JP2001350152A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which suppresses a bias voltage applied to a liquid crystal layer during a non-selected period in a simple matrix driving and ensures a sufficient voltage margin even when the number of scanning electrode lines are increased and to increase the response speed of falling in a liquid crystal display device having active elements. SOLUTION: The liquid crystal display device is provided with a pair of substrates 1, 4, driving electrodes formed at least on one of the substrates, a liquid crystal 5 held between the substrates and a means to apply voltage to the driving electrodes. The driving electrode inside a pixel contains a first electrode comprising a plurality of electrodes C1, S1, S2 arranged in layers and a second electrode C2 arranged in a position different from the first electrode in substrate plane directions. A specified electric field is generated between the first and the second electrodes and carries out displaying by applying voltages to the respective electrodes constituting the first and the second electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a structure of a driving electrode in a liquid crystal display device and an improvement in a method of applying a voltage to the electrode.

[0002]

2. Description of the Related Art FIG. 12 is a sectional view of one pixel in a liquid crystal panel widely used in office automation equipment and the like today.
Each pixel is provided on a substrate A41 and a substrate B42, respectively.
It is composed of two electrodes C1 and S1, and changes the arrangement of liquid crystal molecules in the liquid crystal layer 43 according to a voltage difference applied to each of the electrodes C1 and S1 to perform display.

[0003]

However, this method is
In a liquid crystal display device having no active element and called a simple matrix, a bias voltage is always applied to a liquid crystal layer from the time when a pixel is selected until the next time it is selected. Therefore, the simple matrix liquid crystal display device has a feature of being inexpensive as compared with the active matrix liquid crystal display device, but as the number of scanning electrodes increases, the voltage margin becomes narrower and the contrast decreases. There was a problem.

Also, in the case of a liquid crystal display device having an active element, there is a problem that the response speed, particularly the falling speed is determined only by the elasticity of the liquid crystal material, and it is difficult to increase the speed.

The present invention provides a liquid crystal display device capable of suppressing a bias voltage applied to a liquid crystal layer during a non-selection period in a simple matrix drive and having a sufficient voltage margin even when the number of scanning electrodes increases. The purpose is to do.

It is another object of the present invention to provide a liquid crystal display device having an active element, in which a falling response speed is increased.

[0007]

A liquid crystal display device according to the present invention applies a voltage to a pair of substrates, a driving electrode formed on at least one of the substrates, a liquid crystal sandwiched between the substrates, and a driving electrode. It is assumed that the configuration includes means. And in order to solve the above problem, the driving electrode in one pixel is
A first electrode including a plurality of electrodes arranged in a layered manner and a second electrode arranged at a position different from the first electrode in a substrate surface direction are included. By applying a voltage to each electrode constituting the first electrode and the second electrode, a predetermined electric field is generated between the first electrode and the second electrode to perform display.

In the above structure, the first electrode and the second electrode may be formed separately on different substrates. Further, a plurality of electrodes constituting the first electrode may be formed separately on different substrates.

Further, in the above configuration, the signal electrode may be included in an electrode constituting the first electrode. Further, a configuration may be adopted in which the scanning electrode is included in the electrodes constituting the first electrode.

Further, in the above structure, the liquid crystal molecules may be arranged such that the initial alignment is perpendicular to the substrate.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 schematically shows a cross section of one pixel of a liquid crystal panel in Embodiment 1. On the substrate A1, the electrodes C1, S1,
S2 is formed in layers. This group of electrodes is generally referred to as a first electrode. An electrode C2 facing the first electrode at a predetermined distance in the plane of the substrate is further formed on the substrate A1. The electrode facing the first electrode is generally called a second electrode. Liquid crystal is filled between the substrate B4 on which no electrode is formed and the liquid crystal layer 5 is formed.

FIG. 2 shows electric fields when various voltages are applied to the electrodes C1, C2, S1, and S2. Using FIG.
A driving method in the liquid crystal panel of the present embodiment will be described. The electrodes C1 and C2 are used as scanning electrodes. FIG.
As shown in (a) and (b), a voltage of 0 [v] is applied to each of the electrodes C1 and C2 during the non-selection period. At the time of selection, as shown in FIGS. 2C and 2D, a voltage of + V [v] is applied to the electrode C1 and a voltage of -V [v] is applied to the electrode C2. The electrodes S1 and S2 are used as signal electrodes. That is, when the pixel is to be turned on, when the scanning electrode is selected, as shown in FIG.
-V and + V to the electrode S2. To turn off the light, as shown in FIG.
To −V.

