JP2007118470A - Inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet which can be constantly kept in a flat state because it is hardly curled in a wide range of humidity condition. <P>SOLUTION: In this inkjet recording sheet, at least one ink absorbing layer, which is mainly composed of inorganic ultrafine particles, is provided on a substrate which is mainly composed of wood pulp, and at least one back coat layer is provided on the other side of the ink absorbing layer. The inkjet recording sheet is characterized as follows: the back coat layer contains a hydrated halloysite and an alginate; and the 5-20 pts.mass of alginate is contained based on the 100 pts.mass of hydrated halloysite. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording sheet, and more particularly to an ink jet recording sheet that hardly curls under a wide range of humidity conditions.

  Ink-jet recording is a method that records images, characters, etc. by ejecting micro droplets of ink by various operating principles and attaching them to a recording sheet such as paper, making it easy to achieve high speed, low noise, and multiple colors. They have features such as high flexibility of recording patterns and no need for development-fixing, and are rapidly spreading in various applications as recording devices for various figures and color images including kanji.

Various efforts have been made from the aspect of apparatus and ink composition so that high-quality paper and coated paper used in normal printing and writing can be used as recording sheets used in this ink jet recording system. However, as the performance of inkjet recording devices such as high-speed, high-definition, or full-color printing is improved and applications are expanded, it is required that recording sheets have the following advanced characteristics. Became.
(1) It has excellent transportability under a wide range of temperature and humidity conditions when recording with a normal recording apparatus.
(2) The image recorded on the surface is prevented from being shown through and cockling, and a high-quality recorded image can be obtained under a wide range of temperature and humidity conditions.
(3) The printed image is less likely to curl under a wide range of temperature and humidity conditions.

  Conventionally, many proposals have been made focusing on improvement of specific performance among these. For example, an ink jet recording sheet (for example, see Patent Document 1) in which an ink receiving layer is formed separately on the front and back surfaces of a paper base, an ink holding layer and an ink transport layer on the base, and further ink holding By providing an example of a curl suppressing layer having the same or similar physical properties as the layer (see, for example, Patent Document 2), a back coat layer containing a flat pigment and a binder having a glass transition point in a specific range, An example (for example, refer to Patent Document 3) in which the phenomenon of blurring of recording paper during printing is solved and the paper passing property of the printer is improved is disclosed. In addition, an inkjet recording sheet having a backcoat layer containing hydrous halosite and silyl-modified polyvinyl alcohol has been proposed (see, for example, Patent Document 4).

  Recently, ink jet printers using pigment inks with better weather resistance have been used. Since pigment ink has lower coloring efficiency than conventionally used dye ink, an ink jet recording sheet capable of fixing the pigment ink on the extreme surface of the paper is required to obtain a clear color.

Therefore, an ink jet recording sheet having an ink receiving layer mainly composed of inorganic ultrafine particles having a pore size smaller than the particle size of the pigment ink has been proposed. (See, for example, Patent Documents 5 and 6) An ink jet recording sheet in which such an ink receiving layer containing inorganic fine particles as a main component is provided on a paper support containing wood pulp as a main component is an ink accompanying humidity change. Since the difference in dimensional change between the receiving layer and the paper support is large, the occurrence of curling due to humidity change is very large. Under high humidity conditions, the support is stretched more than the ink receiving layer, and a phenomenon of warping on the printing surface side is likely to occur. Also, under low humidity conditions, the support shrinks more than the ink receiving layer, and the phenomenon of warping on the side opposite to the printing surface side is likely to occur. Such curling appears very tightly and may curl into a cylinder. For this reason, when the conventionally proposed back coat layer is provided, curling cannot be suppressed under a wide range of humidity conditions, and there is a problem that a flat state cannot always be maintained.
JP-A-2-270588 (page 2) JP-A-62-282967 (page 2-7) JP-A-4-298380 (page 2-4) JP 7-101141 A (page 2-4) JP 2000-343810 A (pages 3-7) Japanese Patent Laying-Open No. 2005-1373 (page 4-10)

  An object of the present invention is to provide an ink jet recording sheet that is less likely to curl under a wide range of humidity conditions and can always maintain a flat state.

  As a result of earnest research to achieve the above-mentioned object, it has an ink receiving layer mainly composed of at least one inorganic ultrafine particle on a support mainly composed of wood pulp, on the opposite side. In the inkjet recording sheet having at least one backcoat layer, the backcoat layer contains hydrolyzed halloysite and alginate, and the alginate is contained in an amount of 5 to 20 parts by mass with respect to 100 parts by mass of hydrolyzed halloysite. This is solved by an ink jet recording sheet.

  The ink jet recording sheet of the present invention can obtain a high color developability with a pigment ink, has little curling in a wide range of humidity conditions, and can always maintain a flat state.

