KR20160041921A - Original film for manufacturing optical film - Google Patents

Abstract

(PROBLEMS) To provide a raw material film for optical film production which can produce an optical film with good productivity by being excellent in stretchability, and which is capable of easily producing an optical film having excellent both optical characteristics and color, and a process for producing an optical film .
(1) a vinyl alcohol polymer containing a hydroxymethyl group containing a vinyl alcohol unit and a structural unit represented by the following formula (1), and a raw material film for producing an optical film, And then stretching the film.
[Chemical Formula 1]

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic film for optical film production,

The present invention relates to a raw film for producing an optical film such as a polarizing film containing a hydroxymethyl group-containing vinyl alcohol polymer having a 1,3-diol structure, and a process for producing an optical film using the raw film .

A polarizing plate having light transmission and shielding functions is a fundamental 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 acylate (TAC) film is stuck to the surface of a polarizing film. As the polarizing film constituting the polarizing plate, a vinyl alcohol polymer film (I ₃ ^- , I ₅ ^-, etc.) and dichromatic organic dyes are adsorbed on a matrix obtained by uniaxially stretching a polymer (hereinafter also referred to as " PVA " .

LCDs have been used in a wide range of small-sized devices such as electronic desk calculators and wrist watches, mobile phones, notebook PCs, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, vehicle navigation systems, and measuring instruments used indoors and outdoors In recent years, particularly, display quality has been required to be enhanced. Along with this, there is a demand for a polarizing film that is more sophisticated, and more specifically, a polarizing film having high polarization and transmittance, excellent optical characteristics, and excellent hue is required.

However, some fabric films for producing optical films containing modified PVA have been known. For example, a polyvinyl alcohol film for 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 an? -Hydroxy-? -Olefin group can be used for stretching / It is known that the dichromatic material is excellent in the adsorption treatment property (see Patent Document 1, etc.). It is also known that a specific optical PVA film containing a specific PVA containing a 1,2-glycol bond in the side chain has excellent optical properties and stretchability (see Patent Document 2).

Japanese Unexamined Patent Publication No. 8-201626 JP-A-2009-24076

However, in the case of using a raw material film for optical film production including conventionally known modified PVA, there was room for further improvement in that an optical film excellent in both optical characteristics and color was obtained. In addition, in the case of using a raw material film for producing an optical film containing conventionally known modified PVA, troubles such as breakage of stretching are likely to occur particularly in the case of continuously producing an optical film, There was still room for further improvement.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a raw material film for optical film production, which can produce an optical film with good productivity and excellent optical properties and color, And a method for producing the same.

DISCLOSURE OF THE INVENTION As a result of diligent studies to achieve the above object, the present inventors have found that a film comprising a hydroxymethyl group-containing PVA containing a specific structural unit having a 1,3-diol structure in its main chain has the above- The present invention has been completed on the basis of the above-described findings, thereby completing the present invention.

That is,

[1] A fabric film for optical film production, comprising a hydroxymethyl group-containing PVA containing a vinyl alcohol unit and a structural unit represented by the following formula (1);

[Chemical Formula 1]

[2] The optical film production fabric according to [1], wherein the content of the structural unit represented by the formula (1) in the hydroxymethyl group-containing PVA is 0.1 to 2 mol%;

[3] The optical film production fabric film according to [1] or [2], wherein the hydroxymethyl group-containing PVA further contains an ethylene unit;

[4] The optical film production fabric according to [3], wherein the content of the ethylene unit in the hydroxymethyl group-containing PVA is 1 to 4 mol%;

[5] The optical film fabrication film according to any one of [1] to [4], wherein the hydroxymethyl group-containing PVA has a saponification degree of 95 mol% or more;

[6] A raw material film for optical film production according to any one of [1] to [5], which is a raw material film for polarizing film production;

[7] A process for producing an optical film having a step of uniaxially stretching using the raw material film for producing an optical film according to any one of [1] to [6]

.

Industrial Applicability According to the present invention, it is possible to provide a raw material film for optical film production, which can produce an optical film with excellent productivity and excellent optical characteristics and color, A manufacturing method is provided.

The raw material film for producing an optical film of the present invention comprises a hydroxymethyl group-containing PVA containing a vinyl alcohol unit and a structural unit represented by the following formula (1).

(2)

The stretchability of the raw material film for producing an optical film of the present invention is improved because the hydroxymethyl group-containing PVA contained therein contains a structural unit having a 1,3-diol structure represented by the above formula (1). In addition to the above, according to the raw material film for producing an optical film of the present invention, an optical film excellent in both optical characteristics and color can be easily produced. Although the present invention is not limited at all, the reason why the above-mentioned advantages are obtained is that the crystallinity is lowered by the structural unit represented by the formula (1) and the influence due to the high hydrogen bonding force based on the 1,3- I can think.

