Batteries: thermoelectric and photoelectric – Photoelectric
Reexamination Certificate
2000-03-14
2003-02-25
Sergent, Rabon (Department: 1711)
Batteries: thermoelectric and photoelectric
Photoelectric
C136S251000, C136S252000, C257S431000, C257S433000, C257S788000, C528S045000
Reexamination Certificate
active
06525261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an insulating resin composition and/or a transparent insulating resin composition, and more particularly, it relates to a resin composition suitable for screen printing to use in a thin-film type electronic device, as well as to a resin composition for constituting an insulating film for use in a thin-film electronic device.
The present invention also relates to a solar cell comprising the resin composition above.
2. Description of the Prior Art
In a thin-film type electronic device (i.e., an electronic device constructed by principally stacking thin films) such as a thin-film solar cell, various types of resin composition have been studied for forming an insulating film for use as an interlayer dielectric film in a multilayered structure or an insulating film in a multi-level crossed interconnection.
The resin composition above should possess insulating properties for use as an interlayer insulating film, adhesiveness to adhere the upper and the lower layers, weathering resistance, moistures resistance, heat resistance, wear resistance, resistance against scratches, flexibility, surface hardness, coating applicability of an ink by means of screen printing and the like, and hardenability.
Studies have been made heretofore on thermosetting, thermoplastic, or ultraviolet (UV) curable resin compositions such as styrene resins, saturated polyester resins, unsaturated polyester resins, epoxy resins, alkyd resins, silicone resins, acrylic resins, and fluororesins. Details on the studies as described in, for example, JP-A-61-218625 (the term “JP-A-” as referred herein signifies an “unexamined published Japanese patent application”).
However, in spite of the proposed resin composition above, a resin composition which satisfies the requirements with good balance is yet to be developed.
Particularly, in a multilayered structure comprising stacked thin films such as that in a solar cell or a like thin-film type electronic device with an interlayer insulating film or an insulating film for multi-level crossed interconnections, none of the known resin compositions was found to satisfy the required characteristics enumerated above as well as other characteristics concerning printability of an ink, the hardenability of the printed film, and productivity. Accordingly, no resin composition developed heretofore is suitable for use as an interlayer insulating film or an insulating film for multi-level crossed interconnections.
Furthermore, an extensive study has been made of the resin encapsulant for thin-film electronic devices, especially the resin composition that forms a transparent protective film on the surface of a solar cell of thin-film structure.
The resin composition for such use needs not only transparency but also many characteristic properties required for protective film (such as weather resistance, moisture resistance, heat resistance, wear resistance, scratch resistance, flex resistance, surface hardness, and adhesion to substrate and thin film). It also needs a good printability when used in the form of ink for screen printing.
Conventional resin components for transparent protective film are formed from a variety of thermoplastic and thermosetting resins and UV-curing resins, such as styrene resin, saturated polyester resin, unsaturated polyester resin, epoxy resin, silicone resin, acrylic resin, and fluoroplastics. Their detailed descriptions will be found in Japanese Patent Publication No. 173342/1988 and Japanese Patent Laid-Open Nos. 69874/1981 and 218625/1986.
However, none of the conventional resin compositions meet requirements for the above-mentioned characteristic properties. Especially when used for transparent protective film on solar cells of thin film structure, they are not satisfactory in transparency, properties required of protective film, printability of ink, curability, and productivity.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a resin composition for forming an insulating film or a transparent protective film suitable for a thin-film type electronic device structure, and particularly, to provide a resin composition for fabricating an insulating film suitable for an amorphous silicon solar cell utilizing a flexible resin substrate, yet, with high productivity and utilizing an inexpensive and lightweight base material.
An object of the present invention is, more specifically, to accomplish the improvements below by overcoming the problems.
(1) Improving moisture resistance and water resistance of the insulating film
An object of the present invention is to improve the moisture resistance and water resistance of the resin composition constituting an insulating film, thereby improving weathering resistance of the resin composition.
The transparent resin composition should have good resistance to deterioration by moisture, adequate ability to prevent the penetration of moisture into the inside covered by the transparent protective film comprising the transparent resin composition, and high weathering resistance.
Conventional resin compositions suffered changes in composition due to the reaction with the moisture or water of the surroundings. As a result, due to the deterioration of the amorphous silicon phase or to the denaturation of the electrode material, a solar cell using the resin was found to lose the photoelectric conversion effect and to deteriorate the electric properties with passage of time.
(2) Improving heat resistance and surface hardness of the insulating film
Another object of the present invention is to increase the heat resistance and the hardness of an insulating film comprising the resin composition. More specifically, in the fabrication of a thin-film electronic device such as a solar cell, a flexible printed circuit (FPC) is provided or a lead wire is adhered to the electrode portion that is provided to externally take out the electric power by applying heat under pressure at a temperature of 100° C. or higher for soldering or heat sealing. At the same time, the interlayer insulating film and the multi-level crossed insulating films or an insulator around electrodes are also subjected to heat shock or thermal welding.
The thermal deformation of the insulating films due to heat shock or thermal wedding can be prevented from occurring by increasing the hardness and the heat resistance of the insulating films or transparent protective films. Furthermore, insulating failure and defective appearance can be avoided.
Moreover, the heat resistance of the interlayer insulating film and the multi-level insulation film can be further improved in a device in which heat accumulation occurs during the operation of the device, or in a device which is exposed to a heat at high temperature, such as a car-use solar cells and the like.
Furthermore, in case of forming an ITO (indium tin oxide) transparent electrode, the insulating properties can be maintained by preventing physical or chemical damage from occurring on the printing film and thereby increasing heat resistance of the film.
Vehicle-mounted solar cells, which are subject to high temperatures, are protected from failure and surface scratches, which reduce light transmission and hence conversion efficiency, if they are covered with a protective film having improved hardness and heat resistance
(3) Improving wear resistance
A still other object of the present invention is to improve the wear resistance of an insulating film comprising the resin composition.
In case of laminating thin films by means of, particularly, a roll-to-roll process (a fabrication process which comprises continuously forming the device and the like by performing each of the unit operations such as film deposition, printing, and laser processing while taking up a rolled flexible substrate with another roll), there are problems such as of scratches and the like which generate on the interlayer insulating film or the transparent surface protection film when the surfaces of the upper layer and the lower layer of
Hosokawa Makoto
Isobe Yukihiro
Kubota Yuichi
Takenouchi Akemi
Costellia Jeffrey L.
Semiconductor Energy Laboratory Co,. Ltd.
Sergent Rabon
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