WO2016121507A1

WO2016121507A1 - Film

Info

Publication number: WO2016121507A1
Application number: PCT/JP2016/050967
Authority: WO
Inventors: 勝啓高藤; 磯▲ざき▼　孝徳; 亘大橋
Original assignee: 株式会社クラレ
Priority date: 2015-01-27
Filing date: 2016-01-14
Publication date: 2016-08-04
Also published as: CN107250180A; TWI741974B; JPWO2016121507A1; JP6776129B2; TW201634494A; KR102467101B1; KR20170108013A

Abstract

Provided are a film that makes it possible to easily produce an optical film having exceptional optical properties, durability, and reduced shrinkage, and a method for producing an optical film in which said film is used. A film containing a hydroxymethyl group-containing vinyl alcohol polymer having a 1,2-glycol bond content of 1.5 mol% or less, including vinyl alcohol units and the structural units shown by formula (1); and a method for producing an optical film having a step for uniaxial stretching using this film.

Description

the film

The present invention relates to a film useful as a raw film for producing an optical film such as a polarizing film, which contains a specific hydroxymethyl group-containing vinyl alcohol polymer having a 1,3-diol structure, and uses the same The present invention relates to a method for producing an optical film.

A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light. Many polarizing plates have a structure in which a protective film such as cellulose triacetate (TAC) film is bonded to the surface of the polarizing film in order to prevent the polarizing film from fading or to prevent the polarizing film from shrinking. As the polarizing film constituting the polarizing plate, a vinyl alcohol polymer film (hereinafter, “vinyl alcohol polymer” may be referred to as “PVA”) is uniaxially stretched into a matrix formed with an iodine dye (I ₃ ^- and I ₅ ^-, etc.) or a dichroic dye such as dichroic organic dyes has become mainstream those adsorbed.

LCDs have come to be used in a wide range of small devices such as calculators and watches, mobile phones, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, and measurement devices used indoors and outdoors. In recent years, particularly, reduction in thickness and weight has been demanded. Along with this, thinning of each member of the LCD has progressed, and there is concern about the deterioration of the function of preventing the fading of the polarizing film and preventing the shrinking of the polarizing film with the thinning of the protective film of the polarizing plate. Has been. Therefore, there is a demand for a polarizing film that maintains the conventional characteristics of high polarization and transparency and excellent optical properties, has low fading, excellent durability, and reduced shrinkage.

By the way, several raw film films for producing optical films containing modified PVA are 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 ω-hydroxy-α-olefin group is stretched and oriented. It is known that it has excellent processability and adsorption processability of dichroic substances, and exhibits good optical performance (see Patent Document 1 and the like). In addition, it is known that a specific optical PVA film containing a specific PVA containing a 1,2-glycol bond in the side chain is excellent in optical properties and stretchability (see Patent Document 2).

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

However, when a conventionally known raw film for producing an optical film containing modified PVA is used, there is room for improvement in that an optical film excellent in optical properties, durability performance and shrinkage reduction is obtained.

Therefore, an object of the present invention is to provide a film that can easily produce an optical film excellent in optical characteristics, durability, and shrinkage reduction, and a method for producing an optical film using the film.

As a result of extensive studies by the present inventors to achieve the above object, the main chain contains a specific structural unit having a 1,3-diol structure and the 1,2-glycol bond amount is in a specific range. According to the film containing hydroxymethyl group-containing PVA, it was found that the above-mentioned problems can be solved, and further studies were made based on the findings to complete the present invention.

That is, the present invention
[1] A film containing a vinyl alcohol unit and a hydroxymethyl group-containing PVA containing a structural unit represented by the following formula (1) and having a 1,2-glycol bond amount of 1.5 mol% or less;

[2] The film 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 film according to [1] or [2], wherein the hydroxymethyl group-containing PVA has a saponification degree of 95 mol% or more;
[4] The film according to any one of [1] to [3], which is a raw film for producing an optical film;
[5] The film according to [4], wherein the optical film is a polarizing film;
[6] A method for producing an optical film, comprising a step of uniaxially stretching using the film according to [4] or [5];
About.

According to the present invention, a film capable of easily producing an optical film excellent in optical properties, durability performance and shrinkage reduction, and a method for producing an optical film using the film are provided.

