Coordinate input device

A coordinate input device includes a coordinate input element. The coordinate input element includes a transparent coordinate detector and a controller having a control circuit which drives and controls the coordinate detector and which corrects electrostatic capacitance noise disturbing the coordinate detector. The coordinate input device also includes a liquid crystal display device provided on the back side of the coordinate input element, a casing for holding the coordinate input element and the liquid crystal display device, and an L-shaped and a reverse L-shaped push button switches provided on the upper surface of the casing.

This application claims the benefit of priority to Japanese Patent Application 2001-172455, filed on Jun. 7, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrostatic-capacitance-type coordinate input devices, which are operated with a user's finger and so on, and in which the coordinate position of a touched portion is detected based on a current variation according to a variation in electrostatic capacitance and the coordinate position of the touched portion is input.

2. Description of the Related Art

In recent years, notebook computers have been widely used for space-saving in offices and homes. In this type of computer, a pad-type coordinate input device operated by dragging a finger on a touch board has been widely adopted and put into practical use as a coordinate input device for moving a cursor displayed on a display.

FIG. 7is a perspective view showing the configuration of a critical portion of a coordinate input device100.

The coordinate input device100shown inFIG. 7includes a planar touch board101provided at the top, a film substrate106comprising a dielectric thin film such as a resin film provided on the lower surface of the touch board101, and a circuit board107provided on the lower surface of the film substrate106. The film substrate106is a dielectric substrate. The upper surface of the film substrate106is provided with a plurality of X-electrodes106aat predetermined intervals and the rear surface thereof is provided with a plurality of Y-electrodes106at predetermined intervals. The planar touch board101is bonded to the upper surface of the film substrate106with an adhesive or the like. Also, the film substrate106and the circuit board107are bonded via a dielectric film (not shown).

In the above-described film substrate106, the Y-electrodes106bextend in the direction orthogonal to the X-electrodes106aand the electrodes106aand106bare arranged in a matrix in plan view, with the film substrate106therebetween. Also, the X-electrodes106aand the Y-electrodes106bare printed on the upper surface and the lower surface of the film substrate106respectively, with a silver paste or the like. Further, through-holes108are formed along one edge of the circuit board107and along another edge adjacent to that edge. Also, land portions electrically connected to the electrodes106aand106bare formed on the rear surface of the film substrate106at positions corresponding to first ends of the X-electrodes106aand first ends of the Y-electrodes106b. The land portions and the through-holes108of the circuit board107are electrically connected. That is, the X-electrodes106aand the Y-electrodes106bare electrically connected to a wiring pattern formed on the upper surface of the circuit board107via the through-holes108.

Further, a ground layer109comprising a copper foil or the like is provided at the center of the upper surface of the circuit board107. The ground layer109helps to prevent a signal generated in the lower part of the circuit board107from disturbing the X-electrodes106aand the Y-electrodes106b. Also, a control circuit chip110is soldered to the wiring pattern on the rear surface of the circuit board107. By scanning the touch board101with a finger so that the finger is in soft contact with the touch board101, a part of the electric flux lines formed between the X-electrodes106aand the Y-electrodes106bof the film substrate106is absorbed by the finger, and thus the electric flux lines to the Y-electrodes106bare reduced so that electrostatic capacitance varies. The control circuit chip110converts the variation in the electrostatic capacitance to a variation in an electrical signal and the variation in the electrical signal is converted to a desired coordinate position, whereby the position of the finger on the touch board101can be detected.

The coordinate input device100having the above described configuration is often mounted in front of a keyboard in a notebook personal computer and can be operated without the user moving his/her hands much away from the home position of the keyboard. However, in many pad-type coordinate input devices, a flat touch board is exposed at the surface of the computer. Thus, a person who is not accustomed to operate a computer is often puzzled by the operation method and this type of coordinate input device does not have excellent ease of use.

