阅读说明：本技术 二胺化合物、使用其的聚酰亚胺前体和聚酰亚胺膜 (Diamine compound, polyimide precursor using same, and polyimide film ) 是由 丘冀哲 金炅焕 于 2019-12-17 设计创作，主要内容包括：公开了一种新的二胺,所述新的二胺具有包含分子内酰亚胺基,并且还包含通过酯基连接至酰亚胺基的两侧的芳族环状基团的结构。当使用所述新的二胺作为用于制备聚酰亚胺的可聚合组分时,可以提供在保持光学特性的同时具有显著改善的机械特性和热特性的聚酰亚胺膜。(Disclosed is a novel diamine having a structure comprising an intramolecular imide group and further comprising an aromatic cyclic group connected to both sides of the imide group through an ester group. When the novel diamine is used as a polymerizable component for preparing polyimide, a polyimide film having significantly improved mechanical and thermal characteristics while maintaining optical characteristics can be provided.)

1. A diamine represented by formula 1:

[ formula 1]

In the case of the above-mentioned formula 1,

Z₁to Z₈Each independently being a carbon atom or a nitrogen atom, with the proviso that Z₁To Z₈Not simultaneously being nitrogen atoms, R₁、R₂、R₃And R₄Each independently selected from the group consisting of alkyl groups having 1 to 10 carbon atoms, haloalkyl groups having 1 to 10 carbon atoms, alkenyl groups having 1 to 10 carbon atoms, and aryl groups having 6 to 18 carbon atoms, n₁、n₂、n₃And n₄Each independently an integer of 0 to 4, andx is a single bond or a functional group selected from: o, S, S-S, C (═ O), -C (═ O) O-, ch (oh), S (═ O)₂、Si(CH₃)₂CR 'R ", C (═ O) NH, and combinations thereof, wherein R' and R" are each independently selected from the group consisting of hydrogen atoms, alkyl groups having 1 to 10 carbon atoms, and fluoroalkyl groups having 1 to 10 carbon atoms.

2. Diamine according to claim 1, wherein Z₁To Z₄Must be a carbon atom, and Z₅To Z₈At least one of which must be a carbon atom.

3. Diamine according to claim 1, wherein n₁And n₂Each independently is 0, or R₁And R₂Each independently an alkyl group having 1 to 5 carbon atoms or a haloalkyl group having 1 to 5 carbon atoms.

4. Diamine according to claim 1, wherein Z₁To Z₄All being carbon atoms.

5. Diamine according to claim 1, wherein Z₁To Z₄One of them is a nitrogen atom or Z₅To Z₈One of them is a nitrogen atom.

6. Diamine according to claim 1, wherein Z₁To Z₄Is a nitrogen atom and Z₅To Z₈One of them is a nitrogen atom.

7. The diamine of claim 1, wherein X is a single bond, -O-, -CH₂-、-C(CF₃)-、-C(CH₃)₂-, or-SO₂-。

8. The diamine of claim 1, wherein the diamine of formula 1 is selected from compounds of formulae 1-1 to 1-20:

9. a polyimide precursor obtained by polymerizing polymerization components comprising at least one diamine and at least one acid dianhydride, wherein the diamine comprises the diamine according to any one of claims 1 to 8.

10. A polyimide film produced by using the polyimide precursor according to claim 9.

11. A polyimide film manufactured by a method comprising:

applying a polyimide precursor composition comprising the polyimide precursor of claim 9 on a carrier substrate; and

the polyimide precursor composition is heated and cured.

12. A flexible device comprising the polyimide film according to claim 10 as a substrate.

13. A method for producing a flexible display, comprising:

applying a polyimide precursor composition comprising the polyimide precursor of claim 9 on a carrier substrate;

heating the polyimide precursor composition to imidize a polyamic acid, thereby forming a polyimide film;

forming a device on the polyimide film; and

peeling the polyimide film having the device formed thereon from the carrier substrate.

14. The method for producing a flexible display according to claim 13, wherein the method comprises an LTPS (low temperature polysilicon) method, an ITO method, or an oxide method.

15. A process for preparing a diamine having the structure of formula 1, the process comprising the steps of:

reacting a compound of formula (i) with a compound of formula (ii) below to obtain a compound of formula (iii);

(iv) reacting the compound of formula (iii) with a compound of formula (iv) to obtain a compound of formula (v); and

reducing the compound of formula (v):

wherein the content of the first and second substances,

Z_ato Z_dEach independently being a carbon atom or a nitrogen atom, with the proviso that Z_aTo Z_dNot simultaneously being nitrogen atoms, R₁、R₂And R_aEach independently selected from the group consisting of alkyl groups having 1 to 10 carbon atoms, haloalkyl groups having 1 to 10 carbon atoms, alkenyl groups having 1 to 10 carbon atoms, and aryl groups having 6 to 18 carbon atoms, n₁、n₂And n is each independently an integer from 0 to 4, and X is a single bond or a functional group selected from: o, S, S-S, C (═ O), -C (═ O) O-, ch (oh), S (═ O)₂、Si(CH₃)₂CR 'R ", C (═ O) NH, and combinations thereof, wherein R' and R" are each independently selected from the group consisting of hydrogen atoms, alkyl groups having 1 to 10 carbon atoms, and fluoroalkyl groups having 1 to 10 carbon atoms.

Technical Field

This application claims the benefit of priority from korean patent application No. 10-2018-.

The present invention relates to a novel diamine, and a polyimide precursor and a polyimide film using the same.

Background

In recent years, weight reduction and miniaturization of products have been emphasized in the field of displays. The glass substrates currently used are heavy and brittle and are difficult to apply to a continuous process. Therefore, research is actively conducted to apply a plastic substrate, which has advantages of light weight, flexibility, and applicability to a continuous process and can replace a glass substrate, to a cellular phone, a notebook computer, and a PDA.

In particular, Polyimide (PI) resins have advantages of being easy to synthesize, being formable into thin films, and not requiring a crosslinking agent for curing. Recently, polyimide is widely used as a material for integration in semiconductors such as LCDs, PDPs, and the like, due to weight reduction and precision of electronic products. In particular, many studies have been made on applying PI to a flexible plastic display panel having light and flexible characteristics.

A Polyimide (PI) film produced by forming a polyimide resin into a film is generally prepared by: the method includes polymerizing an aromatic dianhydride with an aromatic diamine or an aromatic diisocyanate solution to prepare a solution of a polyamic acid derivative, coating the solution on a silicon wafer or glass, and curing by heat treatment.

Flexible devices that involve high temperature processes require heat resistance at high temperatures. In particular, Organic Light Emitting Diode (OLED) devices fabricated using a Low Temperature Polysilicon (LTPS) process may have a process temperature of approximately 500 ℃. However, at this temperature, thermal decomposition by hydrolysis tends to occur even with polyimide having excellent heat resistance. Therefore, in order to manufacture a flexible device, excellent chemical resistance and storage stability must be ensured so that thermal decomposition caused by hydrolysis during a high temperature process does not occur.

In addition, the aromatic polyimide resin exhibits poor processability and brown coloration due to intramolecular interaction and Charge Transfer Complexation (CTC). To overcome this, attempts have been made to introduce aliphatic chains, flexible linking groups, fluorinated functional groups, and the like into monomers used in polyimide production. However, the introduction of these substituents causes a problem of deteriorating mechanical characteristics, which is the strength of polyimide.

