JP2005153386A - Ink jetting recording medium and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jetting recording medium not generating a crack even if the medium is curved or bent, and to provide its image forming method. <P>SOLUTION: The ink jet recording medium has at least two ink absorbing layers on a support wherein the ink absorbing layer disposed farthest from the support includes inorganic pigment fine particles. A polymeric compound having side chains bridge-bonded with each other by irradiating a hydrophilic polymeric compound having a functional group in the side chain and a polymerization degree of ≥300 with ionizing radiation is included in the ink absorbing layer disposed farthest from the support. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inkjet recording medium (hereinafter also simply referred to as a recording medium), and more specifically, an inkjet recording medium having a porous layer that prevents cracking and has improved resistance to cracking of a coating film, and The present invention relates to an image forming method used.

  In recent years, the progress of inkjet technology has been remarkable, and it has come to be called photo image quality in combination with improvements in printer technology, ink technology, and dedicated recording medium technology. As the image quality is improved, the storability of inkjet images has been compared with conventional silver salt photographs, and in many dye inks, there is a movement of colorants such as water resistance and weakness of bleed resistance of inkjet images. It has been pointed out that deterioration is accompanied by chemical reactions peculiar to colorants such as deterioration and weakness to light resistance and oxidation resistance gas.

  Among them, many proposals have been made to use pigment inks in order to improve the storage stability of dye ink images. However, in the case of pigment ink, it is not preferable because glossiness like a silver salt photograph may not be obtained or a metallic luster called bronzing may be observed. In addition, the present situation is that sufficient image storability cannot be obtained simply by using pigment ink.

  In addition, among the above problems, many proposals have been made so far for the purpose of improving the image storage stability of ink jet recorded images. As an ink jet recording medium, a layer made of thermoplastic organic polymer particles is provided on the outermost layer of the recording medium, and after recording an image, the thermoplastic organic polymer particles are melted and formed into a film. A technique for achieving improvement in water resistance and weather resistance and imparting gloss to an image by forming a film is disclosed (for example, see Patent Documents 1, 2, 3, 4, and 5). However, with the above technology, the water resistance and light resistance are improved, but the glossiness is still insufficient.

In addition, a glossy layer composed of a colloidal particle and a hydrophilic ionizing radiation cured product having two or more ethylenic double bonds in the molecule has been proposed (for example, see Patent Document 6). However, since the glossy expression layer disclosed in the technology described in the above publication is hard and brittle, there is a disadvantage that cracking occurs when the recording medium is bent or folded. I was at a level I couldn't say.
JP 59-222381 A JP-A-4-21446 Japanese Patent Laid-Open No. 10-315448 Japanese Patent Laid-Open No. 11-5362 JP 11-192775 A JP-A-8-169175

  Accordingly, an object of the present invention is to provide an inkjet recording medium that does not crack when bent or folded, an inkjet recording medium for obtaining an image close to photographic quality, and an image forming method thereof. There is.

The above object of the present invention has been achieved by the following constitution.
(Claim 1)
In an ink jet recording medium having at least two ink absorbing layers on a support and containing inorganic pigment fine particles in the ink absorbing layer located farthest from the support, the position farthest from the support The ink absorbing layer in which the hydrophilic polymer compound having a functional group in the side chain and having a polymerization degree of 300 or more is irradiated with ionizing radiation to contain a polymer compound crosslinked between the side chains. An ink jet recording medium.
(Claim 2)
2. The ink jet recording medium according to claim 1, wherein the ink absorbing layer located farthest from the support contains thermoplastic resin fine particles.
(Claim 3)
The inkjet recording medium according to claim 1 or 2, wherein the polymer compound crosslinked by ionizing radiation is a polymer of a photocurable polyvinyl alcohol derivative.
(Claim 4)
4. An image is formed on the inkjet recording medium according to any one of claims 1 to 3 using a pigment ink, and then heated and pressed under conditions of a pressure of 0.5 to 10 MPa and a temperature of 50 to 150 ° C. An image forming method.

  It was possible to provide an ink jet recording medium having no cracks and excellent surface gloss.

  Hereinafter, the present invention will be described in detail.

  The ink jet recording medium of the present invention is obtained by applying a water-soluble coating liquid that forms a porous layer mainly containing a specific hydrophilic binder and inorganic fine particles on a support to form a porous layer having voids. is there.

<Definition of ionizing radiation curable resin>
What is a hydrophilic polymer compound having a degree of polymerization having a functional group in a side chain of 300 or more used for the ink absorption layer located farthest from the support of the present invention and which is crosslinked by irradiation with ionizing radiation? It is a water-soluble resin that undergoes a cross-linking reaction by reacting between side chains by irradiation with ionizing radiation such as ultraviolet rays and electron beams, and is water-soluble before the cross-linking reaction, but substantially after the cross-linking reaction. It is a water-insoluble resin, and the resin has hydrophilicity even after the crosslinking reaction and maintains sufficient affinity with ink.

  Examples of such resins include saponified polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or derivatives of the above hydrophilic resins, and these It is at least one selected from the group consisting of copolymers, or a hydrophilic resin modified with a modifying group such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, or a photodepolymerization type It is.

  Among these, a resin modified with a photodimerization type or photopolymerization type modification group is preferable from the viewpoint of sensitivity or stability of the resin itself.

  As the photodimerization-type modifying group, those having a diazo group, a cinnamoyl group, a styrylpyridinium group, or a stilquinolium group introduced are preferable, and a resin dyed with a water-soluble dye such as an anionic dye after photodimerization is preferable. Examples of such resins include resins having a cationic group such as a primary amino group or a quaternary ammonium group, such as JP-A Nos. 62-283339, 1-198615, and 60-252341. Photosensitive resins (compositions) described in JP-A-56-67309, JP-A-60-129742, etc., resins that become cationic after curing, such as azide groups that become amino groups by curing treatment, such as Examples thereof include photosensitive resins (compositions) described in JP-A-56-67309.

  Specific examples include the following.

  The photosensitive resin described in JP-A-56-67309 contains the following structural formula in a polyvinyl alcohol structure.

2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following structural formula

It is a resin composition which has 4-azido-3-nitrophenyl carbonyloxyethylene structure represented by these.

  Specific examples of the resin are described in Examples 1 and 2 in the publication, and the constituent components of the resin and the use ratio thereof are described on page 2 of the publication.

  The photosensitive resin described in JP-A-60-129742 is a resin composition having the following structural formula (3) or (4) in a polyvinyl alcohol structure.

  In the formula, R represents a phenyl group.

