High-toughness polaroid based on PMMA modified protective layer and preparation method of high-toughness polaroid

Abstract

The invention discloses a high-toughness polaroid based on a PMMA modified protective layer and a preparation method of the high-toughness polaroid. The high-toughness polaroid based on the PMMA modified protective layer sequentially comprises a release film layer, an optical pressure-sensitive adhesive layer, a high-toughness PMMA protective film, a polarizing substrate layer, a high-toughness PMMA protective film and a surface protective film layer from bottom to top, the high-toughness protective film is prepared by mixing PMMA (polymethyl methacrylate) and a thermal crosslinking agent through a spin coating, spraying or printing method and is formed through annealing treatment; compared with a traditional cellulose acetate (TAC) film, the PMMA film adopted by the invention has higher optical transparency, dimensional stability, weather resistance and mechanical strength, and the production cost is lower. The polaroid provided by the invention not only has excellent polarization characteristics and environmental tolerance, but also can remarkably improve impact resistance and flexibility, and is suitable for liquid crystal displays (LCDs), flexible displays, organic light emitting diode (OLED) displays and other optical display fields.

Description

Technical Field

[0001] The present invention relates to the technical field of polarizers, and particularly relates to a high-toughness polarizer based on a PMMA modified protective layer and a preparation method thereof. Background Art

[0002] Polarizers are important components of modern optical display devices and are widely used in fields such as liquid crystal displays (LCDs), organic light-emitting diode (OLED) displays, sunglasses, anti-glare screens, and optical sensing. Its main function is to regulate the polarization direction of light, improve image contrast, and reduce glare, thereby enhancing the display effect. The basic structure of a polarizer usually consists of a surface protective film layer, a polarizing substrate layer, an inner protective film, an optical pressure-sensitive adhesive layer, and a release film layer. Among them, the polarizing substrate layer is the core part for realizing the light polarization function, and the protective layer is used to provide mechanical strength, environmental stability, and additional functions.

[0003] The working principle of a polarizer is based on the polarization characteristics of light. Ordinary light is unpolarized light, and its vibration direction is randomly distributed in the vertical plane of the propagation direction. When light passes through the polarizing layer, the light perpendicular to the polarizing axis is absorbed, while the light parallel to the polarizing axis passes through, thus achieving linear polarization. Usually, the polarizing substrate layer in a polarizer uses a stretched polyvinyl alcohol (PVA) film and combines with a polarizing dye to arrange the molecular chains in a specific direction to form the function of absorbing polarized light. The protective layer usually uses a cellulose acetate (TAC) film, which can not only protect the polarizing layer from mechanical damage but also enhance the overall strength and durability of the polarizer.

[0004] Currently, the mainstream PVA / TAC polarizers on the market have high polarization efficiency and mature production processes, but they expose some deficiencies in actual use. For example, the PVA film is very sensitive to humidity and temperature and is prone to performance degradation in high-humidity or high-temperature environments; at the same time, the mechanical toughness of TAC is low, and the polarizer is prone to breakage when subjected to external force impact or bending; in addition, the chemical stability of such polarizers is limited and they are easily damaged under the condition of contact with acids, alkalis, or solvents, which limits their use in specific scenarios. To overcome these problems, in recent years, polarizer materials based on polymethyl methacrylate (PMMA) films have been proposed. PMMA films have become a potential alternative material due to their excellent optical transparency, dimensional stability, and weather resistance. Compared with traditional TAC polarizers, PMMA films have higher light transmittance, lower hygrothermal sensitivity, and better ultraviolet resistance. However, the preparation of ordinary PMMA films is prone to brittle fracture during the stretching process and it is difficult to meet the anti-impact and flexibility requirements in flexible displays and portable optical devices.

[0005] Therefore, how to prepare a high-toughness PMMA protective layer while ensuring the excellent optical properties and moisture resistance of the PMMA film has become one of the urgent problems to be solved in this field. Summary of the Invention

[0006] The main object of the present invention is to provide a high-toughness polarizer based on a PMMA modified protective layer, aiming to solve the problem that the existing ordinary PMMA film is prone to brittle fracture during the stretching process and is difficult to meet the impact resistance and flexibility requirements in flexible displays and portable optical devices.

