JPS62101636A - Surface-protecting material - Google Patents

Abstract

PURPOSE:To obtain a surface-protecting material excellent in abrasion resistance, surface lubricity, scratching resistance, moisture-proofing effect and durability and useful in solar batteries, etc., by forming a cured film of a condensate of a specified organosilicon compound on either of the surfaces of a surface- treated fluorocarbon resin and forming an adhesive layer on the other surface. CONSTITUTION:Both of the surfaces of a 25-300mu-thick fluorocarbon resin film such as a tetrafluoroethylene/hexafluoropropylene copolymer resin are subjected to treatment such as high-frequency sputter-etching. One of the surfaces of this film is coated, if necessary, with a silicone primer film of, e.g., a mixture of an aminosilane and an epoxysilane and then coated with a solution of a mixture of 40-90wt% organotrialkoxysilane, 5-40wt% fluoroalkylalkoxysilane and 3-20wt% diorganopolysiloxane having OH groups on both of the molecular terminals in an organic solvent and formed into a 3-10mu-thick cured film of a condensate of an organosilicone compound by heating at 100-200 deg.C for 5-30min. A 50-300mu-thick hot-melt adhesive layer of, e.g., an ethylene/ethyl acrylate copolymer resin is formed on the other surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface protection material used for protecting the surface of articles such as solar cells.

[Conventional technology]

Conventionally, solar cells are known in which aluminum electrodes, stainless steel electrodes, or the like are laminated with amorphous silicon, a transparent electrode, and a glass plate as a surface protection material in this order. However, surface preservation.

Products that use glass plates as lumber have the disadvantage that they are easily damaged, and the adhesion between the glass plate and the sealant (adhesive) that seals the contacts between the transparent electrode and the conductor is not necessarily sufficient. Therefore, there was a drawback that the moisture resistance of the solar cell was impaired.

In view of these circumstances, the present inventors have previously developed a method in which a hot-melt adhesive layer is formed on the treated surface of a fluororesin film whose surface has been subjected to high-frequency sputter etching treatment as a surface protection material for solar cells. A surface protection material was proposed (Japanese Unexamined Patent Publication No. 73942/1983). According to this surface protection material, the fluororesin film adheres to the transparent electrode with good adhesion due to the adhesive layer firmly attached to the film, so that the sealing property between the film and the transparent electrode is good. Moreover, since the film itself has excellent moisture resistance, it can greatly contribute to improving the moisture resistance of solar cells.

[Problem that the invention seeks to solve]

However, the fluororesin film constituting the above-mentioned surface protection material has the drawback of being easily scratched and abraded due to its low hardness.

For this reason, in addition to deteriorating the appearance, when solar cells are installed outdoors, dirt such as dust in the air accumulates on the surface scratches, and this dirt is not easily washed away by rain, so There was a problem in that the transmission of light rays was obstructed, resulting in a significant decrease in the energy conversion efficiency of the solar cell.

Therefore, the present invention can exhibit the same good moisture-proofing effect as the previously proposed surface protection material, has a high surface hardness, exhibits excellent scratch resistance and abrasion resistance, and is suitable for outdoor use. The purpose of the present invention is to provide a surface protective material with good durability that does not cause deterioration of the surface appearance or extreme decrease in the energy conversion efficiency of solar cells even when subjected to long-term use.

[Means for solving problems]

In order to achieve the above object, the inventors conducted extensive studies and found that, while forming an adhesive layer on one side of the fluororesin film similar to the previously proposed adhesive layer, a specific When a condensation cured film made of an organic silicon compound is formed using a specific method, it not only has the excellent moisture-proofing effect required as a surface protection material for solar cells, but also has scratch resistance sufficient to withstand outdoor use. It was discovered that a surface protective material with high surface hardness and excellent abrasion resistance could be obtained, leading to the creation of this invention.

That is, in this invention, on one side of a fluororesin film that has been surface-treated on both sides, an organotrialkoxysilane, a fluoroalkylalkoxysilane, and a diorganopolysiloxane having water 66 and B at both molecular ends are used. The present invention relates to a surface protection material formed by forming a condensation cured film of an organic silicon compound and forming an adhesive layer on the other side.

[Structure and operation of the invention]

Examples of the fluororesin film used in this invention include tetrafluoroethylene-hegisafluoropropylene copolymer resin, ethylene-tetrafluoroethylene copolymer resin, and ethylene-hexafluoropropylene copolymer resin.

These fluororesin films have excellent properties such as moisture resistance, and are therefore suitably used as surface protection materials for articles that require a high degree of moisture resistance, such as solar cells.

