JP2003312122A - Ink jet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording sheet which shows satisfactory ink absorption, smoothness and image density and superb resistance to color variation after printing and curling and further, produces a high-quality ink jet image. <P>SOLUTION: This ink jet recording sheet has a layer containing an emulsion with an inorganic fine particle, a group which can react chemically with the inorganic fine particle or a group which can undergo a hydrogen bonding process and a mordant and an ink absorptive layer containing the inorganic fine particle with an average particle diameter of 3 to 200 nm, the mordant and a water-soluble binder, sequentially formed on a support. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording paper, and more specifically, it has high ink absorbency, is excellent in cockling resistance, color variation resistance after printing and curl resistance, and has high image density and high image quality. The present invention relates to an inkjet recording sheet on which various inkjet images can be obtained.

[0002]

2. Description of the Related Art Ink-jet recording is a technique for ejecting minute droplets of ink by various operating principles and attaching them to a recording sheet such as paper to record images, characters, etc., but at relatively high speed and low speed. It has advantages such as noise and easy multicoloring. In this inkjet method, nozzle clogging and maintenance, which had been a problem in the past, have been improved from both aspects of ink and equipment, and are now rapidly spreading in various fields such as various printers, facsimiles, computer terminals, etc. is doing.

The recording paper used in the above ink jet recording system has high density of print dots, bright and vivid color tone, fast ink absorption, and even when print dots overlap, ink flows or bleeds. It is generally required that the horizontal diffusion of print dots is not unnecessarily large and that the periphery is smooth and has no blur.

Further, in recent years, many attempts have been made to bring the image quality obtained by color ink jet recording closer to that of a silver salt photographic image. Among them, the biggest point of image quality improvement regarding dots is to make each dot invisible to the naked eye, and for that reason, make the ink into small droplets, or, especially, at the highlight part In order to lower the reflection density and make it difficult to identify dots, methods such as using ink with a low dye density in combination have been proposed and put into practical use. For this reason, the amount of ejected ink tends to increase, and as a result, the ink absorption capacity of the inkjet recording paper becomes insufficient, and deterioration of image quality and deterioration of dryness due to the overflow of ink are being observed. .

In contrast to the above problems, when the thickness of the void-type ink absorbing layer of the ink jet recording paper is increased, cracks are likely to occur due to the characteristics of the film, and the coating speed is lowered from the viewpoint of drying ability, so that production Problems such as increased cost have occurred.

On the other hand, when a porous substrate such as plain paper, high-quality paper or coated paper or cast-coated paper is used as a support as an ink jet recording paper, the ink permeates into the support, so that the ink absorption capacity is increased. As a result, undulation due to ink absorption or drying in the printed portion, so-called cockling occurs and print quality is greatly reduced, smoothness and gloss are reduced, or a dye is used. However, there was a problem in that it was difficult to obtain the maximum density due to the penetration of the above into the support, and it was difficult to obtain a clear image. In addition, especially under printing conditions where the amount of ink printed is large,
It was found that the color variation after the passage of time was greater than the color tone immediately after printing.

[0007] With respect to each of the above problems, for example,
No. 282399 has a glass transition temperature of 20 on the support.
An ink absorption layer whose main component is an acrylic resin having a temperature of ℃ or less,
And a method of improving ink receptivity by a recording paper in which a surface layer containing a resin having a glass transition temperature of 80 ° C. or more as a main component is sequentially laminated, and JP-A-5-51.
No. 470, an oil absorption of ≧ 1 consisting of a water-dispersible polymer and beaded colloidal silica between the substrate and the ink absorption layer.
Although a method has been proposed in which a porous layer having a volume of ml / m ² is provided and an ink absorbing layer is provided on the porous layer, the adhesion with a substrate, water resistance, and print quality are improved. The effect according to the present invention was not sufficient. Further, in JP-A-5-85035, there is a method of improving cockling by providing an intermediate layer composed of an adhesive and a pigment having a glass transition point of 30 to 60 ° C. between a plain paper substrate and an ink absorbing layer, Further, JP-A-8-300806 proposes a method of improving the abrasion property during the transportation of the printer and the ink absorption property by providing an anchor layer composed of a self-adhesive pigment between a support composed of wood pulp and the ink absorption layer. However, when applied to a porous substrate such as paper, the effect is still insufficient and further improvement is required.

On the other hand, in JP-B-5-46317, a recording paper having a coating layer containing a binder and a pigment made of a polymer obtained by reacting polyvinyl alcohol, methyl methacrylate and acrylic acid on a support is used. A method for improving ink absorbency and colorability has been proposed. Further, in JP-A-7-276787, an ethylenic unsaturated polymer obtained by emulsion-polymerizing a polyvinyl alcohol polymer having a mercapto group at a terminal as a dispersion stabilizer. A method of improving resolution and water resistance by recording paper using a polymer emulsion composed of a monomer or a diene monomer as a surface sizing agent or a pigment binder for surface coating has been proposed. Since the image density and smoothness cannot be obtained simply by coating the layer containing the binder made of But it can not be said sufficient for the desired effect.

Further, when a support is coated with an ink absorption layer having a high porosity on a porous substrate such as paper, cracks are likely to occur. There is a problem that the gloss is also easily damaged and the production is difficult.

To solve the above problem, for example, Japanese Patent Laid-Open No. 11-2
No. 45506 proposes a method for improving texture, image density, saturation, and glossiness by providing a white pigment layer having elution resistance and an ink absorbing layer made of alumina boehmite on a fibrous substrate. Japanese Patent Laid-Open No. 2000-3377
1 proposes an inkjet recording material using a base paper having a layer containing barium sulfate and thermoplastic hollow fine beads. However, as a result of the earnest research conducted by the present researchers, it was found that the porosity on the white pigment layer could be increased only by imparting the elution resistance of the white pigment to water to the layer composed of the white pigment and the binder such as gelatin. When a high ink absorption layer is applied, cracks tend to occur, so
Not only the smoothness after coating the ink absorbing layer is easily impaired, but also it is difficult to make the ink absorbing layer thin from the viewpoint of the ink absorbing capacity.

Many proposals have been made to improve smoothness and glossiness by calendering the coating layer or providing a coating layer by a casting method, but it is difficult to increase the coating speed in the production process. For reasons such as complexity,
It is difficult to provide inexpensive, high-density, high-quality recording materials.

On the other hand, a method has also been proposed in which a water-soluble polyvalent metal ion is added to an ink jet recording paper in advance and the dye is solidified and fixed during ink jet recording to immobilize the dye. For example, JP-A-55-53591 and 55-55
-150396, 56-86789, 58-8
Nos. 9391 and 58-94491 propose inkjet recording papers containing a water-soluble polyvalent metal salt which forms a sparingly soluble salt by binding with a water-soluble dye. Also, JP-A-60-67190 and JP-A-61-14844.
No. 61-57379, there is proposed an ink jet recording paper containing a cationic polymer and a water-soluble polyvalent metal salt. Also, JP-A-60-25728
No. 6 proposes an ink jet recording paper containing a basic polyaluminum hydroxide compound. Also,
Japanese Patent Application Laid-Open No. 10-258567 discloses a hydrophilic polymer and 4A.
A method of using a water-soluble compound containing a group element in combination is disclosed in Japanese Patent Laid-Open No.
-309862 proposes a method of using a zirconyl compound in combination with a hydrophilic polymer and a polyvalent carboxylic acid.
Further, regarding a compound containing a zirconium element, JP-A-4-7189 proposes a method using a porous pigment and a zirconium oxychloride compound. It is described that in all of the above methods, the addition of zirconium acid chloride salt provided adhesive strength with a relatively small amount of binder and improved image quality. Further, JP-A-6-32046 proposes a method in which a zirconium compound is combined with silica and modified polyvinyl alcohol. further,
European Patent No. 754,560 includes a water-soluble binder,
Patents have been disclosed in which pigments, zirconium compounds, and cationic polymers are used in combination.

However, with respect to any of the above-mentioned proposed methods, the effect of the problem which is the subject of the present invention is insufficient, and there has been a demand for the immediate development of an improved technique for the subject.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to achieve ink absorptivity without unnecessarily increasing the thickness of the ink absorptive layer.
An object of the present invention is to provide an inkjet recording paper which is excellent in cockling resistance, color variation resistance after printing and curl resistance, has a high image density, is inexpensive, and can obtain an inkjet image having high-quality characteristics.

[0015]

The above objects of the present invention have been achieved by the following constitutions.

1. A layer containing inorganic fine particles, an emulsion having a group capable of reacting with the inorganic fine particles or a group capable of hydrogen bonding and a mordant on at least one surface of the support, and inorganic fine particles having an average particle diameter of 3 to 200 nm, a mordant and a water-soluble agent. An ink jet recording paper, which is sequentially provided with an ink absorbing layer containing a hydrophilic binder.

