JPS62134980A - Mother plate for solar battery substrate and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide sufficient insulation in case of depositing an amorphous silicon when a solar battery substrate is formed and to prevent the silicon from separating by forming a thin layer made of nonconductive fine particles and nonconductive filler at least on one side surface of a stainless steel thin plate having 0.5mm or less thick manufactured by cold rolling. CONSTITUTION:Nonconductive fine particles such as metal oxide, metal carbide or metal nitride such as Al2O3, SiO2, SiC, or AlN having 0.1-1mum of particle diameter and metal organic compound such as naphthene acid metal salt of zinc or titanium or alkoxide having preferable wettability with the fine particles are mixed so that the volumetric ratio of the fine particles in the final insulating film becomes 20-80%, sufficiently mixed and the surface of a stainless steel thin plate having 0.5mm or less thick having less fine surface scratches sufficiently managed at rolling time is coated with the mixture as powder state or as suspension solution by alcohol such as butyl alcohol. After drying, the stainless steel thin plate covered with the insulating film is baked at 400-900 deg.C to complete the manufacture of a mother plate for a solar battery substrate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a mother plate for a solar cell substrate and a method for manufacturing the same;
In particular, the present invention relates to a mother plate for a substrate having excellent compatibility with an amorphous layer provided on the light-receiving surface of a solar cell, and a method for producing the same at low cost, and is utilized in the field of solar cell manufacturing.

[Conventional technology]

The solar cell has 01 on the substrate which serves as its mechanical support.
An amorphous silicon layer of ~1 μm L'J is formed. Since the thickness of this amorphous layer is very thin,
Since the reliability of battery manufacturing and the conversion efficiency of sunlight into electrical energy, which is a characteristic of the battery, are strongly influenced by the substrate material, the selection of the substrate material is extremely important as well as economical, which is strongly related to the manufacturing method. This is a serious problem.

Glass-based materials, which have been conventionally used as substrate materials, have the advantage that the substrate itself is transparent and can also protect the battery surface, but the disadvantage is that it is easily damaged, which is the fate of glass. In addition to this, quartz glass, which is free from alkali, is expensive, and there is a problem in that it is not possible to use a roll-to-roll method that is highly mass-producible when manufacturing solar cells.

On the other hand, stainless steel has high mechanical strength and is strong, so it is possible to use a thin plate with a thickness of about 0.8+m, and its flexibility makes it possible to mass-produce it using coiled material. Furthermore, since the amorphous layer is thin, it has excellent properties as a material, such as being able to be arranged in a curved shape as a solar cell if the substrate material has sufficient flexibility.

However, the surface of normally rolled stainless steel sheets has many defects such as oil pits and scratches that occur during rolling. In addition, it is likely that the formation will be non-uniform, and electrical short circuits will occur around these defects, leading to the cell not functioning as a battery. Therefore, when using conventional stainless steel plates as substrate materials for solar cells, generally #1000~
Currently, the method is to perform abrasive polishing in several stages up to about #1500, and then further electrolytic polishing to remove surface flaws that occur during processes such as rolling and achieve a mirror finish.

However, in the Fif@ method as described above, the process operation is complicated and the processing takes a long time, resulting in high processing costs.
Even if the raw material price of stainless steel plate is relatively cheap, the final price is extremely high. Furthermore, with this polishing method, it is difficult to manufacture large-area substrate materials, especially the coiled substrate materials required for roll-to-roll manufacturing, which is considered to be advantageous as a mass production method for solar cells. production becomes even more difficult.

On the other hand, in recent years amorphous silicon thick t1M 74t
Rapid increases in Lb production are demanding thinner, more flexible, and lower cost stainless steel substrates.
Cost reduction cannot be expected by conventionally manufacturing substrates by polishing. In order for solar cells to become popular as a means of generating electricity on par with existing power generation methods, it is necessary to significantly reduce power generation costs compared to the current situation, and for this purpose, substrate materials that are inexpensive and have excellent material properties are required. There is.

