TW202126703A - Film for production of optical film, method for producing optical film, and optical film - Google Patents

Abstract

The present invention provides: a film for the production of an optical film, said film having good productivity, while enabling the achievement of an optical film that exhibits excellent optical performance and wet heat resistance in comparison to those cases where a non-modified PVA having the same degree of polymerization is used; a method for producing an optical film, said method using this film for the production of an optical film; and an optical film. The present invention is a film for the production of an optical film, said film containing a polyvinyl alcohol having a silicon-containing group, wherein: the silicon-containing group is a silanol group or a group that is able to be converted into a silanol group in the presence of water; the polyvinyl alcohol has a viscosity-average degree of polymerization of from 1,000 to 6,000 and a saponification degree of 98.7% by mole or more; and the content of the silicon-containing group relative to all structural units is from 0.01% by mole to 1.0% by mole.

Description

Optical film manufacturing film, optical film manufacturing method, and optical film

The present invention relates to a film for manufacturing an optical film, a method of manufacturing an optical film, and an optical film.

The polarizing plate with the function of light transmission and shielding is the basic component of the liquid crystal display (LCD) as well as the liquid crystal that changes the polarization state of light. Many polarizing plates have a structure in which a protective film such as a triacetate cellulose (TAC) film is attached to the surface of the polarizing film. For polarizing films, iodine-based dyes (I ₃ ^- or I ₅ ^- etc.) or dichroic dyes called dichroic organic dyes are adsorbed on polyvinyl alcohol films (hereinafter referred to as "polyvinyl alcohol" for short). “PVA”) is the mainstream on a substrate (stretched film) formed by uniaxial stretching.

LCD can be used in a wide range of small devices such as electronic computers and watches, smart phones, notebook computers, liquid crystal displays, liquid crystal color projectors, liquid crystal TVs, driving navigation systems, mobile phones, and measuring devices used indoors and outdoors. In recent years, improvements in display quality have been required for these machine systems. Along with this, high performance is required for polarizing films. Specifically, polarizing films with excellent optical properties such as polarization and transmittance are required. In addition, durability is also important in polarizing films, and it is required to maintain good performance even in an environment such as high temperature and humidity. In optical films other than polarizing films, optical performance and durability are similarly required.

As a polarizing film with improved optical properties, moisture and heat resistance, etc., a polarizing film using PVA with a high degree of polymerization is known (Patent Document 1). In Patent Document 1, a PVA film forming solution obtained by dissolving PVA with a high degree of polymerization in a solvent containing dimethyl sulfoxide as a main component is used to form a film. [Prior Technical Literature] [Patent Literature]

Patent Document 1 　 Japanese Patent Laid-Open No. 1-105204

[The problem to be solved by the invention]

In the manufacture of PVA film in industry, generally considering environmental aspects, economic efficiency, etc., an aqueous PVA solution with water as a solvent is used as a film forming solution. However, PVA with a high degree of polymerization has poor film-forming properties due to the increase in the viscosity of the aqueous solution, which is poor in industrial production. Therefore, it is desired to have a method to improve the optical performance or moisture and heat resistance of the optical film in addition to the method of increasing the degree of polymerization of PVA.

The present invention is based on the above situation, and its purpose is to provide: a film for the manufacture of an optical film, which can obtain a film with good productivity and optical performance compared with the case of using unmodified PVA with the same degree of polymerization And an optical film with excellent moisture and heat resistance; a manufacturing method of an optical film using such an optical film manufacturing film; and an optical film. [Means used to solve the problem]

The above-mentioned purpose can be achieved by providing any one of the following. [1] A film for the manufacture of optical films, comprising a polyvinyl alcohol having a silicon-containing group, the silicon-containing group being a silanol group or a group that can be converted into a silanol group in the presence of water, and the viscosity of the polyvinyl alcohol is average The degree of polymerization is 1,000 or more and 6,000 or less, the saponification degree is 98.7 mol% or more, and the content of the silicon-containing group relative to all structural units is 0.01 mol% or more and 1.0 mol% or less; [2] The film for manufacturing an optical film as in [1], wherein the saponification degree is 99.5 mol% or more; [3] The optical film manufacturing film of [1] or [2], wherein the product of the viscosity average degree of polymerization and the content of the silicon-containing group is 100 mol% or more and 2,000 mol% or less; [4] The film for manufacturing an optical film according to any one of [1] to [3], having an average thickness of 1 μm or more and 75 μm or less; [5] The film for manufacturing an optical film as in any one of [1] to [4], with a swelling degree of 140% or more and 400% or less; [6] The film for manufacturing an optical film according to any one of [1] to [5], wherein the optical film is a polarizing film; [7] The film for manufacturing an optical film according to any one of [1] to [6], which is a non-stretched film; [8] A method of manufacturing an optical film, comprising a step of uniaxially stretching the film for manufacturing an optical film as in any one of [1] to [7]; [9] The method of manufacturing an optical film according to [8], wherein the optical film is a polarizing film; [10] An optical film comprising a polyvinyl alcohol having a silicon-containing group, the silicon-containing group being a silanol group or a group that can be converted into a silanol group in the presence of water, and the viscosity of the polyvinyl alcohol has an average degree of polymerization of 1,000 to 6,000, the saponification degree is 98.7 mol% or more, and the content of the silicon-containing group relative to all structural units is 0.01 mol% or more and 1.0 mol% or less; [11] The optical film of [10], which is a polarizing film; and [12] The optical film of [10] or [11], which is a single-layer film. [Effects of Invention]

According to the present invention, it is possible to provide: a film for manufacturing an optical film, which can obtain an optical film with good productivity and excellent optical performance and moisture and heat resistance compared with the case of using unmodified PVA with the same degree of polymerization Films; manufacturing methods of optical films using such films for manufacturing optical films; and optical films.

[Pattern for implementing the invention]

＜Film for manufacturing optical film＞ The film for producing an optical film of the present invention contains polyvinyl alcohol having a silicon-containing group (hereinafter referred to as "silanol-modified PVA").

(Silanol-modified PVA) Silanol-modified PVA is a _{polymer having a vinyl alcohol unit (-CH 2} -CH(OH)-) as a structural unit and a silicon-containing group. The silanol-modified PVA may include structural units having silicon-containing groups, and may further have vinyl ester units such as vinyl acetate units or other structural units.

The lower limit of the viscosity average degree of polymerization of the silanol-modified PVA is 1,000, preferably 2,000, and more preferably 2,500. The viscosity average polymerization degree of PVA modified by silanol is above the above lower limit, and the film for manufacturing an optical film of the present invention has excellent stretching processability, and an optical film with excellent optical properties and moisture and heat resistance can be obtained. On the other hand, the upper limit of the viscosity average degree of polymerization is 6,000, preferably 5,000, and more preferably 4,000. The viscosity average degree of polymerization of PVA modified by silanol is below the above upper limit, which can exhibit good water solubility and can suppress the increase in the viscosity of the aqueous solution. Therefore, by silanol-modified PVA, the viscosity average degree of polymerization is less than the above upper limit, thereby exhibiting good film forming properties and improving the productivity of the optical film manufacturing film of the present invention.

The viscosity average degree of polymerization means the average degree of polymerization measured in accordance with the description of JIS K6726-1994. That is, in this specification, the viscosity average degree of polymerization is based on re-saponification of the remaining vinyl ester groups of PVA, and after purification, the limiting viscosity [η] (unit: deciliter/g) is measured in water at 30°C. From this limit viscosity, it is obtained according to the following formula. Viscosity average degree of polymerization Po=([η]×10 ⁴ /8.29) ^(1/0.62)

The lower limit of the saponification degree of silanol-modified PVA is 98.7 mol%, preferably 99.0 mol%, more preferably 99.5 mol%, further preferably 99.8 mol%, and 99.9 mol% Especially good. When the degree of saponification is not less than the above lower limit, an optical film having excellent optical performance and moisture and heat resistance can be obtained. On the other hand, the upper limit of the degree of saponification is not particularly limited, but from the viewpoint of the productivity of silanol-modified PVA, it is preferably 99.99 mol% or less.

