KR101475735B1 - Transparent polyamicacid solution, transparent polyimide film and prepreg using the same - Google Patents

Abstract

(A) a fluorinated dianhydride or a dianhydride containing the fluorinated dianhydride and a non-fluorinated dianhydride; (b) a fluorinated diamine; Wherein the fluorinated dianhydride comprises 4- (trifluoromethyl) pyromellitic dianhydride (4-TFPMDA) in an amount of from 10 to 100, based on 100 mol% of the dianhydride, and (c) Mol%, a transparent polyimide resin film prepared by imidizing the polyamic acid solution, a transparent polyimide prepreg, and a transparent substrate comprising the prepreg.
In the present invention, by controlling the molar weight% of the fluorinated dianhydride and the fluorinated diamine, it exhibits a high glass transition temperature, a low thermal expansion coefficient and a high light transmittance, so that it can be effectively applied to a flexible display substrate of high resolution.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent polyamic acid solution, a transparent polyimide film, a transparent polyimide film, a transparent polyimide film, a transparent polyimide film, a prepreg,

The present invention relates to a transparent polyamic acid solution that can be applied to a plastic transparent substrate for a thin-light or flexible display, a highly transparent polyimide film made of the polyamic acid solution, a transparent prepreg, To a transparent substrate.

In general, a glass substrate is used for a flat panel display (FPD) such as a plasma display, a liquid crystal display, and an organic light emitting display. As a display using such a glass substrate is becoming thinner and smaller, a transparent plastic substrate has been studied as a substitute for a glass substrate.

A substrate made of polyethylene terephthalate (PET) film or polyether sulfone (PES) film has been developed as a transparent plastic substrate for glass substrate replacement. The PET film or the PES film is a film of a transparent polymer resin. A transparent plastic substrate using such a polymeric resin film has better ductility than a glass substrate, but has a lower glass transition temperature (Tg), resulting in a lower heat resistance. In addition, since the coefficient of thermal expansion (CTE) is larger than that of a glass substrate, deformation occurs easily in a process (for example, a TFT process at 220 ° C or more) at a high temperature during a display manufacturing process. Therefore, development of a transparent plastic substrate material having high heat resistance and low thermal expansion coefficient while showing transparency like a glass substrate has been demanded and various studies have been made.

On the other hand, Korean Patent Laid-Open No. 10-2011-0108898 discloses a technique for producing a colorimetric transparent polyimide film having excellent heat resistance.

Specifically, it is preferable that the light transmittance of 550 nm is 90% or more, the YI (Yellow Index) value of 550 nm is 3% or less, the expansion of the substrate And those having a thermal expansion coefficient of 15 ppm / ° C or lower in the range of 50 to 250 ° C and a glass transition temperature of 250 ° C or higher in order to suppress misalignment of display pixels or wiring on the substrate due to shrinkage.

The materials of the low thermal expansion polyimide known to date include 3,3 ', 4,4'-biphenyl tetracarboxylic acid dianhydride and 3,3', 4,4'-biphenyl tetracarboxylic acid dianhydride, Polyimides formed from p-phenylenediamine are the best known. However, the film obtained from the polyimide has been confirmed to exhibit a thermal expansion coefficient value of 10 ppm / 占 폚 or less, but the light transmittance at 550 nm is nearly 0%. Accordingly, development of a polyamic acid composition material for producing a transparent plastic substrate having high transparency as well as excellent heat resistance and a low coefficient of thermal expansion is required.

The inventors of the present invention have recognized that, in order to obtain a highly transparent polyimide film, introduction of a monomer having a high flexibility into a skeleton or introduction of a fluorine substituent is an effective method, the fluorinated diamine and fluorinated dianhydride monomer of a specific component are adopted, A transparent polyamic acid composition capable of simultaneously exhibiting a high glass transition temperature, a low thermal expansion coefficient and a high light transmittance was prepared.

Accordingly, it is an object of the present invention to provide a method for producing a colorless transparent polyamic acid composition as an organic polymer material capable of obtaining a high transparency, a low thermal expansion, a high glass transition temperature and a flexible film.

Another object of the present invention is to provide a film or prepreg transparent substrate having excellent transparency and high glass transition temperature and low thermal expansion coefficient by using a colorless transparent polyamic acid composition.

In addition, the present invention relates to a plastic transparent substrate for a Thin-Light or Flexible Display of an LCD and an OLED, a TFT substrate, a flexible printed circuit board, a flexible OLED surface illuminated substrate, Another object of the present invention is to provide a transparent flexible film and prepreg for electronic parts suitable for a polishing material for a process.

In order to achieve the above-mentioned object, the present invention provides a fluorinated dianhydride comprising (a) a fluorinated dianhydride or a dianhydride containing the fluorinated dianhydride and a non-fluorinated dianhydride; (b) a fluorinated diamine; Wherein the fluorinated dianhydride comprises 4- (trifluoromethyl) pyromellitic dianhydride (4-TFPMDA) in an amount of from 10 to 100, based on 100 mol% of the dianhydride, and (c) Mol% based on the total weight of the polyamic acid solution.

