JP2007160664A - Inkjet recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording paper which is low in cost, has a high productivity, and is excellent in film strength. <P>SOLUTION: The inkjet recording paper provides a porous ink absorbing layer comprising at least an inorganic fine particle and a hydrophilic resin on a substrate for a recording material obtained by coating at least one face side of a water absorbing substrate with a coating liquid for forming an undercoating layer comprising a resin dispersion to form the undercoating layer, and by applying a pressure processing on the undercoating layer under a condition that voids are not substantially left in the undercoating layer. The inkjet recording paper is characterized in that the hydrophilic resin is crosslinked with a crosslinking agent forming a non-thermally reversible gel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel ink jet recording paper (hereinafter also simply referred to as recording paper), and more particularly to an ink jet recording paper that is low in cost, has high productivity, and has excellent film strength.

  In recent years, in the ink jet recording system, image quality has been improved rapidly, and the image quality is approaching that of silver halide photography. As a means for achieving such a silver salt photographic image quality by the ink jet recording method, rapid technical improvement is also being made on the ink jet recording paper to be used. In particular, when a non-absorbent support is used, there is no cockling (wrinkle) after printing as seen on a water-absorbing support, and a high smooth surface can be maintained, so that a higher quality print print can be obtained. Therefore, a non-water-absorbing resin-coated paper used for a silver salt photographic light-sensitive material called a resin-coated paper is often used.

  Further, as the ink receiving layer, there is an ink jet recording paper having an ink absorbing layer composed of a porous layer having a high porosity in which voids are formed between inorganic fine particles using inorganic fine particles and a relatively small amount of hydrophilic resin. is there. A void-type inkjet recording paper provided with such a porous layer having a minute void as an ink absorbing layer has a relatively high ink absorbability and quick-drying property, and is the closest to the silver salt photographic image quality. Known as the resulting method.

  In the production process of the porous layer, a small amount of hydrophilic binder is adsorbed on the surface of the fine particles and entangled between the hydrophilic binders, or the fine particles are retained by the interaction such as hydrogen bonding between the hydrophilic binders. It is made to form a porous layer. Thereafter, it is considered that the coating film undergoes rapid shrinkage during the drying process, and the film surface is cracked by the shrinkage stress. There is known a method in which polyvinyl alcohol and boric acid or a salt thereof are contained in a coating liquid, followed by cooling and gelation after coating, followed by drying (see Patent Document 1). According to this method, a coating layer having a high film thickness can be obtained without causing cracks. However, boric acid or its salt is a substance that has a concern about the influence on the environment, and further, it is necessary to cool and gelate immediately after coating and before drying. .

  As one of the techniques for solving such a problem, an inkjet recording paper (see Patent Document 2) using an acetoacetyl-modified polyvinyl alcohol and a zirconium compound or an amino group-containing compound as a crosslinking agent, or an epoxy crosslinking agent is used. An ink jet recording sheet containing the ink is disclosed (see Patent Document 3).

When such a crosslinking means is used, a stronger cross-linking bond than boric acid is formed, but there is a problem that the reactivity is low. The higher the drying conditions after coating, the more the crosslinking reaction is promoted because the crosslinking reaction is promoted. However, when resin-coated paper is used as the support, the resin softens during drying at high temperatures. Since blisters called blisters occur, the drying temperature cannot be made sufficiently high, so that the required coating film strength has not been obtained.
US Pat. No. 4,592,951 JP 2004-114457 A JP 10-119423 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an inkjet recording paper that is low in cost, high in productivity, and excellent in film strength.

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

  1. After forming the undercoat layer by applying a coating solution for forming the undercoat layer containing the resin dispersion on at least one surface side of the water-absorbent support, under the condition that substantially no voids remain in the undercoat layer. An ink jet recording paper in which a porous ink absorbing layer composed of at least inorganic fine particles and a hydrophilic resin is provided on a recording material support obtained by pressure treatment, wherein the hydrophilic resin is non-thermo-reversible. An ink jet recording paper, which is cross-linked by a cross-linking agent that forms a conductive gel.

  2. 2. The inkjet recording paper according to 1 above, wherein at least one of the hydrophilic resins is acetoacetyl-modified polyvinyl alcohol crosslinked with a crosslinking agent that reacts with acetoacetyl groups.

  3. At least one of the hydrophilic resins is polyvinyl alcohol, and at least one selected from an epoxy compound, an aldehyde compound, an active vinyl compound and an active halogen compound is used as a crosslinking agent. The inkjet recording paper of 1.

  4). 4. The ink jet recording paper according to any one of 1 to 3, wherein a pressure in the pressure treatment is 5 MPa or more and 50 MPa or less.

  5. 5. The ink jet recording paper according to any one of 1 to 4, wherein the pressure treatment is performed by a calendar machine in a range where the linear pressure is 0.3 kN / cm or more and 2.0 kN / cm or less. .

  6). Any one of 1 to 5 above, wherein the temperature at the time of pressurization in the pressure treatment is Tp, and the glass transition temperature of the resin dispersion is Tg, which satisfies the condition defined by the following formula (1): 2. An ink jet recording paper according to item 1.

Formula (1)
Tg <Tp <Tg + 50
7). When the undercoat layer containing the resin dispersion contains a pigment, the solid content of the pigment contained in the undercoat layer is P, and the solid content of the resin is B, the condition defined by the following formula (2) is satisfied. The inkjet recording paper according to any one of 1 to 6, wherein:

Formula (2)
0.13 <P / (P + B) <0.5
8). 8. The inkjet according to any one of 1 to 7 above, wherein the inkjet is dried under a constant temperature and humidity condition from the start to the end of drying, and the drying temperature is 80 ° C. or higher and 150 ° C. or lower. Recording sheet.

  9. 9. The ink jet recording paper according to any one of 1 to 8, wherein the crosslinking agent is produced by adding to a coating solution for forming the ink absorbing layer immediately before coating.

