JP2007168119A - Ink-jet recording method, ink cartridge and ink-jet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recording method, by which an image with higher image qualities such as the acquisition of an image with a high reflection density at a portion with a relatively higher image density and, at the same time, the acquisition of an image having an inconspicuous graininess at a highlight part having a relatively lower reflection density of an image can be provided. <P>SOLUTION: In this ink-jet recording method, two kinds of water color inks with one and the same color tone and a liquid composition, which reacts with at least one kind between the water color inks are employed. Under the condition that let an ink having the relatively lowest cohesively separating value between the liquid composition and the water color ink be a first water color ink and let an ink having the highest one be a second water color ink, the cohesively separating value of the first water color ink is set to be ≤0.5 and, in order to record the relatively higher dense portion, the first water color ink is employed, while the second water color ink is employed in order to record the relatively lower dense portion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording method using a set of a water-based ink and a liquid composition containing a component that reacts with the water-based ink.

  The ink jet recording method is a printing method in which droplets of ink are ejected and attached to a recording medium such as paper, and printing is performed. However, according to the recording method, a high-resolution and high-quality image can be obtained with an inexpensive apparatus. It is possible to print full color images at high speed. However, in the ink jet recording method, since ink is liquid, when ink is landed on the recording medium, particularly when a recording medium of plain paper is used, ink droplets penetrate into the recording medium and the contour portion In some cases, the image becomes obscured or a boundary blur (so-called color bleeding) occurs between adjacent different colors.

  On the other hand, for the purpose of solving the above problem, a method of applying an ink containing a dye having at least one carboxyl group after applying a solution containing a polyvalent metal salt to a recording medium has been proposed. (See Patent Document 1). That is, according to this method, a solution (reaction solution) containing polyvalent metal ions and an ink containing a dye capable of reacting with the ions are contacted on the recording medium, whereby an insoluble substance is formed. As a result, it is possible to obtain a high-quality image in which the ambiguity of the outline portion is improved, color bleeding does not occur, and color material back-through on the back side of the print is reduced (hereinafter referred to as back-through). Can be obtained.

Further, by using a combination of a black ink that thickens or aggregates due to the action of salt and a color ink containing the salt, a high-quality color image having a high image density and no color bleeding can be obtained. There is also a proposal of a technical means (see Patent Document 2). That is, in each of the above-described techniques, two liquids that react with each other when mixed are used as a set, and a printed matter is formed on a recording medium using these two liquids having different characteristics during image formation. Thus, a good image (hereinafter referred to as a two-component system) is achieved. In addition, various proposals using two liquids have been made (see Patent Documents 3 and 4).
JP-A-5-202328 JP-A-6-106735 JP-A-3-240557 JP-A-3-240558

  The present inventors have made various studies on a two-component system using a liquid composition containing a reactive component and a water-based ink that aggregates or gels when mixed with the liquid composition in forming a recorded matter. went. As a result, in the two-component system, the ambiguity of the contour portion is certainly improved, and when a plurality of inks of different colors are used, color bleeding does not occur, and the showthrough property is excellent. It was confirmed that high-quality image formation was possible. However, on the other hand, in the process of examination, it came to recognize a new problem because of the high reactivity between the liquid composition and the water-based ink.

  That is, because the reactivity between the liquid composition and the water-based ink is high, the water-insoluble colorant contained in the water-based ink aggregates or gels when the liquid composition and the water-based ink come into contact (moment to approximately several hundred msec). It will become. As a result, an image having a high image density can be obtained at a portion where the reflection density of the image is relatively high. However, in the highlight portion where the reflection density of the image is relatively low, depending on the ink composition and the type of the recording medium, the dot does not spread on the recording medium (the dot bleeding rate is small), and the graininess is low. It turns out that there is a new problem that it may stand out.

  Therefore, an object of the present invention is to obtain an image having a high reflection density at a portion where the image density is relatively high, and at the same time obtain an image having no noticeable graininess at a highlight portion where the reflection density of the image is relatively low. It is to provide a recording method capable of providing a higher quality image.

  The above object is achieved by the present invention described below. That is, the ink jet recording method according to the present invention reacts with at least one of two types of water-based inks having the same color tone and containing at least water, a water-insoluble colorant, and a water-soluble organic solvent. An ink jet recording method using a liquid composition containing a reactive component that aggregates or gels a water-insoluble colorant contained in the water-based ink, the coagulation of the liquid composition and the water-based ink. When the ink having a relatively low analysis value is the first water-based ink and the ink having the highest analysis value is the second water-based ink, the coagulation value of the first water-based ink is 0.5 or less and the ink has a relatively high value. The first water-based ink is used when recording the density portion, and the second water-based ink is used when recording the relatively low density portion.

  An ink cartridge according to another embodiment of the present invention is characterized in that it contains the water-based ink having the above-described configuration.

  In addition, an ink jet recording apparatus according to another embodiment of the present invention includes an ink storage unit that stores the water-based ink having the above-described configuration, and an ink-jet head that discharges the water-based ink. .

  According to the present invention, even when, for example, a system in which the reaction liquid is applied to the entire surface of the recording medium is used, the image density of the highlight portion having a relatively low image density is not noticeable, and the image density is further increased. In a high portion, a recording method capable of obtaining an image having a high reflection density is provided.

  Next, the present invention will be described in more detail with reference to preferred embodiments.

  As a result of intensive studies to solve the problems of the above-described technology, the present inventors have used a water-based ink that is used in a portion having a relatively low image density and a portion having a high image density even when an image is formed using a two-component system. The object of the present invention can be achieved by differentiating the types.

  That is, using the first water-based ink having a coagulation value of 0.5 or less indicating the reaction force between the liquid composition and the water-based ink, as in the prior art, the clarity of the contour, color bleeding, and strikethrough In addition to forming excellent images, the second aqueous ink, which is less reactive with the liquid composition than the first aqueous ink, is used to form an image of the highlight portion, thereby recording ink droplets. The present inventors have found that an excellent high quality image with no noticeable graininess can be expressed by improving the bleeding rate after landing on the medium and further suppressing the reflection density of one dot.

  If the coagulation value of the first water-based ink is larger than 0.5, depending on the recording medium and the printing environment, not only the image density of the portion having a relatively high image density cannot be expressed sufficiently, but color bleeding, There may be a case where the strikethrough property is also deteriorated. Furthermore, when the difference between the coagulation values of the first water-based ink and the second water-based ink is 0.4 or more, the effect of the present invention can be expressed more remarkably. Furthermore, it was found that when the coagulation value of the second water-based ink is 0.9 or more, the graininess of the light color portion can be reduced to a level that is hardly recognized by human eyes. Furthermore, it has been found that the above phenomenon is more effective when the concentration of the coloring material in the first aqueous ink is higher than the concentration of the coloring material in the second aqueous ink.

  The coagulation value described in the present invention is an index for judging the reaction force between the water-soluble ink and the liquid composition, and can be determined by the following means.

  5 g of a liquid composition diluted 100 times with pure water is put into a container having an inner diameter of 10 mm, 0.25 g of ink is dropped into the container, and the mixture is allowed to stand for 60 minutes. The ratio of the height was defined as the coagulation value of the aqueous ink relative to the liquid composition.

  Hereinafter, the aqueous ink and liquid composition of the present invention and an image forming method using them will be described.

<Ink>
The color material and aqueous medium that can be used in the ink used in the present invention will be described in detail.

