JP7157859B2 - Electronic device manufacturing method - Google Patents

Description

The present invention relates to polyamic acids, polyamic acid solutions, polyimides, and polyimide substrates.

Electronic devices such as displays, touch panels, and solar cells are required to be thinner, lighter, and more flexible, and the use of resin film substrates instead of glass substrates is being investigated.

In the manufacturing process of these electronic devices, semiconductors such as thin film transistors and electronic elements such as electrodes are formed on substrates. Since the formation of these elements requires high-temperature processes, resin film substrates are required to have high heat resistance. Elements provided on the substrate are generally made of inorganic materials. If the coefficient of linear thermal expansion of the substrate and the coefficient of linear thermal expansion of the inorganic material forming the element are significantly different, the substrate may warp or the element may be destroyed due to stress or the like at the element formation interface. Therefore, the resin film substrate is desired to have a linear thermal expansion coefficient equivalent to that of the inorganic material forming the element. In liquid crystal displays and bottom-emission type organic EL devices, the light from the display device is emitted through the substrate, so the resin film substrate is required to be transparent, and in particular, 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.

Electronic device manufacturing processes are divided into batch type and roll-to-roll type. Resin film substrates can also be applied to the roll-to-roll process, but the production of electronic devices by the roll-to-roll process requires new equipment and introduces new problems associated with roll transport. must be overcome. On the other hand, in the batch process, a film substrate is formed by coating a resin solution on a support, drying it, and then forming elements on it. Existing processing equipment for glass substrates can be used, so it is advantageous in terms of cost. is.

As a resin material capable of achieving high heat resistance, low thermal expansion, and high transparency comparable to glass, polyimide-based materials with excellent heat resistance are being studied. Polyimides using monomers with rigid structures or alicyclic monomers are known to exhibit high transparency and low thermal expansion (Patent Documents 1 and 2). Further, it is known that the polyimide film obtained by adding silicone oil to polyamic acid as a polyimide precursor for imidization exhibits high adhesion to a substrate (Patent Document 3).

JP 2012-041530 A Patent No. 5660249 JP 2015-229691 A

In order to apply the polyimide substrate to the batch process, in addition to high heat resistance, low thermal expansion, and high transparency, it should exhibit moderate adhesiveness with the glass used as the support in the device formation process, and after device formation, It is required that it can be easily peeled off from the glass support. However, the polyimide materials disclosed in Patent Documents 1 to 3 cannot satisfy all of these required properties at the same time.

In view of the above, the present invention provides polyimide having high heat resistance, low thermal expansion, and high transparency, and exhibiting moderate adhesion to glass as a support, and polyamic acid as its precursor. for the purpose of providing

The inventors of the present invention have introduced a rigid structure and an alicyclic structure into the polymer skeleton, and further used a monomer component having a siloxane bond in combination to produce a polyimide satisfying the above properties and a polyamic acid as a precursor thereof. I found what I got.

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 general formula I and a structural unit represented by general formula II.

Both A in general formulas 1 and I and B in general formulas 2 and II are 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 1-5.

Each of the tetravalent aromatic groups A and B is a residue 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, most preferably 1.

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

The present invention relates to a polyimide substrate containing the above polyimide. For example, a polyimide substrate can be obtained by applying a polyamic acid solution containing the above polyamic acid and an organic solvent onto a support, removing the organic solvent, and imidizing the polyamic acid. This polyimide substrate is formed as a polyimide film that is closely laminated to a support. Glass, for example, is used as the support on which the polyamic acid solution is applied.

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

[Structure of polyamic acid and polyimide]
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 below.

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

Both A in the general formulas 1 and I and B in the general formulas 2 and II are tetravalent aromatic groups. The aromatic group may have a single aromatic ring, a combination of multiple aromatic rings, or a condensed polycyclic ring. In general formula 2 and general formula II above, R ¹ and R ² are each independently a divalent hydrocarbon group, and n is an integer of 1-5.

By imidating the polyamic acid having the structural unit of general formula 1 and the structural unit of general formula 2, a polyimide having the structural unit of general formula I and the structural unit of general formula II is obtained. Since polyimide having this structure has excellent adhesion to glass, it is suitable for forming resin film substrates in a batch process and for forming elements on film substrates.