[0007] To achieve the above object, the present invention proposes a high-toughness polarizer based on a PMMA modified protective layer, and the high-toughness polarizer based on a PMMA modified protective layer includes: A release film layer, an optical pressure-sensitive adhesive layer, a high-toughness protective film, a polarizing substrate layer, a high-toughness protective film, and a surface protective film layer are sequentially arranged from bottom to top; The high-toughness protective film is prepared on the upper and lower sides of the polarizing substrate layer, and the material of the high-toughness protective film is formed by mixing PMMA and a thermal cross-linking agent in a certain proportion.

[0008] The present invention also proposes a preparation method of a high-toughness polarizer based on a PMMA modified protective layer, which is applied to the preparation of the high-toughness polarizer based on a PMMA modified protective layer, and the preparation method of the high-toughness polarizer based on a PMMA modified protective layer includes the following steps: Step 1: Dissolve PVA (MW = 89000 - 98000) in deionized water at a mass fraction of 8%, and stir until completely dissolved into a uniform transparent solution under continuous heating at 90°C.

[0009] Step 2: After cooling the solution to room temperature, slowly cast it in a polytetrafluoroethylene mold, and place it in an oven at 50°C to dry into a film.

[0010] Step 3: Take out the PVA film from the polytetrafluoroethylene mold and immerse it in deionized water at 25°C for 1 min to expand it, then immerse the expanded PVA film in an iodine / potassium iodide mixed solution at 25°C for dyeing and unidirectional stretching, so that the iodine molecules are oriented along the stretching direction, wash it with deionized water and then place it in an oven for 5 min and dry it at 50°C to obtain a PVA polarizing film.

[0011] Step 4: Mix PMMA and a thermal cross-linking agent in a proportion, and composite the PMMA / thermal cross-linking agent mixed film on the upper and lower sides of the PVA polarizing film by spin coating, spraying or printing, and use a stable heat source to anneal the PMMA / thermal cross-linking agent mixed film to cross-link it to form a high-toughness protective film layer, and obtain a PMMA modified protective layer.

[0012] Step 5: Assemble the release film layer, the optical pressure-sensitive adhesive layer, and the surface protection film layer on both sides of the highly tough PMMA / PVA polarizing film using an adhesive.

[0013] Step 6: Place the entire polarizer in a heated drying oven for post-annealing treatment.

[0014] The beneficial effects of the present invention are as follows: 1. On the premise of ensuring the excellent optical properties and moisture resistance of the PMMA film, the preparation of a highly tough PMMA protective layer is achieved, enhancing the mechanical strength and durability of the PMMA inner protective film, and reducing the adverse effects of the external environment (such as water, air, and ultraviolet rays) on the PVA polarizing substrate layer film; 2. Using the PMMA film to replace the traditional TAC film makes the polarizer have stronger optical properties and lower production costs; 3. Preparing the highly tough PMMA protective layer by means of thermal cross-linking, the preparation scheme is simple and efficient, providing a new solution to the problem of easy brittle fracture during the preparation process of the PMMA base film. Description of the Drawings

[0015] Figure 1 It is a schematic structural diagram of the highly tough polarizer based on the PMMA modified protective layer of the present invention; In the figure: 1 - surface protection film layer, 2 - highly tough protective film 2, 3 - polarizing substrate layer, 4 - optical pressure-sensitive adhesive layer, 5 - release film layer. Detailed Embodiments

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0018] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0019] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. are based on the orientation or positional relationships shown in the drawings, or the orientation or positional relationships in which the inventive product is customarily placed during use, or the orientation or positional relationships commonly understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0020] In addition, the terms "first", "second", etc. are only used for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0021] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, terms such as "set", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] The following will describe in detail the specific embodiments of the present invention with reference to the drawings.