In view of the above circumstances, a new proposal for surface polishing of stainless steel plates has recently been disclosed in Japanese Patent Laid-Open No. 5.5mm71077. This method combines conventional mechanical polishing by abrasive grain abrasion and anodic dissolution of the base surface of the substrate by electrolytic action using a neutral salt aqueous solution as an electrolyte and simultaneously performs the mirror polishing of the substrate surface. be. However, although this method is said to be able to significantly shorten operation time, its purpose is not to go beyond the conventional method, and it does not only reduce the yield due to the melting of the stainless steel itself, but also increases processing costs. is still at a high level and is far from an essential solution to significantly reduce costs.

Furthermore, as a recent trend, most amorphous silicon solar cells are used in consumer devices that require a voltage output of several volts, and as a result, substrate materials with non-conductive surfaces are required. Flexible solar cells use a substrate material made of a stainless steel plate with a heat-resistant organic film formed thereon.

Furthermore, recent publications have reported that it is possible to produce smooth, flexible, and insulating substrates by applying a glass coating such as a wax coating to the surface of a stainless steel plate. .

However, in the former method, since the insulating film is an organic material, there is a drawback that gas is easily released from the organic insulating film due to heating during vapor deposition of amorphous silicon on the substrate. On the other hand, in the case of the latter, since it is an enamel coating on a stainless steel plate, it is naturally higher than that of ordinary steel.
It is believed that a firing temperature of ℃ is required, and as a result, the stainless steel itself undergoes annealing and softening, and as a result, substrate materials using thin stainless steel sheets of 0.2 os or less are extremely prone to surface bending and are difficult to handle. . As a result, the substrate material needs to have a thickness of 0.2 mm or more, which is disadvantageous in terms of weight reduction. In addition, since pinholes are likely to occur in crawling wax, the film thickness will be several tens of micrometers at most, and when using a thin stainless steel substrate, the negative part of the crawling wax and the substrate material may be too thin. ? There is a drawback that residual stress is generated due to the difference in AItl elongation, resulting in deformation.

[Problem that the invention seeks to solve]

The object of the present invention is to overcome the drawbacks of the above-mentioned conventional technology of solar cell substrates made of stainless steel plates having an insulating film, to have a thinner inorganic insulating film than the conventional method, with less softening of the base plate due to film treatment, Another object of the present invention is to provide a mother plate for a solar cell substrate in which microscopic flaws on the surface of stainless steel are effectively filled, and a method for manufacturing the same.

[Means for solving problems]

The main points of the motherboard for a substrate and the manufacturing method thereof of the present invention are as follows.

First, the gist of the first invention of the motherboard for a substrate is as follows. That is, at least one side of four thin stainless steel plates having a thickness of 0.5 mm or less produced by cold rolling is filled with non-conductive fine particles and a non-conductive filler filling between the fine particles and between the fine particles and the thin stainless steel plate. This is a mother plate for a solar cell substrate, characterized in that it has a thin layer consisting of.

Next, the gist of the second invention regarding the method for manufacturing the motherboard for a substrate is as follows. That is, a mixture of non-conductive fine particles and a non-conductive filler material having good wettability is powdered on at least one side of a thin stainless steel plate A having a thickness of 0.5 NW or less produced by cold rolling. After applying in form or solution form and drying,
This is a method for manufacturing a mother plate for a solar cell substrate, which is characterized by firing at a temperature range of 00 to 900°C.

The details of the present invention and reasons for limitations will be explained. First, the substrate material to which the present invention is applied is limited to stainless steel plates. This is because stainless steel plates are the most suitable material for solar cell substrates because they are relatively inexpensive, flexible, and can be mass-produced. The steel type is not particularly limited and can be arbitrarily selected from all stainless steel types that have corrosion resistance that can withstand the service life of a solar cell.

