Polyimide precursor solution and method for producing same

Abstract

The present invention provides a polyimide film which, by having a fluorine structure adopted into a rigid polyamide chain structure, exhibits not only superb heat resistance but also enhanced optical properties. Additionally, the polyimide according to the present invention, by having the particular structure, exhibits excellent transparency, heat-resistance, mechanical strength and flexibility, and thus can be utilized in a variety of functions such as an element substrate, display cover substrate, optical film, integrated circuit (IC) package, adhesive film, multi-layered flexible printed circuit (FPC), tape, touch panel, and protective film for optical disks.

Claims

1. A polyimide precursor solution which comprises a polyimide precursor consisting of a reaction product of tetracarboxylic dianhydrides of the following Chemical Formula 1 and Chemical Formula 2; and a diamine of the following Chemical Formula 3 in N,N-diethylacetamide, (DEAc), N,N-diethylformamide (DEF), N-ethylpyrrolidone (NEP), or a mixture thereof, wherein the tetracarboxylic dianhydride containing the structure of Chemical Formula 2 is contained in an amount of 10 mol % to 40 mol %, based on the total amount of the tetracarboxylic dianhydrides: ##STR00011## wherein, Q.sub.1 and Q.sub.2 are each independently selected from the group consisting of a single bond, O, C(O), C(O)O, C(O)NH, S, SO.sub.2, a phenylene group and a combination thereof; ##STR00012## wherein, R.sub.1 and R.sub.2 are each independently a substituent selected from a halogen atom selected from the consisting of F, Cl, Br and I, a hydroxyl group (OH), a thiol group (SH), a nitro group (NO.sub.2), a cyano group, a C.sub.1-10 alkyl group, a C.sub.1-4 halogenoalkoxyl group, a C.sub.1-10 halogenoalkyl group, and a C.sub.6-20 aryl group; and Q.sub.3 is selected from the group consisting of a single bond, O, CH.sub.18R.sub.19, C(O), C(O)O, C(O)NH, S, SO.sub.2, a phenylene group and a combination thereof, wherein R.sub.18 and R.sub.19 are each independently selected from the group consisting of a hydrogen atom, a C.sub.1-10 alkyl group and a C.sub.1-10 fluoroalkyl group.

2. The polyimide precursor solution according to claim 1, wherein the tetracarboxylic dianhydride having the structure of Chemical Formula 2 is contained in an amount of 10 mol % to 30 mol %, based on the total amount of the tetracarboxylic dianhydrides.

3. The polyimide precursor solution according to claim 1, wherein the structure of Chemical Formula 2 is selected from structures of the following Chemical Formulas 2a to 2e. ##STR00013##

4. The polyimide precursor solution according to claim 1, wherein the viscosity of the polyimide precursor solution is 2,000 cp to 8,000 cp.

5. A polyimide precursor solution which comprises a polyimide precursor consisting of a reaction product of tetracarboxylic dianhydride containing 60 mol % to 90 mol % tetracarboxylic dianhydride of the following Chemical Formula 1 and 10 mol % to 40 mol % of tetracarboxylic dianhydride of the following Chemical Formula 2; and diamines of the following Chemical Formula 3 and the Chemical Formula 5; in an organic solvent, wherein a concentration of an imide group of a polyimide resin manufactured from the polyimide precursor is 2.00 mmol/g to 3.70 mmol/g: ##STR00014## wherein, Q.sub.1 and Q.sub.2 are each independently selected from the group consisting of a single bond, O, C(O), C(O)O, C(O)NH, S, SO.sub.2, a phenylene group and a combination thereof; ##STR00015## wherein, R.sub.1 and R.sub.2 are each independently a substituent selected from a halogen atom consisting of F, Cl, Br and I, a hydroxyl group (OH), a thiol group (SH), a nitro group (NO.sub.2), a cyano group, a C.sub.1-10 alkyl group, a C.sub.1-4 halogenoalkoxyl group, a C.sub.1-10 halogenoalkyl group, and a C.sub.6-20 aryl group; and Q.sub.3 is selected from the group consisting of a single bond, O, CR.sub.18R.sub.19, C(O), C(O)O, C(O)NH, S, SO.sub.2, a phenylene group and a combination thereof, wherein R.sub.18 and R.sub.19 are each independently selected from the group consisting of a hydrogen atom, a C.sub.1-10 alkyl group and a C.sub.1-10 fluoroalkyl group; ##STR00016## wherein, R.sub.10 and R.sub.11 are each independently C1-20 organic group; and h is an integer of 3 to 200.