  Moreover, as a photopolymerization type | mold modification group, the resin shown below described, for example in Unexamined-Japanese-Patent No. 2000-181062 is preferable from a reactive viewpoint.

In the formula, R ₁ represents Me or H, n represents 1 or 2, X represents — (CH ₂ ) _m COO—, —OCH ₂ COO— or —O—, and Y represents an aromatic ring or a single group. Represents a bond, and m represents 0 or an integer of 1 to 6.

  In the present invention, it is preferable to add a photoinitiator or a photosensitizer. These photoinitiators and photosensitizers may be dissolved or dispersed in a solvent, or may be chemically bonded to the photosensitive resin.

  There is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A conventionally well-known thing can be used.

  The photoinitiator and photosensitizer to be applied are not particularly limited, but as an example, benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4 ′ -Benzophenones such as dimethylaminobenzophenone, thioxanthones such as thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, isopropoxychlorothioxanthone. Anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone and chloroanthraquinone, and acetophenones. Benzoin ethers such as benzoin methyl ether, 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o- Chlorophenyl) -4,5-di (m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5 -Phenylimidazole dimer, 2- (p-methoxyphenyl) -4,5-diphenylimidazole dimer, 2, -di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2, 2,4,5-triarylimidazole dimer of 4-dimethoxyphenyl) -4,5-diphenylimidazole dimer, N-dimethylketal, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1- Propanone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one Benzoins such as phenanthrenequinone, 9,10-phenanthrenequinone, methylbenzoin, ethylbenzoin, acridine derivatives such as 9-phenylacridine, 1,7-bis (9,9′-acridinyl) heptane, bisacylphosphine Examples include oxides and mixtures thereof. The above may be used alone or in combination.

  In particular, water-soluble 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 4- (2-hydroxyethoxy) -phenyl- (2- Water-soluble initiators such as hydroxy-2-propyl) ketone, thioxanthone ammonium salt, and benzophenone ammonium salt are preferable from the viewpoint of crosslink efficiency because of excellent mixing properties.

  In addition to these photoinitiators, accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.

  Examples of the ionizing radiation in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X-rays. However, they are dangerous to the human body, easy to handle, and can be used industrially. Widely used electron beams and ultraviolet rays are preferable.

  Examples of the electron beam irradiation method include a scanning method, a curtain beam method, and a broad beam method. The curtain beam method is preferable from the viewpoint of processing capability.

  The acceleration voltage of the electron beam can be changed as appropriate depending on the specific gravity and film pressure of the coating film, but 20 kV to 300 kV is appropriate. The irradiation amount of the electron beam is preferably in the range of 0.1 to 20 Mrad.

As the ultraviolet light source, for example, a low pressure, medium pressure, high pressure mercury lamp, metal halide lamp or the like having an operating pressure of 10 ² Pa to 10 ⁶ Pa is used. From the viewpoint of wavelength distribution of the light source, a high pressure mercury lamp and a metal halide lamp are preferable. A metal halide lamp is more preferable. Moreover, it is preferable to provide a filter that cuts light having a wavelength of 300 nm or less. As the output of the lamp 400W～30kW, as the illuminance ^{10mW / cm 2 ~10kW / cm 2} , preferably from 0.1mJ / cm ² ~500mJ / cm ² as irradiation ^{energy, 1mJ / cm 2 ~100mJ / cm} 2 is More preferred.

When the light source wavelength includes ultraviolet rays of 300 nm or less, or when the irradiation energy exceeds 500 mJ / cm, the core of the ionizing radiation crosslinkable resin or various coexisting additives are decomposed by ionizing radiation, and the present invention. In addition to not being able to obtain the above effect, there is a possibility of causing problems such as odor derived from the decomposition product, which is not preferable. When the irradiation energy is less than 0.1 mJ / cm ² , the crosslinking efficiency is insufficient, and the effects of the present invention may not be sufficiently obtained.

The illuminance at the time of ultraviolet irradiation is preferably 0.1 mW / cm ² or more and 1 W / cm ² or less. When the illuminance exceeds 1 W / cm ² , the surface curability of the coating is improved, but the deep curability is lowered and a film having only a hard surface is obtained. In that case, the balance of the hardness in the depth direction of the film is lost, and curling or the like occurs.

When the illuminance is lower than 0.1 mW / cm ^{2, the} crosslinking does not proceed sufficiently due to scattering in the film and the effect of the present invention may not be obtained.

When giving the same integrated light quantity (mJ / cm ² ), the preferable range of illuminance is due to the change in the light transmittance. When the concentration distribution of the generated cross-linking reactive species is different due to the transmittance of ultraviolet rays, and the ultraviolet illuminance is high, a high concentration of cross-linking reactive species is generated on the surface layer, and a hard and dense film is formed on the surface of the coating film.

  When the illuminance is in a preferable range, the degree of cross-linking of the surface layer is low and light permeability in the deep direction is high, so that gentle cross-linking is uniformly formed in the deep direction.

  If the illuminance is too low, it takes a long time to give the necessary integrated illuminance, which is not only disadvantageous in terms of equipment introduction, but also because the amount of absolute light due to scattering of ultraviolet rays by the coating film is insufficient. Absent.

  Next, the inorganic pigment fine particles according to the present invention will be described.

  Examples of inorganic pigment fine particles that can be used in the present invention include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, and sulfide. Zinc, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. And white inorganic pigments.

  As the inorganic pigment fine particles, solid fine particles selected from silica and alumina or alumina hydrate are preferably used, and silica is more preferable.

  As the silica, silica synthesized by a usual wet method, colloidal silica, silica synthesized by a gas phase method, or the like is preferably used, and the fine particle silica particularly preferably used in the present invention is a colloidal silica or a gas phase method. Of the fine particle silica synthesized, fine silica obtained by the vapor phase method can obtain a high porosity. Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as amorphous particles, spherical particles, and acicular particles can be used.

  The inorganic pigment fine particles preferably have a particle size of 100 nm or less. For example, in the case of the above-mentioned vapor phase method fine particle silica, the average particle size (particle size in the dispersion state before coating) of the inorganic pigment fine particles dispersed in the primary particle state is preferably 100 nm or less. More preferably, it is 4-50 nm, Most preferably, it is 4-20 nm.

  As the silica synthesized by the vapor phase method in which the average particle diameter of primary particles is 4 to 20 nm, which is most preferably used, for example, Aerosil manufactured by Nippon Aerosil Co., Ltd. is commercially available. The vapor phase fine particle silica can be dispersed to primary particles relatively easily by sucking and dispersing in water using, for example, a jet stream inductor mixer manufactured by Mitamura Riken Kogyo Co., Ltd.

