Abstract:
An input device includes an upper sheet having a resistive film formed on a lower surface thereof and a lower substrate disposed in a co-planar relationship below the upper sheet and spaced apart from the upper sheet by a gap, where the lower substrate has a resistive film formed on an upper surface thereof. The lower substrate has opposite side edge portions disposed along a longitudinal axis of the lower substrate, and the side edge portions have an incline or taper along a thickness axis of the lower substrate. A pair of lower electrodes are formed on the resistive film of the lower substrate, and are disposed parallel to the side edge portions of the lower substrate, such that when pressure is applied to an operation portion of the upper sheet, the upper sheet flexes toward the lower substrate, and planar coordinates of the operation portion are determined based on a voltage between the pair of lower electrodes.

Description:
This application claims the benefit of priority to Japanese Patent Application No. 2004-180461, filed on Jun. 18, 2004, herein incorporated by reference 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an input device, such as a touch panel, or the like, and a display input device using the same. More particularly, the present invention relates to an input device that can prevent a resistive film from being formed on sides of a substrate of the input device with a simple structure and that can reduce a warp of the substrate, and to a display input device using the input device. 
     2. Description of the Related Art 
     Conventionally, as an input device, such as a touch panel or the like, for example, it has been suggested an input device disclosed in Japanese Unexamined Patent Application Publication No. 2002-222055. 
     In Japanese Unexamined Patent Application Publication No. 2002-222055, as shown in  FIG. 6A , a touch panel  101  that is disposed on a screen of a liquid crystal display or the like (not shown) is disclosed. 
       FIG. 6A  is a cross-sectional view of an input device according to the related art.  FIG. 6B  is a diagram illustrating a method of forming a transparent electrode on a lower electrode substrate of the input device shown in  FIG. 6A . 
     The touch panel  101  has a flexible upper electrode sheet  103  that is made of a substantially rectangular transparent film and has a transparent electrode  102  made of ITO (Indium Tin Oxide) or the like formed on the lower surface thereof, and a lower electrode substrate  105  that is made of a transparent plastic substrate having the substantially same shape as the upper electrode sheet  103  and has a transparent electrode  104  formed on the upper surface thereof. The upper electrode sheet  103  and the lower electrode substrate  105  are disposed to face each other at a predetermined gap via a circuit resist  106 , such that the transparent electrodes face each other. The circuit resist  106  is formed to have a predetermined width along the periphery of the rectangular sheet or substrate. 
     The touch panel  101  is disposed on the screen of the liquid crystal display or the like. An operator partially presses the upper electrode sheet with a pen or the like from the top of the upper electrode sheet according to an instruction on a perspective screen while seeing instruction information displayed through the screen. Accordingly, the transparent electrodes of the upper electrode sheet and the lower electrode substrate corresponding to the partially pressed portion come in contact with each other partially and thus the operation position by the pen or the like is detected. 
     However, in Japanese Unexamined Patent Application Publication No. 2002-222055, as shown in  FIG. 6B , the lower electrode substrate  105  has a shape in which side portions  105   a  and  105   b  are orthogonal to an upper surface  105   c  and a lower surface  105   d , and a width of an upper surface  105   c  and a width of a lower surface  105   d  are the same. For this reason, when the transparent electrode  104  made of ITO or the like is formed on the upper surface  105   c  by a vacuum deposition method or a sputtering method, ITO may be attached to the side portions  105   a  and  105   b . As a result, noise signals from the liquid crystal display or the like may enter the touch panel  101  to cause an incorrect operation of the touch panel  101 . 
     In order to prevent the noise signals from entering the touch panel  101  from the liquid crystal display or the like, it is necessary to perform an insulation processing on the side portions  105   a  and  105   b . Accordingly, the structure of the touch panel  101  becomes complex. 
