Polarizing plate and optical display device

Abstract

Provided are a polarizing plate and an optical display device comprising same, the polarizing plate comprising: a polarizer; and an optical film stacked on a light-exit surface of the polarizer, wherein the optical film has a front in-plane retardation of 6000 to 9000 nm at a wavelength of 550 nm, and the difference in retardation value according to equation 1 is 1500 to 2500 nm. [Equation 1] Difference in retardation values =│A - B│ (In equation 1, A is inclined in-plane retardation measured in the ground axis direction of the optical film at a wavelength of 550 nm by irradiating the optical film with light at +45° or -45°, and B is front in-plane retardation measured at a wavelength of 550 nm of the optical film.)

Description

Polarizing plates and optical display devices

[0001] It relates to a polarizing plate and an optical display device.

[0002]

[0003] Liquid crystal displays (LCDs) are becoming increasingly thinner and larger in size. The number of outdoor displays and portable devices for viewing on the go is also increasing. These optical displays require higher thermal stability and moisture resistance.

[0004] From a durability perspective, polyethylene terephthalate (PET) film, with its low moisture permeability, is increasingly being used as the primary protective film for polarizing plates, replacing the previously dominant triacetyl cellulose (TAC) film. PET film boasts superior mechanical properties, chemical resistance, and moisture barrier properties, which can enhance the durability of polarizing plates.

[0005] Meanwhile, PET film has large birefringence in the in-plane and thickness directions. This large birefringence can cause distortion of the polarization state between the polarizer and the display device, resulting in rainbow spots. Conventional polarizing plates containing PET film have improved screen visibility by controlling the refractive index ratio of the PET film or controlling the front-end phase difference value at a wavelength of 550 nm to be close to 0 nm or to be adjusted to 6000 nm or higher to prevent rainbow spots. However, although this method can prevent rainbow spots from being visible when viewed from the front, it has had limitations in preventing rainbow spots from being visible from an oblique direction such as the side.

[0006] The background technology of the present invention is disclosed in Korean Patent No. 10-2120989, etc.

[0007]

[0008] According to one embodiment, a polarizing plate is provided that reduces the difference in color depending on the angle at which the screen is viewed when applied to an optical display device and prevents rainbow spots from being visible at an omnidirectional viewing angle including the front and side.

[0009]

[0010] According to one embodiment, a polarizing plate is provided.

[0011] 1. The above polarizing plate includes a polarizer and an optical film laminated on a light-emitting surface of the polarizer, wherein the optical film has a front-plane phase difference of 6000 to 9000 nm at a wavelength of 550 nm, and a difference in phase difference value according to the following equation 1 is 1500 to 2500 nm:

[0012] [Formula 1]

[0013] Difference in phase difference values ​​= |A - B|

[0014] (In the above equation 1,

[0015] A is the in-plane phase difference (unit: nm) measured in the direction of the ground axis of the optical film at a wavelength of 550 nm when light is irradiated to the optical film at +45° or -45° when the front of the optical film is 0°.

[0016] B is the in-plane phase difference (unit: nm) measured at a wavelength of 550 nm of the optical film.

[0017] In 2.1, the ground axis of the optical film may be 85 to 95° when the MD (machine direction) of the base layer of the optical film is 0°.

[0018] In 3.1-2, the true axis of the optical film may be -5 to 5° when the MD of the base layer of the optical film is 0°.

[0019] In 4.1-3, the optical film may have an average refractive index value of 1.57 to 1.70 calculated by the value of Equation 5 below:

[0020] [Formula 5]

[0021] Average refractive index = (nx + ny) / 2

[0022] (In the above equation 5, nx and ny are the refractive index in the direction of the short axis and the refractive index in the direction of the true axis of the optical film, respectively, at a wavelength of 550 nm).

[0023] In 5.1-4, when the optical film is irradiated with light at an irradiation angle from 0° to -90° and from 0° to +90° in the front, the irradiation angle of the light is the X-axis, and the in-plane phase difference measured in the direction of the ground axis of the optical film is the Y-axis, the in-plane phase difference value may be symmetrical with respect to 0° in the front.