  According to the present invention, it is possible to provide an ink jet recording paper that is low in cost, high in productivity, and excellent in film strength.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventor formed an undercoat layer by applying a coating solution for forming an undercoat layer containing a resin dispersion on at least one surface side of the water-absorbent support. Thereafter, a porous ink absorbing layer composed of at least inorganic fine particles and a hydrophilic resin is provided on a support for recording material obtained by subjecting the undercoat layer to pressure treatment under conditions where substantially no voids remain. Ink jet recording paper, wherein the hydrophilic resin is cross-linked by a cross-linking agent that forms a non-thermo-reversible gel. It has been found that an ink jet recording paper having excellent strength can be realized, and has reached the present invention.

  That is, the ink jet recording paper of the present invention (hereinafter, also simply referred to as recording paper) has a subbing layer formed by applying a coating liquid for forming an undercoat layer containing a resin dispersion to at least one surface side of a water-absorbent support. Is formed on the support for recording material obtained by subjecting the undercoat layer to pressure treatment under conditions where substantially no voids remain in the undercoat layer. Such a support is an aqueous coating liquid. Curling and cockling when applied can be prevented, and the gap between the water-absorbent support and the resin layer is smaller than that of resin-coated paper produced by the conventional resin melt extrusion method. Blisters at the time of high-temperature drying after layer coating can be suppressed.

  Details of the present invention will be described below.

  In the recording paper of the present invention, an undercoat layer-forming coating solution containing a resin dispersion is applied to at least one surface side of the water-absorbent support to form an undercoat layer, and then substantially applied to the undercoat layer. One feature is that a support for recording material obtained by performing pressure treatment under conditions where no voids remain in the substrate is used.

  The void referred to in the present invention is a space in which a liquid formed between the surface of the recording material support and the water-absorbing support can permeate, and the liquid adheres to the surface of the recording material support. In this case, the liquid reaches the water-absorbing support through the gap, and as a result, the liquid reaching the water-absorbing support causes problems such as swelling and deformation of the water-absorbing support.

  Such voids in the coating layer are formed in the process of filling the resin particles in the resin dispersion and the solvent in the resin dispersion volatilizing in the drying process. In the present invention, this coating layer is sufficiently processed by applying pressure after formation to a level at which voids do not substantially remain, thereby suppressing problems such as swelling and deformation of the water-absorbent support. It has been found that a recording material support can be provided that has a high glossiness and can maintain the high glossiness even when a recording layer forming coating solution is applied onto the recording material support.

The confirmation of the presence or absence of voids in the present invention can be confirmed by, for example, directly observing with an electron microscope and confirming the presence thereof, and also by a test method according to the water absorption test method (Cobb) method defined in JIS P 8140. it can. In the measurement method according to the water absorption test method (Cobb) method, if the water absorption is less than 5 g / m ² , it is determined that there is no void, and preferably less than 2 g / m ² .

  In the present invention, it was found that there is a preferable pressure condition for performing the pressure treatment without substantially leaving any voids in the coating layer containing the resin dispersion and for further exerting the object effect of the present invention. . That is, when an aqueous coating solution such as an ink absorbing layer is applied onto the absorbent support and dried at a high temperature, the occurrence of cockling and curling is suppressed without causing blisters.

  In the study that led to the present invention, pressures suitable for two methods of pressurizing in a sheet form and so-called calendering, in which pressurization was performed in a linear or very narrow nip formation were examined.

  First, in the case of planar pressing, it was found that the pressure is preferably in the range of 5 MPa or more and 50 MPa or less. If the pressure is less than 5 MPa, a gap is likely to occur between the resin layer and the water-absorbent support, which may cause blistering. On the other hand, when a high pressure exceeding 50 MPa is applied, the effect of preventing cockling and curling is reduced. Although these reasons are not clear, a certain degree of high pressure is necessary to fill the voids between the resin particles by deforming the resin, but if the pressure is higher than necessary, the voids existing in the water-absorbent support will be lost. It is presumed that the amount of resin entering the resin and covering the surface of the water-absorbing support is substantially reduced.

  Next, in the case of calendar treatment, the linear pressure is preferably in the range of 0.3 kN / cm to 2.0 kN / cm. In this case, it has been found that problems such as blistering, cockling and curling suppression effect are reduced outside the optimum range as in the case of planar pressing.

  Moreover, it is preferable to heat as the temperature at the time of pressurization, and when the temperature Tp at the time of pressurization is in the range of Tg <Tp <Tg + 50 with respect to Tg of the resin dispersion, the effect of the present invention is further improved. It was found to express.

  Therefore, pressurization within the above-mentioned preferable pressure range and a preferable heating temperature range is a more preferable method from the viewpoint of the effect of the present invention.

  In addition, it has been found that it is more effective to continuously perform a plurality of pressurization processes as the pressurization condition from the viewpoint of obtaining the object effect of the present invention. Specifically, the effect of the present invention is more exhibited when performed in the range of 2 to 10 times. In this case, the processing conditions for a plurality of times may be the same or different. In the case of calendar processing, it is particularly preferable to set the number of nips to a plurality.

  Moreover, it is also preferable to provide a drying step after forming the coating layer containing the resin dispersion on at least one surface side of the water-absorbent support and before performing the pressure treatment. The drying process is important in order not to cause defects such as swelling due to moisture remaining during pressurization. It is particularly preferable that the drying temperature is equal to or higher than the Tg of the resin of the resin dispersion used. It is thought that the film formation of the resin proceeds by drying at a temperature equal to or higher than Tg, and therefore, the process of filling the voids in the pressurizing process is easy and the completeness is increased.

  Next, the water absorbing support used in the present invention will be described.

  As the water-absorbing support applicable to the recording material support of the present invention, those composed of natural and synthetic materials can be used, but preferably a paper base material mainly composed of cellulose pulp is used.

  Examples of the raw material for the paper base material mainly composed of cellulose pulp that can be used in the present invention include chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, CGP, RMP, TMP, CTMP, CMP, and PGW, and DIP. It is possible to use wood pulp such as used paper pulp as the main raw material. In addition, various fibrous materials such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as raw materials as necessary.

  Various conventionally known additives such as a sizing agent, pigment, paper strength enhancer, fixing agent, fluorescent whitening agent, wet paper strength agent, and cationizing agent may be added to the paper base as necessary. it can. Higher fatty acids, alkyl ketene dimers, etc. as sizing agents, calcium carbonate, talc, titanium oxide, etc. as pigments, starch, polyacrylamide, polyvinyl alcohol, etc. as paper strength enhancing agents, sulfate bands, cationics as fixing agents However, the present invention is not limited to this.

