Roller for film forming, preparation method of film and film

Abstract

The invention relates to the field of optics, and discloses a film forming roller, a film preparation method and a film wherein the roller comprises a roller body, the surface of the roller body is provided with a polytetrafluoroethylene layer or a ceramic layer, the surface roughness Ra of the polytetrafluoroethylene layer or the ceramic layer is more than or equal to 0.001 [mu] m and less than or equal to 0.08 [mu] m, and the surface roughness Ra of the polytetrafluoroethylene layer or the ceramic layer is more than or equal to 0.01 [mu] m and less than or equal to 0.01 [mu] m. The surface of the roller is treated through the polytetrafluoroethylene layer or the ceramic layer, so that the adhesive capacity between a high-temperature molten material and the surface of the roller is reduced, the stripping force between the molten material and the surface of the roller in the production process is reduced, a film can be conveniently torn off from the roller, and the film surface quality of the plastic film is improved.

Description

Technical Field

[0001] The invention relates to the field of optics, and in particular to a roller for film forming, a method for preparing the film, and the film. Background Art

[0002] Polyvinyl alcohol (PVA) optical film is the core film material of polarizer, a key material for liquid crystal display. In the existing polyvinyl alcohol film production process, during the pre-formed film peeling process, there are differences in the peeling force at each point on the film surface, and the film sticks to the roller on the surface of the high-temperature equipment, resulting in uneven film stretching, which ultimately causes the film's mechanical properties to deteriorate, and the film surface will have obvious marks due to peeling. In addition, material accumulation often occurs at both ends of the mold lip, resulting in a "skirt" on the edge of the polyvinyl alcohol film on the rotating roller / steel belt. The thickened film edge often has adhesion defects due to insufficient drying, making it difficult to peel off the film, and even causing the film to tear. Summary of the invention

[0003] The purpose of the present invention is to overcome the problem of difficulty in peeling off the film in the prior art, which leads to uneven stretching of the film surface and poor mechanical properties of the film, and to provide a roller for film molding and a method for preparing the film and the film. The roller surface has a polytetrafluoroethylene layer or a ceramic layer, which can reduce the adhesion between the high-temperature molten material and the roller surface, and reduce the peeling force between the molten material and the roller surface during the production process, thereby facilitating the film to be peeled off from the roller, which is beneficial to improving the film surface quality of the plastic film.

[0004] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a roller for film forming, wherein the roller includes a roller body, the surface of the roller body has a polytetrafluoroethylene layer or a ceramic layer, and the surface roughness of the polytetrafluoroethylene layer or the ceramic layer is Ra, 0.001μm≤Ra≤0.08μm.

[0005] Polytetrafluoroethylene (also known as Teflon) has the advantages of excellent chemical stability, corrosion resistance, wear resistance, high temperature resistance, excellent anti-sticking property and low roughness, and is widely used in various fields, including chemical, food, medicine, electronics, construction, aviation and other fields. At present, the optical film industry usually adopts electroplating (chrome plating, nickel plating, zinc plating) roller surface treatment to improve the roller's anti-sticking performance and reduce the adhesion between high-temperature materials and the roller. There is no existing technology for treating the roller surface with polytetrafluoroethylene.

[0006] In the present application, a polytetrafluoroethylene layer or a ceramic layer is applied to the surface of the roller to reduce the adhesion between the high-temperature molten material and the roller surface, and the peeling force between the molten material and the roller surface during the production process is reduced, so that the film is easily peeled off from the roller, thereby improving the film surface quality of the plastic film; in addition, in order to solve the problem of material accumulation at both ends of the mold lip, since the adhesion between the film and the roller is reduced, the film and the roller are not easy to stick together, and the film is peeled off more smoothly, and it can also effectively avoid the problem of film tearing and increased deformation caused by uneven moisture content on the film surface.

