Transparent thermoplastic polyamide acid resin, transparent thermoplastic composite film and preparation method and application thereof

Abstract

The invention belongs to the technical field of polyimide composite film manufacturing, and particularly relates to transparent thermoplastic polyamide acid resin, a transparent thermoplastic composite film and a preparation method and application of the transparent thermoplastic polyamide acid resin. The transparent thermoplastic polyamide acid resin comprises a diamine monomer and a dianhydride monomer; the diamine monomer is a mixture of 2, 2 '-bis (trifluoromethyl)-4, 4'-bis (4-aminophenylcarbonylamino) biphenyl and 4, 4 '-bis (3-aminophenoxy) diphenyl sulfone; the dianhydride monomer is a mixture of 2, 3, 3 ', 4'-diphenyl ether tetracarboxylic acid dianhydride and p-phenylene-biphenyl trimellitate dianhydride. The transparent thermoplastic composite film provided by the invention has excellent light transmittance and excellent peel strength.

Description

Technical Field

[0001] The invention belongs to the technical field of polyimide composite film manufacturing, and specifically relates to a transparent thermoplastic polyamic acid resin, a transparent thermoplastic composite film, and a preparation method and application thereof. Background Art

[0002] Transparent polyimide film, with its excellent optical properties, heat resistance, mechanical properties and easy processing, has been widely developed or applied in the fields of flexible display, flexible transparent electrode / flexible solar cell, automotive LED, etc. In the field of flexible display, transparent polyimide film, as the substrate of transparent electrode, is widely used in LCD, OLED and other devices to achieve the transmission of electrical signals and the clean presentation of expected images; in the application of flexible solar cells, transparent polyimide film, as the substrate of transparent electrode, can improve the photoelectric conversion efficiency and output power of the battery, and can also be curled and folded according to needs; in addition, compared with other organic transparent materials, transparent polyimide film can also be used in the fields of precision electronic component protection, LED, etc. with its comprehensive characteristics of high heat resistance, high transparency, anti-aging, anti-discoloration and impact resistance.

[0003] When a transparent polyimide film is used as a substrate for a transparent electrode, the main ways to achieve bonding with metal, circuits or other active substances include: (1) using a thermosetting or photocuring transparent adhesive layer to bond the transparent polyimide film to a metal foil (such as copper foil); (2) directly sputtering or evaporating a metal foil layer or other active film layer on the surface of the transparent polyimide film; however, the transparent adhesive layer in the first approach is generally a transparent thermosetting material such as transparent polyurethane, non-aromatic colorless epoxy resin, etc. The heat resistance, weather resistance, aging resistance, and yellowing resistance of polyurethane, epoxy resin and other adhesive films are far inferior to transparent polyimide. When used in high temperature or extreme environments, there are great hidden dangers in the product, which restricts the application scenarios and service life of the product; in the second approach, due to the high chemical inertness and low surface energy of traditional thermosetting transparent polyimide, it is often difficult to obtain good bonding strength when sputtering or evaporating a metal foil layer or electrode active material on the surface of the transparent polyimide film, which has an adverse effect on subsequent processing and use.

[0004] In order to solve the above technical problems, a Chinese patent with the authorization publication number CN 116144023 B in the prior art discloses a polyimide and its preparation method and application. The polyimide has the formula (1-1) The structure of the polyurethane foam has high heat resistance by building hydrogen bonds, and the glass transition temperature exceeds 350°C, so that it has thermal expansion properties that match copper foil, and has high bonding strength with copper foil. In addition, it is colorless and has high light transmittance. The Chinese patent with the authorization publication number CN 111303424 B discloses a transparent polymer material composition and its application. The polymer material composition of the technical scheme is made of the following components in parts by weight: 17-35 parts of aromatic tetracarboxylic dianhydride, 0.5-1 parts of long-chain aliphatic diamine, 15-25 parts of aromatic diamine, and 100-170 parts of solvent. The polymer material composition is coated on the copper foil through a coating process, and a transparent polyimide layer is formed after baking to obtain a single-sided copper clad laminate; two sets of single-sided copper clad laminates are taken and pressed to obtain a double-sided copper clad laminate. This technical solution effectively improves the transmittance of polyimide by introducing an alicyclic structure, making PI transparent. At the same time, the introduction of a long-chain structure lowers the glass transition temperature Tg of transparent PI, effectively improving the processability of transparent PI and reducing its production cost. However, the peel strength of the polyimide composite film prepared by the above technical solution needs to be improved. Summary of the invention

