Patent Grant
6967639
The present invention relates to image display devices and the like, more particularly, to a technology to contribute high definition of a liquid crystal display device.
As it is generally known, in an active matrix drive display device, the number of driver integrated circuits (ICs) is increased along with an increase in the number of display pixels. Accordingly, such an increase in the number of driver ICs contribute to part of the reason for incurring a cost rise. Moreover, as pixel pitches are narrowed along with an advance in a high-definition screen, connection between a pixel and a driver IC is becoming difficult. To resolve these problems, a display device of a multiplex pixel structure is known in which one data line supplies electric potential to two or more adjacent pixels by time division, thus reducing the number of driver ICs and widening pitches between connective terminals (in Japanese Unexamined Patent Publications No. Hei 5(1993)-265045 or No. Hei 6(1994)-148680, for example).
However, according to the technologies described in Japanese Unexamined Patent Publications No. Hei 5(1993)-265045 and No. Hei 6(1994)-148680, two systems of scan lines are required to drive one pixel row. In this case, if different on/off signals are simply supplied to two systems of the scan lines in order to drive the pixel, waveform control of the on/off signals to be outputted to the respective scan lines will be complicated. In addition, two systems of output control lines are also required for controlling output of these on/off signals. Therefore, a structure of a gate driver will be also complicated. Particularly, these problems becomes more significant when one data line supplies the electric potential to three or more pixels.
A main object of the present invention is to provide an image display device and the like capable of driving a display device of a multiplex pixel structure just by control of simple on/off signals and capable of simplifying a structure of a gate driver thereof.
According to one aspect of the invention, there is provided an image display device comprising a plurality of signal lines for supplying display signals, a plurality of scan lines for supplying scanning signals, m (a number larger than 1) pieces of pixel electrodes with a given signal line, the pixel electrodes being serially selected in one horizontal scanning cycle, output circuits for outputting the scanning signals, the output circuits being connected with respective input terminals of the plurality of scan lines, and a propagation circuit for propagating an inputted signal sequence, the propagation circuit connecting the output circuits, wherein driving of m pieces of the pixel electrodes is controlled by combinations of the scanning signals supplied from a given plurality of the scan lines, and the propagation circuit propagates the scanning signal between the output circuits in one horizontal scanning cycle.
According to another aspect of the invention, there is provided a scan line drive circuit comprising output terminals connected with respective scan lines of an image display device, and a propagation circuit connecting the output terminals, wherein the propagation circuit includes a plurality of first shift registers corresponding to the respective scan lines and partial propagation circuits, each of which is cascade-connected between the first shift registers adjacent each other, the partial propagation circuit propagating a signal inputted to one of the first shift registers to another one of the first shift registers after one horizontal scanning cycle from a moment of input thereof.
According to yet another aspect of the invention, there is provided an image display device comprising a plurality of pixel electrodes, a plurality of scan lines for supplying scanning signals to selected ones of the pixel electrodes, a signal sequence generator for generating a signal sequence including a given number of signals, and a propagation circuit for propagating the signal sequence between the scan lines with a time interval shorter than a time width of the signal sequence.
According to still another aspect of the invention, there is provided a scan line drive circuit comprising a plurality of shift registers corresponding to respective scan lines of an image display device, partial propagation circuits disposed between the shift registers located adjacent one another, and a multiplex rate signal generator or outputting a multiplex rate signal to the partial propagation circuits, the multiplex rate signal indicating a multiplex rate of pixels of the image display device, wherein each of the partial propagation circuits propagates a given signal from one of the shift registers to another one of the shift registers with a time interval to be set up based on the multiplex rate.
According to a further aspect of the invention, there is provided a driver circuit for a display device comprising a plurality of output terminals, output circuits respectively connected to the output terminals, shift registers respectively connected to the output circuits, shift registers cascade-connected between the shift registers, and an output control line for transmitting a control signal to control output of the output circuits.
According to an even further aspect of the invention, there is provided a image display device comprising a plurality of pixels arranged in a matrix, a plurality of scan lines, a plurality of signal lines, m (a number larger than 1) pieces of pixels to be selected in a first horizontal scanning cycle, the pixels being connected with one of the signal lines, m pieces of pixels to be selected in a second horizontal scanning cycle subsequent to the first horizontal scanning cycle, the pixels being connected with the signal line, and a drive circuit connected with the plurality of scan lines, wherein the drive circuit includes a plurality of output terminals connected with the plurality of scan lines, output circuits connected with the respective output terminals, shift registers connected with the output circuits, a (m−1) number of pieces of shift registers cascade-connected between the shift registers, and an output control line for transmitting a control signal to control output of the output circuits.