Therefore, there is a need to develop a technology capable of improving mechanical properties while maintaining the properties of polyimide.

Disclosure of Invention

Technical problem

One problem to be solved by the present invention is to provide a novel diamine capable of producing a polyimide having improved physical properties.

Another problem to be solved by the present invention is to provide a polyimide precursor for producing a polyimide film having improved physical properties.

Still another problem to be solved by the present invention is to provide a polyimide film prepared by using the polyimide precursor.

The present invention also provides a flexible device including the polyimide film and a method of manufacturing the flexible device.

Technical scheme

In order to solve the problems of the present invention, a diamine represented by formula 1 is provided.

[ formula 1]

In the formula 1, the first and second groups,

Z₁to Z₈Each independently being a carbon atom or a nitrogen atomWith the proviso that Z₁To Z₈Not simultaneously being nitrogen atoms, R₁、R₂、R₃And R₄Each independently selected from the group consisting of alkyl groups having 1 to 10 carbon atoms, haloalkyl groups having 1 to 10 carbon atoms, alkenyl groups having 1 to 10 carbon atoms, and aryl groups having 6 to 18 carbon atoms, n₁、n₂、n₃And n₄Each independently is an integer from 0 to 4, and X is a single bond or a functional group selected from: o, S, S-S, C (═ O), -C (═ O) O-, ch (oh), S (═ O)₂、Si(CH₃)₂CR 'R ", C (═ O) NH, and combinations thereof, wherein R' and R" are each independently selected from the group consisting of hydrogen atoms, alkyl groups having 1 to 10 carbon atoms, and fluoroalkyl groups having 1 to 10 carbon atoms.

According to one embodiment, in formula 1, Z₁To Z₄At least one of which may have to be a carbon atom, and Z₅To Z₈At least one of which may necessarily be a carbon atom.

According to one embodiment, in formula 1, n₁And n₂May each independently be 0, or R₁And R₂May each independently be an alkyl group having 1 to 5 carbon atoms or a haloalkyl group having 1 to 5 carbon atoms.

According to one embodiment, in formula 1, Z₁To Z₄May be all carbon atoms.

According to one embodiment, in formula 1, Z₁To Z₄One of them may be a nitrogen atom or Z₅To Z₈One of them may be a nitrogen atom.

According to one embodiment, in formula 1, Z₁To Z₄May be a nitrogen atom and Z₅To Z₈One of them may be a nitrogen atom.

According to one embodiment, in formula 1, X may be selected from a single bond, -O-, -CH₂-、-C(CF₃)-、-C(CH₃)₂-, or-SO₂-。

According to one embodiment, the diamine of formula 1 may be selected from compounds of formulae 1-1 to 1-20.

Further, the present invention provides a polyimide precursor obtained by polymerizing polymerization components comprising at least one diamine and at least one acid dianhydride,

wherein the diamine in the polymerization component comprises a diamine represented by formula 1.

Further, the present invention provides a polyimide film manufactured by using the polyimide precursor.

According to one embodiment, a polyimide film may be manufactured by a method including: applying a polyimide precursor composition comprising a polyimide precursor on a carrier substrate; and

the polyimide precursor composition is heated and cured.

In order to solve another problem of the present invention, a flexible device including the polyimide film as a substrate is provided.

Further, the present invention provides a method for manufacturing a flexible display, the method comprising:

applying a polyimide precursor composition comprising a polyimide precursor on a carrier substrate;

heating the polyimide precursor composition to imidize the polyamic acid, thereby forming a polyimide film;

forming a device on the polyimide film; and

the polyimide film with the devices formed thereon is peeled off the carrier substrate.

According to one embodiment, the method may include an LTPS (low temperature polysilicon) method, an ITO method, or an oxide method.

Further, the present invention provides a method for preparing a diamine having the structure of formula 1, the method comprising the steps of:

reacting a compound of formula (i) with a compound of formula (ii) below to obtain a compound of formula (iii);

(iv) reacting the compound of formula (iii) with the compound of formula (iv) to obtain a compound of formula (v); and

reducing a compound of formula (v):

wherein Z is_aTo Z_dEach independently being a carbon atom or a nitrogen atom, with the proviso that Z_aTo Z_dNot simultaneously being nitrogen atoms, R₁、R₂And R_aEach independently selected from the group consisting of alkyl groups having 1 to 10 carbon atoms, haloalkyl groups having 1 to 10 carbon atoms, alkenyl groups having 1 to 10 carbon atoms, and aryl groups having 6 to 18 carbon atoms, n₁、n₂And n is each independently an integer from 0 to 4, and X is a single bond or a functional group selected from: o, S, S-S, C (═ O), -C (═ O) O-, ch (oh), S (═ O)₂、Si(CH₃)₂CR 'R ", C (═ O) NH, and combinations thereof, wherein R' and R" are each independently selected from the group consisting of hydrogen atoms, alkyl groups having 1 to 10 carbon atoms, and fluoroalkyl groups having 1 to 10 carbon atoms.

Advantageous effects

Disclosed is a novel diamine having a structure comprising an intramolecular imide group and further comprising aromatic ring groups connected through an ester group on both sides of the imide group, which can provide a polyimide film in which mechanical and thermal characteristics are significantly improved while maintaining optical characteristics when the novel diamine is used as a polymerization component in the production of polyimide.

Detailed Description

Since various modifications and changes can be made in the present invention, specific embodiments are shown in the drawings and will be described in detail in the detailed description. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but to include all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. In the following description of the present invention, a detailed description of known functions will be omitted if it is determined that the detailed description of known functions may obscure the gist of the present invention.

In this specification, unless otherwise specified, all compounds or organic groups may be substituted or unsubstituted. Herein, the term "substituted" means that at least one hydrogen contained in a compound or organic group is substituted with a substituent selected from the group consisting of: a halogen atom, an alkyl group or a haloalkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, a carboxyl group, an aldehyde group, an epoxy group, a cyano group, a nitro group, an amino group, a sulfonic acid group, or a derivative thereof.

Aromatic polyimides are widely used in high-tech industries such as microelectronics, aerospace, insulating materials and refractory materials due to their excellent bulk properties such as thermal oxidation stability, high mechanical strength and excellent mechanical strength. However, aromatic polyimides with strong absorption in the uv-visible region show strong coloration from light yellow to dark brown. This limits its widespread use in the field of optoelectronics where transparency and colorless properties are essential requirements. The reason for the coloration in aromatic polyimide resins is the formation of intramolecular charge transfer complexes (CT-complexes) between alternating electron donors (dianhydrides) and electron acceptors (diamines) in the polymer backbone.

To solve this problem, for the development of optically transparent PI films having a high glass transition temperature (Tg), introduction of a functional group in the polymer backbone, introduction of bulky side groups, fluorinated functional groups, or the like, or introduction of flexible units (-S-, -O-, -CH) — has been studied₂-etc.). However, the introduction of these substituents may cause a problem of deteriorating mechanical properties as strength of polyimide.

Accordingly, the present invention provides a diamine represented by the following formula 1 as a polymerization component capable of producing a polyimide having improved mechanical characteristics.

