JP2012006264A - Method for manufacturing inkjet recording sheet for pigment ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a low cost inkjet recording sheet for pigment ink with the hand of coated paper for printing.SOLUTION: An undercoat of a coating liquid containing not less than 20 pts.wt. of pigment with an oil absorption of less than 100 cc/100 g and a binder, is applied to at least one side of a support, so that the dry coating build-up is 2.0 to 16.0 g/m. Further, a top coat of a coating liquid which does not contain a pigment and contains not less than one kind of water-soluble polyvalent metallic salt which is selected from the group consisting of magnesium sulfate, calcium formate, calcium acetate, aluminum sulfate and calcium nitrate, is applied so that the dry coating build-up is 0.2 to 5.0 g/m. After that, the obtained inkjet recording sheet is calendered as a finishing process in the way that its white paper gloss complying with JISP8142 accounts for not less than 40%.

Description

  The present invention relates to a method for producing an ink jet recording sheet used in an ink jet recording system using pigment ink.

In recent years, as a means for displaying image information, etc. produced by a personal computer on a recording sheet, solution dye ink or pigment ink is ejected from the nozzle onto the recording sheet using heat or pressure as a driving source, and an image is formed with the ink. Ink jet recording methods for performing printing and electrophotographic recording methods for performing printing by forming an image by transferring toner onto a recording sheet are used.
Also, in the field of commercial printing, the inkjet recording method and electrophotographic recording method that are optimal for printing a small number of copies and variable information printing (variable printing) because digital information can be directly printed on media such as paper without making a plate. Has been introduced in the field of on-demand printing.
Recently, with the improvement in performance of recording devices such as high-speed, high-definition, and full-color printing, and the expansion of applications, it has a texture similar to that of offset prints on coated paper for printing on inkjet recording sheets. There is a growing demand to create documents.

  However, when an aqueous coating liquid containing a pigment and a binder such as an aqueous resin is applied to a paper and dried, and the manufactured general-purpose printing paper is used in an ink jet recording system, there are various problems. That is, when general-purpose printing paper is used in the ink jet recording method, ink absorption is slow and the ink is difficult to dry. Especially when glossing or smoothing treatment such as super calender or gloss calender is performed, high transparency is achieved. Due to vaporization and pore reduction, the ink absorption is further delayed, and the problem that the ink is difficult to dry tends to occur.

Conventionally, as an ink receiving layer of an ink jet recording sheet, a pigment-based receiving layer having high ink absorbability using amorphous silica (including colloidal silica), alumina, alumina hydrate, and aluminosilicate as a main component, In addition, a resin-based receiving layer that uses a water-soluble resin such as gelatin as a main component and swells ink for recording is used. However, these ink jet recording sheets do not have a texture of coated paper for printing at all, and are expensive, so that they are not practically used in the field of on-demand printing.
For example, a recording body in which a cationic resin is coated on the surface of pigment coated paper (Patent Document 1), a recording body in which a pigment coating layer is formed with a coating liquid containing a cationic resin (Patent Document 2), etc. are proposed. However, the ink absorption speed cannot be sufficiently obtained.

  In addition, as an ink jet recording sheet for pigment ink, a recording body (Patent Documents 3 and 4) in which a colloidal silica layer is provided on an ink absorbing layer, an undercoat layer containing a pigment, and a cationic resin topcoat layer ( Patent Documents 5 and 6) are disclosed, however, the coating of colloidal silica or a cationic resin on the surface impairs ink absorbability and exhibits a unique glossy feeling similar to a silver salt photograph. The texture of the coated paper for printing cannot be obtained. Moreover, it becomes an expensive recording material and is not suitable for the on-demand printing field. In addition, in the recording material (Patent Document 7) provided with a coating layer having 100 to 300 cc / 100 g of pigment and a water-soluble polyvalent metal salt, the paint is low for pigments having an oil absorption of 100 to 300 cc / 100 g or more such as silica. Since the density is high and the pigment is also expensive, it is difficult to obtain an inexpensive paper.

