JP7029119B2 - Laminated structure and its manufacturing method, and flexible electronics element manufacturing method - Google Patents

Description

The present invention relates to a substrate for an organic thin film solar cell, a laminated structure and a method for manufacturing the same, and a flexible electronic device.

In recent years, flexible electronic devices (hereinafter, also referred to as "flexible electronic devices") have attracted attention. Among flexible electronic devices, flexible organic electronic devices are attracting attention because they can be expected to be lightweight and cost-effective, and in particular, expectations for organic thin-film solar cells are increasing.

So far, glass substrates have been mainly used as substrates for thin-film solar cells. However, the glass substrate is fragile, requires sufficient care in handling, and has the disadvantages of low flexibility. Therefore, an organic thin-film solar cell using a flexible resin substrate is attracting attention.

For example, Non-Patent Document 1 describes a solar cell using a polyethylene terephthalate (PET) film as a substrate. Further, Non-Special Document 2 describes that an element is formed on a film obtained by forming parylene by a CVD method.

Nature communications, 2012, 3: 770 Science Advances 2016; Vol. 2: e1501856

However, the PET film described in Non-Patent Document 1 has low surface smoothness. Therefore, when a transparent electrode layer or the like is formed on the PET film, there is a problem that the element is likely to be short-circuited. Further, the film made of parylene described in Non-Patent Document 2 has a problem that not only the surface smoothness but also the mechanical strength and the heat resistance are low.

Further, when an attempt is made to fabricate a member constituting an electronic element (hereinafter, also referred to as an "electronic element portion") on a flexible substrate, the substrate may be bent or distorted, and the substrate may be in a desired position. It is difficult to form the electronic element part with high accuracy. Therefore, it is conceivable to fix the flexible substrate on the rigid substrate to form the electronic element portion. However, this method has a problem that it is difficult to peel off the base material from the electronic element after the electronic element portion is formed, and the electronic element portion is easily damaged. On the other hand, if the base material is easily peeled off, there is a tendency that the flexible substrate is easily peeled off from the base material when the electronic element portion is formed.

The present invention has been made in view of the above circumstances. That is, the present invention provides a substrate for an organic thin film solar cell which has flexibility and high mechanical strength and heat resistance. Further, a laminated structure having a flexible substrate and a rigid substrate, and capable of easily peeling off the rigid substrate after forming the electronic element portion, and a manufacturing method thereof, and a method for manufacturing the same. A method for manufacturing a flexible electronic element used is provided.

That is, the first aspect of the present invention relates to the following organic thin film solar cell substrate.
[1] A substrate for an organic thin-film solar cell that satisfies all of the following (1) to (6).
(1) The maximum transmittance at a wavelength of 400 ± 5 nm at a thickness of 5 μm is 70% or more. (2) The L ^* a ^* b ^* color system b ^* value at a thickness of 5 μm is 5 or less. (3) JIS The number of folding resistance in the MIT folding resistance test at a thickness of 10 μm measured according to P8115 is 10,000 or more. (4) The glass transition temperature is 200 ° C. or more. (5) The thickness is 10 μm or less. (6) The surface roughness (Ra) of at least one surface is 5 nm or less.

（上記一般式（１）において、Ｒ_１は脂環式炭化水素構造を含む炭素数４～１５の２価の基、または炭素数５～１２の２価の直鎖状脂肪族基を表し、Ｙ_１は、芳香環を含む炭素数６～２７の４価の基を表す）

（上記一般式（２）において、Ｒ_２は芳香環を含む炭素数６～２７の２価の基を表し、Ｙ_２は、脂環式炭化水素構造を含む炭素数４～１２の４価の基を表す） [2] The organic thin-film solar cell according to [1], wherein the substrate contains a polyimide having a repeating structural unit represented by the following general formula (1) or a repeating structural unit represented by the following general formula (2). Board for.

(In the above general formula (1), R ₁ represents a divalent group having 4 to 15 carbon atoms or a divalent linear aliphatic group having 5 to 12 carbon atoms including an alicyclic hydrocarbon structure. Y ₁ represents a tetravalent group having 6 to 27 carbon atoms including an aromatic ring)

(In the above general formula (2), R ₂ represents a divalent group having 6 to 27 carbon atoms including an aromatic ring, and Y ₂ is a tetravalent group having 4 to 12 carbon atoms including an alicyclic hydrocarbon structure. Represents a group)

からなる群から選ばれる少なくとも１種の２価の基であり、
前記一般式（１）で表される構成単位のＹ_１が、

からなる群から選ばれる少なくとも１種の４価の基であり、前記一般式（２）で表される構成単位のＲ_２が、

（Ｘ_１～Ｘ_３は、それぞれ独立に、

からなる群から選ばれる単結合または２価の基を表す）からなる群から選ばれる少なくとも一種の２価の基であり、前記一般式（２）で表される構成単位のＹ_２が、

からなる群から選ばれる少なくとも一種の４価の基である、［２］に記載の有機薄膜太陽電池用基板。 [3] R ₁ of the structural unit represented by the general formula (1) is

It is a divalent group of at least one selected from the group consisting of
Y1 of the structural unit represented by the general formula ( ₁ ) is

R ₂ of the structural unit represented by the general formula (2), which is a tetravalent group of at least one selected from the group consisting of

(X ₁ to X ₃ are independent of each other,

It is at least one kind of divalent group selected from the group consisting of (representing a single bond or a divalent group selected from the group consisting of), and Y ₂ of the structural unit represented by the general formula (2) is

The substrate for an organic thin-film solar cell according to [2], which is at least one kind of tetravalent group selected from the group consisting of.

（上記一般式（３）において、Ｒ_１は脂環式炭化水素構造を含む炭素数４～１５の２価の基、または炭素数５～１２の２価の直鎖状脂肪族基を表し、Ｙ_１は、芳香環を含む炭素数６～２７の４価の基を表す）

（上記一般式（４）において、Ｒ_２は芳香環を含む炭素数６～２７の２価の基を表し、Ｙ_２は、脂環式炭化水素構造を含む炭素数４～１２の４価の基を表す） The second aspect of the present invention relates to the following laminated structure and a method for manufacturing the same, and a method for manufacturing a flexible electronic device using the same.
[4] The base material and the substrate for a flexible electronics element are laminated via a fluorine-based resin layer, and the water contact angle of the surface of the fluorine-based resin layer is 13 ° or more and 85 ° or less. Structure.
[5] The substrate for a flexible electronic device includes a polyimide having a repeating structural unit represented by the following general formula (3) or a repeating structural unit represented by the following general formula (4), according to [4]. Laminated structure.

(In the above general formula (3), R ₁ represents a divalent group having 4 to 15 carbon atoms or a divalent linear aliphatic group having 5 to 12 carbon atoms including an alicyclic hydrocarbon structure. Y ₁ represents a tetravalent group having 6 to 27 carbon atoms including an aromatic ring)

(In the above general formula (4), R ₂ represents a divalent group having 6 to 27 carbon atoms including an aromatic ring, and Y ₂ is a tetravalent group having 4 to 12 carbon atoms including an alicyclic hydrocarbon structure. Represents a group)

からなる群から選ばれる少なくとも１種の２価の基であり、前記一般式（３）で表される構成単位のＹ_１が、

からなる群から選ばれる少なくとも１種の４価の基であり、前記一般式（４）で表される構成単位のＲ_２が、

（Ｘ_１～Ｘ_３は、それぞれ独立に、

からなる群から選ばれる単結合または２価の基を表す）からなる群から選ばれる少なくとも一種の２価の基であり、前記一般式（４）で表される構成単位のＹ_２が、

からなる群から選ばれる少なくとも一種の４価の基である、［５］に記載の積層構造体。 [6] R ₁ of the structural unit represented by the general formula (3) is

Y ₁ of the structural unit represented by the general formula (3), which is a divalent group of at least one selected from the group consisting of

R ₂ of the structural unit represented by the general formula (4), which is a tetravalent group of at least one selected from the group consisting of

(X ₁ to X ₃ are independent of each other,

It is at least one kind of divalent group selected from the group consisting of (representing a single bond or a divalent group selected from the group consisting of), and Y ₂ of the structural unit represented by the general formula (4) is

The laminated structure according to [5], which is at least one tetravalent group selected from the group consisting of.

