Touch panel and display device including a pressure-sensitive sensor

A touch panel according to the present invention includes a touch sensor substrate having a touch sensor portion in the central portion of the touch sensor substrate and having a first electrode and a second electrode in the inner peripheral portion of the touch sensor substrate, a protective plate to cover the front surface of the touch sensor substrate, a dielectric sheet provided between the touch sensor substrate and the protective plate, and a conductive member disposed at a position so as to face the first electrode and the second electrode, wherein the first electrode, the second electrode, and the conductive member constitute a pressure-sensitive sensor. With this structure, a touch panel having a pressure-sensitive sensor and a display device provided with the touch panel can be manufactured without an increase in the manufacturing time.

TECHNICAL FIELD

The present invention relates to a touch panel having a pressure-sensitive sensor, and a display device provided with the touch panel.

BACKGROUND ART

In a conventional touch panel having a pressure-sensitive sensor, the pressure-sensitive sensor is provided between the back surface of the touch panel and a marginal portion of the housing. When an operation element such as a touch pen or a human finger touches an operation input screen of the touch panel, the touch panel detects the position touched by the operation element. Then, simultaneously, the pressure-sensitive sensor detects the pressing force. Owing to the detection of the position touched by the operation element as well as the detection of the pressing force by the pressure-sensitive sensor, an input to the touch panel can be determined. With this determination, it is possible to reduce an erroneous input that is not a determined input and is caused alone by a contact of an operation element on the operation input screen of the touch panel (for example, Patent Document 1).

PRIOR ART DOCUMENTS

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

A touch panel having a pressure-sensitive sensor disclosed in Patent Document 1 is structured in such a manner that the pressure-sensitive sensor is disposed between the back surface of the touch panel and the marginal portion of the housing. Therefore, the manufacturing process of the touch panel requires a step to mount the pressure-sensitive sensor onto the marginal portion of the housing and a step to mount the touch panel onto the pressure-sensitive sensor. Thus, a problem arises in that these additional steps lead to an increase in the manufacturing time compared with the manufacturing of a touch panel without a pressure-sensitive sensor.

The present invention is made to solve the problem, and the step to mount the pressure-sensitive sensor onto the marginal portion of the housing and the step to mount the touch panel onto the pressure-sensitive sensor can be simplified in the manufacturing processes of a touch panel having a pressure-sensitive sensor or of a display device provided with the touch panel.

Means for Solving Problem

A touch panel according to the present invention includes a touch sensor substrate having a central portion, an inner peripheral portion, and a touch sensor portion in the central portion, a protective plate to cover the front surface of the touch sensor substrate, a first dielectric sheet provided between the touch sensor substrate and the protective plate, a first electrode and a second electrode disposed in the inner peripheral portion of the front surface of the touch sensor substrate, and a conductive member disposed between the touch sensor substrate and the protective plate and at a position so as to face the first electrode and the second electrode, wherein the first dielectric sheet is disposed between the first electrode and the conductive member, and the second electrode and the conductive member and also between the first electrode and the second electrode, and thus the first electrode, the second electrode, and the conductive member constitute a pressure-sensitive sensor.

Effects of the Invention

According to the present invention, a pressure-sensitive sensor is provided on the touch sensor substrate, so that the two steps—the step to mount the pressure-sensitive sensor onto the marginal portion of the housing and the step to mount the touch panel onto the pressure-sensitive sensor can be eliminated. Thus, a touch panel having a pressure-sensitive sensor and a display device provided with the touch panel can be manufactured without an increase in the manufacturing time.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

First Embodiment

FIG. 1toFIG. 11show a first embodiment for carrying out the present invention. First, referring toFIG. 1toFIG. 3, a structure of a display device1000provided with a touch panel according to the first embodiment will be described.FIG. 1is a plan view of the display device1000according to the first embodiment for carrying out the present invention, andFIG. 2is a cross-sectional view thereof taken along the dash-dotted line A-A shown inFIG. 1. Further,FIG. 3is an exploded perspective view of the display device1000.

The display device1000according to the present invention includes a touch panel1, a dielectric sheet2, a frame3, and a liquid crystal panel4. Note that the dielectric sheet2is an example of the second dielectric sheet described in the claims and the liquid crystal panel4is an example of the display panel described in the claims. A back surface1rof the touch panel1is adhered to a front surface2fof the dielectric sheet2. In addition, a back surface2rof the dielectric sheet2is adhered to a marginal portion3eof the frame3. Further, the back surface2rof the dielectric sheet2is adhered to a display surface4fof the liquid crystal panel4in an opening3aof the frame3.

In addition, the frame3and a rear cover5are fitted and fixed together, and the liquid crystal panel4is housed inside the space surrounded by the frame3and the rear cover5.

As the dielectric sheet2, an optical clear adhesive (OCA) being an adhesive film, an optical clear resin (OCR) being a liquid adhesive, or the like are used. Note that, regarding the types of an OCA and an OCR, an ultraviolet ray curable type, a heat curing type, and the like are available.

Next, an example of a manufacturing method in which an OCA being a film-type adhesive is used for the dielectric sheet2will be described. First, the front surface of the OCA and the back surface1rof the touch panel1are adhered together. Then, the back surface of the OCA and the marginal portion3eof the frame3are adhered together and the back surface of the OCA and the display surface4fof the liquid crystal panel4are adhered together. Then, when the OCA is an ultraviolet ray curable type, the OCA is cured by radiating ultraviolet rays, and when the OCA is a heat curing type, the OCA is cured by heating. Thus, the touch panel1and the liquid crystal panel4are adhered to each other and the touch panel1and the frame3are adhered to each other.