Next, the thickness of the stainless steel plate is limited to 0.5+n+a or less. This is to obtain sufficient flexibility after manufacturing the solar cell, and if the thickness exceeds 0.5 mm, it will not be possible to obtain satisfactory flexibility due to rigidity.

These 1JtR plates are used as rolled or after being subjected to heat treatment such as stress relief annealing or high temperature annealing if necessary, but one of the most important requirements is that they are particularly lightweight and flexible. In particular, when using a thin stainless steel plate with a thickness of 0.2 m+a or less, it is desirable to use a material with high strength as rolled to facilitate handling. The insulating film formed on the surface of these thin stainless steel sheets according to the present invention is characterized by being composed of non-conductive fine particles and a non-conductive substance filling the fine voids between the fine particles and between the fine particles and the surface of the thin stainless steel sheet. be. In the present invention, the term "non-conductive" specifically means a resistivity of 10 5 Ω or more. However, as fine particles, the particle size is 0.1
~1 pm of AIO, SiO.

Stable inorganic substances such as metal oxides, metal carbides, and metal nitrides such as SiC and AIN are preferable, and organic substances or inorganic substances that are easily thermally decomposed are unsuitable.

On the other hand, as a non-conductive filler, it is desirable that it has good wettability with the above-mentioned fine particles, and metal oxides such as zinc oxide and titanium oxide, which are thermal decomposition products of metal organic compounds such as metal salts of naphthenic acid or alkoxides, are preferable. Things are preferable.

Surface defects such as minute scratches on the surface of stainless steel substrates can be effectively removed by an insulating film made of such non-conductive fine particles and a non-conductive filling substance that fills between these fine particles and between the fine particles and the stainless steel thin steel plate. This has the effect of making the insulation film thinner than in the case of only a filling material without fine particles.

The thickness of the insulating film formed on the surface of the stainless thin steel plate according to the present invention is preferably 05 to 20 μm. The reason for this is that when using thin stainless steel sheets that are manufactured under sufficient control and have few surface flaws, the thickness of the insulating film is 0.5 μm.
If there is, it is sufficient to fill in minute defects, and in this case, extremely good flexibility can be obtained, and shape defects such as warping will not occur even during firing during manufacturing. However, if the thickness exceeds 20 μm, it is not only difficult to form an insulating film with a uniform thickness during firing, but also there is a drawback that flexibility is impaired.

Further, in order to obtain a good insulating film, it is desirable that the volume ratio occupied by fine particles in the film is 20 to 80%. This is stainless steel 81M when the volume ratio of fine particles is less than 20%.
It is less effective in filling surface defects on the board, and if it exceeds 80%, the volume ratio of the non-conductive filling material becomes less than 20%, reducing the filling effect, resulting in pinholes etc. This is because amorphous silicon cannot be deposited on the base plate.

Next, a method for manufacturing a mother plate for a solar cell substrate according to the present invention will be explained.

Plate thickness 0.0 with few fine surface defects that are well controlled during one rolling.
A grain size of 0.1 is applied to the surface of a thin stainless steel plate of 5+ma or less.
Non-conductive fine particles such as metal oxides, metal carbides, metal nitrides, etc. of ~1 μn AjO1SiO, SiC, AjN, etc., and naphthenic acid metal salts or alkoxides such as zinc and titanium that have good wettability with these fine particles. The volume ratio of fine particles in the final insulation film is 20 to 80.
%, and after thorough mixing, apply as is in powder form or as a suspension solution in alcohol such as butyl alcohol. After coating the film to a sufficiently uniform thickness, it is dried at a temperature of about 200°C. After drying, the stainless thin steel plate coated with an insulating film is
It is fired at a temperature of 0° C. to form an insulating film with a thickness of 05 to 20 μm.