JP 2000-256992 A JP 2004-209965 A JP 2000-190626 A JP 2001-150800 A JP 2004-262232 A JP 2005-280035 A Patent No. 3986258

  An object of the present invention is to provide an inexpensive method for producing an inkjet recording sheet for pigment ink having a texture of coated paper for printing.

In order to solve the above problems, the present inventors used a white pigment having an oil absorption of less than 100 cc / 100 g used in coated paper for printing, and added a water-soluble polyvalent metal salt in order to increase ink absorbability. Considering blending, depending on the material, when the paint is prepared, the paint thickens excessively, so that it is impossible to apply, or the paint concentration must be lowered, and the drying load It has been found that the problem of increasing
As a result of intensive studies, the present inventors have under-coated a coating liquid mainly composed of a white pigment and a binder, and then include a specific water-soluble polyvalent metal containing no pigment. The inventors have found that the desired white paper gloss and ink absorptivity can be obtained by top-coating a coating solution containing a salt and further carrying out a calendering treatment, thereby achieving the present invention.

(1) A coating liquid containing 20 parts by weight or more of a pigment having an oil absorption of less than 100 cc / 100 g and a binder on at least one side of the support so that the dry coating amount is 2.0 to 16.0 g / m ^2. Undercoating and coating with a coating solution containing at least one water-soluble polyvalent metal salt selected from magnesium sulfate, calcium formate, calcium acetate, aluminum sulfate, calcium nitrate, and calcium nitrate. Pigment ink characterized in that it is top-coated so that the amount is 0.2 to 5.0 g / m ^2, and then finished by calendering so that the gloss of white paper according to JISP8142 is 40% or more. For manufacturing an inkjet recording sheet.
(2) The method for producing an inkjet recording sheet for pigment ink according to (1), wherein the pigment of the undercoat coating liquid is calcined kaolin, kaolin, calcium carbonate, or plastic pigment.
(3) The method for producing an inkjet recording sheet for pigment ink according to (1) or (2), wherein the used part of the binder per 100 parts by weight of the pigment in the undercoat coating liquid is 3 to 50 parts by weight.
(4) The method for producing an ink jet recording sheet for pigment ink according to any one of (1) to (3), wherein the binder of the undercoat coating liquid is starch and / or a styrene butadiene copolymer. .

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the manufacturing method of the inkjet recording sheet for pigment inks which has the texture of the coated paper for printing, and the ink absorptivity of pigment ink is favorable. This recording sheet is inexpensive and suitable as printing paper used in the on-demand printing field.

<Undercoat>
As a pigment, the well-known white pigment generally used for the coating paper for printing can be illustrated. For example, calcium carbonate, kaolin (including clay), zinc oxide, aluminum hydroxide, zeolite, synthetic zeolite, sepiolite, smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, hydrotalcite, styrene, ethylene, Organic polymer fine particles of butadiene, vinyl chloride, polyurethane, acrylic, vinyl acetate, polycarbonate, nylon, and copolymers thereof, styrene plastic pigment, styrene-butadiene plastic pigment, styrene-acrylic plastic pigment, acrylic plastic Pigments, urethane plastic pigments, urea resin plastic pigments, benzoguanamine plastic pigments, amorphous silica, Lumina, aluminosilicate, and the like, and one or more of these are appropriately selected according to the purpose. Particularly, a pigment having an oil absorption of less than 100 cc / 100 g is 20 parts by weight in 100 parts by weight of the pigment. The coating liquid containing the above and the binder is made to have a dry coating amount of 2.0 to 16.0 g / m ² . If the amount of the oil absorption is less than 100 cc / 100 g, and the amount is less than 20 parts by weight, the paint has a low concentration and the cost increases. On the other hand, when the dry coating amount is less than 2.0 g / m ² , it is difficult to obtain a desired white paper gloss, and when it exceeds 16.0 g / m ² , the drying load increases and the cost increases. In addition, when a hollow plastic pigment is blended, glossiness due to the calendar treatment is large and preferable.

