KR101550955B1 - Polyimide film - Google Patents

Abstract

The present invention relates to a polyimide film, and more particularly, to a polyimide film which comprises a repeating unit derived from 3,3'-diaminodiphenylsulfone (3DDS) and 1,4-diaminocyclohexane (TCHD) as a diamine monomer and a repeating unit derived from a dianhydride monomer To a polyimide film which is transparent and which exhibits optical properties with low birefringence.

Description

Polyimide film [0002]

The present invention relates to a polyimide film, and relates to a polyimide film which is transparent and has a low birefringence and an excellent optical property.

In general, a polyimide (PI) film is a film made of a polyimide resin, and a polyimide resin is produced by solution polymerization of an aromatic dianhydride and an aromatic diamine or aromatic diisocyanate to prepare a polyamic acid derivative, Refers to a high heat-resistant resin produced by imidization.

Since polyimide films have excellent mechanical, heat resistance and electrical insulation properties, they are used in a wide range of electronic materials such as semiconductor insulating films and substrates for flexible printed wiring circuits of electrode-protective films of TFT-LCD.

 However, the polyimide resin is colored in brown and yellow due to its high aromatic ring density, and thus has low transmittance in the visible light region and yellowish color to lower the light transmittance and has a large birefringence, making it difficult to use the polyimide resin as an optical member have.

To solve this problem, a method of purifying monomers and a solvent and polymerizing them has been attempted, but the improvement of the transmittance has not been remarkable.

U.S. Patent No. 5,053,480 discloses a method of using an aliphatic cyclic dianhydride component instead of an aromatic dianhydride. In comparison with the purification method, there is an improvement in transparency and color in the case of a solution phase or a film, And thus the high transmittance was not satisfied and the thermal and mechanical properties were deteriorated.

U.S. Patent Nos. 4595548, 4603061, 4645824, 4895972, 5218083, 5093453, 5218077, 5367046, 5338826. 5986036 and 6232428 and Korean Patent Laid-Open Publication No. 2003-0009437 disclose monomers having a backbone structure connected to a linking group such as -O-, -SO ₂ -, or CH ₂ - and the like at an m-position other than the p-position There has been reported a novel structure of polyimide having improved transparency and color transparency as far as the thermal property is not significantly deteriorated by using aromatic dianhydride dianhydride and aromatic diamine monomer having a substituent such as -CF ₃ , But showed insufficient results in birefringence.

The present invention provides a polyimide film which is transparent and exhibits low birefringence optical properties.

Accordingly, the present invention provides, as a first preferred embodiment, a resin composition comprising a repeating unit derived from 3,3'-diaminodiphenylsulfone (3DDS) and 1,4-diaminocyclohexane (TCHD) as a diamine monomer and a repeating unit derived from a dianhydride system There is provided a polyimide film obtained by imidizing a polyamic acid containing a repeating unit derived from a monomer.

The repeating unit derived from the 3,3'-diaminodiphenylsulfone may be 30 to 90% by weight of the repeating units derived from the entire diamine-based monomer.

The repeating unit derived from the 3,3'-diaminodiphenylsulfone may be 30 to 70% by weight of the repeating units derived from the entire diamine-based monomer.

The repeating unit derived from the 3,3'-diaminodiphenylsulfone may be 50 to 70% by weight of the repeating units derived from the entire diamine-based monomer.

The polyimide film may have a birefringence of 0.003 or less.

Wherein the polyimide film has a Ro (plane direction retardation) of 1 nm or less and an Rth (thickness direction retardation) of 70 nm or less (35 mu m in thickness).

The polyimide film may have an average transmittance of 85% or more.