  The paper base material can be manufactured by mixing various fibrous materials such as wood pulp and various additives and using various paper machines such as a long net paper machine, a circular net paper machine, and a twin wire paper machine. Further, if necessary, a size press treatment with starch, polyvinyl alcohol, or the like, a various coating treatment, or a calendar treatment can be performed at the paper making stage or after paper making.

The water-absorbing support that can be preferably used in the present invention is preferably a base paper material mainly composed of cellulose pulp and having a so-called basis weight of 50 g / m ² or more and 250 g / m ² or less. If it is less than 50 g / m ² , the waist is weak and the texture of the paper is not preferred. On the other hand, if it exceeds 250 g / m ^2, an effect such as improvement in glossiness by pressurizing treatment is difficult to be obtained, and when an ink jet recording medium is used, failure is likely to occur due to ink jet printer transportability and the like.

  Next, the resin dispersion according to the present invention will be described.

  As the resin dispersion according to the present invention, a water-dispersible latex that can be used as a latex binder for coated paper can be widely used.

  For example, from SB (styrene butadiene), acrylic, styrene, styrene-acrylic, acrylonitrile-butadiene, vinyl acetate, vinyl acetate-ethylene, vinyl acetate-ethylene-vinyl chloride olefin, urethane, etc. You can choose.

  When the average particle diameter is 0.05 μm or more, the resin particles are suppressed from being buried in the voids of the water-absorbent support during coating, and are likely to contribute to the effect. Moreover, if it is 10 micrometers or less, it is preferable at the point which can suppress that the defect which has a space | gap locally arises, or can eliminate a space | gap by a short time pressure treatment.

  There are no particular restrictions on the ionicity of the resin dispersion. In the case of using an additive such as a pigment in the coating liquid or adding an activator, the liquid can be selected in consideration of the stability of the liquid. Moreover, it can select in consideration of not reducing the stability of the coating liquid apply | coated on the produced water absorbing support body. In these cases, nonionic ones are good and particularly preferred.

  Among nonionic ones, a vinyl acetate latex or an acrylic latex obtained by polymerizing a water-soluble polymer compound as a protective colloid can be particularly preferably used.

As a specific product that can be used as a resin dispersion,
Self-crosslinking molds such as Nipol LX407 series various latexes for styrene butadiene based coated paper manufactured by Nippon Zeon, Nipol V1004, Nipol MH5055, Nipol LX438C, acrylonitrile-butadiene latex (NBR LATEX) Nipol LX874, etc.
Latex for fiber paper processing manufactured by Sumitomo Chemical, vinyl acetate-ethylene, Sumikaflex S-500, 706, 753, etc., vinyl acetate-ethylene-vinyl chloride, S-880, etc.
Asahi Kasei Styrene Butadiene SBR L series (L-1970 etc.),
Polysol EVA series (AD-6 etc.) made by Showa Polymer,
Can be mentioned.

  In addition to the coating layer containing the resin dispersion according to the present invention, pigments, water-soluble binders (eg, starch, casein, soy protein, CMC, PVA, alkali-soluble latex, etc.), dispersants, lubricants, antifoaming Agent, water-proofing agent (wax, insoluble fatty acid, soap, urea, melamine / formalin resin, glyoxal, heavy metal salt, etc.), activator, pH adjuster, fungicide, dye and the like.

  When a pigment is used, it is preferably used in an appropriate amount for adjusting glossiness, white background adjustment and opacity as a support. In particular, a white pigment can be preferably used. Examples of the white pigment include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, and carbonate. Zinc, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, hydrous halloysite, magnesium hydroxide, etc. Organic pigments such as inorganic pigments, styrene plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins, and melamine resins can be used.

  In particular, it is preferable to use a white pigment selected from light calcium carbonate, heavy calcium carbonate, kaolin, talc, silica, and alumina, and it is also preferable to use titanium oxide together if necessary.

  As kaolin, calcined kaolin, engineered kaolin, high-white kaolin, standard white kaolin, etc. manufactured by Imeris can be used.

  As calcium carbonate, various synthetic calcium carbonates (such as Brilliant-15) manufactured by Shiroishi Kogyo Co., Ltd. can be used.

  When adding a pigment, the effect of this invention can be improved further with the addition amount. In this invention, when the pigment solid content in the coating layer containing a resin dispersion is set to P and the resin solid content is set to B, it is preferable to satisfy | fill the conditions prescribed | regulated by the following Formula (2).

Formula (2)
0.13 <P / (P + B) <0.5
If P / (P + B) in the formula (2) is larger than 0.13, the cockling and curl suppressing effects, which are the problems of the present invention, are remarkable, and white background adjustment and opacity improvement are sufficient, which is preferable. Moreover, if P / (P + B) is smaller than 0.5, it is possible to suppress the occurrence of defects in which voids are not completely filled, and the glossiness improving effect is remarkable. In addition, when the recording medium having the ink absorbing layer applied on the support according to the present invention is bent, it is possible to suppress the occurrence of defects such as cracks in the support, and the print density at that location is reduced. This is preferable because there is no risk of causing image defects.

  P / (P + B) defined by Equation (2) is obtained from the total resin amount and the total pigment amount obtained when a plurality of types of resins and pigments are used.

  The viscosity of the coating solution for the coating layer containing the resin dispersion according to the present invention is preferably adjusted to 100 mPa · s or more and 1000 mPa · s or less. This is because it is important to maintain the viscosity required for the coating layer coating liquid so that the coating liquid component does not settle in the voids in the water-absorbent support immediately after coating and in the drying step.

  If the viscosity of the coating layer coating solution is 1000 mPa · s or less, there is no restriction even when the coating film is applied thinly, which is preferable.

In the recording material support of the present invention, the surface of the L ^* a ^* b ^*, so that the conditional range defined below, it is preferable to adjust the white background characteristics.

That is, it is preferable that L ^* > 90 as the lightness index L ^* in the CIE color space, and −7 <a ^* <+ 7, −7 <b ^* <− 7 as the perceptual chromaticity index a ^* and b ^*. .

