WO2015129780A1

WO2015129780A1 - Resin composition for display substrate, resin thin film for display substrate, and method for producing resin thin film for display substrate

Info

Publication number: WO2015129780A1
Application number: PCT/JP2015/055513
Authority: WO
Inventors: 江原　和也
Original assignee: 日産化学工業株式会社
Priority date: 2014-02-28
Filing date: 2015-02-26
Publication date: 2015-09-03
Also published as: JPWO2015129780A1; TWI659064B; CN106062037B; CN106062037A; TW201544546A; KR102312132B1; KR20160127756A; JP6780500B2

Abstract

The present invention provides a resin composition for a display substrate, with which it is possible to form a resin thin film for a display substrate that has a high heat resistance, an appropriate coefficient of linear expansion, and a high tensile strength. The resin composition for a display substrate contains a polyamic acid comprising structural units represented by formula (I) and having a weight-average molecular weight of 10,000 or more, and an organic solvent. In formula (1), X¹ represents a tetravalent aromatic group of formula (3), Y¹ represents a group represented by formula (P), and n represents a number of repeating units.

Description

Resin composition for display substrate, resin thin film for display substrate, and method for producing resin thin film for display substrate

The present invention relates to a resin composition for display substrate, a resin thin film for display substrate, and a method for producing a resin thin film for display substrate.

In recent years, in the field of display devices such as organic electroluminescence displays and liquid crystal displays, in addition to high definition, there has been an increasing demand for weight reduction and flexibility. Under such circumstances, polyimide resins, which are known to be easy to manufacture and have high heat resistance, are attracting attention as display substrate materials that replace glass.
However, to use polyimide as a display substrate material, a value close to the linear expansion coefficient of glass (about 3 to 10 ppm / K) is required, but most polyimides have a linear expansion coefficient of about 60 to 80 ppm / K. Therefore, it is not suitable for a display substrate material.

A high-definition display uses an active matrix drive panel, and high-temperature processing of about 300 to 500 ° C. is required to form an active matrix layer including thin film active elements in addition to matrix-like pixel electrodes. In addition, accurate alignment is also required. However, since polyimide is inferior to glass in terms of linear expansion coefficient characteristics, it contracts or expands more than a glass substrate at high temperatures. For this reason, when polyimide is used as a substrate material, it is often difficult to maintain high dimensional stability in the display manufacturing process.
Therefore, in order to realize a suitable linear expansion coefficient characteristic while utilizing the heat resistance of polyimide, an appropriate molecular design is required.

A polyimide composed of a highly rigid acid dianhydride and a diamine has been proposed as a polyimide exhibiting low linear expansion, but it has high linear expansion in a high temperature region (300 to 500 ° C.) near the glass transition temperature of the polymer. If the rigidity of the polymer skeleton is too high, there are many problems such as damage to the strength and flexibility of the film (Patent Document 1, Non-Patent Document 1), and those that sufficiently satisfy advanced requirements are still unknown. It is not done.

JP 2010-202729 A

Therefore, there is still a need to produce a polyimide-based resin thin film for a display substrate having a high heat resistance, an appropriate linear expansion coefficient and a high tensile strength that can be used as a display substrate material instead of glass. .

The present invention has been made in view of such circumstances, and a resin composition for a display substrate capable of forming a resin thin film for a display device substrate having high heat resistance, an appropriate linear expansion coefficient, and high tensile strength. The purpose is to provide goods.

Specifically, the present invention is mainly composed of a general-purpose acid dianhydride and a diamine, heat resistance that can withstand a display manufacturing process, appropriate flexibility, and appropriate linear expansion coefficient, particularly around 400 to 500 ° C. It aims at providing the resin composition for display substrates which can form the resin thin film which has a moderate linear expansion coefficient in.
The moderate flexibility as used herein refers to such a high flexibility that the resin thin film has a self-supporting property and does not crack even when bent at an angle of 90 degrees or an angle close thereto.

As a result of extensive investigations, the present inventors have unexpectedly found that 3,3′-4,4′-biphenyltetracarboxylic dianhydride (BPDA), p-phenylenediamine (p-PDA), and By using a resin composition containing a specific polyamic acid derived from 4,4 ″ -diamino-p-terphenyl (DATP), heat resistance necessary for the display substrate, moderate flexibility and moderate It was found that a resin thin film having a linear expansion coefficient can be obtained.The obtained resin thin film also has a high bending strength (excellent self-supporting property), and from these characteristics, it has excellent properties to replace glass. In addition to the above components, the present inventors have further found that 2- (3-aminophenyl) -5-aminobenzimid can be used as a display substrate material. The use of polyamic acid using tetrazole (APAB), also found that can further enhance these effects. The present invention is based on these findings.

