JP2006110885A - Substrate for inkjet recording paper, inkjet recording paper using substrate, manufacturing method for substrate for inkjet recording paper, and manufacturing method for inkjet recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and high-gloss substrate for inkjet recording paper, which is excellent in image clarity, inkjet recording paper using the substrate, a manufacturing method for the substrate for the inkjet recording paper, and a manufacturing method for the inkjet recording paper. <P>SOLUTION: This substrate for the inkjet recording paper is characterized as follows: at least one low-moisture-permeation layer is formed on the side of an image recording surface of a water-absorbing base material wherein a moisture permeability is in the range of 4,000-10,000 g/m<SP>2</SP>day and wherein a value of a center line average roughness Ra is 0.2 μm or less, by using a coating liquid wherein 50 mass% or more of a nonsolid component is composed of water; the amount of the coating of the nonsolid component is 35 ml/m<SP>2</SP>or less; the moisture permeation after the formation of the low-moisture-permeation layer is less than 4,000 g/m<SP>2</SP>day; and the value of the center line average roughness Ra on the side of the formation of the low-moisture-permeation layer is 0.3 μm or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel support for ink jet recording paper, an ink jet recording paper using the same, a method for manufacturing the support for ink jet recording paper, and a method for manufacturing the ink jet recording paper.

  Ink-jet recording is a method of recording images and characters by causing ink droplets to fly by various operating principles and attaching them to a recording sheet such as paper, but with relatively high speed, low noise, and multiple colors. In recent years, it has been rapidly spread in various fields such as various printers, facsimiles, computer terminals, and the like because of its advantages such as easy implementation.

  As recording paper used in this ink jet recording method, the density of the printed dots is high, the color tone is bright and vivid, the ink does not flow out or bleed even when the printed dots overlap quickly, In general, it is required that the horizontal spread of the printed dots is not larger than necessary, the periphery is smooth and unblurred, and the like.

  As one of the purposes for improving these characteristics, an ink jet recording sheet provided with an ink absorbing layer having a porous structure as an ink receiving layer has been developed and put into practical use. This ink jet recording sheet has a porous structure and is excellent in ink absorbency by having voids.

  In addition, there has been a remarkable improvement in the storability of printed images in recent years, and the overall image quality and image storability are now rapidly approaching the quality of silver salt photographs. In addition to these, the glossiness and image clarity of the surface of the recording material are also important factors in achieving so-called silver salt photography-like high image quality by ink jet recording. When the glossiness and image clarity are low, the sharpness of the image is lowered, and it is often recognized that the image lacks stereoscopic and depth. For this reason, resin-coated supports (RC supports) in which both sides of a paper base material used in silver salt photography are coated with an olefin resin or the like are used in glossy paper for ink jets that demand photographic image quality. It has been. The resin-coated support has high surface smoothness, high gloss, excellent image clarity, and water resistance, so that when the ink receiving layer or the like is applied on the support, the coating liquid can penetrate into the support. It does not occur, and smoothness, glossiness, and image clarity are not reduced by cockling of the support.

  However, such a high-quality resin-coated support may have limited applications and is expensive compared to a normal paper support because of its special configuration. As a result, the price of inkjet recording paper of this type has to increase.

  On the other hand, instead of the resin coat support, an ink-receiving layer is applied on a water-absorbing paper support, and then a cast process or a calendar process is performed to improve the smoothness of the surface of the recording paper, thereby improving gloss and image clarity. An improved ink jet recording paper has been proposed (see, for example, Patent Documents 1 and 2). When such a water-absorbing support is used, it can be provided at a lower cost than paper using a resin-coated support. However, since the support itself is water-absorbing, the ink solvent is used as the support. Since it penetrates into the inside and induces cockling, there is a problem that glossiness and image clarity are deteriorated particularly in an image forming portion.

Therefore, it is desired to provide a low-cost and high-quality image, that is, an inkjet recording paper having the same high glossiness and good image clarity as in the case of using a resin-coated support, and a support used therefor.
Japanese Patent Laid-Open No. 5-331795 JP-A-10-245799

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to provide an inkjet recording paper support that is low-cost, high-gloss, and excellent in image clarity, an inkjet recording paper using the same, and an inkjet recording paper support. An object of the present invention is to provide a manufacturing method and a manufacturing method of an inkjet recording paper.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
Moisture permeability 4000g / m ² · day or more, below 10000g / m ² · day, and the image recording surface side of the center line average roughness Ra value is 0.2μm or less absorbent substrates, the non-solid component Using the coating liquid comprising 50% by mass or more of water, at least one moisture-permeable layer is formed, and the coating amount of the non-solid component is 35 ml / m ² or less. The moisture permeability after forming the film is less than 4000 g / m ² · day, and the center line average roughness Ra value on the side on which the moisture permeable layer is formed is 0.3 μm or less. Inkjet recording paper support.

(Claim 2)
J. et al. TAPPI paper pulp test method no. 51-87, or the water absorption at a contact time of 10 seconds measured according to the liquid absorptivity test method (Bristow method) of paper and paperboard is 15 ml / m ² or less, and the centerline average roughness Ra value is 0. On the image recording surface side of the water-absorbing substrate having a thickness of 2 μm or less, at least one low moisture-permeable layer is formed using a coating liquid in which 50% by mass or more of the non-solid component is composed of water. The coating amount of the solid component is 35 ml / m ² or less, the moisture permeability after the formation of the low moisture permeable layer is less than 4000 g / m ² · day, and the side on which the low moisture permeable layer is formed. A support for inkjet recording paper, wherein the center line average roughness Ra value is 0.3 µm or less.

(Claim 3)
On a water-absorbing substrate, a water-dispersible polymer or a water-soluble polymer is melted and formed into a film, and a low moisture-permeable layer having a thickness of 1.0 μm or more and 30 μm or less is formed. An ink jet having a moisture permeability of less than 4000 g / m ² · day after being formed, and a center line average roughness Ra value of 0.3 μm or less on the side on which the moisture-permeable layer is formed Support for recording paper.

(Claim 4)
The support for inkjet recording paper according to any one of claims 1 to 3, wherein a center line average roughness Ra value on a surface side on which the moisture-permeable layer is formed is 0.2 µm or less. body.

(Claim 5)
The support for inkjet recording paper according to any one of claims 1 to 4, wherein the moisture-permeable layer forming step does not include a smoothing step by a casting step or a calendar step.

(Claim 6)
6. An ink jet recording paper comprising at least one ink receiving layer containing inorganic fine particles and a hydrophilic binder on the ink jet recording paper support according to any one of claims 1 to 5.

(Claim 7)
Moisture permeability 4000g / m ² · day or more, below 10000g / m ² · day, and the image recording surface side of the center line average roughness Ra value is 0.2μm or less absorbent substrates, the non-solid component A method for producing a support for inkjet recording paper, wherein at least one moisture-permeable layer is formed using a coating solution comprising 50% by mass or more of water, and the coating amount of the non-solid component is 35 ml. / M ² or less, the moisture permeability after forming the low moisture permeability layer is less than 4000 g / m ² · day, and the center line average roughness Ra value on the side where the moisture permeability layer is formed Is 0.3 μm or less, a method for producing a support for ink jet recording paper.

(Claim 8)
J. et al. TAPPI paper pulp test method no. 51-87, or the water absorption at a contact time of 10 seconds measured according to the liquid absorptivity test method (Bristow method) of paper and paperboard is 15 ml / m ² or less, and the centerline average roughness Ra value is 0. Inkjet recording in which at least one low moisture-permeable layer is formed on the image recording surface side of a water-absorbing substrate of 2 μm or less using a coating liquid in which 50% by mass or more of the non-solid component is composed of water. A method for producing a paper support, wherein the coating amount of the non-solid component is 35 ml / m ² or less, and the moisture permeability after the low moisture permeable layer is formed is less than 4000 g / m ² · day, A method for producing a support for inkjet recording paper, characterized in that the center line average roughness Ra value on the side on which the moisture-permeable layer is formed is 0.3 μm or less.