[0023] As Figure 1 shown, the high-toughness polarizer based on the PMMA modified protective layer includes: A release film layer 5, an optical pressure-sensitive adhesive layer 4, a high-toughness protective film 2, a polarizing substrate layer 3, a high-toughness protective film 2, and a surface protective film layer 1 are sequentially arranged from bottom to top; The high-toughness protective film 2 is prepared on the upper and lower sides of the polarizing substrate layer 3, and the material of the high-toughness protective film 2 is formed by mixing PMMA and a thermal cross-linking agent in a certain proportion.

[0024] In one embodiment, the material of the high-toughness protective film 2 is prepared by mixing PMMA and a thermal cross-linking agent; The cross-linking agent is one or more of 3-glycidoxypropyltrimethoxysilane (GOPS), 4-mercaptobenzoic acid (MBA), 3-aminopropyltrimethoxysilane (ATPMs), or SU-negative photoresist; the thickness of the high-toughness protective film 2 is 10 - 20 μm.

[0025] In one embodiment, the material of the release film layer 5 is one of polyethylene terephthalate (PET), polypropylene (PP), or polyimide (PI), and the thickness range is 20 - 40 μm.

[0026] In one embodiment, the material of the optical pressure-sensitive adhesive layer 4 is one of acrylate pressure-sensitive adhesives or silicone pressure-sensitive adhesives, and the thickness ranges from 10 to 50 μm.

[0027] In one embodiment, the material of the polarizing substrate layer 3 is polyvinyl alcohol (PVA), and the thickness ranges from 30 to 60 μm.

[0028] In one embodiment, the surface protective film layer 1 is one of polyethylene (PE) films or PETs with a single-sided coating of ethylene vinyl acetate copolymer (EVA) layer, which protects the surface of the PMMA film, and the thickness is 30 to 100 μm.

[0029] The present invention also provides a method for preparing a high-toughness polarizer based on a PMMA modified protective layer, which is applied to the preparation of the high-toughness polarizer based on the PMMA modified protective layer. The method for preparing the high-toughness polarizer based on the PMMA modified protective layer includes the following steps: Step 1: Dissolve PVA (MW = 89000 - 98000) in deionized water at a mass fraction of 8%, and stir it at a constant heating temperature of 90 °C until it is completely dissolved into a uniform transparent solution; Step 2: After cooling the solution to room temperature, slowly cast it in a polytetrafluoroethylene mold, and place it in an oven at 50 °C to dry into a film; Step 3: Take out the PVA film from the polytetrafluoroethylene mold and immerse it in deionized water at 25 °C for 1 min to make it expand. Then immerse the expanded PVA film in an iodine / potassium iodide mixed solution at 25 °C for dyeing and unidirectional stretching, so that the iodine molecules are oriented along the stretching direction. After washing with deionized water, place it in an oven for 5 min and dry it at 50 °C to obtain a PVA polarizing film; Step 4: Mix PMMA and a thermal crosslinking agent in proportion, and compound the PMMA / thermal crosslinking agent mixed film on both the upper and lower sides of the PVA polarizing film by spin coating, spraying or printing methods, and use a stable heat source to anneal the PMMA / thermal crosslinking agent mixed film to make it crosslink to form a high-toughness protective film layer, thus obtaining a PMMA modified protective layer; Step 5: Assemble the release film layer 5, the optical pressure-sensitive adhesive layer 4 and the surface protective film layer 1 on both sides of the high-toughness PMMA / PVA polarizing film using an adhesive; Step 6: Place the polarizer as a whole in a heated drying oven for post-annealing treatment.

[0030] In one embodiment, in step 4, the thermal crosslinking time ranges from 10 to 30 min, and the thermal crosslinking temperature ranges from 150 to 220 °C.

[0031] In one embodiment, in step 6, the post-annealing time ranges from 5 to 15 min, and the post-annealing temperature ranges from 80 to 150 °C.

