JP2001127327A - Solar cell substrate and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible solar cell substrate which has an excellent handleability, and also to provide a method for manufacturing the substrate. SOLUTION: The solar cell substrate includes a film of polyimide having a specific structure unit, a thermal expansion coefficient of -10 to 10 ppm/ deg.C and a Young's modulus of 700 kg/mm2 or more, a metallic electrode formed on the film, an amorphous silicon layer formed on the electrode, and a transparent electrode formed on the amorphous layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell substrate using a polyimide resin having a remarkably low coefficient of thermal expansion as a base, which is flexible, has excellent handleability, and hardly causes curling, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In general, a solar cell as a photovoltaic device which obtains electric power by sunlight or other light energy generally comprises a film-shaped base on which a metal electrode, a silicon layer, a transparent electrode and, if necessary, a protective layer are further provided in order. It is configured by using a laminated substrate.

[0003] As a solar cell substrate base,
Conventionally, stainless steel and glass plates have been mainly used.

However, solar cells based on stainless steel or glass plates cannot be bent,
There was a major drawback in that the handleability was poor because it was easily broken during production or handling.

In recent years, a polyimide film has been studied as a base of a solar cell. However, the polyimide film is light in specific gravity of 1.4 g / cm ³ , is hard to crack, and is easy to bend. On the other hand, the thermal expansion coefficient is 20 to 30 ppm /
Since the temperature is as large as ° C., there is a problem that a large strain is generated between the silicon having a thermal expansion coefficient of 4 ppm / ° C. and curling easily.

[0006]

SUMMARY OF THE INVENTION The present invention has been achieved as a result of studying to solve the problems in the prior art described above.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a solar cell substrate which is flexible, has excellent handleability, and hardly causes curling, and a method of manufacturing the same.

[0008]

In order to achieve the above object, a solar cell substrate of the present invention comprises a polyimide having a structural unit represented by the following general formulas (I) and (II), A metal electrode is formed on the surface of a polyimide film having a coefficient of −10 to 10 ppm / ° C. and a Young's modulus of 700 kg / mm ² or more, an amorphous silicon layer is formed on the metal electrode, and a transparent electrode is further formed on the amorphous silicon layer. It is characterized by having been formed.

[0009]

Embedded image

[0010]

Embedded image Wherein R ₁ and R ₂ are

[0011]

Embedded imageAny one of the groups represented by₁And R_TwoIs the same
It doesn't matter. Also R _ThreeIs an aromatic group having 6 or more carbon atoms
And the molar ratio of X: Y is 100-20: 0-80.
It is.

In the solar cell substrate of the present invention,
R ₂ in the structural unit of the polyimide represented by the general formula (II) is

[0013]

Embedded image Wherein the molar ratio X: Y of each structural unit of the polyimide represented by the general formulas (I) and (II) is in the range of 80 to 50:20 to 50; The polyimide film is reacted with 4,4′-diaminobenzanilide and 95 to 99.9 mol% of an acid dianhydride in an aprotic polar solvent to form an amine-terminated polyamic acid. Further, during the reaction, diamine and acid dianhydride are added to extend the molecular chain, and the resulting polyamic acid is uniformly stretched to obtain a self-supporting gel film. The gel film is formed by stretching the gel film 1.05 to 2.0 times in the film transport direction and in the direction perpendicular to the film transport direction. , And on the transparent electrode, it is a preferred condition that further form a protective layer, by satisfying these conditions can be expected to obtain a more excellent effect.

The method for producing a solar cell substrate according to the present invention comprises reacting 4,4'-diaminobenzanilide with 95 to 99.9 mol% of an acid dianhydride in an aprotic polar solvent. To form a polyamic acid having an amine terminal, furthermore, a diamine and an acid dianhydride are added during the reaction to extend the molecular chain, and the self-supporting property obtained by uniformly extending the obtained polyamic acid. The surface of the polyimide film formed by thermally or chemically dehydrating and ring-closing the gel film in a fixed state, and further stretching the gel film 1.05 to 2.0 times in the film transport direction and in a direction perpendicular thereto. After forming a metal electrode, an amorphous silicon layer is formed on the metal electrode, and a transparent electrode is formed on the amorphous silicon. And forming a protective layer on the transparent electrode as needed.