(Claim 9)
On the water-absorbent substrate, a water-dispersible polymer or a water-soluble polymer is melted and formed into a low moisture-permeable layer having a thickness of 1.0 μm or more and 30 μm or less. An ink jet having a moisture permeability of less than 4000 g / m ² · day after being formed, and a center line average roughness Ra value of 0.3 μm or less on the side on which the moisture-permeable layer is formed A method for manufacturing a support for recording paper.

(Claim 10)
The method for producing a support for inkjet recording paper according to any one of claims 7 to 9, wherein the forming step of the moisture-permeable layer does not include a smoothing step by a casting step or a calendar step. .

(Claim 11)
11. At least one ink receiving layer containing inorganic fine particles and a hydrophilic binder on an inkjet recording paper support produced by the method for producing an inkjet recording paper support according to any one of claims 7 to 10. A method for producing an ink jet recording paper, characterized in that the ink jet recording paper is produced.

  According to the present invention, there are provided an inkjet recording paper support that is low-cost, high-gloss, and excellent in image clarity, an inkjet recording paper using the same, a method for manufacturing the inkjet recording paper support, and a method for manufacturing the inkjet recording paper. be able to.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

One of the inkjet recording paper support of the present invention, moisture permeability 4000g / m ² · day or more, below 10000g / m ² · day, and the center line average roughness Ra value is 0.2μm or less water At least one low moisture-permeable layer is formed on the image recording surface side of the conductive substrate using a coating liquid in which 50% by mass or more of the non-solid component is composed of water, and the coating amount of the non-solid component Is 35 ml / m ² or less, the moisture permeability after formation of the low moisture permeability layer is less than 4000 g / m ² · day, and the center line average roughness on the side where the moisture permeability layer is formed The Ra value is 0.3 μm or less.

Particularly absorbent substrates that can be used in the present invention, moisture permeability 4000g / m ² · day or more, below 10000g / m ² · day, the center line average roughness Ra value is equal to or 0.2μm or less There is no limitation, and examples include a sheet or paperboard made of general paper base material, synthetic paper, wood, etc., but considering the economic effect, the paper base material is particularly preferable.

  Raw materials for paper base materials include chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, CGP, RMP, TMP, CTMP, CMP and PGW, and wood pulp such as waste paper pulp such as DIP. It can be used. In addition, various fibrous materials such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as raw materials as necessary.

  If necessary, various conventionally known additives such as a sizing agent, pigment, paper strength enhancer, fixing agent, fluorescent whitening agent, wet paper strength agent, and cationizing agent may be added to the paper base material. Can do. Higher fatty acids, alkyl ketene dimers, etc. as sizing agents, calcium carbonate, talc, titanium oxide, etc. as pigments, starch, polyacrylamide, polyvinyl alcohol, etc. as paper strength enhancing agents, sulfate bands, cationics as fixing agents However, the present invention is not limited to this.

  The paper substrate can be produced by mixing various fibrous materials such as wood pulp and various additives and using various paper machines such as a long net paper machine, a circular net paper machine, and a twin wire paper machine. Further, if necessary, a size press treatment with starch, polyvinyl alcohol, or the like, a various coating treatment, or a calendar treatment can be performed at the paper making stage or after paper making.

  Examples of the paper substrate that can be used in the present invention include art paper, coated paper, and cast coated paper. From the viewpoint of smoothness, cast coated paper can be preferably used.

  The glossiness of the paper substrate used in the present invention is preferably 60% glossiness of 35% or more, more preferably 50% or more. In addition, the thickness of the water-absorbing substrate used for the inkjet recording paper support of the present invention is preferably 120 μm or more.

In the present invention, at least one moisture permeable layer is applied on the substrate, and the moisture permeability after the application of the moisture permeable layer is less than 4000 g / m ² · day.

  By adopting the configuration defined in the present invention, the penetration of the ink receiving layer coating liquid into the base material when the ink receiving layer is applied thereon is suppressed, the smoothness is reduced due to cockling of the base material, gloss, Degradation of image clarity can be effectively prevented.

  In the inkjet recording paper support of the present invention, after applying at least one low moisture-permeable layer on the substrate, the center line average roughness Ra value of the surface of the low moisture-permeable layer is 0.3 μm. The following is necessary for obtaining high image clarity, and is preferably 0.2 μm or less.

  In the present invention, a water-based coating solution is used as the coating solution for the low moisture-permeable layer from the viewpoint of high economic efficiency and ease of production. The aqueous coating solution referred to in the present invention means a coating solution in which 50% by mass or more of the non-solid component in the coating solution is occupied by water. The use of a water-based coating liquid is also preferable from the viewpoint of reducing the environmental load.

  For the same reason, in the present invention, in the formation process of the low moisture permeable layer or the ink receiving layer on the low moisture permeable layer, generally used cast processing and calendar processing are performed. It is preferable not to include a surface smoothing step by so-called pressure bonding.

  One feature of the support for inkjet recording paper of the present invention is that a low moisture permeability layer having a thickness of 1.0 μm or more and 30 μm or less is formed using the following water-dispersible polymer or water-soluble polymer. .

  When a water-dispersible polymer is used to form the low moisture-permeable layer, a compound having a glass transition point (Tg) of about 0 to 100 ° C. that melts easily and forms a film in the process of coating and drying the aqueous coating solution. preferable. When the glass transition point is less than 0 ° C., film formation tends to proceed rapidly after coating and drying, and it is difficult to stably form a smooth surface. On the other hand, when Tg is higher than 100 ° C., melt film formation becomes insufficient, and the penetration of moisture in the ink-receiving layer coating solution applied onto the low moisture-permeable layer into the paper substrate results in Causes cockling and decreases gloss and image clarity.

  A preferable average particle size of the water dispersible polymer is 0.1 μm or more and 0.5 μm or less. When the average particle size is less than 0.1 μm, melt film formation proceeds rapidly, and it is difficult to stably form a smooth surface. On the other hand, when the average particle size is larger than 0.5 μm, the melt film formation becomes insufficient, and the gloss and image clarity deteriorate for the same reason as in the case of Tg.

  The water dispersible polymer can be used in the form of an aqueous dispersion of various polymers. Specifically, acrylic, styrene-acrylic, acrylonitrile-acrylic, vinyl acetate, vinyl acetate-acrylic, vinyl acetate-vinyl chloride, polyurethane, silicon-acrylic, acrylic silicon, polyester And epoxy-based polymers.

  Usually, these water-dispersible polymers are obtained by an emulsion polymerization method. What is necessary is just to use what is used by a conventional method about surfactant, a polymerization initiator, etc. which are used by an emulsion polymerization method. Regarding the synthesis method of the water-dispersible polymer, U.S. Pat. Nos. 2,852,368, 2,853,457, 3,411,911, 3,411,912, 4,197,127. Belgian Patent Nos. 688,882, 691,360, 712,823, JP-B 45-5331, JP-A-60-18540, 51-130217, 58-137831, 55-50240 and the like.

  Examples of the water-soluble polymer that can be used in the formation of the low moisture-permeable layer according to the present invention include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, (Color genan κ, ι, λ, etc.), agar, pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. Two or more of these water-soluble binders may be used in combination. Moreover, you may use together with the said water-dispersible polymer.

