JP2009091528A - Inkjet ink set and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink set which is restrained from the occurrence of white lines by a printing formality using an inkjet recording head of a line system and which can form a pictorial image excellent in sharpness; and an inkjet recording method using the inkjet ink set. <P>SOLUTION: The inkjet ink set at least contains a pigment, water, an ink composition containing a water-soluble polymer compound, and an aqueous process liquid for thickening or aggregating the ink composition. The water-soluble polymer compound has plural side chains per its hydrophilic main chain, the side chains being crosslinkable or polymerizable by the irradiation of an active energy line. The aqueous process liquid contains a polyvalent metal salt or a polyallylamine. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet ink set containing an active energy ray-curable compound and an ink jet recording method using the same.

  The ink jet recording method is capable of high-definition image recording with an apparatus having a relatively simple configuration, and has been rapidly developed in recent years. In addition, the inkjet recording system is used in various ways, and a recording medium or inkjet ink suitable for each purpose has been used.

  In particular, in recent years, from the viewpoint of high speed and high image quality of the ink jet recording method, the ink jet recording head can also record a single line in a short time by arranging a plurality of nozzles in the width direction of the recording medium. So-called line-type ink jet recording heads have attracted a great deal of attention (for example, see Patent Document 1). By adopting such a line type ink jet recording head, the ink jet recording speed has been greatly improved, and the possibility of being applicable to light printing applications has also emerged. However, ordinary water-based ink-jet ink is used for printing paper with low ink absorption, such as art paper and coated paper, which are mainly used as recording media for offset printing and gravure printing, and plastic film with no ink absorption. When recording is performed, ink jet ink droplets are mixed on the recording medium, so that a clear image cannot be obtained. In addition, there has been a problem such as so-called color bleeding in which droplets of inkjet inks having different hues are mixed with each other to cause turbidity.

  A so-called hot melt type ink jet recording method has been proposed for the above problem (see, for example, Patent Document 2). The hot melt type ink used for this is said to provide a good print quality regardless of the paper quality because it is in a molten state during ink jet recording and solidifies immediately after adhering to the recording medium, and has little color bleeding. However, the image recorded by such a method has problems such as deterioration of quality due to the rising of the dots and lack of abrasion resistance because the ink jet ink of the landing dots is in the form of soft wax.

  On the other hand, an inkjet recording ink that is cured by irradiation with active energy rays is disclosed (for example, see Patent Document 3). In particular, water-based inkjet recording ink that cures when irradiated with active energy rays has a volatile component such as water in the inkjet ink. It has a feature that an image can be obtained (see, for example, Patent Document 4).

  The inventor of the present invention uses an aqueous inkjet recording ink containing a compound that is cured by irradiating active energy rays, and uses an inkjet image recording method using a line-type inkjet recording head. When an image was formed on a non-ink-absorbing recording medium, it was found that a new problem that white streaks occur in a solid image occurred. The inventor estimates the occurrence of white streaks in the solid image as follows. Since the ink droplets ejected from the line type ink jet recording head land on the recording medium and are fixed by irradiation with active energy rays, the adjacent ink droplets land. Since the droplets attract each other and deviate from the original landing position, a portion where ink is not left remains in a streak shape. As a result, a white streak appears. Therefore, in particular, when a solid image of a different color is superimposed on a solid image of a certain color on a non-ink-absorbing recording medium, for example, a region where the second color ink is not markedly deposited. Is presumed to be streaked.

On the other hand, as an ink-jet ink composition that is excellent in weather resistance, water resistance, etc., does not cause color bleeding, and enables image recording with good print quality, an aqueous ink containing pigments and photoreactive polymer fine particles (hereinafter referred to as this) Has been proposed (for example, refer to Patent Document 5). This is because photoreactive polymer fine particles having acryloyl groups or vinyl ether groups on the surface as photoreactive groups contribute to ink curing by light irradiation, and when ink jet recording was performed using the polymer fine particle type ink. As a result, a new problem has been found that the sharpness is not sufficient.
JP-A-6-183029 U.S. Pat. No. 4,390,369 JP 2002-80767 A JP 2006-249216 A JP 2001-115067 A

  The present invention has been made in view of the above-mentioned problems, and the object thereof is to suppress the occurrence of white stripes and achieve sharpness, particularly by a high-speed printing method using a line-type ink jet recording head. An object of the present invention is to provide an ink jet ink set capable of forming an excellent image and an ink jet recording method using the ink jet ink set.

  The above object of the present invention is achieved by the following configurations.

  1. An ink jet ink set comprising an ink composition containing at least a pigment, water, and a water-soluble polymer compound, and an aqueous treatment liquid for thickening or aggregating the ink composition, wherein the water-soluble polymer compound is , A polymer compound having a plurality of side chains with respect to the hydrophilic main chain and capable of crosslinking or polymerizing between side chains by irradiation with active energy rays, and the aqueous treatment liquid is a polyvalent metal salt or An ink jet ink set comprising polyallylamine.

  2. The water-soluble polymer compound is a saponified product having a hydrophilic main chain of polyvinyl acetate, a saponification degree of 77% or more and 99% or less, and a polymerization degree of 200 or more and 500 or less. 2. The inkjet ink set as described in 1 above.

  3. The ink composition and the aqueous treatment liquid constituting the inkjet ink set described in 1 or 2 above are ejected from an inkjet recording head and attached to a recording medium, and then the ink composition is irradiated with active energy rays to form an image. An ink jet recording method comprising the step of forming

  4). 4. The inkjet recording method described in 3 above, wherein the inkjet recording head is a line type inkjet recording head.

  According to the present invention, in particular, an ink jet ink set capable of suppressing the generation of white stripes and forming an image with excellent sharpness by a printing method using a line type ink jet recording head, and the same are used. An ink jet recording method could be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventor has found that an ink composition containing at least a pigment, water, and a water-soluble polymer compound, an aqueous treatment liquid that thickens or aggregates the ink composition, and The water-soluble polymer compound has a plurality of side chains with respect to the hydrophilic main chain, and can be crosslinked or polymerized between the side chains by irradiation with active energy rays. In particular, a line-type inkjet recording head is used for inkjet image formation using an inkjet ink set characterized in that the aqueous treatment liquid contains a polyvalent metal salt or polyallylamine. The present invention has found that even with a high-speed printing method, it is possible to form an image with suppressed white streaks and excellent sharpness. Led was is up.

  Details of the present invention will be described below.

