JP2001318363A - Driving method for liquid crystal device and liquid crystal device driven by the same driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent picture quality from being deteriorated when a liquid crystal panel is driven by a field sequential system. SOLUTION: An information signal Vin is modulated and reset driving is carried out after the point t5 of time when a black-and-white image is displayed by scanning the liquid crystal panel in line sequence to emit light, and then, the potential Vcom of a counter electrode is also modulated. The image of the liquid crystal panel is erased by this reset driving to exert no effect on an image to be displayed next, and then the color reproducibility of the liquid crystal panel is improved. Further, the potential Vcom of the counter electrode is modulated as mentioned above, so a TFT with a small ON/OFF ratio is usable and the opening ratio, etc., of each pixel is improved to improve the picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal device for displaying a full-color image using liquid crystal, and a liquid crystal device driven by the driving method.

[0002]

2. Description of the Related Art (1) In recent years, liquid crystal devices have been used in devices such as personal computers, video camcorders, and projectors, and various types of information are displayed in color.

(2) There is a liquid crystal device using a so-called field sequential system for performing color display as described above. Hereinafter, an example of the structure of the liquid crystal device will be described with reference to FIGS.

A liquid crystal device of this type includes an active matrix type liquid crystal panel P and a backlight device (light source) B arranged to face the liquid crystal panel P, as shown by reference numeral 1 in FIG. It has.

The liquid crystal panel P has a pair of glass substrates 10a and 10b arranged with a predetermined gap therebetween, and one of the substrates 10a is provided with a counter electrode 6 and the like. Also, as shown in FIG. 3, a large number of scanning lines G ₁ , G ₂ ,... And signal lines S ₁ , S
_2, ... are formed, each pixel of the intersection, the scanning lines _G 1, _{G 2,} ... and the signal lines _S 1, _{S 2,} TFT 4 and connected to ..., TFT (switching element) 4
Are connected to the pixel electrode 5 and the storage capacitor electrode 8, respectively (see FIG. 9). A twisted nematic liquid crystal 7 is arranged in the gap between the glass substrates 10a and 10b and between the opposing electrode 6 and the pixel electrode 5 arranged so as to face each other. The liquid crystal panel P is configured in a circuit as shown in FIG.
Only black and white images are displayed without a color filter.

The other backlight device B is configured to sequentially and selectively irradiate the liquid crystal panel P with red, blue, and green light.

(3) Next, an example of a method of driving the above-described liquid crystal device 1 by a field sequential method will be described with reference to FIG. Here, FIG. 7 is a timing chart showing an example of a driving method of a conventional liquid crystal device. FIG. 7A schematically shows a state in which all the scanning lines G ₁ , G ₂ ,. FIG. 3B is a diagram showing a state of the liquid crystal response of the pixel along the _first scanning line G1, and FIG.
FIG. 9 is a diagram showing a state of a liquid crystal response of a pixel along the last scanning line _Gn , and FIG. 9D is a diagram showing an irradiation timing of each color light.

In this driving method, as shown in FIG. 7, one frame period F ₀ is divided into three field periods F _R ,
F _G, be those divided into F _B to drive the liquid crystal device 1, each of the field period F _R, F _G, monochrome image on the liquid crystal panel P in F _B (image defining the tone of each color of the image) By causing display and irradiating the liquid crystal panel P with monochromatic light from the backlight device B,
The monochrome image on the liquid crystal panel is recognized as a red image, a green image, or a blue image, and these three-color images are visually mixed to be recognized as a full-color image.

When displaying a monochrome image, the liquid crystal panel P
Scan lines _G 1, _{G 2,} and applies a scanning signal _{V g} in a line sequential manner ... (see FIG. (A)), the signal lines _S 1, _{S 2,} is ... to apply the information signal (image signal) . Then, TFT4 of each pixel
Is turned on by the application of the scanning signal _Vg , the information signal is applied to the pixel electrode 5, and the liquid crystal 7 responds as shown in FIGS. The liquid crystal 7 pixels along the first scanning lines G ₁ response at time t ₁ as shown in FIG. 5 (b) is started, the liquid crystal 7 pixels along the last scan line G _n is response at time t ₃ is started as shown in FIG. (c).

On the other hand, the irradiation of the monochromatic light by the backlight unit B, the liquid crystal response of the pixels along the last scan line G _n is completed to some extent, when the entire panel displays a black and white image (reference numeral t ₄₎ Do. The irradiation of such monochromatic light the next field period (e.g., F _G) is stopped immediately before (reference numeral t ₅₎ the beginning of.

(4) Further, another example of a method of driving the above-described liquid crystal device 1 by a field sequential method will be described with reference to FIG. Here, FIG.
A timing chart showing another example of a conventional method of driving a liquid crystal device, (a) represents a view showing the application timing of the scanning signal to be applied to a certain one of the scanning lines G _i, (b), the Is a diagram schematically showing a state in which all the scanning lines G ₁ , G ₂ ,... Are sequentially scanned, (c) is a diagram showing the application timing of an information signal applied to the TFT 4, and (d) is a diagram of the counter electrode 6. FIG. 7E shows a change in potential, FIG. 9E shows a change in the potential of Node A (the potential on the pixel electrode 5 side as shown in FIG. 9), and FIG. 9F shows a change in the voltage applied to the liquid crystal 7. FIG. 3 (g) is a diagram showing a state of a liquid crystal response, and FIG. 3 (h) is a diagram showing an irradiation timing of each color light.