Further, an example of a manufacturing method in which an OCR being a liquid-type adhesive is used for the dielectric sheet2will be described. First, the OCR is applied to the back surface1rof the touch panel1. The back surface2rof the dielectric sheet2and the marginal portion3eof the frame3are adhered together, and the back surface1rof the touch panel1and the display surface4fof the liquid crystal panel4are adhered together. Then, when the OCR is an ultraviolet ray curable type, the OCR is cured by radiating ultraviolet rays, and when the OCR is a heat curing type, the OCR is cured by heating. Thus, the touch panel1and the liquid crystal panel4are adhered to each other and the touch panel1and the frame3are adhered to each other.

Since the OCA and the OCR are cured to such an extent that a certain level of elasticity remains, the dielectric sheet2can hold the touch panel1. The thickness of the dielectric sheet2is set to such an extent that the level difference at the opening3aof the frame3can be filled with the sheet (for example, up to about 1 mm).

Further, the refractive index of the OCA and the OCR after the cure (namely, the refractive index of the dielectric sheet2) are set to be substantially equal to those of the materials for the back surface1rof the touch panel1and the display surface4fof the liquid crystal panel4. Thus, degradation in the visibility of the display screen in the liquid crystal panel4due to multiple reflection of visible light between the back surface1rof the touch panel1and the display surface4fof the liquid crystal panel4does not take place.

Next, the touch panel1will be described in detail. When an operation element such as a touch pen or a human finger touches the front surface1fof the touch panel1, the touch panel1, as the functions thereof, detects the position on the front surface1fand the pressing force of the operation element and outputs the detection information to the outside.

The touch panel1includes a protective plate11made of a transparent plate such as a glass or an acrylic resin, a light-shielding seal12formed by printing or the like provided in the inner peripheral portion on the back surface of the protective plate11, and a touch sensor substrate17made of a transparent plate such as a glass or an acrylic resin. In other words, the light-shielding seal12is provided on a portion of the back surface of the protective plate11(the inner peripheral portion thereof) that faces a portion ranging from the outer periphery of the touch sensor portion1sto be described later, to the outermost periphery of the touch sensor substrate17. In addition, the protective plate11and the touch sensor substrate17are adhered to each other via the dielectric sheet14. Note that the dielectric sheet14is an example of the first dielectric sheet described in the claims. For the dielectric sheet14, similarly to the dielectric sheet2, an OCA being a film-type adhesive or an OCR being a liquid-type adhesive is used. Since the dielectric sheet14is cured to such an extent that a certain level of elasticity remains, the dielectric sheet14can expand and contract in accordance with the pressing force and can hold the protective plate11.

A first electrode15and a second electrode16are formed on a front surface17fof the touch sensor substrate17. A conductive member13is disposed at a position so as to the first electrode15and the second electrode16via the dielectric sheet14. Note that the conductive member13is an example of the conductive member described in the claims. The first electrode15, the second electrode16, and the conductive member13collectively form a pressure-sensitive sensor6. The first electrode15and the second electrode16are connected to a pressure-sensitive sensor detection circuit85, to be described later, via wires (not illustrated). In the present first embodiment, the conductive member13is disposed on the back surface of the protective plate11via the light-shielding seal12.

In addition, the elastic modulus of the dielectric sheet14is generally about between 103and 106Pa. When the amount of deformation caused by the pressing force is larger, the change in the capacitance of the pressure-sensitive sensor6depending on the pressing force is larger. Thus, the detection sensitivity can be increased. In contrast, when the amount of deformation caused by the pressing force is larger, the response time of the pressure-sensitive sensor6becomes longer. Therefore, in accordance with the curing conditions of the above-mentioned OCA and OCR with respect to the ultraviolet ray and the heat, the elasticity and plasticity of the dielectric sheet14are to be appropriately controlled.

Next, the liquid crystal panel4will be described in detail. The liquid crystal panel4, provided with a screen on its display surface4f, has a function to display a movie and a still image on the screen when it receives image signals from the outside. Note that the screen is disposed to fit in the opening3aof the frame3, so that the image screen can be seen from the direction of the front surface1fof the touch panel1. The liquid crystal panel4includes a color filter substrate42with a color filter, a thin film transistor (TFT) array substrate43with TFT, the polarizing plate41on the front surface of the color filter substrate42, a polarizer44on the back surface of the TFT array substrate43, and a backlight module45. The color filter substrate42and the TFT array substrate43are adhered together, having a liquid crystal (not illustrated) sandwiched between them.

Next, the rear cover5will be described in detail. The rear cover5includes a soft cover51and a hard cover52. The soft cover51made of an elastic material such as resin is in contact with the side surfaces and the back surface of the liquid crystal panel4and absorbs shocks being externally transmitted to the liquid crystal panel4. The hard cover52made of a hard material such as a metal contains the soft cover51and protects the liquid crystal panel4from shocks and against water leakage.

Next, referring toFIG. 4andFIG. 5, a structure of the touch sensor substrate17will be described.FIG. 4is a plan view of the front side of the touch sensor substrate17.FIG. 5is a perspective view of a part of the touch sensor substrate17.

