JP2023060809A - Ink set, image formation method, and image formation device - Google Patents

Abstract

To provide an ink set which is excellent in friction fastness and can suppress color bleeding and beading.SOLUTION: An ink set has white ink and color ink, wherein the white ink and the color ink each independently contain water dispersible resin particles having a crosslinkable functional group, and a blocked isocyanate compound having a functional group that can be crosslinked with the water dispersible resin particles having the crosslinkable functional group, an absolute value of a difference in static surface tension at 25°C between the white ink and the color ink is 1.0 mN/m or less, and absolute values of differences in dynamic surface tension at 25°C in bubble life time of 15 msec, 150 msec and 1,500 msec by a maximum bubble pressure method between the white ink and the color ink are each independently 1.0 mN/m or less.SELECTED DRAWING: None

Description

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

In recent years, the ink jet recording method has rapidly become popular because it enables easy recording of a color image and the running cost is low. In addition, dyeing (printing) of fabrics (woven fabrics, knitted fabrics, non-woven fabrics, etc.) is also performed using an inkjet recording method. Conventionally, screen printing, roller printing, etc. have been used as textile printing methods for textiles, but it is advantageous to apply an inkjet recording method from the viewpoint of high-variety, low-volume productivity and immediate printability. Therefore, various studies have been conducted. So-called pigment printing, in which an ink composition is mixed with a pigment and a fixing resin to print a fabric, has also been studied. In the case of pigment printing, it is important to physically fix the pigment to the fibers of the fabric.

For example, when printing on a dark-colored recording medium, a white base is formed by applying white ink to the recording medium to which the pretreatment liquid has been applied, and color ink is applied to the white base. A technique is known for improving the color development property of an image by imparting it (see Patent Document 1).

An object of the present invention is to provide an ink set that is excellent in rubbing fastness and capable of suppressing the occurrence of color bleeding and beading.

The ink set of the present invention as a means for solving the above problems is an ink set having a white ink and a color ink, wherein the white ink and the color ink each independently have a crosslinkable functional group. 25 between the white ink and the color ink, containing water-dispersible resin particles and a blocked isocyanate compound having a functional group capable of cross-linking with the water-dispersible resin particles having the cross-linkable functional group; The absolute value of the difference in static surface tension at °C is 1.0 mN/m or less, and the bubble life time between the white ink and the color ink according to the maximum bubble pressure method is 15 msec, 150 msec, and 1, The absolute value of the difference in dynamic surface tension at 25° C. for 500 msec is independently 1.0 mN/m or less.

According to the present invention, it is possible to provide an ink set that is excellent in fastness to rubbing and that can suppress the occurrence of color bleeding and beading.

FIG. 1 is a schematic perspective view showing an example of the image forming apparatus of the present invention. FIG. 2 is a schematic perspective view showing an example of housing means of the image forming apparatus of the present invention. FIG. 3 is a schematic diagram showing an example of a chart printed using the image forming apparatus of the present invention.

(ink set)
The ink set of the present invention preferably contains a white ink and color inks, further contains a pretreatment liquid, and, if necessary, has other configurations.

In the ink set, the white ink and the color ink independently contain water-dispersible resin particles having a crosslinkable functional group and functional groups capable of crosslinking with the water-dispersible resin particles having a crosslinkable functional group. and a blocked isocyanate compound having
the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink is 1.0 mN/m or less;
The absolute values of the dynamic surface tension differences at 25° C. at bubble life times of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently: It is 1.0 mN/m or less.

In this specification, the term “ink set” means that the white ink and the color ink exist independently. For example, the ink set is not limited to being manufactured and sold in a state in which the white ink containing means containing the white ink and the color ink containing means containing the color ink are integrated. . For example, if the ink set is based on the premise that the white ink and the color ink are used together, even if the white ink storage means and the color ink storage means are manufactured and sold independently, Alternatively, a case where the combination of the white ink and the color ink is substantially induced is included in the ink set of the present invention.

As used herein, "white ink" is a liquid composition that forms a white image when applied to a recording medium. When the ink set contains the pretreatment liquid, the "white ink" is a liquid composition that forms a white image when applied to the area of the recording medium to which the pretreatment liquid has been applied. be.
The white ink forms a white image on a recording medium, for example, functions as a base for a color image formed by the color ink applied to the area to which the white ink is applied, and the color image improve the color development of
In this specification, the term “white” refers to colors commonly referred to as “white” and “white,” including 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 can be appropriately selected depending on the purpose. is particularly preferred. When the Hunter whiteness is 75 or more, the color developability of a color image can be improved.
The Hunter whiteness is obtained by measuring the 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), It can be calculated by the following formula (1). Note that L, a, and b are the color display methods defined by the Commission Internationale de l'Eclairage (CIE), and are also written as L ^* , a ^* , and b ^* .
Hunter whiteness=100−sqr[(100−L) ² +(a ² +b ² )] Calculation formula (1)

The ink set may have one type of the white ink alone, or may have two or more types of the white ink.

As used herein, the term “color ink” refers to a liquid composition that forms a color image when applied to a region of a recording medium to which the white ink has been applied.
In this specification, the term "color" refers to colors that are not included in the above-mentioned "white", and includes, for example, black, cyan, magenta, and yellow.

The ink set may have one kind of the color inks alone, or may have two or more kinds of the color inks.

In the present specification, the term “pretreatment liquid” refers to contact with the white ink or the color ink that is applied to the recording medium and then applied to the area to which the pretreatment liquid has been applied. , a liquid composition that causes aggregation or thickening in the white ink or the color ink.

[Static surface tension]
The absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink of the ink set is 1.0 mN/m or less, but 0.8 mN/m or less. is preferred, 0.6 mN/m or less is more preferred, and 0.5 mN/m or less is even more preferred. When the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink of the ink set approaches 0 mN/m, color bleeding and beading can be further suppressed. Since the static surface tension difference represents an absolute value, it is 0 mN/m or more. When the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink in the ink set exceeds 1.0 mN/m, the white ink is applied to the recording medium. After that, when the color ink is applied to the area of the recording medium to which the white ink has been applied, color bleeding occurs.

Further, when the ink set includes a plurality of the white inks or the color inks, the absolute value of the static surface tension difference may be 1.0 mN/m or less in a predetermined combination of the white ink and the color ink. However, in a predetermined combination of white ink and color ink, the absolute value of the maximum difference in static surface tension is preferably 1.0 mN/m or less, and in all combinations of white ink and color ink, the static More preferably, the absolute value of the difference in surface tension is 1.0 mN/m or less.

The static surface tension at 25° C. of the white ink and the color ink contained in the ink set is preferably 40.0 mN/m or less, and preferably 36.0 mN/m or less. More preferably, it is 30.0 mN/m or less. The static surface tension at 25° C. of the white ink and the color ink is each independently 40.0 mN/m or less, so that not only color bleeding between the white ink and the color ink but also Also, the occurrence of color bleeding between one color ink and another color ink can be suppressed.

Further, when the ink set includes a plurality of the white inks or the color inks, the static surface tensions of the predetermined white ink and the color ink are each independently preferably 40.0 mN/m or less, More preferably, the static surface tensions of all white inks and color inks are each independently 40.0 mN/m or less.

Here, the phrase “independently” means that the white ink and the color ink may be the same as long as the static surface tension at 25° C. is 40.0 mN/m or less, It means that they can be different.

The static surface tension of the white ink or the color ink at 25° C. is measured by a plate method (Wilhelmy method) using an automatic surface tension meter (eg, DY-300, manufactured by Kyowa Interface Science Co., Ltd.). be able to. Also, the temperature of 25° C. at this time is not the temperature of the recording medium, but the temperature of the white ink or the color ink itself.

[Dynamic surface tension]
The absolute values of the dynamic surface tension differences at 25° C. at bubble life times of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently: It is 1.0 mN/m or less, preferably 0.9 mN/m or less. The absolute values of the dynamic surface tension differences at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently Color bleeding and beading can be further suppressed by approaching 0 mN/m. Since the difference in dynamic surface tension represents an absolute value, it is 0 mN/m or more. The absolute value of the difference in dynamic surface tension at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color inks of the ink set is Each independently, if it exceeds 1.0 mN/m, after applying the white ink to the recording medium, when applying the color ink to the area of the recording medium to which the white ink has been applied , color bleeding occurs.

In addition, when the ink set includes a plurality of the white ink or the color ink, in a predetermined combination of the white ink and the color ink, 25 at bubble life times of 15 msec, 150 msec and 1,500 msec according to the maximum bubble pressure method. The absolute value of the difference in dynamic surface tension at °C should be independently 1.0 mN/m or less. , 150 msec, and 1,500 msec at 25° C. The absolute values of the maximum differences in dynamic surface tension are preferably 1.0 mN/m or less independently, and all white inks and color inks In combination, the absolute value of the difference in dynamic surface tension at 25°C at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method shall be 1.0 mN/m or less independently. is more preferred.

Here, the "independently" means the absolute value of the difference in dynamic surface tension at 25°C when the bubble lifetime is 15 msec, and the difference in dynamic surface tension at 25°C when the bubble lifetime is 150 msec. As long as the absolute value and the absolute value of the difference in dynamic surface tension at 25°C at the bubble lifetime of 1,500 msec are both 1.0 mN/m or less, they may be the same or different. It is also good.

The dynamic surface tension at 25° C. of the white ink or the color ink at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec according to the maximum bubble pressure method was measured using a portable dynamic surface tensiometer (for example, SITA Pro line t15, manufactured by Eko Seiki Co., Ltd.) can be used for measurement.

The reason why the occurrence of color bleeding is suppressed in the ink set will be described below.

By adding a cross-linkable resin having a polycarbonate skeleton and a blocked isocyanate compound to the ink composition, the rubbing fastness of the image is improved. It is known to increase the redispersibility of a crosslinkable resin (see Japanese Patent No. 6794746). However, this ink composition has a problem that image defects typified by character blurring are likely to occur, resulting in a large deterioration in image quality.

In addition, in general, when printing is performed on a dark recording medium or the like, white ink is applied to the recording medium to form a base that is a white image. Color development of color images is improved by applying color inks from . However, when the color ink is applied within a short time (for example, within 20 seconds) after applying the white ink, the recording medium has low permeability (including non-permeability) when the amount of white ink applied is large. or when applying color ink without heating the recording medium to which the white ink has been applied until the color ink is applied after applying the white ink, the white ink is not dried properly. Due to the sufficient amount, there has been a problem that color bleeding, in which the white ink and the color ink are mixed, may occur. Similarly, due to insufficient drying of the white ink, the drying property of the color ink that is subsequently applied to the area to which the white ink has been applied is reduced, resulting in density unevenness in the color image. There was also the problem that beading could also occur.

In contrast, the white ink and the color ink in the ink set of the present invention have an absolute value of difference in static surface tension at 25° C. of 1.0 mN/m between the white ink and the color ink. and the absolute values of the dynamic surface tension differences at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink, respectively. Independently, since it is 1.0 mN/m or less, it is possible to suppress the occurrence of color bleeding even when the drying of the white ink may be insufficient.

Also, in the case where the white ink is insufficiently dried as described above, when using a plurality of color inks, in addition to color bleeding where the white ink and each color ink are mixed, on the area to which the white ink is applied Color bleeding, in which color inks come into contact with each other and mix, can also occur.

On the other hand, in the ink set, the absolute value of the difference in dynamic surface tension at 25° C. when the bubble life time is 15 msec according to the maximum bubble pressure method is 1.0 mN/ It is preferably 0.9 mN/m or less, more preferably 0.9 mN/m or less. The absolute value of the difference in dynamic surface tension at 25° C. when the bubble life time is 15 msec according to the maximum bubble pressure method is independently 1.0 mN/m or less between the plurality of color inks, It is possible to suppress color bleeding that occurs between color inks. The difference in dynamic surface tension at 25° C. with a bubble life time of 15 msec by the maximum bubble pressure method between the plurality of color inks is an absolute value, and is 0 mN/m or more.

Further, if the absolute value of the difference in dynamic surface tension at 25° C. at a bubble lifetime of 15 msec according to the maximum bubble pressure method is 1.0 mN/m or less in a combination of predetermined color inks among the plurality of color inks. However, in a combination of predetermined color inks among the plurality of color inks, the absolute value of the maximum difference in dynamic surface tension at 25° C. when the bubble life time is 15 msec according to the maximum bubble pressure method is 1.0 mN/m or less. Preferably, in all combinations of color inks, the absolute value of the difference in dynamic surface tension at 25° C. when the bubble life time is 15 msec by the maximum bubble pressure method is independently 1.0 mN / m or less. Preferably.