The reason why the firing temperature was limited to a range of 400 to 900°C is as follows. That is, when forming an amorphous film on a solar cell substrate, the substrate material is generally heated to 200 to 400°C, and if gas is released during this heating, vapor deposition of amorphous silicon becomes impossible.
It is necessary to release even a small amount of gas in advance by firing at a temperature higher than 0.degree. C., and to stabilize the insulating film layer. However, if the firing temperature is excessively high, exceeding 900° C., the stainless steel material may become soft during firing and may cause surface breakage during handling.

By this firing at 400 to 900° C., the production of the substrate motherboard of the present invention is completed.

〔Example〕

Example 1 A cold-rolled SUS 304 thin stainless steel plate (hereinafter referred to as the mother plate) with a thickness of 0.15 mm was used, and fine alumina powder with a particle size of 0.02 to 02 μm as shown in Table 1 was coated on one surface of the plate. and zinc oxide filler, the volume ratio of fine particles was varied from 13% to 93%, and the thickness of the final insulating film was 0.2%.
After forming various films varying in thickness from 5 to 1.0 μm, a carbon electrode was deposited on the skin surface of each sample material, and a conductivity test was conducted between the carbon electrode and each mother plate, as well as an insulation test of the film. We conducted a vapor deposition test of amorphous silicon using glow discharge.

Table 1 The insulating coatings of each of the above sample materials were formed in the following steps. That is, first, a required amount of alumina powder with a particle size of 0.02 to 02 μm was mixed, and a 20% butanol solution of zinc naphthenate was applied to the stainless steel mother plate, dried at 200°C, and then fired at 600°C. It is something. Therefore, the volume ratio of alumina powder in the film was changed by changing the alumina content in the coating solution, and the film thickness obtained by one film treatment in the whole process was approximately 0.25μm, so this was done multiple times. By repeating the process several times, the thickness was varied from 0.25 to 10 μm.

As is clear from Table 1, the volume ratio of fine alumina powder in the insulation film made of fine alumina powder and zinc oxide is as small as 13%, or the insulation film is extremely thin at 0.25 μm. In .2.3.4, since the effect of covering minute flaws existing on the mother plate surface is small, insulation failure occurs in the flaw area with sharp unevenness, and therefore amorphous silicon (a-3i) and vapor deposited film peel off. will occur.

However, when the volume ratio of alumina powder is 21 to 77%, the film thickness is 0.
In sample material No. 5.6.7.8 with a thickness of 5 to 10 μm, the insulation properties were good (l), and the a-3i vapor deposited film was also good.

However, in sample No. 9.10, in which the volume ratio of alumina powder is excessively large at 93%, the film thickness is 05 to 10 μm due to insufficient zinc oxide as a filler, and although the insulation properties are good, The gap between the alumina powder could not be filled with zinc oxide, and the a-Si vapor deposition became porous, resulting in peeling.

Therefore, in the present invention, the volume ratio of the non-conductive fine powder is limited to 20 to 80% in the final insulating film, and the thickness of the insulating film is reduced to 0.
It was limited to 5 μm or more.

In addition, the hardness of the mother plate after the film treatment that satisfies the limiting requirements of the present invention for sample material No. 5.6.7.8 is 340 Hv, which is about the same as the Hv 350 before treatment. It turned out that there was no such thing. This is because the enameled stainless steel solar cell substrate, which is known as a conventional method, has a high strength of about 180 Hv due to the softening of the base plate due to the high temperature treatment of about 1000 degrees Celsius. This indicates that there is no risk of surface breakage, etc.

Example 2 A cold-rolled SUS 430 stainless thin steel plate with a thickness of 0.1 m was used, and one surface of the plate was coated with a grain size of 005 to 0.5μ.
m silicon carbide (SiC) and silicon nitride (Si3
N4) fine powder and thallium oxide (Ta, O.