(Water-insoluble colorant)
Next, the water-insoluble colorant constituting the water-based ink according to the present invention will be described. Regardless of the dispersion method, the water-insoluble color material constituting the water-based ink according to the present invention is, for example, a resin dispersion type pigment (resin dispersion type pigment) using a dispersant or an activator, or an activator dispersion type pigment. Or a microcapsule-type pigment that can be dispersed without using a dispersant by increasing the dispersibility of the water-insoluble colorant itself, or a self-dispersion type in which a hydrophilic group is introduced on the surface of pigment particles Pigments (self-dispersing pigments), and furthermore, modified pigments (polymer-bonding self-dispersing pigments) in which organic groups containing polymers are chemically bonded to the surface of the pigment particles can be used. . Of course, these pigments having different dispersion methods can also be used in combination. Hereinafter, these pigments that can be used in the present invention will be described.

[Pigment]
The pigment that can be used in the aqueous ink according to the present invention is not particularly limited, and any of those listed below can be used. In addition, a plurality of types of pigments can be used in combination in one water-based ink as necessary. The content of the pigment in the aqueous ink is set according to the use of the aqueous ink.

  Carbon black is suitable for the pigment used in the black ink. For example, carbon black such as furnace black, lamp black, acetylene black and channel black can be used. Specifically, for example, Raven 7000, Rayvan 5750, Rayvan 5250, Rayvan 5000ULTRA, Rayvan 3500, Rayvan 2000, Rayvan 1500, Rayvan 1250, Rayvan 1200, Rayvan 1190ULTRA-II, Rayvan 1170, Rayvan 1255 (and above) Colombia), Black Pearls L, Regal 400R, Regal 330R, Legal 660R, Mogul L, Monarch 700, Monak 800, Monak 880, Monak 900, Monak 1000, Monak 1100 , Monak 1300, Monak 1400, Monak 2000, Vulcan XC-72R Bot), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U , Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (above, manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. Commercial products such as 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical) can be used. Carbon black newly prepared for the present invention can also be used. However, the present invention is not limited to these, and any conventionally known carbon black can be used. Further, the material is not limited to carbon black, and magnetic fine particles such as magnetite and ferrite, titanium black, and the like may be used as a black pigment.

  Specific examples of the organic pigment include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, and pyrazolone red, soluble azo pigments such as lithol red, heliobordeaux, pigment scarlet, and permanent red 2B, alizarin. Derivatives from vat dyes such as indanthrone and thioindigo maroon, phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green, quinacridone pigments such as quinacridone red and quinacridone magenta, perylene pigments such as perylene red and perylene scarlet, Isoindolinone pigments such as indolinone yellow and isoindolinone orange, imidazoles such as benzimidazolone yellow, benzimidazolone orange and benzimidazolone red Pigments, pyranthrone pigments such as pyranthrone red, pyranthrone orange, indigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments, flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow Copper azomethine yellow, perinone orange, anthrone orange, dianslaquinonyl red, dioxazine violet, and the like. Of course, it is not limited to these, Other organic pigments may be used.

  The organic pigment that can be used in the present invention is represented by a color index (CI) number. I. Pigment Yellow: 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 150, 151, 153 154, 166, 168, 180, 185, C.I. I. Pigment Orange: 16, 36, 43, 51, 55, 59, 61, 71, C.I. I. Pigment Red: 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227 228, 238, 240, 254, 255, 272, C.I. I. Pigment violet: 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment Blue: 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment Green: 7, 36, C.I. I. Pigment Brown: 23, 25, 26, etc. can be exemplified.

[Resin dispersion type pigment]
As described above, a resin-dispersed pigment using a dispersant can be used as the water-insoluble colorant contained in the aqueous ink according to the present invention. In this case, as described above, A compound for dispersing a hydrophobic pigment is required. Specifically, so-called dispersants, surfactants, resin dispersants, and the like can be used. The dispersant or the surfactant is not particularly limited, but among them, an anionic or nonionic dispersant or surfactant can be preferably used.

  For example, anionic surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, naphthalene sulfonate formalin condensates, polyoxyethylene Examples thereof include alkyl sulfate salts and substituted derivatives thereof.

  Nonionic surfactants are polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, oxyethylene Examples thereof include oxypropylene block polymers and substituted derivatives thereof.

  Resin dispersants include styrene and its derivatives, vinyl naphthalene and its derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid and its derivatives, maleic acid and its derivatives, itaconic acid and its derivatives , Fumaric acid and its derivatives, vinyl acetate, vinyl alcohol, vinyl pyrrolidone, acrylamide, and block derivatives composed of at least two monomers (of which at least one is a hydrophilic monomer) Examples thereof include a polymer, a random copolymer, a graft copolymer, and salts thereof. Further, a block copolymer and a random copolymer can be used in combination.

[Microcapsule type pigment]
As described above, the water-insoluble colorant contained in the water-based ink according to the present invention uses a microcapsule type pigment obtained by coating a water-insoluble colorant with an organic polymer and microencapsulating it. You can also. Examples of the method of encapsulating a water-insoluble colorant with organic polymers to form microcapsules include a chemical production method, a physical production method, a physicochemical method, and a mechanical production method. Specifically, interfacial polymerization method, in-situ polymerization method, submerged cured coating method, coacervation (phase separation) method, submerged drying method, melt dispersion cooling method, air suspension coating method, spray drying method , Acid precipitation method, phase inversion emulsification method and the like.

  Organic polymers used as materials constituting the wall membrane material of the microcapsule include, for example, polyamide, polyurethane, polyester, polyurea, epoxy resin, polycarbonate, urea resin, melamine resin, phenol resin, polysaccharide, gelatin, and Arabic. Rubber, dextran, casein, protein, natural rubber, carboxypolymethylene, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, cellulose, ethyl cellulose, methyl cellulose, nitrocellulose, hydroxyethyl cellulose, cellulose acetate, polyethylene, Polystyrene, (meth) acrylic acid polymer or copolymer, (meth) acrylic acid ester polymer or copolymer, (meth) acrylic acid- (meth) acrylic acid Ester copolymer, styrene - (meth) acrylic acid copolymer, styrene - maleic acid copolymer, sodium alginate, fatty acids, paraffin, beeswax, water wax, hardened beef tallow, carnauba wax, albumin and the like.

  Among these, organic polymers having an anionic group such as a carboxylic acid group or a sulfonic acid group can be used. Nonionic organic polymers include, for example, polyvinyl alcohol, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, methoxypolyethylene glycol monomethacrylate or their (co) polymers, and 2-oxazoline cationic ring-opening polymers. Can be mentioned. In particular, a completely saponified product of polyvinyl alcohol is particularly preferable because it has low water solubility and is easily dissolved in hot water but difficult to dissolve in cold water.

  When the phase inversion method or the acid precipitation method is selected as the microencapsulation method, an anionic organic polymer is used as the organic polymer constituting the wall membrane material of the microcapsule. The phase inversion method is a composite or composite of an anionic organic polymer having self-dispersibility or solubility in water and a colorant such as a self-dispersible organic pigment or self-dispersible carbon black, or self A mixture of a colorant such as a dispersible organic pigment or self-dispersing carbon black, a curing agent, and an anionic organic polymer is used as an organic solvent phase, and water is added to the organic solvent phase or the organic solvent is submerged in water. In this method, a solvent phase is introduced and microencapsulation is performed while self-dispersion (phase inversion emulsification) is performed. In the above phase inversion method, there is no problem even if the organic solvent phase is produced by mixing a water-soluble organic solvent or additive used in the ink. In particular, it is more preferable to mix an ink liquid medium because a dispersion liquid for ink can be directly produced.

  On the other hand, in the acid precipitation method, a part or all of the anionic group of the anionic group-containing organic polymer is neutralized with a basic compound, and a colorant such as a self-dispersing organic pigment or self-dispersing carbon black; A water-containing cake obtained by a production method comprising a step of kneading in an aqueous medium and a step of neutralizing and acidifying an acidic compound to precipitate an anionic group-containing organic polymer and fixing the pigment to a pigment, This is a method of microencapsulation by neutralizing part or all of an anionic group using a compound. By doing in this way, the anionic microencapsulated pigment which is fine and contains many pigments can be manufactured.

