JP2006168035A - Sheet for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet for inkjet recording which is excellent in a printing density with a dye ink and a pigment ink, suitably for inkjet recording, and enables clear printing of a high-definition image and which is excellent in print storage properties. <P>SOLUTION: The sheet for inkjet recording has a lower layer of an ink accepting layer which has a layer of a pigment and an adhesive and is provided on a substrate and an upper layer of the ink accepting layer having the pigment and the adhesive and provided thereon. The sheet contains an ozone resistance improving agent in the lower layer of the ink accepting layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording sheet having excellent printing density with dye ink and pigment ink as ink jet recording suitability, capable of clearly printing high-definition images, and having excellent print storage stability (particularly printing ozone resistance).

  Ink jet recording method in which water-based ink is ejected from a fine nozzle toward the recording sheet surface to form an image on the recording sheet surface has less noise during recording, and it is easy to form a full-color image. It is widely used in printers, facsimiles, plotters, form printing, and the like because it enables high-speed recording and has a lower recording cost than other printing apparatuses.

  This water-based ink is classified into a dye ink using a dye and a pigment ink using a pigment, and the dye ink is mainly used from the viewpoint of sharpness. However, since it has come to be used for large posters for outdoor exhibitions in recent years, dye ink is oxidized by ultraviolet rays, ozone, etc. when displayed for a long time, and the image fades and looks bad. A drawback has been pointed out that the storability of the printed part cannot be obtained. On the other hand, the pigment ink has the characteristics of excellent light resistance of the printed part, ozone resistance of the printed part, and water resistance of the printed part. Due to the large size, the conventional ink jet recording sheet for dye ink has a problem that a clear printed image cannot be obtained. Therefore, an ink jet recording sheet for dye ink and an ink jet recording sheet for pigment ink have been developed, but there is a demand for an ink jet recording sheet having good color developability for both dye ink and pigment ink. it was high.

A method for containing a water-soluble metal salt or metal oxide in a coating liquid as an ink jet recording sheet that exhibits excellent water resistance and print density by printing with a dye ink (see, for example, Patent Documents 1 to 9). Has been proposed, but the color developability when printed with pigment ink is poor, or the color developability and print storage stability (water resistance, light resistance, ozone resistance) when printed with dye ink are poor Thus, an ink jet recording sheet having excellent recording properties is not obtained regardless of whether printing is performed with dye ink or pigment ink.
Japanese Patent Publication No. 63-11158 JP 58-94491 A JP 60-67190 A Japanese Patent Laid-Open No. 61-74880 JP-A-7-149037 Japanese Patent Laid-Open No. 9-99630 JP-A-9-267546 Japanese Patent Laid-Open No. 4-201594 Japanese Patent Laid-Open No. 7-32725

  None of the ink jet recording sheets described in the above-mentioned patent documents satisfy the color developability and storage stability of the dye ink and the color developability of the pigment ink, and both the dye ink and the pigment ink are excellent. An ink jet recording sheet having color developability and satisfying the storage stability of the dye ink printing portion has not been obtained.

The present invention provides: (1) an ink receiving layer having an ink receiving layer lower layer having a pigment and an adhesive layer on a support, and an ink receiving layer upper layer having a pigment and an adhesive thereon; An ink jet recording sheet comprising an ozone resistance improver in a lower layer.
The ozone resistance improver is preferably zinc sulfate. The ozone resistance improver is preferably malic acid.
(2) The ink jet recording according to (1), wherein the ozone resistance improver is zinc sulfate and is contained in the range of 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment in the lower layer of the ink receiving layer. Sheet.
(3) The inkjet according to (1), wherein the ozone resistance improver is malic acid and is contained in a range of 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the pigment in the lower layer of the ink receiving layer. This is a recording sheet.

(4) The inkjet recording sheet according to any one of (1) to (3), wherein the pigment in the lower layer of the ink receiving layer is amorphous silica having an average particle diameter of 1 to 12 μm.
(5) The ink jet recording sheet according to any one of (1) to (4), wherein a paper surface pH of the upper surface of the ink receiving layer is 5.5 to 7.0.

(6) The upper layer of the ink receiving layer is coated with a coating liquid containing a fine pigment and an adhesive, or is in the middle of drying of the coating liquid layer coated with the coating liquid, and the coating liquid layer is dried at a reduced rate. The inkjet recording sheet according to any one of (1) to (5), which is a layer produced by thickening or cross-linking a coating liquid before film formation.
(7) The support is a gas-permeable support, and the upper layer of the ink receiving layer is a layer that is pressure-treated with a mirror roll in a wet state after applying a coating liquid containing a pigment, an adhesive, and a cationic resin. The inkjet recording sheet according to any one of (1) to (6).
(8) A coating liquid containing a fine pigment having an average particle diameter of 0.01 to 1 μm was applied on the upper layer of the ink receiving layer, and was pressed onto a heated mirror roll while in a wet state. The inkjet recording sheet according to any one of (1) to (6), which has a glossy layer.

(9) An ink receiving layer lower layer coating liquid having a pigment, an adhesive and an ozone resistance improver is applied and dried on the support to provide an ink receiving layer lower layer, and the pigment, adhesive and cationic resin are provided thereon. After the ink receiving layer upper layer coating liquid is applied, the applied coating liquid is formed by thickening or gelling, and dried so that the water content of the ink receiving layer upper layer is 8 to 40% by mass. A method for producing an ink jet recording sheet comprising applying a treatment liquid and applying pressure treatment to a heated mirror drum to impart glossiness.
The moisture measurement here is performed using, for example, an infrared moisture meter KJT-100 (manufactured by Kett Science Laboratory). In addition, if the apparatus which can be measured on the same principle is used, it will not be limited to said thing. The measurement principle is that when light having an absorption wavelength of water in the near infrared region (1.2 μm, 1.45 μm, 1.94 μm) is applied to the coating layer, the light is absorbed according to the moisture content of the coating layer. . The moisture value can be calculated from the amount of attenuation. However, since measurement with only the absorption wavelength is difficult due to the influence of the surface condition and color of the substance, it is difficult to perform stable measurement. Therefore, a near infrared ray (reference wavelength) that is less susceptible to water is set separately, and the absorption wavelength and reference wavelength are set separately. The moisture value is calculated from the ratio of the energy of the two wavelengths of light that are alternately applied and reflected.
The moisture meter is installed in the coater at a position immediately before the surface layer coating liquid is applied. However, if there is a paper roll on the opposite side (rear side) of the coated paper to the measurement surface, the measurement value may cause an error due to the influence of the paper roll. Therefore, the measurement should be performed with the paper in the air.

(10) In the method for producing an ink jet recording sheet according to (9), the ink receiving layer is dried so that the water content in the upper layer of the ink receiving layer is 12 to 40% by mass, and then a treatment liquid is applied and pressure-treated on a heated mirror drum. is there.
(11) The adhesive used for the upper layer of the ink receiving layer is a temperature-sensitive polymer compound that reversibly exhibits hydrophobicity at a temperature higher than the temperature-sensitive point and hydrophilicity at a temperature lower than the temperature-sensitive point; The method for producing an ink jet recording sheet according to (9) or (10), wherein the upper layer of the receiving layer is coated and then thickened or gelled by cooling to a temperature not higher than the temperature sensitive point.

  The ink jet recording sheet of the present invention is excellent in printing density with dye ink and pigment ink as ink jet recording suitability, can clearly print high-definition images, and has excellent print storage stability (especially printing ozone resistance). is there.

"About support"
The support is not particularly limited as long as it is a known sheet-like substrate that can be used for an inkjet recording sheet, and both a gas permeable support and a gas impermeable support can be used.

(About air-permeable support)
Examples of the air-permeable support include high-quality paper, art paper, coated paper, cast coated paper, foil paper, craft paper, baryta paper, board paper, impregnated paper, vapor-deposited paper, water-soluble paper, or general coated paper. Paper bases such as acid paper used in the above, or coated paper base paper such as neutral paper are appropriately used. Moreover, the resin sheet which has air permeability can also be used.

Examples of the paper base material include wood pulp as a main component, and additives containing additives such as fillers and various auxiliary agents as necessary.
As the wood pulp, various chemical pulps, mechanical pulps, recycled pulps and the like can be used. These pulps can be adjusted by a beating machine in order to adjust paper strength, papermaking suitability, and the like. The beating degree (freeness) of the pulp is not particularly limited, but is generally about 250 to 550 ml (CSF: JIS-P-8121). In order to improve smoothness, it is desirable to advance the beating degree. However, when recorded on paper, paper blur and recording image bleeding caused by moisture in the ink often gives better results if the beating is not advanced. . Accordingly, the freeness is preferably about 300 to 500 ml.

  The filler is blended for the purpose of imparting opacity or adjusting the ink absorbability, and calcium carbonate, calcined kaolin, silica, titanium oxide and the like can be used. In particular, calcium carbonate is preferable because it becomes a substrate with high whiteness and glossiness of the ink jet recording paper is enhanced. The content (ash content) of the filler in the paper substrate is preferably about 1 to 20% by mass, and if it is too much, the paper strength may be reduced. If the amount is too small, the air permeability of the paper base material is deteriorated. Therefore, a preferable filler content is 7 to 20% by mass. Within this range, smoothness, air permeability, and paper strength are balanced, and as a result, an inkjet recording sheet excellent in glossiness and image sharpness is easily obtained.

  A sizing agent, a fixing agent, a paper strength enhancer, a cationizing agent, a yield improving agent, a dye, a fluorescent brightening agent, and the like can be added to the paper base as an auxiliary agent. As the paper strength enhancer, a paper strength enhancer such as polyamide / epichlorohydrin resin, N-vinylformamide / vinylamine copolymer, or the like may be added, applied or impregnated. In particular, polyamide epichlorohydrin resin is preferably used because it has an effect of improving the dimensional stability of paper when wet.

Furthermore, starch, polyvinyl alcohol, cationic resin, etc. can be applied and impregnated on the paper base material in the size press process of the paper machine to adjust the surface strength, sizing degree, and the like.
About 1 to 200 seconds is preferable for the steechtite sizing degree of the paper substrate (as 100 g / m ² paper). If the sizing degree is low, there may be operational problems such as wrinkling at the time of coating, and if it is high, the ink absorbability may be lowered, and curling and cockling after printing may be remarkable. A more preferred range of sizing is 4 to 120 seconds. Although the basic weight of a paper base material is not specifically limited, It is about 20-400 g / m < ² >.

