JPH11212053A - Liquid crystal display device, driving method thereof, and liquid crystal projector - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a liquid crystal display device which prevents the occurrence of disclination lines on a pixel electrode due to rubbing processing, a lateral electric field or other factors, and which does not decrease in luminance or responsiveness. A light-transmitting counter electrode for applying a voltage to a liquid crystal layer is provided on an insulating substrate, and an alignment film formed on the counter electrode is not subjected to an alignment process for liquid crystal. An embedded electrode 3 for applying a potential gradient independent of the voltage value of the written image signal to the liquid crystal layer on the pixel electrode.
3. A liquid crystal display device provided with 3 to give a potential gradient to the liquid crystal.

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 and a method of driving the same, and more particularly, to a liquid crystal display device having high luminance and excellent high-speed response and a method of driving the same.

[0002]

2. Description of the Related Art Among liquid crystal display devices to which the present invention is directed,
Regarding the prior art of the transmission type liquid crystal display device, see
No. 6-31036. Here, the prior art will be described with reference to FIGS. 9 to 12 by taking a projection type liquid crystal display device using a reflection mode liquid crystal display system utilizing an electric field control birefringence effect as an example.

As shown in FIG. 9, a projection type liquid crystal display device has a light source 1, a lens 2 for converting light emitted from the light source 1 into parallel light, and reflects one polarized light and transmits the other polarized light. In this way, a polarization beam splitter 7 for realizing an optical system of cross Nicol folding, and an optical member such as a dichroic prism 3 for separating and synthesizing parallel light into three primary colors of red (R), green (G) and blue (B) Color separation and synthesis system.

[0004] The three reflection mode liquid crystal panels 4 which reflect the three primary colors separated by the color separation / combination system as incident light in accordance with the image signals of the respective colors to control and reflect the same.
-R, 4-G, 4-B and a projection lens 6 for synthesizing the reflected light again by a color separation / combination system and enlarging and projecting it on a screen 5.

In this example, a polarizing beam splitter 7 is used,
The projection optical system is constituted by a folded optical system in which the optical axes of the incident light of the reflection mode liquid crystal panels 4-R, 4-G, and 4-B and the exit light are made to coincide with each other. Also,
A mirror is used to shift the optical axis, and two polarizers with a crossed Nicols relationship whose transmission axes are orthogonal to each other are arranged on the entrance side and the exit side of the liquid crystal panel. An off-axis optical system or a dichroic mirror as a color separation / combination system And a projection optical system.

FIG. 10 is a schematic sectional view of a reflection mode liquid crystal panel which is a main part of a projection type liquid crystal display device.

The liquid crystal panel includes a glass substrate 13 formed on a transparent electrode 9 made of transparent and conductive indium / titanium oxide (hereinafter referred to as ITO), and an opposing aluminum or silver electrode. , A plurality of reflective electrodes 8 made of a metal having a high reflectance, a MOS transistor 12 for supplying an AC voltage to each reflective electrode 8 in accordance with an image signal, and a drive element 15 composed of wiring and the like.

Further, the reflection electrode 8 on the driving element 15 and
On the transparent electrode 9 on the opposing substrate 13, an alignment film such as a polyimide resin for controlling the alignment of the liquid crystal is applied by spin coating or printing, baked, and then subjected to an alignment treatment by rubbing.

Between the glass substrate 13 and each of the reflective electrodes 8, a seal for enclosing liquid crystal is applied to the periphery of the substrate and baked, and spacer beads for maintaining a constant distance between the electrodes are dispersed by a dispersion method or the like. Then, the liquid crystal 10 is sealed.

FIG. 10 shows the display operation of the liquid crystal panel.
This will be described below. Of the two types of electrodes constituting the pixel 11, a transparent electrode 9 is provided with a reference potential common to each pixel, and a transistor 12 is driven by an AC voltage modulated according to an image signal output to each reflective electrode 8 by a liquid crystal. Is detected by the polarization beam splitter 7, and the amount of light emitted from each pixel after the detection changes to display an image.

Next, a reflection type liquid crystal display device of a vertical alignment mode using a liquid crystal having a negative dielectric anisotropy will be described as an example.

As a basic operation of the liquid crystal, when a crossed Nicols optical system using a polarizing beam splitter (not shown) is used, the liquid crystal molecules are oriented in a direction perpendicular to the substrate surface in the absence of a voltage. Anisotropy is minimized and black is displayed.