The degree of saponification of PVA means the number of moles of vinyl alcohol units in PVA relative to the total moles of structural units (typically vinyl ester units) and vinyl alcohol units that can be converted into vinyl alcohol units by saponification. The ratio of the number of ears (mol%). The degree of saponification of PVA can be measured in accordance with the description of JIS K6726-1994.

Silanol-modified PVA has silicon-containing groups. The silicon-containing group is a silanol group or a group that can be converted into a silanol group in the presence of water. The silanol group refers to a group having a silicon atom and at least one hydroxyl group bonded to the silicon atom. The number of hydroxyl groups of the silanol group is usually any one of 1 to 3, and 3 is preferred. The hydroxyl group of the silanol group can also exist in the form of a salt (for example, -ONa, -OK, etc.).

It can be converted into a silanol group in the presence of water, which means that PVA can be converted into a silanol group by hydrolyzing it in water under the conditions of a reaction time of 2 hours and a reaction temperature of 150°C. As for the group that can be converted into a silanol group in the presence of water, at least one alkoxy group or a group bonded to a silicon atom can be mentioned. Specifically, a trimethoxysilyl group, three Ethoxysilyl, triisopropoxysilyl, dimethoxymethylsilyl, diethoxymethylsilyl, methoxydimethylsilyl, ethoxydimethylsilyl, Triacetoxysilyl group and the like.

Regarding a silicon-containing group, that is, a silanol group or a group that can be converted into a silanol group in the presence of water, a group represented by any one of the following formulas (1) to (3) can be mentioned. Among these, the group represented by the following formula (1) is preferred.

In the formulas (1) to (3), R ^{1 is} independently a hydrogen atom, a substituted or unsubstituted hydrocarbon group with 1 to 20 carbons, or a substituted or unsubstituted acyl group with 1 to 20 carbons . R ^{2 is} independent of each other, and is a substituted or unsubstituted hydrocarbon group having 1 to 20 carbons.

Regarding ^{the hydrocarbon groups with 1 to 20 carbons represented by R 1} and R ² , aliphatic hydrocarbon groups, alicyclic hydrocarbon groups (cyclohexyl, etc.), aromatic hydrocarbon groups (phenyl, etc.), etc. can be cited. The aliphatic hydrocarbon groups are Better. The aliphatic hydrocarbon group includes alkyl groups such as methyl, ethyl, and propyl, alkenyl groups such as vinyl groups, and alkynyl groups such as ethynyl groups, and alkyl groups are preferred. Regarding ^{the carbon number of the hydrocarbon group represented by R 1} and R ² , 1 to 6 are preferable, and 1 to 3 are more preferable. At least a part of the hydrogen atoms of the hydrocarbon group represented by R ¹ and R ² may be substituted with a halogen atom, a carboxyl group, an alkoxy group (methoxy group, ethoxy group, etc.) or the like.

Examples of the acyl group having 1 to 20 carbon atoms represented by R ¹ include a group in which the above-mentioned hydrocarbon group having 1 to 20 carbon atoms is bonded to a carbonyl group (-CO-). Specifically, an acetyl group, a propyl group, a benzyl group, etc. can be mentioned. Regarding ^{the carbon number of the acyl group represented by R 1} , 1 to 6 are preferable, and 1 to 3 are more preferable. At least a part of the hydrogen atoms contained in the acyl group represented by R ¹ may be substituted with a halogen atom, a carboxyl group, an alkoxy group (such as a methoxy group), and the like.

In the group represented by any one of the above formulas (1) to (3), when ^{at least one of R 1} is a hydrogen atom, the group is a silanol group. In addition, in the group represented by any one of the above formulas (1) to (3), when all R ¹ is not a hydrogen atom, the group is a group that can be converted into a silanol group in the presence of water. To R & lt ^1, the hydrogen atom, or a substituted or unsubstituted hydrocarbon group of 1 to 20 carbon atoms is the preferred.

From the viewpoint of the optical properties of the obtained optical film, etc., it is preferable that the silicon-containing group is directly bonded to the carbon atom in the polymer main chain through a silicon-carbon bond.

The content of silicon-containing groups in all structural units of the silanol-modified PVA is 0.01 mol% or more and 1.0 mol% or less. In this way, by modifying PVA with a set amount of silicon-containing silanol, the optical properties and heat resistance of the resulting optical film are compared to those obtained by using unmodified PVA with the same degree of polymerization. The previous optical film is significantly improved. Furthermore, unmodified PVA refers to PVA obtained by saponifying a single polymer of vinyl ester. On the other hand, if the PVA with a high degree of polymerization has the same optical properties as the obtained optical film, the viscosity of the aqueous solution of the above-mentioned silanol-modified PVA at a high temperature (for example, 80° C.) is low. Therefore, PVA can be modified by using silanol, and the film for manufacturing an optical film has good productivity (film forming properties), and the optical performance and moisture-heat resistance of the obtained optical film are improved. Alternatively, the PVA can be modified by using silanol, and the resulting optical film can exhibit excellent optical performance and moisture and heat resistance, and improve the productivity (film forming properties) of the film for manufacturing the optical film.

The lower limit of the content of silicon groups in all structural units of the silanol-modified PVA is 0.01 mol%, preferably 0.05 mol%, more preferably 0.1 mol%, and further 0.25 mol% Better. By adjusting the content of silicon-containing groups to above the above lower limit, the above-mentioned effects produced by the modification of silanol can be fully exerted. On the other hand, the upper limit of the content of silicon groups in all structural units of the silanol-modified PVA is 1.0 mol%, preferably 0.8 mol%, and more preferably 0.6 mol%. Since the content of the silicon-containing group is adjusted to below the above upper limit, the water solubility of the silanol-modified PVA and the viscosity stability of the aqueous solution become better, and the film productivity (film forming performance) can be improved.

In the silanol-modified PVA, the content (mol %) of silicon-containing groups can be obtained, for example, from the proton NMR of the vinyl ester polymer before saponification. Among them, when measuring the proton NMR of the vinyl ester polymer before saponification, the vinyl ester polymer was purified by hexane-acetone reprecipitation, and the unreacted monomer was completely removed from the polymer, and then carried out at 90°C for 2 days. After drying under reduced pressure, it was dissolved in CDCl ₃ solvent for analysis.

The lower limit of the product of the viscosity average polymerization degree of the silanol-modified PVA and the content of the silicon group is preferably 100 mol%, more preferably 300 mol%, and further preferably 500 mol%. 700 mol% is particularly good. When the above product is equal to or greater than the above lower limit, the resulting optical film has better optical properties and moisture and heat resistance. On the other hand, the upper limit of the above product is preferably 2,000 mol%, more preferably 1,500, and even more preferably 1,200. By making the above product less than the above upper limit, the water solubility of the silanol-modified PVA can be further improved, and the productivity of the optical film manufacturing film can be further improved.

The silanol-modified PVA preferably contains structural units with silicon-containing groups. As for the structural unit having a silicon-containing group, a structural unit represented by the following formula (4) can be cited.

In the formula (4), R ³ is a hydrogen atom or a methyl group. R ⁴ is a single bond or a divalent linking group. R ⁵ is a silicon-containing group.

As for R ³ , a hydrogen atom is preferred.

For the divalent linking group represented by ^{R 4} _{, -(CH 2} ) _n- (n is an integer of 1 to 5) or -CONR ⁶ -R ^7- (R ⁶ is a hydrogen atom or carbon number 1 The alkyl group of ~5. R ⁷ is the group represented by the above -(CH ₂ ) _n -, or the group represented by the divalent hydrocarbon group containing at least one of an oxygen atom and a nitrogen atom).

The divalent hydrocarbon group containing at least one of an oxygen atom and a nitrogen atom includes -CH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ -, -CH ₂ CH ₂ NHCH ₂ CH ₂ -, -CH ₂ CH ₂ NHCH ₂ -, -CH ₂ CH ₂ N(CH ₃ )CH ₂ CH ₂ -, -CH ₂ CH ₂ N(CH ₃ )CH ₂ -, -CH ₂ CH ₂ OCH ₂ CH ₂ CH ₂ -, -CH ₂ CH ₂ OCH ₂ CH ₂ -, -CH ₂ CH ₂ OCH ₂ -and so on. The carbon number of the divalent hydrocarbon group containing at least one of an oxygen atom and a nitrogen atom can be, for example, 2 or more and 6 or less.