According to the present invention, by using a polyimide film as the substrate base, the handleability can be greatly improved as compared with a conventional solar cell substrate using a glass or stainless steel plate as the substrate base.
Further, by controlling the coefficient of thermal expansion of the polyimide film to be as small as the coefficient of thermal expansion of the amorphous silicon layer, it is possible to effectively improve the disadvantage that the substrate base is distorted and curled.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a solar cell substrate and a method of manufacturing the same according to the present invention will be described in detail.

The polyimide constituting the substrate base of the solar cell substrate of the present invention is a polyimide having the structural units represented by the above general formulas (I) and (II).

The polyimide film of the present invention is
4,4'-diaminobenzanilide and 95
A polyamic acid having an amine terminal is formed by reacting ９９99.9 mol% of an acid dianhydride in an aprotic polar solvent, and a diamine and an acid dianhydride are added during the reaction to form a molecular chain. Extended, thermally or chemically dehydrated ring closure in a state where the self-supporting gel film obtained by uniformly spreading the obtained polyamic acid is fixed, and further, the gel film is transported in the film transport direction and orthogonal to this. In this case, the film is formed by stretching by 1.05 to 2.0 times in the respective directions. Specific examples of the acid dianhydride used in the above are

[0019]

Embedded image Etc., among others,

[0020]

Embedded image Is preferably used.

Specific examples of the diamine used in the above are

[0022]

Embedded image Etc., among others,

[0023]

Embedded image Is preferably used.

The aprotic polar solvent used in the above examples includes, for example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, and N, N-
Formamide solvents such as dimethylformamide and N, N-diethylformamide; acetamido solvents such as N, N-dimethylacetamide and N, N-diethylacetamide; N-methyl-2-pyrrolidone; N-vinyl-2-
Pyrrolidone solvents such as pyrrolidone, phenol, o
Phenolic solvents such as-, m- or p-cresol, xylenol, halogenated phenol, catechol,
Alternatively, hexamethylphosphoramide, γ-butyrolactone and the like can be mentioned, and it is desirable to use these alone or as a mixture. Further, aromatic hydrocarbons such as xylene and toluene can be used.

Examples of the dehydrating agent used for chemically dehydrating and ring-closing (imidizing) the polyamic acid include, for example, aliphatic acid anhydrides such as acetic anhydride, aromatic acid anhydrides and the like. Examples of the catalyst include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, picoline and isoquinoline.

The above-mentioned polyamic acid forming the polyimide film may contain 3% by weight or less of an inorganic filler or another polyimide.

In obtaining the polyimide film of the present invention, it is important to limit the amount of the acid dianhydride, the extension of the molecular chain, the stretching ratio of the gel film, and the like as described above. If even one is missing, the thermal expansion coefficient is -10 to 10 ppm / ° C and the Young's modulus is 700 kg / mm ²
The above polyimide film cannot be obtained.

That is, in the first stage polymerization,
If the amount of the acid dianhydride added to 4′-diaminobenzanilide is less than 95 mol%, the resulting polyimide film has a Young's modulus of less than 700 kg / mm ² . On the other hand, if it exceeds 99.5 mol%, the viscosity will increase and the amine terminal will decrease.
For this reason, it is difficult to extend the molecular chain, which is not preferable.

Further, the stretching ratio in either the film transport direction of the gel film or the direction perpendicular thereto is 1.0.
If it is less than 5, the Young's modulus does not reach 700 kg / mm ² . On the other hand, if any one of the stretching ratios exceeds 2.0 times, the gel film is apt to be broken, and the productivity is remarkably reduced, which is not preferable.

The polyimide film thus obtained and used as a substrate base in the solar cell substrate of the present invention has a thermal expansion coefficient of -10 to 10 ppm / ° C, preferably -5 to 5 ppm / ° C, and a Young's modulus. 700 kg / mm ² or more,
Preferably, it is important that the Young's modulus is 720 kg / mm ² or more.

