JP2008231327A - Highly transparent polyimide and method for producing the same - Google Patents

Abstract

（一般式（１）中、Ｐは水素原子等を表し、ｎは１〜３の整数を表し、Ａは二価の芳香族基等を表す。）で表される反復単位を有するポリイミド、その前駆体、それらの製造方法及び当該ポリイミドの製造原料として有用なテトラカルボン酸化合物。
【効果】高透明性、十分な膜靭性、高ガラス転移温度を併せ持つ、各種電子デバイスにおけるフレキシブルディスプレー用プラスチック基板等として有益なポリイミド、その前駆体、それらの製造方法及び当該ポリイミドの製造原料として有用なテトラカルボン酸化合物が提供される。
【選択図】なしProvided are a polyimide useful as a plastic substrate for a flexible display, a precursor thereof, a production method thereof, and a tetracarboxylic acid compound useful as a raw material for producing the polyimide.
SOLUTION: General formula (1)

(In general formula (1), P represents a hydrogen atom, n represents an integer of 1 to 3, A represents a divalent aromatic group, etc.) Tetracarboxylic acid compounds useful as precursors, production methods thereof, and production raw materials for the polyimide.
[Effect] Polyimide useful as a plastic substrate for flexible displays in various electronic devices having high transparency, sufficient film toughness, and high glass transition temperature, its precursor, its production method, and useful as a raw material for producing the polyimide Tetracarboxylic acid compounds are provided.
[Selection figure] None

Description

  The present invention has high transparency, sufficient film toughness, low dielectric constant, and high glass transition temperature. Electrical insulating film and liquid crystal display substrate, organic electroluminescence display substrate, electronic paper substrate, solar cell in various electronic devices The present invention relates to a method for producing polyimide and its precursor, which are useful as an interlayer insulating film for a substrate for a liquid crystal display, particularly a plastic substrate for a flexible liquid crystal display and an integrated circuit.

  Currently, glass substrates are used for liquid crystal displays, but with the trend toward larger screens in recent years, problems of weight reduction and productivity improvement have become serious. As a solution, it is conceivable to use a plastic substrate that is lighter and easier to mold instead of a heavy glass substrate. If there is a plastic substrate that is as transparent as glass and sufficiently tough, a flexible film liquid crystal panel that can be bent and rolled up and stored can be realized.

  However, plastic substrates have the disadvantage that they are inferior in heat resistance as compared to glass substrates. In particular, when a plastic substrate is applied to a full-color TFT type liquid crystal panel, the plastic substrate must withstand a high temperature of 200 to 220 ° C. in the manufacturing process. However, although vinyl polymers and polycarbonates typified by polymethyl methacrylate have extremely high transparency, the glass transitions are inferior in heat resistance at around 100 ° C. and 150 ° C., respectively. Polyethersulfone is excellent in transparency and toughness, but the glass transition temperature is 220 ° C., which is not sufficient in terms of heat resistance. At present, no material has yet been known that satisfies the required characteristics as a plastic substrate for flexible liquid crystal displays, which has both heat resistance, transparency and toughness.

  The polyimide resin excellent in heat resistance is mentioned as the candidate. In general, polyimide is prepared by reacting an aromatic tetracarboxylic dianhydride such as pyromellitic dianhydride with an aromatic diamine such as 4,4′-diaminodiphenyl ether in an equimolar polar solvent such as dimethylacetamide. A polyimide precursor having a high degree of polymerization that is easily obtained is formed into a film or the like, and is obtained by heating and curing.

  These wholly aromatic polyimides have not only excellent heat resistance but also chemical resistance, radiation resistance, electrical insulation, mechanical properties, etc., so they can be used for flexible printed circuit boards and tape automation bonding. Currently, it is widely used in various electronic devices such as base materials, protective films for semiconductor elements, and interlayer insulating films for integrated circuits.

  However, generally used aromatic polyimide has a drawback that the transparency of the film is extremely low because it has a strong electron absorption transition from ultraviolet to visible region. This is due to intramolecular conjugation through aromatic groups in the polyimide chain and intramolecular / intermolecular charge transfer interaction (see, for example, Non-Patent Document 1). For example, a polyimide film obtained from an aromatic tetracarboxylic dianhydride represented by the following formula (6) and an aromatic diamine is strongly colored.

  In order to make the polyimide film transparent, it is effective to use an aliphatic monomer in one or both of acid dianhydride and diamine. As a result, intramolecular conjugation and charge transfer interaction of the polyimide chain are hindered, and as a result, the transparency of the polyimide film and its precursor film in the entire ultraviolet / visible region is dramatically increased. From the viewpoint of chemical and physical heat resistance, an aliphatic monomer having a cyclic structure (alicyclic) is often used rather than a linear structure.

  When a polyimide precursor is polymerized from an alicyclic diamine and various tetracarboxylic dianhydrides, a crosslinkable salt is formed between the carboxyl group and the unreacted amino group in the low molecular weight amic acid generated at the initial stage of the polymerization reaction. Formation occurs. Since the salt is usually low in solubility in the polymerization solvent and excluded from the reaction system as a precipitate, the polymerization will be stopped if it does not dissolve at all. In an extreme case, for example, a combination of pyromellitic dianhydride and trans-1,4-diaminocyclohexane causes a serious problem that the polymerization reaction does not proceed at all due to the formation of a very strong salt. The same applies when 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter referred to as CBDA) is used instead of pyromellitic dianhydride. This is due to the fact that the basicity of aliphatic diamines is much higher than that of commonly used aromatic diamines.

  An interfacial polymerization method is disclosed as a method for avoiding salt formation when using an aliphatic diamine (see, for example, Non-Patent Document 2). In this method, tetracarboxylic dianhydride and alcohol are first reacted to form a dialkyl ester of tetracarboxylic acid, which is then chlorinated and dissolved in an oil layer, and this and an aliphatic diamine dissolved in an alkaline aqueous solution are mixed with oil / water. Polymerization is performed at the interface to obtain an alkyl ester of polyamic acid. This can be heat imidized to obtain an alicyclic polyimide.

  However, in this polymerization method, the production process is complicated and it is difficult to obtain a polyimide precursor having a high degree of polymerization, and the variation in molecular weight from batch to batch is also large. Further, the interfacial polycondensation method has low productivity and is not practical. Furthermore, since the interfacial polymerization method generates chlorine as a serious problem, it is not preferable for use as an electronic material.

  It is possible to make the polyimide transparent by using aliphatic tetracarboxylic dianhydride instead of aromatic as the tetracarboxylic dianhydride component. Currently known cycloaliphatic tetracarboxylic dianhydrides include bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5- (dioxo Tetrahydrofuryl-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 4- (2,5-dioxotetrahydrofuran-3-yl) -tetralin-1,2-dicarboxylic anhydride, tetrahydrofuran-2 , 3,4,5-tetracarboxylic dianhydride, bicyclo-3,3 ′, 4,4′-tetracarboxylic dianhydride, 3c-carboxymethylcyclopentane-1r, 2c, 4c-tricarboxylic acid 1, 4: 2,3-dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4- Cyclo Emissions Tan tetracarboxylic dianhydride, and the like.

  However, except for 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter referred to as CBDA), these alicyclic tetracarboxylic dianhydrides have problems in terms of polymerization reactivity and are sufficient. High molecular weight materials are often not obtained to the extent that they exhibit film toughness.

  As mentioned above, CBDA is exceptionally highly reactive with various aromatic diamines as an alicyclic tetracarboxylic dianhydride, but this is due to steric strain accumulated in the acid anhydride ring of CBDA. It is considered to be. Therefore, the amide acid formation reaction in which the acid anhydride group of CBDA reacts with diamine to open the ring is likely to occur thermodynamically (that is, the polymerization reactivity is high), but conversely, the ring closure reaction of the polyimide precursor (polyamic acid). There is a problem that (imidation reaction) hardly occurs. This means that a higher temperature is required to complete the imidization reaction, and the use of CBDA is not advantageous from the viewpoint of coloring the polyimide film.

  Thus, it is not easy to obtain a transparent and tough polyimide film using an alicyclic tetracarboxylic dianhydride, and a material that satisfies the required characteristics as a plastic substrate for flexible displays is not yet known. is the current situation.

