JP6754607B2 - Alkoxysilane-modified polyimide precursor solution, laminate and flexible device manufacturing method - Google Patents

Description

The present invention relates to an alkoxysilane-modified polyimide precursor solution and a method for producing a precursor solution, a laminate, and a flexible device.

As a flexible device that is thin, lightweight, freely bendable and foldable, and hard to break, application to various devices such as flexible displays is considered. There are various options for producing such a flexible device, but as a method for efficient mass production, a flexible device is used in a normal glass substrate process using a laminate in which a polyimide resin layer is formed on a glass substrate. It has been proposed to produce (Patent Document 1, Non-Patent Document 1). In the process using this laminate, the polyimide resin layer is separated from the glass substrate at the final stage to obtain a flexible device based on polyimide.

The polyimide layer of the laminated body is required to have a small difference in linear expansion coefficient from that of a glass substrate, high heat resistance, and surface smoothness. Since the coefficient of linear expansion of general polyimide is larger than that of glass, suitable materials are naturally limited. For example, Patent Document 2 describes a polyimide precursor obtained from 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, paraphenylenediamine, and 4,4 "diaminoparaterphenyl" on an inorganic substrate. A method is described in which the solution of the above is cast and thermally imidized to obtain a laminate. On the other hand, in the polyimide precursor solution having a specific structure, the polyimide resin layer is easily peeled off from the substrate and the storage stability is high. In order to solve this problem, for example, an alkoxysilane having an amino group is added to an amine-terminal polyamic acid to prepare an alkoxysilane-modified polyimide precursor solution, so that even a thick film can be peeled off. A polyamic acid solution or the like that can form a film and can be stably stored at room temperature has been developed (Patent Document 3).

Special Table 2007-512568 Publication Japanese Unexamined Patent Publication No. 2012-35583 International Publication 2014/123045 Pamphlet

Makoto Locker, Room Temperature Joining and Peeling Technology for Practical Use of Flexible Devices, Functional Materials June 2015, pp. 4-18, CMC Publishing (2015)

However, the present inventors have found that even when the polyamic acid solution of Patent Document 3 is used, it cannot withstand storage for more than one month at room temperature and causes a decrease in viscosity.

The present invention has been made in view of the above background, and a polyimide precursor solution that can form a thick film without peeling and can be stably stored at room temperature, a method for producing the precursor solution, and flexibility. A method for manufacturing a laminate of a polyimide resin and an inorganic substrate that can be suitably used for device production, a method for manufacturing a flexible device using the laminate, specifically, a polyimide having a linear expansion coefficient of 1 to 20 ppm / ° C. It is an object of the present invention to provide a method for producing a laminate of a resin and an inorganic substrate.

As a result of diligent studies, the above-mentioned problems were solved with an alkoxysilane compound containing an amino group, an alkoxysilane-modified polyimide precursor containing 3,3', 4,4'-biphenyltetracarboxylic acid and paraphenylenediamine as main components, and a solvent. An alkoxysilane-modified polyimide precursor solution containing
It has been found that this can be solved by an alkoxysilane-modified polyimide precursor solution characterized in that 15 to 30% of the polyimide precursor is imidized and 85 to 70% is amic acid.

That is, the polyimide precursor solution according to the present invention has the following constitution.
1). Alkoxysilane compound containing an amino group, alkoxysilane-modified polyimide precursor containing 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and paraphenylenediamine as main components, and alkoxysilane-modified solvent. It is a polyimide precursor solution
An alkoxysilane-modified polyimide precursor solution characterized in that 15 to 30% of the polyimide precursor is imidized and 85 to 70% is amic acid.

2). The alkoxysilane-modified polyimide precursor solution according to 1), wherein the water content of the alkoxysilane-modified polyimide precursor solution is 2000 ppm or more and 5000 ppm or less.

3). The alkoxysilane-modified polyimide precursor solution according to 1) or 2), wherein the main component of the solvent is an amide-based solvent.

4). The amount of the alkoxysilane compound added is 0.01 to 0.50 parts by weight when the weight of the polyimide precursor contained in the alkoxysilane-modified polyimide precursor solution is 100 parts by weight 1) to 3 The alkoxysilane-modified polyimide precursor solution according to any one of ().

5). An alkoxysilane compound obtained by reacting an amino group-containing alkoxysilane compound with 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and a polyamic acid containing paraphenylenediamine as a main component in a solvent. By imidizing a part of the polyimide precursor of the modified polyimide precursor solution,
A method for producing an alkoxysilane-modified polyimide precursor solution, wherein 15 to 30% of the polyimide precursor is an imide ring and 85 to 70% is an amic acid.

