WO2013141239A1 - Polyamic acid and polyimide - Google Patents

Abstract

[Problem] To provide a resin composition for a display substrate making it possible to form a useful polyimide film having high heat resistance, a suitable linear expansion coefficient, and suitable flexibility. [Solution] A resin composition for a display substrate, containing a polyamic acid comprising structural units represented by formula (1) and structural units represented by formula (3), or polyimide comprising structural units represented by formula (2) and structural units represented by formula (4). (In formulae (1) to (4), X¹ represents a tetravalent aromatic group or tetravalent aliphatic group, Y¹ and Y² are different from each other and represent a divalent aromatic group or divalent aliphatic group, and n and m represent natural numbers.)

Description

Polyamic acid and polyimide

The present invention relates to a resin composition for display substrates, and in particular, a resin for display substrates capable of forming a useful polyimide film having appropriate heat resistance, transparency, linear expansion coefficient, birefringence, and appropriate flexibility. Relates to the composition.

Polyimide resins are widely used in the field of electrical and electronic materials because of their high heat resistance, flame retardancy, and excellent electrical insulation. Specifically, it is used as a film for flexible printed wiring boards and heat-resistant adhesive tapes as a film, and as a resin varnish for semiconductor insulating films, protective films, and the like.
On the other hand, display devices such as an organic EL (Electro Luminescence) display and a liquid crystal display have been required only for high definition. As such display devices are rapidly expanding their applications to information devices and the like, flexible displays using a plastic film as a substrate are attracting attention in order to satisfy new requirements such as ultra-thinness and light weight.
Conventionally, an active matrix driving panel is used for a high-definition display. In order to form an active matrix layer including a thin film active element in addition to a matrix-like pixel electrode, a high temperature treatment of 200 ° C. or higher is required in the manufacturing process, and extremely accurate alignment is required. However, if the glass substrate is changed to a plastic material to make the display flexible, heat resistance and dimensional stability cannot be satisfied, and it is very difficult to directly form an active element on the glass substrate. It was.

Therefore, several proposals have been made as plastic materials that can avoid the problems of heat resistance and dimensional stability. Patent Document 1 discloses a polyimide film for a display substrate using a polyimide obtained from an alicyclic structure-containing tetracarboxylic dianhydride and various diamines. Patent Document 2 discloses a polyimide film for a display substrate using a polyimide obtained from an alicyclic tetracarboxylic dianhydride having a cyclohexane skeleton and an aromatic diamine containing a sulfone group.

JP 2008-231327 A JP 2008-297360 A

As described above, although materials having improved heat resistance have been proposed as materials for flexible display substrates, the tetracarboxylic dianhydride used in Patent Document 1 also contains aromatic groups. Compared to tetracarboxylic dianhydrides that contain only alicyclic groups and do not contain any group, there is a problem that the transparency of the film obtained by intramolecular conjugation of the polyimide chain and charge transfer interaction is lowered. Moreover, since the acid dianhydride used in Patent Document 2 has a special structure called a cyclohexane skeleton having a cis structure, the versatility is poor, and the production cost of polyimide becomes high, and the resulting product becomes expensive. There is.
In addition, the alicyclic tetracarboxylic dianhydride has a problem in that a high-molecular-weight body having sufficient film toughness may not be obtained from the viewpoint of polymerization reactivity. Among them, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter referred to as CBDA), which is the most popular among tetracarboxylic dianhydrides, exhibits relatively high polymerization reactivity with diamine, Due to its three-dimensional structure, imidation reaction of the polyimide precursor hardly occurs, and a higher temperature is required to complete the imidization reaction, which causes coloring of the polyimide film, and the use of CBDA as a display substrate is not advantageous. Has been pointed out (Patent Document 1 and Patent Document 2).

The present invention has been made in view of such circumstances, and its purpose is a highly transparent film having sufficient film strength as a flexible display substrate and having heat resistance necessary for a thin film transistor (TFT) formation process. Another object of the present invention is to provide a high heat-resistant coating agent for display substrates capable of forming a film having low birefringence.

As a result of intensive studies to achieve the above object, the present inventor has alicyclic tetracarboxylic acid, which has been avoided in the field of display substrates due to reactivity and coloring problems as an acid dianhydride component. Display comprising polyamic acid or polyimide obtained by reacting dianhydride, in particular, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter also referred to as CBDA) and aromatic diamine containing a sulfone group The resin composition for substrates has sufficient film strength, heat resistance necessary for thin film transistor (TFT) formation process, and surprisingly high transparency, low birefringence, and moderate linear expansion It was found that a useful cured film having a coefficient and moderate flexibility was obtained, and the present invention was completed.

That is, as a first aspect, the present invention provides a polyamic acid containing a structural unit represented by the following formula (1) and a structural unit represented by the formula (3), or a structural unit represented by the following formula (2) and It is related with the resin composition for display substrates containing the polyimide containing the structural unit represented by Formula (4).

