JP5428179B2 - Polyimide precursor resin composition and electronic component - Google Patents

Description

  The present invention relates to an insulating material having high heat resistance, a polyimide precursor that can be suitably used as a main component of photosensitive polyimide, a resin composition containing the same, and an electronic component using the same. It is.

  Polymer materials are used in various products around us because of their easy processing and light weight. The polyimide developed by DuPont in 1955 in the United States has been under development because it has excellent heat resistance and its application to the aerospace field has been studied. Since then, detailed research has been conducted by many researchers, and it has become clear that performance such as heat resistance, dimensional stability, and insulation properties are among the highest in organic materials. Application to materials was promoted. At present, it has been used extensively as a chip coating film in a semiconductor element or as a base material for a flexible printed wiring board.

Polyimide is a polymer synthesized from diamine and acid dianhydride. By reacting diamine and acid dianhydride in a solution, it becomes polyamic acid (polyamic acid) which is a precursor of polyimide, and then becomes a polyimide through a dehydration ring closure reaction. In general, since polyimide has poor solubility in a solvent and is difficult to process, it is often made into a polyimide by making it into a desired shape in a precursor state and then heating. Polyimide precursors are often unstable with respect to heat and water and have poor storage stability.
Polyamic acid is generally synthesized by mixing acid dianhydride and diamine in solution. However, since the addition reaction consisting of an acid anhydride group and an amino group is a reversible reaction, the decomposition reaction proceeds in parallel with the addition reaction. doing. Since this addition reaction is an exothermic reaction, polyamic acid is generally stored at a low temperature to suppress a decrease in molecular weight. When the polyamic acid solution contains moisture, the acid anhydride group generated by the reverse reaction with a certain probability reacts with the moisture to become dicarboxylic acid. When dicarboxylic acid is used, the addition reaction with the amino group does not proceed, and the portion is deactivated. Therefore, the molecular weight of polyamic acid decreases with storage. (Non-Patent Document 1)

  In consideration of this point, a polyimide that has been improved so that it can be molded or applied by dissolving in a solvent after introducing a skeleton with excellent solubility in the molecular structure and making it into a polyimide is used. There is a tendency that the chemical resistance and the adhesion to the substrate are inferior to those using a polyimide precursor. Therefore, a method using a polyimide precursor and a method using a solvent-soluble polyimide are selectively used according to the purpose.

Furthermore, a polyimide precursor obtained by esterifying the carboxyl group of polyamic acid has also been proposed. When the carboxyl group is esterified, the reverse reaction does not proceed. Therefore, no decrease in molecular weight is observed, and the storage stability is improved. (Patent Document 1)
However, polyamic acid can be synthesized in one step, whereas polyamic acid ester as in Patent Document 1 is synthesized by synthesizing a dihalf ester compound and then dehydrating using a diamine and a condensing agent such as dicyclohexylcarbodiimide. In order to condense, there exists a subject that it becomes 2 step reaction and the refinement | purification for removing a condensing agent is required, and manufacturing cost starts.
Furthermore, since ester bonds are difficult to thermally decompose, even after imidization from a polyimide precursor to polyimide by a heat treatment at 300 ° C. or higher, ester residue-derived decomposition residues remain, resulting in linear thermal expansion coefficient and humidity expansion. This was a cause of deteriorating polyimide characteristics such as coefficient.

  Patent Document 2 and Patent Document 3 disclose a compound obtained by reacting a vinyl ether compound with a carboxyl group of a polyimide precursor as a main component of a photosensitive polyimide precursor resin composition. However, in Patent Document 2, the introduction rate of the vinyl ether compound (the protection rate of the carboxyl group by the vinyl ether compound) has not been confirmed, and there is a problem that the protection rate of the carboxyl group cannot be managed. Moreover, in patent document 3, since it is a photosensitive resin composition, the amine was contained as a photoinitiator and the carboxyl group density | concentration was 5 mol% or more. When an unreacted carboxyl group remains, there is a problem that the hemiacetal ester bond is decomposed with time due to the action of the carboxyl group and the storage stability is lowered. Furthermore, in order to obtain a negative photosensitive polyimide, a reactive group is introduced into 50% or more of the vinyl ether-derived sites introduced into the polyimide precursor, so that gelation easily proceeds and the storage stability is generally improved. It was a bad polyimide precursor. In addition, since it contains a large amount of reactive groups, the reactive groups are polymerized and become difficult to decompose in the process of imidization by heating, which changes from precursor to polyimide, and is therefore derived from vinyl ether even after imidization. The decomposition residue of this part remained in the polyimide film, causing outgas, and deteriorating the linear thermal expansion coefficient and hygroscopicity.

JP 61-293204 A JP 2002-121382 A JP 2001-194784 A Kreuz, J. A., “J Polym Sci Part A: Polym Chem”, 1990, 28, p.3787.

  The present invention has been achieved in view of the above circumstances, and its purpose is irrespective of the chemical structure of the final polyimide, which can be easily synthesized and obtained at low cost, has high storage stability, The present invention provides a polyimide precursor and a polyimide precursor resin composition that become a polyimide with little residual impurities after imidization.

The polyimide precursor resin composition according to the present invention contains 100 mol% of repeating units represented by the following formula (1) in all repeating units, and the terminal of the polymer does not contain an acid anhydride group or active hydrogen. It contains a polyimide precursor end-capped with a structure, a vinyl ether compound, and a solvent. The vinyl ether compound is contained in an amount of 55 parts by weight or more with respect to 100 parts by weight of the solvent, and the water content in the composition is 1 % By weight or less.

(In Formula (1), R ¹ is a tetravalent organic group derived from an aromatic tetracarboxylic dianhydride, R ² is a divalent organic group derived from a diamine, and R ¹ and R ² are repeated. R ³ and R ⁴ are each independently a monovalent organic group having the structure of the following formula (2), and they may be the same or different. And R ³ and R ^{4 which} are repeated may be the same or different.

(In formula (2), R ⁵ , R ⁶ and R ⁷ are each independently hydrogen, a halogen atom, a substituted or unsubstituted alkyl group, an allyl group or an aryl group. R ⁸ and R ⁹ are each independently A group having a hydrocarbon skeleton, R ⁸ and R ⁹ do not contain an ethylenically unsaturated bond , R ¹⁰ is a hydrogen atom or a halogen atom, and a carbon atom bonded to R ⁸ , R ⁹ , R ¹⁰ and an oxygen atom Is a secondary carbon atom. R ⁵ , R ⁶ , R ⁷ , R ⁸ , and R ⁹ may each represent a cyclic structure in which groups having a hydrocarbon skeleton are bonded to each other.

100% by mole of the repeating unit represented by the above formula (1) used in the present invention is contained in all repeating units, and the ends of the polymer are end-capped with a structure containing no acid anhydride group or active hydrogen. The polyimide precursor has a hemiacetal ester structure due to the reaction of the carboxyl group of the polyamic acid with a secondary vinyl ether compound. The vinyl ether compound used is selected so that R ⁸ and R ⁹ do not contain reactive groups .
The inventor has examined the hemiacetal ester bond of the polyimide precursor in detail, so that a secondary vinyl ether compound in which R ⁸ and R ⁹ do not contain a reactive group can be used via a hemiacetal ester bond. The protective group introduced into the polyimide precursor has thermal stability that can withstand practical use and high storage stability. Furthermore, since the hemiacetal ester bond is rapidly decomposed by heating, the imidized polyimide has its It was found that there was very little residue of decomposition products.

  The aromatic hemiacetal ester bond obtained from the vinyl ether compound is decomposed into polyamic acid and vinyl ether, acetaldehyde, alcohol or the like by heating at 200 ° C. or lower. These compounds generated by thermal decomposition of the hemiacetal ester bond are often liquid at room temperature having a boiling point of 200 ° C. or less, and most of them are volatilized during the heating process. Furthermore, it is presumed that almost all of the film is dissipated by heating at 250 ° C. or higher required for imidization. Therefore, the finally obtained polyimide film has almost no vinyl ether-derived residue and can be very close to a pure polyimide film.

Thereby, it is possible to obtain a polyimide precursor that becomes a substantially pure polyimide after imidization even though the carboxyl group is protected and stable during storage.
The secondary vinyl ether compound in this case refers to a compound in which the carbon atom forming a direct bond with the oxygen atom directly bonded to the vinyl group of the vinyl ether compound is a secondary carbon atom.

  Since the polyimide precursor can be obtained simply by mixing a polyamic acid and a secondary vinyl ether compound and stirring at room temperature, it can be easily obtained at low cost. The reaction of the aromatic carboxylic acid and the vinyl ether compound is slightly different in behavior from the case of the aliphatic carboxylic acid. In many cases, the reaction between an aliphatic carboxylic acid and a vinyl ether compound requires heating or an acid catalyst, but as a result of intensive studies, the inventors have found that an aromatic carboxylic acid and a vinyl ether compound can be obtained only by stirring at room temperature. I found it. Furthermore, at that time, under the dehydration conditions, the reaction yield of polyamic acid and vinyl ether compound was dramatically improved by using a solvent that does not contain a nitrogen atom such as lactones and sulfoxides. It has become possible to completely convert the carboxyl group of the acid to a hemiacetal ester bond.

As one of the polyimide precursors, a structure in which R ⁵ , R ⁶ and R ⁷ in the formula (2) are hydrogen, that is, a polyimide precursor represented by the following formula (1 ′) is used. it can.

(In formula (1 ′), R ¹ , R ² , R ⁸ , R ⁹ and R ¹⁰ are the same as those in formula (1) or formula (2), respectively).

In the polyimide precursor of the present invention, R ⁸ and R ⁹ in the formula (2) are monovalent organic groups having 1 to 30 carbon atoms, and do not contain active hydrogen. To preferred.

In the polyimide precursor of the present invention, R ⁸ in the formula (2) contains an ether bond from the viewpoint of adhesion to a substrate, storage stability, repellency, and decomposition product volatility. preferable.

