Abstract:
As it is often difficult for users of a keyboard to adequately identify and select the correct keys in a keyboard where the light is inadequate, it is desirable to provide a keyboard capable that allows a user to better see keys of the keyboard even in environments where there is not sufficient light to see the keys (e.g., in an airplane). A keyboard of the present invention comprises a substrate, a membrane, an elastic member, a cover sheet, a keytop, and light-emitting means for emitting light from the bottom of the substrate to the keytop. The keytop is illuminated and a legend on a key surface can be seen, so that the chance of incorrect key stroke is reduced.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a keyboard for a portable notebook computer capable of seeing keys even in low light conditions.  
           [0003]    2. Description of the Related Art  
           [0004]    As a notebook computer becomes thinner and lighter, consumers have found that such improvements make it easier to carry to a variety of different locations. Further, there has been a dramatic increase in battery capacity for portable notebooks, thereby allowing users to use a notebook computer for longer periods, often in a continuous format, of time. As a result, the use of a notebook computer in public, in transportation-based environments and outdoors has become more commonplace.  
           [0005]    In general, when a keytop  92  of a key  90  on a keyboard of a notebook computer shown in FIG. 11 is pressed, a rubber member  96  is pushed downward with a pantograph  94 . When a cup portion  98  of the rubber member  96  is thereby compressed, a protrusion  100  pushes a first contact  112   a  of an upper polyester film  104  downward, so that the first contact  112   a  comes in contact with a second contact  112   b  of a lower polyester film  106 . When the two contacts  112   a  and  112   b  touch each other, electrical continuity between wirings on the films  104  and  106  is ensured (i.e., the path is conductive) and an electric signal is transmitted to a controller of the keyboard. From the transmitted electric signal, the controller judges which key  90  was pressed.  
           [0006]    However, since it is hard for a user to visibly see the keys  90  in a dimly-lit environment, such as in an airplane, it is readily conceivable that a user is likely to make an incorrect key stroke often. As such, in order to overcome these errors, it would be useful to provide a lighting fixture to a keyboard so as to illuminate the keys  90 .  
           [0007]    For example, Japanese Unexamined Patent Publication No. (Patent Kokai No.) 11-232957 (1999) and 11-282606 (1999) disclose a key input device having a backlight for illuminating a keyboard. These input devices are for an electronic organizer and handy terminal, and comprise a backlight panel on a substrate or a sheet on which contacts and a circuit are formed. However, in the case of a keyboard of a notebook computer, projections  115  of a substrate  114 , as in FIG. 11, would need to be inserted into holes bored through polyester films  104  and  106  and spacer  108  so as to keep a membrane  110  in a right position, as shown in FIG. 11. Unlike the aforementioned key input devices, holes cannot be bored into the backlight panel, so that the backlight panel cannot be placed on the membrane  110  to illuminate the keys  90 .  
           [0008]    As such, it would be desirable to provide a keyboard capable of enabling a user to better see keys in environments where there is typically an insufficient light source to allow normal viewing, such as in an airplance, for example.  
         SUMMARY OF THE INVENTION  
         [0009]    Accordingly, an object of the present invention is to provide a keyboard capable of seeing keys even in environments where there is not sufficient light to see the keys, for example, in an airplane.  
           [0010]    A keyboard, according to an aspect of the present invention comprises: a substrate; a membrane having contacts for each key formed on the substrate; an elastic member for each key formed over the contacts of the membrane; a keytop for each key formed over the elastic member; and light-emitting means for emitting light from the underside of the substrate to the keytops, wherein the substrate and the membrane are light transmissive at least at portions corresponding to the top surfaces of the keytops, and the keytops are light transmissive at portions corresponding to legends or non-legend areas of the top surfaces of the keytops.  
           [0011]    In another aspect of the present invention, light emitted by the light-emitting means of the keyboard, formed under the substrate, passes through the substrate, membrane and elastic material to the keytops, to thereby provide for each keytop to appear lit.  
