Polarizing plate for display view side

Abstract

The invention provides a polarizing plate for a display viewing side. The polarizing plate comprises a polarizing layer and a polyester protective film located on the front side of the polarizing layer. The polyester protective film comprises: a polyester substrate having an in-plane phase difference of less than or equal to 1200 nm and an average refractive index np; the first undercoat layer is arranged on one side of the polyester base material and has a first refractive index n1; the second priming coat is arranged on the other side of the polyester base material, is adjacent to the polarizing layer and has a second refractive index n2; wherein the refractive indexes of the polyester base material, the first priming coat and the second priming coat meet the relational expression: npgt; n1gt; n1gt; and (np-n1) / (np-n2) is less than or equal to 0.7, so that interference rainbow lines are reduced.

Description

Technical Field

[0001] This invention relates to a polarizing plate for the viewing side of a display, which can reduce the generation of interference rainbow patterns. Background Technology

[0002] Due to the current trends in display devices such as liquid crystal displays (LCDs), organic light-emitting diode displays (OLEDs), and micro LED displays towards higher brightness, thinner and lighter designs, and greater flexibility, coupled with increasing demands for display quality, the functional optical film structures used in displays have become more complex, and the requirements for optical matching between different film layers have become increasingly stringent. To provide polarizing plates with better resistance to water vapor penetration and mechanical strength, whether for linear polarizers in LCDs or circular polarizers in diode displays, the protective capabilities and optical properties of the outer protective film should not be sacrificed for these benefits. It has been suggested to use polyester films with crystalline properties instead of triacetate (TAC) films as protective films for polarizing plates. However, polyester films, such as the common polyethylene terephthalate (PET) film, have a high degree of crystallinity due to their benzene ring structure and a high inherent birefringence after stretching. Therefore, when used as protective films, they can affect the display quality of the monitor, such as causing interference rainbow patterns. To suppress the generation of interference rainbow patterns, polyester films generally need to be polyethylene terephthalate films with an in-plane phase difference (R0) of at least 3000 nm, and surface treatment layers with high haze or high surface roughness should be used to destroy the interference of the transmitted light. More preferably, polyethylene terephthalate films with an in-plane phase difference of up to 8000 nm or above should be used to reduce the interference of interference rainbow patterns.

[0003] However, high in-plane phase difference polyester films with surface coatings exhibiting high haze or high surface roughness significantly impact the image quality and aesthetics of displays. Furthermore, to obtain birefringent films with extremely high in-plane phase difference values, polyester films manufactured using uniaxial or biaxial high elongation processes or with higher thicknesses (e.g., greater than 100 μm) are required to achieve display quality. However, birefringent polyester films produced with high elongation ratios often exhibit reduced tensile strength and inconsistent thermal shrinkage ratios in the elongation and width directions, both of which affect their protective properties. When paired with a polarizing layer also manufactured with high elongation ratios, the stress balance of the laminated polarizing plate must be considered to avoid unexpected stress unevenness patterns or color patches. On the other hand, while increasing the thickness of the polyester film to improve the in-plane phase difference is a more direct approach, it does not align with the current trend of display devices becoming thinner and lighter. Furthermore, if applied to displays with flexible or curved edges, increasing the thickness of the protective layer will alter the overall bending stress distribution of the display, increasing the design difficulty in compatibility with other functional optical film layers.

[0004] Therefore, the present invention provides a polarizing plate for the viewing side of a display, which includes a polyester protective film with a low in-plane phase difference, such as a polyethylene terephthalate film with R0 < 1200 nm. When the polyester protective film is applied to the front side of the polarizing plate, it can still have a good anti-interference rainbow effect without the need for a surface treatment layer with high haze or high surface roughness. Summary of the Invention

[0005] One embodiment of the present invention provides a polarizing plate for the viewing side of a display, comprising a polarizing layer and a polyester protective film located in front of the polarizing layer, wherein the polyester protective film comprises a polyester substrate, has an in-plane phase difference of no more than 1200 nm and an average refractive index n p A first base coating layer is disposed on one side of the polyester substrate and has a first refractive index n1; and a second base coating layer is disposed on the other side of the polyester substrate and adjacent to the polarizing layer, and has a second refractive index n2; wherein the refractive indices of the polyester substrate, the first base coating layer, and the second base coating layer satisfy the following relationship: n p >n1>n2, and (n p -n1) / (n p -n2)≤0.7.

[0006] In a polarizing plate according to one embodiment of the present invention, the birefringence difference (Δn) of the polyester substrate is between 0.003 and 0.015.

[0007] In another embodiment of the polarizing plate of the present invention, the difference between the first refractive index n1 of the first base coating and the second refractive index n2 of the second base coating of the polyester substrate satisfies the relationship: (n1-n2) is greater than or equal to 0.05.

[0008] In another embodiment of the polarizing plate of the present invention, the first refractive index n1 of the first base coating of the polyester substrate is between 1.56 and 1.65, and the second refractive index n2 of the second base coating is between 1.51 and 1.60.

[0009] In another embodiment of the polarizing plate of the present invention, the thickness of the polyester substrate is between 10 μm and 80 μm.

[0010] In another embodiment of the polarizing plate of the present invention, the thickness of the first base coating and the second base coating are both between 0.1 μm and 0.3 μm.

