KR101986710B1 - Polyimide resin comprising a pigment and Polyimide film thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide resin including a pigment and a film thereof, and more particularly, to a polyimide film containing a pigment, which can improve the yellowing property while maintaining thermal stability, Transparent electrode films, optical communication materials, protective films for solar cells, flexible display substrates, and the like.

Description

TECHNICAL FIELD The present invention relates to a polyimide resin containing a pigment,

The present invention relates to a polyimide resin comprising a pigment and a film thereof.

Generally, polyimide (PI) resin refers to a high heat-resistant resin prepared by preparing a polyamic acid derivative by combining an aromatic dianhydride with an aromatic diamine or an aromatic diisocyanate in solution and then dehydrating it by ring-closure dehydration at a high temperature. (PMDA) or biphenyltetracarboxylic acid dianhydride (BPDA) or the like is used as an aromatic dianhydride component, and examples of the aromatic diamine component include oxydianiline (ODA), p (P-PDA), m-phenylenediamine (m-PDA), methylene dianiline (MDA), and bisaminophenylhexafluoropropane (HFDA).

Polyimide resin is an insoluble and non-fusible ultra-high temperature resistant resin. It has excellent heat resistant oxidizing property, heat resistance property, radiation resistance property, low temperature property, chemical resistance and so on. It is a high heat resistant material such as automobile material, , An insulating film, a semiconductor, and an electrode protective film of a TFT-LCD. Recently, a display material such as an optical fiber or a liquid crystal alignment film and a conductive filler are contained in a film or coated on the surface to be used as a transparent electrode film.

However, since the polyimide film is colored in brown or yellow due to its high aromatic ring density, it has a low transmittance in the visible light region and a yellowish color, which lowers the light transmittance and is difficult to use in fields requiring transparency. It has a lower Tg (glass transition temperature) than that of a conventional yellow polyimide film, and thus it is difficult to use in a field requiring a high temperature of 300 ° C or higher.

To solve this problem, attempts have been made to polymerize and purify monomers and solvents with high purity, but the improvement of the transmittance is not significant. When monomers having a rigid structure are used to impart thermal stability, the transmittance becomes significantly worse or the yellowness A phenomenon that has increased.

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 , Mechanical properties, yellowing degree and visible light transmittance are not enough to be used as a substrate for a semiconductor insulating film, a TFT-LCD insulating film, an electrode protecting film, and a flexible display.

Accordingly, it is an object of the present invention to provide a polyimide film improved in yellowness characteristics by keeping the characteristics of a conventional polyimide film and adding a pigment. Pigments should have a high heat resistance-based property so that they do not decompose during the imidation process, and a series capable of shifting the yellow color coordinate to reduce the yellowing of the polyimide film should be selected. In order to disperse the pigment well, it is necessary to physically optimize the dispersion through a mill, a mixer, a high-speed stirrer homogenizer, and an ultrasonic disperser.

It is an object of the present invention to provide a polyimide resin having improved yellowness while maintaining thermal stability by including a pigment and a film thereof.

Accordingly, the present invention provides, as a first preferred embodiment, a polyimide resin copolymerized with a dianhydride and a diamine, wherein the polyimide resin comprises a pigment.

       The content of the pigment according to the embodiment is 0.001 to 0.1 part by weight based on 100 parts by weight of the polyimide resin.

The pigment has a particle size of 0.1 to 7.0 mu m when the particle size is measured by the following method.

≪ Particle size measurement method &

Pigment particle size was measured using a Microtrac S3500 particle size analyzer, using 0.1% by weight of dimethylformamide (DMF) or dimethylacetamide (DMAc) as a solvent, and then using a dispersion treated with ultrasonic waves for 2 hours.

The pigment according to this embodiment is an inorganic pigment or an inorganic pigment made from at least one metal compound selected from the group consisting of zinc, titanium, lead, iron, copper, chromium, and the like.

The pigment according to the embodiment includes a blue-based pigment having a visible light absorption wavelength band of 560 to 680 nm.