  Examples of the solvent used in the microencapsulation as described above include alkyl alcohols such as methanol, ethanol, propanol, and butanol; aromatic hydrocarbons such as benzol, toluol, and xylol; methyl acetate, Esters such as ethyl acetate and butyl acetate; Chlorinated hydrocarbons such as chloroform and ethylene dichloride; Ketones such as acetone and methyl isobutyl ketone; Ethers such as tetrahydrofuran and dioxane; Cellosolves such as methyl cellosolve and butyl cellosolve Is mentioned. The microcapsules prepared by the above method are separated once from these solvents by centrifugation or filtration, and this is stirred and redispersed with water and the necessary solvent to obtain the desired microcapsule type pigment and You can also The average particle diameter of the encapsulated pigment obtained by the above method is preferably 50 nm to 180 nm.

[Self-dispersing pigment]
As described above, the water-insoluble colorant contained in the water-based ink according to the present invention is a self-dispersion type in which the dispersibility of the water-insoluble colorant itself is increased and can be dispersed without using a dispersant or the like. Other pigments can also be used. Self-dispersing pigments include those in which a hydrophilic group is chemically bonded to the pigment particle surface directly or via another atomic group. For example, the hydrophilic group introduced into the pigment particle surface, -COOM1, _-SO 3 M1 and _{-PO 3 H (M1) 2 (} M1 in the formula represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. And the like selected from the group consisting of Furthermore, those in which the other atomic group is an alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, or a substituted or unsubstituted naphthylene group can be preferably used. In addition, a method of oxidizing carbon black with sodium hypochlorite, a method of oxidizing carbon by ozone treatment in water, a method of modifying the carbon black surface by wet oxidation with an oxidizing agent after ozone treatment, etc. A self-dispersing pigment of the surface oxidation treatment type obtained by the above can also be suitably used.

[Polymer-bonded self-dispersing pigment]
As described above, the water-insoluble colorant contained in the water-based ink according to the present invention is a polymer-bonded type in which the dispersibility of the water-insoluble colorant itself is increased and can be dispersed without using a dispersant or the like. Self-dispersing pigments can also be used. This polymer-bonded self-dispersing pigment that does not use a dispersant is a co-polymerization of a functional group that is chemically bonded to the surface of the pigment directly or through another atomic group and an ionic monomer and a hydrophobic monomer. It is preferable to use the one containing the reaction product of the coalescence. That is, if a material having such a structure is used, the copolymerization ratio between the ionic monomer and the hydrophobic monomer, which is a material for forming a copolymer used for modifying the surface, can be appropriately changed. This is preferable because the hydrophilicity of the modified pigment can be appropriately adjusted. Moreover, since the kind of ionic monomer and hydrophobic monomer to be used, and a combination of both can be appropriately changed, various characteristics can be imparted to the pigment surface, which is also preferable from this point.

[Functional group]
The functional group in the polymer-bonded self-dispersing pigment is chemically bonded to the pigment surface directly or through another atomic group. The functional group is for constituting an organic group by reaction with a copolymer described later, and the type of the functional group is selected in relation to the functional group carried by the copolymer. The The reaction between the functional group and the copolymer is a reaction that generates a bond that does not cause hydrolysis, for example, an amide bond, considering that the pigment is dispersed in an aqueous medium. It is preferable that By making the functional group an amino group and supporting the carboxyl group on the copolymer, the copolymer can be introduced to the pigment particle surface via an amide bond. Similarly, the copolymer can be introduced to the pigment particle surface via an amide bond by converting the functional group to a carboxyl group and supporting the amino group on the copolymer.

  Here, the functional group chemically bonded to the pigment surface may be bonded directly to the pigment surface or may be bonded via another atomic group. However, when a copolymer having a relatively large molecular weight is introduced to the pigment surface, it is preferable to introduce a functional group to the pigment surface via another atomic group in order to avoid steric hindrance between the copolymers. Here, the other atomic groups are not particularly limited as long as they are polyvalent elements or organic groups. However, from the viewpoint of controlling the distance of the functional group from the pigment surface, for example, a divalent organic residue is preferably used. Specific examples of the divalent organic residue include an alkylene group and an arylene group (phenylene group).

  More specifically, for example, in the examples described later, the pigment is reacted with aminophenyl (2-sulfoethyl) sulfone to introduce an aminophenyl (2-sulfoethyl) sulfone group on the pigment surface. An amino group as a functional group is introduced by reacting an amino group of hexamine with an aminophenyl (2-sulfoethyl) sulfone group. In this case, it can be said that the amino group is chemically bonded to the pigment surface via an atomic group containing a phenyl (2-sulfoethyl) group.

[Copolymer of polymer-bonded self-dispersing pigment]
As the copolymer composed of the ionic monomer and the hydrophobic monomer, for example, an anionic copolymer having an anionic property or a cationic copolymer having a cationic property is preferably used.

  Examples of the anionic copolymer include a copolymer composed of a hydrophobic monomer and an anionic monomer, or a salt thereof. Typical hydrophobic monomers used in this case include the following monomers, but the present invention is not limited to these. For example, methacrylic acid alkyl esters such as styrene, vinyl naphthalene, methyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethoxyethyl methacrylate, methacrylonitrile, 2-trimethylsiloxyethyl methacrylate, glycidyl methacrylate, p-tolyl methacrylate, sorbyl methacrylate Alkyl acrylates such as methyl acrylate, phenyl acrylate, benzyl acrylate, acrylonitrile, 2-trimethylsiloxyethyl acrylate, glycidyl acrylate, p-tolyl acrylate and sorbyl acrylate.

  Although the anionic monomer used in the above includes the following monomers, the present invention is not limited to these. For example, acrylic acid, methacrylic acid, maleic acid and the like can be mentioned.

  As an embodiment of the copolymer according to the present invention, an anionic copolymer comprising an anionic monomer and a hydrophobic monomer is selected from any of the hydrophobic monomers listed above. It consists of at least two or more monomers with at least one selected from anionic monomers. The copolymer includes a block copolymer, a random copolymer, a graft copolymer, or a salt thereof.

  The acid value of the anionic copolymer is preferably in the range of 100 to 500, and it is preferable to use an acid value whose variation in acid value is within 20% of the average acid value. By setting the acid value within this range, the hydrophilicity of the pigment surface is too high, so that the water and solvent in the ink after printing stays on the pigment surface, and the marker resistance of the ink after printing on the recording medium is improved. Slow expression can be effectively suppressed. In addition, it is possible to effectively suppress the fact that the hydrophilicity of the pigment surface is too low and the pigment is difficult to stably disperse in the ink.

  Examples of the salt include alkali metal salts such as sodium, lithium, and potassium, ammonium salts, alkylamine salts, alkanolamine salts, and the like, and these can be used alone or in combination of several kinds.

  Next, a cationic copolymer comprising a cationic monomer and a hydrophobic monomer as another embodiment of the copolymer according to the present invention will be described. Examples of the cationic copolymer include copolymers composed of the following hydrophobic monomers and cationic monomers, or salts thereof. As the hydrophobic monomer, the monomers listed above can be used.

  Cationic monomers include, for example, allylamine, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 3-butylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl methacrylamide, N-vinylcarbazole, methacrylamide, acrylamide And dimethylacrylamide can be used.

  The cationic copolymer is a block copolymer, a random copolymer, a graft copolymer comprising at least two monomers including a hydrophobic monomer selected from the above monomers and a cationic monomer, or these And the like. In particular, the cationic copolymer having an amine value in the range of 100 to 500 is preferable, and the variation of the amine value is preferably within 20% of the average amine value. The amine value is a value expressed in mg of KOH by neutralizing 1 g of the sample and corresponding to the acid value. The salt includes acetic acid, hydrochloric acid, nitric acid and the like, and these can be used alone or in appropriate combination of several kinds.

