Water-blocking antistatic PMMA (polymethyl methacrylate) optical film for polaroid

Abstract

The invention relates to a water-blocking antistatic PMMA (polymethyl methacrylate) optical film for a polaroid. The water-blocking antistatic PMMA optical film comprises a modified PMMA optical base film and a water-blocking antistatic layer arranged on any surface of the modified PMMA optical base film, the material of the modified PMMA optical base film comprises PMMA resin grafted and copolymerized by modified maleic anhydride, and the material of the water-blocking antistatic layer comprises fluorine-silicon modified polyimide resin. The PMMA resin is subjected to maleic anhydride modification, and the modified PMMA resin and the fluorosilicone modified polyimide are subjected to co-melt extrusion, so that the PMMA film is endowed with excellent water resistance and antistatic property. The water-blocking antistatic PMMA optical film designed by the invention not only can effectively prevent static accumulation and moisture absorption phenomena, but also can improve the weather resistance and the service life of a polaroid.

Description

Technical Field

[0001] The present application relates to the technical field of optical thin films, and particularly to a water-resistant and antistatic PMMA optical film for polarizers. Background Art

[0002] Optical display devices such as liquid crystal displays are widely used in various electronic products. As an important component of them, polarizers need to have excellent optical properties and durability. Traditional polarizers are made of polyvinyl alcohol (PVA), and triacetyl cellulose (TAC) films are usually used as protective films on both the upper and lower sides. However, TAC films have defects such as poor weather resistance and being easily affected by moisture. Therefore, poly(methyl methacrylate) (PMMA) films, with their excellent transparency, weather resistance, and chemical stability, have gradually been applied in the field of large-size display panels to replace TAC films as protective films for polarizers.

[0003] Although PMMA films have many advantages, their antistatic performance and water resistance are insufficient, and static electricity is easily accumulated and moisture is easily absorbed, thus affecting the optical properties and service life of polarizers. Therefore, how to improve the water resistance and antistatic property of PMMA films has become the key to improving the performance of polarizers. Summary of the Invention

[0004] To solve the above problems, the present application proposes a PMMA optical film with excellent water resistance and antistatic performance, which can not only effectively prevent static electricity accumulation and moisture absorption, but also improve the weather resistance and service life of polarizers, and expand the application scope of PMMA films in the field of polarizers.

[0005] In a first aspect, the present application provides a water-resistant and antistatic PMMA optical film for polarizers, including a modified PMMA optical base film and a water-resistant and antistatic layer provided on any surface of the modified PMMA optical base film; the material of the modified PMMA optical base film includes PMMA resin graft copolymerized with modified maleic anhydride, and the material of the water-resistant and antistatic layer includes polyimide resin modified by fluorosilicon.

[0006] More specifically, the preparation method of the modified PMMA optical base film is as follows: PMMA resin, maleic anhydride monomer, and free radical initiator are mixed evenly, heated, and then melt-extruded and stretched to obtain the modified PMMA optical base film.

[0007] More specifically, the stretching includes transverse stretching and longitudinal stretching, and the ratio of the longitudinal stretching to the transverse stretching is 1.5 - 3.0.

[0008] More specifically, the stretching temperature during the longitudinal stretching and the transverse stretching is 130°C - 160°C.

[0009] More specifically, the free radical initiator is selected from any one of benzoyl peroxide and dicumyl peroxide.

[0010] More specifically, the preparation method of the water-blocking and antistatic layer is as follows: The preparation method of the fluorosilicon-modified polyimide resin is as follows: Polyimide, perfluoroalkyl acrylate, and silane coupling agent are fully mixed and reacted in a nitrogen atmosphere at room temperature to obtain the fluorosilicon-modified polyimide resin.

[0011] More specifically, the thickness of the modified PMMA optical base film is 30-80 μm, and the thickness of the water-blocking and antistatic layer is 0.5-2 μm.

[0012] In a second aspect, the present application provides a polarizing plate, including the above-mentioned water-blocking and antistatic PMMA optical film.

