Abstract:
A display device and a method of applying the same are introduced herein. A shielding layer is utilized to interpose between a transparent conductive layer of a touch element and a common electrode layer of a liquid crystal display (LCD) panel. With controlling variances of a first and a second control signals, a coupling current between the transparent conductive layer and common electrode layer can approach none, whereby influences of capacitive coupling effect between the common electrode layer or shielding layer and the transparent conductive layer of the touch element can be reduced. Thus, high touch accuracy of the touch element can be achieved and the noise can be eliminated simultaneously.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims priority to Taiwanese Patent Application No. 098119951 filed on Jun. 15, 2009. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention The present invention relates to a display device and method of applying the same, and more particularly, to a display device and method of applying the same that can reduce the effect of capacitive coupling and influence of noise. 
         [0003]    2. Description of the Prior Art 
         [0004]    Nowadays, touch screens have developed many types, such as resistive, capacitive, optical, acoustic, electromagnetic, and image sensor types. Touch screens induce an input signal through direct touch with a part of the human body such as a finger or with an exclusive stylus. However, the plurality of touch screens can be primarily classified into add-on and embedded types based on the position of sensing circuits in touch screens or differences in fabrication sequences. 
         [0005]    A so-called add-on touch screen is that the external surface of the display device thereof such as liquid crystal display (LCD) panels is additionally laminated with a transparent touch panel (TP) with sensing circuits, such as a capacitive touch panel. The surface of a transparent substrate (e.g., glass) of the plurality of capacitive touch panels is plated with a layer of indium tin oxide (ITO) and a hard coater in sequence. Between the ITO layer of the TP and the LCD panel, a shielding layer of protecting electrical signals is disposed. 
         [0006]    As for an embedded touch screen mentioned previously, a transparent TP with sensing circuits is fabricated directly inside a LCD panel. Because the TP is directly fabricated in an LCD panel of the touch screen, a single ITO layer is merely required in most cases. Comparing with an add-on touch screen, an embedded touch screen has slimmer total thickness of the panel thereof and maintains a higher degree of light transmittance. 
         [0007]      FIG. 1A  shows a cross-section view of an embedded touch screen  1  in the prior art, mainly comprising an embedded touch panel  2 , such as a surface capacitive or a projected capacitive touch panel, and an LCD panel  4 . The embedded touch panel  2  thereinto is embedded on the upper surface of the LCD panel  4 . The LCD panel  4  mainly comprises a first substrate  16  with a colored filter  18 , a common electrode layer  20 , which is formed below the colored filter  18 , a second substrate  26 , and a liquid crystal layer  24 , which is formed between the first substrate  16  and second substrate  26 . The embedded touch panel  2  mainly comprises a polarizer film (PF)  10 , a conductive layer  12 , which is situated below the PF  10  and above the first substrate  16 , and a patterned electrode  14 , which is formed at the periphery of the conductive layer  12 . Because the first conductive layer  12  is an ITO layer used to store electric charge and is installed with capacitive sensing circuits, it seems as though the first conductive layer  12  forms a high-density touch sensing electrode. But, because capacitive sensing circuits are easy to be affected by some noise produced by TFT-LCDs per se, surrounding environments, etc. to be distorted, resulting in incorrect response. For example, when the capacitive touch panel is actuated though the driving voltage signal of the LCD panel  4  has not been turned on yet, predetermined normal aligned lines will be demonstrated as shown on the left side of  FIG. 1C  via the embedded touch panel  2 . However, once the capacitive touch panel is actuated and the driving voltage signal of the LCD panel  4  is turned on, the plurality of lines will become jittering due to serious noise interference as shown on the right side of  FIG. 1C  via the embedded touch panel  2 . 
         [0008]    As  FIGS. 1A and 1B  show, when a human finger  5  touches the embedded touch panel  2 , a finger sensing capacitor Cf is naturally formed between the finger  5  and the first conductive layer  12 , which receives alternating current (AC). And static electricity in the human body flows to the ground to induce comparatively a slight sensing current I f  to charge the sensing capacitor Cf and to flow to the finger  5 . Depending on variation in current of the sensing current I f , a touch point coordinate of the finger  5  on the embedded touch panel  2  can be detected. 
