Patent Publication Number: US-2020278752-A1

Title: Tactile sense presentation device, electronic apparatus, and method of driving tactile sense presentation device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This a continuation of U.S. application Ser. No. 15/080,722 filed Mar. 25, 2016, which is a non-provisional application and which claims priority under 35 U.S.C.§119(a) to Japanese Patent Application No. 2015-064753 filed in Japan on Mar. 26, 2015,and Japanese Patent Application No. 2016-001986 filed in Japan on Jan. 7, 2016, the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD 
     The present invention relates to a tactile sense presentation device, an electronic apparatus, and a method of driving a tactile sense presentation device, and more particularly, to a tactile sense presentation device presenting a tactile sense, an electronic apparatus such as a touch panel or a terminal for a visually-impaired person that includes the tactile sense presentation device, and a drive method for appropriately presenting a tactile sense. 
     BACKGROUND 
     A display device in which a touch panel, for which an input operation can be performed by touching it using a finger or the like, is mounted, by being built in a system controlling a display content and the operation of a device in accordance with an input operation, contributes to the realization of interactive operability enabling easy use. For this reason, information apparatuses such as a smartphone having a touch panel built therein, a tablet terminal, and a notebook personal computer have rapidly been spread widely. 
     Meanwhile, the surface of a display device having a touch panel mounted thereon is evenly hard, and a same tactile sense is acquired when any portion displayed on the screen is touched. For this reason, it is practically difficult to perceive portions of a touch panel for which an effective input can be made through a touch operation and whether or not an effective input is made without seeing the touch panel. Thus, it is difficult to operate such a device only depending on a tactile sense without seeing the screen of the display device. 
     In contrast to this, for example, a remote controller of a television receiver, a conventional mobile phone terminal (feature phone), a keyboard of a personal computer, and the like respectively include independent operation keys, and accordingly, the position of an operation key can be perceived depending on only a tactile sense, and, also when such an operation key is pressed, it can be perceived through a tactile sense. Thus, in a case where the positions and the arrangement of operation keys are memorized, it is not that difficult to operate the operation keys depending on only a tactile sense. 
     From such backgrounds, technologies for applying a tactile sense to a display device have been researched. Such technologies, for example, include a method of mechanically vibrating a display device using a piezoelectric device, an eccentric motor, or the like; a method of presenting a tactile sense (texture sense) when a device is traced using a finger by changing a frictional force between an operator&#39;s finger and a device using an electrostatic force, a so-called method using an electric vibration phenomenon; and a method of driving a nerve axon of a cutaneous mechanoreceptor of a user&#39;s finger by causing an electric current to flow through the finger. 
     Among such methods, relating to the method using the electric vibration phenomenon, for example, in Japanese Patent OPI Publication No. 2011-248884, a tactile sense presentation device has been proposed which includes a conductive face; an insulating face arranged on the conductive face and a controller configured such that a signal is coupled with a user being in contact with the device and thus, causing at least one finger of the user sliding on the insulating face to perceive a tactile sense. 
     A tactile sense presentation device using the electric vibration phenomenon includes an electrode and an insulating layer protecting the electrode and presents a tactile sense to an operator through the following mechanism when an operator&#39;s finger moves on the insulating layer. 
     (1) When a voltage signal is applied to the electrode, an electrostatic force is applied between the electrode and the operator&#39;s finger. The electrostatic force is constantly an attractive force, and the electrostatic force changes according to the frequency of the voltage signal. 
     (2) As a normal reaction applied between the operator&#39;s finger and the surface of the insulating layer changes according to a change in the electrostatic force, when the user slips his finger on the surface of the insulating layer, the frictional force changes according to the frequency of the voltage signal. 
     (3) The change in the frictional force changes a force applied in the shearing direction of the finger, and deformation of the finger according to the frequency of the voltage signal is caused. Such a deformation (mechanical vibration) is detected by a mechanoreceptor of the user&#39;s finger, and accordingly, a rough texture sense is perceived. 
     In order to allow a rough texture sense to be perceived as above, it is necessary to apply an appropriate voltage to the electrode such that an appropriate electrostatic force is applied between the electrode and the operator&#39;s finger. However, it is not easy to apply an appropriate voltage, and, when the voltage applied to the electrode is increased so as to allow a texture sense to be easily perceived, in a case where an insulating film protecting the electrode disappears due to abrasion or the like, a high voltage is applied to the operator&#39;s finger, and there is concern that an inappropriate current flows through the operator&#39;s finger, and it is not desirable from the viewpoint of safety. On the other hand, when the voltage applied to the electrode is decreased, a sufficient texture sense cannot be perceived. 
     Particularly, a contact face (the surface of the insulating layer) of a conventional tactile sense presentation device is flat, and, in case of the flat contact face, the finger is tightly brought into contact with the contact face and is difficult to slide, whereby it is difficult to perceive a texture sense. For this reason, it is necessary to further increase the voltage applied to the electrode, and it is difficult to secure the safety. Accordingly, there is a problem in that it is difficult to achieve both easy perception of a texture sense and a decrease in the voltage applied to the electrode. 
     The present invention is made in consideration of the problems described above, and a main object thereof is to provide a tactile sense presentation device capable of allowing a texture sense to be easily perceived and effectively decreasing the voltage applied to the electrode, an electronic apparatus including the tactile sense presentation device, and a method of driving a tactile sense presentation device. 
     SUMMARY 
     According to one aspect of the present invention, a tactile sense presentation device includes a panel that includes a support substrate, an electrode formed on the support substrate, and an insulating layer covering the electrode, and a drive unit that drives the panel, a tactile sense is presented to an operator based on an electrostatic force generated between the electrode and the operator by the drive unit applying a signal of a voltage to the electrode, a contact face of the insulating layer that is in contact with the operator has a surface roughness Ra of a predetermined range, and the voltage applied to the electrode is a voltage corresponding to the surface roughness Ra of the contact face. 
     According to one aspect of the present invention, a tactile sense presentation device includes a panel that includes a support substrate, a plurality of electrodes formed on the support substrate and extending in a predetermined direction, and an insulating layer covering the plurality of electrodes and a drive unit that drives the panel, a tactile sense is presented to an operator based on an electrostatic force generated between the electrodes and the operator by the drive unit applying a signal of a voltage to the electrodes, a contact face of the insulating layer that is in contact with the operator has a surface roughness Ra of a predetermined range, and the voltage applied to the electrodes corresponding to an area in which the tactile sense is presented to the operator is a voltage corresponding to the surface roughness Ra of the contact face. 
     According to one aspect of the present invention, a tactile sense presentation device includes a panel that includes a support substrate, an electrode formed on the support substrate, and an insulating layer covering the electrode; and a drive unit that drives the panel, a tactile sense is presented to an operator based on an electrostatic force generated between the electrode and the operator by the drive unit applying a signal of a voltage to the electrode, there is a correlation between a surface roughness Ra of a contact face of the insulating layer that is in touch with the operator and a lowest voltage(hereinafter, referred to as a detection threshold voltage) for which the operator can perceive a tactile sense, and the contact face has the surface roughness Ra having the detection threshold voltage lower than the detection threshold voltage at the time of a surface roughness Ra of 0.00 μm. 
     According to one aspect of the present invention, there is provided an electronic apparatus including the tactile sense presentation device described above on a front face or a rear face of a display apparatus of a touch panel type. 
     According to one aspect of the present invention, a method of driving a tactile sense presentation device that includes a panel that includes a support substrate, an electrode formed on the support substrate, and an insulating layer covering the electrode and a drive unit that drives the panel, and presents a tactile sense to an operator based on an electrostatic force generated between the electrode and the operator by applying a signal of a voltage to the electrode by using the drive unit, the method includes a surface roughness Ra of a contact face of the insulating layer that is in contact with the operator being set to a predetermined range, and the drive unit performs applying a signal of a voltage corresponding to the surface roughness Ra of the contact face to the electrode. 
