JP2006083330A - Ink set and image forming method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set having excellent light resistance of the primary color and the secondary color, gas fading resistance, bleeding resistance in long-term storage and ejection property and a method for forming an image by using the ink set. <P>SOLUTION: The ink set contains a magenta ink at least containing water, a dye and a water-soluble organic solvent and a cyan ink at least containing water, a dye and a water-soluble organic solvent. The dye in the magenta ink is expressed by general formula (1), the dye in the cyan ink is expressed by general formula (2), and both of the water-soluble organic solvent in the magenta ink and the water-soluble organic solvent in the cyan ink contain a polyhydric alcohol or a polyhydric alcohol alkyl ether as the water-soluble organic solvent A in an amount of 10-20 mass% based on the total mass of the ink and a 1-3C monohydric alcohol as the water-soluble organic solvent B in an amount of 1-5 mass% based on the total mass of the ink. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink set improved in light resistance, gas fading resistance, bleeding resistance over time, and emission properties in primary and secondary colors, and an image forming method using the same.

  Inkjet recording is a method in which micro droplets of ink are ejected by various operating principles and deposited on a recording medium to record images, characters, etc., but are relatively fast, low noise, and easy to increase in color. Has the advantage of being.

  In recent years, the progress of inkjet technology has been remarkable, and the resulting image quality is called photographic image quality, coupled with improvements in printer technology, ink technology, and dedicated inkjet recording medium technology. With the improvement in image quality, the storability of inkjet images has been compared with conventional silver salt photographs, especially in dye inks, which are accompanied by the movement of colorants, such as the water resistance and poor resistance to bleeding of inkjet images. In addition, deterioration (fading) accompanied by a chemical reaction peculiar to coloring materials such as weakness to light resistance and oxidation resistance gas resistance has been pointed out. In particular, in recent years, discoloration of ink jet recorded images due to ozone gas contained in a minute amount in the atmosphere has become a problem. In printing using an ink set composed of a plurality of inks, the balance of fading between hues is also important. If even one ink has poor fading, the color balance is lost and stable high image quality is achieved. Is a major hindrance in terms of provision.

  Recently, a plurality of color ink compositions are prepared and a color image is formed by ink jet recording. In general, a color image is formed by four colors including a yellow ink composition, a magenta ink composition, and a cyan ink composition, and optionally a black ink composition. In addition, color images may be formed by six colors obtained by adding a light cyan ink composition and a light magenta ink composition to these four colors, or seven colors obtained by further adding a red ink composition, a blue ink composition, and a green ink composition. is there. The ink composition used for the formation of such a color image has a good color developing property, and also develops a good intermediate color when combined with a plurality of ink compositions. In the subsequent storage of the printed matter, it is required to have a balance between bleeding resistance and water resistance between colors and no discoloration. Among them, in particular, many color materials used in the magenta ink composition and the cyan composition are weak in light resistance, and improvement thereof has been an important issue.

  Conventionally, xanthene dyes (for example, see Patent Documents 1 to 3) and H acid azo dyes (for example, see Patent Documents 4 to 6) have been used as magenta dyes. However, the light resistance of these magenta dyes is remarkably inferior to that of yellow dyes and cyan dyes, and ozone resistance and bleeding resistance over time are not sufficient. As magenta dyes for improving the image fastness, anthrapyridone dyes (for example, see Patent Documents 7 to 9) are disclosed, and these anthrapyridone dyes are excellent in light resistance and ozone resistance. is there.

  On the other hand, in the case of a cyan dye, C.I. I. Copper phthalocyanines such as Direct Blue 199 have been widely used. Copper phthalocyanine has very excellent characteristics with respect to light resistance and bleeding resistance over time, but has a drawback that ozone resistance is significantly inferior to magenta dyes and yellow dyes. As a method for solving this problem, in recent years, a method for improving ozone resistance with a cyan dye in which a specific substituent is introduced into copper phthalocyanine and the oxidation potential is controlled more preferentially than 1.0 V (vs SCE) has been disclosed. (For example, refer to Patent Documents 10 and 11).

Certainly, by using the dyes described in Patent Documents 7 to 9 or Patent Documents 10 and 11, image fastness in a cyan image or magenta image is increased, but a blue image which is a mixed portion of cyan ink and magenta ink. As for the light resistance, ozone resistance, and bleeding resistance over time, it is difficult to say that the ink quality is sufficient because each ink has different characteristics.
JP 54-89811 A JP-A-8-60053 JP-A-8-143798 Japanese Patent Laid-Open No. 62-156168 JP-A-3-203970 Japanese Patent Laid-Open No. 7-157698 JP 2000-109464 A JP 2000-169776 A JP 2003-192930 A JP 2002-285050 A JP 2003-213167 A

  The present invention has been made in view of the above problems, and an object of the present invention is to use an ink set excellent in light resistance, gas fading, bleeding resistance and long-term storage in primary and secondary colors, and its use. An image forming method was provided.

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

(Claim 1)
In an ink set having a magenta ink containing at least water, a dye and a water-soluble organic solvent and a cyan ink containing at least water, the dye and the water-soluble organic solvent, the dye contained in the magenta ink is represented by the following general formula (1). The dye contained in the cyan ink is a dye represented by the following general formula (2), and any one of the water-soluble organic solvent contained in the magenta ink and the water-soluble organic solvent contained in the cyan ink The water-soluble organic solvent A contains 10 to 20% by mass of polyhydric alcohol or alkyl ether of polyhydric alcohol as the water-soluble organic solvent A, and monohydric alcohol having 1 to 3 carbon atoms as the water-soluble organic solvent B. An ink set comprising 1 to 5% by mass of the total mass.

[Wherein, R represents a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, a mono- or dialkylaminoalkyl group, or a cyano lower alkyl group, and Y represents a chlorine atom, a hydroxyl group, an amino group, a mono- or dialkylamino group. Represents an aralkylamino group, a cycloalkylamino group, an alkoxy group, a phenoxy group, an anilino group, a naphthylamino group, or a mono- or dialkylaminoalkylamino group, and X represents a bridging group. M represents a hydrogen atom, an alkali metal salt, an alkaline earth metal salt, an alkylamine salt, an alkanolamine salt or an ammonium salt. ]

[Wherein, X _{11 to} X ₁₄ each independently represent —SO—Z, —SO ₂ —Z, —SO ₂ NR ₁ R ₂ , —CONR ₁ R ₂ or —CO ₂ R ₁ . Z is each independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, substituted or unsubstituted Represents a heterocyclic group. R ₁ and R ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, substituted or unsubstituted Represents an aryl group or a substituted or unsubstituted heterocyclic group. Y _{11 to} Y ₁₈ each independently represent a monovalent substituent. a11~a14 each represent a number of substituents X ₁₁ to X _14, represents 1 or 2 are each a11~a14 independently. M is a hydrogen atom, a metal atom or an oxide, hydroxide or halide thereof. ]
(Claim 2)
The ink set according to claim 1, wherein the water-soluble organic solvent A is a polyhydric alcohol.

(Claim 3)
The polyhydric alcohol is at least one selected from glycerin, ethylene glycol, diethylene glycol, propylene glycol, and triethylene glycol, and the monohydric alcohol is ethanol or propanol. Ink set.

(Claim 4)
A color image is printed by ejecting magenta ink and cyan ink onto a void-type inkjet recording medium having an ink absorbing layer containing alumina using the ink set according to any one of claims 1 to 3. An image forming method.

(Claim 5)
A color image is printed by using the ink set according to any one of claims 1 to 3 and discharging magenta ink and cyan ink using an electro-thermal conversion recording head. Image forming method.

  According to the present invention, it is possible to provide an ink set excellent in light resistance, gas fading property, bleeding resistance during long-term storage and emission properties in primary colors and secondary colors, and an image forming method using the same.

  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 inventors have found that in an ink set having a magenta ink containing at least water, a dye and a water-soluble organic solvent and a cyan ink containing at least water, a dye and a water-soluble organic solvent, The dye contained in the magenta ink is a dye represented by the general formula (1), the dye contained in the cyan ink is a dye represented by the general formula (2), and the water-soluble composition contained in the magenta ink Both the water-soluble organic solvent and the water-soluble organic solvent contained in the cyan ink contain 10 to 20% by mass of polyhydric alcohol or alkyl ether of polyhydric alcohol as the water-soluble organic solvent A, and are water-soluble. Ink set characterized by containing 1 to 5% by mass of monohydric alcohol having 1 to 3 carbon atoms as water-soluble organic solvent B, Found that serial problems can be solved, it is completed the invention.