As shown inFIG. 4andFIG. 5, the touch sensor substrate17includes, on a transparent substrate131such as a glass and an acrylic resin, a plurality of row sensor electrodes132arranged in the Y-direction shown in the figure, and an interlayer insulating film133formed so as to cover the row sensor electrodes132. The touch sensor substrate17further includes a plurality of column sensor electrodes134arranged in the X-direction shown in the figure on the interlayer insulating film133and a protective film137formed to cover the column sensor electrodes134. Further, each of the row sensor electrodes132and each of the column sensor electrodes134are connected to a first end of each of lead wires135. In addition, a second end of each of the lead wires135is connected to each of connecting terminals136.

The touch sensor portion1sin which the row sensor electrodes132and the column sensor electrodes134are formed is a portion where a position of an operation element touching on the front surface1fof the touch panel1is to be detected. The first electrode15and the second electrode16are disposed around the touch sensor portion1s. In other words, the first electrode15and the second electrode16are disposed in a portion ranging from the outer periphery of the touch sensor portion1soccupying the central portion of the touch sensor substrate17, to the outermost periphery of the touch sensor substrate17(the inner peripheral portion thereof). The first electrode15and the second electrode16are connected to each of the connecting terminals136through connecting wires139that are each connected to each of those electrodes. The connecting wires139exemplify the wire connected to the first electrode and the wire connected to the second electrode that are described in the claims.

Shielding wires138are provided between the connecting wires139, between the connecting wires139and the touch sensor portion1s, and along the outer periphery of the outermost connecting wire139. An end of each of the shielding wires138is connected to one of the connecting terminals136. In other words, the shielding wires138are each disposed along with each of the connecting wires139.

The shielding wires138are grounded through the connecting terminals136. With this configuration, the breakage of the touch sensor substrate17cause by static electricity (for example, introduced through an operator's finger) introduced into the front surface1fof the touch panel1and the noise overlapping with signals in the connecting wires139can be prevented.

The row sensor electrodes132and the column sensor electrodes134are each formed of a transparent conductive film such as indium tin oxide (ITO), a fine metal mesh wire, and the like. The interlayer insulating film133and the protective film137are each made of a transparent insulating film such as a silicon oxide film, a tetraethyl orthosilicate (TEOS) film, and a silicon nitride film. Generally, the connecting terminals136are connected to a flexible printed circuit (FPC), etc. to be electrically connected to the outside.

Note that, as a formation method for the row sensor electrodes132and the column sensor electrodes134, for example, there is a method in which photolithography and etching are used to form the row and column electrodes after the transparent conductive film, the fine metal mesh wires, etc. are deposited on the transparent substrate131.

In addition, the first electrode15, the second electrode16, the shielding wires138, and the connecting wires139are each formed of a transparent conductive film such as ITO or a conductive member such as metal.

Note that, as a formation method for the first electrode15, the second electrode16, the shielding wires138, and the connecting wires139, for example, there is a method in which photolithography and etching are used to form them after the transparent conductive film, metal, etc. are deposited on the transparent substrate131.

Further, it is possible to form the first electrode15, the second electrode16, the shielding wires138, and the connecting wires139simultaneously or sequentially with the row sensor electrodes132or the column sensor electrodes134. This leads to reduction of manufacturing time of the touch panel.

Next, referring toFIG. 6toFIG. 10, a structure and an operation of the pressure-sensitive sensor6will be described.FIG. 6is a plan view of the pressure-sensitive sensor6and its surroundings.FIG. 7is a cross-sectional view of the sensor taken along the dash-dotted line B-B shown inFIG. 6.FIG. 8is a drawing for explaining capacitance components constituting the capacitance Cpa in the pressure-sensitive sensor6.FIG. 9is a graph showing a relation between the amount of change in the capacitance Cpa of the pressure-sensitive sensor6and the pressing force.FIG. 10is an electrical connection diagram of the pressure-sensitive sensor6.

Referring toFIG. 6andFIG. 7, a plan structure and a cross sectional structure of the pressure-sensitive sensor6will be described. The first electrode15and the second electrode16are formed on the touch sensor substrate17. The conductive member13is disposed on the inner peripheral portion of the back surface of the protective plate11so as to face the first electrode15and the second electrode16via the dielectric sheet14. The distance d indicates the distance from the first electrode15and the second electrode16to the conductive member13. As previously described, when a pressing force is applied by an operation element to the front surface1fof the touch panel1, the dielectric sheet14expands and contracts, so that the distance d changes within a certain range in accordance with the pressing force.

Note that, the conductive member13is formed by using a method such as adhering of a thin conductive plate of metal, etc. or forming of a thin plate by vaporizing a metal material using a deposition technique or the like. It is also possible to use the light-shielding seal12as the conductive member13by giving conductivity to the light-shielding seal12through inclusion of carbon black.

Referring toFIG. 8, the capacitance Cpa that is a main capacitance in the pressure-sensitive sensor6will be described. The main capacitance Cpa of the pressure-sensitive sensor6is a capacitance formed between the first electrode15and the second electrode16. The capacitance Cpa is mainly the sum of two capacitances. One is the capacitance directly formed between the first electrode15and the second electrode16. The other is the capacitance formed via the conductive member13. Here, the capacitance Cp12is defined as the capacitance directly formed, not via the conductive member13, between the first electrode15and the second electrode16, the capacitance Cp1bis defined as the capacitance formed between the first electrode15and the conductive member13, and the capacitance Cp2bis defined as the capacitance formed between the second electrode16and the conductive member13.