For example, when the ink set has black ink, cyan ink, magenta ink, and yellow ink as the plurality of color inks, inks between black ink and cyan ink, between black ink and magenta ink, and between black ink and yellow ink , between cyan ink and magenta ink, between cyan ink and yellow ink, and between magenta ink and yellow ink, the absolute value of the difference in dynamic surface tension at 25 ° C. with a bubble lifetime of 15 msec by the maximum bubble pressure method is , are each independently preferably 1.0 mN/m or less.

Here, the term “independently” means that the absolute values of the differences in dynamic surface tension at 25° C. for 15 msec between the plurality of color inks are the same as long as they are all 1.0 mN/m or less. It can be either or it can be different.

Further, as described above, in the case where the ink set has the plurality of color inks, when the plurality of color inks include black ink, cyan ink, magenta ink, and yellow ink, , the dynamic surface tension at 25° C. when the bubble life time is 15 msec according to the maximum bubble pressure method preferably satisfies the following relational expression (1). In the following relational expression (1), color bleeding occurs as the color ink located on the left side (i.e., color ink having a larger dynamic surface tension value at 25° C. at 15 msec between the plurality of color inks) occurs. However, by satisfying the following relational expression (1), the color ink positioned on the left side in the following relational expression (1) becomes the color ink positioned on the right side (i.e. , the occurrence of color bleeding that penetrates into the color ink having a smaller dynamic surface tension value at 25° C. at 15 msec between the plurality of color inks can be suppressed.
Black ink>Cyan ink≧Magenta ink≧Yellow ink Relational expression (1)

<White ink and color ink>
The white ink and the color ink (hereinafter, the white ink and the color ink may be collectively abbreviated as "ink") are each independently water-dispersible resin particles having a crosslinkable functional group. , the water-dispersible resin particles having a crosslinkable functional group, and a blocked isocyanate compound having a crosslinkable functional group, and further preferably contain an organic solvent, water, a coloring material, and a surfactant. , and optionally other components.

Here, the above-mentioned "independently" means that the composition of the white ink and the color ink are both water-dispersible resin particles having a crosslinkable functional group and a water-dispersible resin having a crosslinkable functional group. As long as the particles and the blocked isocyanate compound having a functional group capable of cross-linking are contained, they may be the same or different.

When the ink set contains the pretreatment liquid in addition to the white ink and the color ink, at least one selected from the colorant and the resin is preferably anionic. may be collectively referred to as "anionic compounds"). At least one selected from the colorant and the resin is anionic, so that when the white ink or the color ink comes into contact with a component (aggregating agent, etc.) contained in the pretreatment liquid, the white color Aggregation or thickening of the ink or the color ink may occur, thereby retaining the white ink or the color ink on the surface of the recording medium.

-Water-dispersible resin particles having a crosslinkable functional group-
The water-dispersible resin particles having a crosslinkable functional group (hereinafter sometimes abbreviated as "water-dispersible resin particles") are not particularly limited, can be appropriately selected according to the purpose, and are stable in water. It may be a self-emulsifying type in which a hydrophilic component necessary for dispersing in water is introduced, or it may be water-dispersible by using an external emulsifier.

The type of the water-dispersible resin particles is not particularly limited and can be appropriately selected according to the purpose. A urethane resin is more preferable because it is easy to obtain the desired physical properties of the film.

The urethane resin is not particularly limited as long as it has a urethane skeleton and is water-dispersible, and can be appropriately selected according to the purpose. , a carboxy group, a sulfo group, an anionic urethane resin having an anionic functional group such as a hydroxy group (an anionic resin having a urethane skeleton).

Specific examples of the anionic urethane resin include Superflex 460, Superflex 460S, Superflex 470, Superflex 840 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Takelac (registered trademark) WS-4022, Takelac ( (Registered Trademark) WS-5100, Takelac (Registered Trademark) WS-5984, or Takelac (Registered Trademark) WS-6021 (manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.).

As the urethane resin, polyether type urethane resin containing an ether bond in the main chain, polyester type urethane resin containing an ester bond in the main chain, polycarbonate type urethane resin containing a carbonate bond in the main chain, etc. are used in addition to the urethane bond. can. Among these, the urethane resin is preferably a polycarbonate-type urethane resin and a polyester-type urethane resin.

These urethane resins may be used singly or in combination of two or more. Furthermore, in addition to the water-dispersible resin particles having the above physical properties, water-dispersible resins other than the water-dispersible resin particles, such as acrylic resins, acrylic-styrene resins, and acetic acid, are added to the extent that the effects of the present invention are not impaired. A vinyl resin, an acryl-vinyl acetate resin, or the like may be used alone or in combination of two or more.

The volume average particle diameter of the water-dispersible resin particles is not particularly limited and can be appropriately selected depending on the purpose. The following are more preferred.
The volume average particle diameter of the water-dispersible resin particles can be measured, for example, with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB).

The content (solid content) of the water-dispersible resin particles in the white ink or the color ink is not particularly limited and can be appropriately selected depending on the purpose. It is preferably 3% by mass or more and 15% by mass or less, more preferably 5% by mass or more and 13% by mass or less, relative to the total mass of the ink. When the content (solid content) of the water-dispersible resin particles is 15% by mass or more, the ejection stability of the ink may decrease, and when it is 3% by mass or less, the rubbing fastness is significantly reduced. may decrease.

-Blocked isocyanate compound having functional groups capable of cross-linking with water-dispersible resin particles having cross-linkable functional groups-
The blocked isocyanate compound having a functional group that can be crosslinked with the water-dispersible resin particles having a crosslinkable functional group (hereinafter sometimes abbreviated as "blocked isocyanate compound") is a water-dispersible resin particle having the crosslinkable functional group. It is blended as a cross-linking agent for the dispersible resin particles.

The blocked isocyanate compound means a compound in which the isocyanate group is protected with a blocking agent, and the blocking agent is dissociated by heating to regenerate the active isocyanate group. The isocyanate groups generated by this heating react with each other of the water-dispersible resin particles such as the urethane resin, and with the crosslinkable functional groups of the water-dispersible resin particles and the functional groups and active hydrogen sites of the recording medium such as fabric. It is conceivable that a crosslinked structure such as a urethane bond or a urea bond is formed.

The blocking agent is not particularly limited and can be appropriately selected depending on the intended purpose. etc. These may be used individually by 1 type, and may use 2 or more types together.

More specifically, the blocked isocyanate compound preferably has a urethane skeleton.

Specific examples of the blocked isocyanate compound having a urethane skeleton include Elastron (registered trademark) series, Elastron (registered trademark) BN series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Takenate (registered trademark) series (Mitsui Chemicals Co., Ltd.), or ADEKA BONDITATER HUX series (ADEKA Co., Ltd.), and more preferably Elastron (registered trademark) E-37, Elastron (registered trademark) H-3- DF, Elaston (registered trademark) H-15, Elaston (registered trademark) NEW BAP-15, Elaston (registered trademark) F-29, Elaston (registered trademark) W-11P (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Takenate (registered trademark) XWB-ST001, Takenate (registered trademark) XWB-ST047 (manufactured by Mitsui Chemicals, Inc.); A commercial item can be used.

From the viewpoint of robustness, the ink film is generally required to have a film thickness of about 10 μm to 300 μm, but such a thick film has the problem of impairing the original texture of the recording medium such as cloth. .
By using the blocked isocyanate compound, the ink set of the present invention can ensure sufficient robustness without forming a thick ink film as in the conventional art, so that the original texture of the recording medium is spoiled. It is advantageous in that there is no In particular, the ink set can form an ink film having strong adhesiveness and robustness by combining the water-dispersible resin particles such as the urethane resin and the blocked isocyanate compound. Advantageous.

The content of the blocked isocyanate compound in the white ink and the color ink is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of securing fastness, especially wet rubbing fastness, it is preferably 0.05 part by mass or more per 1 part by mass (solid content) of the dispersible resin particles, and avoids deterioration of the texture of the recording medium. 1.0 parts by mass or less, more preferably 0.05 to 0.6 parts by mass, and from the viewpoint of the coating properties of the resulting ink film, 0.1 to 0.1 part by mass. More preferably, it is 55 parts by mass.

In addition, the rubbing fastness can be confirmed by measuring the rubbing fastness by the friction tester type I (Crockmeter) method using a friction tester type I according to the method specified in JIS L 0849. In both the dry test and the wet test, the grade is preferably grade 3-4 or higher, more preferably grade 4-5 or higher.

Here, the phrase "independently" means that the content of the blocked isocyanate compound in the white ink and the color ink may be the same or different.

-Organic solvent-
The organic solvent is not particularly limited and can be appropriately selected depending on the intended purpose. Hereinafter, it is preferable to use an organic solvent having a high equilibrium water content and a high boiling point (bp). The selection of such an organic solvent is related to the suppression of color bleeding and beading (in other words, the control of static and dynamic surface tension), but it also contributes to the improvement of ink ejection stability and maintenance mechanism of the image forming apparatus. It is also related to prevention of sticking of waste ink in printing.

The equilibrium water content (%) is obtained by using a saturated aqueous solution in which potassium chloride and sodium chloride are mixed at a ratio of 6:4 (potassium chloride: sodium chloride, parts by mass), and adjusting the temperature and humidity in the desiccator to a temperature of 23 ° C ± 1. C. and RH 80%±3%, a petri dish containing 1 g of each organic solvent was stored in the desiccator, and the equilibrium water content was measured and calculated by the following formula (2).
Equilibrium water content (% by mass) = [water content absorbed by organic solvent/(organic solvent content + water content absorbed by organic solvent)] × 100 Calculation formula (2)

Examples of the wetting agent include polyhydric alcohols having an equilibrium water content of 30% by mass or more in an environment at a temperature of 23° C. and a RH of 80%. Specific examples of such polyhydric alcohols 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. ° 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./ 20 hPa, equilibrium water content 38 mass%), 1,2,3-butanetriol (bp 175 ° C./33 hPa, equilibrium water content 38 mass%), or 1,2,4-butanetriol (bp 190 ° C. to 191 ° C./24 hPa, equilibrium water content of 41% by mass) and the like. These may be used individually by 1 type, and may use 2 or more types together. Among these, the wetting agent is preferably glycerin and 1,3-butanediol.

Wetting agents other than polyhydric alcohols include, for example, 2-methyl-1,3-butanediol (bp 214°C), 3-methyl-1,3-butanediol (bp 203°C), and 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 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), or trimethylolpropane (solid, mp 61°C). These may be used individually by 1 type, and may use 2 or more types together.

The content of the organic solvent (wetting agent) in the white ink or the color ink is not particularly limited and can be appropriately selected depending on the purpose. On the other hand, 10.0 mass % or more and 75.0 mass % or less are preferable, and 15.0 mass % or more and 50.0 mass % or less are more preferable. When the content of the organic solvent (wetting agent) is 10.0% by mass or more, the moisturizing effect in the white ink or the color ink is improved. The drying property of the white ink or the color ink is improved.

When using a low-permeability (including non-permeability) recording medium, the organic solvent should have a solubility parameter (SP value) of 9.0 (cal/cm ³ ) ^1/2 or more and 11.8 (cal /cm ³ ) ^1/2 or less is preferably used. Specific examples of the organic solvent having a solubility parameter of 9.0 (cal/cm ³ ) ^1/2 or more and 11.8 (cal/cm ³ ) ^{1/2 or} less 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 ) , 2-ethyl-1,3-hexanediol (SP value: 10.6 (cal/cm ³ ) ^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 ) 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 ), methyl propylene triglycol (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 ), or 3-methyl- 1,5-pentanediol (SP value: 11.8 (cal/cm ³ ) ^1/2 ) and the like. These may be used individually by 1 type, and may use 2 or more types together.

The content of the organic solvent whose solubility parameter in the white ink or the color ink is 9.0 (cal/cm ³ ) ^1/2 or more and 11.8 (cal/cm ³ ) ^{1/2 or} less is not particularly limited. However, it is preferably 0.5% by mass or more and 5.0% by mass or less, and 1.0% by mass or more, based on the total mass of the white ink or the color ink. 4.0% by mass or less is more preferable. The content of the organic solvent having a solubility parameter of 9.0 (cal/cm ³ ) ^1/2 or more and 11.8 (cal/cm ³ ) ^1/2 or less is 0.5% by mass or more and 5.0% by mass or less. is preferable from the viewpoint of suppressing color bleeding and beading (in other words, control of static surface tension and dynamic surface tension), and also preferable from the viewpoint of the color developability of the white ink or the color ink.

