JP4113977B2 - Color image forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color image forming method using a pigment ink, and more particularly to a color image forming method for forming an image by combining an ink containing a pigment having a specific chemical structure as a colorant.
[0002]
[Prior art]
Many conventional recording inks, particularly inkjet recording water-based inks, have the disadvantage of poor water resistance and light resistance because they use a water-soluble dye as a colorant. In addition, since the dye is dissolved at the molecular level, printing on so-called plain paper such as copy paper commonly used in offices causes bleeding called wrinkle-like feathering, which causes a significant decrease in print quality. .
[0003]
Various so-called pigment inks have been proposed in the past to improve the above drawbacks. For example, resin-dissolved inks and polymers in which carbon black or organic pigments are dispersed using a water-soluble resin as a binder / dispersant. Various resin-dispersed inks that coat colorants as latex or microcapsules have been proposed.
[0004]
In order to obtain a high-quality color image using pigment ink, the type and combination of pigments used are greatly affected. Therefore, Japanese Patent Laid-Open No. 5-155006 discloses a color image forming method for forming an image by combining each color ink containing yellow, magenta, and cyan pigments having a specific color index (CI) number. Japanese Laid-Open Patent Publication No. 5-320551 proposes a color ink for an ink jet printer in which a pigment exhibiting at least yellow, magenta, cyan, and black is dispersed in a non-aqueous solvent in which a resin component is dissolved.
[0005]
However, when performing color printing using inks in which these conventional pigments are combined as a colorant, the color balance of each ink, the color fading balance associated with exposure to sunlight, etc. greatly affects the image quality and its stability. In so-called microcapsules whose pigment surface is coated with resin, there is a variation in microencapsulation with each color pigment, and it is difficult to obtain microcapsules with a constant particle size, making it difficult to maintain the dispersion stability of each color at a certain level Had.
[0006]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a color image forming method using an ink having excellent full color color reproducibility and weather resistance and excellent dispersibility.
[0007]
[Means for Solving the Problems]
As a result of intensive studies in order to solve the above problems, the present inventors have come to solve the present invention.
[0008]
That is, the present invention is characterized in that in a recording ink using a pigment coated with a resin as a colorant, an image is formed by using at least three colors of ink including a phrocyanine pigment, a quinacridone pigment, and a benzimidazolone pigment. A color image forming method is provided.
[0009]
Further, the present invention provides a color image forming method characterized in that an image is formed using a combination of at least three colors of ink comprising carbon black as a colorant, a phthalocyanine pigment, a quinacridone pigment, and a benzimidazolone pigment.
[0010]
In order to perform color image formation, particularly full color image formation, the color tone of the pigment to be used requires a minimum combination of three colors of cyan, magenta, and yellow, and preferably an image of four colors combined with black It is known to form an image by forming or adding a color having a complementary color relationship in addition to the three or four colors.
[0011]
The cyan pigment is required to be a phthalocyanine pigment in terms of color tone and weather resistance. Specific examples of the phthalocyanine pigment include metal-free phthalocyanine, copper phthalocyanine or chlorinated copper phthalocyanine, and other various metal phthalocyanines. Of these, copper phthalocyanine is preferable, and C.I. I. Pigment Blue 15: 4 is more preferable.
[0012]
The magenta color pigment needs to be a quinacridone pigment from the viewpoint of color tone and weather resistance. Specific examples of the quinacridone pigment include dimethylquinacridone and dichloroquinacridone. Among these, C.I. is particularly preferred in terms of color tone and dispersibility when combined with other color pigments. I. Pigment Red 122 is preferable.
[0013]
The yellow color pigment is required to be a benzimidazolone pigment from the viewpoint of color tone and weather resistance. Specific examples of the benzimidazolone pigment include C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 156, C.I. I. Pigment yellow 175. Among these, C.I. is preferred in terms of color tone and dispersibility when combined with other color pigments. I. Pigment Yellow 151 is most preferable.