     Further, according to the related art, a substrate on which the transparent electrode  104  is to be formed has a sufficiently larger area than the lower electrode substrate  105  and then the substrate with the transparent electrode  104  previously formed on the entire surface thereof is cut to have a predetermined area. In this case, after cutting, when an electrode made of silver or the like is formed on the transparent electrode  104  so as to detect the operation position of the pen or the like, the lower electrode substrate  105  is exposed to a high temperature. Accordingly, a warp occurs in the lower electrode substrate  105 , as shown by arrows in  FIG. 6B . 
     SUMMARY OF THE INVENTION 
     The invention has been made in consideration of the above-described problems, and it is an object of the invention to provide an input device that can prevent a resistive film from being formed on sides of a substrate with a simple structure and that can reduce a warp of the substrate, and to a display input device using the input device. 
     According to an aspect of the invention, an input device includes a flexible upper sheet that is provided with a resistive film formed on a lower surface thereof, and a lower substrate that is provided with a resistive film formed on an upper surface thereof, the upper sheet and the lower substrate being disposed at a predetermined gap, such that, when a point on an operation region of the upper sheet is pressed toward the lower substrate, a planar coordinate of the pressed point is detected, a pair of lower electrodes that are provided on the resistive film formed on the lower substrate at a predetermined gap in a direction from one side surface of the lower substrate toward the other side surface opposite to the one side surface. At least the one side surface and the other side surface have inclined surfaces, such that a width between the one side surface and the other side surface gradually narrows along a direction from the upper surface of the lower substrate toward a lower surface thereof. 
     According to the invention, the pair of lower electrodes are provided on the resistive film formed on the lower substrate at the predetermined gap in the direction from the one side surface of the lower substrate toward the other side surface opposite to the one side surface. Further, at least the one side surface and the other side surface have the inclined surfaces, such that the width between the one side surface and the other side surface gradually narrows along the direction from the upper surface of the lower substrate to the lower surface thereof. For this reason, an incorrect operation of the input device can be prevented from occurring since noise signals enter from a display member, such as a liquid crystal display into the input device, without forming the resistive film on the inclined surfaces. This effect is achieved by allowing the side portions to have the inclined surfaces, without performing an insulation treatment on the side portions. As a result, a correct operation of the input device can be performed with a simple structure, without complicating the structure of the input device. 
     In the input device according to the aspect of the invention, it is preferable that the resistive film on the lower substrate is formed from a side edge portion of the one side surface and the upper surface of the lower substrate to a side edge portion of the other side surface and the upper surface of the lower substrate. 
     When the resistive film is formed in such a manner, the lower electrodes can be provided near the side edge portions, respectively, thereby widening the operation region. 
     In the input device according to the aspect of the invention, it is preferable that the lower substrate is formed by means of an injection molding method. 
     For this reason, the inclined surfaces can be easily formed. Further, the substrate can be prevented from being warped due to heat at the time of molding. Further, the lower substrate can be separately molded at a desired size by means of the injection molding method and thus the resistive film can be formed uniformly and reliably on the lower substrate. 
     In the input device according to the aspect of the invention, it is preferable that the lower substrate is made of a transparent norbornene-based resin. 
     The transparent norbornene-based resin has high transmittance and thus it is difficult for double refraction to occur in the lower substrate. For this reason, images and the like displayed on the display member can be projected clearly and the images and the like can be viewed reliably from the top. Further, the transparent norbornene-based resin has superior heat resistance and thus it resists deformation caused by a high temperature at the time of injection molding. Accordingly, the warp at the time of molding of the lower substrate can be reduced. Further, the transparent norbornene-based resin has low hygroscopicity and therefore it absorbs little moisture from air. Accordingly, the strength of the lower substrate can be prevented from being changed due to moisture absorption. 
     Further, in the input device according to the aspect of the invention, the one side surface and the other side surface are surfaces supported by sidewalls of a case. For this reason, the lower substrate is supported by the sidewalls of the case. 
