WO2017159538A1

WO2017159538A1 - Polyamide acid, polyamide acid solution, polyimide, polyimide substrate and method for producing polyimide substrate

Info

Publication number: WO2017159538A1
Application number: PCT/JP2017/009485
Authority: WO
Inventors: 真理宇野
Original assignee: 株式会社カネカ
Priority date: 2016-03-17
Filing date: 2017-03-09
Publication date: 2017-09-21
Also published as: JP2022008353A; TWI735550B; TW201800445A; JP7157859B2; JPWO2017159538A1

Abstract

This polyamide acid contains a constituent unit represented by general formula 1 and a constituent unit represented by general formula 2. Each of A in general formula 1 and B in general formula 2 independently represents a tetravalent aromatic group; each of R¹ and R² in general formula 2 independently represents a divalent hydrocarbon group; and n represents an integer of 1-5. A polyimide is obtained by imidizing this polyamide acid. A polyimide substrate is obtained by imidizing a polyamide acid solution, which contains this polyamide acid and an organic solvent, on a supporting body such as a glass supporting body.

Description

Polyamic acid, polyamic acid solution, polyimide, polyimide substrate, and production method thereof

The present invention relates to a polyamic acid, a polyamic acid solution, a polyimide, and a polyimide substrate.

Electronic devices such as displays, touch panels, and solar cells are required to be thin, light, and flexible, and use of a resin film substrate in place of a glass substrate is being studied.

In the manufacturing process of these electronic devices, semiconductor elements such as thin film transistors and electronic elements such as electrodes are formed on the substrate. Since formation of these elements requires a high temperature process, the resin film substrate is required to have high heat resistance. The element provided on the substrate is generally made of an inorganic material. If the linear thermal expansion coefficient of the substrate and the linear thermal expansion coefficient of the inorganic material constituting the element are greatly different, the substrate may be warped or the element may be destroyed due to stress at the element formation interface or the like. Therefore, the resin film substrate is desired to have a linear thermal expansion coefficient equivalent to that of the inorganic material constituting the element. In a liquid crystal display or bottom emission type organic EL element, since light from the display element is transmitted through the substrate and emitted, the resin film substrate is required to have transparency, and particularly has high light transmittance in the visible light region. Is required. For the above reasons, resin film substrate materials for electronic devices are required to have high heat resistance, low thermal expansion, and high transparency.

The electronic device manufacturing process can be divided into batch type and roll-to-roll type. Resin film substrates can also be applied to the roll-to-roll process, but in addition to the need for new equipment for the manufacture of electronic devices by the roll-to-roll process, there are new problems associated with roll transport. Must be overcome. On the other hand, in the batch process, a resin solution is applied on a support and dried to form a film substrate, and then an element can be formed on the substrate. The current glass substrate process equipment can be used, which is advantageous in terms of cost. It is.

As a resin material that can realize high heat resistance, low thermal expansion, and high transparency comparable to glass, polyimide-based materials having excellent heat resistance are being studied. Polyimides using monomers having rigid structures or alicyclic monomers are known to have high transparency and low thermal expansion (Patent Documents 1 and 2). Moreover, it is known that the polyimide film obtained will show the high adhesiveness to a base material by adding a silicone oil to the polyamic acid as a polyimide precursor, and performing imidization (patent document 3).

JP 2012-041530 A Patent No. 5660249 Japanese Patent Laying-Open No. 2015-229691

In order to apply a polyimide substrate to a batch process, in addition to high heat resistance, low thermal expansion, and high transparency, it exhibits moderate adhesion with glass used as a support in the element formation process, and after element formation. It must be easily peelable from the glass support. However, the polyimide materials disclosed in Patent Documents 1 to 3 cannot satisfy all these required characteristics at the same time.

In view of the above, the present invention has a high heat resistance, a low thermal expansion property, a high transparency, and a polyimide that exhibits appropriate adhesion to glass as a support, and a polyamic acid as a precursor thereof. For the purpose of provision.

The inventors of the present application introduce a rigid structure and an alicyclic structure into a polymer skeleton, and further use a monomer component having a siloxane bond in combination, so that a polyimide satisfying the above characteristics and a polyamic acid as a precursor thereof are obtained. It was found that it can be obtained.

The polyamic acid of the present invention contains a structural unit represented by general formula 1 and a structural unit represented by general formula 2.

The polyimide of the present invention has a structural unit represented by the general formula I and a structural unit represented by the general formula II.

A in General Formula 1 and General Formula I, and B in General Formula 2 and General Formula II are all tetravalent aromatic groups. In General Formula 2 and General Formula II, R ¹ and R ² are each independently a divalent hydrocarbon group, and n is an integer of 1 to 5.

The tetravalent aromatic groups A and B are both residues of an aromatic tetracarboxylic dianhydride, preferably a biphenyl-3,3 ′, 4,4′-tetrayl group. R ¹ and R ² are each independently preferably a methylene group, an ethylene group, or a propylene group, and particularly preferably a propylene group. n is more preferably 1 to 3, and most preferably 1.