           [0012]    Similarly, where a film-like circuit board having contacts for each key is used as a substrate for the membrane, light emitted by the light-emitting means formed under the substrate passes through the substrate, circuit board, elastic material, and keytops, such that each keytop appears to glow.  
           [0013]    In another aspect of the present invention, the light-emitting means under the substrate can illuminate the keytops, thereby improving the likelihood of a user selecting the desired key such that the chance of an incorrect key stroke is reduced. In addition, the thermoelectric generating element is used as a power supply source for light source of the light-emitting means, so that battery duration is not reduced. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    Other aspects, features, and advantages of the present invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings, in which:  
         [0015]    [0015]FIG. 1 shows a structure of a keyboard according to an embodiment of the present invention;  
         [0016]    [0016]FIG. 2 shows a structure of a key on the keyboard according to an embodiment of the present invention;  
         [0017]    FIGS.  3 ( a ) and  3 ( b ) present a top view and a side view, respectively, of a backlight sheet used in the keyboard according to an embodiment of the present invention, and  
         [0018]    [0018]FIG. 3( c ) shows a parallel arrangement of the backlight sheets;  
         [0019]    [0019]FIG. 4( a ) is a perspective view showing another backlight sheet used in the keyboard according to an embodiment of the present invention, and  4 ( b ) shows a parallel arrangement of the backlight sheets;  
         [0020]    [0020]FIG. 5 is a side view of a thermoelectric generating element;  
         [0021]    [0021]FIG. 6( a ) shows a keytop whose surface is made light transmissive, and  
         [0022]    [0022]FIG. 6( b ) shows another keytop with legends made light transmissive;  
         [0023]    [0023]FIG. 7 shows a structure of another key on the keyboard according to an embodiment of the present invention;  
         [0024]    [0024]FIG. 8 shows a key in which a light-emitting diode is used as a substitute for the backlight sheet;  
         [0025]    [0025]FIG. 9 shows a backlight sheet which can be used as a substitute for the backlight sheet, such as that shown in FIG. 2 or  3 ;  
         [0026]    [0026]FIG. 10 is a sectional view of an electro luminescence (EL) panel which can be used as another lighting means; and,  
         [0027]    [0027]FIG. 11 shows a structure of a key on a conventional keyboard. 
     
    
     DETAILED DESCRIPTION  
       [0028]    Embodiments of the keyboard according to the present invention will be described with reference to the accompanying drawings.  
         [0029]    As shown in FIGS. 1 and 2, a keyboard  10  of the present invention comprises: a substrate  34 ; a membrane  30  having contacts  32   a  and  32   b  for each key and a circuit, which is formed over the substrate  34 ; an elastic member  17  for each key formed over the contacts  32   a  and  32   b  of the membrane  30 ; a cover sheet  22  which covers a part of the membrane  30  where the elastic member  17  is not placed; a keytop  12  for each key formed over the elastic member  17 ; and light-emitting means  39  for emitting light from the underside of the substrate  34  to the keytop  12 . The substrate  34  and membrane  30  are preferably made of light transmissive materials. For example, the substrate  34  is made of transparent or translucent acrylic resin or tempered glass. As used herein, a key  11  is preferably composed of the aforementioned keytop  12  and elastic material  17 .  
         [0030]    The membrane  30  comprises upper and lower light transmissive films  24  and  26  such as polyester film and a light transmissive spacer  28  sandwiched therebetween. On the films  24  and  26 , contacts  32   a  and  32   b  for each key and a circuit are formed of a conductive material such as conductive ink and the contacts  32   a  and  32   b  faces each other in a hollow  29  of the spacer  28 . The conductive ink is preferably light transmissive, but it does not have to be light transmissive when the contacts  32   a  and  32   b  and the circuit are too fine to block the optical path of light for illuminating the keytop  12 .  
