JPWO2015115359A1 - Raw film for optical film production - Google Patents

Abstract

An original film for producing an optical film capable of easily producing an optical film having excellent optical properties, hue and durability and low shrinkage stress, and a method for producing an optical film using the same. thing. A raw film for producing an optical film comprising a hydroxymethyl group-containing vinyl alcohol polymer having a content of a structural unit represented by the following formula (1) of 0.1 to 1.9 mol%; and A method for producing an optical film using the raw film for producing an optical film, the method comprising a step of uniaxial stretching. [In the formula, R1 represents an alkyl group having 1 to 3 carbon atoms. ] [Selection figure] None

Description

  The present invention relates to a raw film for producing an optical film such as a polarizing film containing a specific hydroxymethyl group-containing vinyl alcohol polymer, and a method for producing an optical film using the same.

A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a 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. As a polarizing film, a vinyl alcohol polymer film (hereinafter referred to as “vinyl alcohol-based heavy film”) is used. iodine based dye coalescing "the may be referred to as" PVA ") in a matrix formed by uniaxial stretching (I ₃ ^- and I ₅ ^-, etc.) or a dichroic dye such as dichroic organic dyes which are adsorbed Has become the mainstream.

  LCDs have come to be used in a wide range of small devices such as calculators and watches, mobile phones, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, and measurement devices used indoors and outdoors. In recent years, there has been a demand for higher display quality. Along with this, high performance is also demanded for the polarizing film, and specifically, there is a demand for a polarizing film that has a high degree of polarization and transparency, excellent optical properties, and excellent hue. On the other hand, high durability is also required for the polarizing film.

  By the way, some raw film for optical film manufacture containing modified PVA is known. For example, a polyvinyl alcohol film for a raw material of a polarizing film made of a specific PVA containing 0.01 to 1 mol% of a hydrophilic functional group such as a carboxylic acid group or a ω-hydroxy-α-olefin group is stretched and oriented. It is known that the processability and the adsorption processability of the dichroic substance are excellent (see Patent Document 1). Moreover, it is known that the specific optical PVA film containing PVA containing a 1,2-glycol bond in the side chain is excellent in optical properties and stretchability (see Patent Document 2).

JP-A-8-201626 JP 2009-24076 A

  However, in the case of using a conventionally known raw film for producing an optical film containing modified PVA, there is room for further improvement in that an optical film having excellent optical properties, hue, and durability is obtained. . In recent years, LCDs have been made thinner, and as a means for achieving this, it is possible to reduce the thickness of glass used in LCDs. From the standpoint of solving the problem of warping, an optical film having a low shrinkage stress is desired.

  Therefore, the present invention provides a raw film for producing an optical film that can easily produce an optical film with low shrinkage stress that is excellent in all of optical properties, hue, and durability, and a method for producing an optical film using the same. The purpose is to provide.

  As a result of intensive studies by the present inventors to achieve the above object, it has been found that the above problems can be solved by a film containing a specific hydroxymethyl group-containing PVA containing a specific structural unit in the main chain. The present invention was completed through further studies based on the findings.

That is, the present invention
[1] A raw film for producing an optical film comprising a hydroxymethyl group-containing PVA having a content of a structural unit represented by the following formula (1) of 0.1 to 1.9 mol%;

[Wherein, R ¹ represents an alkyl group having 1 to 3 carbon atoms. ]
[2] The raw film for producing an optical film according to [1], wherein the degree of polymerization of the hydroxymethyl group-containing PVA exceeds 2,000;
[3] The raw film for producing an optical film according to [1] or [2], wherein the saponification degree of the hydroxymethyl group-containing PVA is 95 mol% or more;
[4] The raw film for producing an optical film according to any one of [1] to [3], wherein the 1,2-glycol bond amount of the hydroxymethyl group-containing PVA is 1.5 mol% or less;
[5] The raw film for producing an optical film according to any one of [1] to [4], wherein R ^{1 of the} structural unit represented by the formula (1) is a methyl group;
[6] The raw film for producing an optical film according to any one of [1] to [5], having a thickness of 60 μm or less;
[7] The raw film for producing an optical film according to any one of [1] to [6], which is a raw film for producing a polarizing film;
[8] A method for producing an optical film using the raw film for producing an optical film according to any one of [1] to [7], wherein the method comprises a uniaxial stretching process;
About.

  ADVANTAGE OF THE INVENTION According to this invention, the raw film for optical film manufacture which can manufacture easily the optical film with the low shrinkage stress which is excellent in all of an optical characteristic, a hue, and durability, and the manufacturing method of an optical film using the same Is provided.

  The raw film for producing an optical film of the present invention contains a hydroxymethyl group-containing PVA in which the content of the structural unit represented by the following formula (1) is 0.1 to 1.9 mol%.

[Wherein, R ¹ represents an alkyl group having 1 to 3 carbon atoms. ]

  The raw film for producing an optical film of the present invention includes any one of optical properties, hues, and durability because the hydroxymethyl group-containing PVA contained therein contains the structural unit represented by the above formula (1) with a specific content. In addition, it is possible to easily produce an optical film having a low shrinkage stress. Although the present invention is not limited in any way, the reason why the above-described advantages are obtained is that there is an influence of the crystallinity reduction based on the methylene group of the hydroxymethyl group in the structural unit represented by the formula (1), and the hydroxy group. This may be due to the high hydrogen bonding force based on the hydroxyl group of the methyl group.

In the structural unit represented by the above formula (1), R ¹ represents an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. R ¹ is preferably a methyl group or an ethyl group, preferably a methyl group, since the hue of the optical film produced therefrom is improved as the crystallinity of the resulting optical film for producing an optical film decreases. Is particularly preferred.