  The inkjet ink set of the present invention includes an ink composition containing at least a pigment, water, and a water-soluble polymer compound, and an aqueous treatment liquid containing a polyvalent metal salt or polyallylamine that thickens or aggregates the ink. It is composed of

<Ink composition>
First, the details of the invention according to claim 1 of the present invention will be described.

  In the present invention, a water-soluble polymer compound having a plurality of side chains with respect to a pigment, water, and a hydrophilic main chain, and capable of crosslinking or polymerization bonding between the side chains by irradiating active energy rays. Aqueous processing liquid for thickening or agglomerating the ink composition together with the ink composition when a relatively large amount of ink-jet printing is performed on the aqueous ink-jet ink composition (hereinafter also simply referred to as ink composition). Is applied to the recording medium and irradiated with active energy rays, the generation of white streaks can be suppressed. This is because even if an ink droplet ejected from an inkjet recording head suitable for high-speed printing such as a line-type inkjet recording head (hereinafter also simply referred to as a line recording head) hits an adjacent portion, Since the ink droplets are instantly thickened or aggregated by the aqueous treatment liquid according to the invention, the phenomenon that the ink droplets attract each other between adjacent dots is prevented before irradiation with the active energy ray, and the dots are placed at their original positions. As a result, the formation of white stripes can be suppressed. And it is thought that the fixing property of the ink to a recording medium is ensured by the subsequent hardening process by active energy ray irradiation. Thus, the object of the present invention can be achieved by the ink jet ink set containing the ink composition and the aqueous treatment liquid according to the present invention or the recording method thereof.

  In particular, it has been found that the ink composition according to the present invention is superior in sharpness of the formed image as compared with the polymer fine particle type ink containing polymer fine particles in the ink as described above as the prior art. About this reason, it estimates as follows.

  The polymer fine particle type ink described in Patent Document 5 and the like has pigment particles and photoreactive polymer fine particles in an aqueous medium. Both the fine polymer particles have a constant particle size, and dots are formed as they are after drying. Therefore, since the polymer fine particles exist between the pigment particles constituting each dot, the pigment particles are relatively sparse.

  In contrast, in the ink composition containing the water-soluble polymer compound according to the present invention, when the ink droplets landed by the ink jet recording are aggregated by the aqueous treatment liquid, the dissolved polymer is put in the gaps between the pigment particles. The pigment particles are in contact with each other more closely. Therefore, it is considered that a clearer image can be formed. In addition, since the water-soluble polymer compound surrounds the pigment particles and is cured by active energy rays, it is considered that an image having good scratching properties is obtained.

  In addition, the content of the water-soluble polymer compound in the ink composition according to claim 1 is preferably 0.8 to 10% by mass with respect to the total amount of the ink composition from the viewpoint described below.

  Conventionally, there has been a technique for putting a component that cures with active energy rays into ink, but the component to be cured is a monomer, the curing efficiency is poor, and if a considerable amount is not contained in the ink, particularly non-ink-absorbing recording Although it was not possible to print on the medium as it is, conversely, when it was contained at a high density, the swell of the image area was increased, and an image with a high smoothness could not be obtained.

  When the water-soluble polymer compound according to the present invention is used, the effect of the present invention can be exhibited with a small amount of the curing component, and the total solid content in the ink can be suppressed to a small amount. The excitement of becomes very small. As a result, the difference in gloss between the image portion and the non-image portion is small, a high-quality image is obtained, and since it is smooth, it has good scratching properties.

  Further, the water-soluble polymer compound according to the present invention crosslinks or bonds between the side chains originally provided to the main chain having a certain degree of polymerization via a crosslink, so that a general chain reaction is performed. The effect of increasing the molecular weight per photon is remarkably greater than that of an ultraviolet curable resin that is polymerized via a photon. As a result, a very high curing sensitivity can be realized.

  On the other hand, in the conventionally known ultraviolet curable resin, the number of crosslinking points cannot be controlled, so that it is difficult to control the physical properties of the film after curing, and it tends to be a hard and brittle film.

  In the water-soluble polymer compound used in the present invention, the number of cross-linking points can be completely controlled by the length of the hydrophilic main chain and the amount of side chains introduced. Crosslinking with energy rays is particularly excellent in that the physical properties of the ink film can be controlled according to the purpose.

  Therefore, if the content of the water-soluble polymer compound according to the present invention is 10% by mass or less, a low ink absorptive recording medium such as a printing paper, and a non-ink absorptive recording medium such as a plastic film, It is possible to form a high quality image. Further, if the content is 0.8% by mass or more, it is possible to sufficiently increase the viscosity when thickening or aggregating with the aqueous treatment liquid, and the curing by irradiation with active energy rays is sufficient and scratching. Sex is also sufficient.

[Water-soluble polymer compound]
The water-soluble polymer compound according to the invention described in claim 1 has a plurality of side chains with respect to the hydrophilic main chain, and can be crosslinked or polymerized between the side chains by irradiation with active energy rays. For example, a saponified product of polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or the hydrophilic resin. Derivatives, and at least one hydrophilic resin selected from the group consisting of these copolymers, such as photodimerization type, photodecomposition type, photopolymerization type, photomodification type, photodepolymerization type, etc. in the side chain A modified group is introduced. Of these, particularly preferable for achieving the object of the present invention is a saponified product of polyvinyl acetate or polyacrylic acid, and derivatives or copolymers thereof having a main chain.

  The side chain is preferably nonionic, anionic, or amphoteric, and in particular, when used in combination with an anionic pigment, it is preferably nonionic or anionic from the viewpoint of ink storage stability, and particularly preferably nonionic. It is.

  The water-soluble polymer compound according to the invention described in claim 2 is a saponified product having a hydrophilic main chain of polyvinyl acetate, thereby exhibiting sufficient water solubility in the ink composition according to the present invention. Such a clear image can be formed. In the hydrophilic main chain, the degree of saponification is preferably 77 to 99% from the viewpoint of simplicity of introduction of side chains and handling. The average degree of polymerization is preferably 200 to 4000, and the degree of polymerization is preferably 200 to 1800 from the viewpoint of handling. In particular, the case of 200 to 500 is most preferable. The reason is that if the average degree of polymerization is 200 or more, the effect of aggregation or thickening by the aqueous treatment liquid after landing is remarkable, and white streaks are more effectively generated when recording is performed by a line recording head. It can be suppressed. Further, when the average degree of polymerization is 500 or less, so-called intermittent discharge property is good in which the discharge is stopped after a certain period of time and then discharged again. The average degree of polymerization can be calculated according to Japanese Industrial Standard K 6726.