         [0031]    The elastic material  17  is preferably composed of a rubber member  16  and a pantograph  14 . The keytop  12  is supported by the pantograph  14 . Therefore, whichever part of the keytop  12  is pressed, the keytop  12  is pushed straight down. When the keytop  12  is pressed, a rubber member  16  is pushed downward with a pantograph  14 . A cup portion  18  of the rubber member  16  is thereby compressed, and a protrusion  20  pushes the contact  32   a  of the upper film  24  downward. Then the contact  32   a  comes in contact with the contact  32   b  of the lower film  26 . When a finger is moved off the keytop  12 , the rubber member  16  and the pantograph  14  generally revert to the original position, and the contact  32   a  moves away from the contact  32   b . The substrate  34  and membrane  30  are preferably made of light transmissive materials. However, they do not need to be light transmissive in their entirety but may be light transmissive at least at portions corresponding to the top surfaces of the keytops where legends are given.  
         [0032]    The pantograph  14  and rubber member  16  constituting the elastic member  17  are also preferably made of light transmissive materials but may not necessarily be light transmissive if they allow sufficient light transmission to provide acceptable legend readability because of their small size or structure. The cover sheet  22  may be light transmissive in its entirety or locally at portions corresponding to the top surfaces of the keytops. Alternatively, since the cover sheet  22  includes openings in which the rubber members  16  are placed, the cover sheet  22  may be opaque if the elastic member  17  is such as not to block light transmission through the openings.  
         [0033]    As shown in FIGS.  3 ( a ) and  3 ( b ), the light-emitting means is a backlight sheet  39  composed of a light source  40 , a light-guiding plate (light-guiding member)  36  for guiding light from the light source  40  in the direction shown by an arrow, a reflective sheet  38  for reflecting light, and diffusion layers  37  for diffusing light which is formed integral with the light-guiding plate  36 . The light source  40  may be a light-emitting diode or a fluorescent light. The diffusion layers  37  are circular in shape, and the sizes thereof increase with distance from the light source  40 , as shown in FIG. 3( a ).  
         [0034]    Although the amount of light decreases with distance from the light source  40 , the increasing sizes of the layers  37  enable efficient light diffusion and uniform radiation of light from the surface of the light-guiding plate  36 . A plurality of backlight sheets  39  are arranged in accordance with an area of the keyboard  10 . Given that the backlight sheet  39  is 60 millimeters long and 20 millimeters wide, an arrangement of backlight sheets  39  in two rows and twelve per row constitutes the same area as the keyboard  11 , as shown in FIG. 3( c ).  
         [0035]    For example, where a keytop  12  is 18 millimeters long and 18 millimeters wide, three keys  11  can typically be arranged on one backlight sheet  39 . The backlight sheets  39  are arranged in parallel. For example, a uniform radiation backlight sheet LUB 1000 (available from ROHM CO., LTD) is used as the backlight sheet  39 , it operates at 2 V and 0.02 A, and the backlight sheets consume 0.98 watts of power in total.  
         [0036]    The light source  40  is not limited to the one which is provided throughout the one side of the plate  36 , as shown in FIGS.  3 ( a ) to  3 ( c ), but it can be provided partially on the one side of the plate  36 , as shown in FIG. 4( a ) in the case of large size backlight sheets  41 . Such backlight sheets  41  may be arranged in two rows and three per row, as shown in FIG. 4( b ). Examples of the backlight sheet include a 4-inch backlight sheet for monochrome LCD (manufactured by OMRON Corporation, for example). This backlight sheet operates at 4 V and 0.02 A, and six backlight sheets  41  consume 0.48 watts of power in total.  
         [0037]    The power for the light source  40  is derived from a thermoelectric generating element  42  shown in FIG. 5. In the element  42 , p-type semiconductors  48  and n-type semiconductors  50  are connected in series via electrodes  46   a  and  46   b . When a temperature difference occurs between an upper substrate  44  and a lower substrate  45 , a temperature difference also occurs between the electrode  46   a  connected to the substrate  44  and the electrode  46   b  connected to the substrate  45 . Thus, electromotive force is generated due to the Seebeck Effect. Since a plurality of p-type semiconductors  48  and n-type semiconductors  50  are connected in series via the electrodes  46   a  and  46   b , electromotive force becomes large.  