  The anionic or cationic copolymer described above preferably has a weight average molecular weight (Mw) in the range of 1,000 to 20,000, and more preferably in the range of 3,000 to 20,000. Are preferred. Moreover, the polydispersity Mw / Mn (weight average molecular weight Mw, number average molecular weight Mn) of the cationic copolymer segment is preferably 3 or less. The content of such a cationic copolymer in the ink is preferably 5% by mass or more and 40% by mass or less with respect to pigment particles surface-modified with the copolymer. . Further, the polydispersity of the copolymer is such that when the polydispersity is large, the molecular weight distribution of the copolymer becomes wide, and the above-described properties based on the molecular weight of the copolymer are difficult to express. The molecular weight distribution of the polymer is preferably uniform.

  Next, taking carbon black as an example, a method for modifying the pigment by chemically bonding an organic group to the pigment particle surface will be described. The method that can be used in this case is to introduce a functional group on the surface of the pigment particle or a functional group on the surface of the pigment particle, and bond a copolymer composed of an ionic monomer and a hydrophobic monomer to these functional groups. As long as it is a method of chemically bonding the copolymer to the pigment particle surface, any method that is usually used may be used, and there is no particular limitation.

  As a specific example of such a method, for example, the following method can be used. A method in which polyethyleneimine or the like is introduced on the surface of pigment particles such as carbon black, and a copolymer composed of an ionic monomer and a hydrophobic monomer having an amino group at its terminal functional group is bonded by a diazonium reaction, carbon Methods such as a method of bonding a copolymer having an amino group and a carboxyl group in the molecule to the surface of pigment particles such as black by a diazonium reaction can be used. The most typical example of this other method is disclosed in WO 01/51566 A1.

  In the above-described method, for example, when an anionic copolymer is chemically bonded to the surface of the carbon black particles, the following three steps are included.

  1st process; The process of adding an aminophenyl (2-sulfoethyl) sulfone group (APSES) to carbon black by a diazonium reaction.

  Second step: A step of adding polyethyleneimine or pentaethylenehexamine (PEHA) to carbon black subjected to APSES treatment.

  Third step: A step of attaching a copolymer of a hydrophobic monomer and an ionic monomer having a carboxyl group.

  In the second step, the phenyl (2-sulfoethyl) sulfone group chemically bonded to the carbon black surface in the first step is reacted with the amino group of APSES to chemically react with the carbon black surface. An amino group as a functional group formed by bonding is introduced. In the third step, for example, by reacting a part of the carboxyl group of the ionic monomer portion of the copolymer with an amino group to form an amide bond, the copolymer is formed on the surface of carbon black, APSES. A copolymer can be introduced through an atomic group containing a phenyl (2-sulfoethyl) group that is a residue of the above and a residue of PEHA.

  Further, in the above-described method, for example, when the cationic copolymer is chemically bonded to the surface of the carbon black particles, the following two steps are included.

  First step: A step of adding an aminophenyl (2-sulfoethyl) sulfone group (APSES) to carbon black by a diazonium reaction.

  2nd process; The process of attaching the copolymer of a hydrophobic monomer and a cationic monomer. Through the first step, a sulfone group is introduced as a functional group chemically bonded to the carbon black surface. In the second step, for example, a part of the amino group of the ionic monomer portion of the copolymer is reacted with a sulfone group (nucleophilic substitution), the copolymer is placed on the surface of carbon black, and the APSES A copolymer can be introduced through an atomic group containing a phenyl (2-sulfoethyl) group as a residue.

  In consideration of the shape of the dots on the recording medium, in the present invention, the first water-based ink does not contain a resin, and the second water-based ink is used as a resin-containing ink. It becomes possible to express the effect of the above more prominently.

(Aqueous medium)
Examples of the aqueous medium used for the aqueous ink include water or a mixed solvent of water and a water-soluble organic solvent. Specifically, for example, alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; dimethylformamide, Amides such as dimethylacetamide; Ketones or ketoalcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, butylene glycol, tri 2 to 6 alkylene groups such as ethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol Alkylene glycols containing carbon atoms; lower alkyl ether acetates such as polyethylene glycol monomethyl ether acetate; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether, etc. Lower alkyl ethers of polyhydric alcohols; polyhydric alcohols such as trimethylolpropane and trimethylolethane; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. The water-soluble organic solvents as described above can be used alone or as a mixture. Moreover, it is preferable to use deionized water.

  The content of the water-soluble organic solvent contained in the aqueous ink used in the present invention is not particularly limited, but is preferably 3% by mass to 50% by mass based on the total mass of the ink. The water content in the ink is preferably 50% by mass to 95% by mass based on the total mass of the ink.

  Furthermore, in addition to the above-described components, the water-based ink used in the present invention may be added with a moisturizing agent as necessary, and in order to obtain a liquid composition having desired physical properties, a surfactant, You may add an antifoamer, antiseptic | preservative, an antifungal agent, etc.

<Water-based ink of the same color>
Further, the color tone of the water-based ink of the present invention is not particularly limited as long as it has water-based inks having at least the same color tone and different reactivity with the liquid composition. In the present invention, at least inks having the same color tone and different reactivity with the liquid composition may be used in combination with inks having different color tones. In particular, an ink set suitable for forming a multicolor image including at least four types of water-based inks having different color tones of black, cyan, magenta, and yellow is more preferable.

  The water-based ink referred to in the present invention is an ink set composed of an ink tank in which the first water-based ink and the second water-based ink are integrated, an ink tank with a head, or a separate ink tank for the recording apparatus. What is used so as to be removable is substantially referred to as an “ink set”. In any case, in the present invention, the characteristics of the water-based ink alone of the present invention are defined relative to other water-based inks used (in the recording apparatus or as an ink tank). Not only the said form but you may have what kind of deformation | transformation form.

<Liquid composition>
The liquid composition used in the present invention contains a reactive component that insolubilizes or aggregates the coloring material in the ink. More specifically, for example, the liquid composition can be stably dispersed in an aqueous medium by the action of an ionic group. Or a metal salt (especially a polyvalent metal ion and its salt) that can break and agglomerate the dispersion stability of the ink when it comes into contact with an ink having a dissolved colorant on a recording medium. , A low molecular weight cationic compound, and a cationic polymer, and those containing at least one as a reactive component. Hereinafter, these reactive components will be described.

(Polyvalent metal ions and their salts)
Specific examples of preferable polyvalent metal ions that can be used in the liquid composition according to the present invention include divalent metals such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ , Sr ^2+, and Ba ^2+. And trivalent metal ions such as Al ³⁺ , Fe ³⁺ , Cr ³⁺ and Y ^3+, but are not limited thereto. In order to contain these polyvalent metal ions in the liquid composition, a polyvalent metal salt is used. The salt is a metal salt composed of the polyvalent metal ions as mentioned above and an anion that binds to these ions, but is required to be soluble in water. Preferred anions for forming a salt include, for example, Cl ⁻ , NO ₃ ⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , CH ₃ COO ⁻ and HCOO ^−. However, the present invention is not limited to this.

In the present invention, Ca ²⁺ , Mg ²⁺ , Sr ²⁺ , Al ³⁺ and Y ³⁺ are particularly preferable from the viewpoints of reactivity, colorability, ease of handling, etc. ²⁺ is preferred. The anion is particularly preferably NO ₃ ⁻ from the viewpoint of solubility.

