The present application claims priority from Japanese application serial no. 2007-078693 filed on Mar. 26, 2007, the content of which is hereby incorporated by reference into this application.
This invention relates to a display device having picture display elements or pixels arranged in the form of matrix, and more particularly to the structure of pixel electrodes which are driven in a time division fashion in a liquid crystal display (LCD) device.
Of all the display devices recently developed, LCD devices, irrespective of their sizes, are rapidly increasing in number of applications. In an ordinary LCD device, pixels arranged in the form of matrix are driven by selectively energizing one of scanning lines (i.e. gate lines) and by applying signal voltages to the pixels from signal lines (i.e. data lines). Accordingly, each pixel is controlled by a single scanning line and a single signal line.
JP-A-5-188395 discloses an LCD device wherein two pixels are electrically connected with a single signal line, one of the two pixels is controlled by a gate line, and the other pixel is controlled by the gate line and another gate line adjacent to the gate line, so that the number of the used signal lines can be halved.
JP-A-5-265045 discloses an LCD device wherein a signal voltage is applied in a time division manner through a single signal line to two pixels controlled by two adjacent gate lines so that the number of the used signal lines can be halved.
In the LCD device disclosed in JP-A-5-188395, wiring conductors for sending gate signals and signal voltages through them are to be laid out in pixels controlled by two thin film transistors (TFTs) and therefore the aperture, i.e. ratio of light emitting area within a pixel to the entire area of the pixel, will become smaller. In the LCD device disclosed in JP-A-5-265045, on the other hand, even when a signal is sent through a single signal line to two pixels, the number of the gate lines increases so that the aperture is adversely affected. Also, in both LCD devices disclosed in JP-A-5-188395 and JP-A-5-265045, a signal voltage is applied to two pixels through a single signal line. Accordingly, these types of LCD devices can be adapted to at best the double division drive method. As a result, if these devices are to be used with an LSI for the triple division drive (RGB time division drive wherein R, G and B signal voltages are sent through a single line in a time division manner) which has been increasingly put to practice, the resultant circuit structure will be complicated.
One feature of this invention is to supply signals to three pixels through a single signal line by differentiating the selected conditions (on-off conditions) with respect to two adjacent gate lines. Namely, let there be two adjacent gate lines a and b. Then, one of the three pixels is selectively controlled when only the gate line a is turned on, another pixel is selectively controlled when only the gate line b is turned on, and the remaining pixel is selectively controlled when both the gate lines a and b are turned on.
Another feature of this invention is to use a pixel electrode as a path for supplying signal voltages from signal lines to TFTs connected with three pixels.
According to this invention roughly described above, the following advantages (1) through (7) can be enjoyed.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.
Embodiments of this invention will now be described with reference to the attached drawings.
[Embodiment 1]
In
The transparent pixel electrodes I, II and III are connected with their driving TFTs. The gate electrodes of the TFTs connected with the transparent pixel electrodes I and III are connected with the preceding gate line while the gate electrode of the TFT connected with the transparent pixel electrode II is connected with the following gate line. Here, the terms “preceding” and “following” relate to the successive turns in the order in time of scanning. The drain (or source) electrode of the TFT connected with the transparent pixel electrodes II is connected through wiring conductor with the source (or drain) electrode of the TFT connected with the transparent pixel electrode III. Color filter substrates which sandwiches a liquid crystal layer on the TFT substrate 12 are not shown in the figure, but they are disposed in parallel to the TFT substrate 12.
A scanning circuit 13 successively selects the gate lines G1, G2, . . . , etc. In accordance with the selected gate lines G, three signal voltages, e.g. R, G and B signal voltages, are delivered to the relevant signal lines D from a picture signal generation circuit 14.
In
First, when the gate lines G1a and G1b are both driven to “high” level during the sub-period T1, the TFTs connected with the transparent pixel electrodes I, II and III in the first row are turned on. As a result, the signal voltage for the transparent pixel electrode III is written in the capacitances associated with the transparent pixel electrodes I, II and III from the signal lines D1, D2, D3, . . . , etc.
Then, during the sub-period T2, if the gate line G1a remains at “high” level whereas the gate line G1b is driven to “low” level, the TFTs connected with the transparent pixel electrodes II and III are turned off whereas the TFT connected with the transparent pixel electrode I is turned on. Consequently, the signal voltage for the transparent pixel electrode III written in the transparent pixel electrode I is replaced by the signal voltage for the transparent pixel electrode I.