A and B above are preferably aromatic tetracarboxylic dianhydride residues. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3′,4,4-biphenyltetracarboxylic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic 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-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic 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 '-biphenyl ether tetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 4,4'-sulfonyldi phthalic dianhydride, p-terphenyl-3,4,3′,4′-tetracarboxylic dianhydride, meta-terphenyl-3,3′,4,4′-tetracarboxylic dianhydride, 3, 3′,4,4′-diphenyl ether tetracarboxylic acid dianhydride and the like can be mentioned, but not limited to these. A in general formulas 1 and I and B in general formulas 2 and II may be the same or different.

A is a residue of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (biphenyl-3 , 3′,4,4′-tetrayl group) is particularly preferred.

That is, the structural unit of general formula 1 is preferably an amic acid structural unit represented by formula 1A below, and the structural unit of general formula I is an imide structural unit represented by formula IA below. 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 acid dianhydride, since a polyimide having high transparency and a low coefficient of linear expansion can be obtained. That is, the structural unit represented by general formula 2 is preferably an amic acid structural unit represented by general formula 2A below, and the structural unit represented by general formula II is represented by general formula IIA below. is preferably an imide constitutional unit. These structural units are obtained from 3,3',4,4'-biphenyltetracarboxylic dianhydride and siloxane structure-containing diamine.

As mentioned above, A and B may be the same. Both A and B are preferably a biphenyl-3,3',4,4'-tetrayl group from the viewpoint of simultaneously realizing high transparency and a low coefficient of linear expansion of the polyimide film.

Since polyamic acid has excellent reactivity during polymerization and polyimide exhibits low thermal expansion, R ¹ and R ² in general formula 2 and general formula II are each independently a methylene group, an ethylene group, or A propylene group is preferred, and a propylene group is particularly preferred. 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, preferably 1 to 3. More preferably, 1 is most preferred.

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

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

From the viewpoint of giving the polyimide film high heat resistance, low thermal expansion, high transparency, and moderate adhesion to glass, the structural unit represented by general formula I in polyimide and general formula II are represented. The total amount with the structural units is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 95 mol% or more, relative to the total amount of the polyimide. In order to make the total of the structural units represented by the general formula I and the structural units represented by the general formula II within the above range, the structural units represented by the general formula 1 in the precursor polyamic acid and the general The total amount of the constituent units represented by formula 2 is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly 95 mol% or more, relative to 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 all diamine-derived constitutional units constituting the polyamic acid. Since polyimide and polyamic acid have equimolar structural units derived from diamine and structural units derived from acid dianhydride, in polyimide and polyamic acid, the number of moles of structural units derived from all diamines is the number of moles derived from all acid dianhydrides. Equal to the number of moles of the building block.

In addition to high transparency and low thermal expansion, from the viewpoint of obtaining a polyimide having moderate adhesion to the support, the number of moles M _A of the structural unit represented by general formula I in the polyimide and represented by general formula II The ratio M _A /M _B to the number of moles M _B of the structural unit formed is preferably in the range of 95.0/5.0 to 99.9/0.1. That is, the polyimide of the present invention preferably contains 1,4-cyclohexanediamine as the major diamine component and contains a small amount of siloxane structure-containing diamine such as 1,3-bis(3-aminopropyl)tetramethyldisiloxane. Introducing a small amount of siloxane structure into the diamine component tends to improve the adhesion of polyimide to a support such as glass. Therefore, when the polyamic acid solution is applied onto the support for imidization, peeling or lifting between the polyimide and the support can be suppressed.

Adhesion to glass tends to improve as the content of the siloxane structure increases. On the other hand, if the adhesion is excessively high, it may become difficult to peel the polyimide film from the support, or dimensional change or opacification may occur during peeling. When the M _A /M _B ratio is 95.0/5.0 or more, the polyimide film can be peeled off from the support after an electronic element or the like is formed on the polyimide film without any problem. Moreover, if M _A /M _B is 95.0/5.0 or more, the low thermal expansion characteristics and high transparency of the polyimide film can be maintained.

M _A /M _B is more 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 are particularly preferred, and 99.0/1.0 to 99.5/0.5 are most preferred.

