JP2001310547A - Sheet for ink-jet record - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent sheet of an ink-jet record in whiteness of a color material receptive layer that has high resistance to light by which it does not bleed out of a fluorescent brightening agent, even if it is exposed in solar light, a fluorescent light, and so on. SOLUTION: A thermoplastic resin layer is at least fixed on a surface of one side of a base. and in the top of a thermoplastic resin layer of a substrate. It contains an inorganic pigment of fine particles, water-soluble resin and closslinker, which closs-links water-soluble resin at least in the sheet for the ink-jet record. It has a color material receptive layer and thermoplastic resin layer, and then it is formed by melt extrusion. It is the sheet for the ink-jet record, which has a characteristic that fluorescent brightener and a white pigment are contained in the thermoplastic resin layer. It is desirable to be a compound that fluorescence brightening agent is shown with the following structure-type (1). [R1-R4: hydrogen atom, a substitution base or a substitution atom].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording material suitable for ink-jet recording using a liquid ink such as an aqueous ink or an oil-based ink, or a solid ink which is solid at ordinary temperature and is melted and liquefied for printing. More specifically, the present invention relates to a recording sheet having excellent ink receiving performance and high whiteness.

[0002]

2. Description of the Related Art In recent years, with the rapid development of the information industry, various information processing systems have been developed, and recording methods and apparatuses suitable for the information systems have been developed and put into practical use. Among the above recording methods, the ink jet recording method,
It is widely used not only in offices but also in so-called home use because of its ability to record on various types of recording materials, relatively inexpensive hardware (devices), compactness, and excellent quietness. ing.

Further, with the recent increase in resolution of ink jet printers, it has become possible to obtain so-called photo-like high-quality recorded materials. On the other hand, with the development of hardware (devices), various recording sheets for inkjet recording have been developed. As the characteristics required for the recording sheet for the inkjet recording, generally,
(1) fast drying (high ink absorption speed), (2) proper and uniform ink dot diameter (no bleeding), and (3) high dot roundness ,
(4) high color density; (5) high color developability (saturation) (no dullness); (6) good light fastness and water fastness of the printed portion; (7) recording sheet Ink receiving performance such as high whiteness, (8) good storage stability of the recording sheet (no yellowing during long-term storage),
(9) It is difficult to deform and the dimensional stability is good (curl is sufficiently small). (10) The hard running property is good. Further, in addition to the above-described properties, the glossy, surface smoothness,
A photographic paper-like texture similar to silver halide photography is also required.

[0004] In particular, in order to obtain a clear, high-contrast image free from blemishes, the recording surface (color material receiving layer) for receiving and forming an ink-jet ink must be as white as possible. In order to improve the whiteness, a fluorescent whitening agent has been used in the colorant receiving layer. However, when a fluorescent whitening agent is contained in the colorant receiving layer, the light fastness of the ink image recorded on the layer is reduced, and when exposed to ultraviolet light such as sunlight or a fluorescent lamp for a long time, gradually. In addition, there is a tendency that the density of the ink tends to decrease due to fading of the ink, and there is a problem in terms of image storability.

When a support having a thermoplastic resin layer provided on a substrate is used as a support for forming an image forming layer, the thermoplastic resin layer is formed of a bis (alkyl-substituted typified by Ubitex OB). Although a method of adding a fluorescent whitening agent having a benzoxazolyl) thiophene structure has been proposed, there has been a problem that the whitening of the background is reduced due to bleed-out of the fluorescent whitening agent and the like.

As described above, an ink jet recording sheet having high light resistance even under sunlight or fluorescent light, no bleed-out of a fluorescent whitening agent, and excellent whiteness of a colorant receiving layer is still available. It is currently not provided. In addition, at the same time, the color material receiving layer is strong without cracks and the like, has good ink absorbency and glossiness, can form a high-resolution and high-density image, and has a sufficient water resistance to the formed image. It is necessary to satisfy excellent ink receptive performance such as bleeding resistance with time.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, first, the present invention provides an ink jet recording sheet having high light fastness even under sunlight or fluorescent light, no bleed-out of a fluorescent brightener, and excellent whiteness of a colorant receiving layer. The purpose is to provide. Secondly, according to the present invention, the colorant receiving layer is strong without generation of cracks and the like, has good ink absorption and glossiness, and can form a high-resolution and high-density image, and has been formed. An object of the present invention is to provide an inkjet recording sheet having an image having sufficient water resistance and bleeding resistance with time.

[0008]

Means for solving the above problems are as follows. That is, <1> an inorganic pigment fine particle, a water-soluble resin, and a cross-linking agent for cross-linking the water-soluble resin are provided on the thermoplastic resin layer of a support having a thermoplastic resin layer provided on at least one surface of a substrate. An ink jet recording sheet having at least a color material receiving layer, wherein the thermoplastic resin layer is formed by melt extrusion, and the thermoplastic resin layer contains a fluorescent whitening agent and a white pigment. This is a recording sheet.

<2> The colorant-receiving layer is coated with a colorant-receiving layer coating solution containing inorganic pigment fine particles and a water-soluble resin, and is dried simultaneously with or during the drying of the formed coating layer. Before the coating layer shows a reduced drying rate, after applying a solution containing a crosslinking agent capable of crosslinking the water-soluble resin to the coating layer, the coating layer to which the solution has been applied is cross-linked and cured. An obtained inkjet recording sheet according to <1>.

<3> The fluorescent whitening agent has the following structural formula (I)
The inkjet recording sheet according to <1> or <2>, which is a compound represented by the formula:

[0011]

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[In the structural formula (I), R ¹ , R ² , R ³ , R
⁴ each independently represents a hydrogen atom, or a substituent or a substituted atom. ]

<4> The content of the fluorescent whitening agent in the thermoplastic resin layer is 0.02 to 2.0% based on the thermoplastic resin.
The inkjet recording sheet according to any one of <1> to <3>, wherein the content is 0.10% by weight.

<5> The inkjet recording sheet according to any one of <1> to <4>, wherein the thermoplastic resin is a polyolefin resin. <6> The above-described <1> to <<, wherein the white pigment is titanium oxide.
5> The inkjet recording sheet according to any one of the above.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ink jet recording sheet of the present invention has, as a support, a support provided with a thermoplastic resin layer formed by melt extrusion and containing a fluorescent whitening agent and a white pigment. The coloring material receiving layer does not contain a fluorescent whitening agent. Hereinafter, the inkjet recording sheet of the present invention will be described in detail, and through the description, the details of the method for producing the inkjet recording sheet will be clarified.

The ink jet recording sheet of the present invention comprises:
A support in which a thermoplastic resin layer is provided on at least one surface of a substrate has a coloring material receiving layer on the thermoplastic resin layer, and if necessary, other layers may be provided. Good. [Support] The support constituting the ink jet recording sheet of the present invention is provided with a thermoplastic resin layer provided on at least one surface of a substrate, and the thermoplastic resin layer is formed by melt extrusion, and has an increased fluorescence. It contains at least a whitening agent and a white pigment.

(Thermoplastic resin layer) The thermoplastic resin layer contains at least a thermoplastic resin, a fluorescent whitening agent and a white pigment, and may contain other components as necessary. . -Fluorescent whitening agent-The fluorescent whitening agent can be classified by a basic chemical structure that emits fluorescence, and examples thereof include the following. In the present invention, the fluorescent whitening agent is contained in the thermoplastic resin layer, and the thermoplastic resin layer is formed on the substrate by melt extrusion, so that the fluorescent whitening agent can withstand high temperatures during melt extrusion. Those having heat resistance are preferred.

Specifically, diaminostilbene, imidazole, thiazole, oxazole, triazole, oxadiazole, thiadiazole, coumarin, naphthalimide, pyrazoline, pyrene,
Examples thereof include imidazolones, benzidines, diaminocarbazoles, oxacyanines, methines, pyridines, anthrapyridazines, distyryls, and carbostyryls. Some of the exemplified optical brighteners are shown below, but are not limited thereto.