[0013] More specifically, it sequentially includes a functional layer, an upper PVA protective film, a PVA polarizer, a lower PVA protective film, a pressure-sensitive adhesive layer, and a release film from top to bottom. Both the upper PVA protective film and the lower PVA protective film are the water-blocking and antistatic PMMA optical films.

[0014] More specifically, one side of the PVA polarizer is disposed on the side of the upper PVA protective film away from the water-blocking and antistatic layer, and the other side of the PVA polarizer is disposed on the side of the lower PVA protective film away from the water-blocking and antistatic layer.

[0015] Compared with the prior art, the present application provides a water-blocking and antistatic PMMA optical film for a polarizing plate, having the following beneficial effects:

[0016] 1. The water-blocking performance of the PMMA optical film is improved, and the moisture permeability of the film material is reduced, thereby enhancing the weather resistance and service life of the polarizing plate.

[0017] 2. The antistatic performance of the PMMA optical film is enhanced, effectively preventing static electricity accumulation and ensuring the excellent optical performance of the polarizing plate.

[0018] 3. The interfacial bonding force between the PMMA resin and the fluorosilicon-modified polyimide is improved, enhancing the overall performance and reliability of the double-layer film.

[0019] 4. The application range of the PMMA film in the field of polarizing plates is expanded, providing high-quality protective film materials for large-size display panels.

[0020] 5. By modifying the PMMA resin with maleic anhydride, its compatibility and fusion with the fluorosilicon-modified polyimide are improved, ensuring the tight bonding of the double-layer film.

[0021] 6. The optical film is prepared by a co-melting extrusion process, which is simple in operation, low in cost, and conducive to industrial production. Brief Description of the Drawings

[0022] Figure 1 is a schematic structural view of the water-blocking and antistatic PMMA optical film in the present application;

[0023] Figure 2 is a schematic preparation view of the water-blocking and antistatic PMMA optical film in the present application.

[0024] In the figure: 1. Modified PMMA optical base film; 2. Water-blocking and antistatic layer. Detailed Description of the Embodiments

[0025] To make the objectives, technical solutions and advantages of the implementation of the present application clearer, the following provides a clear and complete description of the specific implementation manners of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0026] Example 1

[0027] Prepare modified PMMA resin particles: Pretreat PMMA resin, maleic anhydride monomer and initiator by drying at 70°C for 5 hours respectively to remove moisture and impurities. Add the pretreated PMMA resin, maleic anhydride monomer and initiator benzoyl peroxide into a mixer in a ratio of 100:10:1. Fill the mixer with nitrogen and mix evenly. Add the mixed material into a twin-screw extruder, and set the temperature at 120°C, the screw speed at 50 rpm and stir for 5 hours to carry out a melt grafting reaction. During the reaction process, the initiator decomposes to generate free radicals, which initiate the grafting reaction between the active sites on the PMMA resin molecular chain and the maleic anhydride monomer. Cool the product after the grafting reaction to room temperature, cut it, and perform vacuum drying treatment at 80°C to obtain modified PMMA resin.

[0028] Fluorosilicon modification treatment of polyimide resin: Pretreat the polyimide resin by vacuum drying at 150°C for 4 hours to remove moisture; dissolve the dried polyimide resin in N-methylpyrrolidone solvent, heat it to 120°C and stir until completely dissolved. Dissolve the fluorine-containing monomer (perfluoroalkyl acrylate) and the silicon-containing monomer (silane coupling agent) in the polyimide resin, and react at room temperature for 6 hours under a nitrogen atmosphere to obtain a prepolymer of polyimide containing fluorosilicon in the main chain. Remove impurities and dry the prepolymer to obtain a polyimide resin with fluorosilicon modification in the main chain.

