Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/20—Carboxylic acid amides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
  • C08L29/02—Homopolymers or copolymers of unsaturated alcohols
  • C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L71/00—Compositions of polyethers obtained by reactions forming an ether link in the main chain; Compositions of derivatives of such polymers
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
  • C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
  • C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids

Definitions

• the present invention relates to a polyvinyl alcohol film containing polyvinyl alcohol (A), a nonionic surfactant (B) and an anionic surfactant (C), and a method for producing a polarizing film using the same.
• Polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) film is used for various purposes by utilizing its unique properties such as transparency, optical properties, mechanical strength, and water solubility.
• a PVA film is used as a raw material (raw film) for manufacturing a polarizing film that constitutes a polarizing plate that is a basic component of a liquid crystal display (LCD) by utilizing its excellent optical characteristics.
• Raw film raw material
• polarizing film that constitutes a polarizing plate that is a basic component of a liquid crystal display (LCD) by utilizing its excellent optical characteristics.
• LCD liquid crystal display
• Applications are expanding.
• the polarizing plate for LCD is required to have high optical performance, and the polarizing film which is a component thereof is also required to have high optical performance.
• the polarizing plate is generally manufactured by subjecting a raw PVA film to dyeing, uniaxial stretching, and if necessary, fixing treatment with a boron compound or the like to produce a polarizing film, and then producing cellulose triacetate on the surface of the polarizing film. It is manufactured by laminating a protective film such as a (TAC) film. Then, the original PVA film is generally produced by a method of drying an undiluted film-forming solution containing PVA, such as a cast film-forming method.
• TAC protective film
• Patent Document 1 a PVA resin aqueous solution containing polyoxyethylene laurylamine having a chain number of 2 as a surfactant is prepared, and the PVA resin aqueous solution is cast by contacting it with a drum type roll for a contact time of 30 to 120 seconds. It is described that a PVA film having a water content of 5% by weight or less was obtained by forming a film by the method and setting the evaporation rate of water in the PVA aqueous solution to 15 to 30% by weight/min. According to this, it is said that it is possible to obtain a PVA film having excellent transportability and no optical defects.
• Patent Document 2 PVA resin, sodium dodecyl sulfate as a sulfate ester type anionic surfactant (a), polyoxyethylene dodecyl ether as an ether type nonionic surfactant (b), and a nitrogen-containing nonion.
• a PVA film containing lauric acid diethanolamide as the system surfactant (c) is described. According to this, it is said that it has excellent optical characteristics without optical stripes, optical color unevenness, and the like, and can exert an effect excellent in blocking resistance.
• Patent Document 3 a PVA resin, a polyoxyethylene dodecyl ether as an ether type nonionic surfactant (a), and a polyoxyethylene dodecylamine as two types of nitrogen-containing nonionic surfactants (b) are disclosed.
• PVA films containing lauric acid diethanolamide are described. According to this, it is said that it has excellent optical characteristics such as optical streaks, and can exhibit an excellent blocking resistance.
• the secondary amide type nonionic surfactant has excellent heat resistance as compared with the tertiary amide type nonionic surfactant. That is, it is preferable to use the secondary amide type nonionic surfactant from the viewpoints of economy and productivity during the production of the PVA film.
• the secondary amide type nonionic surfactant is used alone, in the resulting PVA film, the number of aggregates of the active agent is large, the haze value is high, and optical defects occur. The inventors have confirmed.
• the present invention has a small number of activator aggregates, a low haze value, low optical defects, and stretching even when a secondary amide type nonionic surfactant having high heat resistance is used.
• An object of the present invention is to provide a PVA film having a high magnification and a good polarization performance when processed into a polarizing film, and a method for producing a polarizing film using the PVA film.
• the above problem is a polyvinyl alcohol film containing polyvinyl alcohol (A), a nonionic surfactant (B) and an anionic surfactant (C),
• the nonionic surfactant (B) is a secondary amide type aliphatic alkanolamide represented by the following formula (I),
• the content of the nonionic surfactant (B) is 0.01 to 0.12 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A),
• This is solved by providing a polyvinyl alcohol film in which the content of the anionic surfactant (C) is 0.01 to 0.24 parts by mass based on 100 parts by mass of the polyvinyl alcohol (A).
