JP2008246755A - Manufacturing method of inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inkjet recording medium which enables recording of an image having a high density and a high glossiness. <P>SOLUTION: This manufacturing method comprises a dispersion preparing process for preparing (A) an alumina dispersion of pH 4-5 by dispersing a pseudo-boehmite-like alumina hydrate in a water-based solvent by high-pressure dispersing machine, a coating solution making process for making a coating solution by mixing (A) the alumina dispersion, (B) a binder water solution and (C) a crosslinking agent water solution, while keeping the temperatures at 50°C or above, and a layer forming process for forming an ink accepting layer by applying the coating solution to a water-resistant substrate at 50°C or above and by drying it in the condition that a film surface temperature becomes lower than 30°C. The viscosity of the coating solution at 30°C is made 100 mPa s or below. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an inkjet recording medium for obtaining an inkjet recording medium suitable for high-quality image recording.

  With the rapid development of the information technology industry in recent years, various information processing systems have been developed, and recording methods and recording apparatuses suitable for each information processing system have been put into practical use. Among these, the ink jet recording method is widely used because it can record on various recording materials, the hardware (device) is relatively inexpensive and compact, and has excellent quietness. ing. In the recording using the ink jet recording method, it has become possible to obtain a so-called photographic-like high quality recorded matter.

  In general, recording materials for inkjet recording are (1) fast-drying (high ink absorption speed), (2) proper and uniform dot diameter (no bleeding), (3) granular (4) High dot roundness, (5) High color density, (6) High saturation (no dullness), (7) Water resistance of the image area (8) High whiteness, (9) High storage stability (no yellowing or image blurring after long-term storage), (10) It is required to have properties such as being hard to deform and having good dimensional stability (low curl) and (11) good hard running performance.

  In view of the above, in recent years, recording materials in which the ink receiving layer has a porous structure have been put into practical use. According to this, it is said that it is excellent in quick-drying and high gloss is obtained. However, there is a tendency for the quality of the recorded image to be always high. For example, the high density range is dark in terms of image contrast, contrast sharpness, etc., and the appearance is glossy and has a photo-like texture. It is important to have.

In relation to the above, an ink containing alumina hydrate (including pseudoboehmite structure) and a reaction product of aliphatic dialdehyde and polyvinyl alcohol having a polymerization degree of 2000 or more and a saponification degree of 88% or more and less than 100% Ink-jet recording material having a receiving layer, or an ink-receiving layer containing an alumina hydrate having a specific pseudoboehmite structure and polyvinyl alcohol having a polymerization degree of 2000 or more and a saponification degree of 88% or more and less than 100% Recording materials for use are disclosed (for example, see Patent Documents 1 and 2). In these documents, when alumina hydrate and a binder are mixed, a change in viscosity with time is avoided, and polyvinyl alcohol having a polymerization degree of 2000 or more and a saponification degree of 88% or more and less than 100% is preferable for adjusting the coating liquid viscosity. .
JP 11-334197 A JP 10-193777 A

  However, in any of the above documents, secondary agglomerates are easily formed when the alumina hydrate is dispersed, the viscosity is increased, and the glossiness is high with respect to the vapor phase method silica and the like. A good photo-like image cannot be obtained.

  The present invention has been made in view of the above, and manufacture of an ink jet recording medium capable of obtaining an ink jet recording medium capable of recording an image having an overwhelmingly high density and high glossiness with respect to gas phase method silica or the like. The object is to provide a method and to achieve the object.

Specific means for achieving the above object are as follows.
<1> A step of preparing (A) an alumina dispersion in which pseudoboehmite-like alumina hydrate is dispersed in an aqueous solvent by a high-pressure disperser and has a pH (30 ° C.) of 4 to 5, and the (A) alumina The dispersion, (B) an aqueous solution containing a water-soluble binder, and (C) an aqueous solution of a crosslinking agent are mixed while keeping the temperature at 50 ° C. or higher, respectively, and the coating liquid is prepared at a temperature of 50 ° C. or higher. Coating on a water-resistant support, and drying the film at a film surface temperature of less than 30 ° C. to form an ink-receiving layer. The viscosity of the coating solution at 30 ° C. is 100 mPa · s or less. This is a method of manufacturing an inkjet recording medium.

  <2> The method for producing an inkjet recording medium according to <1>, wherein the water-soluble binder is polyvinyl alcohol having a saponification degree of 75 to 90% and an average polymerization degree of 3000 or more.

  <3> The method for producing an inkjet recording medium according to <1> or <2>, wherein the aqueous crosslinking agent solution is mixed by in-line mixing.

  <4> The method for producing an ink jet recording medium according to any one of <1> to <3>, wherein the crosslinking agent contains at least one of boric acid and a salt thereof.

  <5> The above <2> to <4, wherein a mass ratio (al / PVA) of the pseudo boehmite-like alumina hydrate (al) and polyvinyl alcohol (PVA) satisfies al / PVA> 8. The method for producing an inkjet recording medium according to any one of the above.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the inkjet recording medium which can obtain the inkjet recording medium which can record an image with high glossiness with high density | concentration can be provided.

Hereafter, the manufacturing method of the inkjet recording medium of this invention is demonstrated in detail.
In the method for producing an inkjet recording medium of the present invention, a pseudo boehmite-like alumina hydrate is dispersed in an aqueous solvent by a high-pressure disperser, and (A) an alumina dispersion having a pH (30 ° C.) of 4 to 5 is prepared. A step (hereinafter, also referred to as “dispersion preparation step”) and the obtained (A) alumina dispersion, (B) an aqueous solution containing a water-soluble binder, and (C) an aqueous solution of a crosslinking agent, And a step of preparing a coating solution (hereinafter sometimes referred to as “coating solution preparation step”), and applying the prepared coating solution to a temperature of 50 ° C. or higher on a water-resistant support. And a step of forming an ink receiving layer by drying under the condition that the film surface temperature is less than 30 ° C. (hereinafter, also referred to as “layer forming step”), and the viscosity at 30 ° C. of the coating liquid used for coating is provided. 100 mPa · s or less To those that you configured.

  In the present invention, when an ink receiving layer is formed using pseudo boehmite-like alumina hydrate, mixing and coating are performed in a relatively high temperature region of 50 ° C. or higher, and conversely, a low temperature region of less than 30 ° C. is used. By adjusting the viscosity in the vicinity of this low temperature range to 100 mPa · s or less, the film forming property and the thickening effect of the coating liquid and the effect of suppressing the thickening over time are great, and the resulting coating Since unevenness and drying unevenness can be effectively prevented, a photographic-like image with high image density and gloss can be obtained.

  In the present invention, “glossiness” refers to the degree of sharpness of light (fluorescent lamp) reflected on the surface by reflection of light when the surface of the ink receiving layer on which the ink image is formed is observed under the fluorescent lamp. Judgment is made based on whether the light (fluorescent light) is not blurred or distorted by visual inspection, and whether it appears sharp and clear.

Hereafter, the manufacturing method of the inkjet recording medium of this invention is explained in full detail for every process.
(Dispersion preparation process)
In the dispersion preparation step, pseudoboehmite-like alumina hydrate is dispersed in an aqueous solvent by a high-pressure disperser to prepare (A) an alumina dispersion having a pH of 4 to 5. By using a high-pressure disperser to disperse the pseudoboehmite-like alumina hydrate, it is further atomized, so even after the ink solvent penetrates (that is, after recording), the haze is low and the transparency is maintained, so that the concentration is very high. A glossy photo-like image can be obtained.