6). A method for producing a laminate of a polyimide film and an inorganic substrate, which comprises casting the alkoxysilane-modified polyimide precursor solution according to any one of 1) to 4) onto an inorganic substrate and thermally imidizing the solution. ..

7). The method for producing a laminate according to 6), wherein the polyimide film has a coefficient of linear expansion of 1 to 20 ppm / ° C.

8). The thickness of the inorganic substrate is 0.4 to 5.0 mm.
The method for producing a laminate according to 6) or 7), wherein the thickness of the polyimide film is 5 to 50 μm.

9). A method for producing a flexible device, which comprises forming an electronic element on a polyimide film obtained by imidizing the alkoxysilane-modified polyimide precursor solution according to any one of 1) to 4).

According to the present invention, a polyimide precursor solution that can form a thick film without peeling and can be stably stored at room temperature, and a laminate of a polyimide resin and an inorganic substrate that can be suitably used for the production of flexible devices. A method for producing a flexible device using a laminate, specifically, a method for producing a laminate of a polyimide resin having a linear expansion coefficient of 1 to 20 ppm / ° C. and an inorganic substrate can be provided.

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

<Conversion of amic acid moiety in polyamic acid to imide group>
An alkoxysilane-modified polyimide precursor solution (hereinafter, also simply referred to as “solution”), wherein 15 to 30% of the polyimide precursor is imidized and 85 to 70% is amic acid will be described. 15-30% and 85-70%% of the polyimide precursor means mol%.
Normally, the polyimide precursor has a structure composed of a polyamic acid as represented by the general formula (I), but the polyimide precursor of the alkoxysilane-modified polyimide precursor solution of the present invention is one of the polyamic acids. The part is imidized as in the general formula (II) to form an imide ring, and the rest is the amic acid as in the general formula (III).
In other words, the alkoxysilane-modified polyimide precursor of the present invention has a structure of the general formula (II) of 15 to 30% and a structure of the general formula (III) of 85 to 70%.

(However, X is a tetravalent organic group, Y is a residue of an alkoxysilane compound having a divalent organic group or an amino group)
By setting the imidization rate to 15% or more, hydrolysis can be suppressed and stable storage at room temperature becomes possible. On the other hand, when the imidization ratio is 30% or more, the alkoxysilane-modified polyimide precursor solution causes thickening, which is not preferable. This thickening is considered to be due to a decrease in the solubility of the alkoxysilane-modified polyimide precursor.

The alkoxysilane-modified polyimide precursor solution of the present invention can be obtained by several methods. For example, a part of the amic acid moiety can be thermally imidized by heat-treating (cooking) the polyamic acid at about 70 to 100 ° C. for 1 to 24 hours after the polymerization. The heating operation promotes the dissociation of amic acid and the deactivation of acid anhydride due to the reaction with water in the system, and the molecular weight decreases at the same time, but by changing both the temperature and time, any imidization occurs. It is possible to obtain a polyimide precursor of a ratio.

In addition, there is also a method of adding a certain amount of a dehydrating agent such as acetic anhydride, and a method of copolymerizing a monomer containing an imide bond (tetracarboxylic dianhydride, diamine) at a constant ratio.

The method of imidization by cooking mentioned at the beginning is preferable because it only produces water as a by-product and is convenient for mass production.

<Alkoxysilane-modified polyimide precursor solution>
The alkoxysilane-modified polyimide precursor solution is obtained by reacting an amino group-containing alkoxysilane compound with a polyamic acid in the solution. In addition, polyamic acid is obtained by reacting an aromatic diamine with an aromatic tetracarboxylic dianhydride in a solvent.

The raw material and polymerization method of the polyamic acid will be described later, but in the present invention, it is preferable that the polyamic acid terminal is occupied by an amino group rather than a carboxyl group for the purpose of improving storage stability.

Modification with an alkoxysilane compound having an amino group is carried out by adding an alkoxysilane compound having an amino group to a polyamic acid solution in which polyamic acid is dissolved in a solvent and reacting the mixture. Examples of the alkoxysilane compound having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, and 3-aminopropylmethyldimethoxysilane. , 3- (2-Aminoethyl) aminopropyltrimethoxysilane, 3-phenylaminopropyltrimethoxysilane, 2-aminophenyltrimethoxysilane, 3-aminophenyltrimethoxysilane and the like.

The blending ratio of the alkoxysilane compound containing these amino groups to 100 parts by weight of polyamic acid is preferably 0.01 to 0.50 parts by weight, more preferably 0.01 to 0.05 parts by weight. It is preferably 0.01 to 0.03 parts by weight from the viewpoint of suppressing a change in viscosity during storage of the varnish.

By setting the blending ratio of the alkoxysilane compound containing an amino group to 0.01 parts by weight or more, the effect of suppressing peeling on the inorganic substrate is sufficiently exhibited. When the blending ratio of the alkoxysilane compound containing an amino group is 0.50 parts by weight or less, the molecular weight of the polyamic acid is sufficiently maintained, so that problems such as embrittlement do not occur. Further, when it is 0.05 parts by weight or less, the change in viscosity after the addition of the alkoxysilane compound becomes small. In addition, when there is a large amount of unreacted component, it gradually reacts with the polyamic acid to reduce the viscosity, or the alkoxysilanes condense with each other to gel. By suppressing the amount of the alkoxysilane compound containing an amino group added to the minimum necessary, it is possible to suppress the peeling of the polyimide film from the substrate while suppressing unnecessary side reactions such as viscosity reduction and gelation during varnish storage. it can.

Addition of an alkoxysilane compound containing an amino group to a polyamic acid having a majority of terminals having an amino group lowers the viscosity of the polyamic acid solution. The inventors have stated that this is because the acid anhydride group regenerated when the amide bond in the polyamic acid is dissociated reacts with the amino group of the alkoxysilane compound, the modification reaction proceeds, and the molecular weight of the polyamic acid decreases. I presume that. The reaction temperature is preferably 0 ° C. or higher and 80 ° C. or lower, and preferably 20 ° C. or higher and 60 ° C. or lower, because the modification reaction easily proceeds while suppressing the reaction between the acid dianhydride group and water. More preferred.

Although it depends on the type and concentration of the polyamic acid, the denaturation reaction is slow because the concentration of the acid anhydride is small, and if the reaction temperature is low, it may take about 5 days for the viscosity to become constant. When the type and solvent of the polyamic acid are different, the viscosity change with time may be recorded for each reaction temperature, and an appropriate reaction temperature may be selected.

By modifying a part of the end to alkoxysilane in this way, it is possible to suppress peeling (delamination, foaming) of the polyimide film during heating when it is applied on an inorganic substrate.

<Raw material for polyamic acid>
A tetracarboxylic dianhydride component and a diamine component are used as raw materials for the polyamic acid. As described above, a tetracarboxylic acid component or a diamine component containing an imide bond may be used so that the imidization rate is 15 to 30%.

In order to obtain a laminate of a polyimide film having a linear expansion coefficient of 1 to 20 ppm / ° C. and an inorganic substrate, the tetracarboxylic dianhydride component is 3,3', 4,4'-biphenyltetracarboxylic dianhydride. It is preferable to use an anhydride (hereinafter, sometimes abbreviated as BPDA) as a main component, and as a diamine component, it is preferable to use an aromatic diamine having the following formula (1) as a main component.

(N in the formula is an arbitrary number from 1 to 3)
The aromatic diamine of the formula (1) is paraphenylenediamine (hereinafter, also abbreviated as PDA), 4,4'-diaminobenzidine, and 4,4 "-diaminoparaterphenyl (hereinafter, abbreviated as DATP). Of these aromatic diamines, PDA is preferable because of its good availability.

The aromatic tetracarboxylic dianhydride is preferably 3,3', 4,4'-biphenyltetracarboxylic dianhydride. Suitable for flexible device substrates such as low CTE by using an alkoxysilane-modified polyimide precursor containing 3,3', 4,4'-biphenyltetracarboxylic dianhydride and highly linear aromatic diamine. Characteristics can be imparted.

Further, aromatic tetracarboxylic dianhydrides other than PDA, 4,4'-diaminobenzidine, and DATP may be used as long as the characteristics of the present invention are not impaired, or 3,3', 4,4'. -Aromatic diamines other than biphenyltetracarboxylic dianhydride may be used. For example, the following aromatic tetracarboxylic dianhydrides and aromatic diamines may be used in combination of 5 mol% or less with respect to the total raw material of the polyamic acid. Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic acid. Dihydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic Acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 4,4'-oxydiphthalic acid dianhydride, 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'-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, etc. Can be mentioned. The aromatic ring of the acid dianhydride may have an alkyl group-substituted and / or halogen-substituted site. Examples of the aromatic diamine include 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,5- (4-aminophenoxy) pentane, and 1,3-bis (4). -Aminophenoxy) -2,2-dimethylpropane, 2,2-bis (4-aminophenoxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone and bis [4- (3-aminophenoxy) Phenyl] sulfone and the like.

<Polymeric acid polymerization method>
The polyamic acid used in the present invention can be produced by solution polymerization. That is, a polyamic acid solution which is a polyimide precursor by polymerizing in an organic polar solvent using one or more tetracarboxylic dianhydride components and one or two or more diamine components which are raw materials. To get.

