Patent Publication Number: US-9898133-B2

Title: Touchscreen

Description:
TECHNICAL FIELD 
     The present invention relates to a touchscreen and a driving method thereof. 
     BACKGROUND ART 
     In recent years, the size of a display device has been increased. Further, a touchscreen (also referred to as a touch sensor) in which a display device and an input device are combined is widely used. A technique in which a detection region of a touchscreen is divided into four regions is known (e.g., Patent Document 1). 
     REFERENCE 
     Patent Document 
     
         
         [Patent Document 1] Japanese Published Patent Application No. 2011-145752 
       
    
     DISCLOSURE OF INVENTION 
     As in the display device, there is a demand for an increase in the size of a touchscreen. However, unlike in a display device which only displays information, input processing is also performed in the touchscreen; therefore, delay of input data is a problem. The delay of input data triggers malfunction of the touchscreen. 
     An object of an embodiment of the present invention is to prevent malfunction of a large-sized touchscreen. In particular, a main object is to prevent malfunction of a large-sized touchscreen by reduction of wiring delay between a detection region and a controller. 
     An embodiment of the present invention is a touchscreen, in which a detection area is divided, including a plurality of detection regions and a plurality of sensors. Controllers are provided for the respective divided detection regions. All the controllers are electrically connected to one central control device. 
     With the above structure, wiring delay between the detection regions and the controllers can be reduced. Accordingly, malfunction of a large-sized touchscreen can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  illustrates an example of a structure of a touchscreen according to an embodiment of the present invention; 
         FIG. 2  is a circuit diagram illustrating a structure example of a detection region  102  in  FIG. 1 ; 
         FIGS. 3A and 3B  are each a cross-sectional view illustrating a structure example of the detection region  102  in  FIG. 1 ; 
         FIG. 4  is a circuit diagram illustrating a structure example of a controller  106  in  FIG. 1 ; 
         FIG. 5  shows an example of operation of a touchscreen according to an embodiment of the present invention; 
         FIG. 6  shows an example of operation of a touchscreen according to an embodiment of the present invention; and 
         FIGS. 7A and 7B  illustrate an example of a display portion of a touchscreen according to an embodiment of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description and it is easily understood by those skilled in the art that the mode and details can be variously changed without departing from the scope and spirit of the present invention. Accordingly, the present invention should not be construed as being limited to the description of the embodiment below. 
     In this embodiment, a touchscreen of an embodiment of the present invention and operation thereof will be described. Note that in this embodiment, a mode in which a detection region is divided into four regions (quartered) is described as one of the most preferred modes; however, the present invention is not limited thereto. For example, a detection region may be divided into two regions or eight regions. 
       FIG. 1  is a schematic diagram illustrating a touchscreen of an embodiment of the present invention. In a touchscreen  100  illustrated in  FIG. 1 , a touch detection surface (operation surface) is divided into four regions, that is, a first detection region  102 A, a second detection region  102 B, a third detection region  102 C, and a fourth detection region  102 D. 
     The first detection region  102 A is electrically connected to a first controller  106 A through a first controller connection portion  104 A. The second detection region  102 B is electrically connected to a second controller  106 B through a second controller connection portion  104 B. The third detection region  102 C is electrically connected to a third controller  106 C through a third controller connection portion  104 C. The fourth detection region  102 D is electrically connected to a fourth controller  106 D through a fourth controller connection portion  104 D. 
     The first controller  106 A is electrically connected to a central control device  110  through a first central control device connection portion  108 A. The second controller  106 B is electrically connected to the central control device  110  through a second central control device connection portion  108 B. The third controller  106 C is electrically connected to the central control device  110  through a third central control device connection portion  108 C. The fourth controller  106 D is electrically connected to the central control device  110  through a fourth central control device connection portion  108 D. 
     Note that in this specification, in the case where the first detection region  102 A, the second detection region  102 B, the third detection region  102 C, and the fourth detection region  102 D do not need to be distinguished from one another, each of them is referred to as a detection region  102 . 
     Similarly, in the case where the first controller connection portion  104 A, the second controller connection portion  104 B, the third controller connection portion  104 C, and the fourth controller connection portion  104 D do not need to be distinguished from one another, each of them is referred to as a controller connection portion  104 . 