Here, the fluorinated dianhydride preferably further comprises 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydrate (6-FDA).

The non-fluorinated dianhydride may further include at least one selected from the group consisting of pyromellitic dianhydride (PMDA) and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA) .

In the present invention, it is preferable that the fluorinated diamine includes 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (2,2'-TFDB).

According to a preferred embodiment of the present invention, the molar ratio (b / a) of the fluorinated diamine (b) to the dianhydride (a) is preferably in the range of 0.9 to 1.1.

The present invention also provides a transparent polyimide resin film prepared by imidizing the above-mentioned polyamic acid solution.

In addition, the present invention relates to a glass fiber substrate; And a polyimide resin impregnated in the glass fiber substrate, wherein the polyimide resin is a transparent polyimide resin prepared by imidizing the polyamic acid solution described above.

Here, the refractive index difference between the glass fiber substrate and the polyimide resin is preferably 0.05 or less.

Further, the present invention provides a transparent substrate formed by laminating one or more transparent prepregs described above.

In the present invention, it is possible to provide a transparent polyimide film capable of simultaneously realizing high transparency, low thermal expansion, and high glass transition temperature by synthesizing a transparent polyamic acid resin using a monomer containing fluorinated dianhydride and fluorinated diamine.

Further, the present invention can simultaneously realize high transparency, low thermal expansion, and a high glass transition temperature in the same manner as the transparent polyimide film by preparing a prepreg impregnated with a transparent polyimide resin having the above-described properties on a glass fiber substrate A transparent substrate for a flexible display can be provided.

1 is a view showing a transparent substrate according to an example of the present invention.
2 is a view showing a transparent polyimide substrate and a glass fiber-impregnated transparent polyimide prepreg substrate according to an example of the present invention, respectively.
Description of the Related Art
1: release film 2: glass fiber
3: Transparent polyimide resin

Hereinafter, the present invention will be described in detail.

≪ Transparent polyamic acid solution >

The polyamic acid solution of the present invention is for producing a polyimide resin film having high transparency and comprises a fluorinated dianhydride, a fluorinated diamine and an organic solvent, and may further comprise a non-fluorinated dianhydride.

The polyamic acid solution of the present invention comprises a fluorinated dianhydride to which a fluorine substituent is introduced and a fluorinated diamine such as 4- (trifluoromethyl) pyromellitic dianhydride (4-TFPMDA) and 2,2'-bis Methyl) -4,4'-diaminobiphenyl (2,2-TFDB). When a polyimide resin film is produced by imidizing the polyimide resin film, the free volume between molecular chains is reduced, It is possible to manufacture a polyimide resin film having a high thermal expansion coefficient and a low coefficient of thermal expansion while having high transparency due to limited formation of a charge transfer complex (CTC). In fact, the polyimide resin film produced according to the present invention has physical properties similar to those of conventional glass and has characteristics suitable for application to high-resolution flexible display substrates.

On the other hand, 6-FDA in the conventional fluorinated dianhydride is a compound that is very suitable for transparency because the property of limiting the formation of a molecular transfer chain and a charge transfer complex (CTC) in the molecular chain is very large. However, 6-FDA can not lower the CTE (Thermal Expansion Coefficient) because it has the characteristic of increasing free volume between molecular chains due to its flexible molecular structure. In contrast, the 4-TFPMDA used as the fluorinated dianhydride component of the present invention shows a slight increase in the formation of a change transfer complex (CTC) between molecular chains while decreasing the free volume between molecular chains , And formation of a charge transfer complex (CTC) in the molecular chain is limited, and thus it is a compound that is very advantageous for achieving low thermal expansion coefficient and high transparency.

That is, in the present invention, since the rigid monomer structure of 4-TFPMDA and the free volume between molecular chains can be reduced, a change transfer complex (CTC) in the molecular chain, while achieving a low thermal expansion coefficient, , It was adopted as a fluorinated dianhydride component of a transparent polyamic acid solution.

The fluorinated diamine monomer used in the production of the transparent polyamic acid of the present invention is not particularly limited as long as it is a monomer having a fluorinated structure and the diamine monomer having a fluorinated biphenyl structure is selected and used for realizing a high glass transition temperature and low thermal expansion desirable.

Specific examples of the diamine monomers having the fluorinated biphenyl structure include 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (2,2'-bis (trifluoromethyl) -4 , 4'-Diaminobiphenyl, 2,2'-TFDB (A), 2,2'-bis (trifluoromethyl) -4,3'- diaminobiphenyl (2,2'- 4,3'-Diaminobiphenyl, 2,2'-bis (trifluoromethyl) -5,5'-diaminobiphenyl (2,2'- Or a combination of two or more of them may be used.