L ^* , a ^* , b ^* values defined in the present invention are measured according to JIS-Z-8722, 8717, and are displayed according to the color display method defined in JIS-Z-8730. For example, X-rite densitometer (X-Rite 938), Gretag SPM-100 and standard black backing for color measurement, color difference meter (Minolta: CR-100), color analyzer (Murakami Color Co., Ltd. CMS-1200) Etc. can be measured.

By adjusting L ^* , a ^* , and b ^* within the range specified in the present invention, it is preferable that an ink jet recording medium is produced, since the image contrast is increased and a clear and vivid image of pure color is obtained.

  As a method for adjusting the white background as an ink jet recording medium, there is a method of adding a white pigment such as a fluorescent brightening agent or titanium oxide to the ink absorption layer, but it affects the coating solution stability and coating film performance of the ink absorption layer. In many cases, it is preferable to adjust with a support.

When adjusting with a support, when selecting a water-absorbing support, it may be selected in consideration of a white background, or a fluorescent whitening agent or a white pigment may be added to the coating layer containing the resin dispersion. You may adjust it. In particular, when a white pigment is contained in the coating layer containing the resin dispersion according to the present invention, the selection and addition amount of the white pigment to be used are adjusted, and L ^* , a ^{* on the} surface of the support according to the present invention are adjusted ^. , B ^* are particularly preferred.

  In the production process of the recording material support of the present invention, the raw material prepared by adding pulp, band, white pigment, water-soluble polymer, sizing agent, etc. is made with a long net paper machine, and if necessary, size press treatment It is preferable to apply the coating liquid containing the resin dispersion according to the present invention to the base paper, using a roll coater, an air knife coater, a blade coater, and the like, and then perform a calendar process.

  The support for recording material of the present invention can be used as a support for various image recording materials. Examples thereof include an ink jet recording medium, an electrophotographic image receiving material, a sublimation transfer image receiving material, a heat-sensitive color recording material, a thermal transfer image receiving material, and a silver salt photographic light-sensitive material.

  The support for recording material according to the present invention is suitable for applying an aqueous coating solution, and is particularly suitable as a support for an ink jet recording medium. In the recording paper of the present invention, on the support for recording material, A porous ink absorption layer (also referred to as a void-type ink absorption layer) comprising at least inorganic fine particles and a hydrophilic resin is provided, and the hydrophilic resin is crosslinked by a crosslinking agent that forms a non-thermo-reversible gel. It is characterized by that.

  The void-type ink absorbing layer will be described below.

  A polymer compound such as a hydrophilic resin used in the present invention forms a gel having a network structure by a crosslinking reaction. Generally, due to its formation mechanism, it is due to physical aggregation between molecules (hydrogen bond, ionic bond, coordination bond, etc.), and reversible sol-gel transition occurs, accompanied by chemical bond formation and irreversible. There are two types of reaction that form a gel, the former being called a physical gel and the latter also called a chemical gel. Crosslinking by a bonding mode in which the equilibrium of dissociation and non-dissociation changes with changes in the temperature of coordination bonds such as PVA and boric acid is a physical gel, and the non-thermo-reversible gel in the present invention is Examples of such cross-links are chemical gels, cross-linking with cross-linking agents (amine compounds, hydrazine compounds, etc.) that react with acetoacetyl-modified polyvinyl alcohol and acetoacetyl groups, and epoxy compounds of polyvinyl alcohol, isocyanate compounds, Crosslinking with an aldehyde compound, an active vinyl compound, or an active halogen compound is exemplified, and these are preferably applied.

  As the acetoacetyl-modified polyvinyl alcohol, known ones can be used, for example, a method of reacting polyvinyl alcohol with diketene, a method of reacting polyvinyl alcohol with acetoacetate and transesterification, or vinyl acetate and vinyl acetoacetate. It may be produced by any method such as a copolymerization method.

  As polyvinyl alcohol which is a starting material of acetoacetyl-modified polyvinyl alcohol, in addition to ordinary polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate, polyvinyl alcohol whose terminal is cation-modified or anion-modified polyvinyl alcohol having an anionic group Such modified polyvinyl alcohols are also included. The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 200 or more, and particularly preferably has an average degree of polymerization of 1000 to 5000. The saponification degree is preferably 70 to 100%, particularly preferably 80 to 99.5%.

  The modification rate of acetoacetyl-modified polyvinyl alcohol is in the range of 0.01 to 20 mol%, more preferably 1 to 15 mol%, and if it is less than 0.01 mol%, the crosslinking effect as an acetoacetyl group is not expressed. However, it is not much different from ordinary polyvinyl alcohol, and if it exceeds 20 mol%, the solubility and stability in water are poor, which is not preferable.

  In the ink jet recording paper of the present invention, acetoacetyl-modified polyvinyl alcohol contained in the hydrophilic resin is crosslinked by a crosslinking agent that reacts with acetoacetyl groups.

  Examples of the crosslinking agent that reacts with the acetoacetyl group include amine compounds (melamine, acetoguanamine, benzoguanamine, urea, alkylated methylolurea, alkylated methylolmelamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, Aliphatic amines such as trimethylhexamethylenediamine, polyetherdiamine, 1,3-bisaminomethylcyclohexane, aromatic amines such as metaphenylenediamine and metaxylenediamine, etc., aldehyde compounds (formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde) Monoaldehyde such as Glyoxal, Glutanedialdehyde, Malondialdehyde, Succindialdehyde, Maleindialdehyde, Lid Dialdehydes such as dialdehyde), hydrazine compounds and derivatives thereof (hydrazine, hydrazine hydrard, inorganic salts such as hydrazine hydrochloric acid, nitric acid and organic salts such as formic acid, oxalic acid, methyl hydrazine, ethyl, propyl, butyl, Monosubstituted compounds such as allyl and phenyl, asymmetric disubstituted compounds such as 1,1-dimethyl and 1,1-diethyl, and symmetric disubstituted compounds such as 1,2-dimethyl and 1,2-diethyl, propionic acid hydrazide, salicylic acid Hydrazide compounds such as hydrazide, adipic acid hydrazide, sebacic acid hydrazide, isophthalic acid hydrazide, hydrazone compounds such as benzophenone hydrazone, etc., formamide group-containing compounds (monomer polymers such as vinylformamide, N-allylformamide, acrylic formamide, or the like) Copolymer of monomer and vinyl acetate monomer, styrene monomer, methyl (meth) acrylate, etc.), isocyanate compound (hexamethylene diisocyanate, aromatic polyisocyanate, tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tri Range isocyanate adducts, triphenylmethane triisocyanate, methylene bis-4-phenylmethane triisocyanate, methylene bisisophorone diisocyanate, ketoxime block products of methylene bis-4-phenylmethane triisocyanate and methylene bisisophorone diisocyanate, etc.) Of these, amine compounds, hydrazine compounds and derivatives thereof, or isocyanate compounds are preferred. Particularly preferred crosslinking agents are bifunctional or polyfunctional crosslinking agents.

