KR101837947B1 - Composition for forming polyimide-based film, polyimide-based film prepared by using same and method for preparing same - Google Patents

Abstract

The present invention relates to a composition for forming a polyimide film useful for various devices such as a solar cell, an organic light emitting diode, a semiconductor device, or a flexible display device, which can be applied to a flexible display while satisfying high heat resistance and high transmittance, The polyimide-based film and the method for producing the same are provided.
The present invention also relates to a composition for forming a polyimide film, which has excellent surface properties even in a rapid heat treatment process, and in which the defective rate during performing an element forming process by the surface roughness is significantly reduced, a polyimide film prepared using the same, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for forming a polyimide-based film, a polyimide-based film produced therefrom, and a method for producing the same. BACKGROUND ART [0002]

TECHNICAL FIELD The present invention relates to a composition for forming a polyimide film, a polyimide film produced using the same, and a method for producing the same, and more particularly, to a composition for forming a polyimide film which is flexible and has high heat resistance and high permeability simultaneously, A polyimide-based film produced using the same, and a method for producing the same.

Currently, the display industry uses glass-based substrates, and these glass substrate materials have the advantage of being able to form stable devices at high process temperatures and transparency. However, glass-based display devices are not flexible enough to be applied to a flexible display, and are also vulnerable to small impacts.

In the glass-based display industry, which has such a problem, research on flexible devices that are lighter, flexible, and can not be broken by impact is actively conducted. Polycarbonate (PC), Polyimide (PI), Polyethersulfone (PES), Polyarylate (PAR), and Polyarylate (PAR) , Thermoplastic resins such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), cycloolefin copolymer, acrylic resin, epoxy resin, unsaturated polyester, etc. Of a curing resin.

Flexible devices are typically manufactured on the basis of high temperature thin film transistor (TFT) processes. The process temperature may vary depending on the type of the semiconductor layer, the insulating film, and the barrier layer included in the device during the manufacture of the flexible device, but usually a temperature of about 300 to 500 ° C is required in the TFT process. However, the polymer material capable of withstanding such a processing temperature is extremely limited, and polyimide known to have excellent heat resistance is mainly used.

The properties of the polyimide films reported today are divided into two categories. The first is the transparency-based nature of the substrate material, and the second is the heat resistance required at higher process temperatures. Both of these properties are difficult to satisfy at the same time, and are confronted with each other. When transparency is imparted, heat resistance such as thermal expansion coefficient is lowered, and in the case of polyimide having an improved thermal expansion coefficient, transparency is lowered. Therefore, in order for polyimide to be used as a display substrate material, further improvement is required to satisfy both of these trade-off characteristics.

In this connection, Korean Patent No. 10-2014-0016394 discloses a substrate material having a thermal expansion coefficient lower than that of the conventional one by applying a polyimide film for a display substrate. However, 1) it has a higher thermal expansion coefficient than that of glass substrates, and thus it is necessary to further improve the physical properties of OLED processes at high process temperatures, and 2) it is difficult to satisfy transparency and heat resistance at the same time.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and a first object of the present invention is to provide a composition for forming a polyimide film that is flexible, satisfies high heat resistance and high transmittance simultaneously, a polyimide film And a method for producing the same.

The second problem to be solved by the present invention is to provide a composition for forming a polyimide film which has an excellent surface property even in a rapid heat treatment process and in which the defective rate at the time of performing the device formation process by the surface roughness is significantly lowered, a polyimide- And a method for producing the same.

In order to solve the above-mentioned problems, the present invention provides a composition for forming a polyimide film comprising the structural units represented by the following formulas (1) and (2) and R ³ and R ⁴ .

[Chemical Formula 1]

(2)

Wherein R ¹ is an organic group having two or more aromatic trivalent or more organic groups derived from an acid dianhydride and R ² is an organic group containing at least one aromatic organic group derived from an acid dianhydride R ³ is an aromatic divalent organic group derived from a diamine, and R ⁴ is an organic group containing at least two aromatic divalent organic groups derived from a diamine.

According to a preferred embodiment of the present invention, R ³ is an aromatic divalent organic group derived from an aromatic diamine having no substituent having a fluorine atom, and R ⁴ is derived from an aromatic diamine having a substituent having a fluorine atom Aromatic trivalent organic groups.

According to another preferred embodiment of the present invention, R ¹ may be represented by the following formula (3).

(3)

In the above formula (3), R _a may or may not be present, and when R _a is present, it may be selected from the group consisting of a phenylene group, an alkylene group having 1 to 4 carbon atoms, a haloalkylene group having 1 to 4 carbon atoms, do.

According to another preferred embodiment of the invention wherein R ⁴ may be represented by the formula (4) below.

