A modified adhesive layer for FPC manufacturing and its preparation method

Abstract

The present invention provides a modified adhesive layer for FPC manufacturing and a preparation method thereof. The preparation method comprises the following steps: (1) sequentially adding a UV curable resin, a crosslinking resin composition and a modified filler into a solvent-based pressure-sensitive adhesive, then stirring evenly to mix uniformly; continuously adding a photoinitiator; and further adding an NCO type curing agent or an epoxy type curing agent to obtain a mixed colloid; (2) coating the mixed colloid on one side of a PET, then laminating a release film on the adhesive surface and winding it up; (3) further coating the mixed colloid evenly on the other side of the PET, then laminating a release film on the adhesive surface, irradiating both sides of the PET with a UV lamp simultaneously, and then winding up the irradiated tape; (4) finally, subjecting the wound double-sided tape to high-temperature aging at 50 °C to obtain a modified adhesive layer for FPC manufacturing. The modified adhesive layer of the present invention has good adhesiveness, strong high-temperature resistance and no residual glue.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesives, and particularly relates to a modified adhesive layer for FPC manufacturing and a preparation method thereof. Background Art

[0002] FPC is a flexible circuit board made by using a polyester film or a polyimide film as a substrate, plating a copper foil on it to form a conductive pattern, and then through processes such as chemical etching, drilling, and stamping. Compared with traditional rigid circuit boards, it has higher flexibility and plasticity. FPC mainly consists of a substrate, a copper foil, a surface protective layer, and connectors, etc. Among them, the substrate is the main part of the entire FPC, and a polyester film or a polyimide film can be selected as the substrate; the copper foil is the conductive layer, and the wire pattern is printed on the copper foil by chemical methods; the surface protective layer can be selected to cover the copper foil to play a protective role; in the front-end manufacturing process of FPC, in order to improve production efficiency, currently FPC board factories usually temporarily bond two layers of copper foil back-to-back, and then perform processes such as laser, Desmear, black hole, dry film pressing, exposure, development, and film removal on both sides of the copper foil. In the above-described processes, in the laser process, because there is high temperature and the laser area is extremely small, the waste residue after laser can usually remove copper slag and adhesive slag through Desmear. If there is excess adhesive slag not removed, then these adhesive slags will adhere to the copper foil, thus causing an open circuit during the subsequent etching of the circuit.

[0003] As a thin PET double-sided adhesive auxiliary material used in the first copper foil double-sided lamination process during FPC manufacturing, since it needs to participate in the lamination of copper foil, as well as subsequent processes such as high-temperature laser drilling, high-temperature pickling, alkali washing and other chemical solution cleaning, and subsequent hot pressing, the double-sided adhesive is sandwiched between two copper foils during this process. When passing through the laser process, the laser will penetrate the copper foil layer and the double-sided tape layer. During the laser process, the laser will instantaneously reach a temperature of thousands of degrees Celsius. At this time, both the copper foil and the inner double-sided adhesive will melt under the action of the high-temperature laser. Since the copper foil itself is a non-sticky material, the copper slag removed by the laser will be sucked away under high pressure during laser ablation, while the double-sided adhesive sandwiched in it will also melt at high temperature. The double-sided adhesive structure is composed of acrylic pressure-sensitive adhesive coated on both sides of a PET substrate. Since the pressure-sensitive adhesive is a polymer acrylic polymer and has a certain viscosity at room temperature, after laser ablation, if the heat resistance of the pressure-sensitive adhesive polymer is insufficient or the adhesion between the adhesive and the PET substrate is insufficient, then after high temperature, the adhered and unadhered adhesives will stick together. During the subsequent high-temperature peeling, the adhered residual adhesive will transfer to the copper foil surface, resulting in open circuit defects at the residual adhesive parts during the subsequent etching of the circuit, thus affecting the overall production yield. Therefore, the adhesive layers on both sides of the bonding material involved in this process must have good heat resistance and cohesive strength. The adhesive layer commonly used in such applications is a solvent-based acrylic type adhesive. The acrylic adhesive made by the solvent method generally has a molecular weight of less than 1 million. Although the molecular weight of the adhesive at this molecular weight level can be greatly increased by adding a crosslinking agent, the crosslinking density is relatively small. Therefore, when exposed to ultra-high temperature laser, due to insufficient polymer rigidity, the molecular chains melt and shift, resulting in local residual adhesive. This makes the overall rigidity of the adhesive layer insufficient, resulting in easy generation of residual adhesive at the edge of the laser contact part during high-temperature laser ablation, leading to defective production lines in the subsequent process.