  The average particle size of the inorganic pigment fine particles is determined by observing the particles themselves or the particles appearing on the cross section or surface of the surface layer with an electron microscope, obtaining the particle size of 1,000 arbitrary particles, and calculating the simple average value (number Average). Here, the particle diameter of each particle is represented by a diameter assuming a circle equal to the projected area.

  Next, the thermoplastic resin fine particles preferably used in the present invention will be described.

  Examples of the thermoplastic resin fine particles according to the present invention include polycarbonate, polyacrylonitrile, polystyrene, polyacrylic acid, polymethacrylic acid, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyamide, polyether, and the like. And styrene-acrylic acid ester copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ethylene- Acrylic ester copolymers, SBR latex and the like are preferred. The thermoplastic resin fine particles may be used by mixing a plurality of polymers having different monomer compositions, particle sizes, and polymerization degrees.

  In selecting a thermoplastic resin, ink absorbency, glossiness of an image after fixing by heating and pressing, image fastness, and releasability should be taken into consideration.

  Regarding the ink absorptivity, when the particle diameter of the thermoplastic fine particles is less than 0.05 μm, the separation of the pigment particles and the ink solvent in the pigment ink is delayed, and the ink absorption rate is lowered. On the other hand, if it exceeds 10 μm, it is not preferable from the viewpoint of adhesion to the solvent absorbing layer adjacent to the ink receiving layer when coating on the support and coating strength of the inkjet recording medium after coating and drying. For this reason, the thermoplastic resin fine particle diameter is preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm. More preferably, it is 0.1-1 micrometer.

  Moreover, a glass transition point (Tg) is mentioned as a reference | standard of selection of a thermoplastic resin. When Tg is lower than the coating and drying temperature, for example, the coating and drying temperature at the time of manufacturing the recording medium is already higher than Tg, and voids due to the thermoplastic fine particles for allowing the ink solvent to pass through disappear.

  Also, if Tg is higher than the temperature at which the support is denatured by heat, a fixing operation at a high temperature is required for melt film formation after ink jet recording with pigment ink, and the load on the apparatus and the heat stability of the support are stable. Sex is a problem. The preferable Tg of the thermoplastic fine particles is 50 to 150 ° C. Moreover, as minimum film-forming temperature (MFT), the thing of 50-150 degreeC is preferable.

  The thermoplastic fine particles are preferably dispersed in an aqueous system from the viewpoint of environmental suitability, and an aqueous latex obtained by emulsion polymerization is particularly preferable. At this time, the emulsion polymerized type using a nonionic dispersant as an emulsifier is a form that can be preferably used.

  The thermoplastic fine particles to be used preferably have a residual monomer component volatilized from the recording medium of 0.5 ppm or less, particularly 0.3 ppm or less from the viewpoint of odor and safety.

  For the measurement of the remaining monomer that volatilizes, put 100 A4 size unprinted recording media into a vinyl bag, store at 40 ° C./80% RH for 1 week, collect gas from the air in the bag, and then gas chromatograph Can be quantified. For the gas chromatograph, a measuring instrument such as HP5890 manufactured by Hewlett-Packard Company can be used, and the measuring method may be performed according to the instruction manual.

  As a method for keeping the amount of residual monomer low, there is a method for completely terminating the polymerization reaction. However, since it is difficult to complete the reaction, in the present invention, as a result of various investigations on the method for removing the residual monomer, As the removing step, it is preferable to perform a polymerization reaction under a reduced pressure atmosphere by a known method, or to draw a vacuum after the polymerization. Thus, the amount of residual monomer can be controlled.

  In the surface layer according to the present invention, it is preferable to use the thermoplastic resin fine particles together with the inorganic pigment fine particles.

  The surface layer according to the present invention can appropriately contain a water-soluble binder in addition to the above-described configuration.

  Examples of the water-soluble binder include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color ginan (κ, ι, λ, etc.), agar, pullulan, water-soluble polyvinyl butyral. , Hydroxyethyl cellulose, carboxymethyl cellulose and the like. Two or more of these water-soluble resins can be used in combination.

  Among the configurations of the present invention, when the surface layer is a mixed system of thermoplastic resin fine particles and inorganic pigment fine particles, the solid content mass ratio is determined individually by the thermoplastic resin fine particles, inorganic pigment fine particles, other additives, and the like. In the present invention, the ratio (B / F) of the thermoplastic resin (B) to the filler (F) is preferably 2/8 to 8/2, more preferably 3/7 to 7 in the present invention. / 3, more preferably 4/6 to 6/4.

The surface layer according to the present invention may contain a cationic water-soluble polymer having a quaternary ammonium base in the molecule, and usually 0.1 to 10 g, preferably 0.2, per 1 m ^{2 of the} inkjet recording medium. Used in the range of ˜5 g.

  The film thickness of the surface layer according to the present invention is preferably 3 to 15 μm.

  Examples of the method for measuring the film thickness of the surface layer include a method in which a cross section of the recording medium provided with the surface layer is accurately cut in the vertical direction and then observed using an optical microscope or a scanning electron microscope.

  In the ink jet recording medium of the present invention, it is preferable to provide an ink absorbing layer that absorbs the ink solvent between the support and the surface layer.

  The ink absorbing layer of the recording medium is roughly divided into a swelling type and a void type.

  As the swelling type, as the hydrophilic binder, for example, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like applied alone or in combination and used as an ink absorbing layer can be used.

  As the void type, fine particles and a hydrophilic binder are mixed and applied, and particularly glossy ones are preferable. As the fine particles, alumina or silica is preferable, and those using silica having a particle diameter of 0.1 μm or less are particularly preferable. As the hydrophilic binder, for example, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide and the like are preferably used alone or in combination.

  In order to give suitability for continuous or high-speed printing, it is suitable that the ink absorption speed of the recording medium is fast. From this point, the void type can be particularly preferably used.

  Hereinafter, the void-type ink absorbing layer (also referred to as void layer) will be described in more detail.