  In this step, an alumina dispersion may be prepared, or a commercially available alumina dispersion prepared in advance may be obtained and used.

  (A) Alumina dispersion is prepared by mixing pseudoboehmite-like alumina hydrate with an aqueous solvent (for example, ion-exchanged water) and dispersing with a high-pressure disperser. Preferably, pseudo-boehmite-like alumina hydrate is first mixed with water (for example, ion-exchanged water), stirred with a stirrer to prepare a coarse dispersion, and this is further finely dispersed with a high-pressure disperser. Obtain a liquid.

  Examples of the stirrer include a dissolver and a suction disperser. As stirring conditions, the temperature is preferably 10 to 50 ° C., and the stirring time is preferably 1 to 30 minutes from the viewpoint of viscosity.

  As the high-pressure disperser, for example, a high-pressure homogenizer such as an optimizer (for example, HJP25005 manufactured by Sugino Machine Co., Ltd.) that makes pressurized slurry-like raw materials collide with each other at an ultra high speed and a cavitation is used. Can be used.

  The dispersed particle diameter after fine dispersion is preferably 0.10 to 0.14 [mu] m, more preferably 0.10 to 0.12 [mu] m as the particle diameter immediately after fine dispersion from the viewpoint of printing density.

  The concentration of the pseudo boehmite-like alumina hydrate in the (A) alumina dispersion can be selected according to the desired amount required for the coating solution prepared in the subsequent step, but from the viewpoint of the coating solution viscosity, the total mass 20-40 mass% is preferable with respect to.

  In the present invention, the pH (30 ° C.) of the finely dispersed alumina dispersion is in the range of 4-5. If the pH after fine dispersion is less than 4, the coating solution prepared in the coating solution preparation step described below is insufficiently gelled, the film formability is poor, and even if a film can be formed, only a porous structure with a small void volume is obtained. I can't. On the other hand, if the pH exceeds 5, the image density of the recorded image is lowered and the glossiness is also lowered.

  In order to adjust pH to the range of 4-5, the method of using bases, such as ammonia, and acids, such as nitric acid, hydrochloric acid, acetic acid, formic acid, etc. are mentioned, for example. The pH is a value measured by maintaining the coating solution at 30 ° C. using a pH meter (for example, HM-25G manufactured by Toa DKK Co., Ltd.).

-Aqueous solvent-
Examples of the aqueous solvent include water, such as pure and ion exchange water, and a mixed solvent of water and an organic solvent soluble in the water. As the organic solvent soluble in water, for example, methanol, ethanol, propanol, butanol and the like can be selected according to the purpose.

-Pseudo boehmite-like alumina hydrate-
In the present invention, at least one kind of pseudo boehmite-like alumina hydrate is used. By constituting the ink receiving layer using alumina hydrate, the transparency of the layer is improved, and a high-density image can be recorded. Further, the ink absorbability and the absorption speed can be improved.

The pseudo boehmite-like alumina hydrate in the present invention is represented by a constitutional formula of Al ₂ O ₃ .nH ₂ O (1 <n <3), and the alumina hydrate when n is greater than 1 and less than 3. Sure.

  The average pore radius of the alumina hydrate is preferably 1 to 10 nm, and particularly preferably 2 to 7 nm, from the viewpoint of improving the ink absorption rate of the ink receiving layer. When the average pore radius is within the above range, the ink absorptivity is good, the fixing of the dye in the ink is good, and the occurrence of image bleeding can be avoided.

The pore volume of the alumina hydrate is preferably in the range of 0.1 to 0.8 ml / g, particularly in the range of 0.4 to 0.6 ml / g from the viewpoint of improving the ink absorption capacity of the ink receiving layer. A range is preferred. When the pore volume of the ink receiving layer is within the above range, it is possible to avoid the occurrence of cracks and powder falling in the ink receiving layer, and the ink absorption is improved. The pore volume at a pore radius of 2 nm to 10 nm is preferably 0.1 ml / g or more. Within this range, the adsorption of the dye in the ink becomes good. Further, the solvent absorption amount per unit area of the ink receiving layer is preferably 5 ml / m ² or more, and particularly preferably 10 ml / m ² or more. When the solvent absorption amount per unit area is within the above range, it is possible to prevent ink overflow particularly when multicolor printing is performed.

In order for the alumina hydrate to sufficiently absorb and fix the dye in the ink, the BET specific surface area of the alumina hydrate is preferably in the range of 70 to 300 m ² / g. When the BET specific surface area is within the above range, the alumina hydrate can be dispersed well, the pore size distribution is not deviated, the fixing efficiency of the dye in the ink is improved, and image bleeding can be avoided.

In order to increase the concentration of the alumina hydrate dispersion, the number of surface hydroxyl groups of the alumina hydrate is preferably 10 ²⁰ / g or more. When the number of surface hydroxyl groups is small, the alumina hydrate tends to aggregate and it is difficult to increase the concentration of the dispersion.

  In order to stabilize the dispersion of alumina hydrate, various acids are usually added to the dispersion. Examples of such acids include nitric acid, hydrochloric acid, hydrobromic acid, acetic acid, formic acid, ferric chloride, aluminum chloride and the like, but the present invention is not limited thereto.

  The alumina hydrate can be produced by a known method such as hydrolysis of aluminum alkoxide such as aluminum isopropoxide, neutralization of aluminum salt with alkali, hydrolysis of aluminate. The particle size, pore size, pore volume, specific surface area, number of surface hydroxyl groups, etc. of the alumina hydrate can be controlled by the precipitation temperature, aging time, solution pH, solution concentration, coexisting salts and the like.

  For example, JP-A-57-88074, JP-A-62-56321, JP-A-4-275717, JP-A-6-64918, JP-A-7-10535, JP-A-7-267633, U.S. Pat. No. 2,656,321. No., Am. Ceramic Soc. Bull. , 54, 289 (1975), etc. disclose a method for hydrolyzing aluminum alkoxide. These aluminum alkoxides include isopropoxide, propoxide, 2-butoxide and the like. By this method, a highly pure alumina hydrate can be obtained.

  In addition, as a method for obtaining alumina hydrate, as disclosed in JP-A Nos. 54-116398, 55-23034, 55-27824, 56-120508, etc., aluminum Generally, a method for obtaining an inorganic salt or a hydrate thereof as a raw material. Examples of these inorganic salts include inorganic salts such as aluminum chloride, aluminum nitrate, aluminum sulfate, polyaluminum chloride, ammonium alum, sodium aluminate, potassium aluminate, aluminum hydroxide, and hydrates of these inorganic salts. Etc.

  Specifically, for example, an alumina hydrate is obtained by a neutralization reaction between an aqueous solution of an acidic aluminum salt such as aluminum sulfate, aluminum nitrate, or aluminum chloride and a basic aqueous solution such as sodium aluminate, sodium hydroxide, or aqueous ammonia. Can be manufactured. In this case, it is common to mix within a range where the amount of alumina hydrate produced in the liquid does not exceed 5% by mass, and to react under conditions of pH 6 to 10 and temperature 20 to 100 ° C. Further, as described in JP-A-56-120508, a method for growing alumina hydrate crystals by alternately changing the pH to the acid side and the base side, aluminum described in JP-B-4-33728 It can also be produced by a method of rehydrating alumina by mixing alumina hydrate obtained from the inorganic salt and alumina obtained by the Bayer method.