2. 2. The inkjet recording paper according to item 1, wherein the support is a porous base material.

3. 3. The inkjet recording paper as described in 1 or 2 above, wherein the mordant contains at least two kinds of cationic polymers having a quaternary ammonium salt group.

4. Any one of the above items 1 to 3, wherein the inorganic fine particles are silica or alumina.
Ink jet recording paper according to item.

5. 5. The ink jet recording paper according to any one of items 1 to 4, wherein the emulsion is an emulsion polymerized with a polymer dispersant having a hydroxyl group.

6. The polymer dispersant having a hydroxyl group,
6. The inkjet recording paper according to item 5, which is a polyvinyl alcohol-based polymer.

7. 5. The inkjet recording paper according to item 4, wherein the emulsion is a silicon emulsion having a group capable of reacting with a silanol group of silica or a group capable of hydrogen bonding.

8. The average particle size of the emulsion is 0.
1 to 7 characterized in that it is 25 to 0.05 μm
The inkjet recording paper according to any one of items.

9. 9. The inkjet recording paper according to any one of items 1 to 8, which contains a water-soluble polyvalent metal salt.

10. Any one of the above items 1 to 9, wherein the emulsion-containing layer contains a water-soluble plasticizer.
Ink jet recording paper according to item.

The present invention will be described in more detail below. The inkjet recording paper of the present invention comprises a support, a layer containing inorganic fine particles, an emulsion having a group capable of reacting with the inorganic fine particles or a group capable of hydrogen bonding, and a mordant, and inorganic fine particles having an average particle diameter of 3 to 200 nm. And an ink absorbing layer containing a mordant and a water-soluble binder in that order, wherein the support is a porous substrate and the cationic polymer has a quaternary ammonium salt group as a mordant. It is more preferable to contain at least two kinds of

The ink jet recording paper of the present invention (hereinafter,
As the support used in (also simply referred to as recording paper), a known support known in the art can be used.
Particularly when the support is a porous substrate, the effect of improving the ink absorbency, which is the effect of the present invention, is further improved.

The porous substrate for the ink jet recording paper of the present invention will be described. Examples of the porous base material of the present invention include sheets having general paper, synthetic paper, cloth, wood, etc., and particularly, as paper, a sheet shape that is also excellent in cost is preferable. preferable.

The paper support will be described below. Examples of the raw material for the paper support include chemical pulp such as LBKP and NBKP, GP, CGP, RMP, TMP, CTMP,
Mechanical pulp such as CMP, PGW, etc., waste paper pulp such as DIP, etc. can be used as the main raw material, but hardwood pulp is preferably used. As the hardwood pulp, for example, kraft pulp, sulfite pulp, chemithermomechanical pulp, chemimechanical pulp and the like may be used alone or in combination of several kinds. Also,
If necessary, various fibrous substances such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as a raw material.

From the viewpoint of improving the whiteness, it is preferable that the raw material pulp is bleached with a peroxide or the like. The bleaching treatment is, after pulp cooking, chlorine treatment, alkali treatment or extraction or refining, hypochlorite bleaching, chlorine dioxide bleaching and multi-stage bleaching treatment combining them, and further, if necessary, hydrosulfite, hydrogen. It is preferably subjected to reduction bleaching with sodium borohydride or the like. More preferably, the alkaline bleaching treatment with alkaline is performed as a bleaching treatment of the pulp after the pulp is cooked and then the conventionally known pulp bleaching treatment, and thereafter, alkali treatment or extraction or purification is further performed. May be given.

In the paper support, if necessary, for example,
Various conventionally known additives such as a sizing agent, a pigment, a paper strengthening agent, a fixing agent, a fluorescent brightening agent, a wet paper strength agent, and a cationizing agent can be added. Examples of the sizing agent include higher fatty acids, alkyl ketene dimer, rosin, paraffin wax, alkenyl succinic acid and petroleum resin emulsion. As the pigment, for example, calcium carbonate, talc, titanium oxide, urea resin fine particles and the like, and as the paper strengthening agent, for example, starch,
Examples of the fixing agent include polyacrylamide and polyvinyl alcohol, and examples of the fixing agent include a sulfuric acid band and a cationic polymer electrolyte. However, the present invention is not limited thereto.

The paper support is prepared by mixing the above-mentioned fibrous substance such as wood pulp with various additives, and using a Fourdrinier paper machine, a cylinder paper machine,
It can be manufactured with various paper machines such as a twin wire paper machine. If necessary, size press treatment with starch, polyvinyl alcohol, etc., various coat treatments, or calender treatment can be performed at or after the paper making.

The paper density of the paper support is 0.7 to 1.2 g /
m ² (JIS-P-8118) is general. Furthermore,
Stiffness of base paper is 2 under the conditions specified in JIS-P-8143.
0 to 200 g is preferable.

The pH of the paper is preferably 5 to 9 when measured by the hot water extraction method specified in JIS-P-8113.

In the present invention, for the purpose of increasing the adhesive strength between the support and the ink absorbing layer, prior to application of the ink absorbing layer, the support is subjected to corona discharge treatment, undercoating treatment, and intermediate layer coating. And so on.

The thickness of the support is preferably 50 to 350 μm, more preferably 80 to 300 μm, and 140 to
220 μm is particularly preferred.

As the paper support according to the present invention, in the water absorption test method defined in JIS P8140 of a water-absorbent support, when the contact time is 60 seconds, the Cobb water absorption determined using water is is preferably 10 to 50 g / m ^2, and still more preferably from 20 to 40 g / m ^2. When the Cobb water absorption is in the range of 10 to 50 g / m ² , it is easy to prevent cracking and waviness of the coating film in the drying step after manufacturing coating, and when printing on a recording paper using it. Also, cockling is less likely to occur, which is preferable.

The present invention is characterized in that it has an inorganic fine particle, an emulsion having a group capable of reacting with the inorganic fine particle or a group capable of forming a hydrogen bond, and a layer containing a mordant. Is an emulsion resin emulsion-polymerized with a polymer dispersant having a hydroxyl group,
Alternatively, a silicon emulsion having a group capable of reacting with the silanol group of silica or a group capable of hydrogen bonding is more preferable.

The emulsion polymerized by the polymer dispersant having a hydroxyl group according to the present invention will be described below.

The polymer dispersant having a hydroxyl group as referred to in the present invention is a dispersant of a polymer having an average molecular weight of 10,000 or more, in which a hydroxyl group is substituted on the side chain or the terminal, and for example, poly Acrylic polymer such as sodium acrylate, polyacrylamide, copolymerized with 2-ethylhexyl acrylate, polyether such as polyethylene glycol or polypropylene glycol,
Examples thereof include polyvinyl alcohol, and polyvinyl alcohol is particularly preferable.

Polyvinyl alcohol used as a polymer dispersant includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, cation-modified polyvinyl alcohol and anions having anionic groups such as carboxyl groups. Modified polyvinyl alcohol such as modified polyvinyl alcohol and silyl modified polyvinyl alcohol having a silyl group are also included.

The average degree of polymerization of polyvinyl alcohol used as the polymer dispersant is 300 to 5,000.
It is preferably 0, the saponification degree is preferably 70 to 100%, and the average degree of polymerization is in terms of film-forming property (crack resistance) and film strength when forming a layer having a void structure with inorganic fine particles. 1,700 or more is more preferable, 2,4
00 or more is more preferable.

Examples of the emulsion resin emulsion-polymerized with the polymer dispersant include ethylene-based monomers such as acrylic acid esters, methacrylic acid esters, vinyl compounds and styrene compounds, or diene compounds such as butadiene and isoprene. Examples of the homopolymers or copolymers thereof include acrylic resins, styrene-butadiene resins, ethylene-vinyl acetate resins, and the like.

These emulsion resins impart flexibility when forming the void layer of the ink jet recording paper of the present invention, and those having a flexible property at room temperature are suitable, and preferably, they are formed into a film at room temperature. It forms a layer. At this time, Tg when the emulsion resin is formed into a film is preferably 20 ° C. or lower, and −40 to 1
It is more preferably 0 ° C.

The method for producing an emulsion resin emulsion-polymerized with the polymer dispersant having a hydroxyl group according to the present invention is as follows:
There is no particular limitation, and the emulsion can be produced by a known emulsion polymerization method. The average particle size of the emulsion resin emulsion-polymerized with the polymer dispersant having a hydroxyl group according to the present invention is preferably 0.05 to 2.0 μm, more preferably 0.05 to 0.80 μm, and a void structure is formed together with the inorganic fine particles. From the viewpoint of film forming property (crack resistance) and film strength when forming a certain layer, 0.05 to
0.25 μm is particularly preferable.