The dianhydride monomer may be at least one selected from the group consisting of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydride (6FDA), cyclobutane tetracarboxylic dianhydride (CBDA), biphenyltetracarboxyl Ricinanhydride (BPDA), bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA), 4- (2,5-dioxotetra (Tetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), pyromellitic acid dianhydride Benzene tetracarboxylic dianhydride (PMDA), benzophenone tetracarboxylic dianhydride (BTDA), biscarboxyphenyldimethylsilanediamine hydride (SiDA), oxydiphthalic dianhydride (ODPA), bisdicarboxy phenoxy diphenyl sulfide dianhydride (BDSDA), sulfonyl adipic anhydride (SO ₂ DPA) and the Talic The propylidene may be at least one selected from phenoxy-bis phthalic anhydride (6HDBA).

The present invention also provides, as a second preferred embodiment, an image display device comprising the polyimide film.

According to the present invention, it is possible to provide a polyimide film which is transparent and has a low birefringence and an excellent optical property.

Hereinafter, the present invention will be described in more detail.

The present invention relates to a polyimide film improved in birefringence while maintaining physical properties of a conventional transparent polyimide resin which is colorless transparent and excellent in optical properties,

The polyimide film according to one embodiment of the present invention includes a repeating unit derived from 3,3'-diaminodiphenylsulfone (3DDS) and 1,4-diaminocyclohexane (TCHD) as a diamine monomer and a repeating unit derived from dianhydride Or may be obtained by imidizing a polyamic acid containing a repeating unit derived from a monomer.

In this case, 3DDS may be 30 to 90% by weight, preferably 30 to 70% by weight, and more preferably 50 to 70% by weight, of the total diamine.

If the content of 3DDS is less than 30% by weight, there is a problem in birefringence. If the content of 3DDS is more than 90% by weight, polymerization may not be performed well and film formation may be difficult.

When the content of 3DDS is more than 70% by weight, the polymerization viscosity is not sufficiently grown, and therefore, there is a problem that film formation is difficult. When the content is less than 50% by weight, improvement of birefringence is insufficient.

The dianhydride-based monomer used in the present invention is not particularly limited, but may be 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydrate (6FDA), cyclobutane tetracarboxylic dianhydride (CBDA), biphenyl tetracarboxylic dianhydride (BPDA), bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA) 4 - (2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride (PMDA), benzophenone tetracarboxylic dianhydride (BTDA), biscarboxyphenyldimethylsilanediamine hydride (SiDA), oxydipthalic dianhydride Hydride (ODPA), bisdicarboxyphenoxy diphenylsulfide dianhydride (BDSDA), Sulfonated diphthalic anhydride (SO ₂ DPA), and isopropylidene may be at least one selected from phenoxy bisphthalic anhydride (6HDBA).

The polyamic acid solution can be prepared in a nitrogen / argon atmosphere at a reaction temperature of -10 to 80 ° C and a reaction time of 2 to 48 hours at a 1: 1 equivalent ratio of the dianhydride monomer and the diamine monomer.

The solvent for the solution polymerization of the monomers is not particularly limited as long as it is a solvent dissolving the polyamic acid. As the known reaction solvent, there may be used, for example, m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO) One or more polar solvents are used. In addition, a low boiling point solution such as tetrahydrofuran (THF), chloroform or a low-absorbency solvent such as? -Butyrolactone may be used.

The content of the first solvent is preferably 50 to 95% by weight, more preferably 70 to 90% by weight in the total polyamic acid solution in order to obtain the molecular weight and viscosity of the appropriate polyamic acid solution, Is more preferable.

The polyimide resin prepared by imidizing the polyamic acid solution thus prepared preferably has a glass transition temperature of 200 to 400 ° C in consideration of thermal stability.

In the method for producing a transparent polyimide film according to the present invention, in the step of casting and polymerizing the polymerized polyamic acid on a support, imidation methods to be applied include a thermal imidation method, a chemical imidation method, And can be applied by combination of the compounding method and the compounding method.

In the chemical imidation method, a dehydrating agent represented by an acid anhydride such as acetic anhydride and a imidation catalyst represented by tertiary amines such as isoquinoline, p-picoline, and pyridine are added to a polyamic acid solution. When the thermal imidation method or the thermal imidation method and the chemical imidization method are used in combination, the heating conditions of the polyamic acid solution may be varied depending on the type of the polyamic acid solution, the thickness of the polyimide film to be produced, and the like.

More specifically, a polyimide film is prepared by adding a dehydrating agent and an imidation catalyst to a polyamic acid solution. The polyamic acid solution is cast on a support, and then heated at 80 to 200 ° C, Preferably at 100 to 180 ° C to activate the dehydrating agent and the imidization catalyst to partially cure and dry the polyimide film, and then heat at 200 to 400 ° C for 5 to 400 seconds to obtain a polyimide film.

In the present invention, a polyimide film may be prepared from the polyamic acid solution as follows. Namely, after the obtained polyamic acid solution is imidized, the imidized solution is put into a second solvent, followed by precipitation, filtration and drying to obtain a solid content of the polyimide resin, and the solid content of the obtained polyimide resin is added to the first solvent Can be obtained through a film-forming process using a dissolved polyimide solution.

When the polyamic acid solution is imidized, the thermal imidation method, the chemical imidization method, or the thermal imidation method and the compound imidation method may be used in combination as described above. Examples of imidization in the case where the thermal imidation method and the chemical imidization method are used in combination include a method in which a dehydrating agent and an imidation catalyst are added to the obtained polyamic acid solution and heated at 20 to 180 ° C for 1 to 12 hours to form imide It can be changed.

The first solvent may be the same solvent as that used in the polymerization of the polyamic acid solution. The second solvent may be one having a lower polarity than the first solvent in order to obtain the solid content of the polyimide resin, Alcohols, ethers, and ketones.

At this time, the content of the second solvent is not particularly limited, but it is preferably 5 to 20% by weight based on the weight of the polyamic acid solution.

The polyimide resin solids obtained after filtration and drying are preferably subjected to a temperature of 50 to 120 캜 and a time of 3 to 24 hours in consideration of the boiling point of the second solvent.

Thereafter, the polyimide solution in which the solid polyimide resin is dissolved is cast on a support, and heated at a temperature in the range of 40 to 400 ° C for 1 minute to 8 hours while gradually heating the polyimide solution to obtain a polyimide film.

The thickness of the obtained polyimide film is not particularly limited, but is preferably in the range of 10 to 250 탆, more preferably 25 to 150 탆.

The polyimide film obtained by the method as described above has a birefringence of 0.003 or less, an R o (retardation in the thickness direction) of 70 nm or less (based on 35 μm) and an average transmittance of 85% or more.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

≪ Comparative Example 1 &

364.53 g of N, N-dimethylacetamide (DMAc) was charged into a 500-mL reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a condenser while passing nitrogen through the reactor. 18.5 g (0.162 mol) of TCHD and 4.47 g (0.018 mol) of 3DDS were dissolved and the solution was maintained at 60 ° C. 55.98g (0.126mol) of 6FDA and 10.59g (0.054mol) of CBDA were added and reacted at 60 ° C for 1 hour and then cooled to 25 ° C and subjected to 18HR reaction to obtain a polymer having a solid content of 20% by weight and a viscosity of 101 poise solution of polyamic acid was obtained.

After the reaction was completed, the obtained solution was coated on a stainless steel plate, cast to 180 μm, dried with hot air at 150 ° C. for 1 hour, 200 ° C. for 1 hour and 300 ° C. for 30 minutes with hot air, 36 占 퐉 polyimide film was obtained.

≪ Example 2 >

379 g of N, N-dimethylacetamide (DMAc) was charged into a 500-mL reactor equipped with a stirrer, a nitrogen-introducing device, a dropping funnel, a temperature controller and a condenser while nitrogen was passed through the reactor. 14.39 g (0.126 mol) of TCHD was dissolved and the solution was maintained at 60 占 폚. 55.98 g (0.126 mol) of 6FDA was added thereto, and the mixture was reacted by stirring for 1 hour. Then, after the temperature of the reactor was cooled to 25 ° C, 13.409 g (0.054 mol) of 3DDS was added thereto, and the solution was completely dissolved and reacted for 1 hour. Thereafter, 10.59 g (0.054 mol) of CBDA was added, followed by 18HR reaction to obtain a polyamic acid solution having a solid content of 20 wt% and a viscosity of 82 poise.