That is, the polyamic acid of the present invention preferably contains a structural unit represented by the following formula 1A and a structural unit represented by the following formula 2C, and the polyimide of the present invention preferably has the following formula IA And a structural unit represented by the following formula IIC.

The present invention relates to a polyimide substrate containing the above polyimide. For example, a polyimide substrate is obtained by applying a polyamic acid solution containing the above polyamic acid and an organic solvent on a support, and removing the organic solvent and imidating the polyamic acid. This polyimide substrate is formed as a polyimide film adhered and laminated on a support. As the support on which the polyamic acid solution is applied, for example, glass is used.

The polyimide obtained from the polyamic acid of the present invention has appropriate heat adhesion to a support such as glass in addition to high heat resistance, low thermal expansion and high transparency. Therefore, it is suitable as a substrate material for an electronic device that requires appropriate adhesion to a support in a batch process.

[Polyamide acid and polyimide structure]
The polyamic acid of the present invention includes a structural unit represented by the following general formula 1 and a structural unit represented by the general formula 2.

The polyimide of the present invention includes the structural unit represented by the following general formula I and the structural unit represented by the general formula II, and is obtained, for example, by imidizing the polyamic acid having the structure 1 and the structure 2 described above. .

A in the general formula 1 and the general formula I and B in the general formula 2 and the general formula II are all tetravalent aromatic groups. The aromatic group may have a single aromatic ring, may be a combination of a plurality of aromatic rings, or may be a condensed polycycle. In the general formula 2 and the general formula II, R ¹ and R ² are each independently a divalent hydrocarbon group, and n is an integer of 1 to 5.

A polyimide having a structural unit of the general formula I and a structural unit of the general formula II is obtained by imidizing the polyamic acid having the structural unit of the general formula 1 and the structural unit of the general formula 2. Since the polyimide having this structure is excellent in adhesion to glass, it is suitable for use in the formation of a resin film substrate in a batch process and the formation process of elements on the film substrate.

The above A and B are preferably aromatic tetracarboxylic dianhydride residues. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3 ′, 4,4-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid dianhydride. Anhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetra Carboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, 9, 9-bis (3,4-dicarboxyphenyl) fluorene dianhydride, 9,9′-bis [4- (3,4-dicarboxyphenoxy) phenyl] fluorene dianhydride, 3,3 ′, 4,4 ′ -Biphenyle -Tertetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 4,4'-sulfonyldiphthalic acid Dianhydride, paraterphenyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, metaterphenyl-3,3 ′, 4,4′-tetracarboxylic dianhydride, 3,3 ′ , 4,4′-diphenyl ether tetracarboxylic dianhydride and the like, but are not limited thereto. A in General Formula 1 and General Formula I and B in General Formula 2 and General Formula II may be the same or different.

Since a highly transparent and low linear expansion coefficient polyimide can be obtained, A represents a residue of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (biphenyl-3 represented by the following chemical formula). , 3 ′, 4,4′-tetrayl group).

That is, the structural unit of the general formula 1 is preferably an amic acid structural unit represented by the following formula 1A, and the structural unit of the general formula I is an imide structural unit represented by the following formula IA Is preferred. These structural units are obtained from 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 1,4-cyclohexanediamine.

B is particularly preferably a residue of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride because a highly transparent polyimide having a low linear expansion coefficient can be obtained. That is, the structural unit represented by the general formula 2 is preferably an amic acid structural unit represented by the following general formula 2A, and the structural unit represented by the general formula II is represented by the following general formula IIA. It is preferable that it is an imide structural unit. These structural units are obtained from 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and a siloxane structure-containing diamine.

As described above, A and B may be the same. From the viewpoint of simultaneously realizing the high transparency and low linear expansion coefficient of the polyimide film, it is preferable that both A and B are biphenyl-3,3 ', 4,4'-tetrayl groups.

R ¹ and R ² in the general formula 2 and the general formula II are each independently a methylene group, an ethylene group, or an excellent reactivity at the time of polymerization of the polyamic acid and the polyimide exhibits low thermal expansion. A propylene group is preferable, and a propylene group is particularly preferable. Since the polyamic acid exhibits high solubility and the polyimide film exhibits high transparency, n in the general formula 2 and the general formula II is preferably 1 to 5, and preferably 1 to 3. More preferably, 1 is most preferable.

That is, the structural unit of the general formula 2 is preferably an amic acid structural unit represented by the following general formula 2B, and the structural unit of the general formula II is an imide structural unit represented by the following general formula IIB. Preferably there is. These structural units are obtained from aromatic tetracarboxylic dianhydride and 1,3-bis (3-aminopropyl) tetramethyldisiloxane as a diamine component.

As described above, the tetravalent aromatic group B in the general formulas 2 and II is preferably a biphenyl-3,3 ', 4,4'-tetrayl group. Therefore, the structural unit of the general formula 2 is particularly preferably an amic acid structural unit represented by the following formula 2C, and the structural unit of the general formula II is an imide structural unit represented by the following formula IIC. It is particularly preferred. These building blocks are obtained from 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 1,3-bis (3-aminopropyl) tetramethyldisiloxane.