  The content of the polyvalent metal ion in the liquid composition is 0.01% by mass or more and 10% by mass or less, more preferably 1.0% by mass based on the total mass of the liquid composition in consideration of the effect of the present invention. % To 5% by mass or less, and 2.0% by mass or more and 4.0% by mass or less for sufficiently exhibiting the function of destabilizing the ink and obtaining a high level of image uniformity and optical density. It is preferable. Moreover, it is also possible to contain more than 10% of polyvalent metal ions in the liquid composition. However, even if it is added in an amount of more than 10% by mass, it is usually not necessary to make it excessively contained because the function of destabilizing the ink cannot be expected to increase significantly.

  The liquid composition does not contain a color material and is preferably transparent, but does not necessarily need to exhibit no absorption in the visible range. That is, even if absorption is shown in the visible range, absorption may be shown in the visible range as long as it does not substantially affect the image.

<Means for Applying Liquid Composition to Recording Medium>
Examples of the method for adhering the liquid composition to the recording medium include application methods such as a roller coating method, a bar coating method, and a spray coating method. In addition, an ink jet recording method is used in the same manner as the water-based ink, and an image forming region to which the water-based ink adheres and a coating method in which the liquid composition is selectively attached only to the vicinity of the image forming region are possible. As a result of studying several methods for applying the liquid composition to the recording medium, the inventors have found that the distribution of reaction components in the vicinity of the upper layer of the recording medium becomes more uniform than other means even with a small application amount, and the ink application It came to the view that the roller coating method was the most excellent in terms of image quality, which was the unevenness of the solid part afterwards, and also the penetration characteristics.

  In a system for forming an image using two liquids, there are various methods for bringing the liquid composition and ink into contact with each other on a recording medium. For example, a method in which the liquid composition and the ink are in contact with each other in a liquid state on the recording medium, or after the fixing of the liquid composition to the recording medium is completed, that is, the liquid composition droplets are inside the recording medium. For example, a method of contacting with ink after being absorbed. In the process of studying the two-component system, the present inventors satisfy the area factor even with a small amount of liquid, have a large dot spread on a recording medium of ink with low reactivity, and fixability of recorded matter. In view of the above, it was concluded that the method of applying ink after the fixing of the liquid composition was completed was the best. The time point when the fixing property in the present invention is completed is a time when the value of V shown by Bristow's formula is equal to the amount of liquid composition actually applied is t. It means that the time difference from the application of the liquid composition to the medium to the application of the aqueous ink is greater than t.

<Physical properties and coating amount of liquid composition>
The permeability of the liquid composition to plain paper is a Ka value determined by the Bristow method, and is 1.3 mL · m ⁻² · msec ⁻¹ / 2 to 6.0 mL · m ⁻² · msec ^−1/2 or less. More preferably, it is larger than 3.0 mL · m ⁻² · msec ^{−1/2 and not} more than 6.0 mL · m ⁻² · msec ^−1/2 . Further, the coating amount of the liquid composition is preferably 0.5 g / m ² or more and 5 g / m ² or less, and more preferably greater than 2.0 g / m ² and 3.0 g / m ² or less. preferable.

  In the present invention, the coating amount and the like of the coating liquid can be appropriately adjusted depending on the physical properties of the liquid composition, the rotation speed of the roller used in the coating apparatus, the contact pressure of the roller with respect to the recording medium, and the like.

<Inkjet recording apparatus>
FIG. 1 shows an example of an ink jet recording apparatus. This image forming apparatus adopts a serial type ink jet recording system, and includes a recording head 1, a sheet feeding tray 17 for feeding a recording medium (hereinafter also referred to as recording sheet) 19, and the liquid composition of the present invention. A paper feed cassette 16 integrally formed with a means for applying an object, and a drive means for reciprocating the recording head in a direction (main scanning direction) orthogonal to the recording paper transport direction (sub-scanning direction). And control means for controlling driving of these components.

  The recording head 1 is mounted on the carriage 2 so that the surface on which the ink discharge ports are formed is oriented toward the platen 11. Although not shown, the recording head 1 includes the ink discharge port, a plurality of electric heating element elements (for example, heating resistance elements) for heating the ink liquid, and a substrate for supporting the same. The recording head 1 has an ink cartridge mounted in the carriage on the top thereof.

  The carriage 2 carries the recording head 1 and can reciprocate along two guide shafts 9 extending in parallel along the width direction of the recording paper 19. The recording head 1 is driven in synchronism with the reciprocating movement of the carriage and ejects ink droplets onto the recording paper 19 to form an image. The paper feed cassette 16 can be detached from the image forming apparatus main body. The recording paper 19 is stacked and stored on a paper feed tray 17 in the paper feed cassette 16. At the time of paper feeding, the uppermost sheet is pressed against the paper feed roller 10 by a spring 18 that presses the paper feed tray 17 upward. The sheet feeding roller 10 is a roller having a substantially half moon shape in cross section, and is driven and rotated by a motor (not shown) to feed only the uppermost sheet (recording paper 19) by a separation claw (not shown).

  The separated and fed recording paper 19 is transported along the transport surface of the paper feed cassette 16 and the transport surface of the paper guide 27 by the large-diameter intermediate roller 12 and the small-diameter application roller 6 in pressure contact therewith. Is done. These transport surfaces are formed by curved surfaces that draw a concentric arc concentric with the intermediate roller 12. Therefore, the recording paper 19 reverses its transport direction by passing through these transport surfaces. That is, the surface on which the recording paper 19 is printed is directed downward until it is conveyed from the paper feed tray 17 and reaches the intermediate roller 12, but when facing the recording head 1, it is directed upward (recording). Turn to the head side. Therefore, the printing surface of the recording paper always faces the outside of the image forming apparatus.

  The liquid composition application means is provided in the paper feed cassette 16 and is removably supported with a replenishment tank 22 for supplying the liquid composition 15 and a part of the peripheral surface immersed in the tank 22. The intermediate roller 12 and the application roller 6 that is arranged in parallel with the intermediate roller and that contacts the intermediate roller 12 and rotates in the same direction. The application roller 6 is arranged so that the intermediate roller 12 for conveying the recording paper 19 is in contact with and parallel to the peripheral surface. Accordingly, when the recording paper 19 is transported, the intermediate roller 12 and the application roller 6 rotate with the rotation of the intermediate roller 12. As a result, the liquid composition 15 is supplied to the peripheral surface of the application roller 6 by the supply roller 13, and the liquid composition is supplied evenly to the printing surface of the recording paper 19 sandwiched between the application roller 6 and the intermediate roller 12. It is applied by a roller 6.

  In the image forming apparatus, the float 14 is provided in the replenishing tank 22. The float 14 is a substance having a lighter specific gravity than the liquid composition 15 and floats on the liquid surface of the liquid composition 15, so that the remaining amount of the liquid composition containing the reaction component from the outside through the remaining amount display window 21 that is a transparent member. Can be confirmed visually.

  FIG. 2 is a front view of the remaining amount display portion. The remaining amount display portion is provided with a display indicating the level of the remaining amount along the longitudinal direction of the remaining amount display window 21. In the figure, when the liquid level of the liquid composition or the float 14 reaches the position indicated as “Full”, the state is full. On the other hand, when there is a liquid surface or float 14 of the liquid composition at the position labeled “Add”, it indicates that the liquid composition remains little. Therefore, it can be understood at a glance that the liquid composition 15 should be replenished when the liquid composition 15 is gradually reduced and the float 14 is lowered to the Add line.

  As shown in FIG. 3, the replenishment method of the liquid composition is such that the tip of the injection device 23 is inserted into the injection port 20 made of a cut rubber member in a state where the paper feed cassette 16 is pulled out from the image forming apparatus main body. By inserting, the liquid composition is injected into the replenishing tank 22.

  In this way, the recording paper coated with the liquid composition is then fed to the recording unit by a predetermined amount by the main conveying roller 7 and the pinch roller 8 pressed against the main conveying roller 7, and ink is applied from the recording head 1. Is done. The recording sheet 19 fed and printed in the above configuration is discharged and conveyed by the discharge roller 3 and the spur 4 in pressure contact with the discharge roller 3 and stacked on the discharge tray 5.