-water-
The water is not particularly limited and can be appropriately selected depending on the purpose. ) and the like. These may be used individually by 1 type, and may use 2 or more types together.

The content of water in the white ink or the color ink is not particularly limited and can be appropriately selected according to the purpose. It is preferably 10.0% by mass or more and 90.0% by mass or less, more preferably 20.0% by mass or more and 60.0% by mass or less, relative to the total mass of the white ink or the color ink.

-coloring material-
The white ink contains a white colorant, and the color ink contains a color colorant. In this specification, when the white colorant and the color colorant are not distinguished from each other, they are simply referred to as "colorant".

A pigment or the like can be used as the coloring material. The pigment is not particularly limited, and inorganic pigments or organic pigments can be used. These may be used individually by 1 type, and may use 2 or more types together.

As the pigment, for example, a black pigment, a yellow pigment, a magenta pigment, a cyan pigment, a white pigment, a green pigment, an orange pigment, or a lustrous color pigment or metallic pigment (golden, silver, etc.) can be used.

The inorganic pigment is not particularly limited and can be appropriately selected depending on the purpose. Examples include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, Or carbon black etc. are mentioned. Among these inorganic pigments, the white colorant is preferably titanium oxide, and the black colorant is preferably carbon black.

The carbon black is not particularly limited and can be appropriately selected depending on the purpose. For example, channel black, furnace black, gas black, lamp black, and the like.

The organic pigment is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, the organic pigment is preferably an azo pigment or a polycyclic pigment.

Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments.

Examples of the polycyclic pigments 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 basic dye chelates and acid dye chelates.

As the organic pigment, specifically, C.I. I. Pigment yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 408, 109, 110, 117, 120, 128, 139, 150, 151, 155, 153, 180, 183, 185, or 213; I. Pigment Orange 5, 13, 16, 17, 36, 43, or 51; C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52:2, 53: 1, 57:1 (brilliant carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88, 101 (red red), 104, 105, 106, 108 (cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, or 219; C.I. I. Pigment Violet 1 (rhodamine lake), 3, 5:1, 16, 19, 23, or 38; C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15:1, 15:2, 15:3 (phthalocyanine blue), 15:4, 16, 17:1, 56, 60, or 63; C.I. I. Pigment Green 1, 4, 7, 8, 10, 17, 18, or 36 and the like.

The BET specific surface ^{area of} the pigment is not particularly limited and can be appropriately selected depending on ^the purpose ^. g or less is more preferable, and 50 m ² /g or more and 300 m ² /g or less is even more preferable.

A pigment with a desired BET specific surface area can be obtained by performing 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. Examples include ball mill pulverization, jet mill pulverization, and ultrasonic treatment. The pigments may be treated singly or in combination of two or more.

The cumulative 50% volume particle diameter D50 of the pigment is not particularly limited and can be appropriately selected according to the purpose.
The cumulative 50% volume particle diameter D50 of the pigment can be measured, for example, with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB).

The content (solid content) of the pigment in the white ink or the color ink is not particularly limited and can be appropriately selected depending on the purpose. is preferably 1.0% by mass or more and 15.0% by mass or less, more preferably 1.5% by mass or more and 10.0% by mass or less. When the content of the pigment (solid content) is 1.0% by mass or more, the color developability and image density of the white ink or the color ink are improved, and when it is 15.0% by mass or less, Ejectability of the white ink or the color ink is stabilized.

Specific examples of the composite pigment include silica/carbon black composite material, silica/phthalocyanine PB15:3 composite material, silica/disazo yellow composite material, or silica/quinacridone PR122 composite material (the above , manufactured by Toda Kogyo Co., Ltd.) and the like are suitable.

For example, when inorganic pigment particles having a primary particle size of 20 nm are coated with an equal amount of organic pigment, the primary particle size of this composite pigment is about 25 nm. If the primary particles can be dispersed using an appropriate dispersant, a composite pigment-dispersed ink with a very fine dispersed particle diameter of 25 nm can be produced. In the composite pigment, the organic pigment on the coated surface contributes to dispersion, but the properties of the inorganic pigment in the center also appear through the thin layer of the organic pigment with a thickness of about 2.5 nm, so both are dispersed and stabilized at the same time. It is also required to select a pigment dispersant that can be

Further, when the ink set includes the pretreatment liquid in addition to the white ink and the color ink, as described above, the coloring material is preferably anionic, and is preferably an anionic pigment. more preferred.

Examples of the anionic pigment include a surfactant-dispersed pigment obtained by dispersing a pigment with a surfactant, a resin-dispersed pigment obtained by dispersing a pigment with a resin, a resin-coated dispersed pigment obtained by coating the surface of a pigment with a resin, and a pigment surface. Although there are self-dispersing pigments in which a hydrophilic group is provided on the surface of the pigment, it is preferable that the pigment is water-dispersible in any form of dispersion.

When the anionic pigment is the resin-coated dispersible pigment or the self-dispersible pigment, it preferably has at least one hydrophilic group on its surface.

Examples of the hydrophilic group include -COOM, -SO ₃ M, -PO ₃ HM, -PO ₃ M ₂ , -CONM ₂ , -SO ₃ NM ₂ , -NH-C ₆ H ₄ -COOM, -NH- _{C6H4 - SO3M} , -NH- _{C6H4 - PO3HM} , -NH- _{C6H4 - PO3M2} , -NH- _{C6H4 - CONM2 ,} or -NH-C ₆ H ₄ —SO ₃ NM ₂ and the like. These hydrophilic groups can be introduced by known methods. In addition, "M" in the said hydrophilic group shows a counter ion.

Moreover, 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, or tetrahexylammonium ion. etc. Among these, the quaternary ammonium ion is preferably a tetraethylammonium ion, a tetrabutylammonium ion, or a benzyltrimethylammonium ion, more preferably a tetrabutylammonium ion. The white ink or the color ink using such a pigment has excellent storage stability over time and suppresses an increase in viscosity when water evaporates. It is presumed that this is because the hydrophilic group having the quaternary ammonium ion can stably maintain the dispersion of the pigment even when the water-rich ink evaporates and becomes organic solvent-rich.

As the coloring material other than the coloring material having a hydrophilic group on the surface, a polymer emulsion containing a pigment in fine polymer particles is preferable. The pigment may be enclosed in the polymer microparticles, or may be adsorbed on the surface of the polymer microparticles. In this case, not all the pigments need to be enclosed in the polymer fine particles or adsorbed on the surfaces of the polymer fine particles, and some of the pigments may be dispersed in the emulsion. Examples of the polymer for the fine polymer particles include vinyl-based polymers, polyester-based polymers, and polyurethane-based polymers. These may be used individually by 1 type, and may use 2 or more types together. Among these, the polymer for the fine polymer particles is preferably a vinyl-based polymer or a polyester-based polymer.

The mass ratio between the coloring material and the organic solvent is related to the improvement of ink ejection stability and the suppression of waste ink sticking in the maintenance mechanism of the image forming apparatus, so it is preferable to appropriately adjust the mass ratio. For example, when an ink containing a large amount of the coloring material and a small amount of the organic solvent is discharged from an inkjet discharge head, water evaporation near the ink meniscus of the nozzle may progress, resulting in improper discharge. .

-Surfactant-
The white ink and the color ink each preferably contain a surfactant as a means of suppressing color bleeding and beading (in other words, controlling static surface tension and dynamic surface tension).

As the surfactant, for example, a polyether-modified siloxane compound, an acetylene glycol surfactant, an acetylene alcohol surfactant, or a fluorine-based surfactant can be used. These may be used individually by 1 type, and may use 2 or more types together. Moreover, in addition to these surfactants, a silicone surfactant or the like may be used in combination. By using the surfactant, it becomes difficult for the white ink and the color ink to wet the ink-repellent film on the nozzle plate of the inkjet ejection head, and ejection failure due to adhesion of the white ink and the color ink to the nozzles is suppressed. and the ejection stability is improved.

As the polyether-modified siloxane compound, those represented by any one of the following general formulas (1) to (5) are preferable.

In the general formula (1), R ₁ 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, and a represents an integer of 1 to 23. and b represents an integer from 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, c and d each independently Represents an integer from 1 to 10.

In 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 general formula (4), R ₅ represents a polyether group represented by general formula (5) below, and f represents an integer of 1-8.

In general formula (5), R ₆ 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 any one of 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 any one of the following structural formulas (11) to (13).

Furthermore, commercially available polyether-modified siloxane compounds include, for example, DOWSIL 71 Additive, DOWSIL 74 Additive, DOWSIL 57 Additive, DOWSIL 8029 Additive, DOWSIL 8054 Additive, and DOWSIL 8019 Additive. , DOWSIL 8526 Additive, DOWSIL FZ-2123, DOWSIL FZ -2191 (manufactured by DuPont Toray Specialty Materials Co., Ltd.); TSF4440, TSF4445, TSF4446, TSF4450, TSF4452, TSF4460 (manufactured by Momentive Performance Materials); Silface (registered trademark) SAG002, Sil Face (registered trademark) SAG003, Silface (registered trademark) SAG005, Silface (registered trademark) SAG503A, Silface (registered trademark) SAG008, Silface (registered trademark) SJM003 (manufactured by Nissin Chemical Industry Co., Ltd.); TEGO (registered trademark) WetKL245, TEGO (registered trademark) Wet250, TEGO (registered trademark) Wet260, TEGO (registered trademark) Wet265, TEGO (registered trademark) Wet270, TEGO (registered trademark) Wet280 (all manufactured by Evonik); -345, BYK-347, BYK-348, BYK-375, or BYK-377 (manufactured by BYK-Chemie Japan Co., Ltd.).

In addition, as the acetylene glycol surfactant and the acetylene alcohol surfactant, commercially available products can be used. Norphine SE, Surfynol SE-F, Surfynol PSA-336, Surfynol DF110D, Surfynol DF58, Olfine E1004, Olfine E1010, Olfine E1020, Olfine PD-001, Olfine PD-002W, Olfine PD-004, Olfine PD- 005, Olphine EXP. 4001, Olfine EXP. 4200, Olfine EXP. 4123, or Olfine EXP. 4300 (manufactured by Nissin Chemical Industry Co., Ltd.) and the like.

The fluorine-based surfactant is not particularly limited and can be appropriately selected depending on the intended purpose. Alkylethylene oxide adducts, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in side chains, and the like are preferable because of their low foamability.

Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid and perfluoroalkylsulfonate.
Examples of the perfluoroalkylcarboxylic acid compounds include perfluoroalkylcarboxylic acids and perfluoroalkylcarboxylic acid salts.
As the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain, a sulfuric acid ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in a side chain, or a perfluoroalkyl ether group in a side chain and salts of polyoxyalkylene ether polymers having

The counter ion of the _salt in _the fluorine-based surfactant is not particularly limited and can be _{appropriately} selected depending on the _purpose . ₂ (CH ₂ CH ₂ OH) ₂ or NH(CH ₂ CH ₂ OH) ₃ and the like.

The content of the surfactant in the white ink or the color ink is not particularly limited and can be appropriately selected depending on the purpose. 0.001% by mass or more and 5.0% by mass or less is preferable, and 0.01% by mass or more and 3.0% by mass or less is more preferable. When the content of the surfactant is 0.001% by mass or more, the effect of addition of the surfactant can be easily obtained, and when the content exceeds 5.0 mass%, the effect of addition may be saturated.

-Other ingredients-
As the other components in the white ink or the color ink, various known additives can be used as necessary.
Examples of the additives include foam inhibitors (defoamers), pH adjusters, antiseptic and antifungal agents, chelating reagents, rust inhibitors, antioxidants, ultraviolet absorbers, oxygen absorbers, light stabilizers, Alternatively, resins other than the water-dispersible resin particles may be used. These may be used individually by 1 type, and may use 2 or more types together.

-- Anti-foaming agent (anti-foaming agent) --
The antifoaming agent is added in a small amount to the white ink or the color ink to suppress foaming of the white ink or the color ink.
Here, "foaming" means that a liquid becomes a thin film and envelops air. Characteristics such as surface tension and viscosity of the white ink or the color ink are involved in the generation of bubbles. That is, a liquid with high surface tension, such as water, is less likely to foam because a force acts to reduce the surface area of the liquid as much as possible. On the other hand, high-viscosity, high-permeability ink tends to foam due to its low surface tension, and the foam generated due to the viscosity of the solution tends to be maintained and is difficult to disappear.

