JP2002225427A - Ink jet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording medium having an ink absorption layer including an excellent glossiness, fast ink absorbing speed and flexibility and no craze even by rounding or folding. SOLUTION: The ink jet recording medium comprises an air gap type ink absorption layer containing a silica, a dispersant of the silica and a boric acid or its salt and a polyvinyl alcohol by satisfying the relation of 0.005<M/N<0.05 (wherein M: expresses an amount of boron atoms contained in the ink absorption layer per unit area, and N: expresses an amount of a hydroxyl group contained in a polyvinyl alcohol in the ink absorption layer) on a support.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording medium, and more particularly to an ink jet recording medium excellent in glossiness, ink absorption speed and flexibility.

[0002]

2. Description of the Related Art In recent years, the image quality of ink-jet recording has been rapidly improved, and the quality of a photograph is approaching, and the importance of a recording medium has been greatly increased due to a demand for final print quality.

As an example of a recording medium capable of obtaining high image quality, there is a recording medium having a swellable ink absorbing layer mainly composed of a hydrophilic binder on a support, whereby a texture close to that of a photograph can be obtained. However, on the other hand, the speed of ink jet recording has been increasing, and the recording medium has also been required to have high ink absorption and quick drying properties. In addition, there is a problem that mottled unevenness is likely to occur in an image due to coalescence of ink droplets.

In order to overcome this problem, an ink jet recording medium having a high absorption rate by having an ink absorbing layer comprising a porous void layer having a small amount of a hydrophilic binder and a crosslinking agent and a large amount of fine silica particles. It has been known. Generally, polyvinyl alcohol is used as a hydrophilic binder for the void-type recording medium, and boric acid or a salt thereof is used as a crosslinking agent.

[0005]

However, the above-mentioned void-type recording medium has a weak ink absorbing layer,
If the recording medium is rolled or folded while the air is dry, the ink absorbing layer may crack and crack.
It has been found that, in addition to the reduced gloss, the appearance becomes poor, and in severe cases, there is a problem that strips are peeled off.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the purpose of having a flexible ink-absorbing layer which is excellent in glossiness, has a high ink absorption speed, and has a flexible ink-absorbing layer. An object of the present invention is to provide an ink jet recording medium that does not crack.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method comprising the steps of: providing silica, silica dispersant, and M
/ N which satisfies the relation of / N and has a void-type ink absorbing layer containing boric acid or a salt thereof and polyvinyl alcohol;
The silica dispersant has a weight average molecular weight of 300 to 10000, the silica secondary particles have an average particle diameter of 30 to 150 nm, silica, a silica dispersant, and This is achieved by applying a coating solution containing boric acid or a salt thereof and polyvinyl alcohol, which satisfies the above X / Y relationship, and having a pH of 6 to 9 on a support.

Hereinafter, the present invention will be described in detail. The present invention relates to an ink jet recording medium in which an ink absorbing layer provided on a support contains silica, a small amount of polyvinyl alcohol and boric acid or a salt thereof and forms a porous void layer.

In order to form a void type ink absorbing layer,
The ratio of silica and polyvinyl alcohol used is usually from 2: 1 to 20: 1 by mass. If the amount of polyvinyl alcohol is too large, no voids are formed and ink absorbency is poor. If the amount is too small, film-forming properties are poor and a coating film is not formed during coating and drying.

The use of boric acid or a salt thereof is intended to improve the film forming property by crosslinking polyvinyl alcohol contained in the ink absorbing layer. If not used, the film increasing property at the time of coating and drying is remarkably reduced, and cracking at the time of drying is not performed. Occurs.

On the other hand, if the ink absorbing layer of the recording medium after the formation is rolled or folded in a state where the air is dry, the ink absorbing layer may crack and crack, and this phenomenon affects the flexibility of the ink absorbing layer. It was found that the more the amount of boric acid or a salt thereof as a cross-linking agent was, the lower the amount was. However, in order to make the film flexible, it is preferable to reduce boric acid or its salt, but if the amount is reduced as described above, the film-enhancing property at the time of coating and drying is reduced, and cracking occurs at the time of drying. . Therefore, as a result of various studies to increase the flexibility of the coating film while maintaining the crosslinkability by boric acid or a salt thereof, silica and boric acid or a salt thereof were dispersed in a pH range of 6 to 9 using a silica dispersant. The recording medium obtained by preparing a coating liquid by adding polyvinyl alcohol and applying the coating liquid, even if the amount of boric acid or its salt is small, does not decrease the film forming property at the time of drying the coating. It has been found that a flexible ink absorbing layer can be formed without any problem.

