JPH1029367A - Ink jet recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording paper having high ink absorbability and improvising the stickiness immediately after the printing of an obtained image. SOLUTION: This ink jet recording paper is one having a hydrophilic binder layer containing a hydrophilic polymer with an average mol.wt. of 20,000 to 500,000 having an alkaline oxide group as a repeating unit and gelatin and a protective layer and a hydrophilic binder layer containing amino group deactivated gelatin is provided on the side near to a support as compared with the protective layer.

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 sheet for performing recording using an aqueous ink, and more particularly to an ink jet recording sheet having improved ink absorbency and dustiness after recording.

[0002]

2. Description of the Related Art Ink-jet recording is a method in which fine droplets of ink are caused to fly according to various operating principles and adhere to a recording sheet such as paper to record images and characters. It has advantages such as easy noise and multicoloring. With regard to nozzle clogging and maintenance, which has been a problem in the past, improvements have been made from both the ink and device aspects.
It is rapidly spreading in various fields such as facsimile and computer terminals.

[0003] The ink jet recording paper used in this ink jet recording system has a high density of print dots, a bright and vivid color tone, and the ink absorbs quickly so that even when the print dots overlap, the ink flows out. It is required that the print dots do not spread or bleed, that the diffusion of the print dots in the horizontal direction is not unnecessarily large, and that the periphery is smooth and not blurred.

[0004] In particular, when the ink absorption speed is low, when ink droplets of two or more colors are printed in an overlapping manner, the droplets cause a repelling phenomenon on the recording paper to become uneven, It is necessary for recording paper to have a high ink absorbency because the colors of each other are blurred in the boundary region of, and the image quality is easily deteriorated.

[0005] To solve these problems, a great many techniques have been proposed.

[0006] For example, a recording paper described in JP-A-52-53012 in which a coating material for surface processing is wetted on a low-size base paper, and a base material described in JP-A-55-5830 is used. Recording paper provided with an ink-absorbing coating layer, ink jet recording paper containing non-colloidal silica powder as a pigment in a wearable layer described in JP-A-56-157, JP-A-57-107878 Ink-jet recording paper using both an inorganic pigment and an organic pigment described in JP-A-58-110287, an ink-jet recording paper having two pore distribution peaks described in JP-A-58-110287, and JP-A-62-111782. The above described ink jet recording paper comprising two upper and lower porous layers, JP-A-59-68292, JP-A-59-123696 and JP-A-60-18383. Ink-jet recording sheet having an irregular cracks are described, for example, in JP, Sho 61 -
No. 35786, No. 61-148092 and No. 62-1
No. 49475, etc., an ink jet recording paper having a fine powder layer, JP-A-63-252779.
No. JP-A-1-108083, 2-136279
JP-A-57-14, JP-A-57-14, JP-A-57-14, and JP-A-57-14, which include pigments having specific physical properties described in JP-A-3-65376 and JP-A-3-27976.
No. 091, 60-219083, 60-2109
No. 84, No. 61-20797, No. 61-188183
No., JP-A-5-278324, JP-A-6-92011,
6-183134, 7-137431, 7-
JP-A-2-276671, JP-A-3-67684, JP-A-3-215082, JP-A-3-251488, and inkjet recording paper containing fine-particle silica such as colloidal silica described in 276789 and the like.
4-67986, 4-263983 and 5-
Many ink jet recording papers containing alumina hydrate fine particles described in, for example, Japanese Patent No. 16517 are known.

However, when the ink receiving layer is composed of only a layer having many voids for absorbing and retaining ink, the ink receiving layer having many voids often causes an interface with air and microscopic irregularities on the film surface. As a result, the incident light to the ink receiving layer is scattered or the transmission is hindered, so that gloss is hardly produced or opaque.

[0008] Further, there is a disadvantage that, due to the formation of voids, the smoothness of the film surface is reduced due to the unevenness of the pigment itself and the unevenness of the secondary aggregate of the pigment, and gloss is hardly produced.

[0009] On the other hand, there are many known ink jet recording papers of the type which absorbs and retains ink by a swelling action of a binder in an ink absorbing layer without providing a space in a film.

For example, gelatin, casein, starch, alginic acid, polyvinyl alcohol, various modified polyvinyl alcohols, polyvinyl pyrrolidone,
Polyethylene oxide, polypropylene oxide,
A large number of ink jet recording papers and films in which a hydrophilic binder such as carboxymethylcellulose, hydroxyethylcellulose, dextran, pullulan or the like is coated on a support have been known.