  The void layer is mainly formed by soft aggregation of a hydrophilic binder and inorganic fine particles. Conventionally, various methods for forming voids in a film are known. For example, a uniform coating solution containing two or more kinds of polymers is coated on a support, and these polymers are phase-separated from each other in the drying process. A method of forming voids by applying a coating liquid containing solid fine particles and a hydrophilic or hydrophobic binder on a support, and after drying, immersing the inkjet recording medium in water or a liquid containing an appropriate organic solvent A method of forming solid voids by dissolving solid fine particles, a method of forming a void in the film by applying a coating liquid containing a compound having a property of foaming at the time of film formation, and then foaming this compound in the drying process, A method in which a coating liquid containing porous solid fine particles and a hydrophilic binder is coated on a support to form voids in or between the porous fine particles, approximately equal to or more than the hydrophilic binder The coating solution containing the solid particles and or particulate oil and a hydrophilic binder having a volume and coated on a support, and a method of making an air gap between the solid particles are known. In the present invention, it is particularly preferable that the void layer is formed by containing various inorganic solid fine particles having an average particle diameter of 100 nm or less.

  As the inorganic fine particles used for the above purpose, those similar to the inorganic pigment fine particles used in the surface layer can be used.

  Moreover, as a hydrophilic binder, the compound similar to the water-soluble binder described by the above-mentioned surface layer can be mentioned.

The amount of the inorganic fine particles used in the ink absorption layer depends largely on the required ink absorption capacity, the void ratio of the void layer, the type of inorganic fine particles, and the type of water-soluble resin, but in general, an inkjet recording medium 1 m ^2. Usually, it is 5 to 30 g, preferably 10 to 25 g.

  Further, the ratio of the inorganic fine particles and the water-soluble resin used in the ink absorbing layer is usually 2: 1 to 20: 1 by mass ratio, and particularly preferably 3: 1 to 10: 1.

The ink absorbing layer may contain a cationic water-soluble polymer having a quaternary ammonium base in the molecule, and is usually 0.1 to 10 g, preferably 0.2 to 5 g, per 1 m ^{2 of the} inkjet recording medium. Used in a range.

In the void layer, the total amount of voids (void volume) is preferably 20 ml or more per 1 m ² of the recording medium. When the void volume is less than 20 ml / m ² , the ink absorbency is good when the amount of ink at the time of printing is small, but when the amount of ink increases, the ink is not completely absorbed and the image quality deteriorates, Problems such as delay in drying are likely to occur.

  As another type of void type, in addition to forming an ink solvent absorption layer using inorganic fine particles, a polyurethane resin emulsion and a water-soluble epoxy compound or acetoacetylated polyvinyl alcohol were used in combination, and an epichlorohydrin polyamide resin was also used in combination. The ink solvent absorption layer may be formed using a coating liquid. The polyurethane resin emulsion in this case is preferably a polyurethane resin emulsion having a polycarbonate chain, a polycarbonate chain and a polyester chain and a particle diameter of 3.0 μm, and the polyurethane resin of the polyurethane resin emulsion is a polyol having a polycarbonate polyol, a polycarbonate polyol and a polyester polyol. It is more preferable that the polyurethane resin obtained by reacting the olefin and the aliphatic isocyanate compound has a sulfonic acid group in the molecule, and further has an epichlorohydrin polyamide resin and a water-soluble epoxy compound or acetoacetylated vinyl alcohol.

  In the ink solvent absorption layer using the polyurethane resin, it is estimated that weak aggregation of cations and anions is formed, and accordingly, voids having ink solvent absorption ability are formed, so that an image can be formed.

  In the present invention, the average porosity of the entire ink absorbing layer of the inkjet recording medium is preferably 40 to 70%, or the porosity of the surface layer is preferably 30 to 70%.

  The void volume relative to the solid content volume in the entire ink absorbing layer or the surface layer having the ink absorbing ability is referred to as the porosity, and one method can be obtained according to the following equation.

Porosity = 100 × [(total dry film thickness−applied solid film thickness) / (total dry film thickness)]
Further, the porosity of the entire ink absorbing layer or the surface layer can also be measured by the following method. For example, it can be easily obtained by coating all ink absorbing layers or only the surface layer on 100 μm polyethylene terephthalate and measuring the amount of saturated transition or water absorption by Bristow measurement.

  Next, the support used for the inkjet recording medium according to the present invention will be described.

  As a support used in the present invention, a support conventionally used for an inkjet recording medium, for example, a paper support such as plain paper, art paper, coated paper and cast coated paper, a plastic support, and a polyolefin on both sides A paper support coated with, and a composite support obtained by laminating these can be used, but a water-impermeable support is preferably used from the viewpoint of further exerting the effects of the present invention.

  Examples of the water-impermeable support used in the present invention include a plastic resin film support or a support in which both surfaces of paper are coated with a plastic resin film. Examples of the plastic resin film support include a polyester film, a polyvinyl chloride film, a polypropylene film, a cellulose triacetate film, a polystyrene film, and a film support in which these are laminated. These plastic resin films can be transparent or translucent.

  In the present invention, a particularly preferable support is a support in which both sides of paper are coated with a plastic resin, and most preferable is a support in which both sides of paper are coated with a polyolefin resin.

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

  The paper used for the support of the present invention is made from wood pulp as a main raw material and, if necessary, paper using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp. As wood pulp, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, and NUKP can be used, but it is preferable to use more LBKP, NBSP, LBSP, NDP, and LDP with a short fiber content. However, the ratio of LBSP and / or LDP is preferably 10 to 70%. The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful.

  In paper, for example, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc, and titanium oxide, paper strength enhancers such as starch, polyacrylamide, and polyvinyl alcohol, fluorescent whitening agents, polyethylene Water retaining agents such as glycols, dispersants, softening agents such as quaternary ammonium, and the like can be added as appropriate.

  The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the sum of the 24 mesh residue and the 42 mesh residue whose fiber length after beating is defined in JIS P 8207 is 30 to 70% is preferred. The 4 mesh residue is preferably 20% or less.

  The basis weight of the paper is preferably 50 to 250 g, particularly preferably 70 to 200 g. The thickness of the paper is preferably 50 to 210 μm.

The paper can also be given a high smoothness by calendering at the paper making stage or after paper making. The paper density is generally 0.7 to 1.2 g / cm ³ (JIS P 8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS P 8143.

  A surface sizing agent may be applied to the paper surface, and the same sizing agent that can be added to the base paper can be used as the surface sizing agent.

  The pH of the paper is preferably 5 to 9 when measured by the hot water extraction method specified in JIS P8113.

  Next, the polyolefin resin that covers both sides of the paper will be described.

  Examples of the polyolefin resin used for this purpose include polyethylene, polypropylene, polyisobutylene, and polyethylene. Polyolefins such as copolymers mainly composed of propylene are preferable, and polyethylene is particularly preferable.

  Hereinafter, particularly preferred polyethylene will be described.