From the viewpoint of giving polyimide film high heat resistance, low thermal expansion, high transparency, and appropriate adhesion to glass, the structural unit represented by general formula I in polyimide and represented by general formula II 80 mol% or more is preferable with respect to the polyimide whole quantity, and, as for the sum total with a structural unit, 90 mol% or more is more preferable, and 95 mol% or more is especially preferable. In order to make the total of the structural unit represented by the general formula I and the structural unit represented by the general formula II within the above range, the structural unit represented by the general formula 1 in the polyamic acid as a precursor and the general The total of the structural units represented by Formula 2 is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 95 mol% or more, based on the total amount of polyamic acid. preferable.

The number of moles of polyimide is the number of moles of structural units derived from all diamines constituting the polyimide. The number of moles of polyamic acid is the number of moles of structural units derived from all diamines constituting the polyamic acid. Since polyimide and polyamic acid have equimolar constituent units derived from diamine and constituent units derived from acid dianhydride, in polyimide and polyamic acid, the number of moles of constituent units derived from all diamines is derived from all acid dianhydrides. Equal to the number of moles of structural units.

In addition to high transparency and low thermal expansion, the table in view of obtaining a polyimide, a molar number M _A of the general formula II of the structural unit represented by the general formula I in the polyimide having a moderate adhesion between the support the ratio _M a / _{M B} of the moles _{M B} of structural unit is preferably in the range of 95.0 / 5.0 to 99.9 / 0.1. That is, in the polyimide of the present invention, most of the diamine component is 1,4-cyclohexanediamine, and preferably contains a small amount of a siloxane structure-containing diamine such as 1,3-bis (3-aminopropyl) tetramethyldisiloxane. By introducing a small amount of siloxane structure into the diamine component, the adhesion of polyimide to a support such as glass tends to be improved. Therefore, when a polyamic acid solution is applied on the support and imidized, peeling or floating between the polyimide and the support can be suppressed.

As the content of the siloxane structure increases, the adhesion with glass or the like tends to improve. On the other hand, if the adhesiveness is excessively high, it may be difficult to peel the polyimide film from the support, or a dimensional change or opacification may occur during peeling. If the 95.0 / 5.0 or M A _/ M _B, peeling is a feasible without any problem of the polyimide film from the support after forming the electronic element or the like on the polyimide film. _Also, if the _M A / M _B 95.0 / 5.0 or higher, can be maintained low thermal expansion properties and a high transparency of the polyimide film.

M _A / _{M B} is more preferably 96.0 / 4.0 to 99.8 / 0.2, more preferably from 97.0 / 3.0 to 99.7 / 0.3, 98.0 / 2 0.0 to 99.6 / 0.4 is particularly preferable, and 99.0 / 1.0 to 99.5 / 0.5 is most preferable.

In order to make the ratio of the structural unit represented by the general formula I and the structural unit represented by the general formula II in the polyimide within the above range, the structure represented by the general formula 1 in the polyamic acid as the precursor The ratio m _A / m _B of the number of moles m _{A of} units and the number of moles m _{B of} structural units represented by general formula 2 is in the range of 95.0 / 5.0 to 99.9 / 0.1. It is preferably 96.0 / 4.0 to 99.8 / 0.2, more preferably 97.0 / 3.0 to 99.7 / 0.3, and 98.0 / 2.0 to 99.6 / 0.4 is particularly preferable, and 99.0 / 1.0 to 99.6 / 0.4 is most preferable.

The polyamic acid and polyimide of the present invention preferably have a weight average molecular weight in terms of polyethylene oxide by gel permeation chromatography (GPC) of 10,000 to 500,000, and preferably 20,000 to 300,000. More preferably, it is more preferably 30,000 to 200,000. If the weight average molecular weight is 10,000 or more, it becomes possible to use polyamic acid and polyimide as a coating film or film. On the other hand, when the weight average molecular weight is 500,000 or less, sufficient solubility in a solvent is exhibited, so that a coating film or film having a smooth surface and a uniform film thickness is easily obtained.

[Synthesis of polyamic acid and polyimide]
The polyimide containing the above structure I and structure II is obtained by a known method. Polyimide can be synthesized by a synthesis method via a precursor such as polyamic acid or polyimide ester, and a synthesis method not via a precursor. From the availability of monomers and the ease of polymerization, it is preferable to synthesize polyimide by imidation of polyamic acid as a precursor.

The polyamic acid containing the above structures 1 and 2 can be obtained by reacting diamine and tetracarboxylic dianhydride in an organic solvent. For example, the diamine is dissolved or dispersed in a slurry form in an organic solvent to form a diamine solution, and the diamine is dissolved in a solution or solid state in which tetracarboxylic dianhydride is dissolved or dispersed in an organic solvent. What is necessary is just to add in a solution. A diamine may be added to the tetracarboxylic dianhydride solution. Dissolution and reaction of diamine and tetracarboxylic dianhydride are preferably carried out in an inert gas atmosphere such as argon or nitrogen.

