JPH07172039A - Ink-jet recording sheet - Google Patents

Abstract

PURPOSE:To provide a slightly coating ink-jet recording sheet which is excellent in absorption of ink, has high image density or color properties and obtains a recording dot which is close to a prefect round. CONSTITUTION:In an ink-jet recording sheet on a substrate of which an ink receptive layer is provided, the substrate is preferably neutral paper which is comprised by containing calcium carbonate as a filler and an anionic neutral rosin sizing agent as an internal additive sizing agent and an ultraparticulate inorganic pigment which has the primary particle diameter of not exceeding 100nm, more preferably a surface sizing agent having nonpherical cationic colloidal silica and a 10C or higher hydrophobic group are contained. Further preferably the amount of coating of the ink receptive layer and the amount of a surface sizing agent are respectively specified.

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, and more specifically, it has excellent ink absorbency, small ink bleeding unevenness, and high image density and chromaticity recorded in double colors. The handling relates to an ink jet recording sheet of a slightly coated type, which is closer to high quality paper.

[0002]

2. Description of the Related Art An ink jet recording system is one in which minute droplets of ink are ejected according to various operating principles to record an image, characters, etc. on an ink jet recording sheet, but high speed, low noise and multicolor are required. It is rapidly spreading because it is easy and does not require developing and fixing. Further, an image obtained by a multicolor ink jet system is being widely applied to the full-color image recording field because it can obtain a recording comparable to that of the multicolor printing by the plate making system or the printing by the color photographic system. .

As a recording sheet used in this ink jet recording system, efforts have been made from the aspect of the apparatus and ink composition so as to use high-quality paper or coated paper used for ordinary printing and writing. However, as the performance of the inkjet recording apparatus has been improved and the applications have been expanded, such as speeding up, high definition, or full-color of the apparatus, more advanced characteristics have been required for the recording sheet.

That is, as the recording sheet, the density of print dots is high, the color tone is bright and vivid, the ink does not flow out or bleed even when the print dots overlap, and It is required that the diffusion of dots in the lateral direction is not unnecessarily large and that the periphery is smooth and does not blur.

As the form of the ink jet recording sheet, an ink receiving layer is provided on a support surface such as a plain paper type represented by so-called high-quality paper / bonded paper and paper such as high-quality paper, synthetic paper, synthetic resin film and the like. It is roughly divided into coating type.

The coating type includes a low coating type of about 1 to 10 g / m ^{2, a} medium coating type of about 10 to 20 g / m ² , and 20 g / m ^2.
There are high coating type inkjet recording sheets of m ² or more.

Particularly, in recent years, even the low coating type, the minimum coating amount of 0.5 to 5 g / m ² of the fine coating type is close to that of plain paper, and is preferable in terms of appearance and handling. This fine coating type is desired. However, in the case of color recording, not only single-color recording of yellow, magenta, cyan, and black but also superposition of these colors is performed for multi-color recording, and the ink adhesion amount becomes extremely large. Since the ink cannot be completely absorbed by the coating layer, it is necessary to use a base paper of a relatively low size so that the base paper itself of the support absorbs a part of the adhered ink.

In order to solve the above problem, Japanese Patent Publication No. 3-2
Japanese Patent No. 6665 discloses an example of an inkjet recording sheet in which a coating layer containing fine silica particles and a water-soluble polymer binder is provided on a base paper having a Stöcht sizing degree of 4 seconds or less based on a basis weight of 60 g / m ^2. JP-A-59-38087 discloses an example of an ink jet recording material in which an ink absorption layer is provided on a substrate having a size degree of 0 to 10 seconds. Has a Steckigt size of 0
An example of an inkjet recording paper in which polyvinyl pyrrolidone or the like is impregnated into a base paper for 5 seconds is disclosed.

[0009] In these publications, a base paper having a low size is used. This is because when the ink is applied to the inkjet recording sheet, the coating layer, that is, the excess amount of the ink absorbed by the ink receiving layer is absorbed by the base paper, and the base paper has a low size degree. Trying to solve.

