The present application is a 35 U.S.C. §371 National Stage Application of, and claims priority of, International patent application Serial No. PCT/JP2006/302016, filed Feb. 7, 2006, now Publication No. WO 2006/082973, published Aug. 10, 2006, and published in Japanese, the content of which is hereby incorporated by reference in its entirety.
The present invention relates to a technology for thinning a key sheet on which a plurality of keys being input means for handy mobile equipments such as portable phones, personal digital assistants (PDA) or the like are assembled and disposed.
A key sheet is a component constituting a handy mobile equipment such as a portable phone, personal digital assistant (PDA) or the like, and a plurality of key tops which are push buttons each indicating an alphabetical and/or numerical key or a function key are adhered in an arrayed manner to the surface of a single sheet referred to as a key pad. The above-mentioned key pad is a flexible sheet having rubber elasticity such as a silicone rubber, thermoplastic elastomer or the like. On the undersurface of the key sheet thus configured, a printed circuit board provided with a plurality of normally open contacts closed by pressing a push button is closely disposed, so that push button switches are formed, and further a light source for illuminating a key top from the back surface is disposed.
Since the key sheet is thus configured in a state that a plurality of components are piled up in a layered manner, the thicknesses of each one of components are accumulated to have substantial thickness. Therefore, it is requested that the whole handy mobile equipment should be thinned as much as possible so as to further enhance the portability thereof.
However, for example in the method disclosed in Patent Publication 1, there is a structural limit on further thinner configuration because each component to be piled up has a conventional common configuration. Moreover, there is a limit for the thinning of a key sheet only by using an EL sheet thinner than an LED as a light source. That is, while the EL sheet has a thinner thickness compared with an LED (light-emitting diode) which is conventionally used as a light source in a general way, it requires two sheets of resin films as a substrate sheet forming an EL element consisting of the accumulation of an electrode and a light-emitting layer and as a protective sheet. Therefore, despite the fact that thickness of the EL element itself is very thin, there is a limit for thinner configuration (0.2 mm at the lowest under current situation) due to the addition of the thickness of the above-mentioned two resin sheets.
Patent Reference 1: Japanese Laid-Open Patent [Kokai] Publication No. 2002-050258 A
Portable phones are in a trend of having thinner configuration due to emphasis on the design. Along with this trend, it is requested that the thickness of a key sheet should be thinned as much as possible. However, as long as the prior art is followed, there is a limit for the thinning of a key sheet. The limit was 1.5 to 1.6 mm.
Although a light source (LED) for illuminating a key top from the back surface is small, it is a three-dimensional structure having a dimension of length, width and height like a small bean, and in particular its height hampers thinner configuration.
When thinning a key top made of resin, 0.6 mm would be a limit in order to gain necessary strength. Further, when using an LED (light-emitting diode) as a light source, it is necessary to provide a key pad with an LED housing part. The housing part needs the thickness of at least 0.6 mm, and it is necessary to secure an operation part with 0.3 mm for ensuring key strokes, so that it is impossible to set the thickness of the key pad to 0.9 mm or less. Further, when using an EL sheet as a light source, the above-mentioned LED housing part would be unnecessary. However, the thickness of the entire key pad including the above-mentioned operation part needs at least about 0.6 mm, to which the thickness of the above-mentioned EL sheet (0.2 mm or more) is added, so that the thickness of the entire key sheet ends up being 1.4 mm or more.
In consideration of such current situation, the objects to be achieved by the present invention are: to reduce the number of the accumulation of each independent component of the key unit part; and to limit the height of a light source, which is one of the causes for hampering thinner configuration, for illuminating a key top from the back surface, in order to thin the thickness thereof as much as possible so as to further enhance the portability of a handy mobile equipment.
As one means for achieving the above-mentioned objects, the thickness of a key top is limited to about 0.6 mm when it is made of a resin; or when a key top is what is called a film key with its surface being coated with a resin film, and is made of a metal plate such as stainless steel, the thickness thereof is limited to 0.1 to 0.3 mm. When a key top is made of a metal, openings such as letters or the like are perforated by means of laser etching or chemical etching in order to obtain an illumination type key top.