The silica may be used in a state of being uniformly dispersed in a binder as primary particles, or may be used in a state of forming secondary aggregated particles and being dispersed in a binder. From the point of ink absorption speed
The particles are preferably secondary particles, and preferably 150 nm or less to maintain high glossiness. The average particle size of the silica secondary particles is determined by observing the cross section and surface of the ink absorbing layer with a scanning electron microscope, calculating the particle sizes of a plurality of arbitrary particles, and calculating the simple average value (number average value). You can ask. Each particle size is a diameter assuming a circle equal to the projected area.

The silica can be used without any particular limitation as long as it is a synthetic amorphous one, but silica synthesized by a gas phase method is preferred from the viewpoint of easy production of the above-mentioned particle size. The addition amount of the ink absorbing layer, the type of silica, depending on the kind of polyvinyl alcohol, per recording medium 1 m ^2,
Usually, it is 5 to 30 g, preferably 10 to 25 g.

The polyvinyl alcohol used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, polyvinyl alcohol having a cation-modified terminal, anion-modified polyvinyl alcohol having an anionic group, and silyl. Modified polyvinyl alcohol such as silyl-modified polyvinyl alcohol having a substituted group is also included.

The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 300 or more, and particularly preferably has an average degree of polymerization of 1,000 to 5,000. The saponification degree is preferably from 70 to 100%, particularly preferably from 80 to 99.5%.

The cation-modified polyvinyl alcohol is, for example, a polyvinyl alcohol having a primary to primary amino group or a quaternary ammonium group in a main chain or a side chain as described in JP-A-61-10483. Yes, it is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl. (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl. (3-acrylamido-3,3-dimethylpropyl). Ammonium chloride, N-vinylimidazole, N-vinyl-2-methylimidazole, N
-(3-dimethylaminopropyl) methacrylamide,
Hydroxyethyl trimethyl ammonium chloride, trimethyl (methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-dimethylaminopropyl) acrylamide and the like can be mentioned.

The proportion of the cation-modified group-containing monomer in the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, based on vinyl acetate.

The anion-modified polyvinyl alcohol is, for example, a polyvinyl alcohol having an anionic group as described in JP-A No. 1-2060888 or JP-A-61-2.
Copolymers of vinyl alcohol and a vinyl compound having a water-soluble group as described in JP-A-37681 and JP-A-63-307979, and modifications having a water-soluble group as described in JP-A-7-285265 Polyvinyl alcohol.

Examples of the nonionic modified polyvinyl alcohol include polyvinyl alcohol derivatives in which a polyalkylene oxide group is added to a part of vinyl alcohol, as described in JP-A-7-9758.
And block copolymers of a vinyl compound having a hydrophobic group and vinyl alcohol described in US Pat.

These polyvinyl alcohols can be used in combination of two or more kinds, such as different degrees of polymerization and types of modification.

The boric acid or a salt thereof used in the present invention is an oxygen acid having a boron atom as a central atom and a salt thereof, and specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, Includes boric acid and their salts.

The amount of the boric acid or salt thereof varies depending on the type of polyvinyl alcohol, the type of silica, the ratio of polyvinyl alcohol to silica, and the like. 005 <M / N <0.05.

The amount of boric acid or a salt thereof contained in the coating solution is also set so that the relationship with the content of polyvinyl alcohol satisfies the aforementioned relationship of 0.005 <X / Y <0.05.

If the amount of boric acid or a salt thereof is smaller than these conditions, the film-forming property at the time of coating and drying is reduced, and cracks occur at the time of drying. When the recording medium is rolled or folded in a state where the air is dry, the ink absorbing layer is cracked and cracks easily occur.

In the case of using the fine particle silica according to the present invention, the surface area of the silica becomes very large, so that a silica dispersant is required. In particular, the pH dispersed as in the present invention
Is in the range of 5 to 9, the silica dispersion is unstable without a dispersant, and the silica dispersion is immediately aggregated and thickened. Here, the silica dispersant prevents the fine particles from coagulating by adsorbing on the surface of the silica fine particles in a liquid to form an electric double layer or by forming a protective colloid.

Examples of the silica dispersant include low molecular anionic dispersants such as alkyl sulfonates, alkyl benzene sulfonates and alkylamine phosphates, and low molecular non-ionic dispersants such as diethylamine, ethylenediamine and quaternary ammonium salts. Examples include ionic or cationic dispersants, and high molecular dispersants such as sodium polyacrylate, polyacrylamide, polyoxyethylene alkyl ether, and polyethylene glycol ester.

