JP2011073169A - Inkjet recording medium and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which can form an ink receiving layer in a successful coating fluid state, and can secure an high density image compared with the case that an image is recorded on a conventional medium, and can inhibit the generation of curling in a low humidity environment. <P>SOLUTION: The inkjet recording medium includes an ink receiving layer containing vapor-phase silica, hydroxycarboxylate ester with an I/O value of not smaller than 1.5 which is calculated based on an organic concept drawing, and a polyvinyl alcohol where the content of the hydroxycarboxylate ester is not smaller than 0.1 mol but not larger than 2 mol with respect to 1 kg of the vapor-phase silica. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink jet recording medium suitable for receiving an ink ejected by an ink jet method and recording an image, and a manufacturing method thereof.

  In recent years, various information processing systems have been developed. Ink jets are advantageous because they can be recorded on various recording media, the hardware (device) is relatively inexpensive and compact, and excellent in quietness. Recording methods are widely used.

  In the ink jet recording method, an ink jet recording medium in which a recording layer for receiving ink has a porous structure has been proposed and put into practical use. As an example thereof, there is an ink jet recording medium that includes inorganic pigment particles and a water-soluble binder, and a recording layer having a high porosity is provided on a support. It has been proposed as a material capable of recording a photographic-like image, such as having gloss.

  In addition to being able to record fast-drying and high-gloss images due to the quality of the recording material, it is possible to obtain high-quality images with high density and contrast that give bright and dark and clear images, and curl etc. during or after recording It is important that deformation does not occur easily.

  In relation to the above, it is disclosed that an ink receiving layer is formed using a fine particle dispersion containing hydroxy acid such as glycolic acid and lactic acid and polyvinyl alcohol together with alumina hydrate (for example, Patent Document 1). reference). In addition, there is a disclosure relating to an inkjet recording sheet containing a carboxylic acid compound such as lactic acid or propionic acid (see, for example, Patent Document 2).

JP 2005-313490 A JP 2002-316480 A

  However, in the above-described conventional technique in which glycolic acid or lactic acid is included as a hydroxy acid or carboxylic acid compound, the viscosity of the coating solution for layer formation is likely to increase, and when placed in a low humidity environment, the density of the recorded image This is not sufficient in preventing the occurrence of curling, and there is room for improvement in quality as a recording material.

  The present invention has been made in view of the above. The ink receiving layer can be formed in a good coating liquid (for example, viscosity) state and a higher density image can be obtained as compared with the case of recording on a conventional medium. Another object of the present invention is to provide an inkjet recording medium in which the occurrence of curling in a low-humidity environment is suppressed and a method for manufacturing the same, and to achieve the object.

Specific means for achieving the above object are as follows.
<1> Gas phase method silica, hydroxycarboxylic acid ester having an I / O value calculated based on an organic conceptual diagram of 1.5 or more, and polyvinyl alcohol, and 1 kg of gas phase method silica of the hydroxycarboxylic acid ester Is an ink jet recording medium having an ink receiving layer in an amount of 0.1 mol to 2 mol.

  <2> The inkjet recording medium according to <1>, wherein the hydroxycarboxylic acid ester is at least one of a lactic acid ester and a glycolic acid ester.

  <3> The inkjet recording medium according to <1> or <2>, wherein the hydroxycarboxylic acid ester is an alkyl ester of lactic acid or glycolic acid and an alcohol having 1 to 4 carbon atoms.

  <4> A hydroxycarboxylic acid ester having an I / O value calculated on the basis of an organic conceptual diagram of 1.5 or more is added to a silica dispersion containing vapor phase method silica and polyvinyl alcohol, and the hydroxycarboxylic acid is added. A coating solution preparing step of preparing a coating solution in which the amount of ester relative to 1 kg of gas phase method silica is 0.1 mol or more and 2 mol or less; and a layer forming step of coating the coating solution on a support to form an ink receiving layer. A method for producing an ink jet recording medium having

  According to the present invention, the ink-receiving layer can be formed in a good coating liquid (for example, viscosity) state as compared with the case of recording on a conventional medium, and a higher density image can be obtained, and in a low humidity environment. An ink jet recording medium in which the occurrence of curling is suppressed and a method for manufacturing the same can be provided.

Hereinafter, the ink jet recording medium of the present invention will be described in detail.
The inkjet recording medium of the present invention includes vapor-phase process silica, a hydroxycarboxylic acid ester having an I / O value calculated based on an organic conceptual diagram of 1.5 or more, and polyvinyl alcohol. An ink receiving layer having an amount of 0.1 mol or more and 2 mol or less with respect to 1 kg of vapor phase method silica is provided.

  In the present invention, in particular, in a composition system in which vapor-phase process silica is used as the inorganic fine particles and polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) is used as the binder component, the vapor-phase process silica and PVA are mutually mixed. In view of the fact that the liquid viscosity tends to increase due to the action, the liquid preparation property and coating property are hindered, curling occurs after recording, and the desired image density cannot be obtained. In addition to gas phase method silica and PVA, by containing a specific hydroxycarboxylic acid ester, a desired liquid state (viscosity, etc.) can be maintained when it is used as a coating solution, and compared with the case where it is recorded on a conventional medium, A high concentration can be obtained and curling can be suppressed in a low humidity environment.

  The ink jet recording medium of the present invention can be constituted by having a support and at least one ink receiving layer provided on the support, and if necessary, other layers such as an undercoat layer. May be provided.

-Gas phase method silica-
The ink receiving layer in the present invention contains vapor-phase process silica. In the present invention, when vapor phase silica is mixed with PVA described later as inorganic fine particles, the curl that tends to be generated at a low humidity while maintaining the desired liquid state (viscosity, etc.) and increasing the image density. Is prevented from occurring.

  Vapor phase silica is a method by high-temperature vapor phase hydrolysis of silicon halide (flame hydrolysis method), a method in which silica sand and coke are heated and reduced and vaporized by an arc in an electric furnace and oxidized with air ( Anhydrous silica obtained by the arc method). In addition, silica fine particles generally include wet method particles in addition to vapor phase method silica. The wet method particles produce active silica by acid decomposition of silicate, which is obtained by appropriately polymerizing and aggregating and precipitating water. Silica, which is distinguished from vapor phase silica by its production method.

Vapor phase silica is different from hydrous silica in terms of the density of silanol groups on the surface, the presence or absence of vacancies, etc., and exhibits different properties, but is suitable for forming a three-dimensional structure with a high porosity. The reason for this is not clear, but in the case of hydrous silica, the density of silanol groups on the surface of the fine particles is as high as 5 to 8 / nm ^2, and the silica fine particles tend to aggregate (aggregate) easily, In the case of the method silica, the density of silanol groups on the surface of the fine particles is as small as ² to 3 / nm ² , so that it becomes sparse soft agglomeration (flocculate), and as a result, it is estimated that the structure has a high porosity. The

Among vapor phase silica (anhydrous silica), silica particles having a density of silanol groups on the particle surface of 2 to 3 / nm ² are preferred. More preferable gas phase method silica is silica particles having a specific surface area of 200 m ² / g or more by BET method. BET specific surface area of the fumed silica is more preferably at least ^{250m 2 / g, 380m 2 /} g or more is particularly preferable. When the specific surface area of the vapor-phase process silica is 200 or more m ² / g, the ink image-receiving layer is highly transparent and the printing density can be kept high.

  The BET method is based on the technical data of Nippon Aerosil Co., Ltd. 10 is a method for measuring the average diameter of primary particles described in item 2, 2, etc., and is one of the methods for measuring the surface area of a powder by the vapor phase adsorption method. The surface area, that is, the specific surface area is obtained. Generally, nitrogen gas is often used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. The most prominent one representing the isotherm of multimolecular adsorption is the Brunauer Emmett Teller equation (BET equation), which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  The average primary particle diameter of the vapor phase silica is preferably 20 nm or less, more preferably 15 nm or less, and particularly preferably 10 nm or less. When the average primary particle diameter is 20 nm or less, the ink absorption characteristics can be effectively improved, and at the same time, the glossiness of the ink receiving layer surface can be improved.