[0014]
Although there is no restriction | limiting in particular as a black pigment, Carbon black is preferable from the point of a color tone and a weather resistance.
An image obtained by forming a color image using a combination of at least three inks consisting of an ink containing carbon black as a colorant, a phthalocyanine pigment, a quinacridone pigment, and a benzimidazolone pigment has almost no color tone change due to photobleaching. High image quality stability can be obtained.
[0015]
In particular, C.I. I. Pigment Blue 15: 4, C.I. I. Pigment Red 122 and benzimidazolone pigments such as C.I. I. An image obtained by performing color image formation by combining with Pigment Yellow 151 and, if necessary, combining it with carbon black is particularly preferable for image quality stability.
[0016]
Each of the color pigments can be used alone or in combination, and if necessary, other types of dyes and pigments can be used in combination to form an ink.
In order to make an ink using the pigment, the dispersion medium is not particularly limited, but water is preferable from the viewpoint of environmental hygiene, and as other components, a dispersant, a binder resin, an organic solvent, an antibacterial and antiseptic as necessary. Further, pigment dispersion may be performed by a known method using various additives such as a stabilizer. Further, so-called microcapsules in which a pigment is coated with a resin may be dispersed in a dispersion medium. From the viewpoint of dispersion stability, an ink in which microcapsules are dispersed in a dispersion medium is preferable, and an aqueous microcapsule ink using water as a dispersion medium is particularly preferable.
[0017]
Various methods known in the art can be applied to the microencapsulation of the pigment. To make the pigment used in the color image forming method of the present invention a highly stable microcapsule ink, a resin that coats the pigment is used. The self-water-dispersible resin (A) in which at least a part of the acid groups of the synthetic resin (a) having an acid value of 50 or more and 280 or less is neutralized with the base (b), and the colored resin particles must contain water. The ink is preferably dispersed in an aqueous medium as a component.
[0018]
Part or all of the resin coating the pigment may be cross-linked. As a crosslinking means, conventionally known methods can be used. For example, a method of polymerizing by containing a pigment and a crosslinkable monomer component, a synthetic resin solution in which a pigment is dispersed and a crosslinkable monomer is contained in microcapsules A method in which the crosslinkable monomer incorporated in the capsule is crosslinked by heating, at least a part of the anionic functional group of the self-water dispersible resin (A) is neutralized with a monovalent base, and Examples thereof include a method of coating the pigment surface with a self-water dispersible ionomer resin (B) having a structure in which at least another part of the functional group is cross-linked by ionic bonds with polyvalent metal ions.
[0019]
The acid group of the synthetic resin (a) is, for example, a carboxylic acid group, a sulfonic acid group, a sulfinic acid group, and the like, and is not particularly limited. Among these, the carboxylic acid group is general and has a good self Water dispersible resin (A) is given.
[0020]
Any synthetic resin (a) may be used as long as it satisfies the above characteristics. Specific examples include substituted styrene such as styrene or α-methylstyrene, acrylic acid methyl ester, acrylic acid ethyl ester, acrylic resin. At least one monomer selected from acrylic acid butyl ester, acrylic acid ester such as 2-ethylhexyl acrylate, methacrylic acid methyl ester, methacrylic acid ethyl ester, methacrylic acid butyl ester, and methacrylic acid 2-ethylhexyl methacrylate A copolymer containing a unit and at least one monomer unit selected from acrylic acid and methacrylic acid can be used. In particular, as an essential monomer component of the self-water dispersible resin (A), a styrene monomer, an acrylic acid monomer, Methacrylic It is a copolymer using monomers, particularly when the constituent ratio of these essential monomer components is 60 to 90 mol% of styrene monomer, 5 to 15 mol% of acrylic acid monomer, and 5 to 25 mol% of methacrylic acid monomer. Can maximize the color reproduction of the pigment in the color image forming method of the present invention, and enables excellent colored resin particles free from nozzle clogging as ink for inkjet recording.