As the silica dispersant, if the molecular weight is small, the dispersant volatilizes when the dispersion is heated at the time of dispersion and the dispersibility decreases, and if the molecular weight is too large, the viscosity of the dispersion increases. For example, a polymer having a weight-average molecular weight of 300 to 10,000 is preferable because the dispersion becomes unstable, for example.

The amount of the silica dispersant added depends on the type of silica used, but if the amount is small, the dispersibility of the silica is poor, the coating solution becomes unstable and the coating becomes difficult, and the silica is used more than necessary. In this case, the interaction between silica and polyvinyl alcohol as a binder is weakened, and the film-forming property is reduced, and cracks may occur during coating and drying. %, Preferably in the range of 0.1 to 2%.

The ink jet recording medium of the present invention may contain a cationic resin or a water-soluble polyvalent metal ion in order to improve water resistance and bleeding resistance after printing.

As the cationic resin, any polymer resin having primary to tertiary amino and quaternary ammonium bases can be arbitrarily selected and used. However, since discoloration and deterioration of light resistance with time are small. , Preferably a polymer having a quaternary ammonium group, a homopolymer of a monomer having a quaternary ammonium group or a copolymer or polycondensate with one or more monomers to obtain another copolymer paper, Weight average molecular weight of 20,000-100,00
0.

Examples of the water-soluble polyvalent metal ion include M
divalent metal ions such as g ²⁺ , Ca ²⁺ , Zn ²⁺ , Al ³⁺
And water-soluble polyvalent metal ions such as Ti ⁴⁺ , and sulfites, sulfates, nitrates, hydrochlorides, acetates, and carbonates. ,
It is added as a salt such as p-toluenesulfonate. Further, it may be added as a water-soluble inorganic polymer such as polyaluminum chloride.

As a method of adding a cationic resin or a water-soluble polyvalent metal ion, there are a method of directly adding to a coating solution and coating, and a method of adding a cationic resin or a water-soluble polyvalent metal after coating and drying a recording medium. An aqueous solution of a valent metal ion may be overcoated and dried.

Various additives can be added to the ink absorbing layer and other optional layers of the ink jet recording medium of the present invention.
No. 193, No. 57-87988, No. 62-26147
UV absorber described in No. 6, JP-A-57-74192.
Nos. 57-87989, 60-72785, 61-146591, JP-A-1-95091, and 3
No. 13376, etc .;
No. 2993, No. 59-52689, No. 62-2800
No. 69, No. 61-242871, No. 4-219266
PH of fluorescent brightener, sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, etc.
Various known additives such as a regulator, an antifoaming agent, a preservative, a thickener, an antistatic agent, and a matting agent can be exemplified.

The porous ink absorbing layer may be composed of two or more layers. In this case, the constitutions of the ink absorbing layers may be the same or different.

The support used in the ink jet recording medium of the present invention may be water-absorbing or non-water-absorbing.

As the water-absorbing support, a paper support is generally used, but a cloth or a porous film support is also used. Examples of the non-water-absorbing support include a plastic resin film support and a support in which both sides of paper are covered with a plastic resin film.

As a plastic resin film support, polyester film, polyvinyl chloride film,
Examples include a polypropylene film, a cellulose triacetate film, a polystyrene film, and a film support obtained by laminating these. These plastic resin films may be transparent or translucent.

In the present invention, a non-water-absorbing support which does not cause cockling during recording is preferred, and a particularly preferred support is a support in which both sides of a paper are coated with a plastic resin. Is a support coated with a polyolefin resin.

The paper used for the support whose paper is coated on both sides with a polyolefin resin is mainly made of wood pulp and, if necessary, synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester in addition to wood pulp. Paper making. LBKP, LB as wood pulp
SP, NBKP, NBSP, LDP, NDP, LUK
Any of P and NUKP can be used, but LBKP, NBSP, LBSP, NDP, LDP with a large amount of short fibers
Is preferably used more. However, the ratio of LBSP and / or LDP is preferably from 10 to 70% by mass.

As the pulp, a chemical pulp containing a small amount of impurities (sulfate pulp or sulfite pulp) is preferably used, and pulp having improved whiteness by a bleaching treatment is also useful.

