The present invention relates to a liquid crystal display device including an in-cell touch panel.
Conventionally, a display device has been produced which includes a touch panel that has a function to detect a pressed location on a screen. In the past, such a display device including a touch panel was generally configured by attaching a film-shaped touch panel on a display surface of the display device. Meanwhile, recently, a display device including a so-called in-cell touch panel has been actively developed. According to the display device including the in-cell touch panel, wires and the like which are necessary for detecting a pressed location on a screen are incorporated in a display panel that constitutes the display device. Among such display devices, attention is being given to a display device including a so-called electrostatic projection touch panel which is capable of (i) simultaneously detecting a plurality of points and/or (ii) detecting a pressing which is made not only with a finger but also with an artifact such as a pen.
In a case where an in-cell touch panel is provided in a conventional liquid crystal display device, a configuration as below has been generally employed. First, the liquid crystal display device includes a TFT substrate and a color filter substrate. On the TFT substrate, pixel electrodes are provided. On the color filter substrate, a common electrode is provided so as to face the pixel electrodes. The common electrode has a whole sheet shape and is formed on an entire surface of the color filter substrate. According to the configuration, a single common electrode is provided for the pixel electrodes. A drive electrode and a receive electrode (hereinafter, collectively referred to as “detection electrode”), which constitute the touch panel, are provided on the TFT substrate. A pressed location on a display surface is detected by detecting a change in coupling capacitance between the electrodes.
However, such a configuration has a problem that coordinates cannot be detected with high accuracy. The reasons are as follows: A distance between a counter electrode for display and the detection electrode is merely 3 μm to 4 μm. Therefore, a coupling capacitance between the electrodes is extremely large. Meanwhile, a distance between (i) a finger which presses the display surface and (ii) the detection electrode is as long as several millimeters. Therefore, a coupling capacitance between the finger and the detection electrode is extremely small. This causes a change amount of coupling capacitance, which is generated between the drive electrode and the receive electrode when the finger presses the display surface, to be undistinguishable from the coupling capacitance between the counter electrode and the detection electrode. Therefore, an SN ratio obtained when the change amount is detected becomes small, and accordingly coordinates cannot be detected with high accuracy.
In view of this, conventionally, a technique has been proposed in which an in-cell touch panel is provided in a liquid crystal display device which does not include a counter electrode having a whole sheet shape. For example, Patent Literatures 1 and 2 disclose concrete examples of such a technique.
Patent Literature 1 discloses a technique to provide a touch panel in an in-plane-switching (IPS) liquid crystal display device. According to the technique, one of a pair of IPS-based electrodes, which have a comb-teeth shape, is used as a drive electrode or a receive electrode of a touch panel (see FIG. 105 and FIG. 106 of Patent Literature 1).
Patent Literature 2 discloses a technique in which an electrode (a common electrode or a lower electrode) which forms a capacitive element in a pixel is connected to a common voltage line extending in an X direction or a common voltage line extending in a Y direction so that the electrode can be used as a drive electrode or a receive electrode of a touch panel. Both the common electrode and the lower electrode have a comb-teeth shape. A disconnecting part (break) is provided on each of the common voltage lines so as to achieve (i) electrical insulation between the drive electrodes and (ii) electrical insulation between the receive electrodes. This makes it possible to form a drive electrode block and a receive electrode block which have a shape in accordance with locations of the disconnecting parts.
Patent Literature 1: US Patent Application Publication No. US2008/0062139A1 (Publication date: Mar. 13, 2008)
Patent Literature 2: US Patent Application Publication No. US2010/0001973A1 (Publication date: Jan. 7, 2010)
However, according to the techniques of Patent Literatures 1 and 2, an electric potential distribution between the drive electrode and the receive electrode varies depending on whether or not an image is displayed. In order to deal with such a variation, it is necessary to correct a detection signal. The following description will discuss this problem with reference to
(a) of
According to the conventional technique, a pixel electrode 100a having a comb-teeth shape and a common electrode 102a are provided in an identical plane in a certain pixel of a liquid crystal display device (see (a) of
According to the conventional technique, the common electrode 102a serves as a drive electrode of a touch panel, and the common electrode 102b serves as a receive electrode of the touch panel. Hereinafter, the common electrode 102a is referred to as “drive electrode 102a”, and the common electrode 102b is referred to as “receive electrode 102b”.
