JP2001047733A - Ink image receiving sheet and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink image receiving sheet having excellent ink absorbability and ink fixability. SOLUTION: The ink image receiving sheet comprises a base material such as a nonwoven fabric or the like, and a porous film having a dense layer on a surface and voids extended in a thickness direction at the base material side. In this case, a mean particle size of the dense layer is about 0.01 to 1.5 m. A width of the void in a planar direction is about 0.1 to 100 μm, and voids of the porous film surface may be about 20 to 70%. The porous film can be constituted of a resin such as a cellulose derivative, vinyl polymer, polysulfone polymer or the like. The sheet can be manufactured by coating the base material with a resin solution, and then forming a porous film by a phase transition method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink receiving sheet having excellent ink absorbency, ink fixing property, printability, water resistance and durability of a recorded image in an ink jet recording system, and a method for producing the same.

[0002]

2. Description of the Related Art Ink-jet recording systems are easy to achieve full color, have low noise, and are excellent in printing quality. In addition, inkjet printers are widely used as printing / output devices such as recording devices for computers, word processors, and copiers because they are inexpensive and easy to operate at high speed. As an ink component for ink jet recording, a water-based ink is mainly used in terms of safety and recording suitability, and recording is performed by flying small ink droplets from nozzles toward a recording sheet. When the ink absorbency of the recording sheet used is low, the ink scatters around the ejected ink droplets, or the ink remains on the surface of the recording sheet for a long time even after the recording is completed, so that the ink may not reach a part of the apparatus. The recording portion becomes dirty due to contact with the sheet, contact with a handler, or superposition of recording sheets. In the high-density image area,
A large amount of supplied ink is mixed without absorption and flows out, resulting in an unclear image. For this reason, the recording sheet is required to quickly absorb the ink and to have high fixability.

JP-B-63-56876 discloses an ink jet recording sheet provided with a porous resin layer having pores in a continuous film. In such a sheet, it is considered that the ink absorbing property is considerably improved by providing the porous resin layer. However, when the ink absorbing layer is formed only of the porous resin having pores, the printing quality and the ink absorbing property are improved. Has limitations. Japanese Patent Application Laid-Open No. 4-263982 proposes a recording sheet in which a porous layer made of cellulose acetate is provided on a base material, and a dye-carrying layer made of pseudo-boehmite is provided thereover.

Japanese Patent Application Laid-Open No. 61-86251 discloses that a liquid absorbing layer is laminated on at least one side of a substrate film layer, and a porous plastic sheet thin film layer (having a diameter of 0.01 to 0.2 mm) is formed on the liquid absorbing layer. A recording sheet in which a polyethylene or polypropylene film having a large number of 1 μm holes) is laminated by hot pressing is disclosed. However, it does not disclose a method for preparing the porous thin film layer.

[0005] WO 98/25997 discloses a porous membrane composed of a cellulose derivative, a vinyl polymer, a polysulfone polymer or the like, and having a light transmittance at a wavelength of 400 nm of 30% or more. It is described that the porous membrane has a microphase separation structure.

[0006] However, these recording sheets do not yet have sufficient ink absorbency, so that it is not possible to achieve both high levels of ink fixability and ink absorbency.

[0007] In the ink jet recording system,
In order to improve the water resistance, an ink using a pigment has been studied. However, unlike the dye ink, the particulate pigment ink has poor fixability to the ink receiving layer and, consequently, ink absorbency.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ink receiving sheet which is excellent in ink absorbency, ink fixing property and printability even if it is a dye ink or a pigment ink, and a method for producing the same. Is to do.

It is another object of the present invention to provide an ink receiving sheet having high water resistance and capable of improving the durability of an image, and a method for producing the same.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a porous base material having a dense layer on the surface and a void extending in the thickness direction on the base material side. The inventors have found that the ink absorbing sheet, fixing property and water resistance can be improved by forming the ink image receiving sheet with the film, and the present invention has been completed.

That is, the ink image receiving sheet of the present invention comprises:
A porous film is laminated on at least one surface of the substrate, and the porous film has a dense layer on the surface and has voids extending in the thickness direction on the substrate side. The average pore diameter of the pores in the dense layer is about 0.01 to 1.5 μm, the width of the voids in the plane direction is about 0.1 to 100 μm, and the porosity of the porous membrane surface is 20 to 70%. It is about. The porous membrane may be composed of a cellulose derivative, a vinyl polymer, a polysulfone polymer, or the like. Further, the porous membrane may have a micro phase separation structure by a phase inversion method. The substrate may be a nonwoven fabric or the like.

The ink image-receiving sheet of the present invention is provided on a substrate,
It can be produced by applying a resin solution and then forming a porous film by a phase inversion method.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Substrate] The substrate is not particularly limited, and may be a substrate having a two-dimensional structure which may be transparent, translucent or opaque, for example, paper, coated paper, Non-woven fabrics, woven fabrics, plastic films and the like can be mentioned. Among these, a porous substrate having permeability to a solvent, for example, a nonwoven fabric or a woven fabric is preferable.

Examples of the polymer constituting the plastic film include polyolefins such as polyethylene and polypropylene, poly (meth) acrylates,
Polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, cellulose derivatives such as cellulose acetate, polyesters (polyalkylene terephthalate such as polyethylene terephthalate and polybutylene terephthalate, polyalkylene naphthalate such as polyethylene naphthalate and polybutylene naphthalate) , Polycarbonate, polyamide (polyamide 6,
Polyamide 6/6, Polyamide 6/10, Polyamide 6
/ 12), polyester amide, polyimide, polyamide imide, etc., and further, a copolymer, a blend, or a crosslinked product thereof may be used.

Among these films, polyolefins (especially, polypropylene, etc.), polyesters (especially, polyethylene terephthalate, etc.), polyamides and the like are usually used, and polyesters (especially, polyethylene Terephthalate, etc.) are preferred.

If necessary, conventional additives such as an antioxidant, an ultraviolet absorber, a heat stabilizer, a lubricant, and a pigment may be added to a substrate such as a plastic film. Also,
A surface treatment such as a corona discharge treatment or an undercoat treatment may be performed to improve the adhesion to the porous film or the ink absorbing layer.

The type of nonwoven fabric (the type of raw material) is not particularly limited as long as the ink absorbency is not impaired. For example, natural fibers (silk, hemp, cotton, etc.), regenerated fibers (rayon, etc.), semi-synthetic Fibers such as fibers (such as acetate) and synthetic fibers (such as nylon fibers, polyester fibers, acrylic fibers, and polyolefin fibers (such as polypropylene fibers)) can be used alone or in combination. These fibers may be subjected to a surface treatment (for example, a hydrophilic treatment). The average fiber diameter can be selected, for example, from the range of about 0.01 to 100 μm, preferably about 0.1 to 50 μm.

