Patent Publication Number: US-2018046298-A1

Title: Touch display panel

Description:
FIELD 
     The subject matter herein generally relates to a touch display panel. 
     BACKGROUND 
     An on-cell or in-cell type touch screen device can be manufactured by installing a touch device in a display device. Such a touch screen device can be used as an output device for displaying images while being used as an input device for receiving a touch of a user touching a specific area of a displayed image. However, the touch screen device cannot sense the amount of touch force/pressure applied to the touch screen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is an isometric view of an exemplary embodiment of a touch display device. 
         FIG. 2  is a cross-sectional view of a first exemplary embodiment of the touch display device of  FIG. 1 . 
         FIG. 3  is a planar view showing a force sensing electrode layer of the touch display device of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of a second exemplary embodiment of the touch display device of  FIG. 1 . 
         FIG. 5  is a planar view of a color filter substrate of the touch display device of  FIG. 4 . 
         FIG. 6  is a cross-sectional view of a third exemplary embodiment of the touch display device of  FIG. 1 . 
         FIG. 7  a planar view of a color filter substrate of the touch display device of  FIG. 6 . 
         FIG. 8  is a cross-sectional view of a fourth exemplary embodiment of the touch display device of  FIG. 1 . 
         FIG. 9  is a cross-sectional view of a fifth exemplary embodiment of a display device. 
         FIGS. 10 through 12  are diagrammatic views of three types of driving time sequences of a touch display device. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that the exemplary embodiments described herein may be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the exemplary embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “comprising” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like. 
     The touch display panel in the present disclosure can be used in a portable electronic device, such as a mobile phone, a watch, a tablet PC, a personal digital assistant (PDA), or the like, and can also be applied in a notebook computer, a television, and an electronic display screen. The touch display panel in the present disclosure may be a liquid crystal display (LCD) panel, such as a planar switching (IPS) type LCD panel, an edge field switching (FFS) type LCD panel, or the like. 
     The touch display panel in the present disclosure can sense positions and amount of the touch force applied thereon. The touch display panel includes a display module, a touch sensing module, and a force sensing module, wherein the touch sensing module and the force sensing module are integrated into the display module. 
     The display module includes a thin film transistor (TFT) substrate and a color filter (CF) substrate facing the TFT substrate, and the TFT substrate is provided with a common electrode layer. 
     The common electrode layer is supplied with common voltages for display, and the common electrode layer and pixel electrodes cooperatively form an electrical field to rotate liquid crystal molecules; the common electrode layer also functions as touch electrode for detecting touch position. 
     The force sensing module includes a sensing electrode layer. The sensing electrode layer is arranged on the color filter substrate. The sensing electrode layer and the common electrode layer may cooperatively form capacitors for sensing touch force. A distance between the common electrode layer and the sensing electrode layer decreases when a touch is applying on the touch display panel, and capacitances of the capacitors varies, then amount of the touch force can be calculated according to capacitance variations of the capacitors. 
       FIG. 1  and  FIG. 2  illustrate a touch display panel  100  according to a first exemplary embodiment. The touch display panel  100  includes a display module. The display module includes a TFT substrate  11 , a color filter substrate  12  facing the TFT substrate  11 , and a liquid crystal layer (not explicitly shown) between the TFT substrate  11  and the color filter substrate  12 . As shown in  FIG. 2 , a plurality of photo spacers  13  are located between the TFT substrate  11  and the color filter substrate  12  to maintain a distance between the TFT substrate  11  and the color filter substrate  12 . It is understood that the touch display panel  100  may further includes a backlight module (not shown), a first polarizer (not shown), a second polarizer (not shown), and other necessary components (not shown) for functioning of a liquid crystal display device. 
