Manufacturing method of color keypad for a contact of character illumination rubber switch

Abstract: A manufacturing method of a keypad for a contact character illumination rubber switch composed of a surface enriched in color design variation, comprising the steps of forming a black or gray intermediate layer (3) on a surface portion of a color keypad member (1) for a contact character illumination switch of a mobile communication system, electric equipment for car loading or the like, forming a colored surface layer (4) thereon with any color, and applying a laser beam from the upside thereon for burning up and removing the intermediate layer (3) and the colored surface layer (4).

Description: The present invention relates to a manufacturing method of a colour keypad for a contact of character illumination rubber switch in mobile communication systems and electrical equipment for car loading. See for example DE-A-3509519. A manufacturing method of a keypad for a contact of character illumination rubber switch made of rubber which illuminates only either characters or figures is already well known through the Japan Patent Publication No. HEISEI 5-32850. In this method, a laser beam is irradiated so that the laser beam energy is absorbed into a coloured surface layer in the shapes of characters and burns them off. In order to remove the coloured surface layer by means of the laser beam, it is necessary to arrange materials such as carbon black on the surface so that the laser beam is readily absorbed into the coloured layer. Therefore the available keypads manufactured by irradiating laser beam currently have only dark colours such as black or gray or the like as the coloured surface layer. It is possible to emit the laser beam on the coloured surface layer of any colours which are not black or gray and to burns them off; on the contrary, the incomplete removal thereof is readily caused within the coloured surface layer because the coloured surface layer does not completely absorb the laser beam. Moreover, if by increasing the irradiation dose of the laser beam the coloured surface layer is removed, removal or burning thereof is caused on the lower coloured light permeable layer; thus by using the recent laser beam unit, it is difficult to obtain high quality products and the marketing can not be realized. It is the purpose of the present invention to manufacture a keypad having colour variations which are much needed, especially by women and young people, for colour keypads for illuminated character contacts in mobile communication systems and electrical equipment for car loading. The present invention relates to a manufacturing method of a keypad for a contact character illumination rubber switch composed of a surface enriched in colour design variations, comprising the steps of forming a black or gray intermediate layer over a surface section of a colour keypad member for a contact character illumination switch of mobile communication systems, electric equipment or the like, forming a coloured surface layer thereon with any colours, and applying a laser beam from the upside thereof for burning up and removing the intermediate layer and the coloured surface layer. The invention provides a method of manufacturing a keypad for a contact character illumination switch, as defined in claim 1. The invention will be further described, by way of example only, with reference to the accompanying drawings, in which : FIG 1 is a cross section view of a keypad according to the present invention; and FIG 2 is a cross section view of a conventional keypad, Now the present invention will be described more in detail referring to the embodiment as shown in Figs. 1 and 2. A body of a keypad 1 is formed with transparent or semi-transparent elastic material. Such elastic material includes natural rubber (polyisoprene rubber), butadiene rubber, styrene butadiene rubber, chloroprene rubber, nitryl rubber, butyl rubber, ethylene propylene rubber, acrylic rubber, silicone rubber, fluoric rubber, urethane rubber, other synthetic rubber, or styrene base, olefin base, ester base, urethane base thermoplastic elastomer. Over the face thereof, a coloured translucent layer 2, a black or gray dark coloured intermediate layer 3 and a coloured surface layer 4 are formed by painting or printing with polyester base, silicone base or various liquid rubber (urethane base, diene base, polybutene base). For painting method, reciprocation, air, rotary or other well-known methods are employed, while for printing, screen, offset, PAD or other well-known methods are employed. Thereafter, a laser beam is applied to the intermediate layer from the upper side of this coloured surface layer 2, to remove characters or graphic pattern shape portion. When this intermediate layer is removed, the coloured surface layer will be also removed at the same time. Thus, a keypad is realized with its coloured surface with any colours. Example A transparent or semi-transparent silicone rubber is molded by a metal die of keypad shape and a coloured translucent layer 2 is coated using silicone ink white (made by Toshiba Silicone Ltd.) in order to form a coloured translucent layer base. At that time, 20 parts by weight of hardener is added to 100 parts by weight of silicone ink. Next, as an intermediate layer 3, silicone ink black (made by Toshiba Silicone Ltd.) is formed thereon in the shape of key top by silk screen printing. At this time, the key top printing may also be applied with gray silicone ink mixing conveniently white ink and black ink (made by Toshiba Silicone Ltd.) as the intermediate layer 3. Finally, 30 parts by weight of Colour Master Red (made by Toshiba Silicone Ltd.) are added to 100 parts by weight of Silicone Ink Clear (made by Toshiba Silicone Ltd.) as an ink used for the coloured surface layer 4, the liquid obtained as the result is mixed adequately, diluted with solvent and coated on the key top surface. Moreover, on this occasion, 20 parts by weight of the hardener are added to 100 parts by weight of silicone ink. About the silicone rubber keypad coated as mentioned above, the intermediate layer 3 and the coloured surface layer 4 at the same time are removed by a laser marker (made by Fuji Electric Ltd.). As the result, the coloured surface layer and the intermediate layer can be removed in the same shape of the given character and/or symbol as the keypad for conventional black, gray or other character illuminating rubber switch contacts. Similar results are obtained, using blue, green and brown as the coloured surface layer 4. Moreover, a wide variety of colour variation can be realized by preparing colour masters of the coloured surface layer. The thickness of the coloured surface layer 4 is set within the range of 50 µm or less depending on the laser output energy conditions of the laser machine; however, preferably 20 to 30 µm is appropriate. At 15 µm or less, in some cases, the colour of the intermediate layer 3 becomes visible through the coloured surface layer and the colour is not distinct in respect of the outside appearance. At 50 µm or more, the energy efficiency of the intermediate layer is deteriorated, the processing time increases and the removal of some coloured surface layer may occur. By using this method of manufacturing, any colours other than black can be selected for the coloured surface layer having the widest area in respect of the outside appearance, permitting to enrich the variation of key top colour design. Additionally, at that time, products presenting desired qualities, and strongly demanded especially by women and young people, can be manufactured without suffering deterioration of any characters or figures such as discolouration due to the fading of the coloured transparent or translucent layer.

Claims: A method of manufacturing a keypad for a contact character illumination rubber switch made of rubber or other elastic materials, in which a coloured transparent or translucent layer of any colour is expressed and formed, comprising the steps of: forming a coloured transparent or translucent layer (2), over a surface portion of a keypad member (1) for contact made up of rubber molded by using transparent or semi-transparent elastic materials, applying a black, gray or other dark colour layer thereon as an intermediate layer (3) for enhancing optical energy absorption; additionally forming thereon a coloured surface layer (4) with any colour(s) other than black and gray; thereafter irradiating with a laser beam said coloured surface layer in the shapes of characters or figures; burning up said intermediate layer (3) by absorption of laser beam energy; and at the same time, burning up and removing said coloured surface layer (4) by said burning heat.

Inventors: MASAYA KATORI, MASAYA, KATORI, Masaya, Katori, R &amp; D Ctr. of Polymatech. Co. Ltd.
Applicants: POLYMATECH CO LTD, POLYMATECH CO., LTD.
Application year: 1997
Main classification: H01H13
IPC codes: H01H9, H01H13, B23K26, H01H11