Patent Publication Number: US-2010110038-A1

Title: Mutual capacitance touch screen and combined mutual capacitance touch screen

Description:
TECHNICAL FIELD 
     The present invention relates to a touch induction input device, particularly to a touch input device which uses mutual capacitance as an inductor. 
     BACKGROUND ART 
     The touch screen is a touch sense input device which is widely used at present. According to the principle of touch induction, touch screens in the prior art comprise resistance touch screens, capacitance touch screens, surface infrared touch screens, etc., wherein the resistance touch screens are popular for many years because of the advantages of low cost, easy realization, simple control, etc. Recently, the capacitance touch screens are well received by the public because of the advantages of high light transmittance, abrasion resistance, ambient temperature change resistance, ambient humidity change resistance, long service life and the complicated high-grade functions for realizing multipoint touch, etc. 
     Using capacitance change as the induction principle exists for a long time. In order to make the touch screen effectively work, a transparent capacitance sensor array is needed. When a human body or a special touch device such as a handwriting pen approaches to an induction electrode of a capacitor, the capacitance value detected by a sense control circuit can be changed. According to the distribution of capacitance values change in a touch area, the touch condition of the human body or the special touch device in the touch area can be judged. According to capacitance forming modes, the touch screens in the prior art comprise self capacitance touch screens and mutual capacitance touch screens, wherein the self capacitance touch screens use sense electrodes and alternate current grounds or direct current level electrodes to form the change of the capacitance value as a signal of touch sense, the mutual capacitance touch screens use the change of the capacitance value formed between two electrodes as the signal of touch sense, and sometimes, mutual capacitance is also called projection capacitance. 
     As shown in  FIG. 11 , the mutual capacitance touch screen in the prior art comprises a touch plane  100 ′, driving wires  210 ′ and sense wires  310 ′ which are not in the same plane, and a medium plane  910 ′ held between the driving wires  210 ′ and the sense wires  310 ′. As shown in  FIGS. 11-1  and  11 - 2 , the driving wires  210 ′ are parallel mutually, the sense wires  310 ′ are parallel mutually, and the driving wires  210 ′ and the sense wires  310 ′ crossed orthogonally in space. The driving wires  210 ′ are electrically connected with excitation signals, the sense wires  310 ′ are electrically connected with the sense control circuit so as to form mutual capacitance between the driving wires  210 ′ and the sense wires  310 ′, and mutual capacitance C formed at the crossing points of the driving wires  210 ′ and the sense wires  310 ′ is a main capacitance data signal detected by the sense control circuit. As shown in  FIG. 11-3 , mutual capacitance C comprises capacitance C B  between the driving wires  210 ′ and the bottom of the sense wires  310 ′ and capacitance C T  between the driving wires  210 ′ and the top of the sense wires  310 ′, namely C=C B +C T . As shown in  FIG. 11-4 , when a finger  150 ′ comes into contact with the touch plane  100 ′ in the touch area, the finger  150 ′ is equivalent to an electrode above the sense wires  310 ′, which changes the electric field between the driving wires  210 ′ and the top of the sense wires  310 ′. The change can be regarded as that the finger  150 ′ sucks electric field lines between the driving wires  210 ′ and the top of the sense wires  310 ′ so that C T  changes, which results in the change of mutual capacitance C. The sense control circuit detects the change condition of mutual capacitance C in the whole touch area of the touch plane  100 ′ to determine the position and strength of the touched point in the touch area. By reasonable design of the sense control circuit, the sense control circuit can simultaneously detect the distribution situation of multipoint touch on the touch plane  100 ′ and realize the function of multipoint sense touch. The proportion of the change range of the C T  value to mutual capacitance C when touch does not happen is called effective capacitivity. 
     As shown in  FIG. 11 , when the touch screen in the prior art is touched, capacitance C B  between the driving wires  210 ′ and the bottom of the sense wires  310 ′ is not influenced because of touch. Because the bottom of the sense wires  310 ′ is just over against the driving wires  210 ′, the proportion of capacitance C B  to mutual capacitance C is larger, so the effective capacitivity is lower. Generally, the effective capacitivity of the mutual inductance touch screen in the prior art is only about 30%, which makes the signal-to-noise ratio of the touch screen lower, so the complicated sense control circuit is designed to accurately judge the touch condition of the human body or the special touch device to the touch screen, and the design and manufacturing cost of the touch screen is increased. 
     Invention Contents 
     The technical problem the present invention aims to settle is to avoid the defects of the prior art to provide a mutual capacitance touch screen and a combined mutual capacitance touch screen which can greatly increase the effective capacitivity. 
     The present invention solves the technical problem by adopting the following technical schemes: 
     A mutual capacitance touch screen is designed and manufactured. The mutual capacitance touch screen comprises a touch plane made of a transparent insulating medium, a driving layer and a sensor layer which are covered with the touch plane, and a capacitance medium plane which is made of a transparent insulating medium and is held between the driving layer and the sensor layer. Especially, the driving layer comprises plate driving electrodes which are made of transparent conductive materials and distributed at intervals in the same plane; the sensor layer comprises plate sense electrodes which are made of transparent conductive materials and distributed at intervals in the same plane; and the places where the sense electrodes are distributed in the sensor layer are just over against the intervals between the driving electrodes in the driving layer so that the driving electrodes and the sense electrodes together fill the touch area of the touch plane. The driving electrodes are electrically connected with peripheral excitation signal modules of the touch screen, and the sense electrodes are electrically connected with peripheral sense control modules of the touch screen. 
     In order to further increase the effective capacitivity, the touch screen also comprises a shielding layer which is arranged above or below the lower one of the driving layer and the sensor layer or is embedded in the lower layer. The shielding layer comprises plate shielding electrodes made of transparent conductive materials and shielding electrode lead-out wires, the shielding electrodes are just over against the areas occupied by the electrodes in the higher one of the driving layer and the sensor layer, the shielding electrodes electrically hang, or all shielding electrodes are earthed or electrically connected with the peripheral direct current sources of the touch screen by the shielding electrode lead-out wires. 