  The polyimide precursor of the present invention is obtained by reacting a polyamic acid that is not completely dissolved in the solvent and a vinyl ether compound in one or more solvents selected from lactones and sulfoxides. It is preferable. A polyamic acid that does not completely dissolve in one or more solvents selected from lactones and sulfoxides usually achieves a polyimide having a low coefficient of linear expansion. Even with such a polyamic acid, if the reaction temperature is appropriately adjusted in one or more solvents selected from lactones and sulfoxides and reacted with the vinyl ether compound, the carboxyl group of the polyamic acid is reduced to 100%. It is possible to prepare the polyimide precursor of the present invention having a miacetal ester bond. Since the polyimide precursor of the present invention dissolves well in lactones and sulfoxides, the solid content (polyamic acid) not initially dissolved gradually dissolves in the process of converting the carboxyl group of the polyamic acid into a hemiacetal ester bond. To go. Moreover, the polyimide precursor prepared on such conditions is preferable from the viewpoint of ease of synthesis and wide range of structure selection.

  The carboxyl of polyamic acid is obtained by reacting polyamic acid and vinyl ether compound at a reaction temperature of 5 ° C. to 35 ° C. in one or more solvents selected from lactones and sulfoxides. This is preferable from the viewpoint of obtaining a polyimide precursor having a 100% hemiacetal ester bond.

  In the polyimide precursor of the present invention, either the weight average molecular weight or the number average molecular weight is preferably 3,000 to 1,000,000 from the viewpoint of the mechanical properties of the resulting polyimide film. If either the weight average molecular weight or the number average molecular weight is smaller than 3000, the mechanical strength of the polyimide obtained from the polyimide precursor of the present invention is lowered, and if it is larger than 1000000, the solubility is lowered and it is difficult to obtain a high concentration solution. That is not preferable.

In the polyimide precursor of the present invention, the end of the polymer is, since the end-capped with structure free of acid anhydride groups or active hydrogen, is preferred from the viewpoint of storage stability. When the amino group or the like having active hydrogen is terminal, decomposition of the hemiacetal ester bond is promoted, and as a result, storage stability may be lowered.

In the polyimide precursor of the present invention, since R ¹ in the formula (1) is a skeleton derived from aromatic tetracarboxylic dianhydride , the reaction for forming a hemiacetal bond is performed at room temperature without using a catalyst. to proceed rapidly, it synthesizes Ru facilitates der.

In the polyimide precursor of the present invention, it is preferable that 33 mol% or more of R ¹ in the formula (1) has any structure represented by the following formula (3).

The polyamic acid having the structure as described above is not only a polyimide precursor exhibiting high heat resistance and low linear thermal expansion coefficient, but also has an aromatic carboxylic acid, and thus reacts with a vinyl ether compound at room temperature. It is possible to generate hemiacetal ester bonds. Furthermore, the hemiacetal ester bond obtained from the aromatic carboxylic acid as described above is thermally decomposed by heating at a lower temperature than the hemiacetal ester bond obtained from the aliphatic carboxylic acid. There are few decomposition products derived from the vinyl ether in the polyimide finally decomposed quickly. Therefore, the closer the content of the structure represented by the above formula (3) is to 100 mol% of R ^{1 in} the above formula (1), the easier it is to achieve the object of the present invention. The purpose can be achieved by containing 33% or more of R ^{1 in} (1).

In the polyimide precursor of the present invention, it is preferable that 33 mol% or more of R ² in the formula (1) has any structure represented by the following formula (4).

(R ¹⁰ is a divalent organic group, an oxygen atom, a sulfur atom, or a sulfone group, and R ¹¹ and R ¹² are a monovalent organic group or a halogen atom.)

When it has the above structure, the heat resistance of the polyimide finally obtained improves. Therefore, the closer to 100 mol% of R ² in the formula (1), the easier it is to achieve the target of the present invention, but at least 33% or more of R ² in the formula (1) is contained. You can achieve your goal.

The polyimide precursor resin composition according to the present invention, by the coexistence with bi vinyl ether compound, the storage stability of the polyimide precursor is improved.

  In the polyimide precursor resin composition of this invention, it is preferable from the point of storage stability that an acidic substance and an amine are not included substantially.

In the polyimide precursor resin composition of the present invention further comprises a solvent, since the vinyl ether compound relative to the 100 parts by weight of the solvent is contained more than 55 parts by weight, is preferred from the viewpoint of storage stability.

  In the polyimide precursor resin composition of this invention, it is preferable from a heat resistant viewpoint that the glass transition temperature after imidation is 260 degreeC or more.

  In the polyimide precursor resin composition of this invention, it is preferable from a viewpoint of dimensional stability that the linear thermal expansion coefficient after imidation is 60 ppm or less.

  In the polyimide precursor resin composition of this invention, it is preferable from a viewpoint of dimensional stability that the humidity expansion coefficient after imidation is 40 ppm or less.

  In the polyimide precursor resin composition of the present invention, from the viewpoint of storage stability, it is preferable to include a solvent that does not contain a nitrogen atom, and further, from the point of storage stability that does not include a solvent that contains a nitrogen atom. preferable.

In the polyimide precursor resin composition of the present invention, from the viewpoint of improving the storage stability, the water content in the composition is Ru der 1 wt% or less. The hemiacetal ester bond formed from the aromatic carboxylic acid decomposes at room temperature in the presence of water. That is, the said polyimide precursor will act with water and will become polyamic acid, acetaldehyde, and alcohol. Furthermore, the alcohol undergoes an exchange reaction with the hemiacetal ester bond to generate an acetal and a carboxyl group. That is, since one molecule of water will decompose two hemiacetal ester bonds, the storage stability of the polyimide precursor resin composition is lowered.

  The polyimide precursor resin composition of the present invention is suitably used as an insulating material for electronic parts.

The electronic component of the present invention is an electronic component in which at least a part is formed from the polyimide precursor resin composition of the present invention and / or a thermoset thereof.

As described above, the polyimide precursor of the present invention has good storage stability, and a polyimide with very little residual impurities after imidization can be obtained. The polyimide precursor of the present invention can be easily synthesized only by mixing the polyamic acid and the vinyl ether compound at room temperature.
In the polyimide precursor of this invention, since the secondary vinyl ether compound was used, especially storage stability is high and it has heat resistance in a practical range.
Moreover, if the polyimide precursor has a hemiacetal ester bond, a wide range of structures can be selected because a wide range of polyimide precursors can be selected. Therefore, it is widely applied to fields where the characteristics of the imide cyclized product can be utilized.
The polyimide precursor which concerns on this invention becomes very favorable in storage stability by selecting the solvent which does not contain a nitrogen atom, and containing a vinyl ether compound.

The present invention will be described in detail below.
The polyimide precursor of this invention consists of a repeating unit represented by following formula (1).

(In Formula (1), R ¹ is a tetravalent organic group, R ² is a divalent organic group, and R ¹ and R ² that are repeated may be the same or different. R ³ and R ⁴ are each independently a monovalent organic group having the structure of the following formula (2), and they may be the same or different, and repeated R ³ and R ⁴ are Each may be the same or different.)

(In formula (2), R ⁵ , R ⁶ and R ⁷ are each independently hydrogen, a halogen atom or a monovalent organic group. R ⁸ and R ⁹ are each independently a monovalent organic group, The organic group having a reactive group in R ⁸ and R ⁹ is 35 mol% or less, R ¹⁰ is a hydrogen atom or a halogen atom, and R ⁵ , R ⁶ , R ⁷ , R ⁸ , and R ⁹ are bonded to each other. And may have a ring structure.)

The present inventor easily cleaves by heating to generate a carboxyl group for the purpose of obtaining a polyimide precursor that has little residue derived from a protective component of the carboxyl group after imidization and has good storage stability at room temperature. The following findings were obtained when research was conducted focusing on the hemiacetal ester bond.
It is known that polyamic acid, which is a precursor of polyimide, is generally easily hydrolyzed at room temperature, resulting in a decrease in molecular weight. This is said to be derived from the fact that the polyaddition reaction for obtaining a polyamic acid is an equilibrium reaction. In other words, the amide bond of the polyamic acid is constantly cleaved or recombined into an acid anhydride and an amino group. When the acid anhydride group contained in the system reacts with moisture in the system to form dicarboxylic acid, the acid anhydride group deviates from the above equilibrium reaction system, and the amide bond is broken (the molecular weight of the polyamic acid decreases). It is said that the balance moves in the direction.
For this reason, the polyamic acid ester, which is also a polyimide precursor, is esterified with a carboxylic acid, so that the reverse reaction that breaks the molecular chain does not proceed and the molecular weight does not decrease.

  From these findings, the inventor imparts storage stability by esterifying the carboxyl group of the polyamic acid to a hemiacetal ester, while the hemiacetal ester bond is thermally decomposed to polyamic acid in the course of heating accompanying imidization. Returning, the inventors thought that if the carboxyl group-protecting component volatilizes, a polyimide having no residue derived from the carboxyl group-protecting component in the film could be created, and earnestly studied to arrive at the present invention.

  In particular, the hemiacetal ester bond is easily pyrolyzed only by heating as compared with the ester bond, so that the bond is broken by heating at a lower temperature. Many polyimide precursors are generally said to undergo imidization gradually from a temperature in the vicinity of 140 ° C. with heating, and the glass transition temperature (Tg) of the film increases as the imidization rate increases. To go. When Tg increases, the vibration of the molecular chain is suppressed, so that it is difficult to volatilize the substance from the inside of the film. On the other hand, in the case of a hemiacetal ester bond, since it decomposes from around room temperature in some cases, the decomposition reaction occurs with a low imidation rate. Therefore, when a hemiacetal ester bond is combined with the polyimide precursor, the volatility of the decomposition component is good, and the decomposition component volatilizes in the process of heating when converting the polyimide precursor to polyimide, and in the polyimide film It has a feature that there is almost no degradation product derived from the remaining hemiacetal ester binding site.

From the above, the site (hereinafter referred to as a protected site) that is bonded to the polyimide precursor main chain by the hemiacetal ester bond in the present invention and is to be removed later has a low molecular weight, and the structure has volatility after decomposition. A higher value is preferable from the viewpoint of suppressing the decomposition product from remaining on the polyimide film.
Further organic group having a reactive group of the protected site R ⁸ and R ⁹ or less 35 mol%. Therefore, it is preferable because gelation during synthesis and storage of the polyimide precursor can be suppressed, and further, residue in the film can be suppressed. Among these, from the viewpoint of eliminating the residue in the film, it is preferable that the protected site does not substantially contain a crosslinkable (reactive) site.

