JP4502412B2 - Porous membrane and method for producing the same - Google Patents

Description

表１から明らかなように、実施例の記録用シートを用いると、インク吸収性、画像の鮮明性が良好であり、耐水性、耐ブロッキング性も高い。これに対して、比較例の記録用シートを用いると、インク吸収性、画像の鮮明性は比較的良好であるものの、耐水性、耐ブロッキング性が十分でない。
【０１０４】
前記実施例７〜実施例１１および比較例３について、記録用シートとしての評価結果を表２に示す。なお、実施例７〜実施例１１および比較例３においては、耐水性および印刷性を次のようにして評価した。
［耐水性］
印字部を３０℃の水に１分間浸漬した後、垂直に引き上げ、水を良く切り乾燥した。乾燥後、下記の基準で印字部を目視で評価した。
○ 印字部が完全に残っている
△ 印字部に滲みが認められる
× 印字部が残っていない
［印刷状態］
下記の基準で印字部の印刷状態を目視で評価した。
○ 印字部が均一に印字されている
△ 印字部に滲みが認められる
× 印字部の滲みが大きい
【０１０５】
【表２】

実施例２３
厚さ１００μｍの易接着処理済ポリエチレンテレフタレートフィルム（ＩＣＩジャパン（株）製、メリネックス７０５）に、変性酢酸ビニル系共重合体（日本合成化学工業（株）製，ＯＫＳ−７１５８Ｇ）の１５重量％水溶液を塗布し、１２０℃で３分間乾燥することにより、厚さ１５μｍのインク吸収層を形成した。
【０１０６】
ポリメチルメタクリレート（Scientific Polyｍer Products社製）１３重量％のＮ，Ｎ−ジメチルホルムアミド溶液１００重量部に、よく攪拌しながら酢酸３−メトキシブチル１５重量部を添加して塗布液（ドープ）を作製した。この塗布液を前記インク吸収層上に塗布し、温度６０℃、湿度９５％ＲＨの条件で１．５分間乾燥した後、１２０℃で３分間乾燥し、平均孔径０．１５μｍ、空孔率４５％、厚み１０μｍの多孔質層を形成した。
得られた記録用シートの波長４００ｎｍでの光線透過率は７２％であり、優れた透明性を有していた。
また、記録用シートとしての評価を行ったところ、インク吸収性：１分，耐水性：◎，画像の鮮明性：◎，耐ブロッキング性：◎であった。
【０１０７】
実施例２４
厚さ１００μｍの易接着処理済ポリエチレンテレフタレートフィルム（ＩＣＩジャパン（株）製、メリネックス７０５）に、変性酢酸ビニル系共重合体（日本合成化学工業（株）製，ＯＫＳ−７１５８Ｇ）の１５重量％水溶液を塗布し、１２０℃で３分間乾燥することにより、厚さ１５μｍのインク吸収層を形成した。ポリエーテルスルホン（住友化学工業(株)社製，Ｐ４８００）１４重量％のＮ，Ｎ−ジメチルホルムアミド溶液１００重量部に、よく攪拌しながら酢酸３−メトキシブチル１５重量部を添加して塗布液（ドープ）を作製した。この塗布液を前記インク吸収層上に塗布し、温度６０℃、湿度９５％ＲＨの条件で１．５分間乾燥した後、１２０℃で３分間乾燥し、平均孔径０．０５μｍ、空孔率３０％、厚み１０μｍの多孔質層を形成した。
得られた記録用シートの波長４００ｎｍでの光線透過率は７５％であり、優れた透明性を有していた。
また、記録用シートとしての評価を行ったところ、インク吸収性：１分，耐水性：◎，画像の鮮明性：◎，耐ブロッキング性：◎であった。
【０１０８】
比較例９
酢酸セルロース（酢化度５５％、平均重合度１７０）８重量％のアセトン溶液を、乾燥後の厚み３０μｍとなるようにガラス板上に塗布し、２５℃の水に１分間浸漬した。ガラス板から剥離し、自然乾燥したフィルムは、表面が緻密層、下層が孔径３〜８μｍの多孔質層である非対称構造を有するフィルムであり、白色不透明であった。
【０１０９】
比較例１０
酢酸セルロース（酢化度５５％、平均重合度：１７０）８重量％のアセトン溶液を、離型紙上に、乾燥後の厚み３０μｍとなるように塗布し、４０℃、５０％ＲＨの条件で５分乾燥した後、１２０℃で３分間乾燥した。離型紙から剥離し、自然乾燥したフィルムは、光線透過率８５％で高い透明性を示したが、非多孔質フィルムであった。
【０１１０】
比較例１１
アクリロニトリル−Ｎ−ビニルピロリドン共重合体（ダイセル化学工業（株）製，「ＤＵＹ」、組成モル比９８：２）１４重量％のジメチルスルホキシド溶液を、離型紙上に、乾燥後の厚み３０μｍとなるように塗布し、７０℃、９０％ＲＨの条件で１．５分間乾燥した後、１２０℃で３分間乾燥した。離型紙から剥離し、自然乾燥したフィルムは、光線透過率８２％で高い透明性を示したが、非多孔質フィルムであった。
【図面の簡単な説明】
【図１】図１は本発明の実施形態の一例を示す概略断面図である。
【図２】図２は実施例１の多孔質フィルムの断面を示す電子顕微鏡写真（図面代用写真）である。
【図３】図３は実施例１の多孔質フィルムの表面を示す電子顕微鏡写真（図面代用写真）である。
【図４】図４は実施例７の多孔質フィルムの表面を示す電子顕微鏡写真（図面代用写真）である。
【符号の説明】
１：基材
２：インク吸収層
３：多孔質層
４：孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a porous film made of a polymer and excellent in transparency, a laminated film provided with the porous film, and a method for producing the porous film.
[0002]
[Prior art]
Polymer porous membranes have developed rapidly since the creation of an asymmetric cellulose acetate membrane in 1960, for example, purification of water such as ultrapure water, drinking water and industrial water, treatment of industrial and municipal wastewater, Its application fields are expanding without limit, such as substance separation and purification in each process of the chemical industry, pharmaceutical industry, and food industry, and use in the medical field including hemodialysis using an artificial kidney. Many of such polymer porous membranes have an asymmetric structure composed of a skin layer (dense layer) and a support layer (porous layer), and are generally opaque.
[0003]
In applications where transparency is required, as a polymer porous film, for example, JP-A 64-48026 proposes a liquid crystal panel in which a transparent porous film impregnated with liquid crystal molecules is sandwiched between upper and lower panels. ing. However, this document does not describe the material of the transparent porous film.
Japanese Patent Laid-Open No. 3-159791 proposes a thermal transfer recording sheet using a transparent porous resin layer. Although this document describes an ethylene-vinyl chloride copolymer as a resin for forming the porous resin layer, it does not describe a method for forming the porous resin layer.
[0004]
JP-A-3-96332 provides a porous layer having a peak pore size in a pore size distribution curve of 0.06 to 2.0 μm and a surface having a height of 0.2 μm or more and less than 5/4 μm. In addition, a surface porous film having a film haze value of 10% or less has been proposed. The porous layer of this film is formed by applying a coating liquid composed of a water-dispersible polymer and colloidal silica and drying it. Therefore, the water resistance is low, and the transparency is also low due to the difference in refractive index between the water-dispersible polymer and colloidal silica.
[0005]
Japanese Patent Laid-Open No. 3-145005 proposes an electrolyte thin film in which ionic conductors are filled into pores of a solid polymer porous membrane having independent through-holes having an average pore diameter of 0.01 to 0.7 μm. ing. This solid polymer porous membrane is produced by a method of irradiating a polymer thin film with charged particles and alkali-etching the tracks through which the charged particles have passed to form holes. The porous film obtained by this method is translucent, and in order to be transparent, it is necessary to fill the pores with a liquid having a refractive index comparable to that of the film material.
[0006]
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 substrate, and a dye-supporting layer made of pseudoboehmite is provided thereon. The porous membrane is formed by dissolving cellulose acetate in a solvent such as acetone, and applying and drying a coating liquid appropriately added with magnesium perchlorate. Precipitates and transparency decreases.
[0007]
In JP-A-61-86251, a liquid absorption layer is laminated on at least one surface of a base 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 absorption layer. A recording sheet in which a large number of polyethylene or polypropylene films) are laminated by hot pressing is disclosed. However, the method for preparing the porous thin film layer is not described.
[0008]
On the other hand, as a method for producing a polymer porous membrane, (1) a phase separation method in which a polymer is microphase-separated using a good solvent and a poor solvent, (2) a foaming method in which pores are formed by foaming the polymer, ( 3) Stretching method to stretch the polymer film, (4) Radiation irradiation method to form holes by irradiating the polymer film, (5) Solvent-soluble polymer or inorganic salt and insoluble in the solvent An extraction method in which a film made of a polymer is prepared and a soluble component is extracted and removed with the solvent to form pores. (6) Polymer particles are partially fused or hardened with a binder or the like. A sintering method using gaps as holes is known.
[0009]
Of these methods, the phase separation method is the most common production method. For example, Japanese Patent Laid-Open No. 3-246095 discloses that a porous plastic surface layer is formed on a transparent plastic film substrate by applying a plastic solution and wet coagulating it. In this document, a dimethylformamide solution of a saturated copolymerized polyester resin is applied to a substrate, solidified in water, and further immersed in hot water and dried to form a white devitrified porous plastic surface layer. ing.
However, the phase separation method usually produces an asymmetric membrane having a dense layer on the surface and a porous layer (void layer) on the lower layer. And the pore diameter of a void layer is large and a porous membrane becomes opaque. Moreover, even if a transparent film | membrane produces | generates, it is a non-porous film | membrane and cannot utilize in the field | area using a pore. Thus, it is difficult to obtain a porous structure film or film while maintaining high transparency.
[0010]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a highly transparent porous membrane and a method for producing the same.
Another object of the present invention is to provide a porous film having high transparency and ink absorbability and excellent water resistance, and a method for producing the same.
Still another object of the present invention is to provide a method capable of producing a highly transparent porous membrane with high productivity.
[0011]
[Means for Solving the Problems]
  As a result of intensive studies using a dry phase conversion method that is excellent in mass productivity among the methods for producing a polymer porous layer in order to achieve the above-mentioned object, the present inventors have excellent transparency when used in combination with a specific solvent. The present inventors have found that a high molecular porous layer can be obtained.
  That is, the laminated film of the present invention is at least one side of the substrate.ManyA laminated film in which a porous layer is formed, wherein the porous layer is(1) It is composed of at least one polymer selected from the following (a) to (c), (2) the porosity is 10 to 60%, and (3) the light transmittance at a wavelength of 400 nm is 30%. And (4)It has a microphase separation structure.
  (A) cellulose acetate having an acetylation degree of 42 to 62% and a viscosity average polymerization degree of 50 to 800,
  (B) (meth) acrylonitrile, (meth) acrylic acid ester monomer, vinyl ester monomer, heterocyclic vinyl monomer, aromatic vinyl monomer, polymerizable unsaturated dicarboxylic acid or its A homo- or copolymer selected from at least one of (meth) acrylonitrile and (meth) acrylic acid ester monomers selected from derivatives, and
  (C) at least one selected from polysulfone and polyethersulfone
  This porous layer usually has an average pore diameter of 0.002 to 0.35 μm and a maximum pore diameter of about 0.4 μm.Yes.
