JP4367622B2 - Method for producing polyimide / inorganic composite material - Google Patents

Description

  The present invention relates to a method for producing a polyimide / inorganic composite material, and more specifically, after reacting a solvent-soluble transparent polyimide resin and a reactive silane coupling agent with a polyimide end group, a sol-gel The present invention relates to a method for producing a polyimide / inorganic composite material having good dispersibility by linking polyimide molecular chains and an inorganic phase having a crosslinked network structure by a covalent bond and improving the compatibility.

  In general, polyimide resin is a heat-resistant resin obtained by ring-closing reaction of polyamic acid synthesized from aromatic tetracarboxylic acid anhydride and aromatic diamine, which is synthesized by these condensation reactions. It has excellent resistance to thermal decomposition due to stabilization and strong chemical bonding, has high durability against chemical changes such as oxidation or hydrolysis, and has excellent mechanical and electrical properties. In addition, because of its flexibility, it is widely used as a film, coating agent, molded part and insulating material in fields such as the electrical, electronic, automotive and aerospace industries.

  However, with the rapid integration of semiconductor elements in the electronic material field, higher levels of thermal stability and mechanical strength are required. In addition, it has improved compatibility with silicon wafers, thermal expansion and barrier properties, etc., and can be used as an adhesive layer for substrates for electronic industries, or it can be used as an alternative material for metals, glass and ceramics. There is a gradual increase in the need for technological developments that impart polyimide to polyimide.

  In order to give such characteristics to polyimide resin, research to manufacture hybrid materials in which silica with excellent thermal stability, oxidation resistance, electrical insulation and mechanical strength is introduced into polyimide has been actively studied. Yes.

  In the case of a composite material of organic polymer and silica, silica is mainly used as a reinforcing agent or filler. However, when it is attempted to produce by a mixing method, the compatibility of the polyimide / silica composite material is low due to low compatibility with the organic polymer. It is difficult to make the silica content exceed 10% by weight. When the silica content exceeds 10% by weight, white turbidity occurs due to phase separation, and the resulting composition tends to become brittle and to decrease flexibility and adhesion.

  Therefore, the sol-gel method has attracted attention as an effective synthesis method in the production of polyimide / inorganic composite materials. About the manufacturing method of the polyimide / silica composite material by the sol-gel method, polyamic acid, tetraalkoxysilane and distilled water, which are polyimide precursors composed of pyromellitic dianhydride and diaminodiphenyl ether, are added to hydrolyze the tetraalkoxysilane. Then, after obtaining silanol, a process is disclosed in which silanol is gelled simultaneously with imidization of polyamic acid by heat treatment (see Patent Documents 1 to 4). However, in such a method, the condensate of silanol does not form a chemically cross-linked structure with polyimide, so the interaction is weak, the dispersibility of silica is not sufficient, and if the silica content is increased, the homogeneity of the film is increased. There are drawbacks such as a decrease in transparency and a decrease in physical properties.

  A polyamic acid composed of an excess amount of pyromellitic dianhydride and diaminodiphenyl ether was synthesized, and then reacted with the same amount of 3-aminopropylmethyldiethoxysilane as the amount of the terminal acid anhydride group of the polyamic acid. Add a predetermined amount of tetraethoxysilane and distilled water in an active gas atmosphere, perform a sol-gel reaction, perform normal casting using a prepolymer viscous solution obtained by uniform stirring, and perform heat treatment and imidization simultaneously A manufacturing method is disclosed (see Patent Document 5). In this method, the dispersibility is improved because tetraethoxysilane is bonded to the carboxyl group via a silane coupling agent. However, since the silanol obtained by hydrolysis of tetraethoxysilane is gelled, the solvent is volatilized and imidized at the same time, repelling, irregularities, etc. are generated on the surface of the coating, and defects in surface smoothness are likely to occur. In addition, since there is a step of dehydrating imidization after casting, a high-temperature heat treatment is required, resulting in inferior molding processability and difficulty in controlling the film thickness. In addition, since the polyimide itself is brownish in color, there is a problem that it is not applicable to optical uses that require colorlessness and transparency.

JP-A-62-283153 JP-A-63-99234 JP-A-63-99235 JP-A-63-99536 JP-A-8-104749

  An object of the present invention is to solve the problems of the above-mentioned conventional polyimide / inorganic composite material production methods, and to produce a colorless and transparent polyimide / inorganic composite material having excellent heat resistance and flexibility. Is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have reached the present invention. That is, the present invention reacts a semi-aliphatic and / or all-aliphatic polyimide soluble in an organic solvent having a repeating unit represented by the formula (1) with a silane coupling agent having reactivity with the terminal group of the polyimide. The present invention relates to a method for producing a polyimide / inorganic composite material obtained by adding a silicon alkoxide and distilled water and performing a sol-gel reaction.

  The method for producing a polyimide / inorganic composite material according to the present invention uses a silane coupling agent and introduces a chemical cross-linking bond between a polyimide and an inorganic phase by a sol-gel method, and improves compatibility, heat resistance, It is useful for obtaining a colorless and transparent polyimide / inorganic composite material having excellent mechanical strength and flexibility.

  The semialiphatic and / or fully aliphatic polyimide used in the present invention is a semialiphatic and / or fully aliphatic polyimide soluble in an organic polar solvent having a repeating unit represented by the formula (1).

（式中、Ｒ_１は炭素数５〜１６の４価の脂肪族炭化水素基であり、Φは炭素数２〜２８の２価の脂肪族炭化水素基または炭素数１２〜２５の２価の芳香族炭化水素基である。）

(In the formula, R ₁ is a tetravalent aliphatic hydrocarbon group having 5 to 16 carbon atoms, and Φ is a divalent aliphatic hydrocarbon group having 2 to 28 carbon atoms or a divalent aliphatic hydrocarbon group having 12 to 25 carbon atoms. (It is an aromatic hydrocarbon group.)

