TWI636066B - Blank film for optical film manufacturing and manufacturing method of optical film - Google Patents

Abstract

Provided are a raw material film for optical film manufacturing, which is capable of producing an optical film with excellent extensibility and good productivity, and an optical film having excellent optical characteristics and hue, and a method for producing an optical film using the same.

A raw material film for manufacturing an optical film, which is a vinyl alcohol polymer containing a methylol group containing a vinyl alcohol unit and a structural unit represented by the following formula (1); and a method for manufacturing an optical film, The method includes the step of performing uniaxial stretching using the raw material film for optical film production.

Description

Blank film for optical film manufacturing and manufacturing method of optical film

The present invention relates to a raw material film for producing an optical film such as a polarizing film including a methylol-containing vinyl alcohol polymer having a 1,3-diol structure, and a method for producing an optical film using the same.

A polarizing plate having a light transmitting and light blocking function is the same as a basic constituent element of a liquid crystal display (LCD), as is a liquid crystal that changes the polarization state of light. Most polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is laminated on the surface of the polarizing film. As for the polarizing film constituting the polarizing plate, the vinyl alcohol polymer film (hereinafter, there are ("Vinyl alcohol polymer" is referred to as "PVA"), and dichroic dyes such as iodine dyes (I ₃ ^- or I ₅ ^- etc.) or dichroic organic dyes are adsorbed on a substrate obtained by uniaxial stretching. For its mainstream.

LCDs are gradually being used in a wide range of small devices such as computers and watches, mobile phones, notebook computers, LCD screens, LCD color projectors, LCD TVs, car navigation systems, and measuring instruments used indoors and outdoors. In recent years, In particular, advanced display quality is required. Accordingly, high performance is also required for polarizing films. Specifically, polarizing films are required to have high polarization or transmittance, excellent optical characteristics, and excellent hue and durability.

In addition, several kinds of raw material films for optical film production including modified PVA are known. For example, it is known that a polyvinyl alcohol film for a polarizing film of a polarizing film containing a specific PVA containing a hydrophilic functional group such as a carboxylic acid group or an ω-hydroxy-α-olefin group at 0.01 to 1 mole% is extended. ‧Excellent alignment treatment and dichroic substance adsorption treatment (refer to Patent Document 1, etc.). Further, it is known that a specific optical PVA film including a specific PVA having a 1,2-diol bond in a side chain has excellent optical characteristics and extensibility (see Patent Document 2).

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Unexamined Patent Publication No. 8-201626

[Patent Document 2] Japanese Patent Laid-Open No. 2009-24076

However, when using a conventionally known raw material film for optical film manufacturing including modified PVA, there is still room for further improvement in obtaining an optical film having excellent optical characteristics and hue. In addition, when using a conventionally known blank film for optical film manufacturing including modified PVA, especially in the case of continuous production of optical films, problems such as stretch fracture are still prone to occur, and the productivity of optical films has been further improved. Space.

Therefore, the present invention is to provide an optical film for manufacturing an optical film, which is excellent in extensibility and good producibility, and can easily produce an optical film having excellent optical characteristics and hue, and an optical film using the same. Manufacturing method for the purpose.

The present inventors have repeatedly conducted research to achieve the above-mentioned object, and found that the above-mentioned problem can be solved by a thin film containing a methylol group-containing material containing a specific structural unit having a 1,3-diol structure on the main chain. PVA, and based on this knowledge, further repeated research to complete the present invention.

That is, the present invention relates to: [1] A raw material film for producing an optical film, which contains a methylol group-containing PVA containing a vinyl alcohol unit and a structural unit represented by the following formula (1): [2] The blank film for manufacturing an optical film according to [1], wherein the content rate of the structural unit represented by the formula (1) in the methylol-containing PVA is 0.1 to 2 mole%; [3] [1] or [2] The raw material film for optical film production, wherein the PVA group containing methylol further contains an ethylene unit; [4] The raw material film for optical film production such as [3], wherein The content of ethylene units in PVA of hydroxymethyl groups is 1 to 4 mol%; [5] The blank film for producing an optical film according to any one of [1] to [4], wherein the aforementioned hydroxymethyl group The degree of saponification of PVA is 95 mol% or more; [6] The blank film for optical film manufacturing according to any one of [1] to [5], which is a blank film for polarizing film manufacturing; [7] a The manufacturing method of an optical film has the process of uniaxially stretching using the raw material film for optical film manufacture as described in any one of [1] to [6].

According to the present invention, there is provided an optical film for manufacturing an optical film which is capable of producing an optical film with excellent extensibility and good productivity, and which can easily produce an optical film having excellent optical characteristics and hue, and an optical film using the same. Production method.

[Form of Implementing Invention]

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

The raw material film for producing an optical film of the present invention contains a methylol-containing PVA containing a structural unit having a 1,3-diol structure represented by the above formula (1), thereby improving elongation. In addition, according to the blank film for producing an optical film of the present invention, optical characteristics can be easily produced. Optical film with excellent hue. For reasons of obtaining the advantages described above, although it is not a limitation of the present invention, it is considered that the crystallinity is lowered by the structural unit represented by the formula (1); The effect of hydrogen bonding.