  The amount of these crosslinking agents used depends on the type of crosslinking agent, the modification rate of acetoacetyl-modified polyvinyl alcohol, the mass ratio of inorganic fine particles and acetoacetyl-modified polyvinyl alcohol, or the amount of water-soluble resin used in combination. It is preferably used in the range of about 0.1 to 40% by mass, more preferably in the range of 1 to 20% by mass, based on the amount of the modified polyvinyl alcohol used.

  As a method of crosslinking the acetoacetyl-modified polyvinyl alcohol by applying the cross-linking agent to the ink absorption layer, a state in which it is dissolved directly in a coating solution for forming the ink absorption layer or in a solvent such as an aqueous solution of a cross-linking agent or alcohol. There is a method of adding, applying, and drying. In this case, the cross-linking agent and the acetoacetyl-modified polyvinyl alcohol gradually increase in cross-linking reaction immediately after mixing and the coating solution viscosity increases. It may become. Therefore, it is preferable to apply within 30 minutes immediately after adding the crosslinking agent to the coating solution, and more preferably within 15 minutes. In addition, as a method of adding the crosslinking agent to the coating solution, it may be added directly to the pot in which the coating solution is prepared when preparing the coating solution, but during the liquid feeding line to the coater of the coating solution, A method of supplying a hardener by an in-line method from another series immediately before coating is most preferable.

  In the present invention, as a method for applying the crosslinking agent, an acetoacetyl-modified polyvinyl is applied at any time from the start of application of the coating solution for forming the ink absorbing layer on the support to the end of drying. A liquid containing a crosslinking agent that reacts with the acetoacetyl group of alcohol may be applied to the porous layer and dried. The arbitrary period from the start of application to the end of drying as used herein refers to supplying at the same time as applying the porous layer, supplying after applying the porous layer and before starting drying, supplying during drying, Or it means supplying at the end of drying. In the present invention, a solution obtained by dissolving an aqueous solution of a crosslinking agent or a solvent such as alcohol can be overcoated and dried. That is, as a method for applying the crosslinking agent, after coating and drying the coating liquid for forming the ink absorbing layer, the coating solution is directly coated or overcoated with a solution of a crosslinking agent in an aqueous solution or alcohol. It is preferable to supply by. As an overcoat method, a crosslinking agent or a crosslinking agent solution is applied by a bar coating method, a slide hopper coating method, a curtain coating method or an extrusion coating method, supplied by a spray coating method, or a crosslinking agent or a crosslinking agent. You may supply by immersing directly in an agent solution.

  As the hydrophilic binder, various conventionally known hydrophilic binders can be used. For example, gelatin (preferably acid-treated gelatin), polyvinyl pyrrolidone (average molecular weight is preferably about 200,000 or more), pullulan, polyvinyl alcohol and derivatives thereof. , Polyethylene glycol (average molecular weight is preferably 100,000 or more), hydroxyethyl cellulose, dextran, dextrin, and water-soluble polyvinyl butyral. These hydrophilic binders may be used alone or in combination of two or more. You may do it. A particularly preferred hydrophilic binder is polyvinyl alcohol or a derivative thereof.

  Polyvinyl alcohol or a derivative thereof preferably used is preferable because the average degree of polymerization is in the range of 300 to 5,000, and the fragility of the film from which the average molecular weight is 2000 to 5,000 is particularly good. The saponification degree of polyvinyl alcohol or its derivative is preferably 70 to 100%, particularly preferably 80 to 100%.

  The amount of the hydrophilic binder used is as small as possible so that the ink absorbing layer becomes a void layer and is used in a relatively small amount with respect to the inorganic fine particles, and the film can be stably formed and the adhesion to the support can be sufficiently maintained. It is preferable to use less.

  In the present invention, at least one of epoxy compounds, isocyanate compounds, aldehyde compounds, active vinyl compounds, and active halogen compounds can be used as a crosslinking agent that undergoes a thermally irreversible reaction.

  Specific examples of the crosslinking agent include, for example, epoxy-based crosslinking agents (for example, diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N- Diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde-based crosslinking agents (formaldehyde, glioxal, etc.), active vinyl compounds (for example, 1,3,5-trisacryloyl-hexahydro-s) -Triazine, bisvinylsulfonylmethyl ether, etc.), active halogen-based crosslinking agents (for example, 2,4-dichloro-4-hydroxy-1,3,5-s-triazine, etc.) and the like. These crosslinking agents are generally 1 to 50% by mass, preferably 2 to 40% by mass, based on the hydrophilic binder.

  The ink absorption layer according to the present invention contains inorganic fine particles. Examples of the inorganic fine particles used in the ink absorbing layer include light calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydro Examples include talcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, boehmite, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, and magnesium hydroxide.

  These inorganic fine particles may be used in a state of being uniformly dispersed as primary particles, or may be used in a state of being dispersed by forming secondary agglomerated particles.

  The average particle size of the inorganic fine particles is preferably 0.005 to 0.4 μm from the viewpoint of gloss of the ink absorbing layer. The average particle size of the inorganic fine particles referred to here is obtained as a simple average value (number average value) by observing the cross section and surface of the void layer with a scanning electron microscope and determining the particle size of a plurality of arbitrary particles. Can do. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

  In the present invention, silica, alumina or alumina hydrate is preferred as the inorganic fine particles from the viewpoint of forming fine voids in particular, and the average particle size is particularly 0.01 in terms of gloss of the ink absorbing layer of the ink jet recording paper. Pseudoboehmite which is silica or alumina synthesized by a gas phase method of ˜0.4 μm and alumina hydrate is preferable.