  In the laminated film of the present invention, a porous layer may be interposed between the substrates.
  The laminated film is cast or coated on a substrate containing a polymer, a good solvent for the polymer, a boiling point higher than the good solvent, and a poor solvent for the polymer, and the coating film is dried. Can be manufactured.
  In the present specification, the “film” means a two-dimensional structure such as a thin film, a film, or a sheet.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[High molecular]
The porous membrane of the present invention is composed of a polymer and usually has a microphase separation structure. This microphase separation structure is formed by solidification of the gel phase separated by the composition change of the cast polymer solution, and the shape of the pores formed between the particles is usually irregular and irregular. Non-circular.
[0013]
As the polymer, various thermoplastic polymers and thermosetting polymers can be used, and thermoplastic polymers are usually used. The following polymers can be exemplified.
Cellulose derivatives:
Cellulose esters, for example, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate and other organic acid esters; cellulose nitrate, cellulose sulfate, cellulose phosphate and other inorganic acids Esters: Mixed acid esters such as cellulose nitrate acetate
Cellulose ethers such as methyl cellulose, ethyl cellulose, isopropyl cellulose, butyl cellulose, benzyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, cyanoethyl cellulose, etc.)
Vinyl polymer:
Olefin-based polymers such as olefins homopolymers or copolymers (polyethylene, polypropylene, poly 1-butene, polyisobutene, polybutadiene, polyisoprene, polyarene, ethylene-propylene copolymers, etc.), olefins and copolymerizable monomers Copolymers with polymers (ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer, modified polyolefin, etc.)
Halogen-containing vinyl polymers, for example, halogen-containing vinyl monomers alone or copolymers (polyvinyl chloride, polyvinylidene chloride, polyvinyl bromide, polyvinyl fluoride, polyvinylidene fluoride, etc.), halogen-containing vinyl monomers Copolymers with polymerizable monomers (vinyl chloride-vinyl acetate copolymer, vinylidene chloride-vinyl acetate copolymer, vinylidene chloride- (meth) acrylamide copolymer, vinylidene chloride- (meth) acrylic acid copolymer) And vinylidene chloride- (meth) acrylic acid ester copolymers)
Vinyl ester polymers or derivatives thereof, such as polyvinyl acetate, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyvinyl acetal polymers (polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc.)
Styrenic polymer, for example, aromatic vinyl monomer (styrene monomer) homopolymer or copolymer (polystyrene, poly (α-methylstyrene), poly (4-chlorostyrene), etc.), aromatic vinyl Copolymer of monomer and copolymerizable monomer (styrene- (meth) acrylic acid C_1-10Alkyl ester copolymer, styrene-maleic anhydride copolymer, styrene-maleimide copolymer, etc.)
Allyl alcohol polymers such as allyl alcohol-C_1-6Alkyl vinyl ether copolymer (eg, allyl alcohol-methyl vinyl ether copolymer) polyvinyl ketones such as polyvinyl methyl ketone, polyvinyl methyl isobutyl ketone, polymethyl isopropenyl ketone
Polyalkyl vinyl ethers such as polymethyl vinyl ether, methyl vinyl ether-maleic anhydride copolymer
(Meth) acrylic polymer, for example, (meth) acrylic monomer [(meth) acrylonitrile, (meth) acrylic acid ester monomer, etc.] or copolymer, (meth) acrylic monomer And copolymerizable monomers [vinyl monomers such as vinyl ester monomers, heterocyclic vinyl monomers, aromatic vinyl monomers, polymerizable unsaturated dicarboxylic acids or derivatives thereof] Copolymer
Polysulfone polymer:
Polysulfone, polyethersulfone, etc.
Polyoxide polymer:
Polyoxymethylene, polyoxymethylene copolymer (polyacetal resin), polyoxyethylene, polyoxypropylene, polyoxyethylene-polyoxypropylene copolymer, etc.
Polyamide and polyimide polymers:
Polyamide (Nylon 6, Nylon 66, Nylon 11, Nylon 12, Nylon 6/11, Nylon 6/12, etc.), Polyesteramide, Polyimide, Polyamideimide, etc.
Polyester polymer (saturated polyester, etc.):
Poly C_2-6Alkylene terephthalate (polyethylene terephthalate, polybutylene terephthalate, etc.), poly C_2-6Alkylene naphthalate (polyethylene naphthalate, etc.), copolyester (diol component and at least part of terephthalic acid is ethylene glycol, propylene glycol, butanediol, hexanediol, polyoxy C_2-4Diol components such as alkylene glycol and cyclohexanedimethanol, aromatic dicarboxylic acids such as phthalic acid and isophthalic acid, or acid anhydrides thereof, and C such as adipic acid_6-12Polyalkylene terephthalate copolyester and polyalkylene naphthalate copolyester substituted with other diol components such as aliphatic dicarboxylic acids or dicarboxylic acid components)
Polycarbonate:
Aromatic polycarbonate (such as bisphenol A polycarbonate)
Other polymers:
Thermoplastic urethane polymer (polyurethane using polyester diol, polyether diol, etc. as diol component), polyether ether ketone, polyether ester, polyphenylene ether, polyphenylene sulfide, polyethyleneimine, etc.
These polymers can be used alone or in admixture of two or more.
[0014]
Preferred polymers include at least one polymer selected from cellulose derivatives, vinyl polymers and polysulfone polymers.
Preferred cellulose derivatives include cellulose esters, for example, cellulose organic acid esters (for example, esters with organic acids having about 2 to 4 carbon atoms), particularly cellulose acetate (such as cellulose diacetate and cellulose triacetate).
[0015]
The viscosity average polymerization degree of the cellulose derivative (cellulose ester or the like) is, for example, about 50 to 800, preferably about 75 to 500, and more preferably about 100 to 250 (particularly 100 to 200). Cellulose acetate having a viscosity average degree of polymerization of about 100 to 190 can also be used effectively.
[0016]
The viscosity average polymerization degree of cellulose esters such as cellulose acetate can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 105, p. 120-1962, 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 markings of the viscometer at 25 ° C. is measured. On the other hand, the passage time (second) t of the mixed solvent alone is also the same as described above.₀And the viscosity average degree of polymerization is calculated according to the following formula.
η_rel= T / t₀
[Η] = (lnη_rel) / C
DP = [η] / (6 × 10^-Four)
(Where t is the transit time of the solution (seconds), t₀Is the transit time of the solvent (seconds), c is the cellulose ester concentration (g / L) of the solution, η_relIs the relative viscosity, [η] is the limiting viscosity, and DP is the average degree of polymerization)
The average degree of substitution of the cellulose derivative can be selected from a range of about 1 to 3. For example, a preferable cellulose acetate has an average degree of acetylation of about 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 decreases. If the viscosity average degree of polymerization is too small, the pore size of the porous membrane becomes small and tends to be a non-porous membrane. If it is too large, the pore size becomes large and the porous membrane tends to become opaque.
[0017]
Of the vinyl polymers, (meth) acrylonitrile polymers and (meth) acrylic acid ester polymers are preferred. That is, a homo- or copolymer of at least one (meth) acrylic monomer selected from (meth) acrylonitrile and (meth) acrylic acid ester monomers, this (meth) acrylic monomer and others Copolymerizable monomer [at least one monomer selected from vinyl ester monomers, heterocyclic vinyl monomers, aromatic vinyl monomers, polymerizable unsaturated dicarboxylic acids or their derivatives] And a copolymer of the same are preferred.
[0018]
The (meth) acrylonitrile-based polymer includes polyacrylonitrile, polymethacrylonitrile, 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. (Meth) acrylic acid C such as methyl acid, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate_1-10Alkyl esters, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl Alkylamino-alkyl (meth) acrylates such as (meth) acrylate, diethylaminoethyl (meth) acrylate, diethylaminopropyl (meth) acrylate, (meth) acrylamide, N-methyl (meth) acrylamide, methylol (meth) acrylamide, alkoxymethyl (Meth) acrylamide etc.], heterocyclic vinyl monomers (nitrogen atoms such as vinyl pyrrolidone, vinyl pyridine, vinyl piperidine, vinyl imidazole, vinyl carbazole, oxygen 5- or 6-membered heterocyclic vinyl monomers containing at least one hetero atom selected from a thiol and sulfur atoms), aromatic vinyl monomers (styrene, vinyl toluene, α-methylstyrene, etc.), polymerization And unsaturated dicarboxylic acids or derivatives thereof (itaconic acid, maleic acid, maleic anhydride, fumaric acid, lower alkyl esters or 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), (meth) acrylic monomers [(meth) acrylic acid, (meth) acrylic acid C_1-8Alkyl ester, C_1-4Alkylamino-C_2-4Alkyl (meth) acrylates, etc.], nitrogen-containing heterocyclic vinyl monomers (vinyl pyrrolidone etc.) or combinations thereof.
[0019]
Examples of (meth) acrylonitrile-based copolymers include acrylonitrile-vinylpyrrolidone copolymer, acrylonitrile-vinyl acetate copolymer, and acrylonitrile-C._1-8Alkyl (meth) acrylate copolymers (such as acrylonitrile-methyl acrylate copolymer), acrylonitrile-vinylpyrrolidone-C_1-8Alkyl (meth) acrylate copolymer, acrylonitrile-vinyl acetate-C_1-8Alkyl (meth) acrylate copolymer, acrylonitrile- (meth) acrylic acid copolymer, acrylonitrile-vinyl acetate- (meth) acrylic acid copolymer, acrylonitrile-C_1-8Examples thereof include alkyl (meth) acrylate- (meth) acrylic acid copolymers.
[0020]
As the (meth) acrylic acid ester polymer, the above (meth) acrylic acid ester homopolymer or copolymer [for example, poly (meth) acrylic acid, poly (meth) acrylic acid C_1-18Alkyl ester homopolymer or copolymer (poly (meth) acrylate, poly (meth) acrylate, poly (meth) acrylate, methyl methacrylate- (meth) acrylate copolymer, etc.) Acrylic acid C_1-10Alkyl ester- (meth) acrylic acid copolymer, methyl methacrylate-acrylic acid C_1-10Methacrylic acid C such as alkyl ester copolymer_1-10Alkyl ester-acrylic acid C_1-10Alkyl ester copolymers, etc.], (meth) acrylic monomers and copolymerizable monomers (vinyl ester monomers, aromatic vinyl monomers, polymerizable unsaturated dicarboxylic acids or derivatives thereof) Copolymers [for example, (meth) acrylic acid C such as methyl methacrylate-styrene copolymer_1-10(Meth) acrylic acid C such as alkyl ester-styrene copolymer, methyl methacrylate- (meth) acrylic acid-styrene copolymer_1-10Alkyl ester- (meth) acrylic acid-styrene copolymer, etc.].
[0021]
A feature of the present invention is that it is highly transparent despite being a porous membrane (particularly a porous membrane having a microphase separation structure). That is, the light transmittance of the porous film at a wavelength of 400 nm is 30% or more (that is, 30 to 100%), preferably 35 to 100%, more preferably 50 to 100% (for example, 55 to 100%), particularly A porous film having a high transparency of about 60 to 100%, particularly about 70 to 100% and a light transmittance of about 80 to 100% can also be obtained.
[0022]
  The maximum pore diameter of the pores of the porous membrane is 0.5 μm or less (particularly 0.4 μm or less), and the average pore diameter is 0.002 to 0.35 μm (for example, 0.004 to 0.3 μm), preferably Is 0.005-0.3μm(For example, 0.007 to 0.2 μm), more preferably about 0.01 to 0.2 μm (for example, 0.05 to 0.2 μm).
  Furthermore, the porosity of the porous membrane is, for example, about 10 to 60% (for example, 15 to 50%), preferably about 15 to 55%, and more preferably about 20 to 50%.
[0023]
The film 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, and more preferably about 3 to 50 μm. If the film thickness is too small, the strength and water resistance are insufficient, and if it is too thick, the transparency may decrease depending on the application.
[0024]
[Method for producing porous membrane]
The porous membrane of the present invention can be produced by a microphase separation method, for example, a wet phase separation method in which a good solvent solution of a polymer is cast or applied and immersed in a poor solvent for the polymer, A dry phase inversion method, that is, a uniform dope containing a polymer, 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 perform microphase separation. It can be manufactured by generating. In particular, in the dry phase conversion 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.
[0025]
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 high transparency.
Examples of the good solvent include ketones (C, such as acetone, methyl ethyl ketone, methyl propyl ketone, etc.) depending on the type of polymer._3-5Dialkyl ketone, cyclohexanone, etc.), esters (formic acid C such as ethyl formate)_1-4 Acetic acid C such as alkyl ester, methyl acetate, ethyl acetate, butyl acetate_1-4 Cyclic or chain C such as alkyl ester, ethyl propionate, ethyl lactate, etc.), ethers (1,4-dioxane, tetrahydrofuran, tetrahydropyran, diethyl ether, diisopropyl ether, dimethoxyethane, etc.)_4-6 Ether), cellosolves (methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc.)_1-4 Alkyl-cellosolve), cellosolve acetates (methyl cellosolve acetate, ethyl cellosolve acetate, etc.)_1-4 Alkyl-cellosolve acetate), aromatic hydrocarbons (benzene, toluene, xylene, etc.), halogenated hydrocarbons (methylene chloride, ethylene chloride, etc.), amides (formamide, acetamide and other acylamides, N-methylformamide, Mono- or di-C such as N-methylacetamide, N, N-dimethylformamide, N, N-dimethylacetamide_1-4 Diamides such as acylamides) and sulfoxides (dimethylsulfoxide)_1-3 Alkyl sulfoxide), nitriles (acetonitrile, chloroacetonitrile, propionitrile, butyronitrile, etc.)_1-6 Alkyl nitrile, benzonitrile, etc.), organic acids (formic acid, acetic acid, propionic acid, etc.), organic acid anhydrides (maleic anhydride, acetic anhydride, etc.), and mixtures thereof. Good solvents include nitro compounds (nitromethane, nitroethane, nitropropane, etc.), lower alcohols (C, such as methanol, ethanol, etc.)_1-4 Alcohol, diacetone alcohol, etc.).
[0026]
The good solvent can be selected according to the type of polymer. More specifically, preferable good solvents for cellulose derivatives include C such as methyl ethyl ketone._3-5 Dialkyl ketones (especially acetone, methyl ethyl ketone), acetic acid C such as ethyl acetate_1-4 Cyclic or chain C such as alkyl esters (especially methyl acetate, ethyl acetate), dioxane, dimethoxyethane, etc._4-6 C such as ethers and methyl cellosolve_1-4 Alkyl-cellosolves (especially methyl cellosolve, ethyl cellosolve), C of methyl cellosolve acetate, etc._1-4 Alkyl-cellosolve acetates (particularly methyl cellosolve acetate, ethyl cellosolve acetate) and mixed solvents thereof are included. When the cellulose derivative is cellulose acetate, a particularly preferable good solvent is at least C._1-2Solvents containing alkyl-cellosolves (particularly methyl cellosolve) are included.
[0027]
Among vinyl polymers, preferred good solvents for acrylonitrile polymers include amides (formamide, N, N-dimethylformamide, acetamide, N, N-dimethylacetamide, etc.), sulfoxides (dimethylsulfoxide, etc.), ethers (Cyclic ethers such as tetrahydrofuran, tetrahydropyran, 1,4-dioxane), nitriles (acetonitrile, chloroacetonitrile, propionitrile, butyronitrile, malonitrile, fumaronitrile, etc.), organic acid anhydrides (maleic anhydride, acetic anhydride, etc.) And a mixed solvent thereof. A preferable good solvent contains at least amides (particularly N, N-dimethylformamide and the like).
[0028]
Among the vinyl polymers, preferred good solvents for the (meth) acrylic acid polymers include ketones (such as acetone, methyl ethyl ketone, and methyl propyl ketone)._3-5Dialkyl ketone, cyclohexanone, etc.), esters (formic acid C such as ethyl formate)_1-4Acetic acid C such as alkyl ester, methyl acetate, ethyl acetate, butyl acetate_1-4Alkyl esters, ethyl propionate, ethyl lactate, etc.), aromatic hydrocarbons (benzene, toluene, xylene, etc.), halogenated hydrocarbons (methylene chloride, ethylene chloride, etc.), amides (N, N-dimethylformamide, N, N-dimethylacetamide and the like), sulfoxides (dimethylsulfoxide and the like), ethers (cyclic ethers such as tetrahydrofuran and 1,4-dioxane), and mixed solvents thereof.
[0029]
Preferable good solvents for the polysulfone-based polymer include amides (N, N-dimethylformamide, N, N-dimethylacetamide and the like), sulfoxides (dimethylsulfoxide and the like), a mixed solvent thereof and the like.
[0030]
The boiling point of the good solvent is about 35 to 200 ° C. (for example, 35 to 180 ° C.), preferably about 35 to 170 ° C. (for example, 35 to 160 ° C.), and more preferably about 40 to 160 ° C. (for example, 40 to 125 ° C.). Usually, it is about 35-150 degreeC (for example, 35-130 degreeC) grade.
[0031]
The poor solvent means a solvent having no solubility or low solubility in a polymer, and any solvent can be used as long as the boiling point is higher than that of the good solvent. Therefore, the kind of poor solvent is not particularly limited. Examples of the poor solvent include esters (formic acid C such as amyl formate and isoamyl formate)._5-8 C such as alkyl ester, butyl acetate, amyl acetate, hexyl acetate, octyl acetate, 3-methoxybutyl acetate, 3-ethoxybutyl acetate, butyl propionate, 3-methoxybutyl propionate_1-4C optionally having an alkoxy group_2-4Aliphatic carboxylic acid C_3-10Alkyl esters (eg C_1-4Acetic acid C optionally having an alkoxy group_4-10Alkyl ester), methyl benzoate, ethyl benzoate, propyl benzoate and the like benzoic acid C_1-4Alkyl esters), alcohols (cyclopentanol, cyclohexanol, methylcyclohexanol, dimethylcyclohexanol, cyclooctanol, etc.)_1-4C in which the alkyl group may be substituted_4-8C such as cycloalkanol, amyl alcohol, isoamyl alcohol, hexyl alcohol_5-8C such as alcohols, 2-butoxyethanol, 3-butoxypropanol_2-6Alkoxy-C_1-4C, such as alcohols, heterocyclic alcohols such as furfuryl alcohol), ketones (methyl butyl ketone, methyl isobutyl ketone, methyl pentyl ketone, methyl isopentyl ketone, 2,6-dimethyl-4-heptanone, etc.)_3-10Dialkyl ketones (especially C_6-10Dialkyl ketone), acetonyl acetone, acetophenone, etc.), ethers (methyl phenyl ether, methoxy toluene, dibutyl ether, benzyl ethyl ether, etc.)_7-10Ethers), aliphatic hydrocarbons (hexane, octane, nonane, decane, etc.)_5-20Aliphatic hydrocarbons) and mixtures thereof.
[0032]
Preferred poor solvents for cellulose derivatives include esters (formic acid C_5-8Alkyl ester, benzoic acid C_1-4Alkyl esters), C_4-8Cycloalkanol, C_6-10Dialkyl ketones and C_7-10At least one solvent selected from ethers, in particular at least C_5-7Solvents containing cycloalkanols (especially cyclohexanols) are included. Cyclohexanols include mono- or di-C such as cyclohexanol, methylcyclohexanol, and dimethylcyclohexanol._1-2Alkyl substituents are included.
[0033]
Preferred poor solvents for acrylonitrile polymers, (meth) acrylic acid ester polymers, and polysulfone polymers include C_1-4Acetic acid alkyl ester optionally having an alkoxy group (acetic acid C such as 3-methoxybutyl acetate, 3-methoxypentyl acetate, etc.)_1-4Alkoxy C_3-7Alkyl ester), 2-butoxyethanol, 2-hexyloxyethanol, etc._4-8Alkoxy C_1-4Alkyl alcohols, ketones (methyl butyl ketone, methyl isobutyl ketone, methyl pentyl ketone, methyl isopentyl ketone, etc._6-10Dialkyl ketone, acetonyl acetone, acetophenone) and the like.
[0034]
The boiling point of the poor solvent is usually 100 to 230 ° C, preferably about 120 to 200 ° C. The poor solvent usually has a boiling point that is 20 ° C. or higher (about 20 to 60 ° C.), preferably about 30 to 50 ° C. higher than the good solvent.
[0035]
The ratio between the good solvent and the poor solvent is not particularly limited as long as a uniform solution of the polymer can be formed, and is usually 1 to 50 parts by weight (for example, 3 to 50 parts by weight) of the poor solvent with respect to 100 parts by weight of the good solvent. The amount is preferably 2 to 40 parts by weight (for example, 5 to 40 parts by weight), more preferably about 3 to 35 parts by weight (for example, 10 to 35 parts by weight), and usually about 3 to 30 parts by weight.
Furthermore, the polymer content of the dope liquid can be selected according to the degree of polymerization of the polymer, for example, 5 to 30% by weight, preferably 5 to 25% by weight, particularly 5 to 20% by weight (for example, 5 ˜15% by weight).
[0036]
The dope solution contains about 3 to 40 parts by weight of the poor solvent with respect to 100 parts by weight of the good solvent solution of about 5 to 30% by weight of the polymer. The dope solution is preferably 3 to 40 parts by weight (preferably a poor solvent) while suppressing precipitation with respect to 100 parts by weight of a good solvent solution of about 5 to 20% by weight (especially 5 to 15% by weight) of the polymer. It can be prepared by adding about 3 to 30 parts by weight).
[0037]
In the dope solution (coating solution), conventional additives, such as antifoaming agents, coating improvers, thickeners, lubricants, stabilizers (antioxidants, UV absorbers) are used as long as the properties of the porous film are not impaired. Agents, heat stabilizers, etc.), antistatic agents, antiblocking agents and the like may be added.
[0038]
The dope solution is applied to at least one surface of the substrate by a conventional casting or coating method, such as a roll coater, air knife coater, blade coater, rod coater, bar coater, comma coater, gravure coater, silk screen coater method, etc. It is cast or applied on the surface.
Examples of the substrate include paper, coated paper, non-woven fabric, plastic film, glass, ceramics, and metal. A preferred substrate is a release paper, at least a single layer or a composite film composed of a plastic film.
The substrate may be opaque or translucent, but the substrate is usually transparent in order to effectively utilize the transparency of the porous membrane.
[0039]
Examples of the polymer constituting the plastic film include cellulose derivatives such as cellulose acetate, polyolefins such as polyethylene and polypropylene, ethylene-vinyl acetate copolymers, polystyrene, polyvinyl chloride, poly (meth) acrylic acid esters, and polyesters (polyethylene). Terephthalate, polyalkylene terephthalate such as polybutylene terephthalate, polyethylene naphthalate, polyalkylene naphthalate such as polybutylene naphthalate), polyamide (polyamide 6, polyamide 6/6, polyamide 6/10, polyamide 6/12, etc.), Polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polycarbonate, polyesteramide, polyether, polyimide, polyamideimide, polyester Ether esters, their copolymers, blends, and the like crosslinked product. Of these films, polyolefin (particularly polypropylene), polyester (polyethylene terephthalate, etc.), polyamide, etc. are often used.
You may add conventional additives, such as antioxidant, a ultraviolet absorber, a heat stabilizer, a lubricant, and a pigment, to a plastic film as needed. Moreover, in order to improve adhesiveness with a porous film, you may perform a corona discharge process, an undercoat process, etc.
[0040]
In the method for producing a transparent polymer porous membrane of the present invention, first, a dope solution comprising a polymer, a good solvent for the polymer, a higher boiling point than the good solvent, and a poor solvent for the polymer Is applied onto the substrate.
In the drying step of drying the applied dope solution, the good solvent having a low boiling point evaporates preferentially. As the good solvent evaporates, the solubility of the polymer in the dope liquid decreases, and the polymer forms a micelle (gel phase) and phase separates from the poor solvent phase. As the drying further proceeds, the micelles come into contact with each other to form a network structure, and a porous film or a porous film is formed by completing the evaporation of the poor solvent.
[0041]
Therefore, the drying conditions are also important. That is, in the drying process of the applied dope solution, it may be dried in one step, but first, it is dried at a low temperature to evaporate a good solvent having a low boiling point (for example, evaporating a good solvent having a substantially low boiling point). It is preferred to carry out two-stage drying, which is followed by evaporation of the remaining poor solvent by drying at high temperature. The drying conditions for the two-stage drying can be selected according to the type of good solvent and poor solvent used. In general, the first stage drying is performed at a temperature of 10 to 100 ° C. (preferably 20 to 70 ° C., for example, 20 to 60 ° C.). The drying is performed for about 30 seconds to 60 minutes (preferably 1 to 60 minutes), and the drying of the second stage is higher than the temperature of the first stage, for example, about 50 to 150 ° C. (preferably 60 to 130 ° C.). For about 2 seconds to 30 minutes (for example, 2 seconds to 10 minutes). The drying temperature in the second stage can be selected from temperatures usually 20 ° C. or higher (20 to 120 ° C., preferably about 50 to 110 ° C.) higher than the temperature in the first stage. The first stage drying is preferably performed in a high humidity atmosphere having a relative humidity of 50 to 100% RH (preferably 70 to 100% RH).
After drying, a highly transparent porous film or film is obtained by peeling from the substrate.
[0042]
[Laminated film]
In the laminated film of the present invention, a porous film is formed on at least one surface of the substrate. Such a laminated film can be produced without peeling off the porous film formed on the substrate by the above method.
Furthermore, the laminated film of the present invention includes a laminated film in which a porous layer is interposed between a pair of substrates. Such a laminated film can be obtained by forming a porous film on a substrate and further laminating the substrate on the porous film through an adhesive layer as necessary.
[0043]
The porous layer of such a laminated film is impregnated or dispersed with functional materials such as liquid crystal molecules, ionic conductors, and dichroic dyes, and functional films (liquid crystalline films, conductive films, multicolor polarizing plates, etc.) Can be used as Moreover, it can utilize also as an optical interference film colored by interference of light by laminating | stacking the said transparent porous film | membrane on a reflective metal body.
[0044]
The porous membrane of the present invention has excellent transparency. Therefore, it can be used for a wide range of applications requiring transparency, for example, crystal optical elements, recording sheets, functional film materials, separation membranes, analysis elements impregnated with enzymes, and the like. For example, when a porous structure film or film is applied to an ink image-receiving layer of a recording sheet by inkjet or the like, the ink absorbability can be increased.
[Recording sheet]
As shown in FIG. 1, the recording sheet includes a base material 1, an ink absorption layer 2 formed on at least one surface of the base material, the ink absorption layer, and pores 4. And a porous layer 3 having The image receiving layer of the recording sheet is composed of the ink absorbing layer 2 and the porous layer 3.
[0045]
As the substrate, the exemplified substrate can be used. The thickness of a base material can be selected according to a use, and is 5-250 micrometers normally, Preferably it is about 10-200 micrometers, and the thickness of the film for OHP is about 50-200 micrometers, for example.
The ink absorbing layer formed on at least one surface of the substrate is not particularly limited as long as it is made of a material that can absorb ink. The ink absorbing layer can be composed of a polymer. Examples of the polymer include natural polymers or derivatives thereof, cellulose derivatives, olefin polymers, acrylic polymers, styrene polymers, vinyl polymers (vinyl acetate). Copolymers, vinyl ether polymers, etc.), vinyl alcohol polymers, polyalkylene oxides, polyesters, polyamides, polycarbonates, polyurethanes, polysulfones, and polymers derived from epoxides. These polymers may have a hydrophilic group (an acidic group such as a carboxyl group or a sulfonic acid group or a salt thereof, a basic group or a salt thereof).
[0046]
The ink absorbing layer is particularly preferably a coating layer of a water-soluble polymer or a water-insoluble and water-absorbing polymer (hydrophilic polymer).
Water-soluble polymers or water-insoluble and water-absorbing polymers (hydrophilic polymers) include hydrophilic natural polymers or their derivatives (starch, corn starch, sodium alginate, gum arabic, gelatin, casein, dextrin, etc. ), Cellulose derivatives (methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, cellulose sulfate, cyanoethyl cellulose, etc.), vinyl alcohol polymers (polyvinyl alcohol, ethylene-vinyl alcohol copolymers, etc.), ethylene polymers (ethylene- Maleic anhydride copolymer), vinyl acetate copolymer (vinyl acetate-methyl acrylate copolymer, etc.), polyethylene oxide, polymer having carboxyl group or sulfonic acid group or salt thereof [ Kuryl polymers [poly (meth) acrylic acid or salts thereof (alkali metal salts such as ammonium and sodium), methyl methacrylate- (meth) acrylic acid copolymer, acrylic acid-polyvinyl alcohol copolymer, etc.], vinyl ether Polymers (polyvinyl alkyl ethers such as polyvinyl methyl ether and polyvinyl isobutyl ether, methyl vinyl ether-maleic anhydride copolymers), styrene polymers (styrene-maleic anhydride copolymers, styrene- (meth) acrylic acid) Copolymer, sodium polystyrene sulfonate, etc.), sodium polyvinyl sulfonate, etc.], nitrogen-containing polymer (or cationic polymer) or salt thereof (polyvinylbenzyltrimethylammonium chloride, polydiallyldimethylammonium chloride) Quaternary ammonium salts such as rides, polydimethylaminoethyl (meth) acrylate hydrochloride, polyvinyl pyridine, polyvinyl imidazole, polyethylene imine, polyamide polyamine, polyacrylamide, polyvinyl pyrrolidone, etc.), water dispersible polymers (for example, acrylic resin emulsion) Ethylene-vinyl acetate copolymer emulsion, vinyl acetate emulsion, styrene-butadiene copolymer latex, acrylonitrile-butadiene-styrene copolymer latex, polyester emulsion, and the like. These hydrophilic polymers can be used alone or in combination of two or more.
Of these polymers, cellulose derivatives (especially hydroxyethyl cellulose etc.), vinyl alcohol polymers (especially polyvinyl alcohol etc.), vinyl polymers (especially vinyl acetate copolymers etc.), polyvinyl pyrrolidone, etc. are particularly preferred. Vinyl acetate copolymers such as vinyl acetate-methyl acrylate copolymer are preferred.
[0047]
The vinyl acetate copolymer is a copolymer of vinyl acetate and another copolymerizable monomer, and includes partially saponified products (for example, partially saponified products having a saponification degree of about 10 to 90%). . Examples of copolymerizable monomers include olefins or dienes (ethylene, propylene, butadiene, etc.), maleic acid dialkyl esters, (meth) acrylic monomers [methyl (meth) acrylate, ethyl (meth) acrylate, butyl Alkyl (meth) acrylates such as (meth) acrylate, 2-hydroxyethyl (meth) acrylate, hydroxy-containing (meth) acrylates such as 2-hydroxypropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, etc. Amino group-containing acrylates, epoxy group-containing acrylates such as glycidyl (meth) acrylate, amide group-containing monomers such as (meth) acrylamide, vinyl cyanide such as (meth) acrylonitrile, etc.], allyl monomers (ant Monomers containing epoxy groups such as alcohol, allyl isocyanate and allyl glycidyl ether), monomers containing sulfonic acid groups or salts thereof (such as styrene sulfonic acid and sodium salts thereof), monomers containing carboxyl groups or salts thereof ((meta ) A carboxyl group such as acrylic acid, crotonic acid, and maleic acid monoalkyl ester or a salt thereof (such as sodium salt), a monomer containing an acid anhydride group (such as maleic anhydride), a vinyl monomer (vinyl isocyanate) , Aromatic vinyl monomers such as styrene, heterocyclic vinyl amines such as vinyl pyrrolidone and vinyl imidazole, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether, vinyl trisalkoxylane, vinyl chloride Le, a halogen-containing vinyl monomers such as vinylidene chloride) and the like. These copolymerizable monomers can be used alone or in combination of two or more.
[0048]
Preferred copolymerizable monomers include hydrophilic monomers having hydrophilic groups (eg, carboxyl groups, sulfonic acid groups and their salts, hydroxyl groups, ether groups, etc.), especially ether groups, especially oxyalkylene units. (For example, the number of units (addition moles) of alkylene oxide is 1 to 100, preferably 2 to 80 (for example, 5 to 80), more preferably about 5 to 70 (for example, 10 to 50)). A (meth) acrylic acid ester or allyl ether can be used.
Examples of vinyl monomers having an oxyalkylene unit include diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, tripropylene glycol mono ( (Meth) acrylate, polypropylene glycol mono (meth) acrylate, diethylene glycol mono (meth) allyl ether, triethylene glycol mono (meth) allyl ether, polyethylene glycol mono (meth) allyl ether, dipropylene glycol mono (meth) allyl ether , Tripropylene glycol mono (meth) allyl ether, polypropylene glycol mono (meth) allyl ether, and the like. These vinyl monomers can be used alone or in combination of two or more. Preferred monomers include (meth) acrylates, particularly polyoxyalkylene (meth) allyl ethers (especially polyoxyethylene allyl ethers) which are vinyl monomers whose oxyalkylene units are oxyethylene units.
[0049]
The proportion of the copolymerizable monomer can be selected within a range that does not impair the sharpness of the image, water resistance, etc. For example, 0.1 to 50 mol%, preferably 1 to 30 mol%, more preferably 2. It is about 5-25 mol% (for example, 3-20 mol%).
A copolymer (modified vinyl acetate resin) of vinyl acetate and a vinyl monomer having a polyoxyalkylene unit can be obtained, for example, from Nippon Synthetic Chemical Co., Ltd. under the trade name “OKS-7158G”.
[0050]
Other preferred polymers include hydrophilic polymers having an epoxy group. The epoxy group-containing polymer may be any of (1) a homopolymer or copolymer having a monomer unit having an epoxy group, and (2) an epoxidized resin by epoxidation of a resin. Examples of the epoxy group-containing monomer include allyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate, methallyl glycidyl ether, 1-allyloxy-3,4-epoxybutane, and 1- (3-butenyloxy) -2,3-epoxy. Examples thereof include propane and 4-vinyl-1-cyclohexene-1,2 epoxide. These epoxy-containing monomers can be used alone or in combination of two or more. Preferred epoxy-containing monomers include allyl glycidyl ether, glycidyl (meth) acrylate, and the like.
Examples of the copolymerizable monomer that can be copolymerized with the epoxy-containing monomer include vinyl acetate and the above-mentioned copolymerizable monomers, particularly vinyl esters (such as vinyl acetate), vinyl pyrrolidone, and (meth) acrylic monomers. ((Meth) acrylic acid C_1-8Alkyl monomers, etc.), monomers containing a carboxyl group or a salt thereof ((meth) acrylic acid or a salt thereof) can be used. In addition, the unit of vinyl ester in the polymer may constitute a vinyl alcohol unit by hydrolysis.
The use amount (content) of the monomer containing an epoxy group is 0.01 to 10 mol% (for example, 0.01 to 5 mol%), preferably 0.1 to 3 mol, based on the entire monomer. It is about mol% (for example, 0.2 to 2.5 mol%), especially about 0.2 to 2 mol%.
[0051]
In the epoxy group-containing resin (2), as a method for epoxidizing the hydrophilic polymer, epichlorohydrin is added to a water-absorbing polymer or a water-soluble polymer having an active hydrogen atom (for example, hydroxyl group, amino group, carboxyl group, etc.). It is possible to employ a method of introducing an epoxy group.
The introduction amount of the epoxy group is 0.01 to 10 mol% (for example, 0.01 to 5 mol%), preferably 0.1 to 3 mol% (for example, 0 to 0%) with respect to the whole polymer, as described above. 0.2 to 2.5 mol%), more preferably about 0.2 to 2 mol%.
[0052]
Preferred polymers having an epoxy group include, for example, polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble acrylic resins (for example, poly (meth) acrylic acid or salts thereof, (meth) acrylic acid C_1-8It can be composed of at least one selected from alkyl ester- (meth) acrylic acid copolymers or carboxyl group-containing (meth) acrylic resins or salts thereof such as salts thereof.
[0053]
In order to improve water resistance, a cross-linking agent may be added to the ink absorption layer. Examples of the crosslinking agent include organic crosslinking agents [amino resins (urea resins, guanamine resins, melamine resins, etc.), epoxy compounds, amine compounds [ethylene diamine, hexamethylene diamine, polyoxyalkylene diamines or polyamines (ie, polyethers). Aliphatic, cycloaliphatic, aromatic diamine or polyamine], polyvalent carboxylic acid or acid anhydride, polyisocyanate, block polyisocyanate, etc.], inorganic crosslinking agent [boric acid or boric acid Salts (borax etc.), zirconium compounds (eg halides, salts with inorganic acids such as sulfuric acid and organic acids such as acetic acid), titanium compounds (eg alkoxides such as tetraethoxy titanate), aluminum compounds (eg Trimethoxyaluminate Alkoxides, etc.), phosphorus compounds (eg, phosphites, bisphenol A modified polyphosphoric acids, etc.), silane coupling agents (silicone compounds having reactive functional groups such as alkoxy groups, glycidyl groups, etc.)] and the like. . These crosslinking agents can be used alone or in combination of two or more.
Of these cross-linking agents, polyisocyanate is often used. When an epoxy group-containing polymer is used, polycarboxylic acid or acid anhydrides, amines (such as primary or secondary amines), etc. Epoxy curing agents are often used.
[0054]
The addition amount of the crosslinking agent can be selected according to the kind of the polymer and the like, for example, 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight, more preferably, relative to parts by weight of the polymer 100 About 1 to 5 parts by weight.
[0055]
Further, the ink absorption layer may be composed of powder particles (pigments etc.) and a binder resin. Specific examples of the granular material include, for example, inorganic granular materials [white carbon, particulate calcium silicate, zeolite, magnesium aminosilicate, calcined siliceous soil, particulate magnesium carbonate, particulate alumina, and a plurality of single particles. Agglomerated or spherical porous particles such as light calcium carbonate, pigments, talc, kaolin, clay, deramikaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, titanium dioxide, aluminum hydroxide, hydroxide Calcium, magnesium hydroxide, magnesium silicate, calcium sulfate, mineral powder such as sericite, bentonite, smectite, etc.], organic particles [polystyrene resin, acrylic resin, urea resin, melamine resin, benzoguanamine resin, etc. Or non-hanging organic fine particles, fine hollow particles Organic particulate material, such as] the like. These powders can be used by selecting one or more kinds as appropriate.
As the binder resin, the above water-soluble polymer or hydrophilic polymer can be used.
[0056]
The ratio between the powder and the binder resin can be selected depending on the operation characteristics (for example, viscosity and fluidity) of the obtained coating liquid and the characteristics of the obtained ink absorption layer (for example, ink absorbability and ink bleeding). It is about 0.1 to 80 parts by weight, preferably about 0.2 to 50 parts by weight with respect to 100 parts by weight.
[0057]
The thickness of the ink absorbing layer can be selected according to the application, and is, for example, about 5 to 50 μm, preferably about 10 to 30 μm, and usually about 5 to 30 μm.
[0058]
The porous layer formed on the ink absorbing layer is not particularly limited as long as it has wettability with respect to the water-based ink and the water-based ink can penetrate into the pores. The porous layer can be composed of various polymers as described above.
[0059]
A preferred porous layer has high wettability with respect to the water-based ink and has a hydrophilic surface sufficient to allow the water-based ink to enter the pores. Such a porous layer can be composed of a hydrophilic polymer or a hydrophilized polymer. In addition, a hydrophilic polymer or a hydrophilized polymer means a polymer having a contact angle of less than 80 ° (preferably about 0 to 60 °, particularly about 0 to 40 °). The contact angle is an 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 in a state where the spread of the water droplet on the polymer surface is stopped at room temperature.
[0060]
As the hydrophilic polymer, exemplified polymers (hydrophilic polymer similar to the ink absorbing layer, polymer for porous film) can be used. More specifically, examples of the hydrophilic polymer include cellulose derivatives, vinyl polymers [(meth) acrylonitrile polymers, (meth) acrylic polymers, polyvinylpyrrolidone, polyvinyl acetate, and complete or partial thereof. Saponified product (polyvinyl alcohol, etc.), ethylene-vinyl acetate copolymer and its completely or partially saponified product, polyalkyl vinyl ether, carboxyl group-containing polymer or salt thereof, etc.], polyalkylene oxide (polyethylene glycol, etc.), polyamide, polyethylene Examples include imine, polysulfone, and polyethersulfone. These hydrophilic polymers can be used alone or in combination of two or more.
[0061]
Addition and application of surfactants, wetting agents, plasma treatment, corona discharge treatment, etc. even for olefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene, and hydrophobic polymers such as fluororesin Hydrophilicity can be imparted to the surface by this treatment, and the hydrophilic polymer is also included in the hydrophilic polymer.
[0062]
In the recording sheet, the average pore size of the porous layer is, for example, 0.001 to 10 μm (for example, 0.005 to 10 μm), preferably 0.005 to 5 μm (for example, 0.01 to 5 μm), and more preferably. About 0.005-2.5 micrometers (for example, 0.005-1 micrometer) may be sufficient. If the average pore diameter is less than 0.001 μm, the ink absorbency is not improved so much, and if it exceeds 10 μm, the water resistance and the print quality are likely to deteriorate.
[0063]
The porous layer may be transparent, translucent or opaque. The porous layer having high transparency has a maximum pore diameter of 0.4 μm or less and an average pore diameter of 0.01 to 0.35 μm (for example, 0.04 to 0.3 μm), preferably 0.05. It is about -0.3 micrometer (for example, 0.05-0.2 micrometer), More preferably, it is about 0.07-0.2 micrometer.
Such a recording sheet having a highly transparent porous layer usually has a light transmittance at a wavelength of 400 nm of 55% or more (that is, 55 to 100%), preferably 60 to 100%, more preferably. A recording sheet having a high transparency of about 70 to 100%, particularly about 75 to 100% and a light transmittance of about 80 to 100% can be obtained, and is useful as an OHP sheet.
[0064]
The porosity of the porous layer can be selected according to the ink absorbability, and is, for example, 10 to 70% (for example, 10 to 65%), preferably 15 to 65% (for example, 15 to 50%), and more preferably. Is about 20 to 60% (for example, 20 to 45%).
The thickness of the porous layer can be appropriately selected depending on the application, and is, for example, 1 to 100 μm, preferably 3 to 50 μm, particularly about 3 to 20 μm. When the thickness of the porous layer is less than 1 μm, the water resistance is insufficient, and when it exceeds 100 μm, the transparency may be lowered or the ink absorbability may be lowered.
[0065]
[Method for producing recording sheet]
The recording sheet can be obtained by sequentially forming an ink absorbing layer and a porous layer on at least one side of the substrate. The ink absorbing layer can be formed by applying a coating liquid containing the ink absorbing polymer (hydrophilic polymer) to a substrate and drying it. The ink-absorbing layer coating liquid is composed of the polymer (such as a hydrophilic polymer) and a solvent (water or an organic solvent), and may contain an additive to be described later. The porous layer can be formed using the dry phase conversion method.
[0066]
The ratio of the good solvent and the poor solvent in the coating liquid of the dry phase conversion method is not particularly limited as long as a uniform solution of the polymer can be formed, and usually 1-100 parts by weight of the poor solvent with respect to 100 parts by weight of the good solvent, Preferably it can select from the range of about 2-75 weight part, More preferably, 3-60 weight part (for example, 10-50 weight part). As the proportion of the poor solvent increases, the porous layer often becomes opaque. Therefore, when forming a highly transparent porous layer, the ratio of the good solvent to the poor solvent is usually 1 to 50 parts by weight (for example, 3 to 50 parts by weight) of the poor solvent with respect to 100 parts by weight of the good solvent. The amount is preferably 2 to 40 parts by weight (for example, 5 to 40 parts by weight), more preferably about 3 to 35 parts by weight (for example, 10 to 35 parts by weight), and usually about 3 to 30 parts by weight.
Furthermore, the content of the polymer in the coating solution is the same as described above.
[0067]
In the ink absorbing layer and / or porous layer coating liquid, conventional additives such as antifoaming agents, coating property improving agents, agents, and pigments are used as long as the properties of the ink absorbing layer and / or porous layer are not impaired. An antiblocking agent or the like may be added.
The recording sheet is useful as a recording sheet by an ink jet method for recording by ejecting small ink droplets, but can also be used as a printing sheet (particularly, a water-based ink sheet) for offset printing and flexographic printing.
[0068]
The recording sheet of the present invention is excellent in ink absorptivity, water resistance and anti-blocking properties, has good image sharpness (printing quality), and is suitable for ink jet recording. The recording sheet is excellent in transparency while having a porous layer, and is useful for an overhead projector (OHP).
[0069]
【The invention's effect】
The porous membrane of the present invention is highly transparent while being porous. In addition, since a dry phase separation method is used, a highly transparent porous membrane can be produced with high productivity.
[0070]
【Example】
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
The transparency, average pore diameter, and porosity in the examples were evaluated as follows.
[transparency]
Using a spectrophotometer [manufactured by Hitachi, Ltd., spectrophotometer U-3300], the light transmittance at a wavelength of 400 nm was measured and used as an index of transparency.
[Average pore size and porosity]
In an electron microscope surface photograph taken at a magnification of 5000, three predetermined areas (2 cm × 2 cm) were processed with an image processing device, and each hole in the electron microscope surface photograph was measured as a perfect circle, and the hole diameter was measured and averaged. The average pore size was determined.
The porosity (%) was calculated by a calculation formula (total area of holes / measured area) × 100.
[0071]
Example 1
A dope was prepared by adding 23.8 parts by weight of cyclohexanol to 100 parts by weight of a methyl cellosolve solution of 8% by weight of cellulose acetate (acetylation degree 55%, viscosity average polymerization degree 170). It was applied on a release paper so as to have a thickness of 30 μm after drying, dried for 5 minutes at 35 ° C. and 90% RH, and then dried at 100 ° C. for 2 minutes. The film peeled off from the release paper was a porous film having an average pore diameter of 0.08 μm and a porosity of 32%, and the light transmittance was 82%, indicating high transparency.
[0072]
Example 2
A dope was prepared by adding 4.8 parts by weight of cyclohexanol to 100 parts by weight of a methyl cellosolve solution of 10% by weight of cellulose acetate (acetylation degree 55%, viscosity average polymerization degree 180). On the release paper, it was applied to a thickness of 50 μm after drying, dried for 10 minutes at 25 ° C. and 90% RH, and then dried at 120 ° C. for 3 minutes. The film peeled off from the release paper was a porous film having an average pore diameter of 0.10 μm and a porosity of 45%, and the light transmittance was 73%, indicating high transparency.
[0073]
Example 3
A dope was prepared by adding 13.7 parts by weight of 4-methylcyclohexanol to 100 parts by weight of a methyl cellosolve solution of 8% by weight of cellulose acetate (acetylation degree 55%, viscosity average polymerization degree 170). On the release paper, it was applied so that the thickness after drying was 30 μm, dried for 5 minutes at 25 ° C. and 90% RH, and then dried at 120 ° C. for 3 minutes. The film peeled off from the release paper was a porous film having an average pore diameter of 0.07 μm and a porosity of 33%, and the light transmittance was 81%, indicating high transparency.
[0074]
Example 4
A dope is prepared by adding 9.2 parts by weight of 3,5-dimethylcyclohexanol to 100 parts by weight of a methyl cellosolve solution of 8% by weight of cellulose acetate (acetylation degree 55%, viscosity average polymerization degree 170). did. On the release paper, it was applied so that the thickness after drying was 30 μm, dried for 5 minutes at 25 ° C. and 90% RH, and then dried at 120 ° C. for 3 minutes. The film peeled from the release paper was a porous film having an average pore diameter of 0.08 μm and a porosity of 35%, and a light transmittance of 78%, indicating high transparency.
[0075]
Example 5
On the polyethylene terephthalate film, the dope of Example 1 was applied so that the thickness of the porous layer after drying was 5 μm, dried at 35 ° C. and 90% RH for 5 minutes, and then dried at 100 ° C. for 30 seconds. did. The obtained film was a laminated film having a porous layer with an average pore size of 0.08 μm and a porosity of 28% on the surface, and had a light transmittance of 80%, indicating high transparency.
[0076]
Example 6
A dope was prepared by adding 15 parts by weight of cyclohexanol to 100 parts by weight of a methyl cellosolve solution containing 10% by weight of cellulose acetate (acetylation degree 44%, viscosity average polymerization degree 110). On the polyethylene terephthalate film, the dope was applied so that the thickness of the porous layer after drying was 5 μm, dried at 25 ° C. and 90% RH for 10 minutes, and then dried at 100 ° C. for 30 seconds. Furthermore, a laminated film was obtained by laminating a polyethylene terephthalate film coated with a transparent adhesive on the porous layer. The porous layer had an average pore size of 0.08 μm and a porosity of 32%, and the laminated film had a light transmittance of 78% and high transparency.
[0077]
Comparative Example 1
A dimethyl sulfoxide solution of 18% by weight of polyethersulfone was applied on a glass plate so as to have a thickness of 30 μm after drying, and immersed in water at 25 ° C. for 1 minute. The film peeled off from the glass plate and naturally dried was a film having an asymmetric structure in which the surface was a dense layer and the lower layer was a porous layer having a pore diameter of 2 to 7 μm, and was white and opaque.
[0078]
Comparative Example 2
Acrylonitrile-N-vinylpyrrolidone copolymer (manufactured by Daicel Chemical Industries, Ltd., “DUY”, composition molar ratio 98: 2) on a glass plate so that a 14% by weight dimethyl sulfoxide solution has a thickness of 30 μm after drying. And immersed in water at 25 ° C. for 1 minute. The film peeled off from the glass plate and naturally dried was a film having an asymmetric structure in which the surface was a dense layer and the lower layer was a porous layer having a pore diameter of 1 to 5 μm, and was white and opaque.
[0079]
Example 7
Polyacrylonitrile-N-vinylpyrrolidone copolymer (manufactured by Daicel Chemical Industries, Ltd., “DUY”, composition molar ratio 98: 2) with thorough stirring in 100 parts by weight of a 13% by weight N, N-dimethylformamide solution A dope was prepared by adding 15 parts by weight of 3-methoxybutyl acetate. On the release paper, it was applied to a thickness of 30 μm after drying, dried at 70 ° C. and 90% RH for 1.5 minutes, and then dried at 120 ° C. for 3 minutes. The film peeled from the release paper was a porous film having an average pore diameter of 0.3 μm and a porosity of 52%, and had a light transmittance of 40% and excellent transparency. In addition, it replaced with the release paper and obtained the same result as the above even if it carried out similarly to the above except using the polyethylene terephthalate film (PET) which apply | coated polyvinyl alcohol.
[0080]
Example 8
Polyacrylonitrile-methyl acrylate copolymer (Toyobo Co., Ltd., “PAN-A”, composition molar ratio 95: 5) Acetic acid with thorough stirring in 100 parts by weight of 13% by weight N, N-dimethylformamide solution A dope was prepared by adding 15 parts by weight of 3-methoxybutyl. On the release paper, it was applied to a thickness of 30 μm after drying, dried at 70 ° C. and 90% RH for 1.5 minutes, and then dried at 120 ° C. for 3 minutes. The film peeled from the release paper was a porous film having an average pore diameter of 0.2 μm and a porosity of 33%, and had a light transmittance of 40% and excellent transparency.
[0081]
Example 9
Polyacrylonitrile-vinyl acetate-diethylaminoethyl methacrylate copolymer (manufactured by Toyobo Co., Ltd., “PAN-C”, composition molar ratio 89: 8: 3) in 100 parts of a 13 wt% N, N-dimethylformamide solution, A dope was prepared by adding 15 parts by weight of 3-methoxybutyl acetate while stirring well. On the release paper, it was applied to a thickness of 30 μm after drying, dried for 1.5 minutes at 70 ° C. and 90% RH, and then dried at 120 ° C. for 3 minutes. The film peeled from the release paper was a porous film having an average pore diameter of 0.01 μm and a porosity of 10%, and had a light transmittance of 41% and excellent transparency.
[0082]
Example 10
Acrylonitrile-N-vinylpyrrolidone copolymer (manufactured by Daicel Chemical Industries, Ltd., “DUY”, composition molar ratio 98: 2) 2 parts of a 13 wt% N, N-dimethylformamide solution with good stirring -A dope was prepared by adding 15 parts by weight of butoxyethanol. On the release paper, it was applied to a thickness of 30 μm after drying, dried for 1.5 minutes at 70 ° C. and 90% RH, and then dried at 120 ° C. for 3 minutes. The film peeled from the release paper was a porous film having an average pore size of 0.08 μm and a porosity of 48%, and had excellent transparency with a light transmittance of 39%.
[0083]
Example 11
The average pore diameter was 0.1 μm and the porosity was 30 as in Example 7, except that the drying conditions were a temperature of 50 ° C. and a humidity of 90% RH for 1.5 minutes and then drying at 120 ° C. for 3 minutes. %, A porous film having a light transmittance of 36% was obtained.
[0084]
Comparative Example 3
A coating solution was prepared by adding 2.6 parts by weight of 1,2-diethoxyethane to 100 parts by weight of a 15% by weight solution of polysulfone (manufactured by Udel, P-1700) while stirring well. . On the PET film coated with polyvinyl alcohol, the resulting film was applied to a thickness of 30 μm, dried at 25 ° C. and 95% RH for 5 minutes, and then dried at 120 ° C. for 3 minutes.
The obtained film was a porous film having an average pore diameter of 3 μm and a porosity of 32%, and the light transmittance was 2%.
[0085]
Example 12
A dope was prepared by adding 15 parts by weight of 3-methoxybutyl acetate to 100 parts by weight of polymethyl methacrylate (manufactured by Scientific Polymer Products) with 100 parts by weight of an N, N-dimethylformamide solution while stirring well. On the release paper, it was applied to a thickness of 30 μm after drying, dried at 60 ° C. and 95% RH for 1.5 minutes, and then dried at 120 ° C. for 3 minutes. The film peeled off from the release paper was a porous film having an average pore diameter of 0.15 μm and a porosity of 45%, and the light transmittance was 75%, indicating high transparency.
[0086]
Example 13
A dope was prepared by adding 15 parts by weight of 3-methoxybutyl acetate to 100 parts by weight of a polyethersulfone (manufactured by Sumitomo Chemical Co., Ltd.) 14 parts by weight of N, N-dimethylformamide solution while stirring well. On the release paper, it was applied to a thickness of 30 μm after drying, dried for 1.5 minutes at 60 ° C. and 95% RH, and then dried at 120 ° C. for 3 minutes. The film peeled from the release paper was a porous film having an average pore diameter of 0.05 μm and a porosity of 30%, and the light transmittance was 80%, which showed high transparency.
[0087]
[Evaluation as a recording sheet]
The following characteristics as a recording sheet were examined for the laminated films obtained in the following Examples and Comparative Examples.
An ink jet printer (BJC-420J, manufactured by Canon Inc.) was used, and each color of cyan, yellow, magenta, and black was printed solid on the resulting recording sheet to form a recorded image.
[Ink absorbency]
After printing, copy machine (PPC) copy paper is placed on the print section at regular intervals, and the load (250 g / cm²) For 10 seconds, the copy paper was peeled off, the degree of ink set-off was judged visually, and the ink absorbency was evaluated based on the time until no set-off was observed.
[water resistant]
After printing, the printed part is wiped 3 times with a cotton swab soaked in water, and the ink removal is visually judged according to the following criteria.
◎ No change
○ Some ink can be removed, and the printed part becomes thinner.
× The printed part of the wiped area can be completely removed
[Image clarity]
A yellow base and a magenta line (width of 100 μm) were printed on the base, and then magnified 50 times with a microscope. The dots were observed and evaluated according to the following criteria.
◎ The dots are hardly blurred
○ The dots are slightly blurred and the measured value is larger than 120 μm.
× Dot blurs and the border between adjacent yellow and magenta dots cannot be distinguished
[Blocking resistance]
Stack two or more recording sheets and load (40 g / cm²) And stored for 1 day under conditions of a temperature of 40 ° C. and a humidity of 90% RH, and evaluated according to the following criteria.
◎ No matting or blocking
○ Matting is allowed but not blocked
× Blocking.