         [0038]    As shown in FIG. 1, the thermoelectric generating element  42  is provided between a micro processing unit (MPU)  52  and a heat sink  54  on a mother board  51  of a notebook computer, and generates electricity using a temperature difference between the MPU  52  and a heat sink  54 . The thermoelectric generating element  42  generates electricity to be consumed by the light sources  40  of the backlight sheets  39 . In another embodiment of the present invention, instead of the MPU  52 , a chip set for controlling data input and output in a notebook computer may be used.  
         [0039]    An example of the thermoelectric generating element  42  is a thermoelectric generating element TECI-12705 (available form Fujitaka Co., Ltd., for example), which is capable of generating about 1 watt of power (0.2 Amperes at 5 Volts, 0.5 Amperes at 2 Volts, or 0.25 Amperes at 4 Volts) when a temperature difference is about 10 degree Celsius. This thermoelectric generating element can generate larger electricity than the backlight sheets  39  and  41  consumes, so that no battery of the notebook computer is used. An example of the MPU  52  is a PENTIUM III microprocessor (available from Intel Corporation, for example) and an example of the chip set is a chip set 440BX.  
         [0040]    A method of illuminating a keyboard  10  will be described. The MPU  52  generates heat by the use of the notebook computer, and the thermoelectric generating element  42  provided between the MPU  52  and the heat sink  54  generates electricity due to a temperature difference therebetween.  
         [0041]    The light source  40  of the backlight sheet  39  emits light using electricity generated by the thermoelectric generating element  42 . The light emitted from the light source  40  travels through the light-guiding plate  36 , as shown in FIGS.  3 ( a ) and  3 ( b ) by arrows. The light beams traveling through the plate  36  are scattered by the diffusion layer  37 .  
         [0042]    As shown in FIGS.  3 ( a ) and  3 ( b ), the scattered light beams emanate from the surface of the plate  36  and travel in every direction. Furthermore, the light beams are also reflected by the reflective sheet  38 , so that all the light beams are radiated from the surface of the plate  36  into the air. Although only the light source  40  emits light in the backlight sheet  39 , the scattered radiation of light beams from the surface of the plate  36  can make the whole of the plate  36  luminous.  
         [0043]    Passing through the substrate  34 , membrane  30 , cover sheet  22 , and elastic member  17 , the light emanated from the surface of the plate  36  illuminates the keytops  12 . The keytops  12  may be made of a resin such as acrylic resin. The keytops  12  are formed so that non-legend areas of top key surfaces  56  are light transmissive as shown in FIG. 6( a ) or legends  58  are light transmissive as shown in FIG. 6( b ). Therefore, the legends  58  on the keytop  12  can be recognized through the use of light.  
         [0044]    In the keyboard  10  of the present invention, the keytops  12  are illuminated by the backlight sheet  39 , as described above. Therefore, the keys  11  can be seen even in a dimly-lit environment. Further, the light source  40  of the backlight sheet  39  does not draw power from the battery of a notebook computer but from electricity generated by the thermoelectric generating element  42 , so that battery duration is not reduced by the backlight sheet  39 .  
         [0045]    As shown in FIG. 7, the aforementioned keyboard  10  may be modified to include an electrically conductive member  68  in the cup portion  18  of the rubber member  62 , and a film-like circuit board  70  is used as a substitute for the membrane  30 . The key  60  shown in FIG. 7 comprises: a substrate  34 ; the film-like circuit board  70  having contacts  66  for each key and a circuit, which is formed over the substrate  34 ; an elastic member  64  for each key which is formed over the contacts  66  of the board  70  and has an electrically conductive member  68  for providing electrically continuity between the contacts  66 ; a cover sheet  22  which covers a part of the board  70  where the elastic member  64  is not placed; a keytop  12  for each key formed over the elastic member  64 ; and light-emitting means  39  for emitting light from the bottom of the substrate  34  to the keytop  12 . The substrate  34 , film-like circuit board  70 , and cover sheet  22  may be made of light transmissive materials. The backlight sheet  39  shown in FIGS.  3 ( a ) to  3 ( c ) is used as the light-emitting means  39  in FIG. 7.  