Generally, the foam inhibitor destroys the foam by locally lowering the surface tension of the foam film, or by scattering the foam inhibitor insoluble in the foaming liquid on the surface of the foaming liquid. When a polyether-modified siloxane compound that has an extremely strong function of lowering surface tension is used as a surfactant in the ink, the surface tension of the foam film can be locally reduced even if a foam inhibitor based on the former mechanism is used. can't Therefore, it is preferable to use a foam inhibitor that is insoluble in the latter bubbling liquid, but in this case, the stability of the ink may decrease due to the foam inhibitor that is insoluble in the solution.

On the other hand, a foam inhibitor containing a compound represented by the following general formula (6) does not have as strong a function of lowering surface tension as the polyether-modified siloxane compound, but has high compatibility with the polyether-modified siloxane compound. . As a result, the foam inhibitor is efficiently incorporated into the foam film, and the surface of the foam film becomes locally unbalanced due to the difference in surface tension between the polyether-modified siloxane compound and the foam inhibitor, resulting in foam formation. thought to destroy.

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, n represents an integer of 1 to 6;

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 - diols and the like. Among these, the compound represented by the general formula (6) is preferably 2,5,8,11-tetramethyldodecane-5,8-diol because it has a high antifoaming effect and high compatibility with ink. .

The content of the foam inhibitor in the white ink or the color ink is not particularly limited and can be appropriately selected according to the purpose. 0.01% by mass or more and 10.0% by mass or less is preferable, and 0.1% by mass or more and 5.0% by mass or less is more preferable. When the content of the antifoaming agent is 0.01% by mass or more, an antifoaming effect is obtained, and when the content is 10% by mass or less, it suppresses the influence on ink physical properties such as viscosity and particle size. be able to.

--pH adjuster--
The pH adjuster is not particularly limited as long as it can adjust the pH of the white ink or the color ink, and can be appropriately selected according to the purpose. Hydroxides, ammonium hydroxides, phosphonium hydroxides, alkali metal carbonates, and the like. These may be used individually by 1 type, and may use 2 or more types together. Among these, the alcohol amines are preferable as the pH adjuster.

Examples of the alcoholamines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like.

Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, and the like.

Examples of the ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide.

Examples of the phosphonium hydroxide include quaternary phosphonium hydroxide.

Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, potassium carbonate, and the like.

The content of the pH adjuster in the white ink or the color ink is not particularly limited as long as the white ink or the color ink can be adjusted to a desired pH, and can be appropriately selected according to the purpose. can be done.
The pH of the white ink or the color ink is preferably 7 to 11 from the viewpoint of improving the ejection stability of the ink.

-- Antiseptic and antifungal agents --
The antiseptic/antifungal agent is not particularly limited and can be appropriately selected depending on the intended purpose. 1-sodium oxide, sodium benzoate, sodium pentachlorophenol, and the like. These may be used individually by 1 type, and may use 2 or more types together.

The content of the antiseptic/antifungal agent in the white ink or the color ink is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected according to the purpose.

--Chelating reagent--
The chelating reagent is not particularly limited and can be appropriately selected depending on the intended purpose. and sodium. These may be used individually by 1 type, and may use 2 or more types together.

The content of the antiseptic/antifungal agent in the white ink or the color ink is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected according to the purpose.

--anti-rust--
The rust inhibitor is not particularly limited and can be appropriately selected depending on the intended purpose. and ammonium nitrite. These may be used individually by 1 type, and may use 2 or more types together.

The content of the antirust agent in the white ink or the color ink is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected according to the purpose.

--Antioxidant--
The antioxidant is not particularly limited and can be appropriately selected depending on the intended purpose. Examples include antioxidants and phosphorus-based antioxidants. These may be used individually by 1 type, and may use 2 or more types together.

The content of the antioxidant in the white ink or the color ink is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected according to the purpose.

--Ultraviolet absorber--
The ultraviolet absorber is not particularly limited and can be appropriately selected depending on the intended purpose. , or a nickel complex salt-based ultraviolet absorber. These may be used individually by 1 type, and may use 2 or more types together.

The content of the ultraviolet absorber in the white ink or the color ink is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose.

--Other resins--
The other resins are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected depending on the purpose. Resins having properties are useful in image formation, and examples thereof include condensed synthetic resins, addition synthetic resins, and natural polymer compounds. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the condensed synthetic resins include polyester resins, polyepoxy resins, polyamide resins, polyether resins, poly(meth)acrylic resins, acrylic-silicone resins, and fluororesins.
In addition, in this specification, "(meth)acryl" means acryl or methacryl.

Examples of the addition type synthetic resins include polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl ester resins, polyacrylic acid resins, and unsaturated carboxylic acid resins.

Examples of the natural polymer compound include celluloses, rosins, natural rubber, and the like.

The content of the other resin in the white ink or the color ink is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected according to the purpose.

<<Physical properties of white ink or color ink>>
As physical properties of the white ink or the color ink, the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink is 1.0 mN/m or less, and the white ink and the color ink, the absolute value of the difference in dynamic surface tension at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec by the maximum bubble pressure method is independently 1.0 mN /m or less, there is no particular limitation, and it can be appropriately selected according to the purpose.

For example, the viscosity of the white ink or the color ink at 25° C. is preferably 5 mPa·s or more and 25 mPa·s or less, more preferably 6 mPa·s or more and 20 mPa·s or less. When the viscosity of the white ink or the color ink at 25° C. is 5 mPa·s or more, an effect of improving image density and character quality can be obtained. Further, when the viscosity of the white ink or the color ink at 25° C. is 25 mPa·s or less, the ink ejection property can be improved.
The viscosity of the white ink or the color ink can be measured at 25° C. using, for example, a viscometer (RE-85L, manufactured by Toki Sangyo Co., Ltd.).

<<Method for producing white ink or color ink>>
A mixture of the white ink or the color ink can be produced in a stirring and mixing step of stirring and mixing various materials.
Stirring and mixing in the stirring and mixing step can be performed using, for example, a sand mill, homogenizer, ball mill, paint shaker, ultrasonic disperser, or the like.

<Pretreatment liquid>
The pretreatment liquid contains water and a flocculant, preferably resin particles, wax particles, an organic solvent, a surfactant, and, if necessary, other components.

-water-
As the water, for example, pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, distilled water, or ultrapure water (highly pure water) can be used.

The content of water in the pretreatment liquid is not particularly limited and can be appropriately selected according to the purpose. , 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.

- Flocculant -
As used herein, the term “aggregating agent” refers to a component that causes the white ink or the color ink to aggregate or thicken when the pretreatment liquid comes into contact with the white ink or the color ink. Specifically, for example, a component that aggregates the colorant or the water-dispersible resin particles (for example, the anionic compound) contained in the white ink or the color ink can be used. By using the pretreatment liquid containing such an aggregating agent, the white ink or the color ink in contact with the pretreatment liquid is caused to aggregate or thicken, thereby causing the white ink or the color ink to adhere to the surface of the recording medium. It can hold ink.

The flocculant is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include cationic compounds. These may be used individually by 1 type, and may use 2 or more types together. Among these, the flocculant is preferably at least one selected from the group consisting of inorganic metal salts, organic acid metal salts, organic acid ammonium salts, and cationic polymers. More preferably, it is at least one selected from the group consisting of polymers.

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, and 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, chloride Magnesium, sodium sulfate, potassium sulfate, lithium sulfate, sodium hydrogen sulfate, potassium hydrogen sulfate, sodium nitrate, potassium nitrate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium chloride, or potassium chloride. Among these, magnesium sulfate or potassium chloride is preferable as the inorganic metal salt.

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, citric acid, calcium acid, 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, Or sodium potassium tartrate etc. are mentioned.

Each of the inorganic metal salt and the organic acid metal salt is preferably at least one selected from calcium salts, magnesium salts, nickel salts, and aluminum salts. When these salts are used, the aggregation function of the water-dispersible particles contained in the white ink or the color ink is improved, and the occurrence of color bleeding and beading can be further suppressed. These salts are also preferable from the viewpoint of storage stability of the pretreatment liquid.

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

As the cationic polymer, a quaternary ammonium salt type cationic polymer compound is preferable. Specifically, dialkylallylammonium chloride polymer, dialkylaminoethyl (meth)acrylate quaternary ammonium salt polymer, modified polyvinyl An alcohol dialkylammonium salt polymer or a dialkyldiallylammonium salt polymer may be used.
In addition, in this specification, "(meth)acrylate" means an acrylate or a methacrylate.

Further, other cationic polymers include cationic special modified polyamine compounds, cationic polyamide polyamine compounds, cationic urea-formalin resin compounds, cationic polyacrylamide compounds, cationic alkylketene dimers, cationic dicyandiamide compounds, cationic Dicyandiamide-formalin condensate compounds, cationic dicyandiamide-polyamine condensate compounds, cationic polyvinylformamide compounds, cationic polyvinylpyridine compounds, cationic polyalkylenepolyamine compounds, cationic epoxy polyamide compounds, and the like.

Particularly preferred cationic polymers include compounds represented by any one of the following general formulas (7) to (10).

In general formula (7), each R ₁₁ independently represents a methyl group or an ethyl group, Y ^{2 −} represents a halogen ion, and n represents an integer.

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

In the general formula (9), each R ₁₆ independently represents a methyl group or an ethyl group, Y ^{2 −} represents a halogen ion, nitrate ion, nitrite ion or acetate ion, and n represents an integer.

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

The content of the flocculant in the pretreatment liquid is not particularly limited and can be appropriately selected according to the purpose. From the viewpoint of suppressing the more preferred.

-Resin particles-
The pretreatment liquid preferably contains resin particles. By including the resin particles in the pretreatment liquid, the adhesiveness between the white ink and the color ink and the recording medium can be improved.

Since the resin particles coexist with a cationic compound flocculant in the pretreatment liquid, from the viewpoint of long-term storage stability, steric hindrance rather than charge repulsion emulsions that are generally used. It is preferable that the nonionic resin particles are dispersed by When anionic resin particles, which are charge-repulsive emulsions, are used, aggregation occurs when they coexist with an inorganic metal salt, which is an example of the aggregating agent. Coexistence causes aggregation instantly. Further, when cationic resin particles are used, they are sufficiently stable when left at room temperature, but increase in viscosity occurs when they are left under heating as an accelerated test in anticipation of long-term stability. Therefore, as described above, the resin particles are preferably the nonionic resin particles.

The method for determining that the resin particles are the nonionic resin particles is not particularly limited. For example, after isolating the solid content from the pretreatment liquid by centrifugation, pyrolysis GC-MS (for example, GC -17A, manufactured by Shimadzu Corporation) shows that materials containing acidic functional groups such as carboxyl groups and sulfo groups, or basic functional groups such as amino groups are not detected.

The nonionic resin particles are not particularly limited and can be appropriately selected according to the purpose. Examples include polyolefin resins, chlorinated polyolefin resins, polyvinyl acetate resins, polyvinyl chloride resins, polyester resins, polyurethane resins, Acrylic resins, styrene-butadiene resins, or copolymers of polymerizable compounds used for polymerization of these resins can be used. These may be used individually by 1 type, and may use 2 or more types together. Among these, the nonionic resin particles are preferably ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate-vinyl chloride copolymer resin, ethylene-vinyl acetate-vinyl versatate copolymer, or chlorinated olefin resin. These resins can further improve the adhesiveness between the white ink and the color ink and the recording medium.

The glass transition temperature (Tg) of the nonionic resin particles is not particularly limited and can be appropriately selected depending on the purpose. °C or less is more preferable. When the glass transition temperature (Tg) of the nonionic resin particles is −30° C. or higher, the resin film becomes tough, and the layer formed by the pretreatment liquid becomes tough. In addition, when the glass transition temperature (Tg) of the nonionic resin particles is 30° C. or less, the film-forming property of the resin is improved and the flexibility is also ensured. Therefore, the white ink and the color ink and the recording medium It is possible to further improve the adhesion between.

The volume average particle diameter of the nonionic resin particles is not particularly limited and can be appropriately selected depending on the purpose. is more preferred.
The volume average particle diameter of the nonionic resin particles can be measured, for example, with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB).

The content (solid content) of the resin particles in the pretreatment liquid is not particularly limited and can be appropriately selected according to the purpose. It is preferably 5% by mass or more and 20.0% by mass or less. When the resin particle content (solid content) is 0.5% by mass or more and 20.0% by mass or less, the adhesiveness between the white ink and the color ink and the recording medium is further improved. can be made

-wax particles-
The wax particles are not particularly limited and can be appropriately selected according to the purpose. For example, water-dispersible wax particles can be used. Specifically, the wax particles include, for example, plant or animal waxes such as carnauba wax, candelilla wax, beeswax, rice wax, or lanolin; paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, and polyethylene oxide. Wax or petroleum wax such as petrolatum; mineral wax such as montan wax or ozokerite; carbon wax, Hoechst wax, polyethylene wax, or synthetic wax such as stearamide. These may be used individually by 1 type, and may use 2 or more types together. Among these, paraffin wax is used as the wax particles from the viewpoint of further improving the adhesion between the white ink and the color ink and the recording medium, and from the viewpoint of dispersibility in the pretreatment liquid. Alternatively, particles of polyethylene wax are preferred, and particles of paraffin wax are more preferred.