     Similarly, in the case where the first controller  106 A, the second controller  106 B, the third controller  106 C, and the fourth controller  106 D do not need to be distinguished from one another, each of them is referred to as a controller  106 . 
     Similarly, in the case where the first central control device connection portion  108 A, the second central control device connection portion  108 B, the third central control device connection portion  108 C, and the fourth central control device connection portion  108 D do not need to be distinguished from one another, each of them is referred to as a central control device connection portion  108 . 
       FIG. 2  illustrates part of the detection region  102  of the touchscreen  100  illustrated in  FIG. 1 . As illustrated in  FIG. 2 , in the detection region  102 , signal lines  114  and common potential lines  116  are provided to intersect with each other, and a detection pixel  112  is provided at each intersection. A plurality of detection pixels  112  is arranged in a matrix of n rows by m columns (n and m are each a positive integer). Each detection pixel  112  includes a capacitor. Therefore, the touchscreen  100  having the structure illustrated in  FIG. 2  is a capacitive touchscreen. 
     Here, the case where a touch detection position is at a detection pixel  112 ( i,j ) is described as an example (i is an integer greater than or equal to 1 and less than or equal to n, and j is an integer greater than or equal to 1 and less than or equal to m). All the common potential lines  116  are kept at a certain potential. Therefore, when the detection pixel  112 ( i,j ) at a given position is pressed, capacitance of a capacitor in the detection pixel  112 ( i,j ) is changed and a signal is propagated to a signal line  114 ( i ); thus, touch is detected. The signal is transmitted to the controller  106 . 
     In the above manner, the touch position can be detected. 
       FIGS. 3A and 3B  are each a cross-sectional view of the detection region  102 . 
     The detection region  102  illustrated in  FIG. 3A  includes a display portion  122  and a sensor portion  128  in a housing  120 . The display portion  122  includes an element substrate  124  provided with at least a switching element and a pixel electrode, and a counter substrate (sealing substrate)  126  facing the element substrate  124 . The sensor portion  128  is provided closer to an operation surface  130  side than the display portion  122 . 
     A black matrix is preferably provided in the display portion  122  for the prevention of color mixing between adjacent pixels. In the case where a black matrix is provided in the display portion  122 , the sensor portion  128  is preferably provided closer to the operation surface  130  side than the display portion  122  as mentioned above so that malfunction of the sensor portion  128  caused by the black matrix, or the like can be prevented. 
     The detection region  102  illustrated in  FIG. 3B  includes the element substrate  124 , the counter substrate (sealing substrate)  126 , and the sensor portion  128  in the housing  120 . The element substrate  124  is provided with at least a switching element and a pixel electrode. The sensor portion  128  is provided between the element substrate  124  and the counter substrate (sealing substrate)  126 . 
     In the structure illustrated in  FIG. 3B , in the case where a black matrix is provided for the counter substrate (sealing substrate)  126  (e.g., on the element substrate  124  side), the sensor portion  128  is preferably provided for the counter substrate (sealing substrate)  126 , and is preferably provided closer to the operation surface  130  side than the black matrix. In other words, a structure is preferably employed in which the sensor portion  128  is provided for the counter substrate (sealing substrate)  126 , and a black matrix is preferably provided, after the sensor portion  128  is formed, for the counter substrate (sealing substrate)  126  in the manufacturing process. 
       FIG. 4  illustrates a structure example of the controller  106  of the touchscreen  100  illustrated in  FIG. 1 . As illustrated in  FIG. 4 , the controller  106  includes a detection circuit  132 , an amplifier circuit  134 , a noise filter  136 , an A/D converter  138 , an arithmetic circuit  140 , and a signal generation circuit  142 . A signal is input to the detection circuit  132  from the controller connection portion  104 . The arithmetic circuit  140  outputs a signal to the central control device connection portion  108 . The signal generation circuit  142  outputs a signal to the controller connection portion  104 . 
     The detection circuit  132  detects a signal generated by touch detection and supplies the signal to the amplifier circuit  134 . 
     The amplifier circuit  134  amplifies a signal from the detection circuit  132 . 
     The noise filter  136  removes a noise component included in a signal from the amplifier circuit  134 . 
     The A/D converter  138  converts a signal from the noise filter  136 , which is an analog signal, into a digital signal. 
