Embossed film for manufacturing alignment film printing plate and preparation method of embossed film

Abstract

The invention discloses an embossed film for manufacturing an alignment film printing plate and a preparation method of the embossed film. The embossed film comprises a protective film layer, a microstructure pattern layer, a bottom coating and a PET base film layer which are sequentially arranged from top to bottom, and the microstructure pattern layer is an organic silicon coating and a micron-sized regular arrangement pattern formed by embossing the surface of the coating. The preparation method comprises the following steps: coating polyvinyl alcohol cinnamate photoresist on a PET (Polyethylene Terephthalate) base film subjected to surface treatment, exposing, developing and hardening to prepare a soft film with flat-top boss lattice points; coating the light-cured organic silicon resin on the upper surface of the PET base film layer, copying a structure onto the organic silicon resin through a flat-top boss lattice point mold, and curing to form a microstructure pattern layer; and the surface of the microstructure pattern layer is coated with a protective film layer. According to the method, the demolding problem caused by an embossed film coating material is solved, the technical problems of low machining precision of a microstructure pattern and the like are solved, and the machining precision and the machining quality of an alignment film printing plate are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing materials for liquid crystal displays, and more specifically, to an embossed film for manufacturing an alignment film printing plate and a preparation method thereof. Background Art

[0002] In the manufacture of liquid crystal displays, in order to form a liquid crystal alignment film (polyimide film) with uniform film thickness on the electrode forming surface of the glass substrate (TFT / CF) constituting the liquid crystal display element, a flexible printing method that can be produced continuously and has a uniform thickness of the printed oil film can be used. In flexible printing, a flexible printing plate including a flat ink transfer layer is used. The printed ink transfer layer contains a soft and elastic cross-linked resin, and the surface of the printing plate is in a state where the ink that becomes the basis of the liquid crystal alignment film is carried on its surface, and the printing surface such as the electrode forming surface is in contact. The plate surface is usually formed into a rough surface with a specified roughness. The ink transfer layer whose plate surface is roughened is manufactured by the following process using, for example, a photocurable resin that undergoes a curing reaction by irradiation with active light.

[0003] Invention patents CN108454254 (Sumitomo Rubber Industries, Ltd.) and CN111221186 (Wuhan Ruipusai Technology Co., Ltd.) both introduce a technical process for making a printing plate ink transfer layer by embossing technology transfer. This process overcomes the defect of surface oxygen inhibition during the curing process of the photosensitive resin by covering the surface of the photosensitive liquid resin with a layer of embossed film sheet. After curing, the embossed film sheet is peeled off from the surface of the flexible printing plate, thereby forming a microstructure pattern with different regular arrangements on the surface of the printing plate, which is the ink transfer layer required for alignment liquid printing. This process circumvents the defects of film exposure platemaking technology in traditional flexible printing plates, and adjusts the size of the embossed film sheet to form a flexible printing plate in one piece.

[0004] The photosensitive resin used to produce the alignment film printing plate has low mechanical strength (tensile strength is less than 8MPa, elastic modulus is less than 5Mpa). In the above printing plate process, the microstructure resin layer on the surface of the embossed film is solidified and formed using methyl methacrylate materials as the main glue material. The surface energy of the acrylic material is relatively high, resulting in excessive demolding force during the production of the printing plate, making it difficult to tear the film, resulting in the loss of resin on the printing plate surface, and forming surface defects (determined as defective products); secondly, the regularly arranged microstructure pattern on the surface of this type of embossed film is produced by transferring from a master wheel processed by nano / picosecond lasers and CNC precision machine tools. The molding process of these processing ink transfer layer patterns not only has low processing accuracy, which generally exceeds 3μm (especially in the Z-axis direction), but also has high costs for opening the master wheel mold.

[0005] In order to comprehensively solve the demoulding problem caused by the embossed film coating material and the technical difficulties such as low processing precision of the microstructure pattern, the applicant of this application has conducted repeated in-depth research and developed the embossed film and preparation method of this application. Summary of the invention

[0006] An object of the present invention is to provide an embossed film for use in manufacturing an alignment film printing plate and a preparation method thereof, which solves the demolding problem caused by the embossed film coating material and the technical difficulties such as low processing accuracy of the microstructure pattern, and improves the processing accuracy and processing quality of the alignment film printing plate.