[ formula 1]

In the formula 1, the first and second groups,

Z₁to Z₈Each independently being a carbon atom or a nitrogen atom, with the proviso that Z₁To Z₈Is not simultaneously a nitrogen atom,

R₁、R₂、R₃and R₄Each independently selected from the group consisting of alkyl groups having 1 to 10 carbon atoms, haloalkyl groups having 1 to 10 carbon atoms, alkenyl groups having 1 to 10 carbon atoms, and aryl groups having 6 to 18 carbon atoms, n₁、n₂、n₃And n₄Each independently an integer of 0 to 4, and

x is a single bond or a functional group selected from: o, S, S-S, C (═ O), -C (═ O) O-, ch (oh), S (═ O)₂、Si(CH₃)₂CR 'R ", C (═ O) NH, and combinations thereof, wherein R' and R" are each independently selected from the group consisting of hydrogen atoms, alkyl groups having 1 to 10 carbon atoms, and fluoroalkyl groups having 1 to 10 carbon atoms.

Since the diamine according to the present invention includes a diamine containing an imide group in a molecule, a Charge Transfer Complexation (CTC) effect is increased by an increase in the interaction of pi-pi electrons between molecules of a diamine repeating unit including an imide group during polymerization of polyimide. Thus, the mechanical properties are improved and the distance between the molecules is closer, so that the probability of polymerization increases and thus the molecular weight can be increased. In addition, since the aromatic structure is continuously connected due to a structure in which an ester group-substituted aromatic ring group is further bonded to both sides of an imide group, an enhanced CTC effect is suppressed and processability is enhanced, and it enables intermolecular hydrogen bonding, and thus mechanical characteristics can be further improved. That is, while mechanical characteristics are improved due to the enhanced CTC effect resulting from an increase in imidization rate, the CTC effect can be suppressed by the ester group.

According to one embodiment, in formula 1, Z₁To Z₄May be all carbon atoms.

According to another embodiment, Z₁To Z₄One of them may be a nitrogen atom or Z₅To Z₈One of them may be a nitrogen atom, according to another embodiment, Z₁To Z₄One of them may be a nitrogen atom and Z₅To Z₈One of them may be a nitrogen atom.

According to one embodiment, in formula 1, n₁And n₂May each independently be 0, or R₁And R₂May each independently be an alkyl group having 1 to 5 carbon atoms or a haloalkyl group having 1 to 5 carbon atoms.

According to one embodiment, the diamine of formula 1 may be prepared by the same reaction as in scheme 1 below:

[ scheme 1]

Wherein Z_aTo Z_dEach independently being a carbon atom or a nitrogen atom, with the proviso that Z_aTo Z_dIs not simultaneously a nitrogen atom,

R₁、R₂and R_aEach independently selected from the group consisting of alkyl groups having 1 to 10 carbon atoms, haloalkyl groups having 1 to 10 carbon atoms, alkenyl groups having 1 to 10 carbon atoms, and aryl groups having 6 to 18 carbon atoms, n₁、n₂And n is an integer of 0 to 4, and

x is the same as defined in formula 1.

In step (1) of scheme 1, a compound of formula (i) is reacted with a compound of formula (ii) to obtain a compound of formula (iii).

The compound of formula (i) and the compound of formula (ii) may be used in a molar ratio of 1:0.3 to 1:1, for example a molar ratio of 1:0.3 to 1: 0.7.

In the reaction of step (1), Tetrahydrofuran (THF), Ethyl Acetate (EA), or the like may be used as an organic solvent, and propylene oxide may be added as a catalyst to improve the reactivity.

Furthermore, in order to reduce the violent reaction due to the high reactivity, the reaction is advantageously carried out at 0 ℃, and the reaction time may be 1 to 5 hours, for example, 1 to 3 hours.

In step (2) of scheme 1, a compound of formula (iii) is reacted with a compound of formula (iv) to obtain a compound of formula (v).

The compound of formula (iii) and the compound of formula (iv) may be used in a molar ratio of 1:0.3 to 1:1, for example a molar ratio of 1:0.3 to 1: 0.7.

In the reaction of step (2), acetic acid, propionic acid, or the like may be used to disperse the reaction compound, and the reaction temperature may be raised to about 100 ℃, and the reaction time may be 3 hours to 5 hours, for example, 4 hours.

Subsequently, after the reaction temperature is lowered to room temperature, alcohols such as ethanol and isopropanol may be added to obtain a solid.

In step (3) of scheme 1, the compound of formula (v) is reduced to finally obtain the compound of formula 1.

The reduction reaction in step (3) may be carried out in the presence of a palladium on carbon (Pd/C) catalyst in a hydrogen atmosphere for 12 hours to 18 hours, for example, 16 hours. In this case, N-methylpyrrolidone, tetrahydrofuran, or the like can be used as the dispersion medium.

According to one embodiment, the weight average molecular weight of the polyimide precursor prepared by using the diamine having the above structure may exceed 50,000g/mol to improve mechanical characteristics. For example, the weight average molecular weight of the polyimide precursor may be 51,000g/mol to 65,000 g/mol. When the molecular weight is 50,000g/mol or less, the viscosity of the solution is reduced due to the reduction of reactivity of the polyimide, and the viscosity is low compared to the solid content, and thus the film thickness may not be easily controlled during the solution coating process and the final curing process. Further, when the molecular weight is low, mechanical properties may be reduced, which may cause a problem of reduction in film strength.

According to one embodiment, by including a nitrogen atom in the ester group-substituted aromatic ring, CTC effects may be reduced to improve optical properties.

According to one embodiment, the diamine of formula 1 may be selected from compounds of formulae 1-1 to 1-20.

In formula 1, a substituent including fluorine (F) (e.g., a substituent such as a fluoroalkyl group) may reduce stacking within the structure or between chains of polyimide, and may weaken electrical interaction between chromophores due to a steric hindrance effect and an electrical effect, thereby resulting in high transparency in a visible light region.

The polyimide precursor according to the present invention may include a diamine having the structure of formula 2 as a polymerization component:

[ formula 2]

In the formula 2, the first and second groups,

R₅and R₆Each independently a monovalent organic group having 1 to 20 carbon atoms, and h is an integer of 3 to 200.

More specifically, the compound of formula 2 may be a diamine compound of the following formula 2-1.

[ formula 2-1]

In the formula 2-1, the compound represented by the formula,

each R is independently an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 24 carbon atoms, and

p and q are mole fractions, and when p + q is 100, p is 70 to 90 and q is 10 to 30.

The compound of formula 2 may be present in 5 to 50% by weight relative to the total weight of the polymeric components, preferably 10 to 20% by weight relative to the total weight of the polymeric components.

When the polymeric component including the structure of formula 2 is added in excess relative to the total weight of the polymeric component, the mechanical properties of the polyimide, such as modulus, may be deteriorated and the film strength may be reduced, resulting in physical damage of the film during the process, such as tearing. Further, when the diamine having the structure of formula 2 is excessively added, Tg derived from the polymer having a siloxane structure may occur, and thus, Tg occurs at a low process temperature of 350 ℃ or less, and wrinkles may occur on the surface of the film due to a flow phenomenon of the polymer during the inorganic film deposition process of 350 ℃ or more, thereby generating cracks of the inorganic film.