Considering the high transparency, low thermal expansion, and high glass transition temperature, the fluorinated diamine is 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (2, 2'-Bis (trifluoromethyl) -4,4'-Diaminobiphenyl, 2,2'-TFDB (A)). Such 2,2'-TFDB (A) can induce linear polymerization.

The amount of 2,2'-TFDB to be used may be in the range of 60 to 100 mol%, preferably 80 to 100 mol%, based on 100 mol% of the fluorinated diamine.

The fluorinated dianhydride monomer used in the production of the transparent polyamic acid of the present invention is not particularly limited as long as it is an acid anhydride monomer having a fluorinated structure. In order to realize a glass transition temperature, low thermal expansion and high transparency, it is preferable to include a dianhydride monomer having a fluorinated pyromellitic dianhydride structure, and for example, 4- (trifluoromethyl) pyromellitic dianhydride 4- (Trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C).

The 4-TFPMDA represented by the above formula (2) has a reduced free volume between molecular chains during the formation of polyimide resin, and the charge transfer within the molecular chain is limited, so that a linear polymerization, It is preferable because it can achieve low thermal expansion characteristics while inhibiting inhibition of YI characteristics. The content of 4-TFPMDA may range from 10 to 100 mol%, preferably from 20 to 90 mol%, based on 100 mol% of dianhydride.

In addition to the 4-TFPMDA described above, the present invention may further include a dianhydride monomer having a fluorinated structure. Nonlimiting examples of such fluorinated dianhydride monomers include 2,2-bis (3,4-dicarboxy phenyl) hexafluoropropane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 6-FDA (B)).

The 6-FDA represented by the above formula (3) is preferably used when it exhibits high transparency.

On the other hand, as the molar weight percentage increases, the 6-FDA increases the free volume between molecular chains to increase the permeability while increasing the CTE and decrease the refractive index of the transparent polyamic acid. Therefore, it is preferable to appropriately adjust the content of 6-FDA in the present invention. Accordingly, the content of 6-FDA may be in the range of 0 to 90 mol% based on 100 mol% of dianhydride, preferably 0 to 50 mol% Mol%, more preferably in the range of 10 to 40 mol%.

In the present invention, the fluorinated dianhydride monomer may further include a dianhydride monomer having a non-fluorinated structure and may be used in combination. Non-limiting examples of such non-fluorinated dianhydride monomers include pyromellitic dianhydride (PMDA (D)), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3 , 3 ', 4,4'-Biphenyl tetracarboxylic acid dianhydride, BPDA (E)). These may be used alone, or two or more of them may be used in combination.

The amount of PMDA represented by Formula 4 may range from 5 to 90 mol%, preferably from 5 to 70 mol% based on 100 mol% of dianhydride.

The amount of BPDA represented by Formula 5 may be 5 to 95 mol%, preferably 5 to 30 mol% based on 100 mol% of dianhydride.

In the transparent polyamic acid composition of the present invention, the ratio of the fluorinated dianhydride to the non-fluorinated dianhydride is preferably 30 to 100: 0 to 70 mol%. The ratio (b / a) of the number of moles of the fluorinated diamine component (b) to the number of moles of the dianhydride component (a) is preferably 0.9 to 1.1, more preferably 0.99 to 1.

In the transparent polyamic acid composition according to the present invention, it is preferable that the use ratio of 6-FDA and 4-TFPMDA is 10 to 60:40 to 90 mol%, for example, in the case of using only fluorinated dianhydride.

Further, as a preferable example of the two-component dianhydride in which the fluorinated dianhydride and the non-fluorinated dianhydride are mixed, the ratio of 4-TFPMDA to PMDA is preferably 40 to 90: 10 to 60 mol%.

For example, the use ratio of 6-FDA, 4-TFPMDA, and PMDA is 10 to 40:40 to 80:10 to 10:40 to 10:10, 40 mol%. However, the present invention is not limited thereto. Here, the content ratio of 6-FDA and PMDA may be in the range of mole% of the remaining amount satisfying the entire 100 mol% ratio by summing up with the use ratio of 4-TMPMDA.

The materials usable as the organic solvent in the polyamic acid solution of the present invention are not particularly limited as long as they are well known in the art, and examples thereof include N-methylpyrrolidinone (NMP), N, N-dimethylacetamide (DMAc) At least one selected from the group consisting of furan (THF), N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), cyclohexane and acetonitrile.

The polyamic acid solution of the present invention as described above is prepared by mixing 7.5 to 12.5% by weight of dianhydride, 7.5 to 12.5% by weight of fluorinated diamine, and 75 to 85% by weight of organic solvent based on 100% by weight of the total weight of the polyamic acid solution . In the case of the dianhydride, 1.5 to 11.25% by weight of fluorinated dianhydride and 1.25 to 6% by weight of non-fluorinated dianhydride may be included. When the content of each component in the polyamic acid solution is less than the above range, the viscosity of the polyamic acid solution may be too low. On the other hand, if the content of the polyamic acid solution is more than the above range, the viscosity of the polyamic acid solution may become too high.