  The semi-aliphatic and / or all-aliphatic polyimide used in the present invention is a polyimide having a tetravalent tetracarboxylic acid and a divalent diamine as constituent components, and an aliphatic tetracarboxylic acid or a derivative thereof and a diamine. It is a semi-aliphatic and / or wholly aliphatic polyimide obtained by reacting. Aliphatic tetracarboxylic acids or derivatives thereof include aliphatic tetracarboxylic acids, aliphatic tetracarboxylic acid esters, aliphatic tetracarboxylic dianhydrides, etc., preferably aliphatic tetracarboxylic dianhydrides. It is. As the diamine, either an aliphatic diamine or an aromatic diamine may be used, or a mixture thereof may be used. Particularly preferred is a diamine mainly composed of an aliphatic diamine. When the aromatic diamine is used in combination with the aliphatic diamine, the weight ratio of aromatic diamine / aliphatic diamine is preferably 1/3 or less.

  Examples of the aliphatic tetracarboxylic dianhydride include 1,2,4,5-cyclopentanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and bicyclo [2.2.2. ] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and the like. Among these, it is particularly preferable to use 1,2,4,5-cyclohexanetetracarboxylic dianhydride. These aliphatic tetracarboxylic dianhydrides can be used alone or in combination of two or more, but more preferably 1,2,4,5-cyclohexanetetracarboxylic dianhydride is used alone. Is good.

  Examples of the aliphatic diamine include isophorone diamine, ethylene diamine, 4,4-diaminodicyclohexyl methane, tetramethylene diamine, norbornane diamine, paraxylylene diamine, 1,3-bis (aminomethyl) cyclohexane, 1,3-diaminocyclohexane. , Hexamethylenediamine, polyethylene glycol bis (3-aminopropyl) ether, metaxylylenediamine, 4,4-methylenebis (cyclohexylamine), bicyclohexyldiamine, siloxane diamines, and the like. These diamines can be used alone or in combination of two or more.

  Furthermore, examples of the aromatic diamine include diaminodiphenyl ether, diaminodiphenylmethane, dimethylbenzidine, dimethoxybenzidine, diaminodiphenyl sulfide, diaminodiphenyl sulfoxide, diaminodiphenylsulfone, diaminobenzophenone, 2,2-bis (3-aminophenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,4- Bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4, 4-Bis (3-aminophenoxy) biphe 4,4-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3- Aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, etc. Is mentioned. These diamines can be used alone or in combination of two or more.

  The semi-aliphatic and / or fully aliphatic polyimide used in the present invention is soluble in an organic polar solvent. The semi-aliphatic polyimide is a transparent polyimide composed of an aliphatic tetracarboxylic acid or a derivative thereof and an aromatic diamine, and the total aliphatic polyimide is composed of an aliphatic tetracarboxylic acid or a derivative thereof and an aliphatic diamine. It is a colorless and transparent polyimide.

  The organic polar solvent is not particularly limited. For example, γ-butyrolactone, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphoramide, p- An aprotic organic polar solvent such as chlorophenol, m-cresol, and tetrahydrofuran is desirable.

  The semi-aliphatic and / or total aliphatic polyimide used in the present invention is 20 to 100 ° C., preferably 30 to 100 ° C. in an organic polar solvent, and preferably 20 wt.% As a polyimide solid concentration with respect to the total weight part including the organic polar solvent. % Soluble in the range of 50% by weight or more and more preferably in the range of 30% by weight or more and 40% by weight or less. If it is less than 20% by weight, it is difficult to increase the intrinsic viscosity of the polyimide, and if it exceeds 50% by weight, the viscosity of the polyimide solution at the stage where the intrinsic viscosity of the polyimide is increased is too high. It can be a cause.

Specifically, the polyimide / inorganic composite material of the present invention is produced by a method including the following steps.
(1) A step of imidizing an excess amount of an aliphatic tetracarboxylic acid or derivative thereof and a diamine in an organic polar solvent to synthesize a polyimide solution of a polyimide whose terminal is an acid anhydride group, or in an organic polar solvent A process of imidizing an aliphatic tetracarboxylic acid or a derivative thereof and an excess amount of a diamine to synthesize a polyimide solution of a polyimide having a terminal amino group,

(2) At least a silane coupling agent containing an amino group or an isocyanate group having reactivity with an acid anhydride group is added to the polyimide synthesized at the step (1) and having an acid anhydride group at the terminal. The step of preparing a solution containing an end-capped polyimide having an alkoxysilane structure at the end by charging and reacting in an excess amount than the amount of the above, or an isocyanate group having reactivity with an amino group in a polyimide having an amino group at the end A step of preparing a solution containing an end-capped polyimide having an alkoxysilane structure at the end by charging and reacting a silane coupling agent containing at least an amount exceeding the amount of polyimide end groups,

(3) A predetermined amount of silicon alkoxide and distilled water corresponding to the amount of alkoxy groups are added to the end-capped polyimide synthesized by the step (2) in an inert gas atmosphere by a sol-gel reaction method, and water is added. Adding a decomposition catalyst and stirring uniformly to produce a mixed solution containing a compound having a silanol group formed at the terminal and a hydroxide sol of silicon;

(4) The mixed solution containing the compound having a silanol group formed at the terminal and the silicon hydroxide sol, which is produced by the step (3), is heated to obtain a silicon and / or metal hydroxide sol. A step of producing a polyimide / inorganic composite material by performing gelation (sol-gel reaction) and solvent drying.

  In the synthesis of the polyimide described in the step (1), an aliphatic tetracarboxylic acid or a derivative thereof is added to a solution of an organic polar solvent of diamine, and a polyamic acid solution is obtained by maintaining the temperature around room temperature or lower. An azeotropic dehydrating agent such as toluene or xylene and an imidation catalyst are added, and a dehydration reaction is carried out while distilling the produced water out of the system to obtain a polyimide solution.

  Alternatively, after imidization of the reaction intermediate polyamic acid solution using a dehydrating agent such as acetic anhydride, a solvent having poor polyimide solubility such as methanol is added to precipitate the polyimide, followed by filtration, washing and drying. To obtain a polyimide solution dissolved in an organic polar solvent such as γ-butyrolactone. Regarding the imidization catalyst, a tertiary amine such as triethylamine, tributylamine, pyridine or β-picoline can be used in combination.

