JP3160493B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a ferroelectric liquid crystal having an antiferroelectric phase and a ferroelectric phase, and a driving method thereof.

[0002]

2. Description of the Related Art A liquid crystal display device which takes three optical states by an electric field is disclosed in JP-A-2-153322 and JP-A-2-17.
No. 3724 and the like. Later, it was revealed by Chandani et al. (Japanese Journal of Applied Physics, Vol. 28 (1989), page L1265) that this was due to the antiferroelectricity of the liquid crystal.

According to this, a ferroelectric liquid crystal exhibiting antiferroelectricity (hereinafter referred to as an antiferroelectric liquid crystal) dissolves a spiral in a thin substrate gap like a normal ferroelectric liquid crystal, and FIG.
As shown in (a), when there is no electric field (E = 0), the liquid crystal molecules have a structure tilted in the opposite direction for each smectic layer. Therefore, when there is no electric field, the optical axis is directed to the layer normal direction.

The transition to the ferroelectric phase occurs due to the application of an electric field (E> 0, E <0), and the liquid crystal molecules take a structure in which all the layers are tilted in the same direction determined by the direction of the electric field. It becomes one of two directions symmetrical from the normal to the tilted layer normal. This is shown in FIGS. 6 (b) and 6 (c).

When this antiferroelectric liquid crystal is applied to a display device, it is usually sandwiched between two polarizing plates, and the absorption axis of the polarizing plate is set parallel to the layer normal as shown by a double-headed line in FIG. Vertically, two polarizing plates are arranged so as to form a cross Nicol. In this arrangement, the antiferroelectric state in the absence of an electric field is dark,
The ferroelectric state when an electric field is applied becomes a bright state.

The feature of this arrangement is that there are two types of bright states, and a method of switching the applied voltage polarity in the bright state at regular intervals by using this is disclosed in the above-mentioned JP-A-2-173724. This invention is an invention of an antiferroelectric liquid crystal device having a simple matrix configuration, and FIG. 7 shows an example of the driving waveform.

FIG. 7 shows how the voltage applied to the liquid crystal fluctuates with time. The polarity of the voltage applied to the pixel is switched for each frame. As is clear from FIG. 7, the voltage applied to the liquid crystal is averaged over time and becomes zero. This has the advantage that the deterioration of the liquid crystal due to the DC voltage component can be prevented.

[0008]

However, the above-described polarity reversal driving method for each frame has a disadvantage that the screen flickers when the display panel is viewed from an oblique direction. The reason will be described below.

FIG. 8 shows the liquid crystal molecules and the transmission axes of the upper and lower polarizing plates when the display panel is viewed obliquely from the lower right. (A) is a dark state, (b) and (c) are two bright states, each of which is viewed from the front, as shown in FIGS.
(B) and (c).

Compared with (b) and (c), in (b), the liquid crystal molecules are viewed almost from the side, and the effective refractive index anisotropy is not so different from that when viewed from the front.
In (c), the liquid crystal molecules are viewed from near the long axis, and the refractive index anisotropy is significantly smaller than when viewed from the front. For this reason, there is a difference in transmittance between (b) and (c), and this is switched for each frame, so that it appears as flickering.

Further, when viewed obliquely, the optical path length becomes longer, and in the case of (b), the retardation deviates from the optimum value, and the appearance of yellowing is also a factor of flicker.

An object of the present invention is to provide a liquid crystal display device using an antiferroelectric liquid crystal, which has less flickering when the display panel is viewed from the side, and a driving method thereof.

[0013]