[0004] Currently, different manufacturers have adopted different methods to solve such problems: 1. For example, Wule in Suzhou also has products for such applications. Wule uses a coating treatment on the middle layer PET of the tape, which greatly enhances the bonding force between the adhesive layer and the PET layer, and thus can meet the customer's usage requirements to a certain extent. This method requires double-sided coating treatment of the PET film in advance. Commonly used coatings are generally polyurethane coatings, acrylic coatings, and polyester coatings. After the coating treatment, a double-sided adhesive layer is then coated. In this way, the surface of the PET after coating treatment can have excellent adhesion to the adhesive layer. Even if there is residual glue after laser treatment, the residual glue part will have better adhesion to the PET, and most of the residual glue will not transfer to the copper foil, thus reducing the proportion of residual glue transfer. 2. In addition, some manufacturers have adjusted the production process parameters. For example, by adjusting the temperature parameters of coating and drying, as well as the curing method, in order to make the cross-linking degree of the adhesive layer more uniform, thereby reducing the cause of residual glue due to uneven cross-linking degree. This method is to control the temperature of each section of the oven during the coating process of the adhesive layer, so that the adhesive layer will not undergo rapid cross-linking reaction due to excessive local temperature. In addition, since this tape is a double-sided tape and both sides use the direct coating (directly coating the adhesive layer on the PET surface) method, when the first side of the adhesive layer is coated and then the second side of the adhesive layer is coated, the previously coated first adhesive layer will enter the oven again and thus experience two high temperatures, while the second adhesive layer will only experience one high temperature in the end. Therefore, there is a significant difference in the temperature conditions experienced by the two-sided adhesive layers, resulting in an obvious difference in the curing degree of the two-sided adhesive layers. So, by adjusting the drying temperature of the two adhesive layers, such as lowering the drying temperature of the first adhesive layer and raising the drying temperature of the second adhesive layer, and then performing room temperature curing after coating, the difference in the curing degree of the double-sided adhesive layer can be greatly reduced. And after the subsequent normal temperature curing, the overall cross-linking uniformity will be greatly enhanced, thereby also reducing the proportion of residual glue caused by uneven curing and cross-linking of the double-sided adhesive layer.

[0005] Among the two existing common solutions to the residual glue problem, the first solution, that is, the solution of applying a primer to PET, has the most obvious effect, but its operation is also the most cumbersome. First of all, a suitable primer needs to be selected to match the adhesive to be coated. In addition, both sides of PET need to be primed, which increases two processes and the corresponding material and labor costs. Moreover, the operation of multiple processes leads to a significant reduction in the production yield. Since there is no fundamental improvement in the adhesive layer itself, the reduction in the final residual glue incidence is limited. The second solution is to adjust the process conditions during the coating process to improve the uniformity of the colloid cross-linking. This method belongs to the adjustment at the process parameter level, requiring a very high precision of the equipment during the coating process and having a very high dependence on the production equipment, which is specialized for a specific line. In addition, due to the different drying temperatures on both sides, the complexity of the coating operation increases. And because only the drying temperature and curing conditions are adjusted, it can indeed make the curing levels of the adhesive layers on both sides more uniform, but there is also no effective improvement in the rigidity of the adhesive layer. Therefore, the improvement of the residual glue is also relatively limited in the end. Summary of the Invention

[0006] To solve the above problems, the present invention provides a modified adhesive layer for FPC manufacturing and its preparation method.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A preparation method of a modified adhesive layer for FPC manufacturing, the preparation method comprising the following steps:

[0009] (1) Sequentially add UV curable resin, cross-linking resin composition and modified filler to a solvent-based pressure-sensitive adhesive, then stir evenly to mix uniformly; continue to add a photoinitiator, and then continue to stir evenly under a yellow light; then continue to add an NCO type curing agent or an epoxy type curing agent, and continue to stir evenly under a yellow light to obtain a mixed colloid;