  As the binder, a known binder used for conventional coated paper for printing can be used. Oxidized starch, enzyme-modified starch, thermochemically modified starch, esterified starch, etherified starch, cationic starch, amphoteric starch, etc., cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, gelatin, casein, soy protein, natural Rubber, water-soluble polymers such as polyvinyl alcohol, polydienes such as isoprene, neoprene, polybutadiene, polyalkenes such as polybutene, polyisobutylene, polypropylene, polyethylene, vinyl halide, vinyl acetate, styrene, (meth) acrylic acid, (meta ) Vinyl polymers and copolymers such as acrylic esters, (meth) acrylamides, methyl vinyl ethers, synthetic rubber latexes such as styrene-butadiene and methyl methacrylate-butadiene, polyvinyl alcohol Synthetic rubber latex having a nonionic soap as a protective colloid layer, polyurethane resins, polyester resins, polyamide resins, olefin - maleic anhydride resins, synthetic resins such as melamine resins and the like. Among these, one or more kinds are appropriately selected and used according to the purpose. In particular, starch and styrene butadiene copolymer which are generally used for coated paper for printing are preferred.

  Although the compounding quantity of a binder is not specifically limited, It is preferable to set it as 3-50 mass parts with respect to 100 mass parts of all the pigments, and it is more preferable to set it as 5-40 mass parts. When the blending amount is less than 3 parts by mass, the coated surface may be easily scratched. When it exceeds 50 parts by mass, when the paper is stacked in the paper discharge unit or when wound on the roll after printing In addition, due to the effect of a decrease in ink absorbency, set-off occurs, and guide roll stains and paper feed roll stains are likely to occur in the printing process.

  Further, various auxiliary agents as necessary, for example, surfactants, pH regulators, viscosity modifiers, softeners, gloss imparting agents, waxes, dispersants, flow modifiers, stabilizers, antistatic agents, crosslinking agents A sizing agent, a fluorescent brightening agent, a colorant, an ultraviolet absorber, an antifoaming agent, a water-proofing agent, a plasticizer, a lubricant, a preservative, and a fragrance are appropriately blended as necessary.

<Top coat>
A coating solution containing at least one water-soluble polyvalent metal salt selected from magnesium sulfate, calcium formate, calcium acetate, aluminum sulfate, and calcium nitrate without containing a pigment has a dry coating amount of 0.2 to 5. it is preferred to so as to be 0 g / ^{m 2,} and more preferably a 0.5~3.5g / ^{m 2.} Dry coating amount can not be obtained the desired ink absorption is less than 0.2 g / m ^2, if it exceeds 5.0 g / m ^2, the ink absorbency is good, unfavorably high cost. In addition, the water-soluble polyvalent metal salt in the present invention includes hydrates. For example, in the case of magnesium sulfate, either magnesium sulfate anhydrous or magnesium sulfate heptahydrate or both may be used. Monovalent water-soluble metal salts such as sodium and potassium are not preferable because the absorption of the pigment ink is not accelerated.

  If necessary, binders and various auxiliary agents such as starches and latexes, surfactants, pH regulators, viscosity modifiers, softeners, gloss imparting agents, waxes, dispersants, flow modifiers, stabilizers. , Antistatic agents, crosslinking agents, sizing agents, fluorescent whitening agents, colorants, ultraviolet absorbers, antifoaming agents, water resistance agents, plasticizers, lubricants, preservatives, and perfumes are appropriately blended as necessary. .

<Support>
The support according to the present invention is not particularly limited, and examples thereof include a sheet-like paper substrate, a film, and a joined product of the film and the sheet-like paper substrate. As the support, a sheet having water absorption is preferable, and in particular, according to JIS P8140, the Cobb method water absorption with a contact time with water of 20 seconds is 0.12 to 1.3 g / m ² per 1 g / m ^{2 of the} support. m ² is preferable. When it is less than 0.12 g / m ² , the ink absorbability decreases in ink jet recording suitability, and when it exceeds 1.3 g / m ² , the absorption of the coating liquid to the support increases, and wrinkles and the like occur during coating. This is likely to cause manufacturing problems. In the case of a joined product of a film and a sheet-like paper substrate, the water absorption is the Cobb method water absorption per 1 g / m ² of the sheet before joining on the ink receiving layer side.