The content rate of the structural unit represented by the formula (1) in the methylol-containing PVA is not particularly limited, but it is preferable that the molar number of the total structural unit constituting the methylol-containing PVA is 100 mole%. It is in the range of 0.1 to 2 mol%, more preferably in the range of 0.2 to 1.9 mol%, and even more preferably in the range of 0.3 to 1.8 mol%. By setting the content rate to 0.1 mol% or more, the extensibility of the film can be further improved, and an optical film having a better hue can be obtained. On the other hand, when the content is 2 mol% or less, the film can be more effectively prevented from dissolving during the production of the optical film, and an optical film having more excellent optical characteristics can be obtained. In addition, in this specification, a "structural unit" means the repeating unit which comprises a polymer.

The degree of polymerization of hydroxymethyl-containing PVA is preferably in the range of 1,500 to 6,000, more preferably in the range of 1,800 to 5,000, and even more preferably in the range of 2,000 to 4,000. By setting the polymerization degree to 1,500 or more, the durability of optical films such as polarizing films obtained by uniaxially stretching the films can be further improved. On the other hand, by setting the degree of polymerization to 6,000 or less, it is possible to suppress an increase in manufacturing cost, a poor processability during film formation, and the like. In addition, the polymerization degree of hydroxymethyl-containing PVA in this specification means the average polymerization degree measured based on the description of JIS K6726-1994.

From the viewpoint of water resistance of an optical film such as a polarizing film obtained by uniaxially stretching the film, the saponification degree of the PVA containing methylol group is preferably 95 mol% or more, more preferably 96 mol% or more, and even more preferably 98 More than%. In addition, the saponification degree of the PVA containing a methylol group in this specification refers to the content of the PVA containing a methylol group which can be converted into a vinyl alcohol unit (-CH ₂ -CH (OH)-) by saponification. In terms of the total mole number of the structural unit (typically a vinyl ester unit) and the vinyl alcohol unit, the proportion (mole%) of the mole number of the vinyl alcohol unit. The degree of saponification can be measured in accordance with the description of JIS K6726-1994 after taking into account the amounts of all the structural units or derivatives thereof represented by formula (1).

The manufacturing method of a methylol group containing PVA is not specifically limited. For example, there can be mentioned a method of copolymerizing a vinyl ester-based monomer and an unsaturated monomer which can be copolymerized therewith and can be converted into a structural unit represented by formula (1), and then the obtained vinyl ester-based copolymer is copolymerized. The vinyl ester unit is converted into a vinyl alcohol unit, and the structural unit derived from an unsaturated monomer that can be converted into a structural unit represented by formula (1) is converted into a structural unit represented by formula (1). Specific examples of the unsaturated monomer that can be converted into the structural unit represented by the formula (1) are shown in the following formula (2).

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

Examples of the unsaturated monomer represented by the formula (2) include 1,3-diethylfluorenyloxy-2-methylenepropane, 1,3-dipropanyloxy-2-methylenepropane, and 1, 3-dibutoxo-2-methylenepropane and the like. Among them, from the viewpoint of ease of production, 1,3-diacetoxy-2-methylenepropane is preferably used.

The unsaturated monomer represented by formula (2) is generally easier to interact with ethylene than other allyl unsaturated monomers (such as allyl epoxypropyl ether) used in the modification of PVA. The ester monomer is copolymerized. Therefore, there are fewer restrictions on the quality or degree of polymerization during polymerization, and it is easy to obtain a methylol-containing PVA having a high quality and degree of polymerization. Furthermore, since the amount of the unreacted unsaturated monomer remaining at the end of the polymerization can be reduced, the methylol-containing PVA of the present invention is also excellent in environmental and cost aspects when manufactured industrially.

The vinyl ester monomer used in the production of methylol-containing PVA is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, and trimethyl Vinyl acetate, vinyl versatate, vinyl hexanoate, vinyl octoate, vinyl decanoate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate , Vinyl benzoate, etc. From the viewpoint of economy, vinyl acetate is preferred.

When the unsaturated monomer represented by formula (2) is copolymerized with a vinyl ester monomer, the polymerization method may be batch polymerization, semi-batch polymerization, or continuous polymerization. Either polymerization, semi-continuous polymerization, or the like. As the polymerization method, known methods such as a block polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method can be applied. Usually, a block polymerization method or a solution polymerization method in which polymerization is performed in a solvent such as a solvent or an alcohol is used. When a vinyl ester copolymer having a high degree of polymerization is desired, an emulsion polymerization method is also preferred. The solvent of the solution polymerization method is not particularly limited, and is, for example, an alcohol. The alcohol used in the solvent of 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 can be selected according to the polymerization degree of the target methyl PVA containing methyl alcohol and the chain transfer of the solvent. For example, when the solvent is methanol, the mass of the solvent and the total monomer contained in the polymerization system is used. The ratio {= (solvent) / (total monomer)} can be selected from the range of preferably 0.01 to 10, more preferably 0.05 to 3.