[7] The method for manufacturing a laminated structure according to any one of [4] to [6] above, wherein a step of forming a fluorine-based resin layer on a substrate and flexibility on the fluorine-based resin layer. A method for manufacturing a laminated structure, comprising a step of forming a substrate for an electronic element, wherein the water contact angle of the surface of the fluororesin layer is 13 ° or more and 85 ° or less.
[8] The step of forming the electronic element portion on the substrate for the flexible electronic element of the laminated structure according to any one of the above [4] to [6], and after forming the electronic element portion, the flexible electronic element. A method for manufacturing a flexible electronic device, comprising a step of peeling a fluorine-based resin layer and a base material from a substrate for use.

According to the present invention, it is possible to obtain a substrate for an organic thin film solar cell which has flexibility and high mechanical strength and heat resistance.

In the present specification, the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.

1. 1. Substrate for Organic Thin-Film Solar Cell The substrate for organic thin-film solar cells of the present invention (hereinafter, also simply referred to as "substrate for solar cells") is used as a substrate for organic thin-film solar cells. As described above, conventionally, a glass substrate has been mainly used as a substrate for a thin-film solar cell. However, the glass substrate is fragile, requires sufficient care in handling, and has the disadvantages of low flexibility. On the other hand, although the substrate made of resin has flexibility, it often has insufficient mechanical strength and heat resistance. Further, there is a drawback that a short circuit occurs in the element depending on the surface roughness of the substrate.

On the other hand, the substrate for a solar cell of the present invention has high heat resistance, and has appropriate mechanical strength and flexibility. In addition, since it has high light transmission, it can be used as a substrate on the light receiving surface side of an organic thin-film solar cell. Further, since the surface roughness (Ra) is sufficiently small, even if various members of the solar cell are formed on the substrate, a short circuit is unlikely to occur. Further, since it has flexibility (bending resistance), it can be applied to various organic thin-film solar cells. The solar cell substrate of the present invention can be applied not only to a substrate for an organic thin film solar cell but also to a substrate for an organic electroluminescence element. Hereinafter, the solar cell substrate of the present invention will be described in detail.

1-1. Physical Properties The substrate for a solar cell of the present invention (1) has a maximum transmittance of 70% or more, preferably 74% or more, more preferably 78% or more, and further preferably 78% or more at a wavelength of 400 ± 5 nm at a thickness of 5 μm. It is preferably 80% or more, and particularly preferably 85% or more. When the maximum transmittance is in this range, sufficient photoelectric conversion efficiency can be realized when the solar cell substrate is used as the substrate on the light receiving surface side of the organic thin film solar cell. Polyimide is preferably used as a material for constituting the substrate for a solar cell of the present invention, but polyimide generally tends to easily absorb light on the short wavelength side. On the other hand, by setting the maximum transmittance at a wavelength of 400 nm ± 5 nm to 70% or more, the transmittance of light on the short wavelength side becomes high, and the usefulness as a substrate on the light receiving surface side becomes very high.

The maximum transmittance can be adjusted by the type and structure of the resin constituting the solar cell substrate. When the substrate for a solar cell contains polyimide, the maximum transmittance can be remarkably improved by including an alicyclic group in the repeating unit. In addition, the maximum transmittance can be increased by adjusting the conditions at the time of manufacturing the polyimide. For example, by lowering the oxygen concentration in an inert atmosphere (for example, under a nitrogen stream), it is possible to suppress coloring due to oxidation and increase the maximum transmittance.

The light transmittance at a wavelength of 400 nm ± 5 nm is measured by a spectrophotometer, and in the present specification, the maximum transmittance measured within the range of a wavelength of 400 nm ± 5 nm is defined as the maximum transmittance. Further, the maximum transmittance specified in the present specification is a value when the thickness of the solar cell substrate is 5 μm. For example, the maximum transmittance may be measured for a solar cell substrate having a thickness of 5 μm, but the maximum transmittance of solar cell substrates having different thicknesses may be measured, and the measured value shall be measured according to Lambert-Beer's law. It may be converted.

Further, in the solar cell substrate of the present invention, (2) the L ^* a ^* b ^* color system b ^* value at a thickness of 5 μm is 5 or less, preferably 4 or less, and more preferably 3 or less. be. When the b ^* value is in the range, the solar cell substrate becomes colorless and the transparency of visible light becomes good. That is, when the substrate for a solar cell is used as the substrate on the light receiving surface side of the organic thin film solar cell, the photoelectric conversion efficiency tends to increase. The b ^* value can be adjusted depending on the type of resin constituting the solar cell substrate and the like. For example, when the substrate for a solar cell contains polyimide, the b ^* value can be lowered by including a large amount of alicyclic structure in the repeating unit. Further, the b ^* value can be lowered by adjusting the conditions at the time of manufacturing the polyimide. For example, it is possible to suppress coloring due to oxidation and lower the b ^* value by lowering the oxygen concentration in an inert atmosphere (for example, under a nitrogen stream).

The b ^* value of the L ^* a ^* b ^* color system can be measured using a Color Cute i type manufactured by Suga Test Instruments. Specifically, it is specified by calibrating the tester with a white standard plate and then measuring the b ^* value of the solar cell substrate in a transmission mode and a photometric method of 8 ° di. The b ^* value specified in the present specification is a value when the thickness of the solar cell substrate is 5 μm, and the b ^* value may be measured for the solar cell substrate having a thickness of 5 μm. On the other hand, the b ^* values of the solar cell substrates having different thicknesses may be measured and converted according to a conventional method.

Further, the substrate for a solar cell of the present invention has a folding resistance of 10,000 times or more in a MIT folding resistance test at a thickness of 10 μm, which is measured in accordance with (3) JIS P8115, and is preferably 2. It is 10,000 times or more, more preferably 30,000 times or more, and further preferably 50,000 times or more. When the number of folding times of the MIT folding resistance test is 10,000 or more, it is possible to bend the substrate for a solar cell when it is used for an organic thin-film solar cell. Further, if the result of the MIT folding resistance test is 10,000 times or more, it can be said that the solar cell substrate has sufficient strength. Further, if the number of folding times is 30,000 or more, durability can be ensured for 3 years even if the bending is performed 30 times a day. The folding resistance can be adjusted, for example, by the type and structure of the resin constituting the solar cell substrate. When the substrate for a solar cell contains polyimide, the repeating unit may include a structural unit having a relatively flexible structure (for example, a structural unit derived from an alicyclic diamine or a structural unit derived from an aliphatic diamine). Fold resistance can be improved.