Thereafter, a base polyimide film was prepared in the same manner as in Comparative Example 1.

≪ Example 3 >

The reactor was charged with 403.16 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 500-mL reactor equipped with a stirrer, a nitrogen inlet, a dropping funnel, a temperature controller and a condenser. 10.28 g (0.09 mol) of TCHD was then dissolved and the solution was maintained at 60 < 0 > C. 39.98 g (0.09 mol) of 6FDA was added thereto, and the mixture was reacted by stirring for 1 hour. Then, after the temperature of the reactor was cooled to 25 ° C, 22.348 g (0.009 mol) of 3DDS was added thereto, and completely dissolved and reacted for 1 hour. Thereafter, 10.59 g (0.054 mol) of CBDA and 15.99 g (0.036 mol) of 6FDA were added, followed by 18HR reaction to obtain a polyamic acid solution having a solid content of 20% by weight and a viscosity of 42 poise.

Thereafter, a base polyimide film was prepared in the same manner as in Comparative Example 1.

<Example 4>

As a reactor, 416.08 g of N, N-dimethylacetamide (DMAc) was charged while passing nitrogen through a 500-mL reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a condenser. 6.17 g (0.054 mol) of TCHD was dissolved and the solution was maintained at 60 캜. 23.99 g (0.054 mol) of 6FDA was added thereto, and the mixture was reacted by stirring for 1 hour. Then, the temperature of the reactor was cooled to 25 DEG C, and 31.287 g (0.126 mol) of 3DDS was added thereto to completely dissolve and react for 1 hour. Then, 10.59 g (0.054 mol) of CBDA and 31.99 g (0.072 mol) of 6FDA were added and subjected to 18HR reaction to obtain a polyamic acid solution having a solid content of 20 wt% and a viscosity of 2.5 poise.

Thereafter, a base polyimide film was prepared in the same manner as in Comparative Example 1.

&Lt; Example 5 >

The reactor was charged with 435.39 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 500-mL reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a condenser. 2.06 g (0.018 mol) of TCHD was then dissolved and the solution was maintained at 60 &lt; 0 &gt; C. 8 g (0.018 mol) of 6FDA was added thereto, and the mixture was reacted by stirring for 1 hour. Then, after the temperature of the reactor was cooled to 25 ° C, 40.226 g (0.162 mol) of 3DDS was added thereto to completely dissolve and reacted for 1 hour. Thereafter, 10.59 g (0.054 mol) of CBDA and 47.98 g (0.108 mol) of 6FDA were added, followed by 18HR reaction to obtain a polyamic acid solution having a solid content of 20 wt% and a viscosity of 1.8 poise.

Thereafter, a base polyimide film was prepared in the same manner as in Comparative Example 1.

&Lt; Comparative Example 2 &

354.88 g of N, N-dimethylacetamide (DMAc) was charged into a 500-mL reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a condenser while passing nitrogen through the reactor. 20.55 g (0.18 mol) of TCHD was dissolved and the solution was maintained at 60 캜. 55.98 g (0.126 mol) of 6FDA and 10.59 g of CBDA were added and reacted for 1 hour with stirring. The mixture was cooled to 25 ° C and subjected to 18HR reaction to obtain a polyamic acid solution having a solid content of 20 wt% and a viscosity of 67 poise .

Thereafter, a base polyimide film was prepared in the same manner as in Comparative Example 1.

&Lt; Comparative Example 3 &

As a reactor, 447.31 g of N, N-dimethylacetamide (DMAc) was charged while passing nitrogen through a 500-mL reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a condenser. (0.112 mol) of 6FDA and 9.413 g (0.048 mol) of CBDA were added thereto, followed by 18HR reaction to obtain a polyamic acid solution having a solid content of 20% by weight and a viscosity of 3400 poise &Lt; / RTI &gt;

Thereafter, a base polyimide film was prepared in the same manner as in Comparative Example 1.

&Lt; Comparative Example 4 &

N, N-dimethylacetamide (DMAc) 392.98 g was charged into a 500-mL reactor equipped with a stirrer, a nitrogen-introducing device, a dropping funnel, a temperature controller and a condenser as a reactor, and the temperature of the reactor was adjusted to 60 ° C 14.39 g (0.126 mol) of TCHD was dissolved and the solution was maintained at 60 캜. 55.98 g (0.126 mol) of 6FDA was added thereto, and the mixture was reacted by stirring for 1 hour. Then, after the temperature of the reactor was cooled to 25 ° C, 17.292 g (0.054 mol) of TFDB was added thereto to completely dissolve and reacted for 1 hour. Thereafter, 10.59 g (0.054 mol) of CBDA was added, followed by 18HR reaction to obtain a polyamic acid solution having a solid content of 20 wt% and a viscosity of 420 poise.

Thereafter, a base polyimide film was prepared in the same manner as in Comparative Example 1.

The properties of the polyimide films prepared in Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 1 below.

(1) Transmission

The average transmittance at 380 to 780 nm was measured using a UV spectrometer (Varian, Cary100).

(2) Yellowness

Yellowness was measured according to ASTM E313 standard.

(3) Birefringence

The average value was measured three times at 630 nm using a birefringence analyzer (Prism Coupler, Sairon SPA4000).

(4) Viscosity

The Brookfield viscometer (RVDV-II + P) was measured twice at 50 rpm using a 2 or 6 scandal at 25 ° C and averaged.

(5) Retardation

Retardation was measured using RETS from OTSUKA ELECTRONICS. The specimen was mounted on a sample holder in the shape of a square of 1 inch square, fixed at 550 nm using a monochrometer, and the in-plane retardation (R o) was measured at an incident angle of 0 ° to measure R b Thickness direction retardation) can be measured by measuring the incident angle at 45 두께.

_{Ro = (n x -n y)} * d

_{Rth = [(n y -n z} ) * d + (n x -n z) * d] / 2

Here, n _x is the refractive index in the x direction, n _y is the refractive index in the y direction, n _z is the refractive index in the z direction, and d is the thickness of the polyimide film.

ingredient Mole ratio thickness() Permeability (%) Prism Coupler Transverse electric (TE) mode TM (transverse magnetic) mode Birefringence Comparative Example 1 TCHD + 3DDS + 6FDA + CBDA 90: 10: 70: 30 35 85.43 1.5722 1.5694 0.003 Example 2 TCHD + 3DDS + 6FDA + CBDA 70: 30: 70: 30 36 85.94 1.5743 1.5737 0.001 Example 3 TCHD + 3DDS + 6FDA + CBDA 50: 50: 70: 30 35 86.14 1.5868 1.5864 0.000 Example 4 TCHD + 3DDS + 6FDA + CBDA 30: 70: 70: 30 34 86.45 1.5992 1.5995 0.000 Example 5 TCHD + 3DDS + 6FDA + CBDA 10: 90: 70: 30 35 87.12 1.6013 1.6010 0.000 Comparative Example 2 TCHD + 6FDA + CBDA 100: 70: 30 34 89.49 1.5645 1.5594 0.005 Comparative Example 3 TFDB + 6FDA + CBDA 100: 70: 30 35 90.34 1.5590 1.5448 0.014 Comparative Example 4 TCHD + TFDB + 6FDA + CBDA 70: 30: 70: 30 36 88.07 1.5510 1.5411 0.010