However, when attempting to absorb excess ink by using a low-sized base paper, the uniformity of the sizing property in a minute area differs due to the difference in the sizing agent, so that the bleeding unevenness in the width direction of the base paper is uneven. And a clear recorded image is not obtained.

[0011]

As described above, when the ink receiving layer has a low coating amount, the base material having a relatively low size is used to absorb a part of the attached ink by the support itself. However, the uniformity of the sizing property in a minute area varies depending on the size.

Further, the ink-receiving layer coated on the support is not uniformly coated on the surface of the entangled irregularities of the pulp fibers, so that the pulp fibers are exposed to a great extent. Therefore, the deposited ink penetrates into the support, that is, the base paper along the exposed pulp fibers without forming recording dots having a desired shape on the surface of the ink receiving layer, and the recording dots spread and spread. It will take on a shape. In other words, the recorded image lacks sharpness.

In the present invention, among the ink jet recording sheets, in the case of a slightly coated ink jet recording sheet which is closer to plain paper, the recorded image density and color property are particularly high, and recording dots and inks close to a perfect circle are formed. It is an object of the present invention to obtain an inkjet recording sheet which can obtain an image without bleeding unevenness and also has ink absorbability.

[0014]

As a result of intensive studies in view of the above, the inventors of the present invention have found that the lateral diffusion of ink is appropriate, the periphery of dots is smooth, and multicolor printing is performed. The present invention has led to the invention of an ink jet recording sheet that has a high image density and a bright and vivid color tone while having ink absorbability without causing ink to overflow and bleed.

That is, the ink jet recording sheet of the present invention is an ink jet recording sheet in which an ink receiving layer is provided on a support, and in the ink receiving layer composition, a linear or branched saturated or unsaturated carbon atom having 10 or more carbon atoms. It is characterized by containing a surface sizing agent in which at least one kind of saturated hydrocarbon is introduced into a molecule as a hydrophobic group, and an ultrafine particle inorganic pigment having a primary particle diameter of 100 nm or less.

The ink jet recording sheet of the present invention is preferably neutral paper containing calcium carbonate as a filler and an anionic neutral rosin sizing agent as an internal sizing agent.

Further, the ultrafine particle inorganic pigment in the ink receiving layer is preferably non-spherical cationic colloidal silica.

The ink jet recording sheet of the present invention preferably has a coating amount of the ink receiving layer of 0.5 to 5.0.
g / m ² and the surface sizing agent is 0.2 to 5% by weight of the ink receiving layer composition.

Hereinafter, the ink jet recording sheet of the present invention will be described in detail. From the characteristics of the slightly coated type inkjet recording sheet to which the present invention is applicable, the sizing degree of the base paper has a great influence on the image density, the ink absorption speed, and the resolution. For example, as for the influence on the image density, when printing on a small size paper, the ink and the dye deeply penetrate into the inside of the base paper layer, so that the image density is lowered and a satisfactory print quality cannot be obtained. Further, regarding the influence on the ink absorption speed, in the case of color printing in which colors are expressed by mixed colors, when the second color is printed, the ink of the first color is absorbed or hardly remains on the surface in terms of resolution. It is needed and it is one of the important characteristics.

Further, even when printing on strong size paper, the dye does not selectively stay on the paper surface, and the improvement in image density and dot roundness is negligible, which has a negative effect on the absorption speed. Is big.

As described above, the slightly coated type ink jet recording sheet needs to absorb the ink inside the base paper layer. In the coat type, fine powder silica having a large oil absorption amount as disclosed in Japanese Patent Laid-Open No. 133685/1993 is usually used as an ink absorbing material. However, although the powdered silica is excellent in terms of absorption amount, it is somewhat inferior in terms of dye adsorption.

As described above, there are some parts that can be controlled by the size of the base paper and the ink absorbing material, but it has been found that it is impossible to balance the image density, chromaticity and dot shape in multicolor printing. did.

In terms of dye adsorption, the primary particle size is 10
It has been found that the dye in the ink can be selectively adsorbed by using an ultrafine particle inorganic pigment of 0 nm or less, preferably a non-spherical cationic colloidal silica, but this alone improves dot shape, that is, ink bleeding. It became clear that it cannot be prevented.