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

The freeness of the pulp used for papermaking is preferably 200 to 500 ml according to the CSF standard, and the fiber length after beating is 24 mesh residue and 42 mesh residue defined in JIS-P-8207. Is preferably 30 to 70% by mass. In addition, it is preferable that 4 mesh residue is 20 mass% or less.

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

The paper may be calendered at the papermaking stage or after the papermaking to provide high smoothness. Paper density 0.7 ~
1.2 g / m ² (JIS-P-8118) is common. Further, the rigidity of the base paper is preferably from 20 to 200 g under the conditions specified in JIS-P-8143.

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

The pH of the paper is preferably from 5 to 9 as measured by the hot water extraction method specified in JIS-P-8113.

Examples of the polyolefin resin covering both sides of the paper include polyethylene, polypropylene, and polyisobutylene. Polyolefins such as copolymers mainly composed of ethylene and propylene are preferred, and polyethylene is particularly preferred.

The polyethylene covering the front and back surfaces of the paper is mainly made of low density polyethylene (LDPE) and / or
Or high density polyethylene (HDPE) but other L
LDPE, polypropylene and the like can also be partially used.

In particular, the polyethylene layer on the side on which the ink jet recording layer is applied preferably has a opacity and whiteness improved by adding rutile or anatase type titanium oxide therein. The content of titanium oxide is generally 1 to 20% by mass, preferably 2 to 15% by mass based on polyethylene.

In the polyethylene layer, a pigment having high heat resistance and a fluorescent whitening agent for adjusting a white background can be added.

Examples of coloring pigments include ultramarine blue, navy blue, cobalt blue, phthalocyanine blue, manganese blue, cerulean blue, tungsten blue, molybdenum blue, anthraquinone blue and the like.

Examples of the fluorescent whitening agent include dialkylaminocoumarin, bisdimethylaminostilbene, bismethylaminostilbene, 4-alkoxy-1,8-naphthalenedicarboxylic acid-N-alkylimide, bisbenzoxazolylethylene, dialkylstilbene And the like.

The amount of polyethylene used on the front and back of the paper is selected so as to optimize the thickness of the ink absorbing layer and the curl in low and high humidity after the back layer is provided. The polyethylene layer on the side to be applied is 15-40μ
m, the back layer side is in the range of 10 to 40 μm. The ratio of the front and back polyethylene is preferably set so as to adjust the curl that changes depending on the type and thickness of the ink absorbing layer, the thickness of the inner paper, and the like. Usually, the ratio of front / back polyethylene is approximately 3 in thickness. / 1 to 1/3.

Further, the polyethylene-coated paper support preferably has the following properties.

The tensile strength is the strength specified in JIS-P-8113 and is 2 to 30 kg in the vertical direction and 1 to 30 in the horizontal direction.
20kg.

The tear strength was determined by the method specified in JIS-P-8116 to be 20 to 300 g in the vertical direction and 10 in the horizontal direction.
２５０250 g.

Compressive modulus ≧ 9.8 kN / cm ² . The opacity is 80% or more, especially 85 to 98%, as measured by the method specified in JIS-P-8138.

As for whiteness, L ^* , a ^* and b ^* defined by JIS-Z-8727 are L ^* = 80 to 96, a ^* = − 3 to +
5. b ^* =-7 to +2.

[0060] It Clark stiffness in the conveying direction of the recording medium is 50~300cm ^3/100.

The moisture in the base paper is 4-10
Mass%. The glossiness (75-degree specular glossiness) of the surface on which the ink absorbing layer is provided is 10 to 90%.

The ink jet recording medium of the present invention may contain a hardener other than boric acid or a salt thereof. The hardening agent is generally a compound having a group capable of reacting with polyvinyl alcohol or a compound which promotes the reaction between different groups of polyvinyl alcohol. Epoxy hardening agents (diglycidyl ethyl ether) , Ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidylcyclohexane, N, N-diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether,
Glycerol polyglycidyl ether, etc.), aldehyde hardeners (formaldehyde, glyoxazole, etc.),
Active halogen hardeners (2,4-dichloro-4-hydroxy-1,3,5-s-triazine and the like), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bis Vinylsulfonyl ether), aluminum alum, isocyanate compounds and the like.

The amount of the hardener used varies depending on the type of the polyvinyl alcohol, the type of the hardener, the type of silica, the ratio to the polyvinyl alcohol, and the like, but is usually 5 to 500 mg, preferably 10 to 500 g per 1 g of the polyvinyl alcohol.
３００300 mg.