     According to one aspect of the present invention, a method of driving a tactile sense presentation device that includes a panel that includes a support substrate, a plurality of electrodes formed on the support substrate and extending in a predetermined direction, and the insulating layer covers the plurality of electrodes and a drive unit that drives the panel, and presents a tactile sense to an operator based on an electrostatic force generated between the electrodes and the operator by applying a signal of a voltage to the electrodes by using the drive unit, the method includes a surface roughness Ra of a contact face of the insulating layer that is in contact with the operator being set to a predetermined range, and the drive unit performs, specifying an electrode corresponding to an area in which a tactile sense is presented to the operator and applying the signal of a voltage corresponding to the surface roughness Ra of the contact face to the specified electrode. 
     According to a tactile sense presentation device, an electronic apparatus, and a method of driving a tactile sense presentation device according to the present invention, a texture sense can be easily perceived, and a voltage applied to the electrode can be effectively decreased. 
     The reason for this is as follows. The surface roughness of the contact face of the tactile sense presentation device is set to a predetermined range, and there is a correlation between the surface roughness of the contact face and a voltage for which the texture sense can be perceived, and thus, a voltage (a voltage that is the voltage corresponding to the surface roughness or higher) corresponding to the surface roughness is applied to the electrode for driving the electrode. In addition, the contact face has the surface roughness causing a detection threshold voltage lower than the detection threshold voltage at the time of a surface roughness of 0.00 μm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a planar view that illustrates an example of a tactile sense presentation device according to a first embodiment of the present invention; 
         FIG. 2  is a cross-sectional view of the tactile sense presentation device according to the first embodiment of the present invention and illustrates a cross-section taken along line A-A illustrated in  FIG. 1 ; 
         FIG. 3  is a planar view that illustrates another example of the tactile sense presentation device according to the first embodiment of the present invention; 
         FIG. 4  is a cross-sectional view of the tactile sense presentation device according to the first embodiment of the present invention and illustrates a cross-section taken along line B-B illustrated in  FIG. 3 ; 
         FIG. 5  is a diagram that illustrates a method of evaluating the tactile sense presentation device according to the first embodiment of the present invention; 
         FIG. 6  is a table that illustrates an evaluation result of the tactile sense presentation device according to the first embodiment of the present invention; 
         FIG. 7  is a graph that illustrates a relation between the surface roughness and the detection threshold voltage of the tactile sense presentation device according to the first embodiment of the present invention; 
         FIG. 8  is a table that illustrates a relation among the surface roughness, a detection voltage, and a tactile sense perceived by an operator in the tactile sense presentation device according to the first embodiment of the present invention; 
         FIG. 9  is a table that illustrates a result of evaluations of the tactile sense presentation device according to the first embodiment of the present invention that are made by four test subjects; 
         FIG. 10  is a graph that illustrates a relation between the surface roughness and the detection threshold voltage of the tactile sense presentation device according to the first embodiment of the present invention that is a result of a test targeted for men of early 30&#39;s; 
         FIG. 11  is a graph that illustrates a relation between the surface roughness and the detection threshold voltage of the tactile sense presentation device according to the first embodiment of the present invention that is a result of a test targeted for men of late 30&#39;s; 
         FIG. 12  is a graph that illustrates a relation between the surface roughness and the detection threshold voltage of the tactile sense presentation device according to the first embodiment of the present invention that is a result of a test targeted for women of 20&#39;s; 
         FIG. 13  is a planar view that illustrates an example of a tactile sense presentation device according to a second embodiment of the present invention; 
         FIG. 14  is a planar view that illustrates another example of the tactile sense presentation device according to the second embodiment of the present invention; 
         FIG. 15  is an explanatory diagram that illustrates the configuration of a tactile sense presentation device according to a first example of the present invention; 
         FIG. 16  is a diagram that illustrates a method of driving the tactile sense presentation device illustrated in  FIG. 15 ; 
         FIG. 17  is a schematic diagram that illustrates a sectional model of the tactile sense presentation device illustrated in  FIGS. 15 and 16 ; 
         FIG. 18  is a planar view that illustrates a specific shape of electrodes of a tactile sense presentation device according to a second example of the present invention; 
         FIG. 19  is a planar view acquired by enlarging the structure of a connection portion of an X electrode and a Y electrode that is denoted by A in  FIG. 18 ; 
         FIG. 20  is a cross-sectional view that illustrates the structure of the connection portion of the X electrode and the Y electrode denoted by A in  FIG. 18  and illustrates a cross-section taken along line C-C illustrated in  FIG. 19 ; 
         FIG. 21  is an explanatory diagram that illustrates the detailed configuration of an X-electrode driving circuit of a tactile sense presentation device according to a third example of the present invention; 
         FIG. 22  is a timing diagram that illustrates the operation of the X-electrode driving circuit illustrated in  FIG. 21 ; 
         FIG. 23  is a perspective view that illustrates an example of an electronic apparatus including a tactile sense presentation device according to a fourth example of the present invention; 
         FIG. 24  is a perspective view that illustrates an example of a mobile unit including a tactile sense presentation device according to a fourth example of the present invention; and 
         FIG. 25  is a cross-sectional view of a tactile sense presentation device according to a modified example of the first embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     As described above, while a tactile sense presentation device using the electric vibration phenomenon has been proposed, a contact face of a conventional tactile sense presentation device is flat, and, in case of the flat contact face, a finger is tightly brought into contact with the contact face and is difficult to slide, whereby it is difficult to perceive a texture sense depending on an electrostatic force. In order to allow the texture sense to be easily perceived, it is necessary to apply a high voltage of 100 V or higher to the electrodes. Accordingly, the drive circuit is complicated, and, in a case where an insulating film protecting the electrodes disappear by some accident of abrasion or the like, an inappropriate electric current flows through the finger, and thus, there is a problem in that the safety of the device cannot be secured. 
     Regarding this problem, the inventors of the present application generated various tactile sense presentation devices having mutually-different forms of contact faces and checked a detection threshold voltage for which a texture sense can be perceived by the operator in each of the tactile sense presentation devices. As a result, it was found that, by applying an antiglare process for the contact face (by forming the contact face of the insulating layer to be rough), a presented tactile sense could be checked very easily, in other words, a presented tactile stimulation could be perceived by the operator very easily (first finding). 
     The inventors of the present application, as a result acquired by a further experimentation, found that, an increase in the surface roughness of the contact face to a moderate degree through an antiglare process is a factor allowing the operator to easily perceive a tactile stimulus. In other words, it was found that there is a special correlation between the surface roughness of the contact face and a detection threshold voltage that is a lowest voltage for which the operator can perceive a texture sense for the surface roughness (second finding). The surface roughness used in the description presented here is an arithmetic average roughness (represented as a surface roughness Ra as is necessary) defined in annexes of JIS B 0031 and JIS B 0061 and the like. This arithmetic average roughness is acquired by folding a roughness curve at the center line and representing a value acquired by dividing an area acquired by the roughness curve and the center line by a length L in units of micrometers (μm). In addition, instead of the arithmetic average roughness, a maximal height (surface roughness Ry), a ten-point average roughness (surface roughness Rz), or the like defined in the annex of JIS B 0601 and the like may be used. The maximal height is acquired by extracting only a reference length from the roughness curve and representing an interval between the mountain top line and the valley bottom line of the extracted portion in units of micrometers (μm). In addition, the ten-point average roughness is acquired by extracting only a reference length from the roughness curve and representing a sum of the average value of the absolute values of elevations from the highest mountain top to a fifth mountain top and an average value of the absolute values of elevations from the lowest valley bottom to a fifth valley bottom in units of micrometers (μm). 
