JP2014218056A - Laminate for flexible device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate which has good releasability and, when being released from a glass substrate to obtain a flexible device, provides a polyimide film being hardly curled.SOLUTION: A laminate for a flexible device is a laminate of a glass substrate and a polyimide-based film. The adhesive strength between the glass substrate and the polyimide-based film is 7 N/cm or less. The curvature radius of the polyimide-based film released from the glass substrate is 30 mm or more. The polyimide-based film has a multilayer structure of two or more layers.

Description

The present invention relates to a laminate of a polyimide film having excellent heat resistance and dimensional stability and a glass substrate. When a flexible device is produced by forming an electronic element on the polyimide film surface of the laminate. Useful.

Conventionally, in the field of electronic devices such as flat panel displays (FPD) such as liquid crystal displays (LCD), plasma display panels (PDP), organic EL displays (OLED), and electronic paper, electronic elements are mainly provided on glass substrates. Although the formed one is used, there is a problem that the glass substrate is rigid and lacks flexibility so that it is difficult to be flexible.

Therefore, a method has been proposed in which an organic polymer material such as polyimide having flexibility and heat resistance is used as a substrate.

Patent Documents 1 to 3 propose that a polyimide film having a specific chemical structure is laminated on a glass substrate used as a carrier, and this polyimide film is used as a substrate for forming an electronic element. The glass substrate used here is different from a metal substrate etc. in that it has excellent light transmittance, so that the inspection process when forming an electronic element is facilitated, and for producing a flexible device that forms an electronic element on an existing glass substrate. This equipment has the advantage that it can be diverted as it is.

In such a glass substrate laminated with polyimide, since the glass substrate is used as a carrier substrate, it is necessary to finally peel off the polyimide film from the glass substrate after forming an electronic element on the surface of the polyimide film. Since the polyimide film and the glass substrate are relatively firmly adhered to each other, peeling is not easy. To industrially do this, for example, it is immersed in water or amorphous on the glass substrate. A high quality silicon layer must be provided and peeled off by irradiating a laser beam, and improvement in peelability has been demanded.

In order to improve such peelability, Patent Document 4 proposes a method of separately providing a patterned adhesive layer (this becomes a peelable layer) between the polyimide film layer and the glass substrate.

Japanese Unexamined Patent Publication No. 64-774 JP2012-40836A JP2012-102155A JP 2012-199546 A

However, the above method has not improved the peelability sufficiently. Moreover, in the laminate produced by the above method, the polyimide film after peeling tends to curl, and there is a point to be improved in this respect as well.

Then, this invention solves the said subject, and it aims at provision of the laminated body used as the polyimide film which is easy to curl when it peels from a glass substrate and makes it a flexible device.

As a result of earnest research to solve the above problems, the present inventors have found that the above problems can be solved by specifying a specific structure of a laminate composed of a glass substrate and a polyimide film layer in the laminate. As a result, the present invention has been completed.
That is, the present invention has the following purpose.
1) A laminate for a flexible device, which is a laminate of a glass substrate and a polyimide film, and has an interlayer adhesive strength of 7 N / cm or less between the glass substrate and the polyimide film.
2) The said flexible device laminated body characterized by the curvature radius of the polyimide-type film peeled from the glass substrate being 30 mm or more.
3) The laminate for a flexible device, wherein the polyimide film has a multilayer structure of two or more layers.
4) A mold release agent is blended in the polyimide film layer in contact with the glass substrate.
5) A laminate for a flexible device, wherein the polyimide film forming the multilayer structure is disposed so as to cancel each residual strain.

Since the laminated body of this invention has favorable peelability and curling of the polyimide film after peeling is suppressed, it can be used suitably as a laminated body at the time of manufacturing a flexible device.

Hereinafter, the present invention will be described in detail.

The laminate of the present invention comprises a glass substrate and a polyimide film. As the glass substrate, for example, soda lime glass, borosilicate glass, non-alkali glass or the like can be used, and among these, the non-alkali glass substrate can be preferably used.

The thickness of the glass substrate is preferably 0.3 to 5.0 mm. If the thickness is less than 0.3 mm, the handling property of the substrate may be lowered. Moreover, productivity may fall when thickness is thicker than 5.0 mm. These glass substrates may be provided with a release layer in order to improve releasability with the polyimide film layer.

The polyimide film used in the laminate of the present invention is a film formed from a polyimide resin. The polyimide resin is a resin having an imide bond in the main chain, and specific examples include polyimide, polyamideimide, polyesterimide, etc., but are not limited thereto, and a resin having an imide bond in the main chain. Any resin can be used. These resins are usually used alone, but two or more kinds may be mixed and used.

As the polyimide, a precursor type polyimide obtained by thermosetting a polyimide precursor such as polyamic acid dissolved in a solvent or a solvent soluble type polyimide can be used, and a precursor type polyimide can be preferably used.

As said polyimide resin, it is preferable to have 50 mol% or more of structural units derived from an imide bond (however, all the structural units shall be 100 mol%).

A commercially available product may be used as the polyimide resin. That is, for example, polyamic acid type varnishes such as “Uimide AR”, “Uimide AH”, “Uimide CR”, “Uimide CH” (all manufactured by Unitika Ltd.) and U varnish A (manufactured by Ube Industries). Solica-soluble polyimide varnish, Viromax HR-11NN (manufactured by Toyobo Co., Ltd.), etc. dissolved in a solvent such as “Rika Coat SN-20” (manufactured by Shin Nippon Rika Co., Ltd.) Polyamideimide varnish can be used.

The precursor type polyimide is prepared by applying a polyimide precursor solution obtained by reacting a raw material of tetracarboxylic acid or its dianhydride and diamine in a solvent on a glass substrate, followed by drying and thermosetting. (Imidization) to make a polyimide film.

As reaction temperature at the time of manufacturing this polyimide precursor solution, -30-60 degreeC is preferable and -15-40 degreeC is more preferable. In this reaction, the order of addition of the monomer and the solvent is not particularly limited, and may be any order.

Examples of the tetracarboxylic acid or dianhydride thereof include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 3, 3 ', 4,4'-diphenylsulfone tetracarboxylic acid, acid, 3,3', 4,4'-diphenyl ether tetracarboxylic acid, 2,3,3 ', 4'-benzophenone tetracarboxylic acid, 2,3,6 , 7-Naphthalenetetracarboxylic acid, 1,4,5,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ′, 4,4′-diphenylmethanetetracarboxylic acid, 2 , 2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4,9,10- Tracarboxyperylene, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane, 1, 2,3,4-cyclobutanetetracarboxylic acid, 1,2,4,5-cyclopentanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, bicyclo [2,2,2] oct-7- En-2,3,5,6-tetracarboxylic acid and dianhydrides thereof can be used alone or as a mixture, but are not limited thereto.

Here, pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid or their dianhydrides are particularly preferably used.

Examples of the diamine include p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4, 4'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-bis (anilino) ethane, diaminodiphenyl sulfone, diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2 , 2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4-bis (p- Aminophenoxy) benze 4,4′-bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4′-bis (3-aminophenoxyphenyl) diphenylsulfone, 1,3-bis (anilino) hexafluoropropane, 1,4- Bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetradecafluoroheptane, 1,2-ethylenediamine, 1,3-propanediamine, 1,4- Butanediamine, 1,5-pentadiamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine Cis-1,4-diaminocyclohexane, trans-1,4-diaminocyclohexane Xanthone, 1,4-diaminocyclohexane isomer mixture, cis-cis-4,4′-diaminodicyclohexylmethane, cis-trans-4,4′-diaminodicyclohexylmethane, trans-trans-4,4′-diaminodicyclohexylmethane 4,4′-diaminodicyclohexylmethane isomer mixture, cis-1,3-bis (aminoethyl) cyclohexane, trans-1,3-bis (aminoethyl) cyclohexane, 1,3-bis (aminoethyl) cyclohexane isomerism Body mixture, cis-trans-4,4′-methylenebis (2-methylcyclohexylamine), trans-trans-4,4′-methylenebis (2-methylcyclohexylamine), 4,4′-methylenebis (2-methylcyclohexyl) A Min)) isomer mixture, cis-cis-4,4′-diaminodicyclohexylenepropane, cis-trans-4,4′-diaminodicyclohexylenepropane, 4,4′-diaminodicyclohexylenepropane, etc. alone or Although it can be used as a mixture, it is not limited to these.

Here, p-phenylenediamine, 4,4′-diaminodiphenyl ether, and 2,2-bis [4- (4-aminophenoxy) phenyl] propane are particularly preferably used.

As solid content concentration of a polyimide precursor, 1-50 mass% is preferable, and 5-30 mass% is more preferable. This polyamic acid solution may be partially imidized.

The viscosity of the polyimide precursor solution of the present invention at 25 ° C. is preferably 1 to 150 Pa · s, more preferably 5 to 100 Pa · s.

As a solvent used for the polyimide precursor solution, any solvent can be used as long as it dissolves the polyimide precursor. Examples thereof include amide solvents, ether solvents, and water-soluble alcohol solvents.

Specific examples of the amide solvent include N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc) and the like.

Examples of the ether compounds include 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol, tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol. Monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monoethyl ether, tetraethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, di Propylene glycol monoethyl ether, tripropylene glycol monomethyl ether, poly Ji glycol, polypropylene glycol, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and the like.

Examples of water-soluble alcohol compounds include methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, and 1,3-butanediol. 1,4-butadiol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol And diacetone alcohol.

These solvents can be used as a mixture of two or more. Among these solvents, particularly preferred examples include N, N-dimethylacetamide and N-methyl-2-pyrrolidone as the sole solvent, and examples of the mixed solvent include N, N-dimethylacetamide and N- Examples thereof include a combination of methyl-2-pyrrolidone, N-methyl-2-pyrrolidone and methanol, N-methyl-2-pyrrolidone and 2-methoxyethanol.

In the polyimide resin solution such as the polyamic acid solution, a release agent is preferably blended in order to improve releasability from the glass substrate. By doing in this way, it can be easily achieved that the adhesive strength between the glass substrate and the polyimide film is 7 N / cm or less required in the present invention. Here, as said adhesive strength, 6 N / cm or less is more preferable, and 4 N / cm or less is still more preferable. Here, the adhesive strength is a value measured based on JIS K6854.

Examples of the mold release agent include higher fatty acids such as stearic acid and palmitic acid, amides and metal salts thereof, and stearic acid is preferable.

As a compounding quantity, it is preferable to add 0.01-2 mass parts with respect to 100 mass parts of polyimide resin solid content, More preferably, it is 0.01-1 mass part. If the blending amount is less than 0.01 parts by mass, the effect is poor, and if it is more than 2 parts by mass, the effect is not changed, but rather the physical properties such as the mechanical strength of the polyimide film tend to be lowered.

If necessary, for example, various additives such as various surfactants and leveling agents may be added to the polyimide resin solution as long as the effects of the present invention are not impaired. Moreover, the other polymer may be added in the range which does not impair the effect of this invention.

The laminated body of this invention can be manufactured by apply | coating, drying, and thermosetting the said polyimide precursor solution, for example on the said glass substrate.

The polyimide precursor solution can be applied onto the glass substrate continuously or in a single sheet.

The continuous coating on the glass substrate can be performed using a coating machine such as a die coater, lip coater, comma coater, gravure coater, reverse roll coater.

Moreover, single wafer application | coating on a glass substrate can be performed using coating machines, such as a bar coater, a doctor blade coater, and a spin coater.

Here, since continuous application to a glass substrate is often difficult because glass is rigid, single-wafer application is preferable from the viewpoint of industrial production.

As the coating thickness, the thickness of the polyimide film after thermosetting is preferably 3 to 100 μm, and more preferably 10 to 50 μm.

Next, the polyimide precursor solution applied on the glass substrate is dried. Drying as used herein refers to reducing the amount of solvent in the polyimide precursor solution by means such as heating. At this time, it is preferable to remove the solvent until the solid content concentration in the coating film is 50% by mass or more. Any device can be used for drying, and a hot air dryer is preferable, but infrared heating, electromagnetic induction heating, or the like may be used. A temperature range of 50 to 200 ° C. is suitable for drying.

The laminate of the present invention preferably has a multilayer structure of two or more layers by further applying a polyimide precursor to the surface of the dried coating film and drying it.

The polyimide precursor of the second layer may be the same as or different from the polyimide precursor used in the first layer, but in the two or more layers of polyimide film generated after the thermosetting of the polyimide precursor It is preferable to cancel each other's residual strain. In order to do so, for example, as described in Japanese Patent No. 4841103, the curing rate of the first layer polyimide precursor is made slower than the second layer, or the linear expansion coefficient (CTE) of the first layer polyimide is set. ) May be made smaller than the CTE of the second polyimide layer.

By doing in this way, after hardening, the curl of the polyimide film obtained by peeling from a glass substrate can be suppressed.

In the polyimide film obtained from the laminate of the present invention, the radius of curvature of the film, which is one of the indexes for evaluating the curl property, is preferably 30 mm or more, more preferably 50 mm or more, and further preferably 70 mm or more. Here, the radius of curvature is a value obtained by measuring the radius of curvature of a polyimide film piece cut into a 10 cm square.

The dried coating is then heat cured. The thermosetting temperature is 200 ° C. or higher, preferably 300 ° C. or higher. Moreover, an upper limit is about 450 degreeC. Heat treatment is sufficiently performed at such a high temperature. When polyimide is thermally cured, a gas such as water or a solvent is generated. Therefore, the thermal curing is preferably performed under hot air circulation.

The laminate obtained as described above is made into a flexible device by forming an electronic element on the polyimide film surface and then peeling it from the glass substrate. In order to peel, it can peel easily using well-known methods, for example, mechanical apparatuses, such as a drive roll and a robot.

In addition, it is preferable that the polyimide-type film of this invention is transparent. The light transmittance at 500 nm, which is an index of transparency, is preferably 70% or more, and more preferably 80% or more.

As described above, the laminate of the present invention is easy to peel off the polyimide film, and the peeled polyimide film has excellent heat resistance and dimensional stability, and curling is suppressed. It can be suitably used as a laminate for manufacturing flexible devices.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, it is not limited by these Examples.

<Preparation of polyimide precursor solution>
The polyimide precursor solutions used in the examples and comparative examples were prepared as follows.

<Polyimide precursor solution A>
Patent 4841103 gazette By the method described in Reference Example 3, a polyimide precursor solution was obtained from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA). That is, 18.38 g (62.5 mmol) of BPDA was collected in a three-necked flask under a nitrogen gas stream, and 122.5 g of DMAc was added and dissolved. To this, 6.62 g (61.2 mmol) of PDA and 52.5 g of NMP were added and stirred overnight at room temperature to obtain a uniform polyimide precursor solution having a solid content concentration of 12.5% by mass. This is designated as polyimide precursor solution A.

<Polyimide precursor solution B>
Patent No. 4841103 gazette 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 3,3 ′, 4,4′-biphenyltetracarboxylic acid (BPA) ), P-phenylenediamine (PDA) and 4,4′-oxydianiline (ODA) to obtain a uniform polyimide precursor solution. Specifically, ODA 30.03 g (0.15 mol), PDA 91.92 g (0.85 mol), DMAc 1180 g, and NMP 506 g were collected in a three-necked flask under a nitrogen gas stream, and the flask was placed in ice water to contain the above contents. After stirring for 30 minutes, 250.09 g (0.85 mol) of BPDA was added, and the mixture was stirred in a hot water bath at 40 ° C. for 1 hour. Next, 49.54 (0.15 mol) of BPA was added and stirred in a 40 ° C. hot water bath for 2 hours, and further stirred in a 60 ° C. hot water bath for 3 hours to obtain a uniform polyimide resin having a solid concentration of 20% by mass. A solution of the precursor was obtained. This is designated as polyimide precursor solution B.

<Polyimide precursor solution C>
0.5 parts by mass of stearic acid per 100 parts by mass of polyimide solid content was added to the polyimide precursor solution A to obtain a uniform polyimide precursor solution. This is designated as polyimide precursor solution C.

[Example 1]
The polyimide precursor solution C is applied on the surface of a non-alkali glass substrate (Corning Eagle 2000) having a thickness of 0.7 mm by a bar coater so that the thickness of the film after thermosetting is 20 μm, and at 130 ° C. It was dried for 10 minutes to form a polyimide precursor film. Next, under a nitrogen gas stream, the temperature was raised from 100 ° C. to 360 ° C. over 2 hours, followed by heat treatment at 360 ° C. for 2 hours, and the polyimide precursor was thermoset to imidize. Thus, a laminate having a glass substrate and a polyimide film layer having a thickness of about 15 μm was obtained. The obtained polyimide film of the laminate could be easily peeled from the glass plate by hand. (This laminate is referred to as L-1 and the polyimide film as P-1.)

[Example 2]
The polyimide precursor solution C was applied on the surface of a non-alkali glass substrate (Corning Eagle 2000) having a thickness of 0.7 mm by a bar coater so that the thickness of the film after thermosetting was 16 μm, and the temperature was 130 ° C. It was dried for 10 minutes to form a polyimide precursor film. Next, the temperature is returned to room temperature (25 ° C.), and the polyimide precursor solution B is applied onto the polyimide precursor film by a bar coater so that the thickness of the film after thermosetting is 4 μm, and dried at 100 ° C. for 5 minutes. Thus, an outer layer was formed from the second coating film. Subsequently, it was heat-cured similarly to Example 1 and imidized. Thus, a laminate having a glass substrate and a polyimide film layer having a thickness of about 20 μm composed of two layers was obtained. The obtained polyimide film of the laminate could be easily peeled from the glass substrate by hand. (This laminate is referred to as L-2, and the polyimide film as P-2.)

[Comparative Example 1]
A laminate was obtained in the same manner as in Example 1 except that the polyimide precursor solution C was changed to the polyimide precursor solution A. Since the polyimide film of the obtained laminate was difficult to peel from the glass substrate by hand, it was peeled from the glass substrate by being immersed in warm water. (This laminate is referred to as L-3, and the polyimide film as P-3.)

[Comparative Example 2]
A laminate was obtained in the same manner as in Example 2 except that the polyimide precursor solution C was changed to the polyimide precursor solution A. Since the polyimide film of the obtained laminate was difficult to peel from the glass substrate by hand, it was peeled from the glass substrate by being immersed in warm water. (This laminate is designated L-4, and the polyimide film is designated P-4.)

<Evaluation of adhesive strength>
The adhesive strength between the glass substrates of the laminates L-1 to L-4 and the polyimide film layer was measured by a 180 ° peel test based on JIS K6854.

From Table 1, it can be seen that the adhesive strengths of L-1 and L-2 are low values of 3.8 N / cm and 3.5 N / m, respectively, and are excellent in peelability. On the other hand, the adhesive strength of L-3 and L-4 exceeds 7 N / cm, which indicates that peeling is difficult.

<Evaluation of curl characteristics>
The polyimide films P-1 to P-4 were cut into test pieces having a size of 100 mm in length and 100 mm in width and subjected to a heat treatment at 150 ° C. for 30 minutes, and then in an atmosphere of 23 ° C. and 60% RH, respectively. After standing for a period of time, the radius of curvature was measured. The results are shown in Table 2.

From Table 2, it can be seen that the curvature radii of P-1 and P-2 are as high as 35 mm and 90 mm, respectively, and curling is suppressed. On the other hand, the curvature radius of P-3 and P-4 is less than 30 mm, and it can be seen that curling is not sufficiently suppressed.

From the above table, it can be seen that the laminate of the present invention is excellent in releasability, and the peeled polyimide film is curled. Due to this effect, the laminate of the present invention can be suitably used as a laminate for a flexible device.

Claims (5)

A laminate for a flexible device, which is a laminate of a glass substrate and a polyimide film, and has an adhesive strength between the glass substrate and the polyimide film of 7 N / cm or less. The laminate for a flexible device according to claim 1, wherein the curvature radius of the polyimide film peeled off from the glass substrate is 30 mm or more. The laminate for a flexible device according to claim 1 or 2, wherein the polyimide film has a multilayer structure of two or more layers. The laminate for flexible devices according to any one of claims 1 to 3, wherein a release agent is blended in the polyimide film layer in contact with the glass substrate. The laminate for a flexible device according to any one of claims 1 to 4, wherein the polyimide-based film forming the multilayer structure is disposed so as to cancel each residual strain.