  In the formation of the moisture-permeable layer according to the present invention, the water-soluble binder is preferably crosslinked with a curing agent or the like from the viewpoint of improving water resistance.

  The curing agent that can be used in the present invention is not particularly limited as long as it causes a curing reaction with a water-soluble binder, and a known one can be used, and generally has a group capable of reacting with a water-soluble binder. It is a compound that promotes the reaction between different groups of the compound or the water-soluble binder, and is appropriately selected according to the type of the water-soluble binder. Specific examples of the curing agent include, for example, boric acid and salts thereof, epoxy curing agents (for example, diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl). Cyclohexane, N, N-diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde-based curing agents (for example, formaldehyde, glycoxal, etc.), active halogen-based curing agents (for example, 2,4 -Dichloro-4-hydroxy-1,3,5-s-triazine), active vinyl compounds (for example, 1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), aluminum alum Etc. That.

  In the present invention, after the formation of the moisture permeable layer, it is desirable that the film has high water repellency, and the water-soluble polymer is preferably used.

  Further, the low moisture permeability layer may contain inorganic fine particles, but it is more preferable not to contain it in order to maintain the smoothness, optical transparency and low moisture permeability of the film.

  The film thickness of the moisture-permeable layer according to the present invention is preferably 1 μm or more and 15 μm or less. If it is 1 μm or less, the effect of reducing moisture permeability is insufficient, and if it is 15 μm or more, it is difficult to form a highly smooth surface and the image clarity is impaired.

In the present invention, in forming the low moisture-permeable layer, it is one of the features that the coating amount of the non-solid component is 35 ml / m ² or less using the moisture-permeable layer coating liquid. By setting the coating amount of the non-solid component to 35 ml / m ² or less, the occurrence of cockling of the substrate due to the penetration of the coating solution of the low moisture permeable layer into the paper substrate during the formation of the moisture permeable layer is prevented. Good gloss and mapping performance can be obtained.

  In applying the moisture-permeable layer, it can be appropriately selected from known methods, for example, gravure coating method, roll coating method, rod bar coating method, air knife coating method, spray coating method, extrusion coating method, A curtain coating method or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 can be used.

In the present invention, the moisture permeability of the water-absorbing base material for applying the above-mentioned low permeability wetting layer, 4000g / m ² · day or more, and equal to or less than 10000g / m ² · day.

If the moisture permeability of the substrate is 10000 g / m ² · day or less, when applying the moisture permeable layer, it effectively prevents absorption of the non-solid component in the coating solution into the substrate, The occurrence of cockling of the substrate can be suppressed, and excellent gloss and image clarity can be obtained. On the other hand, if the moisture permeability of the base material is 4000 g / m ² · day or more, for example, a moisture permeability similar to that of RC paper coated with a water-insoluble resin layer like resin-coated paper can be realized. Excellent effects can be obtained.

  Moreover, in this invention, the centerline average roughness Ra value of the water absorptive base material which apply | coats the said low moisture-permeable layer is characterized by being 0.2 micrometer or less.

  If the center line average roughness Ra value of the water-absorbent substrate is 0.2 μm or less, good smoothness after application of the ink-receiving layer can be obtained by a normal coating method without applying cast treatment or calendar treatment. As a result, sufficient mapping performance can be obtained. This is due to the fact that the smoothness of the coating layer surface depends on the smoothness of the substrate.

  Therefore, according to the present invention, when a water-absorbing base material having a specific moisture permeability and center line surface roughness is used, and a layer that lowers the moisture permeability of the base material is formed, the cockling of the base material is performed. By forming a coating solution composed of a specific composition with a specific coating amount so as not to induce the use of an aqueous coating solution, it is simple and low without requiring a special manufacturing process such as a casting process. An ink jet recording paper support excellent in gloss and imaging performance can be obtained at low cost.

  The moisture permeability referred to in the present invention is a value measured under the conditions of 40 ° C. and 90% RH according to the method described in JIS-Z-0208. It means that the penetration preventing power is small.

  The centerline average roughness Ra as used in the present invention is defined by JIS-B-0601, and is represented by the centerline average roughness measured with a reference length of 5.0 mm and a cutoff value of 0.8 mm. .

  The centerline average roughness means that a portion of the measurement length L is extracted from the roughness curve in the direction of the centerline, the centerline of this extracted portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve is Y = When expressed by f (X), it means the value obtained by the following formula expressed in μm.

  The larger the center line average roughness Ra value, the rougher the surface is.

  As a specific method for measuring the center line average roughness, the humidity is adjusted for 24 hours in a 25 ° C., 65% RH environment where the samples to be measured are not overlapped, and then measured in the same environment. An example of a measuring apparatus that can be used is Surfcom 500B manufactured by Tokyo Seimitsu Co., Ltd.

In the support for inkjet recording paper of the present invention, the water-absorbing substrate used is J.P. TAPPI paper pulp test method no. One of the characteristics is that the water absorption is 15 ml / m ² or less at a contact time of 10 seconds measured according to 51-87 or the liquid absorbency test method (Bristow method) of paper and paperboard.

The Bristow method referred to in the present invention is a method for measuring the liquid absorption behavior of paper and paperboard in a short time. TAPPI paper pulp test method no. It is measured according to the liquid absorptivity test method (Bristow method) of 51-87 paper or paperboard, and is represented by the amount of water transfer (ml / m ² ) at a contact time of 10 seconds.

  Next, the ink jet recording paper of the present invention will be described.

  The ink jet recording paper of the present invention has an ink receiving layer containing at least one layer of inorganic fine particles and a hydrophilic binder on the support for ink jet recording paper of the present invention.

  Examples of inorganic fine particles that can be used in the present invention include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, and zinc sulfide. , Zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. A white inorganic pigment etc. can be mentioned. Moreover, each may be used independently and multiple types may be used together.

  In the present invention, from the viewpoint of obtaining a high-quality print on an inkjet recording paper, the inorganic fine particles are preferably fine particle silica, alumina, boehmite, or pseudoboehmite synthesized by a vapor phase method, and among them, synthesized by a vapor phase method. Particulate silica is particularly preferred. The silica synthesized by this vapor phase method may have a surface modified with Al. The Al content of vapor-phase process silica whose surface is modified with Al is preferably 0.05 to 5% by mass with respect to silica.

  The inorganic fine particles may have any particle diameter, but the average particle diameter is preferably 4 μm or less. If it is 4 micrometers or less, glossiness and coloring property are favorable, Furthermore, 0.1 micrometer or less is preferable. The lower limit of the particle size is not particularly limited. In particular, in the case of the vapor phase silica, the average primary particle size is preferably 30 nm or less for obtaining a structure having a large porosity, and 3 to 10 nm is particularly preferred for enhancing the transparency of the film.

  The average particle size of the inorganic fine particles is obtained as a simple average value (number average) by observing the cross section and surface of the ink receiving layer with an electron microscope and determining the particle size of 100 arbitrary particles. Here, each particle size is expressed by a diameter assuming a circle equal to the projected area.

  Further, the degree of dispersion of the fine particles is preferably 0.5 or less from the viewpoint of glossiness and color developability. If it is 0.5 or less, the gloss and the density during printing are good. In particular, 0.3 or less is preferable. Here, the dispersity of the fine particles is obtained by observing the fine particles of the ink receiving layer with an electron microscope in the same manner as obtaining the average particle size, and dividing the standard deviation by the average particle size. The above average particle diameter refers to the particle diameter of the independent particles formed in the ink receiving layer when observed with an electron microscope. The content of the fine particles in the water-soluble coating solution is 5 to 40% by mass, and particularly preferably 7 to 30% by mass. As the vapor phase silica fine particles, those dispersed with the aforementioned cationic resin can also be used.