According to another aspect of the invention, there is provided an image display device comprising a plurality of pixels arranged in a matrix, a plurality of scan lines, a plurality of signal lines, m (a number larger than 1) pieces of pixels to be selected in a first horizontal scanning cycle, the pixels being connected with a given signal line out of the plurality of signal lines, m pieces of pixels to be selected in a second horizontal scanning cycle subsequent to the first horizontal scanning cycle, the pixels being connected with the given signal line, and a drive circuit connected with the plurality of scan lines, wherein the m pieces of pixels are selected in the first horizontal scanning cycle by use of a first scan line set comprised of n lines of scan lines, the other m pieces of pixels are selected in the second horizontal scanning cycle by use of a second scan line set comprised of n lines of scan lines respectively shifted by one line from the scan lines of the first scan line set. The drive circuit is controlled by a clock signal, a signal sequence composed of 1 pieces of signals, in which 1 is larger than n, is inputted to the drive circuit, the drive circuit, to which the signal sequence is inputted, outputs scanning signals serially in a range from first timing to m-th timing with respect to groups from a first scan line group to an m-th scan line group which are mutually different combinations of the scan lines selected from the first scan line set in the first horizontal scanning cycle. The drive circuit initiates a process to output scanning signals serially in a range from first timing to m-th timing at m clocks after initiation of a process in the first horizontal scanning cycle with respect to groups from a first scan line group to an m-th scan line group which are mutually different combinations of the scan lines selected from the second scan line set in the second horizontal scanning cycle.
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings.
Now, the present invention will be described in further detail based on embodiments as described with reference to the accompanying drawings.
As shown in
In display area S, the pixel electrodes as many as M (multiplied by) N (M and N are arbitrary integers) are arrayed in a matrix fashion.
As shown in
To begin with, a source electrode of the first TFT M1 is connected with the signal line Dm and a drain electrode thereof is connected with the pixel electrode A1. Meanwhile, a gate electrode of the first TFT M1 is connected with a source electrode of second TFT M2. Here, each TFT is a switching element with three terminals. There is a case that one side connected with a signal line is referred to as a source electrode while another side connected with a pixel electrode is referred to as a drain electrode, However, there is also a case to refer the electrodes in reverse. That is to say, it is not universally settled as to which one of the two electrodes except a gate electrode should be referred to as a source electrode or a drain electrode. Accordingly, the two electrodes except the gate electrode will be hereinafter collectively referred to as source/drain electrodes.
One of source/drain electrodes of second TFT M2 is connected with the gate electrode of first TFT M1, and the other source/drain electrode thereof is connected with a scan line Gn+2. Therefore, the gate electrode of first TFT M1 is connected with scan line Gn+2 via second TFT M2. Meanwhile, a gate electrode of second TFT M2 is connected with a scan line Gn+1. Therefore, first TFT M1 is turned on solely at a moment that the two adjacent scan lines Gn+1 and Gn+2 have selective potential concurrently, whereby electric potential of signal line Dm is supplied to pixel electrode A1. This fact indicates that second TFT M2 controls on/off of first TFT M1.
One of source/drain electrodes of third TFT M3 is connected with signal line Dm, and the other source/drain electrode thereof is connected with pixel electrode B1. Meanwhile, a gate electrode of third TFT M3 is connected with scan line Gn+1. Therefore, third TFT M3 is turned on when scan line Gn+1 has selective potential, whereby the electric potential of signal line Dm is supplied to pixel electrode B1.
The circuit structure of the array substrate A has been described so far from viewpoints of the first TFT M1 to third TFT M3. Now, description will be made regarding the circuit structure of array substrate A from viewpoints of pixel electrode A1 and pixel electrode B1. The display signal is supplied to pixel electrode A1 and pixel electrode B1 from single signal line Dm. That is, signal line Dm can be deemed as a common signal line Dm with respect to pixel electrode A1 and pixel electrode B1. Accordingly, whereas the pixels are arrayed in the matrix composed of M (multiplied by) N, signal lines D consist of N/2 lines.