SUMMARY OF THE INVENTION The present invention is directed to orthogonal
A display panel having a plurality of Ma Torikusu pixels formed by the intersection of a plurality of run scanning signal No. electrodes and a plurality of information signal electrodes that, in the gap between the two electrodes, the anti-ferroelectric phase at the time of no electric field A first stable state, and a ferroelectric liquid crystal that takes a second or third stable state of a ferroelectric phase according to the polarity of the electric field when an electric field is applied ; A liquid crystal display device comprising: a polarizing device for setting a second and a third stable state to a bright state.
A first scanning signal electrode, a first scanning signal electrode,
A second scanning signal electrode; a first information signal electrode;
A first sub-pixel electrode connected to one scanning signal electrode;
A second sub-pixel electrode connected to the second scanning signal electrode;
And wherein the first pixel has the first sub-pixel electrode
And a first sub-picture comprising the first information signal electrode
Element, the second sub-pixel electrode and the first information signal electrode
It consists second subpixel from, composed of the said first
A second pixel different from the first pixel is connected to the first scanning signal power supply.
A pole, the second scanning signal electrode, and the information signal electrode.
Is another second information signal electrode and the first scanning signal electrode
A third sub-pixel electrode connected to the second scanning signal
And a fourth sub-pixel electrode connected to the electrode .
The second pixel is connected to the third sub-pixel electrode and the second information signal.
A third sub-pixel composed of a second sub-pixel and a fourth sub-pixel.
A second electrode composed of a pixel electrode and the second information signal electrode;
Subpixels 4, consists, Ri by the driving device, the first
Are both in the first stable state
The first pixel which is brought into the dark state by taking a state
The first sub-pixel assumes the second stable state and the first sub-pixel
When the second sub-pixel takes the third stable state,
It is characterized by taking a state .

[0014] The present invention also provides a plurality of scans orthogonal to each other.
Formed by the intersection of the test signal electrode and multiple information signal electrodes
Display panel having a plurality of matrix pixels
In the gap between the two electrodes, an anti-ferroelectric phase
The first stable state consisting of
Takes the second or third stable state of ferroelectric phase depending on
Ferroelectric liquid crystal, the first stable state is a dark state, the second
And a polarizing device for setting the third stable state to a bright state.
In a liquid crystal display device, the plurality of matrix pixels
The first pixel has a first scanning signal electrode and a second scanning signal electrode.
A signal electrode, first, second and third information signal electrodes;
Connected to the first, second and third information signal electrodes, respectively.
First, a second and third pixel electrodes, a being, the first
One pixel is connected to the first pixel electrode and the first scanning signal.
A first sub-pixel composed of an electrode and the first pixel
And a second scanning signal electrode.
A sub-pixel, the second pixel electrode, and the first scanning signal electrode;
A third sub-pixel composed of a first electrode and a second pixel
A fourth sub-electrode comprising a pole and the second scanning signal electrode.
A pixel, the third pixel electrode, and the first scanning signal electrode
And the third pixel electrode
And a sixth sub-image comprising the second scanning signal electrode
And a second image different from the first pixel.
The element comprises a first scanning signal electrode, a second scanning signal electrode,
Fourth, fifth and sixth information signal electrodes and their fourth and fifth information signal electrodes
The fourth and the fourth connected to the fifth and sixth information signal electrodes, respectively.
5 and a sixth pixel electrode, wherein the second pixel has
The fourth pixel electrode and the first scanning signal electrode are composed.
A seventh sub-pixel to be formed, the fourth pixel electrode and the
An eighth sub-pixel composed of two scanning signal electrodes,
A fifth pixel electrode and the first scanning signal electrode;
Ninth sub-pixel, the fifth pixel electrode, and the second
A tenth sub-pixel composed of the scanning signal electrodes of
A sixth pixel electrode and the first scanning signal electrode;
Eleventh sub-pixel, the sixth pixel electrode and the
A twelfth sub-pixel composed of two scanning signal electrodes;
The first stable state is established by the driving device.
1st and 2nd sub-pixels that can be darkened by taking
Is clear because the first sub-pixel assumes a second stable state.
When the second sub-pixel enters the third stable state.
It can be turned into a bright state by taking
are doing.

[0015]

Since the present invention is constructed as described above, when a pixel is in a bright state, two states are mixed in one pixel and are replaced every frame, so that the difference between the transmittance and the coloring is averaged. Display with high quality without flicker.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a part of a display panel taken out, and reference numerals 11 and 12 denote scanning signal electrodes (hereinafter simply referred to as scanning lines), and 13 denotes information signal electrodes (hereinafter simply referred to as signal lines). ), 14 and 15 are pixel electrodes. The scanning lines and the pixel electrodes are formed on one substrate, and the signal lines are formed on the other substrate. The short line segment in the pixel electrode represents the direction of the optical axis of the liquid crystal in the pixel. The one parallel to the signal line is in the antiferroelectric (dark) state, and the one inclined is in the ferroelectric (bright) state. Is shown. Reference numerals 16 and 17 denote the axial directions of the upper and lower polarizing plates. Here, the signal line is set in the layer normal direction for convenience, but this is not always necessary and may be in any direction.