Therefore, the present invention relates to the following inventions.
<1> A resin composition for a display substrate, comprising a polyamic acid having a structural unit represented by the following formula (1) and having a weight average molecular weight of 10,000 or more and an organic solvent.

[Where:
X ¹ represents a tetravalent aromatic group of the following formula (3),
Y ¹ represents a group represented by the following formula (P), and
n represents the number of repeating units:

(Where
R represents F, Cl, an alkyl group having 1 to 3 carbon atoms, or a phenyl group;
m represents an integer of 0 to 4, and
r represents an integer of 1 to 3)].

<2> In the above <1>, the structural unit represented by the formula (1) preferably has a random or block copolymer structure composed of two or more repeating units of the formula (1).

<3> In the above <1>, a polyamic acid containing structural units represented by the following formulas (1-1) and (1-2) and having a weight average molecular weight of 10,000 or more, an organic solvent, Should be included.

[Where:
X ¹ represents a tetravalent aromatic group of the above-described formula (3),
Y ² represents a group represented by the following formula (P1) or (P2),
Y ³ represents a group represented by the following formula (P3), and
n ¹ and n ² represent the number of each repeating unit:

(Where
R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ may be the same or different and each represents F, Cl, an alkyl group having 1 to 3 carbon atoms, or a phenyl group;
m1, m2, m3, m4, m5 and m6 may be the same or different and each represents an integer of 0 to 4)].

<4> In any one of the above items <1> to <3>, the polyamic acid may further include a structural unit represented by the following formula (2).

[Where:
X ¹ represents a tetravalent aromatic group of the above-described formula (3),
Y ⁴ represents a group represented by the following formula (P4), and
n ³ represents the number of repeating units:

(Where
R ⁷ and R ⁸ may be the same or different and each represents F, Cl, an alkyl group having 1 to 3 carbon atoms, or a phenyl group;
R ′ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a phenyl group, and l and m may be the same or different and each represents an integer of 0 to 4)].

<5> In the above <3> or <4>, n ¹ and n ² preferably satisfy the condition of n ¹ / n ² = 1.7 to 20.

<6> In the above item <4>, the n ¹ , n ^2, and n ³ may satisfy n ³ / (n ¹ + n ² + n ³ ) ≦ 0.2.

<7> The polyamic acid may contain at least 60 mol% of the structural unit represented by the formula (1) or the structural unit represented by the formula (1-1) and the formula (1-2). .

<8> A resin thin film for a display substrate, produced using the resin composition for a display substrate according to any one of <1> to <7>.

<9> An image display device comprising the display substrate resin thin film of <8>.

<10> A method for producing a resin thin film for a display substrate, comprising using the resin composition for a display substrate according to any one of <1> to <7>. In one preferable aspect, the method for producing a resin thin film for a display substrate includes a step of applying the resin composition for a display substrate to a substrate and heating.
<11> A method for manufacturing an image display device, comprising using the resin thin film for display substrate according to <8>.

The resin composition for a display substrate of the present invention can be produced using a versatile acid dianhydride and a versatile diamine as main components. By using this, a high heat resistance and a moderate amount can be obtained by a wet process. It is possible to obtain a resin thin film having a large area and good reproducibility that has a good flexibility and an appropriate linear expansion coefficient, particularly an appropriate linear expansion coefficient in the vicinity of 400 to 500 ° C.
Therefore, by using the resin composition for a display substrate of the present invention, it is possible not only to reduce the weight and size of the display but also to reduce the cost of the display by reducing raw material costs and improving manufacturing efficiency. Become.

Hereinafter, the present invention will be described in detail.

Resin Composition for Display Substrate The resin composition for a display substrate of the present invention is a polyamic acid containing a structural unit represented by the formula (1) as described above, and its weight average molecular weight is 10,000 or more. It contains polyamic acid and an organic solvent.

As described above, in Formula (1), X ¹ represents a tetravalent aromatic group in Formula (3), and Y ¹ represents a group represented by Formula (P).

In the formula (P), R represents F, Cl, an alkyl group having 1 to 3 carbon atoms, or a phenyl group, and preferably represents F or Cl. Similarly, in the above formula (P), m represents an integer of 0 to 4, preferably 0 to 2, more preferably 0 to 1, and particularly preferably 0. In the formula (P), r represents an integer of 1 to 3.
The alkyl group having 1 to 3 carbon atoms includes methyl, ethyl, n-propyl, and i-propyl. Preferably, the alkyl group having 1 to 3 carbon atoms is methyl, and more preferably, Methyl.

In the formula (1), n represents the number of repeating units, is a positive integer, and is determined according to the weight average molecular weight of the polyamic acid used in the present invention.