  Moreover, it is preferable that the modification rate of the side chain with respect to a hydrophilic main chain is 0.8-4.0 mol%. If it is 0.8 mol% or more, the fixing property is sufficient, and if it is 4.0 mol% or less, the storage stability of the ink composition before the curing reaction is good. Moreover, when combined with the viewpoint of the reaction efficiency of the curing reaction, it is more preferably 1.0 to 3.5 mol%.

  As a photodimerization-type modifying group preferable as a side chain with respect to the hydrophilic main chain, those having a diazo group, a cinnamoyl group, a stilbazolium group, a stilquinolium group or the like introduced are preferable. For example, JP-A-60-129742 The photosensitive resin described in this publication is mentioned.

  The photosensitive resin described in JP-A-60-129742 is a compound represented by the following general formula (1) in which a stilbazonium group is introduced into a polyvinyl alcohol structure.

In the formula, R ₁ represents an alkyl group having 1 to 4 carbon atoms, and A ⁻ represents a counter anion.

  The photosensitive resin described in JP-A-56-67309 includes a 2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following general formula (2) in the polyvinyl alcohol structure, or the following general formula. A resin composition represented by (3) and having a 4-azido-3-nitrophenylcarbonyloxyethylene structure is also preferred.

  Further, a modifying group represented by the following general formula (4) is also preferably used.

  In the formula, R represents an alkylene group or an aromatic ring. A benzene ring is preferred.

  As the photopolymerization type modifying group, for example, a resin represented by the following general formula (5) shown in JP-A Nos. 2000-181062 and 2004-189841 is preferable from the viewpoint of reactivity.

In the formula, R ₂ represents a methyl group or a hydrogen atom, n represents 1 or 2, X represents — (CH ₂ ) _m —COO— or —O—, and Y represents an aromatic ring or a single bond. And m represents an integer from 0 to 6.

  Moreover, it is also preferable to use the photopolymerization type | mold modified group represented by following General formula (6) described in Unexamined-Japanese-Patent No. 2004-161942 for a conventionally well-known water-soluble resin.

In the formula, R ₃ represents a methyl group or a hydrogen atom, and R ₄ represents a linear or branched alkylene group having 2 to 10 carbon atoms.

  From the above, a particularly preferred embodiment as the ink composition according to the present invention is a saponified product containing at least a pigment, water, and a water-soluble polymer compound, and the water-soluble compound having a hydrophilic main chain of polyvinyl acetate. 1 to 10% by mass of a saponification degree of 77 to 99%, a polymerization degree of 200 to 500, and a modification rate of 0.8 to 4.0 mol% with respect to the total amount of the ink composition. Particularly preferred.

  In the present invention, it is also preferable to add a photopolymerization initiator and a sensitizer together with the water-soluble polymer compound according to the present invention. These compounds may be dissolved or dispersed in a solvent, or may be chemically bonded to a water-soluble polymer compound.

  There is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A conventionally well-known thing can be used. A water-soluble compound is preferable from the viewpoints of miscibility and reaction efficiency. In particular, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (HMPK), thioxanthone ammonium salt (QTX), and benzophenone ammonium salt (ABQ) are preferable from the viewpoint of miscibility with an aqueous solvent.

  Furthermore, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (n = 1, HMPK) represented by the following general formula (7) from the viewpoint of compatibility with the resin, An ethylene oxide adduct (n = 2 to 5) is more preferable.

  In the formula, n represents an integer of 1 to 5.

  Other examples include benzophenones such as benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone. Thioxanthones such as thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, and isopropoxychlorothioxanthone. Anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone and chloroanthraquinone. Acetophenones. Benzoin ethers such as benzoin methyl ether. 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di ( m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer, 2- (P-methoxyphenyl) -4,5-diphenylimidazole dimer, 2-di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4,5- Diphenylimidazole dimer 2,4,5-triarylimidazole dimer, benzyldimethyl ketal, 2-benzyl-2-dimethyl Mino-1- (4-morpholinophenyl) butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-hydroxy-2-methyl-1-phenyl -Propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, phenanthrenequinone, 9,10-phenanthrenequinone, Benzoins such as methylbenzoin and ethylbenzoin, 9-phenylacridine, acridine derivatives such as 1,7-bis (9,9'-acridinyl) heptane, bisacylphosphine oxide, and mixtures thereof are preferably used. May be used alone or in combination.

  In addition to these photopolymerization initiators, accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like. These photopolymerization initiators are also preferably grafted to the side chain with respect to the hydrophilic main chain.

[Other additives]
The ink composition according to the present invention contains at least a pigment, water, and a water-soluble solvent together with the water-soluble polymer compound.

(Pigment)
As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used, and anionic pigments are preferred. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Examples include cyclic pigments, dye lakes such as acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as carbon black.

  Specific organic pigments are exemplified below.

  Examples of pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the orange or yellow pigment include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. And CI Pigment Yellow 138.

  Examples of pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

<Dispersant>
As the water-soluble polymer dispersant for stably dispersing the pigment in the ink, the following water-soluble resin can be used, which is preferable from the viewpoint of ejection stability.

  The water-soluble resin used here is preferably a styrene-acrylic acid-alkyl acrylate ester copolymer, a styrene-acrylic acid copolymer, a styrene-maleic acid copolymer, or a styrene-maleic acid-alkyl acrylate. Ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid A water-soluble resin such as a copolymer.

  The content of the water-soluble resin used as the dispersant with respect to the total amount of the ink is preferably 0.1 to 10% by mass, and more preferably 0.3 to 5% by mass.

  Two or more of these water-soluble resins can be used in combination.

<Anionic pigment>
The form of the anionic pigment preferably used in the present invention is preferably a pigment in which the pigment is dispersed with an anionic polymer dispersant or an anion-modified self-dispersing pigment from the viewpoint of dispersion stability.

  The anionic polymer dispersant refers to a dispersant having an anionic group obtained by neutralizing an acidic group in a molecule with a basic compound. Examples of the basic compound used at this time include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamine, and alkanolamine. In the present invention, amines are particularly preferred. preferable.