The coefficient of thermal expansion of the polyimide film is 10 pp
When the temperature exceeds m / ° C., the difference in thermal expansion coefficient between the silicon layer and the silicon layer becomes large, and it is not preferable because the occurrence of curl cannot be prevented. The thermal expansion coefficient is -10 ppm /
If the temperature is lower than ℃, curling is likely to occur similarly, so that it is not suitable for a solar cell substrate.

Further, even when the polyimide film has a coefficient of thermal expansion of -10 to 10 ppm / ° C., its Young's modulus is 70%.
If it is less than 0 kg / mm ² , curling tends to occur due to stress caused by a slight difference in thermal expansion coefficient from the silicon layer, which is not preferable.

Here, the coefficient of thermal expansion referred to in the present invention is 50
It means an average coefficient of thermal expansion between 200C and 200C, and is a value measured using a thermomechanical analyzer TMA50 manufactured by Shimadzu Corporation. The type of metal of the metal electrode formed on the polyimide in the solar cell substrate of the present invention is not particularly limited, and may be, for example, aluminum, gold, silver, copper, iron, tin, or two or more of these metals Alloys and the like can be exemplified.

The transparent electrode formed on the amorphous silicon layer in the solar cell substrate of the present invention can be exemplified by conductive metals such as an indium-tin oxide, tin oxide and indium oxide.

In the solar cell substrate of the present invention,
A protective layer can be further formed on the transparent electrode if necessary. Specific examples of the protective layer include a fluororesin,
A polymer material having high light transmittance and excellent weather resistance, such as transparent polyimide, may be used.

The solar cell substrate of the present invention thus obtained is flexible and bendable, and does not break during manufacturing or handling. Therefore, not only is the handleability excellent, but the substrate base is not distorted. Demonstrates excellent performance without curling.

According to the method for manufacturing a solar cell substrate of the present invention, a solar cell substrate having the above-mentioned excellent performance can be efficiently manufactured.

[0038]

The present invention will be described more specifically with reference to the following examples.

The characteristics in the examples were measured by the following methods. [Coefficient of thermal expansion] The average coefficient of thermal expansion was measured at 50 ° C to 200 ° C using a thermomechanical analyzer TMA50 manufactured by Shimadzu Corporation. [Young's modulus] Measured using Tensilon RTM-250 manufactured by Orientec. [Handling property] 35mm × 120mm obtained solar cell substrate
Was cut into pieces having a size of, and the feel when this was bent by hand was evaluated, and evaluated according to the following criteria. ○ ・ ・ ・ Bendable and good handling. ×: It is impossible to bend and cracks when it is forcibly bent.

[Curl] A 35 mm × 120 mm sample conditioned for 24 hours was placed on a horizontal table, and the lift from the square table was measured. The average value was taken as the curl value. The curl direction was described as positive when the polyimide film was turned upward, and negative when the polyimide film was turned upward. Example 1 In a 500 ml separable flask equipped with a DC stirrer, 26.66 g of 4,4'-diaminobenzanilide (11
7 mmol), N, N'-dimethylacetamide 213.4
Add 8 g and stir at room temperature under a nitrogen atmosphere. 33.47 g (114 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic acid are added in several portions over 30 minutes to 3 hours. The 3,3 ′, 4,4′-biphenyltetracarboxylic acid attached to the powder funnel is washed into the reaction system using 10 ml of N, N′-dimethylacetamide. After stirring for 1 hour, 17.25 g of a pyromellitic dianhydride N, N'-dimethylacetamide solution (6 wt%) is added dropwise over 30 minutes, and the mixture is further stirred for 1 hour. The polyamic acid obtained here was 4000 poise.