  Even if the bis-form anthrapyridone-based magenta dye and sulfamoyl group-substituted phthalocyanine-based cyan dye described in the above-mentioned patent documents having excellent light resistance and ozone resistance are used as they are, B (comprising these magenta dye and cyan dye) In blue) images, it was difficult to say that the image quality was sufficient in terms of light fastness, ozone fastness and bleeding resistance when stored for a long time after printing (hereinafter also referred to as bleeding resistance over time). . One of these causes is considered to be related to the amount of the organic solvent remaining in the blue image composed of the mixed colors. Usually, in the B (blue) image part, which is the secondary color part (mixed color part) of magenta ink and cyan ink, the ink adhesion amount is larger than the primary color, so the remaining organic solvent is inevitably increased. It was considered that the image fastness and the bleeding resistance with time decreased. When such a phenomenon occurs, especially in a full-color image, the progress of fading and bleeding is not uniform, especially in the secondary color, causing the color balance to be lost when the image is stored over a long period of time, This is not preferable because it results in a changed image.

  In the ink set of the present invention, at least dyes to be used for magenta ink and cyan ink are selected from dyes having excellent light resistance, gas fading resistance, and bleeding resistance, and secondary color portions (for example, blue images) are selected. In order to prevent the amount of the water-soluble organic solvent from increasing, the selection of specific water-soluble organic solvents and the content of these water-soluble organic solvents are specified as specific conditions. In the color image formed using the ink set of the present invention, an image excellent in light resistance, gas fading resistance, and bleeding resistance after long-term storage of the primary colors of magenta and cyan and the secondary color of blue formed from them. As a result, it was possible to obtain a stable image with little loss of color balance even after long-term storage.

  Further, in the image forming method using the ink set of the present invention, a magenta ink and a cyan ink according to the present invention are ejected onto a void-type inkjet recording medium having an ink absorbing layer containing alumina, thereby forming a color image. An image forming method characterized by printing, or an image forming characterized by printing a color image by ejecting the magenta ink and cyan ink according to the present invention using an electro-thermal conversion type recording head It has been found that the object and effect of the present invention can be realized by a method.

  Details of the present invention will be described below.

  The ink set of the present invention is characterized by having a magenta ink containing at least water, a dye and a water-soluble organic solvent and a cyan ink containing at least water, a dye and a water-soluble organic solvent. In addition, if necessary, the ink may be composed of yellow ink and black ink, and each ink may be composed of dark and light inks having different dye concentrations.

  One feature of the magenta ink according to the present invention is that the anthrapyridone magenta dye represented by the general formula (1) is used as the dye.

  The anthrapyridone dye represented by the general formula (1) according to the present invention will be described.

  In the general formula (1), R represents a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, a mono- or dialkylaminoalkyl group, or a cyano lower alkyl group, and Y represents a chlorine atom, a hydroxyl group, an amino group, a mono group. Or a dialkylamino group, an aralkylamino group, a cycloalkylamino group, an alkoxy group, a phenoxy group, an anilino group, a naphthylamino group, or a mono- or dialkylaminoalkylamino group, of which a mono- or dialkylamino group is an alkyl group May have a substituent selected from the group consisting of sulfonic acid group, carboxy group and hydroxyl group, and the phenoxy group is selected from the group consisting of sulfonic acid group, carboxy group, acetylamino group, amino group and hydroxyl group May be substituted with a substituent The anilino group may be substituted on the benzene ring with one or two substituents selected from the group consisting of a sulfonic acid group and a carboxy group, and the naphthylamino group may be substituted with a sulfonic acid group. . X represents a crosslinking group. M represents a hydrogen atom, an alkali metal salt, an alkaline earth metal salt, an alkylamine salt, an alkanolamine salt or an ammonium salt.

  As an alkyl group represented by R, C1-C4 alkyl groups, such as a methyl group, an ethyl group, n-propyl group, n-butyl group, are mentioned, for example. Examples of the alkyl in the hydroxy lower alkyl group and the cyano lower alkyl group in R include ethyl and propyl, and ethyl is preferred.

  Examples of the alkylamino group in Y include an alkylamino group having 1 to 8 carbon atoms such as a methylamino group, an ethylamino group, a butylamino group, and a 2-ethylhexylamino group. As a dialkylamino group, C1-C8 dialkylamino groups, such as a diethylamino group, a dibutylamino group, a dihexylamino group, are mentioned, for example. Examples of the aralkylamino group include phenyl (C1-6) alkylamino groups such as benzylamino group, phenethylamino group, and phenylpropylamino group. Examples of the cycloalkylamino group include a cyclohexylamino group, Examples include cyclo (C 5 -C 7) alkylamino groups such as cyclopentylamino group, and the alkoxy group includes, for example, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, butoxy group, etc. 4 alkoxy groups. As alkyl in the alkylamino group which has a sulfonic acid group or a carboxy group, C1-C4 alkyl, such as methyl, ethyl, n-propyl, n-butyl, is mentioned, for example.

  In Y, specific examples of the phenoxy group which may be substituted with a substituent selected from the group consisting of a sulfonic acid group, a carboxy group, an acetylamino group, an amino group and a hydroxyl group include, for example, a 4-sulfophenoxy group, Examples include 4-carboxyphenoxy group, 4-acetylamino-phenoxy group, 4-aminophenoxy group, 4-hydroxyphenoxy group, and the like.

  In Y, specific examples of the alkylamino group having a sulfonic acid group or a carboxy group include, for example, 2-sulfoethylamino group, carboxymethylamino group, 2-carboxyethylamino group, 1-carboxyethylamino group, 1, A 2-dicarboxyethylamino group or a di (carboxymethyl) amino group is exemplified, and specific examples of the alkylamino group having a hydroxyl group include a hydroxyethylamino group and a dihydroxyethylamino group.

  Specific examples of the anilino group which may be substituted with one or two substituents selected from the group consisting of a sulfonic acid group and a carboxy group in Y include, for example, a 2,5-disulfoanilino group, 3- Examples include sulfoanilino group, 2-sulfoanilino group, 4-sulfoanilino group, 2-carboxy-4-sulfoanilino group, 2-carboxy-5-sulfoanilino group and the like.

  Specific examples of the naphthylamino group optionally substituted with a sulfonic acid group in Y include, for example, 3,6,8-trisulfo-1-naphthylamino group, 4,6,8-trisulfo-2-naphthylamino Group, 3,6,8-trisulfo-2-naphthylamino group, 4,8-disulfo-2-naphthylamino group and the like.

As a bridging group for X, a nitrogen atom or an oxygen atom at both ends of a hydrocarbon residue having 1 to 20 carbon atoms which may contain a nitrogen atom, an oxygen atom or a sulfur atom, And a divalent group having an atom as a bond, specifically, —N (H) _m (—A—) _n N (H) _m — or —O—A—O—.
[In the formula, A is a divalent hydrocarbon residue having 1 to 20 carbon atoms and may contain a nitrogen atom, an oxygen atom or a sulfur atom, n is 1 or 2, m is 1 or 0, n When m is 1, m represents 1, and when n is 2, m represents 0.]
The group represented by these is mentioned.

  Examples of the divalent hydrocarbon residue having 1 to 20 carbon atoms of A include, for example, 1 to 15 carbon atoms which may contain 1 to 2 hetero atoms (for example, nitrogen atom, oxygen atom, sulfur atom and the like). A divalent aliphatic group and a divalent aromatic group having 3 to 10 carbon atoms, preferably 5 to 10 carbon atoms, which may contain 1 to 3 hetero atoms (for example, nitrogen atom, oxygen atom, sulfur atom, etc.) And a divalent group formed by combining an aliphatic group and the aliphatic group with the aromatic group. These groups may have a substituent (for example, a sulfonic acid group, a carboxyl group, an amino group, a lower alkyl group in the case of an aromatic group).

Examples of the aliphatic group include a lower alkyl group such as methylene, dimethylene (ethylene), trimethylene (propylene), 2-methyltrimethylene (2-methylpropylene), tetramethylene (butylene), and hexamethylene. Optionally having 1 to 6 carbon atoms (poly) methylene, cyclopentane-1,2- or 13-diyl, cyclohexane-1,2-, -1,3- or -1,4-diyl, cycloheptane- C5-C7 cycloalkylene such as diyl, methylenecyclohexane-1,4-diylmethylene (—CH ₂ —C ₆ H ₁₀ —CH ₂ —), methylenedicyclohexane-diyl (—C ₆ H ₁₀ —CH ₂₎ -C ₆ H ₁₀ -), methylenebis (methylcyclohexane - _{diyl) {- C 6 H 10 (} CH 3) -CH 2 -C 6 H 10 (CH 3) - Cyclohexane - diyl - dimethylene _{(-CH 2 -C 6 H 10 -CH} 2 -) lower alkylene aliphatic group consisting of an aliphatic ring having 5 to 7 carbon atoms (which may be a lower alkyl-substituted) such as , Methyleneoxymethylene (—CH ₂ —O—CH ₂ —), bis (dimethylene) amino (—C ₂ H ₄ —NH—C ₂ H ₄ —), methylenethiomethylene (—CH ₂ —S—CH ₂ —) ), An oxydicyclohexane-diyl (—C ₆ H ₁₀ —O—C ₆ H ₁₀ —), etc. Examples of the divalent aromatic group include aromatic groups having 6 to 10 carbon atoms such as phenylene (—C ₆ H ₄ —) and naphthylene (—C ₁₀ H ₆ —). Examples of the divalent group formed by combining the aliphatic group and the aromatic group include xylylene (—CH ₂ —C ₆ H ₄ —CH ₂ —).