  In particular, gas phase method silica has a silanol group on its surface, and the particles are likely to adhere to each other by hydrogen bonding of the silanol group, and because of the adhesion effect between the particles via the silanol group and polyvinyl alcohol, the above-mentioned When the average primary particle diameter is 20 nm or less as described above, the ink receiving layer has a high porosity and a highly transparent structure can be formed, and the ink absorption characteristics can be effectively improved.

The content of the vapor phase silica in the ink receiving layer is preferably 50% by mass or more, more preferably 60% by mass or more based on the total solid content of the ink receiving layer. When the content of the vapor phase method silica is 50% by mass or more, more preferably 60% by mass or more, an even better porous structure can be formed, and an ink receiving layer having excellent ink absorbability can be obtained. It is done.
Here, the total solid content in the ink receiving layer of the vapor phase method silica is a content calculated based on components other than water among the components constituting the ink receiving layer.

-Hydroxycarboxylic acid ester-
The ink receiving layer in the invention contains at least one hydroxycarboxylic acid ester having an I / O value calculated based on an organic conceptual diagram of 1.5 or more. It is presumed that the interaction between the vapor phase silica and PVA is alleviated by including the hydroxycarboxylic acid ester in the ink receiving layer.

In the present invention, the hydroxycarboxylic acid ester is contained in an amount of 0.1 mol or more and 2 mol or less with respect to 1 kg of the vapor phase silica. When the amount of hydroxycarboxylic acid ester relative to 1 kg of gas phase method silica is less than 0.1 mol, the hydrophobic interaction between the hydroxycarboxylic acid ester adsorbed on the silanol group of gas phase method silica and the acetyl group of PVA is large. The desired liquid state (viscosity, etc.) cannot be maintained. On the other hand, when the amount of the hydroxycarboxylic acid ester exceeds 2 mol / kg, the printing density is remarkably lowered.
The amount of the hydroxycarboxylic acid ester relative to 1 kg of the gas phase method silica is 0.2 mol or more and 1.0 mol from the viewpoint of further maintaining the desired liquid state (viscosity, etc.) and further improving the image density and the anti-curl effect under low humidity. The following is preferred.

  The hydroxycarboxylic acid ester in the present invention may contain one or more carboxyl groups (COOH groups), but from the viewpoint of the effect of the present invention, the number of carboxyl groups in the molecule may be 0 to 1. Is preferred.

Further, the hydroxycarboxylic acid ester in the present invention is preferably a compound having one or more hydroxyl groups (OH group; OH in COOH is not included) in the molecule. By having an OH group, the hydroxycarboxylic acid ester molecule is adsorbed on the silanol group on the surface of the vapor phase silica and inhibits the interaction between the vapor phase silica and PVA. The relaxation effect is increased.
Although there is no restriction | limiting in particular as the number of OH groups in a molecule | numerator, It is preferable that 1 or 2 is contained in a molecule | numerator.

  Further, the hydroxycarboxylic acid ester in the present invention has an I / O value calculated based on an organic conceptual diagram of 1.5 or more. When this I / O value is less than 1.5, it is considered that the hydrophobic interaction is increased between the hydroxycarboxylic acid ester adsorbed on the silanol group of the vapor phase method silica and the acetyl group of PVA. Therefore, the desired liquid state (viscosity or the like) cannot be maintained, and the anti-curl effect under low image density and low humidity is reduced.

The I / O value is a value that treats the polarity of various organic compounds, also called inorganic values / organic values, in terms of organic concepts, and is one of the functional group contribution methods for setting parameters for each functional group. is there. The I / O value is described in detail in an organic conceptual diagram (written by Yoshio Koda, Sankyo Publishing (1984)). The concept of the I / O value is that the properties of a compound are divided into an organic group that represents covalent bonding and an inorganic group that represents ionic bonding, and all organic compounds are orthogonal coordinates named organic and inorganic axes. Each of the above points is shown.
The inorganic value is obtained by quantifying the magnitude of the influence on the boiling point of various substituents and bonds of an organic compound, based on the hydroxyl group. Specifically, when the distance between the boiling point curve of a straight chain alcohol and the boiling point curve of a straight chain paraffin is about 100 ° C., the influence of one hydroxyl group is set to 100 as a numerical value. A value obtained by quantifying the influence on the boiling point of various substituents or various bonds based on this numerical value is the inorganic value of the substituent that the organic compound has. For example, the inorganic value of the —COOH group is 150, and the inorganic value of the double bond is 2. Therefore, the inorganic value of a certain kind of organic compound means the sum of inorganic values such as various substituents and bonds of the compound.
The organic value is determined based on the influence of the methylene group in the molecule as a unit and the boiling point of the carbon atom representing the methylene group. That is, since the average value of the boiling point increase due to the addition of one carbon in the vicinity of 5 to 10 carbon atoms of the linear saturated hydrocarbon compound is 20 ° C., the organic value of one carbon atom is set to 20 on the basis of this. A value obtained by quantifying the influence on the boiling point of various substituents and bonds based on this is the organic value. For example, the organic value of a nitro group (—NO ₂ ) is 70.
An I / O value closer to 0 indicates a non-polar (hydrophobic or organic) organic compound, and a larger value indicates a polar (hydrophilic or inorganic) organic compound. Indicates.

  In the present invention, the I / O value of the hydroxycarboxylic acid ester is determined by the following method. Based on the organicity (O value) and inorganicity (I value) described in Yoshio Koda, Organic Conceptual Diagram-Fundamentals and Applications (1984), p.13, etc. An I / O value (= I value / O value) is calculated. For each compound constituting the ester, the product of its I / O value and mol% in the ester is calculated, and these are summed up to the third decimal place to obtain the I / O value of the hydroxycarboxylic acid ester. And

  The I / O value of the hydroxycarboxylic acid ester is 1.5 or more, and more preferably 2 or more. The upper limit of the I / O value is desirably 6.

Examples of the hydroxycarboxylic acid constituting the hydroxycarboxylic acid ester include glycolic acid, lactic acid, quinic acid, salicylic acid, 3,5-hydroxybenzoic acid, mevalonic acid, ximic acid, 3,4,5-trihydroxybenzoic acid, Examples include 3-hydroxybutyric acid, glyceric acid, and the following compounds 1 and 2.

  Examples of the alcohol constituting the hydroxycarboxylic acid ester include 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, (n-, i-, t-) propyl alcohol, butyl alcohol, and hexyl alcohol. And linear and branched alcohols.

  Examples of hydroxycarboxylic acid esters include esters of glycolic acid such as methyl glycolate and ethyl glycolate (preferably with an alcohol having 1 to 4 carbon atoms) (preferably having 3 to 8 carbon atoms), methyl lactate, and ethyl lactate. And esters of lactic acid (preferably with an alcohol having 1 to 4 carbon atoms) (preferably having 3 to 8 carbon atoms).

  In the present invention, the hydroxycarboxylic acid ester contains an OH group in the molecule, has an I / O value calculated based on an organic conceptual diagram of 1.5 to 10 and is hydroxy for 1 kg of vapor phase silica. The case where the amount of the carboxylic acid ester is 0.1 mol or more and 2.0 mol or less is particularly preferable.

-Polyvinyl alcohol-
The ink receiving layer in the present invention contains at least one polyvinyl alcohol.
The polyvinyl alcohol (PVA) can be selected from polyvinyl alcohol resins such as polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and polyvinyl acetal.

  The degree of saponification of polyvinyl alcohol (PVA) is preferably less than 90 mol% from the viewpoint of curling suppression of the ink jet recording medium and improvement in density after recording (for example, maximum density Dm).

  As a polymerization degree of polyvinyl alcohol (PVA), 1400-5000 are preferable and 2300-4000 are more preferable from the viewpoint of obtaining sufficient film strength.