R ⁴ is preferably a single bond.

Regarding ^{specific examples of the silicon-containing group represented by R 5} , as described above, a group represented by any one of the above formulas (1) to (3) can be cited, and the group represented by the above formula (1) is Better.

The number of silicon-containing groups contained in the structural unit having silicon-containing groups is not particularly limited, but may be one. The content range of the silicon-containing structural unit relative to all structural units of the silanol-modified PVA may be the above-mentioned content range of the silicon-containing structural unit relative to all structural units. In addition, the range of the product of the viscosity average degree of polymerization of the silanol-modified PVA and the content of the silicon-containing structural unit may be the range of the product of the aforementioned viscosity average degree of polymerization and the content of the silicon-containing group.

The silanol-modified PVA may also have vinyl alcohol units, vinyl ester units, and structural units other than the structural units containing silicon groups. However, the content of the above-mentioned other structural units relative to all the structural units of the silanol-modified PVA is preferably 15 mol% or less, more preferably 5 mol% or less, and further preferably 1 mol% or less Preferably, it is more preferably 0.1 mol% or less. PVA modified by silanol is substantially composed of vinyl alcohol units, vinyl ester units, and structural units having silicon-containing groups, so that the effects of the present invention may be more fully exerted.

The optical film manufacturing film may contain one type of silanol-modified PVA alone, or two or more types of silanol-modified PVA with different degrees of polymerization, saponification degree, and content of silyl groups.

The lower limit of the content of the silanol-modified PVA in the optical film manufacturing film is not particularly limited, but is preferably 50% by mass, more preferably 80% by mass, and even more preferably 85% by mass. The effect of the present invention can be further improved by adjusting the content of silanol-modified PVA to above the above lower limit. On the other hand, the upper limit of the content is not particularly limited, and may be 100% by mass, preferably 99% by mass, and more preferably 95% by mass.

(Manufacturing method of silanol-modified PVA) The manufacturing method of silanol-modified PVA is not particularly limited. For example, it can be produced by copolymerizing a vinyl ester monomer and a monomer having a silicon group, and saponifying the obtained vinyl ester polymer.

The vinyl ester monomers include, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl decanoate, vinyl laurate, vinyl stearate, vinyl benzoate, Trimethyl vinyl acetate, vinyl neodecanoate, etc. Among these, vinyl acetate is preferred.

For monomers with silicon groups, vinyl trimethoxy silane, vinyl methyl dimethoxy silane, vinyl dimethyl methoxy silane, vinyl triethoxy silane, vinyl Methyl diethoxy silane, vinyl dimethyl ethoxy silane, allyl trimethoxy silane, allyl methyl dimethoxy silane, allyl dimethyl methoxy silane, allyl Triethoxysilane, allyl methyl diethoxy silane, allyl dimethyl ethoxy silane, vinyl ginseng (β-methoxyethoxy) silane, vinyl isobutyl two Methoxysilane, vinyl ethyl dimethoxy silane, vinyl methoxy dibutoxy silane, vinyl dimethoxy butoxy silane, vinyl tributoxy silane, vinyl methoxy silane Dihexoxysilane, vinyl dimethoxyhexoxy silane, vinyl trihexoxy silane, vinyl methoxy dioctyloxy silane, vinyl dimethoxy octoxy silane, vinyl tris Octyloxysilane, vinyl methoxy dilauryl oxysilane, vinyl dimethoxy lauryl oxy silane, vinyl methoxy dioleyl oxy silane, vinyl dimethoxy oleyl oxy silane, 3 -(Meth)acrylamide-propyl trimethoxysilane, 3-(meth)acrylamide-propyl triethoxysilane, 3-(meth)acrylamide-propyl tris(β- Methoxyethoxy)silane, 2-(meth)acrylamide-ethyltrimethoxysilane, 1-(meth)acrylamide-methyltrimethoxysilane, 2-(meth)propylene Amide-2-methylpropyltrimethoxysilane, 2-(meth)acrylamide-isopropyltrimethoxysilane, N-(2-(meth)acrylamide-ethyl)-amine Trimethoxysilane, (3-(meth)acrylamide-propyl)-oxypropyl trimethoxysilane, 3-(meth)acrylamide-propyltriethoxysilane , 2-(meth)acrylamide-ethyl triacetoxysilane, 4-(meth)acrylamide-butyl triacetoxysilane, 3-(meth)acrylamide-propane Tripropionyloxysilane, 2-(meth)acrylamide-2-methylpropyltriacetoxysilane, N-(2-(meth)acrylamide-ethyl)-amine Propyl triacetoxysilane, 3-(meth)acrylamide-propyl isobutyl dimethoxysilane, 2-(meth)acrylamide-ethyldimethylmethoxysilane , 3-(Meth)acrylamide-propylmethyldiethoxysilane, 2-(meth)acrylamide-2-methylpropylhydrodimethoxysilane, 3-(N- Methyl-(meth)acrylamide)-propyltrimethoxysilane, 2-(N-ethyl-(meth)acrylamide)-ethyltriethoxysilane, etc.

The method of copolymerizing a vinyl ester monomer and a monomer having a silicon group is not particularly limited, and known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method can be mentioned. Among these methods, a bulk polymerization method performed in a solvent-free and a solution polymerization method using a solvent such as alcohol are preferred. Examples of solvents used as solvents during solution polymerization include esters such as methyl acetate and ethyl acetate; aromatic hydrocarbons such as benzene and toluene; lower alcohols such as methanol and ethanol.

As the initiator used for the copolymerization reaction, a previously known azo-based initiator, peroxide-based initiator, redox-based initiator, etc. can be appropriately selected. As for the azo-based initiator, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azo Nitrobis(4-methoxy-2,4-dimethylvaleronitrile) and the like. The peroxide-based initiators include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethyl peroxydicarbonate. Percarbonate compounds such as oxyethyl ester; Peroxyneodecanoic acid tertiary butyl, Peroxyneodecanoic acid α-cumyl peroxyneodecanoate, Peroxyneodecanoic acid tertiary butyl and other perester compounds; Acetyl Cyclohexylsulfonyl peroxide, diisobutyryl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxy acetate, etc. In addition, it is also possible to combine the exemplified above-mentioned peroxide-based starter with potassium persulfate, ammonium persulfate, hydrogen peroxide, etc. as the starter. Examples of the redox initiator include those combining the above-mentioned peroxides with reducing agents such as sodium bisulfite, sodium bicarbonate, tartaric acid, L-ascorbic acid, and Rongalit.

The polymerization temperature during the copolymerization reaction is not particularly limited, but is preferably 0°C or more and 180°C or less, more preferably 20°C or more and 160°C or less, and more preferably 30°C or more and 150°C or less.

When the vinyl ester monomer is copolymerized with a monomer having a silicon group, if it is in a range that does not impair the effect of the present invention, it can be copolymerized with other copolymerizable monomers as needed. The other monomers include, for example, ethylene; propylene, 1-butene, isobutylene, and other olefins with 3 to 30 carbon atoms; acrylic acid or its salts; methyl acrylate, ethyl acrylate, n-propyl acrylate, isobutyl acrylate, etc. Acrylates such as propyl ester, n-butyl acrylate, isobutyl acrylate, tertiary butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and stearyl acrylate; methacrylic acid or its salt; methacrylic acid Methyl methyl, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tertiary butyl methacrylate, 2-methacrylate Ethylhexyl, lauryl methacrylate, stearyl methacrylate and other methacrylates; acrylamide, N-methacrylamide, N-ethacrylamide, N,N-dimethyl Acrylamide, diacetone acrylamide, acrylamide propanesulfonic acid or its salt, acrylamide propyldimethylamine or its salt, N-methylol acrylamide or its derivatives, etc. Derivatives; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid or its salt, methacrylamide propyl dimethyl Methacrylamide derivatives such as amine or its salt, N-methylolmethacrylamide or its derivatives; N-vinylformamide, N-vinylacetamide, N-vinylpyrrole N-vinyl amides such as pyridone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, Vinyl ethers such as tertiary butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; vinyl cyanide such as acrylonitrile and methacrylonitrile; vinyl chloride, vinylidene chloride, vinyl fluoride, Halogenated vinyl groups such as vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salt, ester or anhydride; itaconic acid or its salt, ester or anhydride; isoacetic acid Acrylic etc. The vinyl ester polymer may have a structural unit derived from one type or two or more types among the above-mentioned other monomers.