[0010] (2) Coat the mixed colloid on one side of PET, and then wind it up after laminating the adhesive surface with a release film;

[0011] (3) Then continue to evenly coat the mixed colloid on the other side of PET, and then after laminating the adhesive surface with a release film, irradiate both sides of PET with a UV lamp at the same time, and then wind up the irradiated tape;

[0012] (4) Finally, subject the wound double-sided tape to high-temperature curing at 50 °C to obtain a modified adhesive layer for FPC manufacturing.

[0013] Furthermore, the peel strength of the solvent-based pressure-sensitive adhesive is between 500-800 gf.

[0014] Furthermore, the solvent-based pressure-sensitive adhesive adopts one or more of NT-00 (Jiangxi Ta Yi Lai), Y-1510 (Jiaxing Anzuo Chemical), and C-439U (Nanjing Zongyan).

[0015] Furthermore, the mass percentage of the solvent-based pressure-sensitive adhesive in the mixed colloid is 30-50wt%.

[0016] The preparation method of the cross-linked resin composition comprises: mixing 40-46 parts by mass of cyanate ester and 60-70 parts by mass of prepolymer, stirring at 62-67° C. for 15-20 minutes, adding 1-3 parts by mass of cobalt oxalate and 15-20 parts by mass of N-vinyl pyrrolidone, stirring evenly, then adding 2-5 parts by mass of 1-hydroxycyclohexyl phenyl ketone, stirring evenly, and vacuuming for 10 minutes to obtain the cross-linked resin composition.

[0017] Furthermore, the cyanate ester is selected from at least one of bisphenol A cyanate ester, dicyclopentadiene cyanate ester, and tetramethyl bisphenol F cyanate ester.

[0018] Furthermore, the cyanate ester is bisphenol A type cyanate ester, dicyclopentadiene type cyanate ester, and tetramethyl bisphenol F type cyanate ester in a mass ratio of 1:1.3-1.5:0.4-0.8.

[0019] Bisphenol A cyanate ester, CAS number: 3053-88-4.

[0020] Dicyclopentadiene cyanate ester, CAS number: 68322-12-8.

[0021] Tetramethyl bisphenol F cyanate, CAS: 101657-77-6.

[0022] Furthermore, the prepolymer is selected from at least one of polyurethane acrylate, epoxy acrylate, and isocyanuric acid acrylate.

[0023] Furthermore, the prepolymer is polyurethane acrylate, epoxy acrylate and isocyanuric acid acrylate in a mass ratio of 1.6-1.8:1:0.2-0.5.

[0024] The polyurethane acrylate was purchased from EBECRYL 8213 of Allnex.

[0025] The epoxy acrylate was purchased from Sartomer Products, model CN120NS.

[0026] The isocyanuric acid acrylate was purchased from Sartomer, model SR368NS.

[0027] Furthermore, the mass percentage of the cross-linked resin composition in the mixed colloid is 12-15wt%.

[0028] The present invention chemically modifies the adhesive layer by adding a UV-curable resin to the original solvent-based pressure-sensitive adhesive, improving the adhesion between the adhesive layer and the steel plate and increasing the peel strength from the steel plate. This UV-curable resin can be perfectly dissolved in the solvent and evenly dispersed in the solvent-based pressure-sensitive adhesive. The adhesive layer with the UV-curable resin can be evenly coated on the surface of the PET substrate by coating. After the solvent in the adhesive layer is completely volatilized by drying in an oven at high temperature, a UV light irradiation process is then carried out, so that the UV-curable resin dissolved therein can quickly react and crosslink to completion, thereby greatly increasing the crosslinking degree of the colloid. At the same time, the original solvent-based pressure-sensitive adhesive still retains good pressure sensitivity to meet the adhesion required for bonding. However, under this condition, the peel strength between the adhesive layer and the PI film is not ideal.

[0029] The present invention further adds a crosslinking resin composition to improve the peel strength between the adhesive layer and the PI film. In the system of the present invention, by simultaneously adding a UV-curable resin and a crosslinking resin composition, a polymer network structure resin is formed by photocuring interpenetration, improving the peel strength between the adhesive layer and the PI film and at the same time increasing the high-temperature resistance of the adhesive layer.