  In recent years, increasing the calculation speed of the microprocessor and shortening the rise time of the clock signal have become important issues in the information processing and communication fields, but when using polyimide as an interlayer insulating film of a semiconductor chip, It is necessary to lower the dielectric constant of the polyimide film.

  In order to reduce the dielectric constant of polyimide, it is effective to reduce π electrons by replacing aromatic units with alicyclic units (see Non-Patent Document 3, for example). For this purpose, the use of alicyclic monomers, in particular alicyclic tetracarboxylic dianhydrides, is advantageous.

  However, as described above, alicyclic tetracarboxylic dianhydrides generally have low polymerization reactivity, so if the molecular weight of the polyimide is not sufficiently high, problems such as cracking of the polyimide film and peeling from the substrate may occur. , Greatly impair the reliability of the device.

  If an alicyclic tetracarboxylic dianhydride having a high polymerization reactivity becomes available, it can provide an important material as a transparent plastic substrate for flexible displays, but such an alicyclic tetracarboxylic dianhydride can be provided. And the present condition is that the polyimide derived from it is not known.

Prog. Polym. Sci. , Vol. 26,259- (2001) High Perform Polym. , Vol. 10, 11- (1998) Macromolecules, vol. 32, 4933- (1999)

  The present invention has high transparency, sufficient film toughness, and a high glass transition temperature, and includes electrical insulating films and liquid crystal display substrates, organic EL display substrates, electronic paper substrates, solar cell substrates, and particularly flexible substrates in various electronic devices. A polyimide useful as a plastic substrate for display, a precursor thereof, a production method thereof, and a tetracarboxylic acid compound useful as a raw material for producing the polyimide have been desired.

  In view of the above problems, as a result of earnest research, it is possible to easily obtain a high molecular weight polymer of a polyimide precursor by reacting with various diamines using the alicyclic structure-containing tetracarboxylic acids of the present invention. Furthermore, the polyimide obtained by imidizing it achieves high transparency, high heat resistance and sufficient film toughness. The present invention has been found, and the present invention has been completed.

  According to the present invention, an alicyclic structure-containing polyimide useful as an electrical insulating film or a flexible display plastic substrate in various electronic devices, a precursor thereof, a production method thereof, and a tetracarboxylic acid compound useful as a production raw material of the polyimide are provided. Is done. According to the present invention, by using an alicyclic structure-containing tetracarboxylic dianhydride, a charge transfer interaction can be suppressed and a highly transparent polyimide can be obtained. The polyimide of the present invention is a polyimide having sufficient film toughness, high glass transition temperature, and low dielectric constant. Electrical insulation film and liquid crystal display substrate in various electronic devices, substrate for organic electroluminescence display, substrate for electronic paper, solar It is useful as a substrate for a battery, particularly a transparent plastic substrate for a flexible display.

  That is, the gist of the present invention is as follows.

[1] General formula (1)

(In general formula (1), P represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxy group, n represents an integer of 1 to 3, and A represents a divalent aromatic group or a divalent fat. Represents a group.)

The polyimide which has a repeating unit represented by these.

[2] General formula (2)

(In General Formula (2), Q represents a hydrogen atom, a C1-C12 linear or branched alkyl group, or a trialkylsilyl group, and P, n, and A are synonymous with [1]. )

The polyimide precursor which has a repeating unit represented by these.

[3] The polyimide precursor according to [2], which has an intrinsic viscosity of 0.4 dL / g or more.

[4] General formulas (3) to (5)

(In the general formulas (3) to (5), X represents a halogen atom or a hydroxyl group, R represents a linear or branched alkyl group having 1 to 12 carbon atoms, and P and n are as defined in [1]. .)

A tetracarboxylic acid compound represented by any of the above and a diamine compound are reacted to give a general formula (2)

(In General Formula (2), Q represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, or a trialkylsilyl group, P and n are as defined above, and A is 2 Represents a divalent aromatic group or a divalent aliphatic group.)

After obtaining a polyimide precursor having a repeating unit represented by general formula (1), the polyimide precursor is cyclized (imidized) by heating or using a dehydrating reagent.

(In general formula (1), P, n and A have the same meanings as [1].)

The manufacturing method of the polyimide which has a repeating unit represented by these.

[5] A process for producing a polyimide without isolating a polyimide precursor by subjecting a tetracarboxylic acid compound and a diamine compound to a polycondensation reaction in a single step in a solvent. The manufacturing method of the polyimide of description.

[6] A transparent plastic substrate for liquid crystal display or organic electroluminescence display, comprising the polyimide according to [1].

[7] Glass transition temperature (Tg) is 250 ° C. or higher, light transmittance at a wavelength of 400 nm is 60% or higher, birefringence is 0.01 or lower, and does not break or breaks in a 180 ° bending test. A transparent plastic substrate for a liquid crystal display or organic electroluminescence display, comprising the polyimide according to [1], characterized by having an elongation of 10% or more.

[8] Polyimide precursors according to [2] and [3], and general formulas (3) to (5) which are raw materials for producing the polyimide according to [1] 1

(In General Formulas (3) to (5), X represents a halogen atom or a hydroxyl group, R represents a linear or branched alkyl group having 1 to 12 carbon atoms, and P represents a hydrogen atom or 1 carbon atom. 6 represents an alkyl group or an alkoxy group, and n represents an integer of 1 to 3.)

A tetracarboxylic acid compound represented by any one of

  According to the present invention, by using an alicyclic structure-containing tetracarboxylic dianhydride, a charge transfer interaction can be suppressed and a highly transparent polyimide can be obtained. Furthermore, it is possible to provide a polyimide having sufficient film toughness, high glass transition temperature, and low dielectric constant, and a method for producing the same. The alicyclic structure-containing polyimide of the present invention is useful as an electrical insulating film and a liquid crystal display substrate, an organic electroluminescence display substrate, an electronic paper substrate, a solar cell substrate, and particularly a transparent plastic substrate for flexible displays in various electronic devices. It is.

  By using the alicyclic structure-containing tetracarboxylic dianhydride of the present invention as a monomer, even when an aliphatic diamine is used, salt formation is suppressed during polymerization of the polyimide precursor, and a high molecular weight polyimide precursor can be easily obtained. As a result, the industrially useful material having sufficient film toughness and satisfying the above required characteristics can be provided.

  When an aliphatic diamine is selected as the diamine component to be combined with the tetracarboxylic dianhydride represented by the formulas (3) to (5) during the polymerization of the polyimide precursor, the charge transfer interaction is hindered, resulting in The polyimide obtained is transparent up to the ultraviolet region and can give a polyimide having a very low dielectric constant.

  Even when the tetracarboxylic dianhydride of the present invention is used in the polymerization of the polyimide precursor, salt formation occurs slightly, but the salt is not so strong, and the salt gradually becomes longer by stirring for a long time at room temperature. It is possible to easily obtain a transparent, uniform and highly viscous polyimide precursor solution which is dissolved.

  The strength of salt formation that occurs when using aliphatic diamines depends on the steric structure of the monomer. When the steric structure of the monomer is bulky or has a bulky substituent, the crosslinking density of the salt decreases due to the steric hindrance effect, and the solubility of the salt in the polymerization solvent increases, resulting in prolonged stirring at room temperature. It gradually dissolves and the polymerization reaction can proceed. Unlike CBDA, the tetracarboxylic dianhydride molecule of the present invention contains a cis, cis-cyclohexanedicarboxylic anhydride unit greatly deviated from the planar structure (sterically bent), which is a cross-linked by salt bond. It is thought that it contributes to the progress of the polymerization reaction by lowering the density and consequently increasing the solubility of the salt.

  Embodiments of the present invention will be described in detail below, but these are examples of the embodiments of the present invention and the present invention is not limited to these contents.

Of the tetracarboxylic acids represented by the formulas (3) to (5) of the present invention, P _n is a hydrogen atom in the formulas (3) to (5) from the viewpoint of easy availability of raw materials and production costs. The alicyclic structure-containing tetracarboxylic acids represented by the following formulas (7) to (9) are preferably used.

(In the formula, X represents a halogen atom or a hydroxyl group, and R represents a linear or branched alkyl group having 1 to 12 carbon atoms.)

