JP5822352B2 - Transparent flexible laminate and laminate roll - Google Patents

Description

  The present invention relates to a transparent flexible laminate having a thin film glass film and a polyimide resin layer, and a laminate roll.

  In recent years, displays and solar cells have become highly functional, and substrate materials, which are one of the components, are increasingly required to be lightweight and flexible, in addition to gas barrier properties and heat resistance, which are conventionally required characteristics. . Although glass is often used as an existing substrate material, attempts to replace glass with a resin have progressed in response to the increase in these required characteristics, and replacement of the glass substrate material with a resin has been performed.

  However, since resin has lower heat resistance and inferior gas barrier properties compared to glass, there are problems such as restricting the manufacturing method of displays and solar cells, failing to fully demonstrate its performance, and increasing costs. It has been pointed out. Therefore, at present, the practical application to the application using the resin as the substrate material has been limited to a limited application and scale such as a flexible solar cell.

  As an alternative example of glass to resin, for example, Patent Document 1 proposes a laminate of a resin and glass as a substrate material having excellent gas barrier properties. However, since the technique disclosed here has laminated | stacked resin inferior to heat resistance with glass, when it sees as the whole laminated body, there exists a problem that heat resistance will fall. Moreover, although the polyimide resin is also shown by patent document 1 as an application example of resin with high heat resistance, since a general polyimide resin shows yellow, transparency is calculated | required even if this is applied simply. Not enough for use in applications.

  Patent Document 2 proposes a method of laminating a highly heat-resistant polyimide resin on glass. However, in the present invention, glass is partially used for the purpose of imparting rigidity to the substrate and suppressing thermal expansion. In the experimental example specifically shown in Patent Document 2, there is only one using a relatively thick glass that is not flexible or very low in flexibility. It is difficult to impart flexibility (flexibility) to itself. Therefore, it is difficult to impart flexibility to the display or solar cell that is the final product.

Japanese Patent No. 4122139 JP 2002-297054 A

  The present invention has been made in view of the above circumstances, is excellent in flexibility (flexibility) and transparency, and can be applied to uses such as displays and solar cells, and the warpage of the laminate itself. It is an object of the present invention to provide a laminate and a laminate roll excellent in heat resistance and gas barrier properties.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors used an ultrathin glass film as a glass substrate, and a polyimide resin satisfying predetermined characteristics was laminated on the glass film. If it is a thing, it discovered that the laminated body provided with any of the above performances was obtained, and came to complete this invention.

  That is, the present invention has a glass film having a thickness of 20 to 200 μm and a polyimide resin layer, and the polyimide resin layer has a thermal expansion coefficient of 10 ppm / K or less and has a light transmittance at a wavelength of 500 nm. It is a transparent flexible laminated body characterized by being 80% or more.

  Moreover, this invention is a laminated body roll by which the said transparent flexible laminated body was wound up in roll shape.

  In the transparent flexible laminate in the present invention, a glass film having a thickness of 20 to 200 μm is used. This glass film itself originates from glass, is transparent, and has flexibility. If the thickness of the glass film is less than 20 μm, it cannot be obtained because it is difficult to produce the glass film itself. On the other hand, when the thickness of the glass film exceeds 200 μm, the flexibility is lowered and the glass film is easily cracked. From the viewpoint of achieving both flexibility and handling properties, the thickness of the glass film is preferably in the range of 30 to 100 μm, and more preferably in the range of 50 to 100 μm.

  Such a glass film can use what is marketed, for example, can use OA-10G by Nippon Electric Glass Co., Ltd., and AF32 by Schott AG.

  Usually, when a resin layer is provided on a thin film glass film as described above, there is a problem that heat resistance and transparency are lowered due to characteristics of the resin itself. Further, since different materials are bonded to the glass film, warping due to the difference in characteristics between the two becomes a problem. Therefore, in the present invention, these problems are solved by laminating polyimide resins having specific characteristics.

  That is, the polyimide resin layer laminated on the glass film in the present invention has an imide bond in its structural unit, a thermal expansion coefficient of 10 ppm / K or less, and a light transmittance at a wavelength of 500 nm of 80% or more. The polyimide resin is used. Especially, in order to maintain the heat resistance of the laminated body after lamination | stacking with a glass film, a thing with high heat resistance is preferable. From such a viewpoint, the glass transition temperature of the polyimide resin is preferably 300 ° C. or higher, and more preferably 350 ° C. or higher.