  In addition, when the liquid composition is applied by a roller or the like, the ink can be effectively destabilized with a small application amount and recording can be performed particularly when the viscosity of the liquid composition is higher than the viscosity of the ink. It is preferable because it is good in fixing property. More specifically, the higher the viscosity of the liquid composition, the easier it is for the polyvalent metal ions to stay above the recording medium, and thus more easily react with the ink.

  On the other hand, after the ink reacts with the liquid composition, the coloring material component in the ink stays above the recording medium, and the solvent, water, etc. quickly penetrate into the recording medium, that is, the solid-liquid separation is performed quickly. Therefore, a lower viscosity is preferable from the viewpoint of the fixability of the recorded matter. When the liquid composition is applied by a roller or the like, the viscosity of the liquid composition is preferably 3 mPa · s to 100 mPa · s, and more preferably 5 mPa · s to 60 mPa · s. The viscosity of the liquid composition or ink in the present invention can be measured by a conventional method in an environment of 25 ° C.

<Ink characteristics; inkjet ejection characteristics, permeability to recording media>
The ink set according to the present invention is particularly suitable for inkjet recording. Inkjet recording methods include a recording method in which mechanical energy is applied to ink to eject droplets, and a recording method in which thermal energy is applied to ink and ink droplets are ejected by foaming of the ink. Not only the ink of the invention but also a liquid composition can be used. In that case, it is preferable that the liquid composition and the ink having the above-described configuration according to the present invention have characteristics such that they can be ejected from an inkjet head. From the viewpoint of dischargeability from an inkjet head, the characteristics of these liquids are, for example, a viscosity of 1 to 15 mPa · s, a surface tension of 25 mN / m (dyne / cm) or more, particularly a viscosity of 1 to 5 mPa. -It is preferable that s and surface tension shall be 25-50 mN / m (dyne / cm). Furthermore, since the liquid composition of the present invention needs to react with only a specific ink on a recording medium such as paper, the liquid composition does not bleed in a location other than the recording portion with the specific ink. The surface tension of the liquid composition is preferably within a range that can be ejected from the inkjet head and larger than that of the ink to be destabilized by the liquid composition.

<Recording method>
Two water-based inks having the same color tone, containing at least water, a water-insoluble colorant, and a water-soluble organic solvent, and water contained in the water-based ink reacting with at least one of the water-based inks An ink jet recording method using a liquid composition containing a reactive component that aggregates or gels an insoluble colorant, wherein an ink having a relatively low coagulation value between the liquid composition and the water-based ink is used as a first ink. When the second water-based ink is used as the second water-based ink, the coagulation value of the first water-based ink is 0.5 or less, and the first ink is used when recording a relatively high density portion. An ink jet recording method comprising: using a second water-based ink when recording a relatively low density portion using the water-based ink.

  The image forming method according to the present invention will be described below with specific examples. The image forming method according to the present invention comprises at least water, a water-insoluble colorant, and a water-soluble organic solvent, and two water-based inks having the same color tone and at least one of the water-based inks, An ink jet recording method using a liquid composition containing a reactive component that aggregates or gels a water-insoluble colorant contained in the water-based ink, when recording a relatively high density portion When the first aqueous ink having a low coagulation value between the liquid composition and the aqueous ink is used and a portion having a relatively low concentration is recorded, the coagulation value with the liquid composition is higher than that of the first aqueous ink. A second aqueous ink is used.

In the present invention, a relatively low density means a portion having a relatively small amount of ink applied during image formation, and a relatively high density means a relatively low ink application during image formation. It means the part with a large amount. More specifically, for example, when a state in which 9.6 g / m ² ink is applied to an image formed at 1200 dpi is defined as 100% duty, the portion where the ink application duty is 80% or more, and the color ink The first water-soluble ink is used at the boundary portion, and the second water-soluble ink is used at the portion where the ink application duty is less than 20%. An intermediate portion such as a duty with an ink application duty of 20% to less than 80% is characterized in that an image is formed using both the first water-soluble ink and the second water-soluble ink. Note that the image forming method described above is merely an example, and the ink application duty value and the like are not particularly limited.

  Next, in the ink jet recording method in which the first water-soluble ink is used as the black ink, and recording is performed using the black ink and at least one water-color ink, the image is formed by the image and color formed by the black ink. When forming an image that is adjacent to the image, a recording that is used when performing scanning to apply color ink to a region where the image is formed after scanning to apply black ink is performed. An example of the head is shown in FIG. 8 (BKI: second water-soluble ink, BKII: first water-soluble ink).

  As shown in FIG. 4, the recording head uses an ejection port array for ejecting black ink and color inks of three colors of cyan (C), magenta (M), and yellow (Y). A discharge port array for discharging.

  In the image forming method of the present invention, when a color image is formed, a recording head in which a black ejection port array for ejecting black ink and a color ejection port array for color ink are shifted in the sub-scanning direction. Is preferably used. For this reason, for example, when image formation is performed using the recording head shown in FIG. 4, the entire discharge port array for black is used in the case of image formation only for black. In the case of forming a color image in which black and color are mixed, an image is formed using the portion a in the drawing for black and the portion b in the drawing for C, M, and Y. It is preferable. Hereinafter, the case of forming an image in which black and color are mixed will be described in more detail with reference to FIG.

  In FIG. 4, first, black image data is printed in one-pass printing by scanning the print head in the horizontal direction (main scanning direction) in the drawing using the portion a or b of the black discharge port array. Or the like on a recording medium. Next, the recording medium is transported by a distance a in the vertical direction (sub-scanning direction) in the drawing, and in the forward direction of the main scanning of the next print head, the portion of the color ejection port array c is used as described above. A color image is formed by one-pass printing in the area where the image is formed in the black a row. At this time, the black discharge port array a simultaneously forms an image in the next area. By repeating this process, black and color mixed images are formed.

  Note that the number of passes differs depending on the use of the recording apparatus to be used, and is not limited to one-pass printing.

  FIG. 5 shows another example of a recording head that can be used when performing the image forming method according to the present invention. In FIG. 5, as in FIG. 4, the portion “a” in the drawing of the discharge port array is used for black, and the portion “b” in the drawing corresponding to the entire region of the discharge port row is used for C, M, and Y. Then, black and color mixed image formation is performed in the same manner as described above with reference to FIG.

  FIG. 6 shows another example of a recording head that can be used when performing the recording method according to the present invention. In FIG. 6, as in the case of FIG. 4, “a” in the drawing of the ejection port array is used for black, and “b” in the diagram corresponding to the entire region of the color ejection port array is used for C, M, and Y. Use it to form mixed images of black and color. In the recording head illustrated in FIG. 6, as shown in the drawing, a distance corresponding to the paper feed amount “a” is provided between the “a” portion of the black discharge port array and the “b” portion of the collar. For this reason, the recording head having such a configuration causes an extra time difference for one print scan in a reciprocal period from the formation of a black image to the formation of a color image. Therefore, especially when an image is formed on plain paper, the recording head illustrated in FIG. 6 has a more advantageous configuration for bleeding between black and color than the configuration shown in FIG.

  FIG. 7 shows another example of a recording head that can be used when carrying out the image forming method according to the present invention. Even when a recording head in which black and color discharge port arrays are arranged in a line in this order in the paper feed direction is used, a color image is formed after a black image is formed according to the paper feed. Will be.

