KR20220137594A - Polyimide precursor composition and method for producing polyimide film using the same - Google Patents

Abstract

Disclosed are a polyimide precursor composition that can be used in the manufacture of flexible substrates, a method for manufacturing a polyimide film using the same and a display device including the polyimide film. The polyimide precursor composition may include a mixed solvent including 1-ethyl-2-pyrrolidone and N,N-dimethylpropionamide; and polyamic acid or polyimide.

Description

Polyimide precursor composition and method for producing polyimide film using same

The present invention relates to a polyimide precursor composition and a method for manufacturing a polyimide film using the same, and more particularly, to a polyimide precursor composition that can be used for manufacturing a flexible substrate, a method for manufacturing a polyimide film using the same, and a polyimide It relates to a display device comprising a film.

Recently, the demand for a flat panel display (FPD) that is easy to implement in a large area and can be thin and lightweight is increasing. Such flat panel displays include a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting display (OLED), and the like. However, since the conventional flat panel display uses a glass substrate, it is not flexible, so there is a limit to its applications and uses. Accordingly, a flexible display device manufactured to be bendable using a substrate made of a flexible material such as plastic or foil instead of a glass substrate having no flexibility is being actively developed as a next-generation display device.

A flexible display device is generally manufactured by a high-temperature thin film transistor (TFT) process. Although the process temperature may vary depending on the type of semiconductor layer, insulating film, and barrier layer included in the device, in general, a temperature of about 300 to 500° C. is required for the TFT process. However, polymer materials that can withstand this process temperature are extremely limited, and polyimide, which is known to have excellent heat resistance, is mainly used. Since polyimide materials are flexible and light as well as excellent thermal properties, polyimide substrates are receiving the most attention as plastic substrates that can replace existing glass substrates.

There are several processes for manufacturing a polyimide substrate, among which the most used method is to spin a polyamic acid polymer solution on a carrier glass or use a slit coater. After coating to a certain thickness, a polyimide substrate is manufactured through a thermal imidization reaction through a convection oven or an IR oven. In the flexible display production process, a TFT backplane, an organic light emitting layer, etc. are formed on a polyimide substrate to make a product, and then separated from the carrier glass by a laser lift off method. Since the polyimide material is easy to bend, the subsequent process is performed while the substrate is fixed to the carrier glass. Since the TFT or deposition process proceeds at a relatively high temperature, it is important to have a similar coefficient of thermal expansion because there is a risk that the carrier glass may warp if the difference in the coefficient of thermal expansion between the polyimide material and the carrier glass is large.

, 끓는점: 165.1 ℃), 디메틸포름아미드(Dimethylformamide: DMF,

, 끓는점: 153 ℃), N-메틸피롤리돈(N- Methylpyrrolidone: NMP,

, 끓는점: 202, ℃) 등이 일반적으로 사용되고 있으나, 이들은 환경 규제 대상으로 사용이 제한되어 다른 용매로의 대체가 필요하다.Polyamic acid polymer solution is prepared by polymerizing diamine and Dianhydride in a polar solvent, and the polar solvent is dimethylacetamide (DMAC,

, boiling point: 165.1 ℃), dimethylformamide (Dimethylformamide: DMF,

, boiling point: 153 ℃), N-methylpyrrolidone (N- Methylpyrrolidone: NMP,

, boiling point: 202, ℃), etc. are generally used, but their use is limited due to environmental regulations, and replacement with other solvents is required.

In addition, in the thermal imidization process for manufacturing a polyimide substrate, the lead time is determined by a high-temperature curing process in an oven. Various attempts are being made. In addition, defects occur on the coating surface due to rapid solvent volatilization during a relatively high high-temperature process starting temperature in which the oven is not completely cooled, a high-temperature curing process, and a rapid temperature increase rate. Various methods are being tried to improve this.

An object of the present invention is to provide an eco-friendly polyimide precursor composition using a new mixed solvent replacing the solvent subject to environmental regulation.

Another object of the present invention is to provide a method for producing a polyimide film having excellent properties using the polyimide precursor composition.

In order to achieve the above object, the present invention provides a mixed solvent comprising 1-ethyl-2-pyrrolidone (NEP) and N,N-dimethylpropionamide (DMPA); And it provides a composition comprising a polyamic acid or polyimide.