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 above range, the structure represented by the general formula 1 in the precursor polyamic acid The ratio m _A /m _B of the number of moles m _A of the unit to the number of moles m _B of the structural unit represented by the general formula 2 is in the range of 95.0/5.0 to 99.9/0.1 is preferably 96.0/4.0 to 99.8/0.2, more preferably 97.0/3.0 to 99.7/0.3, 98.0/2.0 to 99.6/0.4 is particularly preferred and 99.0/1.0 to 99.6/0.4 is most preferred.

The polyamic acid and polyimide of the present invention preferably have a weight average molecular weight of 10,000 to 500,000, more preferably 20,000 to 300,000, in terms of polyethylene oxide by gel permeation chromatography (GPC). It is more preferably 30,000 to 200,000. If the weight average molecular weight is 10,000 or more, polyamic acid and polyimide can be used as coatings or films. On the other hand, if the weight-average molecular weight is 500,000 or less, it exhibits sufficient solubility in solvents, so that it is easy to obtain a coating or film having a smooth surface and a uniform thickness.

[Synthesis of polyamic acid and polyimide]
Polyimides containing structure I and structure II above are obtained by known methods. A polyimide can be synthesized by a synthesis method involving a precursor such as polyamic acid or polyimide ester, and a synthesis method not involving a precursor. From the viewpoint of availability of monomers and ease of polymerization, it is preferable to synthesize polyimide by imidization of polyamic acid as a precursor.

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

In synthesizing 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. Polyamic acids having multiple structures can be obtained by using multiple types of diamines and/or multiple types of tetracarboxylic dianhydrides. Also, by blending polyamic acids with different structures, it is possible to obtain a polyamic acid having a plurality of structural units with different structures.

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 represented structural unit is obtained. 3,3',4,4'-Biphenyltetracarboxylic dianhydride is used as the aromatic tetracarboxylic dianhydride , and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is used as the siloxane structure-containing diamine. By using, a polyamic acid having an amic acid constitutional unit represented by formula 1A and an amic acid constitutional unit represented by formula 2C 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 in the range of 95.0/5.0 to 99.9/0.1, m _A /m _B is 95. Polyamic acids ranging from .0/5.0 to 99.9/0.1 are obtained.

The organic solvent used in the polyamic acid synthesis reaction is not particularly limited. The organic solvent is preferably one capable of dissolving the tetracarboxylic dianhydride and diamines used and capable of dissolving polyamic acid produced by polymerization. Specific examples of the organic solvent include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfoxide or sulfone-based solvents such as dimethylsulfoxide, diphenylsulfone, and tetramethylsulfone; N,N-dimethylacetamide (DMAC ), N,N-dimethylformamide (DMF), N,N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), ester solvents such as γ-butyrolactone; amide solvents such as hexamethylphosphoric acid triamide Alkyl halide solvents such as chloroform and methylene chloride; Aromatic hydrocarbon solvents such as benzene and toluene; Phenolic solvents such as phenol and cresol; Ketone solvents such as cyclopentanone; , 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. Two or more organic solvents may be used in combination if necessary. In order to increase the solubility and reactivity of the polyamic acid, the organic solvent used in synthesizing 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 the tetracarboxylic dianhydride proceeds, polyamic acid is produced and the viscosity of the reaction solution increases. Since salt formation may occur when using cycloaliphatic diamines such as 1,4-cyclohexanediamine, the temperature of the synthesis reaction may be in the range of 50° C. to 150° C., if desired. After the salt has dissolved and the polymerization reaction has started to progress, 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 within the range of 10 minutes to 30 hours.

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

Imidation is carried out by dehydration and ring closure of the polyamic acid. Dehydration ring closure is accomplished by azeotropic methods using azeotropic solvents, thermal methods or chemical methods. When imidization is performed in the state of solution, it is preferable to add an imidization agent and/or a dehydration catalyst to the polyamic acid solution to perform chemical imidization. Although the imidizing agent is not particularly limited, it is preferable to use a tertiary amine, and among these, a heterocyclic tertiary amine is preferable. Heterocyclic tertiary amines include pyridine, picoline, quinoline, isoquinoline, imidazoles and the like. Dehydration catalysts include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, γ-valerolactone and the like.

When imidization is performed by removing the solvent from the polyamic acid solution, thermal imidization in which dehydration ring closure is performed by heating is preferred. The method of heating the polyamic acid is not particularly limited, but 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 the range of 80 ° C. to 500 ° C. Do it. The heating time varies depending on the amount of the polyamic acid solution to be treated for dehydration ring closure and the heating temperature, but generally, it is preferable to perform heating for 1 minute to 5 hours after the treatment temperature reaches the maximum temperature. An imidization agent and/or a dehydration catalyst may be added to the polyamic acid solution, and imidization may be performed by heating in the above manner.