  The average particle diameter (average primary particle diameter) of primary particles of alumina hydrate is preferably 5 to 50 nm. In order to obtain higher gloss, it is preferable to use tabular grains having an average primary particle diameter of 5 to 20 nm and an average aspect ratio (ratio of average particle diameter to average thickness) of 2 or more.

The average primary particle diameter of the alumina hydrate may be a nominal value of a commercial product manufacturer.
When measuring the average primary particle size from the prepared recording medium, after removing the ink receiving layer, removing the resin component with hot water, and then collecting only the particles by centrifugation, etc. The obtained particles can be obtained by observation with a TEM (transmission electron microscope). At this time, for example, the same processing is performed on a sample coated with only the ink receiving layer coating solution as a reference sample, and the known particle diameter (nm) of the alumina hydrate particles using the measured value (average value) is used. The average primary particle diameter in the produced recording medium can be determined by comparing and converting the measured value (average value) in the produced recording medium from the difference between the values obtained by the comparison. In addition, in order to obtain | require an average primary particle diameter, about 100-3000 particles are required as a measurement particle number.

  The content of the pseudo boehmite-like alumina hydrate is preferably in the range of 10 to 20% by mass and in the range of 12 to 18% by mass in the coating liquid (or ink receiving layer) prepared in the subsequent step. More preferred. By setting the content of pseudoboehmite-like alumina hydrate within the above range, the transparency of the layer is increased, the transparency after printing is improved, and a high concentration is obtained.

(Coating solution preparation process)
In the coating liquid preparation step, (A) the alumina dispersion obtained in the dispersion preparation step, (B) an aqueous solution containing a water-soluble binder (hereinafter also referred to as a binder aqueous solution), and (C) an aqueous crosslinking agent solution, respectively. Mixing while keeping the temperature at 50 ° C. or higher to prepare a coating solution. By performing the mixing while keeping the temperature at 50 ° C. or higher, secondary aggregation can be suppressed, so that an increase in the viscosity of the liquid can be prevented from being suppressed.

  When mixing (A) alumina dispersion, (B) aqueous binder solution, and (C) aqueous crosslinking agent solution is not kept at a temperature of 50 ° C. or higher and the temperature is lower than 50 ° C., the solution is thickened and applied. I can't. In the present invention, the mixing temperature is preferably 50 to 70 ° C., more preferably 55 to 65 ° C., from the viewpoints of suppression of thickening and gelation and prevention of application failure such as application stripes.

  For example, when pseudoboehmite-like alumina hydrate and PVA are mixed, the viscosity tends to increase or gelate with time. By controlling the temperature of the coating solution within the above range, it is possible to avoid a change with time in the viscosity of the coating solution. Thereby, the coating stability is improved, and the film quality of the coating film surface can be kept good.

There is no restriction | limiting in particular in the mixing method in this process, The method of mixing in arbitrary orders and stirring, for example using a dissolver etc. is mentioned. The stirring temperature is desirably kept at 50 ° C. or more in view of preventing thickening, and is preferably kept at 55 to 65 ° C.
In addition, the aqueous solution of the crosslinking agent can be mixed by in-line mixing from the viewpoint of increasing the viscosity stability over time of the coating liquid, glossiness, and lowering the haze after ink penetration into the solvent (after recording) to obtain a high printing density. preferable. For example, an aqueous crosslinking agent solution may be mixed in-line with a mixed solution of (A) an alumina dispersion and (B) an aqueous binder solution.

In this invention, the coating liquid prepared at this process is prepared so that the viscosity ((eta) ³⁰ ) in ³⁰ degreeC may be 100 mPa * s or less. When the viscosity η ³⁰ is 100 mPa · s or less, the effect of improving the image density and glossiness is remarkable. In the temperature range exceeding 100 mPa · s, the image density hardly changes but the glossiness is lowered.

(A) Alumina dispersion The alumina dispersion in the present invention was prepared in the above-mentioned dispersion preparation step, and the amount of pseudoboehmite-like alumina hydrate contained in the coating liquid was used for the preparation of the coating liquid. Can be used in such an amount as described above.

(B) Aqueous solution containing water-soluble binder The aqueous solution (binder aqueous solution) containing a water-soluble binder in the present invention can be prepared by dissolving one or more water-soluble binders in an aqueous solvent. As an aqueous solvent, the thing similar to the aqueous solvent which can be used at the above-mentioned dispersion liquid preparation process can be used.

  Examples of the water-soluble binder include polyvinyl alcohol (PVA), starch and modified products thereof, gelatin and modified products thereof, natural polymer resins such as casein, pullulan, gum arabic, karaya gum, and albumin or derivatives thereof, cation modification , Modified products of polyvinyl alcohol such as silanol modification, latexes such as SBR latex, NBR latex, methyl methacrylate-butadiene copolymer, ethylene-vinyl acetate copolymer, vinyl polymers such as polyacrylamide and polyvinyl pyrrolidone, polyethyleneimine, Examples thereof include polypropylene glycol, polyethylene glycol, maleic anhydride or a copolymer thereof, but the present invention is not limited to these.

Of the above, polyvinyl alcohol (PVA) is preferable, and in terms of mixing with the alumina hydrate, adjustment of coating liquid viscosity, film formability, and improvement of printing density, average polymerization degree of 3000 or more, particularly saponification. A degree of 75-90% polyvinyl alcohol is preferred.
When the average degree of polymerization is 3000 or more, the coating film strength can be obtained, cracks can be prevented, haze after printing is suppressed, and the printing density tends to increase.
Further, when the degree of saponification is 75% or more, the coating film strength can be obtained and cracks can be prevented, and when it is 90% or less, the reactivity with alumina hydrate is suppressed, and the coating solution is gelled. And haze rise of the image receiving layer after printing can be suppressed, and the printing density tends to be high.

In the present invention, polyvinyl alcohol is used as the water-soluble binder, and the mass ratio (al / PVA) of the pseudoboehmite-like alumina hydrate (al) to polyvinyl alcohol (PVA) satisfies al / PVA> 8. The range is preferable. By setting the mass ratio al / PVA within the above range, haze can be suppressed and high image density and gloss can be obtained.
The mass ratio al / PVA is 8 to 15 in that it suppresses haze and maintains high image density and gloss, while maintaining mixing with alumina hydrate, adjustment of coating solution viscosity, and film formability. A range is more preferred.

  The degree of saponification can be obtained by reacting residual acetic acid groups in PVA with a known amount of sodium hydroxide and determining the saponification ratio in PVA from the amount of sodium hydroxide consumed. Moreover, as an average degree of polymerization of PVA, 3000-5000 are preferable at the point which raises a printing density and film | membrane intensity | strength. The molecular weight can be determined from the product of the average degree of polymerization and the formula weight of the monomer.

  The water-soluble binder may be used alone or in combination of two or more. For example, polyvinyl alcohol and one or more water-soluble binders can be used in combination.