The ratio of structural units derived from the above-mentioned other monomers (monomers other than vinyl ester monomers and monomers having silicon groups) in the vinyl ester polymer may not necessarily be used as long as it does not hinder the effects of the present invention. Limit, but there will be based on the number of moles of all the structural units constituting the vinyl ester polymer, and 15 mole% or less is preferred, 5 mole% or less is more preferred, and 1 mole% or less is used as More preferably, 0.1 mol% or less is a still more preferable case

The vinyl ester polymer is then saponified in a solvent according to a well-known method, and derivatized into silanol-modified PVA. As for the solvent used in the saponification reaction, alcohol is preferred. Alcohols include lower alcohols such as methanol and ethanol, and methanol is particularly suitable for use. The solvent used in the saponification reaction may further contain organic solvents such as acetone, esters such as methyl acetate or ethyl acetate, and toluene in addition to alcohol. Examples of the catalyst used in the saponification reaction include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, alkali catalysts such as sodium methylate, and acid catalysts such as mineral acid. The temperature of the saponification reaction can be set to, for example, 20°C or more and 60°C or less. When a gel-like product precipitates as the saponification reaction progresses, the product can be pulverized, washed, and dried at this point to obtain a silanol-modified PVA.

(Plasticizer) The film for manufacturing an optical film of the present invention preferably contains a plasticizer. The film for optical film manufacturing can improve stretchability and the like by including a plasticizer. As far as plasticizers are concerned, polyols are preferred. As for polyhydric alcohols, ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerol, triethylene glycol, tetraethylene glycol, trimethylolpropane, etc. can be mentioned. Among these, from the viewpoint of the effect of improving the extensibility, glycerin is preferred. One type or two or more types of plasticizers can be used.

Regarding the lower limit of the content of the plasticizer in the optical film manufacturing film of the present invention, relative to 100 parts by mass of silanol-modified PVA, 1 part by mass is preferred, 3 parts by mass is more preferred, and 5 Parts by mass are further preferred. By the content of the plasticizer being above the above lower limit, the extensibility of the film is improved, and the optical properties of the obtained optical film are further improved. On the other hand, with regard to the upper limit of the content of the plasticizer, relative to 100 parts by mass of silanol-modified PVA, 20 parts by mass is preferred, 17 parts by mass is more preferred, and 15 parts by mass is more preferred. good. By making the content of the plasticizer less than the above upper limit, it is possible to suppress the decrease in handleability due to the excessive softness of the film.

(Surfactant) The film for manufacturing an optical film preferably contains a surfactant. By using a film-forming stock solution containing a surfactant to form a film, the film-forming properties are improved, the occurrence of uneven thickness of the film is suppressed, and the film can be easily peeled from the metal roller or conveyor belt used for film formation. When a film for optical film production is produced from a film-forming stock solution containing a surfactant, the obtained film may contain a surfactant.

The type of surfactant is not particularly limited, but from the viewpoint of releasability to metal rollers or conveyor belts, etc., anionic surfactants and nonionic surfactants are preferred.

Examples of anionic surfactants include carboxylic acid types such as potassium laurate; sulfate types such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and sulfonic acid types such as dodecylbenzenesulfonate. Wait.

Examples of nonionic surfactants include alkyl ether types such as polyoxyethylene oleyl ether; alkyl phenyl ether types such as polyoxyethylene octyl phenyl ether; and polyoxyethylene octyl phenyl ether. Alkyl ester type such as lauryl ester; Alkylamine type such as polyoxyethylene lauryl amino ether; Alkyl amine type such as polyoxyethylene lauramide; Polyoxyethylene polyoxypropylene ether Polypropylene glycol ether type; alkanol amide type such as lauric acid diethanolamide and oleic acid diethanolamide type; allyl phenyl ether type such as polyoxyalkylene allyl phenyl ether, etc.

Surfactant can be used individually by 1 type or in combination of 2 or more types.

When the film for optical film manufacturing contains a surfactant, the lower limit of its content is relative to 100 parts by mass of silanol modified PVA, and 0.01 parts by mass is preferred, and 0.02 parts by mass is more preferred. 0.05 parts by mass is more preferable. By making the content of the surfactant more than the above lower limit, film-forming properties and releasability are further improved. On the other hand, the upper limit of the content is relative to 100 parts by mass of silanol-modified PVA, and 0.5 parts by mass is preferred, 0.3 parts by mass is more preferred, and 0.1 parts by mass is still more preferred. By setting the content of the surfactant to be equal to or less than the above upper limit, it is possible to suppress the occurrence of clogging due to the exudation of the surfactant to the surface of the film and the decrease in operability.

(Other additives, etc.) The film for producing an optical film of the present invention may further suitably contain processing stabilizers such as fillers, copper compounds, weather resistance stabilizers, colorants, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, Flame retardants, other thermoplastic resins, lubricants, fragrances, defoamers, deodorants, extenders, stripping agents, mold release agents, reinforcing agents, crosslinking agents, antifungal agents, preservatives, crystallization speed Additives such as retarders.

The film for manufacturing an optical film of the present invention may include PVA other than the above-mentioned silanol-modified PVA. In the optical film manufacturing film of the present invention, the ratio of the total of all PVA, plasticizer and surfactant containing silanol-modified PVA is also preferably 80% by mass or more, and 90% by mass or more as More preferably, it is more preferably 95% by mass or more, and more preferably 99% by mass or more. Since the film for manufacturing an optical film of the present invention is substantially composed of PVA, a plasticizer, and a surfactant, the effects of the present invention can be more fully exhibited.

Regarding the content ratio of the above-mentioned silanol-modified PVA in the total PVA contained in the film for manufacturing the optical film of the present invention, 50% by mass or more is preferred, more preferably 80% by mass or more, and 90% by mass % Or more is more preferable, 95 mass% or more is more preferable, and 99 mass% or more is still more preferable. In the optical film manufacturing film of the present invention, by mainly using silanol-modified PVA as PVA, the effects of the present invention can be more fully exerted. In the optical film manufacturing film of the present invention, the total ratio of silanol-modified PVA, plasticizer, and surfactant is also preferably 80% by mass or more, more preferably 90% by mass or more. It is more preferably 95% by mass or more, and more preferably 99% by mass or more. The film for manufacturing an optical film of the present invention is substantially composed of silanol-modified PVA, a plasticizer, and a surfactant, so that the effects of the present invention can be fully exhibited.

(Shape, physical properties, etc.) The film for manufacturing an optical film of the present invention is a so-called original film used as a material for the optical film. However, the film for manufacturing an optical film of the present invention is not limited to a roll-shaped one.

The average thickness of the film for manufacturing an optical film of the present invention is not particularly limited. As for the lower limit, 1 μm is preferred, 5 μm is more preferred, and 10 μm is still more preferred. Since the average thickness is equal to or greater than the above lower limit, film breakage during the uniaxial stretching process during the production of the optical film can be suppressed. In addition, with regard to the upper limit of the average thickness, 75 μm is preferable, 60 μm is more preferable, 45 μm is more preferable, and 35 μm is still more preferable. Since the average thickness is equal to or less than the above upper limit, uneven stretching during uniaxial stretching treatment can be suppressed. In addition, the "average thickness" means the average value of the thickness measured at any 5 points (hereinafter, the same applies to the average thickness).

The film for manufacturing an optical film of the present invention may be a single-layer film including one PVA layer (a layer including silanol-modified PVA), or a multilayer film including one PVA layer. However, when used in the production of a polarizing film, a single-layer film is preferred. As for the lower limit of the average thickness of the PVA layer of the film for manufacturing the optical film of the present invention, 1 μm is preferred, 5 μm is more preferred, and 10 μm is more preferred. Since the average thickness is equal to or greater than the above lower limit, film breakage during the uniaxial stretching process during the production of the optical film can be suppressed. In addition, with regard to the upper limit of the average thickness, 75 μm is preferable, 60 μm is more preferable, 45 μm is more preferable, and 35 μm is still more preferable. Since the average thickness is equal to or less than the above upper limit, uneven stretching during uniaxial stretching treatment can be suppressed.