  In synthesizing the semi-aliphatic and / or fully aliphatic polyimide in the present invention, the organic polar solvent to be used is not particularly limited, but is preferably an aprotic organic polar solvent. For example, γ-butyrolactone, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphoramide, p-chlorophenol, m-cresol, tetrahydrofuran, etc. Can be mentioned. Of these, colorlessness and transparency are improved by using γ-butyrolactone and N, N-dimethylacetamide. These solvents can be used alone or in admixture of two or more.

  In the step (1), when synthesizing a polyimide whose terminal is an acid anhydride group, the reaction stoichiometric ratio of tetracarboxylic acid and / or dianhydride to diamine is 0.01 to 0.1 excess. It is suitable to make it react. When the excess amount exceeds 0.1, it becomes difficult to form a film due to a low degree of polymerization. On the other hand, when the excess amount is less than 0.01, the number of terminal acid anhydride functional groups is significantly reduced, and the following step ( Not only the reaction rate with the silane coupling agent in 2) is lowered, but also the crosslinking points with the network silica structure formed by the sol-gel reaction are not sufficient.

  In the step (1), the stoichiometric ratio of the diamine to the aliphatic tetracarboxylic acid or its derivative is not particularly limited, but it is appropriate to react by adding an excess of 0.02 to 0.1. If the excess amount exceeds 0.1, it becomes difficult to form a film due to a low degree of polymerization. On the other hand, if the excess amount is less than 0.02, the number of terminal amino groups is remarkably reduced, and in the subsequent step (2), Not only does the reaction rate with the silane coupling agent become low, but the crosslinking point with the network silica structure formed by the sol-gel reaction is not sufficient.

  Moreover, after making into the polyimide solution whose terminal is an acid anhydride group by a process (1), as a silane coupling agent added in order to seal a polyimide terminal in a process (2), an amino group or an isocyanate group is used. Although it will not specifically limit if it contains, It is preferable that it is a structure shown by Formula (2). Furthermore, it is preferable to use an aminosilane coupling agent having a sufficiently high reactivity with an acid anhydride group at room temperature.

（式中、Ｒ_２は炭素数１〜１０のアルキル基、Ｒ_３は炭素数３〜１０の２価の炭化水素基、Ｘはアミノ基又はイソシアネート基を示す。）

(In the formula, R ₂ represents an alkyl group having 1 to 10 carbon atoms, R ₃ represents a divalent hydrocarbon group having 3 to 10 carbon atoms, and X represents an amino group or an isocyanate group.)

  Examples include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, etc. Known compounds can be mentioned. It is desirable that the amount of the silane coupling agent added is at least in excess of the amount of terminal groups calculated from the molecular weight of the resulting polyimide. Moreover, it is preferable to stir for a fixed time between 30-80 degreeC so that reaction may fully advance. When kept at a temperature higher than 80 ° C., the silane coupling agent may be hydrolyzed by moisture remaining in the system, causing dehydration condensation.

  There is no particular limitation on the silane coupling agent that contains an isocyanate group after the polyimide solution having an amino group at the end in step (1) and then the polyimide end is sealed in step (2). Are known compounds such as 3-isocyanatopropyltriethoxysilane and 3-isocyanatopropyltrimethoxysilane. It is desirable that the amount of the silane coupling agent added is at least in excess of the amount of terminal groups calculated from the molecular weight of the resulting polyimide. Since the reaction between the isocyanate and the terminal amino group is sufficiently high at room temperature, it is preferable to stir at room temperature for a certain period of time so that the reaction proceeds sufficiently.

  In the step (3), an alkoxide of silicon and, if necessary, an organic polar solvent are added uniformly to a solution containing the end-capped polyimide obtained by the step (2) under an inert gas atmosphere, for example, a nitrogen stream. After stirring, formulas (3) to (5) in which a predetermined amount of distilled water for hydrolysis is added, a small amount of hydrolysis catalyst is added, and the mixture is stirred at room temperature for a certain time to form a silanol group at the terminal. A mixed solution containing the compound represented by the above and a silicon hydroxide sol is produced.

（式中、Ｒ_１は炭素数５〜１６の４価の脂肪族炭化水素基であり、Φは炭素数２〜２８の２価の脂肪族炭化水素基または炭素数１２〜２５の２価の芳香族炭化水素基である。）

(In the formula, R ₁ is a tetravalent aliphatic hydrocarbon group having 5 to 16 carbon atoms, and Φ is a divalent aliphatic hydrocarbon group having 2 to 28 carbon atoms or a divalent aliphatic hydrocarbon group having 12 to 25 carbon atoms. (It is an aromatic hydrocarbon group.)

（式中、Ｒ_１は炭素数５〜１６の４価の脂肪族炭化水素基であり、Φは炭素数２〜２８の２価の脂肪族炭化水素基または炭素数１２〜２５の２価の芳香族炭化水素基である。）

(In the formula, R ₁ is a tetravalent aliphatic hydrocarbon group having 5 to 16 carbon atoms, and Φ is a divalent aliphatic hydrocarbon group having 2 to 28 carbon atoms or a divalent aliphatic hydrocarbon group having 12 to 25 carbon atoms. (It is an aromatic hydrocarbon group.)

（式中、Ｒ_１は炭素数５〜１６の４価の脂肪族炭化水素基であり、Φは炭素数２〜２８の２価の脂肪族炭化水素基または炭素数１２〜２５の２価の芳香族炭化水素基である。）

(In the formula, R ₁ is a tetravalent aliphatic hydrocarbon group having 5 to 16 carbon atoms, and Φ is a divalent aliphatic hydrocarbon group having 2 to 28 carbon atoms or a divalent aliphatic hydrocarbon group having 12 to 25 carbon atoms. (It is an aromatic hydrocarbon group.)

  As a hydrolysis catalyst in a general silicon alkoxide sol-gel reaction, a known acid catalyst or base catalyst is used. By using an acid catalyst, the hydrolysis reaction rate is accelerated, but the subsequent polycondensation reaction of silanol is slowed, and a low molecular weight linear silica forms a crosslinked network structure. Further, it has been reported that when a basic catalyst is used, hydrolysis is fast but polycondensation reaction is fast, so that the basic skeleton of silica is in the form of particles of several tens to several hundreds of nanometers.

