JP2000012880A - Substrate for solar cells - Google Patents

Abstract

PROBLEM TO BE SOLVED: To meet all the heat resistance, light confining effect, electric insulation, strength and workability by providing a solar cell mounting substrate having specified heat-resistive adhesive between a metal plate and specified heat-resistive film. SOLUTION: A metal plate and heat-resistive adhesive which has a heat absorption factor of 0-20% at 200 deg.C, an absorption factor of 1% or less after leaving at a humidity of 75% and temp. of 50 deg.C for 24 hrs. and a mass reduction ratio of less than 2% after leaving between heat-resistive films in air at 200 deg.C for 5 hrs. whereby a heat substrate durable to the temp. at forming a semiconductor can be obtd., the heat-resistive resin film uses a heat-resistive resin film having irregularities at one surface and its smooth surface is used as an adhesive surface, thereby providing a superior light confining effect. The metal plate and heat-resistive resin film are adhered with the heat-resistive adhesive and hence it is superior in the strength and workability.

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, and more particularly, to an amorphous silicon thin film solar cell in which a photoelectric conversion layer for generating photovoltaic power is formed of an amorphous or microcrystalline silicon thin film. It belongs to the technical field related to the substrate used for.

[0002]

2. Description of the Related Art An amorphous silicon type thin film solar cell has a photovoltaic power generation layer composed of an electrode, an amorphous silicon semiconductor film and the like. The core of the amorphous silicon semiconductor film is
JP-A-52-16990, JP-A-56-104477, and plasma glow discharge method disclosed in JP-A-56-104433, sputter deposition method, ion plating method, etc. It is. It is known that a silicon semiconductor film formed by these methods is usually made of amorphous silicon containing 10 to 30 atomic% of hydrogen or microcrystalline silicon having a crystal grain size of 100 mm or less. Since the light absorption coefficient of the semiconductor film in the visible light region is larger than that of single crystal silicon by one digit or more, it is considered that the film thickness is preferably controlled to 3 μm or less in order to effectively absorb and utilize sunlight. ing.

A substrate for a solar cell using such an amorphous silicon semiconductor film is absolutely required to have electrical insulation properties and heat resistance that can withstand the temperature at which the semiconductor film is formed. Conversely, if the substrate satisfies these two conditions,
An amorphous silicon thin film solar cell can be formed on the substrate. A representative material satisfying these two conditions is glass, and a glass substrate is widely used as a substrate for an amorphous silicon thin film solar cell. However, solar cells using glass substrates have poor flexibility,
There is a drawback that installation restrictions are large and workability is lacking.

A heat-resistant resin typified by polyimide also has electrical insulation properties and heat resistance enough to withstand the temperature at which a semiconductor film is formed, and therefore can be used as a substrate for an amorphous silicon thin-film solar cell. An arbitrarily bendable amorphous silicon solar cell that is used is described in Japanese Patent Application Laid-Open No. 2-181975. In this method, since an amorphous silicon semiconductor film is formed on a polyimide resin film, it can be bent arbitrarily, but has a disadvantage that the strength as a structural material is insufficient.

As a substrate having both electrical insulation and heat resistance enough to withstand the temperature at the time of forming a semiconductor film and having good workability and strength, a material obtained by adding a heat-resistant insulator to a metal plate is considered. Can be Actually, a substrate in which a metal plate is provided with a coating layer made of polyimide is described in JP-A-62-101430. However, when such a substrate is used, there is a problem that the "light confinement effect" having a close connection with the power generation efficiency of the solar cell cannot be sufficiently obtained for the following reasons.

In an amorphous silicon thin film solar cell using a glass substrate, sunlight passes through the substrate and then enters the amorphous silicon thin film to perform photoelectric exchange. The power generation efficiency is improved as the amount of interaction of the elements increases. To this end, it is effective to increase the so-called “light confinement effect” by giving the interface a shape that causes the scattering of sunlight at the interface between the substrate and the amorphous silicon thin film. For this purpose, it is necessary to provide irregularities of 0.1 to 0.3 μm on the surface of the glass substrate.
-503615. The same applies to the case where a transparent polyimide substrate is used, and it is described in the above-mentioned Japanese Patent Application Laid-Open No. 2-181975 that a minute spherical projection of 0.01 to 1 μm is effective for increasing the light confinement effect.