     The arithmetic circuit  140  performs arithmetic processing necessary for detecting touch operation such as obtainment of identification data of the controller  106  and coordinate data, and determination of the identification data. Note that the function of the arithmetic circuit  140  is not limited to arithmetic processing. For example, the arithmetic circuit  140  may control operation other than operation of calculating a detected touch position on the entire panel, to be described later. Further, it is preferable to store data on time when the arithmetic circuit  140  performs arithmetic processing because a problem of deviation of timing or the like does not occur even when signal delay occurs later. 
     The signal generation circuit  142  generates an appropriate signal in accordance with commands from the arithmetic circuit  140  and the central control device  110  and supplies the signal to the controller connection portion  104 . 
     Note that in this specification, the “length of a wiring between a divided detection region and a corresponding controller” is the length of a wiring between the detection region and the arithmetic circuit  140 . The wiring between the detection region and the arithmetic circuit  140  is preferably shorter than a wiring between the controller and the central control device. This is because in the case where the wiring between the detection region and the arithmetic circuit  140  is longer, the signal intensity might be attenuated and the signal itself might be lost in the noise. 
     Next, operation of the touchscreen  100  illustrated in  FIG. 1  will be described with reference to  FIG. 5  and  FIG. 6 .  FIG. 5  is a flow chart showing system startup operation and  FIG. 6  is a flow chart showing touch detection operation. 
     First, the touchscreen is started up (start  200 ). Then, the following loop operation is performed, so that all the controllers are started up (start of loop operation  202 ). The controllers are started up by a startup command sent to the controllers from the central control device  110  (sending of first command  204 ). In the case where all the controllers respond to the first command (loop termination condition  206 ), all the controllers are initialized (initialization  208 ). In the case where there is a controller not responding, the loop operation is performed until all the controllers respond, that is, the first command is sent to the controllers from the central control device  110 . After initialization, the system startup operation is terminated and then processing for detecting touch operation is performed (transfer of processing  210 ). 
     First, detection of touch operation is started (start  250 ). The central control device  110  sends a command (second command) to start detection of touch operation to each of the controllers (sending of second command  252 ). Next, whether touch operation is detected or not is determined (first determination  254 ). In the case where the touch operation is detected, identification data of the controller and coordinate data are obtained (data obtainment  256 ). In the case where touch operation is not detected, the command (second command) to start detection of touch operation is sent again to each of the controllers. In the case where touch operation is detected and identification data of the controller and coordinate data are obtained, first, the identification data of the controller is determined (determination of identification data of controller  258 ), and the detected touch position on the entire panel is calculated using formulae corresponding to the identification data. Specifically, in the case where the identification data of the controller is 1, the position on the entire panel is calculated using Formula 1 and Formula 2 (first calculation  260 ). In the case where the identification data of the controller is 2, the position on the entire panel is calculated using Formula 3 and Formula 2 (second calculation  262 ). In the case where the identification data of the controller is 3, the position on the entire panel is calculated using Formula 1 and Formula 4 (third calculation  264 ). In the case where the identification data of the controller is 4, the position on the entire panel is calculated using Formula 3 and Formula 4 (fourth calculation  266 ). In this manner, the touch position on the entire panel can be calculated. After the touch position on the entire panel is calculated, next processing is started (transfer of processing  268 ). 
     The touchscreen  100  illustrated in  FIG. 1  can operate in the above-described manner. 
     Here, the calculation formulae used for calculating detected touch positions on the entire panel, which correspond to the identification data, are described. In the following description, the x-coordinate of the detected position in the detection region  102  is x 0 , the y-coordinate of the detected position in the detection region  102  is y 0 , the maximum value of the coordinate in the x-axis direction in the detection region  102  is s x max , the maximum value of the coordinate in the y-axis direction in the detection region  102  is s y max , the maximum value of the coordinate in the x-axis direction on the entire touchscreen is w, the maximum value of the coordinate in the y-axis direction on the entire touchscreen is h, the number of divisions (the number of detection regions) in the x-axis direction is x n , and the number of divisions (the number of detection regions) in the y-axis direction is y n . 
     In the case where the identification data of the controller is 1 (i.e., in the case where the detection region  102  is the first detection region  102 A), the position (X,Y) on the entire panel is calculated using the following formulae (first calculation  260 ). 
     