Although these ink jet recording papers are inferior to the recording papers having the above-mentioned voids in ink absorbency, high glossiness, optical density, and clear images can be obtained, and they are useful for high quality recording applications.

Above all, ink jet recording paper containing polyethylene glycol and a hydrophilic polymer similar thereto have particularly good ink absorbency, and are preferable from the viewpoint of ink absorbability.

It has been widely known that polyethylene glycol is incorporated in an ink absorbing layer of an ink jet recording paper.

In JP-A-2-1359, a transparent layer is provided with a hydrophilic layer in which a polyalkylene oxide and an amino group-inactivated gelatin (so-called derivative gelatin) are used in combination to provide ink absorption, transparency and curl characteristics. Are described.

Japanese Patent Application Laid-Open No. 7-9557 discloses that a copolymer of polyethylene oxide and polyalkylene oxide (where the alkylene oxide has 3 to 8 carbon atoms) has excellent light transmittance, beading, An ink jet recording paper having an ink receiving layer with improved color mixing bleeding and aging bleeding is described.

JP-A-6-47924 discloses a polyhydroxyl compound obtained by adding ethylene oxide and / or propylene oxide to a compound having 2 to 4 active hydrogen groups, and a polyhydric carboxylic acid or an acid anhydride thereof or a lower alkyl compound thereof. A liquid containing a polymer having an average molecular weight of 20,000 or more, obtained by reacting an ester, was coated on a substrate, and the drying property of the ink was increased under high temperature and high humidity, and the mechanical strength of the recording surface was increased. An ink jet recording paper is described.

Further, an ink jet recording paper containing a hydrophilic polymer similar to the above is disclosed in JP-A-7-195826.
It is also mentioned in the issue.

However, the inventors of the present invention applied various coating solutions containing such a polyalkylene oxide-based hydrophilic polymer on a support, and performed ink-jet recording to evaluate the results. It was confirmed that the addition of the hydrophilic polymer greatly improved the ink absorbency and improved image quality defects such as beading, image roughness, and color mixing.

Despite these improvements, however, the ink jet recording paper containing a polyalkylene oxide-based hydrophilic polymer has a printed surface that is dull when the prints or other paper are left standing after printing. It turned out that there was a drawback that it was liable to occur.

[0020] This problem is particularly caused when the aqueous ink is used as a solvent.
In addition to water, ethylene glycol, diethylene glycol,
It has been found that this is likely to occur when an ink containing a low volatile polyol such as triethanolamine or glycerin is used.

In particular, this problem is likely to occur when recording is performed with an aqueous ink containing 20% by weight or more of such a low-volatility polyol.

This problem can be improved to some extent by adding coarse particles (average particle size of about 5 to 50 μm) to the printing surface, but this alone cannot be said to be sufficient. If the amount is increased, the glossiness is reduced, or if the particle size of the coarse particles is further increased, troubles such as deterioration of the trace to the extent that the mark can be visually recognized at the time of printing and damage easily occur at the time of transport are likely to occur.

[0023]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide an ink having high ink absorbency, and furthermore, to obtain a sharpness immediately after printing an obtained image. An object of the present invention is to provide an ink jet recording paper in which is improved.

[0024]

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

1. An ink-jet recording sheet having, as a protective layer, a hydrophilic binder layer containing a hydrophilic polymer having an alkylene oxide group as a repeating unit and having an average molecular weight of 20,000 to 500,000, and gelatin, on the side closer to the support than the protective layer. An ink jet recording paper provided with a hydrophilic binder layer containing an amino group-inactivated gelatin.

2. The addition amount of the hydrophilic polymer having an average molecular weight of 20,000 to 500,000 having an alkylene oxide group is 10 to 50% by weight based on gelatin contained in the protective layer.
2. The ink jet recording paper according to the item 1, wherein

3. 3. The ink jet recording paper as described in 1 or 2, wherein the gelatin is an acid-treated gelatin.

4. The above-mentioned 1, wherein the protective layer further contains at least one polymer selected from homopolymers and / or copolymers of vinylpyrrolidone.
4. The ink jet recording paper according to 2 or 3.

5. 5. The ink jet recording paper according to any one of items 1 to 4, wherein the protective layer is hardened with a gelatin hardener.

6. The protective layer has an average particle size of 5 to 40 μm
6. The ink jet recording paper according to any one of the above 1 to 5, wherein the ink jet recording paper contains solid fine particles of the following.

Hereinafter, the present invention will be described in detail.

The hydrophilic polymer having an alkylene oxide group used in the ink jet recording paper of the present invention may be any hydrophilic polymer as long as it has an alkylene oxide group in a polymer molecule. 1) polyethylene oxide,
(2) a homopolymer or copolymer of a monomer having a polyalkylene group in a side chain, and (3) an active hydrogen group having 2 to 4
Compounds having at least one oxide compound selected from ethylene oxide and / or alkylene oxide (provided that the alkylene oxide has 3 carbon atoms).
To 8), a polycarboxylic acid, an acid anhydride of a polycarboxylic acid, a lower alkyl ester of a polycarboxylic acid, a diisocyanate compound, a dihalogenated aliphatic compound, and a bishalogen. Or a hydrophilic polymer obtained by reacting at least one compound selected from a carbonyl compound and a polyepoxy compound.

The hydrophilic polymer (2) having an alkylene oxide group in the side chain is preferably a homopolymer of a vinyl monomer having an alkylene oxide group or another polymer.
Copolymers with more than one type of vinyl monomer are mentioned.

Specific examples of the hydrophilic polymer classified into the above (2) are shown below.

[0035]

Embedded image

The compound obtained by adding at least one oxide compound selected from ethylene oxide and / or alkylene oxide (the alkylene oxide has 3 to 8 carbon atoms) to a compound having 2 to 4 active hydrogen groups. Polyhydroxyl compound, polycarboxylic acid, polycarboxylic acid anhydride, polycarboxylic acid lower alkyl ester, diisocyanate compound, dihalogenated aliphatic compound, bishalogenated carbonyl compound,
The hydrophilic polymer (3) obtained by reacting at least one compound selected from a bishalogenated sulfonyl compound and a polyepoxy compound preferably comprises a repeating unit represented by the following general formula (1). It is a hydrophilic polymer.

Formula (1)-(A-X-A-Y)-In the formula (1), A represents -CH ₂ CH ₂ O- and -C
H ₂ CH (R) - is a unit composed of repeating units of. However, the ratio of —CH ₂ CH ₂ O— in A is 50 to 1
Preferably, it is present in an amount of at least 00 mol%. R represents an aliphatic group having 1 to 6 carbon atoms. In addition, A contains —CH ₂ C
H (R) - if there, -CH ₂ having different R
Two or more types of CH (R)-may be present. X is a residue of an organic compound having 2 to 4 active hydrogen groups;
Are polycarboxylic acids, polycarboxylic acid anhydrides, polycarboxylic acid lower alkyl esters, diisocyanate compounds, dihalogenated aliphatic compounds, bishalogenated carbonyl compounds, bishalogenated sulfonyl compounds, or polyepoxy compounds. Residue.

The hydrophilic polymer represented by the general formula (1) is obtained by reacting the following (a) with the following (b): (a) a compound having 2 to 4 active hydrogen groups, ethylene oxide and And / or a polyhydroxyl compound obtained by adding an alkylene oxide (wherein the alkylene oxide has 3 to 8 carbon atoms). (B) Polyhydric carboxylic acid, polycarboxylic acid anhydride, polycarboxylic acid At least one compound selected from lower alkyl esters, diisocyanate compounds, dihalogenated aliphatic compounds, bishalogenated carbonyl compounds, and polyepoxy compounds.

Examples of the compound having 2 to 4 active hydrogen groups include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, 1,2-cyclohexanediol, and 1,2,4-butane. Triol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, triethanolamine, bisphenol A and the like can be mentioned.

As the alkylene oxide added to these, propylene oxide, butylene oxide, styrene oxide and the like can be mentioned. These may be used in combination of two or more.

In the above (a), the above components are used, for example, in the presence of a caustic alkali such as potassium hydroxide as a catalyst.
The reaction is carried out at a temperature of 0 to 200 ° C. for 1 to 40 hours, and the compound having active hydrogen is obtained by random or block addition polymerization of at least one oxide compound selected from ethylene oxide and / or alkylene oxide. Preferred reactants have an average molecular weight of about 1000 or more, especially 3000 to 20,000.

On the other hand, examples of the polycarboxylic acid include phthalic acid, maleic acid, terephthalic acid, citric acid, adipic acid, sebacic acid, succinic acid and trimellitic acid. Examples of the acid anhydride include phthalic anhydride, maleic anhydride, succinic anhydride, itaconic anhydride, trimellitic anhydride, and 1,8-naphthalic anhydride.

Examples of the lower alkyl ester of the polycarboxylic acid include dimethyl ester, monomethyl ester, diethyl ester and dibutyl ester of the above polycarboxylic acid.

Examples of the diisocyanate include diphenylmethane diisocyanate, hexamethylene diisocyanate, xylene diisocyanate and 4,4.
4'-methylenebis (cyclohexyl isocyanate)
And the like.

Examples of the dihalogenated aliphatic compound include 1,4-dichlorobutane, 1,6-dichlorohexane, 1,6-dibromohexane, and 1,8-dibromooctane.

Examples of the bishalogenated carbonylated aliphatic compound include phthaloyl chloride, terephthaloyl chloride, isophthaloyl chloride, and adipoyl dichloride.

Examples of the polyepoxy compound include 1,2,3,4-diepoxybutane, 1,2,7,
8-diepoxyoctane, for example, diglycidyl hexahydrophthalate and the like.

The preferred ratio of the two in the reaction of (a) and (b) is (a) :( b) = 1: 5 to 5: 1 in molar ratio.

Next, Table 1 shows examples of the hydrophilic polymer represented by the general formula (1). The composition of the hydrophilic polymer was expressed in the form of a reactant. However, the reaction ratio of the raw materials is shown by a molar ratio.

[0050]

[Table 1]

GR: glycerin, DEG: diethylene glycol, EG: ethylene glycol, EO: ethylene oxide, PO: propylene oxide, SO: styrene oxide, TD: dimethyl terephthalate, SA: succinic anhydride, PI: diphenylmethane diisocyanate In the above, the average molecular weight of the hydrophilic polymer having an alkylene oxide group is from 20,000 to 500,000.

When the average molecular weight is less than 20,000, the effect of improving the ink absorbency is small, and the hydrophilic polymer itself easily moves in the film with the passage of time, and the bleeding with the passage of time tends to increase. If the average molecular weight exceeds 500,000, the viscosity of the coating solution containing the hydrophilic binder is significantly increased, and the coating becomes difficult. The amount required to obtain ink absorption cannot be used. The preferred range of the average molecular weight is 50,000 to 400,000.

The protective layer of the ink jet recording paper of the present invention contains the above-mentioned hydrophilic polymer having an alkylene oxide group and an average molecular weight of 20,000 to 500,000, and further contains gelatin.

Here, the protective layer means a layer provided farthest from the support provided on the ink jet recording paper surface side.

As the gelatin used for the protective layer, any of alkali-treated gelatin obtained by treating a raw material of gelatin with lime or the like and acid-treated gelatin obtained by treating with various acids can be used. Acid-treated gelatin is used from the viewpoint of preventing bleeding.

In addition to the above gelatin, an amino group-inactivated gelatin described later can be used for the protective layer. However, when this gelatin is used for the protective layer, the stickiness after printing is reduced. It is preferable to keep the addition amount low, preferably 60% by weight or less, more preferably 30% by weight or less of the above gelatin.

The amount of the hydrophilic polymer having an alkylene oxide group having an average molecular weight of 20,000 to 500,000 in the protective layer is 1 to the gelatin contained in the protective layer.
It is preferably from 0 to 50% by weight.

If the content is less than 10% by weight, it is difficult to obtain a sufficient effect of improving the ink absorbency.
In the case where the value exceeds, it is difficult to obtain the effect of the present invention for improving the stickiness after printing. A particularly preferred addition length is from 20 to 40 with respect to the gelatin contained in the protective layer.
% By weight.

The protective layer may further contain at least one polymer selected from homopolymers and / or copolymers of vinylpyrrolidone, in addition to gelatin and a hydrophilic polymer having an alkylene oxide group. It is preferable from the viewpoint of high ink absorption and prevention of bleeding.

The copolymer of vinylpyrrolidone is a copolymer of vinylpyrrolidone and one or more other copolymerizable vinyl monomers. Examples of such copolymerizable vinyl monomers include vinyl acetate and its complete. Or partially hydrolyzed monomers, vinyl methyl ether, methacrylic acid or acrylic acid and their esters, acrylamide and its N-alkyl adduct, styrene, vinyl chloride,
And maleic acid and esters thereof.

The average molecular weight of the homopolymer or copolymer of vinylpyrrolidone is preferably 50,000 or more,
More than 10,000 is particularly preferable because it does not lower the ink absorbency.

The ratio of the vinylpyrrolidone homopolymer or copolymer to the hydrophilic polymer having an alkylene oxide group is preferably from 20 to 200% by weight, particularly preferably from 40 to 150% by weight.

For the protective layer, other hydrophilic polymers than those described above can be used. Examples of such a hydrophilic binder include pullulan, polyvinyl alcohol or a derivative thereof (preferably having an average molecular weight of about 20,000 or more), polyacetal, polyacrylamide, carboxymethylcellulose, hydroxyethylcellulose, dextran, dextrin, polyacrylic acid and a salt thereof, Agar, κ-carrageenan, λ-carrageenan, ι-carrageenan, xanthen gum, locust bean gum, alginic acid, gum arabic, pullulan, water-soluble polyvinyl butyral, or carboxyl group or sulfonic acid described in JP-A-62-245260 Polymers such as a vinyl monomer having a group alone or a copolymer having these vinyl monomers repeatedly may be mentioned.

The dry thickness of the protective layer is 0.5 to 5 μm.
m is preferred, and more preferably 1 to 3 μm.

The protective layer preferably contains solid fine particles having an average particle size of 5 to 40 μm in order to further improve the stickiness. Preferably, they are solid fine particles having an average particle size larger than the dry film thickness when only the hydrophilic binder is used as the protective layer by 1 μm or more, particularly preferably 5 μm or more.

Examples of the solid fine particles include inorganic and organic fine particles. The type can be appropriately selected from conventionally known solid fine particles.
Organic fine particles (polystyrene, poly-t-butyl acrylate, polymethyl methacrylate, etc.) and inorganic fine particles (eg, silica, zinc oxide,
Calcium carbonate) is preferred.

In the present invention, it is essential to provide a hydrophilic binder layer containing amino-inactivated gelatin on the side closer to the support than the protective layer. Amino group-inactivated gelatin is a gelatin derivative obtained by reacting at least a part of the amino group or imino group of gelatin with an isocyanate such as phenyl isocyanate or an acid anhydride such as phthalic anhydride.

The amino group-inactivated gelatin means that 60% or more of the amino groups in the gelatin have reacted.
Particularly, those in which 80% or more of the amino groups in the gelatin are reacted are preferred in the present invention.

The hydrophilic binder layer containing the amino group-inactivated gelatin may further contain another hydrophilic polymer. The ratio of the amino group-inactivated gelatin to the total hydrophilic polymer is 20% by weight or more. Is particularly preferable, and most preferably 30% by weight or more.

Examples of hydrophilic polymers other than the above-mentioned amino group-inactivated gelatin include acid-treated gelatin, alkali-treated gelatin, pullulan, polyvinyl alcohol or derivatives thereof (preferably having an average molecular weight of about 20,000 or more), polyacrylamide, polyvinyl Acetal, carboxymethylcellulose, hydroxyethylcellulose, dextran, dextrin, polyacrylic acid and its salts, agar, κ-carrageenan, λ-carrageenan, ι-carrageenan, xanthen gum, locust bean gum, alginic acid, gum arabic, pullulan, water-soluble polyvinyl Butyral, or poly (vinyl alcohol) having a carboxyl group or a sulfonic acid group described in JP-A-62-245260 alone or in a copolymer such as a copolymer having these vinyl monomers repeatedly. It can be given over. Among them, preferred hydrophilic polymers are nonionic hydrophilic polymers, particularly hydrophilic polymers having at least an alkylene oxide group used for the protective layer, polyvinyl alcohol, polyvinylpyrrolidone and polyacrylamide.

The thickness of the hydrophilic binder layer, which is provided on the side closer to the support than the protective layer and contains the amino group-inactivated gelatin, depends on the maximum discharge amount of the aqueous ink to be used and the low-evaporation organic content of the ink. Although it varies depending on the type and ratio of the solvent, when the maximum discharge amount is 20 to 25 ml per 1 m ^{2 of the} ink jet recording paper and the ratio of the organic solvent is 25 to 40% by weight, it is approximately 3 to 15 μm. If it is less than 3 μm, it is difficult to obtain an effect of improving the tightness after printing, and if it is more than 15 μm, curling is likely to occur under high or low humidity. Preferably 4 to 12 μm
It is.

The hydrophilic binder layer provided on the side closer to the support than the protective layer and containing the amino group-inactivated gelatin may be two or more layers. Is preferably satisfied.

In the ink jet recording paper of the present invention, at least the protective layer is preferably hardened with a gelatin hardener.

The hardening agent contained in the protective layer cannot itself be specified. That is, the hardener is generally diffusible between the layers,
Even when it is added to the coating solution for forming another layer, the layer not added is hardened as long as the hydrophilic polymer is cross-linkable. Therefore, it is difficult to fix the hydrophilic binder only to a specific layer, but in the present invention, it is generally 0.01 to 10% by weight, preferably 0.05 to 2% by weight based on the total amount of the hydrophilic binder on the ink absorbing layer side. % By weight.

The hardeners usable in the present invention include inorganic hardeners (for example, chromium alum, aluminum sulfate, etc.), aldehyde hardeners (for example, formalin, glyoxal, etc.), epoxy hardeners ( For example, diglycidyl vinyl ether, etc.), ethyleneimino hardener (for example, 1,6-bisethyleneiminopropane), acryloyl hardener (2,4,6-trisacryloylhexahydro-s-triazine, etc.), vinyl Examples thereof include a sulfone hardener (for example, bisvinylsulfonylmethane) and an active halogen hardener (for example, 2,4-dichloro-6-hydroxy-s-triazine).

Various additives can be contained in any layer on the ink receiving layer side of the ink jet recording paper of the present invention, if necessary.

For example, JP-A-57-74193,
UV absorbers described in JP-A-57-87988 and JP-A-62-261476, and JP-A-57-74192.
Nos. 57-87989, 60-72785, 61-146591, and JP-A-1-950.
No. 91, No. 3-13376, etc., anti-fading agents, various anionic, cationic or nonionic surfactants, JP-A-59-42993, JP-A-59-42993.
-52689, 62-280069, 61-242871 and JP-A-4-219266.
Fluorescent whitening agents, sulfuric acid, phosphoric acid,
Various known additives such as pH adjusters such as citric acid, sodium hydroxide, potassium hydroxide and potassium carbonate, defoamers, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents, matting agents, etc. It can also be contained.

As the support of the ink jet recording paper of the present invention, those conventionally known as ink jet recording papers can be appropriately used.

The transparent support is made of, for example, a material such as polyester resin, diacetate resin, triatesate resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyimide resin, cellophane and celluloid. Examples thereof include a film, a plate, and a glass plate. Among them, those having a property of resisting radiant heat when used as OHP are preferable, and polyethylene terephthalate is particularly preferable. The thickness of such a transparent support is preferably about 10 to 200 μm.

As the support used when it is not necessary to be transparent, for example, sheets or plates made of general paper, synthetic paper, resin-coated paper, cloth, wood, metal, etc. Examples of the support include those obtained by making the support opaque by a known means. As the opaque support, a resin-coated paper (so-called RC paper) having a polyolefin resin-coated layer obtained by adding a white pigment or the like to at least one of the base paper, and a so-called white pet obtained by adding a white pigment to polyethylene terephthalate are preferable. Prior to the application of the ink receiving layer, the support is preferably subjected to a corona discharge treatment, an undercoating treatment or the like for the purpose of increasing the adhesive strength between the support and the ink receiving layer. Furthermore, the inkjet recording paper of the present invention does not necessarily need to be colorless,
It may be a colored inkjet recording paper.

In addition to the above, various kinds of inorganic or organic solid fine particles other than those described above can be contained in the ink jet recording paper of the present invention in order to form voids in the film.

The inorganic fine particles used for the above purpose include:
Known in the art, for example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, White inorganic pigments such as aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, aluminum hydroxide, lithopone, zeolite, and magnesium hydroxide can be used.

Such inorganic fine particles may be used in a state of being uniformly dispersed in a binder as primary particles, or may be added in a state of forming secondary aggregated particles and being dispersed in a binder. May be.

On the other hand, examples of organic fine particles include polystyrene, polyacrylates, polymethacrylates, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, copolymers thereof, and urea resins. Or a melamine resin.

The inorganic or organic fine particles used as the primary particles have an average particle diameter of generally 0.005 to 2 μm, preferably 0.007 to 0.5 μm. Also, 2
As the secondary particles, the average particle size is approximately 0.02 to 0.5 μm
Is preferably used.

The amount of the solid fine particles to be added can vary greatly depending on the void volume, particle shape, and binder ratio. From the viewpoint of light resistance, the volume ratio to the binder in the solid fine particle-containing layer is particularly preferably 1.0 to 1.0. Below, it is particularly preferred that it is 0.5 or less.

The method for applying the hydrophilic layer on the support can be appropriately selected from known methods. A preferred method is obtained by applying a coating solution containing a hydrophilic binder capable of sol-gel conversion such as gelatin or κ-carrageenan on a support, followed by drying. In this case, two or more hydrophilic binder layers may be provided, and in this case, two or more layers can be applied simultaneously, and simultaneous application in which all the hydrophilic binder layers are applied only once is preferable.

For example, an ink receiving layer containing a hydrophilic binder capable of converting into a sol-gel such as gelatin described in JP-A-6-64306 is coated on a support, cooled to a gel state, and then subjected to a cold dry method. Is a preferred method.

As the coating method, 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. It is preferably used.

At this time, it is preferable from the viewpoint of productivity that heating is performed under a condition where the set coating solution is not re-dissolved during drying. Usually room temperature to 30 after setting
After evaporating water to some extent within the range of 40 ° C to 40 ° C to 5
Heat to 0 ° C. to dry completely.

The ink jet recording paper of the present invention has at least one back coat on the side opposite to the ink absorbing layer side with respect to the support in order to improve the stickiness after printing. Average particle size is 1 to 40μ
m of solid fine particles. Particularly preferred is an average particle size of 2 to 30 μm.

The layer containing the solid fine particles is preferably the uppermost layer of the back layer (the layer farthest from the support). The amount of the solid fine particles used is 0.001 to 2 times the binder of the back layer. Is preferable, and more preferably 0.0
It is 1 to 1 times.

The water-based ink referred to in the present invention is a recording liquid comprising the following colorant, liquid medium, and other additives.
As the colorant, a water-soluble dye such as a direct dye, an acid dye, a basic dye, a reactive dye, or a food coloring material known in ink jet can be used.

Examples of the solvent for the aqueous ink include water and various water-soluble organic solvents, for example, alcohols such as methyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol and isobutyl alcohol; dimethylformamide, dimethylacetamide and the like. Amides; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol;
Polyhydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, glycerin, triethanolamine; ethylene glycol methyl ether, diethylene glycol And lower alkyl ethers of polyhydric alcohols such as methyl (or ethyl) ether and triethylene glycol monobutyl ether.

Among these many water-soluble organic solvents,
Preferred are polyhydric alcohols such as diethylene glycol, triethanolamine and glycerin, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether.

[0096] Other additives for the aqueous ink include, for example, a pH adjuster, a metal sequestering agent, a fungicide, a viscosity adjuster,
Surface tension adjusters, wetting agents, surfactants, rust inhibitors, and the like.

The water-based ink liquid is used at 20 ° C. to improve the wettability with respect to the ink jet recording paper.
5-60 dyn / cm is preferable, and 30 is more preferable.
It preferably has a surface tension in the range of ５０50 dyn / cm.

[0098]

The present invention will be described below with reference to examples of the present invention.
The present invention is not limited to these examples. In addition,
In the examples, “%” indicates absolute dry weight% unless otherwise specified, and the added amount indicates the amount per 1 m ^{2 of the} ink jet recording paper.

Example 1 100 g / m ² base paper coated on both sides with polyethylene coated paper support (thickness: 140 μm, containing 7% by weight of anatase type titanium dioxide in the polyethylene layer on the ink jet recording side. On the back side, there is a layer containing 5.2 g / m ² of alkali-treated gelatin, 0.03 g / m ² of silica particles having an average particle size of about 13 μm, and a hardener as a back layer). The coating liquid having the following layer constitution was simultaneously applied to prepare inkjet recording paper-1.

First layer: alkali-treated gelatin 6.5 g polyvinyl alcohol (average degree of polymerization 500, saponification degree 88%) 3.2 g surfactant-1 0.02 g second layer: alkali-treated gelatin 1.0 g polyvinyl alcohol (Average polymerization degree 500, saponification degree 88%) 0.5 g silica fine particles (average particle size = 13 μm) 0.07 g surfactant-2 0.04 g surfactant-3 0.08 g The first and second layers were simultaneously coated.

[0101]

Embedded image

On the other hand, in the ink jet recording paper-1, ink jet recording papers-2 to 21 in which the hydrophilic polymer of each layer was changed as shown in Tables 2 and 3 were prepared in the same manner as the ink jet recording paper-1.

In the table, Gel (A) represents alkali-treated gelatin, Gel (S) represents acid-treated gelatin, and PC-Gel.
Is phenylcarbamoylated gelatin (however, amino group blocking rate = 85%), PVA = polyvinyl alcohol (average degree of polymerization = 500, saponification degree = 88%), PVP is polyvinylpyrrolidone (average molecular weight = about 360,000), PEO represents polyethylene oxide having an average molecular weight of about 150,000.

[0104]

[Table 2]

[0105]

[Table 3]

Each of the obtained ink jet recording papers was subjected to ink jet recording using an ink jet printer MJ-5000C manufactured by Seiko Epson Corporation, and the following items were evaluated.

(1) Ink Absorbability: The roughness of a green solid portion formed by uniformly discharging yellow and cyan inks was visually determined, and the distance until the roughness became invisible was determined as follows.

：: No roughness was observed at a distance of 30 cm. Δ: No roughness was observed at a distance of 60 cm. X: Roughness was observed even at a distance of 60 cm or more.

