Method for manufacturing key pad with rigid resin key top

Abstract

A method for manufacturing a highly productive key pad with rigid resin key top, wherein the key top adhesion surface 2, 6 of the key pad 1, 5 or a portion thereof is surface altered by at least one method selected from short wavelength UV irradiation treatment, corona discharge treatment, flame treatment and plasma treatment and can be adhered with reactive hardening resin 3, 7 such as urethane base resin, epoxy base resin, amino base resin, acrylic base resin, cyanoacrylate base resin and photo reactive hardening resin, thereby reducing adhesion operation time, without fear of dislocation during the adhesion.

Description

[0001] This is a continuation of application Ser. No. 09 / 253,406 filed on Feb. 19, 1999, and the entire disclosure of this prior application is considered to be part of the disclosure of the accompanying application and is hereby incorporated by reference therein.[0002] The present inventions relates to a method for manufacturing a beautiful and quality key pad assuring a good durability to be used for portable phone, portable information terminal, remote control of various home electric apparatuses, card remote control or various keyboards.[0003] 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 light masking portion is arranged to dispose graphics formed by cutting out a character, numeral, symbol or picture.[0004] Howe...

AI Technical Summary

Benefits of technology

0016] 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.sup.-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.

0017] 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.

0018] 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.

Problems solved by technology

However, as these silicone base adhesives have weak retention force and exfoliate easily after adhesion, it has been often necessary to dispose 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 100.degree. C. or more.

As the 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.times.10.sup.-4 / .degree.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.

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