     Then, based on the first finding, by setting the surface roughness of the contact face to an appropriate range and, based on the second finding, by applying a voltage (in other words, a voltage that is a detection threshold voltage corresponding to the surface roughness, which is necessarily derived from the special correlation described above, or higher) corresponding to the surface roughness to the electrodes or by configuring the contact face to have a surface roughness causing a detection threshold voltage to be lower than a detection threshold voltage at the time of a surface roughness of 0.00 μm, a texture sense can be easily perceived, and a voltage applied to the electrodes can be effectively decreased, whereby both the securement of the safety and the improvement of the tactile sensitivity of the texture sense can be achieved. 
     Hereinafter, the contents of tests allowing the inventors of the present application to arrive at the first and second findings will be described more specifically. 
     FIRST EMBODIMENT 
     In the following tests, a sample having a flat contact face and samples having fine irregularities of various surface roughnesses formed on the contact faces are prepared, detection threshold voltages are measured for such samples, and the detection threshold voltages are compared with each other and reviewed. 
     (Trial Production of Sample) 
       FIG. 1  is a planar view that illustrates an example of a panel  10   a  of a tactile sense presentation device  10  that is a trial product. In producing the tactile sense presentation device  10 , on a support substrate formed using a transparent insulating material such as glass, a plurality of X electrodes (in the drawing, 32 X electrodes of X 0  to X 31 ) extending in a direction (here, the horizontal direction in the drawing) parallel to the X axis and a plurality of Y electrodes (52 Y electrodes of Y 0  to Y 51  in the drawing) extending in a direction (here, the vertical direction in the drawing) parallel to the Y axis are formed. The X electrodes and the Y electrodes are formed using indium tin oxide (ITO) and are formed to be transparent for visible light. In addition, an insulating layer is formed between the X electrodes and the Y electrodes such that the X electrodes and the Y electrodes are insulated from each other by the insulating layer at intersections thereof. Furthermore, in an upper layer of the X electrodes and the Y electrodes, another insulating layer is formed. The surface of this insulating layer  16  serves as a contact face  17  to be touched by an operator&#39;s finger. 
       FIG. 2  illustrates a cross-sectional view taken along line A-A illustrated in  FIG. 1 . In the tactile sense presentation device  10 , X electrodes  12  and Y electrodes  13  are alternately arranged on a support substrate  11 , and an insulating layer (not illustrated in the drawing) is formed between the X electrodes  12  and the Y electrodes  13 . A detailed structure of portions at which the X electrodes  12  and the Y electrodes  13  intersect each other will be described in a second example to be described later. The insulating layer  16  covering the X electrodes  12  and the Y electrodes  13  is formed using an acrylic resin, and the surface roughness Ra thereof is 0.00 μm (almost flat). The surface of the insulating layer  16  serves as a contact face  17 . The structure and the manufacturing method of this sample are similar to those disclosed in a prior application (Patent Application No. 2013-213009) of the inventors of the present application and will be described in detail in examples to be described later. 
       FIG. 3  is a planar view of a panel  10   a  of another tactile sense presentation device  10  that is a trial product, and  FIG. 4  is a cross-sectional view taken along line B-B illustrated in  FIG. 3 . 
     This tactile sense presentation device  10  has many elements that are in common with the tactile sense presentation device  10  illustrated in  FIGS. 1 and 2 , and the description of the common elements will not be presented. As illustrate in  FIG. 4 , a main difference is that an antiglare layer (insulating layer)  15  having a reflection prevention function for visible light is formed in a further upper layer of the insulating layer  16 , and the surface of the antiglare layer  15  serves as a contact face  17 . 
     This antiglare layer  15  is formed by performing spray coating of the surface of the insulating layer  16  with a coating layer material  15   b  that is in solution having an insulating property such as a resin in which particles  15   a  formed using an insulating material such as silica of a predetermined size are dispersed and performing drying and a hardening process of the coating layer. Then, by changing the content ratio of the particles  15   a  to the coating layer material  15   b , a spraying method, the material, the size, and the shape of the particles  15   a , the material, the viscosity, and the like of the coating layer material  15   b , a plurality of tactile sense presentation devices  10  having mutually-different properties and states (surface roughness) of the antiglare layers  15  are produced as trial products. 
     (Evaluation Sample) 
       FIG. 5  illustrates an overview of a method of evaluating each of the tactile sense presentation devices  10  that are produced as the trial products. Among the plurality of X electrodes  12  and the plurality of Y electrodes  13 , an AC voltage signal having a sinusoidal shape is applied to 13 Y electrodes  13  of Y 20  to Y 32 , and the remaining Y electrodes  13  and all the X electrodes  12  are connected to the ground. In a case where the voltage amplitude of the voltage signal is sufficiently high, when the contact face  17  is traced using a finger (the finger slides on the contact face  17 ), a rough texture sense is felt in an area (an area to which hatching is applied) to which the voltage signal is applied. From this state, the voltage amplitude of the voltage signal applied to the Y electrodes  13  is gradually decreased, and a lowest voltage for which a difference in the tactile sense is considered to be identifiable between an area to which the voltage signal is applied and the other area is recorded. The voltage recorded here is set to be a peak-to-peak value of the AC voltage signal having a sinusoidal shape. This value is a value that is twice a value generally regarded to be the amplitude of an AC voltage signal having a sinusoidal shape. This voltage is a detection threshold voltage, and the detection threshold voltage is measured for each of the plurality of tactile sense presentation devices  10  produced as trial products. 
       FIG. 6  illustrates a result of evaluations of the plurality of tactile sense presentation devices  10 . A sample of reference number  1  is a sample having a surface roughness Ra of 0.00 μm (a sample having a flat contact face  17 ) illustrated in  FIGS. 1  an  2 , and samples of reference numbers  2  to  9  are samples each having a contact face  17  configured by the antiglare layer  15  illustrated in  FIGS. 3 and 4 . In the sample (the sample of reference number  1 ) that has no antiglare layer  15  and has the flat contact face  17 , while an average value of the detection threshold voltage is 178.4 V, in the samples (samples of reference numbers  2  to  9 ) each having the antiglare layer  15  disposed therein, the detection threshold voltages are in the range of 67.8 V to 127.6 V. Thus, it has been proved that the antiglare layer  15  is effective for decreasing the drive voltage. 
     From this, it is understood that a tactile sense of an area in which a voltage signal is not applied to the electrodes, in other words, the tactile sense of the material state of the contact face  17  of the tactile sense presentation device  10  has a big influence on the sensitivity of the tactile sense presented by applying a voltage signal to the electrodes. In other words, it is understood that the tactile sense of the background area in which a voltage signal is not applied to the electrodes has a big influence on the sensitivity of the tactile sense presented by applying a voltage signal to the electrodes. 
     For example, in the sample of reference number  1 , in an area in which a voltage signal is not applied to the electrodes, a contact area between a finger and the contact face becomes relatively large, and thus, a sense of the finger being stuck to the contact face (sticky) is felt. In addition, the tactile sense of an area in which a voltage signal is applied to the electrodes is similarly sticky, and it is difficult to identify a difference between both the tactile senses. On the other hand, in the samples of reference numbers  2  to  9  in which the antiglare layer  15  is disposed, the tactile sense of the material state of the contact face  17  of the tactile sense presentation device  10  is smooth and dry, and, in a case where the tactile sense of the material state is smooth and dry, the rough sense of the area in which a voltage signal is applied to the electrodes is sensitive. 
     As reasons for the occurrence of such a phenomenon, the following two reasons are considered. 
     (1) When a finger continuously slides from the area in which a voltage signal is not applied to the electrodes over the area in which a voltage signal is applied to the electrodes, the smooth and dry tactile sense of the background emphasizes a rough tactile sense. 