  Hereinafter, the ink jet recording sheet of the present invention will be described in detail.

  The ink jet recording sheet of the present invention uses a gas-permeable paper support as a support. Examples of the air-permeable paper support in the present invention include chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP, and wood pulps such as waste paper pulp such as DIP, and conventionally known ones. The main component is a pigment, and a binder, a sizing agent, a fixing agent, a yield improver, a cationizing agent, a paper strength enhancer and the like are mixed using one or more additives, and a long net paper machine, circular net paper machine, A base paper produced by various devices such as a twin-wire paper machine, and further a paper with a size press or anchor coat layer made of starch or polyvinyl alcohol on the base paper, or an art paper with a coat layer on them In addition, coated paper such as coated paper and cast coated paper is also included. Such a paper and coated paper may be provided with the coating layer in the present invention as they are, or a calendar device such as a machine calendar, a TG calendar, or a soft calendar may be used for the purpose of controlling flattening.

  In the ink jet recording sheet of the present invention, an ink receiving layer containing at least one layer of inorganic ultrafine particles as a main component is provided on a support. The ink receiving layer mainly composed of the inorganic ultrafine particles according to the present invention has a high color developability by the pigment ink. Therefore, the pore diameter of the ink receiving layer is made smaller than the particle diameter of the pigment ink, and the pigment ink is received by the ink receiving layer. In order to fix near the surface of the layer, it contains inorganic ultrafine particles as a main component. Further, if there is a crack in the ink receiving layer, the pigment ink falls into the crack and the color developability is lowered, so it is preferable that the crack is less.

  The inorganic ultrafine particles according to the present invention refer to inorganic fine particles having an average secondary particle diameter of 500 nm or less. For example, JP-A-1-97678, 2-275510, 3-281383, 3 Alumina hydrates such as pseudoboehmite sol disclosed in Japanese Patent Publication No. 285814, Japanese Patent Publication No. 3-285815, Japanese Patent Publication No. 4-92183, Japanese Patent Publication No. 4-267180, Japanese Patent Publication No. 4-27517, etc. Gas phase method alumina described in JP-A-8-72387, JP-A-60-219083, JP-A-61-19389, JP-A-61-188183, JP-A-63-178074, JP-A-5-51470 Colloidal silica as described in Japanese Patent Publication No. 4-19037, Japanese Patent Publication No. Sho 62-286787, etc. Silica / alumina hybrid sol, such as described in JP-A-10-119423 and JP-A-10-217601, a silica sol in which vapor phase method silica is dispersed with a high-speed homogenizer, average secondary particles Wet silica pulverized to a diameter of less than 500 nm, other smectite clays such as hectite and montmorillonite (JP-A-7-81210), zirconia sol, chromia sol, yttria sol, ceria sol, iron oxide sol, zircon sol, aluminum oxide sol, oxidation A typical example is antimony sol.

  As the silica sol in which the vapor phase silica used for the inorganic ultrafine particles according to the present invention is dispersed, the vapor phase method silica is present in the presence of a cationic compound, and the average secondary particle diameter of the vapor phase silica is preferably 500 nm or less, preferably Can be used dispersed in 50 to 400 nm, more preferably 100 to 300 nm. The average secondary particle diameter of the vapor phase silica referred to here is obtained by measuring a dilute dispersion with a laser diffraction / scattering type particle size distribution analyzer.

  Vapor phase silica is also called dry silica and is generally made by flame hydrolysis. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known. However, silanes such as methyltrichlorosilane and ethyltrichlorosilane can be used alone or in tetrachloride instead of silicon tetrachloride. It can be used in a mixed state with silicon. Vapor phase silica is commercially available from Nippon Aerosil Co., Ltd. as Aerosil, and from Tokuyama Co., Ltd. as Reolosil.

  As a dispersion method, premixed gas phase silica, a cationic compound, and a dispersion medium by ordinary propeller stirring, turbine type stirring, homomixer type stirring, etc., then a media mill such as a ball mill, a bead mill, a sand grinder, a high pressure It is preferable to perform dispersion using a pressure disperser such as a homogenizer or an ultrahigh pressure homogenizer, an ultrasonic disperser, a thin film swirl disperser, or the like.

  The wet silica pulverized to an average secondary particle size of less than 500 nm used for the inorganic ultrafine particles according to the present invention has an average primary particle size of 50 nm or less, preferably 3 to 40 nm, and an average aggregated particle size of 5 to 50 μm. The wet-process silica fine particles obtained by pulverizing certain wet-process silica particles to an average secondary particle diameter of 500 nm or less, preferably about 50 to 400 nm in the presence of a cationic compound are shown. The average secondary particle size of the pulverized wet process silica mentioned here is obtained by measuring a dilute dispersion with a laser diffraction / scattering type particle size distribution analyzer.