Examples of specific compounds of the emulsion resin include Sumika Flex S manufactured by Sumitomo Chemical Co., Ltd.
Vinyl acetate-ethylene type emulsions such as -400 and Sumikaflex S-401 are listed.

The emulsion resin according to the present invention can be produced by a conventionally known emulsion polymerization method described in JP-A-4-147886.

Next, the silicon emulsion having a group capable of reacting with the inorganic fine particles or a group capable of hydrogen bonding according to the present invention will be described.

The silicone emulsion having a group capable of reacting with the inorganic fine particles or a group capable of forming a hydrogen bond according to the present invention is an emulsion in which silicone oil known as polydimethylsiloxane having a siloxane skeleton is stably dispersed in water. Alternatively, it can be obtained by emulsion-polymerizing a dimethylsiloxane monomer, and by having a group capable of reacting with the inorganic fine particles or a group capable of hydrogen bonding, it is possible to provide the coating with toughness and flexibility. It is a possible silicone emulsion.

Examples of the silicone emulsion include polyether modified silicone emulsion, alcohol modified silicone emulsion, amino modified silicone emulsion, epoxy modified silicone emulsion, phenol modified silicone emulsion, and carboxy modified silicone emulsion.

As the polyether-modified silicone emulsion, a polyether group such as a polyethylene oxide group or a polypropylene oxide group is added to both ends or side chains of silicon in place of a part of the methyl group which silicon has at both ends or side chains. It is introduced, and it is preferable that the end of the polyether group is a hydroxyl group, but the end is a lower alkoxy group (eg, methoxy group, ethoxy group, etc.).
And the like, which are substituted with.
Specific examples include those obtained by emulsifying silicone oil such as SH3771 and SH8400 (both are trade names) manufactured by Toray Dow Corning Silicone Co., Ltd.

Examples of the alcohol-modified silicone emulsion include emulsions in which a part of the methyl groups of the silicone are substituted with a group having a hydroxyl group at the terminal, and -OH is added to the polyether chain terminal of the polyether-modified silicone.
Examples thereof include an emulsion having a group and an alcohol-modified silicone emulsion not containing a polyether group (for example, an alcohol-modified silicone emulsion having a hydroxyaryl group). Specific examples include those manufactured by Toray Dow Corning Silicone Co., Ltd. SM8706 etc. are mentioned.

Examples of amino-modified silicone emulsions include emulsions of silicone in which amino groups are introduced into both ends or side chains of a dimethyl silicone skeleton.
The amino group includes those substituted with a lower alkyl group such as a methyl group and an ethyl group, and primary amines and tertiary amines are preferable. Specifically, for example, SM870 manufactured by Toray Dow Corning Silicone Co., Ltd.
2, BY22-812, BY22-816 and the like.

Examples of the epoxy-modified silicone emulsion include silicone emulsions in which epoxy groups are introduced at both ends or side chains of a dimethyl silicone skeleton, and specific examples thereof include those manufactured by Toray Dow Corning Silicone Co., Ltd. BY16-855D, SF8411, B
Examples include emulsified silicone oil such as Y16-839.

In addition, a phenol-modified silicone emulsion obtained by emulsifying BY16-752 (silicon oil) manufactured by Toray Dow Corning Silicone,
A carboxy-modified silicone emulsion obtained by emulsifying BY22-820 (silicone oil) can also be used in the present invention.

Particularly preferred among the above-mentioned silicone emulsions are amino-modified silicone emulsions, epoxy-modified silicone emulsions and alcohol-modified silicone emulsions having hydroxyaryl groups.

In the present invention, as a method for measuring the particle size of the emulsion, the particle size can be determined by laser diffraction / scattering particle size distribution measurement in the state of being dispersed in an appropriate dispersion medium. In this case, it is necessary to consider the swelling of the dispersoid of the emulsion due to the dispersion medium, but the size is usually negligible. The shape of the dispersoid does not have to be a true spherical diameter, and may be needle-like or plate-like. The average particle size is obtained from the particle size obtained by converting the volume into spheres.

The layer containing the inorganic fine particles according to the present invention, the emulsion and the mordant may contain the following water-soluble binder or hydrophobic resin in combination with the emulsion according to the present invention. In this case, a water-soluble binder is preferable. When the coating liquid is applied onto a porous substrate such as a paper support and dried, the water-soluble resin in the coating liquid (for example,
Polyvinyl alcohol) penetrates into the gaps of the porous substrate,
After the coating film is dried, a sealing action occurs, often impairing the ink absorbency of the porous substrate. Further, when the binder is used alone with polyvinyl alcohol without using the emulsion according to the present invention, that is, when a layer comprising inorganic fine particles, polyvinyl alcohol and a mordant is applied to a paper support, the coating layer is Since the flexibility is low, the ink absorbability inherent in the paper support due to the swelling and expansion and contraction of the pulp fiber of the paper support is largely impaired, and the absorbability is likely to be lowered. Therefore, in order to obtain the ink absorptivity which is the effect of the present invention, when a water-soluble binder is used in combination, the amount thereof is preferably small, and the mass ratio of inorganic fine particles / water-soluble binder is 25 or more. It is preferably, more preferably 50 or more, still more preferably 70 or more.

From the viewpoint of remarkably exerting the effect of the present invention, the average particle size of the inorganic fine particles is preferably 200 nm or less. Further, the inorganic fine particles may be used in a state of being uniformly dispersed in the binder as the primary particles, or may be used in a state of forming secondary aggregated particles and being dispersed in the binder. The latter is more preferred.

When the primary particles of the inorganic fine particles are used in the state of forming the secondary agglomerated particles, the average particle diameter of the primary particles should be 30 nm or less from the viewpoint of image density and smoothness. To more preferred.

The lower limit of the average particle size of the primary particles is not particularly limited, but is usually 3 nm or more, particularly preferably 6 nm or more from the viewpoint of particle production.

In the present invention, the average particle size of the inorganic fine particles is obtained by observing the particles themselves, the cross section and the surface of the void layer with an electron microscope, and obtaining the particle size of 100 arbitrary particles, and obtaining the simple average value (number of particles). Average). Here, each grain size is represented by its diameter assuming a circle equal to the projected area.

Examples of the inorganic fine particles and the water-soluble binder which can be added to the layer containing the emulsion resin according to the present invention include the same inorganic fine particles and water-soluble binder as those described later in the ink absorbing layer. .

Next, the average particle size of the inorganic fine particles used in the ink absorbing layer according to the present invention, which will be described with reference to the ink absorbing layer according to the present invention, is preferably 3 to 200 nm. When inorganic fine particles having an average particle size of more than 200 nm are used, the glossiness of the recording paper is reduced, the circularity of the dots during inkjet recording is reduced, and unnecessary dot spread occurs, or It is difficult to obtain a clear image, because the maximum density is reduced due to diffused reflection in the image. From the viewpoint of remarkably exerting the effect of the present invention, the average particle diameter is more preferably 100 nm or less.
In addition, the inorganic fine particles may be used in a state of being uniformly dispersed in the binder as the primary particles, or may be added in a state of forming secondary aggregated particles and being dispersed in the binder. However, the latter is more preferable.

When the primary particles of the inorganic fine particles are used in a state of forming secondary aggregated particles, it is more preferable from the viewpoint of glossiness that the average particle diameter of the primary particles is 30 nm or less. The lower limit of the average particle diameter of the primary particles is not particularly limited, but from the viewpoint of manufacturing the inorganic fine particles, it is generally 3 or less.
nm or more, particularly 6 nm or more is preferable.

Examples of the inorganic fine particles include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide,
Zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina,
White inorganic pigments such as alumina (including pseudo-boehmite), aluminum hydroxide, lithopone, zeolite, magnesium hydroxide and the like can be mentioned.

The shape of the above-mentioned inorganic fine particles is not particularly limited in the present invention, and may be spherical, rod-shaped, needle-shaped, flat-shaped or beaded.

As the inorganic fine particles, it is possible to use both inorganic fine particles whose surface is anionic and has no fixing property to the dye, and inorganic fine particles which have fixing property to the dye and whose surface is cationic. When using inorganic fine particles whose surface is anionic, a cationic polymer is usually used together, but when a cationic polymer is added to the inorganic fine particles whose surface is anionic, the cationic polymer remains on the surface of the inorganic fine particles. It is presumed that the dye is immobilized and fixed to the immobilized cationic polymer to immobilize the dye.

As the inorganic fine particles having a cationic surface, a silane coupling agent having a quaternary ammonium salt group as described in JP-A-8-34160 is coupled to the surface of the inorganic fine particles. Inorganic fine particles whose surface charge is converted to cationic are also included.