A method for applying various hydrophilic layers, which are appropriately provided as necessary, such as an ink absorbing layer and an undercoat layer, of the ink jet recording medium of the present invention to a support can be appropriately selected from known methods. A preferred method is to apply a coating solution constituting each layer on a support and to dry the coating solution. in this case,
Two or more layers can be applied simultaneously, and simultaneous application in which all the hydrophilic binder layers are applied in one application is particularly preferable.

The coating method may be a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294. Is preferably used.

The recording surface pH of the recording surface of the ink jet recording medium of the present invention is preferably from 3.5 to 9. PH of the film surface is 3.5
If the amount is less than the above range, so-called bronzing, in which the dye is deposited and the gloss changes to a metallic shape when inkjet recording is performed, is likely to occur. If the pH of the film surface exceeds 9, the effect of preventing bleeding is reduced. Measurement of the film surface pH of the recording surface is described in J. Org. TAPPI
Paper pulp test method No. According to the method described in No. 49, measurement is performed after 30 seconds using distilled water. The pH of the recording surface is
After forming the recording surface, it can be adjusted to a predetermined range by overcoating with a suitable pH adjuster. pH
An aqueous solution of an appropriate acid or alkali can be used as the adjusting agent. In this case, the type and concentration of the acid or alkali to be used can be appropriately selected depending on the pH range to be adjusted.

When an image is recorded using the ink jet recording medium of the present invention, an aqueous ink is preferably used, and it may be an aqueous dye ink or an aqueous pigment ink, but an aqueous pigment ink is preferred.

Here, the aqueous dye ink and the aqueous pigment ink are recording liquids having the following colorants, liquid media, and other additives. Examples of the colorant include water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes and food dyes known in the ink jet recording field, or organic pigments such as azo pigments, phthalocyanine pigments, dye lakes, and carbon black. Aqueous pigments such as inorganic pigments can be used. Other additives for aqueous inks include, for example, water-soluble organic solvents (propanol, hexanol, ethylene glycol,
Diethylene glycol, glycerin, hexanediol, urea, etc.), surfactants, water-soluble polymers, preservatives,
Examples include an antifungal agent, a viscosity adjuster, and a pH adjuster.

[0069]

EXAMPLES The present invention will be described below in more detail with reference to examples, but embodiments of the present invention are not limited thereto.
In the examples, "%" indicates% by mass unless otherwise specified.

Example 1 1.2 ml of a nonionic acrylic polymer type dispersant (solid content: 40%, SD-10, manufactured by Toagosei) in 150 ml of pure water
And 0.7 g of borax are dissolved and pH is adjusted with sodium hydroxide.
Adjusted to 11. Here, the average primary particle size is about 12 n.
400 g of a 25% aqueous dispersion of silica (QS-20 manufactured by Tokuyama) was added, and the mixture was dispersed with a high-speed homogenizer.
Next, 280 ml of a 7% aqueous solution of polyvinyl alcohol (Kuraray PVA235) was added to the dispersion.
Finally, pure water was added so that the total volume became 1000 ml, to obtain a translucent coating solution. The pH of this coating solution was 7.
3 (X / Y = 0.016, average particle size of silica secondary particles 40 nm).

The obtained coating solution was applied to a paper support (thickness: 26 g / m ^{2) having} a base paper of 170 g / m ² coated on both sides with polyethylene.
0 μm, the polyethylene layer on the recording surface side contains 6% anatase type titanium dioxide).
After coating at 80 ° C. and cooling at 8 ° C. for 10 seconds, air at 30 ° C. for 60 seconds, air at 50 ° C. for 60 seconds,
After drying for 60 seconds in the air of 0 ° C, 25 ° C and relative humidity of 50
% To obtain inkjet recording medium 1 (M / N
= 0.016).

Example 2 An ink jet recording medium 2 was obtained in the same manner as in Example 1 except that the amount of borax was changed to 1.3 g (M / N = 0.
031).

Example 3 An ink jet recording medium 3 was obtained in the same manner as in Example 1 except that the amount of the dispersant was changed to 2.5 ml (M / N =
0.016).

Example 4 The dispersant was 1 m of a dimethylamine / epichlorohydrin condensate dispersant (solid content: 50%, HP-142A manufactured by SENKA).
Inkjet recording medium 4 was obtained in the same manner as in Example 1 except that l was changed to 1 (M / N = 0.016).