Further, during the sub-period T3, if the gate line G1a is driven to “low” level and the gate line G1b to “high” level, then the TFTs connected with the transparent pixel electrodes I and III are turned off whereas the TFT connected with the transparent pixel electrode II is turned on. Thus, the signal voltage for the transparent pixel electrode III written in the transparent pixel electrode II is replaced by the signal voltage for the transparent pixel electrode II.
In this way, the properly corresponding signal voltages are time-sequentially, i.e. in a time-divisional manner, written respectively in the transparent pixel electrodes I, II and III in the first row.
During the next horizontal period (1H), the same operations are repeated to time-sequentially write the properly corresponding signal voltages in the transparent pixel electrodes I, II and III in the second row.
[Embodiment 2]
The second embodiment of this invention will be described with reference to
Further, although in the first embodiment shown in
[Embodiment 3]
The third embodiment of this invention will be described with reference to
In this third embodiment, as shown in
First, when the gate lines G1a and G1b are both driven to “high” level during the first sub-period T1 of the first horizontal period, the TFTs connected with the transparent pixel electrodes I, II and III are turned on. As a result, the signal voltage for the transparent pixel electrode III is written in the capacitances associated with the transparent pixel electrodes I, II and III from the signal lines D1, D2, D3, . . . , etc.
Then, during the second sub-period T2 of the first horizontal period, if the gate line G1a is driven to “low” level whereas the gate line G1b remains at “high” level, the TFTs connected with the transparent pixel electrodes II and III are turned off whereas the TFT connected with the transparent pixel electrode I is turned on. Consequently, the signal voltage for the transparent pixel electrode III written in the transparent pixel electrode I is replaced by the signal voltage for the transparent pixel electrode I.
Further, during the first sub-period T3 belonging to the second horizontal period, if the gate line G1a is driven to “high” level and the gate line G1b to “low” level, then the TFTs connected with the transparent pixel electrodes I and III are turned off whereas the TFT connected with the transparent pixel electrode II is turned on. Thus, the signal voltage for the transparent pixel electrode III written in the transparent pixel electrode II is replaced by the signal voltage for the transparent pixel electrode II.
Still further, when the gate lines G1c and G1d are both driven to “high” level during the second sub-period T4 of the second horizontal period, the TFTs connected with the transparent pixel electrodes IV, V and VI are turned on. As a result, the signal voltage for the transparent pixel electrode VI is written in the capacitances associated with the transparent pixel electrodes IV, V and VI from the signal lines D1, D2, D3, . . . , etc.
Yet further, during the first sub-period T5 of the third horizontal period, if the gate line G1c remains at “high” level whereas the gate line G1d is driven to “low” level, the TFTs connected with the transparent pixel electrodes V and VI are turned off whereas the TFT connected with the transparent pixel electrode IV is turned on. Consequently, the signal voltage for the transparent pixel electrode VI written in the transparent pixel electrode IV is replaced by the signal voltage for the transparent pixel electrode IV. It is to be noted here that since during this sub-period T5 the transparent pixel electrode IV(1, 1) is not available, this signal voltage is represented by a broken line segment in the waveform diagram in
Finally, during the second sub-period T6 of the third horizontal period, if the gate line G1c is driven to “low” level whereas the gate line G1d is driven to “high” level, then the TFTs connected with the transparent pixel electrodes IV and VI are turned off whereas the TFT connected with the transparent pixel electrode V is turned on. Consequently, the signal voltage for the transparent pixel electrode IV written in the transparent pixel electrode V is replaced by the signal voltage for the transparent pixel electrode V.
In this way, the properly corresponding signal voltages are time-sequentially written respectively in the transparent pixel electrodes I, II, III, IV, V and VI.
During the three following horizontal periods, the same operations are repeated to time-sequentially write the properly corresponding signal voltages in the transparent pixel electrodes I, II, III, IV, V and VI.
[Embodiment 4]
The fourth embodiment of this invention will be described with reference to
How the basic pixel structure 11 shown in
Then, during the sub-period T2, if the gate line G1a is driven to “low” level whereas the gate line G1b remains at “high” level, the TFTs connected with the transparent pixel electrodes II and III are turned off whereas the TFTs connected with the two transparent pixel electrodes I are turned on. Consequently, the signal voltage for the transparent pixel electrode III written in the two transparent pixel electrodes I are replaced by the signal voltage for the transparent pixel electrode I.
Further, during the sub-period T3, if the gate line G1a is driven to “high” level and the gate line G1b to “low” level, then the TFTs connected with the two transparent pixel electrodes I and the transparent pixel electrode III are turned off whereas the TFT connected with the transparent pixel electrode II is turned on. Thus, the signal voltage for the transparent pixel electrode III written in the transparent pixel electrode II is replaced by the signal voltage for the transparent pixel electrode II.