First TFT M1 and second TFT M2 are connected with pixel electrode A1. Accordingly, first TFT M1 is connected with signal line Dm and with second TFT M2 at the same time. Gate electrode of second TFT M2 is connected with scan line Gn+1 subsequent to pixel electrode A1, and one of the source/drain electrodes of second TFT M2 is connected with scan line Gn+2 subsequent to scan line Gn+1. Here, in order to supply the electric potential of signal line Dm to pixel electrode A1, first TFT M1 must be turned on. Moreover, the gate electrode of first TFT M1 is connected with the source/drain electrode of second TFT M2; the gate electrode of second TFT M2 is connected with proper scan line Gn+1; and the source/drain electrode thereof is connected with subsequent scan line Gn+2. Accordingly, second TFT M2 must be turned on in order to turn on first TFT M1. Scan line Gn+1 and scan line Gn+2 must be selected concurrently in order to turn on second TFT M2. Therefore, first TFT M1 and second TFT M2 collectively constitute a switching mechanism which allows passage of a scanning signal in the event that both of scan line Gn+1 and scan line Gn+1 are selected. Eventually, pixel electrode A1 is driven and receives the electric potential from signal line Dm, based on a scanning signal from scan line Gn+1 and a scanning signal from scan line Gn+2.
Third TFT M3 is connected with pixel electrode B1, and the gate electrode thereof is connected with scan line Gn+1. Therefore, the electric potential is supplied from signal line Dm to pixel electrode A2 when proper scan line Gn+1 is selected.
Although description has been made so far regarding pixel electrode A1 and pixel electrode B1, a similar structure is also applied with respect to pixel electrode A2 and pixel electrode B2, a pixel electrode C1 and a pixel electrode D1, a pixel electrode C2 and a pixel electrode D2 and to other relevant combinations of pixels thereon.
Next, description will be made regarding a configuration between gate driver 5 and control circuit 6 with reference to
As shown in
Gate driver 5 is provided with a shift register unit (a propagation circuit) 12 to which the output control signals, the shift pulses and the clock signals are inputted. Shift register unit 12 has a constitution of a cascade connection of disposing first shift registers SR1 and second shift registers (partial propagation circuits) SR2 alternately. Here, first shift register SR1 is provided for each of the scan lines G and is connected with an output terminal Ot connectable with respect to an input terminal of signal line G via a buffer (an output circuit) B. Meanwhile, second shift register SR2 is disposed between first shift registers SR1 adjacent to each other.
Shift register unit 12 of the above-described constitution functions to transfer a shift pulse outputted from pulse generator 9 serially with respect to first shift registers SR1 and second shift registers SR2 while synchronizing the shift pulse with a clock signal outputted from clock signal generator 10. Meanwhile, buffer B provided between first shift register SR1 and scan line G is turned on when an output control signal, which is a binary signal inputted via OE line 11, is “0” and turned off if the output control signal is “1”, thus controlling propriety of outputting a scanning signal from first shift register SR1 to scan line G.
Next, description will be made regarding operations of this liquid crystal display device 1 with reference to a timing chart of scanning signals shown in
In
Moreover, in
As shown in
Nevertheless, second shift register SR2 is not connected with scan line G but first shift register SR1 is solely in a state of outputting the scanning signal with respect to scan line G. Therefore, if output control signal OE is “0”, then as shown in
Accordingly, if the time width of shift pulse SDI is defined as the length equivalent to two horizontal scanning cycles (2H) as shown in
A concrete driving method of pixels is as follows. Specifically, if shift pulse SDI has the waveform as shown in
On the contrary, in Tb2 (second timing) which is the latter half of time period Tb, scan line Gn+2 is set to non-selective electric potential and scan line Gn+1 (a second scan line group) is solely selected. Accordingly, third TFT M3 is solely turned on as shown in
After scan line Gn+1 is set to the non-selective electric potential, the electric potential of signal line Dm changes into electric potential Vc1 to be given to pixel electrode C1.
Here in
Moreover, in Tc2 (second timing) which is the latter half of time period Tc, scan line Gn+3 is set to the non-selective electric potential and scan line Gn+2 is solely selected. Therefore, as shown in
As described above, according to the first embodiment, buffers B are provided corresponding to each of scan lines G, and shift register unit 12 is formed by cascade connection of alternate arrangement of first shift registers SR1 and second shift registers SR2. Moreover, buffers B are connected solely with first shift registers SR1 in shift register unit 12 and shift pulse SDI is serially propagated with respect to cascade-connected first shift registers SR1 and second shift registers SR2, whereby shift pulse SDI is supplied to each buffer B. Further in this case, shift register unit 12 is driven by clock signal DCPV having a H/2 cycle dividing one horizontal scanning cycle 1H with a multiplex rate “2” of the pixels, whereby the shift pulse SDI is propagated serially from alternately disposed first registers SR1 to respective buffers B in a time interval 1H shorter than time width 2H of shift pulse SDI. According to the constitution as described above, it is possible to select two scan lines G adjacent to each other simultaneously for a period of 1H. That is, driving of pixel electrodes A1 and B1 (C1 and D1, and so on) can be controlled within one horizontal scanning cycle (1H) by supplying scanning signals Gn+1Out and Gn+2Out (Gn+2Out and Gn+3Out) from two scan lines of Gn+1 and Gn+2 (Gn+2 and Gn+3).