[0088]
Example 14
A 15% by weight aqueous solution of a modified vinyl acetate copolymer (manufactured by Nippon Gosei Kagaku, OKS-7158G) is applied to a polyethylene terephthalate film having a thickness of 100 μm and subjected to an easy adhesion treatment (manufactured by ICI Japan Co., Ltd., Melinex 705). By drying at 120 ° C. for 3 minutes, an ink absorbing layer having a thickness of 15 μm was formed. A coating solution (dope) was prepared by adding 23.8 parts by weight of cyclohexanol to 100 parts by weight of an 8% by weight methyl cellosolve solution of cellulose acetate (average degree of acetylation: 55, viscosity average degree of polymerization: 170). This coating solution is applied onto the ink absorbing layer, dried in an atmosphere of 35 ° C. and 90% RH for 5 minutes, and then dried at 120 ° C. for 3 minutes, with an average pore size of 0.08 μm and a porosity of 32%. A porous layer having a thickness of 5 μm was formed.
The resulting recording sheet had a light transmittance of 78% at a wavelength of 400 nm, and had excellent transparency.
[0089]
Example 15
A 15% by weight aqueous solution of a modified vinyl acetate copolymer (manufactured by Nippon Gosei Kagaku, OKS-7158G) is applied to a polyethylene terephthalate film having a thickness of 100 μm and subjected to an easy adhesion treatment (manufactured by ICI Japan Co., Ltd., Melinex 705). By drying at 120 ° C. for 3 minutes, an ink absorbing layer having a thickness of 15 μm was formed. A coating solution (dope) is prepared by adding 45 parts by weight of cyclohexanol to 100 parts by weight of an 8% by weight methyl cellosolve solution of cellulose acetate (average degree of acetylation: 55, viscosity average degree of polymerization: 170). It is coated on the ink absorbing layer, dried in an atmosphere of 35 ° C. and 90% humidity for 5 minutes, and then dried at 120 ° C. for 3 minutes. The average pore diameter is 1.1 μm, the porosity is 55%, and the thickness is 5 μm. A white porous membrane was formed.
[0090]
Comparative Example 4
A 15% by weight aqueous solution of a modified vinyl acetate copolymer (manufactured by Nippon Gosei Kagaku, OKS-7158G) is applied to a polyethylene terephthalate film having a thickness of 100 μm and subjected to easy adhesion treatment (manufactured by ICI Japan Co., Ltd., Melinex 705). The ink absorbing layer having a thickness of 15 μm was formed by drying at 120 ° C. for 3 minutes.
[0091]
Example 16
A 10% by weight aqueous solution of polyvinylpyrrolidone (weight average molecular weight: 360,000) is applied to a polyethylene terephthalate film with a thickness of 100 μm and subjected to easy adhesion treatment (Melnex 705, manufactured by ICI Japan Co., Ltd.) and dried at 120 ° C. for 3 minutes. Thus, an ink absorbing layer having a thickness of 10 μm was formed. 13.7 parts by weight of 4-methylcyclohexanol is added to 100 parts by weight of an 8% by weight methyl cellosolve solution of cellulose acetate (average degree of acetylation: 55, viscosity average degree of polymerization: 170) to prepare a coating solution (dope). did. This coating solution is applied onto the ink absorbing layer, dried in an atmosphere of a temperature of 25 ° C. and a humidity of 90% RH for 5 minutes, and then dried at 120 ° C. for 3 minutes, with an average pore size of 0.07 μm and a porosity of 33%. A porous layer having a thickness of 7 μm was formed.
The obtained recording sheet had a light transmittance of 78% at a wavelength of 400 nm, and had excellent transparency.
[0092]
Example 17
A 10% by weight aqueous solution of polyvinylpyrrolidone (weight average molecular weight: 360,000) is applied to a polyethylene terephthalate film with a thickness of 100 μm and subjected to easy adhesion treatment (Melnex 705, manufactured by ICI Japan Co., Ltd.) and dried at 120 ° C. for 3 minutes. Thus, an ink absorbing layer having a thickness of 10 μm was formed. A solution comprising 2 parts by weight of cellulose acetate (average degree of acetylation: 44, degree of viscosity average polymerization: 110), 8 parts by weight of cellulose acetate (average degree of acetylation: 55, degree of viscosity average polymerization: 180) and 90 parts by weight of methyl cellosolve Then, 45.5 parts by weight of cyclohexanol was added to prepare a coating solution (dope). This coating solution is applied onto the ink absorbing layer, dried in an atmosphere of a temperature of 25 ° C. and a humidity of 90% RH for 10 minutes, and then dried at 120 ° C. for 3 minutes, with an average pore diameter of 0.8 μm and a porosity of 53%. A white porous layer having a thickness of 10 μm was formed.
[0093]
Comparative Example 5
A 10% by weight aqueous solution of polyvinylpyrrolidone (weight average molecular weight: 360,000) is applied to a polyethylene terephthalate film having a thickness of 100 μm and an easy-adhesion-treated polyethylene terephthalate film (manufactured by ICI Japan Co., Ltd., MERENEX 705) and dried at 120 ° C. for 3 minutes. Thus, an ink absorbing layer having a thickness of 10 μm was formed.
[0094]
Example 18
Polyethylene terephthalate film with a thickness of 100 μm (ICI Japan Co., Ltd., Melinex 705) and polyvinyl alcohol / allyl glycidyl ether copolymer (hereinafter referred to as PVA / AGE copolymer) Degree of saponification of PVA part : 80%, copolymer composition ratio: PVA / AGE = 99.5 / 0.5 (molar ratio), degree of polymerization: 500) to 100 parts by weight of aqueous solution of polyoxypropylene-α, ω-diamine (molecular weight) The coating liquid prepared by adding 2 parts by weight of a 5 wt% aqueous solution (230) was applied and dried at 120 ° C. for 10 minutes to form an ink absorbing layer having a thickness of 10 μm. A coating solution (dope) was prepared by adding 4.8 parts by weight of cyclohexanol to 100 parts by weight of a 10% by weight methyl cellosolve solution of cellulose acetate (average degree of acetylation: 55, viscosity average degree of polymerization: 180). This coating solution is applied onto the ink absorbing layer, dried in an atmosphere of a temperature of 25 ° C. and a humidity of 90% RH for 10 minutes, and then dried at 120 ° C. for 3 minutes, with an average pore diameter of 0.10 μm and a porosity of 45%. A porous layer having a thickness of 10 μm was formed.
The obtained recording sheet had a light transmittance of 71% at a wavelength of 400 nm, and had excellent transparency.
[0095]
Example 19
A PVA / AGE copolymer (degree of saponification of PVA part: 80%, copolymer composition ratio: PVA / AGE =) on a polyethylene terephthalate film with a thickness of 100 μm and treated with polyethylene terephthalate (manufactured by ICI Japan Co., Ltd., Melinex 705) 2 parts by weight of a 5% by weight aqueous solution of polyoxypropylene-α, ω-diamine (molecular weight: 230) is added to 100 parts by weight of a 10% by weight aqueous solution of 99.5 / 0.5 (molar ratio), polymerization degree: 500). The coating solution prepared in this manner was applied and dried at 120 ° C. for 10 minutes to form an ink absorption layer having a thickness of 10 μm. A coating solution (dope) was prepared by adding 22.3 parts by weight of amyl formate to 100 parts by weight of a 5% by weight dimethoxyethane solution of cellulose acetate (average degree of acetylation: 55, viscosity average degree of polymerization: 170). This coating solution is applied onto the ink absorbing layer, dried under an atmosphere of a temperature of 25 ° C. and a humidity of 70% RH for 5 minutes, and then dried at 120 ° C. for 3 minutes, with an average pore diameter of 1.5 μm and a porosity of 60%. A white porous layer having a thickness of 5 μm was formed.
[0096]
Comparative Example 6
A PVA / AGE copolymer (degree of saponification of PVA part: 80%, copolymer composition ratio: PVA / AGE =) on a polyethylene terephthalate film with a thickness of 100 μm and treated with polyethylene terephthalate (manufactured by ICI Japan Co., Ltd., Melinex 705) 2 parts by weight of a 5% by weight aqueous solution of polyoxypropylene-α, ω-diamine (molecular weight: 230) is added to 100 parts by weight of a 10% by weight aqueous solution of 99.5 / 0.5 (molar ratio), polymerization degree: 500). The coating solution prepared in this manner was applied and dried at 120 ° C. for 10 minutes to form an ink absorption layer having a thickness of 10 μm.
[0097]
Example 20
A PVA / AGE copolymer (degree of saponification of PVA part: 80%, copolymer composition ratio: PVA / AGE =) on a polyethylene terephthalate film with a thickness of 100 μm and treated with polyethylene terephthalate (manufactured by ICI Japan Co., Ltd., Melinex 705) A coating solution prepared by adding 1 part by weight of a 5% by weight aqueous solution of hexamethylenediamine to 100 parts by weight of a 10% by weight aqueous solution of 99.5 / 0.5 (molar ratio), polymerization degree: 500), 120 By drying at 10 ° C. for 10 minutes, an ink absorbing layer having a thickness of 10 μm was formed. Coating solution (dope) by adding 9.2 parts by weight of 3,5-dimethylcyclohexanol to 100 parts by weight of 8% by weight methyl cellosolve solution of cellulose acetate (average degree of acetylation: 55, viscosity average degree of polymerization: 170) Was prepared. This coating solution is applied onto the ink absorbing layer, dried in an atmosphere of a temperature of 25 ° C. and a humidity of 90% RH for 10 minutes, and then dried at 120 ° C. for 3 minutes, with an average pore size of 0.08 μm and a porosity of 35%. A porous layer having a thickness of 10 μm was formed.
The resulting recording sheet had a light transmittance of 76% at a wavelength of 400 nm and had excellent transparency.
[0098]
Example 21
A PVA / AGE copolymer (degree of saponification of PVA part: 80%, copolymer composition ratio: PVA / AGE =) on a polyethylene terephthalate film with a thickness of 100 μm and treated with polyethylene terephthalate (manufactured by ICI Japan Co., Ltd., Melinex 705) A coating solution prepared by adding 1 part by weight of a 5% by weight aqueous solution of hexamethylenediamine to 100 parts by weight of a 10% by weight aqueous solution of 99.5 / 0.5 (molar ratio), polymerization degree: 500), 120 By drying at 10 ° C. for 10 minutes, an ink absorbing layer having a thickness of 10 μm was formed. A coating solution (dope) was prepared by adding 36.8 parts by weight of ethyl benzoate to 100 parts by weight of a 5% by weight methyl cellosolve solution of cellulose acetate (average degree of acetylation: 55, viscosity average degree of polymerization: 170). This coating solution is applied onto the ink absorbing layer, dried in an atmosphere of a temperature of 25 ° C. and a humidity of 80% RH for 10 minutes, and then dried at 130 ° C. for 10 minutes, with an average pore diameter of 1.7 μm and a porosity of 58%. A white porous layer having a thickness of 7 μm was formed.
[0099]
Comparative Example 7
A PVA / AGE copolymer (degree of saponification of PVA part: 80%, copolymer composition ratio: PVA / AGE =) on a polyethylene terephthalate film with a thickness of 100 μm and treated with polyethylene terephthalate (manufactured by ICI Japan Co., Ltd., Melinex 705) A coating solution prepared by adding 1 part by weight of a 5% by weight aqueous solution of hexamethylenediamine to 100 parts by weight of a 10% by weight aqueous solution of 99.5 / 0.5 (molar ratio), polymerization degree: 500), 120 By drying at 10 ° C. for 10 minutes, an ink absorbing layer having a thickness of 10 μm was formed.
[0100]
Example 22
100 μm thick polyethylene terephthalate film with easy adhesion treatment (ICI Japan Co., Ltd., Melinex 705), 100 parts by weight of synthetic amorphous silica (Syloid 74, manufactured by Fuji Devison), polyvinyl alcohol (PVA-613, Kuraray ( Co., Ltd.) 40 parts by weight and cationic resin (Polyfix 601; Showa High Polymer Co., Ltd.) 20 parts by weight is coated with an aqueous coating solution having a solid concentration of 14% by weight and dried at 120 ° C. for 10 minutes. As a result, an ink absorbing layer having a thickness of 10 μm was formed. A coating solution (dope) was prepared by adding 32.4 parts by weight of diisobutyl ketone to 100 parts by weight of a 8% by weight methyl cellosolve solution of cellulose acetate (average degree of acetylation: 55, viscosity average degree of polymerization: 170). This coating solution is applied onto the ink absorbing layer, dried in an atmosphere of a temperature of 25 ° C. and a humidity of 80% RH for 15 minutes, and then dried at 120 ° C. for 3 minutes, with an average pore diameter of 1.8 μm and a porosity of 55%. A white porous layer having a thickness of 10 μm was formed.
[0101]
Comparative Example 8
100 μm thick polyethylene terephthalate film with easy adhesion treatment (ICI Japan Co., Ltd., Melinex 705), 100 parts by weight of synthetic amorphous silica (Syloid 74, manufactured by Fuji Devison), polyvinyl alcohol (PVA-613, Kuraray ( Co., Ltd.) 40 parts by weight and cationic resin (Polyfix 601; Showa High Polymer Co., Ltd.) 20 parts by weight is coated with an aqueous coating solution having a solid concentration of 14% by weight and dried at 120 ° C. for 10 minutes. As a result, an ink absorbing layer having a thickness of 10 μm was formed.
[0102]
And when the characteristic of the recording sheet obtained by the Example and the comparative example was evaluated, the result shown in a table | surface was obtained.
[0103]
[Table 1]

As is apparent from Table 1, when the recording sheet of the example is used, the ink absorbability and the sharpness of the image are good, and the water resistance and blocking resistance are also high. On the other hand, when the recording sheet of the comparative example is used, the ink absorbability and the sharpness of the image are relatively good, but the water resistance and blocking resistance are not sufficient.
[0104]
Table 2 shows the evaluation results as recording sheets for Examples 7 to 11 and Comparative Example 3. In Examples 7 to 11 and Comparative Example 3, water resistance and printability were evaluated as follows.
[water resistant]
The printed part was immersed in water at 30 ° C. for 1 minute, then pulled up vertically, drained well, and dried. After drying, the printed part was visually evaluated according to the following criteria.
○ The printed part remains completely
△ Bleeding is observed in the printed part
× No print area left
[Print Status]
The printing state of the printing part was visually evaluated according to the following criteria.
○ The printed part is printed uniformly.
△ Bleeding is observed in the printed part
× Large blurring on the print
[0105]
[Table 2]

Example 23
A 15% by weight aqueous solution of a modified vinyl acetate copolymer (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., OKS-7158G) on a polyethylene terephthalate film having a thickness of 100 μm and an easily treated polyethylene terephthalate film (MELINEX 705, manufactured by ICI Japan Co., Ltd.) And an ink absorbing layer having a thickness of 15 μm was formed by drying at 120 ° C. for 3 minutes.
[0106]
A coating solution (dope) was prepared by adding 15 parts by weight of 3-methoxybutyl acetate to 100 parts by weight of polymethyl methacrylate (manufactured by Scientific Polymer Products) with 100 parts by weight of N, N-dimethylformamide solution while stirring well. . This coating solution is applied on the ink absorbing layer, dried for 1.5 minutes under the conditions of a temperature of 60 ° C. and a humidity of 95% RH, and then dried at 120 ° C. for 3 minutes, an average pore diameter of 0.15 μm, and a porosity of 45 % And a 10 μm thick porous layer was formed.
The obtained recording sheet had a light transmittance of 72% at a wavelength of 400 nm and had excellent transparency.
When evaluated as a recording sheet, the ink absorptivity was 1 minute, water resistance: ◎, image sharpness: ブ ロ ッ キ ン グ, and blocking resistance: ◎.
[0107]
Example 24
A 15% by weight aqueous solution of a modified vinyl acetate copolymer (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., OKS-7158G) on a polyethylene terephthalate film having a thickness of 100 μm and an easily treated polyethylene terephthalate film (MELINEX 705, manufactured by ICI Japan Co., Ltd.) And an ink absorbing layer having a thickness of 15 μm was formed by drying at 120 ° C. for 3 minutes. Polyethersulfone (Sumitomo Chemical Co., Ltd., P4800) 15 parts by weight of 3-methoxybutyl acetate was added to 100 parts by weight of a 14% by weight N, N-dimethylformamide solution while stirring well. Dope) was prepared. This coating solution is applied onto the ink absorbing layer and dried for 1.5 minutes under the conditions of a temperature of 60 ° C. and a humidity of 95% RH, and then dried at 120 ° C. for 3 minutes, with an average pore diameter of 0.05 μm and a porosity of 30 % And a 10 μm thick porous layer was formed.
The obtained recording sheet had a light transmittance of 75% at a wavelength of 400 nm and had excellent transparency.
When evaluated as a recording sheet, the ink absorptivity was 1 minute, water resistance: ◎, image sharpness: ブ ロ ッ キ ン グ, and blocking resistance: ◎.
[0108]
Comparative Example 9
An acetone solution of cellulose acetate (acetylation degree 55%, average polymerization degree 170) 8% by weight was coated on a glass plate so as to have a thickness after drying of 30 μm, and immersed in water at 25 ° C. for 1 minute. The film peeled off from the glass plate and naturally dried was a film having an asymmetric structure in which the surface was a dense layer and the lower layer was a porous layer having a pore diameter of 3 to 8 μm, and was white and opaque.
[0109]
Comparative Example 10
An acetone solution of 8% by weight of cellulose acetate (acetylation degree 55%, average polymerization degree: 170) was applied on a release paper so as to have a thickness of 30 μm after drying, and was 5 under conditions of 40 ° C. and 50% RH. After partial drying, it was dried at 120 ° C. for 3 minutes. The film peeled off from the release paper and naturally dried showed a high transparency with a light transmittance of 85%, but was a non-porous film.
[0110]
Comparative Example 11
Acrylonitrile-N-vinylpyrrolidone copolymer (manufactured by Daicel Chemical Industries, Ltd., “DUY”, composition molar ratio 98: 2) 14% by weight of dimethyl sulfoxide solution is dried on a release paper to a thickness of 30 μm after drying. After being applied for 1.5 minutes under the conditions of 70 ° C. and 90% RH, it was dried at 120 ° C. for 3 minutes. The film peeled off from the release paper and naturally dried showed a high transparency with a light transmittance of 82%, but was a non-porous film.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an example of an embodiment of the present invention.
FIG. 2 is an electron micrograph (drawing substitute photo) showing a cross section of the porous film of Example 1. FIG.
3 is an electron micrograph (drawing substitute photo) showing the surface of the porous film of Example 1. FIG.
4 is an electron micrograph (drawing substitute photo) showing the surface of the porous film of Example 7. FIG.
[Explanation of symbols]
1: Base material
2: Ink absorbing layer
3: Porous layer
4: Hole

Claims (13)

A laminated film multi porous layer on at least one surface of the substrate is formed, the porous layer (1) is composed of at least one polymeric selected from the following (a) ~ (c), (2) A laminated film having a porosity of 10 to 60%, (3) a light transmittance at a wavelength of 400 nm of 30% or more, and (4) a microphase separation structure.
(A) cellulose acetate having an acetylation degree of 42 to 62% and a viscosity average polymerization degree of 50 to 800,
(B) (meth) acrylonitrile, (meth) acrylic acid ester monomer, vinyl ester monomer, heterocyclic vinyl monomer, aromatic vinyl monomer, polymerizable unsaturated dicarboxylic acid or its A homo- or copolymer selected from at least one of (meth) acrylonitrile and (meth) acrylic acid ester monomers selected from derivatives, and
(C) at least one selected from polysulfone and polyethersulfone   The laminated film according to claim 1, wherein the porous layer has pores having an average pore diameter of 0.002 to 0.35 µm and a maximum pore diameter of 0.4 µm or less.   The laminated film according to claim 1, wherein the light transmittance at a wavelength of 400 nm of the porous layer is 50% or more.   The laminated film according to claim 1, wherein a porous layer is interposed between the substrates.   The dope containing a polymer, a good solvent for the polymer, a boiling point higher than the good solvent, and a poor solvent for the polymer is cast or applied to a substrate, and the coating film is dried. A method for producing a laminated film. The dope is selected from polymers, ketones, esters, ethers, cellosolves, cellosolve acetates, aromatic hydrocarbons, halogenated hydrocarbons, nitro compounds, amides, sulfoxides, and nitriles. And at least one good solvent having a boiling point of 35 to 200 ° C. and at least one good solvent selected from esters, alcohols, ketones, ethers and aliphatic hydrocarbons and having a boiling point of 100 to 230 ° C. The manufacturing method of the laminated | multilayer film of Claim 5 containing a poor solvent. Dope is C _3-5 dialkyl ketone, acetic acid C _1-4 alkyl ester, cyclic or chain C _4-6 ether, C _1-4 alkyl-cellosolve, C _1-4 alkyl-cellosolve acetate, mono or di C _{1 -4} acylamide, di-C _1-3 alkyl sulfoxide, and C _1-6 alkyl nitrile selected from at least one good solvent, formic acid C _5-8 alkyl ester, and C _1-4 alkoxy group Good C _2-4 aliphatic carboxylic acid-C _3-10 alkyl ester, benzoic acid C _1-4 alkyl ester, C _4-8 cycloalkanol optionally having an alkyl group, C _2-6 alkoxy-C _{1 At} least selected from _-4 alcohols, C _6-10 dialkyl ketones, C _7-10 ethers and C _5-20 aliphatic hydrocarbons The manufacturing method of the laminated | multilayer film of Claim 5 containing a kind of poor solvent. The method for producing a laminated film according to claim 5 , wherein the difference in boiling point between the good solvent and the poor solvent is 20 to 60 ° C. The method for producing a laminated film according to claim 5, wherein the film is dried at a temperature of 10 to 100 ° C and a humidity of 50 to 90% RH for 30 seconds to 60 minutes, and further dried at a temperature higher than the temperature for 2 seconds to 30 minutes. . The method for producing a laminated film according to claim 5 , wherein the proportion of the poor solvent is 1 to 50 parts by weight with respect to 100 parts by weight of the good solvent. The method for producing a laminated film according to claim 5 , wherein the dope contains 3 to 40 parts by weight of the poor solvent with respect to 100 parts by weight of the good solvent solution of 5 to 30% by weight of the polymer.   A recording sheet comprising the laminated film according to claim 1, wherein an ink absorbing layer is further interposed between the substrate and the porous layer. The recording sheet according to claim 12 , wherein the porous layer has an average pore size of 0.001 to 10 µm.

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