The weight average molecular weight of the polyamic acid having a repeating unit represented by the formula (1) used in the present invention needs to be 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, more More preferably, it is 30,000 or more. On the other hand, although the upper limit of the weight average molecular weight of the polyamic acid used in the present invention is usually 2,000,000 or less, it is possible to prevent the viscosity of the resin composition (varnish) from becoming excessively high or to be flexible. In consideration of obtaining a high resin thin film with good reproducibility, etc., it is preferably 1,000,000 or less, more preferably 200,000 or less.

The polyamic acid used in the present invention contains at least 50 mol%, preferably at least 60 mol%, more preferably at least 70 mol%, even more preferably at least 80 mol% of the repeating unit represented by the formula (1). Preferably it contains at least 90 mol%. By using polyamic acid in such an amount, a resin thin film having characteristics suitable for a display substrate can be obtained with good reproducibility.

According to a preferred embodiment of the present invention, the polyamic acid is a copolymer only from the repeating unit represented by the formula (1), that is, a polymer containing 100 mol% of these repeating units. At this time, the structural unit represented by the formula (1) in this polyamic acid is not composed of only one specific type of the repeating units represented by the formula (1), but two or more types of the formula (1 It is preferable to have a random or block copolymer structure by repeating units. The type of the repeating unit of the formula (1) that can be used is more preferably 2 to 4, and further preferably 2 to 3.

According to a preferred embodiment of the present invention, the resin composition for display substrate of the present invention is a polyamic acid containing structural units represented by the formulas (1-1) and (1-2) as described above. And a polyamic acid having a weight average molecular weight of 10,000 or more and an organic solvent.

Further, as described above, in the formulas (1-1) and (1-2), X ¹ represents a tetravalent aromatic group of the formula (3), and Y ² represents the formula (P1 ) Or (P2), preferably a group represented by formula (P1), and Y ³ represents a group represented by formula (P3).

In the formula (P1), formula (P2) and formula (P3), R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ may be the same or different, and F, Cl Represents an alkyl group having 1 to 3 carbon atoms, or a phenyl group, and preferably represents F or Cl.
Similarly, in the above formula (P), m1, m2, m3, m4, m5 and m6 may be the same or different and each represents an integer of 0 to 4, preferably 0 to 2, More preferably, it represents 0 to 1, particularly preferably 0.

In Formula (1-1) and Formula (1-2), n ¹ and n ² indicate the number of each repeating unit, and satisfy the condition of n ¹ / n ² = 1.7 to 20. Here, the lower limit value of the numerical range of n ¹ / n ² is preferably 2.1, more preferably 2.2, and even more preferably 2.3. On the other hand, the upper limit of the numerical range of n ¹ / n ² is preferably 19, and more preferably 18.

Considering that a resin thin film having an appropriate linear expansion coefficient, heat resistance, and flexibility (particularly tensile strength) can be obtained with good reproducibility, n ¹ / n ² preferably satisfies 2.1 to 7.5, It is more preferable to satisfy 2.1 to 6.8, even more preferable to satisfy 3.2 to 6.0, and even more preferable to satisfy 3.2 to 5.1.

The polyamic acid used in the present invention contains at least 50 mol%, preferably at least 60 mol%, more preferably at least 70 mol%, of repeating units represented by formulas (1-1) and (1-2). More preferably, it contains at least 80 mol%, more preferably at least 90 mol%. By using polyamic acid in such an amount, a resin thin film having characteristics suitable for a display substrate can be obtained with good reproducibility.

According to a particularly preferred embodiment of the present invention, the polyamic acid is a copolymer comprising only the repeating units represented by the formulas (1-1) and (1-2), that is, these repeating units are contained in 100 mol%. It is a polymer.

The weight average molecular weight of the polyamic acid used in the present invention needs to be 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, and even more preferably 30,000 or more. On the other hand, although the upper limit of the weight average molecular weight of the polyamic acid used in the present invention is usually 2,000,000 or less, it is possible to prevent the viscosity of the resin composition (varnish) from becoming excessively high or to be flexible. In consideration of obtaining a high resin thin film with good reproducibility, etc., it is preferably 1,000,000 or less, more preferably 200,000 or less.

According to a more preferred embodiment of the present invention, the polyamic acid used in the present invention can further contain a structural unit represented by the formula (2).

As described above, in Formula (2), X ¹ represents a tetravalent aromatic group of Formula (3), Y ⁴ represents a group represented by Formula (P4), and , N ³ represents the number of each repeating unit.