In this case, the capacitance between the first electrode15and the second electrode16formed via the conductive member13can be calculated as a serial connection of the capacitance Cp1band the capacitance Cp2b, so that the resultant capacitance value is (Cp1b>, Cp2b/(Cp1b+Cp2b)). Therefore, as previously described, the capacitance Cpa is calculated as follows. Cpa=Cp12+(Cp1b>, Cp2b/(Cp1b+Cp2b)).

The capacitance Cp12has a characteristic such that the capacitance decreases with a decrease of the distance d and increases with an increase of the distance d. Since the conductive member13is disposed at the position so as to face the first electrode15and the second electrode16, this characteristic stems from the capacitance change due to the change in the distance from the first electrode15and the second electrode16to the conductive member.

In contrast, regarding the capacitances Cp1band Cp2b, their characteristics are such that their capacitances increase with a decrease of the distance d and decrease with an increase of the distance d. Their characteristics stem from their capacitance changes due to the changes in the distance between the first electrode15and the conductive member13and the distance between the second electrode16and the conductive member13. As previously described, the first electrode15and the second electrode16are formed on the touch sensor substrate17. The conductive member13is disposed at the position so as to face the first electrode15and the second electrode16via the dielectric sheet14. Thus, the capacitance Cp1band the capacitance Cp2bsimultaneously increase with a decrease of the distance d, and the capacitance Cp1band the capacitance Cp2bsimultaneously decrease with an increase of the distance d. That is, the capacitance (Cp1b×Cp2b/(Cp1b+Cp2b)) for the serial connection of the capacitance Cp1band the capacitance Cp2bhas a characteristic such that the capacitance increases with a decrease of the distance d and decreases with an increase of the distance d.

Referring toFIG. 9, the characteristic of the pressure-sensitive sensor6will be described. The vertical axis represents the change amount ΔCpa of the capacitance Cpa of the pressure-sensitive sensor6, and the horizontal axis represents the pressing force. The larger the pressing force is, the more the distance d decreases (becomes short). That is, the sensor has a characteristic such that the change amount Cpa increases or decreases monotonically in accordance with the pressing force. Such a characteristic can be obtained by properly setting the capacitance Cp12, the capacitance Cp1b, and the capacitance Cp2b. For example, in a case where the capacitance Cp12is set to a larger value compared with the capacitance Cp1band the capacitance Cp2b, the change amount ΔCpa decreases with an increase of the pressing force. In contrast, in a case where the capacitance Cp12is set to a smaller value compared with the capacitance Cp1band the capacitance Cp2b, the change amount ΔCpa increases with an increase of the pressing force.

The capacitance Cp12increases when the distance between the first electrode15and the second electrode16is set smaller or when the length of the adjacent sides of the first electrode15and the second electrode16is set larger. In contrast, the capacitance Cp12decreases when the distance between the first electrode15and the second electrode16is set larger or when the length of the adjacent sides of the first electrode15and the second electrode16is set smaller.

Furthermore, the capacitance Cp1band the capacitance Cp2bincrease when the area of the electrodes facing the conductive member13is set larger. In contrast, the capacitance Cp1band the capacitance Cp2bdecrease when the area of the electrodes facing the conductive member13is set smaller. That is, the change amount ΔCpa of the capacitance Cpa can be set in accordance with the arrangement, the areas, and the shapes of the first electrode15, the second electrode16, and the conductive member13.

Referring toFIG. 10, an equivalent circuit and electrical connection of the pressure-sensitive sensor6will be described. The first electrode15being a first end of the pressure-sensitive sensor6is connected to a first end of the pressure-sensitive sensor detection circuit85via wiring. The second electrode16being a second end of the pressure-sensitive sensor6is connected to a second end of the pressure-sensitive sensor detection circuit85via wiring. Note that, the pressure-sensitive sensor detection circuit85will be described later.

As described above, since the change amount ΔCpa of the capacitance Cpa changes in accordance with the pressing force, when an operation element applies the pressing force to the front surface1fof the touch panel1, the pressure-sensitive sensor detection circuit85can detect the pressing force applied by the operation element to the front surface1fof the touch panel1by detecting the change amount ΔCpa.

Next, the operation in which the pressing force applied by the operation element is detected and the position on the front surface1fof the touch panel1at which the operation element touches the surface is outputted will be described in detail.FIG. 11shows a block diagram of the coordinate detection circuit8that detects a position on the front surface1fof the touch panel1at which the operation element touches the surface, relevant parts on the touch sensor substrate17, and the electrical connection between the circuit and the parts.

First, a method to detect the position at which the operation element touches the front surface1fof the touch panel1will be described. Note that, the method for the touch panel1to be described in the present first embodiment is called mutual capacitance method, which is one of capacitance methods. As described later, the mutual capacitance method is a method in which voltage is applied sequentially to each of the row sensor electrodes132, the electric charge amount in each of the column sensor electrodes134is read out, and the position touched by the operation element is detected.

Referring toFIG. 11, the coordinate detection circuit8includes a touch detection control circuit81, a row sensor electrode detection circuit82, a touch determination circuit83, a column sensor electrode detection circuit84, a pressure-sensitive sensor detection circuit85, a pressure-sensitive detection control circuit86, and a touch coordinate calculation circuit87.