  The anionic polymer dispersant preferably used in the present invention is not particularly limited as long as the molecular weight is 1000 or more. For example, polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, and acrylic acid-acrylonitrile copolymers , Acrylic resins such as potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer Styrene-acrylic resins such as styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, Styrene-maleic acid copolymer, styrene-maleic anhydride Rain acid copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer Polymers, vinyl acetate copolymers such as vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, and copolymers or resins such as salts thereof are, for example, carboxylic acid, sulfonic acid or phosphonic acid. Includes homopolymers, copolymers and terpolymers with acid functionality. Monomers that give acid functionality are, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, mesaconic acid, fumaric acid, citraconic acid, vinyl acetic acid, acryloxypropionic acid, vinyl sulfonic acid, Examples thereof include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, allyl sulfonic acid, allyl phosphonic acid, vinyl phosphonic acid, and vinyl sulfonic acid. % Is preferred. Two or more of these may be used in combination.

  The anion-modified self-dispersing pigment preferably used in the present invention refers to a pigment having an anionic group on the surface and capable of being dispersed without a dispersant. An anionic self-dispersing pigment refers to a pigment in which an acidic group is modified and neutralized with a basic compound, thereby making the anionic group dispersible in water without a dispersant.

  The pigment particle having an acidic group on the surface means a pigment directly modified with an acidic group on the surface of the pigment particle, or an organic substance having an organic pigment mother nucleus and having an acidic group bonded directly or through a joint. .

  Examples of the acidic group (also referred to as polar group) include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a boric acid group, and a hydroxyl group, preferably a sulfonic acid group and a carboxylic acid group, and more preferably a carboxylic acid group. It is an acid group.

  Acid group modifiers include sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt, sulfamic acid and other treatments containing sulfur atoms, and the pigment particle surface is oxidized. Carboxylating agents such as sodium hypochlorite and potassium hypochlorite that introduce carboxylic acid groups can be mentioned. Among them, a sulfonating agent such as sulfur trioxide, sulfonated pyridine salt or sulfamic acid, or a carboxylating agent is preferable. Examples of basic compounds that neutralize acidic groups include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamines, and alkanolamines. In the present invention, amines are used. Is particularly preferred.

  Examples of a method for obtaining pigment particles having a polar group on the surface include WO97 / 48769, JP-A-10-110129, JP-A-11-246807, JP-A-11-57458, and 11-189739. In other words, the surface of the pigment particles described in JP-A-11, JP-A-11-323232, JP-A-2000-265094, etc. is oxidized with an appropriate oxidizing agent, so that at least a part of the pigment surface has a sulfonic acid group or a salt thereof. The method of introduce | transducing such polar groups is mentioned. Specifically, it is prepared by oxidizing carbon black with concentrated nitric acid, or in the case of color pigments by oxidizing with sulfamic acid, sulfonated pyridine salt, amide sulfuric acid, etc. in sulfolane or N-methyl-2-pyrrolidone. can do. In these reactions, the pigment dispersion can be obtained by removing and purifying the substance that has been excessively oxidized and becomes water-soluble. Moreover, when a sulfonic acid group is introduced onto the surface by oxidation, the acidic group may be neutralized with a basic compound as necessary.

  Other methods include a method of adsorbing the pigment derivatives described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. on the surface of pigment particles by a treatment such as milling, and the like. Examples include a method of dissolving the pigment described in 2002-179777, 2002-201401 and the like together with a pigment derivative in a solvent and then crystallization in a poor solvent. Pigment particles having a polar group can be obtained.

  In the present invention, the polar group may be free or in a salt state, or may have a counter salt. Examples of the counter salt include inorganic salts (lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium) and organic salts (triethylammonium, diethylammonium, pyridinium, triethanolammonium, etc.), preferably 1 A counter salt having a valence.

  The average particle diameter of the pigment dispersion used in the inkjet ink according to the present invention is preferably 500 nm or less, more preferably 200 nm or less, preferably 10 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less. If the average particle size of the pigment dispersion exceeds 500 nm, the dispersion becomes unstable. In addition, even when the average particle size of the pigment dispersion is less than 10 nm, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. It is also possible to obtain a particle image with a transmission electron microscope on at least 100 particles and perform statistical processing on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). Is possible.

  Various methods such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used as a pigment dispersion method.

(Water-soluble solvent)
In the ink composition according to the present invention, a mixed solvent such as water and a water-soluble organic solvent is preferably used as the water-soluble solvent.

  Examples of water-soluble organic solvents include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene). Glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene glycol) Monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether Diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl Ether, propylene glycol monophenyl ether, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, Tetra Tylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclics (eg, 2-pyrrolidone) N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (eg dimethyl sulfoxide, etc.) and the like.

(Surfactant)
Surfactants preferably used in the ink composition according to the present invention include alkyl sulfates, alkyl ester sulfates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl phosphates, and polyoxyalkylene alkyl ether phosphates. Anionic surfactants such as salts and fatty acid salts, nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, acetylene glycols, polyoxyethylene-polyoxypropylene block copolymers, and glycerin Activators such as esters, sorbitan esters, polyoxyethylene fatty acid amides, amine oxides, cationic surfactants such as alkylamine salts and quaternary ammonium salts, silicone surfactants, fluorine-based interfaces Gender, and the like. These surfactants can also be used as pigment dispersants, and anionic surfactants can be particularly preferably used.

(Various additives)
In addition, the ink composition according to the present invention may contain conventionally known additives. For example, fluorescent brighteners, antifoaming agents, lubricants, preservatives, thickeners, antistatic agents, matting agents, water-soluble polyvalent metal salts, acid bases, pH adjusters such as buffers, antioxidants, surfaces These are tension adjusters, specific resistance adjusters, rust inhibitors, inorganic pigments and the like.

  In the ink composition according to the present invention, in addition to the above description, according to the purpose of improving the emission stability, the print head and ink cartridge compatibility, the storage stability, the image storage stability, and other various performances as necessary. Various known additives such as viscosity modifiers, specific resistance regulators, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, antifungal agents, and rust preventives may be appropriately selected and used. For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicon oil, ultraviolet absorbers described in JP-A-57-74193, 57-87988, and 62-261476, As described in Kaisho 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. Can be mentioned.

<< Aqueous treatment liquid >>
In the ink-jet ink set of the present invention, an aqueous composition containing a polyvalent metal salt or polyallylamine that thickens or aggregates the ink composition together with the ink composition containing the pigment, water, and a water-soluble polymer compound. And a treatment liquid.

  The aqueous treatment liquid according to the present invention is characterized by having a property of thickening or aggregating the ink composition when associated with the ink composition, and the aqueous treatment liquid contains a polyvalent metal salt or polyallylamine. By ink-jet printing the ink composition and aqueous treatment liquid on a recording medium, the ink composition thickens or aggregates at the timing before it is cured by irradiation with active energy rays, thereby preventing white streaks. can do.