[In Formula (1) thru | or Formula (4),
X ¹ represents a tetravalent aromatic group or a tetravalent aliphatic group,
Y ¹ and Y ² are different from each other and represent a divalent aromatic group or a divalent aliphatic group,
n and m represent natural numbers. ]
As a second aspect, the present invention relates to the display substrate resin composition according to the first aspect, in which X ¹ represents a tetravalent group represented by the following formula (5).

As a third aspect, the Y ¹ represents a divalent group represented by the following formula (6), and Y ² represents a divalent group represented by the following formula (7). The present invention relates to a resin composition for display substrates.

As a fourth aspect, any one of the first to third aspects in which n in the formula (1) and m in the formula (3) satisfy a relational expression of n / (n + m) ≧ 0.2. It is related with the resin composition for display substrates as described in one.
As a fifth aspect, any one of the first to third aspects in which n in the formula (2) and m in the formula (4) satisfy a relational expression of n / (n + m) ≧ 0.2. It is related with the resin composition for display substrates as described in one.
As a 6th viewpoint, it is related with the resin composition for display substrates of any one of the 1st viewpoint thru | or a 5th viewpoint further including a crosslinking agent.
As a seventh aspect, the present invention relates to the display substrate resin composition according to the sixth aspect, wherein the crosslinking agent is contained in an amount of 20 parts by mass or less with respect to 100 parts by mass of the polyamic acid or polyimide.
An eighth aspect relates to a varnish, wherein the display substrate resin composition according to any one of the first to seventh aspects is dissolved in at least one solvent.
As a ninth aspect, the present invention relates to the varnish according to the eighth aspect, which has a viscosity of 0.001 to 5,000 Pa · s.
As a 10th viewpoint, it is related with the cured film obtained by baking the thin film obtained using the varnish as described in an 8th viewpoint or a 9th viewpoint at the suitable temperature within the range of 100 to 450 degreeC.
As an 11th viewpoint, it is related with the cured film as described in a 10th viewpoint which has a film thickness of 1.0 micrometer thru | or 200 micrometers.
As a 12th viewpoint, it is related with the cured film as described in the 10th viewpoint or the 11th viewpoint which has self-supporting property.
As a 13th viewpoint, it is related with a structure provided with at least one layer which consists of a cured film as described in any one of 10th viewpoint thru | or 12th viewpoint on a board | substrate.
As a 14th viewpoint, it is related with the polyamic acid containing the structural unit represented by the structural unit represented by following formula (1), and Formula (3).

[In Formula (1) and Formula (3),
X ¹ represents a tetravalent group represented by the following formula (5):

Y ¹ represents a divalent group represented by the following formula (6), and Y ² represents a divalent group represented by the following formula (7).

n and m represent natural numbers. ]
As a fifteenth aspect, the present invention relates to a polyimide containing a structural unit represented by the following formula (2) and a structural unit represented by the formula (4).

[In Formula (2) and Formula (4),
X ¹ represents a tetravalent group represented by the following formula (5):

Y ¹ represents a divalent group represented by the following formula (6), and Y ² represents a divalent group represented by the following formula (7).

n and m represent natural numbers. ]
As a 16th viewpoint, it is related with the composition containing the polyamic acid as described in a 14th viewpoint, and a crosslinking agent.
As a 17th viewpoint, it is related with the composition containing the polyimide and crosslinking agent as described in a 15th viewpoint.
As an eighteenth aspect, the present invention relates to a varnish characterized in that the composition according to the sixteenth aspect or the seventeenth aspect is dissolved in at least one solvent.
As a 19th viewpoint, it is related with the cured film obtained by baking the thin film obtained using the varnish as described in an 18th viewpoint at the appropriate temperature within the range of 100 to 450 degreeC.

The resin composition for a display substrate of the present invention is a useful curing having required performance as a flexible display substrate, that is, sufficient heat resistance, high transparency, low birefringence, and an appropriate linear expansion coefficient and an appropriate flexibility. A film can be formed. Therefore, the cured film can be used for a base film for a flexible display.
In particular, in the present invention, cycloaliphatic tetracarboxylic dianhydrides (especially 1,2,3,4-cyclobutanetetra) which have been refrained from use due to the problem of film toughness and coloring due to the heating process. A cured film having high transparency can be obtained using carboxylic acid dianhydride), and an increase in display substrate manufacturing cost can be expected by using a special material (acid dianhydride having a special structure). it can.

[Resin composition for display substrate]
The present invention is represented by a polyamic acid containing a structural unit represented by the following formula (1) and a structural unit represented by the formula (3), or a structural unit represented by the following formula (2) and the formula (4). The present invention relates to a resin composition for a display substrate containing polyimide containing a structural unit.