[Chemical Formula 4]

Wherein R _b and R _d are each independently selected from the group consisting of a halogen group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, R _c is absent or may be present, and when R _c is present, it is selected from the group consisting of a phenylene group, an alkylene group having 1 to 4 carbon atoms, a haloalkylene group having 1 to 4 carbon atoms, and combinations thereof, n is independently an integer of 0 to 4;

,

,

,

또는

이며, R²는

,

또는

일 수 있다. According to another preferred embodiment of the present invention, R < ¹ >

,

,

,

or

And R ² is

,

or

Lt; / RTI >

또는

이고, 상기 R⁴는

,

,

,

,

,

,

,

,

또는

일 수 있다.According to another preferred embodiment of the present invention, R < ³ > is

or

, And R < ⁴ >

,

,

,

,

,

,

,

,

or

Lt; / RTI >

According to another preferred embodiment of the present invention, the molar percentage of the structural unit represented by the formula (1) contained in the composition for forming a polyimide-based film may be smaller than the molar percentage of the structural unit represented by the formula (2).

According to another preferred embodiment of the present invention, the copolymer may be a copolymer represented by the following general formula (5).

[Chemical Formula 5]

In formula 5, R ¹ is an aromatic organic group of trivalent comprises a one organic than 2 derived from an acid dianhydride, R ² is an aromatic tetravalent organic group derived from an acid dianhydride, R ³ is from diamine R ⁴ is an organic group containing two or more aromatic divalent organic groups derived from a diamine, and w, x, y and z are mole ratios of repeating units constituting the copolymer And w, x, y, and z are independent and non-zero rational numbers satisfying 0.35? W + x? 0.50, 0.50? Y + z? 0.65 and w + x + y + z = ≫ x and z > y, and the order of bonding of the repeating units constituting the copolymer may be randomly modified.

, R²는

, R³는

, R⁴는

일 수 있다.According to another preferred embodiment of the present invention, R < ¹ >

, R ² is

, R ³ is

, R ⁴ is

Lt; / RTI >

According to another preferred embodiment of the present invention, the solvent is selected from the group consisting of DMF, DMAc, NMP, NEP, 3-methoxy- Dimethyl propionamide, and a compound represented by the following formula (6).

[Chemical Formula 6]

In Formula 6, R _x and R _y are each a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R _z is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

According to another preferred embodiment of the present invention, 0.1 to 1 part by weight of an additive is added to 100 parts by weight of the copolymer represented by the general formula (5), and the additive is selected from the group consisting of an alcohol series, a siloxane series and a fluorine series surfactant And the like.

The present invention also provides (1) a process for producing the polyimide copolymer of any one of claims 1 to 11; (2) preparing a composition for forming a polyimide film comprising the copolymer; (3) heat-treating the composition to produce a polyimide-based film, wherein the initial preparation of the polyimide copolymer in the step (1) is carried out by copolymerizing at 0 to 30 ° C for 1 to 3 hours Based film is produced.

According to a preferred embodiment of the present invention, the polyimide copolymer of the step (1) may be prepared through the reaction of raising the temperature to 30 to 60 ° C. and maintaining the polyimide copolymer for 8 to 24 hours.

According to another preferred embodiment of the present invention, the alcohol-based, siloxane-based or fluorine-based surfactant may be further added after the step (1).

The present invention also provides a polyimide-based film produced by any one of the above methods.

According to a preferred embodiment of the present invention, the polyimide-based film may satisfy all of the following conditions.

(a) a coefficient of thermal expansion (CTE) of -2 to 7 ppm /

(b) a surface roughness Ra of 0.1 to 1 nm

(c) an average transmittance of not less than 65 in a wavelength region of 380 to 780 nm

Hereinafter, terms of the present invention will be described.

In the present specification, all the compounds or functional groups may be substituted or unsubstituted, unless otherwise specified. Herein, the term "substituted" means that at least one hydrogen contained in the compound or the functional group is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group, a cycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, Substituted with a substituent selected from the group consisting of an alkoxy group having 1 to 10 carbon atoms, a carboxylic acid group, an aldehyde group, an epoxy group, a cyano group, a nitro group, an amino group, a sulfonic acid group and derivatives thereof. The alkyl group may be a linear alkyl group or a branched alkyl group.

In the present specification, the term "a combination thereof" means a compound wherein at least two functional groups are bonded to each other through a single bond, a double bond, a triple bond, an alkylene group having 1 to 10 carbon atoms (eg, a methylene group (-CH2-) Fluoroethylene group (-CF2-), perfluoroethylene group (-CF2CF2-) and the like), N, O (-CH2CH2-), etc.), fluoroalkylene group having 1 to 10 carbon atoms (-C═O-), an ether group (-O-), an ester group (-COO-), -S (-S-), or a group containing a hetero atom such as P, S or Si -, -NH-, or -N = N-), or two or more functional groups are condensed and connected to each other.