  Adhesion of the aqueous treatment liquid to the recording medium may be either an aspect in which the aqueous treatment liquid is adhered only to a place where the ink composition is adhered, or an aspect in which the aqueous treatment liquid is adhered to the entire recording medium. However, the former mode is preferable from the viewpoints of drying property and consumption of the aqueous treatment liquid. In that case, the aspect which discharges this aqueous | water-based processing liquid with one head of the units comprised from a line-type inkjet recording head is preferable.

  An aqueous processing liquid containing a polyvalent metal salt or polyallylamine (including a polyallylamine derivative) that can be used in the present invention thickens or aggregates when it comes into contact with the ink composition. Any polyvalent metal salt or polyallylamine can be used as long as it exhibits a function of destroying and aggregating the dispersed state and dissolved state of the pigment and the water-soluble polymer compound in the ink composition.

Preferred examples of the polyvalent metal salt include salts composed of divalent or higher polyvalent metal ions and anions that bind to these polyvalent metal ions and are soluble in water. As specific examples of polyvalent metal ions, cations include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ and Ba ²⁺ , Al ³⁺ and Fe ^3+. And trivalent metal ions. Examples of the anion include Cl ⁻ , NO ₃ ⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ and CH ₃ COO ⁻ .

Particularly preferred is Ca ²⁺ or Mg ²⁺ . The concentration of these polyvalent metal salts in the aqueous treatment liquid is generally from 0.1 to 40% by mass, and more preferably from 5 to 25% by mass.

  A preferred embodiment of the polyvalent metal salt used in the present invention is composed of the above-mentioned polyvalent metal ions and nitrate ions or carboxylate ions bonded to these polyvalent metal ions, and includes those soluble in water. it can.

  The carboxylate ion is preferably derived from a saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms or a carbocyclic monocarboxylic acid having 7 to 11 carbon atoms.

  Particularly preferred examples of the saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms include formic acid and acetic acid, and the hydrogen atom on the saturated aliphatic hydrocarbon of the monocarboxylic acid may be substituted with a hydroxyl group, A preferred example of such a carboxylic acid is lactic acid.

  On the other hand, benzoic acid etc. are mentioned as a preferable example of a C6-C10 carbocyclic monocarboxylic acid.

  The polyallylamine contained in the aqueous treatment liquid includes polyallylamine derivatives, which are cationic polymers that are soluble in water and positively charged in water. For example, the compound represented by the following general formula (a), general formula (b), and general formula (c) can be mentioned.

In the above general formulas, X ⁻ represents a chloride ion, bromide ion, iodide ion, nitrate ion, phosphate ion, sulfate ion or acetate ion.

  The content of these polyallylamines is generally 0.5 to 10% by mass of the aqueous treatment liquid.

  The aqueous treatment liquid according to the present invention contains water and / or an aqueous solvent as an aqueous medium together with a polyvalent metal salt or polyallylamine. As the aqueous solvent, a solvent similar to that used in the ink composition used in combination can be used, and the content thereof is generally 1 to 60% by mass.

<Inkjet recording method>
〔inkjet printer〕
In the ink jet recording method of the present invention, the ink composition and the aqueous treatment liquid constituting the ink jet ink set of the present invention are emitted from the ink jet recording head and adhered to the recording medium, and then the active energy rays are applied to the ink composition. And a step of forming an image by irradiation. Furthermore, it is a preferable aspect that the inkjet recording head is a line-type inkjet recording head from the viewpoint that the white streak suppressing effect is remarkably exhibited.

  The main thing of the inkjet printer provided with the recording head suitable for utilizing the ink set of the present invention is that the image forming means is disposed horizontally with respect to the recording medium, and a plurality of inkjet inks are directed toward the recording medium. A line-type inkjet recording head that discharges from a nozzle, and a light source that irradiates an active energy ray that cures the ink composition that has landed on the recording medium.

  As a member used in the ink jet printer applicable to the present invention, in order to prevent irradiation of the head surface due to active energy rays such as ultraviolet rays or irregular reflection thereof, those having low transmittance and reflectance with respect to the active energy rays are preferable.

  In addition, it is preferable that the active energy ray irradiated portion is equipped with a shutter. For example, when using ultraviolet rays, the ratio of illuminance when the shutter is opened / closed is preferably shutter open / shutter close ≧ 10, more preferably 100 or more. preferable.

(Inkjet recording head)
An ink composition and an aqueous treatment liquid constituting the ink jet ink set according to the present invention are ejected onto a recording medium using an ink jet recording head, and an image is formed. An ass system may be used. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.), and a discharge type (for example, a spark jet type). Can do.

(Line type recording head)
The ink composition and the aqueous treatment liquid constituting the inkjet ink set according to the present invention are particularly effective when a recording method using a line type recording head is applied. The line-type recording head is a recording head that is longer than the width of the recording medium, and may be a long recording head that includes a large number of nozzles. It may be a recording head. By using a line type recording head, the carriage mounted with the recording head scans in a direction perpendicular to the conveyance direction of the recording medium, and the number of recording heads is shorter than that of a serial type recording head. Record and improve productivity dramatically.

  Normally, in image recording using a line-type recording head, the time from the ink droplet landing to the next adjacent ink droplet landing becomes shorter as the image forming speed increases. The previous increase in viscosity was insufficient, and had the problem of easily causing white streaks due to liquid, but in the present invention, the above problem was solved by applying the ink set according to the present invention. It is.

(Drying process)
In the case of image recording using the inkjet ink set according to the present invention, after irradiating the ink composition and the aqueous treatment liquid constituting the inkjet ink set discharged onto the recording medium with an active energy ray, an unnecessary solvent or the like is removed. Drying is preferably performed for the purpose of removal. In particular, when printing is performed on a low ink-absorbing recording medium or a non-ink-absorbing recording medium, it is preferable in that the stickiness is eliminated through a drying process and the fixability of a recorded image is further improved in a short time.

  The drying means used in the drying step is not particularly limited. For example, a method of drying the recording medium by bringing the back surface of the recording medium into contact with a heating roller or a flat heater, a means for blowing warm air on the printing surface with a dryer, or the like. A method of removing volatile components by a decompression process can be appropriately selected or combined. For example, when a method of bringing the recording medium into contact with a heating roller or a flat heater is applied as the heating means, the preferred heating temperature is 30 to 70 ° C. If the temperature is 30 ° C. or higher, the gloss of the printed matter is high. If it is 70 ° C. or less, the recording medium is not deformed and the transportability is good.