[In Formula (1) thru | or Formula (4),
X ¹ represents a tetravalent aromatic group or a tetravalent aliphatic group,
Y ¹ and Y ² represent different divalent aromatic groups or divalent aliphatic groups,
n and m represent natural numbers. ]

<Polyamic acid>
The polyamic acid having the structural unit represented by the formula (1) and the structural unit represented by the formula (3) contained in the resin composition for display substrates of the present invention is at least one acid dianhydride component. And at least two diamine components are polymerized in a solvent.
That is, the polyamic acid is a known method, for example, in an inert gas atmosphere such as nitrogen, the following formula (9):

(Wherein X ¹ represents a tetravalent aromatic group or a tetravalent aliphatic group), and at least one acid dianhydride represented by the following formula (10):
H ₂ N—Y ¹ —NH ₂ (10)
(Wherein Y ¹ represents a divalent aromatic group or a divalent aliphatic group) and at least one diamine represented by the following formula (11):
H ₂ N—Y ² —NH ₂ (11)
(Wherein Y ² represents a divalent aromatic group or a divalent aliphatic group) and at least one diamine (wherein Y ¹ and Y ² are different divalent groups); Is dissolved in a solvent and reacted.

The reaction temperature during polymerization of these acid dianhydrides and diamines is -20 to 100 ° C, preferably 20 to 60 ° C. The reaction time is 1 to 72 hours.

Examples of the acid dianhydride represented by the formula (9) include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6. -Naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,5,6-anthracene Tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,3,3 ′, 4-benzophenone tetracarboxylic dianhydride, bis (3 4-dicarboxyphenyl Ether dianhydride, bis (3,4-dicarboxyphenyl) sulfonic dianhydride, bis (3,4-dicarboxyphenyl) methanoic dianhydride, 2,2-bis (3,4-dicarboxy) Phenyl) propanoic dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis (3,4-dicarboxyphenyl) propanoic dianhydride, bis (3,4-di Carboxyphenyl) dimethylsilane dianhydride, bis (3,4-dicarboxyphenyl) diphenylsilane dianhydride, 2,3,4,5-pyridinetetracarboxylic dianhydride, 2,6-bis (3 , 4-Dicarboxyphenyl) pyridine acid dianhydride and other aromatic tetracarboxylic dianhydrides; 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2-dimethyl-1,2,3 , 4-Cyclobu Tantetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic acid, 5- (2,5-dioxo Tetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid dianhydride, 2,3,5-tricarboxy-2-cyclopentaneacetic acid dianhydride, bicyclo [2.2.2] octo- 7-ene-2,3,5,6-tetracarboxylic dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 3,5,6-tricarboxy-2-norbornaneacetic acid dianhydride object Alicyclic tetracarboxylic dianhydride; and it can include dianhydrides of aliphatic tetracarboxylic acids such as 1,2,3,4-butane tetracarboxylic dianhydride.

Also in the acid dianhydride represented by the formula (9), from the viewpoint that the cured film obtained from the resin composition of the present invention has a sufficiently low linear expansion coefficient and a sufficiently high strength, X ¹ is An acid dianhydride having a structure represented by the following formula (5), that is, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (the following formula (12)) is preferable.

Examples of the aromatic diamine represented by the formula (10) or the formula (11) include p-phenylenediamine, o-phenylenediamine, 2-methyl-1,4-phenylenediamine, 2-trifluoromethyl- 1,4-phenylenediamine, 2-methoxy-1,4-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,5-bis (trifluoromethyl) -1,4-phenylenediamine, 4 , 4'-diaminobenzanilide, 4-aminophenyl-4'-aminobenzoate, benzidine, 3,3'-dimethoxybenzidine, 3,3'-dichlorobenzidine, o-tolidine, m-tolidine, 2,2'- Bis (trifluoromethyl) benzidine, 3,3'-bis (trifluoromethyl) benzidine, octafluorobenzidine 3,3 ′, 5,5′-tetramethylbenzidine, 2,2 ′, 5,5′-tetrachlorobenzidine, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3 -Aminophenoxy) phenyl] sulfone, bis (3-aminophenyl) sulfone, bis (4-aminophenyl) sulfone, and the like. Among these, from the viewpoint that the cured film obtained from the resin composition of the present invention has sufficiently high transparency and sufficiently high strength, p-phenylenediamine and bis [4- (3-aminophenoxy) phenyl Sulfone, bis (3-aminophenyl) sulfone and the like are preferable.

Examples of the aliphatic diamine represented by the formula (10) or the formula (11) include 4,4′-methylenebis (cyclohexylamine), 4,4′-methylenebis (3-methylcyclohexylamine), isophoronediamine, Trans-1,4-cyclohexanediamine, cis-1,4-cyclohexanediamine, 1,4-cyclohexanebis (methylamine), 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2, 6-bis (aminomethyl) bicyclo [2.2.1] heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantane, 2,2-bis (4-aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropane, 1,3-propyl Pandiamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine Etc. Among the aliphatic diamines, from the viewpoint that the cured film obtained from the resin composition of the present invention has a sufficiently low linear expansion coefficient, it is preferable to use a diamine having a rigid and linear molecular structure, For example, trans-1,4-cyclohexanediamine is preferably used.

