JP5040059B2 - Polyimide precursor, polyimide and method for producing them - Google Patents

Description

  The present invention relates to a polyimide precursor that gives a polyimide useful as a substrate for a flexible film liquid crystal display having high transparency, high glass transition temperature, low birefringence, and high toughness, a polyimide, and a method for producing them.

  Currently, glass substrates are used for liquid crystal displays, but with the trend toward larger screens in recent years, the problem that liquid crystal displays become thicker and heavier and the cost becomes more serious. . As a solution, it is considered to use a plastic substrate that is lighter and easier to mold instead of a heavy glass substrate. Furthermore, if there is a highly transparent and tough plastic substrate comparable to that of glass, a flexible film liquid crystal display that can be bent and rolled and stored freely can be realized. The thermal characteristics, optical characteristics, mechanical characteristics and electrical characteristics required for this flexible film liquid crystal display include heat resistance, transparency, glass transition temperature, dielectric constant, low birefringence, toughness of the plastic substrate used. There are elongation at break, coefficient of linear thermal expansion, etc. Among them, high transparency, high glass transition temperature, low birefringence, high toughness, etc. are particularly important as basic characteristics.

  However, the present condition is that the material suitable as a plastic substrate for flexible film liquid crystal displays which has these required characteristics is not yet known. Although the polyimide which is excellent in heat resistance is mentioned as the candidate, only the polyimide which satisfy | fills some of these characteristics is known.

  For example, a polyimide obtained by imidizing a polyimide precursor (reduced viscosity of 2.0 dL / g or more) formed from aromatic dianhydride and trans-1,4-diaminocyclohexane is disclosed (Patent Document 1). ing. However, when a polyimide precursor (polyamic acid) is formed, if a polymerization reaction is carried out by a usual method, an amine salt of acid dianhydride and diamine is formed at the initial stage of the reaction, and in some cases, the polymerization reaction proceeds at all. Or only a low-viscosity polymer is obtained, and there is a problem that a complicated heating and dissolving step of the amine salt is required. In addition, when a small amount of the amine salt remains in the polyimide film, there are problems such as greatly affecting the toughness and hygroscopicity of the film.

  Further, polyimide (Tg 243) which is a thermal transition product of polyisoimide comprising 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride as the acid dianhydride component and 1,4-diaminocyclohexane as the diamine component. And 5% weight reduction temperature of 392 ° C.) are disclosed (Patent Document 2). However, since the polyimide uses 1,4-cyclohexanediamine (cis and trans mixture) which is not sterically controlled as a diamine component, Tg is as low as 243 ° C., and at this temperature, the liquid crystal display is enlarged. In this case, there is a problem that the heat resistance required in the manufacturing process is not sufficient and the screen cannot be enlarged.

JP 2002-161136 A JP-A-8-3314

  An object of the present invention is to provide a polyimide precursor that gives a polyimide useful as a base material for a flexible film liquid crystal display having characteristics such as high transparency, high glass transition temperature, low birefringence, and high toughness, and a polyimide. And Moreover, an object of this invention is to provide the manufacturing method of the polyimide precursor and polyimide which do not form an amine salt in the case of manufacture of a polyimide precursor.

  As a result of intensive studies on the above problems, the present inventors have found that 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and a trans-1,4-diaminocyclohexane compound (particularly trans-1,4). -Diaminocyclohexane) in an organic solvent, a polyimide obtained by subjecting a polyimide precursor having a reduced viscosity equal to or higher than a specific value obtained by polymerization reaction to an imide ring-closing reaction, can solve the above problem, The present invention has been completed

  That is, this invention provides a polyimide precursor, a polyimide, and these manufacturing methods.

［式中、Ｒ^１は水素又は炭素数１〜４の直鎖状若しくは分岐鎖状アルキル基を表す。］
で表されるトランス−１，４−ジアミノシクロヘキサン化合物から得られる一般式（２）

［式中、Ｒ^１は一般式（１）と同義である。］
で表される重合構造単位を有し、０．５ｄＬ／ｇ以上の還元粘度を有するポリイミド前駆体。 Item 1
3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and general formula (1)

[Wherein, R ¹ represents hydrogen or a linear or branched alkyl group having 1 to 4 carbon atoms. ]
General formula (2) obtained from a trans-1,4-diaminocyclohexane compound represented by formula (2)

[Wherein, R ¹ has the same meaning as in general formula (1). ]
And a polyimide precursor having a reduced viscosity of 0.5 dL / g or more.