       
         
           
             
               
                 
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     In the case where the identification data of the controller is 2 (i.e., in the case where the detection region  102  is the second detection region  102 B), in calculation of the position (X,Y) on the entire panel (second calculation  262 ), the x-coordinate is calculated using the following formula. Note that the y-coordinate can be calculated using Formula 2 in the first calculation  260 , and the formula is not repeated here. 
     
       
         
           
             
               
                 
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     In the case where the identification data of the controller is 3 (i.e., in the case where the detection region  102  is the third detection region  102 C), in calculation of the position (X,Y) on the entire panel (third calculation  264 ), the y-coordinate is calculated using the following formula. Note that the x-coordinate can be calculated using Formula 1 in the first calculation  260 , and the formula is not repeated here. 
     
       
         
           
             
               
                 
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     In the case where the identification data of the controller is 4 (i.e., in the case where the detection region  102  is the fourth detection region  102 D), in calculation of the position (X,Y) on the entire panel (fourth calculation  266 ), the x-coordinate is calculated using Formula 3 in the second calculation  262  and the y-coordinate is calculated using Formula 4 in the third calculation  264 . 
     In the above manner, the detected touch position on the entire panel can be calculated. 
     As described in this embodiment, according to an embodiment of the present invention, wiring delay between a detection region and a controller can be reduced. In the case where such a structure is not employed, for example, a structure in which a wiring is formed thick can be employed; however, formation of a thick wiring leads to an increase in manufacturing cost. Further, a thick wiring in a sensor portion leads to a decrease in transmittance. With the use of an embodiment of the present invention, an increase in cost, a decrease in transmittance, and the like are not caused and a large-sized touchscreen which does not malfunction can be provided. 
     Next, a liquid crystal display device will be described with reference to  FIGS. 7A and 7B  as an example of a display device corresponding to a display portion of the touchscreen according to an embodiment of the present invention.  FIG. 7A  is a top view of a liquid crystal display device in which a thin film transistor  320  and a liquid crystal element  326  formed over a first substrate  302  are sealed with a sealant  310  provided between the first substrate  302  and the second substrate  312 .  FIG. 7B  is a cross-sectional view taken along line K-L in  FIG. 7A . 
     In  FIGS. 7A and 7B , the sealant  310  is provided to surround a pixel portion  304  and a scan line driver circuit  308  formed over the first substrate  302 . The second substrate  312  is provided over the pixel portion  304  and the scan line driver circuit  308 . Therefore, together with a liquid crystal layer  316 , the pixel portion  304  and the scan line driver circuit  308  are sealed by the first substrate  302 , the sealant  310 , and the second substrate  312 . Further, a signal line driver circuit  306  is mounted on a region other than the region surrounded by the sealant  310  over the first substrate  302 . Note that the signal line driver circuit  306  is formed with a thin film transistor formed over a separately prepared substrate but is not limited thereto. The case where the signal line driver circuit  306  including a thin film transistor is attached to the first substrate  302  is described in this embodiment. It is preferable that the signal line driver circuit include a thin film transistor using a crystalline semiconductor layer such as a single crystal semiconductor layer and be attached to the first substrate  302 .  FIG. 7B  illustrates a thin film transistor  318  which is formed using a crystalline semiconductor layer and included in the signal line driver circuit  306 . 
     The pixel portion  304  provided over the first substrate  302  includes a plurality of thin film transistors, and in  FIG. 7B , the thin film transistor  320  included in the pixel portion  304  is illustrated. In addition, the signal line driver circuit  306  also includes a plurality of thin film transistors, and in  FIG. 7B , the thin film transistor  318  included in the signal line driver circuit  306  is illustrated. 
     A pixel electrode  324  included in the liquid crystal element  326  is electrically connected to the thin film transistor  320  through a wiring  336 . A counter electrode  334  of the liquid crystal element  326  is formed on the second substrate  312 . A portion where the pixel electrode  324 , the counter electrode  334 , and the liquid crystal layer  316  overlap with one another is the liquid crystal element  326 . 
     The first substrate  302  and the second substrate  312  can each be formed using glass, plastics, or the like. As plastics, a fiber-reinforced plastic (FRP) plate, a polyester film, an acrylic resin film, or the like can be used. 
     A spacer  322  is a bead spacer, and is provided to control a distance (cell gap) between the pixel electrode  324  and the counter electrode  334 . Note that a spacer (post spacer) which is obtained by selectively etching an insulating layer may also be used. 
     A variety of signals (potentials) supplied to the signal line driver circuit  306  which is formed separately, the scan line driver circuit  308 , and the pixel portion  304  are supplied from a flexible printed circuit (FPC)  314  through a lead wiring  328  and a lead wiring  330 . 
     In  FIGS. 7A and 7B , a connection terminal  332  is formed using the same conductive layer as the pixel electrode  324  included in the liquid crystal element  326 . The lead wiring  328  and the lead wiring  330  are formed using the same conductive layer as the wiring  336 . However, this embodiment is not limited to this. 
     The connection terminal  332  is electrically connected to a terminal included in the FPC  314  through an anisotropic conductive layer  338 . 
     Although not illustrated, the liquid crystal display device described in this embodiment includes an alignment film and a polarizing plate, and may also include a color filter, a light-blocking layer, or the like. 
     Note that the structures of the transistors included in the liquid crystal display device are not limited to the ones illustrated in  FIGS. 7A and 7B , and any structure may be employed. 
     An EL display device may be used for the display portion instead of the liquid crystal display device. In this case, metal (typically stainless steel), ceramics, or a sheet in which aluminum foil is sandwiched between polyester films, or the like may be used for one of the first substrate  302  and the second substrate  312 . 
     The display portion of the touchscreen according to an embodiment of the present invention has the above-described structure. 
     Note that a touchscreen module having the above structure is also an embodiment of the present invention. Here, a module refers to a component which can be mounted on an end product. Accordingly, a touchscreen module is a component which can be mounted on a touchscreen. The touchscreen module is not limited only to a component used for a touchscreen; a component which is probably used as a component of a touchscreen is also included in a technical scope of an embodiment of the present invention. 
     REFERENCE NUMERALS 
     