The initiator used in the copolymerization of the unsaturated monomer represented by the formula (2) and the vinyl ester monomer may be a known polymerization initiator depending on the polymerization method, such as an azo initiator and a peroxide. What is necessary is just to select among a system initiator and a redox system initiator. The azo-based initiator is, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4 -Methoxy-2,4-dimethylvaleronitrile) and the like. Peroxide-based initiators are percarbonate compounds such as diisopropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate; Peroxy ester compounds such as tertiary butyl peroxydecanoate, α-cumene peroxy neodecanoate; acetamidinecyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl -2-Phenoxyacetate; Acetyl peroxide. A polymerization initiator may be constituted by combining potassium persulfate, ammonium persulfate, hydrogen peroxide, and the like with the above-mentioned initiator. The redox-based initiator is, for example, The polymerization initiator is a combination of a peroxide initiator and a reducing agent such as sodium bisulfite, sodium bicarbonate, tartaric acid, L-ascorbic acid, and rongalit. Since the amount of the polymerization initiator varies depending on the type of the polymerization initiator, it cannot be generalized, but it can be selected according to the polymerization speed. For example, when 2,2'-azobisisobutyronitrile or acetamidine peroxide is used as the polymerization initiator, it is preferably 0.01 to 0.2 mol%, and more preferably 0.02 to 0.15 mol relative to vinyl ester monomers. %. The polymerization temperature is not particularly limited, and it is suitable from about room temperature to about 150 ° C, and preferably above 40 ° C and below the boiling point of the solvent used.

The copolymerization of the unsaturated monomer represented by the formula (2) and the vinyl ester-based monomer can be performed in the presence of a chain transfer agent. Chain transfer agents are, for example, aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; thiols such as 2-hydroxyethyl mercaptan; and phosphinates such as sodium phosphinate monohydrate. Among them, aldehydes and ketones can be suitably used. The amount of chain transfer agent can be determined according to the chain transfer constant of the chain transfer agent used and the degree of polymerization of the target methylol group-containing PVA. Generally speaking, it is better than 100 parts by mass of vinyl ester monomers. It is 0.1 to 10 parts by mass.

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

The saponification of the vinyl ester copolymer can be performed, for example, in a state where the vinyl ester copolymer is dissolved in an alcohol or a water-containing alcohol. Examples of the alcohol used for saponification include lower alcohols such as methanol and ethanol, and methanol is preferred. The alcohol used for saponification can also contain other solvents, such as acetone, methyl acetate, ethyl acetate, and benzene, in the ratio of 40 mass% or less of its mass, for example. Catalysts used for saponification are, for example, hydroxides of alkali metals such as potassium hydroxide and sodium hydroxide, alkali catalysts such as sodium methoxide, and acid catalysts such as mineral acid. The temperature at which the saponification is performed is not limited, but it is more preferably within a range of 20 to 60 ° C. When a gel-like product precipitates with the progress of saponification, the product is pulverized, washed, and dried to obtain PVA containing methylol. The saponification method is not limited to the aforementioned method, and a known method can be applied.

The methylol group-containing PVA may further contain a structural unit other than the structural unit represented by formula (1), a vinyl alcohol unit, and a vinyl ester unit. Examples of the other structural unit include a structural unit derived from an ethylenically unsaturated monomer copolymerizable with a vinyl ester-based monomer. In addition, it may contain a structural unit derived from an unsaturated monomer which can be copolymerized with the vinyl ester-based monomer and can be converted into a structural unit represented by formula (1) (which is not converted into formula (1) by saponification). The structural unit shown in the structural unit).

When the mole number of the total structural unit constituting the PVA containing methylol group is 100 mole%, the total of the structural unit, vinyl alcohol unit, and vinyl ester unit represented by formula (1) in the methyl alcohol-containing PVA is assumed. The proportion is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and also 99 mol% or more.

Examples of the ethylenically unsaturated monomer include ethylene. , Propylene, n-butene, isobutylene, 1-hexene and other α-olefins; acrylic acid and its salts; unsaturated monomers with acrylate groups; methacrylic acid and its salts; unsaturated with methacrylate groups Monomers; acrylamide, N-methacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid and its salts, Acrylamide derivatives such as acrylamine propyldimethylamine and its salts (such as quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, Methacrylamidine propanesulfonic acid and its salts, methacrylamidine propyl dimethylamine and its salts (such as quaternary salts), and other methacrylamidine derivatives; methyl vinyl ether, ethyl vinyl Ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tertiary butyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether Ethers, vinyl ethers such as 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; Dihalogenated vinylidene such as dichloroethylene, difluoroethylene, etc .; allyl compounds such as 2,3-diethylacetoxy-1-allyloxypropane, chlorinated allyl; maleic acid , Itaconic acid, fumaric acid and other unsaturated dicarboxylic acids and their salts or their esters; vinyl silane compounds such as vinyl trimethoxysilane; isopropenyl acetate and the like. Among these, the productivity of the optical film can be further improved by improving the extensibility and carrying out the stretching at a higher temperature, and reducing the occurrence of problems such as elongation breakage during the manufacture of the optical film. In particular, ethylene is preferred. When the methylol-containing PVA contains an ethylene unit, based on the extensibility or elongation temperature as described above, when the molar number of the total structural unit constituting the methylol-containing PVA is 100 mole%, The content rate is preferably 1 to 4 mole%, and particularly preferably 2 to 3 mole%.

