Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-08-07
2002-09-17
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272600, C156S273300, C156S275700, C156S275500, C156S325000, C200S314000, C200S341000
Reexamination Certificate
active
06451143
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a beautiful and quality key pad assuring good durability to be used for a portable phone; portable information terminal, remote control of various home electric apparatuses, card remote control or various keyboards.
BACKGROUND OF THE INVENTION
Silicon rubber or the like are primarily used for the conventional key pad, because of their excellent low temperature resistance, heat resistance, precise formability and electric insulation. As key top, soft rubber is used for disposing graphics composed of character, numeral, symbol or picture on its surface or a light masking portion is arranged to dispose graphics formed by cutting out a character, numeral, symbol or picture.
However, as silicone base coating is used, in every case, as material of graphics to be formed on theses surfaces, they are worn or broken by finger pressure or friction with clothing resulting in the deterioration of 20 visual recognition or appearance.
Therefore, Japanese Utility Model Laid-Open Shouwa 48-15161, Japanese Patent 2627692 or Japanese Patent Publication Heisei 7-95411 have proposed methods wherein a key top part is formed separately with rigid resin for printing its surface or back or elsewhere and then integrated by engaging with a silicone key pad or adhering with adhesive or double side adhesive tape or the like.
Concerning the addition of different material to silicone rubber, it is also known to treat the surface as described in Japanese Patent Publication Heisei 7-282687 or Japanese Patent Publication Heisei 7-296676.
It should be noted that they are all concerned with the formation of a coating layer and not the adhesion of rigid resin key top with silicone key pad.
SUMMARY AND OBJECTS OF THE INVENTION
As silicone rubber is less adhesive, generally silicone base adhesives have been used or the surface was treated with a substrate for adhering them and there was no other solution. However, as these silicone base adhesives have weak retention force and exfoliate easily after adhesion, it has been often necessary to dispose an additional anti-detachment collar or the like on the key top part to be used in practice.
Moreover, as silicone base adhesives are slow in hardening, it is necessary to heat to 100° C. or more. As a consequence, it was difficult to use resins of low softening point represented by ABS as key to material.
What is more, as silicone rubber presents a high linear dilatation coefficient of 2 to 3×10
−4
/° C., heating expands the key top part enormously and key pitch or the like vary; consequently it has been necessary to fix the key top part and the base key pad portion until the adhesion completion, increasing the time of adhesion process and the number of affixing jigs, and resulting in low productivity and less economy.
The present Invention concerns a method for manufacturing a key pad with rigid resin key top, solving these problems.
It concerns a method for manufacturing a high productivity key pad, comprising the steps for surface-modifying the adhesion surface of a key pad key top or a portion thereof by at least one method selected from the group including short wavelength ultraviolet irradiation treatment, corona discharge treatment, flame treatment and plasma treatment and adhering the key top molded with rigid resin with reactive hardening resin such as urethane base resin, epoxy base resin, amino base resin, cyanoacrylate base resin, photo reactive hardening resin or the like, thereby assuring more hard adhesion between the silicone rubber key pad and the key top, characterized by that low softening point rigid resins represented by ABS may also be used and that the adhesion operation can be completed more rapidly, without dislocation during the adhesion.
Namely, the present Invention concerns a method for manufacturing a key pad with rigid resin key top, comprising steps for surface-modifying the adhesion surface of a silicone rubber key pad for push-button, applying reactive hardening resin and, thereafter, adhering the key top molded with rigid resin.
Members composing a key pad are preferably made of silicone rubber, because of its excellent low temperature resistance, heat resistance, weather resistance, precise formability and electric insulation. Graphics composed of character, number, symbol or picture may be disposed on its surface or light masking may be arranged to dispose graphics formed by cutting out a character, number, symbol or picture.
Silicone rubber, key top member is weakly adhesive, however, the rigid resin key top is so made to be attached firmly with photo reactive hardening resin, by surface treating using at least one method selected from the group including short wavelength ultraviolet irradiation treatment, corona discharge treatment, flame treatment, plasma treatment or substrate treatment.
The short wavelength ultraviolet irradiation treatment used for the Invention consists in irradiating the key pad surface with short wavelength ultraviolet irradiation at a constant illumination, by a constant total light quantity to alter the surface. To be more precise, 184.9 nm and 253.7 nm radiation irradiated from a mercury lamp wherein mercury in contained under the pressure of about 10
−1
mmHg generates ozone under the presence of oxygen, the ozone oxidizes the surface of an object to be treated, generates active groups such as carboxyl group or silanol group and, thereby, improving the adhesion and compatibility of printing inks or paintings.
Corona discharge treatment consists in applying a high tension between electrodes in the atmosphere to provoke dielectric breakdown and discharge, and introducing an object to be treated there-between, thereby oxidizing polymer of the surface layer and introducing active group into the surface to bring out the similar effect.
Flame treatment consists in passing an object to be treated through a strong oxidizing flame to bring out an effect similar to the corona treatment.
Plasma treatment consists in ionizing gas molecular by provoking glow discharge in low pressure inactive gas, oxygen, halogen gas or the like, generating plasma and activating the surface using its chemical activity.
Being dry process, short wavelength ultraviolet irradiation treatment, corona discharge treatment, flame treatment or plasma treatment are simpler in terms of process than the method using surface treatment agent; however, short wavelength ultraviolet irradiation treatment or corona treatment are preferable, because plasma treatment requires vacuum status or expensive equipment and flame treatment is necessarily dangerous.
To obtain a higher holding power, additional surface treatment may also be executed, after this surface-modification, using well-known silane, titanium or aluminum base various coupling agents.
The composition of the reactive hardening resin is not limited to at least one resin selected from the group including urethane base resin, epoxy base resin, amino base resin, acrylic resin and cyanoacrylate base resin.
The color is not particularly limited; however, if the key top part is to be illuminated, the reactive hardening resin should be translucent.
The hardening method of the reactive hardening resin is not particularly limited, but the use of heat reactive hardening resin or photo reactive hardening resin can reduce the adhesion process. As for heat reactive hardening resin allowing to reduce the adhesion time and increase the holding power, urethane base resin or cyanoacrylate base resin are preferable and, particularly, cyanoacrylate base resin would permit to obtain the adhesion within several seconds and reduce the manufacturing time. Photo reactive hardening resin also allows to obtain the adhesion within several seconds and reduce further the adhesion process, and moreover, assures a good stability during application work or conservation and a good workability. On the other hand, as visible ray reactive hardening resin would react even to an ordinary work light, UV hardening type resin is prefe
Ball Michael W.
McGlew and Tuttle , P.C.
Polymatech Co. Ltd.
Rossi Jessica
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