[0032] Example 1 (control group): Step 1: Dissolve PVA (MW = 89000 - 98000) in deionized water at a mass fraction of 8%, and stir until completely dissolved into a uniform transparent solution under continuous heating at 100°C; Step 2: After cooling the solution to room temperature, slowly cast it in a polytetrafluoroethylene mold and place it in an oven to dry into a film at 60°C; Step 3: Take out the PVA film from the polytetrafluoroethylene mold and immerse it in deionized water at 25°C for 1 min to expand it, then immerse the expanded PVA film in an iodine / potassium iodide mixed solution at 25°C for dyeing and unidirectional stretching (stretching ratio is 9 times) to orient the iodine molecules along the stretching direction, wash it with deionized water and then place it in an oven for 5 min and dry at 60°C to obtain a PVA polarizing matrix layer film; Step 4: Mix PMMA and the thermal cross-linking agent GOPS evenly at a ratio of 6:1, and compound the PMMA / thermal cross-linking agent mixed solution on both the upper and lower sides of the PVA polarizing film by printing, and use a stable heat source at 180°C to anneal the PMMA / thermal cross-linking agent mixed solution, with the annealing time being 15 min; Step 5: Use an adhesive to assemble the release film layer, the optical pressure-sensitive adhesive layer and the surface protective film layer on both sides of the high-toughness polarizing film; Step 6: Place the entire polarizing sheet in an oven at 100°C for 5 min for post-annealing treatment.

[0033] Example 2: The difference from Example 1 is that in Step 4, PMMA and the thermal cross-linking agent GOPS are mixed evenly at a ratio of 1:1.

[0034] Example 3: The difference from Example 1 is that in Step 4, PMMA and the thermal cross-linking agent GOPS are mixed evenly at a ratio of 9:1.

[0035] Example 4: The difference from Example 1 is that in Step 4, a stable heat source at 180°C is used to anneal the PMMA / thermal cross-linking agent mixed solution, and the annealing time is 5 min.

[0036] Example 5: The difference from Example 1 is that in Step 4, a stable heat source at 180°C is used to anneal the PMMA / thermal cross-linking agent mixed solution, and the annealing time is 25 min.

[0037] Example 6: The difference from Example 1 lies in that in Step 4, after mixing PMMA and the thermal crosslinking agent ATPMs evenly at a ratio of 6:1, the PMMA / thermal crosslinking agent mixed solution is compounded on the upper and lower sides of the PVA polarizing film by printing.

[0038] Example 7: The difference from Example 1 lies in that in Step 4, after mixing PMMA and the thermal crosslinking agent MBA evenly at a ratio of 6:1, the PMMA / thermal crosslinking agent mixed solution is compounded on the upper and lower sides of the PVA polarizing film by printing.

[0039] Sample Transmittance at 400 - 700 nm Polarization degree at 400 - 700 nm Transmittance at 30% bending strain Polarization degree at 30% bending strain Transmittance at 60% bending strain Polarization degree at 60% bending strain 30% Bending cycle test 60% Bending cycle test Example 1 92% 100% 88% 97% 79% 93% 20,000 times 5,000 times Example 2 87% 94% 76% 92% 69% 90% 20,000 times 5,000 times Example 3 76% 90% 72% 87% 73% 83% 20,000 times 5,000 times Example 4 90% 98% 85% 94% 80% 89% 5,000 times 300 times Example 5 94% 100% 90% 97% 80% 90% 1,000 times 50 times Example 6 69% 100% 54% 94% 32% 87% 10,000 times 3,000 times Example 7 83% 99% 76% 96% 68% 98% 20,000 times 5,000 times As can be seen from the above table, through Examples 1 - 3, it can be seen that by changing the mixing ratio of different PMMA and thermal crosslinking agents, the overall light transmittance and polarization degree of the polarizing film have changed to varying degrees. This is because the introduction of the crosslinking agent has changed the group structure of PMMA, and the optimal ratio of PMMA to the crosslinking agent is 6:1. Comparing Example 1 with Examples 4 - 5, the service life of the high-toughness PMMA inner protective layer has a strong correlation with the annealing time. Excessive annealing time may lead to the breakage of chemical bonds, resulting in a significant reduction in the service life; by comparing Example 1 with Examples 6 - 7, the influence of replacing different thermal crosslinking agents on the performance of the overall polarizing film can be reflected. The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A high-toughness polarizer based on a PMMA modified protective layer, characterized in that: The high-toughness polarizer based on the PMMA modified protective layer includes: From bottom to top, a release film layer, an optical pressure-sensitive adhesive layer, a high-toughness protective film, a polarizing substrate layer, a high-toughness protective film and a surface protective film layer are sequentially arranged; The high-toughness protective film is prepared on the upper and lower sides of the polarizing substrate layer, and the material of the high-toughness protective film is formed by mixing PMMA and a thermal cross-linking agent in a certain proportion.