     (2) Even in a case where an attractive force according to an electrostatic force is changed in the same manner by applying a same voltage signal to electrodes disposed in a lower layer of the contact face  17  of which the material state is sticky and electrodes disposed in a lower layer of the contact face  17  having a smooth and dry tactile sense, the contact face  17  having the smooth and dry tactile sense is more sensitive to a rough feeling. On the contact face  17  of which the material state is sticky, even the operator is in the middle of sliding the finger on the contact face  17 , the sliding is unintentionally stopped. For this reason, a frictional force generated according to a normal reaction applied between the operator&#39;s finger and the surface of the insulating layer includes a component to which a static friction coefficient contributes. On the other hand, on the contact face  17  of which the material state has a smooth and dry tactile sense, the finger smoothly slides on the contact face  17 . Accordingly, a component to which a static friction coefficient contributes is not included in a frictional force generated according to a normal reaction applied between the operator&#39;s finger and the surface of the insulating layer, and a component to which a dynamic friction coefficient contributes is dominant. 
     By examining the detection threshold voltages acquired in the samples of reference numbers  2  to  9 , in which the antiglare layer  15  is disposed, represented in a table illustrated in  FIG. 6 , it can be understood that there is a special correlation between the magnitude of the surface roughness Ra and the detection threshold voltage. In other words, in a case where the surface roughness Ra is more than 0.0206 μm, the detection threshold voltage gradually decreases, and the detection threshold voltage is minimal in the sample (the sample of reference number  4 ) having a surface roughness Ra of 0.0503 μm. In addition, in a case where the surface roughness Ra is more than 0.0503 μm, the detection threshold voltage gradually increases. From this, it has been found that the detection threshold voltage is changed more depending on the surface roughness Ra of the contact face  17  than depending on the presence/absence of the antiglare layer  15 , and a minimal value is present in the detection threshold voltage. 
       FIG. 7  is a graph that illustrates relations between the surface roughnesses Ra and the detection threshold voltages of all the samples illustrated in  FIG. 6 . It can be understood that, by configuring the surface roughness Ra to be more than 0.01 μm, an effect of decreasing the detection threshold voltage is acquired. In addition, it can be understood that, in a case where the surface roughness Ra is more than 0.05 μm, the detection threshold voltage tends to increase. The reasons for the occurrence of the phenomenon of an increase in the detection threshold voltage are considered as below. In a case where the surface roughness Ra becomes too high, the tactile sense of the surface of the material state of the contact face  17  is rough, and it is difficult to discriminate the tactile sense of the surface from the rough sense of the presented tactile sense. In addition, in a case where the surface roughness Ra becomes high, the finger is deformed to follow the irregularities of the contact face  17  and is caught in a protruded portion of the contact face  17  so as not to easily slide, and thus, it is difficult to feel a change in the tactile sense. 
     By referring to the graph illustrated in  FIG. 7 , in a case where a tactile sense presentation device having a detection threshold voltage lower than that of the tactile sense presentation device of reference number  1 , for example, a tactile sense presentation device having a detection threshold voltage of 150 V or lower is desired to be designed, it is preferable to set the surface roughness Ra to a range of 0.01 μm to 0.3 μm. In addition, in a case where a tactile sense presentation device having a detection threshold voltage lower than 178.4 V that is the detection threshold voltage of the tactile sense presentation device of reference number  1  is desired to be designed, it is preferable to set the surface roughness Ra to a range of 0.01 μm to 0.4 μm. 
     A result of a further examination of the relation among the surface roughness Ra, the detection threshold voltage, and the tactile sense felt by the operator is illustrated in  FIG. 8 . In the antiglare layer  15  formed using the coating layer material  15   b  in the solution that includes the particles  15   a , the surface roughness Ra cannot be configured to be very high, and thus, in  FIG. 8 , the antiglare layer  15  is not arranged, and a tactile sense felt by the operator is written also for a sample (KB-115 in the drawing) using a member of a surface roughness Ra of 0.4 μm to 3.2 μm as the insulating layer  16 . 
     Under a condition that the voltage amplitude of the voltage signal applied to the electrode is zero, a sticky sense is felt in a case where the surface roughness Ra is 0.00 μm, a smooth and dry sense is felt in a case where the surface roughness Ra is 0.0206 μm to 0.4 μm, and a rough sense is felt in a case where the surface roughness Ra is 0.8 μm or more. In a case where the surface roughness Ra is 0.8 μm or more, in addition to the feeling of the tracing finger being rough, a frictional force is felt to be large, and accordingly, an effect of decreasing the detection threshold voltage cannot be expected. In addition, in a case where the surface roughness Ra exceeds 0.8 μm, the impression of the tactile sense of the material state is not good. Thus, it is preferable that the surface roughness Ra is set to be less than 0.8 μm. 
     In addition, in  FIG. 8 , also for a sample (a sample of reference number  5 ) having a surface roughness Ra of 0.0564 μm, the presence of a sticky feeling is recorded. A sticky sense may be generated due to an ambient temperature, ambient humidity, the amount of moisture of the tip of the finger, a pressing force of the finger, and the like. In a case where such a sticky sense is generated, the detection threshold voltage instantly increases, and thus, it is preferable to set the surface roughness Ra to be higher than 0.05 μm. 
     Based on the test result described above and the graph illustrated in  FIG. 7 , in order to effectively decrease the detection threshold voltage while a state in which a texture sense can be easily perceived is maintained, it is significant to set the surface roughness Ra to a range higher than 0.01 μm and lower than 0.8 μm, and more preferably, to a range higher than 0.05 μm and lower than 0.8 μm. This range of the surface roughness Ra may be paraphrased as a range rougher than a state in which the operator&#39;s finger is stuck to the contact face as the contact area between the contact face of the insulating layer that is in touch with the operator and the operator&#39;s finger becomes relatively large and is finer than a state in which the operator&#39;s finger is deformed to follow the irregularities of the contact face. In addition, since there is a special correlation between the surface roughness Ra of the contact face  17  and the detection threshold voltage, it is significant to set the voltage amplitude of a signal voltage applied to the electrode to a voltage corresponding to the surface roughness Ra of the contact face  17 . 
     Thus, in one embodiment of the present invention, the antiglare layer  15  is formed such that the surface roughness Ra of the contact face  17  is in the predetermined range described above, and a voltage corresponding to the surface roughness Ra of the contact face  17  is applied to the electrode, and, more preferably, a voltage (while the upper limit is not particularly limited, from a viewpoint of securing the safety by decreasing the applied voltage, a voltage that is the applied voltage of a conventional device or less) that is the detection threshold voltage corresponding to the surface roughness Ra of the contact face  17  or higher is controlled to be applied to the electrode so as to drive the tactile sense presentation device  10 . Accordingly, both the securement of the safety and the improvement of the perception sensitivity of the texture sense are achieved. 
     Here, the configuration and the control method of the tactile sense presentation device  10  may be appropriately changed as long as the surface roughness Ra of the contact face  17  is in the predetermined range described above, and the tactile sense presentation device is driven using a voltage (a voltage that is a detection threshold voltage corresponding to the surface roughness Ra of the contact face  17  or higher) corresponding to the surface roughness Ra of the contact face  17 . 
     For example, in this embodiment, while the antiglare layer  15  formed using the coating layer material  15   b  including the particles  15   a  is arranged in the uppermost layer, irregularities having a surface roughness to be in the predetermined range described above may be formed on the contact face  17 , and the antiglare layer  15  may be omitted. 
     In addition, by forming the insulating layer  16  that is the upper layer of the X electrodes  12  and the Y electrodes  13  using SiO2 or the like and etching the insulating layer  16  to be non-uniform through wet etching using hydrofluoric acid or the like, irregularities having the desired surface roughness can be formed on the contact face  17 . In addition, by partly shaving off the surface of the insulating layer  16  through sand blasting or the like, irregularities having the desired surface roughness can be formed on the contact face  17 . 
     In this embodiment, while the insulating layer  16  is formed in the upper layer of the X electrodes  12  and the Y electrodes  13 , in a case where the coating layer material  15   b  has viscosity of some degree, and a thickness corresponding to a thin portion of the coating layer material  15   b  can be secured, as illustrated in  FIG. 25 , the insulating layer  16  may be omitted, and the antiglare layer  15  may be directly formed in the upper layer of the X electrodes  12  and the Y electrodes  13 . 
     In the case illustrated in  FIG. 4 , while the particles  15   a  have been described as sphere bodies having a uniform diameter, as long as the surface roughness is in the predetermined range described above, the sphere bodies having non-uniform diameters may be mixed, and the sphere bodies may have a flat shape, a cylindrical shape, a shape that is partly sharpened shape, or the like. In addition, in the case illustrated in  FIG. 4 , while the contact face  17  has gentle irregularities, a shape acquired by sharpening the tip ends of convex portions may be employed. 
