lower C: Color chart is 2-3 grade or higher and 3 grade or lower D: Color chart is 2 grade or lower

The evaluation results of inks 1 to 78 obtained in manufacturing examples 1 to 78, and sample images obtained in examples 1 to 17 and comparative examples 1 to 11 are summarized in Tables 22 to 24.

The aspects of the present invention include, for example, the following.
<1>
An ink containing a color material, a first urethane resin, a second urethane resin, and water,
The glass transition point (Tg) of the first urethane resin is 0° C. or lower,
the solid content of the first urethane resin is 5% by mass or more and 15% by mass or less based on the total amount of the ink,
The second urethane resin has a glass transition point (Tg) of 40° C. or higher,
The ink is characterized in that the solid content of the second urethane resin is 0.5% by mass or more and 3% by mass or less based on the total amount of the ink.
＜2＞
The first urethane resin has a glass transition point (Tg) of −45° C. or higher and 0° C. or lower,
The ink according to <1>, wherein the second urethane resin has a glass transition point (Tg) of 40° C. or higher and 80° C. or lower.
＜3＞
The ink contains an organic solvent,
The ink according to any one of <1> and <2>, wherein the organic solvent is a polyhydric alcohol having an equilibrium moisture content of 30% by mass or more at 23° C. and 80% RH.
＜4＞
The ink may contain, as a surfactant, any one selected from the group consisting of an acetylene glycol compound, an acetylene alcohol compound, a polyether-modified siloxane compound, and a fluorine compound.
＜5＞
The ink according to any one of <1> to <4>, which is a white ink;
and the ink according to any one of <1> to <4>, which is a color ink.
＜6＞
The ink set further includes a pretreatment liquid containing water and a flocculant,
The ink set according to <5>, wherein the coagulant is any one selected from the group consisting of inorganic metal salts, organic acid metal salts, organic acid ammonium salts, and cationic polymers.
＜７＞
The ink set according to <6>, wherein the pretreatment liquid contains a nonionic resin.
＜8＞
The ink set according to any one of <6> to <7>, wherein the pretreatment liquid contains a wax.
＜9＞
The ink set according to <8>, wherein the wax is paraffin wax.
＜10＞
a white ink applying step of applying a white ink to a recording medium;
a color ink applying step of applying a color ink to the area of the recording medium to which the white ink has been applied,
the white ink and the color inks each contain a color material, a first urethane resin, a second urethane resin, and water;
The glass transition point (Tg) of the first urethane resin is 0° C. or lower,
the solid content of the first urethane resin is 5% by mass or more and 15% by mass or less based on the total amount of the ink,
The second urethane resin has a glass transition point (Tg) of 40° C. or higher;
The image forming method is characterized in that the solid content of the second urethane resin is 0.5% by mass or more and 3% by mass or less based on the total amount of the ink.
<11>
The image forming method according to <10>, further comprising, before the white ink applying step, a pretreatment liquid applying step of applying a pretreatment liquid to an area of the recording medium to which the white ink is to be applied.
＜12＞
The image forming method according to any one of <10> to <11>, wherein the recording medium is a dark-colored fabric.
＜13＞
a white ink applying means for applying white ink to a recording medium;
a color ink applying unit that applies a color ink to an area of the recording medium to which the white ink has been applied,
the white ink and the color inks each contain a color material, a first urethane resin, a second urethane resin, and water;
The glass transition point (Tg) of the first urethane resin is 0° C. or lower,
The solid content of the first urethane resin is 5% by mass or more and 15% by mass or less based on the total amount of the ink,
The second urethane resin has a glass transition point (Tg) of 40° C. or higher,
The image forming apparatus is characterized in that the solid content of the second urethane resin is 0.5% by mass or more and 3% by mass or less with respect to the total amount of the ink.
＜14＞
The image forming apparatus according to <13> further comprises a liquid delivery device that delivers the white ink and the color ink by applying pressure to the white ink and the color ink.
＜15＞
A pretreatment liquid storage means for storing a pretreatment liquid;
and a pretreatment liquid applying unit that applies the pretreatment liquid to an area of the recording medium to which the white ink is applied, before the white ink is applied.

The ink described in any one of <1> to <4>, the ink set described in any one of <5> to <9>, the image forming method described in any one of <10> to <12>, and the image forming apparatus described in any one of <13> to <15> can solve the above-mentioned problems in the past and achieve the object of the present invention.