For the specific composition and preferred composition of the PVA layer in the film for optical film manufacturing, the description of the specific composition and preferred composition of the above-mentioned optical film manufacturing film itself can be cited.

When the optical film manufacturing film of the present invention is a single-layer film, in order to ensure handleability, the average thickness is preferably 20 μm or more, and more preferably 30 μm or more. On the other hand, when the film for producing an optical film of the present invention is a multilayer film, the average thickness of the PVA layer can be 20 μm or less, or 15 μm or less.

Multilayer film means a film having two or more layers. The number of layers of the multilayer film can be 5 layers or less, or 3 layers or less. The multilayer film includes a film for manufacturing an optical film having a laminated structure of a base resin layer and a PVA layer. The average thickness of the base resin layer is, for example, 20 μm or more and 500 μm or less. The base resin layer in the multilayer film is preferably one that can be uniaxially stretched together with the PVA layer. As for the resin constituting the base resin layer, polyester, polyolefin, etc. can be used. Among them, amorphous polyester resins are preferred, and polyethylene terephthalate, polyethylene terephthalate, isophthalic acid, 1,4-cyclohexanedimethanol, etc. are suitable for use. Amorphous polyester resin copolymerized by copolymerization components. An adhesive layer may also be provided between the base resin layer and the PVA layer.

The width of the film for manufacturing an optical film of the present invention is not particularly limited, and can be determined according to its use and the like. For example, the lower limit of the width of the film for optical film manufacturing is preferably 3 m. In recent years, from the viewpoint of the advancement of LCD TVs and LCD monitors, if the width of the optical film manufacturing film is 3 m or more, it is suitable for use as a final product. On the other hand, the upper limit of the width of the film for optical film manufacturing is preferably 7 m. By making the width 7m or less, in the case of manufacturing an optical film with a practical device, the uniaxial stretching process can be efficiently performed.

The degree of swelling of the film for manufacturing the optical film of the present invention is preferably within the range of 140% or more and 400% or less from the viewpoint of the productivity of the optical film or the optical performance. The lower limit of the degree of swelling is more preferably 180%, and more preferably 190%. In addition, the upper limit of the degree of swelling is more preferably 220%, and more preferably 210%. The swelling degree of the film can be adjusted to a smaller value by, for example, enhancing the heat treatment conditions.

Here, "the degree of swelling of the film" means the value obtained by the following formula. Swelling degree (%)=100×N/M In the formula, N represents the mass (g) of the sample collected from the film and immersed in distilled water at 30°C for 30 minutes, after removing the surface water. M represents the mass (g) of the sample after drying the sample in a dryer at 105°C for 16 hours.

The film for producing an optical film of the present invention is usually a film that is substantially unstretched (non-stretched film, unstretched film). The in-plane retardation of the raw material film for optical film manufacturing is preferably 100 nm or less, and more preferably 50 nm or less. Generally, an optical film can be obtained by subjecting the film for manufacturing an optical film of the present invention to a stretching treatment (uniaxial stretching treatment or biaxial stretching treatment) or the like.

According to the optical film manufacturing film of the present invention, it is possible to obtain an optical film with good productivity and excellent optical properties and moisture and heat resistance compared with the case of using unmodified PVA with the same degree of polymerization. In addition, the optical performance system includes light transmittance, polarization, and the like. The optical film that can be manufactured from the film for manufacturing an optical film includes a polarizing film, a retardation film, a viewing angle improvement film, a brightness improvement film, etc., and a polarizing film is preferred.

＜Manufacturing method of film for optical film manufacturing＞ The manufacturing method of the film for optical film manufacturing of the present invention is not particularly limited, and it is preferable to adopt a manufacturing method in which the thickness and width of the film after film formation become more uniform. For example, it can be produced by using silanol-modified PVA, and optionally further adding one or more of plasticizers, surfactants, and other additives, etc., to a film-forming stock solution that is dissolved in a liquid medium. When the film-forming stock solution contains at least one of a plasticizer, a surfactant, and other additives, it is preferable that these components are uniformly mixed.

As for the liquid medium used in the preparation of the film-forming stock solution, for example, water, dimethyl sulfide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol , Glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, etc., one of these can be used or Two or more kinds. Among these, water is preferred from the viewpoint of causing environmental load or recyclability. In addition, the above-mentioned silanol-modified PVA has good water solubility and can also suppress the increase in viscosity in the case of a higher temperature (for example, 80°C) aqueous solution. From this viewpoint, it is preferable to use water as the liquid medium.

The volatile fraction of the film-forming stock solution (the content ratio of the volatile components such as the liquid medium removed by volatilization or evaporation during film-forming in the film-forming stock solution) is preferably 50% by mass or more and 95% by mass or less , More preferably 55% by mass or more and 90% by mass or less, and more preferably 60% by mass or more and 85% by mass or less. The volatile fraction of the film-forming stock solution is more than 50% by mass, and the viscosity of the film-forming stock solution will not become too high. When the film-forming stock solution is prepared, the filtration or defoaming can be performed smoothly. Manufacturing becomes easy. On the other hand, since the volatile fraction of the film-forming stock solution is 95% by mass or less, the concentration of the film-forming stock solution does not become too low, and the production of industrial films becomes easy.

The temperature of the film-forming stock solution at the time of film formation can be set to, for example, 70°C or more and 90°C or less. The PVA can be modified by using silanol, and the film can be formed at such a relatively high temperature, so that the viscosity of the film-forming stock solution can be lowered, and the film-forming properties can be improved.

The film forming method at the time of forming a film using a film forming stock solution includes, for example, a casting film forming method, an extrusion film forming method, a wet film forming method, a gel film forming method, and the like. Only one type of these film forming methods may be used, or a combination of two or more types may be used. Among these film forming methods, the casting film forming method and the extrusion film forming method can obtain a film with uniform thickness and width and good physical properties, which is preferable. The film can be dried or heat-treated as needed.

As an example of the specific manufacturing method of the film for optical film manufacturing of this invention, the following examples can be mentioned, for example. Using T-shaped slit die, hopper plate, I-die, lip coater die, etc., the film-forming stock solution is uniformly sprayed or cast on the first roller ( Or conveyor belt). The volatile component is evaporated from one side of the film sprayed or cast on the peripheral surface of the first drum (or conveyor belt) to dry it. Then, it is further dried on the peripheral surface of one or more rotating and heated drums arranged on the downstream side thereof, or is further dried by passing through a hot air drying device. Then, the film is taken up by the take-up device. Drying by a heating drum and drying by a hot air drying device can also be implemented in an appropriate combination.

Furthermore, when the film for producing an optical film of the present invention is a multilayer film, the multilayer film can be manufactured by, for example, coating a film-forming stock solution on a base resin film (base resin layer). At this time, in order to improve the adhesion between the PVA layer and the base resin layer, the surface of the base resin film may be modified, or an adhesive may be coated on the surface of the base resin film.

＜Manufacturing method of optical film＞ The method of manufacturing an optical film of the present invention includes a step of uniaxially stretching the above-mentioned film for manufacturing an optical film. Hereinafter, the manufacturing method of a polarizing film is given as an example of the manufacturing method of an optical film, and it demonstrates concretely.

As for the manufacturing method of the polarizing film, it is possible to include a dyeing step of dyeing the film for manufacturing an optical film (hereinafter also referred to as "PVA film") separately, a stretching step of uniaxial stretching, and further use as necessary Methods such as the swelling step of swelling, the crosslinking step of crosslinking, the fixing treatment step of fixing treatment, the washing step of washing, the drying step of drying, and the heat treatment step of heat treatment. In this case, the order of each step is not particularly limited, but it can be performed in the order of, for example, a swelling step, a dyeing step, a cross-linking step, an extension step, a fixing treatment step, and the like. In addition, one or two or more steps may be performed simultaneously, or each step may be performed two or more times.

The swelling step can be performed by immersing the PVA film in water. Regarding the temperature of the water when immersed in water, 20°C or more and 55°C or less are preferred, 22°C or more and 50°C or less is more preferred, and 25°C or more and 45°C or less is more preferred. Moreover, as for the time for immersion in water, for example, 0.1 minute or more and 5 minutes or less are preferable, and 0.5 minute or more and 3 minutes or less are more preferable. In addition, the water when immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or a mixture of water and an aqueous medium.