The melting point of the wax particles is not particularly limited and can be appropriately selected depending on the intended purpose. When the wax particles have a melting point of 50° C. or more and 130° C. or less, the adhesiveness between the white ink and the color ink and the recording medium can be further improved.

The volume average particle diameter of the wax particles is not particularly limited and can be appropriately selected according to the purpose.
The volume average particle diameter of the wax particles can be measured, for example, with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB).

The content (solid content) of the wax particles in the pretreatment liquid is not particularly limited and can be appropriately selected according to the purpose. 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. When the content of the wax particles (solid content) is 0.05% by mass or more and 5.0% by mass or less, the white ink can be retained near the surface of the recording medium, and the Hunter whiteness can be improved. However, when a white ink layer is formed after the pretreatment liquid containing the wax particles is applied, and an image is formed on the white ink layer with color inks, color bleeding occurs as compared with the pretreatment liquid containing no wax particles. may become more likely to occur.

-Organic solvent-
The organic solvent is not particularly limited and can be appropriately selected depending on the intended purpose. For example, a water-soluble organic solvent can be used. Examples of the water-soluble organic solvent include polyhydric alcohols, ethers (e.g., polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, etc.), nitrogen-containing heterocyclic compounds, amides, amines, etc. Examples include sulfur compounds. These may be used individually by 1 type, and may use 2 or more types together.

Specific examples of the water-soluble organic solvent 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, 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-pentane Polyhydric alcohols such as diols or petriol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether polyhydric alcohol alkyl ethers; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether or ethylene glycol monobenzyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1 Nitrogen-containing heterocyclic compounds such as ,3-dimethyl-2-imidazolidinone, ε-caprolactam, or γ-butyrolactone; formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethyl amides such as propionamide or 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, or triethylamine; sulfur-containing compounds such as dimethylsulfoxide, sulfolane, or thiodiethanol; propylene carbonate; ethylene carbonate and the like.

It is preferable to use an organic solvent having a boiling point of 250° C. or less because the organic solvent not only functions as a wetting agent but also provides good drying properties.
Further, when at least one selected from propylene glycol, 1,3-butanediol, and 1,2-butanediol is contained as the organic solvent, the surface of the recording medium is easily wetted, which is preferable.

The content of the organic solvent in the pretreatment liquid is not particularly limited and can be appropriately selected according to the purpose. 5.0% by mass or more and 60.0% by mass or less is preferable, and 10.0% by mass or more and 30.0% by mass or less is more preferable with respect to the total mass of.

-Surfactant-
The surfactant is not particularly limited and can be appropriately selected depending on the purpose. Any active agent can be used. These may be used individually by 1 type, and may use 2 or more types together.

The silicone-based surfactant is not particularly limited and can be appropriately selected depending on the intended purpose, but is preferably one that does not decompose even at high pH. , polydimethylsiloxane modified at one end, or polydimethylsiloxane modified at both side chain ends. Among these, those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferable as the silicone-based surfactant because they exhibit good properties as water-based surfactants. As the silicone-based surfactant, a polyether-modified silicone-based surfactant can also be used, and examples thereof include compounds in which a polyalkylene oxide structure is introduced into the side chain of the Si portion of dimethylsiloxane.

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

The amphoteric surfactant is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include laurylaminopropionate, lauryldimethylbetaine, stearyldimethylbetaine, lauryldihydroxyethylbetaine and the like.

The nonionic surfactant is not particularly limited and can be appropriately selected depending on the intended purpose. Examples include amides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol.

The anionic surfactant is not particularly limited and can be appropriately selected depending on the intended purpose. Ether sulfate salts and the like can be mentioned.

-Other ingredients-
The other components in the pretreatment liquid are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected according to the purpose. agents and the like.

-- Defoamer --
The antifoaming agent is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include silicone antifoaming agents, polyether antifoaming agents, and fatty acid ester antifoaming agents. In addition, the same antifoaming agent (foaming inhibitor) in the white ink or the color ink can also be used. These may be used individually by 1 type, and may use 2 or more types together. Among these, the antifoaming agent is preferably a silicone antifoaming agent because of its excellent foam breaking effect.

--Anti-corrosion and anti-rust agents--
The antiseptic/antifungal agent is not particularly limited and can be appropriately selected depending on the intended purpose.
The rust inhibitor is not particularly limited and can be appropriately selected depending on the purpose. For example, the same rust inhibitor as in the white ink or the color ink can be used.

<Recording medium>
The recording medium to which the white ink, the color ink, the pretreatment liquid, etc. are applied is not particularly limited and can be appropriately selected according to the purpose. Fabrics, films, OHP sheets, general-purpose printing paper, and the like can be mentioned. Among these, the recording medium is likely to cause color bleeding and beading, and from the viewpoint that the effect obtained by applying the ink set is remarkable, low-permeability recording media such as commercial printing paper, signage, etc. A non-permeable recording medium such as a cloth, or the like is preferable. In addition, unlike films and papers, the fabric has a surface structure rich in unevenness, so the amount of white ink and color ink applied tends to be large, resulting in color bleeding and beading. It is a recording medium that makes it easier to

A cloth will be described as an example of the recording medium. As used herein, the term "fabric" refers to fibers in the form of woven fabrics, knitted fabrics, non-woven fabrics, and the like.

The fibers are preferably synthetic fibers, semi-synthetic fibers, regenerated fibers, or organic fibers such as natural fibers.

Examples of the synthetic fibers include fibers such as polyester, polyamide, acrylic, polyolefin, polyvinyl alcohol, polyvinyl chloride, polyurethane, and polyimide.

Examples of the semi-synthetic fibers include fibers such as acetate, diacetate, or triacetate.

Examples of the regenerated fibers include fibers such as polynosic, rayon, lyocell, and cupra.
Examples of the natural fibers include fibers such as cotton, linen, silk, and wool.

Among the fibers forming the cloth, synthetic fibers such as polyester are more likely to cause color bleeding and beading than natural fibers such as cotton, and it is also difficult to retain white ink on the surface. However, the ink set works well on such fabrics, and is advantageous in that it suppresses color bleeding and beading and also allows the white ink to remain on the surface.

The fabric is preferably a deep-colored fabric that is colored by chemically or physically retaining a coloring agent such as a pigment or dye inside or on the surface of the fiber used in the fabric. When the fabric has a dark color, a white undercoat may be formed between the fabric and the color image for the purpose of improving the color developability of the color image formed on the fabric. This is because it is preferable to use the ink set having the white ink and the color ink.

In this specification, the term "dark-colored fabric" means that the lightness (L ^* ) of the fabric is measured using a spectrophotometer (for example, X-Rite eXact, manufactured by X-Rite). Represents a fabric that satisfies the range of 60>L ^* , preferably a fabric that satisfies the range of 50>L ^* , more preferably a fabric that satisfies the range of 40>L ^* , and more preferably a fabric that satisfies the range of 30>L ^* . More preferably, the fabric satisfies the range of 20>L ^* .

(ink cartridge)
The ink cartridge of the present invention contains the ink set of the present invention, and has the ink set, a container, and, if necessary, other members.
The ink cartridge is advantageous in that there is no need to directly touch the ink during operations such as ink replacement, there is no fear of staining fingers or clothes, and foreign matter such as dust can be prevented from entering the ink.

The ink cartridge may house the ink set integrally, or may contain the white ink and the color ink independently. Further, when the ink set includes a plurality of the white ink and the color ink, the ink cartridge may contain the white ink and the color ink integrally or may contain the color inks independently. good.

The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected according to the purpose. things are preferred.

The method for manufacturing the ink cartridge is not particularly limited, and the ink cartridge can be manufactured by appropriately using a known method.

The ink cartridge, for example, contains an ink set contained in a container such as the ink bag, further contained in a cartridge case (for example, a plastic case), and is detachably attached to the image forming apparatus. It is preferable that As a result, ink replenishment and replacement can be simplified, and workability can be improved.

(Image forming apparatus and image forming method)
The image forming apparatus of the present invention has white ink containing means, color ink containing means, white ink applying means, and color ink applying means, and may further have other means as necessary. good.

The image forming method of the present invention has a white ink application step and a color ink application step, and may have other steps as necessary.

The image forming method of the present invention is preferably performed by the image forming apparatus of the present invention. The image forming method of the present invention will be described below together with the description of the image forming apparatus of the present invention.

<White Ink Containing Means>
The white ink containing means is means for containing white ink.
The white ink containing means may be the ink cartridge of the present invention.
The white ink contained in the white ink containing means is the white ink included in the ink set of the present invention.

<Color ink container>
The color ink containing means is a means for containing color ink.
The color ink containing means may be the ink cartridge of the present invention.
The color ink contained in the color ink containing means is the color ink contained in the ink set of the present invention.

<White ink applying means and white ink applying step>
The white ink application means is means for applying white ink to the recording medium.
The white ink applying step is a step of applying white ink to the recording medium.
The white ink applying step is preferably performed by the white ink applying means.
The recording medium is not particularly limited, and can be appropriately selected according to the intended purpose. However, those described in <Recording medium> of the above (Ink set) can be used, and preferred embodiments are the same. be.

A method for applying the white ink is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include an ejection method and a coating method. Among these, the method for applying the white ink is preferably an ejection method, and more preferably an inkjet ejection method.

The ejection method is not particularly limited and can be appropriately selected according to the purpose. For example, a method using an ejection type charge control type head may be used.

The amount (adhesion amount) of the white ink applied to the recording medium varies greatly depending on the type of the recording medium, but is 1 g/m ² or more and 500 g/m ² or less from the viewpoint of improving image quality and drying property. more preferably 5 g/m ² or more and 400 g/m ² or less.
Further, when the cloth is used as the recording medium, the amount (adherence amount) of the white ink applied to the recording medium is preferably 50 g/m ² or more and 500 g/m ² or less, and 100 g/m ² . It is more preferably 400 g/m ² or more, and even more preferably 150 g/m ² or more and 300 g/m ² or less.

<Color ink application means and color ink application process>
The color ink applying means is means for applying 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 application step is preferably performed by the color ink application means.

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 (attachment amount) of the color ink applied to the recording medium varies greatly depending on the type of the recording medium, but is 1 g/m ² or more and 50 g/m ² or less from the viewpoint of improving image quality and drying property. more preferably 5 g/m ² or more and 30 g/m ² or less.
Further, when the fabric is used as the recording medium, the amount (adhesion amount) of the color ink applied to the recording medium is preferably 5 g/m ² or more and 50 g/m ² or less, and 10 g/m ² . It is more preferable to be 30 g/m ² or more.

In the image forming method, the time from when the white ink is applied to the recording medium until when the color ink is applied to the area of the recording medium to which the white ink has been applied (i.e. , the time between the white ink application step and the color ink application step) is preferably as short as possible from the viewpoint of productivity. The time from when the white ink is applied to the recording medium to when the color ink is applied to the area of the recording medium to which the white ink has been applied is the drying of the white ink ( This is the time for aggregation and/or thickening), and is intended to suppress color bleeding and beading caused by insufficient drying (aggregation and/or thickening) of the white ink. The image forming method of the present invention uses the white ink and the color ink having the relationship between the static surface tension and the dynamic surface tension described in the item (Ink set), and applies the white ink to the recording medium. is applied, the color ink is applied to the area of the recording medium to which the white ink has been applied, and color bleeding and beading can be suppressed.

<Other means and other steps>
Examples of the other means include pretreatment liquid storage means, pretreatment liquid application means, heating or drying means, and the like.
Examples of the other processes include a pretreatment liquid application process and a heating or drying process.

<<Pretreatment Liquid Storage Means>>
The pretreatment liquid containing means is a means for containing a pretreatment liquid.
The pretreatment liquid contained in the containing means is the pretreatment liquid contained in the ink set of the present invention.

<<Pretreatment Liquid Application Means and Pretreatment Liquid Application Step>>
The pretreatment liquid applying means is a means for applying the pretreatment liquid in advance to a region of the recording medium to which the white ink is to be applied.
The pretreatment liquid applying step is a step of applying a pretreatment liquid to a region of the recording medium to which the white ink is to be applied before the white ink applying step.
The pretreatment liquid application step is preferably performed by the pretreatment liquid application means.