[0030] Furthermore, the preparation method of the modified filler is as follows:

[0031] (1) Mix silica, yttrium oxide and mica powder in a mass ratio of 1:1.3 - 1.5:0.4 - 0.7 to obtain a mixed filler;

[0032] (2) Disperse 10 parts by mass of the mixed filler in 60 - 70 parts by mass of an ethanol aqueous solution with a concentration of 50 - 60 wt%, add 0.1 - 0.3 parts by mass of the silane coupling agent KH550 and 0.4 - 0.6 parts by mass of cetyltrimethylammonium bromide, react at 60 - 65 °C for 4 - 6 h, and perform centrifugal separation and drying to obtain the modified filler.

[0033] Furthermore, the mica powder is mica powder with a D90 particle size of 6 μm. Shijiazhuang Chenxing Industrial Co., Ltd. The average particle size of the silica is 10 nm and the average specific surface area is 380 m 2 / g. Ningbo Jinlei Nanomaterials Technology Co., Ltd. The particle size of the yttrium oxide is 20 - 30 nm and the average specific surface area is 61 m 2 / g. Ningbo Jinlei Nanomaterials Technology Co., Ltd.

[0034] The present invention attempts to add fillers to the adhesive layer system to improve the effect of no residual adhesive after high-temperature baking of the adhesive layer, but the effect is not ideal. By using mixed fillers with specific parameters and adding them to the system of the present invention through modification, the effect of no residual adhesive after high-temperature baking of the adhesive layer is improved. The modified mixed fillers have better compatibility with other components in the system of the present invention. At the same time, silica, yttrium oxide, and mica powder with specific parameters can adjust the rheological properties of the adhesive layer, which helps to achieve better coating performance during application, form a more uniform adhesive layer, and thus reduce residues during peeling.

[0035] Further, the mass percentage of the modified filler in the mixed colloid is 5-7 wt%.

[0036] Further, the UV curable resin is selected from one of PRO32284 (Sartomer), GD83-02 (Sanhe Chemical), GD83-04 (Sanhe Chemical), 6151 (Showa Chemical of Japan).

[0037] Further, the mass percentage of the UV curable resin in the mixed colloid is 30-50%.

[0038] Further, the photoinitiator is one or more of IRGACURE 184, DAROCUR 1173, IRGACURE 127, IRGACURE2959, LUCIRIN TPO.

[0039] Further, the mass percentage of the photoinitiator in the mixed colloid is 0.5-5%.

[0040] Further, the NCO type curing agent is any one or more of the adduct of toluene diisocyanate and trimethylolpropane, toluene diisocyanate trimer, hexamethylene diisocyanate trimer, and hexamethylene diisocyanate polymer.

[0041] Further, the mass percentage of the NCO type curing agent in the mixed colloid is 0.5-2%.

[0042] Further, the epoxy type curing agent is any one or more of HY-H024 (Huaya New Materials), HY-H026 (Huaya New Materials), NE-100C (Japan Synthetic Rubber), NE-100X (Japan Synthetic Rubber), Y-202 (Jiaxing Anzuo).

[0043] Further, the mass percentage of the epoxy type curing agent in the mixed colloid is 0.5-2%.

[0044] Further, the thickness of the PET is selected from one of 4μm, 6μm, 10μm, 12μm, 25μm.

[0045] Furthermore, the coating thickness of the mixed colloid on either side of the PET is 3 - 10 μm.

[0046] Furthermore, the light wavelength of the UV lamp is any wavelength between 285 nm and 365 nm.

[0047] The present invention also provides a modified adhesive layer for FPC manufacturing prepared by the above preparation method.

[0048] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0049] 1. The present invention chemically modifies the adhesive layer by adding a UV - curable resin to the original solvent - based pressure - sensitive adhesive. This UV - curable resin can be perfectly dissolved in the solvent and evenly dispersed in the solvent - based pressure - sensitive adhesive. In this way, the adhesive layer with the UV - curable resin can be evenly coated on the surface of the PET substrate by traditional coating methods. After the solvent in the adhesive layer is volatilized completely by drying in an oven at high temperature, then the UV light irradiation process is carried out. As a result, the UV - curable resin dissolved in it can quickly react and cross - link to completion, thus greatly improving the cross - linking degree of the colloid. At the same time, the original solvent - based pressure - sensitive adhesive still retains good pressure - sensitivity to meet the viscosity required for adhesion. Therefore, this method only adds a UV light irradiation process at the back end of lamination, and the production process and efficiency remain unaffected. Thus, from the perspective of the adhesive layer itself, the contradiction between the rigidity and viscosity of the adhesive layer is solved, the rigidity of the adhesive layer is greatly improved, and the probability of residual glue is significantly reduced.

[0050] 2. In the system of the present invention, by adding a UV curable resin, a cross - linking resin composition, and a photo - curable interpenetrating polymer network structure resin simultaneously, the peel strength between the adhesive layer and the PI film is improved, and the high - temperature resistance of the adhesive layer is also enhanced.

[0051] 3. The present invention uses a mixed filler with specific parameters, which is added to the system of the present invention after modification, improving the effect of no residual glue after high - temperature baking of the adhesive layer. Detailed Embodiments

[0052] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] Example 1

[0054] This example provides a modified adhesive layer for FPC manufacturing, and the preparation method includes the following steps:

[0055] (1) Add UV light-curing resin, cross-linking resin composition and modified filler to the solvent-based pressure-sensitive adhesive in sequence, and then stir and mix them evenly; continue to add photoinitiator, and then continue to stir evenly under yellow light; then continue to add NCO type curing agent, and continue to stir evenly under yellow light to obtain a mixed colloid;

[0056] (2) Apply the mixed colloid to one side of the PET, and then adhere the colloid surface to the release film and roll it up;

[0057] (3) Continue to evenly apply the mixed colloid to the other side of the PET, and then after the adhesive surface is attached to the release film, both sides of the PET are irradiated with UV light at the same time, and then the irradiated tape is rolled up;

[0058] (4) Finally, the rolled double-sided tape is subjected to high-temperature aging at 50°C to obtain a modified adhesive layer for FPC production.

[0059] The solvent-based pressure-sensitive adhesive used is NT-00 (Jiangxi Ta Yi Lai).

[0060] The preparation method of the cross-linked resin composition is as follows: 43 parts by mass of cyanate ester and 64 parts by mass of prepolymer are mixed, stirred at 65° C. for 18 minutes, 2 parts by mass of cobalt oxalate and 17 parts by mass of N-vinyl pyrrolidone are added, stirred evenly, and then 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone are added, stirred evenly, and vacuumed for 10 minutes to obtain the cross-linked resin composition.

[0061] The cyanate esters are bisphenol A type cyanate ester, dicyclopentadiene type cyanate ester and tetramethyl bisphenol F type cyanate ester in a mass ratio of 1:1.4:0.6.

[0062] The prepolymer is polyurethane acrylate, epoxy acrylate and isocyanuric acid acrylate in a mass ratio of 1.7:1:0.4.

[0063] The polyurethane acrylate was purchased from EBECRYL 8213 of Allnex.

[0064] The epoxy acrylate was purchased from Sartomer Products, model CN120NS.

[0065] The isocyanuric acid acrylate was purchased from Sartomer, model SR368NS.

[0066] The preparation method of the modified filler is:

[0067] (1) mixing silicon dioxide, yttrium oxide and mica powder in a mass ratio of 1:1.4:0.5 to obtain a mixed filler;

[0068] (2) Disperse 10 parts by mass of the mixed filler in 65 parts by mass of an aqueous ethanol solution with a concentration of 55 wt%, add 0.2 parts by mass of silane coupling agent KH550 and 0.5 parts by mass of cetyltrimethylammonium bromide, react at 62 °C for 5 h, carry out centrifugal separation and drying to obtain the modified filler.