[0029] Preparation of water-blocking and antistatic PMMA optical film: 39 parts of modified PMMA resin and 1 part of fluorosilicon-modified polyimide resin are dried and then melt-extruded separately. The discharge amounts of the two resins are controlled by the rotation speeds of the extruder and the gear pump. The discharged molten resins enter the double die head SLOT DIE respectively, and the Open film-making method is adopted. They are stacked and dropped onto the first casting roller (110 °C) in sequence to cool and form a film. The modified PMMA resin is dropped onto the first casting roller first, and the fluorosilicon-modified polyimide resin is dropped onto the PMMA resin. Then it continuously passes through the second casting roller (100 °C) and the third casting roller (95 °C) connected in series to continue cooling and shaping, and a film with a thickness of 200 μm is made. Finally, it undergoes high-temperature longitudinal stretching and high-temperature transverse stretching, is cooled at room temperature, and wound up to obtain a water-blocking and antistatic PMMA optical film with a thickness of 40 μm as shown in Figure 1 The water-blocking and antistatic layer has a thickness of 1 μm. During the longitudinal stretching, the temperature is 140 °C and the stretching ratio is 1.8. During the transverse stretching, the temperature is 138 °C and the stretching ratio is 2.7.

[0030] Example 2

[0031] Preparation of modified PMMA resin particles: The PMMA resin, maleic anhydride monomer and initiator are pre-treated by drying at 70 °C for 5 hours respectively to remove moisture and impurities. The pre-treated PMMA resin, maleic anhydride monomer and initiator benzoyl peroxide are added to a mixer in a ratio of 100:10:1. Nitrogen is filled into the mixer for uniform mixing. The mixed material is added to a twin-screw extruder, and a melt grafting reaction is carried out at 120 °C, a screw rotation speed of 50 rpm and stirring for 5 hours. During the reaction process, the initiator decomposes to generate free radicals, which initiate the grafting reaction between the active sites on the PMMA resin molecular chain and the maleic anhydride monomer. The product after the grafting reaction is cooled to room temperature, cut, and vacuum dried at 80 °C to obtain the modified PMMA resin.

[0032] Fluorosilicon modification treatment of polyimide resin: The polyimide resin is pre-treated by vacuum drying at 150 °C for 4 hours to remove moisture; the dried polyimide resin is dissolved in N-methylpyrrolidone solvent, heated to 120 °C and stirred until completely dissolved. The fluorine-containing monomer (perfluoroalkyl acrylate) and the silicon-containing monomer (silane coupling agent) are dissolved in the polyimide resin, and the reaction is carried out at room temperature for 6 hours under a nitrogen atmosphere to obtain a prepolymer of polyimide with fluorosilicon in the main chain. The prepolymer is subjected to impurity removal and drying to obtain the polyimide resin with fluorosilicon modification in the main chain.

[0033] Preparation of water-blocking and antistatic PMMA optical film: 79 parts of modified PMMA resin and 1 part of fluorosilicon-modified polyimide resin are dried and then melt-extruded separately. The discharge amounts of the two resins are controlled by the rotation speeds of the extruder and the gear pump. The discharged molten resins enter the double die head SLOT DIE respectively, and the Open film-making method is adopted. They are stacked and dropped onto the first casting roll (115 °C) in sequence to cool and form a film. The modified PMMA resin is dropped onto the first casting roll first, and the fluorosilicon-modified polyimide resin is dropped onto the PMMA resin. Then it continuously passes through the second casting roll (105 °C) and the third casting roll (95 °C) connected in series for further cooling and shaping to produce a film with a thickness of 200 μm. Finally, it undergoes high-temperature longitudinal stretching and high-temperature transverse stretching, is cooled at room temperature, and wound up to obtain a water-blocking and antistatic PMMA optical film with a thickness of 40 μm, where the thickness of the water-blocking and antistatic layer is 0.5 μm. The temperature during longitudinal stretching is 140 °C, the stretching ratio is 2.0, the temperature during transverse stretching is 138 °C, and the stretching ratio is 2.8.

[0034] Example 3

[0035] Preparation of modified PMMA resin particles: The PMMA resin, maleic anhydride monomer, and initiator are pre-treated by drying at 70 °C for 5 hours respectively to remove moisture and impurities. The pre-treated PMMA resin, maleic anhydride monomer, and initiator benzoyl peroxide are added to a mixer in a ratio of 100:10:1. The mixer is filled with nitrogen for uniform mixing. The mixed material is added to a twin-screw extruder, and a melt grafting reaction is carried out at 120 °C, a screw rotation speed of 50 rpm, and stirring for 5 hours. During the reaction process, the initiator decomposes to generate free radicals, which initiate the grafting reaction between the active sites on the PMMA resin molecular chain and the maleic anhydride monomer. The product after the grafting reaction is cooled to room temperature, cut, and vacuum-dried at 80 °C to obtain the modified PMMA resin.