     As shown in  FIG. 1  and  FIG. 2 , the TFT substrate  11  includes a first substrate  111  and a common electrode layer  112  formed on a surface of the first substrate  111  adjacent the color filter substrate  12 . It is to be understood that the TFT array substrate  11  further includes conventional elements of a liquid crystal display device, such as a plurality of TFTs (not shown), insulating layers (not shown), pixel electrodes (not shown), scanning lines (not shown), and data lines (not shown). 
     The first substrate  111  is configured to support the other elements (e.g. TFTs, pixel electrodes, and common electrode layer  112 ) of the TFT substrate  11 . The first substrate  111  is transparent. For example, the first substrate  111  may be made of a transparent glass, a transparent plastic, or the like. 
     The common electrode layer  112  supplies common voltages for display and the common electrode layer  112  and pixel electrodes (not shown) cooperatively form electrical fields to rotate liquid crystal molecules. The common electrode layer  112  also functions as electrodes for detecting touch position. That is, the touch sensing module of the touch display device  100  includes the common electrode layer  112 . 
     In the present exemplary embodiment, the common electrodes  1121  are made of a transparent conductive material, such as indium tin oxide (ITO). As shown in  FIG. 1 , the common electrode layer  112  is a patterned conductive layer and includes a plurality of common electrodes  1121  arranged in a matrix. Each common electrode  1121  may be electrically connected to a driving IC (not shown) through a trace  1123 . The driving IC is configured to supply driving signals to the common electrodes  1121 . In other embodiments, the common electrode  1121  may also be a sheet-like electrode. When the touch display panel  100  is used in a planar switching (IPS) type LCD device, each common electrode  1121  may have shape or formation of a comb (not shown). 
     A force sensing electrode layer  124  is formed on a surface of the color filter substrate  12  adjacent to the TFT substrate  11 . In the present exemplary embodiment, the color filter substrate  12  includes a second substrate  121 , a color filter layer  122  on a surface of the second substrate  121  adjacent to the TFT substrate  11 , and a planar layer  123  on a surface of the color filter layer  122  adjacent to the TFT substrate  11 . The force sensing electrode layer  124  is formed on a surface of the planar layer  123  adjacent to the TFT substrate  11 . 
     The second substrate  121  is configured to support the other elements (e.g. color filter layer  122 , the planar layer  123 , and the force sensing electrode layer  124 ) of the color filter substrate  12 . The second substrate  121  is transparent. For example, the second substrate  121  may be made of a transparent glass, a transparent plastic, or the like. 
     The color filter layer  122  is configured for converting the light emitted from the backlight module into red, green, and blue light for display. The color filter layer  122  includes a plurality of color filter units  1221  spaced apart from each other, and a black matrix layer  1222 . Each color filter unit  1221  may be a red (R) color filter unit  1221 , a green (G) color filter unit  1221 , or a blue (B) color filter unit  1221 . The black matrix  1222  is between any two adjacent color filter units  1221 . In the present exemplary embodiment, the black matrix  1222  is made of a black resin material. 
     The planar layer  123  is an electrically insulating layer to cover the color filter layer  122 , and to flatten the surface of the color filter substrate  12  adjacent to the liquid crystal layer. 
     During each force sensing period of the touch display device  100 , the force sensing electrode layer  124 , the common electrode layer  112 , and the photo spacers  13  cooperatively form a plurality of capacitors for sensing touch forces. The force sensing module of the touch display device  100  includes a force sensing electrode layer  124 , the common electrode layer  112 , and the photo spacers  13 . The photo spacers  13  are located between the force sensing electrode layer  124  and the common electrode layer  112 . In the exemplary embodiments, the height of the photo spacers  13  has a relationship with a distance between the force sensing electrode layer  124  and the common electrode layer  112 . Each photo spacer  13  is made of an elastic dielectric material. When a touch force is applied on the touch display device  100 , the photo spacers  13  at the touch position may deform, and a distance between the force sensing electrode layer  124  and the common electrode layer  112  may vary, to vary capacitances of the capacitors. Thus, touch force can be calculated according to capacitance variations of the capacitors. 
     The force sensing electrode layer  124  is a patterned conductive layer. In this exemplary embodiment, the force sensing electrode layer  124  is made of a transparent conductive material, such as ITO. As shown in  FIG. 3( a )  and  FIG. 3( b ) , the force sensing electrode layer  124  may includes a plurality of force sensing electrodes  1241  spaced apart from each other; and each force sensing electrode  1241  extends as a line along a same direction. Alternatively, the force sensing electrode layer  124  may have a mesh shape, as shown in  FIG. 3( c ) . The force sensing electrode layer  124  includes a plurality of first portions  1241   a  and a plurality of second portions  1241   b  crossing with the first portions  1241   a . Each first portion  1241   a  extends as a line along a same first direction; each second portion  1241   b  extends as a line along a same second direction, the first direction is different from the second direction. As shown in  FIG. 3( c ) , the first direction is perpendicular to the second direction. 
     It is understood that a distance between every two force sensing electrodes  1241  as shown in  FIG. 3( a )  and  FIG. 3( b )  is sufficiently large such that electrical signals generated by a conductor (e.g., a finger of a user) touching the touch display device  100  can be transmitted to the common electrodes  1121  below the force sensing electrodes  1241 . Thus, electrical signals of the common electrodes  1121  are affected so that the touch position can be sensed. It is understood that a distance between every adjacent two first portions  1241   a  and a distance between every adjacent two second portions  1241   b  shown in  FIG. 3( c )  is sufficiently large such that electrical signals generated by a conductor (e.g., a finger of a user) touching on the touch display device  100  can be transmitted to the common electrodes  1121  below the force sensing electrode layer  124 , and can affect electrical signals of the common electrodes  1121  so that the touch position can be sensed. 
     The touch display panel  100  drives the display module, the touch sensing module, and the force sensing module by a time division driving method. A single time frame of the touch display panel  100  may be divided into a display period, a touch sensing period, and a touch force sensing period. During the display period, the common electrodes  1121  and pixel electrodes (not shown) cooperatively form an electrical field to rotate liquid crystal molecules. During the touch sensing period, the common electrodes  1121  function as a self-capacitive touch sensor; when finger is touching the touch display panel  100 , the fingers as a conductor affect electrical signals of the common electrodes  1121  corresponding to the touch position, thus touch position can be detected. During the touch force sensing period, the plurality of common electrodes  1121  and the force sensing electrode layer  124  form a plurality of capacitive force sensors. In the present exemplary embodiment, each common electrode  1121  is a block electrode, and the force sensing electrode  1241  is a strip electrode. The common electrodes  1121  and the force sensing electrode layer  124  cooperatively form a plurality of capacitors. Specifically, during the touch force sensing period, a constant voltage (e.g. 1V, −1V, etc.) is provided to the force sensing electrode layer  124 , or the force sensing electrode layer  124  is grounded. Until the touch display panel  100  is not touched, a distance D is between the common electrodes  1121  and force sensing electrode layer  124 , and the capacitor formed between the common electrode  1121  and the force sensing electrode layer  124  has a capacitance C. When the touch display panel  100  is touched, the capacitance C varies with the variation of the distance D, thus amount of the touch force can be calculated according to capacitance variation of the capacitor formed between the common electrode  1121  and the force sensing electrode layer  124 . 
       FIG. 4  illustrates a touch display device  200  according to a second exemplary embodiment. The touch display device  200  is substantially the same as the touch display device  100  of the first exemplary embodiment, except that touch display device  200  includes a force sensing electrode layer  224  that is made of a non-transparent conductive material, such as a conductive metal or a conductive alloy. The force sensing electrode layer  124  of the touch display device  100  is made of a transparent conductive material. 
     As shown in  FIG. 4 , the color filter layer  222  of the touch display device  200  also includes a plurality of color filter units  2221  spaced apart from each other and a black matrix layer  2222 . The force sensing electrode layer  224  is located below the black matrix layer  2222  and is completely covered by the black matrix layer  2222 , thus the force sensing electrode layer  224  has no effect on an aperture ratio of the touch display device  200 . 