Therefore, unlike the prior art, it is not necessary to arrange two systems of scan lines G or to provide two systems of OE lines 11 in order to control driving of pixel electrodes A1, B1 and the like, but control can be performed by supplying the same output control signal OE with the same OE line 11. In other words, it is possible to select a plurality of scan lines G simultaneously without complicating the control of buffers B with output control signal OE or a structure of gate driver 5, whereby the structure of liquid crystal display device 1 having the multiplex pixel structure can be simplified and facilitation of fabrication as well as reduction of costs can be achieved.
Particularly, according to the first embodiment, shift pulse SDI is set up to turn on and off in every cycle of clock signal DCPV, that is, in every H/2 cycle obtained by time division of one horizontal scanning cycle 1H by the multiplex rate of the pixels. At the same time, the time width of shift pulse SDI is set to 2H, which is a time width equal to addition of a 1H time period (an additional time period) to one horizontal scanning cycle 1H (a time width obtained by one horizontal scanning cycle 1H multiplied by the multiplex rate “2”). Moreover, a time interval of shift pulse SDI propagating between respective buffers B is set as twice the cycle of clock signal DCPV or as 1H. Therefore, it is possible to set a time period of 1H for effectuating simultaneous supply of the scan signal to adjacent scan lines G, and it is also possible to control driving of pixel electrodes A1 and B1 (C1 and D1, and so on) in every H/2 time period within 1H cycle. In this way, liquid crystal display device 1 having the multiplex (2:1) pixel structure can be favorably realized.
Description has been heretofore made regarding the first embodiment of the present invention. However, the present invention is not limited to the above-described first embodiment, as other embodiments can be adopted.
For example, in the above-described first embodiment, clock signal DCPV operates to generate a signal of a uniform frequency. However, without limitations to the foregoing, clock signal generator 10 may generate clock signal DCPV of an uneven frequency by varying timing of a leading edge or a trailing edge of each pulse of such clock pulse DCPV.
Specifically, in the case that pixel electrodes A1 and B1 within display area S shown in
Therefore, timing of clock signal DCPV at the leading edge or the trailing edge thereof is varied within a range of a given cycle (within one horizontal scanning cycle (1H), for example), whereby the timing of the scanning signal is varied. In this way, it is possible to alter the writing time periods depending on pixel electrodes A1 or B1, whereby pixel electrodes A1 and B1 can be charged properly.
In addition to the foregoing example, the constitution cited in the above-described embodiment may be partially selected, omitted or modified to another constitution to the extent not deviating from the gist of the present invention.
Next, description will be made regarding a second embodiment of the present invention.
In the above-described first embodiment, two pixels share one signal line Dm in common. On the contrary, in this second embodiment, three pixels share one signal line Dm in common.
Specifically, in array substrate A′ of liquid crystal display device 1′, signal line Dm is shared in common by three pixels as shown in
In order to perform the above-described operations, the second embodiment sets up disposition of first TFT M31 to fifth TFT M35 as switching elements as described below.
Specifically, as shown in
One of source/drain electrodes of second TFT M32 is connected with scan line Gn+3 and the other source/drain electrode thereof is connected with the gate electrode of first TFT M31. Accordingly, the gate electrode of first TFT M31 is connected with scan line Gn+3 via second TFT M32. Meanwhile, a gate electrode of second TFT M32 is connected with scan line Gn+1.
Therefore, first TFT M31 is turned on only in a period when two scan lines Gn+1 and Gn+3 are set to selective electric potential at the same time, whereby the electric potential of signal line Dm is supplied to pixel electrode A31. This fact indicates that second TFT M32 is the switching element for controlling on/off of first TFT M31.
One of source/drain electrodes of third TFT M33 is connected with signal line Dm and the other source/drain electrode thereof is connected with pixel electrode C31. Meanwhile, a gate electrode of third TFT M33 is connected with scan line Gn+1.
One of source/drain electrodes of a fourth TFT M34 is connected with signal line Dm and the other source/drain electrode thereof is connected with pixel electrode B31. Meanwhile, a gate electrode of fourth TFT M34 is connected with a source/drain electrode of a fifth TFT M35.
Moreover, one of source/drain electrodes of fifth TFT M35 is connected with scan line Gn+2 and the other source/drain electrode thereof is connected with the gate electrode of fourth TFT M34. Accordingly, the gate electrode of fourth TFT M34 is connected with scan line Gn+2 via fifth TFT M35. Meanwhile, a gate electrode of fifth TFT M35 is connected with scan line Gn+1. Therefore, fourth TFT M34 is turned on only in a period when two scan lines Gn+1 and Gn+2 are set to selective electric potential at the same time, whereby the electric potential of signal line Dm is supplied to pixel electrode B31. This fact indicates that fifth TFT M35 is the switching element for controlling on/off of fourth TFT M34.
The circuit structure of array substrate A′ has been described above from viewpoints of first TFT M31 to fifth TFT M35. Now, a circuit structure of liquid crystal display device 1′ will be described hereunder from viewpoints of pixel electrode A31 to pixel electrode C31.
A display signal is supplied to pixel electrode A31 to pixel electrode C31 from the single signal line Dm. That is, signal line Dm is a signal line common to pixel electrode A31 to pixel electrode C31. First TFT M31 and second TFT M32 are connected with pixel electrode A31, and first TFT M31 is connected with signal line Dm and also connected with second TFT M32. The gate electrode of second TFT M32 is connected with proper scan line Gn+1, and the source/drain electrode of second TFT M32 is connected with the subsequent scan line Gn+3. Here, first TFT M31 needs to be turned on in order to supply the electric potential of signal line Dm to pixel electrode A31. Moreover, the gate electrode of first TFT M31 is connected with the source/drain electrode of second TFT M32; the gate electrode of second TFT M32 is connected with scan line Gn+1 which is positioned subsequent to pixel electrode A1 as well as pixel electrode B1; and the source/drain electrode thereof is connected with scan line Gn+3 which is subsequent to scan line Gn+1. Accordingly, second TFT M32 needs to be turned on in order to turn on first TFT M31. Scan line Gn+1 and subsequent scan line Gn+3 need to be set to selective electric potential in order to turn on second TFT M32. In this way, pixel electrode A31 is driven based on a scanning signal from scan line Gn+1 and a scanning signal from scan line Gn+3, thus receiving the electric potential from signal line Dm.
Fourth TFT M34 and fifth TFT M35 are connected with pixel electrode B31. Fourth TFT M34 is connected with signal line Dm and also connected with fifth TFT M35. The gate electrode of fifth TFT M35 is connected with scan line Gn+1, and the source/drain electrode of fifth TFT M35 is connected with scan line Gn+2. Here, fourth TFT M34 needs to be turned on in order to supply the electric potential of signal line Dm to pixel electrode B31. Moreover, the gate electrode of fourth TFT M34 is connected with the source/drain electrode of fifth TFT M35; and simultaneously, the gate electrode of fifth TFT M35 is connected with scan line Gn+1 and the source/drain electrode thereof is connected with scan line Gn+2. Accordingly, fifth TFT M35 needs to be turned on in order to turn on fourth TFT M34. Scan line Gn+1 and scan line Gn+2 need to be set to selective electric potential in order to turn on fifth TFT M35. As a consequence, the electric potential is supplied from signal line Dm to pixel electrode B1 only when scan line Gn+1 positioned subsequent to pixel electrode B31 itself and subsequent scan line Gn+2 are set to selective electric potential.
In the meantime, third TFT M33 is connected with pixel electrode C31, and the gate electrode thereof is connected with scan line Gn+1. Accordingly, the electric potential is supplied from signal line Dm to pixel electrode C31 when scan line Gn+1 is selected.
Although description has been made in the foregoing regarding pixel electrode A31 to pixel electrode C31, a similar structure is also applied to pixel electrode D31 to pixel electrode F31, pixel electrode G31 to pixel electrode I31, and to other relevant sets of pixels thereon.