As shown in the figure, one pixel is composed of two pixel electrodes 14 and 15, each constituting a sub-pixel. When the pixel is in the dark state, the two sub-pixels are both in the antiferroelectric state, and the optical axis is oriented in the axis direction of the polarizing plate. In the bright state, the two sub-pixels are in a ferroelectric state with opposite tilts. Since each sub-pixel is driven by inverting the polarity for each frame as in the related art, if the first sub-pixel is right-tilted and the second sub-pixel is left-tilted in a certain frame, the second sub-pixel is tilted in the next frame. One sub-pixel has left tilt, and the second sub-pixel has right tilt.

Since the two sub-pixels are in the opposite bright state, the bright state area is a hybrid of two states having different transmittances and colors, and appears to the eyes as average transmittance and colors. Therefore, there is no difference between frames and no flicker occurs.

FIG. 2 shows the temporal timing of the voltage for driving each electrode of FIG. 51a, 51b, 52
a, 52b,... are scanning line applied voltages, 53 and 54 are signal line applied voltages, 55 is a composite voltage applied to the sub-pixel at the intersection of 51a and 53, and 56 is the sub-pixel at the intersection of 51b and 53. The combined voltage applied, 57 is a combined voltage applied to the sub-pixel at the intersection of 51a and 54, and 58 is a combined voltage applied to the sub-pixel at the intersection of 51b and 54.

There are two scanning lines for each line of the matrix pixel array, which are distinguished by a and b. Immediately before the selection period T, there is a reset period R of 0 volt, which resets all pixels on the line to a dark state. During the non-selection period N after the selection, a DC voltage (bias voltage) for maintaining the written state is applied.

The two types of scanning lines a and b are connected to the first sub-pixel and the second sub-pixel, respectively, and are sequentially selected within one unit period H of the image signal.

In the odd-numbered frames, a positive selection voltage is applied to the scanning line a and a negative selection voltage is applied to the scanning line b in each selection period.
A positive AC signal voltage is applied. When the signal line voltage is positive / negative, it is combined with the scanning line voltage as shown at 55 and 56, the voltage applied to both sub-pixels becomes lower than the threshold value, and the immediately preceding reset (dark) state is maintained. On the other hand, if the signal line voltage is negative
When positive, the voltage applied to the pixel is combined with the scanning line voltage as shown at 57 and 58, and the voltage applied to both sub-pixels is equal to or greater than the threshold value.
One bright state is written to the first sub-pixel, and the other bright state is written to the second sub-pixel. Hereinafter, this operation is repeated for each line to complete one frame.

In an even-numbered frame, as shown in FIG. 2, the polarity of the scanning line voltage is reversed for both a and b, and the polarity of the signal line voltage is also reversed. Therefore, the bright pixels are written with the combined voltage of the opposite polarity to the odd frame, and the tilt state is inverted.

Next, a second embodiment of the present invention will be described.

FIG. 3 shows the embodiment. 6
1-64 are scanning electrodes, 65R, 66R, 65G, 66
G, 65B and 66B are signal lines, and 67 and 68 are pixel electrodes. The scanning electrodes are formed on one substrate, and the signal lines and the pixel electrodes are formed on the other substrate. One pixel is a region 69 surrounded by a dotted line in the figure and straddles two scanning electrodes. One pixel is subdivided into three regions of red R, green G, and blue B by a color filter (not shown), and is further divided into two by a scanning electrode, and is composed of a total of six subpixels.
However, the number of signal lines is three for RGB for one pixel, and another signal line is for pixels that are located one above the other.

FIG. 4 shows the timing of the voltage applied to each signal line and each scanning line in FIG. 71-74 are voltages applied to the scanning electrodes 61-64 of FIG. 3, respectively.
75R and 76R are voltages applied to the signal lines 65R and 66R. 77 is a composite voltage of 71 and 75R,
And 78 is a composite voltage of 72 and 75R, which is applied to the sub-pixel of FIG. Reference numeral 79 denotes a composite voltage of 71 and 76R, which indicates a voltage applied to the sub-pixel (c in FIG. 3) belonging to the immediately higher pixel.

There is a reset period R of 0 volt immediately before the scanning line selection period T, and resets all pixels on the line to a dark state. During the non-selection period N after the selection, a DC voltage for maintaining the written state is applied. These are the same as the first.

