KR20160019466A - Resin composition for display substrates, resin thin film for display substrates, and method for producing resin thin film for display substrates - Google Patents

Abstract

The present invention provides a resin composition for a display substrate capable of forming a resin thin film for a display substrate having a high heat resistance, a suitable linear expansion coefficient and a high tensile strength. Of the present invention is the formula (1-1) and (1-2): wherein, Ar ¹ represents a group of the formula ^(2), Ar 2 represents a group of formula ^(3), Ar 3 is the formula (4) And n ¹ and n ² each represent the number of each repeating unit, and satisfy the following condition: n ¹ / n ² = 1.7 to 8.2]. The polyamic acid contains at least 50 mol% The above problems are solved by a resin composition for a display substrate containing a polyamic acid having a molecular weight of 5,000 or more.

Description

TECHNICAL FIELD [0001] The present invention relates to a resin composition for a display substrate, a resin thin film for a display substrate, and a method for producing a resin thin film for a display substrate,

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

2. Description of the Related Art In recent years, in the field of display devices such as organic electroluminescence displays and liquid crystal displays, demands for lighter weight, more flexible, and the like have been increased in addition to high definition. Under such circumstances, a polyimide resin that is easy to manufacture and known to have high heat resistance has attracted attention as a substrate material for a display to replace glass.

However, in order to use polyimide as a material for a display substrate, a value close to that of glass is required to be close to that of glass (about 3 to 8 ppm / K), but most of the polyimide has a linear expansion of about 60 to 80 ppm / K And is not suitable for the substrate material of the display.

An active matrix drive panel is used for the fixed three displays. In addition to the pixel electrodes on the matrix, when forming the active matrix layer including the thin film active elements, a high temperature treatment of about 300 to 500 DEG C is required, It becomes necessary. However, polyimide shrinks or expands more than the glass substrate at high temperature because it strikes glass in terms of the coefficient of linear expansion coefficient. Therefore, when polyimide is used as a substrate material, it has a high dimensional stability It is often difficult to maintain

Therefore, proper molecular design is required in order to realize the preferable coefficient of linear expansion while making good the heat resistance of the polyimide.

Polyimide having a high linear rigidity and a diamine is proposed as a polyimide exhibiting low linear expansion property. However, it has a high linear expansion property in a high temperature region (300 to 500 占 폚) near the glass transition temperature of the polymer, When the rigidity of the skeleton is excessively high, there are many problems such that the strength and flexibility of the film are impaired (Patent Document 1, Non-Patent Document 1), and it is still unknown that the film satisfies the high requirements.

Japanese Laid-Open Patent Publication No. 2010-202729

 Journal of Applied Polymer Science, Vol. 62, 2303-2310 (1996)

Therefore, it is still desired to produce a polyimide-based resin thin film for a display substrate which has high heat resistance, suitable linear expansion coefficient and high tensile strength, which can be a substrate material for a display to replace glass.

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

More particularly, the present invention relates to a composition comprising a general dianhydride and a diamine as main components and having heat resistance capable of withstanding the manufacturing process of the display, a suitable flexibility and an appropriate linear expansion coefficient, particularly a linear coefficient of linear expansion Which is capable of forming a resin thin film having a low refractive index and a low refractive index.

The suitable flexibility referred to herein means a degree of flexibility that the resin thin film has self-supporting property and is not cracked even when bent at an angle of 90 degrees or the like.

The inventors of the present invention have conducted intensive studies, and as a result, unexpectedly, the inventors of the present invention have found that, unexpectedly, pyramidal acid anhydrides (PMDA), p-phenylenediamine (pPDA), and 4,4'-diamino- A resin thin film having required heat resistance, suitable flexibility and appropriate coefficient of linear expansion can be obtained by using a resin composition containing a specific polyamic acid. It was also found that the resulting resin thin film also had a high tensile strength and could be a substrate material for a display having excellent properties to replace glass from these characteristics. The present invention is based on these findings.

Therefore, the present invention relates to the following invention.

<1> A resin composition for a display substrate comprising a polyamic acid having a weight average molecular weight of 5000 or more as a polyamic acid containing at least 50 mol% of structural units represented by the following formulas (1-1) and (1-2).