  More preferable examples of A include dimethylene, hexamethylene, 1,3-xylylene, methylenedicyclohexane-4,1-diyl, methylenebis (2-methylcyclohexane-4,1-diyl), cyclohexane-1,3. -Diyl-dimethylene.

Examples of the bridging group X include 1,2-diaminoethylene group (—NH—CH ₂ CH ₂ —NH—), 1,4-diaminobutylene group (—NH—C ₄ H ₈ —NH—), 1,6 A diaminoalkylene group such as a diaminohexylene group (—NH—C ₆ H ₁₂ —NH—), a 1,4-piperazinediyl group (—NC ₄ H ₈ N—), a 1,4-diaminophenylene group (—NH _{-C 6 H 4 -p-NH -} ), 1,3- diamino-phenylene group _{(-NH-C 6 H 4 -m} -NH-) diamino phenylene groups such as 4-sulfo-1,3-diamino-phenylene group _{{-NH-C 6 H 4 (} p-SO 3 H) -m-NH -}, 5- carboxy-1,3-diaminophenylene substituted diamino phenylene group alkylene group, 1,3-diamino-xylylene group (- _{NH-CH 2 -C 6 H 4} -m-CH 2 -NH -), 1,4 - diamino xylylene group _{(-NH-CH 2 -C 6 H} 4 -p-CH 2 -NH -), 4,4'- diamino-2-sulfonyl - diphenylamino group _{{-NH-C 6 H 4 (} m _{-SO 3 H) -NH-C 6} H 4 -p-NH -}, 4,4'- diaminodicyclohexylmethane group _{(-NH-C 6 H 10 -4} -CH 2 -C 6 H 10 -4'- NH -), 4,4'-diamino-3,3'-dimethyl-dicyclohexylmethane group _{{-NH-C 6 H 10 (} 3-CH 3) -4-CH 2 -C 6 H 10 (3'-CH 3 ) -4'NH -}, -NH- 1,3- bis (aminomethyl) cyclohexane group _{(-NH-CH 2 -C 6 H} 10 -3-CH 2), dioxyethylene group (-O-CH ₂ CH ₂ -O -), 1,4- di-oxybutylene group _{(-O-C 4 H 8 -O} -), 2,2'- dioxy ethyl ether _{(-O-CH 2 CH 2 -O} -CH 2 CH 2 -O-) dioxy substituted alkylene group such as 1,4-dioxy-phenylene group _{(-O-C 6 H 4 -p} -O -), 1 , 3-dioxyphenylene group (—O—C ₆ H ₄ —m—O—), 4,4′-dioxydiphenyl ether group (—O—C ₆ H ₄ —p—O—C ₆ H ₄ —p) —O—), 4,4′-dioxyphenylenethioether group (—O—C ₆ H ₄ —p—S—C ₆ H ₄ —p—O—), 2,5- and 2,6-norbornanediamino group, 1,4-oxymethyl-cyclohexylene group _{(-O-CH 2 -C 6 H} 10 -4-CH 2 -O-) and the like.

In the formula —N (H) _m (—A—) _n N (H) _m —, when n is 2 and m is 0, the above 1,4-piperazinediyl (—NC ₄ H ₈ N-) and the like.

  Preferable combinations of R, Y, and X include, for example, R is a hydrogen atom or a methyl group, Y is a chlorine atom, a hydroxyl group or an amino group, X is a diaminoethylene group, 1,4-piperazinediyl group, 1,3-diamino A xylylene group, a 4,4′-diaminodicyclohexylmethane group, a 4,4′-diamino-3,3′-dimethyldicyclohexylmethane group, a 1,3-bis (aminomethyl) cyclohexane group, and the like.

  M represents a hydrogen atom, an alkali metal salt, an alkaline earth metal salt, an alkylamine salt, an alkanolamine salt or an ammonium salt, preferably an alkali metal salt such as sodium salt, potassium salt or lithium salt, monoethanolamine salt, Examples include diethanolamine salts, triethanolamine salts, monoisopropanolamine salts, diisopropanolamine salts, alkanolamine salts such as triisopropanolamine salts, and ammonium salts. As a method for preparing the salt, for example, sodium salt is added to the reaction solution of the tertiary condensate obtained above, salted out and filtered to obtain a sodium salt as a wet cake, and the wet cake is dissolved again in water. If crystals obtained by adding hydrochloric acid to adjust the pH to 1 to 2 are filtered, they can be obtained in the form of a free acid (or a part of it as a sodium salt). Furthermore, while the wet cake in the form of the free acid is stirred with water, for example, potassium hydroxide, lithium hydroxide, or aqueous ammonia is added to make it alkaline, thereby obtaining potassium salt, lithium salt, and ammonium salt, respectively. .

  Specific examples of the anthrapyridone compound represented by the general formula (1) according to the present invention are shown below, but the present invention is not limited only to these exemplified dyes.

In the exemplified compounds shown below, diaminoethylene means a 1,2-diaminoethylene group (—NH—CH ₂ CH ₂ —NH—). Ph represents a phenyl group, for example, Ph0 represents a phenoxy group, NHPh represents an anilino group, and so on. NHPh (p-SO ₃ H) represents a 4-sulfoanilino group (p-SO ₃ H represents that the sulfonic acid group is in the para position of the phenyl group), and NHPh (COOH) ₂ (3,5) represents 3 , 5-dicarboxyanilino group {Ph (COOH) ₂ (3,5) indicates that a carboxyl group is substituted at the 3-position and 5-position of the phenyl group}, and the other groups are similarly represented Describe. Naphthyl represents a naphthyl group, NH-2naphthyl (SO ₃ H) ₃ (3,6,8) represents 3,6,8-trisulfo-2-naphthylamino, and NH (cyclohexyl) represents cyclohexylamino.

  The dye represented by the general formula (1) according to the present invention can be obtained by synthesis according to a method known in the art.

  Further, the cyan ink according to the present invention is characterized in that the copper phthalocyanine cyan dye represented by the general formula (2) is used as the dye.

  In the general formula (2), a11 to a14 each independently represents an integer of 1 or 2, and 4 ≦ a11 + a12 + a13 + a14 ≦ 6 is particularly preferable, and among them, a11 = a12 = a13 = a14 = 1 is particularly preferable. Is the time.

X _{11 to} X ₁₄ may be exactly the same substituents, or, for example, X _{11 to} X ₁₄ are all —SO ₂ —Z, but each Z includes a different group. Are the same type of substituents, but may be partially different from each other, or, for example, when —SO ₂ —Z and —SO ₂ NR ₁ R ₂ are substituted at the same time, Different substituents may be included.

  Among the phthalocyanine dyes represented by the general formula (2), particularly preferred combinations of substituents are as follows.

X _{11 to} X ₁₄ are each independently preferably —SO—Z, —SO ₂ —Z, —SO ₂ NR ₁ R ₂ , or —CONR ₁ R ₂ , particularly —SO ₂ —Z or —SO _2. NR ₁ R ₂ is preferred, and —SO ₂ —Z is most preferred.

  Z is independently preferably a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, and most preferably a substituted alkyl group, a substituted aryl group, or a substituted heterocyclic group. . In particular, the case of having an asymmetric carbon in the substituent (use in a racemic form) is preferable because of increasing the solubility of the dye and the ink stability. In addition, for the reason of increasing the association property and improving the fastness, it is preferable that a hydroxyl group, an ether group, an ester group, a cyano group, an amide group, or a sulfonamide group have in the substituent.

R ₁ and R ₂ are each independently preferably a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, and among them, a hydrogen atom, a substituted alkyl group, a substituted An aryl group and a substituted heterocyclic group are most preferred. However, it is not preferable that both R ₁ and R ₂ are hydrogen atoms. In particular, the case of having an asymmetric carbon in the substituent (use in racemic form) is preferable because of increasing the solubility of the dye and the ink stability. In addition, for the reason of enhancing the association property and improving the fastness, it is preferable that the hydroxyl group, the ether group, the ester group, the cyano group, the amide group, or the sulfonamide group have in the substituent.

