JP2008238770A - Inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet which shows a superior image quality for both of a dye ink and a pigmented ink and has stable coating property due to high viscosity stability of a coating liquid during coating process. <P>SOLUTION: An ink receptive layer containing a pigment and a water-soluble binding agent is formed on at least one surface of a support body. In addition, the ink receptive layer contains 0.1 to 10 pts. by mass of branched polyester amide based on 100 pts. by mass of pigment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet recording sheet provided with an ink receiving layer.

An ink jet recording medium 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 formed on the ink receiving layer. Has become established. With the remarkable progress of ink jet printers in recent years and the remarkable spread of digital cameras, the quality required for ink jet recording media is increasing year by year.
By the way, the recording media used in the ink jet recording method are 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 having an ink receiving layer. . Further, coated paper type recording media are roughly divided into a gloss type having gloss in the ink receiving layer and a mat type having no gloss. In particular, for coated paper type ink jet recording media having a gloss comparable to that of conventional silver salt photographs, quality requirements are severe and technological development is actively underway.

  The quality characteristics required for such a glossy inkjet recording medium include a high ink drying speed, a high print density, and no ink overflow or bleeding. In order to improve these characteristics, it is necessary to improve the ink receiving layer. For example, a technique has been reported in which the ink receiving layer has a layer structure of one or more layers, and at least one ink receiving layer contains colloidal particles having an average particle diameter of 300 nm or less and a cationic resin (for example, patents). Reference 1). In the cast coating layer, (1) fine silica particles having an average primary particle diameter of 3 to 40 nm and an average secondary particle diameter of 10 to 400 nm, and (2) an average particle diameter. A technique containing colloidal silica of 200 nm or less has been reported (for example, see Patent Document 2).

  On the other hand, in recent years, pigment inks using pigments as coloring materials are becoming popular due to the development of pigment dispersion technology. When an image is recorded with pigment ink, the storage stability is good, but when printing is performed on a conventional inkjet recording paper designed for dye ink, the color developability of the image is inferior, and the color material (pigment) is recorded on the recording paper. There is a problem of missing from the surface. In order to solve this problem, there has been reported a recording medium capable of obtaining a good recorded image using either dye ink or pigment ink (see Patent Document 3). In this technique, for example, amorphous silica having an average particle diameter of 5 to 20 μm and polyvinyl alcohol having a saponification degree of 90.0 to 97.0 mol% and a polymerization degree of 1000 to 3500 are contained. It is disclosed that an ink receiving layer having a constituent mass ratio of alcohol of 100/100 to 100/20 is provided.

Japanese Patent Laid-Open No. 9-263039 JP 2000-85242 A JP 2003-94794 A

However, in the case of the conventional ink receiving layer coating liquid, when the coating liquid is stored for a long period of time, there is a disadvantage that the viscosity increases with time and coating becomes impossible. In particular, the problem of thickening is conspicuous in a coating liquid in which polyvinyl alcohol having a high polymerization degree is blended as a binder in order to improve the suitability of pigment ink.
Accordingly, an object of the present invention is to provide an ink jet recording sheet having excellent image quality regardless of whether dye ink or pigment ink is used, and high viscosity stability of the coating liquid at the time of coating. It is in.

  As a result of intensive studies on the constitution for improving the viscosity stability of the coating liquid, the present inventors have found that when the branched polyesteramide is added to the ink receiving layer coating liquid, the coating liquid does not thicken over time. .

  Accordingly, in the ink jet recording sheet of the present invention, an ink receiving layer containing a pigment and a water-soluble binder is provided on at least one surface of the support, and the ink receiving layer has 100 parts by weight of the pigment. 0.1 to 10 parts by mass of branched polyesteramide is contained.

The branched polyesteramide may be 1,3-isobenzofurandione, dihydro-2,5-furandione and 1,1-iminobis [2-propanol] -substituted polymer, and / or 2,5-furandione, dihydro- 1,1′iminobis [2-propanol] -substituted polymer is preferable. The water-soluble binder contained in the ink receiving layer is preferably polyvinyl alcohol having a polymerization degree of 2000 or more.
The ink receiving layer is preferably provided by a cast coating method. The ink-receiving layer preferably contains 0.5 to 8 parts by mass of the branched polyesteramide with respect to 100 parts by mass of the water-soluble binder.

  According to the present invention, an ink jet recording sheet having excellent image quality and high viscosity stability of the coating liquid at the time of coating can be obtained regardless of whether the dye ink or the pigment ink is used.

  Hereinafter, embodiments of an ink jet recording medium according to the present invention will be described.

The ink jet recording sheet according to the present invention is provided with an ink receiving layer containing a pigment and a water-soluble binder on at least one surface of a support.
<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. 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.

で表される高分子化合物（２、５−フランジオン、ジヒドロ−、１，１’イミノビス［２−プロパノ−ル］置換ポリマー、CAS番号：362603-93-8）や、式II

で表される高分子化合物（１，３−イソベンゾフランジオン、ジヒドロ−２、５−フランジオン及び１，１イミノビス［２−プロパノ−ル］置換ポリマー、CAS番号：362603-94-9）が挙げられる。 <Ink receiving layer>
(Branched polyester amide)
The ink receiving layer contains a branched polyesteramide. The branched polyester amide means a polymer compound having a branched structure and each branch being a polyester amide.
Examples of branched polyester amides include those of formula I

(2,5-furandione, dihydro-, 1,1′iminobis [2-propanol] -substituted polymer, CAS number: 362603-93-8) represented by the formula II

(1,3-isobenzofurandone, dihydro-2, 5-furandione and 1,1-iminobis [2-propanol] -substituted polymer, CAS number: 362603-94-9) It is done.

  Examples of branched polyesteramides include phthalic anhydride (1,3-isobenzofurandone), succinic anhydride (dihydro-2,5-furandione), maleic anhydride (2,5-furandione), and tetrahydrophthalic anhydride. It can be obtained by polymerizing monomers such as cyclic anhydrides such as glutaric anhydride and di (alkanol) amines such as diisopropanolamine (2-hydroxyisopropylamine) and diisobutanolamine. Specific examples of the branched polyester amide include top brain (trade name, manufactured by Toei Sangyo Co., Ltd.).

When a branched polyesteramide is contained in the ink receiving layer coating solution, the viscosity does not increase with time even if the coating solution is stored for a long time, and the productivity is improved. In particular, in a coating liquid containing polyvinyl alcohol having a high degree of polymerization (2000 or more) as a binder in order to improve the pigment ink suitability as described later, the problem of thickening is remarkable, and branched polyesteramide is Great effect of inclusion.
The ink receiving layer contains 0.1 to 10 parts by mass of a branched polyesteramide based on 100 parts by mass of the following pigment. When the content of the branched polyester amide is less than 0.1 parts by mass, the above-described thickening suppressing effect does not occur. On the other hand, when the content of the branched polyester amide exceeds 10 parts by mass, the printing density by the dye ink is lowered. Although this reason is not clear, it is thought that the transparency of a cast coat layer falls.

  The branched polyesteramide is preferably contained in an amount of 0.5 to 8 parts by mass with respect to 100 parts by mass of the water-soluble binder in the ink receiving layer. The reason why the content ratio of the branched polyesteramide is defined in this way is the same as described above.

(Pigment of ink receiving layer)
The pigment of the ink receiving layer is not particularly limited, and inorganic pigments such as silica, alumina and kaolin, and known organic pigments can be used, but the following colloidal silica and / or synthetic amorphous silica is preferably used.

1. Colloidal silica The primary particle size of colloidal silica used for the pigment of the ink receiving layer is preferably 5 to 55 nm, more preferably 10 to 40 nm. When the primary particle diameter is less than 5 nm, the ink color developability tends to decrease greatly when printing is performed with an ink jet printer using pigment ink. When the primary particle diameter exceeds 55 nm, the voids between the particles increase and the ink absorbency of the glossy layer becomes good, but the opacity increases, so the color developability when ink-jet recording with dye ink tends to decrease. is there.
The ratio of the secondary particle diameter to the primary particle diameter of the colloidal silica (secondary particle diameter / primary particle diameter) is preferably 1.5 to 3.0. If the ratio is less than 1.5, the color developability of the pigment ink and the dye ink may be significantly reduced. The primary particle size and secondary particle size of colloidal silica can be measured by the BET method, dynamic light scattering method, or the like.
By incorporating the colloidal silica having the primary particle size and ratio described above into the gloss layer, the color developability of the pigment ink can be greatly improved. If the primary particle diameter and the ratio are within the above ranges, two or more colloidal silicas having different primary particle diameters and / or ratios can be used in combination.

When the dispersion state of the colloidal silica is observed with a microscope, a large number of spherical single colloidal silica (primary particles) that are continuous (aggregated) are observed. Such an agglomerated state is represented as a peanut shape for convenience. The colloidal silica suitably used in the present invention is a silica (tufted or chain-like) in which at least 5 spherical single colloidal silicas, usually 10 or more, are aggregated when the dispersion state is observed with a microscope. Does not contain colloidal silica). However, the term “not included” as used herein does not mean that the above-described tufted or chain colloidal silica or single colloidal silica is not observed at all when the dispersion state is observed with a microscope. Although colloidal silica may be observed, the said ratio which is a macroscopic physical property should just be 1.5-3.0. Here, the average value of the number of connected primary particles of colloidal silica described above substantially corresponds to the above ratio.
The colloidal silica is preferably synthesized by a sol-gel method using alkoxysilane as a raw material, and the primary particle size (BET method particle size) and secondary particle size (dynamic light scattering method particle size) are controlled according to the synthesis conditions. Examples of colloidal silica that can be used in the present invention include trade name Quartron manufactured by Fuso Chemical Industries.

2. Synthetic Amorphous Silica Synthetic amorphous silica can be broadly classified into wet method silica and gas phase method silica according to its production method, and any of these may be used in the present invention. Synthetic amorphous silica produced by a wet process (hereinafter referred to as “wet process silica” as appropriate) is inferior to gas phase process silica in pigment transparency, but is excellent in paint stability when used in combination with polyvinyl alcohol. Furthermore, compared with gas phase method silica having no internal voids, wet method silica has good dispersibility in the liquid and can increase the coating concentration. Therefore, when wet process silica is used as the pigment for the gloss layer, the pigment ratio in the gloss layer can be increased to increase the absorbability of the gloss layer, so that the ink absorbability can be improved and the color development of the dye ink can be improved. it is conceivable that.
Further, as the wet method silica, there are “gel method silica” produced by a gel method and “precipitation method silica” produced by a precipitation method. As the pigment for the glossy layer, either gel method silica or precipitation method silica may be used alone, or these may be used in combination, but the use of precipitation method silica is preferred because the ink absorbability is further improved.
From the viewpoint of obtaining a high gloss feeling, the preferred secondary particle size of the wet process silica is 1 to 5 μm. Moreover, it is preferable that a BET specific surface area is 150-500 m < ² > / g. As the specific surface area increases, the color developability tends to decrease.

On the other hand, if vapor phase silica is used, the reason is not clear, but the ink receiving layer has good ink wettability, so that unevenness in solid printing tends to be improved.
Vapor phase process silica is also called dry process silica or fumed silica, and is generally produced by flame hydrolysis. Vapor phase silica is specifically produced by vapor phase hydrolysis of volatile silane compounds such as silicon tetrachloride in an oxyhydrogen flame, and the flame temperature, the supply ratio of oxygen and hydrogen, and the raw material tetrachloride. It can be obtained by changing the conditions such as the silicon supply amount. Instead of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane can be used alone or mixed with silicon tetrachloride. Vapor phase process silica is commercially available as Aerosil from Nippon Aerosil Co., Ltd., and is commercially available as Toyoyama Co., Ltd. as Leolosil QS type, and can be easily obtained.
The average primary particle size of the vapor phase method silica is preferably 5 to 50 nm.

Further, (by BET method) a specific surface area of the fumed silica is the is 130m ² / g~300m ² / g, the higher the transparency of the ink receiving layer, and has good stability when formulated into paints This is preferable. When the specific surface area of the vapor phase method silica is smaller than 130 m ² / g, the opacity of the ink receiving layer increases, and problems such as a decrease in printing density when printing with an ink jet printer may occur. When the specific surface area of the vapor phase silica exceeds 300 m ² / g, the transparency of the ink receiving layer is improved and the printing density is improved, but the stability of the paint tends to be inferior and the coating property is lowered. There is.
The blending ratio of the vapor phase silica in the ink receiving layer is preferably 3 to 60 parts by mass of the vapor phase silica with respect to 100 parts by mass of the total amount of colloidal silica and wet type silica. More preferably, the vapor phase silica is 15 to 35 parts by mass with respect to 100 parts by mass of the total amount. When the blending ratio of the vapor phase method silica is small, there is a tendency that the effect of improving unevenness at the time of solid printing is reduced. Further, when the blending ratio of the vapor phase method silica is large, the glossiness of the ink receiving layer tends to be lowered.

3. Mixing ratio of colloidal silica and wet method silica When using colloidal silica and wet method silica in combination, the ratio represented by (mass of the colloidal silica / mass of the synthetic amorphous silica produced by the wet method) is 30 / It is preferable that it is 70-85 / 15, and it is more preferable that it is 40 / 60-70 / 30.
When the ratio is less than 30/70, the blending ratio of the colloidal silica is decreased, and the color developability of the pigment ink tends to be insufficient. In addition, when the ratio exceeds 85/15 and the amount of colloidal silica increases, the color developability of the dye ink tends to decrease, and the operability when applying the gloss layer may decrease. .

4). Other pigments Further, alumina such as aluminum hydroxide, alumina sol, colloidal alumina, pseudo boehmite, etc. (alumina of α-type crystal, θ-type crystal) Other pigments such as alumina, γ-type crystal alumina, etc.), alumina hydrate, kaolin, talc, calcium carbonate, titanium dioxide, clay, and zinc oxide may be contained in the ink receiving layer. The blending ratio of these pigments is preferably 10% by mass or less with respect to the total pigments in the ink receiving layer.

(Water-soluble binder for ink receiving layer)
The water-soluble binder of the ink receiving layer is not particularly limited, and includes, for example, starches such as starch, oxidized starch, and esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; polyvinyl alcohol; polyvinyl pyrrolidone; casein; gelatin; Soy protein; styrene-acrylic resin and derivatives thereof; styrene-butadiene resin, acrylic resin, vinyl acetate resin, vinyl chloride resin, urethane resin, urea resin, alkyd resin, and derivatives thereof may be used alone or in combination. it can. In particular, it is preferable to use polyvinyl alcohol.
1. Polymerization degree of polyvinyl alcohol When the polymerization degree of polyvinyl alcohol is 2000 or more, the print quality (print density, unevenness) at the time of printing with pigment ink is improved, but the ink absorbency when printing with dye ink tends to be inferior. It is in. The reason why the printing density of the pigment ink is improved may be that the higher the degree of polymerization of polyvinyl alcohol, the easier it is to remain on the surface of the glossy layer, and thus the flexibility of the glossy layer becomes higher and cracks (cracks) are reduced. When the cracks in the gloss layer are reduced, it is considered that the colored pigment in the ink tends to stay on the surface of the gloss layer and the color developability (print density) of the pigment ink is improved. For unevenness, the quality is considered to improve for the same reason. On the other hand, when the degree of polymerization of polyvinyl alcohol increases, the solubility of polyvinyl alcohol when it comes into contact with the ink solvent deteriorates, and the ink absorbability of the dye ink tends to decrease.
However, when the polymerization degree of polyvinyl alcohol is increased to 2000 or more, the viscosity stability of the coating solution prepared for the ink receiving layer with time deteriorates and the coating solution tends to increase in viscosity.

On the other hand, when a polyvinyl alcohol having a polymerization degree of less than 2000 is used, the ink absorbability of the dye ink tends to be improved for the reasons described above, and thickening of the coating liquid over time can be suppressed.
In order to improve both the color developability of the pigment ink and the ink absorbability of the dye ink, polyvinyl alcohol having a polymerization degree of 2000 or more and polyvinyl alcohol having a polymerization degree of less than 2000 may be used in combination.

2. Saponification degree of polyvinyl alcohol The lower the saponification degree of polyvinyl alcohol, the more the ink absorbability tends to be improved. This is presumably because the lower the degree of saponification, the higher the hydrophilicity of polyvinyl alcohol and the better the ink absorption. Moreover, it exists in the tendency for color development to improve, so that the saponification degree of polyvinyl alcohol is low. The reason for this is considered to be that the lower the degree of saponification, the higher the transparency, so that the transparency of the coating layer is increased and the printing density is improved.
Polyvinyl alcohol having a low saponification degree includes those having a saponification degree of less than 98%, and polyvinyl alcohol having a high saponification degree includes those having a saponification degree of 98% or more. Here, those having a saponification degree of less than 98% are called partially saponified polyvinyl alcohol and intermediate saponified polyvinyl alcohol. Those having a saponification degree of 98% or more are called fully saponified polyvinyl alcohol.
For example, those having a saponification degree of less than 98% and those having a saponification degree of 98% or more can be used alone or in combination. Also, two or more kinds of polyvinyl alcohol can be used in combination from those having a saponification degree of less than 98% or 98% or more.

  The content ratio of the water-soluble binder contained in the ink receiving layer is preferably 5 to 40 parts by mass.

(Other ingredients)
In addition to the above-described pigment and water-soluble binder, the ink receiving layer includes, for example, a thickener, an antifoaming agent, an antifoaming agent, a pigment dispersing agent, a release agent, a foaming agent, a pH adjusting agent, a surface size. Agent, coloring dye, coloring pigment, fluorescent dye, ultraviolet absorber, antioxidant, light stabilizer, preservative, water-resistant agent, dye fixing agent, surfactant, wet paper strength enhancer, water retention agent, cationic A polymer electrolyte or the like can be appropriately added within a range not impairing the effects of the present invention.

<Coating amount>
The coating amount of the ink receiving layer can be arbitrarily adjusted as long as the surface of the support is covered and sufficient ink absorbability is obtained, but from the viewpoint of achieving both color developability and ink absorbency, It is preferably 5 to 30 g / m ² in terms of solid content.
Further, an undercoat layer having ink absorbability, adhesiveness, and other various functions may be provided between the support and the ink receiving layer. Further, a backcoat layer having ink absorbability, writing property, printer printability, and other various functions may be further provided on the support surface opposite to the surface on which the ink ink receiving layer is provided.
The ink receiving layer may be provided on one side or both sides, and one or more layers may be provided.

<Coating method>
As a method for providing an ink receiving layer on a support, a blade coater, an air knife coater, a roll coater, a brush coater, a kiss coater, a squeeze coater, a curtain coater, a die coater, a bar coater, a gravure coater, a gate roll coater, a short dwell coater, etc. The known coating machine can be appropriately selected from coating methods using on-machine or off-machine. After coating by the above coating method, it is preferable to give gloss by a cast coating method.

<Cast coat method>
As a method for imparting gloss to the surface of the ink receiving layer, a cast coating method using a cast coater is suitable from the viewpoint of production cost. The cast coating method is a method in which a coating liquid mainly composed of a pigment and a water-soluble binder is coated on a support to provide a coating layer, and the coating layer is pressed onto a cast drum to give a gloss finish. It is.
The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressure-bonded to a mirror-finished heating drum while the coating layer is wet, and (2) a wet coating method. Re-wetting method in which the coating layer is once dried or semi-dried and then swelled and plasticized with a rewetting liquid, and the coating layer is pressed against a mirror-finished heating drum and dried. (3) The wet coating layer is gelated by coagulation treatment. There are three types: gelled cast method (coagulation method) in which the coating layer is pressed onto a mirror-finished heating drum and dried. The principle of each method is the same in that the wet coating layer is pressed against the mirror-finished surface to give gloss to the coating layer surface.
In the present invention, gloss is imparted to the surface of the ink receiving layer by forming the ink receiving layer by a cast coating method. Preferably, a gelled cast coating method (coagulation method) is used in that it can provide a surface feel and gloss comparable to silver salt photographs.

As the coagulation liquid used in the coagulation method, those having an action of coagulating the water-soluble binder in the wet coating layer, for example, calcium such as formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid, Solutions of various salts such as zinc and magnesium are used. In particular, when polyvinyl alcohol is used as the water-soluble binder, it is preferable to use a liquid containing boric acid and borate as the coagulating liquid.
By using a mixture of boric acid and borate as the coagulation liquid, it becomes easy to make the coating layer hardness at the time of coagulation appropriate, and good glossiness can be imparted. The method for applying the coagulating liquid is not particularly limited as long as it can be applied to the coating layer, and can be appropriately selected from known methods (for example, roll method, spray method, curtain method, etc.).
Moreover, a release agent can be added to the coating liquid and / or the coagulating liquid as necessary. The melting point of the release agent is preferably 90 to 150 ° C, and particularly preferably 95 to 120 ° C. In the above temperature range, since the melting point of the release agent is substantially equal to the temperature of the mirror finish surface, the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above characteristics, but it is preferable to use a polyethylene wax emulsion.

<Example>
EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this. Unless otherwise specified, “part” and “%” described below represent “part by mass” and “% by mass”, respectively.

(Manufacture of support)
10 parts of talc, 1.0 part of aluminum sulfate, 0.1 part of synthetic sizing agent, and 0.02 part of yield improver for a pulp slurry consisting of 100 parts of hardwood bleached kraft pulp (L-BKP) with a beating degree of 285 ml Was added and paper was made with a paper machine. During paper making, 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 170 g / m ² .

(Formation of ink receiving layer)
One side of this support was coated with a blade coater using the following coating liquid A so that the coating amount was 8 g / m ^2, and air-dried at 140 ° C. Next, 20 g / m ^{2 of} the ink receiving layer coating liquid B is applied to the surface coated with the coating liquid A using a roll coater, and while the coating layer is in a wet state, the coagulating liquid C Was applied to the coating layer to solidify the coating layer. Subsequently, the coating layer was pressure-bonded to the mirror-finished surface heated through a press roll, and the mirror surface was copied to obtain a 198 g / m ² inkjet recording sheet.
Coating liquid A: 100 parts of precipitated silica (Fine Seal X-37B: wet method silica manufactured by Tokuyama Co., Ltd., specific surface area 287 m ² / g) is blended as a pigment, and styrene-butadiene latex (as a water-soluble binder) LX438C: trade name of Sumitomo Chemical Co., Ltd. 5 parts and polyvinyl alcohol (PVA117: product name of Kuraray Co., Ltd.) 24 parts, sizing agent (Polymaron 360: trade name of Arakawa Chemical Co., Ltd.) ) 5 parts was mixed to prepare an aqueous coating solution having a concentration of 20%.
Coating liquid B: Peanut-like colloidal silica as a pigment (Quarton PL-2: Fuso Chemical Industry Co., Ltd., primary particle size 22.9 nm, secondary particle size 51.0 nm, ratio of secondary particle size to primary particle size 1.83) 50 parts of precipitation silica (Fine Seal X-37: wet method silica manufactured by Tokuyama Corporation, specific surface area 275 m ² / g) is blended and partially saponified as a binder. 20 parts of polyvinyl alcohol (PVA-224: trade name of Kuraray Co., Ltd., degree of saponification 88%, degree of polymerization 2400) is blended, and further 2 parts of mold release agent (Maycatex HP50: manufactured by Meisei Chemical Co., Ltd.) Furthermore, 4 parts of branched polyesteramide (Top Brain P4: trade name of Toei Sangyo Co., Ltd.) was blended to prepare a coating solution having a concentration of 27%.
Coagulating liquid C: The compounding ratio represented by (borax / boric acid) is 2, the concentration when borate is converted to Na ₂ B ₄ O ₇ and boric acid is converted to H ₃ BO ₃ is 6%. And 0.25% release agent (Maycatex HP50: manufactured by Meisei Chemical Co., Ltd.), 0.5% penetrant (Pionine D-3120-W: trade name manufactured by Takemoto Yushi Co., Ltd.), and pH adjuster A coagulation liquid was prepared by blending 0.25% malic acid.

  In the coating liquid B, instead of the colloidal silica (Quarton PL-2), peanut-shaped colloidal silica (Quarton PL-3: Fuso Chemical Industries, Ltd., primary particle size 35.6 nm, secondary particle size 65.0 nm) An ink jet recording sheet was obtained in exactly the same manner as in Example 1, except that 50 parts of the ratio of the secondary particle size to the primary particle size was 1.83) and a coating solution having a concentration of 27% was prepared. It was.

In the coating liquid B, the amount of the colloidal silica (Quortron PL-2) was changed to 60 parts, the amount of the precipitated silica (Fine Seal X-37) was changed to 20 parts, and further, as a pigment, Except that 20 parts of gas phase method silica (Aerosil 300: trade name of Nippon Aerosil Co., Ltd.) having a specific surface area of about 300 m ² / g was blended to prepare a coating solution having a concentration of 27%, exactly the same as Example 1. Thus, an ink jet recording sheet was obtained.

In the coating liquid B, the amount of the colloidal silica (Quortron PL-2) was changed to 60 parts, the amount of the precipitated silica (Fine Seal X-37) was changed to 35 parts, and further, as a pigment, Except that a gas phase method silica (Aerosil 300: trade name of Nippon Aerosil Co., Ltd.) having a specific surface area of about 300 m ² / g was blended to prepare a coating solution having a concentration of 27%, exactly the same as Example 1. Thus, an ink jet recording sheet was obtained.

  In the coating liquid B, instead of the partially saponified polyvinyl alcohol (PVA-224), 20 partially saponified polyvinyl alcohol (PVA-235: trade name of Kuraray Co., Ltd., saponification degree 88%, polymerization degree 3500). An ink jet recording sheet was obtained in the same manner as in Example 1 except that a part of the mixture was prepared and a coating solution having a concentration of 27% was prepared.

  In the coating liquid B, instead of the partially saponified polyvinyl alcohol (PVA-224), 20 partially saponified polyvinyl alcohol (PVA-624: trade name of Kuraray Co., Ltd., saponification degree 95%, polymerization degree 2400). An ink jet recording sheet was obtained in the same manner as in Example 1 except that a part of the mixture was prepared and a coating solution having a concentration of 27% was prepared.

  In the coating liquid B, instead of the partially saponified polyvinyl alcohol (PVA-224), 20 partially saponified polyvinyl alcohol (PVA-420: trade name of Kuraray Co., Ltd., saponification degree 80%, polymerization degree 2000) is 20. An ink jet recording sheet was obtained in the same manner as in Example 1 except that a part of the mixture was prepared and a coating solution having a concentration of 27% was prepared.

  An ink jet recording sheet was obtained in exactly the same manner as in Example 1 except that the coating amount of the partially saponified polyvinyl alcohol (PVA-224) in coating liquid B was changed to 5 parts.

  In the coating liquid B, instead of the partially saponified polyvinyl alcohol (PVA-224), 20 partially saponified polyvinyl alcohol (PVA-205: trade name of Kuraray Co., Ltd., saponification degree 88%, polymerization degree 500). An ink jet recording sheet was obtained in the same manner as in Example 1 except that a part of the mixture was prepared and a coating solution having a concentration of 27% was prepared.

  In coating liquid B, Example 1 except that 20 parts of oxidized starch (MS # 3600) was blended in place of the partially saponified polyvinyl alcohol (PVA-224) to prepare a coating liquid with a concentration of 27%. In the same manner as above, an inkjet recording sheet was obtained.

<Comparative Example 1>
An ink jet recording sheet was obtained in exactly the same manner as in Example 1 except that the coating liquid B did not contain the branched polyesteramide.

<Comparative Example 2>
An ink jet recording sheet was obtained in exactly the same manner as in Example 1 except that the amount of the branched polyesteramide was changed to 15 parts in the coating liquid B.

<Evaluation>
(1) Characteristics of colloidal silica (1-1) Measurement of primary particle diameter The specific surface area of colloidal silica used in coating liquid B was measured by a nitrogen adsorption method, and the primary particle diameter was determined by calculation according to the following formula.
d = 6000 / (ρ × S)
In the formula, d: primary particle diameter (nm), ρ: silica density (= 2.2 g / m ³ ), S: specific surface area (m ² / g).
(2-2) Measurement of secondary particle diameter The secondary particle diameter of the colloidal silica used in the coating liquid B was measured using a particle size measuring device (ZETASIZER 3000HAS manufactured by MALVERN INSTRUMENTS).

(2) Printability (2-1) Print density As the ink jet printer, a dye ink printer (PM-950C, manufactured by Seiko Epson Corporation) and a pigment ink printer (PX-G900, manufactured by Seiko Epson Corporation) were used. Black, cyan, magenta, and yellow were solid printed on the ink receiving layer surface of the inkjet recording sheet by each printer, and the print density was measured with a Macbeth densitometer (RD-19, manufactured by Gretag Macbeth). The following comprehensive evaluation was performed according to the measured print density. If both the evaluation with the dye ink and the overall evaluation with the pigment ink are Δ or more, there is no practical problem.
(Evaluation criteria for dye ink)
A: Total of four printing densities is 9.5 or more B: Total of four printing densities is 9.0 or more and less than 9.5 Δ: Total of four printing densities is 8.5 or more and less than 9.0 ×: Printing Total density of less than 8.5 colors (evaluation criteria for pigment ink)
A: The total of four printing densities is 5.0 or more B: The total of four printing densities is 4.5 or more and less than 5.0 Δ: The total of four printing densities is 4.0 or more and less than 4.5 ×: Printing The total density of 4 colors is less than 4.0

(2-2) Ink absorbability As an ink jet printer, a dye ink printer (PM-970C, manufactured by Seiko Epson Corporation) was used. The degree of blur (border blur) at each color boundary portion of the solid print portion was visually evaluated by a five-step evaluation. The visual evaluation 5 was the best, and the visual evaluation 1 was the worst (conspicuous bleeding). This five-step evaluation was performed, and a comprehensive evaluation was performed using the following indicators. If the overall evaluation is Δ or more, there is no practical problem.
◎: Visual evaluation of boundary bleeding is 5 ○: Visual evaluation of boundary bleeding is 4.5 or more Δ: Visual evaluation of boundary bleeding is 4 ×: Visual evaluation of boundary bleeding is 3.5 or less

(2-3) Pigment Unevenness (PX-G900, manufactured by Seiko Epson Corporation) was used as an inkjet printer. The degree of unevenness of each color of the solid printing portion was visually evaluated in five stages. The visual evaluation 5 was the best, and the visual evaluation 1 was the worst (conspicuous unevenness). This five-step evaluation was performed, and a comprehensive evaluation was performed using the following indicators. If the overall evaluation is Δ or more, there is no practical problem.
◎: Visual evaluation of unevenness is 5 ○: Visual evaluation of unevenness is 4.5 or more Δ: Visual evaluation of unevenness is 4 ×: Visual evaluation of unevenness is 3.5 or less

(3) Evaluation of Viscosity Stability Viscosity stability was evaluated by the rate of increase in viscosity after the coating liquid B was allowed to stand for 24 hours.
A: The viscosity after standing for 24 hours is less than 120% of the value immediately after dispensing. ○: The viscosity after standing for 24 hours is not less than 120% and less than 150% of the value immediately after dispensing. Δ: The viscosity after standing for 24 hours. Is not less than 150% and less than 180% of the value immediately after dispensing ×: 180% or more of the value immediately after dispensing after 24 hours of standing

  The obtained results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, in each example, the image quality (print density, ink absorbency, print unevenness) is excellent regardless of whether the dye ink or the pigment ink is used. The viscosity stability of the working fluid became high.
In Example 2 in which peanut-shaped colloidal silica having a large particle size was used as the pigment of the ink receiving layer, the image quality when using pigment ink was particularly excellent.
Further, in Example 8 in which the amount of polyvinyl alcohol used as the water-soluble binder of the ink receiving layer is small, the polymerization degree of polyvinyl alcohol is small (less than 2000) in Example 9, and as the water-soluble binder. In Example 10 using starch instead of polyvinyl alcohol, the image quality when using the dye ink was slightly inferior to the other examples, but there is no practical problem.

On the other hand, in the case of Comparative Example 1 in which the ink-receiving layer coating solution did not contain branched polyesteramide, the viscosity stability of the ink-receiving layer coating solution deteriorated, and the coating solution increased in viscosity over time.
In the case of Comparative Example 2 in which the blended amount of the branched polyesteramide in the ink receiving layer coating liquid exceeded 10 parts (relative to 100 parts of pigment), the printing density with the dye ink was lowered.

Claims (5)

An ink receiving layer containing a pigment and a water-soluble binder is provided on at least one surface of the support, and 0.1 to 10 parts by mass of branched polyesteramide is added to the ink receiving layer with respect to 100 parts by mass of the pigment. An ink jet recording sheet containing The branched polyesteramide may be 1,3-isobenzofurandione, dihydro-2,5-furandione and 1,1-iminobis [2-propanol] -substituted polymer, and / or 2,5-furandione, dihydro- The inkjet recording sheet according to claim 1, which is a 1,1 ′ iminobis [2-propanol] substituted polymer. The inkjet recording sheet according to claim 1, wherein the water-soluble binder contained in the ink receiving layer is polyvinyl alcohol having a polymerization degree of 2000 or more. The inkjet recording sheet according to claim 1, wherein the ink receiving layer is provided by a cast coating method. The inkjet recording sheet according to any one of claims 1 to 4, wherein the ink receiving layer contains 0.5 to 8 parts by mass of the branched polyesteramide with respect to 100 parts by mass of the water-soluble binder.