Generally, in the case where the polyimide contains 10% by weight or more of diamine containing the silicone oligomer structure of formula 2 in the polymerization component, the effect of reducing residual stress can be increased, and in the case of more than 50% by weight, Tg is less than 390 ℃, so that heat resistance may be reduced.

On the other hand, the polyimide according to the present invention can maintain a Tg of 390 ℃ or more although the silicone oligomer is contained in an amount of 10 wt% or more based on the total polymeric components. Therefore, the effect of reducing residual stress due to the structure of the silicone oligomer can also be achieved while maintaining the glass transition temperature at 390 ℃ or higher.

The molecular weight of the silicone oligomer structure contained in the diamine having the structure of formula 2 may be 4000g/mol or more, where the molecular weight means a weight average molecular weight, and the molecular weight may be calculated by calculating the equivalent weight of a reactive group such as amine or dianhydride using NMR analysis or an acid-base titration method.

When the molecular weight of the silicone oligomer structure including the structure of formula 2 is less than 4000g/mol, heat resistance may be reduced, for example, the glass transition temperature (Tg) of the prepared polyimide may be reduced, or the thermal expansion coefficient may be excessively increased.

According to the present invention, the silicon oligomer domains distributed in the polyimide matrix have a continuous phase, for example, having a size of nanometer, for example, 1nm to 50nm, or 5nm to 40nm, or 10nm to 30nm, so that it is possible to minimize residual stress while maintaining heat resistance and mechanical characteristics. If it does not have such a continuous phase, there may be a residual stress reduction effect, but it is difficult to use in the method due to a significant decrease in heat resistance and mechanical properties.

Here, the domain of the silicone oligomer means a region in which a polymer having a silicone oligomer structure is distributed, and the size thereof means the diameter of a circle surrounding the region.

It is preferable that the portions (domains) containing the silicone oligomer structure are connected in a continuous phase in the polyimide matrix, wherein the continuous phase means a shape in which nano-sized domains are uniformly distributed.

Therefore, according to the present invention, the silicone oligomer can be uniformly distributed in the polyimide matrix without phase separation despite having a high molecular weight, so that the haze property is reduced to obtain a polyimide having a more transparent property. In addition, the presence of the silicone oligomer structure in a continuous phase can more effectively improve the mechanical strength and stress relaxation effect of the polyimide. From these characteristics, the composition according to the present invention can provide a flat polyimide film having improved thermal and optical characteristics by reducing the warpage of the substrate after the coating is cured.

In the present invention, by inserting the silicone oligomer structure into the polyimide structure, the modulus of the polyimide can be appropriately improved, and also the stress caused by an external force can be relaxed. The polyimide containing the silicone oligomer structure may exhibit polarity, and phase separation may occur due to a difference in polarity from the polyimide structure not containing the siloxane structure, whereby the siloxane structure may be unevenly distributed throughout the polyimide structure. In this case, it is difficult to exhibit an improvement effect of physical properties of polyimide such as strength improvement and stress relaxation due to the siloxane structure, and haze increases due to phase separation, thereby deteriorating transparency of the film. In particular, when the diamine containing a siloxane structure has a high molecular weight, the polarity of the polyimide thus prepared may be more pronounced, so that the phase separation phenomenon between the polyimides may be more pronounced. At this time, when a siloxane diamine having a low molecular weight structure is used, a large amount of the siloxane diamine must be added to exhibit effects such as stress relaxation. However, this may cause process problems such as low Tg, and thus may deteriorate physical properties of the polyimide film. Therefore, in the case of adding a siloxane diamine having a high molecular weight, a relaxation segment can be formed in a large amount in the molecule, and thus the stress relaxation effect can be effectively exhibited even in a small amount as compared with the case of adding a siloxane diamine having a low molecular weight. Therefore, the present invention can be more uniformly distributed in the polyimide matrix without phase separation by using the compound of formula 2 having a siloxane structure with a high molecular weight.

According to one embodiment, as the acid dianhydride used for polymerizing the polyimide precursor, tetracarboxylic acid dianhydride may be used. For example, as the tetracarboxylic dianhydride, a tetracarboxylic dianhydride containing an aliphatic, alicyclic or aromatic tetravalent organic group, or a combination thereof in the molecule, wherein the aliphatic, alicyclic or aromatic tetravalent organic groups are linked to each other via a crosslinking structure, may be used. Preferably, it may include an acid dianhydride having a structure in which a monocyclic or polycyclic aromatic group, a monocyclic or polycyclic alicyclic group, or two or more of them are linked by a single bond or a functional group. Alternatively, it may include tetracarboxylic dianhydride comprising a tetravalent organic group having an aliphatic ring or an aromatic ring, wherein each ring is a single ring structure, each ring is fused to form a heterocyclic structure, or each ring is connected by a single bond.

For example, the tetracarboxylic dianhydride may include a tetracarboxylic dianhydride containing a tetravalent organic group selected from the structures of the following formulae 3a to 3 e.

[ formula 3a ]

[ formula 3b ]

[ formula 3c ]

[ formula 3d ]

[ formula 3e ]

In formulae 3a to 3e, R₁₁To R₁₇Each independently is a substituent selected from: halogen atoms selected from the group consisting of-F, -Cl, -Br and-I, hydroxyl groups (-OH), thiol groups (-SH), nitro groups (-NO)₂) Cyano, alkyl having 1 to 10 carbon atoms, haloalkoxy having 1 to 4 carbon atoms, haloalkyl having 1 to 10 carbon atoms, and aryl having 6 to 20 carbon atoms,

a1 is an integer from 0 to 2, a2 is an integer from 0 to 4, a3 is an integer from 0 to 8, a4 and a5 are each independently an integer from 0 to 3, a6 and a9 are each independently an integer from 0 to 3, and a7 and a8 are each independently an integer from 0 to 7,

A₁₁and A₁₂Each independently selected from a single bond, -O-, -CR 'R "(wherein, R' and R" are each independently selected from a hydrogen atom, an alkyl group having 1 to 10 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, pentyl, etc.), and a haloalkyl group having 1 to 10 carbon atoms (e.g., trifluoromethyl, etc.)), -C (═ O) -, -C (═ O) O-, -C (═ O) NH-, -S-, -SO-, -and —)₂-、-O[CH₂CH₂O]y- (y is an integer of 1 to 44), -NH (C ═ O) NH-, -NH (C ═ O) O-, a monocyclic or polycyclic cycloalkylene group having 6 to 18 carbon atoms (e.g., cyclohexylene group and the like), a monocyclic or polycyclic arylene group having 6 to 18 carbon atoms (e.g., phenylene, naphthylene, fluorenyleneBasal, etc.), and combinations thereof.

Alternatively, the tetracarboxylic dianhydride may comprise a tetravalent organic group selected from the following formulas 4a to 4 n.