The basis weight of the nonwoven fabric is, for example, 50 g / m ^2.
The above can be selected from the range of preferably 100 g / m ² or more. The fiber density of the nonwoven fabric (a value obtained by dividing the basis weight of the nonwoven fabric by the thickness of the nonwoven fabric) is 100 to 5000 kg / m ³ , preferably about 500 to 2000 kg / m ³ . The air permeability of the nonwoven fabric is about 0.1 to 100 cm ³ / cm ² · sec, preferably about 0.1 to 50 cm ³ / cm ² · sec.

The thickness of the base material can be selected according to the intended use. However, in consideration of the fact that the base material is inserted into an ink jet printer to form an image, for example, 20 to 200 μm
Degree can be selected from the range, preferably 50 to 170 μm
And more preferably about 80 to 150 μm.
If the thickness of the base material is less than 20 μm, insertion and ejection from the printer due to its strength and rigidity, the warpage of the sheet, and the handling of the sheet may become difficult. If the thickness exceeds 200 μm, the price per sheet increases, and the weight of the sheet increases. As the number of sheets increases, the portability of a large number of sheets tends to decrease. When the substrate is a nonwoven fabric, the thickness of the nonwoven fabric is, for example, 50 μm or more.
It is about 2 mm, preferably about 100 μm to 1 mm, and more preferably about 100 to 300 μm.

[Porous Film] The ink receiving sheet of the present invention is formed by laminating a porous film having a dense layer on at least one surface of a substrate, and the porous film is formed on the substrate side. Has a void extending in the thickness direction.

In the porous film, the pigment (eg, pigment or dye) of the ink (eg, aqueous ink which may be a pigment ink) can be captured by the dense layer on the surface side of the porous film. The extended voids can quickly absorb the ink solvent and the like. Therefore, it is possible to obtain a clear image with extremely good coloration and to obtain an apparently dry state on the sheet surface more quickly.

In the ink receiving sheet, the average pore size of the dense layer on the surface is 0.01 to 1.5 μm, preferably 0.02 to 1.2 μm, more preferably 0.05 to 1.5 μm.
It is about 1.0 μm. The average pore size of the dense layer is 0.0
When it is smaller than 1 μm, the ink absorbency decreases, and
If it is larger than 5 μm, the sharpness of the image is reduced. By appropriately adjusting the average pore size of the dense layer, it is possible to improve the fixability of a dye type or pigment type ink.

The voids usually extend in the thickness direction of the ink receiving sheet and are regularly or irregularly adjacent to each other. The shape of the void is not particularly limited,
Usually, it is columnar or curved columnar. In the present specification, the void means a void that is sufficiently larger than a void in the dense layer, and is, for example, 5 voids in the void in the dense layer.
The size is about 200 times, preferably about 7 to 150 times.

The width of the void in the plane direction is 0.1 to 10
The thickness is about 0 μm, preferably about 0.5 to 50 μm, and more preferably about 1 to 30 μm. If the width of the void in the planar direction is less than 0.1 μm, the ink absorbability of the ink decreases, and if it exceeds 100 μm, the sharpness of the image may decrease.

The thickness of the dense layer is, for example, about 1 to 50%, preferably about 5 to 30%, and the thickness of the void layer is, for example, 30 to 90%, preferably about 40%. About 80%. In a porous membrane,
A porous intermediate region may be formed between the dense layer and the void layer.

The ink absorbency is also affected by the porosity of the porous film. In the porous film, the porosity of the film surface (print surface, that is, the surface on the dense layer side) is 20 to 70.
%, Preferably about 30 to 60%. 20 porosity
If it is less than 70%, the surface area of the absorbing surface is small, so that the absorption ability of the film to the ink is low. If it exceeds 70%, the strength of the porous film itself may be reduced.

The porous membrane is made of a resin,
It may have a microphase separation structure, particularly a microphase separation structure by a phase inversion method. This microphase-separated structure can be formed by coagulation of a gel phase that has been phase-separated due to a change in the composition of the cast resin solution.

The resin constituting the porous film is not particularly limited as long as a porous film having the above characteristics can be formed, and various resins (a thermoplastic resin and a thermosetting resin) can be used. A plastic resin is used. The following resins or polymers can be exemplified.

Cellulosic resin (cellulose derivative):
Cellulose esters such as cellulose acetate,
Organic acid esters such as cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate phthalate; cellulose nitrate, cellulose sulfate,
Inorganic acid esters such as cellulose phosphate; mixed acid esters such as cellulose nitrate acetate Cellulose ethers such as methylcellulose, ethylcellulose, isopropylcellulose, butylcellulose, benzylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, carboxyethylcellulose, cyanoethylcellulose Vinyl polymer: olefin polymer, for example, olefin homopolymer or copolymer (polyethylene, polypropylene, poly 1-butene, polyisobutene, polybutadiene, polyisoprene, polyarene, ethylene-propylene copolymer, etc.), Copolymers of olefins and copolymerizable monomers (ethylene-vinyl acetate copolymer, ethylene-
(Meth) acrylic acid copolymer, ethylene- (meth) acrylate copolymer, modified polyolefin, etc.) Halogen-containing vinyl polymer, for example, a homo- or copolymer of halogen-containing vinyl monomer (polyvinyl chloride,
Polyvinylidene chloride, polyvinyl bromide, polyvinyl fluoride, polyvinylidene fluoride, etc.), copolymers of halogen-containing vinyl monomers and copolymerizable monomers (vinyl chloride-vinyl acetate copolymer, vinylidene chloride-acetic acid) Vinyl copolymer, vinylidene chloride- (meth) acrylamide copolymer, vinylidene chloride- (meth) acrylic acid copolymer, vinylidene chloride- (meth) acrylic acid ester copolymer, etc.) Vinyl ester polymer or derivative thereof For example, polyvinyl acetate, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinyl acetal polymer (polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc.) Styrene polymer, for example, aromatic vinyl monomer (styrene Monomer) alone Is a copolymer (polystyrene, poly (α-methylstyrene), poly (4-chlorostyrene), etc.), a copolymer of an aromatic vinyl monomer and a copolymerizable monomer (styrene- (meth) acrylic). Acid C _1-10 alkyl ester copolymer, styrene-maleic anhydride copolymer, styrene-maleimide copolymer, etc.) Allyl alcohol-based polymer, for example, allyl alcohol-C _1-6 alkyl vinyl ether copolymer (allyl Alcohol-methyl vinyl ether copolymer), polyvinyl ketones, for example, polyvinyl methyl ketone, polyvinyl methyl isobutyl ketone, polymethyl isopropenyl ketone, etc. polyalkyl vinyl ethers, for example, polymethyl vinyl ether, methyl vinyl ether-maleic anhydride copolymer (Meth) acrylic polymer, example For example, homo- or copolymers of (meth) acrylic monomers [(meth) acrylonitrile, (meth) acrylic acid ester monomers, etc.), and (meth) acrylic monomers and copolymerizable monomers [ Vinyl ester monomers, heterocyclic vinyl monomers, aromatic vinyl monomers, vinyl monomers such as polymerizable unsaturated dicarboxylic acids or derivatives thereof] and polysulfone polymers: Polysulfone, polyether sulfone, etc. Polyoxide polymers: Polyoxymethylene, polyoxymethylene copolymer (polyacetal resin), polyoxyethylene, polyoxypropylene, polyoxyethylene-polyoxypropylene copolymer, etc. Polyamide and polyimide polymers: Polyamide (nylon 6, nylon 66, nylon 11, nylon 1
2, nylon 6/11, nylon 6/12, etc.), polyester amide, polyimide, polyamide imide, etc. Polyester polymer (saturated polyester, etc.): poly C _2-6 alkylene terephthalate (polyethylene terephthalate, polybutylene terephthalate, etc.), poly C
_2-6 alkylene naphthalate (such as polyethylene naphthalate), copolyester (where at least a part of the diol component and terephthalic acid is ethylene glycol, propylene glycol, butanediol, hexanediol,
Diol components such as polyoxy C _2-4 alkylene glycol and cyclohexane dimethanol; aromatic dicarboxylic acids such as phthalic acid and isophthalic acid; or acid anhydrides thereof;
Polyalkylene terephthalate-based copolyester or polyalkylene naphthalate-based copolyester substituted with another diol component such as C _6-12 aliphatic dicarboxylic acid such as adipic acid or dicarboxylic acid component) Polycarbonate: Aromatic polycarbonate (bisphenol A type) Other polymers: thermoplastic urethane polymers (polyurethane using diol component such as polyester diol, polyether diol, etc.), polyetheretherketone, polyetherester, polyphenyleneether, polyphenylenesulfide, polyethyleneimine, etc. These resins or polymers can be used alone or in combination of two or more.