  The polyethylene covering the front and back surfaces of paper is mainly low density polyethylene (LDPE) or high density polyethylene (HDPE), but other LLDPE, polypropylene, etc. can also be used in part.

  In particular, the polyolefin layer on the coating layer side is preferably one in which rutile or anatase type titanium oxide is added therein to improve opacity and whiteness. The titanium oxide content is generally 1 to 20% by mass, preferably 2 to 15% by mass, based on the polyolefin.

  In the polyolefin layer, a highly heat-resistant coloring pigment or fluorescent brightening agent for adjusting the white background can be added.

  Examples of the color pigment include ultramarine blue, bitumen blue, cobalt blue, phthalocyanine blue, manganese blue, cerulean, tungsten blue, molybdenum blue, and anthraquinone blue.

  Examples of the optical brightener include dialkylaminocoumarin, bisdimethylaminostilbene, bismethylaminostilbene, 4-alkoxy-1,8-naphthalenedicarboxylic acid-N-alkylimide, bisbenzoxazolylethylene, dialkylstilbene, etc. Is mentioned.

  The amount of polyethylene used on the front and back of the paper is selected to optimize the curl at low and high humidity after the ink absorption layer thickness and back layer are provided, but generally the thickness of the polyethylene layer Is in the range of 15 to 50 μm on the ink absorbing layer side and 10 to 40 μm on the back layer side. The ratio of polyethylene on the front and back is preferably set so as to adjust the curl that changes depending on the type and thickness of the ink absorbing layer, the thickness of the inner paper, etc. Usually, the ratio of polyethylene on the front / back is the thickness It is about 3/1 to 1/3.

  Furthermore, the polyethylene-coated paper support preferably has the following characteristics (1) to (7).

  (1) The tensile strength is a strength defined by JIS P 8113, preferably 19.6 to 294N in the vertical direction and 9.8 to 196N in the horizontal direction.

  (2) The tear strength is a strength defined by JIS P 8116, preferably 0.20 to 2.94N in the longitudinal direction and 0.098 to 2.45N in the lateral direction.

(3) The compression modulus is preferably 9.8 kN / cm ² .

  (4) The opacity is preferably 80% or more, particularly preferably 85 to 98%, when measured by the method defined in JIS P 8138.

(5) Regarding whiteness, L ^* , a ^* , and b ^* specified by JIS Z 8727 are L ^* = 80 to 96, a ^* = − 3 to +5, and b ^* = − 7 to +2. preferable.

  (6) The support having a Clark stiffness of 50 to 300 cm 3/100 in the conveyance direction of the recording medium is preferable.

  (7) The moisture in the base paper is preferably 4 to 10% with respect to the middle paper.

  (8) The glossiness (75-degree specular glossiness) for providing the ink absorbing layer is preferably 10 to 90%.

  In the image forming method of the present invention, it is preferable to use a pigment ink as the ink.

  As the ink used for image formation, a water-based ink composition, an oil-based ink composition, a solid (phase change) ink composition, or the like can be used, but a water-based ink composition (for example, 10% by mass or more per total ink mass) A water-based inkjet recording liquid containing the above water can be particularly preferably used.

  As the colorant, in the present invention, a pigment is preferably used from the viewpoint of image preservability, and as a pigment in the pigment ink, an organic pigment such as an insoluble pigment or a lake pigment, and carbon black can be preferably used. .

  The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

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

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

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

  These pigments may use a pigment dispersant as necessary. Examples of the pigment dispersant that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, and sulfosuccinates. , Naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, etc. Activators, or styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives. amount Block copolymer comprising, it may be mentioned random copolymers and salts thereof.

  The method for dispersing the pigment is not particularly limited, but various methods such as ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, etc. Can be used.

  In order to remove the coarse particles of the pigment dispersion according to the present invention, it is also preferable to use a centrifugal separator or a filter.

  The average particle size of the pigment in the pigment ink is selected in consideration of stability in the ink, image density, glossiness, light resistance, etc. In addition, the inkjet pigment image recording method of the present invention improves glossiness. From the viewpoint of improving the texture, it is preferable to select the particle size. In the present invention, the reason for improving gloss and texture is not clear, but it is presumed that the pigment is related to the state that the thermoplastic fine particles are dispersed in the melted film in the image. For the purpose of high-speed processing, the thermoplastic fine particles must be melt-coated in a short time, and the pigment must be sufficiently dispersed in the film. At this time, the surface area of the pigment has a great influence, and therefore it is assumed that an optimum region exists in the average particle diameter.

  The average particle diameter of the pigment particles contained in the pigment ink used in the present invention is preferably 300 nm or less, more preferably 30 to 200 nm, and particularly preferably 30 to 150 nm.

  The water-based ink composition which is a preferable form as the pigment ink preferably uses a water-soluble organic solvent in combination.

  Examples of water-soluble organic solvents include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols (For example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ether (E.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Tylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol Monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine) , Ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.) ), Heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) , Sulfones (for example, sulfolane), urea, acetonitrile, acetone and the like. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.

  One or more water-soluble organic solvents may be used in combination. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to 35% by mass.

  The pigment ink used in the present invention preferably contains an acetylene surfactant. As the acetylenic surfactant, acetylenic diol and its ethylene oxide adduct are preferable.

  As acetylenic diol and its ethylene oxide adduct, Surfynol 82, Surfynol 104, Surfynol 440, Surfynol 465, Surfynol 485, etc. manufactured by Air Products are preferably used.

  Depending on the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances, the ink composition may be thermoplastic fine particles, viscosity modifiers, surface tension modifiers, ratios. Resistance adjusting agents, film forming agents, dispersants, surfactants, ultraviolet absorbers, antioxidants, fading inhibitors, antifungal agents, rust inhibitors, and the like can be added as appropriate.

  In particular, the addition of thermoplastic fine particles is preferable for obtaining the effects of the present invention. As the thermoplastic fine particles, the types described in the description of the thermoplastic resin or fine particles that can be added to the surface layer of the recording medium can be used. In particular, it is preferable to apply those which do not cause thickening or precipitation even when added to the ink. The average particle diameter of the thermoplastic fine particles is preferably 0.5 μm or less, and more preferably selected from the range of 0.2 to 2 times the average particle diameter of the pigment in the ink from the viewpoint of stability.

  The thermoplastic fine particles to be added are preferably those that melt and soften in the range of 50 ° C to 200 ° C.

  The ink composition has a viscosity at the time of flight of preferably 40 mPa · s or less, and more preferably 30 mPa · s or less.