Further, as a result of earnest studies by the present inventors, in order to prevent ink bleeding on the paper surface and to improve the dot shape, the base paper having ink absorbability has 10 carbon atoms with high hydrophobicity. By applying a surface sizing agent that introduces at least one of the above linear or branched saturated or unsaturated hydrocarbons into the molecule as a hydrophobic group, it is possible to obtain a dot shape and absorption rate close to a perfect circle at the same time. There was found.
However, it was also found that the hydrophobic group of the surface sizing agent, which is a commonly used polymer such as styrene-acrylic acid, acrylic acid, or styrene-maleic acid, does not provide a sufficient effect.

On the support described below, an ink-receiving layer composition mainly composed of an ultrafine inorganic pigment having a primary particle diameter of 100 nm or less, preferably non-spherical cationic colloidal silica and the above-mentioned specific surface sizing agent used in the present invention is used. It was found that the image density and the color property can be improved by controlling the dot diameter and the ink absorption rate by applying the composition to the present invention, and the present invention has been completed.

In the ink jet recording sheet of the present invention, the support is preferably a neutral paper containing calcium carbonate as a filler and an anionic neutral rosin sizing agent as an internal sizing agent. I am trying. The reason for this is that the anionic neutral rosin sizing agent in the neutral papermaking has a size developing property in the minute region,
Since the uniformity is exhibited at a comparatively low size degree, the dot shape of the ink absorbed in the base paper portion is rarely deformed. On the other hand, the alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA) sizing agents that are commonly used in neutral papermaking have uneven sizing properties in the micro area, and it is necessary to absorb ink in the base paper part. In the case of a slightly coated type inkjet recording sheet, the shape factor of dots becomes slightly large.

The neutral rosin sizing agent as used in the present invention means p
It is an emulsion type rosin sizing agent obtained by emulsifying various surfactants or water-soluble polymers used in the neutral region of H6-9. Here, as the rosin substance,
Roms such as gum rosin, wood rosin, tall oil rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, aldehyde-modified rosin and rosin ester, and further rosins and acrylic acid, maleic anhydride, fumaric acid, itaconic acid, etc. Examples of the heated reaction product with α, β-unsaturated carboxylic acid include, but insolubilization treatment such as polymerization and water resistance can be performed for the purpose of suppressing elution of the rosin substance in the neutral region.

The ionic character of the neutral rosin sizing agent depends on various surfactants or water-soluble polymers used during emulsification.
Anionic or cationic can be selected. In the present invention, various conventionally used anionic, nonionic, cationic or amphoteric retention aids, polyethylene oxide, polyamide resins, hydrophilic crosslinked polymer particle dispersions, etc. or their derivatives or modified products, etc. As a result of studying a retention system in which a compound such as colloidal silica and bentonite is appropriately combined and used, anionic neutral rosin sizing agent and cationic or amphoteric hydrophilic crosslinked polymer particle dispersion or the like or a derivative thereof Alternatively, it is desirable to combine a yield-improving agent or a retention system whose constituent is a modified product.

Further, for the purpose of expressing the sizing property of the neutral rosin sizing agent, a polyvalent metal compound of aluminum (for example, a sulfuric acid band, polyaluminum chloride, polyaluminum silicate sulfate, sodium aluminate, etc.) is blended. Of course.

As the ultrafine particle inorganic pigment used in the present invention, the following can be exemplified. For example, silica (colloidal silica), alumina or alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or its hydrate, pseudo-boehmite, etc.), surface-treated cationic colloidal silica, aluminum silicate, magnesium silicate, Magnesium carbonate and the like can be mentioned, and non-spherical cationic colloidal silica is preferable. Furthermore, it is more preferable if the primary particles are porous, but even if they are non-porous, they aggregate during preparation of the coating solution or further aggregate during drying of the coating, forming a porous surface-coated surface on the pulp fiber surface. Preferably. In particular, in the present invention, one pulp fiber on the surface of the base paper has a width of 1
It is preferable to coat the pulp fiber itself with an ultrafine particle inorganic pigment having an average particle size of 1/00 or less.