2. The high-toughness polarizer based on PMMA modified protective layer according to claim 1, characterized in that: The material of the high-toughness resistant protective film is prepared by mixing PMMA and a thermal cross-linking agent; The crosslinking agent is one or more of 3-glycidyloxypropyltrimethoxysilane (GOPS), 4-mercaptobenzoic acid (MBA), 3-aminopropyltrimethoxysilane (ATPMs) or SU-negative photoresist; the thickness of the high-toughness protective film is 10-20 μm.

3. The high-toughness polarizer based on PMMA modified protective layer according to claim 1, characterized in that: The release film layer is made of one of polyethylene terephthalate (PET), polypropylene (PP) or polyimide (PI), and has a thickness ranging from 20 to 40 μm.

4. The high-toughness polarizer based on PMMA modified protective layer according to claim 1, characterized in that: The material of the optical pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive or a silicone pressure-sensitive adhesive, and the thickness ranges from 10 to 50 μm.

5. The high-toughness polarizer based on PMMA modified protective layer according to claim 1, characterized in that: The material of the polarizing substrate layer is polyvinyl alcohol (PVA) and has a thickness ranging from 30 to 60 μm.

6. The high-toughness polarizer based on PMMA modified protective layer according to claim 1, characterized in that: The surface protection film layer is a polyethylene (PE) film or a PET film coated with an ethylene vinyl acetate copolymer (EVA) layer on one side, protecting the surface of the PMMA film, and has a thickness of 30-100 μm.

7. A method for preparing a high-toughness polarizer based on a PMMA modified protective layer, applied to the preparation of a high-toughness polarizer based on a PMMA modified protective layer as claimed in any one of claims 1 to 6, characterized in that: The method for preparing a high-toughness polarizer based on a PMMA modified protective layer comprises the following steps: Step 1: Dissolve PVA (MW = 89000~98000) in deionized water at a mass fraction of 8%, and stir under continuous heating at 90°C until it is completely dissolved into a uniform transparent solution; Step 2: After the solution is cooled to room temperature, it is slowly cast into a polytetrafluoroethylene mold and placed in an oven at 50°C to dry into a film; Step 3: Take the PVA film out of the polytetrafluoroethylene mold and immerse it in deionized water at 25°C for 1 min to expand it, then immerse the expanded PVA film in a mixed solution of iodine / potassium iodide at 25°C for dyeing and directional stretching, so that the iodine molecules are oriented along the stretching direction, wash it with deionized water, place it in an oven for 5 minutes, and dry it at 50°C to obtain a PVA polarizing film; Step 4: PMMA and a thermal crosslinking agent are mixed in proportion, and a PMMA / thermal crosslinking agent mixed film is compounded on the upper and lower sides of the PVA polarizing film by spin coating, spray coating or printing, and the PMMA / thermal crosslinking agent mixed film is annealed using a stable heat source to crosslink the PMMA / thermal crosslinking agent mixed film to form a high-toughness protective film layer, thereby obtaining a PMMA modified protective layer; Step 5: Use adhesive to assemble the release film layer, the optical pressure-sensitive adhesive layer and the surface protection film layer on both sides of the high-toughness PMMA / PVA polarizing film; Step 6: Place the entire polarizer in a heated drying oven for post-annealing treatment.

8. The method for preparing a high-toughness polarizer based on a PMMA modified protective layer according to claim 7, characterized in that: In step 4, the time range of thermal crosslinking is 10-30 min, and the temperature range of thermal crosslinking is 150-220°C.

9. The method for preparing a high-toughness polarizer based on a PMMA modified protective layer according to claim 7, characterized in that: In step 6, the time range of post-annealing is 5-15 min, and the temperature range of post-annealing is 80-150° C.

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