When the liquid crystal panel is driven as described above, during each period in which the scanning electrode is not selected, each pixel operates as shown in FIG.
As shown in (a) and (b), an electric field perpendicular to the substrate A1 is generated near the electrodes, but an electric field parallel to the substrate A1 is hardly generated in the liquid crystal layer 5 between the first electrode and the second electrode.
When the scanning electrode is selected, a large electric field parallel to the substrate A1 is generated in the liquid crystal layer 5 in the pixel to be turned on, as shown in FIG. In a pixel to be turned off, as shown in FIG. 2C, an electric field is generated in the substrate A1, but only a small electric field is generated in the liquid crystal layer 5 (arrows in the figure represent the electric field).

A liquid crystal cell is manufactured using the substrates A1 and B4 which have been processed so that the liquid crystal molecules are vertically aligned with the substrates, and a P-type liquid crystal is filled.
When a polarizing plate was arranged on the surface of No. 4 and driven as described above, good display was obtained.

In the conventional liquid crystal panel, a bias voltage is applied to the liquid crystal even during the non-selection period, and this has led to a deterioration in contrast due to an increase in the display capacity of the simple matrix liquid crystal display device. In the present embodiment, during the non-selection period, almost no voltage is applied to the liquid crystal layer as described above, and the voltage margin (ON / OFF ratio of the effective voltage) is greatly improved.

In the above configuration, one pixel is composed of four electrodes, but as shown in FIG. 3, three electrodes C, S1,.
It can also be constituted by S2. Also, as shown in FIG. 4, the same effect can be obtained by providing an electrode C (counter electrode) as the second electrode on the substrate B4. To drive these,
The same voltage as that applied to the scanning electrode C2 in FIG. 2 may be applied to the electrode C. In this way, the number of scanning electrode LSIs does not increase compared to the conventional driving method.

In the above description, one pixel includes the first electrode (electrodes S1, S2, C1) and the second electrode (electrode C).
Although a pair of electrodes facing each other in the direction of the substrate surface is formed in 2), a plurality of these electrodes may be provided to form one pixel.

The distance between the first and second electrodes is desirably designed in consideration of the liquid crystal material and the thickness of the liquid crystal layer, the characteristics of the insulating film material, the drive voltage and the aperture ratio. (Embodiment 2) FIG. 5 schematically shows a cross section of one pixel of a liquid crystal panel in Embodiment 2. The electrodes C1, C2, S are placed on the substrate A11 via insulating layers 12, 13.
Four electrodes 1, 1 and 2 are formed. A liquid crystal is filled between the substrate B14 on which no electrodes are formed and a liquid crystal layer 15 is formed.

FIG. 6 shows electric fields when various voltages are applied to the electrodes C1, C2, S1, and S2. Using FIG.
A driving method of the liquid crystal panel in the present embodiment will be described. The electrodes C1 and C2 are used as scanning electrodes. As shown in FIGS. 6A and 6B, 0 [v] is applied to the electrodes C1 and C2 during the non-selection period. At the time of selection, as shown in FIGS. 6C and 6D, C1 has + V
A voltage of -V [v] is applied to [v] and C2. Also,
The electrodes S1 and S2 are used as signal electrodes. That is, if the scanning electrode is selected to light the pixel,
As shown in FIG. 6D, + V is applied to the electrodes S1 and S2. To turn off the light, -V is applied to the electrodes S1 and S2 as shown in FIG.

If the liquid crystal panel is driven as described above, during the period in which the scanning electrode is not selected, each pixel has
As shown in FIGS. 6A and 6B, an electric field is generated perpendicular to the substrate near the electrodes, but an electric field parallel to the substrate is hardly generated. When the scanning electrode is selected, a large electric field parallel to the substrate is generated in the liquid crystal layer 15 in the pixel to be turned on, as shown in FIG. In a pixel to be turned off, only a small electric field is generated in the liquid crystal layer 15 as shown in FIG.

A liquid crystal panel was manufactured in the same manner as in Embodiment 1 using the substrates A11 and B14 which were processed so that the liquid crystal molecules were vertically aligned with the substrates. Obtained.

In the present embodiment, in order to drive one pixel in the case of the first embodiment, it is necessary to apply different voltages to the electrodes S1 and S2, but to apply the same voltage. The number of signal electrode LSIs does not increase as compared with the conventional method.