The dianhydride according to this embodiment may be selected from the group consisting of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA) Dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), pyromellitic acid dianhydride (PMDA) , Benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), biscarboxyphenyldimethylsilanediamine hydride (SiDA), bisdicarboxyphenoxy diphenylsulfide dianhydride (BDSDA) , Sulfonyldiphthalic anhydride (SO ₂ DPA), isopropylidene is at least one selected from phenoxy bisphthalic anhydride (6HBDA) and a group thereof.

The diamine according to this embodiment may be selected from the group consisting of oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p- methylenediamine (pMDA), m- The reaction was carried out in the same manner as in Example 1 except that phenoxybenzene (133APB), bisaminophenoxybenzene (134APB), bisaminophenoxyphenylhexafluoropropane (4BDAF), bisaminophenylhexafluoropropane (33-6F), bisaminophenylhexafluoropropane (14CHD), cyclohexanediamine (14CHD), bisaminophenoxyphenyl (44CF), bis-aminophenylsulfone (4DDS), bisaminophenylsulfone (3DDS), bistrifluoromethylbenzidine (TFDB), cyclohexanediamine Propane (6HMDA), bisaminohydroxyphenylhexafluoropropane (DBOH), bisaminophenoxy diphenylsulfone (DBSDA), bis (4-aminophenyl) fluorene (FDA), bis Phenyl) fluorene (F-FDA) and one or more of these groups.

The polyimide resin is characterized in that it is copolymerized with an aromatic dicarbonyl compound in addition to dianhydride and diamine.

The aromatic dicarbonyl compounds according to this embodiment can be prepared by reacting terephthaloyl chloride (TPC), terephthalic acid (TPA), isophthaloyl dichloride (IPC), 4,4'-benzoyl chloride (BZC) It is more than one selected.

The present invention also provides, as an example of a second preferred embodiment, a polyimide film made of the polyimide resin.

The polyimide film according to this embodiment has a haze of 2.0 or less, an optical transmittance at a wavelength of 550 nm of 86% or more, a coefficient of thermal expansion (CTE) at 50 to 250 캜 of 15 ppm / 캜 or less, And the yellowness degree is 7 or less.

The present invention also provides, as a third preferred embodiment, a substrate for a display element comprising the polyimide film.

According to the present invention, it is possible to provide a polyimide resin having improved yellowness while maintaining thermal stability and a film thereof.

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

In one aspect, the present invention relates to a polyimide including a pigment capable of Yellow color coordinate shift. More specifically, Every object has its own absorption wavelength. When an object receives sunlight, the light of the original light absorption region is absorbed, so that the light of the absorbed wavelength is less, that is, the color of the object is recognized by the complementary color. The polyimide film has a yellow color as described above. In the present invention, when a small amount of a complementary color (grayish blue, purple) pigment is added, the b * value in the color space of the ink is proportional to the content of the pigment in the positive direction (-: yellow, 0: White, +: Blue) It is possible to improve the yellowness by using the movement.

The pigment according to the present invention preferably contains a blue-based pigment having a visible light absorption wavelength band of 560 to 680 nm. When the blue-based pigment is included, it has the advantage of effectively absorbing the wavelength of the visible light spectrum yellow region (580 to 630 nm), thereby greatly increasing the whitening effect. .

The present invention relates to a polyimide resin containing a pigment and a polyimide film thereof, and it is a conventional problem that even when dispersed on a polyimide resin by ultrasonic waves or various kinds of mills due to the particle size and cohesiveness of the pigment itself, It is difficult to expect uniform dispersibility due to sedimentation or flocculation. In addition, due to polyimide process characteristics, it is necessary to select a pigment to obtain the intended color coordinates without decomposing at high temperatures.

Accordingly, in the present invention, by using an inorganic pigment having good heat resistance and small particle size and performing ultrasonic dispersion treatment, it is possible to improve the mixing property with the resin, the dispersibility, and the heat resistance.