Such a polyamic acid solution of the present invention may have a viscosity ranging from about 3,000 to 50,000 cps, preferably from about 5,000 to 20,000 cps. When the viscosity of the polyamic acid solution falls within the above-mentioned range, it is easy to control the thickness of the polyamic acid solution coating, and the coating surface can be uniformly exerted.

The polyamic acid solution of the present invention may contain a small amount of additives such as a plasticizer, an antioxidant, a flame retardant, a dispersant, a viscosity modifier, and a leveling agent within a range that does not significantly impair the objects and effects of the present invention .

The polyamic acid solution of the present invention can be prepared by charging a fluorinated dianhydride, a fluorinated diamine and, if desired, a non-fluorinated dianhydride into an organic solvent and then reacting. The reaction conditions are not particularly limited, and the reaction temperature is preferably -20 to 80 ° C, and the polymerization time may be 1 to 48 hours, preferably 2 to 12 hours. It is more preferable to carry out the reaction in an inert atmosphere such as argon or nitrogen. A transparent polyamic acid solution can be synthesized by polymerization reaction of the above-mentioned transparent polyamic acid solution in an exothermic solution.

≪ Transparent polyimide film and its manufacturing method >

The present invention provides a polyimide resin film produced by imidizing the polyamic acid solution described above.

The polyimide resin may be in the form of a random copolymer or a block copolymer.

The polyimide resin film of the present invention has a low thermal expansion coefficient and a high glass transition temperature while exhibiting high transparency because it is produced using the polyamic acid solution. Specifically, the polyimide resin film of the present invention has a rigid chemical structure and has a high glass transition temperature of 350 DEG C or higher, a thermal expansion coefficient of 50 to 250 DEG C of 65 ppm / DEG C or less, a light transmittance of 70% or more, (YI) value of each pixel.

The polyimide resin is a polymer material containing an imide ring and is excellent in heat resistance, chemical resistance, abrasion resistance and electrical properties.

The polyimide resin film of the present invention is not particularly limited. For example, the polyamic acid solution may be coated (cast) on a glass substrate and then heated at a temperature ranging from 40 to 400 ° C to 0.5 to 8 Lt; RTI ID = 0.0 > imidazation < / RTI >

The polyamic acid solution may be a fluorinated transparent polyamic acid obtained by solution polymerization of a fluorinated diamine and a fluorinated dianhydride monomer. For example, the polyamic acid solution may be prepared by reacting the monomers 2,2'-TFDB (A) and 4-TFPMDA (DMAc) polymerization reaction using 6-FDA (B), PMDA (D), BPDA (E) or the like.

Such a polyimide resin film (or polyimide resin) of the present invention can be produced, for example, by the reaction shown in the following reaction formula.

[Reaction Scheme]

Here, n is in the range of 1 to 50.

In the above reaction scheme, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (2.2'-TFDB) was used as a fluorinated diamine, 4- (trifluoromethyl) pyromellitic dianhydride as a fluorinated dianhydride (Or polyimide resin) prepared by using a polyamic acid solution obtained by reacting 4-TFPMDA with pyromellitic dianhydride (PMDA) in an organic solvent.

The polyimide resin film of the present invention can be used in various fields, and can be used as a transparent substrate material of a flexible display such as a display for an organic EL device and a display for a liquid crystal device, which are required to have high transparency and heat resistance.

≪ Prepreg and Manufacturing Method Thereof &

The present invention relates to a glass fiber substrate; And a transparent polyimide resin impregnated in the glass fiber substrate.

The prepreg of the present invention can have a low coefficient of thermal expansion such as a glass substrate by including glass fibers.

The glass fiber contained in the prepreg may be any conventional material known in the art without limitation. Non-limiting examples thereof include E glass fiber, C glass fiber, A glass fiber, S glass fiber, D glass fiber, NE glass fiber, T glass fiber and quartz glass fiber. These may be used alone, or two or more of them may be used in combination. At this time, since the refractive index range of the transparent polyimide resin of the present invention is 1.55 to 1.57, it is preferable to use E glass fiber (refractive index of 550 nm: 1.563) which can increase the transmittance by matching the refractive index with the transparent polyimide resin.

On the other hand, the glass fibers and the transparent polyimide resin included in the prepreg of the present invention may have refractive indexes in the same range. At this time, the refractive index difference between the glass fiber and the transparent polyimide resin may be 0.05 or less, preferably 0.001 to 0.03. When a transparent substrate is produced by using the prepreg including the glass fibers and the transparent polyimide resin having the same refractive index as described above, the transparency of the transparent substrate is increased and a transparent substrate having excellent visibility can be provided.

For example, if the E glass fiber having a refractive index of 1.55 to 1.57 and the transparent polyimide resin having a refractive index of 1.55 to 1.57 are used together as the glass fiber, a transparent substrate comprising the transparent prepreg and the transparent prepreg can be manufactured have.

