Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
• • 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
  • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
• • 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

Definitions

• the present invention relates to a polyvinyl alcohol film, a polarizing film using the same, and a polarizing plate.
• a polarizing plate having a light transmitting and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes the polarization state of light.
• LCDs are widely used in small devices such as calculators and wristwatches, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors.
• the polarizing plate is generally a polyvinyl alcohol film (hereinafter, "polyvinyl alcohol” may be abbreviated as "PVA”) dyed, uniaxially stretched, and if necessary, further fixed with a boron compound or the like to form a polarizing film. After production, it is produced by laminating a protective film such as a cellulose triacetate (TAC) film on the surface of the polarizing film.
• a protective film such as a cellulose triacetate (TAC) film
• Patent Document 1 describes a method for producing a PVA film having better flatness than before by suppressing fluctuations during casting using an air knife.
• Patent Document 1 Although better flatness of the film thickness in the MD direction can be obtained than in the past, stress is concentrated on the thin film portion due to the alignment of the thin film thickness portions in the width direction, and visual recognition is possible. Although the property is low, regular unevenness of the polarizing plate can be visually recognized, and there is a problem that it cannot meet the demand for higher transmission of the LCD.
• the present invention provides a PVA film in which unevenness of the polarizing plate at the time of stretching is less likely to be visually recognized, and a polarizing film and a polarizing plate using such a PVA film, even in the case of further increasing the transmission of the LCD.
• the purpose is to provide a PVA film in which unevenness of the polarizing plate at the time of stretching is less likely to be visually recognized, and a polarizing film and a polarizing plate using such a PVA film, even in the case of further increasing the transmission of the LCD.
• the present inventors have further reduced the film thickness unevenness in the MD direction (flow direction) of the PVA film, and in addition, the phase shift of the film film unevenness at a specific position in the TD direction (width direction). It was found that the above-mentioned problems could be achieved by adjusting the above-mentioned problems to a specific range, and further studies were carried out based on the findings to complete the present invention.
• the film thickness profile at an arbitrary point F 0 on the film surface is F 0 (x)
• the film thickness profile at a point -100 mm from F 0 to the TD direction is F -100 (x), from F 0 to the TD direction.
• the film thickness profile at the point of -200 mm is F-200 (x)
• the film thickness profile at the point from F 0 to +100 mm is F +100 ( x )
• the film thickness profile at the point from F0 to the TD direction is +200 mm.
• Polyvinyl alcohol film [2] The polyvinyl alcohol film according to the above [1], which has a width of 4 m or more; [3] The polyvinyl alcohol film according to the above [1] or [2], which has a swelling degree of 170 to 220%; [4] The polyvinyl alcohol film according to any one of the above [1] to [3], which has a thickness of 30 ⁇ m to 65 ⁇ m; [5] The polyvinyl alcohol film according to any one of the above [1] to [4], which is a film for producing an optical film; [6] The polyvinyl alcohol film according to [5] above, wherein the optical film is a polarizing film; [7] A polarizing film produced by using the polyvinyl alcohol film according to any one of [1] to [6] above; [8] A polarizing plate manufactured by attaching a protective film to at least one side of the polarizing film according to the above [7]; [9] A step of forming a polyviny
• a PVA film in which unevenness of the polarizing plate after stretching is less likely to be visually recognized, a polarizing film using such a PVA film, and a polarizing plate.
• ⁇ Measurement of PVA film film thickness The film thickness of the PVA film in the present invention is measured under the following conditions. From the viewpoint of comparing the phase of the film thickness in the width direction, measurement using a two-dimensional film thickness meter is indispensable.
• the PVA film of the present invention is characterized in that the average inclination value in the MD direction (hereinafter referred to as MD average inclination value) is 0.02 ⁇ m / mm or less.
• the MD average inclination value is more preferably 0.018 ⁇ m / mm or less. The detailed calculation method of the MD average slope value will be described below.
• x measures the film thickness profile of 1024 points every 1 mm from 1 mm to 1024 mm along the MD direction when a certain point is 0 mm.
• the 1024-point film thickness profile is measured at each of the 0 mm position, the +100 mm position, the +200 mm position, the -100 mm position, and the ⁇ 200 mm position in the TD direction from the arbitrary point.
• the film thickness profile was measured at 1024 points every 1 mm, but the measurement interval in the MD direction and the number of points for measuring the film thickness profile along the MD direction can be appropriately designed. be.
• the MD average slope value of the present invention is calculated by the following (Equation 1) to (Equation 6).
• the film thickness data at each point of 1024 mm in the MD direction was differentiated, the absolute value of the differential value was averaged at 1024 points, and then the average value for 5 lines was calculated, which was defined as the MD average inclination value.
• the MD average inclination value is a numerical value indicating the strength of the film thickness unevenness in the MD direction, and the larger the numerical value is, the larger the film thickness unevenness is.