The amount of inorganic fine particles used in the ink absorbing layer depends on the type of inorganic fine particles, but is usually 5 to 30 g, preferably 10 to 25 g, per 1 m ^{2 of} inkjet recording paper.

  In the porous ink absorption layer according to the present invention, the ratio (F / B) of the inorganic fine particles (F) to the hydrophilic resin (B) is preferably 3 to 50 times in mass ratio. When the mass ratio is 3 times or more, the porosity of the porous layer is good, and a sufficient void volume is easily obtained. On the other hand, if this ratio is 50 times or less, even when the porous ink absorbing layer is applied as a thick film, it is preferable that cracks do not easily occur. The ratio F / B of the inorganic fine particles to the particularly preferable hydrophilic resin is 5 to 20 times.

The ink absorbing layer according to the present invention preferably has a void volume of 15 to 40 ml / m ² per unit area of the coating film. The void volume as used herein refers to the volume of bubbles generated when a unit volume of the coating film is applied to water, the volume of water that the coating film can absorb, or the recording paper finally obtained. It is defined as the amount of liquid transfer when the contact time is 2 seconds as measured by the liquid absorbency test method (Bristow method) for paper and paperboard specified in TAPPI 51.

  The ink-absorbing layer coating liquid undergoes a crosslinking reaction with the drying following the application to form an ink-absorbing layer. In this invention, it is preferable to manufacture on the conditions that it dries on constant temperature / humidity conditions from the start of drying to completion | finish, and the drying temperature is 80 degreeC or more and 150 degrees C or less. When the drying temperature is less than 80 ° C., the cracking resistance is deteriorated due to insufficient progress of the crosslinking reaction and the productivity is lowered, and when it exceeds 150 ° C., blisters are generated. The drying time is preferably within about 10 minutes, although it depends on the wet film thickness.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Preparation of support for recording material >>
[Preparation of recording material support by surface pressure method (P method)]
(Preparation of recording material support 1)
A coating liquid 1 was prepared by diluting water-dispersible resin L1 (acrylic ester copolymer system, average particle size: 0.20 μm, Tg: 36 ° C., ionic: anionic) to a solid concentration of 40%. .

Rolled base paper A having a width of 230 mm (100 parts of wood pulp, 15 parts of filler (ratio of calcium carbonate 3: talc 1), 0.07 part of sizing agent, 0.8 part of sulfuric acid band, 1.00 part of starch) Using a papermaking material, a paper substrate having a basis weight of 160 g / m ² was obtained with a long paper machine, and then super calendering was performed at a linear pressure of 0.8 kN / cm.) The coating solution 1 was applied so as to give an amount of 50 ml / m ² . After the application, it was dried with hot air of 55 ° C. in a continuous drying process.

  This sample was mirror-finished and then sandwiched with a stainless steel plate that had been subjected to a release property imparting treatment with a silicone-based material, and then treated with a hot press machine under a pressure of 25 MPa to produce a recording material support 1. At this time, the heating press was used by heating and maintaining at 70 ° C.

(Preparation of recording material supports 2 to 8)
In the production of the recording material support 1, a coating solution containing the resin (B) dispersion and the pigment (P) (kaolin, high white kaolin manufactured by Imeris) is used, and the amount of resin, the amount of pigment solids, and heating Recording material supports 2 to 6 were produced in the same manner except that the press treatment conditions were changed to those shown in Table 1.

  In addition, B of Table 1 is resin solid content (g / L), P is pigment solid content (g / L).

[Preparation of support for recording material by calendar machine (C method)]
(Preparation of recording material support 9)
A coating liquid 2 was prepared by diluting a water dispersible resin L2 (styrene butadiene type, average particle size 0.3 μm, Tg 40 ° C., ionic: anionic) to a solid content concentration of 45%.

200 mm wide roll base paper B (wood pulp 100 parts, filler (calcium carbonate) 15 parts, sizing agent 0.07 parts, sulfuric acid band 0.8 parts, starch 1.00 parts, using a papermaking material, after obtaining a paper substrate having a basis weight of 160 g / m ² at Fourdrinier, a was subjected to super calender treatment at a linear pressure of 0.8 kN / cm.), using a bar coater, the coating liquid 2 Was applied to give an amount of 40 ml / m ² . After the application, it was dried with warm air at 70 ° C. in a continuous drying process.

  This sample was measured with a super calender consisting of a steel roll (hard polished hard chrome hardness 87 °) / elastic roll (cotton roll), linear pressure 0.2 kN / cm, roll surface temperature 65 ° C., press speed 6 m / min. The support 9 for recording material was produced by performing pressure treatment under the conditions described above.

(Preparation of recording material supports 10-12)
Recording material supports 10 to 12 were prepared in the same manner except that the calendering conditions (pressure treatment pressure) were changed to the conditions shown in Table 1 in the production of the recording material support 9.

[Production of RC paper support]
(Preparation of recording material support 13)
Thickness of 33 μm of low density polyethylene / high density polyethylene (50/50) by extrusion coating on the back of photographic base paper (LBKP / NBSP = 50/50) having a basis weight of 170 g / m ² subjected to surface size press treatment on both sides It was applied. Next, on the front side, low density polyethylene / high density polyethylene / anatase type titanium oxide (70/26/4) was applied in the same manner to a thickness of 27 μm to produce a recording material support 13.

<< Evaluation of recording material support >>
[Confirmation of gaps]
The following two methods were used to confirm the presence or absence of voids in each of the recording material supports prepared above.

  1) Using a scanning electron microscope (SEM), the surface on which the coating liquid containing the resin dispersion of each support was coated was observed to observe the presence or absence of voids.

Observation conditions: magnification 50000 times 5 points (sample) of 10 μm × 10 μm were selected from a 10 cm × 10 cm support sample, and the presence or absence of voids in the 5 samples was observed.

2) Evaluation was performed by a test method according to the water absorption test method (Cobb) method defined in JIS P8140. When the water absorption was 5 g / m ² or less, it was determined that there was no void.

Evaluation sample area: 100 cm ²
Contact time with water: 120 seconds [Evaluation of support properties after application of ink absorbing layer]
(Ink absorption layer coating)
An ink absorbing layer coating solution having the following composition was applied to the surface of each recording material support on which the coating solution containing the resin dispersion was coated, to prepare samples for evaluation.