• R is an alkyl group having 8 to 18 carbon atoms, and the number of polyoxyethylene chains (n) is 2 to 10].
• the total content (B+C) of the nonionic surfactant (B) and the anionic surfactant (C) is 0.05 to 0.24 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A). Is preferred.
• the content mass ratio (B:C) of the nonionic surfactant (B) and the anionic surfactant (C) is preferably 20:80 to 80:20.
• the film width is preferably 1.5 m or more. It is also preferable that the length of the film is 3000 m or more. It is also preferable that the film thickness is 10 to 70 ⁇ m.
• the above problem can also be solved by providing a method for manufacturing a polarizing film, which has a step of dyeing and a step of stretching the polyvinyl alcohol film.
• the above-mentioned problem is a method for producing a polyvinyl alcohol film containing a polyvinyl alcohol (A), a nonionic surfactant (B) and an anionic surfactant (C), A step of blending polyvinyl alcohol (A), a nonionic surfactant (B) and an anionic surfactant (C) to prepare a stock solution for film formation; And a step of forming a film using the film forming stock solution,
• the nonionic surfactant (B) is a secondary amide type aliphatic alkanolamide represented by the following formula (I),
• the amount of the nonionic surfactant (B) in the stock solution for film formation is 0.01 to 0.12 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A), It is also solved by providing a production method in which the amount of the anionic surfactant (C) in the stock solution for film formation is 0.01 to 0.24 parts by mass with respect to 100 parts by mass of the polyvinyl
• R is an alkyl group having 8 to 18 carbon atoms, and the number of polyoxyethylene chains (n) is 2 to 10].
• the PVA film of the present invention has a small number of activator aggregates, a low haze value, few optical defects, and a high draw ratio. Therefore, by using the PVA film as an original fabric, a polarizing film having good optical performance can be obtained.
• the nonionic surfactant (B) is a secondary amide type having high heat resistance, it is excellent in economic efficiency and productivity during PVA film production.
• the PVA film of the present invention comprises a polyvinyl alcohol (A) (hereinafter sometimes abbreviated as PVA (A)), a nonionic surfactant (B) represented by the following formula (I) and an anionic surfactant ( C) is contained.
• A polyvinyl alcohol
• B nonionic surfactant
• C anionic surfactant
• R is an alkyl group having 8 to 18 carbon atoms, and the number of polyoxyethylene chains (n) is 2 to 10].
• the nonionic surfactant (B) represented by the above formula (I) and the anionic surfactant (C) are used in combination with PVA (A) in a predetermined content. is important.
• the nonionic surfactant (B) represented by the above formula (I) is used alone with respect to PVA (A)
• the present inventors have a large number of surfactant aggregates and a high haze value. We have confirmed that optical defects will occur.
• the present inventors have found that when an anionic surfactant (C) is used alone for PVA (A), the ability to reduce the surface tension is insufficient and the process passability deteriorates, and the PVA film It has been confirmed that optical defects occur in the.
• the nonionic surfactant (B) represented by the above formula (I) and the anionic surfactant (C) are used in combination with PVA (A) at a predetermined content to obtain an active agent. It is possible to obtain a PVA film having a small number of aggregates, a low haze value, few optical defects, a high stretching ratio, and good polarizing performance when processed into a polarizing film.
• the nonionic surfactant (B) is a secondary amide type having high heat resistance, it is excellent in economic efficiency and productivity during PVA film production.
• the nonionic surfactant (B) used in the present invention is a secondary amide type aliphatic alkanolamide represented by the above formula (I).
• a secondary amide type aliphatic alkanolamide represented by the above formula (I)
• a PVA film having a small number of activator aggregates and a low haze value and high film surface quality can be continuously produced. can do.
• the secondary amide type aliphatic alkanolamide represented by the above formula (I) has a great advantage as the nonionic surfactant (B).
• PVA (A) As the PVA (A), a product produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester can be used.
• the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate and the like. These may be used alone or in combination of two or more, but the former is preferred.
• Vinyl acetate is preferable as the vinyl ester from the viewpoints of availability, cost, productivity of PVA (A), and the like.
• vinyl ester examples include, for example, ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene, and isobutene; acrylic acid or salts thereof; methyl acrylate, ethyl acrylate, acrylic acid.