[0005] In view of the above problems, the present invention provides a transparent thermoplastic polyamic acid resin, a transparent thermoplastic composite film and a preparation method and application thereof.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a transparent thermoplastic polyamic acid resin, wherein the transparent thermoplastic polyamic acid resin comprises a diamine monomer and a dianhydride monomer;

[0008] The diamine monomer is a mixture of 2,2'-bis(trifluoromethyl)-4,4'-bis(4-aminophenylcarbonylamino)biphenyl (AB-TFMB) and 4,4'-bis(3-aminophenoxy)diphenyl sulfone (BAPS-M);

[0009] The dianhydride monomer is a mixture of 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride (α-ODPA) and p-phenylene-triphenylene dianhydride (TAHQ).

[0010] In some preferred embodiments, the molar ratio of the diamine monomer to the dianhydride monomer is 1:1-1.1.

[0011] More preferably, the molar ratio of the diamine monomer to the dianhydride monomer is 1:1.005.

[0012] In some preferred embodiments, the molar ratio of the 2,2'-bis(trifluoromethyl)-4,4'-bis(4-aminophenylcarbonylamino)biphenyl to 4,4'-bis(3-aminophenoxy)diphenyl sulfone is 1-2:1.

[0013] More preferably, the molar ratio of the 2,2'-bis(trifluoromethyl)-4,4'-bis(4-aminophenylcarbonylamino)biphenyl to 4,4'-bis(3-aminophenoxy)diphenyl sulfone is 1.8-1.9:1.

[0014] In some preferred embodiments, the molar ratio of the 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride to p-phenylene-diphenyltriphthalate dianhydride is 0.6-1.6:1.

[0015] More preferably, the molar ratio of the 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride to p-phenylene-diphenyltriphthalate dianhydride is 1.5-1.6:1.

[0016] The second aspect of the present invention provides a method for preparing the transparent thermoplastic polyamic acid resin. The method comprises the following steps: a diamine monomer and a dianhydride monomer are polymerized in a non-protonic polar solvent to obtain the transparent thermoplastic polyamic acid resin.

[0017] In some preferred embodiments, the aprotic polar solvent is selected from at least one of N-methylpyrrolidone (NMP), dimethylacetamide (DMAC), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF).

[0018] Further preferably, the aprotic polar solvent is selected from at least one of N-methylpyrrolidone and dimethylacetamide.

[0019] Most preferably, the aprotic polar solvent is N-methylpyrrolidone.

[0020] In some preferred embodiments, the polymerization reaction temperature is 40-60° C., and the polymerization reaction time is 8-12 h.

[0021] More preferably, the polymerization reaction temperature is 50° C., and the polymerization reaction time is 10 h.

[0022] In some preferred embodiments, the preparation method of the transparent thermoplastic polyamic acid resin is specifically as follows: first dissolving BAPS-M and AB-TFMB in a non-protonic polar solvent, then adding TAHQ to carry out polymerization reaction at 40-60°C for 3-5h, and finally adding α-ODPA to carry out polymerization reaction at 40-60°C for 5-7h to obtain a transparent thermoplastic polyamic acid resin.

[0023] Further preferably, the preparation method of the transparent thermoplastic polyamic acid resin is as follows: firstly dissolving BAPS-M and AB-TFMB in a non-protonic polar solvent, then adding TAHQ to carry out polymerization reaction at 50°C for 4 hours, and finally adding α-ODPA to carry out polymerization reaction at 50°C for 6 hours to obtain the transparent thermoplastic polyamic acid resin.