  Since the polyimide precursor can be obtained simply by mixing a polyamic acid and a vinyl ether compound and stirring at room temperature, it can be easily obtained at low cost. The reaction of the aromatic carboxylic acid and the vinyl ether compound is slightly different in behavior from the case of the aliphatic carboxylic acid. In many cases, the reaction between an aliphatic carboxylic acid and a vinyl ether compound requires heating or an acid catalyst, but as a result of intensive studies, the inventors have found that an aromatic carboxylic acid and a vinyl ether compound can be obtained only by stirring at room temperature. I found it. Furthermore, by using a solvent that does not contain nitrogen atoms and further controlling the temperature, the reaction yield of the polyamic acid and the vinyl ether compound has been dramatically improved, and the carboxyl group of the polyamic acid is completely hemihydrated. It became possible to use an acetal ester bond.

By making the vinyl ether compound used when obtaining the polyimide precursor of the present invention a secondary vinyl ether compound, the thermal stability of the polyimide precursor is improved compared to when a tertiary vinyl ether compound is used, and Compared with the case of using a primary vinyl ether compound, the reaction rate between the vinyl ether compound and the carboxylic acid for obtaining a hemiacetal ester bond is improved, and the storage stability is the highest.
That is, by using a secondary vinyl ether compound as the vinyl ether compound to be used, it is possible to obtain a polyimide precursor having a balance between storage stability, detachment of protecting groups, and reactivity to a hemiacetal ester bond. .

In addition, polyamic acids, particularly aromatic polyamic acids, are poorly soluble and are therefore often dissolved in amide-based highly polar solvents. However, the amide solvent has a problem that it is difficult to handle because it is poor in volatility and easily absorbs moisture. When the polyamic acid solution having a high concentration absorbs moisture, the solubility of the polyamic acid is lowered and deposited.
On the other hand, the polyimide precursor of the present invention dissolves in a relatively low-polarity solvent because the carboxyl group is protected by a hemiacetal ester bond. In particular, the solubility in a solvent containing an ester bond is improved. Therefore, it is also possible to prepare a high concentration coating solution.

Next, the structure of the polyimide precursor of the present invention will be described in detail.
The polyimide precursor of the present invention consists essentially of the repeating unit represented by the above formula (1). That is, the repeating unit is substantially free of carboxyl groups. Since the hydrolysis proceeds catalytically in the presence of an acid or base in the hemiacetal ester bond, the polyimide precursor of the present invention has drastically improved storage stability by having substantially no carboxyl group in the repeating unit. Can be improved.

In the above formula (1), generally, R ¹ is a structure derived from tetracarboxylic dianhydride, and R ² is a structure derived from diamine.
Examples of the acid dianhydride applicable to the polyimide precursor of the present invention include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, and cyclopentane tetracarboxylic dianhydride. , Pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, 2 , 2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) Ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane Dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane Anhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4-dicarboxy ) Benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] Phenyl} propane dianhydride,

2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4′-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4′-bis [3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis { 4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [3- (1,2-dicarbox ) Phenoxy] phenyl} sulfone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy ] Phenyl} sulfide dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-hexafulpropane dianhydride 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6,7- Naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetra Carboxylic dianhydride, 3,4,9,10 -Perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride and the like.
These may be used alone or in combination of two or more.

The tetracarboxylic dianhydride preferably used from the viewpoints of the heat resistance, linear thermal expansion coefficient of the finally obtained polyimide film and the reactivity of the protective reaction to the precursor is an aromatic tetracarboxylic dianhydride. It is preferable that there are particularly preferred tetracarboxylic dianhydrides, such as pyromellitic dianhydride, merophanic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3. ', 4,4'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 2,3,2 ', 3'-biphenyltetracarboxylic dianhydride 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1 , 1 1,3,3,3-hexafluoropropane dianhydride and bis (3,4-dicarboxyphenyl) ether dianhydride.
Among these, from the viewpoint of the stability of the hemiacetal ester bond, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride and bis (3,4-dicarboxyphenyl) ether dianhydride are particularly preferred.

  When an acid dianhydride into which fluorine is introduced or an acid dianhydride having an alicyclic skeleton is used as the acid dianhydride to be used in combination, the transparency of the polyimide precursor is improved. In addition, pyromellitic dianhydride, merophanic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride When rigid acid dianhydrides such as 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride are used, it is finally obtained. Since the linear thermal expansion coefficient of the polyimide obtained becomes small, it is preferable. Among these, from the viewpoint of the stability of the hemiacetal ester bond, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride is particularly preferred.

  When the acid dianhydride has an alicyclic skeleton, the transparency of the polyimide precursor is improved, so that a highly sensitive polyimide precursor resin composition is obtained. Furthermore, heating or a catalyst may be required in the reaction for forming the hemiacetal ester bond, but since it is possible to form a hemiacetal ester bond having a relatively high stability, emphasis is placed on storage stability. The case is preferred.

On the other hand, when aromatic tetracarboxylic dianhydride is used, it becomes a polyimide precursor which is excellent in heat resistance and shows a low linear thermal expansion coefficient. Furthermore, since the reaction for forming a hemiacetal ester bond proceeds at room temperature, the target polyimide precursor can be obtained very easily. Furthermore, since it decomposes at a lower temperature, there is an advantage that the decomposition product hardly remains in the film after imidization. Therefore, in the polyimide precursor of the present invention, it is preferable that 33 mol% or more of R ¹ in the formula (1) has any structure represented by the following formula (3).

The polyimide precursor having the structure as described above is not only a polyimide precursor exhibiting high heat resistance and low linear thermal expansion coefficient, but also has an aromatic carboxylic acid, and thus reacts with a vinyl ether compound at room temperature. It is possible to produce a hemiacetal ester bond. Furthermore, the hemiacetal ester bond obtained from the aromatic carboxylic acid as described above is thermally decomposed by heating at a lower temperature than the hemiacetal ester bond obtained from the aliphatic carboxylic acid. There are few decomposition products derived from the vinyl ether in the polyimide finally decomposed quickly. Therefore, the closer the content of the structure represented by the above formula (3) is to 100 mol% of R ^{1 in} the above formula (1), the easier it is to achieve the object of the present invention. The purpose can be achieved by containing 33% or more of R ^{1 in} (1). Among them, the content of the structure represented by the above formula (3) is preferably 50 mol% or more, and more preferably 70 mol% or more of R ¹ in the formula (1).

On the other hand, the diamine component applicable to the polyimide precursor of the present invention can be used alone or in combination of two or more diamines. The diamine component used is not limited, but p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diamino. Diphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4 '-Diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone,
3,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2-di (3-aminophenyl) -1,1,1,3,3,3 -Hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane , 1- ( 3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4- Bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1, 4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4 -Amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α, α-dimethylbenzyl) L) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4- Bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2,6-bis (3-aminophenoxy) benzo Nitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4′-bis (3-aminophenoxy) biphenyl, 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-aminophenoxy) phenyl] sulfide,

Bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-amino) Phenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3 3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] ben 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-amino Phenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -Α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4'-bis [4- (4-aminophenoxy) benzoyl ] Diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzen) ) Phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4 , 4′-Dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 6,6′-bis (3-aminophenoxy) -3,3 3 ′, 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, , 3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis ( -Aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis ( 2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether,

1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane,
1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2-aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3- Aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7 -Diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohexane, 1,3-diamino Cyclohexane, 1,4-diaminocyclohexane, 1,2-di 2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2-aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane, 2,6-bis ( Aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, and some or all of the hydrogen atoms on the aromatic ring of the diamine are fluoro groups. A diamine substituted with a substituent selected from a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group can also be used.
Furthermore, depending on the purpose, any one or two or more of the ethynyl group, benzocyclobuten-4′-yl group, vinyl group, allyl group, cyano group, isocyanate group, and isopropenyl group serving as a crosslinking point, Even if it introduce | transduces into some or all of the hydrogen atoms on the aromatic ring of diamine as a substituent, it can be used.

The diamine can be selected depending on the desired physical properties. If a rigid diamine such as p-phenylenediamine is used, the finally obtained polyimide has a low expansion coefficient. Rigid diamines include p-phenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2, 6 as diamines in which two amino groups are bonded to the same aromatic ring. -Diaminonaphthalene, 2,7-diaminonaphthalene, 1,4-diaminoanthracene and the like can be mentioned.
In addition, diamines in which two or more aromatic rings are bonded by a single bond, and two or more amino groups are each bonded directly or as part of a substituent on a separate aromatic ring, for example, There exists what is represented by following formula (5). Specific examples include benzidine and the like.

(A is a natural number of 1 or more, and an amino group is bonded to a meta position or a para position with respect to a bond between benzene rings. R ¹¹ and R ¹² are a monovalent organic group or a halogen atom.)

Furthermore, in the above formula (5), a diamine having a substituent at a position where the amino group on the benzene ring is not substituted and which does not participate in the bond with another benzene ring can also be used. These substituents are monovalent organic groups, but they may be bonded to each other.
Specific examples include 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diamino. Biphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl and the like can be mentioned.
When the finally obtained polyimide is used as an optical waveguide or an optical circuit component, the transmittance for electromagnetic waves having a wavelength of 1 μm or more can be improved by introducing fluorine as a substituent of the aromatic ring.

  On the other hand, when a diamine having a siloxane skeleton such as 1,3-bis (3-aminopropyl) tetramethyldisiloxane is used as the diamine, the elastic modulus of the finally obtained polyimide is lowered and the glass transition temperature is lowered. be able to.

  Here, the selected diamine is preferably an aromatic diamine from the viewpoint of heat resistance. However, depending on the desired physical properties, the diamine may be an aliphatic diamine or siloxane within a range not exceeding 60 mol%, preferably not exceeding 40 mol%. Non-aromatic diamines such as diamines may be used.

Moreover, in the said polyimide precursor, it is preferable that 33 mol% or more among R < ² > in said Formula (1) is one of the structures represented by following formula (4).

(R ¹⁰ is a divalent organic group, an oxygen atom, a sulfur atom, or a sulfone group, and R ¹¹ and R ¹² are a monovalent organic group or a halogen atom.)

