TW202221059A - Transparent polyimide solution, method for manufacturing the transparent polyimide solution, transparent polyimide film and its application - Google Patents

Abstract

A transparent polyimide solution is disclosed. The transparent polyimide solution includes a polyimide, an additive, and a solvent. The molecular chain of the polyimide includes an active hydrogen atom. The additive includes a carbodiimide group. A ratio of a molarity of the active hydrogen atom and a molarity of the carbodiimide group is in a range of 1: 0.8 to 1: 1.2. A method of preparing the transparent polyimide solution, a transparent polyimide film, and an application of the transparent polyimide film are also disclosed. The transparent polyimide film has a high transparency, a high hardness, excellent mechanical properties and a flexural property, which can meet the needs of touch panel in electronic devices.

Description

Transparent polyimide solution and preparation method thereof, transparent polyimide film and application thereof

The invention relates to the technical field of polymer film preparation, in particular to a transparent polyimide solution and a preparation method thereof, a transparent polyimide film and applications thereof.

With the development of 5G products, electronic products need to retain a large touch screen on the one hand, but also need to be thin and easy to carry. Therefore, foldable electronic products have been developed. The materials of traditional touch panels are mostly glass. Although glass has high transparency and high hardness, it cannot meet the requirements of lightness and thinness, and it cannot be bent.

At present, polyimide (PI) is one of the most promising materials in flexible materials. PI has the characteristics of high heat resistance, chemical resistance, good electrical properties and bending resistance, which can meet the requirements of thinning and thinning of electronic products. The requirements of weather resistance and flexibility are widely used in the field of flexible touch panels. However, traditional polyimide films are usually brown or yellow, with low transparency and low hardness, which cannot meet the demands of touch panels for high transparency and high hardness.

In order to solve the above technical problems, the present invention proposes a transparent polyimide film with both high transparency and high hardness.

In addition, the present invention also provides a transparent polyimide solution for preparing the above-mentioned transparent polyimide film and a preparation method thereof.

The invention provides a transparent polyimide solution, comprising transparent polyimide, an additive and a solvent, the molecular chain of the transparent polyimide contains active hydrogen atoms, the additive contains a carbodiimide group, and the The equivalent ratio of active hydrogen atoms to the carbodiimide group is 1:0.8-1.2.

In the embodiment of the present application, the solid content in the transparent polyimide solution includes the transparent polyimide and the additive, and the solid content of the transparent polyimide solution is 30 wt% to 45 wt%. .

In the embodiment of the present application, the additive includes a solvent-based bridging agent.

In the embodiment of the present application, the solvent includes one or more of N-methylpyrrolidone, dimethylacetamide and 1,4-butyrolactone.

The present invention also provides a method for preparing a transparent polyimide solution, comprising the following steps:

Mixing transparent polyimide, additive and solvent to obtain the transparent polyimide solution, wherein the molecular chain of the transparent polyimide contains active hydrogen atoms, the additive contains a carbodiimide group, so The equivalent ratio of the active hydrogen atom to the carbodiimide group is 1:0.8~1.2.

In the embodiment of the present application, the solid content in the transparent polyimide solution includes the transparent polyimide and the additive, and the solid content of the transparent polyimide solution is 30 wt% to 45 wt%. .

In the embodiment of the present application, the transparent polyimide is formed by a cyclization reaction of a diamine monomer and a dianhydride monomer.

In the embodiment of the present application, the diamine monomer includes 3,3'-diamino-4,4'-dihydroxydiphenylene, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoro One or more of propane and 3,5-diaminobenzoic acid.

In the embodiment of the present application, the dianhydride monomers include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, One or more of pyromellitic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and cyclopentatetraic dianhydride.

In the embodiment of the present application, the solvent includes one or more of N-methylpyrrolidone, dimethylacetamide and 1,4-butyrolactone.

The present invention also provides a method for preparing a transparent polyimide film, comprising the following steps:

A release substrate is provided.