The pigment according to the present invention preferably has a particle size of 0.1 to 7.0 mu m when the particle size is measured by the following method.

≪ Particle size measurement method &

Pigment particle size was measured using a Microtrac S3500 particle size analyzer, using 0.1% by weight of dimethylformamide (DMF) or dimethylacetamide (DMAc) as a solvent, and then using a dispersion treated with ultrasonic waves for 2 hours.

When the particle size is within the above range, the dispersibility of the solvent phase is improved to such an extent that sedimented particles are hardly observed, which is advantageous in that it can be easily injected in a fixed amount.

The inorganic pigment may be 0.001-0.1 part by weight based on 100 parts by weight of the polyimide. When the content of the inorganic pigment particles is less than 0.001 part by weight based on 100 parts by weight of the polyimide, the color coordinate shift of the polyimide film is not expected, If it exceeds the weight part, the optical characteristic of the polyimide film may be deteriorated due to the dark pigment concentration.

The solvent phase size of the inorganic pigment particles may be 0.01 to 20 탆, and preferably 0.01 to 10 탆. In this case, the dispersibility in the polyimide resin solution is good and the color deviation of the polyimide film can be improved.

When the dispersion concentration of the pigment particles relative to the solvent is less than 0.01% by weight, the solid content is low, which makes it difficult to produce the film. When the concentration of the pigment is less than 0.01% by weight, %, The dispersibility in the polyimide resin solution may be lowered due to the aggregation and sedimentation of the particles in the dispersed solution.

At this time, the solvent in which the inorganic pigment particles can be dispersed may be the first solvent used in the polymerization reaction of the polyamic acid described later in terms of workability. Examples thereof include m-crosol, N-methyl-2-pyrrolidone NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), acetone and diethyl acetate.

On the other hand, the polyimide according to the present invention can be obtained by obtaining a copolymerized polyamic acid solution containing dianhydride and diamine, or by obtaining a copolymerized polyamic acid solution containing an aromatic dicarbonyl compound in addition to the dianhydride and diamine, The resulting polyamic acid solution is partially imidized and then added to a second solvent, followed by precipitation, filtration and drying to obtain a polyimide solid fraction. The polyimide film can be prepared by imidizing the solvent-dispersed Inorganic pigment particles in the obtained polyimide solid content.

The dianhydrides which can be used in the present invention include 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydrate (6FDA), biphenyltetracarboxylic dianhydride (BPDA), 4- (2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), pyromellitic acid dianhydride ), Benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), biscarboxyphenyldimethylsilanediamine hydride (SiDA), bisdicarboxyphenoxy diphenylsulfide dianhydride (BDSDA ), Sulfonyldiphthalic anhydride (SO ₂ DPA), isopropylidene is phenoxybisphthalic anhydride (6HBDA), and the type is not limited thereto. The dianhydride may be used singly or in combination of two or more, but is not limited thereto.

On the other hand, as the diamine used in the present invention, oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylenediamine (pMDA), m- , Bisaminophenoxybenzene (133APB), bisaminophenoxybenzene (134APB), bisaminophenoxyphenylhexafluoropropane (4BDAF), bisaminophenylhexafluoropropane (33-6F), bisaminophenylhexafluoro (14CHD), cyclohexanediamine (14CHD), bisaminophenoxine (14CHD), bis-aminophenylsulfone (4DDS), bis-aminophenylsulfone (3DDS), bistrifluoromethylbenzidine (4-aminophenyl) fluorene (FDA), bis (4-aminophenyl) fluorene, bis (aminophenyl) 3-fluorophenyl) fluorene (F-FDA), or the like, And it does not limit a kind referred to this.

Examples of aromatic dicarbonyl compounds usable in the present invention include terephthaloyl chloride (TPC), terephthalic acid (TPA), isophthaloyl dichloride (IPC), 4,4'-benzoyl chloride (BZC) The same ingredients may be mentioned but not limited thereto.