The term " copolymer " used in the present invention is a random copolymer, which is a copolymer composed of three or more repeating units, means that the order of the repeating units is randomly connected, (A) a- (B) b- (C) c- (D) d- ", which is a random copolymer of repeating unit A, repeating unit B, repeating unit C and repeating unit D is - (ABADABABC - (A) a- (B) b- (C) c- (D) - (AACCCBBDB) -, (AADABADABACC) In the d-, a, b, c and d mean the ratio of repeating units A, B, C and D.

The present invention relates to a composition for forming a polyimide film useful for various devices such as a solar cell, an organic light emitting diode, a semiconductor device, or a flexible display device, which can be applied to a flexible display while satisfying high heat resistance and high transmittance, The polyimide-based film and the method for producing the same are provided.

The present invention also relates to a composition for forming a polyimide film, which has excellent surface properties even in a rapid heat treatment process, and in which the defective rate during performing an element forming process by the surface roughness is significantly reduced, a polyimide film prepared using the same, .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph of a CTE of a polyimide-based film according to a preferred embodiment of the present invention, as measured by TMA.
FIG. 2 is a graph of transmittance of a polyimide-based film according to a preferred embodiment of the present invention.
3 is a thermogravimetric analysis (TGA) graph of a polyimide-based film according to one preferred embodiment of the present invention.
4 is a graph showing tensile strength and elongation of a polyimide film according to one preferred embodiment of the present invention.
5 is an AFM image of a polyimide-based film according to a preferred embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains.

As described above, the conventional polyimide film for a display substrate has a higher thermal expansion coefficient than that of a glass substrate, and thus it is necessary to further improve the physical properties at a high process temperature of the conventional OLED process and simultaneously improve transparency and heat resistance There was a difficult problem.

Accordingly, the present invention provides a composition for forming a polyimide film comprising the structural units represented by the following formulas (1) and (2) and R ³ and R ⁴ .

[Chemical Formula 1]

(2)

In the above Chemical Formulas 1 to 4, R ¹ comprises an aromatic trivalent group or more organic than 2 derived from an acid dianhydride and, R ² is an organic group containing aromatic organic groups at least one derived from a dianhydride, R ³ is Wherein R ⁴ is an aromatic divalent organic group derived from a diamine, and R ⁴ is an aromatic divalent organic group derived from a diamine.

Accordingly, the present invention can be applied to flexible displays due to the flexible characteristics of polyimide-based films, and at the same time satisfies high heat resistance and high transmittance, and is useful for various devices such as solar cells, organic light emitting diodes, semiconductor devices, and flexible display devices Can be utilized.

First, R ¹ in the general formulas (1) to (4) is an organic group containing two or more aromatic trivalent or more organic groups derived from an acid dianhydride. The term "organic group containing two or more aromatic trivalent or more organic groups" means that two or more aromatic group-containing organic groups are connected through a chemical bond to form one organic group. Likewise, R ⁴ is an organic group containing two or more aromatic divalent organic groups derived from diamines, which means that two or more aromatic divalent organic groups are connected through a chemical bond to form one organic group .

In addition, the order of bonding of the respective structural units represented by the above formulas (1) and (2) and R ³ and R ⁴ may be randomly modified.

1 is a graph of a thermal expansion coefficient (CTE) of a polyimide-based film according to a preferred embodiment of the present invention by TMA. It can be seen from the graph that the polyimide film of the present invention has a thermal expansion coefficient of preferably 1 to 3 ppm / ° C. It is confirmed that the thermal expansion coefficient is similar to or lower than the thermal expansion coefficient of 3 to 5 ppm / K of the glass material substrate having excellent thermal characteristics, and has a thermal property similar or better than that of the glass material substrate even though it is a polyimide film. That is, the polyimide-based film of the present invention has high inherent characteristics while exhibiting high heat resistance, and thus can be utilized as various semiconductor devices and flexible display devices.

2 is a graph of the transmittance of a polyimide-based film according to a preferred embodiment of the present invention. In the graph, it can be seen that the transmittance of the polyimide film of the present invention is satisfactory even when the transmittance is more than 70% in a wavelength range of 380 to 800 nm, which is a visible light range.

3 is a thermogravimetric analysis (TGA) graph of a polyimide-based film according to one preferred embodiment of the present invention. Referring to the graph, it can be seen that a Td (weight loss) of 1% occurs at a high temperature of 550 ° C or higher. Thus, it can be confirmed that the polyimide-based film of the present invention has remarkably excellent heat resistance.

4 is a graph showing tensile strength and elongation of a polyimide film according to a preferred embodiment of the present invention.

According to a preferred embodiment of the present invention, R ³ is an aromatic divalent organic group derived from an aromatic diamine having no substituent containing a fluorine atom, and R ⁴ is an aromatic diaromatic compound having a substituent containing a fluorine atom Lt; RTI ID = 0.0 > aromatic < / RTI >

The 'aromatic diamine having no substituent group containing a fluorine atom' means an aromatic diamine having no substituent including a fluorine atom, for example, -CF ₃ . The 'aromatic diamine having a substituent containing a fluorine atom' refers to an aromatic diamine in which a substituent containing a fluorine atom is substituted, such as CF ₃ .