     According to another aspect of the invention, a display input device includes the input device as described above, the input device being a touch panel and overlapping on a display panel in a case. The one side surface and the other side surface of the lower substrate are supported by sidewalls of the case. Further, an inclination angle of each of the inclined surfaces provided on both side surfaces of the lower substrate is equal to an inclination angle of each of inclined surfaces provided on both sidewalls of the case. 
     In such a display input device, the inclined surfaces provided on both side surfaces of the lower substrate easily come in contact with the inclined surfaces provided on both sidewalls of the case, respectively, and the lower substrate is easily positioned on and fixed to the case. Further, since the inclined surfaces reliably come in contact with each other, dust or the like from the outside can be prevented from entering in the case. As a result, the input device and the display member can be prevented from deteriorating due to the dust or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an input device of the invention; 
         FIG. 2A  is a rear view of an upper sheet of the invention; 
         FIG. 2B  is a plan view of a lower substrate; 
         FIG. 3  is a cross-sectional view taken along the line III-III of  FIG. 2B ; 
         FIG. 4  is a cross-sectional view when the input device of the invention is positioned on and fixed to a case; 
         FIG. 5  is a diagram illustrating a situation when the lower substrate of the invention is formed by means of a mold; 
         FIG. 6A  is a cross-sectional view of an input device of the related art; and 
         FIG. 6B  is a diagram illustrating a method of forming a transparent electrode on a lower electrode substrate of the input device shown in  FIG. 6A . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a cross-sectional view of an input device according to the invention.  FIG. 2A  is a rear view of an upper sheet of the invention and  FIG. 2B  is a plan view of a lower substrate.  FIG. 3  is a cross-sectional view taken along the line of  FIG. 2B .  FIG. 4  is a cross-sectional view when the input device of the invention is positioned on and fixed to a case.  FIG. 5  is a diagram illustrating a situation when the lower substrate of the invention is formed by means of a mold. Moreover, in order to clear the internal structure of an input device of the invention, in  FIG. 1 , an insulating spacer is shown thicker than the actual one. Further, in order to clear a state in which the input device is positioned on and fixed to a case, in  FIG. 4 , inclined surfaces of the case are shown slower than the actual one. Further, resistive films and electrodes provided on the upper sheet and the lower substrate are omitted. 
     As shown in  FIG. 1 , an input device  1  of the invention has an upper sheet  2  and a lower substrate  3 . Further, as shown in  FIG. 4 , the input device  1  is positioned on and fixed to a case  6  at a predetermined gap above a display panel  4  and a light guiding member  5  of a liquid crystal display or the like. 
     The upper sheet  2  is made of transparent synthetic resin, such as polyethyleneterephthalate, to have flexibility. As shown in  FIG. 1 , on the entire surface of a lower surface  2   a  of the upper sheet  2 , a resistive film  4   a  is formed to have a predetermined thickness. The resistive film  4   a  is made of ITO (Indium Tin Oxide) by a sputtering method, a vacuum deposition method, or the like. In addition, as shown in  FIG. 2A , a pair of upper electrodes  21  and  22  made of silver or the like are formed in parallel with each other on the resistive film  4   a  at a gap in a Y 1 -Y 2  direction. An operation region  23  is formed between the pair of upper electrodes  21  and  22 . 
     The lower substrate  3  is a transparent plastic substrate. As shown in  FIG. 2B , on a predetermined region of an upper surface  3   a  of the lower substrate  3 , like the resistive film  4   a , a resistive film  4   b  made of ITO is formed to have a predetermined thickness. Further, a pair of lower electrodes  31  and  32  made of silver or the like are formed in parallel with each other on the resistive film  4   b  at a gap in an X 1 -X 2  direction. An operation region  33  is formed between the pair of lower electrodes  31  and  32 . Further, on the operation region  33 , a plurality of dot spacers  34  are formed. The dot spacers are provided so as to prevent an erroneous contact from occurring in the lower substrate  3  due to the warp of the upper sheet  2  caused by external factors. Here, it is assumed that a side surface of the lower substrate  3  on the Y 2  side is a front side surface, a side surface on the Y 1  side is a rear side surface, a side surface on the X 1  side is a right side surface, and a side surface on the X 2  side is a left side surface. 