In the synthesis of the polyamic acid, it is preferable to adjust the number of moles of the total amount of the diamine component and the number of moles of the total amount of the tetracarboxylic dianhydride component to be substantially equimolar. A polyamic acid having a plurality of structures can be obtained by using a plurality of types of diamines and / or a plurality of types of tetracarboxylic dianhydrides. Moreover, the polyamic acid which has several types of structural units from which a structure differs can also be obtained by blending the polyamic acid from which a structure differs.

By using an aromatic tetracarboxylic dianhydride as the tetracarboxylic dianhydride and using 1,4-cyclohexanediamine and a siloxane structure-containing diamine as the diamine, the structural unit represented by the general formula 1 and the general formula 2 A polyamic acid containing the structural units represented is obtained. By using 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride as the aromatic diamine and 1,3-bis (3-aminopropyl) tetramethyldisiloxane as the siloxane structure-containing diamine, A polyamic acid having an amic acid structural unit represented by 1A and an amic acid structural unit represented by Formula 1C is obtained. By setting the ratio of the number of moles of 1,4-cyclohexanediamine to the number of moles of the siloxane structure-containing diamine within the range of 95.0 / 5.0 to 99.9 / 0.1, m _A / m _B is 95 A polyamic acid in the range of 0.0 / 5.0 to 99.9 / 0.1 is obtained.

The organic solvent used for the polyamic acid synthesis reaction is not particularly limited. The organic solvent is preferably one that can dissolve the tetracarboxylic dianhydride and diamine to be used and can dissolve the polyamic acid produced by polymerization. Specific examples of the organic solvent include urea solvents such as tetramethylurea and N, N-dimethylethylurea; sulfoxides or sulfone solvents such as dimethylsulfoxide, diphenylsulfone and tetramethylsulfone; N, N-dimethylacetamide (DMAC) ), N, N-dimethylformamide (DMF), N, N′-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, and other ester solvents; hexamethylphosphate triamide, and other amide solvents Alkyl halide solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; phenol solvents such as phenol and cresol; ketone solvents such as cyclopentanone; tetrahydrofuran and 1,3-dioxolane 1,4-dioxane Dimethyl ether, diethyl ether, ether solvents such as p- cresol methyl ether. If necessary, two or more organic solvents may be used in combination. In order to increase the solubility and reactivity of the polyamic acid, the organic solvent used for the synthesis of the polyamic acid is preferably selected from amide solvents, ketone solvents, ester solvents, and ether solvents, particularly DMF, Amide solvents such as DMAC and NMP are preferred.

The temperature conditions for the polyamic acid synthesis reaction are not particularly limited. As the reaction between the diamine and tetracarboxylic dianhydride proceeds, polyamic acid is produced, and the viscosity of the reaction solution increases. When an alicyclic diamine such as 1,4-cyclohexanediamine is used, salt formation may occur. Therefore, the temperature of the synthesis reaction may be in the range of 50 ° C. to 150 ° C. as necessary. After the salt is dissolved and the polymerization reaction starts to proceed, the temperature is preferably 80 ° C. or less, more preferably 0 ° C. to 50 ° C., in order to suppress a decrease in molecular weight due to depolymerization of the polyamic acid. preferable. The reaction time may be arbitrarily set in the range of 10 minutes to 30 hours.

A polyamic acid solution containing a polyamic acid and an organic solvent is obtained by polymerizing diamine and tetracarboxylic dianhydride in an organic solvent. This polymerization solution can be used as it is as a polyamic acid solution. Further, the concentration of the polyamic acid and the viscosity of the solution may be adjusted by removing a part of the solvent from the polymerization solution or adding a solvent. The solvent to be added may be different from the solvent used for the polymerization of the polyamic acid. Alternatively, a polyamic acid solution may be prepared by dissolving a solid polyamic acid resin obtained by removing the solvent from the polymerization solution in a solvent. As the organic solvent of the polyamic acid solution, those having high solubility of the polyamic acid are preferable, and the organic solvents exemplified above can be used as the organic solvent used for the synthesis of the polyamic acid. Of these, amide solvents such as DMF, DMAC, and NMP are preferable.

Imidization is performed by dehydrating and ring-closing the polyamic acid. Dehydration ring closure is performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. When imidation is performed in a solution state, it is preferable to perform chemical imidization by adding an imidizing agent and / or a dehydration catalyst to the polyamic acid solution. Although the imidizing agent is not particularly limited, it is preferable to use a tertiary amine, and among them, a heterocyclic tertiary amine is preferable. Examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, isoquinoline, imidazoles and the like. Examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, γ-valerolactone, and the like.