         
           100 : touchscreen,  102 : detection region,  102 A: first detection region,  102 B: second detection region,  102 C: third detection region,  102 D: fourth detection region,  104 : controller connection portion,  104 A: first controller connection portion,  104 B: second controller connection portion,  104 C: third controller connection portion,  104 D: fourth controller connection portion,  106 : controller,  106 A: first controller,  106 B: second controller,  106 C: third controller,  106 D: fourth controller,  108 : central control device connection portion,  108 A: first central control device connection portion,  108 B: second central control device connection portion,  108 C: third central control device connection portion,  108 D: fourth central control device connection portion,  110 : central control device,  112 : detection pixel,  114 : signal line,  116 : common potential line,  120 : housing,  122 : display portion,  124 : element substrate,  126 : counter substrate (sealing substrate),  128 : sensor portion,  130 : operation surface,  132 : detection circuit,  134 : amplifier circuit,  136 : noise filter,  138 : A/D converter,  140 : arithmetic circuit,  142 : signal generation circuit,  200 : start,  202 : start of loop operation,  204 : sending of first command,  206 : loop terminal condition,  208 : initialization,  210 : transfer of processing,  250 : start,  252 : sending of second command,  254 : first determination,  256 : data obtainment,  258 : determination of identification data of controller,  260 : first calculation,  262 : second calculation,  264 : third calculation,  266 : fourth calculation,  268 : transfer of processing,  302 : substrate,  304 : pixel portion,  306 : signal line driver circuit,  308 : scan line driver circuit,  310 : sealant,  312 : substrate,  314 : FPC,  316 : liquid crystal layer,  318 : thin film transistor,  320 : thin film transistor,  322 : spacer,  324 : pixel electrode,  326 : liquid crystal element,  328 : wiring,  330 : wiring,  332 : connection terminal,  334 : counter electrode,  336 : wiring, and  338 : anisotropic conductive layer. 
       
    
     This application is based on Japanese Patent Application serial no. 2012-080301 filed with Japan Patent Office on Mar. 30, 2012, the entire contents of which are hereby incorporated by reference.