[0024] In 6.1-5, when the optical film is irradiated with light at an irradiation angle from 0° to -90° and from 0° to +90° in the front, the irradiation angle of the light is the X-axis, and the in-plane phase difference measured in the direction of the optical film's true axis is the Y-axis, the in-plane phase difference value may be symmetrical with respect to 0° in the front.

[0025] In 7.1-6, the optical film may have a difference in phase difference value of 1500 to 2500 nm according to the following 2:

[0026] [Formula 2]

[0027] Difference in phase difference values ​​= |C - B|

[0028] (In the above equation 2,

[0029] C is the in-plane phase difference measured in the true axis direction of the optical film at a wavelength of 550 nm when the optical film is irradiated with light at +45° or -45°,

[0030] B is the in-plane phase difference measured at a wavelength of 550 nm of the optical film.

[0031] In 8.1-7, the value of the above formula 2 may be equal to or greater than the value of the above formula 1.

[0032] In 9.1-8, the optical film can satisfy at least one of the following equations 3 and 4:

[0033] [Formula 3]

[0034] 1.0 ≤ A / B ≤ 1.3

[0035] [Formula 4]

[0036] 0.7 ≤ C / B ≤ 1.0

[0037] (In the above equations 3 and 4,

[0038] B is the frontal in-plane phase difference measured at a wavelength of 550 nm of the optical film,

[0039] A is the in-plane phase difference measured in the direction of the ground axis of the optical film at a wavelength of 550 nm when light is irradiated on the optical film at +45° or -45°,

[0040] C is the in-plane phase difference measured in the direction of the optical film's true axis at a wavelength of 550 nm when the optical film is irradiated with light at +45° or -45°.

[0041] In 10.1-9, the optical film may be a MD and TD biaxially stretched film.

[0042] In 11.1-10, the optical film may include a polyester resin film as a base layer.

[0043] In 12.1-11, the optical film may include a polyethylene terephthalate film.

[0044] According to another embodiment, an optical display device is provided.

[0045] The above optical display device includes the above polarizing plate.

[0046]

[0047] According to one embodiment, a polarizing plate is provided that reduces the difference in color depending on the angle at which the screen is viewed when applied to an optical display device and prevents rainbow spots from being visible at an omnidirectional viewing angle including the front and side.

[0048]

[0049] Figure 1 shows the results when light is irradiated at an irradiation angle from 0° to -90° and from 0° to +90° on the optical film used in the examples and comparative examples, where the irradiation angle of light is the X-axis (unit: °), and the in-plane phase difference at a wavelength of 550 nm measured in the slow axis direction of the optical film is the Y-axis (unit: nm).

[0050] Figure 2 shows the results when the optical film used in the examples and comparative examples is irradiated with light at irradiation angles from 0° to -90° and from 0° to +90°, with the irradiation angle of light being the X-axis (unit: °) and the in-plane phase difference at a wavelength of 550 nm measured in the direction of the fast axis of the optical film being the Y-axis (unit: nm).

[0051] Figure 3 is a cross-sectional view of a polarizing plate according to one embodiment.

[0052]

[0053] The present invention is described in detail by way of examples so that those skilled in the art can easily practice it. The present invention may be implemented in various different forms and is not limited to the examples described herein.

[0054] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0055] In this specification, the “in-plane phase difference (Re)” can be expressed by the following formula A:

[0056] [Formula A]

[0057] Re = (nx - ny) xd

[0058] (In the above formula A, nx and ny are the refractive indices in the slow axis direction, the fast axis direction, and the thickness direction of the optical element, respectively, at a wavelength of 550 nm, and d is the thickness of the optical element (unit: nm).) The optical element may be an optical film or a substrate layer.

[0059] In this specification, “refractive index” may be a value measured in the visible light range, for example, at a wavelength of 550 nm.

[0060] As used herein, “(meth)acrylic” means acrylic and / or methacrylic.

[0061] In this specification, “based on solids” means the remaining components excluding the solvent.

[0062] When indicating a numerical range in this specification, “X to Y” means X or more and Y or less (X≤ and ≤Y).

[0063] According to one embodiment, a polarizing plate is provided that reduces the difference in color perception depending on the viewing angle when applied to an optical display device and prevents rainbow fringes from being visible at an omnidirectional viewing angle, including front and side viewing angles. The polarizing plate not only prevents rainbow fringes from being visible from the front, but also prevents rainbow fringes from being visible at side viewing angles, for example, +45° and -45°.

[0064] According to one embodiment, the polarizing plate includes a polarizer and an optical film laminated on a light-emitting surface of the polarizer, wherein the optical film has a front phase difference of 6000 to 9000 nm at a wavelength of 550 nm, and a difference in phase difference values ​​according to the following equation 1 is 1500 to 2500 nm:

[0065] [Formula 1]

[0066] Difference in phase difference values ​​= |A - B|

[0067] (In the above equation 1,

[0068] A is the in-plane phase difference (unit: nm) measured from the ground axis of the optical film at a wavelength of 550 nm when light is irradiated to the optical film at +45° or -45° when the front of the optical film is 0°.

[0069] B is the in-plane phase difference (unit: nm) measured at a wavelength of 550 nm of the optical film.

[0070] First, the slow axis and fast axis of the optical film are described.

[0071] The optical film includes a substrate layer. The ground axis of the optical film is substantially in the same direction as the ground axis of the substrate layer. The fast axis of the optical film is in the same direction as the fast axis of the substrate layer.

[0072] The ground axis and the fast axis of the above-mentioned substrate layer can be defined as the axis with the highest refractive index and the axis with the lowest refractive index among the directions in the plane of the substrate layer, respectively. The ground axis and the fast axis of the above-mentioned substrate layer can be measured by a conventional method known to those skilled in the art. For example, the ground axis and the fast axis of the above-mentioned substrate layer can be determined by the refractive index confirmed by a prism coupler (2010 / M Metricon Co.), but are not limited thereto.

[0073] In one specific example, the ground axis of the optical film may be 85 to 95°, for example, 90°, when the machine direction (MD) of the substrate layer in the optical film is 0°.

[0074] In one specific example, the true axis of the optical film may be -5 to 5°, for example, 0°, when the MD of the base layer in the optical film is 0°.

[0075] In one specific example, the angle between the ground axis and the true axis of the optical film may be 45 to 135°, for example 85 to 95°, for example 90°.

[0076] First, A in the above equation 1 will be explained. In the above equation 1, A means the oblique in-plane phase difference measured in the direction of the ground axis of the optical film when light is irradiated in an oblique direction of +45° or -45° when the front is set to 0° during the process of measuring the normal in-plane phase difference for the optical film. In the above equation 1, B means the normal in-plane phase difference, and means the front in-plane phase difference measured by irradiating light from the front.

[0077] The above formula 1 serves as a standard for determining whether an optical film having a frontal in-plane retardation of 6000 to 9000 nm at a wavelength of 550 nm does not cause rainbow stains not only from the front but also from the side, and whether the substrate layer alone can prevent rainbow stains from being visible from the side. When the difference in the retardation values ​​of the above formula 1 is 1500 to 2500 nm, a polarizing plate having an optical film having a frontal in-plane retardation of 6000 to 9000 nm at a wavelength of 550 nm can minimize the visibility of rainbow stains from the side, particularly at +45° or -45°.

[0078] For example, the difference in the phase difference values ​​of the above formula 1 may be 1500 to 2300 nm, 1500 to 2200 nm. For example, the difference in the phase difference values ​​of the above formula 1 may be 1800 to 2200 nm. In the above range, the visibility of rainbow spots from the side, especially at +45° or -45°, can be minimized with the substrate layer alone.

[0079] In the above formula 1, B can be 6000 to 9000 nm, for example, 7000 to 9000 nm, 7500 to 9000 nm. In the above formula 1, A can be adjusted according to the difference between the value of B in the above formula 1 and the phase difference value in the above formula 1. For example, in the above formula 1, A can be 9000 to 11500 nm or 3500 to 6000 nm.

[0080] According to one embodiment, the difference in the phase difference value of the above formula 1 serves as a criterion for determining whether an optical film having an average refractive index of 1.57 to 1.70 calculated by the value of formula 5 below can minimize the visibility of rainbow spots not only from the front but also from the side, especially at +45° or -45°:

[0081] [Formula 5]

[0082] Average refractive index = (nx + ny) / 2

[0083] (In the above equation 5,

[0084] nx and ny are the refractive indices in the direction of the short axis and the refractive indices in the direction of the true axis of the optical film, respectively, at a wavelength of 550 nm.

[0085] When the optical film has an average refractive index of 1.57 to 1.70, for example, 1.60 to 1.65, and the difference in the phase difference value of the above formula 1 is 1500 to 2500 nm, the visibility of rainbow spots can be minimized not only from the front but also from the side, especially at +45° or -45°.

[0086] According to one embodiment, the difference in the phase difference value of the above formula 1, when irradiating light at an irradiation angle from 0° to -90° in the front and from 0° to +90° in the front, when the irradiation angle is the x-axis and the in-plane phase difference measured in the direction of the ground axis of the optical film is the y-axis, can be used as a criterion for determining whether an optical film having a symmetrical in-plane phase difference value based on 0° in the front has minimized visibility of rainbow spots not only in the front but also in the side, particularly at +45° or -45°.

[0087] Referring to Fig. 1, when light is irradiated on an optical film at irradiation angles from 0° to -90° and from 0° to +90° in the front, the results are shown when the irradiation angle of the light is defined as the X-axis (unit: °), and the in-plane phase difference at a wavelength of 550 nm measured in the direction of the ground axis of the optical film is defined as the Y-axis (unit: nm). As shown in Fig. 1, the optical film may have an in-plane phase difference value that is symmetrical with respect to 0° in the front.

[0088] In addition, the difference in the phase difference value of the above formula 1, when irradiating light at an irradiation angle from 0° to -90° in the front and from 0° to +90° in the front, when the irradiation angle is the x-axis and the in-plane phase difference measured in the direction of the optical film's true axis is the y-axis, can be used as a standard for judging whether an optical film having a symmetrical in-plane phase difference value based on 0° in the front has minimized the visibility of rainbow spots not only in the front but also in the side, especially at +45° or -45°.

[0089] Referring to Fig. 2, when light is irradiated on an optical film at irradiation angles from 0° to -90° and from 0° to +90°, the irradiation angle of the light is represented as the X-axis (unit: °), and the in-plane phase difference at a wavelength of 550 nm measured in the true axis direction of the optical film is represented as the Y-axis (unit: nm). As shown in Fig. 1, the optical film may have an in-plane phase difference value that is symmetrical with respect to 0° in the front.

[0090] According to one embodiment, the optical film has a difference in phase difference values ​​of 1500 to 2500 nm according to Equation 2 below:

[0091] [Formula 2]

[0092] Difference in phase difference values ​​= |C - B|

[0093] (In the above equation 2,

[0094] C is the in-plane phase difference (unit: nm) measured in the direction of the optical film's true axis at a wavelength of 550 nm when light is irradiated to the optical film at +45° or -45° when the front of the optical film is set to 0°.

[0095] B is the front-plane phase difference (unit: nm) measured at a wavelength of 550 nm of the optical film.

[0096] Here, C in the above equation 2 is explained. In the above equation 2, C means the in-plane phase difference measured in the direction of the optical film's true axis when light is irradiated at +45° or -45° when the front is set to 0° during the process of measuring the normal in-plane phase difference for the optical film. In the above equation 2, B means the normal in-plane phase difference, and means the front in-plane phase difference measured by irradiating light from the front.

[0097] The above optical film is a standard for determining whether, when the value of the above formula 2 is 1500 to 2500 nm, the optical film having a front phase difference of 6000 to 9000 nm at a wavelength of 550 nm does not cause rainbow spots to be visible not only from the front but also from the side, and whether the base layer alone prevents rainbow spots from being visible from the side.

[0098] The value of the above formula 2 of 1500 to 2500 nm can be a standard for determining whether an optical film satisfying the above drawings 1 and 2 has a significant effect in minimizing the visibility of rainbow spots not only from the front but also from the side, especially at +45° or -45°.

[0099] For example, the difference in the phase difference values ​​of the above formula 2 may be 1500 to 2300 nm, 1500 to 2200 nm. For example, the difference in the phase difference values ​​of the above formula 2 may be 1800 to 2200 nm. In the above range, the visibility of rainbow spots from the side, especially at +45° or -45°, can be minimized with the substrate layer alone.

[0100] In the above formula 2, B can be 6000 to 9000 nm, for example, 7000 to 9000 nm, 7500 to 9000 nm. In the above formula 2, C can be adjusted according to the difference between the value of B in the above formula 2 and the phase difference value in the above formula 1. For example, in the above formula 3, C can be 9000 to 11500 nm or 3500 to 6000 nm.

[0101] According to one embodiment, the value of the above formula 2 may be equal to or greater than the value of the above formula 1. Preferably, the value of the above formula 2 may be greater than the value of the above formula 1. In this case, rainbow spots may be minimized from the front and side of an optical film having a front phase difference of 6000 to 9000 nm at a wavelength of 550 nm.

[0102] According to one implementation, the optical film can satisfy at least one of the following equations 3 and 4:

[0103] [Formula 3]

[0104] 1.0 ≤ A / B ≤ 1.3

[0105] [Formula 4]

[0106] 0.7 ≤ C / B ≤ 1.0

[0107] (In the above equations 3 and 4,

[0108] A, B and C are the same as defined in Equations 1 and 2 above).

[0109] By satisfying at least one of the above formulas 3 and 4, the effect of minimizing rainbow spots from the front and side of an optical film having a front phase difference of 6000 to 9000 nm at a wavelength of 550 nm can be greatly enhanced.

[0110] For example, in the above formula 3, A / B may be 1.2 to 1.3, for example, 1.2 to 1.25, for example, 1.21 to 1.25, for example, 1.24 to 1.25. For example, in the above formula 4, C / B may be 0.7 to 0.9, 0.7 to 0.8, 0.71 to 0.80, 0.75 to 0.76. In the above ranges, rainbow spots may not be significantly visible from the front and side of an optical film having a front phase difference of 6000 to 9000 nm at a wavelength of 550 nm.

[0111] Preferably, the optical film can simultaneously satisfy Equations 3 and 4.

[0112] The above optical film may include a polyester-based resin film as a substrate layer. The polyester-based resin film has low moisture permeability, which can facilitate improving the reliability of the optical film and polarizing plate.

[0113] The above polyester resin film may be a polyester resin film including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc. Preferably, the polyester resin film may be a polyethylene terephthalate film.

[0114] The above polyester resin film may have a light transmittance of 90%, for example, 95 to 100%, in the visible light range.

[0115] The polyester resin film can be manufactured by stretching in MD and TD biaxially. Specifically, the polyester resin film can be manufactured by manufacturing an unstretched film from a composition including the resin by melt extrusion or solvent casting, and sequentially or simultaneously biaxially stretching the manufactured unstretched film by stretching in MD and TD. The stretching ratio can be appropriately selected in consideration of the thickness of the unstretched film, the target in-plane retardation, the stretching temperature, etc.

[0116] For example, in the TD stretching, the stretching ratio may be 2.5 times or more, for example, 3.0 to 5.5 times. In the TD stretching, the stretching temperature may be controlled according to the glass transition temperature (Tg) of the unstretched film, and may be, for example, 80 to 135°C, for example, 90 to 125°C. The stretching may be performed by a conventional method known to those skilled in the art. The TD stretching may be performed under hot air drying. The stretching ratio may be the ratio of the TD size after the final stretching to the TD size of the unstretched film before the first stretching.

[0117] For example, in the MD stretching, the stretching ratio may be 3.5 times or less, for example, 1.0 to 3.0 times. In the MD stretching, the stretching temperature may be controlled according to the glass transition temperature (Tg) of the unstretched film, and may be, for example, 80 to 135°C, for example, 90 to 120°C. The stretching may be performed by a conventional method known to those skilled in the art.

[0118] In one specific example, the optical film may be composed solely of a substrate layer, i.e., a polyester-based resin film.

[0119] In another specific example, the optical film may include a functional layer laminated on at least one surface of the substrate layer in addition to a polyester resin film as the substrate layer. The functional layer may be a primer layer, an anti-fingerprint layer, a hard coating layer, an anti-reflection layer, or the like.

[0120] The polarizing plate includes a polarizer and an optical film laminated on at least one surface of the polarizer. In one specific embodiment, the optical film may be laminated on the light-emitting surface of the polarizer (e.g., the light-emitting surface of light emitted from a light source of a backlight unit). Preferably, the polarizing plate may be used as a viewing-side polarizing plate in an optical display device.

[0121] A polarizer converts incident natural light or polarized light into linearly polarized light in a specific direction, and can be manufactured from a polymer film containing a polyvinyl alcohol-based resin as a main component. Specifically, the polarizer can be manufactured by dyeing the polymer film with iodine or a dichroic dye and stretching it in the MD (machine direction). In one specific example, the polarizer can be manufactured by subjecting the polyvinyl alcohol-based film to a swelling process, a dyeing step, a stretching step, or optionally, at least one of a complementary color step and a crosslinking step.

[0122] A polarizer has a light absorption axis and a light transmission axis in the in-plane direction, and the light absorption axis can be the MD of the polarizer, and the light transmission axis can be the TD (transverse direction) of the polarizer.

[0123] The polarizer may have a single light transmittance of 40% or more, for example, 40 to 46%, and a polarization degree of 95% or more, for example, 95 to 99.999%. In the above range, when combined with a phase difference layer, anti-reflection performance can be improved. The above "light transmittance" and "polarization degree" are values ​​measured at a wavelength of 380 nm to 780 nm, and are values ​​reflecting the visibility in the corresponding wavelength range.

[0124] The polarizer may have a thickness of 2 to 30 μm, specifically 4 to 25 μm, and may be used in a polarizing plate within the above range.

[0125] According to one embodiment, when the light absorption axis of the polarizer is 0°, the ground axis of the substrate layer of the optical film example may be 85 to 95°, for example, 90°.

[0126] A polarizing plate may further include at least one protective film or a phase difference film on at least one surface of the polarizer. The protective film and the phase difference film may be selected from common types known to those skilled in the art, as long as they do not affect the effects of the present invention.

[0127] Figure 3 is a cross-sectional view of a polarizing plate according to one embodiment.

[0128] Referring to FIG. 3, the polarizing plate may include a polarizer 10, an optical film 20 laminated on one side of the polarizer 10, i.e., a light-emitting side, and a protective film 30 laminated on the other side of the polarizer 10, i.e., a light-incident side.

[0129] The optical display device of the present invention includes the optical film of the present invention.

[0130] The optical display device may be, but is not limited to, a liquid crystal display device, a light emitting diode display device, etc.

[0131] In one specific example, the optical display device may include a backlight unit, a light source-side polarizing plate, an optical display panel, and a viewer-side polarizing plate sequentially stacked, and the viewer-side polarizing plate may include the polarizing plate of the present invention.

[0132]

[0133] Hereinafter, the structure and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way.

[0134]

[0135] Example 1

[0136] After adsorbing iodine on a polyvinyl alcohol film, the film was stretched uniaxially in the machine direction (MD) of the film in a boric acid aqueous solution at 60°C so that the final stretching ratio in the machine direction (MD) was 5.5 to 6.0 times, thereby manufacturing a polarizer (thickness: 17 μm).

[0137] A polarizing plate was manufactured by attaching an optical film to the light-emitting surface of a polarizer and attaching a protective film (triacetyl cellulose film, thickness: 40 μm) to the light-incident surface of the polarizer.

[0138] The above optical film is a PET film composed of a polyethylene terephthalate-based substrate layer, and is manufactured by stretching the film in the transverse direction (TD) at a stretching temperature of 120°C under hot air drying using a tender stretching method using an end clip to a stretching ratio of 4.0 times, and at the same time, stretching the film in the longitudinal direction (MD) at a stretching ratio of 2.0 times from the viewpoint of transporting the film.

[0139] The detailed properties of the optical film are as shown in Table 1 below.

[0140] The ground axis of the optical film forms 90° with respect to the MD of the optical film, and the true axis of the optical film forms 0° with respect to the MD of the optical film.

[0141]

[0142] Examples 2 to 4

[0143] A polarizing plate was manufactured in the same manner as in Example 1, except that the TD stretching ratio and TD stretching temperature were changed during the manufacture of the optical film in Example 1.

[0144]

[0145] Comparative Examples 1 to 3

[0146] A polarizing plate was manufactured in the same manner as in Example 1, except that the TD stretching ratio and TD stretching temperature were changed during the manufacture of the optical film in Example 1.

[0147]

[0148] The specifications of the optical film are described in Table 1 and Figures 1 and 2 below.

[0149] (1) In-plane phase difference of optical film: The in-plane phase difference of the optical film was measured on the slow axis and the fast axis, respectively, while changing the light irradiation angle from 0° to +45° and from 0° to -45° using Axoscan (AXOMETRICS). The measured values ​​were used to calculate the properties shown in Table 1 below.

[0150] (2) Average refractive index of optical film: nx and ny of the optical film were measured using a prism coupler (METRICON) at a wavelength of 550 nm, and the average refractive index was calculated as (nx + ny) / 2. nx and ny are the refractive indices of the optical film in the slow axis direction and the fast axis direction, respectively.

[0151] (3) Rainbow spots: The polarizing plates manufactured in the examples and comparative examples were mounted on a panel for a liquid crystal display device, and the presence or absence of rainbow spots was visually evaluated at a frontal angle (θ) of 0°. If no rainbow spots were visible at all at a frontal angle (θ) of 0°, the product was evaluated as good, and if even a small amount of rainbow spots were visible, the product was evaluated as poor.

[0152] The polarizing plates manufactured in the examples and comparative examples were mounted on a panel for a liquid crystal display device and visually evaluated whether rainbow spots were visible at an azimuth angle (θ) of 45°. If no rainbow spots were visible at all at an azimuth angle (θ) of 45°, it was evaluated as ◎; if a slight rainbow spot was visible but not visible on the screen, it was evaluated as ○; if a rainbow spot was visible and visible on the screen, it was evaluated as △; and if a large rainbow spot was visible and easily visible on the screen, it was evaluated as x.

[0153] Example Comparative Example 1234123 Film PET PET PET PET PET PET Equation 5 (average refractive index) 1.625 1.633 1.637 1.648 1.648 1.635 1.650 In-plane phase difference @ 550 nm 86 28 7 8 6 6 7 5 0 0 8 5 0 0 8 6 2 1 8 1 9 0 7 5 0 0 Equation 1 20 8 8 1 8 1 1 5 0 0 2 5 0 0 2 7 5 8 2 5 9 0 1 3 5 0 Equation 2 21 0 3 1 9 6 0 1 5 0 0 2 5 0 0 2 6 3 6 2 7 0 4 1 2 0 0 Equation 3 1.24 7 1.24 1.20 0 1.29 4 1.3 2 0 1.33 1.18 0 Equation 4 0.76 0.75 0.80 0.71 0.69 0.68 0.84 Rainbow Stained front viewGoodGoodGoodGoodGoodGoodGood@+45°◎◎○○XX△

[0154]

[0155] As shown in FIGS. 1 and 2, when the optical films of the examples and comparative examples are irradiated with light at irradiation angles from 0° to -90° and from 0° to +90° in the front, it can be confirmed that the in-plane retardation values ​​are symmetrical with respect to 0° in the front, when the irradiation angle is the X-axis and the in-plane retardation measured in the direction of the slow axis and the fast axis of the optical film is the Y-axis.

[0156] As can be seen from Table 1 above, the polarizing plate of the embodiment reduces the difference in color depending on the viewing angle of the screen when applying an optical film satisfying the above drawings 1 and 2 to an optical display device, and prevents rainbow spots from occurring at an omnidirectional viewing angle.

[0157] On the other hand, the polarizing plate of the comparative example did not achieve the effect of the embodiment.

[0158]

[0159] Simple modifications or changes of the present invention can be easily implemented by a person having ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims

1. Includes a polarizer and an optical film laminated on the light-emitting surface of the polarizer, The above optical film is a polarizing plate having a front-plane phase difference of 6000 to 9000 nm at a wavelength of 550 nm and a phase difference value difference of 1500 to 2500 nm according to the following equation 1: [Formula 1] Difference in phase difference values ​​= |A - B| (In the above equation 1, A is the in-plane phase difference measured in the direction of the ground axis of the optical film at a wavelength of 550 nm when light is irradiated to the optical film at +45° or -45° when the front of the optical film is set to 0°. B is the in-plane phase difference measured at a wavelength of 550 nm of the optical film.

2. A polarizing plate in the first paragraph, wherein the ground axis of the optical film is 85 to 95° when the MD (machine direction) of the base layer of the optical film is 0°.

3. A polarizing plate in the first paragraph, wherein the true axis of the optical film is -5 to 5° when the MD of the base layer of the optical film is 0°.

4. In the first paragraph, the optical film is a polarizing plate having an average refractive index value of 1.57 to 1.70 calculated by the value of Equation 5 below: [Formula 5] Average refractive index = (nx + ny) / 2 (In the above equation 5, nx and ny are the refractive index in the direction of the short axis and the refractive index in the direction of the true axis of the optical film, respectively, at a wavelength of 550 nm).

5. In the first paragraph, the optical film is a polarizing plate, wherein when light is irradiated at an irradiation angle from 0° to -90° and from 0° to +90° in the front, the irradiation angle of the light is the X-axis, and the in-plane phase difference measured in the direction of the ground axis of the optical film is the Y-axis, the in-plane phase difference value is symmetrical with respect to 0° in the front.

6. In the first paragraph, the optical film is a polarizing plate, wherein when light is irradiated at an irradiation angle from 0° to -90° and from 0° to +90° in the front, the irradiation angle of the light is the X-axis, and the in-plane phase difference measured in the direction of the optical film's true axis is the Y-axis, the in-plane phase difference value is symmetrical with respect to 0° in the front.

7. In the first paragraph, the optical film is a polarizing plate having a difference in phase difference value according to the following 2 of 1500 to 2500 nm: [Formula 2] Difference in phase difference values ​​= |C - B| (In the above equation 2, C is the in-plane phase difference measured in the true axis direction of the optical film at a wavelength of 550 nm when the optical film is irradiated with light at +45° or -45°, B is the in-plane phase difference measured at a wavelength of 550 nm of the optical film.

8. In the 7th paragraph, the value of the above formula 2 is equal to or greater than the value of the above formula 1, a polarizing plate.

9. In the first paragraph, the optical film is a polarizing plate that satisfies at least one of the following formulas 3 and 4: [Formula 3] 1.0 ≤ A / B ≤ 1.3 [Formula 4] 0.7 ≤ C / B ≤ 1.0 (In the above equations 3 and 4, B is the frontal in-plane phase difference measured at a wavelength of 550 nm of the optical film, A is the in-plane phase difference measured in the direction of the ground axis of the optical film at a wavelength of 550 nm when light is irradiated on the optical film at +45° or -45°, C is the in-plane phase difference measured in the direction of the optical film's true axis at a wavelength of 550 nm when the optical film is irradiated with light at +45° or -45°.

10. A polarizing plate according to claim 1, wherein the optical film is a MD and TD biaxially stretched film.

11. A polarizing plate according to claim 1, wherein the optical film comprises a polyester resin film as a base layer.

12. In the first paragraph, the optical film is a polarizing plate including a polyethylene terephthalate film.

13. An optical display device comprising a polarizing plate according to any one of claims 1 to 12.

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