  The total content of the water-soluble binder (for example, PVA, or PVA and other water-soluble binders) in the coating solution is preferably in the range of 5 to 20% by mass with respect to the pseudoboehmite-like alumina hydrate. A range of ˜15 mass% is more preferable. When the amount of the water-soluble binder is within the above range, film formation by application is easy, cracks and powder fall off of the application film can be avoided, and ink absorbability is improved.

The concentration of the water-soluble binder (for example, PVA, or PVA and other water-soluble binders) in the aqueous solution (B) can be selected according to the desired amount of the coating solution, but from the viewpoint of handling the aqueous binder solution Is preferably 3 to 10% by mass relative to the total mass.
In preparing the coating solution, the aqueous binder solution can be used so that the amount of the water-soluble binder contained in the coating solution is within the above range.

(C) Crosslinking agent aqueous solution The crosslinking agent aqueous solution in the present invention can be prepared by dissolving one or more crosslinking agents in an aqueous solvent. By using a cross-linking agent, film formability and water resistance can be improved. As an aqueous solvent, the thing similar to the aqueous solvent which can be used at the above-mentioned dispersion liquid preparation process can be used.

What is necessary is just to select a suitable crosslinking agent suitably in relation to the water-soluble binder contained in an ink receiving layer. Among these, boric acid and / or a salt thereof are preferable in that the crosslinking reaction is rapid. For example, orthoboric acid, metaboric acid, and hypoboric acid can be used as boric acid. The borate is preferably a soluble salt such as Na ₂ B ₄ O ₇ · 10H ₂ O, NaBO ₂ · 4H ₂ O, K ₂ B ₄ O ₇ · 5H ₂ O, NH ₄ HB ₄ O. _{7 · 3H 2 O, NH 4} BO 2 , and the like. However, the present invention is not limited to these.

When gelatin is used as the water-soluble binder, the following compounds other than boric acid and its salts 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 2,983611; Carboximide compounds described in US Pat. No. 3,100,704; Epoxys such as glycerol triglycidyl ether Compounds; ethyleneimino compounds such as 1,6-hexamethylene-N, N′-bisethyleneurea; halogenated carboxaldehyde compounds such as mucochloric acid and mucophenoxycyclolic acid; dioxane such as 2,3-dihydroxydioxane 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, oxazo A low molecule or polymer containing two or more phosphorus groups. A crosslinking agent may be used alone or in combination of two or more.

  The cross-linking agent is contained in the ink-receiving layer-forming coating solution (ink-receiving layer coating solution) prepared in this step, and further added to the coating solution for forming the adjacent layer of the ink-receiving layer. Alternatively, the ink receiving layer coating solution may be applied on a support on which a coating solution containing a crosslinking agent has been applied in advance, or a crosslinking agent-free coating solution for an ink receiving layer may be applied and dried, followed by drying. A cross-linking agent may be supplied to the ink receiving layer by overcoating.

  (C) When the aqueous crosslinking agent solution is mixed with (A) an alumina dispersion or (B) an aqueous binder solution, or a mixture of (A) an alumina dispersion and (B) an aqueous binder solution, the coating solution is heated when the coating solution is heated. (C) Keeping the aqueous solution of the crosslinking agent at 50 ° C. or higher (preferably kept at 50 ° C. or higher) (A) Alumina dispersion or (B) Binder aqueous solution, or (A) Alumina It is preferable to mix with a liquid mixture of the dispersion and (B) an aqueous binder solution.

A crosslinking agent (preferably boric acid and / or a salt thereof) may be used alone or in combination of two or more.
As total content in the coating liquid of a crosslinking agent, 5-40 mass parts is preferable with respect to 100 mass parts of water-soluble binders, and 15-35 mass parts is more preferable. When the content of the cross-linking agent is within the above range, the water-soluble binder can be effectively cross-linked to prevent cracks and the like.

When polyvinyl alcohol (PVA) is used as the water-soluble binder, it is preferable to combine boric acid and / or a salt thereof. In this case, the total amount of boric acid and / or a salt thereof is preferably 10 to 40% by mass, more preferably 20 to 35% by mass with respect to PVA in terms of H ₃ BO ₃ . By making the total amount within the above range, it is possible to improve film formability and water resistance while suppressing an increase in the viscosity of the coating solution to be prepared.

The concentration of the crosslinking agent in the aqueous solution (C) of the crosslinking agent can be selected depending on the desired amount of the coating solution, but is preferably 0.4 to 5% by mass with respect to the total mass.
In preparing the coating solution, the aqueous binder solution can be used so that the amount of the water-soluble binder contained in the coating solution is within the above range.

(D) Other components The coating liquid prepared as described above can be constituted using the following other components in addition to the above components.

--Inorganic fine particles--
The ink receiving layer coating liquid (or ink receiving layer) may contain inorganic fine particles other than the pseudo boehmite-like alumina hydrate described above. The kind of the inorganic fine particles is not particularly limited, but vapor-phase silica and alumina are preferable in terms of gloss and ink absorbability. The inorganic fine particles may be used alone or in combination.

  In the present invention, in addition to the ink-receiving layer containing pseudoboehmite-like alumina hydrate, an ink-receiving layer containing other inorganic fine particles may be provided without containing pseudoboehmite-like alumina hydrate. In addition, the ink receiving layer formed by the dispersion preparation step, the coating solution preparation step, and the layer formation step described above contains inorganic fine particles other than pseudoboehmite-like alumina hydrate as long as the image density and glossiness are not impaired. May be included.

Vapor phase silica is also called a dry method as opposed to a wet method, and is generally made by a flame hydrolysis method. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone or tetrachlorosilane instead of silicon tetrachloride. It can be used in a mixed state with silicon.
Gas phase method silica is commercially available in the Aerosil series manufactured by Nippon Aerosil Co., Ltd., the QS type manufactured by Tokuyama Co., Ltd., etc., and can be easily obtained. The average primary particle diameter of the vapor phase method silica is preferably 5 to 50 nm, and in order to obtain higher gloss, it is preferably 5 to 20 nm and a specific surface area by the BET method of 90 to 400 m ² / g. The BET method is one of the methods for measuring the surface area of a powder by a vapor phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm. 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.

  As the alumina, γ-alumina, which is a γ-type crystal of aluminum oxide, is preferable, and among them, a δ group crystal is preferable. Although γ-alumina can reduce the primary particles to about 10 nm, usually, secondary particles of several thousand to several tens of thousands of nm are converted to 50 to 50 with an ultrasonic wave, a high-pressure homogenizer, a counter collision type jet pulverizer, or the like. What grind | pulverized to about 300 nm is used preferably.

--Cationic compound--
When the ink receiving layer coating liquid (or ink receiving layer) in the present invention contains vapor phase silica as inorganic fine particles, a cationic compound is preferably used in combination. By using a cationic compound in combination, it is possible to prevent cracking of the ink receiving layer and improve water resistance.
In this case, by providing a layer containing colloidal silica and a cationic compound (for example, the uppermost layer) on the ink receiving layer containing the cationic compound, scratch resistance, water resistance, and ink absorbability can be further improved. In addition, aggregation at the interface between the two layers is prevented, and as a result, coating unevenness and gloss unevenness can be eliminated.
As in the case of the upper layer and the lower layer described above, when the ink receiving layer contains alumina hydrate, it is not always necessary to use a cationic compound in combination, and good crack resistance and water resistance can be obtained without using it together. It is done.