In the MIT fold resistance test, one end of the test piece is fixed by a MIT fold resistance tester (for example, Yasuda Seiki Seisakusho, 307 type, etc.), and then the other end is gripped and the test piece is reciprocally bent. It can be specified by measuring the number of bends until the test piece breaks.

The substrate for a solar cell of the present invention has (4) a glass transition temperature of 200 ° C. or higher, preferably 230 ° C. to 370 ° C., more preferably 260 ° C. to 370 ° C., and particularly preferably 280 ° C. to 370 ° C. ℃. When the glass transition temperature of the solar cell substrate is 200 ° C. or higher, the substrate is less likely to be deformed when the organic thin film solar cell is manufactured. Further, an annealing treatment or the like may be performed when the organic thin film solar cell is manufactured, but if the glass transition temperature is 200 ° C. or higher, it is possible to sufficiently withstand such treatment. In particular, since the conductivity of a transparent electrode such as indium tin oxide (ITO) improves when the annealing temperature is raised, it is preferable that the glass transition temperature of the substrate for a solar cell is high. The glass transition temperature of the solar cell substrate can be adjusted by the type and structure of the resin constituting the solar cell substrate. When the substrate for a solar cell contains polyimide, the glass transition temperature can be adjusted by the equivalent amount of imide groups contained in the polyimide, the structure of the diamine component or the tetracarboxylic acid dianhydride component constituting the polyimide, and the like. The glass transition temperature is measured by a thermomechanical analyzer (TMA).

The solar cell substrate of the present invention has (5) a thickness of 10 μm or less, preferably 0.5 μm to 5 μm, and more preferably 1 μm to 3 μm. When the thickness of the solar cell substrate is within the range, the thickness of the organic thin-film solar cell manufactured by using the solar cell substrate can be reduced. However, if the thickness is excessively thin, the mechanical strength of the solar cell substrate tends to decrease.

Further, in the solar cell substrate of the present invention, (6) the surface roughness (Ra) of at least one surface is 5 nm or less, preferably 2 nm or less, and more preferably 1 nm or less. The solar cell substrate of the present invention may have a surface roughness (Ra) of 5 nm or less on only one surface, or may have a surface roughness (Ra) of 5 nm or less on both sides. When the surface roughness (Ra) of only one surface is 5 nm or less, each member of the organic thin-film solar cell is formed on the side where the surface roughness is 5 nm or less.

When the surface roughness (Ra) of the solar cell substrate is 5 nm or less, short circuits and the like are less likely to occur when each member of the thin-film solar cell is laminated on the substrate. The surface roughness of the solar cell substrate can be adjusted by the type of the material constituting the solar cell substrate and the manufacturing method thereof. When the substrate for a solar cell contains polyimide, the surface roughness can be reduced by, for example, a method for forming the substrate (such as forming a free surface by a coating method). Further, depending on the type of resin constituting the substrate for a solar cell, the above surface roughness may be realized by performing precision polishing such as chemical mechanical polishing. When the substrate for a solar cell contains polyimide, the surface roughness can be reduced by adjusting the temperature rise rate at the time of substrate formation (imidization), the viscosity and concentration of the polyamic acid varnish, and the like. The surface roughness (Ra) can be measured by an atomic force microscope (AFM). It is also possible to measure with a contact type surface roughness meter.

1-2. Composition The material constituting the organic thin-film solar cell of the present invention is not particularly limited as long as it has the above physical characteristics and is an organic material, but is represented by the following general formulas (1) and / or general formulas (2). It is preferable to include a polyimide having a repeating unit to be used. The polyimide may contain only one of the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2), or may contain both. .. Further, the polyimide may contain a repeating unit other than the repeating unit represented by the general formula (1) and / or the repeating unit represented by the general formula (2), but the repeating unit constituting the polyimide may be contained. The total amount of the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) is preferably 50 mol% or more, and is 80 mol% or more, based on the total amount of the units. Is more preferable, 90 mol% or more is further preferable, and 95 mol% or more is particularly preferable. When the total amount thereof is 50 mol% or more, a substrate for a solar cell having the above-mentioned physical properties can be easily obtained, the physical properties can be made uniform, and the glass transition temperature can be particularly increased.

上記一般式（１）において、Ｒ_１は脂環式炭化水素構造を含む炭素数４～１５の２価の基、または炭素数５～１２の２価の直鎖状脂肪族基を表す。Ｒ_１の具体例には、以下に示す２価の基が含まれる。

In the above general formula (1), R ₁ represents a divalent group having 4 to 15 carbon atoms or a divalent linear aliphatic group having 5 to 12 carbon atoms including an alicyclic hydrocarbon structure. Specific examples of R ₁ include the following divalent groups.

であることが特に好ましい。 Among these, R ₁ is

Is particularly preferable.

On the other hand, in the above general formula (1), Y ₁ represents a tetravalent group having 6 to 27 carbon atoms including an aromatic ring. Specific examples of Y ₁ include the following tetravalent groups.

であることが特に好ましい。 Among these, Y ₁ is

Is particularly preferable.

また、上記一般式（２）において、Ｒ_２は芳香環を含む炭素数６～２７の２価の基を表す。Ｒ_２の具体例には、以下に示す２価の基が含まれる。

上記式中のＸ_１～Ｘ_３は、それぞれ独立に以下の２価の基を表す。一つの繰返し単位にＸ_２またはＸ_３が複数含まれる場合、これらは互いに同一であってもよく、異なっていてもよい。

Further, in the above general formula (2), R ₂ represents a divalent group having 6 to 27 carbon atoms including an aromatic ring. Specific examples of R ₂ include the following divalent groups.

X ₁ to X ₃ in the above formula independently represent the following divalent groups. When one repeating unit contains a plurality of X ₂ or X ₃ , they may be the same or different from each other.

On the other hand, Y ₂ in the above general formula (2) represents a tetravalent group having 4 to 12 carbon atoms including an alicyclic hydrocarbon structure. Examples of Y ₂ include the tetravalent groups shown below.

1-3. About the organic thin film solar cell The substrate for the solar cell of the present invention can be used as the substrate of the organic thin film solar cell as described above. An example of the configuration of the organic thin-film solar cell is shown below, but the configuration of the organic thin-film solar cell is not limited to the structure. The organic thin-film solar cell may have a structure in which a light receiving surface side substrate / first electrode / electron transport layer / photoelectric conversion layer / hole transport layer / second electrode / back surface side substrate are laminated in this order.

As the light receiving surface side substrate and the back surface side substrate, the above-mentioned solar cell substrate can be used, and may be used for only one of them or for both of them. As described above, the substrate for a solar cell of the present invention has high light transmission. Therefore, it is very useful as a substrate on the light receiving surface side.

Further, the first electrode is a negative electrode and is electrically connected to the photoelectric conversion layer. Since the first electrode is located on the light receiving surface side of the organic thin film solar cell, for example, a transparent conductive metal compound such as indium tin oxide (ITO), aluminum zinc oxide (AZO), zinc oxide (IZO), etc. Consists of.

Further, the electron transport layer is provided between the first electrode and the photoelectric conversion layer, and is a layer having a function of facilitating the transfer of electrons from the photoelectric conversion layer to the first electrode. The electron transport layer may have a function of making it difficult for holes to move from the photoelectric conversion layer to the first electrode. The electron transport layer may be formed of a material having high electron mobility, and may be a layer containing a known organic semiconductor molecule or an inorganic compound such as ZnO.

