JP2000186243A - Ink, method for forming polymer film, and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink capable of forming images excellent in adhesion and water resistance by incorporating a specific water-soluble photopolymerization initiator and at least one compound selected from among water-soluble ultraviolet-polymerizable compounds into an aqueous medium. SOLUTION: A clear ink is provided which contains 0.1-7.0 wt.% water-soluble photopolymerization initiator represented by formula I (wherein n is 2-6), 1-30 wt.% water-soluble ultraviolet-polymerizable compound, 40-90 wt.% water-soluble organic solvent (e.g. ethylene glycol) having a b, p, of 190 deg.C or lower, and a colorant such as a pigment having an average particle size of 25-250 nm. The ultraviolet-polymerizable compounds include basic reactive compounds [e.g. morpholinoethyl (meth)acrylate represented by formula II (wherein X is H or methyl)] and acidic reactive compounds [e.g. tris(acryloyloxoethoxy) phosphate represented by formula III]. A polyhydric alcohol acylic ester, a nonionic polymerizable compound, or the like having a water solubility of 10 wt.% or higher may be jointly used together with the ultraviolet-polymerizable compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous ultraviolet curable ink-jet ink containing an aqueous medium containing a water-soluble ultraviolet-polymerizable compound which is effectively polymerized by ultraviolet light and a water-soluble photopolymerization initiator. The ink of the present invention is used for image printing, and further, a pretreatment before image formation of a printing agent,
Alternatively, it is useful for post-processing after image formation, is excellent in ink adhesion and water resistance, etc., and is transparent when the printing material is light transmissive, and when the printing material is light reflective. Is to enable printing with high gloss and saturation. The present invention also relates to a method for forming a polymer compound film and an image forming method.

[0002]

2. Description of the Related Art In a system using an ultraviolet curable ink in an ink jet apparatus, not only printing of an image but also pretreatment for imparting printability to a material to be printed, for example, pretreatment for forming an undercoat. And post-processing to protect the printed image, add decoration and gloss etc. to the image,
For example, it has been considered useful in a post-treatment for forming an overcoat.

However, no example has been found so far in which an aqueous ultraviolet curable ink is mounted on an on-demand ink jet apparatus having a high degree of integration of nozzles capable of realizing extremely high image quality. That is, using ultraviolet curable ink, printing,
At present, an ink jet apparatus for performing pre-treatment or post-treatment has not reached the stage of commercial practical use.
Therefore, at present, a coating apparatus is used for pre-treatment, and a laminating apparatus is used for post-treatment.

On the other hand, a water-soluble photopolymerization initiator used in an ultraviolet curable ink has a quaternary ammonium group in the molecule or a salt of a tertiary amine to secure water solubility. Things are known. For example, the compounds shown below are water-soluble photopolymerization initiators having a quaternary ammonium group in the molecule.

[0005]

Embedded image Such a compound having a quaternary ammonium group,
The salts of tertiary amines themselves have a high water solubility.

[0006]

The main reason why an ink jet apparatus having a high degree of integration of nozzles for forming a high image quality using an aqueous ultraviolet curable ink has not been put into practical use is that, in terms of ink technology, high density nozzles are required. It is thought that it was difficult to prepare an aqueous ultraviolet curable ink having a low viscosity and a good fluidity property capable of coping with the above.

However, when an aqueous ultraviolet curable ink is used in an ink jet apparatus, the non-contact property between the ink jet apparatus and the printing material is not only in printing but also in pre-processing and post-processing. In addition, the use of the ultraviolet curing method has a feature in environmental protection that the processing time is shortened and volatile substances are not released.
It is desired that an aqueous ultraviolet curable ink can be used.

[0008] Regarding the photopolymerization initiator used in the water-soluble ultraviolet curable ink, a compound having a quaternary ammonium group or a compound as a salt of a tertiary amine shows good water solubility. When an anionic colorant is used as the colorant when the ink is used as a component of the ink, a photopolymerization initiator cannot obtain sufficient stability in the ink depending on the type of the anionic colorant to be combined. There is.

