An epoxy adhesive, a cover film and a printing stencil

Abstract

The present invention relates to an epoxy adhesive, a cover film and a printing stencil. The epoxy adhesive is composed of an epoxy resin, a film-forming resin, a tackifying resin, a curing agent, a curing accelerator and a solvent, and the total mass of the epoxy resin, the film-forming resin, the tackifying resin, the curing agent and the curing accelerator is 1 to 1.2 times the mass of the solvent. By improving the adhesive formula and the cover film, the cover film of the present invention can be formed at a low temperature, and the cover film of the present invention has good bonding performance with the stencil body, is not easy to overflow glue and delaminate, and has good chemical resistance. The printing stencil of the present invention has a long service life, saves material costs, saves the replacement man-hours of the production line, and improves the use efficiency.

Description

[0001] This invention is a divisional application of an epoxy adhesive, a cover film and a printing stencil, with the application date of December 30, 2020, the application number of 2020116166892, and the invention title of "An Epoxy Adhesive, a Cover Film and a Printing Stencil". Technical Field

[0002] This invention specifically relates to an epoxy adhesive, a cover film and a printing stencil. Background Art

[0003] Traditional printing stencils use photosensitive inks coated on steel meshes, and then the desired circuits are obtained through the method of exposing with a film positive + developing and washing with a chemical solution. The traditional method has a large chemical pollution in the process, the service life cycle of the obtained printing stencils is not long enough, the production lines using the stencils need to frequently replace the stencils, which affects the production efficiency and wastes inks, silver pastes, etc. on the production lines. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide an epoxy adhesive, a cover film and a printing stencil that can improve the service life of the printing stencil.

[0005] To achieve the above purpose, this invention adopts the following technical solutions:

[0006] On one hand, this invention provides an epoxy adhesive, which includes the following components by mass percentage:

[0007]

[0008] In this invention, the weight ratio of epoxy resin is selected to be 20 - 60%; if it is lower than 20%, the drug resistance of the system is insufficient; if it is higher than 60%, the adhesive layer is too hard and the bonding performance is affected. The weight ratio of film-forming resin is selected to be 20 - 40%; if it is less than 20%, the shrinkage holes will occur during coating; if it is higher than 40%, the viscosity of the adhesive is too high, which is not conducive to coating and affects the bonding strength.

[0009] Preferably, by mass percentage, the epoxy adhesive includes the following components:

[0010]

[0011] Further preferably, by mass percentage, the epoxy adhesive includes the following components:

[0012]

[0013] Preferably, the epoxy resin is one or a combination of two or more of bisphenol A epoxy, bisphenol F epoxy, phenolic epoxy, biphenyl epoxy, phenol epoxy, and rubber-modified, polyurethane-modified, and acrylic-modified products of the above epoxy resins.

[0014] Further preferably, the epoxy resin is preferably one or a mixture of two or more of bis-component A epoxy, phenolic epoxy, rubber-modified epoxy, and polyurethane-modified epoxy.

[0015] Further preferably, the epoxy resin is a combination of two epoxy resins, such as a mixture of any two of epoxy resin 128E, epoxy resin N740S, epoxy resin NPPN-272H, and epoxy resin NPES901; further preferably, the mass ratio of the two epoxy resins is 1:1 to 2.

[0016] According to a preferred embodiment, the epoxy resin is a combination of epoxy resin 128E and epoxy resin N740S with a mass ratio of 1 to 3.

[0017] According to another preferred embodiment, the epoxy resin is a combination of epoxy resin NPPN-272H and epoxy resin NPES901 with a mass ratio of 1 to 3.

[0018] Preferably, the film-forming resin is a combination of one or more of nitrile rubber, acrylic rubber, and phenoxy resin.

[0019] Preferably, the weight-average molecular weight Mw of the film-forming resin is ≥30,000.

[0020] According to a specific and preferred embodiment, the nitrile rubber is, for example, 1072CG of South Imperial Chemical Industry Co., Ltd. in Taiwan, China, XER-32 and EXR-91 of JSR in Japan, and X-740 of Lanxess in Germany; the acrylic rubber is, for example, G, GXF, Ultra HT; the phenoxy resin is, for example, YP50, YP50S, YP70, and ZX-1356-2 of Nippon Steel & Sumikin Chemical Co., Ltd. in Japan, and 1256, 4250, and 4275 of Mitsubishi Chemical Corporation in Japan.

