Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL 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
  • G02F1/00—Devices 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
  • G02F1/01—Devices 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 
  • G02F1/13—Devices 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
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors

Definitions

• the present invention relates to a polarizing film, a polarizing plate and a liquid crystal panel which are suitably used for a liquid crystal display device.
• the polarizing plate is widely used as a polarization supplying element in an image display device such as a liquid crystal display device.
• a polarizing plate generally has a structure in which a protective film is bonded to a polarizing film using an adhesive (for example, JP 2013-148806 A (Patent Document 1)).
• a polarizing plate particularly a thin polarizing plate
• the polarizing film has an absorption axis direction (MD) and further a transmission axis direction (absorption). Warpage is likely to occur in a direction (TD) perpendicular to the axial direction, for example, in a high temperature environment or a high humidity environment.
• MD absorption axis direction
• Absorption transmission axis direction
• Warpage is likely to occur in a direction (TD) perpendicular to the axial direction, for example, in a high temperature environment or a high humidity environment.
• TD transmission axis direction
• the resulting liquid crystal panel is warped particularly when the liquid crystal cell is thin and has low rigidity. The warpage of the liquid crystal panel may adversely affect the visibility of the liquid crystal display device.
• an object of the present invention is to provide a polarizing film that can provide a polarizing plate with improved warping to such an extent that warping of the liquid crystal panel can be sufficiently suppressed, and a polarizing plate and a liquid crystal panel using the polarizing film.
• the present invention provides the following polarizing film, polarizing plate and liquid crystal panel.
• the polarizing film according to [1] which is a stretched film.
• the polarizing film according to [1] or [2], wherein the thickness is 20 ⁇ m or less.
• a polarizing film having a shrinkage force per width of 2 mm in the absorption axis direction when held at 80 ° C. for 4 hours is 1.5 N or less, A protective film disposed on at least one surface of the polarizing film; A polarizing plate including [7] The polarizing plate according to [6], wherein the protective film has a thickness of 50 ⁇ m or less.
• [8] including a protective film disposed on both sides of the polarizing film;
• the polarizing plate as described in [6] or [7] whose thickness ratio of the other protective film with respect to one protective film is 1.5 or more.
• a liquid crystal panel comprising a liquid crystal cell and the polarizing plate according to any one of [6] to [9] disposed on at least one surface thereof.
• the liquid crystal panel according to [10] wherein the thickness of the substrate constituting the liquid crystal cell is 0.5 mm or less.
• the polarizing film of the present invention it is possible to provide a polarizing plate with improved warping to such an extent that warpage of the liquid crystal panel can be sufficiently suppressed.
• the liquid crystal panel using the polarizing plate of the present invention is suppressed in warpage and can be suitably applied to a thin liquid crystal display device.
• a polarizing film is an optical film having the property of absorbing linearly polarized light having a vibration plane parallel to the absorption axis and transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis (parallel to the transmission axis).
• the polarizing film of the invention is characterized in that the shrinkage force per 2 mm width in the absorption axis direction is 1.5 N or less.
• the absorption axis direction is also referred to as “MD”
• the transmission axis direction (direction orthogonal to the absorption axis) is also referred to as “TD”.
• the present inventor performs various studies on the warpage of a polarizing plate formed by laminating a protective film on one or both sides of a polarizing film, and uses a cut sample of the polarizing plate [Example].
• the ratio of the warpage amount in MD (the warpage amount in the absorption axis direction) and the warpage amount in TD (the warpage amount in the transmission axis direction) of the polarizing plate determined in accordance with the measurement method described in detail in the section (hereinafter referred to as “MD / It was also found that when the TD warpage ratio is adjusted to 1.0 or the vicinity thereof, the warpage of a liquid crystal panel produced using this polarizing plate can be effectively suppressed.
• MD shrinkage the shrinkage force per 2 mm width in the absorption axis direction of the polarizing film
• the polarizing film is usually produced through a stretching process, and the stretching axis in this case is usually MD (the absorption axis is also MD). Therefore, the conventional polarizing plate has a MD / TD warp ratio of 1.0 or larger than the vicinity thereof.
• the MD / TD warpage ratio of the polarizing plate can be set to 1.0 or the vicinity thereof.
• MD contraction force here means MD contraction force of the polarizing film before sticking a protective film to make a polarizing plate, and per 2 mm width in the absorption axis direction when held at 80 ° C. for 4 hours.
• the contraction force is measured using a cut sample of the polarizing film, and the details of the measuring method are as described in the [Example] section. Since it is effective for bringing the MD / TD warpage ratio of the polarizing plate close to 1.0, the MD shrinkage force is preferably 0.1 to 1.3 N, more preferably 0.3 to 1.1 N. is there.
• the shrinkage force per 2 mm width in the transmission axis direction (hereinafter also referred to as “TD shrinkage force”) when kept at 80 ° C. for 4 hours is usually 0.1 to 1.0 N. It is.
• the details of the method for measuring the TD contraction force are as described in the [Example] section.
• the TD contraction force here also means the TD contraction force of the polarizing film before the protective film is bonded to form a polarizing plate.
• the polarizing film of the present invention can be a single (single layer) film made of a stretched thermoplastic resin film, typically a uniaxially stretched polyvinyl alcohol system. A dichroic dye is adsorbed and oriented on a resin film.
• a saponified polyvinyl acetate resin can be used as the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film.
• the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith.
• examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.
• the degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, more preferably 94.0. It is in the range of ⁇ 99.0 mol%.
• (meth) acryl means at least one selected from acrylic and methacrylic. The same applies to cases such as “(meth) acryloyl”.
• the average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1500 to 8000, and further preferably 2000 to 5000.
• the average degree of polymerization of the polyvinyl alcohol resin can be determined according to JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain preferable polarization performance, and if it exceeds 10,000, film processability may be inferior.
• the dichroic dye adsorbed and oriented on the polarizing film can be iodine or a dichroic organic dye.
• the dichroic organic dye include: Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Includes Sky Blue, Direct First Orange S and First Black.
• a dichroic dye may be used individually by 1 type, and may use 2 or more types together.
• the thickness of the polarizing film is usually about 5 to 40 ⁇ m, but from the viewpoint of thinning the polarizing plate and the liquid crystal panel, it is preferable that the thickness is as thin as possible in order to ensure sufficient handling and durability. Therefore, the thickness of the polarizing film is preferably 20 ⁇ m or less, and more preferably 15 ⁇ m or less. However, since the MD / TD warp ratio is likely to be larger than 1 as the thickness is thinner, it is preferable to lower the MD contraction force in order to bring the MD / TD warp ratio closer to 1.
• Polarization characteristics of polarizing film can be mainly expressed by numerical values called single transmittance and degree of polarization.
• Single transmittance ( ⁇ ) 0.5 ⁇ (Tp ( ⁇ ) + Tc ( ⁇ ))
• Polarization degree ( ⁇ ) 100 ⁇ (Tp ( ⁇ ) ⁇ Tc ( ⁇ )) / (Tp ( ⁇ ) + Tc ( ⁇ ))
• Tp ( ⁇ ) is the transmittance (%) of the polarizing film measured in the relationship between the linearly polarized light having the incident wavelength ⁇ nm and the parallel Nicol, and Tc ( ⁇ ) is crossed with the linearly polarized light having the incident wavelength ⁇ nm.
• It is the transmittance
• the single transmittance ( ⁇ ) and the degree of polarization ( ⁇ ) obtained for each wavelength are subjected to sensitivity correction called visibility correction, respectively, and the visibility correction single transmittance (Ty) and the visibility correction polarization, respectively. Called degrees (Py). These Ty and Py values can be measured using, for example, a spectrophotometer.
• the polarizing film preferably has a visibility corrected single transmittance (Ty) of 40% or more, and a visibility corrected polarization degree.
• Ty visibility corrected single transmittance
• Py is preferably 90% or more.
• Ty is more preferably 42% or more, and Py is more preferably 99% or more. More preferably, Ty is 42.8% or more, and Py is 99.99% or more.
• the boron content in the polarizing film is reduced. It is preferably 0.5 to 2.0% by weight.
• the boron content in the polarizing film can be calculated as follows. First, the weight of the polarizing film is measured, and then the polarizing film is immersed in hot water at 95 ° C. for 60 minutes to completely dissolve it. Subsequently, the aqueous solution in which the polarizing film is dissolved is subjected to neutralization titration, and the boron content in the polarizing film is calculated from the weight and titration amount of the polarizing film.
• the polarizing plate of the present invention includes a polarizing film and a protective film disposed on at least one surface thereof.
• the MD shrinkage force of the polarizing film is set to 1.5 N or less as described above, and preferably is set to 0.8. It is 1 to 1.3N, and more preferably 0.3 to 1.1N. Further, the TD shrinkage force of the polarizing film provided in the polarizing plate of the present invention is usually 0.1 to 1.0 N.
• the MD and TD shrinkage forces mentioned here have the same meaning as the shrinkage force described in the above section ⁇ Polarization film> except that the shrinkage force of the polarizing film obtained by removing the protective film from the polarizing plate.
• the details of the measurement method are as described in the [Example] section. Since the heat history may be different before and after the protective film is bonded, the value of the shrinkage force in the above section ⁇ Polarizing film> may be slightly different from the value of the shrinkage force here.
• the protective film that is bonded and disposed on one or both sides of the polarizing film is a thermoplastic resin, for example, a chain polyolefin resin (polypropylene resin, etc.), a cyclic polyolefin resin (norbornene resin, etc.).
• Polyolefin resin such as cellulose triacetate, cellulose ester resin such as cellulose diacetate; polyester resin such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate; polycarbonate resin; polymethyl methacrylate resin (Meth) acrylic resin; or a transparent resin film made of a mixture or copolymer thereof.
• a protective film is normally laminated
• the protective film may be a protective film having both optical functions such as a retardation film and a brightness enhancement film.
• a retardation film provided with an arbitrary retardation value by stretching a transparent resin film made of the above material (uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the film. It can be.
• a surface treatment layer such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, or an antifouling layer can be formed on the surface of the protective film opposite to the polarizing film.
• the method for forming the surface treatment layer on the surface of the protective film is not particularly limited, and a known method can be used.
• these protective films may be the same kind of resin film or a different kind of resin film.
• the protective films on both sides are preferably films made of the same kind of resin, but even when made of different kinds of resins. According to the present invention, the MD / TD warp ratio can be made sufficiently close to 1.0.
• the thickness of the protective film is preferably thin from the viewpoint of reducing the thickness of the polarizing plate, but if it is too thin, the strength is lowered and the processability is poor. Therefore, the thickness of the protective film is preferably 5 to 150 ⁇ m, more preferably 5 to 100 ⁇ m, and still more preferably 10 to 50 ⁇ m.
• the thickness of the protective film is preferably 5 to 150 ⁇ m, more preferably 5 to 100 ⁇ m, and still more preferably 10 to 50 ⁇ m.
• it is conceivable to increase the reinforcing effect of the protective film for example, to increase the thickness of the protective film.
• this means is disadvantageous for making the polarizing plate thinner. According to the present invention, even if the thickness of the protective film is reduced to 50 ⁇ m or less, the MD / TD warpage ratio can be brought close to 1.0.
• these protective films may have the same thickness or different thicknesses.
• As another means for bringing the MD / TD warpage ratio closer to 1.0 it is conceivable to bond protective films on both surfaces of the polarizing film and utilize the reinforcing effect of these protective films. However, in the case of this means, there arises a restriction that the thicknesses of the protective films on both sides must be equal or nearly equal. According to the present invention, even when the thickness ratio of the protective films on both sides is 1.5 or more, and even 2.0 or more, the MD / TD warpage ratio can be close to 1.0.
• the MD / TD warpage ratio can be made close to 1.0 regardless of whether the protective film is laminated on one side or on both sides.
• the polarizing plate of the present invention is advantageous in that the MD / TD warpage ratio can be brought close to 1.0 while maintaining a wide degree of freedom such as the number, material, and thickness of the protective film to be bonded. It is.
• the polarizing plate (polarizing film) can have an appropriate shape and size required for the applied liquid crystal display device. For example, a rectangular shape having a long side of 8 cm or more and a short side of 5 cm or more (for example, Rectangular, square).
• a rectangular shape having a long side of 8 cm or more and a short side of 5 cm or more (for example, Rectangular, square).
• the warpage of the liquid crystal panel tends to become more prominent as the size of the polarizing plate is larger. Even if the side is increased to 100 cm or more, warping of the liquid crystal panel can be satisfactorily suppressed.
• the MD / TD warpage ratio in the polarizing plate of the present invention is 1.0 or in the vicinity thereof, more specifically 1.0 ⁇ 0.4, and preferably 1.0 ⁇ 0. .3, more preferably 1.0 ⁇ 0.2. If it is this range, the curvature of a liquid crystal panel can be suppressed effectively.
• the polarizing plate can have an adhesive layer for bonding to a liquid crystal cell.
• the pressure-sensitive adhesive layer is laminated on the outer surface of the protective film (for example, when a protective film is laminated on both sides of the polarizing film) or on the polarizing film surface (for example, when the protective film is laminated on one side of the polarizing film). Can do.
• the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is usually based on a (meth) acrylic resin, styrene resin, silicone resin or the like, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. It consists of an adhesive composition.
• the thickness of the pressure-sensitive adhesive layer can be about 1 to 40 ⁇ m.
• a polarizing film formed by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film is a step of uniaxially stretching the polyvinyl alcohol resin film; by dyeing the polyvinyl alcohol resin film with a dichroic dye
• a step of adsorbing a dichroic dye a step of treating a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous boric acid solution; and a step of washing after the treatment with an aqueous boric acid solution. it can.
• the thickness of the polyvinyl alcohol resin film as a raw material is, for example, about 10 to 150 ⁇ m. Since the polarizing film having a thickness of 20 ⁇ m or less can be easily produced, the thickness of the polyvinyl alcohol-based resin film is preferably 40 ⁇ m or less.
• the uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after the dyeing of the dichroic dye.
• this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.
• rolls having different peripheral speeds may be uniaxially stretched or may be stretched uniaxially using a hot roll.
• the uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a solvent is used and the polyvinyl alcohol-based resin film is swollen.
• the draw ratio is usually about 3 to 8 times. In order to impart good polarization characteristics, the draw ratio is preferably 4 times or more, more preferably 5 times or more.
• the total draw ratio before the boric acid treatment is more than 1.0 times, preferably 1.01 to 2.5 times.
• the total draw ratio is more preferably 1.01 to 2.1 times, and still more preferably 1.01 to 1.7 times.
• a method of dyeing a polyvinyl alcohol resin film with a dichroic dye for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution (dye solution) containing the dichroic dye is employed.
• the polyvinyl alcohol-based resin film is preferably subjected to an immersion treatment (swelling treatment) in water before the dyeing treatment.
• iodine When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed.
• the content of iodine in this dyeing aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water.
• the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water.
• the temperature of the dyeing aqueous solution is usually about 20 to 40 ° C.
• a method of immersing and dyeing a polyvinyl alcohol-based resin film in a dyeing aqueous solution containing the dichroic organic dye is usually employed.
• the content of the dichroic organic dye in the aqueous dyeing solution is usually about 1 ⁇ 10 ⁇ 4 to 10 parts by weight per 100 parts by weight of water, and preferably about 1 ⁇ 10 ⁇ 3 to 1 part by weight.
• This dyeing aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid.
• the temperature of the dyeing aqueous solution is usually about 20 to 80 ° C.
• the boric acid treatment after dyeing with the dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution.
• the amount of boric acid in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight per 100 parts by weight of water.
• the boron content in the polarizing film is 0.5 to 2%. It is preferable to set it to 0.0% by weight.
• the amount of boric acid in the boric acid-containing aqueous solution is preferably 0.1 to 3 parts by weight per 100 parts by weight of water. More preferred are parts by weight.
• this boric acid-containing aqueous solution preferably contains potassium iodide.
• the amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight per 100 parts by weight of water, and preferably about 5 to 12 parts by weight.
• the temperature of the boric acid-containing aqueous solution is usually about 50 to 85 ° C.
• the polyvinyl alcohol-based resin film after the boric acid treatment is usually washed by being immersed in water or an aqueous potassium iodide solution.
• the temperature of water or potassium iodide aqueous solution in the washing treatment is usually about 5 to 40 ° C.
• a drying process is performed to obtain a polarizing film.
• the drying treatment can be performed using a hot air dryer, a far infrared heater, a hot roll, or the like.
• the temperature for the drying treatment is usually about 30 to 100 ° C., preferably 50 to 80 ° C.
• the film moisture content before the drying treatment is preferably 25 to 55% by weight from the viewpoint of drying efficiency.
• the film moisture content after the drying step is usually 5 to 35% by weight, but from the viewpoint of transportability, it is preferably 6 to 33% by weight.
• the polarizing plate can be obtained by laminating a protective film via an adhesive layer on one side or both sides of a polarizing film (single film) obtained as described above.
• a polarizing film single film obtained as described above.
• an adhesive for forming the adhesive layer a water-based adhesive or a photocurable adhesive can be used.
• the adhesive agent which forms two adhesive bond layers may be the same, and a different kind may be sufficient as it.
• one side may be bonded using a water-based adhesive, and the other side may be bonded using a photocurable adhesive.
• water-based adhesive examples include an adhesive made of a polyvinyl alcohol-based resin aqueous solution and an aqueous two-component urethane emulsion adhesive.
• a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used.
• Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith.
• a polyvinyl alcohol copolymer obtained by saponifying a polymer, or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group thereof can be used.
• the water-based adhesive can include additives such as polyvalent aldehydes, water-soluble epoxy compounds, melamine compounds, zirconia compounds, and zinc compounds.
• the drying temperature is preferably 30 to 100 ° C. When it is lower than 30 ° C., the protective film is easily peeled off from the polarizing film. If the drying temperature exceeds 100 ° C., the polarizing performance of the polarizing film may be deteriorated by heat.
• a curing step of curing at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 45 ° C. for about 12 to 600 hours may be provided.
• the photocurable adhesive refers to an adhesive that is cured by irradiating active energy rays such as ultraviolet rays, for example, an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and a binder.
• active energy rays such as ultraviolet rays
• an adhesive containing a polymerizable compound and a photopolymerization initiator an adhesive containing a photoreactive resin
• a binder containing resin and a photoreactive crosslinking agent
• the thing containing resin and a photoreactive crosslinking agent can be mentioned.
• the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from the photopolymerizable monomer.
• photoinitiator what contains the substance which generate
• the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator an adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.
• the photocurable adhesive When using a photocurable adhesive, after bonding, the photocurable adhesive is cured by irradiating active energy rays.
• the light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable.
• a microwave excitation mercury lamp, a metal halide lamp and the like are preferably used.
• the bonding surface of the polarizing film and / or the protective film Prior to the bonding of the polarizing film and the protective film, the bonding surface of the polarizing film and / or the protective film has a plasma treatment, a corona treatment, an ultraviolet irradiation treatment, a frame (flame) treatment, in order to improve adhesion. Easy adhesion treatment such as saponification treatment may be performed.
• the polarizing plate of the present invention is not limited to the above method, and a polyvinyl alcohol-based resin layer is formed on a base film as described in, for example, JP-A-2009-98653, and this resin layer is used as a polarizer layer ( It can also be produced by a method that corresponds to a polarizing film. This method is advantageous for obtaining a thin polarizer layer.
• the method is After applying a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the base film, a resin layer forming step of forming a polyvinyl alcohol-based resin layer by drying to obtain a laminated film, A stretching step of stretching a laminated film to obtain a stretched film; A dyeing step of obtaining a polarizing laminated film by dyeing a polyvinyl alcohol resin layer of a stretched film with a dichroic dye to form a polarizer layer (corresponding to a polarizing film); The 1st bonding process of bonding a protective film using the adhesive agent on the polarizer layer of a light-polarizing laminated film, and obtaining a bonding film, Peeling process of peeling and removing the base film from the bonding film to obtain a polarizing plate with a single-sided protective film, Can be included in this order.
• the liquid crystal panel of the present invention includes a liquid crystal cell and the polarizing plate according to the present invention which is bonded and disposed on at least one surface thereof.
• the polarizing plate is bonded to the liquid crystal cell via an adhesive layer.
• the liquid crystal panel may include the polarizing plate according to the present invention only on one side or on both sides. From the viewpoint of suppressing warpage of the liquid crystal panel, the polarizing plate according to the present invention is preferably disposed on both surfaces of the liquid crystal cell.
• the liquid crystal cell includes a pair of substrates (for example, a transparent substrate such as a glass substrate) arranged to face each other at a predetermined distance by a spacer, and a liquid crystal layer formed by enclosing a liquid crystal between the pair of substrates.
• a TN Transmission Nematic
• STN Super-Twisted Nematic
• VA Very Alignment
• IPS In-Plane Switching
• the thickness of the substrate constituting the liquid crystal cell is arbitrary, but when the MD / TD warpage ratio is large as in a conventional polarizing plate, the warp of the liquid crystal panel tends to become more prominent as the substrate is thinner. According to the present invention, even if the thickness of the substrate is reduced to, for example, 0.5 mm or less, and further to 0.3 mm or less, the warp of the liquid crystal panel can be satisfactorily suppressed.
• the liquid crystal panel can have an appropriate shape and size required for the applied liquid crystal display device, and can be, for example, a rectangular shape (for example, a rectangle or a square) having a long side of 8 cm or more and a short side of 5 cm or more.
• a rectangular shape for example, a rectangle or a square
• the warpage of the liquid crystal panel tends to become more prominent as the size of the liquid crystal panel (and hence the polarizing plate) increases. Even when the size is increased to, for example, a long side of 200 cm or more and a short side of 100 cm or more, warping of the liquid crystal panel can be satisfactorily suppressed.
• the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
• the boron content in the polarizing film, the polarizing properties of the polarizing film, the MD and TD shrinkage (before and after bonding of the protective film), and the MD / TD warpage ratio are as follows: Measured according to the method.
• MD and TD shrinkage force of polarizing film before bonding protective film From the obtained polarizing film, for measuring MD shrinkage force having a width of 2 mm and a length of 10 mm with the absorption axis direction (MD, stretching direction) as the long side. A sample was cut out. The long side generated when this sample is set on the thermomechanical analyzer (TMA) “EXSTAR-6000” manufactured by SII Nanotechnology, Inc. and kept at 80 ° C. for 4 hours while keeping the dimensions constant. The contraction force (MD contraction force) in the direction (absorption axis direction, MD) was measured.
• TMA thermomechanical analyzer
• TD contraction force was measured in the same manner as described above except that a sample having a width of 2 mm and a length of 10 mm having a long side in the transmission axis direction (direction orthogonal to the absorption axis direction, TD) was used.
• MD contraction force it is the same as MD contraction force except that a polarizing plate piece having a width of 2 mm and a length of 10 mm having a long side in the transmission axis direction (direction orthogonal to the absorption axis direction, TD) is cut out from the polarizing film from which the protective film has been removed. Then, the TD contraction force was measured.
• Two-dimensional dimensional measuring instrument is used to measure the height at 5 points (5, 40, 75, 110, and 145 mm along the long side direction, all located at the center in the short side direction), with one of the short sides of the sample as 0 mm
• the amount of MD warpage (mm) before heating was determined as the difference between the maximum height and the minimum height.
• the sample was then heated at 85 ° C. for 250 hours. With respect to the sample after heating, one of the short sides of the sample is defined as a point 0 mm, and the height at five points (points 5 mm, 40 mm, 75 mm, 110 mm, and 145 mm) along the long side direction (all located at the center in the short side direction).
• the thickness was measured with a two-dimensional dimension measuring device, and the MD warpage amount (mm) after heating was determined as the difference between the maximum height and the minimum height.
• the value obtained by subtracting the MD warp amount before heating from the MD warp amount after heating was defined as the MD warp amount.
• the film was washed by immersing the film in a washing tank filled with 5 ° C. pure water for 2 seconds, followed by drying at 60 ° C. for 160 seconds by passing the film through a hot-air drying furnace to obtain polyvinyl alcohol.
• a long polarizing film in which iodine was adsorbed and oriented was obtained.
• the longitudinal uniaxial stretching process is mainly performed in the dyeing process and the boric acid treatment process, the total stretch ratio before the boric acid treatment process is 2.1 times, and the total stretch ratio from the raw film is 5.5 times. there were.
• the thickness of the polarizing film was 12.5 ⁇ m, and the boron content in the polarizing film was 1.5% by weight.
• an acetoacetyl group-modified polyvinyl alcohol-based resin (trade name “Gosefimer Z-200”, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) is dissolved in pure water to prepare a 10% aqueous solution.
• sodium glyoxylate as a cross-linking agent was mixed so that the weight ratio of the former: the latter solid content was 1: 0.1, and 1 polyvinylacetate resin modified with acetoacetyl group was added to 100 parts by weight of water. What was diluted with pure water so that it might become a weight part was used.
• Example 2 to 4 Example, except that the thickness of the raw film made of polyvinyl alcohol, the drying temperature in the drying process at the time of polarizing plate preparation (after bonding of the protective film), and the thickness of the obtained polarizing film are as shown in Table 1. In the same manner as in Example 1, a polarizing film and a polarizing plate were produced.
• aqueous solution having a weight ratio of potassium iodide / boric acid / water of 12 / 1.5 / 100 for 64 seconds.
• the film was washed with water by immersing the film in a washing tank filled with 5 ° C. pure water for 2 seconds.
• the film was passed through a hot air drying oven and dried at 60 ° C. for 160 seconds to obtain a long polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol.
• the longitudinal uniaxial stretching process is mainly performed in the dyeing process and the boric acid treatment process.
• the total draw ratio before the boric acid treatment process is 3.7 times, and the total draw ratio from the raw film is 5.5 times. there were.
• the thickness of the polarizing film was 13.2 ⁇ m, and the boron content in the polarizing film was 2.4% by weight.
• “Boric acid amount” in Table 1 indicates the content of boric acid per 100 parts by weight of water in the aqueous solution used for boric acid treatment.

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