[0012] The driving method, similarly as described in the above (3), be those of one frame period F ₀ 3 single field period F _R, F _G, divided into F _B to drive the liquid crystal device 1 In each of the field periods F _R , F _G , and F _B , the liquid crystal panel P displays a monochrome image (an image that defines the tone of each color image) and the backlight device B
Irradiates the liquid crystal panel P with monochromatic light to cause a black and white image on the liquid crystal panel to be recognized as a red image, a green image, or a blue image, and visually mixes these three color images as a full color image. It is to let.

[0013] In view of the black-and-white image (see FIG. (A) and (b)) the scan lines G ₁ of the liquid crystal panel _P, G 2, and applies a scanning signal V _g in a line sequential manner _..., the signal line S ₁ , S ₂ ,
... To apply the information signal _{V in (0V ≦ V in ≦} 5V) ( see FIG. (C)). Thereby, the TFT 4 of each pixel is
Is turned on to apply an information signal to the pixel electrode 5 via the TFT 4 (see FIG. 3 (e)). At this time, since a voltage of +5 V is applied to the counter electrode 6 (FIG. 4 (d)). , And a voltage V _data (= V _in −5 V) corresponding to the difference between the pixel electrode 5 and the counter electrode 6 is applied to the liquid crystal 7 of each pixel (see FIG. 6F), and the liquid crystal of each pixel is displayed. 7 starts a response corresponding to each voltage V _data (see FIG. 7 (g)). The liquid crystal 7 of the pixel along the _first scanning line G1
Begins the response at time t _1, the liquid crystal 7 pixels along the last scan line G _n is the response at time t ₃ is started.

[0014] On the other hand, the irradiation of the monochromatic light by the backlight unit B, the liquid crystal response of the pixels along the last scan line G _n is completed to some extent, when the entire panel displays a black and white image (reference numeral t ₄₎ so, the next field period (e.g., F _G) is stopped immediately before (reference numeral t ₅₎ the beginning of.

In this driving method, the signal lines S ₁ , S
_The information signal Vin applied to ₂ ,... Is changed in the range of 0 V to +5 V _in accordance with the display gradation, and the potential of the counter electrode 6 is changed at the start of the next field period (for example, at time t ₁ , t ₁₎ .
At t ₅ , t ₇ ), the voltage is alternately changed to 0 V or 5 V (see FIG. 3D). No reset is performed. Therefore, the potential of the Node A at each pixel, as shown in FIG. (E), * even in the next field period F _G, the potential between -5V~0V in a floating state, the voltage Is written (the point in time when line-sequential scanning is performed.
First becomes 0V~5V potential ₆ reference), in * third field period _{F B,} until before the line sequential scanning is performed a potential of + 5V to + 10V.

[0016]

In the conventional driving methods (3) and (4) described above, the driving state of the liquid crystal 7 in each pixel is not reset, and a new voltage is applied in the next field period. Is applied until the liquid crystal response is completed. Therefore, the time when the irradiation of light in the next field period starts (for example, time t ₄ in FIG. _7), (the relatively liquid crystal response shown in FIG. (B) early in the pixel to be scanned to complete In a pixel that scans slowly (although it has been done), the liquid crystal response is not completed, and the effect of the driving state in the previous field period remains (see FIG. 3C). For this reason, the tone of the monochrome image displayed on the entire panel in each field period is not appropriate, and the color reproducibility of the full-color image recognized through the three field periods is deteriorated (that is, the color reproducibility is low). The color of the full-color image actually recognized by the liquid crystal panel is different from the color of the image to be displayed).

In the case of the above-described conventional driving method (4), the potential of the counter electrode 6 is changed to the next field period F _R , F _R.
G or _F start (first run of scanning the scanning line _{G 1)} at the same time is modulated _B, the scanning lines _G 1, _{G 2,} of ... pixel No
de A is higher potential before the line-sequential scanning is performed (e.g., potential + 5V to + 10V, as shown in FIG. 8 (e) in the third field period _{F B)} it becomes. To turn on the TFT 4 in such a case, the scanning signal _Vg must be V
_It is necessary to take a sufficient on / off ratio with respect to the potentials of _in and Node A (the potential of Node A is between +5 V and +1
In the case of 0 V, an ON voltage of at least 10 V or more and an OFF voltage of at least -5 V or less are required.
T4 has a large withstand voltage (10V + 5V = 15 in the above example).
V withstand voltage). However, a TFT having such a withstand voltage is large in size. As a result, when the liquid crystal panel is of a transmission type, the area inside the pixel where the TFT is arranged becomes large, the aperture ratio decreases, and the light use efficiency decreases. There was a problem that it would decrease. Further, when the liquid crystal panel is of a reflection type, there is a problem that one pixel cannot be made smaller than the size of the TFT, and there is a limit to high definition.