Imidazole, thiazole, oxazole type:

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[0020]

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[0021]

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Triazole type:

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Coumarin type:

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[0024]

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Naphthalimide type:

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Pyrazolin type:

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Others:

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Among the above-mentioned fluorescent whitening agents, from the viewpoint of excellent heat resistance and little bleed-out of the fluorescent whitening agent from the thermoplastic resin layer, they are represented by the following structural formula (I). Are particularly preferred.

[0029]

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In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, or a substituent or a substituted atom.

Examples of the above substituents include those having 1 carbon atom.
Alkyl groups (methyl group, ethyl group, propyl group, butyl group, octyl group, etc.), alkoxy groups having 1 to 12 carbon atoms (methoxy group, ethoxy group, propoxy group, butoxy group, octyloxy group, etc.), An alkoxycarbonyl group having 2 to 12 carbon atoms (such as a methoxycarbonyl group), an acyloxy group having 2 to 12 carbon atoms (such as an acetyloxy group), an aryl group having 6 to 12 carbon atoms (such as a phenyl group or a tolyl group), 6-12 aryloxy groups (phenoxy group, phenoxyethoxy group, etc.), C7-12 aryloxycarbonyl group, hydroxy group, nitro group, cyano group, amino group, C1-12 mono- or dialkylamino Group (dimethylamino group, diethylamino group, etc.), mono- or diarylamino group having 6 to 12 carbon atoms, acyl having 1 to 12 carbon atoms Such amino group (an acetylamino group).

These may further have a substituent, and examples of the substituent include those exemplified above. Examples of further substituents include a benzyl group and a phenethyl group in which an alkyl group is substituted with an aryl group, and a benzyloxy group and the like in which an alkoxy group is substituted with an aryl group. When a part of the substituted atom is exemplified, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom and the like) can be mentioned.

Specific examples of the optical brightener of the structural formula (I) include the following compounds (structural formulas (II) to (VI))
Compound). These may be used in combination of two or more different types. Among them, the following structural formula (IV) has excellent heat resistance and low bleed-out.
And (V) are preferred.

[0034]

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The content of these fluorescent brighteners in the thermoplastic resin is preferably 0.02 to 0.10% by weight, more preferably 0.04 to 0.08% by weight. If the content is less than 0.02% by weight, the effect of improving the whiteness of the background may be reduced. If the content is more than 0.10% by weight, bleed out of the fluorescent whitening agent occurs, and May decrease in whiteness.

The process for producing a fluorescent whitening agent according to the present invention comprises:
There is no particular limitation, and it can be produced by a conventionally known method. In the present invention, a commercially available fluorescent whitening agent can also be used.

-White Pigment- Examples of the white pigment include titanium oxide, barium sulfate, barium carbonate, calcium carbonate, lithopone, alumina white, zinc oxide, silica antimony trioxide, titanium phosphate and the like. These can be used alone or in combination of two or more. Of these, titanium oxide is particularly preferred from the viewpoints of whiteness, dispersibility, and stability.

The white pigment has a particle size of 0.1.
1 to 0.5 μm is preferred. The particle size is 0.1 μ
m, the whiteness may be reduced,
If it exceeds μm, the glossiness may decrease. The content of the white pigment in the thermoplastic resin layer, the type of white pigment,
Although it varies depending on the type of the thermoplastic resin, the thickness of the thermoplastic resin layer, etc., it is usually 5 to 20% by weight based on the thermoplastic resin.
It is about.

The titanium oxide may be of rutile type or anatase type, and these may be used alone or in combination. Further, those manufactured by the sulfuric acid method or those manufactured by the chlorine method may be used. Examples of titanium oxide include those coated with an inorganic substance such as hydrated alumina treatment, hydrated silicon dioxide-based treatment, or zinc oxide treatment, trimethylolmethane, trimethylolethane, trimethylolpropane, and 2,4-dihydroxy-2-methyl. A material that has been surface-coated with an organic substance such as pentane or a material that has been treated with a siloxane such as polydimethylsiloxane can be used as appropriate. Further, known additives such as an antioxidant may be added to the thermoplastic resin layer.

-Thermoplastic resin-The thermoplastic resin is not particularly limited, but a polyolefin resin is preferably used. For example, homopolymers of α-olefins such as polyethylene and polypropylene and mixtures of these various polymers, or random copolymers of ethylene and vinyl alcohol are preferred. Examples of polyethylene include LDPE (low-density polyethylene), HDPE (high-density polyethylene), L-LD
PE (linear low-density polyethylene) can be used alone or in combination. In the case of polyethylene, the melt flow rate before processing is a value measured according to JIS 7201 (condition 4 in Table 1) and is 1.2 to 12 g / 1.
A time of 0 minutes is preferred.

(Substrate) As the substrate, any of a transparent substrate made of a transparent material such as plastic and an opaque substrate made of an opaque material such as paper can be used. In order to utilize the transparency of the colorant receiving layer, it is preferable to use a transparent substrate or a high gloss opaque substrate.

Materials usable for the transparent substrate include:
A material having transparency and a property capable of withstanding radiant heat when used in an OHP or a backlight display is preferable. Examples of the material include polyesters such as polyethylene terephthalate (PET); polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide and the like. Among them, polyesters are preferred, and polyethylene terephthalate is particularly preferred. The thickness of the transparent substrate is not particularly limited, but is preferably 50 to 200 μm from the viewpoint of handleability.

As the high-gloss opaque substrate, those having a glossiness of 40% or more on the surface on which the colorant receiving layer is provided are preferable. The glossiness is in accordance with JIS P-8142
(75 degree specular gloss test method of paper and paperboard) It is a value obtained according to the method described in. Specifically, the following substrates are mentioned.

For example, a high-gloss paper substrate such as art paper, coated paper, cast-coated paper, baryta paper used for a silver halide photographic support, etc .; polyethylene terephthalate (P
Polyesters such as ET), cellulose esters such as nitrocellulose, cellulose acetate, cellulose acetate butyrate, and plastic films such as polysulfone, polyphenylene oxide, polyimide, polycarbonate, and polyamide are made opaque by containing a white pigment and the like. A calendering treatment may be applied.) High gloss film;
Examples of the support include a transparent substrate or a high-gloss film containing a white pigment or the like, and a support provided with a polyolefin coating layer containing or not containing a white pigment on the surface thereof. Further, a white pigment-containing foamed polyester film (for example, foamed PET containing polyolefin fine particles and having voids formed by stretching) can also be suitably mentioned. The thickness of these opaque substrates is not particularly limited, but is preferably 50 to 300 μm from the viewpoint of handleability.

In addition to the above, there is a base paper made of a material generally used as an opaque substrate. For example, softwood, natural pulp selected from hardwood as the main raw material, if necessary, clay, talc, titanium oxide, calcium carbonate, filler rosin such as urea resin fine particles, alkyl ketene dimer, higher fatty acid, epoxidized fatty acid amide, What added a sizing agent such as paraffin wax and alkenyl succinic acid, a paper strength enhancer such as polyacrylamide, starch and polyamide polyamine epichlorohydrin, and a fixing agent such as a sulfate band and a cationic polymer are used.
Further, a softening agent such as an epoxidized fatty acid amide and a surfactant may be added. Further, synthetic pulp may be used in place of the above natural pulp, or natural pulp and synthetic pulp may be mixed in an arbitrary ratio.

The type and thickness of the base of the base paper are not particularly limited, but the basis weight is 40 to 200 g.
/ M ² is desirable, and as high a flatness as possible is desired as a recording material, it is desirable that the surface has excellent smoothness and flatness. Therefore, surface treatment by applying heat and pressure using a machine calender, soft calender, super calender, or the like. Is preferred.