  The ink composition has a surface tension at the time of flight of preferably 20 mN / m or more, and more preferably 30 to 45 mN / m.

  The pigment solid content concentration in the ink can be selected in the range of 0.1 to 10%, and in order to obtain a photographic image, it is preferable to use so-called dark and light inks each having a different pigment solid content concentration, yellow, magenta, It is particularly preferable to use cyan and black dark and light inks, respectively. It is also preferable from the viewpoint of color reproducibility to use special color inks such as red, green, and blue as necessary.

  In order to form the inkjet image of the present invention, there is no particular limitation as long as it has a recording medium storage unit, a conveyance unit, an ink cartridge, and an inkjet print head like a commercially available printer, but at least a roll-shaped recording When using a series of printers consisting of a medium storage unit, transport unit, inkjet print head, cutting unit, pressurizing unit, heating unit if necessary, and recording print storage unit, for commercial use of inkjet photos Useful.

  The recording head may be any of a piezo method, a thermal method, and a continuous method, but the piezo method is preferable from the viewpoint of stability with pigment ink.

  Next, the heat and pressure fixing processing method according to the image forming method of the present invention will be described.

  In the image forming method of the present invention, after the ink is ejected onto the ink jet recording medium having the above-described configuration by ink jetting, a heat and pressure fixing process is performed under a pressure of 0.5 to 10 MPa and a temperature of 50 to 150 ° C. Preferably, the pressure is 0.5 to 5 MPa and the temperature is 70 to 130 ° C.

  The heat and pressure fixing method that can be used in the present invention is not particularly limited, but a pair of heat and pressure rollers, or a pair of heat and pressure belts, or a member that contacts the image portion is a belt, and the back surface of the image portion. It is preferable to use a heating / pressurizing device comprising a belt / roller such as a roller as a member in contact with the roller.

  As the heat and pressure roller, a metal metal roller or a metal core and a coating layer made of an elastic body around a metal core and optionally a surface layer (also referred to as a release layer) are formed. The core metal is made of a cylindrical body made of, for example, iron, aluminum, or SUS. A coating layer is provided on the surface of the cored bar. As the coating layer, a silicone resin having releasability is particularly preferable. For example, it is a silicone resin produced using a curable silicone such as a solvent addition type or a condensation curable type silicone. Among these, solvent addition type silicone is particularly preferable.

  The solvent addition type silicone described above is obtained by reacting linear methyl vinyl polysiloxane having a vinyl group and methyl hydrogen polysiloxane in the presence of a platinum-based catalyst at both ends, or at both ends and chains. can get.

  Specific examples of the solvent addition type silicone include, for example, KS-887, KS-779H, KS-778, KS-835, X-62-2456, X-62-2494, and X-62-2461 manufactured by Shin-Etsu Silicone. , KS-3650, KS-3655, KS-3600, KS-847, KS-770, KS-770L, KS-776A, KS-856, KS-775, KS-830, KS-830E, KS-839, X -62-2404, X-62-2405, KS-3702, X-62-2232, KS-3503, KS-3502, KS-3703, KS-5508, and the like.

  As specific examples of the condensation curable silicone, silicones such as KS-881, KS-882, KS-883, X-62-9490, and X-62-9028 manufactured by Shin-Etsu Silicone are preferably used.

  In addition, a heating element is built in one of the metal cores of the metal roller, and heat treatment and pressure treatment can be performed simultaneously by passing a recording medium between the rollers, or as necessary. You may heat by pinching | interposing a recording medium using two heating rollers. In the heating roller, as a heat source, for example, a heating element made of a halogen lamp heater, a ceramic heater, a nichrome wire, or the like is incorporated.

  The belt member used in the heating and pressing apparatus is preferably seamless nickel brass, and the thickness of the substrate is preferably 10 to 100 μm. In addition to nickel, aluminum, iron, polyethylene, or the like can be used as the base material. Regardless of whether the substrate is a roller or a belt, the thickness of the silicone resin layer is preferably 1 to 50 μm, more preferably 10 to 30 μm.

  In the present invention, in order to achieve the pressure defined above (nip pressure), for example, the pressure roller or both ends of the belt have a specific tension so as to obtain a desired nip pressure in consideration of the nip gap. What is necessary is just to select and install a spring. As the spring at this time, for example, a spring having a tension of 0.2 to 10 MPa can be selected and used.

  The method for measuring the nip pressure can be obtained, for example, by dividing the force applied to the pressure roller or belt by the nip area measured with the pressure sensitive paper or the like, or the pressure measuring paper made of pressure sensitive paper between the pressure rollers. Nip pressure can be obtained from the density of the pressure measurement paper. Examples of the pressure measuring paper include FPD301 (manufactured by Fuji Film Co., Ltd.) ultra-low pressure pressure sensitive paper.

  The conveyance speed of the recording medium when using a heat and pressure roller or a belt is preferably in the range of 1 to 15 mm / second. This is preferable from the viewpoint of image quality in addition to the viewpoint of high-speed processing.

  Next, an example of an apparatus that can be used in the image forming method of the present invention will be described.

  FIG. 1 shows an example of an ink jet recording apparatus having a heat and pressure roller for performing a heat and pressure treatment that can be used in the present invention. FIG. 2 shows another example of an ink jet recording apparatus having a heat and pressure belt that performs heat and pressure treatment that can be used in the present invention.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

<Production of recording medium>
(Preparation of silica dispersion)
125 kg of vapor phase method silica (manufactured by Tokuyama Co., Ltd .: QS-20) having an average primary particle size of about 0.012 μm is pH adjusted with nitric acid using a jet stream inductor mixer TDS manufactured by Mitamura Riken Kogyo Co., Ltd. After being sucked and dispersed in 620 L of pure water adjusted to 2.5 at room temperature, the whole amount was finished to 694 L with pure water.

  Next, while stirring 69.4L of the silica dispersion in 18L of an aqueous solution (pH = 2.3) containing 1.14kg of the cationic polymer P-1, 2.2L of ethanol and 1.5L of n-propanol. Then, 7.0 L of an aqueous solution containing 260 g of boric acid and 230 g of borax was added, and 1 g of an antifoaming agent SN381 (manufactured by San Nopco) was added. This mixed solution was dispersed with a high-pressure homogenizer manufactured by Sanwa Industry Co., Ltd., and the entire amount was finished to 97 L with pure water to prepare a silica dispersion.

(Preparation of coating solution 1 for the lower layer)
While stirring 600 ml of the silica dispersion at 40 ° C., the following additives were sequentially mixed to prepare a lower layer coating solution 1.