Y _{11 to} Y ₁₈ are hydrogen atom, halogen atom, alkyl group, aryl group, cyano group, alkoxy group, amide group, ureido group, sulfonamido group, carbamoyl group, sulfamoyl group, alkoxycarbonyl group, carboxyl group, and sulfo group. A hydrogen atom, a halogen atom, a cyano group, a carboxyl group, and a sulfo group are preferable, and a hydrogen atom is most preferable. a11 to a14 are each independently preferably 1 or 2, particularly preferably all 1. M represents a hydrogen atom, a metal element or an oxide thereof, a hydroxide, or a halide, and Cu, Ni, Zn, and Al are particularly preferable, and Cu is particularly preferable.

  As for the preferable combination of substituents of the compound represented by the general formula (2), a compound in which at least one of various substituents is the above-mentioned preferable group is preferable, and more various substituents are the above-mentioned preferable groups. Certain compounds are more preferred, and compounds in which all substituents are the preferred groups are most preferred.

  The chemical structure of the phthalocyanine dye according to the present invention includes an electron-withdrawing group such as a sulfinyl group, a sulfonyl group, and a sulfamoyl group, at least one for each of the four benzene rings of phthalocyanine, and σp of the substituent of the entire phthalocyanine skeleton. It is preferable to introduce so that the sum of the values is 1.6 or more.

  Hammett's substituent constant σp value is as defined above.

  The phthalocyanine dye analog mixture represented by the general formula (2) is defined by being classified into the following three types based on the substitution position.

  (1) β-position substitution type: phthalocyanine dye having a specific substituent at the 2 and / or 3 position, 6 and / or 7 position, 10 and / or 11 position, 14 and / or 15 position.

  (2) α-position substitution type: phthalocyanine dye having a specific substituent at 1 and / or 4 position, 5 and / or 8 position, 9 and / or 12 position, 13 and / or 16 position.

  (3) α, β-position mixed substitution type: phthalocyanine dye having a specific substituent without regularity at positions 1 to 16.

  Examples of the phthalocyanine derivative used in the present invention include “Phthalocyanine—Chemistry and Function” (P. 1-62), C.K. C. Leznoff-A. B. P. Lever co-authored by VCH and published in 'Phthalogicanes-Properties and Applications' (P. 1-54), etc., can be synthesized by combining quoted or similar methods.

  Examples of the phthalocyanine compound represented by the general formula (2) according to the present invention include a phthalonitrile derivative (compound P) or a diiminoisoindoline derivative (compound Q) represented by the following formula (2-1). Or derived from a tetrasulfophthalocyanine compound obtained by reacting a 4-sulfophthalonitrile derivative (compound R) with a metal derivative represented by the general formula (2-1). Can do.

In the above formulas, Xp corresponds to any one of X _{11 to} X ₁₄ in the general formula (2). Yq and Yq ′ each correspond to any one of Y _{11 to} Y ₁₈ in the general formula (2).

Formula (2-1): M- (Y) _d
In the general formula (2-1), M is the same as M in the general formula (2), and Y is a monovalent or divalent ligand such as a halogen atom, acetate anion, acetylacetonate, or oxygen. D is an integer of 1-4.

  The obtained phthalocyanine compound represented by the general formula (2) is usually a mixture of compounds represented by the following general formulas (a) -1 to (a) -4, which are isomers at each substitution position of Xp. That is, it is a β-position substitution type.

In the above synthesis method, if the same Xp is used, a β-position-substituted phthalocyanine dye in which X ₁₁ , X ₁₂ , X ₁₃ and X ₁₄ are exactly the same substituents can be obtained. On the other hand, by using different combinations of Xp, it is possible to synthesize dyes having the same type of substituents but partially different from each other, or dyes having different types of substituents. . Among the dyes of the general formula (2), these dyes having different electron-withdrawing substituents are particularly preferable because they can adjust the solubility of the dye, the associability, the aging stability of the ink, and the like.

  The phthalocyanine dye represented by the general formula (2) according to the present invention can be synthesized by the method described in JP-A Nos. 2001-226275, 2001-96610, 2001-47013, and 2001-193638. it can. Further, the starting material, the dye intermediate and the synthesis route are not limited by these.

  Specific examples of the cyan dye compound represented by the general formula (2) according to the present invention are shown below, but are not limited thereto.

  In the ink set of the present invention, in addition to the dyes represented by the general formula (1) and the general formula (2) according to the present invention, a yellow dye, a black dye, or a range that does not impair the object effect of the present invention, Known magenta dyes and cyan dyes can be used in combination.

  Water-soluble dyes that can be used for the above-described inks are shown below.

  Examples of water-soluble dyes that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, and the like. The compounds are shown below. However, it is not limited to these exemplified compounds.

[C. I. Acid Yellow)
1, 3, 11, 17, 18, 19, 23, 25, 36, 38, 40, 42, 44, 49, 59, 61, 65, 67, 72, 73, 79, 99, 104, 110, 114, 116, 118, 121, 127, 129, 135, 137, 141, 143, 151, 155, 158, 159, 169, 176, 184, 193, 200, 204, 207, 215, 219, 220, 230, 232, 235, 241, 242, 246
[C. I. Acid Orange)
3, 7, 8, 10, 19, 24, 51, 56, 67, 74, 80, 86, 87, 88, 89, 94, 95, 107, 108, 116, 122, 127, 140, 142, 144, 149, 152, 156, 162, 166, 168
[C. I. Acid Red)
1, 6, 8, 9, 13, 18, 27, 35, 37, 52, 54, 57, 73, 82, 88, 97, 106, 111, 114, 118, 119, 127, 131, 138, 143, 145, 151, 183, 195, 198, 211, 215, 217, 225, 226, 249, 251, 254, 256, 257, 260, 261, 265, 266, 274, 276, 277, 289, 296, 299, 315, 318, 336, 337, 357, 359, 361, 362, 364, 366, 399, 407, 415
[C. I. Acid Violet)
17, 19, 21, 42, 43, 47, 48, 49, 54, 66, 78, 90, 97, 102, 109, 126
[C. I. Acid Blue)
1, 7, 9, 15, 23, 25, 40, 62, 72, 74, 80, 83, 90, 92, 103, 104, 112, 113, 114, 120, 127, 128, 129, 138, 140, 142, 156, 158, 171, 182, 185, 193, 199, 201, 203, 204, 205, 207, 209, 220, 221, 224, 225, 229, 230, 239, 249, 258, 260, 264, 278, 279, 280, 284, 290, 296, 298, 300, 317, 324, 333, 335, 338, 342, 350
[C. I. Acid Green)
9, 12, 16, 19, 20, 25, 27, 28, 40, 43, 56, 73, 81, 84, 104, 108, 109
[C. I. Acid Brown)
2, 4, 13, 14, 19, 28, 44, 123, 224, 226, 227, 248, 282, 283, 289, 294, 297, 298, 301, 355, 357, 413
[C. I. Acid Black)
1, 2, 3, 24, 26, 31, 50, 52, 58, 60, 63, 107, 109, 112, 119, 132, 140, 155, 172, 187, 188, 194, 207, 222
[C. I. Direct yellow)
8, 9, 10, 11, 12, 22, 27, 28, 39, 44, 50, 58, 86, 87, 98, 105, 106, 130, 132, 137, 142, 147, 153
[C. I. (Direct orange)
6, 26, 27, 34, 39, 40, 46, 102, 105, 107, 118
[C. I. (Direct Red)
2, 4, 9, 23, 24, 31, 54, 62, 69, 79, 80, 81, 83, 84, 89, 95, 212, 224, 225, 226, 227, 239, 242, 243, 254
[C. I. Direct violet)
9, 35, 51, 66, 94, 95
[C. I. (Direct blue)
1, 15, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 160, 168, 189, 192, 193, 199, 200, 201, 202, 203, 218, 225, 229, 237, 244, 248, 251, 270, 273, 274, 290, 291
[C. I. (Direct Green)
26, 28, 59, 80, 85
[C. I. (Direct Brown)
44, 106, 115, 195, 209, 210, 222, 223
[C. I. (Direct Black)
17, 19, 22, 32, 51, 62, 108, 112, 113, 117, 118, 132, 146, 154, 159, 169
[C. I. Basic yellow)
1, 2, 11, 13, 15, 19, 21, 28, 29, 32, 36, 40, 41, 45, 51, 63, 67, 70, 73, 91
[C. I. Basic orange)
2, 21, 22
[C. I. (Basic Red)
1, 2, 12, 13, 14, 15, 18, 23, 24, 27, 29, 35, 36, 39, 46, 51, 52, 69, 70, 73, 82, 109
[C. I. Basic violet)
1, 3, 7, 10, 11, 15, 16, 21, 27, 39
[C. I. (Basic Blue)
1, 3, 7, 9, 21, 22, 26, 41, 45, 47, 52, 54, 65, 69, 75, 77, 92, 100, 105, 117, 124, 129, 147, 151
[C. I. Basic green)
1, 4
[C. I. Basic brown)
1
[C. I. (Reactive Yellow)
2, 3, 7, 15, 17, 18, 22, 23, 24, 25, 27, 37, 39, 42, 57, 69, 76, 81, 84, 85, 86, 87, 92, 95, 102, 105, 111, 125, 135, 136, 137, 142, 143, 145, 151, 160, 161, 165, 167, 168, 175, 176
[C. I. (Reactive Orange)
1, 4, 5, 7, 11, 12, 13, 15, 16, 20, 30, 35, 56, 64, 67, 69, 70, 72, 74, 82, 84, 86, 87, 91, 92, 93, 95, 107
[C. I. (Reactive Red)
2, 3, 5, 8, 11, 21, 22, 23, 24, 28, 29, 31, 33, 35, 43, 45, 49, 55, 56, 58, 65, 66, 78, 83, 84, 106, 111, 112, 113, 114, 116, 120, 123, 124, 128, 130, 136, 141, 147, 158, 159, 171, 174, 180, 183, 184, 187, 190, 193, 194, 195, 198, 218, 220, 222, 223, 228, 235
[C. I. (Reactive Violet)
1, 2, 4, 5, 6, 22, 23, 33, 36, 38
[C. I. (Reactive Blue)
2, 3, 4, 5, 7, 13, 14, 15, 19, 21, 25, 27, 28, 29, 38, 39, 41, 49, 50, 52, 63, 69, 71, 72, 77, 79, 89, 104, 109, 112, 113, 114, 116, 119, 120, 122, 137, 140, 143, 147, 160, 161, 162, 163, 168, 171, 176, 182, 184, 191, 194, 195, 198, 203, 204, 207, 209, 211, 214, 220, 221, 222, 231, 235, 236
[C. I. (Reactive Green)
8, 12, 15, 19, 21
[C. I. (Reactive Brown)
2, 7, 9, 10, 11, 17, 18, 19, 21, 23, 31, 37, 43, 46
[C. I. (Reactive Black)
5, 8, 13, 14, 31, 34, 39
These dyes listed above are described in “Dyeing Note 21st Edition” (publishing; Color Dyeing).