A method for reducing the withstand voltage of the TFT is as follows.
Then, the potential of the counter electrode 6 is adjusted as in the driving method (4).
Rather than change every field period, keep it constant
Line S ₁, S₂, ..., as well as the voltage of the signal applied
(For example, modulation from -5V to + 5V)
is there. However, according to this method, the signal line S₁,
S₂The width of the signal to be applied to the
The circuit withstand voltage of the drive circuit 3 must be increased, and the circuit 3
The problem of larger size and increased power consumption
there were.

Accordingly, an object of the present invention is to provide a driving method of a liquid crystal device which prevents a decrease in color reproducibility and the like.

Another object of the present invention is to provide a liquid crystal device in which a decrease in color reproducibility is prevented.

[0021]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and comprises a plurality of scanning lines and a plurality of signal lines, and each pixel connected to the scanning lines and the signal lines. A plurality of switching elements respectively arranged for each, a plurality of pixel electrodes respectively arranged for each pixel in a state of being connected to each switching element, and a counter electrode arranged at a position facing these pixel electrodes A liquid crystal element comprising a liquid crystal disposed between the pixel electrode and the counter electrode, and a light source that selectively irradiates each color light to the liquid crystal element. In the method for driving a liquid crystal device for displaying an image, the method may include applying a scanning signal to the plurality of scanning lines sequentially to turn on the plurality of switching elements in order and applying an image signal to the plurality of signal lines. A voltage is applied to the liquid crystal through the switching element and the pixel electrode to drive the liquid crystal, and the application of the scanning signal to the last scanning line is completed. After the driving is started, the light source irradiates each color light to the liquid crystal element, and then applies a scanning signal to the plurality of scanning lines to turn on the plurality of switching elements and the plurality of signal lines. By applying a reset signal to reset the liquid crystal with a predetermined potential difference between the pixel electrode and the counter electrode, by repeating the series of driving while changing the color of light to be irradiated, It is characterized in that images having different colors are visually mixed to be recognized as a full-color image.

Further, according to the present invention, a plurality of scanning lines and a plurality of signal lines, a plurality of switching elements arranged for each pixel while being connected to the scanning lines and the signal lines, and A plurality of pixel electrodes arranged for each pixel in a connected state, a counter electrode disposed at a position facing the pixel electrodes, and a liquid crystal disposed between the pixel electrodes and the counter electrode A liquid crystal element comprising: a scanning line driving circuit connected to the plurality of scanning lines to apply a scanning signal; and a signal line driving circuit connected to the plurality of signal lines to apply a signal. In a liquid crystal device including a light source for selectively irradiating each color light to an element, the signal line driving circuit is arranged on a side of a last scanning line among a plurality of scanning lines sequentially scanned. And Serial resistance value of each signal line, the composed image in the in-plane luminance distribution of the liquid crystal element is set to a value that does not cause, characterized in that.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
An embodiment of the present invention will be described.

First, the structure of the liquid crystal device driven in this embodiment will be described with reference to FIGS.

The liquid crystal device driven in this embodiment is
As shown by reference numeral 1 in FIG. 2, the liquid crystal display device includes an active matrix type liquid crystal element P and a light source B arranged to face the liquid crystal element P.

As shown in FIG. 3, the liquid crystal element P includes a plurality of scanning lines G ₁ , G ₂ ,... And a plurality of signal lines S ₁ , S ₂ arranged in a matrix in a state of being insulated from each other.
_2, ... and the plurality of scanning lines _G 1, _{G 2,} a scanning line drive circuit 2 connected to ..., the plurality of signal lines _{S 1, S} 2,
, And a signal line driving circuit 3 connected to. Then, these scanning lines G ₁ , G ₂ ,... And signal lines S ₁ ,
S _2, the ... each pixel in the vicinity of each intersection of the scanning lines G _1, G 2, _... and the signal lines S _1, S 2, switching element 4 in a state of being connected to _... it is arranged Each switching element 4 is connected to a pixel electrode 5. A counter electrode 6 is disposed at a position facing the pixel electrodes 5 as shown in FIG. 2, and a liquid crystal 7 is provided between the pixel electrodes 5 and the counter electrode 6.
Is arranged.

Here, the scanning lines G ₁ , G ₂ ,... Are line-sequentially scanned as described later. In FIG. 3, the signal line driving circuit 3 scans the scanning line G _{1 first.} However, as shown in FIG. 5, it may be arranged on the side of the last scanning line _Gn . In this case, the resistance value of each of the signal lines S ₁ , S ₂ ,... Is preferably set to a value that does not cause an in-plane luminance distribution in the image of the liquid crystal element P.

One light source B is configured to selectively irradiate three or more colors of light to the liquid crystal element P for each color.

The light source B has a scanning line G to be scanned first.
It is preferable that the luminance of the _first side is low, and the luminance is continuously increased toward the side of the scanning line to be scanned later (see FIG. 6).

The light source B is denoted by reference numeral 2 in FIG.
As shown by 0, the brightness (light source light conversion efficiency) increases as the temperature decreases (for example, LE
D) may be used (details will be described later).