10% aqueous solution of polyvinyl alcohol (Kuraray Industries, Ltd .: PVA203)
6ml
7% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235)
185ml
Saponin (50% aqueous solution) Appropriate amount Pure water Finished to 1000 ml (preparation of polymer compound crosslinked by ionizing radiation)
With reference to JP-A No. 2000-181062, p- (3-methacryloxy-2-hydroxypropyloxy) benzaldehyde is reacted with polyvinyl alcohol having a polymerization degree of 3000 and a saponification degree of 88%, and a crosslinking group modification rate of 1 mol%, solid An ultraviolet curable polyvinyl alcohol derivative 1 having a partial concentration of 8% was produced.

(Preparation of surface layer coating solution 1)
While stirring 600 ml of the silica dispersion at 40 ° C., the following additives were sequentially mixed to prepare a surface layer coating solution 1.

UV curable polyvinyl alcohol derivative 1 15ml
Irgacure 2959 (Ciba Specialty Chemicals) 60mg
Defoamer SN381 (San Nopco Co., Ltd.) 6.2mg
Saponin (50% aqueous solution) Appropriate amount Pure water Finished with 1000 ml of the total amount After mixing the above additives, pure water was added appropriately so that the viscosity would be 45 mPa · s at 40 ° C to prepare surface layer coating solution 1 did.

Example 1
The above lower layer coating solution having a paper support coated with polyethylene on both sides (thickness 220 μm and containing 13% by mass of anatase-type titanium oxide with respect to polyethylene in the polyethylene on the ink absorption layer side) as the first layer from the support side 1 is applied with a slide hopper, and then the surface layer coating solution 1 is applied as a second layer on the slide hopper, and then an ultraviolet ray having an energy amount of 40 mJ / cm ² is applied with a metal halide lamp having a main wavelength of 365 nm. The recording medium 1 was manufactured by irradiating and then drying.

Example 2
In Example 1 above, the following surface layer coating solution 2 was used instead of the surface layer coating solution 1, and the lower layer coating solution 1 and the surface layer coating solution 2 were simultaneously layered so that the dry film thickness of the surface layer was 7 μm. Application was carried out, and then a recording medium 2 was produced in the same manner as in Example 1.

(Preparation of surface layer coating solution 2)
The upper layer coating liquid 1 used in the production of the recording medium 1 is stirred at 40 ° C., and styrene-acrylic latex (Tg 50 ° C., average particle size 250 nm, solid content 40%) is used as the thermoplastic resin. In addition to the solid content ratio of fine particles / inorganic pigment fine particles (silica) being 50/50, pure water is suitably added so that the viscosity becomes 45 mPa · s at 40 ° C. to prepare surface layer coating solution 2 did.

Example 3
Instead of the styrene-acrylic latex (Tg 50 ° C., average particle size 250 nm) of the surface layer coating solution 2 of Example 2, a solid content of a thermoplastic resin of styrene-acrylic latex (Tg 70 ° C., average particle size 220 nm) is used. A recording medium 3 was obtained in the same manner as in Example 2 except that they were used in the same manner.

Example 4
A recording medium 4 was obtained in the same manner as in Example 2 except that styrene-butadiene latex (Tg 70 ° C., average particle size 220 nm) was used in place of the styrene-acrylic latex of Example 2.

Example 5
A recording medium 5 was prepared in the same manner as in Example 2 except that the UV curable polyvinyl alcohol derivative 1 was used in place of all the polyvinyl alcohol in the lower layer coating solution 1 of Example 2 so that the solid content was the same. Obtained.

Comparative Example 1
A comparative recording medium 1 was prepared in the same manner except that pentaerythritol triacrylate was used instead of the ultraviolet curable polyvinyl alcohol derivative 1 used in the surface layer coating solution of Example 1.

Comparative Example 2
Comparative Example in the same manner except that polyethylene glycol diacrylate (A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.) was used instead of the ultraviolet curable polyvinyl alcohol derivative 1 used in the surface layer coating solution of Example 2. Recording medium 2 was prepared.

Comparative Example 3
A comparative recording medium 3 was prepared in the same manner except that pentaerythritol triacrylate was used in place of the ultraviolet curable polyvinyl alcohol derivative 1 used in the surface layer coating solution of Example 3.

Comparative Example 4
A comparative recording medium 4 was prepared in the same manner except that pentaerythritol triacrylate was used in place of the ultraviolet curable polyvinyl alcohol derivative 1 used in the surface layer coating solution of Example 4.

<Preparation of ink>
[Preparation of pigment ink set]
(Preparation of pigment dispersion)
<Preparation of Yellow Pigment Dispersion 1>
C. I. Pigment Yellow 74 20% by mass
Styrene-acrylic acid copolymer (molecular weight 10,000, acid value 120) 12% by mass
Diethylene glycol 15% by mass
Ion-exchanged water 53% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 60% by volume of 0.3 mm zirconia beads to obtain Yellow Pigment Dispersion 1. The average particle size of the obtained yellow pigment was 112 nm.

<Preparation of magenta pigment dispersion 1>
C. I. Pigment Red 122 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson)
18% by mass in solid content
Diethylene glycol 15% by mass
Ion-exchanged water 42% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to obtain a magenta pigment dispersion 1. The average particle size of the obtained magenta pigment was 105 nm.

<Preparation of Cyan Pigment Dispersion 1>
C. I. Pigment Blue 15: 3 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson)
15% by mass as solid content
Glycerin 10% by mass
Ion-exchanged water 50% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 60% by volume of 0.3 mm zirconia beads to obtain cyan pigment dispersion 1. The average particle diameter of the obtained cyan pigment was 87 nm.

<Preparation of Black Pigment Dispersion 1>
Carbon black 20% by mass
Styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150) 10% by mass
Glycerin 10% by mass
Ion exchange water 60% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60% to obtain a black pigment dispersion 1. The average particle size of the obtained black pigment was 75 nm.

(Preparation of pigment ink set)
<Preparation of yellow dark ink 1>
Yellow pigment dispersion 1 15% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 54.9% by mass
Each of the above compositions was mixed, stirred, and filtered through a 1 μm filter to prepare yellow dark ink 1 which is the aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink was 120 nm, and the surface tension γ was 36 mN / m.

<Preparation of yellow light ink 1>
Yellow pigment dispersion 1 3% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 61.9% by mass
Each of the above compositions was mixed, stirred, and filtered through a 1 μm filter to prepare a yellow light ink 1 which is an aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 118 nm, and the surface tension γ was 37 mN / m.