The molar amount of the dianhydride and the aromatic dicarbonyl compound and the molar amount of the diamine are preferably such that the molar amount of the dianhydride and the aromatic dicarbonyl compound is in an equimolar amount, and the polyamic acid solution may be prepared by dissolving the dianhydride and the aromatic dicarbonyl compound in a first solvent.

      The reaction conditions are not particularly limited, but the reaction temperature is preferably -10 to 80 占 폚, and the reaction time is preferably 2 to 48 hours. It is more preferable that the atmosphere is an inert gas atmosphere such as argon or nitrogen during the reaction. The organic solvent for the solution polymerization of the monomers is not particularly limited as long as it is a solvent dissolving the polyamic acid. As known reaction solvents there may be mentioned m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO) At least one polar solvent selected from ethyl formamide (DEF), diethylacetamide (DEA), propylene glycol monomethyl ether (PGME), and propylene glycol monomethyl ether acetate (PGMEA) is used. In addition, a low boiling point solution such as tetrahydrofuran (THF), chloroform or a low-absorbency solvent such as? -Butyrolactone may be used.

These solvents may be used alone or in combination of two or more.

Although the content of the organic solvent is not particularly limited, the content of the organic 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 a suitable 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 300 ° C or higher but may be lower in temperature depending on the constitution of the raw material used.

The method for producing the polyimide film from the polyamic acid solution obtained is not particularly limited, and conventionally known methods can be used. As the imidization method of the polyamic acid solution, thermal imidization method and chemical imidization method can be mentioned, and it is more preferable to use the chemical imidization method. More preferably, the solution subjected to the chemical imidation method is subjected to precipitation, followed by purification, drying, and then dissolving in a solvent. This solvent is the same as the above-mentioned solvent. In the chemical imidization method, a dehydrating agent represented by an acid anhydride such as acetic anhydride and a imidization catalyst represented by tertiary amines such as isoquinoline, p-picoline, and pyridine are applied to a polyamic acid solution. The thermal imidation method can be used in combination with the chemical imidization method, and the heating conditions can be varied depending on the type of the polyamic acid solution, the thickness of the film, and the like.

After the chemical imidization, it is precipitated, dried and dissolved in a solvent to be applied to a support. The applied film is gelled on the support by dry air and heat treatment. The gelation temperature of the coated film is preferably from 100 to 250 ° C, and a glass plate, an aluminum foil, a circulating stainless belt, a stainless steel drum, or the like can be used as a support.

The treatment time required for gelation varies depending on the temperature, the type of the support, the amount of the applied polyamic acid solution, and the mixing conditions of the catalyst, and is not limited to a certain time. Preferably in a range of 5 minutes to 30 minutes.

The gelled film is heat treated away from the support to complete drying and imidization. The heat treatment temperature is in the range of 100 to 500 ° C. and the treatment time is 1 to 30 minutes. The gelled film is fixed to the support at the time of heat treatment and proceeds. The gel film can be fixed using a pin type frame or using a clip type.

The heat-treated film is heat-treated under a constant tension to remove residual stress inside the film. If the last heat treatment is not performed, the value of the thermal expansion coefficient becomes much smaller than that of the conventional film because a residual stress to shrink in the film reduces thermal expansion. Heat treatment can reduce hysteresis of thermal expansion coefficient. Since the tension and temperature conditions are correlated with each other, the tension condition may vary depending on the temperature. The temperature is preferably maintained between 100 and 500 DEG C, and the time is preferably maintained between 1 minute and 3 hours.

The thickness of the obtained polyimide film is not particularly limited, but is preferably in the range of 10 to 250 탆, more preferably 10 to 100 탆.

The polyimide film produced in the present invention has a coefficient of thermal expansion of 30 ppm / ° C or lower and a glass transition temperature of 350 ° C or higher at 50 to 300 ° C on the basis of a film thickness of 80 μm, A transparency of 86% or more, and a yellowness of 7 or less.