  As the cationic compound, a cationic polymer or a water-soluble polyvalent metal compound is preferably used. These cationic compounds and water-soluble polyvalent metal compounds can be used singly or in combination of two or more.

  Examples of the cationic polymer include water-soluble cationic polymers having a quaternary ammonium group, a phosphonium group, and a primary to tertiary amine acid adduct. For example, polyethylenimine, polydialkyldiallylamine, polyallylamine, allylamine epichlorohydrin polycondensate, JP-A-59-20696, 59-33176, 59-33177, 59-155888, 60-11389 60-49990, 60-83882, 60-109894, 62-198493, 63-49478, 63-115780, 63-280681, JP-A-1-40371, Examples thereof include cationic polymers described in JP-A-6-234268, JP-A-7-125411, and JP-A-10-193976.

  The weight average molecular weight of the cationic polymer is preferably 100,000 or less, more preferably 50,000 or less, and the lower limit is about 2,000. Moreover, the usage-amount of a cationic polymer has the preferable range of 1-10 mass% with respect to a gaseous-phase method silica.

Examples of the polyvalent metal in the water-soluble polyvalent metal compound include calcium, barium, manganese, copper, cobalt, nickel, aluminum, iron, zinc, zirconium, titanium, chromium, magnesium, tungsten, and molybdenum. It can be used as a water-soluble salt of these metals. Specific examples of water-soluble polyvalent metal compounds include calcium acetate, calcium chloride, calcium formate, calcium sulfate, barium acetate, barium sulfate, barium phosphate, manganese chloride, manganese acetate, manganese formate dihydrate, manganese sulfate Ammonium hexahydrate, cupric chloride, ammonium copper (II) chloride dihydrate, copper sulfate, cobalt chloride, cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate, acetic acid Nickel tetrahydrate, nickel ammonium sulfate hexahydrate, amido nickel sulfate tetrahydrate, aluminum sulfate, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate, Ferrous bromide, ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, zinc bromide Zinc chloride, zinc nitrate hexahydrate, zinc sulfate, zirconium acetate, zirconium nitrate, basic zirconium carbonate, zirconium hydroxide, zirconium carbonate / ammonium, zirconium carbonate / potassium, zirconium sulfate, zirconium fluoride, zirconium chloride, zirconium chloride Octahydrate, zirconium oxychloride, hydroxyzirconium chloride, titanium chloride, titanium sulfate, chromium acetate, chromium sulfate, magnesium sulfate, magnesium chloride hexahydrate, magnesium citrate nonahydrate, sodium phosphotungstate, citric acid Examples thereof include sodium tungsten, 12 tungstophosphoric acid n hydrate, 12 tungstosilicic acid 26 hydrate, molybdenum chloride, 12 molybdophosphoric acid n hydrate, and the like. Among these, aluminum or a water-soluble salt of a periodic table group IVa element (zirconium, titanium) is preferable.
Here, “water-soluble” means that 1% by mass or more dissolves in water at room temperature and normal pressure.

As a water-soluble aluminum compound other than the above, a basic polyaluminum hydroxide compound is preferably used. The main component of this compound is represented by the following formula 1, formula 2 or formula 3, and, for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ (OH) ₃₄ ] ⁵⁺ and [Al ₂₁ (OH) ₆₀ ] ^{3+ and the} like are water-soluble polyaluminum hydroxides stably containing a basic and high-molecular polynuclear condensed ion.

[Al ₂ (OH) _n Cl _6-n ] _m Formula 1
[Al (OH) ₃ ] _n AlCl ₃ Formula 2
Al _n (OH) _m Cl _{(3 nm)} [0 <m <3n] Formula 3

  These are water treatment agents under the name of polyaluminum chloride (PAC) from Taki Chemical Co., Ltd., under the name of polyaluminum hydroxide (Paho) from Asada Chemical Co., Ltd., and Purachem from Riken Green Co., Ltd. It is commercially available under the name of WT and from other manufacturers for the same purpose, and various grades can be easily obtained. In the present invention, these commercially available products may be used as they are. These basic polyaluminum hydroxide compounds are also described in Japanese Patent Publication Nos. 3-24907 and 3-42591.

When the water-soluble polyvalent metal compound is contained, the content in the ink receiving layer coating liquid (or ink receiving layer) is preferably 0.1 to 10 g / m ² , more preferably 0.2 to 5 g / m ^2. a m ^2.

--Surfactant--
The ink receiving layer coating liquid (or ink receiving layer) in the present invention can be constituted using a surfactant. When the surfactant is contained, application failure such as application stripes on the coating film formed by application can be suppressed.
The surfactant is preferably a nonionic one. In addition to nonionic properties, any type of anionic, cationic, nonionic, and betaine types can be selected and used as required. Moreover, a low molecular thing or a high molecular thing may be used, and it may be used individually by 1 type or in combination of 2 or more types.
The content of the surfactant in the ink-receiving layer coating liquid (or ink-receiving layer) is preferably 0.001 to 5 parts by mass, more preferably 0 to 100 parts by mass of pseudoboehmite-like alumina hydrate. 0.01 to 3 parts by mass.

--- Oil drops--
Various oil droplets can be contained for the purpose of improving the brittleness of the ink receiving layer. As oil droplets, hydrophobic high boiling point organic solvents (for example, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicon oil, etc.) having a solubility in water at room temperature of 0.01% by mass or less, and polymer particles (for example, , Particles obtained by polymerizing one or more polymerizable monomers such as styrene, butyl acrylate, divinylbenzene, butyl methacrylate, and hydroxyethyl methacrylate). The amount of oil droplets used is preferably in the range of 10 to 50% by mass relative to the hydrophilic binder.

  In addition to the above, the ink receiving layer coating liquid (or ink receiving layer) in the present invention includes colored dyes, colored pigments, ink dye fixing agents, ultraviolet absorbers, antioxidants, pigment dispersants and antifoaming agents. , Various known additives such as leveling agents, preservatives, optical brighteners, viscosity stabilizers, and pH adjusters may be added.

  The ink receiving layer coating solution preferably has a pH in the range of 3.3 to 6.0, particularly preferably in the range of 3.5 to 5.5. By combining the pH of this ink-receiving layer coating solution with the pH of the coating solution for forming the uppermost layer when the uppermost layer contains colloidal silica (= 3.3 to 6), better ink absorbability , Glossy and uniform coated surface.

  Further, in order to improve the resolution of the image, if it does not cause aggregation or the like when mixed with a dispersion of alumina hydrate, the ink receiving layer may be a fluororesin, silicone resin, or alkylketene. By containing a dimer-based water repellent or sizing agent, the resolution of the image can be improved by controlling the print dot diameter. As these water repellents or sizing agents, commercially available ones can be used. In addition, either a solution or an aqueous emulsion can be used. The print dot diameter can be controlled by the amount added to the ink receiving layer. The amount added varies depending on each component and concentration and the desired print dot diameter, but as an effective solid component, it is usually 0.05 to 10% by mass, preferably 0.1%, based on the total solid content of the ink receiving layer. ˜5 mass%.

  From the viewpoint of further improving the coating properties of the coating liquid, or adjusting the dot diameter when the ink adheres to the ink receiving layer, a surfactant may be added to the coating liquid for the ink receiving layer. preferable. The details of the surfactant are as described above.