When an image is displayed, voltages of 0 V to 5 V are applied to the pixel electrode 100a and the pixel electrode 100b, respectively. This voltage varies depending on a material of liquid crystal and on a content to be displayed. Hereinafter, the voltage applied to the pixel electrode 100a is referred to as “V1”, and the voltage applied to the pixel electrode 100b is referred to as “V2” (see (a) of
When a pressing on the display surface is detected, a driving voltage of 3 V to 5 V is applied to the drive electrode 102a. Meanwhile, no voltage is applied to the receive electrode 102b. Hereinafter, the voltage applied to the receive electrode 102b is referred to as “V3”, and the voltage applied to the receive electrode 102b is referred to as “V4”.
In a case where V3=3 V and V4=0 V, lines of electric force 104 are generated between the drive electrode 102a and the receive electrode 102b in order to sense a touch (see (b) of
On the other hand, in a case where no image is displayed, V1=0V (see (c) of
As above described, according to the conventional technique, an electric potential of a pixel electrode varies depending on whether or not an image is displayed. Due to the variation in electric potential, an electric potential distribution between the drive electrode 102a and the receive electrode 102b is changed depending on whether or not an image is displayed. This causes lines of electric force, which contribute to sensing, to be increased or decreased, and accordingly a signal, which is generated when a pressing is detected, is increased or decreased depending on whether or not an image is displayed. In view of this, a technique is required in which a detection signal, which is generated when a pressing is detected, is corrected in accordance with an image to be displayed.
According to the technique of Patent Literature 2, it is necessary to provide a disconnecting part on the common voltage line. This restricts a shape of the electrode block to a certain degree. That is, flexibility in forming a block is low.
The present invention is accomplished in order to solve the problems. An objective of the present invention is to provide a liquid crystal display device including an in-cell touch panel, which (i) does not require correction of a detection signal generated when a pressing is detected and (ii) can (a) group drive electrodes into a block and (b) group receive electrodes into a block, more flexibly.
In order to attain the object, a liquid crystal display device in accordance with an aspect of the present invention includes:
a plurality of pixels which are arranged in a matrix manner for carrying out display;
pixel electrodes provided for the respective plurality of pixels, each of the pixel electrodes having a comb-teeth shaped region;
common electrodes which (i) are provided for the respective plurality of pixels and (ii) face the respective pixel electrodes via an insulating layer, each of the common electrodes having a plate-like shape;
a plurality of drive lines; and
a plurality of receive lines which perpendicularly intersect with the plurality of drive lines,
each of the common electrodes being connected with any of the plurality of drive lines or with any of the plurality of receive lines.
According to the configuration, each of the plate-shaped common electrodes, which are provided independently for the respective pixels, is connected with any of the drive lines or any of the receive lines. Common electrodes connected with the drive lines serve as drive electrodes of the touch panel. Meanwhile, common electrodes connected with the receive lines serve as receive electrodes of the touch panel. As such, an in-cell touch panel is provided in the liquid crystal display device in accordance with an aspect of the present invention.
Each of the drive electrode and the receive electrode is not a comb-teeth shaped electrode but is a plate-like electrode. The drive electrode and the receive electrode are provided in a plane which is different from a plane in which the pixel electrode is provided. Therefore, even in a case where an electric potential of the pixel electrode varies depending on whether or not an image is displayed, the lines of electric force generated between the drive electrode and the receive electrode are not increased or decreased. With the configuration, in a case where identical pressings are made with respect to the display surface, completely identical detection signals are obtained regardless of whether or not an image is displayed. Therefore, it is not necessary to correct a detection signal depending on whether or not an image is displayed.
Whether each of the common electrodes serves as a drive electrode or as a receive electrode is determined based on whether the common electrode is connected with a drive line or with a receive line. Therefore, in a case where a block is intended to be made up of a certain number of common electrodes, such a block can be configured by merely connecting the certain number of common electrodes to drive lines. That is, in a case where a plurality of common electrodes are grouped into a block, it is not necessary to (i) electrically connect the drive line with the receive line or (ii) provide disconnecting parts at arbitrary locations on the drive line and on the receive line. Therefore, according to the liquid crystal display device in accordance with an aspect of the present invention, it is possible to flexibly configure a drive electrode block and a receive electrode block which have arbitrary shape and size.