  FIG. 8 shows another example of a recording head that can be used when performing the image forming method according to the present invention. In the recording head shown in FIG. 8, the color ejection port arrays are cyan (C1, C2), magenta (M1, M2) so that the color ink application sequence is the same in the forward scanning and the backward scanning. ) And yellow (Y1, Y2), two rows each, being symmetrically provided in the main scanning direction. As a result, bidirectional printing is possible even in the formation of black and color mixed images. In this case, a black image is first formed with black a, and then the recording medium is conveyed by a distance a, and the color ejection port is formed in the reverse process of the main scanning of the next print head. A color image is formed by one-pass printing in the region where the image is formed in the above-described black a row using the row b portion.

  Of course, in the bidirectional print head as shown in FIG. 8, as described above, the black and color nozzles are arranged so that an interval of one scan is provided between the black and color image formations. A more advantageous configuration may be used (see FIG. 9). Although the image forming method of the present invention has been described above, the form of the recording head that can be used in the method of the present invention is not limited to FIGS.

(Aspect of the Invention)
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the following description, parts and% are based on mass unless otherwise specified. First, a liquid composition and an ink were prepared as follows.

[Preparation of liquid composition]
The following components were mixed, sufficiently stirred and dissolved, followed by pressure filtration with a microfilter (manufactured by Fuji Film) having a pore size of 0.2 μm to prepare a liquid composition.
・ Calcium nitrate (tetrahydrate) 18 parts ・ Trimethylolpropane 25 parts ・ Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH; manufactured by Kawaken Fine Chemicals)
1 part water 56 parts [Preparation of water-based ink]
The following components were mixed, sufficiently stirred and dissolved, followed by pressure filtration with a 3.0 μm microfilter (manufactured by Fuji Film) to prepare each aqueous ink.

(Pigment dispersion BK1)
10 parts of carbon black having a specific surface area of 210 m ² / g and DBP oil absorption of 74 ml / 100 g and an anionic polymer P-1 (styrene-acrylic acid copolymer, acid value 200, aqueous solution with a solid content of 10%, medium 20 parts of a hydrating agent (potassium hydroxide) and 70 parts of pure water are mixed, charged into a batch type vertical sand mill (manufactured by IMEX), filled with 150 parts of 0.3 mm diameter zirconia beads, and cooled with water. Time dispersion processing was performed. After the dispersion was centrifuged to remove coarse particles, a pigment dispersion BK1 having a pigment solid content of about 12% and a weight average particle size of 100 nm in the final preparation was obtained.

(Composition of black ink 1)
-Pigment dispersion BK1 30 parts-Glycerol 9 parts-Diethylene glycol 6 parts-Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH) 1 part-Water 54 parts The coagulation value of this black ink 1 and the liquid composition is about 0 .3.

(Pigment dispersion BK2)
10 parts of carbon black having a specific surface area of 210 m ² / g and DBP oil absorption of 74 ml / 100 g, anionic polymer P-2 (styrene-acrylic acid copolymer, acid value 250, aqueous solution with a solid content of 10%, neutralization Agent: Potassium hydroxide) 20 parts and 70 parts of pure water are mixed, charged into a batch type vertical sand mill (manufactured by IMEX), filled with 150 parts of 0.3 mm diameter zirconia beads, and cooled with water for 5 hours. Distributed processing was performed. After the dispersion was centrifuged to remove coarse particles, a pigment dispersion BK2 having a pigment solid content of about 12% and a weight average particle size of 100 nm in the final preparation was obtained.

(Composition of black ink 2)
-Pigment dispersion BK2 30 parts-Glycerol 9 parts-Diethylene glycol 6 parts-Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH) 1 part-Water 54 parts The coagulation value of this black ink 2 and the liquid composition is about 0 .5.

(Pigment dispersion BK3)
10 parts of carbon black having a specific surface area of 210 m ² / g and DBP oil absorption of 74 ml / 100 g, anionic polymer P-3 (styrene-acrylic acid copolymer, acid value 300, aqueous solution with a solid content of 10%, neutralization Agent: Potassium hydroxide) 20 parts and 70 parts of pure water are mixed, charged into a batch type vertical sand mill (manufactured by IMEX), filled with 150 parts of 0.3 mm diameter zirconia beads, and cooled with water for 5 hours. Distributed processing was performed. After the dispersion was centrifuged to remove coarse particles, a pigment dispersion BK3 having a solid content of about 12% and a weight average particle size of 100 nm was obtained.

(Composition of black ink 3)
-Pigment dispersion BK3 20 parts-Glycerol 9 parts-Diethylene glycol 6 parts-Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH) 1 part-Water 64 parts The coagulation value of this black ink 3 and the liquid composition is about 0 .6.

(Pigment dispersion BK4)
10 parts of carbon black having a specific surface area of 210 m ² / g and DBP oil absorption of 74 ml / 100 g, an anionic polymer P-4 (styrene-acrylic acid copolymer, acid value 400, aqueous solution with a solid content of 10%, neutralization (Agent: potassium hydroxide) 30 parts and pure water 60 parts are mixed, and these materials are charged into a batch type vertical sand mill (manufactured by IMEX), filled with 150 parts of 0.3 mm diameter zirconia beads, and cooled with water, Dispersion treatment was performed for 5 hours. After the dispersion was centrifuged to remove coarse particles, a pigment dispersion BK4 having a solid content of about 12% and a weight average particle size of 120 nm was obtained.

(Composition of black ink 4)
-Pigment dispersion BK4 30 parts-Glycerol 9 parts-Diethylene glycol 6 parts-Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH) 1 part-Water 54 parts The coagulation value of this black ink 3 and the liquid composition is about 0 .9.

(Composition of black ink 5)
-Pigment dispersion BK3 30 parts-Glycerol 9 parts-Diethylene glycol 6 parts-Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH) 1 part-Water 54 parts The coagulation value of this black ink 5 and the liquid composition is about 0.6.

(Pigment dispersion BK5)
10 parts of carbon black having a specific surface area of 210 m ² / g and DBP oil absorption of 74 ml / 100 g, anionic polymer P-5 (styrene-acrylic acid copolymer, acid value 350, aqueous solution with a solid content of 10%, neutralization Agent: Potassium hydroxide) 20 parts and 70 parts of pure water are mixed, charged into a batch type vertical sand mill (manufactured by IMEX), filled with 150 parts of 0.3 mm diameter zirconia beads, and cooled with water for 5 hours. Distributed processing was performed. After the dispersion was centrifuged to remove coarse particles, a pigment dispersion BK5 having a solid content of about 12% and a weight average particle size of 100 nm was obtained.

(Composition of black ink 6)
-Pigment dispersion BK5 30 parts-Glycerol 9 parts-Diethylene glycol 6 parts-Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH) 1 part-Water 54 parts The coagulation value of this black ink 6 and the liquid composition is about It was 0.7.

  The ink set 1 was obtained by combining the black ink 2 and the black ink 5 prepared above. On-demand recording in which ink is ejected by applying thermal energy according to a recording signal to the following copy plain papers A to E after the liquid composition prepared above is applied in the ink set 1 A black ink 2 is attached to the BK position of the inkjet recording apparatus BJF900 (manufactured by Canon Inc.) having a head, and a black ink 5 is attached to the PC position, and the applied amount of ink is changed to 100% in 10% increments. The solid image was printed. When forming an image, black ink 5 is printed up to an applied amount of 20%, both inks are applied from an applied amount greater than 20% to less than 80%, and black ink 2 is printed up to 80% or more. The printing signal was determined.

  The speed of the roller and the contact pressure of the roller with respect to the recording medium were adjusted so that the coating amount of the liquid composition was 2.4 g / m 2.

The printer driver was executed in the default mode. The default mode setting conditions are shown below.
-Paper type: Plain paper-Print quality: Standard-Color adjustment: Automatic The copy paper shown below was used.