The scanning lines are selected while alternately inverting the polarity one by one. A positive selection voltage is supplied during the selection period 71 and then a negative selection voltage is supplied during the selection period 72. During the period H synchronized with this, 75R
When a negative / positive AC voltage as shown in FIG.
A voltage greater than the positive and negative threshold values is applied to each of the sub-pixels, and a bright state having a reverse tilt is written. When writing a dark state, an opposite-phase (positive / negative) AC voltage may be applied to 65R.

The signal line 66 is synchronized with the selection period 71 and the immediately preceding scanning line (not shown) selection period.
Another AC signal 76R shown in H 'of FIG. 4 is applied to R, and the state of the pixel including the sub-pixel of FIG. 3C is determined. Further, in synchronization with the selection period of 72 and the selection period of the immediately lower scanning line 63 immediately after that, the next AC signal is further applied to the signal line 66R, and the state of the pixel including the sub-pixel in FIG. It is determined. As described above, the alternating-current image signals whose phases are shifted by an anti-period are supplied to the signal lines 65R and 66R.

The other signal lines 65G, 66G, 65B, 66
Similarly, a voltage signal corresponding to the color is supplied to B.

As described above, scanning lines are sequentially selected, one screen is written, and one frame is completed. Next, voltage signals with all the polarities inverted are similarly applied, and the next frame is written.

This embodiment is the same as the first embodiment in that the pixel is divided into two and each is driven by a different scanning electrode.
Since the sub-pixels of the pixels adjacent to each other in the signal line direction have the same scanning electrode, the number of scanning lines is half that of the first embodiment, and the scanning time is also half. Instead, the number of signal lines is doubled.

The antiferroelectric liquid crystal material used in this embodiment is shown in Chemical formula 1.

[0035]

Embedded image Next, a specific cell configuration will be described.

A display panel was made by sandwiching the above-mentioned liquid crystal between two transparent substrates (electrodes formed on the opposing surfaces) at a gap (gap of 2.5 μm).

FIG. 5 shows a cross section of the panel used in the second embodiment.

On one substrate 81, a scanning line electrode 82 is formed, on which a layer rubbed with a nylon thin film 83 (5 nm thick) is covered. Polyimide can be used instead of nylon.

The other substrate 84 has a color filter 85
R, 85G, 85B, a signal line 86 and a pixel electrode 87, on which a mixed film 88 of titanium oxide and zirconium oxide is formed to prevent a short circuit between the substrates, and a surface mainly composed of siloxane is further formed thereon. The processing film 89 covers with a thickness of 10 nm or less.

This surface treatment film has a smaller surface energy than the rubbing film on the opposite side, and therefore has a weaker force for homogeneously aligning the liquid crystal. Therefore, when the liquid crystal is cooled from the isotropic layer, the smectic phase order occurs preferentially from the rubbing film surface side, and there is no alignment defect caused by the random occurrence from both surfaces, resulting in uniform alignment.

[0041]

As described above, according to the present invention,
Each pixel is composed of at least two sub-pixels, such that when the pixel assumes a bright state, one sub-pixel of the pixel is in a second stable state and another one is in a third stable state. As a result, the flicker of the image can be reduced, and the difference between the transmittance and the hue when viewed from an oblique direction is eliminated, so that the viewing angle characteristics are improved as a whole.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing each electrode application voltage and a composite voltage applied to a pixel in the first embodiment.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram illustrating each electrode application voltage and a composite voltage applied to a pixel according to a second embodiment.

FIG. 5 is a sectional view of a liquid crystal display device according to a second embodiment.

FIG. 6 is a diagram showing a liquid crystal molecular arrangement in an antiferroelectric phase and a ferroelectric phase.

FIG. 7 is a diagram showing a conventional example of a driving method of a liquid crystal display element.

8 is an oblique view of the state of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Scan signal electrode 12 Scan signal electrode 13 Information signal electrode 14 Sub-pixel electrode 15 Sub-pixel electrode

Claims (4)