  The content of the structural unit represented by the formula (1) in the hydroxymethyl group-containing PVA is 0.1 to 1.9 mol%, where the number of moles of all structural units constituting the hydroxymethyl group-containing PVA is 100 mol%. It is necessary to be within the range, and the content is preferably 0.2 mol% or more, more preferably 0.3 mol% or more, and further preferably 0.4 mol% or more. Preferably, it is preferably 1.8 mol% or less, more preferably 1.7 mol% or less, for example, 1.2 mol% or less, or 1.1 mol% or less. The hue of the optical film manufactured from the raw film for optical film manufacture obtained by the said content rate being 0.1 mol% or more improves. On the other hand, when the content is 1.9 mol% or less, dissolution of the film when the optical film is produced using the obtained optical film production raw film is effectively prevented, and the optical film is produced. The optical properties of the optical film produced from the production raw film are improved. In the present specification, the structural unit refers to a repeating unit constituting a polymer.

  There is no restriction | limiting in particular in the polymerization degree of hydroxymethyl group containing PVA, For example, although it can be set to 1,500 or more, the optical characteristic and durability of the optical film manufactured from the raw film for optical film manufacture obtained improve Therefore, the degree of polymerization preferably exceeds 2,000, more preferably exceeds 2,100, and more preferably exceeds 2,200. On the other hand, the upper limit of the degree of polymerization is not particularly limited, but the degree of polymerization is preferably 6,000 or less from the viewpoints of production cost and process passability during film formation. In addition, the polymerization degree of the hydroxymethyl group-containing PVA in the present specification means an average polymerization degree measured according to the description of JIS K6726-1994.

The degree of saponification of the hydroxymethyl group-containing PVA is preferably 95 mol% or more, preferably 96 mol% or more, from the viewpoint of the water resistance of an optical film such as a polarizing film produced from the resulting optical film production raw film. More preferably, it is 98 mol% or more, for example, it may be 99 mol% or more, 99.7 mol% or more, or 99.8 mol% or more. The saponification degree of the hydroxymethyl group-containing PVA in this specification is a structural unit (typical) that can be converted into a vinyl alcohol unit (—CH ₂ —CH (OH) —) by saponification, which the hydroxymethyl group-containing PVA has. Is the ratio (mol%) of the number of moles of the vinyl alcohol unit to the total number of moles of the vinyl ester unit) and the vinyl alcohol unit. The degree of saponification can be measured according to the description of JIS K6726-1994, taking into account the amount of the structural unit represented by formula (1) and its derivatives.

  The method for producing the hydroxymethyl group-containing PVA is not particularly limited. For example, a vinyl ester copolymer obtained by copolymerizing a vinyl ester monomer and an unsaturated monomer copolymerizable therewith and convertible to the structural unit represented by the formula (1) A method of converting a vinyl ester unit of the above into a vinyl alcohol unit, and further converting a structural unit derived from an unsaturated monomer that can be converted into a structural unit represented by the formula (1) into a structural unit represented by the formula (1) Is mentioned. A specific example of the unsaturated monomer that can be converted into the structural unit represented by the formula (1) is shown in the following formula (2).

[Wherein, R ¹ represents an alkyl group having 1 to 3 carbon atoms, and R ² represents an alkyl group having 1 to 10 carbon atoms. ]

In the formula (2), description of R ¹ are the same as those of R ¹ in the formula (1) are omitted, wherein the overlapping here.

In the formula (2), the structure of R ² is not particularly limited, and may be a linear alkyl group, or may partially have a branched or cyclic structure. Moreover, a part may be substituted with other functional groups. R ² is preferably an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. And a linear or branched alkyl group such as a pentyl group.

  Examples of the unsaturated monomer represented by the formula (2) include 2-methyl-2-propenyl acetate (methallyl acetate), 2-ethyl-2-propenyl acetate, and the like. Among these, 2-methyl-2-propenyl acetate (methallyl acetate) is preferably used in terms of safety and ease of production.

  The vinyl ester monomer used for the production of the hydroxymethyl group-containing PVA is not particularly limited. For example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, capron Examples thereof include vinyl acidate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate. From the economical viewpoint, vinyl acetate is preferred.

  The polymerization method for copolymerizing the unsaturated monomer represented by formula (2) and the vinyl ester monomer may be any method such as batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. As the polymerization method, known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method can be applied. A bulk polymerization method or a solution polymerization method in which polymerization proceeds in a solvent-free or solvent such as alcohol is usually employed. In order to obtain a vinyl ester copolymer having a high degree of polymerization, an emulsion polymerization method is also preferred. Although the solvent of the solution polymerization method is not particularly limited, for example, alcohol. The alcohol used as the solvent for the solution polymerization method is, for example, a lower alcohol such as methanol, ethanol, or propanol. The amount of solvent used in the polymerization system may be selected in consideration of the chain transfer of the solvent in accordance with the degree of polymerization of the target hydroxymethyl group-containing PVA. For example, when the solvent is methanol, it is included in the solvent and the polymerization system. The mass ratio with respect to all monomers {= (solvent) / (total monomers)} is preferably selected within the range of 0.01 to 10, more preferably within the range of 0.05 to 3.

  The polymerization initiator used for copolymerization of the unsaturated monomer represented by the formula (2) and the vinyl ester monomer is a known polymerization initiator such as an azo initiator or a peroxide initiator. The redox initiator may be selected according to the polymerization method. Examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4- Dimethylvaleronitrile). Examples of the peroxide initiator include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, α- Perester compounds such as cumylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; acetyl peroxide. Potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like may be combined with the above initiator to form a polymerization initiator. The redox initiator is, for example, a polymerization initiator in which the peroxide initiator is combined with a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, or longalite. The amount of the polymerization initiator used varies depending on the type of the polymerization initiator and cannot be determined unconditionally, but may be selected according to the polymerization rate. For example, when 2,2′-azobisisobutyronitrile or acetyl peroxide is used as the polymerization initiator, 0.01 to 0.2 mol% is preferable with respect to the vinyl ester monomer, and 0.02 to 0 More preferred is 15 mol%.