Next, the driving of the liquid crystal device 1 according to the present embodiment will be described.
The operation method will be described with reference to FIG. Where the figure
1 is a diagram showing an example of a method for driving a liquid crystal device according to the present invention.
It is an imaging chart figure, (a) is a certain one scanning line
G_iScan signal V applied to _gIndicates the application timing of
FIG. 4B shows all the scanning lines G.₁, G₂, ... scanned in order
FIG. 4C schematically shows the state of the switching element 4.
Diagram showing the application timing of applied signals, etc.
FIG. 7E shows a change in the potential of the counter electrode 6, and FIG.
Change in potential (potential on the pixel electrode 5 side as shown in FIG. 9)
(F) shows a change in the voltage applied to the liquid crystal 7.
Figure, (g) shows the response of the liquid crystal, (h) shows the illumination of each color light.
It is a figure showing firing timing.

In this embodiment, * the plurality of scanning lines G are₁,
G₂,... In order._gIs applied to the plurality of switches.
The switching elements 4 are sequentially turned on for each scanning line (see FIG.
(See (a) and (b)) together with the signal line driving circuit 3.
The plurality of signal lines S ₁, S₂,... To the image signal V_inMark
In addition (see FIG. 3 (c)), the switching element 4 and
A voltage is applied to the liquid crystal 7 through the pixel electrode 5 to
The liquid crystal 7 is driven (see (e), (f), and (g) in the same figure). * Last scanning line G_nScan signal V to_gEnd of application
And the scanning line G_nLiquid crystal in the pixels along the line starts driving
(After the liquid crystal response is completed to some extent, the image of each color
Black and white image defining the tone of the image is displayed on the liquid crystal element P
Time t₄), From the light source B to the liquid crystal element P
Each black and white image is colored by irradiating each color light for a certain time.
(See (h) in the figure), and then the plurality of scanning lines G₁, G₂, ... scanning signal
No. V_gTo turn on the plurality of switching elements 4.
And the plurality of signal lines S₁, S₂, ... reset
By applying a reset signal, the pixel electrode 5 and the pair
The liquid crystal 7 is reset by setting the potential difference between the
(See (g) in the figure) * Such a series of driving (that is, a table of black and white images)
Display, irradiation of each color light, and reset)
Repeatedly changing the color and the displayed black and white image
By blending, images of different colors are visually mixed
It is designed to be recognized as a full-color image.

[0033] In this specification, a period in which one still color images are displayed (i.e., a time to turn off the display start-beam monochrome image, code F _R in FIG. _1, F
The duration) represented by _G or _{F B} and the field period, 1
A period in which two still full-color images are displayed (a total period of the field periods F _R , F _G , and F _B ) is defined as a frame period.

In the present embodiment, the voltage V corresponding to the difference between the pixel electrode 5 and the counter electrode 6 is applied to the liquid crystal 7.
_Data is applied (see (f) in the figure), and in each pixel, the liquid crystal 7 starts a response according to the voltage V _data (see FIG.
(g)).

In this embodiment, light irradiation
The liquid crystal response at the pixel along the last scan line _Gn is 90
%, When the black-and-white image is almost displayed on the liquid crystal element P, and should be stopped before the next field period starts.

Further, in the present embodiment, the voltage applied to the counter electrode 6 is changed every time each color light is irradiated (that is, for each field period) (see FIG. 1D). ). In this case, the signal lines S ₁ , S ₂ ,
The reset signal applied to... Is substantially equal to the voltage applied to the counter electrode 6, as shown in FIG. 1 (c), and the reset signal applied to the pixel electrode 5 when the liquid crystal 7 is reset. It is preferable that the potential difference between the electrode 6 and the electrode 6 be approximately 0V. Alternatively, the reset signal applied to the signal lines S ₁ , S ₂ ,... May have a value such that the response position of the liquid crystal 7 is in a saturated state as shown in FIG.

The change in the voltage applied to the counter electrode 6
And the plurality of signal lines S₁, S ₂Reset to…
The signal is applied to the plurality of scanning lines G₁, G₂Scan to, ...
It is better to perform this while the signal is being applied.

Next, the effect of the present embodiment will be described.

According to the present embodiment, the driving state of the liquid crystal 7 in each pixel, since the irradiation light is reset at the time point (reference numeral t ₄ in FIG. 1) to be started in the next field period The tone of the black-and-white image displayed by the entire liquid crystal element in each field period is appropriate (that is, only the image of the tone corresponding to the color of the irradiated light without being affected by the image of the previous field period). Is the liquid crystal element P
), And the color reproducibility of the full-color image recognized throughout the entire field period is improved.

Further, according to the present embodiment, the counter electrode 6
And reducing the modulation width of the image signal V _in by changing the potential in each field period. Thus, the withstand voltage of the signal line driving circuit 3 can be reduced, and the size and power consumption of the circuit 3 can be reduced.

