JP2004249716A - Image recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recording method which can improve ink absorption and ink fixation, i.e. drawbacks involved in image formation with a water dispersion type ink containing a water-insoluble colorant. <P>SOLUTION: In this image recording method, ink is deposited on a recording medium including at least one ink receiving layer on a support to form an image. Ink for inkjet recording includes a polymeric dispersant comprising a block copolymer containing at least one hydrophobic block and at least one hydrophilic block, a water-insoluble colorant, a water-soluble organic solvent, and water. The ink receiving layer contains inorganic fine particles and a water-soluble resin and/or a water-dispersible resin. Further, the pH value of the surface of the ink receiving layer is regulated to a range of 3.0 to 6.5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an image recording method optimal for an ink jet recording method. More specifically, a colorant-dispersed ink containing a polymer dispersant composed of a block copolymer composed of at least one hydrophobic block and at least one hydrophilic block has a surface pH of 3.0 to 3.0. The present invention relates to an image recording method in which an ink is fixed by adhering to a recording medium having an ink receiving layer adjusted to a range of 6.5 and aggregating and precipitating the polymer dispersant.

  The ink jet recording method is a recording method for recording an image, a character, or the like by flying fine droplets of ink according to various operating principles and attaching the droplets to a recording medium such as paper. In addition, the ink jet recording system is characterized in that it has excellent high-speed printing properties, low noise, and flexibility in recording patterns, can easily perform multicolor printing, and does not require development and image fixing. In particular, images formed by the multi-color ink jet method can be compared with multi-color printing by the plate making method or images printed by the color photographic method, and when the number of copies is small, a normal image can be obtained. In recent years, it has been rapidly popularized as an image recording device for various information devices, because it has an advantage that printing cost is lower than printing technology and photographic technology. For example, the multi-color inkjet system is widely used in fields that require full-color image recording, such as the output of image designs in the design industry, the production of color printing plates in the printing field where photographic quality is required, and signs and product samples that are frequently replaced. Has been applied.

  In addition, the spread of digital still cameras and computers has increased the opportunities for easily outputting photographic images with an inkjet printer. Against this background, images recorded by inkjet printers are required to have the same high resolution and clarity as silver halide photographs, and the demands for recording devices, recording media, and even inks are becoming higher. I have.

  At present, the mainstream inks used in ink jet printers are those that use a water-soluble dye having excellent coloring properties as a coloring material. However, since the water-soluble dye has high hydrophilicity, the dye forming the image bleeds when the image is recorded with the ink and stored for a long time under high humidity or when water droplets adhere to the recording surface. There was a tendency to go out. Further, when a water-soluble dye ink is used, a uniform image without unevenness can be obtained, particularly when a recording medium having a porous ink absorbing layer is used, but there is a problem that the image is easily discolored after recording. Was.

  In order to solve such a problem, a water-dispersible ink in which a water-insoluble colorant such as a pigment is dispersed in water using a hydrophilic polymer compound or a surfactant is being used. An image made of this ink is excellent in light fastness, water fastness, and ozone fastness, and thus has attracted attention as an ink replacing dye ink in terms of image fastness.

  However, water-dispersible inks containing pigments generally have a lower coloring efficiency than dye inks, and thus require a larger amount of ink for image recording. In other words, a recording medium having excellent ink absorption is required, but in order to improve the ink absorption, in a recording medium in which the ink receiving layer is simply thickened, the coloring material penetrates deeply into the ink receiving layer. On the other hand, in a recording medium in which the coloring property of the coloring material is inferior, the ink solvent overflows in the ink receiving layer, causing a problem such as image bleeding.

  In addition, when an image is formed on a recording medium having a smooth surface and a gloss, using a water-dispersible ink containing a pigment as a coloring material, the pigment particles cannot enter the ink receiving layer, and the pigment particles cannot enter the ink receiving layer. Are left on the surface, so that the scratch resistance of the image is reduced. Therefore, a method of providing irregularities on the surface of the ink receiving layer has been attempted, but this method does not provide sufficiently satisfactory results in ink absorbency during image formation and surface gloss of the obtained image.

  As a method for improving the ink fixing property of the ink receiving layer, many other methods have been disclosed in which a cationic polymer having a tertiary or quaternary ammonium salt is added to the ink receiving layer. However, in order to improve the ink fixability of the ink receiving layer, it is necessary to add a certain amount or more of a cationic polymer to the ink receiving layer, and the amount of the cationic polymer in the ink receiving layer increases. The content is relatively reduced, voids in the ink receiving layer are reduced, and it is difficult to ensure high ink absorbency. In addition, the cationic polymer may deteriorate the stability of the coating liquid for forming the ink receiving layer, and the tendency increases as the amount of the cationic polymer increases. And the smoothness of the surface of the ink receiving layer formed after the coating is deteriorated, and the glossiness is lowered.

  Therefore, another method has been proposed as a new technology. According to these methods, in order to improve the fixability and water resistance of a coloring material on a recording medium, two inks, an ink and an auxiliary liquid that generates aggregates when brought into contact with the ink, are used. Prior to the ejection of the ink, the auxiliary liquid for improving the fixing property of the ink is attached to the recording medium.

  For example, Patent Document 1 discloses a method in which a liquid containing an organic compound having two or more cationic groups per molecule is attached to a recording medium, and recording is performed with an ink containing an anionic dye there. Patent Literature 2 discloses a method in which an acidic liquid containing succinic acid or the like is attached to an ink receiving layer, and recording is performed using an ink containing an anionic dye. A method is disclosed in which a liquid to be insolubilized is attached prior to recording of ink. Patent Document 4 discloses a method in which a reaction liquid containing an anionic reactant and an anionic resin emulsion is attached to a recording medium, and then an aqueous ink composition containing a coloring material and a cationic resin emulsion is attached thereto. It has been disclosed.

  However, also in the above-mentioned method, if the ink absorbency of the recording medium is low, the viscosity of the ink is increased only on the surface of the recording medium, which causes a non-uniform distribution of the ink on the recording medium and a reduction in image uniformity. Further, the abrasion resistance of the formed image is reduced due to the difficulty in drying the image forming surface.For example, when an image is formed by continuous printing on a sheet of a recording medium and the There is a disadvantage that the recorded matter is stained due to ink set-off due to insufficient fixability. Further, the printer requires a discharge mechanism dedicated to the auxiliary liquid, which is disadvantageous in cost.

JP-A-63-29971 JP-A-64-9279 JP-A-64-63185 JP-A-2002-302627

  The present invention has been made in view of the above situation, and has improved ink absorbency and ink fixability, which have been disadvantages when forming an image with a water-dispersible ink containing a water-insoluble colorant. It is intended to provide an image recording method.

  The present inventors have conducted intensive studies on an image recording method capable of forming an image having a high color density and a good color tone, and in particular, as a result of intensive studies on an image recording method excellent in ink absorbency and ink fixability. An inkjet recording ink (hereinafter simply referred to as “ink”) containing a polymer dispersant comprising a block copolymer composed of one hydrophobic block and at least one hydrophilic block has a surface pH of 3.0. When the polymer dispersant adheres to the ink receiving layer adjusted to a range of from 6.5 to 6.5, it is found that the polymer dispersing agent rapidly agglomerates and precipitates, thereby improving the ink absorbency and the ink fixing property, thereby completing the present invention. Reached.

  That is, the present invention provides an image recording method for forming an image by attaching ink to a recording medium having at least one ink receiving layer provided on a support, wherein the ink comprises at least one hydrophobic block. An ink comprising a polymer dispersant comprising a block copolymer containing at least one hydrophilic block, a water-insoluble colorant, a water-soluble organic solvent and water, and wherein the ink-receiving layer comprises inorganic fine particles. And a water-soluble resin and / or a water-dispersible resin, and wherein the surface pH of the ink-receiving layer is controlled in the range of 3.0 to 6.5.

  In the present invention, the ink receiving layer further contains cationic organic fine particles and / or a cationic polymer; the content of the cationic organic fine particles in the ink receiving layer is determined based on the dry mass of the ink receiving layer. 0.1 to 25% by mass; the weight average molecular weight of the cationic organic fine particles is 100,000 to 1,000,000; and the cationic organic fine particles have a glass transition temperature of 60 to 110 ° C. The weight average molecular weight of the cationic polymer is 5,000 to 200,000; and the amount of the cationic polymer used is 0.05 to 5% by mass based on the inorganic fine particles. It is preferable that

  Further, in the present invention, the inorganic fine particles are made of at least one kind of alumina hydrate having an average particle diameter of 100 to 300 nm, silica, alumina, boehmite structure or pseudo-boehmite structure; Further, a water-soluble polyvalent metal salt is contained; the amount of the water-soluble polyvalent metal salt used is 0.1 to 10% by mass based on the inorganic fine particles; At least one selected from the group consisting of oil-soluble dyes, vat dyes and disperse dyes; and the polymer dispersant is a block copolymer obtained by polymerizing vinyl ethers as a monomer, and It is preferable that the polymer chains have a pH stimulus responsiveness that can cause an association of the polymer chains due to a decrease in pH.