[0021]
Although there is no restriction | limiting in particular about the molecular weight range of the said synthetic resin (a), The thing of the molecular weight 1000 or more and 100,000 or less is more preferable. Of course, as long as the self-water dispersible resin (A) obtained from the synthetic resin (a) forms stable colored resin particles in combination with an aqueous medium, it is not particularly limited thereto. Two or more types may be mixed and used at the same time.
[0022]
The acid group of the synthetic resin (a) described above is neutralized with the base (b), that is, neutralization with an alkaline neutralizing agent needs to be neutralized to the extent that the water-dispersible resin does not dissolve in water, and does not dissolve. An alkaline neutralizing agent may be added in excess, but it is preferable to neutralize 60 mol% or more of the acid groups of the synthetic resin (a). When the neutralization rate is 60 mol% or more, colored resin particles having a small particle diameter are obtained, and the dispersion stability is excellent.
[0023]
The amount of the self-water dispersible resin (A) used is not particularly limited, but is preferably such an amount that it is 0.5 to 20% by weight in the finally obtained aqueous ink.
Examples of the base (b) (alkaline neutralizing agent) include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, basic substances such as ammonia, triethylamine and morpholine, and triethanolamine. Alcohol amines such as diethanolamine and N-methyldiethanolamine can be used.
[0024]
Further, the self-water dispersible ionomer resin (B) is an ionomer resin (d) in which a part of an anionic functional group in the synthetic resin (a) is intermolecularly crosslinked through a polyvalent metal ion (c). It is obtained by neutralizing the acid group with the base (b). This polyvalent metal ion (c) is generated by a reaction between an anionic functional group in the synthetic resin (a) and a metal or metal oxide, preferably a polyvalent metal salt (C) soluble in an organic solvent described later. The valence of the polyvalent metal ion (c) may be 2 or more, but is preferably 2 or 3. Particularly preferred as the polyvalent metal ion (c) is at least one selected from calcium ions, barium ions, magnesium ions, zinc ions, and aluminum ions.
[0025]
The crosslinking rate of the ionomer resin (d) when the synthetic resin (a) is crosslinked via the polyvalent metal ion (c) is determined by the acid value, molecular weight, and valence of the polyvalent metal ion (c) of the synthetic resin (a). What is necessary is just to select a crosslinking rate so that the optimal self-water dispersible ionomer resin (B) may be obtained by number.
[0026]
As a method of adding the base (b) to the synthetic resin (a) having the acid group and the ionomer resin (d) for neutralization, the resin may be added to an organic solvent solution of the resin in advance, or the organic of the resin There are methods such as whether to add the solvent solution and the aqueous medium to the aqueous medium when mixing, but the best condition may be selected as to which method is adopted.
[0027]
As a preferred production method in which the pigment used in the color image forming method of the present invention is a colorant coated with a resin, the pigment is dispersed in an organic solvent solution containing a synthetic resin (a) generally called a mill base. In addition, the base (b) is further mixed and dissolved in this colored mill base, neutralized to obtain a self-water dispersible resin (A) (first stage), and then an aqueous medium containing water as an essential component by dropping or the like; It is preferable to mix and emulsify, that is, to perform phase inversion emulsification (second stage).
[0028]
As the organic solvent used for dissolving the resin, any organic solvent that can dissolve the resin can be used. For example, ketone solvents such as acetone, dimethyl ketone, and methyl ethyl ketone, methanol Alcohol solvents such as ethanol and isopropyl alcohol, chlorine solvents such as chloroform and methylene chloride, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, etc. Examples include glycol ether solvents and amides. Among these organic solvents, when the resin component is an acrylic resin, at least one combination selected from a ketone solvent and an alcohol solvent is preferable. The amount of the organic solvent used is not particularly defined as long as the effect of the present invention is achieved, but is preferably such that the weight ratio of the synthetic resin / the organic solvent is 1/1 to 1/20.