In the formula (P4), R ⁷ and R ⁸ may be the same or different and each represents F, Cl, an alkyl group having 1 to 3 carbon atoms, or a phenyl group. R ⁷ preferably represents F or Cl. R ⁸ preferably represents F or Cl.
R ′ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a phenyl group, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom.
Further, l and m may be the same or different and each represents an integer of 0 to 4, preferably 0 to 2, more preferably 0 to 1, and particularly preferably 0.

When the structural unit represented by the formula (2) is used in addition to the structural unit represented by the formula (1), n and n ³ are preferably n ³ / (n + n ³ ) ≦ 0.2, It preferably satisfies n ³ / (n + n ³ ) ≦ 0.1, and more preferably satisfies n ³ / (n + n ³ ) ≦ 0.05. Within such a range, it is advantageous for obtaining a resin thin film having an appropriate linear expansion coefficient, heat resistance, and flexibility (particularly tensile strength) with good reproducibility.

When the structural unit represented by the formula (2) is used in addition to the structural unit represented by the formula (1-1) and the formula (1-2), n ¹ , n ² , and n ³ are each repeated The number of units, preferably n ³ / (n ¹ + n ² + n ³ ) ≦ 0.2, more preferably n ³ / (n ¹ + n ² + n ³ ) ≦ 0.1, even more preferably n ³ / (N ¹ + n ² + n ³ ) ≦ 0.05 is satisfied. Within such a range, it is advantageous for obtaining a resin thin film having an appropriate linear expansion coefficient, heat resistance, and flexibility (particularly tensile strength) with good reproducibility.

The polyamic acid used in the present invention is not limited to the structural unit represented by the formula (1) or the structural units represented by the formula (1-1) and the formula (1-2). ) May be included. The content of such other structural units needs to be less than 50 mol%, preferably less than 40 mol%, more preferably less than 30 mol%, and less than 20 mol%. Is more preferable, and it is further more preferable that it is less than 10 mol%.

Such other structural units include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2-methyl-1,4-phenylenediamine, 5-methyl-1,3-phenylenediamine, and 4-methyl. -1,3-phenylenediamine, 2- (trifluoromethyl) -1,4-phenylenediamine, 2- (trifluoromethyl) -1,3-phenylenediamine and 4- (trifluoromethyl) -1,3- Phenylenediamine, benzidine, 2,2'-dimethylbenzidine, 3,3'-dimethylbenzidine, 2,3'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, 3,3'-bis (tri Fluoromethyl) benzidine, 2,3′-bis (trifluoromethyl) benzidine, 4,4′-diphenylamine 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-diaminobenzanilide, 5-amino-2- (3-aminophenyl) -1H-benzimidazole, 9,9-bis (4 Diamines such as -aminophenyl) fluorene and pyromellitic anhydride (PMDA), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3 ', 4 And a structure derived from an acid dianhydride such as 4,4′-benzophenonetetracarboxylic anhydride.

According to a preferred embodiment of the present invention, the polyamic acid used in the present invention is a 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) (formula (4)) as an acid dianhydride. It can be obtained by reacting p-phenylenediamine (pPDA) (formula (5)) and 4,4 ″ -diamino-p-terphenyl (DATP) (formula (6)) as a diamine.

In the above reaction, it consists of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), p-phenylenediamine (pPDA) and 4,4 ″ -diamino-p-terphenyl (DATP). The charging ratio (molar ratio) of the diamine can be appropriately set in consideration of the molecular weight of the desired polyamic acid, the proportion of the structural unit, and the like. However, with respect to the amine component 1, BPDA0 which is usually an acid anhydride component 0.7 to 1.3, preferably about 0.8 to 1.2.

On the other hand, the charge ratio of pPDA and DATP, which is a diamine, can be set such that the substance amount (m ¹ ) of pPDA is usually about 1.7 to 20 when the substance amount (m ² ) of DATP is ^1. However, it is preferably 2.1 to 20, more preferably 2.2 to 20, still more preferably 2.3 to 19, and still more preferably 2.3 to 18. That is, m ¹ and m ² are usually m ¹ / m ² = 1.7 to 20, preferably 2.1 to 20, more preferably 2.2 to 20, and still more preferably It is 2.3 to 19, more preferably 2.3 to 18.

According to a more preferred embodiment of the present invention, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) as acid dianhydride and p-phenylenediamine (pPDA) as diamine and It can be obtained by reacting 4,4 ″ -diamino-p-terphenyl (DATP) with 2- (3-aminophenyl) -5-aminobenzimidazole (APAB) (formula (7)). .