The dyeing step can be performed by bringing the dichroic dye into contact with the PVA film. For dichroic dyes, iodine-based dyes are generally used. As far as the timing of dyeing is concerned, it can be any stage before uniaxial extension, during uniaxial extension, and after uniaxial extension. Dyeing can preferably be performed by immersing the PVA film in a solution (especially an aqueous solution) containing iodine-potassium iodide, which is a dyeing bath. The concentration of iodine in the dye bath is preferably 0.01% by mass or more and 0.5% by mass or less, and the concentration of potassium iodide is preferably 0.01% by mass or more and 10% by mass or less. In addition, the temperature of the dyeing bath is 20°C or more and 50°C or less, particularly preferably 25°C or more and 40°C or less. The preferred dyeing time is 0.2 minutes or more and 5 minutes or less.

By carrying out the cross-linking step of cross-linking the silanol-modified PVA in the PVA film, the silanol-modified PVA can be effectively inhibited from dissolving into water when the wet stretching is performed at a high temperature. From this point of view, the crosslinking step is preferably performed after the dyeing step and before the extension step. The cross-linking step can be performed by immersing the PVA film in an aqueous solution containing a cross-linking agent. As the crosslinking agent, one or two or more of boron compounds such as boric acid and borax can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 7% by mass or less, and 2% by mass or more and 6% by mass or less To be further preferred. The concentration of the crosslinking agent can be within the above range to maintain sufficient extensibility. The aqueous solution containing the crosslinking agent may also contain potassium iodide and the like. The temperature of the aqueous solution containing the crosslinking agent is preferably 20°C or more and 60°C or less, especially 25°C or more and 55°C or less. By making the temperature within the above range, it is possible to efficiently crosslink.

The stretching step of uniaxially stretching the PVA film can be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution containing boric acid, and can also be carried out in the above-mentioned dyeing bath or the fixed treatment bath described later. In addition, in the case of the dry stretching method, the stretching can be performed directly at room temperature, or stretching while heating, or the PVA film after water absorption can be used in the air. Among these, since it can be stretched with high uniformity in the width direction, the wet stretching method is preferred, and the uniaxial stretching in an aqueous solution containing boric acid is more preferred. The concentration of boric acid in the boric acid aqueous solution is preferably 0.5% by mass to 6.0% by mass, more preferably 1.0% by mass to 5.0% by mass, and particularly preferably 1.5% by mass to 4.0% by mass. In addition, the boric acid aqueous solution may contain potassium iodide, and the concentration of potassium iodide is preferably 0.01% by mass or more and 10% by mass or less. The stretching temperature during uniaxial stretching is preferably 30°C or more and 90°C or less, more preferably 40°C or more and 80°C or less, and particularly preferably 50°C or more and 75°C or less.

The stretching ratio of the uniaxial stretching (total stretching ratio of the non-stretched PVA film) is preferably 5 times or more, and more preferably 5.5 times or more from the viewpoint of the polarization performance of the polarizing film obtained. The upper limit of the stretching ratio is not particularly limited, but the stretching ratio is preferably 8 times or less.

The direction of uniaxial stretching in the case of uniaxial stretching of the long-sized PVA film is not particularly limited, and uniaxial stretching in the longitudinal direction or lateral uniaxial stretching can be adopted. In order to obtain a polarizing film with excellent polarization performance, uniaxial stretching in the longitudinal direction is conventionally preferred. The uniaxial extension in the longitudinal direction can be performed by using an extension device with a plurality of rollers parallel to each other and changing the peripheral speed between the rollers. On the other hand, horizontal uniaxial stretching can be carried out using a tenter type stretching machine.

For the production of the polarizing film, in order to strengthen the adsorption of the dichroic dye (iodine-based dye, etc.) on the PVA film, a fixing treatment step may be carried out after the stretching step. Regarding the fixing treatment bath used in the fixing treatment, an aqueous solution containing one or more types of boron compounds such as boric acid and borax can be used. In addition, an iodine compound or a metal compound may be added to the fixed treatment bath as needed. The concentration of the boron compound in the fixed treatment bath is 2% by mass or more and 15% by mass or less, and more preferably 3% by mass or more and 10% by mass or less. By making the concentration of the boron compound within the above range, the adsorption of the dichroic pigment can be made stronger. The temperature of the fixed treatment bath is 15°C or more and 60°C or less, particularly preferably 25°C or more and 40°C or less.

The washing step is generally performed by immersing the film in distilled water, pure water, aqueous solution, or the like. In this case, from the viewpoint of improving the polarization performance, it is preferable to use an aqueous solution containing an iodide such as potassium iodide as an auxiliary agent, and the concentration of the iodide is preferably 0.5% by mass or more and 10% by mass or less. In addition, the temperature of the aqueous solution in the washing treatment is generally 5°C or higher and 50°C or lower, preferably 10°C or higher and 45°C or lower, and more preferably 15°C or higher and 40°C or lower. By setting the temperature of the aqueous solution within the above range, the polarization performance can be further improved.

The conditions of the drying step are not particularly limited, but it is preferable to dry the PVA film at a temperature above 30°C and below 150°C, especially at a temperature above 50°C and below 130°C. By drying at a temperature within the above range, it is easy to obtain a polarizing film with excellent dimensional stability.

Furthermore, optical films other than polarizing films, such as retardation films, can also be manufactured by a method including a step of uniaxially stretching the film for manufacturing an optical film of the present invention. For the specific manufacturing method, in addition to using the film for manufacturing the optical film of the present invention, a previously known method can be used.

＜Optical film＞ The optical film of the present invention is an optical film comprising a PVA (silanol-modified PVA) having a silicon-containing group, the above-mentioned silicon-containing group is a silanol group or a group that can be converted into a silanol group in the presence of water, the above Silanol-modified PVA has a viscosity average polymerization degree of 1,000 or more and 6,000 or less, a saponification degree of 98.7 mol% or more, and the content of the above-mentioned silicon-containing groups relative to all structural units is 0.01 mol% or more and 1.0 mol% or less.

The optical film of the present invention may be an optical film obtained in accordance with the above-mentioned manufacturing method using the film for manufacturing the optical film of the present invention. The specific structure or content details of the silanol-modified PVA contained in the optical film of the present invention are the same as those of the silanol-modified PVA contained in the optical film manufacturing film of the present invention. In addition, the optical film of the present invention may contain the same other components as the film for manufacturing the optical film of the present invention.

The optical film of the present invention may be a polarizing film, a retardation film, a viewing angle enhancement film, a brightness enhancement film, etc., and a polarizing film is preferred. In this case, the polarizing film usually contains a dichroic dye, and the silanol-modified PVA can be cross-linked.

The optical film of the present invention is preferably a stretched film, and more preferably a uniaxial stretched film. In addition, the optical film of the present invention may be a single-layer film or a multilayer film, but a single-layer film is preferred. In the case of such a film, the optical film of the present invention can be more suitably used as a polarizing film or the like.

When the optical film of the present invention is a polarizing film, the dichroic ratio (R) of the polarizing film is preferably 100 or more. By including the above-mentioned silanol to modify PVA, a polarizing film with such a high dichroic ratio (R) can be produced with good productivity. The dichroic ratio (R) is more preferably 150 or more, and more preferably 190 or more. The upper limit of the dichroic ratio (R) is, for example, 350 or 300.

The calculation method of the dichroic ratio (R) of the polarizing film is as follows. First, the relationship between the transmittance (T') excluding surface reflection and the transmittance (T) of the monomer is expressed by formula (a). At this time, the refractive index of the polarizing film is 1.5, and the reflectance on the surface is 4%. The relationship between the transmittance (T') and the degree of polarization (V) dichroic ratio (R) is represented by formula (b). Therefore, the dichroic ratio (R) of the polarizing film can be calculated by using the values of the monomer transmittance (T) and polarization (V) to solve the equations (a) and (b). T'=T/(1-0.04) ² …(a) R={-ln[T'(1-V)]}/{-ln[T'(1+V)]}…(b)

The polarizing film is usually used as a polarizing plate by laminating an optically transparent and mechanically strong protective film on both sides or on one side. As for the protective film, cellulose triacetate (TAC) film, cycloolefin polymer (COP) film, cellulose acetate butyrate (CAB) film, acrylic film, polyester film, etc. can be used. In addition, the adhesive used for bonding includes PVA-based adhesives, urethane-based adhesives, and acrylate-based ultraviolet curable adhesives. That is, the polarizing plate has: a polarizing film; and a protective film laminated on one or both sides of the polarizing film directly or through the adhesive layer.