     As shown in  FIG. 1 , the upper sheet  2  is combined with the lower substrate  3  so as to face the lower substrate  2  at a predetermined gap via an insulating spacer  50 . Here, the resistive film  4   a  formed the lower surface  2   a  of the upper sheet  2  faces the resistive film  4   b  formed on the lower substrate  3 . Further, the upper electrodes  21  and  22  are disposed on side portions of the upper sheet  2  that do not overlap the lower electrodes  31  and  32 . 
     The case  6  is formed by means of an injection molding method. The case  6  has sidewall portions  6   a  and  6   b  and has a hollow internal structure. Inner surfaces of front ends of the sidewall portions  6   a  and  6   b  have inclined surfaces  6   a   1  and  6   b   1  each having the inclination angle of θa. Accordingly, the case  6  is easily released from a mold at the time of molding by means of the injection molding method. Further, the sidewall portions  6   a  and  6   b  are made of white acrylonitrile butadiene styrene copolymer (ABS) resin so as to efficiently reflect light from the light guiding member  5  inside the case  6 . 
     As shown in  FIG. 1 , as regards the lower substrate  3  of the invention, the right and left side surfaces  3   b  and  3   c  have inclined surfaces each having a predetermined inclination angle of θ with regard to the vertical direction (the Z direction). At this time, a width between both side surfaces (a length in the X 1 -X 2  direction) narrows gradually from the upper surface  3   a  of the lower substrate  3  to the lower surface  3   d  thereof. 
     Here, the resistive film  4   b  made of ITO is film-formed on the upper surface  3   a  of the lower substrate  3  by a sputtering method, a vacuum deposition method, or the like. When being attached to the substrate on which the resistive film is to be formed, sputtered atoms or deposited atoms move thereon. That is, the sputtered atoms or the deposited atoms have progressive property on the substrate. 
     According to the invention, since the right and left side surfaces  3   b  and  3   c  of the lower substrate  3  have the inclined surfaces, when the resistive film  4   b  is film-formed on the upper surface  3   a , there is no probability that the sputtered atoms or the like for forming the resistive film  4   b  wrap around the right and left side surfaces  3   b  and  3   c  and form resistive films on the right and left side surfaces  3   b  and  3   c . As a result, an incorrect operation of the input device  1  can be prevented from occurring since the resistive films are film-formed on parts of the right and left side surfaces  3   b  and  3   c , and the noise signals enter from the liquid crystal display or the like to the input device  1 . This effect is achieved by forming the right and left side surfaces  3   b  and  3   c  to have the inclined surfaces, without performing an insulation treatment on the right and left side surfaces  3   b  and  3   c . For this reason, the incorrect operation of the input device  1  can be prevented with a simple structure. 
     According to the invention, the inclined surfaces need to be provided on, among the side surfaces of the lower substrate  3 , at least side surfaces of the lower substrate  3  in a direction in which the lower electrodes  31  and  32  face each other. Further, according to the invention, in order to widen the operation region  33 , the lower electrodes  31  and  32  are provided near right and left edge portions  3   a   1  and  3   b   1  of the lower substrate  3 , respectively. Here, the right edge portion  3   a   1  is a side edge portion of the upper surface  3   a  and the right side surface  3   b , and the left edge portion  3   a   2  is a side edge portion of the upper surface  3   a  and the left side surface  3   c.    
     For this reason, as indicated by a hatched region in  FIG. 2B , the resistive film  4   b  is film-formed up to the right and left edge portion  3   a   1  and  3   b   1 . As a result, at least the side surfaces in the direction in which the lower electrodes  31  and  32  face each other, that is, the right and left side surfaces  3   b  and  3   c , have the inclined surfaces. 