[0011] In another embodiment of the polarizing plate of the present invention, the polyester substrate is a uniaxially or biaxially stretched polyester film.

[0012] In another embodiment of the polarizing plate of the present invention, the polarizing layer is an iodine-based or dye-based extended polarizing layer or a coated polarizing layer.

[0013] In another embodiment of the polarizing plate of the present invention, the first base layer of the protective layer further includes an anti-glare layer, the total haze of which is less than or equal to 30%.

[0014] In another embodiment of the polarizing plate of the present invention, the thickness of the anti-glare layer is between 2 μm and 10 μm.

[0015] In another embodiment of the polarizing plate of the present invention, the surface of the anti-glare layer further includes an anti-reflective layer.

[0016] In another embodiment of the polarizing plate of the present invention, the thickness of the anti-reflective layer is between 0.1 μm and 0.3 μm.

[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 one embodiment of the polarizing plate of the present invention is shown; Figure 2 A schematic diagram of one embodiment of the polarizing plate of the present invention is shown; Figure 3 A schematic diagram of another embodiment of the polarizing plate of the present invention is shown. Detailed Implementation

[0019] 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 one embodiment without further description or explanation.

[0020] The advantages, features, and technical methods of the present invention will be more readily understood by referring to exemplary embodiments, and the invention may be implemented in different forms. Therefore, it should not be understood as limited to the embodiments set forth herein. Rather, the embodiments provided will enable this disclosure to more thoroughly and completely convey the scope of the invention to those skilled in the art, and the invention will be defined only by the appended claims.

[0021] Unless otherwise defined, all terms (including technical and scientific terms) and proper nouns used below shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and terms such as those defined in commonly used dictionaries shall be understood to have the same meaning as the content of the relevant field, and shall not be interpreted in an overly idealized or overly formal sense unless explicitly defined below.

[0022] In this article, the term "front side of polarizing layer" refers to the side of the polarizing layer of a display polarizing plate that faces the viewer of the display.

[0023] The present invention discloses a polarizing plate for the viewing side of a display, comprising a polarizing layer and a polyester protective film located in front of the polarizing layer, which can provide the display surface with excellent resistance to water vapor penetration and mechanical strength. Although the polarizing plate of the present invention uses a polyester protective film, it can still achieve excellent light transmittance and reduce interface reflection and image light intensity loss, and can avoid interference rainbow patterns on both sides of the polyester protective film caused by polarized light formed by image light or external ambient light passing through the polarizing layer.

[0024] like Figure 1 As shown, one embodiment of the present invention provides a polarizing plate 100 for the viewing side of a display, which includes a polarizing layer 110 and a polyester protective film 200 located in front of the polarizing layer 110. The polyester protective film 200 includes a polyester substrate 210, having an in-plane phase difference of no more than 1200 nm and an average refractive index n. p A first base coating 220 is disposed on one side of the polyester substrate 210 and has a first refractive index n1; and a second base coating 230 is disposed on the other side of the polyester substrate 210 and has a second refractive index n2, wherein the refractive indices of the polyester substrate 210, the first base coating 220, and the second base coating 230 satisfy the following relationship: n p >n1>n2, and (n p -n1) / (n p -n2)≤0.7, and the polarizing layer 110 is disposed on the second base layer 230 side of the polyester protective film 200.

[0025] The polyester substrate 210 suitable for the polarizing plate of the present invention has an in-plane phase difference of not more than 1200 nm, and its average refractive index (n) p The light transmittance is between approximately 1.60 and 1.70, and is at least 85%, preferably more than 88%. Furthermore, the polyester protective film 200 of the present invention can use polyester substrate 210 of different thicknesses according to the application requirements, and its thickness is preferably between 10 μm and 80 μm.

[0026] In the polarizing plate of the present invention, the first refractive index n1 of the first base coating 220 of the polyester protective film 200 is less than the average refractive index n of the polyester substrate 210. p To achieve a lower surface reflectivity. In one embodiment of the polarizing plate of the present invention, the first refractive index n1 of the first base coating 220 is between 1.52 and 1.65, preferably between 1.56 and 1.65.

[0027] Furthermore, the second refractive index n2 of the second base coating layer 230 of the polyester protective film 200 is also less than the average refractive index n of the polyester substrate 210. p To achieve a lower interfacial reflectivity between the second base coating 230 and the polyester substrate 210. Furthermore, this second base coating 230 is used to bond with the polarizing layer 110. Since the polarizing layer 110 is generally an extended polyvinyl alcohol film bonded to a protective film via a polyvinyl alcohol adhesive layer, where the refractive indices of both the polyvinyl alcohol film and the polyvinyl alcohol adhesive layer are between approximately 1.50 and 1.52, the second refractive index n2 of the second base coating 230 is preferably close to the refractive indices of the polyvinyl alcohol film and the polyvinyl alcohol adhesive layer, i.e., the second refractive index n2 of the second base coating 230 is between 1.51 and 1.60, preferably between 1.52 and 1.60, to match the refractive indices of the polyvinyl alcohol film and the polyvinyl alcohol adhesive layer and reduce the interfacial reflectivity with the polarizing layer. Moreover, the second refractive index n2 of the second base coating 230 needs to be less than the first refractive index n1 of the first base coating 220, i.e., n p >n1>n2, so that the ratio of the refractive index difference between the polyester substrate and the bottom coating on both sides must satisfy the following relationship: (n p -n1) / (n p -n2)≤0.7, which helps to reduce the interfacial reflectivity on both sides of the polyester substrate 210 and at the same time reduce the occurrence of interference rainbow patterns.

[0028] In the polarizing plate of the present invention, the applicable polarizing layer can be, for example, an iodine-based or dye-based extended polarizing layer or a coated polarizing layer. When bonded to a polyester substrate with an in-plane phase difference of no more than 1200 nm to form a polarizing plate, the problems of mismatch between the absorption axis of the polarizing layer and the extension axis of the polyester substrate, or the stress distribution pattern problems caused by the inconsistent anisotropic shrinkage stress of the polyester substrate with extremely high in-plane phase difference, can be avoided.

[0029] The average refractive index of the polyester substrate is known to be between approximately 1.60 and 1.70. Therefore, the refractive index difference between the two sides and the interfaces with air and the polarizing layer is relatively large. Furthermore, due to its birefringence, it easily produces high-intensity coherent light, resulting in interference rainbow patterns. Therefore, if the ratio of the refractive index difference between the polyester substrate and the undercoating layers on both sides does not satisfy the relationship: (n...) p -n1) / (n p -n2)≤0.7, representing the refractive index difference (n) between the polyester substrate and the first base coating.p If the refractive index of -n1 is too high, the surface reflectivity of the polyester substrate will be high, or the refractive index difference between the polyester substrate and the second base coating will be too high (n p When the refractive index (-n2) is too low, it relatively increases the refractive index difference between the polarizing layer and the polyester substrate interface, reducing the transmittance of image light between the film layers. This makes it difficult to effectively reduce interference rainbow patterns when using a polyester substrate 210 with an in-plane phase difference of no more than 1200 nm, thus interfering with the quality of the image light emitted by the display. The polarizing plate of this invention does not use a special polyester protective film with an extremely high in-plane phase difference. It can still achieve good anti-interference rainbow pattern effects without the need for a surface treatment layer with high haze or high surface roughness. It can not only obtain excellent light transmittance and reduce interface reflection and image light intensity loss, but also, when combined with a polarizing layer with a high elongation ratio, avoid the problem of texture caused by uneven stress due to axial matching.

[0030] In a preferred embodiment of the polarizing plate of the present invention, the difference between the first refractive index n1 of the first base coating 220 of the polyester protective film and the second refractive index n2 of the second base coating 230 satisfies the relationship: (n1-n2) is greater than or equal to 0.05, which reduces the coherence of light passing through the interfaces on both sides of the polyester substrate, and makes it less likely for light of different wavelengths to produce interference rainbow patterns due to enhanced interference.

[0031] In the polarizing plate of the present invention, the first base coating 220 comprises, but is not limited to, a coating formed of acetalized polyvinyl alcohol, polyurethane, urethane, polyether resin, polyacrylic resin, isocyanate, or combinations thereof, and may selectively increase its refractive index to a desired range by adding metal oxide particles, benzene ring compounds, etc. to the coating. In one embodiment of the polarizing plate of the present invention, the thickness of the first base coating 220 and the second base coating 230 can be between 0.1 μm and 0.3 μm. Base coatings within this thickness range can change the refractive index on both sides of the polyester substrate 210 without significantly increasing the thickness of the polyester protective film 200, thus not affecting the stress distribution after the polarizing plate is formed.

[0032] The polyester substrate 210 of the present invention is a polyester substrate with an in-plane phase difference of no more than 1200 nm. Because this polyester substrate 210 does not belong to the category of high in-plane phase difference substrates, it is not necessary to use a high elongation process to increase the birefringence difference (Δn) between the orthogonal elongation direction and the width direction of the polyester film. Therefore, the polyester substrate 210 suitable for the present invention can be a uniaxially elongated or biaxially elongated polyester film, and its birefringence difference is preferably between 0.003 and 0.015, representing that the polyester film is a uniaxially elongated or biaxially elongated low in-plane phase difference polyester film produced by a low elongation process. Because the polyester substrate of the present invention is a polyester film produced by a low elongation process, it has excellent tensile strength and a uniformly consistent heat shrinkage ratio in the elongation direction and the width direction. When used in polarizing plates, regardless of whether the polarizing layer is a high-elongation-ratio extended polarizing layer or a coating polarizing layer that does not require elongation, it can make the stress distribution on the polarizing plate more uniform, provide better protection, and is also conducive to its application in flexible display devices.

[0033] In the polarizing plate 200 of the present invention, the second base coating 230 of the polyester protective film 200 may use a coating with easy adhesion to facilitate bonding with the polarizing layer and the polyvinyl alcohol adhesive layer, and have a similar refractive index. For example, a coating may be used that includes, but is not limited to, acetalized polyvinyl alcohol, polyurethane, urethane, polyether resin, polyacrylic resin, isocyanate or a combination thereof.

[0034] In another embodiment of the present invention, the first base coating of the polyester protective film may further include optical functional layers such as a hard coating layer, an anti-glare layer, and an anti-reflective layer. (See reference) Figure 2 In one embodiment of the polarizing plate 300 of the present invention, an anti-glare layer 310 may be further applied to the first base coating 220 of the polyester protective film 200. Since the polarizing plate 300 of the present invention does not require the high haze of the anti-glare layer 310 to reduce the light coherence across the two surfaces of the polyester substrate 210, an anti-glare layer 310 with a low total haze can be used. In a preferred embodiment, the total haze of the anti-glare layer 310 may be less than or equal to 30%, preferably less than or equal to 20%, and more preferably less than or equal to 5%. Therefore, even with a low total haze, the anti-interference rainbow effect can still be achieved, and the image quality will not be degraded or the display will appear foggy due to excessive haze, resulting in poor visual perception.

[0035] The anti-glare layer applicable to this invention can be achieved by an anti-glare coating. Generally, an acrylic binder resin mixed with microparticles is applied to a first base layer to form an uneven surface, achieving the anti-glare effect. The microparticles used can be organic microparticles, inorganic micron-sized particles, or combinations thereof.

[0036] Suitable organic microparticles are polymethyl methacrylate resin microparticles, polystyrene resin microparticles, styrene-methyl methacrylate copolymer microparticles, polyethylene resin microparticles, epoxy resin microparticles, polysiloxane resin microparticles, polyvinylidene fluoride resin, polyvinyl fluoride resin microparticles, or combinations thereof, with a particle size between 0.3 µm and 6 µm. Suitable inorganic microparticles are aluminosilicates, talc, mica, silica, or combinations thereof, with a particle size between 0.01 µm and 3 µm.

[0037] In another embodiment of the polarizing plate 300 of the present invention, the thickness of the anti-glare layer 310 is between 2 μm and 10 μm, preferably between 2 μm and 8 μm.

[0038] refer to Figure 3 In another embodiment of the polarizing plate 400 of the present invention, the surface of the anti-glare layer 310 may further include an anti-reflection layer 410 to further reduce the surface reflectivity and avoid reflecting strong light. The anti-glare layer 310 with surface haze also has a certain leveling property, which can make the gloss of the display better.

[0039] The anti-glare layer applicable to the present invention can be achieved by an anti-glare coating. Generally, an acrylic binder resin mixed with nano-silica particles with a particle size between 0.05 µm and 0.3 μm can be used to coat the anti-glare layer 310 to achieve an anti-reflective effect. The thickness of the anti-reflective layer 410 is between 0.1 μm and 0.3 μm.

[0040] The following embodiments are provided to further illustrate the present invention, but the scope of the invention is not limited thereto. Example

[0041] Preparation Example 1: Preparation of Acrylic Adhesive Resin 42 parts by weight of polyurethane acrylate oligomer (functionality 6, molecular weight approximately 2,600, viscosity approximately 62,000 cps (25°C), purchased from Miwon Specialty Chemical Co., Ltd, Korea), 4.5 parts by weight of pentaerythritol triacrylate (PETA), 12 parts by weight of dipentaerythritol hexaacrylate (DPHA), 3 parts by weight of isobornyl acrylate (IBOA), 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.

[0042] Preparation Example 2: Preparation of Anti-glare Coating I 220 parts by weight of the acrylate-based adhesive resin prepared in Example 1, 2.3 parts by weight of polymethyl methacrylate microparticles (SSX-102, average particle size 2 μm, refractive index 1.49, purchased from Sekisui Chemicals Co., Ltd., Japan), 15.1 parts by weight of silica nanoparticle dispersion sol (MEK-ST-UP, solid content 20%, solvent: methyl ethyl ketone, purchased from Nissan Chemical, Japan) with an average primary particle size of 9 nm to 15 nm and connected as long chains of 40 nm to 100 nm, 7.5 parts by weight of acrylate-ether-based surfactant (BYK-UV3535, solid content 10%, solvent: ethyl acetate, purchased from BYK, Germany), and 3.1 parts by weight of silica nanoparticle dispersion sol (NanoBYK-3650, average primary particle size 20 nm to 100 nm) were prepared. nm, with a solid content of 31%, and solvents of propylene glycol methyl ether acetate / propylene glycol methyl ether (purchased from BYK, Germany), 64 parts by weight of ethyl acetate (EAC) and 118 parts by weight of n-butyl acetate (nBAC), were mixed and stirred for 1 hour to disperse them evenly, thus forming anti-glare coating liquid I.

[0043] Preparation Example 3: Preparation of Anti-glare Coating II 220 parts by weight of the acrylate-based adhesive resin prepared in Example 1, 16.2 parts by weight of methyl methacrylate and styrene copolymer microparticles (XX-49IK, average particle size 5 μm, refractive index 1.545, purchased from Sekisui Chemicals Co., Ltd., Japan), 4.2 parts by weight of methyl methacrylate and styrene copolymer microparticles (XX-50IK, average particle size 3.5 μm, refractive index 1.555, purchased from Sekisui Chemicals Co., Ltd., Japan), 6.0 parts by weight of polyether-modified polydimethylsiloxane leveling agent (BYK-333, solid content 10%, solvent ethyl acetate, purchased from BYK, Germany), and 16.4 parts by weight of silica nanoparticle dispersion sol (NanoBYK-3650, average primary particle size 20 μm). The mixture, containing 31% solids and propylene glycol methyl ether acetate / propylene glycol methyl ether (purchased from BYK, Germany), 41.2 parts by weight of ethyl acetate (EAC), 82.4 parts by weight of n-propyl acetate (nPAC), and 41.2 parts by weight of propylene glycol methyl ether acetate (PGMEA), was mixed and stirred for 1 hour to ensure uniform dispersion, thus forming anti-glare coating II.

[0044] Preparation Example 4: Preparation of Antireflective Layer Solution A mixture of 25.4 parts by weight of fluorinated and acrylate-modified polysiloxane resin (X-12-2430C, purchased from Shigeobushi Chemical Co., Ltd., Japan), 1.6 parts by weight of photoinitiator (KIP-160, purchased from IGM Resin, Netherlands), 103.5 parts by weight of a mixture of (meth)acrylamide-modified organosilicon compounds with perfluoropolyether functional groups (X-71-1203E, solid content 20%, solvent methyl ethyl ketone, purchased from Shigeobushi Chemical Co., Ltd., Japan), 211.5 parts by weight of hollow silica nanoparticle dispersion sol (Thrulya 4320, solid content 20%, average particle size 60 nm, solution methyl isobutyl ketone, purchased from Nichibuki Catalyst Chemical Co., Ltd., Japan), 1772 parts by weight of ethyl acetate (EAC), and 886 parts by weight of propylene glycol methyl ether acetate (PGMEA) was stirred for 10 minutes to form an antireflective layer solution.

[0045] Preparation Example 5: Preparation of Polyethylene Terephthalate Film Polyethylene terephthalate (PET) resin raw material particles with a melting point of 250°C to 260°C were heated to a molten state at 280°C. These particles were then extruded using an extruder (model: DNT-EXT01, purchased from JSW, Japan) and cooled to room temperature to form a uniform PET sheet with no crystallinity and orientation. This PET sheet was then subjected to longitudinal stretching at 100°C using a dry stretching machine (model: MA-08, purchased from Shin Ying Machinery, Taiwan, China) at an elongation ratio of 3.0 to improve its crystallinity and transmittance. Subsequently, it was stretched in the width direction at an elongation ratio of 3.0. This resulted in a biaxially stretched PET film with a transmittance greater than 90%, an average refractive index of 1.66, an in-plane phase difference (R0) of 271 nm, and a thickness of 76 µm. The birefringence difference (Δn) was obtained by dividing the in-plane phase difference by the thickness, resulting in a value of 0.004. Example

[0046] The polyethylene terephthalate film prepared in Example 5 was used as the polyester substrate. A first base coat was formed by coating both sides with a photocurable acrylic resin (model: FL219, purchased from Yung Kuan Chemical Co., Ltd.) with a refractive index of 1.61 (n1) and curing it. A second base coat was formed by coating both sides with a photocurable acrylic resin (model: 660G-40L, purchased from Chang Hsing Materials Industry Co., Ltd.) with a refractive index of 1.51 (n2) and curing it.

[0047] The refractive index of the undercoat of the PET protective film was measured by bonding both sides of the PET protective film to a black acrylic sheet. Using a HITACHI U-4150 spectrophotometer in the wavelength range of 380 nm to 780 nm, the average reflectance of diffuse and specular reflection in SCI mode and the average diffuse reflectance in SCE mode were measured on both sides of the PET protective film. The refractive index of the PET polyester substrate and the thickness of each layer were input into the Spectral Reflectance Calculator (Filmetrics) to calculate the refractive indices of the first and second undercoat layers on both sides of the PET protective film. The measurement results are listed in Table 1.

[0048] The polarizing plate of the present invention is formed by attaching a PET protective film with a base coating on both sides to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials corp.) after the surface protective film has been removed, via transparent optical adhesive with the second base coating surface.

[0049] The polarizing plate was evaluated for interference rainbow patterns. The polarizing plate of this invention was attached to the surface of an Acer 27” Agile-Splendor IPS XV272K LCD display without a viewing-side polarizing plate, and the degree of interference rainbow patterns on the viewing-side polarizing plate was evaluated at a 60-degree viewing angle. If no obvious interference rainbow patterns were observed, the evaluation was "Excellent" (〇); if interference rainbow patterns were observed, the evaluation was "Poor" (╳). The evaluation results are listed in Table 1. Example

[0050] A PET film (model: EBQ-410, purchased from Mitsubishi Chemical Corporation, Japan) with a thickness of 50 µm, an in-plane phase difference of 407 nm, a birefringence difference of 0.008, an average refractive index of 1.66, and a first undercoat with a refractive index of 1.61 and a second undercoat with a refractive index of 1.56 on both sides of the film surface was selected as the PET protective film.

[0051] The polarizing plate of the present invention is formed by attaching a PET protective film with a base coating on both sides to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials corp.) after the surface protective film has been removed, via transparent optical adhesive with the second base coating surface.

[0052] The polarizing plate was evaluated for interference rainbow patterns according to the method described in Example 1, and the results are listed in Table 1. Example

[0053] A PET film (model: EBQ-409, purchased from Mitsubishi Chemical Corporation, Japan) with a thickness of 50 µm, an in-plane phase difference of 456 nm, a birefringence difference of 0.009, an average refractive index of 1.66, and a first undercoat with a refractive index of 1.64 and a second undercoat with a refractive index of 1.56 on both sides of the film surface was selected as the PET protective film.

[0054] The polarizing plate of the present invention is formed by attaching a PET protective film with a base coating on both sides to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials corp.) after the surface protective film has been removed, via transparent optical adhesive with the second base coating surface.

[0055] The polarizing plate was evaluated for interference rainbow patterns according to the method described in Example 1, and the results are listed in Table 1. Example

[0056] A PET film (model: QBN-0017, purchased from Mitsubishi Chemical Corporation, Japan) with a thickness of 66 µm, an in-plane phase difference of 713 nm, a birefringence difference of 0.011, an average refractive index of 1.66, and a first undercoat with a refractive index of 1.61 and a second undercoat with a refractive index of 1.54 on both sides of the film surface was selected as the PET protective film.

[0057] The polarizing plate of the present invention is formed by attaching a PET protective film with a base coating on both sides to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials corp.) after the surface protective film has been removed, via transparent optical adhesive with the second base coating surface.

[0058] The polarizing plate was evaluated for interference rainbow patterns according to the method described in Example 1, and the results are listed in Table 1. Example

[0059] A PET film (model: O700E, purchased from Mitsubishi Chemical Corporation, Japan) with a thickness of 75 µm, an in-plane phase difference of 1080 nm, a birefringence difference of 0.014, an average refractive index of 1.66, and a first undercoat with a refractive index of 1.65 and a second undercoat with a refractive index of 1.52 on both sides of the film surface was selected as the PET protective film.

[0060] The polarizing plate of the present invention is formed by attaching a PET protective film with a base coating on both sides to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials corp.) after the surface protective film has been removed, via transparent optical adhesive with the second base coating surface.

[0061] The polarizing plate was evaluated for interference rainbow patterns according to the method described in Example 1, and the results are listed in Table 1.

[0062] Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 Thickness (μm) of polyester substrate 76 50 50 66 75 Birefringence difference of polyester substrate 0.004 0.008 0.009 0.011 0.014 In-plane phase difference (R0, nm) of polyester substrate 271 407 456 713 1080 The refractive index (n p ) of the polyester substrate 1.66 1.66 1.66 1.66 1.66 <![CDATA[First refractive index (n1)]]> 1.61 1.61 1.64 1.61 1.65 <![CDATA[Second refractive index (n2)]]> 1.51 1.56 1.56 1.54 1.52 <![CDATA[(n p -n1) / (n p -n2)]]> 0.33 0.5 0.20 0.42 0.07 <![CDATA[(n1-n2)]]> 0.10 0.05 0.08 0.07 0.13 <![CDATA[60 ° Evaluation of interference rainbow patterns from different perspectives ○ ○ ○ ○ ○ Example

[0063] A PET protective film was prepared according to Example 1. An anti-glare coating liquid I prepared in Example 2 was applied onto the first base layer and dried. The film was then incubated under nitrogen at 80 mJ / cm². 2 UV lamps with a radiation dose are used for photocuring to form an anti-glare layer on a PET protective film, resulting in an anti-glare protective film. The anti-glare protective film is then bonded to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials corp.) after the surface protective film has been removed, using transparent optical adhesive as a second base coat, to form a polarizing plate with anti-glare properties.

[0064] The obtained anti-glare polarizing plate was evaluated for interference rainbow patterns according to Example 1, and the thickness and haze of the anti-glare layer were measured according to the methods described below. The evaluation and measurement results are listed in Table 2.

[0065] Thickness measurement: The thickness of the anti-glare layer was measured using an electronic comparator Extramess 2001 (Mahr Inc., Germany) according to the description in JISK 5600-1-7:2014.

[0066] Haze measurement: The haze of the anti-glare layer was evaluated using NDH-2000 (Nippon Denshoku Corp.) according to the description in JIS K7136. Example

[0067] Using the PET protective film employed in Example 2, a polarizing plate with anti-glare effect was prepared according to Example 6. The obtained polarizing plate with anti-glare effect was evaluated for interference rainbow patterns according to Example 1, and the thickness and haze of the anti-glare layer were measured according to Example 6. The evaluation and measurement results are listed in Table 2. Example

[0068] Using the polyester protective film employed in Example 3, a polarizing plate with anti-glare effect was prepared according to Example 6. The obtained polarizing plate with anti-glare effect was evaluated for interference rainbow patterns according to Example 1, and the thickness and haze of the anti-glare layer were measured according to Example 6. The evaluation and measurement results are listed in Table 2. Example

[0069] Using the PET protective film from Example 4, a polarizing plate with anti-glare effect was prepared according to Example 6. The obtained polarizing plate with anti-glare effect was evaluated for interference rainbow patterns according to Example 1, and the thickness and haze of the anti-glare layer were measured according to Example 6. The evaluation and measurement results are listed in Table 2. Example

[0070] The PET protective film used in Example 5 was coated onto the first base coating to prepare the anti-glare coating liquid II prepared in Example 3, and after drying, it was heated in a nitrogen atmosphere at 80 mJ / cm². 2 UV lamps with a radiation dose are used for photocuring to form an anti-glare layer on a PET protective film to obtain an anti-glare protective film. The anti-glare protective film is then bonded to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials corp.) after the surface protective film has been removed, using transparent optical adhesive as a second base layer, to form a polarizing plate with anti-glare effect.

[0071] The polarizing plate with anti-glare effect was evaluated for interference rainbow pattern according to Example 1, and the thickness and haze of the anti-glare layer were measured according to Example 6. The results are listed in Table 2. Example

[0072] An anti-glare protective film was prepared according to Example 6. The anti-reflective layer solution of Example 4 was then coated onto the surface of this anti-glare layer and dried in an oven at 80°C. The film was then subjected to nitrogen atmosphere and heated to 350 mJ / cm². 2 UV lamps with a radiation dose are used for photocuring to obtain an anti-reflective layer with a thickness of approximately 0.13 μm on the surface of the anti-glare layer, thus obtaining an anti-reflective and anti-glare protective film. The anti-reflective and anti-glare protective film is then bonded to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials Corp.) after the surface protective film has been removed, using transparent optical adhesive as the second base layer, to form a polarizing plate with anti-reflective and anti-glare effects.

[0073] The obtained polarizing plate with anti-reflection and anti-glare effect was evaluated for interference rainbow pattern according to Example 1, and the thickness and haze of the anti-glare layer were measured according to Example 6. The evaluation and measurement results are listed in Table 2.

[0074] Table 2 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Total haze (%) 2.38 1.34 1.32 2.17 29.02 2.27 Anti-glare layer thickness (μm) 6.8 7.0 6.2 5.6 7.8 6.2 <![CDATA[60 ° Evaluation of interference rainbow patterns from different perspectives ○ ○ ○ ○ ○ ○ Comparative Example 1 The polyethylene terephthalate film prepared in Example 5 was used as the polyester substrate, and a photocurable acrylic resin (model: 660G-40L, purchased from Changxing Materials Industry Co., Ltd.) with a refractive index of 1.51 was coated on both sides and cured to form a second base coat to obtain a PET protective film. The refractive index of the base coat after curing was measured according to the method of Example 1. The measurement results are listed in Table 3.

[0075] After applying the anti-glare coating liquid I from Preparation Example 2 onto one of the base layers and drying it, it was then subjected to nitrogen atmosphere at 80 mJ / cm². 2 UV light with a radiation dose is used to cure the PET film, forming an anti-glare layer to prepare an anti-glare protective film. This anti-glare protective film is then bonded to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials corp.) after the surface protective film has been removed, with transparent optical adhesive, to form a polarizing plate with anti-glare effect.

[0076] The obtained polarizing plate with anti-glare effect was evaluated for interference rainbow pattern according to Example 1, and the thickness and haze of the anti-glare layer were measured according to Example 6. The evaluation and measurement results are listed in Table 3.

[0077] Comparative Example 2 A PET film (model: QBN-0015, purchased from Mitsubishi Chemical Corporation, Japan) with a thickness of 52 µm, an in-plane phase difference of 974 nm, a birefringence difference of 0.019, an average refractive index of 1.66, and a first undercoat with a refractive index of 1.56 and a second undercoat with a refractive index of 1.55 on both sides of the film surface was selected as the PET protective film.

[0078] After applying the anti-glare coating liquid I prepared in Example 2 onto the first base layer and drying it, it was then subjected to nitrogen atmosphere at 80 mJ / cm². 2 UV curing with a UV lamp of varying radiation dose was used to form an anti-glare layer on the PET film to prepare an anti-glare protective film. The anti-glare protective layer was then bonded to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials Corp.) after the surface protective film was removed, using a second base coat via transparent optical adhesive, to form a polarizing plate with anti-glare effect. The obtained polarizing plate with anti-glare effect was evaluated for interference rainbow patterns according to the method described in Example 1, and the thickness and haze of the anti-glare layer were measured according to Example 6. The evaluation and measurement results are listed in Table 3.

[0079] Comparative Example 3 A PET film (model: QBN-0015, purchased from Mitsubishi Chemical Corporation, Japan) with a thickness of 75 µm, an in-plane phase difference of 2384 nm, a birefringence difference of 0.032, an average refractive index of 1.66, and a first undercoat with a refractive index of 1.64 and a second undercoat with a refractive index of 1.59 on both sides of the film surface was selected as the PET protective film.

[0080] After applying the anti-glare coating liquid I prepared in Example 2 onto the first base layer and drying it, it was then subjected to nitrogen atmosphere at 80 mJ / cm². 2UV curing with a UV lamp of the radiation dose forms an anti-glare layer on the PET film to prepare an anti-glare protective film. The anti-glare protective layer is then bonded to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials Corp.) after the surface protective film has been removed, via transparent optical adhesive with a second base coating, to form a polarizing plate with anti-glare effect. The obtained polarizing plate with anti-glare effect is evaluated for interference rainbow patterns according to the method described in Example 1, and the thickness and haze of the anti-glare layer are measured according to Example 6. The evaluation and measurement results are listed in Table 3.

[0081] Comparative Example 4 A PET film (model: QBN-0012, purchased from Mitsubishi Chemical Corporation, Japan) with a thickness of 75 µm, an in-plane phase difference of 2490 nm, a birefringence difference of 0.033, an average refractive index of 1.66, and a first undercoat with a refractive index of 1.61 and a second undercoat with a refractive index of 1.59 on both sides of the film surface was selected as the PET protective film.

[0082] After coating and drying the anti-glare coating liquid I prepared in Example 2, it was subjected to nitrogen atmosphere at 80 mJ / cm 2 UV curing with a UV lamp of varying radiation dose was used to form an anti-glare layer on the PET protective film to prepare an anti-glare protective film. This anti-glare protective film was then bonded to the polarizing layer of a commercially available polarizing plate (model: RTT00015TH, BenQ Materials Corp.) after the surface protective film was removed, using a second base coat via transparent optical adhesive, to form a polarizing plate with anti-glare effect. The obtained polarizing plate with anti-glare effect was evaluated for interference rainbow patterns according to the method described in Example 1, and the thickness and haze of the anti-glare layer were measured according to Example 6. The evaluation and measurement results are listed in Table 3.

[0083] Table 3. Measurement values ​​and optical detection results of Comparative Examples 1 to 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Thickness (μm) of polyester substrate 76 52 75 75 Birefringence difference of polyester substrate 0.004 0.019 0.032 0.033 In-plane phase difference (R0, nm) of polyester substrate 271 974 2384 2490 <![CDATA[Refractive index of the polyester substrate (n p )]]> 1.66 1.66 1.66 1.66 <![CDATA[First refractive index (n1)]]> 1.51 1.56 1.64 1.61 <![CDATA[Second refractive index (n2)]]> 1.51 1.55 1.59 1.59 <![CDATA[(n p -n1) / (n p -n2)]]> 1.0 0.91 0.29 0.71 <![CDATA[(n1-n2)]]> 0 0.01 0.05 0.02 Total haze (%) 1.45 1.36 2.62 2.38 Anti-glare layer thickness (μm) 5.6 6.5 6.2 7.4 Evaluation of interference rainbow patterns at a 60° viewing angle ╳ ╳ ╳ ╳ The test results in Tables 1 to 3 show that the in-plane phase difference of the polyester substrate of the polarizer on the viewing side of the display is ≤1200 nm, and this can be achieved by adjusting its average refractive index n. p The first refractive index n1 of the first base coating and the second refractive index n2 of the second base coating make the polyester protective film satisfy the following relationship: n p >n1>n2, and (n p -n1) / (n pWith a haze of -n²) ≤ 0.7, interference rainbow patterns can be avoided. When the surface of the polyester protective film on the viewing-side polarizer of the display further has an anti-glare layer and / or an anti-reflective layer, even if the total haze of the anti-glare layer is ≤ 30%, or even preferably ≤ 5%, interference rainbow patterns can still be avoided. It is not necessary to disrupt the light interference through the interfaces on both sides of the polyester substrate using a surface treatment layer with high haze or high surface roughness, thus avoiding a reduction in image light transmittance or clarity. Furthermore, it is not necessary to use a polyester substrate with an extremely high in-plane phase difference value (≥ 8000 nm) as the protective film substrate for the viewing-side polarizer of the display, thereby reducing interference rainbow patterns.

[0084] 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 refinements 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.

[0085] Symbol Explanation 100, 300, 400: Polarizing plate 110: Polarizing layer 200: Polyester protective film 210: Polyester substrate 220: First base coat 230: Second base coat 310: Anti-glare layer 410: Anti-reflective.

Claims

1. A polarizing plate for a display viewing side, comprising: a polarizing layer, and; A polyester protective film is located on the front side of the polarizing layer, wherein the polyester protective film comprises a polyester substrate having an in-plane retardation of not more than 1200 nm and an average refractive index n p ; a first primer layer disposed on one side of the polyester substrate and having a first refractive index n1; and a second primer layer disposed on the other side of the polyester substrate and adjacent to the polarizing layer, and having a second refractive index n2, wherein, The refractive indexes of the polyester substrate, the first base coat layer, and the second base coat layer satisfy the relationship: n p > n2, and (n p - n1) / (n p - n2) ≤ 0.

7.

2. The polarizing plate for a display viewing side according to claim 1, wherein the birefringence difference of the polyester substrate is between 0.003 and 0.

015.

3. The polarizing plate for a display viewing side according to claim 1, wherein the difference between the first refractive index n1 and the second refractive index n2 satisfies the relationship: (n1-n2) > 0.

05.

4. The polarizing plate for a display viewing side according to claim 1, wherein the first refractive index n1 is between 1.56 and 1.65, and the second refractive index n2 is between 1.51 and 1.

60.

5. The polarizing plate for a display viewing side according to claim 1, wherein the thickness of the polyester substrate is between 10 μm and 80 μm.

6. The polarizing plate for a display viewing side according to claim 1, wherein the thickness of each of the first primer layer and the second primer layer is between 0.1 μm and 0.3 μm.

7. The polarizing plate for a display viewing side according to claim 1, wherein the polyester substrate is a uniaxially stretched or biaxially stretched polyester film.

8. The polarizing plate for a display viewing side according to claim 1, wherein the polarizing layer is an extended polarizing layer or a coated polarizing layer of iodine type or dye type.

9. The polarizing plate for a display viewing side according to claim 1, wherein the first primer layer of the polyester substrate further comprises an anti-glare layer, and the total haze of the anti-glare layer is < 30%.

10. The polarizing plate for a display viewing side according to claim 9, wherein the thickness of the anti-glare layer is between 2 μm and 10 μm.

11. The polarizing plate for a display viewing side according to claim 9, wherein the surface of the anti-glare layer further comprises an anti-reflective layer.

12. The polarizing plate for a display viewing side according to claim 11, wherein the thickness of the anti-reflective layer is between 0.1 μm and 0.3 μm.

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