A part of the obtained polyamic acid is taken on a polyester film, and a uniform film is formed using a spin coater. This is a β-picoline / acetic anhydride mixed solution
(50:50) for 5 minutes for imidization. The obtained polyimide gel film was heated at 120 ° C for 20 minutes and at 300 ° C for 20 minutes.
Heat treatment at 400 ° C. for 5 minutes to obtain a polyimide film. The obtained polyimide has a Young's modulus of 825 kg / mm ² ,
Thermal expansion coefficient: 5.8 ppm / ° C. Example 2 17.61 g (7,4'-diaminobenzanilide) was placed in a 500 ml separable flask equipped with a DC stirrer.
7 mmol), N, 'N-dimethylacetamide 183.6
Add 4 g and stir at room temperature under a nitrogen atmosphere. From 30 minutes to 50 minutes later, 2.11 g (75 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic acid is added in several portions. The 3,3 ′, 4,4′-biphenyltetracarboxylic acid attached to the powder funnel is washed into the reaction system using 10 ml of N, N-dimethylacetamide. After stirring for 1 hour, 5.59 g (52 mmol) of p-phenylenediamine
l), 10 ml of N, N'-dimethylacetamide was added,
Further, 14.74 g (50 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic acid is added over 10 minutes. N,
The 3,3 ', 4,4'-biphenyltetracarboxylic acid attached to the powder funnel is washed into the reaction system using 20 ml of N'-dimethylacetamide. After stirring for 12 hours, 19.00 g of a pyromellitic dianhydride N, N'-dimethylacetamide solution (6 wt%) was added dropwise over 30 minutes,
Stir for an additional hour. The polyamic acid obtained here was 3000 poise. A part of the obtained polyamic acid is taken on a polyester film, and a uniform film is formed using a spin coater. This was immersed in a β-picoline / acetic anhydride mixed solution (50:50) for 5 minutes for imidization. The obtained polyimide gel film was heated at 120 ° C. 20
Heat treatment at 300 ° C. for 20 minutes and 400 ° C. for 5 minutes to obtain a polyimide film. The obtained polyimide had a Young's modulus of 797 kg / mm2 and a thermal expansion coefficient of 6.8 ppm / ° C. Example 3 In a 500 ml separable flask equipped with a DC stirrer, 18.47 g (8,4'-diaminobenzanilide) was added.
1 mmol), N, N'-dimethylacetamide 168.8
Add 2 g and stir at room temperature under a nitrogen atmosphere. After 30 to 50 minutes, pyromellitic dianhydride 17.19
g (79 mmol) are charged in several portions. The pyromellitic acid attached to the powder funnel is washed into the reaction system using 10 ml of N, N'-dimethylacetamide. After stirring for 2 hours, 4,4'-diaminodiphenyl ether 10.84
g (54 mmol), N, N'-dimethylacetamide 5 ml
Add. To this, 7.97 g of 3,3 ′, 4,4′-biphenyltetracarboxylic acid (27 mmol is added in several portions. 3,3 ′ attached to the powder funnel using 20 ml of N, N′-dimethylacetamide). ', 4,4'-Biphenyltetracarboxylic acid is washed into the reaction system, stirred for 30 minutes, and 5.55 g (25 mmol) of pyromellitic dianhydride is added in several portions. -Wash the pyromellitic acid attached to the powder funnel into the reaction system using 20 ml of dimethylacetamide.

After stirring for 16 hours, pyromellitic dianhydride N, N'-dimethylacetamide solution (6 wt%) 1
4.77 g is added dropwise over 30 minutes and stirred for another hour. The polyamic acid obtained here was 3000 poise.

A part of the obtained polyamic acid is taken on a polyester film, and a uniform film is formed using a spin coater. This is a β-picoline / acetic anhydride mixed solution
(50:50) for 5 minutes for imidization. The obtained polyimide gel film was heated at 120 ° C for 20 minutes and at 300 ° C for 20 minutes.
Heat treatment at 400 ° C. for 5 minutes to obtain a polyimide film. The obtained polyimide has a Young's modulus of 720 kg / mm ² ,
Thermal expansion coefficient: 1.6 ppm / ° C. A pseudo solar cell substrate was formed by forming a metal electrode made of aluminum and amorphous silicon on the polyimide film by 0.5 μm each by an ion vapor deposition method, and the handling property and the curl were evaluated. Table 1 shows the evaluation results.
It was also described in. Example 4 In a 500 ml separable flask equipped with a DC stirrer, 7.58 g (33 m) of 4,4'-diaminobenzanilide was placed.
mol), N, N'-dimethylacetamide 165.61 g
And stirred at room temperature under a nitrogen atmosphere. 5 after 30 minutes
After 0 minute, 7.05 g of pyromellitic dianhydride (3
2 mmol) in several portions. The pyromellitic acid attached to the powder funnel is washed into the reaction system using 10 ml of N, N-dimethylacetamide. After stirring for 2 hours, 14.42 g (133 mmol) of p-phenylenediamine, N,
10 ml of N'-dimethylacetamide are added. To this, 9.8 of 3,3 ', 4,4'-biphenyltetracarboxylic acid was added.
1 g (33 mmol) is charged in several portions. The 3,3 ', 4,4'-biphenyltetracarboxylic acid attached to the powder funnel is washed into the reaction system using 20 ml of N, N'-dimethylacetamide. After stirring for 30 minutes, 20.94 g (96 mmol) of pyromellitic dianhydride are added in several portions. N, N'-dimethylacetamide 20ml
The pyromellitic acid adhering to the powder funnel is washed into the reaction system by using.

After stirring for 16 hours, pyromellitic dianhydride N, N'-dimethylacetamide solution (6 wt%) 1
8.18 g is added dropwise over 30 minutes, and the mixture is further stirred for 1 hour. The polyamic acid obtained here was 3000 poise.

A part of the obtained polyamic acid is taken on a polyester film, and a uniform film is formed using a spin coater. This is a β-picoline / acetic anhydride mixed solution
(50:50) for 5 minutes for imidization. The obtained polyimide gel film was heated at 120 ° C for 20 minutes and at 300 ° C for 20 minutes.
Heat treatment at 400 ° C. for 5 minutes to obtain a polyimide film. The obtained polyimide has a Young's modulus of 868 kg / mm ² ,
Thermal expansion coefficient: 0.3 ppm / ° C. Example 5 In a 500 ml separable flask equipped with a DC stirrer, 20.11 g (8,4'-diaminobenzanilide) was added.
8 mmol), N, N'-dimethylacetamide 167.5
Add 8 g and stir at room temperature under a nitrogen atmosphere. After 30 minutes to 50 minutes, pyromellitic dianhydride 18.72
g (86 mmol) are charged in several portions. The pyromellitic acid attached to the powder funnel is washed into the reaction system using 10 ml of N, N'-dimethylacetamide. After stirring for 2 hours, 6.38 g (59 mmol) of p-phenylenediamine,
Add 10 ml of N, N'-dimethylacetamide. To this, 8.68 g (29 mmol) of 3,3 ', 4,4'-biphenyltetracarboxylic acid is added in several portions. N,
The 3,3 ', 4,4'-biphenyltetracarboxylic acid attached to the powder funnel is washed into the reaction system using 20 ml of N'-dimethylacetamide. After stirring for 30 minutes, 6.05 g (28 mmol) of pyromellitic dianhydride are added in several portions. N, N'-dimethylacetamide 20m
Use 1 to wash the pyromellitic acid adhered to the powder funnel into the reaction system.

After stirring for 16 hours, pyromellitic dianhydride N, N'-dimethylacetamide solution (6 wt%) 1
6.08 g was added dropwise over 30 minutes, and the mixture was further stirred for 1 hour. The polyamic acid obtained here had 3,400 poise. A part of the obtained polyamic acid is taken on a polyester film, and a uniform film is formed using a spin coater. This was mixed with a β-picoline / acetic anhydride mixed solution (5
(0:50) for 5 minutes for imidization. The obtained polyimide gel film is 120 ° C. for 20 minutes, 300 ° C. for 20 minutes,
Heat treatment was performed at 400 ° C. for 5 minutes to obtain a polyimide film. The obtained polyimide had a Young's modulus of 754 kg / mm ² and a coefficient of thermal expansion of 0.2 ppm / ° C. A pseudo solar cell substrate was formed by forming a metal electrode made of aluminum and amorphous silicon on the polyimide film by 0.5 μm each by an ion vapor deposition method, and the handling property and the curl were evaluated. The evaluation results are also shown in Table 1. Example 6 7.00 g (31 m) of 4,4'-diaminobenzanilide in a 500 ml separable flask equipped with a DC stirrer
mol), N, N'-dimethylacetamide 166.92 g
And stirred at room temperature under a nitrogen atmosphere. 5 after 30 minutes
After 0 minute, 6.51 g of pyromellitic dianhydride (3
0 mmol) in several portions. The pyromellitic acid attached to the powder funnel is washed into the reaction system using 10 ml of N, N'-dimethylacetamide. After stirring for 2 hours,
13.31 g (123 mmol) of p-phenylenediamine,
Add 10 ml of N, N'-dimethylacetamide. 3,3 ', 4,4'-biphenyltetracarboxylic acid 2
7.17 g (92 mmol) are charged in several portions. N,
The 3,3 ', 4,4'-biphenyltetracarboxylic acid attached to the powder funnel is washed into the reaction system using 20 ml of N'-dimethylacetamide. After stirring for 30 minutes, 5.91 g (27 mmol) of pyromellitic dianhydride is added in several portions. N, N'-dimethylacetamide 20m
Use 1 to wash the pyromellitic acid adhered to the powder funnel into the reaction system.