[0024] The third aspect of the present invention provides a transparent thermoplastic composite film, comprising a transparent thermoplastic polyimide layer obtained by thermal imidization of the transparent thermoplastic polyamic acid resin and a transparent polyimide-based film; the light transmittance of the transparent thermoplastic composite film is ≥88.5%.

[0025] The fourth aspect of the present invention provides a method for preparing the above-mentioned transparent thermoplastic composite film, comprising the following steps: coating a transparent thermoplastic polyamic acid resin on one side of a transparent polyimide-based film, and sequentially drying and thermal imidizing the film, or immersing both sides of the transparent polyimide-based film in a transparent thermoplastic polyamic acid resin, taking it out, and sequentially drying and thermal imidizing the film.

[0026] Preferably, the transparent polyimide-based film is subjected to plasma surface treatment before use.

[0027] Preferably, the plasma surface treatment method is: using nitrogen as the working gas, the discharge frequency is 5-20KHz, the discharge voltage is 100-300V, the plasma treatment speed is 50-100mm / min, and the plasma surface treatment is performed 1-5 times.

[0028] In some preferred embodiments, the drying temperature is 90-110° C., and the drying time is 6-10 min.

[0029] More preferably, the drying temperature is 100° C. and the drying time is 8 minutes.

[0030] In some preferred embodiments, thermal imidization is carried out using a step-by-step temperature increase step, wherein the step-by-step temperature increase step is to maintain at 170-190° C. for 8-12 min, maintain at 250-270° C. for 8-12 min, and maintain at 290-310° C. for 8-12 min.

[0031] Further preferably, the stepwise temperature increase step is maintaining at 180° C. for 10 min, maintaining at 260° C. for 10 min, and maintaining at 300° C. for 10 min.

[0032] In some preferred embodiments, the total thickness of the transparent thermoplastic composite film is 27-60 μm, wherein the transparent polyimide base film has a thickness of 25 μm-50 μm, and the single-sided transparent thermoplastic polyimide layer has a thickness of 2-5 μm.

[0033] Preferably, when the thickness of the transparent polyimide base film is 25 μm, the thickness of the single-sided transparent thermoplastic polyimide layer is 2-3 μm, and when the thickness of the transparent polyimide base film is 50 μm, the thickness of the single-sided transparent thermoplastic polyimide layer is 3-5 μm.

[0034] Further preferably, the method for preparing the transparent thermoplastic composite film comprises the following steps: immersing both sides of the transparent polyimide base film in a transparent thermoplastic polyamic acid resin, taking it out and drying and thermal imidization in sequence, wherein the total thickness of the transparent thermoplastic composite film is 30 μm, wherein the thickness of the transparent polyimide base film is 25 μm, and the thickness of the single-sided transparent thermoplastic polyimide layer is 2.5 μm.

[0035] The fifth aspect of the present invention provides the use of the transparent thermoplastic polyamic acid resin or the transparent thermoplastic composite film in the preparation of a transparent flexible circuit board and a transparent electrode.

[0036] A sixth aspect of the present invention provides a copper foil substrate, which comprises copper foil and the above-mentioned transparent thermoplastic composite film.

[0037] A seventh aspect of the present invention provides a method for preparing the above copper foil substrate, comprising the following steps: laminating a transparent thermoplastic composite film with copper foil or obtaining the copper foil substrate by vacuum sputtering.

[0038] In some preferred embodiments, the pressing pressure is 1800-2200 psi, the pressing temperature is 340-360° C., and the pressing time is 8-12 s.

[0039] More preferably, the pressing pressure is 2000-2200 psi, the pressing temperature is 350° C., and the pressing time is 10 s.

[0040] Preferably, the peel strength of the copper foil substrate is ≥1.4 N / mm.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The transparent thermoplastic composite film formed by the transparent thermoplastic polyamic acid resin obtained by polymerization reaction of a preferred diamine monomer, a preferred dianhydride monomer and a preferred molar ratio of the diamine monomer to the dianhydride monomer and the transparent polyimide-based film of the present invention has both excellent light transmittance (light transmittance ≥ 88.5%) and excellent peel strength.

[0043] 2. The transparent thermoplastic composite film provided by the present invention can be directly bonded to a metal foil layer (such as copper foil) under high temperature and roller pressure conditions, and the peel strength between the film and the copper foil is ≥1.4N / mm, without the need for an additional polyurethane or colorless epoxy resin intermediate film layer.

[0044] 3. Due to the presence of the thermoplastic surface layer, the transparent thermoplastic composite film provided by the present invention can also more firmly bond with metals or electrode active materials when the sputtering process is adopted.

[0045] 4. The transparent thermoplastic composite film provided by the present invention is thinner and smaller, and can be used in more precise or more extreme application scenarios. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0049] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0050] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0051] In the following examples and comparative examples, unless otherwise specified, all raw materials used were commercially available or prepared by conventional methods in the art.

[0052] The HC-25 transparent polyimide film described in the examples and comparative examples is from Jiaxing Ruihuatai Film Technology Co., Ltd., has a thickness of 25 μm, and a light transmittance of 88.7%.

[0053] The method for plasma surface treatment of HC-25 transparent polyimide film is as follows: using a laboratory DBD low-temperature plasma experimental instrument, nitrogen as the working gas, a discharge frequency of 15KHz, a discharge voltage of 200V, a plasma treatment speed of 50mm / min, and one treatment.

[0054] Example 1 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0055] (1) Preparation of transparent thermoplastic polyamic acid resin: 121.0 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol BAPS-M and 0.0195 mol AB-TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.012 mol TAHQ, and the mixture was stirred at 50° C. for 4 h; and 0.01815 mol α-ODPA was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 1635 centipoise.

[0056] (2) Preparation of transparent thermoplastic polyimide composite film: impregnate both sides of the plasma surface treated HC-25 transparent polyimide film with the transparent thermoplastic polyamic acid resin, and use a commercially available coating rod to scrape off excess transparent thermoplastic polyamic acid resin on both sides, and hang the HC-25 transparent polyimide film sample coated with transparent polyamic acid resin on both sides in a blast oven for drying and curing at a drying temperature of 100° C. for 8 min, and then in the blast oven, use a step-by-step heating step to perform high-temperature imidization on the sample, and the step-by-step heating step is 180° C. for 10 min, 260° C. for 10 min, and 300° C. for 10 min to obtain a thermoplastic transparent polyimide composite film. The total thickness of the transparent polyimide composite film is 30 μm, wherein the thickness of the HC-25 transparent polyimide base film is 25 μm, and the thickness of the transparent thermoplastic polyimide layer is 5 μm (2.5 μm on one side).

[0057] Example 2 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0058] (1) Preparation of transparent thermoplastic polyamic acid resin: 118.4 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.015 mol BAPS-M and 0.015 mol AB-TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.012 mol TAHQ, and the mixture was stirred at 50° C. for 4 h; and 0.01815 mol α-ODPA was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 1572 centipoise.

[0059] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0060] Example 3 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0061] (1) Preparation of transparent thermoplastic polyamic acid resin: 125.9 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol BAPS-M and 0.0195 mol AB-TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.018 mol TAHQ, and the mixture was stirred at 50° C. for 4 h; and 0.01215 mol α-ODPA was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 1481 centipoise.

[0062] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0063] Example 4 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0064] (1) Preparation of a transparent thermoplastic polyamic acid resin: 121.0 g of analytically pure DMAC solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol of BAPS-M and 0.0195 mol of AB-TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, and then 0.012 mol of TAHQ was added, and the mixture was stirred at 50° C. for 4 h; 0.01815 mol of α-ODPA was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 855 centipoise.

[0065] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0066] Example 5 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0067] (1) Preparation of transparent thermoplastic polyamic acid resin: same as step (1) of Example 1

[0068] (2) Preparation of a transparent thermoplastic polyimide composite film: Referring to the method for preparing a composite film in Example 1, a transparent polyamic acid resin is dip-coated on one side of the surface of the HC-25 base film; the drying, curing and imidization conditions are the same as in Example 1 to obtain a single-sidedly coated thermoplastic transparent polyimide composite film. The total thickness of the transparent polyimide composite film is 27.5 μm, wherein the thickness of the HC-25 transparent polyimide base film is 25 μm, and the thickness of the transparent thermoplastic polyimide layer is 2.5 μm.

[0069] Comparative Example 1 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0070] (1) Preparation of transparent thermoplastic polyamic acid resin: 120 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol BAPS-M and 0.0195 mol AB-TFMB, and stirring to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.012 mol TAHQ, and stirring at 50° C. for 4 h; and further addition of 0.0177 mol α-ODPA, and stirring at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 1270 centipoise.

[0071] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0072] Comparative Example 2 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0073] (1) Preparation of transparent thermoplastic polyamic acid resin: 99.8 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol BAPS-M and 0.0195 mol TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.012 mol TAHQ, and the mixture was stirred at 50° C. for 4 h; and 0.01815 mol α-ODPA was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 1560 cps.

[0074] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0075] Comparative Example 3 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0076] (1) Preparation of transparent thermoplastic polyamic acid resin: 125.3 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, and 0.003 mol of BAPS-M and 0.027 mol of AB-TFMB were added and stirred to dissolve; the flask was protected by flowing nitrogen, and then 0.012 mol of TAHQ was added, and the temperature was controlled at 50° C. and stirred for 4 h; 0.01815 mol of α-ODPA was added, and the temperature was controlled at 50° C. and stirred for 6 h to obtain a transparent thermoplastic polyamic acid resin with a solid content of 18% and a viscosity of 988 centipoise.

[0077] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0078] Comparative Example 4 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0079] (1) Preparation of transparent thermoplastic polyamic acid resin: 121.0 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol of BAPS-M and 0.0195 mol of AB-TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.012 mol of PHAP (bis[(3,4-dianhydride)phenyl]terephthalate), and the mixture was stirred at 50° C. for 4 h; and 0.01815 mol of α-ODPA was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 1910 centipoise.

[0080] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0081] Comparative Example 5 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0082] (1) Preparation of transparent thermoplastic polyamic acid resin: 121.0 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol of BAPS-M and 0.0195 mol of AB-TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.012 mol of TAHQ, and the mixture was stirred at 50° C. for 4 h; 0.01815 mol of ODPA (4,4'-oxydiphthalic anhydride) was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 1660 centipoise.

[0083] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0084] Comparative Example 6 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0085] (1) Preparation of transparent thermoplastic polyamic acid resin: same as step (1) of Example 1;

[0086] (2) Preparation of transparent thermoplastic polyimide composite film: The difference from step (2) of Example 1 is that the total thickness of the transparent polyimide composite film is 27 μm, of which the thickness of the HC-25 transparent polyimide base film is 25 μm and the thickness of the transparent thermoplastic polyimide layer is 2 μm (1 μm on one side).

[0087] Comparative Example 7 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0088] (1) Preparation of transparent thermoplastic polyamic acid resin: 127.7 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol BAPS-M and 0.0195 mol AB-TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.022 mol TAHQ, and the mixture was stirred at 50° C. for 4 h; and 0.00815 mol α-ODPA was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 981 centipoise.

[0089] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0090] Comparative Example 8 Transparent thermoplastic polyamic acid resin, transparent thermoplastic polyimide composite film and preparation method thereof

[0091] (1) Preparation of transparent thermoplastic polyamic acid resin: 114.3 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by addition of 0.0105 mol of TPE-Q (4,4'-(1,4-phenylenedioxy) dianiline) and 0.0195 mol of AB-TFMB, and the mixture was stirred to dissolve; the flask was protected by flowing nitrogen, followed by addition of 0.012 mol of TAHQ, and the mixture was stirred at 50° C. for 4 h; and 0.01815 mol of α-ODPA was added, and the mixture was stirred at 50° C. for 6 h to obtain a transparent thermoplastic polyamic acid resin having a solid content of 18% and a viscosity of 1860 centipoise.

[0092] (2) Preparation of a transparent thermoplastic polyimide composite film: Same as step (2) of Example 1.

[0093] Comparative Example 9 Transparent Thermoplastic Polyimide Pure Film

[0094] (1) Preparation of transparent thermoplastic polyamic acid resin: The only difference from step (1) of Example 1 is that the solid content of the transparent thermoplastic polyamic acid resin is controlled to 25% and the viscosity is 56,000 centipoise.

[0095] (2) coating a transparent polyamic acid resin on a release film, drying at 100° C. for 8 min until drying is complete to obtain a transparent polyamic acid film, and then peeling off the transparent polyamic acid film as a whole, fixing it on a hollow frame fixture, and performing imidization to obtain a transparent thermoplastic polyimide pure film; imidization conditions: in a forced air oven, the stepwise heating steps are 180° C. for 10 min, 260° C. for 10 min, and 300° C. for 10 min.

[0096] The transparent thermoplastic polyimide pure film thickness is 30μm.

[0097] Application Examples

[0098] The transparent thermoplastic polyimide composite films obtained in Examples 1-5 and Comparative Examples 1-8, the transparent thermoplastic polyimide pure film of Comparative Example 9, and the HC-25 transparent polyimide base film were respectively pressed with 12.5 μm copper foil to obtain a copper foil substrate; the pressing pressure was 2000-2200 psi, the pressing temperature was 350° C., and the pressing time was 10 s.

[0099] Performance Test:

[0100] 1. The light transmittance of the transparent thermoplastic polyimide composite films obtained in Examples 1-5 and Comparative Examples 1-8 and the transparent thermoplastic polyimide pure film of Comparative Example 9 was tested using a KONICA CM-36DG desktop spectrophotometer. The results are shown in Table 1.

[0101] 2. The peel strength of the copper foil substrate was tested using a universal stretching machine, a 180° peeling method, and a stretching speed of 50 mm / min. The results are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] It can be seen from Table 1 that the transparent thermoplastic polyimide composite films obtained in Examples 1 to 5 have a light transmittance of ≥88.50%, a peel strength of ≥1.4 N / mm, and normal performance.

[0106] In Comparative Example 1, since the molar ratio of the diamine monomer to the dianhydride monomer is not within the range of 1:1-1.1, the light transmittance of the obtained transparent thermoplastic polyimide composite film is low;

[0107] In Comparative Example 2, since TFMB was used to replace AB-TFMB, the peel strength of the copper foil substrate obtained was low;

[0108] In Comparative Example 3, since the molar ratio of AB-TFMB to BAPS-M is not within the range of 1-2:1, the peel strength of the obtained copper foil substrate is low;

[0109] In Comparative Example 4, since PHAP was used to replace TAHQ, the light transmittance of the transparent thermoplastic polyimide composite film did not meet the standard;

[0110] In Comparative Example 5, due to the use of ODPA to replace α-ODPA, the peel strength of the copper foil substrate and the light transmittance of the transparent thermoplastic polyimide composite film did not meet the standards;

[0111] In Comparative Example 6, since the thickness of the single-sided transparent thermoplastic polyimide layer was only 1.0 μm, the peel strength of the copper foil substrate did not meet the standard;

[0112] In Comparative Example 7, since the molar ratio of α-ODPA to TAHQ is not in the range of 0.6-1.6:1, the transmittance and peel strength are not up to the standard;

[0113] Comparative Example 8 uses TPE-Q instead of BAPS-M, so the peel strength is normal, but the light transmittance does not meet the standard;

[0114] Although the transparent thermoplastic polyimide pure film of Comparative Example 9 has normal transmittance and peel strength, the elastic modulus of the transparent thermoplastic polyimide pure film is 2051 MPa. When used as an insulating substrate, it cannot effectively support itself. When pressed with copper foil at high temperature (350°C), the sample shrinks and wrinkles.

[0115] The HC-25 transparent polyimide-based film is directly pressed onto the copper foil, and there is almost no peel strength between the film and the copper foil.