     In order to further increase the effective capacitivity, the touch screen also comprises a dummy electrode layer which is arranged above or below the higher one of the driving layer and the sensor layer or is embedded in the higher layer. The dummy electrode layer comprises plate dummy electrodes made of transparent conductive materials, wherein the dummy electrodes are just over against the areas occupied by the electrodes of the lower one of the driving layer and the sensor layer. 
     The mutual capacitance touch screen also comprises driving electrode connecting wires and sense electrode connecting wires which are made of transparent conductive materials, and driving electrode lead-out wires and sense electrode lead-out wires. The driving electrodes are grouped and connected in series through the driving electrode connecting wires, and the position relation between the driving electrode connecting wires in the driving layer comprises collinearity and parallelism. The sense electrodes are grouped and connected in series through the sense electrode connecting wires, the position relation between the sense electrode connecting wires in the sensor layer comprises collinearity and parallelism, and the driving electrode connecting wires are perpendicular to the sense electrode connecting wires. Each driving electrode group is electrically connected with peripheral excitation signal modules of the touch screen by the driving electrode lead-out wires, and each sense electrode group is electrically connected with peripheral sense control modules of the touch screen by the sense electrode lead-out wires. 
     The shapes of the driving electrodes and the sense electrodes can be designed by adopting the following specific proposals: each driving electrode is a rectangular electrode of the same size; each sense electrode is a rectangular electrode of the same size; or, each driving electrode is a rhombic electrode of the same size, and each sense electrode is a rhombic electrode of the same size; or, each driving electrode is a hexagonal electrode of the same size, and each sense electrode is a rhombic electrode of the same size. 
     On the basis of the mutual capacitance touch screen, the present invention provides a combined mutual capacitance touch screen, which can be realized by adopting the following technical proposals: 
     A combined mutual capacitance touch screen is designed and manufactured. The combined mutual capacitance touch screen comprises a touch panel made of transparent insulating media and especially at least two mutual capacitance touch units which are covered with the touch panel and arranged closely, wherein the mutual capacitance touch units together fill the touch area of the touch panel. Each of the mutual capacitance touch units comprises a driving layer, a sensor layer and a capacitance medium plane which is held between the driving layer and the sensor layer and made of transparent insulating media. The driving layer comprises plate driving electrodes which are made of transparent conductive materials and distributed at intervals in the same plane, and the sensor layer comprises plate sense electrodes which are made of transparent conductive materials in the same plane. The places where the sense electrodes are distributed in the sensor layer are just over against the intervals between the driving electrodes in the driving layer so that the driving electrodes and the sense electrodes together fill the touch area of each of the mutual capacitance touch units. The driving electrodes are electrically connected with peripheral excitation signal modules of the combined mutual capacitance touch screen, which are corresponding to the mutual capacitance touch units where the driving electrodes are placed, and the sense electrodes are electrically connected with peripheral sense control modules of the combined mutual capacitance touch screen, which are corresponding to the mutual capacitance touch units where the sense electrodes are placed. 
     The combined mutual capacitance touch screen also comprises shielding layer connecting wires and shielding layer lead-out wires which are made of transparent conductive materials. Each of the mutual capacitance touch unit comprises a shielding layer which is arranged above or below the lower one of the driving layer and the sense layer or embedded in the lower layer. The shielding layer comprises plate shielding electrodes made of transparent conductive materials and shielding electrode lead-out wires, and the shielding electrodes are just over against the areas occupied by the electrodes of the higher one of the driving layer and the sense layer. The shielding electrodes electrically hang; or, respective shielding layers of the mutual capacitance touch units are electrically connected together by the shielding layer connecting wires, and earthed by the shielding layer lead-out wires or electrically connected with peripheral direct current sources of the combined mutual capacitance touch screen; or, respective shielding electrodes of the mutual capacitance touch units are earthed by the shielding electrode lead-out wires or electrically connected with peripheral direct current sources of the combined mutual capacitance touch screen. 
     Each of the mutual capacitance touch units also comprises a dummy electrode layer which is arranged above or below the higher one of the driving layer and the sense layer or is embedded in the higher layer. The dummy electrode layer comprises plate dummy electrodes made of transparent conductive materials, wherein the dummy electrodes are just over against the areas occupied by the electrodes of the lower one of the driving layer and the sensor layer. 
     Compared with those in the prior art, the mutual capacitance touch screen and the combined mutual capacitance touch screen have the technical effects that: 
     The driving electrodes are not over against the sense electrodes in terms of space positions to greatly reduce capacitance C B  formed between the driving electrodes and the bottom of the sense electrodes and increase the proportion of capacitance C T  formed between the driving electrodes and the top of the sense electrodes to mutual capacitance C; consequently, the proportion of C T  change resulted from touch sense to mutual capacitance C at the time of no touch is increased, and the effective capacitivity of the mutual capacitance touch screen is effectively increased; 
     the shielding electrodes and the dummy electrodes can improve electric fields between the driving electrodes and the sense electrodes to reduce capacitance C B  in mutual capacitance C and increase capacitance C T , and the effective capacitivity of the mutual capacitance touch screen is further increased; the dummy electrodes can also make the light transmittance of the mutual capacitance touch screen consistent to increase the performance of the mutual capacitance touch screen; 
     in addition, the combined mutual capacitance touch screen provides a structure of a large-area touch screen to solve the problem of bandwidth reduction of mutual capacitance paths, which is caused by over resistance resulted from the connection of too many driving electrodes or sense electrodes together. 
