Patent Publication Number: US-2018046295-A1

Title: Touch display device

Description:
FIELD 
     The subject matter herein generally relates to a touch display device. 
     BACKGROUND 
     An on-cell or in-cell type touch screen device can be manufactured by installing a touch device in a touch 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 disclosure will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is a planar 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  along line II-II. 
         FIG. 3  is a planar view showing a layout of second electrodes of the touch display device of  FIG. 1 . 
         FIG. 4  is a planar view showing a layout of the first exemplary embodiment of first electrodes of the touch display device of  FIG. 1 . 
         FIG. 5  is a planar view showing a layout of the second exemplary embodiment of the first electrodes of the touch display device of  FIG. 1 . 
         FIG. 6  is a cross-sectional view of the touch display device of  FIG. 2  when being touched by a first touch force. 
         FIG. 7  is a cross-sectional view of the touch display device of  FIG. 2  when being touched by a second touch force. 
         FIG. 8  shows a relationship between a second capacitance and a touch force applied on the touch display device of  FIG. 2 . 
         FIG. 9  shows a relationship between a first capacitance and a touch force applied on the touch display device of  FIG. 2 . 
         FIG. 10  shows a relationship between a total of the first capacitance and the second capacitance and a touch force applied on the touch display device of  FIG. 2 . 
         FIGS. 11 through 13  are diagrammatic views of three types of driving time sequence of the touch display device. 
         FIG. 14  is a cross-sectional view of a second exemplary embodiment of the touch display device of  FIG. 1  along line II-II. 
     
    
    
     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 structures. 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. 
       FIG. 1  and  FIG. 2  illustrate a touch display device  100  according to a first exemplary embodiment. The touch display device  100  includes a cover plate  10 , a housing  30 , and a bonding frame  20  between the cover plate  10  and the housing  30 . The housing  30  defines a receiving space  103  to receive other components of the touch display device  100 . The cover plate  10  covers the receiving space  103 . The cover plate  10  is transparent and can receive touches from objects (e.g., fingers and styluses). The bonding frame  20  is configured to couple the cover plate  10  and the housing  30  together. In this exemplary embodiment, the bonding frame  20  is located at a peripheral portion of the cover plate  10  and surrounds the cover plate  10 . The housing  30  may be made of metal or plastic. 
     As shown in  FIG. 2 , the touch display device  100  further includes a display panel  120  in the receiving space  103 . The display panel  120  includes a first substrate  40 , a second substrate  50  facing the first substrate  40 , and a liquid crystal layer  60  between the first substrate  40  and the second substrate  50  in the receiving space  103 . The first substrate  40 , the liquid crystal layer  60 , and the second substrate  50  are stacked below the cover plate  10 , where the first substrate  40  is adjacent to the cover plate  10 . The first substrate  40  is a color filter substrate comprising a substrate (not explicitly shown) and a color filter layer (not explicitly shown) on the substrate; and the second substrate  50  is a thin film transistor substrate and includes a substrate (not explicitly shown) and a plurality of thin film transistors (not explicitly shown) on the substrate. A plurality of first electrodes  70  are formed on a surface of the first substrate  40  adjacent to the liquid crystal layer  60 , and a plurality of second electrodes  80  are formed on a surface of the second substrate  50  adjacent to the liquid crystal layer  60 . 
     As shown in  FIG. 2 , the touch display device  100  further includes an electrically-conductive frame  90  in the receiving space  103 . The electrically-conductive frame  90  is at a side of the display panel  120  away from the first substrate  40 . An air gap  104  is formed between the second substrate  50  and the electrically-conductive frame  90 . In other embodiments, there may be no air gap and an elastic layer (not explicitly shown) may be installed between the second substrate  50  and the electrically-conductive frame  90 . It is understood that the display panel  120  further includes a backlight module (not explicitly shown) between the second substrate  50  and the electrically-conductive frame  90 . A distance between the second electrodes  80  and the electrically-conductive frame  90  is greater than a thickness of the second substrate  50 . 
     The first electrodes  70  and the second electrodes  80  cooperatively form a first capacitor for sensing touch force, and the second electrodes  80  and the electrically-conductive frame  90  cooperatively form a second capacitor for sensing touch force. The intensity of the touch force can be calculated by variations of capacitances of the first capacitor and the second capacitor. 
     The touch display device  100  further includes a main board  101  and a battery  102  in the receiving space  103 . Both the main board  101  and the battery  102  are between the electrically-conductive frame  90  and the housing  30 . The main board  101  may have a plurality of components, such as an image processor, and the main board  101  may control many functions of the touch display device  100 . The battery  102  supplies power to the touch display device  100 . 
     In the present exemplary embodiment, the second electrodes  80  also function as common electrodes of The touch display device  100  and cooperate with pixel electrodes (not explicitly shown) to form electrical fields to rotate the liquid crystals in the liquid crystal layer  60 . The second electrodes  80  also function as self-capacitance touch sensing electrodes for detecting touch position of the touch display device  100 . When an object (e.g., a finger) is touching on the cover plate  10 , the object as a conductor may affect electrical signals of the second electrodes  80  corresponding to the touch position, thus the touch position can be detected. 
     As shown in  FIG. 3 , the second electrodes  80  are spaced apart from each other and arranged in an array of rows and columns. In the present exemplary embodiment, each second electrode  80  is rectangular. In other embodiments, each second electrode  80  may have other shapes, such as round. Each second electrode  80  is electrically coupled to a driving circuit (not explicitly shown) of the touch display device  100  by conductive lines (not explicitly shown). In the present exemplary embodiment, the driving circuit of the touch display device  100  may be integrated with a touch sensing driver, a touch force sensing driver, and a display driver. In other embodiments, the driving circuit is only a touch sensing driver and a touch force sensing driver; and the display function of the touch display device is driven by an additional display driving circuit. 
     As shown in  FIG. 4 , the first electrodes  70  are spaced apart from each other. Each first electrode  70  extends as a strip along a direction of Y axis in  FIG. 4 . The first electrodes  70  are arranged in one row along a direction of X axis of  FIG. 4 . In the present exemplary embodiment, each first electrode  70  corresponds to one column of the second electrodes  80  along direction of Y axis of  FIG. 3 . Each first electrode  70  may be electrically coupled to the driving circuit (not explicitly shown) by conductive lines (not explicitly shown). 
     As shown in  FIG. 5 , in other embodiments, each first electrode  70  extends as a strip along a direction of X axis in  FIG. 5 . The first electrodes  70  are arranged in one column along a direction of Y axis of  FIG. 5 . In the present exemplary embodiment, each first electrode  70  corresponds to one row of the second electrodes  80  along a direction of X axis of  FIG. 3 . 
     It is understood that a distance between every two adjacent first electrodes  70  is sufficiently large such that electrical signals generated by a conductor (e.g., a finger of a user) touching on the cover plate  10  can be transmitted to the second electrode  80  below the first electrodes  70 , and can affect electrical signals of the second electrode  80  so that the touch position can be sensed. 
     Both the first electrodes  70  and the second electrodes  80  may be made of a transparent conductive material, such as indium tin oxide (ITO). The first electrodes  70  and the second electrodes  80  can alternatively be arranged in a metal mesh pattern. 
     The electrically-conductive frame  90  may be made of an electrically-conductive metal or an electrically-conductive alloy, such as copper (Cu), silver (Ag), molybdenum (Mo), titanium (Ti), aluminum (Al), or tungsten (W). The electrically-conductive frame  90  may be grounded, to avoid the main board  101  and the battery  102  interfering with the display signals and the sensing signals of the touch display device  100 . 
       FIG. 6  is a cross-sectional view of the touch display device  100  when touched by a touch force equal to a first predetermined value a.  FIG. 7  is a cross-sectional view of the touch display device  100  when touched by a touch force of greater the first predetermined value a. In the present exemplary embodiment, a distance between the first electrode  70  and the second electrode  80  is defined as a first distance D 1 , and a distance between the second electrode  80  and the electrically-conductive frame  90  is defined as a second distance D 2 . The first distance D 1  is in a range from about 2 μm to about 4 μm. The second distance D 2  is in a range from about 50 μm to about 300 μm. For example, an approximate formula for capacitance can be expressed as: 
         C=εS/ 4 πkD    (Eq. 1)
 