Next, description will be made regarding a configuration between a gate driver (a scan line drive circuit or a driver circuit for a display device) 5′ and a control circuit (a scan line drive circuit) 6 with reference to
As shown in
Gate driver 5′ is provided with a shift register unit (a propagation circuit) 12′ to which output control signals, shift pulses and clock signals are inputted. Shift register unit 12′ includes first shift registers SR1, each of which is provided corresponding to each scan line G connected with an output terminal Ot connectable with respect to scan line G via a buffer (an output circuit) B. In addition, shift register unit 12′ further includes second shift registers SR2 and third shift registers SR3 (partial propagation circuits). Each of these second shift registers SR2 and each of the third shift registers SR3 are provided one by one corresponding to each first shift register SR1 and serially cascade-connected. In other words, one set of first, second and third shift registers SR1, SR2 and SR3 are disposed corresponding to each scan line G, and a plurality of sets of first, second and third shift registers SR1, SR2 and SR3 corresponding to the number of scan lines G are arranged in a state of cascade connection with respect to one another. In this way, shift register unit 12′ is made capable of transferring a shift pulse outputted from pulse generator 9 serially with respect to first shift registers SR1, second shift registers SR2 and third shift registers SR3 while synchronizing the shift pulse with a clock signal outputted from clock signal generator 10.
Note that buffer B provided between first shift register SR1 and scan line G has a function similar to that in the above-described first embodiment.
Next, description will be made regarding operations of this liquid crystal display device 1′ with reference to a timing chart of scanning signals as shown in
In
Moreover, in
As shown in
Nevertheless, in this case, second shift register SR2 and third shift register SR3 are not connected with scan line G but first shift register SR1 is solely in a state of outputting the scanning signal with respect to scan line G. Therefore, if OE line 11 is “0”, then as shown in
Accordingly, if the time width of shift pulse SDI is defined as, for example, the length equivalent to three horizontal scanning cycles (3H), then considering a first scan line set consisting of scan lines Gn+1, Gn+2 and Gn+3 adjacent to one another other, for example, a time period Td for outputting the scanning signals to all the scan lines Gn+1, Gn+2 and Gn+3 will last for one horizontal scanning cycle (1H). In other words, in time period Td, it is possible to select pixels connected with scan lines Gn+1, Gn+2 and Gn+3.
A concrete driving method of pixels is as follows. Specifically, if shift pulse SDI has the waveform as shown in
Thereafter, in Td2 (second timing) which is a subsequent subperiod to period Td1, the electric potential supplied from signal line Dm changes into electric potential Vb1 to be given to pixel electrode B31. Here in subperiod Td2, scan line Gn+1 and scan line Gn+2 (a second scan line group) are selected as shown in
Furthermore, in Td3 (third timing) which is the last subperiod of time period Td, the electric potential supplied from signal line Dm changes into electric potential Vc1 to be given to pixel electrode C31. Here in subperiod Td3, scan line Gn+1 (a third scan line group) is solely set to selective electric potential as shown in
Subsequently, scan line Gn+1 is set to non-selective electric potential, and then the electric potential from signal line Dm changes into electric potential Vd1 to be given to pixel electrode D31 and the process similar to the foregoing is performed on a second scan line set comprised of scan lines Gn+2 to Gn+4 by shifting respective scan lines G from first scan line set Gn+1 to Gn+3 by one line. In this way, electric potential of pixel electrode D31 to pixel electrode F31 is decided by time division. Note that the process with respect to second scan line set Gn+2 to Gn+4 is initiated one horizontal scanning cycle (1H) after the time when the process with respect to first scan line set Gn+1 to Gn+3 is performed.
In addition, a similar process will be performed thereafter with respect to each scan line set shifting the respective scan lines G thereof by one line from the second line set, in every horizontal scanning cycle (1H).
As described above, according to this second embodiment, buffer B is provided corresponding to each of scan lines G, and shift register unit 12′ is formed by cascade connection of repeated arrangement of the first, second and third shift registers SR1, SR2 and SR3. Moreover, buffers B are connected solely with first shift registers SR1 in shift register unit 12′ and shift pulse SDI is serially propagated with respect to first, second and third shift registers SR1, SR2 and SR3, whereby shift pulse SDI is supplied to each buffer B. Further in this embodiment, shift register unit 12′ is driven by clock signal TCPV having a H/3 cycle dividing one horizontal scanning cycle 1H with a multiplex rate “3” of the pixels, whereby shift pulse SDI is propagated serially from first registers SR1 to the respective buffers B in a time interval 1H shorter than time width 3H of shift pulse SDI. According to the constitution as described above, it is possible to select three scan lines G adjacent to one another simultaneously for a period of 1H. That is, driving of pixel electrodes A31, B31 and C31 (D31, E31, and so on) can be controlled within one horizontal scanning cycle (1H) by supplying scanning signals Gn+1Out, Gn+2Out and Gn+3Out (Gn+2Out, Gn+3Out, G+4Out, and so on) from three scan lines of Gn+1, Gn+2 and Gn+3 (Gn+2, Gn+3, Gn+4, and so on).
Therefore, it is not necessary to arrange three systems of scan lines G or to provide three systems of OE lines 11 in order to control driving of pixel electrodes A31, B31, C31 and the like, but control can be performed by supplying the same output control signal OE with the same OE line 11. In other words, it is possible to select a plurality of scan lines G simultaneously without complicating the control of buffers B with output control signal OE or a structure of gate driver 5′, whereby the structure of liquid crystal display device 1′ having the multiplex pixel structure can be simplified and facilitation of fabrication as well as reduction of costs can be achieved.
Particularly, according to the second embodiment, shift pulse SDI is set up to turn on and off in every cycle of clock signal TCPV, that is, in every H/3 cycle obtained by time division of one horizontal scanning cycle 1H by the multiplex rate of the pixels. At the same time, the time width of shift pulse SDI is set to 3H, which is a time width equal to addition of a 2H time period (an additional time period) to one horizontal scanning cycle 1H (a time width obtained by one horizontal scanning cycle 1H multiplied by multiplex rate “3”). Moreover, a time interval of shift pulse SDI propagating between respective buffers B is set as three times the cycle of clock signal TCPV or as 1H. Therefore, it is possible to set a time period of 1H for effectuating simultaneous supply of the scan signal to three adjacent scan lines G, and it is also possible to control driving of pixel electrodes A31, B31 and C31 (D31, E31 and F1, and so on) in every H/3 time period within 1H cycle. In this way, liquid crystal display device 1′ having multiplex (3:1) pixel structure can be favorably realized.
Description has been heretofore made regarding a second embodiment of the present invention. However, as understood, the present invention is not limited to the above-described second embodiment, as other embodiments, e.g., the first cited earlier, can be adopted from time to time as necessary.
For example, also in the above-described second embodiment, clock signal generator 10 may generate clock signal TCPV of an uneven frequency by varying timing of a leading edge or a trailing edge of each pulse of such clock pulse TCPV as similar to the above-described first embodiment.
Moreover, in the above-described second embodiment, liquid crystal display device 1′, having a multiplex pixel structure of 3:1 (the pixel structure of selecting three pixels in 1H), is driven. If this multiplex rate herein is defined generally as m, which is an arbitrary natural number equal to or larger than 2, then it is possible to drive a liquid crystal display device having a multiplex pixel structure of m:1 by the present invention. Specifically, between a pair of first shift registers SR1 connected with scan lines G via the buffers B, m−1 pieces of other shift registers may be provided such that those shift registers are operated by the same clock signal as the clock signal for first registers SR1. Simultaneously, a cycle of the clock signal may be set to 1/m of one horizontal scanning cycle 1H. In addition, a time width of shift pulse SDI is set to mH. Therefore, m lines of scan lines G can be selected at the same time. In this way, it is possible to drive the display device having the multiplex pixel structure of m:1 favorably.
In this case, it is not always necessary to select m lines of scan lines G upon selecting m pieces of the pixels, but it is also possible to select less than m lines or more than m lines of the scan lines G. Therefore, the time width of the shift pulse may be also smaller than mH or larger than mH.
In addition to the foregoing example, the constitution cited in the above-described embodiment may be partially selected, omitted or modified to another constitution to the extent not deviating from the gist of the present invention.
Next, description will be made regarding a third embodiment of the present invention.
As shown in
Meanwhile, gate driver 5″ is provided with a shift register unit (a propagation circuit) 12″. Shift register unit 12″ includes first shift registers SR1, each of which is provided corresponding to each scan line G and connected with an output terminal Ot connectable with scan line G via a buffer (an output circuit) B. In addition, shift register unit 12″ includes partial propagation circuits 17. This shift register unit 12″ has a constitution of cascade connection of multiple pairs Su, Su, and so on (illustration partially omitted) corresponding to scan lines G, in which Su is a pair of first shift register SR1 and partial propagation circuit 17.
Partial propagation circuit 17 is designed to allow a shift pulse generated by pulse generator 9 to pass therethrough, or is designed to function as a single shift register or as multiple shift registers based on the multiplex rate display signal supplied from multiplex rate display signal generator 15.
In other words, if the multiplex rate display signal indicates “m (where m is an arbitrary natural number equal to or larger than 2)” as the multiplex rate of a display region S, then partial propagation circuit 17 functions as cascade connection of (m−1) shift registers operated synchronously with a clock signal. Alternatively, if the multiplex rate display signal indicates “1” as the multiplex rate of the display region S, then the propagation circuit functions as a circuit to allow the shift pulse to pass directly therethrough.