  Item 2 The polyimide precursor according to Item 1, wherein the reduced viscosity is 2.0 dL / g or more.

Item 3 The polyimide precursor according to Item 1 or 2, wherein R ¹ is hydrogen.

  Item 4 A polymerization reaction of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and a trans-1,4-diaminocyclohexane compound represented by the general formula (1) in an organic solvent. Item 4. The method for producing a polyimide precursor according to any one of Items 1 to 3 above.

［式中、Ｒ^１は一般式（１）と同義である。］
で表されるポリイミド。 Item 5 General formula (3) obtained by subjecting the polyimide precursor according to any one of Items 1 to 3 to an imide ring-closing reaction

[Wherein, R ¹ has the same meaning as in general formula (1). ]
Polyimide represented by

  Item 6 The polyimide according to Item 5, wherein the glass transition temperature is 350 ° C. or higher.

  Item 7 A polyimide film comprising the polyimide according to Item 5 or 6 as a main constituent.

  Item 8 The method for producing a polyimide film according to Item 7, wherein an organic solvent solution of the polyimide precursor obtained in the production method according to Item 4 is cast-coated on a support and imide is ring-closed.

  Item 9 A flexible film liquid crystal display substrate comprising the polyimide according to Item 5 or 6 as a main substrate.

  According to the present invention, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and trans-1,4-diaminocyclohexane compound (form no amine salt during the production of the polyimide precursor) In particular, a polyimide precursor (polyamide acid) having a reduced viscosity of 0.5 dL / g or more (particularly 2.0 dL / g or more) obtained by polymerizing trans-1,4-diaminocyclohexane) in an organic solvent. By carrying out an imide ring-closing reaction, a polyimide having properties such as high transparency, high glass transition temperature, low birefringence and high toughness in a well-balanced manner can be obtained. This polyimide can be suitably used as a substrate for a flexible film liquid crystal display.

  Hereinafter, the present invention will be described in detail.

［式中、Ｒ^１は水素又は炭素数１〜４の直鎖状若しくは分岐鎖状アルキル基を表す。］
で表されるトランス−１，４−ジアミノシクロヘキサン化合物から得られる一般式（２）

で表される重合構造単位を有し、その還元粘度としては、０．５ｄＬ／ｇ以上、好ましくは０．８ｄＬ／ｇ、特に好ましくは２．０ｄＬ／ｇ以上であることが推奨される。これは、ポリイミドフィルムが充分に強靱であるためには、ポリイミド前駆体の重合度は高いほうがより好ましい。還元粘度が０．５ｄＬ／ｇ未満だと強靱さが不足する傾向が見られる。 The polyimide precursor of the present invention comprises 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride (hereinafter referred to as “DSDA”) and a general formula (1).

[Wherein, R ¹ represents hydrogen or a linear or branched alkyl group having 1 to 4 carbon atoms. ]
General formula (2) obtained from a trans-1,4-diaminocyclohexane compound represented by formula (2)

It is recommended that the reduced viscosity be 0.5 dL / g or more, preferably 0.8 dL / g, particularly preferably 2.0 dL / g or more. For the polyimide film to be sufficiently tough, it is more preferable that the degree of polymerization of the polyimide precursor is higher. When the reduced viscosity is less than 0.5 dL / g, there is a tendency that the toughness is insufficient.

  The reduced viscosity is a value measured with an Ostwald viscometer at 30% by weight at 0.5% by weight.

  DSDA, which is an acid dianhydride component used in the present invention, is commercially available or can be easily produced according to known production methods such as JP-A-3-294272 and JP-A-1-197476. The purity is recommended to be 99.0% or more, preferably 99.5% or more.

  Other acid dihydrates can be used in combination with the above-mentioned DSDA as long as the effects of the present invention and the polymerization reactivity are not significantly impaired. For example, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic Acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride and the like can be used. These may be used alone or in combination of two or more.

As the trans-1,4-diaminocyclohexane compound represented by the general formula (1) which is a diamine component used in the present invention, R ¹ is hydrogen or a methyl group, an ethyl group, an n-propyl group, an isopropyl group, Examples thereof include compounds having a linear or branched alkyl group having 1 to 4 carbon atoms such as n-butyl group, iso-butyl group and sec-butyl group, and among these, trans-1,4-diaminocyclohexane , Trans-1,4-diamino-2-methylcyclohexane and trans-1,4-diamino-3-methylcyclohexane are preferable, and trans-1,4-diaminocyclohexane is particularly preferable.

