KR20220159411A - Polyester film for polarizer protection, polarizer and liquid crystal display - Google Patents

Abstract

The subject of this invention is providing the polyester film for polarizer protection which can suppress the curvature of a liquid crystal panel, a polarizing plate, and a liquid crystal display device. The subject can be solved by a polyester film for polarizer protection that satisfies the following requirements (1) and (2). (1) The TD shrinkage stress (F) of the polyester film is 8 MPa or more and 25 MPa or less. (2) The ratio (F/HS) of the TD shrinkage stress (F) of the polyester film and the TD thermal shrinkage (HS) of the polyester film treated at 80°C for 30 minutes is 30 (MPa/%) ) or more and 60 (MPa/%) or less.

Description

Polyester film for polarizer protection, polarizer and liquid crystal display

The present invention relates to a polyester film for polarizer protection, a polarizing plate, and a liquid crystal display device.

BACKGROUND OF THE INVENTION Demand for liquid crystal display devices is expanding for applications such as liquid crystal televisions and liquid crystal displays for personal computers. Usually, 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 thereof, and each polarizing plate is a polarizer (also referred to as a polarizing film). ) is sandwiched between two optical films (for example, a polarizer protective film and a retardation film).

BACKGROUND ART In recent years, a phenomenon in which a liquid crystal panel warps and displays unevenness has been confirmed due to an increase in size and thickness of a liquid crystal television screen. For example, the rigidity changes depending on the thickness of the glass substrate used in the liquid crystal panel, and the slight shrinkage of the polarizer may cause the liquid crystal panel to warp and cause uneven display. In particular, when the thickness of the glass substrate is made thinner than 0.7 mm for further thinning of the liquid crystal panel, occurrence of display unevenness tends to become a problem, and improvement thereof is required.

In patent document 1, the method of improving the curvature of a liquid crystal panel and display unevenness is proposed by making the shrinkage force of the polyester film for polarizer protection laminated|stacked on one surface of a polarizer into a specific range.

International Publication WO2019/054406

In order to suppress the curvature of a liquid crystal panel with the enlargement of a liquid crystal panel and thickness reduction of the glass substrate of a liquid crystal cell, the present inventors found that the shrinkage stress of the polyester film for polarizer protection should be enlarged.

In order to increase the shrinkage stress of the polyester film for polarizer protection, it is one of the effective countermeasures to increase the heat shrinkage rate by treatment at 80 ° C. for 30 minutes, but a liquid crystal panel using a polyester film for polarizer protection with such a high heat shrinkage rate , When placed in a high-temperature environment for a long time, warpage may occur in the liquid crystal panel, particularly when the liquid crystal panel is large.

This invention was made|formed in view of the said problem and situation, and the main subject is to provide the polyester film for polarizer protection which can suppress the curvature of a liquid crystal panel, a polarizing plate, and a liquid crystal display device. In particular, it is an object to provide a polyester film for polarizer protection, a polarizing plate, and a liquid crystal display device capable of suppressing warpage of a liquid crystal panel even when a liquid crystal panel is placed in a high-temperature environment for a long time.

A typical example of the present invention is as follows.

Section 1.

A polyester film for polarizer protection that satisfies the following requirements (1) and (2).

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

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

clause 2.

Further, the polyester film for polarizer protection according to item 1, which satisfies the requirements of (3) below.

(3) In-plane retardation of the said polyester film is 3000-30000 nm.

clause 3.

Furthermore, the polyester film for polarizer protection as described in claim|item 1 or 2 which satisfy|fills the requirements of following (4).

(4) The polyester film has a thickness of 40 to 200 μm.

clause 4.

Polarizer protection according to any one of 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 on the opposite side to the surface on which the polarizer is laminated. polyester film.

Section 5.

A polarizing plate in which the polyester film for polarizer protection according to any one of claims 1 to 4 was laminated on one side of the polarizer.

clause 6.

A polarizing plate in which the polyester film for polarizer protection according to any one of claims 1 to 4 is laminated on one surface of the polarizer, and the film is not laminated on the other surface of the polarizer.

clause 7.

A polarizing plate in which the polyester film for polarizer protection according to any one of items 1 to 4 is laminated on one surface of the polarizer, and an application layer is laminated on the other surface of the polarizer.

Section 8.

The polarizing plate according to claim 7, wherein the coating layer is a hard coat layer or a retardation film.

clause 9.

A liquid crystal display device comprising the polarizing plate according to any one of claims 5 to 8.

ADVANTAGE OF THE INVENTION According to this invention, the polarizer protective film, polarizing plate, and liquid crystal display device which can suppress the curvature of a liquid crystal panel can be provided. In particular, even when the liquid crystal panel is placed under a high temperature environment for a long time, a polyester film for polarizer protection, a polarizing plate, and a liquid crystal display device capable of suppressing warpage of the liquid crystal panel can be provided.

The polyester film for polarizer protection of the present invention is made of a polyester film and laminated on at least one surface of a polarizer (for example, a film made of polyvinyl alcohol and a pigment) to be a polarizer protective film for producing a polarizing plate. desirable.

It is preferable that the value of the TD shrinkage stress (F) of the polyester film for polarizer protection of this invention is 8 Mpa or more and 25 Mpa or less of a polyester film. When the lower limit of the shrinkage stress (F) is 8 MPa or more, warpage of the liquid crystal panel can be sufficiently reduced. In addition, if the upper limit of the shrinkage stress (F) is 25 MPa or less, it is possible to prevent the liquid crystal panel from being bent in the reverse direction. Therefore, the shrinkage stress (F) is preferably within the above range. The lower limit of the shrinkage stress (F) is more preferably 10 MPa or more, and still more preferably 12 MPa or more. The upper limit of the shrinkage stress (F) is more preferably 23 MPa or less, and 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 still more preferably 12 MPa or more and 20 MPa or less.

The shrinkage stress (Fv) of the MD of the polyester film is usually about 1.8 to 2.2 MPa, although stress is generated in the MD due to Poisson contraction when microstretching described later is performed during film forming. this is preferable The MD shrinkage stress (Fv) of the polyester film can be arbitrarily controlled by the MD tension.

The shrinkage stress (F) of TD and the shrinkage stress (Fv) of MD are measured by TMA (thermo mechanical analysis) as described in detail in Examples. In addition, TD is an abbreviation of Transverse Direction, and in this specification, it may be called the width direction and the lateral direction. MD is an abbreviation of Machine Direction, and in this specification, it may be called a film flow direction, a longitudinal direction, and a longitudinal direction.

The polyester film for polarizer protection of the present invention further reduces the curvature of the liquid crystal panel, or from the viewpoint of suppressing the curl (propeller curl) accompanying the twist, the TD shrinkage stress (F) of the polyester film and the polyester film The MD shrinkage 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, still more preferably 1.5 or more and 8 or less.

The polyester film for polarizer protection of the present invention is the TD shrinkage stress (F) (MPa) of the polyester film and the thermal contraction rate (HS) (%) of the TD by the treatment of the polyester film at 80 ° C. for 30 minutes. It is preferable that the ratio (F/HS) is 30 (MPa/%) or more and 60 (MPa/%) or less. By setting the ratio (F/HS) within the above range, it becomes possible to suppress the warpage of the liquid crystal panel even when the liquid crystal panel is placed under a high temperature environment for a long time. The ratio (F/HS) is more preferably 35 (MPa/%) or more and 55 (MPa/%) or less. In addition, when the upper limit of the ratio (F/HS) is 60 (MPa/%) or less, film forming stability is improved and more stable operation can be performed.

It is preferable that the TD thermal contraction rate of the polyester film for polarizer protection of this invention by the process of 80 degreeC of polyester films for 30 minutes is 0.1 to 5 %. The lower limit of the TD thermal contraction rate is preferably 0.1% or more, more preferably 0.15% or more, and most preferably 0.2% or more. The upper limit of the TD thermal contraction rate 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% or less, particularly Preferably it is 0.7% or less, and most preferably 0.5% or less. When the thermal contraction rate of TD is 0.1% or more, it is easy to control the thermal contraction rate without unevenness. In addition, when the thermal contraction rate of TD is 5% or less, there is no fear that the polarizer protective film thermally contracts in one direction due to the heat of the backlight and the curvature of the liquid crystal panel occurs.

The thermal contraction rate of TD can be measured by the method employed in Examples described later.

Usually, in a liquid crystal display device, two polarizing plates are arranged in a crossed Nicols relationship. When two polarizing plates are arranged in a cross Nicols relationship, light usually does not pass through the two polarizing plates. However, as a result of the contraction or bending of the polarizer described above, the perfect cross Nicols relationship is broken, and light leakage may occur. From the viewpoint of suppressing leakage of light, it is preferable that the angle between the direction in which the thermal contraction rate of the polarizer protective film is maximized and the transmission axis of the polarizer is smaller.

It is preferable that the polyester film for polarizer protection of this invention is 40-200 micrometers in thickness. More preferably, it is 40-100 micrometers, More preferably, it is 40-80 micrometers. When the thickness is 40 μm or more, it is difficult to crack and flatness defect due to lack of rigidity is also difficult to occur. Moreover, if the thickness is 200 μm or less, the variation in shrinkage stress in the TD of the film is small, and the cost required for control of the shrinkage stress can also be suppressed. The thickness can be measured by a method employed in Examples described later.

It is preferable that the in-plane retardation of the polyester film for polarizer protection of this invention exists in a specific range from a viewpoint of suppressing the rainbow unevenness observed on the screen of a liquid crystal display device. It is preferable that the lower limit of in-plane retardation is 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 30000 nm or less, more preferably 18000 nm or less, even more preferably 15000 nm or less, still more preferably 10000 nm or less. In particular, from the viewpoint of thinning, the in-plane retardation is preferably less than 10000 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 using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Keisoku Instruments Co., Ltd.). In addition, the refractive index can be obtained by Abbe's refractometer (measurement wavelength: 589 nm).