In the above reaction, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), p-phenylenediamine (pPDA), 4,4 ″ -diamino-p-terphenyl (DATP) and 2 The charging ratio (molar ratio) of the diamine composed of-(3-aminophenyl) -5-aminobenzimidazole (APAB) can be appropriately set in consideration of the molecular weight of the desired polyamic acid, the proportion of structural units, and the like. However, with respect to the amine component 1, the BPDA, which is an acid anhydride component, can usually be about 0.7 to 1.3, preferably about 0.8 to 1.2.

On the other hand, the charge ratio of the diamines pPDA, DATP, and APAB is ¹ when the sum of the substance amount of pPDA (m ¹ ), the substance amount of DATP (m ² ), and the substance amount of APAB (m ³ ) is 1. The amount of APAB (m ³ ) is preferably 0.2 or less, more preferably 0.1 or less, and even more preferably 0.05 or less. That is, m ¹ , m ² and m ³ are preferably m ³ / (
m ¹ + m ² + m ³ ) ≦ 0.2, more preferably m ³ / (m ¹ + m ² + m ³ ) ≦ 0.1, and even more preferably m ³ / (m ¹ + m ² + m ³ ) ≦ 0. .05 is satisfied.

The reaction described above is preferably carried out in a solvent. When a solvent is used, various solvents can be used as long as they do not adversely affect the reaction.
Specific examples include m-cresol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide. 3-methoxy-N, N-dimethylpropylamide, 3-ethoxy-N, N-dimethylpropylamide, 3-propoxy-N, N-dimethylpropylamide, 3-isopropoxy-N, N-dimethylpropylamide, Protic solvents such as 3-butoxy-N, N-dimethylpropylamide, 3-sec-butoxy-N, N-dimethylpropylamide, 3-tert-butoxy-N, N-dimethylpropylamide, γ-butyrolactone, etc. Can be mentioned. You may use these individually or in combination of 2 or more types.

The reaction temperature may be appropriately set in the range from the melting point to the boiling point of the solvent to be used, and is usually about 0 to 100 ° C. However, it prevents imidation of the resulting polyamic acid and maintains a high content of polyamic acid units. Therefore, it is preferably about 0 to 70 ° C, more preferably about 0 to 60 ° C, and still more preferably about 0 to 50 ° C.
Although the reaction time depends on the reaction temperature and the reactivity of the raw material, it cannot be defined unconditionally, but is usually about 1 to 100 hours.

By the method described above, a target reaction solution containing polyamic acid can be obtained.

In the present invention, usually, after filtering the reaction solution, the filtrate is used as it is, or diluted or concentrated, and used as a resin composition (varnish) for a display substrate. By doing in this way, not only the contamination of the impurity which can cause the deterioration of the heat resistance of the resin thin film obtained, flexibility, or a linear expansion coefficient characteristic can be reduced, but a composition can be obtained efficiently.
The solvent used for dilution and concentration is not particularly limited, and examples thereof include those similar to the specific examples of the reaction solvent in the above reaction, and these may be used alone or in combination of two or more. .

Among these, considering that a highly flat resin thin film can be obtained with good reproducibility, the solvents used are N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3 -Dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone and γ-butyrolactone are preferred.

In the present invention, after the polyamic acid is isolated by post-treatment of the reaction solution according to a conventional method, a varnish obtained by dissolving or dispersing the isolated polyamic acid in a solvent is used as a resin composition for a display substrate. You may use as a thing. In this case, considering that a thin film having high flatness can be obtained with good reproducibility, it is preferable that the polyamic acid is dissolved in a solvent. The solvent used for dissolution and dispersion is not particularly limited, and examples thereof include the same specific examples of the reaction solvent for the above reaction, and these may be used alone or in combination of two or more. .

The concentration of the polyamic acid with respect to the total mass of the varnish is appropriately set in consideration of the thickness of the thin film to be produced, the varnish viscosity, etc., but is usually about 0.5 to 30% by mass, preferably about 5 to 25% by mass. is there.

Further, the viscosity of the varnish is appropriately set in consideration of the thickness of the thin film to be produced. However, in particular, when the purpose is to obtain a resin thin film having a thickness of about 5 to 50 μm with good reproducibility, it is usually at 25 ° C. It is about 500 to 50,000 mPa · s, preferably about 1,000 to 20,000 mPa · s.
Here, the viscosity of the varnish can be measured using a commercially available liquid viscosity measuring viscometer with reference to the procedure described in JIS K7117-2, for example, under the condition of a varnish temperature of 25 ° C. . Preferably, a conical plate type (cone plate type) rotational viscometer is used as the viscometer, and preferably a 1 ° 34 ′ × R24 is used as a standard cone rotor in the same type viscometer, and the varnish temperature is 25 ° C. It can be measured under conditions. An example of such a rotational viscometer is TVE-25H manufactured by Toki Sangyo Co., Ltd.