These trans-1,4-diaminocyclohexane compounds include a cis isomer in which the steric configuration of the 1,4-position amino group is a cis configuration and a trans isomer in a trans configuration. Usually, a trans-1,4-diaminocyclohexane compound is obtained by hydrogenating a precursor p-phenylenediamine compound, and is a mixture of a cis isomer and a trans isomer (for example, Japanese Patent Publication No. 51-481987). As a suitable trans-1,4-diaminocyclohexane compound used in the present invention, a product obtained by separating and purifying the hydrogenated compound according to a known method such as distillation or recrystallization is used. The cis-isomer content is not particularly limited as long as the effects of the present invention are not impaired, and the cis-isomer content is usually purified to 50% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less. Is recommended. If the cis-isomer content is increased, the glass transition temperature of the polyimide due to the bent structure of the cis-isomer and the polymerization reactivity of the polyimide precursor due to steric hindrance tend to be reduced.

  In addition, these trans-1,4-diaminocyclohexane compounds may be recrystallized after separating the colored oily component using a solvent such as n-hexane as necessary because the resulting polyimide film may be remarkably colored. It is preferable to use it after purification.

  The trans-1,4-diaminocyclohexane compound may be used in combination with other diamine compounds within a range not impairing the effects of the present invention. For example, 2,2′-bis (trifluoromethyl) benzidine, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4- Diaminodurene, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 4,4′-diaminobenzanilide, benzidine, 3,3′-dihydroxybenzidine, 3,3′-dimethoxybenzidine, o-tolidine, m- Tolidine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) ) Benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, bis (4- (3-aminophenoxy) phenyl) sulfone, bis (4- (4 -Aminophenoxy) phenyl) sulfone, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2- Bis (4-aminophenyl) hexafluoropropane, p-terphenylenediamine and the like can be used. These may be used alone or in combination of two or more.

  First, a method for producing a polyimide precursor will be described. The polyimide precursor is obtained by polymerizing DSDA and a trans-1,4-diaminocyclohexane compound in an organic solvent. In an inert gas atmosphere such as argon or nitrogen, diamine is dissolved in an organic solvent, and DSDA is dissolved in the organic solvent or gradually added in a solid state. In this case, the molar ratio of the acid dianhydride component and the diamine component is preferably adjusted to a range of 0.95 to 1.05.

  The addition method may be reversed, DSDA may be added first, and the diamine component added later.

  The concentration of acid dianhydride and diamine in the solvent at this time can be appropriately set according to various conditions, but the total weight of acid dihydrate and diamine is 5 to 5% of the total solution weight. 30% by weight, preferably 10 to 20% by weight. When the concentration is less than 5% by weight, the degree of polymerization of the polyimide precursor is not sufficiently high, and the polyimide film finally obtained tends to be brittle. On the other hand, salt formation occurs slightly at a high concentration exceeding 30% by weight, and a long polymerization time is required until the formed salt dissolves and disappears, and productivity tends to decrease. Within this concentration range, the formation of amine salt is hardly observed, and the step of heating and dissolving the amine salt (for example, JP-A No. 2002-161136, 80 to 150 ° C.) is not required. Therefore, compared with the conventional manufacturing method, it is a simple and highly productive manufacturing method that does not require a complicated heating and dissolving step of the amine salt.

  The reaction temperature at this time is in the range of 10 to 60 ° C, preferably 20 to 40 ° C. The reaction time is about 30 minutes to 24 hours.

  Here, the organic solvent used for the reaction for forming the polyimide precursor includes N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, dimethyl sulfoxide, and γ-butyrolactone. And aprotic polar solvents such as 1,3-dimethyl-2-imidazolidinone, which may be used alone or as a mixture. The solvent is not particularly limited as long as it dissolves the polyimide precursor.

  Even when the polyimide precursor solution is allowed to stand at room temperature and −20 ° C. for 1 month, it does not precipitate or gel at all, and exhibits extremely high solution storage stability.

  Next, the process of imide ring-closing reaction of the polyimide precursor will be described. When the polyimide precursor is ring-closed with imide, water is generated. The generated water easily hydrolyzes the polyimide precursor and causes a decrease in molecular weight. As a method for ring closure of the imide while removing this water out of the system, usually, a method of heating at 100 to 400 ° C. for 0.5 to 24 hours, or an aliphatic acid dianhydride such as acetic anhydride, and, if necessary, triethylamine Polyimide represented by the general formula (3) can be obtained by a chemical method of adding a tertiary amine such as pyridine, picoline or the like. The glass transition temperature of the obtained polyimide is particularly preferably 350 ° C. or higher.