     Furthermore, by dipping a resin sheet in a solution, forming an antiglare layer on the surface of the resin sheet, and pasting the resin sheet into the insulating layer  16 , an antiglare layer may be formed on the contact face. 
     The inventors of the present application made evaluations that are the same as the evaluation of the samples described above with reference to  FIGS. 5 to 8  with test subjects added. The detection threshold voltages illustrated in  FIGS. 6 to 8  and the tactile sense at the time of a zero signal voltage are results acquired when a man of 40&#39;s is a test subject. The added test subjects are three persons including a man of the first half of 30&#39;s, a man of the second half of 30&#39;s, and a woman of 20&#39;s. 
       FIG. 9  illustrates the detection threshold voltages of a total of four persons including the man of 40&#39;s and the added three test subjects. As a characteristic common to all the four persons, the detection threshold voltage of a sample (a sample of reference number  1 ) having no antiglare layer  15  and a flat contact face  17  is higher than the detection threshold voltages of the other samples (reference numbers  2  to  9 ) each having a certain antiglare layer  15  arranged therein. Based on this result, it has been turned out that the antiglare layer  15  is effective for decreasing the drive voltage. 
     In addition, as the surface roughness Ra is higher than 0.0206 μm, the detection threshold voltage gradually decreases, and the detection voltage is minimal in the sample of reference number  4  having a surface roughness Ra of 0.0503 μm in case of the man of 40&#39;s and the man of the first half of 30&#39;s, the sample of reference number  6  having a surface roughness Ra of 0.093 μm in case of the man of the second half of 30&#39;s, and the sample of reference number  7  having a surface roughness Ra of 0.1375 in case of the woman of 20&#39;s. In a case where the surface roughness Ra is higher than the surface roughness Ra for which the minimal detection threshold voltage is acquired for each test subject, the detection threshold voltage gradually increases. Based on the result described above, it has been found that the detection threshold voltages detected for all the test subjects change depending on the surface roughness Ra, and minimum values thereof are present. 
     Graphs acquired by plotting the relations between the surface roughnesses Ra and the detection threshold voltages of the added three test subjects and giving approximation curves thereof are illustrated in  FIGS. 10, 11, and 12 .  FIG. 10  illustrates the detection threshold voltage of the man of the first half of 30&#39;s,  FIG. 11  illustrates the detection threshold voltage of the man of the second half of 30&#39;s, and  FIG. 12  illustrates the detection threshold voltage of the woman of 20&#39;s. From these drawings, it can be understood that, by setting the surface roughness Ra to be higher than 0.01 μm, an effect of decreasing the detection threshold voltage is acquired, and, in an area in which the surface roughness Ra is higher than the surface roughness Ra at which the detection threshold voltage is worst, the detection threshold voltage tends to increase. This trend can be seen also in the relation between the surface roughness Ra and the detection threshold voltage of the man of 40&#39;s illustrated in  FIG. 7 . In other words, in the results of evaluations of all the four test subjects, the same trend is checked. 
     By referring to the approximation curves illustrated in  FIGS. 7 and 10 to 12 , the surface roughnesses Ra at which the detection threshold voltages are minimal are sequentially 0.05 μm, 0.03 μm, 0.075 μm, and 0.08 μm, and, while an individual difference in the detection threshold voltages of the four persons is recognized, in order to decrease the detection threshold voltage, it is preferable to set the surface roughness Ra to be higher than 0.03 μm. 
     Relating to the tactile sense at the time of a zero signal voltage described with reference to  FIG. 8 , the results of evaluations of a total of four persons including the man of 40&#39;s and the added three test subjects are as follows. Three test subjects feel a smooth and dry sense in a case where the surface roughness Ra is 0.4 μm and feel a rough sense in a case where the surface roughness Ra is 0.8 μm or more. The remaining one test subject feels a smooth and dry sense in a case where the surface roughness Ra is 0.4 μm, feels both a smooth and dry sense and a rough sense in a case where the surface roughness Ra is 0.8 μm, and feels a rough sense in a case where the surface roughness Ra is 1.6 μm or more. From such results, test subjects feel a rough sense in a case where the surface roughness Ra exceeds 0.8 μm. As described above, in a case where the surface roughness Ra is 0.8 μm or more, in addition to the feeling of the tracing finger being rough, a frictional force is felt to be large, and accordingly, an effect of decreasing the detection threshold voltage cannot be expected. Furthermore, the impression of the tactile sense is not good. Thus, it is preferable that the surface roughness Ra is set to be less than 0.8 μm. 
     Based on the results of the evaluations for the four test subjects, in order to effectively decrease the detection threshold voltage while a state in which a texture sense can be easily perceived is maintained, it is understood that the desirable surface roughness Ra is in a range more than 0.01 μm and less than 0.8 μm and, more preferably, in a range more than 0.03 μm and less than 0.8 μm. 
     SECOND EMBODIMENT 
     While the panel of the tactile sense presentation device described above in the first embodiment is configured: by the support substrate; the plurality of electrodes formed on the support substrate and extending in a predetermined direction, and the insulating layer covering the plurality of electrodes, the electrode does not need to be formed as the plurality of electrodes. Thus, in this embodiment, a tactile sense presentation device having one electrode is produced as a trial product. 
     First, the inventors of the present application produced a panel  10   a  of a tactile sense presentation device  10  as illustrated in  FIG. 13  as a trial product. The panel  10   a  of this tactile sense presentation device  10  is configured by a support substrate  11  and one electrode  11   a  formed on the support substrate  11  and a drive unit  19  that outputs a voltage signal to the electrode  11   a  and an insulating layer  16  covering the electrode  11   a , and the surface of this insulating layer  16  serves as a contact face  17 . 
     In addition, the inventors of the present application produced a panel  10   a  of a tactile sense presentation device  10  as illustrated in  FIG. 14 . The panel  10   a  of this tactile sense presentation device  10  is configured by a support substrate  11  and one electrode  11   a  formed on the support substrate  11  and a drive unit  19  that outputs a voltage signal to the electrode  11   a  and an insulating layer  16  covering the electrode  11   a  and an antiglare layer  15  having a reflection prevention function for visible light in a further upper layer of the insulating layer  16 , and the surface of this antiglare layer  15  serves as a contact face  17 . Furthermore, a plurality of tactile sense presentation devices  10  having mutually-different properties and states (surface roughness) of the antiglare layer  15  were produced as trial products. 
     These panels  10   a  are evaluated as below. In a case where the voltage amplitude of the voltage signal output by the drive unit  19  is sufficiently high, when the finger traces the contact face  17  (the finger slides on the contact face), a rough texture sense is felt. From this state, the voltage amplitude of the voltage signal applied to the electrode  11   a  is gradually decreased, and a lowest voltage for which a difference of the tactile sense from the tactile sense at the time of the amplitude of the voltage signal applied to the electrode  11   a  being 0 V is considered to be identifiable is recorded. This voltage is a detection threshold voltage, and the detection threshold voltage was measured for each of the plurality of tactile sense presentation devices  10  produced as trial products. 
     The results are similar to that described with reference to  FIG. 7 . In other words, by applying an antiglare process for the contact face (the contact face of the insulating layer is formed to be rough), a presented tactile can be acquired very easily. In other words, the presented tactile stimulation can be perceived by the operator very easily. In addition, as the surface roughness of the contact face is suitably increased through the antiglare process, the operator can easily perceive a tactile stimulus. In other words, a special correlation is seen between the surface roughness of the contact face and a detection threshold voltage that is a lowest voltage for which the operator can perceive a texture sense for the surface roughness. More specifically, it is understood that, by setting the surface roughness Ra to be higher than 0.01 μm, an effect of decreasing the detection threshold voltage can be acquired. In addition, it is understood that the minimum value of the detection threshold voltage is near a surface roughness Ra of 0.05 μm. Furthermore, it has been disclosed that the detection threshold voltage corresponding to a range in which the surface roughness Ra is higher than 0.01 and less than 0.2392 μm is lower than the detection threshold voltage of a case where the surface roughness Ra is 0.00 μm. 
     As above, the reasons for the operator being able to easily perceive a tactile stimulus by appropriately increasing the surface roughness are as described in the following (1) to (3). The reasons for the operator being able to easily perceive a tactile stimulus in the first embodiment are as follows. 
     (1) Case Where Surface Roughness Is Low and Flat: 