(2) Cut-off: After printing a printing portion at the maximum discharge amount of yellow and magenta, a certain period of time has elapsed, and after elapse of every four hours at 25 ° C. and a relative humidity of 55%, plain paper is superimposed. Load 500g / A4 (5 pieces of A4 paper
(With a load of 00 g).

The stickiness was evaluated by the elapsed time from printing when the paper did not stick to the plain paper to superimposition of the plain paper. (3) Bleeding evaluation: Printing was performed by changing the ejection level with a single color of cyan and printing at room temperature for 2 days. After standing, it was stored at 40 ° C. and 80% relative humidity for one week. The reflection density was measured in red before and after storage, and the density change (ΔD
b) was asked. The reflection density increases as the dots bleed,
The greater the ΔDb, the greater the bleeding. The results obtained are shown in Table 4.

[0111]

[Table 4]

From the results shown in Table 4, it can be seen that all of the recording papers 5 to 21 in which PEO was added to the second layer as the protective layer had improved ink absorbency and good image roughness due to beading. Recognize.

However, recording paper (20, 20) using phenylcarbamoylated gelatin for the second layer (protective layer) was used.
21) and amino-inactivated gelatin (PC
-Gel) is not used, and normal alkali-treated gelatin (Gel (A)) or acid-treated gelatin (Gel (S))
The recording paper (5-8, 11-13) using the ink-jet printing method according to the present invention, while the paper is superimposed on the plain paper to cause crackling unless it is dried for at least 24 hours after printing. Recording paper (9, 10, 14-1
9) does not cause crackling after 12 to 16 hours have passed.

Further, it can be seen that, in the ink jet recording paper of the present invention, the recording paper using acid-treated gelatin or polyvinylpyrrolidone for the protective layer has good bleeding over time.

Example 2 Ink jet recording papers 11 to 1 prepared in Example 1
6, PEO of the second layer is exemplified by hydrophilic polymer PA
Ink jet recording papers-11B to 16B were prepared in the same manner as in Example 1 except that O-5 was changed to O-5.
The ink absorbency and the drying property were evaluated in the same manner as described above. Table 5 shows the results.

[0116]

[Table 5]

From the results shown in Table 5, it can be seen that the same effect as in Example 1 can be obtained even when the hydrophilic polymer having an alkylene oxide group is changed to PAO-5.

Example 3 Inkjet recording papers 11 to 1 prepared in Example 1
In 6, the hardening agent in the coating solution of the second layer is 1, 3
Recording paper 1 containing diglycidyl-2-hydroxypropane
m ² per 20mg added inkjet recording paper 1
1C to 16C were prepared in the same manner as in Example 1. The hardener was added immediately before coating, and after coating and drying, it was left at 40 ° C. for 2 days to harden.

The obtained sample was evaluated in the same manner as in Example 1, and the results shown in Table 6 were obtained.

[0120]

[Table 6]

From the results shown in Table 6, it can be seen that the ink-jet recording paper of the present invention greatly improves the stickiness with a very small amount of the crosslinking agent. On the other hand, the comparative ink-jet recording paper has a small improvement by the hardener.

[0122]

As described above, by using the constitution of the ink jet recording paper of the present invention, it is possible to obtain the ink jet recording paper in which the high glossiness and the ink absorptivity are maintained and the after-printing is prevented.

[0123]

As demonstrated in the examples, the ink jet recording paper according to the present invention has high ink absorbency and has an excellent effect of improving the tightness immediately after printing of the obtained image.

Claims (6)

[Claims] 1. An ink jet recording sheet comprising, as a protective layer, a hydrophilic binder layer containing a hydrophilic polymer having an average molecular weight of 20,000 to 500,000 having an alkylene oxide group as a repeating unit and gelatin as a protective layer. An ink jet recording sheet comprising a hydrophilic binder layer containing an amino group-inactivated gelatin on the side close to the body. 2. The method according to claim 1, wherein the amount of the hydrophilic polymer having an average molecular weight of 20,000 to 500,000 having an alkylene oxide group is 10 to 50% by weight based on gelatin contained in the protective layer. Item 2. An ink jet recording sheet according to item 1. 3. The ink jet recording paper according to claim 1, wherein the gelatin is an acid-treated gelatin. 4. The method according to claim 1, wherein the protective layer further contains at least one polymer selected from homopolymers and / or copolymers of vinylpyrrolidone.
4. The ink jet recording paper according to 2 or 3. 5. The ink jet recording paper according to claim 1, wherein the protective layer is hardened with a gelatin hardener. 6. The ink-jet recording sheet according to claim 1, wherein the protective layer contains solid fine particles having an average particle size of 5 to 40 μm.