     According to the invention, the lower substrate  3  is separately molded to have a desired size by means of the injection molding method. Accordingly, the right and left side surfaces  3   b  and  3   c  can be easily formed to have the inclined surfaces. Further, the electrodes may be formed on a large substrate of a constant area with a resistive film provided thereon and then the large substrate may be cut to prepare a plurality of lower substrates  3  each having a desired size. In this case, the large substrate may be exposed to a high temperature when the lower electrodes  31  and  32  are formed thereon or when the lower electrodes  31  and  32  are printed and dried. However, even though the large substrate is exposed to the high temperature, the large substrate can be prevented from being warped by heat. Further, since the lower substrate  3  is separately molded to have the desired size by means of the injection molding method, the resistive film  4   b  can be film-formed uniformly and reliably on the upper surface  3   a  of the lower substrate  3 . Further, since the right and left side surfaces  3   b  and  3   c  of the lower substrate  3  have the inclined surfaces, as shown in  FIG. 5 , the lower substrate  3  is easily released from a mold at the time of molding of the lower substrate  3 . As a result, the lower substrate  3  having less warp can be obtained. 
     In addition, according to the injection molding method, a linear gate is provided on the Y 1  or Y 2  side along a width of an end portion on the Y 1  or Y 2  side of the lower substrate  3 . A resin for forming the lower substrate  3  is injected from the linear gate into a cavity of a mold  7 . For this reason, the resin is uniformly and planarly injected to form the uniform lower substrate  3 . As a result, double refraction does not occur in the lower substrate  3 , such that images and the like displayed on the liquid crystal display can be reliably viewed from the top. 
     Moreover, in the lower substrate  3  according to the invention, only one of the front and rear side surfaces  3   e  and  3   f  may have an inclined surface, like the right and left side surfaces  3   b  and  3   c , as shown in  FIG. 3 . Alternatively, both side surfaces may have surfaces parallel to the Z axis, not have the inclined surfaces. Here, in the injection molding method of the invention, the linear gate is provided on the Y 1  or Y 2  side along the width of the end portion on the Y 1  or Y 2  side of the lower substrate  3 . For this reason, at least one of the front and rear side surfaces  3   e  and  3   f  has the surface parallel to the Z axis. There is no case in which both side surfaces have the inclined surfaces. 
     In the invention, as described above, the lower substrate has the right and left side surfaces  3   b  and  3   c  as the inclined surfaces. Accordingly, the right side surface  3   b  and the inclined surface  6   a   1  of the case  6  can easily come in contact with each other. Similarly, the left side surface  3   c  and the inclined surface  6   b   1  of the case can easily come in contact with each other. As a result, the lower substrate  3  is supported easily and reliably by the sidewall portions  6   a  and  6   b  of the case  6 . 
     The lower substrate  3  of the invention may be made of a transparent norbornene-based resin. The transparent norbornene-based resin has high transmittance, such that it is difficult for double refraction to occur in the lower substrate  3 . Accordingly, the images and the like displayed on the liquid crystal display can be projected clearly and the images and the like can be viewed reliably from the top. Further, the transparent norbornene-based resin has superior heat resistance and thus resists warping at a high temperature at the time of injection molding. Accordingly, the warp at the time of molding of the lower substrate  3  can be reduced. Further, the transparent norbornene-based resin has low hygroscopicity and thus it absorbs little moisture from air. Accordingly, the strength of the lower substrate  3  can be prevented from being changed due to the moisture absorption. 
     Next, a method of manufacturing the lower substrate  3  of the invention will be described. 
     First, the lower substrate  3  of the desired size is molded by means of the injection molding method. Next, after a portion on which the linear gate is provided is cut, the lower substrate is released from the mold  7 , as shown in  FIG. 5 . Subsequently, a mask layer is disposed on the upper surface  3   a  of the lower substrate  3  and the resistive film  4   b  is film-formed on the mask layer and the portion indicated by the hatched region in  FIG. 2B  by means of the sputtering method or the like. Subsequently, the mask layer is removed. Alternatively, first, the resistive film  4   b  is film-formed on the portion indicated by the hatched region in  FIG. 2B  by the sputtering method or the like. Next, a mask layer is disposed on only a required portion of the resistive film  4   b , while a useless portion thereof is removed by etching or the like. 