• Acrylic esters such as n-propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacryl Acids or salts thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate.
• Methacrylic acid esters such as dodecyl methacrylate, octadecyl methacrylate, etc.; acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N,N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid or its salt, acrylamide propyl dimethyl amine or An acrylamide derivative such as a salt thereof, N-methylolacrylamide or a derivative thereof; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid or a salt thereof, methacrylamidepropyldimethylamine or a salt thereof, N- Methacrylic amide derivatives such as methylol methacrylamide or derivatives thereof; N-vinyl amides such as N-vinyl formamide, N-vinyl acetamide, N-vinyl pyrrolidone; methyl vinyl ether
• These other monomers may be used alone or in combination of two or more. Among them, ethylene and olefins having 3 to 30 carbon atoms are preferable as the other monomer, and ethylene is more preferable.
• the proportion of structural units derived from the other monomer in the vinyl ester polymer is not particularly limited, but is 15 mol% or less based on the number of moles of all structural units constituting the vinyl ester polymer. It is preferably 5 mol% or less, and more preferably 5 mol% or less.
• the degree of polymerization of PVA (A) is not necessarily limited, but it is preferably 200 or more, more preferably 300 or more, and further preferably 400 or more because the film strength tends to decrease as the degree of polymerization decreases. It is particularly preferably 500 or more. Further, if the degree of polymerization is too high, the viscosity of the aqueous solution of PVA (A) or the melted PVA (A) tends to be high, and film formation tends to be difficult, so 10,000 or less is preferable, and more preferable. Is 9000 or less, more preferably 8,000 or less, and particularly preferably 7,000 or less.
• the degree of polymerization of PVA (A) means the average degree of polymerization measured according to the description of JIS K6726-1994.
• PVA (A) is re-saponified and purified, and then measured in water at 30°C.
• the intrinsic viscosity [ ⁇ ] (unit: deciliter/g) is calculated by the following formula.
• Degree of polymerization ([ ⁇ ] ⁇ 10 4 /8.29) (1/0.62)
• the degree of saponification of PVA (A) is not particularly limited and, for example, 60 mol% or more of PVA (A) can be used. However, from the viewpoint of using it as a raw film for producing an optical film such as a polarizing film, PVA The degree of saponification of (A) is preferably 95 mol% or more, more preferably 98 mol% or more, still more preferably 99 mol% or more.
• the degree of saponification of PVA (A) means the total number of moles of structural units (typically vinyl ester monomer units) and vinyl alcohol units which PVA (A) can convert into vinyl alcohol units by saponification. In contrast, the ratio (mol %) occupied by the number of moles of the vinyl alcohol unit.
• the degree of saponification of PVA (A) can be measured according to the description of JIS K6726-1994.
• PVA (A) one type of PVA may be used alone, or two or more types of PVA having different degrees of polymerization, degree of saponification, degree of modification and the like may be used in combination.
• the PVA film has an acidic functional group such as a carboxyl group or a sulfonic acid group; a PVA having an acid anhydride group; a PVA having a basic functional group such as an amino group;
• PVA having a functional group that promotes the above is contained, the secondary processability of the PVA film may be deteriorated due to a crosslinking reaction between PVA molecules.
• PVA (A) having an acidic functional group PVA having an acid anhydride group
• basic The content of PVA having a functional group and the content of these neutralized products are each preferably 0.1% by mass or less, and more preferably not contained.
• the content of PVA (A) in the PVA film is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 85% by mass or more.
• Nonionic surfactant (B) is a secondary amide type aliphatic alkanolamide represented by the following formula (I).
• R is an alkyl group having 8 to 18 carbon atoms, and the number of polyoxyethylene chains (n) is 2 to 10].
• R is an alkyl group having 8 to 18 carbon atoms.
• the alkyl group may be linear or branched, but is preferably linear.
• the carbon number (alkyl chain length) of R is preferably 9 or more, and more preferably 10 or more.
• the carbon number (alkyl chain length) of R exceeds 18, the number of activator aggregates in the PVA film increases and the haze value increases.
• the carbon number (alkyl chain length) of R is preferably 15 or less, and more preferably 13 or less.