400 Image forming apparatus 401 Exterior of image forming apparatus 401c Cover of main body of image forming apparatus 404 Cartridge holder 410p Pretreatment liquid storage means 410w White ink storage means 410k Black ink storage means 410c Cyan ink storage means 411 Storage section 413 Discharge port 414 Storage container case 420 Mechanical section 434 Inkjet ejection head 435 Liquid delivery device 436 Supply tube 100 Printing apparatus 110 Pretreatment liquid application section 110a Pretreatment liquid storage section 120 Ink application section 120a Ink storage section 130 Posttreatment liquid application section 130a Posttreatment liquid storage section 140 Drying section 150 Transport section

Japanese Patent No. 6610710

Claims (15)

An ink containing a color material, a first urethane resin, a second urethane resin, and water,
The glass transition point (Tg) of the first urethane resin is 0° C. or lower,
the solid content of the first urethane resin is 5% by mass or more and 15% by mass or less based on the total amount of the ink,
The second urethane resin has a glass transition point (Tg) of 40° C. or higher,
The ink, characterized in that the solid content of the second urethane resin is 0.5% by mass or more and 3% by mass or less based on the total amount of the ink. The first urethane resin has a glass transition point (Tg) of −45° C. or higher and 0° C. or lower,
The ink according to claim 1 , wherein the second urethane resin has a glass transition point (Tg) of 40° C. or higher and 80° C. or lower. The ink contains an organic solvent,
The ink according to claim 1 , wherein the organic solvent is a polyhydric alcohol having an equilibrium moisture content of 30% by mass or more at 23° C. and 80% RH. The ink according to any one of claims 1 to 2, wherein the ink contains a surfactant selected from the group consisting of an acetylene glycol compound, an acetylene alcohol compound, a polyether-modified siloxane compound, and a fluorine compound. The ink according to claim 1 or 2, which is a white ink;
3. An ink set comprising the ink according to claim 1, which is a color ink. The ink set further includes a pretreatment liquid containing water and a flocculant,
The ink set according to claim 5 , wherein the coagulant is any one selected from the group consisting of inorganic metal salts, organic acid metal salts, organic acid ammonium salts, and cationic polymers. The ink set according to claim 6, wherein the pretreatment liquid contains a nonionic resin. The ink set according to claim 6, wherein the pretreatment liquid contains wax. The ink set according to claim 8, wherein the wax is paraffin wax. a white ink applying step of applying a white ink to a recording medium;
a color ink applying step of applying a color ink to the area of the recording medium to which the white ink has been applied,
the white ink and the color inks each contain a color material, a first urethane resin, a second urethane resin, and water;
The glass transition point (Tg) of the first urethane resin is 0° C. or lower,
the solid content of the first urethane resin is 5% by mass or more and 15% by mass or less based on the total amount of the ink,
The second urethane resin has a glass transition point (Tg) of 40° C. or higher,
The image forming method according to claim 1, wherein the second urethane resin has a solid content of 0.5% by mass or more and 3% by mass or less based on the total amount of the ink. The image forming method according to claim 10, further comprising a pretreatment liquid application step of applying a pretreatment liquid to the area of the recording medium to which the white ink is to be applied, prior to the white ink application step. The image forming method according to any one of claims 10 to 11, wherein the recording medium is a dark-colored fabric. a white ink applying means for applying white ink to a recording medium;
a color ink applying unit that applies a color ink to an area of the recording medium to which the white ink has been applied,
the white ink and the color inks each contain a color material, a first urethane resin, a second urethane resin, and water;
The glass transition point (Tg) of the first urethane resin is 0° C. or lower,
the solid content of the first urethane resin is 5% by mass or more and 15% by mass or less based on the total amount of the ink,
The second urethane resin has a glass transition point (Tg) of 40° C. or higher,
a solid content of the second urethane resin in the ink is 0.5% by mass or more and 3% by mass or less based on the total amount of the ink; The image forming apparatus according to claim 13, further comprising a liquid delivery device that delivers the white ink and the color ink by applying pressure to the white ink and the color ink. A pretreatment liquid storage means for storing a pretreatment liquid;
15. The image forming apparatus according to claim 13, further comprising: a pretreatment liquid applying unit that applies the pretreatment liquid to an area of the recording medium to which the white ink is to be applied, before the white ink is applied.