  When the surface of the ink jet recording sheet is glossed with a mirror roll, the air permeability of the air-permeable support is preferably from 10 to 350 seconds / cc. Incidentally, by setting it as 10 second / 100cc or more, it can suppress that a coating liquid osmose | permeates a support body and the ink receiving layer lower layer formed as needed. By setting it to 350 seconds / 100 cc or less, it is possible to suppress the problem that the operability is inferior when performing a pressure-bonding process with a mirror roll described later. The preferred Oken air permeability is 10 to 200 seconds / 100 cc, more preferably 20 to 100 seconds / 100 cc.

(About non-permeable substrates)
On the other hand, as non-air-permeable support, resin films such as cellophane, polyethylene, polypropylene, soft polyvinyl chloride, hard polyvinyl chloride, polyester, resin-coated paper (for example, polyethylene laminated paper), metal foil, metal foil, synthetic paper Sheet base materials such as non-woven fabrics are appropriately used. Moreover, the bonding sheet | seat which bonded the film etc. on the air-permeable support body can also be used as a non-air-permeable support body. Among these, a resin film or resin-coated paper is preferable because it has a texture close to photographic image quality.

  Examples of the resin film include thermoplastic resins such as polyester resin, polyolefin resin, and nylon. Polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polycyclohexene terephthalate. Polyolefin resins include those made of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene vinyl acetate copolymer, or the main component thereof. Can be illustrated. One or two or more of these thermoplastic resins can be appropriately selected and used, and polystyrene, an acrylate ester copolymer, or the like can be mixed and used as the other thermoplastic resin.

  Films formed by stretching these thermoplastic resins in the machine direction and / or the transverse direction can also be used. In addition, a film may be formed by mixing inorganic fine powder in this thermoplastic resin, and this may be formed into a paper-like layer by, for example, uniaxial stretching treatment or biaxial stretching treatment. In the present invention, a multilayer film obtained by laminating a plurality of such films is used as a support, for example, a 2-3 layer film provided with a base material layer and a paper layer on both sides or one side, Or you may use the 3-5 layer film etc. which formed the surface layer on the paper-like layer of the at least single side | surface further. Such a paper layer made of a thermoplastic resin is generally known as a synthetic paper.

  Examples of the resin-coated paper include paper obtained by extrusion lamination of a thermoplastic resin, and examples of the thermoplastic resin include polyolefin resins such as polypropylene and polyethylene, and polyester resins. In the thermoplastic resin, pigments such as titanium dioxide, dyes, ultraviolet absorbers, and the like can be appropriately blended.

(Other support)
The support may be provided with a layer for adjusting the color with a fluorescent dye or fluorescent pigment on the support surface, an antistatic layer, an anchor layer or a barrier layer may be formed, or may be subjected to corona treatment or the like. Absent.

“Under the ink receiving layer”
The lower layer of the ink receiving layer is a layer having a function of quickly absorbing the solvent component of the ink, and preferably contains a pigment and an adhesive. By forming the lower layer of the ink receiving layer, it is possible to suitably adjust the absorptivity of ink when printing with an ink jet printer, and the printability such as print density, print bleeding and solid uniformity is improved. The present invention is characterized in that an ozone resistance improver is contained in the lower layer of the ink receiving layer.

(About ozone resistance improver)
The ozone resistance improver is a substance having a property that prevents dyes of ink recorded by ink jet recording from fading or discoloring due to contact with ozone present in the atmosphere. Is contained in the lower layer of the ink receiving layer. By containing the ozone resistance improver not in the upper layer of the ink receiving layer but in the lower layer of the ink receiving layer below it, the ozone resistance is further improved.

  Although it does not specifically limit as an ozone resistance improver, Since zinc sulfate and malic acid have a remarkable effect, they are preferable.

  In the case of zinc sulfate, it is preferably contained in a range of 0.5 parts by mass or more and 10 parts by mass or less, more preferably 0.5 to 8 parts by mass with respect to 100 parts by mass of the pigment in the lower layer of the ink receiving layer. is there. By blending 0.5 parts by mass or more, it has an excellent effect on ozone resistance. The more zinc sulfate is added, the more effective the ozone resistance is. However, excessive use tends to be inferior in printing density when recording with dye ink or pigment ink, so use it in the range of 10 parts by mass or less. It is preferable.

  In the case of malic acid, it is preferably contained in the range of 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment in the lower layer of the ink receiving layer. By blending 0.5 parts by mass or more, it has an excellent effect on ozone resistance. The more the malic acid is added, the more effective the ozone resistance is. However, excessive use results in inferior printing density when recording with dye ink or pigment ink. Since the tendency to fall is seen, it is preferable to use in the range of 10 mass parts or less.

(About pigments)
Examples of the pigment blended in the lower layer of the ink receiving layer include kaolin, clay, calcined clay, amorphous silica (also referred to as amorphous silica), synthetic amorphous silica, zinc oxide, aluminum oxide, titanium oxide, aluminum hydroxide, Calcium carbonate, satin white, aluminum silicate, alumina, colloidal silica, zeolite, synthetic zeolite, sepiolite, smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, hydrotalcite, urea resin plastic One or more kinds of various publicly known pigments in the general coated paper manufacturing field, such as pigments and benzoguanamine-based plastic pigments, can be used in combination. Among these, zinc oxide, titanium oxide, and plastic pigments are preferably blended because yellowing of the white paper portion can be prevented. Amorphous silica, alumina, and zeolite are preferably contained as main components because they have high ink absorbability.

  The average particle diameter of the pigment (aggregated particle diameter in the case of an agglomerated pigment) is preferably about 1 to 12 μm, more preferably 2 to 10 μm, and further preferably 2 to 6 μm. By setting the thickness to 1 μm or more, an effect of improving the ink absorption rate can be obtained. By setting the thickness to 12 μm or less, the smoothness and gloss of the upper layer of the ink receiving layer can be prevented. It is also possible to use pigments having different average particle sizes in combination.

  In addition, for the purpose of adjusting the ink absorbency or controlling the penetration of the coating liquid applied on the lower layer of the ink receiving layer, a pigment having a small average particle diameter, for example, an average particle diameter of less than 1 μm, is used as a subcomponent. Can be blended. Examples of such pigments include colloidal silica and alumina sol, and colloidal silica is particularly preferable.

(About adhesive)
Adhesives blended in the lower layer of the ink receiving layer include proteins such as casein, soy protein, synthetic protein, various starches such as starch and oxidized starch, polyvinyl alcohol, cationic polyvinyl alcohol, silyl-modified polyvinyl alcohol and the like. Polyvinyl alcohols including polyvinyl alcohol, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, styrene-butadiene copolymer, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, acrylic polymer latex, ethylene-vinyl acetate copolymer Conventionally known adhesives generally used for coated paper, such as vinyl polymer latexes such as polymers, aqueous polyurethane resins, and aqueous polyester resins, are used alone or in combination.
The aqueous polyurethane resin is also commonly called urethane emulsion, urethane latex, polyurethane latex and the like. The polyurethane resin is obtained from a reaction between a polyisocyanate compound and an active hydrogen-containing compound. It is a polymer compound containing a relatively large number of urethane bonds and urea bonds.

  The blending ratio of the pigment and the adhesive is generally adjusted in the range of 1 to 100 parts by weight, preferably 2 to 50 parts by weight with respect to 100 parts by weight of the pigment, although it depends on the type.

(Other layers below the ink receiving layer)
Various auxiliary agents such as dispersants, thickeners, antifoaming agents, antistatic agents, preservatives and the like used in the production of general coated paper are further appropriately added to the lower layer of the ink receiving layer. In addition, a fluorescent dye or a colorant can be added to the lower layer of the ink receiving layer.

  Further, a thermosensitive polymer compound described later may be blended in the lower layer of the ink receiving layer. By blending the thermosensitive polymer compound, there is a tendency that the print image quality when printed by an ink jet printer becomes clearer. When the ink-receiving layer lower layer containing the temperature-sensitive polymer compound is cooled to the temperature-sensitive point of the temperature-sensitive polymer compound or less at the time of production and then thickened or gelled, and dried by, for example, hot air drying, This is thought to be due to the suppression of minute sag due to wind pressure during drying. However, if a thermosensitive polymer compound is blended, the cost of the material itself is increased, and the temperature of the coating liquid for forming the lower layer of the ink-receiving layer that is formed as necessary is necessary. Therefore, it is preferable not to mix from the viewpoint of cost. Therefore, the blend of the thermosensitive polymer compound in the lower layer of the ink receiving layer is preferably selected as appropriate from the relationship between the desired quality and cost.

(Regarding the formation of the lower layer of the ink receiving layer)
The ink receiving layer lower layer can be formed by applying an ink receiving layer lower layer coating liquid composed of the above-mentioned material onto a support and drying. The ink receiving layer lower layer coating solution is adjusted to a solid content concentration of about 5 to 50% by mass.
The coating amount of the ink receiving layer lower layer coating liquid is, in terms of dry mass, preferably ^{2 to} 60 g / m ² , more preferably about ² to 30 g / m ² , and still more preferably about 4 to ²⁰ g / m ^2. . By setting the coating amount to 2 g / m ² or more, the effect of improving the ink absorbency can be sufficiently obtained, and excellent gloss can be obtained when the upper layer of the ink receiving layer is provided, and to 60 g / m ² or less. As a result, the print density tends to increase, the strength of the coating layer improves, and there is a tendency that powder falls and scratches are less likely to occur.

For coating of the coating solution for the ink receiving layer lower layer, blade coater, air knife coater, roll coater, brush coater, champlex coater, bar coater, lip coater, gravure coater, curtain coater, slot die coater, slide coater, etc. Various known and publicly available coating apparatuses can be used.
Further, after the formation of the lower layer of the ink receiving layer, a smoothing process such as super calendering or brushing can be performed as necessary. Two or more ink receiving layer lower layers may be formed.

About the upper layer of the ink receiving layer
The upper layer of the ink receiving layer is a layer mainly for fixing the dye component and the colored pigment component of the ink for ink jet recording, and is mixed with a pigment and an adhesive, and for the purpose of fixing the ink, a cationic polymer or Cationic compounds such as cationic particles may be blended.