The opaque substrate is preferably one having a surface sizing agent applied to both surfaces thereof. Examples of the surface sizing agent include an aqueous solution of polyvinyl alcohol and / or a modified product thereof, and starch, CMC, HEC, and alginic acid. High molecular compounds such as soda and gelatin, metal salts such as calcium chloride, sodium chloride and sodium sulfate, as well as hygroscopic substances such as glycerin and polyethylene glycol,
Coloring agents such as dyes and fluorescent whitening agents, whitening substances, caustic soda, aqueous ammonia, hydrochloric acid, sulfuric acid, sodium carbonate and other pH control agents may be added. Further, a softening agent such as an epoxidized fatty acid amide and a surfactant may be added. Further, a pigment or the like can be added as needed. As a method of impregnating the base paper, it is preferable to impregnate and apply with a size press, a tab size, a gate roll coater or the like.

Before the thermoplastic resin layer is melt-extruded onto the substrate, the substrate is preferably subjected to a pretreatment in order to strengthen the adhesion between the substrate and the thermoplastic resin layer. Examples of the pretreatment of the substrate include an acid etching treatment with a mixed solution of chromic sulfate, a flame treatment with a gas flame, an ultraviolet irradiation treatment, a corona discharge treatment, a glow discharge treatment, and an anchor coat treatment such as alkyl titanate, which can be freely selected. In particular, corona treatment is preferred from the viewpoint of simplicity. In the case of corona treatment, it is necessary to perform treatment so that the contact angle with water becomes 70 ° or less.

As the anchor coating agent, organic titanium-based, isocyanate-based (urethane-based) polyethyleneimine-based, polybutadiene-based and the like are known. Specifically, as an organic titanium-based compound, tetraisopropyl titanate, tetrabutyl titanate, alkyl titanates such as tetrastearyl titanate, titanium acylates such as butoxytitanium stearate, titanium chelates such as titanium acetylacetonate, and the like are known. I have. As the isocyanate (urethane), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), xylylene diisocyanate (XD
I), isophorone diisocyanate (IPDI) and the like are known.

-Preparation of thermoplastic resin layer- The thermoplastic resin layer is formed by melt extrusion on a substrate. The fluorescent whitening agent and the white pigment are usually used by preparing a so-called compound in which a desired composition ratio is initially contained in the polyolefin resin as the thermoplastic resin. To prepare the compound, the compound is kneaded using a conventionally known kneader. As such a kneading machine, a Banbury mixer, a kneader, a kneading extruder, a two-roll kneading machine, a three-roll kneading machine, or the like is used, and a Banbury mixer and a kneading extruder are preferably used.
These kneaders may be used in combination of two or more. The compound thus produced is melt-extruded onto the substrate by a conventionally known melt extruder.

The thickness of the thermoplastic resin layer that is melt-extruded on the substrate is not particularly limited, but is usually 10 to 60 μm.
Is preferred.

As described above, the thermoplastic resin layer on the support contains a fluorescent whitening agent, and the colorant receiving layer does not need to contain a fluorescent whitening agent. It is possible to improve the whiteness of the color material receiving layer, which is the recording surface, without lowering the printing quality. Therefore, the background portion has high whiteness, high contrast, clear images with no blemishes and vivid hue can be obtained, and even if the image is left under sunlight or fluorescent light for a long time after image formation, the density due to fading is obtained. High image storability can be ensured without any decrease.

[Coloring Material Receiving Layer] The ink jet recording sheet of the present invention has a coloring material receiving layer on the thermoplastic resin layer of the support. The colorant receiving layer comprises at least an inorganic pigment fine particle, a water-soluble resin, and a cross-linking agent for cross-linking the water-soluble resin, and, if necessary, contains other components such as a mordant and a light resistance improver. May be. In addition, the color material receiving layer is preferably formed on a support by a WOW method, as described later.

(Inorganic Pigment Fine Particles) As the anhydrous pigment fine particles, anhydrous pigment fine particles having an average primary particle diameter of 20 nm or less are preferable. As the inorganic pigment fine particles, for example,
Examples thereof include fine silica particles, colloidal silica, titanium dioxide, barium sulfate, calcium silicate, zeolite, kaolinite, halloysite, mica, talc, calcium carbonate, magnesium carbonate, calcium sulfate, boehmite, and pseudoboehmite. Among them, silica fine particles are particularly preferable.

Since the silica fine particles have a particularly large specific surface area, they have high ink absorbency and retention efficiency, and have a low refractive index, so that if they are dispersed to an appropriate particle size, transparency is imparted to the receptor layer. And high color density and good color developability can be obtained. Transparency of the receiving layer means that O
It is important not only in applications requiring transparency such as HP but also in recording sheets such as photo glossy paper from the viewpoint of obtaining high color density and good color development.

The average primary particle diameter of the inorganic pigment fine particles is more preferably 10 nm or less, more preferably 3 to 10 nm.
Is most preferred.

The silica fine particles have a sinoral group on the surface thereof, and the particles easily adhere to each other due to hydrogen bonding by the silanol group. Therefore, when the average primary particle diameter is 10 nm or less as described above, the porosity is large. The structure can be formed, and the ink absorption characteristics can be effectively improved.

The silica fine particles are roughly classified into wet process particles and dry process particles according to the production method. In the wet method, the mainstream is a method in which active silica is generated by acid decomposition of a silicate, which is appropriately polymerized, coagulated and settled to obtain hydrated silica. On the other hand, the dry method is a method based on high-temperature gas phase hydrolysis of silicon halide (flame hydrolysis method), in which silica sand and coke are heated and reduced by an arc in an electric furnace,
A method of obtaining anhydrous silica by a method of oxidizing this with air (arc method) is mainly used.

The hydrated silica and anhydrous silica obtained by these methods have different properties, such as the density of silanol groups on the surface and the presence or absence of vacancies, and show different properties. However, in the case of anhydrous silica (silicic anhydride), Is particularly preferable because a three-dimensional structure having a particularly high porosity is easily formed. Although the reason for this is not clear, in the case of hydrous silica, the density of silanol groups on the surface of the fine particles is as large as 5 to 8 / nm ² , and the silica fine particles are likely to be densely aggregated (aggregate). In the case of (1), since the density of silanol groups on the surface of the fine particles is as small as ² to 3 / nm ² , sparse soft coagulation (flocculate) is caused, and as a result, it is presumed that the structure has a high porosity. . Therefore, in the present invention, it is preferable to use silica (silica fine particles) having a density of 2 to 3 silanol groups / nm ² on the surface of the fine particles.

From the viewpoint of transparency, the type of resin to be combined with the silica fine particles becomes important. When anhydrous silica is used, the water-soluble resin is preferably polyvinyl alcohol (PVA). 99% PVA is more preferred, and PVA with a saponification degree of 70-90% is most preferred.

The PVA has a hydroxyl group in its structural unit, and the hydroxyl group and a silanol group on the surface of the silica fine particles form a hydrogen bond to form a three-dimensional network structure in which the secondary particles of the silica fine particles are chain units. Easy to do. It is considered that by forming the three-dimensional network structure, a colorant receiving layer having a porous structure with a high porosity can be formed. The porous colorant receiving layer thus obtained is used for inkjet recording.
The ink is rapidly absorbed by the capillary action, and a good circularity without ink bleeding can be formed.

The content ratio of the inorganic pigment fine particles (preferably silica fine particles; i) and the water-soluble resin (p) [PB ratio (i:
p), weight of inorganic pigment fine particles per 1 part by weight of water-soluble resin] greatly affects the film structure of the colorant receiving layer.
That is, as the PB ratio increases, the porosity, pore volume, and surface area (per unit weight) increase. Specifically, the P
The B ratio (i: p) is preferably 1.5: 1 to 10: 1. When the PB ratio exceeds 10: 1, that is, when the PB ratio is too large, the film strength is reduced and cracks may easily occur during drying, and the PB ratio is less than 1.5: 1, that is, the PB ratio is too small. As a result, the voids are more likely to be closed by the resin, and as a result, the porosity may decrease and the ink absorbency may decrease.