Preferred resins include at least one resin selected from cellulose derivatives, vinyl polymers and polysulfone polymers.

Preferred polysulfone polymers include, for example, polyether sulfone.

Of the vinyl polymers, (meth) acrylonitrile polymers and (meth) acrylate polymers are preferred. That is, a homo- or copolymer of at least one type of (meth) acrylic monomer selected from (meth) acrylonitrile and (meth) acrylic ester-based monomer, Of at least one monomer selected from a vinyl ester monomer, a heterocyclic vinyl monomer, an aromatic vinyl monomer, a polymerizable unsaturated dicarboxylic acid or a derivative thereof, and the like. Is preferred.

The (meth) acrylonitrile-based polymer includes
Examples include polyacrylonitrile, poly (meth) acrylonitrile, and a copolymer of (meth) acrylonitrile and a copolymerizable monomer. Examples of the copolymerizable monomer include vinyl ester monomers (vinyl formate, vinyl acetate, vinyl propionate, etc.), (meth) acrylic monomers [(meth) acrylic acid, (meth) acrylic C _1-10 (meth) acrylates such as methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate
Alkyl ester; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
Hydroxyalkyl (meth) acrylates such as 4-hydroxybutyl (meth) acrylate; alkylamino- such as glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and diethylaminopropyl (meth) acrylate Alkyl (meth) acrylate;
(Meth) acrylamide, N-methyl (meth) acrylamide, methylol (meth) acrylamide, alkoxymethyl (meth) acrylamide, etc.], heterocyclic vinyl monomers (vinylpyrrolidone, vinylpyridine, vinylpiperidine, vinylimidazole, vinyl A 5- to 6-membered heterocyclic vinyl monomer containing at least one hetero atom selected from nitrogen, oxygen and sulfur atoms such as carbazole, etc., and aromatic vinyl monomers (styrene, vinyl toluene, α -Methylstyrene, etc.), polymerizable unsaturated dicarboxylic acids or derivatives thereof (itaconic acid,
Maleic acid, maleic anhydride, fumaric acid, lower alkyl esters or acid anhydrides thereof, maleimide, N-alkylmaleimide, N-phenylmaleimide, etc.). These copolymerizable monomers can be used alone or in combination of two or more.

Preferred copolymerizable monomers include vinyl ester monomers (such as vinyl acetate) and (meth) acrylic monomers [(meth) acrylic acid, (meth) acrylic acid C
_1-8 alkyl ester, C _1-4 alkylamino-C _2-4 alkyl (meth) acrylate, etc.], a nitrogen-containing heterocyclic vinyl monomer (such as vinylpyrrolidone), or a combination thereof.

(Meth) acrylonitrile copolymer
For example, acrylonitrile-vinylpyrrolidone
Polymer, acrylonitrile-vinyl acetate copolymer,
Lilonitrile-C_1-8Alkyl (meth) acrylate
Polymer (acrylonitrile-methyl acrylate copolymer
Body), acrylonitrile-vinylpyrrolidone-C
_1-8Alkyl (meth) acrylate copolymer, acrylo
Nitrile-vinyl acetate-C_1-8Alkyl (meth) acryl
Rate copolymer, acrylonitrile- (meth) acryl
Acid copolymer, acrylonitrile-vinyl acetate- (meth)
Acrylic acid copolymer, acrylonitrile-C_1-8Archi
(Meth) acrylate- (meth) acrylic acid copolymer
And the like.

As the (meth) acrylic ester-based polymer, homopolymers or copolymers of the above-mentioned (meth) acrylic esters [for example, poly (meth) acrylic acid, poly (meth)
_C1-18 alkyl acrylate homo- or copolymers (poly (methyl) methacrylate, poly (meth) ethyl acrylate, poly (butyl meth) acrylate, methyl methacrylate- (meth) acrylic acid copolymer (Meth) acrylic acid C _1-10 alkyl ester- (meth) acrylic acid copolymer, methyl methacrylate-acrylic acid C
Methacrylic acid C such as _1-10 alkyl ester copolymer
_1-10 alkyl ester-acrylic acid C _1-10 alkyl ester copolymer], (meth) acrylic monomer and copolymerizable monomer (vinyl ester monomer, aromatic vinyl monomer, Polymerizable unsaturated dicarboxylic acid or derivative thereof)
[E.g., (meth) acrylic acid C _1-10 alkyl ester-styrene copolymer such as methyl methacrylate-styrene copolymer, methyl methacrylate- (meth) acrylic acid-styrene copolymer, etc. (Meth) acrylic acid C _1-10 alkyl ester- (meth) acrylic acid-
Styrene copolymer etc.].