• the number of polyoxyethylene chains (n) is 2-10. By setting the number of polyoxyethylene chains (n) in this range, the formation of an active agent aggregate in the PVA film is suppressed when used in combination with the anionic surfactant (C) described later.
• the number of polyoxyethylene chains (n) is less than 2, problems occur that the number of activator aggregates in the PVA film increases and the haze value increases.
• the polyoxyethylene chain number (n) is preferably 4 or more.
• the number of polyoxyethylene chains (n) exceeds 10, many optical defects occur in the PVA film.
• the polyoxyethylene chain number (n) is preferably 8 or less.
• the content of the nonionic surfactant (B) represented by the above formula (I) is 0.01 to 0.12 parts by mass with respect to 100 parts by mass of PVA (A).
• the content of the nonionic surfactant (B) is preferably 0.02 parts by mass or more.
• the content of the nonionic surfactant (B) exceeds 0.12 parts by mass, there arise problems that the number of activator aggregates in the PVA film increases and the haze value increases.
• the content of the nonionic surfactant (B) is preferably 0.1 part by mass or less, more preferably 0.08 part by mass or less, and further preferably 0.06 part by mass or less. ..
• the nonionic surfactant (B) used in the present invention may be used alone or in combination of two or more.
• the content of the anionic surfactant (C) is 0.01 to 0.24 parts by mass with respect to 100 parts by mass of PVA (A).
• the content of the anionic surfactant (C) is preferably 0.02 parts by mass or more, and more preferably 0.03 parts by mass or more.
• the content of the anionic surfactant (C) is preferably 0.18 parts by mass or less, more preferably 0.16 parts by mass or less, and further preferably 0.14 parts by mass or less. , 0.12 parts by mass or less is particularly preferable.
• the anionic surfactant (C) is not particularly limited, but it is preferably at least one selected from the group consisting of sulfate ester type and sulfonate type.
• sulfate ester salt type examples include sodium alkyl sulfate, potassium alkyl sulfate, ammonium alkyl sulfate, triethanolamine alkyl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxypropylene alkyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, and the like. Is mentioned.
• the alkyl is preferably an alkyl having 8 to 20 carbons, and more preferably an alkyl having 10 to 16 carbons.
• Examples of the sulfonate type include sodium alkylsulfonate, potassium alkylsulfonate, ammonium alkylsulfonate, triethanolamine alkylsulfonate, sodium alkylbenzenesulfonate, disodium dodecyldiphenyl ether disulfonate, sodium alkylnaphthalenesulfonate, and alkylsulfosuccinate. Examples thereof include disodium acid salt and disodium polyoxyethylene alkyl sulfosuccinate.
• the alkyl is preferably an alkyl having 8 to 20 carbons, and more preferably an alkyl having 10 to 16 carbons.
• the anionic surfactant (C) is preferably a sulfate ester type from the viewpoint of the ability to reduce the surface tension and the process passability.
• the total content (B+C) of the nonionic surfactant (B) represented by the formula (I) and the anionic surfactant (C) is 100 parts by mass of PVA (A), It is preferably 0.05 to 0.24 parts by mass.
• the total content (B+C) is more preferably 0.06 parts by mass or more.
• the total content (B+C) is more preferably 0.22 parts by mass or less, further preferably 0.2 parts by mass or less, and particularly preferably 0.15 parts by mass or less.
• the content mass ratio (B:C) of the nonionic surfactant (B) represented by the above formula (I) and the anionic surfactant (C) is 20:80 to 80:20.
• the content mass ratio (B:C) is less than 20:80, many optical defects may occur in the PVA film.
• the content mass ratio (B:C) is more preferably 25:75 or more, further preferably 30:70 or more.
• the content mass ratio (B:C) is more than 80:20, problems such as a large number of activator aggregates in the PVA film and a high haze value may occur.
• the critical draw ratio may decrease.
• the content mass ratio (B:C) is more preferably 75:25 or less, and further preferably 70:30 or less.
• the PVA film of the present invention preferably contains a plasticizer.
• plasticizers include polyhydric alcohols, and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane. These may use only 1 type of plasticizer, and may use 2 or more types of plasticizers together. Among them, ethylene glycol or glycerin is preferable from the viewpoint of compatibility with PVA (A) and availability.