In the case where imidization is performed by removing the solvent from the polyamic acid solution, thermal imidization in which dehydration ring closure is performed by heating is preferable. The method for heating the polyamic acid is not particularly limited. For example, after applying the polyamic acid solution to a support such as a glass plate, a metal plate, or PET (polyethylene terephthalate), heat treatment is performed within a range of 80 ° C to 500 ° C. Just do it. The heating time varies depending on the treatment amount and heating temperature of the polyamic acid solution to be dehydrated and closed, but in general, heating is preferably performed for 1 minute to 5 hours after the processing temperature reaches the maximum temperature. An imidizing agent and / or a dehydration catalyst may be added to the polyamic acid solution, and imidation may be performed by heating by the method described above.

The imidation from polyamic acid to polyimide can be performed at an arbitrary ratio of 1 to 100%, and a partially imidized polyamic acid may be synthesized. As imidization from polyamic acid to polyimide proceeds, the solubility in organic solvents and the viscosity of the solution tend to change. Moreover, it is generally not easy to stop imidization at a specific imidization rate. When a film is formed by applying and drying the solution, the solution viscosity and thixotropy affect the film thickness uniformity. Therefore, in consideration of process stability, the imidization agent and dehydration catalyst are not added to the polyamic acid, and the imidation rate is applied to the support with substantially zero, and heating on the support is performed. It is preferable to perform removal of the solvent and imidization.

[Use of polyamic acid and polyimide]
You may use a polyamic acid and a polyimide for production of a product or a member as it is. Composition with addition of thermosetting component, photocurable component, non-polymerizable binder resin, dye, surfactant, leveling agent, plasticizer, silane coupling agent, fine particles, sensitizer, etc. to polyamic acid and polyimide It is good also as a thing. The blending ratio of these optional components is preferably in the range of 0.1 wt% to 95 wt% with respect to the total solid content of the polyimide. In addition, solid content of a composition is all components other than an organic solvent, and a liquid monomer component is also contained in solid content.

Since the polyimide of the present invention is excellent in transparency and heat resistance, it can be used as a transparent substrate for glass substitute applications, and can be expected to be applied to substrates for electronic devices such as TFT substrates and electrode substrates. Among electronic devices, it is preferably used as a substrate for devices that require light transmission, such as liquid crystal display devices, organic EL elements, electronic paper, and touch panels. The polyimide of the present invention can be used as an optical member such as a color filter, an antireflection film or a hologram, or a building material or a structure material. Various inorganic thin films such as metal oxides and transparent electrodes may be formed on the surface of the polyimide of the present invention. The inorganic thin film is formed by, for example, a PVD method such as a sputtering method, a vacuum vapor deposition method and an ion plating method, and a dry process such as a CVD method.

[Production of polyimide substrates and electronic devices]
The polyimide of the present invention is preferably used as a substrate for an electronic device produced by a batch process because it has good adhesion to a support in addition to heat resistance, low thermal expansion and transparency. In the batch process, a polyimide film (substrate) is formed on a support, an element is formed thereon, and then the polyimide substrate on which the element is formed is peeled from the support to obtain an electronic device.

A polyimide film (polyimide substrate) adhered and laminated on the support is obtained by applying a polyamic acid solution on the support, drying by heating, and imidization. The thickness of the polyimide substrate is about 1 to 200 μm, preferably about 5 to 100 μm.

Examples of the support on which the polyamic acid solution is applied include a glass substrate; a metal substrate such as SUS or a metal belt; a resin film such as polyethylene terephthalate, polycarbonate, polyacrylate, polyethylene naphthalate, and triacetyl cellulose. In order to adapt to the current batch type device manufacturing process, it is preferable to use a glass substrate as a support.

When a polyamic acid solution is applied to a support such as glass and heated, imidation of the polyamic acid begins as the solvent evaporates, and water generated by the organic solvent and imidization (dehydration of the polyamic acid) volatilizes from the polyamic acid solution. . At this time, a part of water and / or the organic solvent does not volatilize and stays between the support and the resin film being imidized, causing peeling at the interface between the support and the resin film. The water and / or organic solvent staying at the interface between the support and the resin film is then discharged through the polyimide film in the step of heating at a high temperature, and bubbles remain in the part where peeling or floating occurs. When such bubbles are generated, a problem occurs when an element is formed on the polyimide substrate. In particular, in a thinned or miniaturized device, even fine peeling or floating greatly affects the formation or mounting of elements or the like.

Since the polyamic acid and polyimide of the present invention having a siloxane structure have high adhesiveness to glass, the organic solvent to the interface between the glass support and the resin film during drying and imidization of the solvent on the support Floating or peeling caused by water or stagnation is unlikely to occur. Therefore, it is possible to accurately form and mount elements on a polyimide substrate that is closely stacked on a support. Moreover, peeling from the support body of the polyimide substrate after forming an element can be easily implemented by adjusting the ratio of the alicyclic structure (general formula I) and the siloxane structure (general formula II) in polyimide.

The polyimide film (polyimide substrate) adhered and laminated on the support preferably has a 90 ° peel strength from the support of 0.08 to 5.00 N / cm, preferably 0.09 to 4.00 N / cm. More preferably, it is 0.10 to 3.5 N / cm. In the case of having the above-mentioned adhesion, peeling hardly occurs in the element formation and mounting process, and peeling from the support after the element formation and mounting is easy. The 90 ° peel strength can be measured by the method described in Examples below.

The transparency of the polyimide film can be evaluated by, for example, total light transmittance and haze. The total light transmittance of the polyimide film is preferably 80% or more, and more preferably 85% or more. The haze is preferably 2.0% or less, and more preferably 1.0% or less. Polyimide tends to absorb light on the short wavelength side, and the film itself is often colored yellow. In order to obtain a film with less coloring, the light transmittance at a wavelength of 450 nm of the polyimide film is preferably 70% or more, and more preferably 75% or more. The polyimide of the present invention preferably has the above total light transmittance, haze, and light transmittance at a wavelength of 450 nm when a film having a thickness of 10 μm is formed.

The polyimide substrate containing the polyimide of the present invention has small linear thermal expansion and excellent dimensional stability before and after heating. The linear thermal expansion coefficient of the polyimide film is preferably 30 ppm / K or less, and more preferably 20 ppm / K or less. The linear thermal expansion coefficient can be measured by the method described in Examples described later. The polyimide of the present invention preferably has a linear thermal expansion coefficient in the above range when a film having a thickness of 10 μm is formed.

[Preparation of polyamic acid solution]
<Example 1>
A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring blade and a nitrogen introduction tube was charged with 8.38 g of trans-1,4-cyclohexanediamine (CHDA) and N-methyl-2-pyrrolidone (NMP). 170.0 g was charged and dissolved by stirring at room temperature (23 ° C.). After visually confirming the dissolution of CHDA, 0.02 g of 1,3-bis (3-aminopropyl) tetramethyldisiloxane (PAM-E) was added and further stirred. To this solution, 21.61 g of 3,3 ′, 4,4′-biphenyltetracarboxylic anhydride (BPDA) was added, heated at 80 ° C. for 1 hour, and then stirred at room temperature for 5 hours to obtain a polyamic acid solution. Obtained. The charged concentration of diamine and tetracarboxylic dianhydride in this reaction solution was 15% by weight based on the total amount of the reaction solution.

<Example 2>
A polyamic acid solution was obtained in the same manner as in Example 1 except that the amount of CHDA charged was changed to 8.37 g, the amount of PAM-E charged was 0.04 g, and the amount of BPDA charged was 21.60 g.

<Example 3>
A polyamic acid solution was obtained in the same manner as in Example 1, except that the amount of CHDA charged was 8.36 g, the amount of PAM-E charged was 0.06 g, and the amount of BPDA charged was 21.59 g.

<Example 4>
A polyamic acid solution was obtained in the same manner as in Example 1 except that the amount of CHDA charged was 8.33 g, the amount of PAM-E charged was 0.09 g, and the amount of BPDA charged was 21.58 g.

<Example 5>
A polyamic acid solution was obtained in the same manner as in Example 1, except that the amount of CHDA charged was 8.30 g, the amount of PAM-E charged was 0.13 g, and the amount of BPDA charged was 21.56 g.

<Example 6>
A polyamic acid solution was obtained in the same manner as in Example 1, except that the amount of CHDA charged was 8.28 g, the amount of PAM-E charged was 0.18 g, and the amount of BPDA charged was 21.54 g.

<Example 7>
A polyamic acid solution was obtained in the same manner as in Example 1 except that the amount of CHDA charged was 8.06 g, the amount of PAM-E charged was 0.54 g, and the amount of BPDA charged was 21.40 g.

<Example 8>
A polyamic acid solution was obtained in the same manner as in Example 1 except that the amount of CHDA charged was 7.84 g, the amount of PAM-E was 0.90 g, and the amount of BPDA was 21.26 g.

<Comparative Example 1>
A polyamic acid solution was obtained in the same manner as in Example 1, except that the amount of CHDA charged was changed to 8.39 g and 21.61 g of BPDA was added without adding PAM-E.

<Comparative example 2>
To the polyamic acid solution synthesized in Comparative Example 1, 0.1% by weight of silane coupling agent: γ-aminopropyltriethoxysilane with respect to the polyamic acid was added and stirred for 24 hours to obtain an alkoxysilane-modified polyamic acid solution. Was prepared.

<Comparative Example 3>
The CHDA charge was changed to 8.36 g, and without adding PAM-E, 21.31 g of BPDA and 9,9-bis (3,4-dicarboxyphenyl) fluorenic dianhydride (hereinafter referred to as BPAF) A polyamic acid solution was obtained in the same manner as in Example 1 except that 0.335 g was added simultaneously.

<Comparative example 4>
In a 500-mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring blade and a nitrogen introduction tube, 7.98 g of paraphenylenediamine (PDA) and 170.0 g of NMP were charged and dissolved by stirring at room temperature. After visually confirming the dissolution of PDA, 0.19 g of PAM-E was added and further stirred. Thereafter, 21.83 g of BPDA was added and stirred at 50 ° C. until dissolved, then the temperature of the solution was adjusted to about 90 ° C. and stirring was continued to lower the viscosity of the solution, and the viscosity at 23 ° C. was 28,800 mPa · s. A polyamic acid solution was obtained.