Further, with respect to the ultraviolet-polymerizable compound, there have been many points to be improved in the use of a conventionally known typical compound as a component of an ink for higher-quality ink jet recording. That is, a compound having high solubility in water, high viscosity of the solution when dissolved in water, good UV-polymerizability, and excellent physical properties of a cured film obtained by polymerization has not been found so far. . Among the polyfunctional compounds that dissolve in water, the compound having a polyethylene glycol structure is not necessarily good in water resistance of the coating film obtained by using the compound having the polyethylene glycol structure, and depending on the material of the printing material, In some cases, good adhesion may not be obtained, and the types of printing materials that can be applied may be limited.

Also, an acrylic acid ester of an epichlorohydrin adduct of a polyhydric alcohol, a group of compounds generally called epoxy acrylate, has high water solubility, and the ultraviolet curing speed of an ink using the same is moderate.
Although the obtained coating film is excellent in physical properties, it has a hydroxyl group. Therefore, when the concentration in the ink is increased, the viscosity of the ink is increased, and the recording characteristics of the ink jet apparatus may not be satisfied. For this reason, the use in the ink-jet ink was limited.

The present invention has been made in view of the problems of the prior art in such an ultraviolet curable ink for ink-jet recording, and has as its object the characteristics suitable for an ink-jet apparatus, particularly, the arrangement of nozzles at high density. It is an object of the present invention to provide an ultraviolet-curable ink that satisfies the characteristics that can be suitably applied to an ink-jet apparatus with good balance. Another object of the present invention is to provide a method for forming a polymer compound film which is dense and has excellent adhesion to a substrate. Another object of the present invention is to provide a method for forming a high-quality image having excellent adhesion to a printing material and excellent water resistance and abrasion resistance.

[0012]

An embodiment of the ink according to the present invention comprises a water-soluble photopolymerization initiator represented by the following formula (1) and a water-soluble photopolymerization initiator represented by the following formulas (2) to (14). And at least one selected from the group consisting of acidic ultraviolet-polymerizable compounds.

[0013]

Embedded image

[0014]

Embedded image

[0015]

Embedded image (X in the above formulas (2) to (5) and (14) represents a hydrogen atom or a methyl group.)

Further, one embodiment of the method for forming a polymer compound film according to the present invention comprises, for example, (i) a water-soluble photopolymerization initiator represented by the above formula (1); (1
A step of discharging an ink containing at least one selected from water-soluble ultraviolet-polymerizable compounds represented by 4) in an aqueous medium from a discharge port of an ink jet head and attaching the ink to a predetermined portion of a base material; Irradiating the base material obtained in the step (i) with light to cure the ink adhered to the predetermined portion of the base material. One embodiment of the image forming method according to the present invention includes, for example, (i) a step of applying a first aqueous ink containing a coloring material to the surface of a printing material to form an image; A second ink containing, in an aqueous medium, a water-soluble photopolymerization initiator represented by 1) and at least one selected from water-soluble ultraviolet-polymerizable compounds represented by the above formulas (2) to (14). Applying at least the area of the surface of the printing medium to which the first ink has been applied in the step (i); and (iii) applying the printing medium to which the second ink has been applied in the step (ii). Irradiating light to cure the second ink.

Further, another embodiment of the image forming method according to the present invention includes, for example, (i) a step of preparing a first aqueous ink containing a coloring material; and (ii) a water-soluble solution represented by the above formula (1). A second ink containing, in an aqueous medium, an aqueous photopolymerization initiator and at least one selected from water-soluble ultraviolet-polymerizable compounds represented by the above formulas (2) to (14), (Iii) applying the first ink to the surface of the printing material obtained in the step (ii); and (iv) applying the first ink to an area to which the first ink is to be applied. Irradiating the printing material obtained in the step (iii) with light to cure the second ink on the surface of the printing material. Further, another embodiment of the ink according to the present invention is characterized by including at least one selected from the water-soluble ultraviolet-polymerizable compounds represented by the formulas (5) and (14) and a photopolymerization initiator. .

In one embodiment of the method for forming a polymer compound film according to the present invention, for example, (i) at least one of water-soluble ultraviolet-polymerizable compounds represented by the above formulas (5) and (14) Discharging the ink containing the photopolymerization initiator from the discharge port of the inkjet head to adhere to a predetermined portion of the printing material; and (ii) irradiating the printing material obtained in the step (i) with light. Curing the ink. In another embodiment of the image forming method according to the present invention, for example, (i) at least one selected from the water-soluble ultraviolet-polymerizable compounds represented by the formulas (5) and (14), Ejecting an ink containing an agent and a coloring material from an ejection port of an inkjet head to adhere to a predetermined portion of the printing material; and (ii) irradiating the printing material obtained in step (i) with light Curing the ink on the material to be printed;
It is characterized by having.