(About pigments)
Examples of pigments include kaolin, clay, calcined clay, amorphous silica (also referred to as amorphous silica), synthetic amorphous silica, zinc oxide, aluminum oxide, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, alumina, Colloidal silica, zeolite, synthetic zeolite, sepiolite, smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, hydrotalcite, urea resin plastic pigment, benzoguanamine plastic pigment, etc. Species or more can be used in combination.

  Among these, fine pigments having an average particle diameter of 10 nm to 1000 nm are preferable. By setting the average particle size to 1000 nm or less, the transparency of the upper layer of the ink-receiving layer of the gas-permeable support is lowered, and the color developability of the colorant fixed in the upper layer of the ink-receiving layer when ink-jet recording is reduced. It is possible to suppress the tendency that the print density is not obtained. Further, by setting the average particle diameter to 10 nm or more, it is possible to suppress the tendency that the ink absorbability is reduced, bleeding or the like occurs, and a desired image quality cannot be obtained.

  The average particle diameter of primary particles constituting the fine pigment is preferably 3 nm or more and 40 nm or less. More preferably, they are 5 nm or more and 30 nm or less, More preferably, they are 7 nm or more and 20 nm or less. By setting the average primary particle diameter to 3 nm or more, the voids between the primary particles are remarkably reduced, the ability to absorb the solvent and the colorant in the ink is lowered, and the desired image quality tends not to be obtained. Can be suppressed. In addition, by setting the average primary particle diameter to 40 nm or less, the aggregated secondary particles become large, the transparency of the upper layer of the ink receiving layer is lowered, and the colorant fixed on the upper layer of the ink receiving layer when ink jet recording is performed. It is possible to suppress a tendency that color developability is lowered and a desired print density cannot be obtained.

  A pigment having an average particle size of 0.7 μm or less can be obtained by, for example, a strong force by mechanical means, that is, a so-called breaking down method (a method of fragmenting a bulk material). Mechanical means include: ultrasonic homogenizer, pressure homogenizer, liquid collision homogenizer, high-speed rotary mill, roller mill, container drive medium mill, medium agitator mill, jet mill, mortar, disintegrator (covered in a bowl-shaped container) A device for grinding and kneading the pulverized material with a bowl-shaped stirring bar), a sand grinder, and the like. In order to reduce the particle size, classification and repeated pulverization can be performed.

  The average particle diameter referred to in the present invention is, regardless of whether the pigment is powder or slurry, first, 200 g of a 3% pigment aqueous dispersion is prepared, and then stirred and dispersed at 1000 rpm for 30 minutes with a commercially available homomixer. Immediately observed with an electron microscope (SEM and TEM) (taken 10,000-400,000 times electron micrographs, measured and averaged the diameter of a 5 cm square particle, “Particle Handbook”, Asakura Bookstore, p52, 1991). As a result of measurement by the present inventors, when the pigment is powder (most pigments having a particle diameter of 1 μm or more), it almost matches the manufacturer's catalog value, but in the case of slurry (most pigments having a particle diameter of 1 μm or less). Although the particle size varies greatly depending on the state of aggregation of the slurry, almost the same value can be obtained under the above measurement conditions.

  As the fine pigment, at least one selected from gas phase method silica, mesoporous silica, colloidal material of wet method silica produced by condensing activated silicic acid, alumina oxide, and alumina hydrate is used. It is preferable. Among these, gas phase method silica and alumina oxide are preferably selected. Among the alumina oxides, gas phase method (fumed) alumina oxide is preferable.

  Vapor phase silica preferably used is also called fumed silica and is generally made by flame hydrolysis. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone or silicon tetrachloride instead of silicon tetrachloride. Can be used in a mixed state.

Mesoporous silica is a porous silica material having an average pore diameter of 1.5 to 100 nm. In addition, mesoporous silica into which aluminum, titanium, vanadium, boron, manganese atoms or the like are introduced can also be used. The physical properties of the porous body are not particularly limited, but the BET specific surface area (nitrogen adsorption specific surface area) is preferably 200 to 1500 m ² / g, and the pore volume is preferably 0.5 to 4 cc / g. The method for synthesizing mesoporous silica is not particularly limited, but is described in U.S. Pat. No. 3,556,725, in which a quaternary ammonium salt containing a long-chain alkyl is used as a template. Hydrothermal synthesis method using amorphous silica powder or alkaline silicate aqueous solution described in Table 5-5503499 etc. as a silica source and using a quaternary ammonium salt having a long chain alkyl group or a phosphonium salt as a template, A method of synthesizing a layered silicate such as kanemite as a silica source described in Kaihei 4-238810, etc. by an ion exchange method using a long-chain alkylammonium cation as a template, further dodecylamine, hexadecylamine, etc. Amines, nonionic surfactants, etc. As the template, it is as a source of silica and water glass or the like and a method of synthesis using an active silica obtained by ion exchange. Examples of the method for removing the template from the nanoporous silica precursor include a method of baking at a high temperature and a method of extracting with an organic solvent.

  The wet-process silica colloid produced by condensing activated silicic acid is obtained by adding an alkali to a colloidally dispersed silica seed solution, and at least selected from an aqueous solution of active silicic acid and alkoxysilane. It is a secondary silica dispersion obtained by growing silica fine particles by adding one kind of feed solution little by little, and can be obtained by a method described in, for example, JP-A-2001-354408.

  Alumina oxide is also generally called crystalline alumina oxide having crystallinity. Specific examples include alumina oxide having χ, κ, γ, δ, θ, η, ρ, pseudo γ, and α crystals. In the present invention, gas phase method alumina oxide and alumina oxide having γ, δ, and θ crystals are preferably selected from the viewpoint of gloss and ink absorbability. Vapor phase alumina oxide (fumed alumina) having a sharp particle size distribution and particularly excellent film formability is most preferred.

  Vapor phase alumina oxide is alumina formed by high temperature hydrolysis of gaseous aluminum trichloride, resulting in the formation of high purity alumina particles. The primary particle size of these particles is nano-order, and shows a very narrow particle size distribution (particle size distribution). Such vapor phase alumina oxide has a cationic surface charge. The use of vapor phase alumina oxide in ink jet coating is shown, for example, in US Pat. No. 5,171,626.

  The alumina hydrate is not particularly limited, but boehmite or pseudoboehmite is preferably selected from the viewpoint of ink absorption speed and film formability. The production method of alumina hydrate includes, for example, a method of hydrolyzing aluminum isopropoxide with water (BE Yoldas, Amer. Ceram. Soc. Bull., 54, 289 (1975), etc.) and aluminum alkoxide. And the like (Japanese Patent Laid-Open No. 06-064918).

(About adhesive)
Examples of the adhesive used in the upper layer of the ink receiving layer include proteins such as casein, soybean protein, and synthetic protein, various starches such as starch and oxidized starch, polyvinyl alcohol, cationic polyvinyl alcohol, and modified polyvinyl alcohol such as silyl-modified polyvinyl alcohol. Polyvinyl alcohols containing alcohol, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, styrene-butadiene copolymer, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, acrylic polymer latex, ethylene-vinyl acetate copolymer Conventionally known adhesives generally used for coated paper, such as vinyl polymer latex such as coalescence, aqueous polyurethane resin, and aqueous polyester resin, are used alone or in combination. The aqueous polyurethane resin is also commonly called urethane emulsion, urethane latex, polyurethane latex and the like. The polyurethane resin is obtained from a reaction between a polyisocyanate compound and an active hydrogen-containing compound. It is a polymer compound containing a relatively large number of urethane bonds and urea bonds. Further, a thermosensitive polymer compound described later can also be used.

  The blending ratio of the pigment and the adhesive is generally adjusted in the range of 1 to 100 parts by weight, preferably 2 to 50 parts by weight with respect to 100 parts by weight of the pigment, although it depends on the type.

(About cationic compounds)
If necessary, the coating liquid for the upper layer of the ink receiving layer may be blended with a cationic compound for the purpose of fixing the colorant (dye or colored pigment) component in the ink for inkjet recording.
As the cationic compound, a known cationic compound can be blended. For example, 1) polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof, 2) acrylic polymers having secondary amino groups, tertiary amino groups and quaternary ammonium groups, 3) polyvinyl amines and polyvinyls Amidines, 4) Dicyan-based cationic compounds represented by dicyandiamide / formalin copolymer, 5) Polyamine-based cationic compounds represented by dicyandiamide / polyethyleneamine copolymer, 6) Epichlorohydrin / dimethylamine copolymer, 7) diallyldimethylammonium -SO ₂ double condensate, 8) diallylamine salt -SO ₂ double condensate, 9) diallyldimethyl ammonium chloride polymers, 10) diallyldimethyl ammonium chloride - acrylamide copolymers, 11 Allylamine salt copolymer, 12) Dialkylaminoethyl (meth) acrylate quaternary salt copolymer, 13) Acrylamide / diallylamine copolymer, 14) Cationic compound such as cationic resin having 5-membered ring amidine structure, etc. Can be illustrated.

  1-30 mass parts is preferable with respect to 100 mass parts of pigments, and, as for the compounding quantity of a cationic compound, More preferably, it is 3-20 mass parts. When the amount of the cationic compound is less than 1 part by mass, it is difficult to obtain the effect of improving the printing density. When the amount of the cationic compound is more than 30 parts by mass, the excess cationic compound blocks the gap, and the ink absorbability is hindered and the image blurs. There is also a risk of unevenness.

(About cationic fine pigments)
In addition, when the cationic compound is blended, it is preferable that at least a part of the cationic compound is mixed with the pigment in advance. In particular, when fine silica is used as a pigment, the silica is generally anionic. When a cationic compound is added to the fine silica particles during mixing, the fine silica particles are aggregated and adjusted to the specific particle size. May be difficult to do.
Therefore, in this case, before the amorphous silica (a relatively large secondary particle size of several microns) which is generally commercially available is pulverized into fine particles by applying a strong force by mechanical means, the amorphous After the cationic compound is mixed and dispersed together with the porous silica and then dispersed and pulverized by mechanical means, or the cationic compound is mixed with the finely divided silica secondary particle dispersion and once thickened and aggregated The specific particle diameter can be adjusted by taking a method of mechanical dispersion / pulverization again.
The pigment treated in this way has a structure in which a cationic compound is partly bonded, and is a slurry that is stably dispersed, or it is difficult to agglomerate even if an additional cationic compound is further added. Have In the present invention, a fine pigment treated with such a cationic substance is referred to as a cationic fine pigment.