[0069] The mica powder is mica powder with a D90 particle size of 6 μm. Shijiazhuang Chenxing Industrial Co., Ltd. The average particle size of silica is 10 nm and the average specific surface area is 380 m 2 / g. Ningbo Jinlei Nanomaterials Technology Co., Ltd. The particle size of yttrium oxide is 20 - 30 nm and the average specific surface area is 61 m 2 / g. Ningbo Jinlei Nanomaterials Technology Co., Ltd.

[0070] The UV curable resin is selected from PRO32284 (Sartomer).

[0071] The photoinitiator is IRGACURE 184 (BASF).

[0072] The NCO type curing agent is tolylene diisocyanate trimer (Covestro).

[0073] The mass percentage of the solvent-based pressure-sensitive adhesive in the mixed colloid is 36 wt%. The mass percentage of the cross-linked resin composition in the mixed colloid is 14 wt%. The mass percentage of the modified filler in the mixed colloid is 6 wt%. The mass percentage of the UV curable resin in the mixed colloid is 40%. The mass percentage of the photoinitiator in the mixed colloid is 3%. The mass percentage of the NCO type curing agent in the mixed colloid is 1%.

[0074] The thickness of the PET is 10 μm.

[0075] The coating thickness of the mixed colloid on either side of the PET is 5 μm.

[0076] The light wavelength of the UV lamp is 365 nm.

[0077] Example 2

[0078] This example provides a modified adhesive layer for FPC manufacturing, and the preparation method includes the following steps:

[0079] (1) Sequentially add the UV curable resin, cross-linked resin composition and modified filler to the solvent-based pressure-sensitive adhesive, then stir evenly to mix well; continue to add the photoinitiator, and then continue to stir evenly under a yellow light; then continue to add the epoxy type curing agent and continue to stir evenly under a yellow light to obtain a mixed colloid;

[0080] (2) Coat the mixed colloid on one side of the PET, then laminate the adhesive side with a release film and wind it up;

[0081] (3) Continue to evenly apply the mixed colloid to the other side of the PET, and then after the adhesive surface is attached to the release film, both sides of the PET are irradiated with UV light at the same time, and then the irradiated tape is rolled up;

[0082] (4) Finally, the rolled double-sided tape is subjected to high-temperature aging at 50°C to obtain a modified adhesive layer for FPC production.

[0083] The solvent-based pressure-sensitive adhesive used was Y-1510 (Jiaxing Anzuo Chemical).

[0084] The preparation method of the cross-linked resin composition is as follows: 40 parts by mass of cyanate ester and 70 parts by mass of prepolymer are mixed, stirred at 62° C. for 15 minutes, 1 part by mass of cobalt oxalate and 20 parts by mass of N-vinyl pyrrolidone are added, stirred evenly, and then 2 parts by mass of 1-hydroxycyclohexyl phenyl ketone are added, stirred evenly, and vacuumed for 10 minutes to obtain the cross-linked resin composition.

[0085] The cyanate esters are bisphenol A type cyanate ester, dicyclopentadiene type cyanate ester and tetramethyl bisphenol F type cyanate ester in a mass ratio of 1:1.3:0.8.

[0086] The prepolymer is polyurethane acrylate, epoxy acrylate and isocyanuric acid acrylate in a mass ratio of 1.6:1:0.5.

[0087] The polyurethane acrylate was purchased from EBECRYL 8213 of Allnex.

[0088] The epoxy acrylate was purchased from Sartomer Products, model CN120NS.

[0089] The isocyanuric acid acrylate was purchased from Sartomer, model SR368NS.

[0090] The preparation method of the modified filler is:

[0091] (1) mixing silicon dioxide, yttrium oxide and mica powder in a mass ratio of 1:1.3:0.7 to obtain a mixed filler;

[0092] (2) Disperse 10 parts by mass of the mixed filler in 60 parts by mass of a 60 wt% ethanol aqueous solution, add 0.1 parts by mass of a silane coupling agent KH550 and 0.6 parts by mass of hexadecyltrimethylammonium bromide, react at 60° C. for 6 h, centrifuge and dry to obtain a modified filler.

[0093] The mica powder is mica powder with a D90 particle size of 6 μm. Shijiazhuang Chenxing Industrial Co., Ltd. The average particle size of silicon dioxide is 10 nm and the average specific surface area is 380 m 2 / g. Ningbo Jinlei Nanomaterials Technology Co., Ltd. The particle size of yttrium oxide is 20-30nm, and the average specific surface area is 61m2 / g. Ningbo Jinlei Nanomaterial Technology Co., Ltd.

[0094] The UV light curing resin was selected from GD83-02 (Sanhe Chemical).

[0095] The photoinitiator was DAROCUR 1173 (BASF).

[0096] The epoxy type curing agent is HY-H024 (Huiya New Materials).

[0097] The mass percentage of the solvent-based pressure-sensitive adhesive in the mixed colloid is 44.5 wt%. The mass percentage of the cross-linked resin composition in the mixed colloid is 15 wt%. The mass percentage of the modified filler in the mixed colloid is 5 wt%. The mass percentage of the UV light-curing resin in the mixed colloid is 30%. The mass percentage of the photoinitiator in the mixed colloid is 5%. The mass percentage of the epoxy type curing agent in the mixed colloid is 0.5%.

[0098] The thickness of PET is 10 μm.

[0099] The coating thickness of the mixed colloid on either side of PET is 5 μm.

[0100] The wavelength of UV light is 365nm.

[0101] Comparative Example 1

[0102] The difference between this comparative example and Example 2 is that the mass percentage of the cross-linked resin composition in the mixed colloid is 30wt%, and the mass percentage of the UV light-curable resin in the mixed colloid is 15%.

[0103] Comparative Example 2

[0104] The difference between this comparative example and Example 1 is that the cyanate ester is bisphenol A type cyanate ester, dicyclopentadiene type cyanate ester and tetramethyl bisphenol F type cyanate ester in a mass ratio of 1:1:1.

[0105] Comparative Example 3

[0106] The difference between this comparative example and Example 1 is that the prepolymer is polyurethane acrylate, epoxy acrylate and isocyanuric acid acrylate in a mass ratio of 1:1:1.

[0107] The polyurethane acrylate was purchased from EBECRYL 8213 of Allnex.

[0108] The epoxy acrylate was purchased from Sartomer Products, model CN120NS.

[0109] The isocyanuric acid acrylate was purchased from Sartomer, model SR368NS.

[0110] Comparative Example 4

[0111] The difference between this comparative example and Example 1 is that the polyurethane acrylate is a Sartomer product, model CN9001NS.

[0112] The epoxy acrylate is purchased from Sartomer products, model CN104NS.

[0113] The isocyanuric acid type acrylate is purchased from Wuhan Kemike Biopharmaceutical Technology Co., Ltd., tris(2-acryloyloxyethyl) isocyanurate.

[0114] Comparative Example 5

[0115] The difference between this comparative example and Example 1 is that silica, yttrium oxide and mica powder are mixed in a mass ratio of 1:1:1.

[0116] Comparative Example 6

[0117] The difference between this comparative example and Example 1 is that the mica powder is mica powder with a D90 particle size of 20 μm. Shijiazhuang Chenxing Industry Co., Ltd. The average particle size of silica is 50 nm and the average specific surface area is 210 m 2 / g. Ningbo Jinlei Nanomaterials Technology Co., Ltd. The particle size of yttrium oxide is 30 - 70 nm and the average specific surface area is 53 m 2 / g. Ningbo Jinlei Nanomaterials Technology Co., Ltd.

[0118] Performance Test

[0119] The performance of the modified adhesive layers prepared in Examples 1 - 2 and Comparative Examples 1 - 6 was tested.

[0120] 1. Referring to GB / T 2792 - 1998, the peel strength between the modified adhesive layer and the steel plate was measured.

[0121] 2. Referring to GB / T 2792 - 1998, the peel strength between the modified adhesive layer and the PI film was measured.

[0122] 3. Referring to GB / T 2792 - 1998, the peel strength of the modified adhesive layer after being attached to the PI film at high temperature was measured.

[0123] 4. The modified adhesive layer was attached to the PI film and baked at 180 °C for 60 minutes. If there was no debonding, no bulging, no bubble generation, no residual adhesive and no foreign impurities remaining after peeling, it was recorded as qualified. Otherwise, it was recorded as unqualified.

[0124] The test results are shown in Table 1.

