WO2011162259A1 - Method for manufacturing polarizing film - Google Patents

Method for manufacturing polarizing film Download PDF

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Publication number
WO2011162259A1
WO2011162259A1 PCT/JP2011/064169 JP2011064169W WO2011162259A1 WO 2011162259 A1 WO2011162259 A1 WO 2011162259A1 JP 2011064169 W JP2011064169 W JP 2011064169W WO 2011162259 A1 WO2011162259 A1 WO 2011162259A1
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WO
WIPO (PCT)
Prior art keywords
widening
film
stretching
roll
treatment
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PCT/JP2011/064169
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French (fr)
Japanese (ja)
Inventor
圭二 網谷
容鉉 權
民載 丁
鐘熙 朴
廷敏 趙
昶植 康
Original Assignee
住友化学株式会社
東友ファインケム株式会社
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Application filed by 住友化学株式会社, 東友ファインケム株式会社 filed Critical 住友化学株式会社
Priority to KR1020137000813A priority Critical patent/KR101760541B1/en
Priority to CN201180030543.2A priority patent/CN102947735B/en
Publication of WO2011162259A1 publication Critical patent/WO2011162259A1/en

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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/023Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets using multilayered plates or sheets
    • B29C55/026Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets using multilayered plates or sheets of preformed plates or sheets coated with a solution, a dispersion or a melt of thermoplastic material
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/30Polarising elements
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/30Polarising elements
    • G02B5/3083Birefringent or phase retarding elements
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/04Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
    • B29C55/06Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2029/00Use of polyvinylalcohols, polyvinylethers, polyvinylaldehydes, polyvinylketones or polyvinylketals or derivatives thereof as moulding material
    • B29K2029/04PVOH, i.e. polyvinyl alcohol
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0018Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular optical properties, e.g. fluorescent or phosphorescent
    • B29K2995/0034Polarising