     where C is a capacitance of a capacitor, S is an area of the overlapping region, D is a depth of a insulating layer, ε is a dielectric constant of the insulating layer, and k is an electrostatic constant. When ε, S, π, and k are fixed, the distance D varies proportionally with the capacitance C. As shown in  FIG. 6  and  FIG. 7 , when a finger is touching on the cover plate  10  of the touch display device  100 , the first distance D 1  and the second distance D 2  both decrease, and a first capacitance C 1  of the first capacitor between the first electrode  70  and the second electrode  80  may vary. A second capacitance C 2  of the second capacitor between the second electrode  80  and the electrically-conductive frame  90  may vary. Thus, the intensity or amount of the touch force can be calculated according to the variation of the respective capacitances of the first capacitor and the second capacitor. The touch display device  100  can thereby sense touch forces over a wide range. 
     As shown in  FIGS. 6 and 7 , when the touch force is equal to or greater than the first predetermined value a, the display panel  120  may deform towards the electrically-conductive frame  90 , and be in direct contact with the electrically-conductive frame  90 . The second distance D 2  may reach a minimum value and may no longer vary. 
     In the present exemplary embodiment, the relationship between the second capacitance C 2  and the touch force X applied on the cover plate  10  is defined by: 
         C 2= f ( X )   (Eq. 2)
 
     When the touch force X is less than the first predetermined value a, the greater the touch force X, the less the second distance D 2  will be, and the greater the second capacitance C 2  will be (as illustrated in  FIG. 8 ). When the touch force X is not less than the first predetermined value a, the second distance D 2  reaches the minimum and may no longer vary, thus the second capacitance C 2  reaches a maximum value and may no longer vary. 
     In the present exemplary embodiment, the relationship between the first capacitance C 1  and the touch force X applied on the cover plate  10  is defined by: 
         C 1= g ( X )   (Eq. 3)
 