[0036] Fluorosilicon modification treatment of polyimide resin: The polyimide resin is pre-treated by vacuum drying at 150 °C for 4 hours to remove moisture; the dried polyimide resin is dissolved in N-methylpyrrolidone solvent, heated to 120 °C, and stirred until completely dissolved. The fluorine-containing monomer (perfluoroalkyl acrylate) and the silicon-containing monomer (silane coupling agent) are dissolved in the polyimide resin solution. Under a nitrogen atmosphere, a reaction is carried out at room temperature for 6 hours to obtain a prepolymer of polyimide with fluorosilicon in the main chain. The prepolymer is subjected to impurity removal and drying to obtain the polyimide resin with fluorosilicon modification in the main chain.

[0037] Preparation of water-blocking and antistatic PMMA optical film: 26 parts of modified PMMA resin and 1 part of fluorosilicon-modified polyimide resin are dried and then melt-extruded respectively. The discharge amounts of the two resins are controlled by the rotation speeds of the extruder and the gear pump. The discharged molten resins enter the dual die head SLOT DIE respectively, and the Open film-making method is adopted. They are stacked and dropped onto the first casting roll (105 °C) in sequence to cool into a film. The modified PMMA resin is dropped onto the first casting roll first, and the fluorosilicon-modified polyimide resin is dropped onto the PMMA resin. Then it continuously passes through the second casting roll (100 °C) and the third casting roll (90 °C) connected in series to continue cooling and shaping, and a film with a thickness of 200 μm is made. Finally, it undergoes high-temperature longitudinal stretching and high-temperature transverse stretching, is cooled at room temperature, and wound up to obtain a water-blocking and antistatic PMMA optical film with a thickness of 40 μm, where the thickness of the water-blocking and antistatic layer is 1.5 μm. The temperature during longitudinal stretching is 140 °C, the stretching ratio is 1.8, the temperature during transverse stretching is 135 °C, and the stretching ratio is 2.5.

[0038] Comparative Example 1

[0039] Compared with Example 1, the graft modification step of PMMA resin and maleic anhydride monomer is missing, and PMMA resin is directly used, and the rest are the same.

[0040] Comparative Example 2

[0041] Compared with Example 1, the fluorosilicon modification treatment step of polyimide resin is missing, and polyimide resin is directly used, and the rest are the same.

[0042] Comparative Example 3

[0043] Compared with Example 1, the preparation and melt co-extrusion steps of fluorosilicon-modified polyimide resin are missing, and a modified PMMA optical base film without a water-blocking and antistatic layer is directly used, and the rest are the same.

[0044] Perform performance tests on Examples 1-3 and Comparative Examples 1-3. The test methods are as follows:

[0045] Test method for glass transition temperature Tg of PMMA optical film:

[0046] Take about 15 g of the sample, and under the conditions of a nitrogen flow rate of 30 ml / min and a heating rate of 20 °C / min, use a differential scanning calorimeter DSC to measure the glass transition temperature Tg (°C) according to the JIS-K7121 standard.

[0047] Test method for water vapor transmission rate of PMMA optical film:

[0048] The calcium chloride-permeability cup method is adopted. 30 g of calcium chloride is placed in the permeability cup, and the PMMA optical film in this application is used to cover the mouth of the permeability cup. Under the conditions of a temperature of 40 °C and a humidity of 90% RH, the weight of calcium chloride before and after 24 h of testing is measured. The water vapor permeability = the weight difference of calcium chloride before and after / the area of the cup mouth, with the unit g / m 2 / day.

[0049] The performance test results are shown in the following table:

[0050]

[0051] According to the performance test results, the test results of the examples are all better than those of the comparative examples. In the examples.