  Furthermore, the method for producing the polyimide film of the present invention is not particularly limited. For example, after applying a reaction solvent solution of a polyimide precursor on a support (for example, a glass plate, a stainless plate, a copper plate, an aluminum plate, etc.) A method of imide ring closure by drying and heating, a method of dissolving the polyimide obtained by the above-described method in an organic solvent, applying the solution on a glass plate, and removing the solvent are possible. The application method to these supports is not particularly limited, and conventionally known application methods can be applied.

  As the organic solvent, an aprotic polar solvent is preferable from the viewpoint of solubility. Specifically, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphor Preferable examples include amide, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone and the like. These can be used alone or as a mixed system. Moreover, it is preferable to make content of the polyimide resin in this case into the range of 5 to 50 weight%, especially 10 to 30 weight%.

  More specifically, the polyimide precursor coated on the glass plate is dried at a drying temperature of 50 to 150 ° C. and a drying time of about 0.5 to 80 minutes, and further 200 to 400 ° C., preferably 250. A polyimide film can be obtained by heat treatment at a temperature of about ˜350 ° C. If it exceeds 400 ° C., the polyimide film tends to be remarkably colored, which is not preferable. Further, the imide ring closure is preferably performed under reduced pressure or in a nitrogen atmosphere in order to suppress coloring of the polyimide film, but may be performed in air unless the temperature is particularly high.

  Moreover, although the smaller one is preferable as a pressure in pressure reduction, if it is the said heating conditions and the pressure which can remove water, it will not restrict | limit in particular, Specifically, it is about 0.09 MPa-0.0001 MPa.

  Furthermore, in the polyimide film obtained in this way, within the range that does not impair the effects of the present invention, when producing polyimide from a polyimide precursor, a small amount of other polyimides are blended or other crosslinkable resins, thermosetting. In addition, additives such as oxidation stabilizers, end-capping agents, fillers, silane coupling agents, photosensitizers, photopolymerization initiators, and sensitizers may be mixed as necessary. May be.

  The polyimide thus obtained has basic characteristics such as high transparency, high glass transition temperature, low birefringence and high toughness, and therefore can be used as a substrate for flexible film liquid crystal displays.

  EXAMPLES The present invention will be specifically described below with reference to examples, but it should not be construed that the invention is limited thereto. In addition, the analysis value and physical property value in each example were determined by the following methods.

A reduced viscosity 0.5 wt% polyimide precursor solution was measured at 30 ° C. using an Ostwald viscometer.

Glass transition temperature (Tg)
Using a dynamic viscoelasticity measuring device (trade name “TMA-DTA4010”, manufactured by Mac Science Co., Ltd.), dynamic viscoelasticity was measured, and a loss peak at a frequency of 0.1 Hz and a heating rate of 5 ° C./min. I asked for it.

Using a 5% weight reduction temperature differential thermothermal weight simultaneous measurement device (trade name “TG-DTA2000”, manufactured by Mac Science Co., Ltd.), the thermogravimetric change (TG) of the polyimide film was measured using an air or nitrogen flow rate of 100 ml / min. Measured at a rate of temperature increase of 10 ° C./min; sample amount of 10 mg, and the temperature at which the weight decreased by 5% was determined

Breaking elongation polyimide film specimen (width 1 cm, length 10 cm) was carried out tensile test (Instron measurements) was determined elongation when the film was broken (percent).

Using a linear thermal expansion coefficient dynamic viscoelasticity measuring device (trade name “TMA-DTA4010”, manufactured by Mac Science Co., Ltd.), a test piece at a load of 0.5 g / film thickness of 1 μm and a heating rate of 5 ° C./min. From the elongation, the linear thermal expansion coefficient was determined as an average value in the range of 100 to 200 ° C.

Cut-off wavelength (transparency)
Visible / ultraviolet transmittance from 200 nm to 1000 nm was measured with a spectrophotometer (trade name “V-520”, manufactured by JASCO Corporation). The wavelength (cutoff wavelength) at which the transmittance was 1% or less was used as an index of transparency. The shorter the cutoff wavelength, the better the transparency.