As such, according to the liquid crystal display device in accordance with an aspect of the present invention, it is not necessary to correct a detection signal generated when a pressing is detected, and it is possible to group the drive electrodes into a block and to group the receive electrodes into a block, more flexibly.
For a fuller understanding of the other objects, natures, excellent points, and advantages of the present invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.
According to the liquid crystal display device in accordance with an aspect of the present invention, it is not necessary to correct a detection signal generated when a pressing is detected, and it is possible to group the drive electrodes into a block and to group the receive electrodes into a block, more flexibly.
The following description will discuss an embodiment of the present invention, with reference to
(Configuration of Liquid Crystal Display Device 1)
The following description will discuss a configuration of a liquid crystal display device 1 of the present embodiment, with reference to
The liquid crystal display device 1 includes at least a pair of transparent substrates 2 and 4 and a liquid crystal layer 6 provided between the transparent substrates 2 and 4 (see
The liquid crystal display device 1 includes a plurality of pixels arranged in a matrix for carrying out display. Specifically, the plurality of pixels are a pixel group of N rows (N is an integer not smaller than 2)×M columns (M is an integer not smaller than 2). Each of the plurality of pixels is made up of three sub-pixels. Accordingly, the liquid crystal display device 1 has sub-pixels whose number is N rows×M rows×3. Each of the sub-pixels is provided for displaying any of primary colors, i.e., red, green, and blue. By thus having the three kinds of sub-pixels, the liquid crystal display device 1 can display an intended color image.
Note that the terms “pixel” and “sub-pixel” are uses merely for convenience. In other words, the technical scope of the present invention of course encompasses even a configuration in which members, which are referred to as “sub-pixel” in the present embodiment, are instead referred to as “pixel”.
The liquid crystal display device 1 includes a plurality of gate bus lines 10 and a plurality of data bus lines 12 which perpendicularly intersect with the plurality of gate bus lines 10. The plurality of gate bus lines 10 and the plurality of data bus lines 12 are formed in the TFT substrate 2. According to the present embodiment, the number of the gate bus lines 10 is N, which is equal to the number of pixel rows. Moreover, the number of the data bus lines 12 is 3×M, which is equal to the number of sub-pixel columns. The sub-pixels are provided at respective intersections of the gate bus lines 10 and the data bus lines 12.
Each of the sub-pixels is made up of at least a TFT 18, a pixel electrode 20, and a common electrode 24. These members are formed in the TFT substrate 2. The TFT 18 has a gate with which the gate bus line 10 is connected. The TFT 18 has a source with which the data bus line 12 is connected. The TFT 18 has a drain with which the pixel electrode 20 is connected.
The common electrode 24 is provided on a surface of a transparent substrate 30, which surface is located on a liquid crystal layer 6 side (see
In each of the pixel electrodes 20, a plurality of long and thin slits 22 are formed and arranged side by side (see
Each of the pixel electrode 20 and the common electrode 24 is made of a transparent conductive material such as ITO or IZO.
The color filter substrate 4 is configured by a transparent substrate 34, a color filter 36r for displaying red, a color filter 36g for displaying green, and a color filter 36b for displaying blue (see
In this specification, a character “n” given to each reference numeral means an integer which is not smaller than 1 and is not larger than N. A character “m” given to each reference numeral means an arbitrary integer which is not smaller than 1 and is not larger than M. A character “r” means red, a character “g” means green, and a character “b” means blue. For example, a “gate bus line 10n” indicates an n-th gate bus line 10. A “data bus line 12b(m)” indicates a data bus line 12 which corresponds to green sub-pixels included in respective pixels in an m-th column. A “pixel electrode 20g(m,n)” indicates a pixel electrode 20 constituting a blue sub-pixel included in a pixel located in an n-th row and an m-th column. These rules are similarly applied to the other constituent members.
(CSY Line 14 and CSX Line 16)
The liquid crystal display device 1 includes a plurality of CSY lines 14 (drive line) and a plurality of CSX lines 16 (receive line) which perpendicularly intersect with the plurality of CSY lines 14 (see
According to the present embodiment, the number of the CSY lines 14 is equal to that of the gate bus lines 10, and the number of the CSX lines 16 is equal to that of the data bus lines 12.