         [0046]    Further, the power for the backlight sheet  39  is derived from the thermoelectric generating element  42  shown in FIG. 5.  
         [0047]    Passing through the substrate  34 , film-like circuit board  70 , elastic member  64 , and cover sheet  22 , the light emanated from the surface of the light-guiding plate  36  illuminates the keytops  12 . The keytop  12  is formed so that the top key surface  56  except legends is made light transmissive as shown in FIG. 6( a ) or legends  58  are made light transmissive as shown in FIG. 6( b ).  
         [0048]    As in the case of the aforementioned keyboard  10 , the key  60  shown in FIG. 7 can be seen by a user even in a dimly-lit environment. Further, the backlight sheet  39  does not draw power from the battery of a notebook computer but from electricity generated by the thermoelectric generating element  42 , so that battery duration of a notebook computer is not reduced by the backlight sheet  39 .  
         [0049]    While the embodiments of the present invention have thus been described, it should be understood that the present invention can be materialized in other embodiments. For example, as shown in FIG. 8, a light-emitting diode  74  can be provided to each key  72 . Further, light from an arbitrary light source can be guided to the bottom of the key  72  through optical fibers to illuminate the keytop  12 .  
         [0050]    Additionally, luminescent color of the light source  40  is not particularly limited. The color of the keytop  12  may vary depending on the luminescent color of the light source  40  or by the color of the light transmissive material of the keytop  12 . When the substrate  34 , cover sheet  22  and membrane  30  or circuit board  70  are transparent or translucent in their entirety, there may occur light leakage between the keys  11 . Therefore, in order to prevent light leakage between the keys  11 , it is preferable to make one or more of them opaque at areas between the keys  11 .  
         [0051]    Further, in addition to backlight sheets  39  and  41  shown in FIGS.  3 ( a ),  3 ( b ),  3 ( c ),  4 ( a ) and  4 ( b ), a backlight  76  such as that shown in FIG. 9 can be also used. In the backlight  76 , the light emitted from one or more light sources  78  is uniformly radiated through a lighting curtain  82  and a diffusion sheet  84  which in combination act to produce uniformly distributed light. A fluorescent lump can be used as the light source  78 .  
         [0052]    In a further embodiment, an electro luminescence (EL) panel  85  shown in FIG. 10 can be used as another light-emitting means. In the EL panel  85 , a fluorescent element  88  is sandwiched between a metal plate  89  and a transparent conductive film  87 . The fluorescent element  88  emits light through the application of voltage, and the emitted light is released from the surface of a transparent protective film  86 .  
         [0053]    In the key  11  shown in FIG. 1, the keytops  12  are always illuminated by the backlight sheet  39 . However, when a notebook computer is used in a well-lit area, it is not necessary to illuminate the keytops  12 . Therefore, where a notebook computer has a photosensor anywhere therein and is used in a well-lit area, it is possible to stop providing electricity to the light source  40  of the backlight sheet  39 . The electricity generated by the thermoelectric generating element  42  can then be used for recharging battery or as a power source to operate various electronic devices.  
         [0054]    Alternatively, instead of a photosensor, a software program can be stored in a memory of a notebook computer for controlling light emission and shutoff of the light source  40 .  
         [0055]    The thermoelectric generating element  42  generates electricity through the use of the Seebeck effect, however, it may serve as a cooling device using the Peltier effect by flowing an electric current. Therefore, when a notebook computer is used in a well-lit area, it is possible to cool the MPU  52  and the chip set using the Peltier effect by flowing a current into the element  42 .  
         [0056]    Further, where a desktop personal computer has to be used in a dimly-lit environment, a backlight sheet can be placed under a substrate of a keyboard so as to illuminate keytops.  
         [0057]    Various changes, modifications and improvements can be made to the embodiments on the basis of knowledge of those skilled in the art without departing from the scope of the invention.