Also, when the area of the touch board101is greatly reduced, the operability and ease of use of the above-described coordinate input device are reduced. Thus, it is inevitable that the touch board101occupies a predetermined space in the operating portion of a notebook personal computer. Therefore, it is difficult to further miniaturize the touch board in a notebook personal computer including the coordinate input device100. Accordingly, the inventors of the present invention have considered adding another function to the portion occupied by the coordinate input device100and have investigated improving the ease of use of the coordinate input device and electronic equipment including the same, and as a result, the present invention has completed.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an inexpensive coordinate input device which has transparency and a high light transmittance and which operates stably so that another function can be easily added to the coordinate input device.

In order to achieve the above-described object, the present invention adopts the following configuration.

The coordinate input device according to the present invention comprises: a coordinate detector including a first insulating layer which has transparency and which is formed at the top; a first electrode layer having a plurality of linear transparent electrodes formed in parallel on the lower surface of the first insulating layer; a second insulating layer which has transparency and which is formed on the lower surface of the first electrode layer; a second electrode layer having a plurality of linear transparent electrodes which are aligned in parallel and which extend in the direction orthogonal to the transparent electrodes of the first electrode layer, the second electrode layer being formed on the lower surface of the second insulating layer; and a third insulating layer which has transparency and which is formed on the lower surface of the second electrode layer, and a controller which is electrically connected to the two electrode layers of the coordinate detector so as to drive and control the electrode layers and which has a circuit for correcting electrostatic capacitance noise that disturbs the coordinate detector.

In the coordinate input device according to the present invention, the coordinate detector is configured by sandwiching the second insulating layer with the two electrode layers and providing the first insulating layer and the third insulating layer on each of the electrode layers respectively. Also, by forming each of the layers by using a transparent material, the transparent coordinate input device is realized. In the configuration of the coordinate input device in the known art shown inFIG. 7, each layer is laminated in the following order: the ground layer109, the insulating layer, the Y-electrodes106b, the insulating layer, the X-electrodes106a, and the touch board101, from the side of the circuit board107. On the other hand, the coordinate detector of the coordinate input device according to the present invention does not have a layer corresponding to the ground layer109shown inFIG. 7. The light transmittance of the coordinate detector is high because the coordinate detector does not include the ground layer. In the coordinate input device100shown inFIG. 7, the ground layer109is provided so that a noise, which is caused when the control circuit chip is driven, does not disturb the electrostatic capacitance generated between the electrodes106aand106b. Thus, when the ground layer109is not provided, a method for preventing the disturbance of the noise is necessary. The coordinate input device of the present invention operates stably without the ground layer, because the control circuit includes a correction unit for removing noise. Accordingly, the coordinate input device of the present invention has a transparent coordinate detector whose light transmittance is high, and can operate stably.

That is, in the coordinate input device of the present invention, at least the coordinate detector is transparent. Thus, the object placed on the back side of the coordinate detector can be seen from the side of the coordinate detector surface. Also, another function can be added to the portion occupied by the coordinate input device and the space can be effectively used. For example, by displaying the method for operating the coordinate input device so that the method is transmitted through the coordinate detector, the coordinate input device can be easily operated by even a person who is not accustomed to operate the coordinate input device. Accordingly, the usability of the device can be significantly improved.

Also, the coordinate input device of the present invention comprises: a coordinate detector including a first insulating layer which has transparency and which is formed at the top; a first electrode layer having a plurality of linear transparent electrodes formed in parallel on the lower surface of the first insulating layer; a second insulating layer which has transparency and which is formed on the lower surface of the first electrode layer; a second electrode layer having a plurality of linear transparent electrodes which are aligned in parallel and which extend in the direction orthogonal to the transparent electrodes of the first electrode layer, the second electrode layer being formed on the lower surface of the second insulating layer; and a third insulating layer which has transparency and which is formed on the lower surface of the second electrode layer, and a display device placed on the back side of the coordinate detector. A scanning frequency for scanning the electrodes of the coordinate input device is different from a driving frequency of the display device.