     After the resistive film  4   b  is film-formed on the portion of the upper surface  3   a  indicated by the hatched region, as described above, the lower electrodes  31  and  32  are molded on the resistive film  4   b  through printing and then the dot spacers  34  are formed. 
     Next, the operation of the input device  1  of the invention will be described. 
     For example, when an arbitrary point in the operation region  23  of the upper sheet  2  is pressed downward by an input pen (not shown) or the like, first, the upper sheet  2  is deformed such that the resistive film  4   a  formed on the upper sheet  2  comes in contact with the resistive film  4   b  formed on the lower substrate  3  between operation regions  23  and  33 . 
     If doing so, a voltage is alternately applied across the upper electrodes  21  and  22  and across the lower electrodes  31  and  32  by a control unit (not shown) several times at predetermined time intervals. When the voltage is applied across the upper electrodes  21  and  22 , a coordinate position in the Y direction of the operation region  23  by the input pen or the like is detected from the contact point of the resistive film  4   a  and the resistive film  4   b  and the resistance ratio between the upper electrodes  21  and  22 . Similarly, when the voltage is applied across the lower electrodes  31  and  32 , a coordinate position in the X direction of the operation region  23  by the input pen or the like is detected from the contact point and the resistance ratio between the lower electrodes  31  and  32 . In such a manner, the coordinate positions on the XY plane of the operation region  23  by the input pen or the like are detected. 
     The input device  1  of the invention is a touch panel which can be integrally mounted on a display panel  4 , such as a liquid crystal display, as shown in  FIG. 4 . In this case, the input device  1  and the display panel  4  are combined with each other and are used as a display input device  10 . 
     The display input device  10  has the input device of the invention and thus the operation from the input device  1  is accurately transmitted, without being influenced by the noise signals. 
     Further, as shown in  FIG. 4 , the lower substrate  3  is supported by the sidewall portions  6   a  and  6   b  of the case and therefore the input device  1  is positioned on and fixed to the case  6 . At this time, the right side surface  3   b  of the lower substrate  3  comes in contact with the inclined surface  6   a   1  of the case  6 , such that the right side surface  3   b  is supported by the sidewall portion  6   a . Further, the left side surface  3   c  of the lower substrate  3  comes in contact with the inclined surface  6   b   1  of the case  6 , such that the left side surface  3   c  is supported by the sidewall portion  6   b . For this reason, dust or the like from the outside can be prevented from entering the hollow case  6 . As a result, the input device  1  and the display member  4  can be more reliably prevented from deteriorating due to the dust or the like. 
     Further, the inclination angle θ of each of the inclined surfaces, that is, the right and left side surfaces  3   b  and  3   c  of the lower substrate  3  is equal to the inclination angle θa of each of the inclined surfaces  6   a   1  and  6   b   1  of the case. In this case, the right and left side surfaces  3   b  and  3   c  more easily come into contact with the inclined surfaces  6   a   1  and  6   b   1 , respectively, and thus the lower substrate  3  is easily positioned on and fixed to the case. Further, since the right and left sides  3   b  and  3   c  more reliably come in contact with the inclined surfaces  6   a   1  and  6   b   1 , respectively, such that the case  6  is shielded by the lower substrate  3 . Therefore, the dust or the like from the outside can be prevented from entering the hollow of the case  6 . As a result, the input device  1  and the display member  4  can be more reliably from deteriorating due to the dust or the like. 
     In order to achieve the above-described effects, it is preferable that the inclination angle θ of each of the inclined surfaces of the right and left side surfaces  3   b  and  3   c  is in a range of from 2° to 10°. 
     In accordance with the input device according to the aspect of invention, the resistive film can be prevented from being formed on the side of the substrate of the input device with a simple structure. Further, the warp of the substrate can be reduced.