[0029]
As a suitable production method for using the ionomer resin (d) to obtain a colorant in which a pigment is coated with a resin, a polyvalent metal salt (C) and, if necessary, an organic material are used in the mill base of the phase inversion emulsification method. A solvent-soluble chelating agent is dissolved, and the water-soluble monovalent base (b) is mixed and dissolved to neutralize the ion-crosslinked synthetic resin (a) to make it self-dispersible. What is necessary is just to mix and emulsify with the aqueous medium which uses as an essential component.
[0030]
The polyvalent metal salt (C) soluble in the organic solvent is not particularly limited as long as it is a bivalent or higher metal alcoholate, acylate or chelate and is soluble in the organic solvent described later.
[0031]
In view of the fact that the resin particles having a structure in which intermolecular crosslinking is performed through metal ions are colorless, less toxic, exhibit good toughness, and good thermoplasticity, the metal alcoholate having a valence of 2 or more is preferably used. Examples thereof include alcoholates of polyvalent metals such as calcium, barium, magnesium, zinc and aluminum. Examples of acylates of divalent or higher metals are obtained from the aforementioned alcoholates and organic carboxylic acids such as acetic acid, propionic acid and butyric acid. As the chelating agent, the alcoholate, acylate and β-diketone represented by acetylacetone, propionylacetone, acetoacetic acid alkyl ester, diacetacetic acid alkyl ester represented by β-keto acid ester Chelates obtained from chelating agents such as . More preferred are acylates and chelates of these polyvalent metals. An example is trisacetylacetonatoaluminum. These polyvalent metal salts may be used in combination.
[0032]
Crosslinking of the synthetic resin (a) with the polyvalent metal salt (C) seems to obtain resin particles optimal for the intended use depending on the acid value, molecular weight, and valence of the polyvalent metal ion (c) of the synthetic resin (a). A suitable crosslinking rate may be selected. Usually, the amount of the polyvalent metal salt (C) used is sufficient to correspond to about 1 to 30 mol% of the total anionic functional group, but 100 mol% may be added. Even if the addition amount of the polyvalent metal salt (C) reaches 100 mol% of the total anionic functional group, an amount of the chelating agent that is excessive (surplus) with respect to the polyvalent metal ion is added to the synthetic resin ( a), added to a solution of an organic solvent containing the monovalent base compound (b) and the polyvalent metal salt (C), and the reaction is carried out in the presence of this, or the above-mentioned (a), (b), ( C) If a measure such as adding an excessive amount of a chelating agent is added to the organic solvent solution containing the self-water dispersible ionomer resin (B) before emulsification obtained by reacting the component, etc., crosslinking of the resin The mask effect occurs, and fine particles can be emulsified without gelation.
[0033]
In the synthetic resin solution, if necessary, a dispersant, a plasticizer, an antioxidant, an ultraviolet absorber and the like may be used together with a solvent, a resin and a colorant as additives.
The water used in the aqueous medium mixed with the colored resin solution is preferably water of a grade higher than ion-exchanged water in order to avoid nozzle clogging when used mainly as jet ink. In order to prevent the ink for inkjet recording from drying, it is preferable that a water-soluble organic solvent is present in the ink as a drying inhibitor. The anti-drying agent may be added to the aqueous medium at the time of phase inversion emulsification or after emulsification. Such an anti-drying agent has an effect of preventing the ink from drying at the jet nozzle opening of the ink jet, and usually has a boiling point equal to or higher than the boiling point of water. Examples of such anti-drying agents include conventionally known polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and glycerin, or alkyl ethers thereof, N-methyl. Examples include pyrrolidones such as -2-pyrrolidone and 2-pyrrolidone, amides, dimethyl sulfoxide, and imidazolidinone. Although the usage-amount of the said drying inhibitor changes with kinds, it is normally selected suitably from the range of 1-150 weight part with respect to 100 weight part of water. Among these ranges, 10 to 50 parts by weight is preferable when using glycerin and a combination of other drying inhibitors.