, titanium oxide (TiO3) or barium titanate (
A non-conductive material consisting of Ba2Tie, ) was mixed, an insulating film was formed by the same method as in Example 1, and an insulation test and an a-Si vapor deposition test using glow discharge were similarly conducted. The results are shown in Table 2. Regarding the film formation method, titanium tetrabutoxide (Ti (QC4H,) 4) was used instead of zinc naphthenate in Example 1.
Alternatively, a thermal decomposition product of naphthenic acid salts of Ta and Ba is used, and a suspension solution of the above-mentioned fine powder is applied to a stainless steel base plate, and then dried at 200°C and fired at 600°C. The film thickness was adjusted using the same method as in Example 1.

As is clear from Table 2, all of the sample materials No. 41 to 10 were manufactured using a manufacturing method that satisfies the requirements of the present invention. Good results were obtained in the vapor deposition test.

Table 2 [Effects of the Invention] As is clear from the above examples, the mother plate for a solar cell substrate according to the present invention has non-conductive fine particles on one or both sides of a thin stainless steel plate having a thickness of 0.5+nm or less, and the amount of the fine particles. It is characterized by having an insulating thin layer made of a non-conductive filler filling between the fine particles and the thin stainless steel plate, and when manufacturing the fine particles, a mixture of the fine particles and the filler is prepared in the form of a powder or a solution. By applying this to the surface of a thin stainless steel plate, drying it, and then firing it at a temperature in the range of 400 to 900°C, we were able to achieve the following effects.

(a) The absolute thin layer formed on the surface of the thin stainless steel plate according to the present invention fills minute defects on the surface of the thin stainless steel plate,
In addition, since it is completely adhered, it has sufficient insulation properties even during amorphous silicon deposition during the formation of a solar cell substrate, and there is no possibility of peeling.

(b) The hardness of the stainless steel base plate after the insulation coating treatment according to the present invention is 340 to 350 Hv, which is almost the same as before the treatment, so it is 01 to 0.15+n+
Even if ++ II4 steel plate is used, defects such as surface bending will not occur.

(c) Since the insulating film layer according to the present invention is extremely thin at 05 to 20 μm, the base plate as a whole has extremely good flexibility.

(d) Since the manufacturing process of the mother plate for solar cell substrates according to the present invention is short and simple, it can be provided at a significantly lower cost than mirror-finished materials made by conventional polishing methods of stainless thin steel plates.

In the description and examples of the present invention, the thin insulating layer formed on the surface of the thin stainless steel plate has been described only on one side, but it is obvious that it can be formed on both sides as well.

am Hitonakaji Takeo

Claims (5)

[Claims] (1) Non-conductive fine particles on at least one side of a stainless thin steel plate having a thickness of 0.5 mm or less manufactured by cold rolling, and a non-conductive filler filling between the fine particles and between the fine particles and the stainless thin steel plate. A mother plate for a solar cell substrate, characterized in that it has a thin layer consisting of. (2) Powder a mixture of non-conductive fine particles and a non-conductive filler material having good wettability with the fine particles on at least one side of a thin stainless steel plate with a thickness of 0.5 mm or less manufactured by cold rolling. 1. A method for producing a mother plate for a solar cell substrate, which comprises coating the base plate in a form or a solution, drying it, and then baking it in a temperature range of 400 to 900°C. (3) The volume ratio of the non-conductive fine particles and the filler material in the insulating film is 20 to 80%, and the film thickness is 0.5 to 20 μm. A mother plate for a solar cell substrate as described in . (4) The non-conductive fine particles are metal oxides such as aluminum oxide, silicon oxide, silicon carbide, aluminum nitride,
The method for manufacturing a mother plate for a solar cell substrate according to claim 2, wherein the mother plate is a metal carbide or a metal nitride. (5) The solar cell substrate according to claim 2, wherein the non-conductive filling material is a metal oxide such as zinc oxide or titanium oxide, which is a metal salt of naphthenic acid or a thermal decomposition product of a metal organic compound. Method of manufacturing motherboard for use.