     As shown in  FIG. 9 , when the touch force X is less than a second predetermined value b, the greater the touch force X, the less the first distance D 1  will be, and the greater the first capacitance C 1  will be. When the touch force X is not less than the second predetermined value b, the first distance D 1  reaches a minimum value and may no longer vary. The first capacitance C 1  reaches a maximum value and may no longer vary. In addition, when the touch force X applied to the cover plate  10  is greater than the first predetermined value a and less than the second predetermined value b, a variation in magnitude of the first capacitance C 1  when increasing one unit of the touch force X is greater than that when the touch force X applied to the cover plate  10  is less than the first predetermined value a. 
     The first capacitance C 1  and the second capacitance C 2  are added together to be a total capacitance C. In the present exemplary embodiment, a relationship between the total capacitance C and the touch force X applied on the cover plate  10  may be defined by: 
         C=a*f ( X )+ b*g ( X )+ c    (Eq. 4)
 
     wherein a, b, and c are constants. The Equation (4) may be obtained by combining Equation (2) and Equation (3). As shown in  FIG. 10 , the total capacitance C increases linearly with the touch force X. When the touch force X is less than the second predetermined value b, the capacitance C increases. The total capacitance C reaches a maximum value and may no longer vary when the touch force X is not less than the second predetermined value b. Thus, the intensity of the touch force can be calculated according to the variation of the total capacitance C. It is understood that the relationship between the total capacitance C and the touch force X applied on the cover plate  10  is not limited to that suggested by  FIG. 10 . 
       FIGS. 11, 12 and 13  show three different driving time sequences of the touch display device  100  of the first exemplary embodiment. The touch display device  100  is driven by a time division driving method. 
     As shown in  FIG. 11 , 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  100  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. 12 , 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. 13 , 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 device  100  of the first exemplary embodiment, each second electrode  80  may be applied with a common voltage, the electrically-conductive frame  90  may be electrically grounded, and each first electrode  70  may be floating or have a common voltage applied thereto. 
     During the touch sensing period or the touch sensing sub-period, for the touch display device  100  of the first exemplary embodiment, each second electrode  80  may be applied with a signal pulse voltage, the electrically-conductive frame  90  may be electrically grounded, and each first electrode  70  may be floating or have a common voltage applied thereto. 
     During the force sensing period or the force sensing sub-periods, for the touch display device  100  of the first exemplary embodiment, each second electrode  80  may be applied with a signal pulse voltage, the electrically-conductive frame  90  may be electrically grounded or receive a signal pulse voltage, and each first electrode  70  may be floating or may receive a signal pulse voltage. 
       FIG. 14  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 the second electrodes  80  are divided into a plurality of first sub-electrodes  811  and a plurality of second sub-electrodes  812 . The first sub-electrodes  811  and the first electrodes  70  cooperatively form a first capacitor for sensing touch force and the first sub-electrodes  811  and the electrically-conductive frame  90  cooperatively form a second capacitor for sensing touch force. The second sub-electrodes  812  function as electrodes of the touch display device  200  for detecting touch position. The first sub-electrodes  811  and the second sub-electrodes  812  also function as common electrodes of the touch display device  100  and cooperate with pixel electrodes (not explicitly shown) to form electrical fields to rotate the liquid crystals in the liquid crystal layer  60 . 
     Each first sub-electrode  811  and each first electrode  70  are spaced apart from each other. The shape and arrangement of the first sub-electrode  811  and the second sub-electrode  812  are not limited. 
     The touch display device  200  is also driven by a time division driving method. The three different driving time sequences shown in  FIG. 11  through  FIG. 13  may also suitable for the touch display device  200  of the second exemplary embodiment. 
     During the display period or the display sub-periods, for the touch display device  200  of the second exemplary embodiment, each first sub-electrode  811  and each second sub-electrode  812  may receive a common voltage and the electrically-conductive frame  90  may be electrically grounded. Each first electrode  70  may be floating or may receive a common voltage. 
     During the touch sensing period or the touch sensing sub-period, for the touch display device  200  of the second exemplary embodiment, each first sub-electrode  811  may receive a common voltage. Each second sub-electrode  812  may be applied with a signal pulse voltage and the electrically-conductive frame  90  may be electrically grounded. Each first electrode  70  may be floating or may receive a common voltage. 
     During the force sensing period or the force sensing sub-periods, for the touch display device  200  of the second exemplary embodiment, each first sub-electrode  811  may receive a signal pulse voltage. Each second electrode  80  may receive a common voltage or be electrically grounded. The electrically-conductive frame  90  may be electrically grounded or it may receive a signal pulse voltage, and each first electrode  70  may be floating or receive a signal pulse voltage. 
     In one exemplary embodiment, it is desirable that each first electrode  70  receives a common voltage during the DM and the TM. Each first electrode  70  and each second electrode  80  receive a common voltage during the DM. Thus, the voltages of the touch display device during display periods are more stable, and the performance of the touch display device can be improved. 
     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.