In particular, in the diamines represented by the formula (10) and the formula (11) (these are diamines different from each other), one of the cured films obtained from the resin composition of the present invention has sufficiently high transparency. From the viewpoint of providing, it is preferable to use a diamine having an electron withdrawing group. On the other hand, from the viewpoint of obtaining a cured film having high transparency and a sufficiently low linear expansion coefficient, an electron withdrawing group is used. It is preferable to use a diamine having a rigid and linear molecular structure.
As such a diamine, the diamine represented by the formula (10) and the formula (11) is preferably a diamine in which Y ^{1 and} Y ² are aromatic groups having a sulfonic acid group.
For example, as the diamine represented by the formula (10), a diamine having a divalent group represented by Y ¹ represented by the following formula (6) (that is, bis [4- (3-aminophenoxy) phenyl] sulfone) is particularly preferred. preferable.
As the diamines represented by the formula (11), a diamine having a divalent group Y ² is expressed by the following formula (7) (i.e. bis (3-aminophenyl) sulfone) are particularly preferred.

The solvent used in the polymerization reaction of the polyamic acid is not particularly limited. For example, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, 3- Methoxy-N, N-dimethylpropylamide, 3-ethoxy-N, N-dimethylpropylamide, 3-propoxy-N, N-dimethylpropylamide, 3-isopropoxy-N, N-dimethylpropylamide, 3-butoxy -N, N-dimethylpropylamide, 3-sec-butoxy-N, N-dimethylpropylamide, 3-tert-butoxy-N, N-dimethylpropylamide, hexamethylphosphoramide, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, 1,2-dimethyl Aprotic solvents such as xylene-bis (2-methoxyethyl) ether, tetrahydrofuran, 1,4-dioxane, picoline, pyridine, acetone, chloroform, toluene, xylene, and phenol, o-cresol, m-cresol, p- Examples thereof include protic solvents such as cresol, o-chlorophenol, m-chlorophenol, and p-chlorophenol. These solvents may be used alone or in combination of two or more.

In the polymerization reaction of the polyamic acid, the ratio of the diamine component is the diamine represented by the above formula (10) (that is, the diamine having a divalent group represented by the above formula (6)) and the above formula (11). The molar ratio with the diamine represented (that is, the diamine having a divalent group represented by the above formula (7)) is preferably 10/90 to 99/1, and obtained from the resin composition of the present invention. From the viewpoint that the cured film to be obtained has a sufficiently low linear expansion coefficient and a sufficiently high strength, 20/80 to 80/20 is more preferable.

In the above reaction, the ratio of the acid dianhydride component to the diamine component is preferably acid dianhydride component / diamine component = 0.8 to 1.2 in terms of molar ratio. Similar to the normal polycondensation reaction, the closer the molar ratio is to 1, the higher the degree of polymerization of the polymer produced. If the degree of polymerization is too small, the strength of the polyimide cured film to be formed later will be insufficient, and if the degree of polymerization is too large, the workability at the time of forming the polyimide cured film may be deteriorated.

The weight average molecular weight of the produced polyamic acid is preferably 3,000 to 300,000 in terms of polystyrene in order to maintain the strength of the cured film obtained from the resin composition for display substrate containing polyamic acid. If the weight average molecular weight is less than 3,000, the resulting film may become brittle. On the other hand, if the weight average molecular weight exceeds 300,000, the viscosity of the polyamic acid varnish may be too high. This is because handling becomes difficult.
In order to satisfy such a numerical range, n and m in the above formulas (1) and (3) are n + m, usually 6 to 180, preferably 10 to 100, more preferably 10 to 50.

As described above, the number of repeating structural units in the polyamic acid composed of the structural unit represented by the above formula (1) and the structural unit represented by the formula (3) is represented by the formula (1). It is preferable that n and m in the above formula (3) have a relationship of n / (n + m) ≧ 0.2 (the ratio of n is 20% or more with respect to the total number of n and m).

In the present invention, the reaction solution of polyamic acid can be used as it is or diluted to be used in an imidation reaction for obtaining a polyimide described later, and this can be used as the resin composition of the present invention. Alternatively, the polyamic acid precipitated and recovered from the reaction solution can be redissolved in an appropriate solvent and used for the imidization reaction, and this can be used as the resin composition of the present invention. The solvent used for dilution and re-dissolution is not particularly limited as long as it can dissolve the obtained polyamic acid. For example, 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, 3-butoxy-N, N-dimethylpropylamide, 3-sec-butoxy-N, N-dimethylpropylamide, 3 -Tert-butoxy-N, N-dimethylpropylamide, γ-butyrolactone, etc. . These solvents may be used alone or in combination of two or more.

<Polyimide>
The polyimide contained in the resin composition for display substrates of the present invention can be obtained by subjecting the polyamic acid synthesized as described above to dehydration ring closure (thermal imidization) by heating. At this time, polyamic acid can be converted to imide in a solvent and used as a solvent-soluble polyimide. Moreover, the method of chemically ring-closing using a well-known dehydration ring-closing catalyst is also employable. The method by heating can be performed at an arbitrary temperature of 100 to 500 ° C., preferably 120 to 450 ° C. The method of chemically cyclizing can be performed, for example, in the presence of pyridine, triethylamine or the like and acetic anhydride, and the temperature at this time can be selected from -20 to 200 ° C. .