[0007] In order to solve the above technical problems, the present invention provides an embossed film for manufacturing an alignment film printing plate, comprising a protective film layer, a microstructure pattern layer, a primer layer, and a PET base film layer arranged in sequence from top to bottom, wherein the microstructure pattern layer is a silicone coating and a micron-level regularly arranged pattern formed by embossing the coating surface.

[0008] Preferably, the protective film layer is made of polyethylene with a thickness of 20-50 μm; the microstructure pattern layer is formed by curing silicone resin with a thickness of 30-100 μm; the primer layer is coated with water-based polyurethane with a thickness of 0.5-3 μm; and the PET base film layer has a thickness of 100-300 μm.

[0009] Preferably, the protective film layer has a thickness of 30 μm; the microstructure pattern layer has a thickness of 40-80 μm; and the PET base film layer has a thickness of 150-200 μm.

[0010] Preferably, the silicone resin contained in the microstructure pattern layer is made of the following raw materials in parts by weight: 50-90 parts of silicone acrylate prepolymer, 0-30 parts of active diluent, 1-5 parts of photoinitiator, 0.5-2 parts of leveling agent, and 0.1-1 parts of defoaming agent.

[0011] Preferably, the pattern on the microstructure pattern layer is printed on the upper surface of the embossed film through a soft film with flat-top boss dots to form a regular pattern, the height of the circular boss on the soft film surface is 5-30 μm; the boss diameter is 5-50 μm, and the number of pattern arrangement lines on the microstructure pattern layer is 200-900.

[0012] Preferably, the height of the circular bosses on the surface of the soft film is 8-18 μm; and the number of pattern arrangement lines on the microstructure pattern layer is 400-800.

[0013] Preferably, the soft film is made of polyvinyl cinnamate negative photoresist and a soft sheet underneath, and the soft sheet is a metal sheet or a polymer film.

[0014] Preferably, the microstructure feature size accuracy on the microstructure pattern layer does not exceed 3 μm.

[0015] The present invention also provides a method for preparing an embossed film for manufacturing an alignment film printing plate, comprising the following steps: Step 1, soft film production: polyvinyl cinnamate photoresist is coated on the surface treated PET base film by slit coating, and then after exposure, development and hardening, a soft film with "flat-top convex dots" is obtained; Step 2: Mix the light-curing silicone resin and evenly apply it on the upper surface of the PET base film layer online, replicate the structure on the silicone resin through a flat-top boss dot mold on the upper surface of the soft film, and then perform UV curing under a UV curing lamp to form a microstructure pattern layer, and then roll it up after curing; Step 3: Lay a protective film layer on the surface of the microstructure pattern layer after curing in the above step 2 by a composite roller.

[0016] Preferably, in step 2, the PET base film layer is first coated with a primer layer before coating the photocurable silicone resin to facilitate the adhesion of the photocurable silicone resin; in step 1, the viscosity of the polyvinyl cinnamate photoresist is 1000-5000mPa.s, and the exposure of the photoresist is achieved by active UV light through a mask, and the number of pattern lines on the mask is 200-900.

[0017] The present invention has at least the following beneficial effects: 1. The microstructure pattern of the embossed film of the present invention is realized by photolithography technology. The photolithography technology and materials used in semiconductor manufacturing are adopted to further improve the processing accuracy of the microscopic pattern on the surface of the embossed film, which does not exceed 3μm, thereby improving the processing accuracy and processing quality of the alignment film printing plate.

[0018] 2. The present invention can adjust the depth and apparent contour volume of the soft film (mother film) microstructure layer by changing the pattern (number of lines, diameter) on the photolithography mask (film), that is, the mother film with a precise pattern is manufactured by photolithography, and the pattern arrangement can be adjusted according to the pattern design on the photomask, and the apparent contour volume of the soft film surface is 3-15μm 3 / μm 2 , with a depth of 5-20μm. The transfer to the printing plate can increase the ink storage volume, and then the printing plate with ink transfer layer with different storage volumes can be produced to meet the needs of thick film printing.

[0019] 3. The present invention uses silicone UV glue and adjusts the coating thickness of the glue layer to maintain the optical transmittance of the (meth)acrylate resin coating while also improving the surface smoothness of the film layer and avoiding film defects such as pores and pinholes.

[0020] 4. The surface coating of the embossed film manufactured by the present invention is made of organic silicon material, which has low surface energy and weak interaction with the printing plate resin, making it easy to tear the film after molding (low demoulding force).