On the other hand, in an amorphous silicon thin film solar cell using a substrate having a metal plate provided with a heat-resistant insulating material,
Since sunlight cannot pass through the substrate, the sunlight has to enter the amorphous silicon thin film from the surface opposite to the substrate.
The penetrated light is reflected by the metal electrode formed at the interface between the substrate and the amorphous silicon thin film. Therefore, in order to improve the power generation efficiency, it is effective to provide unevenness at the interface between the substrate and the amorphous silicon thin film for the same reason as in the case of providing the unevenness.
However, when unevenness is applied to the resin-coated substrate, a problem occurs in that the resin layer is broken at the time of unevenness processing, causing serious damage to insulation. Therefore, a method of attaching a resin film having an uneven shape to a metal plate using an adhesive is conceivable, but a resin film having heat resistance enough to withstand a temperature of about 200 ° C. when forming a semiconductor film is considered.
No adhesive / metal substrate combination has yet been found. Therefore, it is not possible to provide unevenness or unevenness at the interface between the substrate and the amorphous silicon thin film. Therefore, the “light confinement effect” due to such unevenness is not increased, and the “light confinement effect” is not increased. I can't get enough.

For the above reasons, an amorphous silicon thin film solar cell which satisfies all of heat resistance (heat resistance to withstand the temperature at the time of forming a semiconductor film), electric insulation, light confinement effect, strength and workability. The substrate has not been realized yet.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to provide heat resistance, electrical insulation, and light confinement effects capable of withstanding the temperature at the time of forming a semiconductor film. It is an object of the present invention to provide a solar cell substrate that satisfies all requirements for strength, workability and workability.

[0010]

Means for Solving the Problems In order to achieve the above object, a solar cell substrate according to the present invention is a solar cell substrate according to claims 1 to 3, which has the following structure. Things.

That is, the solar cell substrate according to claim 1 is
A metal plate and a heat-resistant resin film having a heat shrinkage at 200 ° C of 0% or more and 2% or less, a humidity of 75%, and a moisture absorption of 1% or less when left at 50 ° C for 24 hours. And a heat-resistant adhesive layer having a mass reduction rate of 2% or less when held at 200 ° C. for 5 hours in the air. 1st invention).

According to a second aspect of the present invention, in the solar cell substrate, the surface of the heat-resistant resin film on which the solar cell module is formed is formed into a hill-and-valley-like surface shape having a pitch of 5 μm or more and 150 μm or less. The height divided by the pitch is
The solar cell substrate according to claim 1, which is not less than 0.3 (second invention). The solar cell substrate according to claim 3, wherein the metal plate is made of aluminum or an aluminum alloy, and the heat-resistant resin film is made of polyphenylene sulfide resin, polyethylene naphthalate resin, polyethylene terephthalate resin or polyetherimide resin. The solar cell substrate according to claim 1, wherein the heat-resistant adhesive layer is made of a silicone-based resin (third invention).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The solar cell substrate according to the present invention comprises:
For example, it is made in the following form. That is, first, the heat shrinkage at 200 ° C. is 0% or more and 2% or less, the humidity is 75%,
A heat-resistant resin film having a moisture absorption of 1% or less when left at a temperature of 50 ° C. for 24 hours, for example, a heat-resistant resin film made of a polyphenylene sulfide-based resin or the like is prepared. , Eg pitch: 20
μm, height of uneven portion: formed into a surface shape having unevenness of 20 μm. Further, a heat-resistant adhesive having a mass reduction rate of 2% or less when kept at 200 ° C. in air for 5 hours after curing, such as a heat-resistant adhesive made of a silicone resin, and a metal plate such as aluminum Prepare an alloy plate.

Next, the heat-resistant adhesive is applied to the smooth surface (the surface opposite to the surface having irregularities) of the heat-resistant resin film, and the adhesive is bonded to the metal plate. Is held for a time equal to or longer than the required curing time, and the metal plate and the heat-resistant resin film are bonded to each other. In addition, the said heat resistant adhesive becomes a heat resistant adhesive layer after hardening. By doing so, the solar cell substrate according to the present invention can be obtained.

Hereinafter, the operation and effect of the present invention will be mainly described.

For a solar cell, a heat-resistant resin film having an uneven shape is adhered to a metal plate with a heat-resistant adhesive such that the smooth surface of the film (the surface opposite to the surface having the unevenness) is the adhesive surface. Substrates are basically excellent in light confinement effect, electrical insulation, strength, and workability, but as described above, conventional substrates still do not have heat resistance that can withstand the temperature (about 200 ° C) during semiconductor film formation. It has not been found and there is a problem in heat resistance at such a temperature. Therefore, if such a solar cell substrate can be provided with heat resistance that can withstand the temperature during the formation of the semiconductor film, heat resistance that can withstand the temperature during the formation of the semiconductor film,
A solar cell substrate that satisfies all of electrical insulation, light confinement, strength, and workability should be obtained.

Therefore, the present inventors bonded various heat-resistant resin films and metal plates with various heat-resistant adhesives, and formed a heat-resistant adhesive layer between the metal plate and the heat-resistant resin film. A solar cell substrate was prepared, and its characteristics were examined mainly for heat resistance at a temperature at the time of forming a semiconductor film. As a result, the heat-resistant resin film had a heat shrinkage at 200 ° C. of 0% or more and 2% or less, a humidity of 75%, and a temperature of 50%.
Heat-resistant resin film having a moisture absorption of 1% or less when left at 24 ° C. for 24 hours, and as a heat-resistant adhesive, cured at 200 ° C. in air for 5 hours after curing. When a heat-resistant adhesive having a reduction rate of 2% or less is used (the heat-resistant adhesive layer is made to be a heat-resistant adhesive layer having such a mass reduction rate), the obtained solar cell substrate is
We have obtained a new finding that it has heat resistance enough to withstand the temperature at the time of forming a semiconductor film. The present invention has been completed based on such findings.

The details will be described below.

In order for a solar cell substrate having a heat-resistant adhesive layer between a metal plate and a heat-resistant resin film to have heat resistance that can withstand the temperature at the time of forming a semiconductor film,
The heat-resistant resin film needs to have a positive heat shrinkage. It is a property of expanding by heating, that is, after bonding a heat-resistant resin film having a negative heat shrinkage rate to a metal plate, when heated, wrinkles are concentrated at the center of the bonding surface of the film and peeling occurs, As a result, many blisters are generated on the film, and it is practically impossible to form a semiconductor film on such a solar cell substrate. That is, the solar cell substrate in which the heat-resistant resin film is peeled and blisters are generated by heating, the heat-resistant resin film is peeled and blisters are generated by the heating in forming the semiconductor film, and the condition is poor.

When the heat-resistant resin film has a positive heat shrinkage, the film shrinks by heating.
Peeling from the bonding surface can only occur at the edge of the bonding surface. In order to suppress the peeling at the end, it is necessary that the heat shrinkage of the heat-resistant resin film is smaller than a certain size.

Further, it is necessary that the heat-resistant resin film has a low moisture absorption. That is, a typical heat-resistant resin is a polyimide resin, but generally, the polyimide resin has a property of easily absorbing moisture, that is, a hygroscopic property. When a film made of a heat-resistant resin having such properties is bonded to a metal plate and then heated, steam generated by heating is concentrated at the center of the bonding surface, and as a result, many blisters are generated in the film, It is practically impossible to form a semiconductor film on such a solar cell substrate. On the other hand, when the moisture absorption of the heat-resistant resin film is low, steam hardly occurs due to heating, so that there is no trouble such as blistering of the film, and the adhesiveness does not deteriorate. Therefore, in order to have heat resistance that can withstand the temperature at the time of forming the semiconductor film, the heat-resistant resin film also needs to have a low moisture absorption.

Further, with respect to the heat-resistant adhesive layer, if the weight (mass) reduction rate upon heating is large,
Volatile components generated by thermal decomposition expand between the heat-resistant resin film and the metal plate, and as a result, a large number of blisters are generated on the film, and it is virtually impossible to form a semiconductor film on such a solar cell substrate. Impossible. That is, in such a solar cell substrate, blisters are generated in the heat-resistant resin film due to heating during the formation of the semiconductor film, and the condition is poor. Therefore, in order to have heat resistance that can withstand the temperature at the time of forming the semiconductor film, it is necessary that the above-mentioned heat-resistant adhesive layer has a small mass reduction rate when heated.

In order to prevent swelling of the heat-resistant resin film and peeling at the end of the bonding surface as described above, 3
The two conditions, namely, heat shrinkage and moisture absorption of the heat-resistant resin film, which can prevent blisters from being generated in the heat-resistant resin film by heating during the formation of the semiconductor film and can prevent peeling at the end of the adhesive surface And the mass reduction rate of the heat-resistant adhesive layer during heating was examined. As a result, the heat-resistant resin film should have a heat shrinkage at 200 ° C. of 0% or more and 2% or less, a humidity of 75% and a moisture absorption of 1% or less when left at a temperature of 50 ° C. for 24 hours. It has been found that the heat-resistant adhesive layer needs to have a mass reduction rate of 2% or less when kept in air at 200 ° C. for 5 hours.

The present invention has been completed based on the above findings. The solar cell substrate according to the present invention has a metal plate and a heat shrinkage at 200 ° C. of 0% or more and 2% or less. And a heat-resistant resin film having a moisture absorption of 1% or less when left at a humidity of 75% and a temperature of 50 ° C. for 24 hours.
The heat-resistant adhesive layer has a mass reduction rate of 2% or less when held at 200 ° C. in air for 5 hours. Therefore, the solar cell substrate according to the present invention has heat resistance enough to withstand the temperature during the formation of the semiconductor film.

Here, a heat-resistant resin film having an uneven shape on one side is used as the heat-resistant resin film, and the smooth surface (the surface opposite to the surface having the unevenness) of the film is an adhesive surface. Can be. Then, a solar cell substrate basically having an excellent light confinement effect can be obtained.

Also, the solar cell substrate according to the present invention is basically formed by bonding a metal plate and a heat-resistant resin film with a heat-resistant adhesive layer. Excellent in nature.

Therefore, the solar cell substrate according to the present invention comprises:
The heat resistance, the light confinement effect, the electric insulation, the strength, and the workability that can withstand the temperature at the time of forming the semiconductor film can be satisfied.

In the solar cell substrate according to the present invention, the heat shrinkage rate, the moisture absorption rate, and the mass reduction rate of the heat-resistant adhesive layer of the heat-resistant resin film are set to the above-mentioned ranges.
This is because a solar cell substrate having heat resistance enough to withstand the temperature at which the semiconductor film is formed is formed. Outside of this range, it is difficult to obtain a solar cell substrate having such heat resistance. That is, the heat shrinkage of the heat-resistant resin film at 200 ° C .:
If it is less than 0% (negative heat shrinkage), a large number of blisters are generated on the heat-resistant resin film due to heating during the formation of the semiconductor film, while the heat shrinkage at 200 ° C. exceeds 2%. In such a case, peeling occurs at the end of the bonding surface due to heating during the formation of the semiconductor film. When the moisture absorption of the heat-resistant resin film is more than 1% when left at a humidity of 75% and a temperature of 50 ° C. for 24 hours, blisters are generated on the heat-resistant resin film by heating when forming the semiconductor film. . When the mass reduction rate of the heat-resistant adhesive layer after holding at 200 ° C. for 5 hours in air is more than 2%, blisters are generated in the heat-resistant resin film due to heating at the time of forming the semiconductor film.

[0029] In the solar cell substrate according to the present invention, the surface of the heat-resistant resin film on which the solar cell module is formed is formed into a hill-and-valley-like uneven surface having a pitch of 5 µm or more and 150 µm or less, and the height of the uneven portion Divided by the pitch
If the angle is 0.3 or more (that is, the angle of the convex portion is equal to or less than 118 degrees), the light confinement effect becomes more excellent. Further, the pitch may be 10 μm or more and 150 μm or less, and / or the value divided by the pitch may be 0.5 or more (that is, the angle of the convex portion is 90 degrees or less). Preferably, then, the light confinement effect will be even higher. Here, the solar cell module is configured such that individual photoelectric cells are connected in series or in parallel so that necessary current and voltage can be obtained. The surface of the heat-resistant resin film on which the solar cell module is formed is the surface of the surface of the heat-resistant resin film where the solar cell module is formed. The pitch is a distance between pitches, and the pitch (distance between pitches) is a distance (interval) between convex portions of the concave and convex portions. The angle of the convex portion refers to the internal angle of the convex portion, that is, the angle formed between the inclined portions, and for example, the angle θ as shown in FIGS.
That is.

When the surface of the heat-resistant resin film on which the solar cell module is formed is formed to have the above-mentioned uneven surface shape, the light confinement effect is improved. The reason for this is not yet clear, but generally for the following reasons.

That is, in an amorphous silicon thin film solar cell using a glass substrate, as described above, sunlight passes through the substrate and then enters the amorphous silicon thin film to perform photoelectric exchange. In order to improve the light confinement effect in order to improve the effect, it is effective to give the interface a shape that causes "scattering" of sunlight at the interface between the substrate and the amorphous silicon thin film. In order to scatter light, it is generally known that irregularities smaller than the wavelength of the light are effective.In particular, in the case of an amorphous silicon thin film solar cell using a glass substrate, the wavelength of visible light is 0.4. It is effective that irregularities of 0.1 to 0.3 μm shorter than 0.8 μm are effective.
It is described in JP-A-2-503615.

On the other hand, in an amorphous silicon thin film solar cell using a substrate having a metal plate provided with a heat-resistant insulator, as described above, sunlight cannot pass through the substrate.
The sunlight enters the amorphous silicon thin film from the surface opposite to the substrate and performs photoelectric exchange. The penetrated light is reflected by the metal electrode formed at the interface between the substrate and the amorphous silicon thin film. It is effective to give a shape such that the optical path length increases by reflection or refraction to the interface between the substrate and the amorphous silicon thin film. In other words, it is effective to give the interface a shape that causes `` reflection and irregular reflection '' of light, and the `` reflection and irregular reflection '' of light is different from the `` scattering '' of light. ~ 0.
Although the irregularities of 3 μm are effective in increasing the “scattering” of light, they have no effect of causing “reflection and irregular reflection” of light, and cannot increase this. In order to cause “reflection and irregular reflection” of light, it is considered that the unevenness needs to be equal to or larger than the wavelength of the light.

The inventors of the present invention have made intensive studies based on the above-described concept. As a result, when the size of the unevenness is 5 μm or more and the angle of the convex portion is 118 ° or less, the light confinement effect is excellent. It has been found that when the substrate becomes a solar cell substrate and the size of the unevenness is 10 μm or more and / or the angle of the convex portion is 118 ° or less, the light confinement effect is further improved to a higher level. Such irregularities have the above-mentioned "irregularities causing light reflection and irregular reflection", that is, "shapes such that the optical path length increases due to multiple reflection and refraction inside the amorphous silicon thin film". it is conceivable that.
There is no upper limit to the size of the unevenness (distance between the pitches) from the viewpoint of the light confinement effect. However, if the size is more than 150 μm, it is not preferable in forming an amorphous silicon thin film. It is desirable to set the upper limit of the distance to 150 μm.

Japanese Patent Application Laid-Open No. 8-139347 discloses that an organic polymer resin having an uneven surface is used as a sealing material for a solar cell module to reduce reflected light on the surface of the solar cell module to reduce the number of people in the vicinity. Japanese Patent Application Laid-Open No. 9-55524 describes a method for reducing the discomfort of a solar cell module and a stainless steel substrate as a reinforcing material through a hard film having irregularities. Are described, but in the methods described in these publications, the unevenness formed on the resin film reduces the reflected light as described above or improves the adhesive strength, and the present invention The structure and the function and effect of the unevenness of the solar cell substrate according to the above are essentially different, and the function and effect of enhancing the light confinement effect cannot be exhibited.

In the solar cell substrate according to the present invention, the type of the metal plate is not particularly limited, and for example, aluminum (Al) or an Al alloy can be used. This Al
In the case of using Al and Al alloys, it is possible to obtain a lighter solar cell than in the case of using iron or stainless steel, and it is possible to produce a solar cell at a lower cost than in the case of using a non-ferrous metal other than Al such as magnesium or titanium. There is.

As the heat-resistant resin film, thermal shrinkage at 200 ° C .: 0% or more and 2% or less, humidity 75%, temperature 50 ° C.
It is necessary to satisfy the condition of a moisture absorption rate of 1% or less when left for a while, but the type is not particularly limited as long as the condition is satisfied. As a material that satisfies such conditions, for example, a heat-resistant resin film made of a polyphenylene sulfide resin, a polyethylene naphthalate resin, a polyethylene terephthalate resin, or a polyetherimide resin can be used. When these heat-resistant resin films are used, there is an advantage that industrially easily available and relatively inexpensive solar cell substrates can be manufactured.

The heat-resistant adhesive layer must satisfy a condition of a mass reduction rate of 2% or less when held in air at 200 ° C. for 5 hours. There is no particular limitation. As a material that satisfies such conditions, for example, a heat-resistant adhesive layer made of a silicone resin can be mentioned. The use of this silicone resin has the advantage that it is easily available industrially and a relatively inexpensive solar cell substrate can be produced.

[0038]

EXAMPLES (1) Measurement of heat shrinkage of heat-resistant resin film at 200 ° C. With respect to the heat-resistant resin films shown in Table 1, a 2 cm × 5 cm sample piece was cut out from each film and scratched with a blade at intervals of 4 cm. To make a sign (with a mark of 4 cm distance between marks),
The specimen pre-23 ° C., and after standing for 72 hours in an atmosphere of 55% humidity, it was read distance A ₀ between the labels. Next, this sample piece was placed in a commercially available oven and heated in air at 200 ° C. for 5 hours. Thereafter, the sample piece was taken out, 23 ° C., allowed to stand 72 hours under an air atmosphere of 55% humidity, were read distance A ₁ between the labels. Then, the heat shrinkage at 200 ° C. of the heat-resistant resin film was determined from the formula of 100 × (A ₀ −A ₁ ) / A ₀ = heat shrinkage (%). The heat shrinkage is shown in Table 1.

(2) Moisture absorption of heat resistant resin film (humidity 75
%, Left at a temperature of 50 ° C. for 24 hours) Measurement of the heat-resistant resin films shown in Table 2 (same as the above-mentioned heat-resistant resin films) from each film by 50 mm × 50 mm
The test piece was cut out and dried in a thermostat kept at 50 ° C for 24 hours (under an air atmosphere at 50 ° C).
Allowed to cool in a desiccator, it was measured of the initial weight B _0. Then, the test piece temperature 50 ° C., after standing for 24 hours in a constant temperature and humidity bath kept at humidity of 75% was measured wet weight B _1. From the formula of 100 × (B ₁ −B ₀ ) / B ₀ = moisture absorption (%) of the heat-resistant resin film, the moisture absorption of the heat-resistant resin film when left at a humidity of 75% and a temperature of 50 ° C. for 24 hours. I asked. Table 2 shows the moisture absorption rate.

(3) Weight loss rate of the cured adhesive (in air
(Measurement at 200 ° C. for 5 hours) About 5 mg of the adhesive shown in Table 3 after curing was weighed, and this was used as a sample, and the weight loss rate was measured using a thermobalance (TG8101D, manufactured by Rigaku Denki). Was. That is, the weight C ₀ of the sample at room temperature was measured, and then the heating temperature was set at 200 ° C.
Performs holding for 5 hours in air and weighed C ₁ of the sample. From the formula of 100 × (C ₀ −C ₁ ) / C ₀ = weight loss rate (%), the weight loss rate when the cured adhesive is kept at 200 ° C. for 5 hours in the air is determined. Was. Table 3 shows the weight loss rate.

(4) Process of imparting uneven surface shape to heat-resistant resin film and observation of the shape Using a steel mold having an uneven surface shape on the inner surface of the mold, the various heat-resistant resin films are hot-pressed. Pressing was performed to give an uneven surface shape to one surface of the heat-resistant resin film. Next, the pitch interval and the cross-sectional shape of the irregularities on the film were observed using an optical microscope and a scanning microscope. The results are shown in Tables 8 to 11 below together with the test results of the solar cell substrate.