The weight average molecular weight of the polyimide produced is preferably 3,000 to 300,000 in terms of polystyrene in order to maintain the strength of the cured film obtained from the resin composition for display substrate containing polyimide. If the weight average molecular weight is less than 3,000, the resulting film may be brittle, while if the weight average molecular weight exceeds 300,000, the viscosity of the polyimide varnish may be too high, and as a result, This is because handling becomes difficult.
In order to satisfy such a numerical range, n and m in the above formulas (2) and (4) are usually n + m and are usually 6 to 180, preferably 10 to 100, more preferably 10 Thirty to fifty.

As described above, the number of repeating structural units in the polyimide composed of the structural unit represented by the above formula (2) and the structural unit represented by the formula (4) is n in the above formula (2). And m in the above formula (4) preferably have a relationship of n / (n + m) ≧ 0.2 (the ratio of n is 20% or more with respect to the total number of n and m).

In the present invention, the obtained polyimide can be used as a resin composition as it is or diluted with the reaction solution, or a polyimide recovered by precipitation by adding a poor solvent such as methanol or ethanol to the reaction solution is appropriately used. After re-dissolving in a solvent, it can be used as a resin composition. The solvent used for dilution and re-dissolution is not particularly limited as long as it can dissolve the obtained polyimide. For example, 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, 3-butoxy-N, N-dimethylpropylamide, 3-sec-butoxy-N, N-dimethylpropylamide, 3- and tert-butoxy-N, N-dimethylpropylamide, γ-butyrolactone, and the like. These solvents may be used alone or in combination of two or more.

<Resin composition>
The ratio of the solid content in the resin composition for display substrates of the present invention is 1 to 100% by mass, or 5 to 100% by mass, or 50 to 100% by mass, or 80 to 100% by mass.
Here, solid content is the remaining component which removed the solvent mentioned later from all the components including the said polyamic acid of the resin composition for display substrates, and the said polyimide.
The content of the polyamic acid or polyimide in the resin composition for display substrates of the present invention is 8 to 100% by mass, preferably 40 to 100% by mass, more preferably based on the solid content of the resin composition. Is 70 to 100% by mass.

<Other optional components: Solvent>
The resin composition for display substrates of the present invention can contain a solvent. Examples of such a solvent include the solvents listed as solvents that can be used for redissolving polyamic acid and polyimide (solvents described in paragraphs [0023] and [0027]).

<Other optional components: cross-linking agent>
The resin composition for display substrates of the present invention can contain a crosslinking agent (hereinafter also referred to as a crosslinkable compound).

The crosslinkable compound can react with an organic group contained in at least one of polyamic acid and polyimide in the step of converting the coating film (thin film) obtained using the resin composition for display substrates into a cured film. If it is a compound which has group, it will not specifically limit. Examples of such a compound include a compound containing two or more epoxy groups, a melamine derivative having a hydrogen atom of an amino group substituted by a methylol group, an alkoxymethyl group, or both, a benzoguanamine derivative, or glycoluril. Etc. The melamine derivative and benzoguanamine derivative may be a dimer or a trimer, or may be a mixture arbitrarily selected from a monomer, a dimer and a trimer. These melamine derivatives and benzoguanamine derivatives preferably have an average of 3 or more and less than 6 methylol groups or alkoxymethyl groups per one triazine ring.
Moreover, you may use the crosslinking agent used for this invention individually or in combination of 2 or more types.

Although the specific example of a crosslinkable compound is given to the following, it is not limited to this.
Examples of the compound containing two or more epoxy groups include cyclohexene structures such as epolide GT-401, epolide GT-403, epolide GT-301, epolide GT-302, ceroxide 2021, and ceroxide 3000 (manufactured by Daicel Corporation). Epicoat 1001, Epicoat 1002, Epicoat 1003, Epicoat 1004, Epicoat 1007, Epicoat 1009, Epicoat 1010, Epicoat 828 (above, Japan Epoxy Resin Co., Ltd. (currently Mitsubishi Chemical Corporation, presently jER) Bisphenol A type epoxy compounds such as Epicote 807 (manufactured by Japan Epoxy Resin Co., Ltd. (currently Mitsubishi Chemical Corporation, presently jER (registered trademark) series))) Poxy compounds; Epicoat 152, Epicoat 154 (above, Japan Epoxy Resin Co., Ltd. (currently Mitsubishi Chemical Corporation, presently jER (registered trademark) series)), EPPN201, EPPN202 (above, Nippon Kayaku Co., Ltd.) Phenol novolac type epoxy compounds such as ECON-102, ECON-103S, ECON-104S, ECON-1020, ECON-1025, ECON-1027 (above, manufactured by Nippon Kayaku Co., Ltd.), Epicort 180S75 (Japan Epoxy Resin ( Cresol novolac type epoxy compounds such as (manufactured by Mitsubishi Chemical Corporation, currently jER (registered trademark) series); naphthalene type epoxy compounds such as V8000-C7 (manufactured by DIC Corporation); Denacol EX-252 ( Nagase ChemteX Corporation), CY175, C Y177, CY179, Araldite CY-182, Araldite CY-192, Araldite CY-184 (above, manufactured by BASF), Epicron 200, Epicron 400 (above, manufactured by DIC Corporation), Epicoat 871, Epicoat 872 (above, Japan) Cycloaliphatic epoxy compounds such as Epoxy Resin Co., Ltd. (currently Mitsubishi Chemical Co., Ltd., present jER (registered trademark) series), ED-5661, ED-5661 (above, Celanese Coating Co., Ltd.); Denacol EX-611, Denacol EX-612, Denacol EX-614, Denacol EX-622, Denacol EX-411, Denacol EX-512, Denacol EX-522, Denacol EX-421, Denacol EX-313, Denacol EX-314, Denacor EX-31 (Above, manufactured by Nagase ChemteX Corporation) aliphatic polyglycidyl ether compounds, and the like.