  From the tetracarboxylic acids represented by the above formulas (7) to (9) and a diamine, a polyimide precursor represented by the following formula (10) can be obtained.

(In general formula (10), Q and A have the same meanings as in formula (4).)

  By subjecting the polyimide precursor represented by the formula (10) to a heat dehydration cyclization (imidization) reaction or by subjecting the tetracarboxylic acids represented by the formulas (7) to (9) to a polycondensation reaction, A polyimide represented by the formula (11) can be obtained.

(In general formula (11), A has the same meaning as in formula (4).)

<Method for producing alicyclic structure-containing tetracarboxylic acids>
Of the alicyclic structure-containing tetracarboxylic acids represented by the formulas (3) to (5) of the present invention, as an example, in the formulas (3) to (5), all the Ps are hydrogen atoms. A method for producing tetracarboxylic acids represented by 7) to (9) will be described.

  First, although the manufacturing method of the tetracarboxylic dianhydride represented by Formula (7) is demonstrated, it is not limited to this.

  As an example of the method for producing the tetracarboxylic dianhydride represented by the formula (7), the general formula (12)

(In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms.)

In the solvent, the biphenyltetracarboxylic acid ester represented by the formula (13) is hydrogenated with hydrogen in the presence of a catalyst.

(In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms.)

The compound of the general formula (13) is hydrolyzed to cyclohexylphenyltetracarboxylic acid, and further dehydrated to obtain the cyclohexylphenyltetracarboxylic dianhydride represented by the formula (7). Can be converted.

  Here, as the biphenyltetracarboxylic acid ester represented by the general formula (12), 1,1′-biphenyl-3,3 ′, 4,4′-tetracarboxylic acid tetramethyl, 1,1′-biphenyl Examples include tetraethyl -3,3 ', 4,4'-tetracarboxylate, tetrabutyl 1,1'-biphenyl-3,3', 4,4'-tetracarboxylate, and the like.

  The solvent used in the method of the present invention is not limited as long as it is a solvent that dissolves the biphenyltetracarboxylic acid ester represented by the general formula (12) and does not cause a side reaction under hydrogenation conditions. Examples thereof include alcohols such as methanol, ethanol, and 2-propanol, ethers such as tetrahydrofuran, diethyl ether, and diisopropyl ether, and esters such as methyl acetate and ethyl acetate. The amount of the solvent used is not particularly limited as long as the biphenyltetracarboxylic acid ester represented by the general formula (12) is sufficiently dissolved, but is usually 2 to 100 times the mass of the raw material compound. It is preferable that

  As the catalyst used in the method of the present invention, a nickel catalyst and a noble metal catalyst can be used. The noble metal catalyst is a preferred catalyst for the process of the present invention because it enables hydrogenation of the compound of the general formula (12) at a lower temperature and a lower pressure. As the noble metal catalyst, for example, a catalyst in which a noble metal catalyst component such as palladium carbon, ruthenium carbon, rhodium carbon, palladium alumina or the like is supported on a carrier is used. As the noble metal catalyst component carrier, activated carbon, alumina, silica or the like is preferably used. Among these, the palladium carbon catalyst has advantages such as a small amount of by-products such as bicyclohexyl tetracarboxylic acid ester and a large surface area of the support and a high hydrogenation rate, and is suitable for the method of the present invention. Used.

  The amount of the noble metal catalyst component contained in the noble metal supported catalyst is usually 0.1 to 10% by mass relative to the total mass of the supported catalyst.

  In the method of the present invention, the catalyst amount of the noble metal catalyst contained in the reaction system is preferably 0.5 to 20% by mass with respect to the mass of the biphenyl tetracarboxylic acid ester represented by the general formula (12). If the amount of the catalyst is less than 0.5% by mass, the hydrogenation reaction rate may be extremely slow, and if it exceeds 20% by mass, the catalytic effect is saturated and no particular improvement in the effect is observed. is there.

  Examples of the nickel catalyst used in the method of the present invention include a nickel diatomaceous earth catalyst. The nickel content in the nickel diatomaceous earth catalyst is usually 30 to 60% by mass.

  The catalyst amount of the nickel catalyst contained in the reaction system of the method of the present invention is usually 5 to 40% by mass with respect to the mass of the biphenyltetracarboxylic acid ester represented by the general formula (12).

  Although the hydrogenation reaction with hydrogen in the method of the present invention proceeds even at normal pressure, it is preferably hydrogenated under pressure to increase the reaction rate, and the hydrogen pressure is preferably 0.5 to 10 MPa. More preferably, it is 1.0 to 5.0 MPa. When the hydrogen pressure is less than 0.5 MPa, the hydrogenation reaction rate becomes extremely slow, and the remaining amount of unreacted biphenyltetracarboxylic acid ester may increase. As a product, the amount of perhydrogenated product such as bicyclohexyl tetracarboxylic acid ester may increase.

  In the method of the present invention, the hydrogenation reaction temperature is preferably 70 to 170 ° C. When the temperature is less than 70 ° C., the reaction rate becomes extremely slow and the residual amount of unreacted biphenyltetracarboxylic acid ester may increase. When the temperature is higher than 170 ° C., formation of by-products The amount may increase.

  The progress of the reaction can be determined by determining the amount of hydrogen absorbed in the reaction system using a pressure gauge. In order to reduce the production amount of the perhydride, it is preferable to cool the reaction system when the hydrogen absorption amount reaches 100 to 120% of the theoretical amount. When the reaction is stopped in a state where the hydrogen absorption amount is less than 100% of the theoretical amount, unreacted biphenyltetracarboxylic acid ester is likely to remain, and this residual compound is represented by the general formula (13), which is the target compound. Separation from cyclohexyl phenyl tetracarboxylic acid ester may be difficult. When the hydrogen absorption amount is more than 120% of the theoretical amount, the amount of bicyclohexyl tetracarboxylic acid ester that is a perhydrogenated product may be excessive.

  When the hydrogenation reaction is carried out under the above preferred reaction conditions, a reaction time of 0.5 to 20 hours is sufficient.

  After completion of the reaction, the catalyst is filtered off from the reaction system, and then the reaction solution is concentrated under reduced pressure and cooled to easily obtain a high-purity cyclohexylphenyltetracarboxylic acid ester with a small content of inorganic salt. be able to. In this case, salt-containing wastewater with a large environmental load is not generated.

  The cyclohexyl phenyl tetracarboxylic acid ester represented by the general formula (13) obtained by the above method is hydrolyzed to form cyclohexyl phenyl tetracarboxylic acid, and further dehydrated, whereby the formula (7) Can be converted to the represented cyclohexylphenyltetracarboxylic dianhydride. Further, the cyclohexyl phenyl tetracarboxylic acid ester represented by the general formula (13) is heated in the presence of a low-boiling point carboxylic acid anhydride while removing the low-boiling point carboxylic acid ester produced. It can convert into the cyclohexyl phenyl tetracarboxylic dianhydride represented by said Formula (7).

  Next, although the manufacturing method of the tetracarboxylic acid represented by Formula (8) is demonstrated, it is not limited to this. The tetracarboxylic acid represented by the formula (8) can be easily obtained by hydrolyzing the tetracarboxylic dianhydride represented by the formula (7). Specifically, the tetracarboxylic dianhydride is dissolved in a water-soluble solvent such as tetrahydrofuran and added dropwise to a dilute alkaline aqueous solution having a pH of 7 to 10 kept at room temperature to 100 ° C. with stirring. The produced precipitate is separated by filtration and washed with water, redissolved in a water-soluble solvent such as tetrahydrofuran, and dropped into a dilute acidic aqueous solution having a pH of 3 to 7 maintained at room temperature to 100 ° C. with stirring. The produced precipitate is filtered off and washed with water, followed by vacuum drying at 40 to 100 ° C. to obtain the target tetracarboxylic acid.