Further, in the photoelectric conversion layer, a known p-type organic semiconductor having electron donating property and a known n-type organic semiconductor having electron acceptability and forming a bulk heterojunction with the p-type organic semiconductor are mixed at the nano level. It can be a layer or the like. Examples of the p-type organic semiconductor include the polymer compounds described in JP-A-2016-17117. On the other hand, n-type organic semiconductors include carbon materials such as fullerene, fullerene derivatives, carbon nanotubes, and chemically modified carbon nanotubes, fused ring aromatic compounds, 5- to 7-membered heterocyclic compounds, polyarylene compounds, and fluorene. Examples thereof include a compound, a cyclopentadiene compound, a silyl compound, and a metal complex having a nitrogen-containing heterocyclic compound as a ligand. It is also effective to use a perovskite-type compound for the photoelectric conversion layer depending on the purpose. Further, depending on the purpose, it is also possible to use a current or electroluminescent material for the photoelectric conversion layer to make a light emitting device.

Further, the hole transport layer is provided between the second electrode and the photoelectric conversion layer, and is a layer having a function of facilitating the movement of holes from the photoelectric conversion layer to the second electrode. The hole transport layer may have a function of making it difficult for electrons to move from the photoelectric conversion layer to the first electrode. The hole transport layer can be, for example, a layer containing a known conductive polymer, an inorganic compound such as MoO ₃ or WO ₃ , an organic semiconductor molecule, or the like.

Further, the second electrode is an anode and is electrically connected to the photoelectric conversion layer. The material of the second electrode is not particularly limited as long as it has conductivity, and for example, a metal such as Au, Pt, Ag, Cu, Al, Mg, Li, K, or a carbon electrode can be used. ..

1-4. Method for Manufacturing a Substrate for a Solar Cell The method for manufacturing a substrate for a solar cell of the present invention is not particularly limited as long as the substrate for a solar cell satisfies the above-mentioned physical properties. For example, as a method for producing a substrate for a solar cell containing the above-mentioned polyimide, a diamine having a specific structure and a tetracarboxylic acid dianhydride having a specific structure are polymerized in a solvent to contain an amid acid. As a varnish, the amic acid-containing varnish is applied onto the substrate. Then, it is obtained by imidizing (imide closing) the amic acid on the substrate and then peeling the polyimide substrate (solar cell substrate) from the substrate.

However, if the polyamic acid varnish is directly applied onto the base material to imidize the polyamic acid, it may be difficult to peel off the obtained polyimide substrate from the base material. Therefore, it is preferable to manufacture the substrate for a solar cell by the method described in "Method for manufacturing a laminated structure". The diamine, tetracarboxylic dianhydride, and solvent used for the production of polyimide and various production conditions will be described in detail in "Method for producing laminated structure".

2. 2. Laminated Structure The laminated structure of the present invention has a structure in which a base material, a fluorine-based resin layer, and a substrate for a flexible electronics element (hereinafter, also referred to as “element substrate”) are laminated.

Generally, when an electronic element portion is formed on a flexible element substrate, the element substrate may be bent or distorted, the position of the electronic element portion may be displaced, or the obtained flexible electronic element may be formed. Distortion may occur. Therefore, it is conceivable to fix the element substrate to the base material and form the electronic element portion in a state where the element substrate is supported by the base material. However, this method has a problem that it is difficult to peel off the base material from the element substrate after the electronic element portion is formed, and the obtained element is easily damaged.

On the other hand, in the laminated structure of the present invention, the base material and the substrate for the element are laminated via the fluorine-based resin layer. Therefore, after the electronic element portion is formed on the element substrate of the laminated structure, it can be easily peeled off at the interface between the element substrate and the fluorine-based resin layer.
Hereinafter, each configuration of the laminated structure of the present invention will be described.

2-1. Base material The base material is not particularly limited as long as it has rigidity enough to support a substrate for an element and can uniformly form a fluorine-based resin layer described later on the surface thereof. The shape of the base material is appropriately selected according to the shape of the electronic element to be manufactured, and may be, for example, a flat plate-shaped substrate, a substrate having a bent structure, or the like.

The material of the base material is not particularly limited, and may be an alkali glass substrate containing an alkali metal oxide (Na ₂ O, K ₂ O) or a non-alkali glass substrate. Further, as the base material, a Si wafer, a highly rigid polymer film, or the like may be used.

Furthermore, the thickness of the base material is usually preferably 50 to 3000 μm, more preferably 100 to 1000 μm, and even more preferably 100 to 700 μm. When the thickness of the base material is within the range, the handleability when forming the electronic element portion on the laminated structure becomes good. In addition, the strength of the laminated structure tends to increase. An inorganic glass plate having a thickness of 100 μm or less may have a slightly lower strength, but when such an inorganic glass plate is used as a base material, a curable resin coating that fills cracks on the surface is used to prevent damage. It can be suitably used by treating with.

Further, among the surfaces of the base material, the surface roughness (Ra) of the surface on which the substrate for the flexible electronic device is laminated is preferably sufficiently small, preferably 10 nm or less, and more preferably 5 nm or less. preferable. Surface roughness can be measured by an atomic force microscope (AFM). The surface roughness (Ra) can also be measured by a contact type surface roughness meter. When the surface roughness becomes large, the base material may be easily cracked, the substrate for a flexible electronic element may be difficult to peel off, or backscattering may become large.

2-2. Fluorine-based resin layer The fluorine-based resin layer is a layer formed between a base material and a substrate for a flexible electronic element, and is a layer containing a resin containing fluorine in its molecular structure. The water contact angle on the surface of the fluororesin layer is 13 ° or more and 85 ° or less, and the water contact angle is preferably 23 ° or more and 80 ° or less, and more preferably 23 ° or more and 70 ° or less. As will be described later, the device substrate is usually formed by applying a varnish or the like containing a resin precursor on a fluorine-based resin layer. At this time, if the water contact angle on the surface of the fluororesin layer is too high, the varnish is repelled and the device substrate cannot be uniformly formed. On the other hand, when the water contact angle on the surface of the fluororesin layer is 85 ° or less, the element substrate can be formed uniformly and evenly. On the other hand, if the water contact angle on the surface of the fluorine-based resin layer is high, peeling at the interface between the element substrate and the fluorine-based resin layer is less likely to occur when the element substrate is peeled off after the electronic element portion is formed. By setting the water contact angle on the surface of the fluorine-based resin layer to 13 ° or more, good peelability can be easily obtained. The water contact angle on the surface of the fluororesin layer can be adjusted by the type of the fluororesin layer, the surface treatment, and the like.

Here, the water contact angle on the surface of the fluorine-based resin layer is the water contact angle when the fluorine-based resin layer is exposed, and can be measured, for example, by peeling the element substrate from the laminated structure. can. Further, the water contact angle on the surface of the fluororesin layer can be measured by the sessile drop method.

The fluorine-based resin layer can be formed, for example, by applying a known fluorine-based resin (for example, hydrofluoroether) onto a substrate and drying it. Examples of commercially available fluororesin products include Novell 2702, 1700, 1720, 7000, 7100, 7200, 7300, 71IPE (all manufactured by 3M); Teflon® AF1600, AF2400 (all Mitsui and DuPont Fluorochemicals). (Manufactured by the company) etc. are included. These can be used alone or in combination of two or more.

Further, the fluorine-based resin layer may be one that has been subjected to, for example, oxygen plasma treatment after the formation of the layer containing the fluorine-based resin. By performing oxygen plasma treatment, the water contact angle can be adjusted to a desired range.