The row sensor electrode detection circuit82is connected individually with each of the plurality of row sensor electrodes132. Here, for the description of the operation, it is assumed that the number of the row sensor electrodes132from the top to the bottom in the drawing is n (n is a natural number), the top of the row sensor electrodes132in the drawing is assigned with Wy(1), and the electrodes from the top to the bottom in the drawing are assigned with Wy(1), Wy(2), . . . Wy(n−1), Wy(n) in order.

Similarly, the column sensor electrode detection circuit84is connected individually with each of the plurality of column sensor electrodes134. Note that, for the description of the operation, it is assumed that the number of the column sensor electrodes134from the left to the right in the drawing is m (m is a natural number), the left-most of the column sensor electrodes134in the drawing is assigned with Wx(1), and the electrodes from the left to the right in the drawing are assigned with Wx(1), Wx(2), . . . Wx(m−1), Wx(m) in order.

Upon instruction from the touch detection control circuit81, the row sensor electrode detection circuit82applies excitation pulses with a predetermined peak voltage value to the row sensor electrodes: Wy(1), Wy(2), . . . Wy(n−1), Wy(n), in order at a predetermined time interval T1. Further, upon instruction from the touch detection control circuit81, the column sensor electrode detection circuit84detects the electric charge amounts at intersections between the row sensor electrodes132and the column sensor electrodes134within the time interval T1via the column sensor electrodes134: Wx(1), Wx(2), . . . Wx(m−1), Wx(m), performs A/D conversion on the analog signals corresponding to the electric charge amounts, and then outputs the digital signals to the touch determination circuit83. In addition, the touch detection control circuit81outputs a signal synchronized with the time interval T1to the touch determination circuit83. Through these operations, the touch determination circuit83acquires the position information (referred to as coordinates of intersection) of all the intersections between the row sensor electrodes132and the column sensor electrodes134as well as the information on the electric charge amounts corresponding to the coordinates of the intersections.

Further, the signals corresponding to all of the coordinates of the intersections and the electric charge amounts are outputted from the touch determination circuit83to the touch coordinate calculation circuit87to be stored therein.

When an operation element touches the front surface1fof the touch panel1, the capacitance at the intersection between the row sensor electrode132and the column sensor electrode134corresponding to the touched position changes, and accordingly, the electric charge amount at the intersection changes. Therefore, it can be seen that the coordinates on the operation screen (referred to as touch coordinates) at which the operation element touches the front surface1fof the touch panel1is in the vicinity of the coordinates of intersections in which the electric charge amounts locally differ among the electric charge amounts in the coordinates of all the intersections.

The pressure-sensitive sensors6, the positions of which are indicated by P1to P4, are each connected to the pressure-sensitive sensor detection circuit85. Upon instruction of the pressure-sensitive detection control circuit86, the pressure-sensitive sensor detection circuit85, at a predetermined timing, detects the capacitance Cpa of each of the pressure-sensitive sensors6located at the positions P1to P4, performs A/D conversion on the analog signal corresponding to the capacitance Cpa of each of the pressure-sensitive sensors6at the positions P1to P4, and outputs the resultant signals to the touch determination circuit83.

Further, an operation in which whether the operation element touches the front surface1fof the touch panel1is determined and the touch coordinates are outputted will be described. When the sum of the change amounts ΔCpa of the capacitances Cpa of the pressure-sensitive sensors6located at the positions P1to P4equals to or exceeds a predetermined value, the touch determination circuit83determines that the touch panel is pressed. Then, the touch determination circuit83instructs the touch coordinate calculation circuit87to output the touch coordinates to the outside.

Upon instruction from the touch determination circuit83to output the touch coordinates to the outside, the touch coordinate calculation circuit87calculates the touch coordinates from all of the coordinates of the intersections and the electric charge amounts that are stored and outputs the signals corresponding to the touch coordinates. Note that, the period (hereinafter, referred to as touch detection frame) in which the mutual capacitance values at all the intersections between the column sensor electrodes134and the row sensor electrodes132are obtained by sequentially scanning all the row sensor electrodes132: Wy (1), Wy (2), . . . Wy (n−1), Wy (n) in the touch panel and the period (hereinafter, referred to as pressure-sensitive detection frame) in which the capacitance values of all the pressure-sensitive sensors6are obtained are synchronized. One touch detection frame may correspond to one pressure-sensitive detection frame. Instead, one touch detection frame may correspond to a plurality of pressure-sensitive detection frames, so that the pressure detection accuracy can be improved by the averaging. Further, one touch detection frame and one pressure-sensitive detection frame may be separated in terms of time. In addition, one touch detection frame may include a part of or the whole of one pressure-sensitive detection frame.

In this way, from the detection result on the pressing force caused by the operation element based on the capacitance changes of the pressure-sensitive sensors6, the input can be determined. With this determination, an input error that is not a determined input and caused alone by a contact of an operation element on the operation screen of the touch panel1can be reduced, and thereby the operability can be improved.

With the following method, an input error that is not a determined input can be further reduced. When the sum of the change amounts Cpa of the capacitances Cpa of the pressure-sensitive sensors6at the positions P1to P4equals or exceeds a predetermined value, it is determined that the touch panel is pressed, and then a region of the touch coordinates estimated from the distribution of the pressing force detected by the pressure-sensitive sensors6at the positions P1to P4(hereinafter, called region of barycentric coordinates) is calculated. When the region of barycentric coordinates and the touch coordinates are close to each other or the touch coordinates is within the region of barycentric coordinates, the touch determination circuit83instructs the touch coordinate calculation circuit87to output the touch coordinates to the outside. That is, when the calculated distance between the region of barycentric coordinates and the touch coordinates is equal to or less than a predetermined distance, the touch determination circuit83instructs the touch coordinate calculation circuit87to output the touch coordinates to the outside. With such a method described above, an erroneous input can be further reduced.