       FIG. 5  is a planar view of a color filter substrate  22  of the touch display device  200  viewed from a side of the color filter substrate  22  having the force sensing electrode layer  224 . As shown in  FIG. 5 , the black matrix layer  2222  is located in regions between any two adjacent color filter units  2221 . As shown in  FIG. 5 , the force sensing electrode layer  224  may have a mesh shape. The force sensing electrode layer  224  includes a plurality of first portions  2241   a  and a plurality of second portions  2241   b  crossing with the first portions  2241   a . Each first portion  2241   a  extends as a line along a same first direction D 1  and each second portion  2241   b  extends as a line along a same second direction D 2 . The first direction D 1  is different from the second direction D 2 . In the exemplary embodiment, the first direction D 1  is perpendicular to the second direction D 2 . 
     As shown in  FIG. 5 , the force sensing electrode layer  224  overlaps with the black matrix layer  2222 . Each first portion  2241   a  is between two adjacent color filter units  2221  along the second direction D 2  and has a width that is less than a width of the black matrix layer  2222  between the two adjacent color filter units  2221 . Each second portion  2241   b  is between two adjacent color filter units  2221  along the first direction D 1  and has a width that is less than a width of the black matrix layer  2222  between the two adjacent color filter units  2221 . 
     When the touch display device  200  is touched by a conductor (e. g. a finger), the force sensing electrode layer  224  is a conductive component between the conductor (e. g. a finger) and the common electrode layer  212 , thus the force sensing electrode layer  224  may affect an electrical field between the conductor (e. g. a finger) and the common electrode layer  212 , thus affect touch sensing results. Therefore, it is necessary to reduce an area size of the force sensing electrode layer  224  to reduce its effect on the touch sensing. In the exemplary embodiment, the force sensing electrode layer  224  is designed to have a mesh shape as shown in  FIG. 5  or  FIG. 3( c )  to reduce its area size. In other embodiments, the force sensing electrode layer  224  may also be designed to have a plurality of force sensing electrodes parallel to each other as shown in  FIG. 3( a )  and  FIG. 3( b ) . Each force sensing electrode has a line shape and each force sensing electrode may be between two adjacent color filter units  2221  and has a width that is less than a width of the black matrix layer  2222  between the two adjacent color filter units  2221 . 
       FIG. 6  illustrates a touch display device  300  according to a third exemplary embodiment. The touch display device  300  is substantially the same as the touch display device  200  of the second exemplary embodiment, except that the force sensing electrode layer  324  of the touch display device  300  includes not only a conductive metal layer  3242  but also a transparent conductive layer  3241  stacked on the conductive metal layer  3242 . Herein, the transparent conductive layer  3241  is more adjacent to the second substrate  321  compared with conductive metal layer  3242 . The conductive metal layer  3242  is also located below the black matrix layer  3222  and completely covered by the black matrix layer  3222 , thus the force sensing electrode layer  324  has no effect on an aperture ratio of the touch display device  300 . 
       FIG. 7  is a planar view of a color filter substrate of the touch display device  300  viewed from a side of the color filter substrate  32  having the force sensing electrode layer  324 . As shown in  FIG. 7 , the black matrix layer  3222  is located in regions between any two adjacent color filter units  3221 . As shown in  FIG. 7 , the conductive metal layer  3242  and the transparent conductive layer  3241  may have a mesh shape. The conductive metal layer  3242  between any two adjacent color filter units  3221  has a width that is less than a width of the transparent conductive layer  3241  between the two adjacent color filter units  3221 . 
       FIG. 8  illustrates a touch display device  400  according to a fourth exemplary embodiment. The touch display device  400  is substantially the same as the touch display device  100  of the first exemplary embodiment, except that the touch display device  400  includes no additional force sensing electrode layer  324 ; and the black matrix layer  4222  of the touch display device  400  is made of a conductive metal or a conductive alloy, and the black matrix layer  4222  functions as a force sensing electrode layer. During the touch force sensing period, the common electrode layer  412  and the black matrix layer  4222  form a plurality of capacitors for sensing touch force. 
       FIG. 8  illustrates a touch display device  500  according to a fifth exemplary embodiment. The touch display device  500  includes a color filter substrate  52  that is substantially the same as the color filter substrate  12  of the touch display device  100  of the first exemplary embodiment, except that the touch display device  500  includes a TFT substrate  51  that is different from the TFT substrate  11  of the touch display device  100 . 
     A first force sensing electrode layer  524  is formed on a surface of the color filter substrate  52  adjacent to the TFT substrate  51 . The TFT substrate  51  includes a first substrate  511 , a common electrode layer  512  on a side of the first substrate  111  adjacent to the color filter substrate  52 , a second force sensing electrode layer  513  on a side of the common electrode layer  512  adjacent to the color filter substrate  52 , and a pixel electrode layer  514  on a side of the second force sensing electrode layer  513  adjacent to the color filter substrate  52 . It is understood that the common electrode layer  512 , the second force sensing electrode layer  513 , and the pixel electrode layer  514  are insulated from each other. That is, an insulating layer (not shown) is formed between the common electrode layer  512  and the second force sensing electrode layer  513 . Another insulating layer (not shown) is formed between the second force sensing electrode layer  513  and the pixel electrode layer  514 . 
     During the display period, the common electrode layer  512  and the pixel electrode layer  514  cooperatively form electrical fields to rotate liquid crystal molecules. During the touch sensing period, the second force sensing electrode layer  513  functions as a self-capacitive sensor for sensing touch position. During the touch force sensing period, the second force sensing electrode layer  513  and the first force sensing electrode layer  524  may form a plurality of capacitors for sensing touch force. 
     The present disclosure also provides a determination in a method for establishing whether or not capacitance variation of the force sensing module of the above-described touch display panel is caused by a user touch. The method may include the following steps. 
     Step S 11 : setting a threshold value of the capacitance variation ΔC of a force sensing module. 
     Step S 12 : measuring a capacitance value C of the force sensing module in a touched state, and calculating the capacitance variation ΔC according to the capacitance value C and a capacitance value C′ of the force sensing module when untouched. 
     Step S 13 : If the capacitance variation ΔC is equal to or greater than the threshold value, it is determined that there is a touch, and if the capacitance variation ΔC is less than the threshold value, it is determined that there is no touch. 
     In addition, since the dielectric constant £ of the liquid crystal may change with the variations of grayscale levels of the displaying image, and the dielectric constant £ of the liquid crystal has a large influence on the capacitance value C of the force sensing module. So the grayscale level of the displaying image may also affect the capacitance value C. Therefore, it is necessary to compensate for the capacitance variation caused by the variations of grayscale levels. 
     A compensating method for obtaining a capacitance value C′ of the force sensing module when untouched is provided herein. The compensating method may include the following steps. 
     S 121 : partitioning the common electrode layer  112  into several parts, and measuring capacitance values C′ corresponding to each part at different average grayscale levels when there is no touch. For example, each part may include at least one common electrode  1121  as shown in  FIG. 1 . 
     S 123 : constructing a grayscale level vs capacitance chart including capacitance values C′ corresponding to each part at different average grayscale levels when there is no touch. 
     S 125 : looking up the table to obtain the capacitance value C′ of the part according to the average grayscale level. 
     Thus, the capacitance variation ΔC can be calculated by subtracting the capacitance value C′ from the capacitance value C. 
     The following example shows details of a method of obtaining the capacitance variation ΔC and determining whether there is a touch on the touch display panel. 
     For example, the four common electrodes  1121  as shown in  FIG. 1  may be represented by the numbers 1, 2, 3, and 4, respectively. 
     Table 1 is an example of a grayscale level vs capacitance chart. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Condition 
                   
