WO2021070622A1

WO2021070622A1 - Film for production of optical film, method for producing optical film, and optical film

Info

Publication number: WO2021070622A1
Application number: PCT/JP2020/036028
Authority: WO
Inventors: さやか清水; 喬士練苧; 慎二中井; 匡希中谷
Original assignee: 株式会社クラレ
Priority date: 2019-10-08
Filing date: 2020-09-24
Publication date: 2021-04-15
Also published as: TW202126703A; JPWO2021070622A1; KR20220074860A; CN114450329A

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 producing an optical film, a method for producing an optical film, and an optical film.

A polarizing plate having a function of transmitting and shielding light is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes the polarization state of light. Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film. The polarizing film, a polyvinyl alcohol film (hereinafter, the "polyvinyl alcohol" may be abbreviated as "PVA".) Matrix produced by uniaxially stretching a (stretched film) to iodine dye (I ₃ ^- and I ₅ ^- Etc.) and dichroic dyes such as dichroic organic dyes are mainly adsorbed.

LCDs are widely used in small devices such as calculators and wristwatches, smartphones, laptop computers, LCD monitors, LCD color projectors, LCD TVs, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors. In recent years, these devices have been required to improve display quality. Along with this, the polarizing film is also required to have high performance, and specifically, a polarizing film having excellent optical performance such as polarization degree and transmittance is required. Durability is also important for polarizing films, and it is required that good performance be maintained even in a high temperature and high humidity environment, for example. Optical performance and durability are also required for optical films other than polarizing films.

As a polarizing film having improved optical performance, moisture and heat resistance, etc., a polarizing film using PVA having a high degree of polymerization is known (Patent Document 1). In Patent Document 1, film formation is performed using a PVA film formation solution in which PVA having a high degree of polymerization is dissolved in a solvent containing dimethyl sulfoxide as a main component.

Japanese Unexamined Patent Publication No. 1-105204

In the production of industrial PVA films, it is common to use a PVA aqueous solution in which water is used as a solvent as a film-forming solution in consideration of environmental aspects, economic efficiency, and the like. However, PVA having a high degree of polymerization has poor film-forming property because the viscosity of the aqueous solution increases, which is not preferable for industrial production. Therefore, a method for improving the optical performance and moisture heat resistance of the optical film is desired other than the method for increasing the degree of polymerization of PVA.

The present invention has been made based on the above circumstances, and an object thereof is optical performance and moisture heat resistance as compared with the case of using non-modified PVA having good productivity and the same degree of polymerization. It is an object of the present invention to provide a film for producing an optical film capable of obtaining an excellent optical film, a method for producing an optical film using such a film for producing an optical film, and an optical film.

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

According to the present invention, an optical film manufacturing film capable of obtaining an optical film having good productivity and excellent optical performance and moisture heat resistance as compared with the case of using non-modified PVA having the same degree of polymerization, It is possible to provide an optical film manufacturing method and an optical film using such an optical film manufacturing film.

<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, may be referred to as "silanol-modified PVA").

(Silanol-modified PVA)
The silanol-modified PVA is a polymer having a vinyl alcohol unit (-CH _2- CH (OH)-) as a structural unit, and has a silicon-containing group. The silanol-modified PVA may contain a structural unit containing a silicon-containing group, and may further have a vinyl ester unit such as a vinyl acetate unit or another structural unit.

The lower limit of the viscosity average degree of polymerization of silanol-modified PVA is 1,000, preferably 2,000, and more preferably 2,500. When the viscosity average degree of polymerization of the silanol-modified PVA is at least the above lower limit, the film for producing an optical film of the present invention has excellent stretchability, and an optical film having excellent optical performance and moisture heat resistance can be obtained. it can. 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. When the viscosity average degree of polymerization of silanol-modified PVA is not more than the above upper limit, good water solubility is exhibited and an increase in the viscosity of the aqueous solution is suppressed. Therefore, when the viscosity average degree of polymerization of silanol-modified PVA is not more than the above upper limit, good film-forming property can be exhibited and the productivity of the film for producing an optical film of the present invention can be enhanced.

The viscosity average degree of polymerization means the average degree of polymerization measured according to the description of JIS K6726-1994. That is, in the present specification, the viscosity average degree of polymerization is determined from the extreme viscosity [η] (unit: decylliter / g) measured in water at 30 ° C. after reseminating and purifying the residual vinyl ester group of PVA. It is calculated by 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 preferable. When the saponification degree is at least the above lower limit, an optical film having excellent optical performance and moisture heat resistance can be obtained. On the other hand, the upper limit of the saponification degree is not particularly limited, but is preferably 99.99 mol% or less from the viewpoint of productivity of silanol-modified PVA.

The degree of saponification of PVA is the ratio of the number of moles of vinyl alcohol units to the total number of moles of structural units (typically vinyl ester units) and vinyl alcohol units that can be converted into vinyl alcohol units by saponification (PVA). Mol%). The degree of saponification of PVA can be measured according to the description of JIS K6726-1994.

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

A group that can be converted to a silanol group in the presence of water means a group that can be converted to a silanol group when PVA is hydrolyzed in water under conditions of a reaction time of 2 hours and a reaction temperature of 150 ° C. Examples of the group that can be converted to a silanol group in the presence of water include a group in which at least one alkoxy group or an acyloxy group is bonded to a silicon atom, and specifically, a trimethoxysilyl group and a triethoxysilyl group. , Triisopropoxysilyl group, dimethoxymethylsilyl group, diethoxymethylsilyl group, methoxydimethylsilyl group, ethoxydimethylsilyl group, triacetoxysilyl group and the like.

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

In formulas (1) to (3), R ¹ is independently a hydrogen atom, a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted acyl group having 1 to 20 carbon atoms. It is a group. R ² is an independently substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms.

Examples of the hydrocarbon group having 1 to 20 carbon atoms represented by R ¹ and R ² include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group (cyclohexyl group, etc.), an aromatic hydrocarbon group (phenyl group, etc.) and the like. The aliphatic hydrocarbon group is preferable. Examples of the aliphatic hydrocarbon group include an alkyl group such as a methyl group, an ethyl group and a propyl group, an alkenyl group such as a vinyl group and an alkynyl group such as an ethynyl group, and an alkyl group is preferable. The ^{number of carbon atoms of the hydrocarbon group represented by R 1} and R ² is preferably 1 to 6, and more preferably 1 to 3. At ^{least a part of the hydrogen atom contained in the hydrocarbon group represented by R 1} and R ² may be substituted with a halogen atom, a carboxy group, an alkoxy group (methoxy group, ethoxy group, etc.) and the like.