The inorganic fine particles according to the present invention are preferably those having a low refractive index and a small average particle diameter. For example, among the above-mentioned inorganic fine particles, silica, colloidal silica, calcium silicate, calcium carbonate, pseudoboehmite,
Inorganic fine particles such as aluminum hydroxide or a hydrate thereof are preferable, inorganic fine particles of silica or alumina are more preferable, and since the cost is low and the fine particles have a low refractive index capable of obtaining a high reflection density, the surface is Silica or colloidal silica synthesized by a gas phase method is particularly preferable as the anionic inorganic fine particles, and pseudoboehmite is particularly preferable as the inorganic fine particles having a cationic surface.

The method for producing silica fine particles is roughly classified into a dry method (gas phase method) and a wet method. As a dry method, a method by gas phase hydrolysis of silicon halide at high temperature (flame hydrolysis method), and There is known a method (arc method) in which silica sand and coke are heated and reduced by an arc in an electric furnace to be vaporized and air-oxidized. As a wet method, there is known a method in which activated silica is generated by acid decomposition of silicate and then excessively polymerized to cause aggregation / precipitation.

In the present invention, among the silica fine particles, silica synthesized by the gas phase method is the most preferable. The fine particle silica synthesized by the gas phase method is usually a silica powder having an average primary particle diameter of 5 to 500 nm obtained by burning silicon tetrachloride with hydrogen and oxygen at a high temperature. Those having an average primary particle diameter of 30 nm are preferable in terms of glossiness.

The colloidal silica preferably used in the present invention is obtained by heating and aging a silica sol obtained by metathesis with an acid such as sodium silicate or passing through an ion exchange resin layer. This colloidal silica is used for ink jet recording paper. For example, Japanese Unexamined Patent Publication No.
No. 7-14091, No. 60-219083,
60-219084, 61-20792, 61-188183, 63-17807.
JP-A-4-93284, JP-A-5-2783.
No. 24, No. 6-92011, No. 6-1831.
No. 34, No. 6-297830, No. 7-812.
No. 14, gazette 7-101142, gazette 7-179.
No. 029, No. 7-137431, and International Patent Publication No. WO94 / 26530.

The preferred average particle size of colloidal silica is usually 5 to 100 nm, but an average particle size of 7 to 30 nm is particularly preferred.

The silica and colloidal silica synthesized by the gas phase method may have their surfaces cation-modified, or may be those treated with Al, Ca, Mg and Ba. .

Next, the water-soluble resin will be described. The recording paper of the present invention has an ink absorbing layer having a void structure, but when inorganic fine particles are included to form voids, it is a stable film that contains a water-soluble binder in the ink absorbing layer. Are required to form the.

Examples of the water-soluble binder for the ink absorbing layer include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color genin (λ, ι, etc.), agar, pullulan. , Water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. Two or more of these water-soluble binders can be used in combination. Among them, polyvinyl alcohol is preferable as the water-soluble binder in the present invention.

The polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, polyvinyl alcohol having a cation-modified terminal and anion-modified polyvinyl alcohol having an anionic group. The modified polyvinyl alcohol of is also included. The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly has an average degree of polymerization of 1,
Those of 500 to 5,000 are preferably used. The saponification degree is preferably 70 to 100%, and 85 to 99.
5% is particularly preferable.

As the cation-modified polyvinyl alcohol, for example, as described in JP-A-61-10483, primary to tertiary amino groups and quaternary ammonium groups are added to the main chain or side chain of polyvinyl alcohol. Examples thereof include polyvinyl alcohol, which can be obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate. The ethylenically unsaturated monomer having a cationic group,
For example, trimethyl- (2-acrylamide-2,2-
Dimethylethyl) ammonium chloride, trimethyl- (3-acrylamido-3,3-dimethylpropyl)
Ammonium chloride, N-vinyl imidazole, N
-Vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyltrimethylammonium chloride, N, N, N-
Trimethyl- (3-methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-dimethylaminopropyl) acrylamide and the like can be mentioned.
The ratio of the cation-modified group-containing monomer in the cation-modified polyvinyl alcohol is 0.1 to vinyl acetate.
It is 10 mol%, preferably 0.2 to 5 mol%.

Examples of the anion-modified polyvinyl alcohol include polyvinyl alcohol having an anionic group as described in JP-A-1-206088, JP-A-61-237681 and JP-A-63-3.
A copolymer of a vinyl alcohol and a vinyl compound having a water-soluble group as described in JP-A-07979 and a modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265. To be

As the nonion-modified polyvinyl alcohol, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, JP-A-8-25795. Examples thereof include block copolymers of a vinyl compound having a hydrophobic group and vinyl alcohol, which are described in Japanese Patent Laid-Open Publication No. 2003-242242.

Polyvinyl alcohol may be used in combination of two or more kinds having different degrees of polymerization and kinds of modification.

The ratio of the inorganic fine particles to the water-soluble binder in the ink absorbing layer according to the present invention is preferably 3 times or more in terms of mass ratio from the viewpoint that high porosity and high film strength can be obtained. If it is 3 times or more, a high porosity can be achieved in which a sufficient ink absorption capacity (void volume) can be obtained, and a sufficient film strength after inkjet recording can be obtained. From this point, more preferably, the mass ratio of the inorganic fine particles to the water-soluble binder is 6 or more.

The void volume as referred to in the present invention is a value obtained by subtracting the total volume of solid contents such as binder and various fillers in the void layer from the dry film thickness of the void layer. For example, the gap layer having inorganic particles (specific gravity 2.0) 6g / m ² and a water-soluble binder (specific gravity 1.0) 1g / m ^2, cationic polymer mordant (specific gravity 1.0) 1g / m ² on a dry Film thickness 10
When it is μm, the void volume is 5 ml /
It is calculated as m ² .

10- (6 / 2.0)-(1 / 1.0)-
(1 / 1.0) = 5 On the other hand, since the rigidity of the coating is too high during the shrinking of the coating during the drying after the coating of the void layer, the coating is locally formed due to the slight waviness and unevenness of the support surface. Fine cracks may occur, and the upper limit of the ratio of the inorganic fine particles to the water-soluble binder in the inkjet recording paper of the present invention is usually 20 or less, but preferably 8 or less.

Next, the mordant used in the recording paper of the present invention will be described. When fine particles having an anionic surface are used in the ink absorbing layer or the layer containing an emulsion resin of the recording paper of the present invention, from the viewpoint of obtaining the effect of the present invention, first-class dyes having fixability to dyes are used. It is preferable to include a mordant such as a cationic polymer having a tertiary amino group or a quaternary ammonium base.

As the cationic polymer, known polymers can be used. Examples thereof include polyethyleneimine, polyallylamine, dicyandiamide polyalkylenepolyamine, condensates of dialkylamine and epichlorohydrin, polyvinylamine, polyvinylpyridine, polyvinylimidazole. Examples thereof include condensates of diallyldimethylammonium salts and quaternary compounds of polyacrylic acid esters. Particularly, JP-A-10-193776,
Those described in JP-A-10-217601 and JP-A-11-20300 are preferable.

As the cationic polymer, there is little discoloration or deterioration of light resistance during long-term storage (also referred to as aging),
A cationic polymer having a quaternary ammonium salt group is preferable because the dye has a sufficiently high mordant ability. In particular, a homopolymer of a monomer having a quaternary ammonium salt group or a copolymer with another copolymerizable monomer or monomers is preferable.

In the ink jet recording paper of the invention according to claim 3, it is preferable to use at least two kinds of cationic polymers having a quaternary ammonium salt group as mordants. The two types of cationic polymers referred to here are
The composition of the polymer is a polymer in which the composition of the repeating units is different from each other, and does not include a polymer having a different degree of polymerization. In addition, two kinds of cationic polymers having the same repeating unit composition but different polymer-forming molar ratios are also included in the preferred embodiment defined in the present invention, but have a quaternary ammonium salt group. It is preferable to use two or more kinds of cationic polymers in which the repeating units themselves have different structures.

As an example of the cationic polymer having a quaternary ammonium salt group used in the present invention, there is disclosed in Japanese Unexamined Patent Publication (Kokai) No. Sho 5
7-64591, a cationic polymer having a guanidyl group, dimethyldiallylammonium chloride described in JP-A-59-20696, JP-A-59-3
Polyamine sulfones described in 3176, JP-A-63
No. 115780, alkyl (meth) acrylate quaternary ammonium salt or (meth) acrylamidoalkyl quaternary ammonium salt type cationic polymer;
4-9776 and 64-75281, copolymers of dimethylallylammonium chloride and acrylamide, and cationic polymers containing two or more quaternary nitrogen atoms in the repeating unit described in JP-A-3-133686. Polymer, polyvinylpyrrolidone having a quaternary ammonium base described in JP-A-4-288283, JP-A-6-92010 and JP-A-6-234268.
Cationic polymer obtained by reaction of secondary amine with epihalohydrin described in Japanese Patent No. 99-6
Examples thereof include polystyrene-type cationic polymers described in JP-A No. 4248, and cationic polymers composed of repeating units having two or more kinds of cationic groups described in JP-A No. 11-348409.