[Chemical Formula 1]

[Wherein,

Ar ¹ represents a divalent group represented by the following formula (2)

Ar ² represents a divalent group represented by the following formula (3)

Ar ³ represents a tetravalent group represented by the following formula (4), and

n ¹ and n ² represent the number of each repeating unit and satisfy the condition of n ¹ / n ² = 1.7 to 8.2].

(2)

<2> In the above-mentioned <1>, it is preferable that n ¹ and n ² in the formula (1-1) and the formula (1-2) satisfy the condition of n ¹ / n ² = 1.5 to 6.0.

<3> The polyamic acid according to any one of <1> and <2>, wherein the polyamic acid contains at least 80 mol% of structural units represented by formulas (1-1) and (1-2).

<4> It is preferable that any one of the above-mentioned <1> to <3>, wherein the resin composition for a display substrate is dissolved in a solvent.

&Lt; 5 &gt; A resin thin film for a display substrate produced using the resin composition for a display substrate according to any one of &lt; 1 &gt; to &lt; 4.

&Lt; 6 &gt; An image display device comprising the resin thin film for a display substrate of the above-mentioned &lt; 5 &gt;.

&Lt; 7 &gt; A method for producing a resin thin film for a display substrate, wherein the resin composition for a display substrate according to any one of &lt; 1 &gt; In one preferred embodiment, 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 then heating.

&Lt; 8 &gt; A method for manufacturing an image display apparatus, characterized by using the resin thin film for a display substrate according to &lt; 5 &gt;.

INDUSTRIAL APPLICABILITY The resin composition for a display substrate of the present invention can be produced using a general-purpose acid dianhydride and a general-purpose diamine as a main component, and by using such a resin composition, it is possible to provide a resin composition for a display substrate having a high heat resistance, a suitable flexibility and a suitable linear expansion coefficient A resin thin film having an appropriate coefficient of linear expansion in the vicinity of 400 to 500 DEG C can be obtained with good reproducibility over a large area.

Therefore, by using the resin composition for a display substrate of the present invention, it is possible not only to make the display light-weight and compact, but also to reduce the raw material cost and the display cost by improving the manufacturing efficiency

Hereinafter, the present invention will be described in detail.

Resin composition for display substrate

As described above, the resin composition for a display substrate of the present invention is a polyamic acid containing at least 50 mol% of structural units represented by the formulas (1-1) and (1-2) and having a weight average molecular weight of 5000 or more It contains polyamic acid.

As described above, in the formulas (1-1) and (1-2), Ar ¹ represents a divalent group represented by the formula (2), Ar ² represents a divalent group represented by the formula (3) Ar ³ represents a tetravalent group represented by the formula (4).

In the formulas (1-1) and (1-2), n ¹ and n ² represent the number of each repeating unit and satisfy the condition of n ¹ / n ² = 1.7 to 8.2. Here, the lower limit of the numerical range of n ¹ / n ² is preferably 2.1, more preferably 3.2. On the other hand, the upper limit of the numerical range of n ¹ / n ² is preferably 7.5, more preferably 6.8, even more preferably 6.0, still more preferably 5.1.

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

The polyamic acid to be used in the present invention contains at least 50 mol%, preferably at least 60 mol%, more preferably at least 70 mol%, and more preferably at least 50 mol% of repeating units represented by the formulas (1-1) Preferably 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 from only the repeating units represented by the formulas (1-1) and (1-2), that is, a polymer containing these repeating units in an amount of 100 mol%.

The weight average molecular weight of the polyamic acid used in the present invention should be 5000 or more, preferably 10,000 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 preferable to suppress the excessively high viscosity of the resin composition (varnish), to obtain a resin thin film with high flexibility with good reproducibility Considering this, it is preferably 1,000,000 or less, and more preferably 200,000 or less.

The polyamic acid used in the present invention may contain other structural units (repeating units) in addition to the structural units represented by formulas (1-1) and (1-2). The content of such another structural unit should be less than 50 mol%, preferably less than 40 mol%, more preferably less than 30 mol%, even more preferably less than 20 mol%, further preferably less than 10 mol% Do.