  Wet process silica is classified into precipitated silica and gel process silica depending on the production method. Precipitated silica is produced by reacting sodium silicate and sulfuric acid under alkaline conditions, and the silica particles that have grown are agglomerated and settled, and are then commercialized through processes of filtration, washing, drying, pulverization and classification. Precipitated silica is commercially available, for example, from Nippon Silica Co., Ltd. as a nip seal, and from Tokuyama Co., Ltd. as Toku Seal. Gel silica is produced by reacting sodium silicate and sulfuric acid under acidic conditions. During the ripening, the fine particles dissolve and reprecipitate so as to bind other primary particles, so that the distinct primary particles disappear and form relatively hard aggregated particles having an internal void structure. For example, it is marketed as a nip gel from Nippon Silica Co., Ltd. and as a syloid and silo jet from Grace Japan Co., Ltd.

  Among the above-mentioned inorganic ultrafine particles, alumina hydrate is particularly preferable. When alumina hydrate is used, cracks are less likely to occur on the surface of the ink receiving layer, and the separation performance of the pigment ink and the solvent component of the pigment ink can be improved.

The alumina hydrate used in the present invention can be represented by the general formula Al ₂ O ₃ .nH ₂ O. Alumina hydrates are classified into dipsite, vialite, norstrandite, boehmite, boehmite gel (pseudoboehmite), diaspore, amorphous amorphous, etc., depending on the composition and crystal form. In particular, in the above formula, when the value of n is 1, it represents an alumina hydrate having a boehmite structure, and when n is more than 1 and less than 3, it represents an alumina hydrate having a pseudo boehmite structure, where n is 3 or more represents an amorphous alumina hydrate. In particular, the preferred alumina hydrate for the present invention is an alumina hydrate having a pseudo boehmite structure in which at least n is more than 1 and less than 3.

  In order to stabilize the dispersion of alumina hydrate, various acids are usually added to the dispersion. Examples of such acids include nitric acid, hydrochloric acid, hydrobromic acid, acetic acid, formic acid, ferric chloride, aluminum chloride and the like, but the present invention is not limited thereto.

  The shape of the alumina hydrate used in the present invention may be any of a flat plate shape, a fiber shape, a needle shape, a spherical shape, a rod shape, and the like, and a preferable shape is a flat shape from the viewpoint of ink absorbability. The plate-like alumina hydrate has an average aspect ratio of 3 to 8, and preferably an average aspect ratio of 3 to 6. The aspect ratio is expressed as the ratio of the “diameter” to the “thickness” of the particles. Here, the diameter of the particle represents the diameter of a circle equal to the projected area of the particle when the alumina hydrate is observed with an electron microscope.

  The alumina hydrate used in the present invention can be produced by a known method such as hydrolysis of aluminum alkoxide such as aluminum isopropoxide, neutralization of aluminum salt with alkali, hydrolysis of aluminate. The physical properties of alumina hydrate, such as particle size, pore size, pore volume, and specific surface area, should be controlled by conditions such as precipitation temperature, aging temperature, aging time, solution pH, solution concentration, and coexisting compounds. Can do.

  As methods for obtaining alumina hydrates from alkoxides, JP-A-57-88074, JP-A-62-256321, JP-A-4-275717, JP-A-6-64918, JP-A-7-10535, JP-A-7-267633, US Pat. No. 2,656,321 and the like disclose a method for hydrolyzing aluminum alkoxide. These aluminum alkoxides include isopropoxide, 2-butoxide and the like.

  The alumina hydrate used in the present invention is preferably an alumina hydrate having an average primary particle size of 3 nm to 25 nm. A particularly preferable average primary particle diameter is 5 nm to 20 nm. Moreover, it is preferable to set it as 50 nm-200 nm as an average secondary particle diameter which these connected.

  The ink receiving layer mainly composed of the inorganic ultrafine particles according to the present invention may be provided directly on the support, or may be provided on another ink receiving layer provided on the support, and is not particularly limited. . In addition, the ink receiving layer mainly composed of inorganic ultrafine particles and other ink receiving layers are provided by coating and drying the ink receiving layer coating liquid on a support.

  The method for coating the ink receiving layer coating liquid is not particularly limited, and a known coating method can be used. For example, coating with various devices such as air knife coater, curtain coater, slide bead coater, die coater, blade coater, gate roll coater, bar coater, rod coater, roll coater, bill blade coater, short dwell blade coater, size press, etc. can do.

  In the present invention, the method of drying after coating the coating liquid is not particularly limited, and a known drying method can be used. A method of drying by heating, such as a method of blowing hot air or a method of irradiating infrared rays, is preferably used with good productivity. Further, in the case of using a coating liquid for an ink receiving layer whose viscosity is increased by cooling, it is preferable that cracking of the ink receiving layer can be easily prevented by a method of spraying low temperature dry air.