[0021] Preferably, the tackifying resin is a combination of one or two or more of rosin resin, rosin derivatives, terpene resin, petroleum resin, dicyclopentadiene (DCPD) resin, coumarone-indene resin, and alkylphenolic resin. Among them, rosin and its derivative resins are, for example, GA-85, GA90, GA100, and GA115 of Arakawa Chemical Industries, Ltd. in Japan, rosin terpene resins T803, T901, T805, and T85, hydrogenated rosin GA-85H and GH100, petroleum resins are, for example, FTR6100 and FTR8100 of Mitsui Chemicals, Inc. in Japan, and alkylphenolic resins include alkylphenolic resins with tert-butyl, octyl, nonyl, phenyl, and cyclohexyl groups at the ortho-position, para-position (or ortho-position) of phenol.

[0022] Preferably, the curing agent is at least one of phenolic curing agents, organic amine curing agents, and acid anhydride curing agents, or a combination of two or more of them. Among them, phenolic curing agents such as linear phenol formaldehyde resin, linear bisphenol A formaldehyde resin, and linear o-cresol formaldehyde resin curing agent; organic amines such as dicyandiamide (DICY), 4,4-diaminodiphenyl sulfone (4,4-DDS), diaminodiphenyl methane (DDM); acid anhydride curing agents such as methyl nadic anhydride MNA-A, and polyazelanic anhydride; among which, preferably, it is a mixture of one or more of DICY, 4,4-DDS, linear phenol formaldehyde resin, and linear bisphenol A formaldehyde resin.

[0023] Preferably, the curing accelerator is at least one of amine accelerators, substituted urea accelerators, imidazole and its salt accelerators, boron trifluoride amine complex, phenolic accelerators, metal organic salt accelerators, and phosphine accelerators, or a combination of two or more of them.

[0024] More preferably, the curing accelerator is 2-ethyl-4-methylimidazole (2E4MZ), 1-cyanoethyl-2-ethyl-4-methylimidazole 2E4MZ-CN, 2,4-diamino-6[2'-ethyl-4'-methylimidazole-(1')]ethyl-S-triazine 2E4MZ-A, 2-methylimidazole-trimeric isocyanate 2MZ-OK, etc., and more preferably 2E4MZ-CN.

[0025] Preferably, the epoxy adhesive further includes a solvent, and the total mass of the epoxy resin, the film-forming resin, the tackifying resin, the curing agent, and the curing accelerator is 1 to 1.2 times the mass of the solvent.

[0026] The second aspect of the present invention provides a cover film, including a polyimide (PI) thin film layer and an adhesive layer formed on the polyimide thin film layer, and the adhesive layer is formed by the above-mentioned epoxy adhesive.

[0027] Preferably, the thickness of the polyimide thin film layer is 5 to 25 μm; the thickness of the adhesive layer is 3 to 20 μm. If the adhesive layer is too thin, the bonding effect of the adhesive layer will be affected; if it is too thick, glue overflow will occur to the other side of the printing stencil, thus affecting the laser processing. If the thickness of the polyimide thin film layer is too thick, the efficiency of laser processing will also be affected, requiring greater laser energy and longer processing time, and too high laser energy and too long processing time will punch through the stencil, increasing the rejection rate.

[0028] The third aspect of the present invention is to provide a method for preparing the cover film, corona-treating the polyimide thin film, then coating the epoxy adhesive on the corona-treated surface of the polyimide thin film, and then drying and curing to obtain the cover film.

[0029] Preferably, the drying temperature is 70 - 130°C, and the drying time is 1 - 10 min; the curing temperature is 40 - 50°C, and the curing time is 20 - 30 h.

[0030] A fourth aspect of the present invention is to provide a printing stencil, including a stencil body. The printing stencil further includes a covering film disposed on the stencil body, and an adhesive layer of the covering film is in contact with the stencil body; the covering film has a hollow out portion for forming a desired circuit.

