polarizing plate

Abstract

The present invention relates to a polarizing plate. The present invention provides a polarizing plate for a display side of a display, comprising: a polarizing layer having an absorption axis; and a protective layer disposed on a display surface of the polarizing layer, the protective layer comprising a birefringent substrate adjacent to the polarizing layer, the birefringent substrate having mutually perpendicular slow and fast axes, and a birefringence difference of not more than 0.10, and an interference cancellation layer disposed on a display side surface of the birefringent substrate, the interference cancellation layer comprising a diffusing layer disposed on the birefringent substrate and a refractive index matching layer disposed on the diffusing layer, wherein the total haze of the protective layer is between 30% and 75%, and the reflectance of the protective layer satisfies the relationship (R SCI − R SCE ) ≦ 1.0%, and R SCE / (R SCI − R SCE ) ≧ 1.6, R SCI being the diffuse and specular average reflectance of the protective layer, and R SCE being the diffuse average reflectance of the protective layer.

Description

Technical Field

[0001] The present invention relates to a polarizing plate for a display device, and more particularly to a display-side polarizing plate having the function of eliminating rainbow patterns caused by interference of reflected light. Background Technology

[0002] Display devices typically feature periodically arranged display panel pixels. When a highly transparent protective layer is used on the display side, interference fringes can easily form due to specific wavelengths of display image light or ambient light reflecting off the display panel. This can usually be eliminated by creating a rough or uneven surface on the protective layer of the display panel to disrupt the periodicity of the transmitted light. However, this results in poor surface gloss and can easily cause defects such as white haze and blurring of the displayed image. Furthermore, due to current requirements for display quality and the trend towards higher brightness, thinner profiles, and greater flexibility in display devices such as liquid crystal displays (LCDs), organic light-emitting diode displays (OLEDs), and micro LED displays, the optical film structure used on the display side has become more complex. The matching of optical characteristics between multiple film layers is crucial to simultaneously enhance display quality, achieve thinness, and provide good flexibility. Even when the outer protective layer is used in conjunction with a high-transmittance polarizing plate or a circular polarizing plate for electroluminescent displays, its protective capabilities and optical characteristics cannot be sacrificed for these benefits. Currently, polyester materials with crystalline properties are often used to replace traditional triacetate cellulose (TAC), which lacks in-plane phase difference (R0≈0nm), as a protective layer to provide better resistance to water vapor penetration and mechanical strength. However, polyester materials, such as the common polyethylene terephthalate (PET), have a high inherent birefringence due to their high crystallinity caused by the benzene ring structure. After uniaxial or biaxial stretching processes, a protective layer with high birefringence and a high in-plane phase difference (R0≧3000nm) is formed.

[0003] Because of the high inherent birefringence and high in-plane phase difference of this type of polyester protective layer, unlike the near-zero in-plane phase difference of cellulose triacetate as a protective layer, it cannot be used as an inner protective layer for polarizing plates near the display panel. Furthermore, when this material with high in-plane phase difference is used as a protective layer on the outer display side, the reflectivity of the polyester material is approximately 5.0% or higher due to the difference in refractive index between the polyester material and air. Therefore, in addition to the bright and dark interference fringes formed by the reflection of light of specific wavelengths through the periodically arranged display panel pixels, under strong ambient light, rainbow patterns are more likely to occur at the interface between the two sides of the birefringent protective layer due to the inconsistent optical path difference between the transmission and reflection of different visible light wavelengths, thus affecting display quality. Moreover, the high inherent birefringence of polyester materials easily leads to significant uneven changes in in-plane phase difference due to slight deviations in film thickness, providing more conditions and areas for the formation of interference rainbow patterns, which are difficult to eliminate by using rough or uneven surfaces to disrupt the periodicity of light, unlike ordinary interference fringes.

[0004] like Figure 1 The diagram shows a known polarizing plate 10 for the display side of a monitor. Since the polarizing layer 100 and protective layer 110 of the polarizing plate 10 are generally manufactured using an extension process, it has an absorption axis 100a and a slow axis 110a parallel to the main extension direction. Here, the absorption axis 100a is configured in a conventional horizontal display direction (X-axis), and the slow axis 110a is configured in the Y-axis direction, for example. Ambient light L, such as outdoor sunlight or indoor lighting, typically has a relatively high illumination angle relative to the display device. When ambient light L enters the protective layer 110 of the polarizing layer 100 from air with a low refractive index at a non-zero incident angle θ, it forms an s-axis component with a polarization direction perpendicular to the optical path plane (i.e., the YZ plane) and a p-axis component with a polarization direction parallel to the optical path plane. Since the reflectivity of the s-axis component is greater than that of the p-axis component, especially when the incident angle θ of the ambient light L conforms to the Brewster angle, the reflected light L1 at the interface between the protective layer 110 and the air will be 100% s-axis polarized. The p-axis component, refracted into the protective layer 110 and then propagated, is delayed by the in-plane phase difference and also transforms into a partial s-axis component as the ellipticity increases, resulting in the reflected light L2 having a larger s-axis component. Therefore, the reflected light L1 and L2 at the interfaces on both sides of the protective layer 110 have high coherence and are prone to interference, forming inhomogeneous rainbow patterns.

[0005] Known methods for resolving rainbow patterns in protective layers include, for example, Taiwan Patent TWI406001, which discloses an optical laminate with a higher retardation (i.e., in-plane phase difference, R0) of over 8000 nm, and overcomes rainbow inhomogeneity and interference fringes by matching the refractive index of the base coat, hard coat, and polyester substrate. Another example is Taiwan Patent TWI531472, which discloses a protective film for a polarizing plate with an in-plane retardation (R0) greater than 10000 nm and a thickness direction retardation (Rth) of 10000 nm to 12000 nm to solve the rainbow spot problem. All of the above-mentioned known technologies require a considerably high in-plane phase difference. The in-plane phase difference R0 can be calculated using equation (1): R0 = (nx - ny)d. As shown in equation (1), the in-plane phase difference R0 can only be increased by two methods: increasing the difference between the refractive index nx in the slow axis direction and the refractive index ny in the fast axis direction (nx-ny) and increasing the thickness d of the protective layer. Methods to increase the birefringence difference between the slow and fast axes include modifying the functional groups of the polyester material or increasing the elongation ratio in the film deposition process to increase the molecular alignment. However, these methods will change the rigidity of the polyester material itself. Excessive elongation of the polyester material, which significantly increases the birefringence difference, may also lead to excessive rigidity and loss of flexibility. Furthermore, the changes in functional group modification and elongation processes increase the overall manufacturing difficulty. While increasing the thickness d is a more direct method, it does not align with the current trend of thinner and lighter display devices. Increasing the thickness d of the protective layer also alters the overall bending stress distribution of the flexible display, increasing the design difficulty of matching other film layers in the display. Therefore, the method of significantly increasing the in-plane phase difference of the polyester protective layer to avoid interference phenomena caused by visible light at the interfaces on both sides of the film layer is not ideal and may cause unexpected defects. Summary of the Invention

[0006] One embodiment of the present invention provides a polarizing plate for the display side of a display, comprising: a polarizing layer having an absorption axis; a protective layer disposed on the display surface of the polarizing layer, the protective layer comprising a birefringent substrate adjacent to the polarizing layer, the birefringent substrate having mutually perpendicular slow and fast axes, and a birefringence difference (Δn) not greater than 0.10; and an interference cancellation layer disposed on the display side surface of the birefringent substrate, comprising a diffuse layer disposed on the birefringent substrate and a refractive index matching layer disposed on the diffuse layer, wherein the total haze of the protective layer is between 30% and 75%, and the diffuse average reflectance R of the protective layer is... SCE The reflectance is between 0.8% and 2.0%, and the reflectance satisfies the relationship: (R SCI -R SCE )≦1.0%, and R SCE / (R SCI -R SCE )≧1.6, where RSCI R represents the diffuse and specular average reflectance of the protective layer. SCE This represents the diffuse average reflectivity of the protective layer.

[0007] In another embodiment of the polarizing plate of the present invention, the angle between the absorption axis of the polarizing layer and the horizontal viewing angle direction of the display is between 0° and 45°.

[0008] In another embodiment of the polarizing plate of the present invention, the birefringence difference of the birefringent substrate is preferably between 0.02 and 0.09, and more preferably between 0.02 and 0.08.

[0009] In another embodiment of the polarizing plate of the present invention, the protective layer (R) SCI -R SCE The percentage is between 0.1% and 1.0%.

[0010] In another embodiment of the polarizing plate of the present invention, the diffuse layer has a refractive index n1, the refractive index matching layer has a refractive index n2, and the refractive index n2 is less than the refractive index n1.

[0011] In another embodiment of the polarizing plate of the present invention, the refractive index n1 is between 1.50 and 1.70, and the refractive index n2 is between 1.20 and 1.50.

[0012] In another embodiment of the polarizing plate of the present invention, the total haze of the protective layer is the sum of the surface haze of the protective layer and the internal haze of the protective layer, wherein the surface haze of the protective layer is greater than 25%.

[0013] In another embodiment of the polarizing plate of the present invention, the thickness of the diffuse layer is between 2 μm and 10 μm.

[0014] In another embodiment of the polarizing plate of the present invention, the thickness of the refractive index matching layer is between 0.1 μm and 0.3 μm.

[0015] In another embodiment of the polarizing plate of the present invention, the thickness of the birefringent substrate is preferably between 10 μm and 150 μm.

[0016] In another embodiment of the polarizing plate of the present invention, the birefringent substrate is a uniaxially or biaxially extended polyester film.

[0017] The foregoing summary is intended to provide a simplified overview of this disclosure, enabling the reader to gain a basic understanding of its contents. This summary is not a complete overview of the invention, nor is it intended to identify key elements of the embodiments or define the scope of the invention. Upon reviewing the following description of embodiments, those skilled in the art will readily understand the basic spirit of the invention and the technical means and implementation methods employed. Attached Figure Description

[0018] Figure 1 A schematic diagram of a known polarizing plate for the display side of a display is shown;

[0019] Figure 2 This diagram shows a polarizing plate for the display side of a display disclosed in an embodiment of the present invention;

[0020] Figure 3 A schematic diagram showing the reflectance measurement principles of SCI mode and SCE mode.

[0021] [Symbol Explanation]

[0022] 10, 20: Polarizing plate

[0023] 100, 200: Polarizing layer

[0024] 100a, 200a: Absorption shaft

[0025] 110, 210: Protective layer

[0026] 110a, 211a: Slow axis

[0027] 211: Birefringent substrate

[0028] 211b: Fast axis

[0029] 212: Interference Offset Layer

[0030] 2121: Diffuse Layer

[0031] 2122: Refractive index matching layer

[0032] 30: Light source

[0033] 40: Test Item

[0034] 50: Points Ball

[0035] 60: Detector

[0036] 70: Optical Trap

[0037] L: Ambient light

[0038] L1, L1', L2, L2', L4: Reflected light

[0039] L3: Light

[0040] L4': diffuse light

[0041] θ: Angle of incidence

[0042] p: p optical component

[0043] s: s-optical component Detailed Implementation

[0044] To make the description of the present invention more detailed and complete, illustrative descriptions of the embodiments and specific examples of the present invention are provided below; however, these are not the only forms of implementing or applying the specific examples of the present invention. The various embodiments disclosed below can be combined or substituted with each other where advantageous, and other embodiments can be added to the embodiments without further description or explanation.

[0045] The advantages, features, and technical methods of implementing this invention will be more readily understood by referring to exemplary embodiments. This invention may be implemented in different forms and should not be construed as limited to the embodiments set forth herein. Rather, the embodiments provided will enable those skilled in the art to more thoroughly and completely convey the scope of this invention, which will be defined only by the appended claims.

[0046] Unless otherwise defined, all terms (including technical and scientific terms) and proper nouns used herein shall, in substance, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. For example, terms defined in commonly used dictionaries shall be understood to have the same meaning as those in the relevant field, and shall not be interpreted in an overly idealized or overly formal sense unless explicitly defined herein.

[0047] Furthermore, in this article, the term "(meth)acrylate" refers to methacrylates and acrylates.

[0048] Please refer to Figure 2 In an embodiment of the present invention, a polarizing plate 20 for the display side of a display is provided, comprising: a polarizing layer 200 having an absorption axis 200a; and a protective layer 210 disposed on the display surface of the polarizing layer 200, the protective layer 210 comprising a birefringent substrate 211 adjacent to the polarizing layer 200, the birefringent substrate 211 having mutually perpendicular slow axes 211a and fast axes 211b, and a birefringence difference (Δn) not greater than 0.10; and an interference cancellation layer 212 disposed on the display side surface of the birefringent substrate 211; the interference cancellation layer 212 comprises a diffuse layer 2121 disposed on the birefringent substrate 211, and a refractive index matching layer 2122 disposed on the diffuse layer 2121, wherein the total haze of the protective layer 210 is between 30% and 75%, and the diffuse average reflectance R of the protective layer 210 is... SCE The reflectance is between 0.8% and 2.0%, and the reflectance satisfies the relationship: (R SCI -R SCE )≦1.0%, and R SCE / (R SCI -RSCE )≧1.6, where R SCI R represents the diffuse and specular average reflectivity of the protective layer 210. SCE The diffuse average reflectivity of the protective layer 210.

[0049] The polarizing layer 200 and the birefringent substrate 211 of the polarizing plate 20 are generally manufactured using an extension process and are produced in rolls. This results in the polarizing layer 200 having an absorption axis 200a parallel to the main extension direction, and the birefringent substrate 211 having a slow axis 211a parallel to the main extension direction and a fast axis 211b perpendicular to each other. The angle between the absorption axis 200a of the polarizing layer 200 and the slow axis 211a of the birefringent substrate 211 is between 0° and 90°, and can be adjusted according to the slow axis angle formed by the birefringent substrate 211 in the uniaxial or biaxial extension process. Furthermore, especially when the absorption axis 200a is not perfectly perpendicular to the horizontal viewing angle of the display, when ambient light L enters the interference cancellation layer 212, in addition to the high-haze diffuse layer 2121 disrupting the coherence and directionality of the light, the s-light component generated in the birefringent substrate 211, which is in the same direction as the absorption axis 200a, can also be absorbed by the polarizing layer 200, further reducing the reflection intensity. Even if the polarization direction of the p-light component changes to a more strongly reflected s-light component due to passing through the birefringent substrate 211, it can still be absorbed by the polarizing layer 200. Therefore, even if reflected light L2' is generated again after passing through the interference cancellation layer 212, its intensity has been greatly reduced, and it will not interfere with the reflected light L1' reflected from the surface of the birefringent substrate 211 by the interference cancellation layer 212.

[0050] In the polarizing plate of this embodiment, the angle between the absorption axis 200a of the polarizing layer 200 and the horizontal viewing angle of the display can be selectively between 0° and 45° depending on the type of display panel or different display application requirements. Since this angle range has a certain horizontal projection component relative to the absorption axis 200a for ambient light sources illuminating from above the display, it is sufficient to counteract the reflection intensity of the s-ray component.

[0051] It is known that polyester materials, when used as protective layers, have a reflectivity greater than 5.0% even without any surface treatment. Therefore, a high in-plane phase difference (R0) of over 8000 nm and a high-scattering surface, or a thicker polyester film, are often required to reduce rainbow patterns and interference fringes. However, the birefringent substrate 211 used in the protective layer of this invention does not require an extremely high in-plane phase difference (R0), i.e., an in-plane phase difference (R0) not greater than 8000 nm. Therefore, birefringent substrates with a thickness between 10 μm and 150 μm are suitable, preferably between 15 μm and 100 μm.

[0052] Therefore, the present invention has a better tolerance for the in-plane phase difference value R0 of the birefringent substrate 211. It is preferred that conventional polyester materials with an in-plane phase difference value R0 of 1000nm to 6000nm can be used, and rainbow defects are less likely to appear. However, it is not limited to birefringent substrate 211 with this range of in-plane phase difference value. As long as the birefringent substrate 211 is a polyester film material with a birefringence difference of not more than 0.10 made of a material with appropriate crystallinity and elongation ratio while having a certain mechanical strength and water vapor penetration resistance, and is combined with the absorption axis of the interference cancellation layer 212 and the polarizing layer 200 to form the polarizing plate 20.

[0053] Furthermore, the present invention reduces the degree of rainbow and interference fringes when the protective layer 210 of the polarizer 20 uses a birefringent substrate 211. This is mainly achieved by simultaneously reducing the intensity of reflected light and reducing the coherence and directionality of reflected light. This ensures that even with continuously thinning and increasing transmittance of the polarizer, it still possesses sufficient scattering light path and reduces reflected light intensity, thus achieving the effect of reducing rainbow and interference fringes. From equation (2), R = (N2 - N1). 2 / (N2+N1) 2 It is known that the reflectivity R of light at the interface between film materials is related to the refractive indices of the media on both sides of the interface. When light is incident from an air layer with refractive index N1 or a film material onto a birefringent substrate with refractive index N2, in order to increase the birefringence difference of the birefringent substrate, the refractive index of the slow axis parallel to the main extension direction is often significantly increased, which is not conducive to reducing the overall reflectivity R. Therefore, the birefringence difference of the birefringent substrate should preferably not exceed 0.10, and preferably further between 0.02 and 0.09, especially between 0.02 and 0.08.

[0054] The interference cancellation layer 212 of the protective layer of the present invention has a composite structure of a diffuse layer 2121 and a refractive index matching layer 2122. It can simultaneously reduce the coherence of reflected light through the diffuse layer 2121 and reduce the intensity of reflected light through the refractive index matching layer 2122. In the protective layer 210 of the present invention, the diffuse layer 2121 of the interference cancellation layer 212 has a refractive index n1, and the refractive index matching layer 2122 has a refractive index n2, wherein the refractive index n2 is less than the refractive index n1, wherein the refractive index n1 is between 1.50 and 1.70, and the refractive index n2 is between 1.20 and 1.50. Due to the high crystallinity of polyester materials, even if the birefringence difference is reduced to less than or equal to 0.10, its average refractive index is still about 1.60 or higher. Therefore, when there is a diffuse layer 2121 with a refractive index between 1.00 and 1.60 and a refractive index matching layer 2122 between the birefringent substrate 211 and the external air layer (refractive index about 1.00), for example, the diffuse layer 2121 is made of a material with a refractive index n1 of 1.55 and the refractive index matching layer 2122 is made of a material with a refractive index n2 of 1.40. The refractive index n2 is less than the refractive index n1. According to the calculation results of the aforementioned formula (2), the effect of a lower total reflectivity of external ambient light can also be obtained without changing the destructive homogeneity effect after the external ambient light repeatedly penetrates the diffuse layer 2121.

[0055] The reflectance was measured by attaching the protective layer 210 to a black acrylic plate, which served as a replacement for the display panel with an orthogonal polarizer, using optical adhesive. A HITACHI U-4150 spectrophotometer was used to measure the average diffuse and specular reflectance in SCI (Specular Component Included) mode and the average diffuse reflectance in SCE (Specular Component Excluded) mode on the display-side surface of the protective layer 210 within the visible light wavelength range of 380 nm to 780 nm. Please refer to [reference needed]. Figure 3 This diagram illustrates the measurement principles of SCI and SCE modes. Light L3 emitted from light source 30 is incident on the test sample 40 at a fixed angle, forming directly reflected specular light L4 and diffuse light L4'. These are collected by integrating sphere 50 and then received by detector 60. The reflectance obtained by detector 60 from the specular reflected light L4 and diffuse light L4' is defined as the average reflectance R of diffuse and specular reflection in SCI mode. SCI When the specularly reflected light L4 is absorbed by the optical trap 70, the reflectance obtained by the detector 60 receiving only the diffuse light L4' is defined as the diffuse average reflectance R of the SCE mode. SCE Because of the poor coherence of diffuse light, specular reflection L4 can be considered as the main component of interference, through (R SCI -R SCEThe average reflectivity of the specular reflected light L4 can be obtained by controlling the protective layer (R) of the polarizing plate of the present invention. SCI -R SCE The reflectivity ratio R of diffuse light L4' and specular light L4' of the overall protective layer is less than or equal to 1.0%. SCE / (R SCI -R SCE When the light intensity is greater than or equal to 1.6, the formation of rainbow fringes and interference fringes can be reduced, or due to insufficient light intensity and contrast, even if rainbow fringes and interference fringes are formed, they will not be easily detected by the human eye. Furthermore, the diffuse average reflectance R of this protective layer... SCE Preferably less than 2.0%, more preferably between 0.8% and 2.0%, so that the protective layer maintains a visual appearance close to that without the interference cancellation layer, avoiding the large deflection of light caused by the known rough surface structure, resulting in excessive diffuse and backscattered light and white fogging. Moreover, for the image light emitted by the display, after passing through the protective layer of the polarizing plate, the light transmittance is not sacrificed due to the diffuse layer 2121 in the interference cancellation layer 212, or the surface gloss of the protective layer is affected.

[0056] In another embodiment of the polarizing plate of the present invention, the protective layer (R) SCI -R SCE The optimal concentration is between 0.1% and 1.0%. This ensures that the protective layer still has a certain degree of surface gloss without compromising the interference cancellation effect, thus avoiding poor visual experience for the user.

[0057] In another embodiment of the polarizing plate of the present invention, the total haze of the protective layer 210 is the sum of the surface haze and the internal haze of the protective layer 210. By controlling the total haze to be greater than 30%, the transmission direction and coherence of ambient light entering the diffuse layer 2121 inside the interference cancellation layer 212 are changed, rather than relying solely on the surface roughness of the protective layer 210 to change the direction of reflected light. In a preferred embodiment of the present invention, the protective layer 210 has a surface haze of greater than 25%. Since the light path of ambient light entering the protective layer 210 first contacts the surface of the interference cancellation layer 212 and then penetrates the birefringent substrate 211 and is reflected, the internal haze and surface haze of the diffuse layer 2121 inside the interference cancellation layer 212 can provide a longer reciprocating light path for ambient light within a unit thickness, without excessively increasing the overall thickness of the interference cancellation layer 212 (e.g., less than or equal to 10 μm), thereby increasing the light path and diffusion effect and avoiding blurring of the displayed image or reducing the light penetration intensity of the displayed image. Furthermore, for the rainbow effect that is more easily observed from an oblique perspective, the longer path of the lateral incident scattered light inside the film layer can provide more effective compensation for the rainbow effect.

[0058] In another embodiment of the polarizer's interference cancellation layer 212, the diffuse layer 2121 only needs a thickness between 2 μm and 10 μm, preferably 3 μm to 8 μm, to provide a diffused light path that can disrupt the coherence of ambient light. The thickness of the refractive index matching layer 2122 is much smaller than the thickness of the diffuse layer 2121, for example, about 0.1 μm to 0.3 μm, which reduces the reflection of visible light wavelengths from the ambient light. The combined effect of the diffuse layer 2121 and the refractive index matching layer 2122 of the interference cancellation layer 212 of the protective layer 210 of the present invention is far superior to the known method of increasing the thickness of polyester material with a birefringence difference of 0.10 or more to 80 μm or more to obtain an in-plane phase difference value of 8000 nm or more in order to improve the effectiveness of interference fringes and rainbow patterns.

[0059] In another embodiment of the polarizing plate of the present invention, the birefringent substrate 211 used for the protective layer 210 is a uniaxially or biaxially extended polyester film with a light transmittance of 90% or more, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or polyethylene naphthalate (PEN). In the polarizing plate of the present invention, the optical film may use a birefringent substrate containing an ultraviolet (UV) light absorber.

[0060] In the polarizing plate of the present invention, the diffuse layer 2121 of the interference cancellation layer 211 of the protective layer 210 contains an acrylic binder resin and a plurality of amorphous silica microparticles, and organic microparticles may be added as needed.

[0061] In the protective layer 210 of the polarizing plate 20 of the present invention, the amorphous silica microparticles suitable for use in the diffuser layer 2121 have an average laser-derived particle size between 3.0 μm and 10 μm and a BET specific surface area between 60 m² and 10 μm. 2 / g to 100m 2 The amount of amorphous silica microparticles used is between 6 and 25 parts by weight per 100 parts by weight of the acrylic adhesive resin.

[0062] In the protective layer 210 of the polarizing plate 20 of the present invention, organic microparticles may be selectively added to the diffuser layer 2121. These organic microparticles are monodisperse and have an average particle size smaller than that of the amorphous silica microparticles. Suitable organic microparticles are those with a laser-derived average particle size between 2.0 μm and 8.0 μm. In the diffuser layer 2121, the amount of these organic microparticles used is between 6 parts by weight and 40 parts by weight per 100 parts by weight of the acrylic binder resin.

[0063] The organic microparticles suitable for the diffuser layer 2121 may be polymethyl methacrylate resin microparticles, polystyrene resin microparticles, styrene-methyl methacrylate copolymer microparticles, polyethylene resin microparticles, melamine microparticles, epoxy resin microparticles, polysiloxane resin microparticles, polyvinylidene fluoride resin, or polyvinyl fluoride resin microparticles. The refractive index of the suitable organic microparticles is between 1.40 and 1.70.

[0064] In the diffuser layer 2121 of the protective layer 210 of the polarizing plate 20 of the present invention, the total amount of amorphous silica microparticles and organic microparticles used in the acrylic adhesive resin is between 15 parts by weight and 50 parts by weight per 100 parts by weight of the acrylic adhesive resin. Furthermore, the weight ratio of the organic microparticles to the amorphous silica microparticles is not less than 0.3 and not more than 5.

[0065] In the protective layer 210 of the polarizing plate 20 of the present invention, the acrylic adhesive resin used in the diffuser layer 2121 comprises a (meth)acrylate composition and an initiator, wherein the (meth)acrylate composition in the acrylic adhesive resin comprises 35 to 50 parts by weight of a polyurethane (meth)acrylate oligomer with a functionality of 6 to 15, 12 to 20 parts by weight of a (meth)acrylate monomer with a functionality of 3 to 6, and 1.5 to 12 parts by weight of a (meth)acrylate monomer with a functionality of less than 3, wherein the polyurethane (meth)acrylate oligomer with a functionality of 6 to 15 preferably is an aliphatic polyurethane (meth)acrylate oligomer with a molecular weight between 1,500 and 4,500.

[0066] In acrylic adhesive resins, suitable (meth)acrylate monomers with a functionality of 3 to 6 are (meth)acrylate monomers with a molecular weight of less than 800, such as pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), dipentaerythritol pentaacrylate (DPPA), or a combination thereof, but not limited to these. Suitable (meth)acrylate monomers with a functionality of less than 3 can be (meth)acrylate monomers with a functionality of 1 or 2 and a molecular weight of less than 500, such as 1,6-hexanediol diacrylate (HDDA), cyclotrihydromethylpropane methyl acetal acrylate (CTFA), 2-phenoxyethyl acrylate (PHEA), or isobornyl acrylate (IBOA), or a combination thereof, but not limited to these.

[0067] In the protective layer 210 of the polarizing plate 20 of the present invention, the suitable initiator in the acrylic adhesive resin used in the diffuser layer 2121 of the interference cancellation layer 212 can be any initiator known to be usable in this art, and there are no particular limitations. For example, acetophenone initiators, diphenyl ketone initiators, phenylacetone initiators, benzoyl initiators, bifunctional α-hydroxy ketone initiators, or acylphosphine oxide initiators can be used. The aforementioned initiators can be used alone or in combination.

[0068] In the protective layer 210 of the polarizing plate 20 of the present invention, a leveling agent may be added to the diffuser layer 2121 to improve the coating coverage or smoothness. Fluorine-based, (meth)acrylate-based, or silicone-based leveling agents may be used in the diffuser layer 2121 of the protective layer 210 of the polarizing plate 20 of the present invention.

[0069] In the protective layer 210 of the polarizer 20 of the present invention, the refractive index matching layer 2122 of the interference cancellation layer 211 is coated on the film surface of the diffuser layer 2121. The refractive index matching layer 2122 comprises a binder resin, a plurality of hollow silica nanoparticles, and a leveling agent comprising a (meth)acrylyl-modified organosilicon compound having perfluoropolyether functional groups, wherein the average primary particle size of the hollow silica nanoparticles is between 50 nm and 100 nm.

[0070] In the protective layer 210 of the polarizer 20 of the present invention, the binder resin used in the refractive index matching layer 2122 of the interference cancellation layer 212 can be a (meth)acrylic resin or a polysiloxane resin modified with fluorine and acrylate. In an embodiment of the refractive index matching layer 2122 of the protective layer 210 of the polarizer 20 of the present invention, the (meth)acrylic resin that can be used in the refractive index matching layer 2122 can be at least one or a combination of pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and dipentaerythritol tetra(meth)acrylate. When (meth)acrylic resin is used as the binder resin for the refractive index matching layer 2122, the amount of hollow silica nanoparticles used in the refractive index matching layer 2122 is between 60 parts by weight and 130 parts by weight per 100 parts by weight of the aforementioned (meth)acrylic resin.

[0071] In another embodiment of the protective layer 210 of the polarizer 20 of the present invention, the fluorinated and acrylate-modified polysiloxane resin that can be used in the refractive index matching layer 2122 of the interference cancellation layer 212 is a polysiloxane resin having a siloxane backbone, fluorinated alkyl branches, and acrylate functional groups. Suitable fluorinated and acrylate-modified polysiloxane resins may include, for example, but are not limited to, commercially available siloxane resins, such as X-12-2430C (purchased from Shigeobu Kagaku, Japan). When a fluorinated and acrylate-modified polysiloxane resin is used as the binder resin of the refractive index matching layer 2122, the amount of hollow silica nanoparticles used in the refractive index matching layer 2122 is between 90 parts by weight and 350 parts by weight per 100 parts by weight of the fluorinated and acrylate-modified polysiloxane resin.

[0072] In an embodiment of the protective layer 210 of the polarizer 20 of the present invention, the refractive index matching layer 2122 of the interference cancellation layer 212 may contain a leveling agent. Suitable leveling agents may be perfluoropolyether-functionalized (meth)acrylamide-modified silicone compounds. Suitable perfluoropolyether-functionalized (meth)acrylamide-modified silicone compounds include, but are not limited to, commercially available X-71-1203E, KY-1203, KY-1211, or KY-1207 (purchased from Shigeobushi Chemical Industry Co., Ltd., Japan). The amount of leveling agent used varies depending on the type of binder resin used. When a (meth)acrylic resin is used as the binder resin for the refractive index matching layer 2122, the amount of leveling agent used is between 5 parts by weight and 20 parts by weight per 100 parts by weight of the (meth)acrylic resin. When a fluorinated and acrylate-modified polysiloxane resin is used as the binder resin for the refractive index matching layer 2122, the amount of leveling agent used in the refractive index matching layer 2122 is between 1 part by weight and 45 parts by weight per 100 parts by weight of the fluorinated and acrylate-modified polysiloxane resin.

[0073] The initiators suitable for use in the refractive index matching layer 2122 of the interference cancellation layer 212 of the protective layer 210 of the polarizer 20 of the present invention are, for example, but not limited to, commercially available products, such as Esacure KIP-160, Esacure One, Omnirad 184, Omnirad 907, Omnirad TPO purchased from IGM Resins BV in the Netherlands, and TR-PPI-ONE purchased from Strong New Materials Co., Ltd. in Hong Kong, China.

[0074] This invention also provides a method for preparing a polarizing plate, comprising preparing a diffuse layer coating liquid and applying it onto a birefringent substrate, drying the birefringent substrate coated with the diffuse layer coating liquid, and then curing it by radiation or electron beam to form a diffuse layer on the birefringent substrate, then preparing a refractive index matching layer coating liquid, applying the refractive index matching layer coating liquid onto the diffuse layer, drying to remove the solvent, and then curing it by radiation or electron beam to form a refractive index matching layer on the diffuse layer. The resulting protective film can be bonded with the slow axis of the birefringent substrate and the absorption axis of the polarizing layer at an angle between 0° and 90°, and the angle between the absorption axis of the polarizing layer of the polarizing plate of this invention and the horizontal viewing angle direction of the display is between 0° and 45°.

[0075] The preparation of the diffuse coating liquid of the present invention comprises mixing a polyurethane (meth)acrylate oligomer with a functionality of 6 to 15, a (meth)acrylate monomer with a functionality of at least 3 to 6, a (meth)acrylate monomer with a functionality of at least less than 3, and an initiator with a suitable solvent to form an acrylic adhesive resin solution; adding a plurality of amorphous silica microparticles, a leveling agent, and an organic solvent to the acrylic adhesive resin solution, and mixing them to form a diffuse coating liquid. In another embodiment of the present invention, a plurality of organic microparticles may optionally be added to the diffuse coating liquid.

[0076] The preparation of the refractive index matching coating liquid of the present invention comprises mixing a binder resin, a plurality of hollow silica nanoparticles, an initiator, a leveling agent and a suitable solvent uniformly to form the coating liquid.

[0077] In other embodiments of the present invention, additives such as antistatic agents, colorants, flame retardants, ultraviolet absorbers, antioxidants, surface modifiers, antibacterial agents, or defoamers may be added as needed to prepare the aforementioned diffuse coating liquid or refractive index matching coating liquid to provide different functional properties.

[0078] The solvent used in the preparation method of the present invention described above can be any organic solvent widely used in this technical field, such as ketones, aliphatic or cycloaliphatic hydrocarbons, aromatic hydrocarbons, ethers, esters, or alcohols. One or more organic solvents can be used in the acrylate composition, the diffuse coating, and the refractive index matching coating. Suitable solvents include, for example, acetone, butanone, cyclohexanone, methyl isobutyl ketone, hexane, cyclohexane, dichloromethane, dichloroethane, toluene, xylene, propylene glycol methyl ether, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isopropanol, n-butanol, isobutanol, cyclohexanol, diacetone alcohol, propylene glycol methyl ether acetate, or tetrahydrofuran, or their analogues, but are not limited thereto.

[0079] The aforementioned coating methods can include, for example, roller coating, doctor blade coating, dip coating, roller coating, spin coating, spray coating, slot coating, and other coating methods widely used in this technical field.

[0080] The protective layer obtained by the aforementioned method is preferably continuously laminated in a roll-to-roll manner. In an embodiment, when the polarizing plate of the present invention is laminated to the display side of the display, the angle between the absorption axis of the polarizing layer and the horizontal viewing angle direction of the display is between 0° and 45°.

[0081] The following embodiments are provided to further illustrate the present invention, but the scope of the invention is not limited thereto.

[0082] Example

[0083] Preparation Example 1: Preparation of Acrylic Adhesive Resin

[0084] 42 parts by weight of polyurethane acrylate oligomer (functionality 6, molecular weight approximately 1,600, viscosity approximately 36,000 cps (25°C), purchased from IGM, Taiwan), 4.5 parts by weight of pentaerythritol triacrylate (PETA), 12 parts by weight of dipentaerythritol hexaacrylate (DPHA), 3 parts by weight of cyclotrimethylolpropane methyl acetal acrylate (CTFA), 4 parts by weight of photoinitiator (Chemcure-481, purchased from Heng Chiao Industry, Taiwan), 24.5 parts by weight of ethyl acetate (EAC), and 10 parts by weight of n-butyl acetate (nBAC) were mixed and stirred for 1 hour to form an acrylate-based adhesive resin.

[0085] Example 1

[0086] 154.5 parts by weight of the acrylic adhesive resin prepared in Example 1, and 9.3 parts by weight of amorphous silica microparticles ( The following components were mixed and stirred until uniformly dispersed to form the first coating solution: SS-50B (average particle size 4 μm, refractive index 1.45–1.47, purchased from Tosoh Silicon Chemical Co., Ltd., Japan); 1.7 parts by weight of dispersant (DisperBYK-2150, solid content 5%, solvent: ethyl acetate and propylene glycol methyl ether acetate, purchased from BYK, Germany); 30.9 parts by weight of polyether-modified acrylate copolymer leveling agent (BYK-UV3535, solid content 10%, solvent: ethyl acetate, purchased from BYK, Germany); 7 parts by weight of silica nanoparticle dispersion sol (NanoBYK-3650, average primary particle size 20 nm, solid content 31%, solvent: propylene glycol methyl ether acetate / propylene glycol methyl ether, purchased from BYK, Germany); 38.6 parts by weight of ethyl acetate (EAC); and 108.1 parts by weight of n-butyl acetate (nBAC). The first coating solution was applied to a polyethylene terephthalate (PET) substrate (trade name: O321E, purchased from Mitsubishi Chemical Corporation, Japan) with a birefringence difference (Δn) of 0.043 at 50 μm and an in-plane phase difference R0 (550 nm) of 2136 nm measured under high intensity visible light at a wavelength of 550 nm. After drying, it was subjected to nitrogen atmosphere at 298 mJ / cm². 2 UV lamps with varying radiation doses are used for photocuring to form a diffuse layer with a thickness of 5.5 μm on a PET substrate.

[0087] A second coating solution was formed by mixing and stirring 35 parts by weight of fluorinated and acrylate-modified polysiloxane resin (X-12-2430C, purchased from Shigeobushi Chemical Co., Ltd., Japan), 2 parts by weight of photoinitiator (KIP-160, purchased from IGM Resin, Netherlands), 22 parts by weight of a mixture of organosilicon compounds modified with perfluoropolyether functional groups (X-71-1203E, solid content 20%, solvent: methyl ethyl ketone, purchased from Shigeobushi Chemical Co., Ltd., Japan), 187 parts by weight of hollow silica nanoparticle dispersion sol (Thrulya 4320, solid content 20%, average primary particle size 60 nm, solvent: methyl isobutyl ketone, purchased from Nichibukai Chemical Co., Ltd., Japan), 1377 parts by weight of ethyl acetate (EAC) and 1377 parts by weight of propylene glycol methyl ether acetate (PGMEA) for 10 minutes. Next, the second coating solution is applied onto the diffuser layer, and the film coated with the second solution is dried in an oven at 80°C and then dried under nitrogen atmosphere at 350 mJ / cm². 2 UV lamps with a radiation dose are used for photocuring to obtain a refractive index matching layer with a thickness of approximately 0.13 μm on the diffuse layer. This provides a protective layer with an interference cancellation layer for use in polarizing plates.

[0088] The protective layer obtained in Example 1 was subjected to the following optical analysis, and the results are listed in Table 1.

[0089] Haze measurement: Haze was evaluated using an NDH-2000 (Nippon Denshoku Corp.) according to the description in JIS K7136.

[0090] Measurement of internal and surface haze: A 40μm TAC film (Fujifilm, T40UZ) was applied to the surface of the protective layer using transparent optical adhesive to flatten the uneven surface of the protective layer. In this state, the haze was evaluated using an NDH-2000 (Nippon Denshoku Corp.) according to the description of JIS K7136 to obtain the internal haze value. Then, the surface haze value was obtained by subtracting the internal haze value from the total haze value.

[0091] Transmittance measurement: Transmittance was evaluated using an NDH-2000 (Nippon Denshoku Corp.) according to the description in JISK7361.

[0092] Gloss measurement: The protective layer was bonded to a black acrylic plate, which served as an alternative to the display panel with orthogonal polarizing plates, via a transparent optical adhesive. The gloss was measured using a BYK micro-gloss meter, according to the description of JIS Z 8741, with gloss values ​​selected at 20, 60, and 85 degrees.

[0093] Sharpness measurement: Cut the protective layer into 5x8 cm pieces. 2 Size was measured using a SUGA ICM-IT image sharpness meter according to the description of JIS K7374, and the values ​​of the slit measurements at 0.125mm, 0.25mm, 0.50mm, 1.00mm and 2.00mm were summed.

[0094] Reflectivity Measurement: Similarly, the protective layer was bonded to a black acrylic plate that served as a replacement for the display panel with an orthogonal polarizer. The average reflectivity of the protective layer in SCI mode and the average reflectivity of SCE mode were measured using a HITACHI U-4150 spectrophotometer in the wavelength range of 380 to 780 nm.

[0095] Evaluation of Rainbow Pattern Degree: The protective layer was bonded to an 8K LCD monitor (SHARP, AQUOS LC-70X500T) with the surface protective layer removed using transparent optical adhesive. The rainbow pattern degree of the protective layer used for the polarizing plate was evaluated at 0 degrees and 60 degrees at the L255 brightness level of the LCD monitor. If there was no obvious rainbow pattern, it was rated as "extremely excellent" (◎). If there was a slight rainbow pattern but no problem in use, it was rated as "excellent" (〇). If there was an obvious rainbow pattern, it was rated as "poor" (×).

[0096] Evaluation of white fog sensation: The protective film is attached to the black acrylic board with transparent optical adhesive. The white fog sensation of the optical film is evaluated from 0-degree and 60-degree viewing angles. If there is no obvious white fog sensation, it is rated as "extremely excellent" (◎). If there is a slight white fog sensation but no problem in use, it is rated as "excellent" (〇). If there is an obvious white fog sensation, it is rated as "poor" (×).

[0097] Example 2

[0098] 120.3 parts by weight of the acrylic adhesive resin prepared in Example 1, 9.6 parts by weight of polystyrene microparticles (XX-40IK, average particle size 3 μm, refractive index 1.59, purchased from Sekisui Chemicals Co., Ltd., Japan), and 9.6 parts by weight of amorphous silica microparticles (… A first coating solution was prepared by mixing and stirring SS-50B, 2.6 parts by weight of dispersant (DisperBYK-2150), 8.1 parts by weight of polyether-modified acrylate copolymer leveling agent (BYK-UV3535), 5.4 parts by weight of silica nanoparticle dispersion sol (NanoBYK-3650), 48.1 parts by weight of ethyl acetate (EAC), and 96.2 parts by weight of n-butyl acetate (nBAC) for 1 hour to achieve uniform dispersion. This first coating solution was then applied to a polyethylene terephthalate (PET) substrate (trade name: O321E, purchased from Mitsubishi Chemical Corporation, Japan) with a birefringence difference (Δn) of 0.043 at 50 μm and an in-plane phase difference value R0 (550 nm) of 2136 nm. After drying, the solution was subjected to nitrogen atmosphere at 298 mJ / cm². 2 UV lamps with varying radiation doses are used for photocuring to form a diffuse layer with a thickness of 5.5 μm on a PET substrate.

[0099] The second coating solution was prepared in the same manner as in Example 1. This second coating solution was then applied to the diffuser layer, and the film coated with the second solution was dried in an oven at 80°C. The film was then dried under nitrogen atmosphere at a pressure of 350 mJ / cm². 2 UV lamps with a radiation dose are used for photocuring to obtain a refractive index matching layer with a thickness of approximately 0.13 μm on the diffuse layer. This provides a protective layer with an interference cancellation layer for use in polarizing plates.

[0100] The protective layer obtained in Example 2 was subjected to optical analysis according to the detection method of Example 1, and the results are listed in Table 1.

[0101] Example 3

[0102] 100 parts by weight of the acrylic adhesive resin prepared in Example 1, and 7.5 parts by weight of amorphous silica microparticles ( SS-50B, with an average particle size of 4 μm and a refractive index of 1.45–1.47, was purchased from Tosoh Silicon Chemical Co., Ltd., Japan. 2.06 parts by weight of dispersant (DisperBYK-2150), 6.7 parts by weight of polyether-modified acrylate copolymer leveling agent (BYK-UV3535), 4.5 parts by weight of silica nanoparticle dispersion sol (NanoBYK-3650), 80 parts by weight of ethyl acetate (EAC), and 20.2 parts by weight of n-butyl acetate (nBAC) were mixed and stirred for 1 hour to ensure uniform dispersion, thus forming the first coating solution. This first coating solution was applied to a polyethylene terephthalate (PET) (trade name: O321E, purchased from Mitsubishi Chemical Corporation, Japan) substrate with a 50 μm birefringence difference (Δn) of 0.043 and an in-plane phase difference value R0 (550 nm) of 2136 nm, identical to that in Examples 1 and 2. After drying, it was subjected to nitrogen atmosphere at 298 mJ / cm². 2 UV lamps with varying radiation doses are used for photocuring to form a diffuse layer with a thickness of 5.2 μm on a PET substrate.

[0103] A second coating solution was prepared by mixing and stirring 18.3 parts by weight of a fluorinated and acrylate-modified polysiloxane resin (X-12-2430C), 6.1 parts by weight of a hexafunctional fluorinated polyurethane oligomer (LR6000, purchased from Miwon, South Korea), 1.6 parts by weight of a photoinitiator (KIP-160), 15 parts by weight of a mixture of (meth)acrylyl-modified organosilicon compounds with perfluoropolyether functional groups (X-71-1203E), 160 parts by weight of a hollow silica nanoparticle dispersion sol (Thrulya 4320), and 2144 parts by weight of ethyl acetate (EAC) for 10 minutes. This second coating solution was then applied to a diffuser layer, and the coated film was dried in an oven at 80°C, followed by drying under nitrogen atmosphere at 350 mJ / cm². 2 UV curing with a UV lamp of varying radiation dose is used to obtain a refractive index matching layer with a thickness of approximately 0.13 μm on the diffuse layer. This provides a protective layer with an interference cancellation layer for use in polarizing plates.

[0104] The protective layer obtained in Example 3 was subjected to optical analysis according to the detection method of Example 1, and the results are listed in Table 1.

[0105] Example 4

[0106] The protective layer was prepared in the same manner as in Example 1, except that a polyethylene terephthalate (PET) substrate (trade name: O321E, purchased from Mitsubishi Chemical Corporation, Japan) with a birefringence difference (Δn) of 0.049 and an in-plane phase difference value R0 (550nm) of 3654nm was used. A diffuse layer with a thickness of 4μm was formed on the PET substrate, and a refractive index matching layer with a thickness of approximately 0.13μm was coated on the diffuse layer. Thus, a protective layer with an interference cancellation layer for use in a polarizing plate was obtained.

[0107] The protective layer obtained in Example 4 was subjected to optical analysis according to the detection method of Example 1, and the results are listed in Table 1.

[0108] Example 5

[0109] The protective layer was prepared in the same manner as in Example 2, except that a polyethylene terephthalate (PET) substrate (trade name: O321E, purchased from Mitsubishi Chemical Corporation, Japan) with a birefringence difference (Δn) of 0.049 and an in-plane phase difference value R0 (550nm) of 3654nm was used. A diffuse layer with a thickness of 7μm was formed on the PET substrate, and a refractive index matching layer with a thickness of approximately 0.13μm was coated on the diffuse layer. Thus, a protective layer with an interference cancellation layer for use in a polarizing plate was obtained.

[0110] The protective layer obtained in Example 5 was subjected to optical analysis according to the detection method of Example 1, and the results are listed in Table 1.

[0111] Comparative Examples 1 and 2

[0112] Polyethylene terephthalate (PET) substrates (trade name: O321E, purchased from Mitsubishi Chemical Corporation, Japan) with a 50 μm birefringence difference (Δn) of 0.043 and an in-plane phase difference R0 (550 nm) of 2136 nm, and uncoated with any coating, and polyethylene terephthalate (PET) substrates (trade name: O321E, purchased from Mitsubishi Chemical Corporation, Japan) substrates with a 75 μm birefringence difference (Δn) of 0.049 and an in-plane phase difference R0 (550 nm) of 3654 nm, were tested for transmittance, haze, SCI diffuse reflection, and specular average reflectance (R0) according to the detection method in Example 1. SCI (%) and SCE diffuse mean reflectance (R) SCE The results of the analysis (,%) are listed in Table 1.

[0113] Table 1 Optical detection results of Examples 1 to 5 and Comparative Examples 1 to 2

[0114]

[0115] Example 6

[0116] The protective layer was prepared in the same manner as in Example 1, except that a polyethylene terephthalate (PET) substrate (trade name: O321E, purchased from Mitsubishi Chemical Corporation, Japan) with a birefringence difference (Δn) of 0.052 and an in-plane phase difference value R0 (550nm) of 5168nm was used. A diffuse layer with a thickness of 5.0μm was formed on the PET substrate, and a refractive index matching layer with a thickness of approximately 0.13μm was coated on the diffuse layer. Thus, a protective layer with an interference cancellation layer for use in a polarizing plate was obtained.

[0117] The protective layer obtained in Example 6 was subjected to optical analysis according to the detection method of Example 1, and the results are listed in Table 2.

[0118] Example 7

[0119] The protective layer was prepared in the same manner as in Example 1, except that a polyethylene terephthalate (PET) substrate (trade name: V7610, purchased from Sunkyung Chemical Co., Ltd., South Korea) with a birefringence difference (Δn) of 0.071 and an in-plane phase difference value R0 (550nm) of 3526nm was used. A diffuse layer with a thickness of 6.6μm was formed on the PET substrate, and a refractive index matching layer with a thickness of approximately 0.13μm was coated on the diffuse layer. Thus, a protective layer with an interference cancellation layer for use in a polarizing plate was obtained.

[0120] The protective layer obtained in Example 7 was subjected to optical analysis according to the detection method of Example 1, and the results are listed in Table 2.

[0121] Example 8

[0122] The protective layer was prepared in the same manner as in Example 1, except that a polyethylene terephthalate (PET) substrate (trade name: V7610P, purchased from Sunkyung Chemical Co., Ltd., South Korea) with a birefringence difference (Δn) of 0.034 and an in-plane phase difference value R0 (550nm) of 2514nm was used. A diffuse layer with a thickness of 6.0μm was formed on the PET substrate, and a refractive index matching layer with a thickness of approximately 0.13μm was coated on the diffuse layer. Thus, a protective layer with an interference cancellation layer for use in a polarizing plate was obtained.

[0123] The protective layer obtained in Example 8 was subjected to optical analysis according to the detection method of Example 1, and the results are listed in Table 2.

[0124] Example 9

[0125] The protective layer was prepared in the same manner as in Example 2, except that a polyethylene terephthalate (PET) substrate (trade name: V7610P, purchased from Sunkyung Chemical Co., Ltd., South Korea) with a birefringence difference (Δn) of 0.034 and an in-plane phase difference value R0 (550nm) of 2514nm was used. A diffuse layer with a thickness of 6.4μm was formed on the PET substrate, and a refractive index matching layer with a thickness of approximately 0.13μm was coated on the diffuse layer. Thus, a protective layer with an interference cancellation layer for use in a polarizing plate was obtained.

[0126] The protective layer obtained in Example 9 was subjected to optical analysis according to the detection method of Example 1, and the results are listed in Table 2.

[0127] Comparative Example 3

[0128] Polyethylene terephthalate (PET) substrates (trade name: V7610, purchased from Sunkyung Chemical Co., Ltd., South Korea) with a 50 μm birefringence difference (Δn) of 0.071 and an in-plane phase difference R0 (550 nm) of 3526 nm, without any coating, were tested for transmittance, haze, SCI diffuse reflection, and specular average reflectance (R0) according to the testing method in Example 1. SCI (%) and SCE diffuse mean reflectance (R) SCE The results of the analysis (,%) are listed in Table 2.

[0129] Table 2 Optical detection results of Examples 6 to 9 and Comparative Example 3

[0130]

[0131]

[0132] The measurement data in Tables 1 and 2 both show that when paired with a polyester substrate with a birefringence difference of less than 0.10, and its reflectivity conforms to the relationship (R... SCI -R SCE )≦1.0%, and R SCE / (R SCI -R SCE When the total haze is ≥1.6, the total haze of the embodiments is between 30% and 75%. Regardless of whether the haze is contributed by internal haze or surface haze, it can improve the rainbow effect caused by interference from the low R0 (550nm) birefringent substrate in the external ambient light. Even though the R0 (550nm) of the polyethylene terephthalate (PET) used is only about 2000nm, no rainbow effect was observed. This makes the applicability of the birefringent substrate less limited by the in-plane phase difference, and there is no need to select special products with a higher in-plane phase difference R0 (550nm). Moreover, the light transmittance and appearance of the protective layer can be maintained at a level comparable to the comparative example without the interference cancellation layer, and the white haze is not easily detected.

[0133] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A polarizing plate, comprising: The polarizing layer has an absorption axis; and A protective layer is disposed on the display surface of the polarizing layer, the protective layer comprising: A birefringent substrate, adjacent to the polarizing layer, having mutually perpendicular slow and fast axes, and a birefringence difference of no more than 0.10; and An interference cancellation layer is disposed on the display side surface of the birefringent substrate, comprising a diffuse layer disposed on the birefringent substrate and a refractive index matching layer disposed on the diffuse layer; in, The total haze of the protective layer is between 30% and 75%, and the diffuse average reflectance R of the protective layer is... SCE The reflectance is between 0.8% and 2.0%, and the reflectance satisfies the following relationship: (R SCI -R SCE ) ≦1.0%, and R SCE / (R SCI -R SCE )≧1.6, where R SCI R represents the diffuse and specular average reflectance of the protective layer. SCE This represents the diffuse average reflectivity of the protective layer.

2. The polarizing plate according to claim 1, wherein the angle between the absorption axis of the polarizing layer and the horizontal viewing angle direction of the display is between 0° and 45°.

3. The polarizing plate according to claim 1, wherein the birefringence difference of the birefringent substrate is between 0.02 and 0.

09.

4. The polarizing plate according to claim 1, wherein the protective layer (R) SCI -R SCE The percentage is between 0.1% and 1.0%.

5. The polarizing plate according to claim 1, wherein the diffuse layer has a refractive index n1, the refractive index matching layer has a refractive index n2, and the refractive index n2 is less than the refractive index n1.

6. The polarizing plate according to claim 5, wherein the refractive index n1 is between 1.50 and 1.70, and the refractive index n2 is between 1.20 and 1.

50.

7. The polarizing plate according to claim 1, wherein the total haze of the protective layer is the sum of the surface haze of the protective layer and the internal haze of the protective layer, wherein the surface haze of the protective layer is greater than 25%.

8. The polarizing plate according to claim 1, wherein the thickness of the diffuse layer is between 2 μm and 10 μm.

9. The polarizing plate according to claim 1, wherein the thickness of the refractive index matching layer is between 0.1 μm and 0.3 μm.

10. The polarizing plate according to claim 1, wherein the thickness of the birefringent substrate is between 10 μm and 150 μm.

11. The polarizing plate according to claim 1, wherein the birefringent substrate is a uniaxially or biaxially extended polyester film.

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