Specific examples of the repeating unit having a quaternary ammonium salt group are shown below.

[0092]

[Chemical 1]

[0093]

[Chemical 2]

The cationic polymer according to the present invention comprises the fourth
It may be a homopolymer or a condensate of a repeating unit having a quaternary ammonium salt group, or a copolymer with a quaternary ammonium salt group or another copolymerizable repeating unit having no tertiary amino group. It may be.

The copolymerizable repeating unit is derived from a monomer having one or more copolymerizable unsaturated bonds, and specific examples of such a monomer include:
The following examples can be given.

Styrene, vinyl chloride, vinylidene chloride,
(Meth) acrylic acid, (meth) acrylic acid ester (methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, octyl (meth) acrylate, hydroxyethyl (meth) acrylate, (Hydroxylpropyl (meth) acrylate, etc.), (meth) acrylamide, butadiene, ethylene, vinyl acetate, vinyl methyl ether, acrylonitrile, N-vinyl-2-pyrrolidone, maleic acid, divinylbenzene and the like.

When the cationic polymer having a quaternary ammonium salt group is the above-mentioned copolymer, the repeating unit having a quaternary ammonium salt group has a ratio of the cationic polymer of 10 mol% or more, particularly 20 mol% or more. Is preferred.

Specific examples of the cationic polymer which can be used in the present invention, particularly in the invention according to claim 3, include the polymers shown in Table 1 below.

In Table 1, CM represents a repeating unit having a quaternary ammonium salt group, and Q1, Q2,
Q3 each represents a repeating unit having no quaternary ammonium salt group and is represented by the following abbreviations.

ST: Styrene MMA: methyl methacrylate EMA: ethyl methacrylate NPMA: N-propyl methacrylate NBA: N-butyl methacrylate HEMA: hydroxyl ethyl methacrylate AA: Acrylamide VP: N-vinyl-2-pyrrolidone The copolymerization ratio is shown in the parentheses in Table 1 in mol%.

[0101]

[Table 1]

Among the ink jet recording papers according to claim 3, at least one kind of cationic polymer is a cationic polymer represented by the following general formula (1), and at least one kind of cationic polymer is It is preferably a cationic polymer represented by the formula (2).

[0103]

[Chemical 3]

In the general formula (1), R represents a hydrogen atom or an alkyl group, and R ₁ , R ₂ and R ₃ each represent an alkyl group or a benzyl group. J is just a bond or 2
Represents a valent organic group. X ⁻ represents an anion group. A represents a repeating unit having no quaternary ammonium salt group in the molecule. z represents a positive number from 0 to 6. x represents 5 to 100 and y represents 0 to 95 (both are molar ratios).

[0105]

[Chemical 4]

In the general formula (2), Q represents a repeating unit represented by the following general formula (2A), general formula (2B) or general formula (2C), and A has the same meaning as A in the general formula (1). Is. x'represents 5 to 100 and y'represents 0 to 95 (both in molar ratio).

[0107]

[Chemical 5]

In the general formula (2A), R, R ₁ , R ₂ ,
R ₃ and X ⁻ have the same meaning as R, R ₁ , R ₂ , R ₃ and X ^{− in the} general formula (1). J ₁ represents a simple bond or a divalent organic group. B is —O— or —NR ₅ — (R ₅ represents a hydrogen atom, an alkyl group, an allyl group or a benzyl group).
m represents a positive number of 1 to 6.

[0109]

[Chemical 6]

[0110] In the general formula (2B), R and X ^- is the general formula (1) R and X ^- in the above formula, J ₁ is the general formula (2
It is synonymous with J _{1 in} A). R ₄ represents an alkyl group.

[0111]

[Chemical 7]

[0112] In the general formula (2C), R and X ^- is R and X in the general formula (1) ^- which is synonymous. R ₄ is a general formula (2
It has the same meaning as R _{4 in} B).

In the recording paper of the present invention, it is more preferable that the cationic polymer having a quaternary ammonium salt group is contained in all coating layers from the viewpoint of the effect of the present invention.

In the invention according to claim 3, at least one kind of the above-mentioned two or more kinds of cationic polymers is used in each of the layer containing the emulsion, the inorganic fine particles, the mordant and the ink absorbing layer according to the present invention. Is preferable, and two or more kinds can be used in combination in the ink absorbing layer. The amount of the two cationic polymers used in combination is preferably 20 mol% or more based on the total weight of the cationic polymers. When three kinds are used in combination, each content is preferably 10% or more with respect to the total cationic polymer. When the ink absorbing layer is formed of two or more layers, the selection of the cationic polymer for each ink absorbing layer is made by optimizing the combination with the ink, but generally, it is more preferable than the dye. It is preferable to use a cationic polymer, which tends to have a high dyeing property, in the ink absorbing layer separated from the support because it gives a high density and the color change with time is small.

In the recording paper of the present invention, the amount of the cationic polymer having a quaternary ammonium salt group used is 0.3 to 10 g, preferably 0.5 per 1 m ² of the recording paper.
The range is from 5 to 5.

The average molecular weight of the cationic polymer according to the present invention is preferably in the range of 2,000 to 500,000, more preferably 10,000 to 200,000. The average molecular weight referred to here is the number average molecular weight, and refers to a polyethylene glycol equivalent value obtained from gel permeation chromatography.

When the cationic polymer according to the present invention is added to the coating liquid in advance, it may be added not only uniformly to the coating liquid but also in the form of forming composite particles with the inorganic fine particles. As a method of producing composite particles by the inorganic fine particles and the cationic polymer, a method of adsorbing and coating the inorganic fine particles with a cationic polymer,
Examples thereof include a method of aggregating the coated particles to obtain higher-order composite particles, and a method of mixing coarse particles obtained by mixing to form more uniform composite particles by a disperser.

The cationic polymer according to the present invention generally has water-soluble groups and therefore exhibits water-solubility, but it may not be dissolved in water depending on the composition of the copolymerization component. From the viewpoint of ease of production, it is preferably water-soluble,
Even if it is poorly soluble in water, it can be dissolved in a water-miscible organic solvent and used. The water-miscible organic solvent referred to herein is, for example, alcohols such as methanol, ethanol, isopropanol, n-propanol, glycols such as ethylene glycol, diethylene glycol, glycerin, ethyl acetate, esters such as propyl acetate, acetone, acetone, Ketones such as methyl ethyl ketone, N,
It refers to an organic solvent such as amides such as N-dimethylformamide, which can be dissolved in water in an amount of about 10% or more. In this case, the amount of the organic solvent used is preferably less than the amount of water used.

In the invention according to claim 9, it is preferable to contain a water-soluble polyvalent metal salt. Density fluctuation after printing and recording,
In order to improve light resistance and bleeding resistance, it is preferable to add a water-soluble polyvalent metal salt. Examples of the water-soluble polyvalent metal salt according to the present invention include metal salts such as aluminum, calcium, magnesium, zinc, iron, strontium, barium, nickel, copper, scandium, gallium, indium, titanium, zirconium, tin, and lead. , Sulfate,
It is added as a salt such as nitrate, formate, succinate, malonate, chloroacetate, p-toluenesulfonate. A water-soluble inorganic polymer such as polyaluminum chloride may be used as the water-soluble polyvalent metal salt. The water solubility is preferably at least 0.1% by mass, more preferably 1% by mass. Of these, water-soluble salts composed of aluminum, calcium, aluminum, magnesium and zinc are preferable because their metal ions are colorless.

In the ink jet recording paper of the present invention, the content of the water-soluble polyvalent metal salt of the present invention is 5 to 30.
0 mg (converted to the mass of metal ion) / m ² is preferable, and 10 to 150 mg / m ² is more preferable.

As the method for adding the water-soluble polyvalent metal salt, in addition to the method of directly adding to the coating solution and coating, an aqueous solution of a cationic resin or a water-soluble polyvalent metal salt is overcoated after coating and drying the recording medium. Then, it may be dried.

In the tenth aspect of the invention, it is preferable that the emulsion-containing layer contains a water-soluble plasticizer. As the water-soluble plasticizer according to the present invention, for example, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, glycerin, diglycerin, butanediol, butanetriol, triethanolamine, ethanolacetamide, Urea and its derivatives, sorbitol, monosaccharides such as mannitol can be mentioned,
The curl resistance can be improved when the support is a porous support, particularly a paper support.