  In the inkjet recording paper of the present invention, the ratio of the inorganic fine particles to the hydrophilic binder in the ink receiving layer is preferably 2 to 50 times in terms of mass ratio. If the mass ratio is 2 times or more, the ink receiving layer has a good porosity, it is easy to obtain a sufficient void volume, and an excessive hydrophilic binder can be prevented from swelling during ink jet recording and closing the void. On the other hand, when this ratio is 50 times or less, it is preferable that cracks do not occur when the ink receiving layer is applied as a thick film. A particularly preferable ratio of the inorganic fine particles to the hydrophilic binder is 2.5 to 20 times, and 5 to 15 times is more preferable from the viewpoint of resistance to breakage of the dry coating film.

In order to obtain an ink receiving layer having a high porosity, the specific surface area measured by the BET method is preferably 100 m ² / g or more. The BET method referred to in the present invention is a method for measuring the specific surface area by a method for determining the surface area per 1 g from the gas phase adsorption isotherm.

The ink receiving layer according to the present invention preferably has a capacity of 15 to 40 ml / m ² per unit area of the coating film. This capacity is defined by the volume of bubbles generated when a coating film of a unit area is immersed in water, or the volume of water that the coating film can absorb.

  The hydrophilic binder contained in the ink receiving layer according to the present invention is not particularly limited, and conventionally known hydrophilic binders can be used. Examples thereof include gelatin, polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, and polyvinyl alcohol. Polyvinyl alcohol from the viewpoint that the hygroscopic property of the binder is relatively small, the curling of the recording paper is smaller, and the binder ability of the inorganic fine particles is high and the cracking and film-forming properties are excellent with a small amount of use. Is particularly preferred.

  As polyvinyl alcohol preferably used in the present invention, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal or anion-modified polyvinyl alcohol having an anionic group. Alcohol is also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 300 or more, particularly preferably an average degree of polymerization of 1,000 to 5,000, and a saponification degree of 70. ~ 100% is preferable, and 80 ~ 99.8% is particularly preferable.

  Examples of the cation-modified polyvinyl alcohol include polyvinyl having a primary to tertiary amino group or a quaternary amino group in the main chain or side chain of the polyvinyl alcohol as described in JP-A No. 61-10383. These are alcohols, which are obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-methylvinylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxyethyltrimethylammonium chloride, trimethyl- (3-methacrylamidopropyl) ammonium chloride, and the like.

  The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Examples of the anion-modified polyvinyl alcohol include polyvinyl alcohol having an anionic group described in JP-A-1-206088, vinyl alcohol described in JP-A-61-237681 and JP-A-63-330779, and water-soluble. And a copolymer with a vinyl compound having a functional group, and a modified polyvinyl alcohol having a water-soluble group described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group described in JP-A-7-9758 to a part of vinyl alcohol, and described in JP-A-8-25795. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol.

  Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification. In particular, when using polyvinyl alcohol having a degree of polymerization of 2,000 or more, the degree of polymerization is from 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the inorganic fine particles. Addition of 2,000 or more polyvinyl alcohol is preferred because there is no significant thickening.

  In the present invention, the above-mentioned hydrophilic binder is preferably cured by a hardener, and the hardener is generally a compound having a group capable of reacting with the hydrophilic binder or a different group possessed by the hydrophilic binder. It is a compound that promotes the reaction between them, and is appropriately selected according to the type of the hydrophilic binder.

As the hardening agent, a conventionally known crosslinking agent can be used, and inorganic crosslinking agents (for example, chromium compounds, aluminum compounds, zirconium compounds, boric acids, etc.) and organic crosslinking agents (for example, epoxy crosslinking agents). , Isocyanate crosslinking agents, aldehyde crosslinking agents, N-methylol crosslinking agents, acryloyl crosslinking agents, vinyl sulfone crosslinking agents, active halogen crosslinking agents, carbodiimide crosslinking agents, ethyleneimino crosslinking agents, etc.) can do.
Specific examples include, for example, epoxy hardeners (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl-4- Glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde hardeners (formaldehyde, glioxal, etc.), active halogen hardeners (2,4-dichloro-4-hydroxy-1,3) , 5-s-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), boric acid, its salts, borax, aluminum alum, etc. Can be mentioned.

  When polyvinyl alcohol or cation-modified polyvinyl alcohol is used as the hydrophilic binder, inorganic hardeners and epoxy hardeners such as compounds containing Group 3 and 4 elements, especially boric acids, aluminum compounds, zirconium compounds, etc. Agents are preferred. Most preferred is a hardener selected from boric acid or a salt thereof.

  As boric acid or a salt thereof, oxygen acid having a boron atom as a central atom and a salt thereof are shown. Specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, octaboric acid Or a salt thereof.

  The amount of the hardener used varies depending on the type of hydrophilic binder, the type of hardener, the type of inorganic fine particles, the ratio to the hydrophilic binder, etc., but usually 5 to 500 mg, preferably 10 to 10 g per hydrophilic binder. 300 mg.

  Two or more hardeners may be used in combination. Moreover, it may be mixed and applied to a coating solution containing an ink receiving layer, or a solution containing a hardener without containing a porous substance may be supplied after being coated and dried. Preferably, simultaneously with application of the ink receiving layer or after application of the ink receiving layer and before the layer exhibits a reduced drying rate, an overcoat solution containing a hardener and not containing a porous material is overcoated, It is preferable to supply a hardener because the risk of aggregation of the porous material is reduced and production efficiency is good.

  Further, as the hydrophilic binder of the ink receiving layer according to the present invention, it is preferable to use a polymer compound that is crosslinked or polymerized by ionizing radiation. The high molecular compound that is crosslinked or polymerized by ionizing radiation is a water-soluble resin that undergoes a reaction to undergo crosslinking or polymerization by irradiation with ionizing radiation such as ultraviolet rays and electron beams, and is water-soluble before the reaction. However, it is a resin that becomes substantially water-insoluble after the reaction. The resin has hydrophilicity after the reaction and maintains sufficient affinity with ink.

  Such resins include saponified polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or derivatives of the hydrophilic resins, and It is at least one selected from the group consisting of copolymers, or a hydrophilic resin modified with a modifying group such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, or a photodepolymerization type It is. Among them, a resin modified with a photodimerization type or a photopolymerization type modification group is preferable from the viewpoint of sensitivity or stability of the resin itself. As the photodimerization-type modifying group, those having a diazo group, a cinnamoyl group, a styrylpyridinium group, or a stilquinolium group introduced are preferable, and a resin that is dyed with a water-soluble dye such as an anionic dye after photodimerization is preferable. Examples of such resins include resins having a cationic period such as primary amino group or quaternary ammonium group, such as JP-A-62-283339, JP-A-1-198615, JP-A-60-252341. No., JP-A 56-67309, JP-A 60-129742, etc., photosensitive resins (compositions), and after curing, become cationic after curing such as an azide group that becomes an amino group Examples of the resin include photosensitive resins (compositions) described in JP-A-56-67309.

  Specific examples include the following compounds, but the present invention is not limited only to these compounds.

  The photosensitive resin described in JP-A-56-67309 contains the following formula (I) in a polyvinyl alcohol structure.

2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following formula (II)

It is a resin composition which has 4-azido-3-nitrophenyl carbonyloxyethylene structure represented by these.

  Specific examples of the photosensitive resin are described in Examples 1 and 2 in the official gazette, and the constituent components and usage ratio of the photosensitive resin are described on page 2 of the official gazette.

  JP-A-60-129742 discloses the following formulas (III) and (IV) in a polyvinyl alcohol structure as a photosensitive resin.