After stirring for 16 hours, pyromellitic dianhydride N, N'-dimethylacetamide solution (6 wt%) 1
6.78 g is added dropwise over 30 minutes, and the mixture is further stirred for 1 hour. The polyamic acid obtained here was 3000 poise.

A part of the obtained polyamic acid is taken on a polyester film, and a uniform film is formed using a spin coater. This is a β-picoline / acetic anhydride mixed solution
(50:50) for 5 minutes for imidization. The obtained polyimide gel film was heated at 120 ° C for 20 minutes and at 300 ° C for 20 minutes.
Heat treatment at 400 ° C. for 5 minutes to obtain a polyimide film. The obtained polyimide has a Young's modulus of 752 kg / mm ² ,
Thermal expansion coefficient: 2.4 ppm / ° C. A pseudo solar cell substrate was formed by forming a metal electrode made of aluminum and amorphous silicon on the polyimide film by 0.5 μm each by an ion vapor deposition method, and the handling property and the curl were evaluated. The evaluation results are also shown in Table 1. Comparative Example 1 In a 500 ml separable flask equipped with a DC stirrer, 31.12 g (155 mmo) of 4,4′-oxydianiline was added.
l), 276.46 g of N, N-dimethylacetamide was added, and the mixture was stirred at room temperature under a nitrogen atmosphere. From 30 minutes to 1 hour, 48.58 g of pyromellitic dianhydride (15
1 mmol) in several portions. The pyromellitic dianhydride adhering to the powder funnel is washed into the reaction system using 20 ml of N, N-dimethylacetamide. After stirring for 12 hours, 25.04 g of a solution of pyromellitic dianhydride N, N-dimethylacetamide (6 wt%) is added dropwise over 30 minutes, and the mixture is further stirred for 1 hour. The polyamic acid obtained here was 3000 poise.

A part of the obtained polyamic acid is taken on a polyester film, and a uniform film is formed using a spin coater. This is a β-picoline / acetic anhydride mixed solution
(50:50) for 5 minutes for imidization. The obtained polyimide gel film was heated at 120 ° C for 20 minutes and at 300 ° C for 20 minutes.
Heat treatment at 400 ° C. for 5 minutes to obtain a polyimide film. The obtained polyimide has a thickness of 50 μm and a Young's modulus:
370 kg / mm ² , linear expansion coefficient: 25 ppm / ° C. A pseudo solar cell substrate was formed by forming a metal electrode made of aluminum and amorphous silicon on the polyimide film by 0.5 μm each by an ion vapor deposition method, and the handling property and the curl were evaluated. The evaluation results are also shown in Table 1. Comparative Example 2 16.37 g (151 mmol) of p-phenylenediamine was placed in a 500 ml separable flask equipped with a DC stirrer.
l), 220.23 g of N, N-dimethylacetamide was added, and the mixture was stirred at room temperature under a nitrogen atmosphere. From 30 minutes to 1 hour later, 44.53 g (151 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride are added in several portions. Using 20 ml of N, N-dimethylacetamide, the pyromellitic dianhydride adhering to the powder funnel is washed into the reaction system. Stir for 12 hours. The polyamic acid obtained here was 3000 poise.