  Next, the back coat layer according to the present invention will be described. The back coat layer contains hydrous halloysite and alginate, and contains 5 parts by mass or more and 20 parts by mass or less of alginate with respect to 100 parts by mass of hydrolyzed halloysite.

  In the back coat layer according to the present invention, an aqueous alginate solution is added to a dispersion of hydrohalosite to prepare a back coat layer coating solution, which is opposite to the case where the support ink-receiving layer is provided. It is formed by applying to the surface and subsequently drying. The aqueous alginate solution is preferably a monovalent metal salt of alginic acid such as ammonium alginate or sodium alginate.

  The content of the alginate with respect to the hydrolyzed halloysite is 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the hydrolyzed halloysite. When the content of the alginate is less than 5 parts by mass, the curl suppressing effect is not sufficient, and curling tends to occur on the ink receiving layer side. On the other hand, when the amount exceeds 20 parts by mass, curling toward the backcoat layer becomes too large, and large curling occurs particularly under low humidity conditions.

  Although the anti-curl prevention mechanism of the backcoat layer of the present invention is not clear, it is presumed that the combined use of alginate and hydrohalosite suppresses the elongation and shrinkage of the backcoat layer accompanying changes in humidity. In addition, when other pigments are used instead of hydrohalosite, curling to the ink-receiving layer side at high humidity cannot be sufficiently suppressed, and problems such as large curling to the backcoat layer side at low humidity are caused. Arise. In addition, when other water-soluble polymers such as polyvinyl alcohol and starch are used instead of alginate, the degree of curling changes greatly due to changes in humidity, and it should always be kept flat regardless of changes in humidity. I can't.

  Moreover, binders other than alginate can also be contained in a backcoat layer. The binder other than alginate is not particularly limited, but it is an aqueous emulsion of a water-insoluble resin for the purpose of easy addition to the backcoat layer coating solution and the purpose of suppressing the elongation and shrinkage of the backcoat layer accompanying changes in humidity. Is preferred. Specific examples thereof include conjugated diene copolymer latex such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, and methyl methacrylate-butadiene copolymer, and polymers or copolymers of acrylate ester and methacrylate ester. Acrylic copolymer latex such as polymer, ethylene-vinyl acetate copolymer, vinyl copolymer latex such as vinyl chloride-vinyl acetate copolymer, polyurethane resin latex, alkyd resin latex, unsaturated polyester resin latex, Alternatively, latex binders such as functional group-modified copolymer latex with functional group-containing monomers such as carboxy groups of these various copolymers may be mentioned, but the invention is not limited thereto.

  The content of the binder other than the alginate contained in the back coat layer according to the present invention is preferably 50 parts by mass or less with respect to 100 parts by mass of the hydrous halloysite. If the content exceeds 50 parts by mass, curling may not be sufficiently suppressed to the ink receiving layer side.

  The range of the dry coating amount of the backcoat layer according to the present invention is 20% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 60% by mass or less, of the total dry coating amount of the ink receiving layer. is there. By setting the dry coating amount of the backcoat layer within this range, a sufficient curling suppression effect can be obtained, and the ink jet recording sheet can be prevented from becoming rigid due to the backcoat layer coating, and a supple state is maintained. I can do things.

  In the backcoat layer according to the present invention, as additives, pigment dispersants, thickeners, fluidity improvers, surfactants, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, Coloring dyes, coloring pigments, fluorescent brighteners, ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, water resistance agents, wetting power enhancers, dry paper strength enhancing agents, and the like can be appropriately blended.

  The method for applying the coating liquid for the backcoat layer according to the present invention is not particularly limited, and a known coating method can be used. For example, coating with various devices such as air knife coater, curtain coater, slide bead coater, die coater, blade coater, gate roll coater, bar coater, rod coater, roll coater, bill blade coater, short dwell blade coater, size press, etc. can do.

  In the present invention, the method of drying after coating the coating liquid is not particularly limited, and a known drying method can be used. In particular, a method of drying by heating, such as a method of blowing hot air or a method of irradiating infrared rays, is used. The productivity is good and it is preferably used.

  In the present invention, after coating and drying the backcoat layer, it may be smoothed by calendaring for the purpose of controlling flattening. Examples of the calendar processing device at that time include a gloss calendar, a super calendar, and a soft calendar.

Examples Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” and “%” indicate parts by mass and mass% unless otherwise specified.

<Support 1>
100 parts of wood pulp comprising 70 parts of LBKP with a freeness of 450 ml CSF and 30 parts of NBKP with a freeness of 450 ml CSF, 5 parts of a pigment having a light calcium carbonate / heavy calcium carbonate / talc ratio of 30/35/35, and a commercially available alkyl ketene dimer After preparing 0.1 part, 0.03 part of commercially available cationic acrylamide, 1.0 part of commercially available cationized starch, and 0.5 part of sulfuric acid band, the paper was made with a net paper machine at a basis weight of 105 g / m ^2. A support 1 was obtained.