  There is no particular limitation on the manufacturing method and type of pulp constituting the sheet-like paper substrate, for example, chemical pulp such as KP, mechanical pulp such as SGP, RGP, BCTMP, CTMP, waste paper pulp such as deinked pulp, kenaf, Non-wood pulp such as bamboo, straw, hemp, etc. is used. In addition, organic synthetic fibers such as polyamide fibers and polyester fibers, recycled fibers such as polynosic fibers, and inorganic fibers such as glass fibers, ceramic fibers, and carbon fibers can be mixed. Among these, use of chlorine-free pulp such as ECF pulp and TCF pulp is preferable.

  In addition, a filler may be blended in the sheet-like paper substrate as necessary. As the filler, various pigments generally used for fine paper can be used, such as kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, zinc oxide, alumina, magnesium carbonate, magnesium oxide, Mineral pigments such as aluminosilicate, silica, white carbon, bentonite, zeolite, sericite and smectite, and micro hollow particles of polystyrene resin, urea resin, melamine resin, acrylic resin and vinylidene chloride resin, dense Organic pigments such as mold particles and through-hole particles.

  In addition to the pulp fibers and fillers, various anionic, nonionic, and cationic materials that have been used in the past are included in the paper material when the sheet-like paper substrate is made, as long as the desired effects of the present invention are not impaired. Various additive agents for paper making, such as a neutrality or amphoteric yield improver, freeness improver, starch, paper strength enhancer, and internal sizing agent, can be appropriately selected and used as necessary. Furthermore, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

  The paper-making method of the sheet-like paper substrate is not particularly limited. For example, the acidic paper-making method is carried out when the paper-making pH is around 4.5. All papermaking methods such as neutral papermaking with a weak alkalinity of about 9 can be applied, and the paper machine also uses the long net paper machine, twin wire paper machine, circular net paper machine, Yankee paper machine as appropriate can do.

On one or both sides of the sheet-like paper substrate obtained by the above method, a pigment, a binder, a surface sizing agent, a cationic resin, an anionic resin, a nonionic resin, a surfactant, a pH adjusting agent, a viscosity adjusting agent, a softness Agent, gloss imparting agent, waxes, dispersant, flow modifier, stabilizer, antistatic agent, cross-linking agent, sizing agent, fluorescent whitening agent, colorant, ultraviolet absorber, antifoaming agent, water resistance agent, One kind or two or more kinds of water-soluble metal salts, plasticizers, lubricants, preservatives, fragrances and the like are appropriately adjusted, and the underlayer may be applied. The coated sheet-like paper substrate can be used as a support. The basis weight of the support used in the present invention is not particularly limited, but is usually from 30 g to 300 g.
The thing of the range of g / m < ² > is used.

  Examples of the film that is a support used in the present invention include acetate film, cellulose triacetate film, nylon film, polyester film, polycarbonate film, polystyrene film, polyphenylene sulfide film, polypropylene film, polyimide film, cellophane and the like. I can do it. A film containing additives such as an inorganic pigment, an organic pigment, an ultraviolet absorber, a light stabilizer, an antioxidant, a fluorescent dye, a crosslinking agent, a lubricant, and a release agent is used as necessary. The method for producing the film is not particularly limited, and a known method can be used. The film used as the support according to the present invention includes what is generally called synthetic paper. Although the thickness of this film is not specifically limited, Usually, the thing of the range of 40 micrometers-300 micrometers is used.