The content of PVA in the ink-receiving layer prevents the film strength from being reduced and cracks during drying due to the insufficient content, and the excessive content makes it easy for the voids to be blocked by the resin. From the viewpoint of preventing the ink absorbency from decreasing due to a decrease in the porosity, 5 to 30% by mass is preferable and 10 to 20% by mass is more preferable with respect to the total solid content of the ink receiving layer.
Polyvinyl alcohol may be used alone or in combination of two or more.

  PVA (polyvinyl alcohol-based resin) has a hydroxyl group in its structural unit. Since this hydroxyl group and the surface silanol group of the vapor phase silica form a hydrogen bond, the secondary particles of the silica particles are defined as network chain units. It is easy to form a three-dimensional network structure. By forming this three-dimensional network structure, it is considered that an ink receiving layer having a porous structure with a high porosity and sufficient strength can be formed. As described above, the porous ink receiving layer can absorb ink rapidly by capillary action, and can form dots with good roundness without ink bleeding.

  The ink receiving layer is mainly composed of vapor phase silica and PVA, but the vapor phase silica and PVA used may be a single material or a mixed system of a plurality of materials. The water-soluble resin component in the ink receiving layer may be a mixed system in which another water-soluble resin is used in combination with PVA. In that case, the amount of PVA in the total mass of the water-soluble resin is preferably 50% by mass or more. The mass% or more is more preferable.

  The content ratio of the vapor phase silica (s) and PVA (p) [PB ratio (s / p), the mass of the vapor phase silica with respect to 1 part by mass of PVA] is formed by coating with a coating solution for forming an ink receiving layer. This greatly affects the film structure of the ink receiving layer. That is, as the PB ratio increases, the porosity, pore volume, and surface area (per unit mass) increase. Specifically, as the PB ratio (s / p), a decrease in film strength and cracking during drying caused by the PB ratio being too large are prevented, and the PB ratio is too small, From the viewpoint of preventing the ink absorbability from being lowered due to the resin being easily clogged and reducing the porosity, 1.5 / 1 to 10/1 is preferable.

  In addition, when the ink jet recording medium passes through the conveyance system of the ink jet printer, stress may be applied to the medium, and therefore the ink receiving layer needs to have sufficient film strength. Furthermore, when the medium is cut into a sheet, the ink receiving layer needs to have sufficient film strength to prevent cracking and peeling of the ink receiving layer. From such a viewpoint, the PB ratio (s / p) is preferably 6/1 or less, and preferably 3/1 or more from the viewpoint of ensuring high-speed absorption of the ink.

-Crosslinking agent-
The ink receiving layer in the invention can contain at least one crosslinking agent that crosslinks PVA.

As the crosslinking agent, a boron compound is preferable in that the crosslinking reaction is rapid. Examples of the boron compound include borax, boric acid, borate (for example, orthoborate, InBO ₃ , ScBO ₃ , YBO ₃ , LaBO ₃ , Mg ₃ (BO ₃ ) ₂ , Co ₃ (BO ₃ ) ₂ , diboric acid. Salt (eg, Mg ₂ B ₂ O ₅ , Co ₂ B ₂ O ₅ ), metaborate (eg, LiBO ₂ , Ca (BO ₂ ) ₂ , NaBO ₂ , KBO ₂ ), tetraborate (eg, Na ₂ B ₄ O ₇ · 10H ₂ O), pentaborate (for example, KB ₅ O ₈ · 4H ₂ O, Ca ₂ B ₆ O ₁₁ · 7H ₂ O, CsB ₅ O ₅ ), etc. Borax, boric acid and borates are preferable, and boric acid is more preferable in that a crosslinking reaction can be promptly caused.

  The content of the crosslinking agent in the ink receiving layer is preferably in the range of 0.05 to 0.50 parts by mass, more preferably in the range of 0.08 to 0.30 parts by mass with respect to 1.0 part by mass of PVA. . When the content of the crosslinking agent is within the above range, it is possible to effectively crosslink PVA and effectively prevent the occurrence of cracks after layer formation.

  In addition to PVA, when gelatin is used as another water-soluble resin, the following compounds other than boron compounds can also be used as a crosslinking agent. For example, aldehyde compounds such as formaldehyde, glyoxal and glutaraldehyde; ketone compounds such as diacetyl and cyclopentanedione; bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1,3,5- Active halogen compounds such as triazine and 2,4-dichloro-6-S-triazine sodium salt; divinylsulfonic acid, 1,3-vinylsulfonyl-2-propanol, N, N′-ethylenebis (vinylsulfonylacetamide) ), Active vinyl compounds such as 1,3,5-triacryloyl-hexahydro-S-triazine; N-methylol compounds such as dimethylolurea and methyloldimethylhydantoin; melamine resins (for example, methylolmelamine, alkylated methylolmelamine) Epoxy resin; 1,6- Isocyanate compounds such as hexamethylene diisocyanate; Aziridine compounds described in US Pat. Nos. 3,017,280 and 2,983,611; Carboximide compounds described in US Pat. No. 3,100,704; Glycerol triglycidyl ether, etc. Epoxy-based compounds; ethyleneimino-based compounds such as 1,6-hexamethylene-N, N′-bisethyleneurea; halogenated carboxaldehyde-based compounds such as mucochloric acid and mucophenoxycyclolic acid; 2,3-dihydroxydioxane and the like Dioxane compounds: titanium lactate, aluminum sulfate, chromium alum, potash alum, metal-containing compounds such as zirconyl acetate and chromium acetate, polyamine compounds such as tetraethylenepentamine, hydrazide compounds such as adipic acid dihydrazide, o A low molecule or polymer containing two or more xazoline groups. Said crosslinking agent may be used individually by 1 type, and may be used in combination of 2 or more type.

The crosslinking agent may be added to the coating solution for forming the ink receiving layer and / or the coating solution for forming the adjacent layer of the ink receiving layer when forming the ink receiving layer, or a coating containing a crosslinking agent in advance. A coating solution for forming an ink-receiving layer is applied on a support on which the solution has been applied, or a coating solution for forming an ink-receiving layer that does not contain a crosslinking agent is applied and dried, and then the coating solution is overcoated. Thus, a crosslinking agent can be supplied to the ink receiving layer. From the viewpoint of production efficiency, it is preferable to add a crosslinking agent to the coating solution for forming the ink receiving layer or the coating solution for forming the adjacent layer, and supply the crosslinking agent simultaneously with the formation of the ink receiving layer. In particular, from the viewpoint of improving image density and glossiness, it is preferably contained in a coating solution for forming an ink receiving layer.
In addition, the concentration of the crosslinking agent in the ink receiving layer is preferably 0.05 to 10% by mass, and more preferably 0.1 to 7% by mass with respect to the total solid content of the layer.

The cross-linking agent can be suitably applied to the ink receiving layer as follows, for example. Here, a boron compound will be described as an example. That is,
When the ink receiving layer is a layer obtained by crosslinking and curing the coating layer coated with the coating liquid for forming the ink receiving layer (first liquid), the crosslinking curing is performed by (1) coating the coating layer by applying the first liquid. At the same time as the formation, or (2) either during the drying of the coating layer formed by applying the first liquid and before the coating layer exhibits reduced-rate drying, the pH is 7.1. This can be done by applying the above basic solution (second liquid) to the coating layer. The boron compound as the crosslinking agent may be contained in either the first liquid or the second liquid, and may be contained in both the first liquid and the second liquid.

-Cationic resin-
The ink receiving layer in the invention may contain at least one cationic resin. The cationic resin is a homopolymer of a monomer having a secondary to tertiary amino group or a quaternary ammonium base (mordant monomer), or a co-polymer of the mordant monomer with another monomer (non-mordant monomer). Examples thereof include a polymer mordant obtained as a polymer or a condensation polymer. Examples of the mordant monomer and the non-mordant monomer that form a polymer mordant include monomers described in paragraphs [0044] to [0051] of JP-A-2005-81645. Further, polymer mordants described in paragraph numbers [0052] to [0053] of JP-A-2005-81645 are also included.
Further, these cationic resins can be used in any form of a water-soluble polymer or water-dispersible latex particles.

