A transparent thermoplastic polyamic acid resin, a transparent thermoplastic composite film, and its preparation method and application

Abstract

The present invention belongs to the technical field of polyimide composite film manufacturing, and in particular to a transparent thermoplastic polyamic acid resin, a transparent thermoplastic composite film, and its preparation method and application. 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 dianhydride and p-phenylene-bis(triphenylene)diamine dianhydride. The transparent thermoplastic composite film provided by the present invention has both excellent light transmittance and excellent peel strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyimide composite film manufacturing, and in particular 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 films, with their excellent optical properties, heat resistance, mechanical properties, and ease of processing, have been widely developed and applied in flexible displays, flexible transparent electrodes / flexible solar cells, automotive LEDs, and other fields. In the flexible display field, transparent polyimide films, as the substrate for transparent electrodes, are widely used in devices such as LCDs and OLEDs, enabling the transmission of electrical signals and the clear presentation of expected images. In flexible solar cell applications, transparent polyimide films, as the substrate for transparent electrodes, can improve the cell's photoelectric conversion efficiency and output power, and can also be curled and folded as needed. In addition, compared with other organic transparent materials, transparent polyimide films, with their high heat resistance, high transparency, anti-aging, anti-discoloration, and impact resistance, can also be used in precision electronic component protection and LEDs.

[0003] When transparent polyimide film is used as the substrate of transparent electrode, the main ways to achieve bonding with metal, circuit or other active materials include: (1) using thermosetting or photocuring transparent adhesive layer to bond transparent polyimide film to metal foil (such as copper foil); (2) directly sputtering or evaporating metal foil layer or other active film layer on the surface of transparent polyimide film; however, the transparent adhesive layer in the first way is generally transparent thermosetting materials such as transparent polyurethane, non-aromatic ring 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 environment, there are great hidden dangers in the product, which restricts the application scenarios and service life of the product; in the second way, 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 metal foil layer or electrode active material on the surface of 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 achieves high heat resistance by forming hydrogen bonds, with a glass transition temperature exceeding 350°C, giving it thermal expansion properties that match those of copper foil, and high bonding strength with copper foil. In addition, it is colorless and has high light transmittance. A Chinese patent with authorization publication number CN 111303424 B discloses a transparent polymer material composition and its application. The polymer material composition of this technical solution 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 copper foil through a coating process, and after baking, a transparent polyimide layer is formed to obtain a single-sided copper-clad laminate; two sets of single-sided copper-clad laminates are taken and pressed together 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 object, the technical solution adopted by the present invention is as follows:

[0007] A 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 dianhydride (α-ODPA) and p-phenylene trimellitic 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'-diphenylether tetracarboxylic dianhydride to the p-phenylene-diphenyltrimellitate dianhydride is 0.6-1.6:1.

[0015] More preferably, the molar ratio of the 2,3,3',4'-diphenylether tetracarboxylic dianhydride to p-phenylene-diphthalate 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 an aprotic 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: BAPS-M and AB-TFMB are first dissolved in an aprotic polar solvent, and then TAHQ is added to carry out polymerization at 40-60°C for 3-5 hours, and finally α-ODPA is added to carry out polymerization at 40-60°C for 5-7 hours to obtain a transparent thermoplastic polyamic acid resin.

[0023] Further preferably, the preparation method of the transparent thermoplastic polyamic acid resin is specifically as follows: BAPS-M and AB-TFMB are first dissolved in an aprotic polar solvent, then TAHQ is added and polymerization reaction is carried out at 50°C for 4 hours, and finally α-ODPA is added and polymerization reaction is carried out at 50°C for 6 hours to obtain a 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 imidization, 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 imidization.

[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 minutes.

[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 stepwise temperature increase step, wherein the stepwise 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] More preferably, the stepwise heating step comprises 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 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.

[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; 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 preparation method of 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] A 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 transparent flexible circuit boards and transparent electrodes.

[0036] A sixth aspect of the present invention provides a copper foil substrate, comprising 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-mentioned 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 base 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 with 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 more firmly bond with metals or electrode active materials when a 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 rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

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

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 any conflict with any incorporated document, the contents 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 described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative 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 was sourced from Jiaxing Ruihuatai Film Technology Co., Ltd., had 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 1 treatment.

[0054] Example 1 Transparent Thermoplastic Polyamic Acid Resin, Transparent Thermoplastic Polyimide Composite Film and Preparation Method Thereof

[0055] (1) Preparation of a transparent thermoplastic polyamic acid resin: 121.0 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by the 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 the addition of 0.012 mol of TAHQ, and the mixture was stirred at 50° C. for 4 h. 0.01815 mol of α-ODPA was then 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 the plasma surface treated HC-25 transparent polyimide film on both sides with the transparent thermoplastic polyamide acid resin, and use a commercially available coating rod to scrape off excess transparent thermoplastic polyamide acid resin on both sides. Hang the HC-25 transparent polyimide film sample coated with transparent polyamide acid resin on both sides in a blast oven for drying and curing at a drying temperature of 100°C for 8 minutes. Then, in the blast oven, adopt a step-by-step heating step to perform high-temperature imidization on the sample. The step-by-step heating step is 180°C for 10 minutes, 260°C for 10 minutes, and 300°C for 10 minutes 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 a transparent thermoplastic polyamic acid resin: 118.4 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by the addition of 0.015 mol of BAPS-M and 0.015 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 further 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 a transparent thermoplastic polyamic acid resin: 125.9 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by the 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 0.018 mol of TAHQ was added, and the mixture was stirred at 50°C for 4 h. 0.01215 mol of α-ODPA was further 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 analytical grade DMAC solvent was added to a 250 mL three-necked flask, followed by the 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 further 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 was dip-coated on one side of the surface of the HC-25 base film; the drying, curing, and imidization conditions were 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 was 27.5 μm, wherein the thickness of the HC-25 transparent polyimide base film was 25 μm, and the thickness of the transparent thermoplastic polyimide layer was 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 a transparent thermoplastic polyamic acid resin: 120 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by the 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. 0.0177 mol of α-ODPA was further 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 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 a transparent thermoplastic polyamic acid resin: 99.8 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by the addition of 0.0105 mol of BAPS-M and 0.0195 mol of TFMB, and the mixture was stirred to dissolve. The flask was protected by flowing nitrogen, followed by the addition of 0.012 mol of TAHQ, and the mixture was stirred at 50°C for 4 h. 0.01815 mol of α-ODPA was then 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 centipoise.

[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 a transparent thermoplastic polyamic acid resin: 125.3 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by 0.003 mol of BAPS-M and 0.027 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 further 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 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 a transparent thermoplastic polyamic acid resin: 121.0 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by the 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 PHAP (bis[(3,4-dianhydride)phenyl]terephthalate) was added, and the mixture was stirred at 50° C. for 4 h; 0.01815 mol of α-ODPA was further 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 the 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 ODPA (4,4'-oxydiphthalic anhydride) was further added, and the mixture was stirred at 50°C for 6 h to obtain a transparent thermoplastic polyamic acid resin with 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 a 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, wherein the thickness of the HC-25 type 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 a transparent thermoplastic polyamic acid resin: 127.7 g of analytical grade NMP solvent was added to a 250 mL three-necked flask, followed by the 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 0.022 mol of TAHQ was added, and the mixture was stirred at 50°C for 4 h. 0.00815 mol of α-ODPA was further 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 the 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 and dissolved; 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 further added, and the mixture was stirred at 50°C for 6 h to obtain a transparent thermoplastic polyamic acid resin with 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) A transparent polyamic acid resin is coated on a release film and dried at 100°C for 8 minutes until it is completely dry to obtain a transparent polyamic acid film. The transparent polyamic acid film is then peeled off as a whole, fixed on a hollow frame fixture, and imidized to obtain a transparent thermoplastic polyimide pure film; imidization conditions: in a forced air oven, the stepwise heating steps are 180°C for 10 minutes, 260°C for 10 minutes, and 300°C for 10 minutes.