  Next, although the synthesis method of the tetracarboxylic acid derivative represented by Formula (9) is demonstrated, it is not limited to this. This is easily obtained from the tetracarboxylic dianhydride represented by the formula (7). Specifically, the dicarboxylic acid dialkyl ester is quantitatively determined by adding an excessive amount of dehydrated alcohol (carbon number 1 to 12) to the tetracarboxylic dianhydride of the formula (7) and heating to reflux for 1 to 12 hours. can get. In this case, a lower alcohol such as methanol, ethanol, propanol or the like is preferably used as the alcohol from the viewpoint of easy distillation after the reaction. Next, an excess amount of a chlorinating agent is added to the obtained dicarboxylic acid dialkyl ester and heated to quantitatively synthesize a high-purity dialkyl ester dicarboxylic acid dichloride that can be used for polymerization by chlorinating the carboxylic acid moiety. be able to. Thionyl chloride is preferably used as the chlorinating agent because it is easy to remove the chlorinating agent after the chlorination reaction. When chlorinating with thionyl chloride, a catalyst such as N, N-dimethylformamide or pyridine can be added to accelerate the reaction. In order to further increase the purity, dialkyl ester dicarboxylic acid dichloride can be recrystallized using a nonpolar solvent. At this time, a low-polarity inert solvent such as n-hexane, cyclohexane, benzene, toluene, ethyl acetate, ether, chloroform, or a mixture thereof is suitably used as the recrystallization solvent.

<Polymer precursor polymerization method>
Below, the manufacturing method of the polyimide precursor represented by Formula (4) of this invention is demonstrated. As an example, a method for producing a polyimide precursor represented by the formula (10) by reacting with a diamine using a tetracarboxylic dianhydride (hereinafter referred to as CPDA) represented by the formula (7) will be described. It is not limited to. Specifically, diamine is first dissolved in a polymerization solvent, and the alicyclic structure-containing tetracarboxylic dianhydride (CPDA) powder of the present invention is gradually added to the solution, and a mechanical stirrer is used at room temperature for 1 to 72. Stir for hours. In a polymerization system using an aromatic diamine, the total monomer component concentration is 5 to 40% by weight, preferably 10 to 30% by weight. In a polymerization system using an aliphatic diamine, the monomer concentration is 5 to 30% by weight, preferably It is in the range of 7 to 20% by weight. By carrying out polymerization in this monomer concentration range, a polyimide precursor solution having a uniform and high degree of polymerization can be obtained.

  In the aromatic diamine system, when polymerization is performed at a concentration lower than the above monomer concentration range, the polymerization degree of the polyimide precursor is not sufficiently high, and the finally obtained polyimide film may be brittle. Polymerization at a higher concentration is not preferred because the monomer may not be sufficiently dissolved or the reaction solution may become non-uniform and gel. On the other hand, in the case of aliphatic diamine system, if the polymerization is performed at a concentration lower than the above concentration range, the degree of polymerization may be lowered, and at a higher concentration, a strong salt is formed and a long polymerization reaction time is required until the salt is completely dissolved. There is a risk of lowering productivity.

  A polyimide precursor represented by the formula (10) can be polymerized by using a CPDA derivative represented by the formula (9) instead of CPDA. As an example, the case where a CPDA derivative in which X is a chlorine atom and R is a methyl group in formula (9) will be described, but is not limited thereto. Specifically, first, diamine is dissolved in a polymerization solvent containing a hydrochloric acid scavenger (base), the CPDA derivative powder is gradually added to the solution, and the mixture is stirred at room temperature for 1 to 72 hours using a mechanical stirrer. The total concentration of the monomer components is 5 to 40% by weight, preferably 10 to 30% by weight. By carrying out polymerization in this monomer concentration range, a polyimide precursor solution having a uniform and high degree of polymerization can be obtained. In the polymerization, an organic base such as pyridine or triethylamine is preferably used as the base.

  Although it does not specifically limit as aliphatic diamine which can be used in the range which does not impair the polymerization reactivity of the polyimide precursor which concerns on this invention, and the required characteristic of a polyimide, For example, 4,4'- methylenebis (cyclohexylamine), 4,4 '-Methylenebis (3-methylcyclohexylamine), 4,4'-methylenebis (3-ethylcyclohexylamine), 4,4'-methylenebis (3,5-dimethylcyclohexylamine), 4,4'-methylenebis (3 5-diethylcyclohexylamine), 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-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7 -Heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine and the like. Two or more of these may be used in combination.

  Although it does not specifically limit as aromatic diamine which can be used in the range which does not impair the polymerization reactivity of the polyimide precursor which concerns on this invention, and the required characteristic of a polyimide, For example, p-phenylenediamine, m-phenylenediamine, 2,4- Diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, 4,4′-methylenedianiline, 4,4′-methylenebis (3-methylaniline), 4,4 ′ -Methylenebis (3-ethylaniline), 4,4'-methylenebis (2-methylaniline), 4,4'-methylenebis (2-ethylaniline), 4,4'-methylenebis (3,5-dimethylaniline), 4,4′-methylenebis (3,5-diethylaniline), 4,4′-methylenebis (2,6-dimethylaniline), , 4′-methylenebis (2,6-diethylaniline), 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 2,4′-diaminodiphenyl ether, 2,2 ′ -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, 2,2′-bis (trifluoromethyl) benzidine, 2,2′-bis (trifluoromethyl) -4, 4′-oxydianiline, 1,4-bis (4-aminophenoxy) ) Benzene, 1,4-bis (3-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) Examples include propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, and p-terphenylenediamine. Two or more of these may be used in combination.

  In the general formula (1), the general formula (2), the general formula (10), the general formula (11), etc., the divalent aromatic group or divalent aliphatic group represented by A is the above-mentioned aliphatic diamine or It maintains the structure derived from the structure of the diamine used in the production of the polyimide of the present invention, such as an aromatic diamine (structure formed between two amino groups). Examples of the divalent aliphatic group represented by A include, for example, “unsubstituted, or one or more substituted with a further C1-C6 alkyl group represented by a halogen atom represented by fluorine or a methyl group ( C2-C6 cycloalkyl)-(C1-C6 alkyl)-(C5-C6 cycloalkane) "is a divalent aliphatic group having a structure in which one hydrogen atom is removed from each cycloalkyl moiety; Two or more hydrogen atoms from “C5 to C6 cycloalkene” which may be substituted with one or more further C1 to C6 alkyl groups represented by a methyl group and may have a ketone structure in the structure Divalent aliphatic group having a structure excluding “a divalent aliphatic group having a structure in which two hydrogen elements are removed from“ C5 to C6 cycloalkane ””; “(C1 to C3 alkyl)-(C5 to C6 cyclohexane”); Alkyl -(C1-C3 alkane) "is a divalent aliphatic group having a structure in which one hydrogen atom is removed one by one from the two alkyl moieties; including" adamantane structure, (C7-C12 bicyclo or tricycloalkane) "to 2 A divalent aliphatic group having a structure in which two hydrogen atoms are removed; a divalent aliphatic group having a structure in which two hydrogen atoms are removed from “C2 to C12 alkane”, and the like. In addition, examples of the divalent aromatic group represented by A include, for example, “C6— which is substituted with one or more C1-C6 alkyl groups including benzene, which are unsubstituted or represented by a methyl group. A divalent aromatic group having a structure in which two hydrogen atoms are removed from "C18 aromatic hydrocarbon"; "unsubstituted or two or more benzene rings are substituted with one or more C1-C6 alkyl groups represented by a methyl group" It may be A divalent aromatic group having a structure in which one hydrogen atom is removed from two benzene nuclei of diphenyl- (C1-C6 alkane) optionally substituted with one or more halogen atoms represented by fluorine. A divalent fragrance having a structure in which one hydrogen atom is removed from two benzene nuclei of “unsubstituted or diphenyl ether optionally substituted with one or more C1-C3 haloalkyl group represented by trifluoromethyl group”; A divalent aromatic group having a structure in which one hydrogen atom is removed from two benzene nuclei of “diphenylsulfone”; a group having a structure in which one hydrogen atom is removed from two benzene nuclei of “benzophenone” A divalent aromatic group having a structure in which a hydrogen atom is removed one by one from two benzene nuclei of “benzanilide”; “unsubstituted or C1 typified by a hydroxyl group and a methyl group” One from two benzene nuclei of “biphenyl optionally substituted with one or more C1 to C6 alkoxy group represented by C6 alkyl group, C1 to C6 alkoxy group represented by methoxy group or C1 to C3 haloalkyl group represented by trifluoromethyl group” A divalent aromatic group having a structure in which hydrogen atoms are removed one by one; a divalent aromatic group having a structure in which one hydrogen atom is removed from each of the two benzene nuclei at the ends of “bis (phenoxy) phenyl”; A divalent aromatic group having a structure in which one hydrogen atom is removed from two benzene nuclei at the end of “phenoxy) biphenyl”; one hydrogen atom from each of the two benzene nuclei at the end of “bis (phenoxyphenyl) sulfone” A divalent aromatic group having a structure excluding bis; “unsubstituted or bis (phenoxyphenyl) in which the alkane moiety may be substituted with one or more halogen atoms represented by fluorine” -(C1-C6 alkane) "divalent aromatic group having a structure in which one hydrogen atom is removed from each of the two benzene nuclei; one hydrogen atom from each of the two benzene nuclei of" terphenyl " And divalent aromatic groups such as a divalent aromatic group having a structure excluding.