Examples of such other structural units include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2-methyl-1,4-phenylenediamine, Phenylenediamine, 2- (trifluoromethyl) -1,4-phenylenediamine, 2- (trifluoromethyl) -1,3-phenylenediamine and 4- (tri Dimethylbenzidine, 2,3'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) -1,3-phenylenediamine, benzidine, 2,2'-dimethylbenzidine, ) Benzidine, 3,3'-bis (trifluoromethyl) benzidine, 2,3'-bis (trifluoromethyl) benzidine, 4,4'- Phenoxy) biphenyl, 4,4'-diaminobenzanilide, 5-amino-2- (3-aminophenyl) -1H-benzoimidazole and 9,9-bis Diamine, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride, 4,4'-oxydiphthalic anhydride, 3, 3 ', 4,4'-benzophenone And structures derived from acid dianhydrides such as tetracarboxylic acid anhydrides.

The polyamic acid used in the present invention is a mixture of pyromellitic anhydride (PMDA) (formula (5)) as acid dianhydride and p-phenylenediamine (pPDA) (formula (6) Diamino-p-terphenyl (TPDA) (formula (7)).

(3)

In the above reaction, the injection ratio (molar ratio) of pyromellitic anhydride (PMDA), diamine consisting of p-phenylenediamine (pPDA) and 4,4'-diamino-p- terphenyl (TPDA) But it is usually about 0.7 to 1.3, and preferably about 0.8 to 1.2, of PMDA which is an acid anhydride component with respect to the amine component 1.

On the other hand, the injection ratio of the diamine and the pPA TPDA is the amount of substance of TPDA (m ²⁾ (M &^lt; ¹ &gt;) of the pPDA, But it is preferably from 2.1 to 7.5, more preferably from 2.1 to 6.8, even more preferably from 3.2 to 6.0, still more preferably from 3.2 to 5.1. That is, m ¹ and m ² are usually in the range of m ¹ / m ² = 1.7 to 8.2, preferably 2.1 to 7.5, more preferably 2.1 to 6.8, still more preferably 3.2 to 6.0, It is 3.2 ~ 5.1.

The above reaction is preferably carried out in a solvent. When a solvent is used, various solvents may be used so far as they do not adversely affect the reaction.

Specific examples include m-cresol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N- N-dimethylformamide, 3-methoxy-N, N-dimethylpropylamide, 3-ethoxy-N, Butoxy-N, N-dimethylpropylamide, 3-tert-butoxy-N, N-dimethylacetamide, , N-dimethylpropylamide, and? -Butyrolactone. These may be used alone or in combination of two or more.

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. In order to prevent imidization of the resulting polyamic acid and maintain a high content of the polyamic acid unit, Is about 0 to 70 ° C, more preferably about 0 to 60 ° C, and even more preferably about 0 to 50 ° C.

The reaction time depends on the reaction temperature and the reactivity of the raw material, and therefore can not be uniformly defined, but is usually about 1 to 100 hours.

The reaction solution containing the target polyamic acid can be obtained by the above-described method.

In the present invention, the reaction solution is usually filtered, and the filtrate is directly used, diluted or concentrated to be used as a resin composition (varnish) for a display substrate. By doing so, it is possible not only to reduce the incorporation of impurities which may cause deterioration of the heat resistance, flexibility or linear expansion coefficient characteristics of the resulting resin thin film, but also to obtain the composition efficiently.

The solvent used for the dilution or concentration is not particularly limited and, for example, the same solvents as the specific examples of the reaction solvent for the above reaction may be used, and these solvents may be used alone or in combination of two or more.

Among them, in consideration of obtaining a resin thin film having high flatness with good reproducibility, it is preferable to use N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl- 3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone and? -Butyrolactone are preferable.

In the present invention, a varnish obtained by post-treating the reaction solution according to a conventional method to isolate the polyamic acid and dissolving or dispersing the isolated polyamic acid in a solvent may be used as the resin composition for a display substrate. In this case, it is preferable that the polyamic acid is dissolved in a solvent in consideration of obtaining a highly flat thin film with good reproducibility. The solvent used for dissolving or dispersing is not particularly limited and, for example, the same solvents as the specific examples of the reaction solvent for the above reaction may be used, and these solvents may be used alone or in combination of two or more.

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

The viscosity of the varnish is suitably set in consideration of the thickness of the thin film to be produced. In particular, when it is intended to obtain a resin thin film having a thickness of about 5 to 50 mu m with good reproducibility, 50,000 mPa · s, preferably about 1,000 to 20,000 mPa · s.

