JP2008036998A - Inkjet recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inkjet recording paper with no coating unevenness and a highly white blank paper part. <P>SOLUTION: The inkjet recording paper provides an underlayer and an ink receiving layer on a substrate in this order so as to come into contact with each other. Using consciousness chromaticity indexes a* and b* by CIELAB of the surface of the substrate, the surface of the underlayer and the surface of the ink receiving layer, both values of A<SB>1</SB>and A<SB>2</SB>obtained by the following formulae are ≤7. A<SB>1</SB>=ä(a*<SB>1</SB>-a*<SB>2</SB>)<SP>2</SP>+(b*<SB>1</SB>-b*<SB>2</SB>)<SP>2</SP>}<SP>1/2</SP>, A<SB>2</SB>=ä(a*<SB>2</SB>-a*<SB>3</SB>)<SP>2</SP>+(b*<SB>2</SB>-b*<SB>3</SB>)<SP>2</SP>}<SP>1/2</SP>, wherein a*<SB>1</SB>and b*<SB>1</SB>: consciousness chromaticity index of the surface of the substrate; a*<SB>2</SB>and b*<SB>2</SB>: consciousness chromaticity index of the surface of the underlayer; a*<SB>3</SB>and b*<SB>3</SB>: consciousness chromaticity index of the surface of the ink receiving layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording paper used for ink jet recording.

  Inkjet recording paper has a structure in which an ink-receiving layer containing a porous pigment such as silica or alumina and a binder is provided on the surface of a support such as paper, and ink droplets are fixed on the ink-receiving layer. It is supposed to do. The quality required of ink jet recording paper is increasing year by year due to remarkable progress of ink jet printers in recent years and the remarkable spread of digital cameras.

  By the way, the recording paper used for the ink jet recording system is roughly classified into a plain paper type having a texture similar to so-called high-quality paper and PPC paper and a coated paper type clearly showing that it has an ink receiving layer. . Further, coated paper type recording media are roughly classified into a gloss type having gloss in the ink receiving layer and a mat type having no gloss. In particular, in an inkjet recording medium having a gloss comparable to that of a conventional silver salt photograph, quality requirements are strict and technological development is actively being carried out.

  The quality characteristics required for such coated paper type ink jet recording media include high ink drying speed, high print density, and no ink overflow or bleeding. The whiteness of the part (white paper part) is high. In order to improve these characteristics, it is necessary to improve the ink receiving layer.

In particular, for improving the whiteness of the white paper portion, for example, a technique of containing a high white type fluorescent dye in the ink receiving layer has been reported (see, for example, Patent Document 1 and Patent Document 2). In addition, a technique for improving color reproducibility by making the perceived chromaticity index (a * and b *) on the surface of the ink receiving layer or the support surface into a specific range has been reported. (For example, see Patent Document 3)
Japanese Patent Laid-Open No. 2002-2101 JP 2003-266923 A Japanese Patent Laid-Open No. 10-181194

  However, in the above technique, a large amount of fluorescent whitening agent is blended in order to obtain a high white ink-receiving layer, so that the coating property of the ink-receiving layer coating solution is lowered and uneven coating occurs in the ink-receiving layer. There was a problem to do. Further, since the color of the support and the ink receiving layer containing a large amount of fluorescent whitening agent is different, even a slight coating unevenness is conspicuous and the aesthetic appearance is remarkably impaired.

  In addition, even when the support itself is made high white, since the color of the ink receiving layer is different, coating unevenness similarly occurs and becomes a problem. Accordingly, an object of the present invention is to obtain an ink jet recording paper having no coating unevenness and having a white portion of high white.

  As a result of intensive studies, the present inventors have provided an under layer and an ink receiving layer in this order so as to contact each other on the support, and provided the support surface, the under layer surface provided on the support, and the under layer. When the respective chromaticity indexes (a * and b *) of the surface of the obtained ink receiving layer satisfy a certain relationship, coating unevenness becomes invisible on the surface of the ink receiving layer of the finally obtained ink jet recording paper. (Or inconspicuous) and found the present invention.

That is, the present invention relates to an inkjet recording paper in which an under layer and an ink receiving layer are provided on a support so as to be in contact with each other in this order, and the CIELAB on the surface of the support, the surface of the under layer, and the surface of the ink receiving layer. A value of A ₁ and A ₂ obtained by the following formula using the perceptual chromaticity indexes a * and b * of the ink jet recording paper is 7 or less.

A ₁ = {(a * ₁ −a * ₂ ) ² + (b * ₁ −b * ₂ ) ² } ^1/2
_{A 2 = {(a * 2} -a * 3) 2 + (b * 2 -b * 3) 2} 1/2
Where a * ₁ , b * ₁ : perceived chromaticity index of the support surface
a * ₂ , b * ₂ : Perceived chromaticity index of the underlayer surface
a * ₃ , b * ₃ : Perceptual chromaticity index of the surface of the ink receiving layer Further, the present invention is an ink jet recording paper provided on the support so that the ink receiving layer is in contact with the under layer surface and the ink receiving surface. ink-jet recording sheet, wherein the value of a ₃ obtained by the following equation using the perceptual chromaticity indices by CIELAB layer surface a * and b * of 7 or less.

A ₃ = {(a * ₁ −a * ₃ ) ² + (b * ₁ −b * ₃ ) ² } ^1/2
Where a * ₁ , b * ₁ : perceived chromaticity index of the support surface
a * ₃ , b * ₃ : perceived chromaticity index of the ink receiving layer surface

  Furthermore, it is preferable to adjust the chromaticity index by blending a coloring pigment or a coloring dye into at least one of the support, the under layer and the ink receiving layer.

  In the present invention, even when a colorant is added to the ink receiving layer in order to make the white paper portion white, it is possible to obtain an ink jet recording paper that does not show coating unevenness or coating defects on the outermost surface of the ink receiving layer. it can.

Embodiments of the present invention will be described below. The ink jet recording medium of the present invention is one in which an under layer and an ink receiving layer are provided on at least one surface of a support, or an ink receiving layer is provided directly on a support. In the present invention, the values of A ₁ , A ₂ , and A ₃ calculated for the perception degree index of the under layer and the ink receiving layer by the above-described formula are all 7 or less, and particularly preferably 6 or less. When the values of A ₁ , A ₂ , and A ₃ exceed 7, defects such as color unevenness and streaks due to coating amount fluctuations are conspicuous and become a problem. A streak is an elongated flaw that occurs when an ink receiving layer is applied, and foreign matter (for example, undispersed pigments, etc.) present in the ink receiving layer coating liquid is caught in the coater head of the coating machine. Etc.

  The perceptual chromaticity index in the present invention is a perceptual chromaticity index according to CIELAB (L * a * b * color system abbreviation recommended by Commission Internationale de l "Echairage"), and represents an attribute of color perception composed of hue and saturation. It is the coordinates a *, b * of the L * a * b * color system. This is specified in JIS Z 8730.

<Coloring pigments and coloring dyes>
In the present invention, the value of the perceptual chromaticity index can be adjusted by adding a color pigment or a color dye to the support, the under layer, and the ink receiving layer. From the viewpoint of storage stability, it is preferable to use a color pigment. It is preferable to use blue or magenta colored pigments or dyes from the viewpoint of visually white, specifically, blue pigments such as cobalt blue, ultramarine blue, cecilian blue, and phthalocyanine blue, cobalt violet, fast violet, manganese. Magenta pigments such as purple can be used alone or in appropriate combination.

<Support>
As the support used in the present invention, any support can be used as long as it is in the form of a sheet, but a support having air permeability is preferable. For example, paper such as coated paper and uncoated paper can be suitably used for the support. The raw material pulp of the paper includes chemical pulp (coniferous bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (ground pulp, thermomechanical pulp, chemisermomechanical pulp, etc.), deinking Pulp or the like can be used alone or mixed at an arbitrary ratio. The pH of the paper may be acidic, neutral or alkaline. Further, in order to improve the opacity, it is preferable to contain a filler in the paper, but this filler is hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, synthetic resin fine particles, etc. It can be appropriately selected from known fillers. From the viewpoint of operability, the air permeability of the paper is preferably 1000 seconds or less, and from the viewpoint of coating properties, the paper sizing degree is preferably 5 seconds or more.

  In order to improve the whiteness of the support, there is a method of using a high white pulp or a fluorescent dye, but it is particularly preferable to use a high white pulp from the viewpoint of storage stability. In addition, as a high white pulp, ISO whiteness of 85-95% is preferable. If the pulp is 85% or less, sufficient whiteness cannot be achieved as a final recording medium, and pulp having an ISO whiteness of 95% or more tends to have short fibers and poor texture. The ISO whiteness of the pulp is measured according to the method defined in JIS P 8212.

<Under layer>
In the present invention, the under layer is provided between the support and the ink receiving layer, and includes a pigment and a binder containing a water-soluble polymer.
[Binder]
The water-soluble polymer is used to ensure the coating liquid properties of the underlayer coating liquid. If the water-soluble polymer is not contained in the binder, the coating liquid physical properties are appropriate. It doesn't become a thing. Although there is no restriction | limiting in particular as water-soluble polymer used for a binder, When the polyvinyl alcohol (henceforth "PVA" suitably) which is a highly transparent binder is used, the color density of a printing part will improve. Therefore, it is preferable. In particular, fully saponified polyvinyl alcohol is more preferable. The polymerization degree of polyvinyl alcohol is preferably 500 to 2400, more preferably 1000 to 2000.
When an ethylene / vinyl acetate copolymer (hereinafter referred to as “EVA” as appropriate) is used in combination as a binder, the strength of the coating layer increases and paper dust during cutting is reduced. Further, since the contact angle of the ethylene / vinyl acetate copolymer itself with water is smaller than that of other synthetic resins (for example, styrene butadiene copolymer (SBR)), the ink absorbency of the under layer is improved. In particular, when the following polyvinyl alcohol / ethylene / vinyl acetate graft copolymer is used, these effects increase.

  The ethylene / vinyl acetate copolymer is, for example, a dry emulsion obtained by copolymerizing ethylene and vinyl acetate in an aqueous system in which polyvinyl alcohol is present as an emulsifier. The polymerization initiator mainly acts on ethylene and vinyl acetate, but depending on the reaction conditions and the amount of polyvinyl alcohol as an emulsifier, the ethylene / vinyl acetate copolymer is branched from the polyvinyl alcohol chain, and grows polyvinyl alcohol / ethylene. -An emulsion of vinyl acetate graft copolymer may be formed. As the ethylene / vinyl acetate copolymer used in the present invention, it is preferable to use an emulsion in which a number of molecules obtained by grafting an ethylene / vinyl acetate copolymer onto polyvinyl alcohol is increased. In addition, an under layer is formed by apply | coating the coating liquid containing an above-described emulsion, the pigment mentioned later, etc., and drying.

  The glass transition point (Tg) of the ethylene / vinyl acetate copolymer is preferably 0 ° C. or less, and the particle diameter of the emulsion is preferably 1 μm or less. When Tg is 0 ° C. or lower, the cutting edge at the time of cutting the cutter is improved, the falling off of the coating layer (under layer and ink receiving layer) is reduced, and the generation of paper dust tends to be further reduced. This is presumably because the flexibility of the coating layer (under layer and ink receiving layer) is increased. On the other hand, when the particle diameter is 1 μm or less, the transparency of the under layer is increased, and the printing color density tends to be improved (particularly in the case of dye ink). The effect of improving the cut at the time of cutting described above is particularly great when an ink receiving layer is provided by a casting method described later. On the other hand, when Tg exceeds 0 ° C., the flexibility of the coating layer is lowered, so that the amount of paper dust generated during cutting tends to increase. On the other hand, when the particle diameter exceeds 1 μm, the transparency is lowered and the transparency of the obtained coating layer is also lowered, so that the printing color density tends to be lowered.

The blending amount of the ethylene / vinyl acetate copolymer in the binder for the under layer is not particularly limited, but is preferably 10 to 50 parts by mass, more preferably 20 to 40 parts by mass with respect to 100 parts by mass of the pigment. When the blending amount of the ethylene / vinyl acetate copolymer exceeds 50 parts by mass, the hydrophobicity of the binder becomes remarkable and the ink absorbability tends to decrease.

  Further, the blending amount of the water-soluble polymer (for example, PVA) in the binder for the under layer is not particularly limited, but 100 parts by mass of the pigment from the viewpoint of having coating layer strength, ink absorbability, coating suitability, and the like. The amount is preferably 2 to 50 parts by mass, and more preferably 3 to 25 parts by mass.

[Pigment]
The pigment used for the under layer mainly contains synthetic silica, and 20% by mass or more of the synthetic silica is preferably synthetic silica having a secondary particle diameter of 5 to 15 μm. Thereby, the coating layer intensity | strength of an under layer improves and it can reduce paper dust generation | occurrence | production at the time of cutting. In particular, it is preferable to use a synthetic silica produced by a gel method since the coating layer strength is improved, and a synthetic silica produced by a precipitation method is used because the color developability is improved. When the secondary particle diameter is less than 5 μm, the coating layer strength is lowered, and a large amount of paper powder tends to be generated during cutting. In order to improve the coating layer strength, the secondary particle diameter of the synthetic silica is preferably larger, and more preferably 7 μm or more. However, if it exceeds 15 μm, the voids of the layer will increase, and on the under layer The ink receiving layer to be provided tends not to be formed uniformly, and the coating property of the under layer coating liquid tends to be lowered and productivity tends to be lowered. The secondary particle diameter of synthetic silica can be measured by a laser diffraction / scattering method.

Further, when the ratio of the synthetic silica having a secondary particle diameter of 5 to 15 μm is less than 20 mass% in the whole synthetic silica, the ink absorption of the under layer is good, but the coating layer strength is lowered.
The blending amount of the synthetic silica having the secondary particle size is preferably large, preferably 30% by mass or more, more preferably 60% by mass or more of the total synthetic silica in the pigment for the under layer. All of the synthetic silica may be synthetic silica having the secondary particle size. The proportion of synthetic silica in the entire pigment is preferably 90% by mass or more.

[Other ingredients]
In addition to the above-described components, a known pigment that can be contained in the ink receiving layer described later and a known binder can be used in combination with the under layer as long as the effects of the present invention are not impaired. Other additives include dye fixing agents, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, colored dyes, colored pigments, fluorescent enhancers. Whitening agents, ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, and the like can be appropriately blended in the layers.

[Coating method]
Next, a method for providing an under layer on the support will be described.

In the present invention, the under layer can be provided as one or more layers on one or both sides of the support. Further, when a plurality of underlayers are provided, the coating liquid composition may be different without the scope of the present invention. Preferably the coating amount of the under layer is 3 to 30 g / ^{m 2,} more preferably from 5 to 20 g / ^{m 2.} When it is less than 3 g / m ² , the support cannot be sufficiently covered, and unevenness occurs in the coated paper. When it exceeds 30 g / m ² , the coating layer strength is not sufficient, which causes the under layer to peel off.

  In the present invention, the apparatus for coating the coating liquid for forming the under layer includes various blade coaters, roll coaters, air knife coaters, bar coaters, gate roll coaters, curtain coaters, die coaters, short dwell coaters, gravure coaters, Various apparatuses such as a flexographic gravure coater, a spray coater, and a size press can be used on-machine or off-machine.

  It is also possible to perform surface treatment with a calendar device such as a machine calendar, a super calendar, or a soft calendar before or after coating the under layer.

<Ink receiving layer>
In the ink jet recording medium of the present invention, an ink receiving layer is provided on the under layer. The ink receiving layer is composed of the above-described pigments, binders, and the like, and has a function of holding the coloring components in the ink. As the pigment used in the ink receiving layer, the same pigments used in the under layer can be used. For example, synthetic amorphous silica, colloidal silica, light calcium carbonate-silica composite particles, kaolin, clay, calcium carbonate , Talc, alumina, hydrated alumina (alumina sol, colloidal alumina, pseudoboehmite, etc.), aluminum hydroxide, magnesium carbonate, satin white, titanium dioxide, montmorillonite, plastic pigment, etc., alone or in combination of two or more It can also be used.
In the present invention, it is preferable to use compatible amorphous silica or alumina, which has high transparency and improves color developability when ink jet recording is performed.

  The polymer compound is the same as the binder used for the under layer, such as polyvinyl alcohol and derivatives thereof, starches such as oxidized starch and esterified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, polyvinylpyrrolidone, casein, Gelatin, soy protein, styrene-acrylic resin and derivatives thereof, styrene-butadiene latex, acrylic emulsion, vinyl acetate emulsion, vinyl chloride emulsion, urethane emulsion, urea emulsion, alkyd emulsion, and derivatives thereof may be used alone or in combination. it can.

  When a pigment having a so-called self-binding function (for example, colloidal silica) that can form a film without using a binder is used in the ink-receiving layer, the binder may not be used in combination. It is also possible to form the receiving layer with the binder alone.

  In addition, for the ink receiving layer, a pigment dispersant, a fluidity improver, a water retention agent, a thickener, an antifoaming agent, a defoaming agent, a release agent, a surface property modifier, a foaming agent, a penetrating agent, if necessary Various auxiliary agents such as colored dyes, colored pigments, fluorescent brighteners, ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, pH adjusters, softeners, and ink fixing agents can also be added.

[Cast coat]
In the present invention, when the ink receiving layer is provided also by a cast coating method, high gloss comparable to silver salt photography can be obtained. At this time, if the under layer pigment contains a light calcium carbonate-silica composite, an appropriate void is generated in the under layer due to the shape of the pigment particles, and air permeability is improved. Evaporated vapor is easily removed when pressed against the cast drum and is dried, and troubles such as fogging of the cast drum and coating layer trail are reduced.

  The cast coating method is a method in which a coating liquid for an ink receiving layer is applied onto an under layer, a coating layer in a plastic state is pressed against a cast drum (mirror-finished surface), and a gloss finish is performed. In the present invention, any of a direct method, a coagulation method, and a rewet method can be used. From the viewpoint that high gloss can be obtained, the coagulation method improves the productivity. Is preferred.

  When the ink receiving layer is provided on the support by the rewetting cast coating method, the ink receiving layer coating solution is applied and dried on the support, and the binder is plasticized on the dried coating layer. A processing solution having a function of converting into a coating is applied, and then it is pressure-bonded to a heated mirror surface to give gloss. In the case of the rewet method cast coating method, the ink-receiving layer is in a dry state when applying the treatment liquid, so it is difficult to copy the mirror drum surface, and the surface has a lot of minute irregularities and the glossiness tends to decrease slightly. However, productivity can be improved because the coating speed can be increased compared to other methods.

  When the ink receiving layer is provided on the support by the solidification cast coating method, the ink receiving layer coating liquid is applied onto the support, and the binder is solidified while the coating layer is wet. A treatment liquid having an action of (or cross-linking) is applied, and then pressed onto a heated mirror surface to give gloss. For example, when casein is used as a binder, it contains an aqueous solution containing a compound that coagulates casein. When polyvinyl alcohol is used as a binder, it contains a compound that coagulates polyvinyl alcohol. Any aqueous solution can be used. When polyvinyl alcohol is used as the binder, it is particularly preferable to use a treatment liquid containing boric acid and borate. By mixing and using, it becomes easy to obtain solidification with an appropriate hardness, and it is possible to obtain a cast-coated paper for ink jet recording having a good gloss feeling.

  As a method for applying the ink receiving layer coating liquid on the under layer, a known blade coater, air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, bar coater, gravure coater, etc. It can be used by appropriately selecting from methods for coating using a coating machine. Examples of the method for applying the treatment liquid include, but are not limited to, a roll, a spray, and a curtain method.

The coating amount of the ink receiving layer can be arbitrarily adjusted within the range that covers the surface of the under layer and sufficient ink absorbency can be obtained, but from the viewpoint of achieving both recording density and ink absorbency, The solid content is preferably ³ to 30 g / m ² . Furthermore preferably ^{5g / m 2 ~20g / m 2} . If it exceeds 30 g / m ² , the peelability from the mirror drum is lowered, and problems such as adhesion of the coating layer to the mirror drum occur.

In the ink jet recording medium of the present invention, in addition to the under layer and the ink receiving layer, organic or inorganic fine particles, polymer compounds, etc. are used for the purpose of adjusting the glossiness and adjusting the friction coefficient on the ink receiving layer. An overcoat layer consisting of can also be provided. In the present invention, if necessary, a back layer for imparting writing property, antistatic property, antifouling property, slipperiness and the like may be provided on the support opposite to the surface on which the ink receiving layer is provided. Is possible.
Ru

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. “Part” and “%” represent “part by mass” and “% by mass”, respectively, unless otherwise specified.

<Example 1>
(Manufacture of support)
10 parts of talc, 0.1 part of synthetic sizing agent, and 0.02 part of yield improver are added to a pulp slurry consisting of 100 parts of hardwood bleached kraft pulp (L-BKP) with a beating degree of 285 ml. Blue: Nippon Kayaku Co., Ltd.) was added in an amount of 0.0031 parts, and paper was made with a paper machine. At the time of papermaking, starch was applied to both sides of the paper so that the solid content per side was 2.5 g / m ² to obtain a support having a basis weight of 190 g / m ² .

(Formation of under layer)
One side of this support was coated with a blade coater using the following coating liquid A so that the coating amount was 15 g / m ^2, and air-dried at 140 ° C. to provide an under layer.
Coating solution A: 100 parts of precipitated silica (Fine Seal X-37B: wet method silica manufactured by Tokuyama Corporation, specific surface area 287 m ² / g) is blended as a pigment, and styrene butadiene latex (LX438C: 10 parts of Sumitomo Chemical Co., Ltd. (trade name) and 30 parts of polyvinyl alcohol (PVA 117: trade name of Kuraray Co., Ltd.) are blended, and a sizing agent (Polymarlon 360: trade name of Arakawa Chemical Industries, Ltd.) An aqueous coating solution having a concentration of 20% was prepared by blending 0.024 part of a color pigment (EMT Blue DS-18: Toyo Ink Manufacturing Co., Ltd.).

(Formation of ink receiving layer)
On top of the under layer, 10.5 g / m ^{2 of} coating liquid B is applied using a roll coater, and while the coating layer is in a wet state, the coagulation liquid C is applied to the coating layer and applied. The construction layer was solidified. Next, the coating layer was pressure-bonded to the mirror-finished surface heated through a press roll, and the mirror surface was copied to obtain an ink jet recording paper of 210 g / m ² .
Coating liquid B: As a pigment, peanut-shaped colloidal silica (Quarton PL-1: Fuso Chemical Industry Co., Ltd., primary particle diameter 14 nm, secondary particle diameter 33.4 nm, the ratio of the secondary particle diameter to the primary particle diameter is 2 .39) 60 parts, gas phase method silica (Aerosil 380S: trade name of Nippon Aerosil Co., Ltd., primary particle diameter 5 nm, specific surface area about 380 m ² / g), and precipitation method silica (Fine Seal X-37B: 20 parts by wet method silica manufactured by Tokuyama Co., Ltd., specific surface area 287 m ² / g), partially saponified polyvinyl alcohol (PVA-617: Kuraray Co., Ltd. trade name, 95% saponification degree) as a binder , Degree of polymerization 1700) 10 parts, 2 parts of mold release agent (Maycatex HP 50: manufactured by Meisei Chemical Co., Ltd.), color pigment (EMT Blue DS-18: Toyo Nki manufacturing, Ltd.) were blended 0.037 parts to prepare a 20% concentration of the coating liquid.

Coagulating liquid C: Boron sand (converted to Na ₂ B ₄ O ₇ ) 5%, boric acid (converted to H ₃ BO ₃ ) 5%, release agent (Mecatex HP50: manufactured by Meisei Chemical Co., Ltd.) 0.25 %, Penetrant (Pionine D-3120-W: trade name of Takemoto Yushi Co., Ltd.) 0.5%, and malic acid 0.25% were blended to prepare a coagulation liquid.

<Example 2>
An ink jet recording paper was prepared in the same manner as in Example 1 except that the coating liquid B was applied so that the coating amount was 11.5 g / m ² .

<Example 3>
An ink jet recording paper was prepared in the same manner as in Example 1 except that 0.036 parts of the color pigment was added to the coating layer A and 0.0091 parts of the color pigment was added to the coating liquid B.

<Example 4>
An ink jet recording paper was prepared in the same manner as in Example 3 except that the coating liquid B was applied so that the coating amount was 11.5 g / m ² .

<Example 5>
An ink jet recording paper was prepared in the same manner as in Example 3 except that 0.049 part of the color pigment was added to the coating liquid A.

<Example 6>
An inkjet recording paper was prepared in the same manner as in Example 5 except that the coating liquid B was applied so that the coating amount was 11.5 g / m ² .

<Example 7>
An ink jet recording paper was prepared in the same manner as in Example 5 except that 0.0020 part of a colored dye was added to the support, paper was made, and coating liquid B was directly coated thereon.

<Example 8>
An ink jet recording paper was prepared in the same manner as in Example 7 except that 0.0031 part of a colored dye was added to the support, paper was made, and coating liquid B was directly coated thereon.

<Example 9>
An ink jet recording paper was prepared in the same manner as in Example 7 except that 0.0063 part of a colored dye was added to the support, paper was made, and coating liquid B was directly coated thereon.

<Comparative Example 1>
An ink jet recording paper was prepared in the same manner as in Example 9 except that there was no coloring pigment in coating solution A and 0.092 part of coloring pigment was added to coating solution B.
<Comparative example 2>
An inkjet recording paper was prepared in the same manner as in Comparative Example 1 except that the coating liquid B was applied so that the coating amount was 11.5 g / m ² .
<Comparative Example 3>
An ink jet recording paper was prepared in the same manner as in Comparative Example 1 except that 0.049 part of the color pigment was added to the coating liquid A and the color pigment of the coating liquid B was omitted.
<Comparative Example 4>
An inkjet recording paper was prepared in the same manner as in Comparative Example 3 except that the coating liquid A was applied so that the coating amount was 16 g / m ² .
<Comparative Example 5>
An ink jet recording paper was prepared in the same manner as in Comparative Example 1 except that the colored dye of the support was omitted.
<Comparative Example 6>
An ink jet recording paper was prepared in the same manner as in Comparative Example 1 except that the color pigment of the coating liquid B was omitted.
<Comparative Example 7>
An inkjet recording paper was prepared in the same manner as in Comparative Example 5 except that the support was not provided with a colored dye and the coating liquid B was directly coated thereon.
<Comparative Example 8>
An ink jet recording paper was prepared in the same manner as in Comparative Example 3 except that the coating liquid B was directly coated on the support.

(Evaluation)
The inkjet recording papers obtained in the examples and comparative examples were evaluated by the methods shown below.
<Color difference>
Using a high-speed spectrophotometer for whiteness (CMS-35SPX: manufactured by Murakami Color Research Laboratory Co., Ltd.), the perception of the surface of the under layer provided on the support and the surface of the ink receiving layer provided on the under layer The chromaticity index was measured, and A (color difference) was determined from the following formula.

A ₁ = {(a * ₁ −a * ₂ ) ² + (b * ₁ −b * ₂ ) ² } ^1/2
_{A 2 = {(a * 2} -a * 3) 2 + (b * 2 -b * 3) 2} 1/2
A ₃ = {(a * ₁ −a * ₃ ) ² + (b * ₁ −b * ₃ ) ² } ^1/2
Where a * ₁ , b * ₁ : perceived chromaticity index of the support surface
a * ₂ , b * ₂ : Perceived chromaticity index of the underlayer surface
a * ₃ , b * ₃ : perceived chromaticity index of the ink receiving layer surface

<Color unevenness due to variation in coating amount>
The color unevenness on the surface of the ink receiving layer was judged visually under the condition of a fluorescent lamp.
○: Less uneven color ×: More uneven color <Coating defects>
The presence or absence of elongated flaws (streaks) that could be scraped off during the application of the under layer or cast layer was judged visually.
○: Scratches are inconspicuous ×: Clear scratches are conspicuous

Table 1 shows that Examples 1 to 9, which are products of the present invention, were ink jet recording papers with less color unevenness and coating defects, whereas in Comparative Examples 1 to 8 where the color difference exceeded 7, color unevenness and coating It can be seen that both the construction defects are large and inferior.

Claims (3)

An ink jet recording paper having an under layer and an ink receiving layer on a support so as to be in contact with each other in this order, and a perceptual chromaticity index by CIELAB of the surface of the support, the surface of the under layer, and the surface of the ink receiving layer An inkjet recording paper characterized in that the values of A ₁ and A ₂ obtained by the following formula using a * and b * are 7 or less.
A ₁ = {(a * ₁ −a * ₂ ) ² + (b * ₁ −b * ₂ ) ² } ^1/2
_{A 2 = {(a * 2} -a * 3) 2 + (b * 2 -b * 3) 2} 1/2
Where a * ₁ , b * ₁ : perceived chromaticity index of the support surface
a * ₂ , b * ₂ : Perceived chromaticity index of the underlayer surface
a * ₃ , b * ₃ : perceived chromaticity index of the ink receiving layer surface
An inkjet recording paper provided with an ink receiving layer in contact with a support, which is obtained by the following formula using perceptual chromaticity indices a * and b * by CIELAB of the under layer surface and the ink receiving layer surface: ink-jet recording sheet, wherein the value of a ₃ is 7 or less.
A ₃ = {(a * ₁ −a * ₃ ) ² + (b * ₁ −b * ₃ ) ² } ^1/2
Where a * ₁ , b * ₁ : perceived chromaticity index of the support surface
a * ₃ , b * ₃ : perceived chromaticity index of the ink receiving layer surface
The inkjet recording paper according to claim 1 or 2, wherein a coloring pigment or a coloring dye is blended in at least one of the support, the under layer, and the ink receiving layer.