<Comparative Example 5>
A 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring blade and a nitrogen introduction tube was charged with 8.34 g of CHDA and 170.0 g of NMP and dissolved by stirring at room temperature. After visually confirming the dissolution of CHDA, 0.13 g of reactive silicone oil manufactured by Shin-Etsu Silicone: KF-8010 (amine equivalent: 430 g / mol) was added and further stirred. 21.53 g of BPDA was added to this solution, heated at 80 ° C. for 1 hour, then cooled, and stirred at room temperature (23 ° C.) for 5 hours to obtain a polyamic acid solution.

<Comparative Example 6>
The CHDA charge amount was changed to 8.36 g and the BPDA charge amount was changed to 21.50 g. As a reactive silicone oil, instead of KF-8010, a reactive silicone oil made by Shin-Etsu Silicone: X-22-168AS (acid anhydride) 0.15 g of product equivalent: 500 g / mol) was added. Except for these changes, a polyamic acid solution was obtained in the same manner as in Comparative Example 5.

[Evaluation of polyamic acid]
<Molecular weight>
The weight average molecular weight (Mw) was determined under the conditions shown in Table 1.

[Preparation of polyimide film]
The polyamic acid solutions obtained in the above Examples and Comparative Examples were diluted with NMP so that the solid concentration was 10%. The diluted solution was cast on a 150 mm × 150 mm non-alkali glass plate (Corning Eagle XG, thickness 0.7 mm) using a bar coater so that the thickness after drying was 10 μm. The film was dried in an oven at 80 ° C. for 30 minutes to form a polyamic acid coating film on the glass plate. After heating the laminated body of the glass plate and the polyamic acid coating film from a temperature of 20 ° C. to 350 ° C. at a rate of 5 ° C./min in a nitrogen atmosphere, the coating film is imidized by heating at 350 ° C. for 1 hour A laminate of polyimide film and glass was obtained. Only in Comparative Example 4, the polyamic acid solution was cast so that the thickness after drying was 20 μm, the drying temperature in a hot air oven was 120 ° C., and the temperature was increased to 450 ° C. at a temperature rising rate of 7 ° C./min in a nitrogen atmosphere. After raising the temperature, imidization was carried out by heating at 450 ° C. for 10 minutes.

In Comparative Example 1, many bubbles were observed between the glass and the polyimide film. Except for Comparative Example 1, no bubbles due to peeling of the polyimide film were confirmed. On the other hand, in Example 8, since the adhesiveness between the glass and the polyimide film was high and could not be peeled off from the glass, the following physical property evaluation was not performed.

[Evaluation of polyimide film]
<Peel strength>
The laminate of the glass plate and the polyimide film was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH for humidity control, and then the 90 ° peel strength was measured in accordance with ASTM D1876-01 standard. A 10 mm wide cut was made in the polyimide film with a cutter knife, and the tensile tester (Strograph VES1D) manufactured by Toyo Seiki was used. A peel test was conducted, and the average peel strength was defined as the peel strength. In Examples 6 and 7, the peel strength exceeded the maximum load (5.0 N) of the load cell.

<Linear thermal expansion coefficient (CTE)>
The linear thermal expansion coefficient was measured using TMA / SS7100 manufactured by Hitachi High-Tech Science Co., Ltd. (sample size: width 3 mm × length 10 mm; the film thickness was measured and the cross-sectional area of the film was calculated), and the load was 29.4 mN. The temperature is once raised from 10 ° C. to 350 ° C. at 10 ° C./minute, then lowered at 40 ° C./minute, and the linear expansion coefficient is obtained from the amount of change in strain of the sample per unit temperature at 100 to 300 ° C. It was.

<Light transmittance>
Using a UV-visible near-infrared spectrophotometer (V-650) manufactured by JASCO Corporation, the light transmittance at 200 to 800 nm was measured, and the light transmittance at a wavelength of 450 nm was defined as the transmittance of the polyimide film.

<Total light transmittance (TT) and haze of polyimide film>
It was measured by a method described in JIS K7105-1981 using an integrating sphere haze meter 300A manufactured by Nippon Denshoku Industries Co., Ltd.

Examples and Comparative Examples of monomer charge during polyamic acid polymerization (molar ratio of acid dianhydride and diamine), weight average molecular weight of polyamic acid and presence or absence of modification, film thickness of polyimide film, glass during imidization Table 2 shows the evaluation results of the presence or absence of peeling from the plate, the peel strength of the polyimide film from the glass plate, and the characteristics of the polyimide film.