The imidization of polyamic acid into polyimide can be carried out at any ratio of 1 to 100%, and partially imidized polyamic acid may be synthesized. As the imidization of polyamic acid to polyimide proceeds, the solubility in organic solvents and the viscosity of the solution tend to change. Also, it is generally not easy to stop imidization at a specific imidization rate. When forming a film by applying and drying a solution, the viscosity and thixotropy of the solution affect the uniformity of the film thickness. Therefore, considering the stability of the process, the polyamic acid was coated on the support with an imidization rate of almost zero without adding an imidizing agent or a dehydration catalyst, and then heated on the support. Solvent removal and imidization are preferably carried out by

[Applications of polyamic acid and polyimide]
Polyamic acid and polyimide may be used as they are for production of products and members. Composition by adding thermosetting components, photocurable components, non-polymerizable binder resins, dyes, surfactants, leveling agents, plasticizers, silane coupling agents, fine particles, sensitizers, etc. to polyamic acid and polyimide. It can be a thing. The mixing ratio of these optional components is preferably in the range of 0.1% by weight to 95% by weight based on the total solid content of the polyimide. The solid content of the composition is all components other than the organic solvent, and liquid monomer components are also included in the solid content.

Since the polyimide of the present invention has excellent transparency and heat resistance, it can be used as a transparent substrate such as a substitute for glass, 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 requiring optical transparency, such as liquid crystal display devices, organic EL elements, electronic paper, and touch panels. The polyimide of the present invention can also be used as a color filter, an antireflection film, an optical member such as a hologram, or a building material or structural 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 sputtering method, a PVD method such as a vacuum deposition method and an ion plating method, and a dry process such as a CVD method.

[Production of polyimide substrate and electronic device]
The polyimide of the present invention is preferably used as a substrate for electronic devices manufactured 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, an electronic device is obtained by forming a polyimide film (substrate) on a support, forming elements thereon, and then peeling the polyimide substrate with the elements formed thereon from the support.

A polyamic acid solution is applied onto a support, dried by heating, and imidized to obtain a polyimide film (polyimide substrate) adhered and laminated on the support. 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 glass substrates; metal substrates such as SUS or metal belts; resin films such as polyethylene terephthalate, polycarbonate, polyacrylate, polyethylene naphthalate, triacetyl cellulose, and the like. For compatibility with current batch-type device manufacturing processes, it is preferable to use a glass substrate as the support.

When the polyamic acid solution is applied to a support such as glass and heated, the imidization of the polyamic acid begins as the solvent evaporates, and the organic solvent and water generated by imidization (dehydration of polyamic acid) volatilize from the polyamic acid solution. . At this time, part of the water and/or organic solvent does not volatilize and remains between the support and the resin film during imidization, causing peeling at the interface between the support and the resin film. The water and/or organic solvent remaining 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, leaving air bubbles in the portions where peeling or floating occurs. The generation of such air bubbles causes problems when forming elements on the polyimide substrate. In particular, in thinned or miniaturized devices, even minute peeling or floating has a great influence on the formation or mounting of elements.

The polyamic acid and polyimide of the present invention having a siloxane structure have high adhesion to glass. It is difficult to cause floating or peeling due to stagnation of water or water. Therefore, it is possible to accurately form and mount elements on the polyimide substrate that is closely laminated on the support. Also, by adjusting the ratio of the alicyclic structure (general formula I) and the siloxane structure (general formula II) in the polyimide, the polyimide substrate can be easily peeled off from the support after forming the device.

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, more preferably 0.09 to 4.00 N/cm. and more preferably 0.10 to 3.5 N/cm. When the adhesive has the above-mentioned adhesion, it is difficult to cause delamination during the device formation and mounting processes, and the device can be easily detached from the support after device formation and mounting. The 90° peel strength can be measured by the method described in Examples below.

The transparency of the polyimide film can be evaluated, for example, by total light transmittance and haze. The total light transmittance of the polyimide film is preferably 80% or more, more preferably 85% or more. The haze is preferably 2.0% or less, 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 less colored film, the light transmittance of the polyimide film at a wavelength of 450 nm is preferably 70% or more, more preferably 75% or more. The polyimide of the present invention preferably has a total light transmittance, a haze, and a light transmittance at a wavelength of 450 nm when formed into a film having a thickness of 10 μm within the above ranges.