Here, the viscosities of the varnishes can be measured under the conditions of a varnish temperature of 25 deg. C, for example, with reference to the procedure described in JIS K7117-2, using a commercially available viscometer for viscosity measurement of liquids. Preferably, a conical plate type (cone plate type) rotational viscometer is used as the viscometer, preferably a viscometer of the same type, and measurement is made under the condition of a varnish temperature of 25 DEG C using 1 DEG 34 'x R24 as a standard cone rotor have. As such a rotational viscometer, for example, TVE-25H manufactured by Toki Industry Co., Ltd. can be mentioned.

By applying the resin composition for a display substrate of the present invention described above to a substrate and then heating it, a resin thin film made of polyimide having high heat resistance, suitable flexibility, and appropriate linear expansion coefficient can be obtained.

As the substrate (substrate), for example, a plastic (polycarbonate, polymethacrylate, polystyrene, polyester, polyolefin, epoxy, melamine, triacetylcellulose, ABS, AS, norbornene- ), Wood, paper, glass, slate, and the like.

The coating method is not particularly limited. For example, a coating method such as a cast coating method, a spin coating method, a blade coating method, a dip coating method, a roll coating method, a bar coating method, a die coating method, an ink jet method, , Flat panel, screen printing, etc.).

As a method of imidizing the polyamic acid contained in the resin composition for a display substrate of the present invention, it is also possible to heat-imidize the resin composition coated on the substrate as it is, And the like.

In the catalyst imidization of polyamic acid, a catalyst thin film is obtained by adding a catalyst to the resin composition of the present invention and stirring the mixture to adjust the catalyst-added resin composition, applying the composition to the substrate, and heating. The amount of the catalyst is 0.1 to 30 moles, preferably 1 to 20 moles, of the amide group. Acetic anhydride or the like may be added as a dehydrating agent to the catalyst-containing resin composition. The amount thereof is 1 to 50 molar equivalents, preferably 3 to 30 molar equivalents, of the amide acid group.

As the imidation catalyst, it is preferable to use a tertiary amine. As the tertiary amine, pyridine, substituted pyridines, imidazole, substituted imidazoles, picoline, quinoline, isoquinoline and the like are preferable.

The heating temperature at the time of heat imidization and catalyst imidization is preferably 450 캜 or lower. If the temperature exceeds 450 ° C, the resin thin film to be obtained becomes fragile, and a resin thin film suitable for display substrate use may not be obtained.

In consideration of heat resistance and linear expansion coefficient characteristics of the obtained resin thin film, the applied resin composition is heated at 50 to 100 DEG C for 5 minutes to 2 hours, and then is heated stepwise as it is, It is preferable to heat at 450 占 폚 for 30 minutes to 4 hours.

Particularly, the applied resin composition is heated at 50 ° C to 100 ° C for 5 minutes to 2 hours, then heated at 100 ° C to 200 ° C for 5 minutes to 2 hours, then at 200 ° C to 375 ° C for 5 minutes to 2 hours, Finally, it is preferable to heat at 375 DEG C to 450 DEG C for 30 minutes to 4 hours.

Examples of the apparatus used for heating include a hot plate, an oven, and the like. The heating atmosphere may be air or inert gas, or may be normal pressure or reduced pressure.

The thickness of the resin thin film is typically about 1 to 60 mu m, preferably about 5 to 50 mu m when the substrate is used as a substrate for a flexible display, and a resin thin film having a desired thickness is formed by adjusting the thickness of the coating film before heating.

The resin thin film described above is optimum for use as a base film of a flexible display substrate in that it satisfies all the conditions required as a base film of a flexible display substrate.

Example

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

[1] A drug used in Examples

The abbreviations used in this embodiment are as follows.

<Anhydrous>

PMDA: pyromellitic anhydride

<Amine>

 pPDA: p-phenylenediamine

 TPDA: 4,4'-diamino-p-terphenyl

<Solvent>

NMP: N-methyl-2-pyrrolidone

[2] Adjustment of resin composition for display substrate (synthesis of polyamic acid)

&Lt; Example 1 &gt;

0.825 g (0.00763 mol) of pPDA and 0.271 g (0.00104 mol) of TPDA were dissolved in 22.05 g of NMP. Then, 1.854 g (0.00850 mol) of PMDA was added and the reaction was allowed to proceed at 23 占 폚 for 24 hours under a nitrogen atmosphere.