The porous layer may have a high wettability to the aqueous ink and have a hydrophilic surface sufficient for the aqueous ink to penetrate into the pores. Such a porous layer can be composed of a hydrophilic resin. In addition, the hydrophilic resin is
The contact angle is less than 80 ° (preferably 0 to 60 °, especially 0 to 60 °)
(Approximately 40 °). The contact angle is the angle between the tangent to the water droplet and the polymer surface at the intersection of the surface of the water droplet and the polymer surface at room temperature with the spread of the water droplet on the polymer surface stopped.

The thickness of the porous membrane is not particularly limited and can be selected according to the application, and is, for example, about 1 to 300 μm, preferably about 3 to 250 μm, and more preferably about 5 to 50 μm. If the film thickness is too small, the strength will be insufficient. [Ink Absorbing Layer] An ink absorbing layer may be interposed between the substrate and the porous layer.

The ink absorbing layer can be made of a substance capable of absorbing the ink or a solvent component of the ink, and is not particularly limited. In the ink jet recording system, since an aqueous ink is frequently used, the ink absorbing layer can be usually formed of a hydrophilic polymer (hydrophilic resin).

Examples of the hydrophilic polymer include a hydrophilic natural polymer or a derivative thereof (starch, corn starch, sodium alginate, gum arabic, gelatin,
Casein, dextrin, etc.), cellulose derivatives (methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, cellulose sulfate, cyanoethylcellulose, etc.), vinyl alcohol polymers (polyvinyl alcohol, ethylene-vinyl alcohol copolymer, etc.), ethylene polymer Copolymer (ethylene-maleic anhydride copolymer, etc.), vinyl acetate copolymer (vinyl acetate-methyl acrylate copolymer, etc.), polyalkylene oxide (polyethylene oxide, ethylene oxide-propylene oxide block copolymer, etc.) , A polymer having a carboxyl group or a sulfonic acid group or a salt thereof [acrylic polymer (poly (meth) acrylic acid or a salt thereof (alkaline such as ammonium and sodium) Metal salts), methyl methacrylate -
(Meth) acrylic acid copolymers, acrylic acid-polyvinyl alcohol copolymers, etc.), vinyl ether polymers (polyvinyl alkyl ethers such as polyvinyl methyl ether and polyvinyl isobutyl ether, methyl vinyl ether-maleic anhydride copolymers), Styrene-based polymers (styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, sodium polystyrenesulfonate, etc.), sodium polyvinylsulfonate, etc.], nitrogen-containing polymers (or cationic polymers)
Or salts thereof (quaternary ammonium salts such as polyvinylbenzyltrimethylammonium chloride and polydiallyldimethylammonium chloride, polydimethylaminoethyl (meth) acrylate hydrochloride, polyvinylpyridine, polyvinylimidazole, polyethyleneimine, polyamidepolyamine, polyacrylamide, polyvinylpyrrolidone) Etc.). These hydrophilic polymers can be used alone or in combination of two or more.

Among these hydrophilic polymers, cellulose derivatives (especially hydroxyethyl cellulose), vinyl alcohol polymers (especially polyvinyl alcohol, etc.), vinyl ester polymers (especially vinyl acetate copolymers, etc.), Pyrrolidone and the like are preferred.

Further, (1) a polyoxyalkylene unit,
(2) acetoacetyl group, (3) carboxyl group,
Also preferred are hydrophilic polymers having at least one functional group selected from (4) acid anhydride groups and (5) amino groups.

(1) The hydrophilic polymer having a polyoxyalkylene unit includes a vinyl ester polymer (polyoxyalkylene having a hydrophilic group such as an ether group) similar to the polymer constituting the porous membrane. -Vinyl acetate copolymer).

(2) The acetoacetyl group-modified hydrophilic polymer includes an acetoacetyl group-containing hydrophilic polymer formed by a reaction between a hydroxyl group-containing hydrophilic polymer and an acetoacetate ester, for example, an acetoacetyl group-modified hydrophilic polymer. Vinyl acetate copolymer (acetoacetyl group-containing polyvinyl alcohol, acetoacetyl group-containing cellulose derivative, etc.)
Is included.

(3) Carboxyl group-modified hydrophilic polymer includes (3a) carboxyl group-modified polyvinyl alcohol,
For example, a reaction between a vinyl ester (eg, vinyl acetate) and a carboxyl group-containing unsaturated monomer (eg, monocarboxylic acid such as (meth) acrylic acid, dicarboxylic acid such as maleic acid, or acid anhydride or monoalkyl ester thereof) (3b) carboxyl group-containing polysaccharides, such as partially saponified copolymers, for example, saponified styrene- (meth) acrylic acid copolymers, vinyl acetate- (meth) acrylic acid copolymers, etc. Carboxy C _1-4 alkyl cellulose, carboxymethyl dextran and the like.

(4) Acid anhydride group-containing hydrophilic polymers include:
Alkyl vinyl ether-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, (meth) acrylic ester-maleic anhydride copolymer and the like are included.

(5) Amino group-containing hydrophilic polymers include polyamide-polyamine, polyvinylamine, and poly (N-
Vinylformamide), amino group-containing polysaccharides, and the like.

A crosslinking agent may be added to the hydrophilic polymer in order to impart water resistance. The crosslinking agent is not particularly limited as long as it can crosslink the hydrophilic polymer. For example, when the hydrophilic polymer has a hydroxyl group, the crosslinking agent may be an organic crosslinking agent [a compound having a carboxyl group or an acid anhydride group (such as a polyvalent carboxylic acid or an acid anhydride thereof), or an aldehyde group]. Compounds, compounds having an epoxy group, nitrogen-containing compounds (amino resins such as urea resins, guanamine resins, and melamine resins; ethylenediamine, hexamethylenediamine, polyoxyalkylene-type diamines or polyamines (that is, polyether-type diamines or polyamines), etc. Aliphatic, alicyclic,
Inorganic cross-linking agents such as compounds having an acrylamide group, compounds having an isocyanate group (such as polyisocyanates and block-type polyisocyanates), and metal compounds [boric acid or borate (such as borax)] , Zirconium compounds (eg, salts with inorganic acids such as halides, sulfuric acid and the like, and organic acids such as acetic acid), titanium compounds (eg, alkoxides such as tetraethoxytitanate), aluminum compounds (eg, trimethoxyaluminate etc.) Alkoxides), phosphorus compounds (for example, phosphites, bisphenol A-modified polyphosphoric acid and the like), silane coupling agents (silicone compounds having a reactive functional group such as an alkoxy group and a glycidyl group), and the like; Polycarboxylic acid Its acid anhydride, metal compound, etc. are preferable. For example, when the hydrophilic polymer has a carboxyl group, a compound having an epoxy group, a compound having an isocyanate group, and a metal compound can be used. These crosslinking agents can be used alone or in combination of two or more.

When a polycarboxylic acid or a salt thereof, or a polycarboxylic acid anhydride is combined with a hydroxyl group-containing hydrophilic polymer, ink absorption, anti-blocking properties, image clarity (print quality) and water resistance can be obtained. Performance can be improved.

Examples of the polyvalent carboxylic acid include compounds having two or more carboxyl groups in the molecule, for example, aliphatic polycarboxylic acids (oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, C _2-10 aliphatic saturated polycarboxylic acids such as sebacic acid, fumaric acid, maleic acid, maleic anhydride,
Citraconic acid, mesaconic acid, etc. C _4-6 aliphatic unsaturated polycarboxylic acids such as itaconic acid), alicyclic polycarboxylic acid (1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydrophthalic acid, hymic acid C _8-10 alicyclic polycarboxylic acids, etc.), aromatic polycarboxylic acids (phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.
_8-12 Aromatic polycarboxylic acid or acid anhydride thereof), oxypolycarboxylic acid (C _3-6 oxypolycarboxylic acid such as tartronic acid, malic acid, tartaric acid, citric acid, etc.), nitrogen, oxygen and sulfur Heterocyclic polycarboxylic acids having at least one hetero atom selected from atoms (pyridine carboxylic acid, pyridine tricarboxylic acid, pyridine tetracarboxylic acid, isosaccharide acid, tropic acid, etc.) can be exemplified. These polycarboxylic acids include aliphatic, cycloaliphatic or aromatic C _2-10 polycarboxylic acids (particularly C _3-10 polycarboxylic acids).

More preferred polyvalent carboxylic acids are often water-soluble or water-dispersible, and are soluble in water at a temperature of 30 ° C. of 5 g or more (preferably 10 g or more, more preferably 30 g or more) in 100 g of water. It is a polycarboxylic acid. Such polycarboxylic acids include C _2-6 aliphatic polycarboxylic acids (particularly, C _3-5 aliphatic polycarboxylic acids). As the polycarboxylic acid, maleic acid or an acid anhydride thereof (maleic anhydride) is particularly preferred.

The polycarboxylic acid can be used as a salt, and a part or all of the carboxyl groups of the polycarboxylic acid may form a salt with a base. The polyvalent carboxylate includes a salt with an inorganic base (eg, an alkali metal such as ammonia, potassium, and sodium) and a salt with an organic base (eg, a tertiary amine).

Examples of the compound having an aldehyde group include compounds having a plurality of aldehyde groups, such as glyoxal, malondialdehyde, glutaraldehyde, terephthalaldehyde, dialdehyde starch, and acrolein copolymerized acrylic resin.

Examples of the compound having an epoxy group include compounds having a plurality of epoxy groups, for example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl. Ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, 1, 2-3, 4
-Diepoxybutane and the like.

A curing agent (a curing catalyst or a curing accelerator) may be added to the ink absorbing layer in order to promote a curing reaction. Examples of the curing agent include an organic tin compound, an organic aluminum compound, an organic titanium compound, an organic zirconium compound, an acidic compound, an acidic phosphate, and a mixture or a reaction product of the acidic phosphate and an amine. These curing agents can be used alone or in combination of two or more.

The amount of the curing agent used is in a range capable of promoting the curability, for example, 0.01 to 10 parts by weight, preferably 100 parts by weight, in terms of solid content, based on 100 parts by weight of the resin composition composed of a hydrophilic polymer. Is about 0.1 to 5 parts by weight.

The thickness of the ink-absorbing layer can be selected according to the application, for example, 5 to 50 μm, preferably 10 to 30 μm.
m, usually about 5 to 30 μm.

When the ink absorbing layer is provided, the thickness of the porous film is 1 μm or more (for example, about 1 to 15 μm), preferably about 1.5 to 12 μm.

The porous film and / or the ink-absorbing layer may be provided with a coloring agent (dye) for improving the fixability of the coloring agent (dye) as necessary.
It is advantageous to include a dye fixative, in particular a polymeric dye fixative. The dye fixing agent usually has a cationic group (particularly, a strong cation group of a guanidyl group or a quaternary ammonium salt type) in the molecule. The dye fixative may be water-soluble.

Examples of the dye fixing agent include dicyan fixing agents (eg, dicyandiamide-formalin polycondensate), polyamine fixing agents [for example, aliphatic polyamines such as diethylenetriamine, triethylenetetramine, dipropylenetriamine and polyallylamine, and phenylenediamine]. Such as aromatic polyamines, condensates of dicyandiamide and (poly) C _2-4 alkylene polyamines (such as polycondensates of dicyandiamide-diethylenetriamine), and polycationic fixing agents. Examples of the polycationic fixing agent include, for example, epichlorohydrin-di C
_1-4 alkylamine addition polymer (epichlorohydrin-
Dimethylamine addition polymer), polymer of allylamine or a salt thereof (polymer of polyallylamine or a hydrochloride thereof, for example, Nitto Boseki Co., Ltd., PAA-10C, PAA-HCl-3L, P
AA-HCl-10L, etc.), a polymer of diallyl C _1-4 alkylamine or a salt thereof (a polymer of diallylmethylamine or a hydrochloride thereof, for example, Nitto Boseki Co., Ltd., PAS-M-1 etc.),
A polymer of diallyl di C _1-4 alkyl ammonium salt (polymer of diallyl dimethyl ammonium chloride, such as Nitto Boseki Co., Ltd., PAS-H-5L, PAS-H-10L, etc.), diallylamine or a salt thereof and sulfur dioxide Copolymer of
(Diallylamine hydrochloride-sulfur dioxide copolymer, for example, Nitto Boseki Co., Ltd., PAS-92, etc.), diallyldi C _1-4
Alkyl ammonium salt-sulfur dioxide polymer (diallyldimethylammonium chloride-sulfur dioxide copolymer, for example, Nitto Boseki Co., Ltd., PAS-A-1, PAS-A-5, PA
SA-120L, PAS-A-120A, etc.), copolymers of diallyl di C _1-4 alkylammonium salts with diallylamine or salts or derivatives thereof (copolymers of diallyldimethylammonium chloride-diallylamine hydrochloride derivatives, for example, Nitto) Spinning Co., Ltd., PAS-880, etc.), polymers of di C _1-4 alkylaminoethyl (meth) acrylate quaternary salts,
Diallyldi C _1-4 alkylammonium salt-acrylamide copolymer (diallyldimethylammonium chloride-acrylamide copolymer, such as Nitto Boseki Co., Ltd., PAS-J-81, etc.), amine-carboxylic acid copolymer (for example, Nitto Boseki Co., Ltd., PAS-410, etc.). These dye fixing agents may be used alone or in combination of two or more.

The amount of the dye fixing agent used is within a range in which the fixing property can be improved, for example, 0.1 to 40 parts by weight, preferably 1 to 40 parts by weight, based on 100 parts by weight of the resin constituting the porous membrane in terms of solid content. It can be selected from the range of 30 parts by weight, more preferably about 2 to 20 parts by weight.

The porous film and / or the ink-absorbing layer may contain powders if necessary. By containing the powder, the printability and ink absorbability of the ink image receiving sheet are further improved. Examples of the powders include inorganic powders (silicon dioxide (white carbon, colloidal silica, etc.), particulate calcium silicate, zeolite, magnesium aminosilicate, calcined silica, particulate magnesium carbonate, particulate alumina, talc) , Kaolin, delamikaolin, clay, diatomaceous earth, heavy calcium carbonate, light calcium carbonate, zinc carbonate, magnesium carbonate, titanium dioxide, zinc oxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, magnesium silicate, aluminum silicate, sulfuric acid Mineral particles such as calcium, barium sulfate, sericite, bentonite, smectite, etc.), organic particles [polystyrene resin, acrylic resin,
Crosslinked or non-crosslinked organic fine particles such as urea resin, melamine resin, and benzoguanamine resin, and organic powders such as fine hollow particles]. One or more of these powders may be appropriately selected and used together. The average particle size is 10 nm to 20 μm, preferably 10 nm to 10 μm.
m (for example, 50 nm to 5 μm).

The content of the powder is 0.1 to 40 parts by weight per 100 parts by weight of the resin constituting the porous film or the ink absorbing layer.
Parts by weight (for example, 1 to 30 parts by weight), preferably 0.2
About 30 parts by weight (for example, 5 to 20 parts by weight),
Usually, it is about 1 to 20 parts by weight. The amount of powder added is 4
Exceeding 0 parts by weight is not preferred because the bonding strength of the porous membrane may decrease.

Further, the porous film and / or the ink absorbing layer may contain conventional additives such as a coating improver, a thickener, a lubricant, a stabilizer (an antioxidant, an ultraviolet absorber, a heat stabilizer, etc.), It may contain an antistatic agent, an antiblocking agent, and the like.

[Production Method of Ink Image Receiving Sheet] The production method of the porous film is not particularly limited. For example, a polymer (resin) such as a polymer is microphase-separated using a good solvent and a poor solvent. Phase change method, foaming method to form pores by foaming polymer such as polymer, stretching method to stretch polymer film, radiation irradiation method to irradiate polymer film with radiation to form pores, solvent An extraction method in which a film composed of a soluble polymer or an inorganic salt and a polymer insoluble in the solvent is formed, and an extraction method of forming a pore by extracting and removing a component soluble in the solvent, a polymer particle. A sintering method that partially fuses or solidifies with a binder or the like and uses a gap generated between particles as a hole can be used.

In the ink image receiving sheet of the present invention, in order to efficiently obtain the porous film having the above-mentioned specific structure, it is preferable that the ink receiving sheet is manufactured by a phase inversion method.

The porous membrane is made of, for example, a polymer (resin).
And a uniform dope (resin solution) containing a good solvent for the polymer and a poor solvent for the polymer, is cast or applied to a substrate, and the solvent is evaporated to cause phase separation. Can be produced by a wet phase inversion method, that is, casting or coating a dope (resin solution) containing at least a good solvent for the polymer (resin), and immersing in a poor solvent for the polymer. It is preferable to form a porous layer by causing phase separation to perform precise pore size control. By immersing in a poor solvent, a dense layer can be formed on the surface and a void extending in the thickness direction from the base material side can be formed.

In the above-mentioned manufacturing method, in order to control the structure of the porous film, the solvent in the dope may be a combination of a good solvent and a poor solvent.

The porous film may be formed directly on at least one surface of the substrate, or may be formed via an ink absorbing layer.

When the substrate is a non-permeable substrate, for example, a plastic film, a porous film may be formed and then laminated on the substrate.

A good solvent means one having solubility in a resin. Examples of the good solvent used in the phase inversion method include ketones (C _3-5 dialkyl ketone such as acetone, methyl ethyl ketone and methyl propyl ketone, cyclohexanone, etc.) and esters (formic acid) according to the kind of the polymer. Formic acid C _1-4 alkyl ester such as ethyl, methyl acetate, ethyl acetate, acetic acid C _1-4 alkyl ester such as butyl acetate, ethyl propionate,
Ethyl lactate, etc.), ethers (1,4-dioxane,
Cyclic or chain C _4-6 ethers such as tetrahydrofuran, tetrahydropyran, diethyl ether, diisopropyl ether, dimethoxyethane, etc., cellosolves (C _1-4 alkyl _- cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve), cellosolve acetates (C _1-4 alkyl-cellosolve acetate such as methyl cellosolve acetate and ethyl cellosolve acetate), aromatic hydrocarbons (benzene, toluene, xylene, etc.), halogenated hydrocarbons (methylene chloride,
Mono- or di-C _1-4 acylamides such as ethylene chloride, amides (acylamides such as formamide and acetamido), N-methylformamide, N-methylacetamido, N, N-dimethylformamide and N, N-dimethylacetamido ), Sulfoxides (di C _1-3 alkyl sulfoxide such as dimethyl sulfoxide),
Nitriles (acetonitrile, chloroacetonitrile,
Select from C _1-6 alkyl nitriles such as propionitrile and butyronitrile, benzonitrile), organic acids (formic acid, acetic acid, propionic acid, etc.), organic acid anhydrides (maleic anhydride, acetic anhydride, etc.), and mixtures thereof it can. Good solvents may include nitro compounds (nitromethane, nitroethane, nitropropane, etc.) and lower alcohols (C _1-4 alcohols such as methanol and ethanol, diacetone alcohols, etc.).

The good solvent can be selected according to the type of the resin.
For example, good solvents for the polysulfone polymer include amides (such as N, N-dimethylformamide and N, N-dimethylacetamide), sulfoxides (such as dimethyl sulfoxide), and mixtures thereof. Among the cellulose derivatives, preferred good solvents for cellulose esters include C _3-5 dialkyl ketones such as acetone (especially acetone and methyl ethyl ketone), and C _1-4 alkyl esters such as ethyl acetate (especially methyl acetate and ethyl acetate). ), Cyclic or linear C _4-6 ethers such as dioxane and dimethoxyethane, and C _1-4 such as methyl cellosolve.
Alkyl-cellosolves (especially methyl cellosolve, ethyl cellosolve), methylcellosolve acetate, etc.
_1-4 alkyl-cellosolve acetates (especially methyl cellosolve acetate, ethyl cellosolve acetate) and mixtures thereof. If the cellulose derivative is cellulose acetate, particularly preferred good least C _{3- 5} dialkyl ketones in solvents (particularly acetone), C _1-2 alkyl - cellosolves (particularly methyl cellosolve), and the solvent and the like.

Furthermore, the content of the resin in the resin solution constituting the porous membrane can be selected according to the degree of polymerization of the resin (polymer), and is, for example, 1 to 30% by weight, preferably 1 to 30% by weight.
It is about 25% by weight, especially about 3 to 20% by weight (for example, about 3 to 15% by weight).

The resin solution is prepared by adding 100 parts by weight of a good solvent solution containing about 5 to 30% by weight of the resin to 0 to 170% by weight of the poor solvent.
It may contain about parts by weight.

The resin solution (coating liquid) may contain conventional additives such as an antifoaming agent, a coating improver, a thickener, a lubricant, a stabilizer (an antioxidant) as long as the properties of the porous film are not impaired. , An ultraviolet absorber, a heat stabilizer, etc.), an antistatic agent, an antiblocking agent and the like.

[0076] The resin solution is applied to at least one of the substrates by a conventional casting or coating method such as a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater, a comma coater, a gravure coater, or a silk screen coater method. It is cast or coated on one side.

The poor solvent means a solvent having no solubility or low solubility in the resin.
There is no particular limitation. Examples of the poor solvent include water, esters, alcohols, ketones, ethers, aliphatic hydrocarbons, and mixtures thereof.

Preferred poor solvents for the polysulfone polymer include water, alcohols (eg, C _1-20 alkyl alcohols such as methanol, ethanol, isopropanol and butanol, polyhydric alcohols such as ethylene glycol, polyethylene glycol and glycerin), and C. _1-4 alkyl acetates which may have an alkoxy group (acetic acid 3
- methoxybutyl acetate, etc. C _1-4 alkoxy C _{3 -7} alkyl esters such as acetic acid 3-methoxy-pentyl), 2-
C _4-8 alkoxy C _1-4 alkyl alcohols such as butoxyethanol and 2-hexyloxyethanol; ketones (C _6-10 dialkyl ketones such as methyl butyl ketone, methyl isobutyl ketone, methyl pentyl ketone and methyl isopentyl ketone; Acetonylacetone, acetophenone) and the like.

Preferred poor solvents for cellulose derivatives include
Water, alcohol (C _1-20 alkyl alcohol such as methanol, ethanol, isopropanol, polyhydric alcohol, etc.), esters (C _5-8 alkyl formate,
At least one solvent selected from benzoic acid C _1-4 alkyl esters), C _4-8 cycloalkanols, C _6-10 dialkyl ketones and C _7-10 ethers.

After the ink image-receiving sheet is immersed in a poor solvent to form a microphase-separated structure, it may be washed and dried if necessary.

The ink image-receiving sheet obtained by the above-mentioned manufacturing method is useful as a recording sheet by an ink jet system for recording by flying small ink droplets. It can also be used as an ink sheet).

The ink image-receiving sheet of the present invention is excellent in ink absorbency and ink fixability, and provides clear images (print quality).
And is suitable for recording by inkjet.

[0083]

The ink image-receiving sheet of the present invention comprises:
Since it is composed of a porous layer having a dense layer on the surface and a void extending in the thickness direction on the side of the base material, the ink absorption is fast and the fixability is high. In addition, a clear image having high water resistance can be obtained.

[0084]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

The average pore size, porosity, void width, water resistance, printability, and ink absorbency of the ink image receiving sheets obtained in Examples and Comparative Examples were evaluated as follows.

For image formation, an ink jet printer (NOVAJET PRO manufactured by ENCAD) was used, and the ink image receiving sheets obtained in Examples and Comparative Examples were applied to the image receiving sheets.
Pigment type aqueous ink (yellow, magenta, cyan,
(Each color of black) was printed solid to form a recorded image.

[Average pore diameter and porosity] In an electron microscope surface photograph taken at a magnification of 5,000 times, 2 cm × 2 cm
The three arbitrary points were processed by an image processing apparatus, the hole diameters were measured with each hole being a perfect circle, and the average was determined to obtain an average hole diameter.

The porosity (%) was calculated by a formula (total area of holes / measured area) × 100.

[Void Width] The width of the void in the plane direction was determined by measuring and averaging the widths of ten voids in an electron micrograph taken at a magnification of 100 times.

[Water resistance] The printed portion was rubbed 10 times with a cotton swab sufficiently containing water at 25 ° C., and the printed portion was visually evaluated according to the following criteria.

◎ The printed portion remains completely. 滲 The bleeding is observed in the printed portion. × The printed portion does not remain. [Printability] The printed image forming portion was visually evaluated based on the following criteria.

◎ There is no bleeding and it is clear ○ Slight bleeding is generated X Intense bleeding is generated [Ink absorption] After printing, copy paper for PPC is placed on the printing unit at regular intervals and overloaded from the top of the copy paper. (250 g / cm ² ) for 10 seconds, the copy paper was peeled off, the degree of ink set-off was visually judged, and the ink absorption was evaluated based on the time until no set-off was observed.

◎ Time until no set-off was observed within 1 minute ○ Time until no set-off was detected × 3 minutes or less × Time until no set-off was recognized within 5 minutes Example 1 Polyether Sulfone ("Sumika Excel 5200
P "(manufactured by Sumitomo Chemical Co., Ltd.), 35 parts by weight of polyethylene glycol (# 200) were added to 65 parts by weight of a 20% by weight dimethyl sulfoxide solution with good stirring to prepare a dope. This dope was treated with a polyester nonwoven fabric (manufactured by Japan Vilene Co., Ltd., “MF-180K”, average fiber diameter 1).
5 μm, basis weight 180 g / m ² , thickness 200 μm, fiber density 900 kg / m ³ , air permeability 2.0 cm ³ / cm ² · s
ec), coating the dried porous film so as to have a thickness of 150 μm, leaving it to stand at 25 ° C. and 60% RH for 30 seconds, and immersing it in a coagulation bath filled with water at 40 ° C. for 2 minutes. , Phase change. Further, the ink was dried for about 1 minute under blowing at room temperature (about 20 ° C.) to obtain an ink image receiving sheet. FIG. 1 shows an electron micrograph of the surface (dense layer) of the porous film of the obtained ink receiving sheet, and FIG. 2 shows a micrograph of a cross section of the ink receiving sheet. As shown in FIGS. 1 and 2, the porous film has a dense layer on the surface, has voids extending in the thickness direction on the substrate side, and has an average pore diameter of 0.3 μm on the surface.
The porosity of the surface was 48.2%, and the void width was 13 μm.

Example 2 Polyacrylonitrile-based polymer (acrylonitrile content: 85 mol%) in 18% by weight dimethyl sulfoxide solution 9
0 parts by weight, 10 parts by weight of water is added with good stirring,
A dope was prepared. This dope was applied to the same polyester nonwoven fabric as in Example 1 so that the thickness of the porous layer was 100 μm, left at 20 ° C. and 90% RH for 10 seconds, and then filled with water at 50 ° C. It was immersed in a coagulation bath for 2 minutes and the phase was changed. Further, the ink was dried for about 1 minute under blowing at room temperature (about 20 ° C.) to obtain an ink image receiving sheet. The porous film of the obtained ink image receiving sheet has a dense layer on the surface, has voids extending in the thickness direction on the substrate side, the average pore diameter of the surface is 0.7 μm, and the porosity of the surface is 50.6
%, Void width was 54 μm.

Example 3 40 parts by weight of ethylene glycol was added to 60 parts by weight of a 30% by weight dimethyl sulfoxide solution of cellulose acetate (average degree of acetylation: 60.5, viscosity average degree of polymerization: 260) while stirring well. Prepared. This dope was prepared in Example 1.
To a non-woven polyester fabric as described above, so that the thickness of the porous layer after drying becomes 100 μm,
After being left for 30 seconds under the condition of H, it was immersed in a coagulation bath filled with water at 40 ° C. for 2 minutes to perform phase change. Further, the ink was dried for about 1 minute under blowing at room temperature (about 20 ° C.) to obtain an ink image receiving sheet. The porous film of the obtained ink receiving sheet has a dense layer on the surface, has voids extending in the thickness direction on the substrate side, the average pore diameter of the surface is 0.8 μm, and the porosity of the surface is 42.4%, and the void width was 59 μm.

Comparative Example 1 Cellulose acetate (average acetylation degree 55, viscosity average polymerization degree 17)
0) to 100 parts by weight of an 8% by weight methyl cellosolve solution,
13.7 parts by weight of 4-methylcyclohexanol was added to prepare a dope. This dope was applied to the same polyester nonwoven fabric as in Example 1 and the thickness of the porous film after drying was 50%.
μm, and dried at 40 ° C. and 90% RH for 10 minutes to obtain an ink image receiving sheet. The average pore diameter of the porous film surface of the obtained ink image receiving sheet is 0.2 μm,
The porosity was 39.3%, but no voids were formed.

Comparative Example 2 An ink image-receiving sheet was prepared in the same manner as in Example 1 except that the concentration of the dimethyl sulfoxide solution of polyether sulfone was changed to 15% by weight. The obtained ink image receiving sheet had no holes on the surface.

Comparative Example 3 Modified polyvinyl alcohol (Nippon Synthetic Chemical Industry Co., Ltd.)
100 parts by weight of aluminum oxide particles having a particle size of 10 μm were added to 100 parts by weight of a 5% by weight aqueous solution of “OKS7158G” manufactured by Kabushiki Kaisha, with a saponification degree of 88%) to prepare a coating solution.
This coating solution was applied to a polyethylene terephthalate film (Dupont Japan, Melinex 339, thickness 75 μm).
m) was applied so that the thickness of the porous film after drying was 20 μm, and dried at 120 ° C. for 3 minutes to obtain an ink image receiving sheet. The average pore diameter of the porous film surface of the obtained ink receiving sheet was 7.1 μm, and the porosity was 20.3%.
No voids were formed.

The printing characteristics of the ink image receiving sheets obtained in Examples and Comparative Examples were evaluated in accordance with the above evaluation. Table 1 shows the results.

[0100]

[Table 1]

As is clear from the table, in the ink image receiving sheet of the embodiment in which the porous film has the dense layer on the surface side and the void on the substrate side, any of the water resistance, the printability and the ink absorptivity can be obtained. Is also good. On the other hand, the sheets of Comparative Examples 1 and 3 in which the porous film does not have such a structure (in particular, does not have voids inside) have printability, water resistance,
None of the ink absorptivity is insufficient as compared with the embodiment. In particular, in Comparative Example 3, since the average pore diameter on the surface of the porous film was large, the sharpness (printability) of the image was poor due to excessive penetration of the pigment ink into the inside of the recording sheet. Further, in the sheet of Comparative Example 2 in which the porous film was not formed, all of the above characteristics were inferior to those of the example.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (5,000-fold magnification) of the surface of an ink image-receiving sheet obtained in Example 1.

FIG. 2 is an electron micrograph (at a magnification of 700) of a cross section of the ink image-receiving sheet obtained in Example 1.

Continuing on the front page F-term (reference) 2H086 BA02 BA15 BA22 BA34 BA41 4F074 AA02 AA48 AA49 AA87 CB91 CC28Y CC29X CC30X DA02 DA03 DA20 DA24 DA52 4F100 AJ06A AK02A AK25A AK27A AK41 AK55A AT00B BA02B12A01 E12B01B01A01 YY00A

Claims (9)

[Claims] 1. A sheet in which a porous film is laminated on at least one surface of a substrate, wherein the porous film has a dense layer on the surface and has voids extending in the thickness direction on the substrate side. Image receiving sheet. 2. An average pore diameter of pores in the dense layer is 0.01 to 2.
The ink receiving sheet according to claim 1, which has a thickness of 1.5 µm. 3. The width of the void in the plane direction is 0.1 to 100.
The ink image-receiving sheet according to claim 1, wherein the thickness of the image-receiving sheet is μm. 4. The ink image receiving sheet according to claim 1, wherein the porosity of the surface of the porous film is 20 to 70%. 5. The ink image receiving sheet according to claim 1, wherein the porous film is made of at least one selected from a cellulose derivative, a vinyl polymer and a polysulfone polymer. 6. The porous membrane according to claim 1, wherein the porous membrane is made of at least one selected from cellulose ester, (meth) acrylonitrile-based polymer, (meth) acrylate-based polymer and polysulfone-based polymer. Ink receiving sheet. 7. The ink image-receiving sheet according to claim 1, wherein the porous film has a micro-phase separation structure by a phase change method. 8. The ink image receiving sheet according to claim 1, wherein the substrate is a nonwoven fabric. 9. The method according to claim 1, wherein a porous film is formed by a phase inversion method after applying the resin solution on the substrate.