The thickness of the fluororesin layer is preferably 0.01 to 10 μm, more preferably 0.1 to 3 μm. When the thickness of the fluororesin layer is 0.01 μm or more, the peelability of the element substrate tends to be sufficiently enhanced.

2-3. Substrate for flexible electronics element The element substrate may be a substrate for forming a flexible electronics element, and the type thereof is not particularly limited. Examples of flexible electronic devices include, for example, solar cells such as organic thin film solar cells, LED devices, organic electroluminescence devices, transistors and the like.

Here, the substrate for an element has the same physical properties as the substrate described in the above-mentioned substrate for an organic thin-film solar cell from the viewpoints of heat resistance, flexibility, transparency, etc., and is a substrate containing the above-mentioned polyimide. Is preferable.

2-4. Method for Manufacturing a Laminated Structure The above-mentioned laminated structure is manufactured by performing a step of forming a fluorine-based resin layer on a base material and a step of forming a substrate for an element on the fluorine-based resin layer. be able to.

-Fluorine-based resin layer forming step First, the above-mentioned base material is prepared, and the composition for forming a fluorine-based resin layer is applied onto the base material. The composition for forming a fluorine-based resin layer can be a composition containing the above-mentioned fluorine-based resin or a precursor thereof and a solvent.

The method for applying the composition for forming a fluororesin layer is not particularly limited, and examples thereof include a spin coating method, a bar coating method, a dip coating method, a slit coating method, a spray coating method, a gravure coating method, and a die coating method. ..

After applying the composition for forming a fluororesin layer, the solvent in the composition is removed and dried. The drying method is appropriately selected according to the components contained in the composition for forming the fluororesin layer, and may be, for example, heat-dried or room-temperature dried.

Further, after the composition for forming the fluororesin layer is dried, the surface may be subjected to oxygen plasma treatment or the like, if necessary. The treatment conditions for oxygen plasma are appropriately selected so that the water contact angle on the surface of the fluororesin layer is 13 ° or more and 85 ° or less.

-Step of forming the element substrate Next, the element substrate is formed on the above-mentioned fluorine-based resin layer. The method for forming the substrate for an element is appropriately selected depending on the type of resin, but as a method for producing a substrate for an element mainly containing polyimide, a diamine having a specific structure and a tetracarboxylic acid having a specific structure are used. The acid dianhydride is polymerized in a solvent to obtain an amic acid-containing varnish. Then, the amidic acid-containing varnish is applied onto the fluororesin layer, and then the amidic acid is imidized (imide ring closure). As a result, a laminated structure in which the base material, the fluorine-based resin layer, and the substrate for the element are laminated can be obtained.

(Preparation of polyamic acid varnish)
First, a diamine having a predetermined structure and a tetracarboxylic acid dianhydride having a specific structure are polymerized in a solvent to obtain an amic acid-containing varnish.

Diamine and tetracarboxylic dianhydride are appropriately selected according to the structure of the polyimide to be prepared. For example, when a substrate for an element containing a polyimide having a repeating structure represented by the above general formula (1) is produced, a diamine or a linear aliphatic diamine having an alicyclic hydrocarbon structure and a tetracarboxylic containing an aromatic ring are produced. Polyamide acid is prepared by reacting with an acid dianhydride. The diamine and the tetracarboxylic dianhydride may be used alone or in combination of two or more.

Examples of diamines having an alicyclic hydrocarbon structure include cyclobutanediamine, cyclohexanediamine, bis (aminomethyl) cyclohexane], diaminobicycloheptane, diaminomethylbicycloheptane (including norbornanediamines such as norbornanediamine), and diaminooxy. Includes bicycloheptane, diaminomethyloxybicycloheptane (including oxanorbornanediamine), isophoronediamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis (aminocyclohexyl) methane, bis (aminocyclohexyl) isopropylidene, etc. ..

Examples of linear aliphatic diamines are 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diamino. Decan, 1,11-diaminoundecane, 1,12-diaminododecane and the like are included.

Examples of tetracarboxylic acid dianhydrides containing aromatic rings include pyromellitic acid dianhydrides, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydrides, 2,3,3', 4. '-Biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 1,4-bis (3) , 4-Dicarboxyphenoxy) benzene dianhydride, 2,2-bis [(3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) biphenyl Dianhydride, Naphthalene 2,3,6,7-Tetracarboxylic Acid Dianhydride, Naphthalene1,2,5,6-Tetracarboxylic Acid Dianhydride, 4,4'-(9-Fluorenilidene) Bisphthalic Anhydride Etc. are included.

On the other hand, in the case of producing a substrate for an element containing a polyimide having a repeating structure represented by the above general formula (2), a diamine containing an aromatic ring and a tetracarboxylic acid dianhydride containing an alicyclic hydrocarbon structure are used. The reaction is carried out to prepare a polyamic acid. The diamine and the tetracarboxylic dianhydride may be used alone or in combination of two or more.

Examples of diamines containing an aromatic ring are p-phenylenediamine, m-phenylenediamine, p-xylylene diamine, m-xylylene diamine, which are diamines having one benzene ring; diamines having two benzene rings. There are 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'- Diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-di (4-aminophenyl) propane, 1 , 5-Diaminonaphthalene ,; 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3), a diamine having three benzene rings. -Aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-Aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 2,6-bis (3-aminophenoxy) pyridine; 4,4'-bis, a diamine having four benzene rings. (3-Aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, Bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-amino) phenyl] Phenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (4-aminophenoxy) phenyl] Propane; etc. are included.

On the other hand, examples of tetracarboxylic acid dianhydrides containing an alicyclic hydrocarbon structure include cyclobutanetetracarboxylic acid dianhydrides, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydrides, 1,2, 4,5-Cyclohexanetetracarboxylic acid dianhydride, bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo [2.2.2. ] Oct-7-en-2,3,5,6-tetracarboxylic acid dianhydride, Bicyclo [2.2.2] Octane-2,3,5,6-tetracarboxylic acid dianhydride, 2,3 , 5-Tricarboxycyclopentylacetic acid dianhydride, Bicyclo [2.2.1] heptane-2,3,5-tricarboxylic acid-6-acetic acid dianhydride, 1-methyl-3-ethylcyclohex-1-ene -3- (1,2), 5,6-tetracarboxylic acid dianhydride, decahydro-1,4,5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, 4 -(2,5-Dioxotetracarboxylate-3-yl) -tetralin-1,2-dicarboxylic acid dianhydride, 3,3', 4,4'-dicyclohexyltetracarboxylic acid dianhydride and the like are included.

The polyamic acid varnish can be obtained, for example, by polymerizing the above diamine and tetracarboxylic acid dianhydride in an aprotic polar solvent or a water-soluble alcohol-based solvent. Examples of aprotonic polar solvents include N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, etc .; ether-based compounds, 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, tri Ethylene Glycol Monoethyl Ether, Tetraethylene Glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, Dipropylene Glycol, Dipropylene Glycol Monomethyl Ether, Dipropylene Glycol Monoethyl Ether, Tripropylene Glycol Monomethyl Ether, Polyethylene Glycol, polypropylene glycol, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether and the like are included. Examples of water-soluble alcohol solvents include methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol. 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butane-1,4-diol, 2-methyl-2,4-pentanediol, 1,2,6-hexane Includes triol, diacetone alcohol and the like.

These solvents can be used alone or in combination of two or more. Among these, N, N-dimethylacetamide, N-methylpyrrolidone or a combination thereof is preferable.

There are no particular restrictions on the procedure for preparing the polyamic acid varnish. For example, prepare a container equipped with a stirrer and a nitrogen introduction pipe. The above-mentioned solvent is put into a nitrogen-substituted container, diamine is added so that the solid content concentration becomes about 30% by weight, and the mixture is stirred and dissolved. To this solution, tetracarboxylic dianhydride is added so that the molar ratio is about 1 with respect to the diamine compound, the temperature is adjusted, and the mixture is stirred for about 1 to 50 hours. This makes it possible to obtain a polyamic acid varnish in which the polyamic acid is dispersed in a solvent.

(Applying and imidizing polyamic acid varnish)
The above-mentioned polyamic acid varnish is applied onto the above-mentioned fluororesin layer and heated to imidize the polyamic acid. Here, the method for applying the polyamic acid varnish is not particularly limited, and for example, a spin coating method, a bar coating method, a dip coating method, a slit coating method, a spray coating method, a gravure coating method, a die coating method, or the like can be used.

The imidization of the polyamic acid can be carried out in a normal heating and drying oven. As the atmosphere of the drying furnace, air, inert gas (nitrogen, argon) or the like can be used, but it is preferable to use an inert gas atmosphere having an oxygen concentration of 5% or less. By lowering the oxygen concentration in the environmental atmosphere, the transparency of the obtained element substrate (polyimide substrate) can be improved. In addition, the folding resistance and tensile strength of the obtained element substrate (polyimide substrate) are likely to increase. The oxygen concentration of the inert gas in the environmental atmosphere is more preferably 0.1% or less.

On the other hand, the average heating rate during imidization can be, for example, 0.25 to 50 ° C./min, preferably 1 to 10 ° C./min, and more preferably 2 to 5 ° C./min in the range of 50 to 300 ° C. Minutes. The rate of temperature rise may be constant or may be changed to two or more steps. When changing to two or more steps, it is preferable to set each heating rate to 0.25 to 50 ° C./min. The transparency of the obtained element substrate (polyimide substrate) is increased, and the tensile strength and folding resistance are also increased. Further, the temperature rise may be continuous or stepwise (sequential), but the continuous temperature rise can suppress the appearance defect of the obtained element substrate (polyimide substrate) and the whitening due to the imidization reaction. preferable. The coating film does not necessarily have to be heated to 300 ° C. When the temperature rise end temperature is less than 300 ° C., the average temperature rise rate in the range from 150 ° C. to the temperature rise end temperature is preferably 0.25 to 50 ° C./min.

The temperature at which the temperature rise ends (reached maximum) is usually preferably a higher temperature, specifically, a temperature higher than the glass transition temperature Tg of the polyimide by 10 ° C. or more. By setting the temperature at which the temperature rise ends (maximum reached) to that temperature, it becomes easier to remove the residual solvent contained in the coating film. In addition, the folding resistance of the obtained element substrate (polyimide substrate) is improved. The temperature at which the temperature rise ends (reached maximum) is, for example, preferably 200 to 300 ° C, more preferably 250 to 290 ° C, and even more preferably 270 to 290 ° C. The heating time after the temperature rise is completed can be, for example, about 1 second to 10 hours.

2-5. Method for manufacturing a flexible electronic element using a laminated structure When manufacturing a flexible electronic element using the above-mentioned laminated structure, first, a step of forming an electronic element portion on a substrate for the element of the laminated structure is performed. After that, a step of peeling the fluororesin layer and the base material from the substrate for the flexible electronic element is performed.

According to the method of the present invention, it is possible to form an electronic element portion while being supported by a rigid base material. Therefore, the element substrate does not bend when the electronic element portion is formed, and the electronic element portion can be accurately formed at a desired position.

On the other hand, after forming the electronic device portion, the base material and the fluorine-based resin layer can be easily peeled off from the device substrate. Therefore, it is possible to perform peeling without damaging the electronic element portion, and a flexible electronic element can be easily obtained.

Hereinafter, the present invention will be described with reference to examples. By way of examples, the scope of the invention is not construed as limiting.

1. 1. Preparation of laminated structure [Examples 1 and 2 and Comparative Examples 1 to 3]
-Formation of a fluorine-based resin layer A composition for forming a fluorine-based resin layer in which a fluorine-based coating agent 1 (3M, NOVEC 1700) and a fluorine-based coating agent 2 (3M, NOVEC 7100) are mixed in the mass ratio shown in Table 1. 200 μl of the substance was dropped onto a substrate made of an inorganic glass plate (alkali glass, 0.7 mm thick) and spin-coated. The conditions for spin coating were 2000 rpm and 60 seconds. Then, the laminated body was allowed to stand at room temperature for 3 minutes to form a fluorine-based resin layer having a thickness of 100 nm on an inorganic glass plate. The surface of the obtained fluorine-based resin layer was treated with oxygen plasma. The plasma treatment was carried out on a PC300 manufactured by SAMCO with an oxygen gas flow rate of 5 sccm and an electric power of 50 W for 30 seconds. The water contact angle on the surface of the obtained fluorine-based resin layer was measured by the sessile drop method. The water contact angle was measured at 5 points and used as the average value. The results are shown in Table 1.

-Preparation of polyimide substrate (substrate for flexible electronics element) 5.71 g (CHDA) of 1,4-diaminocyclohexane (CHDA) was placed in a 300 mL 5-port separable flask equipped with a thermometer, agitator, nitrogen introduction tube, and dropping funnel. 0.05 mol), 7.11 g (0.05 mol) of 1,4-bis (aminomethyl) cyclohexane (14BAC) and 229.7 g of N, N-dimethylacetamide (DMAc) were added and stirred.

30.9 g (0.1 mol) of bis (3,4-dicarboxyphenyl) ether dianhydride (ODPA) was charged therein, and the reaction vessel was bathed in an oil bath maintained at 120 ° C. for 5 minutes. , It was confirmed that it was rapidly redissolved. After removing the oil bath, the mixture was further stirred at room temperature for 18 hours to obtain a polyamic acid varnish containing polyamic acid. The polyamic acid varnish was dropped onto the above-mentioned fluororesin layer at a rate of 200 μl / cm ² and spin-coated. The conditions for spin coating were 5000 rpm and 60 seconds. Then, the laminate was heated to 270 ° C. at a heating rate of 2 ° C./min in an inert oven and fired at 270 ° C. for 2 hours. As a result, a polyimide substrate having a thickness of 1 μm was formed on the inorganic glass plate.

[Comparative Example 4]
A polyimide substrate was produced in the same manner as in Example 1 except that the polyamic acid varnish was applied onto the inorganic glass plate.

-Evaluation With respect to the obtained laminated structure, the film-forming property of the polyimide substrate and the peelability of the polyimide substrate were evaluated as follows.

(Film film property of polyimide substrate)
Regarding the surface of the polyimide substrate of the obtained laminated structure, whether or not there is a thick film region due to partial aggregation or a region (non-uniform region) where film formation is not possible (extremely thin) due to liquid repelling. It was confirmed visually. Then, the film forming property was evaluated according to the following criteria.
〇: The area of the non-uniform area with respect to the whole was generally less than 10% ×: The area of the non-uniform area with respect to the whole was 10% or more.