FIG. 7 shows another driving method. The figure shows the voltage during the non-selection period. (A ′) and (b ′) show the states when −V is applied to the electrodes C1 and C2, and (a ″) and (b ″) show the states when + V is applied. . As shown, the electrodes S1,
When the polarity of the voltage applied to S2 and the voltage applied to the electrodes C1 and C2 are opposite ((b ′), (a ″)), an electric field is generated near the electrodes, but the liquid crystal layer between the electrodes is formed. Almost no voltage is applied to the electrode 15. Also, when the voltage applied to the electrodes S1 and S2 and the voltage applied to the electrodes C1 and C2 are the same ((a '), (b ")), Liquid crystal layer 15
No voltage is applied to. On the other hand, the voltage application state at the time of selection is the same as in FIGS. 6 (c) and 6 (d). In order to perform such a driving method, one of the electrodes C1 and C2 may be changed, for example, from + V to −V each time the voltage of the scanning electrodes C1 and C2 is scanned. The electrodes C1 and C2 after scanning are all-
A voltage of + V is applied to the electrodes C1 and C2 before scanning, and + V and -V are applied to the selected pixel, respectively. By driving in this manner, the electrodes C2 and C1 of the adjacent lines
They can be connected to each other and driven as one electrode.
In that case, the first line electrode C1 and the last line electrode C2 are driven independently. Therefore, the total number of electrodes as a drive unit only needs to be added one more than the conventional number of electrodes when one line is constituted by one scanning electrode. If the additional one electrode is driven by another circuit, the number of scanning electrode LSIs does not increase as compared with the conventional method. Third Embodiment FIG. 8 schematically shows a cross section of one pixel of a liquid crystal panel according to a third embodiment. On a substrate A21, electrodes C1, C2, S1, S
Two four electrodes are formed. Liquid crystal is filled between the substrate B23 on which no electrodes are formed, and a liquid crystal layer 24 is formed.

FIG. 9 shows electric fields when various voltages are applied to the electrodes C1, C2, S1, and S2. Referring to FIG.
A driving method of the liquid crystal panel in the present embodiment will be described. The electrodes C1 and C2 are used as scanning electrodes. FIG.
As shown in (a) and (b), a voltage of 0 [v] is applied to each of the electrodes C1 and C2 during the non-selection period. At the time of selection, as shown in FIGS. 9C and 9D, a voltage of −V [v] is applied to the electrode C1 and a voltage of + V [v] is applied to the electrode C2. The electrodes S1 and S2 are used as signal electrodes. That is, when the pixel is to be turned on, when the scanning electrode is selected, as shown in FIG.
To turn off + V to the electrode S2, and to turn off the light, + V is applied to the electrode S1 and -V is applied to the electrode S2 as shown in FIG. 9C.

When the liquid crystal panel is driven as described above, during the period when the scanning electrode is not selected, each pixel has
As shown in FIGS. 9A and 9B, an electric field is generated in the substrate, but not so much in the liquid crystal layer 24. When a scanning electrode is selected, a large electric field parallel to the substrate is generated in the liquid crystal layer 24 in the pixel to be turned on, as shown in FIG. 9D. In the pixel to be turned off, an electric field is generated near the electrode as shown in FIG.
No electric field parallel to the substrate is generated.

A liquid crystal panel was manufactured in the same manner as in Embodiment 1 using the substrates A21 and B23 processed so that the liquid crystal molecules were oriented vertically to the substrate, and when driven as described above, a good display was obtained. Obtained.

Although the electrodes C2 and S2 are provided in the above example,
For example, the electrode C2 is grounded without applying the electrode S2 (0 V applied).
By doing so, a similar effect can be obtained, and an increase in LSI can be suppressed. (Embodiment 4) FIG. 10 schematically shows a cross section of one pixel of a liquid crystal panel in Embodiment 4. Board A31
The electrodes C1 and S2 are formed on the substrate B32, and the electrodes C2 and S1 are formed on the substrate B32. Liquid crystal is filled between the substrate A31 and the substrate B32 to form a liquid crystal layer 33.

FIG. 11 shows electric fields when various voltages are applied to the electrodes C1, C2, S1, and S2. A driving method of the liquid crystal panel in the present embodiment will be described with reference to FIG. The electrodes C1 and C2 are used as scanning electrodes. FIG.
As shown in FIGS. 1A and 1B, a voltage of 0 [v] is applied to the electrodes C1 and C2 during the non-selection period. At the time of selection, as shown in FIGS.
A voltage of -V [v] is applied to 1, and a voltage of + V [v] is applied to the electrode C2. The electrodes S1 and S2 are used as signal electrodes. That is, when the pixel is to be turned on, when the scanning electrode is selected, as shown in FIG.
-V and + V to the electrode S2. To turn off the light, as shown in FIG.
2 is applied with -V.

When the liquid crystal panel is driven as described above, during the period when the scanning electrode is not selected, each pixel has
As shown in FIGS. 11A and 11B, a small electric field is generated in the liquid crystal layer 23 in parallel with the substrate. Further, in the pixel to be turned on when the scanning electrode is selected, FIG.
As described above, a large electric field parallel to the substrate is generated in the liquid crystal layer 23. In the pixel to be turned off, as shown in FIG. 11C, an electric field is generated perpendicular to the substrate, and no electric field is generated parallel to the substrate.

A liquid crystal panel was manufactured using the substrate A21 and the substrate B22 which were processed so that the liquid crystal molecules were vertically aligned with the substrate, and driving was performed as described above. As a result, good display was obtained.