When a water-soluble plasticizer is added, from the viewpoint of the effect of the present invention, particularly from the viewpoint of crack resistance and curl resistance, it is added to a layer containing inorganic fine particles, an emulsion and a mordant adjacent to the support, It is preferably coated, and is preferably 5 to 50% by mass with respect to the inorganic fine particles of the layer,
35 mass% is more preferable.

The coating amount of the coating layer according to the present invention is generally determined by the porosity of the coating film and the required void amount, but in the ink jet recording paper of the present invention, the solid coating amount during drying is 7 to 7. It is preferably 30 g / m ² . When the coating amount of the solid content of the ink absorbing layer during drying is in the range of 7 to 30 g / m ² , it is preferable in terms of cockling, glossiness and maximum density,
In addition, it is easy to suppress the occurrence of cracks in the film that may occur during the process of shrinking the film during the drying after the application of the void layer. Further, since the drying load is small and the productivity is good, there is an advantage that the manufacturing cost can be suppressed.

Although a hardener can be used in the ink absorbing layer or the layer containing an emulsion resin according to the present invention, boric acid and its salt are preferable as the hardener which can be used in the present invention. Other known compounds can be used, and generally, a compound having a group capable of reacting with the water-soluble binder or a compound that promotes reaction between different groups of the water-soluble binder. It is appropriately selected and used according to. Examples of the hardener include epoxy hardeners (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether,
1,6-diglycidylcyclohexane, N, N-diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde hardener (formaldehyde, glyoxal, etc.), active halogen hardener (2,
4-dichloro-4-hydroxy-1,3,5, -s-triazine etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether etc.), aluminum Examples include alum.

The boric acid or a salt thereof means an oxyacid having a boron atom as a central atom and a salt thereof, and specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid,
Pentaboric acid and octaboric acid and their salts are mentioned. Boric acid having a boron atom and a salt thereof as a hardener may be used as an aqueous solution alone or as a mixture of two or more kinds. Particularly preferred is a mixed aqueous solution of boric acid and borax.

Each of the aqueous solutions of boric acid and borax can be added only in a relatively dilute aqueous solution, but by mixing them, a concentrated aqueous solution can be obtained and the coating solution can be concentrated. it can. Further, there is an advantage that the pH of the added aqueous solution can be controlled relatively freely.

The amount of the hardener added is preferably 1 to 200 mg, and more preferably 2 to 100 mg, per 1 g of the water-soluble binder.

If desired, various additives may be incorporated in any layer on the ink absorbing layer side of the ink jet recording paper of the present invention. For example, JP-A-57-741
No. 93, No. 57-87988, and No. 62-2.
UV absorbers described in JP-A-61476, JP-A-57-
74192, 57-87989, and 60-7.
No. 2,785, No. 61-146591, No. 1-95091, No. 3-13376, etc., anti-fading agents, various surfactants of anions, cations or nonions. No. 422993, No. 59-52689, No. 62-28006.
No. 9, JP-A No. 61-242871, and Japanese Patent Laid-Open No. Hei.
Fluorescent whitening agents described in JP-A-219266,
PH adjusting agents such as sulfuric acid, phosphoric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents,
Various known additives such as a lubricant such as diethylene glycol, a preservative, a thickener, an antistatic agent, a matting agent and the like can be contained.

The porous ink absorbing layer may be composed of two or more layers. In this case, the structures of these ink absorbing layers may be the same as or different from each other.

The recording paper of the present invention comprises at least one layer containing the emulsion and the inorganic fine particles and at least one layer containing the inorganic fine particles having an average particle diameter of 3 to 200 nm, a mordant and a water-soluble resin, which are coated on the layer. Is a recording sheet having
The coating layer may have two or more layers, and in this case, the ratio of the inorganic fine particles to the water-soluble binder in the two or more ink absorbing layers may be different from each other.

On the side having the ink absorbing layer of the recording paper of the present invention and the side opposite to the support, various backing layers are used to prevent curling and to further improve sticking and ink transfer when superposed immediately after printing. Layers may be provided.

The recording paper of the present invention having the above constitution is
For example, it can be obtained by the following method.

First, the above-mentioned material for forming a coating layer is added to a suitable solvent such as water, alcohol or various organic solvents to prepare a coating solution, which is coated on the support.
It is dried to form a coating layer. As a finished recording material,
In order to obtain more preferable ink absorbency, a layer containing emulsion and inorganic fine particles, an ink absorbing layer containing inorganic fine particles having an average particle diameter of 3 to 200 nm, a mordant and a water-soluble resin are simultaneously formed on the support according to the present invention. Most preferably, it is applied in multiple layers. In particular, a coating material having high ink absorbability can be obtained by simultaneously applying multiple layers of the coating layer according to the present invention onto the porous base material to make full use of the ink absorbency of the porous base material. . As a result, since the coating layer can be made thin, the manufacturing cost can be suppressed, and there is an advantage that a high quality and inexpensive recording material can be provided.

The method for coating the coating layer on the support can be appropriately selected from known methods. As a coating method, for example, a roll coating method, a rod bar coating method, an air knife coating method, a blade coater method, a spray coating method, a curtain coating method or an extrusion using a hopper described in US Pat. No. 2,681,294. The coating method is preferably used.

Drying after coating the coating layer is preferably carried out by cooling once to increase the viscosity of the coating liquid or by gelling and then blowing warm air to dry. The coating liquid temperature of the coating layer is usually 25 to 60 ° C, preferably 30 to 50 ° C. Cooling is preferably performed so that the temperature of the film surface after coating is 20 ° C. or lower, further 5 to 15 ° C., and the subsequent drying is performed by blowing air of 20 to 60 ° C. to obtain a uniform film surface. From the viewpoint of obtaining

The wet film thickness for applying the coating layer varies depending on the intended dry film thickness, but is generally 50 to 300 μm, preferably 70 to 250 μm, and the coating speed largely depends on the drying ability, but is usually 20 to 200 m. / Min. The drying time is generally 2 to 10 minutes.

Next, the water-based ink preferably used in the ink jet recording paper of the present invention will be described.

The aqueous ink is a recording liquid which usually contains a water-soluble dye, a liquid medium, and other additives. As the water-soluble dye, a direct dye, an acid dye, a basic dye, a reactive dye or a water-soluble dye known as a dye for food, which is known in inkjet, can be used, but the direct dye or the acid dye is preferable.

The solvent of the water-based ink is mainly composed of water, but usually has a boiling point of about 120 ° C. or more in order to prevent the dye from precipitating when the ink liquid dries and clogging at the nozzle tip or the ink supply path. At room temperature a high boiling organic solvent is used. The high-boiling organic solvent is required to have a vapor pressure much lower than that of water in order to prevent the formation of coarse precipitates by the precipitation of solid components such as dyes when water is evaporated. Must be highly miscible with.

For such purpose, a high boiling point organic solvent is usually used, and specific examples include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerin, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol. Ethylene glycol monobutyl ether, glycerin monomethyl ether, 1,2,
3-butanetriol, 1,2,4-butanetriol, 1,2,4-pentanetriol, 1,2,6-hexanetriol, thiodiglycol, triethanolamine, polyethylene glycol (average molecular weight of about 30
Alcohols such as 0 or less). In addition to the above, dimethylformamide, N-methylpyrrolidone and the like can also be used. Among these many high boiling point organic solvents, polyhydric alcohols such as diethylene glycol, triethanolamine, glycerin and triethanolamine, and lower alkyl ethers of polyhydric alcohol such as triethylene glycol monobutyl ether are preferable.

Other additives contained in the water-based ink include, for example, pH adjusting agents, sequestering agents, fungicides, viscosity adjusting agents, surface tension adjusting agents, wetting agents, surfactants and rust preventives. Is mentioned.

The aqueous ink liquid is used at 25 ° C. for 25 to 50 m for the purpose of improving the wettability with respect to the recording paper and stabilizing the ejection from the ink jet nozzle.
It preferably has a surface tension in the range of N / m, preferably 28-40 mN / m.

The viscosity of the water-based ink is usually 2 to 40 mPa · s at 25 ° C., preferably 2.5 to 30 mP.
a · s. The pH of the aqueous ink is usually in the range of 4-10.

When the minimum ink droplet ejected from the ink nozzle has a capacity of 1 to 30 pl, 20 on the recording paper.
It is preferable because a minimum dot diameter of -60 μm can be obtained. A color print printed with such a dot diameter gives a high quality image. It is preferable that a droplet having a volume of 2 to 20 × 10 pl is ejected as the minimum droplet.

Further, in a system in which two types of inks, each of which has a density which is at least twice as high as that of magenta and cyan, are used as the water-based ink, since the ink of low density is used in the highlight portion, the dots are identified. However, the present invention can be applied even when such a recording method is adopted.