6. The polyimide precursor solution according to claim 5, wherein the polyimide resin manufactured from the polyimide precursor solution has at least one glass transition temperature at 150 C. to 380 C., and at least one glass transition temperature in a temperature range of lower than 0 C.

Description

EXAMPLE

<Example 1> TFMB(0.999)/PMDA(0.9)_BPFA(0.1)

(1) N,N-diethylacetamide (DEAc, partition coefficient: 0.32, density: 0.9130 g/cm.sup.3) 80 g was filled in a reactor under nitrogen atmosphere, and then 2,2-bis(trifluoromethyl)-4,4-biphenyl diamine (TFMB) 11.4 g was dissolved while maintaining the temperature of the reactor to 25 C. Pyromellitic Dianhydride (PMDA) 7 g and 9,9-bis(3,4-dicaroxyphenyl)fluorene dianhydride (BPFA) 1.63 g were added to the TFMB solution at the same temperature, and dissolved with stirring for a predetermined period of time. DEAc was added to the polyimide precursor solution prepared from the above reaction to make the solid concentration of 10 wt % to 15 wt %. Viscosity of the polyimide precursor solution thus obtained was 5,300 cp.

<Example 2> TFMB(0.999)/PMDA(0.85)_BPFA(0.15)

(2) N,N-diethylacetamide (DEAc, partition coefficient: 0.32, density: 0.9130 g/cm.sup.3) 86 g was filled in a reactor under nitrogen atmosphere, and then 2,2-bis(trifluoromethyl)-4,4-biphenyl diamine (TFMB) 12.0 g was dissolved while maintaining the temperature of the reactor to 25 C. Pyromellitic Dianhydride (PMDA) 7 g and 9,9-bis(3,4-dicaroxyphenyl)fluorene dianhydride (BPFA) 2.59 g were added to the TFMB solution at the same temperature, and dissolved with stirring for a predetermined period of time. DEAc was added to the polyimide precursor solution prepared from the above reaction to make the solid concentration of 10 wt % to 15 wt %. Viscosity of the polyimide precursor solution thus obtained was 4,800 cp.

<Example 3> TFMB(0.999)/PMDA(0.8)_BPFA(0.20)

(3) N,N-diethylacetamide (DEAc, partition coefficient: 0.32, density: 0.9130 g/cm.sup.3) 94 g was filled in a reactor under nitrogen atmosphere, and then 2,2-bis(trifluoromethyl)-4,4-biphenyl diamine (TFMB) 12.0 g was dissolved while maintaining the temperature of the reactor to 25 C. Pyromellitic Dianhydride (PMDA) 7 g and 9,9-bis(3,4-dicaroxyphenyl)fluorene dianhydride (BPFA) 2.59 g were added to the TFMB solution at the same temperature, and dissolved with stirring for a predetermined period of time. DEAc was added to the polyimide precursor solution prepared from the above reaction to make the solid concentration of 10 wt % to 15 wt %. Viscosity of the polyimide precursor solution thus obtained was 4,100 cp.

<Comparative Example 1> TFMB(0.99)/PMDA(1.0)

(4) N,N-diethylacetamide (DEAc, partition coefficient: 0.32, density: 0.9130 g/cm.sup.3) 100 g was filled in a reactor under nitrogen atmosphere, and then 2,2-bis(trifluoromethyl)-4,4-biphenyl diamine (TFMB) 10.17 g was dissolved while maintaining the temperature of the reactor to 25 C. Pyromellitic Dianhydride (PMDA) 7 g was added to the TFMB solution at the same temperature, and dissolved with stirring for a predetermined period of time. DEAc was added to the polyimide precursor solution prepared from the above reaction to make the solid concentration of 10 wt % to 10.5 wt %. Viscosity of the polyimide precursor solution thus obtained was 9,500 cp.