The R ¹ may be represented by the following formula (3).

(3)

In the above formula (3), Ra may be absent or may be present, and when Ra is present, it is selected from the group consisting of a phenylene group, an alkylene group having 1 to 4 carbon atoms, a haloalkylene group having 1 to 4 carbon atoms, and a combination thereof.

The reason that R _a may not be present is that the two aromatic organic groups bonded to both sides of R _a are not bonded through a substituent but the C ^sp2 are directly connected to each other.

In addition, R ⁴ may be represented by the following formula (4).

[Chemical Formula 4]

Wherein R _b and R _d are each independently selected from the group consisting of a halogen group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, R _c is absent or may be present, and when R _c is present, it is selected from the group consisting of a phenylene group, an alkylene group having 1 to 4 carbon atoms, a haloalkylene group having 1 to 4 carbon atoms, and combinations thereof, n is independently an integer of 0 to 4;

R _b and R _d are each independently selected from the group consisting of a halogen group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, and combinations thereof Meaning that R _b and R _d, which are different substitution units, may be different from each other, for example, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, and combinations thereof do.

Also, the meaning of 'each of m and n is independently an integer of 1 to 4' means that m and n may be selected from integers of 1 to 4 differently from each other.

The fact that R _c may not exist also means that two aromatic organic groups bonded to both sides of R _c are not bonded through a substituent, but C ^sp2 are directly connected to each other.

,

,

,

또는

일 수 있고, 상기 R²는

,

또는

일 수 있으며, 상기 R³는

또는

이고, 상기 R⁴는

,

,

,

,

,

,

,

,

또는

일 수 있다.According to a preferred embodiment of the present invention, R < ¹ >

,

,

,

or

And R < ^{2 >} is

,

or

And R < ³ >

or

, And R < ⁴ >

,

,

,

,

,

,

,

,

or

Lt; / RTI >

According to a preferred embodiment of the present invention, the molar percentage of the structural unit represented by the formula (1) contained in the composition for forming a polyimide-based film may be smaller than the molar percentage of the structural unit represented by the formula (2). In this case, there is an advantage that the thermal expansion coefficient and the transmittance can be more excellent.

According to a preferred embodiment of the present invention, the copolymer may be a copolymer represented by the following general formula (5).

[Chemical Formula 5]

In formula 5, R ¹ is an organic group containing an aromatic trivalent group or more organic than 2 derived from an acid dianhydride, R ² is an aromatic organic group derived from an acid dianhydride, R ³ is derived from a diamine R ⁴ is an organic group containing two or more aromatic divalent organic groups derived from diamines, and w, x, y and z represent molar ratios of the repeating units constituting the copolymer , w, x, y and z are independent and non-zero ratios satisfying 0.35? w + x? 0.50, 0.50? y + z? 0.65 and w + x + y + z = The order of bonding of repeating units constituting the repeating unit may be randomly modified. Preferably 0.37? W + x? 0.48, 0.52? Y + z? 0.63, and w + x + y + z = Further, it is advantageous that the condition of w? X and z? Y is satisfied.

When w, x, y and z satisfy the above ranges, a polyimide film useful for various devices such as a solar cell, an organic light emitting diode, a semiconductor device, or a flexible display device is obtained by simultaneously satisfying high transmittance and high heat resistance . If w + x is less than 0.35, the heat resistance at high temperature may be lowered, and if it exceeds 0.50, the transmittance may decrease or the thermal expansion coefficient may decrease. If y + z is less than 0.50, the transmittance may be lowered. If y + z is more than 0.65, the heat resistance at a high temperature may be lowered and the elasticity of the film may be lowered.

The weight average molecular weight of the copolymer of formula (5) may be 10,000 g / mol to 300,000 g / mol, preferably 50,000 to 150,000 g / mol. If the weight average molecular weight is less than 10,000 g / mol, cracks may occur in the film. If the weight average molecular weight is more than 300,000 g / mol, the viscosity may deteriorate due to high viscosity. Therefore, the weight average molecular weight of the copolymer preferably satisfies the above range Do.

, R²는

, R³는

, R⁴는

일 수 있다. According to a preferred embodiment of the present invention, R < ¹ >

, R ² is

, R ³ is

, R ⁴ is

Lt; / RTI >

The composition for forming a polyimide film of the present invention may contain 200 to 1000 parts by weight, preferably 400 to 900 parts by weight, of a solvent based on 100 parts by weight of the copolymer represented by the general formula (5). If the solvent is less than 200 parts by weight, the copolymer may be difficult to completely dissolve. If the solvent is more than 1000 parts by weight, the thickness of the film may be excessively thin.