In the present invention, the impregnating amount of the transparent polyimide resin impregnated in the glass fiber is not particularly limited, and can be appropriately adjusted in consideration of physical properties and thickness of the prepared prepreg. In order to form a good transparent polyimide resin layer in the glass fiber, 40 to 60 parts by weight of a transparent polyimide resin can be impregnated based on 100 parts by weight of the prepreg. For example, the ratio of the transparent polyimide resin to the glass fiber may range from 40 to 60: 60 to 40 parts by weight.

The prepreg of the present invention can be prepared by any conventional method known in the art. For example, a transparent polyamic acid resin solution-polymerized using a fluorinated monomer is impregnated into a glass fiber, followed by drying .

At this time, the method of impregnating transparent polyamic acid resin can be realized by impregnating glass fiber with a transparent polyamic acid solution having a low molecular weight and then drying it at 140 ° C for 1 to 10 minutes.

The prepreg of the present invention thus prepared can be used in various fields, and can be usefully used as a material for a transparent substrate for a display which requires excellent transparency, heat resistance and durability.

≪ Transparent substrate and manufacturing method thereof >

The present invention provides a transparent substrate including the prepreg described above. Specifically, the transparent substrate of the present invention may have a structure in which the prepreg is a single layer or a laminated structure of two or more layers.

The transparent substrate of the present invention can be produced according to a conventional method known in the art. For example, the transparent substrate may be prepared by laminating the prepreg in a single layer or two or more layers, followed by heating / pressing. The heating / pressing conditions of the prepreg are not particularly limited. For example, the prepreg can be heated at a pressure of 5 to 45 kgf / cm ² and at a temperature of 100 to 350 ° C for 30 to 120 minutes.

The transparent substrate according to the present invention may be manufactured by wrapping both sides of a single layer or two or more layers of prepregs with a release film, followed by heating / pressing (see FIG. 1).

Here, the release film has a function of easily separating the transparent substrate so as to maintain its shape without damaging the transparent substrate after heating / pressing, and may be a commonly used film-type release material.

The releasing agent used in the releasing film is not particularly limited to the releasing agent as long as the releasing film can be peeled completely from the releasing film, and a conventional releasing agent component known in the art can be used. Non-limiting examples of the releasing agent include an epoxy-based releasing agent, a releasing agent comprising a fluororesin, a silicone-based releasing agent, an alkyd resin-based releasing agent, and a water-soluble polymer. The thickness of the release film is not particularly limited. The release film used in the present invention can be removed before the transparent substrate is barrier coated or hard coated.

Since the transparent substrate of the present invention is produced by using a prepreg in which a transparent polyimide resin having a high glass transition temperature is impregnated with a glass fiber having a substantially identical refractive index and a low coefficient of thermal expansion, Transition temperature and low thermal expansion coefficient.

In addition, since the refractive index of the transparent polyimide resin and the glass fiber are controlled within the same range, and the prepreg manufactured to have a high transmittance is used, excellent light transmittance can be exhibited. Accordingly, the present invention can provide a transparent substrate having transparency, high glass transition temperature, and low thermal expansion.

The above-described transparent substrate of the present invention can be applied to various fields, and can be used as a substrate for a flexible display such as an OLED display and a liquid crystal display, which are required to have high transparency and heat resistance.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples and comparative examples.

[Example 1]

1. Preparation of transparent polyamic acid resin

39.894 g of N, N-dimethylacetamide (DMAc) was charged while passing nitrogen through a 100 mL three-necked round bottom flask at a flow rate of 50 mL / min, the temperature of the reactor was raised to 50 캜 And 5 g (0.0156 mol) of 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (2,2'-TFDB (A)) were added and stirred for 1 hour to obtain 2,2'- TFDB (A) was completely dissolved. After that, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 6-FDA (B) and 4- ( 1.387g (0.0031mol) and 3.586g (0.0125mol) of tetrafluoromethyl pyromellitic dianhydride (4-TFPMDA (C)) were added to the mixture, . At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 50 poise (5000 CPs) at 25 ° C.

2. Preparation of transparent polyimide film

The polyamic acid solution was spin-coated on a glass for LCD and dried in a convection oven at 80 DEG C for 30 minutes, 150 DEG C for 30 minutes, 200 DEG C for 1 hour, and 300 DEG C for 1 hour, Imidazation reaction proceeded. Thus, a transparent polyimide film having a film thickness of 10 탆 with an imidization ratio of 85% or more was produced. Thereafter, the glass was etched with hydrofluoric acid to obtain a polyimide film.

3. Preparation of prepreg

45 parts by weight (solvent: 225 parts by weight) of the transparent polyamic acid resin prepared above and 55 parts by weight of glass fiber (product name: "3313 " manufactured by Asahi Chemical Industry Co., Ltd.) having a thickness of 85 μm and a refractive index of 1.563, And the solvent (DMAc) was volatilized for 2 minutes. Thereafter, the transparent polyimide resin was impregnated with glass fiber through squeezing, and dried in an oven at 140 ° C for 3 minutes to prepare a prepreg.