As the melamine derivative, benzoguanamine derivative or glycoluril having a group in which the hydrogen atom of the amino group is substituted with a methylol group, an alkoxymethyl group or both, an average of 3.7 methoxymethyl groups are substituted per triazine ring. MX-750, MW-30 substituted with an average of 5.8 methoxymethyl groups per triazine ring (above, manufactured by Sanwa Chemical Co., Ltd.); Cymel 300, Cymel 301, Cymel 303, Cymel 350, Methoxymethylated melamines such as Cymel 370, Cymel 771, Cymel 325, Cymel 327, Cymel 703, Cymel 712, etc .; Butoxymethylated melamines such as Cymel 506 and Cymel 508; carboxyl group-containing methoxymethylated isobutoxymethylated melamines such as Cymel 1141; methoxymethylated ethoxymethylated benzoguanamines such as Cymel 1123; Methoxymethylated butoxymethylated benzoguanamine; butoxymethylated benzoguanamine such as Cymel 1128; carboxyl-containing methoxymethylated ethoxymethylated benzoguanamine such as Cymel 1125-80; butoxymethylated glycoluril such as Cymel 1170; Cymel 1172 Such as methylolated glycoluril (made by Mitsui Cyanamid Co., Ltd. (currently Cytec Industries)).

In the resin composition for display substrates of the present invention, the content in the case of using a crosslinking agent is not particularly limited, but from the viewpoint of further improving the storage stability of the resin composition, relative to 100 parts by mass of polyamic acid or polyimide From the viewpoint that the cured film obtained from the resin composition of the present invention has a sufficiently low linear expansion coefficient, it is more preferably contained at 15 parts by mass or less. .

[Varnish and cured film]
As a specific method for forming a cured film comprising the resin composition for a display substrate of the present invention, first, the resin composition is dissolved or dispersed in a solvent to form a varnish (film forming material), and the varnish is used as a substrate. Apply by 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 plate, planographic plate, screen printing, etc.) A coating film (thin film) is obtained. And the cured film is formed by baking the obtained coating film with a hotplate, oven, etc. FIG. The firing temperature is usually 100 to 500 ° C, preferably 120 to 450 ° C. Firing may be performed a plurality of times at different temperatures. The atmosphere is preferably nitrogen or under reduced pressure.
Examples of the substrate include plastic (polycarbonate, polymethacrylate, polystyrene, polyester, polyolefin, epoxy, melamine, triacetyl cellulose, ABS, AS, norbornene resin, etc.), metal, wood, paper, glass, slate, and the like. Can be mentioned.

The solvent used in the form of the varnish is not particularly limited as long as it dissolves the resin composition for display substrates. For example, the solvent used in the polymerization reaction of the polyamic acid, or the re-use of polyamic acid or polyimide is used. The solvent etc. which were mentioned as a solvent which can be used for dissolution are mentioned. These solvents may be used alone or in combination of two or more.
Moreover, the density | concentration which dissolves or disperses | distributes a resin composition to the said solvent is arbitrary, However, The resin composition for display substrates with respect to the resin composition for display substrates and the total mass (total mass, ie, total mass of varnish) The solid content is 5 to 50% by mass, preferably 10 to 40% by mass from the viewpoint of further improving the storage stability of the resin composition, and more preferably from the viewpoint of more uniformly applying the resin composition. Is 10 to 30% by mass.
The varnish preferably has a viscosity of 0.001 to 5,000 Pa · s.
Although the thickness of the cured film formed from the resin composition for display substrates or the varnish obtained from this composition is not specifically limited, For example, it is 1 to 200 micrometers, Usually 1 to 100 micrometers, Preferably it is 5 to 60 micrometers.