The polarizing plate can be used as a part of LCD after being coated with an acrylic adhesive and then attached to a glass substrate. Furthermore, to the polarizing plate, a retardation film, a viewing angle improvement film, a brightness improvement film, etc. may be further laminated. [Example]

Hereinafter, the present invention will be described in more detail with examples, but the present invention is not limited in any way by these examples. The methods of each measurement and evaluation are as described below.

[Polymerization degree of PVA (Viscosity average degree of polymerization)] Regarding the PVA synthesized in the following synthesis examples, the viscosity average degree of polymerization was measured in accordance with the description of JIS K6726-1994.

[Saponification degree of PVA] Regarding the PVA synthesized in the following synthesis examples, the degree of saponification was measured in accordance with the description of JISK6726-1994.

[The content of silicon-containing groups in PVA] Regarding the PVA synthesized in the following synthesis examples, the content of silicon-containing groups relative to all structural units was measured from the proton NMR of the vinyl ester polymer before saponification. When measuring the proton NMR of the vinyl ester polymer before saponification, the vinyl ester polymer is purified by reprecipitation with hexane-acetone to completely remove unreacted monomers from the polymer, and then depressurize at 90°C for 2 days After drying, dissolve in CDCl ₃ solvent for analysis.

[Viscosity of 10% by mass PVA aqueous solution] Weigh 10 g of the PVA synthesized in the following synthesis example in a sample bottle, and add pure water to make the total 100 g. After stirring this with a stirrer and dissolving it in a 95°C water bath for 4 hours, it was allowed to stand overnight in a 80°C dryer to defoam. The viscosity of the obtained 10% by mass PVA aqueous solution at 80°C was measured with a B-type viscometer.

[Swelling degree of film] The films (films for manufacturing optical films) obtained in the following Examples and Comparative Examples were cut into 1.5 g and immersed in 1000 g of distilled water at 30°C for 30 minutes. After immersing for 30 minutes, the film was taken out, and the water on the surface was absorbed with filter paper, and its mass (N) was measured. Then, the film was dried in a dryer at 105°C for 16 hours, and then the mass (M) after drying was measured. From the obtained mass (N) and mass (M), the swelling degree of the film is calculated according to the following formula. Swelling degree (%)=100×N/M

[Dichroic ratio of polarizing film (optical performance)] From the central part in the width direction of the polarizing film obtained in the following Examples and Comparative Examples, a sample of 4 cm in the rectangular shape was collected in the length direction of the polarizing film. For this sample, a spectrophotometer with an integrating sphere (“V7100” manufactured by JASCO Corporation) was used to measure the visual sensitivity of the visible light area with a C light source and a 2° field of view in accordance with JIS Z8722 (Method for Measuring Object Color). After calibration, the monomer transmittance (T) and polarization (V) are measured.

The dichroic ratio (R) of the polarizing film is calculated by solving the following formulas (a) and (b) from the obtained monomer transmittance (T) and polarization (V) values. Among them, the refractive index of the polarizing film is 1.5, and the reflectance on the surface is 4%. T'=T/(1-0.04) ² …(a) R={-ln[T'(1-V)]}/{-ln[T'(1+V)]}…(b)

[Moisture and heat resistance of polarizing film] The polarizing film obtained in the following Examples and Comparative Examples was fixed to a metal frame, and a spectrophotometer with integrating sphere (“V7100” manufactured by JASCO Corporation) was used according to JIS Z8722 ( Measurement method of object color), after the C light source, the visual sensitivity of the visible light region of the 2° field of view is corrected, the single transmittance (T ₀ ) and polarization (V ₀ ) are measured. In addition, the polarizing film fixed on the metal frame was subjected to 12 hours of wet heat treatment at 60°C and 90% RH, and the transmittance (T ₁₂ ) and polarization degree after 12 hours were similarly measured by a spectrophotometer. (V ₁₂ ). The increase in light transmittance (T ₁₂ -T ₀ :%) and the decrease in polarization (V ₀ -V ₁₂ :%) after the wet heat treatment are used as indicators of heat and humidity resistance.

[Synthesis Example 1] Synthesis of PVA-1 Add 2590 g of vinyl acetate, 410 g of methanol, and 5.3 g of vinyl trimethoxysilane to a 6L reaction tank equipped with a mixer, nitrogen inlet, additive inlet, and starter addition port. After the temperature is raised to 60°C, The system was replaced with nitrogen by introducing nitrogen gas bubbles for 30 minutes. The temperature in the reaction tank was adjusted to 60°C, and 0.32 g of 2,2'-azobis(isobutyronitrile) was added to start polymerization. From the time when the polymerization started, 135 g of methanol containing 2.5% by mass of vinyl methoxysilane was added to the system, and the polymerization reaction was carried out for 3 hours at the same time, and the polymerization was stopped at this time. The polymerization rate at the point when the polymerization reaction was stopped was 26.8%. In addition, during the polymerization, the polymerization temperature was maintained at 60°C. Then, unreacted vinyl acetate was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate (hereinafter, abbreviated as PVAc in some cases). Adjust the concentration of the obtained PVAc methanol solution to 23.5%, and add NaOH methanol solution (10% concentration) so that the alkali molar ratio (the molar number of NaOH/the molar number of vinyl ester unit in PVAc) becomes 0.04 , Carry out saponification. The obtained polyvinyl alcohol was washed with methanol. The degree of polymerization (average degree of polymerization in viscosity) of PVA-1 obtained by the above operation is 2,400, the degree of saponification is 99.9 mol%, the content of silicon group is 0.2 mol%, and the 10% by mass aqueous solution at 80°C The viscosity is 920mPa·s.

[Synthesis example 2~11] Synthesis of PVA-2~PVA-11 According to Synthesis Example 1, and appropriately adjusting the ratio of the monomers used, the polymerization conditions and the saponification conditions, the polymerization degree (viscosity average degree of polymerization), saponification degree and SiOH group content (silicon group content) as described in Tables 1 to 3 are obtained. ) PVA-2~PVA-11.

[Example 1] Prepared containing 100 parts by mass of PVA-1, 10 parts by mass of glycerin as a plasticizer, and 0.1 parts by mass of polyoxyethylene lauryl ether sodium sulfate as a surfactant, and the PVA content rate was 9.5% by mass Aqueous solution, as the film-forming stock solution. The film-forming stock solution was dried on a metal drum at 80°C, and the resulting film was heat-treated in a hot-air dryer at 120°C for 10 minutes to adjust the swelling degree to 200%, and the average thickness of the film was 30μm PVA film (film for manufacturing optical film).

A sample having a width of 5 cm × a length of 9 cm was cut from the central part in the width direction of the obtained PVA film, so that the range of the width of 5 cm × length of 5 cm could be uniaxially stretched. The sample was immersed in pure water at 30° C. for 60 seconds while uniaxially stretched 2.0 times in the longitudinal direction to perform swelling treatment. Then, it was immersed in an aqueous solution containing 0.05% by mass of iodine and 5.0% by mass of potassium iodide (dyeing bath: temperature 32°C) for 120 seconds, and simultaneously uniaxially stretched 1.2 times (2.4 times overall) in the longitudinal direction to adsorb iodine. Then, it was immersed in an aqueous solution containing 2.6% by mass of boric acid (boric acid cross-linking treatment bath: temperature 32° C.) for 120 seconds, and simultaneously uniaxially stretched 1.25 times in the longitudinal direction (total 3.0 times). It was further immersed in a 58°C aqueous solution (uniaxial stretching treatment bath) containing boric acid at a ratio of 2.8% by mass and potassium iodide at a ratio of 5% by mass, and simultaneously stretched uniaxially in the longitudinal direction to 6.0 times the total. Then, the film was washed by immersing in a potassium iodide aqueous solution (washing bath) at a temperature of 22° C. containing 1.5% by mass of boric acid and 3.5% by mass of potassium iodide for 5 seconds. Finally, it was dried at 80°C for 4 minutes to obtain a polarizing film.

Using the obtained polarizing film, the monomer transmittance (T) and the degree of polarization (V) were measured by the above-mentioned method, and the dichroic ratio (R) was obtained. In addition, according to the above-mentioned method, the heat and humidity resistance of the polarizing film was evaluated. The results are shown in Table 1.

[Examples 2 to 5 and Comparative Examples 1 to 4] Except for using the PVA (PVA-2~PVA-9) described in Tables 1 to 3, and adjusting the PVA content of the film-forming stock solution and the heat treatment temperature so that the average thickness of the PVA film becomes 30μm and the swelling degree becomes 200%. In the same manner as in Example 1, the production and evaluation of the PVA film were performed. Using the obtained PVA film, production and evaluation of a polarizing film were performed in the same manner as in Example 1. The results are shown in Tables 1 to 3.

[Comparative Example 5] The PVA film was produced in the same manner as in Example 1, except that PVA-10 was used as the PVA, and the PVA content of the film-forming stock solution and the heat treatment temperature were adjusted so that the average thickness of the PVA film was 30 μm and the swelling degree was 200%. However, it was broken in the uniaxial stretching treatment bath, and a polarizing film could not be obtained.

[Comparative Example 6] Using PVA-11 as PVA, I want to make a film-forming stock solution and a 10% by mass PVA aqueous solution, but the PVA does not dissolve, and the film-forming stock solution cannot be made.

[Table 1] Example 1 Example 2 Example 3 Comparative example 1 PVA PVA-1 PVA-2 PVA-3 PVA-6 Degree of polymerization - 2400 2400 2400 2400 Saponification degree mol% 99.9 99.9 99.9 99.9 SiOH group content mol% 0.2 0.05 0.4 0 Degree of polymerization × SiOH group content mol% 480 120 960 0 10% by mass aqueous solution viscosity mPa･s 920 910 1500 910 Dichroism ratio - 208 175 266 162 Humidity and heat resistance (after 12hr) Increase in transmittance % 3.6 4.9 2.0 4.9 Polarization reduction % 9.4 13.4 2.8 15.1

[Table 2] Example 4 Comparative example 2 PVA PVA-4 PVA-7 Degree of polymerization - 3300 3300 Saponification degree mol% 99.9 99.9 SiOH group content mol% 0.2 0 Degree of polymerization × SiOH group content mol% 660 0 10% by mass aqueous solution viscosity mPa･s 2790 2740 Dichroism ratio - 237 201 Humidity and heat resistance (after 12hr) Increase in transmittance % 1.9 3.7 Polarization reduction % 2.6 9.2

[table 3] Example 5 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 PVA PVA-5 PVA-8 PVA-9 PVA-10 PVA-11 Degree of polymerization 1700 1700 1700 500 2400 Saponification degree mol% 99.9 99.9 98.5 99.9 99.9 SiOH group content mol% 0.2 0 0.2 0.5 1.1 Degree of polymerization × SiOH group content mol% 340 0 340 250 2640 10% by mass aqueous solution viscosity mPa･s 310 320 190 8 Can't dissolve Dichroism ratio 187 137 156 Can't extend - Humidity and heat resistance (after 12hr) Increase in transmittance % 9.7 12.5 46.3 - - Polarization reduction % 29.3 37.8 97.7 - -

As shown in Tables 1~3, the PVA1~PVA-5 used in Examples 1~5 are fully water-soluble and can be adjusted into a film-forming stock solution, and the resulting PVA film (film for optical film manufacturing) can be processed Used to obtain sufficient extension of the polarizing film. In this way, it can be seen that the PVA films of Examples 1 to 5 have good productivity. In addition, the polarizing films obtained from the PVA films of Examples 1 to 5 are superior in optical properties (dichroic ratio) and moisture and heat resistance compared to polarizing films using unmodified PVA with the same degree of polymerization. Specifically, as shown in Table 1, the polarizing films of Examples 1 to 3 using silanol-modified PVA with a degree of polymerization of 2,400 are compared with the polarizing film of Comparative Example 1 using unmodified PVA with a degree of polymerization of 2,400 In contrast, the dichroic ratio is high and the degree of polarization reduction is small. The polarizing film of Example 4 using silanol to modify PVA with a degree of polymerization of 3,300 is compared with the polarizing film of Comparative Example 2 using unmodified PVA with a degree of polymerization of 3,300, and has a higher dichroic ratio and light transmission The degree of increase in degree and decrease in degree of polarization are small. The polarizing film of Example 5 using silanol-modified PVA with a degree of polymerization of 1,700 is compared with the polarizing films of Comparative Example 3 and Comparative Example 4 using unmodified PVA with a degree of polymerization of 1,700, and the dichroism is higher High and small increase in transmittance and decrease in polarization.

In addition, for example, if Comparative Example 1 using unmodified PVA with a degree of polymerization of 2,400 is used as a reference, and Comparative Example 2 is compared with Example 1, the following results can be seen. Compared with Comparative Example 1, Comparative Example 2 uses PVA with a high degree of polymerization. Compared with Comparative Example 1, Example 1 uses silanol-modified PVA. The dichroic ratio of Comparative Example 2 was 201, and the dichroic ratio of Example 1 was 208. Compared with Comparative Example 1 having a dichroic ratio of 162, the dichroic ratio was increased to the same extent in either case. However, if compared with the viscosity of the aqueous solution of PVA, the viscosity of the PVA in Comparative Example 1 is 910 mPa·s, and the viscosity of the PVA in Comparative Example 2 is greatly increased to 2,740 mPa·s. On the other hand, the viscosity of the PVA of Example 1 was 920 mPa·s, and the increase in the viscosity was suppressed. That is, if PVA is modified with the silanol of the examples, it can be said that while maintaining good film-forming properties (productivity), the optical performance and moisture-heat resistance of the optical film can be improved. [Industrial availability]

The film for manufacturing an optical film of the present invention is suitable for use as a constituent material of LCD, that is, a material such as a polarizing film.

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Claims (12)

A film for manufacturing an optical film, which comprises a polyvinyl alcohol having a silicon-containing group, wherein the silicon-containing group is a silanol group or a group that can be converted into a silanol group in the presence of water, and the viscosity of the polyvinyl alcohol has an average degree of polymerization It is 1,000 or more and 6,000 or less, the saponification degree is 98.7 mol% or more, and the content of the silicon-containing group relative to all structural units is 0.01 mol% or more and 1.0 mol% or less. The film for manufacturing an optical film according to claim 1, wherein the saponification degree is 99.5 mol% or more. The optical film manufacturing film of claim 1 or 2, wherein the product of the viscosity average degree of polymerization and the content of the silicon-containing group is 100 mol% or more and 2,000 mol% or less. The film for manufacturing an optical film according to any one of claims 1 to 3, which has an average thickness of 1 μm or more and 75 μm or less. Such as the optical film manufacturing film of any one of claims 1 to 4, which has a swelling degree of 140% or more and 400% or less. The film for manufacturing an optical film according to any one of claims 1 to 5, wherein the optical film is a polarizing film. The film for manufacturing an optical film according to any one of claims 1 to 6, which is a non-stretched film. A method for manufacturing an optical film, comprising the step of uniaxially stretching the film for manufacturing an optical film as claimed in any one of claims 1 to 7. The method for manufacturing an optical film according to claim 8, wherein the optical film is a polarizing film. An optical film comprising a polyvinyl alcohol having a silicon-containing group, wherein the silicon-containing group is a silanol group or a group that can be converted into a silanol group in the presence of water, and the viscosity of the polyvinyl alcohol has an average degree of polymerization of 1,000 or more 6,000 or less, the saponification degree is 98.7 mol% or more, and the content of the silicon-containing group relative to all structural units is 0.01 mol% or more and 1.0 mol% or less. Such as the optical film of claim 10, which is a polarizing film. Such as the optical film of claim 10 or 11, which is a single-layer film.