When the image forming apparatus has the pretreatment liquid storage unit and the pretreatment liquid application unit, the white ink application unit applies the white ink to the area of the recording medium to which the pretreatment liquid has been applied. It can be rephrased as a means to
Further, when the image forming method includes the pretreatment liquid application step, the white ink application step can be rephrased as a step of applying the white ink to a region of the recording medium to which the pretreatment liquid has been applied. can be done.

The method for applying the pretreatment liquid is not particularly limited, and can be appropriately selected depending on the purpose. be.

^The application amount (attachment amount) of the pretreatment liquid to the recording medium varies greatly depending on the type of the recording medium ^. It is preferably 1 g/m ² or more and 400 g/m ² or less.
Further, when the fabric is used as the recording medium, the amount (adhesion amount) of the pretreatment liquid applied to the recording medium is preferably 100 g/m ² or more and 500 g/m ² or less, and preferably 200 g/m 2 or more. It is more preferably ² or more and 500 g/m ² or less, and even more preferably 300 g/m ² or more and 400 g/m ² or less.

<<Heating or drying means and heating or drying process>>
The heating or drying means heats or dries various liquids such as the white ink, the color ink, or the pretreatment liquid applied to the recording medium.
The heating or drying step is a step of heating or drying various liquids such as the white ink, the color ink, or the pretreatment liquid applied to the recording medium.
The heating or drying step is preferably performed by the heating or drying means.

The heating or drying means is not particularly limited, and can be appropriately selected from known heating means, such as roll heaters, drum heaters, hot air generators, and heat presses.

Further, the drying step is not particularly limited as long as various liquids such as the white ink, the color ink, or the pretreatment liquid applied to the recording medium can be dried, and natural drying is performed after applying the various liquids. methods and the like. In this specification, the “drying step” means applying another liquid after more than 20 seconds have elapsed since applying a certain liquid. For example, the time between the application of the white ink to the recording medium and the application of the color ink to the area of the recording medium to which the white ink has been applied is longer than 20 seconds. In some cases, the imaging method will include a drying step. Therefore, applying another liquid within 20 seconds after applying a certain liquid is not included in the drying step.

As described above, the image forming method does not include a heating or drying step of heating or drying the recording medium to which the white ink has been applied, between the white ink applying step and the color ink applying step. Since the occurrence of color bleeding and beading can be suppressed even in the case of It is preferable not to include a heating or drying step of heating or drying the.
Similarly, the image forming apparatus heats or heats the recording medium to which the white ink is applied between the application of the white ink by the white ink application unit and the application of the color ink by the color ink application unit. It preferably has no drying heating or drying means.

The image forming apparatus of the present invention will be specifically described below with reference to FIGS. 1 and 2, but the present invention is not limited to this.

FIG. 1 is a schematic perspective view showing an example of the image forming apparatus of the present invention. FIG. 2 is a schematic perspective view showing an example of storage means (white ink storage means, color ink storage means, or pretreatment liquid storage means) of the image forming apparatus of the present invention.

An image forming apparatus 400 shown in FIG. 1 is an image forming apparatus having a serial type inkjet ejection head. A mechanical unit 420 is provided inside the exterior 401 of the image forming apparatus 400 . The storage portions 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 made of, for example, aluminum. It is formed by a packaging member such as a laminate film. The accommodating portion 411 is accommodated in, for example, a plastic container case 414 . Accordingly, each containing means 410 is used as an ink cartridge.

On the other hand, a cartridge holder 404 is provided behind the opening when the cover 401c of the main body of the image forming apparatus 400 is opened. Each storage means 410 (p, w, k, and c) is detachably attached to the cartridge holder 404 . As a result, the outlet 413 of each container 410 (p, w, k, and c) communicates with the inkjet ejection head 434 via each supply tube 436, and the pretreatment liquid is supplied from the inkjet ejection head 434 to the recording medium. And each ink can be ejected.
In the image forming apparatus 400 shown in FIG. 1, the pretreatment liquid is applied to the recording medium by an inkjet ejection method.

The image forming apparatus 400 may have heating or drying means for heating or drying various liquids such as white ink, color ink, or pretreatment liquid applied to the recording medium. It is preferable that there is no heating or drying means for heating or drying the recording medium to which the white ink has been applied from the time of application to before the application of the color ink. Such heating or drying means is provided for the purpose of suppressing color bleeding and beading caused by insufficient drying of the white ink by heating or drying the white ink. This is because the ink set of (1) can suppress color bleeding and beading without having heating or drying means.

EXAMPLES The present invention will be specifically described below with reference to Preparation Examples, Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these Preparation Examples, Production Examples, and Examples.

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 manufactured by Cabot Corporation (carbon black having a BET specific surface area of 343 m ² /g and a dibutyl phthalate absorption (DBPA) of 105 mL/100 g), 100 mmol of sulfanilic acid, and 1 L of high-purity water were added at room temperature (23° C.). ±0.5° C.) and mixed at 6,000 rpm using a Silverson (registered trademark) mixer to obtain a slurry.
Next, 100 mmol of nitric acid was added to the resulting slurry, and after 30 minutes, 100 mmol of sodium nitrite dissolved in 10 mL of high-purity water was slowly added. Further, the mixture was heated to 60° C. with stirring and allowed to react 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 weight tetrabutylammonium hydroxide methanol solution, and after 30 minutes, a modified pigment dispersion was obtained. Next, this modified pigment dispersion and high-purity water were subjected to ultrafiltration with a dialysis membrane, followed by ultrasonic dispersion to obtain a surface-modified black pigment dispersion containing 20% by mass of pigment solids.
The surface treatment level of the pigment in the resulting surface-modified black pigment dispersion was 0.75 mmol/g. The particle diameter D50 was 120 nm.

(Preparation Example 2: Preparation of surface-modified magenta pigment dispersion)
1 kg of a pigment dispersion SMART Magenta 3122BA (CI Pigment Red 122 surface-treated dispersion, pigment solid content 14.5% by mass) manufactured by SENSIENT was precipitated with a 0.1N hydrochloric acid aqueous solution.
Next, the pH was adjusted to 9 with a 10 mass % tetraethylammonium hydroxide aqueous solution, and after 30 minutes, a modified pigment dispersion was obtained. A modified pigment dispersion containing a pigment bound with at least one aminobenzoic acid group or a tetraethylammonium aminobenzoate salt and high-purity water are subjected to ultrafiltration with a dialysis membrane, followed by ultrasonic dispersion to obtain a pigment solid. A surface-modified magenta pigment dispersion containing 20 wt.
The resulting surface-modified magenta pigment dispersion was measured with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB) to find 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 (CI Pigment Blue 15:4 surface treatment dispersion, pigment solid content 14.5% by mass) manufactured by SENSIENT was precipitated with a 0.1N hydrochloric acid aqueous solution.
Next, the pH was adjusted to 9 with a 40% by weight benzyltrimethylammonium hydroxide methanol solution, and after 30 minutes, a modified pigment dispersion was obtained. A modified pigment dispersion containing a pigment bound with at least one aminobenzoic acid group or benzyltrimethylammonium aminobenzoate and high-purity water are subjected to ultrafiltration with a dialysis membrane, followed by ultrasonic dispersion to obtain a pigment. A surface-modified cyan pigment dispersion containing 20% by weight of solids was obtained.
The surface-modified cyan pigment dispersion thus obtained was measured with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB) to find that the cumulative 50% volume particle diameter D50 was 116 nm.

(Preparation Example 4: Preparation of surface-modified yellow pigment dispersion)
Pigment dispersion SMART Yellow 3074BA (CI Pigment Yellow 74 surface treatment dispersion, pigment solid content 14.5% by mass) manufactured by SENSIENT was adjusted to pH 9 with a 10% by mass tetrabutylammonium hydroxide methanol solution. , to give a modified pigment dispersion after 30 minutes. A modified pigment dispersion containing a pigment bonded with at least one aminobenzoic acid group or tetrabutylammonium aminobenzoate is used, and high-purity water is used to perform ultrafiltration with a dialysis membrane, and then ultrasonically disperse the pigment. A surface modified yellow pigment dispersion containing 20% solids was obtained.
The surface-modified yellow pigment dispersion thus obtained was measured with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB), and the cumulative 50% volume particle diameter D50 was 145 nm.

(Preparation Example 5: Preparation of Magenta Pigment-Containing Polymer Fine Particle Dispersion)
After the interior of a 1 L flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube, and dropping funnel was sufficiently replaced with nitrogen gas, 11.2 g of styrene, 2.8 g of acrylic acid, and 12 g of lauryl methacrylate were added. 0 g, 4.0 g of polyethylene glycol methacrylate, 4.0 g of styrene macromer, and 0.4 g of mercaptoethanol were mixed in a flask and heated to 65°C. Next, styrene 100.8 g, acrylic acid 25.2 g, lauryl methacrylate 108.0 g, polyethylene glycol methacrylate 36.0 g, hydroxylethyl methacrylate 60.0 g, styrene macromer 36.0 g, mercaptoethanol 3.6 g, azobismethyl valero. A mixed solution of 2.4 g of nitrile and 18 g of methyl ethyl ketone was dropped into the flask over 2.5 hours. After dropping, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After stirring for 1 hour at 65° C., 0.8 g of azobismethylvaleronitrile was added and further stirred for 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added into the flask to obtain 800 g of polymer solution A having a concentration of 50% by mass.

Next, 28 g of polymer solution A and C.I. I. 42 g of Pigment Red 122, 13.6 g of 1 mol/L potassium hydroxide aqueous solution, 20 g of methyl ethyl ketone, and 13.6 g of high-purity water were sufficiently stirred and kneaded using a roll mill. The obtained paste was poured into 200 g of high-purity water, and after sufficiently stirring, methyl ethyl ketone and water were distilled off using an evaporator. Pressure filtration was performed using a filter to obtain a magenta pigment-containing polymer fine particle dispersion containing 15% by mass of pigment solids and 20% by mass of total solids.
The resulting magenta pigment-containing polymer fine particle dispersion was measured with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB), and the cumulative 50% volume particle diameter D50 was 127 nm.

(Preparation Example 6: Preparation of Cyan Pigment-Containing Polymer Fine Particle Dispersion)
In Preparation Example 5, C.I. I. Pigment Red 122 was changed to a phthalocyanine pigment (C.I. Pigment Blue 15:3) in the same manner as in Preparation Example 5, containing 15% by mass of pigment solids and 20% by mass of total solids. A cyan pigment-containing polymer fine particle dispersion was prepared.
When the polymer fine particles in the resulting cyan pigment-containing polymer fine particle dispersion were measured with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB), the cumulative 50% volume particle diameter D50 was 93 nm.

(Preparation Example 7: Preparation of Yellow Pigment-Containing Polymer Fine Particle Dispersion)
Pigment Red 122 as the pigment in Preparation Example 5 was changed to a bisazo yellow pigment (CI Pigment Yellow 155), in the same manner as in Preparation Example 5, to obtain a pigment solid content of 15. A dispersion of yellow pigment-containing polymer microparticles containing 20% by weight of total solids was prepared.
The polymer fine particles in the yellow pigment-containing polymer fine particle dispersion thus obtained were measured with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB), and the cumulative 50% volume particle diameter D50 was 76 nm.

(Preparation Example 8: Preparation of black pigment-containing polymer fine particle dispersion)
Pigment Red 122 as the pigment in Preparation Example 5 was changed to carbon black (FW100, manufactured by Degussa) in the same manner as in Preparation Example 5, containing 15% by mass of pigment solids, A black pigment-containing polymer microparticle dispersion containing 20% by weight of total solids was prepared.
The polymer fine particles in the black pigment-containing polymer fine particle dispersion thus obtained were measured with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB) to find that the cumulative 50% volume particle diameter D50 was 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, and 377.4 g of high-purity water After sufficiently stirring, it was put into a bead mill (Dyno Mill) and dispersed until the cumulative 50% volume particle diameter D50 became 300 nm or less. Furthermore, in order to remove coarse particles, this dispersion was pressure-filtered through a polyvinylidene fluoride membrane filter having an average pore size of 5.0 μm to obtain a polymer-dispersed white pigment dispersion containing 50% by mass of white pigment solids.
The pigment particles in the resulting polymer-dispersed white pigment dispersion were measured with a particle size distribution analyzer (Nanotrac Wave II-UT151, manufactured by Microtrac MRB), and the cumulative 50% volume particle diameter D50 was 283 nm.