The bonded product of the film and the sheet-like paper substrate can be obtained by a known method. The thickness of the joined product of the film and the sheet-like paper substrate used as the support is not particularly limited, but usually a thickness in the range of 40 μm to 300 μm is used.
When the paint is provided on one side, various known coating layers can be provided on the back side for antistatic, curl prevention, adhesion improvement, printing suitability, improvement in feeding / discharging suitability with a printer, etc. . It is of course possible to add application suitability to the back surface by applying various processes such as adhesion, magnetism, flame resistance, heat resistance, water resistance, oil resistance, and slip resistance.

<Coating device>
The method for applying the undercoat and the topcoat is not particularly limited, and a commonly used coating apparatus is used. For example, blade coater, air knife coater, spray coater, rod blade coater, roll coater, reverse roll coater, bar coater, curtain coater, die slot coater, gravure coater, champlex coater, brush coater and two-roll coater, and metering blade Various known coating apparatuses such as a size press coater, a bill blade coater, a short dwell coater, a lip coater, and a gate roll coater can be used.

(Glossing and smoothing treatment)
After applying the undercoat and the topcoat on the support, a calendar process is performed. As a processing apparatus, a normal super calendar, gloss calendar, soft calendar, shoe nip calendar, or the like is used. Processing is performed by appropriately adjusting the processing conditions such as the configuration of the pressure device, the number of pressure nips, and heating.

  The present invention will be specifically described by the following examples, but of course, they are not intended to limit the scope of the present invention. In the examples, “parts” and “%” represent “parts by mass (solid component)” and “mass%” unless otherwise specified.

Example 1
(Production of support)
100 parts hardwood bleached kraft pulp, 10 parts light calcium carbonate, 0.3 parts cationic starch (trade name: Kate F, manufactured by Oji National), paper strength enhancer (trade name: Polymaron 619, manufactured by Arakawa Chemical Industries) 0 .1 part, alkyl ketene dimer (trade name: SPK-910, manufactured by Arakawa Chemical Industries, Ltd.) 0.02 part, add water and mix well to prepare a stock with a slurry concentration of 0.05%. Using a long mesh multi-cylinder paper machine, using a two-roll size press machine, 2% solids starch (trade name: Ace B, manufactured by Oji Cornstarch Co., Ltd.) per side of the base paper Cobb water absorption of 75 g / m ² (cobb water absorption per 1 g / m ^{2 of} support) with a solid content of 0.5 g / m ^{2 applied} , dried, and a contact time with water specified in JIS P8140 of 20 seconds. 0.75 g / m ² ), basis weight Produced a support of 100 g / m ² .

[Preparation of paint A]
To 60 parts of calcined kaolin (trade name: Ansilex 93, manufactured by BASF, oil absorption 88 cc / 100 g), 0.3 part of a dispersant (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) is added, and water is added. Then, water dispersion was performed using a Coreless disperser, and then 40 parts of a plastic pigment (trade name: AE852, manufactured by JSR) was added to prepare a pigment slurry. To 100.3 parts of this pigment slurry, 2 parts of starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), 15 parts of latex (trade name: PA-7070, Nippon A & L Co., Ltd.), defoamer (trade name) : SN777, manufactured by San Nopco Co., Ltd.) 0.2 parts, optical brightener (trade name: Kaya Hall BPS Liquid Conk, manufactured by Nippon Kayaku Co., Ltd.) 0.3 parts, water was added and paint A having a solid content concentration of 34% Was prepared.

[Preparation of paint B]
Magnesium sulfate was added to water and dissolved to prepare paint B having a solid content concentration of 18%.

[Preparation of inkjet recording sheet for pigment ink]
The coating A (undercoat) was applied to both sides of the 100 g / m ² support obtained above using a blade coater so that the dry coating mass per side was 6.5 g / m ² . Then, the coating material B (top coat) was applied and dried using a blade coater so that the dry coating mass per side was 1.5 g / m ² . Thereafter, calendar treatment was performed to prepare an ink jet recording sheet for pigment ink having a basis weight of 116 g / m ² .