[0007] The second aspect of the present invention provides a method for preparing a film, wherein the method comprises: coating a film slurry on a film forming roller to form a coating liquid film, performing a first drying and then peeling the film with a film peeling roller to obtain a preformed film, and performing a second drying on the preformed film to obtain an optical film;

[0008] The film peeling angle during the film peeling is θ, 60°≤θ≤120°, wherein the film peeling angle refers to: a first tangent line tangent to the film forming roller along the film peeling position and a second tangent line tangent to the traction roller along the traction position, and the angle between the two is the film peeling angle;

[0009] The humidity of the coating liquid film after the first drying is a, 10%≤a≤45%.

[0010] The transverse direction of the film is TD, and the longitudinal direction of the film is MD.

[0011] The pre-stretching problem of the film prepared by this method in the MD direction is improved, the maximum deformation M in the MD direction does not exceed 0.6mm, the film thickness is uniform, the thickness error is controlled within ±1μm, the stretching extension ratio is above 5.8 times, especially when the humidity when the film is removed is less than 30%, there is no peeling mark on the film surface after the film is removed.

[0012] The third aspect of the present invention provides a film produced by the preparation method described in the second aspect of the present invention.

[0013] The above technical scheme performs special treatment on the roller surface through a polytetrafluoroethylene layer or a ceramic layer, thereby reducing the adhesion between the high-temperature molten material and the roller surface, reducing the peeling force between the molten material and the roller surface during the production process, and facilitating the peeling of the film from the roller, thereby improving the film surface quality of the plastic film. In addition, in order to address the problem of material accumulation at both ends of the mold lip, since the adhesion between the film and the roller is reduced, the film and the roller are not easy to stick together, and the film peeling is smoother. It can also effectively avoid the problem of film tearing and increased deformation caused by uneven moisture content on the film surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1It is a schematic diagram of the structure of the roller;

[0015] Figure 2 It is a schematic diagram of the film peeling process.

[0016] Description of Reference Numerals

[0017] 1-inner cylinder; 2-outer cylinder; 3-heat medium flow channel; 4-reinforcement ribs; 5-polytetrafluoroethylene layer or ceramic layer; A-film peeling site; B-traction site; C-first tangent line; D-second tangent line. DETAILED DESCRIPTION

[0018] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0019] A first aspect of the present invention provides a roller for film forming, wherein the roller comprises a roller body, the surface of the roller body has a polytetrafluoroethylene layer or a ceramic layer, and the surface roughness of the polytetrafluoroethylene layer or the ceramic layer is Ra, 0.001μm≤Ra≤0.08μm.

[0020] In some embodiments, preferably, 0.001 μm ≤ Ra ≤ 0.04 μm, preferably, 0.025 μm ≤ Ra ≤ 0.04 μm.

[0021] The surface roughness of the coating affects the ease of peeling off the film and whether marks or even damage will be left on the film after peeling off the film. Therefore, it is very important to control the surface roughness of the coating. The surface roughness of the coating can be any value within the range of any two numbers of 0.001μm, 0.015μm, 0.02μm, 0.025μm, 0.03μm, 0.035μm, 0.04μm, 0.05μm, 0.06μm, 0.07μm, and 0.08μm.

[0022] In some embodiments, preferably, the thickness of the polytetrafluoroethylene layer or the ceramic layer is δ, 0.04 mm≤δ≤0.1 mm.

[0023] In some embodiments, preferably, 0.04 mm ≤ δ ≤ 0.08 mm, preferably, 0.05 mm ≤ δ ≤ 0.08 mm.

[0024] If the thickness of the PTFE layer or ceramic layer is too thick, it will affect the heat transfer effect of the roller and the average temperature difference of the roller surface cannot be guaranteed to be less than 0.5°C. If the thickness of the PTFE layer or ceramic layer is too thin, it will affect the strength and processing performance, and further affect the roughness of the roller surface. If the thickness of the PTFE layer or ceramic layer is too thick or too thin, it may cause the coating to crack. The thickness of the coating can be any value within the range of any two numbers of 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, and 0.1mm.