Definitions

  • the present invention relates to a method for producing a polarizing film used for producing a polarizing plate used in a liquid crystal display device.
  • a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol film has been used. That is, an iodine polarizing film using iodine as a dichroic dye, a dye polarizing film using a dichroic dye as a dichroic dye, and the like are known. These polarizing films are usually used as polarizing plates by laminating a protective film such as triacetyl cellulose via an adhesive made of an aqueous solution of a polyvinyl alcohol resin on at least one side, preferably both sides thereof. (LCD) is used for, for example, a liquid crystal television, a monitor for a personal computer, a display screen of a mobile phone, and the like.
  • LCD liquid crystal television, a monitor for a personal computer, a display screen of a mobile phone, and the like.
  • a nip roll and a guide roll are used, and after the polyvinyl alcohol film is immersed in water and swollen, it is dyed with the dichroic dye, stretched, and then iodine is formed into the film.
  • a method is known in which a polyvinyl alcohol film is treated with boric acid (crosslinking treatment), washed with water and then dried. At this time, the film is stretched by giving a peripheral speed difference to the nip rolls before and after the treatment bath, the film transport direction is changed by the guide roll, and the film is introduced into and taken out of the treatment liquid.
  • the polarizing film used for the liquid crystal display device is also required to increase in optical properties and in-plane uniformity at the same time.
  • absorption axis the light absorption axis (hereinafter sometimes referred to as absorption axis) of the obtained polarizing film varies.
  • the optical properties tend to deteriorate. Further, when the in-plane optical characteristics are not uniform, display unevenness occurs when the image display device is formed.
  • Patent Document 1 in the method for producing a polarizing film in which uniaxial stretching is performed in the boric acid treatment step and / or the previous step, in order to obtain a polarizing film with fewer scratches and wrinkles and no folds, It is disclosed that a widening roll is used as at least one guide roll in the liquid.
  • a widening roll is used as at least one guide roll in the liquid.
  • the method described in Patent Document 1 for example, when stretching is performed at 1.6 times or more with an integral stretching ratio using a widening roll in a dyeing tank, variations in absorption axis occur, and the resulting polarizing film There has been a problem that the optical characteristics of the above deteriorate.
  • An object of the present invention is to provide a method for producing a polarizing film having excellent optical characteristics.
  • the present inventors conducted a uniaxial stretching of 1.6 times or more at an integrated stretching ratio while widening with a widening roll.
  • the present inventors have found a new fact that dispersion of the absorption axis of the obtained polarizing film is suppressed and a polarizing film having good optical properties can be obtained, and the present invention has been completed.
  • the manufacturing method of the polarizing film of this invention has the following structures. (1) It has a step of processing a polyvinyl alcohol film in the order of swelling treatment, dyeing treatment, boric acid treatment and washing treatment, and the peripheral speed difference between two nip rolls is determined before or during any of these steps.
  • the cumulative stretching ratio up to the stretching process (however, if there is no other stretching process up to the widening stretching process) is 1.6 times or more, and is unloaded from the widening roll in the widening stretching process.
  • the angle of the widening direction of the widening roll with respect to the film unloading direction is ⁇ 40 ° to 70 ° (however, when the film flowing direction is viewed from left to right, The direction of carrying out from the roll is 0 °, the clockwise angle from the carrying direction is-, and the counterclockwise angle is +).
  • the widening roll in the widening and stretching step is a sponge rubber roll, the hardness of the sponge is 20 to 60 degrees on the JIS Shore C scale, the density is 0.4 to 0.6 g / cm 3, and the surface roughness is 10 to 30S.
  • the method according to any one of (1) to (4), wherein the stretching in the widening stretching step is performed by wet stretching, and the temperature of the liquid used is 20 ° C. to 40 ° C. (6)
  • the cumulative stretching ratio up to the widening stretching step (however, when there is no other stretching step up to the step, the stretching ratio in the step) is 2 times or more (1) to (5) The method described.
  • the method for producing a polarizing film of the present invention it is possible to produce a polarizing film having excellent optical properties by suppressing variations in the absorption axis of the obtained polarizing film.
  • Examples of the polyvinyl alcohol-based resin that forms the polyvinyl alcohol-based film in the present invention include those obtained by saponifying a polyvinyl acetate-based resin.
  • the degree of saponification is usually about 85 mol% or more, preferably about 90 mol% or more, more preferably about 99 mol% to 100 mol%.
  • Polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymer. Examples include coalescence.
  • Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids.
  • the degree of polymerization of the polyvinyl alcohol resin is usually about 1000 to 10,000, preferably about 1500 to 5,000.
  • polyvinyl alcohol resins may be modified.
  • polyvinyl formal modified with aldehydes polyvinyl acetal, polyvinyl butyral, and the like may be used.
  • an unstretched film of a polyvinyl alcohol-based resin film having a thickness of about 20 ⁇ m to 100 ⁇ m, preferably about 30 ⁇ m to 80 ⁇ m is used as a starting material for producing a polarizing film.
  • an unstretched film of a polyvinyl alcohol-based resin film having a thickness of about 20 ⁇ m to 100 ⁇ m, preferably about 30 ⁇ m to 80 ⁇ m is used.
  • the width of the film is practically about 1500 mm to 6000 mm.
  • the unstretched film is processed in the order of swelling treatment, dyeing treatment, boric acid treatment (crosslinking treatment), water washing treatment, and finally dried to obtain a polyvinyl alcohol polarizing film having a thickness of, for example, about 5 to 50 ⁇ m. is there.
  • a polarizing film which is a polyvinyl alcohol uniaxially stretched film in which a dichroic dye is adsorbed and oriented is generally obtained by subjecting an unstretched polyvinyl alcohol film to a solution treatment in the order of swelling treatment, dyeing treatment, boric acid treatment and water washing treatment. In addition, it is obtained by carrying out uniaxial stretching in a boric acid treatment step and, if necessary, a previous step by wet or dry method and finally drying.
  • the uniaxial stretching in the present invention may be performed by only one widening stretching process or may be performed by two or more processes.
  • stretching method is employable except having at least 1 widening extending
  • Known stretching methods include inter-roll stretching that stretches with a difference in peripheral speed between two nip rolls that transport the film, a hot roll stretching method as described in Japanese Patent No. 2731813, a tenter stretching method, and the like.
  • the widening and stretching step may be performed a plurality of times. The order of the steps is basically as described above, but there are no restrictions on the number of treatment baths or treatment conditions.
  • the swelling step is performed for the purpose of removing foreign matter from the film surface, removing the plasticizer in the film, imparting easy dyeability in the next step, and plasticizing the film.
  • the treatment conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme dissolution and devitrification of the base film do not occur.
  • the film is immersed in an aqueous solution at about 20 ° C. to 70 ° C., preferably about 30 ° C. to 60 ° C.
  • the immersion time of the film is preferably about 30 seconds to 300 seconds, more preferably about 60 seconds to 240 seconds.
  • the film When the unstretched original film is swollen from the beginning, the film is immersed, for example, in an aqueous solution of about 10 ° C. to 50 ° C., preferably about 20 ° C. to 40 ° C.
  • the immersion time of the film is preferably about 30 seconds to 300 seconds, more preferably about 60 seconds to 240 seconds.
  • uniaxial stretching may be performed in the swelling step, and the stretching ratio in that case is usually 1.2 to 3 times, preferably 1.3. ⁇ 2.5 times.
  • boric acid described in JP-A-10-153709
  • chloride described in JP-A-06-281816
  • inorganic acid inorganic salt
  • water solution is used as the swelling treatment bath to be used. It is also possible to use an aqueous solution to which a basic organic solvent, alcohols and the like are added in an amount of about 0.01 to 10% by weight.
  • the dyeing step with the dichroic dye is performed for the purpose of adsorbing and orienting the dichroic dye on the film.
  • the treatment conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme dissolution and devitrification of the base film do not occur.
  • An immersion treatment is performed at a concentration of about 0.1 to 10/100 for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds.
  • potassium iodide instead of potassium iodide, other iodides such as zinc iodide may be used. Other iodides may be used in combination with potassium iodide. Further, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it is distinguished from the following boric acid treatment in that it contains iodine. Any dye containing about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water can be regarded as a dyeing tank.
  • the immersion treatment is performed at a concentration of about 0.1 / 100 for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds.
  • the aqueous solution of the dichroic dye to be used may have a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate, a surfactant or the like.
  • the dichroic dye may be used alone, or two or more dichroic dyes may be used at the same time.
  • the film When a polyvinyl alcohol film is treated in the order of swelling treatment, dyeing treatment, and boric acid treatment, the film is usually stretched in a dyeing tank.
  • the cumulative draw ratio until the dyeing treatment (or the draw ratio in this step when there is no drawing step before this step) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times.
  • the draw ratio of integration up to the dyeing process is less than 1.6 times, the frequency of film breakage increases, and the yield tends to deteriorate. Stretching is performed by a method of giving a peripheral speed difference between the nip rolls before and after the dyeing tank.
  • a widening roll (expander roll), a spiral roll, a crown roll, a cross guider, a bend bar, and the like can be installed in the dyeing bath and / or at the bath entrance / exit.
  • the uniaxial stretching in the present invention can be applied in any of the swelling process, the dyeing process, the boric acid treatment process, and the washing process.
  • the boric acid treatment is performed by immersing a polyvinyl alcohol film dyed with a dichroic dye in an aqueous solution containing about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water.
  • the dichroic dye is iodine
  • iodide include potassium iodide and zinc iodide.
  • compounds other than iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, etc. may coexist.
  • This boric acid treatment is carried out for water resistance, hue adjustment (preventing bluishness, etc.) by crosslinking, and the like.
  • a cross-linking agent such as glyoxal or glutaraldehyde can be used in addition to or together with boric acid, if necessary.
  • the boric acid treatment for water resistance may be referred to by names such as water resistance treatment, crosslinking treatment, and immobilization treatment.
  • boric acid treatment for hue adjustment may be referred to by a name such as complementary color treatment or re-dyeing treatment.
  • This boric acid treatment is performed by appropriately changing the concentrations of boric acid and iodide and the temperature of the treatment bath according to the purpose.
  • the boric acid treatment for water resistance and the boric acid treatment for hue adjustment are not particularly distinguished, but are carried out under the following conditions.
  • about 3 to 10 parts by weight of boric acid and 100% by weight of iodide Is carried out at a temperature of about 50 ° C. to 70 ° C., preferably about 53 ° C. to 65 ° C.
  • the immersion time is usually about 10 to 600 seconds, preferably 20 to 300 seconds, more preferably 20 to 200 seconds.
  • the temperature of the boric acid treatment bath is usually about 50 ° C. to 85 ° C., preferably about 55 ° C. to 80 ° C.
  • boric acid treatment for hue adjustment may be performed.
  • the dichroic dye is iodine
  • a boric acid treatment bath containing about 1 to 5 parts by weight of boric acid and about 3 to 30 parts by weight of iodide for 100 parts by weight of water is used for this purpose. And is usually carried out at a temperature of about 10 ° C to 45 ° C.
  • the immersion time is usually about 1 to 300 seconds, preferably 2 to 100 seconds.
  • boric acid treatments may be performed a plurality of times and are usually performed 2 to 5 times in many cases.
  • the aqueous solution composition and temperature of each boric acid treatment tank to be used may be the same or different within the above range.
  • the boric acid treatment for water resistance and the boric acid treatment for hue adjustment may be performed in a plurality of steps, respectively.
  • the final integrated draw ratio of the polarizing film in the invention is usually about 4.5 to 7 times, preferably about 5 to 6.5 times.
  • boric acid treatment After boric acid treatment, it is washed with water.
  • the water washing treatment is performed, for example, by immersing a polyvinyl alcohol film treated with boric acid for water resistance and / or color tone adjustment in water, spraying water as a shower, or combining immersion and spraying.
  • the temperature of water in the water washing treatment is usually about 2 to 40 ° C., and the immersion time is preferably about 2 to 120 seconds.
  • the polyvinyl alcohol film is dried in a drying furnace at a temperature of about 40 to 100 ° C. for about 60 to 600 seconds to obtain a polarizing film.
  • a widening roll can also be used in the boric acid treatment step and the washing treatment step.
  • these films are uniaxially drawn between two nip rolls. That is, the peripheral speed of the nip roll on the downstream side in the film transport direction is made larger than the peripheral speed of the nip roll on the upstream side, and the film is stretched with tension.
  • At least one of the stretching steps is provided with at least one widening roll between two nip rolls, and is uniaxially stretched while widening the film (widening stretching step).
  • the integral draw ratio up to the widening and stretching step in which the widening roll of the present invention is installed is 1.6 times. As described above, it is preferably 2 times or more, and usually 7 times or less, preferably 6.5 times or less, and thereby the effect of suppressing the variation of the absorption axis is sufficiently exhibited. If the cumulative stretching ratio up to the widening stretching step is less than 1.6 times, there is a risk that it will not be possible to obtain a sufficient absorption axis variation suppressing effect, and as described above, up to the dyeing step where the stretching step is performed.
  • the cumulative stretching ratio is the total sum of the ratios of uniaxial stretching and widening stretching.
  • uniaxial stretching and widening stretching are performed a plurality of times, the total stretching ratio is the sum of all of them.
  • Stretching may be either dry or wet, but is preferably performed by a so-called wet stretching method in which the film is stretched while being immersed in a predetermined solution. Since this wet stretching method is sufficient for the film to be sufficiently stretched and not easily broken, the necessary optical properties are easily obtained, and the degree of polarization is higher than that of the dry stretching method.
  • FIG. 1 is an explanatory view showing an embodiment of the widening and stretching step in the present invention
  • FIG. 2 is a front view showing an example of the widening roll in the present invention.
  • the treatment tank 10 shown in FIG. 1 is filled with a treatment liquid 4 (for example, iodine, potassium iodide aqueous solution), and a nip roll 2 and a downstream side on the upstream side in the transport direction of the polyvinyl alcohol film 1 passing through the treatment tank 10.
  • a treatment liquid 4 for example, iodine, potassium iodide aqueous solution
  • a nip roll 2 ' is installed in the nip roll, and a widening roll 3 and a guide roll 5 are installed between the two nip rolls.
  • the widening roll 3 has a curved shape.
  • the polyvinyl alcohol film 1 is immersed in the treatment liquid 4 and stretched with a difference in peripheral speed between the two nip rolls 2 and 2 ′ while being stretched through the widening roll 3.
  • a plurality of widening rolls 3 may be provided.
  • FIGS. 3A to 3C are explanatory views showing the relationship between the widening direction M of the widening roll and the film carry-out direction.
  • the widening direction M of the widening roll 3 is important for improving the optical characteristics of the polarizing film, and the angle ⁇ of the widening direction M with respect to the unloading direction of the film 1 is ⁇ 40 ° to 70 °, more preferably ⁇ 30 ° to The range is 30 °.
  • FIGS. 3 (a) to 3 (c) when the direction in which the film 1 flows is viewed from the left to the right, the unloading direction of the film 1 is 0 °, and the clockwise angle from the unloading direction is set to 0 °.
  • the radius of curvature of the widening roll 3 to be used is preferably 1000 to 50000 mm, more preferably 10,000 to 40000 mm, and the diameter d of the widening roll 3 is preferably 50 to 300 mm, more preferably 75 to 200 mm.
  • the widening roll 3 may be disposed in the air (in the atmosphere) or in the liquid, but as shown in FIG. 1, the present invention is applied to the widening roll 3 installed in the air.
  • the present invention is applied to the widening roll 3 installed in the air.
  • at least one widening roll 3 is installed in the air and the present invention is applied.
  • Optical characteristics can be improved while suppressing the generation of wrinkles.
  • the present invention is applied to all widening rolls 3, that is, all the widening rolls 3 are divided into two nip rolls 2, It is highly preferred to install between 2 '.
  • Examples of the material for the widening roll during the production process of the present invention include rubber and sponge, but a sponge rubber roll is more preferable.
  • the polyvinyl alcohol film swells in both the longitudinal and width directions due to absorption of the bath solution, but wrinkles and folds are likely to occur on the roll when tension is applied without the swelling in the width direction ending.
  • a sponge rubber roll is used as the widening roll, it can exert a sufficient widening force due to the high film gripping force based on its high surface roughness, and it also demonstrates the meandering prevention function, which is another role of the widening roll. , Wrinkles are reduced and folding is eliminated.
  • the sponge rubber roll used in the present invention has a sponge hardness of about 20 to 60 degrees, more preferably about 25 to 50 degrees, and a density of about 0.4 on the JIS Shore C scale measured by the test method of JIS K 6301. ⁇ 0.6g / cm 3, approximately expressed more preferably about 0.42 ⁇ 0.57g / cm 3 and a surface roughness JIS B 0601 average local peaks of the roughness curve spacing (surface roughness) S It is preferably 10 to 30S, more preferably about 15 to 25S.
  • the temperature of the solution in which the film is immersed may be usually 2 to 70 ° C., but in particular 20 to 40 ° C., preferably 25 to 35 ° C.
  • the film is stretched through a widening roll, it is possible to stretch the film without degrading the optical properties most.
  • tension control may be performed so that the tension of the film becomes substantially constant.
  • tension control it is preferable to perform tension control also for these steps.
  • the tension in each step may be the same or different.
  • the tension applied to the film in the tension control is not particularly limited, and is appropriately set within a range of about 150 N / m to 2000 N / m, preferably about 600 N / m to 1500 N / m per unit width.
  • the tension per unit width is calculated from the film width near the entrance of the process and the tension value of the tension detector.
  • tension control when tension control is performed, there are cases where the film is inevitably slightly stretched or shrunk, but in the present invention, this is not included in the stretching process.
  • a polarizing plate can be obtained by pasting a protective film with an adhesive on at least one surface of the polarizing film thus produced.
  • the protective film for example, a film made of an acetyl cellulose resin such as triacetyl cellulose or diacetyl cellulose, a film made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate, or a film made of a polycarbonate resin , A film made of a cycloolefin resin, an acrylic resin film, and a polypropylene resin film.
  • the polarizing film and / or protective film may be subjected to corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc.
  • a surface treatment may be applied.
  • Example 1 While immersing a 75 ⁇ m-thick polyvinyl alcohol film (Kuraray Vinylon VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) in pure water at 30 ° C., the film is sufficiently swollen, Uniaxial stretching was performed 1.30 times. Next, as shown in FIG. 1, the iodine / potassium iodide / water is immersed in a dyeing bath at 30 ° C. with a weight ratio of 0.02 / 2.0 / 100 and the integrated draw ratio is 2.80 times. Uniaxial stretching was performed.
  • the angle of the widening direction of the widening roll with respect to the carrying-out direction of the film carried out from the widening roll at this time (however, when the film flowing direction is viewed from left to right, the carrying-out direction of the film 1 is 0 °, The clockwise angle from the direction was-and the counterclockwise angle was +) (hereinafter referred to as the holding angle of the widening roll) was carried at 0 °. Thereafter, uniaxial stretching was carried out until the cumulative total draw ratio from the original fabric became 5.5 times while being immersed in a 55 ° C. aqueous solution of potassium iodide / boric acid / water in a weight ratio of 12 / 4.4 / 100.
  • Example 2 A polarizing film was obtained in the same manner as in Example 1 except that the holding angle of the widening roll in the dyeing tank was 30 °. The dispersion of the absorption axis of the obtained polarizing film (difference between maximum and minimum) was 0.08 °.
  • Example 3 A polarizing film was obtained in the same manner as in Example 1 except that the holding angle of the widening roll in the dyeing tank was 60 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.12 °.
  • Example 4 A polarizing film was obtained in the same manner as in Example 1 except that the holding angle of the widening roll in the dyeing tank was ⁇ 30 °. The dispersion of the absorption axis of the obtained polarizing film (difference between maximum and minimum) was 0.09 °.
  • Example 5 While immersing a 75 ⁇ m-thick polyvinyl alcohol film (Kuraray Vinylon VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) in pure water at 30 ° C., the film is sufficiently swollen, Uniaxial stretching was performed 1.30 times. Next, as shown in FIG. 1, the iodine / potassium iodide / water is immersed in a dyeing bath at 30 ° C. with a weight ratio of 0.02 / 2.0 / 100 and the integrated draw ratio is 1.65 times. Uniaxial stretching was performed. The holding angle of the widening roll at this time was conveyed at 0 °.
  • Example 6 A polarizing film was obtained in the same manner as in Example 5 except that the holding angle of the widening roll in the dyeing tank was 30 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.13 °.
  • Example 7 A polarizing film was obtained in the same manner as in Example 5 except that the holding angle of the widening roll in the dyeing tank was 60 °. The variation in absorption axis (maximum and minimum difference) of the obtained polarizing film was 0.15 °.
  • Example 1 A polarizing film was obtained in the same manner as in Example 1 except that the holding angle of the widening roll in the dyeing tank was 90 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.23 °.
  • Example 2 A polarizing film was obtained in the same manner as in Example 5 except that the holding angle of the widening roll in the dyeing tank was 90 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.24 °.
  • Examples 1 to 4 and Comparative Example 1 described above are shown below. From Table 1, it can be seen that Examples 1 to 7 have less absorption axis variation (maximum-minimum difference) than Comparative Examples 1 and 2.
  • Example 8 In the swelling tank, uniaxial stretching as shown in FIG. 1 is performed through a widening roll in the air with a hugging angle of 0 °, and then, as shown in FIG. A polarizing film was obtained in the same manner as in Example 1 except that the uniaxial stretching as shown in FIG. 1 was performed at 2.80 times (the holding angle of the widening roll in the dyeing tank was 0 °). The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.11 °.
  • Example 3 A polarizing film was obtained in the same manner as in Example 8 except that the holding angle of the widening roll in the swelling tank was 90 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.34 °.
  • Example 8 has lower absorption axis variation (maximum-minimum difference) than Comparative Example 3.

Abstract

Provided is a method for manufacturing a polarizing film, which has steps in which a polyvinyl alcohol based film (1) is sequentially subjected to swelling treatment, dyeing treatment, boric acid treatment, and cleaning treatment, and the polyvinyl alcohol based film (1) is uniaxially stretched before or during any one of said steps by using the circumferential speed difference between two nip rolls (2, 2'), wherein the method for manufacturing a polarizing film has a step in which at least one wide roll (3) is disposed between the two nip rolls (2, 2') to perform widening and uniaxial stretching. The accumulated draw ratio until the widening step (including the widening step) is equal to or greater than 1.6 (the draw ratio of the widening step when no other stretching step is performed before the widening step). In the widening step, the angle between the widening direction of the wide roll (3) and the carry-out direction of the film (1) carried out from the wide roll (3) is -40° to 70° (if the direction in which the film travels is viewed from left to right, the carry-out direction of the film from the wide roll is 0°, and clockwise angles from the carry-out direction are negative (-) and counterclockwise angles are positive (+)).

Description

偏光フィルムの製造方法Manufacturing method of polarizing film
 本特許出願は、日本国特許出願第2010-141429号(2010年6月22日出願)に基づくパリ条約上の優先権を主張するものであり、ここに引用することによって、上記出願に記載された内容の全体が、本明細書中に組み込まれるものとする。
 本発明は、液晶表示装置に使用される偏光板の製造に用いる偏光フィルムの製造方法に関する。
This patent application claims priority under the Paris Convention based on Japanese Patent Application No. 2010-141429 (filed on June 22, 2010), and is incorporated herein by reference. The entire contents of which are incorporated herein.
The present invention relates to a method for producing a polarizing film used for producing a polarizing plate used in a liquid crystal display device.
 偏光フィルムとしては、従来から、ポリビニルアルコール系フィルムに二色性色素を吸着配向させたものが用いられている。すなわち、ヨウ素を二色性色素とするヨウ素系偏光フィルムや、二色性染料を二色性色素とする染料系偏光フィルムなどが知られている。これらの偏光フィルムは、通常、その少なくとも片面、好ましくは両面にポリビニルアルコール系樹脂の水溶液からなる接着剤を介してトリアセチルセルロース等の保護フィルムを貼合して、偏光板とされ、液晶表示装置(LCD)として、例えば、液晶テレビ、パソコン用モニター、携帯電話の表示画面等に用いられる。 Conventionally, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol film has been used. That is, an iodine polarizing film using iodine as a dichroic dye, a dye polarizing film using a dichroic dye as a dichroic dye, and the like are known. These polarizing films are usually used as polarizing plates by laminating a protective film such as triacetyl cellulose via an adhesive made of an aqueous solution of a polyvinyl alcohol resin on at least one side, preferably both sides thereof. (LCD) is used for, for example, a liquid crystal television, a monitor for a personal computer, a display screen of a mobile phone, and the like.
 偏光フィルムの製造方法としては、ニップロール、ガイドロールを使用し、ポリビニルアルコール系フィルムを水に浸漬させて膨潤させた後、前記二色性色素で染色し、これを延伸し、ついでヨウ素をフィルムに定着させるためにポリビニルアルコール系フィルムをホウ酸処理(架橋処理)し、水洗した後、乾燥する方法が知られている。この際、処理浴前後のニップロールに周速差を与えてフィルムの延伸を行い、ガイドロールによってフィルムの搬送方向を変更し、処理液へのフィルムの導入、取り出しを行っている。
また、近年では、液晶表示装置の大型化、機能向上及び輝度向上に伴い、それに用いられる偏光フィルムも大型化と同時に、光学特性の向上及び面内均一性の向上が求められている。しかしながら、大型の偏光フィルムを得るためには、広幅の原反フィルムを均一に一軸延伸することが必要であるが、得られる偏光フィルムの光線吸収軸(以下、吸収軸ということがある)がばらつき、光学特性が悪化する傾向にある。さらに、面内の光学特性が均一でない場合、画像表示装置の形成時に表示ムラが発生する。
As a method for producing a polarizing film, a nip roll and a guide roll are used, and after the polyvinyl alcohol film is immersed in water and swollen, it is dyed with the dichroic dye, stretched, and then iodine is formed into the film. In order to fix it, a method is known in which a polyvinyl alcohol film is treated with boric acid (crosslinking treatment), washed with water and then dried. At this time, the film is stretched by giving a peripheral speed difference to the nip rolls before and after the treatment bath, the film transport direction is changed by the guide roll, and the film is introduced into and taken out of the treatment liquid.
Further, in recent years, along with the increase in size, function and brightness of liquid crystal display devices, the polarizing film used for the liquid crystal display device is also required to increase in optical properties and in-plane uniformity at the same time. However, in order to obtain a large polarizing film, it is necessary to uniaxially stretch a wide original film, but the light absorption axis (hereinafter sometimes referred to as absorption axis) of the obtained polarizing film varies. The optical properties tend to deteriorate. Further, when the in-plane optical characteristics are not uniform, display unevenness occurs when the image display device is formed.
一方、特許文献1には、ホウ酸処理工程および/またはその前の工程で一軸延伸を行う偏光フィルムの製造方法において、より傷や皺が少なく、折れ込みのない偏光フィルムを得るために、処理液中の少なくとも一つのガイドロールとして拡幅ロールを用いることが開示されている。しかしながら、特許文献1に記載の方法において、例えば染色槽で拡幅ロールを用いて、積算延伸倍率で1.6倍以上の延伸を行う場合には、吸収軸のバラツキが発生し、得られる偏光フィルムの光学特性が低下する問題があった。 On the other hand, in Patent Document 1, in the method for producing a polarizing film in which uniaxial stretching is performed in the boric acid treatment step and / or the previous step, in order to obtain a polarizing film with fewer scratches and wrinkles and no folds, It is disclosed that a widening roll is used as at least one guide roll in the liquid. However, in the method described in Patent Document 1, for example, when stretching is performed at 1.6 times or more with an integral stretching ratio using a widening roll in a dyeing tank, variations in absorption axis occur, and the resulting polarizing film There has been a problem that the optical characteristics of the above deteriorate.
特開2005-227650号公報JP 2005-227650 A
 本発明の課題は、光学特性に優れた偏光フィルムの製造方法を提供することである。 An object of the present invention is to provide a method for producing a polarizing film having excellent optical characteristics.
本発明者らは、上記課題を解決すべく鋭意検討を重ねた結果、拡幅ロールで拡幅しながら積算延伸倍率で1.6倍以上の一軸延伸を行うにあたり、拡幅ロールの拡幅方向を所定の方向にすることにより、得られる偏光フィルムの吸収軸のバラツキが抑制され、良好な光学特性を有する偏光フィルムが得られるという新たな事実を見出し、本発明を完成するに至った。 As a result of intensive studies to solve the above-mentioned problems, the present inventors conducted a uniaxial stretching of 1.6 times or more at an integrated stretching ratio while widening with a widening roll. Thus, the present inventors have found a new fact that dispersion of the absorption axis of the obtained polarizing film is suppressed and a polarizing film having good optical properties can be obtained, and the present invention has been completed.
 すなわち、本発明の偏光フィルムの製造方法は、以下の構成を有する。
(1)ポリビニルアルコール系フィルムを膨潤処理、染色処理、ホウ酸処理および洗浄処理の順に処理する工程を有し、これらのいずれかの工程の前または工程中に2つのニップロール間の周速差を利用して一軸延伸を行う偏光フィルムの製造方法であって、前記2つのニップロール間に少なくとも1台の拡幅ロールを設置して拡幅と一軸延伸を行う拡幅延伸工程を含み、拡幅延伸工程を含む拡幅延伸工程までの積算延伸倍率(但し、拡幅延伸工程までに他の延伸工程がない場合は拡幅延伸工程での延伸倍率)が1.6倍以上であり、拡幅延伸工程において、拡幅ロールから搬出される前記フィルムの搬出方向に対する拡幅ロールの拡幅方向の角度が-40°~70°(但し、フィルムの流れる方向を左から右に見たときの、フィルムの拡幅ロールからの搬出方向を0°とし、該搬出方向より時計回りの角度を-、反時計回りの角度を+とする。)である方法。
(2)拡幅延伸工程を2つ以上有する(1)に記載の方法。
(3)拡幅延伸工程における拡幅ロールを気中に配置する(1)または(2)に記載の方法。
(4)拡幅延伸工程における拡幅ロールがスポンジゴムロールであり、そのスポンジの硬度がJISショアCスケールで20~60度、密度が0.4~0.6g/cmおよび表面粗さが10~30Sである(1)~(3)のいずれかに記載の方法。
(5)拡幅延伸工程における延伸が湿式延伸により行われ、使用する液の温度が20℃~40℃である(1)~(4)のいずれかに記載の方法。
(6)拡幅延伸工程までの積算延伸倍率(但し、該工程までに他の延伸工程がない場合は該工程での延伸倍率)が2倍以上である(1)~(5)のいずれかに記載の方法。
That is, the manufacturing method of the polarizing film of this invention has the following structures.
(1) It has a step of processing a polyvinyl alcohol film in the order of swelling treatment, dyeing treatment, boric acid treatment and washing treatment, and the peripheral speed difference between two nip rolls is determined before or during any of these steps. A method for producing a polarizing film that performs uniaxial stretching using a method, comprising a widening and stretching step in which at least one widening roll is installed between the two nip rolls for widening and uniaxial stretching, and includes a widening and stretching step. The cumulative stretching ratio up to the stretching process (however, if there is no other stretching process up to the widening stretching process) is 1.6 times or more, and is unloaded from the widening roll in the widening stretching process. The angle of the widening direction of the widening roll with respect to the film unloading direction is −40 ° to 70 ° (however, when the film flowing direction is viewed from left to right, The direction of carrying out from the roll is 0 °, the clockwise angle from the carrying direction is-, and the counterclockwise angle is +).
(2) The method as described in (1) which has two or more widening extending processes.
(3) The method according to (1) or (2), wherein the widening roll in the widening and stretching step is disposed in the air.
(4) The widening roll in the widening and stretching step is a sponge rubber roll, the hardness of the sponge is 20 to 60 degrees on the JIS Shore C scale, the density is 0.4 to 0.6 g / cm 3, and the surface roughness is 10 to 30S. The method according to any one of (1) to (3), wherein
(5) The method according to any one of (1) to (4), wherein the stretching in the widening stretching step is performed by wet stretching, and the temperature of the liquid used is 20 ° C. to 40 ° C.
(6) The cumulative stretching ratio up to the widening stretching step (however, when there is no other stretching step up to the step, the stretching ratio in the step) is 2 times or more (1) to (5) The method described.
 本発明の偏光フィルムの製造方法によれば、得られる偏光フィルムの吸収軸のバラツキを抑制し、光学特性に優れた偏光フィルムを製造することができるという効果が奏される。 According to the method for producing a polarizing film of the present invention, it is possible to produce a polarizing film having excellent optical properties by suppressing variations in the absorption axis of the obtained polarizing film.
本発明における拡幅ロールを設置して拡幅と一軸延伸を行う拡幅延伸工程の一実施形態を示す説明図である。It is explanatory drawing which shows one Embodiment of the widening extending | stretching process which installs the widening roll in this invention and performs widening and uniaxial stretching. 本発明における拡幅ロールの一例を示す正面図である。It is a front view which shows an example of the widening roll in this invention. 拡幅ロールの拡幅方向とフィルムの搬出方向との関係を示す説明図であり、フィルムの搬出方向に対する拡幅ロールの拡幅方向の角度が(a)は70°、(b)は0°、(c)は-40°の場合をそれぞれ示している。It is explanatory drawing which shows the relationship between the widening direction of a widening roll, and the carrying out direction of a film, The angle of the widening direction of a widening roll with respect to the carrying out direction of a film is 70 degrees, (b) is 0 degree, (c) Indicates the case of −40 °.
 (偏光フィルムの製造方法)
本発明におけるポリビニルアルコール系フィルムを形成するポリビニルアルコール系樹脂は、通常、ポリ酢酸ビニル系樹脂をケン化したものが例示される。ケン化度としては、通常約85モル%以上、好ましくは約90モル%以上、より好ましくは約99モル%~100モル%である。ポリ酢酸ビニル系樹脂としては、酢酸ビニルの単独重合体であるポリ酢酸ビニルのほか、酢酸ビニルとこれに共重合可能な他の単量体との共重合体、例えば、エチレン-酢酸ビニル共重合体などが挙げられる。共重合可能な他の単量体としては、例えば不飽和カルボン酸類、オレフィン類、ビニルエーテル類、不飽和スルホン酸類などが挙げられる。ポリビニルアルコール系樹脂の重合度としては、通常約1000~10000、好ましくは約1500~5000程度である。
(Production method of polarizing film)
Examples of the polyvinyl alcohol-based resin that forms the polyvinyl alcohol-based film in the present invention include those obtained by saponifying a polyvinyl acetate-based resin. The degree of saponification is usually about 85 mol% or more, preferably about 90 mol% or more, more preferably about 99 mol% to 100 mol%. Polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymer. Examples include coalescence. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polyvinyl alcohol resin is usually about 1000 to 10,000, preferably about 1500 to 5,000.
これらのポリビニルアルコール系樹脂は変性されていてもよく、例えば、アルデヒド類で変性されたポリビニルホルマール、ポリビニルアセタール、ポリビニルブチラールなども使用しうる。通常、偏光フィルム製造の開始材料としては、厚さが約20μm~100μm、好ましくは約30μm~80μmのポリビニルアルコール系樹脂フィルムの未延伸フィルムを用いる。工業的には、フィルムの幅は約1500mm~6000mmが実用的である。
この未延伸フィルムを、膨潤処理、染色処理、ホウ酸処理(架橋処理)、水洗処理の順に処理し、最後に乾燥して得られるポリビニルアルコール系偏光フィルムの厚みは、例えば約5~50μm程度である。
These polyvinyl alcohol resins may be modified. For example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like may be used. Usually, as a starting material for producing a polarizing film, an unstretched film of a polyvinyl alcohol-based resin film having a thickness of about 20 μm to 100 μm, preferably about 30 μm to 80 μm is used. Industrially, the width of the film is practically about 1500 mm to 6000 mm.
The unstretched film is processed in the order of swelling treatment, dyeing treatment, boric acid treatment (crosslinking treatment), water washing treatment, and finally dried to obtain a polyvinyl alcohol polarizing film having a thickness of, for example, about 5 to 50 μm. is there.
二色性色素を吸着配向せしめたポリビニルアルコール系一軸延伸フィルムである偏光フィルムは、一般に、未延伸のポリビニルアルコール系フィルムを水溶液で膨潤処理、染色処理、ホウ酸処理および水洗処理の順に溶液処理し、ホウ酸処理工程および必要ならその前の工程で湿式または乾式にて一軸延伸を行い、最後に乾燥することにより得られる。 A polarizing film which is a polyvinyl alcohol uniaxially stretched film in which a dichroic dye is adsorbed and oriented is generally obtained by subjecting an unstretched polyvinyl alcohol film to a solution treatment in the order of swelling treatment, dyeing treatment, boric acid treatment and water washing treatment. In addition, it is obtained by carrying out uniaxial stretching in a boric acid treatment step and, if necessary, a previous step by wet or dry method and finally drying.
本発明における一軸延伸は、1つの拡幅延伸工程のみで行ってもよく、2つ以上の工程で行ってもよい。2つ以上の工程で行う場合、拡幅延伸工程を少なくとも1つ有すること以外は、公知の延伸方法を採用することができる。公知の延伸方法としては、フィルムを搬送する2つのニップロール間に周速差をつけて延伸を行うロール間延伸、特許第2731813号公報に記載のような熱ロール延伸法、テンター延伸法などがある。もちろん、拡幅延伸工程を複数回行ってもよい。また、基本的に工程の順序は、上記の通りであるが、処理浴の数や、処理条件などに制約は無い。
 また、上記工程に記載の無い工程を別の目的で挿入することも自由であることは言うまでもない。この工程の例として、ホウ酸処理後に、ホウ酸を含まないヨウ化物水溶液による浸漬処理(ヨウ化物処理)またはホウ酸を含まない塩化亜鉛等を含有する水溶液による浸漬処理(亜鉛処理)工程等が挙げられる。
The uniaxial stretching in the present invention may be performed by only one widening stretching process or may be performed by two or more processes. When performing by two or more processes, a well-known extending | stretching method is employable except having at least 1 widening extending | stretching process. Known stretching methods include inter-roll stretching that stretches with a difference in peripheral speed between two nip rolls that transport the film, a hot roll stretching method as described in Japanese Patent No. 2731813, a tenter stretching method, and the like. . Of course, the widening and stretching step may be performed a plurality of times. The order of the steps is basically as described above, but there are no restrictions on the number of treatment baths or treatment conditions.
Needless to say, a process not described in the above process can be freely inserted for another purpose. As an example of this process, after boric acid treatment, immersion treatment (iodide treatment) with an aqueous iodide solution not containing boric acid or immersion treatment (zinc treatment) step with an aqueous solution containing zinc chloride not containing boric acid, etc. Can be mentioned.
膨潤工程は、フィルム表面の異物除去、フィルム中の可塑剤除去、次工程での易染色性の付与、フィルムの可塑化などの目的で行われる。処理条件はこれらの目的が達成できる範囲で、かつ基材フィルムの極端な溶解、失透などの不具合が生じない範囲で決定される。あらかじめ気体中で延伸したフィルムを膨潤させる場合には、例えば約20℃~70℃、好ましくは約30℃~60℃の水溶液にフィルムを浸漬して行われる。フィルムの浸漬時間は、好ましくは約30秒~300秒、更に好ましくは約60秒~240秒程度である。はじめから未延伸の原反フィルムを膨潤させる場合には、例えば約10℃~50℃、好ましくは約20℃~40℃の水溶液にフィルムを浸漬して行われる。フィルムの浸漬時間は、好ましくは約30秒~300秒、更に好ましくは約60秒~240秒程度である。
 なお、ポリビニルアルコール系フィルムを膨潤、染色、ホウ酸処理する場合は、膨潤工程において一軸延伸を行ってもよく、その場合の延伸倍率としては、通常1.2~3倍、好ましくは1.3~2.5倍である。
The swelling step is performed for the purpose of removing foreign matter from the film surface, removing the plasticizer in the film, imparting easy dyeability in the next step, and plasticizing the film. The treatment conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme dissolution and devitrification of the base film do not occur. When a film previously stretched in a gas is swollen, for example, the film is immersed in an aqueous solution at about 20 ° C. to 70 ° C., preferably about 30 ° C. to 60 ° C. The immersion time of the film is preferably about 30 seconds to 300 seconds, more preferably about 60 seconds to 240 seconds. When the unstretched original film is swollen from the beginning, the film is immersed, for example, in an aqueous solution of about 10 ° C. to 50 ° C., preferably about 20 ° C. to 40 ° C. The immersion time of the film is preferably about 30 seconds to 300 seconds, more preferably about 60 seconds to 240 seconds.
When the polyvinyl alcohol film is swollen, dyed or treated with boric acid, uniaxial stretching may be performed in the swelling step, and the stretching ratio in that case is usually 1.2 to 3 times, preferably 1.3. ~ 2.5 times.
膨潤処理工程では、フィルムが幅方向に膨潤してフィルムにシワが入るなどの問題が生じやすいので、拡幅ロール(エキスパンダーロール)、スパイラルロール、クラウンロール、クロスガイダー、ベンドバー、テンタークリップなど公知の拡幅装置でフィルムのシワを取りつつフィルムを搬送することが好ましい。浴中のフィルム搬送を安定化させる目的で、膨潤浴中での水流を水中シャワーで制御したり、EPC装置(Edge Position Control装置:フィルムの端部を検出し、フィルムの蛇行を防止する装置)などを併用したりすることも有用である。本工程では、フィルムの走行方向にもフィルムが膨潤拡大するので、フィルムに積極的な延伸を行わない場合は、搬送方向のフィルムのたるみを無くすために、例えば処理槽前後の搬送ロールの速度をコントロールするなどの手段を講ずることが好ましい。また、使用する膨潤処理浴には、純水の他、ホウ酸(特開平10-153709号公報に記載)、塩化物(特開平06-281816号公報に記載)、無機酸、無機塩、水溶性有機溶媒、アルコール類などを約0.01重量%~10重量%の範囲で添加した水溶液を使用することも可能である。 In the swelling process, problems such as swelling of the film in the width direction and wrinkling of the film are likely to occur. It is preferable to transport the film while removing wrinkles of the film with an apparatus. In order to stabilize the film transport in the bath, the water flow in the swelling bath is controlled by an underwater shower, or an EPC device (Edge-Position-Control device: a device that detects the edge of the film and prevents meandering of the film) It is also useful to use these together. In this process, since the film swells and expands in the running direction of the film, when the film is not actively stretched, for example, the speed of the transport roll before and after the treatment tank is set to eliminate sagging of the film in the transport direction. It is preferable to take measures such as control. In addition to pure water, boric acid (described in JP-A-10-153709), chloride (described in JP-A-06-281816), inorganic acid, inorganic salt, water solution are used as the swelling treatment bath to be used. It is also possible to use an aqueous solution to which a basic organic solvent, alcohols and the like are added in an amount of about 0.01 to 10% by weight.
二色性色素による染色工程は、フィルムに二色性色素を吸着、配向させるなどの目的で行われる。処理条件はこれらの目的が達成できる範囲で、かつ基材フィルムの極端な溶解、失透などの不具合が生じない範囲で決定される。二色性色素としてヨウ素を用いる場合、例えば、約10℃~45℃、好ましくは約20℃~35℃の温度で、かつ重量比でヨウ素/KI/水=約0.003~0.2/約0.1~10/100の濃度で約30秒~600秒、好ましくは約60秒~300秒浸漬処理を行う。ヨウ化カリウムに代えて、他のヨウ化物、例えばヨウ化亜鉛などを用いてもよい。また、他のヨウ化物をヨウ化カリウムと併用してもよい。また、ヨウ化物以外の化合物、例えばホウ酸、塩化亜鉛、塩化コバルトなどを共存させてもよい。ホウ酸を添加する場合、ヨウ素を含む点で下記のホウ酸処理と区別される。水100重量部に対し、ヨウ素を約0.003重量部以上含んでいるものであれば染色槽と見なせる。 The dyeing step with the dichroic dye is performed for the purpose of adsorbing and orienting the dichroic dye on the film. The treatment conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme dissolution and devitrification of the base film do not occur. When iodine is used as the dichroic dye, for example, at a temperature of about 10 ° C. to 45 ° C., preferably about 20 ° C. to 35 ° C., and in a weight ratio, iodine / KI / water = about 0.003 to 0.2 / An immersion treatment is performed at a concentration of about 0.1 to 10/100 for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds. Instead of potassium iodide, other iodides such as zinc iodide may be used. Other iodides may be used in combination with potassium iodide. Further, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it is distinguished from the following boric acid treatment in that it contains iodine. Any dye containing about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water can be regarded as a dyeing tank.
二色性色素として水溶性二色性染料を用いる場合、例えば約20℃~80℃、好ましくは約30℃~70℃の温度で、かつ重量比で二色性染料/水=約0.001~0.1/100の濃度で約30秒~600秒、好ましくは約60秒~300秒浸漬処理を行う。使用する二色性染料の水溶液は、染色助剤などを有していてもよく、例えば硫酸ナトリウムなどの無機塩、界面活性剤などを含有していてもよい。二色性染料は単独でもよいし、2種類以上の二色性染料を同時に用いることもできる。 When a water-soluble dichroic dye is used as the dichroic dye, for example, at a temperature of about 20 ° C. to 80 ° C., preferably about 30 ° C. to 70 ° C., and dichroic dye / water by weight ratio = about 0.001. The immersion treatment is performed at a concentration of about 0.1 / 100 for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds. The aqueous solution of the dichroic dye to be used may have a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate, a surfactant or the like. The dichroic dye may be used alone, or two or more dichroic dyes may be used at the same time.
 ポリビニルアルコール系フィルムを膨潤処理、染色処理、ホウ酸処理の順に処理する場合は、通常、染色槽でフィルムの延伸を行う。染色処理までの積算の延伸倍率(該工程までに延伸工程がない場合は該工程での延伸倍率)は、通常1.6~4.5倍、好ましくは1.8~4倍である。また、染色処理までの積算の延伸倍率が1.6倍未満の場合、フィルムの破断の頻度が多くなり、歩留りを悪化させる傾向にある。
 延伸は染色槽の前後のニップロールに周速差を持たせるなどの方法で行われる。また、膨潤工程と同様に、拡幅ロール(エキスパンダーロール)、スパイラルロール、クラウンロール、クロスガイダー、ベンドバーなどを、染色浴中および/または浴出入り口に設置することもできる。なお、本発明における一軸延伸は、膨潤工程、染色工程、ホウ酸処理工程および洗浄工程のいずれにおいても適用されうる。
When a polyvinyl alcohol film is treated in the order of swelling treatment, dyeing treatment, and boric acid treatment, the film is usually stretched in a dyeing tank. The cumulative draw ratio until the dyeing treatment (or the draw ratio in this step when there is no drawing step before this step) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times. Moreover, when the draw ratio of integration up to the dyeing process is less than 1.6 times, the frequency of film breakage increases, and the yield tends to deteriorate.
Stretching is performed by a method of giving a peripheral speed difference between the nip rolls before and after the dyeing tank. Similarly to the swelling step, a widening roll (expander roll), a spiral roll, a crown roll, a cross guider, a bend bar, and the like can be installed in the dyeing bath and / or at the bath entrance / exit. In addition, the uniaxial stretching in the present invention can be applied in any of the swelling process, the dyeing process, the boric acid treatment process, and the washing process.
ホウ酸処理は、水100重量部に対してホウ酸を約1~10重量部含有する水溶液に、二色性色素で染色したポリビニルアルコール系フィルムを浸漬することにより行われる。二色性色素がヨウ素の場合、ヨウ化物を約1~30重量部含有させることが好ましい。
ヨウ化物としてはヨウ化カリウム、ヨウ化亜鉛などが挙げられる。また、ヨウ化物以外の化合物、例えば塩化亜鉛、塩化コバルト、塩化ジルコニウム、チオ硫酸ナトリウム、亜硫酸カリウム、硫酸ナトリウムなどを共存させてもよい。
このホウ酸処理は、架橋による耐水化や色相調整(青味がかるのを防止する等)等のために実施される。架橋による耐水化のための場合には、必要に応じて、ホウ酸以外に、またはホウ酸と共に、グリオキザール、グルタルアルデヒドなどの架橋剤も使用することができる。
なお、耐水化のためのホウ酸処理を、耐水化処理、架橋処理、固定化処理などの名称で呼称する場合もある。また、色相調整のためのホウ酸処理を、補色処理、再染色処理などの名称で呼称する場合もある。
The boric acid treatment is performed by immersing a polyvinyl alcohol film dyed with a dichroic dye in an aqueous solution containing about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. When the dichroic dye is iodine, it is preferable to contain about 1 to 30 parts by weight of iodide.
Examples of iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, etc. may coexist.
This boric acid treatment is carried out for water resistance, hue adjustment (preventing bluishness, etc.) by crosslinking, and the like. In the case of water resistance by cross-linking, a cross-linking agent such as glyoxal or glutaraldehyde can be used in addition to or together with boric acid, if necessary.
In addition, the boric acid treatment for water resistance may be referred to by names such as water resistance treatment, crosslinking treatment, and immobilization treatment. In addition, boric acid treatment for hue adjustment may be referred to by a name such as complementary color treatment or re-dyeing treatment.
このホウ酸処理は、その目的によって、ホウ酸およびヨウ化物の濃度、処理浴の温度を適宜変更して行なわれる。
耐水化のためのホウ酸処理、色相調整のためのホウ酸処理は特に区別されるものではないが、下記の条件で実施される。
原反フィルムを膨潤、染色、ホウ酸処理をする場合で、ホウ酸処理が架橋による耐水化を目的としている時は、水100重量部に対してホウ酸を約3~10重量部、ヨウ化物を約1~20重量部含有するホウ酸処理浴を使用し、通常、約50℃~70℃、好ましくは約53℃~65℃の温度で行われる。浸漬時間は、通常、約10~600秒程度、好ましくは20~300秒、より好ましくは20~200秒である。
なお、予め延伸したフィルムを染色、ホウ酸処理を行う場合、ホウ酸処理浴の温度は、通常、約50℃~85℃、好ましくは約55℃~80℃である。
This boric acid treatment is performed by appropriately changing the concentrations of boric acid and iodide and the temperature of the treatment bath according to the purpose.
The boric acid treatment for water resistance and the boric acid treatment for hue adjustment are not particularly distinguished, but are carried out under the following conditions.
When the raw film is swollen, dyed or treated with boric acid, and the boric acid treatment is intended for water resistance by crosslinking, about 3 to 10 parts by weight of boric acid and 100% by weight of iodide Is carried out at a temperature of about 50 ° C. to 70 ° C., preferably about 53 ° C. to 65 ° C. The immersion time is usually about 10 to 600 seconds, preferably 20 to 300 seconds, more preferably 20 to 200 seconds.
In the case where a previously stretched film is dyed and treated with boric acid, the temperature of the boric acid treatment bath is usually about 50 ° C. to 85 ° C., preferably about 55 ° C. to 80 ° C.
耐水化のためのホウ酸処理後、色相調整のためのホウ酸処理を行ってもよい。例えば二色性染料がヨウ素の場合、この目的のためには、水100重量部に対してホウ酸を約1~5重量部、ヨウ化物を約3~30重量部含有するホウ酸処理浴を使用し、通常、約10℃~45℃の温度で行われる。浸漬時間は、通常、1~300秒程度、好ましくは2~100秒である。 After boric acid treatment for water resistance, boric acid treatment for hue adjustment may be performed. For example, when the dichroic dye is iodine, a boric acid treatment bath containing about 1 to 5 parts by weight of boric acid and about 3 to 30 parts by weight of iodide for 100 parts by weight of water is used for this purpose. And is usually carried out at a temperature of about 10 ° C to 45 ° C. The immersion time is usually about 1 to 300 seconds, preferably 2 to 100 seconds.
これらのホウ酸処理は複数回行っても良く、通常、2~5回行われることが多い。この場合、使用する各ホウ酸処理槽の水溶液組成、温度は上記の範囲内で同じであっても、異なっていてもよい。上記耐水化のためのホウ酸処理、色相調整のためのホウ酸処理をそれぞれ複数の工程で行ってもよい。 These boric acid treatments may be performed a plurality of times and are usually performed 2 to 5 times in many cases. In this case, the aqueous solution composition and temperature of each boric acid treatment tank to be used may be the same or different within the above range. The boric acid treatment for water resistance and the boric acid treatment for hue adjustment may be performed in a plurality of steps, respectively.
本発明における偏光フィルムの延伸の最終的な積算延伸倍率は、通常約4.5~7倍、好ましくは約5~6.5倍である。 The final integrated draw ratio of the polarizing film in the invention is usually about 4.5 to 7 times, preferably about 5 to 6.5 times.
ホウ酸処理後、水洗される。水洗処理は、例えば、耐水化および/または色調調整のためにホウ酸処理したポリビニルアルコール系フィルムを水に浸漬、水をシャワーとして噴霧、あるいは浸漬と噴霧を併用することによって行われる。水洗処理における水の温度は、通常、約2~40℃程度であり、浸漬時間は約2~120秒程度であるのがよい。
その後、ポリビニルアルコール系フィルムを乾燥炉中で約40~100℃の温度で約60~600秒乾燥させることにより、偏光フィルムを得ることができる。
 なお、ホウ酸処理工程および洗浄処理工程においても、拡幅ロールを使用することができる。
After boric acid treatment, it is washed with water. The water washing treatment is performed, for example, by immersing a polyvinyl alcohol film treated with boric acid for water resistance and / or color tone adjustment in water, spraying water as a shower, or combining immersion and spraying. The temperature of water in the water washing treatment is usually about 2 to 40 ° C., and the immersion time is preferably about 2 to 120 seconds.
Thereafter, the polyvinyl alcohol film is dried in a drying furnace at a temperature of about 40 to 100 ° C. for about 60 to 600 seconds to obtain a polarizing film.
A widening roll can also be used in the boric acid treatment step and the washing treatment step.
(拡幅延伸工程)
上記した処理工程のいずれか、またはこれらの工程とは別の延伸工程において、フィルムは2つのニップロール間で一軸延伸される。すなわち、フィルムの搬送方向における下流側のニップロールの周速度を上流側のニップロールの周速度よりも大きくして、フィルムに張力を与えて延伸する。
(Wide stretching process)
In any of the processing steps described above, or in a separate drawing step, these films are uniaxially drawn between two nip rolls. That is, the peripheral speed of the nip roll on the downstream side in the film transport direction is made larger than the peripheral speed of the nip roll on the upstream side, and the film is stretched with tension.
その際、本発明では、延伸工程のうち少なくとも1つの工程において、2つのニップロール間に少なくとも1台の拡幅ロールを設置し、フィルムを拡幅させつつ一軸延伸させる(拡幅延伸工程)。 At this time, in the present invention, at least one of the stretching steps is provided with at least one widening roll between two nip rolls, and is uniaxially stretched while widening the film (widening stretching step).
 本発明の拡幅ロールが設置された拡幅延伸工程までの積算延伸倍率(但し、拡幅工程までに延伸工程がない場合は拡幅延伸工程での延伸倍率を意味する。以下同じ)は、1.6倍以上、好ましくは2倍以上であり、また、通常は7倍以下、好ましくは6.5倍以下であり、これにより吸収軸のバラツキを抑制する効果が十分に発揮される。拡幅延伸工程までの積算延伸倍率が1.6倍未満の場合、十分な吸収軸のバラツキの抑制効果を得ることができなくなるおそれがあり、また、前記の通り、延伸工程を行う染色工程までの積算延伸倍率が1.6倍より低い場合は、フィルムの破断の頻度が多くなる傾向にある。積算延伸倍率は、一軸延伸と拡幅延伸の倍率を合計した倍率であり、一軸延伸、拡幅延伸それぞれが複数回行われる場合には、それらの全てを積算した倍率となる。
 延伸は乾式および湿式のいずれでもよいが、フィルムを所定の溶液中に浸しながら延伸する、いわゆる湿式延伸法で行うのが好ましい。この湿式延伸法はフィルムが破断しにくく充分に延伸できるので、必要な光学特性が得やすく、乾式延伸法に比べて偏光度が高くなる。
The integral draw ratio up to the widening and stretching step in which the widening roll of the present invention is installed (however, when there is no stretching step before the widening step, it means the draw ratio in the widening and stretching step; the same applies hereinafter) is 1.6 times. As described above, it is preferably 2 times or more, and usually 7 times or less, preferably 6.5 times or less, and thereby the effect of suppressing the variation of the absorption axis is sufficiently exhibited. If the cumulative stretching ratio up to the widening stretching step is less than 1.6 times, there is a risk that it will not be possible to obtain a sufficient absorption axis variation suppressing effect, and as described above, up to the dyeing step where the stretching step is performed. When the cumulative draw ratio is lower than 1.6 times, the frequency of film breakage tends to increase. The cumulative stretching ratio is the total sum of the ratios of uniaxial stretching and widening stretching. When uniaxial stretching and widening stretching are performed a plurality of times, the total stretching ratio is the sum of all of them.
Stretching may be either dry or wet, but is preferably performed by a so-called wet stretching method in which the film is stretched while being immersed in a predetermined solution. Since this wet stretching method is sufficient for the film to be sufficiently stretched and not easily broken, the necessary optical properties are easily obtained, and the degree of polarization is higher than that of the dry stretching method.
以下、図面を用いて、本発明における一軸延伸の実施形態を詳しく説明する。図1は、本発明における拡幅延伸工程の一実施形態を示す説明図であり、図2は本発明における拡幅ロールの一例を示す正面図である。 Hereinafter, embodiments of uniaxial stretching in the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing an embodiment of the widening and stretching step in the present invention, and FIG. 2 is a front view showing an example of the widening roll in the present invention.
図1に示す処理槽10には、処理液4(例えば、ヨウ素、ヨウ化カリウム水溶液)が満たされており、その中を通るポリビニルアルコール系フィルム1の搬送方向の上流側にニップロール2、下流側にニップロール2’が設置されており、2つのニップロール間には拡幅ロール3、ガイドロール5が設置されている。拡幅ロール3は、図2に示すように、湾曲した形状を有する。
この拡幅延伸工程では、ポリビニルアルコール系フィルム1は、処理液4に浸漬され、拡幅ロール3を介して延伸されながら、2つのニップロール2、2’間の周速差で延伸される。なお、この場合、拡幅ロール3は複数台あってもよい。
The treatment tank 10 shown in FIG. 1 is filled with a treatment liquid 4 (for example, iodine, potassium iodide aqueous solution), and a nip roll 2 and a downstream side on the upstream side in the transport direction of the polyvinyl alcohol film 1 passing through the treatment tank 10. A nip roll 2 'is installed in the nip roll, and a widening roll 3 and a guide roll 5 are installed between the two nip rolls. As shown in FIG. 2, the widening roll 3 has a curved shape.
In this widening and stretching step, the polyvinyl alcohol film 1 is immersed in the treatment liquid 4 and stretched with a difference in peripheral speed between the two nip rolls 2 and 2 ′ while being stretched through the widening roll 3. In this case, a plurality of widening rolls 3 may be provided.
また、図3(a)~(c)は、拡幅ロールの拡幅方向Mとフィルムの搬出方向との関係を示す説明図である。
拡幅ロール3の拡幅方向Mは、偏光フィルムの光学特性を向上させる上で重要であり、フィルム1の搬出方向に対する拡幅方向Mの角度θは-40°~70°、より好ましくは-30°~30°の範囲である。但し、図3(a)~(c)に示すように、フィルム1の流れる方向を左から右に見たときの、フィルム1の搬出方向を0°とし、該搬出方向より時計回りの角度を-、反時計回りの角度を+とする。図3において、フィルムの搬出方向に対する拡幅ロールの拡幅方向の角度が(a)は70°、(b)は0°、(c)は-40°の場合をそれぞれ示している。角度θが上記の範囲を外れた場合、偏光フィルムの吸収軸が一定方向(フィルムの搬送方向)に揃わず、そのためフィルムの光学特性が低下してしまうという問題が起こる。
FIGS. 3A to 3C are explanatory views showing the relationship between the widening direction M of the widening roll and the film carry-out direction.
The widening direction M of the widening roll 3 is important for improving the optical characteristics of the polarizing film, and the angle θ of the widening direction M with respect to the unloading direction of the film 1 is −40 ° to 70 °, more preferably −30 ° to The range is 30 °. However, as shown in FIGS. 3 (a) to 3 (c), when the direction in which the film 1 flows is viewed from the left to the right, the unloading direction of the film 1 is 0 °, and the clockwise angle from the unloading direction is set to 0 °. -, Counterclockwise angle is +. In FIG. 3, the angle of the widening direction of the widening roll with respect to the film unloading direction is 70 °, (b) is 0 °, and (c) is −40 °. When the angle θ is out of the above range, there is a problem that the absorption axis of the polarizing film is not aligned in a certain direction (film transport direction), and therefore the optical characteristics of the film are deteriorated.
使用する拡幅ロール3の曲率半径は、好ましくは1000~50000mm、より好ましくは10000~40000mm、拡幅ロール3の径dは、好ましくは50~300mm、より好ましくは75~200mmである。 The radius of curvature of the widening roll 3 to be used is preferably 1000 to 50000 mm, more preferably 10,000 to 40000 mm, and the diameter d of the widening roll 3 is preferably 50 to 300 mm, more preferably 75 to 200 mm.
拡幅ロール3は、気中(大気中)、液中のどちらに配置されていても構わないが、図1に示すように、気中に設置された拡幅ロール3に本発明を適用するのが、光学特性を向上させるうえで好ましい。
 特に、フィルムの膨潤による幅寸法の変化が大きい膨潤工程や染色工程において、拡幅ロールが複数設置される場合においては、少なくとも1つの拡幅ロール3を気中に設置し、本発明を適用することでシワの発生を抑制しつつ光学特性を向上させることができる。
 拡幅ロール3が複数台設置される場合は、本発明を適用する拡幅ロール3が多い方が好ましく、全ての拡幅ロール3に本発明を適用する、すなわち全ての拡幅ロール3を2つのニップロール2、2’間に設置することが非常に好ましい。
The widening roll 3 may be disposed in the air (in the atmosphere) or in the liquid, but as shown in FIG. 1, the present invention is applied to the widening roll 3 installed in the air. In order to improve the optical characteristics, it is preferable.
In particular, when a plurality of widening rolls are installed in a swelling process or a dyeing process in which a change in width dimension due to film swelling is large, at least one widening roll 3 is installed in the air and the present invention is applied. Optical characteristics can be improved while suppressing the generation of wrinkles.
When a plurality of widening rolls 3 are installed, it is preferable that there are many widening rolls 3 to which the present invention is applied. The present invention is applied to all widening rolls 3, that is, all the widening rolls 3 are divided into two nip rolls 2, It is highly preferred to install between 2 '.
本発明の製造工程中の拡幅ロールの素材としては、ゴム、スポンジ等が挙げられるが、より好ましくはスポンジゴムロールであることが好ましい。ポリビニルアルコール系フィルムは浴液吸収により長手、幅両方向に膨潤するが、特に幅方向の膨潤が終息しないまま張力をかけるとロール上でシワや折れ込みが発生しやすい。拡幅ロールとしてスポンジゴムロールを使用すると、その高表面粗度に基づくフィルム把持力の高さから、十分な拡幅力を発揮でき、且つ拡幅ロールのもう一つの役割である蛇行防止機能も最大限発揮し、シワが少なくなり、折れ込みが無くなる。 Examples of the material for the widening roll during the production process of the present invention include rubber and sponge, but a sponge rubber roll is more preferable. The polyvinyl alcohol film swells in both the longitudinal and width directions due to absorption of the bath solution, but wrinkles and folds are likely to occur on the roll when tension is applied without the swelling in the width direction ending. If a sponge rubber roll is used as the widening roll, it can exert a sufficient widening force due to the high film gripping force based on its high surface roughness, and it also demonstrates the meandering prevention function, which is another role of the widening roll. , Wrinkles are reduced and folding is eliminated.
本発明において使用されるスポンジゴムロールとしては、スポンジの硬度がJIS K 6301の試験方法で測定したJISショアCスケールで約20~60度、より好ましくは約25~50度、密度が約0.4~0.6g/cm、より好ましくは約0.42~0.57g/cmおよび表面粗さがJIS B 0601(表面粗さ)の粗さ曲線の局部山頂の平均間隔Sで表して約10~30S、より好ましくは約15~25Sであることが好ましい。 The sponge rubber roll used in the present invention has a sponge hardness of about 20 to 60 degrees, more preferably about 25 to 50 degrees, and a density of about 0.4 on the JIS Shore C scale measured by the test method of JIS K 6301. ~ 0.6g / cm 3, approximately expressed more preferably about 0.42 ~ 0.57g / cm 3 and a surface roughness JIS B 0601 average local peaks of the roughness curve spacing (surface roughness) S It is preferably 10 to 30S, more preferably about 15 to 25S.
また、前記拡幅延伸工程における延伸が湿式延伸である場合、フィルムを浸す溶液の温度は、通常2~70℃であればよいが、特に20~40℃、好ましくは25~35℃の範囲の温度で拡幅ロールを介して延伸する場合に、最も光学特性を低下させずに延伸することが可能である。 Further, when the stretching in the widening stretching process is wet stretching, the temperature of the solution in which the film is immersed may be usually 2 to 70 ° C., but in particular 20 to 40 ° C., preferably 25 to 35 ° C. When the film is stretched through a widening roll, it is possible to stretch the film without degrading the optical properties most.
拡幅延伸工程後のそれぞれの工程において、フィルムの張力がそれぞれ実質的に一定になるように張力制御を行ってもよい。
 ホウ酸処理後に、上記したヨウ化物処理または亜鉛処理を行う場合には、これらの工程についても張力制御を行うことが好ましい。
In each step after the widening stretching step, tension control may be performed so that the tension of the film becomes substantially constant.
When the above-described iodide treatment or zinc treatment is performed after the boric acid treatment, it is preferable to perform tension control also for these steps.
それぞれの工程における張力は同じであっても良く、異なっていてもよい。張力制御におけるフィルムへの張力は、特に限定されるものではなく、単位幅当たり、約150N/m~2000N/m、好ましくは約600N/m~1500N/mの範囲内で適宜設定される。張力が約150N/mを下回ると、フィルムにシワなどができやすくなる。一方、張力が約2000N/mを超えると、フィルムの破断やベアリングの磨耗による低寿命化などの問題が生じることがある。また、この単位幅当たりの張力は、その工程の入口付近のフィルム幅と張力検出器の張力値から算出する。
なお、張力制御を行った場合に、不可避的に若干延伸・収縮される場合があるが、本発明においては、これは延伸処理に含めない。
The tension in each step may be the same or different. The tension applied to the film in the tension control is not particularly limited, and is appropriately set within a range of about 150 N / m to 2000 N / m, preferably about 600 N / m to 1500 N / m per unit width. When the tension is less than about 150 N / m, the film is likely to be wrinkled. On the other hand, if the tension exceeds about 2000 N / m, problems such as film breakage and shortened life due to bearing wear may occur. The tension per unit width is calculated from the film width near the entrance of the process and the tension value of the tension detector.
In addition, when tension control is performed, there are cases where the film is inevitably slightly stretched or shrunk, but in the present invention, this is not included in the stretching process.
このようにして製造された偏光フィルムの少なくとも片面に保護フィルムを接着剤で貼合することにより、偏光板を得ることができる。
保護フィルムとしては、例えば、トリアセチルセルロースやジアセチルセルロースのようなアセチルセルロース系樹脂からなるフィルム、ポリエチレンテレフタレートやポリエチレンナフタレート、ポリブチレンテレフタレートのようなポリエステル系樹脂からなるフィルム、ポリカーボネート系樹脂からなるフィルム、シクロオレフィン系樹脂からなるフィルム、アクリル系樹脂フィルム、ポリプロピレン系樹脂フィルムが挙げられる。
A polarizing plate can be obtained by pasting a protective film with an adhesive on at least one surface of the polarizing film thus produced.
As the protective film, for example, a film made of an acetyl cellulose resin such as triacetyl cellulose or diacetyl cellulose, a film made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate, or a film made of a polycarbonate resin , A film made of a cycloolefin resin, an acrylic resin film, and a polypropylene resin film.
接着剤と偏光フィルム及び/又は保護フィルムとの接着性を向上させるために、偏光フィルム及び/又は保護フィルムに、コロナ処理、火炎処理、プラズマ処理、紫外線照射、プライマー塗布処理、ケン化処理などの表面処理を施してもよい。 In order to improve the adhesiveness between the adhesive and the polarizing film and / or protective film, the polarizing film and / or protective film may be subjected to corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc. A surface treatment may be applied.
 次に、本発明の実施例を挙げて具体的に説明するが、本発明はこれらの実施例によりなんら制限されるものではない。
 <吸収軸の測定方法>
 フィルムの幅方向を基準とし、その基準軸に対して長手方向50mm、幅方向は全幅で帯状フィルム片を採取し、自動複屈折測定装置(大塚電子社製、商品名「RETS」)を用いて、当該フィルム片を幅方向に9等分した各箇所について、吸収軸角度を測定した。得られた軸角度のうち、最大値と最小値を差し引いた値を吸収軸のバラツキとして採用した。
Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
<Measurement method of absorption axis>
Using the width direction of the film as a reference, a strip-like film piece is collected with a longitudinal direction of 50 mm with respect to the reference axis, and the width direction is full width, using an automatic birefringence measuring apparatus (trade name “RETS” manufactured by Otsuka Electronics Co., Ltd.) The absorption axis angle was measured for each part of the film piece divided into 9 equal parts in the width direction. Of the obtained shaft angles, a value obtained by subtracting the maximum value and the minimum value was adopted as the variation of the absorption axis.
〔実施例1〕
厚さ75μmのポリビニルアルコールフィルム(クラレビニロンVF-PS#7500、重合度2,400 、ケン化度99.9モル%以上 )を30℃の純水に浸漬してフィルムを十分に膨潤させつつ、1.30倍に一軸延伸を行った。
次にヨウ素/ヨウ化カリウム/水が重量比で0.02/2.0/100 の30℃の染色槽に浸漬しつつ、積算延伸倍率で2.80倍となるように図1に示すような一軸延伸を行った。この時の拡幅ロールから搬出される前記フィルムの搬出方向に対する拡幅ロールの拡幅方向の角度(但し、フィルムの流れる方向を左から右に見たとき、フィルム1の搬出方向を0°とし、該搬出方向より時計回りの角度を-、反時計回りの角度を+とする。)(以下、拡幅ロールの抱き角という)は0°で搬送を行った。その後、ヨウ化カリウム/ホウ酸/水が重量比で12/4.4/100 の55℃水溶液に浸漬しつつ原反からの積算総延伸倍率が5.5倍になるまで一軸延伸を行った後、ヨウ化カリウム/ホウ酸/水が重量比で9/2.9/100の40℃水溶液に浸漬した。続いて5℃の純水で8秒間洗浄し、70℃で3分乾燥して、偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.04°であった。
[Example 1]
While immersing a 75 μm-thick polyvinyl alcohol film (Kuraray Vinylon VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) in pure water at 30 ° C., the film is sufficiently swollen, Uniaxial stretching was performed 1.30 times.
Next, as shown in FIG. 1, the iodine / potassium iodide / water is immersed in a dyeing bath at 30 ° C. with a weight ratio of 0.02 / 2.0 / 100 and the integrated draw ratio is 2.80 times. Uniaxial stretching was performed. The angle of the widening direction of the widening roll with respect to the carrying-out direction of the film carried out from the widening roll at this time (however, when the film flowing direction is viewed from left to right, the carrying-out direction of the film 1 is 0 °, The clockwise angle from the direction was-and the counterclockwise angle was +) (hereinafter referred to as the holding angle of the widening roll) was carried at 0 °. Thereafter, uniaxial stretching was carried out until the cumulative total draw ratio from the original fabric became 5.5 times while being immersed in a 55 ° C. aqueous solution of potassium iodide / boric acid / water in a weight ratio of 12 / 4.4 / 100. Then, potassium iodide / boric acid / water was immersed in a 40 ° C. aqueous solution having a weight ratio of 9 / 2.9 / 100. Subsequently, the film was washed with pure water at 5 ° C. for 8 seconds and dried at 70 ° C. for 3 minutes to obtain a polarizing film. The dispersion of the absorption axis of the obtained polarizing film (difference between maximum and minimum) was 0.04 °.
〔実施例2〕
 染色槽における拡幅ロールの抱き角を30°とした以外は実施例1と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.08°であった。
[Example 2]
A polarizing film was obtained in the same manner as in Example 1 except that the holding angle of the widening roll in the dyeing tank was 30 °. The dispersion of the absorption axis of the obtained polarizing film (difference between maximum and minimum) was 0.08 °.
〔実施例3〕
染色槽における拡幅ロールの抱き角を60°とした以外は実施例1と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.12°であった。
Example 3
A polarizing film was obtained in the same manner as in Example 1 except that the holding angle of the widening roll in the dyeing tank was 60 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.12 °.
〔実施例4〕
 染色槽における拡幅ロールの抱き角を-30°とした以外は実施例1と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.09°であった。
Example 4
A polarizing film was obtained in the same manner as in Example 1 except that the holding angle of the widening roll in the dyeing tank was −30 °. The dispersion of the absorption axis of the obtained polarizing film (difference between maximum and minimum) was 0.09 °.
〔実施例5〕
 厚さ75μmのポリビニルアルコールフィルム(クラレビニロンVF-PS#7500、重合度2,400 、ケン化度99.9モル%以上 )を30℃の純水に浸漬してフィルムを十分に膨潤させつつ、1.30倍に一軸延伸を行った。
次にヨウ素/ヨウ化カリウム/水が重量比で0.02/2.0/100 の30℃の染色槽に浸漬しつつ、積算延伸倍率で1.65倍となるように図1に示すような一軸延伸を行った。この時の拡幅ロールの抱き角は0°で搬送を行った。その後、ヨウ化カリウム/ホウ酸/水が重量比で11/3.5/100 の53℃水溶液に浸漬しつつ原反からの積算延伸倍率が5.8倍になるまで一軸延伸を行った後、ヨウ化カリウム/ホウ酸/水が重量比で11/3.5/100の40℃水溶液に浸漬した。続いて5℃の純水で8秒間洗浄し、70℃で3分乾燥して、偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.10°であった。
Example 5
While immersing a 75 μm-thick polyvinyl alcohol film (Kuraray Vinylon VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) in pure water at 30 ° C., the film is sufficiently swollen, Uniaxial stretching was performed 1.30 times.
Next, as shown in FIG. 1, the iodine / potassium iodide / water is immersed in a dyeing bath at 30 ° C. with a weight ratio of 0.02 / 2.0 / 100 and the integrated draw ratio is 1.65 times. Uniaxial stretching was performed. The holding angle of the widening roll at this time was conveyed at 0 °. Thereafter, uniaxial stretching was performed until the cumulative draw ratio from the raw material was 5.8 times while being immersed in a 53 ° C. aqueous solution of potassium iodide / boric acid / water in a weight ratio of 11 / 3.5 / 100. Then, it was immersed in a 40 ° C. aqueous solution of potassium iodide / boric acid / water at a weight ratio of 11 / 3.5 / 100. Subsequently, the film was washed with pure water at 5 ° C. for 8 seconds and dried at 70 ° C. for 3 minutes to obtain a polarizing film. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.10 °.
〔実施例6〕
 染色槽における拡幅ロールの抱き角を30°とした以外は実施例5と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.13°であった。
Example 6
A polarizing film was obtained in the same manner as in Example 5 except that the holding angle of the widening roll in the dyeing tank was 30 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.13 °.
〔実施例7〕
 染色槽における拡幅ロールの抱き角を60°とした以外は実施例5と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.15°であった。
Example 7
A polarizing film was obtained in the same manner as in Example 5 except that the holding angle of the widening roll in the dyeing tank was 60 °. The variation in absorption axis (maximum and minimum difference) of the obtained polarizing film was 0.15 °.
〔比較例1〕
 染色槽における拡幅ロールの抱き角を90°とした以外は実施例1と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.23°であった。
[Comparative Example 1]
A polarizing film was obtained in the same manner as in Example 1 except that the holding angle of the widening roll in the dyeing tank was 90 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.23 °.
〔比較例2〕
 染色槽における拡幅ロールの抱き角を90°とした以外は実施例5と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.24°であった。
[Comparative Example 2]
A polarizing film was obtained in the same manner as in Example 5 except that the holding angle of the widening roll in the dyeing tank was 90 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.24 °.
 上記した実施例1~4および比較例1の結果を以下に示す。
Figure JPOXMLDOC01-appb-T000001

 表1より、実施例1~7は、比較例1、2より吸収軸のバラツキ(最大-最小の差)が少ないことがわかる。
The results of Examples 1 to 4 and Comparative Example 1 described above are shown below.
Figure JPOXMLDOC01-appb-T000001

From Table 1, it can be seen that Examples 1 to 7 have less absorption axis variation (maximum-minimum difference) than Comparative Examples 1 and 2.
〔実施例8〕
膨潤槽において、抱き角を0°とした気中の拡幅ロールを介して延伸倍率が2.20倍となる、図1に示すような一軸延伸を行い、続けて染色槽にて積算延伸倍率で2.80倍となる、図1に示すような一軸延伸を行った(染色槽における拡幅ロールの抱き角は0°)以外は実施例1と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.11°であった。
Example 8
In the swelling tank, uniaxial stretching as shown in FIG. 1 is performed through a widening roll in the air with a hugging angle of 0 °, and then, as shown in FIG. A polarizing film was obtained in the same manner as in Example 1 except that the uniaxial stretching as shown in FIG. 1 was performed at 2.80 times (the holding angle of the widening roll in the dyeing tank was 0 °). The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.11 °.
〔比較例3〕
膨潤槽における拡幅ロールの抱き角を90°とした以外は実施例8と同様にして偏光フィルムを得た。得られた偏光フィルムの吸収軸のバラツキ(最大と最小の差)は0.34°であった。
[Comparative Example 3]
A polarizing film was obtained in the same manner as in Example 8 except that the holding angle of the widening roll in the swelling tank was 90 °. The obtained polarizing film had a variation in absorption axis (difference between maximum and minimum) of 0.34 °.
 上記した実施例8および比較例3の結果を以下に示す。
Figure JPOXMLDOC01-appb-T000002

 表2より、実施例8は、吸収軸のバラツキ(最大-最小の差)が比較例3より低いことがわかる。
The results of Example 8 and Comparative Example 3 described above are shown below.
Figure JPOXMLDOC01-appb-T000002

From Table 2, it can be seen that Example 8 has lower absorption axis variation (maximum-minimum difference) than Comparative Example 3.
1: ポリビニルアルコールフィルム、2、2’:ニップロール、3:拡幅ロール、4:処理液、5:ガイドロール、10: ホウ酸処理槽(延伸処理)、M:拡幅方向、d:拡幅ロール3の径 1: polyvinyl alcohol film, 2, 2 ′: nip roll, 3: widening roll, 4: treatment liquid, 5: guide roll, 10: boric acid treatment tank (stretching treatment), M: widening direction, d: widening roll 3 Diameter

Claims (6)

  1.  ポリビニルアルコール系フィルムを膨潤処理、染色処理、ホウ酸処理および洗浄処理の順に処理する工程を有し、これらのいずれかの工程の前または工程中に2つのニップロール間の周速差を利用して一軸延伸を行う偏光フィルムの製造方法であって、
     ここで、前記一軸延伸が、2つのニップロール間に少なくとも1台の拡幅ロールを設置して拡幅と一軸延伸を行う拡幅延伸工程を含み、拡幅延伸工程を含む拡幅延伸工程までの積算延伸倍率(但し、拡幅延伸工程までに他の延伸工程がない場合は拡幅延伸工程での延伸倍率)が1.6倍以上であり、拡幅延伸工程において、拡幅ロールから搬出される前記フィルムの搬出方向に対する拡幅ロールの拡幅方向の角度が-40°~70°(但し、フィルムの流れる方向を左から右に見たときの、フィルムの拡幅ロールからの搬出方向を0°とし、該搬出方向より時計回りの角度を-、反時計回りの角度を+とする。)である方法。
    It has a step of processing a polyvinyl alcohol film in the order of swelling treatment, dyeing treatment, boric acid treatment and washing treatment, and utilizes the difference in peripheral speed between two nip rolls before or during any of these steps. A method for producing a polarizing film that performs uniaxial stretching,
    Here, the uniaxial stretching includes a widening stretching step in which at least one widening roll is installed between two nip rolls to perform widening and uniaxial stretching, and an integrated stretching ratio up to the widening stretching step including the widening stretching step (however, When there is no other stretching step before the widening stretching step, the stretching ratio in the widening stretching step) is 1.6 times or more, and in the widening stretching step, the widening roll with respect to the carry-out direction of the film unloaded from the widening roll The angle in the widening direction of the film is −40 ° to 70 ° (however, when the film flowing direction is viewed from the left to the right, the film unloading direction from the widening roll is 0 °, and the clockwise angle from the unloading direction. Is-, and the counterclockwise angle is +).
  2.  拡幅延伸工程を2つ以上有する請求項1に記載の方法。 The method of Claim 1 which has two or more widening extending processes.
  3.  拡幅延伸工程における拡幅ロールを気中に配置する請求項1または2に記載の方法。 The method according to claim 1 or 2, wherein the widening roll in the widening stretching step is disposed in the air.
  4.  拡幅延伸工程における拡幅ロールがスポンジゴムロールであり、そのスポンジの硬度がJISショアCスケールで20~60度、密度が0.4~0.6g/cmおよび表面粗さが10~30Sである請求項1に記載の方法。 The widening roll in the widening and stretching step is a sponge rubber roll, the sponge has a hardness of 20 to 60 degrees on a JIS Shore C scale, a density of 0.4 to 0.6 g / cm 3 and a surface roughness of 10 to 30S. Item 2. The method according to Item 1.
  5.  拡幅延伸工程における延伸が湿式延伸により行われ、使用する液の温度が20℃~40℃である請求項1に記載の方法。 The method according to claim 1, wherein the stretching in the widening stretching step is performed by wet stretching, and the temperature of the liquid to be used is 20 ° C to 40 ° C.
  6.  拡幅延伸工程までの積算延伸倍率(但し、該工程までに他の延伸工程がない場合は該工程での延伸倍率)が2倍以上である請求項1に記載の方法。 2. The method according to claim 1, wherein the cumulative stretching ratio up to the widening stretching step (however, when there is no other stretching step up to the step, the stretching ratio in the step) is 2 times or more.
PCT/JP2011/064169 2010-06-22 2011-06-21 Method for manufacturing polarizing film WO2011162259A1 (en)

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