The molar ratio obtained by dividing the total number of moles of tetracarboxylic acid dihydrogens by the total number of moles of aromatic diamines is preferably 0.980 or more and less than 1.000, and more preferably 0.995 or more and 0. It is 998 or less. By setting the molar ratio to less than 1.000, the ratio of the polyamic acid terminal occupied by the amino group becomes higher than the ratio occupied by the acid anhydride group, and the storage stability can be improved. This effect is further improved by reducing the molar ratio, but is not significantly improved below 0.998. On the other hand, in order to obtain a tough polyimide film, it is necessary to bring the molar ratio close to 1.000 and sufficiently increase the molecular weight. When the molar ratio is 0.980 or more, a durable polyimide film can be obtained. In addition, the molar ratio should be preferably 0.998 or more to prepare for a decrease in molecular weight during storage or imidization.

Preferred solvents for synthesizing polyamic acid are amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, etc. Is. By appropriately selecting and using these solvents, the characteristics of the polyamic acid solution and the characteristics of the polyimide film after imidization on the inorganic substrate can be controlled. The main component of the solvent is preferably an amide-based solvent. For example, when the total weight of the solvent is 100 parts by weight, the weight of the amide solvent is preferably 50 to 100 parts by weight, more preferably 70 to 100 parts by weight.

In the study by the present inventors, when N, N-dimethylacetamide was used as the solvent, the storage stability of the polyamic acid was deteriorated, and the coefficient of linear expansion of the polyimide film was increased. When N-methyl-2-pyrrolidone is used as the solvent, the storage stability of the polyamic acid solution is high, and the coefficient of linear expansion of the polyimide film is lower. Although better properties can be obtained by using N-methyl-2-pyrrolidone in terms of storage stability, one of them is not superior in terms of properties such as the coefficient of linear expansion. For example, if it is preferable that the polyimide film is harder, N-methyl-2-pyrrolidone is used, and if it is preferable that the polyimide film is soft, N, N-dimethylacetamide is used. Solvent should be selected.

It is preferable that the reaction device is provided with a temperature control device for controlling the reaction temperature. The reaction temperature when polymerizing the polyamic acid is preferably 0 ° C. or higher and 80 ° C. or lower, and further, 20 ° C. or higher and 60 ° C. or lower suppresses the dissociation of the amide bond, which is the reverse reaction of the polymerization, and moreover, the polyamic acid. It is preferable because the viscosity tends to increase.

Further, in the present invention, it is preferable to cook after polymerization for the purpose of adjusting the imidization ratio. By adjusting the temperature and time, a polyimide precursor having an imidization ratio of 15 to 30% (15 to 30% of the polyimide precursor is an imide ring) can be obtained. The temperature is preferably 70 to 100 ° C, more preferably 85 to 100 ° C. A temperature lower than 70 ° C. is not preferable because the imidization takes a very long time. At a temperature higher than 100 ° C., imidization and molecular weight reduction proceed very quickly, making it difficult to adjust with time, which is not preferable. It is more preferable that the temperature is 85 ° C. or higher and 100 ° C. or lower because the imidization target value can be obtained by adjusting the cooking time. In a high-viscosity system, it is not uncommon for heating and cooling to take 10 minutes or more, so the time is preferably 1 to 24 hours for fine adjustment. As described above, the heat treatment promotes the dissociation of the amic acid and the deactivation of the acid anhydride due to the reaction with water in the system. Therefore, the viscosity and imidization rate suitable for the subsequent operation are simultaneously obtained in advance. To achieve this, it is preferable to examine the molar ratio of tetracarboxylic acid dihydrates to aromatic diamines. It is preferable to carry out the polymerization reaction and cooking separately, but it is also possible to carry out the polymerization reaction and cooking at once by setting the reaction temperature to 70 to 100 ° C. from the beginning.

As for the weight% of the polyamic acid in the polyamic acid solution, 5 to 30% by weight, preferably 8 to 25% by weight, and more preferably 10 to 20% by weight of the polyamic acid is not yet dissolved in the organic solvent. It is preferable because it suppresses gelation caused by abnormal polymerization of the dissolution raw material and the viscosity of the polyamic acid tends to increase.

<Moisture of alkoxysilane-modified polyimide precursor solution>
The water content in the alkoxysilane-modified polyimide precursor solution is preferably 2000 ppm or more and 5000 ppm or less. When the water content is 5000 ppm or less, the effect of improving storage stability is sufficiently exhibited, which is preferable. Moisture in the solution can be divided into those derived from raw materials and those derived from the working environment. There are various methods for reducing the water content, but it is not preferable to reduce the water content more than necessary by using extra processes or excessive equipment because it increases the cost. Although it depends on the molecular structure and concentration, in the present invention, imidization of the polyimide precursor produces a considerable amount of water. For example, when a polyamic acid solution consisting of BPDA and PDA having a solid content concentration of 15% is imidized by 30%, the water content of the solution increases by about 4000 ppm. It is not preferable to reduce the water content to less than that because the cost increases.

As a method of reducing the water content, it is effective to strictly store the raw materials to avoid mixing of the water content and replace the reaction atmosphere with dry air, dry nitrogen or the like. Further, the treatment may be performed under reduced pressure.

<Spreading and thermal imidization of alkoxysilane-modified polyimide precursor solution>
The laminate composed of the polyimide film and the inorganic substrate can be produced by casting the above-mentioned alkoxysilane-modified polyimide precursor solution on the inorganic substrate and thermally imidizing it.

Examples of the inorganic substrate include a glass substrate and various metal substrates, but a glass substrate is preferable. Soda lime glass, borosilicate glass, non-alkali glass and the like are used for the glass substrate. In particular, since non-alkali glass is generally used in the manufacturing process of the thin film transistor, non-alkali glass is more preferable as the inorganic substrate. The thickness of the inorganic substrate used is preferably 0.4 to 5.0 mm. If the inorganic substrate is thinner than 0.4 mm, it becomes difficult to handle the inorganic substrate, which is not preferable. Further, if the inorganic substrate is thicker than 5.0 mm, the heat capacity of the substrate increases and the productivity in the heating / cooling process decreases, which is not preferable.

As a method of spreading the solution, a known method can be used. For example, known casting methods such as a gravure coating method, a spin coating method, a silk screen method, a dip coating method, a bar coating method, a knife coating method, a roll coating method, and a die coating method can be mentioned.

As the alkoxysilane-modified polyimide precursor solution, the above-mentioned reaction solution may be used as it is, or the solvent may be removed or added as needed. Solvents that can be used in the polyimide precursor solution include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and others. For example, dimethyl sulfoxide, hexamethylphospholide, acetonitrile, acetone, tetrahydrofuran can be mentioned. In addition, as auxiliary solvents, xylene, toluene, benzene, diethylene glycol ethyl ether, diethylene glycol dimethyl ether, 1,2-bis- (2-methoxyethoxy) ethane, bis (2-methoxyethyl) ether, butyl cellosolve, butyl cellosolve acetate, propylene glycol methyl Ether and propylene glycol methyl ether acetate may be used in combination.

An imidization catalyst, inorganic fine particles and the like may be added to the polyimide precursor solution, if necessary.

It is preferable to use a tertiary amine as the imidization catalyst. As the tertiary amine, a heterocyclic tertiary amine is more preferable. Preferred specific examples of the heterocyclic tertiary amine include pyridine, 2,5-diethylpyridine, picoline, quinoline, isoquinoline and the like. The amount of the imidizing agent used is preferably 0.01 to 2.00 equivalents, particularly 0.02 to 1.20 equivalents, relative to the reaction site of the polyimide precursor. If the amount of the imidization catalyst is less than 0.01 equivalent, the effect of the catalyst cannot be sufficiently obtained, which is not preferable. If it is more than 2.00 equivalents, the proportion of catalysts not involved in the reaction increases, which is not preferable in terms of cost.

Examples of the inorganic fine particles include fine particle silicon dioxide (silica) powder, inorganic oxide powder such as aluminum oxide powder, and inorganic salt powder such as fine particle calcium carbonate powder and calcium phosphate powder. In the field of the present invention, since the coarse particles of these inorganic fine particles may cause defects in the next step and thereafter, it is preferable that these inorganic fine particles are uniformly dispersed.

Thermal imidization is a method in which the imidization reaction proceeds only by heating without the action of a dehydration ring closure agent or the like. The heating temperature and the heating time at this time can be appropriately determined, and may be, for example, as follows. First, in order to volatilize the solvent, it is heated at a temperature of 100 to 200 ° C. for 3 to 120 minutes. The heating atmosphere can be carried out under air, under reduced pressure, or in an inert gas such as nitrogen. Further, as the heating device, a known device such as a hot air oven, an infrared oven, a vacuum oven, or a hot plate can be used. Next, in order to further promote imidization, the mixture is heated at a temperature of 200 to 500 ° C. for 3 to 300 minutes. The heating conditions at this time are preferably from low temperature to gradually high temperature. The maximum temperature is preferably in the range of 300 to 500 ° C. If the maximum temperature is lower than 300 ° C., thermal imidization is difficult to proceed and the mechanical properties of the obtained polyimide film are deteriorated, which is not preferable. If the maximum temperature is higher than 500 ° C., the thermal deterioration of the polyimide progresses and the characteristics deteriorate, which is not preferable.

When a conventional polyamic acid solution is used, depending on the type and thickness of the polyamic acid, the type and surface condition of the inorganic substrate, the heating conditions during heating, and the heating method, the polyimide film naturally becomes more natural than the inorganic substrate during the heat treatment. Easy to peel off. However, if an alkoxysilane-modified polyimide precursor solution is used, spontaneous peeling can be suppressed and the process window can be greatly expanded.

The thickness of the polyimide film is preferably 5 to 50 μm, more preferably 10 to 50 μm.
When the thickness of the polyimide film is 5 μm or more, the mechanical strength required for the substrate film can be secured. Further, when the thickness of the polyimide film is 50 μm or less, the laminate of the polyimide film and the inorganic substrate can be obtained without spontaneous peeling only by adjusting the heating conditions.
If the thickness of the polyimide film is 5 μm or less, it becomes difficult to secure the mechanical strength required for the substrate film, which is not preferable. If the thickness of the polyimide film is 50 μm or more, it becomes difficult to stably obtain the laminate due to the above-mentioned natural peeling or the like, which is not preferable. The laminate obtained by the present invention is excellent in storage stability and process consistency, and can be suitably used for manufacturing a flexible device by a known thin film transistor process for liquid crystal panels.

A polyimide having a linear expansion coefficient of 1 to 20 ppm / ° C. is obtained by casting a solution of the polyimide precursor on an inorganic substrate and thermally imidizing it, and further selecting a specific structure for the polyimide precursor skeleton. A laminate composed of a film and an inorganic substrate can be obtained. Then, by using this laminated body, a flexible device having excellent characteristics can be obtained.

<Electronic element formation / peeling>
By using the laminate of the present invention, a flexible device having excellent characteristics can be obtained. That is, a flexible device can be obtained by forming an electronic element on the polyimide film of the laminate of the present invention and then peeling the polyimide film from the inorganic substrate. Further, the above process has an advantage that a production device using an existing inorganic substrate can be used as it is, can be effectively used in the field of electronic devices such as flat panel displays and electronic paper, and is also suitable for mass production. A known method can be used as a method for peeling from the inorganic substrate. For example, it may be peeled off by hand, or it may be peeled off using a mechanical device such as a drive roll or a robot. Further, a method of providing a release layer between the inorganic substrate and the polyimide film may be used. Further, for example, a method of forming a silicon oxide film on an inorganic substrate having a large number of grooves and peeling it off by infiltrating the etching solution, and a method of providing an amorphous silicon layer on the inorganic substrate and separating it by laser light. Can be mentioned.

In the flexible device of the present invention, the polyimide film has excellent heat resistance and a low coefficient of linear expansion, and not only is excellent in light weight and impact resistance, but also has excellent characteristics that warpage is improved. ing. In particular, with regard to warpage, a flexible device having improved warpage can be obtained by adopting a method of directly casting and laminating a polyimide film having a low linear expansion coefficient equivalent to that of an inorganic substrate on an inorganic substrate.

Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to these examples, and the embodiments can be changed without departing from the spirit of the present invention (characteristic evaluation method).
(moisture)
Volumetric Titration Using a Karl Fischer Moisture Analyzer 890 Tightland (manufactured by Metrohm Japan Ltd.), the water content in the solution was measured according to the volumetric titration method of JIS K0068. However, when the resin was precipitated in the titration solvent, a 1: 4 mixed solution of Aquamicron GEX (manufactured by Mitsubishi Chemical Corporation) and N-methylpyrrolidone was used as the titration solvent.

(viscosity)
The viscosity was measured according to JIS K7117-2: 1999 using a viscometer RE-215 / U (manufactured by Toki Sangyo Co., Ltd.). The attached constant temperature bath was set to 23.0 ° C, and the measurement temperature was always constant.

(Immidization rate of polyimide precursor)
The imidization rate of the alkoxysilane-modified polyimide precursor was determined by ¹ H-NMR measurement. The sample was dissolved in deuterated dimethyl sulfoxide (DMSO-d ₆ ), and ¹ H-NMR spectrum was obtained by ¹ H-NMR spectrum by VNMR 600 manufactured by VARIAN. Near 7~9ppm is an aromatic ¹ H-derived peak (A), 10~11ppm is the peak derived from an amide bond (B). When all are polyamic acids having an amide bond, the integral ratio can be obtained from the raw materials tetracarboxylic dianhydride and aromatic diamines, so the imidization rate of the polyimide precursor can be obtained from the following formula. ..
[Immidization rate] (%) = 100- [Integral ratio when polyamic acid] x [Integral value of peak (B)] / [Integral value of peak (A)] x 100

(Coefficient of linear expansion)
The coefficient of linear expansion was evaluated by thermomechanical analysis by the tensile load method using TMA / SS7100 manufactured by SII Nanotechnology Co., Ltd. The polyimide layer was peeled off from the polyimide laminate of the example to prepare a sample of 10 mm × 3 mm, a load of 29.4 mN was applied to the long side, and the temperature was once raised from 20 ° C. to 500 ° C. at 10 ° C./min. Linear expansion of the amount of change in sample strain per unit temperature in the range of 100 ° C to 300 ° C at the time of the second temperature rise when the temperature is cooled to 20 ° C and further raised to 500 ° C at 10 ° C / min. It was used as a coefficient.

[Synthesis Example 1]
<Manufacturing of polyamic acid solution>
122.16 kg of N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP) is placed in a 200 L SUS304 reaction tank equipped with an anchor type stirring blade, a jacket that can be heated with low pressure steam, and a nitrogen introduction tube. , Para-phenylenediamine (hereinafter, sometimes referred to as PDA) (6.23 kg), 4,4'-diaminodiphenyl ether (hereinafter, sometimes referred to as ODA), 0.093 kg, and 10.00 kg of NMP on the side surface. The adhered raw material was washed away, and the solution was stirred for 30 minutes in a nitrogen atmosphere in which nitrogen was flowed at 20 L / min while heating the solution at 50.0 ° C.

After confirming that the raw materials were uniformly dissolved, 17.000 kg of BPDA was added, and the temperature of the solution was adjusted to about 85 ° C. while stirring for 10 minutes in a nitrogen atmosphere until the raw materials were completely dissolved. While checking the viscosity, heating and stirring were continued at a temperature of 85 ° C. for 7 hours and 50 minutes to obtain a viscous polyimide precursor solution having a viscosity of 19.0 Pa · s.

The concentration of the diamine compound and the tetracarboxylic dianhydride in this polyimide precursor solution was 15% by weight based on the total reaction solution, and the total number of moles of the tetracarboxylic dianhydride was changed to the total number of moles of the diamine. The molar ratio divided by is 0.995. When the molecular weight of the polyamic acid was measured, it was Mw = 67000.

<Modification with alkoxysilane compound>
The reaction solution was rapidly cooled in a water bath and the temperature of the solution was adjusted to about 50 ° C. Next, 1.17 kg of a 1% NMP solution of 3-aminopropyltriethoxysilane (hereinafter sometimes referred to as γ-APS) was added, and the mixture was stirred for 2 hours. The blending ratio of the alkoxysilane compound component in this reaction is 0.050 parts by weight with respect to 100 parts by weight of the polyamic acid.

[Example 1]
To the polyamic acid (alkoxysilane-modified polyimide precursor) solution obtained in Synthesis Example 1, 0.47 kg of a 1% NMP solution of an acrylic leveling agent DISPARON LF-1980 (manufactured by Kusumoto Kasei) was added, and the solid content concentration was 13. It was diluted with NMP so as to be 1% by weight. In this way, an alkoxysilane-modified polyimide precursor solution having a viscosity of 7290 mPa · s and a water content of 2700 ppm was obtained. When the ¹ H-NMR spectrum of this sample was measured, the [integral value of peak (B)] / [integral value of peak (A)] was 0.1649. Since the integral ratio when using polyamic acid was 0.1996, the imidization ratio was 17%. The obtained solution was stored in a tightly closed glass bottle in an environment of 23 ° C. and 55% RH for 31 days, and the viscosity was measured again and found to be 7580 mPa · s (+ 4.0%).

<Manufacturing of polyimide laminate>
The obtained polyimide precursor acid solution was poured on a square non-alkali glass plate (Eagle XG manufactured by Corning Inc.) having both sides of 150 mm and a thickness of 0.7 mm so that the thickness after drying was 20 μm with a bar coater. , Dryed in a hot air oven at 120 ° C. for 30 minutes. Then, the alkali-free glass plate is heated from 20 ° C. to 180 ° C. at 4 ° C./min under a nitrogen atmosphere, held for 30 minutes, further heated to 450 ° C. at 4 ° C./min, and 10 at 450 ° C. Heated for minutes. As a result, a polyimide laminate having a polyimide layer thickness of 20 μm was obtained. When observing the obtained laminate, no bubbles or floats were observed between the polyimide film and the non-alkali glass plate, and the laminate did not spontaneously peel off during heating. It was possible to peel off the polyimide film from the non-alkali glass plate. Table 1 shows the evaluation results of the polyimide film.

[Synthesis Example 2]
<Manufacturing of polyamic acid solution>
850.0 g of N, N-dimethylacetamide (DMAc) was placed in a 2 L glass separable flask equipped with a stirrer with a polytetrafluoroethylene seal stopper, a stirring blade, and a nitrogen introduction tube, and 40 PDA was added. 0.0 g and 0.6 g of ODA were added, and the solution was stirred in a nitrogen atmosphere for 30 minutes while heating to 50.0 ° C. in an oil bath.

After confirming that the raw materials were uniformly dissolved, 109.4 g of BPDA was added, and the temperature of the solution was adjusted to about 80 ° C. while stirring for 10 minutes in a nitrogen atmosphere until the raw materials were completely dissolved. Further, while checking the viscosity, heating and stirring were continued at a temperature of 80 ° C. for 2 hours and 30 minutes to obtain a viscous polyamic acid solution having a viscosity of 106.4 Pa · s at 23 ° C.

The concentration of the diamine compound and the tetracarboxylic dianhydride in this polyamic acid solution was 15% by weight based on the total reaction solution, and the total number of moles of the tetracarboxylic dianhydride was calculated as the total number of moles of the diamine. The divided molar ratio is 0.998. When the molecular weight of the polyamic acid was measured, it was Mw = 129000.

<Modification with alkoxysilane compound>
The reaction solution was rapidly cooled in a water bath and the temperature of the solution was adjusted to about 50 ° C. Next, 7.5 g of a 1% DMAc solution of 3-aminopropyltriethoxysilane (hereinafter sometimes referred to as γ-APS) was added, and the mixture was stirred for 2 hours. The blending ratio of the alkoxysilane compound component in this reaction is 0.050 parts by weight with respect to 100 parts by weight of the polyamic acid.

[Comparative Example 1]
The alkoxysilane-modified polyimide precursor solution obtained in Synthesis Example 2 was diluted by adding DMAc so that the solid content concentration was 11.7% by weight. In this way, an alkoxysilane-modified polyimide precursor solution having a viscosity of 13470 mPa · s and a water content of 1100 ppm was obtained. When the ¹ H-NMR spectrum of this sample was measured, the [integral value of peak (B)] / [integral value of peak (A)] was 0.1786. Since the integral ratio when using polyamic acid was 0.1994, the imidization ratio was 10%.

When the obtained solution was stored in a tightly closed glass bottle in an environment of 23 ° C. and 55% RH for 31 days and the viscosity was measured again, it was 12100 mPa · s (-10.2%). Using the obtained solution, a polyimide laminate was obtained in the same manner as in Example 1. As a result, a polyimide laminate having a polyimide layer thickness of 20 μm was obtained. When observing the obtained laminate, no bubbles or floats were observed between the polyimide film and the non-alkali glass plate, and the laminate did not spontaneously peel off during heating. It was possible to peel off the polyimide film from the non-alkali glass plate. Table 1 shows the evaluation results of the polyimide film.

As described above, in Example 1 having a high imidization rate, the change in viscosity is small and the storage stability is improved.

Claims (5)

Alkoxysilane obtained by reacting an amino group-containing alkoxysilane compound with 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and a polyamic acid containing paraphenylenediamine as a main component in a solvent. By imidizing a part of the bonding site of the polyimide precursor of the modified polyimide precursor solution,
15 to 30% of the polyimide precursor is an imide ring, and 85 to 70% is an amic acid .
The temperature at which a part of the binding site of the polyimide precursor of the alkoxysilane-modified polyimide precursor solution is imidized is 85 to 100 ° C.
A method for producing an alkoxysilane-modified polyimide precursor solution, wherein the main component of the solvent is N-methyl-2-pyrrolidone . A polyimide film and an inorganic substrate, characterized in that the alkoxysilane-modified polyimide precursor solution obtained by the method for producing an alkoxysilane-modified polyimide precursor solution according to claim 1 is cast on an inorganic substrate and thermally imidized. Method of manufacturing a laminate with. The method for producing a laminate according to claim 2 , wherein the polyimide film has a coefficient of linear expansion of 1 to 20 ppm / ° C. The thickness of the inorganic substrate is 0.4 to 5.0 mm.
The method for producing a laminate according to claim 2 or 3 , wherein the thickness of the polyimide film is 5 to 50 μm. A flexible device characterized in that an electronic element is formed on a polyimide film obtained by imidizing an alkoxysilane-modified polyimide precursor solution obtained by the method for producing an alkoxysilane-modified polyimide precursor solution according to claim 1. Production method.