White inks and color inks were produced by the methods described in Production Examples 1-1 to 1-50 below.

(Production Example 1-1: Production of Ink 1)
In a container equipped with a stirrer, 2.00 parts by weight of 2,2,4-trimethyl-1,3-pentanediol, 25.00 parts by weight of glycerin, 5.00 parts by weight of propylene glycol, and 2,4 ,7,9-tetramethyldecane-4,7-diol was added in an amount of 0.12 parts by mass, and mixed and stirred for 30 minutes. Next, 0.05 parts by mass of an antiseptic and antifungal agent (PROXEL (registered trademark) GXL) and 26.67 parts by mass of the magenta pigment-containing polymer fine particle dispersion of Preparation Example 5 were added and mixed and stirred for 20 minutes. 33.33 parts by mass of Takelac (registered trademark) WS-6021 as water-dispersible resin particles, 1.25 parts by mass of Takenate (registered trademark) XWB-ST001 as a cross-linking agent, and 100 parts by mass as a whole. amount of high-purity water was added and 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 to obtain Ink 1 .

(Production Examples 1-2 to 1-50: Production of Inks 2 to 50)
Inks 2 to 50 were obtained in the same manner as in Production Example 1-1, except that the ink formulation was changed to the materials and contents shown in Tables 1-1 to 1-10 below. .
In Tables 1-1 to 1-10 below, the unit for the content of various materials is "% by mass", and the content is not the amount of solid content or the amount of active ingredients, but the total amount.

The details of various materials shown in Tables 1-1 to 1-10 below are as follows.

--coloring material--
・ Polymer-dispersed white pigment dispersion: AC-AW62 (manufactured by Dainichiseika Kogyo Co., Ltd., pigment solid content 50% by mass)

--Water-dispersible resin particles--
・Superflex 460: Polyurethane dispersion, solid content 38% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 460S: Polyurethane dispersion, solid content 38% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Superflex 470: Polyurethane Dispersion, solid content 38% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Takelac (registered trademark) WS-5984: Polyurethane dispersion, solid content 40% by mass, manufactured by Mitsui Chemicals, Inc. ・Takelac (registered trademark) WS-6021 : Polyurethane dispersion, solid content 30% by mass, manufactured by Mitsui Chemicals, Inc.

--Blocked isocyanate compound--
・Elastron (registered trademark) E-37: 28% by mass of active ingredient, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Elaston (registered trademark) H-3-DF: 27.5% by mass of active ingredient, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.・ Takenate (registered trademark) XWB-ST001: 40% by mass of active ingredient, manufactured by Mitsui Chemicals, Inc. ・ ADEKA BONTITER HUX-3861: 35% by mass of active ingredient, manufactured by ADEKA Corporation

--Surfactant--
- Compound represented by structural formula (8): polyether-modified siloxane compound, active ingredient 100%
・ TEGO (registered trademark) Wet 270: polyether-modified siloxane compound, manufactured by Evonik, active ingredient 100%
・ Silface SAG503A: polyether-modified siloxane compound, manufactured by Nissin Chemical Industry Co., Ltd., active ingredient 100%
・Surfinol 104E: 2,4,7,9-tetramethyl-5-decyne-4,7-diol, manufactured by Nissin Chemical Industry Co., Ltd., active ingredient 50%
・ Unidyne DSN403N: polyoxyethylene perfluoroalkyl ether, manufactured by Daikin Industries, Ltd., active ingredient 100%

-- Antiseptic and antifungal agents --
・PROXEL (registered trademark) GXL: An antiseptic and antifungal agent containing 1,2-benzothiazolin-3-one as a main component (manufactured by Avecia, component 20%, containing dipropylene glycol)

<Physical properties of white ink and color ink>
Inks 1 to 50 obtained in Production Examples 1-1 to 1-50 were measured for various physical properties such as viscosity, pH, static surface tension, and dynamic surface tension as follows. The results are shown in Tables 2-1 and 2-2 below.

-viscosity-
The viscosities of inks 1 to 50 obtained in Production Examples 1-1 to 1-50 were measured at 25° C. using a viscometer (RE85L, manufactured by Toki Sangyo Co., Ltd.).

-pH-
The pH of inks 1 to 50 obtained in Production Examples 1-1 to 1-50 was measured at 25° C. using a pH meter (HM-30R type, manufactured by Toa DKK Co., Ltd.).

－Static surface tension－
The static surface tension of inks 1 to 50 obtained in Production Examples 1-1 to 1-50 was measured using an automatic surface tensiometer (DY-300, manufactured by Kyowa Interface Science Co., Ltd.) using a plate method (Wilhelmy method). was measured at 25°C by

－Dynamic surface tension－
The dynamic surface tension of the inks 1 to 50 obtained in Production Examples 1-1 to 1-50 at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec by the maximum bubble pressure method was measured using a portable dynamic surface tensiometer ( It was measured at 25° C. using SITA Pro line t15 (manufactured by Eiko Seiki Co., Ltd.).
In Tables 2-1 and 2-2 below, "Relationship of dynamic surface tension between color inks (15 msec)", "B" indicates black ink, "C" indicates cyan ink, and "M ' indicates magenta ink, and 'Y' indicates yellow ink.

A pretreatment liquid was prepared by the method described in Production Examples 2-1 to 2-12 below.

(Production Example 2-1: Production of pretreatment liquid 1)
12.50 parts by mass of magnesium sulfate was weighed into a glass beaker, and 50.00 parts by mass of high-purity water was added, followed by stirring for 5 minutes. Next, 3.00 parts by mass of propylene glycol, 17.14 parts by mass of nonionic resin emulsion (Takelac (registered trademark) W-635), 0.05 parts by mass of antiseptic and antifungal agent (PROXEL (registered trademark) GXL), and 0.10 parts by mass of 1,2,3-benzotriazole were added, and mixed and stirred for 15 minutes. Furthermore, high-purity 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 subjected to pressure filtration through a polyvinylidene fluoride membrane filter having an average pore size of 5.0 μm to remove dust such as insoluble matter, and a pretreatment liquid 1 was prepared.

(Production Examples 2-2 to 2-12: Production of pretreatment liquids 2 to 12)
In Production Example 2-1, except that the formulation of the pretreatment liquid was changed to the materials and contents shown in Tables 3-1 and 3-2 below, pretreatment liquids 2 to 2 were prepared in the same manner as in Production Example 2-1. 12 was prepared.
In Tables 3-1 and 3-2 below, the unit for the content of various materials is "% by mass", and the content is not the amount of solid content or the amount of active ingredients, but the total amount.

Details of various materials shown in Tables 3-1 and 3-2 below are as follows.

-- Cationic polymer --
・Charol (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 Co., Ltd.

--Nonionic resin particles--
・Takelac (registered trademark) 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, 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%, manufactured by BYK Japan Co., Ltd. ・AQUACER 531: Modified polyethylene wax, active ingredient 45% by mass , manufactured by BYK Japan Co., Ltd.

-- Antiseptic and antifungal agents --
・PROXEL (registered trademark) GXL: An antiseptic and antifungal agent containing 1,2-benzothiazolin-3-one as a main component (manufactured by Avecia, component 20%, containing dipropylene glycol)

Images were formed using the ink sets by the methods described in Examples 1 to 16 and Comparative Examples 1 to 7 below.

(Examples 1 to 14 and Comparative Examples 1 to 7)
Using an inkjet printer (Direct to Garment Printer RICOH Ri 6000, manufactured by Ricoh Co., Ltd.) under environmental conditions adjusted to 23°C ± 0.5°C and 50% ± 5% RH, the amount of ink ejected becomes uniform. By varying the driving voltage of the piezoelectric element, the setting was made so that the same amount of ink adhered to the recording medium.

First, as shown in Tables 4-1 and 4-2 below, a predetermined pretreatment liquid was applied to a predetermined recording medium by a predetermined application method (coating method) so as to have a predetermined adhesion amount. . After that, if the recording medium is a dark colored polyester T-shirt (00300-ACT), it is dried in an oven at 130°C for 90 seconds, and if it is a dark colored cotton T-shirt (00085-CVT), it is dried in an oven at 165°C. Allow to dry for 90 seconds.

Next, white ink and color ink contained in the predetermined ink sets shown in Tables 4-1 and 4-2 below are respectively filled in the inkjet printing apparatus, and the area of the recording medium to which the pretreatment liquid has been applied 17 seconds after the application of the white ink, the white ink is applied to the area of the recording medium to which the white ink has been applied. On the other hand, the chart shown in FIG. 3 was formed by applying the color ink in the predetermined adhesion amounts shown in Tables 4-1 and 4-2 below.
Note that the recording medium was not heated between the application of the white ink and the application of the color ink.

Next, when the recording medium having the chart shown in FIG. , sample images were obtained by drying in an oven at 165° C. for 2 minutes.
In FIG. 3, "W" represents a white solid image portion as a base, "Y" represents a yellow solid image formed on the base W, and "M" formed on the base W. "C" represents a cyan solid image formed on the background W, "P" represents a magenta solid image formed on the background W, “V” represents a blue solid image portion formed on the background W, “G” represents a green solid image portion formed on the background W, and “K” represents a black color formed on the background W. “k ₁ ” to “k ₆ ” represent a black character “R” formed on the background W, and “y” represents a yellow character “R ” represents. The chart shown in FIG. 3 was created based on an image converted into data without color correction using software Photoshop (registered trademark) (manufactured by Adobe (registered trademark)) and printed at 600 dpi × 600 dpi. .

(Example 15)
A sample image was obtained in the same manner as in Example 1, except that in printing the sample image of Example 1, the time from the application of the white ink to the application of the color ink was changed from 17 seconds to 60 seconds. .

(Example 16)
In printing the sample image of Example 1, there was no 17 seconds between the application of the white ink and the application of the color ink, and immediately after the application of the white ink, the color ink was dried in an oven at 165°C for 90 seconds. A sample image was obtained in the same manner as in Example 1, except that it was applied.

Details of various recording media shown in Tables 4-1 and 4-2 below are as follows.
・ 00300-ACT: Dark polyester T-shirt, glimmer (registered trademark) 00300-ACT Black, manufactured by TMS Co., Ltd. ・ 00085-CVT: Dark-colored cotton T-shirt, Printstar (registered trademark) 00085-CVT Black, manufactured by TMS Co., Ltd.

In Tables 4-1 and 4-2 below, "white ink - color ink application time" refers to the period from application of white ink to application of color ink in printing the sample images of Examples 1 to 16 and Comparative Examples 1 to 7. indicates the time to
Further, in Tables 4-1 and 4-2 below, the “heating step after applying white ink” refers to the printing of the sample images of Examples 1 to 16 and Comparative Examples 1 to 7 after applying the white ink and after applying the color ink. The presence or absence of the heating process before applying the ink, and the heating conditions (temperature and time) when the heating process is "yes" are shown.

<Evaluation of sample images>
The sample images obtained in Examples 1 to 16 and Comparative Examples 1 to 7 were evaluated for Hunter whiteness, color bleeding, beading, and fastness to rubbing as follows. The results are shown in Tables 5-1 to 5-4 below.