The content of the structural unit represented by the formula (1) in the hydroxymethyl group-containing PVA is not particularly limited, but it is preferably 0.1 to 2 mol%, more preferably 0.1 to 2 mol%, based on 100 mol% of the total structural units constituting the hydroxymethyl group- , More preferably in a range of 0.2 to 1.9 mol%, and still more preferably in a range of 0.3 to 1.8 mol%. When the content is 0.1 mol% or more, the stretching property of the film is further improved and an optical film having better color is obtained. On the other hand, when the content is 2 mol% or less, the optical film can be more effectively prevented from dissolving the film during production of the optical film, and an optical film having better optical properties can be obtained. In the present specification, the structural unit refers to a repeating unit constituting the polymer.

The degree of polymerization of the hydroxymethyl group-containing PVA is preferably within the range of 1,500 to 6,000, more preferably within the range of 1,800 to 5,000, and still more preferably within the range of 2,000 to 4,000. When the degree of polymerization is 1,500 or more, the durability of an optical film such as a polarizing film obtained by uniaxially stretching the film can be further improved. On the other hand, when the degree of polymerization is 6,000 or less, it is possible to suppress the increase of the production cost and the defective processability in film formation. The degree of polymerization of the hydroxymethyl group-containing PVA in the present specification means an average polymerization degree measured in accordance with JIS K 6726-1994.

The saponification degree of the hydroxymethyl group-containing PVA is preferably 95 mol% or more, more preferably 96 mol% or more, and more preferably 98 mol% or more in terms of the water resistance of an optical film such as a polarizing film obtained by uniaxially stretching the film More preferable. The saponification degree of the hydroxymethyl group-containing PVA in the present specification means that the hydroxymethyl group-containing PVA has a structural unit which can be converted into a vinyl alcohol unit (-CH ₂ -CH (OH) -) by saponification Refers to the ratio (mol%) of the number of moles of the vinyl alcohol unit to the total number of moles of the vinyl alcohol unit). The degree of saponification can be measured according to the description of JIS K 6726-1994 after taking into consideration the amount of the structural unit represented by the formula (1) and the amount of the derivative thereof.

The production method of the hydroxymethyl group-containing PVA is not particularly limited. For example, a copolymer of a vinyl ester monomer and an unsaturated monomer copolymerizable therewith and convertible into a structural unit represented by the formula (1) is obtained, and the vinyl ester unit of the obtained vinyl ester copolymer is converted into a vinyl alcohol unit , And a method of converting a structural unit derived from an unsaturated monomer convertible to a structural unit represented by the formula (1) into a structural unit represented by the formula (1), on the other hand. Specific examples of the unsaturated monomer convertible into the structural unit represented by the formula (1) are shown in the following formula (2).

(3)

In the formula (2), R represents an alkyl group having 1 to 10 carbon atoms. The structure of R is not particularly limited and may have a branched or cyclic structure in a part thereof. In addition, some of them may be substituted with other functional groups. R is preferably an alkyl group having 1 to 5 carbon atoms and examples of the alkyl group include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, An alkyl group having a straight chain or a branch. Examples of the substituent that R may have include an alkoxy group, a halogen atom, and a hydroxyl group. The plurality of Rs present may be the same or different from each other.

Examples of the unsaturated monomer represented by the formula (2) include 1,3-diacetoxy-2-methylene propane, 1,3-dipropionyloxy-2-methylene propane, Methylene propane and the like. Among them, 1,3-diacetoxy-2-methylene propane is preferably used in view of ease of production.

The unsaturated monomer represented by the formula (2) tends to undergo a copolymerization reaction with the vinyl ester monomer, as compared with other allyl type unsaturated monomers (for example, allyl glycidyl ether) generally used for the modification of PVA . Therefore, the hydroxymethyl group-containing PVA having a small amount of modification and polymerization degree at the time of polymerization and a high degree of modification and polymerization can be easily obtained. In addition, since the amount of the unreacted unsaturated monomer remaining at the end of the polymerization can be reduced, the hydroxymethyl group-containing PVA in the present invention is also excellent in environmental aspects and cost in industrial production.

The vinyl ester monomer used in the production of the hydroxymethyl group-containing PVA is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl versatate, Vinyl propionate, vinyl propionate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate and vinyl benzoate. From an economic standpoint, vinyl acetate is preferred.

The polymerization method when the unsaturated monomer represented by the formula (2) is copolymerized with the vinyl ester monomer may be any of a batch polymerization, a half batch polymerization, a continuous polymerization, a semi-continuous polymerization and the like. , A solution polymerization method, a suspension polymerization method, an emulsion polymerization method and the like can be applied. A bulk polymerization method or a solution polymerization method in which polymerization is allowed to proceed in a solvent such as a solvent or alcohol is usually employed. In the case of obtaining a vinyl ester-based copolymer having a high polymerization degree, an emulsion polymerization method is also preferable. The solvent of the solution polymerization method is not particularly limited, but is, for example, an alcohol. Alcohols used in the solvent of the solution polymerization method are, for example, lower alcohols such as methanol, ethanol and propanol. The amount of the solvent to be used in the polymerization system may be selected in consideration of the chain transfer of the solvent depending on the degree of polymerization of the desired hydroxymethyl group-containing PVA. For example, when the solvent is methanol, Is preferably selected within the range of 0.01 to 10, more preferably 0.05 to 3, in terms of the mass ratio with respect to the monomer (= (solvent) / (total monomer)}.

The polymerization initiator used for copolymerization of the unsaturated monomer represented by the formula (2) and the vinyl ester monomer may be selected from known polymerization initiators such as an azo-based initiator, a peroxide-based initiator, and a redox- . Examples of azo-based initiators include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis -2,4-dimethylvaleronitrile). Examples of the peroxide-based initiator include percarbonate-based compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; organic peroxides such as t-butyl peroxyneodecanate, And peroxyneodecanate, acetylcyclohexylsulfonylperoxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, and acetyl peroxide. Potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like may be combined with the initiator to form a polymerization initiator. The redox-type initiator is, for example, a polymerization initiator obtained by combining the peroxide-based initiator with a reducing agent such as sodium hydrogen sulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid, and ronic acid. The amount of the polymerization initiator to be used can not be determined in a word because it varies depending on the kind of the polymerization initiator, but may be selected depending on the polymerization rate. For example, when 2,2'-azobisisobutyronitrile or acetyl peroxide is used as the polymerization initiator, the amount is preferably 0.01 to 0.2 mol%, more preferably 0.02 to 0.15 mol% based on the vinyl ester monomer. The polymerization temperature is not particularly limited, but is suitably from room temperature to 150 ° C, preferably 40 ° C or more, and is not more than the boiling point of the solvent used.

The copolymerization of the unsaturated monomer represented by the formula (2) and the vinyl ester monomer may be carried out 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; and phosphinic acid salts such as sodium phosphinate sodium monohydrate . Among them, aldehydes and ketones are preferably used. The amount of the chain transfer agent to be 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 desired hydroxymethyl group-containing PVA, but is generally 0.1 to 10 parts by mass per 100 parts by mass of the vinyl ester monomer.

The hydroxymethyl group-containing PVA can be obtained by saponifying a vinyl ester-based copolymer obtained by copolymerization of an unsaturated monomer represented by the formula (2) and a vinyl ester monomer. By saponifying the vinyl ester-based copolymer, the vinyl ester unit in the vinyl ester-based copolymer is converted into a vinyl alcohol unit. The ester bond of the structural unit derived from the unsaturated monomer represented by the formula (2) is also saponified and converted into a structural unit having a 1,3-diol structure represented by the formula (1). Therefore, the hydroxymethyl group-containing PVA can be produced even after saponification without further performing a reaction such as hydrolysis.

The saponification of the vinyl ester-based copolymer can be carried out, for example, in a state in which the vinyl ester-based copolymer is dissolved in an alcohol or a hydrated alcohol. The alcohol used for the saponification includes, for example, 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, benzene and the like in a proportion of 40% by mass or less of the mass thereof. The catalyst used for the saponification is, for example, a hydroxide of an alkali metal such as potassium hydroxide or sodium hydroxide, an alkali catalyst such as sodium methylate, or an acid catalyst such as a mineral acid. The temperature at which the saponification is carried out is not limited, but is preferably in the range of 20 to 60 占 폚. When a gel-like product precipitates as the saponification proceeds, the resulting product is pulverized, washed and dried to obtain a hydroxymethyl group-containing PVA. The saponification method is not limited to the above-mentioned method, but a known method can be applied.

The hydroxymethyl group-containing PVA may further contain a structural unit other than the structural unit represented by the formula (1), a vinyl alcohol unit and a vinyl ester unit. Examples of other structural units include structural units derived from ethylenically unsaturated monomers copolymerizable with vinyl ester monomers. Further, a structural unit derived from an unsaturated monomer which is copolymerizable with the above-mentioned vinyl ester monomer and can be converted into a structural unit represented by the formula (1) (a structural unit derived from saponification and not converted into a structural unit represented by the formula (1) ). ≪ / RTI >

In the hydroxymethyl group-containing PVA, the proportion of the total of the structural unit represented by formula (1), the vinyl alcohol unit and the vinyl ester unit accounts for 100 mole% of the total structural units constituting the hydroxymethyl group-containing PVA , Preferably 80 mol% or more, more preferably 90 mol% or more, further preferably 95 mol% or more, and 99 mol% or more.

Examples of the ethylenically unsaturated monomers include:? -Olefins such as ethylene, propylene, n-butene, isobutylene and 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylate group; methacrylic acid Acrylamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid and salts thereof, acrylic acid amides such as acrylic acid and methacrylic acid, Acrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid and salts thereof, acrylamide derivatives such as amidepropyldimethylamine and salts thereof (for example, quaternary salt) Methacrylamide derivatives such as propyldimethylamine and salts thereof (for example, quaternary salts), methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl Vinyl ethers such as ethyl ether, n-butyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether and 2,3-diacetoxy-1-vinyloxypropane; Vinylidene chloride such as vinyl chloride and vinyl chloride, halogenated vinylidene chloride such as vinylidene chloride and vinylidene fluoride, allyl acrylate, 2,3-diacetoxy-1- Allyl compounds such as allyloxypropane and allyl chloride, unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid, and salts and esters thereof, vinylsilyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate. Of these, ethylene is preferred because it can be stretched at a higher temperature while the stretchability is improved, the occurrence of troubles such as breakage of stretching at the time of producing an optical film is reduced, and the productivity of the optical film is further improved . When the hydroxymethyl group-containing PVA contains an ethylene unit, the content of the ethylene unit is preferably 100 mol% or more, more preferably 100 mol% or less, , Preferably 1 to 4 mol%, and particularly preferably 2 to 3 mol%.

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

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

The content of the plasticizer in the raw film for producing an optical film of the present invention is preferably within a range of 1 to 20 parts by mass and more preferably within a range of 3 to 17 parts by mass with respect to 100 parts by mass of the hydroxymethyl group- And more preferably in the range of 5 to 15 parts by mass. When the content is 1 part by mass or more, the stretching property of the film is further improved. On the other hand, when the content is 20 parts by mass or less, the film becomes excessively flexible and the handling property can be suppressed from being lowered.

The raw material film for optical film production of the present invention may further contain a processing stabilizer such as a filler and a copper compound, a weather stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a flame retardant, other thermoplastic resin, Additives such as antifoaming agents, deodorants, extenders, exfoliating agents, releasing agents, reinforcing agents, crosslinking agents, antifungal agents, preservatives and crystallization rate retarders may be appropriately added as needed.

The total amount 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 mass% or more, more preferably 90 mass% or more based on the mass of the raw material film for optical film production And more preferably 95 mass% or more.

The degree of swelling of the material film for producing an optical film of the present invention is preferably in a range of 160 to 240%, more preferably in a range of 170 to 230%, and particularly preferably in a range of 180 to 220%. When the swelling degree is 160% or more, the progress of crystallization can be suppressed to an extreme, and the stretching can be stably performed at a higher magnification. On the other hand, when the degree of swelling is not more than 240%, dissolution at the time of stretching is suppressed, and stretching can be performed even at a higher temperature. In the present specification, the degree of swelling of the raw film for optical film production refers to a value obtained by dividing the mass when the raw film for optical film production is immersed in distilled water at 30 DEG C for 30 minutes divided by the mass after drying at 105 DEG C for 16 hours after immersion Quot; means the percentage by weight of the total weight of the composition. Specifically, the concentration can be measured by the method described later in Examples.

The thickness of the raw material film for producing an optical film of the present invention is not particularly limited, but it is preferably 1 to 100 占 퐉, more preferably 5 to 75 占 퐉, particularly 10 to 60 占 퐉. If the thickness is too small, stretching tends to occur easily in the uniaxial stretching process for producing an optical film such as a polarizing film. If the thickness is excessively large, unevenness in stretching tends to occur in the uniaxial stretching process for producing an optical film.

The width of the raw material film for producing an optical film of the present invention is not particularly limited and can be determined depending on the use of the optical film to be produced and the like. In recent years, when the width of the raw material film for optical film production is set to 3 m or more in view of the progress of making the liquid crystal television or the liquid crystal monitor large screen, it is preferable for these applications. On the other hand, when the width of the raw material film for optical film production is too large, it is difficult to uniformly conduct the uniaxial stretching itself in the case of producing an optical film with a device that is practically used. 7 m or less.

The production method of the raw material film for producing an optical film of the present invention is not particularly limited and a production method in which the thickness and the width of the film after film formation are more uniform can be preferably employed and for example, The hydroxymethyl group-containing PVA and, if necessary, the plasticizer, the additive, and the surfactant described later are dissolved in the liquid medium, the hydroxymethyl group-containing PVA, the hydroxymethyl group-containing PVA, And a film forming stock solution in which a hydroxymethyl group-containing PVA containing at least one of a plasticizer, an additive, a surfactant, and a liquid medium, etc., is further melted if necessary. When the stock solution for film formation contains at least one of a plasticizer, an additive and a surfactant, it is preferable that the components are uniformly mixed.

Examples of the liquid medium used for the preparation of the film-forming solution include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, Triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, and the like, and one or more of these may be used. Among them, water is preferred from the viewpoints of environmental load and recoverability.

The volatile fraction of the stock solution for forming the film (the content ratio of the volatile component such as a liquid medium removed by volatilization or evaporation at the time of film formation in the stock solution for film formation) varies depending on the film-forming method, film forming conditions, 95% by mass, more preferably within a range of 55% by mass to 90% by mass, and still more preferably within a range of 60% by mass to 85% by mass. When the volatilization rate of the stock solution is 50 mass% or more, the viscosity of the stock solution does not become excessively high, so that filtration and defoaming at the time of preparation of the stock solution are performed smoothly, and production of a film with few foreign matters or defect is facilitated. On the other hand, when the volatilization rate of the film-forming raw liquid is 95 mass% or less, the concentration of the film-forming stock solution is not excessively low, and production of an industrial film is facilitated.

It is preferable that the stock solution contains a surfactant. By containing the surfactant, the film formability is improved, the occurrence of the thickness variation of the film is suppressed, and the film from the belt or the metal roll used for film formation is easily peeled off. When a raw material film for optical film production is produced from a raw film forming solution containing a surfactant, the film may contain a surfactant. The kind of the surfactant is not particularly limited, but an anionic surfactant or a nonionic surfactant is preferable from the viewpoint of peelability from a metal roll or a belt.

Examples of the anionic surfactant include carboxylic acid type such as potassium laurate, sulfuric acid ester type such as polyoxyethylene lauryl ether sulfate and octylsulfate, and sulfonic acid type such as dodecylbenzenesulfonate Do.

Examples of the nonionic surfactant include alkyl ether types such as polyoxyethylene oleyl ether and the like, alkylphenyl ether types such as polyoxyethylene octylphenyl ether and the like, alkyl ester types such as polyoxyethylene laurate, Alkyl amines such as ethylene lauryl amino ether, alkyl amide types such as polyoxyethylene lauryl amide, polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether, diethanol amide laurate, diethanol amide oleic acid and the like And an allylphenyl ether type such as polyoxyalkylene allylphenyl ether and the like are preferable.

These surfactants may be used singly or in combination of two or more kinds.

When the stock solution contains a surfactant, the content thereof is preferably in the range of 0.01 to 0.5 part by mass, more preferably 0.02 to 0.3 part by mass, relative to 100 parts by mass of the hydroxymethyl group-containing PVA contained in the stock solution And particularly preferably in the range of 0.05 to 0.1 part by mass. When the content is 0.01 part by mass or more, the film formability and the peelability are further improved. On the other hand, when the content is 0.5 parts by mass or less, it is possible to suppress deterioration in handleability due to bleaching out of the surface active agent to the surface of the raw film for optical film production.

Examples of the film forming method for forming the raw film for optical film production using the above-mentioned raw film forming solution include cast film forming method, extrusion film forming method, wet film forming method, and gel film forming method. 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 in that a raw material film for producing an optical film having a uniform thickness and width and good physical properties can be obtained. The film thus formed can be dried or heat-treated as required.

An example of a specific method for producing a raw material film for producing an optical film of the present invention is a method of producing a raw material film for optical film production using a T-shaped slit die, hopper plate, I-die, lip coater die, (Or belt), and the volatile component is evaporated from one side of the discharged or softened film on the circumferential surface of the first roll (or belt) Dried again on the circumferential surface of one or a plurality of heated rolls arranged on the downstream side thereof, or dried again after passing through a hot-air drying apparatus and then wound up by a winding device Can be industrially favorably employed. The drying by the heated roll and the drying by the hot air drying apparatus may be carried out in an appropriate combination.

The raw material film for producing an optical film of the present invention is used as a raw film for producing an optical film. Examples of such an optical film include a polarizing film and a retardation film. Such an optical film can be produced, for example, by subjecting the raw film for optical film production of the present invention to a treatment such as uniaxial stretching.

The method for producing the polarizing film using the raw material film for producing an optical film of the present invention is not particularly limited and any conventionally employed method may be employed. In such a method, for example, dyeing and uniaxial stretching are applied to a raw film for producing an optical film of the present invention, or uniaxial stretching is applied to a raw film for producing an optical film of the present invention containing a dye Method. As a more specific method for producing the polarizing film, the raw material film for producing an optical film of the present invention is subjected to swelling, dyeing, uniaxial stretching and, if necessary, further crosslinking treatment, fixing treatment, drying and heat treatment . 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 may be simultaneously carried out. In addition, one or two or more of the treatments may be performed twice or more.

The swelling can be carried out by immersing the raw film for optical film production in water. The temperature of water at the time of immersion in water is preferably within a range of 20 to 40 캜, more preferably within a range of 22 to 38 캜, and still more preferably within a range of 25 to 35 캜. The time for immersing in water is preferably within a range of, for example, 0.1 to 5 minutes, and more preferably within a range of 0.5 to 3 minutes. Further, the water at the time of immersion 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 can be carried out by bringing a dichromatic dye into contact with a raw film for producing an optical film. As the dichroic dye, an iodine dye is generally used. The dyeing may be performed at any stage before uniaxial stretching, uniaxial stretching, or uniaxial stretching. The dyeing is generally carried out by immersing a raw film for producing an optical film in a solution (particularly an aqueous solution) containing iodine-iodide as a dyeing bath, and such a dyeing method is preferably employed also in the present invention. The concentration of iodine in the dyeing bath is preferably in the range of 0.01 to 0.5 mass%, and the concentration of potassium iodide is preferably in the range of 0.01 to 10 mass%. The temperature of the dyeing bath is preferably 20 to 50 캜, particularly 25 to 40 캜.

By performing the crosslinking treatment on the raw film for optical film production, it is possible to more effectively prevent the hydroxymethyl group-containing PVA from being eluted into water upon wet stretching at a high temperature. From this point of view, the crosslinking treatment is preferably carried out after uniaxially stretching as a treatment after bringing the dichroic dye into contact. The crosslinking treatment can be carried out by immersing a raw film for optical film production in an aqueous solution containing a crosslinking agent. As the crosslinking agent, boron compounds such as boric acid salts such as boric acid and borax can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably within a range of 1 to 15 mass%, more preferably within a range of 2 to 7 mass%, and further preferably within a range of 3 to 6 mass%. The concentration of the cross-linking agent is in the range of 1 to 15 mass%, so that sufficient stretchability can be maintained. The aqueous solution containing the crosslinking agent may contain an auxiliary agent such as potassium iodide. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50 캜, particularly in the range of 25 to 40 캜. The crosslinking can be effected efficiently by setting the temperature within the range of 20 to 50 ° C.

The uniaxial stretching may be carried out by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it may be carried out in an aqueous solution containing boric acid, or in a fixed bath described later or in a dyeing bath described later. In the case of the dry stretching method, stretching may be carried out at room temperature, stretching while heating, or may be carried out in the air using a raw material film for optical film production after absorption. Among them, the wet drawing method is preferable, and the uniaxial drawing is more preferable in an aqueous solution containing boric acid. The concentration of boric acid in the aqueous solution of boric acid is preferably within a range of 0.5 to 6.0 mass%, more preferably within a range of 1.0 to 5.0 mass%, and particularly preferably within a range of 1.5 to 4.0 mass%. The boric acid aqueous solution may contain potassium iodide, and the concentration thereof is preferably within a range of 0.01 to 10 mass%.

The stretching temperature in the uniaxial stretching is preferably in the range of 30 to 90 占 폚, more preferably in the range of 40 to 80 占 폚, and particularly preferably in the range of 50 to 70 占 폚.

The stretching magnification in the uniaxial stretching is preferably 6.8 times or more, more preferably 6.9 times or more, and particularly preferably 7.0 times or more, in terms 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 in the case of monoaxially stretching a raw material film for producing a long optical film, and uniaxial stretching or transverse uniaxial stretching in the longitudinal direction can be adopted. However, From the viewpoint of obtaining a film, uniaxial stretching in the long direction is preferable. The uniaxial stretching in the long direction can be carried out by changing the peripheral speed between the rolls by using a stretching device having a plurality of rolls parallel to each other. On the other hand, transverse uniaxial stretching can be carried out using a tenter-type stretching machine.

In the production of the polarizing film, it is preferable to carry out fixing treatment to strengthen the adsorption of the dichroic dye (iodine dye or the like) to the film. As the fixed treatment bath to be used for the fixing treatment, an aqueous solution containing one kind or two or more kinds of boron compounds such as boric acid and borax can be used. If necessary, an iodine compound or a metal compound may be added to the fixed treatment bath. The concentration of the boron compound in the fixed treatment bath is generally preferably about 2 to 15 mass%, particularly about 3 to 10 mass%. By making the concentration within the range of 2 to 15 mass%, the adsorption of the dichroic dye can be made stronger. The temperature of the fixed treatment bath is preferably 15 to 60 ° C, particularly 25 to 40 ° C.

The drying conditions are not particularly limited, but it is preferable to carry out the drying at a temperature in the range of 30 to 150 ° C, particularly in the range of 50 to 130 ° C. It is easy to obtain a polarizing film having excellent dimensional stability by drying at a temperature within the range of 30 to 150 ° C.

The polarizing film thus obtained is usually used as a polarizing plate by adhering a protective film having optical transparency and mechanical strength on both sides or one side thereof. As the protective film, a cellulose triacetate (TAC) film, an acetic acid-butyric acid cellulose (CAB) film, an acrylic film, a polyester film and the like are used. As the adhesive for bonding, PVA adhesive, urethane adhesive and the like can be mentioned, and among them, PVA adhesive is preferable.

The polarizing plate obtained as described above can be used as a component of an LCD after being coated with a pressure-sensitive adhesive such as an acryl-based adhesive and then adhered to a glass substrate. At the same time, it may be laminated with a retardation film, a viewing angle improving film, a luminance improving film or the like.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples at all. Each measurement or evaluation method employed in the following examples and comparative examples is shown below.

Primary structure of PVA

The primary structures of the PVA (hydroxymethyl group-containing PVA in the examples and various modified PVA in the comparative examples) used in the following examples and comparative examples were analyzed using 270 MHz ¹ H-NMR. Deuterated DMSO was used as a solvent for ¹ H-NMR measurement.

Swelling degree of fabric 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 캜 for 30 minutes. After immersing for 30 minutes, the film was taken out, and water on the surface was taken with a filter paper to determine the mass " N ". Subsequently, the film was dried in a dryer at 105 DEG C for 16 hours, and the mass "M" was obtained. From the obtained masses " N " and " M ", the degree of swelling of the raw material film for optical film production was calculated by the following formula (3).

Swelling degree (%) = 100 x N / M (3)

Tensile Properties of Fabric Film for Optical Film Production

A sample having a width of 5 cm and a length of 8 cm was cut from the center in the width direction of the raw material film for optical film production obtained in the following Examples or Comparative Examples so as to be uniaxially stretched in the range of 5 cm in width and 5 cm in length. This sample was uniaxially stretched in the longitudinal direction by 1.5 times while immersed in pure water at 30 占 폚. Subsequently, while being dipped in an aqueous solution (dyeing bath) (temperature 30 ° C) containing 0.03 mass% of iodine and 3.0 mass% of iodide, the composition was uniaxially stretched in the longitudinal direction at 1.6 times (2.4 times as a whole) Iodine was adsorbed. Subsequently, while being immersed in an aqueous solution (crosslinking bath) (at a temperature of 30 ° C) containing 3 mass% of boric acid and 3 mass% of potassium iodide, uniaxial stretching was performed in the longitudinal direction at 1.1 times (2.6 times as a whole). The film was uniaxially stretched in the longitudinal direction until it was cut while immersing it in an aqueous solution (drawing bath) containing 4 mass% boric acid and 6 mass% potassium iodide in addition to the length of the raw film for optical film production before stretching The magnification of the length at the time of cutting was defined as the limiting draw ratio. However, the temperature of the drawing bath was changed from an appropriate temperature by 1 DEG C to measure the critical draw ratio, and the temperature at which the critical draw ratio was the highest was selected.

Optical properties of polarizing film (dichroism ratio)

(1) Measurement of transmittance (Ts)

Two samples of 2 cm in length direction of the polarizing film were taken from the central part of the polarizing film obtained in the following examples or comparative examples, and using a spectrophotometer ("V7100" manufactured by Nippon Denshoku Co., Ltd.) , And the visual sensitivity of the C light source and the visible range of the visible light in the 2 ° field of view were measured in accordance with JIS Z 8722 (measuring method of object color), and the transmittance of light with a tilt of +45 degrees with respect to the longitudinal direction and -45 And the transmittance of light when tilted was measured, and their average value Ts1 (%) was obtained. In the same manner for the other one sample, the transmittance of light when tilted by + 45 ° and the transmittance of light when tilted by -45 ° were measured, and their average value Ts 2 (%) was determined. Ts1 and Ts2 were averaged by the following formula (4) to be the transmittance Ts (%) of the polarizing film.

Ts = (Ts1 + Ts2) / 2 (4)

(2) Measurement of polarization degree V

The transmittance T∥ (%) of the light when the two samples collected by the measurement of the transmittance Ts are superimposed so that their lengthwise directions become parallel to each other, and the transmittance T⊥ (%) of the light when they are superimposed so that the longitudinal directions thereof are perpendicular to each other (1) Measurement of transmittance Ts ", and the degree of polarization V (%) was determined by the following equation (5).

V = {(T∥ -T⊥) / (T∥ + T⊥)} ^1/2 × 100 (5)

(3) Calculation of 2-color ratio when the transmittance is 44%

In each of the following examples and comparative examples, the concentration of iodine in the dyeing bath was varied from 0.02 to 0.04 mass% and the concentration of potassium iodide was varied within the range of from 2.0 to 4.0 mass% four times (the iodine concentration : Concentration of potassium iodide = 1: 100), and four polarizing films having different dichroic dye adsorption amounts from the polarizing films prepared in Examples and Comparative Examples were prepared. The transmittance Ts (%) and the polarization degree V (%) were determined for each of the four polarizing films by the above-described method. For each of Examples and Comparative Examples, transmittance Ts (% And a point based on the transmittance Ts (%) and the polarization degree V (%) of the polarizing film obtained in each of the Examples and the Comparative Examples were also plotted on a vertical axis to obtain an approximate curve, , The degree of polarization V ₄₄ (%) when the transmittance Ts (%) was 44% was determined.

From the obtained degree of polarization V ₄₄ (%), the dichroic ratio when the transmittance was 44% according to the following formula (6) was determined and used as an index of the polarization performance.

44% transmittance ratio of one second color when = log (44/100 - 44/100 × V 44/100) / log (44/100 + 44/100 × V 44/100) (6)

The color of the polarizing film (parallel b value)

(%) And transmittance T? (%) When the polarization degree V of the four polarizing films in which the adsorption amount of the dichroic dye is different is obtained in the above "optical characteristics (dichroism ratio)" of the polarizing film , The b value at the time of measurement of the transmittance T∥ (%) was taken as a parallel b value, and the b value at the time of measuring the transmittance T ⊥ (%) was taken as an orthogonal b value. For each of the examples and comparative examples, a total of five points including a parallel b value and a perpendicular b value of the polarizing film obtained in the respective examples or comparative examples were also included in the graph And an approximate curve was obtained. From this approximate curve, the parallel b value when the orthogonal b value was -4 was obtained. Further, the closer the parallel b value is to 0, the better the hue of the polarizing film is.

[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 1,3-diacetoxy-2-methylene propane as modified PVA, 10 parts by mass of glycerin as a plasticizer, 0.1 part by mass of sodium polyoxyethylene lauryl ether sulfate as an activator, and using an aqueous solution having a content of modified PVA of 10% by mass as an undiluted solution, drying the resulting solution on a metal roll at 80 ° C, The swelling degree was adjusted to 200% by heat treatment at a temperature of 1 minute to prepare a fabric film for optical film production having a thickness of 30 탆.

Using the obtained raw material film for producing an optical film, the stretchability was evaluated by the above-mentioned method. 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 center in the width direction of the raw film for optical film production obtained in the above (1) so as to be uniaxially stretched in the range of 5 cm in width and 5 cm in length. This sample was uniaxially stretched in the longitudinal direction by 1.5 times while immersed in pure water at 30 占 폚. Subsequently, while being dipped in an aqueous solution (dyeing bath) (temperature 30 ° C) containing 0.03 mass% of iodine and 3.0 mass% of iodide, the composition was uniaxially stretched in the longitudinal direction at 1.6 times (2.4 times as a whole) Iodine was adsorbed. Subsequently, while being immersed in an aqueous solution (crosslinking bath) (at a temperature of 30 ° C) containing 3 mass% of boric acid and 3 mass% of potassium iodide, uniaxial stretching was performed in the longitudinal direction at 1.1 times (2.6 times as a whole). And further immersed in an aqueous solution (drawing bath) containing 4 mass% of boric acid and 6 mass% of potassium iodide (the temperature at which the maximum stretching magnification obtained from the above "stretching property of the optical film production raw film" is the highest) And uniaxially stretched in the longitudinal direction to a magnification of 0.2 times lower than the critical stretching magnification. Thereafter, the film was immersed in an aqueous solution (cleansing bath) (at a temperature of 30 DEG C) containing potassium iodide in a proportion of 3 mass% for 5 seconds, and finally dried at 60 DEG C for 4 minutes to prepare a polarizing film.

Using the obtained polarizing film, the optical characteristics (dichroism ratio) and hue (parallel b value) of the polarizing film were evaluated by the above-described method. The results are shown in Table 1.

[Comparative Examples 1 to 3]

Unmodified PVA (Comparative Example 1) shown in Table 1 obtained by saponifying a vinyl acetate homopolymer in place of the modified PVA in Example 1, a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene as the modified PVA Modified PVA (Comparative Example 2) shown in Table 1 obtained by saponifying a copolymer, or modified PVA shown in Table 1 (Comparative Example 3) obtained by saponifying a copolymer of vinyl acetate and itaconic acid as modified PVA A raw material film and a polarizing film for optical film production were produced in the same manner as in Example 1 except that each measurement or evaluation was performed. The results are shown in Table 1.

[Examples 2 to 4]

The hydroxymethyl group-containing PVA (Examples 2 and 3) shown in Table 1 obtained by saponifying a copolymer of vinyl acetate and 1,3-diacetoxy-2-methylenepropane as the modified PVA in Example 1, Except that the hydroxymethyl group-containing PVA (Example 4) shown in Table 1 obtained by saponifying a ternary copolymer of vinyl acetate and 1,3-diacetoxy-2-methylene propane and ethylene as the modified PVA was used A raw material film and a polarizing film for optical film production were prepared in the same manner as in Example 1, and each measurement or evaluation was carried out. The results are shown in Table 1.

[Table 1]

As is apparent from the above results, it can be seen that the raw material films for producing optical films of Examples 1 to 4 satisfying the requirements of the present invention are excellent in stretchability and can be produced with good productivity. Further, the stretching property is high, so that the area of the obtained optical film can be increased, and more optical films can be obtained. In addition to the above, according to the raw material films for optical film production of Examples 1 to 4 satisfying the requirements of the present invention, an optical film excellent in both optical characteristics and color can be easily produced. Further, in Example 4 using a hydroxymethyl group-containing PVA further containing an ethylene unit, the stretchability was further improved and the stretchable temperature was also increased, and it was found that the optical film could be produced with better productivity.

Claims (7)

A vinyl alcohol polymer containing a hydroxymethyl group containing a vinyl alcohol unit and a structural unit represented by the following formula (1).
[Chemical Formula 1]

The method according to claim 1,
Wherein the content of the structural unit represented by the formula (1) in the hydroxymethyl group-containing vinyl alcohol polymer is 0.1 to 2 mol%. 3. The method according to claim 1 or 2,
Wherein the hydroxymethyl group-containing vinyl alcohol polymer further contains an ethylene unit. The method of claim 3,
Wherein the hydroxymethyl group-containing vinyl alcohol polymer has an ethylene unit content of 1 to 4 mol%. 5. The method according to any one of claims 1 to 4,
Wherein the hydroxymethyl group-containing vinyl alcohol polymer has a saponification degree of 95 mol% or more. 6. The method according to any one of claims 1 to 5,
Fabric film for manufacturing optical film, which is a fabric film for polarizing film production.  A method for producing an optical film having a monoaxial stretching step using the raw material film for producing an optical film according to any one of claims 1 to 6.