At least one hydrogen atom in the tetravalent organic group of formulae 4a to 4n may be substituted with a substituent selected from: halogen atoms selected from the group consisting of-F, -Cl, -Br and-I, hydroxyl groups (-OH), thiol groups (-SH), nitro groups (-NO)₂) Cyano, alkyl having 1 to 10 carbon atoms, haloalkoxy having 1 to 4 carbon atoms, haloalkyl having 1 to 10 carbon atoms and aryl having 6 to 20 carbon atoms. For example, the halogen atom may be fluorine (-F), and the haloalkyl group is a fluoroalkyl group having 1 to 10 carbon atoms containing a fluorine atom, and is selected from a fluoromethyl group, a perfluoroethyl group, a trifluoromethyl group, and the like. The alkyl group may be selected from methyl, ethyl, propyl, isopropyl, t-butyl, pentyl and hexyl, and the aryl group is selected from phenyl and naphthyl. More preferably, at least one hydrogen atom in the tetravalent organic group of formulae 4a to 4n may be substituted with a fluorine atom or a substituent comprising a fluorine atom such as fluoroalkyl.

Alternatively, the tetracarboxylic dianhydride may comprise a tetravalent organic group containing an aliphatic ring or an aromatic ring, wherein each ring is a rigid structure (i.e., a single ring structure), the rings are connected by a single bond, or the rings are directly connected to form a heterocyclic structure.

According to one embodiment, as a polymerization component of the polyimide, one or more diamines may be included in addition to the diamine of formula 1. For example, it may comprise a diamine comprising a divalent organic group selected from: a monocyclic or polycyclic aromatic divalent organic group having 6 to 24 carbon atoms, a monocyclic or polycyclic alicyclic divalent organic group having 6 to 18 carbon atoms, or a divalent organic group having a structure in which two or more of them are connected by a single bond or a functional group. Alternatively, it may comprise a diamine comprising a divalent organic group having an aliphatic or aromatic ring, wherein each ring is a single ring structure, each ring is fused to form a heterocyclic structure, or each ring is connected by a single bond.

For example, the diamine may comprise a divalent organic group selected from the following formulas 5a to 5 e.

[ formula 5a ]

[ formula 5b ]

[ formula 5c ]

[ formula 5d ]

[ formula 5e ]

In the formulae 5a to 5e,

R₂₁to R₂₇Each independently is a substituent selected from: halogen atoms selected from the group consisting of-F, -Cl, -Br and-I, hydroxyl groups (-OH), thiol groups (-SH), nitro groups (-NO)₂) Cyano, alkyl having 1 to 10 carbon atoms, haloalkoxy having 1 to 4 carbon atoms, haloalkyl having 1 to 10 carbon atoms and aryl having 6 to 20 carbon atoms,

A₂₁and A₂₂Each independently selected from a single bond, -O-, -CR 'R "-wherein R' and R" are each independently selected from a hydrogen atom, an alkyl group having 1 to 10 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, pentyl, etc.), and a group having 1 to 10Haloalkyl group having carbon atom (for example, trifluoromethyl group)), -C (═ O) -, -C (═ O) O-, -C (═ O) NH-, -S-, -SO ═ O)₂-、-O[CH₂CH₂O]y- (y is an integer of 1 to 44), -NH (C ═ O) NH-, -NH (C ═ O) O-, monocyclic or polycyclic cycloalkylene having 6 to 18 carbon atoms (e.g., cyclohexylene and the like), monocyclic or polycyclic arylene having 6 to 18 carbon atoms (e.g., phenylene, naphthylene, fluorenylene and the like), and combinations thereof,

b1 is an integer from 0 to 4, b2 is an integer from 0 to 6, b3 is an integer from 0 to 3, b4 and b5 are each independently an integer from 0 to 4, b7 and b8 are each independently an integer from 0 to 9, and b6 and b9 are each independently an integer from 0 to 3.

For example, the diamine may comprise a divalent organic group selected from the following formulas 6a to 6 p.

Alternatively, the diamine may comprise a divalent organic group in which an aromatic ring or an aliphatic structure forms a rigid chain structure, for example, a divalent organic group having an aliphatic ring or an aromatic ring, in which each ring is a single ring structure, each ring is connected by a single bond, or each ring is fused to form a heterocyclic structure.

According to one embodiment of the present invention, the reaction molar ratio of the acid dianhydride to the diamine may be 1:1.1 to 1.1: 1. The reaction molar ratio may vary depending on the desired reactivity and processability.

According to one embodiment of the present invention, the molar ratio of acid dianhydride to diamine may be from 1:0.98 to 0.98:1, preferably from 1:0.99 to 0.99: 1.

The reaction of the acid dianhydride with the diamine can be carried out by a conventional polymerization method of polyimide or a precursor thereof, for example, solution polymerization.

Organic solvents that may be used in the polymerization of polyamic acid may include: ketones such as gamma-butyrolactone, 1, 3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, and 4-hydroxy-4-methyl-2-pentanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene;glycol ethers (cellosolves) such as ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol diethyl ether and triethylene glycol monoethyl ether; ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, ethanol, propanol, ethylene glycol, propylene glycol, carbitol, Dimethylpropionamide (DMPA), Diethylpropionamide (DEPA), dimethylacetamide (DMAc), N-diethylacetamide, Dimethylformamide (DMF), Diethylformamide (DEF), N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), N-dimethylmethoxyacetamide, dimethyl sulfoxide, pyridine, dimethyl sulfone, hexamethylphosphoramide, tetramethylurea, N-methylcaprolactam, tetrahydrofuran, m-dimethyldiglycolAlkane, para-diAlkane, 1, 2-dimethoxyethane, bis (2-methoxyethyl) ether, 1, 2-bis (2-methoxyethoxy) ethane, bis [2- (2-methoxyethoxy)]Ether, Equamide M100, Equamide B100, or the like, and these solvents may be used alone or as a mixture of two or more.

According to one embodiment, as the organic solvent for polymerizing the polymerization component, a solvent having a positive partition coefficient (Log P) at 25 ℃ may be used. By using an organic solvent having a positive Log P, Tg can be maintained at a high temperature of 390 ℃ or higher even for a composition in which a methylphenyl silicone oligomer is contained in an amount of 10% by weight or greater.

The organic solvent having a positive partition coefficient as described above can reduce white turbidity generated by phase separation due to a polarity difference between the flexible polyimide repeating structure and other polyimide structures containing a siloxane structure such as a silicone oligomer. Conventionally, to solve the phase separation problem, two organic solvents are used. However, the present invention can reduce white turbidity due to phase separation even using one organic solvent, so that a more transparent polyimide film can be produced.

There is a method of mixing a polar solvent and a non-polar solvent to solve the above problems. However, since the polar solvent has high volatility, it may be volatilized in advance during the production process, which may cause problems such as deterioration in process reproducibility. In addition, the problem of phase separation cannot be completely solved, resulting in high haze and low transparency of the produced polyimide film.

More specifically, by using a solvent whose molecule has an amphiphilic structure, process problems caused by the use of a polar solvent can be solved. Furthermore, due to the amphiphilic molecular structure, the polyimide can be uniformly distributed even if only one solvent is used, which makes it very useful for solving problems caused by phase separation. Accordingly, a polyimide in which haze characteristics are significantly improved can be provided.

A solvent having a positive partition coefficient value means that the polarity of the solvent is hydrophobic. According to the studies of the present inventors, it was found that when a specific solvent having a positive partition coefficient value is used to prepare a polyimide precursor composition, an edge back (edge back) phenomenon is improved. Further, in the present invention, by using the solvent having a positive Log P as described above, it is possible to control the edge receding phenomenon of the solution without using an additive for controlling the surface tension of the material and the smoothness of the coating film, such as a leveling agent. Since additional additives such as additives are not used, quality problems and process problems such as the presence of low molecular substances in the final product can be eliminated, and a polyimide film having uniform characteristics can be more efficiently formed.