The polyester film for polarizer protection of the present invention has a ratio (Re/Rth) of in-plane retardation (Re) and thickness direction retardation (Rth) of preferably 0.2 or more, 0.3 or more, or 0.4 or more, more preferably is 0.5 or more, more preferably 0.6 or more. As the ratio of the in-plane retardation to the thickness direction retardation (Re/Rth) increases, the action of birefringence increases the isotropy, and occurrence of rainbow-like color unevenness due to the viewing angle tends to be less likely to occur. In a perfect uniaxial (uniaxially symmetric) film, the ratio (Re / Rth) of the in-plane retardation and the thickness direction retardation is 2, so the ratio (Re / Rth) of the in-plane retardation and the thickness direction retardation As for an upper limit, 2 is preferable. A preferable upper limit of Re/Rth is 1.2 or less. Further, thickness direction retardation means an average of values obtained by multiplying two birefringences ΔNxz and ΔNyz by the film thickness d when the film is viewed in a cross section in the thickness direction, respectively.

From the viewpoint of suppressing rainbow-like color unevenness, the polyester film for polarizer protection of the present invention preferably has an NZ coefficient of 2.5 or less, more preferably 2 or less, still more preferably 1.8 or less. Preferably it is 1.6 or less. And since the NZ coefficient becomes 1 in a perfect uniaxial (uniaxial symmetry) film, the lower limit of the NZ coefficient is 1. There exists a tendency for the mechanical strength of the direction orthogonal to an orientation direction to improve, so that NZ coefficient is large.

The NZ coefficient is represented by |Ny-Nz|/|Ny-Nx|, where Ny is the refractive index of the polyester film in the slow axis direction, and Nx is the refractive index in the direction orthogonal to the slow axis (refractive index in the fast axis direction). , Nz represents the refractive index in the thickness direction. Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Instruments Co., Ltd.), the orientation axis of the film is obtained, and the refractive index of the two axes (Ny, Nx, and Ny) of the orientation axis direction and the direction orthogonal to this >Nx), and the refractive index (Nz) in the thickness direction are obtained with an Abbe refractometer (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm). The value obtained in this way can be substituted into |Ny-Nz|/|Ny-Nx| to obtain the NZ coefficient.

Moreover, as for the polyester film for polarizer protection of this invention, the value of Ny-Nx of a polyester film is preferably 0.05 or more, more preferably 0.07 or more, still more preferably from a viewpoint of suppressing rainbow-like color unevenness more. is 0.08 or more, more preferably 0.09 or more, and most preferably 0.1 or more. The upper limit of Ny-Nx is not particularly limited, but is preferably about 0.15 in the case of a polyethylene terephthalate-based film.

The polyester film for polarizer protection of this invention can be obtained from arbitrary polyester resins. The kind 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.

Examples of the dicarboxylic acid component usable for production of the polyester resin include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonedicarboxylic acid, anthracenedicarboxylic 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-dimethylglutaric acid, adipic acid, 2 -Methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecane dicarboxylic acid, and the like.

Examples of the diol component usable for producing the polyester resin include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, and deca Methylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxy Phenyl) sulfone etc. are mentioned.

1 type or 2 or more types can be used for all the dicarboxylic acid component and diol component which comprise a polyester resin. Suitable polyester resins constituting the polyester film include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and the like, more preferably polyethylene terephthalate and polyethylene. Although naphthalate is mentioned, these may also contain other copolymerization components further. These resins are excellent in transparency and also excellent in thermal and mechanical properties. In particular, polyethylene terephthalate is a suitable material because it can achieve a high modulus of elasticity and is also relatively easy to control the thermal contraction rate.

When it is necessary to highly increase the heat shrinkage rate of the polyester film, it is preferable to moderately lower the crystallinity by adding a copolymerization component. Moreover, it is generally difficult to highly increase the thermal contraction rate because the rate of elastic strain or permanent strain is high for deformation below the vicinity of the glass transition temperature. Therefore, it is also a preferable embodiment to introduce a component with a low glass transition temperature as needed. As a component with a low glass transition temperature, propylene glycol, 1, 3- propanediol, etc. are mentioned specifically,.

It is also possible to give a corona treatment, coating treatment, flame treatment, etc. to the polyester film for polarizer protection, in order to make adhesiveness with a polarizer favorable.

(Provision of easily adhesive layer)

In order to improve adhesiveness with functional layers, such as a hard-coat layer, and a polarizer, it is preferable to have an easily bonding layer on at least one side|surface of a polyester film. A polyester film having such an easily bonding layer is also included in the polyester film for polarizer protection of the present invention.

It is preferable to have an easily bonding layer containing at least one selected from the group consisting of polyester resins (including co-polyester resins), polyurethane resins, and polyacrylic resins as a main component on at least one side of the polyester film. Here, the "main component" refers to a component that is 50% by mass or more of the solid components constituting the easily bonding layer. The coating liquid used for formation of the easily bonding layer is preferably an aqueous coating liquid containing at least one selected from the group consisting of water-soluble or water-dispersible co-polyester resins, polyacrylic resins, and polyurethane resins. As such a coating liquid, for example, Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, Japanese Patent No. 4150982, etc. and the disclosed water-soluble or water-dispersible co-polyester resin solution, acrylic resin solution, polyurethane resin solution and the like.

The easily bonding layer is, for example, after applying the coating solution to one side or both sides of an unstretched film or a uniaxially stretched film in the longitudinal direction, drying at 100 to 150 ° C., and further stretching in the transverse direction. can be obtained by It is preferable to manage the final application amount of the easily bonding layer (application amount after drying) at 0.05 to 0.2 g/m 2 . Adhesiveness with the light polarizer obtained as an application quantity is 0.05 g/m<2> or more is sufficient. On the other hand, when the application amount is 0.2 g/m 2 or less, blocking resistance is improved. In the case of providing an easily bonding layer on both sides of a polyester film, the coating amount of the easily bonding layer on both sides may be the same or different, and can be independently set within the above range.

It is preferable to add particles to the easily bonding layer in order to impart easy activity. As the particles, it is preferable to use fine particles having an average particle diameter of 2 μm or less. If the average particle diameter of the particles is 2 μm or less, dropping of the particles can be suppressed. Examples of particles included in the easily bonding layer include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, and lithium fluoride. , inorganic particles such as calcium fluoride, organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicon. These may be added individually to the easily bonding layer, or may be added in combination of 2 or more type.

Moreover, a well-known method can be used as a method of apply|coating a coating liquid. Examples include a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brush method, a spray coating method, an air knife coating method, a wire bar coating method, a pipe doctor method, and the like. It can be done alone or in combination.

In addition, the average particle diameter of the said particle|grain 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 (the distance between the two most distant points) is measured at the same magnification as when the size of one of the smallest particles is 2 to 5 mm. , and the average value is taken as the average particle diameter.

(Provision of Functional Layer)

On the surface opposite to the surface on which the polarizer is laminated, of the polyester film for polarizer protection of the present invention, a hard coat layer, an anti-glare layer, an anti-reflection layer, a low-reflection layer (including a low-reflection anti-glare layer and a low-reflection anti-glare layer), anti-reflection It is preferable to have a functional layer, such as an antiglare layer and an antistatic layer. It is preferable that the shrinkage stress (F) and the ratio (F/HS) have the above conditions in the state where these functional layers are laminated on the polyester film.

Since the polarizing plate using the polyester film for polarizer protection of the present invention is preferably integrated with the glass plate of the liquid crystal cell in a state where the thermal contraction rate of the polyester film remains, when a functional layer is provided, the drying temperature is set low. However, it is a preferable embodiment to perform by a method with a small thermal history, such as UV irradiation or electron beam irradiation. In addition, since it becomes possible to integrate the polarizing plate of this invention and the glass plate of a liquid crystal cell, providing these functional layers in the film forming process of a polyester film is a more preferable embodiment, without impairing the improved thermal contraction rate.

(Method for producing polyester film)

A polyester film can be manufactured according to the manufacturing method of a general polyester film. For example, after melting a polyester resin, extruding it into a sheet form, and stretching the molded non-oriented polyester in the longitudinal direction at a temperature equal to or higher than the glass transition temperature using a difference in roll speed, the tenter A method of stretching in the transverse direction and performing heat treatment (heat setting) is exemplified. The polyester film may be a uniaxially stretched film or a biaxially stretched film, and is preferably a uniaxially stretched film strongly stretched mainly in the transverse direction, even if slightly stretched in a direction perpendicular to the main direction of stretching. do.

When the film forming conditions of the polyester film are explained concretely, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130°C, respectively, and particularly preferably 90 to 120°C. The longitudinal stretch ratio is preferably 1 to 3.5 times, and particularly preferably 1 to 3 times. Further, the transverse stretch 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 preferable to control the ratio of the longitudinal stretch magnification and the transverse stretch magnification. In the subsequent heat treatment (heat setting), the treatment temperature is preferably 100 to 250°C, particularly preferably 180 to 245°C.

It is preferable to guide the film through the stretching/heat setting zone to a cooling zone having a set temperature lower than that of the heat setting zone, and finely stretch in TD. Depending on the temperature and microstretching magnification at the time of microstretching, the TD shrinkage stress and thermal contraction rate can be controlled. The TD shrinkage stress (F) tends to increase by raising the film yarn temperature during microstretching or by increasing the TD microstretching magnification. In addition, as the room temperature of the film during microstretching decreases, F/HS tends to decrease. In order to make the TD shrinkage stress (F) and the ratio (F/HS) of the TD shrinkage stress (F) and the TD thermal contraction rate (HS) within the above preferred range, the following formula:

TD microstretching magnification = (TD width after microstretching - TD width before microstretching) / TD width before microstretching

It is preferable that the TD microstretching ratio represented by is in the range of 1.5% to 5%. Further, the degree of room temperature of the film at the end of fine stretching is preferably approximately 120°C to 150°C. The room temperature of the film can be controlled by the amount of heat brought in from the previous zone (accompanying flow), the temperature, wind speed, nozzle arrangement, and the like in that zone.

As for the polarizing plate of this invention, the polyester film for polarizer protection of this invention is laminated|stacked on at least one surface of a polarizer. It is preferable that a film having no birefringence such as a TAC film, an acrylic film, or a norbornene film is laminated on the other surface of the polarizer. Alternatively, a polarizing plate in which no film is laminated on the other surface of the polarizer is also a preferable aspect from the viewpoint of thinness. In this case, the film is not laminated on the other side of the polarizer, but the application layer may be laminated on the polarizer. The application layer may be a functional layer such as a hard coat layer or a retardation film to be formed by coating.

Further, when films or coating layers other than the polyester film for polarizer protection of the present invention are laminated on the polarizer, shrinkage stress of the film or coating layer other than the polyester film for polarizer protection in a direction parallel to the transmission axis of the polarizer, And the shrinkage stress of films other than the polyester film for polarizer protection or the coating layer in the direction parallel to the absorption axis of the polarizer is preferably equal to or less than the value of the TD shrinkage stress of the polyester film for polarizer protection, more preferably is equal to or less than the value of MD shrinkage stress of the polyester film for polarizer protection.

In addition, films other than the polyester film for polarizer protection in a direction parallel to the transmission axis of the polarizer, the shrinkage force of the coating layer, and the film other than the polyester film for polarizer protection in the direction parallel to the absorption axis of the polarizer The shrinkage force of the coating layer is preferably 250 N/m or less, more preferably 200 N/m or less. For films and coating layers other than the polyester film for polarizer protection, the shrinkage force (N/m) in the specific direction to be evaluated is the thickness of the film or coating layer (mm) × modulus of elasticity in the specific direction (N/mm2) × 80 ° C. It is defined as thermal contraction rate (%) ÷ 100 × 1000 in a specific direction by treatment for 30 minutes.

In addition, an elastic modulus evaluates according to JIS-K7244 (DMS) after stationary for 168 hours in an environment of 25°C and 50RH% using a dynamic viscoelasticity measuring device (DMS6100) manufactured by Seiko Instruments. The temperature dependence at 25 ° C. to 120 ° C. is measured under the conditions of tension mode, drive frequency 1 Hz, distance between chucks 5 mm, temperature increase rate 2 ° C./min, and the average storage modulus at 30 ° C. to 100 ° C. is taken as the elastic modulus.

Industrially, it is preferable that the polarizing plate of this invention laminates the long thing of a polarizer and the long thing of a polyester film for polarizer protection in the form of a roll-to-roll through an adhesive agent. And since a polarizer is usually manufactured by extending|stretching in the longitudinal direction, it has an absorption axis in MD and a transmission axis in TD.

In the polarizing plate of the present invention, the polarizer and the polyester film for polarizer protection are preferably laminated so that the transmission axis of the polarizer and the TD of the polyester film for polarizer protection are substantially parallel. Here, substantially parallel means that the angle formed by the transmission axis of the polarizer and the TD of the polyester film for polarizer protection is preferably 0°±15° or less, more preferably 0°±10° or less, still more preferably is 0°±8° or less, more preferably 0°±5° or less, particularly preferably 0°±3° or less, and most preferably 0°.

Moreover, in the polarizing plate of this invention, it is preferable that the polarizer and the polyester film for polarizer protection are laminated|stacked so that the transmission axis of a polarizer and the slow axis of the polyester film for polarizer protection may become substantially parallel. Here, substantially parallel means that the angle formed by the transmission axis of the polarizer and the slow axis of the polyester film for polarizer protection is preferably 0°±15° or less, more preferably 0°±10° or less, still more preferably It is preferably 0°±8° or less, more preferably 0°±5° or less, particularly preferably 0°±3° or less, and 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 at least has a backlight source and a liquid crystal cell disposed between the two polarizing plates. It is preferable that at least one of the said two polarizing plates is the polarizing plate of this invention, ie, the polarizing plate which uses the polyester film for polarizer protection of this invention as a polarizer 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.

Although the polyester film for polarizer protection of this invention can be used for any size liquid crystal display device, Preferably it is 42 inches or more, More preferably, it is 46 inches or more, More preferably, it is 50 inches or more, Still more preferably, it is 55 inches. Above, it can be used for liquid crystal display devices of 60 inches or more particularly preferably.

The polyester film for polarizer protection of the present invention is preferably used at the position of the polarizer protective film on the visual side starting from the polarizer of the polarizing plate on the visual side and / or the polarizer protective film on the light source side starting from the polarizer of the polarizing plate on the light source side. do.

Usually, a liquid crystal display device has a rectangular shape (the two polarizing plates used in the liquid crystal display device are also rectangular), one polarizing plate has its long side and its absorption axis parallel, and the other polarizing plate has its long side parallel to the absorption axis. The transmission axes are parallel and the absorption axes are arranged in a perpendicular relationship with each other. And, usually, 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 is a liquid crystal display device. It is used as a light source side polarizing plate.

The problem of the shape factor in which curling easily occurs due to contraction of the polarizer having a long side in the direction of the absorption axis of the polarizer with high shrinkage stress (curling is generally easy to occur in the long side direction), or an asymmetric configuration of upper and lower polarizers in a liquid crystal panel Due to the influence of this, the liquid crystal panel tends to be convex toward the polarizer side where the polarizer transmission axis of the upper and lower polarizers arranged in crossed Nicols becomes the longer side.

At least, as a polarizing plate in which the long side of the polarizing plate and the transmission axis have a parallel relationship, it is preferable to use the polarizing plate of the present invention from the viewpoint of suppressing warpage of the liquid crystal panel. Moreover, it is also preferable to use the polarizing plate of this invention for both the polarizing plate in which the long side of a polarizing plate has a parallel relationship with the transmission axis, and the polarizing plate in which the long side of the polarizing plate and the absorption axis have a parallel relationship.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be carried out with appropriate changes within the range that can be suitable for the purpose of the present invention. and they are all included in the technical scope of the present invention.

(1) MD, TD shrinkage stress of polyester film

After standing still for 168 hours in an environment of 25°C and 50RH%, it was measured using a thermomechanical analyzer (manufactured by Hitachi High-Tech Science Co., Ltd., TMA7100). A film sample having a width of 1 mm and a sample length of 15 mm was gripped with a minimum load of 19 mN, and the temperature was raised from 30°C to 260°C at 5°C/min, and the shrinkage load was measured. From the obtained shrinkage load curve, the maximum shrinkage load exhibited from 80°C to 150°C was divided by the initial cross-sectional area to obtain the shrinkage stress (MPa).

In addition, when measuring shrinkage stress of MD, the length of the film sample was set to be parallel to MD, and when measuring shrinkage stress of TD, the length of the film sample was set to be parallel to TD.

(2) Thermal contraction rate of TD of polyester film

After the polyester film was allowed to stand in an environment of 25°C/50RH% for 168 hours, a circle having a diameter of 80 mm was drawn, and the diameter of the circle was measured at every 1° using an image size measuring machine (Image Measurer IM6500 manufactured by KEYENCE), and the length before treatment. made with Next, heat treatment is performed for 30 minutes using a gear oven set at 80°C, and then cooled for 10 minutes in an environment set at a room temperature of 25°C. made in length In addition, the said process was performed with the polyester film single-piece|unit for polarizer protection.

The TD thermal shrinkage rate was obtained by putting the values of the length before the TD treatment and the length after the treatment into the following calculation formula.

Heat shrinkage rate = (length before treatment - length after treatment) / length before treatment × 100

(3) Film thickness

The thickness (mm) of the polyester film was measured using an electric micrometer (Militron 1245D, manufactured by Fine Leup Co., Ltd.) after being left still in an environment of 25°C and 50RH% for 168 hours, and the unit was converted into mm.

(4) Warpage of the liquid crystal panel

The liquid crystal panels produced in each Example and Comparative Example were subjected to heat treatment for 2 hours in a gear oven set at 80°C and 5% RH, and then cooled for 30 minutes in an environment set at room temperature of 25°C and 50% RH. After that, it was placed on a horizontal surface with the convex side down, and the heights of the four corners were measured with a measure, and the maximum value was taken as the amount of deflection. The amount of warpage was evaluated as follows. In addition, the liquid crystal panel was subjected to the heat treatment and cooling treatment described above in a state where four corners were supported by prisms and the panel was left horizontally on top of the prisms (that is, the panel was raised except for the four corners).

○: 0 mm or more, less than 1.5 mm

×: 1.5 mm or more

(5) Warpage of the liquid crystal panel after being placed in a high-temperature environment for a long time

The liquid crystal panel produced in each Example and Comparative Example was subjected to heat treatment for 240 hours in a gear oven set at 70°C and 5% RH, and then cooled for 30 minutes in an environment set at room temperature of 25°C and 50% RH. After that, it was placed on a horizontal surface with the convex side down, and the heights of the four corners were measured with a measure, and the maximum value was taken as the amount of deflection. The amount of warpage was evaluated as follows. In addition, the liquid crystal panel was subjected to the heat treatment and cooling treatment described above in a state where four corners were supported by prisms and the panel was left horizontally on top of the prisms (that is, the panel was raised except for the four corners).

○: 0 mm or more, less than 3.0 mm

×: 3.0 mm or more

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

In-plane retardation is a parameter defined by the product (ΔNxy × d) of the anisotropy of the refractive index of two orthogonal axes on the film (ΔNxy = |Nx-Ny|) and the film thickness (d) (nm), optical isotropy, It is a measure of anisotropy. The biaxial refractive index anisotropy (ΔNxy) was obtained by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Instruments Co., Ltd.), the direction of the slow axis of the film is determined, and the direction of the slow axis is parallel to the long side of the sample for measurement. 4 cm × 2 cm A rectangle of was cut out and used as a sample for measurement. For this sample, the refractive index of 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 (Nz) in the thickness direction were measured with an Abbe refractometer (manufactured by Atago Co., Ltd., NAR). -4T, measurement wavelength 589 nm), and the absolute value (|Nx-Ny|) of the biaxial refractive index difference was taken as the refractive index anisotropy (ΔNxy). The thickness (d) (nm) of the film was measured using an electric micrometer (Militron 1245D, manufactured by Fine Lupe Co., Ltd.), and the unit was converted into nm. The in-plane retardation (Re) was determined from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the film thickness (d) (nm).

(7) Thickness direction retardation (Rth)

Retardation in the thickness direction is a retardation obtained by multiplying two birefringents, ΔNxz (= |Nx-Nz|) and ΔNyz (= |Ny-Nz|), respectively, by the film thickness (d) when viewed from the cross section in the film thickness direction. It is a parameter representing the average of . In the same way as in the measurement of in-plane retardation, Nx, Ny, Nz and film thickness (d) (nm) are obtained, and the average value of (ΔNxz × d) and (ΔNyz × d) is calculated to obtain thickness direction retardation ( Rth) was obtained.

(Preparation Example 1 - Polyester A)

When the temperature of the esterification reaction tube was raised and reached 200° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added, and 0.017 part by mass of antimony trioxide and magnesium acetate tetrahydrate were added as a catalyst while stirring. 0.064 mass part and 0.16 mass part of triethylamine were put. Then, after pressurizing and heating up and performing pressurized esterification under conditions of a gauge pressure of 0.34 MPa and 240°C, the esterification reaction tube was returned to normal pressure and 0.014 parts by mass of phosphoric acid was added. Furthermore, it heated up at 260 degreeC over 15 minutes, and added 0.012 mass part of trimethyl phosphate. Then, after 15 minutes, dispersion treatment was performed with a high-pressure dispersing machine, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction tube, and polycondensation reaction was performed under reduced pressure at 280°C.

After completion of the polycondensation reaction, filtering is performed with a Naslon filter having a 95% cut diameter of 5 μm, extruded in strand form from a nozzle, and cooled using cooling water previously subjected to filtering (pore diameter: 1 μm or less) , solidified and cut into pellets. The obtained polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl/g, and was substantially free of inert particles and internally precipitated particles. (Hereafter abbreviated as PET (A).)

(Preparation Example 2 - Polyester B)

Dried UV absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one) 10 parts by mass, particle-free PET (A) (intrinsic viscosity 0.62 dl/g) was mixed with 90 parts by mass, and a polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained using a kneading extruder (hereinafter abbreviated as PET (B)).

(Preparation Example 3-Preparation of Adhesion Modifying Coating Solution)

A transesterification reaction and a polycondensation reaction were performed by the usual method, and 46 mol% of terephthalic acid, 46 mol% of isophthalic acid, and 8 mol% of sodium 5-sulfonatoisophthalate were used as dicarboxylic acid components (with respect to the entire dicarboxylic acid component). A co-polyester resin containing a water-dispersible sulfonic acid metal base having a composition of 50 mol% of ethylene glycol and 50 mol% of neopentyl glycol as the glycol component (relative to the total glycol component) was prepared. Next, after mixing 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 part by mass of a nonionic surfactant, heat stirring and reach 77°C, the above water-dispersible sulfonic acid metal After adding 5 parts by mass of a base-containing co-polyester resin and continuing stirring until resin lumps disappear, the aqueous resin dispersion is cooled to room temperature to obtain a uniform water-dispersible co-polyester resin solution having a solid content concentration of 5.0 mass%. got it Further, after dispersing 3 parts by mass of aggregated silica particles (Sylysia 310 manufactured by Fuji Silysia Co., Ltd.) in 50 parts by mass of water, 0.54 parts by mass of the aqueous dispersion of Silysia 310 in 99.46 parts by mass of the water-dispersible co-polyester resin solution. Part by mass was added, and 20 parts by mass of water was added while stirring to obtain an adhesion modifying coating liquid.

(Example 1)

<Manufacture of polyester film 1 for polarizer protection>

As a raw material for the base film intermediate layer, 90 parts by mass of particle-free PET (A) resin pellets and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber were dried at 135° C. for 6 hours under reduced pressure (1 Torr). Then, it was supplied to the extruder 2 (for the middle layer II layer), and PET (A) was dried by a conventional method, supplied to the extruder 1 (for the outer I layer and the outer layer III layer), respectively, and melted at 285 ° C. These two types of polymers are each filtered with a filter medium of a stainless steel sintered body (nominal filtration accuracy of 10 μm particles, 95% cut), laminated in a two-type three-layer merged block, and extruded into a sheet form from a die After that, it was wound around a casting drum with a surface temperature of 30°C using an electrostatic application casting method and cooled and solidified to make an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thicknesses of the I layer, II layer, and III layer was 10:80:10.

Subsequently, the adhesion modifying coating liquid was applied to both sides of the unstretched PET film by a 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 holding the ends of the film with clips, it was guided to a hot air zone at a temperature of 105°C and stretched 4.0 times in TD. Next, a heat treatment was performed at a temperature of 180° C. for 30 seconds, then the film was guided to a cooling zone at 120° C., the film was stretched 2.5% in the width direction (fine stretching), and then the film cooled to 60° C. A clip holding both ends is opened and pulled out with a tension of 350 N/m to obtain a jumbo roll made of a uniaxially oriented PET film with a film thickness of about 80 µm. The obtained jumbo roll is divided into three parts, Slit rolls (L (left), C (center), R (right)) were obtained. A polyester film 1 for polarizer protection was obtained from the slit roll located at R. The room temperature of the film during running at the end of the 2.5% stretching in the width direction was measured with a non-contact radiation thermometer, and was about 125°C.

<production of liquid crystal panel>

The polyester film 1 for polarizer protection was affixed on one side of the polarizer made of PVA, iodine, and boric acid so that the transmission axis of the polarizer and the TD of the polyester film 1 for polarizer protection might be parallel. Further, a TAC film (manufactured by Fujifilm Co., Ltd., thickness: 80 μm) was affixed on the surface opposite to the polarizer to prepare a light source side polarizing plate.

A liquid crystal panel was taken out of 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. Remove the light source-side polarizing plate from the liquid crystal panel, and instead of the light source-side polarizing plate prepared above, PSA so that the transmission axis of the polarizer coincides with the transmission axis direction (parallel to the horizontal direction) of the light source-side polarizing plate before removal. It bonded together to the liquid crystal cell through (pressure sensitive adhesive), and produced the liquid crystal panel.

Moreover, the light source side polarizing plate was bonded together to the liquid crystal cell so that the polyester film 1 for polarizer protection might become a distal side (opposite side) to a liquid crystal cell. Moreover, the visual side polarizing plate was laminated|stacked with the TAC film on both surfaces of a polarizer, and was bonded to the liquid crystal cell so that the direction of the absorption axis of a polarizer might become parallel to the horizontal direction.

(Example 2)

<Manufacture of polyester film 2 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180°C for 30 seconds, it is guided to a cooling zone at 120°C and polarizer protection except that the film is stretched by 3.0% in the width direction. It carried out similarly to the polyester film 1, and obtained the polyester film 2 for polarizer protection.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 2 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Example 3)

<Manufacture of polyester film 3 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180°C for 30 seconds, guide to a cooling zone at 120°C, and polarizer protection except that the film was stretched by 3.5% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 3.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 3 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Example 4)

<Manufacture of polyester film 4 for polarizer protection>

In the film formation of the polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180°C for 30 seconds, it is guided to a cooling zone at 120°C and the film is for polarizer protection except that the film is stretched 4.0% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 4.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 4 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Example 5)

<Manufacture of polyester film 5 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180° C. for 30 seconds, it is guided to a cooling zone at 120° C., and polarizer protection except that the film is stretched by 4.5% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 5.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 5 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Comparative Example 1)

<Manufacture of polyester film 6 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180°C for 30 seconds, it is guided to a cooling zone at 120°C and polarizer protection except that the film is stretched by 5.0% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 6.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 6 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Comparative Example 2)

<Manufacture of polyester film 7 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180°C for 30 seconds, guide to a cooling zone at 100°C, and polarizer protection except that the film was stretched 1.0% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 7. The film room temperature during running at the end of 1.0% stretching in the width direction was measured with a non-contact radiation thermometer, and was about 115°C.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 7 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Comparative Example 3)

<Manufacture of polyester film 8 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180° C. for 30 seconds, guide to a cooling zone at 100° C., and polarizer protection except that the film was stretched by 1.5% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 8.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 8 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Comparative Example 4)

<Manufacture of polyester film 9 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180° C. for 30 seconds, it is guided to a cooling zone at 100° C., and polarizer protection except that the film is stretched 2.0% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 9.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 9 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Comparative Example 5)

<Manufacture of polyester film 10 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180°C for 30 seconds, it is guided to a cooling zone at 100°C and polarizer protection except that the film is stretched by 2.5% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 10.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 10 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

(Comparative Example 6)

<Manufacture of polyester film 11 for polarizer protection>

In film formation of polyester film 1 for polarizer protection of Example 1, after performing heat treatment at a temperature of 180°C for 30 seconds, it is guided to a cooling zone at 100°C and polarizer protection except that the film was stretched by 3.5% in the width direction. It carried out similarly to the polyester film 1, and obtained the polarizer protective film 11.

<production of liquid crystal panel>

In Example 1, except having replaced the polyester film 1 for polarizer protection with the polyester film 11 for polarizer protection, it carried out similarly to Example 1, and produced the liquid crystal panel.

[Table 1]

From the results shown in Table 1, it was recognized that the polarizing plate using the polyester film for polarizer protection of this invention can suppress the curvature of a liquid crystal panel compared with the polarizing plate of a comparative example.

In Examples 1-5, the liquid crystal panel was produced similarly except having not used the TAC film as the liquid crystal cell side protective film of the light source side polarizing plate. The liquid crystal panel of each Example obtained a favorable result (○) in any of the evaluations of the above-mentioned "curvature of liquid crystal panel" and "curvature of liquid crystal panel after long-time, high-temperature arrangement".

ADVANTAGE OF THE INVENTION According to this invention, the polyester film for polarizer protection which can suppress the curvature of a liquid crystal panel, a polarizing plate, and a liquid crystal display device can be provided.

Claims (9)

A polyester film for polarizer protection that satisfies the following requirements (1) and (2):
(1) TD shrinkage stress (F) of the polyester film is 8 MPa or more and 25 MPa or less,
(2) The ratio (F/HS) of the TD shrinkage stress (F) of the polyester film and the TD heat shrinkage (HS) of the polyester film treated at 80°C for 30 minutes is 30 (MPa/%) ) or more and 60 (MPa/%) or less. According to claim 1,
A polyester film for polarizer protection that further satisfies the following requirements (3):
(3) In-plane retardation of the said polyester film is 3000-30000 nm. According to claim 1 or 2,
A polyester film for polarizer protection that further satisfies the following requirements (4):
(4) The thickness of the polyester film is 40 to 200 μm. According to any one of claims 1 to 3,
The polyester film for polarizer protection which has a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, or an antireflection antiglare layer on the surface of the said polyester film opposite to the surface on which the polarizer is laminated|stacked. A polarizing plate in which the polyester film for polarizer protection according to any one of claims 1 to 4 was laminated on one side of the polarizer. A polarizing plate in which the polyester film for polarizer protection according to any one of claims 1 to 4 is laminated on one surface of the polarizer, and the film is not laminated on the other surface of the polarizer. A polarizing plate in which the polyester film for polarizer protection according to any one of claims 1 to 4 is laminated on one surface of the polarizer, and an application layer is laminated on the other surface of the polarizer. According to claim 7,
The polarizing plate in which the said application layer is a hard coat layer or a retardation film. A liquid crystal display device comprising the polarizing plate according to any one of claims 5 to 8.