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

[Measurement of number average molecular weight and weight average molecular weight]
The weight average molecular weight (hereinafter abbreviated as Mw) and the molecular weight distribution of the polymer were measured using a GPC apparatus (Shodex [registered trademark] columns SB803HQ and SB804HQ) manufactured by Tosoh Corporation, with dimethylformamide as the elution solvent at a flow rate of 0.9 mL / Minutes and column temperature of 40 ° C. In addition, Mw was made into the polystyrene conversion value.

[Synthesis of polyamic acid and resin composition for display substrate (varnish)]
<Example 1>
13. N-methyl-2-pyrrolidone containing 3.51 g (0.0081 mol) of bis [4- (3-aminophenoxy) phenyl] sulfone and 0.504 g (0.0020 mol) of bis (3-aminophenyl) sulfone After dissolving in 0 g and adding 1.99 g (0.010 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, the mixture was reacted at 23 ° C. for 24 hours in a nitrogen atmosphere. The obtained polymer had Mw of 28,700 and a molecular weight distribution of 2.1. The obtained reaction solution was used as the resin composition for display substrate of Example 1 as it was.

<Comparative Example 1>
Bis [4- (3-aminophenoxy) phenyl] sulfone (4.13 g, 0.0095 mol) was dissolved in N-methyl-2-pyrrolidone (14.0 g), and 1,2,3,4-cyclobutanetetracarboxylic acid After adding 1.87 g (0.0095 mol) of anhydride, the mixture was reacted at 23 ° C. for 24 hours under a nitrogen atmosphere. Mw of the obtained polymer was 19,800 and molecular weight distribution was 2.1. The obtained reaction solution was used as the display substrate resin composition of Comparative Example 1 as it was.

<Comparative example 2>
2.35 g (0.013 mol) of bis (3-aminophenyl) sulfone was dissolved in 14.0 g of N-methyl-2-pyrrolidone, and 2.65 g of 1,2,3,4-cyclobutanetetracarboxylic dianhydride. (0.014 mol) was added, and the mixture was reacted at 23 ° C. for 24 hours under a nitrogen atmosphere. Mw of the obtained polymer was 13,600 and molecular weight distribution was 3.1. The obtained reaction solution was used as the resin composition for display substrate of Comparative Example 2 as it was.

[Heat resistance evaluation]
The resin compositions for display substrates of Example 1 and Comparative Examples 1 and 2 were applied onto a glass substrate with a doctor blade, and the pressure was reduced at 120 ° C. for 10 minutes, then at 180 ° C. for 10 minutes, and subsequently at 240 ° C. for 60 minutes. Baking was performed below to obtain a cured film. The cured film thus obtained was heated from 50 ° C. to 500 ° C. at 10 ° C./min using TG-DTA (manufactured by Bruker AXS Co., Ltd., TG / DTA 2000SA), and 5 mass% by thermal decomposition. The temperature causing mass reduction was determined and the heat resistance was evaluated. The results are shown in Table 1.

As shown in Table 1, the cured film produced using the display substrate resin composition of Example 1 has higher heat resistance than the cured films produced using the display substrate resin compositions of Comparative Example 1 and Comparative Example 2. Showed sex.

[Self-supporting evaluation]
The resin compositions for display substrates of Example 1 and Comparative Examples 1 and 2 were applied onto a glass substrate with a doctor blade, and the pressure was reduced at 120 ° C. for 10 minutes, then at 180 ° C. for 10 minutes, and subsequently at 240 ° C. for 60 minutes. Baking was performed below to obtain a cured film. For the cured film thus obtained, visually check the fragility (crack, crack, tear, etc.) of the film when the film is peeled from the glass substrate and when the peeled film is bent or pulled by hand. The self-supporting property was evaluated. The obtained results are shown in Table 2.

As shown in Table 2, the cured film obtained from the resin composition for display substrate of Comparative Example 2 can be confirmed to be partially cloudy, and the film is brittle, and the film is cracked and torn when peeled from the glass substrate. As a result, the peeled film was easily broken, and the film strength as a display substrate was insufficient.
On the other hand, the cured film produced using the resin composition for display substrate of Example 1 is less susceptible to cracking and tearing when peeled from the glass substrate, and the peeled film is also difficult to break and has a sufficiently high film strength. A film having a uniform self-supporting property having a thickness of 30 μm could be formed.

[Evaluation of linear expansion coefficient]
The resin compositions for display substrates of Example 1 and Comparative Examples 1 and 2 were applied onto a glass substrate with a doctor blade, and the pressure was reduced at 120 ° C. for 10 minutes, then at 180 ° C. for 10 minutes, and subsequently at 240 ° C. for 60 minutes. Baking was performed below to obtain a cured film. The cured film thus obtained was heated at 50 ° C. to 300 ° C. at a rate of 10 ° C./min using TMA-4000SA (manufactured by Bruker AXS Co., Ltd.), and a linear expansion coefficient of 50 ° C. to 250 ° C. Was measured. The obtained results are shown in Table 3.