     The contact face and the surface of the operator&#39;s finger are tightly brought into contact with each other, and intermolecular forces are strongly applied between the contact face and the surface. At this time, in a case where appropriate moisture is present, a hydrogen bond is generated, and accordingly, the intermolecular forces become strong. Considering a normal reaction that is a factor of a frictional force applied between the surface and the contact face when the operator moves his finger, there is an electrostatic force as one element of the normal reaction, and there is an intermolecular force as the other element. Since the intermolecular force is high, the ratio of the electrostatic force is small, and the rate of change in the normal reaction is low even in a case where the electrostatic force is controlled to be changed. For this reason, the rate of change in the friction is small, and it is difficult for the operator to perceive a tactile stimulus. 
     (2) Case Where Surface Roughness is Higher Than (1) and is Appropriate: 
     A gap is partly generated between the surface and the contact face, and the intermolecular force applied between the contact face and the surface rapidly decreases due to the gap. While there is an electrostatic force as one element of the frictional force, and there is an intermolecular force as the other element, as the ratio of the electrostatic force increases, the strength of the electrostatic force can be easily appear in the change of the friction. 
     (3) Case Where Surface Roughness is Further Higher Than (2): 
     When the operator moves his finger, the surface thereof is deformed to follow the irregularities of the contact face, and a frictional force accompanied with the deformation increases. Since the frictional force is high, the rate of change in the frictional force changing according to a change in the electrostatic force is low. For this reason, it is difficult for the operator to feel a texture sense. 
     Hereinafter, an example of a specific structure, a drive method, and a use form of the tactile sense presentation device  10  (particularly, the tactile sense presentation device  10  according to the first embodiment) having the above-described configuration will be described. 
     EXAMPLE 1 
     First, a first example of the present invention will be described with reference to  FIGS. 15 to 18 . In this example, a specific example of the frequency of the voltage signal applied to the X electrodes and the Y electrodes of the tactile sense presentation device  10  will be described. 
       FIG. 15  is an explanatory diagram that illustrates the configuration of the tactile sense presentation device  10  according to the first example of the present invention. In a panel part of the tactile sense presentation device  10 , on a support substrate  11  having a flat shape, a plurality of X electrodes  12  extending in the X-axis direction and a plurality of Y electrodes  13  extending in the Y direction are formed. 
     The X electrodes  12  and the Y electrodes  13  intersect each other at the intersections thereof through an insulating layer (not illustrated in the drawing), and an electrical insulating property therebetween is maintained by the insulating layer. In addition, on the X electrodes  12  and the Y electrodes  13 , an insulating layer and/or an antiglare layer (not illustrated in the drawings) are formed, and the electrical insulating property between the X electrodes  12  and the finger and the Y electrodes  13  and the finger at the time of touching the contact face of the tactile sense presentation device  10  using the finger is maintained by the insulating layer and/or the antiglare layer. 
     Each of the X electrodes  12  is connected to an X-electrode driving circuit (drive unit)  20 , and each of the Y electrodes  13  is connected to a Y-electrode driving circuit (drive unit)  30 , and the X-electrode driving circuit  20  and the Y-electrode driving circuit  30  are connected to a control unit  40 . The control unit  40  specifies an electrode corresponding to an area in which a tactile sense is presented to the operator based on information input from the outside (for example, a processor controlling the operation of an electronic apparatus in which the tactile sense presentation device  10  is mounted), outputs a control signal used for driving the specified electrode to the X-electrode driving circuit  20  and the Y-electrode driving circuit  30 , and the X-electrode driving circuit  20  and the Y-electrode driving circuit  30  apply a voltage signal having a voltage amplitude corresponding to the surface roughness of the insulating layer or the antiglare layer to the X electrodes  12  and the Y electrodes  13  based on the control signal. By employing such a configuration, the tactile sense presentation device  10  can present a texture sense to a desired area. In the claims, the control unit  40  outputting a control signal and the electrode driving circuits applying a voltage to the electrodes based on the control signal are collectively referred to as a drive unit. 
       FIG. 16  is an explanatory diagram that illustrates a method of driving the tactile sense presentation device  10  illustrated in  FIG. 15 . Here, the X electrodes  12  and the Y electrodes  13  will be discriminated form each other using different symbols. In the example illustrated in  FIG. 16 , while  28  X electrodes  12  and  46  Y electrodes  13  are formed on the support substrates  11 , the X electrodes  12  will be respectively referred to as X 00  to X 27  from the bottom in the upward direction, and the Y electrodes  13  will be referred to as Y 03  to Y 48  from the right side toward the left side. Here, an area in which a texture sense is to be presented is assumed to be a target area  50 . The target area  50  is in the range of X 11  to X 14  in the X direction and is in the range of Y 24  to Y 27  in the Y direction. The control unit  40  applies control signals to the X-electrode driving circuit  20  and the Y-electrode driving circuit  30  based on information of the target area  50  supplied from the outside. 
     As the control signals are received, the X-electrode driving circuit  20  applies an AC voltage signal having a first frequency (here, the frequency f 1 =1000 Hz) to X 11  to X 14 , and the Y-electrode driving circuit  30  applies an AC voltage signal having a second frequency (the frequency f 2 =1240 Hz) to Y 24  to Y 27 . In addition, in the case illustrated in  FIG. 16 , in order to prevent the application of a voltage according to capacitance coupling between the electrodes, the X-electrode driving circuit  20  and the Y-electrode driving circuit  30  apply the ground or a DC voltage to the X electrodes  12  and the Y electrodes  13  other than the electrodes described above. 
     In the configuration described above, in an area acquired by excluding the target area  50  from the area disposed above the X electrodes  12  of X 11  to X 14 , a texture sense corresponding to the voltage signal applied to the electrode is not presented (only a texture sense of the material state is presented). In addition, in an area acquired by excluding the target area  50  from the area disposed above the Y electrodes  13  of Y 24  to Y 27 , a texture sense corresponding to the voltage signal applied to the electrode is not presented (only a texture sense of the material state is presented). From this, it has been checked that a human&#39;s finger has a characteristic of not perceiving a texture sense according to a voltage signal in a case where the frequency of the voltage signal applied to the electrode is 1000 Hz or 1240 Hz. 
     Meanwhile, in the target area  50 , since the X electrode  12  to which a voltage signal having f 1 =1000 Hz is applied and the Y electrode  13  to which a voltage signal having f 2 =1240 Hz is applied are adjacent to teach other, a beat known in the field of a wave motion is generated, and the texture sense is presented using the beat. Thus, in this example, a texture sense corresponding to a voltage signal is not presented at the frequency of the voltage signal applied to each electrode, but the frequency of the voltage signal applied to each electrode is set such that a texture sense according to a voltage signal is presented using a frequency defined in the beat, and the target area  50  can be determined based on the tactile sense. 
       FIG. 17  is a schematic diagram that illustrates a sectional model of the tactile sense presentation device  10  illustrated in  FIGS. 15 and 16 . As described above, the plurality of X electrodes  12  and the plurality of Y electrodes  13  are arranged on the support substrate  11  having a planar shape to be neighboring to each other. Among the X electrodes  12  and the Y electrodes  13 , at a position facing two X electrodes  12  and two Y electrodes  13  arranged inside the target area  50 , one electrode  51  modeling a finger is arranged. Since the human body has a grounding effect to some degree, this electrode  51  can be modeled as being grounded through a resistor  52  having a resistance value R. 
     Here, a voltage signal V 1  represented as V 1 =Acos(2πf 1 t) is applied to the X electrodes  12  disposed inside the target area  50 . The amplitude of the voltage signal V 1  is A, the frequency is f 1 , and t represents the time. In addition, a voltage signal V 2  represented as V 2 =Acos(2πf 2 t) is applied to the Y electrodes  13  disposed inside the target area  50 . The amplitude of the voltage signal V 2  is A that is the same as the amplitude of the voltage signal V 1 , and the frequency is f 2 . 
     Between the electrode  51  and each of the X electrodes  12  disposed inside the target area  50  can be modeled as a parallel flat plate capacitor having electrostatic capacitance C. 
     In addition, between the electrode  51  and each of the Y electrodes  13  disposed inside the target area  50  can be modeled as a parallel flat plate capacitor having electrostatic capacitance C. 
     At this time, when the resistance value R is sufficiently high, a voltage V P  appearing at the electrode  51  can be represented using 
     
       
         
           
             
               
                 
                   Equation 
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     When an electrostatic force applied between one X electrode  12  and the electrode  51  acquired by modeling a finger is F e1 , the electrostatic force F e1  can be represented as Equation 2 by using a known formula as a force applied between the electrodes of the parallel flat plate capacitor. 
     Here, ϵ is a dielectric constant, and S is the area of the electrode of the parallel flat plate capacitor. 
     
       
         
           
             
               
                 
                   
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     Similarly, when an electrostatic force applied between one Y electrode  13  and the electrode  51  acquired by modeling a finger is F e2 , the electrostatic force F e2  can be represented as Equation 3. 
     
       
         
           
             
               
                 
                   
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     In a case where the gap between the electrodes is so fine that the electrostatic force F e1  and the electrostatic force F e2  cannot be discriminated by a person&#39;s the fingertip, it can be regarded that a force acquired by summing the electrostatic forces F e1  and F e2  is macroscopically applied to the finger. 
     A sum F of all the forces applied to the electrode  51  acquired by modeling a finger is F=2(F e1 +F e2 ) by referring to  FIG. 17 , and accordingly, by using V 1 , V 2 , and Equations 2 and 3 described above, can be represented using Equation 4. 
     
       
         
           
             
               
                 
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     Based on Equation 4, it can be understood that the sum F of all the forces applied to the modeled electrode  51  is acquired by multiplying a periodic function having a range of [0, A 2 C 2 /(ϵS)] and a frequency of the absolute value of (f 1 +f 2 ) by a periodic function having a range of [0, 2] and a frequency of the absolute value of (f 1 -f 2 ). The frequency of the envelope thereof is the absolute value of (f 1 -f 2 ). 
     In this example, since the frequency f 1 =1000 Hz, and the frequency f 2 =1240 Hz, the absolute value of a difference thereof is 240 Hz. For this reason, the frequency of the attractive force applied to the finger, as represented in Equation (4), changes to 240 Hz. 
     Thus, in a case where a person traces the contact face  17  of the tactile sense presentation device  10  using his finger, a change in the frictional force occurs at the frequency of 240 Hz. Since 240 Hz is a frequency for which a person&#39;s cutaneous mechanoreceptor has sensitivity, a texture sense can be perceived. 
     In addition, a voltage signal having a frequency f 1  is applied to all the X electrodes  12  disposed on the support substrate  11 , and a voltage signal having a frequency f 2  is applied to all the Y electrodes  13 , and the presence/absence of the perception of a texture sense for the absolute value of a difference between the frequencies f 1  and f 2  has been checked through a test. As a result, it has been checked that a texture sense is perceived in a case where the absolute value of the difference between the frequencies f 1  and f 2  is higher than 10 Hz and lower than 1000 Hz, and a texture sense is not perceived in a case where the absolute value of the difference between the frequencies f 1  and f 2  is lower than 10 Hz or higher than 1000 Hz. 
     In addition, the same voltage signal is applied to the X electrodes  12  and the Y electrodes  13 , and the presence/absence of the perception of a texture sense has been checked through a test while changing the frequency of the voltage signal. As a result, it has been checked that a texture sense is perceived in a case where the frequency of the voltage signal is in a range higher than 5 Hz and lower than 500 Hz, and a texture sense is not perceived in a case where the frequency of the voltage signal is out of the range. 
     Based on such results, in a case where the frequency of the voltage signal applied to the X electrodes  12  is set to f 1 , and the frequency of the voltage signal applied to the Y electrodes  13  is set to f 2 , by setting the frequencies f 1  and f 2  such that both the frequencies f 1  and f 2  are 500 Hz or higher, and the absolute value of a difference between the frequencies f 1  and f 2  is higher than 10 Ha and lower than 1000 Hz, a tactile sense presentation device  10  can be realized which presents a texture sense corresponding to the voltage signal to an area in which the X electrode  12  to which the voltage signal of the frequency f 1  is applied and the Y electrode  13  to which the voltage signal of the frequency f 2  is applied interest each other but does not present a texture sense corresponding to the voltage signal to the other area (only the texture sense of the material state of the contact face  17  is presented). 
     Here, the frequencies of the voltage signals applied to the X electrodes  12  and the Y electrodes  13  are not limited to those described above but may be appropriately change according to the surface roughness of the contact face  17 , the detection threshold voltage, and the like. In addition, in the description presented above, while the AC voltage signals having a sinusoidal shape are applied to the X electrodes  12  and the Y electrodes  13 , voltage signals having a pulse shape in which On and Off are intermittently repeated may be applied. 
     EXAMPLE 2 
     Next, a second example of the present invention will be described with reference to  FIGS. 18 to 20 . In this example, specific shapes of the X electrodes and the Y electrodes of the tactile sense presentation device  10  and a method of manufacturing the tactile sense presentation device  10  will be described. 
       FIG. 18  is a planar view that illustrates specific shapes of the support substrate  11 , the X electrodes  12  and the Y electrodes  13  of the tactile sense presentation device  10  illustrated in  FIG. 15 . In  FIG. 18 , the X electrodes  12  and wirings thereof are illustrated using broken lines, and the Y electrodes  13  and wirings thereof are illustrated using solid lines. 
     The X electrodes  12  have a shape in which a plurality of electrodes having a rhombus shape are connected through connection portions in a rosary shape. In other words, one X electrode  12  has a shape in which rhombus-shaped electrodes neighboring to the left and right sides are electrically connected through connection portions. These X electrodes  12  are arranged at an interval of 2 mm in the Y-axis direction. In other words the pitch of the X electrodes  12  is 2 mm. Similarly, the Y electrodes  13  have a shape in which a plurality of electrodes having a rhombus shape are connected through connection portions in a rosary shape. In other words, one Y electrode  13  has a shape in which rhombus-shaped electrodes neighboring to the upper and lower sides are electrically connected through connection portions. These Y electrodes  13  are arranged at an interval of 2 mm in the X-axis direction. In other words the pitch of the Y electrodes is 2 mm. 
     The X electrodes  12  and the Y electrodes  13  are formed such that the connection portions of the rhombus-shaped electrodes overlap each other through the insulating film in the plan view. In addition, a major portion of the rhombus-shaped portion of the X electrode  12  and a major portion of the rhombus-shaped portion of the Y electrode  13  are formed not to overlap each other. In other words, a shape is formed such that the major portion of the rhombus-shaped portion of the X electrode  12  and the major portion of the rhombus-shaped portion of the Y electrode  13  are neighboring to each other in the plan view. 
       FIGS. 19 and 20  are diagrams acquired by enlarging the structure of the connection portion of the X electrodes  12  and the Y electrodes  13  illustrated in  FIG. 18 ,  FIG. 19  is a planar view that illustrates a mutual connection portion of electrodes represented as a block A illustrated in  FIG. 18 , and  FIG. 20  is a cross-sectional view taken along line C-C illustrated in  FIG. 19 . 
     The X electrodes  12  are configured such that rhombus-shaped electrodes are connected to each other through a bridge electrode  12   a . In addition, the Y electrodes  13  are configured such that rhombus-shaped electrodes are connected to each other through a connection portion  13   a  using the same material as that of the Y electrodes  13 . The bridge electrode  12   a  and the connection portion  13   a  of the Y electrode  13  are insulated by the insulating layer  14 . 
     The cross-sectional structure of the connection portions of the X electrodes  12  and the Y electrodes  13  and the manufacturing sequence will be described with reference to  FIG. 20 . First, on a support substrate  11  formed using a transparent insulating material such as glass, a bridge electrode  12   a  is formed using a transparent conductive material such as ITO. 
     Next, an insulating layer  14  is formed using an organic material on the bridge electrode  12   a . By forming the insulating layer  14  using the organic material, the film thickness of the insulating layer  14  can be formed to be large, and thus, coupling capacitance, which is originally unnecessary, formed at the intersection between the X electrode  12  and the Y electrode  13  can be decreased. In order to insulate the connection portion  13   a  of the Y electrode  13  and the bridge electrode  12   a  from each other, this insulating layer  14  is formed in a shape covering the bridge electrode  12   a  in the Y-axis direction (the depth direction in the diagram) but not covering the end portion of the bridge electrode  12   a  in the X-axis direction (the horizontal direction in the diagram) such that the bridge electrode  12   a  and the rhombus-shaped portion of the X electrode  12  are in contact with each other. Next, the X electrodes  12 , the Y electrodes  13 , the connection portions  13   a , the other wirings, and the terminal  18  are formed together using a transparent conductive material such as ITO. 
     Next, an insulating layer  16  is formed as a film using an organic material, and, thereon, spray coating of a coating layer material  15   b  in a solution that includes particles  15   a  formed using silica having a predetermined size or the like is performed, the coated coating layer material is dried, and an antiglare layer  15  is formed. At that time, by changing the content ratio of the particles  15   a  to the coating layer material  15   b , a spraying method, the material, the size, and the shape of the particles  15   a , the material, the viscosity, and the like of the coating layer material  15   b , the antiglare layer  15  is formed such that surface roughness Ra of the antiglare layer  15  is in a range higher than 0.01 μm (more preferably, 0.05 μm)) and lower than 0.8 μm. Thereafter, a contact hole is formed in the terminal  18  portion. 
     A plurality of terminals  18  formed on the support substrate  11  are connected to the X electrodes  12  or the Y electrodes  13  through wirings. Then, one end of a flexible printed circuit (FPC) is attached to the terminal  18  through an anisotropic conductive film (ACF), and the other end of the FPC is connected to a printed board in which the X-electrode driving circuit  20  and the Y-electrode driving circuit  30  are mounted. 
     Through the process described above, the tactile sense presentation devices  10  having the structures illustrated in  FIGS. 18 to 20  can be manufactured. The shapes of the X electrodes  12  and the Y electrodes  13  of the tactile sense presentation device  10  described above and the above-described method of manufacturing the tactile sense presentation device  10  are only examples and can be appropriately changed. 
     EXAMPLE 3 
     Next, a third example of the present invention will be described with reference to  FIGS. 21 and 22 . In this example, a specific configuration of electrode driving circuits of the tactile sense presentation device  10  and an operation method thereof will be described. 
       FIG. 21  is an explanatory diagram that illustrates the detailed configuration of the X-electrode driving circuit  20  of the tactile sense presentation device  10  illustrated in  FIG. 15 . The Y-electrode driving circuit  30  and the X-electrode driving circuit  20  have the same configuration, and thus, here, only the configuration of the X-electrode driving circuit  20  will be described. 
     The X-electrode driving circuit  20  includes a data input terminal  21   a  and a clock input terminal  21   b  and a start pulse input terminal  21   c  as input terminals. Such input terminals are connected to the control unit  40  and receive control signals generated by the control unit  40 . 
     In addition, the X-electrode driving circuit  20  includes a plurality of output terminals  22  outputting voltage signals to be applied to the X electrodes  12  as output terminals. In the example illustrated in  FIG. 21 , the number of the output terminals  22  is 50 and are respectively represented as A 0  to A 49 . 
     In addition, the X-electrode driving circuit  20 , in addition to such input/output terminals, includes: an AC voltage generating unit  23   a  that generates an AC voltage having a frequency f 1  an AC voltage generating unit  23   b  that generates an AC voltage having a frequency f 2  and an AC voltage generating unit  23   c  that generates an AC voltage having a frequency f 5 . The frequencies f 1 , f 2 , and f 5  are respectively, 1000 Hz, 1240 Hz, and 3000 Hz. 
     Furthermore, the X-electrode driving circuit  20  includes a shift register  24  of 50 bits. The shift register  24  includes 50 output terminals (Q 0  to Q 49 ), and such output terminals are respectively connected to data registers  25  each having two bits. Each two-bit data register  25  is connected to the data input terminal  21   a  and a bus. 
     An output signal output from each two-bit data register  25  is connected to a two-input four-output decoder  26 . The two-input four-output decoder  26  receives an input signal of two bits as input and outputs a voltage signal of a high level to one of four output terminals in accordance with this input signal. The input two-bit signal and the output terminal to which the voltage signal of the high level is output have one-to-one correspondence. 
     One of the output terminals of the two-input four-output decoder  26  is not used in this example, and the gate electrodes of switch transistors  27  are connected to the remaining three output terminals. The switch transistors  27  that are respectively connected to these three output terminals will be referred to as SW 1  to SW 3 . 
     An output terminal of the switch transistor  27  is connected to the input of the amplifier  28 . The input terminals SW 1  to SW 3  of the switch transistor  27  are respectively connected to output terminals of the AC voltage generating units  23   a  to  23   c . In other words, AC voltages having frequencies f 1 , f 2 , and f 5  are respectively input to the input terminals SW 1  to SW 3 . The two-input four-output decoder  26  has a function for selectively switching AC voltages to be output to the amplifiers  28  among voltages of the frequencies in accordance with an output from the two-bit data register  25 . 
     Then, AC voltages amplified by the amplifiers  28  are output from the output terminals  22  to the X electrodes  12 . In other words, the X-electrode driving circuit  20  achieves the function of a circuit selecting one AC voltage signal among the signals of frequencies f 1 , f 2 , and f 5  in accordance with a signal input from the control unit  40  through the data input terminal  21   a  and outputting the selected signal to the X electrode  12  through the output terminal  22 . 
       FIG. 22  is a timing diagram that illustrates the operation of the X-electrode driving circuit  20  illustrated in  FIG. 21 . “CLK” represented in the drawing is a clock waveform voltage input from the control unit  40  through the clock input terminal  21   b . “D[ 1 : 0 ]” is a two-bit data signal input from the control unit  40  through the data input terminal  21   a . “ST” is a start pulse waveform voltage that is input from the control unit  40  through the start pulse input terminal  21   c.    
     Here, D[ 1 : 0 ] input from the control unit  40  through the data input terminal  21   a  is a binary representation and thus, may have four kinds of values including “00”, “01”, “10”, and “11”. The shift register  24  latches the value of ST for each rising edge of CLK and outputs the latched value to the output terminal Q 0  of the shift register. Then, the value of Q 0  is delayed by one period of CLK and is output to the output terminal Q 1 . In addition, the value of Q 1  is delayed by one period of CLK and is output to the output terminal Q 2 . In this way, the shift register  24  outputs a pulse waveform voltage synchronized with the rising edge of CLK sequentially to the output terminals Q 0  to Q 49 . 
     When the pulse waveform voltage is output to the output terminal of the shift register  24 , a registered value of the two-bit data register  25  is updated with the value of data D[ 1 : 0 ] of that time in synchronization with the rising edge and is output to the output terminal of the two-bit data register  25 . 
     The two-input four-output decoder  26  receives signals output to the terminals of the two-bit data register  25  and turns on one switch transistor  27  among the switch transistors SW 1  to SW 3 , and one AC voltage signal among voltage signals of frequencies f 1 , f 2 , and f 5  is output to the output terminal  22  in accordance therewith. 
     The X-electrode driving circuit  20  associates the frequency f 1  with the data D[ 1 : 01 ]=00, associates the frequency f 2  with the data D[ 1 : 0 ]=01, and associates the frequency f 5  with the data D[ 1 : 0 ]=10. 
     For this reason, at time t 1  illustrated in  FIG. 22 , a voltage signal having the frequency f 5  is output to A 0  of the output terminal  22 , at time t 2 , a voltage signal having the frequency f 2  is output to A 1  of the output terminal  22 , and, at time t 3 , a voltage signal having the frequency f 1  is output to A 2  of the output terminal  22 . The amplitude of each voltage signal is 70 V. Here, D[ 1 : 0 ]=11 is not used. 
     The frequency of the voltage signal output to the output terminal  22  is not changed until a next pulse waveform voltage is input to the start pulse input terminal  21   c , and the registered value of the two-bit data register  25  is updated. 
     In  FIG. 22 , the output waveforms of output terminals Q 0  to Q 2  among the  50  output terminals Q 0  to Q 49  of the shift register  24  are illustrated as an example, but the other output waveforms are not illustrated. Similarly, for the voltage signals of the  50  output terminals  22  A 0  to A 49  of the X-electrode driving circuit  20 , A 0  to A 2  are illustrated as an example, but the other voltage signals are not illustrated. The configuration and the driving method of the electrode driving circuits described above are examples and can be appropriately changed. 
     EXAMPLE 4 
     Next, a fourth example of the present invention will be described with reference to  FIGS. 23 and 24 . In this example, an example of the use form of the tactile sense presentation devices  10  illustrated in the embodiments and the first to third examples described above will be described. 
       FIG. 23  is a perspective view that illustrates the configuration of an electronic apparatus  100  according to an application of the present invention. The electronic apparatus  100 , for example, is a smartphone, a tablet terminal, an electronic book reader, a notebook personal computer, or the like. 
     The electronic apparatus  100  includes a display apparatus  101  of the touch panel type, and the tactile sense presentation device  10  described above is arranged on the front face or the rear face of the display apparatus  101  of the touch panel type. Here, in a case where a touch panel of an electrostatic capacitance type is employed as the display apparatus  101  of the touch panel type, the function thereof and the function of the tactile sense presentation device  10  are not achieved together, it is preferable to use an optical touch panel or the like. 
     In the electronic apparatus  100 , a result of a process executed by a built-in processor  103  is displayed on the display apparatus  101  of the touch panel type, and a user performs operation input of the display apparatus  101  of the touch panel type in accordance with the display. In addition, it may be configured such that the processor is not built in the electronic apparatus  100 , the display apparatus  101  of the touch panel type displays a result of the process executed by an external apparatus, and an operation input according thereto is returned to the external apparatus. 
     On the display apparatus  101  of the touch panel type, a plurality of operation keys  102  are displayed, and, in accordance therewith, the tactile sense presentation device  110  presents a plurality of isolated texture senses at positions corresponding to the operation keys  102 . A user can detect the positions of the operation keys  102  based on the texture senses, and key input can be performed without seeing the operation key  102 . In this way, for example, a visually-impaired user can use the electronic apparatus  100 . 
     In addition, this electronic apparatus  100  can be used as a navigation apparatus mounted on a mobile unit such as a vehicle, a bicycle, a two-wheeled vehicle, an airplane, a train, or a ship.  FIG. 24  is a perspective view that illustrates the configuration of a mobile unit  200  according to an application of the present invention. The mobile unit  200  includes a driver&#39;s seat  201  on which a user (driver) sits and a dashboard  202  having the electronic apparatus  100  illustrated in  FIG. 23  as a navigation apparatus mounted therein and steering mechanisms  203  such as a handle, an accelerator, and a brake and the like. 
     This electronic apparatus  100 , like the example illustrated in  FIG. 23 , presents a plurality of isolated texture senses at positions corresponding to the operation keys  102 . The user can perform operation key input based on the texture senses. As route information presented as a result of the process, by presenting a texture sense to a route displayed on a map, the display of the route can be represented to be visually noticeable. Accordingly, the user can perform an operation of the navigation apparatus while attending to the front of the vehicle, and therefore, safe driving can be continued. 
     The present invention is not limited to the embodiments and the examples described above but the configuration, the manufacturing method, the driving method, the use method, and the like of the tactile sense presentation device  10  can be appropriately changed unless departing from the concept of the present invention. 
     For example, in the first embodiment and the examples, while the configuration including the X electrodes  12  extending in the X-axis direction and the Y electrodes  13  extending in the Y-axis direction has been described, a configuration including only electrodes extending in one direction may be employed. 
     The present invention can be used for a tactile sense presentation device presenting a tactile sense, an electronic apparatus including the tactile sense presentation device such as a touch panel and a terminal for a visually-impaired person, and a method of driving the tactile sense presentation device. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present invention(s) has(have) been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.