The surface sizing agent used in the present invention is a polymer of maleic anhydride or a derivative thereof which introduces a commercially available olefin or unsaturated olefin as a hydrophobic group, styrene, α-methylstyrene, divinylbenzene or the like. Acrylic acid or methacrylic acid, which is a derivative introduced as a hydrophobic group, or a polymerized product thereof with a derivative, as well as a ketene dimer or succinic anhydride, is protected by a colloidalizing agent with an emulsifier having a colloid ability. It is a sizing agent in which a linear or branched saturated or unsaturated hydrocarbon of several tens or more is replaced with at least one kind of hydrophobic group or is newly introduced as a hydrophobic group.

The ink receiving layer composition of the present invention contains, in addition to the above main components, a water-soluble polymer binder which is usually used,
For example, polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, carboxymethyl cellulose, cellulose derivatives such as hydroxyethyl cellulose, casein, gelatin, soybean protein, silyl modified polyvinyl alcohol, etc .; maleic anhydride resin, styrene-butadiene copolymer, Conjugated diene copolymer latex such as methyl methacrylate-butadiene copolymer; polymer or copolymer of acrylic acid ester and methacrylic acid ester,
Acrylic polymer latex such as polymer or copolymer of acrylic acid and methacrylic acid; vinyl polymer latex such as ethylene vinyl acetate copolymer; or functional group-containing unit such as carboxyl group of these various polymers Polymer latex modified with functional groups; water-based binder such as thermosetting synthetic resin such as melamine resin, urea resin; polymethylmethacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, alkyd resin Examples of the binder include synthetic resin binders such as the above, and at least one kind can be used. Further, a cationic resin may be used in combination for the purpose of fixing a conventionally known dye.

The pulp for base paper according to the present invention is LBK.
Chemical pulp such as P, NBKP, GP, PGW, RMP,
Mechanical pulp such as TMP, CTMP, CMP, CGP, D
Used paper pulp such as IP and wood pulp such as can be used. Further, the filler must contain calcium carbonate, but it can be used in combination with a conventionally known pigment. Further, in the paper material, together with the internally added sizing agent and the polyvalent metal compound of Al as described above, in a range that does not impair the desired effect of the present invention,
Binder, fixing agent, yield improving agent, cationizing agent,
Various additives such as a paper strengthening agent can be used if necessary. These raw materials are mixed and produced by various devices such as a Fourdrinier paper machine, a cylinder paper machine, and a twin wire paper machine, but in the present invention, a base paper that has not been size-pressed, further, a base paper, starch, Both the size-pressed base papers such as polyvinyl alcohol are included. The surface coating may be used as it is on such a base paper, or a calender device such as a machine calender, a TG calender or a soft calender may be used for the purpose of controlling flattening.

As the ink receiving layer composition of the present invention, in addition to the ultrafine particle inorganic pigment and the surface sizing agent of the present invention, a surface of a commonly used polymer such as styrene-acrylic acid, acrylic acid, styrene-maleic acid, etc. A sizing agent, a dye, a fluorescent whitening agent, a dye fixing agent, a surface strength agent and the like can be contained as necessary.

When coating the ink receiving layer of the present invention,
Various blade coaters, roll coaters, air knife coaters, bar coaters, rod coaters, gate roll coaters,
Various devices such as a curtain coater, a short dwell coater, a gravure coater, a flexo gravure coater, and a size press can be used on-machine or off-machine. However, in the present invention, an air knife coater or a gate roll coater is preferable. Further, after coating, it may be finished using a calendar such as a machine calendar, a TG calendar, a super calendar or a soft calendar.

The aqueous ink referred to in the present invention is a recording liquid containing the following colorant, liquid medium and other additives.
Examples of the colorant include water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes and food dyes.