The polymer obtained had a weight average molecular weight (Mw) of 89,000 and a molecular weight distribution (Mw / Mn) of 9.3. This solution was used as a resin composition for a display substrate.

The measurement of the weight molecular weight (Mw) and the molecular weight distribution was carried out by using a GPC apparatus (column: OHpak SB803-HQ and OHpak SB804-HQ; column: Shimadzu Corporation; eluent: dimethylformamide / LiBr.H ₂ O (Mw: standard polystyrene conversion value) was used as a solvent (H ₃ PO ₄ (29.6 mM) / THF (0.1 wt%); flow rate: 1.0 ml / min; column temperature: 40 ° C .

The viscosity of the varnish solution was measured using a cone plate type rotational viscometer TVE-25H manufactured by Toray Industries, Inc. (varnish temperature: 25 ° C).

&Lt; Example 2 &gt;

0.799 g (0.00739 mol) of pPDA and 0.313 g (0.00120 mol) of TPDA were dissolved in 22.05 g of NMP, and 1.837 g (0.00842 mol) of PMDA was added, followed by reaction at 23 占 폚 for 24 hours under a nitrogen atmosphere.

The Mw of the obtained polymer was 86,600 and the molecular weight distribution was 9.4. This solution was used as a resin composition for a display substrate.

&Lt; Example 3 &gt;

0.724 g (0.00670 mol) of pPDA and 0.436 g (0.00167 mol) of TPDA were dissolved in 22.05 g of NMP, and 1.790 g (0.00821 mol) of PMDA was added, followed by reaction at 23 占 폚 for 24 hours under a nitrogen atmosphere.

The Mw of the obtained polymer was 82,600 and the molecular weight distribution was 9.7. This solution was used as a resin composition for a display substrate.

<Example 4>

0.665 g (0.00615 mol) of pPDA and 0.533 g (0.00205 mol) of TPDA were dissolved in 22.05 g of NMP, 1.752 g (0.00803 mol) of PMDA was added and the reaction was allowed to proceed at 23 占 폚 for 24 hours under a nitrogen atmosphere.

The Mw of the obtained polymer was 93,300 and the molecular weight distribution was 8.7. This solution was used as a resin composition for a display substrate.

&Lt; Example 5 &gt;

0.608 g (0.00562 mol) of pPDA and 0.627 g (0.00241 mol) of TPDA were dissolved in 22.05 g of NMP, 1.716 g (0.00787 mol) of PMDA was added, and the reaction was allowed to proceed at 23 占 폚 for 24 hours under a nitrogen atmosphere.

The polymer obtained had Mw of 85,700 and a molecular weight distribution of 9.6. This solution was used as a resin composition for a display substrate.

&Lt; Example 6 &gt;

0.553 g (0.00511 mol) of pPDA and 0.716 g (0.00275 mol) of TPDA were dissolved in 22.05 g of NMP. Then, 1.681 g (0.00771 mol) of PMDA was added and the reaction was allowed to proceed at 23 占 폚 for 24 hours under a nitrogen atmosphere.

The Mw of the obtained polymer was 91,100 and the molecular weight distribution was 9.5. This solution was used as a resin composition for a display substrate.

&Lt; Comparative Example 1 &

0.852 g (0.00788 mol) of pPDA and 0.228 g (0.00088 mol) of TPDA were dissolved in 22.05 g of NMP. Then, 1.871 g (0.00858 mol) of PMDA was added and the reaction was allowed to proceed at 23 占 폚 for 24 hours under a nitrogen atmosphere.

The obtained polymer had Mw of 92,100 and a molecular weight distribution of 9.7. This solution was used as a resin composition for a display substrate.

&Lt; Comparative Example 2 &

0.500 g (0.00462 mol) of pPDA and 0.803 g (0.00308 mol) of TPDA were dissolved in 22.05 g of NMP, and 1.647 g (0.00755 mol) of PMDA was added, followed by reaction at 23 占 폚 for 24 hours under a nitrogen atmosphere.

The polymer obtained had Mw of 112,000 and a molecular weight distribution of 9.1. This solution was used as a resin composition for a display substrate.