  The copolymerization of the unsaturated monomer represented by the formula (2) and the vinyl ester monomer may be performed in the presence of a chain transfer agent. Examples of the chain transfer agent include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; phosphinic acid salts such as sodium phosphinate monohydrate and the like. Of these, aldehydes and ketones are preferably used. The amount of chain transfer agent used can be determined according to the chain transfer coefficient of the chain transfer agent to be used and the degree of polymerization of the target hydroxymethyl group-containing PVA. The amount is preferably 0.1 to 10 parts by mass.

  The above hydroxymethyl group-containing PVA can be obtained by saponifying a vinyl ester copolymer obtained by copolymerization of an unsaturated monomer represented by formula (2) and a vinyl ester monomer. . By saponifying the vinyl ester copolymer, the vinyl ester unit in the vinyl ester copolymer is converted to a vinyl alcohol unit. In addition, the ester bond of the structural unit derived from the unsaturated monomer represented by the formula (2) is also saponified and converted to the structural unit represented by the formula (1). Therefore, the hydroxymethyl group-containing PVA can be produced without further reaction such as hydrolysis after saponification.

  The saponification of the vinyl ester copolymer can be performed, for example, in a state where the vinyl ester copolymer is dissolved in alcohol or hydrous alcohol. Examples of the alcohol used for saponification include lower alcohols such as methanol and ethanol, preferably methanol. The alcohol used for saponification may contain other solvents such as acetone, methyl acetate, ethyl acetate, and benzene at a ratio of 40% by mass or less of the mass, for example. The catalyst used for saponification is, for example, an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide, an alkali catalyst such as sodium methylate, or an acid catalyst such as mineral acid. The temperature at which saponification is performed is not limited, but is preferably in the range of 20 to 60 ° C. When a gel-like product precipitates as saponification proceeds, the product is pulverized, washed and dried to obtain a hydroxymethyl group-containing PVA. The saponification method is not limited to the method described above, and a known method can be applied.

  The hydroxymethyl group-containing PVA can further include other structural units other than the structural unit represented by the formula (1), the vinyl alcohol unit, and the vinyl ester unit. Examples of the other structural unit include a structural unit derived from an ethylenically unsaturated monomer copolymerizable with a vinyl ester monomer. Further, a structural unit derived from an unsaturated monomer that can be copolymerized with the above-described vinyl ester monomer and can be converted to a structural unit represented by the formula (1) (shown by the formula (1) by saponification). A structural unit that has not been converted to a structural unit).

  In the hydroxymethyl group-containing PVA, the proportion of the total of the structural unit represented by the formula (1), the vinyl alcohol unit and the vinyl ester unit is 100 mol% of the number of moles of all the structural units constituting the hydroxymethyl group-containing PVA. 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, particularly preferably 99 mol% or more, and 100 mol%. Also good.

  Examples of the ethylenically unsaturated monomer include α-olefins such as ethylene, propylene, n-butene, isobutylene and 1-hexene; acrylic acid and a salt thereof; an unsaturated monomer having an acrylate group. Body; methacrylic acid and salt thereof; unsaturated monomer having methacrylic acid ester group; acrylamide; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and salt thereof Acrylamide derivatives such as acrylamidopropyldimethylamine and salts thereof (for example, quaternary salts); methacrylamide; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyl Methacrylamide derivatives such as methylamine and its salts (for example, quaternary salts); methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether , Vinyl ethers such as stearyl vinyl ether and 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene chloride and fluoride Vinylidene halides such as vinylidene; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, allyl chloride; maleic acid, itaconic acid, fumaric acid, etc. Unsaturated dicarboxylic acids and salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate.

  The arrangement order of the structural unit represented by the formula (1) in the hydroxymethyl group-containing PVA, the vinyl alcohol unit, and other arbitrary structural units is not particularly limited, and may be any of random, block, alternating, and the like.

  The 1,2-glycol bond amount of the hydroxymethyl group-containing PVA is preferably 1.5 mol% or less, more preferably 1.4 mol% or less, and 1.2 mol% or less. Further preferred. When the 1,2-glycol bond amount of the hydroxymethyl group-containing PVA is within the above range, the durability of the optical film produced from the obtained optical film production raw film is improved. A hydroxymethyl group-containing PVA having a 1,2-glycol bond amount of 1.5 mol% or less is a raw material of a vinyl ester copolymer obtained by polymerizing a vinyl ester monomer at a temperature of 40 ° C. or less. Can be manufactured as. From the viewpoint of the polymerization rate of the vinyl ester monomer, the industrially possible lower limit of the polymerization temperature is about −50 ° C. From this viewpoint, the lower limit of the 1,2-glycol bond amount of the hydroxymethyl group-containing PVA is 0. Often about 5 mol% is the limit. The 1,2-glycol bond amount is the number of moles of bonds between adjacent vinyl alcohol units bonded by 1,2-glycol bonds to the total number of moles of bonds between adjacent vinyl alcohol units. The ratio (mol%) is referred to and can be determined by NMR measurement.

  The raw film for producing an optical film of the present invention can contain a plasticizer in addition to the hydroxymethyl group-containing PVA. Preferred plasticizers include polyhydric alcohols, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. The raw film for producing an optical film of the present invention can contain one or more of these plasticizers. Among these, glycerin is preferable in terms of the effect of improving stretchability.

  The content of the plasticizer in the raw film for producing an optical film of the present invention is preferably in the range of 1 to 20 parts by mass with respect to 100 parts by mass of the hydroxymethyl group-containing PVA contained therein, and 3 to 17 parts by mass. More preferably, it is in the range of 5 to 15 parts by mass. When the content is 1 part by mass or more, the stretchability of the film is further improved. On the other hand, when the content is 20 parts by mass or less, it is possible to prevent the film from becoming too flexible and handling properties from being lowered.