(Removability of polyimide substrate)
The polyimide substrate was peeled off from the obtained laminated structure. Specifically, cuts were made with a scalpel on the four sides of the inorganic glass plate of the polyimide substrate on the outer peripheral side. Then, tape was adhered to the four sides to obtain a polyimide substrate having a "square" shape. The peeling was performed while holding the tape by hand or with tweezers. The peelability of the polyimide substrate at this time was evaluated according to the following criteria.
〇: Polyimide film was formed on 90% or more of the “B” -shaped substrate Δ: Polyimide film was formed on 50% or more and less than 90% of the “B” -shaped substrate. ×: The formation area of the polyimide film was less than 50% of the “square” -shaped substrate due to tearing or remaining on the inorganic glass plate.

As shown in Table 1 above, when the polyimide substrate is formed on a fluorine-based resin layer having a water contact angle of 13 ° or more and 85 ° or less on the surface, the film-forming property of the polyimide substrate and the peelability of the polyimide substrate are formed. Was good (Examples 1 and 2). On the other hand, when the water contact angle of the fluorine-based resin layer exceeds 85 °, the film-forming property of the polyimide substrate deteriorates (Comparative Example 1), and when the water contact angle of the fluorine-based resin layer becomes less than 13 °, the polyimide substrate (Comparative Examples 2 to 4).

[Examples 3 to 5 and Comparative Examples 5 to 6]
-Formation of a fluorine-based resin layer A composition for forming a fluorine-based resin layer in which a fluorine-based coating agent 3 (3M, NOVEC 2702) and a fluorine-based coating agent 4 (3M, NOVEC 7200) are mixed in the mass ratio shown in Table 2. A laminated structure in which a glass substrate, a fluorinated resin layer, and a polyimide substrate (a substrate for a flexible electronics element) were laminated was produced in the same manner as in Example 1 except that a material was used. Table 2 shows the results of evaluating the film-forming property of the polyimide substrate and the peelability of the polyimide substrate for the laminated structure in the same manner as in Example 1. At the same time, Table 2 also shows the evaluation results of the above-mentioned Comparative Example 4 (not including the fluororesin layer) laminated structure.

As shown in Table 2 above, when the polyimide substrate is formed on a fluorine-based resin layer having a water contact angle of 13 ° or more and 85 ° or less on the surface, the film-forming property of the polyimide substrate and the peelability of the polyimide substrate are formed. Was good, and there was no problem in practical use (Examples 3 to 5). On the other hand, when the water contact angle was less than 13 °, the peelability of the polyimide substrate decreased (Comparative Examples 4 to 6).

2. 2. Fabrication of Organic Thin-Film Solar Cell [Example 6]
-Preparation of laminated structure A base material (alkaline glass, 0.7 mm thick) made of an inorganic glass plate was prepared. Then, the inorganic glass plate was subjected to oxygen plasma treatment with a PC300 manufactured by SAMCO for 10 minutes at an oxygen gas flow rate of 5 sccm and an electric power of 300 W. Then, a composition for forming a fluorine-based resin layer in which a fluorine-based coating agent 1 (3M, NOVEC 1700) and a fluorine-based coating agent 2 (3M, NOVEC 7100) were mixed at a mass ratio of 1: 6 was obtained from inorganic glass. 200 μl was dropped onto the plate and spin coated. The conditions for spin coating were 2000 rpm and 60 seconds. Then, the laminated body was allowed to stand at room temperature for 3 minutes to form a fluorine-based resin layer having a thickness of 100 nm on an inorganic glass plate. The surface of the obtained fluorine-based resin layer was subjected to oxygen plasma treatment for 30 seconds with a PC300 manufactured by SAMCO at an oxygen gas flow rate of 5 sccm and an electric power of 50 W. The water contact angle on the surface of the obtained fluorine-based resin layer was 29.0 °. The water contact angle was taken as the average value of the results of measurements at 5 points by the liquid method. Subsequently, a polyimide substrate (thickness 1.3 μm) was produced on the fluorine-based resin layer in the same manner as in Example 1. The physical characteristics of the polyimide substrate are shown in Table 3.

-Preparation of Organic Thin Film Solar Cell An indium tin oxide (ITO) layer was formed by a sputtering method on a polyimide substrate of the above-mentioned laminated structure. The thickness of the ITO layer (first electrode) was 100 nm. The obtained ITO layer was subjected to oxygen plasma treatment for 1 minute with a PC300 manufactured by SAMCO at an oxygen gas flow rate of 5 sccm and an electric power of 300 W.
Subsequently, a solution prepared by dissolving 549 mg of zinc acetate dihydrate and 160 μl of ethanolamine in 5 ml of 2-methoxyethanol was added dropwise onto the ITO layer and spin-coated. The conditions for spin coating were 5000 rpmm and 30 seconds. Then, the laminate was heated to 70 ° C., heated to 180 ° C., held for 30 minutes, and cooled to room temperature to obtain a ZnO layer (electron transport layer).

Next, PNTz4T having a structure represented by the following formula (7) and PC71BM having a structure represented by the following formula (8) were dissolved in o-dichlorobenzene at a mass ratio of 1: 2. The solution was prepared. Then, heat spin coating was performed on the ZnO layer. The conditions for spin coating were 100 ° C., 600 rpm, and 20 seconds. As a result, a photoelectric conversion layer having a thickness of 250 to 300 nm was obtained.

Subsequently, an oxidized MoO _x layer (hole transport layer) and an Ag layer (second electrode) were formed on the photoelectric conversion layer by a vacuum vapor deposition method. The pressure at the time of film formation was set to less than 1 × 10 ^-3 Pa. Further, the film formation rate of molybdenum oxide was 0.1 Å / s or less, and the film formation rate of silver was 1 Å / s or less. The thickness of the MoO ₃ layer was 7.5 nm, and the thickness of the Ag layer was 100 nm. Then, the inorganic glass plate and the fluorine-based resin layer were peeled off from the laminate to obtain an organic thin-film solar cell.

[Comparative Example 7]
Instead of CHDA, 14BAC, ODPA, 20.0 g (0.100 mol) of 4,4'-oxydianiline (ODA) and 21.8 g (0.100 mol) of pyromellitic anhydride (PMDA) were used. A polyamic acid varnish containing polyamic acid was obtained in the same manner as in Example 1 except that the amount of DMAc used was changed to 177.7 g. Then, an organic thin-film solar cell was produced by the same method as in Example 6.

[Comparative Example 8]
An organic thin-film solar cell was produced in the same manner as in Example 6 except that an inorganic glass plate (alkaline glass, thickness 0.7 mm) was used instead of the laminated structure.

[evaluation]
The physical characteristics of the polyimide substrate produced in Example 6, the polyimide substrate used in Comparative Example 7, and the inorganic glass plate used in Comparative Example 8 were evaluated. The results are shown in Table 3.

(Measurement of maximum transmittance at a wavelength of 400 nm ± 5 nm at a thickness of 5 μm)
Using each of the polyamic acid varnishes used in Example 6 and Comparative Example 7, a polyimide substrate having a thickness of 5 μm was prepared by changing only the spin coating conditions.
The light transmittance of the obtained polyimide substrate and the inorganic glass plate used in Comparative Example 8 at a wavelength of 400 nm ± 5 nm was measured with a spectrophotometer (MultiSpec-1500) manufactured by Shimadzu Corporation. Then, the maximum transmittance at a wavelength of 400 nm ± 5 nm at a thickness of 5 μm was calculated.