    
    
     
       DESCRIPTION OF FIGURES 
         FIG. 1  relates to schematic diagrams of the structure and the principle of the first preferred embodiment of the present invention “mutual capacitance touch screen”, including: 
         FIG. 1-1  shows the front schematic diagram of the orthographic projection of the sensor layer  300  of the first preferred embodiment; 
         FIG. 1-2  shows the front schematic diagram of the orthographic projection of the driving layer  200  of the first preferred embodiment; 
         FIG. 1-3  shows the front schematic diagram of the orthographic projection of the first preferred embodiment; 
         FIG. 1-4  shows the A-A section schematic diagram of  FIG. 1-3 ; 
         FIG. 1-5  shows the schematic diagram of electric field distribution when the point O 1  in  FIG. 1-4  is not touched; 
         FIG. 1-6  shows the schematic diagram of electric field distribution when the point O 1  in  FIG. 1-4  is touched; 
         FIG. 2  relates to schematic diagrams of the structure and the principle of the second preferred embodiment of the present invention “mutual capacitance touch screen”, including: 
         FIG. 2-1  shows the front schematic diagram of the orthographic projection of the shielding layer  400  of the second preferred embodiment; 
         FIG. 2-2  shows the front schematic diagram of the orthographic projection of the driving layer  200  and the shielding layer  400  of the second preferred embodiment, which are embedded together. 
         FIG. 2-3  shows the bottom section schematic diagram of the orthographic projection of the second preferred embodiment; 
         FIG. 2-4  shows the schematic diagram of electric field distribution when the point O 2  in  FIG. 2-3  is not touched; 
         FIG. 2-5  shows the schematic diagram of electric field distribution when the point O 2  in  FIG. 2-3  is touched; 
         FIG. 3  relates to schematic diagrams of the connection modes between the driving layer  200 , the shielding layer  400  and peripheral devices of the touch screen of the second preferred embodiment; specifically, four connection modes are included in  FIG. 3-1  to  FIG. 3-4 ; 
         FIG. 4  relates to schematic diagrams of the structure and the principle of the third preferred embodiment of the present invention “mutual capacitance touch screen”, including: 
         FIG. 4-1  shows the front schematic diagram of the orthographic projection of the dummy electrode layer  500  of the third preferred embodiment; 
         FIG. 4-2  shows the front schematic diagram of the orthographic projection of the sensor layer  300  and the dummy electrode layer  500  of the third preferred embodiment, which are embedded together; 
         FIG. 4-3  shows the bottom section schematic diagram of the orthographic projection of the third preferred embodiment; 
         FIG. 4-4  shows the schematic diagram of electric field distribution when the point O 3  in  FIG. 4-3  is not touched; 
         FIG. 4-5  shows the schematic diagram of electric field distribution when the point O 3  in  FIG. 4-3  is touched; 
         FIG. 5  relates to schematic diagrams of the structure and the principle of the fourth preferred embodiment of the present invention “mutual capacitance touch screen”, including: 
         FIG. 5-1  shows the bottom section schematic diagram of the orthographic projection of the fourth preferred embodiment; 
         FIG. 5-2  shows the schematic diagram of electric field distribution when the point O 4  in  FIG. 5-1  is not touched; 
         FIG. 5-3  shows the schematic diagram of electric field distribution when the point O 4  in  FIG. 5-1  is touched; 
         FIG. 6  relates to schematic diagrams of the fifth preferred embodiment of the present invention “mutual capacitance touch screen”, including: 
         FIG. 6-1  shows the front schematic diagram of the orthographic projection of the driving layer  200  of the fifth preferred embodiment; 
         FIG. 6-2  shows the front schematic diagram of the orthographic projection of the sensor layer  300  of the fifth preferred embodiment; 
         FIG. 6-3  shows the front schematic diagram of the orthographic projection of the shielding layer  400  of the fifth preferred embodiment; 
         FIG. 6-4  shows the front schematic diagram of the orthographic projection of the dummy electrode layer  500  of the fifth preferred embodiment; 
         FIG. 6-5  shows the section schematic diagram of the fifth preferred embodiment in the B-B direction in  FIG. 6-1 . 
         FIG. 7  shows schematic diagram of the sixth preferred embodiment of the present invention “mutual capacitance touch screen”, including: 
         FIG. 7-1  shows the front schematic diagram of the orthographic projection of the driving layer  200  of the sixth preferred embodiment; 
         FIG. 7-2  shows the front schematic diagram of the orthographic projection of the sensor layer  300  of the sixth preferred embodiment; 
         FIG. 7-3  shows the front schematic diagram of the orthographic projection of the shielding layer  400  of the sixth preferred embodiment; 
         FIG. 7-4  shows the front schematic diagram of the orthographic projection of the dummy electrode layer  500  of the sixth preferred embodiment; 
         FIG. 7-5  shows the section schematic diagram of the sixth preferred embodiment in the C-C direction in  FIG. 7-1 . 
         FIG. 8  relates to schematic diagrams of the seventh preferred embodiment of the combined mutual capacitance touch screen of the present invention, including: 
         FIG. 8-1  shows the front schematic diagram of the orthographic projection of the seventh preferred embodiment; 
         FIG. 8-2  shows the bottom schematic diagram of the orthographic projection of the seventh preferred embodiment. 
         FIG. 9  relates to schematic diagrams of the eighth preferred embodiment of the present invention “combined mutual capacitance touch screen”, including: 
         FIG. 9-1  shows the front schematic diagram of the orthographic projection of the eighth preferred embodiment; 
         FIG. 9-2  shows the bottom schematic diagram of the orthographic projection of the eighth preferred embodiment. 
         FIG. 10  relates to schematic diagrams of the ninth preferred embodiment of the present invention “combined mutual capacitance touch screen”, including: 
         FIG. 10-1  shows the front schematic diagram of the orthographic projection of the ninth preferred embodiment; 
         FIG. 10-2  shows the bottom schematic diagram of the orthographic projection of the ninth preferred embodiment. 
         FIG. 11  relates to schematic diagrams of the structure and the principle of the mutual capacitance touch screen in the prior art, including: 
         FIG. 11-1  shows the front schematic diagram of the orthographic projection of the touch screen; 
         FIG. 11-2  shows the bottom section schematic diagram of  FIG. 11-1 ; 
         FIG. 11-3  shows the schematic diagram of electric field distribution when the touch screen is not touched; 
         FIG. 11-4  shows the schematic diagram of electric field distribution when the touch screen is touched. 
     
    
    
     MODE OF CARRYING OUT THE INVENTION 
     All the preferred embodiments are further detailed as follows in conjunction with the figures. 
     The present invention relates to a mutual capacitance touch screen for covering the surface of a display screen of a graphical or videographic display device and controlling the contents displayed by the graphical or videographic display device through a peripheral control device. As shown in  FIG. 1  to  FIG. 7 , the mutual capacitance touch screen comprises the touch plane  100  made of transparent insulating media, the driving layer  200  and the sensor layer  300  covered with the touch plane  100 , and the capacitance medium plane  910  which is made of transparent insulating media and held between the driving layer  200  and the sensor layer  300 . In addition, a protection plane  120  made of transparent insulating materials can also be arranged, and the driving layer  200 , the sensor layer  300  and the capacitance medium plane  910  are arranged between the touch plane  100  and the protection plane  120  which comes into contact with the display screen of the graphical or videographic display device. 
     The driving layer  200  comprises plate driving electrodes  210  which are made of transparent conductive materials and distributed at intervals in the same plane; the sensor layer  300  comprises plate sense electrodes  310  which are made of transparent conductive materials and distributed at intervals in the same plane; and the places where the sense electrodes  310  are distributed in the sensor layer  300  are just over against the intervals between the driving electrodes  210  in the driving layer  200  so that the driving electrodes  210  and the sense electrodes  310  together fill the touch area  110  of the touch plane  100 . The driving electrodes  210  are electrically connected with the peripheral excitation signal modules  600  of the touch screen, and the sense electrodes  310  are electrically connected with the peripheral sense control modules  700  of the touch screen. 
     The driving electrodes  210  and the sense electrodes  310  of the mutual capacitance touch screen can not be just over against each other, so capacitance C B  formed between the driving electrodes  210  and the bottom of the sense electrodes  310  is smaller than capacitance C B  formed between the driving wires  210 ′ and the bottom of the sense wires  310 ′ in the prior art. As a result, the proportion of capacitance C B  of the present invention to mutual capacitance C is small so that the effective capacitivity of mutual capacitance C is raised. 
     The shapes and the situations of connection distribution in the corresponding driving layer  200  and the corresponding sensor layer  300  of the driving electrodes  210  and the sense electrodes  310  of the mutual capacitance touch screen can be varied, and the present invention discloses several shapes and situations of connection distribution, which are suitable for application and practice of the first preferred embodiment to the seventh preferred embodiment. 
     The mutual capacitance touch screen in each preferred embodiment adopts the following technical proposal: the mutual capacitance touch screen also comprises the driving electrode connecting wires  220  and the sense electrode connecting wires  320  which are made of transparent conductive materials, the driving electrode lead-out wires  230  and the sense electrode lead-out wires  330 ; the driving electrodes  210  are grouped and connected in series by the driving electrode connecting wires  220  which are mutually collinear or parallel in the driving layer  200 ; the sense electrodes  310  are grouped and connected in series by the sense electrode connecting wires  320  which are mutually collinear or parallel in the sensor layer  300 ; the driving electrode connecting wires  220  are perpendicular to the sense electrode connecting wires  320 ; each driving electrode group  240  is electrically connected with the peripheral excitation signal module  600  of the touch screen by the driving electrode lead-out wires  230 ; and each sense electrode group  340  is electrically connected with the peripheral sense control modules  700  by the sense electrode lead-out wires  330 . As shown in  FIGS. 1 to 7 , the position relation of the driving electrode connecting wires  220  or the sense electrode connecting wires  320  comprises collinearity and parallelism in each preferred embodiment; namely, the geometric centers of the driving electrodes  210  in the driving electrode groups  240  and the driving electrode connecting wires  220  are on the same straight line, and the straight lines on which the driving electrode connecting wires  220  of the driving electrode groups  240  are positioned are mutually parallel; the geometric centers of the sense electrodes  310  in the sense electrode groups  340  and the sense electrode connecting wires  320  are on the same straight line, and the straight lines on which the sense electrode connecting wires  320  of the sense electrode groups  340  are positioned are mutually parallel; and that is, for the driving electrode connecting wires  220  in the driving layer  200  and the sense electrode connecting wires  320  in the sensor layer  300 , the electrode connecting wires in the electrode groups are collinear, and the electrode connecting wires between the electrode groups are parallel. 
     In the first preferred embodiment as shown in  FIG. 1 , each driving electrode  210  is a rectangular driving electrode  211 , and  25  rectangular driving electrodes  211  exist; and each sense electrode  310  is a rectangular sense electrodes  311 , and  36  rectangular sense electrodes  311  exist. 
     As shown in  FIG. 1-1 , the rectangular sense electrodes  311  are grouped and connected in series in six sense electrode groups  340  through sense electrode connecting wires  320 , and the geometric centers of the rectangular sense electrodes  311  in each sense electrode group  340  and the connecting wires  320  of the rectangular sense electrodes  310  are on the same straight line; the straight lines on which the sense electrode connecting wires  320  in the sense electrode groups  340  are positioned are mutually parallel. Each sense electrode group  340  is electrically connected with the peripheral sense control modules  700  of the touch screen by the sense electrode lead-out wires  330 . 
     As shown in  FIG. 1-2 , the rectangular driving electrodes  211  are grouped and connected in series in five driving electrode groups  240  by the driving electrode connecting wires  220 , and the geometric centers of the rectangular driving electrodes  211  in each driving electrode group  240  and the driving electrode connecting wires  220  are on the same straight line; the straight lines on which the driving electrode connecting wires  220  in the driving electrode groups  240  are positioned are mutually parallel. Each driving electrode group  240  is electrically connected with the peripheral excitation signal modules  600  of the touch screen by the driving electrode lead-out wires  230 . 
     As shown in  FIG. 1-3 , the places where the rectangular sense electrodes  311  are distributed in the sensor layer  300  are just over against the intervals between the rectangular driving electrodes  211  in the driving layer  200 , and the rectangular driving electrodes  211  and the rectangular sense electrodes  311  together fill the touch area  110  of the touch screen. The driving electrode connecting wires  220  are perpendicular to the sense electrode connecting wires  320 . 
     As shown in  FIGS. 1-3  and  1 - 4 , the areas occupied by the rectangular sense electrodes  311  and the areas occupied by the rectangular driving electrodes  211  are complementary in the entire touch area  110  so that the rectangular sense electrodes  311  can not be just over against the rectangular driving electrodes  211 . 
     In terms of the point O 1  shown in  FIG. 1-4 , when the point O 1  is not touched, the situation of electric field distribution at the point O 1  is shown in  FIG. 1-5 ; when the point O 1  is touched by the finger  150 , the situation of electric field distribution at the point O 1  is shown in  FIG. 1-6 . Because the bottom of the rectangular sense electrodes  311  is not just over against the rectangular driving electrodes  211 , the value of capacitance C B  formed between the bottom of the rectangular sense electrodes  311  and the rectangular driving electrodes  211  is much smaller than that in the prior art; namely, the proportion of capacitance C B  formed between the bottom of the rectangular sense electrodes  311  and the rectangular driving electrodes  211  to mutual capacitance C at the point O 1  is greatly reduced so that the effective capacitivity of mutual capacitance C of the mutual capacitance touch screen is effectively increased. 
     The second preferred embodiment is shown in  FIG. 2 : The driving layer  200  and the sensor layer  300  are exactly the same as those of the first example embodiment but the shielding layer  400  is added, wherein the shielding layer  400  is arranged above or below the lower one of the driving layer  200  and the sensor layer  300  or is embedded in the lower layer. The shielding layer  400  comprises the plate shielding electrodes  410  made of transparent conductive materials, and the shielding electrodes  410  are just over against the areas occupied by the electrodes in the higher one of the driving layer  200  and the sensor layer  300 . 
     In the preferred embodiment, the sensor layer  300  is positioned above the driving layer  200 ; consequently, as shown in  FIG. 2-1 , the places where the shielding electrodes  410  are distributed in the shielding layer  400  are over against the areas occupied by the sense electrodes  310  in the sensor layer  300 , and the shielding electrodes  410  are connected into six shielding electrodes  410 ; to tell from another angle, the places where the shielding electrodes  410  are distributed in the shielding layer  400  are just over against the intervals between the driving electrodes  210  in the driving layer  200 . 
     As shown in  FIG. 2-2 , the areas occupied by the shielding electrodes  410  and the rectangular driving electrodes  211  are complementary. In the example embodiment, the shielding layer  400  and the driving layer  200  are embedded as shown in  FIG. 2-3 ; namely, the shielding layer  400  and the driving layer  200  are in the same layer. 
     In terms of the point O 2  shown in  FIG. 2-3 , when the point O 2  is not touched, the situation of electric field distribution at the point O 2  is shown in  FIG. 2-4 ; when the point O 2  is touched by the finger  150 , the situation of electric field distribution at the point O 2  is shown in  FIG. 2-5 . As shown in  FIGS. 2-4  and  2 - 5 , the action of the shielding electrode  410  is to change the electric fields at the bottom of the rectangular sense electrodes  311  so as to further reduce the capacitance formed between the bottom of the rectangular sense electrodes  311  and the rectangular driving electrodes  211 , which can be understood in the way that the shielding electrodes  410  suck part of the electric field lines in the electric fields of the rectangular driving electrodes  211  and the bottom of the rectangular sense electrodes  311 . 
     The shielding electrodes  410  can electrically hang; namely, the shielding electrodes  410 , are not electrically connected with any peripheral excitation signal, alternating current ground and direct current source of the mutual capacitance touch screen. The following proposal can also be adopted: as shown in  FIG. 3 , the shielding layer  400  also comprises the shielding electrode lead-out wires  430 , and the shielding electrodes  410  are earthed or electrically connected with the peripheral direct current sources  800  of the touch screen by the shielding electrode lead-out wires  430 . In addition, in order to reduce the number of the shielding electrode lead-out wires  430 , all the shielding electrodes  410  are electrically connected with the direct current sources  800  or directly connected with the alternating current grounds generally by one or two shielding electrode lead-out wires  430 . Meanwhile, the shielding electrode lead-out wires  430 , the driving electrode lead-out wires  230  and the sense electrode lead-out wires  330  are prevented from being crossed as much as possible. In terms of the second example embodiment, four lead-out situations of the shielding electrode lead-out wires  430  are shown in  FIG. 3 , wherein  FIGS. 3-1  and  3 - 2  show that all the shielding electrodes  410  are electrically connected with the alternating current ground or the direct current sources  800  by two shielding electrode lead-out wires  430 , and  FIGS. 3-3  and  3 - 4  show that all the shielding electrodes  410  are electrically connected with the alternating current grounds by one shielding electrode lead-out wire  430 . In terms of other preferred embodiments with the shielding layer  400 , the way in which the shielding electrodes  410  are earthed or electrically connected with the peripheral direct current sources  800  of the touch screen can be any one shown in  FIG. 4  and also can be other ways in which the shielding electrode lead-out wires  430  and the driving electrode lead-out wires  230  are mutually disjoint in space. 
     In terms of the third preferred embodiment as shown in  FIG. 4 , the driving layer  200  and the sensor layer  300  are exactly the same as those of the first preferred embodiment but the dummy electrode layer  500  is added, wherein the dummy electrode layer  500  is arranged above or below the higher one of the driving layer  200  and the sensor layer  300  or is embedded in the higher layer. The dummy electrode layer  500  comprises the plate dummy electrodes  510  made of transparent conductive materials, and the dummy electrodes  510  are just over against the areas occupied by the electrodes in the lower one of the driving layer  200  and the sensor layer  300 . 
     In the preferred embodiment, the driving layer  200  is positioned below the sensor layer  300 ; consequently, as shown in  FIG. 4-1 , the dummy electrodes  510  are just over against the areas occupied by the electrodes in the sensor layer  200 ; to tell from another angle, the places where the dummy electrodes  510  are distributed in the shielding layer  400  are just over against the areas occupied by the driving electrodes  210  in the driving layer  200 . The places where a plurality of dummy electrodes  510  filling the area can be distributed or only one dummy electrode  510  can also be arranged in the dummy electrode layer  500  are just over against the area of some driving electrode  210  of the driving layer  200 . In the preferred embodiment, the places where sixteen dummy electrodes  510  with smaller area are closely distributed in the dummy electrode layer  500  are over against the driving electrode  210 , and the structure can make the electric fields distributed more uniformly, which is favorable for touch sense. The dummy electrodes are not mutually connected or electrically connected with any signal excitation source, direct current source or ground wire like common electrodes but are in the electrically hanging state, so the name of a dummy electrode or Dummy Cell is given. 
     As shown in  FIG. 4-2 , the areas occupied by the dummy electrodes  410  and the rectangular sense electrodes  311  are complementary. In the preferred embodiment, the dummy electrode layer  500  and the sensor layer  300  are embedded as shown in  FIG. 4-3 ; namely, the dummy electrode layer  500  and the sensor layer  300  are in the same layer. 
     In terms of the point O 3  shown in  FIG. 4-3 , when the point O 3  is not touched, the situation of electric field distribution at the point O 3  is shown in  FIG. 4-4 ; when the point O 3  is touched by the finger  150 , the situation of electric field distribution at the point O 3  is shown in  FIG. 5-5 . As shown in  FIGS. 4-4  and  4 - 5 , the action of the dummy electrodes  510  is to change the electric field at the top of the rectangular sense electrode  311  so that capacitance C T  formed between the top of the rectangular sense electrode  311  and the rectangular driving electrodes  211  is increased to further widen the range of C T , which can be understood in the way that the dummy electrodes  510  increase electric field lines of the electric field of the rectangular driving electrodes  211  and the top of the rectangular sense electrode  311 ; in addition, the action of the dummy electrode  510  is to make the light transmittances of the touch screen consistent. 
     The fourth preferred embodiment is shown in  FIG. 5 : the driving layer  200  and the sensor layer  300  are exactly the same as those of the first preferred embodiment, but the shielding layer  400  which is the same as that of the second preferred embodiment and the dummy electrode layer  500  which is the same as that of the third preferred embodiment are added. 
     As shown in  FIG. 5-1 , the shielding layer  400  and the driving layer  200  are embedded together, and the dummy electrode layer  500  and the sense layer  300  are embedded together. 
     In terms of the point O 4  shown in  FIG. 5-1 , when the point O 4  is not touched, the situation of electric field distribution at the point O 4  is shown in  FIG. 5-2 ; when the point O 4  is touched by the finger  150 , the situation of electric field distribution at the point O 4  is shown in  FIG. 5-3 . As shown in  FIGS. 6-2  and  5 - 3 , under the combined action of the shielding electrodes  410  and the dummy electrodes  510 , capacitance C B  formed between the bottom of the rectangular sense electrodes  311  and the rectangular driving electrodes  211  is further reduced, and capacitance C T  formed between the top of the rectangular sense electrodes  311  and the rectangular driving electrodes  211  is further increased so that the effective capacitivity of mutual capacitance C is further increased. 
     The fifth preferred embodiment is shown in  FIG. 6 : The mutual capacitance touch screen comprises the driving layer  200 , the sensor layer  300 , the shielding layer  400  and the dummy electrode layer  500 . 
     As shown in  FIG. 6-1 , the driving layer  200  comprises the driving electrodes  210  which are rhombic driving electrodes  212 , and the preferred embodiment has 25 rhombic driving electrodes  212 . The rhombic driving electrodes  212  are grouped and connected in series in five driving electrode groups  240  through the driving electrode connecting wires  220 , wherein the geometric centers of the rhombic driving electrodes  212  in each driving electrode group  240  and the driving electrode connecting wires  220  are on the same straight line, and the straight lines on which the connecting wires  220  of the driving electrodes in the driving electrode groups  240  are positioned are parallel. The situations of electrical connection between the driving electrode groups  240  and the peripheral excitation signal modules  600  of the touch screen are the same as those of the first preferred embodiment. 
     As shown in  FIG. 6-2 , the driving layer  300  comprises the sense electrodes  310  which are rhombic driving electrodes  312 , and the preferred embodiment has 36 rhombic sense electrodes  312 . The rhombic sense electrodes  312  are grouped and connected in series in six sense electrode groups  340  through the sense electrode connecting wires  320 , wherein the geometric centers of the rhombic sense electrodes  312  in each sense electrode group  340  and the rhombic sense electrode connecting wires  320  are on the same straight line, and the straight lines on which the sense electrode connecting wires  320  in the sense electrode groups  340  are positioned are parallel. The situations of electrical connection between the sense electrode groups  340  and the peripheral sense control modules  700  of the touch screen are the same as those of the first preferred embodiment. 
     The places where the rhombic sense electrodes  312  are distributed in the sensor layer  300  are just over against the intervals between the rhombic driving electrodes  212  in the driving layer  200  so that the rhombic driving electrodes  212  and the rhombic sense electrodes  312  together fill the touch area  110  of the touch screen. The connecting wires  220  of the driving electrodes are perpendicular to the sense electrode connecting wires  320 . 
     In the fifth preferred embodiment, the driving layer  200  is positioned above the sensor layer  300 ; as shown in  FIG. 6-3 , the shielding layer  400  comprises the plate shielding electrodes  410  made of transparent conductive materials, and the shielding electrodes  410  are just over against the areas occupied by the rhombic driving electrodes  212  in the driving layer  200 ; namely, the places where the shielding electrodes  410  are distributed in the shielding layer  400  are just over against the intervals between the sense electrodes  310  in the sensor layer  300 . The action of the shielding layer  400  of the preferred embodiment is basically the same as that of the second and fourth preferred embodiments. 
     In the fifth preferred embodiment, the driving layer  200  is positioned above the sensor layer  300 ; as shown in  FIG. 6-4 , the dummy electrode layer  500  comprises plate dummy electrodes  510  which are made of transparent conductive materials and distributed at intervals, the dummy electrodes  510  of the preferred embodiment are rhombic, and the dummy electrodes  510  are just over against the areas occupied by the rhombic sense electrodes  312  in the sensor layer  300 ; namely, the places where the dummy electrodes  510  are distributed in the dummy electrode layer  500  are just over against the intervals between the driving electrodes  210  in the driving layer  200 . At the places of the dummy electrode layer  500  which are just over against certain sense electrode  310  of the sensor layer  300 , only one dummy electrode  510  is used. The action of the dummy electrode layer  500  of the preferred embodiment is basically the same as that of the third and fourth preferred embodiments. 
     As shown in  FIG. 6-5 , the dummy electrode layer  500  is positioned above the driving layer  200 , and the shielding layer  400  is positioned below the sensor layer  300 . Mutual capacitance C formation and the situation of electric field distribution of the preferred embodiment are basically the same as those of the fourth preferred embodiment, so the embodiment can effectively improve the effective capacitivity of mutual capacitance C. 
     The sixth preferred embodiment is shown in  FIG. 7 : The mutual capacitance touch screen comprises the driving layer  200 , the sensor layer  300 , the shielding layer  400  and the dummy electrode layer  500 . 
     As shown in  FIG. 7-1 , the driving layer  200  comprises the driving electrodes  210  which are hexagonal driving electrodes  213 , and the preferred embodiment has 16 hexagonal driving electrodes  213 . The hexagonal driving electrodes  213  are grouped and connected in series in four driving electrode groups  240  through the driving electrode connecting wires  220 , wherein the geometric centers of the hexagonal driving electrodes  213  of the driving electrode groups  240  and the driving electrode connecting wires  220  are on the same straight line, and the straight lines on which the driving electrode connecting wires  220  in the driving electrode groups  240  are positioned are parallel. The situations of electrical connection between the driving electrode groups  240  and the peripheral excitation signal modules  600  of the touch screen are the same as those of the first preferred embodiment. 
     As shown in  FIG. 7-2 , the sensor layer  300  comprises the sense electrodes  310  which are rhombic sense electrodes  313 , and the preferred embodiment has 25 rhombic sense electrodes  313 . The rhombic sense electrodes  313  are grouped and connected in series in five sense electrode groups  340  through the sense electrode connecting wires  320 , wherein the geometric centers of the rhombic sense electrodes  313  in each sense electrode group  340  and the rhombic sense electrode connecting wires  320  are on the same straight line, and the straight lines on which the sense electrode connecting wires  320  in the sense electrode groups  340  are positioned are parallel. The situations of electrical connection between the sense electrode groups  340  and the peripheral sense control modules  700  of the touch screen are the same as those of the first preferred embodiment. 
     The places where the rhombic sense electrodes  313  are distributed in the sensor layer  300  are just over against the intervals between the hexagonal driving electrodes  213  in the driving layer  200  so that the hexagonal driving electrodes  213  and the rhombic sense electrodes  313  together fill the touch area  110  of the touch screen. The driving electrode connecting wires  220  are perpendicular to the sense electrode connecting wires  320 . 
     In the sixth preferred embodiment, the driving layer  200  is positioned below the sensor layer  300 ; as shown in  FIG. 7-3 , the shielding layer  400  comprises plate shielding electrodes  410  which are made of transparent conductive materials, and the shielding electrodes  410  are just over against the areas occupied by the sense electrodes  310  in the sensor layer  300 ; namely, the places where the shielding electrodes  410  are distributed in the shielding layer  400  are just over against the intervals between the driving electrodes  210  in the driving layer  200 . The action of the shielding layer  400  of the preferred embodiment is basically the same as that of the second and fourth preferred embodiments. 
     In the sixth preferred embodiment, the driving layer  200  is positioned below the sensor layer  300 ; as shown in  FIG. 7-4 , the dummy electrode layer  500  comprises the plate dummy electrodes  510  which are made of transparent conductive materials and distributed at intervals, wherein the dummy electrodes  510  are just over against the areas occupied by the driving electrodes  210  in the driving layer  200 ; namely, the places where the dummy electrodes  510  are distributed in the dummy electrode layer  500  are just over against the intervals between the sense electrodes  310  in the sensor layer  300 . The dummy electrode  510  of the preferred embodiment is in the shape of a triangle, and six dummy electrodes  510  need to be arranged in the places of the dummy electrode layer  500 , which are just over against the places where one hexagonal driving electrode  213  is positioned in the driving layer  200 ; as stated above, owing to the design, the area of the dummy electrode  510  is reduced, and the electric field distribution is uniform, which is favorable for touch sense. The action of the dummy electrode layer  500  of the preferred embodiment is basically the same as that of the third and fourth preferred embodiments. 