4. Transparent Substrate Manufacturing

A release film was placed on both surfaces of one prepreg prepared above, and heated / pressed at a pressure of 30 kgf / cm ² and a temperature of 250 캜 for 30 minutes using a press machine to produce a transparent substrate having a thickness of 95 (1 탆.

[Example 2]

After 42.837 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B) and 4 (4-dicarboxyphenyl) (0.0078 mol) and 2.241 g (0.0078 mol) of 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) . At this time, the solid content was 20%, and then stirred for 2 hours. After completion of the reaction, the solution was naturally cooled to obtain a clear polyamic acid solution having a solution viscosity of 64 poise (6400 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 3]

After 42.837 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). After that, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B) and 4- (0.0125 mol) and 0.897 g (0.0031 mol) of 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) . At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of 72 poise (7200 CPs) of clear polyamic acid solution at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 4]

After 37.07 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Then, a mixture of pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) 0.681 g (0.0031 mol) and 3.586 g (0.0125 mol) were added, respectively, and the mixture was heated at 60 캜 to dissolve. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 63 poise (6300 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 5]

After 35.777 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Then, a mixture of pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) (0.0078 mol) and 2.241 g (0.0078 mol), respectively, and then dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a clear polyamic acid solution having a solution viscosity of 85 poise (8500 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 6]

After 34.484 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 캜, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Then, a mixture of pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) (0.0125 mol) and 0.897 g (0.0031 mol), respectively, and then dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 141 poise (14100 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 7]

In Example 1, 38.48 g of N, N-dimethylacetamide (DMAc) was charged. After the temperature of the reactor was raised to 50 캜, 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride Three monomers, pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) 0.616 g (0.0016 mol), 0.341 g (0.0016 mol) and 3.586 g (0.0125 mol), respectively, were added and dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 58 poise (5800 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 8]

In Example 1, 39.307 g of N, N-dimethylacetamide (DMAc) was charged. After the temperature of the reactor was raised to 50 캜, 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Then, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), pyromellitic dianhydride Three monomers, pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) 0.0034 mol (0.0039 mol), 0.851 g (0.0039 mol) and 2.241 g (0.0078 mol) of water were added and dissolved by heating at 60 ° C. The solid content at this time was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 74 poise (7400 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 9]

In Example 1, 41.74 g of N, N-dimethylacetamide (DMAc) was charged. After the temperature of the reactor was raised to 50 캜, 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride Three monomers, pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) (0.0078 mol), 0.851 g (0.0039 mol) and 1.117 g (0.0039 mol), respectively, and then dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 69 poise (6900 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 10]

In Example 1, 38.21 g of N, N-dimethylacetamide (DMAc) was charged. After the temperature of the reactor was raised to 50 캜, 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride Three monomers, pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) 1.739 g (0.0039 mol), 1.703 g (0.0078 mol) and 1.117 g (0.0039 mol) were added, respectively, and dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a transparent polyamic acid solution having a solution viscosity of 94 poise (9400 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 11]

In Example 1, 40.132 g of N, N-dimethylacetamide (DMAc) was charged. After the temperature of the reactor was raised to 50 캜, 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride Three monomers, pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) (0.0062 mol), 1.362 g (0.0062 mol) and 0.897 g (0.0031 mol), respectively, and then dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 105 poise (10500 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 12]

After 45.34 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride Three monomers, pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) (0.0125 mol), 0.341 g (0.0016 mol) and 0.447 g (0.0016 mol), respectively, were added and dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 61 poise (6100 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Example 13]

After 35.46 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride Three monomers, pyromellitic dianhydride (PMDA (D)) and 4- (trifluoromethyl) pyromellitic dianhydride, 4-TFPMDA (C) (0.0016 mol), 2.724 g (0.0125 mol) and 0.447 g (0.0016 mol), respectively, were added and dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 155 poise (15500 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Comparative Example 1]

After 36.45 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride 2.724 g (0.0031 mol) and 1.387 g (0.0125 mol) of a monomer of pyromellitic dianhydride (PMDA (D)) were added and dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 183 poise (18300 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Comparative Example 2]

After 40.68 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C and 2,2'-bis (trifluoromethyl) -4,4'- 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride 3.468 g (0.0078 mol) and 1.703 g (0.0078 mol) of a monomer of pyromellitic dianhydride (PMDA (D)) were added and dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 93 poise (9300 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Comparative Example 3]

After 44.92 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Thereafter, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride 5.549g (0.0125mol) and 0.681g (0.0031mol) of a monomer of pyromellitic dianhydride (PMDA (D)) were added and dissolved by heating at 60 ° C. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a clear polyamic acid solution having a viscosity of 77 poise (7700 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Comparative Example 4]