         [0009]    Please further refer to  FIGS. 1A and 1B . In general, the common electrode layer  20  of the LCD panel  4  receives direct current (DC) of about 3V to 5V as a control signal to activate the LCD panel  4 , so a huge coupling capacitance C will be naturally formed between the conductive layer  12  of the embedded touch panel  2  and the common electrode layer  20  of the LCD panel  4 . The coupling capacitance C is much huger than the capacitance of the above-mentioned finger sensing capacitor Cf, so the sensing current I f  flowing through the sensing capacitor Cf is very tiny, which further affects sensing intensity of the embedded touch panel  2 . In this way, the sensitivity will worsen when the finger  5  touches the embedded touch panel  2 , which makes it more difficult in sensing correctly or sensing positions. 
       SUMMARY OF THE INVENTION 
       [0010]    One objects of the present invention is to provide a display device and method of applying the same. The display device is equipped with an additional shielding layer, which is interposed between the transparent conductive layer of the touch panel (TP) and the common electrode layer of the liquid crystal display panel (LCD panel). By controlling a first control signal and a second control signal, the effect of capacitive coupling on touch sensing of the TP can be reduced so that the touch sensitivity of the TP can be enhanced. 
         [0011]    Another object of the present invention is to provide a display device and method of applying the same. The display device is equipped with an additional shielding layer, which is interposed between the transparent conductive layer of the TP and the common electrode layer of the LCD panel, to block out surrounding noise or noise produced by the LCD per se. 
         [0012]    According to the present invention, a display device comprises a liquid crystal display panel and a touch panel thereon. The touch panel comprises a first conductive layer for receiving a first control signal, a contact layer on the first conductive layer for being touched by an object, a patterned electrode around the first conductive layer for delivering a corresponding sensing signal as soon as the contact layer is touched by the object, and a second conductive layer disposed between the contact layer of the touch panel and the liquid crystal display panel, or disposed within the liquid crystal display panel, for receiving a second control signal to enhance the sensing signal. 
         [0013]    In one aspect of the present invention, the second control signal and the first control signal are synchronous. 
         [0014]    In another aspect of the present invention, the first control signal and the second control signal are different, and the second control signal is floating. 
         [0015]    Also, the present invention further provides a method of applying the display device. The method comprises the following steps:
       making the transparent conductive layer receive the first control signal and form a first capacitance in response to a human contact on the transparent conductive layer, and   making patterned electrode transmit a sensing signal to the first capacitance based on the human contact,   making the shielding layer receive the second control signal to mask noise of the TP to prevent the sensing signal from being affected, and forming a second capacitance between the shielding layer and the transparent conductive layer, so that a coupling signal flows through the second capacitance; and   controlling the first control signal and the second control signal to synchronize the first and second control signals or to make the first and second control signals having the same voltage level, or to make the first and second control signals have different voltage levels while the second control signal becomes floating, so as to lower the coupling signal to enhance the touch sensitivity of the sensing signal.       
 
         [0020]    Therefore, in the present invention, by controlling the first and second control signals, the coupling signal formed between the transparent conductive layer and shielding layer can be extremely close to zero. Thus, the possibility that the effect of either capacitive coupling of the shielding layer or the common electrode layer on the transparent conductive layer affects the sensing of the TP is reduced. In consequence, the touch sensitivity of the TP is enhanced. 
         [0021]    These and other objects of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1A  shows a cross-section view of a conventional embedded touch screen. 
           [0023]      FIG. 1B  shows a human finger touching the embedded touch panel. 
           [0024]      FIG. 1C  illustrates a plurality of lines become jittering due to serious noise interference via the embedded touch panel. 
           [0025]      FIG. 2A  shows a cross-section view of an embedded touch screen according to a first preferred embodiment of the present invention. 
           [0026]      FIG. 2B  shows an equivalent circuit diagram of a display device of  FIG. 2A . 
           [0027]      FIG. 3A  shows a cross-section view of an embedded touch screen according to a second preferred embodiment of the present invention. 
           [0028]      FIG. 3B  shows an equivalent circuit diagram of a display device of  FIG. 3A . 
           [0029]      FIG. 4A  shows a cross-section view of an embedded touch screen according to a third preferred embodiment of the present invention. 