(57) [Claims] (1) orthogonal to each otherMultiple runsProbe signal electrodeAnd multiple
NumberFormed by the intersection with the signal electrodeMultiple
A display panel having a Trix pixel;
In the gap, a first safety member made of an antiferroelectric phase when no electric field is applied.
Take a steady state, electric fieldWhen applyingDepending on the polarity of the electric field
Ferroelectric liquid crystal in a second or third stable state comprising a phase
The first stable state is a dark state, and the second and thirdStable
Liquid crystal display device equipped with a polarizing device that changes the state to a bright state.
AndA first pixel of the plurality of matrix pixels is a first pixel.
Scan signal electrode, second scan signal electrode, and first information
A signal electrode; and a first electrode connected to the first scanning signal electrode.
Connected to the sub-pixel electrode and the second scanning signal electrode
A second sub-pixel electrode; and The first pixel includes the first sub-pixel electrode and the first sub-pixel electrode.
A first sub-pixel comprising an information signal electrode;
2 subpixel electrodes and the first information signal electrode.
A second sub-pixel, A second pixel different from the first pixel is the first pixel.
A signal electrode, the second scanning signal electrode, and the information signal
A second information signal electrode separate from the first electrode and the first scanning signal;
A third sub-pixel electrode connected to the signal electrode;
A fourth sub-pixel electrode connected to the test signal electrode, The second pixel includes the third sub-pixel electrode and the second sub-pixel electrode.
A third sub-pixel composed of an information signal electrode and the third sub-pixel;
4 subpixel electrodes and the second information signal electrode.
A fourth sub-pixel,  By driveThe first sub-pixel and the second sub-pixel
Both take the first stable state, and the dark state and
Wherein the first sub-pixel has the second sub-pixel
Assume a stable state and the second sub-pixel is in the third stable state
Taking the light state by taking the stateLiquid characterized by
Crystal display device. (2)Multiple scanning signal electrodes orthogonal to each other
Number of information signal electrodes
A display panel having a Trix pixel;
In the gap, a first safety member made of an antiferroelectric phase when no electric field is applied.
It takes a fixed state and ferroelectrics according to the polarity of the electric field when an electric field is applied.
The second or third stable state consisting of phases Take ferroelectric liquid crystal
The first stable state is a dark state, and the second and third stable states are
Liquid crystal display device equipped with a polarizing device that changes the state to a bright state.
And A first pixel of the plurality of matrix pixels is a first pixel.
Scan signal electrode, the second scan signal electrode, and the first and second scan signal electrodes.
And third information signal electrodes, and the first, second and
1st, 2nd, and 3rd connected respectively to the 3 information signal electrodes.
And a pixel electrode of The first pixel is connected to the first pixel electrode and the first pixel electrode.
A first sub-pixel composed of an inspection signal electrode;
Pixel electrode and the second scanning signal electrode
A second sub-pixel, the second pixel electrode, and the first scan
A third sub-pixel composed of a signal electrode and the second sub-pixel;
A second scanning signal electrode including a pixel electrode and the second scanning signal electrode;
4 sub-pixels, the third pixel electrode, and the first scanning signal.
A fifth sub-pixel composed of a third pixel and a third pixel.
A sixth electrode composed of an elementary electrode and the second scanning signal electrode;
And a sub-pixel of A second pixel different from the first pixel is a first scanning signal.
Electrodes, a second scanning signal electrode, and fourth, fifth, and sixth electrodes.
Information signal electrodes, and the fourth, fifth, and sixth information signals;
Fourth, fifth and sixth pixel electrodes respectively connected to signal electrodes
And having The second pixel is connected to the fourth pixel electrode and the first line.
A seventh sub-pixel composed of an
Pixel electrode and the second scanning signal electrode
An eighth sub-pixel, the fifth pixel electrode, and the first scan
A ninth sub-pixel composed of a signal electrode and the fifth sub-pixel;
A second scanning signal electrode including a pixel electrode and the second scanning signal electrode;
Ten sub-pixels, the sixth pixel electrode, and the first scan
An eleventh sub-pixel comprising a signal electrode;
Pixel electrode and the second scanning signal electrode
A twelfth sub-pixel, The drive unit is in the dark state by taking the first stable state.
The first and second sub-pixels that can be in the
When the sub-pixel enters the second stable state and becomes a bright state
The second sub-pixel takes a third stable state,
Liquid crystal display device characterized in that
Place. 3. The first scanning signal electrode and the second scanning signal.
A positive voltage is applied to one of the scanning signal electrodes.
Is applied to the other scanning signal electrode Negative polarity
2. The method according to claim 1, wherein a pressure is applied.
Liquid crystal display. 4. The first scanning electrode and the second scanning electrode
A positive voltage is applied to one of the scan electrodes
In this case, a negative voltage is applied to the other scan electrode.
The liquid crystal display device according to claim 2, wherein: