Composite optical film as well as uniaxial stretching preparation method and application thereof

Abstract

The invention provides a composite optical film and a uniaxial stretching preparation method and application thereof. The composite optical film at least comprises a layer A and a layer B. The layer A comprises a cycloolefin polymer with the structure shown in the formula 1, and the layer B comprises an ethylene and cycloolefin copolymer shown in the formula 2. In the formula 1 and the formula 2, R1, R2, R3 and R4 can be the same or different and are independently selected from hydrogen and C1-10 alkyl. According to the composite optical film, by combining materials with different refractive indexes, propagation and reflection of light rays can be accurately controlled, so that the transmissivity is improved, the reflectivity is reduced, and the light rays are more uniformly distributed. Therefore, the composite optical film has important application in the fields of display technology, spectacle lenses, photographic equipment and the like.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, specifically relating to a composite optical film and its preparation method and application by uniaxial stretching. Background Technology

[0002] TAC film, short for triacetate cellulose film, is a commonly used material that plays a crucial role in the production of liquid crystal display (LCD) polarizers. TAC film possesses excellent light uniformity, transparency, acid and alkali resistance, and UV resistance. Furthermore, TAC film boasts a light transmittance exceeding 93%, second only to optical glass, and is itself a negative C-plate, allowing for perfect bonding with PVA (polyvinyl alcohol) film. TAC film is primarily used in the production of LCD polarizers, with the bare TAC film typically used as the inner layer, while the functional TAC film is used as the outermost layer. Functional TAC films are obtained through surface treatment methods such as coating and sputtering, and possess specific functions. TAC film is manufactured by dissolving, filtering, plasticizing, injection molding, and drying powdered TAC particles. The production process requires extremely high control to ensure the flatness, mechanical properties, and optical properties of the final product.

[0003] TAC films have a high water absorption rate, typically between 2-5 wt%. Over long-term use, this water absorption leads to decreased light transmittance and warping. In recent years, companies such as Zeon in Japan have proposed using films made from cyclic olefin polymers (COPs) through melt processing to replace TAC films in LCD polarizers. COP films have extremely low water absorption rates, generally less than 0.2 wt%, and can be melt-processed, resulting in low processing costs and minimal environmental pollution. Currently, they show potential to replace TAC films.

[0004] Zeon Optical Films from Japan are generally made using cyclic olefin polymer resins, resulting in films with high light transmittance and high strength. However, cyclic olefin polymers are expensive, leading to high film costs and limiting their applications. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A composite optical film, the composite optical film comprising at least layer A and layer B, wherein layer A comprises a cyclic olefin polymer having the structure shown in Formula 1, and layer B comprises a copolymer of ethylene and cyclic olefin having the structure shown in Formula 2;

[0007]

[0008] In Equations 1 and 2, R1, R2, R3, and R4 may be the same or different, and are independently selected from hydrogen and C. 1-10 Alkyl groups (e.g., at least one of methyl, n-propyl, and isopropyl);

[0009] m, n, and p can be the same or different, and can be selected independently from 1 to 1000, for example, 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900.

[0010] According to an embodiment of the present invention, the cyclic olefin polymer is selected from at least one of Zeonex K26R, K22R, E48R, F52R, T62R, 330R and 480R from Zeon Corporation of Japan.

[0011] According to an embodiment of the present invention, the copolymer of ethylene and cyclic olefins is preferably a copolymer of ethylene and norbornene, for example, including but not limited to at least one of TOPAS 5013F, TOPAS 6013F, TOPAS 7010F, TOPAS 8007F, and TOPAS 9506F from Japan.

[0012] According to an embodiment of the present invention, the glass transition temperature (Tg) of the cyclic olefin polymer is in the range of 80-200°C, preferably in the range of 100-180°C, for example, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, or 170°C.

[0013] According to an embodiment of the present invention, the glass transition temperature (Tg) of the copolymer of ethylene and cyclic olefins is 80-200°C, preferably 100-180°C, for example 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, or 170°C.

[0014] According to an embodiment of the present invention, the Tg difference between the cyclic olefin polymer and the copolymer of ethylene and cyclic olefins is no more than 30°C, preferably no more than 20°C.

[0015] According to an embodiment of the present invention, the refractive index of the cyclic olefin polymer is between 1.45 and 1.80, for example, 1.5, 1.6, or 1.7.

[0016] According to an embodiment of the present invention, the refractive index of the copolymer of ethylene and cyclic olefins is between 1.45 and 1.80, for example, 1.5, 1.6, or 1.7.

[0017] According to an embodiment of the present invention, the refractive index difference between the cyclic olefin polymer and the copolymer of ethylene and cyclic olefin is no more than 0.5, preferably no more than 0.2, for example no more than 0.1.

[0018] According to embodiments of the present invention, the composite optical film optionally further includes a C layer. Preferably, the C layer comprises a cyclic olefin polymer or a copolymer of ethylene and a cyclic olefin.

[0019] According to a preferred embodiment of the present invention, the layer structure of the composite optical film is selected from at least one of the following: AB structure, ABC structure, and CAB structure. Preferably, the layer structure of the composite optical film in the present invention refers to a top-to-bottom structure, where A refers to layer A, B refers to layer B, and C refers to layer C. For example, the AB structure refers to layers A and B from top to bottom; the ABC structure refers to layers A, B, and C from top to bottom, wherein layer C is a cyclic olefin polymer or a copolymer of ethylene and cyclic olefins; the CAB structure refers to layers C, A, and B from top to bottom, wherein layer C is a cyclic olefin polymer or a copolymer of ethylene and cyclic olefins.

[0020] According to an embodiment of the present invention, the total thickness of the composite optical film is 10-50 micrometers, preferably 10-30 micrometers, for example 15 micrometers, 20 micrometers, or 25 micrometers.

[0021] According to an embodiment of the present invention, in the composite optical film, the ratio of the total thickness of layer A to the total thickness of layer B can be 10-90:10-90, preferably 20-80:20-80, for example 25:75, 30:70, 35:65, 40:55, 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, 75:25.

[0022] According to an embodiment of the present invention, the composite optical film has a tensile strength of 30-60 MN·m in the longitudinal and / or transverse directions. -2 For example, 35MN·m -2 40MN·m -2 50MN·m -2 55MN·m -2 .

[0023] According to an embodiment of the present invention, the composite optical film exhibits thermal deformation of less than 1% in the longitudinal and / or transverse directions, for example, 0.5%.

[0024] According to an embodiment of the present invention, the water absorption rate of the composite optical film is less than 0.5%, for example, 0.1%, 0.2%, 0.3%, or 0.4%.

[0025] According to an embodiment of the present invention, the transmittance of the composite optical film is not less than 91%, for example, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%.

[0026] According to an embodiment of the present invention, the refractive index of the composite optical film is 1.50-1.60.

[0027] The present invention also provides a method for preparing the above-mentioned composite optical film, wherein the preparation method is a uniaxial stretching method, and the preparation method includes: preparing a sheet having the above-mentioned layer structure by multi-layer co-extrusion of raw materials; and then obtaining the composite optical film by uniaxial stretching method.

[0028] According to an embodiment of the present invention, the multilayer co-extrusion can be carried out using methods known in the art, and no specific limitation is made in the present invention. For example, a melt extrusion device known in the art can be used.

[0029] According to an embodiment of the present invention, the raw materials are selected according to the film structure of the composite optical film, wherein layer A uses a cyclic olefin polymer having the structure shown in Formula 1 as the first raw material, layer B uses a copolymer of ethylene and cyclic olefin having the structure shown in Formula 2 as the second raw material, and layer C uses a cyclic olefin polymer having the structure shown in Formula 1 or a copolymer of ethylene and cyclic olefin having the structure shown in Formula 2 as the third raw material.

[0030] According to an embodiment of the present invention, the temperature for multi-layer co-extrusion can be selected from temperatures known in the art, for example, an extrusion temperature of 150-260°C, preferably 180-250°C. Preferably, during multi-layer co-extrusion, the die temperature of the extruder is 190-240°C.

[0031] According to an embodiment of the present invention, the sheet material needs to be cooled before uniaxial stretching. Preferably, the cooling can be quenching. Exemplarily, quenching refers to cooling using a cooling roller, preferably with cooling water as the cooling liquid. In this invention, the purpose of quenching is to ensure that the sheet melt has a certain strength after rapid cooling.

[0032] According to an embodiment of the present invention, the quenching temperature is 15-30°C, preferably 20-25°C.

[0033] According to an embodiment of the present invention, the uniaxial stretching method refers to uniaxial stretching in one direction (e.g., longitudinal) under certain temperature and stretching speed. In the present invention, longitudinal refers to the direction along the film extrusion process, and transverse refers to the direction perpendicular to the film extrusion process.

[0034] According to an embodiment of the present invention, in the uniaxial stretching method, the difference T1-Tg between the stretching temperature T1 and the highest glass transition temperature Tg' in the raw material is -10℃ to 30℃, preferably 0 to 30℃, for example 10℃ or 20℃.

[0035] According to an embodiment of the present invention, the unidirectional stretching is longitudinal stretching, and the stretching temperature is 90-180℃, preferably 100-150℃.

[0036] According to an embodiment of the present invention, the unidirectional stretching can be a one-step stretching, or a two-step stretching or a three-step stretching.

[0037] According to an embodiment of the present invention, in the uniaxial stretching method, the uniaxial stretching ratio (e.g., the longitudinal stretching ratio) can be set according to the performance requirements of the membrane. Preferably, the longitudinal stretching ratio is 3-30 times, more preferably 5-20 times, for example 10 times or 15 times.

[0038] According to an embodiment of the present invention, preheating and / or micro-stretching may be optionally performed before the unidirectional stretching. Preferably, the micro-stretching refers to stretching with a longitudinal stretching ratio of less than 1.5 times. Preferably, the longitudinal stretching ratio of the micro-stretching is 1.1-1.3 times, more preferably 1.1-1.2 times.

[0039] According to an embodiment of the present invention, the preheating refers to preheating the sheet on both sides to the stretching temperature (i.e., above the softening point of the raw material). Preferably, the preheating temperature is 90-200°C, more preferably 100-180°C.

[0040] According to an embodiment of the present invention, after unidirectional stretching, a further shaping process is performed. Preferably, the shaping refers to heat treatment using heat-setting rollers. Further, the shaping temperature is 100-140°C, preferably 110-120°C. In this invention, shaping can eliminate internal stress in the film and reduce longitudinal shrinkage.

[0041] According to an embodiment of the present invention, after the uniaxial stretching method is completed, the composite optical film can be subjected to secondary cooling. Preferably, the secondary cooling can be performed using methods known in the art, and no specific limitation is made in this invention.

[0042] The present invention also provides uses of the above-mentioned composite optical film in the optical field (e.g., display technology, eyeglass lenses and photographic equipment), such as in polarizers.

[0043] A polarizer, the polarizer comprising at least the aforementioned composite optical film.

[0044] Beneficial effects of the present invention

[0045] Compared to single-layer COP films, the composite optical film provided by this invention has the following advantages:

[0046] (1) Higher optical performance: By combining materials with different refractive indices, the composite optical film of the present invention can precisely control the propagation and reflection of light, thereby improving transmittance and reducing reflectance, resulting in a more uniform distribution of light. Therefore, the composite optical film of the present invention has important applications in display technology, eyeglass lenses, and photographic equipment.

[0047] (2) Greater design flexibility: The design of multilayer composite films can be customized according to specific needs. By adjusting the combination of materials and thicknesses of each layer, optical composite films with both high light transmittance and high refractive index can be obtained, thereby achieving different optical effects and functions.

[0048] Terminology Definitions and Explanations

[0049] Term "C" 1-10 "Alkyl" should be understood as representing a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 10 carbon atoms. For example, "C 1-10 "alkyl" indicates a straight-chain or branched alkyl group having 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms, preferably "C". 1-8 Alkyl or C 1-6 Alkyl group. "C" 1-8 "Alkyl" refers to straight-chain and branched alkyl groups having 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms. 1-6 "Alkyl" means a straight-chain or branched alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, or 1,2-dimethylbutyl, or their isomers. Detailed Implementation

[0050] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0051] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0052] In the following embodiments, the detection indicators and detection standards of the composite optical film are shown in Table 1.

[0053] Table 1

[0054]

[0055] Example 1:

[0056] The composite optical film in this embodiment has the following structure: AB type structure, with the thicknesses of layer A and layer B being 8μm and 8μm, respectively; wherein layer A is Zeonex 480R resin and layer B is TOPAS 6013F resin.

[0057] The specific method for preparing the composite optical film in this embodiment is as follows:

[0058] Using a two-layer co-extrusion equipment, the resins of layer A and layer B are extruded in equal proportions. The co-extruded molten resin enters a cold roll with a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls with temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 10 times that of the cold rolls. The film then enters a heat-setting roll with a temperature of 110°C, followed by a cooling roll with a temperature of 30°C. Finally, the film is trimmed and wound up. A composite optical film with a thickness of 16±1 micrometers is prepared, and the test results are listed in Table 2.

[0059] Example 2:

[0060] The composite optical film in this embodiment has the following structure: an AB type structure, with the thicknesses of layer A and layer B being 6μm and 10μm, respectively; wherein layer A is Zeonex 480R resin and layer B is TOPAS 6013F resin.

[0061] The specific method for preparing the composite optical film in this embodiment is as follows:

[0062] Using a two-layer co-extrusion equipment, the resins of layer A and layer B are extruded at a ratio of 6:10. The co-extruded molten resin enters a cold roll with a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls with temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 10 times that of the cold rolls. The film then enters a heat-setting roll with a temperature of 110°C, followed by a cooling roll with a temperature of 30°C. Finally, the film is trimmed and wound up. A composite optical film with a thickness of 16±1 micrometers is prepared, and its test data are listed in Table 2.

[0063] Example 3:

[0064] The composite optical film in this embodiment has the following structure: AB type structure, with the thicknesses of layer A and layer B being 4μm and 12μm, respectively; wherein layer A is Zeonex 480R resin and layer B is TOPAS 6013F resin.

[0065] The specific method for preparing the composite optical film in this embodiment is as follows:

[0066] Using a two-layer co-extrusion apparatus, the resins of layer A and layer B are extruded at a ratio of 4:12. The co-extruded molten resin enters a cold roll at a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls at temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 10 times that of the cold rolls. The film then enters a heat-setting roll at a temperature of 110°C, followed by a cooling roll at a temperature of 30°C. Finally, the film is trimmed and wound up. A composite optical film with a thickness of 16±1 micrometers was prepared, and its test data are listed in Table 2.

[0067] Example 4:

[0068] The composite optical film in this embodiment has the following structure: an AB type structure, with the thicknesses of layer A and layer B being 10 μm and 6 μm, respectively; wherein layer A is Zeonex 480R resin and layer B is TOPAS 6013F resin.

[0069] The specific method for preparing the composite optical film in this embodiment is as follows:

[0070] Using a two-layer co-extrusion equipment, the resins of layer A and layer B are extruded in a 4:12 ratio. The co-extruded molten resin enters a cold roll with a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls with temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 10 times that of the cold rolls. The film then enters a heat-setting roll with a temperature of 110°C, followed by a cooling roll with a temperature of 30°C. Finally, the film is trimmed and wound up. A composite optical film with a thickness of 16±1 micrometers is prepared, and its test data are listed in Table 2.

[0071] Example 5:

[0072] The composite optical film in this embodiment has the following structure: AB type structure, with the thicknesses of layer A and layer B being 12μm and 4μm, respectively; wherein layer A is Zeonex 480R resin and layer B is TOPAS 6013F resin.

[0073] The specific method for preparing the composite optical film in this embodiment is as follows:

[0074] Using a two-layer co-extrusion apparatus, the resins of layer A and layer B are extruded at a ratio of 2:14. The co-extruded molten resin enters a cold roll at a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls at temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 10 times that of the cold rolls. The film then enters a heat-setting roll at a temperature of 110°C, followed by a cooling roll at a temperature of 30°C. Finally, the film is trimmed and wound up. A composite optical film with a thickness of 16±1 micrometers was prepared, and its test data are listed in Table 2.

[0075] Comparative Example 1:

[0076] This comparative example is a single-layer optical film made of Zeonex 480R resin.

[0077] The specific method for preparing the monolayer optical film in this comparative example is as follows:

[0078] Using a single-layer extrusion device, the co-extruded molten resin enters a cold roll at a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls at temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 10 times that of the cold rolls. The film then enters a heat-setting roll at a temperature of 110°C, followed by a cooling roll at a temperature of 30°C. Finally, the film is trimmed and wound up. A single-layer optical film with a thickness of 16±1 micrometers is obtained, and its test data are listed in Table 2.

[0079] Comparative Example 2:

[0080] This comparative example is a single-layer optical film made of Zeonex 480R and TOPAS 6013F resin.

[0081] The specific method for preparing the monolayer optical film in this comparative example is as follows:

[0082] The above resins were mixed in a 1:1 ratio and co-extruded using a single-layer extrusion device. The molten resin was fed into a cold roll at a temperature of 30°C to obtain a sheet. The sheet was then rapidly fed from the cold roll into two sets of hot rolls at temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, was adjusted so that the linear speed of the traction rolls was 10 times that of the cold rolls. The film then entered a heat-setting roll at a temperature of 110°C, followed by a cooling roll at a temperature of 30°C. Finally, the film was trimmed and wound up. A single-layer optical film with a thickness of 16±1 micrometers was prepared. The test data are listed in Table 2.

[0083] Example 6:

[0084] The composite optical film in this embodiment has the following structure: AB type structure, with the thicknesses of layer A and layer B being 10μm and 10μm respectively. Layer A is Zeonex 480R resin and layer B is TOPAS 6013F resin.

[0085] The specific method for preparing the composite optical film in this embodiment is as follows:

[0086] Using a two-layer co-extrusion equipment, the resins of layer A and layer B are extruded in equal proportions. The co-extruded molten resin enters a cold roll with a temperature set at 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls with temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 10 times that of the cold rolls. The film then enters a heat-setting roll with a temperature of 110°C, followed by a cooling roll with a temperature of 30°C. Finally, the film is trimmed and wound up. A composite optical film with a thickness of 20±1 micrometers is prepared. Its test data are listed in Table 2.

[0087] Example 7:

[0088] The composite optical film in this embodiment has the following structure: an AB type structure, with the thicknesses of layer A and layer B being 6μm and 6μm, respectively; wherein layer A is Zeonex 480R resin and layer B is TOPAS 6013F resin.

[0089] The specific method for preparing the composite optical film in this embodiment is as follows:

[0090] Using a two-layer co-extrusion equipment, resin layers A and B are extruded in equal proportions. The co-extruded molten resin enters a cold roll at a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls at temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 10 times that of the cold rolls. The film then enters a heat-setting roll at a temperature of 110°C, followed by a cooling roll at a temperature of 30°C. Finally, the film is trimmed and wound up. A composite optical film with a thickness of 12±1 micrometers is obtained. The test data are listed in Table 2.

[0091] Example 8:

[0092] The composite optical film in this embodiment has an ABA-type structure, with the thicknesses of layers A, B, and C from top to bottom being 6μm, 4μm, and 6μm, respectively; wherein layers A and C are made of Zeonex 480R resin, and layer B is made of TOPAS 6013F resin.

[0093] The specific method for preparing the composite optical film in this embodiment is as follows:

[0094] Using a three-layer co-extrusion machine, resins of layers A, B, and C, corresponding from top to bottom, are extruded in a ratio of 4:10:4. The co-extruded molten resin enters a cold roll at a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls at temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 16 times that of the cold rolls. The film then enters a heat-setting roll at a temperature of 110°C, followed by a cooling roll at a temperature of 30°C. Finally, the film is trimmed and wound up to obtain a composite optical film with a thickness of 16±1 micrometers. The test data are listed in Table 2.

[0095] Example 9: The composite optical film structure of this example is a CAB type structure, with the thicknesses of the C layer, A layer and B layer from top to bottom being 6μm, 4μm and 6μm respectively; wherein, the A layer is Zeonex 480R resin and the B layer is TOPAS 6013F resin.

[0096] The specific method for preparing the composite optical film in this embodiment is as follows:

[0097] Using a three-layer co-extrusion machine, resins of layers B, A, and B, from top to bottom, are extruded in a 6:4:6 ratio. The co-extruded molten resin enters a cold roll at a temperature of 30°C to obtain a sheet. The sheet then rapidly enters two sets of hot rolls at temperatures of 110°C and 160°C. The speed ratio of the hot and cold rolls, as well as the speed ratio of the subsequent traction rolls, is adjusted so that the linear speed of the traction rolls is 30 times that of the cold rolls. The film then enters a heat-setting roll at a temperature of 110°C, followed by a cooling roll at a temperature of 30°C. Finally, the film is trimmed and wound up to obtain a composite optical film with a thickness of 16±1 micrometers. The test data are listed in Table 2.

[0098] Table 2 Performance results of composite optical films

[0099]

[0100] Analysis of the above experimental results shows that the multilayer composite optical film prepared by the present invention has mechanical properties, thermal properties and water absorption rate that are similar to or better than those of single-layer films. However, the multilayer composite optical film of the present invention can significantly improve the transmittance and refractive index of the optical film, and is more suitable for use in the field of polarizers.

[0101] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite optical film, characterized in that, The composite optical film includes at least layer A and layer B, wherein layer A comprises a cyclic olefin polymer having the structure shown in Formula 1, and layer B comprises a copolymer of ethylene and cyclic olefin having the structure shown in Formula 2. In Equations 1 and 2, R1, R2, R3, and R4 may be the same or different, and are independently selected from hydrogen and C. 1-10 alkyl.

2. The composite optical film according to claim 1, characterized in that, The cyclic olefin polymer is selected from at least one of Zeonex K26R, K22R, E48R, F52R, T62R, 330R and 480R from Zeon Corporation of Japan. Preferably, the copolymer of ethylene and cyclic olefins is a copolymer of ethylene and norbornene, including but not limited to at least one of TOPAS 5013F, TOPAS 6013F, TOPAS 7010F, TOPAS 8007F, and TOPAS 9506F from Japan.

3. The composite optical film according to claim 1, characterized in that, The glass transition temperature (Tg) of the cyclic olefin polymer is between 80 and 200 °C. Preferably, the glass transition temperature (Tg) of the copolymer of ethylene and cyclic olefins is between 80 and 200°C. Preferably, the Tg difference between the cyclic olefin polymer and the copolymer of ethylene and cyclic olefins does not exceed 30°C. Preferably, the refractive index of the cyclic olefin polymer is between 1.45 and 1.

80. Preferably, the refractive index of the copolymer of ethylene and cyclic olefins is between 1.45 and 1.

80. Preferably, the refractive index difference between the cyclic olefin polymer and the copolymer of ethylene and cyclic olefins is no more than 0.

5.

4. The composite optical film according to claim 1, characterized in that, The composite optical film may optionally include a C layer. Preferably, the C layer comprises a cyclic olefin polymer or a copolymer of ethylene and a cyclic olefin. Preferably, the layer structure of the composite optical film is selected from at least one of the following: AB structure, ABC structure, and CAB structure. Preferably, the total thickness of the composite optical film is 10-50 micrometers. Preferably, in the composite optical film, the ratio of the total thickness of layer A to the total thickness of layer B is 10-90:10-90.

5. The composite optical film according to claim 1, characterized in that, The composite optical film has a tensile strength of 30-60 MN·m in the longitudinal and / or transverse directions. -2 . Preferably, the composite optical film exhibits thermal deformation of less than 1% in the longitudinal and / or transverse directions. Preferably, the water absorption rate of the composite optical film is less than 0.5%. Preferably, the transmittance of the composite optical film is not less than 91%. Preferably, the refractive index of the composite optical film is 1.50-1.

60.

6. The method for preparing the composite optical film according to any one of claims 1-5, characterized in that, The preparation method is a uniaxial stretching method, which includes: preparing a sheet with the layered structure by multi-layer co-extrusion of raw materials; and then obtaining the composite optical film by uniaxial stretching method.

7. The preparation method according to claim 6, characterized in that, The raw materials are selected according to the film structure of the composite optical film. The A layer uses a cyclic olefin polymer with the structure shown in Formula 1 as the first raw material, the B layer uses a copolymer of ethylene and cyclic olefins with the structure shown in Formula 2 as the second raw material, and the C layer uses a cyclic olefin polymer with the structure shown in Formula 1 or a copolymer of ethylene and cyclic olefins with the structure shown in Formula 2 as the third raw material. Preferably, the extrusion temperature of the multilayer co-extrusion is 150-260℃. Preferably, the sheet needs to be cooled before unidirectional stretching, and the cooling is rapid cooling. Preferably, the rapid cooling temperature is 15-30℃.

8. The preparation method according to claim 6 or 7, characterized in that, The uniaxial stretching method refers to stretching in one direction under certain temperature and stretching speed. Preferably, in the uniaxial stretching method, the difference between the stretching temperature T1 and the highest glass transition temperature Tg' in the raw material, T1-Tg, is between -10°C and 30°C. Preferably, the unidirectional stretching is longitudinal stretching, and the stretching temperature is 90-180℃. Preferably, in the uniaxial stretching method, the longitudinal stretching ratio is 3-30 times. Preferably, preheating and / or micro-stretching are optionally performed before the unidirectional stretching. Preferably, the preheating refers to preheating the sheet on both sides to the stretching temperature. Preferably, after unidirectional stretching, a further shaping process is performed. Preferably, the shaping refers to heat treatment using heat-setting rollers. Further, the shaping temperature is 100-140°C. Preferably, after the uniaxial stretching method is completed, the composite optical film is further cooled.

9. Use of the composite optical film according to any one of claims 1-5 in the field of optics.

10. A polarizer, characterized in that, The polarizer comprises at least the composite optical film as described in any one of claims 1-5.

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