Electricity: circuit makers and breakers – Solid contact – Membrane type
Reexamination Certificate
2003-05-28
2004-05-11
Friedhofer, Michael A. (Department: 2832)
Electricity: circuit makers and breakers
Solid contact
Membrane type
C200S517000, C200S314000, C200S341000
Reexamination Certificate
active
06734382
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a push switch, such as a pushbutton switch used in the operation portion of an electronic apparatus, a portable device, a vehicle-mounted switch, a remote controller etc., or a membrane switch used in an electronic apparatus, for example, as a thin switch input device.
More specifically, the present invention relates to a method for forming, on a pushbutton switch, an indicator portion in which color design images such as letters, patterns, and designs are indicated, and to a pushbutton switch having the indicator portion.
Also, the present invention relates to a method for forming, on a membrane switch, an indicator portion in which color design images such as letters, patterns, and designs are indicated, and a membrane switch having the indicator portion.
2. Description of the Related Art
Pushbutton switches used in electronic apparatuses such as portable telephones have an indicator layer for the indication of color design images such as letters, numerals, figures, symbols, and design patterns. Such an indicator layer is formed by printing shapes corresponding to letters, symbols, or the like on a key top mainly formed of a resin, by screen printing, pad printing, or the like.
However, with the recent trend toward miniaturization and an increase in the functions of electronic apparatuses, key tops of pushbutton switches are also becoming increasingly smaller in size. Thus, there is a need to enable indication of as many letters or numerals as possible, or complex figures, symbols, design patterns, etc. formed using multiple colors, on a small key top having a limited space. Consequently, with the conventional methods such as screen printing or pad printing, it has become increasingly difficult to form an indicator layer which is capable of high resolution, the resolution being a measure of the meticulousness of a drawing or the smoothness of an image, and on which fine, sharp designs are rendered. Further, the screen printing and the pad printing require the use of a printing plate for each color, so that the number of printing steps increases as the number of colors for printing increases, thus necessitating sophisticated printing techniques that enable a fine positional adjustment, or measures for preventing the intrusion of contaminants. Further, when changing the design of a pushbutton switch, it is necessary to prepare new printing plates. Thus, the printing plates are prepared in accordance with colors required for each product, so that a great deal of time, labor, and costs is involved in storing and maintaining the printing plates. Due to the reasons described above, conventional methods based on printing, for example screen printing and pad printing, have proved inadequate to quickly respond to the diversity of designs and shorter life cycles, making it impossible to meet such demands as the simplification of the production steps, reduction in cost, and higher resolution.
In contrast, as an alternative method for preparing an indicator layer on a pushbutton switch to the conventional printing methods, there is a method of bonding onto a key top a photographic sheet formed on a resin sheet by graphic photo-printing using a printer. A similar technique is described in JP 2000-231849 A. However, with the above method, it is necessary to perform a post-processing of cutting the photographic sheets along the outer peripheral configurations of individual key tops using a carbon dioxide laser or a punching edge. In addition, because a rather thick photographic sheet is cut, burrs are easily produced on the cut surfaces. Further, the photographic sheet is integrated with the key top, making the above method unsuitable for dealing with the demand for reduced thickness.
Membrane switches are used as thin switch input devices in, for example, electronic apparatuses. An example of conventional membrane switches is shown in
FIGS. 17 and 18
. Such a conventional membrane switch, denoted
100
, commonly has a construction as shown in
FIGS. 17 and 18
. That is, the membrane switch is generally composed of a front-side film, or sheet material
101
that is exposed to the outward appearance of a not-shown electronic apparatus, a back-side film, or sheet material
102
received within the inner portion of the electronic apparatus, and a spacer
103
arranged between the two film materials. Formed on the two sheet materials
101
and
102
are contact electrodes
101
a
and
102
a
, respectively. When pressed from above, the contact electrode
101
a
of the front-side sheet material
101
is brought into conducting contact with the contact electrode
102
a
of the back-side sheet material
102
by way of a through hole
103
a
formed in the spacer
103
. Establishing such conducting contact makes it possible to attain a predetermined switch function of the electronic apparatus. Advantages of the membrane switch
100
described above reside in the simplicity of its construction and its small thickness. As such, the switch is employed in various apparatuses as a switch input device of an electrical apparatus for which there is a particularly strong demand for miniaturization.
In such a membrane switch
100
, in general, letters, numerals, symbols, figures etc. are colors for indication or a colored exterior film
104
is bonded onto a portion thereof which is exposed to the outward appearance of the electronic apparatus. Such an exterior film
104
is typically obtained by screen-printing a coating material onto a resin film. However, with screen printing, it is necessary to prepare a printing plate for each color, which places a large burden in terms of both labor and cost. Further, when changing the design, it is necessary to prepare all new printing plates from scratch, which leads to a further increase in labor and cost. To overcome the above problem, there is proposed a method for forming the exterior film
104
which includes: preparing a design by a personal computer; printing the design on a base sheet (not shown) such as paper or a PET film using a commercially available color printer to thereby prepare the external film
104
; and stacking the exterior film
104
on the front-side film material
101
using an adhesive tape or the like (for a similar technique, see Japanese Utility Model Application Laid-open No. Hei 5-90762).
However, with the above-described method, it is also necessary to perform a step of cutting the exterior film
104
along the outer peripheral configurations of individual membrane switches using a carbon dioxide laser or a punching edge. In addition, burrs are easily generated resulting from the cutting step. Further, with the above-described method, it is commonly necessary to provide a protection sheet for protecting the printing surface subjected to printing using a color printer, which leads to a considerable increase in the overall thickness inclusive of the thickness of the base sheet. If the resulting structure is integrated as a part of the membrane switch, the flexibility of a portion subjected to pressing operation with, for example fingers is impaired, resulting in such problems that the operational feel as a membrane switch is degraded, on/off operation of the switch is not properly effected by the pressing operation, and the like. Therefore, the above-described method is not suitable for application to membrane switches whose structural advantages reside in their small thicknesses. On the other hand, to avoid the problem described above, the printing surface subjected to printing by a color printer may be bonded onto a portion that is exposed to the outward appearance of the electronic apparatus. With this arrangement, however, the color design image is viewed from the back (from the side opposite to the printing surface), so that the image appears distorted. Thus, it is often difficult to view the image with good reproducibility while maintaining high resolution.
SUMMARY OF THE INVENTION
The present invention enables forming an indicator portion having
Arai Hiroshi
Honmatsu Yoshifumi
Friedhofer Michael A.
Polymatech Co. Ltd.
Rader & Fishman & Grauer, PLLC
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