  The ink additive layer coating solution was prepared by sequentially mixing the following additives and water.

Gas phase method silica (A-300, primary average particle size 7 nm, manufactured by Nippon Aerosil Industry Co., Ltd.)
10% as solid content
Polyvinyl alcohol (PVA235, manufactured by Kuraray Co., Ltd.) 2% as solid content
Cationic polymer (P-1) 0.2% as solid content
Water-soluble polyaluminum chloride 0.15% as solid content in terms of aluminum oxide
Water was added to finish 100% by mass.

Next, the ink absorbing layer coating solution is applied on a surface coated with a coating solution containing the resin dispersion of each support with a coater under the condition that the silica solid content is 18.0 g / m ^2. After refrigeration setting, it dried with the continuous drying line, and produced for each evaluation.

<Evaluation of cockling resistance>
About each support body which coated the ink absorption layer produced above, the occurrence of cockling (wrinkle) was visually observed, and cockling resistance was evaluated according to the following criteria.

3: The occurrence of cockling is not observed at all. 2: The occurrence of cockling is observed slightly, but it is a quality acceptable for practical use. 1: A strong cockling is generated, and the quality is not practical. Evaluation of curling resistance>
About each support body which coated the ink absorption layer produced above, the occurrence state of curl was visually observed, and the curl resistance was evaluated according to the following criteria.

4: No curling is observed 3: Very weak curling is observed 2: Although weak curling is observed, the curling is removed when left in a laminated state 1: Strong curling occurs and the laminated state However, curl is not resolved, and there is a risk of hindering printer conveyance. Table 2 shows the results obtained as described above.

  As is apparent from the results shown in Table 2, the water-absorbing support of the water component is formed even when the support having the structure defined in the present invention is coated with a water-based ink absorbing layer on the comparative example (support 5). It can be seen that excellent cockling resistance and curl resistance equivalent to RC paper (support 13) having a high production cost and a complicated production process can be obtained.

Example 2
<< Preparation of inorganic fine particle dispersion >>
[Preparation of inorganic fine particle dispersion A]
Gas phase method silica having an average primary particle diameter of 12 nm and a specific surface area of 200 m ² / g measured by the BET method in 700 ml of 1% ethanol aqueous solution adjusted to pH 4.0 with nitric acid using a high-speed stirring disperser 200 g of was gradually added and dispersed. Next, 85 g of 25% aqueous solution of the cationic polymer (P-1) was added to this liquid, and further dispersed with a sand mill so that the average particle size of the inorganic fine particles in the dispersion was less than 0.4 μm. Was added to obtain 1000 ml of inorganic fine particle dispersion A.

[Preparation of inorganic fine particle dispersion B]
Using a high-speed stirring disperser, 2.5 mL of 5% nitric acid, 11 mL of ethanol, 1.7 g of boric acid, and 1.4 g of borax were dissolved in 500 mL of pure water, and the average primary particle size was 12 nm and measured by the BET method. 200 g of gas phase method silica having a specific surface area of 200 m ² / g was gradually added and dispersed. Next, 85 g of 25% aqueous solution of the cationic polymer (P-1) was added to this liquid, and further dispersed with a sand mill so that the average particle size of the inorganic fine particles in the dispersion was less than 0.4 μm. And finished to 1000 ml to obtain inorganic fine particle dispersion B.

<< Preparation of acetoacetyl-modified polyvinyl alcohol >>
80 g of acetic acid is added to 200 g of polyvinyl alcohol powder (saponification degree 99.4%, polymerization degree 1700) to swell and heated to 60 ° C. while stirring, and then a mixture of 35 g of diketene and 3 g of acetic acid is added dropwise. For 2 hours. After completion of the reaction, the dispersion was washed with methanol and dried to obtain an acetoacetyl-modified polyvinyl alcohol powder having a modification rate of 4.0 mol%.

<Production of recording paper>
[Preparation of recording paper 1]
While stirring 500 ml of the inorganic fine particle dispersion A at 40 ° C., 170 ml of a 10% aqueous solution of the acetoacetyl-modified polyvinyl alcohol (polymerization degree 1700, modification rate 4 mol%) is gradually added, and finally the whole amount is added with pure water. Finishing to 1000 ml, an ink absorbing layer coating solution was prepared. The mass ratio (F / B) of the inorganic fine particles (F) to the acetoacetyl-modified polyvinyl alcohol (B) is 6.0.

  Next, 14 ml of a 5% aqueous solution of adipic acid hydrazide as a crosslinking agent was added to the ink absorbing layer coating solution, and the ink absorbing layer coating solution was added to the recording material support 3 produced in Example 1 within 3 minutes after the addition. Then, the recording paper 1 was prepared by applying with a slide hopper type coater so that the wet film thickness was 160 μm, and drying with hot air at 80 ° C.

  At this time, the addition ratio (H / B) of the crosslinking agent (H) to the acetoacetyl-modified polyvinyl alcohol (B) is 0.04.

[Preparation of recording paper 2]
In the production of the recording paper 1, the recording paper 2 was produced in the same manner except that the hot air temperature during drying was changed to 70 ° C.

[Preparation of recording paper 3]
The recording paper 3 was prepared in the same manner as in the preparation of the recording paper 1 except that the hot air temperature during drying was changed to 150 ° C.

[Preparation of recording paper 4]
The recording paper 4 was prepared in the same manner as in the preparation of the recording paper 1 except that the hot air temperature during drying was changed to 160 ° C.

[Preparation of recording paper 5]
A recording paper 5 was produced in the same manner as in the production of the recording paper 1 except that the recording material support 3 was changed to the recording material support 13 produced in Example 1.

[Preparation of recording paper 6]
While stirring 500 ml of the above inorganic fine particle dispersion B at 40 ° C., 283 ml of a 6% aqueous solution of polyvinyl alcohol (PVA235, manufactured by Kuraray Co., Ltd.) is gradually added, and finally the whole amount is made up to 1000 ml with pure water to absorb ink. A layer coating solution was prepared.