A: PPC paper PB PAPER made by Canon
B: Canon, PPC paper SC-250C
C: Xerox PPC paper 4200
D: Xerox, PPC paper 4024
E: High white paper SW-101 made by Canon

  The ink set 2 was obtained by combining the black ink 2 and the black ink 4 prepared above. Ink set 2 printed the same image in the same manner as ink set 1. However, in the case of ink set 2, black ink 2 was attached to the BK position of BJF900 (manufactured by Canon), and black ink 4 was attached to the PC position. When forming an image, black ink 4 is printed up to an applied amount of 20%, both inks are applied from an applied amount of more than 20% to less than 80%, and black ink 2 is printed up to 80% or more. The printing signal was determined.

  The ink set 3 was obtained by combining the black ink 1 and the black ink 6 prepared above. Ink set 3 printed the same image in the same manner as ink set 1. However, in the case of ink set 3, black ink 1 was attached to the BK position of BJF900 (manufactured by Canon), and black ink 6 was attached to the PC position. When forming an image, black ink 6 is printed up to an applied amount of 20%, both inks are applied from an applied amount greater than 20% to less than 80%, and black ink 1 is printed up to 80% or more. The printing signal was determined.

  The ink set 4 was obtained by combining the black ink 2 and the black ink 3 prepared above. Ink set 4 printed the same image in the same manner as ink set 1. However, in the case of ink set 4, black ink 2 was attached to the BK position of BJF900 (manufactured by Canon), and black ink 3 was attached to the PC position. When forming an image, it is assumed that black ink 3 is printed up to an applied amount of 20%, both inks are applied from an applied amount greater than 20% to less than 80%, and black ink 2 is printed up to 80% or more. The printing signal was determined.

<Comparative Example 1>
The ink set 5 was obtained by combining the black ink 5 and the black ink 6 prepared above. Ink set 5 also printed the same image in the same manner as ink set 1. However, in the case of ink set 5, black ink 5 was attached to the BK position of BJF900 (manufactured by Canon), and black ink 6 was attached to the PC position. When forming an image, black ink 6 is printed up to an applied amount of 20%, both inks are applied from an applied amount greater than 20% to less than 80%, and black ink 5 is printed up to 80% or more. The printing signal was determined.

<Comparative example 2>
The ink set 6 was formed by combining the black ink 1 and the black ink 2 prepared above. Ink set 6 printed the same image in the same manner as ink set 1. However, in the case of ink set 6, black ink 2 was attached to the BK position of BJF900 (manufactured by Canon), and black ink 1 was attached to the PC position. When forming an image, it is assumed that black ink 1 is used up to an application amount of 20%, both inks are applied from an application amount greater than 20% to less than 80%, and black ink 2 is used up to 80% or more. The printing signal was determined.

<Comparative Example 3>
The ink set 7 was formed by combining the black ink 1 and the BK black ink 5 prepared above. Ink set 7 printed the same image in the same manner as ink set 1. However, in the case of ink set 7, black ink 5 was attached to the BK position of BJF900 (manufactured by Canon), and black ink 1 was attached to the PC position. When forming an image, printing is performed using black ink 1 up to an application amount of 20%, both inks from an application amount greater than 20% to less than 80%, and black ink 5 using 80% or more. The printing signal was determined.

<Comparative example 4>
The ink set 8 was obtained by combining the black ink 2 and the black ink 2 prepared above. Ink set 8 printed the same image in the same manner as ink set 1. However, in the case of the ink set 8, the black ink 2 was attached to the BK position and the PC position of BJF900 (manufactured by Canon), and image formation was performed using only the black ink 2 ink.

[Evaluation]
1. Print Density In the above Examples and Comparative Examples, the printed matter printed on the copy plain papers A to E was left for 1 day, and after 1 day of printing, the print density of 100% solid part was measured. The print density of each image was measured using a reflection densitometer (trade name: Macbeth RD-918; manufactured by Macbeth).

(Print mode)
-Paper type: Plain paper-Print quality: Standard-Color adjustment: Automatic Using the print density obtained as a result of the measurement as described above, the following criteria were used for evaluation.
The evaluation results are shown in Table 1.
A: A sufficient image density can be obtained with all papers.
○: A sufficient image density cannot be obtained with some paper, but there is no problem in actual use.
(Triangle | delta): Sufficient image density was not obtained with some paper.
X: A sufficient image density was not obtained with all papers.

2. Graininess In the above Examples and Comparative Examples, the printed matter printed on the copy plain papers A to E is left for 1 day, and after 1 day of printing, the graininess of the highlight portion (10% and 20% solid portion) is increased. It was confirmed visually. The evaluation criteria are shown below. The evaluation results are shown in Table 1.
A: No graininess was felt on all the papers.
○: Some paper feels grainy, but there is no problem in actual use.
Δ: A graininess was felt on some papers.
X: A granular feeling was felt on all the papers.

3. Gradation In the examples and comparative examples described above, the printed matter printed on the copy plain papers A to F was left for 1 day, and after 1 day of printing, the gradation of the obtained image was visually observed. As a result, Examples 2 and 3 showed good gradation expression. In Examples 1 and 4 and Comparative Example 1, although the gradation expression is slightly inferior to that in Example 2, it was at a level where there is no problem in actual use. In Comparative Examples 2 to 4, the gradation was clearly poor in the evaluation.

It is a schematic sectional side view which shows an example of an inkjet recording device. FIG. 2 is a front sectional view of a liquid composition remaining amount display unit provided in the ink jet recording apparatus of FIG. 1. FIG. 2 is a schematic cross-sectional side view showing a liquid composition replenishment state in the ink jet recording apparatus of FIG. 1. FIG. 3 is a diagram illustrating an example of a configuration of a recording head. FIG. 3 is a diagram illustrating an example of a configuration of a recording head. FIG. 3 is a diagram illustrating an example of a configuration of a recording head. FIG. 3 is a diagram illustrating an example of a configuration of a recording head. FIG. 3 is a diagram illustrating an example of a configuration of a recording head. FIG. 3 is a diagram illustrating an example of a configuration of a recording head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording head 2 Carriage 3 Paper discharge roller 4 Spur 5 Paper discharge tray 6 Coating roller 7 Main conveyance roller 8 Pinch roller 9 Guide shaft 10 Paper feed roller 11 Platen 12 Intermediate roller 13 Supply roller 14 Float 15 Liquid composition 16 Paper feed cassette 17 Paper Tray 18 Spring 19 Recording Medium (Recording Paper)
20 Inlet 21 Remaining capacity display window 22 Replenishment tank 23 Injection machine 27 Paper guide

Claims (7)

Two water-based inks having the same color tone, containing at least water, a water-insoluble colorant, and a water-soluble organic solvent, and water contained in the water-based ink reacting with at least one of the water-based inks An inkjet recording method using a liquid composition containing a reactive component that aggregates or gels an insoluble colorant,
When the ink having a relatively low coagulation value between the liquid composition and the aqueous ink is the first aqueous ink and the highest ink is the second aqueous ink, the coagulation value of the first aqueous ink is 0. 5 or less,
An ink jet recording characterized by using a first water-based ink when recording a relatively high-density portion and using a second water-based ink when recording a relatively low-density portion. Method.   The inkjet recording method according to claim 1, wherein a difference in coagulation value between the first water-based ink and the second water-based ink with respect to the liquid composition is 0.4 or more.   The inkjet recording method according to claim 1 or 2, wherein the coagulation value of the second aqueous ink is 0.9 or more.   The inkjet recording method according to claim 1, wherein the content concentration of the coloring material of the first aqueous ink is higher than the content concentration of the coloring material of the second aqueous ink.   The inkjet recording method according to claim 1, wherein the liquid composition is applied to a recording medium prior to the water-based ink.   An ink cartridge containing the water-based ink according to any one of claims 1 to 5.   An ink jet recording apparatus comprising: an ink storage unit that stores the water-based ink according to claim 1; and an ink-jet head that discharges the water-based ink.

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