The electrode C1 has -V and the electrode C2 has + V.
If this embodiment is applied to a liquid crystal panel having an active element by constantly applying a voltage of V and changing the voltage applied to the electrodes S1 and S2, the response speed, especially the fall speed, is greatly improved. Is done.

For example, two active elements are provided for each pixel, and the respective outputs are connected to S1 and S2. A voltage of 0 [v] is applied to C1 and a voltage of + V [v] is applied to C2,
Each pixel is charged through an active element by a signal applied according to the display pattern, and S1 and S2 are set to 0 [v].
Is set so that a voltage whose sum becomes V (S1 + S2 = V) is applied between the voltage and + V [v]. As a result, an electric field as shown in FIGS. 11C and 11D and an electric field in an intermediate state are formed in each pixel, and the direction of liquid crystal molecules is controlled between a state parallel to the substrate and a state perpendicular to the substrate. it can.
This control is by changing the direction of the electric field,
Therefore, the response speed (falling speed) can be greatly improved.

In each of the above embodiments, if the voltage applied to each electrode is adjusted, the number of electrically independent electrodes required for one pixel may be at least three.
The present invention can be implemented without increasing the number of I as compared with the conventional method.

In each of the embodiments described above, an example is shown in which one set of the first and second electrodes is used for one pixel.
A plurality of sets of electrodes may be used for one pixel. In addition, although the homeotropic liquid crystal panel has been described, it can also be used for an IPS mode liquid crystal panel used in a TFT, a guest-host type liquid crystal panel in which a dichroic dye is mixed in a homeotropic liquid crystal, and the like. If used, colorization can be easily performed.

[0035]

According to the present invention, since one pixel is composed of a first electrode composed of a plurality of electrodes formed in layers and a second electrode, the voltage applied to each electrode can be adjusted. Thereby, the voltage applied to the liquid crystal between the first and second electrodes during the non-selection period can be suppressed. Thus, when applied to a simple matrix liquid crystal display device, a voltage margin is greatly improved as compared with a conventional simple matrix liquid crystal display device, and a high-contrast liquid crystal display device can be realized without significantly increasing the cost.

If the present invention is applied to a liquid crystal panel having an active element, a high-speed response can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a liquid crystal panel in Embodiment 1.

FIG. 2 is a schematic cross-sectional view illustrating an electric field during driving according to the first embodiment.

FIG. 3 is a cross-sectional view of a liquid crystal panel according to a modification of the first embodiment.

FIG. 4 is a cross-sectional view of a liquid crystal panel according to another modification of the first embodiment.

FIG. 5 is a cross-sectional view of a liquid crystal panel in Embodiment 2.

FIG. 6 is a schematic cross-sectional view illustrating an electric field during driving according to the second embodiment.

FIG. 7 is a schematic cross-sectional view showing an electric field during driving in a modification of the second embodiment.

FIG. 8 is a cross-sectional view of a liquid crystal panel in Embodiment 3.

FIG. 9 is a schematic cross-sectional view illustrating an electric field during driving according to the third embodiment.

FIG. 10 is a cross-sectional view of a liquid crystal panel in Embodiment 4.

FIG. 11 is a schematic cross-sectional view illustrating an electric field during driving in Embodiment 4.

FIG. 12 is a cross-sectional view of a conventional liquid crystal panel.

[Explanation of symbols]

 1, 11, 21, 31 Substrate A 2, 3, 12, 13, 22, 23 Insulating film 4, 14, 23, 32 Substrate B 5, 15, 24, 33 Liquid crystal layer C, C1, C2, S1, S2 Electrode

Claims (7)

[Claims] 1. A liquid crystal display device comprising: a pair of substrates; a driving electrode formed on at least one of the substrates; a liquid crystal interposed between the substrates; and a means for applying a voltage to the driving electrodes. The drive electrode in one pixel includes a first electrode composed of a plurality of electrodes arranged in a layer and a second electrode arranged at a position different from the first electrode in the substrate surface direction. A liquid crystal display that performs display by applying a voltage to each of the first and second electrodes to generate a predetermined electric field between the first and second electrodes. apparatus. 2. The liquid crystal display device according to claim 1, wherein the first electrode and the second electrode are formed separately on different substrates. 3. The liquid crystal display device according to claim 1, wherein the plurality of electrodes constituting the first electrode are formed separately on different substrates. 4. The liquid crystal display device according to claim 1, wherein the signal electrode is included in an electrode constituting the first electrode. 5. The liquid crystal display device according to claim 4, wherein a scanning electrode is included in the electrodes forming the first electrode. 6. The liquid crystal display device according to claim 1, wherein the initial alignment of the liquid crystal molecules is perpendicular to the substrate. 7. An image display application device having the liquid crystal display device according to claim 1. Description: