JP2012040836A - Laminate, and utilization thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate which includes a polyimide film and an inorganic substrate and can suitably be used for a member for a flat panel display or for a flexible device, specifically a laminate which includes a polyimide film excellent in transparency and thermal resistance and an inorganic substrate, and to provide a member for a flat panel display or a flexible device wherein electronic elements are formed on the polyimide.SOLUTION: The laminate which includes a polyimide film and an inorganic substrate is formed by casting a solution of a polyimide precursor having a specific structure on an inorganic substrate, drying and imidizing thereof. The laminate has a haze of less than 2% and a total ray transmittance of not less than 85% in the condition that the thickness of the polyimide is 10 μm, and an amount of outgassing from the polyimide is less than 0.5% at 300°C.

Description

  The present invention relates to a laminate of a polyimide and an inorganic substrate having excellent transparency and heat resistance, a flat panel display member using the laminate, and a flexible device.

  At present, glass substrates are mainly used in the field of electronic devices such as flat panel displays and electronic paper. However, glass substrates are heavy and easily broken, so they are not necessarily ideal substrates. Therefore, studies have been actively conducted to realize a flexible device in which the substrate is replaced with glass from a polymer material. However, since many of these technologies require new production technologies and equipment, they have not been mass-produced.

  In recent years, as a method for manufacturing a flat panel display, a method of using a material in which a polyimide layer is provided on a thin glass substrate has been proposed as a material that is lightweight and difficult to break. That is, a laminate in which a polyimide layer is formed on a glass substrate is prepared, and a thin film transistor (hereinafter referred to as TFT), a transparent electrode, or the like is formed on the polyimide surface, and can be used as a display member. Further, as a method for manufacturing a member for a flexible device, a method of peeling and removing a glass substrate after forming a thin film transistor, a transparent electrode, or the like on the polyimide surface of the laminate has been proposed. (Non-Patent Document 1).

  The laminates or polyimides used in these materials are required to have sufficient transparency for display applications and heat resistance that can withstand high-temperature processes during production. Particularly in the formation of thin film transistors and transparent conductive films, heat resistance of 300 ° C. or higher is required. Specifically, the outgas from polyimide at 300 ° C. is required to be less than 0.5%.

  Moreover, as transparency, it is calculated | required that haze is low and a total light transmittance is high, Furthermore, it is calculated | required that the transmittance | permeability of light with a wavelength of 400 nm is 50% or more.

  A polyimide material obtained from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,2′-bis (trifluoromethyl) benzidine has been proposed as a material having good transparency and heat resistance. Yes. (Patent Document 1, Patent Document 2). Patent Document 1 describes that a film obtained by a chemical conversion method (a method of adding a catalyst solution) is excellent in transparency with a total light transmittance of 70% or more and has a low thermal expansion coefficient. However, there is no description about outgas.

  Patent Document 2 was obtained by reacting 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,2′-bis (trifluoromethyl) benzidine in m-cresol. Although it is described that the polyimide was obtained by gradually heating the polyamic acid to 300 ° C., details other than the thermophysical properties are not described.

  In addition, Non-Patent Document 1 describes that a polyimide was obtained by adding a dehydration catalyst and an imidizing agent to a solution obtained by using both monomers. It only describes the thermophysical properties of the gel, not the physical properties of the film.

  As described above, a polyimide produced using 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,2′-bis (trifluoromethyl) benzidine has been conventionally known. There is no description of occurrence or use for the aforementioned purposes. Furthermore, the above polyimide has not been used in this application because it tends to become cloudy due to crystallization when heated at a high temperature, and it is considered difficult to apply to a high temperature process.

JP2007-046054 U.S. Pat.

Nikkei FPD2008 vol. 1 Trends and Strategies, pages 144-151, Nikkei Business Publications (2008)

  The objective of this invention aims at providing the laminated body which consists of a polyimide film and an inorganic substrate which can be used suitably for the member for flat panel displays, or a flexible device. Specifically, it aims to provide a laminate of a polyimide film and an inorganic substrate having excellent transparency and heat resistance, and further, a flat panel display member in which an electronic element is formed on a polyimide or a flexible The purpose is to provide a device.

As a result of intensive studies, the present inventors have cast a solution of a polyimide precursor having a specific structure on an inorganic substrate, dried and imidized at a specific temperature range, and thereby whitened the film by crystallization (high haze). It was found that a laminate of polyimide and an inorganic substrate with reduced gas generation at 300 ° C. can be easily produced, and the present invention has been achieved. That is, the present invention relates to the following.
1) Compound group (1)

At least one tetracarboxylic dianhydride selected from the group of compounds (2)

A laminate comprising a polyimide film obtained by casting a solution of a polyimide precursor obtained from at least one diamine selected from the above onto an inorganic substrate, drying and imidizing, and the inorganic substrate; And the maximum temperature in the step of imidizing is more than 300 ° C. and not more than 400 ° C., the thickness of the polyimide film is 10 μm, the haze is less than 2%, the total light transmittance is 85% or more, and at 300 ° C. A laminate having an outgas from the polyimide film of less than 0.5%.
2) The laminate according to 1), wherein a maximum temperature in the drying and imidization step is more than 310 ° C and not more than 350 ° C.
3) The said inorganic substrate is a glass substrate, The electronic element is formed on the polyimide film of the laminated body in any one of 1) or 2) characterized by 4) 1) -3) characterized by the above-mentioned. A flat panel display member characterized by the above.
5) A flexible device, wherein an electronic element is formed on the polyimide film of the laminate according to any one of 1) to 3), and then the polyimide film is peeled from the inorganic substrate.

  The laminate of the present invention has reduced gas generation at 300 ° C., has excellent transparency and heat resistance, and can be suitably used for the production of flat panel display members and flexible displays. Moreover, the flat panel display member and flexible device in which the electronic element was formed on the polyimide film of this invention are excellent in lightweight property and impact resistance.

  An embodiment of the present invention will be described as follows, but the present invention is not limited to this.

  The present invention is a laminate comprising a polyimide film obtained by casting a polyimide precursor solution having a specific structure on an inorganic substrate, drying and imidizing, and an inorganic substrate, and when the thickness of the polyimide is 10 μm, there is no haze. The laminate is characterized by having a light transmittance of less than 2%, a total light transmittance of 85% or more, and an outgas from polyimide at 300 ° C. of less than 0.5%.

(A) Polyimide precursor solution The polyimide precursor solution used in the present invention is a compound group (1).

At least one tetracarboxylic dianhydride selected from the group of compounds (2)

It is the polyimide precursor solution obtained from the at least 1 sort (s) of diamine selected more.

  The tetracarboxylic dianhydrides and diamines can be used alone or in combination of two or more.

  In addition, in the tetracarboxylic dianhydrides of the compound group (1), the compound is particularly advantageous in that it is easy to obtain a polyimide having a light transmittance of 50% or more at a wavelength of 400 nm, and is excellent in heat resistance and availability. Group (3)

It is preferable to use at least one tetracarboxylic dianhydride more selected.

  In the diamines of the compound group (2), the compound group (4) is excellent in transparency, heat resistance and availability.

It is preferable to use at least one diamine more selected.

  The solvent for the polyimide precursor solution is not particularly limited as long as tetracarboxylic dianhydride and diamines can be dissolved and reacted. However, the polyimide precursor solution is excellent in solubility and promotes the reaction. N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), hexamethylphosphoryl Solvents such as amide, acetonitrile, acetone and tetrahydrofuran can be used alone or as a mixture, and N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMAc) can be preferably used.

(Method for producing polyimide precursor solution)
The polyimide precursor solution comprises an acid dianhydride component comprising at least one acid dianhydride and a diamine component comprising at least one diamine in an organic solvent, and the acid dianhydride and diamine. Can be obtained by reacting them so that they are substantially equimolar. Alternatively, when two or more types of acid dianhydride components and two or more types of diamine components are used, the molar ratio of the total amount of plural diamine components and the molar ratio of the total amount of plural acid dianhydride components are substantially equimolar. If adjusted so as to be, a polyamic acid copolymer can be arbitrarily obtained.

  As a typical method of the above reaction, a solution obtained by dissolving the diamine component in an organic solvent and then adding the acid dianhydride component to dissolve the polyamic acid (hereinafter referred to as a polyamic acid solution). ). Here, “dissolved” means a state where the solvent is completely dissolved in the solute, and a state where the solute is uniformly dispersed or diffused in the solvent and is substantially in the same dissolved state. Shall be included. The order of adding the diamine component and the acid dianhydride component is not limited to the above, and those skilled in the art can appropriately change, modify, or modify the addition method. That is, for example, the above addition method may be a method in which an acid dianhydride component is dissolved or diffused in an organic solvent, and then a diamine component is added to obtain a polyimide precursor solution. Alternatively, first, an appropriate amount of the diamine component is added to the organic solvent, and then an acid dianhydride component containing an acid dianhydride that is excessive with respect to the diamine in the diamine component is added, and the excess of the acid dianhydride is added. A method may be used in which a diamine component containing an amount of diamine corresponding to the amount is added to obtain a polyimide precursor solution.

  The temperature condition of the reaction between the acid dianhydride and the diamine (polyamide acid synthesis reaction) is not particularly limited as long as the acid dianhydride and the diamine can be polymerized, but is preferably 80 ° C. or less. More preferably, it is in the range of 0 to 50 ° C. The reaction time is not particularly limited as long as the polymerization reaction between the acid dianhydride and the diamine can be completed, but may be arbitrarily set within a range of 30 minutes to 50 hours.

  The weight average molecular weight of the polyimide precursor is preferably in the range of 3,000 to 1,000,000, more preferably 5,000 to 500,000, more preferably 10,000 to 500,000 in terms of the mechanical strength of the polyimide obtained by heating. Is more preferable. If the weight average molecular weight is less than 3,000, the resulting polyimide tends to have insufficient mechanical strength and become brittle. On the other hand, when the weight average molecular weight exceeds 1,000,000, the handleability of the precursor as a solution tends to be difficult.

  The concentration and viscosity of the polyimide precursor solution are preferably adjusted to a solid content concentration and viscosity suitable for the coating thickness and the like, which is a method of coating the inorganic substrate with the solution.

  For example, when producing a 10 μm polyimide, it is preferable to adjust in the range of 10 cP (centipoise) to 100,000 cP (centipoise) in the temperature range of solid content concentration of 5 to 30% and viscosity of 20 ° C. to 25 ° C. .

(Laminate manufacturing method)
The laminate of the present invention can be produced by casting a polyimide precursor solution onto an inorganic substrate, drying and imidizing.

  In the laminate of the present invention, in order that the thickness of the polyimide film is 10 μm, the haze is less than 2%, the total light transmittance is 85% or more and the outgas from the polyimide film at 300 ° C. is less than 0.5%, The heating conditions for drying and imidization are important.

  In order to reduce outgas, it is effective to raise the heating temperature, but there is a tendency that haze increases or total light transmittance decreases due to crystallinity or coloring of polyimide. On the other hand, when the heating is performed at a relatively moderate temperature for the purpose of reducing transparency and suppressing coloring, the outgas cannot be reduced, and imidation does not proceed sufficiently, and the mechanical strength of polyimide tends to be insufficient.

  As an effective method for reducing the outgas without impairing transparency, it is necessary to appropriately set the temperature and the heating time as the heating conditions.

  As a heating condition (drying and imidization condition), as a result of intensive studies, when a film of 10 μm to 50 μm is manufactured, it is casted at a temperature range of 100 ° C. to 150 ° C. for 10 minutes to 30 minutes, and then 150 ° C. It is preferable to heat at ~ 200 ° C for 10 minutes to 30 minutes, further at 200 ° C to 250 ° C for 5 minutes to 10 minutes, and finally at the maximum temperature for 5 to 10 minutes. In particular, it has been found that it is preferable to lengthen the time for heating at a temperature of 200 ° C. or less as compared with the heating time exceeding 200 ° C.

  The maximum temperature needs to be higher than 300 ° C. and lower than or equal to 400 ° C. regardless of the thickness of the film, and is preferably heated higher than 310 ° C. and lower than 350 ° C.

  When the maximum temperature is 300 ° C. or lower, outgas cannot be reduced, and imidation tends to be insufficient. Conversely, when the temperature exceeds 400 ° C., whitening tends to become remarkable due to crystallization of polyimide and the like.

  Moreover, when manufacturing the film which thickness exceeds 50 micrometers, it is preferable to employ | adopt the time which multiplied the thickness ratio for the said time. For example, in the case of producing a film having a thickness of 100 μm, it is preferable to heat for twice the above time.

  Since the laminate manufactured as described above is excellent in transparency and does not generate outgas even in a high temperature process in forming the TFT and the transparent conductive film, the TFT and the transparent conductive film can be formed satisfactorily.

  Moreover, a catalyst solution for promoting imidization can be added to the polyimide precursor solution immediately before casting. The catalyst solution is not particularly limited as long as it has a function of promoting imidization. For example, (1) one or more dehydrating agents such as aliphatic or aromatic acid anhydrides and (2) A solution in which one or two or more catalysts such as an aliphatic tertiary amine such as triethylamine, an aromatic tertiary amine such as dimethylaniline, or a heterocyclic tertiary amine such as pyridine is mixed can be preferably used.

  Although it will not specifically limit as an inorganic base material used for the laminated body of this invention if it has the tolerance to a high temperature process, Glass can be used preferably at the point which has handleability and transparency.

(Optical identification of polyimide film)
In the laminate of the present invention, the polyimide film has a thickness of 10 μm, a haze of less than 2%, and a total light transmittance of 85% or more.

  When the haze is 2% or more, the cloudiness of the film becomes strong. Therefore, when used in a display, the sharpness of the image quality tends to decrease.

  If the total light transmittance is less than 85%, light is hardly transmitted. Therefore, when used for a display, the whole tends to be dark. In order to make it bright, the light emission of the light source will be strengthened, and the power consumption will increase.

  Further, in light transmittance, it is particularly preferable that the transmittance at a wavelength of 400 nm is 50% or more. When the transparency is less than 50%, when used in a display, yellow tends to be stronger than other colors and the color balance tends to be poor.

(Electronic bundle formation / peeling)
The laminated body of this invention can be preferably used for the member for flat panel displays by forming an electronic element on a polyimide film.

  Since this laminated body can improve the impact resistance of an inorganic base material with a polyimide film, even if it makes thin inorganic base materials, such as glass, it tends to become difficult to break. By reducing the thickness of the inorganic substrate, the flat panel display can be reduced in weight and thickness. Although materials other than polyimide film can improve impact resistance, they cannot withstand high process temperatures when forming electronic elements on the film.

  As a method for casting or coating the polyimide precursor solution on the inorganic substrate, a known method can be used. For example, a suitable method can be selected and used depending on the properties of the polyimide precursor solution, the coating thickness, the type of inorganic substrate, and the like, such as a die coating method, a bar coating method, a spin coating method, and a spray coating method.

  Moreover, the laminated body of this invention can obtain the flexible device which has the outstanding characteristic by forming an electronic element on a polyimide film and peeling this polyimide film from an inorganic board | substrate after that. Furthermore, the above process has an advantage that a production apparatus using an existing glass substrate can be used as it is, can be used effectively in the field of electronic devices such as flat panel displays and electronic paper, and is 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 a person, or may be peeled off by using a mechanical device such as a drive roll or a robot. Furthermore, a method of providing a release layer between an inorganic substrate and a polyimide film is also known. For example, a method of forming a silicon oxide film on a glass substrate having a large number of grooves and peeling it by infiltrating an etching solution, and a method of providing an amorphous silicon layer on a glass substrate and separating them by laser light I can do it.

  Also, rather than laminating a polyimide film on an inorganic substrate, a solution of a polyimide precursor is cast on the inorganic substrate, dried and imidized to form a polyimide film, and thus an existing electronic device production apparatus can be efficiently used. Can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

[Measurement of outgas amount]
Using TG / DTA220 manufactured by Seiko Instruments Inc., the weight reduction amount was measured under the following conditions, and the weight reduction rate (%) at 300 ° C. when the weight at 100 ° C. was taken as 100% was defined as the outgas amount.
(Measurement condition)
Sample amount: about 10mg
Measurement temperature range: room temperature to 400 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Nitrogen (flow rate 50 ml / min).

[Measurement of total light transmittance and haze]
The haze and total light transmittance (TT) of the film were measured using NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd.

[Measurement of UV-VIS absorption spectrum]
Using a V650DS manufactured by JASCO Corporation, UV-VIS absorption spectrum of 220 to 800 nm was measured, and the transmittance of light having a wavelength of 400 nm was measured.

Example 1
(Preparation of polyimide precursor solution)
A 500 ml separable flask was charged with 22.2 g (69.1 mmol) of 2,2′-bis (trifluoromethyl) benzidine (hereinafter referred to as TFMB) and dissolved in 175 g of dimethylacetamide (DMAc) in a 25 ° C. water bath. Stir with. Thereto, 22.4 g (73.4 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter, BPDA) was added and stirred at room temperature for 3 hours to obtain a homogeneous solution. Further, a solution prepared by dissolving 1.1 g (3.4 mmol) of 2,2′-bis (trifluoromethyl) benzidine in 6 g of DMAc was added to this solution. The 2,2′-bis (trifluoromethyl) benzidine solution was added to the solution and stirred for about 4 hours to obtain a polyimide precursor solution 1 having a solid content concentration of 15.0% by weight.

(Preparation of laminate of polyimide film and inorganic substrate)
The obtained polyimide precursor solution 1 was cast on glass of an inorganic substrate (manufactured by Matsunami Glass Industry Co., Ltd., micro slide glass S9111, 0.8-1 mm thickness), and it was 15 minutes at 110 ° C. and 15 minutes at 170 ° C. The laminate was heated at 230 ° C. for 8 minutes and at 320 ° C. for 8 minutes to produce a laminate having a 10 μm thick polyimide formed on glass.

  The polyimide was peeled from the obtained laminate, and the amount of outgas, total light transmittance (T. T), haze, and transmittance of light having a wavelength of 400 nm were measured. The results are shown in Table 1.

(Example 2)
The polyimide precursor solution 2 and the laminate were prepared in the same manner as in Example 1 except that 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (hereinafter referred to as 6FDA) was used instead of BPDA. The various properties of polyimide were measured and the results are shown in Table 1.

(Example 3)
A polyimide precursor solution 3 and a laminate were prepared in the same manner as in Example 1 except that 4,4′-oxydiphthalic dianhydride (hereinafter referred to as ODPA) was used instead of BPDA. The characteristics were measured and the results are shown in Table 1.

Example 4
Example 1 except that 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3 ', 4,4'-tetracarboxylic dianhydride (hereinafter referred to as ESDA) was used instead of BPDA. The polyimide precursor solution 4 and the laminate were prepared by the same method as above, and various characteristics of the polyimide were measured. The results are shown in Table 1.

(Example 5)
A polyimide precursor solution 5 and a laminate were prepared in the same manner as in Example 1 except that BPDA and 6FDA were mixed at a molar ratio of 1: 1, and various properties of the polyimide were measured. It is shown in Table 1.

(Example 6)
A polyimide precursor solution 6 and a laminate were prepared in the same manner as in Example 1 except that ODPA and 6FDA were mixed at a molar ratio of 1: 1, and various properties of the polyimide were measured. It is shown in Table 1.

(Example 7)
The polyimide precursor solution 7 and the laminate were prepared in the same manner as in Example 1 except that 9,9-bis (4-amino-3-fluorophenyl) fluorene (hereinafter, BFAF) was used instead of TFMB. The various properties of polyimide were measured and the results are shown in Table 1.

(Comparative Example 1)
A polyimide precursor solution 8 and a laminate were prepared in the same manner as in Example 1 except that pyromellitic dianhydride (hereinafter referred to as PMDA) was used instead of BPDA, and various properties of the polyimide were measured. The results are shown in Table 1.

(Comparative Example 2)
The polyimide precursor solution 1 is cast on an inorganic substrate glass (manufactured by Matsunami Glass Industry Co., Ltd., micro slide glass S9111, 0.8 to 1 mm thickness), 15 minutes at 100 ° C., 15 minutes at 150 ° C., 200 ° C. For 30 minutes and at 300 ° C. for 30 minutes to produce a laminate in which polyimide having a thickness of 10 μm was formed on glass.

  The polyimide was peeled from the obtained laminate, and the amount of outgas, total light transmittance (T. T), haze, and transmittance of light having a wavelength of 400 nm were measured. The results are shown in Table 1.

Claims (5)

Compound group (1)

At least one tetracarboxylic dianhydride selected from the group of compounds (2)

A laminate comprising a polyimide film obtained by casting a solution of a polyimide precursor obtained from at least one diamine selected from the above onto an inorganic substrate, drying and imidizing, and the inorganic substrate; And the maximum temperature in the step of imidizing is more than 300 ° C. and not more than 400 ° C., the thickness of the polyimide film is 10 μm, the haze is less than 2%, the total light transmittance is 85% or more, and at 300 ° C. A laminate having an outgas from the polyimide film of less than 0.5%. 2. The laminate according to claim 1, wherein a maximum temperature in the drying and imidizing step is more than 310 ° C. and 350 ° C. or less. The laminate according to claim 1 or 2, wherein the inorganic substrate is a glass substrate. A flat panel display member comprising an electronic element formed on the polyimide film of the laminate according to claim 1. The flexible device which formed the electronic element on the polyimide film of the laminated body in any one of Claims 1-3, and peeled this polyimide film from the inorganic board | substrate after that.