[0125] Table 1 Performance Test Results

[0126]

[0127] As can be seen from the above performance test results, the modified adhesive layers of Examples 1-2 have good adhesion, strong high-temperature resistance, and no residual glue. In particular, the comprehensive performance of Example 1 is the most prominent, which is mainly due to the synergistic effect of multiple components.

[0128] In the comparative examples, since the necessary technical solutions were not adopted, the corresponding performance tests were significantly worse than those of the examples. In Comparative Example 1, the addition amounts of the UV curable resin and the crosslinked resin composition were changed, and it can be seen that the adhesion effect decreased, proving that the compounding scheme of the UV curable resin and the crosslinked resin composition has an important influence on the peeling effect. In Comparative Examples 5-6, the modified filler scheme was not used, and it can be seen from the results that there was residual glue after peeling. The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0129] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a modified adhesive layer for FPC, characterized in that: The preparation method comprises: (1) Adding UV light-curing resin, cross-linking resin composition and modified filler to the solvent-based pressure-sensitive adhesive in sequence, and then stirring and mixing uniformly; adding photoinitiator, and continuing to stir uniformly under yellow light; then adding NCO type curing agent or epoxy type curing agent, and stirring uniformly under yellow light to obtain a mixed colloid; The preparation method of the cross-linked resin composition comprises: mixing 40-46 parts by mass of cyanate ester and 60-70 parts by mass of prepolymer, stirring at 62-67° C. for 15-20 minutes, adding 1-3 parts by mass of cobalt oxalate and 15-20 parts by mass of N-vinyl pyrrolidone and stirring evenly, adding 2-5 parts by mass of 1-hydroxycyclohexyl phenyl ketone and stirring evenly, and vacuuming for 10 minutes to obtain the cross-linked resin composition; (2) Apply the mixed colloid to one side of the PET, adhere the colloid surface to the release film and then roll it up; (3) The mixed colloid is evenly coated on the other side of the PET, and then the adhesive surface is attached to the release film. Both sides of the PET are irradiated with UV light at the same time, and the irradiated tape is rolled up; (4) The rolled double-sided tape is cured at 50°C and used for the modified adhesive layer made of FPC; The cyanate ester is bisphenol A cyanate, dicyclopentadiene cyanate, and tetramethyl bisphenol F cyanate in a mass ratio of 1:1.3-1.5:0.4-0.8; the prepolymer is polyurethane acrylate, epoxy acrylate, and isocyanuric acid acrylate in a mass ratio of 1.6-1.8:1:0.2-0.5; The preparation method of the modified filler is as follows: (1) mixing silicon dioxide, yttrium oxide and mica powder in a mass ratio of 1:1.3-1.5:0.4-0.7 to obtain a mixed filler; (2) dispersing 10 parts by mass of the mixed filler in 60-70 parts by mass of a 50-60wt% ethanol aqueous solution, adding 0.1-0.3 parts by mass of a silane coupling agent KH550 and 0.4-0.6 parts by mass of hexadecyltrimethylammonium bromide, reacting at 60-65°C for 4-6h, centrifuging and drying to obtain a modified filler; The mica powder is mica powder with a D90 particle size of 6 μm; the average particle size of silicon dioxide is 10 nm and the average specific surface area is 380 m 2 / g; the particle size of yttrium oxide is 20-30nm, and the average specific surface area is 61m 2 / g; polyurethane acrylate is Allnex EBECRYL 8213; epoxy acrylate is Sartomer product, model CN120NS; isocyanuric acid acrylate is Sartomer product, model SR368NS; the cross-linking resin composition accounts for 12-15wt% of the mixed colloid mass; UV light curing resin accounts for 30-50% of the mixed colloid mass.

2. The method for preparing a modified adhesive layer for FPC according to claim 1, characterized in that: The photoinitiator is one or more of IRGACURE 184, DAROCUR 1173, IRGACURE 127, IRGACURE 2959, and LUCIRIN TPO.

3. The method for preparing a modified adhesive layer for FPC according to claim 1, characterized in that: The coating thickness of the mixed colloid on either side of PET is 3-10 μm.

4. A modified adhesive layer for FPC prepared according to the preparation method according to any one of claims 1 to 3.

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