[Explanation of figures]
Next, the ink composition constituting the ink jet ink set of the present invention, the ink jet printer (printer member, ink jet recording head, etc.) used for emission of the aqueous treatment liquid, and the active energy ray irradiation method will be specifically described with reference to the drawings. . Note that the present invention is not limited to the illustrated configurations.

  FIG. 1 is a schematic top view illustrating an example of an ink jet printer in which an ink jet recording head unit including a plurality of line type ink jet recording heads, a light irradiation device, and a drying process are arranged.

In FIG. 1, an ink group composed of an ink composition (in FIG. 1, ink composed of a yellow pigment ink, a magenta pigment ink, a cyan pigment ink, and a black pigment ink) is placed on a platen 2 holding a recording medium P. An inkjet recording head unit HU comprising line recording heads H _y , H _m , H _c and H _{k on} which an example of a set is mounted) and a line recording head H _{g on} which an aqueous treatment liquid is mounted; The example of the inkjet printer 1 provided with the light irradiation apparatus 3 and the drying process 4 is shown. The ink composition containing the pigment constituting the ink set according to the present invention includes at least one kind of pigment ink, and may be a multicolor ink or a single color ink, or a dark ink. It may contain ink and light ink.

In FIG. 1, the recording medium held on the platen 2 is conveyed from the upstream direction, and as a first step, an aqueous processing liquid is ejected from the line recording head _Hg to the recording medium, and then an image is formed. the equipped with line recording head H _y, H _m, from H _c and H _k, for emitting respective color ink composition. At this time, the aqueous treatment liquid previously applied on the recording medium and each color ink come into contact with each other to cause the ink composition to thicken or agglomerate. Simultaneous association of droplets can be prevented.

  After emitting the aqueous treatment liquid and each color ink composition, by irradiating the formed image with active energy rays by the light irradiation device 3 incorporating the active energy irradiation light source disposed downstream as the second step, Curing of the ink composition is performed. In the present invention, if necessary, a drying step 4 may be further provided on the downstream side for the purpose of removing the solvent remaining in the cured image.

  In the ink jet recording method according to the third aspect, the ink composition and the aqueous treatment liquid are subjected to ink jet printing, and then an active energy ray is irradiated to form an image. The landing order of the ink composition and the aqueous treatment liquid contained in the ink set according to the present invention is not limited.

1, as an example, a particularly preferred line recording head H _g equipped with equipped with line recording head and an aqueous treatment liquid of the ink composition as a constituent, has been described as the configuration shown from the upstream side to below 1), 1 ) in addition to the configuration shown, if desired, as shown below 2), a method of placing the most downstream line recording equipped with the aqueous treatment liquid in the head H _g, the ink as shown below 3) a composition equipped with the line recording head and the aqueous treatment liquid mounted with the line recording head H _g and one configuration, the method alternately arranged or as shown in the following 4), a nozzle unit for emitting ink composition And a line recording head in which a nozzle portion equipped with an aqueous treatment liquid is integrated.

1) _Hg / _Hy / _Hm / _Hc / _Hk
2) _Hy / _Hm / _Hc / _Hk / _Hg
3) _Hg / _Hy / _Hg / _Hm / _Hg / _Hc / _Hg / _Hk
4) _Hy + _Hg / _Hm + _Hg / _Hc + _Hg / _Hk + _Hg
[Active energy ray irradiation]
The present invention is characterized in that an ink composition containing a water-soluble polymer compound is emitted from a recording head onto a recording medium, and is then cured by irradiating the ink composition landed with active energy rays.

  Hereinafter, irradiation of active energy rays according to the present invention will be described.

(Active energy rays, irradiation method)
The active energy ray as used in the present invention includes, for example, electron beam, ultraviolet ray, α ray, β ray, γ ray, X ray and the like. However, it is dangerous to human body, easy to handle, and industrially used. Electron beams and ultraviolet rays are widely used.

  When using an electron beam, the amount of the electron beam to be irradiated is preferably in the range of 0.1 to 30 Mrad. This is because a sufficient irradiation effect can be obtained if it is 0.1 Mrad or more, and there is little possibility of deteriorating the support or the like if it is 30 Mrad or less.

  When using ultraviolet rays, the light source is a low pressure, medium pressure, high pressure mercury lamp, metal halide lamp, xenon lamp having a light emission wavelength in the ultraviolet region, cold cathode tube, hot cathode tube, for example, having an operating pressure of 0.1 kPa to 1 MPa. A conventionally well-known thing, such as LED, is used.

(Light irradiation conditions after ink landing)
As the irradiation condition of actinic rays, actinic rays are preferably irradiated between 0.001 and 1.0 seconds after ink landing, and more preferably 0.001 to 0.5 seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

(Installation of lamp)
As a method for irradiating actinic rays, the basic method is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method of the present invention.

  In another preferred embodiment, irradiation with actinic rays is divided into two stages, and actinic rays are first irradiated by the above-described method between 0.001 and 2.0 seconds after ink landing, and further irradiated with actinic rays. It is. By dividing the irradiation of actinic rays into two stages, it is possible to further suppress the shrinkage of the recording medium that occurs during ink curing.

"recoding media"
As a recording medium on which an image is formed using the ink set according to the present invention, a low ink-absorbing recording medium or a non-ink-absorbing medium can be used in addition to paper such as coated paper and non-coated paper. In particular, when recording on a low ink absorptive recording medium or a non-ink absorptive medium using a line recording head, white streaks that are the subject of the present invention are likely to occur. It can be significantly suppressed.

  Here, the low ink-absorptive recording medium and the non-ink-absorptive recording medium are a recording medium made of a material having no ink absorptivity or a material having a low ink absorptivity, or a material having no ink absorptivity or a low ink absorptivity. A recording medium having a surface layer (surface layer of a printing surface) made of a material, for example, art paper or coated paper mainly used as a recording medium for offset printing or gravure printing, and various plastic films Any metal, leather, leather, etc. that are generally used can be used. For example, there are a polyester film, a polyolefin film, a polyvinyl chloride film, a polyvinylidene chloride film and the like, and a resin-coated paper which is a photographic printing paper and a YUPO paper which is a synthetic paper can also be used.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

<< Preparation of aqueous treatment liquid >>
[Preparation of aqueous treatment liquid 1]
Magnesium nitrate hexahydrate 25%
Triethylene glycol monobutyl ether 5%
Glycerin 20%
Aqueous treatment solution 1 was prepared by adding ion exchange water to 100%.