Example 2
An ink jet recording sheet for pigment ink was prepared in the same manner as in the preparation of the coating material B of Example 1, except that magnesium sulfate was calcium formate and the solid content was 10%.
Example 3
An ink jet recording sheet for pigment ink was prepared in the same manner except that magnesium sulfate was changed to calcium acetate (monohydrate) in the preparation of the coating material B of Example 1.

Example 4
An ink jet recording sheet for pigment ink was prepared in the same manner except that magnesium sulfate was changed to aluminum sulfate (anhydrous) in the preparation of paint B in Example 1.
Example 5
An ink jet recording sheet for pigment ink was prepared in the same manner as in the preparation of paint B of Example 1, except that magnesium sulfate was changed to calcium nitrate (tetrahydrate).

Example 6
An inkjet recording sheet for pigment ink was prepared in the same manner as in Example 2, except that the dry coating amount per side of calcium formate was 0.3 g / m ² .

Example 7
An ink jet recording sheet for pigment ink was prepared in the same manner as in Example 5, except that the solid content concentration of calcium nitrate was 30% and the dry coating amount per side was 4.7 g / m ² .
Example 8
An ink jet recording sheet for pigment ink was prepared in the same manner as in Example 1, except that the dry coating amount per side of the coating material A (undercoat) was 1.5 g / m ² .

Example 9
In the preparation of paint A (undercoat) of Example 1, 70 parts of kaolin (trade name: UW-90, manufactured by BASF, oil absorption 46 cc / 100 g), light calcium carbonate (trade name TP121, Okutama Kogyo Co., Ltd.) Manufactured, oil absorption amount 47 cc / 100 g) 30 parts, solid content concentration 50%, and dry coating amount per side of 15.0 g / m ² in the same manner as in Example 1 for inkjet recording sheet for pigment ink Was made.

Comparative Example 1
In the preparation of paint A (undercoat) in Example 1, the pigment slurry was changed to 82 parts of silica (trade name: Carplex BS304F, Evonik, oil absorption 215 cc / 100 g), kaolin (trade name: UW-90, BASF). An ink jet recording sheet for pigment ink was prepared in the same manner except that the oil absorption was 46 parts / cc, 100 parts), the solid content was 14%, and 2.5 g / m ² per side.

Comparative Example 2
An ink jet recording sheet for pigment ink was prepared in the same manner as in Comparative Example 1 except that the dry coating amount per side of the undercoat was 6.5 g / m ² . The undercoat was coated with a die coater because a desired coating amount could not be obtained with a blade coater.
Comparative Example 3
An ink jet recording sheet for pigment ink was prepared in the same manner except that magnesium sulfate was sodium sulfate and the solid content was 10% in the preparation of paint B of Example 1.

Comparative Example 4
An inkjet recording sheet for pigment ink was prepared in the same manner as in Example 1 except that the dry coating amount per side of magnesium sulfate was 0.1 g / m ² .
Comparative Example 5
An ink jet recording sheet for pigment ink was prepared in the same manner as in Example 1, except that the dry coating amount per side of magnesium sulfate was 5.3 g / m ² .

Comparative Example 6
[Preparation of paint C]
To 60 parts of calcined kaolin (trade name: Ansilex 93, manufactured by BASF, oil absorption 88 cc / 100 g), 0.3 part of a dispersant (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) is added, and water is added. Then, water dispersion was performed using a Coreless disperser, and then 40 parts of a plastic pigment (trade name: AE852, manufactured by JSR) was added to prepare a pigment slurry. To 100.3 parts of this pigment slurry, 2 parts of starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), 15 parts of latex (trade name: PA-7070, Nippon A & L Co., Ltd.), surfactant (trade name) : Leox 2160C, chemical name: 1 part polyoxyethylene polyoxypropylene lauryl myristyl ether, manufactured by Lion Corporation, 40 parts water-soluble metal salt (chemical name: magnesium sulfate (anhydrous)), antifoaming agent (trade name: SN777, Sannopco Co., Ltd.) 0.2 parts, fluorescent whitening agent (trade name: Kaya Hall BPS Liquid Conk, Nippon Kayaku Co., Ltd.) 0.3 parts were added, and water was added to prepare a paint C having a solid content concentration of 30%. .