  In the magenta ink and the cyan ink according to the present invention constituting the ink set of the present invention, the water-soluble organic solvent contained in each ink is a polyhydric alcohol or a polyhydric alcohol alkyl ether as the water-soluble organic solvent A. It is characterized by containing 10 to 20% by mass of the total mass of the ink and 1 to 5% by mass of monohydric alcohol having 1 to 3 carbon atoms as the water-soluble organic solvent B based on the total mass of the ink.

  First, the water-soluble organic solvent A according to the present invention will be described.

  Examples of the water-soluble organic solvent A include polyhydric alcohols or alkyl ethers of polyhydric alcohols from the viewpoints of solubility of the dye according to the present invention, drying prevention (wetability) and safety in a recording head that discharges ink. Chosen from the inside.

  Specifically, as polyhydric alcohols, for example, ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6- Examples include hexanetriol, acetylene glycol derivatives, glycerin, trimethylolpropane, and the like. Examples of alkyl ethers of polyhydric alcohols include ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, and triethylene glycol mono. Examples include ethyl (or butyl) ether.

  In the present invention, the water-soluble organic solvent A is preferably a polyhydric alcohol, and more preferably at least one selected from glycerin, ethylene glycol, diethylene glycol, propylene glycol and triethylene glycol.

  In the present invention, these polyhydric alcohols or alkyl ethers of polyhydric alcohols are used when the total mass of the ink is 100% by mass from the viewpoint of drying prevention (wetting properties) of the recording head and bleeding resistance during long-term storage. It is used in the range of 10 to 20% by mass. When the content is less than 10% by mass, there is a concern that clogging may occur in the nozzle portion of the recording head. Conversely, when the content exceeds 20% by mass, a secondary color image, particularly a blue image, is formed. This is not preferable because the resistance to bleeding during long-term storage deteriorates.

  Next, the water-soluble organic solvent B according to the present invention will be described.

  The water-soluble organic solvent B is characterized by using a monohydric alcohol having 1 to 3 carbon atoms from the viewpoint of reducing bleeding over time in the image portion of the secondary color. The monohydric alcohol having 1 to 3 carbon atoms is specifically selected from methanol, ethanol, propanol, and isopropanol, and more preferably ethanol or propanol.

  The water-soluble organic solvent B according to the present invention is used in the range of 1 to 5% by mass when the total mass of the ink is 100% by mass from the viewpoint of dry clogging of the recording head and bleeding resistance during long-term storage. It is characterized by doing. Since the water-soluble organic solvent B has a property that is more volatile than the water in the ink, from the viewpoint of the effect of promoting drying in the image area, when the content is less than 1% by mass, When a color image, particularly a blue image, is formed, it is not preferable because the resistance to bleeding during long-term storage deteriorates rather. Conversely, in the region exceeding 5% by mass, there is a concern that clogging may occur in the nozzle portion of the recording head.

Further, in inks other than the cyan ink and magenta ink according to the present invention constituting the ink set of the present invention, known organic solvents can be used. Organic solvents that can be used for those inks are not particularly limited. However, a water-soluble organic solvent is preferable, specifically, alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, 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 (for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol) Monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol Coal monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol dimethyl ether, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N -Ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N- Dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, -Cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (eg dimethyl sulfoxide etc.), sulfones (eg sulfolane etc.), sulfonates (eg 1 -Butanesulfonic acid sodium salt, etc.), urea, acetonitrile, acetone and the like.

  Various surfactants can be used in the ink according to the present invention. Each surfactant that can be used in the present invention is not particularly limited, and examples thereof include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl ethers, and the like. Nonionic surfactants such as oxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

  In the ink of the present invention, a polymer surfactant can also be used. For example, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-acrylic acid. Alkyl ester copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid A copolymer, a vinyl naphthalene-maleic acid copolymer, etc. can be mentioned.

  In addition to the above description, the ink according to the present invention is publicly known depending on the purpose of improving the emission stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Various additives, such as viscosity modifiers, specific resistance regulators, film forming agents, UV absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust inhibitors, etc. can be appropriately selected and used, For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent brightening 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.

  Next, the ink jet recording medium according to the present invention will be described.

  One of the characteristics of the ink jet recording medium (hereinafter also referred to as the recording medium of the present invention) used in the image forming method of the present invention is that it contains alumina.

  The ink jet recording medium according to the present invention preferably has an ink absorbing layer on a support. The ink absorbing layer is roughly divided into a swelling layer type ink absorbing layer and a void type ink absorbing layer.

  The swelling type ink absorbing layer has high glossiness, and because it uses a swellable polymer, it can absorb a large amount of ink as long as the polymer can swell, and can be manufactured at low cost. Although it is mentioned, since the swelling polymer is used, the point of light resistance is inferior.

  On the other hand, the void-type ink absorbing layer has a high ink absorption speed and is less likely to cause unevenness during printing, the surface is apparently dry immediately after printing, and both water resistance and ink absorption speed can be satisfied simultaneously. .

  In the present invention, from the viewpoint of high ink absorption and high drying properties, a void-type ink absorption layer is preferable.

  The swelling type ink absorbing layer is mainly composed of a hydrophilic polymer that swells with respect to the ink solvent. Examples of such hydrophilic polymers include gelatin (alkali-treated gelatin, acid-treated gelatin, derivative gelatin obtained by blocking amino groups with phenyl isocyanate, phthalic anhydride, etc.), polyvinyl alcohol (average polymerization degree: 300 to 4000, saponification). The degree is preferably 80 to 99.5%), polyvinyl pyrrolidone, polyethylene oxide, hydroxyl ethyl cellulose, agar, pullulan, dextran, acrylic acid, carboxymethyl cellulose, casein, alginic acid and the like. it can.

The swelling ink absorbing layer may contain fine particles such as inorganic fine particles and organic fine particles within a range that does not affect the swelling property of the hydrophilic polymer, but it is usually 100% by mass or less with respect to the hydrophilic polymer. The amount of the hydrophilic polymer provided in the swelling layer is usually 3 to 20 g, preferably 5 to 15 g, per 1 m ² of the recording medium.

  A preferred void-type ink absorbing layer in the recording medium according to the present invention is a porous film having voids in the ink absorbing layer and having voids containing inorganic fine particles and a small amount of a hydrophilic polymer.

  Examples of such inorganic fine particles include, for example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, carbonate White inorganic such as zinc, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide In the present invention, silica or alumina is preferable, and at least alumina is particularly preferable.

  In the present invention, alumina is alumina (aluminum oxide) obtained by vaporizing aluminum chloride and oxidizing it with an oxidizing gas in a gas phase. Known crystal types include γ, δ, θ types, and amorphous types. The alumina fine particles preferably have a small particle diameter, and the average primary particle diameter is preferably 4 to 100 nm. When it is larger than 100 nm, the alumina aggregate becomes too large and the glossiness is lowered. If it is less than 4 nm, the dispersibility of the alumina fine particles as a coating liquid becomes unstable, which causes gelation, which is not preferable.

  In particular, alumina fine particles synthesized by a vapor phase method are advantageous for gloss because they are easily atomized and have a narrow particle size distribution.

  Since alumina according to the present invention is cationic fine particles, it is not necessary to use additives such as addition of a cationic polymer for ensuring dispersibility like silica fine particles and addition of a mordant to dye ink. Since these additives can often cause ink absorption impediments, the use of alumina fine particles as inorganic fine particles is extremely advantageous in increasing ink absorbency.

  The inorganic fine particles can be used as primary particles or in a state where secondary aggregated particles are formed.

  As the hydrophilic polymer used in the void layer, the same hydrophilic polymer used in the swelling ink absorbing layer is used, but a preferred hydrophilic polymer is polyvinyl alcohol.

  The polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal and anion-modified polyvinyl alcohol having an anionic group. Alcohol is also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 300 or more, and particularly preferably has an average degree of polymerization of 1000 to 5000.

  The saponification degree is preferably 70 to 100%, particularly preferably 80 to 99.5%.

  The ratio of the inorganic fine particles and the hydrophilic polymer used in the void-type ink absorbing layer is usually 2: 1 to 10: 1 by mass ratio, and 3: 1 to 8: 1 is particularly preferable.

  By setting the ratio of the inorganic fine particles to the hydrophilic polymer to a large value as described above, the ink absorption layer can achieve a high porosity. A preferable porosity is 40 to 80%, and 50 to 70% is particularly preferable. The porosity is a value obtained according to the following formula.

Porosity = 100 × [(total dry film thickness−applied solid film thickness) / total dry film thickness]
Further, when the void layer contains polyvinyl alcohol as a hydrophilic polymer, it is preferable to add a hardener to improve the film forming property of the film and increase the strength of the film, for example, an epoxy compound Boric acid or a salt thereof, and boric acid or a salt thereof is preferably contained. As boric acid or a salt thereof, oxygen acid having a boron atom as a central atom and a salt thereof are shown, and specifically, orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid and salts thereof are included.

  The amount of boric acid or a salt thereof can vary widely depending on the amount of inorganic fine particles and hydrophilic polymer in the coating solution, but is usually 1 to 60% by mass, preferably 5 to 40% by mass with respect to the hydrophilic polymer. .

  In the present invention, the ink absorption speed is high, image unevenness is small, and the amount of curling is relatively small because the amount of hydrophilic polymer used is relatively small. Therefore, the ink absorption layer is a porous film having voids. Preferably there is.

  Various additives other than those described above can be added to the ink absorbing layer of the ink jet recording medium according to the present invention.

  Among these, a cationic mordant is preferable for improving water resistance and moisture resistance after printing.

  As the cationic mordant, a polymer mordant having a primary to tertiary amino group and a quaternary ammonium base is used, but there is little discoloration or deterioration of light resistance with time, and the mordant ability of the dye is sufficiently high. Therefore, a polymer mordant having a quaternary ammonium base is preferable.

  A preferable polymer mordant is obtained as a homopolymer of a monomer having the quaternary ammonium base, a copolymer with other monomers, or a condensation polymer.

  Other than the above, for example, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, and JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, JP-A-3-13376, and the like, various anionic, cationic or nonionic surfactants, Fluorescent whitening agents and antifoams described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771 and JP-A-4-219266 Various known additives such as a lubricant, a lubricant such as diethylene glycol, an antiseptic, a thickener, an antistatic agent, and a matting agent may be contained.

  In applying the ink absorbing layer on the support, it is preferable to perform corona discharge treatment, subbing treatment or the like on the support for the purpose of increasing the adhesive strength between the surface and the coating layer.

  Various types of back layers can be provided on the side opposite to the side having the ink absorbing layer of the ink jet recording medium of the present invention in order to prevent curling and to further improve the sticking and ink transfer when superimposed immediately after printing. .

  The configuration of the back layer varies depending on the type and thickness of the support and the configuration and thickness on the front side, but generally a hydrophilic binder or a hydrophobic binder is used. The thickness of the back layer is usually in the range of 0.1 to 10 μm.

  Further, the back layer is preferably roughened in order to prevent sticking to other recording media, improve writing performance, and further improve transportability in an ink jet recording apparatus. Organic or inorganic fine particles having a particle diameter of 2 to 20 μm are preferably used for this purpose.

  These back layers may be provided in advance, or may be provided after applying the coating composition of the present invention.

  As the ink absorption layer coating method, roll coating method, rod bar coating method, air knife coating method, spray coating method, curtain coating method or extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferable. Used. When polyolefin resin-coated paper is used as the support, it is preferable that drying be performed in the range of approximately 0 to 80 ° C. If the temperature exceeds 80 ° C., the polyolefin resin softens, making it difficult to convey or unevenness in the gloss of the recording layer surface. A preferable drying temperature is 0 to 60 ° C.

  As the support used for the recording medium according to the present invention, both a water-absorbing support and a non-water-absorbing support can be used. However, no wrinkles are generated after printing, and there is no difference in smoothness. The non-water-absorbing support is preferable because a glossy surface can be easily formed.

  The water-absorbing support is typically a paper support mainly composed of natural pulp, but may be a mixture of synthetic pulp and natural pulp. Examples of the non-water-absorbing support include a plastic resin film support or a support in which both surfaces of paper are covered with a plastic resin film. Examples of the plastic resin film support include a polyester film, a polyvinyl chloride film, a polypropylene film, a cellulose triacetate film, a polystyrene film, and a film support in which these are laminated. These plastic resin films may be transparent or translucent. A particularly preferred support in the present invention is a support in which both sides of paper are coated with a plastic resin, and most preferred is a support in which both sides of paper are coated with a polyolefin resin.

  Hereinafter, a support having both sides of paper, which is a particularly preferable support, coated with a polyolefin resin will be described.

  The paper used for the support is made from wood pulp as a main raw material and, if necessary, paper using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp. As wood pulp, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, NUKP (L is hardwood, N is conifer, BK is exposed to sulfate, BS is exposed to sulfite, and P is an abbreviation of pulp) Although it can be used, it is preferable to use more LBKP, NBSP, LBSP, NDP, and LDP with a short fiber content. However, the ratio of LBSP and / or LDP is preferably 10 to 70%.

  The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful. In paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancers such as starch, polyacrylamide and polyvinyl alcohol, fluorescent brighteners, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as quaternary ammonium, and the like can be appropriately added.

The freeness of pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is the sum of 24 mesh residue and 42 mesh residue defined by JIS P 8207 is 30 to 70% is preferable. The 4 mesh residue is preferably 20% or less. The basis weight of the paper is preferably 50 to 250 g, particularly preferably 70 to 200 g. The thickness of the paper is preferably 50 to 210 μm. The paper can be given a high smoothness by calendering at the paper making stage or after paper making. The paper density is generally 0.7 to 1.2 g / cm ³ (JIS P 8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS P 8143.

  A surface sizing agent may be applied to the paper surface, and the same sizing agent that can be added to the base paper can be used as the surface sizing agent. The pH of the paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS P8113.

  Next, the polyolefin resin that covers both sides of the paper will be described. Examples of the polyolefin resin used for this purpose include polyethylene (PE), polypropylene (PP), polyisobutylene, and the like, but polyolefins such as copolymers mainly composed of propylene are preferable, and polyethylene is particularly preferable.

  Hereinafter, particularly preferred polyethylene will be described. The polyethylene covering the paper front and back is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but some other LLDPE (linear low-density polyethylene), PP, etc. are also used. be able to. In particular, the polyolefin layer on the coating layer side is preferably one in which rutile or anatase type titanium oxide is added therein to improve opacity and whiteness. The titanium oxide content is generally 1 to 20%, preferably 2 to 15%, based on the polyolefin. In the polyolefin layer, a pigment having high heat resistance and a fluorescent brightening agent for adjusting the white background can be added.