That is, in the coordinate input device of the present invention, since the display device is placed on the back side of the transparent coordinate detector, information displayed on the display device is transmitted through the coordinate detector so that an operator can see the information. With this configuration, by displaying necessary information such as hints for operation on the display device as required, a person who is not accustomed to operate the device can easily operate the coordinate input device or electronic equipment including the same. Alternatively, the display device can display an image, a calendar, time, and so on.

In the coordinate input device of the present invention, a scanning frequency for scanning the electrodes of the coordinate detector in a predetermined direction is different from a driving frequency for driving the display device. With this arrangement, the coordinate detector and the display device do not mutually disturb. Accordingly, deterioration in the detecting accuracy and malfunction of the coordinate input device and distortion of the display of the display device can be effectively prevented, and thus a stable operation can be realized.

Preferably, the coordinate input device further comprises a controller which is electrically connected to the two electrode layers of the coordinate detector so as to drive and control the electrode layers and which has a correction unit for removing electrostatic capacitance noise that disturbs the coordinate detector. With this configuration, disturbance from the display device provided on the back side of the coordinate detector and electronic equipment including the coordinate input device can be canceled. Accordingly, a malfunction of the coordinate input device can be prevented.

The display device may be a liquid crystal display device or an EL display device in which electroluminescent elements are aligned.

The advantage of the coordinate input device of the present invention can be achieved by using either of the above-mentioned display devices. Also, a thin and low-power-consumption coordinate input device can be realized by using either of the display devices.

For a liquid crystal display device as the display device according to the present invention, any type can be adopted without problems. Specifically, any of a transmissive-type, a reflective-type, and a transflective-type can be used. Furthermore, the driving method may be any of a passive matrix and an active matrix.

In addition, an arbitrary type of EL display device, such as a display device in which a gray scale is displayed by a variation in the luminance of EL elements or a display device using light of EL elements as lighting and including a liquid crystal device as an optical modulation element, can be used. Also, the EL element may be selected from an inorganic EL element, a polymer organic EL element, and a low-molecular organic EL element.

Also, a ground layer comprising a conductor may be provided on the back side of the display device. With this configuration, the coordinate detector and the display device can be electrically operated stably and an electrical disturbance from electronic equipment including the coordinate input device can be prevented. The ground layer comprising a copper foil or the like is provided at the center of the upper surface of a circuit board. The ground layer helps to prevent a signal generated in the lower part of the circuit board from disturbing X-electrodes and Y-electrodes.

Preferably, the controller comprises a reference signal storing unit for storing a reference signal, which is a detection signal obtained by scanning the electrodes of the first electrode layer and the second electrode layer while no operation is performed; and a correction value calculating unit for subtracting the reference signal from a detection signal while an operation is performed, thereby correcting the detection signal during the operation.

In the coordinate input device of the present invention, the electrodes are scanned when an indicating device such as a finger or a pen is not in contact with or is not approaching the coordinate detector (while no operation is performed), and an obtained detection signal is stored as a reference signal. Then, by subtracting the reference signal from a detection signal obtained by scanning the electrodes while the indicating device is put on the coordinate detector (during operation), variation in electrostatic capacitance generated by the indicating device is calculated so as to detect the coordinate position of the indicating device. Accordingly, variation in the electrostatic capacitance between the electrodes and the disturbance of noise from the control circuit can be removed from the detection result, and thus the coordinate input device which has a high detection accuracy and which operates stably can be achieved.

Each of the first insulating layer, the second insulating layer, and the third insulating layer may comprise a flexible resin substrate.

With this arrangement, the coordinate detector is flexible and thus the coordinate detector can be placed at a curved surface. Accordingly, the freedom of arrangement of the coordinate input device can be enhanced.

The light transmittance of the coordinate detector is preferably 90% or more.

With this arrangement, information displayed on the back side of the coordinate detector can be clearly seen. For example, by displaying the method for using the coordinate input device on the back side of the coordinate detector, a user can easily know the method, and thus the usability of the coordinate input device can be improved.