The above-mentioned transparent polyimide solution is coated on the release surface of the release substrate to obtain an intermediate film layer.

And, heating the intermediate film layer to obtain the transparent polyimide film.

The transparent polyimide solution includes polyimide, an additive and a solvent, the molecular chain of the polyimide contains active hydrogen atoms, the additive contains a carbodiimide group, and the active hydrogen atom is associated with the The equivalent ratio of the carbodiimide groups is 1:0.8-1.2, and the active hydrogen atoms and the carbodiimide groups are heated and cross-linked to form a cross-linked structure.

In the embodiment of the present application, within the wavelength range of 400 nm to 700 nm of visible light, the light transmittance of the transparent polyimide film is greater than or equal to 88%.

In the embodiment of the present application, the hardness of the transparent polyimide film is greater than or equal to 4H.

The present invention also provides an electronic device, the electronic device includes a touch panel, and the touch panel includes the above-mentioned transparent polyimide film.

Compared with the prior art, the polyimide film of the present invention has high transparency, and at the same time, by introducing active hydrogen atoms into the polyimide molecular chain, the active hydrogen atoms can interact with the carbodiimide in the additive. The group undergoes a cross-linking reaction to improve the hardness and mechanical properties of the transparent polyimide film.

The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The names of technical means used in the description of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention.

The embodiments described below and features in the embodiments may be combined with each other without conflict.

An embodiment of the present invention provides a transparent polyimide solution, comprising a transparent polyimide, an additive and a solvent, the molecular chain of the transparent polyimide contains active hydrogen atoms, and the additive comprises carbodiimide ( N=C=N) group. When the transparent polyimide solution is heated, the active hydrogen atoms and the carbodiimide group can undergo a cross-linking reaction, and the carbodiimide group can also self-crosslink, thereby improving the transparent polyimide Hardness and mechanical properties of imide films. Wherein, the degree of crosslinking of the two can be controlled by adjusting the equivalent ratio of the active hydrogen atoms to the carbodiimide group, thereby controlling the light transmittance, hardness and mechanical properties of the transparent polyimide film.

In this embodiment, the equivalent ratio of the active hydrogen atom to the carbodiimide group is 1:0.8˜1.2, preferably 1:1.

In this embodiment, the solid content of the polyimide solution includes polyimide and additives, and the solid content of the polyimide solution is 30wt%-45wt%.

In this embodiment, the additive is a bridging agent, and specifically, a solvent-based bridging agent of Anfeng Industrial Co., Ltd. model V-03, V-05 or V-07 can be used. The solid content of V-03 is 50wt%, the solvent is toluene, and the equivalent weight of NCN is 216. The solid content of V-05 is 100 wt%, and the equivalent weight of NCN is 262. The solid content of V-07 is 50 wt%, the solvent is toluene, and the equivalent weight of NCN is 200. Specifically, in this embodiment, V-05 is selected as the bridging agent, which is a solvent-based bridging agent.

In this embodiment, the solvent includes one or more of N-methylpyrrolidone, dimethylacetamide and 1,4-butyrolactone.

The present invention also provides a method for preparing the above transparent polyimide solution, the preparation method comprising: mixing polyimide, an additive and a solvent to obtain a transparent polyimide solution. Wherein, the molecular chain of the polyimide contains active hydrogen atoms, and the additive contains carbodiimide groups.

In this embodiment, transparent polyimide is synthesized by cyclization reaction of diamine monomer and dianhydride monomer in a solvent.

Specifically, the reaction process of polyimide is as follows:

Among them, the molecular structure design of polyimide needs to meet certain requirements. The traditional preparation method of polyimide requires the imidization reaction at a high temperature above 300 °C. Under this reaction condition, the π electron on the conjugated benzene ring will produce a conjugation effect, and at the same time, the intermolecular and intramolecular The charge transfer complex effect will occur. The above two effects will cause the polyimide to have strong absorption in the visible light region, so the polyimide will become opaque, mostly brown and yellow.

In order to make the synthesized polyimide transparent, the present invention will contain polar molecular chain groups (such as -O-, -SO ₂ -, -CO-, ester group, nitrogen-containing heterocycle, -CF ₃ , etc.), Asymmetric structures (e.g. monomeric 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl (TFMB), 1,3-bis(3-aminophenoxy)benzene (APBN), 9 ,9-bis(4-amino-3-fluorophenyl)fluorene (BFAF), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis(3 -Amino-4-hydroxyphenyl)hexafluoropropane (6FAP, etc.), aliphatic (without benzene ring) or relatively large free volume side chains (eg monomeric TFMB, BFAF, 6FDA, 6FAP, etc.) are introduced into the main chain On the other hand, the structure of intermolecular and intramolecular charge transfer complexes is minimized, thereby improving the transparency of the polyimide film. At the same time, the obtained transparent polyimide still has good heat resistance and chemical resistance.

In addition, the present invention can also be combined with the carbodiimide in the additive by introducing a functional group (such as -OH, -COOH or -NH ₂ , etc.) containing active hydrogen atoms into the side chain of the transparent polyimide molecule. The groups react to form a network structure, thereby improving the hardness and mechanical properties of the transparent polyimide, so as to meet the needs of touch panels for electronic products.

In this embodiment, the active hydrogen atom can be introduced through the diamine monomer structure, that is, the structure of Y in the above reaction formula includes a functional group having an active hydrogen atom.

Specifically, the reactive hydrogen atom in the transparent polyimide molecule and the carbodiimide group in the additive are crosslinked and the reaction formula of the carbodiimide group self-crosslinking is as follows:

The carboxylic acid group -COOH reacts with the NCN group:

Amino- _NH2 reacts with NCN group:

The hydroxyl-OH reacts with the NCN group:

The NCN group itself undergoes a cross-linking reaction:

In this embodiment, the diamine monomer includes, but is not limited to, 3,3'-diamino-4,4'-dihydroxydiphenylene (3,3'-DABS), 2,2-bis(3 - One or more of amino-4-hydroxyphenyl) hexafluoropropane (6FAP) and 3,5-diaminobenzoic acid (3,5-DABA).

In this embodiment, the dianhydride monomer may be an aromatic or aliphatic tetracarboxylic dianhydride, specifically including but not limited to 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 4 ,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), pyromellitic dianhydride (H-PMDA), bicyclo[2.2.2]oct-7-ene-2,3, One or more of 5,6-tetracarboxylic dianhydride (BTA) and cyclopentatetraic acid dianhydride (CPDA).

In this embodiment, the additive is a bridging agent, specifically V-03, V-05 or V-07. The solid content of V-03 is 50wt%, the solvent is toluene, and the equivalent weight of NCN is 216. The solid content of V-05 is 100 wt%, and the equivalent weight of NCN is 262. The solid content of V-07 is 50 wt%, the solvent is toluene, and the equivalent weight of NCN is 200. Specifically, in this embodiment, V-05 is selected as the bridging agent, which is a solvent-based bridging agent.

In this embodiment, the solvent includes, but is not limited to, one or more of N-methylpyrrolidone (NMP), dimethylacetamide (DMA) and 1,4-butyrolactone (GBL). Specifically, the mixed solvent of GBL and NMP is adopted, wherein the addition ratio of GBL and NMP is 1:1.

In this embodiment, the solvent further includes xylene.

In this embodiment, the temperature of the cyclization reaction is 180°C to 190°C, and the reaction time is 16h to 18h.