  Among the above diamines, it is particularly preferable to use an aliphatic diamine from the viewpoint of characteristics required for a plastic substrate for a flexible liquid crystal display, particularly film transparency. In addition, the use of an aromatic diamine containing an electron-withdrawing group such as a trifluoromethyl group or a sulfonyl group can also be expected to be effective in improving transparency because the charge transfer interaction is suppressed. Such aromatic diamines include 2,2′-bis (trifluoromethyl) benzidine, 2,2′-bis (trifluoromethyl) -4,4′-oxydianiline, 2,2-bis (4 -(4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, and the like.

  Among the above diamines, from the viewpoint of characteristics required for a plastic substrate for flexible liquid crystal displays, particularly film toughness, diamines containing a flex bond such as an ether group, a sulfonyl group, and a methylene group in the main chain are preferable. '-Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 2,4'-diaminodiphenyl ether, 2,2'-diaminodiphenyl ether, 2,2'-bis (trifluoromethyl) -4 , 4′-oxydianiline, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (3-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, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 2,2-bis (4-aminophenyl) hexafluoro In addition to propane and the like, diamines containing a methylene group or an isopropylidene group in the main chain, that is, 4,4′-methylenedianiline, 4,4′-methylenebis (3-methylaniline), 4,4′-methylenebis (3 -Ethylaniline), 4,4'-methylenebis (2-methylaniline), 4,4'-methylenebis (2-ethyl) Aniline), 4,4′-methylenebis (3,5-dimethylaniline), 4,4′-methylenebis (3,5-diethylaniline), 4,4′-methylenebis (2,6-dimethylaniline), 4, 4'-methylenebis (2,6-diethylaniline), 4,4'-methylenebis (cyclohexylamine), 4,4'-methylenebis (3-methylcyclohexylamine), 4,4'-methylenebis (3-ethylcyclohexylamine) ), 4,4′-methylenebis (3,5-dimethylcyclohexylamine), 4,4′-methylenebis (3,5-diethylcyclohexylamine), isophoronediamine, 1,4-cyclohexanebis (methylamine), 2, 5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl) Cyclo [2.2.1] heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 2,2-bis (4-aminocyclohexyl) propane, 2,2-bis ( 4-aminocyclohexyl) hexafluoropropane and the like are preferably used.

  In addition to the cycloaliphatic structure-containing tetracarboxylic dianhydride (CPDA) represented by formula (7), the polymerization reactivity of the polyimide precursor according to the present invention and the required characteristics of the polyimide are not significantly impaired. The aliphatic tetracarboxylic dianhydride that can be used is not particularly limited. For example, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5- (Dioxotetrahydrofuryl-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 4- (2,5-dioxotetrahydrofuran-3-yl) -tetralin-1,2-dicarboxylic anhydride, Tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, bicyclo-3,3 ′, 4,4′-tetracarboxylic dianhydride, 3c-carboxymethylcyclopentane-1 r, 2c, 4c-tricarboxylic acid 1,4: 2,3-dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride Products, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, etc. Two or more of these may be used in combination.

  Moreover, aromatic tetracarboxylic dianhydride components other than CPDA can be partially used within a range that does not significantly impair the polymerization reactivity of the polyimide precursor and the required characteristics of the polyimide according to the present invention. The copolymerizable aromatic dianhydride is not particularly limited, and examples thereof include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4, 4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride, 2 , 2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, hydroquinone bis (trimellitic amine Hydride), 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride and the like. These may be used alone or in combination of two or more as copolymerization components.

  Among the copolymer components used in combination with the CPDA of the present invention, it is preferable to use an aliphatic tetracarboxylic dianhydride from the viewpoint of the characteristics required for a plastic substrate for flexible liquid crystal displays, particularly the transparency of the film.

  When the CPDA of the present invention and the tetracarboxylic dianhydride are co-polymerized, the content of CPDA is 50 to 100 mol%, more preferably 70 to 100 mol% of the total tetracarboxylic dianhydride used. It is a range.

  The solvent used in the polymerization reaction of the polyimide precursor is preferably an aprotic solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, etc. If a monomer and the polyimide precursor to produce | generate melt | dissolve, there will be no problem and it will not be specifically limited to the structure. Specific examples of such solvents include amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, γ-butyrolactone, γ-valerolactone, and δ-valerolactone. , Γ-caprolactone, ε-caprolactone, cyclic ester solvents such as α-methyl-γ-butyrolactone, carbonate solvents such as ethylene carbonate and propylene carbonate, glycol solvents such as triethylene glycol, m-cresol, p-cresol, 3- Phenol solvents such as chlorophenol and 4-chlorophenol, acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide and the like are preferably employed. In addition, other common organic solvents such as phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, ptyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, Tetrahydrofuran, dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, terpene, mineral spirit, petroleum naphtha solvent Etc. can also be added and used.

  The polyimide precursor of the present invention is applied to a solution (varnish) or a substrate and dried to be used as a film, and after appropriate dilution of the varnish, it is dropped and filtered in a large amount of poor solvent such as water or methanol. -It can also be dried and isolated as a powder.

  The intrinsic viscosity of the polyimide precursor according to the present invention is preferably as high as possible from the viewpoint of the toughness of the polyimide film, but is preferably at least 0.4 dL / g or more, more preferably 1.0 dL / g or more. It is especially preferable that it is 5 dL / g or more. When the intrinsic viscosity value is less than 0.4 dL / g, the film forming property is remarkably deteriorated, and a serious problem such as cracking of the cast film may occur. Further, from the viewpoint of handleability of the polyimide precursor, the intrinsic viscosity value is desirably lower than 5.0 dL / g.

  It is not necessary to use a polymer dissolution accelerator, that is, a metal salt such as lithium bromide or lithium chloride, which is often added during the polymerization of polyamide or the like, in the polymerization reaction of the polyimide precursor in the present invention. These metal salts should not be used because if the metal ions remain in the polyimide film even in a trace amount, the reliability as an electronic device is remarkably lowered.

<Production method of polyimide>
The alicyclic structure-containing polyimide of the present invention can be produced by subjecting the polyimide precursor obtained by the above method to a dehydration ring-closing reaction (imidation reaction). At this time, examples of the usable form of polyimide include a film, a metal substrate / polyimide film laminate, a powder, a molded product, and a solution.

  First, a method for producing a polyimide film will be described. A solution (varnish) of the polyimide precursor is cast on a substrate of glass, copper, aluminum, stainless steel, silicon or the like, and dried in an oven at 40 to 180 ° C., preferably 50 to 150 ° C. The polyimide film of the present invention is produced by heating the obtained polyimide precursor film on a substrate in vacuum, in an inert gas such as nitrogen, or in air at 200 to 400 ° C., preferably 250 to 350 ° C. be able to. The heating temperature is preferably 200 ° C. or higher from the viewpoint of sufficiently carrying out the imidization ring-closing reaction, and 400 ° C. or lower from the viewpoint of the thermal stability of the produced polyimide film. The imidization is preferably performed in a vacuum or in an inert gas, but if the imidization temperature is not too high, it may be performed in air.

  The imidation reaction can also be performed by immersing the polyimide precursor film in a solution containing a dehydrating cyclization reagent such as acetic anhydride in the presence of a tertiary amine such as pyridine or triethylamine instead of thermally. is there. In addition, a polyimide precursor film partially or completely imidized is prepared by previously charging and stirring these dehydrating cyclization reagents in a polyimide precursor varnish, and casting and drying them on the substrate. You can also. This may be further heat-treated in the above temperature range.