  Specifically, the polyimide resin satisfying the above characteristics can be formed as follows. That is, a case where a glass film is used as a base material will be described as an example. First, a predetermined glass film is prepared, and a polyimide precursor resin solution (hereinafter referred to as a polyamic acid solution) which is a polyimide resin precursor is prepared on the glass film. .) Is dried, the solvent is dried by heat treatment, and the polyimide precursor is imidized by heating at a higher temperature to obtain a flexible laminate in which a polyimide resin is laminated on a glass film. .

〔式中、Ａｒ₁は芳香環を有する４価の有機基を表し、Ａｒ₂は下記一般式（２）又は（３）で表される２価の有機基である。

（ここで、一般式（２）又は一般式（３）におけるＲ₁〜Ｒ₈は、互いに独立に水素原子、フッ素原子、炭素数１〜５までのアルキル基若しくはアルコシキ基、又はフッ素置換炭化水素基であり、一般式（２）にあってはＲ₁〜Ｒ₄のうち、また、一般式（３）にあってはＲ₁〜Ｒ₈のうち、それぞれ少なくとも一つはフッ素原子又はフッ素置換炭化水素基である。 And as preferable polyimide resin formed on a glass film, what has a structural unit represented by following General formula (1) is mentioned, More preferably, the structural unit represented by this General formula (1) It is good that it is a polyimide resin containing 80-100 mol%.

[In the formula, Ar ₁ represents a tetravalent organic group having an aromatic ring, and Ar ₂ represents a divalent organic group represented by the following general formula (2) or (3).

(Here, R _{1 to} R ₈ in the general formula (2) or the general formula (3) are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms or an alkoxy group, or a fluorine-substituted hydrocarbon. In the general formula (2), at least one of R _{1 to} R ₄ and R _{1 to} R _{8 in} the general formula (3) is a fluorine atom or a fluorine-substituted group. It is a hydrocarbon group.

  Other polyimide resins that may be added at a maximum of 20 mol% in addition to the polyimide resin according to the general formula (1) are not particularly limited, and general acid anhydrides and diamines can be used. However, among the acid anhydrides preferably used, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,4-cyclohexanedicarboxylic acid, 1, 2,3,4-cyclobutanetetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, etc., and 4,4′-diamino as diamine Diphenylsulfone, trans-1,4-diaminocyclohexane, 4,4′-diaminocyclohexylmethane, 2,2′-bis (4-aminocyclohexyl) -hexafluoropropane, 2,2′-bis (trif Oromechiru) -4,4'-diamino-bi cyclohexane.

As described above, the polyimide resin used for the polyimide resin layer preferably has a fluorine atom or a fluorine-substituted hydrocarbon group in part of its chemical structure. For that purpose, a fluorine atom or a fluorine-substituted hydrocarbon group may be contained in Ar ₁ in the general formula (1), may be contained in Ar ₂ , or may be contained in both. As a more preferable embodiment, in the general formula (2) or (3), at least one of R _{1 to} R ₄ may be a fluorine atom or a fluorine-substituted hydrocarbon group.

Preferable specific examples of R _{1 to} R ₄ include —H, —CH ₃ , —OCH ₃ , —F, —CF _{3 and the} like. More preferably, at least one of R _{1 to} R ₄ is — F, or may be from either -CF _3.

Moreover, specific examples of Ar _{1 in} the general formula (1) include the following tetravalent acid anhydride residues.

Further, as a specific diamine residue give Ar ₂ in the general formula (1), for example, include the following.

Among the polyimide resins exemplified above, those having a structural unit represented by the following formula (4) or (5) at a ratio of 80 mol% or more are preferable from the viewpoint of reduction in thermal expansion coefficient and heat resistance.