For example, in the process of coating the polyimide precursor composition on the glass substrate, an edge receding phenomenon may occur due to shrinkage of the coating layer during curing or under conditions in which the coating solution is allowed to stand in a humid condition. The edge receding phenomenon of the coating solution may cause variation in the film thickness. Therefore, the film may be cut or the edge of the film may be damaged at the time of cutting due to the lack of bending resistance of the film, thereby causing problems of poor process workability and reduced productivity.

Further, when a fine foreign substance having polarity is introduced into the polyimide precursor composition applied on the substrate, for the polyimide precursor composition including the polar solvent having a negative Log P, sporadic coating cracks or thickness variation may occur based on the position of the foreign substance due to the polarity of the foreign substance. In the case of using a hydrophobic solvent having a positive Log P, even when fine foreign substances having polarity are introduced, the occurrence of thickness variation due to cracking of the coating layer can be reduced or suppressed.

Specifically, in the polyimide precursor composition including a solvent having a positive Log P, the edge receding ratio defined by the following equation 1 may be 0% to 0.1% or less.

[ equation 1]

Edge receding ratio (%) [ (a-B)/a ] × 100

Wherein the content of the first and second substances,

a: the area of the polyimide precursor composition completely coated on the substrate (100mm x 100mm),

b: area after the edge receding phenomenon from the edge of the substrate on which the polyimide precursor composition or the PI film is coated.

The edge receding phenomenon of the polyimide precursor composition and the film may occur within 30 minutes after the polyimide precursor composition solution is applied, and in particular, the film may be rolled up from the edge to make the thickness of the edge thicker.

After the polyimide precursor composition according to the present invention is coated on a substrate and then left to stand in a humidity condition for 10 minutes or more (e.g., 10 minutes or more, e.g., 40 minutes or more), the edge receding ratio of the coated resin composition solution may be 0.1% or less. For example, even after standing for 10 minutes to 50 minutes at a temperature of 20 ℃ to 30 ℃ and in a humidity condition of 40% or more (more specifically, in a humidity condition in the range of 40% to 80%, i.e., in each of 40%, 50%, 60%, 70%, 80%, for example, in a humidity condition of 50%), the edge receding ratio may be 0.1% or less, preferably 0.05%, more preferably almost 0%.

After the polyimide precursor composition is coated on a substrate and then left to stand at a temperature of 20 to 30 ℃ and in a humidity condition of 40% or more (more specifically, in a humidity condition in the range of 40 to 80%, i.e., in each of 40%, 50%, 60%, 70%, 80%, for example, in a humidity condition of 50%), for 10 to 50 minutes, the edge receding ratio as described above is maintained even after curing, for example, the edge receding ratio of the coated resin composition solution is 0.1% or less. That is, even during curing by heat treatment, there may be little or no edge receding phenomenon, and specifically, the edge receding ratio may be 0.05% or less, more preferably almost 0%.

By solving such an edge receding phenomenon, the polyimide precursor composition according to the present invention can obtain a polyimide film having more uniform characteristics, thereby further improving the yield of the manufacturing process.

Furthermore, the density of the solvent according to the invention may be 1g/cm, as measured by the standard ASTM D1475³Or smaller. If the density is more than 1g/cm³The relative viscosity may increase and the process efficiency may decrease.

The solvent having a positive partition coefficient (Log P) may be at least one selected from the group consisting of N, N-diethylacetamide (DEAc), N-Diethylformamide (DEF), N-ethylpyrrolidone (NEP), Dimethylpropionamide (DMPA) and Diethylpropionamide (DEPA).

The boiling point of the solvent may be 300 ℃ or less. More specifically, the partition coefficient Log P at 25 ℃ may be from 0.01 to 3, or from 0.01 to 2, or from 0.1 to 2.

The partition coefficient may be calculated using an ACD/Log P module from the ACD/Percepta platform of ACD/Labs. The ACD/Log P module uses an algorithm based on a QSPR (Quantitative Structure-Property Relationship) method using a 2D molecular Structure.

In addition, aromatic hydrocarbons such as xylene and toluene can also be used. To facilitate the dissolution of the polymer, about 50 wt% or less of an alkali metal salt or an alkaline earth metal salt may also be added to the solvent, based on the total amount of the solvent.

Further, in the case of synthesizing a polyamic acid or polyimide, a blocking agent in which the end of a molecule is reacted with a dicarboxylic anhydride or a monoamine to block the end of the polyimide may also be added to inactivate an excess of the polyamino group or the acid anhydride group.

The reaction of the tetracarboxylic dianhydride with the diamine can be carried out by a conventional polymerization method of a polyimide precursor such as solution polymerization. Specifically, it can be prepared by: the diamine is dissolved in an organic solvent, and then tetracarboxylic dianhydride is added to the resulting mixed solution to perform polymerization.

The polymerization reaction may be carried out in a flow of inert gas or nitrogen, and may be carried out under anhydrous conditions.

The reaction temperature during the polymerization reaction may be-20 ℃ to 80 ℃, preferably 0 ℃ to 80 ℃. If the reaction temperature is too high, reactivity may become high and molecular weight may become large, and viscosity of the precursor composition may increase, which may be disadvantageous in the process.

The polyamic acid solution prepared according to the above-described manufacturing method preferably contains a solid content in an amount such that the composition has an appropriate viscosity, in view of workability such as coating characteristics during film formation.

The polyimide precursor composition including the polyamic acid may be in the form of a solution dissolved in an organic solvent. For example, when the polyimide precursor is synthesized in an organic solvent, the solution may be a reaction solution as obtained, or may be obtained by diluting the reaction solution with another solvent. When the polyimide precursor is obtained as a solid powder, it may be dissolved in an organic solvent to prepare a solution.

According to one embodiment, the content of the composition may be adjusted by adding an organic solvent such that the total polyimide precursor content is 8 to 25 wt%, preferably 10 to 25 wt%, more preferably 10 to 20 wt%.

The polyimide precursor composition may be adjusted to have a viscosity of 3,000cP or more at a solid content concentration of 20 wt% or less, and the polyimide precursor composition may be adjusted to have a viscosity of 10,000cP or less, preferably 9,000cP or less, more preferably 8,000cP or less. When the viscosity of the polyimide precursor composition is greater than 10,000cP, defoaming efficiency during processing of the polyimide film is reduced. This not only results in a decrease in the efficiency of the process, but also results in deterioration of the surface roughness of the produced film due to bubble generation. This may cause deterioration of electrical, optical, and mechanical characteristics.

Then, a polyimide precursor resulting from the polymerization reaction may be imidized by chemical imidization or thermal imidization to prepare a transparent polyimide film.

According to one embodiment, a polyimide film may be manufactured by a method including: applying a polyimide precursor composition to a substrate; and

the applied polyimide precursor composition is heated and cured.

As the substrate, a glass substrate, a metal substrate, a plastic substrate, or the like can be used without any particular limitation. Among them, a glass substrate can be preferred: which is excellent in thermal stability and chemical stability during imidization and curing processes for a polyimide precursor, and can be easily separated even without any treatment with an additional release agent, while not damaging a polyimide film formed after curing.