The coordinate detector and the controller of the coordinate input device may be connected to each other by a flexible wiring board, and the flexible wiring board may be placed on a side of the display device so that the controller is placed on the back side of the display device.

With this arrangement, the controller does not protrude outward from the coordinate detector in the coordinate input device, and thus the space for the coordinate input device can be reduced and the space in electronic equipment including the coordinate input device can be effectively used. Since the coordinate detector is transparent, it is not preferable to place the controller on the back side of the coordinate detector. However, by providing the display device on the back side of the coordinate detector and providing the controller on the back side of the display device, the controller can not be seen from the coordinate detector side.

The coordinate detector and the display device may be held on a casing and one or a plurality of push button switches may be provided on the upper surface of the casing. With this arrangement, operation buttons can be integrated into the coordinate input device. Accordingly, the coordinate input device can be easily integrated into electronic equipment and separate operation buttons are not required. Therefore, the manufacturing cost can be reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a plan view showing an example of a coordinate input device according to an embodiment of the present invention andFIG. 2is an exploded perspective view of the coordinate input device1shown inFIG. 1. The coordinate input device1shown inFIGS. 1 and 2includes a coordinate input element10, a liquid crystal display device (display device)20placed on the back side of the coordinate input element10, a casing30for holding the coordinate input element10and the liquid crystal display device20, and two push button switches40and41provided on the casing30.

The liquid crystal display device20is placed at the center on the upper side of the casing30so as to be sandwiched by the coordinate input element10and the casing30. The display area of the liquid crystal display device20faces the back side of a coordinate detector11of the coordinate input element10. The push button switches40and41are formed in an L-shape and a reverse L-shape, respectively, in plan view, first ends of the push button switches40and41are fixing portions40A and41A, and the other ends are operation buttons40B and41B operated by a user. The L-shaped push button switch40and the reverse L-shaped push button switch41are placed symmetrically, with the center being the opposing portions of the ends of the operation buttons40B and41B. These push button switches40and41are placed so as to surround part of the liquid crystal display device20. The fixing portions40A and41A are fixed to the casing30at the center of both sides of the liquid crystal display device20.

Next, the coordinate input element10will be described with reference toFIGS. 3 to 5.

FIG. 3is a plan view of the coordinate input element10shown inFIGS. 1 and 2,FIG. 4is a perspective plan view of the coordinate detector11of the coordinate input element10, andFIG. 5is a cross-sectional view of the coordinate detector11shown inFIG. 4.

As shown inFIG. 3, the coordinate input element10includes the coordinate detector11for detecting information scanned by a finger of the user, a pen, or the like and a controller12provided on one side (left side in the figure) of the coordinate detector11. In the coordinate input element10of the embodiment, the coordinate detector11and the controller12are integrated so as to share a substrate (a second insulating layer)16. As shown inFIG. 3, the controller12has a control circuit12afor driving and controlling the coordinate detector11on the substrate16shared by the coordinate detector11. The control circuit12ais electrically connected to the coordinate detector11through transparent circuit wiring lines (not shown) formed on the substrate16.

As shown inFIGS. 4 and 5, in the coordinate detector11, a plurality of (thirteen inFIG. 4) linear transparent electrodes (a first electrode layer)16aextending in the direction orthogonal to the longitudinal direction of the substrate16are provided in parallel on the upper surface of the flat substrate (second insulating layer)16, which comprises a transparent resin film and glass. Also, on the lower surface of the substrate16, a plurality of (five inFIG. 4) strip-like transparent electrodes (a second electrode layer)16bextending in the direction orthogonal to the transparent electrodes16aprovided on the upper surface of the substrate16are formed in parallel.