[0031] The stencil body in the present invention is a printing steel mesh in the prior art.

[0032] A fifth aspect of the present invention is to provide a preparation method of the printing stencil. The adhesive layer of the covering film is adhered to one side of the stencil body, then hot-pressed at 80 - 120°C and 0.5 - 1 MPa for 30 - 60 min, and then the covering film is processed by laser to make a hollow out portion to obtain the printing stencil.

[0033] By adopting laser processing in the present invention, finer hollow out portions can be obtained. During printing, silver paste is transferred and adhered to the product through these hollow out portions, so that finer line drawings can be obtained, thereby saving material costs.

[0034] Due to adopting the above technical solutions, the present invention has the following advantages compared with the prior art:

[0035] Through the improvement of the adhesive formula and the covering film, the covering film of the present invention can be hot-pressed at a low temperature, and the covering film of the present invention has good bonding performance with the stencil body, is not easy to overflow glue and delaminate, and has good chemical resistance.

[0036] The printing stencil of the present invention has a long service life, saves material costs, saves the replacement man-hours of the production line, and improves the use efficiency. Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of the covering film adhered to the stencil body;

[0038] Figure 2 It is a schematic diagram of processing the covering film by laser. Detailed Embodiments

[0039] The technical solutions of the present invention will be further described below in combination with specific implementation cases, but the present invention is not limited to the following embodiments. The implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0040] The raw materials and reagents used in the present invention can all be obtained commercially.

[0041] Example 1

[0042] Epoxy resin 128E / 20 parts, epoxy resin NPPN-272H / 30 parts, rosin resin: GA90A / 10 parts, nitrile rubber 1072CG / 40 parts, 4,4-DDS / 15 parts, 2E4MZ-CN / 0.5 parts, using methyl ethyl ketone solvent / 100 parts, dissolve or disperse to make an epoxy adhesive.

[0043] Pre-corona treat the PI film, coat the epoxy adhesive on the corona-treated surface of the PI film, dry the solvent at 80°C / 5 mins, laminate with release paper, wind up and place in an oven for curing at 45°C / 24H to make a PI cover film.

[0044] After tearing off the release paper from the above PI cover film, bond the adhesive layer to one side of the stencil, then perform hot pressing in a hot press under the hot pressing conditions of 120°C / 60 mins / 0.5 - 1.0 Mpa. For the stencil after hot pressing, locally hollow out the PI cover film on the stencil by laser to obtain the desired circuit.

[0045] Example 2

[0046] Epoxy resin 128E / 30 parts, epoxy resin NPPN-272H / 30 parts, rosin resin: GA100 / 10 parts, nitrile rubber 1072CG / 30 parts, 4,4-DDS / 18 parts, 2E4MZ-CN / 0.5 parts, using methyl ethyl ketone solvent / 100 parts, dissolve or disperse to make an epoxy adhesive.

[0047] Pre-corona treat the PI film, coat the epoxy adhesive on the corona-treated surface of the PI film, dry the solvent at 80°C / 5 mins, laminate with release paper, wind up and place in an oven for curing at 45°C / 24H to make a PI cover film.

[0048] After tearing off the release paper from the above PI cover film, bond the adhesive layer to one side of the stencil, then perform hot pressing in a hot press under the hot pressing conditions of 120°C / 60 mins / 0.5 - 1.0 Mpa. For the stencil after hot pressing, locally hollow out the PI cover film on the stencil by laser to obtain the desired circuit.

[0049] Example 3

[0050] Epoxy resin 128E / 30 parts, epoxy resin NPPN-272H / 30 parts, rosin resin: GA100 / 10 parts, nitrile rubber 1072CG / 40 parts, DICY / 6 parts, 2E4MZ-CN / 0.5 parts, using methyl ethyl ketone solvent / 100 parts, dissolve or disperse to make an epoxy adhesive.

[0051] Pre-corona treat the PI film, coat the epoxy adhesive on the corona-treated surface of the PI film, dry the solvent at 80°C for 5 minutes, laminate with release paper, wind up and place in an oven for curing at 45°C for 24 hours to make the PI cover film.

[0052] After tearing off the release paper from the above PI cover film, bond the adhesive layer to one side of the stencil, and then perform hot pressing in a hot press under the hot pressing conditions of 120°C / 60 minutes / 0.5 - 1.0 Mpa. For the hot-pressed stencil, locally hollow out the PI cover film on the stencil by laser to obtain the desired circuit.

[0053] Example 4

[0054] Epoxy resin N740S / 20 parts, epoxy resin NPPN-272H / 40 parts, nitrile rubber 1072CG / 30 parts, rosin resin: GB120 / 10 parts, 4,4-DDS / 16 parts, 2E4MZ-CN / 0.5 parts, use methyl ethyl ketone solvent / 100 parts, dissolve or disperse to make the epoxy adhesive.

[0055] Pre-corona treat the PI film, coat the epoxy adhesive on the corona-treated surface of the PI film, dry the solvent at 80°C for 5 minutes, laminate with release paper, wind up and place in an oven for curing at 45°C for 24 hours to make the PI cover film.

[0056] After tearing off the release paper from the above PI cover film, bond the adhesive layer to one side of the stencil, and then perform hot pressing in a hot press under the hot pressing conditions of 120°C / 60 minutes / 0.5 - 1.0 Mpa. For the hot-pressed stencil, locally hollow out the PI cover film on the stencil by laser to obtain the desired circuit.

[0057] Example 5

[0058] Epoxy resin N740S / 20 parts, epoxy resin NPES901 / 40 parts, nitrile rubber 1072CG / 30 parts, rosin resin: GB120 / 10 parts, 4,4-DDS / 2 parts, DICY / 4 parts, 2E4MZ-CN / 0.5 parts, use methyl ethyl ketone solvent / 100 parts, dissolve or disperse to make the epoxy adhesive.

[0059] Pre-corona treat the PI film, coat the epoxy adhesive on the corona-treated surface of the PI film, dry the solvent at 80°C for 5 minutes, laminate with release paper, wind up and place in an oven for curing at 45°C for 24 hours to make the PI cover film.

[0060] After the above-mentioned PI cover film is peeled off the release paper, the adhesive layer is bonded to one side of the stencil, and then hot-pressed in a hot press under the hot-pressing conditions of 120°C / 60 mins / 0.5 - 1.0 Mpa. For the stencil after hot-pressing forming, the PI cover film on the stencil is locally hollowed out by laser to obtain the desired circuit.

[0061] Comparative Example 1

[0062] Epoxy resin 128E / 20 parts, epoxy resin NPPN-272H / 10 parts, nitrile rubber 1072CG / 60 parts, rosin resin: GB120 / 10 parts, 4,4-DDS / 9 parts, 2E4MZ-CN / 0.5 parts, using methyl ethyl ketone solvent / 100 parts, dissolve or disperse to make an epoxy adhesive.

[0063] Pre-corona treat the PI film in advance, coat the epoxy adhesive on the corona-treated surface of the PI film, dry the solvent at 80°C / 5 mins, laminate with the release paper, wind up and place in an oven for curing treatment at 45°C / 24H to make a PI cover film.

[0064] After the above-mentioned PI cover film is peeled off the release paper, the adhesive layer is bonded to one side of the stencil, and then hot-pressed in a hot press under the hot-pressing conditions of 120°C / 60 mins / 0.5 - 1.0 Mpa. For the stencil after hot-pressing forming, the PI cover film on the stencil is locally hollowed out by laser to obtain the desired circuit.

[0065] Comparative Example 2

[0066] Epoxy resin 128E / 30 parts, epoxy resin NPPN-272H / 55 parts, nitrile rubber 1072CG / 10 parts, rosin resin: GB120 / 5 parts, 4,4-DDS / 24 parts, 2E4MZ-CN / 0.5 parts, using methyl ethyl ketone solvent / 100 parts, dissolve or disperse to make an epoxy adhesive.

[0067] Pre-corona treat the PI film in advance, coat the epoxy adhesive on the corona-treated surface of the PI film, dry the solvent at 80°C / 5 mins, laminate with the release paper, wind up and place in an oven for curing treatment at 45°C / 24H to make a PI cover film.

[0068] After the above-mentioned PI cover film is peeled off the release paper, the adhesive layer is bonded to one side of the stencil, and then hot-pressed in a hot press under the hot-pressing conditions of 120°C / 60 mins / 0.5 - 1.0 Mpa. For the stencil after hot-pressing forming, the PI cover film on the stencil is locally hollowed out by laser to obtain the desired circuit.

[0069] Comparative Example 3

[0070] 128E epoxy resin / 20 parts, NPPN-272H epoxy resin / 40 parts, 1072CG nitrile rubber / 30 parts, rosin resin: GB120 / 10 parts, 4,4-DDS / 15 parts, using methyl ethyl ketone solvent / 100 parts, dissolve or disperse to make an epoxy adhesive.

[0071] Pre-corona treat the PI film, coat the epoxy adhesive on the corona side of the PI film, dry the solvent at 80°C for 5 minutes, laminate the release paper, wind it up and place it in an oven for curing at 45°C for 24 hours to make a PI cover film.

[0072] After removing the release paper from the above PI cover film, bond the adhesive layer to one side of the stencil, and then perform hot pressing in a hot press. The hot pressing conditions are 120°C / 60 minutes / 0.5 - 1.0 Mpa. For the stencil after hot pressing, locally hollow out the PI cover film on the stencil by laser to obtain the desired circuit.

[0073] The sources of the above raw materials are as follows:

[0074] 128E epoxy resin, Nan Ya, Taiwan, China

[0075] N740S epoxy resin, Nantong Xingchen Chemical

[0076] NPPN-272 epoxy resin, Nan Ya, Taiwan, China

[0077] NPES901 epoxy resin, Nan Ya, Taiwan, China 1072CG nitrile rubber, South Imperial Chemical Industries Co., Ltd., Taiwan, China

[0078] 4,4-DDS, Atul, India

[0079] DICY, Ningxia Jiafeng Chemical

[0080] 2E4MZ-CN, Shikoku Chemicals, Japan

[0081] Rosin resins GA90A, GA100, GB120 are products of Arakawa Chemical Industries, Ltd., Japan

[0082] The experimental data of the above examples and comparative examples are as follows:

[0083]

[0084] Comprehensive evaluation

[0085] "○" represents qualified performance, "◎" represents excellent performance, "△" represents average performance, and "×" represents poor performance.

[0086] Evaluation method:

[0087] Bonding strength: After the PI cover film and the stencil are hot pressed, they are cut into 1cm×20cm pieces, the PI film at the ends in the length direction is opened, and the film is peeled off at 180° at a speed of 100mm / min.

[0088] Dry to touch: After the hot pressing of the above PI cover film, touch the adhesive surface with your finger. If there is no stickiness, it is OK; if there is stickiness, it is NG.

[0089] Glue overflow: Use a 10mm diameter puncher to punch 5 holes on the PI cover film, and hot press it with the stencil at 120℃ / 60mins / 0.5Mpa. Use an electron microscope to measure the amount of glue overflowing from the circular holes.

[0090] Chemical resistance: Soak the laser-cut stencil in the slurry for 24 hours, then wipe it dry and observe through a microscope whether the slurry has penetrated into the space between the PI and the adhesive layer on the cover film, or between the adhesive layer and the stencil, and whether floating or delamination occurs. If so, it is NG, otherwise it is OK.

[0091] (Slurry composition: silver powder / 80%, bisphenol A epoxy / 10%, anhydride curing agent 2%, methylimidazole / 0.5%, butyl acetate / 5%, active diluent 692 / 1.5%, tetraethyl titanate / 0.5%, polyamide wax / 0.5%).

[0092] Dimensional stability: After the PI covering film of 200mm*200mm is hot pressed with the stencil, select ABCD at the four corners of the PI film and make dot marks with an oil pen. Use the second element to test the spacing between the four points AB, BC, CD, and DA, AB', BC', CD', and DA'. Use a printed scraper to scrape 10,000 times, and then measure the spacing between the four points. Calculate the shrinkage rate 1 = [(AB'-AB) / AB+(CD'-CD) / CD] / 2, calculate the shrinkage rate 2 = [(BC'-BC) / BC+(DA'-DA) / DA] / 2, and record the maximum value of the shrinkage rates 1 and 2 as the value of dimensional stability.

[0093] The above detailed description of the present invention is intended to enable those skilled in the art to understand the contents of the present invention and implement them, but it does not limit the protection scope of the present invention. The present invention is not limited to the above embodiments, and any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. An epoxy adhesive, characterized in that: The epoxy adhesive is composed of epoxy resin, film-forming resin, tackifying resin, curing agent, curing accelerator and solvent. The total mass of the epoxy resin, the film-forming resin, the tackifying resin, the curing agent and the curing accelerator is 1 to 1.2 times the mass of the solvent. The epoxy resin is a mixture of any two of epoxy resin 128E, epoxy resin N740S, epoxy resin NPPN-272H and epoxy resin NPES901, and the mass ratio of the two epoxy resins is 1:(1 to 2); The film-forming resin is nitrile rubber; The tackifying resin is rosin resin; The curing agent is at least one or a combination of two or more of phenolic curing agents, organic amine curing agents and acid anhydride curing agents; The curing accelerator is at least one or a combination of two or more of amine accelerators, substituted urea accelerators, imidazole and its salt accelerators, boron trifluoride amine complex, phenolic accelerators, metal organic salt accelerators and phosphine accelerators. Based on the total mass of the epoxy resin, the film-forming resin, the tackifying resin, the curing agent and the curing accelerator being 100%, Epoxy resin 40 - 60%; Film-forming resin 25 - 35%; Tackifying resin 5 - 10%; Curing agent 5 - 16%; Curing accelerator 0.1 - 1%.

2. The epoxy adhesive according to claim 1, characterized in that: The epoxy resin is 50 - 60 parts, the film-forming resin is 30 - 40 parts, the tackifying resin is 10 parts, the curing agent is 6 - 18 parts, the curing accelerator is 0.5 part, and the solvent is 100 parts.

3. The epoxy adhesive according to claim 1, wherein: The weight-average molecular weight Mw of the film-forming resin ≥ 30000; and / or, The phenolic curing agent is selected from linear phenol formaldehyde resin, linear bisphenol A formaldehyde resin and linear o-cresol formaldehyde resin curing agent. The organic amine curing agent is selected from dicyandiamide, 4,4-diaminodiphenyl sulfone and diaminodiphenyl methane. The acid anhydride curing agent is selected from methyl nadic anhydride and polyazelaic anhydride; and / or, The curing accelerator is selected from 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2,4-diamino-6[2'-ethyl-4'-methylimidazole-(1')]ethyl-S-triazine and 2-methylimidazole-trimeric isocyanate.

4. A covering film, characterized in that: It includes a polyimide film layer and a bonding layer formed on the polyimide film layer. The bonding layer is formed by the epoxy adhesive according to any one of claims 1 to 3.

5. The cover film according to claim 4, wherein: The bonding layer is formed after the epoxy adhesive dries the solvent.

6. The cover film according to claim 4, characterized in that: The thickness of the polyimide film layer is 5 - 25 μm; the thickness of the bonding layer is 3 - 20 μm.

7. A method for preparing a cover film according to any one of claims 4 to 6, characterized in that: The polyimide film is subjected to corona treatment, then the epoxy adhesive is coated on the corona surface of the polyimide film, and then dried and cured to obtain the cover film.

8. The method for preparing a cover film according to claim 7, characterized in that: The drying temperature is 70 - 130°C, and the drying time is 1 - 10 min; the curing temperature is 40 - 50°C, and the curing time is 20 - 30 h.

9. A printing stencil, comprising a stencil body, characterized in that: The described printing stencil further includes a covering film as described in any one of claims 4 to 6 provided on the stencil body, and the adhesive layer of the covering film is in contact with the stencil body; the covering film has a hollowed-out portion for forming a required circuit.

10. A method for preparing a printing stencil as described in claim 9, characterized in that: The adhesive layer of the covering film is adhered to one side of the stencil body, and then hot-pressed at 100 to 160 °C and 0.5 to 1 MPa for 30 to 80 minutes, and then the covering film is subjected to a hollowing-out treatment by a laser method to obtain the printing stencil.

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