  Next, the ink absorbing layer coating solution was applied to the recording material support 3 produced in Example 1 with a slide hopper type coater so that the wet film thickness was 160 μm, and dried with hot air at 80 ° C. Recording paper 6 was produced.

[Preparation of recording paper 7]
Recording paper 7 was prepared in the same manner as in the preparation of recording paper 1 except that the amount of the adipic acid hydrazide aqueous solution added was changed to 21 ml.

[Preparation of recording paper 8]
In the production of the recording paper 7, the recording paper 8 was produced in the same manner except that the aqueous solution of adipic hydrazide was applied with in-line mixing immediately before application.

[Preparation of recording paper 9]
While stirring 500 ml of the above inorganic fine particle dispersion A at 40 ° C., 283 ml of a 6% aqueous solution of polyvinyl alcohol (PVA235, manufactured by Kuraray Co., Ltd.) is gradually added, and finally the whole amount is made up to 1000 ml with pure water to absorb ink. A layer coating solution was prepared.

  Next, the recording material support 3 produced in Example 1 is slid so as to have a wet film thickness of 160 μm while in-line mixing 25 ml of a 2% aqueous solution of ethylene glycol glycidyl ether as a crosslinking agent into the ink absorbing layer coating solution. The recording paper 9 was produced by applying with a hopper type coater and drying with hot air of 80 ° C.

[Preparation of recording paper 10]
A recording paper 10 was prepared in the same manner as in the preparation of the recording paper 9, except that the crosslinking agent was changed to 17 ml of a 2% aqueous solution of glyoxal.

[Preparation of recording paper 11]
Recording paper 11 was prepared in the same manner as in the preparation of recording paper 9, except that the crosslinking agent was changed to 13 ml of a 5% aqueous solution of 2,4-dichloro-4-hydroxy-1,3,5-s-triazine.

[Preparation of recording paper 12]
Recording paper 12 was prepared in the same manner as in the preparation of recording paper 9, except that the crosslinking agent was changed to 11 ml of a 5% aqueous solution of bisvinylsulfonylmethyl ether.

[Preparation of recording sheets 13 to 23]
In the production of the recording paper 1, the recording materials 13 to 23 were produced in the same manner except that the recording material support 3 was changed to the recording material support 1, 2, 4 to 12 produced in Example 1. did.

<Evaluation of recording paper>
About each recording paper produced by the above, evaluation of cockling resistance and curl resistance and evaluation of crack resistance and heat resistance (blister resistance) were performed according to the method described below in the same manner as described in Example 2. It was.

[Evaluation of crack resistance]
The surface of the ink absorbing layer of each of the recording papers prepared was observed with a magnifying glass, the number of cracks on the film surface generated per 100 cm ² was counted, and the crack resistance was evaluated according to the following criteria. If it was more than Δ, it was determined that the quality was satisfactory for practical use.

◎: Number of cracks generated is less than 3 ○: Number of cracks generated is 3 or more and less than 10 △: Number of cracks generated is 10 or more and less than 20 x: 21 or more [Heat resistance (blister resistance) Evaluation of〕
Each of the prepared recording sheets was visually observed for the occurrence of irregularities (blisters) on the surface of the ink absorbing layer, and the heat resistance (blister resistance) was evaluated according to the following criteria. If it was more than Δ, it was determined that the quality was satisfactory for practical use.

○: No blisters are generated. Δ: Blisters are rarely generated but are very slight. ×: Clear blisters are generated. The results obtained as described above are shown in Table 3.

  As is clear from the results shown in Table 3, the recording paper having the configuration defined in the present invention has excellent cockling resistance and curl resistance as compared with the results of Example 2, and crack resistance as compared with the comparative example. It is clear that productivity improvement (drying at high temperature) could be achieved without any reduction. The recording paper 5 using RC paper (recording material support 13) has a practically problematic level of blister resistance in the recording paper 7 using boric acid as a crosslinking agent. Further, the recording papers 7 and 8 having an increased amount of the crosslinking agent have improved cracking resistance, but the recording paper 7 added directly to the coating solution has increased viscosity of the coating solution, and the film surface is slightly disturbed accordingly. Occurred.

Claims (9)

After forming the undercoat layer by applying a coating solution for forming the undercoat layer containing the resin dispersion on at least one surface side of the water-absorbent support, under the condition that substantially no voids remain in the undercoat layer. An ink jet recording paper in which a porous ink absorbing layer composed of at least inorganic fine particles and a hydrophilic resin is provided on a recording material support obtained by pressure treatment, wherein the hydrophilic resin is non-thermo-reversible. An ink jet recording paper, which is cross-linked by a cross-linking agent that forms a conductive gel. The inkjet recording paper according to claim 1, wherein at least one of the hydrophilic resins is acetoacetyl-modified polyvinyl alcohol crosslinked with a crosslinking agent that reacts with acetoacetyl groups. At least one of the hydrophilic resins is polyvinyl alcohol, and at least one selected from an epoxy compound, an aldehyde compound, an active vinyl compound, and an active halogen compound is used as a crosslinking agent. Item 10. The inkjet recording paper according to Item 1. The inkjet recording paper according to any one of claims 1 to 3, wherein a pressure in the pressure treatment is 5 MPa or more and 50 MPa or less. The inkjet recording according to any one of claims 1 to 4, wherein the pressure treatment is performed by a calendar machine in a range of a linear pressure of 0.3 kN / cm to 2.0 kN / cm. Paper. The temperature at the time of pressurization in the pressure treatment is Tp, and the glass transition temperature of the resin dispersion is Tg. The condition defined by the following formula (1) is satisfied: The inkjet recording paper of any one of Claims.
Formula (1)
Tg <Tp <Tg + 50 When the undercoat layer containing the resin dispersion contains a pigment, the solid content of the pigment contained in the undercoat layer is P, and the solid content of the resin is B, the condition defined by the following formula (2) is satisfied. The inkjet recording paper according to any one of claims 1 to 6.
Formula (2)
0.13 <P / (P + B) <0.5 It was dried under conditions of constant temperature and humidity from the start to the end of drying, and the drying temperature was 80 ° C or higher and 150 ° C or lower. Inkjet recording paper. The inkjet recording paper according to any one of claims 1 to 8, wherein the crosslinking agent is produced by adding to a coating solution for forming the ink absorbing layer immediately before coating.