The ink according to the present invention may further contain a coloring material, if necessary, and used as an ink for coloring in an ink jet apparatus, whereby an image can be formed on a material to be printed. Pretreatment and post-treatment (surface treatment) of a printing material can be performed by using a coloring material in an ink jet apparatus.

Specifically, when an image is formed on a printing material with another aqueous ink (first ink), the ink according to the present invention is applied before applying the first ink to the printing material. After applying, the first ink is applied, and then the printing material is irradiated with light to cure the ink according to the present invention, whereby an image having excellent water resistance and adhesion can be formed.
The same effect can be obtained by applying the ink according to the present invention after applying the first ink to the printing material, and subsequently irradiating the printing material with light to cure the ink according to the present invention. Can be obtained.

The ink of the present invention uses the compound represented by the above formula (1) as a photopolymerization initiator, thereby improving the stability of the ink composition, reducing the viscosity of the ink, and increasing the reactivity. Can be achieved, and an aqueous ultraviolet curable inkjet ink that can be applied to an inkjet device having a high-density nozzle arrangement can be provided. For example, the ink of the present invention has an ink absorbing property like plain paper, but it is difficult to improve the color of the pigment or to improve the rubbing property. Can be provided. In addition, ultraviolet curable inks have been used exclusively for printing on non-ink-absorbing printing materials such as metals and plastics, but according to the ink of the present invention, non-absorbable inks such as metals and plastics are used. It is possible to provide an effective printing method using an ultraviolet curable ink on an absorbent printing material such as paper, in addition to the printing material described above.

That is, the image forming method of the present invention is characterized in that the method comprises a step of discharging the ink having the above-described structure from a discharge port of an ink jet head and attaching the ink to a predetermined portion of a printing material. Further, the image forming method of the present invention includes a step of attaching the ink having the above-described configuration to a printing material. Further, the surface treatment method for a printing material according to the present invention is characterized in that the ink having the above-described configuration is attached to at least one of the printing materials before and after image formation. preferable.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A water-soluble photopolymerization initiator used as a component of an ink according to the present invention has a structure represented by the following formula (1).

[0024]

Embedded image (In the formula, n represents an integer of 2 to 6.) This compound can be synthesized, for example, by the following method. First method: a method of providing an ethylene glycol group

[0025]

Embedded image Second method: a method of providing a hydroxyl group

[0026]

Embedded image N in the compound of the above formula (1) represents any integer of 2 to 6. When n is 0, the solubility in water is slight, and when n is 1, the solubility is increased, but the substantial suitability such as storage stability and ejection sustainability is insufficient. When n is 7 or more, the function itself as a photopolymerization initiator does not decrease, but the molecular size increases, and the addition weight itself to the ink for securing the required number of molecules in the ink increases. And the economic efficiency is reduced.

An essential structure for causing radical cleavage for ultraviolet curing is a structure having a hydroxyl group or an atomic group equivalent to a hydroxyl group at the α-position. In that sense,
Among the above synthesis methods, the second method, in which such distribution is unlikely to occur, is more preferable than the first method, in which the distribution of the number of n's can be easily formed. Since the compound of the above formula (1) does not have an ion-dissociating group, it is a particularly preferred photopolymerization initiator in terms of co-solubility with an aqueous dispersion of a water-soluble dye or pigment having an anionic dissociating group.

The UV-polymerizable compound that can be used in the present invention is:
In the presence of the above-mentioned photopolymerization initiator, a polymer which is polymerized by irradiation of ultraviolet rays to obtain desired properties of a cured film and also satisfies the properties as an ink-jet ink when used as an ink is used. Examples of such compounds include compounds represented by the following formulas (2) to (14). (Reactive compound exhibiting basicity)

[0029]

Embedded image (X in the above formulas (2) to (5) represents a hydrogen atom or a methyl group.) (Reactive compound exhibiting acidity)

[0030]

Embedded image

[0031]

Embedded image (X in the above formula (14) represents a hydrogen atom or a methyl group.) Each compound of the above formulas (2) to (14) satisfies each requirement of low viscosity, high reactivity, and water solubility. Yes, it is preferable because it also has the effect of expanding the permissible range when another compound (for example, an oligomer) that is polyfunctional and can increase the viscosity of the ink is used in combination with the ink.