Also, as shown inFIG. 5, a protective layer (a first insulating layer)17comprising a transparent resin substrate is bonded to the substrate16with a transparent adhesive so as to cover the transparent electrodes16aand a lower insulating layer (a third insulating layer)18comprising a transparent resin material is bonded to the substrate16with a transparent adhesive so as to cover the transparent electrodes16bon the lower side of the substrate16. A transparent hard coat layer having surface unevenness may be bonded to the upper surface of the protective layer17with a transparent adhesive or the like. When such a layer is provided, the friction between the tip of a finger or a pen and the scanned surface is reduced when the surface of the coordinate detector11is scanned by the finger or the pen, and thus the usability can be improved.

One end in the longitudinal direction (the lower end inFIG. 4) of each of the transparent electrodes16ais connected to one end of corresponding circuit wiring line13comprising a transparent conductive material. The other end of each circuit wiring line13is connected to the control circuit12ashown inFIG. 3so that the control circuit12aand the transparent electrodes16aare electrically connected. On the other hand, one end in the longitudinal direction (the left end inFIG. 4) of each of the transparent electrodes16bformed on the lower surface of the substrate16is connected to one end of corresponding circuit wiring line14comprising a transparent conductive material. The other end of each circuit wiring line14is connected to the control circuit12aso that the control circuit12aand the transparent electrodes16bare electrically connected.

In the embodiment, each of the substrate16(second insulating layer), the protective layer17(first insulating layer), and the lower insulating layer18(third insulating layer) comprises a transparent resin substrate. However, these layers can be formed by applying a liquid resin material and then curing. For example, in order to form the protective layer17with this method, a light setting resin or a thermosetting resin is applied to cover the transparent electrodes16aso that the resin is cured by ultraviolet radiation or heating. Also, only the lower insulating layer18may be a transparent resin substrate and the other layers may be formed by applying a resin and curing it as described above.

By forming each of the layers by application of a resin and curing, an extremely thin layer can be easily formed. Accordingly, the light transmittance of the coordinate detector11can be easily increased compared to the case where the resin substrate is bonded with an adhesive.

The display area of the liquid crystal display device20is placed on the back side of the coordinate detector11and the liquid crystal display device20is sandwiched by the coordinate input element10and the casing30. In the coordinate input device1of the embodiment, the size of the liquid crystal display device20is substantially the same as that of the coordinate detector11. Also, information displayed on the liquid crystal display device20is transmitted through the coordinate detector11so that the user can see the information. Also, a conductive ground layer is provided on a plane surface of the liquid crystal display device20so as to keep the coordinate detector11and the liquid crystal display device20electrically stable and to prevent an electrical disturbance from the electronic equipment.

The liquid crystal display device20may be any of a reflective-type, a transmissive-type, and a transflective-type. In particular, the advantage of the coordinate input device of the present invention becomes significant when a reflective or transflective liquid crystal display device is used. The reason is as follows. In a reflective or transflective liquid crystal display device, display is performed by reflecting an external light at the reflective layer inside the device and thus the luminance greatly depends on the amount of external light. The coordinate input element10of the present invention has a high light transmittance, and thus attenuation of the light entering the liquid crystal display device and the light radiated from the device can be suppressed when the light is transmitted through the coordinate detector11. Accordingly, a bright display can be realized. Also, when a transmissive liquid crystal display device is used, the light radiated from the liquid crystal display device20is transmitted through the coordinate detector11with little attenuation so as to reach the user, and thus a clear and bright display can be obtained.

The operation buttons40B and41B of the push button switches40and41are movable vertically and are urged upward by tact switches (not shown) provided on the back side of these buttons. When one of the operation buttons40B and41B is pushed downward by the user, the tact switch on the back side is turned on and the tact switch is turned off when the user releases the button. Although two push button switches are used in the embodiment, the number of push button switches may of course be one or more than two. The number of push button switches may be selected according to the required functionability.