(5) Production of Solar Cell Substrate A heat-resistant adhesive was applied to the smooth surface (the surface opposite to the surface having the irregularities) of the heat-resistant resin film provided with the irregular surface shape as described above. This was applied and bonded to a metal plate made of a 5052-based aluminum alloy, and then kept in this state at room temperature for 24 hours. By this method, a solar cell substrate was produced.

(6) Heat Resistance Test of Solar Cell Substrate The solar cell substrate thus prepared was placed in a commercial oven and heated at 200 ° C. for 5 hours in air to obtain a heat-resistant resin film. The state of adhesion of the metal plate was visually observed. The results are shown in Tables 4 to 7. "No abnormality" in these tables indicates that no blisters and peeling were observed.

As can be seen from Tables 4 to 7, the substrates for solar cells (Tables 5 and 7) according to the comparative examples have blistering and peeling and are insufficient in heat resistance. The solar cell substrates (Tables 4 and 6) showed no blistering or peeling, and were extremely excellent in heat resistance.

(7) Measurement of Diffuse Reflectance of Solar Cell Substrate Gold (Au) was applied to the surface of the heat-resistant resin film of the solar cell substrate manufactured by the above method using a vacuum evaporation apparatus.
Evaporation was performed to a thickness of 500 mm, and the diffuse reflectance was measured. For this measurement, use a spectrophotometer (UV-24
Using 0), the diffuse reflectance in the wavelength region of 300 nm and 850 nm was determined. The results are shown in Tables 8 to 11. The diffuse reflectance is a characteristic value indicating the degree of reflection and irregular reflection. The larger the diffuse reflectance, the higher the light confinement effect and the higher the power generation efficiency.

As can be seen from Tables 8 to 11, the solar cell substrates according to the comparative examples (Tables 9 and 11) have a low diffuse reflectance at a wavelength region of 300 nm and a low diffuse reflectance at a wavelength region of 850 nm, and have a light confinement effect. Although small, the solar cell substrates (Tables 8 and 10) according to the example of the present invention (second invention) have high diffuse reflectance in the wavelength region of 300 nm and diffuse reflectance in the wavelength region of 850 nm, and have a light confinement effect. Very good.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

[0052]

[Table 6]

[0053]

[Table 7]

[0054]

[Table 8]

[0055]

[Table 9]

[0056]

[Table 10]

[0057]

[Table 11]

[0058]

The solar cell substrate according to the present invention has the above-described structure and functions, and has heat resistance, light confinement effect, electric insulation, and the like that can withstand the temperature at the time of semiconductor film formation. Strength and workability can all be satisfied, and therefore, it can be suitably used as a substrate for various solar cells. A remarkable effect that the use can be expanded can be achieved.

[Brief description of the drawings]

FIG. 1 is a view for explaining an angle of a convex portion of a concave-convex portion formed on the surface of a heat-resistant resin film.

FIG. 2 is a view for explaining an angle of a convex portion of a concave-convex portion formed on the surface of a heat-resistant resin film.

Continued on the front page (72) Inventor Kazuhisa Fujisawa 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo F-term in Kobe Steel, Ltd. Kobe Research Institute 5F051 AA04 AA05 GA02 GA05 GA06 GA11 GA20

Claims (3)

[Claims] 1. A metal sheet having a heat shrinkage at 200 ° C. of 0% or more and 2% or less, a humidity of 75% and a moisture absorption of 1% or less when left at a temperature of 50 ° C. for 24 hours. A solar cell having a heat-resistant adhesive layer having a mass reduction rate of 2% or less when held at 200 ° C. in air for 5 hours between the film and a certain heat-resistant resin film. Substrate. 2. The surface of the heat-resistant resin film on which the solar cell module is formed has a peak-and-valley-like unevenness having a pitch of 5 μm or more and 150 μm or less, and the value obtained by dividing the height of the unevenness by the pitch is as follows. The solar cell substrate according to claim 1, which is 0.3 or more. 3. The heat resistant resin film, wherein the metal plate is made of aluminum or an aluminum alloy, the heat resistant resin film is made of a polyphenylene sulfide resin, a polyethylene naphthalate resin, a polyethylene terephthalate resin or a polyetherimide resin. 3. The solar cell substrate according to claim 1, wherein the agent layer is made of a silicone resin.