               
               
                   
                 capacitance value C′ at different gray levels 
               
               
                   
                 (no touch) 
               
            
           
           
               
               
               
            
               
                 Sensor part 
                 average gray level = 0 
                 average gray level = 255 
               
               
                   
               
            
           
           
               
               
               
            
               
                 1 
                 20 
                 200 
               
               
                 2 
                 10 
                 190 
               
               
                 3 
                 15 
                 180 
               
               
                 4 
                 5 
                 195 
               
               
                   
               
            
           
         
       
     
     For example, a threshold of ΔC is 100. As shown in Table 2, if ΔC is more than 100, a touch is deemed made on the panel. If ΔC is less than 100, no touch is deemed. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 ΔC 
                   
               
               
                   
                   
                   
                 (Capacitance 
                 Determine 
               
               
                 Sensor 
                 Current 
                 Capacitance 
                 after be 
                 whether touch 
               
               
                 patch 
                 gray level 
                 C1′ 
                 compensated) 
                 on panel 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 1 
                 255 
                 200 
                 0 
                 NO 
               
               
                 2 
                 0 
                 300 
                 290 
                 YES 
               
               
                 3 
                 255 
                 250 
                 70 
                 NO 
               
               
                 4 
                 0 
                 110 
                 105 
                 YES 
               
               
                   
               
            
           
         
       
     
       FIG. 10  through  FIG. 12  show three different driving time sequences of the touch display devices  100 ,  200 ,  300 ,  400  of the first through the fourth exemplary embodiments. The touch display devices  100 ,  200 ,  300 ,  400  are driven by a time division driving method. 
     As shown in  FIG. 10 , one frame of time, or a single frame, is divided into a display period (DM), a touch sensing period (TM), and a touch force sensing period (FM). The driving circuit of the touch display device alternately drives the touch display device to display during the DM, to detect touch position during the TM, and to detect touch force during the FM in one frame time. 
     As shown in  FIG. 11 , one frame time, or a single frame, is divided into a plurality of display sub-periods (DM 1  through DM n ), a plurality of touch sensing sub-periods (TM 1  through TM n ), and a touch force sensing period (FM). The display sub-periods (DM 1  through DM n ) and the touch sensing sub-periods (TM 1  through TM n ) are alternating. The driving circuit of the touch display device alternately drives the touch display device to display during each display sub-period and to detect touch position during each touch sensing sub-period; and finally drives the touch display device to detect touch force during the FM, in one frame of time. 
     As shown in  FIG. 12 , one frame of time, or a single frame, is divided into a plurality of display sub-periods (DM 1  through DM n ), a plurality of touch sensing sub-periods (TM 1  through TM n ), and a plurality of touch force sensing sub-periods (FM 1  through FM n ). The display sub-periods (DM 1  through DM n ), the touch sensing sub-periods (TM 1  through TM n ), and the touch force sensing sub-periods (FM 1  through FM n ) are alternating. The driving circuit of the touch display device alternately drives the touch display device to display during each display sub-period, to detect touch position during each touch sensing sub-period, and to detect touch force during each touch force sensing sub-period in one frame of time. 
     During the display period or the display sub-periods, for the touch display devices  100 ,  200 ,  300 ,  400 , each common electrode may be supplied with a common voltage, each pixel electrode may be applied with a voltage different from the common voltage, and the force sensing electrode layer may be electrically floating. 
     During the touch sensing period or the touch sensing sub-period, for the touch display devices  100 ,  200 ,  300 ,  400 , each common electrode may be supplied with a voltage, each pixel electrode and the force sensing electrode layer may be floating. 
     During the force sensing period or the force sensing sub-periods, for the touch display devices  100 ,  200 ,  300 ,  400 , each common electrode may be supplied with a voltage, the force sensing electrode layer may be may be electrically grounded, and each pixel electrode may be floating. 
     It is to be understood, even though information and advantages of the present exemplary embodiments have been set forth in the foregoing description, together with details of the structures and functions of the present exemplary embodiments, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present exemplary embodiments to the full extent indicated by the plain meaning of the terms in which the appended claims are expressed.