By applying the resin composition for display substrates of the present invention described above to a substrate and heating, a resin thin film made of polyimide having high heat resistance, appropriate flexibility, and appropriate linear expansion coefficient is obtained. Can do.

As the substrate (substrate), for example, plastic (polycarbonate, polymethacrylate, polystyrene, polyester, polyolefin, epoxy, melamine, triacetyl cellulose, ABS, AS, norbornene resin, etc.), metal (silicon wafer, etc.), wood, Examples include paper, glass, and slate.

The coating method is not particularly limited, but for example, cast coating method, spin coating method, blade coating method, dip coating method, roll coating method, bar coating method, die coating method, ink jet method, printing method (letter plate) , Intaglio, lithographic, screen printing, etc.).

In addition, as a method for imidizing the polyamic acid contained in the resin composition for display substrates of the present invention, thermal imidization in which the resin composition coated on the substrate is heated as it is, and a catalyst is added to the resin composition. Heating catalytic imidization is mentioned.

In the catalyst imidization of polyamic acid, a catalyst is added to the resin composition of the present invention, the catalyst-added resin composition is adjusted by stirring, and then applied to a substrate and heated to obtain a resin thin film. The amount of the catalyst is 0.1 to 30 mol times, preferably 1 to 20 mol times of the amic acid group. Further, acetic anhydride and the like can be added as a dehydrating agent to the catalyst-added resin composition, and the amount thereof is 1 to 50 mol times, preferably 3 to 30 mol times the amic acid group.

A tertiary amine is preferably used as the imidization catalyst. As the tertiary amine, pyridine, substituted pyridines, imidazole, substituted imidazoles, picoline, quinoline, isoquinoline and the like are preferable.

The heating temperature during thermal imidization and catalyst imidation is preferably 450 ° C. or lower. If it exceeds 450 ° C., the resulting resin thin film becomes brittle, and a resin thin film suitable for display substrate use may not be obtained.
Further, considering the heat resistance and linear expansion coefficient characteristics of the resin thin film obtained, the applied resin composition is heated at 50 ° C. to 100 ° C. for 5 minutes to 2 hours, and then the heating temperature is gradually increased as it is. In particular, it is desirable to heat at over 375 ° C. to 450 ° C. for 30 minutes to 4 hours.
In particular, the applied resin composition is heated at 50 ° C. to 100 ° C. for 5 minutes to 2 hours, then over 100 ° C. to 200 ° C. for 5 minutes to 2 hours, and then over 200 ° C. to 375 ° C. for 5 minutes to 2 hours. Heating is preferably performed for a time, and finally at a temperature exceeding 375 ° C. to 450 ° C. for 30 minutes to 4 hours.
Examples of the appliance used for heating include a hot plate and an oven. The heating atmosphere may be under air or under an inert gas, and may be under normal pressure or under reduced pressure.

The thickness of the resin thin film is usually about 1 to 60 μm, preferably about 5 to 50 μm, particularly when used as a substrate for a flexible display. The thickness of the coating film before heating is adjusted to obtain a resin having a desired thickness. A thin film is formed.

The resin thin film described above satisfies the various conditions necessary for a base film of a flexible display substrate, and is optimal for use as a base film of a flexible display substrate.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[1] Abbreviations used in the examples The abbreviations used in the examples are as follows.
<Solvents>
NMP: N-methyl-2-pyrrolidone <Amines>
p-PDA: p-phenylenediamine APAB: 2- (3-aminophenyl) -5-aminobenzimidazole DATP: 4,4 "-diamino-p-terphenyl BABP: bis (4-aminophenoxy) benzophenone DABA: N -(4-Aminophenyl) -4-aminobenzamide <Acid dianhydride>
BPDA: 3,3′-4,4′-biphenyltetracarboxylic dianhydride TAHQ: p-phenylenebis (trimellitic acid monoester anhydride)
PMDA: pyromellitic dianhydride NTCDA: naphthalene-1,4,5,8-tetracarboxylic dianhydride

[2] Measurement of number average molecular weight and weight average molecular weight The weight average molecular weight (hereinafter abbreviated as Mw) and molecular weight distribution (Mw / Mn) of the polymer are GPC devices manufactured by JASCO Corporation (Shodex ™ columns KF803L and KF805L). Was used to measure dimethylformamide as an elution solvent at a flow rate of 1 ml / min and a column temperature of 50 ° C. In addition, Mw was made into the polystyrene conversion value. Here, Mn is an abbreviation for number average molecular weight.