  In order to disperse or pulverize a mixture or aggregate of the pigment and the cationic substance, a homomixer, a pressure homogenizer, an ultrasonic homogenizer, a microfluidizer, an optimizer, a nanomizer, a high-speed rotary mill, a roller mill, a container drive medium A mill, a medium stirring mill, a jet mill, a sand grinder, a Clare mix, or the like is used.

When the average secondary particle diameter of the cationic fine pigment exceeds 1000 nm, it can be sufficiently dispersed by processing with a weak mechanical force such as a homomixer. However, a stronger machine is required to grind the average secondary particle diameter to 1000 nm or less. It is effective to apply force, and it is preferable to use a pressure dispersion method.
In the present invention, the pressure dispersion method is a method in which a slurry mixture of raw material particles is continuously passed through an orifice at a high pressure and pulverized under high pressure, and the treatment pressure is 19.6 × 10 ^{6 to} 343.2 × 10. ⁶ Pa (200 to 3500 kgf / cm ² ), more preferably 49.0 × 10 ^{6 to} 245.3 × 10 ⁶ Pa (500 to 2500 kgf / cm ² ), and even more preferably 98.1 × 10 ^{6 to} 196. 2 × 10 ⁶ Pa (1000 to 2000 kgf / cm ² ). Good dispersion or pulverization can be achieved by the above high-pressure pulverization. Further, it is more preferable to use a dispersion or pulverization method in which the slurry-like mixture that has passed through the orifice at a high pressure collides with each other. In the method of opposing collision, the dispersion is pressurized and guided to the inlet side, the dispersion is branched into two passages, and the flow path is narrowed by an orifice to accelerate the flow velocity and collide the particles by colliding with each other. Crush. As a material constituting the portion where the dispersion is accelerated or collided, diamond is preferably used for the reason of suppressing wear of the material.
As the high-pressure pulverizer, a pressure homogenizer, an ultrasonic homogenizer, a microfluidizer, and a nanomizer are used. In particular, a microfluidizer and a nanomizer are preferable as the high-speed collision type homogenizer.
The cationic fine pigment thus treated is generally obtained as an aqueous dispersion (slurry or colloidal particles) having a solid content concentration of about 5 to 20% by mass.

  In addition, an average secondary particle diameter is a particle diameter observed with an electron microscope (SEM and TEM) (take an electron micrograph of 10,000 to 400,000 times, measure the Martin diameter of particles in 5 cm square, Averaged, as described in “Particulate Handbook” (Asakura Shoten, P52, 1991).

  When such a cationic fine pigment is contained in the upper layer of the ink receiving layer, the ink is more uniformly absorbed, resulting in uniform color development with less blurring and an excellent image without color unevenness.

  As the pigment used for the cationic fine pigment, silica and aluminosilicate are preferable, silica is more preferable, and vapor phase method silica is more preferable.

The cationic substance used for the cationic fine pigment is not particularly limited. For example, 1) polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof, 2) secondary amino groups, and tertiary. Acrylic polymer having amino group or quaternary ammonium group, 3) Polyvinylamine and polyvinylamidines, 4) Dicyan-based cationic compounds represented by dicyandiamide / formalin copolymer, 5) Dicyandiamide / polyethyleneamine copolymer polyamine cationic compound represented by, 6) epichlorohydrin - dimethylamine copolymers, 7) diallyldimethyl ammonium -SO ₂ double condensate, 8) diallylamine salt -SO ₂ double condensate, 9) diallyl dimethyl ammonium chloride polymer 10) diallyldimethylammonium chloride-acrylamide copolymer, 11) copolymer of allylamine salt, 12) dialkylaminoethyl (meth) acrylate quaternary salt copolymer, 13) acrylamide-diallylamine copolymer, 14) 5 And cationic substances such as a cationic resin having a membered ring amidine structure.

  Among them, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride-acrylamide copolymer, hydrochloride of acrylamide / diallylamine copolymer, dicyandiamide-polyethyleneamine copolymer, and a cationic resin having a 5-membered ring amidine structure It is preferable to use at least one selected from the group consisting of excellent color developability, little blurring, uniform color development, and excellent image without color unevenness.

  The ratio (mass ratio) between the pigment and the cationic compound in the cationic fine pigment is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass with respect to 100 parts by mass of the pigment. is there.

  When the cationic fine pigment is used, the transparency of the ink receiving layer upper layer is excellent when the ratio of the cationic fine pigment in the total pigment in the coating liquid for the ink receiving layer upper layer is 50% by mass or more. Therefore, it is preferable. When the ratio of the cationic fine pigment in the total pigment is less than 50% by mass, the transparency of the upper layer of the ink receiving layer is lowered, and the image quality such as the print density may be lowered.

(Other ink receiving layer upper layer)
Various auxiliary agents such as preservability improvers, antifoaming agents, colorants, fluorescent brighteners, antistatic agents, preservatives, dispersants, thickeners, and the like are appropriately added to the ink receiving layer upper layer coating liquid. can do.

  The ink receiving layer upper layer coating liquid may be formed by coating and drying on the ink receiving layer lower layer. Further, when a so-called casting method is employed in which the coated upper surface of the ink receiving layer is wet and pressed against a heated mirror roll (for example, a cast drum) and dried, a high gloss inkjet recording sheet is obtained. Therefore, it is preferable. As the casting method, a known wet method, rewetting method, and solidification method can be employed.

The coating liquid for the upper layer of the ink receiving layer is generally adjusted to a solid content concentration of about 5 to 50% by mass. A preferable solid content concentration is 5 to 20% by mass. The coating amount of the ink receiving layer for an upper layer coating liquid, by dry weight, preferably from 2 to 15 g / ^{m 2,} more preferably 2 to 10 g / ^{m 2,} more preferably from 3 to 8 g / ^{m 2.} When gloss finishing is performed using a mirror roll in a subsequent process, by setting the coating amount to 2 g / m ² or more, excellent gloss can be obtained when cast processing is performed, and ink absorbability is also improved. By setting it to 15 g / m ² or less, cracking of the coating layer is suppressed, and dot roundness when ink jet recording is improved.

  For coating of the ink receiving layer upper layer coating solution, blade coater, air knife coater, roll coater, brush coater, champlex coater, bar coater, lip coater, gravure coater, curtain coater, slot die coater, slide coater, spray Various publicly known coating apparatuses such as the above can be used. Among these, air knife coaters, lip coaters, slide coaters, curtain coaters, and slot die coaters are preferably used.

  In addition, it is preferable that the paper surface pH of the upper surface of the ink receiving layer is 5.5 to 7.0, since a printing density is high and a clear image can be obtained when printing with dye ink or pigment ink. In particular, when printing with pigment ink, if the paper surface pH is too low, the pigment ink agglomerates on the paper surface, and a decrease in print density and print gloss is observed.

(Preferred upper layer of ink receiving layer)
More preferably, the upper layer of the ink receiving layer is applied simultaneously with the application of the coating liquid containing the fine pigment and the adhesive, or during the drying of the coating liquid layer to which the coating liquid has been applied. It is a layer produced by forming a film by thickening or crosslinking the coating liquid before showing. By forming such a layer, excellent printability can be obtained not only with dye ink but also with pigment ink without causing cracks on the surface, and an ink receiving layer upper layer having a highly smooth surface can be produced. . Specifically, the methods listed in the following (A) to (C) can be exemplified and can be appropriately adopted, but are not limited to these methods.

For example,
(A) It contains a hydrophilic resin that forms a hydrogel by electron beam irradiation, and immediately after coating or during the drying of the coated coating layer, the coating layer has a reduced drying rate. Before showing, thickening the coating layer by electron beam irradiation (form hydrogel),
(B) The upper layer of the ink receiving layer is a coating liquid containing an adhesive, and immediately after coating or during the drying of the coated coating liquid layer, the coating liquid layer has a reduced drying rate. Before showing, a method of thickening and crosslinking the paint with a compound having crosslinkability with an adhesive,
(C) The coating liquid that forms the upper layer of the ink receiving layer reversibly shows hydrophilicity and hydrophobicity due to temperature change, and the coating liquid thickens or gels in the temperature range showing hydrophilicity. A method of thickening and crosslinking the coating by changing the temperature to a temperature range showing hydrophilicity after coating in a temperature range showing hydrophobicity using a coating liquid containing a thermophilic polymer compound,
Etc. can be exemplified.

(About (A) method)
When the upper layer of the ink receiving layer is formed by the above method (A), the adhesive has a hydrophilic property that does not have a radical polymerizable unsaturated bond and forms a hydrogel by irradiating an aqueous solution with an electron beam. Using an adhesive, a coating solution containing 1 to 100 parts by weight of a hydrophilic adhesive is applied to 100 parts by weight of the pigment, and then the applied coating solution is hydrogelated by irradiating an electron beam. It is good to form after making it dry.

  Examples of the hydrophilic adhesive that does not have a radical polymerizable unsaturated bond and forms a hydrogel by irradiating an aqueous solution with an electron beam include, for example, polyvinyl alcohol, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, water-soluble Polyvinyl acetal, poly-N-vinylacetamide, polyacrylamide, polyacryloylmorpholine, polyhydroxyalkyl acrylate, polyacrylic acid, hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, gelatin, casein, and water-soluble derivatives thereof And copolymers thereof, and the like, and these may be used alone or in combination.

As the electron beam irradiation method, for example, a scanning method, a curtain beam method, a broad beam method, or the like is adopted, and an acceleration voltage at the time of irradiation with an electron beam is appropriately about 50 to 300 kV. The amount of electron beam irradiation is preferably adjusted in the range of about 1 to 200 kGy. If it is less than 1 kGy, it is not sufficient to gel the coating layer, and irradiation exceeding 200 kGy is not preferable because it may cause deterioration or discoloration of the substrate or the coating layer.
As a method of performing electron beam irradiation, (1) coating, electron beam irradiation, and drying may be repeated, or (2) the next layer may be coated and dried after electron beam irradiation, (3) There are methods such as applying multiple layers simultaneously and irradiating with an electron beam.

  In addition, the coating liquid for the ink receiving layer upper layer is applied to a blade coater, an air knife coater, a roll coater, a brush coater, a champlex coater, a bar coater, a lip coater, a gravure coater, a curtain coater, a slot die coater, and a slide coater. Various publicly known coating devices such as sprays can be used. Among these, air knife coaters, lip coaters, slide coaters, curtain coaters, and slot die coaters are preferably used. When these coating apparatuses are used, the glossiness tends to be better because the coating layer can be formed with a uniform thickness that is not easily affected by minute irregularities of the air-permeable substrate or the undercoat layer.