The application process can be carried out according to conventional application methods. Specifically, a spin coating method, a bar coating method, a roll coating method, an air knife method, a gravure printing method, a reverse roll method, a kiss roll method, a doctor blade method, a spray coating method, a dipping method, a brush coating method, or the like can be used. Among them, it is more preferable to carry out by a casting method which allows a continuous process and enables the imidization rate of polyimide to be increased.

Further, the polyimide precursor composition may be applied on the substrate in a thickness range suitable for the thickness of the display substrate so that the polyimide film to be finally produced has a thickness suitable for the substrate.

Specifically, it may be applied in an amount such that the thickness is 10 μm to 30 μm. After the polyimide precursor composition is applied, a drying process for removing a solvent remaining in the polyimide precursor composition may also be optionally performed before the curing process.

The drying process may be carried out according to a conventional method. Specifically, the drying process may be performed at a temperature of 140 ℃ or less, or 80 ℃ to 140 ℃. If the drying temperature is lower than 80 deg.C, the drying process becomes long. If the drying temperature exceeds 140 ℃, imidization rapidly proceeds, making it difficult to form a polyimide film having a uniform thickness.

The polyimide precursor composition is then applied to a substrate and heat treated in an IR oven, in a hot air oven, or on a hot plate. The heat treatment temperature may vary from 300 ℃ to 500 ℃, preferably from 320 ℃ to 480 ℃. The heat treatment may be performed in a multi-step heating process in the above temperature range. The heat treatment process may be performed for 20 minutes to 70 minutes, and preferably for 20 minutes to 60 minutes.

The residual stress immediately after curing of the polyimide film prepared as described above may be 40MPa or less, and the residual stress change after leaving the polyimide film standing at 25 ℃ and 50% humidity for 3 hours may be 5MPa or less.

The polyimide film may have a yellowness of 15 or less, and preferably 13 or less. Further, the haze of the polyimide film may be 2 or less, and preferably 1 or less.

Further, the polyimide film may have a transmittance at 450nm of 75% or more, a transmittance at 550nm of 85% or more, and a transmittance at 630nm of 90% or more.

The polyimide film may have high heat resistance, for example, a thermal decomposition temperature (Td — 1%) in which mass loss is 1% may be 500 ℃ or more.

The modulus of the polyimide film prepared as described above may be 3GPa to 6 GPa. When the modulus (elastic modulus) is less than 3GPa, the film has low rigidity and is easily broken by external impact. When the elastic modulus exceeds 6GPa, the cover film (cover film) is excellent in rigidity, but sufficient flexibility cannot be obtained.

Further, the polyimide film may have an elongation of 90% or more, preferably 91% or more, and a tensile strength of 130MPa or more, preferably 138MPa or more.

In addition, the polyimide film according to the present invention may have excellent thermal stability against temperature change. For example, after n +1 heating and cooling processes (n is an integer of at least 0) in a temperature range of 100 ℃ to 350 ℃, the coefficient of thermal expansion thereof may be-10 ppm/DEG C to 100 ppm/DEG C, preferably-7 ppm/DEG C to 90 ppm/DEG C, more preferably 80 ppm/DEG C or less.

Further, retardation (R) in the thickness direction of the polyimide film according to the present invention_th) May be-150 nm to +150nm, preferably-130 nm to +130nm, to exhibit optical isotropy to improve visual acuity.

According to one embodiment, the adhesion force of the polyimide film to the carrier substrate may be 5 gf/inch or more, and is preferably 10 gf/inch or more.

Further, the present invention provides a method for manufacturing a flexible device, the method comprising the steps of:

preparing a polyimide precursor composition;

applying a polyimide precursor composition on a carrier substrate and then heating to imidize the polyamic acid, thereby forming a polyimide film;

forming a device on the polyimide film; and

the polyimide film with the devices formed thereon is peeled off the carrier substrate.

In particular, the method of manufacturing the flexible device may include a Low Temperature Polysilicon (LTPS) method, an ITO method, or an oxide method.

For example, a flexible device comprising an LTPS layer may be obtained by: an LTPS layer is formed by an LTPS film manufacturing method, which includes: forming SiO-containing film on polyimide film₂The barrier layer of (1);

depositing an a-Si (amorphous silicon) film on the barrier layer;

performing dehydrogenation annealing by heat-treating the deposited a-Si thin film at a temperature of 450 ℃ + -50 ℃; and

the a-Si thin film is crystallized by an excimer laser or the like.

The oxide thin film method may perform the heat treatment at a lower temperature than the method using silicon, for example, the heat treatment temperature of the ITO TFT method may be 240 ℃ ± 50 ℃, and the heat treatment temperature of the oxide TFT method may be 350 ℃ ± 50 ℃.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

< preparation example 1> preparation of Compound of formula 1-1

The compound of formula a (35.0g, 166.7mmol) was dissolved in THF (270mL) under a nitrogen atmosphere and pyridine (pyr) (26.4g, 333.4mmol) was added, followed by cooling to 0 ℃. The compound of formula B (11.6g, 83.4mmol) was introduced into the solution in 4 portions at 10 minute intervals. After 3 hours, hexane (270mL) was added to give a solid. The solid obtained after filtration was washed with hexane/ethyl acetate (10/7) to prepare the compound of formula C (23.8g, 91.3% yield).

MS[M+H]⁺＝314

The compound of formula C (20g, 63.9mmol) and the compound of formula D (10.2g, 32.0mmol) were dispersed in glacial acetic acid (200mL) and heated to 100 ℃. After 4 hours, the temperature was lowered to room temperature, and then ethanol was added to obtain a solid. The solid obtained after filtration was washed with water and ethanol to prepare a compound of formula E (25.9g, yield 88.8%).

MS[M+H]⁺＝911

After dispersing the compound of formula E (20g, 22.0mmol) in NMP (N-methylpyrrolidone) (180mL), palladium on carbon (Pd/C) (0.60g) was added and stirred under a hydrogen atmosphere for 16 hours. After completion of the reaction, water (180mL) was added to the filtrate obtained after filtration to produce a solid. The solid obtained after filtration was recrystallized from NMP and ethyl acetate to prepare a compound of formula 1-1 (14.8g, yield 79.9%).

MS[M+H]⁺＝851

< preparation example 2> preparation of Compound of formula 1-2

A compound of formula G was prepared in the same manner as the method for preparing a compound of formula C, except that a compound of formula F was used instead of the compound of formula B in preparation example 1.

A compound of formula H is prepared in the same manner as the process for preparing a compound of formula E, except that a compound of formula G is used instead of a compound of formula C. Finally, the compound of formula 1-2 is prepared in the same manner as the method for preparing the compound of formula 1-1, except that the compound of formula H is used instead of the compound of formula E.

MS[M+H]⁺＝853

< preparation example 3> preparation of Compounds of formulae 1 to 9

A compound of formula J was prepared in the same manner as the method for preparing a compound of formula E, except that a compound of formula I was used instead of the compound of formula D in preparation example 1.

Compounds of formulae 1-9 are prepared in the same manner as the method for preparing compounds of formulae 1-1, except that a compound of formula J is used instead of a compound of formula E.