  When a polyimide-based silica composite material is obtained by using such a sol-gel reaction, an acid catalyst has an especially important effect. Specific examples of the acid catalyst include inorganic acids or organic acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid and oxalic acid, and hydrochloric acid is particularly preferred.

  The amount of silicon alkoxide added is not particularly limited, but is preferably 10 to 40% by weight, more preferably 20 to 30% by weight, based on the weight of the polyimide solid content in terms of the silica component. If it is less than 10% by weight, the silica content is insufficient to obtain a silica crosslinked product having sufficient physical properties by the sol-gel reaction. If it exceeds 40% by weight, the amount of the poor solvent for the polyimide in the system is excessive. The solubility of polyimide decreases and solids precipitate, and the subsequent drying process causes the organic phase of polyimide and the inorganic phase of silica to cause phase separation, causing the film to become cloudy and colorless and transparent. However, there is a drawback that the film is liable to crack because the flexibility is insufficient, and the film becomes tattered.

  Examples of the silicon alkoxide used in the present invention include a tetraalkoxysilane monomer and a tetraalkoxysilane partial condensate. Although it does not restrict | limit especially as a tetraalkoxysilane monomer, For example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane etc. are mentioned, It is preferable to use tetramethoxysilane with the highest reactivity among these. . The tetraalkoxysilane partial condensate can be used without limitation as long as it is composed of the above-exemplified monomers, but it is a methyl silicate oligomer (average silicon atom) that is commercially available at a relatively low price. It is preferable to use an ethyl silicate oligomer having a number of 2 to 11) or an ethyl silicate oligomer (average number of silicon atoms is 2 to 11), and a methyl silicate oligomer having a particularly high reactivity is the best. By using a silicate oligomer having a large boiling point, the rate at which silanol or alkoxysilane volatilizes and disappears in the drying step in the subsequent step (4) is significantly reduced, and the alcohol component produced in the system by dehydration condensation is reduced. be able to. When the average number of silicon atoms of these tetraalkoxysilane partial condensates exceeds 11, not only can a cyclic silicon oligomer be remarkably formed and a highly crosslinked silica structure cannot be obtained, but also particulate silica is associated. By forming secondary particles having a grown particle size, phase separation occurs and problems such as white turbidity of the film occur. The optimal average number of silicon atoms is 2-4.

  In combination with the silicon alkoxide used in the step (3), a metal alkoxide containing a metal element selected from the group of magnesium, aluminum, zirconium, and titanium may be used. For example, diethoxymagnesium, di- i-isopropoxymagnesium, di-n-butoxymagnesium, triethoxyaluminum, tri-n-butoxyaluminum, tri-i-isopropoxyaluminum, tetraethoxyzirconium, tetra-n-butoxyzirconium, tetra-i-isopropoxyzirconium , Tetraethoxytitanium, tetra-n-butoxytitanium, tetra-i-isopropoxytitanium and the like. One or more metal alkoxides can be used in combination with silicon alkoxide.

  In the step (4), the temperature at which the mixed solution containing the compound having a silanol group formed at the terminal and the silicon hydroxide sol is dried by casting by a normal casting method is 60 to 80 ° C. Preferably there is. When the temperature is lower than 60 ° C., the gelation of the silicon hydroxide sol is hardly caused. When the temperature is higher than 80 ° C., the crosslinking between the polyimide molecules and the silica phase and the gelation of the silicon hydroxide sol sufficiently progress. Before the process, the solvent evaporates, resulting in defects such as white turbidity of the film. Also, rapid thermal conversion tends to leave traces of water and alcohol components evaporating from the film surface as pores, and in order to prevent this, it is required to perform heat treatment gradually at a low temperature. The semi-dry polyimide / silica composite material thus obtained is maintained at a temperature of 150 ° C. to 350 ° C. in an inert gas atmosphere such as nitrogen to strengthen the silica and dry the residual solvent of the film.

  When the polyimide / inorganic composite material of the present invention is used as, for example, a molding material such as an electronic material, a film, or a sheet, or a coating material, a conventionally known and commonly used compounding agent such as an antioxidant, an ultraviolet ray, or the like is used. Any of an absorbent, a heat stabilizer, a colorant and the like can be used without particular limitation.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to these examples.

  The physical properties of the polyimide solution and the polyimide / inorganic composite material (film) were measured by the following methods.

<Intrinsic viscosity measurement>
A polyimide solution obtained by putting the polyimide solution prepared in Production Examples 1 to 6 into anhydrous methanol, precipitating a solid and removing the unreacted monomer, followed by filtration and vacuum drying at 80 ° C. for 12 hours. 0.1 g was dissolved in 20 mL of N-methyl-2-pyrrolidone, and the intrinsic viscosity at 30 ° C. was measured using a Canon Fenske viscometer. The intrinsic viscosity (μ) was determined by the following formula.
_{μ = ln (t s / t} 0) / C
t ₀ : Time when the solvent flows t _s : Time when the dilute polymer solution flows C: 0.5 g / dL

<Pyrolysis start temperature>
The heat resistance of the polyimide / inorganic composite material was increased to 1000 ° C. at 10 ° C./min in the atmosphere using a TGA-40M thermogravimetric apparatus manufactured by Shimadzu Corporation, and the thermal decomposition start temperature (hereinafter abbreviated as T _d ). ) Was measured.

<Tensile strength>
The mechanical properties of the polyimide / inorganic composite material (film) were measured in accordance with ASTM D882-88, and the tensile strength at break was measured using a Strograph V1-C manufactured by Toyo Seiki Seisakusho.

<YI value and haze H>
A color difference / turbidity measuring device COI-300A manufactured by Nippon Denshoku Industries Co., Ltd. is used as an index for evaluating the colorlessness and transparency according to “JIS K7105 Transparency Test Method” using a polyimide / inorganic composite material (film). YI value and haze H were determined.