[0041] Further, according to this embodiment, the timing of changing the potential of the counter electrode 6 is up before the next field period since the scanning signal V _g is applied for resetting the image is started for the next field period _F R, _{F G} or potential of each pixel in since the start of _{F B} before the line-sequential scanning is performed Node a (absolute value)
Can be kept small. Therefore, requires on / off ratio of the scanning signal V _g applied to the switching element 4 is small,
The withstand voltage of the switching element 4 can be reduced. as a result,
The switching element 4 can be reduced in size, the aperture ratio and the light use efficiency can be improved when the liquid crystal element P is of a transmissive type, and the pixel size can be reduced when the liquid crystal element P is of a reflective type. And high definition can be achieved.

[0042]

The present invention will be described below in more detail with reference to examples. (Embodiment 1) In this embodiment, as shown in FIG.
A backlight device (light source) B was arranged so as to face an active matrix type liquid crystal panel (liquid crystal element) P, and a liquid crystal device 1 was produced.

The liquid crystal panel P has a pair of glass substrates 10a and 10b arranged with a predetermined gap therebetween, and the counter electrode 6 and the alignment control film 11a are formed on one of the glass substrates 10a. Also, the other glass substrate 10b
As shown in FIG. 3, a number of signal lines S ₁ , S ₂ ,.
Are arranged in the illustrated Y direction, and a large number of scanning lines G
_{1, G 2,} arranged ... respectively the X direction (in FIG. 5
, The signal lines S ₁ , S ₂ ,... Are connected to the signal line driving circuit 3, and the scanning lines G ₁ , G ₂ ,.
Connected to. Moreover, these signal lines _S 1, _{S 2,} ..., and scan lines _G 1, _{G 2,} ... were arranged TFT (switching element) 4 and the pixel electrode 5 and the storage capacitor electrode 8 for each pixel of the intersection of the. In addition, a twisted nematic liquid crystal 7 is disposed between the counter electrode 6 and the pixel electrode 5 in the gap between the glass substrates 10a and 10b. Reference numeral 11b indicates an orientation control film, and reference numeral 12 indicates an insulating film.

Next, a method of driving the liquid crystal device 1 will be described with reference to FIG. Here, FIG. 1 is a timing chart showing an example of a driving method of the liquid crystal device according to the present invention, and FIG. 1 (a) shows an application timing of a scanning signal applied to _one scanning line G1. FIG, (b), all of the scanning lines G _1, G 2, shows how the scanning _... sequentially schematically, (c) is a diagram showing an application timing of the signal V _in applied to the TFT 4, (d) is a diagram showing a change in the potential of the counter electrode 6, (e) is a diagram showing a change in the potential of Node A (the potential on the pixel electrode 5 side as shown in FIG. 9), and (f) is a diagram showing the liquid crystal 7 FIG. 7 (g) is a diagram showing a change in voltage applied to the liquid crystal, FIG. 7 (g) is a diagram showing a state of a liquid crystal response, and FIG.

In this embodiment, one frame period F ₀
Were divided into three field periods _{F R, F G, F B} , * the first field period F _R, irradiated with red light by the backlight device B and displays a black-and-white image corresponding to the red image by the liquid crystal panel P display red image by * in the second field period F _G, displays a green image by irradiating the green light by the backlight device B and displays a black-and-white image corresponding to the green image by the liquid crystal panel P and, * the third field period F _B, to display a blue image by irradiating a blue light by the backlight device B and displays a black-and-white image corresponding to the blue image by the liquid crystal panel P, it was decided.

First, the first field period F_RTime
t₁~ T₃All scanning lines G₁, G₂, ... line-sequential
Scanning was performed (see FIG. 3 (b)). Specifically, each scanning line
G₁, G ₂,... Have the scanning signal V as shown in FIG._g
And each signal line S₁, S₂, ... are the image signals V_in
(See FIG. 3 (c)). This allows you to run
Scanned line G₁, G₂, ... all connected to
The switching element 4 is turned on, and each signal V_inIs each sui
Applied to each pixel electrode 5 via the switching element 4
(See Figure (e)). At this time, a voltage of 5 V was applied to the counter electrode 6.
The liquid crystal 7 has a pixel electrode 5 and a counter electrode 6
V corresponding to the difference between_data(= V_{i n}-5V)
Is applied (see (f) in the figure), and the liquid crystal 7 of each pixel is
Voltage V_{d ata}Start response in response to ((g) in the figure)
reference).

The driving ends of the last scanning line G _n, further liquid crystal response of a pixel along the scan line G _n of said last 90
Once t ₄ when finished to about%, and irradiated with red light by turning on the backlight device B to the liquid crystal element P (see FIG. (H)). As a result, a red image was displayed.

After that, the scanning signal _Vg is applied to all the scanning lines G ₁ , G ₂ ,... (See FIG. 7A), and the potentials of all the signal lines S ₁ , S ₂ ,. At the time t ₅ ′ immediately after that, as shown in FIG.
V (see (d) in the figure). As a result, the voltage applied to the liquid crystal 7 becomes 0 V in all the pixels (see FIG. 7 (f)), the liquid crystal panel P enters a transmissive state, and the red image is reset (see FIG. 7 (g)).

Thereafter, the backlight device B was turned off (see FIG. 8H).