(Layer formation process)
In the layer formation step, the coating solution prepared in the coating solution preparation step is applied to a water-resistant support at a temperature of 50 ° C. or higher, and dried under the condition that the film surface temperature is less than 30 ° C. to form an ink receiving layer. To do.

  The coating in this step is performed with the coating solution kept at a temperature of 50 ° C. or higher. When the temperature of the coating solution at the time of coating is less than 50 ° C., the coating solution tends to thicken with time and a uniform coated surface cannot be obtained. The coating solution temperature is preferably 50 to 70 ° C., more preferably 50 to 60 ° C., for the same reason as described above. By setting the coating solution temperature to 70 ° C. or lower, the film surface temperature of the coating film can be easily lowered during the drying process, and a uniform coated surface state can be obtained.

  Application | coating can be performed using a coating apparatus. As a coating method, for example, a known coating method such as a slide hopper method, a curtain method, an extrusion method, an air knife method, a roll coating method, or a rod bar coating method is used.

  The ink receiving layer is provided on at least one side of the water-resistant support, but may be provided on both sides of the water-resistant support for the purpose of preventing curling.

The coating amount of the coating liquid for the ink receiving layer is preferably 3 to 50 g / ^{m 2} in terms of solid content, more preferably 20~45g / ^{m 2.} When the coating amount is within the above range, the drying property of the coating film is good, and the occurrence of cracks can be avoided.

  Drying in this step is performed under conditions including the case where the film surface temperature of the coating film is less than 30 ° C. That is, in the drying process, it is only necessary to include a drying stage in which the film surface temperature is less than 30 ° C., the film surface temperature may be 30 ° C. or less in the initial stage of drying, and a predetermined time has elapsed from the start of drying. The film surface temperature may be lowered to 30 ° C. or lower after or after drying. Among these, from the viewpoint of uniform coated surface shape and void volume, it is preferable to carry out the drying step in which the film surface temperature is less than 30 ° C. at the initial stage of drying, particularly immediately after the start of drying. By performing drying so that the film surface temperature is less than 30 ° C. at the initial stage of drying (particularly immediately after the start of drying), uneven drying can be avoided even when the coating solution has a low viscosity, and glossiness can be enhanced. When the initial drying stage is dried at a high temperature, particularly when the viscosity of the coating solution is low, uneven drying occurs and glossiness decreases.

Unless a drying step in which the film surface temperature is less than 30 ° C. is not provided, the coating solution is not thickened and a uniform coated surface cannot be obtained. Moreover, as film surface temperature, 0-30 degreeC is preferable and 5-20 degreeC is still more preferable. By setting the film surface temperature to 0 ° C. or higher, it is possible to suppress the excessive increase in the viscosity of the coating liquid, prevent the formation of unevenness on the surface of the coating film, and obtain a glossy feeling.
Here, the film surface temperature is the temperature of the coating film surface during drying, and can be measured with a radiation thermometer.

In the present invention, the drying is performed so as to include the drying stage in which the film surface temperature is less than 30 ° C. as described above, but the film surface temperature in this drying stage (30 ° C.) or a temperature close to the film surface temperature. The viscosity is important, and in the present invention, the viscosity η ³⁰ at 30 ° C. is set to 100 mPa · s or less. When the viscosity η ³⁰ exceeds 100 mPa · s, glossiness cannot be obtained. Among them, the viscosity η ³⁰ is preferably ³⁰ to 100 mPa · s, and more preferably 40 to 80 mPa · s. By setting the viscosity η ^{30 to 30} mPa · s or more, an appropriate viscosity can be maintained and coating can be performed more uniformly, and by setting the viscosity η ³⁰ or less to 100 mPa · s or less, unevenness of the coating film surface is suppressed and glossiness is further improved. be able to.

  Although drying temperature is based also on the heat resistance of a water-resistant support body, 60-200 degreeC is preferable, More preferably, it is 70-150 degreeC. When the drying temperature is within the above range, the ink receiving layer can be sufficiently dried to improve the ink absorbency when heat-treated within a range that does not adversely affect the support, and the ink receiving layer has water resistance. It can be improved. The temperature of the heat treatment here depends on the heat resistance of the water-resistant support, but is preferably 100 to 200 ° C, more preferably 120 to 150 ° C.

  In addition to the above, coating conditions (coating apparatus, coating liquid temperature, viscosity, etc.) and drying conditions (drying temperature, drying time, temperature gradient, air volume, how to apply wind, humidity) of the ink receiving layer coating liquid Etc.) can be selected as appropriate to control the physical properties of the ink receiving layer to be formed.

-Water resistant support-
Examples of the water-resistant support (hereinafter also simply referred to as a support) constituting the ink jet recording medium of the present invention include, for example, a thermoplastic film, resin-coated paper, coated paper, glass, aluminum foil, vapor-deposited paper, vapor-deposited film, It can be appropriately selected depending on the purpose or the like from a support or the like on which an ink receiving layer such as fabric can be provided.

  As the thermoplastic film, polyester, polypropylene, polyamide, polyvinyl chloride, polystyrene, polymethyl methacrylate, cellulose acetate, polyethylene, polycarbonate, or the like can be used.

  The water resistant support may be provided with an anchor layer for the purpose of improving the adhesion between the ink receiving layer and the support. The anchor layer can contain a hydrophilic binder such as gelatin, a solvent-soluble binder such as polyvinyl butyral, latex, a curing agent, a pigment, a surfactant, and the like in an appropriate combination.

  Various back coat layers can be coated on the support in the present invention for antistatic properties, transport properties, curl prevention properties, writing properties, gluing properties, and the like. In the backcoat layer, an inorganic antistatic agent, an organic antistatic agent, a hydrophilic binder, latex, a curing agent, a pigment, a lubricant, a surfactant and the like can be appropriately combined.

  The present invention can also be applied to highly transparent inkjet recording media that can also be used as an OHP film, but the composition of the ink-receiving layer can also be applied to a recording material that requires translucency, such as an OHP film. Not only is the properties of the support important. As for the light transmittance when used as an OHP film, haze (cloudiness) is closer to human sense than total light transmittance, and haze (cloudiness) according to JIS-K-7105 is 3.0 or less. The transparent support is particularly preferable.

  Further, the haze of the ink jet recording medium when used as an OHP film is the haze (cloudiness) according to JIS-K-7105 of the ink jet recording medium in which an ink receiving layer is provided on a support. Particularly preferably, it is 0 or less.

  In the case of an inkjet recording medium that requires translucency, such as an OHP film, the thickness of the support is not particularly limited, and is preferably about 50 to 200 μm from the viewpoints of handling properties and printer paper passing suitability.

  In addition, not only the composition of the ink receiving layer but also the characteristics of the support are important in order to obtain an ink jet recording medium having glossiness and texture like photographic paper. In order to obtain gloss and texture of photographic paper tone, it is preferable to use a polyester film or resin-coated paper, and the hunter whiteness measured by JIS-P-8123 of the support is 65% or more. It is particularly preferable that the 60-degree specular gloss measured by JIS-Z-8741 on the ink receiving layer side is 30% or more.

  As a method for increasing the whiteness of the polyester film, a method of containing inorganic fine particles such as barium sulfate, titanium dioxide, calcium carbonate, silicon dioxide, aluminum oxide, kaolin, and talc inside the polyester film, and a method of applying a white paint on the surface Etc.