As the ink jet recording method preferably used in the present invention, various conventionally known methods can be used, and details thereof are described in, for example, the trend of ink jet recording technology (edited by Koichi Nakamura, March 31, 1995, Japan). Published by Scientific Information Co., Ltd.).

[0148]

EXAMPLES The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

In the examples, "%" means absolutely dry mass% unless otherwise specified. Example 1 <Preparation of Porous Substrate> 70 parts by mass of hardwood kraft pulp (LBKP) beaten to a Canadian standard freeness of 330 ml, and hardwood bleached sulfite pulp (LBSP) 25 beaten to a Canadian standard freeness of 280 ml. Parts by mass and 5 parts by mass of softwood kraft pulp (NBKP) beaten to a Canadian standard freeness of 280 ml were mixed, and the mass average fiber length was 1.
Beaten pulp of 20 mm was obtained. For each 100 parts of beaten pulp, 2.0 parts of cationized starch, 0.4 part of alkyl ketene dimer resin as a sizing agent, 0.1 part of anionic polyacrylamide resin, 0.7 parts of polyamide polyamine epichlorhydrin resin After adding 1 part and adjusting the pH to 7.5 with caustic soda, a porous substrate 1 made of a paper support having a basis weight of 190 g and a thickness of 180 μm was prepared with a Fourdrinier paper machine. The Cobb's water absorption at a contact time of 60 seconds using water was 25 g, and the Beck's smoothness was 180 seconds.

<< Preparation of Additives >> (Preparation of Emulsion) Using sodium dodecylbenzenesulfonate as an emulsifier, the method described in JP-A-4-147886.
An emulsion (5) of an alkyl acrylate copolymer resin was synthesized according to the emulsion polymerization method described in JP-A No. The emulsion (5) was neutralized to pH 7.0 after the completion of the emulsion polymerization reaction. Next, this emulsion (5) was diluted with water by a factor of 2 and measured with a laser diffraction particle size analyzer (LA-700, manufactured by Horiba Ltd.). The average particle size was 0.7.
was μm. Also, this emulsion (5) was dried at 60 ° C. in a vacuum dryer and then Tg was measured with a differential scanning calorimeter.
It was -30 degreeC as a result of measuring.

Emulsions (1) to (4) shown in Table 2 were synthesized in the same manner. In addition, PVA described in Table 2
Is an abbreviation for polyvinyl alcohol.

[0152]

[Table 2]

(Preparation of Silica Dispersion-1) 125 kg of vapor phase method silica (manufactured by Tokuyama: Reorosil QS-20) having an average primary particle size of about 0.014 μm is jet stream manufactured by Mitamura Riken Kogyo Co., Ltd.・ Inductor mixer TDS was used to suction and disperse at room temperature in 620 L of pure water whose pH was adjusted to 3.0 with nitric acid.
x NFW liquid (manufactured by Ciba Specialty Chemicals Co., Ltd.) (1.5 L) was added with stirring and dispersion, and then the total amount was adjusted to 694 L with pure water. When this dispersion was diluted and electron micrographs of the particles were taken, it was confirmed that most of the particles had a size of 0.02 μm or less and the primary particles were dispersed.

(Preparation of Silica Dispersion Liquid-2) 1.63 Kg of cationic polymer (CP-12), ethanol 2.
2 L, an aqueous solution containing 1.5 L of n-propanol (p
H = 3.0) 18L, silica dispersion-1 69.4L
Was added with stirring, and then 1 g of antifoaming agent SN381 (manufactured by San Nopco Ltd.) was added. This mixed solution
It was dispersed by a high pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the total amount was adjusted to 97 L with pure water to prepare a silica dispersion liquid-2. As a result of diluting this silica dispersion liquid-2 and coating it on a transparent support and observing with an electron microscope, the average particle diameter was about 50.
The size was nm (secondary particles).

<< Preparation of Coating Liquid >> (Preparation of Coating Liquid-1) While stirring 650 ml of the above-prepared silica dispersion liquid-2 at 40 ° C., the following additives were sequentially mixed to prepare coating liquid-1. did.

1: 10% aqueous solution of polyvinyl alcohol (Kuraray industry: PVA203) 6 ml 2: 5% aqueous solution of polyvinyl alcohol (Kuraray industry: PVA235) 260 ml 3: Polyvinyl alcohol (Kuraray industry: 5% aqueous solution of PVA245) 95 ml 4: Surfactant (S-1) 30% solution 4 ml 5: Anionic fluorescent whitening agent (UVITEX NFW LIQUID9 manufactured by Ciba Specialty Chemicals) 10 ml 10 ml Pure water for a total volume of 1050 ml Finished. The pH of the coating solution was about 4.5.

[0157]

[Chemical 8]

(Preparation of coating liquid-2) While stirring 650 ml of the silica dispersion liquid-2 prepared above at 40 ° C., the following emulsions were mixed to prepare coating liquid-2.

1: Polyvinyl alcohol (Kuraray Industries Co., Ltd .: PVA203) 10% aqueous solution 6 ml 2: Emulsion (1) (active ingredient 20%) 150 ml Pure water was added to a total volume of 1000 ml. The pH of the coating solution was about 4.5.

<< Preparation of Recording Paper >> (Preparation of Recording Paper 101) On the porous substrate 1, the coating liquid-2 as a lower layer has a wet film thickness of 40 μm, and the coating liquid-1 as an upper layer has a wet film thickness. Apply in this order to 90 μm and once cool to about 7 ° C, then 20-65 ° C
The air was blown to dry the recording paper 101.
The dry thickness of the void layer of the recording paper 1 thus produced was 33 μm, and the solid content coating amount during drying was 20.5 g / m ² .

(Preparation of Recording Papers 102 to 107) Kind of Emulsion and Cationic Polymer (Silica Dispersion Liquid-2) in Lower Coating Liquid-2 and Cationic Polymer in Upper Liquid-1 ( Recording papers 102 to 107 were prepared in the same manner as the recording paper 101, except that the silica dispersion-2) was changed to the combination shown in Table 3 below.

(Preparation of Recording Sheet 108) Recording Sheet 1
In the preparation of No. 07, as a lower layer coating liquid, a 5% polyvinyl alcohol aqueous solution (polymerization degree: 1) was added to the emulsion (5).
Recording paper 108 was prepared in the same manner except that 22 g of 700 and a saponification degree of 88.5 mol%) were additionally added and the coating liquid was adjusted to have the same finished volume.

(Production of Recording Paper 109) Porous Base Material 1
Then, the above-mentioned coating liquid-1 was applied so as to have a wet film thickness of 130 μm, cooled once to about 7 ° C., and then blown with air at 20 to 65 ° C. to dry the recording paper 109.

<< Characteristic Evaluation of Each Recording Paper >> (Evaluation of Smoothness) The unprinted sheet surface of each recording paper is JI
According to the method specified in S B 0601, the center line surface roughness (each has a reference length of 2.5 mm, a cutoff value of 0.
(Measured at 8 mm) was determined and smoothness was determined according to the following criteria. The acceptable levels in terms of quality are A and B.

A: The center line surface roughness Ra is 1.0 μm or less and does not impair the aesthetic appearance B: The center line surface roughness Ra is 1.0 to 1.5 μm,
It does not spoil the appearance C: Center line surface roughness Ra is larger than 1.5 μm, and there is a practical problem that spoils the appearance D: Many cracks occur on the entire surface of the coating film by visual evaluation, and practical use cannot be endured ( Evaluation of ink absorbency) Solid green printing is performed on each recording paper by using an ink jet printer PM900C manufactured by Seiko Epson Corporation, and the printed portion immediately after printing is rubbed with a finger to visually evaluate the disturbance of the image. The ink absorbency was evaluated according to the above. The acceptable level for quality is ◎
And ○.

⊚: The image is not disturbed at all even when the printed image surface is rubbed with a finger. ◯: The image is slightly disturbed when the printed image surface is rubbed with a finger. Δ: The image is slightly imaged when the printed image surface is rubbed with a finger. Rubbed and smudged, outside the practical range ×: When the surface of the printed image is rubbed with a finger, the image rubs and smears out of the allowable range for practical use XX: The ink overflow in the printed image is severe, and the image is smeared when printed with a printer. Is out of the permissible range for practical use (evaluation of cockling) Cockling is printed on each recording paper by an inkjet printer manufactured by Seiko Epson.
Solid green printing was performed using PM900C, the sheet surface after printing was visually observed, and evaluation was performed according to the following criteria.
The acceptable levels in terms of quality are ◯ and Δ.