  When the polyimide precursor varnish obtained by the polymerization reaction is appropriately diluted as it is or with the same solvent and then heated to 150 to 200 ° C., the polyimide itself is dissolved in the solvent used. A polyimide solution (varnish) can be easily produced. When insoluble in a solvent, polyimide powder can be obtained as a precipitate. At this time, toluene, xylene or the like may be added in order to azeotropically distill off water which is a by-product of the imidization reaction. Further, a base such as γ-picoline can be added as a catalyst. After imidation, this reaction solution can be dropped and filtered in a large amount of poor solvent such as water or methanol to isolate the polyimide as a powder. Alternatively, the polyimide powder can be redissolved in the polymerization solvent to obtain a polyimide varnish.

  Furthermore, the polyimide of the present invention can be polymerized in one step without isolating the polyimide precursor by reacting tetracarboxylic dianhydride and diamine in a solvent at a high temperature. At this time, the polymerization solution may be maintained in the range of 130 to 250 ° C., preferably 150 to 200 ° C., from the viewpoint of promoting the reaction. When the polyimide is insoluble in the solvent used, the polyimide is obtained as a precipitate, and when soluble, it is obtained as a polyimide varnish. The polymerization solvent is not particularly limited, and examples of usable solvents include aprotic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide. However, a phenol solvent such as m-cresol or an amide solvent such as NMP is more preferably used. In order to azeotropically distill off water, which is a by-product of the imidization reaction, to these solvents, toluene, xylene, or the like can be added. A base such as γ-picoline can be added as an imidization catalyst. After the reaction, the solution can be dropped and filtered into a large amount of poor solvent such as water or methanol to isolate the polyimide as a powder. When the polyimide is soluble in a solvent, the powder can be redissolved in the above solvent to obtain a polyimide varnish.

  The polyimide film according to the present invention can also be formed by applying the polyimide varnish on a substrate and drying at 40 to 400 ° C., preferably 100 to 350 ° C.

  A polyimide molded body can be produced by heat-compressing the polyimide powder obtained as described above at 200 to 450 ° C., preferably 250 to 430 ° C.

  It is an isomer of polyimide by adding and stirring a dehydrating reagent such as N, N-dicyclohexylcarbodiimide or trifluoroacetic anhydride in the polyimide precursor solution and reacting at 0 to 100 ° C., preferably 0 to 60 ° C. Polyisoimide is formed. The isoimidization reaction can also be performed by immersing the polyimide precursor film in a solution containing the dehydrating reagent. After forming into a film in the same procedure as the above using this polyisoimide varnish, it can be easily converted to polyimide by heat treatment at 250 to 450 ° C., preferably 270 to 400 ° C.

  In the polyimide of the present invention and its precursor, if necessary, an oxidation stabilizer, a filler, an adhesion promoter, a silane coupling agent, a photosensitizer, a photopolymerization initiator, a sensitizer, a terminal blocking agent, a crosslinking agent, etc. Additives can be added.

  As a characteristic required for applying the polyimide according to the present invention to a plastic substrate for a flexible liquid crystal display, the glass transition temperature of the polyimide is preferably 250 ° C. or higher, and more preferably 300 ° C. or higher. The cut-off wavelength, which is an index of transparency of the polyimide film, is preferably 360 nm or less, and more preferably 340 nm or less. Similarly, the light transmittance at a wavelength of 400 nm, which is an index of transparency, is preferably 60% or more, and more preferably 70% or more. Further, the polyimide film can be applied to the industrial field as long as it is not broken by a 180 ° bending test as an index of film toughness. However, it is more preferable that the polyimide film has a breaking elongation of 10% or more in the tensile test, and more preferably 30% or more. preferable. If the birefringence is 0.01 or less, there is no serious problem in applying to the optical material, but 0.005 or less is more preferable. From the viewpoint of heat resistance against the heat process during the production of the TFT type liquid crystal display, the glass transition temperature of the polyimide film is preferably 250 ° C. or higher, and more preferably 270 ° C. or higher. As the polyimide of the present invention in which polyimide is used for a plastic substrate for a flexible liquid crystal display, “the glass transition temperature (Tg) is 250 ° C. or more, the light transmittance at a wavelength of 400 nm is 60% or more, and the birefringence is 0.01 Examples of preferable examples include those having the following properties in a well-balanced state of “not breaking in a 180 ° bending test or having a breaking elongation of 10% or more”.

  Since the polyimide of the present invention has an alicyclic structure, it is slightly inferior to long-term thermal stability as compared to wholly aromatic polyimides not containing this, but has a glass transition temperature of 250 ° C. or higher, TFT type liquid crystal display or semiconductor chip The short-term heat resistance required at the time of production is sufficiently high, and there is no problem in application to the industrial field.

<Application>
Since the polyimide of the present invention has high transparency, sufficient film toughness, high glass transition temperature and relatively low dielectric constant, it can be used as an electrical insulating film in various electronic devices, a substrate for liquid crystal display, a substrate for organic electroluminescence display, and an electronic paper. It is useful as a substrate for a display, a substrate for a solar cell, particularly a plastic substrate for a flexible display.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, it is not limited to these Examples. The physical property values in the following examples were measured by the following methods.

<Infrared absorption spectrum>
Using a Fourier transform infrared spectrophotometer (FT-IR5300 manufactured by JASCO Corporation), the infrared absorption spectra of the polyimide precursor and the polyimide thin film were measured by a transmission method. In order to confirm the molecular structure of the synthesized tetracarboxylic acids, an infrared absorption spectrum was measured by the KBr method.

^<1 H-NMR spectrum>
In order to confirm the molecular structure of the synthesized alicyclic tetracarboxylic dianhydride, ¹ H-NMR of the synthesized product in deuterated dimethyl sulfoxide using a JEOL NMR spectrophotometer (ECP400). The spectrum was measured.

<Differential scanning calorimetry (melting point and melting curve)>
The melting point and melting curve of the synthesized alicyclic tetracarboxylic dianhydride were measured using a differential scanning calorimeter (DSC3100) manufactured by Bruker Ax in a nitrogen atmosphere at a heating rate of 2 ° C./min.

<Intrinsic viscosity>
A 0.5% by weight polyimide precursor solution (solvent: N, N-dimethylacetamide) was measured at 30 ° C. using an Ostwald viscometer.

<Glass transition temperature: Tg>
The glass transition temperature of the polyimide film was determined from the loss peak at a frequency of 0.1 Hz and a heating rate of 5 ° C./min by dynamic viscoelasticity measurement using a thermomechanical analyzer (TMA4000) manufactured by Bruker Ax.

<Linear thermal expansion coefficient: CTE>
Using a thermal mechanical analyzer (TMA4000) manufactured by Bruker Ax Co., the range of 100 to 200 ° C. from the elongation of the test piece at a load of 0.5 g / film thickness of 1 μm and a heating rate of 5 ° C./min by thermomechanical analysis. The linear thermal expansion coefficient of the polyimide film was determined as an average value at.

<5% weight loss temperature: Td5>
Using a thermogravimetric analyzer (TG-DTA2000) manufactured by Bruker Ax, the initial weight of the polyimide film was reduced by 5% in the temperature rising process at a temperature rising rate of 10 ° C./min in nitrogen or air. The temperature was measured. Higher values indicate higher thermal stability.

<Cutoff wavelength (transparency)>
Using a UV-visible spectrophotometer (V-520) manufactured by JASCO Corporation, the visible / ultraviolet transmittance from 200 nm to 900 nm was measured. The wavelength (cutoff wavelength) at which the transmittance was 0.5% or less was used as an index of transparency. The shorter the cutoff wavelength, the better the transparency of the polyimide film.

<Light transmittance (transparency)>
The light transmittance at 400 nm was measured using an ultraviolet-visible spectrophotometer (V-520) manufactured by JASCO Corporation. The higher the transmittance, the better the transparency of the polyimide film.

<Birefringence>
Using an Abbe refractometer (Abbe 4T) manufactured by Atago Co., Ltd., the refractive index in the direction parallel to the polyimide film (nin) and the direction perpendicular to the polyimide film (nout) was measured with an Abbe refractometer (using a sodium lamp, wavelength 589 nm). The birefringence (Δn = nin−nout) was determined from the difference in refractive index.