[0034]
When the ink used in the image forming method of the present invention is a water-based ink, a water-soluble resin, a pH adjuster, a surfactant for dispersing / defoaming / penetrating paper, a preservative, and a chelating agent as necessary Additives such as can be added.
[0035]
Furthermore, in the case of a method of forming an image by an ink jet recording method, a water-solubility exhibiting a permeability imparting effect as a penetrability imparting agent in order to allow the ink adhered by jetting to penetrate the paper better if necessary. An organic solvent may be added. As such a permeability imparting agent, lower alcohols such as ethanol and isopropyl alcohol, glycol ethers such as diethylene glycol-N-butyl ether, and the like can be used, but are not limited thereto. The amount of the penetrability-imparting agent is not particularly defined as long as the effect of the present invention is achieved, but is preferably such an amount as 0.1 to 10% by weight in the finally obtained aqueous ink. These additives may be added to the aqueous medium in advance, or may be added when the self-water dispersible resin solution containing the colorant is mixed with the aqueous medium, or may be added after mixing them. However, it is preferable to avoid adding additives after the final filtration.
[0036]
As described above, the ink used in the image forming method of the present invention is obtained by a phase inversion emulsification method as a specific example. That is, as a first step, a colored mill base in which a pigment is dispersed in a solution containing the synthetic resin (a) neutralized with the base (b) is prepared. As the second stage, an encapsulation process is carried out to obtain water-dispersible resin particles covering the colorant by mixing the colored mill base obtained in the first stage with an excess amount of an aqueous medium. In the production of the water-based ink, it is preferable that a third step is a desolvation step for removing the organic solvent used in the first step of the mill base step in order to increase the dispersion stability of the capsule particles in the ink. If necessary in this desolvation step, water may be removed. Of course, this third step may be omitted in some cases. At this time, after the second or third stage process is completed, it is preferable to remove the large particle size by filter filtration, centrifugation, or the like. The ink thus obtained is excellent in full-color color reproducibility and weather resistance, and has excellent dispersibility. When the image is formed using the color image forming method of the present invention, particularly the ink jet recording method, the ink is obtained. Is optimal.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
At least a part of the anionic functional group of the self-water-dispersible resin is a monovalent base containing at least three colors of ink consisting of a phthalocyanine pigment, a quinacridone pigment and a benzimidazolone pigment, and an ink containing carbon black as a colorant. Taking as an example the case of producing by a method in which the pigment surface is coated with a self-water dispersible ionomer resin having a structure in which at least another part of the functional group is cross-linked by ionic bonds with polyvalent metal ions. The explanation is as follows.
[0038]
As a synthetic resin, an acid value of 50 or more and 280 or less, molecular weight obtained by copolymerizing at least one monomer unit selected from styrene, substituted styrene, and (meth) acrylic acid ester and (meth) acrylic acid A polyvalent metal salt and an organic solvent-soluble chelating agent are dissolved in an organic solvent solution of a vinyl copolymer of 1,000 or more and 100,000 or less, and a pigment is dispersed to obtain a colored mill base.
[0039]
A base capable of neutralizing the acid group of the synthetic resin is added to the colored mill base, mixed and stirred, and further an aqueous medium containing water is added dropwise with stirring to perform phase inversion emulsification, whereby a pigment is obtained from the ionomer resin. An aqueous dispersion containing colorant resin particles coated with is obtained. In addition, the organic solvent used to dissolve the synthetic resin and the chelating agent (solvent) used to prevent the gelation of the resin with polyvalent metals are removed by distillation under reduced pressure, and then a drying inhibitor, water-soluble as necessary. After adjusting the ink by adding additives such as resin, pH adjuster, dispersion aid, antifoaming agent, paper permeability imparting agent, preservative, chelating agent and water for concentration adjustment, large particle size The aqueous ink for inkjet recording is obtained by removing the particles. The obtained ink is color-printed on an inkjet-dedicated recording paper using a commercially available inkjet printer.