Using a birefringence Abbe refractometer (trade name “Abbe refractometer 4T”, manufactured by Atago Co., Ltd.), the refractive index (sodium lamp) _{in the} direction parallel to the polyimide film (n _in ) and the direction (n _out ) Use, wavelength 589 nm), and birefringence was calculated from the difference between these refractive indexes according to the following equation.
Δn = n _in −n _out

Using the refractive index measured using a dielectric constant Abbe refractometer (trade name “Abbe Refractometer 4T”, manufactured by Atago Co., Ltd.), the average refractive index of the polyimide film [n _av = (2n _in + n _out ) / 3], the dielectric constant (ε) at 1 MHz was calculated by the following equation using the following equation. In practice, the lower the dielectric constant, the better.
ε = 1.1 × n _av ² (1 MHz)

Example 1
Put recrystallized / purified trans-1,4-diaminocyclohexane (5.710 g, 0.05 mol) in a well-dried sealed reaction vessel with a stirrer and dissolve in 200 ml of fully dehydrated N, N-dimethylacetamide. After that, 17.91 g (0.05 mol) of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride was gradually added to this solution and stirred for 2 hours at room temperature to obtain a transparent and viscous polyimide. A precursor solution was obtained. This polyimide precursor solution did not precipitate or gel at all even when allowed to stand at room temperature and −20 ° C. for 1 month, and exhibited extremely high solution storage stability. The reduced viscosity of the polyimide precursor measured at 30 ° C. in N, N-dimethylacetamide was 2.0 dL / g, which was a very high polymer. The polyimide precursor film obtained by applying this polyimide precursor solution to a glass substrate and drying at 60 ° C. for 1 hour is heat-treated stepwise on the substrate for 30 minutes at 250 ° C. under reduced pressure and further for 30 minutes at 300 ° C. Then, imidization was performed to obtain a transparent and tough polyimide film having a thickness of 30 μm. The physical property evaluation results of the obtained polyimide film are shown in Table 1.

As a result of infrared absorption spectrum analysis of the obtained polyimide precursor film and polyimide film, the polyimide precursor film was confirmed to have characteristic absorption of polyamic acid (1640, 2800 to 3600 cm ⁻¹ ), and the polyimide film was a polyimide precursor. Characteristic absorption based on the body was not observed, and characteristic absorption of imide ring carbonyl groups at 1780 and 1720 cm ⁻¹ was confirmed.

Example 2
A transparent and viscous polyimide precursor solution was obtained in the same manner as in Example 1 except that the reaction solvent N, N-dimethylacetamide was used in an amount of 100 ml and the reaction time was 4 hours. The reduced viscosity of this polyimide precursor was 0.83 dL / g, and it carried out similarly to Example 1 from this precursor solution, and obtained the polyimide film. The physical property evaluation results of the obtained polyimide film are shown in Table 1.

Comparative Example 1
A viscous polyimide precursor solution was obtained in the same manner as in Example 1 except that 4,4′-oxydianiline (0.05 mol) was used instead of trans-1,4-diaminocyclohexane as the diamine component. It was. The reduced viscosity of this polyimide precursor was 0.97 dL / g, and it carried out similarly to Example 1 from this precursor solution, and obtained the polyimide film. The physical property evaluation results of the obtained polyimide film are shown in Table 1.

  The obtained polyimide film sufficiently satisfies the required characteristics in terms of heat resistance and film toughness, but the film was remarkably colored and was completely insufficient in terms of transparency.

Comparative Example 2
3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride (0.05 mol) instead of 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride as the acid dianhydride component A polyimide precursor solution was prepared by conducting a polymerization reaction in the same manner as in Example 1 except that was used. However, a reaction time of 3 days or more was required until a viscous and uniform polyimide precursor solution was obtained. This is a result of the polymerization reaction not proceeding smoothly because the solubility of the salt formed at the initial stage of the polymerization reaction was very low, and the intrinsic viscosity of the obtained polyimide precursor was 0.58 dL / g. It carried out similarly to Example 1 from this polyimide precursor, and obtained the polyimide film. The physical property evaluation results of the obtained polyimide film are shown in Table 1.

Comparative Example 3
3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (0.05 mol) instead of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride as the acid dianhydride component A viscous polyimide precursor solution was obtained in the same manner as in Example 1 except that was used. The reduced viscosity of this polyimide precursor was 0.88 dL / g, and it carried out similarly to Example 1 from this precursor solution, and obtained the polyimide film. The physical property evaluation results of the obtained polyimide film are shown in Table 1.

Comparative Example 4
Instead of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride as the acid dianhydride component, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (0 0.05 mol) was carried out in the same manner as in Example 1 to obtain a viscous polyimide precursor solution. The reduced viscosity of this polyimide precursor was 0.77 dL / g, and it carried out similarly to Example 1 from this precursor solution, and obtained the polyimide film. The physical property evaluation results of the obtained polyimide film are shown in Table 1.