     As shown in  FIG. 7-5 , the dummy electrode layer  500  is positioned below the sensor layer  300 , and the shielding layer  400  is positioned above the driving layer  200 . Mutual capacitance C formation and the situation of electric field distribution of the preferred embodiment are basically the same as those of the fourth preferred embodiment, so the preferred embodiment can effectively increase the effective capacitivity of mutual capacitance C. 
     The present invention also relates to a combined mutual capacitance touch screen which is applicable to the touch screen with larger area. When the area of the mutual capacitance touch screen is larger, the number of the driving electrodes and sense electrodes needs to be increased, over resistance caused by long electrode group results in the reduction of the bandwidth of the mutual capacitance paths, which brings inconvenience to circuit driving and sensing. In order to avoid the situation, the present invention provides the combined mutual capacitance touch screen which is formed by the combination of mutual capacitance touch screens. 
     As shown in  FIGS. 8 to 10 , the combined mutual capacitance touch screen comprises a touch panel  1100  made of transparent insulating media, particularly at least two mutual capacitance touch units  1000  which are covered with the touch panel  1100  and distributed closely, and the mutual capacitance touch units  1000  together fill the touch area of the touch panel  1100 . The structure of the mutual capacitance touch units  1000  similar to that of the mutual capacitance touch screen comprises the driving layer  200 , the sensor layer  300 , and a capacitance medium plane  910  which is made of transparent insulating media and is held between the driving layer  200  and the sensor layer  300 . The driving layer  200  comprises plate driving electrodes  210  which are made of transparent conductive materials and distributed at intervals in the same plane; the sensor layer  300  comprises plate sense electrodes  310  which are made of transparent conductive materials and distributed at intervals in the same plane; the places where the sense electrodes  310  are distributed in the sensor layer  300  are just over against the intervals between the driving electrodes  210  in the driving layer  200  so that the driving electrodes  210  and the sense electrodes  310  together fill the touch area  110  of the mutual capacitance touch units  1000  occupied by the driving electrodes  210  and the sense electrodes  310 ; and the driving electrodes  210  are electrically connected with the peripheral excitation signal modules  600  of the combined mutual capacitance touch screen and are corresponding to the mutual capacitance touch units  1000  where the sense electrodes  310  are placed, and the sense electrodes  310  are electrically connected with the peripheral sense control modules  700  of the combined mutual capacitance touch screen and are corresponding to the mutual capacitance touch units  1000  where the sense electrodes  310  are placed. 
     The seventh preferred embodiment is shown in  FIG. 8 : The combined mutual capacitance touch screen comprises four mutual capacitance touch units  1000 , and the structures of the driving layer  200  and the sensor layer  300  of each mutual capacitance touch unit  1000  can use any one of the structures in the preferred embodiments 1 to 6. The combined mutual capacitance touch screen collects the capacitance distribution data of the mutual capacitance touch units  1000  respectively through the peripheral control circuit, and accurately judges the touched condition on the whole touch panel  1100  by data summarization and analysis. 
     The eighth preferred embodiment is shown in  FIG. 9 : On the basis of the seventh preferred embodiment, the shielding layer  400  is added to each mutual capacitance touch unit  1000 , wherein the shielding layer  400  is arranged above or below the lower one of the driving layer  200  and the sensor layer  300  or is embedded in the lower layer. 
     The shielding layer  400  comprises the plate shielding electrodes  410  made of transparent conductor materials and the shielding electrode lead-out wires  430 , and the shielding electrodes  410  are just over against the areas occupied by the electrodes in the higher one of the driving layer  200  and the sensor layer  300 . The shielding electrodes  410  can electrically hang and can also be connected with alternating current grounds, and the shielding electrodes  410  of the mutual capacitance touch units  1000  are electrically connected with the peripheral direct current sources  800  of the combined mutual capacitance touch screen by the shielding electrode lead-out wires  430  in the preferred embodiment. 
     The ninth preferred embodiment is shown in  FIG. 10 : On the basis of the seventh preferred embodiment, the shielding layer  400  and the dummy electrode layer  500  are added to each mutual capacitance touch unit  1000 . The structure of the shielding layer  400  is the same as that of the eighth preferred embodiment, and the dummy electrode layer  300  is arranged above or below the higher one of the driving layer  200  or the sensor layer  300  or embedded in the higher layer. The dummy electrode layer  500  comprises the plate dummy electrodes  510  made of transparent conductor materials, and the dummy electrodes  510  are just over against the areas occupied by the electrodes in the lower one of the driving layer  200  or the sensor layer  300 . 
     In addition, as shown in  FIG. 10 , the ninth preferred embodiment different from the eighth preferred embodiment also comprises shielding layer connecting wires  1420  made of transparent conductor materials and shielding layer lead-out wires  1430 ; the shielding layers  400  of the mutual capacitance touch units  1000  are electrically connected together by the shielding layer connecting wires  1420  and are earthed by the shielding layer lead-out wires  1430 ; and certainly, the shielding electrodes can electrically hang or can be electrically connected with the peripheral direct current sources of the combined mutual capacitance touch screen. 
     The structures of the driving layer  200 , the sensor layer  300 , the shielding layer  400  and the dummy electrode layer  500  in the preferred embodiments 7 to 9 can refer to the any one of the structures of the preferred embodiments 1 to 6 or any structure conforming to the technical proposal of the present invention. 
     The transparent conductive materials are general materials in the prior art, which comprise Indium Tin Oxide (short for ITO) and Antimony Tin Oxide (short for ATO).