• the differential values of F 0 (x), F +100 (x), F +200 (x), F- 100 (x), and F- 200 (x) are F'0 (x) and F' +100 (, respectively). It can be expressed as x), F'+ 200 (x), F' - 100 (x), F'-200 (x).
• k in (Equation 1) to (Equation 6) is a function of x, F'0 (x), F'+ 100 (x), F' +200 (x), F'- 100 (x), In F'- 200 (x), it is a symbol indicating that each of 1 to 1024 is substituted for x.
• Derivative values of F 0 (x), F +100 (x), F +200 (x), F- 100 (x), F- 200 (x) can be defined as these gradient values, for example.
• a value obtained by dividing the difference between F 0 (x) and F 0 (x + 1) by the distance between the points x and the point (x + 1) can also be defined as a slope value.
• the difference between the film thickness profile of the point x and the point (x + 1) is the difference between the point x and the point.
• the value divided by the distance (x + 1) can also be defined as the slope value.
• the PVA film of the present invention needs to have an MD average inclination value calculated from the above formula of 0.02 ⁇ m / mm or less, preferably 0.019 ⁇ m / mm or less, and preferably 0.016 or less. Is more preferable. If the MD average tilt value is larger than 0.02, uneven polarization when processed into a polarizing plate is strongly visually recognized, and the display quality of the LCD is impaired.
• the MD average inclination value (c) of the position + 200 mm calculated from the above formula is preferably 0.019 ⁇ m / mm or less, and more preferably 0.016 ⁇ m / mm or less.
• the MD average inclination value (e) at the position ⁇ 200 mm is preferably 0.019 ⁇ m / mm or less, and more preferably 0.016 ⁇ m / mm or less.
• the method for obtaining a PVA film having an MD average gradient value of 0.02 or less is not particularly limited, but for example, a polyvinyl alcohol film is formed using a polyvinyl alcohol aqueous solution having a concentration of 32% by mass or less, and the water content of the polyvinyl alcohol film is high.
• a method of producing a polyvinyl alcohol film by stretching at a stretching ratio of 1.075 to 1.135 when the amount of the film is 20% by mass or more can be mentioned.
• phase parameter ( ⁇ ) 0.015 ⁇ m / mm or more and the above-mentioned MD average inclination value is 0.02 or less at the same time.
• the phase parameter ( ⁇ ) is more preferably 0.016 ⁇ m / mm or more.
• the phase parameter ( ⁇ ) in the present invention is a numerical value defined by the following equation.
• C n in the following formula is the point where
• is the minimum is less than 1024 points.
• Equation 12 is a symbol indicating that each of C 1 to C n is substituted for C n in ⁇ (C n ) which is a function of C n .
• the phase parameter ( ⁇ ) in the present invention is the MD direction of the node causing the film thickness unevenness at the position of 0 mm in the TD direction and the node causing the film thickness unevenness at four positions deviated from the phase in the TD direction. It is a parameter indicating the consistency of the positions of, and it is shown that the larger this value is, the more uneven the nodes that cause the film thickness unevenness at 5 points in the width direction, and the less likely the film thickness unevenness is to occur.
• the PVA film of the present invention needs to have a phase parameter ( ⁇ ) calculated from the above formula of 0.015 or more, preferably 0.0153 or more.
• ⁇ phase parameter
• the method for obtaining a PVA film having a phase parameter ( ⁇ ) of 0.015 or more is not particularly limited, but for example, a polyvinyl alcohol film is formed using a polyvinyl alcohol aqueous solution having a concentration of 32% by mass or less, and the water content of the polyvinyl alcohol film is formed.
• a ratio is 20% by mass or more, a method of stretching at a stretching ratio of 1.075 to 1.135 to produce a polyvinyl alcohol film can be mentioned.
• the PVA film of the present invention has an MD average inclination value of 0.02 or less and a phase parameter ( ⁇ ) of 0.014 or more on the film surface, but at least one surface of the PVA film has an MD average.
• the tilt value may be 0.02 or less and the phase parameter ( ⁇ ) may be 0.014 or more, and at least both sides of the PVA film have an MD average tilt value of 0.02 or less and the phase parameter ( ⁇ ). May be 0.014 or more.
• the width of the PVA film of the present invention is preferably 4 m or more, more preferably 4.5 m or more, from the viewpoint of being used for a large-sized liquid crystal television.
• the width of the PVA film is 7 m or less. It is preferable to have.
• the PVA film of the present invention preferably has a swelling degree of 170% or more, more preferably 180% or more.
• the degree of swelling of the PVA film is preferably 220% or less, and more preferably 210% or less. If the degree of swelling is less than 170%, uneven swelling occurs, and there is a tendency that uniform dyeing cannot be performed at the time of dyeing. If the degree of swelling is larger than 220%, wrinkles are generated in the process, which tends to be unfavorable.
• a method of adjusting the swelling degree of the PVA film within these ranges for example, a method of appropriately adjusting the temperature of the heat treatment after the drying of the PVA film can be mentioned.
• the degree of swelling is an index showing the water retention capacity when the PVA film is immersed in water, and is the mass after immersing the PVA film in water at 30 ° C. for 30 minutes and the mass after drying at 105 ° C. for 16 hours after immersion. It can be obtained as a percentage by dividing it.
• the volatile fraction of the film-forming stock solution used for film-forming the PVA film of the present invention is preferably 70% by mass or more, and more preferably 71% by mass or more. If the volatile fraction of the PVA aqueous solution used for film formation is less than 70% by mass, the effect of reducing the film thickness unevenness due to the leveling effect at the time of casting cannot be expected, and the MD average inclination value becomes high, which is not preferable. If the volatile fraction of the film-forming stock solution of the PVA aqueous solution is too large, the drying time increases and the productivity decreases, which is not preferable.
• the "volatile fraction of the film-forming stock solution” in the present invention means the volatile fraction obtained by the following formula.
• Volatile fraction of membrane-forming stock solution (mass%) ⁇ (Wa-Wb) / Wa ⁇ x 100
• Wa represents the mass (g) of the film-forming stock solution
• Wb represents the mass (g) of the film-forming stock solution of Wa (g) when it is dried in an electric heat dryer at 105 ° C. for 16 hours.
• the draw ratio which is the stretching ratio
• the draw ratio is controlled by the speed ratio of the transport roll, and as the draw ratio increases, the critical draw ratio during the draw process decreases and the probability of stretch breakage during the draw process increases.
• the draw ratio when the draw ratio is 1.12 or more, a step of mitigating the influence of the draw ratio may be required. Further, if the draw ratio is higher than 1.135, the critical draw ratio during the stretching process is significantly lowered, which is not preferable. Further, if the draw ratio is smaller than 1.075, the phase parameter ( ⁇ ) becomes small, which is not preferable from the viewpoint of visibility of unevenness of the polarizing plate. Further, as a condition for forming the PVA film, the water content at the time of drawing is preferably 20% by mass or more, and more preferably 22% by mass or more. If the water content at the time of drawing is lower than 20% by mass, the phase parameter ( ⁇ ) is less likely to increase. For the above reasons, it is necessary to set the moisture content and draw ratio at the time of drawing within the above ranges.
• PVA PVA
• the PVA resin contained in the PVA film of the present invention include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatic acid, vinyl laurate, vinyl stearate, vinyl benzoate, and acetic acid.
• examples thereof include those obtained by saponifying a polyvinyl ester obtained by polymerizing one or more vinyl esters such as isopropenyl.
• vinyl esters vinyl acetate is preferable from the viewpoint of ease of production, availability, cost and the like of PVA.
• the PVA may be modified with one or more kinds of graft-copolymerizable monomers as long as the effect of the present invention is not impaired.
• the graft copolymerizable monomer include unsaturated carboxylic acid or a derivative thereof; unsaturated sulfonic acid or a derivative thereof; and an ⁇ -olefin having 2 to 30 carbon atoms.
• the proportion of structural units derived from the graft-copolymerizable monomer in PVA is preferably 5 mol% or less based on the number of moles of all structural units constituting PVA.
• PVA may or may not have a part of its hydroxyl group crosslinked. Further, the above-mentioned PVA may have a part of its hydroxyl group reacted with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure, or may not react with these compounds to form an acetal structure. May be.
• an aldehyde compound such as acetaldehyde or butyraldehyde
• the degree of polymerization of PVA is preferably 2000 or more, more preferably 2200 or more, and even more preferably 2400 or more. When the degree of polymerization is less than 2000, the durability of the obtained polarizing film tends to decrease.
• the degree of polymerization of PVA is preferably 2700 or less, more preferably 2650 or less, and even more preferably 2600 or less. On the other hand, when the degree of polymerization exceeds 2700, the manufacturing cost tends to increase and the process passability during film formation tends to deteriorate.
• the degree of polymerization of PVA referred to in the present specification means the average degree of polymerization measured according to the description of JISK6726-1994.
• the saponification degree of PVA is preferably 98 mol% or more, more preferably 98.5 mol% or more, and further preferably 99 mol% or more from the viewpoint of water resistance of the polarizing film. If the degree of saponification is less than 98 mol%, the water resistance of the obtained polarizing film tends to deteriorate.
• the degree of saponification of PVA in the present specification refers to the total number of moles of structural units (typically vinyl ester units) and vinyl alcohol units possessed by PVA that can be converted into vinyl alcohol units by saponification. The ratio (mol%) of the number of moles of vinyl alcohol unit.
• the degree of saponification can be measured according to the description of JIS K6726-1994.
• the PVA film of the present invention preferably contains a plasticizer.
• the plasticizer include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylolpropane, and the PVA film of the present invention includes these.
• the content of the plasticizer in the PVA film of the present invention is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and 5 parts by mass or more with respect to 100 parts by mass of PVA contained therein. Is even more preferable.
• the content of the plasticizer is 1 part by mass or more, the stretchability of the PVA film can be further improved.
• the content of the plasticizer in the PVA film is preferably 20 parts by mass or less, more preferably 17 parts by mass or less, and further preferably 15 parts by mass or less with respect to 100 parts by mass of PVA. ..
• the amount of the plasticizer is 20 parts by mass or less, it is possible to prevent the PVA film from becoming too flexible and the handleability from being deteriorated.
• the PVA film of the present invention preferably contains a surfactant.
• a surfactant By producing a PVA film using a film-forming stock solution containing a surfactant, the film-forming property of the PVA film is improved. As a result, the occurrence of thickness unevenness of the PVA film is suppressed, and the PVA film can be easily peeled off from the metal roll or belt used for film formation.
• the obtained PVA film contains the surfactant.
• the type of the surfactant is not particularly limited, but an anionic surfactant and a nonionic surfactant are preferable from the viewpoint of the peelability of the PVA film from the metal roll or the belt.
• anionic surfactant for example, a carboxylic acid type such as potassium laurate; a sulfate ester type such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and a sulfonic acid type such as dodecylbenzene sulfonate are suitable.
• a carboxylic acid type such as potassium laurate
• a sulfate ester type such as polyoxyethylene lauryl ether sulfate and octyl sulfate
• a sulfonic acid type such as dodecylbenzene sulfonate
• nonionic surfactant examples include an alkyl ether type such as polyoxyethylene oleyl ether; an alkylphenyl ether type such as polyoxyethylene octylphenyl ether; an alkyl ester type such as polyoxyethylene laurate; and 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 oleic acid diethanolamide
• the allylphenyl ether type of the above is suitable.
• surfactants may be used alone or in combination of two or more.
• the lower limit of the content of the surfactant in the PVA film of the present invention is preferably 0.01 part by mass, more preferably 0.02 part by mass, and 0.05 part by mass with respect to 100 parts by mass of PVA. It is more preferable to be a part.
• the upper limit of the content of the surfactant in the PVA film is preferably 0.5 parts by mass, more preferably 0.3 parts by mass, and 0.2 parts by mass with respect to 100 parts by mass of PVA. It is more preferable to be a part.
• the PVA film of the present invention may further contain components such as an antioxidant, an antioxidant, a pH adjuster, a concealing agent, an antioxidant, an oil agent, and a surfactant described later, if necessary.
• the shape of the PVA film of the present invention is not particularly limited, but a long film is preferable. As a result, a more uniform PVA film can be continuously and easily produced, and the polarizing film can be continuously used even when the polarizing film is produced by using the PVA film.
• the length of the long film (length in the length direction) is not particularly limited and can be appropriately set according to the intended use, for example, in the range of 5 to 30,000 m.
• the thickness of the PVA film of the present invention is preferably 30 to 65 ⁇ m. If the thickness of the PVA film is smaller than 30 ⁇ m, the handleability at the time of stretching is deteriorated, and if the thickness of the PVA film is larger than 65 ⁇ m, it is not preferable as a polarizing plate for a thin display.
• the method for producing a PVA film is not particularly limited, but a casting film forming method and a wet film forming method (poor solvent) are used by using a film-forming stock solution homogenized by adding a solvent, an additive, etc. to PVA. (Discharge into), dry-wet film-forming method, gel film-forming method (a method in which the undiluted film-forming solution is once cooled and gelled, and then the solvent is extracted and removed to obtain a PVA film), or a combination of these is used to form a film.
• any method can be adopted, such as a melt extrusion film forming method or an inflation forming method, in which the above-mentioned undiluted film-forming solution is obtained by using an extruder or the like and extruded from a T-die or the like to form a film. ..
• the casting film forming method and the melt extrusion film forming method are preferable because a homogeneous film can be obtained with high productivity.
• a casting film forming method or a melt extrusion film forming method for a PVA film will be described.
• a polyvinyl alcohol film is formed using a polyvinyl alcohol aqueous solution having a concentration of 32% by mass or less, and 1.075 to 1 when the water content of the polyvinyl alcohol film is 20% by mass or more.
• a method for producing a polyvinyl alcohol film which comprises a step of stretching at a stretching ratio of .135, can be mentioned. By adopting this manufacturing method, it is possible to manufacture a film having no uneven thickness.
• Specific methods for alleviating the influence of the stretching ratio include a method of irradiating the polyvinyl alcohol film with infrared rays or microwaves, a stretching ratio when the water content of the polyvinyl alcohol film is 15 to 5% by mass, and a cumulative stretching ratio (plural).
• a method of reducing the product of the stretching ratio when stretching once) a method of applying a plasticizer after stretching, a method of drying with superheated steam, a method of drying at a high temperature, a method of performing heat treatment with a floating dryer, etc. Any method can be adopted, and each method may be combined or carried out a plurality of times.
• the above-mentioned film forming stock solution is poured into a film on a support such as a metal roll or a metal belt and heated to generate a solvent. By being removed, it solidifies into a film.
• the solidified film is peeled off from the support, dried by a drying roll, a drying oven, etc. as necessary, further heat-treated as necessary, and wound up to form a long roll-shaped PVA film. Obtainable.
• the method for preparing the undiluted film-forming solution for example, a method of dissolving PVA and additives such as a plasticizer and a surfactant in a dissolution tank or the like, or PVA in a water-containing state using a uniaxial or twin-screw extruder.
• a method of melt-kneading together with a plasticizer, a surfactant, and the like when melt-kneading for example, a method of dissolving PVA and additives such as a plasticizer and a surfactant in a dissolution tank or the like, or PVA in a water-containing state using a uniaxial or twin-screw extruder.
• a method of melt-kneading together with a plasticizer, a surfactant, and the like when melt-kneading for example, a method of melt-kneading together with a plasticizer, a surfactant, and the like when melt-knea
• Liquid media used to prepare the film-forming stock solution include, for example, water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and the like. Trimethylol propane, ethylenediamine, diethylenetriamine and the like can be mentioned, and one or more of these can be used. Of these, water is preferably used in terms of environmental load and recoverability.
• the dried PVA film can be further heat-treated if necessary.
• the surface temperature of the heat treatment roll for performing the heat treatment is preferably 60 ° C. or higher.
• the surface temperature of the heat treatment roll is preferably 135 ° C. or lower, more preferably 130 ° C. or lower. If the surface temperature of the heat-treated roll is too high, the amount of heat given is too large, the size of the lamella crystals in the PVA film becomes large, and it becomes difficult for the swelling degree of the PVA film to satisfy the above range.
• the PVA film thus produced is further subjected to humidity control treatment, cutting of both ends (ears) of the film, and the like, and is wound into a roll on a cylindrical core, if necessary. It is packaged in a moisture-proof package and becomes a product.
• the volatile fraction of the PVA film finally obtained by the above-mentioned series of treatments is not necessarily limited.
• the volatile fraction of the finally obtained PVA film is preferably 1% by mass or more, and more preferably 2% by mass or more.
• the volatile fraction of the finally obtained PVA film is preferably 5% by mass or less, and more preferably 4% by mass or less.
• the PVA film of the present invention is suitably used as a film for manufacturing an optical film because the film thickness unevenness in the MD direction is reduced and the phase shift of the film thickness unevenness in the TD direction is adjusted to a specific range.
• the optical film include a polarizing film, a viewing angle improving film, a retardation film, and a brightness improving film, as described later, but a polarizing film is preferable.
• unevenness of the polarizing plate after the stretching process is less visible than in the past.
• the polarizing film can usually be produced by using a PVA film as a raw film and undergoing treatment steps such as a swelling step, a dyeing step, a cross-linking step, a stretching step, and a fixing treatment step.
• the treatment liquid used in each step include a swelling treatment liquid used for swelling treatment, a dyeing treatment liquid (staining liquid) used for dyeing treatment, a cross-linking treatment liquid used for cross-linking treatment, and a stretching treatment liquid.
• a stretching treatment liquid a fixing treatment liquid used for the fixing treatment
• cleaning treatment liquid cleaning liquid
• the cleaning treatment is preferably performed by immersing the PVA film in the cleaning treatment liquid, but it can also be performed by spraying the cleaning treatment liquid on the PVA film.
• water can be used as the cleaning treatment liquid.
• the temperature of the cleaning treatment liquid is preferably 20 ° C. or higher, more preferably 22 ° C. or higher, further preferably 24 ° C.
• the temperature of the cleaning treatment liquid is preferably 40 ° C. or lower, more preferably 38 ° C. or lower, further preferably 36 ° C. or lower, and particularly preferably 34 ° C. or lower. Further, when the temperature of the cleaning treatment liquid is 40 ° C. or lower, it is possible to prevent a part of the surface of the PVA film from melting and the films from sticking to each other to deteriorate the handleability.
• the swelling treatment can be performed by immersing the PVA film in a swelling treatment liquid such as water.
• the temperature of the swelling treatment liquid is preferably 20 ° C. or higher, more preferably 22 ° C. or higher, and even more preferably 24 ° C. or higher.
• the temperature of the swelling treatment liquid is preferably 40 ° C. or lower, more preferably 38 ° C. or lower, and even more preferably 36 ° C. or lower.
• the time for immersing in the swelling treatment liquid is, for example, preferably 0.1 minutes or longer, and more preferably 0.5 minutes or longer. Further, the time for immersing in the swelling treatment liquid is preferably, for example, 5 minutes or less, and more preferably 3 minutes or less.
• the water used as the swelling treatment liquid is not limited to pure water, and may be an aqueous solution in which various components such as a boron-containing compound are dissolved, or may be a mixture of water and an aqueous medium.
• the type of the boron-containing compound is not particularly limited, but boric acid or borax is preferable from the viewpoint of handleability.
• the swelling treatment liquid contains a boron-containing compound, the concentration thereof is preferably 6% by mass or less from the viewpoint of improving the stretchability of the PVA film.
• the dyeing treatment is preferably carried out using an iodine-based dye as the dichroic dye, and the dyeing time may be any stage before the stretching treatment, during the stretching treatment, or after the stretching treatment.
• the dyeing treatment is preferably carried out by using a solution containing iodine-potassium iodide (preferably an aqueous solution) as the dyeing treatment liquid and immersing the PVA film in the dyeing treatment liquid.
• concentration of iodine in the dyeing solution is preferably in the range of 0.005 to 0.2% by mass, and potassium iodide / iodine (mass) is preferably in the range of 20 to 100.
• the temperature of the dyeing treatment liquid is preferably 20 ° C.
• the temperature of the dyeing treatment liquid is preferably 50 ° C. or lower, more preferably 40 ° C. or lower.
• the dyeing solution may contain a boron-containing compound such as boric acid as a cross-linking agent. If the PVA film used as the raw film contains a dichroic dye in advance, the dyeing process can be omitted. Further, it is also possible to preliminarily contain a boron-containing compound such as boric acid or borax in the PVA film used as the raw film.
• Cross-linking In the production of the polarizing film, it is preferable to carry out a cross-linking treatment after the dyeing treatment for the purpose of strengthening the adsorption of the dichroic dye on the PVA film.
• the cross-linking treatment can be performed by using a solution containing a cross-linking agent (preferably an aqueous solution) as the cross-linking treatment liquid and immersing the PVA film in the cross-linking treatment liquid.
• a cross-linking agent preferably an aqueous solution
• the cross-linking agent one or more boron-containing compounds such as boric acid and borax can be used.
• the concentration of the cross-linking agent in the cross-linking treatment liquid is preferably 1% by mass or more, more preferably 1.5% by mass or more, and further preferably 2% by mass or more.
• the concentration of the cross-linking agent in the cross-linking treatment liquid is preferably 6% by mass or less, more preferably 5.5% by mass or less, and further preferably 5% by mass or less.
• the cross-linking treatment liquid may contain an iodine-containing compound such as potassium iodide. If the concentration of the iodine-containing compound in the cross-linking treatment liquid is too high, the reason is unknown, but the heat resistance of the obtained polarizing film tends to decrease. Further, if the amount is too small, the effect of suppressing the elution of the dichroic dye tends to be reduced.
• the concentration of the iodine-containing compound in the cross-linking treatment liquid is preferably 1% by mass or more, more preferably 1.5% by mass or more, and further preferably 2% by mass or more.
• the concentration of the iodine-containing compound in the cross-linking treatment liquid is preferably 6% by mass or less, more preferably 5.5% by mass or less, and further preferably 5% by mass or less.
• the temperature of the cross-linking treatment liquid is preferably 20 ° C. or higher, more preferably 22 ° C. or higher, and even more preferably 25 ° C. or higher.
• the temperature of the cross-linking treatment liquid is preferably 45 ° C. or lower, more preferably 40 ° C. or lower, and even more preferably 35 ° C. or lower.
• the PVA film may be stretched during or between the above-mentioned treatments.
• stretching pre-stretching
• the total stretching ratio of the pre-stretching is 4 times or less based on the original length of the PVA film of the original fabric before stretching from the viewpoint of the polarization performance of the obtained polarizing film. It is preferably 3.5 times or less, and more preferably 3.5 times or less.
• the total draw ratio of the pre-stretching is more preferably 1.5 times or more based on the original length of the PVA film of the original fabric before stretching from the viewpoint of the polarization performance of the obtained polarizing film.
• the draw ratio in the swelling treatment is preferably 1.1 times or more, more preferably 1.2 times or more, still more preferably 1.4 times or more, based on the original length of the PVA film. ..
• the draw ratio in the swelling treatment is preferably 3 times or less, more preferably 2.5 times or less, still more preferably 2.3 times or less, based on the original length of the PVA film.
• the draw ratio in the dyeing treatment is preferably 2 times or less, more preferably 1.8 times or less, still more preferably 1.5 times or less, based on the original length of the PVA film.
• the draw ratio in the dyeing treatment is more preferably 1.1 times or more based on the original length of the PVA film.
• the draw ratio in the crosslinking treatment is preferably 2 times or less, more preferably 1.5 times or less, still more preferably 1.3 times or less, based on the original length of the PVA film.
• the draw ratio in the crosslinking treatment is more preferably 1.05 times or more based on the original length of the PVA film.
• the stretching treatment may be performed by either a wet stretching method or a dry stretching method.
• a solution containing a boron-containing compound such as boric acid preferably an aqueous solution
• the stretching treatment liquid can be used. It can also be performed in the treatment liquid.
• the dry stretching method it can be carried out in the air using a PVA film after water absorption.
• the wet stretching method is preferable, and uniaxial stretching is more preferable in an aqueous solution containing boric acid.
• the concentration of the boron-containing compound in the stretching treatment liquid is preferably 1.5% by mass or more because the stretchability of the PVA film can be improved. It is more preferably 0% by mass or more, and further preferably 2.5% by mass or more.
• the concentration of the boron-containing compound in the stretching treatment liquid is preferably 7% by mass or less, more preferably 6.5% by mass or less, and more preferably 6% by mass, because the stretchability of the PVA film can be improved. The following is more preferable.
• the stretching treatment liquid contains an iodine-containing compound such as potassium iodide. If the concentration of the iodine-containing compound in the stretching solution is too high, the hue of the obtained polarizing film tends to be bluish, and if it is too low, the reason is unknown, but the heat resistance of the obtained polarizing film is high. The sex tends to decrease.
• the concentration of the iodine-containing compound in the stretching treatment liquid is preferably 2% by mass or more, more preferably 2.5% by mass or more, and further preferably 3% by mass or more.
• the concentration of the iodine-containing compound in the stretching treatment liquid is preferably 8% by mass or less, more preferably 7.5% by mass or less, and further preferably 7% by mass or less.
• the temperature of the stretching treatment liquid is preferably 50 ° C. or higher, more preferably 52.5 ° C. or higher, and even more preferably 55 ° C. or higher.
• the temperature of the stretching treatment liquid is preferably 70 ° C. or lower, more preferably 67.5 ° C. or lower, and even more preferably 65 ° C. or lower.
• the preferred range of the stretching temperature when the stretching treatment is performed by the dry stretching method is also as described above.
• the stretching ratio in the stretching treatment is preferably 1.2 times or more, more preferably 1.5 times or more, and more preferably 1.5 times or more, because a polarizing film having better polarizing performance can be obtained when the stretching ratio is high. It is more preferable that the amount is double or more.
• the total draw ratio (magnification obtained by multiplying the draw ratio in each step) including the draw ratio of the pre-stretch described above is the original length of the raw material PVA film before stretching from the viewpoint of the polarization performance of the obtained polarizing film. Based on the above, it is preferably 5.5 times or more, more preferably 5.7 times or more, and further preferably 5.9 times or more.
• the upper limit of the draw ratio is not particularly limited, but if the draw ratio is too high, the PVA film is likely to be stretched and broken, so it is preferably 8 times or less.
• uniaxial stretching in the long direction can be performed by using a stretching device including a plurality of rolls parallel to each other and changing the peripheral speed between the rolls.
• the maximum stretching speed (% / min) when the stretching treatment is performed by uniaxial stretching is not particularly limited, but the maximum stretching speed is preferably 200% / min or more, preferably 300% / min or more. More preferably, 400% / min or more is further preferable.
• the maximum stretching speed is the fastest stretching speed among the three or more rolls having different peripheral speeds when the PVA film is stretched in two or more stages. Say that.
• the stretching speed at that step becomes the maximum stretching rate.
• the stretching speed means an increase in the length of the PVA film increased by stretching with respect to the length of the PVA film before stretching per unit time.
• the stretching speed of 100% / min is the speed at which the PVA film is deformed from the length before stretching to twice the length in one minute.
• the higher the maximum stretching speed the higher the stretching treatment (uniaxial stretching) of the PVA film can be performed, and as a result, the productivity of the polarizing film is improved, which is preferable.
• the maximum stretching speed becomes too high, excessive tension may be locally applied to the PVA film in the stretching treatment (uniaxial stretching) of the PVA film, and stretching fracture is likely to occur. From this point of view, it is preferable that the maximum stretching speed does not exceed 900% / min.
• the cleaning treatment is preferably performed by immersing the PVA film in the cleaning treatment liquid, but it can also be performed by spraying the cleaning treatment liquid on the PVA film.
• water can be used as the cleaning treatment liquid.
• the water is not limited to pure water, and may contain an iodine-containing compound such as potassium iodide.
• the cleaning treatment liquid may contain a boron-containing compound, but in that case, the concentration of the boron-containing compound is preferably 2.0% by mass or less.
• the temperature of the cleaning treatment liquid is preferably 5 ° C. or higher, more preferably 7 ° C. or higher, and even more preferably 10 ° C. or higher.
• the temperature of the cleaning treatment liquid is preferably 40 ° C. or lower, more preferably 38 ° C. or lower, and even more preferably 35 ° C. or lower.
• the temperature of the cleaning treatment liquid is 5 ° C. or higher, it is possible to suppress the breakage of the PVA film due to freezing of water. Further, when the temperature of the cleaning treatment liquid is 40 ° C. or lower, the optical characteristics of the obtained polarizing film are improved.
• Specific methods for producing the polarizing film include a method of subjecting the PVA film to a dyeing treatment, a stretching treatment, a crosslinking treatment and / or a fixing treatment.
• the stretching treatment may be performed in any of the treatment steps prior to the above, or may be performed in multiple stages of two or more stages.
• a polarizing film can be obtained by subjecting the PVA film after each of the above treatments to a drying treatment.
• the drying treatment method is not particularly limited, and examples thereof include a contact type method in which the film is brought into contact with a heating roll, a method in which the film is dried in a hot air dryer, and a floating type method in which the film is dried by hot air while floating. ..
• the polarizing film of the present invention is manufactured by attaching a protective film to at least one side in order to supplement the mechanical strength.
• the polarizing film of the present invention is usually used as a polarizing plate by laminating a protective film that is optically transparent and has mechanical strength.
• a protective film a cellulose triacetate (TAC) film, a cellulose acetate / butyrate (CAB) film, an acrylic film, a polyester film, or the like is used.
• TAC cellulose triacetate
• CAB cellulose acetate / butyrate
• acrylic film a polyester film, or the like
• examples of the adhesive for bonding include PVA-based adhesives and urethane-based adhesives, and PVA-based adhesives are particularly preferable.
• the polarizing plate obtained as described above can be used as an LCD component by being coated with an adhesive such as acrylic and then bonded to a glass substrate. At the same time, it may be bonded to a retardation film, a viewing angle improving film, a brightness improving film, or the like.
• ⁇ Measurement of swelling degree of PVA film> About 1.5 g of a test piece was cut out from the PVA film obtained in the following Example or Comparative Example. Next, this test piece was immersed in 1000 g of distilled water at 30 ° C. After soaking for 30 minutes, the test piece was taken out, the water on the surface was absorbed with a filter paper, and then the mass (We) was measured. Subsequently, the test piece was placed in a hot air dryer and dried at 105 ° C. for 16 hours, and then its mass (Wf) was measured. From the obtained masses We and Wf, the degree of swelling of the PVA film was determined by the following formula. Swelling degree (%) (We / Wf) ⁇ 100
• Example 1 Melt extruder using 100 parts by mass of PVA (saponification degree 99.9 mol%, polymerization degree 2400), 10 parts by mass of glycerin as a plasticizer, 0.1 parts by mass of lauric acid diethanolamide as a surfactant, and 233 parts by mass of water.
• a film-forming stock solution (volatile content of 70% by mass) was prepared by melting and mixing with.
• a PVA film was formed on the support by discharging the T-die onto the support (surface temperature 98 ° C.) in the form of a film. When the moisture content of the discharged PVA film reached 24%, the draw ratio was set to 1.10 by controlling the speed ratio of the roll, and the film was stretched.
• the heat treatment roll in the latter half was subjected to contact heat treatment at 105 ° C. to obtain a PVA film having a width of 5 m and a film thickness of 60 ⁇ m.
• the PVA film to be conveyed was torn off between the rolls to which the draw was applied, the mass (Ww) was measured, the film was placed in a hot air dryer, and the film was dried at 105 ° C. for 16 hours. Later, its mass (Wd) was measured.
• the obtained PVA film was slit to a width of 650 mm, and the film was continuously subjected to swelling treatment, dyeing treatment, cross-linking treatment, stretching treatment, washing treatment, and drying treatment in this order to continuously produce a polarizing film.
• the swelling treatment was carried out by uniaxially stretching 2.00 times in the length direction while immersing in pure water (swelling treatment liquid) at 25 ° C.
• the dyeing treatment is carried out while being immersed in a potassium iodide / iodine water-soluble staining solution (staining treatment solution) (potassium iodide / iodine (mass ratio) 23, iodine concentration 0.03 to 0.05% by mass) at a temperature of 32 ° C.
• the iodine concentration in the dyeing treatment liquid is 0.03 to 0.05 so that the simple substance transmittance of the polarizing film obtained after uniaxial stretching in the stretching treatment is in the range of 43.5% ⁇ 0.2%. Adjusted within the range of mass%.
• the cross-linking treatment was carried out by uniaxially stretching 1.19 times in the length direction while immersing in a boric acid aqueous solution (cross-linking treatment liquid) (boric acid concentration 2.6% by mass) at 32 ° C. The stretching treatment is performed 2.00 times in the length direction while being immersed in a 55 ° C.
• boric acid / potassium iodide aqueous solution (stretching treatment liquid) (boric acid concentration 2.8% by mass, potassium iodide concentration 5% by mass). It was uniaxially stretched.
• the washing treatment is carried out by immersing in a potassium iodide / boric acid aqueous solution (washing liquid) (potassium iodide concentration 3 to 6% by mass, boric acid concentration 1.5% by mass) at 22 ° C. for 12 seconds without stretching. gone.
• Examples 2 to 4 Comparative Examples 1 to 3
• the production and evaluation of the PVA film were carried out in the same manner as in Example 1 except that the production conditions of the PVA film were changed as shown in Table 1.
• the volatile fraction of the film-forming stock solution was adjusted by adjusting the amount of water to be melt-mixed with a melt extruder. The results are shown in Table 1.
• the PVA film of the present invention suppresses color unevenness during stretching.

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• 2021
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