&Lt; Comparative Example 3 &gt; (PMDA (98) // PDA (100)) [

0.999 g (0.00916 mol) of pPDA was dissolved in 22.05 g of NMP, 1.959 g (0.00898 mol) of PMDA was added, and the mixture was allowed to react at 23 deg. C for 24 hours under a nitrogen atmosphere.

The Mw of the obtained polymer was 79,100 and the molecular weight distribution was 9.9. This solution was used as a resin composition for a display substrate.

The composition ratios and physical properties of the resin composition for each display substrate in the above Examples and Comparative Examples are summarized in Table 1 below.

[3] Production of resin thin film for display substrate (Production of polyimide film)

&Lt; Resin thin film 1 (Example) &gt;

The resin composition for a display substrate obtained in Example 1 was used as a varnish, coated on a silicon wafer substrate using a doctor blade of 300 mu m after baking, baked at 90 DEG C for 20 minutes in air, At 180 ° C for 20 minutes, then at 240 ° C for 20 minutes, then at 300 ° C for 20 minutes, then at 400 ° C for 20 minutes, then at 450 ° C for 60 minutes , And baked to prepare a resin thin film.

&Lt; Resin Thin Films 2 to 6 (Examples) and Resin Thin Films C1 to C3 (Comparative Example) &gt;

Except that the resin composition for a display substrate obtained in each of the resin thin films 2 to 6 (Examples) and Comparative Examples 1 to 3 was used as a varnish in place of the resin composition for a display substrate obtained in Example 1, To prepare each resin thin film.

[4] Evaluation of resin thin film

The resulting resin thin film was evaluated according to the following method. Thin films were also prepared for each evaluation test.

&Lt; Measurement of film thickness &

The film thickness of the resin thin film was measured using a micrometer manufactured by Mitsutoyo Co., Ltd.

&Lt; Evaluation of heat resistance &

For evaluating the heat resistance of the resin film, the 1% mass reduction temperature (Td 1% (° C)) and the 5% mass reduction temperature (Td 5% (° C)) of the resin thin film were measured. The measurement was carried out using TG / DTA2000SA manufactured by Bruker A.X. (temperature rise rate: from 50 ° C to 800 ° C at 10 ° C per minute).

&Lt; Measurement of linear expansion coefficient &

The linear expansion coefficient of the resin thin film was measured using TMA-60 manufactured by Shimadzu Corporation (temperature increase rate: 5 ° C / min to 50 ° C to 560 ° C) (specimen: width 4 mm, length 12 mm, load: 3.0 g). The coefficient of linear expansion was an average value in the temperature range of 100 ° C to 400 ° C and 400 ° C to 500 ° C.

<Tensile test>

The tensile strength of the resin thin film was measured. The tensile test was performed at room temperature (25 ± 2 ° C) using AUTOGRAPH / AGS-X manufactured by Shimadzu Corporation (specimen size: 50 mm x 10 mm x 0.013 - 0.016 mm, chuck distance: Tensile speed: 5 mm / min). In addition, each value in the result shows an average value of four measurements.

The results were as shown in Table 2.

Claims (8)

A polyamic acid comprising at least 50 mol% of structural units represented by the following formulas (1-1) and (1-2), and a polyamic acid having a weight average molecular weight of 5000 or more.
[Chemical Formula 1]

[Wherein,
Ar ¹ represents a divalent group represented by the following formula (2)
Ar ² represents a divalent group represented by the following formula (3)
Ar ³ represents a tetravalent group represented by the following formula (4), and
n ¹ and n ² represent the number of each repeating unit and satisfy the condition of n ¹ / n ² = 1.7 to 8.2].
(2)

The method according to claim 1,
Wherein n ¹ and n ² in the above formulas (1-1) and (1-2) satisfy the condition of n ¹ / n ² = 1.5 to 6.0. 3. The method according to claim 1 or 2,
Wherein the polyamic acid contains at least 80 mol% of structural units represented by the formulas (1-1) and (1-2). 4. The method according to any one of claims 1 to 3,
Wherein the resin composition is dissolved in a solvent. A resin thin film for a display substrate produced by using the resin composition for a display substrate according to any one of claims 1 to 4. An image display apparatus comprising the resin thin film for a display substrate according to claim 5. A method for producing a resin thin film for a display substrate, which comprises using the resin composition for a display substrate according to any one of claims 1 to 4. A manufacturing method of an image display apparatus characterized by using the resin thin film for a display substrate according to claim 5.