  The raw film for producing an optical film of the present invention further 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, Flame retardants, other thermoplastic resins, lubricants, fragrances, defoamers, deodorants, extenders, release agents, mold release agents, reinforcing agents, cross-linking agents, fungicides, preservatives, crystallization rate retarders Additives such as can be blended as needed.

  The proportion of the total of the hydroxymethyl group-containing PVA and the plasticizer in the raw film for producing an optical film of the present invention is preferably 80% by mass or more based on the mass of the original film for producing an optical film, 90 More preferably, it is more than 95 mass%, and it is still more preferable that it is 95 mass% or more.

  The degree of swelling of the raw film for producing an optical film of the present invention is preferably in the range of 160 to 240%, more preferably in the range of 170 to 230%, and in the range of 180 to 220%. It is particularly preferred. When the swelling degree is 160% or more, the film can be stably stretched to a higher magnification. On the other hand, when the degree of swelling is 240% or less, dissolution during stretching is suppressed, and stretching is possible even under higher temperature conditions. In this specification, the degree of swelling of the optical film-producing original film refers to the mass when the optical film-producing original film is immersed in distilled water at 30 ° C. for 30 minutes, and is dried at 105 ° C. for 16 hours after immersion. It means the percentage of the value obtained by dividing by the mass after the measurement, and can be specifically measured by the method described later in the examples. The degree of swelling can be adjusted, for example, by changing the conditions for heat treatment, and the degree of swelling can usually be lowered by increasing the heat treatment temperature and lengthening the heat treatment time.

  According to the raw film for producing an optical film of the present invention, an optical film having excellent shrinkage stress and excellent optical characteristics, hue and durability can be easily produced. It can be used particularly effectively in a raw film for production. The thickness of the raw film for producing an optical film is preferably 60 μm or less, more preferably 55 μm or less, further preferably 50 μm or less, particularly preferably 40 μm or less, and 35 μm or less. Is most preferable, and may be 25 μm or less, and further 20 μm or less. When the thickness is too thick, stretch spots tend to occur during uniaxial stretching for producing an optical film. In addition, when the thickness is too thin, the thickness is preferably 1 μm or more because there is a tendency that stretching breakage is likely to occur during uniaxial stretching treatment for producing an optical film such as a polarizing film, More preferably, it is 5 μm or more, and further preferably 10 μm or more.

  The width | variety in particular of the raw film for optical film manufacture of this invention is not restrict | limited, It can determine according to the use etc. of the optical film manufactured. In recent years, since the enlargement of screens of liquid crystal televisions and liquid crystal monitors has progressed, it is preferable for these applications to have a width of the original film for producing optical films of 3 m or more. On the other hand, if the width of the raw film for producing an optical film is too large, it is difficult to uniformly carry out uniaxial stretching itself when producing an optical film with an apparatus that has been put into practical use. The width of the anti-film is preferably 7 m or less.

  The production method of the raw film for producing an optical film of the present invention is not particularly limited, and a production method in which the thickness and width of the film after film formation are more uniform can be preferably employed. Film formation in which one or two or more of the above-mentioned hydroxymethyl group-containing PVA constituting the anti-film and the above-described plasticizer, additive and surfactant described later are dissolved in a liquid medium as necessary. A raw material, a hydroxymethyl group-containing PVA and, if necessary, a plasticizer, an additive, a surfactant, a liquid medium, etc. It can be produced using a membrane stock solution. When the film-forming stock solution contains at least one of a plasticizer, an additive, and a surfactant, it is preferable that these components are uniformly mixed.

  Examples of the liquid medium used for the preparation of the membrane forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol. , Trimethylolpropane, ethylenediamine, diethylenetriamine and the like, and one or more of them can be used. Among these, water is preferable from the viewpoint of environmental load and recoverability.

  The volatile fraction of the film-forming stock solution (content ratio in the film-forming stock solution of volatile components such as liquid media removed by volatilization or evaporation during film formation) varies depending on the film-forming method, film-forming conditions, etc. Specifically, it is preferably in the range of 50 to 95% by mass, more preferably in the range of 55 to 90% by mass, and still more preferably in the range of 60 to 85% by mass. The film-forming stock solution has a volatile content of 50% by mass or more, so that the viscosity of the film-forming stock solution does not become too high, and filtration and defoaming are smoothly performed during the preparation of the film-forming stock solution, and there are 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 is facilitated.

  The film-forming stock solution preferably contains a surfactant. By including the surfactant, the film-forming property is improved and the occurrence of uneven thickness of the film is suppressed, and the film is easily peeled off from the metal roll or belt used for film formation. When a raw film for producing an optical film is produced from a film-forming stock solution containing a surfactant, the film may contain a surfactant. Although the kind of said surfactant is not specifically limited, From a viewpoint of the peelability from a metal roll or a belt, an anionic surfactant or a nonionic surfactant is preferable.

  Suitable examples of the anionic surfactant include carboxylic acid types such as potassium laurate; sulfate ester types such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and sulfonic acid types such as dodecylbenzene sulfonate.

  Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxyethylene laurylamino Alkylamine type such as ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as lauric acid diethanolamide and oleic acid diethanolamide; polyoxy An allyl phenyl ether type such as alkylene allyl phenyl ether is preferred.

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

  When the film-forming stock solution contains a surfactant, the content thereof is preferably in the range of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the hydroxymethyl group-containing PVA contained in the film-forming stock solution. , More preferably in the range of 0.02 to 0.3 parts by mass, and particularly preferably in the range of 0.05 to 0.1 parts by mass. When the said content is 0.01 mass part or more, film forming property and peelability improve more. On the other hand, when the content is 0.5 parts by mass or less, it is possible to suppress that the surfactant bleeds out to the surface of the optical film-producing raw film, resulting in blocking and deterioration in handling properties. it can.