A part of the obtained polyamic acid is taken on a polyester film, and a uniform film is formed using a spin coater. This is a β-picoline / acetic anhydride mixed solution
(50:50) for 5 minutes for imidization. The obtained polyimide gel film was heated at 120 ° C for 20 minutes and at 300 ° C for 20 minutes.
Heat treatment at 400 ° C. for 5 minutes to obtain a polyimide film. The obtained polyimide has a thickness of 50 μm and a Young's modulus:
991kg / mm ^2, linear expansion coefficient: was 15.8ppm / ℃.
A pseudo solar cell substrate was formed by forming a metal electrode made of aluminum and amorphous silicon on the polyimide film by 0.5 μm each by an ion vapor deposition method, and the handling property and the curl were evaluated. The evaluation results are also shown in Table 1. Comparative Example 3 A metal electrode made of aluminum and amorphous silicon were each formed on a glass plate having a thickness of 5 mm by ion deposition to form a metal electrode.
A pseudo solar cell substrate was formed by forming each 5 μm, and the handling property and the curl were evaluated. The evaluation results are also shown in Table 1.

[0051]

[Table 1]

[0052]

As described above, the solar cell substrate of the present invention is flexible and bendable, and does not break during manufacturing or handling. It has excellent performance without curling.

According to the method for manufacturing a solar cell substrate of the present invention, a solar cell substrate having the above-mentioned excellent performance can be efficiently manufactured.

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Claims (6)

[Claims] 1. A compound represented by the following general formulas (I) and (II)
It is made of polyimide having structural units and has a thermal expansion coefficient of-
10 ~ 10ppm / ℃, Young's modulus is 700kg / mm^TwoMore poly
A metal electrode is formed on the surface of the imide film,
An amorphous silicon layer is formed on the
Specially, a transparent electrode was formed on a morphus silicon layer.
Solar cell substrate. Embedded imageEmbedded image[However, in the formula, R₁And R_TwoIsAny one of the groups represented by₁And R_TwoIs the same
It doesn't matter. Also R _ThreeIs an aromatic group having 6 or more carbon atoms
And the molar ratio of X: Y is 100-20: 0-80.
It is. 2. The polyimide represented by the general formula (II)
R in the structural unit _ThreeIs2. A group represented by any one of the following:
A solar cell substrate according to item 1. 3. The polyimide according to claim 1, wherein the molar ratio X: Y of each of the structural units represented by the general formulas (I) and (II) is 80-5.
2. The method according to claim 1, wherein the range is from 0:20 to 50.
Or the solar cell substrate according to 2. 4. The method according to claim 1, wherein the polyimide film is reacted with 4,4′-diaminobenzanilide and 95 to 99.9 mol% of an acid dianhydride in an aprotic polar solvent. A state in which a self-supporting gel film obtained by forming a polyamic acid, further extending a molecular chain by adding a diamine and an acid dianhydride during the reaction, and uniformly extending the obtained polyamic acid is fixed. The ring is thermally or chemically dehydrated, and the gel film is formed by stretching the gel film 1.05 to 2.0 times in the film transport direction and in the direction perpendicular thereto. Claim 1
4. The solar cell substrate according to any one of items 3 to 3. 5. The solar cell substrate according to claim 1, wherein a protective layer is further formed on the transparent electrode. 6. A polyamic acid having an amine terminal is reacted by reacting 4,4'-diaminobenzanilide with 95 to 99.9 mol% of an acid dianhydride in an aprotic polar solvent. Formed and further added diamine and acid dianhydride during the reaction to extend the molecular chain, and to uniformly extend the obtained polyamic acid, heat or chemically fix the self-supporting gel film obtained. The gel film is further dehydrated and closed in a film transport direction and a direction perpendicular to the film transport direction.
After forming a metal electrode on the surface of the polyimide film formed by stretching to 2.0 times, forming an amorphous silicon layer on the metal electrode, forming a transparent electrode on the amorphous silicon, A method for manufacturing a solar cell substrate, comprising forming a protective layer on a transparent electrode as necessary.