[0025] The second aspect of the present invention provides a method for preparing a film, wherein the method comprises: coating a film slurry on a film forming roller to form a coating liquid film, performing a first drying, and then using a film peeling roller to peel off the film to obtain a preformed film, and performing a second drying on the preformed film to obtain an optical film; the peeling angle during the peeling is θ, 60°≤θ≤120°, wherein the peeling angle refers to: a first tangent line tangent to the film forming roller along the peeling position, and a second tangent line tangent to the traction roller along the traction position, and the angle between the two is the peeling angle;

[0026] The humidity of the coating liquid film after the first drying is a, 10%≤a≤45%.

[0027] If the peeling angle is too large, the film is not dried sufficiently, the moisture content of the film joint does not meet the standard, the pre-stretching deformation of the film increases, causing the film to deform in the MD direction, which is not conducive to the improvement of the film's mechanical properties. If the peeling angle is too small, the film will be over-dried, which is not conducive to the film heat treatment and causes the film's mechanical properties to deteriorate. The peeling angle can be any value within the range of any two numbers from 60°, 70°, 80°, 90°, 100°, 110°, and 120°.

[0028] The humidity of the coating liquid film after the first drying affects the film peeling effect. If the humidity is too high, the film cannot be formed. If the humidity is too low, it affects the subsequent drying process, which leads to poor film performance. The roller design provided in this application can make the film peeling process possible at a higher humidity, which is conducive to improving the film peeling effect, increasing the roller speed, and increasing product output. The humidity can be any value within the range of any two numbers of 10%, 15%, 25%, 35%, and 45%.

[0029] In some embodiments, preferably, 10%≤a≤20%.

[0030] In some embodiments, preferably, the membrane slurry comprises: polyvinyl alcohol, a solvent and a plasticizer. Preferably, the mass ratio of the polyvinyl alcohol to the solvent is 1:2-10, preferably 1:2-7, more preferably 1:3-5, and the mass ratio of the polyvinyl alcohol to the plasticizer is 1:0.08-0.12, preferably 1:0.08-0.1.

[0031] By using the roller provided by the present invention, it is no longer necessary to add a surfactant to the film slurry, the mass ratio of polyvinyl alcohol to the solvent can be any value within the range formed by any two numbers of 1:2, 1:3, 1:5, 1:7, 1:9, and 1:10, and the mass ratio of polyvinyl alcohol to the plasticizer can be any value within the range formed by any two numbers of 1:0.08, 1:0.09, 1:0.1, and 1:0.12.

[0032] The polymerization degree of polyvinyl alcohol is P, which is 500-6000, preferably 1000-6000, more preferably 1500-4500, further preferably 2000-4000, and most preferably 2000-3000; the alcoholysis degree of polyvinyl alcohol is n, which is n≥99.8%, preferably 99.8-99.99%, and more preferably 99.9-99.99%.

[0033] In some embodiments, preferably, the plasticizer comprises glycerol;

[0034] The membrane slurry further includes an ultraviolet absorber, and the amount of the ultraviolet absorber is 0.001-0.015wt% based on the total amount of the polyvinyl alcohol and glycerol. The ultraviolet absorber can be further added to the membrane slurry to improve the anti-ultraviolet performance of the membrane. The ultraviolet absorber can be any one or more of BP-1, BP-2, BP-3, BP-4, and BP-8. Based on the total amount of the polyvinyl alcohol and glycerol, the amount of the ultraviolet absorber can be any value within the range of any two numbers of 0.001wt%, 0.005wt%, 0.01wt%, 0.012wt%, and 0.015wt%.

[0035] In addition, the plasticizer may further include isopropanol and / or ethylene glycol. The present invention has no particular limitation on the source of the plasticizer, and the plasticizer may be a commercial product or prepared by the skilled person in the art.

[0036] The third aspect of the present invention provides a film produced by the preparation method described in the second aspect of the present invention.

[0037] In some embodiments, preferably, the film has a thickness of 10-80 μm, and a thickness error of ≤±1 μm.