  Examples of the film forming method for forming an optical film manufacturing raw film using the above film forming stock solution include a cast film forming method, an extrusion film forming method, a wet film forming method, and a gel film forming method. Can be mentioned. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, the cast film forming method and the extrusion film forming method are preferable because a raw film for producing an optical film having a uniform thickness and width and good physical properties can be obtained. The formed film can be dried or heat-treated as necessary.

  As a specific example of the method for producing the raw film for producing an optical film of the present invention, for example, using the T-type slit die, hopper plate, I-die, lip coater die, etc. The film discharged or cast uniformly on the peripheral surface of the rotating heated first roll (or belt) located on the upstream side and discharged or cast on the peripheral surface of the first roll (or belt) Volatile components are evaporated and dried from one side, and then further dried on the peripheral surface of one or more rotating heated rolls arranged downstream thereof, or in a hot air dryer After passing and further drying, the method of winding with a winding device can be preferably employed industrially. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.

  The original film for producing an optical film of the present invention is used as an original film for producing an optical film. Examples of such an optical film include a polarizing film and a retardation film, and a polarizing film is preferable. Such an optical film can be produced, for example, by a method using the raw film for producing an optical film of the present invention, and a method having a uniaxial stretching process. Specifically, the optical film of the present invention is produced. Film or the film derived from the original film for producing an optical film of the present invention (hereinafter referred to as “the original film for producing an optical film of the present invention”). The “films derived from the raw film for producing an optical film of the present invention” may be collectively referred to as “films according to the present invention”), and may be produced by a method having a step of uniaxially stretching.

  The method in particular when manufacturing a polarizing film using the raw film for optical film manufacture of this invention is not restrict | limited, You may employ | adopt any method employ | adopted conventionally. Examples of such a method include a method in which a film based on the present invention is dyed and uniaxially stretched, or a film based on the present invention containing a dye is uniaxially stretched. As a more specific method for producing a polarizing film, the film based on the present invention is subjected to swelling, dyeing, uniaxial stretching, and, if necessary, crosslinking treatment, fixing treatment, drying, heat treatment, etc. A method is mentioned. In this case, the order of each treatment such as swelling, dyeing, crosslinking treatment, uniaxial stretching, and fixing treatment is not particularly limited, and one or two or more treatments can be performed simultaneously. Also, one or more of each process can be performed twice or more.

  Swelling can be performed by immersing the film according to the present invention in water. The temperature of the water when immersed in water is preferably within a range of 20 to 40 ° C, more preferably within a range of 22 to 38 ° C, and within a range of 25 to 35 ° C. Further preferred. Moreover, as time to immerse in water, it is preferable to exist in the range of 0.1 to 5 minutes, for example, and it is more preferable to be in the range of 0.5 to 3 minutes. In addition, the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

  Dyeing can be carried out by bringing a dichroic dye into contact with the film according to the invention. As the dichroic dye, an iodine dye is generally used. The dyeing time may be any stage before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. Dyeing is generally performed by immersing the PVA film in a solution (especially an aqueous solution) containing iodine-potassium iodide which is a dyeing bath. In the present invention, such a dyeing method is suitably employed. The The iodine concentration in the dyeing bath is preferably in the range of 0.01 to 0.5% by mass, and the potassium iodide concentration is preferably in the range of 0.01 to 10% by mass. Moreover, it is preferable that the temperature of a dyeing bath shall be 20-50 degreeC, especially 25-40 degreeC.

  By subjecting the film based on the present invention to a crosslinking treatment, it is possible to more effectively prevent the hydroxymethyl group-containing PVA from eluting into water when wet-stretching at a high temperature. From this viewpoint, the crosslinking treatment is preferably performed after the treatment for bringing the dichroic dye into contact and before the uniaxial stretching. The crosslinking treatment can be performed by immersing the film according to the present invention in an aqueous solution containing a crosslinking agent. As the crosslinking agent, one or more of boron compounds such as boric acid and borate such as borax can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1 to 15% by mass, more preferably in the range of 2 to 7% by mass, and in the range of 3 to 6% by mass. More preferably. Sufficient stretchability can be maintained when the concentration of the crosslinking agent is in the range of 1 to 15% by mass. The aqueous solution containing a crosslinking agent may contain potassium iodide and the like. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50 ° C, particularly in the range of 25 to 40 ° C. It can bridge | crosslink efficiently by making the said temperature into the range of 20-50 degreeC.

Uniaxial stretching of the film according to the present invention 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, or can be carried out in the dyeing bath described above or in a fixing treatment bath described later. In the case of the dry stretching method, the stretching may be performed at room temperature, may be performed while heating, or may be performed in the air using the film based on the present invention after water absorption. Among these, the wet stretching method is preferable because it can be uniformly stretched 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 in the range of 0.5 to 6.0% by mass, more preferably in the range of 1.0 to 5.0% by mass, It is especially preferable to be within the range of ˜4.0% by mass. The aqueous boric acid solution may contain potassium iodide, and the concentration of potassium iodide is preferably in the range of 0.01 to 10% by mass.
The stretching temperature in the uniaxial stretching is preferably in the range of 30 to 90 ° C, more preferably in the range of 40 to 80 ° C, and particularly preferably in the range of 50 to 70 ° C.
In addition, the draw ratio in uniaxial stretching is preferably 6.6 times or more, more preferably 6.8 times or more, and 7.0 times or more from the viewpoint of the polarizing performance of the obtained polarizing film. Is particularly preferred. 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 in the case of uniaxially stretching a long film according to the present invention, and uniaxial stretching or lateral uniaxial stretching in the long direction can be adopted. Since it is obtained, uniaxial stretching in the longitudinal direction is preferable. Uniaxial stretching in the longitudinal direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, lateral uniaxial stretching can be performed using a tenter type stretching machine.