Further, an attention was paid to a light source for illuminating a key top from the back surface, which hampers thinner configuration. An EL-integrated thin key sheet is configured by using, instead of a conventional three-dimensional light source such as LED or the like, a thin film EL (electro-luminescence) element which can reduce the thickness (height) by a large extent, and by forming the thin film EL element on the back surface of a key top by means of printing. Moreover, with regard to the wiring to the thin EL light source, further thinner configuration is tried to be achieved by using a film-forming method for a metal thin film such as deposition, sputtering or the like on a key pad.
While the limit of the thickness of a key unit according to the prior art was 1.5 to 1.6 mm, the limit is broken by carrying out the present invention, enabling thinner configuration down to about 1.0 mm.
Further, by forming an EL element on the back surface of the key top by printing, a base film of the EL element is eliminated, so that the key sheet can be thinned by the eliminated space.
Further, by forming an EL element on the back surface of the key top by printing, a base film of the EL element can become unnecessary, so that the key sheet feel can be enhanced.
Thinner configuration of a key sheet is tried to be achieved with an embodiment in which a base film of an EL sheet was eliminated by printing an EL element directly on the back surface of the key top and an embodiment in which the wiring to an EL element is formed by means of printing, deposition, sputtering or the like on a key pad which is a flexible sheet having rubber elasticity such as a silicone rubber.
The shapes of mobile phones are roughly classified into a type in which a display part and a key top part are disposed on the same surface and which has a bar shape (straight type) as a whole and into a folding type in which a hinge is disposed between a display part and a key top part so that folding is possible. The key sheet thinning according to the present invention can be applied to either type. Thus, an application example for the folding type (see
As shown in
On the back surface of each key top 2, an EL element 8, 8 . . . which is a light source for illuminating letters, symbols, graphics or the like indicating the functions of each of the keys 2a, 2a, . . . , 2b, 2b, . . . , and 2c is directly formed by means of an appropriate printing method such as screen printing or the like (see
Moreover, when each key top 2, 2 . . . is made of a transparent hard resin, there is formed, on the back surface thereof, a letter-printed layer 9 which indicates, in a positive or in a negative form, alphabets, symbols and/or numerals or the like indicative of the functions of each of the keys 2a, 2a, . . . , 2b, 2b, . . . , and 2c by means of an appropriate method such as screen printing (see
As shown in
As a light source for transparent illumination, EL (Electro-luminescence) elements 8, 8 are each formed on the back surface of each of the key tops 2, 2 by means of printing or the like. For a wiring for supplying power to each EL element 8, the wiring pattern 3b of the key pad 3 made of a silicone rubber or the like is used. The key tops 2, 2, . . . having the above-mentioned configuration are fixed on predetermined locations on the top surface of the key pad 3 by means of the adhesive 7. At the same time, the EL element 8 is electrically connected to the printed circuit board 5 by the wiring pattern 3b formed on the key pad.
In the case of the thin key sheet 1 which adopts a key top 2 made of a thin metal plate such as stainless steel or the like shown in the above-mentioned Embodiment 1, it becomes possible to use as a key top 2 a metal plate with a thickness of 0.1 to 0.3 mm, and in addition it becomes possible to set the thickness of the combination of the metal plate and a metal dome 4 with a thickness of 0.2 to 0.3 mm plus the thickness of the key pad 3, i.e., the thickness from the surface of the key top 1 to the surface of the printed circuit board 5 to about 0.88 to 0.98 mm. Moreover, a key top 2 having further thinner configuration would be effective in order to thin the key sheet. However, if it becomes too thin, it end up being deformed and not being restored to its original shape when some stress is applied to the key top 2. Therefore, the thickness of about 0.2 to 0.3 mm is desirable under current situation. However, using a material or a method which solves the problem of the deformation due to stress could enable the thickness of 0.1 mm or less. While omitting illustration and detailed explanation, for example, a structure of sandwiching a metal plate by and between two thin resin films (laminate structure) could enable to further thin the thickness of the metal plate itself without lowering the strength or shape restorability necessary for the key top 2.