(About (B) method)
When the upper layer of the ink receiving layer is formed by the method (B), a known adhesive used for inkjet recording sheets can be used. Examples thereof include water-soluble resins such as polyvinyl alcohol, polyvinyl pyrrolidone, casein, soybean protein, synthetic proteins, starch, carboxymethyl cellulose, and cellulose derivatives such as methyl cellulose. In particular, polyvinyl alcohol having high adhesion to the pigment is preferably used. In particular, in order to improve the balance between film formability and ink absorbability, it is preferable to use polyvinyl alcohol having a polymerization degree of 2000 or more, and polyvinyl alcohol having a polymerization degree of 3600 to 5000 is more preferable. In order to improve ink absorbability, etc., two or more kinds of adhesive materials (for example, a mixture of two or more water-soluble resins, a mixture of one or more water-soluble resins and one or more latexes) are used. May be.

  Various known crosslinking agents and gelling agents can be used as the compound having crosslinkability with the adhesive. Compounds having crosslinkability to polyvinyl alcohol include aldehyde-based crosslinking agents such as glyoxal, epoxy-based crosslinking agents such as ethylene glycol diglycidyl ether, vinyl-based crosslinking agents such as bisvinylsulfonylmethyl ether, and boron-containing compounds such as boric acid and borax. Examples thereof include compounds, glycidyl compounds, zirconium compounds, aluminum compounds, chromium compounds, etc. Among them, boron-containing compounds are particularly preferable because thickening or gelation occurs quickly.

The boron-containing compound is an oxygen acid having a boron atom as a central atom and a salt thereof. Examples include orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid, and their sodium, potassium, and ammonium salts. Among these, orthoboric acid and disodium tetraborate are preferably used because they have an effect of moderately thickening the paint.
Although content of a boron compound is based also on the polymerization degree of a boron compound and polyvinyl alcohol, it is preferable to contain 0.01-2.0 g / m < ² > on the single side | surface of a base material. When it is more than 2.0 g / m ² , the crosslink density with the hydrophilic adhesive becomes high, the coating film becomes hard and is easily broken. On the other hand, when the amount is less than 0.01 g / m ² , the crosslinking with the hydrophilic adhesive is weak, the gelation of the coating is weakened, and the coating film is easily cracked.

  For example, the upper layer of the ink receiving layer may be prepared by, for example, preliminarily applying and impregnating a cross-linking agent to the upper layer of the ink receiving layer, and applying a coating liquid for the upper layer of the ink receiving layer, It may be prepared by a method such as applying in advance, or applying a coating liquid for the upper layer of the ink receiving layer, and then applying a cross-linking agent. However, application of the cross-linking agent in advance may increase viscosity or gelation. This is preferable because a uniform upper layer of the ink receiving layer can be obtained.

  In addition, the coating liquid for the ink receiving layer upper layer is applied to a blade coater, an air knife coater, a roll coater, a brush coater, a champlex coater, a bar coater, a lip coater, a gravure coater, a curtain coater, a slot die coater, and a slide coater. Various publicly known coating devices such as sprays can be used. Among these, air knife coaters, lip coaters, slide coaters, curtain coaters, and slot die coaters are preferably used. When these coating apparatuses are used, the glossiness tends to be better because the coating layer can be formed with a uniform thickness that is not easily affected by minute irregularities of the air-permeable substrate or the undercoat layer.

(About (C) method)
When the upper layer of the ink receiving layer is formed by the above method (C), the adhesive reversibly shows hydrophilicity and hydrophobicity due to temperature change, and the coating liquid thickens or gels in the temperature range showing hydrophilicity. It is preferable to use a temperature-sensitive polymer compound characterized by this. The temperature at which the hydrophilicity-hydrophobicity changes is referred to as “temperature sensitive point”. This thermosensitive polymer compound can be blended as a main component of the adhesive of the upper layer of the ink receiving layer.

The coating liquid containing the temperature-sensitive polymer compound is easily coated without increasing the viscosity of the coating liquid by coating in a temperature range where the temperature-sensitive polymer compound exhibits hydrophobicity. Moreover, a coating layer is gelatinized by changing temperature to the temperature range which shows hydrophilicity after coating. Thereafter, the upper layer of the ink receiving layer can be formed by drying the coating layer.
This method is more uniform than the gelation of the upper layer of the ink receiving layer by using a gelling agent, so that the gloss is further improved, and the printing portion when printing with an ink jet printer is used. The solid uniformity of the is improved.

A thermosensitive polymer compound characterized by reversibly showing hydrophilicity and hydrophobicity due to temperature changes, and the coating liquid thickens or gels in the temperature range where hydrophilicity is exhibited. It is a compound that exhibits different properties of hydrophilicity and hydrophobicity.
Examples of such compounds include (1) thermosensitive polymer compounds that are hydrophobic at temperatures above the temperature sensitive point and are hydrophilic at temperatures below the temperature sensitive point, and (2) temperature sensitive. It is also possible to use a temperature-sensitive polymer compound that exhibits hydrophobicity in a temperature range below the point and exhibits hydrophilicity in a temperature range higher than the temperature-sensitive point. “Hydrophilic” means that in a system in which a thermosensitive polymer compound and water coexist, the thermosensitive polymer compound is more stable when mixed with water than when it is phase-separated. `` Hydrophobic '' means that in a system in which a thermosensitive polymer compound and water coexist, the thermosensitive polymer compound is more stable in a phase separated from water than in a compatible state. means.
In the present invention, a temperature-responsive polymer compound that exhibits hydrophilicity in a temperature range below the predetermined temperature and exhibits hydrophobicity in a temperature range higher than the predetermined temperature is preferable. Hereinafter, the suitable polymer compound will be described as an example.

By the way, the change of hydrophilicity-hydrophobicity is, for example, a rapid viscosity change accompanying a temperature change of a system in which a thermosensitive polymer compound and water coexist, or a system in which a thermosensitive polymer compound and water coexist. It appears as a sudden change in the transparency of the water, and a rapid change in the solubility of the thermosensitive polymer compound in water.
That is, the viscosity when the temperature of the system in which the thermosensitive polymer compound and water coexist is gradually lowered from the temperature range where the thermosensitive polymer compound is hydrophobic (temperature higher than the temperature sensitive point). A temperature-sensitive point can be obtained as a transition point at which the temperature-viscosity curve obtained by measurement changes (thickens) abruptly. Alternatively, when an aqueous dispersion of a temperature-sensitive polymer compound obtained in a temperature range where the temperature-sensitive polymer compound is hydrophobic (temperature higher than the temperature point) is gradually cooled, the dispersion becomes transparent. Alternatively, the temperature sensitive point of the temperature sensitive polymer compound can be determined as the temperature at which gelation begins.

  Although the temperature sensitive point of a thermosensitive polymer compound is not specifically limited, It is preferable that it is 0-30 degreeC. Incidentally, when the temperature is 0 ° C. or higher, it is possible to suppress deterioration in cooling efficiency when the coating liquid layer is thickened or gelled by cooling after coating the coating liquid for the upper layer of the ink receiving layer. If the cooling efficiency is deteriorated, the coating liquid may permeate into the air-permeable support, which may cause a decrease in glossiness. By setting it as 30 degrees C or less, the tendency for a coating liquid to gelatinize in the case of coating and to become unable to manufacture stably can be suppressed. A particularly preferred temperature sensitive point is 10 to 25 ° C.

  When forming the ink receiving layer upper layer, the temperature sensitive polymer compound is preferably used in the form of a polymer emulsion containing the temperature sensitive polymer compound in the coating liquid for forming the ink receiving layer upper layer. This polymer emulsion has a temperature (temperature sensitive point) at which the viscosity changes suddenly due to the influence of the hydrophilic-hydrophobic change due to the temperature change of the temperature-sensitive polymer compound contained.

  It is preferable that the coating liquid for the upper layer of the ink receiving layer containing this compound is adjusted to a temperature higher than the temperature sensitive point, and the coating liquid is applied to the air-permeable support to form a coating liquid layer. Then, if it cools to the temperature below a temperature sensitive point as needed, a temperature sensitive high molecular compound will be thickened or gelatinized and a coating liquid layer will be formed. It is preferable that the surface temperature of the air-permeable support is adjusted to a temperature lower than the temperature sensitive point before applying the coating liquid. The surface temperature of the air-permeable support before coating is preferably kept below the temperature sensitive point with cold air or cold water.

As a method for preparing the coating liquid for forming the upper layer of the ink receiving layer, for example, it can be carried out as follows. First, a polymer emulsion containing a thermosensitive polymer compound is prepared as described in JP-A-2003-040916.
That is, in the temperature range higher than the temperature sensitive point of the thermosensitive polymer compound, the polymerization reaction is performed using the above-described monomer in the presence of polyvinyl alcohol and / or polyvinyl alcohol derivative. More specifically, a surfactant is dissolved in water, and the above-mentioned polyvinyl alcohol and / or polyvinyl alcohol derivative and a copolymerization monomer component such as a main monomer (M) and a submonomer (N) are added and emulsified to start radical polymerization. In addition to a method of performing emulsion polymerization by a reaction by batch charging with an agent added, there may be mentioned a method of supplying the above-mentioned copolymerization component or radical polymerization initiator to the reaction system by a method such as continuous dropping or divided addition.
Such polymer emulsions are commercially available, for example, from Asahi Kasei Corporation as temperature sensitive resins under trade names such as ALB-8.01 and ALB-22.03.
By mixing the polymer emulsion, the pigment, and optional components, a coating liquid for forming the ink receiving layer upper layer can be obtained.
The coating liquid for forming the upper layer of the ink receiving layer is preferably heated or kept at a temperature higher than the temperature sensitive point after preparation until coating.

  In addition, the coating liquid for the ink receiving layer upper layer is applied to a blade coater, an air knife coater, a roll coater, a brush coater, a champlex coater, a bar coater, a lip coater, a gravure coater, a curtain coater, a slot die coater, and a slide coater. Various publicly known coating devices such as sprays can be used. Among these, air knife coaters, lip coaters, slide coaters, curtain coaters, and slot die coaters are preferably used. When these coating apparatuses are used, the glossiness tends to be better because the coating layer can be formed with a uniform thickness that is not easily affected by minute irregularities of the air-permeable substrate or the undercoat layer.