As shown in Table 3, when the cured film produced using the display substrate resin composition of Example 1 had a value of the linear expansion coefficient comparable to or slightly lower than that of the cured film obtained from Comparative Example 1. As a result, an appropriate linear expansion coefficient as a display substrate was shown. On the other hand, as described above, the self-supporting film was not obtained in Comparative Example 2, and the linear expansion coefficient was not measured.

[Evaluation of birefringence]
The resin compositions for display substrates of Example 1 and Comparative Examples 1 and 2 were applied onto a glass substrate with a doctor blade, and the pressure was reduced at 120 ° C. for 10 minutes, then at 180 ° C. for 10 minutes, and subsequently at 240 ° C. for 60 minutes. Baking was performed below to obtain a cured film. The film thicknesses of the obtained cured films were all 30 μm. The birefringence of the cured film thus obtained was measured using a prism coupler (manufactured by METRICON, MODEL 2010). The results are shown in Table 4.

As shown in Table 4, the cured film produced using the display substrate resin composition of Example 1 exhibited sufficiently low birefringence as a display substrate film.

[Transparency evaluation]
The resin compositions for display substrates of Example 1 and Comparative Examples 1 and 2 were applied onto a glass substrate with a doctor blade, and the pressure was reduced at 120 ° C. for 10 minutes, then at 180 ° C. for 10 minutes, and subsequently at 240 ° C. for 60 minutes. Baking was performed below to obtain a cured film. The film thicknesses of the obtained cured films were all 30 μm. With respect to the transparency of the cured film thus obtained, the total light transmittance was measured using a haze meter (NDH 5000, manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 5.

As shown in Table 5, the cured film produced using the display substrate resin composition of Example 1 exhibited sufficiently high transparency as a display substrate film.

Claims (19)

1. A structural unit represented by the following formula (1) and a polyamic acid containing a structural unit represented by the formula (3) or a structural unit represented by the following formula (2) and a structural unit represented by the formula (4) The resin composition for display substrates containing the containing polyimide.
   

   

   [In Formula (1) thru | or Formula (4),
   X ¹ represents a tetravalent aromatic group or a tetravalent aliphatic group,
   Y ¹ and Y ² are different from each other and represent a divalent aromatic group or a divalent aliphatic group,
   n and m represent natural numbers. ]
2. The resin composition for display substrates according to claim 1, wherein X ¹ represents a tetravalent group represented by the following formula (5).
   

   
3. The resin composition for display substrates according to claim 1, wherein Y ¹ represents a divalent group represented by the following formula (6), and Y ² represents a divalent group represented by the following formula (7). object.
   

   
4. 4. The n according to claim 1, wherein n in the formula (1) and m in the formula (3) satisfy a relational expression of n / (n + m) ≧ 0.2. Resin composition for display substrate.
5. The n in said Formula (2) and m in said Formula (4) satisfy | fill the relational expression of n / (n + m)> = 0.2, It is any one of Claim 1 thru | or 3 characterized by the above-mentioned. Resin composition for display substrate.
6. Furthermore, the resin composition for display substrates of any one of Claims 1 thru | or 5 containing a crosslinking agent.
7. The resin composition for display substrates according to claim 6, wherein the crosslinking agent is contained in an amount of 20 parts by mass or less with respect to 100 parts by mass of the polyamic acid or polyimide.
8. A varnish, wherein the display substrate resin composition according to any one of claims 1 to 7 is dissolved in at least one solvent.
9. The varnish according to claim 8, having a viscosity of 0.001 to 5,000 Pa · s.
10. The cured film obtained by baking the thin film obtained using the varnish of Claim 8 or Claim 9 at the suitable temperature within the range of 100 to 450 degreeC.
11. The cured film according to claim 10, having a film thickness of 1.0 μm to 200 μm.
12. The cured film according to claim 10 or 11, which has self-supporting property.
13. A structure comprising at least one layer formed of the cured film according to any one of claims 10 to 12 on a substrate.
14. A polyamic acid comprising a structural unit represented by the following formula (1) and a structural unit represented by the formula (3).
    

    

    [In Formula (1) and Formula (3),
    X ¹ represents a tetravalent group represented by the following formula (5):
    

    

    Y ¹ represents a divalent group represented by the following formula (6), and Y ² represents a divalent group represented by the following formula (7).
    

    

    n and m represent natural numbers. ]
15. A polyimide containing a structural unit represented by the following formula (2) and a structural unit represented by the formula (4).
    

    

    [In Formula (2) and Formula (4),
    X ¹ represents a tetravalent group represented by the following formula (5):
    

    

    Y ¹ represents a divalent group represented by the following formula (6), and Y ² represents a divalent group represented by the following formula (7).
    

    

    n and m represent natural numbers. ]
16. A composition comprising the polyamic acid according to claim 14 and a crosslinking agent.
17. A composition comprising the polyimide according to claim 15 and a crosslinking agent.
18. A varnish, characterized in that the composition according to claim 16 or 17 is dissolved in at least one solvent.
19. The cured film obtained by baking the thin film obtained using the varnish of Claim 18 at the suitable temperature within the range of 100 to 450 degreeC.