[0040]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following examples, “part” represents “part by weight”.
[0041]
Reference Example 1 (Cyan ink example)
20 parts of styrene acrylic resin (styrene / acrylic acid / methacrylic acid = 77/13/10; acid value 160; molecular weight 40,000), C.I. I. Pigment Blue 15: 420 parts, trisacetylacetonatoaluminum 4.7 parts (amount corresponding to a crosslinking rate of 80%), acetylacetone 10 parts, methyl ethyl ketone 45 parts together with 150 parts of 0.2 mm diameter glass beads using a paint shaker Dispersed for 6 hours.
[0042]
To 89.7 parts of the dispersion excluding the glass beads, 40 parts of methyl ethyl ketone and 40 parts of isopropyl alcohol are added and mixed. Further, 8.9 parts of triethanolamine (an amount corresponding to a neutralization rate of 110%) is added and stirred. Then, a mixed liquid of 71 parts of glycerin and 429 parts of ion-exchanged water was added dropwise at a rate of 5 ml per minute to obtain a colored composition dispersion. The organic solvent was distilled off from the obtained colored composition dispersion using a rotary evaporator to obtain an aqueous dispersion of a colored composition having a particle size of 0.2 μm. After the concentration adjustment, filtration was performed using a 1.5 μm membrane filter to obtain an ink for an ink jet printer.
[0043]
The obtained ink was stable in a glass container at room temperature for 1 year. It was well dispersed and did not generate agglomerates. As a result of a jet test using a piezo ink jet printer, nozzles were not clogged and stable jetting was achieved. The printed paper obtained was bright and excellent in water resistance.
[0044]
Reference example 2 (magenta ink example)
Instead of the pigment of the cyan ink example, C.I. I. Similarly, a magenta water-based ink composed of colored microcapsules having an average particle diameter of 0.2 μm was obtained using CI Pigment Red 122.
[0045]
The obtained ink was stable in a glass container at room temperature for 1 year. It was well dispersed and did not generate agglomerates. As a result of a jet test using a piezo ink jet printer, nozzles were not clogged and stable jetting was achieved. The printed paper obtained was bright and excellent in water resistance.
[0046]
Reference example 3 (yellow ink example)
Instead of the pigment of the cyan ink example, C.I. I. Similarly, a yellow aqueous ink composed of colored microcapsules having an average particle diameter of 0.2 μm was obtained using CI Pigment Yellow 151.
[0047]
The obtained ink was stable in a glass container at room temperature for 1 year. It was well dispersed and did not generate agglomerates. As a result of a jet test using a piezo ink jet printer, nozzles were not clogged and stable jetting was achieved. The printed paper obtained was bright and excellent in water resistance.
[0048]
Reference Example 4 (Black ink example)
In place of the pigment of the cyan ink example, carbon black was used to obtain a black aqueous ink composed of colored microcapsules having an average particle diameter of 0.1 μm.
[0049]
The obtained ink was stable in a glass container at room temperature for 1 year. It was well dispersed and did not generate agglomerates. As a result of a jet test using a piezo ink jet printer, nozzles were not clogged and stable jetting was achieved. The printed paper obtained had a high black density and excellent water resistance.
[0050]
Example 1
As a result of four-color printing on ink jet recording paper using a piezo-type jet printer using the inks of the respective color ink examples, vivid full-color reproduction was achieved. The obtained printed matter was irradiated with a xenon lamp for 300 hours (equivalent to two years of sun exposure), but almost no change in color tone was visually observed, and there was little change in the print density (reflection density) of each solid color portion. (Figure 1)
Comparative Reference Example 1 (Magenta ink comparative example)
In place of the pigment of the magenta ink example, C.I. I. In the same manner, microencapsulation was attempted using Pigment Red 57: 1 (Kermin 6B), but aggregation was caused at the mill base stage, and no ink was obtained.