  Various polyimide resins as described above can be obtained by imidizing polyamic acid. Here, the polyamic acid resin solution is substantially composed of aromatic diamine and aromatic dianhydride as raw materials. It can be obtained by using equimolar amounts and reacting in an organic solvent. More specifically, after dissolving an aromatic diamine in an organic polar solvent such as N, N-dimethylacetamide under a nitrogen stream, an aromatic tetracarboxylic dianhydride is added and allowed to react at room temperature for about 5 hours. Can be obtained. The weight average molecular weight of the obtained polyamic acid is preferably 10,000 to 300,000 from the viewpoint of uniform film thickness during coating and mechanical strength of the resulting polyimide film. In addition, the preferable molecular weight range of a polyimide resin layer is also the same molecular weight range as a polyamic acid.

  In addition, in order to laminate the glass film and the polyimide resin layer, after applying the polyamic acid solution on the glass film, after applying the polyamic acid solution on a predetermined substrate in addition to the so-called casting method of drying and curing , The solvent is dried and the uncured film is peeled off, cured by heat treatment to form a polyimide film, and this polyimide film and glass film are heat-pressed to form a polyimide resin layer, or on a predetermined substrate After the polyamic acid solution is applied to the substrate, it is dried and cured to form a polyimide film, which is then peeled off from the substrate, and the polyimide film and the glass film are heat-bonded.

  In the present invention, any of these methods may be used, and although not limited to these methods, the polyamic acid solution is directly applied on the glass film constituting the present invention, and then dried and cured. The casting method is most suitable from the viewpoint of easy control of the adhesiveness to the glass film and the thermal expansion coefficient, surface roughness, retardation reduction, and the simplicity of the manufacturing process. Here, when the surface roughness Ra of the polyimide resin exceeds 5 nm and the retardation exceeds 10 nm, the thickness and optical characteristics of elements such as a display and a solar cell on the substrate are not uniform, and the performance may be deteriorated. is there. Therefore, it is preferable that the surface roughness Ra of the polyimide resin layer is 5 nm or less, and that the retardation in the surface direction of the polyimide resin layer of the obtained laminate is 10 nm or less. Furthermore, it is preferable that the polyimide resin layer formed by the cast method is 1-50 micrometers in thickness from a viewpoint of the simplicity of the manufacturing process in drying and hardening. The surface roughness Ra represents the arithmetic average roughness (JIS B 0601-1994).

  If the production example of the laminate of the present invention is more specifically shown, for example, the polyamic acid solution obtained by the above reaction is applied on a glass film serving as a support using an applicator or the like, and the temperature is 150 ° C. or lower. And for 2 to 20 minutes, followed by heat treatment at a temperature of about 130 to 360 ° C. for about 2 to 30 minutes to remove the solvent and imidization.

  In the present invention, the thickness of the polyimide resin layer is not particularly limited, but is preferably in the range of 1 to 100 μm, and more preferably in the range of 1 to 50 μm. If the thickness of the polyimide resin layer is less than 1 μm, it is difficult to control with an applicator and the thickness tends to be non-uniform. Conversely, if the thickness exceeds 100 μm, heat resistance and light transmittance may be reduced. In particular, when the thickness of the glass film is Gt and the thickness of the polyimide resin layer is Pt, a relationship of 2 ≦ Pt ≦ Gt / 10 is preferable. By satisfying this relationship, a transparent flexible laminate having a uniform thickness can be provided.

  Incidentally, as described above, the transparent flexible laminate of the present invention requires that the polyimide resin layer has a light transmittance of 80% or more at a wavelength of 500 nm. In order to make the light transmittance within this range, it is important to select a chemical structure of the polyimide resin to obtain a polyimide resin layer having a high transmittance. In order to obtain a transparent flexible laminate that can be bent even when the radius of curvature is 150 mm or less, it is important to select a glass film having a thickness of 20 μm to 200 μm to form a flexible glass layer. It is.

  That is, by selecting a polyimide resin with an appropriate chemical structural unit, adopting predetermined manufacturing conditions, and laminating it with a predetermined glass film, the thermal expansion of the polyimide resin layer is enhanced while increasing the light transmittance as described above. The coefficient can be 10 ppm / K or less, and the difference in thermal expansion coefficient between the glass film and the polyimide resin layer can be set in the range of 0 to 3 ppm / K, and the warpage of the laminate can be further reduced. Furthermore, by making the thickness of the glass film 0.2 mm or less, the flexibility can be further improved. By making the transparent flexible laminate into a long shape, this can be made into a roll shape. It can be wound up and can be provided as a laminate roll.

  Therefore, a transparent flexible laminate satisfying these characteristics is preferably produced by using a polyimide raw material constituting the structural unit of the general formula (4) to produce a polyamic acid solution. It can be manufactured by applying a predetermined thickness on a glass film and drying it at 150 ° C. or lower for 2 to 20 minutes, followed by heat treatment at a temperature of about 130 to 360 ° C. for about 2 to 30 minutes. .

  Here, from the viewpoint of uniformly controlling the film thickness when coating using an applicator or the like, the degree of polymerization of the polyamic acid and the polyimide used to form the polyimide resin layer is the viscosity range of the polyamic acid solution. The solution viscosity is preferably in the range of 500 to 200,000 cP. The solution viscosity can be measured with a cone plate viscometer with a thermostatic water bath.

  The transparent flexible laminate of the present invention is useful as a flexible substrate material because it is excellent in transparency, has no warpage, and has both heat resistance and gas barrier properties. For example, it is suitable for use as a flexible substrate in a display device that displays an image such as organic EL or electronic paper, or as a transparent substrate in a solar cell. It can also be used for an ion battery or the like. Therefore, it can be used in a wide range of fields, such as using the transparent flexible laminate of the present invention as an alternative material for a glass substrate that has been mainly used so far, and contributes greatly to the industry.

  Hereinafter, the contents of the present invention will be described more specifically based on examples and the like, but the present invention is not limited to the scope of these examples.

Abbreviations for the polyimide raw materials used in the examples and the like are shown below.
TFMB: 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl
PMDA: pyromellitic dianhydride
6FDA: 2,2-bis (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride
BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride
BAPP: 2,2-bis (4- (4-aminophenoxy) phenyl) propane
m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl
DMAc: N, N-dimethylacetamide

  In addition, measurement methods and conditions for various physical properties in the examples are shown below.

[viscosity]
The viscosity was measured at 25 ° C. for the polyamic acid solution obtained in the synthesis example with a cone plate viscometer (manufactured by Tokimec Co., Ltd.) equipped with a constant temperature water bath.

[Coefficient of thermal expansion (CTE)]
Tensile test of polyimide film with a size of 3mm x 15mm in a temperature range from 30 ° C to 260 ° C at a constant heating rate (20 ° C / min) while applying a 5.0g load with a thermomechanical analysis (TMA) device The coefficient of thermal expansion (ppm / K) was measured from the amount of elongation of the polyimide film with respect to temperature.

[Light transmittance]
The light transmittance at 500 nm was determined for a polyimide film (50 mm × 50 mm) with a U4000 self-recording spectrophotometer.

[warp]
The transparent flexible laminate was placed on a flat plate, and the distance between the four corners of the plate and the laminate was measured. When the transparent flexible laminate was curled to one side, the curled inner side was placed facing upward.

[Surface roughness]
The surface roughness Ra of the polyimide resin layer in the transparent flexible laminate was observed using a “Multi Mode 8”, an atomic force microscope (AFM) manufactured by Bruker, and 4 points within a 10 μm square field of view. Measurements were made and their average values were determined.

[Retardation]
Using a spectropolarimeter “Poxi-spectra” manufactured by Tokyo Instruments, retardation in the in-plane direction of the polyimide resin layer of the transparent flexible laminate was determined.

[Flexibility]
The transparent flexible laminate was cut into a 10 cm square and visually confirmed for the presence or absence of defects such as cracks when adhered to a roll having a radius of 150 mm.

(Synthesis Examples 1-4)
First, in order to synthesize the polyamic acid A, the diamine shown in Table 1 was dissolved in the solvent DMAc while stirring in a 200 ml separable flask under a nitrogen stream. Then, the acid dianhydride shown in Table 1 was added. Thereafter, the solution was stirred at room temperature for 5 hours to conduct a polymerization reaction, and kept for a whole day and night. A viscous polyamic acid solution was obtained, and it was confirmed that a polyamic acid having a high degree of polymerization was produced. Table 1 shows the solid content and solution viscosity of the obtained polyamic acid A solution (hereinafter referred to as polyamic acid solution A). Here, the solid content is the polyamic acid concentration. The results are summarized in Table 1.

  An example using polyamic acid A was used as synthesis example 1, and synthesis of polyamic acids B to D was performed in the same manner as in the case of polyamic acid A except that the composition ratios of synthesis examples 2 to 4 shown in Table 1 were followed. Went. These solid contents and solution viscosities are summarized in Table 1.

Example 1
The polyamic acid solution A shown in Table 1 was applied onto a commercially available glass film having a thickness of 50 μm using an applicator so that the film thickness after heat treatment was about 5 μm, and 90 ° C. at a rate of 22 ° C. per minute. To 360 ° C. to obtain a laminate having a single-layer polyimide layer on a glass film. The glass film used here had a thermal expansion coefficient of 3.8 ppm / K, a transmittance at 500 nm of 90%, and an elastic modulus of 30 GPa / g · cm ⁻³ .

  About the laminated body which concerns on Example 1 obtained above, curvature, surface roughness, and flexibility were measured. Moreover, the polyimide film was peeled off from the glass film of the obtained laminate, and the light transmittance, retardation, and thermal expansion coefficient (CTE) of the obtained polyimide film were measured. The results are summarized in Table 2.

(Example 2)
A laminate according to Example 2 was obtained in the same manner as in Example 1 except that the polyamic acid solution B shown in Table 1 was used. Various evaluations were performed on the obtained laminate in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 1)
A laminate according to Comparative Example 1 was obtained in the same manner as in Example 1 except that the polyamic acid solution C shown in Table 1 was used. Various evaluations were performed on the obtained laminate in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 2)
A laminate according to Comparative Example 2 was obtained in the same manner as in Example 1 except that the polyamic acid solution D shown in Table 1 was used. Various evaluations were performed on the obtained laminate in the same manner as in Example 1. The results are shown in Table 2.

  As is clear from the results obtained from Examples 1 and 2 and Comparative Examples 1 and 2, the transparent flexible laminate comprising the glass film and the polyimide resin layer satisfying the conditions of the present invention is transparent. Further, there was no warp, and the surface roughness and retardation of the polyimide resin layer surface were low. On the other hand, what consists of the polyimide resin layer which does not satisfy | fill the conditions of this invention has low transparency (comparative example 1), and when it laminated | stacks with a thin glass film, curvature generate | occur | produced largely (comparative example 1). Comparative Example 2).

Claims (7)

It has a glass film having a thickness of 20 to 200 μm and a polyimide resin layer, and the polyimide resin layer has a thermal expansion coefficient of 10 ppm / K or less and a light transmittance of 80% or more at a wavelength of 500 nm , Moreover, the said polyimide resin layer consists of a polyimide resin which contained 80-100 mol% of structural units represented by following General formula (1), The transparent flexible laminated body characterized by the above-mentioned.

[In the formula, Ar ₁ represents a tetravalent organic group having an aromatic ring, and Ar ₂ represents a divalent organic group represented by the following general formula (2) or (3).

(Here, R _{1 to} R ₈ in the general formula (2) or the general formula (3) are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms or an alkoxy group, or a fluorine-substituted hydrocarbon. In the general formula (2), at least one of R _{1 to} R ₄ and R _{1 to} R _{8 in} the general formula (3) is a fluorine atom or a fluorine-substituted group. Hydrocarbon group.)]   The transparent flexible laminate according to claim 1, wherein a difference in thermal expansion coefficient between the glass film and the polyimide resin layer is in a range of 0 to 3 ppm / K.   The transparent flexible laminate according to claim 1, which can be bent to a curvature radius of 150 mm or less. The transparent flexible laminate according to any one of claims 1 to 3 , wherein the retardation in the surface direction of the polyimide resin layer is 10 nm or less. The transparent flexible laminate according to any one of claims 1 to 4 , wherein the polyimide resin layer has a thickness of 1 to 50 µm and a surface roughness Ra of 5 nm or less. The transparent flexible laminate according to any one of claims 1 to 5 , which is used for a display device for displaying an image or a transparent substrate of a solar cell. The laminated body roll by which the transparent flexible laminated body in any one of Claims 1-6 was wound up by roll shape.