[3] Preparation of resin composition for display substrate (synthesis of polyamic acid)
<Example 1: Synthesis of polyamic acid (P1)>
BPDA (98) // p-PDA (90) / DATP (5) / APAB (5)
17.8 g (0.165 mol) of p-PDA, 2.38 g (0.009 mol) of DATP, and 2.05 g (0.009 mol) of APABI were dissolved in 420 g of NMP, and 52.8 g (0.179) of BPDA. MMP) was added at the same time, 5 g of NMP was added again, and the mixture was reacted at 23 ° C. for 24 hours under a nitrogen atmosphere.
The weight average molecular weight (Mw) of the obtained polymer was 63800, and the molecular weight distribution (Mw / Mn) was 11.3. This solution was used as a resin composition for display substrates.

<Example 2: Synthesis of polyamic acid (P2)>
BPDA (98) // p-PDA (70) / DATP (25) / APAB (5)
12.9 g (0.119 mol) of p-PDA, 11.1 g (0.043 mol) of DATP, and 1.90 g (0.009 mol) of APABI were dissolved in 420 g of NMP, and 49.1 g (0.167 mol) of BPDA. ) Was added at the same time, 5 g of NMP was added again, and the mixture was reacted at 23 ° C. for 24 hours in a nitrogen atmosphere.
Mw of the obtained polymer was 65500, and molecular weight distribution (Mw / Mn) was 12.8. This solution was used as a resin composition for display substrates.

<Example 3: Synthesis of polyamic acid (P3)>
BPDA (98) // p-PDA (70) / DATP (30)
12.8 g (0.119 mol) of p-PDA and 13.2 g (0.051 mol) of DATP were dissolved in 420 g of NMP, 48.9 g (0.167 mol) of BPDA was added simultaneously, and 5 g of NMP was again added. The mixture was added and reacted at 23 ° C. for 24 hours under a nitrogen atmosphere.
Mw of the obtained polymer was 66300, and molecular weight distribution (Mw / Mn) was 12.9. This solution was used as a resin composition for display substrates.

<Comparative Example 1: Synthesis of polyamic acid (HP1)>
TAHQ // p-PDA
p-PDA (2.33 g, 0.022 mol) was dissolved in NMP (700 g), TAHQ (9.67 g, 0.021 mol) was added, NMP (88 g) was added again, and nitrogen atmosphere was added at 23 ° C. for 24 hours. Reacted.
Mw of the obtained polymer was 75200, and molecular weight distribution (Mw / Mn) was 2.6. This solution was used as a resin composition for display substrates.

<Comparative Example 2: Synthesis of polyamic acid (HP2)>
BPDA // DATP
DATP (7.11 g, 0.027 mol) and p-PDA (7.88 g, 0.027 mol) were dissolved in NMP (85 g), and BPDA (7.88 g, 0.027 mol) was added. The reaction was carried out at 24 ° C for 24 hours.
Mw of the obtained polymer was 70700, and molecular weight distribution (Mw / Mn) was 9.7. This solution was used as a resin composition for display substrates.

<Comparative Example 3: Synthesis of polyamic acid (HP3)>
BPDA // p-PDA
4.09 g (0.004 mol) of p-PDA was dissolved in 85 g of NMP, and 10.9 g (0.037 mol) of BPDA was added, followed by reaction at 23 ° C. for 24 hours in a nitrogen atmosphere.
Mw of the obtained polymer was 65000, and molecular weight distribution (Mw / Mn) was 2.3. This solution was used as a resin composition for display substrates.

<Comparative Example 4: Synthesis of polyamic acid (HP4)>
PMDA // p-PDA
8.23 g (0.031 mol) of p-PDA was dissolved in 85 g of NMP, 6.76 g (0.031 mol) of PMDA was added, and the mixture was reacted at 23 ° C. for 24 hours under a nitrogen atmosphere.
Mw of the obtained polymer was 45000 and molecular weight distribution (Mw / Mn) was 10.6. This solution was used as a resin composition for display substrates.

<Comparative Example 5: Synthesis of polyamic acid (HP5)>
BPDA / NTCDA // p-PDA / DBAB / BABP
3.07 g (0.029 mol) of p-PDA, 0.27 g (0.001 mol) of DABA, and 0.12 g (0.0003 mol) of BABP were dissolved in 88 g of NMP, and 7.73 g (0.026 g) of BPDA was dissolved. Mol) and 0.80 g (0.003 mol) of NTCDA were added, followed by reaction at 23 ° C. for 24 hours in a nitrogen atmosphere.
Mw of the obtained polymer was 57000, and molecular weight distribution (Mw / Mn) was 9.3. This solution was used as a resin composition for display substrates.