  Examples of the color pigment include ultramarine blue, bitumen blue, cobalt blue, phthalocyanine blue, manganese blue, cerulean blue, tungsten blue, molybdenum blue, and anthraquinone blue. Examples of the optical brightener include dialkylaminocoumarin, bisdimethylaminostilbene, bismethylaminostilbene, 4-alkoxy-1,8-naphthalenedicarboxylic acid-N-alkylimide, bisbenzoxazolylethylene, and dialkylstilbene. It is done.

  The amount of polyethylene (PE) used on the front and back of the paper is selected so as to optimize the curl at low humidity and high humidity after the ink absorption layer thickness and back layer are provided. The thickness is 15 to 40 μm on the ink absorbing layer side and 10 to 30 μm on the back layer side. The ratio of the front and back PEs is preferably set so as to adjust the curl that changes depending on the type and thickness of the ink absorbing layer, the thickness of the inner paper, etc. Usually, the front / back PE ratio is about 3 in thickness. / 1-1 / 3. Furthermore, it is preferable that the support of the paper coated with PE has the following characteristics (1) to (7).

(1) The tensile strength is preferably the strength specified by JIS P 8113 and preferably 2-30 kg in the longitudinal direction and 1-20 kg in the lateral direction. (2) The tear strength is the strength specified by JIS P 8116. And preferably 10 to 300 g in the longitudinal direction and 20 to 400 g in the transverse direction. (3) The compression modulus is preferably 9.8 × 10 ⁷ Pa or more. (4) The opacity is determined by the method specified in JIS P 8138. When measured, it is preferably 50% or more, particularly preferably 85 to 98%. (5) The whiteness is L ^* , a ^* , b ^* defined by JIS Z 8729, L ^* = 80 to 95, a ^* =-3. ~ + 5, b ^* = is preferably -6 + 2 (6) Clark stiffness, the support Clark stiffness in the conveying direction of the recording medium is 20~400cm ^3/100 is preferred (7) in the base paper Moisture Preferably 4% to 10% Next, a description is given of an image forming method of the present invention.

  In general, an on-demand method or a continuous method is used for an ink jet head used in an image forming method, and an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, Bender type, piston type, shear mode type, shared wall type, etc.), electro-thermal conversion method (eg, thermal ink jet type, bubble jet (registered trademark) type, etc.), electrostatic attraction method (eg, electric field control type, slit) Jet type etc.) and discharge type (for example, spark jet type) etc. are widely used as specific discharge type. However, in the image forming method of the present invention, an electric-heat conversion type ( For example, a recording head using a thermal ink jet type, a bubble jet (registered trademark) type, etc. Hereinafter, an ink jet printer provided with an electro-thermal conversion type recording head) is one of the features of using the ink having the configuration of the present invention, and the effect of the ink set of the present invention, in particular, high ejection stability. Can be realized. Further, from the viewpoint of achieving higher discharge stability, it is preferable to perform discharge by a double pulse method in which two means of preheating and foaming heating are combined.

  Hereinafter, an image forming method using the double pulse method will be described.

  In the ink ejection method based on the electro-thermal conversion type ink jet, when thermal energy is applied to the ink, bubbles are generated in the ink, and the generation of the bubbles generates discharge energy for discharging the ink from the discharge port of the recording head.

  FIG. 1 is a schematic configuration diagram of an ink jet recording apparatus used for ink jet recording.

  The ink jet recording apparatus shown in FIG. 1 is an apparatus for carrying out the image forming method of the present invention, and the ink loaded in the ink tank 1 is supplied to the recording head 3 through the ink flow path 2. A recording signal is sent to the recording head 3 from the drive circuit 4, and ejection energy generating means (for example, a heater) of the recording head 3 is driven according to the recording signal to heat the heater to generate bubbles, thereby generating ink liquid. Recording is performed on a recording medium 6 such as paper by ejecting the droplets 5.

  The recording head 3 is provided with a wall arranged in parallel on the substrate and a wall forming a liquid chamber. Furthermore, a top plate is disposed on the wall. An ink supply port is formed in the top plate, and ink flows into the liquid chamber from the ink supply port. Between the walls, there is a nozzle through which the ink passes. A heater for applying thermal energy corresponding to the recording signal to the ink is provided on the substrate in the middle of each nozzle. Bubbles are generated in the ink by the heat energy from the heater, and the ink is discharged from the discharge port of the nozzle.

  The recording head is usually installed on a carriage and records an image on a recording medium. The carriage moves along a pair of parallel guide rails. Along with this movement, fine droplets of ink are ejected from the recording head at a predetermined timing, and image recording is performed. The recording medium is moved in the downstream direction by the conveyance roller, and recording is performed sequentially.

  In the image recording method of the present invention, in the image forming method by continuous ink ejection, when bubbles generated on the recording medium expand due to the application of thermal energy and become a predetermined size, they pass through the discharge port and communicate with the outside air. Hereinafter, this point will be described.

  FIG. 2 is a cross-sectional view showing an example of the principle of flying ink microdroplets by the electrical-thermal conversion method.

  In FIG. 2, a section of one nozzle provided in the recording head shows a state before foaming in FIG. When an electric current is instantaneously supplied to the heater 12 and the ink 13 in the vicinity of the heater 12 is heated in a pulsed manner, the ink 13 is rapidly boiled, and bubbles 16 are generated vigorously and start to expand (see FIG. 2B).

  The bubble 16 continues to expand, grows toward the discharge port 15 having a particularly small inertia (inertia), and further penetrates the discharge port 15 to communicate with the outside air (see FIG. 2c).

  The ink 13 on the ejection port 15 side of the bubble 16 jumps forward due to the momentum given from the bubble 16 by this moment, and eventually becomes an independent ink droplet 17 and jumps to a recording medium such as paper (FIG. See d) of 2. After the ink 3 has ejected, the gap formed at the tip of the nozzle 15 is filled with new ink 3 due to the surface tension of the rear ink 13 and the wetting of the nozzle wall, and the state before ejection (a in FIG. 2). Return to).

  In the case of using an electro-thermal conversion type recording head from which ink droplets are emitted by the basic mechanism as described above, in the case of water-soluble ink using a conventional anthrapyridone-based dye, it is rapidly heated by a heater. In this case, the heater portion is likely to cause kogation, and as a result, it causes discharge failure when continuous emission is performed.

  In the image forming method of the present invention, as described above, the specific water-soluble solvent is defined in a specific addition amount range together with the dyes represented by the general formula (1) and the general formula (2). Even when such an electrical-thermal conversion type ink jet recording head is used, stable ejection can be realized without the occurrence of kogation or the like.

  In the image forming method of the present invention, the ink set of the present invention is preferably ejected by a double pulse method.

  In the present invention, the double pulse method is a method in which bubbles are generated in the ink liquid according to the method shown in FIG. This is a method that combines preheating that heats ink in advance, and in the image forming method using the ink of the present invention, by adopting this double pulse method, the ink is ejected without being heated rapidly. In addition to reducing kogation and the like, it is less susceptible to the influence of the printing environment (for example, the outside air temperature), and stable ejection can be realized.

  Both preheating and foaming heating are performed by the heater 12 provided in the nozzle 15. That is, preheating and foaming heating are performed by applying a pulsed voltage to the heater 12.

  In the present invention, the preheating is performed by, for example, one or more pulses (hereinafter referred to as a preheating pulse). The pattern of the preheating pulse is as follows: 1) When a single pulse having a relatively long pulse width is used, 2) When a preheating pulse is performed using two pulses having different voltages, 3) A preheating pulse is set as a pulse For example, it may be composed of a plurality of pulses having a relatively short width. In addition, foaming heating is normally performed by one pulse (the pulse which performs foaming heating is hereafter called a foaming heating pulse).

  In this way, preheating and foaming heating are performed by a series of pulses, the last one of such a series of pulses being a foaming heating pulse, and a pulse prior to foaming heating being a preheating pulse. It is.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<< Preparation of dye ink >>
[Preparation of magenta dye ink]
(Preparation of magenta dye ink M1)
Illustrative magenta dye: M dye-4 2.5% by mass
Ethylene glycol 5.0% by mass
Glycerin 10.0% by mass
2-propanol 2.0% by mass
Surfinol 465 (manufactured by Air Products) 1.5% by mass
Urea 5.0% by mass
Magenta dye ink M1 was prepared by finishing 100% by mass with water.

(Preparation of other magenta dye inks)
Magenta dye inks M2 to M9 and light magenta dye inks LM1 to LM9 were prepared in the same manner as in the preparation of the magenta dye ink M1, except that the types and addition amounts of the dye and the water-soluble organic solvent were changed as shown in Table 1. Was prepared.