In particular, the water-soluble polymerizable compounds represented by the above formulas (5) and (14) have high reactivity, and the polymer film after the reaction is a high-quality one that is dense and hard to be damaged. Become.

For example, as a formulation of the aqueous ultraviolet curable ink, 55% by weight of water, 3% by weight of a water-soluble photopolymerization initiator, 30% by weight of a water-soluble ultraviolet-polymerizable compound, and 12% by weight of ethylene glycol are used. When employed, when the compound of formula (1) is used as the water-soluble photopolymerization initiator and the compound of formula (17) described below is used as the UV-polymerizable compound, the viscosity of the ink becomes 12.2 mPsec. On the other hand, when the compound of the formula (4) is used as the ultraviolet-polymerizable compound, the viscosity of the ink is 4.5 mPsec. Thus, it becomes possible to further lower the viscosity of the ink while containing the ultraviolet polymerizable compound at a high content of 30% by weight.

On the other hand, examples of the compound which can be used in combination with the above-mentioned ultraviolet polymerizable compound include a water-soluble polyfunctional polymerizable compound and a water-soluble nonionic polymerizable compound.

As the water-soluble polyfunctional polymerizable compound that can be used in combination, a compound having two or more acryloyl groups in one molecule and having a solubility in water of 10% by weight or more can be suitably used. Examples thereof include (meth) acrylates of polyhydric alcohols and (meth) acrylates of glycidyl ether derived from polyhydric alcohols. Specific examples of (meth) acrylic acid esters of polyhydric alcohols include, for example, polyethylene glycols such as polyethylene glycol # 200 diacrylate and polyethylene glycol #dimethacrylate. Further, specific examples of the (meth) acrylic acid ester of glycidyl ether include the following formulas (15) to (18).

[0036]

Embedded image In addition, these polyhydric alcohols may be those in which the inside is an ethylene oxide chain and the chain length is extended by addition of ethylene oxide.

Further, nonionic water-soluble polymerizable compounds include (meth) acrylic esters of polyols having two or more hydroxyl groups such as monosaccharides and disaccharides, triethanolamine, diethanolamine, trishydroxyaminomethane, trishydroxy and the like. (Meth) acrylic acid esters such as aminoethane can be exemplified.

Further, as the water-soluble polyfunctional compound that can be used in combination, a compound in which a water-soluble group is added to a polyester polyacrylate or polyurethane polyacrylate skeleton, or the like can be used.

These compounds which can be used in combination can be used in combination of two or more kinds as long as the object effect of the present invention can be obtained.
Under the conditions in which the compound (14) is used, the ratio of the compound to be added can be 1 to 10% by weight.

As the aqueous medium for dissolving the water-soluble polymerizable compound and the water-soluble photopolymerization initiator, those obtained by adding a water-soluble organic solvent to water as needed are preferably used. be able to. The water-soluble organic solvent is mainly used for imparting non-volatility to the ink, lowering the viscosity, and ensuring the wettability of the ink on the printing material, and is suitable for such purpose. If available. When the printing material is non-absorbable, the aqueous medium is formed only of water, or when a water-soluble organic solvent is used, the aqueous medium is easily evaporated, or the entire aqueous medium is in the cured film. It is preferable that it is taken in.

A water-soluble organic solvent having a property of being easily evaporated and dried has a boiling point at atmospheric pressure of about 19
Those having a temperature of 0 ° C. or lower can be suitably used. Specific examples include ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, 1,2,4-butanetriol, 1,2,6-hexanetriol, 1,2,5-pentanetriol,
1,2-butanediol, 1,3-butanediol,
1,4-butanediol, dimethyl sulfoxide, diacetone alcohol, glycerin monoallyl ether,
Propylene glycol, butylene glycol, polyethylene glycol 300, thiodiglycol, N-methyl-2-pyrrolidone, 2-pyrrolidone, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, sulfolane, trimethylolpropane, trimethylol Ethane, neopentyl glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether ,
Propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, β-dihydroxyethylurea, urea, acetonylacetone, pentaerythritol, 1,4-cyclohexanediol, hexylene glycol, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol Monoisobutyl ether, ethylene glycol monophenyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetra Ethylene glycol diethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, glycerin monoacetate, glycerin diacetate, glycerin triacetate, ethylene glycol monomethyl ether Acetate, diethylene glycol monomethyl ether acetate, cyclohexanol, 1,2-cyclohexanediol, 1-butanol, 3-methyl-1,5-pentanediol, 3-
Hexene-2,5-diol, 2,3-butanediol, 1,5-pentanediol, 2,4-pentanediol, 2,5-hexanediol and the like, and one or more of these can be mentioned. Can be used in combination.