Examples of the acyl group having 1 to 20 carbon atoms represented by R ¹ include a group in which a carbonyl group (−CO−) is bonded to the above-mentioned hydrocarbon group having 1 to 20 carbon atoms. Specific examples thereof include an acetyl group, a propionyl group, and a benzoyl group. The ^{number of carbon atoms of the acyl group represented by R 1} is preferably 1 to 6, and more preferably 1 to 3. At ^{least a part of the hydrogen atom of the acyl group represented by R 1} may be substituted with a halogen atom, a carboxy group, an alkoxy group (methoxy group or the like) or the like.

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

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

The content of silicon-containing groups with respect to all structural units of silanol-modified PVA is 0.01 mol% or more and 1.0 mol% or less. As described above, by using silanol-modified PVA having a predetermined amount of silicon-containing groups, the optical performance and moist heat resistance of the obtained optical film can be obtained by using non-modified PVA having the same degree of polymerization. Significantly improved compared to film. The non-modified PVA is PVA obtained by saponifying a homopolymer of vinyl ester. On the other hand, the silanol-modified PVA has a lower viscosity of the aqueous solution at a high temperature (for example, 80 ° C.) than the PVA having a high degree of polymerization having the same optical performance of the obtained optical film. Therefore, by using silanol-modified PVA, the optical performance and moist heat resistance of the obtained optical film can be improved while the film for producing the optical film has good productivity (film forming property). Alternatively, by using silanol-modified PVA, the productivity (film-forming property) of the optical film-making film can be improved while the obtained optical film exhibits excellent optical performance and moisture-heat resistance.

The lower limit of the content of silicon-containing groups with respect to all structural units of silanol-modified PVA is 0.01 mol%, preferably 0.05 mol%, more preferably 0.1 mol%, further 0.25 mol%. preferable. By setting the content of the silicon-containing group to the above lower limit or more, the above effect by silanol modification can be sufficiently exhibited. On the other hand, the upper limit of the content of the silicon-containing group with respect to all the structural units of the silanol-modified PVA is 1.0 mol%, preferably 0.8 mol%, and more preferably 0.6 mol%. By setting the content of the silicon-containing group to the above upper limit or less, the water solubility of the silanol-modified PVA and the viscosity stability of the aqueous solution are improved, and the film productivity (film-forming property) can be improved.

In silanol-modified PVA, the content (mol%) of silicon-containing groups can be determined, for example, by proton NMR of the vinyl ester polymer before saponification. Here, when measuring the proton NMR of the vinyl ester polymer before saponification, the vinyl ester polymer is reprecipitated and purified with hexane-acetone to completely remove unreacted monomers from the polymer, and then at 90 ° C. After drying under reduced pressure for 2 days, _{it is dissolved in a CDCl 3} solvent and subjected to analysis.

The lower limit of the product of the viscosity average degree of polymerization of silanol-modified PVA and the content of silicon-containing groups is preferably 100 mol%, more preferably 300 mol%, further preferably 500 mol%, and particularly preferably 700 mol%. When the product is at least the above lower limit, the optical performance and moisture heat resistance of the obtained optical film become more excellent. On the other hand, the upper limit of the product is preferably 2,000 mol%, more preferably 1,500, and even more preferably 1,200. When the product is not more than the above upper limit, the water solubility of the silanol-modified PVA can be further increased, and the productivity of the film for producing the optical film can be further increased.

The silanol-modified PVA preferably has a structural unit having a silicon-containing group. Examples of the structural unit having a silicon-containing group include a structural unit represented by the following formula (4).

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

As R ^3, a hydrogen atom is preferred.

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

Examples of the divalent hydrocarbon group containing at least one oxygen atom and a nitrogen _{_{_{_{atom, -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-, etc. can be mentioned. The number of carbon atoms 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.

Specific examples of the silicon-containing group represented by R ⁵ are as described above, and a group represented by any of the above formulas (1) to (3) can be mentioned, and the above formula (1) can be used. The group represented is preferred.

The number of silicon-containing groups contained in the structural unit having silicon-containing groups is not particularly limited, but may be 1. The range of the content of the structural unit having a silicon-containing group with respect to all the structural units of the silanol-modified PVA may be the range of the content of the silicon-containing group with respect to all the structural units described above. Further, the range of the product of the viscosity average degree of polymerization of silanol-modified PVA and the content of the structural unit having a silicon-containing group may be the range of the product of the above-mentioned viscosity average degree of polymerization and the content of the silicon-containing group. ..

The silanol-modified PVA may have other structural units other than the vinyl alcohol unit, the vinyl ester unit, and the structural unit having a silicon-containing group. However, the content of the above other structural units with respect to all the structural units of silanol-modified PVA is preferably 15 mol% or less, more preferably 5 mol% or less, further preferably 1 mol% or less, and 0.1 mol% or less. It may be even more preferable. When the silanol-modified PVA is substantially composed of a vinyl alcohol unit, a vinyl ester unit, and a structural unit having a silicon-containing group, the effects of the present invention may be more fully exhibited.

The film for producing an optical film may contain one kind of silanol-modified PVA alone, or contains two or more kinds of silanol-modified PVA having different degrees of polymerization, saponification, silicon-containing group content and the like. May be good.

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

(Method for producing silanol-modified PVA)
The method for producing 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-containing group and saponifying the obtained vinyl ester polymer.

Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerianate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatic acid and the like. it can. Among these, vinyl acetate is preferable.