The composition according to the present invention uses a new mixed solvent replacing the solvent subject to environmental regulation. From the use of a new mixed solvent, it is possible to shorten the lead time of the polyimide film manufacturing process by a high-temperature curing and quick-drying process. In addition, it is possible to obtain a polyimide film having good transmittance and surface properties by using a mixed solvent including two solvents having different volatility.

Hereinafter, the present invention will be described in detail.

The composition of the present invention comprises a mixed solvent comprising 1-ethyl-2-pyrrolidone (NEP) and N-dimethylpropionamide (DMPA); and polyamic acid or polyimide.

, 끓는점: 212℃) 및 N,N-디메틸프로피온아미드(N,N-Dimethylpropionamide; DMPA,

, 끓는점: 174-176℃)를 포함하며, 고온 공정 시 용매의 급격한 휘발로 인한 표면 결함을 방지하고, 폴리이미드 필름의 투과율과 표면 특성을 개선할 수 있다.The mixed solvent used in the present invention is two substances having different volatility, 1-ethyl-2-pyrrolidone (1-Ethyl-2-pyrrolidone; NEP,

, boiling point: 212° C.) and N,N-dimethylpropionamide (N,N-Dimethylpropionamide; DMPA,

, boiling point: 174-176 ℃), it is possible to prevent surface defects due to rapid volatilization of the solvent during high-temperature processing, and to improve the transmittance and surface properties of the polyimide film.

The mixing ratio (weight ratio) of 1-ethyl-2-pyrrolidone (NEP):N,N-dimethylpropionamide (DMPA) is 1:9 to 9:1, preferably 3:7 to 7:3 days may be, for example, a weight ratio of 5:5. Here, if the amount of 1-ethyl-2-pyrrolidone used is too small, there is a problem in that the film surface is poor in the quick-drying process, and if the amount of 1-ethyl-2-pyrrolidone is too large, the film coatability is advantageous. However, there is a problem that the transmittance is lowered.

The polyamic acid used in the composition of the present invention is a compound having an amine group and a carboxyl group in a molecule, and is a polymer that reacts with an amine group and a carboxyl group by heating to form an imine group. In the mixed solvent, a diamine monomer and a dianhydride monomer are reacted. can be manufactured.

As the diamine monomer, p-phenylenediamine (p-Phenylenediamine: PPDA), 4,4'-oxydianiline (4,4'-Oxydianiline: ODA), 4,4'-methylenedianiline (4,4' -Methylenedianiline: MDA), m-Tolidin (m-Tolidin; 2,2'-Dimethyl-4,4'-Diaminobiphenyl), 1,3-bis (4'-aminophenoxy) benzene (1,3-BIS) (4'-Aminophenoxy)benzene: TPE-R) and 2,2'-bis(trifluoromethyl)benzidine (2,2'-Bis(trifluoromethyl)benzidine: TFMB) containing a fluorine group, 2,2' -Bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (2,2-BIS[4-(4-Aminophenoxy)Phenyl]Hexafluoropropane:HFBAPP), 2,2-bis(3-amino-4 -Hydroxyphenyl) hexafluoropropane (2,2-Bis (3-amino-4-hydroxyphenyl) hexafluoropropane: BIS-AP-AF), 1,3-diamino-2,4,5,6-tetrafluoro Robenzene (1,3-Diamino-2,4,5,6-Tetrafluorobenzene: DRFB) , 3,3'-diaminodiphenyl sulfone containing a sulfur group (3,3'-Diaminodiphenyl Sulfone: DDS), 4, 4'-diaminodiphenyl sulfide (4,4'-Diaminodiphenyl Sulfide: ASD), bis [4- (4-aminophenoxy) phenyl] sulfone (Bis [4- (4-aminophenoxy) phenyl] sulfone: BAPS) , 2,2-bis [4- (3-aminophenoxy) benzene] sulfone (2,2-Bis [4- (3-Aminophenoxy) Benzene] Sulfone: m-BAPS) and the like can be used. Among them, single or a mixture of two or more monomers can be used, and p-Phenylenediamine (PPDA), a monomer having an aromatic structure, is suitable to secure high heat resistance.