The ink of the present invention can be used as a colorless (clear) ink containing no coloring material, or as a coloring ink by containing a coloring material.

As a coloring material for forming the coloring ink, a pigment or a dye can be used. It is essential that the pigment is dispersed in the form of fine particles in an aqueous medium,
The particle size distribution as a dispersion is 25 nm to 20 in average particle diameter.
It is preferably in the range of 0 nm, which can be adjusted so that the viscosity of the final ink does not affect the ejection, and has good compatibility with components essential for ultraviolet curability. Examples of such pigments include the following. Pigment Yellow 1, 2, 3, 1
2, 13, 14, 16, 17, 55, 73, 74, 7
5, 83, 93, 95, 97, 98, 109, 110,
114, 128, 138, 139, 150, 151, 1
54 and 180. As magenta pigments, Pigment Red 5, 7, 12, 48 (C
a), 48 (Mn), 57: 1, 57 (Sr), 57:
2, 122, 123, 168, 184, 202, 238
And the like. Examples of cyan pigments include Pigment Blue 1, 2, 3, 16, 22, 60, 15: 2 and 13: 3; and Bat Blue 4 and 60.

The following can be mentioned as dyes. As yellow dyes, Acid Yellow 11, 17, 23, 25, 29, 42, 49, 61 and 71; Direct Yellow 12, 24, 26, 44 and 8
6, 87, 98, 100, 130, 86, 132 and 1
42 and the like. As magenta dyes,
Acid Red 1, 6, 8, 32, 35, 37, 51,
52, 80, 85, 87, 92, 94, 115, 18
0, 254, 256, 289, 315 and 317; Direct Red 1, 4, 13, 17, 23, 28, 31,
62, 79, 81, 83, 89, 227, 240, 24
2 and 243. As cyan dyes, Acid Blue 9, 22, 40, 59, 93, 1
02, 104, 113, 117, 120, 167, 22
9, 234 and 254; Direct Blue 6, 22, 2
5, 71, 78, 86, 90, 106, and 199.

Uses of the clear ink include pretreatment such as formation of an undercoat for improving or improving printability of a printing material, protection of a printed image, and improvement of image quality by imparting gloss to an image. There are post-treatments such as formation of a desired overcoat. In such applications, the content of the aqueous medium is preferably in the range of 40 to 90% by weight, the lower limit being 60% by weight, and the upper limit being more preferably 75% by weight. Further, the content of the ultraviolet polymerizable compound is from 1 to 4
The range is preferably 0% by weight, the lower limit being 5% by weight, and the upper limit being more preferably 30% by weight. The content of the water-soluble photopolymerization initiator is preferably in the range of 0.1% by weight to 7% by weight, and the lower limit is preferably 0.3% by weight and the upper limit is more preferably 4% by weight.

Further, the clear ink may contain a colorless pigment, fine particles and the like not intended for coloring in a dispersed state. They can improve various properties such as image quality, fastness, workability (handling), etc. of the printed matter in both undercoat and overcoat. As these added pigments or fine particles, synthetic silica known as an inorganic extender, alumina, ceramic powder, clay, talc, mica, metal powder, natural products such as bentonite, or polystyrene fine particles, polymethyl methacrylate fine particles, polyurethane, Organic fine particles made of silicone, melamine resin, phenol resin and the like can be mentioned, and the addition amount can be 0.01 to 10% by weight.

Since the coloring ink containing the coloring material is mainly used for printing an image, it is preferable to adjust the composition in accordance with the absorption characteristics of the coloring material. The content of the aqueous medium in the coloring ink is preferably in the range of 40 to 90% by weight, and the lower limit is more preferably 60% by weight and the upper limit is more preferably 75% by weight. The content of the ultraviolet polymerizable compound is preferably in the range of 1 to 30% by weight, the lower limit is 5% by weight, and the upper limit is more preferably 20% by weight. The content of the water-soluble photopolymerization initiator is preferably in the range of 0.1% by weight to 7% by weight, and the lower limit is preferably 0.3% by weight and the upper limit is more preferably 5% by weight.