  In producing the polarizing film, it is preferable to perform a fixing treatment in order to strengthen the adsorption of the dichroic dye (iodine dye or the like) to the film. As the fixing treatment bath used for the fixing treatment, an aqueous solution containing one or more of boron compounds such as boric acid and borax can be used. Moreover, you may add an iodine compound and a metal compound in a fixed treatment bath as needed. The concentration of the boron compound in the fixing treatment bath is generally about 2 to 15% by mass, particularly about 3 to 10% by mass. By making the said density | concentration in the range of 2-15 mass%, adsorption | suction of a dichroic dye can be strengthened more. The temperature of the fixing treatment bath is preferably 15 to 60 ° C, particularly preferably 25 to 40 ° C.

  The drying conditions are not particularly limited, but it is preferable to perform the drying at a temperature within the range of 30 to 150 ° C, particularly within the range of 50 to 130 ° C. A polarizing film excellent in dimensional stability is easily obtained by drying at a temperature in the range of 30 to 150 ° C.

According to the raw film for producing an optical film of the present invention, an optical film having a low shrinkage stress can be easily produced. The contraction stress of the obtained polarizing film is 3 as the contraction stress in the length direction (stretching direction at the time of manufacturing the polarizing film) in the polarizing film after the humidity control is performed under the conditions of a temperature of 20 ° C. and a relative humidity of 20%. It is preferably 5 N / mm ² or less. When the shrinkage stress is 3.5 N / mm ² or less, the polarizing film is less likely to warp the LCD. In view of the LCD of warpage, the shrinkage stress is more preferably 3.2 N / mm ² or less, still more preferably 3N / mm ² or less, particularly not less 2.7 N / mm ² or less preferable. There is no particular limitation on the lower limit of the shrinkage stress, the shrinkage stress, for example 1N / mm ² or more, or even at 2N / mm ² or more.

The shrinkage stress can be measured as follows. That is, a humidity control process is first performed on a polarizing film sample (length 12 cm × width 1.5 cm) to be measured under conditions of a temperature of 20 ° C. and a relative humidity of 20%. Here, the humidity control process is performed to measure the shrinkage stress. When the humidity control process is not performed, the value of the contraction stress usually increases, but by performing this process, the value of the contraction stress can be decreased and a more accurate value can be obtained. . After performing the humidity control treatment, the length direction of this sample was fixed at 5 cm between chucks, and then stretched in the length direction under conditions of a temperature of 40 ° C. and a relative humidity of 5%, and the tension reached 2N. The stretching is sometimes stopped and held, and in that state, the shrinkage stress (N / mm ² ) in the length direction when the temperature is raised to 80 ° C. and 4 hours elapses is obtained. More specifically, the shrinkage stress can be measured by the method described later in the examples.

  The polarizing film obtained as described above is usually used as a polarizing plate by bonding a protective film having optical transparency and mechanical strength on both sides or one side. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. Examples of the adhesive for bonding include PVA adhesives, urethane adhesives, acrylate ultraviolet curable adhesives, and the like.

  The polarizing plate obtained as described above can be used as a component of an LCD after being coated with an acrylic adhesive or the like and then bonded to a glass substrate. At the same time, it may be bonded to a retardation film, a viewing angle improving film, a brightness improving film, or the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples. In addition, each measurement or evaluation method employ | adopted in the following examples and comparative examples is shown below.

Primary structure of PVA The primary structure of PVA (hydroxymethyl group-containing PVA in Examples and various modified PVA in Comparative Examples) used in the following Examples and Comparative Examples was analyzed using 400 MHz ¹ H-NMR. Deuterated DMSO was used as a solvent for ¹ H-NMR measurement.

The degree of swelling of the raw film for optical film production The raw film for optical film production obtained in the following examples or comparative examples was cut to 1.5 g and immersed in distilled water at 30 ° C. for 30 minutes. After immersion for 30 minutes, the film was taken out, the surface water was taken out with a filter paper, and the mass “N” was determined. Subsequently, the film was dried with a dryer at 105 ° C. for 16 hours, and then the mass “M” was determined. From the obtained masses “N” and “M”, the degree of swelling of the raw film for optical film production was calculated by the following formula (3).
Swelling degree (%) = 100 × N / M (3)

Stretchability of the optical film production raw film From the center in the width direction of the optical film production raw film obtained in the following examples or comparative examples, the width of the width 5 cm × length 5 cm is uniaxially stretched. A 5 cm × 8 cm long sample was cut. This sample was uniaxially stretched in the length direction by a factor of 1.5 while being immersed in pure water at 30 ° C. Subsequently, while being immersed in an aqueous solution (dyeing bath) (temperature 30 ° C.) containing 0.03% by mass of iodine and 3.0% by mass of potassium iodide for 60 seconds, the ratio is 1.6 times (2.4 in total). Uniaxially stretching in the length direction to adsorb iodine. Next, the length was 1.1 times (2.6 times in total) while being immersed in an aqueous solution (crosslinking bath) (temperature 30 ° C.) containing 3% by weight of boric acid and 3% by weight of potassium iodide. Uniaxially stretched in the direction. Further, while being immersed in an aqueous solution (stretching bath) containing 4% by mass of boric acid and 6% by mass of potassium iodide, the film is uniaxially stretched in the length direction until it is cut, and the raw film for producing an optical film before stretching. The ratio of the length at the time of cutting with respect to the length of the film was defined as the limit stretch ratio. However, the temperature of the stretching bath was changed by 1 ° C. from an appropriate temperature, the limiting stretching ratio was measured, and the temperature at which the limiting stretching ratio was the highest was selected.

Optical properties of polarizing film (dichroic ratio)
(1) Measurement of transmittance Ts From the central part of the polarizing film obtained in the following examples or comparative examples, two 2 cm samples were taken in the length direction of the polarizing film, and a spectrophotometer with an integrating sphere (Japan) Using “V7100” manufactured by Spectroscopic Co., Ltd., in accordance with JIS Z 8722 (measuring method of object color), the visibility of the visible light region of the C light source and 2 ° field of view is corrected. The light transmittance when tilted by + 45 ° with respect to the vertical direction and the light transmittance when tilted by −45 ° were measured, and an average value Ts1 (%) thereof was obtained. In the same manner for the other sample, the light transmittance when tilted by + 45 ° and the light transmittance when tilted by −45 ° were measured, and an average value Ts2 (%) thereof was obtained. Ts1 and Ts2 were averaged by the following formula (4) to obtain the transmittance Ts (%) of the polarizing film.
Ts = (Ts1 + Ts2) / 2 (4)

(2) Measurement of polarization degree V Light transmittance T‖ (%) and length direction when two samples collected by measurement of transmittance Ts are stacked so that their length directions are parallel to each other. Are measured in the same manner as in the case of “(1) Measurement of transmittance Ts”, and the degree of polarization V ( %).
V = {(T‖−T⊥) / (T‖ + T⊥)} ^1/2 × 100 (5)

(3) Calculation of dichroic ratio when transmittance is 44% In each of the following Examples and Comparative Examples, the iodine concentration in the dyeing bath is 0.02 to 0.04% by mass, and the potassium iodide concentration is 2. The same operation was carried out by changing 4 times within the range of 0 to 4.0% by mass (however, the iodine concentration: potassium iodide concentration = 1: 100), and each example or comparative example was produced. Four polarizing films having different dichroic dye adsorption amounts were produced. For each of these four polarizing films, the transmittance Ts (%) and the degree of polarization V (%) were determined by the method described above, and the transmittance Ts (%) was plotted on the horizontal axis and the degree of polarization for each example and comparative example. With V (%) as the vertical axis, a total of 5 points including one point based on the transmittance Ts (%) and the degree of polarization V (%) of the polarizing film obtained in each example or comparative example are plotted on a graph. Thus, an approximate curve was obtained, and from the approximate curve, the degree of polarization V ₄₄ (%) when the transmittance Ts (%) was 44% was obtained.
From the obtained degree of polarization V ₄₄ (%), the dichroic ratio at a transmittance of 44% was determined by the following formula (6) and used as an index of polarization performance. In addition, the higher the dichroic ratio, the better the optical properties of the polarizing film. When the dichroic ratio is 66 or more, it is determined as “◯” (good), and when it is less than 66, “X” (defect). It was determined.
Dichroic ratio when the transmittance 44% = log (44 / 100-44 / 100 × V 44/100) / log (44/100 + 44/100 × V 44/100) (6)

Color of polarizing film (parallel b value)
In the above “optical properties (dichroic ratio) of the polarizing film”, when obtaining the polarization degree V of four polarizing films having different amounts of adsorption of the dichroic dye, the transmittance T） (%) and the transmittance are obtained. Lab color space is measured when measuring T⊥ (%), b value when measuring transmittance T‖ (%) is a parallel b value, and b value when measuring transmittance T⊥ (%) is an orthogonal b value. It was. For each example and comparative example, including the parallel b value as the horizontal axis and the orthogonal b value as the vertical axis, including one point based on the parallel b value and orthogonal b value of the polarizing film obtained in each example or comparative example A total of 5 points were plotted on a graph to obtain an approximate curve, and a parallel b value when the orthogonal b value was −4 was obtained from the approximate curve. In addition, the hue of the polarizing film is better as the parallel b value is closer to 0, and the case where the parallel b value is less than 2.2 is determined as “◯” (good), and the case where the parallel b value is 2.2 or more is determined as “×” (Defect) was determined.

Durability of polarizing film (absorbance remaining rate)
For each example or comparative example, the four polarizing films produced in the above-mentioned “Optical characteristics of the polarizing film (dichroic ratio)” with different amounts of adsorption of the dichroic dye, and each example or comparative example were obtained. The absorbance at a wavelength of 610 nm (orthogonal absorbance) obtained at the time of measuring the transmittance T ⊥ (%) is in the range of 44 to 45% of the total of five polarizing films obtained. One polarizing film of 2.95 to 3.05 was selected.
The polarizing film was exposed for 4 hours in an environment of 60 ° C. and 90% RH, and the orthogonal absorbance at an initial wavelength of 610 nm was A _0h and the orthogonal absorbance at a wavelength of 610 nm after exposure for 4 hours was A _4h. The residual rate of orthogonal absorbance (absorbance residual rate) D (%) determined by 7) was evaluated as the durability of the polarizing film. The higher the residual absorbance rate, the better the durability of the polarizing film. When the residual absorbance rate is 33% or more, it is judged as “◯” (good), and when it is less than 33%, “x” (bad). It was determined.
D (%) = 100 × A _4h / A _0h (7)

From the central part of the polarizing film obtained in Examples or Comparative Examples below the contraction stress of the polarizing film, a rectangular sample of 12 cm in the length direction of the polarizing film and 1.5 cm in the width direction is collected, and the temperature is 20 ° C. The humidity was adjusted for 16 hours under the condition of a relative humidity of 20%. Next, this sample was fixed to an autograph “AG-X” manufactured by Shimadzu Corporation so that the length direction was fixed at 5 cm between chucks, and 1 mm / min under conditions of a temperature of 40 ° C. and a relative humidity of 5%. The film was stretched in the length direction at a speed, and when the tension reached 2N, the stretching was stopped and held, and in that state, the temperature was raised to 80 ° C., and the tension after 4 hours was measured. By dividing by (unit: mm ² ), the contraction stress (contraction stress in the length direction) of the polarizing film was determined. A case where the shrinkage stress was 3.5 N / mm ² or less was determined as “◯” (good), and a case where the shrinkage stress exceeded 3.5 N / mm ² was determined as “x” (defective).