Examples of the monomer having a silicon-containing group include vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, allyltrimethoxysilane, and allylmethyldimethoxysilane. Allyldimethylmethoxysilane, Allyltriethoxysilane, Allylmethyldiethoxysilane, Allyldimethylethoxysilane, Vinyltris (β-methoxyethoxy) silane, Vinylisobutyldimethoxysilane, Vinylethyldimethoxysilane, Vinylmethoxydibutoxysilane, Vinyldimethoxybutoxysilane , Vinyl tributoxysilane, vinylmethoxydihexyloxysilane, vinyldimethoxyhexyloxysilane, vinyltrihexyloxysilane, vinylmethoxydioctyloxysilane, vinyldimethoxyoctyloxysilane, vinyltrioctyloxysilane, vinylmethoxydilauryloxysilane , Vinyldimethoxylauryloxysilane, vinylmethoxydioleyloxysilane, vinyldimethoxyoleyloxysilane, 3- (meth) acrylamide-propyltrimethoxysilane, 3- (meth) acrylamide-propyltriethoxysilane, 3- (meth) acrylamide -Propyltri (β-methoxyethoxy) silane, 2- (meth) acrylamide-ethyltrimethoxysilane, 1- (meth) acrylamide-methyltrimethoxysilane, 2- (meth) acrylamide-2-methylpropyltrimethoxysilane, 2- (Meta) acrylamide-isopropyltrimethoxysilane, N- (2- (meth) acrylamide-ethyl) -aminopropyltrimethoxysilane, (3- (meth) acrylamide-propyl) -oxypropyltrimethoxysilane, 3- (Meta) acrylamide-propyltriacetoxysilane, 2- (meth) acrylamide-ethyltriacetoxysilane, 4- (meth) acrylamide-butyltriacetoxysilane, 3- (meth) acrylamide-propyltripropionyloxysilane, 2-( Meta) acrylamide-2-methylpropyltriacetoxysilane, N- (2- (meth) acrylamide-ethyl) -aminopropyltriacetoxysilane, 3- (meth) acrylamide-propylisobutyldimethoxysilane, 2- (meth) acrylamide- Ethyldimethylmethoxy Silane, 3- (meth) acrylamide-propylmethyldiacetoxysilane, 2- (meth) acrylamide-2-methylpropylhydrogendimethoxysilane, 3- (N-methyl- (meth) acrylamide) -propyltrimethoxysilane, 2 -(N-Ethyl- (meth) acrylamide) -ethyltriacetoxysilane and the like can be mentioned.

The method for copolymerizing the vinyl ester monomer and the monomer having a silicon-containing group is not particularly limited, and examples thereof include known methods such as a massive polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among these methods, a massive polymerization method performed without a solvent and a solution polymerization method performed using a solvent such as alcohol are preferable. Examples of the solvent used as a solvent in 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 in the copolymerization reaction, conventionally known azo-based initiators, peroxide-based initiators, redox-based initiators and the like are appropriately selected. Examples of the azo initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (4-methoxy-2,4-). Dimethylvaleronitrile) and the like. Peroxide-based initiators include percarbonate compounds such as dinormalpropyl peroxydicarbonate, diisopropylperoxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethylperoxydicarbonate; t-butylper. Perester compounds such as oxyneodecanate, α-cumylperoxyneodecanate, t-butylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide, diisobutyryl peroxide; 2,4,4-trimethylpentyl-2- Examples thereof include peroxyphenoxyacetate. Further, potassium persulfate, ammonium persulfate, hydrogen peroxide and the like can be combined with the above-exemplified peroxide-based initiator to prepare the initiator. Examples of the redox-based initiator include a combination of the above-mentioned peroxide and a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, and longalit.

The polymerization temperature when the copolymerization reaction is carried out is not particularly limited, but is preferably 0 ° C. or higher and 180 ° C. or lower, more preferably 20 ° C. or higher and 160 ° C. or lower, and further preferably 30 ° C. or higher and 150 ° C. or lower.

When copolymerizing a vinyl ester monomer and a monomer having a silicon-containing group, it is possible to copolymerize another copolymerizable monomer, if necessary, as long as the effect of the present invention is not impaired. it can. Other monomers include, for example, ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butyl, and isobutene; acrylate or a salt thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylate, and the like. Acrylic acid esters such as i-propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid or a salt thereof; methacryl Methyl acidate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, methacryl Methacrylate esters such as octadecyl acid; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamide propanesulfonic acid or its salts, acrylamidepropyldimethylamine or its salts, N-methylol Acrylamide derivatives such as acrylamide or derivatives thereof; methacrylamide, N-methylmethacrylate, N-ethylmethacrylate, methacrylamide propanesulfonic acid or a salt thereof, methacrylamidepropyldimethylamine or a salt thereof, N-methylolmethacrylate or a derivative thereof. Methacrylate derivatives such as N-vinylformamide, N-vinylacetamide, N-vinylamide such as N-vinylpyrrolidone; methylvinyl ether, ethylvinyl ether, n-propylvinyl ether, i-propylvinyl ether, n-butylvinyl ether, i-butyl Vinyl ethers such as vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; vinyl cyanide such as acrylonitrile and methacrylonitrile; vinyl halide such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl acetate, chloride Allyl compounds such as allyl; maleic acid or a salt thereof, ester or acid anhydride; itaconic acid or a salt thereof, ester or acid anhydride; isopropenyl acetate and the like can be mentioned. The vinyl ester polymer can have a structural unit derived from one or more of the other monomers described above.

The proportion of structural units derived from the above-mentioned other monomers (monomers other than the vinyl ester monomer and the monomer having a silicon-containing group) in the vinyl ester polymer is not necessarily limited as long as the effect of the present invention is not impaired, but the vinyl ester weight Based on the number of moles of all structural units constituting the coalescence, 15 mol% or less is preferable, 5 mol% or less is more preferable, 1 mol% or less is further preferable, and 0.1 mol% or less may be further preferable. ..

The vinyl ester polymer is then saponified in a solvent according to a known method, leading to silanol-modified PVA. Alcohol is preferable as the solvent used for the saponification reaction. Examples of the alcohol include lower alcohols such as methanol and ethanol, and methanol is particularly preferably used. In addition to alcohol, the solvent used in the saponification reaction may further contain acetone, an ester such as methyl acetate or ethyl acetate, or an organic solvent such as toluene. Examples of the catalyst used in the saponification reaction include hydroxides of alkali metals such as potassium hydroxide and sodium hydroxide, alkaline catalysts such as sodium methylate, and acid catalysts such as mineral acid. The temperature of the saponification reaction can be, for example, 20 ° C. or higher and 60 ° C. or lower. When a gel-like product is precipitated as the saponification reaction progresses, the product is pulverized at that time, washed, and dried to obtain silanol-modified PVA.

(Plasticizer)
The film for producing an optical film of the present invention preferably contains a plasticizer. Since the film for producing an optical film contains a plasticizer, the stretchability can be improved. A polyhydric alcohol is preferable as the plasticizer. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane and the like. Among these, glycerin is preferable from the viewpoint of improving stretchability. As the plasticizer, one kind or two or more kinds can be used.