[Preparation of inkjet recording sheet for pigment ink]
The coating material C was applied to both sides of the 100 g / m ² support of Example 1 using a blade coater, and dried so that the dry coating mass per side was 6.5 g / m ^2. The ink-jet recording sheet for pigment ink having a basis weight of 113 g / m ² was prepared.

Comparative Example 7
An inkjet recording sheet for pigment ink was prepared in the same manner except that magnesium sulfate was changed to calcium formate in the preparation of paint C of Comparative Example 6.
Comparative Example 8
An ink jet recording sheet for pigment ink was prepared in the same manner except that magnesium sulfate was changed to calcium acetate (monohydrate) in the preparation of the paint C of Comparative Example 6.

Comparative Example 7
An inkjet recording sheet for pigment ink was prepared in the same manner except that magnesium sulfate was changed to aluminum sulfate (anhydrous) in the preparation of paint C of Comparative Example 6.
Comparative Example 7
An inkjet recording sheet for pigment ink was prepared in the same manner except that magnesium sulfate was changed to calcium nitrate (tetrahydrate) in the preparation of the paint C of Comparative Example 6.

  The obtained inkjet recording sheet for pigment ink was evaluated by the following method. The obtained results are shown in Table 1.

(Evaluation)
[Inkjet recording suitability]
Ink absorbability evaluation Solid printing was performed with an inkjet printer (trade name: GP-700, manufactured by Epson Corporation), and the time until ink droplet erasing immediately after printing was measured. If it is 4 seconds or more, it may cause problems such as setback, which is not preferable.

[Blank gloss]
In accordance with JISP8142, measurements were made using a 75 degree gloss meter.
[Operability]
The undercoat and topcoat paints were heated to 45 ° C. and subjected to blade coating.
○: Operation was possible without any particular problems.
(Triangle | delta): Although the coating material scraped off with the blade increased in viscosity, it did not become poor circulation and operation was possible.
X: The paint scraped off by the blade increased in viscosity, resulting in poor circulation, and operation was impossible.

  As is clear from Table 1, the recording sheet manufacturing method of the present invention is a glossy paper having no operational trouble and good pigment ink absorbability in the ink jet recording system.

  INDUSTRIAL APPLICABILITY The present invention is a glossy type ink jet recording sheet that has no trouble in operation and has good absorbability of pigment ink, is close to the texture of coated paper for printing, and is inexpensive. It is extremely useful as a recording sheet.

Claims (4)

On at least one surface of the support, an undercoat is applied so that the dry coating amount is 2.0 to 16.0 g / m ² with a coating solution containing 20 parts by weight or more of a pigment having an oil absorption of less than 100 cc / 100 g and a binder. In addition, the coating amount containing one or more water-soluble polyvalent metal salts selected from magnesium sulfate, calcium formate, calcium acetate, aluminum sulfate, calcium nitrate, and calcium nitrate is 0. Inkjet recording for pigment ink, characterized in that the top coat is applied so as to be ² to 5.0 g / m ^2, and then finished with a calender treatment so that the gloss of white paper according to JISP8142 is 40% or more. Sheet manufacturing method. 2. The method for producing an inkjet recording sheet for pigment ink according to claim 1, wherein the pigment of the undercoat coating liquid is calcined kaolin, kaolin, calcium carbonate, or plastic pigment. The method for producing an ink jet recording sheet for pigment ink according to claim 1 or 2, wherein the used part of the binder per 100 parts by weight of the pigment in the undercoat coating liquid is 3 to 50 parts by weight. The method for producing an inkjet recording sheet for pigment ink according to any one of claims 1 to 3, wherein the binder of the undercoat coating liquid is starch and / or a styrene butadiene copolymer.