Typically, the solvent used for the polyimide is an amide solvent such as DMF, DMAc, NMP, NEP, and the above solvents are chemicals harmful to human body. They are currently regulated substances or solvents that are likely to be regulated in the future. The solvent of the present invention may be selected from the group consisting of DMF, DMAc, NMP, NEP, 3-methoxy-dimethylpropionamide, and a compound represented by the following formula (6) .

[Chemical Formula 6]

In Formula 6, R _x and R _y are each a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R _z is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

The compound represented by Formula 6 is an amphoteric compound having an alkyl group and an amide group at the same time and unlike the other chemical substances described above, it is not a substance to be regulated and can be substituted without being harmful to the human body.

According to a preferred embodiment of the present invention, the additive is added in an amount of 0.5 to 60 parts by weight based on 100 parts by weight of the copolymer represented by the general formula (5), more preferably the additive is added to 100 parts by weight of the copolymer To 50 parts by weight. Further, the additive may be any one or more selected from the group consisting of alcohol-based, siloxane-based and fluorine-based surfactants, and more preferably a fluorine-based surfactant.

When a polyimide-based film is produced using the composition of the present invention, the optical characteristics and the thermal deformation characteristics can be determined according to the surface characteristics of the film. When the additives are used, the surface roughness is controlled, Can be reduced.

Specific examples of the commercial fluorinated surfactants usable in the present invention include EFTOP EF301 and EF303 (manufactured by Shin-Akita Kasei Co., Ltd.), FLUORAD FC 430 and 431 (manufactured by Sumitomo 3M Limited), MEGAFAC F171, (Manufactured by Dainippon Ink and Chemicals, Inc.), SURFLON S-382, SC101, 102, 103, 104, 105 and 106 (manufactured by Asahi Glass Co., Ltd.) .

In addition, the composition for forming a polyimide film of the present invention can further contain additives such as a sensitizer, an adhesion-promoting agent, a surfactant, a flame retardant, an inorganic particle, an antioxidant and an antistatic agent within a range that does not impair the properties desired to be obtained by the present invention .

The sensitizer may be any of those generally used in the art, and is not particularly limited, but it is preferable to use at least one selected from perylene, anthracene, thioxanthone, Michler's ketone, benzophenone, and fluorene.

The adhesive force improving agent may be any of those generally used in the art and is not particularly limited, but it is preferable to use at least one compound selected from a titanium chelate compound and an aluminum chelate compound.

The present invention further provides (1) a process for producing any one of the above polyimide copolymers; (2) preparing a composition for forming a polyimide-based film containing the copolymer, and (3) heat-treating the composition to prepare a polyimide-based film, wherein the polyimide- The initial preparation of the mid copolymer is carried out through copolymerization reaction at 0 to 30 ° C for 1 to 3 hours to prepare a polyimide-based film.

Due to the flexible nature of the polyimide film, it can be applied to flexible displays, while simultaneously satisfying high heat resistance and high transmittance, and thus can be usefully used in various devices such as solar cells, organic light emitting diodes, semiconductor devices, or flexible display devices Based film can be provided. Also, the polyimide-based film of the step (1) may be initially prepared at 0 to 30 ° C to provide a polyimide-based film having improved physical properties only by a simple process.

Hereinafter, the present invention will be described in detail except for the contents overlapping with the above description.

First, (1) the step of producing any one of the polyimide copolymers will be explained.

As described above, the polyimide copolymer contains the structural units represented by the above formulas (1) to (4). In order to prepare such a polyimide copolymer, two kinds of acid dianhydrides and two kinds of diamines are added, The reaction should be carried out.

The two kinds of acid dianhydrides mean acid dianhydrides having different formulas, and preferably one type of acid dianhydride has a rigid structure as compared with the other acid dianhydrides It is possible to produce a composition for forming a polyimide film satisfying both the transmittance and the high heat resistance simultaneously. Specifically, the more rigid acid dianhydride may be the acid dianhydride containing R ² , and the less-rigid acid dianhydride may be the acid dianhydride containing R ¹ .

In addition, the above-mentioned two types of diamines refer to diamines having different formulas, and preferably, when one type of diamine has a bulky structure as compared with other types of diamines, A composition for forming a polyimide film satisfying both high heat resistance can be produced. Specifically, the more bulky diamine may be a diamine including the R ⁴ , and the less bulky diamine may be a diamine including the R ³ .

According to a preferred embodiment of the present invention, the copolymerization reaction can be carried out by completely dissolving all of the diamines in two types, and then adding two kinds of acid dianhydrides.

The initial production of the polyimide copolymer in the step (1) is carried out through copolymerization reaction at 0 to 30 ° C for 1 to 3 hours. The total amount of the two diamines is added, and then the two kinds of acid dianhydrides Means that the initial reaction temperature of the copolymerization reaction, which is carried out by introducing the acid dianhydride, is started at 0 to 30 ° C, and that the reaction is carried out for 1 to 3 hours after all the two kinds of acid dianhydrides are charged.