The lower limit of the content of the plasticizer in the film for producing an optical film of the present invention is preferably 1 part by mass, more preferably 3 parts by mass, and even more preferably 5 parts by mass with respect to 100 parts by mass of silanol-modified PVA. When the content of the plasticizer is at least the above lower limit, the stretchability of the film is improved, and the optical performance of the obtained optical film can be further improved. On the other hand, the upper limit of the content of this plasticizer is preferably 20 parts by mass, more preferably 17 parts by mass, and even more preferably 15 parts by mass with respect to 100 parts by mass of silanol-modified PVA. When the content of the plasticizer is not more than the above upper limit, it is possible to prevent the film from becoming too flexible and the handleability from being lowered.

(Surfactant)
The film for producing an optical film preferably contains a surfactant. By forming a film using a film-forming stock solution containing a surfactant, the film-forming property is improved and the occurrence of thickness unevenness of the film is suppressed, and the film is peeled off from the metal roll or belt used for film-forming. Becomes easier. When a film for producing an optical film is produced from a film-forming stock solution containing a surfactant, the resulting film may contain a surfactant.

The type of surfactant is not particularly limited, but an anionic surfactant and a nonionic surfactant are preferable from the viewpoint of peelability from a metal roll or a belt.

Examples of the anionic surfactant include a carboxylic acid type such as potassium laurate; a sulfate ester type such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and a sulfonic acid type such as dodecylbenzene sulfonate.

Examples of the nonionic surfactant include an alkyl ether type such as polyoxyethylene oleyl ether; an alkylphenyl ether type such as polyoxyethylene octylphenyl ether; an alkyl ester type such as polyoxyethylene laurate; and a polyoxyethylene lauryl amino ether. Alkylamine type such as; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as laurate diethanolamide and oleic acid diethanolamide; polyoxyalkylene Examples thereof include an allylphenyl ether type such as allylphenyl ether.

The surfactant can be used alone or in combination of two or more.

When the film for producing an optical film contains a surfactant, the lower limit of the content thereof is preferably 0.01 part by mass, more preferably 0.02 part by mass, and 0.05 part by mass with respect to 100 parts by mass of silanol-modified PVA. Parts by mass are even more preferred. By setting the content of the surfactant to the above lower limit or more, the film-forming property and the peelability are further improved. On the other hand, the upper limit of this content is preferably 0.5 parts by mass, more preferably 0.3 parts by mass, and even more preferably 0.1 parts by mass with respect to 100 parts by mass of silanol-modified PVA. By setting the content of the surfactant to the above upper limit or less, it is possible to prevent the surfactant from bleeding out to the surface of the film, causing blocking and deteriorating the handleability.

(Other additives, etc.)
Further, the film for producing an optical film of the present invention includes a filler, a processing stabilizer such as a copper compound, a weather resistance stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, and a flame retardant. , Other thermoplastic resins, lubricants, fragrances, defoamers, deodorants, bulking agents, release agents, mold release agents, reinforcing agents, cross-linking agents, fungicides, preservatives, crystallization rate retarders, etc. Additives may be appropriately contained as needed.

The film for producing an optical film of the present invention may contain PVA other than the silanol-modified PVA described above. The total proportion of all PVA including silanol-modified PVA, the plasticizer and the surfactant in the film for producing an optical film of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, and 95% by mass. The above is more preferable, and in some cases, 99% by mass or more is even more preferable. When the film for producing 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.

The content ratio of the above-mentioned silanol-modified PVA in all PVA contained in the film for producing an optical film of the present invention is preferably 50% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 90% by mass or more. 95% by mass or more is further preferable, and 99% by mass or more is even more preferable. By mainly using silanol-modified PVA as PVA in the film for producing an optical film of the present invention, the effect of the present invention can be more fully exhibited.
The total proportion of the silanol-modified PVA, the plasticizer and the surfactant in the film for producing an optical film of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more. In some cases, 99% by mass or more is even more preferable. When the film for producing an optical film of the present invention is substantially composed of silanol-modified PVA, a plasticizer and a surfactant, the effects of the present invention can be more fully exhibited.

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

The average thickness of the film for producing an optical film of the present invention is not particularly limited, but the lower limit is preferably 1 μm, more preferably 5 μm, and even more preferably 10 μm. When the average thickness is at least the above lower limit, it is possible to suppress breakage during the uniaxial stretching process when manufacturing an optical film. The upper limit of the average thickness is preferably 75 μm, more preferably 60 μm, further preferably 45 μm, and even more preferably 35 μm. When the average thickness is not more than the above upper limit, stretching spots during the uniaxial stretching treatment can be suppressed. The "average thickness" refers to the average value of the thickness measured at any five points (hereinafter, the same applies to the average thickness).

The film for producing an optical film of the present invention may be a single-layer film composed of one PVA layer (a layer containing silanol-modified PVA) or a multilayer film including one PVA layer. However, when it is used for producing a polarizing film, it is preferably a single-layer film. The lower limit of the average thickness of the PVA layer contained in the film for producing an optical film of the present invention is preferably 1 μm, more preferably 5 μm, still more preferably 10 μm. When the average thickness is at least the above lower limit, it is possible to suppress breakage during the uniaxial stretching process when manufacturing an optical film. The upper limit of the average thickness is preferably 75 μm, more preferably 60 μm, further preferably 45 μm, and even more preferably 35 μm. When the average thickness is not more than the above upper limit, stretching spots during the uniaxial stretching treatment can be suppressed.

As the specific composition and suitable composition of the PVA layer in the film for producing an optical film, the above-mentioned description of the specific composition and the suitable composition of the film for producing an optical film itself can be cited.

When the film for producing an optical film of the present invention is a single-layer film, the average thickness is preferably 20 μm or more, more preferably 30 μm or more, in order to ensure handleability. 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.

A multilayer film is a film having two or more layers. The number of layers of the multilayer film may be 5 or less, and may be 3 or less. Examples of the multilayer film include a film for producing 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 the resin constituting the base resin layer, polyester, polyolefin or the like can be used. Of these, an amorphous polyester resin is preferable, and polyethylene terephthalate and an amorphous polyester resin obtained by copolymerizing polyethylene terephthalate with a copolymerization component such as isophthalic acid and 1,4-cyclohexanedimethanol are preferably used. An adhesive layer may be provided between the base resin layer and the PVA layer.

The width of the film for producing an optical film of the present invention is not particularly limited and can be determined according to its application and the like. For example, the lower limit of the width of the optical film manufacturing film is preferably 3 m. In recent years, since the screen size of liquid crystal televisions and liquid crystal monitors has been increasing, if the width of the film for producing an optical film is set to 3 m or more, it is suitable for applications in which these are final products. On the other hand, the upper limit of the width of the optical film manufacturing film is preferably 7 m. By setting the width to 7 m or less, it is possible to efficiently perform the uniaxial stretching process when manufacturing an optical film with a practical device.