ingredient Mole ratio thickness() Viscosity (poise) Phase difference meter (RETS) Ro Rth Comparative Example 1 TCHD + 3DDS + 6FDA + CBDA 90: 10: 70: 30 35 101 0.79 102 Example 2 TCHD + 3DDS + 6FDA + CBDA 70: 30: 70: 30 36 82 0.92 65.664 Example 3 TCHD + 3DDS + 6FDA + CBDA 50: 50: 70: 30 35 42 0.90 63.42 Example 4 TCHD + 3DDS + 6FDA + CBDA 30: 70: 70: 30 34 25 0.82 65.12 Example 5 TCHD + 3DDS + 6FDA + CBDA 10: 90: 70: 30 35 1.8 0.78 62.12 Comparative Example 2 TCHD + 6FDA + CBDA 100: 70: 30 34 67 0.74 186.00 Comparative Example 3 TFDB + 6FDA + CBDA 100: 70: 30 35 3400 0.82 435.21 Comparative Example 4 TCHD + TFDB + 6FDA + CBDA 70: 30: 70: 30 36 420 0.52 223.344

As a result of the physical property evaluation, it was confirmed that when the content of 3DDS was 30% or more, the birefringence was close to zero, and the Rth value was extremely small as 70 nm or less.

From the results of the examples, it can be seen that the birefringence characteristics are lowered as the 3DDS content in the polyimide film is increased. This is because the 3DDS is structurally difficult to align the molecules due to the m-position of the connecting group, have.

On the other hand, the higher the content of 3DDS, the lower the viscosity and the difficulty in film production. Therefore, the content of 3DDS is preferably about 30 to 70 mol%.

Comparing Example 2 and Comparative Example 4, it can be seen that the birefringence value is increased about 10 times when 30 mol% of TFDB having a relatively large number of Benzene rings in the molecule is used instead of 30 mol% of 3DDS.

Claims (9)

A polyamide comprising a repeating unit derived from 3,3'-diaminodiphenylsulfone (3DDS) and 1,4-diaminocyclohexane (TCHD) as a diamine-based monomer and a repeating unit derived from a dianhydride-based monomer Acid is obtained by imidation,
The content of the repeating unit derived from the 3,3'-diaminodiphenylsulfone is 30 to 90% by weight in the repeating units derived from the entire diamine-based monomer,
Wherein the film has a birefringence of 0.003 or less.
delete The method according to claim 1,
Wherein the content of the repeating unit derived from the 3,3'-diaminodiphenylsulfone is 30 to 70% by weight in the repeating units derived from the whole diamine-based monomer.
The method of claim 3,
Wherein the content of the repeating unit derived from the 3,3'-diaminodiphenylsulfone is 50 to 70% by weight based on the total repeating units derived from the diamine-based monomer.
delete The method according to claim 1,
Wherein the polyimide film has a Ro (plane direction retardation) of 1 nm or less and an Rth (thickness direction retardation) of 70 nm or less (35 mu m in thickness).
The method according to claim 1,
Wherein the polyimide film has an average transmittance at 380 to 780 nm of 85% or more.
The method according to claim 1,
The dianhydride monomer may be at least one selected from the group consisting of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydride (6FDA), cyclobutane tetracarboxylic dianhydride (CBDA), biphenyltetracarboxyl Ricinanhydride (BPDA), bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA), 4- (2,5-dioxotetra (Tetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), pyromellitic acid dianhydride Benzene tetracarboxylic dianhydride (PMDA), benzophenone tetracarboxylic dianhydride (BTDA), biscarboxyphenyldimethylsilanediamine hydride (SiDA), oxydiphthalic dianhydride (ODPA), bisdicarboxy phenoxy diphenyl sulfide dianhydride (BDSDA), sulfonyl adipic anhydride (SO ₂ DPA) and the Talic Propylidene bis phenoxy phthalic anhydride polyimide film, characterized in that the selected one or more species of (6HDBA).
An image display device comprising the polyimide film according to any one of claims 1 to 7.