[0038] The present invention will be described in detail by way of examples. In the following examples, all raw materials used are commercially available. The detection method of the maximum deformation variable M in the TD direction and the maximum deformation variable m in the MD direction can be found in CN116587646A; the stretching extension ratio and the testing equipment can be found in CN115855659A; peeling marks: detected by online optical defect detection equipment, the defect morphology is irregular petal-shaped, the equipment detects a petal-shaped defect with different light and dark, and the defect area is greater than 0.5 cm 2 It is a seriously defective product.

[0039] Example 1

[0040] like Figure 1 As shown, a roller for film forming comprises a roller body, the surface of the roller body has a polytetrafluoroethylene layer or a ceramic layer 5, the surface roughness of the polytetrafluoroethylene layer or the ceramic layer 5 is Ra, 0.001μm≤Ra≤0.08μm, preferably, 0.001μm≤Ra≤0.04μm, more preferably, 0.025μm≤Ra≤0.04μm.

[0041] Specifically, the roller body is a sleeve roller, comprising an inner cylinder 1 and an outer cylinder 2 which are sleeved together, wherein the inner cylinder 1 is provided with reinforcing ribs 4, the space between the inner cylinder 1 and the outer cylinder 2 is arranged with a heat medium flow channel 3, and the surface of the outer cylinder 2 has the polytetrafluoroethylene layer or ceramic layer 5, and the thickness of the polytetrafluoroethylene layer or ceramic layer 5 is δ, 0.04mm≤δ≤0.1mm, preferably, 0.04mm≤δ≤0.08mm, and more preferably, 0.05mm≤δ≤0.08mm.

[0042] The following film forming roller provided in Example 1 is used to prepare the film. The process state when peeling the film is as follows: Figure 2 As shown, the prepared film is located on the roller provided in the present application, and a first tangent line C tangent to the film forming roller is made along the film peeling position A, and a second tangent line D tangent to the traction roller is made along the traction position B. The angle between the first tangent line C and the second tangent line D is the film peeling angle θ.

[0043] Example 2

[0044] According to the mass ratio, polyvinyl alcohol, propylene glycol and water are mixed in a ratio of 10:1:20 to obtain a membrane slurry, wherein the degree of polymerization of polyvinyl alcohol is 2400 and the degree of alcoholysis is 99.99%. The above-mentioned membrane slurry is dissolved and homogenized in a reactor, and enters an extruder after coarse filtration. After precise filtration, the slurry enters a mold for forming, and then the slurry is coated on the roller provided in this application to form a coating liquid film, and the coating liquid film is dried for the first time at a drying temperature of 85°C. After the film stays on the roller for 11 / 12 turns, the film is peeled off to obtain a preformed film, and then the preformed film is dried for the second time at a drying temperature of 70°C and a pulling tension of 5N to obtain an optical film with a thickness of 60μm.

[0045] The surface of the coating roller has a polytetrafluoroethylene layer, the surface roughness of which is 0.03 μm and the thickness is 0.06 mm; the moisture content a of the film when peeling off is 15%, and the peeling angle θ is 120°.

[0046] Example 3

[0047] The method of Example 2 was followed, except that polyvinyl alcohol, glycerol, BP-4 and water were mixed in a mass ratio of 10:1:0.0003:20 to obtain a membrane slurry.

[0048] Example 4

[0049] The method of Example 2 was followed, except that the ratio of polyvinyl alcohol: glycerol: water was 10:1:30, the degree of polymerization of polyvinyl alcohol was 2600, the degree of alcoholysis was 99.99%, and the film peeling angle θ was 90°.

[0050] Example 5

[0051] The process was carried out in the same manner as in Example 4, except that polyvinyl alcohol: glycerol: BP-4: water = 10: 1: 0.0006: 20.

[0052] Example 6

[0053] Proceed in the manner of Example 2, except that: the moisture content a of the film is 30% when the film is peeled off.