When the recording sheet passes through the transport system of the ink jet printer, stress may be applied to the recording sheet.
The colorant receiving layer needs to have sufficient film strength. Further, when the sheet is cut into a sheet, the color material receiving layer needs to have a sufficient film strength in order to prevent the color material receiving layer from being cracked or peeled off. In this case, the PB ratio is preferably 5: 1 or less, and is preferably 2: 1 or more from the viewpoint of securing high-speed ink absorption by an inkjet printer.

For example, anhydrous silica fine particles having an average primary particle diameter of 20 nm or less and a water-soluble resin are mixed with a PB ratio of 2: 1 to 5:
When a coating solution completely dispersed in an aqueous solution is coated on a support in 1 and the coating layer is dried, a three-dimensional network structure having secondary particles of silica fine particles as chain units is formed, and the average pore diameter is reduced. 30 nm or less, porosity of 50% or more, pore specific volume of 0.
A translucent porous film having a specific surface area of at least 5 ml / g and a specific surface area of at least 100 m ² / g can be easily formed.

(Water-soluble resin) As the water-soluble resin,
For example, a resin having a hydroxyl group as a hydrophilic structural unit, such as polyvinyl alcohol (PVA), cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, polyvinyl acetal, a cellulose resin [methyl cellulose (MC), ethyl cellulose ( EC), hydroxyethylcellulose (HEC), carboxymethylcellulose (CMC), etc.], chitins, chitosans, starch; polyethylene oxide (PEO) which is a resin having an ether bond, polypropylene oxide (PP
O), polyethylene glycol (PEG), polyvinyl ether (PVE); and resins having an amide group or an amide bond, such as polyacrylamide (PAAM) and polyvinyl pyrrolidone (PVP). Further, having a carboxyl group as a dissociable group, polyacrylate,
Maleic acid resins, alginates and gelatins can be mentioned. Among the above, polyvinyl alcohols are particularly preferred.

The content of the water-soluble resin is preferably from 9 to 40% by weight, more preferably from 16 to 33% by weight, based on the total solid weight of the colorant receiving layer. The content is
If the amount is less than 9% by weight, the film strength is reduced, and cracks may easily occur during drying. If the amount is more than 40% by weight, the voids are easily closed by the resin, resulting in a decrease in the porosity and ink. Absorption may decrease.

The inorganic pigment fine particles and the water-soluble resin, which mainly constitute the colorant receiving layer, may be a single material or a mixture of a plurality of materials.

(Crosslinking Agent) The colorant receiving layer contains a crosslinking agent for crosslinking the water-soluble resin. A solution (crosslinking agent solution) further containing at least a crosslinking agent is applied to the coating layer (porous layer) coated with the inorganic pigment particles and the water-soluble resin, and the water-soluble resin is crosslinked by the crosslinking reaction. Preferably, it is cured.

Specifically, the cross-linking agent solution is applied simultaneously with the application of the coating liquid for forming the porous color material receiving layer (the coating material for the color material receiving layer) in the WOW method described later. ,
Alternatively, it is preferably performed before a coating layer formed by applying the coating material for a colorant receiving layer exhibits a reduced drying rate. By this operation, it is possible to effectively prevent the occurrence of cracks that occur during the drying of the coating layer. That is, the cross-linking agent solution permeates into the coating layer at the same time as when the coating liquid is applied or before the coating layer exhibits a reduced drying rate, and quickly reacts with the water-soluble resin in the coating layer, By gelling (curing) the water-soluble resin, the film strength of the coating layer is immediately and greatly improved.

As the cross-linking agent capable of cross-linking the water-soluble resin, a suitable cross-linking agent may be appropriately selected in relation to the water-soluble resin used in the colorant receiving layer. Among them, a cross-linking reaction is rapid. From the above, boron compounds are preferable, for example, borax,
Boric acid, borate (eg, orthoborate, InBO ₃ , S
_{cBO 3, YBO 3, LaBO 3} , Mg 3 (BO 3) 2, Co
₃ (BO ₃ ) ₂ , diborate (eg, Mg ₂ B ₂ O ₅ , Co ₂ B ₂
O ₅ ), metaborate (eg, LiBO ₂ , Ca (B
O ₂ ) ₂ , NaBO ₂ , KBO ₂ ), tetraborate (eg, N
a ₂ B ₄ O ₇ .10H ₂ O), pentaborate (for example, KB ₅ O _{8
· 4H 2 O, Ca 2 B} 6 O 11 · 7H 2 O, CsB 5 O 5),
Glyoxal, melamine / formaldehyde (eg, methylol melamine, alkylated methylol melamine), methylol urea, resole resin, polyisocyanate, epoxy resin and the like can be mentioned. Among them,
Borax, boric acid, and borate are preferred from the viewpoint of promptly causing a cross-linking reaction. In particular, it is more preferred to use a water-soluble resin in combination with polyvinyl alcohol.

When gelatin is used as the water-soluble resin, the following compounds known as hardeners for gelatin can be used as crosslinking agents. For example, aldehyde compounds such as formaldehyde, glyoxal and glutaraldehyde; ketone compounds such as diacetyl and cyclopentanedione; bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1,3,5
-Halogen compounds such as triazine, 2,4-dichloro-6-S-triazine sodium salt; divinylsulfonic acid, 1,3-vinylsulfonyl-2-propanol, N, N'-ethylenebis (vinylsulfonylacetate) Active vinyl compounds such as amide), 1,3,5-triacryloyl-hexahydro-S-triazine; N-methylol compounds such as dimethylolurea and methyloldimethylhydantoin;

Isocyanate compounds such as 1,6-hexamethylene diisocyanate; US Patent No. 301
Nos. 7280 and 29836311; aziridine compounds; carboximide compounds described in U.S. Pat. No. 3,100,704; epoxy compounds such as glycerol triglycidyl ether; and 1,6-hexamethylene-N, N '. Ethyleneimino compounds such as bisethyleneurea; halogenated carboxaldehyde compounds such as mucochloric acid and mucophenoxycyclolic acid; dioxane compounds such as 2,3-dihydroxydioxane; chromium alum, potassium alum, zirconium sulfate; Chromium acetate and the like. The crosslinking agent may be used alone or in combination of two or more.

The crosslinking agent solution is prepared by dissolving the crosslinking agent in water and / or an organic solvent. The concentration of the crosslinking agent in the crosslinking agent solution is 0.05% with respect to the weight of the crosslinking agent solution.
Is preferably from 10 to 10% by weight, and particularly preferably from 0.1 to 7% by weight. As a solvent constituting the crosslinking agent solution, water is generally used, and an aqueous mixed solvent containing an organic solvent miscible with the water may be used. As the organic solvent, any one can be used as long as it can dissolve the crosslinking agent, for example,
Alcohols such as methanol, ethanol, isopropyl alcohol and glycerin; ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate and ethyl acetate;
Aromatic solvents such as toluene; ethers such as tetrahydrofuran; and halogenated carbon-based solvents such as dichloromethane.

(Other Components) The colorant receiving layer preferably contains a mordant from the viewpoint of improving water resistance and bleeding resistance over time. That is, the mordant is a cationic organic compound (cationic mordant), and when present in the colorant receiving layer, interacts with a liquid ink having an anionic dye as a colorant to stabilize the colorant. And water resistance and bleeding over time can be improved.

However, if this is added directly to the coating solution for forming the colorant receiving layer, there is a possibility that aggregation may occur with inorganic pigment fine particles having an anionic charge such as silica. If the method of preparing and applying the solution as another solution is used, there is no need to worry about aggregation of the inorganic pigment fine particles. Therefore, in the present invention, it is preferable to use it in a crosslinking agent solution containing the crosslinking agent.