Specifically, the above-mentioned diamine and dianhydride (equivalent ratio of 1:1) and mixed solvent GBL/NMP (weight ratio of 1:1) were added to a 500ml reaction flask, and the solid content was 20wt% to 25wt%. Stir for 12 hours, then heat to 80°C, and stir and react for 4 hours to generate a polyamide acid solution. During the reaction, add xylene (1/5 of the weight of the mixed solvent GBL/NMP), and then heat up to 180°C ~ 190°C and heat up. Set up a reflux tube, react at 180°C to 190°C for 16 hours to 18 hours, and cyclize polyimide to obtain polyimide. After adding additive V-05, stir evenly at room temperature to obtain a transparent polyimide solution. .

The present invention also provides a transparent polyimide film 100, the transparent polyimide film 100 is obtained by heating and curing the above-mentioned transparent polyimide solution. In the visible light wavelength range of 400nm-700nm, preferably 550nm, the light transmittance of the transparent polyimide film is greater than or equal to 88%, and the hardness is greater than or equal to 4H. The prepared transparent polyimide film 100 has the excellent properties of traditional polyimide such as corrosion resistance, high temperature resistance and high mechanical strength, and at the same time improves light transmittance and hardness, and can meet the use of touch panels in electronic products. Require.

In this embodiment, the tensile strength of the transparent polyimide film 100 is greater than or equal to 150 MPa.

In this embodiment, the heating temperature is 120°C to 150°C, and the heating time is 30 min to 60 min. During the heating and curing process, the active hydrogen atoms in the transparent polyimide molecule undergo a cross-linking reaction with the carbodiimide group in the bridging agent, and the carbodiimide group can also cross-link itself to form a thermosetting transparent The polyimide film 100 has good mechanical properties, transparency and hardness.

Please refer to FIG. 1, the present invention also provides the above-mentioned preparation method of the transparent polyimide film 100, comprising the following steps:

In the first step, a mirror surface copper plate 200 is provided, and the above-mentioned transparent polyimide solution is coated on the mirror surface side of the mirror surface copper plate 200 to obtain an intermediate film layer 300 .

In this embodiment, the roughness of the mirror surface copper plate is Ra<0.02um, and the thickness of the intermediate film layer is about 12um.

In the second step, the above-mentioned intermediate film layer 300 is baked and cured at a temperature of 120° C. to 150° C. for 30 minutes to 60 minutes to obtain a transparent polyimide film 100 .

In the third step, the above-mentioned transparent polyimide film 100 is wound to obtain a thermosetting transparent finished transparent polyimide film 100 . The present invention also provides an electronic device, the electronic device includes a touch panel, and the touch panel includes the above-mentioned transparent polyimide film 100 .

The solution of the present application will be further described below with specific examples.

The following synthesis examples 1-5 are all specific embodiments of the transparent polyimide solution without additives. The solid content of the synthesized polyimide solution without additives is 20wt%~25wt%, and the synthesized solution is on a mirror surface. The copper plate (Ra<0.02um) is coated with a thickness of 12um and baked at 120℃~150℃ for 30min~60min, the solvent is removed and cured to obtain a polyimide film without additives, and the light transmittance of the above film is measured. , hardness and mechanical properties of the test. The specific formula and test results are shown in Table 1.

Synthesis Example 1

3.3'-DABS (0.1 mol, 28.03 g) and solvent GBL+NMP (weight ratio of 1:1, 142.92 g) were sequentially added to a 500ml reaction flask, and after stirring until dissolved, CBDA (0.1 mol, 19.61 g) was added. g), stir for 12 h, then heat to 80 °C, stir and dissolve for 4 h, add xylene (28.58 g) during the reaction, then heat up to 180 °C, set up a reflux tube, add xylene to the reflux tube, and keep stirring at a constant temperature of 180 °C 16h~18h to obtain an uncrosslinked transparent polyimide solution.

Synthesis Example 2

6FAP (0.1 mol, 36.63 g) and solvent GBL+NMP (weight ratio of 1:1, 168.71 g) were sequentially added to a 500ml reaction flask, and after stirring until dissolved, CBDA (0.1 mol, 19.61 g) was added, Stir for 12 hours, then heat to 80 °C, stir and dissolve for 4 hours, add xylene (33.74 g) during the reaction, then heat up to 180 °C, set up a reflux tube, add xylene to the reflux tube, and keep stirring at a constant temperature of 180 °C for 16h~18h , to obtain an uncrosslinked transparent polyimide solution.

Synthesis Example 3

3.3'-DABS (0.1 mol, 28.03 g) and solvent GBL+NMP (weight ratio of 1:1, 217.36 g) were sequentially added to the 500ml reaction flask, and after stirring until dissolved, 6FDA (0.1 mol, 44.42 g) was added. g), stir for 12 h, then heat to 80 °C, stir and dissolve for 4 h, add xylene (43.47 g) during the reaction, then heat up to 180 °C, set up a reflux tube, add xylene to the reflux tube, and keep stirring at a constant temperature of 180 °C 16h~18h to obtain an uncrosslinked transparent polyimide solution.

Synthesis Example 4

6FAP (0.1 mol, 36.63 g) and solvent GBL+NMP (weight ratio of 1:1, 243.15 g) were sequentially added to a 500ml reaction flask, and after stirring until dissolved, 6FDA (0.1 mol, 44.42 g) was added, Stir for 12 h, then heat to 80 °C, stir and dissolve for 4 h, add xylene (48.63 g) during the reaction, then heat up to 180 °C, set up a reflux tube, add xylene to the reflux tube, and keep stirring at a constant temperature of 180 °C for 16h~18h , to obtain an uncrosslinked transparent polyimide solution.

Synthesis Example 5

4.4'-DDS (0.1 mol, 24.83 g) and solvent GBL+NMP (weight ratio of 1:1, 207.76 g) were sequentially added to a 500ml reaction flask, and after stirring until dissolved, 6FDA (0.1 mol, 44.42 g) was added. g), stir for 12h, then heat to 80°C, stir and dissolve for 4h, add xylene (41.55 g) during the reaction, then heat up to 180°C, set up a reflux tube, add xylene to the reflux tube, and keep stirring at a constant temperature of 180°C 16h~18h to obtain an uncrosslinked transparent polyimide solution.

Table 1 project Synthesis Example 1 Synthesis Example 2 Synthesis Example 3 Synthesis Example 4 Synthesis Example 5 Diamine (mol) CBDA 0.1 0.1 6FDA 0.1 0.1 0.1 Dianhydride (mol) 3,3'-DABS 0.1 0.1 6FAP 0.1 0.1 4,4' DDS 0.1 solvent NMP(wt%) 50 50 50 50 50 GBL(wt%) 50 50 50 50 50 NMP+ GBL(g) 142.92 168.71 217.36 243.15 207.76 Transmittance(%) 550nm 91 93 91 92 88 pencil hardness IPC-TM-650 2.4.27.2 1H 1H 1H 1H 1H Tensile Strength(Mpa) ASTM D638 123 119 131 134 126 Elongation (%) 6.1 5.2 5.7 5.3 5.8

Polar monomers (such as -CF ₃ , -SO ₂ -) and aliphatics are introduced into the molecular backbone of the transparent polyimide synthesized in Synthesis Examples 1-5 in Table 1, which reduces the degree of intermolecular and intramolecular charge transfer. , synthesizing a transparent solution, and the light transmittance of the transparent polyimide film obtained at the same time is more than 88% (550nm), but it can also be seen from Table 1 that the hardness of the mold obtained in Synthesis Examples 1-5 is small, all Only 1H, less than 4H, it is difficult to meet the hardness requirements of electronic product touch panels. In addition, the diamine monomers of Synthesis Examples 1-4 all selected functional groups (-OH) with active hydrogen atoms. It can be seen that the introduction of functional groups containing active hydrogen atoms into the molecular chain of transparent polyimide does not It affects the chemical synthesis and transparency of polyimide, and these functional groups can also undergo cross-linking reaction with carbodiimide group (NCN) without catalyst to further improve the hardness of the film.

The following examples 1-8 are all specific embodiments of the transparent polyimide solution added with additives. The solid content of the synthesized transparent polyimide solution is 30wt%~45wt%, and the synthesized transparent polyimide solution Coat 12um thickness on the mirror copper plate (Ra<0.02um) and bake at 120℃~150℃ for 30min~60min, remove the solvent and cure to obtain a transparent polyimide film, and test the light transmittance of the above film, Testing of hardness and mechanical properties. The specific formula and test results are shown in Table 2.

Example 1

Synthesize example 1 (10 g) and additive (V-05, 2.20 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Example 2

Synthesize example 2 (10 g) and additive (V-05, 1.87 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Example 3

Synthesize Example 3 (10 g) and additive (V-05, 1.45 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Example 4

Synthesize Example 4 (10 g) and additive (V-05, 1.30 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Example 5

Synthesize example 1 (10 g) and additive (V-05, 3.30 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Example 6

Synthesize example 2 (10 g) and additive (V-05, 2.81 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Example 7

Synthesize example 3 (10 g) and additive (V-05, 2.17 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Example 8

Synthesize Example 4 (10 g) and additive (V-05, 1.95 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Table 2 project Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Polyimide (g) Synthesis Example 1 10 10 Synthesis Example 2 10 10 Synthesis Example 3 10 10 Synthesis Example 4 10 10 N=C=N (V-05) Weight (g) 2.20 1.87 1.45 1.30 3.30 2.81 2.17 1.95 Equivalent ratio 0.8 0.8 0.8 0.8 1.2 1.2 1.2 1.2 Transmittance(%) 550nm 89 91 90 91 88 89 88 89 pencil hardness IPC-TM-650 2.4.27.2 4H 4H 5H 5H 6H 6H 6H 6H Tensile Strength(Mpa) ASTM D638 159 163 168 173 223 242 239 252 Elongation (%) 8.6 7.8 8.9 7.5 2.9 2.3 2.8 2.2

The following comparative examples 1-9 are the specific embodiments of the transparent polyimide solution, the solid content of the synthesized transparent polyimide solution is 30wt% ~ 45wt%, and the synthesized transparent polyimide solution is placed on a mirror copper plate ( Ra < 0.02um) coated with a thickness of 12um and baked at 120℃~150℃ for 30min~60min, remove the solvent and cure to obtain a transparent polyimide film, and test the light transmittance, hardness and mechanical properties of the above film. 's test. The specific formula and test results are shown in Table 3.

Comparative Example 1

Synthesize example 5 (10 g) and additive (V-05, 2 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Comparative Example 2

Synthesize example 1 (10 g) and additive (V-05, 1.92 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Comparative Example 3

Synthesize example 2 (10 g) and additive (V-05, 1.64 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Comparative Example 4

Synthesize example 3 (10 g) and additive (V-05, 1.27 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Comparative Example 5

Synthesize Example 4 (10 g) and additive (V-05, 1.14 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Comparative Example 6

Synthesize Example 1 (10 g) and additive (V-05, 3.57 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Comparative Example 7

Synthesize example 2 (10 g) and additive (V-05, 3.04 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Comparative Example 8

Synthesize Example 3 (10 g) and additive (V-05, 2.35 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

Comparative Example 9

Synthesize example 4 (10 g) and additive (V-05, 2.11 g) in sequence in a 100 ml reaction flask, and after stirring for 6 h, a thermosetting transparent polyimide solution can be obtained.

table 3 project Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Polyimide (g) Synthesis Example 1 10 10 Synthesis Example 2 10 10 Synthesis Example 3 10 10 Synthesis Example 4 10 10 Synthesis Example 5 10 N=C=N (V-05) Weight (g) 2.00 1.92 1.64 1.27 1.14 3.57 3.04 2.35 2.11 Equivalent ratio — 0.7 0.7 0.7 0.7 1.3 1.3 1.3 1.3 Transmittance(%) 550nm 86 90 92 90 91 86 87 85 87 pencil hardness IPC-TM-650 2.4.27.2 2H 2H 3H 3H 3H 6H 6H 6H 6H Tensile Strength(Mpa) ASTM D638 81 153 158 161 167 231 252 249 263 Elongation (%) 1.5 7.8 6.9 7.7 6.7 2.5 1.7 2.3 1.5

It can be seen from the comparison between Synthesis Examples 1-5 in Table 1 and Examples 1-8 in Table 2 that after adding V-05 with a carbodiimide group, due to the active hydrogen on the transparent polyimide molecular chain Atoms can undergo cross-linking reaction with carbodiimide groups, and the mechanical properties and hardness of the obtained transparent polyimide film are significantly improved, from 1H to greater than or equal to 4H. In addition, due to the addition of active hydrogen atoms and carbodiimide The equivalent ratio of amine groups is controlled between 1:0.8 and 1.2. Within this range, the cross-linking of the two has no effect on the light transmittance of the transparent polyimide film, and the polyimide film still has a high The light transmittance (the light transmittance of Examples 1-8 are all greater than or equal to 88%). In addition, from the comparison of Example 1-4 and Example 5-8, it can be seen that the increase of the addition amount of V-05 will further improve the hardness of the transparent polyimide film. This is because the carbodiimide group can interact with the The functional group (-OH) containing active hydrogen atoms on the transparent polyimide molecule undergoes a cross-linking reaction. On the other hand, the carbodiimide group itself can also undergo a cross-linking reaction. After the hydroxyl group reaction is complete, the carbodiimide group itself continues to undergo cross-linking reaction, which further increases the degree of cross-linking and improves the mechanical properties and hardness of the membrane material. However, since V-05 is a transparent yellow-brown liquid, as the addition amount increases, when the addition amount exceeds the above ratio, the transparency also decreases, and the crosslinking degree increases, and the relative elongation tends to decrease.

It can be seen from the comparison between Comparative Examples 2-5 and Examples 1-8 that when the amount of added carbodiimide groups is too low (the ratio of the equivalent of active hydrogen atoms to carbodiimide groups is lower than 0.8), the mechanical properties In terms of hardness and hardness, it cannot meet the needs of electronic product consoles. It can be seen from the comparison between Comparative Examples 6-9 and Examples 1-8 that when the amount of carbodiimide groups added is too high (the ratio of the equivalent of active hydrogen atoms to the equivalent of carbodiimide groups is greater than 1.2), the permeability The light rate will be severely reduced, and the elongation will be too low due to too high crosslinking to meet the needs of electronic product consoles. Therefore, in order to ensure that the transparent polyimide film has high light transmittance, high hardness and excellent mechanical properties at the same time, the optimal range of the ratio of the equivalents of active hydrogen atoms to carbodiimide groups is 1:0.8~1.2.

In addition, in Comparative Example 1, Synthesis Example 5 was used as the transparent polyimide, and the transparent polyimide synthesized in Synthesis Example 5 had no functional group of active hydrogen atoms in the molecular chain, so it could not be combined with the carbodiimide group. In the cross-linking reaction, the carbodiimide group itself can carry out the cross-linking reaction, but there is no chemical bond between the carbodiimide group and the transparent polyimide molecule, and the two appear phase separation, resulting in a decrease in mechanical properties.

In summary, the transparent polyimide film of the present invention has high transparency, and at the same time, by introducing active hydrogen atoms into the transparent polyimide molecular chain, the active hydrogen atoms can interact with the carbodiimide in the additive. The group undergoes a cross-linking reaction to improve the hardness and mechanical properties of the transparent polyimide film.