The polyamic acid solution of Comparative Example 1 obtained from BPDA as the acid dianhydride and CHDA as the diamine has a large number of gaps between the glass plate and the polyimide film during thermal imidization after coating on the glass plate. Bubbles were generated, and 25% or more of the coated area was peeled off from the glass plate. In Comparative Example 2 in which the polyamic acid of Comparative Example 1 was modified with a silane coupling agent, the adhesion to the glass plate was improved as compared with Comparative Example 1, but the peel strength was small and the adhesion was sufficient. It wasn't. The same was true for Comparative Example 3 in which 1 mol% of BPAF was added to BPDA as an acid dianhydride.

In Comparative Example 5 and Comparative Example 6 in which the reactive silicone oil was added to the monomer component, the adhesion with the glass plate was improved as compared with Comparative Example 1, but the peel strength was small and the adhesion was not sufficient. . Moreover, in Comparative Example 5 and Comparative Example 6, the obtained polyimide film had a high linear thermal expansion coefficient (CTE), inferior dimensional stability, and transparency was lowered.

Examples 1 to 8 using PAM-E having a siloxane structure in addition to CHDA as the diamine component all showed good adhesion to glass. Examples 1 to 7 in which the CHA / PAM-E mole ratio m _A / m _B is 97/3 to 99.0 / 0.1 are all low CTE and high transparency equivalent to Comparative Example 1 Was maintained. In Example 8 in which the ratio m _A / m _{B of} CHDA / PAM-E was 95/5, the characteristics of the polyimide film were not evaluated. However, when the polyimide film formed on the glass plate was visually observed, The transparency was the same as in Examples 1-7. In addition, Example 8 is presumed to maintain the same low CTE and high transparency as Example 7 because the composition of polyamic acid and polyimide is similar to Example 7. In Comparative Example 4 using PDA instead of CHDA, the peel strength equivalent to that of Examples 1 and 2 was shown, but the transparency (particularly the visible light short wavelength side) was greatly reduced, and coloring was observed. It was.

In Examples 1 to 8, there was a tendency for the peel strength to increase as the amount of PAM-E charged increased and the adhesion to glass to improve. After forming a polyimide film on a glass plate and forming and mounting elements on the polyimide film as necessary, considering the ease of peeling when peeling the polyimide film from the glass plate, it contains a siloxane structure The amount of diamine used is preferably 5 mol% or less, particularly preferably 1 mol% or less, based on the total amount of diamine.

As can be understood from the comparison between the above examples and comparative examples, the polyamic acid of the present invention has good processability during film formation on the glass support and heating imidization, and the glass support. Excellent adhesion. The polyimide film obtained by imidation of the polyamic acid of the present invention has low thermal expansion even in a high temperature range of 100 to 300 ° C. and has high transparency, so that it can be used as a transparent substrate material instead of glass. Application can be expected.

Claims

Polyamic acid containing a structural unit represented by the general formula 1 and a structural unit represented by the general formula 2:

A in formula 1 and B in formula 2 are each independently a tetravalent aromatic group; R 1 and R 2 in formula 2 are each independently a divalent hydrocarbon group; It is an integer of 5.
The ratio m A / m B of the moles m B of structural units represented the moles m A of structural units represented by the general formula 1 in the general formula 2, 95.0 / 5.0 to 99 The polyamic acid according to claim 1, which is in the range of .9 / 0.1.
The polyamic acid according to claim 1 or 2, wherein the structural unit represented by the general formula 2 is a structural unit represented by the formula 2B.
The structural unit represented by the general formula 1 is a structural unit represented by the formula 1A, and the structural unit represented by the general formula 2 is a structural unit represented by the formula 2C. The polyamic acid described.
A polyamic acid solution containing the polyamic acid according to any one of claims 1 to 4 and an organic solvent.
An application of the polyamic acid solution according to claim 5 on a support, removal of the organic solvent and imidation of the polyamic acid, and formation of a polyimide film adhered and laminated on the support. Production method.
The method for producing a polyimide substrate according to claim 6, wherein the support is glass.
Polyimide containing a structural unit represented by general formula I and a structural unit represented by general formula II:

A in formula I and B in formula II are each independently a tetravalent aromatic group; R 1 and R 2 in formula 2II are each independently a divalent hydrocarbon group; It is an integer of 5.
The ratio M A / M B of the moles M B of structural units represented the moles M A of structural units represented by the general formula I by the general formula II is 95.0 / 5.0 to 99 9. Polyimide according to claim 8, in the range of .9 / 0.1.
The polyimide according to claim 8 or 9, wherein the structural unit represented by the general formula II is a structural unit represented by the formula IIB.
The structural unit represented by the general formula I is a structural unit represented by the formula IA, and the structural unit represented by the general formula II is a structural unit represented by the formula IIC. The polyimide described.
A polyimide substrate comprising the polyimide according to any one of claims 8 to 11.
The polyimide substrate according to claim 12, wherein the light transmittance at a wavelength of 450 nm is 70% or more.
The polyimide substrate according to claim 12 or 13, wherein the linear thermal expansion coefficient at 100 to 300 ° C is 30 ppm / K or less.
An electronic device comprising an electrode and / or an electronic element on the polyimide substrate according to any one of claims 12 to 14.