Next, description will be made regarding operations in the case that control circuit 6′ and gate driver 5″ having the above-described constitutions are set as circuits for outputting a scanning signal to scan lines G of liquid crystal display device 1.
In this case, clock signal generator 10 outputs a clock signal in which m cycles thereof correspond to one horizontal scanning cycle (1H) of a screen.
In the meantime, pulse generator 9 outputs a shift pulse (a signal sequence) in which a time width thereof corresponds to two horizontal scanning cycles (2H), for example. Note that this shift pulse is set to turn on and off in each cycle of the clock signal.
Here, when the shift pulse is generated by pulse generator 9, this shift pulse is serially transferred through first shift registers SR1 and partial propagation circuits 17. Here, focusing on two adjacent first shift registers SR1, for example, a first shift register SR1(n) located in an n-th position in a direction of propagation of the shift pulse and a first shift register SR1(n+1) located in an n+1-th position, for example, then shift pulse SDI at first shift register SR1(n) passes through partial propagation circuit 17 and is inputted to the next first shift register SR1(n+1) in arrears of m cycles of the clock signal, that is, in arrears of one horizontal scanning cycle. Here, since the time width of shift pulse is 2 horizontal scanning cycles, the shift pulse will partially coexist in first shift registers SR1(n) and SR1(n+1) for a given time period as long as one horizontal scanning cycle (1H). Accordingly, it is possible to output the scanning signal with respect to both of scanning lines Gn and Gn+1 respectively connected with these first shift registers SR1(n) and SR1(n+1), by opening buffer B in a period including this given time period.
In addition, it is possible to output the scanning signal simultaneously to a scan line set consisting of m line of scan lines G by setting the time width of shift pulse SDI as longer horizontal scanning periods (mH). Accordingly, it is possible to control driving of pixels in display area S of a m-fold pixel structure, by controlling selection or non-selection of these scan lines G in accordance with each moment of H/m.
As described above, in this third embodiment, buffer B is provided corresponding to each scan line G and shift register unit 12″ is formed by cascade connection of alternate arrangements of first shift registers SR1 and partial propagation circuits 17. In addition, buffers B are connected solely with first shift registers SR1 of shift register unit 12″. Moreover, shift pulse SDI is supplied to respective buffers B by serially propagating shift pulse SDI with respect to these first shift registers SR1 and partial propagation circuits 17. In this case, shift register unit 12″ is driven by the clock signal having a H/M cycle dividing one horizontal scanning cycle 1H with a multiplex rate “m” of the pixels, whereby it is possible to propagate shift pulse SDI serially from shift register SR1 to each of the buffers B in a time interval of 1H which is shorter than time width mH of shift pulse SDI. In this way, it is possible to select m lines of scan lines G adjacent to one another simultaneously for a 1H period of time, whereby driving of m pieces of pixel electrodes to which a signal is supplied from the same signal line D can be controlled within one horizontal scanning cycle 1H by supplying the scanning signal from m lines of scan lines G.
Therefore, it is not necessary to arrange m systems of scan lines G or to provide m systems of OE lines 11 in order to control driving of m pieces of the pixel electrodes within one horizontal scanning cycle 1H, but control can be performed by supplying the same output control signal OE with the same OE line 11. In other words, it is possible to select a plurality of scan lines G simultaneously without complicating the control of the buffers B with the output control signal OE or a structure of the gate driver 5″, whereby the structure of liquid crystal display device 1′ having the multiplex pixel structure can be simplified and facilitation of fabrication as well as reduction of costs can be achieved.
Furthermore, since control circuit 6′ and gate driver 5″ are adoptable to a display device having a m:1 multiplex pixel structure of an arbitrary natural number, the present invention is significantly versatile. For example, clock signal generator 10 may generate a clock signal of an uneven frequency by varying timing of a leading edge or a trailing edge of each pulse of such a clock pulse. Moreover, in this above-described third embodiment, it is also acceptable to select less than m lines or more than m lines of scan lines G upon selection of m pieces of the pixels. Therefore, the time width of the shift pulse may be also smaller than mH or larger than mH.
As described above, according to the present invention, it is possible to drive a display device having a multiplex pixel structure only with simple on/off signals, and it is also possible to simplify a structure of a scan line drive circuit.
Although the preferred embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and alternations can be made therein without departing from spirit and scope of the inventions as defined by the appended claims.
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