An aromatic dianhydride compound is suitable as the dianhdride monomer, and 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (3,3',4,4'-Benzophenonetetracarboxylic dianhydride: BTDA), pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3'4,4'-Biphenyl tetracarboxylicacid dianhydride: BPDA), 2, 2-bis (3,4-anhydrodicarboxyphenyl) -hexafluoropropane dianhydride (2,2-Bis (3,4-anhydrodicarboxyphenyl) -hexafluoropropane dianhydride: 6FDA), 2,3,3',4- Biphenyltetracarboxylic dianhydride (2,3,3',4-biphenyl tetracarboxylicacid dianhydride: a-BPDA), 4,4'-oxydiphthalic anhydride (4,4'-oxydiphthalic Anhydride: ODPA), 3,3' ,4,4'-diphenylsulfonetetracarboxylic dianhydride (3,3',4,4'-Diphenylsulfone-tetracarboxylic Dianhydride: DSDA), 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl] propane dianhydride (2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride: BPADA), hydroquinone diphthalic anhydride (HQDA), and the like may be used. Of these, single or a mixture of more than one type of monomer can be used, and 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3'4,4'-Biphenyl tetracarboxylicacid dianhydride) : BPDA) is appropriate.

The composition of the present invention may further include additives if necessary. The additive may be a material including an epoxy polyfunctional group, and may serve to improve defects on the coating surface. The additive is, for example, [Formula 1-1] Ethylene glycol diglycidyl ether, [Formula 1-2] N,N-Diglycidyl -4-Glycidyloxyaniline represented by the following formula [Formula 1-3] 1,4-Bis ( (2,3-epoxypropoxy)methyl) cyclohexane, [Formula 1-4] 2,2'-[1,3-Phenylenebis (oxymethylene)] dioxirane, [Formula 1-5] 4,4'-methylene bis (N, N-diglicidyl aniline) may be used, but is not limited thereto, and a resin including an epoxy polyfunctional group may be used as an additive.

The additive may be added in an amount of 0.02 to 1.2 parts by weight based on 100 parts by weight of the polyamic acid or polyimide. Here, if the amount of the additive is too small, there may be a problem that the surface of the film is lifted, and if the amount of the additive is too large, there is a problem that the transmittance of the film is lowered (less than 50%).

The additive may be dissolved in a solvent and then added to the composition of the present invention, and the solvent in which the additive is dissolved is a mixture comprising 1-ethyl-2-pyrrolidone (NEP) and N-dimethylpropionamide (DMPA). It may be a solvent, but is not limited thereto, and other types of solvents may be used to improve physical properties.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Chemistry 1-4]

[Formula 1-5]

In the composition of the present invention, the amount of the polyamic acid or polyimide may be 5 to 30 parts by weight, preferably 8 to 20 parts by weight, more preferably 10 to 15 parts by weight, based on 100 parts by weight of the mixed solvent. Here, if the content of the polyamic acid or polyimide is too small, it is difficult to obtain a polyimide film of a uniform thickness due to low viscosity, and the surface is likely to be poor due to rapid solvent volatilization when added to high-temperature bake, and if too much, the viscosity is high During slit coating, it is difficult to control the film thickness, so a relatively thick film is highly likely to be formed.

In the composition of the present invention, the viscosity of the composition may be 1,000 to 20,000 cP. When the viscosity is less than 1,000 cP, a relatively large number of low molecules exist, and a thin polyimide thin film can be formed due to high flowability during coating. It can be difficult to obtain an appropriate polyimide film thickness as a fairly thick thick film is formed.

Next, a method for manufacturing a polyimide film according to the present invention will be described.

In order to manufacture the polyimide film according to the present invention, first, the composition is coated on a carrier substrate (carrier glass, etc.) to a thickness of 400 μm (wet thickness) using an applicator. At this time, as the carrier substrate, glass, metal substrate, or plastic substrate, etc. may be used without particular limitation, and among them, the polyimide precursor formed after curing has excellent thermal and chemical stability during the curing process for the polyimide precursor, and without a separate release agent treatment. A glass substrate that can be easily separated without damage to the mid-based film is preferred. The coating (applying) process may be performed according to a conventional coating method, and specifically, a spin coating method, a bar coating method, a roll coating method, an air-knife method, a gravure method, a reverse roll method, a kiss roll method, a doctor blade method , a spray method, an immersion method, or a brushing method may be used.