[Example 1]
(1) 100 parts by mass of a hydroxymethyl group-containing PVA shown in Table 1 obtained by saponifying a copolymer of vinyl acetate and 2-methyl-2-propenyl acetate as a modified PVA, 10 parts by mass of glycerin as a plasticizer, And an aqueous solution containing 0.1 part by mass of polyoxyethylene lauryl ether sodium sulfate as a surfactant and having a modified PVA content of 10% by mass as a film-forming stock solution, and drying it on a metal roll at 80 ° C. Then, the degree of swelling was adjusted to 200% by subjecting the obtained film to a heat treatment at a predetermined temperature for 1 minute in a hot air dryer to produce an original film for producing an optical film having a thickness of 30 μm.
The stretchability was evaluated by the above-described method using the obtained optical film for optical film production. The results are shown in Table 1.

(2) A sample having a width of 5 cm and a length of 8 cm was cut from the central portion in the width direction of the original film for producing an optical film obtained in (1) so that a range of width 5 cm × length 5 cm could be uniaxially stretched. . This sample was uniaxially stretched in the length direction by a factor of 1.5 while being immersed in pure water at 30 ° C. Subsequently, while being immersed in an aqueous solution (dyeing bath) (temperature 30 ° C.) containing 0.03% by mass of iodine and 3.0% by mass of potassium iodide for 60 seconds, the ratio is 1.6 times (2.4 in total). Uniaxially stretching in the length direction to adsorb iodine. Next, the length was 1.1 times (2.6 times in total) while being immersed in an aqueous solution (crosslinking bath) (temperature 30 ° C.) containing 3% by weight of boric acid and 3% by weight of potassium iodide. Uniaxially stretched in the direction. Further, an aqueous solution (stretching bath) containing 4% by mass of boric acid and 6% by mass of potassium iodide (a temperature at which the limit stretching ratio determined in the above “stretchability of the raw film for producing optical film” becomes the highest) ) Was uniaxially stretched in the length direction to a magnification 0.2 times lower than the limit draw ratio. Thereafter, it was immersed in an aqueous solution (cleaning bath) containing 3% by mass of potassium iodide (temperature 30 ° C.) for 5 seconds, and finally dried at 60 ° C. for 4 minutes to produce a polarizing film.
Using the obtained polarizing film, the optical properties (dichroic ratio), hue (parallel b value), durability and shrinkage stress of the polarizing film were evaluated by the method described above. The results are shown in Table 1.

[Examples 2 to 5]
In Example 1, hydroxymethyl group-containing PVA (Examples 2 to 5) shown in Table 1 obtained by saponifying a copolymer of vinyl acetate and 2-methyl-2-propenyl acetate as a modified PVA was used. Except for the above, a raw film for producing an optical film and a polarizing film were produced in the same manner as in Example 1, and each measurement or evaluation was performed. The results are shown in Table 1.

[Comparative Examples 1 to 4 and Reference Example 1]
In Example 1, unmodified PVA shown in Table 1 obtained by saponifying a homopolymer of vinyl acetate instead of modified PVA (Comparative Example 1); vinyl acetate and 2-methyl-2-acetate as modified PVA Hydroxymethyl group-containing PVA shown in Table 1 obtained by saponifying the copolymer with propenyl (Comparative Example 2); As a modified PVA, a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene was used. Modified PVA shown in Table 1 obtained by saponification (Comparative Example 3); Modified PVA shown in Table 1 obtained by saponifying a copolymer of vinyl acetate and itaconic acid as modified PVA (Comparative Example 4) Or modified PVA shown in Table 1 obtained by saponifying a copolymer of vinyl acetate and 7-acetoxy-1-heptene as modified PVA (Reference Example 1) Except for the use respectively, to produce a raw film and polarizing film for an optical film prepared in the same manner as in Example 1 were each measured or evaluated. The results are shown in Table 1.

  As is clear from the above results, according to the original film for producing an optical film of Examples 1 to 5 satisfying the regulations of the present invention, the optical film having a low shrinkage stress, which is excellent in any of optical characteristics, hue and durability. It can be seen that can be easily manufactured.

Claims (8)

The raw film for optical film manufacture containing the hydroxymethyl group containing vinyl alcohol polymer whose content rate of the structural unit shown by following formula (1) is 0.1-1.9 mol%.

[Wherein, R ¹ represents an alkyl group having 1 to 3 carbon atoms. ]   The raw film for producing an optical film according to claim 1, wherein the degree of polymerization of the hydroxymethyl group-containing vinyl alcohol polymer exceeds 2,000.   The raw film for producing an optical film according to claim 1 or 2, wherein the saponification degree of the hydroxymethyl group-containing vinyl alcohol polymer is 95 mol% or more.   The raw film for optical film production according to any one of claims 1 to 3, wherein the hydroxymethyl group-containing vinyl alcohol polymer has a 1,2-glycol bond amount of 1.5 mol% or less. The raw film for optical film manufacture according to any one of claims 1 to 4, wherein R ^{1 of the} structural unit represented by the formula (1) is a methyl group.   The raw film for optical film production according to any one of claims 1 to 5, wherein the thickness is 60 µm or less.   The original film for optical film manufacture according to any one of claims 1 to 6, which is an original film for manufacturing a polarizing film.   The manufacturing method which has the process of uniaxially stretching, It is a manufacturing method of the optical film using the raw film for optical film manufacture of any one of Claims 1-7.