           [0030]      FIG. 4B  shows an equivalent circuit diagram of a display device of  FIG. 4A . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    Please refer to  FIGS. 2A and 2B , first. Both of the figures show a display device  6  of a first preferred embodiment of the present invention. The display device  6  mainly comprises a touch panel (TP)  8 , a LCD panel  9 , and at least one shielding layer  91 . In the present embodiment, the TP  8 , which can be either a surface capacitive touch panel, a projected capacitive touch panel, or other touch panels with similar technology, is embedded (e.g., film formation) on the upper surface of the LCD panel  9 . The TP  8  comprises a polarized light contact layer  80  situated at the outermost layer position (e.g., a polarizer film (PF), which can act as a hard coater (HC) layer as well), which allows a part of the human body such as the finger  5  to touch directly, a transparent conductive layer  82  (e.g., ITO, which is situated beneath the polarized light contact layer  80  and receives a first control signal S 1 ), and a plurality of patterned-electrode layer  84  comprised by conductive electrodes, which are disposed at the periphery of the transparent conductive layer  82  and electrically connected with the transparent conductive layer  82 . The patterned-electrode layer  84  transmit the first control signal S 1  and form an electric field on the transparent conductive layer  82  to detect an induced signal induced by static electricity in the human body such as the current value of the induced current I f . 
         [0032]    The LCD panel  9  such as a TFT-LCD comprises a first substrate (not shown), a color filter  93 , a common electrode layer  94 , which is disposed beneath the color filter  93  and receives a DC driving control signal so as to display the LCD panel  9 , a second substrate  98  such as a TFT Array substrate, and a liquid crystal layer  96 , which is formed between the first and second substrates. 
         [0033]    The shielding layer  91 , such as an additional ITO conduction layer, is placed between the transparent conductive layer  82  of the TP  8  and the common electrode layer  94  of the LCD panel  9  to receive a second control signal S 2  to mask external noise received by the TP  8  or noise produced by the LCD panel  9 . 
         [0034]    When the finger  5  does not touch the exterior surface of the polarized light contact layer  80  of the TP  8 , the patterned-electrode layer  84  practically transmit the first control signal S 1  (e.g., alternating current (AC)) to the transparent conductive layer  82  to form a uniform electric field with the same electric potential. Thus, no induced current will flow through the TP  8 . As  FIGS. 2A and 2B  show, once the finger  5  touches the polarized light contact layer  80  of the TP  8 , an induction capacitor Cf will be formed naturally between the finger  5  and the transparent conductive layer  82  (roughly the same position as the polarized light contact layer  80 ), which receives the first control signal S 1 , because the human body is a good conductor; that is, the finger  5  and the transparent conductive layer  82  act as both ends of the induction capacitor Cf. Meanwhile, static electricity in the human body produced by the finger  5  which touches the polarized light contact layer  80  of the TP  8  seems to form an external touch signal flowing to the ground and changing the previously mentioned electric field. The patterned-electrode layer  84  transmit a feeble induced current I f , which charges the induction capacitor Cf and flows to the finger  5  via the transmittance of the transparent conductive layer  82 . With help of the production of the current value of the induced current I f , a touch point coordinate of the finger  5  on the TP  8  can be detected. 
         [0035]    Similarly, under the effect of capacitive coupling, a coupling capacitance C 2  is naturally formed between the transparent conductive layer  82  of the TP  8 , which receives the first control signal S 1 , and the shielding layer  91 , which receives the second control signal S 2 , and an induced current I 2  is formed as well, flowing to the shielding layer  91  via the coupling capacitance C 2 . In addition, a coupling capacitance C 3  is naturally formed between the common electrode layer  94 , which receives a DC driving control signal, and the shielding layer  91 , which receives the second control signal S 2 , and an induced current is formed as well, flowing through the coupling capacitance C 3 . By controlling level variations of the first control signal S 1  and second control signal S 2 , the current value of the induced current I 2  can be changed, and even the current value of the induced current I 2  can be controlled to become extremely close to zero to impede current conduction between the transparent conductive layer  82  and the shielding layer  91 . Thus, the induced current I 2  is not able to charge the coupling capacitance C 2 , which prevents the effect of capacitive coupling formed between either the common electrode layer  94  or the shielding layer  91  and the transparent conductive layer  82  from affecting the induction of the TP  8 ; that is, in order to avoid the induced current I 2  from affecting the induced current L the current value of the induced current I 2  (e.g., The induced current I f  is larger than the induced current I 2 .) is lowered to enhance the touch sensitivity of the TP  8 . 
         [0036]    Please also refer to  FIGS. 3A and 3B , which show a display device  60  of a second preferred embodiment of the present invention. The display device  60  mainly comprises a TP  62  and a LCD panel  64 . The TP  62  similarly comprises a contact layer  621 , a transparent conductive layer  623  (e.g., ITO thin films receive a first control signal S 1 ), and patterned-electrode layer  624 , which are disposed at the periphery of the transparent conductive layer  623  and electrically connected with the transparent conductive layer  623 . 
         [0037]    The LCD panel  64  such as a TFT-LCD comprises a first substrate  642 , a color filter  644 , a shielding layer  646  (e.g., ITO layer), which is placed beneath the color filter  644  and receives a second control signal S 2  to mask external noise of the TP  62  or noise produced by the LCD panel  64 , a common electrode layer  648 , which receives a DC driving control signal to enable the LCD panel  64 , an insulating layer  650  (e.g., overcoat (OC) layer), which is disposed between the shielding layer  646  and common electrode layer  648  to provide electrical insulation, a second substrate  654  (e.g., TFT Array substrate), and a liquid crystal layer  652 , which is formed between the first and second substrates,  642  and  654 . 
         [0038]    Similarly, as shown in  FIG. 3A  and  FIG. 3B , when the finger  5  touches the TP  62 , an induction capacitor Cf is naturally formed between the finger  5  and the transparent conductive layer  623 , which receives the first control signal S 1  (roughly in the position of the contact layer  621 ); meanwhile, static electricity in the human body seems to form an external touch signal to make the patterned-electrode layer  624  transmit a feeble induced current I f , which charges the induction capacitor Cf and flows to the finger  5  via the conduction of the transparent conductive layer  623 . 
         [0039]    Although a coupling capacitance C 2  is naturally formed between the transparent conductive layer  623 , which receives the first control signal S 1 , and the shielding layer  646 , which receives the second control signal S 2 , and an induced current I 2  is formed, flowing to the shielding layer  646  via the coupling capacitance C 2 , and although a coupling capacitance C 3  is naturally formed between the common electrode layer  648 , which receives a DC driving control signal, and the shielding layer  646 , which receives the second control signal S 2 , and an induced current is formed, flowing through the coupling capacitance C 3 , the first control signal S 1  is arranged as an AC signal, and the second control signal S 2  as a floating signal; that is, there is no signal sources connected. In this way, the current conduction between the transparent conductive layer  623  and the shielding layer  646  can be impeded so that the current value of the induced current I 2  can be controlled to be reduced to be close to zero; that is, by reducing the current value of the induced current I 2  (e.g., The induced current I f  is larger than the induced current I 2 ), the induced current I 2  is prevented from affecting the induced current I f  to enhance the touch sensitivity of the TP  62 . 
         [0040]    Please also refer to  FIGS. 4A and 4B , which show a display device  70  of a third preferred embodiment of the present invention. The display device  70  mainly comprises a TP  72  and a LCD panel  74 . Differing from the second embodiment, the TP  72  of the third embodiment comprises a contact layer  721 , a transparent conductive layer  723  (e.g., ITO thin films receive a first control signal S 1 ), a shielding layer  728  (e.g., ITO layer), which receives a second control signal S 2  to mask external noise of the TP  72  or noise produced by the LCD panel  74 , an insulating layer  726  (e.g., overcoat (OC) layer), which is disposed between the shielding layer  728  and transparent conductive layer  723  to provide electrical insulation, and a patterned-electrodes layer  724  for transmitting induced current I f , which are placed at the periphery of the transparent conductive layer  723  and electrically connected with the transparent conductive layer  723 . 
         [0041]    The LCD panel  74  such as a TFT-LCD comprises a first substrate  742 , a color filter  744 , a common electrode layer  750 , which is placed beneath the color filter  744  and receives a DC driving control signal so as to display the LCD panel  74 , a second substrate  754  (e.g., TFT Array substrate), and a liquid crystal layer  752 , which is formed between the first and second substrates,  742  and  754 . 