The resin composition which has the following structure is mentioned.

  In the present invention, among the hydrophilic resins that are cross-linked by ionizing radiation, examples of the photopolymerizable modifying group include a structural unit represented by the following general formula (A) disclosed in JP-A No. 2000-181062. Polyvinyl acetate saponified product having the above is preferable from the viewpoint of reactivity.

In the general formula (A), R ₁ represents a hydrogen atom or a methyl group, Y represents an aromatic ring or a simple bond, and X represents — (CH ₂ ) _m —COO—, —O—CH ₂ —. COO- or -O- is represented, m is an integer of 0-6, n represents 1 or 2.

  In the present invention, it is preferable to add a photoinitiator or a sensitizer together with a hydrophilic binder containing a polymer compound polymerized by ionizing radiation. These compounds may be chemically bonded to a hydrophilic binder containing the above polymer compound in a state of being dissolved or dispersed in a solvent.

  The photoinitiator and photosensitizer to be applied are not particularly limited, and conventionally known photoinitiators or photosensitizers can be used. For example, benzophenones (for example, benzophenone, hydroxybenzophenone, bis- N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4′-dimethylaminobenzophenone, etc.), thioxanthones (eg, thixatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, Isopropoxychlorothioxanthone), anthraquinones (eg, ethyl anthraquinone, benzanthraquinone, aminoanthraquinone, chloroanthraquinone, etc.), acetophenones, benzoin ethers (eg, benzoin) Tilether, etc.), 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4, 5-di (m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer , 2- (p-methoxyphenyl) -4,5-diphenylimidazole dimer, 2, -di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) 2,4,5-diphenylimidazole dimer 2,4,5-triarylimidazole dimer, benzyldimethyl ketal, 2- N-di-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-hydroxy-2 -Methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, phenanthrenequinone, 9,10 -Benzoins such as phenanthrenequinone, methylbenzoin, ethylbenzoin, acridine derivatives (for example, 9-phenylacridine, 1,7-bis (9,9'-acridinyl) heptane, etc.), bisacylphosphine oxide and the like The above-mentioned compounds may be used alone or in combination of two or more.

  In particular, water-soluble 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 4- (2-hydroxyethoxy) -phenyl- (2- Water-soluble initiators such as hydroxy-2-propyl) ketone, thioxanthone ammonium salt, and benzophenone ammonium salt are preferable from the viewpoint of crosslink efficiency because of excellent mixing properties.

  In addition to these initiators, accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.

  In such a resin, the polymerization degree of the mother polyvinyl alcohol resin is preferably 300 or more, and more preferably 1700 or more. The modification rate of the ionizing radiation reaction-modifying group with respect to the segment is preferably 4 mol% or less, more preferably 1 mol% or less. If the polymerization degree of the segment is 300 or less or the modification rate exceeds 4 mol%, the crosslinking density of the coating film is too high, and the breakability of the dried coating film is remarkably deteriorated. At the same time, if the crosslinking density is too high, the balance between hygroscopicity and dimensional stability with the substrate is poor, and curling resistance is deteriorated.

  In the method for producing an inkjet recording paper of the present invention, when a polymer compound is used as the hydrophilic binder by the ionizing radiation, a coating liquid containing the polymer compound is applied by the ionizing radiation, and the total solid content of the coating layer is obtained. The coating layer is gelled by irradiating ionizing radiation at a concentration of 5 to 90%, and then dried. Examples of the ionizing radiation in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X-rays. In view of the widespread use of electron beam, ultraviolet rays or ultraviolet rays are preferable.

  Examples of the electron beam irradiation method include a scanning method, a curtain beam method, and a broad beam method. The curtain beam method is preferable from the viewpoint of processing capability. The acceleration voltage of the electron beam can be changed as appropriate depending on the specific gravity and film pressure of the coating film, but 20 kV to 300 kV is appropriate. The irradiation amount of the electron beam is preferably in the range of 0.1 to 20 Mrad.

  As the ultraviolet light source, for example, low pressure, medium pressure, high pressure mercury lamp, metal halide lamp and the like having an operating pressure of 100 Pa to 1 MPa are used. From the viewpoint of wavelength distribution of the light source, a high pressure mercury lamp and a metal halide lamp are preferable, and a metal halide lamp is more preferable. preferable.

In particular, when the wavelength of the light source includes ultraviolet rays of 300 nm or less, or when the irradiation energy exceeds 100 J / cm ² , the core of the ionizing radiation crosslinkable resin or various coexisting additives are decomposed by ionizing radiation. In addition to not being able to obtain the effects of the present invention, there is a possibility that problems such as odor derived from the decomposition products may occur. On the contrary, when the irradiation energy is less than 0.1 mJ / cm ² , the crosslinking efficiency is insufficient and the effect of the present invention cannot be sufficiently obtained. Therefore, it is preferable to provide a filter that cuts light having a wavelength of 300 nm or less as the light source, and the output of the lamp is preferably 400 W to 30 kW and the illuminance is preferably 10 mW / cm ^{2 to} 10 kW / cm ² . Preferably as the radiation energy is 0.1mJ / cm ² ~100mJ / cm ² in the present invention, more preferably ^{1mJ / cm 2 ~50mJ / cm 2} .

When giving the same integrated light quantity (mJ / cm ² ), the preferable range of illuminance is due to the change in the light transmittance. When the concentration distribution of the generated cross-linking reactive species is different due to the transmittance of ultraviolet rays, and the ultraviolet illuminance is high, a high concentration of cross-linking reactive species is generated on the surface layer, and a hard and dense film is formed on the surface of the coating film. When the illuminance is in a preferable range, the degree of cross-linking of the surface layer is low and light permeability in the deep direction is high, so that gentle cross-linking is uniformly formed in the deep direction. If the illuminance is too low, it takes a long time to give the necessary integrated illuminance, which is not only disadvantageous in terms of equipment introduction, but also because the amount of absolute light due to scattering of ultraviolet rays by the coating film is insufficient. Absent.

  For the ink receiving layer according to the present invention, a mordant of a coloring material can be used, and a compound containing an aluminum atom can be particularly preferably used as the mordant. The compound containing an aluminum atom may be any of a single salt and double salt of an inorganic acid or an organic acid, an organic metal compound, a metal complex, etc., but a polyaluminum chloride compound, a polyaluminum sulfate compound, a polyaluminum sulfate silicate Particularly preferred are compounds.

The polyaluminum chloride compound is represented by the general formula [Al ₂ (OH) _n Cl _6-n ] m, [Al (OH) ₃ ] n · AlCl ₃ , for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ (OH) ₃₄ ] ⁵⁺ and other basic and highly positively charged polynuclear condensed ions (polymeric) as active ingredients, It is a polyaluminum chloride containing stably.

Examples of commercially available products of polyaluminum chloride include polyaluminum hydroxide (Paho) manufactured by Asada Chemical Co., Ltd., polyaluminum chloride (PAC) manufactured by Taki Chemical Co., Ltd., and Pukeram manufactured by Riken Green Co., Ltd. WT. The polyaluminum sulfate compound is represented by the general formula [Al ₂ (OH) _n (SO ₄ ) _{6-n / 2} ] m (provided that 0 <n <6). As a commercially available product, Asada Examples include basic aluminum sulfate (AHS) manufactured by Chemical Co., Ltd. As a commercial item of a polysulfuric acid aluminum silicate compound, PASS made from Nippon Light Metal Co., Ltd. is mentioned.

  Various additives can be added to the water-soluble coating liquid forming the porous material layer. Such additives include, for example, cationic mordants, crosslinking agents, surfactants (cations, nonions, anions, amphoterics), white color tone modifiers, fluorescent whitening agents, antifungal agents, viscosity modifiers, low boiling points. Organic solvents, high-boiling organic solvents, latex emulsions, anti-fading agents, UV absorbers, polyvalent metal compounds (water-soluble or water-insoluble), matting agents, silicone oils, etc., among which cationic mordants are printing It is preferable for improving water resistance and moisture resistance later. As the cationic mordant, a cationic polymer having the same primary to tertiary amino groups and quaternary ammonium bases as those of the above-described cationic organic resin is preferable.

  As the cationic polymer, a known polymer can be used, for example, polyethyleneimine, polyallylamine and a modified product thereof, dicyandiamide polyalkylene polyamine, a condensate of dialkylamine and epichlorohydrin, polyvinylamine, polyvinylpyridine, Polyvinyl imidazole, diallyldimethylammonium salt condensate, polyacrylic acid ester quaternized product, etc., but the discoloration with time and deterioration of light resistance are small, and the mordanting ability of the dye is sufficiently high. A homopolymer of a monomer having a quaternary ammonium base or a copolymer with one or more other monomers capable of copolymerization, JP-A-10-193976, JP-A-10-217601, JP-A-11-20300 What is described in the publication, etc. Amine-modified product is preferred. As the polyallylamine-modified product, one obtained by adding acrylonitrile, chloromethylstyrene or the like is known.

  These mordants may be mixed and applied to a porous substance-containing coating solution that forms the ink receiving layer, or may be independently applied as a separate solution. As in the case of the above hardener, it is preferable to overcoat the base material having the porous material layer with a separate liquid simultaneously with or after the application of the porous material layer. In this case, you may mix and add with a hardener.

  In the present invention, a polyvalent metal compound can be added to the ink receiving layer.

Examples of the polyvalent metal compound include sulfates such as Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Zr ²⁺ , Ni ²⁺ , and Al ³⁺ , chlorides, nitrates, and acetates. In addition, inorganic polymer compounds such as basic polyaluminum hydroxide and zirconyl acetate are also included as examples of preferable water-soluble polyvalent metal compounds. Many of these water-soluble compounds generally have a function of improving light resistance and improving bleeding and water resistance. These water-soluble polyvalent metal ions are generally used in a range of 0.05 to 20 mmol, preferably 0.1 to 10 mmol, per 1 m ^{2 of} recording paper.

  In the ink jet recording paper support of the present invention, a back layer may be provided on the surface opposite to the surface on which the ink receiving layer is provided for the purpose of improving slipperiness and charging characteristics. The binder for the back layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, a latex polymer having a Tg of −30 to 60 ° C., an antistatic agent such as a cationic polymer, various surfactants, A matting agent having an average particle diameter of about 0.5 to 20 μm can also be added. The thickness of the back layer is generally 0.1 to 1 μm, but in the case where the back layer is provided for preventing curling, it is generally in the range of 1 to 20 μm. Further, the back layer may be composed of two or more layers.

  In coating the undercoat layer and the back layer, it is preferable to use a surface treatment such as corona treatment or plasma treatment on the surface of the substrate.

  In the present invention, the coating method for providing the ink receiving layer or the like on the support for inkjet recording paper of the present invention can be appropriately selected from known methods. For example, gravure coating method, roll coating method, rod A bar coating method, an air knife coating method, a spray coating method, an extrusion coating method, a curtain coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used.

  In the present invention, when two or more ink receiving layers are formed, it is preferable to apply all the layers simultaneously from the viewpoint of reducing the manufacturing cost.

In the ink jet recording paper of the present invention having the above structure, the surface of the ink jet recording paper is measured by the method described in JIS-Z-8722, and the chromaticity index a ^* , b ^* defined in JIS-Z-8730 is measured ^. Are preferably -2 to +4, or -11 to 0. More preferably, the chromaticity indices a ^* and b ^* are −2 to +4 and −11 to −5. The chromaticity of the recording surface side surface of the recording paper depends on its use and preference, but in general, in the case of printing paper, it is generally measured by the method specified in JIS-Z-8722. However, it seems that a ^* and b ^* when expressed in JIS-Z-8730 are preferably −2 to +2 and −4 to +4, respectively. However, according to the study by the present inventors, in order to obtain a high-quality image having a so-called silver salt photograph texture on an inkjet recording paper, the chromaticity of the recording paper recording surface side is the above-mentioned conventional one. The range is not always sufficient.

If b ^* is greater than 0, the image, particularly the white to light color image portion, is weakened even if the hue of the white background is within the allowable range. A decrease in sharpness can be felt.

In the inkjet recording paper of the present invention, it is necessary for the surface chromaticity to be relatively blue, that is, b ^* is -11 to 0 in order to obtain a clear image, and b ^* is If it is -11--5, a still higher clear feeling will be acquired and it is preferable.

When b ^* is smaller than -11, the white background becomes bluish and uncomfortable, and the entire image is bluish, so that the state becomes a so-called cyan fog. It will decline.

The lightness index L ^* of the recording surface side surface of the inkjet recording paper of the present invention is preferably 90 or more, and more preferably 95 or more. Here, the lightness index L ^* is measured by the method described in JIS-Z-8722, and is displayed by the method defined in JIS-Z-8730.

In the present invention, as one of the methods for achieving a ^* and b ^* defined above, it is preferable to add a fluorescent whitening agent to the ink absorbing layer.

  The fluorescent whitening agent that can be used in the present invention has, as its basic chemical structure, a diaminostilmene, imidazole, thiazole, oxazole, triazole, oxadiazole, thiadiazole, coumarin, Examples include phthalimide, pyrazoline, pyrene, imidazolone, benzidine, diaminocarbazole, oxacyanine, methine, pyridine, anthrapyridazine, distyryl, and carbostyryl.

  Commercially available fluorescent brighteners include C.I. I. Fluorescent St. Brightner 226, C.I. I. Fluorescent St. Brightner 363, C.I. I. Fluorescent Brightening Agent 52, C.I. I. Fluorescent Brightening Agent 135, Mika White ACR, Mika White ATN, Kayphor 3BS, Blankophor (manufactured by Bayer), Hostalux (manufactured by Hoechst), Palani, Ultrapho (manufactured by BASF), Uvitex (manufactured by Ciba Geigy) , Whiteex (manufactured by Sumitomo Chemical Co., Ltd.) and the like. The manufacturing method of the optical brightener used for this invention does not have a restriction | limiting in particular, It can manufacture by a conventionally well-known method.

  Although there is no restriction | limiting in particular as content of a fluorescent whitening agent, 0.1-20 mass% of solid content contained in a surface layer is preferable. If the amount is less than 0.1% by mass, the effect on the white background is small. If the amount exceeds 20% by mass, the ink absorbability decreases, the coating failure occurs, and the fluorescent whitening agent itself is colored. Becomes noticeable and is not preferable.

  The film surface pH of the recording surface of the inkjet recording paper of the present invention is preferably 3.5 to 9. When the film surface pH is less than 3.5, so-called bronzing, in which the dye is deposited and the gloss is changed to a metallic state during ink jet recording, is likely to occur. On the other hand, if the film surface pH exceeds 9, the effect of preventing bleeding is reduced. The measurement of the film surface pH of the recording surface is described in J. Org. TAPPI paper pulp test method no. According to the method described in 49, it is measured after 30 seconds using distilled water. The film surface pH of the recording surface can be set to a predetermined range by overcoating an appropriate pH adjusting agent after forming the recording surface. As the pH adjuster, an appropriate aqueous solution of acid or alkali can be used. In this case, the type and concentration of the acid or alkali to be used can be appropriately selected depending on the pH range to be adjusted.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “%” represents mass% unless otherwise specified.