The coated coating layer is cooled in an undried state or in a slightly dried state. The method for cooling is not particularly limited as long as the coated surface can be cooled, such as a cold air machine, a cooling roll, and a low-temperature gas. By cooling, the coating liquid layer thickens or gels.
The cooling may be performed to a temperature at which the coating liquid layer is thickened or gelled. For example, the coating liquid layer may be cooled to a temperature sensitive point or less of the thermosensitive polymer compound blended in the coating liquid layer. However, excessive cooling increases the degree of gelation and may deteriorate the glossiness, so it is preferable to cool to a temperature 10 ° C. lower than the temperature sensitive point. In order to increase the cooling efficiency, the sheet (the air-permeable support and the undercoat layer formed as necessary) before applying the coating liquid can be cooled in advance and is preferable.

In particular, a method in which a treatment liquid (for example, cold water or the like) lower than the temperature sensitive point is applied to the sheet before the application of the coating liquid is most preferable because the temperature of the sheet can be quickly changed. If the temperature of the liquid at the time of applying the treatment liquid is 10 ° C. or more lower than the temperature sensitive point, it is preferable because the temperature change of the ink receiving layer upper layer coating liquid can be performed rapidly. In this case, the ink jet recording paper can perform uniform recording and can obtain excellent recording suitability for pigment ink.
The treatment liquid is preferably a solvent or water, and is particularly preferably water because it is simple in use. In addition, a method of coating the ink receiving layer upper layer coating liquid containing the thermosensitive polymer compound while the treatment liquid is undried is preferable because the temperature change of the ink receiving layer upper layer coating liquid is particularly rapidly performed. The treatment liquid preferably contains a cationic compound and a preservability improver, so that it can penetrate into the support or the undercoat layer when applied, and an effect of improving water resistance and heat and moisture bleeding is seen. Further, the treatment liquid may contain an auxiliary agent such as a crosslinking agent such as a boron compound or a zirconium compound, a pH adjuster, a surfactant, an antifoaming agent or a preservative.

  In addition, water is used as the solvent of the coating solution, but the adjustment of the temperature sensitive point of the thermosensitive polymer compound and the drying at the time of casting are slowed down to obtain an upper layer of an ink receiving layer with good printability. Therefore, it is also preferable to mix or use an organic solvent.

In the case of the compound (2), after applying the coating liquid adjusted to a temperature lower than the temperature sensitive point, the coating liquid is thickened or gelled by heating to a temperature higher than the temperature sensitive point. Become.
Examples of such a compound include compounds disclosed in JP-A-8-244334. For example, the coating layer is thickened or gelled by raising the temperature by a method capable of heating the coated surface, such as a hot air machine or an infrared heater.

“Glossing”
The upper layer of the ink receiving layer formed by the above method has a high glossiness and excellent recording suitability, but can be subjected to a gloss treatment in order to further improve the glossiness. As the gloss process, a calendar process, a cast process, or a method of forming a gloss developing layer can be obtained.
(Calendar processing)
Gloss can be expressed by applying pressure to the obtained upper layer of the ink receiving layer with a known calendar device such as a calendar, a soft calendar, or a super calendar.
(Cast process)
While the upper layer of the ink receiving layer is in a wet state, the smooth surface can be transferred to the surface of the upper layer of the ink receiving layer by press-contacting a mirror roll (mirror drum) or a smooth film.

  For example, when the support is an air-permeable support, the gloss is obtained by a so-called casting method in which the ink-receiving layer upper layer is pressed and dried on a heated mirror-finished metal surface (for example, a mirror roll) while it is wet. It is particularly preferable that the best glossiness can be obtained. Specifically, after the ink receiving layer upper layer is applied, it is pressed against the mirror surface roll without passing through the drying step, or after the ink receiving layer upper layer is applied, it is pressed against the mirror surface roll in a semi-dried state that is slightly dried, After applying the upper layer of the ink receiving layer, apply a wetting liquid to the semi-dried state that has been slightly dried and press contact with the mirror surface roll, or after applying the upper layer of the ink receiving layer, dry and apply the wetting liquid to the mirror surface roll. A method such as pressure welding is adopted.

  In this case, it is preferable to use a release agent in order to smoothly peel the upper layer of the ink receiving layer from the mirror surface roll. A release agent may be used by at least one of the method of blending with the ink receiving layer upper layer coating liquid, coating on the mirror roll surface, and blending with the wetting liquid.

  Examples of mold release agents include higher fatty acid amides such as stearamide and oleic amide, polyolefin waxes such as polyethylene wax, polyethylene oxide wax and polypropylene wax, calcium stearate, zinc stearate, potassium oleate and ammonium oleate. Examples thereof include higher fatty acid alkali salts, silicone compounds such as lecithin, silicone oil and silicone wax, and fluorine compounds such as polytetrafluoroethylene. Of these, the use of a cationic release agent is particularly preferred.

  In addition, the wetting liquid contains various types of synthetic resin latex such as styrene-butadiene latex and methyl methacrylate-butadiene copolymer latex, proteins such as casein, soy protein, synthetic protein, starch and oxidized starch, as necessary. Various thickening agents such as starch, polyvinyl alcohol, cellulose derivatives such as carboxymethylcellulose and methylcellulose, polycarboxylic acid, polyacrylic acid, acrylic emulsion, polyamide, polyester, alkali thickening type and nonionic surfactant, and flow modification Agent, sodium chloride, ammonium chloride, zinc chloride, magnesium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, zinc sulfate, magnesium sulfate, ferrous sulfate, sodium nitrate, ammonium nitrate, monobasic sodium phosphate, ammonium phosphate, Calcium acid, sodium polyphosphate, sodium hexametaphosphate, sodium formate, ammonium formate, sodium acetate, potassium acetate, sodium monochloroacetate, sodium malonate, sodium tartrate, potassium tartrate, potassium citrate, sodium lactate, sodium gluconate, adipic acid Ammonium and metal salts of inorganic and organic acids such as sodium, sodium dioctylsulfosuccinate and sodium aluminate, and amines such as methylamine, diethanolamine, diethylenetriamine, diisopropylamine, triethanolamine, ethanolamine and ethanolamine , Phosphate ester, polyoxyethylene alkylphenol ether phosphate ester salt, polyoxyethylene ether phosphate ester salt, Phosphate esters such as alkylphenol ether phosphates, polyoxyethylene, alkyl ethers, polyoxyethylene and aqueous ammonia, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, polyethylene glycol diglycyl ether, polypropylene glycol diglycidyl ether Various additives such as polyfunctional epoxy compounds such as diglycidyl ester and adipic acid, urea-formaldehyde, polyamide-epichlorohydrin, glyoxal, etc. It is also possible to adjust by adding in the range of 0.05 to 10% by mass, preferably 0.1 to 5% by mass.

  Furthermore, various auxiliary agents such as a dispersant, an antifoaming agent, a colorant, a fluorescent dye, an antistatic agent, and an antiseptic are added to the wetting liquid as appropriate. As an auxiliary agent, pigments such as alumina, silica, clay and calcium carbonate can be added.

  The wetting liquid may be applied in a plurality of times. By dividing into a plurality of times, for example, a combination of a plurality of additives that aggregate when mixed can be applied as a wetting liquid.

(Formation of glossy layer)
A glossy expression layer can also be formed by applying a coating liquid containing a fine pigment having an average particle diameter of 0.01 to 1 μm on the upper layer of the ink receiving layer. As such a fine pigment, the fine pigment shown in the upper layer of the ink receiving layer can be used, and a colloidal material of wet-process silica produced by condensing vapor-phase process silica, mesoporous silica, and active silicic acid, alumina oxidation Product, alumina hydrate, and colloidal silica. The fine pigment may be in the form of a monodispersion or an aggregated particle dispersion. However, in order to obtain a high print density and high gloss, the fine pigment monodispersion or aggregated particles may be used. Among the dispersions, those having a small particle diameter are mainly preferably used. In the case of a monodisperse, the average primary particle diameter is preferably 3 to 100 nm, more preferably 10 to 80 nm. In the case of an aggregated particle dispersion, a fine pigment having an average primary particle size of 3 to 70 nm, preferably 5 to 40 nm, and an average (secondary) particle size of 700 nm or less, preferably 400 nm or less is preferable.

The gloss developing layer is a gloss developing layer of the ink jet recording sheet, and it is necessary to provide a very thin layer on the upper layer of the ink receiving layer so as not to impair the ink absorbability. The solid coating amount of the glossy layer is preferably in the range of 0.1 to 10 g / ^{m 2,} more preferably 0.2-5 g / ^{m 2,} more preferably 0.5 to 2 g / ^{m 2.} If the coating amount is small, the coating film becomes thin and interference colors due to light are likely to be generated. On the other hand, if the coating amount is large, the ink absorption rate may be significantly reduced.

  Further, at the nip portion between the mirror roll and the press roll, a paint reservoir for the gloss developing layer is formed between the upper surface of the ink receiving layer and the mirror roll, and after the gloss developing layer is applied, A coating method in which a heated mirror-finished metal surface is pressure-bonded is particularly preferable because it exhibits a very large effect on gloss improvement.

  When a gas-permeable support is used as the support, the gloss-developing layer may be dried with a mirror roll after being pressed onto the mirror roll, but if the drying is insufficient, it may be dried in a subsequent step. It is also possible to assist drying with infrared rays or the like from the back surface during pressure bonding and drying. Moreover, in order to correct the curl of the obtained ink jet recording material, a humidity control area may be provided after drying.

  When a non-permeable support (for example, resin-coated paper) is used as the support, it is not dried on a mirror-finished metal surface (mirror roll), but is crimped (nip) on a mirror-finish metal surface (mirror roll). Then, it is good to peel and to dry in a post process. The drying method for the post-process is not particularly limited, and various conventionally known drying methods such as hot air drying, gas heater drying, high-frequency drying, electric heater drying, infrared heater drying, laser drying, and electron beam drying can be used. Used as appropriate. Of these, hot air drying is preferred because it is advantageous in terms of cost.