The thickness of the fluororesin film is 25 to 300 μm.
is appropriate.

Such a fluororesin film has low surface energy and poor adhesion, so even if a condensation cured film of an organic silicon compound or an adhesive layer is directly formed on the surface of the film, good adhesion cannot be obtained.

Therefore, in order to increase the adhesive strength of the adhesive layer to improve moisture resistance, and to increase the adhesive strength of the condensation cured coating to exhibit the scratch resistance and abrasion resistance inherent to this coating,
It is necessary to perform appropriate surface treatment on both sides of the film in advance.

As the surface treatment method, any of the above methods can be used, but it is preferable to use high frequency sputter etching treatment, which is most effective in increasing adhesive strength.

By this high frequency sputter etching process, countless fine needle-like protrusions are formed on the surface of the fluororesin film, resulting in very good adhesion with the cured film and adhesive layer provided on the surface of the film. becomes.

The high frequency sputter etching process can be carried out by already known methods. Various gases can be used as the atmospheric gas, and among them, inert gases such as argon and helium, nitrogen gas, carbon dioxide gas, water vapor, and the like are preferred. In addition, the atmospheric pressure is 0.005 to 0.
5 Torr, preferably 0.05 to 0.2 Torr. Discharge processing amount, that is, discharge power (W/
Cn! ) and processing time (seconds) is IW・seconds/c1)
1 or more, preferably 1 to 45 W・sec/crA, and for practical purposes, the discharge power is usually O1 to 5 W.
/Cd1 is preferably set within the range of 0.2 to 2 W/cnl, and the processing time is generally set within the range of 1 to 300 seconds.

A condensation cured film of an organosilicon compound is formed on one side of the fluororesin film thus surface-treated. The above compound used here is a mixture of organotrialkoxysilane, fluoroalkylalkoxysilane, and diorganopolysiloxane having hydroxyl groups at both ends of the molecule.

The above-mentioned organotrialkoxysilane is a component that mainly increases the hardness of the cured film and contributes to improving the scratch resistance and abrasion resistance. As a general formula, R+ Si (
ORz )3, in which R, , R2 are the same or different hydrocarbon groups having 1 to 6 carbon atoms. Specific examples include methyltriethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane, and phenyltriethoxysilane.

In addition, fluoroalkylalkoxysilane mainly contributes as a component that imparts lubricity to the cured film and increases scratch resistance and wear resistance. General formula %): In the formula, R1 is a perfluoroalkyl group having up to 6 carbon atoms such as a trifluoromethyl group, a pentafluoroethyl group, or a heptafluoropropyl group, and R4 and R5 are a perfluoroalkyl group having 1 to 6 carbon atoms. is a hydrocarbon group, a is 0°■ or 2.

Specific examples of such fluoroalkylalkoxysilane include F3 CCH2CH2S i (OCH3)3F3
CCH2CH2S i (OCz Hs)iFil
CCH2CH2S i (OCH3)Z? CH.

FS C2CH2CH2S i (OCH:+)+
F7 C:l CH2CH2S I (OCH3
) 3 etc.

Furthermore, the diorganopolysiloxane having hydroxyl groups at both ends of the molecule undergoes a dehydration condensation reaction with the above two silane compounds.
This is to cause a dealcoholization condensation reaction to form the desired condensation cured film. The general formula of this siloxane is shown below, where R6 is a monovalent hydrocarbon group such as a methyl group, a propyl group, a butyl group, or a phenyl group,
n is an integer from 10 to 25. Specific examples include dimethylpolysiloxane, methylethylpolysiloxane, methylphenylpolysiloxane, and the like.

From the viewpoint of synergistically exhibiting the respective functions mentioned above, the mixing ratio of the above-mentioned organosilicon compounds is -FN, 40 to 90% by weight of organotrialkoxysilane, and 5 to 40% by weight of fluoroalkylalkoxysilane. , it is desirable that the diorganopolysiloxane content be 3 to 20% by weight.

To form a condensation cured film using an organosilicon compound made of such a mixture, first the above mixture is mixed with a suitable solvent, such as a lower alcohol such as methanol, ethanol, or butanol, and ethylene glycol, dipropylene glycol monomethyl ether. , dissolved in a mixed solvent with a high boiling point solvent such as ethylene glycol monobutyl ether, and stirred and mixed uniformly at room temperature or under heating at 40 to 60°C. At this time, a dilute solution of sulfuric acid, hydrochloric acid, phosphoric acid, etc. may be added as a catalyst for the condensation reaction.