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

Here, the "film swelling degree" means a value obtained by the following equation.
Swelling degree (%) = 100 x N / M
In the formula, N represents the mass (g) of the sample after immersing the sample collected from the film in distilled water at 30 ° C. for 30 minutes and then removing the water on the surface. 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 not substantially stretched (non-stretched film, unstretched film). The in-plane phase difference of the raw film for manufacturing an optical film is preferably 100 nm or less, more preferably 50 nm or less. Usually, an optical film can be obtained by stretching a film for producing an optical film of the present invention (uniaxial stretching treatment or biaxial stretching treatment).

According to the film for producing an optical film of the present invention, it is possible to obtain an optical film having good productivity and excellent optical performance and moisture heat resistance as compared with the case of using non-modified PVA having the same degree of polymerization. .. The optical performance includes light transmission, polarization, and the like. Examples of the optical film that can be produced by the optical film manufacturing film include a polarizing film, a retardation film, a viewing angle improving film, a brightness improving film, and the like, and a polarizing film is preferable.

<Manufacturing method of film for manufacturing optical film>
The method for producing the film for producing an optical film of the present invention is not particularly limited, but a method for producing a film having a more uniform thickness and width after film formation can be preferably adopted. For example, it can be produced using silanol-modified PVA and, if necessary, a film-forming stock solution in which one or more of plasticizers, surfactants and other additives are dissolved in a liquid medium. it can. 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.

Examples of the liquid medium used for preparing the film-forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and tri. Examples thereof include methylolpropane, ethylenediamine, and diethylenetriamine, and one or more of these can be used. Of these, water is preferable from the viewpoint of environmental load and recoverability. In addition, the silanol-modified PVA described above has good water solubility, and an increase in viscosity when used as an aqueous solution at a relatively high temperature (for example, 80 ° C.) is suppressed. From this point as well, water can be preferably used as the liquid medium.

The volatile content of the film-forming stock solution (the content of volatile components such as a liquid medium removed by volatilization or evaporation during film-forming in the film-forming stock solution) is preferably, for example, 50% by mass or more and 95% by mass or less, and 55% by mass. % Or more and 90% by mass or less is more preferable, and 60% by mass or more and 85% by mass or less is further preferable. When the volatile content of the membrane-forming stock solution is 50% by mass or more, the viscosity of the membrane-forming stock solution does not become too high, filtration and defoaming during preparation of the membrane-forming stock solution are smoothly performed, and a film with few foreign substances and defects. Is easy to manufacture. On the other hand, when 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 industrial film production becomes easy.

The temperature of the film-forming stock solution at the time of film-forming can be, for example, 70 ° C. or higher and 90 ° C. or lower. By using silanol-modified PVA and performing film formation at such a relatively high temperature, the viscosity of the film-forming stock solution can be suppressed to a relatively low level, and the film-forming property can be improved.

Examples of the film forming method when forming a film using the undiluted film forming solution include a cast film forming method, an extrusion film forming method, a wet film forming method, and a gel film forming method. These film forming methods may adopt only one kind or a combination of two or more kinds. Among these film-forming methods, the cast film-forming method and the extrusion film-forming method are preferable because a film having a uniform thickness and width and good physical characteristics can be obtained. The formed film can be dried or heat-treated as needed.

Examples of a specific manufacturing method for the optical film manufacturing film of the present invention include the following examples. Using a T-shaped slit die, hopper plate, I-die, lip coater die, etc., the film-forming stock solution is uniformly discharged or uniformly discharged onto the peripheral surface of the rotating heated first roll (or belt) located on the most upstream side. Disseminate. Volatile components are evaporated and dried from one surface of the membrane discharged or cast on the peripheral surface of the first roll (or belt). Subsequently, it is further dried on the peripheral surface of one or more rotating heated rolls arranged on the downstream side thereof, or is further dried by passing through a hot air drying device. Then, the film is wound by the winding device. Drying with a heated roll and drying with a hot air drying device may be carried out in an appropriate combination.

When the film for producing an optical film of the present invention is a multilayer film, a multilayer film can be produced, for example, by applying a film-forming stock solution on a base resin film (base resin layer). At this time, in order to improve the adhesiveness between the PVA layer and the base resin layer, the surface of the base resin film may be modified or an adhesive may be applied to the surface of the base resin film. Good.

<Manufacturing method of optical film>
The method for producing an optical film of the present invention includes a step of uniaxially stretching the above-mentioned film for producing an optical film. Hereinafter, a method for producing a polarizing film will be specifically described as an example of a method for producing an optical film.

Examples of the method for producing a polarizing film include a dyeing step of dyeing a film for manufacturing an optical film (hereinafter, also referred to as “PVA film”), a stretching step of uniaxially stretching, and a swelling step of further swelling, if necessary. Examples thereof include a method including a cross-linking step for cross-linking, a fixing treatment step for fixing treatment, a washing step for washing, a drying step for drying, and a heat treatment step for heat treatment. In this case, the order of each step is not particularly limited, but for example, the swelling step, the dyeing step, the cross-linking step, the stretching step, the fixing treatment step, and the like can be performed in this order. Further, one or more steps can be performed at the same time, and each step can be performed twice or more.

The swelling step can be performed by immersing the PVA film in water. The temperature of the water when immersed in water is preferably 20 ° C. or higher and 55 ° C. or lower, more preferably 22 ° C. or higher and 50 ° C. or lower, and further preferably 25 ° C. or higher and 45 ° C. or lower. The time for immersion in water is, for example, preferably 0.1 minutes or more and 5 minutes or less, and more preferably 0.5 minutes or more and 3 minutes or less. 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. Iodine-based pigments are generally used as the dichroic pigments. The timing of dyeing may be any stage before uniaxial stretching, during uniaxial stretching, and after uniaxial stretching. A method of dyeing is preferably performed by immersing the PVA film in a solution (particularly an aqueous solution) containing iodine-potassium iodide, which is a dyeing bath. The concentration of iodine in the dyeing 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. The temperature of the dyeing bath is preferably 20 ° C. or higher and 50 ° C. or lower, particularly preferably 25 ° C. or higher and 40 ° C. or lower. A suitable dyeing time is 0.2 minutes or more and 5 minutes or less.