In this way, the properly corresponding signal voltages are time-sequentially written respectively in the two transparent pixel electrodes I, the transparent pixel electrode II and the transparent pixel electrode III in the first row.
During the next horizontal period (1H), the same operations are repeated to time-sequentially write the properly corresponding signal voltages in the two transparent pixel electrodes I, the transparent pixel electrode II and the transparent pixel electrode III in the second row.
As shown in
As shown in
[Embodiment 5]
The fifth embodiment of this invention will be described with reference to
As shown in the waveform diagram in
Now, let it be assumed that the total of the electric capacitance of the transparent pixel electrode IIa and its parasitic capacitance is denoted by Ca and that the total of the electric capacitance of the transparent pixel electrode IIb and its parasitic capacitance is denoted by Cb. Then, the signal voltage V(IIb(1,1)) is written in the transparent pixel electrode IIb during the sub-period T1 whereas the signal voltage at the transparent pixel electrode IIa is replaced by the signal voltage V(I(1, 1)) of the transparent pixel electrode I during the sub-period T2. Accordingly, the electric charges accumulated during the sub-periods T1 and T2 are averaged to develop a voltage represented by the following expression.
V(II(1,1))=(Ca×V(I(1, 1))+Cb×V(IIb(1,1)))/(Ca+Cb),
where V(II(1,1)) is the signal voltage at the transparent pixel electrode II after averaging. The signal voltage V(IIb(1,1)) is calculated from the target signal voltage V(II(1,1)) and the signal voltage V(I(1,1)) by using this expression. By applying the calculated signal voltage V(IIb(1,1)) to the signal line D, the target signal voltage V(I(1,1)) and the signal voltage V(II(1,1)) can be applied respectively to the transparent pixel electrodes I and II.
According to this embodiment, a signal voltage can be supplied from a single signal line D to two pixels without increasing the number of gate lines G. Further, since the transparent pixel electrode IIa is used for signal transfer, the aperture can be prevented from deteriorating.
[Embodiment 6]
The sixth embodiment of this invention will now be described with reference to
As shown in
[Embodiment 7]
The seventh embodiment of this invention will now be described with reference to
In
Then, during the sub-period T2, the TFTs connected with the transparent pixel electrodes I and II are turned off by keeping the gate line G1 at “high” level and driving the gate line G2 to “low” level. During the sub-period T2, signal voltages are to be supplied to non-existent transparent pixel electrodes I(0,1) and I(0,2) from the signal lines D1 and D2 and therefore such signal voltages are represented by broken line segments in
The TFTs connected with the transparent pixel electrodes I and II in the second row are turned on by driving both the gate lines G2 and G3 to “high” level during the sub-period T1 of the second horizontal period (1H), so that the signal voltage for the transparent pixel electrode II is written in the capacitances of the transparent pixel electrodes I and II in the second row from the signal lines D1,D2, etc.
Then, during the sub-period T2, by keeping the gate line G2 at “high” level and driving the gate line G3 to “low” level, the TFTs connected with the transparent pixel electrodes II in the second row are turned off while the TFTs connected with the transparent pixel electrodes I in the first row are turned on. Accordingly, the signal voltage for the transparent pixel electrode II written in the transparent pixel electrodes I is replaced by the signal voltage for the transparent pixel electrode I.
In this way, the properly corresponding signal voltage is first written in the transparent pixel electrodes II in the first row, the properly corresponding signal voltage is secondly written in the transparent pixel electrodes II in the second row, and the properly corresponding signal voltage is thirdly written in the transparent pixel electrodes I in the first row. By repeating this operation consecutively on successive rows, all the transparent pixel electrodes I and II are loaded with their properly corresponding signal voltages.
It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-078693 | Mar 2007 | JP | national |
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| Number | Date | Country |
|---|---|---|
| 1920649 | Feb 2007 | CN |
| 5-188395 | Jul 1993 | JP |
| 5-265045 | Oct 1993 | JP |
| 2005-4212 | Jan 2005 | JP |
| 2006-500617 | Jan 2006 | JP |
| 2006-126842 | May 2006 | JP |
| Entry |
|---|
| Office Action issued in Chinese Patent Application No. 2008100048908 on Dec. 18, 2009. |
| Office Action issued in Japanese Patent Application No. 2007-078693 on Jul. 6, 2011. |
| Office Action issued in Japanese Patent Application No. 2007-078693 on Mar. 16, 2011. |
| Number | Date | Country | |
|---|---|---|---|
| 20080238817 A1 | Oct 2008 | US |