When a pigment is used as a coloring material of the coloring ink, the particle diameter of the pigment is about 25 nm in average particle diameter.
It is preferable to use one having a range of about 250 nm.
It is preferable to use a pigment within this range. A pigment having a smaller particle size is more preferable, but if it has an average particle size within this range, transparency which is practically no problem can be obtained.

The ink according to the present invention can be prepared by mixing necessary components in an aqueous medium. The order of mixing the components is not particularly limited, but it is preferable that the mixing be performed quickly without maintaining a non-uniform state for a long time.
When a pigment dispersion is used, it is preferable to further stir the mixture so as not to impair the uniformity.

As a printing system used for processing a printing material using the ink of the present invention, a system having a structure in which an ultraviolet irradiation device is mounted on an ink jet printer mechanism can be suitably used. The ultraviolet irradiation device is typically arranged at a position illustrated in FIG. The ultraviolet light is emitted from above or below the printing surface of the recording material exiting the printing station. In the case of a transparent material to be printed, irradiation from both the upper and lower sides is effective if necessary. The time interval from the print head to the irradiation area is such that the ink component is uniform on or near the surface of the printing material before the ink penetrates when using an absorbing printing material such as paper. It is preferable to set so that ultraviolet irradiation can be performed in a time range in which a certain state is maintained.

As the ultraviolet lamp used in the ultraviolet irradiation device, a so-called low-pressure mercury lamp in which the vapor pressure of mercury is 1 to 10 Pa during operation, a high-pressure mercury lamp having a higher pressure, or a phosphor is applied. Mercury lamps and the like are preferred. The emission spectrum of these mercury lamps in the ultraviolet region is in the range of 184 nm to 450 nm, and is suitable for efficiently reacting the ultraviolet polymerizable compound in black or colored ink. In addition, since a small power supply can be used even when the power supply is mounted on the printer, it is also suitable in that sense. As mercury lamps, metal halide lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon flash lamps, deep UV lamps, UV lasers, and the like have been put into practical use.The emission wavelength range includes the above range, so the power supply size, input intensity, It can be appropriately selected and used depending on the lamp shape and the like. The light source is preferably selected in consideration of suitability for the photopolymerization initiator to be used.

The required ultraviolet intensity is preferably one having a total ultraviolet energy of about ² to 50 mW / cm ^{2 in} order to obtain a better heavy / strong speed. If the integrated irradiation amount is insufficient, the adhesion of the fixed ink to the printing material may not be sufficient, and the water resistance of the printing ink may not be sufficient in color recording. It is preferable that the irradiation process is performed in consideration of a necessary integrated irradiation amount, since there may be a shortage in performance. By curing the ink with ultraviolet light and fixing the ink to the printing material, good fixing, abrasion resistance, water resistance, and the like can be obtained. At the same time, deformation of the printing material itself, such as curl and cockle, is suppressed, and handleability and storability can be improved.

[0053]

The present invention will be described in more detail with reference to the following examples. Example 1 The components shown in Table 1 were mixed to prepare a transparent clear ink.

[0054]

[Table 1] *): X is a hydrogen atom. Example 2 The following components were mixed to prepare a colored ink containing an organic pigment. The measurement of the average particle diameter is a numerical value obtained by a dynamic light scattering method.

[0055]

[Table 2] *) It contains a dispersion of Pigment Yellow 13, and the physical properties of the dispersion are as follows. Average particle diameter: 120 nm; Dispersant: styrene / acrylic acid / ethyl acrylate copolymer (glass transition temperature: 70 ° C .; number average molecular weight: 3000) **) X is a hydrogen atom.

[0056]

[Table 3] *) Contains a dispersion of Pigment Red 122. The physical properties of the dispersion are as follows. Average particle diameter: 150 nm; Dispersant: styrene / acrylic acid / ethyl acrylate copolymer (glass transition temperature: 70 ° C .; number average molecular weight: 3000) **) X is a hydrogen atom.

[0057]

[Table 4] *) Contains a dispersion of Pigment Blue 15: 3. The physical properties of the dispersion are as follows. Average particle diameter: 134 nm; Dispersant: styrene / acrylic acid / ethyl acrylate copolymer (glass transition temperature: 70 ° C .; number average molecular weight: 3000) **) X is a hydrogen atom.