As the solvent for the aqueous ink, water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, C1-C4 alkyl alcohols such as isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol, polypropylene glycol Polyalkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol,
Alkylene glycols having 2 to 6 alkylene groups such as thiodiglycol, hexylene glycol and diethylene glycol; polyhydric alcohols such as glycerin, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol and monomethyl ether Lower alkyl ethers and the like can be mentioned. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferable. Other additives include, for example, a pH adjusting agent, a sequestering agent, an antifungal agent, a viscosity adjusting agent,
Surface tension adjusting agents, wetting agents, surfactants, rust preventives and the like can be mentioned.

The ink jet recording sheet according to the present invention is not limited to use as an ink jet recording sheet, but can be used as any recording sheet using a liquid ink during recording. For example, an ink sheet in which a heat-fusible ink containing a heat-fusible substance, a pigment or the like as a main component is coated on a thin support such as a resin film, high-density paper, or synthetic paper is heated from the back surface of the ink sheet, An image-receiving sheet for thermal transfer recording that melts and transfers ink, an inkjet recording sheet that heat-melts a heat-melting ink to form fine droplets, and flight recording, an inkjet recording sheet that uses an ink in which an oil-soluble dye is dissolved, An image receiving sheet corresponding to a light and pressure sensitive donor sheet using microcapsules containing a polymerizable monomer and a colorless or colored dye / pigment may be mentioned.

The common point of these recording sheets is that the ink is in a liquid state at the time of recording. The liquid ink penetrates or spreads in the depth direction or the horizontal direction of the ink receiving layer of the recording sheet before being cured, solidified, or fixed. The various recording sheets described above require absorptivity according to their respective systems, and the inkjet recording sheet of the present invention can be used as the various recording sheets described above without any limitation.

Further, the ink jet recording sheet according to the present invention can be used as a recording sheet for heating and fixing the toner of the electrophotographic recording system which is widely used in copying machines, printers and the like.

[0041]

The ink jet recording sheet of the present invention exhibits effective characteristics not only in monochrome but also in color recording. Although its mechanism is not clearly understood, it is presumed that it is expressed by the following actions.

That is, in the ink jet recording sheet of the present invention, the surface of the ink receiving layer can have a kind of water repellent function by using a specific surface sizing agent in the ink receiving layer. The function of the surface sizing agent is to control the permeation speed of the ink that permeates into the base paper from the ink receiving layer when the ink is applied to the ink receiving layer. The dye in the ink can be quickly adsorbed in the fine voids of the ultrafine inorganic pigment.

Furthermore, when a base paper containing calcium carbonate as a filler and an anionic neutral rosin sizing agent as an internally added sizing agent is used, the size expression in the minute region is high due to the internally added sizing agent, and the longitudinal direction of the base paper is high. Direction (thickness direction)
It is possible to suppress the spread of the base paper in the width direction by penetrating the ink.

As a result, the ink dot shape on the surface of the ink receiving layer can be made into a perfect circle, and although it is a finely coated paper, the image density is high, the ink absorbency is excellent, and the print quality equal to or higher than that of the coat type is obtained. It seems that it has become possible to obtain it.

[0045]

EXAMPLES The present invention will be described in detail below with reference to examples. The present invention is not limited to the examples.
All parts and% in the following are by weight.
The value showing the coating amount is the weight after drying unless otherwise specified.

The surface sizing agent of the present invention was prepared in the following Preparation Example 1 and Preparation Example 2. [Preparation Example 1] A salt of a linear saturated fatty acid having 10 carbon atoms reacted with phosphorus trichloride is subjected to a dehydrochlorination reaction in the presence of a tertiary amine catalyst to form a ketene dimer having 10 carbon atoms. Obtained. Next, cationized starch that was heated and dissolved (trade name:
Kate F, Oji National Co., Ltd.) 18 parts, sodium polystyrene sulfonate 2 parts and carbon number 10 ketene dimer 80 parts and adjusted so that the solid content concentration is 20%,
It was melted at 75 degrees and emulsified under the conditions of 200 kg / m ² using a high pressure discharge type homogenizer to prepare an emulsion of a surface sizing agent composed of a ketene dimer having 10 carbon atoms.