The film of the present invention contains a vinyl alcohol unit and a hydroxymethyl group-containing PVA containing a structural unit represented by the following formula (1) and having a 1,2-glycol bond amount of 1.5 mol% or less.

The film of the present invention has improved stretchability because the hydroxymethyl group-containing PVA contained therein contains a structural unit having a 1,3-diol structure represented by the above formula (1). According to this, an optical film having excellent optical properties can be easily produced. Moreover, it has the characteristic that the shrinkage force of an optical film reduces. Although the present invention is not limited in any way, the reason why the above-described advantages can be obtained is that the crystallinity is lowered by the structural unit represented by the formula (1) and the high based on the 1,3-diol structure. The influence of hydrogen bonding force is considered.

The content of the structural unit represented by the formula (1) in the hydroxymethyl group-containing PVA is not particularly limited, but is 0.1 to 2 when the number of moles of all structural units constituting the hydroxymethyl group-containing PVA is 100 mol%. It is preferably in the range of mol%, more preferably in the range of 0.2 to 1.9 mol%, still more preferably in the range of 0.3 to 1.8 mol%. When the content is 0.1 mol% or more, the stretchability of the film is further improved, and an optical film that is excellent by reducing the shrinkage force can be obtained. On the other hand, when the content is 2 mol% or less, dissolution of the film during the production of the optical film can be more effectively prevented, and an optical film excellent in optical properties can be obtained. In the present specification, the structural unit refers to a repeating unit constituting a polymer.

Further, when the 1,2-glycol bond amount of the hydroxymethyl group-containing PVA is 1.5 mol% or less, an optical film with less fading and excellent durability performance can be obtained. The 1,2-glycol bond amount is preferably 1.4 mol% or less, more preferably 1.2 mol% or less, and further preferably 1.0 mol% or less. The lower the 1,2-glycol bond amount, the better the durability of the resulting polarizing film.
Note that the modified PVA having a 1,2-glycol bond amount in the above range is a vinyl ester monomer of less than 50 ° C., preferably less than 40 ° C., more preferably less than 30 ° C., and even more preferably less than 20 ° C. Preferably, it can be easily produced by polymerization at a temperature of less than 5 ° C. From the viewpoint of the polymerization rate of the vinyl ester monomer, the lower limit of the industrially possible polymerization temperature is about −50 ° C. From this viewpoint, the lower limit of the 1,2-glycol bond amount of the hydroxymethyl group-containing PVA is About 0.5 mol% is the limit. The 1,2-glycol bond amount of the hydroxymethyl group-containing PVA can be determined by a known NMR measurement method.

The degree of polymerization of the hydroxymethyl group-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 2,000 to 4,000. More preferably, it is in the range. 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 an increase in manufacturing cost, poor process passability during film formation, and the like. In addition, the polymerization degree of the hydroxymethyl group-containing PVA in the present specification means an average polymerization degree measured according to the description of JIS K6726-1994.

The saponification degree of the hydroxymethyl group-containing PVA is preferably 95 mol% or more, more preferably 96 mol% or more from the viewpoint of water resistance of an optical film such as a polarizing film obtained by uniaxially stretching the film. Preferably, it is 98 mol% or more. In this specification, the degree of saponification of hydroxymethyl group-containing PVA is a structural unit (typical) of hydroxymethyl group-containing PVA that can be converted into vinyl alcohol units (—CH ₂ —CH (OH) —) by saponification. Is the ratio (mol%) of the number of moles of the vinyl alcohol unit to the total number of moles of the vinyl ester unit) and the vinyl alcohol unit. The degree of saponification can be measured according to the description of JIS K6726-1994, taking into consideration the amount of the structural unit represented by formula (1) and its derivatives.

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

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 partially have a branched or cyclic structure. Moreover, a part may be substituted with other functional groups. R is preferably an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, Examples thereof include a linear or branched alkyl group such as a pentyl group. Examples of the substituent that R may have include an alkoxy group, a halogen atom, and a hydroxyl group. A plurality of R may be the same or different from each other.

Examples of the unsaturated monomer represented by the formula (2) include 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyryloxy-2. -Methylenepropane and the like. Of these, 1,3-diacetoxy-2-methylenepropane is preferably used from the viewpoint of ease of production.