<Backcoat layer coating solution 1>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and 50 parts of a 10% solid sodium alginate aqueous solution is mixed therewith. % Backcoat layer coating solution 1 was prepared.

<Backcoat layer coating solution 2>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and 100 parts of a 10% solid sodium alginate aqueous solution is mixed with this. A 5% backcoat layer coating solution 2 was prepared.

<Backcoat layer coating solution 3>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and 200 parts of a 10% solid sodium alginate aqueous solution is mixed with this. % Backcoat layer coating solution 3 was prepared.

<Backcoat layer coating solution 4>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and 100 parts of an aqueous solution of ammonium alginate having a solid content of 10% is mixed therewith. A 5% backcoat layer coating solution 4 was prepared.

<Backcoat layer coating solution 5>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Co., Ltd.) is dispersed in 220 parts of water using a homogenizer, and 50 parts of a 10% solid sodium alginate aqueous solution and 50% styrene butadiene having a solid content of 10%. 30 parts of a latex (LX407F, manufactured by Nippon Zeon Co., Ltd.) was mixed to prepare a backcoat layer coating solution 5 having a solid content concentration of 30%.

<Backcoat layer coating solution 6>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and 100 parts of a 10% solid sodium alginate aqueous solution and 50% styrene butadiene having a solid content of 10%. 20 parts of a latex (LX407F, manufactured by Nippon Zeon Co., Ltd.) was mixed to prepare a backcoat layer coating solution 6 having a solid content concentration of 28.6%.

<Backcoat layer coating solution 7>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Co., Ltd.) was dispersed in 200 parts of water using a homogenizer, and 100 parts of an aqueous solution of ammonium alginate having a solid content of 10% and styrene butadiene having a solid content of 50%. System latex (LX407F, manufactured by Nippon Zeon Co., Ltd.) (20 parts) was mixed to prepare a backcoat layer coating solution 7 having a solid content concentration of 28.6%.

<Backcoat layer coating solution 8>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, to which 50 parts of a 10% solid sodium alginate aqueous solution and 10% solids concentration polyvinyl alcohol are dispersed. 150 parts of an aqueous solution (PVA117, manufactured by Kuraray Co., Ltd.) was mixed to prepare a backcoat layer coating solution 8 having a solid concentration of 24%.

<Backcoat layer coating solution 9>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and 100 parts of an aqueous solution of sodium alginate with a solid content of 10% and polyvinyl alcohol with a solid content of 10% are obtained. 100 parts of an aqueous solution (PVA117, manufactured by Kuraray Co., Ltd.) was mixed to prepare a backcoat layer coating solution 9 having a solid content concentration of 24%.

<Backcoat layer coating solution 10>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and 100 parts of an aqueous solution of ammonium alginate with a solid content of 10% and polyvinyl alcohol of 10% with a solid content of 10%. 100 parts of an aqueous solution (PVA117, manufactured by Kuraray Co., Ltd.) was mixed to prepare a backcoat layer coating solution 10 having a solid content concentration of 24%.

<Backcoat layer coating solution 11>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and a 50% solid content styrene butadiene latex (LX407F, manufactured by Nippon Zeon Co., Ltd.) ) 10 parts were mixed to prepare a backcoat layer coating solution 11 having a solid content concentration of 33.9%.

<Backcoat layer coating solution 12>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and a 50% solid content styrene butadiene latex (LX407F, manufactured by Nippon Zeon Co., Ltd.) 40 parts were mixed to prepare a backcoat layer coating solution 12 having a solid content concentration of 35.3%.

<Backcoat layer coating solution 13>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) is dispersed in 200 parts of water using a homogenizer, and a 10% solid content polyvinyl alcohol aqueous solution (PVA117, manufactured by Kuraray Co., Ltd.) 50 The back coat layer coating liquid 13 having a solid content concentration of 30% was prepared.

<Backcoat layer coating solution 14>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) was dispersed in 200 parts of water using a homogenizer, and a polyvinyl alcohol aqueous solution (PVA117, manufactured by Kuraray Co., Ltd.) 200 having a solid content of 10% was dispersed therein. The back coat layer coating liquid 14 having a solid content concentration of 24% was prepared.

<Backcoat layer coating solution 15>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) was dispersed in 200 parts of water using a homogenizer, and 10% solid content silyl group-modified polyvinyl alcohol aqueous solution (R-1130, Kuraray ( 50 parts) was mixed to prepare a backcoat layer coating solution 15 having a solid content concentration of 30%.