This mixed solution is applied to one surface of the fluororesin film subjected to the surface treatment by dip coating, roll coating, flow coating, or the like. After coating, heat treatment is carried out at usually 100 to 200° C., preferably 150 to 180° C., for 5 to 30 minutes, whereby a condensation curing reaction occurs as the solvent evaporates, and the desired condensation cured film is formed. The thickness of this coating is preferably about 3 to 10 μm.

Note that prior to forming the above-mentioned cured film, an appropriate silicone-based primer film may be formed on the surface of the fluororesin film in advance, and a condensation-cured film of an organosilicon compound may be formed on this film by the method described above. good. According to this, good results can be obtained due to the adhesive strength of the condensation cured coating to the fluororesin film.

As such a primer film, a mixture of aminosilane and epoxysilane or a copolymer of (meth)acrylicoxysilane and (meth)acrylic acid alkyl ester is used, and these are dissolved in a solvent such as a lower alcohol. In general, the mixture may be heated and mixed at 40 to 80°C, applied to the surface of the fluororesin film, and heat-cured. The thickness of this primer is about 1 to 5 μm.

The condensation cured film made of the organosilicon compound thus formed has high hardness and lubricity, and has excellent adhesive strength to the surface of the fluororesin film. Therefore, the surface of the film has excellent scratch resistance and abrasion resistance, and has good durability characteristics that can withstand outdoor use.

On the other hand, an adhesive layer is formed on the other surface of this fluororesin film. The type of adhesive is not particularly limited, but hot melt type adhesives such as ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, and ethylene-glycidyl methacrylate-vinyl acetate ternary random copolymer are generally preferred. . The appropriate thickness of the adhesive layer is 50 to 300 μm.

Such an adhesive layer may be formed by coating directly on the surface of the fluororesin film, but in the case of a hot melt type, a film-like material is made in advance by extrusion molding, and this is heat-pressed onto the surface of the fluororesin film. It can be formed by The adhesive layer formed by these methods has excellent anchoring properties with the surface of the fluororesin film because it has been surface-treated as described above. Since it can be adhered to the surface to which it is adhered with good adhesion, the sealing property at the interface between the fluororesin film and the surface to be adhered to is maintained through this adhesive layer.

Note that the above adhesive layer may contain an ultraviolet absorber and an antioxidant in order to prevent deterioration due to ultraviolet rays and heat. Examples of the ultraviolet absorber include benzophenone type and benzotriazole type, and examples of the antioxidant include phenol type antioxidant.

The surface protective material of the present invention thus obtained is particularly useful as a surface protective material for solar cells due to the above-mentioned functions of this protective material. In addition to the above-mentioned uses, it can also be suitably used as a surface protection material for solar heat collectors, sunlight selective absorption films, etc., and furthermore as a surface protection material for general articles.

〔Effect of the invention〕

As described above, the surface protection material of the present invention is obtained by surface-treating both sides of a fluororesin film to form a condensation cured film made of a specific organosilicon compound on one side, and an adhesive layer on the other side. This structure has excellent moisture-proofing effects when used as a surface protection material for solar cells, etc., and has high surface hardness and appropriate surface lubricity, making it highly scratch resistant and resistant. Because it has excellent abrasion resistance, it does not cause extreme deterioration of the surface appearance or significant decrease in the energy conversion efficiency of the solar cell even when used outdoors, and has a significantly improved durability. demonstrate.

〔Example〕

EXAMPLES Below, this invention will be described in more detail with reference to Examples. In addition, in the following, parts shall mean parts by weight.

Example 1 0.0, 1.0. High frequency spatter etching treatment was performed in an argon gas atmosphere of I Torr with a discharge treatment amount of IOW·sec/c1)1.

On the other hand, 60 parts of methyltrimethoxysilane and 3 (l) of trifluoropropyltrimethoxysilane were added to a mixed solvent of ethanol and ethylene glycol in a weight ratio of 1:1, mixed and stirred uniformly, and then the mixed solution 10 parts of dimethylpolysiloxane and 5 parts of a 2% by weight solution of hydrochloric acid were added thereto and stirred at room temperature for 60 minutes to prepare a solution for forming a condensation cured film.

Separately, 5% each of aminosilane and epoxysilane
A primer solution was prepared by mixing 0 parts each in an ethanol solution and then heating this solution at 50° C. for 100 minutes.

Applying the above primer solution to one side of the fluororesin film that has been subjected to the high frequency sputter etching treatment,
Heat treatment was performed at 80° C. for 10 minutes to form a silicon-based primer film with a thickness of 2 μm. Next, apply the above condensation cured film forming solution onto this primer film,
Heat treatment was performed at 180° C. for 10 minutes to form a condensation cured film with a thickness of 5 μm.

Separately, as an adhesive layer, a mixture of 100 parts of ethylene-ethyl acrylate copolymer resin and 0.2 parts of benzophenone ultraviolet absorber was extruded to a thickness of 50 μm to form an adhesive film. Then, this film was applied to the other side of the fluororesin film on which the condensation cured film was formed by hot pressing at 120° C. and 5 kg/cJ for 5 minutes to form an adhesive layer. A surface protection material was obtained.

Example 2 A 0.05 m thick fluororesin film made of ethylene-tetrafluoroethylene copolymer resin was coated on both sides with 0.05 m thick.
High frequency sputter etching treatment was performed in a water vapor atmosphere of I Torr with a discharge treatment amount of IW·sec/ctA.

Further, a mixture consisting of 50 parts of ethyltriethoxysilane, 20 parts of trifluoropropyltriethoxysilane, and 20 parts of dimethylpolysiloxane is added to a mixed solvent of ethanol and ethylene glycol in a weight ratio of 1:1, and mixed by stirring. In this way, a solution for forming a condensation cured film was obtained.

The same primer solution as in Example 1 was applied to one side of the fluororesin film that had been subjected to the high-frequency sputter etching process, and heat treated at 80°C for 10 minutes to give a thickness of 2 μm.
A silicone-based primer film of 180 ml was formed, and then the above condensation cured film forming solution was applied to this film, and 180 ml of
A condensation cured film having a thickness of 5 μm was formed by heat treatment at °C for 10 minutes.

Separately, as an adhesive layer, a film-like material made of an ethylene-glycidyl methacrylate-vinyl acetate ternary random copolymer resin extruded to a thickness of 50 μm was used as an adhesive layer. 150℃, 5kg/c++! on the other side of the film! The surface protective material of the present invention was obtained by applying a hot press for 5 minutes to form an adhesive layer.

Example 3 A surface protection material of the present invention was obtained in the same manner as in Example 1, except that an ethylene-hexafluoropropylene copolymer resin having a thickness of 0.1 μm was used as the fluororesin film.

Example 4 Example 1 except that the same fluororesin film as in Example 3 was used and the amount of trifluoropropyltrimethoxysilane used was changed from 30 parts to 20 parts.
A surface protection material of the present invention was obtained in the same manner as above.

Comparative Example 1 The same fluororesin film as in Example 3 was used, except that the amount of methyltrimethoxysilane used was changed from 60 parts to 40 parts, and the use of trifluoropropyltrimethoxysilane and dimethylpolysiloxane was omitted. A surface protection material for comparison was obtained in the same manner as in Example 1.

Comparative Example 2 The same fluororesin film as in Example 3 was used, and the same procedure was carried out except that the formation of the silicone-based primer film and the condensation-cured film of the organosilicon compound was omitted (therefore, the surface treatment was applied to only one side). A surface protection material for comparison was obtained in the same manner as in Example 1.

A solar cell was produced using the surface protection material obtained in each of the above Examples and Comparative Examples, and the initial and 60%
The results of measuring the energy conversion efficiency after being left outdoors for days are as shown in the table below.

As is clear from the above table, the surface protection material of this invention not only has excellent moisture resistance, but also has excellent scratch resistance and abrasion resistance, so it maintains its appearance even when left outdoors for a long time. It can be seen that no significant decrease in the energy conversion efficiency of the solar cell, as well as any deterioration of the solar cell, was observed.

Patent applicant: Nitto Electric Industry Co., Ltd. The representative is a Japanese patent attorney named Wataru Newa.

1゜ [two

Claims (5)

[Claims] (1) Condensation curing of an organosilicon compound consisting of an organotrialkoxysilane, a fluoroalkylalkoxysilane, and a diorganopolysiloxane having hydroxyl groups at both molecular ends on one side of a fluororesin film that has been surface-treated on both sides. A surface protection material that forms a film and an adhesive layer on the other side. (2) Claim No. 1 in which both surfaces of the fluororesin film are surface-treated by high-frequency sputter etching.
) The surface protection material described in section 2. (3) The surface protection material according to claim (1) or (2), wherein a silicone-based primer film is formed between a fluororesin film and a condensation-cured film of an organic silicon compound. (4) Claim (3) in which the silicone-based primer film is a cured film of a mixture of aminosilane and epoxysilane or a copolymer of (meth)acrylic acid oxysilane and (meth)acrylic acid alkyl ester surface protection agent. (5) The surface protection material according to any one of claims (1) to (4), wherein the adhesive layer is a hot melt adhesive layer.