[0050] performing such driving second and third field period _F G, even _{F B.} However, the potential of the counter electrode 6 was alternately set to 0 V or +5 V at the timing of resetting, and the potentials of all the signal lines S ₁ , S ₂ ,.

Next, the effect of this embodiment will be described.

According to this embodiment, the full-color image displayed on the liquid crystal panel P has good color reproducibility.

In addition, a signal line driving circuit 3 having a small circuit withstand voltage can be used, so that downsizing and power saving can be achieved.

Further, according to the present embodiment, the potential Node A (absolute value) of each pixel can be suppressed to a small value.
A small FT4 can be used, and the liquid crystal panel P
The display quality could be improved by improving the aperture ratio of.

By the way, the response speed of the liquid crystal is slow when performing halftone display, fast when performing white display or black display, and further faster when shifting to a stable state when no voltage is applied. Since the reset in this embodiment is performed by shifting to a stable state when no voltage is applied, the response speed of the liquid crystal at that time is considerably high. This can prevent a display state in which image information is mixed in adjacent field periods.

(Embodiment 2) In this embodiment, the same liquid crystal panel P as in Embodiment 1 was driven by the method shown in FIG. Here, FIG. 4 is a timing chart showing another example of the driving method of the liquid crystal device according to the present invention.
Shows the application timing of the scanning signal to be applied to a certain one of the scanning lines G _i, (b), all of the scanning lines G _1, G _2, ...
Is a diagram schematically showing a state in which scanning is sequentially performed, and FIG.
Shows the application timing or the like of the applied signal V _in to,
(d) is a diagram showing a change in the potential of the counter electrode 6, and (e) is a diagram showing Nod.
e is a diagram showing a change in the potential of A (the potential on the pixel electrode 5 side as shown in FIG. 9), (f) is a diagram showing a change in the voltage applied to the liquid crystal 7, and (g) is a state of the liquid crystal response. And (h) is a diagram showing the irradiation timing of each color light.

[0057] drive of the present embodiment, before applying the liquid crystal reset (e.g., to time t ₁ ~t 5 _'in the first field period F _R) has been in the same manner as in Example 1,
While applying a liquid crystal reset (e.g., between time t _{5 '~t 5} in the first field period F _R) and the driving of differently from the first embodiment. That is, in the first embodiment, the potential of the counter electrode 6 and the signal lines S ₁ ,
The potential of S ₂ ,... Was set to the same potential at 0 V or +5 V,
In this embodiment, when the potential of the counter electrode 6 is 0 V, the potentials of the signal lines S ₁ , S ₂ ,... Are set to +5 V. When the potential of the counter electrode 6 is +5 V, the signal lines S ₁ , S ₂ ,. Potential of 0V
I made it. Then, reset was performed by causing the liquid crystal to respond in a direction opposite to the stable state when no voltage was applied. For example, when a normally white liquid crystal was used, black reset was performed.

According to the present embodiment, substantially the same effects as in the first embodiment were obtained.

(Embodiment 3) The scanning line G
₁, G₂When displaying images by line-sequential scanning of
If the backlight device B is turned on after scanning,
At scan line G₁, G₂, ...
Scan line G scanned first₁Is the longest (t in the case of FIG. 1).
₁~ T₄), Scanning line G to be scanned later₂, ... short
The last scanning line G_nIs the shortest (t in the case of FIG. 1).
₃~ T₄). Then, in the plane of the liquid crystal panel P,
Scan line G to be scanned₁The brightness of the pixels along
Scan line G to be scanned₂, ..., the lower the brightness, the more line-sequential
The occurrence of transmittance distribution (luminance distribution) in the scanning direction
Becomes Such a tendency is caused by the scanning line G₁, G₂,… Number
The more liquid crystal panels, the more noticeable. For example, one frame period
1/60 sec and 1 field period is 1/18
0 sec ≒ 5.5 msec, and all scanning lines G₁, G₂,
.. (Time t in FIG. 1)₁~
t₃) For 2.8 msec, and turn on the backlight device B.
And then reset to start the next field period
Time (t in the case of FIG. 1)₄~ T₅) For 2.0 mse
c, the first scanning line G₁Is scanned,
The time until the lighting device B is turned on (in the case of FIG. 1,
t₁~ T₄) Is 3.5 msec, whereas the last
Scanning line G _nBacklight unit B is turned on after scanning
Time (t in the case of FIG. 1)₃~ T₄) Is 0.7
msec only.

[0060] Therefore, in this embodiment, the positions of the signal line drive circuit 3, rather than the side of the scanning lines G ₁ to be scanned first, as shown in FIG. 3, the end of the scan, as shown in FIG. 5 It was on the side of the line _Gn . Further, the resistance values of the signal lines S ₁ , S ₂ ,... Were set to values such that the above-described in-plane luminance distribution did not occur. Other configurations and driving methods were the same as those in the first embodiment.

According to the present embodiment, the luminance distribution of the liquid crystal panel P can be reduced, and the image quality can be improved.