By performing a cross-linking step of cross-linking silanol-modified PVA in the PVA film, it is possible to effectively suppress elution of silanol-modified PVA into water during wet stretching at a high temperature. From this point of view, the cross-linking step is preferably performed after the dyeing step and before the stretching step. The cross-linking step can be performed by immersing the PVA film in an aqueous solution containing a cross-linking agent. As the cross-linking agent, one or more boron compounds such as borate such as boric acid and borax can be used. The concentration of the cross-linking agent in the aqueous solution containing the cross-linking 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 further preferably 2% by mass or more and 6% by mass or less. Sufficient stretchability can be maintained when the concentration of the cross-linking agent is within the above range. The aqueous solution containing the cross-linking agent may contain potassium iodide or the like. The temperature of the aqueous solution containing the cross-linking agent is preferably 20 ° C. or higher and 60 ° C. or lower, particularly 25 ° C. or higher and 55 ° C. or lower. By keeping the temperature within the above range, cross-linking can be performed efficiently.

The stretching step of uniaxially stretching the PVA film may 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, in the above-mentioned dyeing bath or in the fixing treatment bath described later. Further, in the case of the dry stretching method, stretching may be carried out at room temperature, stretching may be carried out while heating, or may be carried out in air using a PVA film after water absorption. Among these, the wet stretching method is preferable because it can be stretched with high uniformity in the width direction, and uniaxial stretching is more preferable in an aqueous solution containing boric acid. The concentration of boric acid in the boric acid aqueous solution is preferably 0.5% by mass or more and 6.0% by mass or less, more preferably 1.0% by mass or more and 5.0% by mass or less, and 1.5% by mass or more and 4. 0% by mass or less is particularly preferable. Further, 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 in uniaxial stretching is preferably 30 ° C. or higher and 90 ° C. or lower, more preferably 40 ° C. or higher and 80 ° C. or lower, and particularly preferably 50 ° C. or higher and 75 ° C. or lower.

The draw ratio in uniaxial stretching (total draw ratio from 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 obtained polarizing film. The upper limit of the draw ratio is not particularly limited, but the draw ratio is preferably 8 times or less.

There is no particular limitation on the direction of uniaxial stretching when the long PVA film is uniaxially stretched, and uniaxial stretching or lateral uniaxial stretching in the long direction can be adopted. Since a polarizing film having excellent polarization performance can be obtained, uniaxial stretching in the long direction is preferable. Uniaxial stretching in the long direction can be performed by using a stretching device including a plurality of rolls parallel to each other and changing the peripheral speed between the rolls. On the other hand, the lateral uniaxial stretching can be performed using a tenter type stretching machine.

In the production of the polarizing film, a fixing treatment step can be performed after the stretching step in order to strengthen the adsorption of the dichroic dye (iodine dye, etc.) on the PVA film. As the fixing treatment bath used for the fixing treatment, an aqueous solution containing one or more kinds of boron compounds such as boric acid and borax can be used. Further, if necessary, an iodine compound or a metal compound may be added to the fixing treatment bath. The concentration of the boron compound in the fixing treatment bath is preferably 2% by mass or more and 15% by mass or less, particularly preferably 3% by mass or more and 10% by mass or less. By keeping the concentration of the boron compound within the above range, the adsorption of the dichroic dye can be further strengthened. The temperature of the fixing treatment bath is preferably 15 ° C. or higher and 60 ° C. or lower, particularly preferably 25 ° C. or higher and 40 ° C. or lower.

The cleaning process is generally performed by immersing the film in distilled water, pure water, an aqueous solution, or the like. At this time, from the viewpoint of improving the polarization performance, it is preferable to use an aqueous solution containing iodide such as potassium iodide as an auxiliary agent, and the concentration of iodide is preferably 0.5% by mass or more and 10% by mass or less. The temperature of the aqueous solution in the cleaning treatment is generally 5 ° C. or higher and 50 ° C. or lower, preferably 10 ° C. or higher and 45 ° C. or lower, and further 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 of 30 ° C. or higher and 150 ° C. or lower, particularly 50 ° C. or higher and 130 ° C. or lower. By drying at a temperature within the above range, a polarizing film having excellent dimensional stability can be easily obtained.

An optical film other than the polarizing film, such as a retardation film, can also be produced by a method including a step of uniaxially stretching the film for producing an optical film of the present invention. As a specific manufacturing method, a conventionally known method can be adopted except that the film for manufacturing an optical film of the present invention is used.

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

The optical film of the present invention may be an optical film obtained by the above-mentioned manufacturing method using the film for manufacturing the optical film of the present invention. The specific structure, content, and the like 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 film for producing an optical film of the present invention. Further, the optical film of the present invention may contain other components similar to the film for producing an optical film of the present invention.

The optical film of the present invention may be a polarizing film, a retardation film, a viewing angle improving film, a brightness improving film, or the like, and is preferably a polarizing film. In this case, the polarizing film usually contains a dichroic dye, and the silanol-modified PVA may be crosslinked.

The optical film of the present invention is preferably a stretched film, more preferably a uniaxially stretched film. Further, the optical film of the present invention may be a single-layer film or a multilayer film, but a single-layer film is preferable. In the case of such a film, the optical film of the present invention can be more preferably used as a polarizing film or the like.

When the optical film of the present invention is a polarizing film, the dichroism ratio (R) of the polarizing film is preferably 100 or more. By including the silanol-modified PVA described above, a polarizing film having such a high dichroism ratio (R) can be produced with high productivity. The dichroism ratio (R) is more preferably 150 or more, and even more preferably 190 or more. The upper limit of the dichroism ratio (R) is, for example, 350 and may be 300.

The method for calculating the dichroism ratio (R) of the polarizing film is as follows. First, the relationship between the transmittance (T') excluding surface reflection and the simple substance transmittance (T) is expressed by the formula (a). At this time, it is assumed that the refractive index of the polarizing film is 1.5 and the reflectance on the surface is 4%. The relationship between the transmittance (T'), the degree of polarization (V) and the dichroism ratio (R) is expressed by the formula (b). Therefore, after measuring the simple substance transmittance (T) and the degree of polarization (V), the dichroism ratio (R) of the polarizing film is calculated by solving the equations (a) and (b) using these values. can do.
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 a protective film that is optically transparent and has mechanical strength on both sides or one side thereof. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, a cellulose acetate / butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. In addition, examples of the adhesive for bonding include a PVA-based adhesive, a urethane-based adhesive, and an acrylate-based ultraviolet curable adhesive. That is, the polarizing plate has a polarizing film and a protective film laminated directly or via an adhesive layer on one side or both sides of the polarizing film.