[0096] The transparent thermoplastic polyimide pure film has a thickness of 30 μm.

[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 laminated with 12.5 μm copper foil to obtain a copper foil substrate; the lamination pressure was 2000-2200 psi, the lamination temperature was 350° C., and the lamination time was 10 s.

[0099] Performance testing:

[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 measured 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 tensile machine, a 180° peeling method, and a tensile speed of 50 mm / min. The results are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] As can be seen from Table 1, 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 was not within the range of 1-2:1, the peel strength of the obtained copper foil substrate was low;

[0109] In Comparative Example 4, the light transmittance of the transparent thermoplastic polyimide composite film did not meet the standard due to the use of PHAP instead of TAHQ;

[0110] In Comparative Example 5, due to the use of ODPA instead of 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, the copper foil substrate peeling strength did not meet the standard because the thickness of the single-sided transparent thermoplastic polyimide layer was only 1.0 μm;

[0112] In Comparative Example 7, since the molar ratio of α-ODPA to TAHQ was not within the range of 0.6-1.6:1, both the transmittance and the peel strength did not meet the standards;

[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, which cannot effectively support itself when used as an insulating substrate. 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 peeling strength between the film and the copper foil.

[0116] The above further describes the present invention in conjunction with specific embodiments. However, 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 solutions of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, and such modifications and replacements shall 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 dianhydride and p-phenylene-diphenyltrimethylol dianhydride; The molar ratio of the diamine monomer to the dianhydride monomer is 1:1-1.1; The molar ratio of the 2,2'-bis(trifluoromethyl)-4,4'-bis(4-aminophenylcarbonylamino)biphenyl and 4,4'-bis(3-aminophenoxy)diphenyl sulfone is 1-2:1; The molar ratio of the 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride to p-phenylene-diphenyl trimellitic dianhydride is 0.6-1.6:

1.

2. The method for preparing the transparent thermoplastic polyamic acid resin according to claim 1, wherein: The preparation method comprises the following steps: a diamine monomer and a dianhydride monomer are polymerized in a non-proton polar solvent to obtain a transparent thermoplastic polyamic acid resin.

3. The preparation method according to claim 2, characterized in that The aprotic polar solvent is selected from at least one of N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethyl sulfoxide and tetrahydrofuran.

4. The preparation method according to claim 3, characterized in that The aprotic polar solvent is selected from at least one of N-methylpyrrolidone and dimethylacetamide.

5. The preparation method according to claim 2, characterized in that The polymerization reaction temperature is 40-60° C., and the polymerization reaction time is 8-12 hours.

6. A transparent thermoplastic composite film, characterized in that The transparent thermoplastic polyamic acid resin of claim 1 or the transparent thermoplastic polyamic acid resin obtained by the preparation method of any one of claims 2 to 5 is thermally imidized and comprises a transparent thermoplastic polyimide layer and a transparent polyimide base film; the light transmittance of the transparent thermoplastic composite film is ≥88.5%; 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.

7. The method for preparing the transparent thermoplastic composite film according to claim 6, 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, 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.

8. The preparation method according to claim 7, characterized in that 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.

9. Use of the transparent thermoplastic polyamic acid resin according to claim 1 or the transparent thermoplastic composite film according to claim 6 in the preparation of transparent flexible circuit boards and transparent electrodes.

10. A copper foil substrate, characterized in that The copper foil substrate comprises copper foil and the transparent thermoplastic composite film according to claim 6 or the transparent thermoplastic composite film obtained by the preparation method according to any one of claims 7-8.

11. The method for preparing the copper foil substrate according to claim 10, wherein: The following steps are involved: The transparent thermoplastic composite film is pressed onto the copper foil or the copper foil substrate is obtained by vacuum sputtering.

Images