[0051]
Comparative Reference Example 2 (Yellow ink comparative example)
In place of the pigment of the yellow ink example, C.I. I. Similarly, yellow aqueous ink composed of colored microcapsules having an average particle diameter of 0.2 μm was obtained using CI Pigment Yellow 14 (Disazo).
[0052]
Comparative Example 1
As a result of performing four-color printing on an inkjet-dedicated recording paper with a piezo-type jet printer using the ink of the yellow ink comparative reference example instead of the yellow ink of the color image formation example, vivid full color reproduction was achieved. However, when the obtained printed matter was irradiated with a xenon lamp for 300 hours (equivalent to sunlight exposure for 2 years), the secondary color green changed to cyan, red changed to magenta, and the yellow portion was completely faded. . (Figure 2)
The time for crosslinking the self-water dispersible resin (A) with a polyvalent metal ion (trisacetylacetonatoaluminum) is not particularly problematic. Even if it is finally crosslinked, the same properties can be obtained.
[0053]
【The invention's effect】
The color image forming method of the present invention enables recording with excellent printing quality, weather resistance (light resistance) and stability, and enables stable ink jet ejection characteristics without nozzle clogging.
[Brief description of the drawings]
FIG. 1 is a table showing a change in reflection density of a printed matter obtained in a color image formation example when a solid portion of each color is irradiated with a xenon lamp for 300 hours (equivalent to sun exposure for 2 years).
FIG. 2 is a graph showing changes in reflection density when a solid xenon lamp is irradiated for 300 hours (equivalent to sun exposure for 2 years) using a yellow ink comparative example (CI Pigment Yellow 14) that has faded in a color image comparative example. FIG.

Claims (6)

In a color image forming method using a recording ink having a pigment coated with a resin as a colorant, the pigment is C.I. I. Pigment blue 15: 4 and C.I. I. Pigment red 122 , C.I. I. There line image formed by the ink jet recording method using at least three color inks consists of Pigment Yellow 151, the three colors of inks, dispersed in an aqueous medium in which the pigment coated with the resin as an essential component with water The resin is a self-water dispersible resin obtained by neutralizing at least a part of acid groups of the synthetic resin (a) having an acid value of 50 or more and 280 or less with a base (b). A characteristic color image forming method. Further , an image is formed by an ink jet recording method using a combination of a recording ink containing carbon black as a colorant, and the recording ink is a resin-coated carbon black dispersed in an aqueous medium containing water as an essential component. The resin is a self-water dispersible resin obtained by neutralizing at least part of acid groups of the synthetic resin (a) having an acid value of 50 or more and 280 or less with a base (b). The color image forming method according to claim 1. The self-water-dispersible resin is a copolymer comprising styrene monomer 60 to 90 mol%, acrylic acid monomer 5 to 15 mol%, and methacrylic acid monomer 5 to 25 mol% as essential monomer components. 3. A color image forming method according to 2. The color image forming method according to claim 1, wherein a part of the self-water dispersible resin is crosslinked. In some crosslinking of the self-water dispersible resin, at least a part of the anionic functional group of the self-water dispersible resin is neutralized with the base (b), and at least another part of the functional group is The color image forming method according to claim 4, wherein the color image forming method is formed by intermolecular crosslinking by ionic bonding with polyvalent metal ions. In the ink, the first step of producing a colored mill veil in which a pigment is dispersed in an organic solvent solution containing a synthetic resin (a) neutralized with a base (b), and the colored mill base obtained in the first step are water-based 2. The color image forming method according to claim 1, wherein the color image forming method is produced through a second step of obtaining water-dispersible resin particles covering the pigment by mixing with a medium.

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