◯: Cockling is unknown and aesthetics are not adversely affected Δ: Cockling is small and does not impair aesthetics ×: Cockling is large and aesthetics is impaired (maximum density) On each recording sheet, Seiko Epson Using inkjet printer PM900C manufactured by
Performs solid printing of yellow, magenta, cyan, and black,
Three hours after printing, the reflection densities of the optical densitometer (X
-Rite X-Rite 938).

(Color fluctuation after printing) On each recording sheet, an ink jet printer P manufactured by Seiko Epson Co., Ltd.
Using M900C, solid brown printing is performed, and after 3 hours of printing and 24 hours of printing, Minolta colorimeter CM-2022
(Standard light C, 2 ° field of view)
E ^* was calculated, and the color variation after printing was evaluated according to the following criteria.

⊚: ΔE ^* is less than 2.0 and there is almost no color shift over time. ○: ΔE ^* is from 2.0 to less than 5.0, color shift is small, and practicable quality Δ: ΔE ^* is 5.0 to less than 10.0, color misalignment is not very noticeable, and is in a practically acceptable range. ×: ΔE ^* is 10.0 or more, color misregistration is large, and practically acceptable. Table 3 shows the respective evaluation results obtained by the above out-of-range.

[0170]

[Table 3]

As is clear from Table 3, the recording paper 109 provided with a coating layer using only polyvinyl alcohol as a binder on all layers not only has insufficient ink absorbency, but also exhibits color variation after printing. The result is large and the image quality is not favorable. Next, it is understood that the recording paper 107 using the emulsion (5) of the comparative example in the lower layer has cracks in the coating layer, has poor smoothness, and causes cockling, which is not preferable. Further, the recording paper 108 of the comparative example produced by additionally adding polyvinyl alcohol to the lower layer containing the emulsion (5) also has cracks, deteriorates ink absorbability, and has a color change after printing.
The result is undesired. From this, it was confirmed that the effect of the present invention could not be obtained only by using the emulsion in which the activator was a dispersant and polyvinyl alcohol in combination.

On the other hand, the recording paper of the present invention 10
Nos. 1 to 106 have excellent ink absorbency, smoothness,
It was found that the maximum density and the color variation after printing were also good. Comparing the recording papers 101, 102 and 104 of the present invention, it can be seen that the emulsion according to the present invention preferably has a small particle size and a high degree of polymerization of polyvinyl alcohol as a dispersant. Further, it was found that the recording paper 105 has a high image density and a sharp image is obtained, which is particularly preferable.

Example 2 << Preparation of recording sheet >> (Preparation of recording sheet 201) Recording sheet 1 described in Example 1
In the preparation of No. 05, except that the vapor phase method silica (manufactured by Tokuyama: Reorosil QS-20) used was changed to wet method silica (manufactured by Tokuyama: Fineseal X-37, average particle diameter of primary particles was 2.7 μm). Similarly, recording paper 2
01 was produced.

(Preparation of Recording Paper 202) A recording paper 202 was prepared in the same manner as in the preparation of the recording paper 105 described in Example 1 except that the cationic polymers in the upper and lower layers were changed as shown in Table 5. It was made.

(Preparation of Recording Sheet 203) Recording Sheet 2
In the preparation of No. 02, the lower layer emulsion was changed to SM8702C (manufactured by Toray Dow Corning Co., Ltd.), which is a preferred silicone emulsion of the present invention, as shown in Table 5, except that the active ingredients were changed to be the same. A recording paper 203 was produced.

(Preparation of Recording Papers 204 to 206) An overcoat solution (a) containing the water-soluble polyvalent metal ions shown in Table 4 was formed on the upper layer forming surface of the recording paper 105 prepared above.
The solid content of (b) and (c) is 0.6 g /
After overcoating to m ² and drying, further apply nitric acid aqueous solution or sodium hydroxide aqueous solution uniformly on the coated surface to adjust the film surface pH to 4.5 ± 0.2. The recording sheets 204 to 206 were prepared.

[0177]

[Table 4]

<< Characteristic Evaluation of Each Recording Paper >> The recording paper 105 prepared in Example 1 was added to the recording papers 201 to 206 prepared as described above, and the ink absorbency was measured according to the method described in Example 1. The maximum density and the color variation after printing were evaluated, and the obtained results are shown in Table 5.

[0179]

[Table 5]

As is clear from Table 5, the recording paper 201 in which the average particle diameter of the inorganic fine particles in the upper ink absorbing layer is 200 nm or more is deteriorated in ink absorbency, the maximum density is lowered, and the color fluctuation after printing is changed. Also increases, which is not preferable. Next, with respect to the recording paper 105, recording papers 202 and 20 having different cationic polymers and different emulsions are used.
Also in No. 3, good results were obtained, and it is understood that this is a preferable configuration. Further, the recording sheet 105 and the recording sheet 20
Comparing Nos. 4 to 206, it can be seen that preferable results can be obtained from the viewpoints of ink absorbency, maximum density, and color variation after printing regardless of which of the overcoat liquids A to C is used.

Example 3 << Preparation of recording sheet >> (Preparation of recording sheet 301) Recording sheet 1 described in Example 1
In the preparation of No. 05, a recording paper 301 was prepared in the same manner except that 100 ml of an 80% aqueous solution of glycerin as a water-soluble plasticizer was added to the coating liquid-2 so that the final volumes were the same.

(Production of Recording Paper 302) In the production of the recording paper 204 described in Example 2, 100 ml of 80% aqueous solution of glycerin as a water-soluble plasticizer was added to the coating liquid-2 so that the finished volume would be the same. A recording sheet 302 was prepared in the same manner except that the above was prepared. Example-1
Evaluate in the same manner as above, and evaluate curl resistance,
The results shown in Table-8 were obtained.

<< Characteristic Evaluation of Each Recording Sheet >> In addition to the recording sheets 301 and 302 produced as described above, the recording sheet 105 produced in Example 1 and the recording sheet 20 produced in Example 2
4 was added, and according to the method described in Example 1, ink absorbency, maximum density, color variation after printing, and in addition, curl resistance was evaluated according to the following method, and the obtained results are shown in Table 6.
Shown in.

(Evaluation of Curling Resistance) The unprinted recording paper was conditioned under an environment of 23 ° C. and a relative humidity of 20% and 80% for 1 hour, and then the curl was measured. For curl measurement, place it on a horizontal desk, and in the case of plus curl, print side up,
In the case of a negative curl, the printed surface was faced down, and the average of curl heights at four corners (mm unit) was obtained, and curl resistance was evaluated according to the following criteria.

◯: The curl is ± 5 mm or less, which is a preferable characteristic Δ: The curl is ± 5 to ± 20 mm, but is in the practically acceptable range ×: The curl is larger than ± 20 mm, and is outside the practically acceptable range Is

[0186]

[Table 6]

As is clear from Table 6, the recording papers 301 and 302 in which the emulsion-containing layer according to the present invention is used in combination with the water-soluble plasticizer can not only obtain the effect of the present invention, but also further curl resistance. In particular, it can be seen that the curl resistance at the time of storage under high humidity (80% RH) is improved.

[0188]

According to the present invention, ink absorbency, smoothness,
It was possible to provide an inkjet recording paper having a good image density, excellent color variation resistance and curl resistance after printing, and capable of obtaining a high quality inkjet image.

Claims (10)

[Claims] 1. A layer containing an inorganic fine particle, an emulsion having a group capable of reacting with the inorganic fine particle or a group capable of hydrogen bonding and a mordant on at least one surface of a support, and an inorganic particle having an average particle diameter of 3 to 200 nm. An ink jet recording sheet comprising an ink absorbing layer containing fine particles, a mordant and a water-soluble binder, which are sequentially provided. 2. The ink jet recording paper according to claim 1, wherein the support is a porous base material. 3. The ink jet recording paper according to claim 1, wherein the mordant contains at least two kinds of cationic polymers having a quaternary ammonium salt group. 4. The inkjet recording paper according to claim 1, wherein the inorganic fine particles are silica or alumina. 5. The ink jet recording paper according to claim 1, wherein the emulsion is an emulsion obtained by emulsion polymerization with a polymer dispersant having a hydroxyl group. 6. The ink jet recording paper according to claim 5, wherein the polymer dispersant having a hydroxyl group is a polyvinyl alcohol polymer. 7. The ink jet recording paper according to claim 4, wherein the emulsion is a silicon emulsion having a group capable of reacting with a silanol group contained in silica or a group capable of hydrogen bonding. 8. The emulsion has an average particle size of 0.2.
It is 5-0.05 micrometers, It is characterized by the above-mentioned.
The inkjet recording paper according to any one of 1. 9. The inkjet recording paper according to claim 1, further comprising a water-soluble polyvalent metal salt. 10. The inkjet recording paper according to claim 1, wherein the layer containing the emulsion contains a water-soluble plasticizer.