As the cationic mordant, a polymer mordant having a primary to tertiary amino group or a quaternary ammonium group as a cationic group is preferably used, but a cationic non-polymer mordant is also used. can do. Examples of the polymer mordant include a homopolymer of a monomer having a primary to tertiary amino group and a salt thereof, or a monomer (mordanting monomer) having a quaternary ammonium group, or a mordant monomer and another monomer (hereinafter, referred to as a mordant monomer). Those obtained as a copolymer or a condensed polymer with “non-mordanting polymer”) are preferred. These polymer mordants can be used in the form of either a water-soluble polymer or water-dispersible latex particles.

Examples of the monomer (mordanting monomer) include trimethyl-p-vinylbenzylammonium chloride, trimethyl-m-vinylbenzylammonium chloride, triethyl-p-vinylbenzylammonium chloride, and triethyl-m-vinylbenzylammonium. Chloride, N, N-dimethyl-N-ethyl-Np-vinylbenzylammonium chloride,
N, N-diethyl-N-methyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-Nn
-Propyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-Nn-octyl-Np
-Vinylbenzylammonium chloride, N, N-dimethyl-N-benzyl-Np-vinylbenzylammonium chloride, N, N-diethyl-N-benzyl-
Np-vinylbenzylammonium chloride, N,
N-dimethyl-N- (4-methyl) benzyl-Np-
Vinylbenzylammonium chloride, N, N-dimethyl-N-phenyl-Np-vinylbenzylammonium chloride,

Trimethyl-p-vinylbenzylammonium bromide, trimethyl-m-vinylbenzylammonium bromide, trimethyl-p-vinylbenzylammonium sulfonate, trimethyl-m-vinylbenzylammonium sulfonate, trimethyl-p-vinylbenzylammonium acetate, trimethyl- m
-Vinylbenzylammonium acetate, N, N, N
-Triethyl-N-2- (4-vinylphenyl) ethylammonium chloride, N, N, N-triethyl-N
-2- (3-vinylphenyl) ethylammonium chloride, N, N-diethyl-N-methyl-N-2- (4
-Vinylphenyl) ethylammonium chloride,
N, N-diethyl-N-methyl-N-2- (4-vinylphenyl) ethylammonium acetate;

N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth)
Acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N Methyl chloride of N-diethylaminopropyl (meth) acrylamide,
Ethyl chloride, methyl bromide, ethyl bromide, a quaternary compound with methyl iodide or ethyl iodide, or a sulfonate, an alkyl sulfonate, an acetate or an alkyl carboxylate in which an anion thereof is substituted, may be mentioned.

Specifically, for example, trimethyl-2-
(Methacryloyloxy) ethylammonium chloride, triethyl-2- (methacryloyloxy) ethylammonium chloride, trimethyl-2- (acryloyloxy) ethylammonium chloride, triethyl-2- (acryloyloxy) ethylammonium chloride, trimethyl-3- (methacryloyl) Oxy)
Propyl ammonium chloride, triethyl-3-
(Methacryloyloxy) propylammonium chloride, trimethyl-2- (methacryloylamino) ethylammonium chloride, triethyl-2- (methacryloylamino) ethylammonium chloride, trimethyl-2- (acryloylamino) ethylammonium chloride, triethyl-2- (acryloyl) Amino) ethylammonium chloride, trimethyl-3-
(Methacryloylamino) propylammonium chloride, triethyl-3- (methacryloylamino) propylammonium chloride, trimethyl-3- (acryloylamino) propylammonium chloride, triethyl-3- (acryloylamino) propylammonium chloride,

N, N-dimethyl-N-ethyl-2- (methacryloyloxy) ethylammonium chloride,
N, N-diethyl-N-methyl-2- (methacryloyloxy) ethylammonium chloride, N, N-dimethyl-N-ethyl-3- (acryloylamino) propylammonium chloride, trimethyl-2- (methacryloyloxy) ethylammonium Bromide, trimethyl-3- (acryloylamino) propylammonium bromide, trimethyl-2- (methacryloyloxy) ethylammonium sulfonate, trimethyl-
3- (acryloylamino) propyl ammonium acetate and the like can be mentioned. In addition, as copolymerizable monomers, N-vinylimidazole, N-vinyl-2-methylimidazole and the like can also be mentioned.

The non-mordanting polymer does not contain a basic or cationic moiety such as a primary to tertiary amino group and a salt thereof, or a quaternary ammonium base, and has an interaction with a dye in an inkjet ink. A monomer that does not show or has substantially small interaction. Examples of the non-mordanting monomer include: (meth) acrylic acid alkyl ester; (meth) acrylic acid cycloalkyl ester such as (meth) acrylic acid cycloacrylate; (meth) acrylic acid aryl ester such as phenyl (meth) acrylate; Aralkyl esters such as benzyl (meth) acrylate; aromatic vinyls such as styrene, vinyltoluene and α-methylstyrene; vinyl acetate, vinyl propionate;
Vinyl esters such as vinyl versatate; allyl esters such as allyl acetate; halogen-containing monomers such as vinylidene chloride and vinyl chloride; vinyl cyanides such as (meth) acrylonitrile; olefins such as ethylene and propylene. No.

The (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid having 1 to 18 carbon atoms in the alkyl moiety.
Alkyl acrylates are preferred, for example, methyl (meth) acrylate, ethyl (meth) acrylate,
Propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate,
Examples include hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate. Among them, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and hydroxyethyl methacrylate are preferred. The non-mordanting monomers can also be used alone or in combination of two or more.

Further, as a polymer mordant, polydiallyldimethylammonium chloride, polymethacryloyloxyethyl-β-hydroxyethyldimethylammonium chloride, polyethyleneimine, polyallylamine, polyallylamine hydrochloride, polyamide-polyamine resin, cationized starch, dicyandiamide Formalin condensate, dimethyl-2-hydroxypropylammonium salt polymer, polyamidine, polyvinylamine and the like can also be mentioned as preferable ones.

The molecular weight of the polymer mordant is 1
000 to 200,000 is preferred. The molecular weight is 100
If it is less than 0, the water resistance tends to be insufficient, and 2
If it exceeds 00000, the viscosity may be too high and the handling adequacy may decrease.

The colorant receiving layer may contain the following components, if necessary. For the purpose of suppressing the deterioration of the coloring material, various ultraviolet absorbers, antioxidants, singlet oxygen quencher and the like may be included. Examples of the ultraviolet absorber include cinnamic acid derivatives, benzophenone derivatives, and benzotriazolylphenol derivatives. For example,
α-cyano-phenyl cinnamate butyl, o-benzotriazolephenol, o-benzotriazole-p-chlorophenol, o-benzotriazole-2,4-di-
t-butylphenol, o-benzotriazole-2,
4-di-t-octylphenol and the like. A hindered phenol compound can also be used as an ultraviolet absorber, and specifically, a phenol derivative in which at least one of the 2- and 6-positions is substituted with a branched alkyl group is preferable.

Further, a benzotriazole ultraviolet absorber, a salicylic acid ultraviolet absorber, a cyanoacrylate ultraviolet absorber, an oxalic acid anilide ultraviolet absorber, and the like can also be used. For example, JP-A-47-1053
No. 7, No. 58-111942, No. 58-212844
Nos. 59-19945, 59-46646, 59-109055, 63-53544, JP-B-36-10466, 42-26187, and 48-
No. 30492, No. 48-31255, No. 48-415
No. 72, No. 48-54965, No. 50-10726
Nos. 2,719,086 and 3,707,
No. 375, No. 3,754,919, No. 4,220,7
No. 11, etc.

A fluorescent whitening agent can also be used as an ultraviolet absorber, and examples thereof include coumarin-based fluorescent whitening agents. Specifically, Japanese Patent Publication Nos. 45-4699 and 54-5324
No. etc.