[Preparation of cyan dye ink]
(Preparation of cyan dye ink C1)
Illustrative cyan dye: C dye-26 1.5% by mass
Ethylene glycol 8.0% by mass
Glycerin 8.0% by mass
2-propanol 3.0% by mass
Surfinol 465 (manufactured by Air Products) 1.5% by mass
7.0% by mass of urea
Cyan dye ink C1 was prepared by finishing 100% by mass with water.

(Preparation of other cyan dye inks)
In the preparation of the cyan dye ink C1, the cyan dye inks C2 to C9 and the light cyan dye inks LC1 to LC9 were similarly prepared except that the types and addition amounts of the dye and the water-soluble organic solvent were changed as shown in Table 2. Was prepared.

  The details of the abbreviations of the water-soluble organic solvents and surfactants listed in Tables 1 and 2 are as follows.

EG: Ethylene glycol DEG: Diethylene glycol TEGBE: Triethylene glycol monobutyl ether Gly: Glycerin MeOH: Methanol 2-PN: 2-propanol S465: Surfynol 465
Comparative C dye: C.I. I. Direct Blue 199
<< Inkjet image recording and evaluation >>
Each of the dye inks prepared above was loaded into each ink cartridge of a BJF-900 printer equipped with an electric-thermal conversion type recording head manufactured by Canon, and SP101 (alumina-containing void-type ink jet containing alumina) was used as a recording medium. Using the recording medium, the following images were output for evaluation.

[Evaluation of light resistance]
On the recording medium, magenta (M) and cyan (C) single color wedge images (primary color images) using ink sets 1 to 8 composed of combinations of the magenta dye ink and the cyan dye ink described in Table 3, and A mixed wedge image (secondary color image) of blue (B) using magenta dye ink and cyan dye ink is printed, and each image part having a reflection density of about 1.0 is xenon fade meter (manufactured by Suga Test Instruments Co., Ltd.). Was irradiated for 240 hours at 70,000 lux in an environment of a temperature of 25 ° C. and a humidity of 50%. The reflection density before and after the light irradiation was measured with a reflection densitometer, the residual density ratio (%) of each image was determined according to the following formula, and the light resistance was evaluated according to the following criteria.

Density residual ratio (%) = (reflection density after light irradiation / reflection density before light irradiation) × 100
A: Concentration residual ratio is 95% or more B: Concentration residual ratio is 85% to 94%
Δ: Concentration residual ratio is 70% to 84%
X: Concentration residual rate is less than 70% [Evaluation of ozone fading resistance]
For a magenta (M) and cyan (C) single color wedge image and a blue (B) mixed color wedge image created by magenta dye ink and cyan dye ink, the image portion having a reflection density of about 1.0 Was exposed for 48 hours at an ozone concentration of 10 ppm in an environment of a temperature of 25 ° C. and a humidity of 50% using an ozone weather meter (OMS-H Suga Test Machine Co., Ltd.). The reflection density before and after exposure was measured with a reflection densitometer, the residual density rate (%) was determined according to the following formula, and the ozone fading resistance was evaluated according to the following criteria.

Concentration remaining rate (%) = (reflection density after exposure to ozone / reflection density before exposure to ozone) × 100
A: Concentration residual ratio is 95% or more B: Concentration residual ratio is 85% to 94%
Δ: Concentration residual ratio is 70% to 84%
X: Concentration residual ratio is less than 70% [Evaluation of bleeding resistance after long-term storage]
Using ink sets 1 to 8 consisting of combinations of the magenta dye ink and the cyan dye ink shown in Table 3 on the recording medium, single color solid images of magenta (M) and cyan (C) and magenta dye ink and cyan Blue (B) mixed color solid images are printed with dye ink, and black lines with a line width of about 0.3 mm are printed on each solid image using genuine black ink for Canon BJF-900 printer. Then, image storage processing for 3 days was performed at a temperature of 50 ° C. and a humidity of 85%. The line width before and after image storage was measured with a microdensitometer (the width of the portion where the reflection density is 50% of the maximum density was taken as the line width), the bleeding rate was calculated according to the following formula, and after long-term storage according to the following criteria The bleeding resistance was evaluated.

Bleeding rate = (Line width after saving image) / (Line width before saving image)
A: Bleeding rate is 1.0 to 1.2 times B: Bleeding rate is 1.3 to 1.4 times B: Bleeding rate is 1.5 to 1.6 times X: Bleeding rate is 1.7 times or more [Evaluation of color balance]
For each solid color image of blue (B) after each light irradiation, ozone exposure and image storage created by the light resistance evaluation, ozone fading resistance evaluation, and bleeding resistance evaluation after long-term storage, color balance (color tone) ) And hue deviation were visually observed, and color balance was evaluated according to the following criteria.

○: Color balance is lost in the solid image and hue change is not observed. Δ: Color balance is lost in the solid image, and hue change is observed. ×: Clear color balance and hue change is clearly observed in the solid image, and there is a sense of incongruity. [Evaluation of light emission]
In an environment of 20 ° C. and 30% RH, each ink set was loaded into the printer, and after 10 minutes of continuous ejection without cleaning operation, ejection was performed after 10 minutes of rest, and nozzle clogging at that time was confirmed. The evaluation was made according to the following criteria.

○: All nozzles were not clogged and emitted normally. Δ: Nozzle ejection failure due to clogging was observed in nozzles 1 to 3. ×: Failure due to clogging was observed at 4 nozzles or more. The results are shown in Table 3.

  As is clear from the results shown in Table 3, the image formed using the ink set having the configuration defined in the present invention is light fastness in the primary color magenta image, cyan image and further secondary color blue image. Further, it can be seen that ozone fading resistance, bleeding resistance after long-term storage, and light-emitting properties are excellent, and there is no collapse of color balance after long-term storage, and a stable image can be obtained.

  On the other hand, when a dye different from the structure defined in the present invention is used, light resistance, ozone fading resistance, and bleeding resistance after long-term storage are extremely reduced, and a water-soluble organic material having a structure different from that of the present invention. When a solvent is used, the light resistance, ozone fading resistance, and bleeding resistance after long-term storage in a blue image that is a secondary color image are remarkably deteriorated, and in addition, the image has a sense of incongruity due to the loss of color balance.

Claims (5)

In an ink set having a magenta ink containing at least water, a dye and a water-soluble organic solvent and a cyan ink containing at least water, the dye and the water-soluble organic solvent, the dye contained in the magenta ink is represented by the following general formula (1). The dye contained in the cyan ink is a dye represented by the following general formula (2), and any one of the water-soluble organic solvent contained in the magenta ink and the water-soluble organic solvent contained in the cyan ink The water-soluble organic solvent A contains 10 to 20% by mass of polyhydric alcohol or alkyl ether of polyhydric alcohol, and the water-soluble organic solvent B contains monohydric alcohol having 1 to 3 carbon atoms. An ink set comprising 1 to 5% by mass of the total mass.

[Wherein, R represents a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, a mono- or dialkylaminoalkyl group, or a cyano lower alkyl group, and Y represents a chlorine atom, a hydroxyl group, an amino group, a mono- or dialkylamino group. Represents an aralkylamino group, a cycloalkylamino group, an alkoxy group, a phenoxy group, an anilino group, a naphthylamino group, or a mono- or dialkylaminoalkylamino group, and X represents a bridging group. M represents a hydrogen atom, an alkali metal salt, an alkaline earth metal salt, an alkylamine salt, an alkanolamine salt or an ammonium salt. ]

[Wherein, X _{11 to} X ₁₄ each independently represent —SO—Z, —SO ₂ —Z, —SO ₂ NR ₁ R ₂ , —CONR ₁ R ₂ or —CO ₂ R ₁ . Z is each independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, substituted or unsubstituted Represents a heterocyclic group. R ₁ and R ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, substituted or unsubstituted Represents an aryl group or a substituted or unsubstituted heterocyclic group. Y _{11 to} Y ₁₈ each independently represent a monovalent substituent. a11~a14 each represent a number of substituents X ₁₁ to X _14, represents 1 or 2 are each a11~a14 independently. M is a hydrogen atom, a metal atom or an oxide, hydroxide or halide thereof. ] The ink set according to claim 1, wherein the water-soluble organic solvent A is a polyhydric alcohol. The polyhydric alcohol is at least one selected from glycerin, ethylene glycol, diethylene glycol, propylene glycol, and triethylene glycol, and the monohydric alcohol is ethanol or propanol. Ink set. A color image is printed by ejecting magenta ink and cyan ink onto a void-type inkjet recording medium having an ink absorbing layer containing alumina using the ink set according to any one of claims 1 to 3. An image forming method. A color image is printed by using the ink set according to any one of claims 1 to 3 and discharging magenta ink and cyan ink using an electro-thermal conversion recording head. Image forming method.