[3] Preparation and evaluation of resin thin film for display substrate (Preparation and evaluation of polyimide film)
<Pre-cure film thickness>
Each of the prepared polyamic acids was applied onto a 100 mm × 100 mm glass substrate using a bar coater, and the oven was heated at a temperature of 10 degrees / minute 120 degrees 10 minutes, 300 degrees 60 minutes, 450 degrees, 60 minutes. Was fired to obtain a film.
The film thickness of the obtained coating film was measured using a contact-type film thickness measuring device (Dektak 3ST manufactured by ULVAC, Inc.).
The results obtained are listed in Table 1.
Thereafter, the glass substrate was allowed to stand in 70-degree pure water in a 1 L beaker, and the film was peeled off.

<Linear expansion coefficient>
A strip of 20 mm × 5 mm was prepared from the film obtained above, and the linear expansion coefficient from 50 degrees to 500 degrees was measured using TMA-4000SA (manufactured by Bruker AXS Co., Ltd.).
The results obtained are listed in Table 1.

<Weight reduction>
A strip of 20 mm × 3 mm was prepared from the film obtained above, and the weight loss from 50 degrees to 600 degrees was measured using TGA-DTA-2000SR (Bruker AXS Co., Ltd.) A weight loss of 5% was confirmed.
The results obtained are listed in Table 1.
In addition, when not reducing 5% weight at 600 degrees, “600 degrees>” is described in the table.
From the results, it was found that the resin thin film according to the present invention has excellent heat resistance.

<Self-supporting>
The film obtained above was bent at 90 ° or more, and the self-supporting property was evaluated according to the following evaluation criteria.
The results obtained are listed in Table 1.
From the results, it was found that the resin thin film according to the present invention has good flexibility and high flexibility that does not break even when bent at an angle of 90 degrees or close thereto.

[Evaluation criteria]
○: Self-supporting. △: Self-supporting, but breaks when bent ×: No self-supporting ××: Decomposes on substrate

Claims

The resin composition for display substrates containing the polyamic acid which contains the structural unit represented by following formula (1), and whose weight average molecular weight is 10,000 or more, and an organic solvent.

[Where:
X 1 represents a tetravalent aromatic group of the following formula (3),
Y 1 represents a group represented by the following formula (P), and
n represents the number of repeating units:

(Where
R represents F, Cl, an alkyl group having 1 to 3 carbon atoms, or a phenyl group;
m represents an integer of 0 to 4, and
r represents an integer of 1 to 3)].
The resin composition for display substrates according to claim 1, wherein the structural unit represented by the formula (1) has a random or block copolymer structure composed of two or more repeating units of the formula (1).
The polyamic acid comprising a structural unit represented by the following formula (1-1) and formula (1-2), having a weight average molecular weight of 10,000 or more, and an organic solvent: Resin composition for display substrate.

[Where:
X 1 represents a tetravalent aromatic group of the above-described formula (3),
Y 2 represents a group represented by the following formula (P1) or (P2),
Y 3 represents a group represented by the following formula (P3), and
n 1 and n 2 represent the number of each repeating unit:

(Where
R 1 , R 2 , R 3 , R 4 , R 5 and R 6 may be the same or different and each represents F, Cl, an alkyl group having 1 to 3 carbon atoms, or a phenyl group;
m1, m2, m3, m4, m5 and m6 may be the same or different and each represents an integer of 0 to 4)].
The resin composition for a display substrate according to any one of claims 1 to 3, wherein the polyamic acid further comprises a structural unit represented by the following formula (2).

[Where:
X 1 represents a tetravalent aromatic group of the above-described formula (3),
Y 4 represents a group represented by the following formula (P4), and
n 3 represents the number of repeating units:

(Where
R 7 and R 8 may be the same or different and each represents F, Cl, an alkyl group having 1 to 3 carbon atoms, or a phenyl group;
R ′ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a phenyl group, and l and m may be the same or different and each represents an integer of 0 to 4)].
5. The resin composition for a display substrate according to claim 3, wherein n 1 and n 2 satisfy a condition of n 1 / n 2 = 1.7 to 20.
The resin composition for a display substrate according to claim 4, wherein the n 1 , n 2, and n 3 satisfy n 3 / (n 1 + n 2 + n 3 ) ≦ 0.2.
The polyamic acid contains at least 60 mol% of the structural unit represented by the formula (1) or the structural unit represented by the formula (1-1) and the formula (1-2). The resin composition for display substrates as described in any one of these.
A resin thin film for a display substrate produced using the resin composition for a display substrate according to any one of claims 1 to 7.
An image display device comprising the resin thin film for a display substrate according to claim 8.
A method for producing a resin thin film for a display substrate, comprising using the resin composition for a display substrate according to any one of claims 1 to 7.
A method for manufacturing an image display device, comprising using the resin thin film for a display substrate according to claim 8.