When it has the above structure, the heat resistance of the polyimide finally obtained improves. Therefore, the closer to 100 mol% of R ² in the formula (1), the easier it is to achieve the target of the present invention, but at least 33% or more of R ² in the formula (1) is contained. You can achieve your goal. Of these the content of the structure represented by the above formula (4) is preferably the at formula (1) 50 mol% or more of R ² in, it is more preferably 70 mol% or more.

In the formula (1), R ³ and R ⁴ are each independently a monovalent organic group having the structure of the following formula (2), and they may be the same or different and are repeated R ³ and R ⁴ may be the same or different.

(In formula (2), R ⁵ , R ⁶ and R ⁷ are each independently hydrogen, a halogen atom or a monovalent organic group. R ⁸ and R ⁹ are each independently a monovalent organic group, The organic group having a reactive group in R ⁸ and R ⁹ is 35 mol% or less, R ¹⁰ is a hydrogen atom or a halogen atom, and R ⁵ , R ⁶ , R ⁷ , R ⁸ , and R ⁹ are bonded to each other. And may have a ring structure.)

  The hemiacetal ester bond represented by the above formula (2) can be obtained by, for example, the following reaction between a carboxyl group and a vinyl ether compound.

That is, when a hemiacetal ester bond is formed by an addition reaction between a carboxylic acid and a vinyl ether compound, R ^{5 to} R ^{10 in} the above formula (2) are determined by the structure of the vinyl ether compound. The structure represented by the above formula (2) may be formed by using a cyclic vinyl ether compound such as dihydropyrans, but in this case, the reactivity is poor and the reaction time becomes long. It is preferable to form using a compound.
R ⁵ , R ⁶ and R ⁷ are preferably hydrogen or a substituted or unsubstituted alkyl group, allyl group or aryl group. In particular, hydrogen is preferable because of easy availability of raw materials. Further, it is preferable not to include a primary, secondary, or tertiary amino group, or a substituent having an active hydrogen such as a hydroxyl group.
The substituent having active hydrogen in this case is a substituent that can exchange with a hemiacetal ester bond, and specifically includes a hydroxyl group, a primary amino group, a secondary amino group, a carboxyl group, a mercapto group, and the like. (Chemical Dictionary Tokyo Chemical Doujin)

R ⁸ and R ^{9 in} the above formula (2) are each independently a monovalent organic group having 1 or more carbon atoms, and the organic group having a reactive group among R ⁸ and R ⁹ is 35 mol% or less. is there. That is, when the total number of moles of the protected sites R ⁸ and R ⁹ is 100 mol%, the total of R ⁸ having a reactive group and R ⁹ having a reactive group is 35 mol% or less. Examples of R ⁸ and R ⁹ include groups having a hydrocarbon skeleton. They may contain bonds or substituents other than hydrocarbons such as heteroatoms, or such heteroatoms may be incorporated into an aromatic ring to form a heterocycle. Examples of the group having a hydrocarbon skeleton include a linear or branched or alicyclic saturated or unsaturated hydrocarbon group, a linear or branched saturated or unsaturated halogenated alkyl group, or phenyl and naphthyl. And further a group containing an ether bond in a linear or branched saturated or unsaturated hydrocarbon skeleton (for example, — (R—O) _n —R ′, where R and R ′ Is a substituted or unsubstituted saturated or unsaturated hydrocarbon, n is an integer greater than or equal to 1; -R "-(O-R"') _m , where R "and R"' are substituted or unsubstituted saturated or unsaturated Saturated hydrocarbon, m is an integer of 1 or more,-(O-R "') _m is bonded to a carbon different from the terminal of R"; and the like), linear or branched saturated or A group containing a thioether bond in an unsaturated hydrocarbon skeleton, linear or branched, saturated or unsaturated Hydrogen skeleton on a halogen atom, a cyano group, a silyl group, a nitro group, an acetyl group, an acetoxy group, and a variety of groups groups containing formed by bonding a heteroatom or heteroatoms such as a sulfonic group. R ⁸ and R ⁹ may be bonded to each other to show a cyclic structure.

When a primary, secondary, or tertiary amino group or a substituent having an active hydrogen such as a hydroxyl group is included, the hemiacetal ester bond is likely to be decomposed, so that the storage stability is lowered. Therefore, the above formula (2) R ⁸ and R ⁹ preferably do not contain active hydrogen.
Furthermore, when R ⁸ and R ⁹ in the above formula (2) contain a reactive group such as an ethylenically unsaturated bond having reactivity, the storage stability tends to deteriorate. Furthermore, decomposition residues are likely to remain in the polyimide after imidization. Therefore, even if it contains a reactive unsaturated bond, the amount is preferably small, and the organic group having a reactive group in R ⁸ and R ⁹ is 35 mol% or less. From the viewpoint of making it difficult for the decomposition product of R ⁸ and R ⁹ after the cleavage of the hemiacetal ester bond to remain in the polyimide film, the reactive group is represented by R ⁸ and R ⁹ in the above formula (2). It is preferable not to contain.

R ⁸ and / or R ⁹ in the above formula (2) contains an ether bond in the hydrocarbon skeleton particularly from the viewpoint of adhesion to the substrate, storage stability, repellency, and decomposition product volatility. Is preferred. It may contain a polyoxyalkylene skeleton. When the polyoxyalkylene skeleton is included, the number of repeating oxyalkylenes is preferably 15 or less from the viewpoint of the volatility of the decomposition product.

The hemiacetal ester bond is decomposed into carboxylic acid and other products by heating, and the decomposition temperature is generally the carbon to which R ^{8 to} R ¹⁰ in the above formula (2) are bonded, that is, the oxygen atom. The carbon to be bonded increases in the order of tertiary carbon atom <secondary carbon atom <substituent of primary carbon atom. That is, the thermal stability is highest for the primary carbon atom.
On the other hand, the reaction between a vinyl ether compound and a carboxylic acid to obtain a hemiacetal ester bond generally involves the carbon to which R ^{8 to} R ¹⁰ in the above formula (2) are bonded, that is, the carbon bonded to the oxygen atom is A high reaction rate is shown in the order of substituents of primary carbon atom <secondary carbon atom <tertiary carbon atom.

Therefore, in the case of a polyimide precursor obtained by using a secondary vinyl ether compound in which the carbon bonded to the oxygen atom is a secondary carbon atom as in the present invention, compared with the case of using a tertiary vinyl ether compound. As a result, the thermal stability of the polyimide precursor is improved, and the reaction rate of the vinyl ether compound and the carboxylic acid for obtaining a hemiacetal ester bond is improved as compared with the case of using a primary vinyl ether compound, and the coexistence with the vinyl ether compound. Storage stability is the highest when it is used.
That is, by using a secondary vinyl ether compound as the vinyl ether compound to be used, it exhibits characteristics between the case of the primary vinyl ether compound and the case of the tertiary vinyl ether compound, storage stability, detachment of protecting groups, And a polyimide precursor with a balance of reactivity to the hemiacetal ester bond can be obtained.

R ⁸ and R ⁹ in the formula (2) preferably have 1 to 30 carbon atoms from the viewpoint of the volatility of the decomposition product, and more preferably 1 to 15 carbon atoms.

A particularly preferred combination in the structure of R ⁸ and R ⁹ in the formula (2) is a structure containing no active hydrogen and one ether bond in a linear, branched or cyclic saturated hydrocarbon skeleton. It is a structure including the above.

Although it does not specifically limit as R < ⁸ > and R < ⁹ > in said Formula (2), For example, a methyl group, an ethyl group, an ethynyl group, a propyl group, an isopropyl group, n-butyl group, t-butyl group, n-hexyl group Cyclohexyl group, cyclohexylmethyl group, methoxyethyl group, ethoxyethyl group, propoxyethyl group, butoxyethyl group, cyclohexyloxyethyl group, methoxypropyl group, ethoxypropyl group, propoxypropyl group, butoxypropyl group, cyclohexyloxypropyl group, Etc.

On the other hand, R ¹⁰ in the above formula (2) is hydrogen or a halogen atom. From the viewpoint of easy availability of raw materials, R ^{10 in the} above formula (2) is preferably hydrogen.

  Examples of the method for producing the polyimide precursor of the present invention include, but are not limited to, a method of synthesizing a polyamic acid that is a precursor from an acid dianhydride and a diamine, and a reaction with a vinyl ether compound. Tetracarboxylic acid may be reacted with 2 equivalents of a vinyl ether compound to obtain a dicarboxydihemiacetal ester compound, and then polymerized by a dehydration condensation reaction with diamine.

  The polyimide precursor is generally obtained from a polyamic acid and a vinyl ether compound, but according to the results of studies by the inventors, the reaction is carried out in a solvent having an active hydrogen such as an amino group or a hydroxyl group, or an amino group. In the presence of a compound having an active hydrogen such as a hydroxyl group, the yield of obtaining a hemiacetal ester bond tended to be low. In addition, when using a solvent containing a nitrogen atom in a form other than a nitro group in the skeleton, the yield was low, so the case where the skeleton contains a solvent containing a nitrogen atom in a form other than a nitro group may also be included. It is not preferable.

In general, a polyimide having a low linear thermal expansion coefficient is often an aromatic polyimide, and an aromatic polyamic acid that is a precursor thereof is an amide solvent containing a nitrogen atom such as N-methylpyrrolidone or dimethylacetamide. Shows high solubility, but is often poorly soluble in solvents that do not contain nitrogen atoms, such as non-amide solvents. In particular, an aromatic polyamic that can realize low expansion, R ¹ is any structure represented by the above formula (3), and R ² is any structure represented by the above formula (5) Acids are not completely soluble in non-amide solvents such as lactones and sulfoxides. Here, the term “not completely dissolved” means that the polyamic acid cannot be completely dissolved at a concentration required for the reaction or coating formation, for example, 16.5% by weight in a solvent at 23 ° C.
In the conventional technique such as Patent Document 3 described above, the reaction is performed with the vinyl ether compound in a state where the aromatic polyamic acid is dissolved in a solvent. Therefore, conventionally, an aromatic compound capable of realizing low expansion, R ¹ is any structure represented by the above formula (3), and R ² is any structure represented by the above formula (5). A polyimide precursor derived from polyamic acid and 100% hemiacetal esterified has not been synthesized.