The composition may be applied on the substrate in a thickness range such that the finally manufactured polyimide film has a thickness suitable for a display substrate. Specifically, after solvent evaporation and curing, it may be applied in an amount such that the final thickness is 1 to 30 μm. After the coating (application) process, a drying process for removing the solvent present in the composition prior to the curing process may be optionally further performed. The drying process may be carried out according to a conventional method, and specifically may be carried out at a temperature of 140° C. or less, or 80 to 140° C. If the temperature at which the drying process is performed is less than 80° C., the drying process is lengthened, and when it exceeds 140° C., imidization proceeds rapidly, making it difficult to form a polyimide film having a uniform thickness.

On the other hand, since the curing process through the thermal imidization process takes a very long time, the production can be increased only by reducing the curing process time. Therefore, an attempt is being made to shorten the process time by inserting the next coated substrate in a state where the oven is not completely cooled. In the present invention, the polyimide film is heated to 450° C. at a temperature increase rate of 5 to 10° C. per minute in an oven in which cooling is not completed during the curing process, for example, a convection oven having a temperature of 100° C. can be manufactured. In some cases, the curing process may be performed by heating to a temperature of 300 to 450°C. In addition, the curing process may be performed as a multi-step process through step-by-step heat treatment within the above temperature range, for example, primary heat treatment at a temperature of 200° C., secondary heat treatment at a temperature of 300° C., and a temperature of 350° C. It may be performed by tertiary heat treatment, but is not limited thereto. In addition, the curing time during the curing process is not particularly limited, and may be performed for 3 to 60 minutes as an example.

In addition, after the curing process, a subsequent heat treatment process may be optionally further performed to increase the imidization rate of the polyimide-based resin in the polyimide film to form a polyimide-based film having excellent physical properties. The subsequent heat treatment process may be performed at 200° C. or higher, or at 200 to 450° C. for 1 minute to 30 minutes. In addition, the subsequent heat treatment process may be performed once or may be performed twice or more in multiple steps. Specifically, the first heat treatment at 200 to 220°C, the second heat treatment at 300 to 350°C, and the third heat treatment at 400 to 450°C may be performed in three steps. Then, it can be completed by peeling the polyimide film formed on the substrate after cooling from the carrier substrate according to a conventional method.

When the composition of the present invention contains polyimide together with a mixed solvent, since imidization is already performed, the polyimide film can be prepared by evaporating the solvent after coating the composition. Evaporation of the solvent may be performed, for example, by heating to a temperature of 200° C. or higher, but is not limited thereto.

A display substrate and device including the polyimide film may be provided. Specifically, the device may be any solar cell having a flexible substrate (eg flexible solar cell), organic light emitting diode (OLED) lighting (eg flexible OLED lighting), any semiconductor having a flexible substrate. The device may be a flexible display device such as an organic electroluminescent device, an electrophoretic device, or an LCD device having a flexible substrate.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are intended to illustrate the present invention, but the present invention is not limited by the following examples.

[Example 1] Preparation of polyimide precursor composition :

In 529.2 g of a mixed solvent of 1-ethyl-2-pyrrolidone (NEP) and N,N-dimethylpropionamide (DMPA) in a ratio of 1:9 (weight ratio), 21.62 g of p-phenylenediamine (PPDA) (0.2 mol) was completely dissolved at room temperature, and then 58.84 g (0.2 mol) of 3,3'4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added to react, and stirred for 18 hours and then terminated. A composition containing 15 parts by weight of polyamic acid (polyimide precursor) was obtained based on 100 parts by weight. The viscosity of the composition was measured using a BrookField viscometer in order to confirm that polymerization proceeds well and film formation is possible, and the viscosity of the obtained polyamic acid composition was 15400 cps.

[Example 2] Preparation of polyimide precursor composition :

In the same manner as in Example 1, except that the mixing ratio of 1-ethyl-2-pyrrolidone (NEP) and N,N-dimethylpropionamide (DMPA) was 3:7, polyamic acid (polyimide precursor) ) to obtain a composition. The viscosity of the obtained polyamic acid composition was 14760 cps.

[Example 3] Preparation of polyimide precursor composition :

In the same manner as in Example 1, except that the mixing ratio of 1-ethyl-2-pyrrolidone (NEP) and N,N-dimethylpropionamide (DMPA) was 5:5, polyamic acid (polyimide precursor) ) to obtain a composition. The viscosity of the obtained polyamic-acid composition was 14000 cps.

[Example 4] Preparation of polyimide precursor composition :

A polyamic acid (polyimide precursor) was used in the same manner as in Example 1, except that the mixing ratio of 1-ethyl-2-pyrrolidone (NEP) and N,N-dimethylpropionamide (DMPA) was 7:3. ) to obtain a composition. The viscosity of the obtained polyamic acid composition was 13500 cps.

[Example 5] Preparation of polyimide precursor composition :

A polyamic acid (polyimide precursor) was used in the same manner as in Example 1, except that the mixing ratio of 1-ethyl-2-pyrrolidone (NEP) and N,N-dimethylpropionamide (DMPA) was 9:1. ) to obtain a composition. The viscosity of the obtained polyamic-acid composition was 12900 cps.

[Examples 1-1 to 1-5] Preparation of polyimide film :

In the polyamic acid composition obtained in Example 1, N,N-Diglycidyl-4-Glycidyloxyaniline was mixed and stirred according to the addition amount of Table 1 compared to the amount of the polyamic acid monomer solid content to prepare a coating solution composition. The prepared coating solution composition was coated on a carrier glass to a thickness of 400 μm (wet thickness) using an applicator, and heated in a convection oven to 450° C. at a temperature increase rate of 8° C. per minute. A thermal imide reaction was carried out. The external shape and optical properties of the obtained polyimide film were analyzed and shown in Table 1.

[Examples 2-1 to 2-5] Preparation of polyimide film :

Thermally in the same manner as in Example 1-1, except that N,N-Diglycidyl-4-Glycidyloxyaniline was mixed with the polyamic acid composition obtained in Example 2 according to the amount of the polyamic acid monomer solids added in Table 2 The imide reaction was performed, and the external shape and optical properties of the obtained polyimide film were analyzed and shown in Table 2.

[Examples 3-1 to 3-5] Preparation of polyimide film :

Thermally in the same manner as in Example 1-1, except that N,N-Diglycidyl-4-Glycidyloxyaniline was mixed in the polyamic acid composition obtained in Example 3 according to the addition amount of Table 3 relative to the amount of the polyamic acid monomer solid content. The imide reaction was carried out, and the external shape and optical properties of the obtained polyimide film were analyzed and shown in Table 3.

[Examples 4-1 to 4-5] Preparation of polyimide film :

Thermally in the same manner as in Example 1-1, except that N,N-Diglycidyl-4-Glycidyloxyaniline was mixed in the polyamic acid composition obtained in Example 4 according to the addition amount of Table 4 relative to the amount of the polyamic acid monomer solid content. The imide reaction was performed, and the external shape and optical properties of the obtained polyimide film were analyzed and shown in Table 4.

[Examples 5-1 to 5-5] Preparation of polyimide film :

Thermally in the same manner as in Example 1-1, except that N,N-Diglycidyl-4-Glycidyloxyaniline was mixed in the polyamic acid composition obtained in Example 5 according to the addition amount of Table 5 compared to the amount of the polyamic acid monomer solid content. The imide reaction was carried out, and the external shape and optical properties of the obtained polyimide film were analyzed and shown in Table 5.

[Comparative Examples 1-1 to 1-5] Preparation of polyimide film :

A thermal imide reaction was performed in the same manner as in Examples 1-1 to 1-5, except that the polyamic acid composition was prepared using only 1-ethyl-2-pyrrolidone (NEP) as a solvent, and the obtained The external shape and optical properties of the polyimide film were analyzed and shown in Table 6.

[Comparative Examples 2-1 to 2-5] Preparation of polyimide film :

A polyimide obtained by performing a thermal imide reaction in the same manner as in Examples 1-1 to 1-5, except that the polyamic acid composition was prepared using only N,N-dimethylpropionamide (DMPA) as a solvent. The external shape and optical properties of the film were analyzed and shown in Table 7.