  Moreover, in order to provide cushioning properties and concealment properties, a cavity-containing film containing a large number of cavities inside the film, such as a foamed polyester film, can also be used.

  When a polyester film is used as the water-resistant support, the thickness is not particularly limited, and is preferably about 10 to 200 μm from the viewpoints of handling properties and printer paper passing suitability.

  Even when resin-coated paper is used as the support, the thickness is not particularly limited, and is preferably about 50 to 300 μm from the viewpoints of handling properties and printer paper passing suitability. Moreover, in order to obtain the texture of a photographic printing paper, the thing of about 200-300 micrometers is preferable.

The base paper for the resin-coated paper is not particularly limited, and generally used paper can be used. Preferably, for example, a smooth base paper used for a photographic support is preferable.
As the pulp constituting the base paper, natural pulp, regenerated pulp, synthetic pulp or the like can be used alone or in combination. In general, additives such as a sizing agent, a paper strength enhancer, a filler, an antistatic agent, a fluorescent whitening agent, and a dye used for papermaking can be blended with the base paper. Further, a surface sizing agent, a surface paper strength agent, a fluorescent brightening agent, an antistatic agent, a dye, an anchor agent, and the like may be applied on the surface.

The base paper is preferably one having high surface smoothness that is compressed by applying pressure with a calendar or the like during or after paper making, and the smoothness of the Beck measured by JIS-P-8119 is 200 seconds or more. Those are particularly preferred. Moreover, the basic weight has the preferable range of 30-250 g / m < ² >.

  As for the whiteness of the base paper, when the Hunter whiteness measured according to JIS-P-8123 is 65% or more, the whiteness is high, and a high-quality recording material can be obtained. A brown base paper that is unbleached and used in combination with natural pulp may be used. Moreover, you may use the base paper colored using colorants, such as dye.

As the coating resin for resin-coated paper, a polyolefin resin is preferable, and a polyethylene resin is particularly preferable. Also, low density polyethylene, medium density polyethylene, high density polyethylene or mixtures thereof can be used. Here, the low density polyethylene is polyethylene having a density of 0.915 to 0.930 g / cm ³ and is usually produced by a high pressure method. On the other hand, the high density polyethylene is polyethylene having a density of 0.950 g / cm ³ or more, and is usually produced by a low pressure method or an intermediate pressure method.
These polyethylene resins can be used alone or in admixture of two or more kinds having various densities and melt flow rates.

  A resin-coated paper used as a water-resistant support can be produced by a so-called extrusion coating method in which a heated and melted polyolefin resin is cast on a traveling base paper. In order to improve the adhesion between the resin and the base paper, it is preferable to subject the base paper to an activation treatment such as corona discharge treatment or flame treatment before coating the resin on the base paper. The surface (front side) of the support to which the ink receiving layer is applied has a glossy surface, a matte surface, etc., depending on the application, and is particularly preferably configured as a glossy surface. Although it is not always necessary to coat the resin on the back surface, it is preferable to coat the resin from the viewpoint of curling prevention. The back surface is usually a matte surface, and an active treatment such as corona discharge treatment or flame treatment can be applied to the front surface or both the front and back surfaces as required.

  The configuration of the resin layer of the resin-coated paper may be either a single layer or a multilayer of two or more layers. Also in this case, the above polyolefin resins can be used alone or in admixture of two or more. In addition, the multilayer layers can have different compositions or the same composition. As a method for forming a resin layer composed of multiple layers, either a coextrusion coating method or a sequential coating method may be employed.

  On the other hand, the resin layer of the resin-coated paper can also be formed by coating a latex having a film forming ability. For example, a latex having a low minimum film formation temperature (MFT) can be formed by coating a base paper for resin-coated paper and then heating to a temperature equal to or higher than the minimum film formation temperature.

  There is no restriction | limiting in particular as the thickness of the coating resin layer of resin-coated paper, Generally 5-50 micrometers is preferable, and it coats only the surface or both surfaces by the thickness of this range.

  In the resin of the resin-coated paper, white pigments such as titanium oxide, zinc oxide, talc and calcium carbonate, fatty acid amides such as stearic acid amide and arachidic acid amide, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate Fatty acid metal salts such as 2,6-di-t-butyl-p-cresol, antioxidants such as triphenyl phosphite, blue pigments and dyes such as cobalt blue, ultramarine blue, cecilian blue, and phthalocyanine blue, cobalt violet Various additives such as magenta pigments and dyes such as fast violet and manganese purple, fluorescent brighteners, and ultraviolet absorbers can be added in appropriate combinations.

  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. Further, in this example, an example of producing an ink jet recording sheet as an example of the ink jet recording medium is mainly shown.

Example 1
-Preparation of alumina white transparent dispersion-
While stirring 2042 g of ion-exchanged water with a dissolver, 708 g of Cataloid AP-5 (manufactured by Catalytic Chemical Industry Co., Ltd .; pseudoboehmite-like alumina hydrate) was added to obtain a white coarse dispersion of alumina. The number of revolutions of the dissolver at this time was 3000 rpm, and the rotation time was 10 minutes.

  Subsequently, the alumina coarse dispersion is finely dispersed with a high-pressure disperser (Ultimizer HJP25005, manufactured by Sugino Machine Co., Ltd.) to obtain a white transparent alumina dispersion (alumina white transparent dispersion) having a solid content concentration of 25%. It was. The pressure at this time was 100 MPa, and the discharge rate was 600 g / min.

  About the obtained alumina white transparent dispersion, the liquid temperature was adjusted to 30 ° C., and diluted with ion-exchanged water so that the transmittance measured with LA-920 (manufactured by Horiba, Ltd.) was 80%. The particle diameter of the dispersed particles was measured with LA-920 (manufactured by Horiba, Ltd.). As a result of the measurement, the particle diameter was 0.1043 μm. Moreover, when the pH of the alumina white transparent dispersion was measured at a liquid temperature of 30 ° C. using a pH meter, it was pH 4.62. The viscosity of the alumina white transparent dispersion was also measured in the same manner as described below.

-Preparation of coating solution for ink receiving layer-
100 parts of the alumina white transparent dispersion obtained from the above, 74.6 parts of PVA-245 (polyvinyl alcohol having a saponification degree of 88% and an average degree of polymerization of 3500, manufactured by Kuraray Co., Ltd.) 34.6 parts, 7 9.7 parts of 5% boric acid aqueous solution (crosslinking agent aqueous solution) 9.7 parts, 10% surfactant aqueous solution (Emulgen 109P, manufactured by Kao Corporation, HLB 13.6; surfactant), and ion-exchanged water 40 .5 parts were preliminarily kept at 60 ° C. before mixing, and the respective liquids after the heat were mixed well while keeping at 60 ° C. to prepare an ink receiving layer coating solution.
The viscosity at 30 ° C. measured using a B-type viscometer of the obtained ink receiving layer coating solution was 56 mPa · s. Here, the mass ratio (al / PVA) of alumina hydrate to PVA is 10.