<Dielectric constant>
Using an Abbe refractometer (Abbe 4T) manufactured by Atago Co., based on the average refractive index [nav = (2nin + nout) / 3] of the polyimide film, the dielectric constant of the polyimide film at 1 MHz according to the following formula: εcal = 1.1 × nav2 (Εcal) was calculated.

<Water absorption rate>
A polyimide film (film thickness: 20 to 30 μm) vacuum-dried at 50 ° C. for 24 hours was immersed in water at 25 ° C. for 24 hours, and then excess moisture was wiped off, and the water absorption (%) was determined from the increase in mass.

<Elastic modulus, elongation at break>
Using a tensile tester (Tensilon UTM-2) manufactured by Toyo Baldwin Co., Ltd., a tensile test (stretching speed: 8 mm / min) was performed on a polyimide film test piece (3 mm × 30 mm), and the initial slope of the stress-strain curve From the elastic modulus, the elongation at break (%) was determined from the elongation at the time the film was broken. Higher elongation at break means higher film toughness.

(Example 1)
<Synthesis of tetracarboxylic dianhydride (CPDA)>
Tetracarboxylic dianhydride (CPDA) represented by the formula (7) was synthesized as follows.
Production of tetramethyl 3,3 ′, 4,4′-cyclohexylphenyltetracarboxylate In an autoclave with a 2 liter stirrer, 200 g of tetramethyl 3,3 ′, 4,4′-biphenyltetracarboxylate (hereinafter referred to as BPTM) (0.518 mol), 43.2 g of 5% palladium-carbon (water content 53.1%), and 865 g of 2-propanol were charged, and the air in the autoclave was charged three times at a nitrogen pressure of 0.3 MPa, followed by a hydrogen pressure of 0. Replaced 3 times with 3 MPa. While maintaining the hydrogen pressure in the autoclave at 3.5 MPa, heating and stirring were started, the temperature was raised to 105 ° C., and heating and stirring was continued. Five hours after the start of heating, hydrogen absorption reached a theoretical amount, so heating was stopped. After cooling the reaction system to room temperature, the pressure in the autoclave was returned to normal pressure, and the catalyst was removed by filtration from the reaction mixture. When the obtained reaction liquid was analyzed by capillary gas chromatography, the content of the contained compound was as follows: tetramethyl 3,3 ′, 4,4′-cyclohexylphenyltetracarboxylate (hereinafter referred to as CPTM): 90%, BPTM: 0%, 3,3 ′, 4,4′-bicyclohexyltetracarboxylate tetramethyl (hereinafter referred to as BCTM): 9%. The reaction solution was concentrated under reduced pressure to 58% by mass of the original mass, and stirred at 20 ° C. for crystallization. The precipitated crystals were collected by filtration and then heat-dried under reduced pressure to obtain 126 g of CPTM. When the obtained CPTM was analyzed by capillary gas chromatography, three peaks derived from stereoisomers were observed, and the area percentage of each peak was 86%, 8%, and 6%.

(1) Melting point: 78.5-80 ° C
(2) IR spectrum (KBr tablet method): 1724 cm ⁻¹ (v _{C = 0} )
(3) ¹ H-NMR spectrum: δ (ppm) 1.3 to 2.4 (m, 2H, cyclohexane ring methylene hydrogen), 2.6 (m, 2H, carboxymethyl group-bonded methine hydrogen), 3.3 (M, 1H, phenyl group-bonded methine hydrogen), 3.6 (d, 6H, cyclohexane side ester methyl hydrogen), 3.8 (d, 6H, aromatic ring side ester methyl hydrogen), 7.3 to 7.7 (M, 3H, aromatic ring hydrogen)
(4) GC-MS: 392 (M ⁺ )

Synthesis of 3,3 ′, 4,4′-cyclohexylphenyltetracarboxylic acid A 500 ml reaction vessel was charged with 39.2 g (0.10 mol) of CPTM, 17.6 g (0.44 mol) of sodium hydroxide and 350 ml of distilled water, The temperature of the reaction system was raised and refluxed for 2 hours. After cooling the resulting reaction solution, 50 g of toluene was added thereto and washed three times in order to remove neutral components. After adding 900 g of 3% sulfuric acid aqueous solution to the aqueous layer in the mixed solution, this was extracted with 500 ml of ethyl acetate, washed with 100 ml of distilled water, dried over sodium sulfate, concentrated, and 3, 3 ′, 4 , 4′-cyclohexylphenyltetracarboxylic acid 29.5 g was obtained. The yield was 88.0% and the purity was 98.6%.

Synthesis of 3,3 ′, 4,4′-cyclohexylphenyltetracarboxylic dianhydride—1
In a 100 ml reaction vessel, 39.5 g (0.09 mol) of 3,3 ′, 4,4′-cyclohexylphenyltetracarboxylic acid and 45.4 g (0.45 mol) of acetic anhydride were charged. The temperature was raised and refluxed for 2 hours. The obtained reaction liquid was concentrated and dried to obtain 3,3 ′, 4,4′-cyclohexylphenyltetracarboxylic dianhydride, that is, 22.8 g of tetracarboxylic dianhydride represented by the formula (7). It was. The yield was 85.1% and the purity was 99.7%.

Synthesis of 3,3 ′, 4,4′-cyclohexylphenyltetracarboxylic dianhydride-2
In a 200 ml reactor equipped with a rectifying column, 39.2 g (0.10 mol) of CPTM, 27.0 g (0.45 mol) of acetic acid, 13.3 g (0.07 mol) of paratoluenesulfonic acid, 100 ml of xylene, The mixture was gradually warmed. That is, while removing methyl acetate having a low boiling point from the mixture out of the reaction system, it was heated to 140 ° C. and aged at this temperature for 8 hours. When the product was analyzed by liquid chromatography, it was found that the yield of 3,3 ′, 4,4′-cyclohexylphenyltetracarboxylic dianhydride, that is, tetracarboxylic dianhydride represented by the formula (7) was 91. 4%. Infrared absorption spectrum (KBr method), ¹ H-NMR spectrum and differential scanning calorimetry curve (melting curve) are shown in FIG. 1, FIG. 2 and FIG. 3, respectively.

(Example 2)
In a well-dried sealed reaction vessel equipped with a stirrer, 5 mmol of 2,2′-bis (trifluoromethyl) benzidine (hereinafter referred to as TFMB) was dissolved in N-methyl-2-pyrrolidone (NMP). A tetracarboxylic dianhydride (hereinafter referred to as CPDA) powder represented by the formula (7) described in 5 above is gradually added and stirred at room temperature for 72 hours to obtain a uniform, transparent and viscous polyimide precursor solution. Obtained. The solute concentration at this time is 20.1% by weight. This polyimide precursor solution did not precipitate or gel at all even when allowed to stand at room temperature and −20 ° C. for one month, and showed extremely high solution storage stability. The intrinsic viscosity of the polyimide precursor measured in NMP at 30 ° C. was 0.912 dL / g, which was a high polymer. The polyimide precursor solution obtained by applying this polyimide precursor solution to a glass substrate and drying in a hot air dryer at 80 ° C. for 2 hours is heat-treated at 320 ° C. for 2 minutes and then heat-treated at 320 ° C. for 2 hours. A transparent and tough polyimide film having a thickness of about 20 μm was obtained. The completion of imidization was confirmed from the infrared absorption spectrum. The polyimide film was not broken by a 180 ° bending test and showed flexibility. (Table 1) shows the physical properties of the polyimide film. It has an extremely high glass transition temperature of 337 ° C., a transmittance of 81.5% at a cutoff wavelength of 322 nm and 400 nm, good transparency, an elongation at break of 76.6% and sufficient film toughness, and birefringence Δn = 0. The thermal stability was sufficiently high at 480 ° C. in nitrogen and 442 ° C. in air, and the required characteristics as a plastic substrate for flexible liquid crystal displays were satisfied. Further, the dielectric constant was relatively low at 2.78, and excellent characteristics as various insulating films were exhibited. Infrared absorption spectra of the polyimide precursor and the polyimide thin film are shown in FIGS.