For example, even when the capacitance at an intersection between a row sensor electrode132and a column sensor electrode134is changed by a water droplet or the like sticking to the front surface1fof the touch panel1or by the disturbance noise entering from the outside of the device via its power supply or the like, erroneous detection of the touch coordinates can be prevented by determining the input on the basis of the pressing force detected by the pressure-sensitive sensors6.

According to the present first embodiment, the pressure-sensitive sensor6is formed on the touch sensor substrate17. Therefore, compared with the touch panel provided with a conventional pressure-sensitive sensor disclosed in Patent Document 1, the step to mount the pressure-sensitive sensor onto the marginal portion of the housing and the step to mount the touch panel onto the pressure-sensitive sensor can be eliminated. That is, the touch panel having a pressure-sensitive sensor can be manufactured without an increase in the manufacturing time, and thus the manufacturing cost can also be reduced.

As previously described, the first electrode15, the second electrode16, the shielding wires138, and the connecting wires139can be formed simultaneously or sequentially with the row sensor electrodes132or the column sensor electrodes134, and thus the manufacturing processes of the touch panel can be shortened and the manufacturing cost can be further reduced.

In addition, in the touch panel having the conventional pressure-sensitive sensor as disclosed in Patent Document 1, since the pressure-sensitive sensor is disposed between the back surface of the touch panel and the marginal portion of the housing, wires need to be formed to connect the pressure-sensitive sensor to a circuit detecting the capacitance of the pressure-sensitive sensor, and the wires need to be provided on the housing or around the periphery of the touch panel. In contrast, according to the present first embodiment, the pressure-sensitive sensor6is connected to one of the connecting terminals136via the connecting wires139on the transparent substrate131. That is, the wires that is formed to connect the pressure-sensitive sensor to a circuit detecting the capacitance of the pressure-sensitive sensor need not to be provided on the housing or around the periphery of the touch panel. Thus, the manufacturing time can be shortened and the manufacturing cost can be reduced when compared with a conventional touch panel.

Note that, since the conductive member13only needs to be disposed so as to face the first electrode15and the second electrode16and wires connecting the conductive member13to the outside are not required, compared with a conventional touch panel, the manufacturing time can be shortened and the manufacturing cost can be reduced.

Furthermore, a display device provided with the touch panel including the conventional pressure-sensitive sensor disclosed in Patent Document 1 has an air gap between the touch panel and the display panel. Thus, multiple reflection of visible light occurs between the back surface of the touch panel and the screen of the display panel that form boundaries of the air gap, so that a problem arises in that the visibility of the display panel is degraded.

In contrast, according to the present first embodiment, the display device1000is provided with a structure in which the touch panel1is adhered to and is held by the frame3and the liquid crystal panel4via the dielectric sheet2. That is, the back surface of the touch sensor substrate17(the back surface1rof the touch panel1) and the display surface4fof the liquid crystal panel4are adhered to each other via the dielectric sheet2. Further, the refractive index of the dielectric sheet2is set to be substantially the same as those of the materials forming the back surface1rof the touch panel1and the display surface4fof the liquid crystal panel4. Thus, degradation in the visibility of the display screen in the liquid crystal panel4due to multiple reflection of visible light between the back surface1rof the touch panel1and the display surface4fof the liquid crystal panel4does not take place.

Further, in a display device provided with the touch panel including the conventional pressure-sensitive sensor as shown in Patent Document 1, the touch panel is held by the housing (frame) via the pressure-sensitive sensor. Thus, when vibration or shock is applied to the display device, the stress depending on the weight of the touch panel may be applied to the pressure-sensitive sensor. In particular, when such a conventional display device is used for a portable electronic device such as a tablet, the problem may become more serious because it may be frequently exposed to vibration and shock.

In contrast, according to the present first embodiment, the pressure-sensitive sensor is formed inside the touch panel1, and the back surface1rof the touch panel1is adhered not only to the display surface4fof the liquid crystal panel4, but also to the marginal portion3eof the frame3, via the dielectric sheet2. Being capable of holding the touch panel1, the dielectric sheet2can prevent excessive stress on the pressure-sensitive sensors even when vibration or shock is applied to the display device.

Note that, although the first electrode15and the second electrode16in the present first embodiment are exemplified to be rectangular in shape, the shape is not limited to be rectangular. As previously described, as long as the change amount ΔCpa monotonically increases or decreases in accordance with the pressing force, the shape and the size of the first electrode15and the second electrode16can be selected depending on the place to be disposed and the extent of the area.

Second Embodiment

In the first embodiment, the first electrode15and the second electrode16are exemplified to be rectangular in shape and to be arranged side by side in the same direction. Further, the capacitance Cp12, the capacitance Cp1b, and the capacitance Cp2bare set so that the change amount ΔCpa can monotonically increase or decrease in accordance with the pressing force. In the second embodiment, a structure of the touch panel will be described in which the shapes of the first electrode15and the second electrode16are selected to make the capacitance Cp12be larger compared with the capacitance Cp1band the capacitance Cp2b, and also the change amount ΔCpa relative to the capacitance Cpa is increased to make the pressure-sensitive sensor detection circuit85readily detect the change amount ΔCpa.