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

The raw material film for producing an optical film of the present invention may contain a plasticizer in addition to the above-mentioned hydroxymethyl-containing PVA. Examples of preferred plasticizers include polyhydric alcohols. Specific examples include ethylene glycol, glycerol, propylene glycol, diethylene glycol, diglycerol, triethylene glycol, tetraethylene glycol, and trihydroxy alcohol. Methylpropane and the like. The raw material film for producing an optical film of the present invention may contain one or two or more of these plasticizers. Among these, glycerin is preferred from the viewpoints of elongation improving effect and the like.

The content of the plasticizer of the raw material film for optical film manufacturing of the present invention is preferably within a range of 1 to 20 parts by mass, more preferably 3 to 100 parts by mass of PVA containing methylol groups. It is in a range of ~ 17 parts by mass, and even more preferably in a range of 5 to 15 parts by mass. When the content is 1 part by mass or more, the stretchability of the film can be further improved. On the other hand, when the content is 20 parts by mass or less, it is possible to prevent the film from being too soft and lowering the handling properties.

In the raw material film for optical film manufacturing of the present invention, processing stabilizers, weather stabilizers, colorants, ultraviolet absorbers, light stabilizers, antioxidants, Static agents, flame retardants, other thermoplastic resins, lubricants, fragrances, defoamers, deodorants, extenders, release agents, mold release agents, reinforcing agents, cross-linking agents, mold inhibitors, preservatives, crystals Additives such as chemical retarder.

Based on the quality of the blank film for optical film manufacturing, the present invention The total ratio of the methylol-containing PVA and the plasticizer in Mingzhi's optical film manufacturing film is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

The swelling degree of the blank film for optical film manufacturing of the present invention is preferably in the range of 160 to 240%, more preferably in the range of 170 to 230%, and particularly preferably in the range of 180 to 220%. By making the degree of swelling to 160% or more, the progress of crystallization can be suppressed as much as possible, and the stretching can be performed stably to a high magnification. On the other hand, when the degree of swelling is 240% or less, the dissolution during stretching can be suppressed, and the stretching can be performed even at a higher temperature. In addition, in this specification, the swelling degree of a raw material film for optical film manufacturing refers to the mass when the raw material film for optical film manufacturing is immersed in distilled water at 30 ° C for 30 minutes divided by the mass after impregnation and drying at 105 ° C for 16 hours. The percentage of the value obtained by mass can be specifically measured by the method mentioned later in an Example.

The thickness of the blank film for optical film manufacturing of the present invention is not particularly limited, but is generally preferably about 1 to 100 μm, more preferably about 5 to 75 μm, and particularly preferably about 10 to 60 μm. If the thickness is too thin, the film tends to be easily stretched during uniaxial stretching for producing an optical film such as a polarizing film. Moreover, if this thickness is too thick, there is a tendency that uneven stretching is liable to occur during uniaxial stretching processing 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 may be determined depending on the application of the optical film to be produced and the like. In recent years, in order to advance the enlargement of a liquid crystal television or a liquid crystal screen, if the width of a raw material film for optical film production is 3 m or more, it is suitable for these applications. On the other hand, the material film for optical film manufacturing If the width is too large, it is easier and more difficult to uniformly uniaxially stretch the optical film in a practical device. Therefore, the width of the blank film for optical film production is preferably 7 m or less.

The manufacturing method of the raw material film for optical film manufacturing of the present invention is not particularly limited, and a manufacturing method in which the thickness and width of the film after film formation are more uniform can be preferably used. For example, the following film forming stock solution can be used for manufacturing: One or two or more of the above-mentioned plasticizers, additives, and surfactants described later are dissolved in the liquid medium, as required, of the methylol-containing PVA constituting the raw material film for optical film manufacturing, as required. A film-forming stock solution obtained from the above; or PVA containing methylol, and optionally one or more of plasticizers, additives, surfactants, and liquid media, etc., and containing methylol PVA melted film-forming stock solution. When the film-forming dope contains at least one of a plasticizer, an additive, and a surfactant, it is preferable to uniformly mix these components.

Examples of the liquid medium used for preparing the film-forming stock solution include water, dimethylmethylene, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, and propyl. Triol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, etc., one or two or more of these can be used. Among these, water is preferable in terms of environmental burden or recyclability.

The volatile content of the film-forming raw liquid (the proportion of the volatile components in the film-forming raw liquid of the liquid medium and the like removed by evaporation and evaporation during film-forming) varies depending on the film-forming method and film-forming conditions, etc. In other words, it is preferably in the range of 50 to 95% by mass, more preferably in the range of 55 to 90% by mass, and even more preferably in the range of 60 to 85% by mass. Make the volatiles of the film-forming stock solution The ratio is 50% by mass or more, so that the viscosity of the film-forming dope will not be too high, and filtering or defoaming during the preparation of the film-forming dope can be smoothly performed, and a thin film with less impurities or defects is easily produced. On the other hand, by setting the volatile content of the film-forming dope to 95% by mass or less, the concentration of the film-forming dope is not excessively low, and industrial production of a thin film becomes easy.