However, the polyimide precursor having a hemiacetal ester bond used in the present invention is improved in solubility due to the carboxyl group being converted into a hemiacetal ester, and is not compared with a solvent not containing a nitrogen atom such as a non-amide solvent. Even high solubility.
Therefore, when the reaction between the polyamic acid and the vinyl ether compound is performed in a solvent that does not contain a nitrogen atom, the reaction efficiency is improved. In that case, a polyimide having a low linear expansion coefficient is achieved at the beginning as described above. In many cases, polyamic acid is not completely dissolved. However, in the present invention, the polyimide precursor was dissolved in the reaction solvent as the reaction of the polyamic acid progressed, and finally it was prepared so as to be completely dissolved.

  From the point that it is possible to prepare the polyimide precursor of the present invention in which the carboxyl group of polyamic acid has a 100% hemiacetal ester bond, the reaction solvent of polyamic acid and vinyl ether is a solvent that does not contain a nitrogen atom. Lactones and sulfoxides are preferably used. While dimethyl sulfoxide has high solubility, it is difficult to be oxidized and mutagenicity has been confirmed, and there are problems in stability and safety as a solvent. Therefore, lactones are particularly preferable. Examples of lactones include γ-butyrolactone, α-acetyl-γ-butyrolactone, ε-caprolactone, γ-hexanolactone, and δ-hexanolactone. Examples of sulfoxides include dimethyl sulfoxide, methyl ethyl sulfoxide, and diethyl. Examples thereof include sulfoxide.

Moreover, from the point which can prepare the polyimide precursor of this invention which made the carboxyl group of polyamic acid 100% a hemiacetal ester bond, as temperature at the time of reaction of polyamic acid and vinyl ether, 5-35 degreeC is 10-30 degreeC is more preferable. When the reaction temperature is higher than this, side reactions such as decomposition of the hemiacetal ester bond proceed, and thus there is a tendency that a polyimide precursor having a 100% hemiacetal ester bond cannot be obtained.
In addition, since the polyimide precursor used for this invention shows high solubility with respect to a low boiling point non-amide type solvent, operativity improves in processes, such as application | coating.

The secondary vinyl ether compound is appropriately selected and used according to the desired structure of the hemiacetal ester bond. For example, specific examples include vinyl ether compounds having a linear or branched saturated or unsaturated hydrocarbon skeleton such as isopropyl vinyl ether, sec-butyl vinyl ether, sec-pentyl vinyl ether; cyclohexyl vinyl ether, tricyclodecanyl vinyl ether, pentacyclo Vinyl ether compounds containing an alicyclic saturated hydrocarbon skeleton such as pentadecanyl vinyl ether; 1-methoxyethyl vinyl ether, 1-ethoxyethyl vinyl ether, 1-methyl-2-methoxyethyl vinyl ether, 1-methyl-2-ethoxyethyl vinyl ether And vinyl ethers containing an ether bond in a linear or branched saturated or unsaturated hydrocarbon skeleton.
Of the above vinyl ether compounds, when the polyoxyalkylene residue is contained, the number of oxyalkylene residue repeats is preferably 15 or less from the viewpoint of volatility after decomposition.

Moreover, in the polyimide precursor of this invention, it is preferable from the point of storage stability that the terminal of the polymer is end-capped by the structure which does not contain an acid anhydride group or active hydrogen.
As a method of end-capping with a structure not containing an acid anhydride group or active hydrogen, for example, in the case of an amine-terminated polyimide precursor, a method of amidation with acetic anhydride, phthalic anhydride or a few -The method of making an terminal an amic acid with acid anhydrides, such as a naphthalic anhydride, etc. are mentioned.
If the terminal is an aromatic carboxylic acid, even if it has active hydrogen, it reacts with vinyl ether at room temperature to form a hemiacetal ester, and in this case, storage stability is not lowered.

The weight average molecular weight or number average molecular weight of the polyimide precursor is preferably in the range of 3,000 to 1,000,000, and in the range of 5,000 to 700,000, depending on the application. Is more preferable, and the range of 7,000 to 100,000 is more preferable. When the weight average molecular weight or number average molecular weight is less than 3,000, it is difficult to obtain sufficient strength when a coating film or film is used. In addition, the strength of the film is reduced when heat treatment is performed to obtain polyimide. On the other hand, when the weight average molecular weight or number average molecular weight exceeds 1,000,000, the viscosity increases and the solubility decreases, so that it is difficult to obtain a coating film or film having a smooth surface and a uniform film thickness.
The molecular weight used here is a molecular weight obtained by a known method, and is exemplified by a value in terms of polystyrene by gel permeation chromatography (GPC), and the number average molecular weight is the value of the end portion determined from the ¹ H-NMR spectrum. Examples thereof include a method of determining from an integration ratio between a peak derived from a repeating unit and a peak derived from a non-terminal repeating unit.

Next, the polyimide precursor resin composition according to the present invention contains the polyimide precursor according to the present invention and a vinyl ether compound.
Since the polyimide precursor resin composition of the present invention contains a vinyl ether compound, the storage stability is dramatically improved.
When the polyimide precursor is isolated, it can be hydrolyzed by the action of moisture in the air with the passage of time in the course of storage and gradually return to the polyamic acid. In particular, unlike an aliphatic hemiacetal ester bond composed of a relatively stable aliphatic carboxylic acid and a vinyl ether compound, an aromatic hemiacetal ester bond obtained from a reaction of an aromatic carboxylic acid and a vinyl ether compound, etc., only mixes the two. While the reaction proceeds at room temperature, when it is present alone, it often reacts with moisture in the air and is hydrolyzed.
However, the polyimide precursor having a hemiacetal ester bond coexists with a vinyl ether compound, whereby the carboxylic acid generated by hydrolysis is converted to a hemiacetal ester again. That is, like the polyimide precursor having a hemiacetal ester bond immediately after synthesis, a polyimide precursor in which substantially all of the carboxyl groups are hemiacetal esterified is obtained. Therefore, when the polyimide precursor coexists with a vinyl ether compound, the storage stability as a resin composition is improved.
The polyimide precursor used in the present invention has a structure obtained by reacting a secondary vinyl ether compound, but the secondary vinyl ether compound has a higher reaction rate with a carboxylic acid than the primary vinyl ether compound. When the polyimide precursor used in the invention coexists with a vinyl ether compound, particularly high storage stability is exhibited.

  Further, when coexisting with the vinyl ether compound, acetaldehyde generated simultaneously with the polyamic acid is hardly oxidized and is not easily converted to acetic acid. Furthermore, since alcohol also becomes an acetal compound by an exchange reaction with other hemiacetal ester bonds, as a result, the resin composition does not contain active hydrogen.

Therefore, when an excessive amount of vinyl ether compound is contained with respect to the amount of the compound containing active hydrogen, the polyamic acid formed by the active hydrogen quickly becomes a hemiacetal ester bond. The characteristics of the resin composition do not change.
By continuing this cycle, moisture and the like mixed in the resin composition is consumed from the air and the like, and the hemiacetal ester bond is regenerated, so that good solution stability is exhibited.

As content of a vinyl ether compound, it is preferable that it is 1 to 90 weight% in the whole polyimide precursor resin composition containing a solvent, and it is further more preferable that it is 5 to 70 weight%. Moreover, when a vinyl ether compound contains a solvent, it is preferable from the point of the storage stability of a polyimide precursor that it is contained 55 parts weight or more with respect to 100 weight part of solvents. When no solvent is contained, a vinyl ether compound is substituted for the solvent.
The greater the amount of the vinyl ether compound, the better the storage stability. On the other hand, when a polyimide precursor containing a large amount of aromatic skeleton is used, the solubility tends to decrease.
Therefore, from the viewpoint of improving the storage stability, it is preferable that the amount of the vinyl ether compound is as large as possible within a range in which the solid content in the polyimide precursor resin composition does not precipitate.

  Moreover, since the vinyl ether compound used for the synthesis | combination of the polyimide precursor of this invention is a secondary vinyl ether compound, it is preferable that the vinyl ether compound mixed with a polyimide precursor resin composition is a secondary vinyl ether compound. However, primary and tertiary vinyl ether compounds may be used, and primary, secondary, and tertiary vinyl ether compounds may be mixed as appropriate.

In the polyimide precursor resin composition according to the present invention, the polyimide precursor according to the present invention may be used by mixing two or more kinds of polyimide precursors synthesized separately. Furthermore, a polyimide precursor synthesized using a primary vinyl ether compound or a polyimide precursor synthesized using a tertiary vinyl ether compound may be appropriately mixed and used according to the purpose.
In the polyimide precursor resin composition according to the present invention, the solid content of the polyimide precursor is 0. 0% in the entire resin composition containing a solvent from the viewpoint of film properties of the film obtained, particularly film strength and heat resistance. It is preferably 1% by weight to 80% by weight, and more preferably 0.5% by weight to 50% by weight. When the solid content concentration is less than 0.1% by weight, the film thickness of the obtained coating film is thin, the followability with respect to the substrate having irregularities on the surface is lowered, and uneven coating tends to occur. On the other hand, when the solid content concentration is larger than 80% by weight, the viscosity increases and film thickness unevenness due to volatilization of the solvent during the coating tends to occur.
Further, in the resin composition according to the present invention, the solid content of the polyimide precursor is a solid excluding the solvent in the resin composition and the vinyl ether compound described below from the viewpoint of film properties obtained, particularly film strength and heat resistance. It is preferable to contain 30% by weight or more and 50% by weight or more with respect to the whole portion.

The resin composition of the present invention preferably does not contain active hydrogen, and preferably does not contain a compound containing active hydrogen. In particular, it is preferable not to contain water. When these are included, the hemiacetal ester bond is gradually decomposed and storage stability is lowered.
When a hemiacetal ester bond coexists with a compound having active hydrogen such as a hydroxyl group, an exchange reaction with them may occur. Since hemiacetal bonds are usually more stable than hemiacetal ester bonds, when the polyimide precursor and a hydroxyl group-containing compound coexist, the hemiacetal ester bonds are consumed by hydroxyl groups to produce polyamic acid. That is, the stability of the polyimide precursor is lowered when it coexists with a compound having active hydrogen such as a hydroxyl group. The rate of the decomposition reaction of the hemiacetal ester bond varies depending on its chemical structure, and the higher the rate of the reaction that forms the hemiacetal ester bond, the higher the decomposition rate.
Further, from the viewpoint of improving storage stability, the water content in the resin composition is preferably 1% by weight or less, and more preferably 0.1% by weight or less. Furthermore, it is most preferable that it does not contain water substantially. Here, “substantially free of water” means that the content of water in the composition is so small that a decrease in storage stability due to water is not observed. Specifically, it refers to a state where the moisture content in the composition is less than about 0.005% by weight, and further less than 0.001% by weight.