[0058]

[Table 5] *) Contains a dispersion of Pigment Black 7. The physical properties of the dispersion are as follows. Average particle diameter: 103 nm; Dispersant: styrene / acrylic acid / ethyl acrylate copolymer (glass transition temperature: 70 ° C .; number average molecular weight: 3000)

[0059]

[Table 6] *) It contains a dispersion of Pigment Yellow 93. The physical properties of the dispersion are as follows. Average particle diameter: 130 nm; Dispersant: Phosphanol RE610 (phosphoric acid surfactant, Toho Chemical) **) X is a hydrogen atom. Comparative Example 1 A comparative ink containing no ultraviolet-polymerizable compound and no photopolymerization initiator was prepared using the following components.

[0060]

[Table 7] *) As in Example 2, containing a dispersion of Pigment Black 7.

[0061]

[Table 8] Example 3 The following tests were performed using the inks prepared in Example 2 and Comparative Example 1.

EW500 (manufactured by Canon Inc.), which is an electrophotographic copying paper as a printing material, is provided with YMCK and R
A pattern in which each color of GB was arranged and characters written in each color were printed by the ink jet method. Irradiation conditions were set such that the average UV intensity was 6 mW / cm ² . After printing, it takes about 10 seconds to pass through the UV irradiation area.
Seconds. The print samples prepared under these conditions were evaluated for (1) water resistance, (2) adhesion, and (3) a continuous printing test of 50 sheets. The evaluation methods for these items are as follows, and the results are shown in Table 1. (1) Water resistance The print sample was immersed in water for 1 minute, taken out, rubbed with a soft paper and wiped off, and then bleeding to the non-printing peripheral portion and checking whether there was a decrease in the density of the solid print portion. The sample was compared with a sample that had been left standing without performing such an operation, and evaluated according to the following criteria. Evaluation criteria: good: no bleeding to the peripheral part, and no decrease in density. Normal: Stain occurs, but does not affect reading. Poor: There is considerable oozing and elution, which makes it unpractical. (2) Adhesion The solid printed portion and the character portion were rubbed with an eraser to determine the degree of disappearance. Evaluation criteria: Very good: Does not disappear at all. Good: hardly disappears. Normal: It disappears a little, but it takes a long time to completely erase it. Bad: Most of the printed part disappears in a short time. (3) Suitability for continuous printing The initial sample was compared with the sample on the 50th sheet, and the density of the solid printing portion was compared. At the same time, character quality was compared. Evaluation criteria; good: both are almost the same. Normal: There is a slight decrease in density and a decrease in character quality (the presence of disordered dots). Poor: There is a considerable reduction in density, the character dot disturbance is large, and it looks blurred.

[0063]

[Table 9] Example 4 The following printing test was performed using the clear ink prepared in Example 1. First, three sheets of HG201 (manufactured by Canon Inc.), a glossy film for inkjet printing, on which full-color images were printed by an inkjet method were prepared. For each of these, clear-in (Cink) was performed using the apparatus used in Example 3 equipped with an ultraviolet irradiation device.
Solid printing was performed on the entire surface on which the image was printed by ejecting each of 1 to 3) from the nozzle for black ink. That is, printing was performed in a state where a clear lacquer was applied. After completion of printing and irradiation with ultraviolet light, the samples were dried at 60 ° C. for 5 minutes to obtain final samples A to C. These samples were compared with Sample D obtained by image printing on ordinary plain paper, and the following evaluation items were evaluated. Table 8 shows the results. (1) Image quality Canon bubble jet color printer, BJC-4
When the density and glossiness were improved as compared with an image (reference image) of plain paper created using plain paper EW-500 using 65J, it was regarded as good. (2) Scratchability: good A case where there was almost no change when rubbed with an eraser was regarded as good. (3) Contamination The water was dropped, and immediately rubbed to wipe off the water, but the operation was performed without any trouble and the image was not degraded. (4) Image comparison with reference image The case where the saturation and density of plain paper were improved and gloss was obtained was regarded as good.