(Embodiment 4) In the present embodiment, the same liquid crystal panel (liquid crystal element) P as in Embodiment 1 was used, but the backlight device B was provided with scanning lines G ₁ , G ₂ ,. those having a luminance distribution indicated by reference sign M in Fig 6 in a direction of progressive scanning (i.e., the lowest luminance of the portion opposed to the scanning lines G ₁ to be scanned first, the scanning lines are scanned after G _2, ... in The higher the brightness, the higher the brightness of the portion facing the last scanning line _Gn .

In the liquid crystal panels P of the first and second embodiments,
As described in 3, scanning line G₁, G ₂The number of…
In this case, a transmittance distribution occurs in the plane (see FIG. 6).
Reference sign N). Then, the in-plane luminance is applied to the backlight device B.
When the liquid crystal panel P is uniform,
Is not uniform, and the LCD panel side
A degree distribution results.

However, in the present embodiment, since the backlight device B having the above-described luminance distribution is used, the transmittance distribution of the liquid crystal panel P is canceled out, and the light emitted from the backlight device B is emitted from the liquid crystal panel P. The amount of light transmitted through P becomes substantially uniform in the plane (as long as the tone of the displayed image is uniform), the luminance distribution on the liquid crystal panel side is eliminated, and the image quality can be improved.

The backlight device B having a light guide may be provided with the above-described brightness distribution by adjusting the density of dot-like reflectors disposed on the back of the light guide,
There is a method of providing a lamp on the side of the scanning lines G ₁ , G ₂ ,.

Embodiment 5 In general, as shown by reference numeral 21 in FIG. 10, the liquid crystal has a characteristic that the response speed increases as the temperature increases (in terms of luminance, the luminance increases as the temperature increases). Characteristic). Further, a cold cathode tube generally used as a backlight device has a characteristic that the light source light conversion efficiency (luminance) increases as the temperature increases, as indicated by reference numeral 22 in FIG. Therefore, when such a cold-cathode tube is used for a liquid crystal panel, both the response speed of the liquid crystal and the brightness of the cold-cathode tube increase as the temperature increases, and the screen brightness of the liquid crystal panel becomes extremely high. That is, when a cold cathode tube is used, the brightness of the liquid crystal panel greatly changes depending on the temperature.

On the other hand, the LED is denoted by reference numeral 2 in FIG.
As shown by 0, the light source light conversion efficiency (luminance) decreases as the temperature increases.
When D is used for a liquid crystal panel, the characteristics inherent to the liquid crystal (the characteristics indicated by reference numeral 21 in FIG. 10, which is that the response speed increases and the luminance increases as the temperature increases) and the characteristics of the LED ( The characteristic indicated by reference numeral 20 in FIG.
The characteristic that the light source light conversion efficiency (luminance) decreases as the temperature increases) cancels out, and the liquid crystal panel can obtain a substantially constant screen luminance regardless of the temperature.

[0068]

As described above, according to the present invention,
Since the driving state of the liquid crystal in each pixel is reset when light irradiation is started in the next field period, the tone of the monochrome image displayed on the entire liquid crystal element in each field period is appropriate. (That is, only the image of the tone corresponding to the color of the irradiated light is displayed on the liquid crystal element without being affected by the image of the previous field period), and the full-color image which is recognized throughout the entire field period is displayed. Color reproducibility is improved.

Further, according to the present invention, the modulation width of the image signal is reduced by changing the potential of the counter electrode for each field period. Thus, the withstand voltage of the signal line driver circuit can be reduced, and the size and power consumption of the circuit can be reduced.

Further, according to the present invention, the timing of changing the potential of the counter electrode is from the application of the scanning signal for resetting the image to the start of the next field period. The potential (absolute value) of each pixel from the start of the period to before the line-sequential scanning is performed can be kept small. For this reason, the on / off ratio of the scanning signal applied to the switching element can be small, and the withstand voltage of the switching element can be reduced. As a result, the size of the switching element can be reduced, and the aperture ratio and the light use efficiency can be improved when the liquid crystal element is of a transmission type.
When the liquid crystal element is of a reflection type, high definition can be achieved by reducing the size of the pixel.

[Brief description of the drawings]

FIG. 1 is a timing chart showing an example of a method for driving a liquid crystal device according to the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a structure of a liquid crystal device driven by applying the present invention.

FIG. 3 is a plan view illustrating an example of a structure of a liquid crystal device driven by applying the present invention.

FIG. 4 is a timing chart showing another example of the method for driving the liquid crystal device according to the present invention.

FIG. 5 is a plan view showing an example of the structure of a liquid crystal device according to the present invention.

FIG. 6 is a diagram illustrating a luminance distribution of a backlight device used in the present invention.

FIG. 7 is a timing chart illustrating an example of a driving method of a conventional liquid crystal device.

FIG. 8 is a timing chart showing another example of a method for driving a conventional liquid crystal device.

FIG. 9 is an equivalent circuit diagram illustrating a structure of a liquid crystal panel.

FIG. 10 is a diagram illustrating temperature characteristics of a liquid crystal and a light source.