  An image recording method for forming an image by attaching an ink to a recording medium having at least one ink receiving layer provided on a support, wherein the ink comprises at least one hydrophobic block and at least one hydrophilic And a water-insoluble coloring material, a water-soluble organic solvent and water, and the ink receiving layer is composed of inorganic fine particles, a water-soluble resin and / or a water-soluble resin. Alternatively, by using a recording medium containing a water-dispersible resin (and may further contain other components), and further having a surface pH of the ink receiving layer controlled in a range of 3.0 to 6.5, It is possible to provide an image recording method excellent in ink absorption and ink fixability.

Next, the present invention will be described in more detail with reference to preferred embodiments.
The ink used in the present invention includes a polymer dispersant comprising a block copolymer containing at least one hydrophobic block and at least one hydrophilic block, a water-insoluble colorant, a water-soluble organic solvent, and water. The polymer dispersant preferably has a pH stimulus responsiveness such that a polymer chain associates when the pH of the ink decreases.

  According to the present invention, by using a block copolymer containing at least one hydrophobic block and at least one hydrophilic block as the polymer dispersant, the hydrophobic part of the polymer dispersant is colored. The colorant particles can be uniformly attached to the surface of the colorant particles, so that the polymer dispersant can uniformly coat the colorant particles, that is, encapsulate the colorant particles without exposing the colorant particles to the outside. As a result, even in a printed image after recording, since the coloring material is protected by the capsule of the polymer dispersant, a case where a part of the coloring material particles is originally exposed to the outside or when the ink is ejected. It is considered that the robustness of the coloring material is improved as compared with the case where a part of the surface of the coloring material particles is exposed.

Further, since the hydrophilic portion of the polymer dispersant is blocked, the affinity between the polymer dispersant and the ink medium is improved, and the high molecular weight of the polymer obtained by random polymerization containing a hydrophobic group in the hydrophilic portion is improved. It is considered that the dispersion stability of the colorant-dispersed particles is greatly improved as compared with the case where the molecular dispersant is used. Accordingly, it is considered that aggregation and settling of the colorant-dispersed particles in the ink hardly occur, and that not only the stability of the ink ejection but also the stability of the ink during storage is improved.
Hereinafter, the constituent materials of the ink according to the present invention will be described in detail.

(Polymer dispersant)
In the present invention, the polymer dispersant used in the ink may be a block copolymer having at least one hydrophilic block and at least one hydrophobic block, and one or more hydrophilic blocks. Those having two or more hydrophobic blocks, or those having two or more hydrophilic blocks and one or more hydrophobic blocks can also be used. In this case, two or more hydrophilic blocks and / or two or more hydrophilic blocks can be used. The above hydrophobic blocks may be the same or different. A single block copolymer or a mixture of two or more block copolymers can be used. Examples of the form of the copolymer include a linear type and a graft type, and a linear type block copolymer is preferable.

  The polymer dispersant having a polyvinyl ether structure obtained by polymerizing vinyl ethers as a monomer is preferable because it forms a stable dispersion with the colorant particles. Among them, at least one hydrophilic block of the polymer dispersant is a block of an anionic polyvinyl ether, or a diblock composed of a block of a nonionic polyvinyl ether and a block of an anionic polyvinyl ether. The polymer dispersant is more preferable because the stability of the colorant-dispersed particles in the ink medium is further improved. In the case where at least one hydrophilic block of the polymer dispersant is a diblock body composed of a block of a nonionic polyvinyl ether and a block of an anionic polyvinyl ether, When the block copolymer is composed of a block-a block of nonionic hydrophilic polyvinyl ether-a block of anionic hydrophilic polyvinyl ether, the coloring material dispersed particles in the ink medium are It is more desirable because the stability is further improved.

As the block of the hydrophobic polyvinyl ether forming the polymer dispersant, a block having a repeating unit structure represented by the following general formula (1) is preferable.
-(CH ₂ -CH (OR ¹ ))-(1)
In the above general formula (1), R ¹ represents an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group, a cycloalkyl group or a cycloalkenyl group, a phenyl group, a pyridyl group, a benzyl group, a toluyl group, a xylyl group, Represents an aromatic hydrocarbon group in which a carbon atom may be substituted with a nitrogen atom, such as an alkylphenyl group, a phenylalkyl group, a biphenyl group, a phenylpyridyl group and the like. Moreover, the hydrogen atom on the aromatic ring may be substituted with a hydrocarbon group. The carbon number of R ¹ is preferably 1 to 18.

R ¹ may be a group represented by — (CH (R ² ) —CH (R ³ ) —O) _p —R ⁴ or — (CH ₂ ) _m — (O) _n —R ⁴ . In this case, R ² and R ³ each independently represent a hydrogen atom or a methyl group, and R ⁴ represents an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group, a cycloalkyl group or a cycloalkenyl group, a phenyl group, a pyridyl group. An aromatic hydrocarbon group in which a carbon atom may be substituted by a nitrogen atom such as a benzyl group, a toluyl group, a xylyl group, an alkylphenyl group, a phenylalkyl group, a biphenyl group and a phenylpyridyl group hydrogen atoms may be substituted with a hydrocarbon group), - CO-CH = CH 2, -CO-C (CH 3) = CH 2, -CH 2 -CH = CH 2, -CH 2 - It represents C (CH ₃ ) ＣＨCH _2, and a hydrogen atom in these groups may be substituted with a halogen atom such as a fluorine, chlorine, or bromine atom to the extent chemically possible. The number of carbon atoms of R ⁴ is 1 to 18 is preferred. p is preferably 1 to 18, m is preferably 1 to 36, and n is preferably 0 or 1.

In R ¹ and R ⁴ , examples of the alkyl group or alkenyl group include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, Examples thereof include dodecyl, tetradecyl, hexadecyl, octadecyl, and oleyl. Examples of the cycloalkyl group or cycloalkenyl group include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclooctyl.

Next, as the block of the vinyl ether having hydrophilicity, a block having a repeating unit structure represented by the following general formula (2) is preferable.
-(CH ₂ -CH (OR ⁵ ))-(2)
In the above general formula (2), R ⁵ _{is, - (CH 2 -CH 2 -O} ) k -R 6, - (CH 2) m - (O) n -R 6, -R 7 -X, - It is a group represented by (CH ₂ —CH ₂ —O) _k —R ⁷ —X and — (CH ₂ ) _m — (O) _n —X. In this case, R ⁶ is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, and —CO—CH ＝ CH ₂ , —CO—C (CH ₃ ) ＝ CH ₂ , —CH ₂ -CH = CH _2, represents _{-CH 2 -C (CH 3) =} CH 2, R 7 is an alkylene group, an alkenylene group, an aliphatic hydrocarbon group such as cycloalkylene group or cycloalkenylene group, a phenylene group, Aromatic hydrocarbon groups in which carbon atoms may be substituted by nitrogen atoms, such as pyridylene groups, benzylene groups, toluylene groups, xylylene groups, alkylphenylene groups, phenylenealkylene groups, biphenylene groups, phenylpyridylene groups and the like ( The hydrogen atom on the aromatic ring may be substituted with a hydrocarbon group), and the hydrogen atom in these groups is fluorine, chlorine, odor or the like as far as it is chemically possible. It may be substituted with a halogen atom such as atomic. X represents an anionic group selected from a carboxylic acid group, a sulfonic acid group and a phosphoric acid group. The carbon number of R ⁷ is preferably 1 to 18. k is preferably 1 to 18, m is preferably 1 to 36, and n is preferably 0 or 1.

  The structures of the above monomers (Ia to Io) and the block copolymers (II-a to II-e) composed of the above monomers are exemplified below, and the structure of the block copolymer used in the present invention is as follows. Is not limited to these.

  Further, the number of repeating units of the block copolymer (m, n, and l in the above-described exemplified repeating units (II-a) to (II-e)) is independently 1 to 10,000. Is preferred. Further, the total is more preferably (m + n + 1 in (II-a) to (II-e)) and 10 to 20,000. The number average molecular weight is preferably from 500 to 20,000,000, more preferably from 1,000 to 5,000,000, and most preferably from 2,000 to 2,000,000.

  The proportion of these polymer dispersants in the ink is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, based on the total mass of the ink. The average particle size of the dispersed particles of the water-insoluble colorant dispersed by the polymer dispersant is desirably 80 nm or less.

  In the present invention, the pH stimulus responsiveness of the polymer dispersant used in the ink is such that the polymer chains of the polymer dispersant are associated with each other due to a decrease in the pH of the ink, and a property of increasing the viscosity of the ink. It has. Above all, when the pH stimulus responsiveness is a stimulus responsiveness that increases the ink viscosity after the pH stimulus response to preferably 50 times or more, more preferably 100 times or more the ink viscosity before the pH stimulus response, The fixability is improved.

(Water-insoluble colorant)
In the present invention, as the coloring material used for the ink, any coloring material that hardly dissolves in water can be used. Specifically, the coloring material has a solubility in water of preferably 0.5% by mass or less, more preferably 0.1% by mass or less. Examples of such coloring materials include oil-soluble dyes, vat dyes, disperse dyes, pigments, and the like. Among them, oil-soluble dyes are more preferable because they form a stable colorant dispersion with the polymer dispersant.

Hereinafter, examples of the water-insoluble coloring material will be described, but the present invention is not limited thereto.
(Oil-soluble dye)
C. I. Solvent Yellow 1, 2, 3, 13, 14, 19, 22, 29, 36, 37, 38, 39, 40, 43, 44, 45, 47, 62, 63, 71, 76, 81, 85, 86; C. I. Solvent Red 27, 35, 36, 37, 38, 39, 40, 58, 60, 65, 69, 81, 86, 89, 91, 92, 97, 99, 100, 109, 118, 119, 122; I. Solvent Blue 14, 24, 25, 26, 34, 37, 39, 42, 43, 45, 48, 52, 53, 55, 59; I. Solvent Black 5, 7, 8, 14, 17, 19, 20, 22, 24, 26, 28, 43 and the like.

(Vat dye)
C. I. Bat yellow 2, 4, 10, 20, 33; I. Bat orange 1, 2, 3, 5, 7, 9, 13, 15; I. Butt Red 1, 2, 10, 13, 15, 16, 61; I. Bat blue 1, 3, 4, 5, 6, 8, 12, 14, 18, 19, 20, 29, 35, 41; I. Bat Black 1, 8, 9, 13, 14, 20, 25, 27, 29, 36, 56, 57, 59, 60 and the like.

(Disperse dye)
C. I. Disperse Yellow 5, 42, 83, 93, 99, 198, 224; I. Disperse Orange 29, 49, 73; C.I. I. Disperse Red 92, 126, 145, 152, 159, 177, 181, 206, 283; I. Disperse Blue 60, 87, 128, 154, 201, 214, 224, 257, 287, 368, etc.

(Pigment)
Raven-760 Ultra, -1060 Ultra, -1080, -1100 Ultra, -1170, -1200, -1250, -1255, -1500, -2000, -2500 Ultra, -3500, -5250, -5750, -7000, -5000 ULTRA-II, -1190 ULTRA-II (trade name, manufactured by Columbian Carbon Co., Ltd.); Black Pearls-L, MOGUL-L, RegaL-400R, -660R, -330R, Monarch-800, -880,- 900, -1000, -1300, -1400 (trade name, manufactured by Cabot Corporation);
Color Black-FW1, -FW2, -FW200, -18, -S160, -S170, Special Black-4, -4A, -6, -550, Printex-35, -45, -55, -85, -95, -U, -140U, -V, -140V (trade name, manufactured by Degussa);
No. 25, no. 33, no. 40, no. 45, no. 47, no. 52, no. 900, No. 970, no. 2200B, No. 2300, no. 2400B, MCF-88, MA600, MA77, MA8, MA100, MA230, MA220 (trade name, manufactured by Mitsubishi Chemical Corporation);
C. 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; I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71; 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; I. Pigment Violet 19, 23, 29, 30, 37, 40, 50; I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64; I. Pigment Green 7, 36; C.I. I. Pigment Brown 23, 25, 26, etc.

  The content of the water-insoluble coloring material in the ink used in the present invention is preferably 0.1 to 20% by mass, more preferably 1.0 to 10% by mass, based on the total mass of the ink. If the amount of the water-insoluble coloring material is less than 0.1% by mass, it may be difficult to obtain a sufficient color density. If the amount of the ink exceeds 20% by mass, the ejection stability is reduced due to clogging of the ink in the nozzles. Is more likely to occur. When the content ratio of the water-insoluble colorant (A) and the polymer dispersant (B) in the ink is A: B = 100: 1 to 1: 2 in terms of the solid content mass ratio, the ink ejection is performed. It is desirable from the viewpoint of stability and storage stability. In addition, these water-insoluble colorants can be used alone or in combination of two or more.

(Water-soluble organic solvent)
As the water-soluble organic solvent in the ink used in the present invention, any organic solvent can be used as long as it is water-soluble, and it can be used as a mixed solvent of two or more water-soluble organic solvents. When used as such a mixed solvent, a solid water-soluble organic compound may be contained as long as the mixed solvent is liquid.

Above all, the water-soluble organic solvent has a solubility parameter in the range of 0.0 to +10.0 (J / cm ³ ) ^1/2 with respect to the solubility parameter of the hydrophilic block portion of the polymer dispersant. A water-soluble organic solvent is preferred because clogging of the nozzles of the inkjet head is less likely to occur. This solubility parameter (δ (J / cm ³ ) ^1/2 ) is expressed as the square root of the cohesive energy density of the solvent, where δ = (ΔE / V) ^1/2 (where ΔE is the molar evaporation of the solvent) Heat, V is a solvent-specific value calculated from the formula of the solvent, which is the solubility of the solvent. For example, δ = 47.0 for water, δ = 25.7 for ethanol, and δ for hexane. = 14.9.

Further, the solubility parameter (δ) of the polymer dispersant is a value calculated experimentally assuming that the solubility parameter of the solvent giving the infinite solubility or the maximum swelling degree of the polymer dispersant = the solubility parameter of the polymer dispersant. And a value calculated from the molecular aggregation energy of the functional group of the polymer dispersant. As the solubility parameter of the polymer dispersant and the water-soluble organic solvent in the present invention, a value calculated from the molecular aggregation energy of the functional groups of the polymer dispersant and the water-soluble organic solvent is used. Method for calculating the polymeric dispersing agent and a solubility parameter of the water-soluble organic solvent ([delta]) from the molecular cohesive energy of functional groups, respectively, δ = (ΔE / V) 1/2 = (ΣΔe i / ΣΔv i) 1 ^{/ 2} (wherein, Delta] E is the molar heat of vaporization, V is the respective molar volume, .DELTA.e _i is an atomic group evaporation energy (J / mol), Δv _i is the molar volume of the atomic group (cm ³ / mol). )). In addition, the evaporation energy of each atomic group and the molar volume of each atomic group were calculated using the value of Fedors.

  Examples of such a water-soluble organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol and tert-butyl alcohol; ethylene glycol, diethylene glycol , Triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, thiodiglycol, 1,4-cyclohexane Diols such as diols; triols such as glycerin, 1,2,4-butanetriol, 1,2,6-hexanetriol and 1,2,5-pentanetriol; Hindered alcohols such as bread, trimethylolethane, neopentyl glycol, and pentaerythritol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether Glycol ethers such as triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether; dimethyl sulfoxide, glycerin monoallyl ether, polyethylene glycol, N-methyl-2- Pyrrolidone, 2-pyrrolidone, γ-butyrola Octone, 1,3-dimethyl-2-imidazolidinone, sulfolane, β-dihydroxyethylurea, urea, acetonylacetone, dimethylformamide, dimethylacetamide, acetone, diacetone alcohol, tetrahydrofuran, dioxane and the like.

  Among them, it is preferable to use a water-soluble organic solvent having a boiling point of 120 ° C. or more, because ink concentration at the nozzle tip is suppressed. The proportion of these water-soluble organic solvents in the ink is preferably 5 to 50% by mass, more preferably 10 to 30% by mass, based on the total mass of the ink.

  The above are the constituent materials of the ink used in the present invention. In addition to these materials, various additives such as a surfactant, a pH adjuster, an antioxidant, and a fungicide may be added.

(Recording medium)
On the other hand, the basic configuration of the recording medium used in the present invention is that at least one ink receiving layer is provided on a support, and the ink receiving layer contains inorganic fine particles and a water-soluble resin and / or a water-dispersible resin. In addition, the surface pH of the ink receiving layer is controlled in the range of 3.0 to 6.5.

(Support)
Examples of the support of the recording medium in the present invention include, for example, appropriately sized paper, unsized paper, coated paper, cast-coated paper, and resin-coated paper in which both sides of the paper are coated with a resin such as polyolefin ( (Hereinafter referred to as resin-coated paper); transparent thermoplastics such as polyethylene, polypropylene, polyester, polylactic acid, polystyrene, polyacetate, polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polymethyl methacrylate and polycarbonate. A film made of a resin; a sheet-like material (synthetic paper or the like) made of a film made opaque by filling with an inorganic substance or fine foam; and a sheet made of glass or metal.

  In the present invention, the ink receiving layer is formed on the support. From the viewpoint of increasing the gloss of the surface of the ink receiving layer, it is preferable to use a non-water-absorbing, highly smooth resin-coated paper and film. Preferably, it can be used without any problem as long as the surface on which the ink receiving layer is formed has a 60 ° specular glossiness of 5% or more according to JIS Z8741. Further, in order to improve the adhesive strength between the support and the ink receiving layer, the surface of the support can be subjected to corona discharge treatment or various undercoat treatments.

(Inorganic fine particles)
In the present invention, the inorganic fine particles contained in the ink receiving layer of the recording medium are preferably inorganic fine particles having a high ink absorbing ability, excellent color development, and capable of forming a high-quality image. As such inorganic fine particles, for example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, hydrotalcite, aluminum silicate, calcium silicate, magnesium silicate, diatomaceous earth, alumina, colloidal alumina, aluminum hydroxide, boehmite structure Alumina hydrate, alumina hydrate having a pseudo-boehmite structure, synthetic amorphous silica, colloidal silica, lithopone, zeolite and the like can be mentioned, and these can be used alone or in combination of two or more. Among them, silica, alumina, and alumina hydrate having a boehmite structure or a pseudo-boehmite structure having the following average particle diameters are more preferably used.

  The form of the inorganic fine particles is preferably in the range of 100 to 300 nm, more preferably in the range of 150 to 250 nm, for imparting appropriate gloss and transparency to the ink receiving layer. When the average particle diameter of the inorganic fine particles is smaller than 100 nm, the ink absorbency in the ink receiving layer is reduced, and bleeding occurs in an image formed when printing with a printer having a large amount of ejected ink or a high-speed output printer. Beading occurs. On the other hand, when the average particle size is larger than 300 nm, the transparency of the ink receiving layer may be lowered and the gloss may be lowered. When the ink receiving layer in the present invention is composed of multiple layers, the type and form of the inorganic fine particles used for each layer may be the same or different.