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

[Preparation of polyamic acid solution]
<Example 1>
Trans-1,4-cyclohexanediamine (CHDA) 8.38 g and N-methyl-2-pyrrolidone (NMP) were placed in a 500 mL glass separable flask equipped with a stirrer equipped with stainless steel stirring blades and a nitrogen inlet tube. 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 form a polyamic acid solution. Obtained. The concentration of diamine and tetracarboxylic dianhydride charged in this reaction solution was 15% by weight with respect to 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 charged amount of CHDA was changed to 8.37 g, the charged amount of PAM-E was changed to 0.04 g, and the charged amount of BPDA was changed to 21.60 g.

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

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

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

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

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

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

<Comparative Example 1>
A polyamic acid solution was obtained in the same manner as in Example 1, except that the charged amount of CHDA 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 a silane coupling agent: γ-aminopropyltriethoxysilane was added to the polyamic acid, and the mixture was stirred for 24 hours to obtain an alkoxysilane-modified polyamic acid solution. was prepared.

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

<Comparative Example 4>
7.98 g of paraphenylenediamine (PDA) and 170.0 g of NMP were charged into a 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring blade and a nitrogen inlet tube, 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. Then add 21.83 g of BPDA and stir at 50°C until dissolved, then adjust the temperature of the solution to about 90°C and continue stirring to reduce the viscosity of the solution until the viscosity at 23°C is 28,800 mPa s. A polyamic acid solution was obtained.

<Comparative Example 5>
8.34 g of CHDA and 170.0 g of NMP were charged into a 500 mL glass separable flask equipped with a stirrer equipped with a stainless steel stirring blade and a nitrogen inlet tube, and dissolved by stirring at room temperature. After visually confirming the dissolution of CHDA, 0.13 g of Shin-Etsu Silicone's reactive silicone oil: 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 charged amount of CHDA was changed to 8.36 g and the charged amount of BPDA was changed to 21.50 g, and as the reactive silicone oil, KF-8010 was replaced with Shin-Etsu Silicone's reactive silicone oil: X-22-168AS (acid anhydride physical equivalent: 500 g/mol) was added. A polyamic acid solution was obtained in the same manner as in Comparative Example 5 except for these changes.

[Evaluation of polyamic acid]
<Molecular weight>
The weight average molecular weight (Mw) was obtained 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 content concentration was 10%. The diluted solution was cast on a 150 mm × 150 mm non-alkali glass plate (Eagle XG manufactured by Corning, thickness 0.7 mm) using a bar coater so that the thickness after drying was 10 µm, followed by heating with hot air. It was dried in an oven at 80° C. for 30 minutes to form a coating film of polyamic acid on the glass plate. A laminate of a glass plate and a polyamic acid coating film is heated from 20° C. to 350° C. at a rate of 5° C./min under a nitrogen atmosphere, and then heated at 350° C. for 1 hour to imidize the coating film. , a laminate of the polyimide film and the 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 the hot air oven was 120 ° C., and the temperature was increased to 450 ° C. at a rate of 7 ° C./min under a nitrogen atmosphere. After raising the temperature, imidization was performed by heating at 450° C. for 10 minutes.

In Comparative Example 1, many air bubbles were confirmed between the glass and the polyimide film. Except for Comparative Example 1, air bubbles due to peeling of the polyimide film were not observed. On the other hand, in Example 8, the adhesion between the glass and the polyimide film was so high that the polyimide film could not be separated from the glass.

[Evaluation of Polyimide Film]
<Peel strength>
A laminate of a glass plate and a polyimide film was allowed to stand in an environment of 23° C. and 55% RH for 24 hours for humidity conditioning, and then measured for 90° peel strength according to ASTM D1876-01. A cut of 10 mm width is made in the polyimide film with a cutter knife, and a tensile tester (Strograph VES1D) manufactured by Toyo Seiki Co., Ltd. is used, under conditions of 23 ° C. and 55% RH, a tensile speed of 50 mm / min, a peel length of 50 mm and a peel length of 90. A peel test was carried out, and the average value of the peel strength was taken as the peel strength. In Examples 6 and 7, the peel strength exceeded the maximum load (5.0 N) of the load cell.

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

<Light transmittance>
Using an ultraviolet-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 taken as the transmittance of the polyimide film.

<Total light transmittance (TT) and haze of polyimide film>
Measured by the method described in JIS K7105-1981 using an integrating sphere type haze meter 300A manufactured by Nippon Denshoku Industries.

Monomer charge amount (molar ratio of acid dianhydride and diamine) during polymerization of polyamic acid in Examples and Comparative Examples, weight average molecular weight of polyamic acid and presence/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 properties of the polyimide film.

The polyamic acid solution of Comparative Example 1, obtained from BPDA as the dianhydride and CHDA as the diamine, formed a large number of polyacids between the glass plate and the polyimide film during thermal imidization after coating on the glass plate. Air 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 adhesiveness to the glass plate was improved compared to Comparative Example 1, but the peel strength was small and the adhesiveness was sufficient. It wasn't. The same was true in Comparative Example 3 in which 1 mol % of BPAF was added to BPDA as an acid dianhydride.

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

Examples 1 to 8 using PAM-E having a siloxane structure in addition to CHDA as a diamine component exhibited good adhesion to glass. Examples 1 to 7, in which the molar ratio m _A /m _B of CHDA/PAM-E is 97/3 to 99.0/0.1, have low CTE and high transparency equivalent to Comparative Example 1. was maintained. In Example 8 where the CHDA/PAM-E molar ratio m _A /m _B was 95/5, the properties of the polyimide film were not evaluated, but the polyimide film formed on the glass plate was visually observed. It had transparency similar to Examples 1-7. In addition, it is presumed that Example 8 maintains the same low CTE and high transparency as Example 7 because the compositions of polyamic acid and polyimide are similar to those of Example 7. Comparative Example 4, in which PDA was used instead of CHDA, exhibited peel strength equivalent to that of Examples 1 and 2, but the transparency (especially on the short wavelength side of visible light) was significantly reduced, and coloration was difficult. was taken.

In Examples 1 to 8, as the amount of PAM-E charged increased, the peel strength increased and the adhesion to glass tended to improve. Considering the ease of peeling the polyimide film from the glass plate after the polyimide film is formed on the glass plate and, if necessary, the elements are formed or mounted on the polyimide film, the siloxane structure-containing It can be said that the amount of diamine used is preferably 5 mol % or less, particularly preferably 1 mol % or less, relative to 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 a glass support and thermal imidization, and is compatible with the glass support. Excellent adhesion. The polyimide film obtained by imidization 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 it can be used as a transparent substrate material as a substitute for glass. Application is expected.

Claims (6)

Containing the structural unit represented by the general formula 1 and the structural unit represented by the general formula 2, and the number of moles of the structural unit represented by the general formula 1 m _A and the mole of the structural unit represented by the general formula 2 A polyamic acid solution containing a polyamic acid having a ratio m _A /m _B to several m _B ranging from 97.0/3.0 to 99.9/0.1 and an organic solvent is coated on a support. Then, the organic solvent is removed and the polyamic acid is imidized to form a polyimide film adhered and laminated on the support. After forming an element on the polyimide film, the element is formed. A method for manufacturing an electronic device, wherein the polyimide film is peeled from the support,
The method for producing an electronic device, wherein the total amount of the structural unit represented by the general formula 1 and the structural unit represented by the general formula 2 is 80 mol% or more with respect to the total amount of the polyamic acid.

A in General Formula 1 and B in General Formula 2 are each independently a tetravalent aromatic group; R ¹ and R ² in General Formula 2 are each independently a divalent hydrocarbon group; n is 1 to An integer of 5. 2. The method of manufacturing an electronic device according to claim 1, wherein the ratio m _A /m _B is in the range of 99.3/0.7 to 99.9/0.1. 3. The method for producing an electronic device according to claim 1, wherein the polyamic acid contains only the structural units represented by the general formula 1 and the structural units represented by the general formula 2 as structural units. The method for manufacturing an electronic device according to any one of claims 1 to 3, wherein the structural unit represented by general formula 2 is a structural unit represented by 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. A method for manufacturing an electronic device according to any one of claims 1 to 3.

The method for manufacturing an electronic device according to any one of claims 1 to 5, wherein the support is glass.