Referring toFIG. 12andFIG. 13, a structure of a pressure-sensitive sensor6baccording to the second embodiment will be described.FIG. 12is a plan view showing a structure of the pressure-sensitive sensor6baccording to the second embodiment.FIG. 13is a cross-sectional view of the sensor taken along the dash-dotted line C-C shown inFIG. 12. Note that, instead of the pressure-sensitive sensor6shown inFIGS. 1 to 4andFIG. 11of the first embodiment, in the second embodiment, the pressure-sensitive sensor6bis disposed. Note that, inFIG. 12andFIG. 13, the same numerals or the same signs as used inFIG. 1toFIG. 11denote the same or equivalent components shown in the first embodiment, and thus the detailed description will be omitted.

As shown inFIG. 12, the first electrode15and the second electrode16are comb-shaped electrodes including a plurality of rectangular portions. In addition, the rectangular portions of the first electrode15and the rectangular portions of the second electrode16are arranged adjacent to each other at a plurality of locations. In addition, the conductive member13is disposed so as to face the first electrode15and the second electrode16via the dielectric sheet14. With such an arrangement of the first electrode15and the second electrode16, the capacitance Cp12can be increased compared with the arrangement shown as an example in the first embodiment in which only one side of the first electrode15and one side of the second electrode16are placed adjacent to each other. Thus, the change amount ΔCpa relative to the capacitance Cpa is improved, and the detection sensitivity of the pressure-sensitive sensor detection circuit85can be improved.

In addition to the effects brought about in the first embodiment, an effect in the present second embodiment is such that the detection sensitivity of the pressure-sensitive sensor detection circuit85can be increased. Further, the first electrode15and the second electrode16are described as being comb-shaped electrodes including the plurality of rectangular portions, and the capacitance Cp12can be increased when the rectangular portions are protruding. In other words, it suffices that the first electrode15and the second electrode16are the comb-shaped electrodes each having a plurality of protruding portions, the protruding portions of the first electrode15and the second electrode16being structured to be adjacent to each other.

Third Embodiment

In the second embodiment, a structure described is that the shapes of the first electrode15and the second electrode16are selected to make the capacitance Cp12larger compared with the capacitance Cp1band the capacitance Cp2b. In the present third embodiment, a structure of the touch panel will be described in which the first electrode15and the second electrode16are arranged so as to make the capacitance Cp12be smaller compared with the capacitance Cp1band the capacitance Cp2band also the change amount ΔCpa relative to the capacitance Cpa is improved to make the pressure-sensitive sensor detection circuit85readily detect the change amount ΔCpa.

Referring toFIG. 14andFIG. 15, a structure of a pressure-sensitive sensor6caccording to the present third embodiment will be described.FIG. 14is a plan view showing a structure of the pressure-sensitive sensor6caccording to the third embodiment. Note that, instead of the pressure-sensitive sensor6shown inFIGS. 1 to 4andFIG. 11of the first embodiment, the pressure-sensitive sensor6cis disposed.FIG. 15shows a positional relation among extended lines of the sides of the first electrode15and the second electrode16with respect to the first electrode15and the second electrode16. InFIG. 14andFIG. 15, the same numerals or the same signs as used inFIG. 1toFIG. 11denote the same or equivalent components as shown in the first embodiment, and their detailed description will be omitted.

As shown inFIG. 14, both the first electrode15and the second electrode16are rectangular in shape and are arranged in such a manner that whole of or a part of each side is arranged not to be adjacent to each other. In addition, the conductive member13is disposed to face the first electrode15and the second electrode16. With this arrangement of the first electrode15and the second electrode16, the capacitance Cp12can be made smaller compared with the arrangement in which a side of the first electrode15and a side of the second electrode16are disposed adjacent to each other. Thus, the change amount ΔCpa relative to the capacitance Cpa is improved, so that the detection sensitivity of the pressure-sensitive sensor detection circuit85can be enhanced.

Referring toFIG. 15, the above arrangement of the first electrode15and the second electrode16will be described again. The figure shows the first electrode15, its extended lines of the short sides15S, its extended lines of the long sides15L, the second electrode16, its extended lines of the short sides16S, and its extended lines of the long sides16L. Both the extended lines of the short sides15S and the extended lines of the long sides15L of the first electrode15do not intersect with the second electrode16. Similarly, both the extended lines of the short sides16S and the extended lines of the long sides16L of the second electrode16do not intersect with the first electrode15. In other words, an arrangement of the first electrode15and the second electrode16in which the capacitance Cp12can be reduced is the arrangement in which extended lines of the sides of one electrode do not intersects with the sides of the other electrode.

In addition to the effects brought about in the first embodiment, an effect in the present third embodiment is such that the detection sensitivity of the pressure-sensitive sensor detection circuit85can be enhanced.

Fourth Embodiment

Structures described in the first embodiment to the third embodiment are that the first electrode15and the second electrode16are provided at a plurality of locations in the periphery of the touch sensor portion1s, and the first electrode15and the second electrode16are connected to the connecting terminals136via the connecting wires139. In the present fourth embodiment, a structure will be described in which a first electrode15band a second electrode16bare each formed in a loop to surround the touch sensor portion1sin the inner peripheral portion of the front surface of the touch sensor substrate17b.

FIG. 16shows a structure of the touch sensor substrate17baccording to the fourth embodiment. InFIG. 16, the same numerals and the same signs as used inFIG. 1toFIG. 11denote the same or equivalent components as shown in the first embodiment, and their detailed description will be omitted.

As shown inFIG. 16, the first electrode15band the second electrode16bare each formed in a loop to surround the touch sensor portion1sin the inner peripheral portion of the front surface of the touch sensor substrate17b, and the both ends of the first electrode15band the second electrode16bare connected to the connecting terminals136. The conductive member13(not illustrated) is disposed at a position so as to face the first electrode15band the second electrode16b, and thereby forming a pressure-sensitive sensor6d.

In comparison with the first embodiment, with the structure described above, it is possible to increase the capacitance Cp1bor the capacitance Cp2bbecause the area of the first electrode15bor the second electrode16bcan be increased, and it is also possible to increase the capacitance Cp12because the first electrode15band the second electrode1611can be arranged side by side in a longer length. Thus, the capacitance Cpa and the change amount ΔCpa of the pressure-sensitive sensor6dcan be increased, so that the sensitivity of the pressure-sensitive sensor6dcan be enhanced. In addition, for the pressure-sensitive sensor detection circuit85that detects the change in the capacitance Cpa of the pressure-sensitive sensor6d, the number of input capacitance is one, so that its circuit structure can be simplified, leading to reduction of the manufacturing cost.

That is, in the present fourth embodiment, in addition to the effects brought about in the first embodiment, an effect is such that the detection sensitivity of the pressure-sensitive sensor detection circuit85can be enhanced and the manufacturing cost can be reduced.

Fifth Embodiment

In the fourth embodiment, the first electrode15band the second electrode16bare each formed in a loop to surround the touch sensor portion1sin the inner peripheral portion of the front surface of the touch sensor substrate17b. In a fifth embodiment, a structure will be described in which the first electrode and the second electrode each formed in a loop are divided.

FIG. 17shows a structure of a touch sensor substrate17caccording to the fifth embodiment. InFIG. 17, the same numerals and the same signs as used inFIG. 1toFIG. 11denote the same or equivalent components as shown in the first embodiment, and their detailed description will be omitted.

As shown inFIG. 17, a first electrode15cand a second electrode16care each strip-shaped, and provided in such a manner that the long side of the first electrode15cand the long side of the second electrode16cextend along the periphery of the touch sensor portion1s. The conductive member13(not illustrated) is disposed at a position so as to face the first electrode15cand the second electrode16c, and thereby forming a pressure-sensitive sensor6e. Furthermore, a plurality of pressure-sensitive sensors6eare formed. In the present fifth embodiment, four of the pressure-sensitive sensors6eare disposed. Each of the first electrodes15cis connected to a first end of one of the connecting wires139and a second end of the one of the connecting wire139is connected to one of the connecting terminals136. In the same manner, each of the second electrodes16cis connected to a first end of another one of the connecting wires139and a second end of the another one of the connecting wire139is connected to another one of the connecting terminal136.

In comparison with the first embodiment, with the structure described above, it is possible to increase the capacitance Cp1bor the capacitance Cp2bbecause the area of the first electrode15cor the second electrode16ccan be increased, and it is also possible to increase the capacitance Cp12because the first electrode15cand the second electrode16ccan be arranged side by side in a longer length. Thus, the capacitance Cpa and the change amount ΔCpa of the pressure-sensitive sensor6ecan be increased, so that the sensitivity of the pressure-sensitive sensor6ecan be enhanced. Furthermore, since the plurality of pressure-sensitive sensors6eare formed, it is possible to calculate a region of barycentric coordinates. As previously described, when the region of barycentric coordinates and the touch coordinates are close to each other or the touch coordinates is within the region of barycentric coordinates, the touch determination circuit83instructs the touch coordinate calculation circuit87to output the touch coordinates to the outside. That is, when the calculated distance between the region of barycentric coordinates and the touch coordinates is equal to or less than a predetermined distance, the touch determination circuit83instructs the touch coordinate calculation circuit87to output the touch coordinates to the outside. With such a method described above, an erroneous input can be further reduced.

The first electrode15and the second electrode16described above are strip-shaped, however, the shape is not limited to be strip-shaped. It suffices that these electrodes are formed in the inner peripheral portion of the front surface of the touch sensor substrate17calong the touch sensor portion1s.

The touch panels in the first embodiment to the fifth embodiment are described by taking an example of the mutual capacitance method from among capacitance methods. The present invention, however, is not limited by the method of the touch panel. For example, the methods of touch panels include a resistive film method, a surface acoustic wave method, and an infrared method.

The display panels in the first embodiment to the fifth embodiment are described by taking an example of the liquid crystal panel4. The present invention, however, is not limited by the type of the display panel. For example, in the types of display panels, there are an organic electro luminescence (EL) panel, a plasma panel, and a segment panel.

In addition, in the first embodiment to the fifth embodiment, the structures are described in which the dielectric sheet14is sandwiched between the first electrode and the second electrode. However, in a case where the sensitivity of the pressure-sensitive sensor is high enough, it is not necessary that the dielectric sheet2, etc. be sandwiched between the first electrode and the second electrode. For example, in a case where the areas for the first electrode and the second electrode are large enough or in a case where the gap between the first electrode and the second electrode can be shortened, the gap may be left as an air gap.

Furthermore, within the scope of the invention, each embodiment can be freely combined, or each embodiment can properly be modified or be omitted.

DESCRIPTION OF SYMBOLS