Example 1
<< Preparation of Ink Receptive Layer Coating Liquid A-1 >>
In 150 ml of pure water, 1.2 ml of a nonionic acrylic polymer type dispersant (solid content 40%, SD-10 manufactured by Toa Gosei) was dissolved, and the pH was adjusted to 11.0 with sodium hydroxide. Here, 435 g of a 23% aqueous dispersion of silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle diameter of about 7 nm was added and dispersed with a high-speed homogenizer to obtain a dispersion of vapor phase silica.

  Next, 280 ml of polyvinyl alcohol (Kuraray PVA224, 8% aqueous solution with a polymerization degree of 2400, 78.4 ml of 25% solution of the following cationic polymer 1 and 0.7 g of borax were added to this dispersion. Then, pure water was added so that the total volume was 1000 ml to prepare a translucent ink receiving layer coating solution A-1.

<Production of recording paper>
[Production of Sample 101: Comparative Example]
The first layer, the second layer, and the third layer are formed from the side close to the base material, and the ink-receiving layer coating liquid A-1 is used as the coating liquid for the first to third layers. 3 ml of a 5% solution of betaine surfactant-1 (* 1) was added and filtered with the following filter.

(filter)
1st layer-2nd layer: Two-stage structure of Toyo Filter Paper Co., Ltd. TCP10 Third layer: Two-stage structure of Toyo Filter Paper Co., Ltd. TCP30 * 1) Betaine type surfactant-1:
C ₈ H ₁₇ SO ₂ NH (CH ₂ ) ₃ N ⁺ (CH ₃ ) ₂ CH ₂ COO ⁻
Each layer coating solution prepared as described above was printed on cast coated paper (mirror coated satin Kanto, 209.3 g of Oji Paper Co., Ltd.) as a base material, and the first layer (62 μm) and second layer on the cast surface side. (62 [mu] m) and a third layer (62 [mu] m) were applied simultaneously for three layers. The numerical value in parentheses is the wet film thickness.

  The coating is performed by a slide type curtain coating method while keeping each coating solution at 40 ° C., and after cooling for 10 seconds in a cooling zone maintained at 5 ° C. immediately after coating, the coating liquid is passed through a drying zone at 50 ° C. and dried. It was. After drying, the humidity was adjusted at 25 ° C. and a relative humidity of 50% to obtain a sample 101 composed of three ink receiving layers.

[Preparation of Sample 102: Present Invention]
On the cast coated paper for printing (mirror coated satin Kinto, 209.3 g Oji Paper) used for the preparation of the sample 101, HYDLTH2255R (manufactured by Dainippon Ink & Chemicals, Inc.) was used and the dry film thickness was 10 μm. The undercoat layer was applied in such a manner that it was dried by passing through a drying zone at 50 ° C. After drying, an aging treatment was performed at 77 ° C. for 12 hours, and then the humidity was adjusted to 50% relative humidity to obtain a base material for producing the recording paper 102.

  Next, each ink receiving layer coating solution was applied onto the substrate in the same manner as Sample 101, dried and conditioned to obtain Sample 102.

[Production of Sample 103: Comparative Example]
Sample 103 was prepared in the same manner as in the preparation of Sample 101, except that the coated paper for printing (Artpost Yasutsubo 256 g, made by Hokuetsu Paper) was used instead of the cast coated paper for printing.

[Production of Sample 104: Comparative Example]
Sample 104 was prepared in the same manner as in the preparation of Sample 102, except that the coated paper for printing (Artpost Yasutsubo 256 g, manufactured by Hokuetsu Paper) was used instead of the cast coated paper for printing.

[Production of Sample 105: Comparative Example]
In the preparation of Sample 101, Sample 105 was prepared in the same manner except that a high-quality paper (Shiraoi 157 tsubo made by Nippon Daishowa Paperboard) was used instead of the cast-coated paper for printing.

[Production of Sample 106: Comparative Example]
Sample 106 was prepared in the same manner as in the preparation of Sample 102, except that a high-quality paper (Shiraoi 157 tsubo made by Nippon Daishowa Paperboard) was used instead of the cast-coated paper for printing.

<< Evaluation of each characteristic >>
About each sample produced by the above, each characteristic was evaluated in accordance with the method as described below.

[Measurement of moisture permeability]
About the base material used for preparation of each recording paper and the base material on which an undercoat layer is formed, according to the method described in JIS-Z-0208, moisture permeability (g / m ² · day) under the conditions of 40 ° C. and 90% RH Was measured.

[Measurement of centerline average roughness Ra value]
The substrate used for the preparation of each recording paper and the substrate on which an undercoat layer was formed were conditioned for 24 hours under the condition that the measurement samples were not superimposed in an environment of 25 ° C. and 65% RH, and then JIS-B-0601. According to the method defined by the above, the center line average roughness Ra when measured with a reference length of 5.0 mm and a cutoff value of 0.8 mm was measured.

[Glossiness measurement]
About each sample which is an inkjet recording paper which apply | coated each ink receiving layer, the incident and reflection angles by the side of an ink receiving layer coating surface are measured using the variable angle glossiness meter (VGS-1001DP) by Nippon Denshoku Industries Co., Ltd. Measured the glossiness at 60 °.

[Measurement of C value]
Each sample, which is an ink jet recording sheet coated with each ink receiving layer, is mapped at a reflection of 60 ° and an optical comb of 2 mm on the ink receiving layer coating surface side by means of an image clarity measuring device ICM-1DP (manufactured by Suga Test Instruments Co., Ltd.). The property (C value%) was measured.

(Measurement of liquid absorption)
The base material used for the production of each recording paper and the base material on which an undercoat layer was formed were evaluated by the Bristow method according to the liquid absorptivity test method for paper or paperboard. The liquid absorptivity in the present invention is indicated by the amount of water transfer (ml / m ² ) at a contact time of 10 seconds in the measurement.

  The results obtained as described above are shown in Table 1.

  As is clear from the results shown in Table 1, water-absorbent paper having moisture permeability, centerline average roughness Ra value, and water absorption by the Bristow method in the range specified by the present invention is used as a base layer. The sample 102 having the moisture permeability and Ra value after coating in the ranges specified in the present invention was measured by applying an undercoat layer (low moisture permeability layer) to the glossiness and C as an inkjet recording paper after coating the ink receiving layer. It can be seen that the glossiness and C value are remarkably improved in comparison with the sample 101 in which the ink receiving layer is directly applied to the paper substrate.

  On the other hand, although the moisture permeability by the Bristow method is within the range defined by the present invention, the sample 104 using the base material whose centerline average roughness Ra value exceeds the range defined by the present invention, and the moisture permeability, Sample 106 using a base material whose center line average roughness Ra value, and further, the water absorption amount by the Bristow method is outside the range specified in the present invention, is a sample 103 in which an ink receiving layer is directly applied to each base material, The improvement in glossiness and C value from 105 is small or hardly recognized.

Example 2
[Production of Sample 201: Comparative Example]
In the preparation of the sample 101 described in Example 1, the base material was changed to cast coated paper for printing, and polyethylene coated paper (both on the ink receiving layer coating surface side) in which both base papers having a basis weight of 170 g / m ² were coated with polyethylene. The polyethylene layer contains 8% anatase-type titanium oxide, and also has a gelatin subbing layer of 0.05 g / m ² on the side where the ink receiving layer is coated, and the other side is a latex having a Tg of about 80 ° C. A recording paper 201 was prepared in the same manner except that a back layer containing 0.2 g / m ^{2 of} polymer was used (hereinafter referred to as RC base paper).