-Formation of ink receiving layer-
And after cooling this coating liquid for ink receiving layers to 50 degreeC, ultrasonic deaeration process was performed for 10 minutes, keeping at 50 degreeC. Immediately after the ultrasonic defoaming treatment, the ink receiving layer coating solution was added to a transparent polyester film (trade name: Lumirror 125T (haze (cloudiness value) according to JIS-K-7105 = 2.19, surface-adhesion treated). (Toray Industries, Inc .; water-resistant support) was applied so that the dry solid content of pseudoboehmite alumina was 40 g / m ² . After coating, set drying was performed for 2 minutes so that the film surface temperature was 20 ° C., and then drying was performed at 80 ° C. for 10 minutes to form an ink receiving layer. The film surface temperature was measured with a radiation thermometer in a state where moisture was 200 g / m ² .
As described above, the inkjet recording sheet of the present invention was produced.

(Example 2)
In Example 1, after mixing an alumina white transparent dispersion, a 7% aqueous solution of PVA-245, a 10% surfactant aqueous solution, and ion-exchanged water, 30% before application, a 7.5% boric acid aqueous solution ( An inkjet recording sheet was prepared in the same manner as in Example 1 except that the aqueous crosslinking agent solution was mixed in-line. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Examples 3 to 4)
In Example 1, except that the amount (10 parts) of PVA-245 used for the preparation of the ink receiving layer coating solution was changed to 8 parts and 15 parts as shown in Table 2 below, respectively. Similarly, an inkjet recording sheet was produced. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Examples 5-7)
In Example 1, PVA-245 used for the preparation of the ink receiving layer coating liquid was PVA-235 (saponification degree 88%, average polymerization degree 3500, manufactured by Kuraray Co., Ltd.), PVA-220 (saponification degree). 88%, average polymerization degree 2000, manufactured by Kuraray Co., Ltd.), PVA-145 (saponification degree 99%, average polymerization degree 4500, manufactured by Kuraray Co., Ltd.). An ink jet recording sheet was prepared in the same manner as in Example 1 except that the solid content was 2.5 parts. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Comparative Example 1)
A comparative inkjet recording sheet was produced in the same manner as in Example 1 except that fine dispersion by a high-pressure disperser was not performed in the preparation of the alumina white transparent dispersion of Example 1. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Comparative Example 2)
In the preparation of the alumina white transparent dispersion of Example 1, instead of fine dispersion by a high-pressure disperser, a bead mill disperser (Dynomill KD-20B, manufactured by Zr) was used, a bead diameter of 0.65 mm, a filling rate of 70%, a flow rate of 5 L. A comparative ink jet recording sheet was prepared in the same manner as in Example 1 except that dispersion (not high pressure dispersion) was performed under the conditions of / min. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Comparative Examples 3-4)
A comparative inkjet recording sheet was prepared in the same manner as in Example 1 except that the pH of the alumina white transparent dispersion of Example 1 was adjusted to 5.4 and 3.6 using ammonia or nitric acid, respectively. Produced. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Comparative Example 5)
In Example 1, a comparative inkjet recording sheet was produced in the same manner as in Example 1 except that the amount (10 parts) of PVA-245 used for preparing the ink receiving layer coating solution was changed to 20 parts. did. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Comparative Example 6)
In the preparation of the ink-receiving layer coating liquid of Example 1, the temperature of each liquid was set to 40 ° C., and the mixing after the temperature was performed at 40 ° C. A sheet was produced. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Comparative Example 7)
In Example 1, a comparative inkjet recording sheet was prepared in the same manner as in Example 1 except that the film surface temperature during drying after coating was changed from 20 ° C to 40 ° C. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Comparative Example 8)
A comparative inkjet recording sheet was prepared in the same manner as in Example 1 except that the 7.5% boric acid aqueous solution was not used for preparing the ink receiving layer coating solution in Example 1. Further, in the same manner as in Example 1, the particle diameter and pH of the alumina white transparent dispersion and the viscosity of the ink receiving layer coating solution were measured.

(Evaluation)
The following measurements and evaluations were carried out for the respective ink jet recording media obtained in the above examples and comparative examples. The results of measurement and evaluation are shown in Table 2 below.

1) Print density Black (Bk) solid printing was performed using an inkjet printer PM-G800 (manufactured by Seiko Epson Corporation). The image density of the solid print portion was measured using Gretag Spectrolino SPM-50 (manufactured by Gretag) under the conditions of a viewing angle of 2 °, a light source D50, and no filter.

2) Glossiness The surface of the ink receiving layer of each ink jet recording sheet was measured using a digital variable angle glossmeter UGV-5D (measuring hole 8 mm, manufactured by Suga Test Instruments Co., Ltd.) with an incident angle of 60 ° and a light receiving angle of 60 °. The glossiness was measured at.

3) Glossiness 1) The solid print portion printed in the same manner as the print density was observed under a fluorescent lamp, and the glossiness of the solid print portion was evaluated according to the following evaluation criteria.
<Evaluation criteria>
○: The fluorescent light was clearly blurred, and it appeared sharp without distortion.
Δ: The fluorescent lamp looked slightly blurred.
X: A fluorescent lamp was not reflected so much.

4) Haze Inkjet printer PM-G800 (manufactured by Seiko Epson Corporation) was prepared, and each color ink solvent was loaded into an empty ink tank, and solid printing was performed in black. After solid printing, after leaving for 3 hours in an environment of 23 ° C. and 50%, haze was measured with a haze meter (HGM-2DP, manufactured by Suga Test Instruments Co., Ltd.).
The details of the ink solvent for each color are shown in Table 1 below.

As shown in Table 2, in the example, an image having a high density and a high glossiness could be obtained. Further, the haze was also good, and the haze after the ink solvent permeated (that is, after recording) was suppressed to be low, and image recording with high transparency and high density was possible. In Example 2 in which the crosslinking agent was mixed in-line, an improvement effect was observed with respect to glossiness, print density, and haze. Further, as is clear from Examples 1, 3, and 4, when the mass ratio (al / PVA) of pseudoboehmite-like alumina hydrate to PVA is larger than 8, glossiness, print density, and haze are further improved. It improved.
On the other hand, in the comparative example, the glossiness was lowered, and the print density and haze were also inferior.

Claims (5)

A step of preparing an (A) alumina dispersion having pseudo-boehmite-like alumina hydrate dispersed in an aqueous solvent by a high-pressure disperser and having a pH (30 ° C.) of 4 to 5;
Mixing the (A) alumina dispersion, (B) an aqueous solution containing a water-soluble binder, and (C) an aqueous crosslinking agent solution while keeping the temperature at 50 ° C. or higher, respectively, and preparing a coating solution;
Applying the coating solution on a water-resistant support at a temperature of 50 ° C. or higher, and drying the coating solution under conditions where the film surface temperature is less than 30 ° C. to form an ink receiving layer;
And the viscosity of the coating solution at 30 ° C. is 100 mPa · s or less.   The method for producing an ink jet recording medium according to claim 1, wherein the water-soluble binder is polyvinyl alcohol having a saponification degree of 75 to 90% and an average polymerization degree of 3000 or more.   The method for producing an ink jet recording medium according to claim 1 or 2, wherein the aqueous crosslinking agent solution is mixed by in-line mixing.   The method for producing an ink jet recording medium according to any one of claims 1 to 3, wherein the cross-linking agent contains at least one of boric acid and a salt thereof. The mass ratio (al / PVA) of the pseudo boehmite-like alumina hydrate (al) and polyvinyl alcohol (PVA) satisfies al / PVA> 8. 2. A method for producing an ink jet recording medium according to item 1.