  The particle diameter of the inorganic fine particles is measured by a dynamic light scattering method, and is described in “Polymer Structure (2) Scattering Experiment and Morphological Observation Chapter 1 Light Scattering” (edited by Kyoritsu Shuppan Polymer Society) or J. Chem.Phys. , 70 (B), 15 Appl., 3965 (1979), and can be obtained as an average hydrodynamic particle diameter from the analysis using the cumulant method. Actually, for example, it can be easily measured using a laser particle size analyzer PARIII (trade name, manufactured by Otsuka Electronics Co., Ltd.). Hereinafter, the “inorganic fine particles” will be described mainly with alumina hydrate as a typical example.

In the present invention, as the alumina hydrate used for the ink receiving layer of the recording medium, those represented by the following general formula (3) can be used.
Al ₂ O _3-n (OH) _2n · mH ₂ O (3)
In the formula, n represents an integer of 0, 1, 2 or 3, and m represents a value of 0 to 10, preferably 0 to 5. Since mH ₂ O often represents a detachable aqueous phase that does not participate in the formation of a crystal lattice, m can take a non-integer value. Further, when this type of alumina hydrate is calcined, m may reach a value of 0 in some cases.

  In general, alumina hydrate having a boehmite structure is a layered compound whose (020) crystal plane forms a giant plane, and shows a diffraction peak specific to an X-ray diffraction pattern. The boehmite structure includes a structure called "pseudo-boehmite" in which excess water is contained between layers on the (020) plane in addition to complete boehmite. The X-ray diffraction pattern of this pseudo-boehmite shows a broader diffraction peak than perfect boehmite. Since complete boehmite and pseudo-boehmite cannot be clearly distinguished, hereinafter, unless otherwise specified, they are referred to as alumina hydrate showing a boehmite structure including both.

(Water-soluble resin and / or water-dispersible resin)
In the present invention, examples of the water-soluble resin and / or water-dispersible resin contained in the ink receiving layer include starch, gelatin, casein and modified products thereof, cellulose derivatives such as methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose; Or partially saponified polyvinyl alcohol or a modified product thereof (cation modified, anion modified, silanol modified, etc.), urea resin, melamine resin, epoxy resin, epichlorohydrin resin, polyurethane resin, polyethylene imine resin, polyamide resin Resin, polyvinylpyrrolidone-based resin, polyvinylbutyral-based resin, poly (meth) acrylic acid or its copolymer, acrylamide-based resin, maleic anhydride-based copolymer, polyester-based resin, SBR latex, N R latex, methyl methacrylate-butadiene copolymer latex, acrylic polymer latex such as acrylate copolymer, vinyl polymer latex such as ethylene-vinyl acetate copolymer, and cations to these various polymer latexes Functional group-modified polymer latexes having a functional group or an anionic group.

  Preferred is polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate and having an average degree of polymerization of 300 to 5,000. The saponification degree is preferably from 70 to less than 100 mol%, particularly preferably from 80 to 99.5 mol%. These water-soluble resins and / or water-dispersible resins can be used alone or as a mixture of two or more.

  The use amount of the water-soluble resin and / or the water-dispersible resin (A) is preferably A: B = 1: 30 to 1: 1 in terms of a mixing mass ratio to the alumina hydrate (B), and more preferably A: B. = 1: 20 to 1: 3. When the amount of the water-soluble resin and / or the water-dispersible resin is within these ranges, the formed ink receiving layer is less likely to crack or fall off, and has good ink absorbency.

  In the present invention, the surface pH of the ink receiving layer of the recording medium is in the range of 3.0 to 6.5. Preferably, the surface pH of the ink receiving layer is in the range of 3.0 to 6.0. When the surface pH of the ink receiving layer is less than 3.0, a device used for forming the ink receiving layer, such as a coating machine and a dryer, may corrode, which is not practical. Further, when the surface pH of the ink receiving layer is higher than 6.5, it is not preferable because the responsiveness to pH stimulation of the polymer dispersant in the ink may not be sufficiently exhibited.

In the present invention, various acids can be used to adjust the pH of the surface of the ink receiving layer to pH 3.0 to 6.5. Such acids include formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, malonic acid, succinic acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid Organic acids such as acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, pimelic acid, and suberic acid; and inorganic acids such as hydrochloric acid, nitric acid, and phosphoric acid. They can be used in combination.
In the present invention, the surface pH refers to J. TAPPI paper pulp test method No. According to the method described in No. 49, the value measured after 30 seconds using ion-exchanged water having a pH of 6.7.

(Cationic organic fine particles)
In the present invention, the ink receiving layer preferably contains cationic organic fine particles. By containing the cationic organic fine particles, the porosity in the ink receiving layer is increased, the ink absorbency can be increased, and the ink is fixed by bonding the polymer dispersant contained in the ink to the hydrophilic block. Performance can be improved. As the cationic organic fine particles used in the present invention, for example, fine particles composed of a polymer compound having a cationic group such as an amino group and / or an amidino group are preferable. Such a polymer compound is composed of a monomer having a cationic functional group and a monomer copolymerizable therewith.

  Examples of the monomer having a cationic functional group include a (meth) acrylate monomer having an amino group represented by the following general formula (4) and an amino group represented by the following general formula (5). (Meth) acrylamide-based monomers and the like. The monomers represented by the general formulas (4) and (5) may be N-alkyl-substituted or N, N-dialkyl-substituted monomers, and may be quaternized with a halogenated hydrocarbon or the like. May be. Generally, it is preferable to use an N, N-dialkyl-substituted product or a quaternary-chlorinated N, N-dialkyl-substituted product, and these can be used alone or in combination of two or more.

（式中、Ｒ¹は水素原子或いはメチル基を表わす。またＲ²およびＲ³は、それぞれ水素原子或いは炭素数１〜４までのアルキル基を表わし、Ｒ²およびＲ³は、それぞれ同じであっても異なっていてもよい。また、Ｘは炭素数２〜１８までのアルキレン基を表わす。）

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² and R ³ each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ² and R ³ are the same. And X represents an alkylene group having 2 to 18 carbon atoms.)

（式中、Ｒ¹は水素原子或いはメチル基を表わし、Ｒ²およびＲ³は、炭素数１〜４までのアルキル基を表わす。Ｒ²およびＲ³はそれぞれ同じであっても異なっていてもよい。また、Ｘは炭素数２〜１８までのアルキレン基を示す。）

(Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² and R ³ represent an alkyl group having 1 to 4 carbon atoms. R ² and R ³ may be the same or different. X is an alkylene group having 2 to 18 carbon atoms.)

  As the monomer copolymerizable with the monomer having a cationic functional group described above, any monomer may be used as long as it is an unsaturated monomer other than the compounds represented by the general formulas (4) and (5). The cationic organic fine particles used in the present invention can use at least an acrylate, a methacrylate, and a styrene derivative as monomers. More specifically, it is a monomer represented by the following general formulas (6) and (7). In particular, the cationic organic fine particles suitable for the present invention are those comprising the above-mentioned monomer having a cationic functional group and a cationic acrylic copolymer emulsion resin obtained from acrylate, methacrylate and / or styrene derivative. It is.

（式中、Ｒ¹は水素原子或いはメチル基を表わす。また、Ｒ²は、炭素数２〜１８までのアルキル基、シクロヘキシル基、フェニル基、ベンジル基、グリシジル基、および−Ｒ³ＯＲ⁴で表わされる基（ただし、Ｒ³は、炭素数２〜４のアルキレン基、Ｒ⁴は水素原子或いは炭素数１〜４のアルキル基である）を表わす。）

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² represents an alkyl group having 2 to 18 carbon atoms, a cyclohexyl group, a phenyl group, a benzyl group, a glycidyl group, and —R ³ OR ⁴ . (Where R ³ represents an alkylene group having 2 to 4 carbon atoms, and R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms).

（式中、Ｒ¹は水素原子、炭素数１〜４のアルキル基を表わす。また、Ｒ²〜Ｒ⁶は水素原子、塩素原子、炭素数１〜４のアルキル基、アルコキシ基、ビニル基を表わす。）

(Wherein, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ^{2 to} R ⁶ represent a hydrogen atom, a chlorine atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a vinyl group. Show.)

  As a method for imparting cationicity to the organic fine particles used in the present invention, an initiator containing an amidino group can be used in addition to using the monomers of the above-mentioned general formulas (4) and (5). Examples of the initiator containing an amidino group include 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (N-phenylamidino) propane] dihydrochloride, 2,2 '-Azobis {2- [N- (4-chlorophenyl) amidino] propane} dihydrochloride, 2,2'-azobis {2- [N- (4-hydroxyphenyl) amidino] propane} dihydrochloride, 2, 2'-azobis [2- (N-benzylamidino) propane] dihydrochloride, 2,2'-azobis [2- (N-allylamidino) propane] dihydrochloride, 2,2'-azobis {2- [ N- (2-hydroxyethyl) amidino] propane dihydrochloride and the like, and one or more of these can be selected.

  Examples of the monomer that can be polymerized or copolymerized using the amidino group-containing initiator include the above-mentioned monomers having a cationic functional group represented by the general formulas (4) and (5) and the monomers represented by the general formulas (6) and (7). And copolymerizable monomers.

  Further, the cationic organic fine particles used in the present invention may be copolymerized with a compound having an ultraviolet absorbing ability or a light stabilizing function, if necessary. For example, 2- (2'-hydroxy-5'-methacryloyloxyethylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-methacryloyloxyphenyl) -benzotriazole, 2- (2'-hydroxy -5'-methacryloyloxyphenyl) -5-chlorobenzotriazole, 2-hydroxy-4- (2-methacryloyloxy) ethoxybenzophenone, and the like. One or more of these may be selected and used. Can be.

  The weight average molecular weight of the cationic organic fine particles used in the present invention is preferably 60,000 or more, more preferably 100,000 to 1,000,000. If the weight average molecular weight is less than 60,000, the cationic organic fine particles are likely to be deformed, the porosity between the fine particles is reduced, and the ink absorbency may be reduced.

  The weight average particle diameter of the cationic organic fine particles used in the present invention can be measured by a dynamic light scattering method, as a preferred range of 10 to 300 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. It is. When the weight average particle size is less than 10 nm, there is a problem that the space between the fine particles is insufficient, the ink absorbency is insufficient, and the drying property and the image quality are deteriorated. Further, when the weight average particle diameter is larger than 300 nm, the transparency of the layer containing the cationic organic fine particles is reduced, the visibility of the coloring material in or under the layer is reduced, and the color density is reduced. Occurs.

  The cationic organic fine particles used in the present invention preferably have a glass transition temperature of 40 ° C or higher, more preferably 60 to 110 ° C. If the glass transition temperature is lower than 40 ° C., the cationic organic fine particles may be fused or formed into a film during the drying process after coating, and the porosity between the fine particles may be reduced, thereby lowering the ink absorbency. The above-mentioned glass transition temperature can be determined from a DSC curve measured by a differential scanning calorimeter based on JIS K 7121.

  The cationic organic fine particles used in the present invention can be produced by a conventionally known emulsion polymerization method or mechanical emulsification method. For example, in the emulsion polymerization method, one or more monomers are charged at once and polymerized in the presence of a dispersant and an initiator. Polymerization can be carried out while continuously supplying one or more monomers to obtain an aqueous dispersion of substantially organic fine particles, generally called an emulsion.

  In the present invention, the amount of the cationic organic fine particles used in the recording medium is preferably from 0.1 to 25% by mass, more preferably from 1 to 25% by mass, based on the dry mass of the ink receiving layer. Further, the mixing amount with respect to the inorganic fine particles is preferably in the range of 1 to 30% by mass, and more preferably in the range of 5 to 30% by mass. Within this range, the coating suitability is not adversely affected, and the ink absorbency and ink fixability of the recorded image can be effectively improved.

(Cationic polymer)
The ink receiving layer in the invention preferably contains the inorganic fine particles, a water-soluble resin and / or a water-dispersible resin, cationic organic fine particles and / or a cationic polymer. The cationic polymer used in the present invention dissociates when dissolved or dispersed in water to exhibit cationicity, and is preferably a primary to tertiary amine or quaternary ammonium salt oligomer or polymer. Such cationic polymers include, for example, dimethylamine / epichlorohydrin polycondensate, acrylamide / diallylamine copolymer, polyvinylamine copolymer, dicyandiamide, or a polymer mainly composed of dimethyldiallyl / ammonium chloride. Can be

  The arrangement of the monomer units in the polymer chain of the polycondensate or copolymer is not particularly limited, and may be any of a random copolymer, an alternating copolymer, a block copolymer, and a multi-block copolymer. The structure may be used. The molecular weight and the molecular weight distribution are not particularly limited, but the weight average molecular weight is preferably 5,000 to 200,000 in consideration of the viscosity of an aqueous solution or aqueous dispersion.

  The amount of the cationic polymer used in the present invention is preferably 0.05 to 5% by mass based on the inorganic fine particles. When the amount used is less than 0.05% by mass, there is no effect on the ink fixing property, and when the amount used exceeds 5% by mass, the content of the inorganic fine particles is relatively reduced, and the porosity is reduced. And the ink absorbency decreases. Further, with such a large amount of use, the viscosity of the coating liquid for forming the ink receiving layer increases. Therefore, use amounts outside the above range are not preferred.

(Water-soluble polyvalent metal salt)
In the present invention, the water-soluble polyvalent metal salt contained in the ink receiving layer is preferably a divalent or higher valent metal salt. In the case of a monovalent metal salt such as Na or K, since it has little effect on the polymer dispersant, it must be used in a large amount in order to obtain the same effect as the polyvalent metal salt. Therefore, the properties of the coating liquid and the properties of the recording paper are adversely affected.

Examples of the metal of the water-soluble polyvalent metal salt include Mg, Zn, Al, Ca, Ba, Cu, Fe, Ni, Pb, and Co. Cl, NO ₃ , I, Br, ClO ₃ , and SO ₄ And those forming a salt with anions such as COO. Above all, Ni, Pb, Co salts and the like are highly toxic, and therefore, Mg, Zn, Al, Ca, Ba, Cu, Fe salts and the like, which have low toxicity and are relatively easy to handle, are particularly preferable. These polyvalent metal salts may be used alone or in combination of two or more. In this case, different metals may be used, or a combination of different salts of the same metal such as a sulfate and a chloride of the same metal may be used.

  The amount of the water-soluble polyvalent metal salt to be used is preferably 0.1 to 10% by mass relative to the inorganic fine particles, more preferably 0.1 to 8% by mass. In the case of a recording medium having a water-soluble polyvalent metal salt content of less than 0.1% by mass, the ink fixing property is insufficient due to a weak action on the polymer dispersant, and recording is performed when the recording medium is laminated by continuous printing. Things may get dirty. On the other hand, a recording medium exceeding 10% by mass is not preferable because it adversely affects coating suitability.

(Hardener)
In the present invention, it is preferable to use a hardener in order to improve the film forming property, water resistance and film strength of the film formed by the water-soluble resin and / or the water-dispersible resin. In general, the hardener is selected from various ones depending on the type of the reactive group of the resin to be used. For example, in the case of a polyvinyl alcohol-based resin, an epoxy-based hardener, boric acid or a water-soluble aluminum salt is used. Examples of the hardening agent used in the present invention include a boron compound such as an oxyacid having a boron atom as a central atom or a salt thereof, specifically, orthoboric acid and metaborate. Acids, hypoboric acid, tetraboric acid, pentaboric acid and salts thereof can be preferably used.

  The amount of the boron compound as described above varies depending on the amount of the water-soluble resin and / or the water-dispersible resin used as the binder, but is generally 0.1 to 30 with respect to the water-soluble resin and / or the water-dispersible resin. It is advisable to add at a ratio of mass%. If the content of the boron compound is less than 0.1% by mass with respect to the water-soluble resin and / or the water-dispersible resin, the film-forming properties of the ink receiving layer may be reduced and sufficient water resistance may not be obtained. . On the other hand, when the amount exceeds 30% by mass, the viscosity of the coating liquid for forming the ink receiving layer greatly changes with time, and the coating stability may be poor.

  The recording medium used in the present invention is prepared by preparing a coating liquid containing inorganic fine particles, a water-soluble resin and / or a water-dispersible resin, and other optional components such as cationic organic fine particles and / or a cationic polymer. The coating liquid is obtained by applying and drying the coating liquid as at least one of a surface of a support or a multilayer formed on the support to form an ink receiving layer. Further, the above-mentioned acid for adjusting the surface of the ink receiving layer to pH 3.0 to 6.5 may be added to the coating liquid or overcoated on the ink receiving layer.

  The aqueous medium of the coating liquid for forming the ink receiving layer in the present invention is not particularly limited as long as it is water or a mixed solution of water and an organic solvent that can be mixed with water. Examples of water-miscible organic solvents include alcohols such as methanol, ethanol and propanol: lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether: ketones such as acetone and methyl ethyl ketone: tetrahydrofuran Ethers and the like.

  Various additives can be blended within a range that does not impair the effects of the present invention. Examples of such additives include surfactants, pigment dispersants, thickeners, defoamers, dot conditioners, colorants, fluorescent brighteners, antioxidants, ultraviolet absorbers, preservatives, and the like. Can be.

  As a method of applying the prepared coating liquid on the support, any known coating method can be applied, for example, a blade coating method, an air knife coating method, a curtain coating method, a slot die coating method, a bar coating method. , Gravure coating method, roll coating method and the like can be applied, and then dried using a drying device such as a hot air drier, a heat drum, a far infrared drier to form an ink receiving layer. be able to. The ink receiving layer may be formed by changing the composition ratio of the inorganic fine particles, the water-soluble resin and / or the water-dispersible resin, and other additives, and may be formed on one or both surfaces of the support. Is also possible. Further, for the purpose of improving the resolution of an image and the transportability of a recording medium, a smoothing process may be performed using a device such as a calendar.

The preferable range of the coating amount of the coating liquid on the support is 0.5 to 60 g / m ² in terms of solid content, and the more preferable range is 5 to 55 g / m ² . When the coating amount is less than 0.5 g / m ² , the formed ink receiving layer cannot sufficiently absorb the moisture of the ink, and the ink may flow or the image may bleed, and the ink receiving layer may have an amount of 60 g / m ^2. If it exceeds 2,000, curling may occur during drying, or a remarkable effect may not be exhibited as expected in printing performance.

  The above-mentioned range of the coating amount is also applied to the case where the ink receiving layer is composed of a multi-layer. In this case, the range of the layer containing inorganic fine particles, resin, and others (such as cationic organic fine particles and cationic polymer) is used. The coating amount is preferably at least 1/20 of the total coating amount including all the other layers. If the coating amount is less than this range, a sufficient effect on the fixability of the ink may not be obtained.

  The reason why the recording medium used in the present invention exhibits good ink fixability as described above is probably because a block copolymer composed of at least one hydrophobic block and at least one hydrophilic block. When the colorant-dispersed ink containing a polymer dispersant consisting of the following is attached to the ink receiving layer whose surface pH is adjusted to a range of 3.0 to 6.5, the molecules of the polymer dispersant rapidly aggregate. It is considered that the particles precipitated and wrapped the coloring material particles while being complicatedly entangled with each other, and exhibited strong ink fixing properties. When cationic organic fine particles and / or a cationic polymer or a polyvalent metal ion are present at the same time, these cationic substances and the like and the hydrophilic block of the polymer dispersant (or the carboxyl in the block) are used. It is considered that strong ink fixability was exhibited due to the ionic bond with the group.

  As a method for performing image recording by applying the ink to the recording medium, an ink jet recording method is particularly preferable. As the ink jet recording method, the ink is effectively separated from the nozzles and the ink is applied to the recording medium. Any method can be used as long as the method can provide the. In particular, an ink jet method in which thermal energy is applied to ink to cause a rapid volume change by the method described in JP-A-54-59936, and the ink is ejected from a nozzle by the action force due to this state change. Can be used effectively.

Hereinafter, the present invention will be specifically described with reference to examples. In the following examples, “parts” and “%” are based on mass unless otherwise specified.
<Preparation of polymer dispersant A>
Synthesis of AB type diblock copolymer consisting of one kind of hydrophobic block and one kind of hydrophilic block:
After replacing the inside of the glass container equipped with the three-way cock with nitrogen, the glass container was heated at 250 ° C. in a nitrogen gas atmosphere to remove adsorbed water. After returning the system to room temperature, 12 mmol of 2-decanoloxyethyl vinyl ether, 16 mmol of ethyl acetate, 0.1 mmol of 1-isobutoxyethyl acetate and 11 cm ³ of toluene were added, and the temperature in the system reached 0 ° C. By the way, 0.2 mmol of ethyl aluminum sesquichloride was added to start the polymerization, and an A block of AB type diblock copolymer was synthesized.

  The molecular weight was monitored in a time-division manner using molecular sieve column chromatography (GPC), and after the polymerization of the A block was completed, the carboxyl group of 4- (2-vinyloxyethoxy) benzoic acid (B block) was converted to ethyl. A block B was synthesized by adding 12 mmol of a vinyl monomer esterified with a group. The polymerization reaction was stopped by adding a 0.3% ammonia / methanol solution to the system.

The esterified carboxyl group was hydrolyzed with a sodium hydroxide / methanol solution to change the ester form into a carboxyl group. Dichloromethane was added to the mixed solution after the reaction, and the mixture was diluted, washed three times with a 0.6N hydrochloric acid solution and then three times with distilled water, subjected to desalting treatment, neutralized with aqueous ammonia, and concentrated with an evaporator. -The dried product was vacuum-dried to obtain an AB type diblock copolymer (polymer dispersant A). The compound was identified using NMR and GPC (Mn = 3.5 × 10 ⁴ , Mn / Mw = 1.2). When the pH responsiveness of the obtained polymer dispersant was confirmed, it was found that stimulus responsiveness was exhibited when the pH was lowered to 6.5 or less.

<Preparation of Colorant Dispersion I>
A commercially available oil-soluble dye, C.I. I. Solvent Yellow 14 (1.0 part) and acetone (99.0 parts) were mixed, heated to 40 ° C., and stirred well so as to be uniformly dissolved. This mixed solution was added to a solution obtained by dissolving 1.0 part of the polymer dispersant A in 99.0 parts of tetrahydrofuran, mixed, and then 10.0 parts of water was added. Thereafter, acetone and tetrahydrofuran were removed with a rotary evaporator to obtain a coloring material dispersion I. The concentration of acetone and tetrahydrofuran in the obtained colorant dispersion was analyzed by gas chromatography, but neither was detected, and the result was judged to be not remaining in the colorant dispersion.

<Preparation of Ink 1>
-40.0 parts of the above colorant dispersion I-15.0 parts of tripropylene glycol-5.0 parts of triethylene glycol-40.0 parts of ion-exchanged water

  The above components were mixed and sufficiently stirred to obtain a desired ink 1. When the pH of the obtained ink was measured, it was 8.0. The average particle size of the colorant dispersion in the obtained ink was 47 nm when measured by an apparatus “ELS-800” (trade name, manufactured by Otsuka Electronics Co., Ltd.) by a laser light scattering method.

<Preparation of colorant dispersion II>
A commercially available oil-soluble dye, C.I. I. Solvent Yellow 14 (1.0 part) and acetone (99.0 parts) were mixed, heated to 40 ° C., and stirred well so as to be uniformly dissolved. This mixed solution was added to a solution in which 1.0 part of a styrene-maleic acid random copolymer (number average molecular weight 10,000) was dissolved as a polymer dispersant in 99.0 parts of tetrahydrofuran, mixed, and then mixed with water. 10.0 parts were added. Thereafter, acetone and tetrahydrofuran were removed with a rotary evaporator to obtain a coloring material dispersion II. The presence or absence of pH stimulus responsiveness of the polymer dispersant used was confirmed, but no stimulus responsiveness was observed.

<Preparation of Ink 2>
-50.0 parts of the above colorant dispersion II-10.0 parts of diethylene glycol-10.0 parts of thiodiglycol-30.0 parts of ion-exchanged water The above components were mixed and sufficiently stirred to obtain Ink 2. .

<Production of alumina hydrate>
Aluminum dodexide was prepared by the method described in U.S. Pat. No. 4,242,271. Next, the aluminum dodexide was hydrolyzed by the method described in U.S. Pat. No. 4,202,870 to produce an alumina slurry. Water was added to the alumina slurry until the alumina hydrate solid content became 7.7%. At this time, the pH of the alumina slurry was 9.3, and the pH was adjusted to 6.0 by adding a 3.9% nitric acid solution.

  Next, using an autoclave, aging was performed at an aging temperature of 150 ° C. and an aging time of 6.5 hours to obtain a colloidal sol. The colloidal sol was spray-dried at an inlet temperature of 87 ° C. to obtain an alumina hydrate powder. The obtained powder was an alumina hydrate having a flat particle shape and a boehmite crystal structure. Further, an alumina hydrate dispersion A was prepared by mixing the alumina hydrate powder having the boehmite structure at a concentration of 19% in ion-exchanged water.

  The dispersion A obtained by the above method was redispersed with an ultrasonic homogenizer “MUS-600CCVP-12” (trade name, manufactured by Nippon Seiki Seisakusho), and then coarse particles were removed by centrifugation to remove ions. By adding water, a 17% -concentrated alumina hydrate dispersion B was prepared.

  The dispersion A was adjusted to a concentration of 17% by adding ion-exchanged water to obtain an alumina hydrate dispersion C. The average particle size of the alumina hydrate thus obtained was measured using a laser particle size analyzer “PARIII” (trade name, manufactured by Otsuka Electronics Co., Ltd.), and the dispersion B was 167.8 nm. And the dispersion C was 264.2 nm.

<Example 1>
A solution obtained by adding 17.0 parts (3% based on alumina hydrate) of a 3% boric acid aqueous solution to 100 parts (a solid content of 17%) of alumina hydrate dispersion liquid B and polyvinyl alcohol (PVA-235, ( A coating solution was prepared by dissolving 1.7 parts of Kuraray Co., Ltd. in 15.3 parts of water. Next, this coating solution was die-coated on polyethylene-coated paper (60 ° specular gloss of the surface to be coated according to JIS Z8741: 64%) so as to have a dry coating amount of 35 g / m ^2, and this was oven ( It was dried with hot air at 100 ° C. for 15 minutes using Yamato Scientific Co., Ltd. to form an ink receiving layer. Further, a 0.5N sulfuric acid aqueous solution was overcoated on the ink receiving layer by a bar coating method, and the pH of the surface of the ink receiving layer was adjusted to 3.5 to obtain a recording medium (1).

Next, evaluation of the image recording method in the present invention was performed by the following method.
<Evaluation of ink fixability>
The ink 1 is mounted on an inkjet recording apparatus “BJF-660” (trade name, manufactured by Canon) having an on-demand type multi-recording head that ejects ink by applying thermal energy according to a recording signal to the ink, After performing solid printing on the recording medium (1), the medium was allowed to stand for 2 hours. Next, when a silk-bon paper is placed on the print portion and the non-print portion of the recording medium (1), and a weight of 200 g / cm ² is further placed thereon, and the paper is reciprocated 5 times on the print portion and the non-print portion. Of the non-printed portion and the degree of rubbing of the printed portion were evaluated by the following evaluation criteria. Table 1 shows the results.
：: There was no stain on the non-printed portion and no rubbing of the printed portion.
Δ: The non-printed area was slightly stained, and the printed area was slightly rubbed.
X: The non-printed portion was stained, and a part of the printed portion was scraped off.

<Example 2>
In Example 1, the coating was performed in the same manner as in Example 1 except that the alumina hydrate dispersion B was replaced with the alumina hydrate dispersion C, and the surface pH of the ink receiving layer was adjusted to 4.7. A recording medium (2) was produced. Next, in the evaluation of the ink fixing property, the same evaluation as in Example 1 was performed by changing the recording medium (1) to the recording medium (2). Table 1 shows the results.

<Comparative Example 1>
Example 1 Example 1 was repeated except that the aqueous solution of 0.5N sulfuric acid was changed to a 1% aqueous solution of sodium hydroxide and overcoated to adjust the surface pH of the ink receiving layer to 7.5. In the same manner as in the above, a recording medium (3) was produced. Next, in the evaluation of the ink fixing property, the same evaluation as in Example 1 was performed except that the recording medium (1) was changed to the recording medium (3). Table 1 shows the results.

<Comparative Example 2>
In the evaluation of the ink fixing property, the evaluation was performed in the same manner as in Example 1 except that the ink 1 was replaced with the ink 2. Table 1 shows the results.

<Example 3>
To 100 parts of alumina hydrate dispersion B (solid content 17%), 17.0 parts of a 3% boric acid aqueous solution (3% based on alumina hydrate), and “XCPP104” (trade name, as a cationic organic fine particle) 5.67 parts (10% based on alumina hydrate) of 30% dispersion, particle diameter: 35 nm, glass transition temperature: 100 ° C., manufactured by Mitsui Chemicals, Inc., PAA-HCL- as a cationic polymer 0.68 parts (2% based on alumina hydrate) of 3 L (allylamine-based polymer, 50% aqueous solution, manufactured by Nitto Boseki Co., Ltd.) and polyvinyl alcohol (“PVA-235”, trade name) A solution prepared by dissolving 1.7 parts of water and 15.3 parts of water was prepared. Next, this coating liquid was die-coated on polyethylene-coated paper (60 ° specular gloss of the surface to be coated according to JIS Z8741: 64%) so as to have a dry coating amount of 35 g / m ^2, and dried with hot air. An ink receiving layer was formed. Further, a 0.5N aqueous sulfuric acid solution was overcoated on the ink receiving layer by a bar coating method, and the pH of the surface of the ink receiving layer was adjusted to 3.5 to obtain a recording medium (4). Next, the effects of the image recording method according to the present invention were evaluated by the following methods. Table 2 shows the results.

<Evaluation of ink absorbency>
The ink 1 is mounted on an ink-jet recording apparatus BJF-660 (manufactured by Canon) having an on-demand type multi-recording head for discharging ink by applying thermal energy according to a recording signal to the ink. Magenta (M), cyan (C), and black (Bk) inks are monochromatic and have an ink ejection amount of 100%, are two-color mixed and have an ink ejection amount of 200%, and are three-color mixed and have an ink ejection amount of 300%. The solid printing was performed on the sample of the recording medium (4). After printing, the recording portion was touched with a finger, the degree of adhesion of the ink to the finger was observed, and the ink absorbency was evaluated according to the following evaluation criteria.
A: The ink did not adhere to the finger at a hit amount of 300% (mixing of three colors).
：: The ink did not adhere to the finger at the ejection amount of 200% (mixing of two colors).
Δ: The ink did not adhere to the finger at an ink ejection amount of 100%.
X: The ink adhered to the finger at an ink ejection amount of 100%.

<Evaluation of ink fixability>
Evaluation was performed in the same manner as in Examples 1 and 2. However, the recording medium (4) was used as the recording medium, and the standing time after printing was 30 minutes. The evaluation criteria were as follows.
A: There was no stain on the non-printed area and no rubbing of the printed area.
：: The non-printed portion was slightly stained, and the printed portion was slightly rubbed.
Δ: The non-printed portion was stained, and a part of the printed portion was scraped.
X: The non-printed portion was very dirty, and the entire printed portion was scraped.

<Example 4>
In Example 3, the cationic organic fine particles were changed to XCPP105 (manufactured by Mitsui Chemicals, Inc., 30% dispersion, particle diameter: 66 nm, glass transition temperature: 100 ° C.), and 17.0 parts (alumina hydrate) was used. Recording medium (5) was produced in the same manner as in Example 3 except that the recording medium (30% based on the composition) was added. Next, using the obtained recording medium (5), the ink absorbency and the ink fixing property were evaluated in the same manner as in Example 3. Table 2 shows the results.

<Example 5>
In Example 3, the coating was performed in the same manner as in Example 3, except that the alumina hydrate dispersion B was replaced with the alumina hydrate dispersion C and the surface pH of the ink receiving layer was adjusted to 4.7. A recording medium (6) was produced. Next, using the obtained recording medium (6), evaluation of ink absorbency and ink fixability was performed in the same manner as in Example 3. Table 2 shows the results.

<Comparative Example 3>
A recording medium (7) was produced in the same manner as in Example 3, except that PAA-HCL-3L was not added. Next, the obtained recording medium (7) was evaluated for ink absorbency and ink fixability in the same manner as in Example 3 except that ink 2 was used instead of ink 1. Table 2 shows the results.

<Comparative Example 4>
A recording medium (8) was produced in the same manner as in Example 3, except that XCPP 104 was not added. Next, the obtained recording medium (8) was evaluated for ink absorbency and ink fixability in the same manner as in Example 3 except that ink 2 was used instead of ink 1. Table 2 shows the results.

<Comparative Example 5>
Example 3 Example 3 was repeated except that the 0.5N aqueous solution of sulfuric acid was changed to a 1% aqueous solution of sodium hydroxide, which was overcoated to adjust the surface pH of the ink receiving layer to 7.5. In the same manner as in the above, a recording medium (9) was produced. Next, using the obtained recording medium (9), evaluation of ink absorbency and ink fixability was performed in the same manner as in Example 3. Table 2 shows the results.

<Comparative Example 6>
In the evaluation of the ink absorbency and the ink fixing property, the evaluation was performed in the same manner as in Example 3 except that the ink 1 was replaced with the ink 2. Table 2 shows the results.

<Comparative Example 7>
A coating liquid was prepared in the same manner as in Example 4 except that XCPP105 was used in an amount of 22.67 parts (40% based on alumina hydrate). Could not be formed successfully. Therefore, evaluation of ink absorbency and ink fixability was not performed.

<Example 6>
To 100 parts of alumina hydrate dispersion B (solid content 17%), 1.36 parts of magnesium acetate tetrahydrate (manufactured by Kishida Chemical Co., Ltd.) (8% based on alumina hydrate), and 3% boric acid An aqueous solution obtained by adding 17.0 parts (3% based on alumina hydrate) and a solution obtained by dissolving 1.7 parts of polyvinyl alcohol (PVA-235, manufactured by Kuraray Co., Ltd.) in 15.3 parts of water were used. The mixture was mixed to prepare a coating solution. Next, this coating solution was die-coated on polyethylene-coated paper (60 ° specular gloss of the surface to be coated according to JIS Z8741: 64%) so as to have a dry coating amount of 35 g / m ^2, and this was oven ( It was dried with hot air at 100 ° C. for 15 minutes using Yamato Scientific Co., Ltd. to form an ink receiving layer. Further, a 0.5N aqueous sulfuric acid solution was overcoated on the ink receiving layer by a bar coating method, and the pH of the surface of the ink receiving layer was adjusted to 3.5 to obtain a recording medium (10).

Next, the evaluation of the image recording method in the present invention was performed by the following method.
<Evaluation of ink fixability>
Evaluation was performed by the same method and evaluation criteria as in Examples 1 and 2. However, the recording medium (10) was used as the recording medium, and the standing time after printing was 1 hour. Table 3 shows the results.

<Example 7>
In Example 6, the alumina hydrate dispersion B was replaced with the alumina hydrate dispersion C, the magnesium acetate was replaced with magnesium sulfate (manufactured by Kishida Chemical Co.), and the added amount was 0.51 part (alumina hydrate). The recording medium (11) was produced in the same manner as in Example 6, except that the surface pH of the ink receiving layer was adjusted to 4.7. Next, in the evaluation of the ink fixing property, the same evaluation as in Example 6 was performed by changing the recording medium (10) to the recording medium (11). Table 3 shows the results.

<Comparative Example 8>
A recording medium (12) was produced in the same manner as in Example 6, except that magnesium acetate was not added. Next, in the evaluation of the ink fixing property, the same evaluation as in Example 6 was performed except that the recording medium (10) was changed to the recording medium (12) and the ink 2 was used instead of the ink 1. . Table 3 shows the results.

<Comparative Example 9>
Example 6 Example 6 was repeated except that the aqueous solution of 0.5N sulfuric acid was changed to a 1% aqueous solution of sodium hydroxide and overcoated to adjust the surface pH of the ink receiving layer to 7.5. In the same manner as in the above, a recording medium (13) was produced. Next, in the evaluation of the ink fixing property, the same evaluation as in Example 6 was performed except that the recording medium (10) was changed to the recording medium (13). Table 3 shows the results.

<Comparative Example 10>
In the evaluation of the ink fixing property, the evaluation was performed in the same manner as in Example 6 except that the ink 1 was replaced with the ink 2. Table 3 shows the results.

(Preparation of polymer dispersant B)
Synthesis of AB type diblock copolymer consisting of one kind of hydrophobic block and one kind of hydrophilic block:
After replacing the inside of the glass container with the three-way cock with nitrogen, the mixture was heated at 250 ° C. in a nitrogen gas atmosphere to remove adsorbed water. After returning the system to room temperature, 12 mmol of isobutyl vinyl ether, 16 mmol of ethyl acetate, 0.1 mmol of 1-isobutoxyethyl acetate, and 11 cm ³ of toluene were added. When the temperature in the system reached 0 ° C., ethyl aluminum sesquichloride was added. The polymerization was started by adding 0.2 mmol, and the A block of the AB type diblock copolymer was synthesized.

  The molecular weight is monitored in a time-division manner using molecular sieve column chromatography (GPC), and after the polymerization of the component A is completed, 12 mmol of a vinyl monomer in which the hydroxyl group of 2-hydroxyethyl vinyl ether is silylated with trimethylchlorosilane is added. Was used to synthesize the B block. The polymerization reaction was stopped by adding a 0.3% ammonia / methanol solution to the system.

Hydrolysis of the hydroxyl group silylated by trimethylchlorosilane was performed by adding water. Dichloromethane was added to the mixed solution after the reaction, and the mixture was diluted, washed three times with a 0.6N hydrochloric acid solution and then three times with distilled water, concentrated and dried with an evaporator, and dried under vacuum to obtain AB-type. A diblock copolymer (polymer dispersant B) was obtained. The compound was identified using NMR and GPC (Mn = 3.7 × 10 ⁴ , Mn / Mw = 1.3). When the pH responsiveness of the obtained polymer dispersant was confirmed, it was found that stimulus responsiveness was exhibited when the pH was lowered to 6.5 or less.

<Examples 8 and 9>
An image was formed in the same manner as in Examples 1 and 2, except that the polymer dispersant B was used in place of the polymer dispersant A in Examples 1 and 2, and the same results as in Examples 1 and 2 were obtained. Was.

(Preparation of Polymer Dispersant C)
Synthesis of ABC Type Triblock Copolymer Consisting of One Kind of Hydrophobic Block and Two Kinds of Hydrophilic Blocks:
After replacing the inside of the glass container equipped with the three-way cock with nitrogen, the glass container was heated at 250 ° C. in a nitrogen gas atmosphere to remove adsorbed water. After returning the system to room temperature, 12 mmol of n-octadecyl vinyl ether, 16 mmol of ethyl acetate, 0.1 mmol of 1-isobutoxyethyl acetate and 11 cm ³ of toluene were added, and when the temperature in the system reached 0 ° C., ethyl aluminum was added. The polymerization was started by adding 0.2 mmol of sesquichloride to synthesize an A block of an ABC type triblock copolymer.

  The molecular weight was monitored in a time-division manner using molecular sieve column chromatography (GPC), and after completion of polymerization of the A block, 2- (2- (2- (2- (2-methoxyethoxy) ethoxy) ethoxy) ethoxy) ethoxyvinyl ether (B (Block) 24 mmol was added and polymerization was continued. Similarly, the molecular weight was monitored by GPC, and after the polymerization of the B block was completed, 12 mmol of a vinyl monomer obtained by esterifying a carboxyl group of 6- (2-vinyloxyethoxy) hexanoic acid (C block) with an ethyl group was added. By adding, a C block was synthesized. The polymerization reaction was stopped by adding a 0.3% ammonia / methanol solution to the system.

The esterified carboxyl group was hydrolyzed with a sodium hydroxide / methanol solution to convert to a carboxyl group. Dichloromethane was added to the mixed solution after the reaction, and the mixture was diluted, washed three times with a 0.6N hydrochloric acid solution and then three times with distilled water, concentrated and dried by an evaporator, and dried under vacuum to obtain AB. A -C type triblock copolymer (polymer dispersant C) was obtained. The compound was identified using NMR and GPC (Mn = 3.7 × 10 ⁴ , Mn / Mw = 1.2). When the pH responsiveness of the obtained polymer dispersant was confirmed, it was found that stimulus responsiveness was exhibited when the pH was lowered to 6.5 or less.

<Examples 10 to 12>
An image was formed in the same manner as in Examples 3 to 5 except that the polymer dispersant C was used in place of the polymer dispersant A in Examples 3 to 5, and the same results as in Examples 3 to 5 were obtained. Was.

(Preparation of Polymer Dispersant D)
Synthesis of AB type diblock copolymer consisting of one kind of hydrophobic block and one kind of hydrophilic block:
After replacing the inside of the glass container equipped with the three-way cock with nitrogen, the glass container was heated at 250 ° C. in a nitrogen gas atmosphere to remove adsorbed water. After returning the system to room temperature, 12 mmol of n-octadecyl vinyl ether, 16 mmol of ethyl acetate, 0.1 mmol of 1-isobutoxyethyl acetate and 11 cm ³ of toluene were added, and when the temperature in the system reached 0 ° C., ethyl aluminum was added. Polymerization was started by adding 0.2 mmol of sesquichloride, and an A block of an AB type diblock copolymer was synthesized.

  The molecular weight was monitored in a time-division manner using molecular sieve column chromatography (GPC), and after the polymerization of the A block was completed, 48 mmol of a vinyl monomer in which the hydroxyl group of heptaethylene glycol vinyl ether (B block) was silylated with trimethylchlorosilane was used. The B block was synthesized by the addition. The polymerization reaction was stopped by adding a 0.3% ammonia / methanol solution to the system.

Hydrolysis of the hydroxyl group silylated by trimethylchlorosilane was performed by adding water. Dichloromethane was added to the mixed solution after the reaction, and the mixture was diluted, washed three times with a 0.6N hydrochloric acid solution and then three times with distilled water, concentrated and dried by an evaporator, and dried under vacuum to obtain AB. A diblock copolymer (polymer dispersant D) was obtained. The compound was identified using NMR and GPC (Mn = 3.5 × 10 ⁴ , Mn / Mw = 1.3). When the pH responsiveness of the obtained polymer dispersant was confirmed, it was found that stimulus responsiveness was exhibited when the pH was lowered to 6.5 or less.

<Examples 13 and 14>
An image was formed in the same manner as in Examples 6 and 7, except that the polymer dispersant D was used in place of the polymer dispersant A in Examples 6 and 7, and the same results as in Examples 6 and 7 were obtained. Was.

  An image recording method for forming an image by attaching an ink to a recording medium having at least one ink receiving layer provided on a support, wherein the ink comprises at least one hydrophobic block and at least one hydrophilic And a water-insoluble coloring material, a water-soluble organic solvent and water, and the ink receiving layer is composed of inorganic fine particles, a water-soluble resin and / or a water-soluble resin. Alternatively, by using a recording medium containing a water-dispersible resin (and may further contain other components), and further having a surface pH of the ink receiving layer controlled in a range of 3.0 to 6.5, An image recording method excellent in ink absorbency and ink fixability could be provided.

Claims (14)

  In an image recording method for forming an image by adhering an ink to a recording medium having at least one ink receiving layer provided on a support, the ink comprises at least one hydrophobic block and at least one hydrophilic block. A polymer dispersant comprising a block copolymer containing at least a block, a water-insoluble colorant, a water-soluble organic solvent and an ink for inkjet recording comprising water, and wherein the ink-receiving layer contains inorganic fine particles and water-soluble An image recording method, comprising a resin and / or a water-dispersible resin, wherein the surface pH of the ink receiving layer is controlled in a range of 3.0 to 6.5.   The image recording method according to claim 1, wherein the ink receiving layer further contains cationic organic fine particles and / or a cationic polymer.   The image recording method according to claim 2, wherein the content of the cationic organic fine particles in the ink receiving layer is 0.1 to 25% by mass relative to the dry mass of the ink receiving layer.   The image recording method according to claim 2, wherein the cationic organic fine particles have a weight average molecular weight of 100,000 to 1,000,000.   The image recording method according to claim 2, wherein the cationic organic fine particles have a glass transition temperature of 60 to 110 ° C. 4.   The image recording method according to claim 2, wherein the weight average molecular weight of the cationic polymer is 5,000 to 200,000.   The image recording method according to claim 2, wherein the amount of the cationic polymer used is 0.05 to 5% by mass based on the inorganic fine particles.   The image recording method according to claim 1, wherein the inorganic fine particles are made of at least one of silica, alumina, alumina hydrate having a boehmite structure or a pseudo-boehmite structure having an average particle diameter of 100 to 300 nm.   The image recording method according to claim 1, wherein the ink receiving layer further contains a water-soluble polyvalent metal salt.   The image recording method according to claim 9, wherein the amount of the water-soluble polyvalent metal salt used is 0.1 to 10% by mass relative to the inorganic fine particles.   The image recording method according to claim 1, wherein the water-insoluble coloring material is at least one selected from the group consisting of pigments, oil-soluble dyes, vat dyes, and disperse dyes.   The polymer dispersant is a block copolymer obtained by polymerizing vinyl ethers as a monomer, and has a pH stimulus responsiveness in which a polymer chain of the polymer is capable of causing an association when the pH of the ink is reduced. 2. The image recording method according to 1. 2. The method according to claim 1, wherein at least one of the monomers constituting the block copolymer is at least one monomer selected from vinyl ethers represented by formulas (Ia) to (Io). 3. Image recording method.

  The image recording method according to claim 1, wherein the block copolymer has a number average molecular weight of 500 to 20,000,000.