－Hunter Whiteness－
The color values L, a, and b of the image densities in the white solid image portions of the sample images obtained in Examples 1 to 16 and Comparative Examples 1 to 7 were measured using a spectral density colorimeter (X-Rite eXact, X - Rite), the Hunter whiteness was calculated by the following formula (1), and evaluated based on the following evaluation criteria.
The image density was measured by placing a sample image on five sheets of medium-thick colored high-quality paper (manufactured by Hokuetsu Corporation) stacked one on top of the other.
Hunter whiteness=100−sqr[(100−L) ² +(a ² +b ² )] Calculation 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 white degree is less than 70

-color bleed-
In each of the sample images obtained in Examples 1 to 16 and Comparative Examples 1 to 7, color bleeding (for example, "W" in FIG. 3) between a color solid image portion and an adjacent white solid image portion color boundary bleed between "Y") and color bleed between a solid image portion of one color and an adjacent solid image portion of another color (e.g., "K" and "y" in FIG. 3). Or, the degree of color boundary bleeding between "k ₁ " and "Y") was visually observed by a professional evaluator and evaluated based on the following evaluation criteria.
[Evaluation criteria]
A+: No color boundary bleeding A: Very slight color boundary bleeding B: Slight color boundary bleeding C: Color boundary bleeding D: Significant color boundary Bleeding occurs

－Beading－
The degree of beading (density unevenness) in the color solid image portion of each sample image obtained in Examples 1 to 16 and Comparative Examples 1 to 7 was visually observed by a professional evaluator based on the following evaluation criteria. evaluated.
[Evaluation criteria]
A: No density unevenness B: Slight density unevenness C: Density unevenness D: Significant density unevenness

－Fastness to Rubbing－
According to the method specified in JIS L 0849, the test was performed by the friction tester type I (crockmeter) method using a friction tester type I. "Dry friction" was tested according to the dry test specified in JIS L0849, "wet friction" was tested according to the wet test specified in JIS L0849, and evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: Color chart grade 4-5 to 5 B: Color chart grade 3-4 to 4 C: Color chart grade 2-3 to 3 D: Color chart grade 2 or less

Embodiments of the present invention include, for example, the following.
<1> An ink set comprising a white ink and a color ink,
The white ink and the color ink independently contain water-dispersible resin particles having a crosslinkable functional group, and blocked isocyanate having a functional group capable of crosslinking with the water-dispersible resin particles having a crosslinkable functional group. containing a compound and
the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink is 1.0 mN/m or less;
The absolute values of the dynamic surface tension differences at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently The ink set is characterized by being 1.0 mN/m or less.
<2> The white ink and the color ink each independently contain 0.1 to 0.1 parts by mass of the blocked isocyanate compound with respect to 1 part by mass of the water-dispersible resin particles having the crosslinkable functional group. The ink set according to <1>, containing 55 parts by mass.
<3> The ink set according to any one of <1> to <2>, wherein the white ink and the color ink each independently have a static surface tension of 40.0 mN/m or less at 25°C. is.
<4> the color ink is a plurality of color inks including black ink, cyan ink, magenta ink, and yellow ink;
The absolute value of the difference in dynamic surface tension at 25° C. when the bubble life time is 15 msec by the maximum bubble pressure method is independently 1.0 mN/m or less between the plurality of color inks;
The dynamic surface tension of the black ink, the cyan ink, the magenta ink, and the yellow ink at 25° C. with a bubble lifetime of 15 msec according to the maximum bubble pressure method satisfies the following relational expression (1): <1> 3. The ink set according to any one of <3>.
Black ink>Cyan ink≧Magenta ink≧Yellow ink Relational expression (1)
<5> The ink set further includes a pretreatment liquid,
The pretreatment liquid contains water and a flocculating agent,
The flocculant is at least one selected from the group consisting of inorganic metal salts, organic acid metal salts, organic acid ammonium salts, and cationic polymers, according to any one of <1> to <4>. Ink set.
<6> The ink set according to <5>, wherein the pretreatment liquid further contains nonionic resin particles.
<7> The ink set according to any one of <5> to <6>, wherein the pretreatment liquid further contains wax particles.
<8> The ink set according to <7>, wherein the wax particles are particles of paraffin wax.
<9> a white ink application step of applying white ink to the recording medium;
a color ink applying step of applying color ink to the area of the recording medium to which the white ink has been applied;
including
The white ink and the color ink independently contain water-dispersible resin particles having a crosslinkable functional group, and blocked isocyanate having a functional group capable of crosslinking with the water-dispersible resin particles having a crosslinkable functional group. containing a compound and
the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink is 1.0 mN/m or less;
The absolute values of the dynamic surface tension differences at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently The image forming method is characterized in that the density is 1.0 mN/m or less.
<10> The image according to <9>, further comprising, before the white ink applying step, a pretreatment liquid applying step of applying a pretreatment liquid to a region of the recording medium to which the white ink is applied. formation method.
<11> The above <9> to <10>, which does not include a heating or drying step of heating or drying the recording medium to which the white ink has been applied, between the white ink applying step and the color ink applying step. The image forming method according to any one of .
<12> The time between the application of the white ink to the recording medium and the application of the color ink to the area of the recording medium to which the white ink has been applied is 20 seconds or less. The image forming method according to any one of <9> to <11> above.
<13> The image forming method according to any one of <9> to <12>, wherein the recording medium is dark-colored fabric.
<14> The white ink and the color ink independently contain 0.1 to 0.1 parts by mass of the blocked isocyanate compound with respect to 1 part by mass of the water-dispersible resin particles having the crosslinkable functional group. The image forming method according to any one of <9> to <13>, containing 55 parts by mass.
<15> The image formation according to any one of <9> to <14>, wherein the white ink and the color ink each independently have a static surface tension of 40.0 mN/m or less at 25°C. The method.
<16> the color ink is a plurality of color inks including black ink, cyan ink, magenta ink, and yellow ink;
The absolute value of the difference in dynamic surface tension at 25° C. when the bubble life time is 15 msec by the maximum bubble pressure method is independently 1.0 mN/m or less between the plurality of color inks;
The dynamic surface tension of the black ink, the cyan ink, the magenta ink, and the yellow ink at 25° C. with a bubble lifetime of 15 msec according to the maximum bubble pressure method satisfies the following relational expression (1): <9> The image forming method according to any one of <15> to <15>.
Black ink>Cyan ink≧Magenta ink≧Yellow ink Relational expression (1)
<17> The pretreatment liquid contains water and a coagulant,
The flocculant is at least one selected from the group consisting of inorganic metal salts, organic acid metal salts, organic acid ammonium salts, and cationic polymers, according to any one of <10> to <16>. An image forming method.
<18> The image forming method according to <17>, wherein the pretreatment liquid further contains nonionic resin particles.
<19> The image forming method according to any one of <17> to <18>, wherein the pretreatment liquid further contains wax particles.
<20> The image forming method according to <19>, wherein the wax particles are particles of paraffin wax.
<21> white ink containing means containing white ink;
a color ink containing means containing color ink;
white ink applying means for applying the white ink to a recording medium;
a color ink applying means for applying the color ink to the area of the recording medium to which the white ink has been applied;
has
The white ink and the color ink independently contain water-dispersible resin particles having a crosslinkable functional group, and blocked isocyanate having a functional group capable of crosslinking with the water-dispersible resin particles having a crosslinkable functional group. containing a compound and
the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink is 1.0 mN/m or less;
The absolute values of the dynamic surface tension differences at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently The image forming apparatus is characterized in that it is 1.0 mN/m or less.
<22> a pretreatment liquid containing means containing a pretreatment liquid;
pretreatment liquid applying means for applying the pretreatment liquid in advance to the area of the recording medium to which the white ink is to be applied;
The image forming apparatus according to <21>, further comprising:
<23> The image forming apparatus according to any one of <21> to <22>, which does not include heating or drying means for heating or drying the recording medium to which the white ink has been applied.
<24> The image forming apparatus according to any one of <21> to <23>, wherein the recording medium is dark-colored fabric.
<25> The white ink and the color ink independently contain 0.1 to 0.1 parts by mass of the blocked isocyanate compound with respect to 1 part by mass of the water-dispersible resin particles having the crosslinkable functional group. The image forming apparatus according to any one of <21> to <24>, containing 55 parts by mass.
<26> The image formation according to any one of <21> to <25>, wherein the white ink and the color ink each independently have a static surface tension of 40.0 mN/m or less at 25°C. It is a device.
<27> the color ink is a plurality of color inks including black ink, cyan ink, magenta ink, and yellow ink;
The absolute value of the difference in dynamic surface tension at 25° C. when the bubble life time is 15 msec by the maximum bubble pressure method is independently 1.0 mN/m or less between the plurality of color inks;
The dynamic surface tension of the black ink, the cyan ink, the magenta ink, and the yellow ink at 25° C. with a bubble lifetime of 15 msec according to the maximum bubble pressure method satisfies the following relational expression (1): <21> The image forming apparatus according to any one of <26>.
Black ink>Cyan ink≧Magenta ink≧Yellow ink Relational expression (1)
<28> The pretreatment liquid contains water and a coagulant,
The flocculant is at least one selected from the group consisting of inorganic metal salts, organic acid metal salts, organic acid ammonium salts, and cationic polymers, according to any one of <22> to <27>. It is an image forming apparatus.
<29> The image forming apparatus according to <28>, wherein the pretreatment liquid further contains nonionic resin particles.
<30> The image forming apparatus according to any one of <28> to <29>, wherein the pretreatment liquid further contains wax particles.
<31> The image forming apparatus according to <30>, wherein the wax particles are particles of paraffin wax.

The ink set according to any one of <1> to <8>, the image forming method according to any one of <9> to <20>, and the image forming apparatus according to any one of <21> to <31>. can solve the above-mentioned conventional problems and achieve the above-mentioned object of the present invention.

400 image forming apparatus 401 exterior of image forming apparatus 401c main body cover 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 outlet 414 storage Container case 420 Mechanism part 434 Ink jet ejection head 436 Supply tube

JP 2008-266853 A

Claims (15)

An ink set having white ink and color ink,
The white ink and the color ink independently contain water-dispersible resin particles having a crosslinkable functional group, and blocked isocyanate having a functional group capable of crosslinking with the water-dispersible resin particles having a crosslinkable functional group. containing a compound and
the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink is 1.0 mN/m or less;
The absolute values of the dynamic surface tension differences at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently An ink set characterized by being 1.0 mN/m or less. The white ink and the color ink each independently contain 0.1 to 0.55 parts by mass of the blocked isocyanate compound with respect to 1 part by mass of the water-dispersible resin particles having the crosslinkable functional group. The ink set according to claim 1, comprising: 2. The ink set according to claim 1, wherein the static surface tension at 25[deg.] C. of said white ink and said color ink is independently 40.0 mN/m or less. wherein the color ink is a plurality of color inks including black ink, cyan ink, magenta ink, and yellow ink;
The absolute value of the difference in dynamic surface tension at 25° C. when the bubble life time is 15 msec by the maximum bubble pressure method is independently 1.0 mN/m or less between the plurality of color inks;
The dynamic surface tension of the black ink, the cyan ink, the magenta ink, and the yellow ink at 25° C. with a bubble lifetime of 15 msec according to the maximum bubble pressure method satisfies the following relational expression (1): Ink set as described.
Black ink>Cyan ink≧Magenta ink≧Yellow ink Relational expression (1) the ink set further has a pretreatment liquid,
The pretreatment liquid contains water and a flocculating agent,
2. The ink set according to claim 1, wherein the aggregating agent is at least one selected from the group consisting of inorganic metal salts, organic acid metal salts, organic acid ammonium salts, and cationic polymers. 6. The ink set according to claim 5, wherein the pretreatment liquid further contains nonionic resin particles. 6. The ink set according to claim 5, wherein the pretreatment liquid further contains wax particles. 8. The ink set according to claim 7, wherein the wax particles are particles of paraffin wax. a white ink application step of applying white ink to the recording medium;
a color ink applying step of applying color ink to the area of the recording medium to which the white ink has been applied;
including
The white ink and the color ink independently contain water-dispersible resin particles having a crosslinkable functional group, and blocked isocyanate having a functional group capable of crosslinking with the water-dispersible resin particles having a crosslinkable functional group. containing a compound and
the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink is 1.0 mN/m or less;
The absolute values of the dynamic surface tension differences at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently An image forming method, characterized in that the density is 1.0 mN/m or less. 10. The image forming method according to claim 9, further comprising a pretreatment liquid applying step of applying a pretreatment liquid to a region of said recording medium to which said white ink is to be applied, before said white ink applying step. 10. The image forming method according to claim 9, which does not include a heating or drying step of heating or drying the recording medium to which the white ink has been applied, between the white ink applying step and the color ink applying step. The time from when the white ink is applied to the recording medium until when the color ink is applied to the area of the recording medium to which the white ink is applied is within 20 seconds. The image forming method according to claim 9 . 10. The image forming method according to claim 9, wherein the recording medium is dark-colored fabric. a white ink containing means containing white ink;
a color ink containing means containing color ink;
white ink applying means for applying the white ink to a recording medium;
a color ink applying means for applying the color ink to the area of the recording medium to which the white ink has been applied;
has
The white ink and the color ink independently contain water-dispersible resin particles having a crosslinkable functional group, and blocked isocyanate having a functional group capable of crosslinking with the water-dispersible resin particles having a crosslinkable functional group. containing a compound and
the absolute value of the difference in static surface tension at 25° C. between the white ink and the color ink is 1.0 mN/m or less;
The absolute values of the dynamic surface tension differences at 25° C. at bubble lifetimes of 15 msec, 150 msec, and 1,500 msec measured by the maximum bubble pressure method between the white ink and the color ink are independently 1.0 mN/m or less, an image forming apparatus. a pretreatment liquid containing means containing a pretreatment liquid;
pretreatment liquid applying means for applying the pretreatment liquid in advance to the area of the recording medium to which the white ink is to be applied;
15. The image forming apparatus of claim 14, further comprising:

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