[Preparation of aqueous treatment liquid 2]
Polyallylamine PAA-10C (resin component 10%, manufactured by Nittobo) 30%
Triethylene glycol monobutyl ether 10%
Glycerin 8%
Aqueous treatment liquid 2 was prepared by adding ion exchange water to 100%.

[Preparation of aqueous treatment liquid 3 (comparative aqueous treatment liquid)]
Triethylene glycol monobutyl ether 10%
Glycerin 8%
Ion exchange water was added to 100% to prepare an aqueous treatment liquid 3 for comparison.

<Synthesis of water-soluble polymer compound>
[Synthesis of water-soluble polymer compound 1]
A water-soluble polymer compound 1 was synthesized according to the following method.

  Glycidyl methacrylate (58 g), p-hydroxybenzaldehyde (42 g), pyridine (3 g), and N-nitroso-phenylhydroxyamine ammonium salt (1 g) were placed in a reaction vessel, and stirred in a hot water bath at 80 ° C. for 8 hours.

  Subsequently, 45 g of polyvinyl acetate saponified product having an average degree of polymerization of 2200 and a saponification rate of 88% was dispersed in 225 g of ion-exchanged water, and then 4.5 g of phosphoric acid and p- (3-methacryloxy) obtained by the above reaction were added to this solution. 2-Hydroxypropyloxy) benzaldehyde was added with a modification rate of 3.0 mol% with respect to polyvinyl alcohol, and the mixture was stirred at 90 ° C. for 6 hours. After cooling the obtained aqueous solution to room temperature, 30 g of basic ion exchange resin was added and stirred for 2 hours.

  Thereafter, the ion exchange resin was filtered, and Irgacure 2959 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a photopolymerization initiator was mixed at a rate of 0.5 g with respect to 100 g of a 15% aqueous solution, and then diluted with ion exchange water. As a result, a 10% aqueous solution of the water-soluble polymer compound 1 was obtained.

[Synthesis of water-soluble polymer compound 2]
In the synthesis of the water-soluble polymer compound 1, a polyvinyl acetate saponified product having an average polymerization degree of 330 and a saponification rate of 88% is used as the polyvinyl acetate saponified product, and p- (3- A 10% aqueous solution of the water-soluble polymer compound 2 was obtained in the same manner except that the amount of methacryloxy-2-hydroxypropyloxy) benzaldehyde was appropriately adjusted.

<Preparation of ink set>
<Preparation of ink set>
Ink sets 1 to 3 were prepared according to the following method. In addition, the particle size measurement of the pigment contained in each following pigment dispersion liquid was performed using Malvern Co., Ltd. Zetasizer 1000HS. Further, Jonkrill 61 used in the preparation of the following pigment dispersion is a styrene acrylic resin dispersant manufactured by Johnson, and has a solid content of 30%.

(Preparation of pigment dispersion)
(Adjustment of magenta pigment dispersion)
The following additives were mixed and dispersed using a sand grinder filled with 0.6 mm zirconia beads at a volume ratio of 50% to prepare a magenta pigment dispersion having a magenta pigment content of 15%. The average particle diameter of the magenta pigment particles contained in this magenta pigment dispersion was 120 nm.

C. I. Pigment Red 122 15 parts Jonkrill 61 (manufactured by Johnson) 10 parts Glycerin 15 parts Ion-exchanged water 60 parts (adjustment of black pigment dispersion)
A carbon black self-dispersion Cabojet 300 manufactured by Cabot was diluted with ion-exchanged water to prepare a black pigment dispersion having a carbon black content of 15%. The average particle size of the carbon black particles contained in this black pigment dispersion was 130 nm.

(Adjustment of yellow pigment dispersion)
The following additives were mixed and dispersed using a sand grinder filled with 0.6 mm zirconia beads at a volume ratio of 50% to prepare a yellow pigment dispersion having a yellow pigment content of 15%. The average particle diameter of the yellow pigment particles contained in this yellow pigment dispersion was 110 nm.

C. I. Pigment Yellow 74 15 parts Jonkrill 61 (manufactured by Johnson) 10 parts Glycerin 15 parts Ion-exchanged water 60 parts (Preparation of cyan pigment dispersion)
The following additives were mixed and dispersed using a sand grinder filled with 0.6 mm zirconia beads at a volume ratio of 50% to prepare a cyan pigment dispersion having a cyan pigment content of 15%. The average particle diameter of the cyan pigment particles contained in this cyan pigment dispersion was 130 nm.

C. I. Pigment Blue 15 15 parts Jonkrill 61 (manufactured by Johnson) 10 parts Glycerin 15 parts Ion-exchanged water 60 parts [Preparation of ink set 1]
(Preparation of each color ink)
<Preparation of magenta pigment ink 1>
Magenta pigment dispersion (solid content 15%) 24 parts Water-soluble polymer compound 1 (solid content 10%) 30 parts Propylene glycol 28 parts Ethylene glycol 10 parts Olfine E1010 (manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part Antifungal agent: Proxel GXL (Made by Avicia) 0.3 parts Ion exchange water was added to finish 100 parts to prepare magenta pigment ink 1.

<Preparation of Black Pigment Ink 1>
A black pigment ink 1 was obtained in the same manner as in the preparation of the magenta pigment ink 1 except that a black pigment dispersion was used instead of the magenta pigment dispersion.

<Preparation of yellow pigment ink 1>
A yellow pigment ink 1 was obtained in the same manner as in the preparation of the magenta pigment ink 1 except that a yellow pigment dispersion was used instead of the magenta pigment dispersion.

<Preparation of cyan pigment ink 1>
Cyan pigment ink 1 was obtained in the same manner as in the preparation of magenta pigment ink 1 except that a cyan pigment dispersion was used instead of the magenta pigment dispersion.

(Preparation of ink set)
A combination of the magenta pigment ink 1, the black pigment ink 1, the yellow pigment ink 1, and the cyan pigment ink 1 prepared as described above was used as an ink set 1.

[Preparation of ink set 2]
In the preparation of the magenta pigment ink 1, the black pigment ink 1, the yellow pigment ink 1, and the cyan pigment ink 1, 10% of the water-soluble polymer compound 2 was used instead of 10% of the water-soluble polymer compound 1. In the same manner, magenta pigment ink 2, black pigment ink 2, yellow pigment ink 2, and cyan pigment ink 2 were prepared, and this combination was designated as ink set 2.