The unsaturated monomer represented by the formula (2) is a vinyl ester monomer compared with other allylic unsaturated monomers (for example, allyl glycidyl ether) generally used for modification of PVA. The copolymerization reaction proceeds easily. Therefore, there are few restrictions on the amount of modification and the degree of polymerization during polymerization, and a hydroxymethyl group-containing PVA having a high degree of modification and a high degree of 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 excellent in terms of environment and cost during industrial production. Yes.

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

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

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

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

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

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

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

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

Examples of the ethylenically unsaturated monomer include α-olefins such as ethylene, propylene, n-butene, isobutylene and 1-hexene; acrylic acid and salts thereof; unsaturated monomer having an acrylate group. Body; methacrylic acid and salts thereof; unsaturated monomer having methacrylic ester group; acrylamide; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and salts thereof Acrylamide derivatives such as acrylamidepropyldimethylamine and salts thereof (for example, quaternary salts); methacrylamide; N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propane sulfonic acid and salts thereof, methacrylamide propylene Methacrylamide derivatives such as dimethylamine and its salts (eg quaternary salts); methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether , Vinyl ethers such as stearyl vinyl ether and 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene chloride and fluoride Vinylidene halides such as vinylidene; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, allyl chloride; maleic acid, itaconic acid, fumaric acid, etc. An unsaturated dicarboxylic acid and a salt or ester thereof; vinylsilyl compounds such as vinyltrimethoxysilane; and isopropenyl acetate. Among these, since the stretchability is improved and the film can be stretched at a higher temperature, the occurrence of troubles such as breakage of the stretch during the production of the optical film is reduced, and the productivity of the optical film is further improved. preferable. When the hydroxymethyl group-containing PVA contains an ethylene unit, the content of the ethylene unit is 100 in terms of the number of moles of all structural units constituting the hydroxymethyl group-containing PVA from the viewpoints of stretchability and stretchable temperature as described above. The mol% is preferably 1 to 4 mol%, particularly preferably 2 to 3 mol%.

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

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

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

The film of the present invention further includes a filler, a processing stabilizer such as a copper compound, a weather resistance stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a flame retardant, and other heat. Additives such as plastic resins, lubricants, fragrances, defoamers, deodorants, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, fungicides, preservatives, crystallization rate retarders, It can mix | blend suitably as needed.

The proportion of the total of the hydroxymethyl group-containing PVA and the plasticizer in the film of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more based on the mass of the film, and 95% by mass. % Or more is more preferable.

The degree of swelling of the film 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%. When the degree of swelling is 160% or more, the crystallization can be prevented from proceeding extremely, and the film can be stably stretched to a higher magnification. On the other hand, when the degree of swelling is 240% or less, dissolution during stretching is suppressed, and stretching is possible even under higher temperature conditions. In this specification, the degree of swelling of the film is a value obtained by dividing the mass when the film is immersed in distilled water at 30 ° C. for 30 minutes by the mass after drying at 105 ° C. for 16 hours. It means percentage, and can be specifically measured by the method described later in Examples.

The thickness of the film of the present invention is not particularly limited, but is generally 1 to 100 μm, more preferably 5 to 75 μm, and particularly preferably about 10 to 60 μm. When the thickness is too thin, there is a tendency that stretching breakage is likely to occur during uniaxial stretching treatment for producing an optical film such as a polarizing film. Moreover, when the said thickness is too thick, at the time of the uniaxial stretching process for manufacturing an optical film, it will become easy to generate | occur | produce a stretching spot.

The width of the film of the present invention is not particularly limited, and can be determined according to the use of the optical film to be produced. In recent years, liquid crystal televisions and liquid crystal monitors have been increasing in screen size, so that the film width of 3 m or more is suitable for these applications. On the other hand, if the width of the film is too large, it is difficult to uniformly carry out uniaxial stretching per se when an optical film is produced with an apparatus that has been put into practical use. Therefore, the width of the film is preferably 7 m or less. .