MS[M+H]⁺＝731

< preparation example 4> preparation of Compounds of formulae 1 to 10

A compound of formula G was prepared in the same manner as the method for preparing a compound of formula C, except that a compound of formula F was used instead of the compound of formula B in preparation example 1.

A compound of formula K is prepared in the same manner as the process for preparing a compound of formula E, except that a compound of formula G is used instead of a compound of formula C, and a compound of formula I is used instead of a compound of formula D. Finally, the compound of formula 1-10 is prepared in the same manner as the method for preparing the compound of formula 1-1, except that the compound of formula K is used instead of the compound of formula E.

MS[M+H]⁺＝733

< preparation example 5> preparation of Compounds of formulae 1 to 13

A compound of formula M was prepared in the same manner as the method for preparing a compound of formula C, except that a compound of formula L was used instead of the compound of formula B in preparation example 1.

A compound of formula O is prepared in the same manner as the process for preparing a compound of formula E, except that a compound of formula M is used instead of a compound of formula C and a compound of formula N is used instead of a compound of formula D.

Finally, the compound of formula 1-13 is prepared in the same manner as the method for preparing the compound of formula 1-1, except that the compound of formula O is used instead of the compound of formula E.

MS[M+H]⁺＝731

< preparation example 6> preparation of Compounds of formulae 1 to 14

A compound of formula Q was prepared in the same manner as the method for preparing a compound of formula C, except that a compound of formula P was used instead of the compound of formula B in preparation example 1.

A compound of formula R is prepared in the same manner as the process for preparing a compound of formula E, except that a compound of formula Q is used instead of a compound of formula C and a compound of formula N is used instead of a compound of formula D.

Finally, the compounds of formula 1-14 are prepared in the same manner as the method for preparing the compound of formula 1-1, except that the compound of formula R is used instead of the compound of formula E.

MS[M+H]⁺＝733

< preparation example 7> preparation of Compounds of formulae 1 to 15

A compound of formula M was prepared in the same manner as the method for preparing a compound of formula C, except that a compound of formula L was used instead of the compound of formula B in preparation example 1.

A compound of formula T is prepared in the same manner as the process for preparing a compound of formula E, except that a compound of formula M is used instead of a compound of formula C and a compound of formula S is used instead of a compound of formula D.

Finally, the compound of formula 1-15 is prepared in the same manner as the method for preparing the compound of formula 1-1, except that the compound of formula T is used instead of the compound of formula E.

MS[M+H]⁺＝867

< preparation example 8> preparation of Compounds of formulae 1 to 16

A compound of formula Q was prepared in the same manner as the method for preparing a compound of formula C, except that a compound of formula P was used instead of the compound of formula B in preparation example 1.

A compound of formula U is prepared in the same manner as the process for preparing a compound of formula E, except that a compound of formula Q is used instead of a compound of formula C and a compound of formula S is used instead of a compound of formula D.

Finally, compounds of formulae 1 to 16 are prepared in the same manner as the method for preparing the compound of formula 1-1, except that a compound of formula U is used instead of a compound of formula E.

MS[M+H]⁺＝869

< comparative example 1>6-FDA/TFMB

130g of DEAC (diethylacetamide) was charged into the reactor in a nitrogen stream, and then 0.0500mol of TFMB (2,2' -bis (trifluoromethyl) benzidine) was added to dissolve it while maintaining the reactor temperature at 25 ℃. To the solution to which TFMB was added, 0.0500mol of 6-FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and 40g of DEAC were added and reacted for 48 hours to obtain a polyimide precursor solution.

< example 1> 6-FDA/diamine of formula 1-1

200g of DEAC (diethylacetamide) was charged into a reactor in a nitrogen stream, and then 0.0413mol of the diamine of formula 1-1 prepared in preparation example 1 was added to dissolve it while maintaining the reactor temperature at 25 ℃. To the solution to which the diamine of formula 1-1 was added 0.0413mol of 6-FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and 60g of DEAC were added and reacted for 48 hours to obtain a polyimide precursor solution.

< example 2> 6-FDA/diamine of formula 1-2

200g of DEAC (diethylacetamide) was charged into a reactor in a nitrogen stream, and then 0.0413mol of the diamine of formula 1-2 prepared in preparation example 2 was added to dissolve it while maintaining the reactor temperature at 25 ℃. To the solution to which the diamine of formula 1-2 was added 0.0413mol of 6-FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and 60g of DEAC were added and reacted for 48 hours to obtain a polyimide precursor solution.

< example 3> 6-FDA/diamines of formulae 1-9

180g of DEAC (diethylacetamide) was charged into the reactor in a nitrogen stream, and then 0.0413mol of the diamine of formulae 1 to 9 prepared in preparation example 3 was added to dissolve it while maintaining the reactor temperature at 25 ℃. To the solution to which the diamine of the formula 1 to 9 was added 0.0413mol of 6-FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and 60g of DEAC were added and reacted for 48 hours to obtain a polyimide precursor solution.

< example 4> 6-FDA/diamines of formulae 1 to 10

180g of DEAC (diethylacetamide) was charged into the reactor in a nitrogen stream, and then 0.0413mol of the diamine of formulae 1 to 10 prepared in preparation example 4 was added to dissolve it while maintaining the reactor temperature at 25 ℃. To the solution to which the diamine of the formula 1 to 10 was added 0.0413mol of 6-FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and 60g of DEAC and reacted for 48 hours to obtain a polyimide precursor solution.

< Experimental example 1>

The viscosity of the polyimide precursor solutions prepared in examples 1 to 4 and comparative example 1 and the molecular weight of the polyamic acid were measured, and the results are shown in table 1 below.

< measurement of viscosity >

Viscosity was measured using Viscotek TDA 302.

< measurement of molecular weight >

Molecular weight was measured using Viscotek GPCmax VE 2001.

< Experimental example 2>

Each of the polyimide precursor solutions prepared in examples 1 to 4 and comparative example 1 was spin-coated on a glass substrate. The glass substrate coated with the polyimide precursor solution was put into an oven, heated at a rate of 5 ℃/min and cured at 80 ℃ for 30 minutes, cured at 250 ℃ for 30 minutes and cured at 400 ℃ for 30 to 40 minutes to prepare a polyimide film. The characteristics of each film were measured, and the results are shown in table 1 below.

< modulus (GPa), tensile strength (MPa) and elongation (%) >)

A film 5mm by 50mm long and 10 μm thick was stretched at a speed of 10 mm/min with a tensile tester (Instron 3342, manufactured by Instron) to measure modulus (GPa), tensile strength (MPa) and elongation (%).

[ Table 1]

As can be seen from the results of table 1, the polyimide precursor solution including the diamine according to the present invention may have a viscosity of 3000cPs or more at a solid content concentration of 20 wt% or less, and thus polyamic acid having a higher molecular weight was produced as compared to comparative example 1 using TFMB. Further, it can be seen that the polyimide film prepared from the polyamic acid having such a high molecular weight has improved mechanical strength as compared to the polyimide film of comparative example 1.

While the present invention has been particularly shown and described with reference to particular embodiments thereof, it will be obvious to those skilled in the art that the particular description is of a preferred embodiment only and that the scope of the invention is not limited thereby. It is intended, therefore, that the scope of the invention be defined by the claims appended hereto and their equivalents.