TWI536055B - Polarizing plates and optical display apparatuses including the polarizing plates - Google Patents

Description

Polarizing plate and optical display device including the same Technical field

The present application relates to a polarizing plate and an optical display device including the same.

Background technique

The polarizing plate typically includes a polarizer having a polarizing function and an optical film attached to one or both sides of the polarizer to protect the polarizer. According to the type of the optical display device to which the polarizing plate is mounted, a retardation compensation film, a bonding layer, an adhesive layer, a surface treatment layer, and the like may be additionally stacked on the optical film of the polarizing plate. In addition to providing polarizer protection, optical films can be used to provide delay and optical axis correction.

As an optical film for a polarizing plate, a triethylenesulfonyl cellulose (TAC) film has been used. Since the TAC film has a high glass transition temperature (Tg) and is manufactured by casting, the film exhibits a stable length shrinkage in the mechanical direction (MD) or the transverse direction (TD). Further, the production of the TAC film does not require a stretching process and thus does not exhibit heat shrinkage.

In recent years, polyparaphenylene has been used by variations in optical films for polarizers. A film of ethylene dicarboxylate (PET). A replacement film such as PET is a stretched film and has a relatively high MD or TD extension. Therefore, the PET film can exhibit a heat shrinkage and expansion reaction. Further, the PET film has a lower glass transition temperature than the TAC film, and thus can exhibit heat shrinkage, which in turn causes distortion of the optical axis of the polarizer in the manufacture of the polarizing plate, thereby reducing the degree of polarization.

For this reason, techniques for controlling MD or TD shrinkage of PET films have been developed. Although the basic physical properties or bending properties of the film can be controlled by controlling MD or TD shrinkage, such control is represented only by shrinkage in the longitudinal/lateral direction, and cannot be prevented from occurring in the manufacture of the polarizing plate or the driving of the polarizing plate. The optical axis is distorted.

Summary of invention

According to some embodiments of the present invention, a polarizing plate includes a polarizer; and at least one optical film on at least one side of the polarizer, wherein the optical film comprises a polyester film, as described with respect to a reference direction The longitudinal direction (MD) or the transverse direction (TD) of the polyester film having a length contraction in the first diagonal direction and a length contraction in the second diagonal direction of about -0.1% to about +0.1% The difference between the shrinkage.

The length contraction in the first diagonal direction can be expressed by Equation 1: [Equation 1] The length contraction (%) of the first diagonal direction = (AB) / A × 100, in Equation 1, A is The polyester film sample corresponds to an initial length in the first diagonal direction with respect to the reference direction, and B is the sample after being placed at 85 ± 5 ° C for 30 minutes, the polyester film sample is corresponding In the first The length of the diagonal direction.

The length contraction of the second diagonal direction can be expressed by Equation 2: [Equation 2] The length contraction (%) of the second diagonal direction is (CD) / C × 100, and in Equation 2, C is The polyester film sample corresponds to an initial length in a second diagonal direction with respect to the reference direction, and D is the sample after being placed at 85 ± 5 ° C for 30 minutes, the polyester film sample is corresponding The length in the second diagonal direction.

Here, the angle between the first diagonal direction and the second diagonal direction is not 0°.

An angle between the first diagonal direction and the reference direction may be about 30° to about 60°, and an angle between the second diagonal direction and the reference direction may be about 120° Up to about 150°.

The angle between the first diagonal direction and the second diagonal direction may be from about 60° to about 120°.

Both the first diagonal direction and the second diagonal direction may have a length contraction of from about -0.15% to about +0.15%.

The optical film may be at least one selected from the group consisting of polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, and polybutylene naphthalate resin. A film formed of a resin.

The polarizing plate may further include an optical film having a longitudinal direction (MD) or a lateral direction (TD) of the optical film as a reference direction, the optical film having a first pair of about -0.05% to about +0.05% The difference in shrinkage between the length contraction in the angular direction and the length contraction in the second diagonal direction.

According to another embodiment of the present invention, an optical display device includes the polarizing plate.

10‧‧‧ polarizer

20‧‧‧First optical film

30‧‧‧Second optical film

50‧‧‧ represents film/PET film

50A‧‧‧film samples

100,200,210,240,300‧‧‧polar plates

270‧‧‧ LCD panel

400‧‧‧LCD display

A, B, C‧‧‧ length

The features and advantages and other features and advantages of the embodiments of the present invention will become more <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; 2 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention; FIG. 3 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention; and FIG. 4 is an embodiment of the present invention. A cross-sectional view of an optical display device; Fig. 5 is a conceptual view showing measurement of length shrinkage in a polyester film according to an embodiment of the present invention; and Fig. 6 shows a portion of a polyester film measuring length shrinkage.

detailed description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the present invention may be embodied in various forms and is not limited to the embodiments described below. In the drawings, elements that are not related to the description of the present invention are omitted for clarity. Throughout the specification, similar elements are denoted by like reference numerals. As used herein, terms such as "upper side" and "lower side" are used with reference to the drawings. Limited. Therefore, it is understood that the term "upper side" can be used interchangeably with the term "lower side".

As used herein, the length contraction in the first diagonal direction of the polyester film and the length contraction in the second diagonal direction with respect to the longitudinal direction (MD) or the transverse direction (TD) of the polyester film as the reference direction The difference in shrinkage between can be measured as follows.

Referring to Fig. 5, the x-axis direction indicates the lateral direction (TD) of the film 50, and the y-axis direction indicates the longitudinal direction (MD) of the film 50, and the x-axis direction and the y-axis direction are orthogonal to each other. Film sample 50A (for example, a quadrangular shape such as a square or the like) is taken from PET film 50. In film sample 50A, the first diagonal direction has an angle a with respect to TD and has a length A. After leaving the film sample 50A at 85 ± 5 ° C for 30 minutes, the film sample was measured to correspond to the length B of the first diagonal direction. Then, the length contraction of the first diagonal direction is calculated by Equation 1.

The length contraction (%) of the first diagonal direction of Equation 1 = (AB) / A × 100, in Equation 1, A is the initial length of the polyester film sample corresponding to the first diagonal direction with respect to the reference direction And B is the length of the polyester film sample corresponding to the first diagonal direction after the film sample was left at 85 ± 5 ° C for 30 minutes.

Further, the second diagonal direction of the film sample 50A has an angle β with respect to TD and has a length C. After the film sample 50A was placed at 85 ± 5 ° C for 30 minutes, the length D of the film sample 50A corresponding to the second diagonal direction was measured. Then, the length contraction of the film sample in the second diagonal direction is calculated according to Equation 2: the length contraction (%) of the second diagonal direction of Equation 2 = (CD) / C × 100, and in Equation 2, C is a poly The ester film sample corresponds to the reference direction The initial length of the second diagonal direction, and D is the length of the polyester film sample corresponding to the second diagonal direction after the film sample was left at 85 ± 5 ° C for 30 minutes.

Here, the angle between the first diagonal direction and the second diagonal direction is not 0°. Although the above description has been made with reference to the lateral direction, it should be understood that the above description is also applicable to the longitudinal direction.

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to FIG. 1 is a cross-sectional view of a polarizing plate in accordance with an embodiment of the present invention.

Referring to FIG. 1, a polarizing plate 100 according to an embodiment includes a polarizer 10, a first optical film 20 formed on a first side (such as the side) of the polarizer 10, and a second side stacked on the polarizer 10 (the following side) a second optical film 30, wherein the first optical film 20 can be a polyester film having a shrinkage difference of from about -0.1% to about +0.1%, for example, about -0.1, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0, +0.01, +0.02, +0.03, +0.04, +0.05, +0.06, +0.07, +0.08, +0.09 or 0.1%. When the shrinkage difference of the polyester film is less than -0.1% or more than 0.1%, the polyester film is shrunk due to heat generated in the manufacture or operation of the polarizing plate, so that the optical axis of the polarizer on the polyester film is distorted. Thereby reducing the degree of polarization of the polarizing plate.

Referring to Figure 5, the angle a can be from about 30 to about 60, such as about 45, relative to TD, and the angle β can be from about 120 to about 150, such as about 135, relative to TD. The angle of the first diagonal direction and the second diagonal direction may be from about 60° to about 120°.

The length of the first diagonal direction and the second diagonal direction The shrinkage may be from about -0.15% to about +0.15%, such as about -0.15, -0.14, -0.13, -0.12, -0.11, -0.1, -0.1, -0.09, -0.08, -0.07, -0.06, - 0.05, -0.04, -0.03, -0.02, -0.01, 0, +0.01, +0.02, +0.03, +0.04, +0.05, +0.06, +0.07, +0.08, +0.09, +0.1, +0.11, + 0.12, +0.13, +0.14 or +0.15%. Within this range, although there is distortion of the optical axis of the polarizer, the degree of polarization of the polarizing plate may not be lowered. .

Length shrinkage can be measured using film samples obtained at some locations on the film. When the film is a stretched film, the force is mainly concentrated on the central portion of the film with respect to the transverse direction such that the film is stretched laterally mainly at the central portion, and the stretch is oriented toward the two of the film with respect to the lateral direction. The end gradually decreases. This affects the direction of heat shrinkage when the polarizing plate shrinks due to heat generated during the manufacture or operation of the polarizing plate. Therefore, it is preferred to measure the length contraction at the end portion of the film with respect to the transverse direction of the film. Here, the end portion may refer to a portion within 0 to 2.5% of one end of the film in the lateral direction.

Specifically, referring to FIG. 6, the x-axis direction represents the lateral direction (TD) of the film 50, and the y-axis direction represents the longitudinal direction (MD) of the film 50, and the x-axis direction and the y-axis direction are orthogonal to each other. The film may be divided into d1, d2, and d3 with respect to TD, where d1 and d3 each correspond to a portion within 0 to 2.5% from one end of the film. The length contraction can be measured using a sample taken from the portion d1 or d3. More particularly, the length shrinkage can be measured for a sample taken from a portion of the film that is greater than 0 and no more than 2.5%, such as between about 0.001% and 2.5%, relative to the TD distance film.

The polyester film may be a film stretched at a high elongation, and may have an ultra-high phase difference to prevent image quality deterioration by suppressing generation of rainbow spots when used in a polarizing plate of an optical display. In one embodiment, At a wavelength of 550 nm, the polyester film may have a thickness of from about 25 μm to about 500 μm, specifically from about 25 μm to about 115 μm, and a plane of from about 5,000 nm to about 15,000 nm, specifically from about 10,100 nm to about 12,000 nm. Phase difference (Ro). Within this range, when used as a protective film for a polarizer, the polyester film can prevent generation of rainbow spots, side light leakage, and an increase in phase difference due to a change in phase difference depending on an incident angle of light. .

The polyester film may be a polyester film in which nx is a refractive index in the x-axis direction of the polyester film at a wavelength of 550 nm and ny is an x-axis direction of the polyester film at a wavelength of 550 nm When the refractive index is one, one of nx and ny is about 1.65 or more. If both nx and ny are less than 1.65, or both nx and ny are 1.65 or more, when the polyester film may be a protective film of a polarizer, it may cause rainbow spots due to birefringence. In one embodiment, nx may be about 1.65 or more, specifically about 1.67 to about 1.75, such as about 1.67, 1.68, 1.69, 1.70, 1.71, 1.72, 1.73, 1.74, or 1.75, and ny may be from 1.45 to about 1.55. For example, about 1.45, 1.46, 1.47, 1.48, 1.49, 1.50, 1.51, 1.52, 1.53, 1.54, or 1.55. In another embodiment, ny can be about 1.65 or greater, specifically from about 1.67 to about 1.72, such as about 1.67, 1.68, 1.69, 1.70, 1.71, or 1.72, more specifically from about 1.69 to about 1.72, nx can be From about 1.45 to about 1.55, for example about 1.45, 1.46, 1.47, 1.48, 1.49, 1.50, 1.51, 1.52, 1.53, 1.54 or 1.55. The absolute value of nx-ny (|nx-ny|) may be from about 0.1 to about 0.2, such as about 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or 0.2, in particular about 0.12. To about 0.18. Within this range, the polyester film can improve the viewing angle and suppress rainbow spots.

At a wavelength of 550 nm, the polyester film can have biaxiality (NZ) The degree is about 1.8 or less, such as from about 1.0 to about 1.8, as represented by Equation 3. Within this range, the polyester film can suppress rainbow spots due to birefringence: Equation 3 NZ = (nx - nz) / (nx - ny), and in Equation 3, nx, ny, and nz are respectively at 550 nm The refractive index of the polyester film in the x-axis, y-axis, and z-axis directions at the wavelength.

At a wavelength of 550 nm, the polyester film may have an out-of-plane retardation (Rth) of about 15,000 nm or less, for example, about 10,000 nm to about 12,000 nm, as represented by Equation 4. Within this range, the polyester film can suppress rainbow spots due to birefringence.

Equation 4 Rth=((nx+ny)/2-nz)×d, in Equation 4, nx, ny, and nz are the x-axis, y-axis, and z-axis of the polyester film at a wavelength of 550 nm, respectively. The refractive index, d is the thickness of the polyester film (unit: nm).

The polyester film may be a film which is stretched in the transverse direction but not stretched in the longitudinal direction, and may be stretched in the transverse direction to about 2 times to about 10 times its original length and stretched in the machine direction to about 1 of its original length. A film of about 1.1 times the length. Here, "about 1 to about 1.1 times the length in the longitudinal direction to the original length thereof" means that no stretching is performed except for stretching by a mechanical method (in the longitudinal direction), and the stretching ratio is 1 to the film of the film. Non-stretched state. Within this range, the polyester film can become an ultra high retardation film, and image quality is improved by preventing the generation of rainbow spots. In one embodiment, the polyester film can be pulled only in the transverse direction The absolute molecular orientation angle (θr) extending to the polyester molecule is about 5° or less with respect to the transverse direction of the polyester film, for example, from about 0° to about 5°. Within this range, the polyester film can be used as an ultra high retardation film to improve image quality by preventing generation of rainbow spots. The polyester film can be stretched at a high magnification in the transverse direction and can exhibit a molecular orientation angle which is uneven with respect to the lateral direction. The molecular orientation angle can be measured using any typical apparatus in the art, such as KOBRA-21ADH2 (Oji Co., Ltd.) and AXOSCAN (Axometrics Co., Ltd).

As the polyester film, any transparent film of a polyester resin can be used without being limited thereto. In one embodiment, the polyester film may be selected from the group consisting of polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, and polybutylene naphthalate resin. At least one resin is formed.

The polyester film may have a thickness of from about 25 μm to about 500 μm. Within this range, the polyester film can be used as a protective film for a polarizing plate.

The polyester film can be prepared by a method comprising stretching the melt-extruded polyester resin to a length of from about 2 to about 10 times its original length only in the transverse direction. The polyester film does not cause rainbow spots within the range of the draw ratio. In particular, the polyester film may have a draw ratio of about 3 to about 8 times its original length.

The stretching may be by a glass transition temperature Tg (Tg-20) ° C to (Tg + 50) ° C with respect to the polyester resin, particularly from about 70 ° C to about 150 ° C, more specifically from about 80 ° C to about It is carried out at 130 ° C, more specifically at least one of dry stretching and wet stretching at a stretching temperature of from about 90 ° C to about 120 ° C. In the pull Within the range of the stretching temperature, it is possible to obtain uniform stretching of the polyester film.

After stretching the polyester film, the method may further comprise reducing the transverse stretch of the polyester film while heating the tension-relaxation of the stretched polyester film at a predetermined temperature range. By the tension-relaxation, the polyester film can be stretched in the transverse direction while the crystallization and stabilization of the polyester film are achieved by heat treatment, thereby achieving the shrinkage difference according to the present invention. In particular, in the tension-relaxation, the polyester film may be heated in an oven above the glass transition temperature of the polyester resin, for example, at about 100 ° C to about 300 ° C for about 1 second to about 2 hours. Here, the polyester film may be transversely stretched to a length of from about 0 to about 3 times, particularly from about 0.1 to about 2 times, more specifically from about 0.1 to about 1 time.

The polarizer 10 aligns the direction of light transmitted through the optical film and decomposes the incident beam into two polarized components that are orthogonal to each other such that only one component is allowed to pass therethrough and the other component is absorbed or diffused. In the present invention, any polarizer generally used for manufacturing a polarizing plate can be used without being limited thereto. The polarizer can be produced by dyeing a polyvinyl alcohol film with iodine or a dichroic dye, followed by stretching the dyed polyvinyl alcohol film in a certain direction. In particular, the polarizer can be fabricated by expansion, dyeing, stretching, and crosslinking. Various methods are generally known to those skilled in the art.

The polarizer 10 may have a thickness of, for example, about 20 μm to about 100 μm, without being limited thereto. Within this thickness range, a polarizer can be used in the polarizing plate.

The second optical film 30 can be a typical transparent optical film. For example, the second optical film may be formed of at least one of a cellulose film such as a triethylenesulfonated cellulose film or the like, a polycarbonate film, an acrylic film, and an olefin film such as a cycloolefin film, and a polyester film. .

The second optical film 30 may have a length contraction of a first diagonal direction of from about -0.1% to about 0.1% and a length contraction of a second diagonal direction of from about -0.1% to about 0.1%. The second optical film may have a shrinkage difference between a length contraction in the first diagonal direction and a length contraction in the second diagonal direction of from about -0.05% to about 0.05%. Within this range, the polarizing plate does not undergo bending and twisting of the optical axis when the polarizing plate is operated. The difference in length shrinkage and shrinkage of the second optical film can be measured in the same manner as the first optical film.

The second optical film 30 may have a thickness of about 25 μm to about 500 μm. Within this thickness range, the second optical film 30 can be used as a protective film for a polarizing plate.

Although not shown in FIG. 1, the first optical film and the second optical film may be surface treated to impart additional functions. The surface treatment provides functionality to the optical film and includes, for example, anti-reflective treatment, anti-glare treatment, anti-glare/low reflection treatment, hard coat treatment, and the like. In addition, although not shown in FIG. 1, the polarizing plate according to an embodiment of the present invention may include a retardation compensation film, a retardation film, a bonding layer, and an adhesive layer, depending on the application.

The polarizing plate can be fabricated by stacking a first optical film on a first side of the polarizer and a second optical film on a second side of the polarizer. The method for stacking the optical film on the polarizer is not particularly limited, and any typical adhesive such as at least one of a water-based adhesive and a pressure-sensitive adhesive may be used.

Next, a polarizing plate according to another embodiment will be described with reference to FIG. 2 is a cross-sectional view of a polarizing plate in accordance with another embodiment of the present invention.

Referring to FIG. 2, the polarizing plate 200 according to this embodiment includes a polarizer 10. A first optical film 20 formed on a first side (upper side) of the polarizer 10, and a first optical film 20 formed on a second side (eg, a lower side) of the polarizer 10, wherein the first optical film 20 may be a polyester film having a shrinkage difference of from about -0.1% to about +0.1%. The polarizing plate 200 according to this embodiment is substantially the same as the polarizing plate of the above embodiment except that the first optical film formed on the second side of the polarizer has a shrinkage difference of about -0.1% to about +0.1%.

Next, a polarizing plate according to another embodiment of the present invention will be described with reference to 3. 3 is a cross-sectional view of a polarizing plate in accordance with another embodiment of the present invention.

Referring to FIG. 3, a polarizing plate 300 according to another embodiment includes a polarizer 10 and a first optical film 20 formed on a first side (upper side) of the polarizer 10, wherein the first optical film 20 may have about -0.1 % to about +0.1% shrinkage of the polyester film. When the shrinkage difference of the polyester film is less than -0.1% or more than 0.1%, the polyester film may shrink due to heat generated in the manufacture or operation of the polarizing plate, so that the optical axis of the polarizer on the polyester film is distorted, Thereby the degree of polarization of the polarizing plate is lowered.

Although not shown in FIG. 3, the polarizing plate 300 may further include a protective layer on the second side (eg, the lower side) of the polarizer 10.

According to the present invention, an optical display device may include a polarizing plate according to an embodiment of the present invention. The optical display device may include an organic light emitting diode display or a liquid crystal display, without being limited thereto.

4 illustrates a cross-sectional view of a liquid crystal display in accordance with an embodiment of the present invention. Referring to FIG. 4, the liquid crystal display 400 may include a liquid crystal panel 270 and a first one formed on an upper side and a lower side of the liquid crystal panel 270, respectively. And the second polarizing plates 210, 240, wherein at least one of the first and second polarizing plates 210, 240 may include a polarizing plate according to an embodiment of the present invention.

Next, the present invention will be explained in more detail with reference to the following examples. However, the examples are provided for illustrative purposes only and are not to be construed as limiting the invention.

The details of the components used in the examples and comparative examples are as follows:

(A) Polarizer: polyvinyl alcohol film (VF-PS6000, Kuraray Co., Ltd., thickness: 60 μm)

(B) Protective film: using the first diagonal direction listed in Table 1 (relative to the 45° diagonal direction of TD) and the second diagonal direction (relative to the 135° diagonal of TD) The direction of the length of the shrinkage polyethylene terephthalate (PET) film and the triethylenesulfonated cellulose (TAC) film.

The melt extruded film was stretched to 6.1 times its original length and stretched in the MD direction only by melt extrusion of the polyethylene terephthalate resin, and then listed in Table 1. The tension-relaxation treatment was carried out under the conditions to prepare an optical film 1. Optical films 2 to 5 were prepared in the same manner except that the tension-relaxation conditions listed in Table 1 were used. The optical film 6 is a triethylenesulfonated cellulose film KC4DR-1 (thickness: 40 μm, Konica Co., Ltd.), which has a length contraction in the first diagonal direction and a length contraction in the second diagonal direction of 0.1%, respectively. .

It is measured by Equations 1 and 2 on a sample taken from the end of the film having a thickness of 100 μm (the portion within 2.6 mm from the end of the film with respect to the film) and being square (100 mm x 100 mm, length x width) The length shrinks, each side of the sample has a length of 100 mm, and thus Calculate the difference in shrinkage between length shrinkages. Nx, ny, and Ro at a wavelength of 550 nm were measured using Axoscan (Axometrixs).

Examples 1 to 4 and Comparative Example 1

A polarizer is prepared by dyeing, stretching, or the like. Specifically, the polyvinyl alcohol film was stretched twice at 150 ° C, then subjected to iodine absorption, and then stretched 2.5 times in an aqueous solution of boric acid at 40 ° C to prepare a polarizer. An optical film having the combination shown in Table 2 was stacked on the upper and lower sides of the polarizer using an acrylic adhesive to prepare a polarizing plate.

The r-axis scattering of the polarizing plate representing the distortion of the optical axis is measured. The AxoScan (Traverse System) polarizer-based fast optical axis is used to calculate the R-axis scattering by measuring the distortion value of the pol axis. The polarization of each polarizing plate was measured using V-7100 (Japan JASCO Co., Ltd.).

As shown in Table 2, the polarizing plate according to the present invention prevents the difference in length shrinkage of the polyethylene terephthalate film used as the optical film to -0.1% to 0.1%, and even when the polarization The plate also has an r-axis scattering of about 0.5 when attached to the polarizer, thereby preventing distortion of the optical axis. Accordingly, the present invention provides a polarizing plate including a polyester film as a protective film and capable of preventing distortion of an optical axis at the time of manufacture or processing of a polarizing plate. Further, the present invention provides a polarizing plate comprising a polyester film as a protective film and having a high degree of polarization.

In contrast, the polarizing plate of Comparative Example 1 in which the PET film had a difference in length shrinkage deviation in the range of -0.1% to 0.1% exhibited a low degree of polarization, and thus the effects of the present invention could not be obtained.

Although a few embodiments have been disclosed herein, it is understood that these embodiments are provided by way of illustration only, and various modifications, changes and changes may be made without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be limited only by the scope of the appended claims and their equivalents.

10‧‧‧ polarizer

20‧‧‧First optical film

30‧‧‧Second optical film

100‧‧‧Polar plate

Claims (7)

A polarizing plate comprising: a polarizer; at least one optical film on at least one side of the polarizer; and wherein the optical film comprises a polyester film, the polyester film being oriented in a longitudinal or transverse direction relative to the polyester film Between -0.1% to +0.1% of the difference in shrinkage between the length contraction in the first diagonal direction of the film and the length contraction in the second diagonal direction, the length contraction in the first diagonal direction It is expressed by Equation 1: [Equation 1] The length contraction (%) of the first diagonal direction = (AB) / A × 100, and in Equation 1, A is a polyester film sample corresponding to the reference direction The initial length of the first diagonal direction, and B is the length of the polyester film sample corresponding to the first diagonal direction after the sample is placed at 85 ± 5 ° C for 30 minutes, the second diagonal The length contraction of the direction is expressed by Equation 2: [Equation 2] The length contraction (%) of the second diagonal direction = (CD) / C × 100, and in Equation 2, C is the corresponding sample of the polyester film The initial length in the second diagonal direction relative to the reference direction, and D is the sample after being placed at 85 ± 5 ° C for 30 minutes, The polyester film sample is in a length corresponding to the second diagonal direction, and The angle between the first diagonal direction and the second diagonal direction is not 0°, and the polarizer is a polyvinyl alcohol film having an iodine or a dichroic dye, the polarizer allowing a polarization of light The component passes therethrough and the other component of the light is absorbed, an adhesive layer being between the polarizer and the optical film. The polarizing plate of claim 1, wherein an angle between the first diagonal direction and the reference direction is 30° to 60°, and an angle between the second diagonal direction and the reference direction is 120 ° to 150°. The polarizing plate of claim 1, wherein an angle between the first diagonal direction and the second diagonal direction is 60° to 120°. The polarizing plate of claim 1, wherein a length contraction of the first diagonal direction and the second diagonal direction is -0.15% to +0.15%, respectively. The polarizing plate of claim 1, wherein the optical film is selected from the group consisting of polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, and polynaphthalene dicarboxylic acid. A film formed of at least one resin in a butadiene resin. The polarizing plate of claim 1, wherein the polarizing plate further comprises an optical film having a length of -0.05% to +0.05% in the first pair with respect to a longitudinal MD or a lateral direction TD of the optical film as a reference direction The difference in shrinkage between the length contraction in the angular direction and the length contraction in the second diagonal direction. An optical display device comprising: the polarizing plate according to any one of claims 1 to 6.