<Backcoat layer coating solution 16>
100 parts of hydrous halloysite (Kaolin KA, manufactured by Daiharu Chemical Industry Co., Ltd.) was dispersed in 200 parts of water using a homogenizer, and 10% solid content silyl group-modified polyvinyl alcohol aqueous solution (R-1130, Kuraray ( 200 parts) was mixed to prepare a backcoat layer coating solution 16 having a solid concentration of 24%.

<Backcoat layer coating solution 17>
100 parts of kaolinite (NUCLAY, manufactured by ENGELHARD, USA) is dispersed in 200 parts of water using a homogenizer, and then mixed with 100 parts of a 10% solid sodium alginate aqueous solution to form a back coat having a solid content of 27.5%. A layer coating solution 17 was prepared.

<Backcoat layer coating solution 18>
100 parts of kaolinite (KAOGLOSS 90, manufactured by Thiele Kaolin, USA) is dispersed in 200 parts of water using a homogenizer, and 100 parts of a 10% solid sodium alginate aqueous solution is mixed with the resulting mixture to obtain a back concentration of 27.5%. A coating layer coating solution 18 was prepared.

<Ink-receiving layer coating solution 1>
To 472 parts of water, 4 parts of dimethyldiallylammonium chloride homopolymer (molecular weight 9,000) with a solid content of 50% and 100 parts of gas phase method silica (average primary particle diameter 12 nm, specific surface area 200 m ² / g by BET method) are added. Then, a preliminary dispersion was prepared using a sawtooth blade type disperser. The obtained preliminary dispersion was treated with a high-pressure homogenizer, and the concentration was adjusted by adding water to obtain a gas phase method silica dispersion having a silica concentration of 17.2%. The average secondary particle diameter of the vapor phase method silica fine particles obtained by measuring this dispersion with a laser diffraction / scattering particle size distribution analyzer was 200 nm. To 500 parts of the dispersion thus obtained, 210 parts of an aqueous solution of polyvinyl alcohol having a solid content concentration of 10% (saponification degree 88%, polymerization degree 2400), 100 parts of a 4% solid content concentration boric acid aqueous solution, and 190 parts of water were mixed. Ink-receiving layer coating solution 1 containing inorganic ultrafine particles having a concentration of 11.1% as a main component was prepared.

<Ink-receiving layer coating liquid 2>
Ion-exchanged water 1200 g and isopropyl alcohol 900 g were charged into a 3 L reactor and heated to 75 ° C. 408 g of aluminum isopropoxide was added, and hydrolysis was performed at 75 ° C. for 24 hours and at 95 ° C. for 4 hours. Thereafter, 24 g of acetic acid was added, and the mixture was stirred at 95 ° C. for 40 hours, and then concentrated so that the solid content concentration was 16% to obtain a white alumina hydrate dispersion. The average secondary particle diameter of the alumina hydrate obtained by measuring this dispersion with a laser diffraction / scattering particle size distribution analyzer was 180 nm.

When this sol was dried at room temperature and measured for X-ray diffraction, it showed a pseudo-boehmite structure. Further, when the average particle diameter was measured with a transmission electron microscope, it was about 20 nm and was an alumina hydrate having a flat pseudoboehmite structure with an aspect ratio of 6. Further, when the BET specific surface area, the average pore radius, the pore volume with a pore radius of 1 nm to 30 nm, and the pore volume with a pore radius of 2 nm to 10 nm were measured by a nitrogen adsorption / desorption method, 136 m ² / g, 0.8 nm, 0.54 ml / g, and 0.50 ml / g.

  Using the above dispersion of an ultrafine particulate alumina hydrate having a solid concentration of 16%, 625 parts of an alumina hydrate dispersion, and polyvinyl alcohol having a solid content of 10% (saponification degree 88%, polymerization degree 2400) 60 parts of an aqueous solution and 5 parts of a 4% solid content concentration boric acid aqueous solution were mixed to prepare an ink receiving layer coating solution 2 mainly composed of inorganic ultrafine particles having a solid content concentration of 15.4%.

<Ink-receiving layer coating solution 3>
472 parts of water, 4 parts of dimethyldiallylammonium chloride homopolymer (molecular weight 9,000) with a solid content of 50%, precipitated silica (specific surface area 130 m ² / g by BET method, average primary particle diameter 16 nm, average aggregate particle diameter 6 μm ) 100 parts were added and a preliminary dispersion was prepared using a sawtooth blade type disperser. The obtained preliminary dispersion was treated with a bead mill, and the concentration was adjusted by adding water to obtain a wet silica dispersion having a silica concentration of 17.2%. The average secondary particle diameter of the wet silica fine particles obtained by measuring this dispersion with a laser diffraction / scattering particle size distribution analyzer was 250 nm. To 580 parts of the silica dispersion thus obtained, 200 parts of an aqueous solution of polyvinyl alcohol having a solid content of 10% (saponification degree 88%, polymerization degree 2400) and 20 parts of an aqueous solution of boric acid having a solid content of 4% are mixed. Ink-receiving layer coating solution 3 containing% inorganic ultrafine particles as a main component was prepared.