(Example 3)
Similar to the method described in Example 2, except that 2,2′-bis (trifluoromethyl) -4,4′-oxydianiline (hereinafter referred to as TFMODA) was used as the diamine instead of TFMB. The polyimide precursor was polymerized and imidized to produce a polyimide film, and the physical properties were evaluated. Physical property values are shown in Table 1. It showed high Tg, high transparency, sufficient film toughness, low birefringence and relatively low dielectric constant. Infrared absorption spectra of the polyimide precursor and the polyimide thin film are shown in FIGS.

Example 4
A polyimide precursor is polymerized and imidized in the same manner as described in Example 2 except that 4,4′-oxydianiline (hereinafter referred to as ODA) is used as the diamine instead of TFMB. Fabricated and evaluated for physical properties. Physical property values are shown in Table 1. It showed high Tg, relatively high transparency, very high film toughness and low birefringence. The infrared absorption spectra of the polyimide precursor and the polyimide thin film are shown in FIGS.

(Example 5)
A polyimide precursor was polymerized according to the method described in Example 2 using 4,4′-methylenebis (cyclohexylamine) (hereinafter referred to as MBCHA) instead of TFMB as diamine. Although salt formation was observed at the initial stage of polymerization due to the addition of CPDA, the salt gradually dissolved relatively easily by continuing stirring at room temperature, and finally a uniform, transparent and viscous polyimide precursor was obtained. A body solution was obtained. This is the effect of using CPDA for tetracarboxylic dianhydride. The polymerization started at a monomer concentration of 20.0% by weight and was diluted to 15% by weight to promote dissolution of the salt formed. In the same manner as described in Example 2, the polyimide precursor varnish was cast and imidized to prepare a polyimide film, and the physical properties were evaluated. Physical property values are shown in Table 1. It showed high Tg, high transparency, sufficient film toughness and very low birefringence. Infrared absorption spectra of the polyimide precursor and the polyimide thin film are shown in FIGS.

(Example 6)
A polyimide precursor was polymerized and cast in the same manner as described in Example 5 except that 4,4′-methylenebis (3-methylcyclohexylamine) (hereinafter referred to as MBMCHA) was used as the diamine instead of MBCHA. A polyimide film was prepared to evaluate the physical properties. Physical property values are shown in Table 1. It showed high Tg, high transparency, sufficient film toughness and low birefringence. Infrared absorption spectra of the polyimide precursor and the polyimide thin film are shown in FIGS.

(Example 7)
A polyimide film was prepared by polymerizing, casting, and imidizing a polyimide precursor in the same manner as described in Example 5 except that isophoronediamine (hereinafter referred to as IPDA) was used instead of MBCHA as a diamine, and physical properties were evaluated. did. Physical property values are shown in Table 1. It showed high Tg, high transparency, sufficient film toughness and low birefringence. The infrared absorption spectrum of the polyimide thin film is shown in FIG.

(Example 8)
The polyimide precursor was polymerized, cast and imidized in the same manner as described in Example 5 except that trans-1,4-cyclohexanediamine (hereinafter referred to as CHDA) was used instead of MBCHA as the diamine. Fabricated and evaluated for physical properties. Physical property values are shown in Table 1. It showed high Tg, high transparency, sufficient film toughness and low birefringence. The infrared absorption spectrum of the polyimide thin film is shown in FIG.

(Comparative Example 1)
The polyimide precursor was polymerized in the same manner as described in Example 4 except that 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was used instead of CPDA as tetracarboxylic dianhydride. And imidized to prepare a polyimide film. However, this polyimide film was intensely colored, and the transmittance at 400 nm was 0%. This is because charge transfer interaction occurred due to the use of wholly aromatic tetracarboxylic dianhydride.

(Comparative Example 2)
Bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride which is an alicyclic tetracarboxylic dianhydride instead of CPDA as tetracarboxylic dianhydride Polymerization was carried out in the same manner as described in Example 4 except that the product (hereinafter referred to as BTA) was used to obtain a polyimide precursor having an intrinsic viscosity of 0.38 dL / g. However, since the cast film was severely cracked, a high-quality polyimide film could not be obtained and the film physical properties could not be evaluated. This is because the polymerization reactivity of the BTA used was low and a sufficiently high molecular weight necessary for film formation could not be obtained.

  The polyimide obtained by the present invention has high transparency, sufficient film toughness and high glass transition temperature, and is used for electrical insulating films and liquid crystal display substrates, organic EL display substrates, electronic paper substrates, and solar cells in various electronic devices. The present invention provides a tetracarboxylic acid compound that is suitable as a substrate, particularly as a plastic substrate for flexible displays, and is useful as a useful polyimide, a precursor thereof, a production method thereof, and a production raw material of the polyimide.

2 is an infrared absorption spectrum of tetracarboxylic dianhydride described in Example 1. 2 is a 1H-NMR spectrum of tetracarboxylic dianhydride described in Example 1. FIG. 2 is a differential scanning calorimetry curve of tetracarboxylic dianhydride described in Example 1. 2 is an infrared absorption spectrum of a polyimide precursor thin film described in Example 2. 2 is an infrared absorption spectrum of a polyimide thin film described in Example 2. 4 is an infrared absorption spectrum of a polyimide precursor thin film described in Example 3. 3 is an infrared absorption spectrum of a polyimide thin film described in Example 3. It is an infrared absorption spectrum of the polyimide precursor thin film described in Example 4. 4 is an infrared absorption spectrum of a polyimide thin film described in Example 4. 5 is an infrared absorption spectrum of a polyimide precursor thin film described in Example 5. 6 is an infrared absorption spectrum of a polyimide thin film described in Example 5. It is an infrared absorption spectrum of the polyimide precursor thin film described in Example 6. It is an infrared absorption spectrum of the polyimide thin film as described in Example 6. 7 is an infrared absorption spectrum of a polyimide thin film described in Example 7. It is an infrared absorption spectrum of the polyimide thin film as described in Example 8.

Claims (8)

General formula (1)

(In general formula (1), P represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxy group, n represents an integer of 1 to 3, and A represents a divalent aromatic group or a divalent fat. Represents a group.)
The polyimide which has a repeating unit represented by these. General formula (4)

(In General Formula (2), Q represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, or a trialkylsilyl group, and P, n, and A have the same meanings as in claim 1. )
The polyimide precursor which has a repeating unit represented by these.   The polyimide precursor according to claim 2, which has an intrinsic viscosity of 0.4 dL / g or more. General formula (3)-(5)

(In the general formulas (3) to (5), X represents a halogen atom or a hydroxyl group, R represents a linear or branched alkyl group having 1 to 12 carbon atoms, and P and n are as defined in claim 1. .)
A tetracarboxylic acid compound represented by any of the above and a diamine compound are reacted to give a general formula (2)

(In General Formula (2), Q represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, or a trialkylsilyl group, P and n are as defined above, and A is 2 Represents a divalent aromatic group or a divalent aliphatic group.)
After obtaining a polyimide precursor having a repeating unit represented by general formula (1), the polyimide precursor is cyclized (imidized) by heating or using a dehydrating reagent.

(In the general formula (1), P, n and A have the same meaning as in claim 1).
The manufacturing method of the polyimide which has a repeating unit represented by these.   The polyimide according to claim 4, wherein a polyimide is produced without isolating a polyimide precursor by subjecting a tetracarboxylic acid compound and a diamine compound to a polycondensation reaction in a single step in a solvent. Manufacturing method.   A transparent plastic substrate for liquid crystal display or organic electroluminescence display, comprising the polyimide according to claim 1. Glass transition temperature (Tg) is 250 ° C. or more, light transmittance at a wavelength of 400 nm is 60% or more, birefringence is 0.01 or less, and it does not break in a 180 ° bending test or break elongation is 10%. A transparent plastic substrate for a liquid crystal display or an organic electroluminescence display, comprising the polyimide according to claim 1, characterized in that it has the above. General formulas (3) to (5), which are the polyimide precursors according to claim 2 and 3, and the raw materials for producing the polyimide according to claim 1.

(In general formulas (3) to (5), X represents a halogen atom or a hydroxyl group, R represents a linear or branched alkyl group having 1 to 12 carbon atoms, and P represents a hydrogen atom or 1 carbon atom. 6 represents an alkyl group or an alkoxy group, and n represents an integer of 1 to 3.)
A tetracarboxylic acid compound represented by any one of

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