When the two kinds of acid dianhydrides are introduced, it is preferable to apply all of the rigid acid dianhydrides first, followed by the addition of rigid acid dianhydrides. In this case, when the dripped acid dianhydride is introduced, the internal temperature rise is controlled to be within 2 ° C., and when the acid dianhydride is charged, the internal temperature rise is controlled to be within 4 ° C. In this case, The physical properties can be improved.

Preferably, the polyimide copolymer of the above step (1) may be prepared through the reaction of raising the temperature to 30 to 60 ° C. and maintaining the temperature for 8 to 24 hours after the copolymerization in the initial preparation.

The imidization catalyst may be pyridine, methylpyridine, lutidine, n-methylmorpholine, or the like. The imidization catalyst may be an imidation catalyst, , N-ethylpiperidine, and trialkylamines may be used. The dehydrating agent may be selected from the group consisting of acetic anhydride, propionic anhydride, n-butyric anhydride, maleic anhydride, And benzoic anhydride may be used.

Next, the step of (2) preparing a composition for forming a polyimide film containing the copolymer will be described.

As described above, the composition may be prepared to contain 200 to 1000 parts by weight, preferably 400 to 900 parts by weight, of solvent relative to 100 parts by weight of the copolymer.

On the other hand, in step (2), an alcohol-based, siloxane-based or fluorine-based surfactant may be added as an additive. Preferably, after the completion of the copolymerization reaction in the step (1), the surfactant may be added, followed by stirring for 1 to 2 hours.

As described above, the composition contains 0.01 to 5 parts by weight of the surfactant relative to 100 parts by weight of the copolymer, more preferably 0.1 to 1 part by weight of the additive relative to 100 parts by weight of the copolymer have.

Next, (3) a step of heat-treating the composition to prepare a polyimide-based film will be described.

A film can be prepared from the composition through the heat treatment.

Preferably, the composition is used after being filtered through a filter such as a syringe filter. At this time, a filter used for filtration is preferably a polytetrafluoroethylene filter, a polyethylene filter or a nylon filter having a thickness of 1 mu m or less, more preferably 0.5 mu m or less.

Specifically, the heat treatment may be performed by pre-baking the composition at 80 to 120 ° C for 10 to 50 minutes, followed by heat treatment to 420 to 480 ° C, followed by heat treatment for 10 to 30 minutes have.

It is preferable that the heating rate is controlled to 2 to 10 ° C / min during the heat treatment, and the physical properties of the polyimide-based film produced thereby can be improved.

Further, the present invention provides a polyimide-based film produced by any one of the above methods.

As described above, the polyimide-based film of the present invention preferably satisfies all of the following conditions in order to satisfy both high flexibility and high heat resistance, and excellent physical properties.

(a) a coefficient of thermal expansion (CTE) of -2 to 7 ppm /

(b) a surface roughness Ra of 0.1 to 1 nm

(c) an average transmittance of at least 65 in a wavelength region of 380 to 780 nm

As described above, the coefficient of thermal expansion of the polyimide-based film of the present invention may preferably be -2 to 7 ppm / ° C., more preferably -1 to 6 ppm / ° C., more preferably 1 to 4 ppm / Lt; 0 > C. In addition, the thermal expansion coefficient can be determined differently within the above range depending on the content of each structural unit or the heat treatment condition according to the present invention.

If the thermal expansion coefficient is more than 7.0 ppm / 占 폚, heat resistance is low and thermal deformation is easy, which may be unsuitable for use as a display substrate. The LTPS process temperature, which is a key point in a high-temperature TFT (thin film transistor) process, is about 450 ° C. At this time, the glass substrate or formed structure used as a support A problem such as warpage or cracking may occur due to the difference in thermal expansion coefficient between the two layers. Therefore, a thermal expansion coefficient similar to that of the glass substrate is required, and it is desirable to satisfy the thermal expansion coefficient within the above range.

In addition, the polyimide-based film of the present invention may have an average transmittance of 65 or more, more preferably 69 or more, and most preferably 72 or more in the wavelength region of 380 to 780 nm. Accordingly, the polyimide-based film of the present invention can satisfy both high heat resistance and high transparency, and thus can be utilized in various devices. If the transmittance in the wavelength range is less than 65, the transparency is lowered, which may be unsuitable for a display process application.

5 is an AFM image of a polyimide-based film according to a preferred embodiment of the present invention. It can be seen from the above drawings that the surface roughness of the polyimide film of the present invention is 0.1 to 1 nm, and more preferably 0.1 to 0.6 nm. Accordingly, the optical characteristics and the heat resistance of the film of the present invention can be excellently expressed, and the defective rate can be reduced in the device formation process. If the surface roughness exceeds 1 nm, the performance as a display device may be deteriorated or a process failure rate may increase.