<Reference example>
Synthesis of 1,2,4,5-cyclohexanetetracarboxylic dianhydride Catalyst with 552 g of pyromellitic acid and Rh supported on activated carbon in a 5 liter Hastelloy (HC22) autoclave 200 g and 1656 g of water were charged, the inside of the reaction vessel was replaced while stirring, and the hydrogen pressure of the reactor was 5.0 MPa, and the temperature was raised to 60 ° C. The reaction was carried out for 2 hours while maintaining the hydrogen pressure at 5.0 MPa. The hydrogen gas in the reaction vessel was replaced with nitrogen gas, the reaction solution was extracted from the autoclave, and the reaction solution was subjected to aging filtration to separate the catalyst. The filtrate was concentrated by removing water with a rotary evaporator under reduced pressure to precipitate crystals. The precipitated crystals were solid-liquid separated at room temperature, dried and dried to 481 g of 1,2,4,5-cyclohexanetetracarboxylic acid (yield). 85.0%). Subsequently, 481 g of the obtained 1,2,4,5-cyclohexanetetracarboxylic acid and 4000 g of acetic anhydride were charged into a 5-liter glass separable flask, and the inside of the reaction vessel was replaced with nitrogen gas while stirring. . The temperature was raised to the reflux temperature of the solvent under a nitrogen gas atmosphere, and the solvent was refluxed for 10 minutes. While stirring, the mixture was cooled to room temperature to precipitate crystals. The precipitated crystals were separated into solid and liquid and dried to obtain primary crystals. Further, the separated mother liquor was concentrated under reduced pressure using a rotary evaporator to precipitate crystals. The crystals were separated into solid and liquid and dried to obtain secondary crystals. The primary crystal and the secondary crystal were combined to obtain 375 g of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (anhydrous yield of 96.6%).

<Production Example 1>
Synthesis of semi-aliphatic acid anhydride group-terminated polyimide In a 500 mL five-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction ring, and a condenser tube with a fractionator, 19.52 g (0.097 mol) of diaminodiphenyl ether As a solvent, 168.58 g of γ-butyrolactone was charged and dissolved, and cooled to 5 ° C. using an ice water bath. While maintaining the same temperature, 22.62 (0.1 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 0.50 g (0.005 mol) of triethylamine as an imidization catalyst were added all at once. . After completion of dropping, the ice water bath was removed and the mixture was stirred at room temperature for 1 hour. Next, 12.0 g of metaxylene as an azeotropic dehydrating agent was added and the temperature was raised to 190 ° C., and the mixture was refluxed for 3 hours while distilling off the distillate as needed to raise the temperature to 200 ° C. to complete the reaction. Was cooled to 60 ° C. and the reaction solution was taken out. The weight of this polyimide solution was 205.26 g, and the total weight of the distillate was 17.66 g. The excess of 1,2,4,5-cyclohexanetetracarboxylic dianhydride relative to diaminodiphenyl ether is 0.03. After cooling the polyimide solution to room temperature, it was poured into 1 L of methanol to precipitate the polymer, filtered and washed with methanol, and then dried in a vacuum dryer at 100 ° C. for 24 hours to obtain 37.3 g of white powder (yield) 96.8%). The IR spectrum of this powder is shown in FIG. Absorption at 1702 and 1770 cm ⁻¹ peculiar to the imide group was observed.
The intrinsic viscosity of the polyimide solution was measured. The results are shown in Table 1.

<Example 1>
Preparation of polyimide / silica composite material The polyimide solution obtained by the production method 1 was charged into a 500 mL separable flask, and 1.11 g (0.005) of 3-aminopropyltriethoxysilane (APTE) with a dropping funnel with a side tube. The mixture was stirred at room temperature for 2 hours while gradually adding (mol). Next, 21.07 g of tetramethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., silica component of about 40%) was added and stirred uniformly, and then 9.11 g of distilled water, a small amount of hydrochloric acid, and γ- for dilution as required. Butyrolactone was added and reacted at room temperature for 2 hours to obtain a mixed solution containing a compound in which a silanol group was formed at the terminal having a silica content of 20% by weight with respect to the polyimide solid content and a silicon hydroxide sol.
Next, a mixed solution containing a compound having a silanol group formed at the terminal and a silicon hydroxide sol was cast on a stainless steel substrate using a gap coater, and then dried in the atmosphere at 60 ° C. for 6 hours. Then, after forming a wet gel film in which polyimide molecular chains and siloxane are linearly bonded, the process of aging the silica gel and drying the residual solvent of the solvent by heat treatment at 250 ° C. for 3 hours in a nitrogen atmosphere is repeated five times. A polyimide / silica composite film in which 10 to 20 μm thick polyimide and silica chemically formed a crosslinked structure was produced. Using these films, the YI value and haze H were determined. Thermal decomposition start temperature and tensile strength were measured. The results are shown in Table 1.

<Example 2>
After reacting with APTE in the same manner as in Example 1 using the semi-aliphatic anhydride group-terminated polyimide obtained by the method of Production Example 1, methyl silicate oligomer (manufactured by Tama Chemical Co., Ltd., average silicon) 17.24 g of 4 atoms, silica component of about 50%), distilled water, hydrochloric acid catalyst and dilute γ-butyrolactone were charged, and the silica content was 20% by weight with respect to the polyimide solid content as in Example 1. A mixed solution containing a compound in which a silanol group was formed and a silicon hydroxide sol was obtained. A polyimide / silica composite film was produced in the same manner as in Example 1, and the YI value, haze H, thermal decomposition start temperature, and tensile strength were measured. The results are shown in Table 1.

<Production Example 2>
Synthesis of semi-aliphatic amino group-terminated polyimide In a 500 mL five-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction ring, and a condenser tube with a fractionator, 20.72 g (0.103 mol) of diaminodiphenyl ether and a solvent 173.41 g of γ-butyrolactone was charged and dissolved, and cooled to 5 ° C. using an ice water bath. While maintaining the same temperature, 22.62 (0.1 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 0.50 g (0.005 mol) of triethylamine as an imidization catalyst were added all at once. . After completion of dropping, the ice water bath was removed and the mixture was stirred at room temperature for 1 hour. Next, 12.0 g of metaxylene as an azeotropic dehydrating agent was added and the temperature was raised to 190 ° C., and the mixture was refluxed for 3 hours while distilling off the distillate as needed to raise the temperature to 200 ° C. to complete the reaction. Was cooled to 60 ° C. and the reaction solution was taken out. The weight of this solution was 203.95 g, and the total weight of the distillate was 16.82 g. The excess of diaminodiphenyl ether relative to 1,2,4,5-cyclohexanetetracarboxylic dianhydride is 0.03. After cooling the polyimide solution to room temperature, it was poured into 1 L of methanol to precipitate the polymer, filtered and washed with methanol, and then dried in a vacuum dryer at 100 ° C. for 24 hours to obtain 39.1 g of white powder (yield) 98.5%). The IR spectrum of this powder is shown in FIG. Absorption at 1706 and 1766 cm ⁻¹ peculiar to the imide group was observed.