[0064]

[Table 10]

Example 5 A coloring ink containing an organic pigment was prepared by mixing the following components. The measurement of the average particle diameter is a numerical value obtained by a dynamic light scattering method. (Yellow ink 3)

[Table 11] *) It contains a dispersion of Pigment Yellow 13, and the physical properties of the dispersion are as follows. Average particle diameter: 120 nm Dispersant: styrene / acrylic acid / ethyl acrylate copolymer (glass transition temperature: 70 ° C., number average molecular weight: 3000) **) X is a hydrogen atom. (Yellow Ink 4) The ultraviolet polymerizable compound of the formula (5) in the yellow ink 3 is converted to the formula (14) (X = H)
A yellow ink 4 was prepared in exactly the same manner except that the ultraviolet polymerizable compound was used. Printing was performed in the same manner as in Example 3 using the yellow inks 3 and 4, and each item was evaluated in the same manner as in Example 3. The results are shown in Table 12 below.

[Table 12]

[0066]

As described above, by using the aqueous ultraviolet curable ink of the present invention, it is possible to increase the content of the ultraviolet polymerizable compound in the ink while being aqueous. As a result, it is possible to stabilize the pattern density and the character product in stable and continuous printing on the ink jet device. Further, even when a pigment is used as a coloring material, the water resistance and the adhesion are remarkably improved. Furthermore, when used as a clear ink, gloss is increased, and there is an improvement in abrasion property that hardly changes even when rubbed with an eraser, and it is easy to wipe off various kinds of contamination. Appropriateness is seen. When used as an undercoat material, it is possible to obtain an image with good saturation and density even on uncoated paper. As described above, the handleability of the printed matter in the inkjet printing can be improved as compared with the ordinary printed matter using the oil-based ink.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a printer applicable to printing using an aqueous ultraviolet curable ink of the present invention.

Claims (15)

[Claims] 1. An aqueous medium comprising a water-soluble photopolymerization initiator represented by the following formula (1) and at least one selected from water-soluble ultraviolet-polymerizable compounds represented by the following formulas (2) to (14): An ink comprising: Embedded image Embedded image Embedded image (X in the above formulas (2) to (5) and (14) represents a hydrogen atom or a methyl group.) 2. The method according to claim 1, wherein the water-soluble ultraviolet-polymerizable compound is
The ink according to claim 1, comprising from about 40% by weight. 3. The ink according to claim 1, further comprising a coloring material. 4. The method according to claim 1, wherein the water-soluble UV-polymerizable compound is
The ink according to claim 3, wherein the ink comprises about 30% by weight. 5. The ink according to claim 3, wherein the coloring material is a pigment or a dye. 6. A step of (i) discharging the ink according to any one of claims 1 to 5 from a discharge port of an ink jet head and attaching the ink to a predetermined portion of a substrate, and (ii) the step (i). B) irradiating the substrate obtained by the method with light to cure the ink adhered to the predetermined portion of the substrate. 7. The method according to claim 6, wherein the polymer compound film forms at least a part of an image. 8. A step of (i) applying a first aqueous ink containing a coloring material to the surface of a printing material to form an image; and (ii) using the second ink according to any one of claims 1 to 5 to form an image. Applying the first ink to at least the area of the surface of the printing material to which the first ink has been applied in the step (i); and (iii) the printing material to which the second ink has been applied in the step (ii). Irradiating the second ink with light to cure the second ink. 9. (i) a step of preparing a first aqueous ink containing a coloring material; (ii) applying the second ink of any one of claims 1 to 5 to at least the first ink on the surface of a printing material. (Iii) applying the first ink to the surface of the printing material obtained in the step (ii); and (iv) applying the first ink to the area to which the ink is to be applied. Irradiating the printing material obtained by the method with light to cure the second ink on the surface of the printing material. 10. The image forming method according to claim 8, wherein the attachment of at least one of the first ink and the second ink to the printing material is performed using an inkjet discharge method. 11. An ink comprising at least one selected from water-soluble ultraviolet-polymerizable compounds represented by the following formulas (5) and (14) and a photopolymerization initiator. Embedded image (X in the above formulas (5) and (14) represents a hydrogen atom or a methyl group.) 12. The ink according to claim 11, further comprising a coloring material. 13. The ink according to claim 12, wherein the coloring material is a pigment or a dye. And (ii) discharging the ink according to any one of claims 11 to 13 from a discharge port of an ink jet head and attaching the ink to a predetermined portion of a printing material; and (ii) performing the step (i). Irradiating the obtained printing material with light to cure the ink; and a method of forming a polymer compound film. 15. An image forming method, comprising the step of ejecting the ink according to claim 12 from an ejection port of an inkjet head and attaching the ink to a predetermined portion of a printing material.