Polarizer protective polyester film, polarizing plate, and liquid crystal display device

Abstract

The present invention aims to provide a polarizer protective polyester film, a polarizing plate, and a liquid crystal display device that can suppress warping of a liquid crystal panel. This problem can be solved by a polarizer protective polyester film that satisfies the following characteristics (1) and (2). (1) The shrinkage stress F in the TD of the polyester film is 8 MPa or more and 25 MPa or less. (2) The ratio (F / HS) of the shrinkage stress F in the TD of the polyester film to the heat shrinkage rate HS of the TD of the polyester film after treatment at 80°C for 30 minutes is 30 (MPa / %) or more and 60 (MPa / %) or less.

Description

Technical Field

[0001] The present invention relates to a polyester film for protecting a polarizer, a polarizing plate and a liquid crystal display device. Background Art

[0002] Liquid crystal display devices are seeing increasing demand for applications such as LCD televisions and personal computer monitors. Typically, a liquid crystal display device consists of a liquid crystal cell (a component consisting of a transparent electrode, liquid crystal layer, and color filter) sandwiched between glass substrates, and two polarizing plates placed on either side. Each polarizing plate is composed of a polarizer (also called a polarizing film) sandwiched between two optical films (e.g., a polarizer protective film and a retardation film).

[0003] In recent years, it has been confirmed that the LCD panels are warping and displaying unevenness due to the increasing size and thinness of LCD TV screens. For example, the rigidity of the LCD panel can vary depending on the thickness of the glass substrate used in the LCD panel, and slight shrinkage of the polarizer can affect the LCD panel, causing warping and uneven display. In particular, in order to further thin the LCD panel, when the thickness of the glass substrate is reduced to less than 0.7 mm, the occurrence of uneven display is likely to become a problem, and improvement is required.

[0004] Patent Document 1 proposes a method for improving warpage and display unevenness of a liquid crystal panel by adjusting the shrinkage force of a polarizer-protecting polyester film laminated on one surface of a polarizer to a specific range.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: WO2019 / 054406 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] As liquid crystal panels become larger and glass substrates of liquid crystal cells become thinner, the present inventors have discovered that it is necessary to increase the shrinkage stress of a polarizing plate protective polyester film in order to suppress warping of the liquid crystal panel.

[0010] In order to increase the shrinkage stress of the polarizer protective polyester film, an effective countermeasure is to increase the thermal shrinkage rate after treatment at 80°C for 30 minutes. However, if a liquid crystal panel using such a polarizer protective polyester film with increased thermal shrinkage rate is placed in a high temperature environment for a long time, warping may sometimes occur in the liquid crystal panel, especially when the liquid crystal panel is large.

[0011] The present invention has been developed in light of the above-mentioned problems and circumstances, and its main object is to provide a polarizer-protective polyester film, a polarizing plate, and a liquid crystal display device that can suppress warping of a liquid crystal panel. In particular, the present invention is to provide a polarizer-protective polyester film, a polarizing plate, and a liquid crystal display device that can suppress warping of a liquid crystal panel even when the liquid crystal panel is exposed to a high-temperature environment for a long period of time.

[0012] Solutions for solving problems

[0013] Representative embodiments of the present invention are as follows.

[0014] Item 1.

[0015] A polarizing plate protective polyester film satisfying the following characteristics (1) and (2).

[0016] (1) The shrinkage stress F in TD of the polyester film is 8 MPa or more and 25 MPa or less.

[0017] (2) The ratio (F / HS) of the shrinkage stress F in TD of the polyester film to the heat shrinkage HS in TD after the polyester film is treated at 80°C for 30 minutes is 30 (MPa / %) or more and 60 (MPa / %) or less.

[0018] Item 2.

[0019] The polarizing plate protective polyester film according to item 1 further satisfies the following feature (3).

[0020] (3) The in-plane retardation of the polyester film is 3,000 to 30,000 nm.

[0021] Item 3.

[0022] The polarizing plate protective polyester film according to item 1 or 2 further satisfies the feature of the following (4).

[0023] (4) The thickness of the polyester film is 40 to 200 μm.

[0024] Item 4.

[0025] The polarizer-protective polyester film according to any one of items 1 to 3, comprising a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, or an antireflection and antiglare layer on the surface of the polyester film opposite to the surface on which the polarizer is laminated.

[0026] Item 5.

[0027] A polarizing plate comprising the polarizing plate-protecting polyester film according to any one of items 1 to 4 laminated on one surface of a polarizer.

[0028] Item 6.

[0029] A polarizing plate comprising: a polarizing plate having the polarizing plate-protecting polyester film according to any one of items 1 to 4 laminated on one surface of the polarizer; and no film laminated on the other surface of the polarizer.

[0030] Item 7.

[0031] A polarizing plate comprising: a polarizing plate; a polarizing plate-protecting polyester film according to any one of items 1 to 4; and a coating layer on the other surface of the polarizing plate.

[0032] Item 8.

[0033] The polarizing plate according to item 7, wherein the coating layer is a hard coat layer or a retardation film.

[0034] Item 9.

[0035] A liquid crystal display device comprising the polarizing plate according to any one of items 5 to 8.

[0036] Effects of the Invention

[0037] The present invention can provide a polarizer protective film, a polarizing plate, and a liquid crystal display device that can suppress warping of a liquid crystal panel. In particular, the present invention can provide a polarizer protective polyester film, a polarizing plate, and a liquid crystal display device that can suppress warping of a liquid crystal panel even when the liquid crystal panel is exposed to a high temperature environment for a long period of time. DETAILED DESCRIPTION

[0038] The polarizer protective polyester film of the present invention is preferably a polarizer protective film formed of a polyester film and laminated on at least one surface of a polarizer (eg, a film formed of polyvinyl alcohol and a pigment) for producing a polarizing plate.

[0039] For the polarizer protective polyester film of the present invention, the value of the shrinkage stress F of the TD of the polyester film is preferably 8 MPa or more and 25 MPa or less. If the lower limit of the shrinkage stress F is 8 MPa or more, the warping of the liquid crystal panel can be fully reduced. In addition, if the upper limit of the shrinkage stress F is 25 MPa or less, the situation in which the liquid crystal panel warps back in the opposite direction can also be prevented. Therefore, the shrinkage stress F is preferably in the aforementioned range. The lower limit of the shrinkage stress F is more preferably 10 MPa or more, and further preferably 12 MPa or more. The upper limit of the shrinkage stress F is more preferably 23 MPa or less, and further 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.

[0040] Regarding the shrinkage stress Fv in the MD of a polyester film, when microstretching (described later) is performed during normal film formation, stress is also generated in the MD due to Poisson shrinkage, but a shrinkage stress of approximately 1.8 to 2.2 MPa is preferred. The shrinkage stress Fv in the MD of a polyester film can be arbitrarily controlled by adjusting the tension in the MD.

[0041] The shrinkage stress F in TD and the shrinkage stress Fv in MD were measured by TMA (thermomechanical analysis) as described in detail in the Examples. It should be noted that TD stands for Transverse Direction and is sometimes referred to as the width direction or transverse direction in this specification. MD stands for Machine Direction and is sometimes referred to as the film flow direction, length direction, or longitudinal direction in this specification.

[0042] In the polarizer protective polyester film of the present invention, from the viewpoint of further reducing warpage of the liquid crystal panel or suppressing curling associated with torsion (propeller curl), the ratio (F / Fv) of the shrinkage stress F in the TD of the polyester film to the shrinkage stress Fv in the MD of the polyester film is preferably 1.5 or more and 15 or less. The range of the above ratio (F / Fv) is more preferably 1.5 or more and 12 or less, further preferably 1.5 or more and 10 or less, and even more preferably 1.5 or more and 8 or less.

[0043] For the polarizer protective polyester film of the present invention, the ratio (F / HS) of the shrinkage stress F (MPa) of the polyester film in TD to the thermal shrinkage rate HS (%) of the polyester film in TD after being treated at 80°C for 30 minutes is preferably 30 (MPa / %) or more and 60 (MPa / %) or less. By making the ratio (F / HS) within the aforementioned range, the warping of the liquid crystal panel can be suppressed even when the liquid crystal panel is placed in a high temperature environment for a long time. The ratio (F / HS) is more preferably 35 (MPa / %) or more and 55 (MPa / %) or less. It should be noted that if the upper limit value of the ratio (F / HS) is 60 (MPa / %) or less, the film forming stability is improved, and a more stable operation can be performed.

[0044] For the polarizer protective polyester film of the present invention, the thermal shrinkage of the TD after the polyester film is treated at 80°C for 30 minutes is preferably 0.1 to 5%. The lower limit of the thermal shrinkage of the 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 thermal shrinkage of the 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, further preferably 1% or less, particularly preferably 0.7% or less, and most preferably 0.5% or less. If the thermal shrinkage of the TD is 0.1% or more, the thermal shrinkage can be easily controlled without fluctuation. In addition, if the thermal shrinkage of the TD is 5% or less, there is no concern that the polarizer protective film will shrink in one direction due to the heat of the backlight, causing the liquid crystal panel to warp.

[0045] The thermal shrinkage rate of TD can be measured by the method used in the examples described later.

[0046] Typically, liquid crystal displays are configured so that two polarizers form a crossed prism relationship. If the two polarizers are arranged in a crossed prism relationship, light generally does not pass through them. However, shrinkage or warping of the polarizers can disrupt the perfectly crossed prism relationship, leading to concerns about light leakage. To prevent light leakage, it is preferable that the angle between the polarizer protective film's maximum thermal shrinkage and the polarizer's transmission axis be as small as possible.

[0047] The polarizer protective polyester film of the present invention preferably has a thickness of 40 to 200 μm. It is more preferably 40 to 100 μm, and even more preferably 40 to 80 μm. A thickness of 40 μm or greater is less likely to cause cracking and poor planarity due to insufficient rigidity. Furthermore, a thickness of 200 μm or less minimizes fluctuations in the film's shrinkage stress in the TD, thus reducing the cost required to control shrinkage stress. The thickness can be measured using the method described in the Examples below.

[0048] For the polarizer protective polyester film of the present invention, from the viewpoint of suppressing rainbow spots observed on the screen of the liquid crystal display device, the in-plane retardation is preferably within a specific range. The lower limit of the 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 the in-plane retardation is preferably 30000 nm or less, more preferably 18000 nm or less, further preferably 15000 nm or less, and further more preferably 10000 nm or less. In particular, from the viewpoint of thin film formation, the in-plane retardation is preferably less than 10000 nm or 9000 nm or less.

[0049] The retardation of the polyester film can also be determined by measuring the refractive index and thickness in the biaxial directions, or by using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.) The refractive index can be determined using an Abbe refractometer (measurement wavelength: 589 nm).

[0050] For the polarizer protective polyester film of the present invention, the ratio of the in-plane retardation (Re) to the thickness direction retardation (Rth) (Re / Rth) is preferably 0.2 or more, 0.3 or more, or 0.4 or more, more preferably 0.5 or more, and further preferably 0.6 or more. The larger the ratio of the in-plane retardation to the thickness direction retardation (Re / Rth), the more isotropic the effect of birefringence becomes, and there is a tendency to become less likely to produce rainbow spots caused by the observation angle. In a completely uniaxial (uniaxially symmetrical) film, the ratio of the in-plane retardation to the thickness direction retardation (Re / Rth) becomes 2, and therefore, the upper limit of 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. It should be noted that the thickness direction retardation refers to the average of the values ​​obtained by multiplying the two birefringences △Nxz and △Nyz when observing the film from a cross-section in the thickness direction by the film thickness d.

[0051] In the polarizer protective polyester film of the present invention, from the perspective of further suppressing rainbow color spots, the NZ coefficient of the polyester film is preferably 2.5 or less, more preferably 2 or less, further preferably 1.8 or less, and even more preferably 1.6 or less. In addition, in a completely uniaxial (uniaxially symmetric) film, the NZ coefficient is 1, so the lower limit of the NZ coefficient is 1. There is a tendency that the larger the NZ coefficient, the better the mechanical strength in the direction perpendicular to the orientation direction.

[0052] The NZ coefficient is expressed as |Ny-Nz| / |Ny-Nx|, where Ny is the refractive index in the slow axis direction of the polyester film, Nx is the refractive index in the direction perpendicular to the slow axis (refractive index in the fast axis direction), and Nz is the refractive index in the thickness direction. The film's orientation axis is determined using a molecular orientation meter (MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.). The refractive indices in the orientation axis and the direction perpendicular to it (Ny and Nx, where Ny>Nx) and the refractive index in the thickness direction (Nz) are determined using an Abbe refractometer (NAR-4T, manufactured by ATAGO CO., LTD., measuring wavelength 589 nm). The NZ coefficient can be calculated by substituting the values ​​thus obtained into |Ny-Nz| / |Ny-Nx|.

[0053] Furthermore, in the polarizer protective polyester film of the present invention, from the perspective of further suppressing rainbow unevenness, the Ny-Nx value of the polyester film is preferably 0.05 or greater, more preferably 0.07 or greater, even more preferably 0.08 or greater, even more preferably 0.09 or greater, and most preferably 0.1 or greater. While the upper limit of Ny-Nx is not particularly limited, it is preferably approximately 0.15 for polyethylene terephthalate films.

[0054] The polarizer protective polyester film 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.

[0055] Examples of the dicarboxylic acid component that can be used in the production of the polyester resin include terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl sulfone dicarboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, and dodecanedicarboxylic acid.

[0056] Examples of the diol component that can be used in the production of the polyester resin include ethylene glycol, propylene glycol, hexylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

[0057] The dicarboxylic acid component and the diol component that constitute the polyester resin can be used in combination of one or more. Suitable polyester resins for constituting the polyester film include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. More preferably, polyethylene terephthalate and polyethylene naphthalate are used, but they may further contain other copolymer components. These resins have excellent transparency, thermal properties, and mechanical properties. In particular, polyethylene terephthalate can achieve a high elastic modulus and is relatively easy to control thermal shrinkage, making it a suitable raw material.

[0058] When it is necessary to significantly increase the thermal shrinkage of a polyester film, it is ideal to add a copolymer component and moderately reduce the crystallinity. Furthermore, since the ratio of elastic strain to permanent strain is high for deformations below the glass transition temperature, it is generally difficult to significantly increase the thermal shrinkage. Therefore, introducing a component with a low glass transition temperature as needed is also a preferred embodiment. Specifically, propylene glycol and 1,3-propanediol are examples of components with a low glass transition temperature.

[0059] In order to improve the adhesion to the polarizer, the polarizer-protective polyester film may be subjected to a corona treatment, a coating treatment, a flame treatment, or the like.

[0060] (Provision of an easy-adhesion layer)

[0061] In order to improve adhesion to functional layers such as hard coat layers and polarizers, it is preferred that the polyester film has an easy-adhesion layer on at least one side. Such a polyester film having an easy-adhesion layer is also included in the polarizer-protective polyester film of the present invention.

[0062] It is preferred that at least one side of the polyester film has an easy-adhesive layer having at least one selected from the group consisting of a polyester resin (including a copolyester resin), a polyurethane resin and a polyacrylic resin as the main component. Here, "main component" refers to a component that is 50% by mass or more of the solid content constituting the easy-adhesive layer. The coating liquid used in the formation of the easy-adhesive layer preferably comprises an aqueous coating liquid of at least one selected from the group consisting of a water-soluble or water-dispersible copolyester resin, a polyacrylic resin and a polyurethane resin. As these coating liquids, for example, water-soluble or water-dispersible copolyester resin solutions, acrylic resin solutions, polyurethane resin solutions disclosed in Japanese Patent No. 3567927 Gazette, Japanese Patent No. 3589232 Gazette, Japanese Patent No. 3589233 Gazette, Japanese Patent No. 3900191 Gazette, Japanese Patent No. 4150982 Gazette, etc. can be cited.

[0063] The easy-adhesion layer can be obtained by, for example, applying the coating liquid to one or both sides of an unstretched film or a uniaxially stretched film in the longitudinal direction, drying at 100-150°C, and further stretching in the transverse direction. The final coating amount of the easy-adhesion layer (coating amount after drying) is preferably controlled to be 0.05-0.2 g / m 2 If the coating amount is 0.05g / m 2 On the other hand, if the coating amount is 0.2 g / m 2 When the adhesive layer is provided on both sides of the polyester film, the coating amount of the adhesive layer on both sides may be the same or different and may be independently set within the above range.

[0064] In order to impart slipperiness to the easy-adhesive layer, particles are preferably added. Particles preferably use fine particles with an average particle size of 2 μm or less. If the average particle size of the particles is 2 μm or less, the falling of the particles can be suppressed. As particles contained in the easy-adhesive layer, for example, inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silicon dioxide, aluminum oxide, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconium oxide, tungsten oxide, lithium fluoride, calcium fluoride, and organic polymer particles such as styrene, acrylic acid, melamine, benzoguanamine, and silicone can be cited. These can be added to the easy-adhesive layer alone or in combination of two or more.

[0065] As a method for applying the coating liquid, known methods may be used, such as reverse roll coating, gravure coating, lip coating, roller brush coating, spray coating, air knife coating, wire bar coating, and tubular doctor blade coating, and these methods may be used alone or in combination.

[0066] In addition, the average particle size of the above particles was measured according to the following method.

[0067] The particles were photographed using a scanning electron microscope (SEM). The maximum diameters (the distance between the two most distant points) of 300 to 500 particles were measured at a magnification such that the size of the smallest particle was 2 to 5 mm. The average value was taken as the average particle size.

[0068] (Provision of functional layer)

[0069] The polarizer protective polyester film of the present invention preferably has functional layers such as a hard coat layer, an anti-glare layer, an anti-reflection layer, a low-reflection layer (including an anti-low-reflection layer and a low-reflection anti-glare layer), an anti-reflection anti-glare layer, and an antistatic layer on the surface opposite to the surface to be laminated with the polarizer. When these functional layers are laminated on the polyester film, the shrinkage stress F and the ratio (F / HS) preferably meet the above-mentioned conditions.

[0070] Since the polarizing plate using the polarizer-protective polyester film of the present invention is preferably integrated with the glass plate of the liquid crystal cell while the thermal shrinkage of the polyester film remains, when adding a functional layer, it is ideal to set the drying temperature to a low level or to use a method with a low thermal history, such as UV irradiation or electron beam irradiation. Furthermore, adding these functional layers during the polyester film forming process allows the polarizing plate of the present invention to be integrated with the glass plate of the liquid crystal cell without compromising the already improved thermal shrinkage, which is a more ideal embodiment.

[0071] (Method for producing polyester film)

[0072] Polyester film can be produced using conventional polyester film production methods. For example, the following method can be used: a polyester resin is melted, extruded into a sheet, and formed into an unoriented polyester. The unoriented polyester is then stretched longitudinally at a temperature above its glass transition temperature using a roller speed differential, then stretched transversely using a tenter frame, and heat-treated (heat-set). The polyester film can be either uniaxially or biaxially stretched, preferably uniaxially stretched primarily in the transverse direction. Alternatively, the film can be slightly stretched perpendicular to the primary stretching direction.

[0073] If the film forming conditions of the polyester film are specifically described, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130°C, particularly preferably 90 to 120°C. The longitudinal stretching ratio is preferably 1 to 3.5 times, particularly preferably 1 to 3 times. In addition, the transverse stretching ratio is preferably 2.5 to 6 times, particularly preferably 3 to 5.5 times. In order to control the retardation within the above range, it is preferred to control the ratio of the longitudinal stretching ratio to the transverse stretching ratio. In the subsequent heat treatment (heat setting), the treatment temperature is preferably 100 to 250°C, particularly preferably 180 to 245°C.

[0074] Preferably, the film is introduced into a cooling zone with a set temperature lower than that of the heat setting zone through the stretching / heat setting zone, and micro-stretched along the TD. The shrinkage stress and thermal shrinkage rate of the TD can be controlled by the temperature and micro-stretching ratio during micro-stretching. By increasing the actual temperature of the film during micro-stretching or increasing the TD micro-stretching ratio, the shrinkage stress F of the TD tends to increase. In addition, as the actual temperature of the film during micro-stretching becomes lower, there is a tendency for F / HS to decrease. In order to make the shrinkage stress F of the TD and the ratio of the shrinkage stress F of the TD to the thermal shrinkage rate HS of the TD (F / HS) within the aforementioned preferred range, the TD micro-stretching ratio shown in the following formula is preferably in the range of 1.5% to 5%.

[0075] TD micro-stretching ratio = (TD transverse width after micro-stretching - TD transverse width before micro-stretching) / TD transverse width before micro-stretching

[0076] The actual film temperature at the end of microstretching is preferably approximately 120° C. to 150° C. The actual film temperature can be controlled by the heat introduced from the front zone (trailing flow), the temperature / wind speed / nozzle arrangement of the zone, and the like.

[0077] The polarizing plate of the present invention is a polarizer protective polyester film of the present invention laminated on at least one surface of the polarizer. Preferably, a film without birefringence such as a TAC film, an acrylic film, or a norbornene film is laminated on the other surface of the polarizer. Alternatively, from the perspective of thinness, a polarizing plate in which no film is laminated on the other surface of the polarizer is also a preferred embodiment. In this case, although a film is not laminated on the other surface of the polarizer, a coating layer may be laminated on the polarizer. The coating layer may be a functional layer such as a hard coat layer, or a phase difference film formed by coating.

[0078] It should be noted that, when a film or coating layer other than the polarizer protective polyester film of the present invention is laminated on a polarizer, the shrinkage stress of the film or coating layer other than the polarizer protective polyester film in a direction parallel to the transmission axis of the polarizer, and the shrinkage stress of the film or coating layer other than the polarizer protective polyester film in a direction parallel to the absorption axis of the polarizer are preferably less than the value of the shrinkage stress in TD of the polarizer protective polyester film, and more preferably less than the value of the shrinkage stress in MD of the polarizer protective polyester film.

[0079] In addition, the shrinkage force of the film other than the polarizer protective polyester film and the coating layer in the direction parallel to the transmission axis of the polarizer, and the shrinkage force of the film other than the polarizer protective polyester film and the coating layer in the direction parallel to the absorption axis of the polarizer are preferably 250 N / m or less, and more preferably 200 N / m or less. For the film other than the polarizer protective polyester film and the coating layer, the shrinkage force (N / m) in the specific direction of the evaluation object is calculated by the thickness (mm) of the film or coating layer × the elastic modulus (N / mm) in the specific direction. 2 )×heat shrinkage in a specific direction after treatment at 80°C for 30 minutes (%)÷100×1000.

[0080] The elastic modulus was evaluated in accordance with JIS-K7244 (DMS) using a dynamic viscoelasticity measuring apparatus (DMS6100) manufactured by Seiko Instruments Inc. after standing for 168 hours in an environment at 25°C and 50% RH. The temperature dependence was measured from 25°C to 120°C under the conditions of tensile mode, a drive frequency of 1 Hz, a chuck gap of 5 mm, and a heating rate of 2°C / min. The average of the storage moduli from 30°C to 100°C was used as the elastic modulus.

[0081] Industrially, the polarizing plate of the present invention is preferably formed by laminating a long strip of polarizer and a long strip of polarizer protective polyester film in a roll-to-roll manner with the aid of an adhesive. Furthermore, polarizers are typically manufactured by stretching in the longitudinal direction and therefore have an absorption axis in the MD and a transmission axis in the TD.

[0082] In the polarizing plate of the present invention, the polarizer and the polarizer-protective polyester film are preferably laminated so that the transmission axis of the polarizer and the TD of the polarizer-protective polyester film are approximately parallel. Here, "approximately parallel" means that the angle formed by the transmission axis of the polarizer and the TD of the polarizer-protective polyester film is preferably 0°±15° or less, more preferably 0°±10° or less, further preferably 0°±8° or less, further more preferably 0°±5° or less, particularly preferably 0°±3° or less, and most preferably 0°.

[0083] In the polarizing plate of the present invention, the polarizer and the polarizer protective polyester film are preferably laminated so that the transmission axis of the polarizer and the slow axis of the polarizer protective polyester film are approximately parallel. Here, "approximately parallel" means that the angle formed by the transmission axis of the polarizer and the slow axis of the polarizer protective polyester film is preferably 0°±15° or less, more preferably 0°±10° or less, further preferably 0°±8° or less, further more preferably 0°±5° or less, particularly preferably 0°±3° or less, and most preferably 0°.

[0084] The liquid crystal display device of the present invention is not particularly limited as long as it includes the polarizing plates of the present invention. It typically comprises at least: a backlight source; and a liquid crystal cell disposed between two polarizing plates. At least one of the two polarizing plates is preferably a polarizing plate of the present invention, i.e., a polarizing plate using the polarizer-protective polyester film of the present invention as a polarizer protective film. Both of the two polarizing plates of the liquid crystal display device may be polarizing plates of the present invention.

[0085] The thickness of the glass substrate as a constituent member of the liquid crystal cell is preferably 0.7 mm or less, more preferably 0.6 mm or less, further preferably 0.5 mm or less, and most preferably 0.4 mm or less.

[0086] The polarizer-protective polyester film of the present invention can be used for liquid crystal displays of any size, but is preferably used for liquid crystal displays of 42 inches or larger, more preferably 46 inches or larger, further preferably 50 inches or larger, further more preferably 55 inches or larger, and particularly preferably 60 inches or larger.

[0087] The polarizer protective polyester film of the present invention is preferably used at the position of the polarizer protective film on the viewing side with the polarizer of the viewing side polarizing plate as the starting point and / or at the position of the polarizer protective film on the light source side with the polarizer of the light source side polarizing plate as the starting point.

[0088] Typically, a liquid crystal display device has a rectangular shape (the two polarizing plates used in a liquid crystal display device are also rectangular). One polarizing plate has its long side parallel to the absorption axis, while the other polarizing plate has its long side parallel to the transmission axis, and they are arranged so that the absorption axes are perpendicular to each other. Furthermore, the polarizing plate with its long side parallel to the absorption axis is typically used as the viewing-side polarizing plate of the liquid crystal display device, while the polarizing plate with its long side parallel to the transmission axis is used as the light source-side polarizing plate of the liquid crystal display device.

[0089] The polarizing plate with a large shrinkage stress and whose absorption axis is in the long side direction has a problem of a shape factor that is prone to curling due to shrinkage (curling is usually prone to occur in the long side direction), or there is an influence caused by the asymmetric structure of the upper and lower polarizing plates in the liquid crystal panel, and the liquid crystal panel tends to be convex on the polarizing plate side where the transmission axis of the polarizing plate of the upper and lower polarizing plates arranged in the cross prism is the long side.

[0090] From the perspective of suppressing warping of the liquid crystal panel, it is preferred to use at least the polarizing plate of the present invention as a polarizing plate having its long side parallel to the transmission axis. Furthermore, it is also preferred to use the polarizing plate of the present invention for both the polarizing plate having its long side parallel to the transmission axis and the polarizing plate having its long side parallel to the absorption axis.

[0091] Example

[0092] Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples and can be implemented with appropriate modifications within the scope consistent with the gist of the present invention. All of these modifications are included in the protection scope of the present invention.

[0093] (1) Shrinkage stress in MD and TD of polyester film

[0094] After standing for 168 hours in a 25°C / 50% RH environment, measurements were performed using a thermomechanical analyzer (TMA7100, manufactured by Hitachi High-Tech Science Inc.). Film samples with a width of 1 mm and a length of 15 mm were fixed under a minimum load of 19 mN. The temperature was raised from 30°C to 260°C at a rate of 5°C / minute, and the shrinkage load was measured. From the resulting shrinkage load curve, the maximum shrinkage load observed from 80°C to 150°C was divided by the initial cross-sectional area to determine the shrinkage stress (MPa).

[0095] When measuring shrinkage stress in MD, the film sample length was set so as to be parallel to MD, and when measuring shrinkage stress in TD, the film sample length was set so as to be parallel to TD.

[0096] (2) TD thermal shrinkage of polyester film

[0097] After the polyester film was left to stand for 168 hours in a 25°C / 50% RH environment, a circle with a diameter of 80 mm was drawn and the diameter of the circle was measured at 1° intervals using an image sizer (Image Measure IM6500, manufactured by KEYENCE). This was used as the length before treatment. Next, the film was heat treated in a Gel aging oven set at 80°C for 30 minutes. After cooling for 10 minutes in an environment set at room temperature of 25°C, the film was evaluated at 1° intervals using the same method as before treatment. This was used as the length after treatment. It should be noted that this treatment was performed on the polarizer protective polyester film alone.

[0098] The heat shrinkage rate of TD was determined by substituting the values ​​of the length of TD before treatment and the length after treatment into the following calculation formula.

[0099] Thermal shrinkage = (length before treatment - length after treatment) / length before treatment × 100

[0100] (3) Film thickness

[0101] The thickness (mm) of the polyester film was measured by using an electric micrometer (Militron 1245D manufactured by Feinpruf) after standing for 168 hours under an environment of 25° C. and 50 RH%, and the unit was converted into mm.

[0102] (4) Warping of LCD panels

[0103] For the liquid crystal panels produced in each embodiment / comparative example, a heat treatment is performed for 2 hours in a Gill aging thermostat set at 80°C and 5% RH. After that, the panels are cooled for 30 minutes in an environment set at room temperature of 25°C and 50% RH. Then, the panels are placed on a horizontal surface with the convex side facing downward. The heights of the four corners are measured with a tape measure, and the maximum value is taken as the amount of warping. The amount of warping is evaluated as follows. It should be noted that the liquid crystal panels are supported at the four corners by prisms, and the panel is placed horizontally on the prisms (i.e., the panel is in a floating state except for the four corners). The heat treatment and cooling treatment are performed.

[0104] ○: 0mm or more and less than 1.5mm

[0105] ×: 1.5mm or more

[0106] (5) Warping of LCD panels after long-term use in high-temperature environments

[0107] For the liquid crystal panels produced in each embodiment / comparative example, a heat treatment is performed for 240 hours in a Gill aging thermostat set at 70°C and 5% RH. After that, the panels are cooled for 30 minutes in an environment set at room temperature of 25°C and 50% RH. Then, the panels are placed on a horizontal surface with the convex side facing downwards. The heights of the four corners are measured with a tape measure, and the maximum value is taken as the amount of warping. The amount of warping is evaluated as follows. It should be noted that the liquid crystal panels are supported at the four corners by prisms, and the panel is placed horizontally on the prisms (i.e., the panel is in a floating state except for the four corners). The heat treatment and cooling treatment are performed.

[0108] ○: 0 mm or more and less than 3.0 mm

[0109] ×: 3.0mm or more

[0110] (6) Refractive index and in-plane retardation (Re) of polyester film

[0111] In-plane retardation is a parameter defined by the product of the refractive index anisotropy (ΔNxy = |Nx - Ny|) along two orthogonal axes of a film and the film thickness d (nm). It is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) is determined by the following method. The slow axis direction of the film is determined using a molecular orientation meter (MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.). The sample for measurement is cut into a 4 cm x 2 cm rectangle with the slow axis parallel to the long side of the sample. For this sample, the refractive indices along two orthogonal axes (refractive index in the slow axis direction: Ny, refractive index in the direction orthogonal to the slow axis direction: Nx) and the refractive index in the thickness direction (Nz) were determined using an Abbe refractometer (manufactured by ATAGO CO., LTD., NAR-4T, measurement wavelength 589 nm). The absolute value of the difference in refractive index between the two axes (|Nx - Ny|) was taken as the refractive index anisotropy (ΔNxy). The film thickness d (nm) was measured using an electric micrometer (manufactured by Feinpruf, Millitron 1245D) and the unit was converted to nm. The in-plane retardation (Re) was calculated from the product of the refractive index anisotropy (ΔNxy) and the film thickness d (nm) (ΔNxy × d).

[0112] (7) Thickness direction retardation (Rth)

[0113] Thickness retardation is a parameter representing the average of the two birefringence values, ΔNxz (=|Nx - Nz|) and ΔNyz (=|Ny - Nz|), when observed in a cross-section along the film's thickness, multiplied by the film thickness d. Nx, Ny, and Nz, along with the film thickness d (nm), are determined using the same method as for in-plane retardation measurement. The thickness retardation (Rth) is then calculated by averaging (ΔNxz × d) and (ΔNyz × d).

[0114] (Production Example 1-Polyester A)

[0115] The esterification reaction vessel was heated, and when it reached 200°C, 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added. While stirring, 0.017 parts by mass of antimony trioxide, 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were added as catalysts. Subsequently, the pressure was increased under the conditions of 0.34 MPa gauge pressure and 240°C. After the pressure in the esterification reaction vessel was returned to normal, 0.014 parts by mass of phosphoric acid was added. Furthermore, the temperature was raised to 260°C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, the mixture was dispersed using a high-pressure disperser. After 15 minutes, the resulting esterification reaction product was transferred to a polycondensation reaction vessel for a polycondensation reaction at 280°C under reduced pressure.

[0116] After the polycondensation reaction, the product was filtered through a NASLON filter with a 95% cutoff diameter of 5 μm, extruded from a nozzle into strands, cooled and solidified using pre-filtered cooling water (pore size: 1 μm or less), and cut into pellets. The resulting polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl / g and contained virtually no inactive particles or internally precipitated particles. (Hereinafter, abbreviated as PET (A))

[0117] (Production Example 2-Polyester B)

[0118] 10 parts by mass of the dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one) and 90 parts by mass of PET (A) (intrinsic viscosity 0.62 dl / g) containing no particles were mixed and extruded using a kneading machine to obtain a polyethylene terephthalate resin (B) containing an ultraviolet absorber (hereinafter abbreviated as PET (B)).

[0119] (Manufacturing Example 3 - Preparation of Adhesion-Modified Coating Liquid)

[0120] A water-dispersible metal sulfonate-based copolyester resin was prepared by conducting an ester exchange reaction and a polycondensation reaction using conventional methods. The composition comprised of 46 mol% of terephthalic acid, 46 mol% of isophthalic acid, and 8 mol% of sodium 5-sulfoisophthalate as dicarboxylic acid components (relative to the total dicarboxylic acid components), and 50 mol% of ethylene glycol and 50 mol% of neopentyl glycol as diol components (relative to the total diol components). Subsequently, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant were mixed and heated with stirring until the temperature reached 77°C. Five parts by mass of the water-dispersible metal sulfonate-based copolyester resin was then added. Stirring was continued until the resin lumps disappeared, and the resin aqueous dispersion was cooled to room temperature to obtain a uniform water-dispersible copolyester resin solution having a solids concentration of 5.0% by mass. Furthermore, 3 parts by mass of aggregated silica particles (SILYSIA 310, manufactured by FUJI SILYSIA CHEMICAL LTD.) were dispersed in 50 parts by mass of water. Then, 0.54 parts by mass of the aqueous dispersion of SILYSIA 310 was added to 99.46 parts by mass of the above-mentioned water-dispersible copolyester resin liquid. 20 parts by mass of water was added while stirring to obtain an adhesion-modified coating liquid.

[0121] (Example 1)

[0122] <Manufacture of Polarizer Protective Polyester Film 1>

[0123] 90 parts by mass of PET (A) resin pellets containing no particles and 10 parts by mass of PET (B) resin pellets containing a UV absorber, which served as raw materials for the intermediate layer of the substrate film, were dried under reduced pressure (1 Torr) at 135°C for 6 hours and then fed to extruder 2 (for intermediate layer II). Separately, PET (A) was dried using conventional methods and fed to extruders 1 (for outer layer I and outer layer III), where it was dissolved at 285°C. The two polymers were filtered using a stainless steel sintered filter medium (nominal filtration accuracy, 95% cutoff for 10 μm particles), laminated using two three-layer confluence blocks, extruded from a nozzle into a sheet, and then wound onto a casting drum at a surface temperature of 30°C using an electrostatic casting method. The sheets were cooled and solidified to produce unstretched films. The discharge rates of the extruders were adjusted to achieve a thickness ratio of 10:80:10 for layer I, layer II, and layer III.

[0124] Then, the coating was applied by a reverse roll method to a coating weight of 0.08 g / m 2 The adhesiveness-modifying coating liquid was applied to both sides of the unstretched PET film and then dried at 80° C. for 20 seconds.

[0125] The unstretched film with the coating layer was introduced into a tenter stretching machine. While the film's ends were secured with clamps, it was introduced into a hot air zone at 105°C and stretched to 4.0 times in the TD direction. Subsequently, it was heat treated at 180°C for 30 seconds, then introduced into a cooling zone at 120°C and stretched 2.5% in the width direction (microstretching). The clamps securing the ends of the film, which had been cooled to 60°C, were then released, and the film was pulled at a tension of 350 N / m. A large-diameter roll of uniaxially oriented PET film with a thickness of approximately 80 μm was collected and divided into three equal parts to obtain three slit rolls (L (left), C (center), and R (right)). Polarizer protective polyester film 1 was obtained from the slit roll located at R. The actual temperature of the film during travel at the end of the 2.5% stretch in the width direction was measured using a non-contact radiation thermometer and was found to be approximately 125°C.

[0126] LCD Panel Manufacturing

[0127] A polarizer protective polyester film 1 was adhered to one side of a polarizer containing PVA, iodine, and boron so that the transmission axis of the polarizer was parallel to the TD of the polarizer protective polyester film 1. Furthermore, a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was adhered to the opposite surface of the polarizer to prepare a light source side polarizing plate.

[0128] The liquid crystal panel was removed from a 65-inch IPS-type liquid crystal television using a 0.4mm thick glass substrate in the liquid crystal cell. The light source side polarizing plate was peeled off from the liquid crystal panel and replaced with the previously prepared light source side polarizing plate. The polarizing plate was adhered to the liquid crystal cell with a pressure-sensitive adhesive (PSA) so that the transmission axis of the polarizer aligned with the transmission axis of the light source side polarizing plate before peeling (parallel to the horizontal direction). This produced a liquid crystal panel.

[0129] The light source side polarizing plate was attached to the liquid crystal cell with the polarizer protective polyester film 1 facing away from (on the opposite side of) the liquid crystal cell. Furthermore, the viewing side polarizing plate was formed by laminating TAC films on both sides of the polarizer, and was attached to the liquid crystal cell with the absorption axis of the polarizer parallel to the horizontal direction.

[0130] (Example 2)

[0131] <Manufacturing of Polarizer Protective Polyester Film 2>

[0132] In the film formation of the polarizer protective polyester film 1 of Example 1, a polarizer protective polyester film 2 was obtained in the same manner as the polarizer protective polyester film 1 except that the film was heat treated at 180°C for 30 seconds, then introduced into a cooling zone at 120°C, and stretched 3.0% in the width direction.

[0133] LCD Panel Manufacturing

[0134] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizer-protective polyester film 1 was replaced with the polarizer-protective polyester film 2 .

[0135] (Example 3)

[0136] <Manufacturing of Polarizer Protective Polyester Film 3>

[0137] Polarizer protective film 3 was obtained in the same manner as polarizer protective polyester film 1 except that the polarizer protective polyester film 1 was heat treated at 180°C for 30 seconds, then introduced into a cooling zone at 120°C, and stretched 3.5% in the width direction.

[0138] LCD Panel Manufacturing

[0139] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizing plate protective polyester film 1 was replaced with the polarizing plate protective polyester film 3 .

[0140] (Example 4)

[0141] <Manufacturing of Polarizer Protective Polyester Film 4>

[0142] Polarizer protective film 4 was obtained in the same manner as polarizer protective polyester film 1 except that the polarizer protective polyester film 1 was heat treated at 180°C for 30 seconds, then introduced into a cooling zone at 120°C, and stretched 4.0% in the width direction.

[0143] LCD Panel Manufacturing

[0144] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizer-protective polyester film 1 was replaced with the polarizer-protective polyester film 4 .

[0145] (Example 5)

[0146] <Manufacturing of Polarizer Protective Polyester Film 5>

[0147] Polarizer protective film 5 was obtained in the same manner as polarizer protective polyester film 1 except that the film was heat treated at 180°C for 30 seconds, introduced into a cooling zone at 120°C, and stretched 4.5% in the width direction.

[0148] LCD Panel Manufacturing

[0149] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizing plate protective polyester film 1 was replaced with the polarizing plate protective polyester film 5 .

[0150] (Comparative Example 1)

[0151] <Manufacturing of Polarizer Protective Polyester Film 6>

[0152] Polarizer protective film 6 was obtained in the same manner as polarizer protective polyester film 1 except that the polarizer protective polyester film 1 was heat treated at 180°C for 30 seconds, then introduced into a cooling zone at 120°C, and stretched 5.0% in the width direction.

[0153] LCD Panel Manufacturing

[0154] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizing plate protective polyester film 1 was replaced with the polarizing plate protective polyester film 6 .

[0155] (Comparative Example 2)

[0156] <Manufacturing of Polarizer Protective Polyester Film 7>

[0157] Polarizer Protective Film 7 was obtained in the same manner as for Polarizer Protective Polyester Film 1, except that the film was heat treated at 180°C for 30 seconds, then introduced into a cooling zone at 100°C and stretched 1.0% in the width direction. The actual temperature of the film during its travel at the completion of the 1.0% stretching in the width direction was measured using a non-contact radiation thermometer and was found to be approximately 115°C.

[0158] LCD Panel Manufacturing

[0159] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizing plate protective polyester film 1 was replaced with the polarizing plate protective polyester film 7 .

[0160] (Comparative Example 3)

[0161] <Manufacturing of Polarizer Protective Polyester Film 8>

[0162] Polarizer protective film 8 was obtained in the same manner as polarizer protective polyester film 1 except that the film was heat treated at 180°C for 30 seconds, then introduced into a cooling zone at 100°C, and stretched 1.5% in the width direction.

[0163] LCD Panel Manufacturing

[0164] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizing plate protective polyester film 1 was replaced with the polarizing plate protective polyester film 8 .

[0165] (Comparative Example 4)

[0166] <Manufacturing of Polarizer Protective Polyester Film 9>

[0167] Polarizer Protective Film 9 was obtained in the same manner as in Example 1 except that the film was heat treated at 180°C for 30 seconds, then introduced into a cooling zone at 100°C, and stretched 2.0% in the width direction.

[0168] LCD Panel Manufacturing

[0169] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizing plate protective polyester film 1 was replaced with the polarizing plate protective polyester film 9 .

[0170] (Comparative Example 5)

[0171] <Manufacturing of Polarizer Protective Polyester Film 10>

[0172] In the preparation of the polarizer protective polyester film 1 of Example 1, a polarizer protective film 10 was obtained in the same manner as the polarizer protective polyester film 1 except that the film was heat treated at 180°C for 30 seconds, introduced into a cooling zone at 100°C, and stretched 2.5% in the width direction.

[0173] LCD Panel Manufacturing

[0174] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizer-protective polyester film 1 was replaced with the polarizer-protective polyester film 10 .

[0175] (Comparative Example 6)

[0176] <Manufacturing of Polarizer Protective Polyester Film 11>

[0177] In the preparation of the polarizer protective polyester film 1 of Example 1, a polarizer protective film 11 was obtained in the same manner as the polarizer protective polyester film 1 except that the film was heat treated at 180°C for 30 seconds, introduced into a cooling zone at 100°C, and stretched 3.5% in the width direction.

[0178] LCD Panel Manufacturing

[0179] A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizer-protective polyester film 1 was replaced with the polarizer-protective polyester film 11 .

[0180] [Table 1]

[0181]

[0182] From the results shown in Table 1, it was confirmed that the polarizing plate using the polarizer-protective polyester film of the present invention can suppress the warping of the liquid crystal panel as compared with the polarizing plate of the comparative example.

[0183] In Examples 1 to 5, liquid crystal panels were produced in the same manner except that a TAC film was not used as the protective film on the liquid crystal cell side of the light source-side polarizer. The liquid crystal panels of each example all achieved good results (0) in both the evaluations of "liquid crystal panel warpage" and "liquid crystal panel warpage after prolonged exposure to high temperature."

[0184] Industrial applicability

[0185] According to the present invention, a polarizer-protecting polyester film, a polarizing plate, and a liquid crystal display device capable of suppressing warping of a liquid crystal panel can be provided.

Claims

1. A polarizing plate protective polyester film, which satisfies the following characteristics (1), (2) and (3), (1) The shrinkage stress F in the width direction of the polyester film is greater than or equal to 8 MPa and less than or equal to 25 MPa; (2) the ratio F / HS of the shrinkage stress F in the width direction of the polyester film to the heat shrinkage HS in the width direction of the polyester film after treatment at 80°C for 30 minutes is 30 MPa / % or more and 60 MPa / % or less, (3) The thickness of the polyester film is 40 to 200 μm.

2. The polarizer protective polyester film according to claim 1, further satisfying the following feature (4): (4) The in-plane retardation of the polyester film is 3000 to 30000 nm.

3. The polarizer protective polyester film according to claim 1 or 2, wherein The polyester film has a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer or an antireflection and antiglare layer on the surface opposite to the surface on which the polarizing plate is to be laminated. 4 . A polarizing plate comprising the polarizer-protective polyester film according to claim 1 laminated on one surface of a polarizer. 5 . A polarizing plate comprising: a polarizer; a polarizer-protective polyester film according to claim 1 , laminated on one surface of the polarizer; and no film laminated on the other surface of the polarizer. 6 . A polarizing plate comprising: a polarizer; a polarizer-protective polyester film according to claim 1 , laminated on one surface of the polarizer; and a coating layer laminated on the other surface of the polarizer.

7. The polarizing plate according to claim 6, wherein The coating layer is a hard coating layer or a phase difference film. 8 . A liquid crystal display device comprising the polarizing plate according to claim 4 .

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