[Explanation of symbols]

1 liquid crystal device 4 TFT (switching element) 5 pixel electrode 6 opposing electrode 7 LCD B backlight device (light source) _G 1, _{G 2,} ... scan lines P (liquid crystal element) _S 1, _{S 2,} ... signal line

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G09G 3/20 624 G09G 3/20 624C 642 642J 3/36 3/36 (72) Inventor Hirohide Munekata Tokyo 3-30-2 Shimomaruko, Ota-ku F-term (reference) in Canon Inc. BB05 CC03 DD01 DD07 EE30 FF11 JJ02 JJ04 JJ05 JJ06

Claims (8)

[Claims] 1. A plurality of scanning lines and a plurality of signal lines, a plurality of switching elements arranged for each pixel while being connected to the scanning lines and the signal lines, and a plurality of switching elements connected to each switching element. In the state, a plurality of pixel electrodes respectively arranged for each pixel, a counter electrode disposed at a position facing these pixel electrodes, and a liquid crystal disposed between these pixel electrodes and the counter electrode. A liquid crystal device including a liquid crystal device, and a light source for selectively irradiating each color light to the liquid crystal device, in a method for driving a liquid crystal device displaying a color image, wherein the plurality of scanning lines are sequentially scanned. By applying a signal to sequentially turn on the plurality of switching elements and applying an image signal to the plurality of signal lines, the liquid crystal is applied to the liquid crystal through the switching elements and the pixel electrodes. The liquid crystal is driven by applying pressure, the application of the scanning signal to the last scanning line is completed, and the driving of the liquid crystal in the pixels along the scanning line is started. Irradiating each color light, and thereafter applying a scanning signal to the plurality of scanning lines to turn on the plurality of switching elements and applying a reset signal to the plurality of signal lines, so that the pixel electrode is opposed to the pixel electrode. The liquid crystal is reset by setting the potential difference between the electrodes to a predetermined value, and the series of driving is repeated while changing the color of light to be irradiated, whereby images of different colors are visually mixed to be recognized as a full-color image. A method for driving a liquid crystal device. 2. The method according to claim 1, wherein a voltage applied to the counter electrode is changed every time each color light is irradiated, a reset signal applied to the signal line is substantially equal to a voltage applied to the counter electrode, 2. The method according to claim 1, wherein a potential difference between the pixel electrode and the counter electrode when the liquid crystal is reset is set to approximately 0V. 3. The voltage applied to the counter electrode is changed each time light of each color is irradiated, and the reset signal applied to the signal line is set to a value such that the response position of the liquid crystal becomes saturated. The method for driving a liquid crystal device according to claim 1, wherein: 4. The method according to claim 1, wherein changing the voltage applied to the counter electrode and applying a reset signal to the plurality of signal lines are performed while a scan signal is being applied to the plurality of scan lines. The method for driving a liquid crystal device according to claim 2. 5. A plurality of scanning lines and a plurality of signal lines, a plurality of switching elements arranged for each pixel while being connected to the scanning lines and the signal lines, and a plurality of switching elements connected to each of the switching elements. In the state, a plurality of pixel electrodes respectively arranged for each pixel, a counter electrode disposed at a position facing these pixel electrodes, a liquid crystal disposed between these pixel electrodes and the counter electrode, A liquid crystal element comprising: a scanning line driving circuit connected to a plurality of scanning lines to apply a scanning signal; and a signal line driving circuit connected to the plurality of signal lines to apply a signal. A light source for selectively irradiating each color light, wherein the signal line drive circuit is disposed on the side of the last scanning line among a plurality of scanning lines sequentially scanned, and Each of the signal lines Resistance value becomes is set to a value such as plane luminance distribution does not occur in the image of the liquid crystal device, a liquid crystal device, characterized in that. 6. A plurality of scanning lines and a plurality of signal lines, a plurality of switching elements arranged for each pixel while being connected to the scanning lines and the signal lines, and a plurality of switching elements connected to each of the switching elements. In the state, a plurality of pixel electrodes respectively arranged for each pixel, a counter electrode disposed at a position facing these pixel electrodes, a liquid crystal disposed between these pixel electrodes and the counter electrode, A liquid crystal element comprising: a scanning line driving circuit connected to a plurality of scanning lines to apply a scanning signal; and a signal line driving circuit connected to the plurality of signal lines to apply a signal. A light source that selectively irradiates each color light with a light source, wherein the light source has a lower luminance on the side of the scanning line scanned first, and the luminance continuously decreases toward the side of the scanning line scanned later. Brightness distribution To the liquid crystal device, characterized in that. 7. A plurality of scanning lines and a plurality of signal lines, a plurality of switching elements arranged for each pixel while being connected to the scanning lines and the signal lines, and a plurality of switching elements connected to each of the switching elements. In the state, a plurality of pixel electrodes respectively arranged for each pixel, a counter electrode disposed at a position facing these pixel electrodes, a liquid crystal disposed between these pixel electrodes and the counter electrode, A liquid crystal element comprising: a scanning line driving circuit connected to a plurality of scanning lines to apply a scanning signal; and a signal line driving circuit connected to the plurality of signal lines to apply a signal. A liquid crystal device comprising: a light source that selectively irradiates each color light with the light source, wherein the light source has a characteristic that the luminance increases as the temperature decreases. 8. The liquid crystal device according to claim 7, wherein the light source is an LED.