• the content of the plasticizer is preferably in the range of 1 to 30 parts by mass with respect to 100 parts by mass of PVA (A).
• the content of the plasticizer is 1 part by mass or more, problems are unlikely to occur in mechanical properties such as impact strength and process passability during secondary processing.
• the content of the plasticizer is 30 parts by mass or less, the film becomes moderately flexible and the handleability is improved.
• the PVA film of the present invention may further contain components other than PVA, a surfactant and a plasticizer, if necessary.
• components other than PVA include water, antioxidants, ultraviolet absorbers, lubricants, colorants, fillers (inorganic particles/starch, etc.), preservatives, antifungal agents, and components other than the above-mentioned components. Examples thereof include polymer compounds.
• the content of other components in the PVA film is preferably 10% by mass or less.
• the width of the PVA film of the present invention there is no particular limitation on the width of the PVA film of the present invention. Since a polarizing film having a wide width is required in recent years, the width is preferably 1.5 m or more. Further, if the width of the PVA film is too wide, the manufacturing cost of the film forming apparatus for forming the PVA film increases, and further, when the optical film is manufactured by a practically used manufacturing apparatus, it is uniform. The width of the PVA film is usually 7.5 m or less because it may be difficult to stretch the PVA film.
• the shape of the PVA film of the present invention is not particularly limited, but it is long because of its ability to continuously and smoothly produce a more uniform PVA film, and continuous use when producing an optical film or the like. It is preferably a full length film.
• the length of the long film (length in the flow direction) is not particularly limited and can be set as appropriate.
• the length of the film is preferably 3000 m or more.
• the length of the film is preferably 30,000 m or less.
• a long film is preferably wound into a core to form a film roll.
• the thickness of the PVA film of the present invention is not particularly limited and can be set appropriately. From the viewpoint of use as a raw film for producing an optical film such as a polarizing film, the thickness of the film is preferably 10 to 70 ⁇ m. In addition, the thickness of the PVA film can be obtained as an average value of values measured at arbitrary 10 places.
• the haze of the PVA film of the present invention and the number of activator aggregates are measured by the methods described in the examples below.
• the value of such haze is preferably 0.5 or less, and more preferably 0.4 or less.
• the number of such activator aggregates is preferably 550 or less, more preferably 420 or less, and further preferably 300 or less.
• the method for producing the PVA film of the present invention is not particularly limited, but a suitable production method is a polyvinyl alcohol film containing polyvinyl alcohol (A), a nonionic surfactant (B) and an anionic surfactant (C).
• a method of manufacturing comprising the steps of preparing polyvinyl alcohol (A), a nonionic surfactant (B) and an anionic surfactant (C) to prepare a stock solution for film formation, and a process for producing the stock solution using the film.
• a nonionic surfactant (B) is a secondary amide type aliphatic alkanolamide represented by the formula (I), and the nonionic surfactant (B) in the stock solution for film formation is included.
• a liquid medium may be further added in the step of preparing the film-forming stock solution.
• the liquid medium at this time include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, Examples thereof include diethylenetriamine, and one or more of these can be used. Among them, water is preferable from the viewpoint of low environmental load and recoverability.
• a method for producing a PVA film of the present invention for example, PVA (A), a nonionic surfactant (B) represented by the above formula (I), an anionic surfactant (C), a liquid medium, and if necessary,
• a known method such as a casting film forming method or a melt extrusion film forming method can be adopted by using a film forming solution containing the above-mentioned plasticizer and other components.
• the film-forming stock solution may be PVA (A) dissolved in a liquid medium or may be PVA (A) melted.
• the volatile content ratio of the stock solution for film formation (content ratio of volatile components such as liquid medium removed by volatilization or evaporation during film formation in the stock solution for film formation) varies depending on the film forming method, film forming conditions, etc. It is preferably in the range of 90% by mass, more preferably in the range of 55 to 80% by mass.
• the volatile matter content of the film-forming stock solution is 50% by mass or more, the viscosity of the film-forming stock solution does not become too high, and film formation is facilitated.
• the volatile content of the film-forming stock solution is 90% by mass or less, the thickness uniformity of the obtained PVA film is improved without the viscosity of the film-forming stock solution becoming too low.
• the blending amount of the nonionic surfactant (B) in the stock solution for film formation is preferably 0.01 to 0.12 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A).
• the blending amount of the nonionic surfactant (B) is more preferably 0.02 part by mass or more.
• the blending amount of the nonionic surfactant (B) exceeds 0.12 parts by mass, there arises a problem that the number of activator aggregates in the obtained PVA film increases and the haze value increases. ..
• the blending amount of the nonionic surfactant (B) is more preferably 0.1 part by mass or less, further preferably 0.08 part by mass or less, and particularly preferably 0.06 part by mass or less. preferable.
• the nonionic surfactant (B) used in the present invention may be used alone or in combination of two or more.
• the blending amount of the anionic surfactant (C) in the stock solution for film formation is preferably 0.01 to 0.24 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A).
• the compounding amount of the anionic surfactant (C) is less than 0.01 part by mass, there arises a problem that the number of activator aggregates in the obtained PVA film increases and the haze value increases. In addition, the critical stretch ratio of the PVA film obtained decreases.
• the content of the anionic surfactant (C) is more preferably 0.02 part by mass or more, further preferably 0.03 part by mass or more.
• the compounding amount of the anionic surfactant (C) exceeds 0.24 parts by mass, not only the number of activator aggregates in the obtained PVA film increases but also bubbles are mixed in the PVA film. May occur.
• the content of the anionic surfactant (C) is more preferably 0.18 parts by mass or less, further preferably 0.16 parts by mass or less, and particularly preferably 0.14 parts by mass or less. It is most preferably 0.12 parts by mass or less.
• the PVA film of the present invention is suitably produced by a casting film forming method or a melt extrusion film forming method using the above film forming solution.
• the specific manufacturing method at this time is not particularly limited, and for example, it is obtained by casting or discharging the film-forming stock solution in a film form on a support such as a drum or a belt, and drying on the support. You can If necessary, the obtained film may be further dried by a drying roll or a hot air drying device, may be heat-treated by a heat treatment device, or may be conditioned by a humidity control device.
• the manufactured PVA film is preferably wound into a core to form a film roll. Further, both ends in the width direction of the manufactured PVA film may be cut off.
• the PVA film of the present invention can be suitably used as a raw film for producing a polarizing film, a retardation film, a special light condensing film and the like. According to the present invention, a PVA film having high light transmittance and high quality can be obtained. Therefore, the optical PVA film is a preferred embodiment of the present invention.
• a preferred embodiment of the present invention is a method for producing a polarizing film, which has a step of dyeing the PVA film and a step of stretching.
• the manufacturing method may further include a fixing treatment step, a drying treatment step, a heat treatment step, and the like.
• the order of dyeing and stretching is not particularly limited, and the dyeing treatment may be performed before the stretching treatment, the dyeing treatment may be performed simultaneously with the stretching treatment, or the dyeing treatment may be performed after the stretching treatment. .. Further, the steps such as stretching and dyeing may be repeated multiple times. In particular, it is preferable to divide the stretching into two or more stages because uniform stretching is facilitated.
• Dyes used for dyeing PVA films include iodine or dichroic organic dyes (for example, DirectBlack 17, 19, 154; DirectBrown 44, 106, 195, 210, 223; DirectRed 2, 23, 28, 31, 37, 39). , 79, 81, 240, 242, 247; DirectBlue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; DirectViolet 9, 12, 51, 98; DirectGreen 1, 85; Direct Yellow 8, 12, 44, 86, 87; dichroic dyes such as Direct Orange 26, 39, 106, 107) and the like can be used. These dyes can be used alone or in combination of two or more. Dyeing can usually be carried out by immersing the PVA film in a solution containing the above dye, but the processing conditions and processing method are not particularly limited.
• the method for stretching the PVA film there are a uniaxial stretching method and a biaxial stretching method, and the former is preferable.
• the uniaxial stretching for stretching the PVA film in the machine direction (MD) or the like may be carried out by either a wet stretching method or a dry heat stretching method, but from the viewpoint of the performance and the stability of the quality of the polarizing film obtained, the wet stretching method is used. Is preferred.
• the wet stretching method include a method in which a PVA film is stretched in pure water, an aqueous solution containing various components such as additives and water-soluble organic solvents, or an aqueous dispersion liquid in which various components are dispersed.
• the uniaxial stretching method by the wet stretching method include a method of uniaxially stretching in warm water containing boric acid, a method of uniaxially stretching in a solution containing the dye or in a fixing treatment bath described below.
• the PVA film after absorbing water may be uniaxially stretched in the air, or may be uniaxially stretched by another method.
• the stretching temperature for uniaxial stretching is not particularly limited, but for wet stretching, a temperature in the range of preferably 20 to 90°C, more preferably 25 to 70°C, further preferably 30 to 65°C is adopted and dry In the case of hot stretching, a temperature within the range of 50 to 180° C. is preferably adopted.
• the stretching ratio of the uniaxial stretching treatment is preferably as much as possible until just before the film is cut from the viewpoint of polarization performance, and specifically, it is 4 times or more. Is more preferable, 5 times or more is more preferable, and 5.5 times or more is still more preferable.
• the upper limit of the stretching ratio is not particularly limited as long as the film is not broken, but it is preferably 8.0 times or less in order to perform uniform stretching.
• a fixing treatment in order to strengthen the adsorption of the dye on the uniaxially stretched PVA film.
• a method of immersing the PVA film in a treatment bath to which general boric acid and/or a boron compound is added can be adopted. At that time, if necessary, an iodine compound may be added to the treatment bath.
• the PVA film that has been uniaxially stretched or uniaxially stretched and fixed is then subjected to a drying treatment or a heat treatment.
• the temperature of the drying treatment or heat treatment is preferably 30 to 150°C, and particularly preferably 50 to 140°C. If the temperature is too low, the dimensional stability of the polarizing film obtained tends to deteriorate. On the other hand, if the temperature is too high, the polarization performance is likely to deteriorate due to decomposition of the dye.
• a protective film that is optically transparent and has mechanical strength can be attached to both sides or one side of the polarizing film obtained as described above to form a polarizing plate.
• a cellulose triacetate (TAC) film, an acetic acid/cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like is used as the protective film.
• a PVA-based adhesive or a urethane-based adhesive is generally used, and among them, the PVA-based adhesive is preferably used.
• the polarizing plate obtained as described above can be used as a component of a liquid crystal display device after being coated with an adhesive such as an acrylic resin and then attached to a glass substrate.
• an adhesive such as an acrylic resin
• a retardation film, a viewing angle improving film, a brightness improving film and the like may be attached simultaneously.
• Heat resistance of nonionic surfactant (B) A region of 10 m from the surface side of the PVA film roll to be measured was cut out, and a sample piece of MD 100 mm ⁇ TD 100 mm (thickness 60 ⁇ m) was taken from an arbitrary position. The collected sample was pretreated under the following conditions.
• Pretreatment condition 1. Precisely weigh 0.3 g of sample into a 50 ml sample tube. 2. Add 15 ml of HFIP (hexafluoroisopropanol) and dissolve with stirring at 50°C. 3. After dissolution, the mixture is cooled to room temperature, dropped into 60 ml of methanol (room temperature, with stirring), and reprecipitated. 4. Filter with a cotton plug to remove the precipitate. 5. The filtrate is concentrated with an evaporator (40° C.). 6. After concentration, the volume was adjusted to 2 ml with methanol to obtain an analytical sample.
• HFIP hexafluoroisopropanol
• the pretreated sample is quantified by HPLC to determine the retention rate of the nonionic surfactant (B) (content of nonionic surfactant in film/content of nonionic surfactant compounded during film production) It was HPLC was performed under the following conditions.
• Method for measuring the number of activator aggregates A region of 10 m from the surface side of the PVA film roll to be measured was cut out, and a sample piece of MD50 mm ⁇ TD50 mm (thickness 60 ⁇ m) was collected from an arbitrary position. Images of the collected samples were taken at positions at intervals of about 1 ⁇ m in the film thickness direction using a microscope VHX6000 (magnification: 1000) manufactured by Keyence Corporation, and the number of activator aggregates reflected in the taken images was counted. ..
• a sample having a size of 100 mm MD ⁇ 50 mm TD was sampled from a PVA film roll to be measured, and a marked line having a length of 50 mm was written in the center of the sample.
• Four samples with marked lines were attached to a stretching jig, and while being immersed in water at a temperature of 30°C for 1 minute, the sample was uniaxially 2.0 times its original length in the length direction (MD). It was stretched (first stage stretching). The sample was then immersed for 2 minutes in the dyeing bath at a temperature of 32° C. containing iodine in a concentration of 0.02 to 0.05% by mass and potassium iodide in a concentration of 1.0% by mass. Uniaxially stretched (2nd stage stretching) in the length direction (MD) up to 2.5 times.
• the sample was lengthwise (MD) up to 3.6 times the original length. Uniaxial stretching (third stage stretching) was performed. Further, the sample was uniaxially stretched (4th stage stretching) while being immersed in a stretching bath containing boric acid at a concentration of 2.8% by mass and potassium iodide at a concentration of 5.0% by mass at a temperature of 57°C. When two of the four sheets were cut, they were taken out of the drawing bath. The distance between the marked lines of the two uncut samples was measured, and the distance between the marked lines after stretching was divided by the distance between the marked lines before stretching (50 mm). It was defined as the limit draw ratio at °C.
• the light transmittance when tilted at 45° and the light transmittance when tilted at ⁇ 45° were measured, and their average value Ts2 (%) was determined.
• the transmittance Ts (%) of the polarizing film was calculated by averaging Ts1 and Ts2 by the following formula (1).
• Ts (Ts1+Ts2)/2 (1)
• C Measurement of degree of polarization V
• the transmittance T ⁇ (%) of light in the case of overlapping so that the vertical directions are orthogonal to each other is measured in the same manner as in the case of “(b) Measurement of transmittance Ts”, and the polarization degree is calculated by the following formula (2).
• V (%) was calculated.
• V ⁇ (T ⁇ -T ⁇ )/(T ⁇ +T ⁇ ) ⁇ 1/2 ⁇ 100...
• Example 1 As PVA (A), chips of PVA (saponification product of homopolymer of vinyl acetate) having a degree of polymerization of 2400 and a degree of saponification of 99.9 mol% were used. After immersing 100 parts by mass of the PVA chips in 2500 parts by mass of distilled water at 35° C., centrifugal dehydration was performed to obtain PVA water-containing chips with a volatile content of 60% by mass.
• PVA PVA
• This stock solution for film formation was cooled to 100° C. by a heat exchanger, and then extruded into a film having a surface temperature of 90° C. from a coat hanger die having a width of 180 cm, and further dried using a hot air dryer, and then dried.
• a PVA film having a thickness of 60 ⁇ m and a width of 165 cm was continuously manufactured by cutting off both ends of the film thickened by neck-in during film formation.
• a length of 4000 m of the manufactured PVA film was wound around a cylindrical core to form a film roll.
• Examples 2-9, Comparative Examples 1-5 A PVA film was produced in the same manner as in Example 1 except that the types and amounts of the nonionic surfactant (B) and the anionic surfactant (C) were changed as shown in Table 3. evaluated.
• the anionic surfactant (C) sodium alkylsulfonate having an alkyl chain having 15 carbon atoms was used.
• a tertiary amide type lauric acid diethanolamide was used as the nonionic surfactant (B). The results are shown in Table 3.
• the PVA films of Examples 1 to 9 had a small number of activator aggregates and a low haze value.
• the PVA films of Examples 7 and 8 had optical defects in some places, but were at a level usable as products.
• the PVA films of Examples 1 to 9 were difficult to cut because of the high critical stretching ratio, and were excellent in polarization performance.
• the PVA film of Comparative Example 1 in which the nonionic surfactant (B) represented by the above formula (I) was not used had many optical defects.
• the PVA film of Comparative Example 4 containing a large amount of the systematic surfactant (C) had a large number of surfactant aggregates and a high haze value. Further, the PVA films of Comparative Examples 2 to 4 were films that had a low limit stretch ratio and were easily cut, and their polarizing performance was not good.
• Comparative Example 5 in which lauric acid diethanolamide was used as the nonionic surfactant, the heat resistance of the nonionic surfactant was low, the number of surfactant aggregates was large, and the haze value was high.
• the PVA film of Comparative Example 5 was a film that had a low limit stretching ratio and was easily cut, and the polarizing performance was not good.

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