The film-forming dope is preferably containing a surfactant. By including a surfactant, the film-forming property can be improved and the uneven thickness of the film can be suppressed. At the same time, the film can be easily peeled from the metal roller or belt used for film-making. When a raw material film for optical film manufacturing is produced from a film-forming dope containing a surfactant, the film may contain a surfactant. The type of the above-mentioned surfactant is not particularly limited, and is preferably an anionic surfactant or a nonionic surfactant from the standpoint of releasability from a metal roll or a belt.

Suitable anionic surfactants are, for example, carboxylic acid types such as potassium laurate; sulfate types such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and sulfonic acids such as dodecylbenzenesulfonate Type and so on.

Suitable nonionic surfactants are, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl esters such as polyoxyethylene laurate Type; alkylamine types such as polyoxyethylene laurylamine ether; alkylamine types such as polyoxyethylene laurate amine; polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether; diethanolamine laurate, Alkanolamines such as diethanolamine oleate and allylphenylethers such as polyoxyalkylene allylphenyl ether.

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

When the film-forming dope contains a surfactant, the content is preferably in the range of 0.01 to 0.5 parts by mass, and more preferably 0.02 to 0.3 parts by mass, relative to 100 parts by mass of methylol-containing PVA contained in the film-forming dope. Within the range, particularly preferred is within a range of 0.05 to 0.1 parts by mass. When the content is 0.01 parts by mass or more, film-forming properties and peelability can be further improved. On the other hand, when the content is 0.5 parts by mass or less, it is possible to prevent the surfactant from oozing out from the surface of the base film for optical film production and causing blocking, which may reduce handling properties.

Examples of the film forming method in the case of using the above-mentioned film forming stock solution to produce a thin film for optical film production include a casting film forming method, an extrusion film forming method, a wet film forming method, and a colloidal film method. These film forming methods may be used alone or in combination of two or more. Among these film-forming methods, a cast film method and an extrusion film-forming method are preferred in terms of obtaining a raw material film for optical film production with uniform thickness and width and good physical properties. The produced film can be dried or heat-treated as required.

As an example of a specific manufacturing method of the blank film for manufacturing an optical film of the present invention, for example, this method can be preferably used industrially: using a T-shaped slit die, a hopper plate, an I-shaped die, and a lip coating die coater die), etc., to uniformly discharge or cast the above-mentioned film-forming dope to the peripheral surface of the first rotating (heated) roll (or belt) located on the most upstream side, so that volatile components are discharged or cast to the first One side of the film on the peripheral surface of one roll (or belt) evaporates to dry, and is further dried on the peripheral surface of one or more rotating and heated rolls arranged on the downstream side, or passed through hot air After being further dried in the drying device, it is wound by a winding device. Can also be appropriately combined with drying by heating roller And drying by a hot air drying device.

The raw material film for manufacturing an optical film of the present invention is used as a raw material film for manufacturing an optical film. Examples of such an optical film include a polarizing film and a retardation film. Such an optical film can be manufactured by the method of performing processing, such as uniaxial stretching, using the blank film for optical film manufacturing of this invention.

The method for manufacturing a polarizing film using the blank film for optical film manufacturing of the present invention is not particularly limited, and any method conventionally used can be adopted. Examples of such a method include a method of dyeing and uniaxially stretching the raw material film for optical film manufacturing of the present invention, or uniaxially stretching the raw material film for optical film manufacturing of the present invention containing a dye. As a more specific method for manufacturing a polarizing film, the raw material film for optical film manufacturing of the present invention may be swelled, dyed, uniaxially stretched, and further subjected to cross-linking treatment, fixing treatment, drying, heat treatment, etc. as required. method. At this time, 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 performed simultaneously. In addition, one or two or more kinds of each treatment can be performed twice or more.

Swelling can be performed by immersing a raw material film for optical film production in water. The temperature of water when immersed in water is preferably in the range of 20 to 40 ° C, more preferably in the range of 22 to 38 ° C, and even more preferably in the range of 25 to 35 ° C. The time for immersion in water is, for example, preferably within a range of 0.1 to 5 minutes, and more preferably within a range of 0.5 to 3 minutes. The water when immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or a mixture of water and an aqueous medium.

Dyeing can be performed by contacting a raw material film for optical film manufacturing with a dichroic dye. As a dichroic pigment, an iodine-based pigment is generally used. The time point of dyeing can be any stage before uniaxial extension, during uniaxial extension, or after uniaxial extension. Dyeing is generally performed by immersing a raw material film for optical film manufacturing in a solution (particularly, an aqueous solution) containing iodine-potassium iodide as a dyeing bath, and this dyeing method is also suitably used in the present invention. The concentration of iodine in the dyeing bath is preferably within a range of 0.01 to 0.5% by mass, and the concentration of potassium iodide is preferably within a range of 0.01 to 10% by mass. The temperature of the dyeing bath is preferably 20 to 50 ° C, and particularly preferably 25 to 40 ° C.

By performing a cross-linking treatment on the raw material film for optical film manufacturing, it is possible to more effectively prevent PVA containing methylol from dissolving in water when wet stretching is performed at a high temperature. From this viewpoint, the cross-linking treatment is preferably performed after the treatment for contacting the dichroic pigment, that is, before the uniaxial stretching. The crosslinking treatment can be performed by immersing a raw material film for optical film production in an aqueous solution containing a crosslinking agent. As this crosslinking agent, one or two or more kinds of boron compounds such as borate 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 in the range of 1 to 15% by mass, more preferably in the range of 2 to 7% by mass, and even more preferably in the range of 3 to 6% by mass. When the concentration of the crosslinking agent is in the range of 1 to 15% by mass, sufficient extensibility can be maintained. The aqueous solution containing a crosslinking agent may contain adjuvants, such as potassium iodide. The temperature of the aqueous solution containing a crosslinking agent is preferably within a range of 20 to 50 ° C, and particularly preferably within a range of 25 to 40 ° C. When the temperature is in the range of 20 to 50 ° C, crosslinking can be performed efficiently.

Uniaxial extension can use either wet or dry extension method To carry out. For example, in the wet-drawing method, it can be performed in an aqueous solution containing boric acid, or it can be performed in the dyeing bath described above or in a fixed treatment bath described later. In the case of the dry stretching method, stretching may be performed at room temperature directly, or heating may be performed while stretching, or a raw material film for optical film manufacturing after water absorption may be used in the air. Among these, a wet stretching method is preferred, and uniaxial stretching is more preferably performed in an aqueous solution containing boric acid. The concentration of boric acid in the boric acid aqueous solution is preferably within a range of 0.5 to 6.0% by mass, more preferably within a range of 1.0 to 5.0% by mass, and particularly preferably within a range of 1.5 to 4.0% by mass. The boric acid aqueous solution may contain potassium iodide, and its concentration is preferably set in a range of 0.01 to 10% by mass.

The uniaxial stretching temperature 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.

Moreover, from the viewpoint of the polarization performance of the obtained polarizing film, the stretching magnification of uniaxial stretching is preferably 6.8 times or more, more preferably 6.9 times or more, and particularly preferably 7.0 times or more. The upper limit of the stretching magnification is not particularly limited, and the stretching magnification is preferably 8 times or less.

There is no particular limitation on the direction of uniaxial extension when uniaxial stretching is performed on a long-length optical film manufacturing blank film. A uniaxial extension in the longitudinal direction or a uniaxial extension in the lateral direction can be used, but a polarizing film with excellent polarization performance can be obtained It is preferable to extend uniaxially in the longitudinal direction. The uniaxial extension in the longitudinal direction can be performed by changing the peripheral speed between the rollers using an extension device having a plurality of rollers parallel to each other. On the other hand, transverse uniaxial stretching can be performed using a tenter type stretching machine.

In the case of manufacturing a polarizing film, it is preferable to perform a fixing treatment in order to make the film more strongly adsorbed by a dichroic dye (such as an iodine dye). As the fixed treatment bath used for the fixed treatment, an aqueous solution containing one or two or more boron compounds such as boric acid and borax can be used. In addition, an iodine compound or a metal compound may be added to the fixed processing bath as required. The concentration of the boron compound in the fixed treatment bath is generally 2 to 15% by mass, and particularly preferably about 3 to 10% by mass. When the concentration is in the range of 2 to 15% by mass, the adsorption of the dichroic pigment can be further strengthened. The temperature of the fixed treatment bath is preferably 15 to 60 ° C, especially 25 to 40 ° C.

The drying conditions are not particularly limited, but drying is preferably performed at a temperature in a range of 30 to 150 ° C, particularly in a range of 50 to 130 ° C. By drying at a temperature in the range of 30 to 150 ° C, a polarizing film having excellent dimensional stability can be easily obtained.

The polarizing film obtained as described above is usually a protective film that is optically transparent and mechanically bonded on both sides or one side of the film, and is used as a polarizing plate. As the protective film, cellulose triacetate (TAC) film, acetic acid can be used. Cellulose butyrate (CAB) film, acrylic film, polyester film, etc. Examples of the adhesive used for bonding include PVA-based adhesives, urethane-based adhesives, and the like. Among them, PVA-based adhesives are more suitable.

The polarizing plate obtained as described above can be used as an LCD part after being adhered to a glass substrate after being coated with an acrylic-based adhesive. At the same time, it can also be laminated with retardation film, viewing angle enhancement film, and brightness enhancement film.

[Example]

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by these examples. In addition, the following Each measurement or evaluation method used in the following examples and comparative examples is given.

Primary structure of PVA

The primary structure of the PVA used in the following examples and comparative examples (PVA containing methylol in the examples or various modified PVA in the comparative examples) was analyzed by 270 MHz ¹ H-NMR. The solvent used in the ¹ H-NMR measurement was deuterated DMSO.

Swelling degree of the base film for optical film manufacturing

The raw material film for optical film production obtained in the following examples or comparative examples was cut into 1.5 g, and immersed in distilled water at 30 ° C. for 30 minutes. After being immersed for 30 minutes, the film was taken out, and the surface water was absorbed by a filter paper to obtain a mass "N". Then, the film was dried in a dryer at 105 ° 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 manufacturing was calculated according to the following formula (3).