<Ink-receiving layer coating solution 4>
100 parts of synthetic amorphous silica (average particle size 2.5 μm, oil absorption 280 ml / 100 g) is dispersed in 400 parts of water using a homogenizer, and 10% solid content polyvinyl alcohol (complete saponification, degree of polymerization 1700) An ink receiving layer coating solution 4 having a solid content concentration of 16.7% was prepared by mixing 250 parts of an aqueous solution.

The ink receiving layer coating liquid 1 heated to 40 ° C. was applied to the support 1 having a temperature of 20 ° C. prepared above using a slide bead coater so that the dry solid content was 25 g / m ² , It was dried with a drying air having a dew point of −5 ° C. to form a crack-free ink receiving layer mainly composed of inorganic ultrafine particles. Next, the back coat layer coating solution 1 was applied to the surface opposite to the support on which the ink receiving layer was provided using an air knife coater so as to have a dry solid content of 11 g / m ² . A back coat layer was formed by drying with hot air, and an inkjet recording sheet of Example 1 was produced.

  An inkjet recording sheet of Example 2 was produced under the same conditions as in Example 1 except that the backcoat layer coating liquid 2 was used instead of the backcoat layer coating liquid 1 in Example 1.

  An ink jet recording sheet of Example 3 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 3 was used instead of the backcoat layer coating solution 1 in Example 1.

  An inkjet recording sheet of Example 4 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 4 was used instead of the backcoat layer coating solution 1 in Example 1.

  An ink jet recording sheet of Example 5 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 5 was used instead of the backcoat layer coating solution 1 in Example 1.

  An inkjet recording sheet of Example 6 was produced under the same conditions as Example 1 except that the backcoat layer coating solution 6 was used instead of the backcoat layer coating solution 1 in Example 1.

  An inkjet recording sheet of Example 7 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 7 was used instead of the backcoat layer coating solution 1 in Example 1.

  An inkjet recording sheet of Example 8 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 8 was used instead of the backcoat layer coating solution 1 in Example 1.

  An inkjet recording sheet of Example 9 was produced under the same conditions as Example 1 except that the backcoat layer coating solution 9 was used instead of the backcoat layer coating solution 1 in Example 1.

  An inkjet recording sheet of Example 10 was produced under the same conditions as Example 1 except that the backcoat layer coating solution 10 was used instead of the backcoat layer coating solution 1 in Example 1.

The ink receiving layer coating liquid 4 at 20 ° C. is applied on the support 1 having a temperature of 20 ° C. prepared above using an air knife coater so as to have a dry solid content of 13 g / m ^2, and dried by hot air at 150 ° C. The first ink receiving layer was formed. Further, the ink receiving layer coating liquid 2 at 20 ° C. was applied on the first ink receiving layer adjusted to 20 ° C. using an air knife coater so as to have a dry solid content of 12 g / m ^2. And dried with hot air to form a second ink-receiving layer having no cracks and containing inorganic ultrafine particles as a main component. Next, the back coat layer coating liquid 2 was applied to the surface opposite to the support on which the ink receiving layer was provided using an air knife coater so as to have a dry solid content of 11 g / m ² . A back coat layer was formed by drying with hot air, and an inkjet recording sheet of Example 11 was produced.

  An ink jet recording sheet of Example 12 was produced under the same conditions as Example 11 except that the ink receiving layer coating solution 3 was used instead of the ink receiving layer coating solution 2 in Example 11.

  An inkjet recording sheet of Example 13 was produced under the same conditions as Example 11 except that the backcoat layer coating solution 6 was used instead of the backcoat layer coating solution 2 in Example 11.

  The same conditions as in Example 11 except that the ink receiving layer coating liquid 3 was used instead of using the ink receiving layer coating liquid 2 in Example 11, and the back coating layer coating liquid 6 was used instead of using the back coating layer coating liquid 2. Thus, an inkjet recording sheet of Example 14 was produced.

  An inkjet recording sheet of Example 15 was produced under the same conditions as Example 11 except that the backcoat layer coating solution 9 was used instead of the backcoat layer coating solution 2 in Example 11.

  The same conditions as in Example 11 except that the ink receiving layer coating liquid 3 was used instead of using the ink receiving layer coating liquid 2 in Example 11, and the back coating layer coating liquid 9 was used instead of using the back coating layer coating liquid 2. Thus, an inkjet recording sheet of Example 16 was produced.

Instead of applying so that the back coat layer coating solution 1 in the dry solids 11g / m ² in Example 1, except that the slurry was applied to a dry solids 5 g / m ² is carried out under the same conditions as in Example 1 The ink jet recording sheet of Example 17 was produced.