(Drive Electrode and Receive Electrode)
According to the liquid crystal display device 1, each of the common electrodes 24 is connected with any of the CSY lines 14 or with any of the CSX lines 16 via a connection line 26. A common electrode 24 connected with a CSY line 14 serves as a drive electrode of a touch panel, and a common electrode 24 connected with a CSX line 16 serves as a receive electrode of the touch panel.
The liquid crystal display device 1 further includes a sensing driving circuit (not illustrated). The sensing driving circuit is connected with all the CSY lines 14 so as to supply a driving signal for sensing via the CSY lines 14. The term “sensing” means a process of detecting a pressed location on a display surface (sensor surface) of the liquid crystal display device 1.
The liquid crystal display device 1 further includes a sensing detection circuit (not illustrated). The sensing detection circuit is connected with all the CSX lines 16 so as to receive detection signals supplied via the CSX lines 16. By analyzing received detection signals, coordinates of a pressed location on the sensor surface are calculated.
(Connection Pattern of Common Electrodes 24)
In one (1) pixel row, (i) a pixel having common electrodes 24 connected with a CSY line 14 and (ii) a pixel having common electrodes 24 connected with respective CSX lines 16 are alternately arranged (see
Moreover, although not illustrated in
Note that, also in one (1) pixel column, (i) a pixel having common electrodes 24 connected with a CSY line 14 and (ii) a pixel having common electrodes 24 connected with respective CSX lines 16 are alternately arranged. More specifically, in one (1) sub-pixel column, (i) a sub-pixel having a common electrode 24 connected with a CSY line 14 and (ii) a sub-pixel having a common electrode 24 connected with a CSX line 16 alternate with each other for each sub-pixel. For example, the R sub-pixel 20r(m,n) is connected with the CSY line 14(n), and an R sub-pixel 20r(m,n+1), which is a next sub-pixel in an identical column, is connected with a CSX line 16r(m). Similarly, the G sub-pixel 20g(m,n) is connected with the CSY line 14(n), and a G sub-pixel 20g(m,n+1), which is a next sub-pixel in an identical column, is connected with a CSX line 16r(m).
Although not illustrated in
(Forming of Drive Electrode Block and Receive Electrode Block)
According to the liquid crystal display device 1, a plurality of CSY lines 14, which are arranged side by side, are bundled and connected with one (1) common drive line, and it is therefore possible to cause common electrodes 24, which are connected with the bundled CSY lines 14, to serve as one (1) drive electrode block. Meanwhile, a plurality of CSX lines 16, which are arranged side by side, are bundled and connected with one (1) common receive line, and it is therefore possible to cause common electrodes 24, which are connected with the bundled CSX lines 16, to serve as one (1) receive electrode block.
In the example illustrated in
Moreover, in the example illustrated in
Meanwhile, in the example illustrated in
Moreover, in the example illustrated in
As such, according to the example illustrated in
Note that, in the example illustrated in
(Equivalent Circuit)
In the example illustrated in
(Detection Principle)
Here, in a case where a driving voltage V is applied to the drive electrode 40a, an output from the receive electrode 40b is ultimately detected as V2=Ctr×V÷C (see (c) of
(Necessity of Correcting Detection Signal)
As illustrated in
(Improvement in Sensing Efficiency)
(a) of
According to the liquid crystal display device of the conventional technique, the drive electrodes 120a are aligned in one line, and the receive electrodes 120b are aligned in one line (see (a) of
On the other hand, according to the liquid crystal display device 1 in accordance with an embodiment of the present invention, the drive electrodes 40a and the receive electrodes 40b are arranged in a staggered manner (see (b) of
As illustrated in (a) and (b) of
As above described, according to the liquid crystal display device 1 in accordance with an embodiment of the present invention, the drive electrodes 40a and the receive electrodes 40b are arranged in the staggered manner. This makes it possible to improve sensing efficiency, as compared with the liquid crystal display device in accordance with the conventional technique.
