Electricity: circuit makers and breakers – Electric switch details – Actuators
Reexamination Certificate
2000-08-29
2001-08-21
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Actuators
C200S0050EA, C200S314000, C200S517000
Reexamination Certificate
active
06278072
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a sheet-like key top used for pushbutton switches for equipment such as electronics, portables, and remote controls.
PRIOR ART
The construction of pushbutton switches used for the input portion of equipment such as electronics and portables has been diversified into a wide variety of designs. For example, pushbutton switches comprising key tops made from synthetic rubber, pushbutton switches in which key tops made from resin and key pads made from synthetic rubber are integrally attached together, and pushbutton switches in which a film is integrally attached to one surface of each key top made from resin are widely used. Above all, there has been an increasing demand for pushbutton switches in which a film is integrally attached to one surface of each key top made from resin, since in the case of switches of this type, a rich variety of display layers can be designed, the thickness can be made small, and prices are low.
The construction of a pushbutton switch in which a film is integrally attached to one surface of a key top made from resin is mentioned in the Japanese Patent Gazette Laid-Open No. HEI 2-14726. The above-mentioned construction is such that a film, on the back of which is present a display layer formed by printing, is deformed by bending to the same form as that of the key top main body and is integrally attached to the upper side of the key top. Furthermore, by way of one of the methods of manufacturing the above-mentioned key top is described in the Japanese Patent Gazette Laid-Open No. HEI 6-44859 a manufacturing method whereby a film having a printed display layer is firmly held by means of a mold for forming key top main bodies, and is deformed by the action of the pressure and the heat of the molten resin which are generated during the forming of the key top, thus being pushed upward, then is removed from the mold after the molten resin is cured.
However, a pushbutton switch in which a film is integrally attached to one surface of a key top made from resin has had a problem in that the display layer softens by the action of the pressure and the heat of the molten resin generated during the forming of thermoplastic resin, resulting in the display portion
2
for characters, symbols, and the like being liable to get distorted or in a crack
6
being liable to occur in the display layer
3
, as shown in FIG.
2
.
Furthermore, there has been another problem in that in a case where a metallic-looking display layer with metal filler mixed is present, the display layer softens by the action of the pressure and the heat of the molten resin generated during the forming of thermoplastic resin, resulting in an uneven dispersion
7
being liable to occur, as shown in FIG.
5
.
SUMMARY OF THE INVENTION
For the purpose of solving the above-mentioned problems, the present invention provides a high-yield, high-quality sheet-like key top in which a protective film is laminated to the backside of the display layer so that the heat of the molten resin generated during the forming of thermoplastic resin will not directly affect the display layer, thereby preventing display portion from being distorted and the display layer from being cracked.
Namely, the present invention provides a sheet-like key top constructed such that a base film equipped with a display layer on its backside which is formed to the same shape as that of the upper surface of a main body of the key top is integrally attached to the main body of key top, wherein a protective film is laminated to the backside of the display layer.
PREFERRED EMBODIMENTS OF THE INVENTION
Any and every flexible, heat-resistant film may be used as a protective film of the present invention. For example, polyethylene terephthalate (PET) films, polyamide films, polycarbonate films, and fluorine films may be enumerated. Furthermore, any protective film with a thickness of 15 &mgr;m or more is capable of protecting a display layer from molten resin.
Reference being had to drawings, typical embodiments of the present invention are explained.
REFERENCES:
patent: 5234744 (1993-08-01), Kenmochi
patent: 5399821 (1995-03-01), Inagaki et al.
patent: 5807002 (1998-09-01), Tsai
patent: 6023033 (2000-02-01), Yagi et al.
patent: 6103346 (2000-08-01), Nakajo et al.
patent: 2-14726 (1990-01-01), None
patent: 6-44859 (1994-02-01), None
Friedhofer Michael
McGlew and Tuttle , P.C.
Polymatech Co. Ltd.
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