Examples of the antioxidant include EP-A-223239, EP-A-309401, JP-A-309402, JP-A-310551, and JP-A-31551.
Nos. 0552 and 594416, German Patent No. 3435443, and JP-A-54-48535.
JP-A-60-107384 and JP-A-60-107384
No. 383, No. 60-125470, No. 60-125
No. 125471, No. 60-125472, No. 60-287485, No. 60-287486, No. 60-287487, No. 60-28748.
No. 8, No. 61-160287, No. 61-18
Nos. 5483, 61-211079 and 62
-146678, 62-146680,
JP-A-62-146679, JP-A-62-282885, JP-A-62-262047, and JP-A-63-0511
Nos. 74, 63-89877 and 63-88
Nos. 380, 66-88381, 63-1
No. 13536,

Nos. 63-163351 and 63-2
03372, 63-224989, 6
JP-A-3-251282, JP-A-63-267594, JP-A-63-182484, JP-A-1-23992
No. 82, JP-A-2-262654, JP-A-2-7
No. 1262, No. 3-121449, No. 4-2
Nos. 91686, 4-291684, 5-
Nos. 61166, 5-119449, 5-
188687, 5-18886, 5
No. 110490, No. 5-1108437,
No. 5-170361, JP-B-48-43295, JP-B-48-33212, U.S. Pat.
No. 262, No. 4,980,275 and the like.

Specifically, 6-ethoxy-1-phenyl-2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-1-octyl-2,2,4-trimethyl-1,2 -Dihydroquinoline, 6-ethoxy-1-
Phenyl-2,2,4-trimethyl-1,2,3,4-
Tetrahydroquinoline, 6-ethoxy-1-octyl-
2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline, nickel cyclohexanoate, 2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) -2 -Ethyl hexane, 2
-Methyl-4-methoxy-diphenylamine, 1-methyl-2-phenylindole and the like.

The lightfastness improvers may be used alone or in combination of two or more. The lightfastness improver may be made water-soluble, dispersed, or emulsified, or may be contained in microcapsules. The addition amount of the light resistance improver is preferably 0.01 to 10% by weight of the coating material for the colorant receiving layer.

Further, in order to enhance the dispersibility of the inorganic pigment fine particles, various inorganic salts and acids or alkalis as a pH adjuster may be contained. Furthermore, various surfactants are used for the purpose of improving the suitability for application and surface quality, and surfactants having ionic conductivity and metal oxide fine particles having electronic conductivity are used for the purpose of suppressing frictional charging and peeling charging of the surface. In addition, various matting agents may be included for the purpose of reducing the friction characteristics of the surface.

Preparation of ink jet recording sheet: W
OW method-As described above, it is preferable that a crosslinking agent and, if necessary, a mordant are introduced into the colorant receiving layer in the process of applying the crosslinking agent solution. That is, the colorant-receiving layer is coated with a colorant-receiving layer coating solution containing inorganic pigment fine particles having an average primary particle diameter of 20 nm or less and a water-soluble resin, and simultaneously with or during drying of the formed coating layer. Before the coating layer exhibits a reduced drying rate, a solution (crosslinking agent solution) containing a crosslinking agent capable of crosslinking a water-soluble resin and, if necessary, a mordant is applied to the coating layer. After that, the coating layer to which the solution is applied is cross-linked and cured (WOW method; W
It is preferably formed by an on-wet method.

The colorant receiving layer of the ink jet recording sheet of the present invention comprises a coating solution containing fine inorganic pigment particles and a water-soluble resin, and a solution containing a crosslinking agent, and a barrier solution comprising a material which does not react with the crosslinking agent. (However, a mordant may be contained in at least one of the solution containing a crosslinking agent or the barrier liquid.) It can also be obtained by simultaneously applying the mixture on a support in a state where it is sandwiched and curing.

As described above, when the mordant is applied simultaneously with the crosslinking agent, the water resistance of the colorant receiving layer can be further improved. That is, when the mordant is added to the coating solution for the colorant receiving layer, the mordant is cationic, and therefore, aggregation may occur in the presence of inorganic pigment fine particles having an anionic charge on the surface such as silica. However, if a method including independently preparing a solution containing a mordant and a coating solution for a colorant receiving layer and applying each individually is not necessary, it is not necessary to consider aggregation of the inorganic pigment fine particles, and the selection range of the mordant can be selected. Spreads.

In the present invention, a coating material for a color material receiving layer containing at least inorganic pigment fine particles and a water-soluble resin (hereinafter, may be referred to as a “color material receiving layer coating solution”).
Can be prepared, for example, as follows. That is, silica fine particles having an average primary particle diameter of 20 nm or less are added to water (for example, 10 to 20% by weight), and a high-speed rotating wet colloid mill (for example, CLEARMIX (manufactured by M Technique Co., Ltd.)) is used. For example, after dispersing for 20 minutes (preferably 10 to 30 minutes) under the condition of high-speed rotation of, for example, 10,000 rpm (preferably 5,000 to 20,000 rpm), a polyvinyl alcohol aqueous solution (for example, silica 1
Of PVA having a weight of about ３), and further dispersed under the same rotation conditions as described above. The obtained coating solution is a uniform sol, and by coating this on a support by the following coating method, a porous colorant receiving layer having a three-dimensional network structure can be formed. If necessary, a surfactant, a pH adjuster, an antistatic agent, and the like can be further added to the colorant receiving layer coating solution.

The application of the coating material for the colorant receiving layer may be performed, for example, by using an extrusion die coater, an air doctor coater, or the like.
The coating can be performed by a known coating method such as a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, and a bar coater.

In the case where the WOW method is adopted, a cross-linking agent solution is applied to the coating layer after applying the coating solution for the colorant receiving layer. It may be given before the speed is shown. That is, it is preferably produced by introducing a crosslinking agent while the coating layer exhibits a constant rate of drying after the application of the coating material for the colorant receiving layer. Here, "before the coating layer exhibits a reduced drying rate" generally refers to a few minutes immediately after the application of the coating material for the colorant receiving layer, and during this time, in the applied coating layer, It shows the constant rate drying rate, which is a phenomenon in which the content of the solvent decreases in proportion to time. The time showing the constant rate drying rate is described in Chemical Engineering Handbook (pp. 707-712, published by Maruzen Co., Ltd., October 25, 1980).

As described above, after the application of the coating material for the colorant receiving layer, the coating layer is dried until the coating layer exhibits a reduced rate drying rate.
This is performed for 10 minutes (preferably, 0.5 to 5 minutes). The drying time varies depending on the coating amount, but the above range is appropriate.

As a method of applying the crosslinking agent solution before the coating layer exhibits a reduced drying rate, a method of further applying the crosslinking agent solution onto the coating layer, a method of spraying by a method such as spraying, A method in which the support on which the coating layer is formed is immersed in a crosslinking agent solution.

In the above method, as a coating method for applying the crosslinking agent solution, for example, a curtain flow coater,
Known application methods such as an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, and a bar coater can be used. However, it is preferable to use a method such as an extrusion die coater, a curtain flow coater, a bar coater, or the like, in which the coater does not directly contact an already formed coating layer.

The coating amount of a coating solution (crosslinking agent solution) containing at least a crosslinking agent and a mordant applied on the colorant receiving layer is generally 0.01 to 10 g / m ^{2 in} terms of a crosslinking agent. And 0.05 to 5 g / m ² is preferable.

After the application of the crosslinking agent solution, generally, 40 to 1
Heating is performed at 80 ° C. for 0.5 to 30 minutes to perform drying and curing. Especially, it is preferable to heat at 40 to 150 ° C. for 1 to 20 minutes. For example, when borax or boric acid is used as a cross-linking agent contained in the cross-linking agent solution,
Preferably, heating at 100 ° C. is performed for 5 to 20 minutes.

The cross-linking agent coating liquid may be applied at the same time as the coating liquid for the colorant receiving layer is applied. in this case,
The coating material for the color material receiving layer and the cross-linking agent solution are simultaneously coated on the support such that the coating solution for the color material receiving layer comes into contact with the support (multi-layer coating), and then dried and cured to receive the color material. Layers can be formed.