<Preparation of magenta dark ink 1>
Magenta pigment dispersion 1 15% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 54.9% by mass
The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare magenta dark ink 1 that is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 113 nm, and the surface tension γ was 35 mN / m.

<Preparation of magenta light ink 1>
Magenta pigment dispersion 1 3% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 61.9% by mass
Each of the above compositions was mixed, stirred, and filtered through a 1 μm filter to prepare magenta light ink 1 that is the aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink was 110 nm, and the surface tension γ was 37 mN / m.

<Preparation of cyan dark ink 1>
Cyan pigment dispersion 1 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 59.9% by mass
Each of the above compositions was mixed, stirred, and filtered through a 1 μm filter to prepare Cyan Dark Ink 1 which is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 95 nm, and the surface tension γ was 36 mN / m.

<Preparation of cyan light ink 1>
Cyan pigment dispersion 1 2% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 0.2% by mass
Ion-exchanged water 62.8% by mass
The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare cyan light ink 1 that is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 92 nm, and the surface tension γ was 33 mN / m.

<Preparation of black dark ink 1>
Black pigment dispersion 1 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 59.9% by mass
Each of the above compositions was mixed, stirred, and filtered through a 1 μm filter to prepare Black Dark Ink 1 which is the aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink was 85 nm, and the surface tension γ was 35 mN / m.

<Preparation of black light ink 1>
Black pigment dispersion 1 2% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 62.9% by mass
Each of the above compositions was mixed, stirred, and filtered through a 1 μm filter to prepare a black light ink 1 which is an aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 89 nm, and the surface tension γ was 36 mN / m.

<< Inkjet image formation >>
The prepared pigment ink set is set in an ink jet printer having a pair of heat and pressure rollers that simultaneously perform the heat and pressure fixing process shown in FIG. 1, and the prepared recording media 1 to 6 are fed into a sheet, and yellow and magenta A solid image of cyan, black, and an image made up of a grid-like test chart each having Y, M, C, B, G, R, and Bk bands each having a width of 1 cm in length and width were output. Thereafter, heat and pressure treatment was performed at a surface temperature of the fixing device of 110 ° C. in a heating and pressure fixing device in the apparatus.

  Of the heat and pressure roller pair, the heat and pressure roller disposed on the surface side in contact with the surface layer of the recording medium was a metal roller having a coating layer and a halogen heater having a surface roughness of 100 nm. A releasable layer was applied to the surface of the metal roller by the following method.

(Applying a releasable layer)
1. Preparation of release layer coating solution Release layer coating solution KS830E (manufactured by Shin-Etsu Chemical Co., Ltd.) 500 g
Curing catalyst CAT-PL-50T (manufactured by Shin-Etsu Chemical Co., Ltd.) 5 ml
Toluene 1500ml
The above materials were mixed and stirred to prepare a release layer coating solution.

2. Coating of the releasable layer 2 L of the obtained releasable layer coating solution is put into a cylindrical beaker having an inner diameter of 15 cm and a height of 50 cm, and an iron roller having a diameter of 50 mm and a length of 200 mm is set in a commercially available dip type coating machine. Then, the roller was lowered and dipped in a beaker, and coating was performed with the lifting speed set to 15 mm per second. Then, after leaving at room temperature for 5 minutes, it heated in 100 degreeC oven for 1 hour, and applied the release layer.

  According to the above image forming method, the type of recording medium and the heat and pressure fixing conditions are combined as shown in Table 1, and high-definition color digital standard image data [N5 / bicycle] image issued by the Japan Standards Association is obtained. Produced.

<Characteristic evaluation of formed image>
Each characteristic evaluation was performed according to the following method about the recording paper produced by the said method, and a formed image.

[Characteristic evaluation of recording paper]
(Bending resistance)
The recording paper produced as described above was evaluated for resistance to breakage according to the method described below and shown in Table 1.

  Breaking: The recording paper cut into a strip of 5 × 10 cm was placed on a paper tube having a core outer diameter of 3 cm, and cracking of the breaking was visually evaluated in five stages.

◎: No fold cracks ○: No more than 5 fold cracks △: No more than 6 to 20 fold cracks ×: No more than 21 to 100 fold cracks XX: 101 or more fold cracks In practice, x and below have no commercial value.

(Evaluation of glossiness)
For each of the images prepared above, a color silver salt photographic image was prepared for comparison, the glossiness thereof was visually observed, and glossiness was determined according to the following criteria.

A: Gloss equivalent to or better than color silver salt photographic image B: Gloss almost similar to color silver salt photographic image Δ: Slightly less than the gloss of color silver salt photographic image, but practical In the above allowable range: x: Quality that is clearly inferior in gloss to a color silver salt photographic image and is a problem in practical use Table 1 shows the results obtained as described above.

  It can be seen that the recorded image formed using the inkjet recording medium of the present invention has no cracks and is excellent in surface gloss.

An example of an ink jet recording apparatus having a heat and pressure roller for performing heat and pressure treatment that can be used in the present invention is shown. Another example of an ink jet recording apparatus having a heating and pressing belt that performs heating and pressing treatment that can be used in the present invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Recording medium 2 Recording medium conveying means 21 Conveying roller pair 3 Recording head 34 Recording medium holding part 4 Heating and pressing means 41 Heating roller 42 Pressure roller 43 Heating body 44 Heating belt 45 Lower pressure bonding belt 46 Driven roller 5 Temperature sensor 6 Recording medium cutting means 61, 62 Cutter 7 Slack forming means 71 First roller pair 72 Second roller pair

Claims (4)

In an ink jet recording medium having at least two ink absorbing layers on a support and containing inorganic pigment fine particles in the ink absorbing layer located farthest from the support, the position farthest from the support The ink absorbing layer in which the hydrophilic polymer compound having a functional group in the side chain and having a polymerization degree of 300 or more is irradiated with ionizing radiation to contain a polymer compound crosslinked between the side chains. An ink jet recording medium. 2. The ink jet recording medium according to claim 1, wherein the ink absorbing layer located farthest from the support contains thermoplastic resin fine particles. The inkjet recording medium according to claim 1 or 2, wherein the polymer compound crosslinked by ionizing radiation is a polymer of a photocurable polyvinyl alcohol derivative. 4. An image is formed on the inkjet recording medium according to any one of claims 1 to 3 using a pigment ink, and then heated and pressed under conditions of a pressure of 0.5 to 10 MPa and a temperature of 50 to 150 ° C. An image forming method.

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