Comparative Example 5
A polyimide precursor solution was prepared in the same manner as in Example 1 except that pyromellitic dianhydride was used instead of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride as the acid dianhydride component. Was prepared. However, an extremely strong amine salt was formed at the beginning of the reaction, and even when heated at 150 ° C. or higher, this salt did not dissolve and the polymerization reaction did not proceed at all.

Comparative Example 6
1,2,3,4-Cyclobutanetetracarboxylic dianhydride (0.05 mol) is used in place of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride as the acid dianhydride component The polyimide precursor solution was prepared in the same manner as in Example 1. However, an extremely strong amine salt was formed at the beginning of the reaction, and even when heated at 150 ° C. or higher, this salt did not dissolve and the polymerization reaction did not proceed at all.

Comparative Example 7
1,2,4,5-cyclohexanetetracarboxylic dianhydride instead of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride as the acid dianhydride component, the reaction time was 48 hours Except for the above, the same procedure as in Example 1 was performed, and a salt was formed at the initial stage of polymerization, but a transparent and viscous polyimide precursor solution was obtained. The reduced viscosity of this polyimide precursor was 0.40 dL / g, and it carried out similarly to Example 1 from this precursor solution, and obtained the polyimide film. The physical property evaluation results of the obtained polyimide film are shown in Table 1.

  This polyimide film exhibited extremely high transparency and a high glass transition temperature (350 ° C. or higher), but was poor in toughness and fragile because the degree of polymerization did not increase.

Comparative Example 8
Preparation of polyimide precursor in the same manner as in Example 1 except that 1,4-diaminocyclohexane (trans / cis mixture, trans / cis ratio 25/75) was used instead of trans-1,4-diaminocyclohexane as the diamine component. Went. During polymerization, no salt formation occurred, and after stirring for 2 hours, a viscous and uniform solution was obtained. The reduced viscosity of this polyimide precursor was 0.42 dL / g, and it carried out similarly to Example 1 from this precursor solution, and obtained the polyimide film. However, since the degree of polymerization did not increase, the obtained polyimide film had poor toughness and was brittle.

In Table 1, each abbreviation refers to the following compound.
DSDA: 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride BTDA: 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride s-BPDA: 3,3 ′, 4 4'-biphenyltetracarboxylic acid and anhydride 6FDA: 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride
PMDA: pyromellitic dianhydride CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride HPMDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride CHDA: trans-1,4- Diaminocyclohexane ODA: 4,4'-oxydianiline

According to the present invention, a polyimide having characteristics such as high transparency, high glass transition temperature, low birefringence, and high toughness can be efficiently and industrially produced advantageously. This polyimide can be suitably used as a substrate for a flexible film liquid crystal display, and has extremely high industrial utility value.
Patent applicant New Nippon Rika Co., Ltd.

Claims (9)

3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and general formula (1)

[Wherein, R ¹ represents hydrogen or a linear or branched alkyl group having 1 to 4 carbon atoms. ]
General formula (2) obtained from a trans-1,4-diaminocyclohexane compound represented by formula (2)

[Wherein, R ¹ has the same meaning as in general formula (1). ]
And a polyimide precursor having a reduced viscosity (measuring solvent: N, N-dimethylacetamide, measuring temperature: 30 ° C.) of 0.5 dL / g or more. The polyimide precursor according to claim 1, wherein the reduced viscosity is 2.0 dL / g or more. The polyimide precursor according to claim 1, wherein R ¹ is hydrogen. Characterized in that 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and a trans-1,4-diaminocyclohexane compound represented by the general formula (1) are polymerized in an organic solvent. The manufacturing method of the polyimide precursor in any one of Claims 1-3 to do. General formula (3) obtained by carrying out the imide ring-closing reaction of the polyimide precursor in any one of Claims 1-3.

[Wherein, R ¹ has the same meaning as in general formula (1). ]
Polyimide represented by The polyimide according to claim 5, which has a glass transition temperature of 350 ° C. or higher. The polyimide film which uses the polyimide of Claim 5 or 6 as a main structural component. The method for producing a polyimide film according to claim 7, wherein an organic solvent solution of the polyimide precursor obtained in the production method according to claim 4 is cast-coated on a support, and imide ring closure is performed. The base material for flexible film liquid crystal displays which uses the polyimide of Claim 5 or 6 as a main base material.