The simultaneous coating (multilayer coating) can be performed by a coating method using, for example, an extrusion die coater or a curtain flow coater. After the simultaneous coating, the formed coating layer is dried. In this case, the drying is generally performed by heating the coating layer at 40 to 150 ° C. for 0.5 to 10 minutes, preferably 40 to 100 ° C.
It is performed by heating at a temperature of 0.5 to 5 minutes. For example, when using borax or boric acid as a crosslinking agent contained in the crosslinking agent solution, it is preferable to heat at 60 to 100 ° C. for 5 to 20 minutes.

When the simultaneous coating (multi-layer coating) is performed by, for example, an extrusion die coater, the two kinds of coating liquids discharged at the same time are close to the discharge port of the extrusion die coater, that is, before being transferred onto the support. Is formed on the support, and is then coated on the support. When the two-layer coating solution, which has been layered before coating, is transferred to the support, a crosslinking reaction is likely to occur at the interface between the two components, so the two components to be discharged are mixed near the discharge port of the extrusion die coater. And the viscosity increases, which may hinder the application operation. Therefore, in the case of simultaneous coating as described above, the coating solution for the colorant receiving layer and the cross-linking agent solution containing the cross-linking agent and the mordant are applied, and the barrier layer solution (intermediate layer Liquid) is preferably interposed between the two liquids for simultaneous three-layer coating.

The barrier layer liquid can be selected without particular limitation as long as it can form a liquid film without reacting with a crosslinking agent. For example, an aqueous solution containing a trace amount of a water-soluble resin that does not react with the crosslinking agent, water, or the like can be used. The water-soluble resin is used in consideration of coatability for the purpose of a thickener and the like, for example, hydroxypropyl methylcellulose,
Methyl cellulose, hydroxyethyl methyl cellulose
And polymers such as polyvinylpyrrolidone and gelatin. Incidentally, the mordant may be contained in the barrier layer liquid.

After the color material receiving layer is formed on the support, the color material receiving layer is subjected to a calender treatment through a roll nip under heat and pressure by using, for example, a super calendar, a gloss calendar, etc. It is possible to improve the properties, glossiness, transparency and coating strength. However, since the calendering treatment may cause a decrease in the porosity (that is, the ink absorbency may be reduced), it is necessary to set a condition under which the porosity does not decrease much.

The roll temperature for calendering is preferably from 30 to 150 ° C, more preferably from 40 to 100 ° C. The linear pressure between the rolls during the calendering treatment is preferably 50 to 400 kg / cm, and is preferably 10 to 400 kg / cm.
0 to 200 kg / cm is more preferable.

In the case of ink jet recording, the layer thickness of the color material receiving layer needs to have an absorption capacity to absorb all of the liquid droplets, and thus needs to be determined in relation to the porosity in the layer. is there. For example, if the ink amount is 8 nL / mm ²
If the porosity is 60%, the layer thickness is about 15 μm.
The above film is required. Considering this point, in the case of inkjet recording, the layer thickness of the colorant receiving layer is 1
0 to 50 μm is preferred.

The pore size of the colorant receiving layer is preferably from 0.005 to 0.030 μm in median diameter, and from 0.01 to 0.030 μm.
0.025 μm is more preferred. The porosity and the median pore diameter can be measured using a mercury porosimeter (trade name: Pore Sizer 9320-PC2, manufactured by Shimadzu Corporation).

The color material receiving layer is preferably excellent in transparency. As a rule, the haze value when the color material receiving layer is formed on a transparent film support is 30%.
% Or less, and more preferably 20% or less. The haze value is measured with a haze meter (HG
M-2DP: Suga Test Instruments Co., Ltd.).

On the support, for the purpose of increasing the adhesiveness between the colorant receiving layer and the support and adjusting the electric resistance, etc.
An undercoat layer may be provided. The color material receiving layer may be provided on only one surface of the support, or may be provided on both surfaces of the support for the purpose of suppressing deformation such as curling. When used in OHP or the like, and the color material receiving layer is provided only on one surface of the support, the opposite surface, or both surfaces,
An antireflection film may be provided for the purpose of increasing light transmittance.

[0115]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. still,
“Parts” and “%” in the examples all represent “parts by weight” and “% by weight”.

(Example 1) -Preparation of support- Corona discharge treatment was performed on the wire surface (back surface) side of a high-quality paper (manufactured by Kishu Paper Co., Ltd.) with a weight of 159 g / m ² , a thickness of 187 μm, and a whiteness of 82%. After that, high-density polyethylene was coated to a thickness of 20 μm using a melt extruder to form a resin layer composed of a mat surface (hereinafter, the resin layer surface is referred to as a “back surface”). This resin layer on the back side is further subjected to corona discharge treatment, and then, as an antistatic agent,
A dispersion obtained by dispersing aluminum oxide (alumina sol 100, manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (Snowtex O, manufactured by Nissan Chemical Industries, Ltd.) in water at a ratio (weight ratio) of 1: 2, Coating was performed so that the dry weight was 0.2 g / m ² .

Further, after a corona discharge treatment was applied to the felt surface (surface) on the side where the resin layer was not provided, 10% by weight of anatase type titanium dioxide, a very small amount of ultramarine blue, and the aforementioned structural formula (V) 0.01% by weight of optical brightener represented by
(To polyethylene), low-density polyethylene having an MFR (melt flow rate) of 3.8 was melt-extruded to a thickness of 25 μm using a melt extruder, and a high-gloss thermoplastic resin layer was formed on the base paper. It was formed on the front surface side (hereinafter, this high gloss surface is referred to as “front surface”), and used as a support.

-Preparation of Coating Solution for Coloring Material Receiving Layer- In the following composition, and were mixed, and the mixture was rotated at 10,000 rpm for 20 minutes using a high-speed rotating colloid mill (CLEARMIX, manufactured by M Technique Co., Ltd.). After dispersing into a silica dispersion, 1N aqueous ammonia was added to 82.5 parts of the silica dispersion, a 9% aqueous solution of polyvinyl alcohol was further added, and the mixture was further dispersed under the same conditions as described above. A 7% colorant receiving layer coating solution was prepared. Weight ratio of silica fine particles to water-soluble resin (PB ratio /
:) was 3.5: 1.

[Composition of the coating material for the colorant receiving layer] Silica fine particles: 12 parts (average primary particle diameter: 7 nm; Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.) Ion exchange water: 88 parts 1N ammonia water 5.3 parts polyvinyl alcohol 9% aqueous solution (water-soluble resin) 41.3 parts (PVA420, manufactured by Kuraray Co., Ltd., saponification degree 82%, polymerization degree 2000)

-Preparation of Crosslinking Agent Solution (1)-In 1.5 parts of borax, 95.8 parts of ion-exchanged water and a 10% aqueous solution of a surfactant (F-144D, manufactured by Dainippon Ink and Chemicals, Inc.) 0.2 parts and 2.5 parts of a 60% aqueous solution of a cationic polymer (PAS-M-1, Nitto Boseki Co., Ltd.) were added as a mordant and stirred to obtain a crosslinking agent solution (1). .

—Preparation of Ink-Jet Recording Sheet— The coating material for a colorant receiving layer obtained above was applied onto the glossy surface of the support at an application amount of 200 cc / m ² using an extrusion die coater. Then, it was dried at 80 ° C. (wind speed 3 m / sec) for 3 minutes using a hot air drier. The coating layer exhibited a constant rate of drying during this period. Immediately thereafter, it was immersed in the crosslinking agent solution (1) for 1 second (step of applying the crosslinking agent solution), and further dried at 80 ° C. for 10 minutes (drying step). As a result, an ink jet recording sheet (1) of the present invention was prepared, in which a coloring material receiving layer having a dry film thickness of 35 μm was provided on the thermoplastic resin layer of the support.

(Examples 2 to 5) As shown in Table 1, 0.0% of the fluorescent whitening agent represented by the structural formula (V) used in Example 1 was used.
Except that 1% by weight was replaced by 0.03% by weight (relative to polyethylene), 0.06% by weight (relative to polyethylene), 0.09% by weight (relative to polyethylene) and 0.13% by weight (relative to polyethylene) In the same manner as in Example 1, the inkjet recording sheets (2) to (5) of the present invention were produced.

Example 6 Fine paper used as a substrate in Example 1 was coated with 157 g / m ² , 129 μm thick and 82% whiteness coated paper (Shiorai Coat, manufactured by Daishowa Paper Co., Ltd.). In addition, 0.01% by weight of the optical brightener represented by the structural formula (V) was replaced by 0.06% by weight (based on polyethylene) of the optical brightener represented by the structural formula (IV) Except that, in the same manner as in Example 1, an ink jet recording sheet (6) of the present invention was produced.

Example 7 An ink jet recording sheet of the present invention was prepared in the same manner as in Example 1, except that the high-quality paper used as the substrate in Example 1 was replaced with a photographic paper base paper prepared by the following procedure. (7) was produced.

[Preparation of base paper for photographic paper] A wood pulp consisting of 100 parts of LBKP was beaten to a canadian freeness of 300 ml with a double disc refiner, and 0.5 parts of epoxidized behenamide, 1.0 part of anionic polyacrylamide, and 1.0 part of polyamide polyamine epichlorohydrin. 0.1 part and 0.5 part of cationic polyacrylamide were added at an absolute dry weight ratio to pulp, and weighed with a Fourdrinier paper machine to produce a base paper of 170 g / m ² .
To adjust the surface size of the base paper, an optical brightener (Whitex BB,
0.04% of Sumitomo Chemical Co., Ltd.) was impregnated into the base paper so as to have an absolute dry weight of 0.5 g / m ² , dried, and then calendered. A base paper adjusted to a density of 1.05 was obtained.

Comparative Example 1 Comparative Example 1 was carried out in the same manner as in Example 1 except that 0.01% by weight of the optical brightener represented by the structural formula (V) used in Example 1 was not contained. To prepare an ink jet recording sheet (8).

(Comparative Example 2) To the crosslinking agent solution (1) prepared in Example 1, 0.04 parts of a fluorescent whitening agent (Whitex BB, manufactured by Sumitomo Chemical Co., Ltd.) was further added to form a crosslinking agent solution. (2) was prepared. Then, in Comparative Example 1, an ink jet recording sheet (9) of Comparative Example was produced in the same manner as in Comparative Example 1, except that the crosslinking agent solution (2) was used instead of the crosslinking agent solution (1). .

<Evaluation of Performance> The following evaluations were performed on the ink jet recording sheets (1) to (7) of the present invention obtained above and the ink jet recording sheets (8) to (9) of the comparative examples. Was. The evaluation results are shown in Table 1 below. (Glossiness) The 60 ° glossiness on the surface of the colorant receiving layer of the recording sheet before printing was measured using a digital variable-angle glossmeter (UGV-
50DP, manufactured by Suga Test Instruments Co., Ltd.).

(Light fastness) Ink jet printer (PM
Y (yellow), M (magenta), C (cyan), K (black), B (blue), and G on the color material receiving layer of each recording sheet using -750C (manufactured by Seiko Epson Corporation). After printing solid images of (green) and R (red), Xe is passed through a film that cuts ultraviolet rays in a wavelength region of 365 nm or less.
non weather-meter Ci65A
The lamp was turned on for 3.8 hours under the environmental conditions of 25 ° C. and 32% RH using an ATLAS (manufactured by ATLAS), and then the lamp was turned off for 1 hour under the environmental conditions of 20 ° C. and 91% RH with the lamp turned off.
A cycle of standing for 96 hours was performed for 96 hours, and the degree of fading of each color density of the image was visually evaluated according to the following criteria. [Criteria] ◎: Almost no fading was observed. 〇: Slight fading was observed. Δ: Remarkable fading was observed. X: The degree of fading was remarkable.

(Measurement of Whiteness of Support) Before the formation of the colorant receiving layer, the whiteness of the support was measured using a color analyzer type 607 manufactured by Hitachi, Ltd. at a reflectance [%] at a wavelength of 440 nm. Was measured and used as an index indicating whiteness.

(Measurement of Whiteness of Color Material Receiving Layer) The color material receiving layer was irradiated with an ultraviolet lamp having an emission center wavelength of 420 nm and an output of 40 W for 10 seconds, and further irradiated with an ultraviolet lamp having an emission center wavelength of 365 nm and an output of 40 W for 15 seconds. After irradiation, 440 was applied using a color analyzer 607 manufactured by Hitachi, Ltd.
The reflectance [%] at a wavelength of nm was measured and used as an index indicating whiteness.

(Presence / absence of bleed-out of fluorescent whitening agent) The presence / absence of bleed-out of the fluorescent whitening agent was evaluated from the decrease in whiteness of the support. That is, the support provided with the thermoplastic resin layer was heat-treated at 120 ° C. for 3 minutes, then cooled, and the decrease in whiteness after heat treatment at 100 ° C. for 24 hours was visually evaluated according to the following criteria. [Criteria] ○: Little yellowing. Δ: Slight yellowing was observed. X: Yellowing was noticeably observed.

[0133]

[Table 1]

From the results shown in Table 1 above, the ink jet recording sheets (1) to (7) in which the fluorescent whitening agent was contained in the thermoplastic resin layer and not contained in the colorant receiving layer had sufficient light resistance. It was obtained and had high whiteness. On the other hand, the ink jet recording sheet (8) that did not contain the fluorescent whitening agent did not provide sufficient whiteness, and the ink jet recording sheet (9) that contained the fluorescent whitening agent only in the colorant receiving layer did not. Although whiteness was improved, it was inferior in light resistance.

[0135]

According to the present invention, an ink jet recording sheet having high light resistance even under sunlight or fluorescent light, no bleed-out of a fluorescent whitening agent, and excellent whiteness of a colorant receiving layer. Can be provided. In addition, the colorant receiving layer is strong without cracks and the like, exhibits good ink absorption and gloss, can form a high-resolution and high-density image, and has a sufficient water resistance to the formed image. And excellent ink receiving performance, such as having bleeding resistance with time.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) B29L 7:00 B29L 7:00 31:00 31:00 F term (reference) 2H086 BA02 BA12 BA15 BA31 BA33 BA34 BA35 4D075 BB05Y CA35 CB09 DA04 DB18 DC27 EA02 EA06 EA17 EB45 EC11 4F207 AA03 AB03 AB12 AD05 AD08 AG03 KA01 KA17 KB13 KF02

Claims (4)

[Claims] An inorganic pigment fine particle, a water-soluble resin and a crosslinking agent for crosslinking the water-soluble resin are provided on the thermoplastic resin layer of a support having a thermoplastic resin layer provided on at least one surface of a substrate. An ink jet recording sheet having at least a color material receiving layer, wherein the thermoplastic resin layer is formed by melt extrusion, and the thermoplastic resin layer contains a fluorescent whitening agent and a white pigment. Recording sheet. 2. The colorant-receiving layer is coated with a colorant-receiving layer coating solution containing inorganic pigment fine particles and a water-soluble resin, and simultaneously with or during the drying of the formed coating layer. Before the coating layer exhibits a reduced drying rate, a solution containing a crosslinking agent capable of crosslinking the water-soluble resin is applied to the coating layer, and then the coating layer to which the solution has been applied is crosslinked and cured. The ink jet recording sheet according to claim 1, which is obtained. 3. The ink jet recording sheet according to claim 1, wherein the fluorescent whitening agent is a compound represented by the following structural formula (I). Embedded image [In the structural formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, or a substituent or a substituent atom. ] 4. The content of the fluorescent whitening agent in the thermoplastic resin layer is 0.02 to 0.1 with respect to the thermoplastic resin.
The inkjet recording sheet according to claim 1, wherein the content is 0% by weight.