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CN-122011638-A - Modified polyvinyl alcohol optical film and preparation method and application thereof

CN122011638ACN 122011638 ACN122011638 ACN 122011638ACN-122011638-A

Abstract

The invention relates to the technical field of preparation of high polymer materials and optical films, in particular to a modified polyvinyl alcohol optical film, and a preparation method and application thereof. The modified polyvinyl alcohol optical film consists of a substrate and a modified monomer, wherein the substrate is PVA resin, the alcoholysis degree of the PVA resin is more than or equal to 99%, the polymerization degree of the PVA resin is 1700-2000, the modified monomer is EVOH, the ethylene unit content in the EVOH is 7-9 mol%, the thickness of the modified polyvinyl alcohol optical film is 10-60 mu m, the swelling degree is 90-115%, and the wet uniaxial stretching ratio is 6.75-6.95 times. The modified PVA optical film has low swelling degree, high wet uniaxial stretching rate, low birefringence and excellent wet thermal stability, can realize higher stretching rate under the wet uniaxial stretching condition, is not easy to break, inhibits in-plane uneven orientation in the drying film forming process, is favorable for obtaining a PVA optical base film with good optical uniformity, and is suitable for optical applications such as liquid crystal display and the like.

Inventors

  • Wang Guqiuzi
  • HE HONGXI
  • WANG HONGXING
  • JIANG XIAOYUN
  • HUANG JIE
  • SHEN KAIQING
  • AN ZHIMIN

Assignees

  • 重庆光谱新材料科技有限公司

Dates

Publication Date
20260512
Application Date
20260210

Claims (10)

  1. 1. The modified polyvinyl alcohol optical film is characterized by comprising a matrix and a modified monomer; the matrix is PVA resin, the alcoholysis degree of the PVA resin is more than or equal to 99%, and the polymerization degree is 1700-2000; The modified monomer is EVOH, and the ethylene unit content in the EVOH is 7-9 mol%; the thickness of the modified polyvinyl alcohol optical film is 10-60 mu m, the swelling degree is 90-115%, and the stretching ratio is 6.75-6.95 times.
  2. 2. The modified polyvinyl alcohol optical film according to claim 1, wherein the vinyl content of the modified polyvinyl alcohol optical film is 2 to 5mol%.
  3. 3. A method of making the modified polyvinyl alcohol optical film of claim 1 or 2, comprising: S1, mixing EVOH dispersion liquid, a plasticizer and a surfactant to obtain a pre-blending system; s2, adding PVA aqueous solution into the pre-blending system in the step S1 for mixing to form modified blending casting film liquid; S3, forming a film from the blending film casting liquid in the step S2 by adopting a tape casting process.
  4. 4. The method according to claim 3, wherein in the step S1, the method for producing the EVOH dispersion comprises adding an EVOH resin to water, and swelling the EVOH resin with stirring at a stirring rate of 200 to 400rpm for 0.5 to 3 hours at a temperature of 80 to 130 ℃.
  5. 5. The method according to claim 3 or 4, wherein in step S1, the plasticizer is one or more selected from the group consisting of glycerin, diglycerin, triethylene glycol, trimethylolpropane and polyethylene glycol; the surfactant is a nonionic surfactant, the HLB value is 11-17, preferably 12-15, and the surfactant is preferably one or more selected from fatty alcohol polyoxyethylene ether, tween and nonylphenol polyoxyethylene ether.
  6. 6. The method according to claim 5, wherein the fatty alcohol-polyoxyethylene ether is one or more selected from the group consisting of AEO-7, AEO-9, AEO-10 and AEO-12; The tween is selected from one or more of tween-20, tween-40, tween-60 and tween-80; the nonylphenol polyoxyethylene ether is selected from one or more of NP-8, NP-10, NP-12 and NP-15.
  7. 7. The method according to any one of claims 3 to 6, wherein in step S1, the mass ratio of the EVOH dispersion, plasticizer to surfactant is 1:0.015 to 0.045:0.0003 to 0.006, wherein the EVOH dispersion is based on the mass of the EVOH solid; preferably, the mass ratio of the EVOH dispersion liquid to the surfactant is 1:0.0005-0.003, wherein the EVOH dispersion liquid is based on the mass of EVOH solid; the mixing condition comprises the temperature of 80-130 ℃, the stirring speed of 200-400 rpm and the time of 0.5-3 h.
  8. 8. The preparation method according to any one of claims 3 to 7, wherein in step S2, the mass fraction of the PVA aqueous solution is 10 to 15wt%; The mass ratio of the pre-blending system to the PVA aqueous solution is 0.3-0.5:1; The mixing condition comprises that the pre-blending system is gradually added into PVA water solution under the condition that the temperature is 80-130 ℃, the stirring speed is 250-350 rpm, and the stirring time is 1-2 h; Preferably, the modified blending casting film liquid needs to be subjected to defoaming and filtering treatment, and the defoaming adopts a vacuum defoaming mode, and the defoaming time is 10-20 min.
  9. 9. The preparation method according to any one of claims 3 to 8, wherein in the step S3, the casting conditions comprise uniformly coating the modified blend casting solution on a casting roller through a flat die head, drying in sections, stripping after drying is finished to obtain a dried film, and winding to obtain a modified polyvinyl alcohol optical film; Preferably, the casting roller is made of mirror stainless steel or chrome-plated steel; preferably, the sectional drying adopts a multi-roller contact drying mode, comprising pre-drying, heat setting and cooling; the pre-drying conditions comprise that the temperature of a drying roller is 80-100 ℃, preferably 80-90 ℃, and the speed ratio of the drying roller is 1-1.004; The heat setting condition comprises that the temperature of a drying roller is 90-120 ℃, preferably 90-100 ℃, and the speed ratio of the drying roller is 1-1.003; The cooling condition comprises that the temperature of a drying roller is 60-80 ℃, and the speed ratio of the drying roller is 0.992-0.998; the speed ratio of the drying roller is the ratio of the peripheral speed of each roller to the peripheral speed of the first roller, and the peripheral speed of the first roller is 7-8 m/min, preferably 7.4-7.8 m/min.
  10. 10. Use of the modified polyvinyl alcohol optical film according to claim 1 or 2 for the production of liquid crystal display devices, precision optical elements and optical compensation devices.

Description

Modified polyvinyl alcohol optical film and preparation method and application thereof Technical Field The invention relates to the technical field of preparation of high polymer materials and optical films, in particular to a modified polyvinyl alcohol optical film, and a preparation method and application thereof. Background Polyvinyl alcohol (PVA) films, which are an important role in the field of optical materials, are widely used in display technology and precision optics by virtue of their excellent high transparency and good optical uniformity, particularly as core materials for polarizer base films of liquid crystal displays. However, the traditional pure PVA optical film has a remarkable performance short plate, limits the application expansion of the PVA optical film in high-performance scenes, and has the advantages that PVA molecular chains have extremely strong hydrophilicity, unmodified films are easy to severely swell and deform in water or high-humidity environments, and are insufficient in thermal stability and wet-heat dimensional stability, meanwhile, the pure PVA film is crisp in texture, low in elongation at break and narrow in stretching processing window, when the high-quality film with the thickness of less than 60 mu m is prepared, the problems of excessively high initial swelling speed, uneven crystal growth in the drying process, pre-orientation of a wet film in advance and the like are easy to occur, so that the film is excessively fast in transverse shrinkage, easy to wrinkle and easy to break in the subsequent uniaxial stretching process, and the high-magnification stretching process requirement is difficult to be met. In order to improve the water resistance and toughness of PVA films, various modification attempts have been made in the industry to improve the flexibility by adding plasticizers such as glycerol and ethylene glycol, but significantly weaken the wet-heat durability of the films, to introduce cross-linking agents such as boride and aldehydes to improve the structural stability, to increase the process complexity and possibly reduce the transparency of the films, and to generate Kong Sanshe phenomena due to poor compatibility and to seriously affect the optical haze and birefringence control when the films are blended with vinyl acetate polymers. For applications such as polarizing film base films and the like with extremely high requirements on optical uniformity, the traditional modification method is difficult to synchronously improve the tensile property and the moisture-proof stability of the film, meanwhile, the uniformity and the orientation stability of the film are maintained, and uneven structures or local defects are easily introduced, so that the polarization efficiency, the brightness uniformity and the damp-heat reliability of the polaroid are affected, and the application of the polaroid in the field of high-performance display is limited. In the study of ethylene-modified polyvinyl alcohol polymer films of Japanese colali company, an in-plane birefringence determination system has been proposed, in which the refractive indices nMD, nTD and nz of the film in the mechanical flow direction (MD), width direction (TD) and thickness direction (z) are measured to define the difference in refractive index between the mechanical flow direction (MD) and thickness direction (z) asn(MD)=nMDNz, refractive index difference between the width direction (TD) and the thickness direction (z) isn(TD)=nTDNz. And further adopts thickness direction averagingN (MD) Ave andN (TD) Ave to evaluate the overall orientation state of the film. The birefringence parameters are limited to a strict range (e.gN (TD) Ave≤2.5×10-3 andn(MD)Ave-0.1×10-3≤n(TD)Ave≤N (MD) Ave+0.25×10-3) to distinguish whether the film forming process forms a non-uniform pre-orientation. In the above-mentioned description of the invention,N (MD) Ave represents a value obtained by averaging the birefringence in the mechanical flow direction of the ethylene-modified polyvinyl alcohol polymer film in the thickness direction of the film,N (TD) Ave represents a value obtained by averaging the birefringence in the width direction of the ethylene-modified polyvinyl alcohol polymer film in the thickness direction of the film. Meanwhile, by accurately controlling the volatile area, the speed ratio of the drying roller and the coiling speed ratio, the unexpected orientation of the PVA film in the drying stage is effectively inhibited, so that the ethylene modified PVA film can realize higher multiplying power and higher optical uniformity in the subsequent wet stretching. The research results show that the modification of the ethylene unit in the range of 1-4 mol% not only improves the wet toughness, but also improves the birefringence uniformity and the stretching processing window of the final film. In summary, the prior art lacks a modification scheme capable of remarkably improving the wet expansion resistance, t