Example 5 Dispersant: dimethylamine / epichlorohydrin condensate dispersant (solid content: 50%, HP-182A manufactured by SENKA) 2 m
Inkjet recording medium 5 was obtained in the same manner as in Example 1 except that l was changed to 1 (M / N = 0.016).

Comparative Example 1 In Example 1, after dispersing the dispersant and borax in pure water, adding and dispersing a silica dispersion without adjusting the pH,
When polyvinyl alcohol was added, the coating solution was remarkably thickened and could not be applied. The pH of the coating solution was 4.3.

Comparative Example 2 In Example 1, borax was dissolved in pure water without adding a dispersant, and then adjusted to pH 11 with sodium hydroxide. A silica dispersion was added thereto and dispersed with a high-speed homogenizer. However, it thickened and could not be dispersed.

Comparative Example 3 An ink jet recording medium 6 was produced in the same manner as in Example 1 except that the amount of borax was changed to 0.1 g, but fine cracks occurred during drying (M / N = 0.00
2).

Comparative Example 4 An ink jet recording medium 7 was obtained in the same manner as in Example 1 except that the amount of borax was changed to 0.1 g (M / N = 0.
002).

Comparative Example 5 An ink jet recording medium 8 was obtained in the same manner as in Example 1, except that the volume of polyvinyl alcohol was changed to 450 ml of a 13% aqueous solution. At this time, the mass ratio of silica to polyvinyl alcohol was 1.7: 1 and M / N = 0.006.

<Evaluation> With respect to each of the obtained ink jet recording media, the ink absorbency, glossiness, and flexibility of the ink absorbing layer were evaluated by the following methods.

(Ink Absorption) Green solid printing was performed with an ink jet printer PM800C manufactured by Seiko Epson Corporation, and the printed portion immediately after printing was rubbed with a finger to visually observe the disturbance of the image. No image distortion Δ: The image was slightly rubbed and stained, but there was no practical problem. X: The image was rubbed and stained, and evaluated on a three-point scale outside the practically acceptable range.

(Gloss) A 75-degree specular gloss was measured with a variable angle photometer (VGS-101DP) manufactured by Nippon Denshoku Industries Co., Ltd.

(Film Flexibility) Each ink jet recording medium was conditioned at 23 ° C. and a relative humidity of 20% for 24 hours, wound around cylindrical stainless steel caps having diameters of 10 mm, 20 mm, 30 mm and 40 mm, respectively. The rod diameter at which cracks occurred was examined. The smaller the value is, the more flexible the ink absorbing layer is. The one having a value of 30 nm or less has no practical problem. The ink jet recording medium 6 could not be evaluated because the surface was originally cracked.

Table 1 shows the above results.

[0086]

[Table 1]

From the above, it is understood that the ink jet recording medium according to the present invention is excellent in all of the ink absorbency, glossiness and flexibility of the ink absorbing layer.

[0088]

According to the present invention, the ink absorbing layer is excellent in glossiness and the ink absorbing layer is flexible without deteriorating the ink absorbing property.
An ink jet recording medium that does not crack even when it is rolled or bent can be obtained.

Claims (5)

[Claims] 1. A silica, a silica dispersant,
And an ink-jet recording medium having a void-type ink absorbing layer containing boric acid or a salt thereof and polyvinyl alcohol satisfying the following relationship. 0.005 <M / N <0.05 [wherein, M is the amount per unit area of boron atoms contained in the ink absorbing layer (mmol / m ² ), and N is contained in the polyvinyl alcohol in the ink absorbing layer. Of the hydroxyl groups (mmol / m ² ). ] 2. The silica dispersant is added to silica in an amount of 0.0
The ink jet recording medium according to claim 1, wherein the content is 5 to 5% by mass. 3. The silica dispersant has a weight average molecular weight of 30.
3. The method according to claim 1, wherein the number is from 0 to 10,000.
3. The ink jet recording medium according to claim 1. 4. The secondary silica particles have an average particle size of 30-1.
The inkjet recording medium according to claim 1, 2 or 3, wherein the thickness is 50 nm. 5. A method comprising applying silica, a dispersant for silica, and a coating solution containing boric acid or a salt thereof and polyvinyl alcohol satisfying the following relationship and having a pH of 6 to 9 to a support. An ink jet recording medium characterized by the above-mentioned. 0.005 <X / Y <0.05 [where X is the amount of boron atoms contained in 1 L of coating solution (mmol / L), and Y is the amount (mmol) of hydroxyl groups contained in polyvinyl alcohol in 1 L of coating solution. / M ² ). ]