<Physical Analysis of Poly Amic Acid and Polyimide Film>

[Viscosity Measurement]

The average value was measured after three measurements at 25 using a rotary type high viscosity viscometer (BrookField's Corn-Plate method).

[Film thickness]

The thickness of the film was measured 10 times using an ultrasonic thickness measuring device (Qnix4500), and the average value and standard deviation were confirmed.

[Measurement of transmittance]

The average transmittance in the visible light region was measured 5 times using an optical measuring device (Nippon Denshoku, COH-400), and then the average value was measured.

[Mechanical properties- Stress, Strain]

In order to measure the mechanical properties of the polyimide film, Ametek LLOYD Instrument's UTM (Universal Test Machine) was used. After preparing a film specimen with a width of 5 mm and a length of 70 mm or more, the Grip To Grip size was set to 30 mm, and the Tension Rate was measured 10 times at a speed of 10 mm/min to check the average value and standard deviation.

(NEP:DMPA = 1:9) division Example 1-1 Example 1-2 Examples 1-3 Examples 1-4 Examples 1-5 Additive dosage
(ppm) 100 200 5,000 12,000 12,500 Transmittance (%) 60 57 55 52 49 film surface condition Surface unevenness and lifting good surface good surface good surface good surface thickness
(μm) Average 16.94 17.15 17.32 17.65 17.59 stdev 2.1 1.0 1.2 0.9 1.0 Stress
(MPa) Average 352.1 348.2 355.1 364.1 360.1 stdev 10.2 10.8 10.3 11.6 12.0 strain
(%) Average 28.2 27.3 29.2 27.2 28.1 stdev 0.9 1.0 0.9 1.2 1.1

(NEP:DMPA = 3:7) division Example 2-1 Example 2-2 Example 2-3 Example 2-4 Example 2-5 Additive dosage
(ppm) 100 200 5,000 12,000 12,500 Transmittance (%) 58 56 53 50 48 film surface condition Surface unevenness and lifting good surface good surface good surface good surface thickness
(μm) Average 17.11 17.31 17.38 17.59 17.51 stdev 1.5 0.7 1.0 0.9 0.8 Stress
(MPa) Average 345.1 355.8 357.1 362.1 360.7 stdev 8.1 7.8 9.1 7.8 8.3 strain
(%) Average 29.1 30.2 33.2 31.5 30.9 stdev 0.7 0.8 0.8 0.7 0.6

NEP:DMPA = (5:5) division Example 3-1 Example 3-2 Example 3-3 Example 3-4 Example 3-5 Additive dosage
(ppm) 100 200 5,000 12,000 12,500 Transmittance (%) 56 55 53 52 48 film surface condition Surface unevenness and lifting good surface good surface good surface good surface thickness
(μm) Average 17.52 16.78 17.11 17.32 17.39 stdev 1.3 0.2 0.3 0.1 0.3 Stress
(MPa) Average 341.2 58.1 361.2 362.8 361.7 stdev 8.3 4.5 3.4 4.9 4.0 strain
(%) Average 27.1 30.2 31.8 30.8 33.5 stdev 0.5 0.4 0.3 0.3 0.4

(NEP:DMPA = 7:3) division Example 4-1 Example 4-2 Example 4-3 Example 4-4 Example 4-5 Additive dosage
(ppm) 100 200 5,000 12,000 12,500 Transmittance (%) 57 51 50 50 46 film surface condition Surface unevenness and lifting good surface good surface good surface good surface thickness
(μm) Average 17.77 17.15 17.25 16.94 17.38 stdev 1.2 0.8 0.96 1.0 1.1 Stress
(MPa) Average 335.2 348.2 350.2 358.1 351.0 stdev 10.2 8.2 8.3 7.5 7.8 strain
(%) Average 25.6 28.1 27.6 28.7 29.1 stdev 1.0 0.7 0.6 0.7 0.8

(NEP:DMPA = 9:1) division Example 5-1 Example 5-2 Example 5-3 Example 5-4 Example 5-5 Additive dosage
(ppm) 100 200 5,000 12,000 12,500 Transmittance (%) 55 52 51 51 47 film surface condition Surface unevenness and lifting good surface good surface good surface good surface thickness
(μm) Average 17.15 16.87 16.93 17.18 17.35 stdev 1.5 1.0 1.3 1.5 1.1 Stress
(MPa) Average 335.1 351.1 347.1 352.3 355.1 stdev 15.2 11.2 10.5 9.1 10.3 strain
(%) Average 24.1 28.1 27.9 29.1 28.2 stdev 1.7 1.2 1.0 0.9 1.6

(NEP 100%) division Comparative Example 1-1 Comparative Example 1-2 Comparative Example 1-3 Comparative Example 1-4 Comparative Example 1-5 Additive dosage
(ppm) 100 200 5,000 12,000 12,500 Transmittance (%) 51 50 48 48 46 film surface condition Surface unevenness and lifting Surface unevenness and lifting Surface unevenness and lifting Surface unevenness and lifting Surface unevenness and lifting thickness
(μm) Average 17.52 16.58 17.11 17.38 17.27 stdev 2.1 1.7 1.6 1.2 1.5 Stress
(MPa) Average 320.4 334.2 345.2 349.3 344.7 stdev 20.1 17.2 15.2 12.4 15.7 strain
(%) Average 22.1 24.6 27.1 27.3 25.4 stdev 1.7 1.2 1.3 1.4 1.7

(DMPA 100%) division Comparative Example 2-1 Comparative Example 2-2 Comparative Example 2-3 Comparative Example 2-4 Comparative Example 2-5 Additive dosage
(ppm) 100 200 5,000 12,000 12,500 Transmittance (%) 64 63 60 57 52 film surface condition Surface unevenness and lifting Surface unevenness and lifting Surface unevenness and lifting Surface unevenness and lifting Surface unevenness and lifting thickness
(μm) Average 17.25 16.85 17.11 17.36 16.55 stdev 2.2 1.6 1.7 1.9 1.2 Stress
(MPa) Average 330.2 338.2 329.8 334.5 327.3 stdev 19.2 16.4 13.6 15.7 14.9 strain
(%) Average 20.5 26.3 22.5 27.3 23.4 stdev 1.8 1.5 1.7 1.5 1.4

As can be seen from Tables 1 to 7, it can be seen that by using the mixed solvent, the surface state of the polyimide film is good and transmittance of 50% or more can be exhibited. However, it can be seen that, when the amount of the additive is small, the transmittance is excellent, but the state of the surface may be poor, and when an excessive amount of the additive is added, the transmittance is significantly lowered to less than 50%.

In addition, when NEP or DMPA, not the mixed solvent of the present invention, was used alone, it was confirmed that all of the film surface conditions were poor. It can be seen that there is an effect that can be improved,

In particular, even when a fast-drying treatment is performed at a high temperature increase rate, for example, at a temperature increase rate of 8°C as in Examples, the composition using the mixed solvent in the present invention has a good effect on the surface condition of the prepared film, whereas DMPA and It can be confirmed that the surface condition of the film is not good when the same type of solvent is used.

Furthermore, in terms of the standard deviation of the film thickness, it can be seen that the standard deviation of the thickness is 1 or less, that is, the difference in thickness is not large by using the mixed solvent of the present invention, so that the reliability of the thickness during film formation is excellent,

Also in stress and strain, when the mixed solvent of the present invention was used, the deviation was 10 or less and 1 or less, respectively, and from this, the mechanical properties of the polyimide film prepared using the mixed solvent It turns out that a large fluctuation|variation does not generate|occur|produce and it is excellent in the reliability of a polyimide film.

Claims (1)

a mixed solvent comprising 1-ethyl-2-pyrrolidone and N,N-dimethylpropionamide;
polyamic acid or polyimide; and
Ethylene glycol diglycidyl ether, N,N-diglycidyl-4-ricidyloxyaniline, 1,4-bis((2,3-epoxypropoxy)methyl)cyclohexane, 2,2'-[ 1,3-phenylenebis (oxymethylene)] dioxirane, and 4,4'-methylene bis N,N-diglycidyl aniline comprising one or more additives selected from the group consisting of, ,
The 1-ethyl-2-pyrrolidone:N,N-dimethylpropionamide mixing ratio (weight ratio) is 1:9 to 9:1,
Wherein the additive is included in an amount of 0.02 to 1.2 parts by weight based on 100 parts by weight of the polyamic acid or polyimide.