Furthermore, hydrolysis of the hemiacetal ester bond proceeds catalytically in the presence of an acid or a base. Therefore, the storage stability of the polyimide precursor of the present invention having a 100% hemiacetal ester bond can be improved by substantially not containing an acidic substance or a base in the resin composition. When an acidic substance or a base is contained in the resin composition, the polyimide precursor is decomposed into polyamic acid, and the molecular weight is likely to further decrease.
Here, “substantially free of acidic substances and bases” means that the content of acidic substances and bases in the composition is so small that deterioration of storage stability due to acidic substances and bases is not observed. Specifically, it refers to a state in which the content of acidic substances or bases in the composition is less than about 0.005% by weight, and further less than 0.001% by weight.

Various general-purpose solvents can be used as a solvent for dissolving, dispersing or diluting the resin composition. Moreover, you may use the reaction solvent at the time of preparing a polyimide precursor as it is. These may be used alone or in admixture of two or more. However, in order to increase the storage stability of the resin composition, it is preferable to use a solvent containing no active hydrogen. Furthermore, for the same purpose, a solvent that does not contain a nitrogen atom such as an amide bond in the skeleton is preferable. Moreover, it is preferable not to contain the solvent containing a nitrogen atom.
Moreover, you may use the solution obtained by the synthesis reaction of the polyimide precursor as it is, and mix another component as needed.
The vinyl ether compound contained in the resin composition of the present invention may be substituted for the solvent depending on the structure selected. In that case, a solvent for dissolving, dispersing or diluting the polyimide precursor resin composition may not be included.

Usable general-purpose solvents include, for example, ethers such as diethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether; methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclopentanone Ketones such as cyclohexanone; ethyl acetate, butyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, acetate esters of the above glycol monoethers (for example, methyl cellosolve acetate, ethyl cellosolve) Acetate), methoxypropyl acetate, ethoxypropyl acetate, dimethyl oxalate, methyl lactate, ethyl lactate and the like; Halogenated hydrocarbons such as tylene, 1,1-dichloroethane, 1,2-dichloroethylene, 1-chloropropane, 1-chlorobutane, 1-chloropentane, chlorobenzene, bromobenzene, o-dichlorobenzene, m-dichlorobenzene; -Lactones such as butyrolactone; sulfoxides such as dimethyl sulfoxide, other organic polar solvents, and the like. Furthermore, aromatic hydrocarbons such as benzene, toluene, xylene, and other organic nonpolar solvents And so on. These solvents are used alone or in combination.
Among these, lactones and sulfoxides are preferably used from the viewpoint of high storage stability, excellent solubility, and the ability to prepare a high-concentration solution.

  The resin composition according to the present invention may be a simple mixture of a polyimide precursor, a vinyl ether compound, and, if necessary, a solvent alone, and further appropriately blend other components such as a surfactant, A resin composition may be prepared.

  The resin composition according to the present invention is blended with various organic or inorganic low-molecular or high-molecular compounds in addition to impart processing characteristics and various functionalities, as long as the object and effect of the present invention are not hindered. May be. For example, dyes, surfactants, leveling agents, plasticizers, fine particles and the like can be used. The fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, inorganic fine particles such as colloidal silica, carbon, and layered silicate, and these may have a porous or hollow structure. The function or form includes pigments, fillers, fibers, and the like.

  The blending ratio of other optional components is appropriately selected depending on the properties of the optional components and is not particularly limited, but is in the range of 0.1% by weight to 30% by weight with respect to the entire solid content excluding the solvent and vinyl ether compound of the resin composition. Is preferred. If it is less than 0.1% by weight, the effect of adding the additive is difficult to be exhibited, and if it exceeds 30% by weight, the properties of the finally obtained cured resin are hardly reflected in the final product.

  The resin composition according to the present invention can be used in various coating processes and molding processes to produce a film (film) or a three-dimensional shaped molded body.

Since the polyimide obtained from the resin composition of the present invention is excellent in the detachability of the hemiacetal esterification site of the precursor, it contains little decomposition residue derived from the protective component. Therefore, the original properties such as heat resistance, dimensional stability and insulation of polyimide are not impaired and are good.
For example, the 5% weight loss temperature measured in nitrogen of polyimide obtained from the resin composition of the present invention is preferably 250 ° C. or higher, and more preferably 300 ° C. or higher. In particular, when used in applications such as electronic parts that pass through the solder reflow process, if the 5% weight loss temperature is 300 ° C. or less, defects such as bubbles occur due to the decomposition gas generated in the solder reflow process. There is a fear.
Here, the 5% weight reduction temperature is the time when the weight of the sample is reduced by 5% from the initial weight when the weight loss is measured using a thermogravimetric analyzer (in other words, the sample weight becomes 95% of the initial weight). Temperature). Similarly, the 10% weight reduction temperature is a temperature at which the sample weight is reduced by 10% from the initial weight.

The glass transition temperature of the polyimide obtained from the resin composition of the present invention is preferably 260 ° C. or higher from the viewpoint of heat resistance. This is important for electronic members that have a solder reflow process. In applications where a thermoforming process is considered, such as an optical waveguide, it is preferable to exhibit a glass transition temperature of about 120 ° C. to 400 ° C., and more preferably a glass transition temperature of about 200 ° C. to 370 ° C.
Here, when the polyimide obtained from the resin composition can be formed into a film shape, the glass transition temperature in the present invention is tan δ (tan δ = loss elastic modulus (E ″) / storage) by dynamic viscoelasticity measurement. It is obtained from the peak temperature of the elastic modulus (E ′). The dynamic viscoelasticity measurement can be performed, for example, with a viscoelasticity measuring apparatus Solid Analyzer RSA II (manufactured by Rheometric Scientific) at a frequency of 1 Hz and a temperature increase rate of 5 ° C./min. When the polyimide obtained from the resin composition cannot be formed into a film shape, the determination is made based on the temperature of the inflection point of the baseline of the differential thermal analyzer (DSC).

From the viewpoint of dimensional stability, the polyimide obtained from the resin composition of the present invention preferably has a linear thermal expansion coefficient of 60 ppm or less, and more preferably in the range of 0 ppm to 40 ppm. In the case of forming a film on a silicon wafer in a manufacturing process of a semiconductor element or the like, the range of 0 ppm to 25 ppm is more preferable from the viewpoint of adhesion and warpage of the substrate. Here, the linear thermal expansion coefficient in this invention can be calculated | required with the thermomechanical analyzer (TMA) of the film of the polyimide obtained from the polyimide precursor resin composition obtained by this invention. Using a thermomechanical analyzer (for example, Thermo Plus TMA8310 (manufactured by Rigaku Corporation), the heating rate is 10 ° C./min, and the tensile load is 1 g / 25,000 μm ² so that the weight per cross-sectional area of the evaluation sample is the same. .

Similarly, the polyimide obtained from the resin composition of the present invention preferably has a humidity expansion coefficient of 40 ppm or less, more preferably 20 ppm or less, from the viewpoint of dimensional stability. Ideally, 10 ppm to 0 ppm is preferable.
Here, the humidity expansion coefficient in this invention can be calculated | required with the humidity variable mechanical analyzer (S-TMA) of the film of the polyimide obtained from the resin composition obtained by this invention. With a variable humidity mechanical analyzer (for example, Thermo Plus TMA8310 modified (manufactured by Rigaku Corporation)), the temperature is kept constant at 25 ° C., and the humidity is 50% with the sample stabilized in an environment of 20% RH. The change in sample length when it is changed to Rh and becomes stable is divided by the change in humidity (in this case, 30 of 50-20), and the value divided by the sample length is the humidity expansion coefficient. . The tensile load is 1 g / 25000 μm ² so that the weight per cross-sectional area of the evaluation sample is the same.

A film or a molded body comprising the resin composition according to the present invention can be produced by a known method. For example, the film can be obtained by applying the resin composition of the present invention on a substrate and drying it. At this time, the substrate is an object on which a polyimide film is to be formed, and examples thereof include metals such as copper and stainless steel, inorganic materials such as silicon, metal oxides, and metal nitrides, and organic materials such as polyimide and polybenzoxazole. However, in the present invention, although the adhesiveness and the like slightly change depending on the substrate, the substrate is not particularly limited because the pattern formation and the characteristics of the obtained film are essentially not changed.
Examples of the application method include spin coating, die coating, and dip coating, but are not particularly limited, and known methods can be used. The pattern forming method of the present invention can be used for a film obtained by any coating method.
For drying, a known heating method such as a hot plate or an oven can be appropriately used.

The polyimide precursor of the present invention can be made into polyimide by a known method. Usually, imidization is often performed by heating with an oven or a hot plate.
In general, it is said that polyamic acid gradually undergoes imidization from about 150 ° C., and imidization is almost completed at a temperature of 200 ° C. or higher. However, when higher reliability is required, it is necessary to proceed with imidization more completely. In that case, it is ideal to heat the polyimide film finally obtained at a temperature equal to or higher than Tg. is there. However, in general, a polyimide film having sufficiently practical reliability can be obtained by heating at a temperature of 300 ° C. to 400 ° C.

  In the case of the resin composition of the present invention, the hemiacetal ester bond is almost completely decomposed at about 150 ° C. Can be promoted. The longer the heating time, the better from the viewpoint of reducing the residue in the polyimide. However, in order to balance the productivity, the heating is performed at a temperature in the range of 40 ° C. to 150 ° C. for 1 minute to 180 minutes in total. The heating is preferably performed for 5 minutes to 120 minutes.