The same conditions as in Example 1 except that the back coat layer coating liquid 1 was applied to a dry solid content of 11 g / m ² instead of the dry solid content of 11 g / m ² in Example 1. Thus, an ink jet recording sheet of Example 18 was produced.

(Comparative Example 1)
An inkjet recording sheet of Comparative Example 1 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 11 was used instead of the backcoat layer coating solution 1 in Example 1.

(Comparative Example 2)
An inkjet recording sheet of Comparative Example 2 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 12 was used instead of the backcoat layer coating solution 1 in Example 1.

(Comparative Example 3)
An inkjet recording sheet of Comparative Example 3 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 13 was used instead of the backcoat layer coating solution 1 in Example 1.

(Comparative Example 4)
An inkjet recording sheet of Comparative Example 4 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 14 was used instead of the backcoat layer coating solution 1 in Example 1.

(Comparative Example 5)
An ink jet recording sheet of Comparative Example 5 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 15 was used instead of the backcoat layer coating solution 1 in Example 1.

(Comparative Example 6)
An inkjet recording sheet of Comparative Example 6 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 16 was used instead of the backcoat layer coating solution 1 in Example 1.

(Comparative Example 7)
An inkjet recording sheet of Comparative Example 7 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 17 was used instead of the backcoat layer coating solution 1 in Example 1.

(Comparative Example 8)
An inkjet recording sheet of Comparative Example 8 was produced under the same conditions as in Example 1 except that the backcoat layer coating solution 18 was used instead of the backcoat layer coating solution 1 in Example 1.

(Comparative Example 9)
Instead of applying the backcoat layer coating solution 1 so as to have a dry solid content of 11 g / m ² in Example 1, it was carried out except that the backcoat layer coating solution 12 was applied so as to have a dry solid content of 5 g / m ^2. An ink jet recording sheet of Comparative Example 9 was produced under the same conditions as in Example 1.

(Comparative Example 10)
Instead of applying the backcoat layer coating solution 1 to a dry solid content of 11 g / m ² in Example 1, the backcoat layer coating solution 12 was applied to a dry solid content of 17.5 g / m ^2. Produced the inkjet recording sheet of Comparative Example 10 under the same conditions as in Example 1.

(Comparative Example 11)
Instead of applying the backcoat layer coating solution 1 to a dry solid content of 11 g / m ² in Example 1, the procedure was carried out except that the backcoat layer coating solution 16 was applied to a dry solid content of 5 g / m ^2. An ink jet recording sheet of Comparative Example 11 was produced under the same conditions as in Example 1.

(Comparative Example 12)
Instead of applying the backcoat layer coating solution 1 to a dry solid content of 11 g / m ² in Example 1, the backcoat layer coating solution 16 was applied to a dry solid content of 17.5 g / m ^2. Prepared an inkjet recording sheet of Comparative Example 12 under the same conditions as in Example 1.

Evaluation The A4 size sheets were obtained by cutting the ink jet recording sheets prepared in Examples 1 to 18 and Comparative Examples 1 to 12 so that the long sides thereof were parallel to the flow direction at the time of producing the support. The sheet was placed under the following conditions: 30 ° C., relative humidity 80%, 30 ° C., relative humidity 15%, 20 ° C., relative humidity 50%, 10 ° C., relative humidity 80% and 10 ° C., relative humidity 15%. The center of the short piece was hung with a clip and left for 24 hours. After 24 hours, place the top of the sheet on a horizontal and flat base in the direction of rising from the base, measure the distance between each top and the base plane, and calculate the average distance between the four tops and the base to obtain the curl value. . The curl direction is defined as + if the ink receiving layer surface is on the upper side and-if the back coat layer surface is on the upper side when the vertex of the sheet is lifted from the table, and the results are shown in Table 1. . In Table 1, all numerical values are in millimeters.

  In Table 1, as shown in Examples 1 to 18, a back coat layer containing hydrous halloysite and alginate and containing 5 parts by mass or more and 20 parts by mass or less of alginate with respect to 100 parts by mass of hydrolyzed halloysite is provided. The ink jet recording sheet had little curling due to changes in temperature and humidity, and had good flatness.

  On the other hand, Comparative Examples 1-6 and 9-12, which contain hydrous halloysite in the backcoat layer but do not contain alginate, and Comparative Examples 7 and 8, which contain kaolinite instead of hydrous halloysite, The difference in curl value at low humidity was large and the flatness was poor.

Claims (1)

  In an ink jet recording sheet having an ink receiving layer mainly composed of at least one inorganic ultrafine particle on a support mainly composed of wood pulp, and having at least one back coat layer on the opposite surface The ink jet recording sheet, wherein the back coat layer contains hydrous halloysite and an alginate, and contains an alginic acid salt in an amount of 5 to 20 parts by mass with respect to 100 parts by mass of the hydrous halloysite.