[0021] 5. The present invention provides a manufacturing method for using the manufactured embossed film to further produce printing plates with lower costs and more diverse categories than existing printing plates.

[0022] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the cross-sectional structure of the embossed film provided by the present invention; Figure 2 Schematic diagram of the surface pattern of the soft film used in the manufacture of the embossed film of the present invention; Figure 3 This is a schematic diagram of the embossed film manufacturing process provided by the present invention.

[0024] Description of reference numerals: 1. Protective film layer, 2. Microstructure pattern layer, 3. Primer layer, 4. PET base film layer, 5. Flat-top boss dots, 6. Unwinding roller, 7. Winding roller, 8. Auxiliary roller, 9. Guide roller, 10. Soft film, 11. UV curing lamp. DETAILED DESCRIPTION

[0025] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement it according to the description.

[0026] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0027] like Figure 1 As shown, the present invention provides an embossed film, which comprises, from top to bottom, a protective film layer 1, a microstructure pattern layer 2, a primer layer 3, and a PET base film layer 4. The microstructure pattern layer is a regularly arranged pattern at the micrometer level formed by embossing the surface of the organic silicon coating and the coating.

[0028] Among them, the protective film layer is made of polyethylene (PE) material, with a thickness of 20-50μm, preferably about 30μm; the microstructure pattern layer is cured and formed by silicone photosensitive resin, with a thickness of 30-100μm, preferably 40-80μm; the PET primer layer is coated with water-based polyurethane, with a thickness of about 0.5-3μm; the thickness of the PET base film layer is about 100-300μm, preferably 150-200μm.

[0029] Among them, the main components of the silicone resin glue are silicone acrylate and its modified resin, which are prepared according to the following formula design (mass fraction): 50-90 parts of silicone acrylate prepolymer, Active diluent 10-30 parts, 1-5 parts of photoinitiator, Leveling agent 0.5-2 parts Defoaming agent 0.1-1 part.

[0030] The pattern making process on the microstructure pattern layer requires the use of a soft film ("mother film") with flat-topped boss dots 5, such as Figure 2 As shown, the dot microstructure is transferred to the upper surface of the embossed film to form a regular pattern. The height of the circular boss on the soft film surface is 5-30μm, preferably 8-18μm; the boss diameter is 5-50μm, which can be accurately designed in combination with the number of pattern arrangement lines. The number of pattern arrangement lines on the microstructure pattern layer ranges from 200 to 900. In order to meet the printing requirements of the liquid crystal alignment film, the number of lines is preferably 400-800. The microstructure feature size accuracy does not exceed 3μm.

[0031] The soft film used in the manufacturing is made of i-line polyethylene oxyethanol cinnamate negative photoresist and a soft sheet underneath. The soft sheet can be a metal sheet, such as aluminum film, copper film; or a polymer film, polyvinyl chloride, acrylic, polyester (PET, polyethylene terephthalate), polypropylene, etc. Considering the technical practicality, PET film is preferred.

[0032] The apparent contour volume of the soft film surface is 3-15μm 3 / μm 2 , with a depth of 5-20μm.

[0033] The present invention also provides a method for preparing an embossed film for manufacturing an alignment film printing plate, comprising the following steps: (1) Soft film production: Polyvinyl cinnamate photoresist is coated on the surface-treated PET base film by an offline slit coating method. After exposure, development and hardening, a soft film with "flat-top boss dots" is obtained.

[0034] (2) Mix the photocurable silicone resin and evenly apply it online to the upper surface of the PET base film layer. On the upper surface of the soft film, the flat-top boss dot mold is used to replicate the structure onto the silicone resin. Then, the film is UV cured under a UV curing lamp to form a microstructure pattern layer. After curing, the film is rolled up. Before applying the photocurable silicone resin, the PET base film layer is first coated with a primer layer to facilitate the adhesion of the photocurable silicone resin.

[0035] The specific preparation process is as follows Figure 3 The device shown is completed. Figure 3 The preparation device includes an unwinding roller 6 and a winding roller 7 on both sides, which are used to unwind the PET base film layer before preparation and to wind up the film with the microstructure pattern layer after preparation. A plurality of auxiliary rollers 8 for stretching the soft film 10 are also arranged between the unwinding roller and the winding roller, and a plurality of guide rollers 9 are arranged below the auxiliary rollers. The PET base film layer passes through the unwinding roller, between the auxiliary roller and the guide roller, and the winding roller in sequence, and is tightened. Ultraviolet curing lamps 11 are also arranged at the corresponding positions of the auxiliary rollers and the guide rollers for irradiation curing. Before the PET base film layer enters between the auxiliary rollers and the guide rollers, it is also coated with organic silicone water.

[0036] (3) A PE protective film layer is coated on the surface of the microstructure pattern layer after curing in the above step (2) by a composite roller.

[0037] The viscosity of the polyvinyl cinnamate photoresist in step (1) is 1000-5000 mPa.s, more preferably 2000-3000 mPa.s.

[0038] In step (1), the exposure of the photoresist is achieved by active UV light through a mask, and the number of pattern lines on the mask ranges from 200 to 900, and more preferably from 400 to 800.

[0039] The complete implementation process is described in detail below.

[0040] Production of soft film: A PET film with a thickness of 188 μm, a length of 1.3 m, and a width of 0.8 m was laid flat on the exposure machine. Polyvinyl cinnamate photoresist (customized by Guangzhou Songda New Materials, with a viscosity of about 13000 cp) was evenly coated on the surface of the PET film by slit coating. The coating thickness was controlled at 100-120 μm. The upper glass substrate with a film (ordered from Luwei Optoelectronics, 400-800 lines / inch) was lowered to the preset working position and exposed for 45 seconds (365 nm, 8 mW / cm 2); Fix the exposed mother film (soft film) on the cleaning machine through a clamp, use developer to spray and clean the uncured photoresist, then use pure water to clean the developer, and after drying, use 254nm UV exposure for 5 minutes to harden the film. The "dots" on the surface of the mother film are arranged as follows Figure 2 shown.

[0041] Preparation of silicone resin glue: The embossed film microstructure layer of the present invention adopts silicone photocuring glue, which is compounded from commercially available resins. Considering the hardness, toughness and smoothness of the embossed film layer after curing, the inventors have screened the silicone resin and its formula design many times. The formula data of several representative embodiments are shown in Table 1 below.

[0042] Table 1 Organic silicon resin glue formula of various embodiments of the present invention The comparative example uses acrylic glue (Comparative Example 1); Comparative Example 2 is an embossed film material for mass production (the formula ingredients are unknown, but the main material is acrylic), and the relevant comparative example formulas are shown in Table 2 below.

[0043] Table 2 Glue formulas of various comparative examples of the present invention The data of the hardness, toughness, smoothness and other properties of the embossed film layer after curing evaluated in the above-mentioned embodiments and comparative examples are shown in Table 3 below.

[0044] Table 3 Evaluation performance data of various embodiments and comparative examples Embossed film forming: The molding process is mainly divided into two steps: coating and molding curing. First, as the PET substrate (i.e., PET base film layer) moves forward, the silicone resin glue is evenly coated on the surface of the PET substrate by the coating of the line roller. Secondly, the mother film with the "flat-top dot" microstructure is placed on the roller, and under the irradiation of the UV lamp, the microstructure is cured and formed on the surface of the film on the PET substrate coated with glue. After demolding, the target structure embossed film can be obtained (process as shown in the figure). Figure 3 as shown).

[0045] Print version production: The manufacturing process of the flexible printing plate refers to patent CN103144458A, that is, the embossed film in the embodiment and the comparative example is laid flat on the lower glass substrate of the exposure machine, a certain thickness of liquid photosensitive resin is coated, and the other side is covered with a reinforced sheet (PET material), and ultraviolet light (365nm, irradiation intensity 5mW / cm 2) The photosensitive resin is exposed and cured through the embossed film sheet. After curing, the printing plate is transferred and the embossed film sheet is peeled off, thereby forming an ink transfer layer with a micron-level "concave and convex" structure on the surface of the printing plate. According to printing needs, the printing plate is cut, laser engraved, cleaned, dried, etc.

[0046] Production of liquid crystal alignment film: The flexographic printing plates prepared in the examples and comparative examples were placed on an anilox roller (with a unit volume of 6.5 cc / m 2 ) was assembled into a flexographic printing machine (A45 manufactured by Nakan, Japan) for printing the liquid crystal alignment film. Next, the ink for the liquid crystal alignment film (liquid crystal alignment agent manufactured by Shenzhen Dalton Technology Co., Ltd., PI content 6wt%) was supplied to the flexible printing plate, and the ink was printed on a soda-lime glass substrate with an ITO transparent electrode on the surface, and then pre-dried at 120°C for 30 minutes to form a liquid crystal alignment film.