After 43.06 g of N, N-dimethylacetamide (DMAc) was charged in Example 1, the temperature of the reactor was raised to 50 ° C, and then 2,2'-bis (trifluoromethyl) 5 g (0.0156 mol) of diaminobiphenyl (2,2'-TFDB (A)) was added and stirred for 1 hour to completely dissolve the 2,2'-TFDB (A). Then, 2,2-bis (3,4-dicarboxyphenyl) hexa fluoropropane dianhydride, 6-FDA (B), 3 (0.0078 mol), 3,3 ', 4,4'-biphenyl tetracarboxylic acid dianhydride, and 3', 4,4'-biphenyl tetracarboxylic acid dianhydride, g (0.0078 mol), and the mixture was dissolved by heating at 60 캜. At this time, the solid content was 20%, and then stirred for 2 hours. After the reaction was completed, the solution was naturally cooled to obtain a solution of a transparent polyamic acid having a solution viscosity of 86 poise (8600 CPs) at 25 ° C.

A transparent polyimide film and a polyester resin, and a transparent substrate impregnated with glass fiber were prepared in the same manner as in Example 1, respectively.

[Property evaluation]

The properties of transparent polyimide films prepared in Examples 1 to 13 and Comparative Examples 1 to 4 and transparent substrates impregnated with glass fibers were evaluated by the following methods. The results are shown in Table 1 below.

< Measurement of Physical Properties of Transparent Polyimide Film and Transparent Substrate>

1. Measurement of glass transition temperature (Tg)

DMA was measured using a Q800V7.5 Build 127 apparatus according to the DMA method (IPC-TM-650 2.4.24.4) at a temperature profile of 30 to 350 DEG C and a heating rate of 5 DEG C / min.

2. Coefficient of thermal expansion (CTE) measurement

2940 TMA V2.4E device at a temperature profile of 50 to 250 占 폚 and a heating rate of 10 占 폚 / min according to the TMA method (IPC-TM-650 2.4.24.5).

3. Measurement of light transmittance and YI (Yellow Index)

The measurement was performed at a viewing angle of 2 degrees with a C light source of ASTM E313-73 using a UV-Vis NIR Spectrophotometer and a birefringence measuring device (Retarder, Otsuka RETs-100) at a wavelength of 550 nm.

4. Measurement of refractive index

A transparent polyamic acid resin was coated on a silicon wafer to a thickness of 1 μm or less, followed by drying and imidization ring closure. The refractive index was measured using a non-contact refractive index measuring device (Elli-RP, Ellipso technology) at a wavelength of 550 nm.

Transparent polyamic acid solution polymerization composition Results of physical property evaluation Diamine Dianhydride (acid anhydride) Transparent polyimide film Impregnated with glass fiber
Transparent substrate 2,2'-
TFDB
(A) 6-FDA
(B) 4-TFPMDA (C) PMDA
(D) BPDA
(E) Glass transition temperature
(° C @ DMA Tg) Thermal Expansion Coefficient (ppm / ° C) Transmittance (% @ 550 nm) Refractive index Thermal Expansion Coefficient (ppm / ° C) Transmittance (% @ 550 nm) Example 1 0.0156
mol 0.0031
mol 0.0125
mol 383 14 90.4 1.61 9.7 80.2 Example
2 0.0156
mol 0.0078
mol 0.0078
mol 364 35 90.8 1.59 14.3 82.5 Example
3 0.0156
mol 0.0125
mol 0.0031
mol 342 61 91.3 1.57 17.8 85.3 Example
4 0.0156
mol 0.0125
mol 0.0031
mol 396 9.7 90.1 1.61 9.3 80.5 Example
5 0.0156
mol 0.0078
mol 0.0078
mol 407 8.8 89.3 1.62 8.8 78.2 Example
6 0.0156
mol 0.0031
mol 0.0125
mol 416 6.7 88.5 1.64 8.4 71.6 Example
7 0.0156
mol 0.0016
mol 0.0125
mol 0.0016
mol 389 11.2 90.7 1.61 9.3 80.4 Example
8 0.0156
mol 0.0039
mol 0.0078
mol 0.0039
mol 380 13.2 90.1 1.60 9.5 81.7 Example
9 0.0156
mol 0.0078
mol 0.0039
mol 0.0039
mol 371 25 90.9 1.59 13.0 82.6 Example
10 0.0156
mol 0.0039
mol 0.0039
mol 0.0078
mol 386 12.4 89.7 1.61 9.9 81.5 Example
11 0.0156
mol 0.0062
mol 0.0031
mol 0.0062
mol 379 23 90.5 1.59 12.7 83.1 Example
12 0.0156
mol 0.0125
mol 0.0016
mol 0.0016
mol 351 55 91.2 1.57 18.9 86.1 Example
13 0.0156
mol 0.0016
mol 0.0016
mol 0.0125
mol 402 9.8 88.9 1.62 8.6 78.9 Comparative Example
One 0.0156
mol 0.0031
mol 0.0125
mol 381 16.1 86.2 1.62 11.7 79.8 Comparative Example
2 0.0156
mol 0.0078
mol 0.0078
mol 369 22.5 90.2 1.60 13.1 81.7 Comparative Example
3 0.0156
mol 0.0125
mol 0.0031
mol 347 51 90.9 1.59 15.7 83.2 Comparative Example
4 0.0156
mol 0.0078
mol 0.0078
mol 355 24 90.3 1.60 12.7 81.9