Swelling (%) = 100 × N / M (3)

Extensibility of blank film for optical film manufacturing

From the central portion in the width direction of the blank film for manufacturing an optical film obtained in the following examples or comparative examples, a sample having a width of 5 cm × a length of 8 cm was cut so that a range of 5 cm × 5 cm in length could be uniaxially stretched. This sample was immersed in pure water at 30 ° C while being uniaxially extended up to 1.5 times in the longitudinal direction. Next, it was immersed in an aqueous solution (dyeing bath) (temperature: 30 ° C.) containing iodine and potassium iodide in a ratio of 0.03% by mass and 3.0% by mass for 60 seconds while performing uniaxial extension in the longitudinal direction by 1.6 times (2.4 times for the whole). ) To adsorb iodine. Next, it was immersed in an aqueous solution (crosslinking bath) containing boric acid and potassium iodide (temperature: 30 ° C.) at a ratio of 3% by mass and 3% by mass, and uniaxially extended 1.1 times in the longitudinal direction (2.6 times as a whole). ). Further, dipping It is stained with an aqueous solution (extension bath) containing boric acid and potassium iodide at a ratio of 4% by mass and 6% by mass, and uniaxially extended in the longitudinal direction until it breaks, so as to be equal to the length of the blank film for optical film manufacturing before stretching The ratio of the length at the time of breaking is regarded as the limit extension ratio. However, as for the temperature of the extension bath, the limit extension magnification is measured every 1 ° C change from an appropriate temperature, and the temperature at which the limit extension magnification is maximized is selected.

Optical properties of polarizing film (dichroic ratio)

(1) Measurement of transmittance Ts

From the central portion of the polarizing film obtained in the following examples or comparative examples, two 2 cm samples were taken along the length of the polarizing film, and a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) was used based on JIS. Z 8722 (Measurement method of object color). Correct the visibility of the visible light region of C light source and 2 ° visual field. For a piece of sample, measure the light transmittance and tilt -45 ° when tilted by + 45 ° from the longitudinal direction. The light transmittance at this time was calculated as their average Ts1 (%). The light transmittance at a tilt of + 45 ° and the light transmittance at a tilt of -45 ° were similarly measured for another sample, and their average Ts2 (%) was obtained. Ts1 and Ts2 are averaged according to the following formula (4), and this is taken as the transmittance Ts (%) of the polarizing film.

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

(2) Measurement of polarization degree V

In the same manner as in the case of "(1) Measurement of the transmittance Ts" described above, the light transmission when the two samples taken in the measurement of the transmittance Ts are overlapped so that their longitudinal directions are parallel is measured. Transmittance T // (%), so that The light transmittance T⊥ (%) when the longitudinal directions are overlapped so as to be orthogonal, and the degree of polarization V (%) is obtained by the following formula (5).

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

(3) Calculation of dichroism ratio at 44% transmittance

In each of the following examples and comparative examples, the concentration of iodine and the concentration of potassium iodide in the dyeing bath were changed 4 times in each of the ranges of 0.02 to 0.04% by mass and 2.0 to 4.0% by mass (but, the iodine concentration was set: The concentration of potassium iodide = 1: 100), and the same operation was performed to produce four polarizing films having different adsorption amounts of the dichroic pigments from the polarizing films produced in the respective examples or comparative examples. For each of the four polarizing films, the transmittance Ts (%) and the polarization degree V (%) were obtained by the above method, and according to the examples and comparative examples, the transmittance Ts (%) was taken as the horizontal axis, The degree of polarization V (%) is the vertical axis, and a total of 5 points including 1 point of the transmittance Ts (%) and the degree of polarization V (%) of the polarizing film obtained from each example or comparative example are also plotted. An approximate curve is obtained, and from this approximate curve, the polarization degree V ₄₄ (%) when the transmittance Ts (%) is 44% is obtained.

From the obtained polarization degree V ₄₄ (%), a dichroism ratio at a transmittance of 44% was obtained according to the following formula (6), and this was used as an index of polarization performance.

Transmittance of 44% when the dichroic ratio = log (44 / 100-44 / 100 × V 44/100) / log (44/100 + 44/100 × V 44/100) (6)

Hue (parallel b-value) of polarizing film

In the above-mentioned "optical characteristics of polarizing film (dichroic ratio)", when determining the polarization degree V of four polarizing films having different adsorption amounts of dichroic pigments, it is based on the transmittance T // ( %) And transmittance T⊥ (%) are measured during the measurement of Lab, and the b value during the measurement of the transmittance T // (%) is parallel to the b value. The b value at the time of measuring the ratio T⊥ (%) is an orthogonal b value. According to each embodiment and comparative example, the parallel b value is the horizontal axis and the orthogonal b value is the vertical axis. The parallel b value and the orthogonal b value of the polarizing film obtained from the respective embodiments or comparative examples are also included. A total of 5 points were drawn into a graph to obtain an approximate curve. From the approximate curve, a parallel b-value when the orthogonal b-value was -4 was obtained. In addition, the closer the parallel b value is to 0, the better the hue of the polarizing film.

[Example 1]

(1) 100 parts by mass of modified PVA is contained in the methylol-containing group shown in Table 1 obtained by saponifying a copolymer of vinyl acetate and 1,3-diacetoxy-2-methylenepropane Based PVA, 10 parts by mass of glycerin as a plasticizer, and 0.1 parts by mass of polyoxyethylene lauryl ether sodium sulfate as a surfactant, and a modified PVA containing 10% by mass of an aqueous solution, Used as a film-forming stock solution, by drying it on a metal roll at 80 ° C., and subjecting the obtained film to heat treatment in a hot-air dryer at a predetermined temperature for 1 minute to adjust the swelling degree to 200% to produce an optical thickness of 30 μm The raw material film for film production.

Using the obtained raw material film for optical film manufacture, the extensibility was evaluated by the method described above. The results are shown in Table 1.

(2) From the central portion in the width direction of the blank film for optical film manufacturing obtained in the above (1), a sample having a width of 5 cm × a length of 8 cm was cut so that a range of 5 cm × 5 cm in length could be uniaxially stretched. This sample was immersed in pure water at 30 ° C while being uniaxially extended up to 1.5 times in the longitudinal direction. Next, it was immersed in an aqueous solution (dyeing bath) (temperature: 30 ° C.) containing iodine and potassium iodide in a ratio of 0.03% by mass and 3.0% by mass for 60 seconds while performing uniaxial extension in the longitudinal direction by 1.6 times (2.4 times for the whole). ) And Iodine adsorption. Next, it was immersed in an aqueous solution (crosslinking bath) containing boric acid and potassium iodide (temperature: 30 ° C.) at a ratio of 3% by mass and 3% by mass, and uniaxially extended 1.1 times in the longitudinal direction (2.6 times as a whole). ). Furthermore, it was immersed in an aqueous solution (extension bath) containing boric acid and potassium iodide in the proportions of 4% by mass and 6% by mass (the extensibility of the raw material film for optical film production described above) so that the ultimate elongation ratio becomes (The highest temperature), and uniaxial stretching is performed in the length direction to a magnification that is 0.2 times lower than the limit stretching magnification. Thereafter, it was immersed in an aqueous solution (washing bath) (temperature: 30 ° C.) containing potassium iodide in a proportion of 3% by mass for 5 seconds, and finally dried at 60 ° C. for 4 minutes to prepare a polarizing film.

Using the obtained polarizing film, the optical characteristics (dichroic ratio) and hue (parallel b value) of the polarizing film were evaluated according to the methods described above. The results are shown in Table 1.

[Comparative Examples 1 to 3]

Except that they were used separately in Example 1: unmodified PVA shown in Table 1 (Comparative Example 1) obtained by saponifying a vinyl acetate homopolymer instead of modified PVA; as modified PVA, vinyl acetate was used. The modified PVA shown in Table 1 (Comparative Example 2) obtained by saponifying a copolymer of an ester and 3,4-diacetamido-1-butene; or, as a modified PVA, vinyl acetate and Itacone Except for the modified PVA (Comparative Example 3) shown in Table 1 obtained by saponification of an acid copolymer, a base film and a polarizing film for optical film production were produced in the same manner as in Example 1, and each measurement or evaluation was performed. The results are shown in Table 1.

[Examples 2 to 4]

Except that they were used separately in Example 1: As a modified PVA, the methylol-containing compounds shown in Table 1 were obtained by saponifying a copolymer of vinyl acetate and 1,3-diacetoxy-2-methylenepropane. Based PVA (Examples 2 and 3); or In order to modify PVA, a methylol-containing PVA shown in Table 1 obtained by saponifying a terpolymer of vinyl acetate, 1,3-diethylacetoxy-2-methylenepropane and ethylene (implementation) Except for Example 4), a blank film and a polarizing film for optical film production were produced in the same manner as in Example 1, and each measurement or evaluation was performed. The results are shown in Table 1.

From the above results, it is clear that the raw material films for optical film manufacturing of Examples 1 to 4 satisfying the requirements of the present invention are excellent in extensibility and can be manufactured with good productivity. Moreover, since the stretchability is high, the area of the obtained optical film can be enlarged, and a larger amount of optical film can be obtained. Furthermore, in addition to the above, it is known that according to the raw material films for optical film production of Examples 1 to 4 that satisfy the requirements of the present invention, it is easy to produce optical films having excellent optical characteristics and hue. Furthermore, in Example 4 using a methylol group-containing PVA further containing an ethylene unit, it is known that the extensibility can be further improved, and at the same time, the extensibility temperature can be increased, and an optical film can be produced with better productivity.

Claims (6)

A raw material film for manufacturing an optical film, which is a raw material film for manufacturing an optical film including a vinyl alcohol unit and a structural unit represented by the following formula (1) and a methylol-containing vinyl alcohol polymer, wherein The content ratio of the structural unit represented by formula (1) in the methylol-containing vinyl alcohol polymer is 0.1 mol% or more and less than 2 mol%: The raw material film for optical film manufacturing according to claim 1, wherein the methylol-containing vinyl alcohol-based polymer further includes an ethylene unit. The raw material film for optical film manufacturing according to claim 2, wherein the content of ethylene units in the methylol-containing vinyl alcohol-based polymer is 1 to 4 mole%. The raw material film for optical film manufacturing according to claim 1 or 2, wherein the saponification degree of the vinyl alcohol polymer containing methylol group is 95 mol% or more. The raw material film for optical film manufacturing according to claim 1 or 2 is a raw material film for polarizing film manufacturing. The manufacturing method of the optical film which has the process of uniaxially stretching using the raw material film for optical film manufacture as described in any one of Claims 1-5.