[0047] Evaluation of the thickness of the liquid crystal alignment film: The printed glass substrate was sampled in the front end and the rear end area of ​​the printing direction, left, middle and right, cut and prepared (cross-section), and the thickness of the PI alignment film was measured by an electron scanning electron microscope (SEM). Five thickness values ​​were measured for each group, and the thickness of the alignment film and the uniformity of the film thickness of the printing plate were evaluated, as shown in Table 4 below.

[0048] Table 4 Evaluation of alignment film parameters of various embodiments and comparative examples The surface contour volume Vvc (Core void volume) is a functional volume parameter of the 3D confocal profilometer, and this parameter is used to make a quantitative judgment on the contour volume of the embossed film in the present application technology.

[0049] It is understood that the present invention is described by some embodiments, and those skilled in the art are aware that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation mode, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, other modifications can be easily implemented, so without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

1. An embossed film for making an alignment film printing plate, characterized in that: It includes a protective film layer, a microstructure pattern layer, a primer layer, and a PET base film layer arranged in sequence from top to bottom, wherein the microstructure pattern layer is a micrometer-level regularly arranged pattern formed by an organic silicon coating and embossing on the coating surface.

2. The embossed film for producing an alignment film printing plate according to claim 1, wherein: The protective film layer is made of polyethylene with a thickness of 20-50 μm; the microstructure pattern layer is formed by curing silicone resin with a thickness of 30-100 μm; the primer layer is coated with water-based polyurethane with a thickness of 0.5-3 μm; and the PET base film layer has a thickness of 100-300 μm.

3. The embossed film for producing an alignment film printing plate according to claim 2, wherein: The thickness of the protective film layer is 30 μm; the thickness of the microstructure pattern layer is 40-80 μm; and the thickness of the PET base film layer is 150-200 μm.

4. The embossed film for producing an alignment film printing plate according to claim 1, wherein: The organic silicon resin contained in the microstructure pattern layer is made of the following raw materials in parts by weight: 50-90 parts of organic silicon acrylate prepolymer, 0-30 parts of active diluent, 1-5 parts of photoinitiator, 0.5-2 parts of leveling agent, and 0.1-1 parts of defoaming agent.

5. The embossed film for producing an alignment film printing plate according to claim 1, wherein: The pattern on the microstructure pattern layer is printed on the upper surface of the embossed film through a soft film with flat-top boss dots to form a regular pattern. The height of the circular boss on the soft film surface is 5-30 μm; the boss diameter is 5-50 μm, and the number of pattern arrangement lines on the microstructure pattern layer is 200-900.

6. The embossed film for producing an alignment film printing plate according to claim 5, characterized in that: The height of the circular boss on the surface of the soft film is 8-18 μm; and the number of pattern arrangement lines on the microstructure pattern layer is 400-800.

7. The embossed film for producing an alignment film printing plate according to claim 5, characterized in that: The soft film is made of polyvinyl alcohol cinnamate negative photoresist and a lower soft sheet material, and the soft sheet material is a metal sheet material or a polymer film.

8. The embossed film for producing an alignment film printing plate according to claim 5, wherein: The microstructure feature size accuracy on the microstructure pattern layer does not exceed 3 μm.

9. The method for preparing an embossed film for producing an alignment film printing plate according to any one of claims 1 to 8, characterized in that: The steps include: Step 1, soft film production: polyvinyl cinnamate photoresist is coated on the surface treated PET base film by slit coating, and then after exposure, development and hardening, a soft film with "flat-top convex dots" is obtained; Step 2: Mix the light-curing silicone resin and evenly apply it on the upper surface of the PET base film layer online, replicate the structure on the silicone resin through a flat-top boss dot mold on the upper surface of the soft film, and then perform UV curing under a UV curing lamp to form a microstructure pattern layer, and then roll it up after curing; Step 3: Lay a protective film layer on the surface of the microstructure pattern layer after curing in the above step 2 by a composite roller.

10. The method for preparing an embossed film for producing an alignment film printing plate according to claim 9, wherein: In step 2, before coating the photocurable silicone resin, the PET base film layer is first coated with a primer layer to facilitate the adhesion of the photocurable silicone resin; in step 1, the viscosity of the polyvinyl cinnamate photoresist is 1000-5000mPa.s, and the exposure of the photoresist is achieved by active UV light through a mask, and the number of pattern lines on the mask is 200-900.

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