<Example 3>
Preparation of polyimide / silica composite material The polyimide varnish obtained by the production method 2 was charged into a 500 mL separable flask, and 1.24 g (0.005) of 3-isocyanatopropyltriethoxysilane (IPTE) with a dropping funnel with a side tube. The mixture was stirred at room temperature for 3 hours while gradually adding (mol). Next, 21.56 g of tetramethoxysilane was added and stirred uniformly. Then, 9.31 g of distilled water, a small amount of hydrochloric acid, and a diluted GBL solvent were added as necessary, and the mixture was reacted at room temperature for 2 hours. Thus, a mixed solution containing a compound having a silanol group formed at the terminal and a silicon hydroxide sol having a silica content of 20% by weight was obtained. A polyimide / silica composite film was produced in the same manner as in Example 1, and the YI value, haze H, thermal decomposition start temperature, and tensile strength were measured. The results are shown in Table 1.

<Example 4>
After reacting with IPTE in the same manner as in Example 3 using the semi-aliphatic amino group-terminated polyimide obtained by the method of Production Example 2, methyl silicate oligomer (manufactured by Tama Chemical Co., Ltd., average number of silicon atoms) (4, silica component: about 50%) 17.24 g, distilled water, hydrochloric acid catalyst and dilute γ-butyrolactone solvent were charged, and a sol-gel reaction was carried out. A mixed solution containing a compound having a silanol group formed at the terminal and a silicon hydroxide sol in weight% was obtained. A polyimide / silica composite film was produced in the same manner as in Example 1, and the YI value, haze H, thermal decomposition start temperature, and tensile strength were measured. The results are shown in Table 1.

<Production Example 3>
Synthesis of total aliphatic acid anhydride-terminated polyimide A 500 mL five-necked flask equipped with a thermometer, a stirrer, a nitrogen-introducing ring, and a condenser tube with a fractionator was charged with 20.51 g of 0,4-diaminodicyclohexylmethane (0 0.097 mol) and 80.54 g of N-methyl-2-pyrrolidone and 20.13 g of N, N-dimethylacetamide as a solvent were dissolved and cooled to 5 ° C. using an ice water bath. While maintaining the same temperature, 22.62 g (0.1 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 0.50 g (0.005 mol) of triethylamine as an imidization catalyst were added all at once. In the same manner as in Production Example 1, an acid anhydride group-terminated polyimide solution was produced. The weight of this solution was 143.82 g, and the total weight of the distillate was 16.54 g. The excess of 1,2,4,5-cyclohexanetetracarboxylic dianhydride relative to 4,4-diaminodicyclohexylmethane is 0.03.
After cooling the polyimide solution to room temperature, it was poured into 1 L of methanol to precipitate the polymer, filtered and washed with methanol, and then dried in a vacuum dryer at 100 ° C. for 24 hours to obtain 37.3 g of white powder (yield) 94.7%). The IR spectrum of this powder is shown in FIG. Absorption at 1689 and 1764 cm ⁻¹ peculiar to the imide group was observed.

<Example 5>
After reacting with APTE in the same manner as in Example 1 using the semi-aliphatic acid anhydride group-terminated polyimide obtained by the method of Production Example 3, methyl silicate oligomer (manufactured by Tama Chemical Co., Ltd., average silicon) 16.52 g of 4 atoms, silica component (about 50%), distilled water, hydrochloric acid catalyst and dilute γ-butyrolactone were charged, and a silanol group was formed at the terminal having a silica content of 20% by weight with respect to the polyimide solid content. A mixed solution containing the compound and a silicon hydroxide sol was obtained. A polyimide / silica composite film was produced in the same manner as in Example 1, and the YI value, haze H, thermal decomposition start temperature, and tensile strength were measured. The results are shown in Table 1.

<Production Example 4>
Synthesis of total aliphatic amino group-terminated polyimide In a 500 mL five-necked flask equipped with a thermometer, a stirrer, a nitrogen introducing ring, and a condenser tube with a fractionator, 21.77 g (0.103 g) of 4,4-diaminodicyclohexylmethane was added. Mol) and 132.53 g of N-methyl-2-pyrrolidone and 33.13 g of N, N-dimethylacetamide as a solvent were dissolved and cooled to 5 ° C. using an ice water bath. While maintaining the same temperature, 22.62 g (0.1 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 0.50 g (0.005 mol) of triethylamine as an imidization catalyst were added all at once. An amino group-terminated polyimide solution was produced in the same manner as in Production Example 2. The weight of this solution was 148.75 g, and the total weight of the distillate was 16.54 g. The excess of 4,4-diaminodicyclohexylmethane relative to 1,2,4,5-cyclohexanetetracarboxylic dianhydride is 3 mol%. After cooling the polyimide solution to room temperature, it was poured into 1 L of methanol to precipitate a polymer, filtered and washed with methanol, and then dried in a vacuum dryer at 100 ° C. for 24 hours to obtain 38.8 g (yield) 95.0%). The IR spectrum of this powder is shown in FIG. Absorption at 1691 and 1764 cm ⁻¹ peculiar to the imide group was observed.

<Example 6>
After reacting with IPTE in the same manner as in Example 3 using the total aliphatic amino group-terminated polyimide obtained by the method of Production Example 4, methyl silicate oligomer (manufactured by Tama Chemical Co., Ltd., average number of silicon atoms) And a compound having a silanol group formed at the terminal, which is charged with distilled water, hydrochloric acid catalyst and diluted γ-butyrolactone, and having a silica content of 20% by weight with respect to the polyimide solid content, A mixed solution containing a silicon hydroxide sol was obtained. A polyimide / silica composite film was produced in the same manner as in Example 1, and the YI value, haze H, thermal decomposition start temperature, and tensile strength were measured. The results are shown in Table 1.

<Comparative Example 1>
20.12 g (0.1 mol) of diaminodiphenyl ether and 168.58 g of γ-butyrolactone as a solvent were charged and dissolved, and cooled to 5 ° C. using an ice water bath. While maintaining the same temperature, 22.62 (0.1 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 0.50 g (0.005 mol) of triethylamine as an imidization catalyst were added all at once. . After completion of dropping, the ice water bath was removed and the mixture was stirred at room temperature for 1 hour. Next, 12.0 g of metaxylene as an azeotropic dehydrating agent was added and the temperature was raised to 190 ° C., and the mixture was refluxed for 3 hours while distilling off the distillate as needed to raise the temperature to 200 ° C. to complete the reaction. Was cooled to 60 ° C. and the reaction solution was taken out. This solution was cast on a glass substrate using a gap coater, and then dried in air at 100 ° C. for 1 hour to obtain a primary dry film. This film was fixed to a stainless steel frame, and was subjected to main drying at 200 ° C. for 3 hours in a nitrogen atmosphere to produce a colorless and transparent polyimide film, and the YI value, haze H, thermal decomposition start temperature, and tensile strength were measured. The results are shown in Table 1.

<Comparative example 2>
After reacting with APTE in the same manner as in Example 1 using the semi-aliphatic anhydride group-terminated polyimide obtained by the method of Production Example 1, methyl silicate oligomer (manufactured by Tama Chemical Co., Ltd., average silicon) A mixture solution containing a compound having a silanol group formed at the terminal and a silicon hydroxide sol was prepared so that the silica content was 5% by weight. This solution was cast on a stainless steel substrate using a gap coater, dried in the atmosphere at 60 ° C. for 6 hours to form a wet gel film, and then heat treated at 250 ° C. for 3 hours in a nitrogen atmosphere. The process of aging and drying of the residual solvent was repeated 5 times to produce a polyimide / silica composite film having a film thickness of 12 μm and a chemically crosslinked structure of polyimide and silica. YI value, haze H, thermal decomposition start Temperature and tensile strength were measured. The results are shown in Table 1.

<Comparative Example 3>
After reacting with IPTE in the same manner as in Example 3 using the semi-aliphatic amino group-terminated polyimide obtained by the method of Production Example 1, methyl silicate oligomer (manufactured by Tama Chemical Co., Ltd., average number of silicon atoms) 4 and a silica component of about 50%) were prepared so that the silica content was 40% by weight, and a mixed solution containing a compound having a silanol group formed at the terminal and a silicon hydroxide sol was obtained. This solution was cast on a stainless steel substrate using a gap coater and then dried in the atmosphere at 60 ° C. for 6 hours to form a wet gel film. However, the whole film became cloudy and a colorless and transparent film could not be obtained. It was. A heat treatment was performed at 250 ° C. for 3 hours in a nitrogen atmosphere to ripen the silica gel and dry the residual solvent. However, the film was brittle and cracked. The thermal decomposition start temperature and the tensile strength were measured. The results are shown in Table 1.

<Production Example 5>
Synthesis of acid anhydride group-terminated polyimide 19.92 g (0.099 mol) of diaminodiphenyl ether and 170.19 g of γ-butyrolactone as a solvent were charged and dissolved, and cooled to 5 ° C. using an ice water bath. While maintaining the same temperature, 22.62 g (0.1 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 0.50 g (0.005 mol) of triethylamine as an imidization catalyst were added all at once. An acid anhydride-terminated polyimide solution was produced in the same manner as in Production Example 1. The weight of this solution was 208.43 g, and the total weight of the distillate was 18.14 g. The excess of 1,2,4,5-cyclohexanetetracarboxylic dianhydride relative to diaminodiphenyl ether is 1 mol%.
After cooling the polyimide solution to room temperature, it was poured into 1 L of methanol to precipitate the polymer, filtered and washed with methanol, and then dried in a vacuum dryer at 100 ° C. for 24 hours to obtain 37.3 g of white powder (yield) 96.8%). The IR spectrum of this powder is shown in FIG. Absorption at 1702 and 1770 cm ⁻¹ peculiar to the imide group was observed.

<Production Example 6>
Synthesis of amino-terminated polyimide 20.33 g (0.101 mol) of diaminodiphenyl ether and 171.80 g of γ-butyrolactone as a solvent were charged and dissolved, and cooled to 5 ° C. using an ice water bath. While maintaining the same temperature, 22.62 g (0.1 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 0.50 g (0.005 mol) of triethylamine as an imidization catalyst were added all at once. An acid anhydride-terminated polyimide solution was produced in the same manner as in Production Example 1. The weight of this solution was 206.22 g, and the total weight of the distillate was 16.98 g. The excess of diaminodiphenyl ether relative to 1,2,4,5-cyclohexanetetracarboxylic dianhydride is 1 mol%.
The polyimide solution is cooled to room temperature, poured into 1 L of methanol to precipitate a polymer, filtered, washed with methanol, dried in a vacuum dryer at 100 ° C. for 24 hours, and white powder 38.0 g (yield) 96.6%). The IR spectrum of this powder is shown in FIG. Absorption at 1700 and 1765 cm ⁻¹ peculiar to the imide group was observed.

<Comparative example 4>
After reacting with APTE in the same manner as in Example 1 using the acid anhydride group-terminated polyimide obtained by the method of Production Example 5, methyl silicate oligomer (manufactured by Tama Chemical Co., Ltd., having an average number of silicon atoms) 4, about 50% silica component) was prepared so that the silica content was 20% by weight, and a mixed solution containing a compound having a silanol group formed at the terminal and a hydroxide sol of silicon was obtained. This solution was cast on a stainless steel substrate using a gap coater and then dried in the atmosphere at 60 ° C. for 6 hours. However, a self-supporting film could not be obtained because the film was cracked with the evaporation of the solvent. The wet gel after drying was transparent. The thermal decomposition start temperature and the tensile strength were measured. The results are shown in Table 1.

<Comparative Example 5>
After reacting with IPTE in the same manner as in Example 3 using the amino group-terminated polyimide obtained by the method of Production Example 6, methyl silicate oligomer (manufactured by Tama Chemical Co., Ltd., having an average number of silicon atoms of 4, Silica component (about 50%) was charged so as to have a silica content of 20% by weight to obtain a mixed solution containing a compound having a silanol group formed at the terminal and a hydroxide sol of silicon. This solution was cast on a stainless steel substrate using a gap coater and then dried in the atmosphere at 60 ° C. for 6 hours to form a wet gel film. However, the whole film became cloudy and a colorless and transparent film could not be obtained. It was. The thermal decomposition start temperature and the tensile strength were measured. The results are shown in Table 1.

<Comparative Example 6>
In a 500 mL five-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet ring, and a condenser tube with a fractionator, 21.14 g (0.1 mol) of 4,4-diaminodicyclohexylmethane and N-methyl-as a solvent were used. 80.54 g of 2-pyrrolidone and 20.13 g of N, N-dimethylacetamide were charged and dissolved, and cooled to 5 ° C. using an ice water bath. While maintaining the same temperature, 22.62 g (0.1 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 0.50 g (0.005 mol) of triethylamine as an imidization catalyst were added all at once. After completion of dropping, the ice water bath was removed and the mixture was stirred at room temperature for 1 hour. Next, 12.0 g of metaxylene as an azeotropic dehydrating agent was added and the temperature was raised to 190 ° C., and the mixture was refluxed for 3 hours while distilling off the distillate as needed to raise the temperature to 200 ° C. to complete the reaction. Was cooled to 60 ° C. and the reaction solution was taken out. This solution was cast on a glass substrate using a gap coater, and then dried in air at 100 ° C. for 1 hour to obtain a primary dry film. This film was fixed to a stainless steel frame, and was subjected to main drying at 200 ° C. for 3 hours in a nitrogen atmosphere to produce a colorless and transparent polyimide film, and the YI value, haze H, thermal decomposition start temperature, and tensile strength were measured. The results are shown in Table 1.

Infrared absorption spectrum of the polyimide powder obtained in Production Example 1 Infrared absorption spectrum of the polyimide powder obtained in Production Example 2 Infrared absorption spectrum of the polyimide powder obtained in Production Example 3 Infrared absorption spectrum of the polyimide powder obtained in Production Example 4 Infrared absorption spectrum of the polyimide powder obtained in Production Example 5 Infrared absorption spectrum of the polyimide powder obtained in Production Example 6.

Claims (9)

The manufacturing method of the polyimide / inorganic composite material including the process of following (1)-(4) .
(1) A polyimide in which one of an aliphatic tetracarboxylic acid or an aliphatic tetracarboxylic dianhydride and a diamine is imidized in an excess amount in an organic polar solvent, and the terminal group is an acid anhydride group or an amino group. A step of synthesizing a polyimide solution of polyimide having a repeating unit represented by formula (1) and having an intrinsic viscosity in the range of 0.43 to 0.55;
(2) A solution containing an end-capped polyimide having a terminal alkoxysilane structure is produced by reacting the polyimide solution synthesized in the step (1) with a silane coupling agent having reactivity with the terminal group of the polyimide. The process of
(3) A silicon alkoxide corresponding to a silica content of 10 to 30% by weight and distilled water is added to the solution containing the end-capped polyimide obtained by the step (2). A step of producing a mixed solution containing a compound having a silanol group formed at the terminal and a hydroxide sol of silicon,
(4) A process for producing a polyimide / inorganic composite material by heating the mixed solution obtained in the step (3), gelling a silicon hydroxide sol (sol-gel reaction) and drying the solvent.

(Wherein R ₁ is a tetravalent cyclohexane ring or a cyclopentane ring , and Φ is a divalent aliphatic hydrocarbon group having 2 to 28 carbon atoms or a divalent aromatic hydrocarbon group having 12 to 25 carbon atoms. .) The method for producing a polyimide / inorganic composite material according to claim 1, wherein the silane coupling agent has a structure represented by formula (2).

(In the formula, R ₂ represents an alkyl group having 1 to 10 carbon atoms, R ₃ represents a divalent hydrocarbon group having 3 to 10 carbon atoms, and X represents an amino group or an isocyanate group.) The aliphatic tetracarboxylic dianhydride used in the step (1) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride or 1,2,4,5-cyclopentanetetracarboxylic dianhydride. The method for producing a polyimide / inorganic composite material according to claim 1 or 2. The organic polar solvent is γ-butyrolactone, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphoramide, p-chlorophenol, m-cresol The method for producing a polyimide / inorganic composite material according to any one of claims 1 to 3, wherein the polyimide / inorganic composite material is one or more selected from the group consisting of tetrahydrofuran and tetrahydrofuran. The polyimide obtained in the step (1) is soluble in an organic polar solvent at 20 to 100 ° C. in a range of 20% by weight or more and 50% by weight or less as a polyimide solid concentration with respect to the total weight part including the organic polar solvent. The method for producing a polyimide / inorganic composite material according to claim 1.   In the step (1), the reaction stoichiometric ratio of aliphatic tetracarboxylic acid or aliphatic tetracarboxylic dianhydride to diamine is 1.01 to 1.1, or aliphatic tetracarboxylic acid or aliphatic tetracarboxylic The method for producing a polyimide / inorganic composite material according to any one of claims 1 to 5, wherein an imidization reaction is performed at a reaction stoichiometric ratio of diamine to acid dianhydride of 1.02 to 1.1. The metal alkoxide containing at least one metal element selected from the group consisting of magnesium, aluminum, zirconium and titanium is used in combination with the silicon alkoxide in the step (3). A method for producing a polyimide / inorganic composite material according to claim 1. The haze of the polyimide / inorganic composite material is in the range of 0.33 to 0.88. The method for producing a polyimide / inorganic composite material according to any one of claims 1 to 7. The method for producing a polyimide / inorganic composite material according to claim 1, wherein the polyimide / inorganic composite material has a YI value in the range of 1.6 to 2.5.

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