Thereafter, in order to completely proceed with imidization, heating is performed in the range of 180 ° C. to 450 ° C., preferably 200 ° C. to 400 ° C. depending on the purpose. Preferably, the maximum heating temperature is 251 ° C. or higher and 400 ° C. or lower.
In particular, when a temperature of 100 ° C. or higher is applied, it is preferably performed in an inert atmosphere such as nitrogen or argon in order to prevent oxidation of the polyimide or the substrate. Furthermore, in order to reduce the residue in a polyimide, it is preferable to carry out under reduced pressure.

  As described above, the polyimide precursor according to the present invention has high storage stability because it has a hemiacetal ester bond that can be easily synthesized with an inexpensive raw material. In addition, the polyimide precursor having a hemiacetal ester bond is finally decomposed by the high volatility of decomposition products other than polyamic acid generated by the decomposition of the hemiacetal ester bond and the decomposition of the hemiacetal ester bond. There is almost no residue in the resulting polyimide film. Furthermore, since hemiacetal esterification can be applied to various skeletons, there is a wide range of selection of the skeleton of the polyimide precursor to be used.

  The polyimide precursor and resin composition according to the present invention use resin materials such as printing inks, adhesives, fillers, electronic materials, optical circuit components, molding materials, resist materials, building materials, three-dimensional modeling, and optical members. Can be used in all known fields and products

Since the polyimide precursor and the resin composition according to the present invention can select a polyimide precursor having a wide range of structures, the cured product obtained thereby has characteristically polyimides such as heat resistance, dimensional stability, and insulation. Since the function can be imparted, it is suitable as a film, coating film or three-dimensional structure for all known members to which polyimide is applied.
The polyimide precursor and resin composition according to the present invention are used in a wide range of fields and products in which properties such as heat resistance, dimensional stability, and insulation are effective, such as paints or printing inks, color filters, and flexible displays. Films, semiconductor devices, electronic parts, interlayer insulating films, wiring coating films, optical circuits, optical circuit parts, antireflection films, holograms, optical members, or building materials are suitably used. Especially, the polyimide precursor resin composition of this invention is used suitably as an insulating material for electronic components.

  Moreover, in this invention, the electronic component by which the polyimide precursor which concerns on this invention and / or its thermosetting material or the polyimide precursor resin composition and / or its thermosetting material at least one part is formed is provided. The Here, the thermoset is a product obtained by partially or completely polyimide-curing a polyimide precursor by heat.

Example 1
A 100 ml three-necked flask was heated in a nitrogen stream and dried thoroughly, then polymerized with a dimethylacetamide solvent, paying careful attention to moisture in the air, reprecipitated with acetone, and then dried BPDA -0.99 g of white solid of ODA (number average molecular weight Mn = 12000 determined from polyamic acid NMR consisting of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether), dried 5 ml of γ-butyrolactone was added, and 5 g of cyclohexyl vinyl ether (CVE) was added. One hour after the addition, the polyamic acid was not completely dissolved.
The mixture was stirred with a magnetic stirrer at room temperature (25 ° C.) for 88 hours under a dried nitrogen stream. Initially, BPDA-ODA was not dissolved in γ-butyrolactone, but as the reaction progressed, the solid dissolved and became a brown solution. Thereafter, half of the reaction solution was reprecipitated with dried diethyl ether to quantitatively obtain a white solid of BPDA-ODA cyclohexyl vinyl ether protector (polyimide precursor 1) represented by the following formula. Analyzed by ¹ H-NMR, the protection ratio (carboxyl) was determined from the integral value of the hydrogen peak bound to carbon between oxygen and oxygen of the hemiacetal ester bond around 6.2 ppm and the integral ratio of the hydrogen peak of the aromatic ring of diphenyl ether. It was confirmed that the reaction rate of the hemiacetal ester bond to the group was 100%.

(Examples 2-3)
Synthesis was performed under the same conditions as in Example 1, except that cyclohexyl vinyl ether was changed to other vinyl ether compounds shown in Table 1. In all experiments, gelation did not occur and white solids of polyimide precursors 2 to 3 were obtained. Analysis was conducted by ¹ H-NMR in the same manner as in Example 1, and it was confirmed that the protection rate (reaction rate of hemiacetal ester bond to carboxyl group) in Examples 2 to 3 was 100%.

Example 4
Polyamic acid is BPDA-4PPD-1ODA (acid dianhydride is 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, diamine is paraphenylenediamine and 4,4′-diaminodiphenyl ether. The polyimide precursor 4 was synthesized under the same conditions as in Example 1 except that the polyamic acid synthesized by mixing at a molar ratio of 4: 1 was changed to the number average molecular weight Mn determined from NMR (14000).

  At the same time, the reaction liquids half left in Examples 1 to 4 were designated polyimide precursor resin compositions 1 to 4. The polyimide precursor resin compositions 1 to 4 did not change in gelation or precipitate formation until 450 hours after storage at room temperature.

(Comparative Example 1)
The reaction was carried out under the same conditions as in Example 1, except that the vinyl ether used was changed to 5 g of VEEA (manufactured by Nippon Shokubai) having the following structural formula. As a result, the reaction solution gelled after 200 hours.

(Comparative Example 2)
Under the same conditions as in Example 1, the reaction was carried out by changing the vinyl ether used to VEEA (manufactured by Nippon Shokubai Co., Ltd.) and n-butyl vinyl ether at a molar equivalent of 1: 1 in 5 g. As a result, the reaction solution gelled after 290 hours.

(Comparative Example 3)
When the reaction was carried out under the same conditions as in Example 1 except that the solvent was changed to dried n-methylpyrrolidone, the protection rate was 25%, and the polyimide precursor of the present invention was not obtained.

(Comparative Example 4)
When the reaction was carried out under the same conditions as in Example 1 except that the solvent was changed to dried dimethylacetamide, the protection rate was 26%, and the polyimide precursor of the present invention was not obtained.

(Comparative Example 5)
The reaction was carried out under the same conditions as in Example 1, except that the solvent was dried and tetrahydrofuran: methanol = 4: 1. The degree of protection was 67% 170 hours after the start of the reaction.

(Comparative Example 6)
When the reaction was carried out by changing the vinyl ether used in the conditions of Example 1 to 5 g of n-butyl vinyl ether, the protection rate was 100% 112 hours after the start of the reaction (Comparative polyimide precursor 6). The reaction solution half left in Comparative Example 6 was designated as Comparative Polyimide Precursor Resin Composition 6.

(Comparative Example 7)
When the reaction was carried out by changing the vinyl ether used under the conditions of Example 1 to 5 g of t-butyl vinyl ether, the protection rate was 100% 48 hours after the start of the reaction (Comparative polyimide precursor 7). The reaction liquid half left in Comparative Example 7 was designated as Comparative Polyimide Precursor Resin Composition 7.

(Comparative Example 8)
When the vinyl ether used under the conditions of Example 1 was changed to 5 g of ethylene glycol butyl vinyl ether, the reaction rate was 100% after 112 hours from the start of the reaction (Comparative polyimide precursor 8). The reaction liquid half left in Comparative Example 8 was designated as Comparative Polyimide Precursor Resin Composition 8.

(Reference Example 1)
Under the same conditions as in Example 1, the reaction was carried out by changing the vinyl ether used to VEEA (manufactured by Nippon Shokubai) and n-butyl vinyl ether in a molar equivalent of 35:65 to 5 g. As a result, there was no change in gelation or precipitate formation until 350 hours after storage at room temperature.

  From the above results, although the polyimide precursors 1 to 4 of the present invention derived from the secondary vinyl ether compound require a reaction time more than the comparative polyimide precursor 7 derived from the tertiary vinyl ether compound, they are derived from the primary vinyl ether compound. It was confirmed that the reaction was completed in a shorter time than the comparative polyimide precursor 6 and the comparative polyimide precursor 8.

Synthesis of model compounds (Synthesis Examples 1-6)
In the same manner as in Example 1, model compounds 1 to 6 having the following structures were synthesized. In any experiment, gelation did not occur, and the protection rate of the carboxyl group was 100%.

<Storage stability evaluation>
With respect to the 2 wt% heavy dimethyl sulfoxide solution (non-dehydrated) of the model compounds 1 to 6 obtained in the above synthesis examples, the decomposition rate of the hemiacetal ester bond after storage for 24 hours at room temperature was measured. The decomposition rate was determined by the following formula after measuring the protection rate using 1H-NMR in the same manner as in Example 1.
Decomposition rate (%) = (1−protection rate after storage / protection rate immediately after preparation) × 100

Both PMDA and BPDA are typical acid dianhydrides used for polyimides exhibiting a low coefficient of linear thermal expansion. From this result, it is more stable to use BPDA than PMDA for acid dianhydrides. It was revealed that a high hemiacetal ester bond was formed. Furthermore, the vinyl ether compounds used for protection showed higher stability in the order of grade 3 <grade 2 <grade 1 (the smaller the decomposition rate, the more stable).
After 24 hours in solution, the PMDA system was found to be almost completely degraded.

  A similar experiment was conducted using a polyimide precursor 1 obtained in the above-mentioned Examples and Comparative Examples, and a 2 wt% heavy dimethyl sulfoxide solution of non-comparative polyimide precursor 6, comparative polyimide precursor 7 and comparative polyimide precursor 8 (non- For dehydration, the degradation rate of the hemiacetal ester bond was measured after storage at room temperature for 24 hours and after storage for 120 hours. The decomposition rate was determined from the integration ratio of the peaks using 1H-NMR as in Example 1.

The influence of the structure of the protecting group on the storage stability showed the same tendency in the polyimide precursor as in the experiment with the model compound.
In addition, it was confirmed by comparison with the model compound that the higher the molecular weight, the higher the decomposition stability.

<Thermal decomposition evaluation>
Using a polyimide precursor 1, a 2% by weight heavy dimethyl sulfoxide solution (non-dehydrated) of the comparative polyimide precursor 6, the comparative polyimide precursor 7, and the comparative polyimide precursor 8, the protection ratio when heated was measured. The degree of protection was determined from the integration ratio of the peaks using 1H-NMR in the same manner as in Example 1 after heating in an NMR tube at each temperature for 5 minutes. A graph showing the relationship between the heating temperature and the protection rate of each polyimide precursor is shown in FIG.

  As shown in FIG. 1, the thermal degradability showed the same tendency as the storage stability. From this result, it was found that all hemiacetal ester bonds were cleaved in the solution when heated at about 120 ° C. The comparative polyimide precursor 7 had a protection rate of 100% immediately after preparation, but decomposition of the protecting group proceeded during the measurement operation, and the protection rate at room temperature at the start of the measurement was not 100%.

<Stability evaluation during heating of coating film>
Next, the stability at the time of heating in an actual coating film was confirmed using infrared spectroscopy.
The sample uses polyimide precursor resin composition 1 and forms a 1 μm ± 0.1 μm-thick film on chrome-plated glass, and from room temperature to 150 ° C. at a rate of 5 ° C. per minute on a hot plate. The IR spectrum was measured in real time while raising the temperature.
FIG. 2 shows a diagram in which the initial peak intensity is normalized to 100 and the peak intensity is plotted with respect to the temperature for the 1120 cm ⁻¹ peak derived from the acetal site in the obtained spectrum.

The peak intensity no longer changes around the normalized intensity of about 10 in the high temperature region. This is probably because there is a spectrum baseline in this part or the tail of the adjacent peak is hung. Therefore, it is presumed that in the polyimide precursor 1, the protecting group is almost completely cleaved at around 110 ° C.
In addition, the normalized peak intensity gradually decreased with heating because it overlapped with the peak of the vinyl ether compound remaining in the film, so that the intensity decreased with the volatilization of the vinyl ether compound from the film. thinking.

Compared with the evaluation of thermal decomposability with a solution, the decomposition temperature was increased by 30 to 40 ° C.
From these results, it was confirmed that the polyimide precursor 1 exhibited thermal stability in a practical range of 50 ° C. to 80 ° C. with respect to heat applied during the process such as drying of the film. .

<Thermal weight reduction evaluation>
The polyimide precursor 1 was heated at a rate of 10 ° C./min while flowing nitrogen at a flow rate of 50 mL / min to determine the thermogravimetric decrease.
As a result, the weight loss at 300 ° C. was 33.6%. The value was close to the theoretical weight reduction of 33.8% when deprotection and imidization proceeded completely, confirming that the elimination reaction and imidization of the protecting group proceeded almost completely. From this, it was suggested that when the polyimide precursor of the present invention was used, the decomposition product did not remain in the polyimide film, and no outgassing or lowering of reliability occurred.

<Infrared spectroscopic evaluation>
When each of the polyimide precursor 1 and BPDA-ODA was heat-treated in a nitrogen atmosphere at 350 ° C. for 1 hour (temperature increase rate from room temperature: 10 ° C./min), an infrared spectrum was measured for each sample. However, the main peaks all have the same wave number and show almost the same spectrum.

<Glass transition temperature after imidization>
The polyimide precursor resin composition 1 and the polyimide precursor resin composition 4 are applied to an Upilex S 50S (trade name: Ube Industries) film affixed on glass, and dried on a hot plate at 80 ° C. for 10 minutes. After drying, the film was peeled off to obtain 20 μm thick films.
Similarly, a 15% by weight NMP solution of BPDA-ODA and BPDA-4PPD-1ODA was applied to a Upilex S 50S (trade name: Ube Industries) film pasted on glass, and dried on a hot plate at 80 ° C. for 10 minutes. Then, the film was peeled off to obtain films each having a thickness of 15 μm.
The above four samples were heated at 350 ° C. for 1 hour in a nitrogen atmosphere (temperature increase rate: 10 ° C./min), polyimide precursor 1, polyimide precursor 4, BPDA-ODA, BPDA-4PPD-1ODA (each thickness) 11 μm ± 1 μm), each imidized film was obtained.

The above-mentioned film was subjected to dynamic viscoelasticity measurement at a frequency of 1 Hz and a heating rate of 5 ° C./min using a viscoelasticity measuring apparatus Solid Analyzer RSA II (manufactured by Rheometric Scientific).
As a result, the glass transition temperature after imidization of the polyimide precursor 1 is 260 ° C., the glass transition temperature after imidization of the polyimide precursor 4 is 310 ° C., and the film after imidization of BPDA-ODA is The film after imidation of 258 ° C. and BPDA-4PPD-1ODA was 308 ° C.

<Linear thermal expansion coefficient after imidization>
Four types of films prepared for measuring the glass transition temperature were cut into a width of 5 mm and a length of 20 mm and used as evaluation samples. The linear thermal expansion coefficient was measured by a thermomechanical analyzer Thermo Plus TMA8310 (manufactured by Rigaku Corporation). The measurement conditions were such that the observation length of the evaluation sample was 15 mm, the heating rate was 10 ° C./min, and the tensile load was 1 g / 25,000 μm ² so that the weight per cross-sectional area of the evaluation sample was the same.
As a result, the linear thermal expansion coefficient after imidization of the polyimide precursor 1 was 42.5 ppm, the linear thermal expansion coefficient after imidization of the polyimide precursor 4 was 19.1 ppm, and the film after imidization of BPDA-ODA The film after imidation of 43.9 ppm and BPDA-4PPD-1ODA was 18.9 ppm.

<Humidity expansion coefficient after imidization>
Four types of films prepared for measuring the glass transition temperature were cut into a width of 5 mm and a length of 20 mm and used as evaluation samples. The humidity expansion coefficient was measured by a humidity variable mechanical analyzer Thermo Plus TMA8310 (manufactured by Rigaku Corporation). When the temperature is constant at 25 ° C. and the humidity is stable in an environment of 20% RH, the humidity is changed to 50% RH. And the value obtained by dividing the value by the sample length was defined as the humidity expansion coefficient. The tensile load was 1 g / 25000 μm ² so that the weight per cross-sectional area of the evaluation sample was the same.
As a result, the humidity expansion coefficient after imidization of the polyimide precursor 1 is 21.5 ppm, the humidity thermal expansion coefficient after imidization of the polyimide precursor 4 is 11.3 ppm, and the film of BPDA-ODA is 21 The film after imidation of .8 ppm, BPDA-4PPD-1ODA was 11.4 ppm.

It is a graph showing the relationship between heating temperature and the protection rate of each polyimide precursor. It is the figure which plotted the intensity | strength of the peak of 1120cm < ^-1 > derived from an acetal site | part about the polyimide precursor 1 with respect to temperature.

Claims (16)

A polyimide precursor containing 100 mol% of a repeating unit represented by the following formula (1) in all repeating units and having a polymer terminal end-capped with a structure containing no acid anhydride group or active hydrogen; A polyimide precursor resin composition comprising a vinyl ether compound and a solvent, wherein the vinyl ether compound is contained in an amount of 55 parts by weight or more with respect to 100 parts by weight of the solvent, and the water content in the composition is 1% by weight or less. .
(In Formula (1), R ¹ is a tetravalent organic group derived from an aromatic tetracarboxylic dianhydride, R ² is a divalent organic group derived from a diamine, and R ¹ and R ² are repeated. R ³ and R ⁴ are each independently a monovalent organic group having the structure of the following formula (2), and they may be the same or different. And R ³ and R ^{4 which} are repeated may be the same or different.
(In formula (2), R ⁵ , R ⁶ and R ⁷ are each independently hydrogen, a halogen atom, a substituted or unsubstituted alkyl group, an allyl group or an aryl group. R ⁸ and R ⁹ are each independently A group having a hydrocarbon skeleton, R ⁸ and R ⁹ do not contain an ethylenically unsaturated bond , R ¹⁰ is a hydrogen atom or a halogen atom, and a carbon atom bonded to R ⁸ , R ⁹ , R ¹⁰ and an oxygen atom Is a secondary carbon atom. R ⁵ , R ⁶ , R ⁷ , R ⁸ , and R ⁹ may each represent a cyclic structure in which groups having a hydrocarbon skeleton are bonded to each other. 2. The polyimide precursor resin composition according to claim 1, wherein R ⁵ , R ⁶ , and R ⁷ in the formula (2) are hydrogen in the polyimide precursor. 3. The polyimide precursor according to claim 1, wherein R ⁸ and R ⁹ in the formula (2) are organic groups having 1 to 30 carbon atoms and do not contain active hydrogen. Polyimide precursor resin composition. The polyimide precursor resin composition according to any one of claims 1 to 3, wherein in the polyimide precursor, R ⁸ and / or R ⁹ in the formula (2) contains an ether bond.   The polyimide precursor is obtained by reacting a vinyl ether compound with a polyamic acid that is not completely dissolved in the solvent in one or more solvents selected from lactones and sulfoxides. The polyimide precursor resin composition according to any one of 1 to 4.   The polyimide precursor is obtained by reacting a polyamic acid and a vinyl ether compound at a reaction temperature of 5 ° C. to 35 ° C. in one or more solvents selected from lactones and sulfoxides. The polyimide precursor resin composition according to any one of claims 1 to 5.   The polyimide precursor resin composition according to any one of claims 1 to 6, wherein the polyimide precursor has a weight average molecular weight or a number average molecular weight of 3000 to 1000000. The polyimide according to any one of claims 1 to 7, wherein in the polyimide precursor, 33 mol% or more of R ¹ in the formula (1) is any structure represented by the following formula (3). Precursor resin composition.
In the polyimide precursor, the formula (1) 33 mol% or more of R ² in is any of structures represented by the following formula (4), a polyimide according to any one of claims 1 to 8 Precursor resin composition.
(R ¹⁰ is a divalent organic group, an oxygen atom, a sulfur atom, or a sulfone group, and R ¹¹ and R ¹² are a monovalent organic group or a halogen atom.)   The polyimide precursor resin composition according to any one of claims 1 to 9, which is substantially free of an acidic substance and an amine.   The polyimide precursor resin composition in any one of Claims 1 thru | or 10 whose glass transition temperature after imidation is 260 degreeC or more.   The polyimide precursor resin composition according to any one of claims 1 to 11, wherein a linear thermal expansion coefficient after imidization is 60 ppm or less.   The polyimide precursor resin composition according to any one of claims 1 to 12, wherein a humidity expansion coefficient after imidation is 40 ppm or less.   The polyimide precursor resin composition in any one of Claims 1 thru | or 13 containing the solvent which does not contain a nitrogen atom.   The polyimide precursor resin composition according to claim 1, which is used as an insulating material for electronic parts.   An electronic component having at least a part formed of the polyimide precursor resin composition according to claim 1 and / or a thermoset thereof.