[Preparation of ink set 3]
(Preparation of each color ink)
<Preparation of magenta pigment ink 3>
Magenta pigment dispersion (solid content 15%) 24 parts Aqueous UV curable urethane acrylate resin emulsion (solid content 40%, manufactured by Taisei Kako Co., Ltd., trade name: WBR-839) 7.5 parts 2-pyrrolidinone 15 parts ethylene glycol 10 parts Orphin E1010 (manufactured by Nissin Chemical Co., Ltd.) 1 part Antifungal agent: Proxel GXL (manufactured by Avicia) 0.3 part Ion exchange water was added to finish to 100 parts.

<Preparation of Black Pigment Ink 3, Yellow Pigment Ink 3, and Cyan Pigment Ink 3>
In the preparation of the magenta pigment ink 3, the black pigment ink 3 and the yellow pigment ink 3 were similarly used except that a black pigment dispersion, a yellow pigment dispersion, and a cyan pigment dispersion were used instead of the magenta pigment dispersion. A cyan pigment ink 3 was prepared.

(Preparation of ink set)
A combination of the magenta pigment ink 3, the black pigment ink 3, the yellow pigment ink 3, and the cyan pigment ink 3 prepared as described above was used as an ink set 3.

<Inkjet image recording method>
Images 1 to 6 were prepared by performing image formation with the following ink jet recording apparatus using a combination of the ink set shown in Table 1 and the aqueous treatment liquid.

As the ink jet recording apparatus, image recording was performed using a line recording head group having the configuration shown in FIG. The line recording head unit HU shown in FIG. 1 has five nozzles having a nozzle diameter of 25 μm, a nozzle number of 512, a minimum droplet amount of 14 pl, and a nozzle density of 180 dpi (where dpi represents the number of dots per 2.54 mm). A piezo-type inkjet recording head is arranged so as to cover the print width perpendicular to the conveyance direction of the recording medium. The line recording heads H _g , H _y , H _m , H _c , and H _k constituting the line recording head unit HU include aqueous treatment liquid, yellow pigment ink, magenta pigment ink, cyan pigment ink, and black pigment ink, respectively. The ink set was installed. Using the line recording head unit HU having this configuration, each image was created at a conveyance speed of 300 mm / second.

Next, as the light irradiation device 3, a 160 W / cm metal halide lamp (MAN200 (N) L manufactured by Nippon Battery Co., Ltd.) is arranged in the same width as the line recording head, and the recording image formed on the upstream side is irradiated with active energy ray irradiation means. The recorded image was irradiated with active energy rays. At this time, the distance between the last line recording head H _k and the active energy ray irradiation light source of the light irradiation device 3 is 5.5 cm, the printing speed is 0.6 m / sec, printing and irradiation with the active energy ray are performed, and then drying is performed. It dried using the heating fan in the process 4.

<Evaluation of formed image>
Each image created by the above-described inkjet image recording method was evaluated according to the following method.

[Evaluation of sharpness]
4-point and 6-point MS for each color of yellow, magenta, cyan, and black in combination with aqueous processing liquid on coated paper (OK Top Coat, Oji Paper Co., Ltd.) and polyethylene terephthalate film (also called PET film) as recording media In the Mincho style, the characters of the Chinese characters “mouth, fourth, day, times, cause, trouble, solid, country, eyes, figure” are printed in white, the printed character image is visually observed, and sharpness is observed according to the following evaluation criteria Was evaluated. Here, the white character means a printing method in which each color ink is ejected to the background portion and not to the character portion.

○: For each color image, a 4-point character image can be read. Δ: For each color image, a 4-point character image is difficult to read, but a 6-point character image can be read. ×: For each color image, 6 The point is also difficult to interpret the character image.

[Evaluation of white stripe resistance]
A solid solid image is formed on a coated paper (OK Top Coat Oji Paper Co., Ltd.) and a PET film as a recording medium using a 10 cm × 10 cm aqueous treatment liquid, a magenta pigment ink, and a yellow pigment ink. The presence or absence of white streaks was visually observed, and white streaks were evaluated according to the following criteria.

◯: No white stripes are observed Δ: Slight stripes are generated vertically in the transport direction, but acceptable for practical use ×: Vertical stripes are clearly observed in the transport direction.

  The results obtained as described above are shown in Table 1.

  As is clear from the results shown in Table 1, it can be seen that when an image is formed with a line recording head using the ink set according to the present invention, both white streak resistance and sharpness are excellent.

  It can be seen that when the water-based polymer compound contained in the pigment ink used in the present invention has a polymerization degree of 300, the effects of the present invention are further remarkably exhibited. However, it is possible to confirm that the sharpness is better by using the aqueous polymer compound as in the present invention for the ink set 3 composed of the polymer fine particle type ink using the emulsion as the resin. It was.

It is a schematic top view showing an example of an ink jet printer in which an ink jet recording head unit composed of a plurality of line type ink jet recording heads, a light irradiation device, and a drying step are arranged.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Platen 3 Light irradiation apparatus 4 Drying process HU Inkjet recording head unit H _y Line recording head for yellow pigment ink H _m Line recording head for magenta pigment ink H _c Line recording head for cyan pigment ink H _{k For} black pigment ink line recording head H _g aqueous treatment liquid line recording head P recording medium

Claims (4)

  An ink-jet ink set comprising an ink composition containing at least a pigment, water, and a water-soluble polymer compound, and an aqueous treatment liquid that thickens or aggregates the ink composition, wherein the water-soluble polymer compound is , A polymer compound having a plurality of side chains with respect to the hydrophilic main chain and capable of crosslinking or polymerization bonding between the side chains by irradiation with active energy rays, and the aqueous treatment liquid is a polyvalent metal salt or An ink jet ink set comprising polyallylamine.   The water-soluble polymer compound is a saponified product having a hydrophilic main chain of polyvinyl acetate, a saponification degree of 77% or more and 99% or less, and a polymerization degree of 200 or more and 500 or less. The inkjet ink set according to claim 1.   The ink composition and the aqueous treatment liquid constituting the ink jet ink set according to claim 1 or 2 are emitted from an ink jet recording head and attached to a recording medium, and then the ink composition is irradiated with active energy rays. An ink jet recording method comprising a step of forming an image.   4. The ink jet recording method according to claim 3, wherein the ink jet recording head is a line type ink jet recording head.

Images