In the key sheet 1A, when adopting a hard resin plate as the key top 2, the limit of the thickness is 0.6 mm, so that it becomes possible to set the thickness from the surface of the key top 1 to the surface of the printed circuit board 5 to about 1.28 mm. Since the configuration other than those mentioned above of a key sheet 1A basically has the configuration similar to the key sheet 1 of Embodiment 1, descriptions are omitted for the parts with the similar configuration by using the same symbols as those used for the descriptions of the key sheet 1.
A through hole 3c for electrically connecting wiring patterns 3b, 3b at the front/back sides is formed on the key pad 3. The through hole 3c is filled with conductive rubber or conductive ink 3d. That is, the through hole 3c is filled by printing rubber or conductive ink after the completion of the electrical connection between the top surface and the undersurface. The key tops 2, 2, . . . having the above-mentioned configuration are fixed on predetermined locations on the top surface of the key pad 3 by means of adhesive 7. At the same time, the EL element 8 is electrically connected to the printed circuit board 5 by the wiring pattern 3b formed on the key pad.
Each key top 2 of the key sheet 1B can be thinner in its thickness than the key top 2 of the above-mentioned key sheet 1A the whole of which is formed by a hard resin due to the enhanced strength by the film 10 for coating the surface, thus allowing the thickness of 0.3 mm. Therefore, the entire thickness thereof fell within about 0.98 mm. Since the configuration other than those mentioned above of a key sheet 1B basically has the configuration similar to the key sheet 1A of embodiment 2, descriptions are omitted for the parts with the similar configuration by using the same symbols as those used for the descriptions of the key sheet 1.
A through hole 3c for electrically connecting wiring patterns 3b, 3b at the front/back sides is formed on the key pad 3. The key tops 2, 2, . . . having the above-mentioned configuration are fixed on predetermined locations on the top surface of the key pad 3 by means of the adhesive 7. At the same time, the EL element 8 is electrically connected to the printed circuit board 5 by the wiring pattern 3b formed on the key pad.
The appearances of the key sheet 1C of the Embodiment 4 are approximately the same as the key sheet 1A shown in
A metal dome 4 is interposed between the pressing element 3a, 3a, . . . on the undersurface of the key pad 3 and the printed circuit board 5. The metal dome 4 is made of a material having conductivity and shape memory capacity such as phosphor bronze, and its name is derived from its dome-like shape. The metal dome 4 does not always need to have such dome-like shape. It is sufficient for the metal dome 4 to have a shape and a structure in which: when the key top 2 is pressed down, normally open contacts are closed for certain by being pressed by the pressing element 3a of the key pad 3; and when the key top 2 is not pressed down, the metal dome 4 can be restored to its original shape. When a specific key top 2 is pressed down, the metal dome 4 functions to close, in response to the press-down movement of the metal dome element, normally open contacts printed-wired on the printed circuit board 5 disposed therebelow so as to form an electric circuit.
The letter-printed layer 9 which corresponds to decorations including letters, symbols or the like which indicate the function of each key is applied to the top surface or the undersurface of the key top 2 by means of various arbitrary decoration methods. Even when the key top is made of a metal, if not giving a metal-like appearance to the key sheet, various types of paintings can also be applied to its surface.
Since the present invention relates to a thin key sheet for use in mobile equipment such as portable phones, and personal digital assistants (PDA), it has a wide range of applicability in industrial fields seeking thinner configuration of these equipment provided with keys, including manufacturing industries of electronic equipment and the various components thereof.
Number | Date | Country | Kind |
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2005-029994 | Feb 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2006/302016 | 2/7/2006 | WO | 00 | 8/6/2007 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2006/082973 | 8/10/2006 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5797482 | LaPointe et al. | Aug 1998 | A |
7070349 | Dombrowski et al. | Jul 2006 | B2 |
7273993 | Tanner et al. | Sep 2007 | B1 |
Number | Date | Country |
---|---|---|
11-134961 | May 1999 | JP |
2002-025374 | Jan 2002 | JP |
2002-050258 | Feb 2002 | JP |
2003-007161 | Jan 2003 | JP |
2004-193060 | Jul 2004 | JP |
WO 2004038746 | May 2004 | WO |
Number | Date | Country | |
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20080277253 A1 | Nov 2008 | US |