[0054] Example 7

[0055] The process was carried out in the manner of Example 4, except that the ratio of polyvinyl alcohol: glycerol: water was 10:0.8:50, the surface of the roller used for coating had a ceramic layer with a surface roughness of 0.08 μm and a thickness of 0.1 mm, and the moisture content a of the film when peeling off was 20%.

[0056] Example 8

[0057] The process was carried out in the same manner as in Example 4, except that the surface of the roller used for coating had a ceramic layer with a surface roughness of 0.001 μm and a thickness of 0.04 mm.

[0058] Example 9

[0059] The method of Example 4 is followed, except that the peeling angle θ is 60°.

[0060] Comparative Example 1

[0061] The process is carried out in the same manner as in Example 4, with the only difference being that Ra=0.1 μm.

[0062] Comparative Example 2

[0063] The method of Example 4 is followed, except that the peeling angle θ is 40°.

[0064] Comparative Example 3

[0065] The method of Example 4 is followed, except that the peeling angle θ is 150°.

[0066] Comparative Example 4

[0067] The process was carried out in the same manner as in Example 4, except that the humidity of the coating liquid film after the first drying was 5%.

[0068] Comparative Example 5

[0069] The method of Example 4 was followed, except that the roller used for coating the film was a chrome-plated mirror roller with a roughness Ra < 0.008 μm.

[0070] Comparative Example 6

[0071] The method of Example 3 is followed, except that the roller used for coating the film is a chrome-plated mirror roller with a roughness Ra < 0.008 μm.

[0072] The maximum deformation amount M, stretching extension ratio, thickness uniformity and film imprint of the preformed films prepared in Examples 2-9 and Comparative Examples 1-6 were tested in the MD direction. The results are shown in Table 1.

[0073] Table 1 Test results

[0074]

[0075]

[0076] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A film forming roller, characterized in that: The roller comprises a roller body, the surface of which has a polytetrafluoroethylene layer or a ceramic layer, and the surface roughness of the polytetrafluoroethylene layer or the ceramic layer is Ra, 0.001 μm≤Ra≤0.08 μm.

2. The film forming roller according to claim 1, wherein 0.001 μm≤Ra≤0.04 μm, preferably, 0.025 μm≤Ra≤0.04 μm.

3. The film forming roller according to claim 1 or 2, wherein: The thickness of the polytetrafluoroethylene layer or the ceramic layer is δ, 0.04mm≤δ≤0.1mm.

4. The film forming roller according to claim 3, wherein: 0.04mm≤δ≤0.08mm, preferably, 0.05mm≤δ≤0.08mm.

5. A method for preparing a thin film, characterized in that: The preparation method comprises: coating a film slurry on a film forming roller to form a coating liquid film, performing a first drying and then peeling the film with a film peeling roller to obtain a preformed film, and performing a second drying on the preformed film to obtain an optical film; The film peeling angle during the film peeling is θ, 60°≤θ≤120°, wherein the film peeling angle refers to: a first tangent line tangent to the film forming roller along the film peeling position and a second tangent line tangent to the traction roller along the traction position, and the angle between the two is the film peeling angle; The humidity of the coating liquid film after the first drying is a, 10%≤a≤45%.

6. The preparation method according to claim 5, wherein: 10％≤a≤20％。 7. The preparation method according to claim 5 or 6, wherein: The membrane slurry comprises: polyvinyl alcohol, a solvent and a plasticizer. Preferably, the mass ratio of the polyvinyl alcohol to the solvent is 1:2-10, and the mass ratio of the polyvinyl alcohol to the plasticizer is 1:0.08-0.

12.

8. The preparation method according to claim 7, wherein: The plasticizer includes glycerol; The membrane slurry further comprises an ultraviolet light absorber, and the amount of the ultraviolet light absorber is 0.001-0.015 wt % based on the total amount of the polyvinyl alcohol and glycerol.

9. A film obtained by the preparation method according to any one of claims 5 to 8.

10. The film according to claim 9, wherein The film has a thickness of 10-80 μm, and a thickness error of ≤±1 μm.

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