Among these, as the polymer mordant, polyallylamine or a derivative thereof is preferable. In particular, from the viewpoint of suppressing color change after printing, polyallylamine having a weight average molecular weight of 100,000 or less or a derivative thereof is preferable. Examples of polyallylamine or derivatives thereof include various known allylamine polymers and derivatives thereof. Examples of the derivatives include salts of polyallylamine and acids (acids include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, Methane sulfonic acid, toluene sulfonic acid, acetic acid, propionic acid, cinnamic acid, organic acids such as (meth) acrylic acid, or combinations thereof, allylamine partially salted), polyallylamine derivative by polymer reaction , And copolymers of polyallylamine and other copolymerizable monomers (specific examples of the monomer include (meth) acrylic acid esters, styrenes, (meth) acrylamides, acrylonitrile, vinyl esters). It is done.
Specific examples of the polyallylamine and derivatives thereof include the compounds described in JP-A-2005-81645, paragraph [0056].

  The cationic resin is preferably a polydiallylamine derivative, more preferably a polydiallyldimethylammonium salt (as the counter anion of the salt, for example, chloride ion, acetate ion, sulfate ion, etc.), More preferred is polydiallyldimethylammonium chloride.

The molecular weight of the cationic resin is preferably in the range of 2000 to 100,000 in terms of weight average molecular weight. When the molecular weight is 2000 or more, the viscosity stability when a silica dispersion or a coating liquid for forming an ink receiving layer is prepared is improved, and a significant increase in the liquid viscosity is suppressed. When the molecular weight is 100,000 or less, The increase in viscosity is suppressed, the viscosity stability of the coating liquid for forming the ink receiving layer is further improved, and a significant increase in the viscosity of the coating liquid is suppressed.
Here, the liquid viscosity of the silica dispersion or the coating liquid for forming the ink receiving layer can be measured using a commercially available viscometer (such as a B-type viscometer).

The content of the cationic resin in the ink receiving layer is preferably in the range of 0.5 to 10% by mass and more preferably in the range of 2.0 to 6.0% by mass with respect to the vapor phase silica. When the content of the cationic resin is 2.0% by mass or more, the viscosity stability of the silica dispersion is improved, and when the content is 6.0% by mass or less, a decrease in the void volume of the ink receiving layer is suppressed. The
Here, the void volume of the ink receiving layer can be measured using a commercially available mercury porosimeter or the like.

-Aqueous dispersion of cationically modified self-emulsifying polymer-
The ink receiving layer in the invention is preferably formed using a coating solution containing an aqueous dispersion of a self-emulsifying polymer that has been cation-modified, particularly for the purpose of suppressing wet heat bleeding. “Cation-modified self-emulsifying polymer” means a polymer that can be a naturally stable emulsified dispersion in an aqueous dispersion medium without using an emulsifier or a surfactant, or even if used in a very small amount. Means a compound. Quantitatively, “cation-modified self-emulsifying polymer” refers to a polymer substance having stable emulsification and dispersion at a concentration of 0.5% by mass or more with respect to an aqueous dispersion medium at room temperature of 25 ° C. The concentration is preferably 1% by mass or more, more preferably 3% by mass or more.

  More specifically, the “cation-modified self-emulsifying polymer” is, for example, a polyaddition or polycondensation polymer having a cationic group such as a primary to tertiary amino group or a quaternary ammonium group. Compounds.

  Examples of a vinyl polymerization polymer effective as a polymer include polymers obtained by polymerizing the following vinyl monomers. That is, acrylic acid esters and methacrylic acid esters (the ester group is an alkyl group or aryl group which may have a substituent, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n- Butyl group, sec-butyl group, tert-butyl group, hexyl group, 2-ethylhexyl group, tert-octyl group, 2-chloroethyl group, cyanoethyl group, 2-acetoxyethyl group, tetrahydrofurfuryl group, 5-hydroxypentyl group Cyclohexyl group, benzyl group, hydroxyethyl group, 3-methoxybutyl group, 2- (2-methoxyethoxy) ethyl group, 2,2,2-tetrafluoroethyl group, 1H, 1H, 2H, 2H-perfluorodecyl Group, phenyl group, 2,4,5-tetramethylphenyl group, 4-chlorophenyl group, etc.);

  Vinyl esters, specifically, aliphatic carboxylic acid vinyl esters which may have a substituent (for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl Chloroacetate, etc.), optionally substituted aromatic carboxylic acid vinyl ester (for example, vinyl benzoate, vinyl 4-methylbenzoate, vinyl salicylate, etc.);

  Acrylamides, specifically, acrylamide, N-monosubstituted acrylamide, N-disubstituted acrylamide (the substituent is an alkyl group, aryl group, silyl group which may have a substituent, such as a methyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, tert-octyl group, cyclohexyl group, benzyl group, hydroxymethyl group, alkoxymethyl group, phenyl group, 2,4,5-tetramethylphenyl group , 4-chlorophenyl group, trimethylsilyl, etc.);

  Methacrylamide, specifically, methacrylamide, N-monosubstituted methacrylamide, N-disubstituted methacrylamide (substituents are optionally substituted alkyl, aryl, silyl groups, for example , Methyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, tert-octyl group, cyclohexyl group, benzyl group, hydroxymethyl group, alkoxymethyl group, phenyl group, 2,4,5- Tetramethylphenyl group, 4-chlorophenyl group, trimethylsilyl, etc.);

  Olefins (for example, ethylene, propylene, 1-pentene, vinyl chloride, vinylidene chloride, isoprene, chloroprene, butadiene, etc.), styrenes (for example, styrene, methylstyrene, isopropylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, etc.) Vinyl ethers (for example, methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether, etc.);

  Other vinyl monomers include crotonic acid ester, itaconic acid ester, maleic acid diester, fumaric acid diester, methyl vinyl ketone, phenyl vinyl ketone, methoxyethyl vinyl ketone, N-vinyl oxazolidone, N-vinyl pyrrolidone, methylene malon nitrile, diphenyl Examples include 2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2-methacryloyloxyethyl phosphate, and the like.

  Examples of the monomer having a cationic group include monomers having a tertiary amino group such as dialkylaminoethyl methacrylate and dialkylaminoethyl acrylate.

Examples of the polyurethane applicable to the cationic group-containing polymer include polyurethanes synthesized by a polyaddition reaction using various combinations of the following diol compounds and diisocyanate compounds.
Specific examples of the diol compound include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 2,2 -Dimethyl-1,3-propanediol, 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 3,3-dimethyl-1,2-butanediol 2-ethyl-2-methyl-1,3-propanediol, 1,2-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 2-methyl-2, 4-pentanediol, 2,2-diethyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 1,7-heptane All, 2-methyl-2-propyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2-ethyl-1,3-hexanediol, 1,2-octanediol, 1, 8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, hydroquinone, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol (average molecular weight = 200,300,400,600,1000,1500,4000), polypropylene glycol (average molecular weight = 200,400,1000), polyester polyol, 4,4′-dihydroxy-diphenyl-2,2-propane, 4,4 ′ -Dihydroxyphenyls Luhon etc. are mentioned.

  Examples of the diisocyanate compound include methylene diisocyanate, ethylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-xylylene diisocyanate, 1, 5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, 3,3′-dimethylbiphenylene diisocyanate, 4,4′-biphenylene diisocyanate, dicyclohexylmethane diisocyanate , Methylenebis (4-cyclohexylisocyanate) and the like.