[0116] The above is a further description of the present invention in conjunction with specific embodiments, but these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

Claims

1. A transparent thermoplastic polyamic acid resin, characterized in that: The transparent thermoplastic polyamic acid resin includes a diamine monomer and a dianhydride monomer; The diamine monomer is a mixture of 2,2'-bis(trifluoromethyl)-4,4'-bis(4-aminophenylcarbonylamino)biphenyl and 4,4'-bis(3-aminophenoxy)diphenyl sulfone; The dianhydride monomer is a mixture of 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride and p-phenylene-diphenyltrimethylol dianhydride.

2. The transparent thermoplastic polyamic acid resin according to claim 1, characterized in that: The molar ratio of the diamine monomer to the dianhydride monomer is 1:1-1.

1.

3. The transparent thermoplastic polyamic acid resin according to claim 2, characterized in that: The molar ratio of the 2,2'-bis(trifluoromethyl)-4,4'-bis(4-aminophenylcarbonylamino)biphenyl to 4,4'-bis(3-aminophenoxy)diphenyl sulfone is 1-2:

1.

4. The transparent thermoplastic polyamic acid resin according to claim 3, characterized in that: The molar ratio of the 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride to p-phenylene-diphenyltrimethylol dianhydride is 0.6-1.6:

1.

5. The method for preparing the transparent thermoplastic polyamic acid resin according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: a diamine monomer and a dianhydride monomer are polymerized in a non-protonic polar solvent to obtain a transparent thermoplastic polyamic acid resin.

6. The preparation method according to claim 5, characterized in that: The aprotic polar solvent is selected from at least one of N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethyl sulfoxide and tetrahydrofuran.

7. The preparation method according to claim 6, characterized in that: The aprotic polar solvent is selected from at least one of N-methylpyrrolidone and dimethylacetamide.

8. The preparation method according to claim 7, characterized in that: The polymerization reaction temperature is 40-60° C., and the polymerization reaction time is 8-12 hours.

9. A transparent thermoplastic composite film, characterized in that: The transparent thermoplastic polyamic acid resin according to any one of claims 1 to 4 or the transparent thermoplastic polyamic acid resin obtained by the preparation method according to claims 5 to 8 is thermally imidized, and the transparent thermoplastic polyimide layer and the transparent polyimide-based film; the light transmittance of the transparent thermoplastic composite film is ≥88.5%.

10. The method for preparing the transparent thermoplastic composite film according to claim 9, characterized in that: The method comprises the following steps: coating a transparent thermoplastic polyamic acid resin on one side of a transparent polyimide base film, and then drying and thermal imidizing the film in sequence; or immersing both sides of the transparent polyimide base film in a transparent thermoplastic polyamic acid resin, and then taking the film out and drying and thermal imidizing the film in sequence.

11. The preparation method according to claim 10, characterized in that: The thermal imidization is carried out by adopting a step-by-step temperature increase step, wherein the step-by-step temperature increase step is to maintain at 170-190° C. for 8-12 min, to maintain at 250-270° C. for 8-12 min, and to maintain at 290-310° C. for 8-12 min.

12. The preparation method according to claim 10, characterized in that: The total thickness of the transparent thermoplastic composite film is 27-60 μm, wherein the thickness of the transparent polyimide base film is 25 μm-50 μm, and the thickness of the single-sided transparent thermoplastic polyimide layer is 2-5 μm.

13. Use of the transparent thermoplastic polyamic acid resin according to any one of claims 1 to 4 or the transparent thermoplastic composite film according to claim 9 in the preparation of transparent flexible circuit boards and transparent electrodes.

14. A copper foil substrate, characterized in that: The copper foil substrate comprises copper foil and the transparent thermoplastic composite film according to claim 9 or the transparent thermoplastic composite film obtained by the preparation method according to claims 10-12.

15. The method for preparing the copper foil substrate according to claim 14, characterized in that: The following steps are involved: The transparent thermoplastic composite film is pressed with the copper foil or the copper foil substrate is obtained by vacuum sputtering.

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