(Main Points)
As above described, according to the liquid crystal display device 1 in accordance with the present embodiment, each of the common electrodes 24, which have a plate-like shape and are provided independently for respective pixels, is connected with any of the CSY lines 14 or with any of the CSX lines 16. Common electrodes 24 connected with the CSY lines 14 serve as drive electrodes 40a of the touch panel. Meanwhile, common electrodes 24 connected with the CSX lines 16 serve as receive electrodes 40b of the touch panel. As such, an in-cell touch panel is provided in the liquid crystal display device 1.
According to the liquid crystal display device 1, each of the drive electrode 40a and the receive electrode 40b has a plate-like shape and is provided in a plane which is different from a plane in which the pixel electrode 20 is provided. Therefore, there is no cause that increases or decreases an electric potential distribution generated between the drive electrode 40a and the receive electrode 40b. From this, it is not necessary to correct a detection signal, which is generated when a pressing on the display surface is detected, depending on whether or not an image is displayed.
Whether each of the common electrodes 24 serves as a drive electrode or as a receive electrode is determined based on whether the common electrode 24 is connected with a CSY line 14 or with a CSX line 16. Therefore, in a case where a block is intended to be made up of a certain number of common electrodes 24, such a block can be configured by merely connecting the certain number of common electrodes 24 to CSY lines 14. That is, in a case where a plurality of common electrodes 24 are grouped into a block, it is not necessary to (i) electrically connect the CSY line 14 with the CSX line 16 or (ii) provide disconnecting parts at arbitrary locations on the CSY line 14 and on the CSX line 16. Therefore, according to the liquid crystal display device 1 in accordance with an embodiment of the present invention, it is possible to flexibly configure a drive electrode block and a receive electrode block which have arbitrary shape and size.
According to the liquid crystal display device in accordance with an aspect of the present invention, it is preferable that some of the common electrodes, each of which is connected with any of the plurality of drive lines, and the other of the common electrodes, each of which is connected with any of the plurality of receive lines, are arranged in a staggered manner.
According to the configuration, the number of receive electrodes, which abut on one (1) drive electrode, becomes up to four. Therefore, the number of lines of electric force formed between the drive electrode and the receive electrodes becomes twice as many as that obtained in a configuration in which drive electrodes and receive electrodes are arranged in a stripe manner. This makes it possible to further enhance sensing efficiency.
According to the liquid crystal display device in accordance with an aspect of the present invention, it is preferable that the plurality of drive lines are grouped into bundles each of which has a predetermined number of drive lines arranged side by side, the predetermined number of drive lines being connected with one (1) common drive line; and the plurality of receive lines are grouped into bundles each of which has a predetermined number of receive lines arranged side by side, the predetermined number of receive lines being connected with one (1) common receive line.
According to the configuration, a plurality of common electrodes, which are connected with the predetermined number of the plurality of drive lines, can be used as one (1) drive electrode block. Meanwhile, a plurality of common electrodes, which are connected with the predetermined number of the plurality of receive lines, can be used as one (1) receive electrode block. With the configuration, by changing the number of bundled drive lines and the number of bundled receive lines as appropriate, it is possible to form a drive electrode block and a receive electrode block which have intended sizes.
According to the liquid crystal display device in accordance with an aspect of the present invention, it is preferable that the pixel electrodes and the common electrodes are configured so as to correspond to an advanced fringe field switching mode.
According to the configuration, it is possible to enhance an aperture ratio of a pixel and to sufficiently increase a viewing angle of the liquid crystal display device 1.
(Example of Block Patterns)
According to the liquid crystal display device 1, the drive electrode blocks and the receive electrode blocks can have any of various shapes and arrangements. It is therefore possible to easily diversify an intended wiring pattern which is to be formed in the touch panel.
(Electrostatic Switch)
As such, according to the liquid crystal display device 1, it is possible to enhance accuracy in detecting a pressing on the sensor surface. Further, it is possible to group the drive electrodes into a block and to group the receive electrodes into a block, more flexibly.
The present invention is not limited to the embodiments and the examples, but can be altered by a skilled person in the art within the scope of the claims. An embodiment derived from a proper combination of technical means altered within the scope of the claims is also encompassed in the technical scope of the present invention.
The present invention is widely applicable to a liquid crystal display device including an in-cell touch panel.
Number | Date | Country | Kind |
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2011-046895 | Mar 2011 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2012/054836 | 2/27/2012 | WO | 00 | 8/30/2013 |