<Comparative Example 2> TFMB(0.99)/BPFA(1.0)

(5) N,N-diethylacetamide (DEAc, partition coefficient: 0.32, density: 0.9130 g/cm.sup.3) 135 g was filled in a reactor under nitrogen atmosphere, and then 2,2-bis(trifluoromethyl)-4,4-biphenyl diamine (TFMB) 13.9 g was dissolved while maintaining the temperature of the reactor to 25 C. 9,9-bis(3,4-dicaroxyphenyl)fluorene dianhydride (BPFA) 20 g was added to the TFMB solution at the same temperature, and dissolved with stirring for a predetermined period of time. DEAc was added to the polyimide precursor solution prepared from the above reaction to make the solid concentration of 10 wt % to 15 wt %. Viscosity of the polyimide precursor solution thus obtained was 3,800 cp.

Test Example 1

(6) Each of the polyimide precursor solutions manufactured in Examples 1 to 3 and Comparative Examples 1 and 2 was spin coated on a glass substrate to a thickness of 9.5 m to 11 m. The polyimide precursor solution-coated glass substrate was put in an oven and heated at a rate of 2 C./min, and heat-treated at 0 C. for 15 min, at 150 C. for 30 min, at 220 C. for 30 min and at 380 C. for 1 hour to perform a curing process. After the curing process is completed, the glass substrate was immersed in water. The film formed on the glass substrate was peeled off and dried in an oven at 100 C. to manufacture a polyimide film.

(7) Haze characteristic and CTE of the film was measured by the following method and the results were shown in Table 1.

(8) Haze was measured by the method according to ASTM D1003 using Haze Meter HM-150.

(9) The films were prepared in the size of 5 mm20 mm, and a sample was loaded thereon using an accessory. The actual measured length of the films was same as 16 mm, and the force pulling the film was set to 0.02 N. The thermal expansion change pattern, when the 1.sup.st heating process was performed within the temperature ranging from 100 C. to 400 C. at a heating rate of 5 C./min and then the cooling process is performed within the temperature ranging from 400 C. to 100 C. at a cooling rate of 4 C./min, was measured with TMA (Q400, TA Instruments).

(10) TABLE-US-00001 TABLE 1 Comparative Comparative Example Example Example Analysis item Example 1 Example 2 1 2 3 Solid content (%) 10.0 15 13.2 14.6 13.5 Mw 89,000 65,000 68,000 67,000 62,000 Viscosity(cp) 9,500 3,800 5,300 4,800 4,100 Thickness (m) 9.5 9.9 10.0 10.1 10.2 CTE 1.sup.st 21 80 5.57 12.1 19.9 100~400 C. cooling (ppm/ C.) Tg( C.) N.D. 390 N.D. N.D. N.D. Td 1%( C.) 538 547 544.6 544.3 541.7 Transmittance 450 nm 70 82.1 77.2 77.6 78.8 % 550 nm 86 89.9 88.0 88.1 88.3 Yellowness index 25 3.5 13.7 13.3 12.1 Rth 1800 30 1000 850 660 Haze 0.45 0.35 0.41 0.4 0.34 Modulus (Gpa) 7.7 7.0 7.7 7.1 6.5 Peel strength (gf/inch) 120 180 148 160 175

(11) According to the results of Table 1, the polyimide precursor solutions of Example 1 to Example 3 according to the present invention can realize low viscosity at high solid content without changing a molar ratio. Accordingly, the solutions can be more uniformly coated during film processing, time for defoaming the solutions can be reduced, and defoaming efficiency can be more enhanced. Further, the films manufactured from the polyimide precursor solutions of Examples 1 to 3 showed CTE value of very small negative value or a positive value range, and it means that the shrinkage characteristic of the film during a heating and cooling processes was significantly reduced compared to Comparative Example 1. The film of Comparative Example 1 showed big negative CTE value, and it means that the film was severely shrunk. The film of Comparative Example 2 only comprising BPFA as a dianhydride showed very big positive CTE value, and it means that the film was severely expanded by cooling.

(12) The CTE value of the polyimide precursor solution according to the present invention can be controlled in a certain range by optimizing the contents of BPFA and PMDA, and therefore, a film with improved thermal expansion and shrinkage characteristics can be provided.

(13) Further, in the present invention, the thickness retardation of the film and distortion of light are significantly reduced by containing the repeating structure, which contains a fluorene structure like BPFA, in the polyimide structure, thereby enhancing visual sensitivity.

<Example 4> TFMB(0.954)/PMDA(0.7)_BPFA(0.3)+X22-1660B-3

(14) While inserting nitrogen gas into a 3 L separable flask equipped with an oil bath and a stirring rod, a both terminal amine modified methylphenyl silicone oil (manufactured by Shin-etsu chemical: X22-1660B-3 (Number average molecular weight: 4400)) 8.0 g and DEAc were added thereto, and continuously BPFA 45.0 g was added thereto followed by stirring for 30 min. Then, after adding TFMB 100 g thereto and complete dissolution of the TFMB was confirmed. PMDA 50 g was added thereto, stirred for 3 hours at a room temperature, heated to 80 C. and then stirred for 4 hours. After removing the oil bath, the temperature was cooled to a room temperature to obtain a polyimide precursor solution. Weight average molecular weight (Mw) of the polyimide precursor and the test results of the film cured at 350 C. were shown in the following Table 2.

Test Example 2

(15) <Evaluation of Glass Transition Temperature>

(16) For measuring glass transition temperature at a temperature higher than room temperature range (hereinafter, Tg1), the polyimide film was subjected to thermomechanical analysis using a thermomechanical analyzer (TMA-50, manufactured by Shimadzu) under the conditions of a load of 5 g, a heating rate of 10 C./min and a nitrogen atmosphere (flow rate of 20 ml/min), elongation of a specimen was measured in a temperature range from 50 C. to 450 C., and then a inflection point of a curve was regarded as a glass transition temperature.

(17) For measuring glass transition temperature in a temperature range of lower than a room temperature (hereinafter, Tg2) which can't be measured by the above method, the polyimide film thus obtained was subjected to a dynamic rheometer (RHEOVIBRON MODEL RHEO-1021, manufactured by Orientec) in a range of 150 C. to 400 C., a inflection point in a temperature region of lower than a room temperature of E prime was measured, and the inflection point was regarded as a glass transition temperature at a low temperature.

(18) <Evaluation of Tensile Elongation and Rupture Strength>

(19) A polyimide film cured at 350 C. (sample size: 550 mm, thickness: 20 m) was elongated using a tensile tester (manufactured by A and D company limited: RTG-1210) at a rate of 100 mm/min to measure tensile elongation and rupture strength.

(20) <Evaluation of Residual Stress>

(21) Polyamic acid was coated by a bar coater on a 6 inch silicon wafer (thickness: 625 m25 m), whose bending quantity was measured in advance using a residual strength measuring device (manufactured by Tencor, model name: FLX-2320) and then pre-baked. Then, heat curing was performed at 350 C. for 1 hour using a vertical cure furnace (manufactured by Koyo Lindbergh Co., Ltd, model name: VF-2000B) under nitrogen atmosphere to manufacture a silicon water on which a polyimide film in 10 m thick was formed. Bending quantity of the wafer was measured by the above residual stress measuring device, and residual stress formed between the silicon water and the polyimide film was evaluated.

(22) TABLE-US-00002 TABLE 2 Residual Tensile Break Analysis Tg1 Tg2 stress elongation strength item ( C.) ( C.) (MPa) (%) (MPa) Example 350 60 17 50 300 4

(23) Although specific embodiments of the present invention are described in detail as described above, it will be apparent to those skilled in the art that the specific description is merely desirable exemplary embodiment and should not be construed as limiting the scope of the present invention. Therefore, the substantial scope of the present invention is defined by the accompanying claims and equivalent thereof.