In this method, in a normal casting method, the wet paint is brought into contact with a mirror surface roll and dried in the contacted state, so that moisture in the paint becomes vapor and escapes to the back surface. However, in the case of a non-permeable support, the generated vapor has no escape space and exists between the support and the mirror roll. At this time, the vapor that has lost its escape during contact with the mirror roll may lift the support and destroy the weakest part of the coating layer (the upper layer of the ink receiving layer, the gloss developing layer, and the undercoat layer). Alternatively, when the adhesion of the paint to the mirror-finished heated mirror roll is weak, it peels off at the interface between the coating layer and the mirror roll, and the mirror surface of the mirror roll cannot be sufficiently copied, so-called poor adhesion phenomenon. Will cause. Alternatively, if the undried coating layer is weaker than the adhesive force between the mirror surface roll and the paint, it will break inside the coating layer, so a part of the coating layer will remain on the surface of the mirror surface roll and stain the mirror surface roll. Will cause.
In either case, it is impossible to form a beautiful cast surface, resulting in quality and operational problems. In the present invention, when using a non-air-permeable support such as a resin-coated paper or a plastic film, it is preferable that the film is peeled after being pressed against a mirror surface roll and dried in a subsequent step.

  The surface temperature of a metal surface such as a mirror roll is preferably 80 to 120 ° C. If the surface temperature of the metal surface is less than 80 ° C, the drying effect is poor and the productivity may be reduced. If the surface temperature exceeds 120 ° C, the surface layer coating liquid bumps on the metal surface, resulting in glossiness and printability. May decrease.

  Moreover, it is preferable to add a release agent to the gloss developing layer coating liquid for the purpose of imparting releasability from a mirror-finished metal surface or the like in the gloss developing layer coating liquid. It is also possible to apply a release agent to the mirror roll in advance.

  Examples of mold release agents include higher fatty acid amides such as stearamide and oleic amide, polyolefin waxes such as polyethylene wax, polyethylene oxide wax and polypropylene wax, calcium stearate, zinc stearate, potassium oleate and ammonium oleate. Examples thereof include higher fatty acid alkali salts, silicone compounds such as lecithin, silicone oil and silicone wax, and fluorine compounds such as polytetrafluoroethylene. Of these, the use of a cationic release agent is particularly preferred.

  The compounding quantity of a mold release agent is 0.1-50 mass parts with respect to 100 mass parts of fine pigments, Preferably it is 0.3-30 mass parts, More preferably, it adjusts in the range of 0.5-20 mass parts. If the blending amount is small, it is difficult to obtain the effect of improving the releasability. On the other hand, if the blending amount is large, the gloss may be decreased, or the ink repellency or the print density may be decreased.

  In addition, for the glossy layer coating liquid, if necessary, synthetic resin latex such as styrene-butadiene latex and methyl methacrylate-butadiene copolymer latex, proteins such as casein, soy protein, synthetic protein, starch and oxidized Various starches such as starch, cellulose derivatives such as polyvinyl alcohol, carboxymethylcellulose and methylcellulose, various thickeners such as polycarboxylic acid, polyacrylic acid, acrylic emulsion, polyamide, polyester, alkali thickener and nonionic surfactant Agent, flow modifier, sodium chloride, ammonium chloride, zinc chloride, magnesium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, zinc sulfate, magnesium sulfate, ferrous sulfate, sodium nitrate, ammonium nitrate, sodium monophosphate, ammonium phosphate Calcium, calcium phosphate, sodium polyphosphate, sodium hexametaphosphate, sodium formate, ammonium formate, sodium acetate, potassium acetate, sodium monochloroacetate, sodium malonate, sodium tartrate, potassium tartrate, potassium citrate, sodium lactate, sodium gluconate, Ammonium salts and metal salts of inorganic and organic acids such as sodium adipate, sodium dioctylsulfosuccinate and sodium aluminate, as well as methylamine, diethanolamine, diethylenetriamine, diisopropylamine, triethanolamine, ethanolamine, ethanolamine, etc. Amines, phosphates, polyoxyethylene alkylphenol ether phosphates, polyoxyethylene ether phosphates Phosphate esters such as tellurium salt, alkylphenol ether phosphate ester salt, polyoxyethylene, alkyl ether, polyoxyethylene and aqueous ammonia, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, polyethylene glycol diglycyl ether, polypropylene glycol diester Various additives such as polyfunctional epoxy compounds such as glycidyl ether and adipic acid diglycidyl ester, various water-proofing agents such as urea-formaldehyde, polyamide-epichlorohydrin, and glioxal, and a printing suitability improver in a wetting liquid It is also possible to adjust by adding 0.05 to 10 mass%, preferably 0.1 to 5 mass%.

  Furthermore, various auxiliary agents such as a dispersant, an antifoaming agent, a colorant, a fluorescent dye, an antistatic agent, and a preservative are appropriately added to the glossy layer coating liquid.

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

(Production of air-permeable support (paper substrate))
Wood pulp (LBKP: freeness 440 ml CSF) 100 parts, filler (calcium carbonate 3: talc 1 ratio) 15 parts, commercially available sizing agent (trade name: Fibran 81K, manufactured by NSC Japan) 0.05 part , Using a papermaking material consisting of 0.45 parts of sulfuric acid band, 0.45 parts of starch, 0.4 parts of polyamide / epichlorohydrin resin as a paper strength enhancer and a little yield improver, and a basis weight of 192 g on a long net paper machine After obtaining a paper substrate of / m ² , super calendering was performed at a linear pressure of 150 kg / cm to obtain a paper substrate.
The obtained paper substrate had a thickness of 205 μm and an air permeability of 30 seconds / 100 cc.

"Preparation of coating solution for ink receiving layer lower layer"
Ink-receiving layer lower layer coating liquids A to D having the following compositions and characteristics were prepared.

(Ink-receiving layer lower layer coating solution A)
Synthetic amorphous silica (trade name: Fine Seal X-45, manufactured by Tokuyama Corporation, average secondary particle diameter 4.5 μm) 100 parts, silyl-modified polyvinyl alcohol (trade name: R1130, manufactured by Kuraray Co., Ltd.) 25 Part, fluorescent dye (trade name: Whitetex BPS (H), manufactured by Sumitomo Chemical Co., Ltd.) 2 parts Zinc sulfate 1 part (manufactured by Toho Zinc Co., Ltd.) Solid content concentration 15%.

(Ink-receiving layer lower layer coating solution B)
Synthetic amorphous silica (trade name: Fine Seal X-45, manufactured by Tokuyama Corporation, average secondary particle diameter 4.5 μm) 100 parts, silyl-modified polyvinyl alcohol (trade name: R1130, manufactured by Kuraray Co., Ltd.) 25 Part, fluorescent dye (trade name: Whitetex BPS (H), manufactured by Sumitomo Chemical Co., Ltd.) 2 parts zinc sulfate 5 parts (manufactured by Toho Zinc Co., Ltd.) solid content concentration 15%.

(Ink-receiving layer lower layer coating solution C)
Synthetic amorphous silica (trade name: Fine Seal X-45, manufactured by Tokuyama Corporation, average secondary particle diameter 4.5 μm) 100 parts, silyl-modified polyvinyl alcohol (trade name: R1130, manufactured by Kuraray Co., Ltd.) 25 Part, fluorescent dye (trade name: Whitetex BPS (H), manufactured by Sumitomo Chemical Co., Ltd.) 2 parts malic acid 5 parts (manufactured by Iwata Chemical Co., Ltd.) solid content concentration 15%.

(Ink-receiving layer lower layer coating solution D)
Synthetic amorphous silica (trade name: Fine Seal X-45, manufactured by Tokuyama Corporation, average secondary particle diameter 4.5 μm) 100 parts, silyl-modified polyvinyl alcohol (trade name: R1130, manufactured by Kuraray Co., Ltd.) 25 Part, fluorescent dye (trade name: Whitetex BPS (H), manufactured by Sumitomo Chemical Co., Ltd.) 2 parts solid content concentration 15%.

"Preparation of cationic fine pigment"
Commercially available vapor phase silica (trade name: Leolosil QS-30, average primary particle size 9 nm, specific surface area 300 m ² / g, manufactured by Tokuyama Corporation) was dispersed and pulverized with a sand grinder, then nanomizer (trade name: Nanomizer, Using a nanomizer), pulverization and dispersion were repeated, and after classification, a 10% dispersion having an average secondary particle diameter of 80 nm was prepared.
10 parts of diallyldimethylammonium chloride-acrylamide copolymer (trade name: PAS-J-81, manufactured by Nitto Boseki Co., Ltd.) is added as a cationic compound to the dispersion to agglomerate the pigment and increase the dispersion. After causing viscosity, pulverization and dispersion were repeated using a nanomizer again to prepare a 12% dispersion liquid having an average secondary particle diameter of 300 nm to obtain a cationic fine pigment.

“Preparation of coating solution for upper layer of ink receiving layer”
Ink-receiving layer upper layer coating liquids A to D having the following compositions and characteristics were prepared.

(Ink-receiving layer upper layer coating solution A)
100 parts of the above-mentioned cationic fine pigment, 20 parts of a thermosensitive polymer compound (ALB-221, manufactured by Asahi Kasei Corporation, temperature sensitive point 24 ° C.), 0.1 part of an antifoaming agent. Solid content concentration 10%. In addition, the temperature at the time of mixing each material was 40 degreeC.

(Ink receiving layer upper layer coating solution B)
100 parts of the above-mentioned cationic fine pigment, 5 parts of cationic acrylic resin (Colopearl 2013; manufactured by Seiko Chemical Co., Ltd., quaternary amine-modified acrylic aqueous resin), cationic polyurethane resin (F-8564D; manufactured by Daiichi Kogyo Kagaku, Tg = 73 ° C. ) 30 parts, mold release agent (Pertor N-856; manufactured by Modern Chemical Industry, polyethylene wax) 10 parts solid content concentration 12%

(Ink-receiving layer upper layer coating solution C)
100 parts of the above cationic fine pigment, 20 parts of polyvinyl alcohol (trade name: PVA145, manufactured by Kuraray Co., Ltd.), 0.1 part of an antifoaming agent. Solid content concentration 10%.

(Ink-receiving layer upper layer coating solution D)
100 parts of the above-mentioned cationic fine pigment, 20 parts of thermosensitive polymer compound (ALB-221, manufactured by Asahi Kasei Co., Ltd., temperature sensitive point 24 ° C.), 0.1 part of antifoaming agent 1 part of zinc sulfate (Toho Zinc Co., Ltd.) )). Solid content concentration 10%. In addition, the temperature at the time of mixing each material was 40 degreeC.
(Method for measuring moisture content in coating layer)
In the following examples and comparative examples, those having the moisture value of the coating layer are values measured using an infrared moisture meter (KJT-100, manufactured by Kett Scientific Laboratory).

Example 1
On the paper substrate, the ink receiving layer lower layer coating liquid A was applied and dried with an air knife coater so as to have a dry mass of 5 g / m ² to form an ink solvent absorption layer.
After adjusting the temperature of the ink receiving layer lower layer surface to 23 ° C., the ink receiving layer upper layer coating liquid A is applied to the ink receiving layer lower layer at a coating liquid temperature of 45 ° C. and 5 g / m ² in an absolutely dry mass. Coating with a die coater so that the temperature becomes 20 ° C. using a cool air machine, gel the coating solution, and dry the coating layer so that the moisture content is 22%. It was pressed onto a mirror drum having a surface temperature of 100 ° C., dried and finished to obtain an ink jet recording sheet.

Example 2
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the ink receiving layer lower layer coating solution B was used as the ink receiving layer lower layer coating solution.

Example 3
An ink jet recording sheet was obtained in the same manner as in Example 1, except that the ink receiving layer lower layer coating liquid C was used as the ink receiving layer lower layer coating liquid.

Comparative Example 1
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the ink receiving layer lower layer coating solution D was used as the ink receiving layer lower layer coating solution.

Comparative Example 2
In Example 1, the ink receiving layer lower layer coating solution D was used as the ink receiving layer lower layer coating solution, and the ink receiving layer upper layer coating solution D was used as the ink receiving layer upper layer coating solution. An ink jet recording sheet was obtained in the same manner as in Example 1 except that.

Example 4
On the paper base material, the ink receiving layer lower layer coating solution B was applied and dried with an air knife coater so as to have a dry mass of 5 g / m ² to form an ink receiving layer lower layer.
On the lower layer of the ink receiving layer, the coating liquid B for the upper layer of the ink receiving layer is dried and coated so as to have a dry mass of 5 g / m ^2. The ink-jet recording sheet was obtained by press-contacting to a mirror drum having a temperature of 90 ° C., drying and finishing.

Comparative Example 3
An ink jet recording sheet was obtained in the same manner as in Example 4 except that the ink receiving layer lower layer coating liquid B of Example 4 was changed to the ink receiving layer lower layer coating liquid D.

Example 5
On the paper base material, the ink receiving layer lower layer coating solution B was applied and dried with an air knife coater so as to have a dry mass of 5 g / m ² to form an ink receiving layer lower layer.
On the ink receiving layer lower layer, the ink receiving layer upper layer coating liquid C was applied and dried so as to have an absolute dry mass of 5 g / m ² to form an ink receiving layer upper layer.
On the upper layer of the ink receiving layer, the following glossy layer coating liquid A was applied, and while in a wet state, pressed onto a mirror drum having a surface temperature of 100 ° C. and dried to obtain an inkjet recording sheet.

[Glossy layer coating liquid A]
Composite emulsion of acrylic emulsion and glass colloidal silica having a glass transition point of 100 ° C. (trade name: Aquabrid 906, manufactured by Daicel Corporation, acrylic emulsion and colloidal silica are 20:80 in mass ratio, and average particle diameter of colloidal silica is 20 to 30 nm. , Emulsion particle diameter 40 nm) 100 parts, release agent (potassium stearyl phosphate, trade name: Wopol 1800, manufactured by Matsumoto Yushi Co., Ltd.) 1 part.

Comparative Example 4
An ink jet recording sheet was obtained in the same manner as in Example 5 except that the ink receiving layer lower layer coating liquid B of Example 5 was changed to the ink receiving layer lower layer coating liquid D.

Example 6
On the paper substrate, the ink receiving layer lower layer coating liquid A was applied and dried with an air knife coater so that the dry mass was 5 g / m ² to form an ink receiving layer lower layer.
After adjusting the temperature of the ink receiving layer lower layer surface to 23 ° C., the ink receiving layer upper layer coating liquid A is applied to the ink receiving layer lower layer at a coating liquid temperature of 45 ° C. and 5 g / m ² in an absolutely dry mass. Coating with a die coater so that the temperature becomes 20 ° C. using a cool air machine, gel the coating solution, and dry the coating layer so that the moisture content is 22%. I let you. Subsequently, the following glossy layer coating liquid B was applied to the coating layer, immediately pressed onto a mirror drum having a surface temperature of 100 ° C., dried and finished to obtain an ink jet recording sheet.

[Glossy layer coating liquid B]
5 parts of a cationic release agent was added to 100 parts of cation-modified colloidal silica having an average particle size of 45 nm to prepare an 8% aqueous solution.

Example 7
An ink jet recording sheet was obtained in the same manner as in Example 6 except that the ink receiving layer lower layer coating liquid A of Example 6 was changed to the ink receiving layer lower layer coating liquid B.

Comparative Example 5
An ink jet recording sheet was obtained in the same manner as in Example 6 except that the ink receiving layer lower layer coating liquid A of Example 6 was changed to the ink receiving layer lower layer coating liquid D.

Example 8
On the paper base material, the ink receiving layer lower layer coating solution B was applied and dried with an air knife coater so as to have a dry mass of 5 g / m ² to form an ink receiving layer lower layer.
After adjusting the temperature of the ink receiving layer lower layer surface to 23 ° C., 1 g / m ^{2 of} borax aqueous solution was applied to the ink receiving layer lower layer, and then the ink receiving layer upper layer coating liquid C was applied to a coating liquid temperature of 23 ° C. Then, the coating material was quickly gelled by coating with a die coater so that the absolute dry mass was 5 g / m ² . Then, it dried with the hot air dryer until the water | moisture content of the coating layer became 5%. Subsequently, the glossy layer coating liquid B was applied to the coating layer, immediately pressed onto a mirror drum having a surface temperature of 100 ° C., dried and finished to obtain an ink jet recording sheet.

Comparative Example 6
An ink jet recording sheet was obtained in the same manner as in Example 7 except that the ink receiving layer lower layer coating liquid B of Example 8 was changed to the ink receiving layer lower layer coating liquid D.

Example 9
A cast coated paper was obtained in the same manner as in Example 1 except that 20 parts of zinc sulfate was used in the ink-receiving layer lower layer coating liquid A of Example 1.

Example 10
A cast coated paper was obtained in the same manner as in Example 3 except that 20 parts of malic acid in the ink receiving layer lower layer coating liquid C of Example 3 was used.

(Evaluation method and evaluation criteria)
About the cast coated paper obtained by the said Example and the comparative example, glossiness and the printability in inkjet recording were evaluated on the following reference | standard. The results are shown in Table 1.

"Paper pH"
The surface pH of the cast coated paper was measured with an indicator. (JAPAN TAPPI Paper Pulp Test Method NO.49-2 Coating Method)

"Print density"
Using a commercially available dye ink type ink jet printer (trade name: PM-G800, manufactured by Seiko Epson Corporation), black and yellow solid printing is performed, and the printing density is measured with a Macbeth reflection densitometer (Macbeth RD-914). It was measured.

"Ozone resistance"
Magenta 100% solid and ISO-400 images ("High-definition color digital standard image data ISO / JIS-SCID", image name: Portrait, issued by the Japanese Standards Association), commercially available dye ink type inkjet printer ( Product name: PM-G800, manufactured by Seiko Epson Co., Ltd.), printed in photographic paper mode, ozone concentration: 40 ppm, temperature: 24 ° C., humidity: 60% using an ozone fade meter (manufactured by Suga Test Instruments) Processing was continued for 5 hours under conditions, and compared with an unprocessed image.
(Survival rate)
The print density was measured before and after the treatment of the magenta solid part, and the residual ratio was calculated.
Residual rate (%) = printing density after processing / printing density before processing × 100

(Hue)
The hue change before and after the portrait image processing was evaluated according to the following criteria.
◯: There is little fading on the entire image, and the color balance is good.
Δ: Fading is observed in the entire image, but the color balance is good.
X: The entire image has faded and the color balance is very poor.

“Pigment ink suitability”
Using a commercially available pigment ink type ink jet printer (trade name: PX-G900, manufactured by Seiko Epson Corporation), black solid printing is performed, and the printed part is rubbed with a cotton swab 30 seconds after printing, and its scratch resistance. Was evaluated according to the following criteria.
○: Pigment in the printed part is difficult to remove ×: Pigment in the printed part is easily removed

  The ink jet recording sheet of the present invention is excellent in printing density with dye ink and pigment ink as ink jet recording suitability, can clearly print high-definition images, and has excellent print storage stability, such as a digital camera. This is useful for output.

Claims (8)

Ink jet recording sheet having an ink-receiving layer lower layer having a pigment and an adhesive layer on a support, and an ink-receiving layer upper layer having a pigment and an adhesive on the support. An ink jet recording sheet comprising: The ink jet recording sheet according to claim 1, wherein the ozone resistance improver is zinc sulfate and is contained in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment in the lower layer of the ink receiving layer. The ink jet recording sheet according to claim 1, wherein the ozone resistance improver is malic acid and is contained in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment in the lower layer of the ink receiving layer. . The inkjet recording sheet according to any one of claims 1 to 3, wherein the pigment in the lower layer of the ink receiving layer is amorphous silica having an average particle diameter of 1 to 12 µm. The ink jet recording sheet according to any one of claims 1 to 4, wherein a paper surface pH of the surface of the upper layer of the ink receiving layer is 5.5 to 7.0. The upper layer of the ink receiving layer is coated with a coating liquid containing a fine pigment and an adhesive, or is in the middle of drying of the coating liquid layer coated with the coating liquid, and the coating liquid layer exhibits a decreasing rate of drying. The ink jet recording sheet according to any one of claims 1 to 5, which is a layer produced by previously forming a film by thickening or crosslinking the coating liquid. The support is a gas permeable support, and the upper layer of the ink receiving layer is a layer that has been coated with a coating liquid containing a pigment, an adhesive, and a cationic resin and then pressure-treated with a mirror roll in a wet state. The sheet | seat for inkjet recording as described in any one of 1-6. A glossy expression layer formed by applying a coating liquid containing a fine pigment having an average particle diameter of 0.01 to 1 μm on the upper layer of the ink receiving layer and pressing the coated liquid onto a heated mirror roll while in a wet state. The sheet for inkjet recording according to any one of claims 1 to 6, comprising: