Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/11—Anti-reflection coatings
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/14—Protective coatings, e.g. hard coatings
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/02—Diffusing elements; Afocal elements
• • 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
• • 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
  • G02F1/133528—Polarisers

Definitions

• the present invention relates to a polyester film for protecting a polarizer, a polarizing plate, and a liquid crystal display device.
• a liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter, etc. are sandwiched between glass substrates, and two polarizing plates provided on both sides of the cell, and each polarizing plate is polarized.
• the child also referred to as a polarizing film
• two optical films for example, a polarizing element protective film and a retardation film.
• the LCD panel warps due to the enlargement and thinning of the LCD TV screen, resulting in uneven display.
• the rigidity changes depending on the thickness of the glass substrate used for the liquid crystal panel, and the minute shrinkage of the polarizer affects the warp of the liquid crystal panel, which may cause display unevenness.
• the thickness of the glass substrate is made thinner than 0.7 mm, display unevenness tends to occur, and improvement thereof is required.
• Patent Document 1 proposes a method for improving warpage and display unevenness of a liquid crystal panel by setting the shrinkage force of a polyester fill for protecting a polarizer laminated on one surface of a polarizer within a specific range.
• the shrinkage stress of the polyester film for protecting a polarizer must be increased in order to suppress the warp of the liquid crystal panel as the size of the liquid crystal panel becomes larger and the glass substrate of the liquid crystal cell becomes thinner. I found it.
• increasing the heat shrinkage rate by treatment at 80 ° C. for 30 minutes is one of the effective measures.
• the present invention has been made in view of the above problems and circumstances, and a main problem thereof is to provide a polyester film for protecting a polarizing element, a polarizing plate, and a liquid crystal display device capable of suppressing warpage of a liquid crystal panel.
• a polyester film for protecting a polarizing element, a polarizing plate, and a liquid crystal display device capable of suppressing warpage of the liquid crystal panel even when the liquid crystal panel is placed in a high temperature environment for a long time.
• a typical invention is as follows.
• Item 1. A polyester film for protecting a polarizer that satisfies the following requirements (1) and (2).
• the shrinkage stress F of the TD of the polyester film is 8 MPa or more and 25 MPa or less.
• the ratio (F / HS) of the shrinkage stress F of the TD of the polyester film to the heat shrinkage rate HS of the TD after treatment of the polyester film at 80 ° C. for 30 minutes is 30 (MPa /%) or more and 60 (MPa /%). %) Or less.
• Item 2. Item 2.
• the in-plane retardation of the polyester film is 3000 to 30,000 nm.
• Item 3. The polyester film for protecting a polarizer according to Item 1 or 2, which further satisfies the requirement (4) below. (4) The thickness of the polyester film is 40 to 200 ⁇ m.
• Items 1 to 3 having a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, or an antireflection antiglare layer on the surface of the polyester film opposite to the surface on which the polarizer is laminated.
• Item 5. A polarizing plate in which the polyester film for protecting a polarizer according to any one of Items 1 to 4 is laminated on one surface of a polarizing element.
• Item 7. A polarizing plate in which the polyester film for protecting a polarizer according to any one of Items 1 to 4 is laminated on one surface of a polarizing element, and a coating layer is laminated on the other surface of the polarizer.
• Item 9. A liquid crystal display device comprising the polarizing plate according to any one of Items 5 to 8.
• a polarizer protective film, a polarizing plate, and a liquid crystal display device capable of suppressing warpage of a liquid crystal panel.
• a polyester film for protecting a polarizing element, a polarizing plate, and a liquid crystal display device that can suppress warpage of the liquid crystal panel even when the liquid crystal panel is placed in a high temperature environment for a long time.
• the polarizer protective polyester film of the present invention is a polarizing element protective film made of a polyester film and laminated on at least one surface of a polarizer (for example, a film composed of polyvinyl alcohol and a dye) to prepare a polarizing plate. It is preferable to have.
• a polarizer for example, a film composed of polyvinyl alcohol and a dye
• the value of the shrinkage stress F of the TD of the polyester film is 8 MPa or more and 25 MPa or less.
• the lower limit of the shrinkage stress F is set to 8 MPa or more, the warp of the liquid crystal panel can be sufficiently reduced.
• the upper limit value of the shrinkage stress F is set to 25 MPa or less, it is possible to prevent the liquid crystal panel from warping in the opposite direction. Therefore, the contraction stress F is preferably in the above range.
• the lower limit of the shrinkage stress F is more preferably 10 MPa or more, still more preferably 12 MPa or more.
• the upper limit of the shrinkage stress F is more preferably 23 MPa or less, still more preferably 20 MPa or less.
• the range of the shrinkage stress F is more preferably 10 MPa or more and 23 MPa or less, and further preferably 12 MPa or more and 20 MPa or less.
• the contraction stress Fv of the MD of the polyester film is usually about 1.8 to 2.2 MPa, although stress is also generated in the MD due to Poisson contraction when the film formation is performed by microstretching, which will be described later. ..
• the contraction stress Fv of the MD of the polyester film can be arbitrarily controlled by the tension of the MD.
• TD is an abbreviation for Transverse Direction, and may be referred to as a width direction or a lateral direction in the present specification.
• MD is an abbreviation for Machine Direction, and in the present specification, it may be referred to as a film flow direction, a longitudinal direction, or a vertical direction.
• the polyester film for protecting a polarizer of the present invention has a shrinkage stress F of TD of the polyester film and MD of the polyester film from the viewpoint of further reducing the warp of the liquid crystal panel and suppressing curl (propeller curl) accompanied by twisting.
• the contraction stress Fv ratio (F / Fv) is preferably 1.5 or more and 15 or less.
• the range of the ratio (F / Fv) is more preferably 1.5 or more and 12 or less, still more preferably 1.5 or more and 10 or less, and even more preferably 1.5 or more and 8 or less.
• HS is preferably 30 (MPa /%) or more and 60 (MPa /%) or less.
• the ratio (F / HS) is more preferably 35 (MPa /%) or more and 55 (MPa /%) or less.
• the upper limit of the ratio (F / HS) is 60 (MPa /%) or less, the film forming stability is improved and more stable operation can be performed.
• the polyester film for protecting a polarizer of the present invention preferably has a heat shrinkage rate of TD of 0.1 to 5% after treatment of the polyester film at 80 ° C. for 30 minutes.
• the lower limit of the heat shrinkage rate of TD is preferably 0.1% or more, more preferably 0.15% or more, and most preferably 0.2% or more.
• the upper limit of the heat shrinkage rate of TD is preferably 5% or less, 4.5% or less, 4% or less, 3% or less, or 2% or less, more preferably 1.5% or less, still more preferably 1%. Below, it is particularly preferably 0.7% or less, and most preferably 0.5% or less.
• the heat shrinkage rate of TD is 0.1% or more, it is easy to control the heat shrinkage rate without variation. Further, when the heat shrinkage rate of the TD is 5% or less, the heat of the backlight causes the polarizer protective film to heat shrink in one direction, and there is no possibility that the liquid crystal panel will warp.
• the heat shrinkage rate of TD can be measured by the method adopted in the examples described later.
• two polarizing plates are arranged so as to have a cross Nicol relationship.
• light usually does not pass through the two polarizing plates.
• the complete cross-nicol relationship may be broken and light leakage may occur.
• the polyester film for protecting a polarizer of the present invention preferably has a thickness of 40 to 200 ⁇ m. It is more preferably 40 to 100 ⁇ m, and even more preferably 40 to 80 ⁇ m. When the thickness is 40 ⁇ m or more, it is difficult to crack and the flatness is unlikely to be poor due to insufficient rigidity. Further, when the thickness is 200 ⁇ m or less, the variation in shrinkage stress in the TD of the film is small, and the cost required for controlling the shrinkage stress can be suppressed. The thickness can be measured by the method adopted in the examples described later.
• the polyester film for protecting a polarizer of the present invention preferably has in-plane retardation within a specific range from the viewpoint of suppressing rainbow spots observed on the screen of a liquid crystal display device.
• the lower limit of in-plane retardation is preferably 3000 nm or more, 4000 nm or more, 5000 nm or more, 6000 nm or more, 7000 nm or more, or 8000 nm or more.
• the upper limit of in-plane retardation is preferably 30,000 nm or less, more preferably 18,000 nm or less, still more preferably 15,000 nm or less, still more preferably 10,000 nm or less.
• the in-plane retardation is preferably less than 10,000 nm or 9000 nm or less.
• the retardation of the polyester film can be obtained by measuring the refractive index and thickness in the biaxial direction, or can be obtained by using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Measuring Instruments Co., Ltd.).
• the refractive index can be determined by an Abbe refractive index meter (measurement wavelength 589 nm).
• the ratio (Re / Rth) of the in-plane retardation (Re) to the thickness direction retardation (Rth) is preferably 0.2 or more, 0.3 or more, or 0. It is 4 or more, more preferably 0.5 or more, and further preferably 0.6 or more.
• the larger the ratio (Re / Rth) of the in-plane retardation to the thickness direction retardation the more isotropic the action of birefringence, and the less likely it is that iridescent color spots will occur depending on the observation angle.
• the ratio (Re / Rth) of the in-plane retardation to the thickness direction retardation is 2 in a completely uniaxial (uniaxially symmetric) film
• the ratio of the in-plane retardation to the thickness direction retardation (Re / Rth) ) Is preferably 2.
• the preferred upper limit of Re / Rth is 1.2 or less.
• the thickness direction retardation means the average of the values obtained by multiplying the two birefringence ⁇ Nxz and ⁇ Nyz when the film is viewed from the cross section in the thickness direction by the film thickness d, respectively.
• the polyester film for protecting a polarizer of the present invention preferably has an NZ coefficient of 2.5 or less, more preferably 2 or less, still more preferably 1. It is 8 or less, more preferably 1.6 or less. Since the NZ coefficient is 1 in a completely uniaxial (uniaxially symmetric) film, the lower limit of the NZ coefficient is 1. The larger the NZ coefficient, the higher the mechanical strength in the direction orthogonal to the orientation direction tends to be.
• the NZ coefficient is represented by
• Use a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.) to determine the orientation axis of the film, and the refractive index (Ny, Nx, but in the direction perpendicular to the orientation axis direction).
• Ny> Nx and the refractive index (Nz) in the thickness direction are determined by an Abbe refractive index meter (manufactured by Atago, NAR-4T, measurement wavelength 589 nm). The value thus obtained can be substituted into
• the value of Ny—Nx of the polyester film is preferably 0.05 or more, more preferably 0.07 or more, from the viewpoint of suppressing more iridescent color spots. It is more preferably 0.08 or more, even more preferably 0.09 or more, and most preferably 0.1 or more.
• the upper limit of Ny—Nx is not particularly limited, but in the case of a polyethylene terephthalate film, it is preferably about 0.15.
• the polyester film for protecting the polarizer of the present invention can be obtained from any polyester resin.
• the type of polyester resin is not particularly limited, and for example, any polyester resin obtained by condensing a dicarboxylic acid component and a diol component can be used.
• dicarboxylic acid component examples include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 1 , 5-Naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyetanedicarboxylic acid, diphenylsulfonedicarboxylic acid, anthracendicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid , Hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-
• diol component examples include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, and 1 , 3-Propylenediol, 1,4-Butanediol, 1,5-Pentanediol, 1,6-Hexanediol, 2,2-bis (4-hydroxyphenyl) propane, Bis (4-hydroxyphenyl) sulfone, etc. Can be mentioned.
• polyester resins constituting the polyester film include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and more preferably polyethylene terephthalate and polyethylene naphthalate. Further, other copolymerization components may be contained. These resins are excellent in transparency as well as thermal and mechanical properties.
• polyethylene terephthalate is a suitable material because it can achieve a high elastic modulus and the heat shrinkage rate can be controlled relatively easily.
• the polyester film When it is necessary to increase the heat shrinkage rate of the polyester film to a high degree, it is desirable to add a copolymerization component to appropriately reduce the crystallinity. Further, since the ratio of elastic strain and permanent strain is high for deformation below the glass transition temperature, it is generally difficult to increase the heat shrinkage rate to a high degree. Therefore, it is also a preferable embodiment to introduce a component having a low glass transition temperature as needed. Specific examples of the component having a low glass transition temperature include propylene glycol and 1,3-propanediol.
• the polyester film for protecting the polarizer can be subjected to corona treatment, coating treatment, flame treatment, etc. in order to improve the adhesiveness with the polarizer.
• an easy-adhesion layer In order to improve the adhesiveness with a functional layer such as a hard coat layer and a polarizer, it is preferable to have an easy-adhesion layer on at least one side of the polyester film.
• a polyester film having such an easy-adhesion layer is also included in the polyester film for protecting a polarizer of the present invention. It is preferable that at least one side of the polyester film has an easy-adhesion layer containing at least one selected from the group consisting of polyester resin (including copolymerized polyester resin), polyurethane resin, and polyacrylic resin as a main component.
• the coating liquid used for forming the easy-adhesion layer is preferably an aqueous coating liquid containing at least one selected from the group consisting of a water-soluble or water-dispersible copolymerized polyester resin, a polyacrylic resin, and a polyurethane resin.
• these coating solutions include water-soluble or water-dispersible copolymers disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, Japanese Patent No. 4150982, and the like.
• Examples thereof include a polymerized polyester resin solution, an acrylic resin solution, and a polyurethane resin solution.
• the easy-adhesion layer can be obtained, for example, by applying the coating liquid to one or both sides of an unstretched film or a longitudinally uniaxially stretched film, drying at 100 to 150 ° C., and further stretching in the lateral direction. Can be done.
• the final coating amount of the easy-adhesion layer (coating amount after drying) is preferably controlled to 0.05 to 0.2 g / m 2. When the coating amount is 0.05 g / m 2 or more, the adhesiveness with the obtained polarizer is sufficient. On the other hand, when the coating amount is 0.2 g / m 2 or less, the blocking resistance is improved.
• the coating amounts of the easy-adhesion layers on both sides may be the same or different, and can be independently set within the above ranges.
• the particles contained in the easy-adhesion layer include, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectrite, zirconia, tungsten oxide, lithium fluoride, etc.
• examples thereof include inorganic particles such as calcium fluoride and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles. These may be added to the easy-adhesion layer alone, or may be added in combination of two or more.
• a known method can be used as a method of applying the coating liquid.
• a known method can be used.
• the reverse roll coating method, the gravure coating method, the kiss coating method, the roll brush method, the spray coating method, the air knife coating method, the wire bar coating method, the pipe doctor method, etc. can be mentioned, and these methods can be used alone. Alternatively, it can be performed in combination.
• the average particle size of the above particles is measured by the following method.
• the particles are photographed with a scanning electron microscope (SEM), and the maximum diameter of 300 to 500 particles (between the two most distant points) is magnified so that the size of one of the smallest particles is 2 to 5 mm. Distance) is measured, and the average value is taken as the average particle size.
• SEM scanning electron microscope
• a hard coat layer, an antiglare layer, an antireflection layer, and a low reflection layer (low antireflection layer and low reflection) are formed on the surface of the polyester film for protecting a polarizer of the present invention on the side opposite to the surface on which the polarizer is laminated. It is preferable to have a functional layer such as an antiglare layer), an antireflection antiglare layer, and an antistatic layer. It is preferable that the shrinkage stress F and the ratio (F / HS) have the above-mentioned conditions in a state where these functional layers are laminated on the polyester film.
• the polarizing plate using the polyester film for protecting a polarizer of the present invention be integrated with the glass plate of the liquid crystal cell in a state where the heat shrinkage rate of the polyester film remains, when a functional layer is added.
• the drying temperature is set low, or a method having a small heat history such as UV irradiation or electron beam irradiation is used.
• the polyester film can be produced according to a general method for producing a polyester film.
• a non-oriented polyester obtained by melting a polyester resin and extruding it into a sheet is stretched in the vertical direction by utilizing the speed difference of rolls at a temperature equal to or higher than the glass transition temperature, and then stretched in the horizontal direction by a tenter.
• a method of applying heat treatment heat fixing
• the polyester film may be a uniaxially stretched film or a biaxially stretched film, preferably a uniaxially stretched film that is strongly stretched mainly in the lateral direction, and may be slightly stretched in a direction perpendicular to the main stretching direction. good.
• the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130 ° C., particularly preferably 90 to 120 ° C., respectively.
• the longitudinal stretching ratio is preferably 1 to 3.5 times, particularly preferably 1 to 3 times.
• the lateral stretching ratio is preferably 2.5 to 6 times, particularly preferably 3 to 5.5 times.
• the treatment temperature is preferably 100 to 250 ° C, particularly preferably 180 to 245 ° C.
• the shrinkage stress and heat shrinkage of TD can be controlled by the temperature at the time of fine stretching and the fine stretching ratio.
• the contraction stress F of TD tends to increase by increasing the actual film temperature at the time of microstretching or increasing the TD microstretching ratio.
• the F / HS tends to decrease as the actual film temperature during fine stretching decreases.
• TD microstretching ratio (TD width after microstretching-TD width before microstretching) /
• the TD microstretching ratio represented by TD width before microstretching is preferably in the range of 1.5% to 5%. ..
• the actual film temperature at the end of fine stretching is preferably about 120 ° C. to 150 ° C.
• the actual temperature of the film can be controlled by the amount of heat brought in from the front zone (accompanied flow), the temperature of the zone, the wind speed, the nozzle arrangement, and the like.
• the polyester film for protecting the polarizer of the present invention is laminated on at least one surface of the polarizer. It is preferable that a film having no birefringence, such as a TAC film, an acrylic film, and a norbornene film, is laminated on the other surface of the polarizer.
• a polarizing plate on which no film is laminated on the other surface of the polarizer is also a preferable embodiment from the viewpoint of thinness.
• the film is not laminated on the other surface of the polarizer, but the coating layer may be laminated on the polarizer.
• the coating layer may be a functional layer such as a hard coat layer, or may be a retardation film formed by coating.
• shrinkage of the film or coating layer other than the polarizer protective polyester film in a direction parallel to the transmission axis of the polarizer is preferably equal to or less than the value of the TD shrinkage stress of the polarizer protective polyester film. , More preferably, it is equal to or less than the value of the shrinkage stress of MD of the polarizing element protective polyester film.
• the shrinkage force of the film or coating layer other than the polyester film for protecting the polarizer in the direction parallel to the transmission axis of the polarizer and the polyester film other than the polyester film for protecting the polarizer in the direction parallel to the absorption axis of the polarizer.
• the shrinkage force of the film or the coating layer is preferably 250 N / m or less, more preferably 200 N / m or less.
• the shrinkage force (N / m) in the specific direction to be evaluated is the thickness (mm) of the film or coating layer x elastic modulus in the specific direction (N / mm 2 ).
• the elastic modulus is evaluated using a dynamic viscoelasticity measuring device (DMS6100) manufactured by Seiko Instruments Inc. in accordance with JIS-K7244 (DMS) after standing in an environment of 25 ° C. and 50 RH% for 168 hours.
• the temperature dependence of 25 ° C to 120 ° C was measured under the conditions of tension mode, drive frequency 1 Hz, distance between chucks 5 mm, and heating rate 2 ° C / min, and the average storage elastic modulus of 30 ° C to 100 ° C was defined as the elastic modulus. do.
• a long product of a polarizer and a long product of a polyester film for protecting a polarizer are laminated in a roll-to-roll format via an adhesive. Since the polarizer is usually manufactured by being stretched in the vertical direction, the MD has an absorption axis and the TD has a transmission axis.
• the polarizer and the polyester film for protecting the polarizer are laminated so that the transmission axis of the polarizer and the TD of the polyester film for protecting the polarizer are substantially parallel to each other.
• substantially parallel means that the angle formed by the transmission axis of the polarizer and the TD of the polyester film for protecting the polarizer is preferably 0 ° ⁇ 15 ° or less, more preferably 0 ° ⁇ 10 ° or less. , More preferably 0 ° ⁇ 8 ° or less, even more preferably 0 ° ⁇ 5 ° or less, particularly preferably 0 ° ⁇ 3 ° or less, and most preferably 0 °.
• the polarizer and the polyester film for protecting the polarizer may be laminated so that the transmission axis of the polarizer and the slow axis of the polyester film for protecting the polarizer are substantially parallel to each other.
• substantially parallel means that the angle formed by the transmission axis of the polarizer and the slow axis of the polyester film for protecting the polarizer is preferably 0 ° ⁇ 15 ° or less, more preferably 0 ° ⁇ 10. ° or less, more preferably 0 ° ⁇ 8 ° or less, even more preferably 0 ° ⁇ 5 ° or less, particularly preferably 0 ° ⁇ 3 ° or less, most preferably 0 °.
• the liquid crystal display device of the present invention is not particularly limited as long as it includes the polarizing plate of the present invention, but usually has at least a backlight light source and a liquid crystal cell arranged between the two polarizing plates. It is preferable that at least one of the two polarizing plates is the polarizing plate of the present invention, that is, a polarizing plate in which the polyester film for protecting the polarizer of the present invention is used as the polarizing element protective film. In the liquid crystal display device, both of the two polarizing plates may be the polarizing plates of the present invention.
• the thickness of the glass substrate which is a constituent member of the liquid crystal cell, is preferably 0.7 mm or less, more preferably 0.6 mm or less, still more preferably 0.5 mm or less, and most preferably 0.4 mm or less. be.
• the polarizing element protective polyester film of the present invention can be used for liquid crystal display devices of any size, but is preferably 42 inches or more, more preferably 46 inches or more, still more preferably 50 inches or more, and even more preferably 55 inches or more. , Especially preferably, it can be used for a liquid crystal display device of 60 inches or more.
• the position of the polarizing element protection film on the viewing side starting from the polarizer of the polarizing plate on the viewing side and / or the position of the polarizer protective film on the light source side starting from the polarizer of the polarizing plate on the light source side is preferable to be used for.
• a liquid crystal display has a rectangular shape (the two polarizing plates used in the liquid crystal display are also rectangular), and one polarizing plate has its long side parallel to the absorption axis and the other.
• the polarizing plate of No. 1 is arranged so that its long side and the transmission axis are parallel to each other and the absorption axes are perpendicular to each other.
• a polarizing plate having a parallel relationship between the long side of the polarizing plate and the absorption axis is used as a viewing side polarizing plate of a liquid crystal display device, and a polarizing plate having a parallel relationship between the long side of the polarizing plate and the transmission axis.
• the polarizing plate of the present invention is used as a polarizing plate having a parallel relationship between the long side of the polarizing plate and the transmission axis from the viewpoint of suppressing warpage of the liquid crystal panel.
• the polarizing plate of the present invention for both the polarizing plate having a parallel relationship between the long side of the polarizing plate and the transmission axis and the polarizing plate having a parallel relationship between the long side of the polarizing plate and the absorption axis.
• the shrinkage stress of MD and TD of the polyester film was allowed to stand for 168 hours in an environment of 25 ° C. and 50 RH%, and then measured using a thermomechanical analyzer (TMA7100 manufactured by Hitachi High-Tech Science Co., Ltd.).
• the film sample had a width of 1 mm and a sample length of 15 mm, was gripped with a minimum load of 19 mN, heated from 30 ° C. to 260 ° C. at 5 ° C./min, and a shrinkage load was measured. From the obtained contraction load curve, the maximum contraction load appearing from 80 ° C. to 150 ° C. was divided by the initial cross-sectional area to obtain the contraction stress (MPa).
• MPa contraction stress
• the liquid crystal panel is subjected to the above heat treatment and cooling treatment in a state where the four corners are supported by prisms and the panel is allowed to stand horizontally on the prisms (that is, the panels are floating except for the four corners).
• the biaxial refractive index anisotropy ( ⁇ Nxy) was determined by the following method.
• the film thickness d (nm) was measured using an electric micrometer (Millitron 1245D, manufactured by Fine Wolf Co., Ltd.), and the unit was converted to nm.
• the in-plane retardation (Re) was determined from the product ( ⁇ Nxy ⁇ d) of the anisotropy of the refractive index ( ⁇ Nxy) and the thickness d (nm) of the film.
• ) and ⁇ Nyz (
• the intrinsic viscosity of the obtained polyethylene terephthalate resin (A) was 0.62 dl / g, and it contained substantially no inert particles and internally precipitated particles. (Hereafter, it is abbreviated as PET (A).)
• Example 1 Manufacturing of polyester film 1 for protector protection> After 90 parts by mass of PET (A) resin pellets containing no particles and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber are dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours as raw materials for the base film intermediate layer. , Supply to extruder 2 (for intermediate layer II layer), and PET (A) is dried by a conventional method and supplied to extruder 1 (for outer layer I layer and outer layer III layer), respectively, and melted at 285 ° C. bottom.
• the adhesive modification coating liquid was applied to both sides of the unstretched PET film by the reverse roll method so that the coating amount after drying was 0.08 g / m 2 , and then dried at 80 ° C. for 20 seconds. ..
• the unstretched film on which this coating layer was formed was guided to a tenter stretching machine, and while gripping the end of the film with a clip, it was guided to a hot air zone having a temperature of 105 ° C. and stretched 4.0 times to TD. Next, heat treatment was performed at a temperature of 180 ° C. for 30 seconds, and then the film was led to a cooling zone at 120 ° C., the film was stretched (slightly stretched) by 2.5% in the width direction, and then both ends of the film cooled to 60 ° C.
• the clip holding the part is opened and taken up with a tension of 350 N / m, a jumbo roll made of a uniaxially oriented PET film having a film thickness of about 80 ⁇ m is collected, and the obtained jumbo roll is divided into three equal parts to three pieces.
• Slit rolls (L (left side), C (center), R (right side)) were obtained.
• a polyester film 1 for protecting a polarizer was obtained from a slit roll located at R.
• the actual temperature of the film during running at the end of 2.5% stretching in the width direction was measured with a non-contact radiation thermometer and found to be about 125 ° C.
• a polyester film 1 for protecting a polarizer was attached to one side of a polarizer composed of PVA, iodine, and boric acid so that the transmission axis of the polarizer and the TD of the polyester film 1 for protecting the polarizer were parallel to each other. Further, a TAC film (manufactured by FUJIFILM Corporation, thickness 80 ⁇ m) was attached to the opposite surface of the polarizer to prepare a polarizing plate on the light source side.
• the liquid crystal panel was taken out from a 65-inch size IPS type liquid crystal television using a glass substrate having a thickness of 0.4 mm for the liquid crystal cell.
• the light source side polarizing plate is peeled off from the liquid crystal panel, and instead, the light source side polarizing plate manufactured above is subjected to the transmission axis direction (parallel to the horizontal direction) of the light source side polarizing plate before the transmission axis of the polarizer is peeled off.
• a liquid crystal panel was produced by bonding to a liquid crystal cell via a PSA (pressure sensitive adhesive) so as to match.
• PSA pressure sensitive adhesive
• a polarizing plate on the light source side was attached to the liquid crystal cell so that the polyester film 1 for protecting the polarizer was on the distal side (opposite side) of the liquid crystal cell. Further, the viewing side polarizing plate was formed by laminating TAC films on both sides of the polarizing element, and was bonded to the liquid crystal cell so that the absorption axis direction of the polarizing element was parallel to the horizontal direction.
• Example 2 ⁇ Manufacturing of polyester film 2 for protector protection>
• the film formation of the polyester film 1 for protecting the polarizer of Example 1 after heat treatment was performed at a temperature of 180 ° C. for 30 seconds, the film was led to a cooling zone at 120 ° C., and the film was stretched by 3.0% in the width direction.
• a polyester film 2 for protecting a polarizer was obtained in the same manner as the polyester film 1 for protecting a polarizer except for the above.
• ⁇ Manufacturing of liquid crystal panel> In Example 1, a liquid crystal panel was produced in the same manner as in Example 1 except that the polyester film 1 for protecting the polarizer was replaced with the polyester film 2 for protecting the polarizer.
• Example 3 ⁇ Manufacturing of polyester film 3 for protecting a polarizer>
• the film formation of the polyester film 1 for protecting the polarizer of Example 1 after heat treatment was performed at a temperature of 180 ° C. for 30 seconds, the film was led to a cooling zone at 120 ° C., and the film was stretched by 3.5% in the width direction.
• a polarizer protective film 3 was obtained in the same manner as the polyester film 1 for protecting the polarizer except for the above.
• ⁇ Manufacturing of liquid crystal panel> In Example 1, a liquid crystal panel was produced in the same manner as in Example 1 except that the polyester film 1 for protecting the polarizer was replaced with the polyester film 3 for protecting the polarizer.
• Example 4 ⁇ Manufacturing of polyester film 4 for protector protection>
• the film formation of the polyester film 1 for protecting the polarizer of Example 1 after heat treatment was performed at a temperature of 180 ° C. for 30 seconds, the film was led to a cooling zone at 120 ° C., and the film was stretched by 4.0% in the width direction.
• a polarizer protective film 4 was obtained in the same manner as the polyester film 1 for protecting the polarizer except for the above.
• ⁇ Manufacturing of liquid crystal panel> In Example 1, a liquid crystal panel was produced in the same manner as in Example 1 except that the polyester film 1 for protecting the polarizer was replaced with the polyester film 4 for protecting the polarizer.
• Example 5 ⁇ Manufacturing of polyester film 5 for protector protection>
• the film formation of the polyester film 1 for protecting the polarizer of Example 1 after heat treatment was performed at a temperature of 180 ° C. for 30 seconds, the film was led to a cooling zone at 120 ° C., and the film was stretched by 4.5% in the width direction.
• a polarizer protective film 5 was obtained in the same manner as the polyester film 1 for protecting the polarizer except for the above.
• ⁇ Manufacturing of liquid crystal panel> A liquid crystal panel was produced in the same manner as in Example 1 except that the polyester film 1 for protecting the polarizer was replaced with the polyester film 5 for protecting the polarizer in Example 1.
• Example 1 a liquid crystal panel was produced in the same manner except that the TAC film was not used as the liquid crystal cell side protective film of the light source side polarizing plate.
• good results ( ⁇ ) were obtained in both the evaluations of the “warp of the liquid crystal panel” and the “warp of the liquid crystal panel after being placed in a long-time / high temperature environment”.
• the present invention it is possible to provide a polyester film for protecting a polarizer, a polarizing plate, and a liquid crystal display device capable of suppressing warpage of a liquid crystal panel.

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