[Production of Sample 202: Comparative Example]
A 6.5% aqueous solution of polyvinyl alcohol (PVA224 manufactured by Kuraray Co., Ltd., polymerization degree 2400) is cast on cast coated paper for printing (mirror coated satin kinto, 209.3 g Oji Paper), and the dry film thickness is 1.5 μm. It applied so that it might become, and it dried by passing through a 50 degreeC drying zone. After drying, the humidity was adjusted at 25 ° C. and a relative humidity of 50% to obtain a base material for producing the recording paper 202.

  Next, an ink receiving layer was applied on the substrate in the same manner as in the sample 201, dried and conditioned to obtain a sample 202.

[Preparation of Sample 203: Present Invention]
A sample 203 was prepared in the same manner as in the preparation of the sample 102 described in Example 1, except that the dry film thickness of HYDLITH2255R was changed to 1.5 μm.

[Production of Sample 204: Present Invention]
Sample 204 was prepared in the same manner as in the preparation of Sample 203 except that the dry film thickness of HYDLITH2255R was changed to 20 μm.

[Preparation of Sample 205: Present Invention]
A sample 205 was prepared in the same manner as in the preparation of the sample 102 described in Example 1, except that the coating solution of HYDLTH2255R was diluted 1.5 times.

[Production of Sample 206: Comparative Example]
A sample 206 was prepared in the same manner as in the preparation of the sample 102 described in Example 1, except that the coating solution of HYDLTHH2255R was diluted two times.

[Preparation of Sample 207: Present Invention]
HYDLTHH2024 (manufactured by Dainippon Ink & Chemicals, Inc.) was applied to a cast coated paper for printing (mirror coated satin kinto, 209.3 g Oji Paper) so that the dry film thickness was 10 μm. An undercoat layer was formed by passing through a drying zone and drying. After drying, an aging treatment was carried out at 77 ° C. for 12 hours, and then the humidity was adjusted at 50% relative humidity to obtain a base material for producing the recording paper 109.

  Next, an ink receiving layer was applied onto the substrate in the same manner as in the sample 201, dried, and prepared to obtain a sample 207.

<< Evaluation of each characteristic >>
Each sample prepared as described above and the samples 101 and 102 prepared in Example 1 were evaluated in the same manner as in the method described in Example 1, and the obtained results are shown in Table 2.

  As is clear from the results shown in Table 2, when the characteristics of the comparative sample 201 and the sample 102 of the present invention are compared, the sample 102 having the configuration of the present invention has a gloss equivalent to that of the sample 201 using RC base paper. It can be seen that excellent image quality performance can be obtained even when water-absorbent paper having a C value and a lower cost than RC base paper is used as a base material.

On the other hand, if the coating amount of the non-solid content exceeds 35 ml / m ² in the undercoat layer, the recording paper after application of the ink receiving layer can be used even if a substrate having moisture permeability and Ra value within the scope of the present invention is used. It is clear from the result of the sample 206 that the glossiness and the C value are greatly reduced.

  In addition, even when the undercoat layer thickness and the amount of the non-solid content are within the range specified in the present invention, if the moisture permeability after the undercoat layer coating is outside the range specified by the present invention, the ink receiving layer is applied. It is shown by the result of the sample 202 that the glossiness and C value of the subsequent recording paper are greatly reduced.

Claims (11)

Moisture permeability 4000g / m ² · day or more, below 10000g / m ² · day, and the image recording surface side of the center line average roughness Ra value is 0.2μm or less absorbent substrates, the non-solid component Using the coating liquid comprising 50% by mass or more of water, at least one moisture-permeable layer is formed, and the coating amount of the non-solid component is 35 ml / m ² or less. The moisture permeability after forming the film is less than 4000 g / m ² · day, and the center line average roughness Ra value on the side on which the moisture permeable layer is formed is 0.3 μm or less. Inkjet recording paper support. J. et al. TAPPI paper pulp test method no. 51-87, or the water absorption at a contact time of 10 seconds measured according to the liquid absorptivity test method (Bristow method) of paper and paperboard is 15 ml / m ² or less, and the centerline average roughness Ra value is 0. On the image recording surface side of the water-absorbing substrate having a thickness of 2 μm or less, at least one low moisture-permeable layer is formed using a coating liquid in which 50% by mass or more of the non-solid component is composed of water. The coating amount of the solid component is 35 ml / m ² or less, the moisture permeability after the formation of the low moisture permeable layer is less than 4000 g / m ² · day, and the side on which the low moisture permeable layer is formed. A support for inkjet recording paper, wherein the center line average roughness Ra value is 0.3 µm or less. On a water-absorbing substrate, a water-dispersible polymer or a water-soluble polymer is melted and formed into a film, and a low moisture-permeable layer having a thickness of 1.0 μm or more and 30 μm or less is formed. An ink jet having a moisture permeability of less than 4000 g / m ² · day after being formed, and a center line average roughness Ra value of 0.3 μm or less on the side on which the moisture-permeable layer is formed Support for recording paper. The support for inkjet recording paper according to any one of claims 1 to 3, wherein a center line average roughness Ra value on a surface side on which the moisture-permeable layer is formed is 0.2 µm or less. body. The support for inkjet recording paper according to any one of claims 1 to 4, wherein the moisture-permeable layer forming step does not include a smoothing step by a casting step or a calendar step. 6. An ink jet recording paper comprising at least one ink receiving layer containing inorganic fine particles and a hydrophilic binder on the ink jet recording paper support according to any one of claims 1 to 5. Moisture permeability 4000g / m ² · day or more, below 10000g / m ² · day, and the image recording surface side of the center line average roughness Ra value is 0.2μm or less absorbent substrates, the non-solid component A method for producing a support for inkjet recording paper, wherein at least one moisture-permeable layer is formed using a coating solution comprising 50% by mass or more of water, and the coating amount of the non-solid component is 35 ml. / M ² or less, the moisture permeability after forming the low moisture permeability layer is less than 4000 g / m ² · day, and the center line average roughness Ra value on the side where the moisture permeability layer is formed Is 0.3 μm or less, a method for producing a support for ink jet recording paper. J. et al. TAPPI paper pulp test method no. 51-87, or the water absorption at a contact time of 10 seconds measured according to the liquid absorptivity test method (Bristow method) of paper and paperboard is 15 ml / m ² or less, and the centerline average roughness Ra value is 0. Inkjet recording in which at least one low moisture-permeable layer is formed on the image recording surface side of a water-absorbing substrate of 2 μm or less using a coating liquid in which 50% by mass or more of the non-solid component is composed of water. A method for producing a paper support, wherein the coating amount of the non-solid component is 35 ml / m ² or less, and the moisture permeability after the low moisture permeable layer is formed is less than 4000 g / m ² · day, A method for producing a support for inkjet recording paper, characterized in that the center line average roughness Ra value on the side on which the moisture-permeable layer is formed is 0.3 μm or less. On the water-absorbent substrate, a water-dispersible polymer or a water-soluble polymer is melted and formed into a low moisture-permeable layer having a thickness of 1.0 μm or more and 30 μm or less. An ink jet having a moisture permeability of less than 4000 g / m ² · day after being formed, and a center line average roughness Ra value of 0.3 μm or less on the side on which the moisture-permeable layer is formed A method for manufacturing a support for recording paper. The method for producing a support for inkjet recording paper according to any one of claims 7 to 9, wherein the forming step of the moisture-permeable layer does not include a smoothing step by a casting step or a calendar step. . 11. At least one ink receiving layer containing inorganic fine particles and a hydrophilic binder on an inkjet recording paper support produced by the method for producing an inkjet recording paper support according to any one of claims 7 to 10. A method for producing an ink jet recording paper, characterized in that the ink jet recording paper is produced.