[0052] As can be seen from Table 1, the PMMA optical films prepared according to the schemes described in Examples 1-3 have good water resistance. The thicker the water-resistant antistatic layer, the better the water resistance effect, improving the water resistance of the PMMA film.

[0053] Compared with Examples 1 to 3, Comparative Example 1 lacks the modification of PMMA grafted maleic anhydride monomer and does not introduce carboxyl and ester functional groups, and these functional groups can enhance the interaction with polyimide. Therefore, the adhesion of the water-resistant antistatic layer is poor.

[0054] Comparative Example 2 lacks the modification treatment of polyimide resin with fluorosilicon, and its antistatic property is poor. Fluorine atoms have a large electronegativity and can absorb and release charges, thereby reducing the static charge accumulation on the material surface. Introducing polyimide can disrupt the electron cloud conjugation in the molecular structure of polyimide, reduce the charge accumulation on the molecular chain, and further improve the antistatic performance. The fluorosilicon group can also form a "barrier layer" between molecular chains to prevent the rapid transfer of charges between molecules and further improve the antistatic performance.

[0055] Comparative Example 3 lacks the steps of preparing fluorosilicon-modified polyimide resin and melt coextrusion. The optical film made has no water-resistant antistatic layer, and its water resistance and antistatic property are poor.

[0056] The above has made a detailed description of the embodiments of this application, but this application is not limited to the described embodiments. For those skilled in the art, without departing from the principles and spirit of this application, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of this application.

Claims

1. A water-blocking and antistatic PMMA optical film for polarizer, characterized in that: It comprises a modified PMMA optical base film and a water-blocking and antistatic layer arranged on any surface of the modified PMMA optical base film; the material of the modified PMMA optical base film comprises a PMMA resin grafted copolymerized with modified maleic anhydride, and the material of the water-blocking and antistatic layer comprises a fluorine-silicon modified polyimide resin.

2. The water-blocking and antistatic PMMA optical film according to claim 1, characterized in that: The preparation method of the modified PMMA optical base film is specifically as follows: PMMA resin, maleic anhydride monomer and free radical initiator are uniformly mixed, heated, melted, extruded and stretched to obtain the modified PMMA optical base film.

3. The water-blocking and antistatic PMMA optical film according to claim 2, characterized in that: The stretching includes transverse stretching and longitudinal stretching, and the ratio of the longitudinal stretching to the transverse stretching is 1.5 to 3.

0.

4. The water-blocking and antistatic PMMA optical film according to claim 3, characterized in that: The stretching temperature during the longitudinal stretching and the transverse stretching is 130°C to 160°C.

5. The water-blocking and antistatic PMMA optical film according to claim 2, characterized in that: The free radical initiator is selected from any one of benzoyl peroxide and dicumyl peroxide.

6. The water-blocking and antistatic PMMA optical film according to claim 1, characterized in that: The preparation method of the fluorine-silicon modified polyimide resin is specifically as follows: polyimide, perfluoroalkyl acrylate and silane coupling agent are fully mixed, and reacted in a nitrogen atmosphere at room temperature to obtain the fluorine-silicon modified polyimide resin.

7. The water-blocking and antistatic PMMA optical film according to claim 1, characterized in that: The modified PMMA optical base film has a thickness of 30 to 80 μm, and the water-blocking and antistatic layer has a thickness of 0.5 to 2 μm.

8. A polarizing plate, characterized in that: It comprises the water-blocking and antistatic PMMA optical film as described in any one of claims 1 to 7.

9. The polarizing plate according to claim 8, characterized in that: From top to bottom, it includes a functional layer, an upper PVA protective film, a PVA polarizer, a lower PVA protective film, a pressure-sensitive adhesive layer, and a release film. The upper PVA protective film and the lower PVA protective film are both the water-blocking and antistatic PMMA optical films.

10. The polarizing plate according to claim 9, characterized in that: One side of the PVA polarizer is arranged on a side of the upper PVA protective film away from the water-blocking and antistatic layer, and the other side of the PVA polarizer is arranged on a side of the lower PVA protective film away from the water-blocking and antistatic layer.

Images