Cationic groups contained in the cationic group-containing polyurethane include cationic groups such as primary to tertiary amines and quaternary ammonium salts. As the self-emulsifying polymer, a urethane resin having a cationic group such as a tertiary amine and a quaternary ammonium salt is preferable.
The cationic group-containing polyurethane can be obtained, for example, by using a product obtained by introducing a cationic group into a diol as described above during the synthesis of polyurethane. In the case of a quaternary ammonium salt, a polyurethane containing a tertiary amino group may be quaternized with a quaternizing agent.

  The diol compound and diisocyanate compound that can be used for the synthesis of polyurethane may be used alone or in various ways (for example, adjustment of glass transition temperature (Tg) of polymer, improvement of solubility, binder) 2 or more types can be used at an arbitrary ratio, depending on the compatibility with the dispersion, the stability improvement of the dispersion, etc.).

  Furthermore, examples of polyesters applicable to cationic group-containing polymers include polyesters synthesized by a polycondensation reaction using various combinations of the following diol compounds and dicarboxylic acid compounds. Examples of the dicarboxylic acid compound include oxalic acid, malonic acid, succinic acid, glutaric acid, dimethylmalonic acid, adipic acid, pimelic acid, α, α-dimethylsuccinic acid, acetone dicarboxylic acid, sebacic acid, 1,9-nonanedicarboxylic acid. , Fumaric acid, maleic acid, itaconic acid, citraconic acid, phthalic acid, isophthalic acid, terephthalic acid, 2-butyl terephthalic acid, tetrachloroterephthalic acid, acetylenedicarboxylic acid, poly (ethylene terephthalate) dicarboxylic acid, 1,2-cyclohexane Examples include dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, ω-poly (ethylene oxide) dicarboxylic acid, p-xylylene dicarboxylic acid, and the like.

  When performing a polycondensation reaction with a diol compound, the dicarboxylic acid compound may be used in the form of an alkyl ester of a dicarboxylic acid (for example, dimethyl ester) and an acid chloride of the dicarboxylic acid, or maleic anhydride or succinic anhydride. You may use in the form of an acid anhydride like an acid and a phthalic anhydride.

  As the diol compound, the same compounds as the diols exemplified in the polyurethane can be used.

  The cationic group-containing polyester can be obtained by synthesis using a dicarboxylic acid compound having a cationic group such as a primary, secondary, tertiary amine, or quaternary ammonium salt.

  The diol compound and dicarboxylic acid compound used for the synthesis of the polyester may be used singly or for various purposes (for example, adjustment of the glass transition temperature (Tg) of the polymer, solubility, Depending on the compatibility and the stability of the dispersion, two or more of them can be mixed and used in an arbitrary ratio.

  0.1-5 mmol / g is preferable and, as for content of the cationic group in the polymer containing a cationic group, 0.2-3 mmol / g is more preferable. In addition, when there is too little content of the said cationic group, the dispersion stability of a polymer will become small, and when too large, compatibility with a binder will fall.

  As the self-emulsifying polymer containing a cationic group, a polymer having a cationic group such as a tertiary amino group or a quaternary ammonium base is preferable, and a urethane resin having a cationic group as described above is most preferable.

  When self-emulsifying polymers are used in the ink receiving layer, the glass transition temperature is particularly important. In order to suppress the bleeding of the image over time after the image is formed by inkjet recording, it is preferable that the self-emulsifiable polymer has a glass transition temperature of less than 50 ° C. Further, the self-emulsifiable polymer having a glass transition temperature of 30 ° C. or lower is more preferable, and a glass transition temperature of 15 ° C. or lower is most preferable. When the glass transition temperature is less than 50 ° C., dimensional stability (curl) is suppressed. In addition, although there is no restriction | limiting in particular in the minimum of this glass transition temperature, In normal use, it is about -30 degreeC, and if it is based on this, the manufacturability at the time of preparing an aqueous dispersion will be kept favorable.

  The mass average molecular weight (Mw) of the self-emulsifying polymer is usually preferably 1000 to 200000, more preferably 2000 to 50000. When the molecular weight is 1000 or more, a stable aqueous dispersion is obtained, and when the molecular weight is 200000 or less, the solubility is good and the liquid viscosity is suppressed, and the average particle size of the aqueous dispersion is reduced. It can be controlled to 0.05 μm or less.

  In the ink receiving layer of the present invention, the content of the self-emulsifying polymer is preferably from 0.1 to 30% by mass, more preferably from 0.3 to 20% by mass, based on the total solid content constituting the ink receiving layer. In particular, 0.5 to 15% by mass is most preferable. When the content is 0.1% by mass or more, an effect of improving bleeding with time can be obtained. On the other hand, when the content is 30% by mass or less, the ratio of the fine particles and the binder component is maintained, and high image quality is achieved. Good ink absorbency to recording paper.

Next, a method for preparing an aqueous dispersion of a self-emulsifiable polymer will be described.
The above self-emulsifiable polymer is mixed with an aqueous solvent, an additive is mixed as necessary, and the mixture is finely granulated using a disperser, whereby water having an average particle size of 0.05 μm or less is mixed. A dispersion can be obtained. Dispersers used for obtaining the aqueous dispersion include conventionally known high-speed rotary dispersers, medium stirring dispersers (ball mill, sand mill, bead mill, etc.), ultrasonic dispersers, colloid mill dispersers, high pressure dispersers, and the like. Various dispersers can be used. From the viewpoint of efficiently dispersing the formed fine particles, a medium stirring type disperser, a colloid mill disperser, or a high pressure disperser is preferable.

  The high-pressure disperser (homogenizer) is described in detail in US Pat. No. 4,533,254, JP-A-6-47264, etc., but as a commercially available apparatus, a Gorin homogenizer (APV GAULIN) is used. INC.), A microfluidizer (MICROFLUIDEX INC.), An optimizer (Sugino Machine Co., Ltd.) and the like can be used. In recent years, a high-pressure homogenizer having a mechanism for atomizing in an ultrahigh-pressure jet stream as described in US Pat. No. 5,720,551 is particularly effective for emulsification dispersion of the present invention. DeBEE2000 (BEE INTERNIONAL LTD.) Is an example of an emulsifying apparatus using this ultra-high pressure jet stream.

  Water, an organic solvent, or a mixed solvent thereof can be used as the aqueous solvent in the dispersion step. Examples of the organic solvent that can be used for the dispersion include alcohols such as methanol, ethanol, n-propanol, i-propanol, and methoxypropanol, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, acetonitrile, ethyl acetate, and toluene. It is done.

  The self-emulsifying polymer itself can be a naturally stable emulsion dispersion, but a small amount of a dispersing agent (surfactant) can be used in order to make the emulsion dispersion more quickly or more stable. Good. Examples of such surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, naphthalene sulfonate formalin condensates, polyoxy Anionic surfactants such as ethylene alkyl sulfate ester salt, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine, Nonionic surfactants such as glycerin fatty acid esters and oxyethyleneoxypropylene block copolymers are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred. Further, pages (37) to (38) of JP-A-59-157,636, Research Disclosure No. Those listed as surfactants described in 308119 (1989) can also be used.

  In order to stabilize immediately after emulsification, a water-soluble polymer can be added in combination with the surfactant. As the water-soluble polymer, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, polyacrylic acid, polyacrylamide or a copolymer thereof is preferably used. It is also preferable to use natural water-soluble polymers such as polysaccharides, casein, and gelatin.

  When the self-emulsifying polymer is dispersed in an aqueous medium by the emulsion dispersion method, it is important to control the particle size. In order to increase color purity and color density when forming an image by the inkjet method, it is preferable to reduce the average particle size of the self-emulsifying polymer in the aqueous dispersion. Specifically, in the ink receiving layer of the present invention, the volume average particle diameter of the self-emulsifying polymer is preferably 0.05 μm or less, the average particle diameter is more preferably 0.04 μm or less, and further 0 0.03 μm or less is preferable.

-Water-soluble polyvalent metal salt-
The ink receiving layer in the invention may contain at least one water-soluble polyvalent metal salt. Thereby, the dispersibility of vapor-phase method silica can be improved more.

  Examples of the water-soluble polyvalent metal salt include water-soluble salts of metals selected from calcium, barium, manganese, copper, cobalt, nickel, aluminum, iron, zinc, zirconium, chromium, magnesium, tungsten, and molybdenum. Specifically, calcium acetate, calcium chloride, calcium formate, calcium sulfate, barium acetate, barium sulfate, barium phosphate, manganese chloride, manganese acetate, manganese formate dihydrate, manganese ammonium sulfate hexahydrate, chloride chloride Dicopper, ammonium copper (II) chloride dihydrate, copper sulfate, cobalt chloride, cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, nickel sulfate Ammonium hexahydrate, nickel amidosulfate tetrahydrate, aluminum sulfate, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate, ferrous bromide, ferric chloride Ferrous, ferric chloride, ferrous sulfate, ferric sulfate, zinc bromide, zinc chloride, zinc nitrate hexahydrate Zinc sulfate, zirconyl acetate, zirconium chloride, zirconium oxychloride octahydrate, hydroxy zirconium chloride, chromium acetate, chromium sulfate, magnesium sulfate, magnesium chloride hexahydrate, magnesium citrate nonahydrate, sodium phosphotungstate, Examples thereof include sodium tungsten citrate, 12 tungstophosphoric acid n hydrate, 12 tungstosilicic acid 26 hydrate, molybdenum chloride, 12 molybdophosphoric acid n hydrate, and the like.

  The water-soluble polyvalent metal salt is preferably at least one selected from a water-soluble salt of aluminum, a water-soluble salt of zirconium, and a water-soluble salt of titanium. Examples of the water-soluble salt of aluminum include, for example, aluminum chloride or a hydrate thereof, aluminum sulfate or a hydrate thereof, and ammonium alum. Furthermore, the basic polyaluminum hydroxide compound which is an inorganic aluminum-containing cationic polymer is mentioned. In particular, a basic polyaluminum hydroxide compound is preferable.

The basic polyaluminum hydroxide compound is represented by the following formula 1, 2 or 3, for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ ( OH) ₃₄ ] ⁵⁺ , [Al ₂₁ (OH) ₆₀ ] ³⁺ , and the like, which are water-soluble polyaluminum hydroxides that stably contain basic and high-molecular polynuclear condensed ions.
_{[Al 2 (OH) n Cl 6} -n ] _m · · · Formula 1
[Al (OH) ₃ ] _n AlCl ₃ Formula 2
Al _n (OH) _m Cl _(3n-m) 0 <m <3n Formula 3

The water-soluble salt of zirconium is not particularly limited and various compounds can be used. For example, zirconyl acetate, zirconium chloride, zirconium oxychloride, zirconium zirconium chloride, zirconium nitrate, basic zirconium carbonate, zirconium hydroxide, carbonic acid Zirconium / ammonium, zirconium carbonate / potassium, zirconium sulfate, zirconium fluoride compounds and the like can be mentioned. Zirconyl acetate is particularly preferable.
The water-soluble salt of titanium is not particularly limited, and various compounds can be used. Examples thereof include titanium chloride and titanium sulfate.

  Some of these compounds have an inappropriately low pH. In that case, the pH can be appropriately adjusted and used. In the present invention, the term “water-soluble” means that 1% by mass or more dissolves in water at room temperature and normal pressure.

The water-soluble polyvalent metal salt in the present invention is preferably a water-soluble salt of zirconium from the viewpoint of the viscosity of the coating liquid for forming the ink receiving layer, and is weakly acidic from the viewpoint of the viscosity stability of the coating liquid. A water-soluble salt of zirconium is preferred, and zirconyl acetate is more preferred.
When using this zirconyl acetate, it is preferable from the viewpoint of viscosity stability of the coating solution that zirconyl acetate is previously contained in the dispersion of the vapor phase method silica, and then this dispersion and PVA are mixed, and more preferable. The method is a method in which zirconyl acetate is preliminarily coexisted in a liquid containing vapor phase silica before the vapor phase silica is dispersed.

In the present invention, the content of the water-soluble polyvalent metal salt in the ink receiving layer is preferably 0.5 to 10% by mass, more preferably 1.0 to 5.0% by mass with respect to the vapor phase silica. is there. When the content is 0.5% by mass or more, the viscosity stability of the silica dispersion is improved, and when the content is 10% by mass or less, cracks on the surface of the ink receiving layer are less likely to occur.
The water-soluble polyvalent metal salt may be used alone or in combination of two or more.

-Other components-
The ink receiving layer in the present invention includes, as other components, a mordant, a surfactant, various ultraviolet absorbers, an antioxidant, an antifading agent such as a singlet oxygen quencher, a high boiling point organic solvent, a pH adjuster, and a dispersion. Various components such as an agent, an antifoaming agent and an antistatic agent can be contained. Further, for the purpose of suppressing surface frictional charge and peeling charge, the metal oxide fine particles having electronic conductivity may contain various matting agents for the purpose of reducing the surface frictional characteristics.

The ink jet recording medium of the present invention can be produced by forming an ink receiving layer by applying a coating liquid for forming an ink receiving layer on a support and drying it. The ink jet recording medium of the present invention may be produced by any method as long as the ink receiving layer as described above can be formed on the support.
The inkjet recording medium of the present invention includes, for example, a hydroxy dispersion ester having a I / O value calculated on the basis of an organic conceptual diagram of 1.5 or more in a silica dispersion containing vapor-phase process silica and polyvinyl alcohol. A coating solution preparation step of preparing a coating solution in which the amount of the hydroxycarboxylic acid ester relative to 1 kg of vapor phase method silica is 0.1 mol or more and 2 mol or less, and applying the prepared coating solution on a support It can be suitably produced by a method of forming an ink receiving layer by providing a layer forming step for forming an ink receiving layer (a method for producing an ink jet recording medium of the present invention).

  In the coating liquid preparation step, a silica dispersion containing gas phase method silica is prepared in advance, hydroxycarboxylic acid ester and polyvinyl alcohol are added to the silica dispersion, and the amount of hydroxycarboxylic acid ester relative to 1 kg of gas phase method silica is increased. A coating solution for forming an ink receiving layer that is 0.1 mol or more and 2 mol or less is prepared.

The coating liquid for forming the ink receiving layer for forming the ink receiving layer in the present invention can be prepared, for example, as follows.
First, vapor phase silica (preferably having an average primary particle size of 15 nm or less), diallyldimethylammonium chloride, and a water-soluble polyvalent metal salt are added to water, and using a dissolver or a suction disperser, for example, a rotational speed of 3000 rpm (preferably Is pre-dispersed for 20 minutes (preferably 10 to 30 minutes) under conditions of high-speed rotation of 500 to 4000 rpm. Then, a silica dispersion can be prepared by finely dispersing using a desired disperser. Dispersers used for dispersion include various types of conventionally known dispersers such as high-speed rotary dispersers, medium stirring dispersers (ball mill, bead mill, sand mill, etc.), ultrasonic dispersers, colloid mill dispersers, and high pressure dispersers. Although it can be used, a medium stirring type disperser, a colloid mill disperser, and a high pressure disperser (homogenizer) are preferable in order to efficiently disperse the generated fine particles. As the disperser, a medium stirring type disperser such as a bead mill is preferably used. However, from the viewpoint of promoting atomization and high print density characteristics, a high-speed wet colloid mill disperser (for example, CLEA manufactured by MTechnic Co., Ltd.) is used. Mix W motion, etc.) and high-pressure homogenizer (eg, an optimizer manufactured by Sugino Machine Co., Ltd.) are also used.
Next, after adding a boron compound (for example, 0.5 to 20% by mass of gas phase method silica) and a hydroxycarboxylic acid ester to the prepared silica dispersion, an aqueous polyvinyl alcohol solution (for example, 1 / of gas phase method silica) is added. For example, using a dissolver and stirring for 10 minutes (preferably 10 to 30 minutes) under high-speed rotation conditions of, for example, 2000 rpm (preferably 1000 to 3000 rpm). Can be prepared.
The obtained coating liquid is a uniform sol, and a porous ink receiving layer having a three-dimensional network structure can be obtained by coating this on a support by a desired coating method.

  In the layer forming step, the ink receiving layer forming coating solution prepared in the coating solution preparing step is applied onto a support and dried to form an ink receiving layer. The coating solution can be applied by a known coating method such as an extrusion die coater, an air doctor coater, a blade coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, or a bar coater.

  The ink receiving layer is preferably formed on the surface of the support by applying a coating solution for forming an ink receiving layer to the coating layer (1) at the same time or (2) by coating. When the coating film is in the process of being dried and before the coating film exhibits reduced-rate drying, a basic solution having a pH of 7.1 or more is applied to cross-link and cure the coating film. Thus, an ink receiving layer can be formed. That is, it is preferable to introduce a basic solution having a pH of 7.1 or more from the time of applying the coating liquid for forming the ink receiving layer to the time when the coating film shows constant drying. It is more preferable to provide the ink-receiving layer that has been crosslinked and cured in this way in terms of ink absorbability and prevention of film cracking.

  The basic solution having a pH of 7.1 or higher can contain a crosslinking agent or the like as necessary. By using a basic solution having a pH of 7.1 or more as an alkaline solution, hardening of the coating film is promoted. When the pH is in the range of 7.1 or more, which is not too close to the acidic side, the cross-linking reaction of the PVA in the coating film proceeds satisfactorily by the cross-linking agent, and avoids defects such as bronzing and cracks in the ink receiving layer. Can do.

  A basic solution having a pH of 7.1 or more can be prepared, for example, by adding a basic compound (for example, 1 to 5%), boric acid, a metal compound, or the like to ion-exchanged water and stirring sufficiently. it can. In addition, all "%" of each composition means solid content mass%.

  “Before the coating film comes to show reduced-rate drying” usually means a process for several minutes immediately after coating of the coating solution, and during this period, the solvent (dispersion medium) in the coated layer is included. It shows the phenomenon of “constant rate drying rate” in which the amount decreases in proportion to time. About the time which shows this "constant rate drying speed", it describes in chemical engineering handbook (pages 707-712, Maruzen Co., Ltd. issue, October 25, 1980), for example.

  The coating liquid for the ink receiving layer is generally dried at 40 to 180 ° C. for 0.5 to 10 minutes (preferably, 0.5 to 10 minutes) until the coated film shows reduced-rate drying after coating. ~ 5 minutes). The drying time varies depending on the coating amount, but usually the above range is appropriate.

  In the present invention, from the viewpoints of glossiness and ink receptivity, the coating film is dried at 70 to 120 ° C. until the solid concentration is 14 to 20%, and then the coating film is further dried at a solid concentration of 21. It is preferable to dry at 40 to 60 ° C. until ˜30%.

-Support-
As the support, an opaque support using an opaque material such as paper can be used.
The opaque support is preferably one having a glossiness of 40% or more on the surface on which the ink receiving layer is provided. The glossiness is a value determined according to the method described in JIS P-8142 (75-degree specular gloss test method for paper and paperboard). Specifically, the following supports are mentioned. For example, high gloss paper support such as art paper, coated paper, cast coated paper, baryta paper used for silver salt photographic support, etc .; polyesters such as polyethylene terephthalate (PET), nitrocellulose, cellulose acetate , Cellulose esters such as cellulose acetate butyrate, and plastic films such as polysulfone, polyphenylene oxide, polyimide, polycarbonate, and polyamide are made opaque by adding a white pigment or the like (surface calendering may be applied). Glossy film; or a support in which a polyolefin coating layer containing or not containing a white pigment is provided on the surface of a highly glossy film containing various paper supports, transparent supports or white pigments. Etc. A white pigment-containing foamed polyester film (for example, foamed PET containing polyolefin fine particles and forming voids by stretching) can also be suitably exemplified. Furthermore, resin-coated paper used for silver salt photographic printing paper is also suitable.
There is no restriction | limiting in particular in the thickness of an opaque support body, and 50-300 micrometers is preferable at the point of the ease of handling. Moreover, it is preferable to use the surface of the support that has been subjected to corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, etc., in order to improve wettability and adhesion.

Next, a base paper used for a paper support such as resin-coated paper will be described.
As the base paper, wood pulp is used as a main raw material, and paper is made using synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester in addition to wood pulp as necessary. As the 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 large amount of short fibers. preferable. However, the ratio of LBSP and / or LDP is preferably 10% by mass to 70% by mass.

  As the pulp, a chemical pulp (sulfate pulp or sulfite pulp) with few impurities is suitably used, and a pulp whose whiteness is improved by performing a bleaching treatment is also useful.

  In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added.

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

The basis weight of the base paper is preferably 30 to 250 g / ^{m 2,} especially 50 to 200 g / ^{m 2} is preferred. The thickness of the base paper is preferably 40 to 250 μm. The base paper can be given a high smoothness by calendering at the paper making stage or after paper making. The density of the base paper 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. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS P-8113.

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

When the front and back sides of the base paper are covered with polyethylene, the polyethylene used for the coating is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but other LLDPE, polypropylene, etc. Some can be used.
In particular, when a polyethylene layer is provided on the side of the support on which the ink-receiving layer is formed, rutile or anatase type titanium oxide, fluorescent whitening agent, ultramarine blue is contained in polyethylene, as is widely done in photographic paper. Those having improved opacity, whiteness and hue are preferred. Here, as a titanium oxide content, about 3-20 mass% is preferable with respect to polyethylene, and 4-13 mass% is more preferable. Although the thickness of a polyethylene layer does not have limitation in particular, 10-50 micrometers is suitable for both front and back layers. Further, an undercoat layer can be provided on the polyethylene layer in order to provide adhesion to the ink receiving layer. As the undercoat layer, aqueous polyester, gelatin and PVA are preferable. Moreover, as thickness of this undercoat layer, 0.01-5 micrometers is preferable.

  Polyethylene-coated paper can be used as glossy paper, or when it is coated by melt-extruding polyethylene onto the surface of the base paper, a matte or silky surface that can be obtained with ordinary photographic printing paper by performing a so-called molding process. Can also be used.

  A back coat layer may be provided on the support. Examples of components that can be added to the backcoat layer include white pigments, aqueous binders, and other components. Details and preferred embodiments of the white pigment, the aqueous binder, and other components contained in the backcoat layer are described in paragraphs [0063] to [0064] of JP-A-2009-107319.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

(Examples 1-8, Comparative Examples 1-12)
-Production of support-
50 parts of LBKP made of acacia and 50 parts of LBKP made of aspen were beaten to 300 ml of Canadian freeness by a disc refiner to prepare a pulp slurry. Next, to the obtained pulp slurry, 1.3% by mass of cation modified starch (CAT0304L manufactured by NSC Japan), 0.15% by mass of anionic polyacrylamide (DA4104 manufactured by Seiko PMC), Arakawa Chemical Co., Ltd. Size Pine K) 0.29% by mass, epoxidized behenamide 0.29% by mass, and polyamide polyamine epichlorohydrin (Arakawa Chemical Co., Ltd. Arafix 100) 0.32% by mass After the addition, 0.12% by weight of antifoam was added.

In the process of making the pulp slurry obtained as described above with a long paper machine and drying the web by pressing the felt surface of the web against the drum dryer cylinder through the dryer canvas, the tensile force of the dryer canvas is 1.6 kg. After drying at a setting of / cm, 1 g / m ² of polyvinyl alcohol (manufactured by Kuraray Co., Ltd .: KL-118) was applied to both sides of the base paper with a size press and dried to perform calendar treatment. The basis weight of the base paper was made at 166 g / m ² to obtain a base paper (base paper) having a thickness of 160 μm.

After the corona discharge treatment is performed on the wire surface (back surface) side of the obtained base paper, a high-density polyethylene is coated to a thickness of 25 g / m ² using a melt extruder, and heat generated from the mat surface A plastic resin layer was formed. The thermoplastic resin layer on the back side is further subjected to corona discharge treatment, and then, as an antistatic agent, aluminum oxide (“Alumina Zil 100” manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (Nissan Chemical Industry Co., Ltd.). A dispersion obtained by dispersing “Snowtex O” manufactured in water at a mass ratio of 1: 2 was applied so that the dry mass was 0.2 g / m ² . Subsequently, the front surface opposite to the back surface was subjected to corona discharge treatment, and a melt extruder was used so that 0.93 g / cm ³ of polyethylene having 10% by mass of titanium oxide was 24 g / m ^2. And coated.

-Preparation of silica dispersion-
Vapor phase silica fine particles (Aerosil 300SF75, manufactured by Nippon Aerosil Co., Ltd.) 19.5 kg, Charol DC902P (Daiichi Kogyo Seiyaku Co., Ltd. cationic resin aqueous solution) 1.70 kg, Zircozol ZA-30 (First Mixing 1.05 kg of zirconyl acetate aqueous solution (water-soluble polyvalent metal salt) manufactured by Rare Element Chemical Co., Ltd. and 77.74 kg of ion-exchanged water with a suction disperser (CONTI-TDS, manufactured by Dalton Co., Ltd.) Then, it was dispersed at a pressure of 130 MPa using a counter collision type high-pressure homogenizer (manufactured by Optimizer Sugino Machine Co., Ltd.). Thereafter, this dispersion was heated to 45 ° C. and held for 20 hours to prepare a silica dispersion having a silica concentration of 19.5% by mass relative to the total mass of the dispersion.

-Preparation of coating solution-
Hydroxycarboxylic acid compound 0 such as 4.69 parts of ion-exchanged water, 6.56 parts of a 5% by weight boric acid aqueous solution, and hydroxycarboxylic acid esters shown in Table 1 below are added to 45.65 parts of the silica dispersion prepared above. .56 parts, Himax SC507 (manufactured by Hymo Co., Ltd .; polyalkylene polyamine-dimethylamine-epichlorohydrin polycondensate) 0.05 part, PVA-235 (manufactured by Kuraray Co., Ltd .; degree of saponification 88%, degree of polymerization 3500) 7 mass% aqueous solution 25.93 parts, Emulgen 109P (polyoxyethylene lauryl ether, HLB 13.6, manufactured by Kao Corporation) 0.5 mass parts 10 mass% aqueous solution, butisenol 20P (manufactured by Kyowa Hakko Chemical Co., Ltd.) 0.27 parts of diethylene glycol monobutyl ether and Superflex 6500-5 (Daiichi Kogyo Seiyaku Co., Ltd.) Ltd., was added cationic polyurethane latex) 1.76 parts of 30 ° C., to prepare a coating solution.

-Preparation of basic solution-
Components having the following composition were mixed and stirred to prepare a basic solution.
<Composition>
・ Boric acid (crosslinking agent) ・ ・ ・ 0.65 parts ・ Ammonium carbonate (first grade: manufactured by Kanto Chemical Co., Ltd.) ・ ・ ・ 4.0 parts ・ Ion-exchanged water ・ ・ ・ 89.35 parts ・ Polyoxyethylene lauryl Ether (10% by mass aqueous solution) 6 parts (Emulgen 109P, manufactured by Kao Corporation)

-Preparation of aqueous polyaluminum chloride solution-
The following components were mixed and stirred to prepare a polyaluminum chloride aqueous solution.
・ Alphaine 83 ... 20 parts (Daimei Chemical Co., Ltd .; basic polyaluminum chloride aqueous solution)
・ Ion exchange water: 80 parts

-Preparation of inkjet recording paper-
After the corona discharge treatment was performed on the front surface of the support, an ink obtained by in-line mixing a polyaluminum chloride aqueous solution with 132 g / m ² of the coating liquid on the front surface at a speed of 9.1 ml / m ^2. A coating solution for forming a receiving layer was applied. Thereafter, it was dried at 80 ° C. (wind speed 3 to 8 m / sec) using a hot air dryer until the solid content concentration of the coating film became 23% by mass. The coated layer showed constant rate drying during this period. Then, it was immersed in a basic solution for 3 seconds before showing reduced-rate drying, 8 g / m ² was adhered on the coating layer, and further dried at 80 ° C. for 10 minutes.
Inkjet recording paper was produced as described above.

-Evaluation-
The following evaluation was performed about the coating liquid and ink jet recording paper for ink receiving layer which were obtained by the above. The results of measurement evaluation are shown in Table 1 below.

(1) Coating liquid state After storing the coating liquid for forming the ink receiving layer obtained as described above at 30 ° C. for 24 hours, the liquid temperature of the coating liquid was set to 30 ° C. )), The viscosity η was measured at a rotor rotational speed of 60 rpm, and evaluated according to the following evaluation criteria using the obtained viscosity value as an index.
<Evaluation criteria>
A: The viscosity was 200 mP · s or less.
(Triangle | delta): The viscosity exceeded 200 mP * s and was 500 mP * s or less.
X: The viscosity exceeded 500 mP · s.

(2) Concentration (Dmax)
For each of the obtained ink jet recording papers, black was used under the conditions that the black density was maximum (K-Dm) using an ink jet printer PM-A820 (manufactured by Seiko Epson) at 23 ° C. and 50% RH environmental conditions. A solid image was formed. After recording, this black solid image was left under environmental conditions of 23 ° C. and 50% RH for 24 hours, and the visual reflection density was measured with a densitometer (X-rite 538, manufactured by X-rite).

(3) Low-humidity curl The obtained inkjet recording medium was used as an A4-sized sample piece, and was left for 7 days at 27 ° C. and 35% RH environmental conditions. After the completion of the standing, a black solid image was formed on the sample piece using an inkjet printer PM-A820 (manufactured by Seiko Epson) under the same environment. The image formation surface of the sample piece was placed on the desk with the surface facing upward, the height from the desk surface of the four corners floating on the desk was measured, and the degree of low-humidity curl was evaluated from the average value according to the following evaluation criteria.
<Evaluation criteria>
○: Less than 3 mm Δ: 3 mm or more and less than 8 mm ×: 8 mm or more

  As shown in Table 1, in the examples, a high-density image was obtained while maintaining the viscosity of the coating solution low, and the occurrence of curling under low humidity was prevented. On the other hand, in Comparative Examples 1-6, the viscosity of the coating liquid for ink receiving layers could not be kept low, and was inferior in coating suitability. In addition, when a compound having no COOH group or one and having an I / O value of 1.5 or more but not an ester is used, the liquid viscosity cannot be kept low, or the image density is lowered or the humidity is low. The curl could not be suppressed.

Claims (4)

  Gas phase method silica, hydroxycarboxylic acid ester having an I / O value calculated based on an organic conceptual diagram of 1.5 or more, and polyvinyl alcohol, the amount of hydroxycarboxylic acid ester relative to 1 kg of gas phase method silica is An ink jet recording medium having an ink receiving layer of 0.1 mol or more and 2 mol or less.   The inkjet recording medium according to claim 1, wherein the hydroxycarboxylic acid ester is at least one of a lactic acid ester and a glycolic acid ester.   The inkjet recording medium according to claim 1 or 2, wherein the hydroxycarboxylic acid ester is an alkyl ester of lactic acid or glycolic acid and an alcohol having 1 to 4 carbon atoms. A hydroxycarboxylic acid ester having an I / O value calculated based on an organic conceptual diagram of 1.5 or more is added to a silica dispersion containing vapor-phase process silica, and polyvinyl alcohol is added. A coating solution preparation step of preparing a coating solution having an amount of 0.1 mol to 2 mol with respect to 1 kg of phase method silica;
A layer forming step of forming an ink receiving layer by applying the coating liquid on a support;
A method for producing an ink jet recording medium comprising: