JP2000158798A - Ink image receiving sheet and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink image receiving sheet having a porous film excellent in strength, adhesive properties to a base material and ink absorbency or the like. SOLUTION: The ink image receiving sheet is constituted of a porous film having a mean pore size of at least one surface of 0.05 to 3 μm a pore fraction of a surface of 20 to 70%, and containing a urethane resin. The resin may be a cationic urethane resin. The film may be constituted of the urethane resin and a non-urethane resin, and a ratio of the urethane resin may be about 10 to 100 pts.wt. to 100 pts.wt. of the non-urethane resin. As the non-urethane resin, a cellulose resin, a vinyl polymer, a polysulfone polymer or the like can be used. The film may have a phase separation microstructure by a dry phase conversion. The sheet can be constituted of at least a porous film and manufactured by dry phase converting a coating film containing a thermoplastic resin composition containing an urethane resin, and a good solvent and a poor solvent to the composition, and forming the porous film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink image receiving sheet and a method for manufacturing the same. More specifically, the present invention relates to an ink image-receiving sheet having excellent ink absorbency, ink fixability, and printability 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, the ink absorption can be improved by providing the porous resin layer, but there is a limit to the improvement of the ink fixing property and the printing quality.

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-bearing layer made of pseudo-boehmite is provided thereon. 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 0.1 μm) is formed on the liquid absorbing layer. Polyethylene or polypropylene film with many holes)
Are laminated by a hot press. However, it does not disclose a method for preparing the porous thin film layer.

[0005] WO 98/25997 discloses a porous film composed of a cellulose derivative, a vinyl-type polymer, a polysulfone-based polymer and the like, and having a light transmittance of 30% or more at a wavelength of 400 nm. Has a microphase-separated structure.

When a recording sheet is actually used in a printer or the like, the strength of the porous film is important. Further, when a porous film is formed on a substrate, adhesion between the substrate and the porous film is required. However, in the recording sheet as described above, since the porous film itself does not have sufficient strength, there is a possibility that the recording sheet is easily scratched or broken.
Further, even if the strength is practically sufficient, it is difficult to improve the adhesion between the substrate and the porous film and also improve the ink fixing property unless the surface of the substrate is treated.

[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 low fixability to the ink receiving layer and, consequently, low water resistance.

[0008]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an ink receiving apparatus which is capable of improving the adhesion to a substrate, has excellent ink absorption, ink fixing properties and printability, and has improved image durability. It is to provide a sheet and a manufacturing method thereof.

It is another object of the present invention to provide an ink image receiving sheet having further improved ink absorbency and a method for producing the same. Still another object of the present invention is to provide an ink image receiving sheet capable of forming a high quality image even with a dye ink or a pigment ink, and a method of manufacturing the same.

[0010]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and have found that a porous film contains a urethane-based resin using a urethane-based resin and a non-urethane-based resin. And found that the strength of the porous film and the adhesion between the porous film and the substrate can be significantly improved, and thus completed the present invention.

That is, the ink image receiving sheet of the present invention comprises:
The average pore diameter of at least one surface is 0.05 to 3 μm
m, a porous film having a porosity of 20 to 70% on the surface and containing at least a urethane resin. The urethane-based resin may be a cationic urethane-based resin. In the porous membrane, the pores may increase from the one surface to the other surface, and the average pore diameter of the other surface may be 2 to 20 times the average pore diameter of the one surface. The porous membrane may be composed of a urethane-based resin and a non-urethane-based resin, and the ratio of the urethane-based resin may be about 10 to 100 parts by weight based on 100 parts by weight of the non-urethane-based resin. As the non-urethane resin, a cellulose resin, a vinyl polymer, a polysulfone polymer, or the like can be used. The porous membrane may have a micro phase separation structure by dry phase inversion. The porous film may be formed on at least one surface of the substrate in a state where pores having an average pore diameter of 0.05 to 3 μm are located on the surface, and an ink may be formed between the porous film and the substrate. An absorbing layer may be formed.

The ink image-receiving sheet of the present invention can be constituted by at least the above-mentioned porous film, and a dry phase inversion of a coating film containing a thermoplastic resin composition containing a urethane resin and a good solvent and a poor solvent for the resin composition. Then, it can be manufactured by forming the porous film.

In the present specification, the non-urethane-based resin refers to a resin other than the urethane-based resin.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. [Porous film] The porous film constituting the ink image-receiving sheet of the present invention comprises a urethane resin and a non-urethane resin.

The urethane resin can be composed of a urethane polymer obtained by reacting a diisocyanate component with a polyol component. In the above reaction, a diamine component may be used as a chain extender, if necessary. The urethane polymers can be used alone or in combination of two or more.

The diisocyanate component includes, for example, aromatic diisocyanates (for example, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane
4,4′-diisocyanate, etc.), araliphatic diisocyanate (eg, xylylene diisocyanate), alicyclic diisocyanate (eg, isophorone diisocyanate), aliphatic diisocyanate (eg, 1,6-hexamethylene diisocyanate, lysine diisocyanate) Etc.) are included. The diisocyanate component can be used alone or in combination of two or more. The diisocyanate component may be an adduct, and if necessary, may be used in combination with a polyisocyanate component such as triphenylmethane triisocyanate.

The polyol component includes, for example, polyester polyol, polyether polyol, polycarbonate polyol and the like. Among the polyols, diols (polyester diol, polyether diol, polycarbonate diol, etc.) are particularly preferable. The polyol components can be used alone or in combination of two or more.

The polyester diol is not limited to the reaction with diol, dicarboxylic acid or its reactive derivative (lower alkyl ester, acid anhydride), but may be derived from lactone. Diols include, for example, aliphatic diols (eg, ethylene glycol, trimethylene glycol,
C _2-10 alkylene diols such as propylene glycol, 1,3-butanediol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, polyoxy C _2-4 alkylene glycols such as diethylene glycol and triethylene glycol, etc.), alicyclic Diols and aromatic diols. The diols can be used alone or in combination of two or more. The diol may be used in combination with a polyol such as trimethylolpropane or pentaerythritol, if necessary.
The diol is usually an aliphatic diol.

Examples of the dicarboxylic acid include aliphatic dicarboxylic acids (eg, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, etc.), alicyclic dicarboxylic acids, and aromatic dicarboxylic acids (eg, phthalic acid) , Terephthalic acid, isophthalic acid, etc.). The dicarboxylic acids can be used alone or in combination of two or more. The dicarboxylic acid may be used in combination with a polycarboxylic acid such as trimellitic acid, if necessary.

Lactones include, for example, butyrolactone,
It includes valerolactone, caprolactone, laurolactone, and the like, and can be used alone or in combination of two or more. The urethane-based polymer may be a polyether-type urethane-based polymer using a polyether diol (such as polyoxytetramethylene glycol) as a diol component, but at least a polyester diol (particularly, a reaction component mainly containing an aliphatic component). Polyester-type urethane-based polymer (for example, C _2-6 alkylene diol such as 1,4-butane diol), C _4-12 aliphatic dicarboxylic acid such as adipic acid, and isophthalic acid It is preferable to use a polyester diol obtained by reaction with an acid or phthalic acid or a urethane resin obtained by reacting a polyester diol derived from the lactone with a diisocyanate such as isophorone diisocyanate).

The urethane resin may be used as an organic solvent solution, an aqueous solution, or an aqueous emulsion. The aqueous solution or the aqueous emulsion of the urethane resin may be prepared by dissolving or emulsifying and dispersing the urethane resin using an emulsifier, such as a free carboxyl group or a tertiary amino group in the molecule of the urethane resin. It may be prepared by introducing an ionic functional group and dissolving or dispersing the urethane resin using an alkali or an acid. Such a urethane-based resin having a free carboxyl group or a tertiary amino group introduced into a molecule thereof is obtained by reacting a diisocyanate component with a diol component (particularly, a polymer diol) having a free carboxyl group or a tertiary amino. can get. The diol having a free carboxyl group (particularly, a polymer diol) is, for example, a diol component and a polycarboxylic acid having three or more carboxyl groups or an anhydride thereof (for example,
Reaction with polybasic acid anhydrides such as pyromellitic anhydride, etc.) and polycarboxylic acids having sulfonic acid groups (such as sulfoisophthalic acid), and ring-opening polymerization of lactones using dimethylolpropionic acid as an initiator And the like. Further, a diol having a tertiary amino group (particularly, a polymer diol) can be prepared by ring-opening polymerization of an alkylene oxide or a lactone using N-methyldiethanolamine or the like as an initiator. Tertiary amino groups may form quaternary ammonium salts.

Preferred urethane resins are, for example, cationic urethane resins (cationic urethane resins) such as urethane polymers into which the tertiary amino group or quaternary ammonium salt has been introduced. Such cationic urethane resins include, for example, Permarin UC-
20 (manufactured by Sanyo Chemical Industries, Ltd.) or the like may be used.

The non-urethane resin is not particularly limited, and various non-urethane resins (thermoplastic resins and thermosetting resins) can be used.
A film-forming thermoplastic 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; cellulose ethers such as mixed acid esters such as cellulose nitrate acetate; for example, methyl cellulose, ethyl cellulose, isopropyl cellulose, butyl cellulose, benzyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, cyanoethyl cellulose Preferred cellulose derivatives such as cellulose esters, for example,
Cellulose organic acid esters (for example, esters with organic acids having about 2 to 4 carbon atoms), especially cellulose acetate (cellulose diacetate, cellulose triacetate, etc.) are included.

The viscosity average degree of polymerization of the cellulose derivative (eg, cellulose ester) is, for example, 50 to 800, preferably 75 to 500, and more preferably 100 to 250.
(Especially 100 to 200). Viscosity average degree of polymerization 1
Cellulose acetate of about 00 to 190 can also be used effectively.

The viscosity-average degree of polymerization of cellulose esters such as cellulose acetate is determined by the limiting viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, Journal of the Textile Society, Vol. 18, No. 1, 105-105).
120, 1962). That is,
A precisely weighed cellulose ester is dissolved in a mixed solution of methylene chloride / methanol = 9/1 (weight ratio) to prepare a solution having a predetermined concentration c (2.00 g / L). This solution is poured into an Ostwald viscometer, and the time (second) t during which the solution passes between the marking lines of the viscometer at 25 ° C. is measured. on the other hand,
For the mixed solvent alone, the transit time (second) t ₀ is measured in the same manner as above, and the viscosity average polymerization degree is calculated according to the following equation.

Η _rel = t / t ₀ [η] = (ln η _rel ) / c DP = [η] / (6 × 10 ^-4 ) (where, t is the solution transit time (sec), and t ₀ is The solvent transit time (seconds), c is the cellulose ester concentration of the solution (g /
L), η _rel is the relative viscosity, [η] is the intrinsic viscosity, DP is the average degree of polymerization.) The average degree of substitution of the cellulose derivative is 1
It can be selected from a range of about 3 to 3. For example, in a preferred cellulose acetate, for example, the average acetylation degree 42 to 62
% (43 to 60%), preferably about 42 to 57%. If the degree of substitution (degree of acetylation) is too small, the solubility in the solvent will decrease. On the other hand, if the viscosity average degree of polymerization is too small, the pore size of the porous membrane becomes small, and it tends to become a non-porous membrane. If it is too large, the pore size tends to become large.

Vinyl polymer: an olefin polymer, for example, an olefin homo- or copolymer (poly 1-butene, polyisobutene, polybutadiene, polyisoprene, ethylene-propylene copolymer, etc.), copolymerized with oleophiles Copolymers with hydrophilic monomers (ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer,
Ethylene- (meth) acrylate copolymer, modified polyolefin, etc.) Halogen-containing vinyl polymer, for example, halogen-containing vinyl monomer alone or copolymer (polyvinyl chloride, polyvinylidene chloride, etc.), halogen-containing vinyl monomer Copolymer of monomer and copolymerizable monomer (vinyl chloride-vinyl acetate copolymer, vinylidene chloride-vinyl acetate copolymer, vinylidene chloride- (meth) acrylamide copolymer, vinylidene chloride- (meth) Acrylic acid copolymers, vinylidene chloride- (meth) acrylate copolymers, etc.) vinyl ester polymers or derivatives 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, homo- or copolymer (polystyrene, poly (α- Methylstyrene), poly (4-chlorostyrene), etc., copolymers of aromatic vinyl monomers and copolymerizable monomers (styrene- (meth) acrylic acid C _1-10 alkyl ester copolymers, 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-
Polymethyl vinyl ethers such as polyvinyl methyl ketone, polyvinyl methyl isobutyl ketone, and polymethyl isopropenyl ketone, such as polymethyl vinyl ether, methyl vinyl ether-maleic anhydride copolymer, etc. ) Acrylic polymers, for example,
Homogenous or copolymer of (meth) acrylic monomer [(meth) acrylonitrile, (meth) acrylate monomer, etc.], (meth) acrylic monomer and copolymerizable monomer [vinyl ester] Monomer, a heterocyclic vinyl monomer, an aromatic vinyl monomer, a vinyl monomer such as a polymerizable unsaturated dicarboxylic acid or a derivative thereof], (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
Polyacrylonitrile, polymethacrylonitrile,
A copolymer of (meth) acrylonitrile and a copolymerizable monomer is included. As the copolymerizable monomer, for example,
Vinyl ester monomers (vinyl formate, vinyl acetate, vinyl propionate, etc.), (meth) acrylic monomers [(meth) acrylic acid, methyl (meth) acrylate,
C _1-10 alkyl (meth) acrylates such as ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2- (meth) acrylate Hydroxyalkyl (meth) acrylates such as hydroxyethyl and 2-hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and diethylaminopropyl (meth) acrylate Alkylamino-alkyl (meth) acrylate, (meth) acrylamide, N-methyl (meth) acrylamide, methylol (meth) acrylamide, alkoxymethyl (meth) acrylamide, etc.), heterocyclic vinyl monomer (vinyl Pyrrolidone, vinyl pyridine,
5- to 6-membered heterocyclic vinyl-based monomers containing at least one hetero atom selected from nitrogen, oxygen and sulfur, such as vinylpiperidine, vinylimidazole and vinylcarbazole), aromatic vinyl monomers (Styrene, vinyltoluene, 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.

(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) acrylate-based polymer, a homo- or copolymer of the above-mentioned (meth) acrylate [eg, poly (meth) acrylic acid, poly (meth) acrylate]
_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.].

Polysulfone polymer: polysulfone, polyether sulfone, etc. Polyoxide polymer: polyoxymethylene or polyoxymethylene copolymer (polyacetal resin), polyoxyethylene, polyoxypropylene, polyoxyethylene-polyoxypropylene copolymer Polyamide and polyimide polymer: 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: 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. The ratio of the urethane resin is 1 to 100 parts by weight of the non-urethane resin.
It is about 0 to 100 parts by weight, preferably about 20 to 80 parts by weight, and more preferably about 30 to 60 parts by weight.

In the porous film composed of the polyurethane resin and the non-urethane resin, the average pore diameter on at least one surface is 0.05 to 3 μm, preferably 0.1 to 3 μm.
To 3 μm, more preferably about 0.3 to 2.5 μm. When the average pore diameter is less than 0.05 μm, the ink is hardly absorbed by the pores, and the drying property, the ink fixing property and the durability of the image are reduced. When the average pore diameter exceeds 3 μm, the sharpness of the image and the strength of the coating film are reduced. descend.

The pore diameter of the porous membrane is not particularly limited and may be uniform or non-uniform, and the pore diameter increases from at least one surface to the other surface in the thickness direction. It may be. In such a porous membrane, the pore diameter of the pores on the other surface is generally larger than the pores on the other surface. Therefore, at the time of printing, the ink (such as a water-based ink which may be a pigment ink or the like) flying on the one surface passes through the pores on one surface side and becomes relatively large on the other surface side. Because it is quickly absorbed by the pores, a clear image can be obtained,
The apparent dry state of the sheet surface can be obtained faster.

The maximum pore size in the porous membrane is 2 to 20 times, preferably 5 to 15 times, the average pore size on the one surface.
And more preferably about 7 to 10 times. When the maximum pore diameter is less than twice, the ink is hardly absorbed by the pores, and the drying property, the ink fixing property, and the durability of the image decrease. When the maximum pore diameter exceeds 20 times, the sharpness of the image decreases. There is a fear.

The ink absorbency is also affected by the porosity of the porous film. In the porous membrane, the porosity of the membrane surface is 20
To 70%, preferably about 30 to 60%. If the porosity is less than 20%, the surface area of the absorbing surface is small, so that the absorbing ability of the film to ink is low. If it exceeds 70%, the strength of the porous film itself may be reduced.

The porous layer may be transparent, translucent or opaque. In the present invention, by adjusting the pore size and the porosity, it is possible to obtain a highly transparent porous film depending on the application. A highly transparent porous membrane has, for example, a maximum pore size of 0.4 μm or less and an average pore size of
It is about 0.1 to 0.2 μm. Such an ink image-receiving sheet has a light transmittance at a wavelength of 400 nm of 55% or more (that is, 55 to 100%), preferably 60 to 10%.
0%, more preferably 70-100%, especially 75-1
If it is about 00%, it is also useful as an OHP sheet. When importance is placed on transparency, the porosity of the porous film is, for example, 20 to 70%, preferably 20 to 60% (for example,
(20-45%).

The porous membrane is made of the resin as described above, and may have a microphase separation structure, particularly a microphase separation structure by dry phase conversion. This microphase-separated structure is formed by coagulation of the gel phase separated by the composition change of the resin solution cast, and the shape of the pores formed between the particles is usually irregular, irregular and irregular. It is circular.

The porous layer may have 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. For example, it is 1 to 100 μm, preferably 2 to 70 μm (eg, 3 to 50 μm), and more preferably about 5 to 50 μm. . If the film thickness is too small, the strength will be insufficient. Further, when an ink receiving sheet having high transparency is desired, if the film thickness exceeds 100 μm, the transparency may be reduced.

In the ink receiving sheet of the present invention, a porous film may be formed on at least one surface of the substrate. When the pores in the porous film become larger from one surface to the other surface, the porous film may be formed so that the other surface is in contact with the base material, and the base material and the porous film may be further formed. An ink absorbing layer may be interposed between them. [Substrate] The material of the substrate is not particularly limited, and a substrate having a two-dimensional structure that may be any of transparent, translucent, and opaque, such as paper, coated paper, nonwoven fabric, and plastic film And the like, and among these, a plastic film is preferable. For example, when used for an overhead projector (OHP), the substrate is typically a transparent plastic film. Examples of the polymer constituting the plastic film include polyolefins such as polyethylene and polypropylene, poly (meth) acrylate, polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, cellulose derivatives such as cellulose acetate, and polyester (polyethylene terephthalate). , Polyalkylene terephthalate such as polybutylene terephthalate, polyalkylene naphthalate such as polyethylene naphthalate, polybutylene naphthalate, etc.), polycarbonate, polyamide (polyamide 6, polyamide 6/6, polyamide 6/10, polyamide 6/12, etc.) , Polyester amide, polyimide, polyamide imide and the like,
Further, these copolymers, blends and crosslinked products may be used.

Of these films, polyolefins (especially, polypropylene, etc.), polyesters (especially, polyethylene terephthalate, etc.), polyamides and the like are usually used. In particular, polyester (especially, polyethylene) is preferred in terms of mechanical strength and workability. 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 thickness of the substrate can be selected as desired by those skilled in the art depending on the application. However, in consideration of forming an image by inserting it into an ink jet printer, for example,
It can be selected from a range of about 20 to 200 μm, preferably about 50 to 170 μm, and more preferably 80 to 150 μm.
It is about μm. If the thickness of the base material is less than 20 μm, insertion into the printer, warpage of the sheet, and handling of the sheet may be difficult due to the strength and rigidity. If the thickness of the base material is more than 200 μm, the price per sheet increases, and the weight of the sheet increases. Due to the increase, the portability of a large number of sheets is likely to decrease.

When a porous film is provided on a substrate, the thickness of the porous film is 1 μm or more (for example, about 1 to 15 μm),
Preferably it is about 1.5 to 12 μm. [Ink Absorbing Layer] The ink absorbing layer can be made of a substance capable of absorbing 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 generally 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, sodium, etc.) 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), vinyl ester polymers (especially vinyl acetate copolymer), polyvinyl acetate 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 the reaction of a hydroxyl group-containing hydrophilic polymer with 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) The hydrophilic polymer containing an acid anhydride group includes:
Alkyl vinyl ether-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, (meth) acrylic ester-maleic anhydride copolymer and the like are included.

(5) Examples of the amino group-containing hydrophilic polymer 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 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 polycarboxylic acids are often water-soluble or water-dispersible, and at a temperature of 30 ° C., 5 g or more (preferably 10 g or more) per 100 g of water.
(More preferably 30 g or more). Such polycarboxylic acids include C _2-6
And 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 group 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 (curing catalyst or 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 porous film and / or the ink absorbing layer may contain a dye fixing agent, if necessary. Also,
The porous film and / or the ink absorbing layer may be treated (impregnated, dipped, etc.) with a dye fixing agent. When a dye fixing agent is used, for example, even if a dye ink is used, the fixing property of the dye,
The sharpness of the image and the durability of the image can be improved. The dye fixing agent (polymer dye fixing agent) usually has a cationic group (particularly, a guanidyl group or a strong quaternary ammonium salt type cationic group) 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 [such as aliphatic polyamines such as diethylenetriamine, triethylenetetramine, dipropylenetriamine, and polyallylamine; Such as aromatic polyamines, condensates of dicyandiamide and (poly) C _2-4 alkylene polyamine (eg, dicyandiamide-diethylenetriamine polycondensate), 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, etc.), 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,
PAA-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), diallyldiamine Polymers of C _1-4 alkyl ammonium salts (polymers of diallyl dimethyl ammonium chloride, such as Nitto Boseki Co., Ltd., PAS-H-5L, PAS-H-10L, etc.), and diallylamine or a salt thereof with sulfur dioxide Copolymer (diallylamine hydrochloride-sulfur dioxide copolymer, such as Nitto Boseki Co., Ltd., PAS-92), diallyl di C _1-4 alkylammonium salt-sulfur dioxide copolymer (diallyldimethylammonium chloride-sulfur dioxide) Copolymers, for example, Nitto Boseki Co., Ltd., PAS-A-1,
PAS-A-5, PAS-A-120L, PAS-A-120A, etc.), copolymer of diallyldi C _1-4 alkylammonium salt and diallylamine or a salt or derivative thereof (diallyldimethylammonium chloride-diallylamine hydrochloride derivative) Copolymer, for example, Nitto Boseki Co., Ltd., PAS-880),
Diallyl di C _1-4 alkyl ammonium salt polymer, di C
Polymer of _1-4 alkylaminoethyl (meth) acrylate quaternary salt, diallyldi C _1-4 alkylammonium salt-
Acrylamide copolymer (diallyldimethylammonium chloride-acrylamide copolymer, for example, Nitto Boseki Co., Ltd., PAS-J-81), amine-carboxylic acid copolymer (for example, Nitto Boseki Co., Ltd., PAS-410) Etc.) can be exemplified. 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 fixability can be improved, for example, 0.1 to 40 parts by weight, preferably 1 to 30 parts by weight, based on 100 parts by weight of resin in terms of solid content.
More preferably, it can be selected from the range of about 2 to 20 parts by weight.

In the ink absorbing layer, if necessary,
Other components, for example, an aqueous emulsion (for example, an acrylic resin emulsion, an ethylene-vinyl acetate copolymer emulsion, a vinyl acetate emulsion, etc.) may be contained.

The porous film and / or the ink absorbing layer may contain a powder (eg, a pigment). Examples of the powders include inorganic powders (white carbon, particulate calcium silicate, zeolite, magnesium aminosilicate, calcined silica, particulate magnesium carbonate, particulate alumina, silica, talc, kaolin, delamikaolin, Clay, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, magnesium silicate, calcium sulfate, mineral powder such as sericite, bentonite, smectite, etc.) And organic powders [crosslinked or non-overseas organic fine particles such as polystyrene resin, acrylic resin, 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. In the case of using a powdery or granular material, the hydrophilic polymer (hydrophilic resin) is used as the binder resin.
Can be used.

The ratio of the powder and the granule to the binder resin is, for example, 0.1 wt.
To 80 parts by weight, preferably about 0.2 to 50 parts by weight. The porous film and / or the ink-absorbing layer may be formed of a conventional additive such as an antifoaming agent, a coating improver, a thickener, a lubricant, a stabilizer (an antioxidant, an ultraviolet absorber) as long as the properties are not impaired. , Heat stabilizers, etc.), antistatic agents, anti-blocking agents and the like.

The thickness of the ink absorbing layer can be selected according to the intended use, and is, 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 1.5 to 1 μm.
It is about 2 μm.

In the ink receiving sheet of the present invention, since the porous film is composed of a urethane resin and a non-urethane resin, the strength of the porous film and the adhesion to the substrate or the ink absorbing layer are greatly improved. As a result, the strength of the ink image receiving sheet is improved. [Production Method of Ink Image Receiving Sheet] The ink image receiving sheet of the present invention is obtained by dry phase inversion of a coating film containing a thermoplastic resin composition containing a urethane resin and a good solvent and a poor solvent for the resin composition. It can be manufactured by forming a porous film. Further, the porous film may be formed in a state where pores having an average pore diameter of 0.05 to 3 μm are located on at least one surface of the base material, and the porous film may be formed on at least one surface of the base material. An ink absorbing layer may be formed, and a porous film may be formed on the ink absorbing layer.

The porous membrane is produced by a microphase separation method, for example, a wet phase separation method in which a good solvent solution of a resin constituting the porous membrane is cast or applied and immersed in a poor solvent for the resin. Although possible, the dry phase inversion method, that is, a thermoplastic resin composition containing a urethane resin, a good solvent for the resin composition, and a uniform dope containing a poor solvent for the resin composition as a base material It can be produced by casting or coating and evaporating the solvent to cause microphase separation. In particular, in the dry phase inversion method, it is important to use a solvent having a higher boiling point than the good solvent (high boiling point solvent) as the poor solvent.

In the dry phase separation process, it is important to select a good solvent and a poor solvent in order to control the pore size of the porous membrane and obtain a porous membrane having the above characteristics. Examples of the good solvent include ketones (eg, C _3-5 dialkyl ketone such as acetone, methyl ethyl ketone, and methyl propyl ketone, and cyclohexanone) according to the type of the resin.
Esters (formic acid C _1-4 alkyl esters such as ethyl formate, methyl acetate, ethyl acetate, acetic acid C _1-4 alkyl ester such as butyl acetate, ethyl propionate, ethyl lactate), ethers (1,4- dioxane Cyclic or chain C _4-6 ethers such as tetrahydrofuran, tetrahydropyran, diethyl ether, diisopropyl ether, dimethoxyethane), cellosolves (C _1-4 alkyl-cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve), cellosolve acetate (C _1-4 alkyl-cellosolve acetate such as methyl cellosolve acetate, ethyl cellosolve acetate), aromatic hydrocarbons (benzene, toluene, xylene, etc.), halogenated hydrocarbons (methylene chloride, ethylene chloride, etc.), amides Kind Formamide, acyl amides, such as acetamide, N- methyl formamide, N
Mono- or di-C such as -methylacetamide, N, N-dimethylformamide, N, N-dimethylacetamide
_1-4 acyl amides), sulfoxides (di-C _1-3 alkyl sulfoxides such as dimethyl sulfoxide), nitriles (acetonitrile, chloroacetonitrile, propionitrile, C _1-6 alkyl nitriles such as butyronitrile, and benzonitrile), organic Acids (formic acid, acetic acid,
Propionic acid, etc.), organic acid anhydrides (maleic anhydride,
Acetic anhydride), and mixtures thereof. 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, preferred good solvents for cellulose derivatives include C _3-5 dialkyl ketones such as acetone (especially acetone,
Methyl ethyl ketone), acetic acid C _1-4 alkyl esters such as ethyl acetate (in particular methyl acetate, ethyl acetate), dioxane, cyclic, such as dimethoxyethane or linear C _4-6
C _1-4 alkyl such as ethers and methyl cellosolve;
Cellosolves (especially methyl cellosolve, ethyl cellosolve), C _1-4 alkyl such as methyl cellosolve acetate -, and the like cellosolve acetates (especially methyl cellosolve acetate, ethyl cellosolve acetate) and mixed solvents thereof. When the cellulose derivative is cellulose acetate, particularly preferred good solvents include at least C _3-5 dialkyl ketones (particularly acetone),
Solvents including C _1-2 alkyl-cellosolves (among others, methyl cellosolve) are included.

The boiling point of the good solvent is 35 to 200 ° C. (for example, 35 to 180 ° C.), preferably 35 to 170 ° C. (for example, 35 to 160 ° C.), more preferably 40 to 16 ° C.
It can be selected from a range of about 0 ° C (for example, 40 to 125 ° C), and is usually 35 to 150 ° C (for example, 35 to 130 ° C).
It is about.

The temperature at which the vapor pressure of the good solvent reaches 200 mmHg is 10 to 70 ° C., preferably about 10 to 50 ° C. Poor solvent means that it has no solubility in resin,
Alternatively, it means a solvent having low solubility, and any solvent can be used as long as it has a higher boiling point than the above-mentioned good solvent. Therefore, the type of the poor solvent is not particularly limited. Examples of the poor solvent include esters (C _5-8 alkyl formate such as amyl formate and isoamyl formate, butyl acetate, amyl acetate,
C _2-4 aliphatic carboxylic acid which may have a C _1-4 alkoxy group such as hexyl acetate, octyl acetate, 3-methoxybutyl acetate, 3-ethoxybutyl acetate, butyl propionate, and 3-methoxybutyl propionate Acid C _3-10 alkyl esters (eg, C _4-10 alkyl acetate optionally having a C _1-4 alkoxy group), methyl benzoate, ethyl benzoate, benzoic acid C _1- such as propyl benzoate and the like. C4 alkyl groups such as _4- alkyl esters) and alcohols (cyclopentanol, cyclohexanol, methylcyclohexanol, dimethylcyclohexanol, cyclooctanol and the like, which may be substituted by C _1-4 alkyl groups)
_4-8 cycloalkanols, amyl alcohol, isoamyl alcohol, C _5-8 alcohols such as hexyl alcohol, 2-butoxyethanol, C _2-6 alkoxy -C _1-4 alcohols such as 3-butoxy propanol,
Heterocyclic alcohols such as furfuryl alcohol, etc.), ketones (methyl butyl ketone, methyl isobutyl ketone, methyl pentyl ketone, methyl isopentyl ketone, 2,6-dimethyl-4-heptanone, etc.
_3-10 dialkyl ketones (especially C _6-10 dialkyl ketones), acetonylacetone, acetophenone, etc., ethers (C _7-10 ethers such as methylphenyl ether, methoxytoluene, dibutyl ether, benzyl ethyl ether), aliphatics Hydrocarbons ( _C5-20 aliphatic hydrocarbons such as hexane, octane, nonane, and decane)
And mixtures thereof.

Preferred poor solvents for cellulose derivatives include
Esters (C _5-8 alkyl formate, benzoic acid C
_At least one solvent selected from C _4-8 cycloalkanols, C _6-10 dialkyl ketones and C _7-10 ethers, especially at least C
Solvents containing _5-7 cycloalkanols (especially cyclohexanols) are included. Cyclohexanols include cyclohexanol, methylcyclohexanol,
Mono- or di-C _1-2 alkyl substituents such as dimethylcyclohexanol are included.

The boiling point of the poor solvent is usually from 100 to 230.
° C, preferably about 120 to 200 ° C. The poor solvent is usually at least 20 ° C (20 to 60 ° C)
Degree), preferably about 30 to 50 ° C.

The temperature at which the poor solvent has a vapor pressure of 200 mmHg is 50 to 200 ° C., preferably 70 to 150 ° C.
It is about. The difference in temperature at which the vapor pressure of each of the good solvent and the poor solvent reaches 200 mmHg is 50 to 200.
° C, preferably about 70 to 150 ° C.

The ratio between the good solvent and the poor solvent is not particularly limited as long as a homogeneous solution of the resin can be formed.
1 to 200 parts by weight of the poor solvent (eg, 2 parts by weight)
To 200 parts by weight), preferably 3 to 180 parts by weight (for example, 5 to 180 parts by weight), more preferably 5 to 170 parts by weight.
Parts by weight (for example, 10 to 170 parts by weight), and usually about 5 to 150 parts by weight.

Further, the content of the resin in the dope solution can be selected according to the degree of polymerization of the resin (polymer).
-30% by weight, preferably 3-25% by weight, especially 3-2%
It is about 0% by weight (for example, 3 to 15% by weight).

The dope solution contains about 5 to 170 parts by weight of a poor solvent with respect to 100 parts by weight of a good solvent solution containing about 5 to 30% by weight of a resin. The dope is preferably a resin 5
With respect to 100 parts by weight of a good solvent solution of about 20 to 20% by weight (particularly 5 to 15% by weight),
It can be prepared by adding about 170 parts by weight (preferably 5 to 150 parts by weight).

The dope solution (coating solution) 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.

The dope solution can be formed in 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. It is cast or coated on one side.

[0085] WO98 / 25997 discloses a method of drying a dope solution in two stages under high humidity. However, in the present invention, drying in two stages under high humidity is unnecessary, and a porous membrane can be formed simply and efficiently.

In the drying step of drying the applied dope, a good solvent having a low boiling point evaporates preferentially. As the evaporation of the good solvent progresses, the solubility of the resin in the dope decreases, and the resin forms micelles (gel phase) and separates from the poor solvent phase. When the drying proceeds further, the micelles come into contact with each other to form a network structure, and the completion of the evaporation of the poor solvent forms a porous film or a porous film.

In the step of drying the applied dope solution, the dope solution may be dried in a single step. First, the dope solution is dried at a low temperature to evaporate a good solvent having a low boiling point (for example, evaporation of a good solvent having a substantially low boiling point is carried out). ), Followed by two-stage drying in which the remaining poor solvent is evaporated by drying at a high temperature. In the case of two-stage drying, the drying conditions can be selected according to the type of a good solvent and a poor solvent to be used.
0 to 100 ° C (preferably 20 to 70 ° C, for example, 20
~ 60 ° C) for about 30 seconds to 60 minutes (preferably 1-60
Min), and the second-stage drying is performed at a temperature higher than the first-stage temperature, for example, a temperature of 50 to 150 ° C. (preferably 60 ° C.).
About 130 ° C.) for about 2 seconds to 30 minutes (eg, 2 seconds to 10 minutes).
Minutes). The drying temperature of the second stage can be usually selected from a temperature higher than the temperature of the first stage by 20 ° C. or more (20 to 120 ° C., preferably about 50 to 110 ° C.). For example, when a C _3-5 dialkyl ketone such as acetone is used as a good solvent, and a cycloalkanol such as cyclohexanol is used as a poor solvent, drying can be easily performed without performing two-stage drying. A microphase separation membrane can be easily obtained.

When a porous film is produced by the dry phase inversion, it is possible to produce an ink receiving sheet having excellent ink absorbency and ink fixability with high productivity. The ink 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 droplets of ink. However, a sheet for printing such as offset printing and flexographic printing (particularly a sheet for aqueous ink) ) Can also be used.

The ink 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.

[0090]

Since the ink image-receiving sheet of the present invention comprises a porous film containing at least a urethane-based resin, the strength of the porous film and the adhesion to the substrate can be improved, and the ink absorbing property and the ink absorption can be improved. It has excellent fixability and printability, and can improve image durability. In addition, since the ink receiving sheet is formed of a porous film whose pore diameter increases from one surface in the thickness direction, a high quality image can be formed even with a dye ink or a pigment ink. Further, since the ink image receiving sheet is constituted by the porous film and the ink absorbing layer, the ink absorbing property can be greatly improved.

[0091]

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

In the following description, parts and% are by weight unless otherwise specified. The average pore size, porosity, water resistance, printability, ink absorbency, and strength of the porous film in the ink receiving sheets obtained in Examples and Comparative Examples were evaluated as follows.

An image was formed using an ink jet printer (NOVAJET PRO manufactured by ENCAD), and the recording sheet obtained in each of Examples and Comparative Examples was applied to a pigment type aqueous ink (yellow, magenta, cyan, black). Each color) was printed solid to form a recorded image.

[Average pore diameter, porosity] In an electron microscope surface photograph taken at a magnification of 5,000 times, three predetermined areas (2 cm × 2 cm) were processed by an image processing apparatus, and each hole in the electron microscope surface photograph was identified as true. The average pore diameter on one surface was determined by measuring the pore diameter as a circle and averaging.

The average pore diameter of the back surface (the other surface) was determined by peeling the porous film from the release paper, the base material or the ink absorbing layer, and measuring the average pore diameter in the same manner as the one surface. The porosity (%) is calculated by the formula (total area of hole / measured area) × 100.
Was calculated by

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

A: The printed portion remains completely. B: Bleeding is observed in the printed portion. B: No printed portion remains. [Printability] The printed image forming portion was visually evaluated based on the following criteria.

◎ The image is clear without bleeding ○ Slightly bleeding × Intense bleeding [Ink absorption] After printing, P
Place the copy paper for PC on top of the copy paper (25
0 g / cm ² ) for 10 seconds, the copy paper was peeled off, the degree of ink set-off was visually determined, and the ink absorption was evaluated based on the time until no set-off was observed.

◎ The time until no set-off is recognized is within 1 minute ○ The time until no set-off is recognized is within 3 minutes × The time until no set-off is recognized is 5 minutes or less [Adhesion of porous film] 1
Cuts were made in a grid pattern so that 100 squares of 1 mm ^{2 in} cm ² were formed, and cellophane tape was adhered to the cuts, and the sheet was vigorously peeled off. The condition of the sheet surface was judged according to the following criteria.

◎ The porous film is not peeled at all ○ The peeling is less than 10/100 × The peeling is 10/100 or more [Strength of the porous film] A porous film is prepared on a release paper. The paper was peeled from the release paper, cut into a size of 5 cm × 2.5 cm, and the peel strength was measured at a crosshead speed of 10 mm / min using Tensilon UCT-5T manufactured by Orientec Co., Ltd.

Example 1 5 parts by weight of a urethane resin ("Permarin UC-2")
0 "(manufactured by Sanyo Chemical Industries, Ltd.) and 10 parts by weight of cellulose acetate (acetylation degree 51%, viscosity average polymerization degree 250, hereinafter CA)
To 100 parts by weight of an acetone solution containing 100 parts by weight of cyclohexanol with good stirring. The thickness after drying is 5 on release paper.
It was applied to a thickness of 0 μm and dried at 110 ° C. for 5 minutes. The film peeled from the release paper had an average pore diameter on one surface of 1.1 μm, an average pore diameter on the back surface of 5.2 μm,
It was a porous film having a porosity of 53% on the membrane surface.

Example 2 Polyethylene terephthalate (hereinafter abbreviated as PET)
The dope of Example 1 was applied on the film so that the thickness of the porous layer after drying was 50 μm, and dried at 110 ° C. for 5 minutes. The resulting film has an average pore diameter of 0. 0 on the surface.
It was a laminated film having a porous layer of 9 μm, the average pore diameter of the surface (back surface) in contact with the PET film of 4.7 μm, and the porosity of the film surface of 49% on the surface.

Example 3 A 20% by weight modified polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., “OKS7158”) was placed on a PET film.
G ", degree of saponification 88%)
A coating solution to which 2 parts by weight of maleic acid was added was applied so that the thickness of the dried ink absorbing layer was 10 μm.
The ink was dried at 3 ° C. for 3 minutes to form an ink absorbing layer. Further, the dope of Example 1 was applied to the ink absorbing layer so that the thickness of the porous layer after drying was 5 μm.
Dried for minutes. The obtained film had a porous layer having an average pore diameter of 0.9 μm on the surface, an average pore diameter of 4.7 μm on the surface (rear surface) in contact with the ink absorbing layer, and a porosity of 49% on the film surface. It was a laminated film having.

Example 4 5 parts by weight of a urethane resin ("Permarin UC-2")
Acrylonitrile (A) containing “0”, manufactured by Sanyo Chemical
N) -vinylpyrrolidone (VP) copolymer (DUY, A
N / VP = 0.98 / 0.02 molar ratio, 15 parts by weight of 3-methoxybutyl acetate was added to 100 parts by weight of a 10% N, N-dimethylformamide solution (manufactured by Daicel Chemical Industries, Ltd.) with good stirring. This was added to prepare a coating solution. PET
The coating liquid is applied on the film via the ink absorbing layer in the same manner as in Example 3 so that the thickness of the dried film is 5 μm, and dried at 70 ° C. and 90% RH for 1.5 minutes. After that, it was dried at 120 ° C. for 3 minutes. The obtained film has on its surface a porous layer having an average pore diameter of 0.3 μm on the surface, an average pore diameter of 1.4 μm on the surface (back side) in contact with the ink absorbing layer, and a porosity of 48% on the film surface. It was a laminated film.

Example 5 5 parts by weight of a urethane resin ("Permarin UC-2")
0 "(manufactured by Sanyo Chemical Co., Ltd.) (manufactured by Scientific Polymer Products, hereinafter PMM
A) was added to 15 parts by weight of 3-methoxybutyl acetate while stirring well to 100 parts by weight of a 10% N, N-dimethylformamide solution of A). On a PET film, via an ink absorbing layer as in Example 3,
The coating solution was applied so that the thickness of the dried film was 5 μm, dried at 60 ° C. and 95% RH for 1.5 minutes, and then dried at 120 ° C. for 3 minutes. The obtained film has a porous layer having an average pore diameter of 0.6 μm on the surface, an average pore diameter of 2.0 μm on the surface (rear surface) in contact with the ink absorbing layer, and a porosity of 43% on the film surface. It was a laminated film.

Example 6 5 parts by weight of a urethane resin ("Permarin UC-2")
0 "(manufactured by Sanyo Chemical Co., Ltd.) and 100 parts by weight of a 11% N, N-dimethylformamide solution of a polyether sulfone [manufactured by Sumitomo Chemical Co., Ltd .; A coating solution was prepared by adding 30 parts by weight of 3-methoxybutyl acetate. On PET film,
Applying the coating liquid via the ink absorbing layer in the same manner as in Example 3 so that the thickness of the dried film is 5 μm,
After drying at 60 ° C. and 95% RH for 1.5 minutes,
Dry at 20 ° C. for 3 minutes. The obtained film is a laminated film having a porous layer having an average pore diameter of 0.8 μm on the surface, an average pore diameter of 2.8 μm on the surface in contact with the ink absorbing layer, and a porosity of 44% on the film surface. there were.

Comparative Example 1 A film was produced in the same manner as in Example 1 except that the urethane resin was not used. The obtained film was a laminated film having a porous layer having an average pore diameter of 1.3 μm on the surface, an average pore diameter of 6.8 μm on the surface in contact with the ink absorbing layer, and a porosity of 56% on the film surface. there were.

Comparative Example 2 A film was produced in the same manner as in Example 2 except that the urethane resin was not used. The obtained film was a laminated film having a porous layer having an average pore diameter of 1.0 μm on the surface, an average pore diameter of 5.5 μm on the surface in contact with the ink absorbing layer, and a porosity of 52% on the film surface. there were.

Comparative Example 3 A film was produced in the same manner as in Example 3 except that the urethane resin was not used. The obtained film was a laminated film having a porous layer having an average pore diameter of 1.0 μm on the surface, an average pore diameter of 5.5 μm on the surface in contact with the ink absorbing layer, and a porosity of 52% on the film surface. there were.

Comparative Example 4 A 5% by weight modified polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., “OKS7158”) was placed on a PET film.
G ", a saponification degree of 88%) A coating solution obtained by adding 100 parts by weight of aluminum oxide particles having a particle size of 5 µm to 100 parts by weight of an aqueous solution was applied so that the thickness after drying became 20 µm, Dried for minutes. The resulting film has a porous layer having an average pore diameter of 4.6 μm on the front surface, an average pore diameter of 4.3 μm on the surface (rear surface) in contact with the PET film, and a porosity of 20.3% on the film surface. Was a laminated film.

The results are shown in Table 1. In the table, the surface indicates one surface of the porous film (that is, the printing surface), and the back surface indicates the other surface of the porous film (that is, the surface opposite to the printing surface).

[0112]

[Table 1]

As is clear from the table, when the ink image-receiving sheet of the example was used, all of the water resistance, printability, ink absorbency and strength of the porous film were good. On the other hand, in the comparative example containing no urethane-based resin, although the water resistance, the printability and the ink absorption were relatively good, the strength of the porous film and the adhesion to the substrate or the ink absorption layer were higher than those of the examples. Is reduced. In Comparative Example 4, in which the size of the pores was relatively uniform, the water resistance and the ink absorption were relatively good, but the printability was insufficient.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of the surface of a porous film obtained in Example 1.

FIG. 2 is an electron micrograph of the back surface of the porous film obtained in Example 1.

Continued on front page F-term (reference) 2H086 BA12 BA15 4F074 AA02 AA08 AA09 AA15 AA22 AA23 AA25 AA26 AA32 AA33 AA35 AA36 AA37 AA41 AA42 AA43 AA44 AA45 AA47 AA48 AA49 AA50 AAA AA AA AA AA AA AA AA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A AH04 CB32 CB47 CC10X CC28Y CC29Y CC32Y DA02 DA03 DA13 DA23 DA52

Claims (13)

[Claims] An ink comprising a porous film containing at least one surface having an average pore diameter of 0.05 to 3 μm, a porosity of the film surface of 20 to 70%, and containing at least a urethane resin. Image receiving sheet. 2. The ink receiving sheet according to claim 1, wherein the urethane resin is a cationic urethane resin. 3. The porous membrane, wherein pores increase from one surface to the other surface, and the average pore diameter of the other surface is 2 to 20 times the average pore diameter of the one surface. The ink image receiving sheet according to claim 1. 4. The ink image-receiving sheet according to claim 1, wherein the film thickness is 5 to 50 μm. 5. The ink image receiving sheet according to claim 1, wherein the porous film is composed of a urethane resin and a non-urethane resin. 6. The ink image receiving sheet according to claim 5, wherein the proportion of the urethane-based resin is 10 to 100 parts by weight based on 100 parts by weight of the non-urethane-based resin. 7. The ink image receiving sheet according to claim 5, wherein the non-urethane resin is at least one selected from a cellulose resin, a vinyl polymer and a polysulfone polymer. 8. The ink according to claim 5, wherein the non-urethane resin is at least one selected from a cellulose ester, a (meth) acrylonitrile polymer, a (meth) acrylate polymer and a polysulfone polymer. Image receiving sheet. 9. The ink image-receiving sheet according to claim 1, wherein the porous film has a micro phase separation structure by dry phase inversion. 10. The porous membrane has an average pore diameter of 0.0 on the surface.
2. The ink receiving sheet according to claim 1, wherein the ink receiving sheet is formed on at least one surface of the base material with holes of 5 to 3 [mu] m positioned. 11. The ink image receiving sheet according to claim 1, wherein an ink absorbing layer is formed between the porous film and the substrate. 12. The ink receiving sheet according to claim 11, wherein the ink absorbing layer is a hydrophilic resin. 13. An ink image receiving apparatus for forming a porous film according to claim 1, wherein a coating film containing a thermoplastic resin composition containing a urethane resin and a good solvent and a poor solvent for the resin composition is subjected to dry phase inversion. Sheet manufacturing method.