(L ^* a ^* b ^* b ^* value in the munsell color system at a thickness of 5 μm)
Using each of the polyamic acid varnishes used in Example 6 and Comparative Example 7, a polyimide substrate having a thickness of 5 μm was prepared by changing only the spin coating conditions.
The L ^* a ^* b ^* b ^* values in the color system of the obtained polyimide substrate and the inorganic glass plate used in Comparative Example 8 were set to the transmission mode and the photometric method 8 ° using the Color Cute i type manufactured by Suga Test Instruments Co., Ltd. After calibrating with a white standard plate with di, the measurement was performed. For the inorganic glass plate used in Comparative Example 8, the measured value was converted into the b ^* value when the thickness of the substrate was 5 μm.

(MIT fold resistance)
Using each of the polyamic acid varnishes used in Example 6 and Comparative Example 7, a polyimide substrate having a thickness of 10 μm was prepared by changing only the spin coating conditions.
The obtained polyimide substrate was cut into a shape having a length of about 120 mm and a width of 15 mm to obtain a test piece. This test piece is set in a MIT type folding resistance tester (307 type) manufactured by Yasuda Seiki Seisakusho, and has a radius of curvature of 0.38 mm, a load of 0.5 kg, a bending accuracy of 270 degrees (left and right 135 degrees), and a bending speed of 175 times /. The number of times until it broke was measured under the condition of minutes. The folding resistance of the glass substrate used in Comparative Example 8 could not be measured.
For the folding resistance, a MIT folding resistance tester (manufactured by Yasuda Seiki Seisakusho, type 307) was used, and after fixing one end of the test piece, the other end was gripped and the test piece was bent back and forth. , The number of bends until the test piece broke was measured. The measurement conditions were as follows.
At the time of the test, bending to one side of the test piece was counted as one time. The test was performed three times, and the arithmetic mean value of the three test results was rounded to the nearest double digit as the measurement result of folding resistance. The upper limit of the folding resistance measurement result was set to 1 million times.

(Measurement condition)
Bending radius: R = 0.38mm
Load: 0.5kgf
Bending angle: 270 ° (135 ° left and right)
Bending speed: 175 times / min Number of tests: n = 3

(Measurement of glass transition temperature (Tg))
Using each of the polyamic acid varnishes used in Example 6 and Comparative Example 7, a polyimide substrate having a thickness of 5 μm was prepared by changing only the spin coating conditions.
The obtained polyimide substrate was cut into a width of 4 mm and a length of 20 mm. This was measured with a thermal analyzer (TMA-50) manufactured by Shimadzu Corporation.

(Measurement of surface roughness (Ra))
The surface roughness (Ra) of the polyimide substrate used in Example 6 and the inorganic glass plate used in Comparative Example 8 was measured by AFM (NanoNavi IIs Nanocute manufactured by SII).

(Standardized photoelectric conversion efficiency (PCE))
The thin-film solar cells (active region 0.04 cm ² ) produced in Example 6 and Comparative Example 8 were irradiated with light under AM 1.5 G conditions with a solar simulator at an irradiation intensity of 1000 W / m ² , and under atmospheric pressure, Caseley Co., Ltd. The current-voltage characteristics were measured with a 2400 source meter manufactured by Japan. The normalized photoelectric conversion efficiency (PCE) was measured from the obtained current-voltage curve.

As shown in Table 3, the maximum transmittance at a wavelength of 400 nm ± 5 nm at a thickness of 5 μm is 70% or more, the L ^* a ^* b ^* color system b ^* value at a thickness of 5 μm is 5 or less, and The organic thin-film solar cell manufactured by using a polyimide substrate having a glass transition temperature of 200 ° C. or higher and a surface roughness (Ra) of 5 nm or less is different from that of an organic thin-film solar cell using a glass substrate (Comparative Example 8). The same standardized photoelectric conversion efficiency (PCE) could be realized (Example 6). It is presumed that the polyimide substrate for the organic thin-film solar cell not only has high light transmittance, but also has heat resistance and has a small surface roughness, so that short circuits and the like are unlikely to occur. In addition, the polyimide substrate had sufficiently high MIT folding resistance and sufficient flexibility.

On the other hand, when an organic thin-film solar cell is manufactured using a polyimide substrate whose maximum transmittance and b ^* value do not satisfy the above specifications, the light transmittance is low and sufficient photoelectric conversion efficiency can be obtained. There was no (Comparative Example 7). On the other hand, in an organic thin-film solar cell using a glass substrate, it was possible to obtain sufficient photoelectric conversion efficiency, but the flexibility was low (Comparative Example 8).

The substrate for an organic thin-film solar cell of the present invention has high light transmission, flexibility, and low surface roughness. Therefore, it can be applied to various organic thin film solar cells. Further, the laminated structure of the present invention can easily peel off the substrate for the flexible electronic device. Therefore, it can be used for manufacturing various flexible electronic devices.

Claims (5)

The base material and the substrate for flexible electronic devices are laminated via a fluorine-based resin layer.
The water contact angle on the surface of the fluororesin layer is 13 ° or more and 85 ° or less.
The substrate for a flexible electronic device satisfies all of the following (1) to (6).
Laminated structure.
(1) The maximum transmittance at a wavelength of 400 ± 5 nm at a thickness of 5 μm is 70% or more. (2) The L ^* a ^* b ^* color system b ^* value at a thickness of 5 μm is 5 or less. (3) JIS The number of fold resistance in the MIT fold resistance test at a thickness of 10 μm measured according to P8115 is 10,000 or more. (4) The glass transition temperature is 200 ° C or more. (5) The thickness is 0. .5 to 5 μm (6) The surface roughness (Ra) of at least one surface is 5 nm or less. The substrate for a flexible electronic device includes a polyimide having a repeating structural unit represented by the following general formula (3) or a repeating structural unit represented by the following general formula (4).
The laminated structure according to claim 1 .

(In the above general formula (3), R ₁ represents a divalent group having 4 to 15 carbon atoms or a divalent linear aliphatic group having 5 to 12 carbon atoms including an alicyclic hydrocarbon structure. Y ₁ represents a tetravalent group having 6 to 27 carbon atoms including an aromatic ring)

(In the above general formula (4), R ₂ represents a divalent group having 6 to 27 carbon atoms including an aromatic ring, and Y ₂ is a tetravalent group having 4 to 12 carbon atoms including an alicyclic hydrocarbon structure. Represents a group) R ₁ of the structural unit represented by the general formula (3) is

It is a divalent group of at least one selected from the group consisting of
Y ₁ of the structural unit represented by the general formula (3) is

It is a tetravalent group of at least one selected from the group consisting of
R ₂ of the structural unit represented by the general formula (4) is

(X ₁ to X ₃ are independent of each other,

Represents a single bond or divalent group selected from the group consisting of
It is at least one kind of divalent group selected from the group consisting of
Y ₂ of the structural unit represented by the general formula (4) is

At least one tetravalent group selected from the group consisting of,
The laminated structure according to claim 2 . The method for manufacturing a laminated structure according to any one of claims 1 to 3 .
The process of forming a fluororesin layer on the substrate and
The process of forming a substrate for flexible electronic devices on a fluorine-based resin layer,
Including
The water contact angle on the surface of the fluororesin layer is 13 ° or more and 85 ° or less.
A method for manufacturing a laminated structure. A step of forming an electronic device portion on a flexible electronic device substrate of the laminated structure according to any one of claims 1 to 3 .
After forming the electronic element portion, a step of peeling the fluorine-based resin layer and the base material from the substrate for the flexible electronic element, and
A method for manufacturing a flexible electronic device.