         [0042]    As shown in  FIG. 4A  and  FIG. 4B , when the finger  5  touches the TP  72 , an induction capacitor Cf is naturally formed between the finger  5  and the transparent conductive layer  723 , which receives the first control signal S 1 . Meanwhile, static electricity in the human body from the finger  5  seems to form an external touch signal to make the patterned-electrode layer  724  transmit a feeble induced current I f , which charges the induction capacitor Cf and flows to the finger  5  via the conduction of the transparent conductive layer  723 . A coupling capacitance C 2  is naturally formed between the transparent conductive layer  723 , which receives the first control signal S 1 , and the shielding layer  728 , which receives the second control signal S 2 . Besides, a coupling capacitance C 3  is naturally formed as well between the common electrode layer  750 , which receives the DC driving control signal, and the shielding layer  728 , which receives the second control signal S 2 . By connecting the first control signal S 1  and the second control signal S 2  to the same AC voltage source or by adding an OP amplifier shunt circuit to split current, the first and second control signals can be controlled to have the same or synchronous electric potential in order to reduce the current value of the induced current I 2  between the transparent conductive layer  723  and the shielding layer  728  to be close to zero so that the current conduction between the transparent conductive layer  723  and the shielding layer  728  is impeded and unable to charge the coupling capacitance C 2 . In this way, the effect of capacitive coupling produced by either the common electrode layer  750  or the shielding layer  728  and the transparent conductive layer  723  is prevented from affecting the induction of the electric field of the TP  72 ; that is, by lowering the current value of the induced current I 2  (e.g., The induced current I f  is larger than the induced current I 2 ), the induced current I 2  is prevented from affecting the induced current I f  in order to enhance the touch sensitivity of the TP  72 . 
         [0043]    In addition, one preferred embodiment of the present invention further provides a method of applying the display device. The method has the following steps (Please refer to  FIG. 4A  as well):
       providing a LCD panel which comprises a common electrode layer, and providing a TP embedded on the LCD panel comprising a touch layer, a transparent conductive layer, patterned-electrode layer disposed at the periphery of the transparent conductive layer and electrically connected with the transparent conductive layer, a shielding layer, and an insulating layer disposed between the transparent conductive layer and shielding layer;   making the transparent conductive layer receive a first control signal, forming a first capacitance in the contact layer between the transparent conductive layer and shielding layer, and making patterned-electrode layer correspondingly produce a first induction signal, which flows to the first capacitance via the transparent conductive layer, based on static electricity, which seems to form an external touch signal when the human body touches the contact layer.   making the shielding layer receive a second control signal to mask noise received by the TP, forming a second capacitance between the shielding layer and transparent conductive layer, and making a second induction signal flow through the second capacitance; and   controlling the variations of the first and second control signals (e.g., level), for example, to make the first and second control signals have the same or synchronous electric potential so as to control the second induction signal to be smaller than the first induction signal or even to be close to zero.       
 
         [0048]    In addition, another preferred embodiment of the present invention further provides a method of applying the display device. The method has the following steps (Please refer to  FIG. 3A  as well):
       providing a LCD panel which comprises at least a common electrode layer, a shielding layer, and an insulating layer disposed between the common electrode layer and shielding layer, providing a TP embedded on the LCD panel with a contact layer, a transparent conductive layer, and patterned-electrode layer situated beneath the transparent conductive layer and contact layer;   making the transparent conductive layer receive a first control signal, forming a first capacitance between the transparent conductive layer and shielding layer, and making the patterned-electrode layer correspondingly produce a first induction signal which flows to the first capacitance via the transparent conductive layer based on static electricity, which seems to form an external touch signal when the human body touches the contact layer;   making the shielding layer receive a second control signal to mask noise received by the TP, forming a second capacitance, and making a second induction signal flow through the second capacitance; and   controlling the variations of the first and second control signals to make the first and second control signals different and the second control signal as a floating signal so as to control the second induction signal to be smaller than the first induction signal, or even to be close to zero.       
 
         [0053]    According to the above-mentioned embodiments, the present invention provides a display device and method of applying the same. The methods are that an additional shielding layer is inserted into the transparent conductive layer of the TP and the common electrode layer of the LCD panel, and that the level variations of the first and second control signals are controlled to make the induction current between the shielding layer and the transparent conductive layer of the TP be reduced to be close to zero in order to lower the possibility that the effect of capacitive coupling produced by either the shielding layer or the common electrode layer on the transparent conductive layer affects the induction of the electrical field of the TP; that is, by avoiding the induced current I f  touched by the finger from being affected, the touch sensitivity of the TP can be thus enhanced. Meanwhile, the shielding layer can mask noise from the LCD panel as well to further reduce the effect of the noise. 
         [0054]    The present invention has been described with reference to certain preferred and alternative embodiments which are intended to be exemplary only and not limited to the full scope of the present invention as set forth in the appended claims.