The production method of the film of the present invention is not particularly limited, and a production method in which the thickness and width of the film after film formation are more uniform can be preferably employed. For example, the above-described hydroxymethyl group-containing PVA constituting the film And, if necessary, a film-forming stock solution in which one or more of the plasticizers, additives, and surfactants described later are dissolved in a liquid medium, and a hydroxymethyl group-containing PVA, In addition, if necessary, it is produced using a film-forming stock solution containing one or more of plasticizers, additives, surfactants, liquid media, etc., in which the hydroxymethyl group-containing PVA is melted. can do. When the film-forming stock solution contains at least one of a plasticizer, an additive, and a surfactant, it is preferable that these components are uniformly mixed.

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

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

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

As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate; a sulfuric acid ester type such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and a sulfonic acid type such as dodecylbenzene sulfonate are suitable.

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

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

When the film-forming stock solution contains a surfactant, the content thereof is preferably in the range of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the hydroxymethyl group-containing PVA contained in the film-forming stock solution. The content is more preferably in the range of 0.02 to 0.3 parts by mass, and particularly preferably in the range of 0.05 to 0.1 parts by mass. When the said content is 0.01 mass part or more, film forming property and peelability improve more. On the other hand, when the content is 0.5 parts by mass or less, it is possible to prevent the surfactant from bleeding out on the surface of the film to cause blocking and lowering the handleability.

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

As an example of a specific method for producing the film of the present invention, for example, a T-type slit die, a hopper plate, an I-die, a lip coater die or the like is used to rotate the above film forming stock solution on the most upstream side. Volatile from one surface of the film discharged or cast on the peripheral surface of the heated first roll (or belt) uniformly discharged or cast on the peripheral surface of the first roll (or belt) The ingredients are evaporated to dryness, followed by further drying on the circumference of one or more rotating heated rolls located downstream thereof, or by passing through a hot air drying apparatus for further drying. Thereafter, a method of winding with a winding device can be preferably employed industrially. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.

The use of the film of the present invention is not particularly limited. For example, a film for medicine packaging, a base film for hydraulic transfer, a base film for embroidery, a release film for molding artificial marble, a film for seed packaging, a film for filth-containing bag However, according to the film of the present invention, an optical film excellent in optical properties, durability, and shrinkage reduction can be easily produced, and thus an optical film is produced. It is preferable to use it as a raw film for the purpose (a raw film for producing an optical film). Examples of such an optical film include a polarizing film and a retardation film, and a polarizing film is preferable. Such an optical film can be produced, for example, by subjecting the film of the present invention to a treatment such as uniaxial stretching.

The method for producing a polarizing film using the film of the present invention is not particularly limited, and any method conventionally employed may be employed. As such a method, for example, dyeing and uniaxial stretching may be performed on the film of the present invention, or uniaxial stretching may be performed on the film of the present invention containing a dye. As a more specific method for producing a polarizing film, a method of subjecting the film of the present invention to swelling, dyeing, uniaxial stretching, and, if necessary, crosslinking treatment, fixing treatment, drying, heat treatment, etc. Is mentioned. In this case, the order of each treatment such as swelling, dyeing, crosslinking treatment, uniaxial stretching, and fixing treatment is not particularly limited, and one or two or more treatments can be performed simultaneously. Also, one or more of each process can be performed twice or more.

Swelling can be performed by immersing the film in water. The temperature of the 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 preferably in the range of 25 to 35 ° C. Further preferred. The time for immersion in water is preferably in the range of 0.1 to 5 minutes, for example, and more preferably in the range of 0.5 to 3 minutes. In addition, the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

Dyeing can be performed by bringing a dichroic dye into contact with the film. As the dichroic dye, an iodine dye is generally used. The dyeing time may be any stage before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. Dyeing is generally performed by immersing the film in a solution (particularly an aqueous solution) containing iodine-potassium iodide as a dyeing bath, and such a dyeing method is also preferably used in the present invention. The iodine concentration in the dyeing bath is preferably in the range of 0.01 to 0.5% by mass, and the potassium iodide concentration is preferably in the range of 0.01 to 10% by mass. The temperature of the dyeing bath is preferably 20 to 50 ° C., particularly 25 to 40 ° C.

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

Uniaxial stretching may be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution containing boric acid, or can be carried out in the dyeing bath described above or in a fixing treatment bath described later. In the case of the dry stretching method, the stretching may be performed at room temperature, may be performed while heating, or may be performed in the air using a film after water absorption. Among these, the wet stretching method is preferable, and uniaxial stretching is more preferable in an aqueous solution containing boric acid. The concentration of boric acid in the boric acid aqueous solution is preferably within the range of 0.5 to 6.0% by mass, more preferably within the range of 1.0 to 5.0% by mass, It is particularly preferably within the range of ˜4.0% by mass. Further, the aqueous boric acid solution may contain potassium iodide, and its concentration is preferably in the range of 0.01 to 10% by mass.
The stretching temperature in the uniaxial stretching is preferably in the range of 30 to 90 ° C, more preferably in the range of 40 to 80 ° C, and particularly preferably in the range of 50 to 70 ° C.
Further, the draw ratio in uniaxial stretching is preferably 6.8 times or more, more preferably 6.9 times or more, and 7.0 times or more from the viewpoint of the polarizing performance of the obtained polarizing film. Is particularly preferred. The upper limit of the draw ratio is not particularly limited, but the draw ratio is preferably 8 times or less.

There is no particular restriction on the direction of uniaxial stretching in the case of uniaxially stretching a long film, and uniaxial stretching or lateral uniaxial stretching in the long direction can be adopted, but a polarizing film excellent in polarizing performance can be obtained. Uniaxial stretching in the longitudinal direction is preferred. Uniaxial stretching in the longitudinal direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, lateral uniaxial stretching can be performed using a tenter type stretching machine.

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

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

The polarizing film obtained as described above is usually used as a polarizing plate by attaching an optically transparent protective film having mechanical strength to both sides or one side. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. Examples of the adhesive for bonding include PVA adhesives and urethane adhesives, among which PVA adhesives are suitable.

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

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, each measurement or evaluation method employ | adopted in the following example, the reference example, and the comparative example is shown below.

Primary structure of PVA The primary structure of PVA used in the following examples, reference examples and comparative examples (contents of structural units of modified species, 1,2-glycol bond amount and saponification degree) is 400 MHz ¹ H-NMR. And analyzed. Deuterated DMSO was used as a solvent for the ¹ H-NMR measurement.

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

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

Optical properties of polarizing film (dichroic ratio)
(1) Measurement of transmittance Ts Two 2 cm samples were taken in the length direction of the polarizing film from the central part of the polarizing film obtained in the following Examples, Reference Examples or Comparative Examples, and the spectrophotometer with integrating sphere Using a meter (“V7100” manufactured by JASCO Corporation), in accordance with JIS Z 8722 (measuring method of object color), the visibility correction in the visible light region of C light source and 2 ° field of view is performed, and one sample The light transmittance when tilted by + 45 ° with respect to the length direction and the light transmittance when tilted by −45 ° were measured, and the average value Ts1 (%) was obtained. Similarly, with respect to the other sample, the light transmittance when tilted by + 45 ° and the light transmittance when tilted by −45 ° were measured, and an average value Ts2 (%) thereof was obtained. Ts1 and Ts2 were averaged by the following formula (4) to obtain the transmittance Ts (%) of the polarizing film.
Ts = (Ts1 + Ts2) / 2 (4)

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

(3) Calculation of the dichroic ratio at a transmittance of 44% In each of the following Examples, Reference Examples and Comparative Examples, the iodine concentration in the dyeing bath was 0.02 to 0.04 mass% and the potassium iodide concentration Was changed four times within each range of 2.0 to 4.0% by mass (however, iodine concentration: potassium iodide concentration = 1: 100), and the same operation was performed. Four polarizing films having different dichroic dye adsorption amounts were produced from the polarizing films produced in Examples or Comparative Examples. The transmittance Ts (%) and the degree of polarization V (%) were determined for each of these four polarizing films by the method described above, and the transmittance Ts (%) was plotted on the horizontal axis for each example, reference example, and comparative example. In addition, a total of 5 including one point based on the transmittance Ts (%) and the degree of polarization V (%) of the polarizing film obtained in each example, reference example or comparative example, with the degree of polarization V (%) as the vertical axis. The points were plotted on a graph to obtain an approximate curve, and the degree of polarization V ₄₄ (%) when the transmittance Ts (%) was 44% was obtained from the approximate curve.
From the obtained degree of polarization V ₄₄ (%), the dichroic ratio at a transmittance of 44% was determined by the following formula (6) and used as an index of polarization performance.
Dichroic ratio when the transmittance 44% = log (44 / 100-44 / 100 × V 44/100) / log (44/100 + 44/100 × V 44/100) (6)

Durability of polarizing film Two polarizing films obtained in Examples, Reference Examples or Comparative Examples below were fixed to a metal frame, overlapped with crossed Nicols, and the initial absorbance (at 0 hours) (wavelength 610 nm). Value) was measured with a spectrophotometer. Further, the polarizing film fixed to the metal frame was stored for 8 hours in an atmosphere of 60 ° C. and 90% RH, and then superimposed on crossed Nicols, and the absorbance B (value at a wavelength of 610 nm) after 8 hours was measured with a spectrophotometer. It was measured. The value of absorbance B / absorbance A × 100 was defined as the residual rate (an index of color fading from the PVA-iodine complex).

A rectangular sample of 12 cm in the length direction of the polarizing film and 1.5 cm in the width direction was collected from the central portion of the polarizing film obtained in the examples, reference examples or comparative examples below the shrinkage force of the polarizing film. Humidity was adjusted for 18 hours under the conditions of 20 ° C. and 20% relative humidity. Next, this sample was fixed to an autograph “AG-X” manufactured by Shimadzu Corporation so that the length direction was fixed at 5 cm between chucks, and 1 mm / min under conditions of a temperature of 40 ° C. and a relative humidity of 5%. Stretching in the length direction at a speed, when the tension reaches 2N, the stretching is stopped and held, and in that state, the temperature is raised to 80 ° C., and the tension is measured after 4 hours. Power.

[Example 1]
(1) Hydroxymethyl group-containing PVA100 shown in Table 1 obtained by saponifying a copolymer obtained by copolymerizing vinyl acetate and 1,3-diacetoxy-2-methylenepropane at a polymerization temperature of 40 ° C. An aqueous solution containing 10 parts by mass of glycerin as a plasticizer and 0.1 parts by mass of sodium polyoxyethylene lauryl ether sulfate as a surfactant and having a hydroxymethyl group-containing PVA content of 10% by mass The film was dried on a metal roll at 80 ° C., and the resulting film was heat-treated at a predetermined temperature for 1 minute in a hot air dryer to adjust the degree of swelling to 200%, and the thickness was 30 μm. The film was manufactured.
Using the obtained film, stretchability was evaluated by the method described above. The results are shown in Table 1.

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

[Example 2, Reference Example 1, Comparative Examples 1 and 2]
As PVA, hydroxymethyl group-containing PVA shown in Table 1 obtained by saponifying a copolymer obtained by copolymerizing vinyl acetate and 1,3-diacetoxy-2-methylenepropane at a polymerization temperature of 20 ° C. Example 2 Hydroxymethyl shown in Table 1 obtained by saponifying a copolymer obtained by copolymerizing vinyl acetate and 1,3-diacetoxy-2-methylenepropane at a polymerization temperature of 60 ° C. Group-containing PVA (Reference Example 1): Unmodified PVA shown in Table 1 obtained by saponifying a polymer obtained by polymerizing vinyl acetate at a polymerization temperature of 60 ° C. (Comparative Example 1); Polymerizing vinyl acetate A film and a film were obtained in the same manner as in Example 1 except that unmodified PVA (Comparative Example 2) shown in Table 1 obtained by saponifying a polymer obtained by polymerization at a temperature of 40 ° C. was used. It manufactures polarizing film were carried each measured or evaluated.
The results are shown in Table 1.

As is clear from the above results, it can be seen that according to the films of Examples 1 and 2 satisfying the regulations of the present invention, an optical film excellent in optical properties, durability performance and shrinkage reduction can be easily produced.

Claims

A film comprising a vinyl alcohol polymer containing a hydroxymethyl group and containing a vinyl alcohol unit and a structural unit represented by the following formula (1) and having a 1,2-glycol bond amount of 1.5 mol% or less.
The film 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%.
The film according to claim 1 or 2, wherein the hydroxymethyl group-containing vinyl alcohol polymer has a saponification degree of 95 mol% or more.
The film according to any one of claims 1 to 3, which is a raw film for producing an optical film.
The film according to claim 4, wherein the optical film is a polarizing film.
The manufacturing method of an optical film which has the process of carrying out uniaxial stretching using the film of Claim 4 or 5.