As a result, the present invention provides a composition for forming a polyimide film that can be applied to a flexible display, satisfying both high heat resistance and high transmittance, a polyimide film produced using the composition, and a method for manufacturing the same, A diode, a semiconductor device, or a flexible display device.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

Example  One

In a 1000 mL round-bottomed flask, 727 g of 3-methoxy- N, N- dimethylpropionamide was added and 12.44 g (0.115 mol) of pPDA (p-phenylenediamine) and 2,2'-bis-Trifluoromethyl-4,4'-diaminobiphenyl (0.116 mol) were added thereto, and the whole amount was dissolved at 30 캜, and then the temperature was lowered to 10 캜. Next, 25.36 g (0.086 mol) of BPDA (biphenyl-tetracarboxylic acid dianhydride) was added, and the internal temperature rise was controlled within 2 ° C. Next, 31.00 g (0.138 mol) of PMDA (pyromellitic dianhydride) was slowly added thereto, and the internal temperature rise was controlled to be within 4 캜. And maintained at 10 DEG C for 2 hours to perform the initial copolymerization reaction. Thereafter, the reaction temperature was raised to 50 캜 and maintained for 12 hours to complete the polymerization reaction. Next, FC-4430 (3M Company) was diluted in 50 g of the remaining solvent, and the mixture was stirred for 2 hours. The composition containing the copolymer was filtered through a 0.45 μm filter, defoamed, and applied to a 0.5 mm glass substrate using a slot die coater (3.2 g, 120 mm × 125 mm). The glass substrate to which the varnish had been applied was then pre-baked at 120 ° C for 20 minutes using an IR-oven. Thereafter, the temperature was raised to 450 캜 at a rate of 7 캜 / minute, and the temperature was maintained at 450 캜 for 20 minutes to complete the heat treatment process, thereby producing a polyimide film.

Example  2 to 3

The procedure of Example 1 was repeated except that a copolymer represented by the ratio shown in Table 1 below was prepared.

Example  4

The procedure of Example 1 was repeated except that the polymerization was carried out under the initial polymerization temperature conditions shown in Table 1 below.

Example  5 to 6

The procedure of Example 1 was repeated except that the heat treatment was performed under the conditions shown in Table 1 below.

Example  7

The procedure of Example 1 was repeated except that a copolymer represented by the ratio shown in Table 1 below was prepared.

Example  8

The procedure of Example 1 was repeated except that the copolymer was represented by the ratio shown in Table 1 below and the solvent was used.

Comparative Example  One

The procedure of Example 1 was repeated except that the polymerization was carried out under the initial polymerization temperature conditions shown in Table 2 below.

Comparative Example 2  ~ 3

The procedure of Example 1 was repeated except that a copolymer represented by the ratio shown in Table 2 below was prepared.

Comparative Example 4

The same procedure as in Example 1 was carried out except for the preparation of the copolymer represented by the ratio shown in the following Table 2 and the heat treatment condition.

Table 1.

Table 2.

* The composition ratios in Tables 1 and 2 are expressed as a ratio of anhydride: diamine = 100: 100 with an anhydride and a diamine as 100, respectively.

Experimental Example  1. Thermal expansion coefficient ( CTE ) Measure

The coefficient of thermal expansion (CTE) of the polyimide-based films prepared in Examples and Comparative Examples was measured at 100 to 450 ° C using a thermal expansion coefficient meter (TMA), and the results are shown in Table 3 below.

Experimental Example  2. Measurement of permeability

The transmittance of the polyimide film prepared in the above Examples and Comparative Examples was measured in a wavelength range of 380 to 780 nm using a colorimeter, and the transmittance at 550 nm is shown in Table 3 below.

table 3.

Referring to Tables 1, 2 and 3, it can be seen that Example 1 satisfies an appropriate coefficient of thermal expansion of 2.1 ppm / and exhibits a transmittance of 75 as excellent. On the other hand, in Examples 2 and 3, the coefficient of thermal expansion was 7, 6.8 ppm /, and the permeability was 70% or less. Thus, Example 1 is more advantageous in terms of heat resistance and permeability.

In the case of Example 5, the physical properties of the film were not lowered even though the heating rate was 14 ° C / min. However, at the maximum heat treatment temperature of 480 ° C, which is the condition of Example 6, the transmittance and tensile strength characteristics of the film were deteriorated.

In the case of Comparative Example 1, the initial polymerization temperature was higher than 30 ° C, and when the initial polymerization temperature was too high, the film properties were sharply lowered as compared with Example 1. In Comparative Examples 2 and 4, the coefficient of thermal expansion was less than -2 ppm / or more than 7 ppm /. In Comparative Example 3, the transmittance was less than 65, indicating that heat resistance and permeability were not excellent at the same time .

Claims (16)

A structural unit represented by the following formula (1), a structural unit represented by the following formula (2), R³And R⁴And a polyimide copolymer containing a substituent represented by the formula
The R³And R⁴Is bonded to at least one nitrogen of the structural unit represented by the following general formula (1) or (2).
[Chemical Formula 1]

(2)

In Formula 1, R^OneIs an organic group containing two or more aromatic trivalent or more organic groups derived from an acid dianhydride, and R²Is an organic group containing at least one aromatic organic group derived from an acid dianhydride, R³Is an aromatic divalent organic group derived from a diamine, R⁴Is an organic group containing two or more aromatic divalent or higher organic groups derived from a diamine.
The method according to claim 1,
Wherein R ³ is an aromatic divalent organic group derived from an aromatic diamine having no substituent having a fluorine atom and R ⁴ includes an aromatic trivalent organic group derived from an aromatic diamine having a substituent having a fluorine atom Wherein the polyimide-based film-forming composition is a polyimide-based film-forming composition.
The method according to claim 1,
Wherein R < ¹ > is represented by the following formula (3).
(3)

In Formula 3,
R < _{a >} is absent or may be present,
When R _a is present, it is selected from the group consisting of a phenylene group, an alkylene group having 1 to 4 carbon atoms, a haloalkylene group having 1 to 4 carbon atoms, and a combination thereof.
The method according to claim 1,
Wherein R ⁴ is formula (4) A polyimide-based film-forming composition, characterized in that represented by the below.
[Chemical Formula 4]

Wherein R _b and R _d are each independently selected from the group consisting of a halogen group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms,
R < _c > may be absent or present,
When R _c is present, it is selected from the group consisting of a phenylene group, an alkylene group having 1 to 4 carbon atoms, a haloalkylene group having 1 to 4 carbon atoms,
M and n are each independently an integer of 0 to 4;
The method according to claim 1,
Wherein R < ^{1 &}

,

,

or

Lt;
R ² is

,

or

Based on the weight of the polyimide-based film-forming composition.
The method according to claim 1,
R < ³ >

or

ego,
R < ⁴ >

,

,

,

,

,

,

,

,

or

Based on the weight of the polyimide-based film-forming composition.
The method according to claim 1,
Wherein the molar percentage of the structural unit represented by the formula (1) contained in the composition for forming a polyimide film is smaller than the molar percentage of the structural unit represented by the formula (2).
The method according to claim 1,
Wherein the polyimide copolymer is a copolymer represented by the following formula (5).
[Chemical Formula 5]

In Formula 5,
R ¹ is an organic group containing two or more aromatic trivalent or more organic groups derived from an acid dianhydride, R ² is an aromatic tetravalent organic group derived from an acid dianhydride, and R ³ is an aromatic di R ⁴ is an organic group containing two or more aromatic divalent organic groups derived from diamine,
Wherein w, x, y and z represent the molar ratio of the repeating units constituting the copolymer, and w, x, y and z are independent and satisfy 0.35? W + x? 0.50, 0.50? Y + w + x + y + z = 1, w? x and z? y,
The order of bonding of the repeating units constituting the copolymer may be randomly modified.
9. The method of claim 8,
Wherein R < ^{1 &}

, R ² is

, R ³ is

, R ⁴ is

Based on the weight of the polyimide-based film-forming composition.
9. The method of claim 8,
Wherein the solvent is selected from the group consisting of DMF, DMAc, NMP, NEP, 3-methoxy-dimethylpropionamide, and a compound represented by the following formula (6) Wherein the polyimide-based film-forming composition is selected from the group consisting of polyimide-based films and polyimide-based films.
[Chemical Formula 6]

In Formula 6,
R _x and R _y are a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R _z is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
9. The method of claim 8,
0.1 to 1 part by weight of an additive is added to 100 parts by weight of the copolymer represented by the formula (5)
Wherein the additive is at least one selected from the group consisting of alcohol-based, siloxane-based and fluorine-based surfactants.
(1) preparing the polyimide copolymer of any one of claims 1 to 11;
(2) preparing a composition for forming a polyimide-based film comprising the copolymer; and
(3) heat-treating the composition to produce a polyimide-based film,
The polyimide-based film of claim 1, wherein the polyimide copolymer is prepared by a copolymerization reaction at 0 to 30 ° C for 1 to 3 hours.
13. The method of claim 12,
Wherein the polyimide copolymer of step (1) is produced through a reaction of heating to 30 to 60 ° C. and maintaining the temperature of the polyimide copolymer for 8 to 24 hours.
13. The method of claim 12,
Wherein after the step (1), an alcohol-based, siloxane-based or fluorine-based surfactant is further added.
A polyimide-based film produced by the method of claim 12.
16. The method of claim 15,
Wherein the polyimide-based film satisfies all of the following conditions.
(a) a coefficient of thermal expansion (CTE) of -2 to 7 ppm /
(b) a surface roughness Ra of 0.1 to 1 nm
(c) an average transmittance of not less than 65 in a wavelength region of 380 to 780 nm

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