The descriptions of the above embodiments and comparative examples are only used to help understand the method of the present invention and its core idea; in addition, for those of ordinary skill in the art, various other corresponding changes and modifications can be made according to the technical idea of the present invention , and all these changes and deformations should belong to the protection scope of the claims of the present invention.

100: Polyimide film 200: Mirror copper plate 300: interlayer film

FIG. 1 is a flow chart of the preparation of a polyimide film provided by an embodiment of the present invention. The following specific embodiments will further illustrate the present invention in conjunction with the above drawings.

100: Polyimide film

200: Mirror copper plate

300: interlayer film

Claims (14)

A transparent polyimide solution, comprising transparent polyimide, an additive and a solvent, the molecular chain of the transparent polyimide contains active hydrogen atoms, the additive contains a carbodiimide group, and the active The equivalent ratio of hydrogen atoms to the carbodiimide group is 1:0.8~1.2. The transparent polyimide solution according to claim 1, wherein the solid content in the transparent polyimide solution comprises the transparent polyimide and the additive, and the transparent polyimide solution has The solid content is 30 wt%~45 wt%. The transparent polyimide solution according to claim 1, wherein the additive comprises a solvent-based bridging agent. The transparent polyimide solution according to claim 1, wherein the solvent comprises one or more of N-methylpyrrolidone, dimethylacetamide and 1,4-butyrolactone. A kind of preparation method of transparent polyimide solution, wherein, comprises the following steps: Mixing transparent polyimide, additives and solvent to obtain the transparent polyimide solution, Wherein, the molecular chain of the transparent polyimide contains active hydrogen atoms, the additive contains carbodiimide groups, and the equivalent ratio of the active hydrogen atoms to the carbodiimide groups is 1:0.8~ 1.2. The method for preparing a transparent polyimide solution according to claim 5, wherein the solid content in the transparent polyimide solution comprises the transparent polyimide and the additive, and the transparent polyimide The solid content of the amine solution ranges from 30 wt% to 45 wt%. The method for preparing a transparent polyimide solution according to claim 6, wherein the polyimide is formed by a cyclization reaction of a diamine monomer and a dianhydride monomer. The method for preparing a transparent polyimide solution according to claim 7, wherein the diamine monomer comprises 3,3'-diamino-4,4'-dihydroxydiphenylene, 2,2-bis One or more of (3-amino-4-hydroxyphenyl) hexafluoropropane and 3,5-diaminobenzoic acid. The method for preparing a transparent polyimide solution according to claim 7, wherein the dianhydride monomers include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 4,4'-(hexamethylene dianhydride) Fluoroisopropylidene) diphthalic anhydride, pyromellitic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and cyclopentatetraic acid One or more of dianhydrides. The method for preparing a transparent polyimide solution according to claim 6, wherein the solvent comprises one or more of N-methylpyrrolidone, dimethylacetamide and 1,4-butyrolactone. A kind of preparation method of transparent polyimide film, wherein, comprises the following steps: Provide a release substrate; Applying the transparent polyimide solution according to any one of claims 1 to 4 on the release surface of the release substrate to obtain an intermediate film layer; and heating the intermediate film layer to obtain the transparent polyimide film, The transparent polyimide solution includes polyimide, an additive and a solvent, the molecular chain of the polyimide contains active hydrogen atoms, the additive contains a carbodiimide group, and the active hydrogen atom is associated with the The equivalent ratio of the carbodiimide groups is 1:0.8-1.2, and the active hydrogen atoms and the carbodiimide groups are heated and cross-linked to form a cross-linked structure. The method for preparing a transparent polyimide film according to claim 11, wherein, within the wavelength range of 400 nm to 700 nm of visible light, the light transmittance of the transparent polyimide film is greater than or equal to 88%. The method for preparing a transparent polyimide film according to claim 11, wherein the hardness of the transparent polyimide film is greater than or equal to 4H. An electronic device, wherein the electronic device includes a touch panel, and the touch panel includes the transparent polyimide film according to any one of claims 11 to 13.

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