The polyimide film of the present invention satisfying the above optical transmittance, yellowing degree, and heat resistance can be used as a protection film or a diffusion film for a TFT-LCD or a coating film which is limited in use due to the yellow of a conventional polyimide film, Interlayer, gate insulator, liquid crystal alignment film, etc., can be used in fields requiring transparency, and TFT-LCD can be manufactured when the above transparent polyimide is applied as a liquid crystal alignment film. It can also be used as a flexible display substrate and a hard coating film to replace glass in conventional displays.

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.

≪ Example 1 >

1-1: Preparation of polyimide

       N, N-dimethylacetamide (DMAc) 734.1 g was charged into a 1 L reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a condenser while nitrogen was passed through the reactor, 67.25 g (0.210 mol) of TFDB was dissolved and the solution was kept at 25 캜. 17.73 g (0.040 mol) of 6FDA was added thereto, followed by stirring and stirring for a certain time. The reactor temperature was lowered to 10 ° C, and 142.27 g of N, N-dimethylacetamide (DMAc) and 29.27 g of propylene oxide were added to react. After the temperature of the solution was maintained at 8 ° C, 33.26 g (0.164 mol) of TPC was added and reacted at 25 ° C. for 12 hours to obtain a polyamic acid solution having a solid content of 12 wt% and a viscosity of 250 poise.

13.95 g of pyridine and 18.01 g of acetic anhydride were added to the polyamic acid solution, stirred for 30 minutes, and further stirred at 80 ° C for 1 hour. The mixture was cooled to room temperature and precipitated with 20 L of methanol. The precipitated solid was filtered After drying at 100 DEG C under vacuum for 6 hours, 97.7 g of a solid content powder of copolymerized polyimide was obtained.

Subsequently, 0.03 g of a pigment (Shepherd, Cobalt and Aluminum Blue, 603 nm in visible light absorption wavelength band) was added to 30 g of N, N-dimethylacetamide (DMAc) and ultrasonicated for 2 hours to prepare a pigment dispersion Weight: 0.1% by weight). 5.0 g of the obtained pigment dispersion and 100 g of the solid polyimide prepared above were added to a 1 L reactor equipped with a stirrer filled with 703.2 g of N, N-dimethylacetamide (DMAc), a nitrogen inlet, a dropping funnel, a temperature controller and a condenser, , And dissolved by stirring.

When the particle size of the pigment was measured by the following method, the particle size was 1.0 탆.

≪ Particle size measurement method &

Pigment particle size was measured using a Microtrac S3500 particle size analyzer, a 0.1% by weight solution of dimethylacetamide (DMAc) as a solvent, and a dispersion solution treated with ultrasonic waves for 2 hours.

The particle size of a pigment to be described later was measured in the same manner as described above.

1-2: Preparation of polyimide film

     The melted mixture was coated on a glass plate, cast and dried for 30 minutes with hot air at 120 DEG C, and then the film was peeled off from the glass plate and pinned to the frame. The film-fixed frame was placed in an oven, heated from 100 ° C to 280 ° C, and then separated from the frame to obtain a polyimide film.

≪ Example 2 >

A polyimide film was prepared in the same manner as in Example 1 except that 0.03 g of a pigment (HEUCODUR, Cobalt and Aluminum Blue, 592 nm in visible light absorption wavelength band) was added to 30 g of N, N-dimethylacetamide (DMAc) And subjected to ultrasonic treatment for 2 hours to obtain a pigment dispersion (dispersion weight: 0.1 wt%). 5.0 g of the obtained pigment dispersion and 100 g of the solid polyimide of Example 1-1 were charged in a 1 L reactor equipped with a stirrer filled with 703.2 g of N, N-dimethylacetamide (DMAc), a nitrogen inlet, a dropping funnel, a temperature controller and a condenser The reactor was charged with passing nitrogen, and dissolved by stirring. Then, a polyimide film was obtained in the same manner as in Example 1 above.

At this time, when the particle size of the pigment was measured by the following method, the particle size was 0.7 mu m.

≪ Example 3 >

A polyimide film was prepared in the same manner as in Example 1 except that 0.03 g of pigment (Shepherd, Cobalt violet, 563 (nm) in visible light absorption wavelength band) was added to 30 g of N, N-dimethylacetamide (DMAc) And subjected to ultrasonic treatment for 2 hours to obtain a pigment dispersion (dispersion weight: 0.1 wt%). 0.03 g of a pigment (Shepherd, Cobalt and Aluminum Blue, 603 (nm) in visible light absorption wavelength band) was added to 30 g of N, N-dimethylacetamide (DMAc) and ultrasonicated for 2 hours to prepare a pigment dispersion : 0.1% by weight). 2.5 g each of the obtained pigment dispersion and 100 g of the solid polyimide of Example 1-1 were mixed with 703.2 g of N, N-dimethylacetamide (DMAc) in an agitator filled with nitrogen, a dropping funnel, a temperature controller and a condenser 1 L reactor while passing nitrogen through it, and dissolved by stirring. Then, a polyimide film was obtained in the same manner as in Example 1 above.

At this time, when the particle size of the pigment was measured by the following method, the particle size was 1.2 탆.

≪ Comparative Example 1 &

One- 1: Polyimide  Produce

N, N-dimethylacetamide (DMAc) 734.1 g was charged into a 1 L reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a condenser while nitrogen was passed through the reactor, 67.25 g (0.210 mol) of TFDB was dissolved and the solution was kept at 25 캜. 17.73 g (0.040 mol) of 6FDA was added thereto, followed by stirring and stirring for a certain time. The reactor temperature was lowered to 10 ° C, and 142.27 g of N, N-dimethylacetamide (DMAc) and 29.27 g of propylene oxide were added to react. After the temperature of the solution was maintained at 8 ° C, 33.26 g (0.164 mol) of TPC was added and reacted at 25 ° C. for 12 hours to obtain a polyamic acid solution having a solid content of 12 wt% and a viscosity of 250 poise.

13.95 g of pyridine and 18.01 g of acetic anhydride were added to the polyamic acid solution, and the mixture was stirred for 30 minutes and then stirred at 80 ° C for 1 hour. The mixture was cooled to room temperature and precipitated with 20 L of methanol. The precipitated solid was filtered After drying at 100 DEG C under vacuum for 6 hours, 97.7 g of a solid content powder of copolymerized polyimide was obtained.

One- 2: Polyimide  Production of film

100 g of the solid polyimide of Example 1-1 was charged into a 1 L reactor equipped with a stirrer filled with 703.2 g of N, N-dimethylacetamide (DMAc), a nitrogen inlet, a dropping funnel, a temperature controller and a condenser while passing nitrogen And dissolved by stirring.

The dissolved mixture (solid content concentration: 12.54%) was coated on a glass plate, cast and dried for 30 minutes with hot air at 120 ° C, and then the film was peeled off from the glass plate and pinned to the frame. The film-fixed frame was placed in an oven, heated from 100 ° C to 280 ° C, and then separated from the frame to obtain a polyimide film.

(1) Optical transmittance

The films prepared in Examples and Comparative Examples were measured for optical transmittance at 550 nm using a UV spectrometer (Kotikaminolta CM-3700d).

(2) Yellow Index (Y.I.)

The yellowing degree was measured according to the ASTM E313 standard using a UV spectrometer (Kotikaminolta CM-3700d).

(3) Lab color coordinates

The color coordinates were measured using a UV spectrometer (Kotikaminolta CM-3700d).

(4) Thickness measurement

The thickness was measured with an Anritsu Electronic Micrometer and the deviation of the device was less than ± 0.5%.