[Preparation Example 2] An emulsion of a surface sizing agent comprising a ketene dimer having 8 carbon atoms was prepared under the same conditions as in Preparation Example 1 except that a straight chain saturated fatty acid having 8 carbon atoms was used.

[Preparation of base paper 1] Freeness 380 mlcsf
LBKP 70 parts, freeness 450 mlcsf NBKP
Light calcium carbonate (trade name: TP-121, manufactured by Okutama Kogyo Co., Ltd.) as a filler in 30 parts of pulp slurry.
10 parts, amphoteric starch (trade name: Cato3210, manufactured by Oji National Co., Ltd.) 0.8 part, sulfuric acid band 0.6 part, alkyl ketene dimer type sizing agent (trade name: size pine K)
903 (manufactured by Arakawa Chemical Co., Ltd.) was added, and the paper was dried with a Fourdrinier paper machine and machine calendered to prepare a base paper having a basis weight of 80 g / m ² . The prepared paper had a Steckigt sizing degree of 30 seconds.

[Preparation of base paper 2] Freeness 450 mlcsf
LBKP 90 parts, freeness 480 mlcsf NBKP
Light calcium carbonate (trade name: TP-121, manufactured by Okutama Kogyo Co., Ltd.) as a filler in 10 parts of pulp slurry.
10 parts, amphoteric starch (trade name: Cato 3210, manufactured by Oji National Co., Ltd.) 0.8 part, sulfuric acid band 1.0 part, anionic neutral rosin sizing agent (trade name: NT-80, manufactured by Arakawa Chemical Co., Ltd.) 6 parts were added, paper-making was dried with a Fourdrinier paper machine, and machine calendering was carried out to prepare a base paper having a basis weight of 85 g / m ² . The prepared paper had a Steckigt sizing degree of 27 seconds.

Example 1 100 g of spherical cationic colloidal silica (trade name: Snowtex-AK (3), primary particle diameter 10 to 20 nm, manufactured by Nissan Chemical Industries, Ltd.) as an ultrafine particle inorganic pigment was prepared on the base paper 1 prepared as described above. Parts, water-soluble polymer as adhesive (trade name: PVA117, manufactured by Kuraray Co., Ltd.) 50 parts, cationic resin as dye fixing agent (trade name: Sumireze Resin 100)
1, cation charge 3.5 meq./g, Sumitomo Chemical Co., Ltd.) 30
Part, and 1 part of a surface sizing agent having a hydrophobic group having 16 carbon atoms (trade name: Carbumeule SS362, manufactured by Nippon PMC Co., Ltd.) were uniformly mixed to prepare an ink-receiving layer coating liquid having a solid content concentration of 10%. . Using a roll coater, the prepared ink-receiving layer coating liquid is coated on the above base paper so as to have a dry solid content of 2.0 g / m ² , dried, and supercalendered to have a Beck smoothness of 80 seconds. Then, an inkjet recording sheet of Example 1 was produced.

Example 2 Example 2 was repeated except that spherical colloidal silica (trade name: Snowtex YL, average primary particle size 65 nm, manufactured by Nissan Chemical Industries, Ltd.) was used in place of the ultrafine inorganic pigment used in Example 1. An ink jet recording sheet of Example 2 was prepared in the same manner as in Example 1.

Example 3 Instead of the ultrafine particle inorganic pigment used in Example 1, alumina hydrate (trade name: Cataloid AS-3, primary particle size about 1) was used.
0 nm, manufactured by Catalysts & Chemicals Industry Co., Ltd.) was used.
An inkjet recording sheet of Example 3 was prepared in the same manner as in.

Example 4 Instead of the ultrafine inorganic pigment used in Example 1, needle-like cationic colloidal silica (trade name: ST-UP-AK) was used.
An inkjet recording sheet of Example 4 was produced in the same manner as in Example 1 except that (1), primary particle diameter 11 to 12 nm, manufactured by Nissan Chemical Industries, Ltd. was used.

Example 5 Instead of the ultrafine particle inorganic pigment used in Example 1, plate-like cationic colloidal silica (trade name: PT-3-AK) was used.
An inkjet recording sheet of Example 5 was produced in the same manner as in Example 1 except that (1), primary particle diameter 4 to 6 nm, manufactured by Nissan Chemical Industries, Ltd.) was used.

Example 6 In place of the surface sizing agent in the ink receiving layer coating liquid used in Example 1, the surface sizing agent prepared in Preparation Example 1 which is a linear saturated fatty acid having 10 carbon atoms was used. An inkjet recording sheet of Example 6 was prepared in the same manner as in Example 1.

Example 7 Instead of the surface sizing agent in the ink receiving layer coating liquid used in Example 1, a surface sizing agent having 22 carbon atoms (trade name: KS28) was used.
5, manufactured by Arakawa Chemical Co., Ltd.) was used to prepare an inkjet recording sheet of Example 7 in the same manner as in Example 1.

Example 8 The coating amount of the ink receiving layer coating liquid used in Example 1 was 0.5 g /
An inkjet recording sheet of Example 8 was produced in the same manner as in Example 1 except that m ² was used.

Example 9 The coating amount of the ink receiving layer coating liquid used in Example 1 was 5.0 g /
An inkjet recording sheet of Example 9 was produced in the same manner as in Example 1 except that m ² was used.

Example 10 An ink jet recording sheet of Example 10 was prepared in the same manner as in Example 1 except that the amount of the surface sizing agent added to the ink receiving layer coating liquid used in Example 1 was 5 parts. .

Example 11 An ink jet recording sheet of Example 11 was prepared in the same manner as in Example 1 except that the amount of the surface sizing agent added to the coating liquid for the ink receiving layer used in Example 1 was 7 parts. .

Example 12 An ink jet recording sheet of Example 12 was prepared in the same manner as in Example 5 except that the base paper 1 of Example 5 was used as the base paper 2.

Example 13 An ink jet recording sheet of Example 13 was produced in the same manner as in Example 6 except that the base paper 1 of Example 6 was used as the base paper 2.

Example 14 An ink jet recording sheet of Example 14 was produced in the same manner as in Example 8 except that the base paper 1 of Example 8 was used as the base paper 2.

Comparative Example 1 Instead of the ultrafine particle inorganic pigment used in Example 1, spherical colloidal silica (trade name: Snowtex PST-3,
An inkjet recording sheet of Comparative Example 1 was prepared in the same manner as in Example 1 except that a primary particle diameter of 300 ± 30 nm, manufactured by Nissan Chemical Industries, Ltd.) was used.

Comparative Example 2 Instead of the ultrafine inorganic pigment used in Example 1, silica (trade name: Nipsil E220A, average particle size 1.0 μm) was used.
m, manufactured by Nippon Silica Industry Co., Ltd.) was used to prepare an inkjet recording sheet of Comparative Example 2 in the same manner as in Example 1.

Comparative Example 3 The surface sizing agent in the coating liquid for the ink receiving layer used in Example 1 was replaced with the surface sizing agent prepared in Preparation Example 2 which was a straight chain saturated fatty acid having 8 carbon atoms. An inkjet recording sheet of Comparative Example 3 was prepared in the same manner as in Example 1.

Comparative Example 4 A surface sizing agent having a styrene hydrophobic group (trade name: KN500, manufactured by Harima Kasei Co., Ltd.) was used in place of the surface sizing agent in the ink receiving layer coating liquid used in Example 1. In the same manner as in Example 1, an inkjet recording sheet of Comparative Example 4 was produced.

Comparative Example 5 An ink jet recording sheet of Comparative Example 5 was prepared in the same manner as in Example 1 except that the surface sizing agent in the ink receiving layer coating liquid used in Example 1 was not added.

Comparative Example 6 The base paper 1 produced as described above was used as it is as an ink jet recording sheet of Comparative Example 6.

The ink jet recording sheets of Examples 1 to 14 and Comparative Examples 1 to 6 produced as described above were evaluated by the evaluation methods described below, and the results are shown in Table 1. [Dot shape factor] Inkjet printer (IO-7
20: Sharp Co., Ltd.) is used to print a single color dot of black ink, and an image analyzer (Luzex 5000, manufactured by Nireco) is used as an evaluation of ink bleeding.
At, the peripheral length of the dot and the area of the dot were measured, and the shape factor SF2 was calculated. The shape factor SF2 is an index that is closer to 100 as it approaches a perfect circle.

[Ink Absorption and Chromaticity] Ink absorption and image sharpness (resolution) are determined by the boundaries between solid color solid printing portions, for example, red printing (magenta + yellow) and green printing (cyan + yellow). The degree of ink bleeding at the boundary was visually determined. When the red printed portion and the green printed portion did not overlap and were separated, the characteristics were good, and when the overlapping was large and a black line was formed, the characteristics were bad. A material having poor ink absorbability remarkably impairs image quality, and therefore, it does not make any sense even if other characteristics, such as image density, are good. As for the color property, the vividness of the color in the above-mentioned heavy color portion was visually evaluated. As the evaluation criteria, A is good in characteristics and B is
Is good in a range where there is no practical problem, C is a problem in practical use, and
Indicates a defective property.

[Image Density] The image density was measured by using a reflection densitometer (trade name: Macbeth RD918, manufactured by Macbeth Co., Ltd.) on a portion solidly printed with black ink. The higher the numerical value, the higher the image density, which is good, but normally, 1.25 or more is good.

[0073]

[Table 1]

From the results of the ink jet recording sheets prepared in Examples 1 to 14 in Table 1 above, ultrafine inorganic pigments of 100 nm or less, preferably cationic colloidal silica and a surface sizing agent having 10 or more carbon atoms in the hydrophobic group When the ink was contained in the ink receiving layer, the image density, chromaticity, dot shape, and ink absorbency were good. Further, the characteristics were improved by using the base paper containing the anionic neutral rosin sizing agent as the internal sizing agent.

On the other hand, in the ink jet recording sheets of Comparative Example 1 and Comparative Example 2, when a pigment having a large particle size was used, the ink absorbability was good, but the image density and color quality were poor. Further, in the ink jet recording sheets of Comparative Examples 3 and 4, the surface sizing agent having a small hydrophobic group having a carbon number of less than 10 was used, but the ink passed through the ink receiving layer on the surface and penetrated into the base paper layer. Since the dyeing time is short, the dye is not sufficiently adsorbed on the ink receiving layer, resulting in poor image density and color. The same applies when no surface sizing agent is added as in Comparative Example 5. Comparative Example 6 was a case of printing on a base paper, but the image density, the chromaticity, and the dot shape were not usable as an inkjet recording sheet.

[0076]

The ink jet recording sheet of the present invention is
Preferably, an ultrafine inorganic pigment having a primary particle size of 100 nm or less is used, more preferably a non-spherical cationic pigment, on a support containing calcium carbonate as a filler and an anionic neutral rosin sizing agent as an internal sizing agent. An ink-receiving layer containing colloidal silica and a surface sizing agent having a hydrophobic group having 10 or more carbon atoms is coated, whereby the ink absorbability is excellent, the image density and color are high, and the true circle is A recording dot shape close to is obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Matsushita 3-4-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Paper Mills, Ltd.

Claims (4)

[Claims] 1. An inkjet recording sheet having an ink-receiving layer provided on a support, wherein the ink-receiving layer composition contains at least one linear or branched saturated or unsaturated hydrocarbon having 10 or more carbon atoms. An inkjet recording sheet comprising a surface sizing agent introduced into a molecule as a hydrophobic group and an ultrafine particle inorganic pigment having a primary particle size of 100 nm or less. 2. The support is calcium carbonate as a filler,
An ink jet recording sheet according to claim 1, which is a neutral paper containing an anionic neutral rosin sizing agent as an internally added sizing agent. 3. The ink jet recording sheet according to claim 1, wherein the ultrafine inorganic pigment is non-spherical cationic colloidal silica. 4. The coating amount of the ink receiving layer is 0.5 to 5.0.
g / m ² and the surface sizing agent is 0.2 to 5% by weight of the ink receiving layer composition.
3. The inkjet recording sheet according to any one of 3 above.