The polarizing plate can be used as an LCD component by, for example, coating it with an adhesive such as acrylic and then adhering it to a glass substrate. A retardation film, a viewing angle improving film, a brightness improving film, or the like may be further attached to the polarizing plate.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. The methods of each measurement and evaluation are as follows.

[PVA Polymerization Degree (Viscosity Average Degree of Polymerization)]
For the PVA synthesized in the following synthesis example, the viscosity average degree of polymerization was measured according to the description of JIS K6726-1994.

[Saponification degree of PVA]
The degree of saponification of PVA synthesized in the following synthetic examples was measured according to the description of JIS K6726-1994.

[Content of silicon-containing groups in PVA]
The PVA synthesized in the following synthesis example was measured by proton NMR of the vinyl ester polymer before saponification of the content of silicon-containing groups with respect to all structural units. When measuring the proton NMR of the vinyl ester polymer before saponification, the vinyl ester polymer is reprecipitated with hexane-acetone to completely remove unreacted monomers from the polymer, and then dried under reduced pressure at 90 ° C. After 2 days, it _{was dissolved in CDCl 3} solvent and subjected to analysis.

[Viscosity of 10% by mass PVA aqueous solution]
10 g of PVA synthesized in the following synthesis example was weighed in a sample bottle, and pure water was added so as to have a total of 100 g. This was dissolved in a water bath at 95 ° C. for 4 hours while stirring with a stirrer, and then allowed to stand overnight in a dryer at 80 ° C. for defoaming. The viscosity of the obtained 10 mass% PVA aqueous solution at 80 ° C. was measured with a B-type viscometer.

[Film swelling degree]
The films (films for producing optical films) obtained in the following Examples and Comparative Examples were cut to 1.5 g and immersed in 1000 g of distilled water at 30 ° C. for 30 minutes. After soaking for 30 minutes, the film was taken out, water on the surface was absorbed with a filter paper, and the mass (N) was measured. Subsequently, 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 degree of swelling of the film was determined by the following formula.
Swelling degree (%) = 100 x N / M

[Dichroism ratio of polarizing film (optical performance)]
A rectangular sample of 4 cm in the length direction of the polarizing film was taken from the central portion in the width direction of the polarizing films obtained in the following Examples and Comparative Examples. For this sample, a spectrophotometer with an integrating sphere (“V7100” manufactured by JASCO Corporation) was used, and in accordance with JIS Z8722 (measurement method of object color), a C light source and a visible light region with a 2 ° field of view. After correcting the visual sensitivity, the single transmittance (T) and the degree of polarization (V) were measured.

The dichroism ratio (R) of the polarizing film was calculated by solving the following equations (a) and (b) from the obtained simple substance transmittance (T) and polarization degree (V) values. Here, the refractive index of the polarizing film is assumed to be 1.5, and the reflectance on the surface is assumed to be 4%.
T'= T / (1-0.04) ² ... (a)
R = {-ln [T'(1-V)]} / {-ln [T'(1 + V)]} ... (b)

[Moisture resistance of polarizing film]
The polarizing films obtained in the following examples and comparative examples were fixed to a gold frame, and a spectrophotometer with an integrating sphere (“V7100” manufactured by JASCO Corporation) was used to make JIS Z8722 (measurement method of object color). _{According to this, the single transmittance (T 0} ) and the degree of polarization (V ₀ ) were measured after correcting the visual sensitivity of the visible light region of the C light source and the 2 ° field. Further, the polarizing film fixed to the metal frame is subjected to a wet heat treatment for 12 hours in an atmosphere of 60 ° C. and 90% RH, and then the transmittance (T ₁₂ ) and the degree of polarization (V ₁₂ ) after 12 hours are similarly measured with a spectrophotometer. It was measured. The amount of increase in transmittance (T _12- T ₀ :%) and the amount of decrease in polarization (V _0- V ₁₂ :%) after the moist heat treatment were used as indicators of moist heat resistance.

[Synthesis Example 1] Synthesis of PVA-1 2590 g of vinyl acetate, 410 g of methanol and 5.3 g of vinyl trimethoxysilane are charged into a 6 L reaction vessel equipped with a stirrer, a nitrogen inlet, an additive inlet and an initiator additive. After the temperature was raised to 60 ° C., the inside of the system was replaced with nitrogen by nitrogen bubbling for 30 minutes. The temperature in the reaction vessel was adjusted to 60 ° C., and 0.32 g of 2,2'-azobis (isobutyronitrile) was added to initiate polymerization. From the start of the polymerization, the polymerization reaction was carried out for 3 hours while adding 135 g of methanol containing 2.5% by mass of vinylmethoxysilane into the system, and the polymerization was stopped at that time. The polymerization rate at the time when the polymerization reaction was stopped was 26.8%. The polymerization temperature was maintained at 60 ° C. during the polymerization. Then, unreacted vinyl acetate was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate (hereinafter, may be abbreviated as PVAc).
The concentration of the obtained PVAC methanol solution was adjusted to 23.5%, and the NaOH methanol solution (10) so that the alkali molar ratio (the number of moles of NaOH / the number of moles of vinyl ester units in PVAc) was 0.04. % Concentration) was added and the mixture was saponified. The obtained polyvinyl alcohol was washed with methanol.
The degree of polymerization (viscosity average degree of polymerization) of PVA-1 obtained by the above operation was 2,400, the degree of saponification was 99.9 mol%, the content of silicon-containing groups was 0.2 mol%, and the temperature was 80 ° C. The viscosity of the 10 mass% aqueous solution was 920 mPa · s.

[Synthesis Examples 2 to 11] Synthesis of PVA-2 to PVA-11 According to Synthesis Example 1, the proportion of the monomers used, the polymerization conditions and the saponification conditions were appropriately adjusted, and the degree of polymerization (viscosity) shown in Tables 1 to 3 was adjusted as appropriate. PVA-2 to PVA-11 having a degree of polymerization), a degree of saponification and a content of SiOH groups (content of silicon-containing groups) were obtained.

[Example 1]
An aqueous solution 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 having a PVA content of 9.5% by mass is formed into a film. Prepared as undiluted solution. This film-forming stock solution is dried on a metal roll at 80 ° C., and the obtained film is heat-treated at a temperature of 120 ° C. for 10 minutes in a hot air dryer to adjust the degree of swelling to 200% and have an average thickness. A PVA film (film for producing an optical film) having a thickness of 30 μm was produced.