The coordinate input device1according to the embodiment having the above-described configuration can be used as, for example, a pointing device of a notebook personal computer. In this case, by scanning the upper surface of the coordinate detector11with a finger or a pen, a part of the electric flux lines formed between the transparent electrodes16aand16bshown inFIG. 4is absorbed by the finger or the pen at the positions where the transparent electrodes16aand16bcross, and the current applied to the transparent electrodes16bvaries and thus the electrostatic capacitance varies. The variation in the electrostatic capacitance is converted to a variation in an electrical signal by the control circuit12aprovided in the controller12, and the variation in the electrical signal is externally output as coordinate position information. Then, the cursor displayed on the display of the personal computer moves based on the coordinate position information.

In the coordinate input device1of the present invention, since all the members of the coordinate detector11of the coordinate input element10are formed by transparent material, the user can see the display on the liquid crystal display device20through the coordinate detector11. Consequently, by displaying the operating method, hints for operation, and so forth of the coordinate input element10on the liquid crystal display device20, a user unaccustomed to operate the device can easily operate the coordinate input element10. The liquid crystal display device20can display arbitrary information. Accordingly, by changing information to be displayed as required, the usability of electronic equipment including the coordinate input device1can be significantly improved.

The control circuit12aprovided in the coordinate input element10of the embodiment scans the transparent electrodes16aand16bof the coordinate detector11while the coordinate input element10is not being operated (when a finger or a pen is not in contact with or is not approaching the coordinate detector11) and stores an electrical signal obtained by the scan as a reference signal. Also, the control circuit12asubtracts the reference signal from the detection signal obtained by scanning the transparent electrodes16aand16bso as to correct the detection signal during an operation of the coordinate input element10(when the surface of the coordinate detector11is scanned by a finger or a pen).

That is, by comparing the electrostatic capacitance of the coordinate detector11while no operation is performed and the electrostatic capacitance of the coordinate detector11while an operation is performed, the change in the electrostatic capacitance caused by a finger or a pen during an operation can be extracted as a detection signal. Also, even when the electrostatic capacitance is gradually disturbed by external influences, the change in the electrostatic capacitance caused by the disturbance can be canceled by performing the above-described correction. Accordingly, a malfunction is less likely to occur in the coordinate input device.

Further, with the above-described correction method, a noise disturbing the coordinate detector11from a circuit of electronic equipment including the coordinate input device1and the drive circuit of the display device can be canceled in the same way. Therefore, the coordinate input device1operates extremely stably.

Also, since a ground layer comprising metal is not provided at the bottom of the coordinate detector11, extremely high light transmittance can be realized. On the other hand, the electrostatic capacitance generated between the transparent electrodes16aand16bis likely to be unsteady due to the variation in the electrostatic capacitance itself and noise caused by driving the control circuit. However, the variation in the electrostatic capacitance can be canceled by the function of the above-described control circuit12a.

In addition, in the coordinate input device1of the embodiment, the coordinate input element10is preferably operated in a mode wherein the frequency for scanning the transparent electrodes16ais different from the frequency for driving the liquid crystal display device20. With this configuration, a malfunction of the coordinate input element10and distortion of the display of the liquid crystal display device20can be prevented, and thus the coordinate input device1of the present invention can operate stably.

In the above-described embodiment, the controller12is placed on a side of the coordinate detector11. However, the controller12can be placed on the back side of the liquid crystal display device20, as shown inFIG. 6, if the substrate16is a flexible substrate. With this configuration, the casing30can be miniaturized in both cases where the liquid crystal display device20is a reflective-type and a transmissive-type, and thus the space for the coordinate input device1can be reduced in proportion to the reduction in size of the coordinate input element10shown inFIG. 1. Therefore, the space required in electronic equipment can be effectively used.

The substrate16on which the coordinate detector11and the controller12are formed is a flexible substrate in the above-described embodiment. However, in order to achieve the above configuration, at least the wiring portion for connecting the coordinate detector11and the controller12may be a flexible substrate. That is, the coordinate detector11and the controller12are formed on separate substrates and are connected by a flexible wiring board (flexible printed board) so that the coordinate detector11and the controller12may be electrically connected by the circuit wiring lines formed on the wiring board.