Pigment type Pigment
Input (g) thickness
(탆) Optical Transmittance (%) Yellowing degree
(YI) L * a * b * Comparative Example 1 - 0 80 88.22 4.80 95.79 -0.23 2.13 Example 1 Blue (Shepherd) 0.005 80 86.41 3.65 94.91 -0.22 1.77 Example 2 Blue
(HEUCDUR) 0.005 80 86.11 2.26 94.36 -0.6 1.54 Example 3 Blue +
Violet 0.0030
0.0020 80 86.01 2.12 94.00 0.72 0.59

As a result of the physical property evaluation, it can be seen that the yellow color coordinate moves in the blue direction according to the color of the pigment. However, the transmittance characteristic is lowered compared with the polyimide film (Comparative Example) produced without using the pigment. This is due to the high absorbance of the blue or violet pigments at 550 to 685 nm, which is inversely proportional to the content.

It can be seen that there is a method of minimizing the deterioration of the permeability as the yellowness improves but the ratio of the pigment mixture of one or more pigments in which the decrease of the transmittance is minimized in the section where the adjustment of the appropriate pigment content or the yellowness is improved.

Claims (12)

Dianhydride and diamine, wherein the polyimide resin comprises a blue-based pigment having a visible light absorption wavelength band of 560 to 680 nm and a haze of 2.0 or less. The polyimide resin according to claim 1, wherein the content of the pigment is 0.001 to 0.1 part by weight based on 100 parts by weight of the polyimide resin. The polyimide resin according to claim 1, wherein the pigment has a particle size of 0.1 to 7.0 mu m when the particle size is measured by the following method.
≪ Particle size measurement method &
Pigment particle size was measured using a Microtrac S3500 particle size analyzer, using 0.1% by weight of dimethylformamide (DMF) or dimethylacetamide (DMAc) as a solvent, and then using a dispersion treated with ultrasonic waves for 2 hours. The polyimide resin according to claim 1, wherein the pigment is an inorganic pigment or an inorganic pigment produced from at least one metal compound selected from the group consisting of zinc, titanium, lead, iron, copper, chromium and a group thereof. delete The method of claim 1, wherein the dianhydride is selected from the group consisting of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydrate (6FDA), biphenyltetracarboxylic dianhydride (BPDA), 4 - (2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), pyromellitic acid dianhydride (PMDA), benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), biscarboxyphenyldimethylsilanediamine hydride (SiDA), bisdicarboxyphenoxy diphenylsulfide dianhydride BDSDA), sulfonyldiphthalic anhydride (SO ₂ DPA), isopropylidene phenoxybisphthalic anhydride (6HBDA), and a group of these polyamides. The method of claim 1, wherein the diamine is selected from the group consisting of oxadiazines (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p- methylenediamine (pMDA) , Bisaminophenoxybenzene (133APB), bisaminophenoxybenzene (134APB), bisaminophenoxyphenylhexafluoropropane (4BDAF), bisaminophenylhexafluoropropane (33-6F), bisaminophenylhexafluoro (14CHD), cyclohexanediamine (14CHD), bisaminophenoxine (14CHD), bis-aminophenylsulfone (4DDS), bis-aminophenylsulfone (3DDS), bistrifluoromethylbenzidine (4-aminophenyl) fluorene (FDA), bis (4-aminophenyl) fluorene, bis (aminophenyl) 3-fluorophenyl) fluorene (F-FDA) and one or more of these groups Polyimide resin to. The polyimide resin according to claim 1, wherein the polyimide resin is copolymerized with an aromatic dicarbonyl compound in addition to dianhydride and diamine. 9. The method of claim 8, wherein the aromatic dicarbonyl compound is selected from the group consisting of terephthaloyl chloride (TPC), terephthalic acid (TPA), isophthaloyl dichloride (IPC), 4,4'-benzoyl chloride (BZC) Wherein the polyimide resin is at least one selected from the group consisting of polyimide resins. A polyimide film produced from the polyimide resin according to any one of claims 1 to 4 and 6 to 9. The film according to claim 10, wherein the polyimide film has an optical transmittance of at least 86% at a wavelength of 550 nm, a coefficient of thermal expansion (CTE) at 50 to 250 캜 of 15 ppm / 7. The polyimide film according to claim 1, A substrate for a display element comprising the polyimide film according to claim 10.