A sample having a width of 5 cm and a length of 9 cm was cut from the central portion of the obtained PVA film in the width direction so that a range of 5 cm in width × 5 cm in length could be uniaxially stretched. This sample was uniaxially stretched 2.0 times in the length direction while being immersed in pure water at 30 ° C. for 60 seconds for swelling treatment. Subsequently, it was immersed in an aqueous solution containing 0.05% by mass of iodine and 5.0% by mass of potassium iodide (dyeing treatment bath: temperature 32 ° C.) for 120 seconds while being 1.2 times longer (2.4 times as a whole). Iodine was adsorbed by uniaxial stretching in the longitudinal direction. Next, the boric acid was uniaxially stretched 1.25 times (3.0 times in total) while being 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. .. Further, while immersing in an aqueous solution (uniaxial stretching treatment bath) at 58 ° C. containing 2.8% by mass of boric acid and 5% by mass of potassium iodide, the whole is uniaxially stretched up to 6.0 times in the length direction. did. Then, the film was washed by immersing it in a potassium iodide aqueous solution (washing bath) having 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 simple substance transmittance (T) and the degree of polarization (V) were measured by the above-mentioned method, and the dichroism ratio (R) was determined. In addition, the moisture and heat resistance of the polarizing film was evaluated by the above method. The results are shown in Table 1.

[Examples 2 to 5 and Comparative Examples 1 to 4]
Using the PVAs (PVA-2 to PVA-9) listed in Tables 1 to 3, the PVA content and heat treatment temperature of the film-forming stock solution so that the average thickness of the PVA film is 30 μm and the swelling degree is 200%. The PVA film was prepared and evaluated in the same manner as in Example 1 except that the above was adjusted. Using the obtained PVA film, a polarizing film was produced and evaluated in the same manner as in Example 1. The results are shown in Tables 1 to 3.

[Comparative Example 5]
PVA-10 was used as PVA, and PVA was adjusted in the same manner as in Example 1 except that 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%. A film was prepared. However, it broke in the uniaxial stretching treatment bath, and a polarizing film could not be obtained.

[Comparative Example 6]
Using PVA-11 as PVA, an attempt was made to prepare a film-forming stock solution and a 10% by mass PVA aqueous solution, but PVA did not dissolve and the film-forming stock solution could not be prepared.

As shown in Tables 1 to 3, the PVA1 to PVA-5 used in Examples 1 to 5 have sufficient water solubility, so that a film-forming stock solution can be prepared, and the obtained PVA film can be prepared. (Film for manufacturing an optical film) could be sufficiently stretched to obtain a polarizing film. As described above, it can be seen that the PVA films of Examples 1 to 5 have good productivity. Further, the polarizing films obtained from the PVA films of Examples 1 to 5 are superior in optical performance (dichroism ratio) and moisture heat resistance as compared with the polarizing films using non-modified PVA having the same degree of polymerization. It was. Specifically, as shown in Table 1, the polarizing films of Examples 1 to 3 using silanol-modified PVA having a degree of polymerization of 2,400 were compared using non-modified PVA having a degree of polymerization of 2,400. Compared with the polarizing film of Example 1, the dichroism ratio was high and the amount of decrease in degree of polymerization was small. The polarizing film of Example 4 using a silanol-modified PVA having a degree of polymerization of 3,300 has a higher dichroism ratio than the polarizing film of Comparative Example 2 using a non-modified PVA having a degree of polymerization of 3,300. , The amount of increase in transparency and the amount of decrease in degree of polarization were small. The polarizing film of Example 5 using the silanol-modified PVA having a degree of polymerization of 1,700 has two colors as compared with the polarizing films of Comparative Example 3 and Comparative Example 4 using the non-modified PVA having a degree of polymerization of 1,700. The sex ratio was high, and the amount of increase in transparency and the amount of decrease in degree of polarization were small.

Further, for example, when Comparative Example 2 and Example 1 are compared with reference to Comparative Example 1 using non-modified PVA having a degree of polymerization of 2,400, the following can be found. Comparative Example 2 uses PVA having a higher degree of polymerization than Comparative Example 1. Example 1 uses PVA modified with silanol with respect to Comparative Example 1. The dichroism ratio of Comparative Example 2 is 201, and the dichroism ratio of Example 1 is 208, both of which have the same dichroism ratio as that of Comparative Example 1 having a dichroism ratio of 162. It is increasing. However, when compared with the viscosity of the aqueous solution of PVA, the viscosity of PVA in Comparative Example 1 was 910 mPa · s, whereas the viscosity of PVA in Comparative Example 2 was 2,740 mPa · s, which was significantly increased. On the other hand, the viscosity of PVA of Example 1 is 920 mPa · s, and the increase in viscosity is suppressed. That is, according to the silanol-modified PVA of the example, it can be said that the optical performance and the heat resistance to moisture and heat of the optical film can be improved while maintaining good film forming property (productivity).

The film for producing an optical film of the present invention can be suitably used as a material such as a polarizing film which is a constituent material of an LCD.

Claims

Contains polyvinyl alcohol with silicon-containing groups
The silicon-containing group is a silanol group or a group that can be converted to a silanol group in the presence of water.
The viscosity average degree of polymerization of the polyvinyl alcohol 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 with respect to all structural units is 0.01 mol% or more and 1.0. A film for producing an optical film having a molar% or less.
The film for producing an optical film according to claim 1, wherein the saponification degree is 99.5 mol% or more.
The film for producing an optical film according to 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 producing an optical film according to any one of claims 1 to 3, wherein the average thickness is 1 μm or more and 75 μm or less.
The film for producing an optical film according to any one of claims 1 to 4, wherein the degree of swelling is 140% or more and 400% or less.
The film for producing an optical film according to any one of claims 1 to 5, wherein the optical film is a polarizing film.
The film for producing an optical film according to any one of claims 1 to 6, which is a non-stretched film.
A method for producing an optical film, comprising a step of uniaxially stretching the film for producing an optical film according to 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.
Contains polyvinyl alcohol with silicon-containing groups
The silicon-containing group is a silanol group or a group that can be converted to a silanol group in the presence of water.
The viscosity average degree of polymerization of the polyvinyl alcohol 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 with respect to all structural units is 0.01 mol% or more and 1.0. An optical film that is less than or equal to a molar percentage.
The optical film according to claim 10, which is a polarizing film.
The optical film according to claim 10 or 11, which is a single-layer film.