Examples 4 and 7 corresponding to the transparent polyimide film of the present invention show the moles of the fluorinated dianhydride monomer 4- (trifluoromethyl) pyromellitic dianhydride (4-TFPMDA (C)) As the% by weight increased, it showed high glass transition temperature, low thermal expansion coefficient and high light transmittance. This indicates that the use of 4-TFPMDA (C) exhibited excellent properties of high transmittance and low thermal expansion coefficient due to limitation of charge transfer in the molecular chain while decreasing free volume between molecular chains . This is a level close to that of conventional glass and confirmed that it is suitable for application to high resolution flexible display substrates.

For the fluorinated diamine monomer of the present invention, for the purpose of realizing high permeability and low thermal expansion property (2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (2,2'-TFDB ) Is an optimal monomer Respectively.

On the other hand, as the molar weight percentage of the fluorinated dianhydride monomer 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA (B)) increases, It can be confirmed that the coefficient of thermal expansion (CTE) is increased and the coefficient of thermal expansion similar to that of glass can not be obtained. This indicates that the use of 6-FDA (B) increases the free volume between molecular chains to increase the permeability but increase the coefficient of thermal expansion (CTE). These results can be confirmed in Comparative Examples 1 to 4.

On the other hand, pyromellitic dianhydride (PMDA (D)), a non-fluorinated dianhydride monomer, and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3' (BPDA) (E)), but it has a low thermal expansion coefficient as the molar weight percentage of 4,4'-Biphenyl tetracarboxylic acid dianhydride and BPDA (E) Charge Transfer), the permeability was found to be poor (see Comparative Examples 1 to 4).

In Examples 3 and 12, as the molar weight percentage of 6-FDA (B) as the fluorinated dianhydride monomer was increased, the free volume between molecular chains increased and the refractive index of the transparent polyamic acid decreased. This is because the transmittance of the glass fiber impregnated prepreg and the transparent substrate using the transparent polyimide resin gradually increases because the refractive index (1.57) of the transparent polyamic acid becomes more and more consistent with the refractive index (1.565) of the E glass fiber Able to know. However, since these characteristics have low transmittance and high thermal expansion coefficient compared to conventional glass, it has been confirmed that it is suitable to be applied to a low-resolution advertisement display board rather than a high-resolution flexible display substrate.

Claims (13)

(a) a dianhydride containing a fluorinated dianhydride;
(b) a fluorinated diamine; And
(c) an organic solvent,
The fluorinated dianhydride includes 4- (trifluoromethyl) pyromellitic dianhydride (4-TFPMDA) in an amount of 10 to 100 mol% based on 100 mol% of the dianhydride,
The fluorinated diamine is preferably used in an amount of 60 to 100 moles, based on 100 mol% of the fluorinated diamine, of 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (2,2'-TFDB) % &Lt; / RTI &gt; by weight of the polyamic acid solution. The transparent polyamic acid composition of claim 1, wherein the fluorinated dianhydride further comprises 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydride (6-FDA) solution. The method of claim 2, wherein the 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydride (6-FDA) Mol% based on the total weight of the transparent polyamic acid solution. The method of claim 1, wherein the dianhydride is one selected from the group consisting of pyromellitic dianhydride (PMDA) and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA) &Lt; / RTI &gt; or more of a non-fluorinated dianhydride. The process of claim 4, wherein the pyromellitic dianhydride (PMDA) is in the range of 5 to 90 mole percent, based on 100 mole percent of the dianhydride,
Wherein the 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA) is in the range of 5 to 50 mol% based on 100 mol% of the dianhydride. The transparent polyamic acid solution according to claim 4, wherein the ratio of the fluorinated dianhydride to the non-fluorinated dianhydride is 30 to 100: 0 to 70 mol%. delete delete The transparent polyamic acid solution according to claim 1, wherein the ratio (b / a) of the number of moles of the fluorinated diamine (b) to the dianhydride (a) ranges from 0.9 to 1.1. A transparent polyimide resin film produced by imidizing a transparent polyamic acid solution of any one of claims 1 to 6 and 9. Glass fiber substrates; And
And a polyimide resin impregnated in the glass fiber substrate,
Wherein the polyimide resin is a transparent polyimide resin prepared by imidizing the transparent polyamic acid solution of any one of claims 1 to 6 and 9. The transparent prepreg according to claim 11, wherein a difference in refractive index between the glass fiber substrate and the polyimide resin is 0.05 or less. A transparent substrate formed by laminating one or more transparent prepregs of claim 11.

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