Further, the retardation of the liquid crystal is increased by applying a voltage, and the product Δ of the refractive index anisotropy Δn and the liquid crystal gap d is obtained.
By adjusting n · d to λ / 4, which is の of the wavelength λ, that is, to λ / 2 by the optical path difference of the round trip, the outgoing light can pass through the polarization beam splitter of the crossed Nicols optical system, so Can be displayed.

In this embodiment, a liquid crystal panel utilizing the electric field control birefringence effect has been described as an example. However, the display device to which the present invention is applied is a reflection mode liquid crystal panel, which is a reflection mode twisted nematic liquid crystal. Panel, guest-host type liquid crystal panel, liquid crystal panel using ferroelectric liquid crystal,
In the transmission mode, a liquid crystal panel of a twisted nematic type, a liquid crystal panel using a ferroelectric liquid crystal, or the like can be used with almost the same configuration.

In the vertical alignment mode using a liquid crystal having a negative dielectric anisotropy, the phase difference in the entire wavelength region becomes almost zero without applying a voltage, so that a high contrast ratio can be obtained without using a phase plate. can get.

As the driving element, in addition to the MOS driving element in which a MOS transistor is formed on the silicon substrate described in this embodiment, a TFT driving element in which a thin film transistor and a reflective electrode or a transparent electrode are integrally formed on a glass substrate. Can be used as well.

The electric operation of the conventional liquid crystal display device will be described with reference to an equivalent circuit shown in FIG. The liquid crystal panel 4 has a pixel 11 electrically operating as a capacitor, a transistor 12 for writing a voltage to the pixel 11, and a storage capacitor 16 for holding the written voltage until the next writing operation in an array. A display matrix 19 comprising an image signal scanning line 17 for supplying a scanning signal to each transistor and a signal line 18 for supplying a voltage corresponding to the image signal.
And a scanning side driving circuit 20 for supplying a desired voltage to the display matrix 19, a signal side driving circuit 21, and a control circuit 22 for controlling these driving circuits.

An image signal 24 including a synchronizing signal input to the liquid crystal panel 4 from an image source 23 is supplied to a control circuit 22 by a control circuit 22.
Scanning side drive circuit 20 necessary for display operation of liquid crystal panel 4
And the control signals 25 and 26 of the signal side drive circuit 21 and the converted image signal 27 converted to the voltage level necessary for the liquid crystal display, and input to the scan side drive circuit 20 and the signal side drive circuit 21. I do.

The control signals 25 and 26 and the image signal 27 are used to write line-sequentially to the pixels 11 in an array.

The display operation of one frame is completed by writing to all the pixels 12, and in the next frame, a voltage of the opposite polarity based on the transparent electrode voltage 28 on the side opposite to the previous frame is written to each pixel. AC drive can be performed.

As described above, by inverting the polarity for each frame and driving the liquid crystal by AC, deterioration of the liquid crystal can be prevented, and the display quality can be maintained and reliability can be secured.

FIG. 12 is a schematic view showing a conventional driving method of a liquid crystal display device. The driving method is classified according to a method of applying a voltage to the pixel 11 composed of the matrix-shaped reflective electrode, the transparent electrode and the liquid crystal opposed to each other.

A frame inversion drive in which all the voltage polarities of a plurality of pixels 11 in one frame are written and displayed equally, and the polarity of the write is inverted for each frame. Dot inversion drive that combines writing and display by always inverting the voltage polarity in both the row and column directions, and aligning the write voltage polarity of the pixel 11 in one of the row and column directions, and in the other direction 1
Four types of driving methods are known: column inversion driving, in which polarity is inverted for each dot, and writing and display are combined with frame inversion driving, and row inversion driving described above.

Among the above four driving methods, the dot inversion driving method can average flicker caused by direct current superposition due to a difference in writing voltage depending on polarity at a pitch lower than the resolution of the human eye. As a result, the occurrence of flicker can be suppressed, and since the poorly-aligned region of the liquid crystal called the disclination line is fixed, the response speed decreases due to the low-speed response characteristic of the liquid crystal near the disclination line. And stable display is possible.

On the other hand, the frame inversion driving is a driving method in which a horizontal electric field is not applied at all between pixels because an equal voltage of the same polarity is applied between adjacent pixels during uniform luminance display. Therefore, by applying frame inversion driving to a reflection mode liquid crystal display device having a higher aperture ratio than a transmission type liquid crystal display device, the occurrence of disclination lines due to a lateral electric field is prevented. And a display with a high contrast ratio and a high luminance can be realized.

Further, in the direct-view type reflection mode liquid crystal display device, there is no increase in black luminance due to the disclination line between pixels in black display or at the edge of the pixel electrode. Therefore, it is not necessary to provide a light-shielding layer on the side of the opposing substrate, which requires a light-shielding layer. From this, high luminance can be realized by using the frame inversion drive.

[0027]

However, of the four types of prior art driving methods described above, in the dot inversion driving, voltages of different polarities are always applied to the pixels 11 adjacent in both directions of the matrix.

As a result, the brightness is reduced by applying a horizontal electric field between pixels in the white display as shown in FIG. 13 and in the vicinity of the pixels. On one or two sides, a low-luminance portion called a disclination line always occurs in which the alignment direction 31 of the liquid crystal molecules by the rubbing process does not match the alignment direction by the electric field.

Since the disclination line 32 due to the rubbing does not depend on the display pattern of the image, the white display luminance is further reduced. Note that in FIG. 13 and other drawings, liquid crystal molecules in a black display state are displayed in black, and liquid crystal molecules in a white display state are displayed in white for easy understanding.

The frame inversion driving method is shown in FIG.
As shown in FIG. 14A, the characteristics in the uniform luminance display are good. However, as shown in FIG. 14B, when different potentials (black-and-white display) are given between adjacent pixels, horizontal characteristics due to a potential difference between pixels are generated. An electric field is generated, and a disclination line 32 similar to that in the dot inversion drive is generated near different pixel ends in the direction of the horizontal electric field and the alignment direction 31 by rubbing.

This phenomenon does not occur in the case of full white display, so that the white luminance does not decrease. However, the state changes from FIG. 14 (b) to FIG. 14 (a) when the black figure moves. In such a case, a phenomenon is seen in which the direction of the horizontal electric field in the disclination line generating portion changes and the response of the liquid crystal decreases.

The row inversion drive and the column inversion drive are driving methods intermediate between the dot inversion drive and the frame inversion drive, and cannot completely solve the problems of both.

It has been disclosed that the disclination line caused by rubbing can be reduced by providing an alignment control window disclosed in Japanese Patent Application Laid-Open No. 7-64089 on the counter electrode side. Since a disclination line is generated at the center of the alignment control window due to the discontinuous potential gradient due to the window, the brightness of the panel is reduced particularly when the pixel size of the panel is reduced to achieve high definition or when the panel is downsized. There is a concern that this will lead to a decline.

An object of the present invention is to provide a rubbing process, a horizontal electric field,
Another object of the present invention is to provide a high-brightness liquid crystal display device in which a disclination line on a pixel electrode caused by other factors is prevented and luminance does not decrease.

Another object of the present invention is to provide a frame inversion driving method capable of further increasing the brightness as compared with dot inversion driving, row inversion driving, and column inversion driving. An object of the present invention is to provide a high-brightness and high-quality liquid crystal display device without any reduction.

Another object of the present invention is to provide a liquid crystal projector using the above liquid crystal display device.

[0037]

The gist of the present invention to achieve the above object is as follows.

At least one of the light-transmitting opposing 2
A sheet of insulating substrate, a liquid crystal layer having dielectric anisotropy and refractive index anisotropy sandwiched between the insulating substrate, at least one of the insulating substrate, a matrix-shaped pixel electrode,
A voltage application unit that applies an AC voltage according to an image signal to the liquid crystal layer, and a light transmissive counter electrode that applies a voltage to the liquid crystal layer on another insulating substrate facing the same, and An alignment film formed thereon is a liquid crystal display device in which alignment processing for liquid crystal is not performed, and a potential gradient independent of a voltage value of an image signal written to the pixel electrode is applied to a liquid crystal layer on the pixel electrode. The liquid crystal display device is characterized in that it is configured to provide an electrode to be applied to the substrate and to apply a potential gradient.

In particular, in the liquid crystal display device, the potential gradient direction of the liquid crystal on the pixel electrode is configured to be the same direction or a combination of the opposite directions in all the pixels in the liquid crystal display device. .

Specifically, a buried electrode that is electrically insulated from the pixel electrode is arranged below each pixel, and two or more voltages having different voltages are applied to the buried electrode. And means for applying a voltage of which at least the first voltage is equal to or higher than the maximum value of the voltage applied to the pixel electrode and the second voltage is equal to or lower than the minimum value of the voltage applied to the pixel electrode. is there.

Further, the first and second buried electrodes, which are electrically insulated and formed in stripes, are formed below each pixel.
And a means for alternately applying the above-mentioned voltage at a predetermined cycle, so as to apply a potential gradient independent of the voltage value of the image signal written to the pixel electrode to the liquid crystal on the pixel electrode.

A feature of the driving method of the liquid crystal display device of the present invention that achieves the above object is that a plurality of embedded electrodes that are electrically insulated from the pixel electrodes are arranged below each pixel. Out of two or more different voltages applied to the embedded electrode, the first voltage is equal to or greater than the maximum value of the voltage applied to the pixel electrode, and the second voltage is equal to or less than the minimum value of the voltage applied to the pixel electrode. At the same time, the first and second voltages are alternately applied to each of the embedded electrodes at a predetermined cycle, and the timing of switching between the first and second voltages to be applied to each of the embedded electrodes is changed by the scanning of the scanning electrode. Synchronize or precede timing.

Also, a light source, a lens for converting light emitted from the light source into parallel light, a polarization beam splitter for reflecting one of the polarized lights and transmitting the other, and separating the parallel light into three primary colors of red, green and blue. A color separating / combining means for combining, three reflective liquid crystal display devices for controlling and reflecting the reflectance according to an image signal using each of the three primary color lights as incident light, and reflected by the liquid crystal display device A liquid crystal projector having a projection unit for projecting an image obtained by combining the reflected light by the color separation / synthesis unit onto a screen, the liquid crystal projector using the liquid crystal display device.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described with reference to the drawings. In the following embodiments, a reflection type liquid crystal display device using an electric field control birefringence mode will be described as an example. However, a projection type or direct view type liquid crystal display device having a reflection mode electrode structure, or between electrodes or electrode ends It is needless to say that the present invention can be applied to all liquid crystal display devices using a display mode in which a light shielding layer is not provided in a portion and a discrimination line of a horizontal electric field type is recognized.

Embodiment 1 FIGS. 1 to 4 and FIG.
Next, an example in which the present invention is applied to a reflection type liquid crystal display device by a column-by-column inversion driving method will be described.

As the liquid crystal material, any material having a positive or negative dielectric anisotropy can be used. However, a liquid crystal having a negative dielectric anisotropy, which has a high contrast ratio and high image quality, can be used. A membrane was used.

Further, since the column-by-column inversion driving method is used, a disclination line is always generated between pixels in the row direction due to a horizontal electric field, and white luminance is reduced as compared with the frame inversion driving method. Since the disclination line is fixed irrespective of the image, the response speed in the row direction does not decrease as in the related art. Therefore, description will be made mainly on the column direction in which the effect of the present embodiment can be obtained.

The basic configuration is almost the same as that of the conventional projection type and direct-view type reflection type liquid crystal display devices shown in FIGS. 9 to 11, except that the reflection electrode and the reflection electrode are provided below the reflection electrode between the pixel electrodes. By disposing an insulated embedded electrode and applying two or more different voltages to the embedded electrode, a potential gradient is applied to the liquid crystal on the reflective electrode without depending on the image signal, and the liquid crystal is stabilized by the potential gradient. Is to orientate.

FIG. 2 is a plan view of the liquid crystal panel of this embodiment. The buried electrodes 33 are arranged in stripes between the rows of the respective reflective electrodes 8, and a voltage + V _BE higher in positive polarity than any voltage applied to the reflective electrodes 8 and the transparent electrode 9 (not shown), a negative electrode Low voltage -V _BE
Is applied to the embedded electrode 33 with the polarity inverted for each row.

Thus, the electric field distribution on the reflection electrode 8 can be controlled in the column direction.

Hereinafter, the control of the electric field on the pixel electrode by the buried electrode 33 will be described in detail. The process of writing a voltage from the image source to each of the reflective electrodes by the scanning drive circuit and the signal control circuit is the same as in the prior art. Therefore, the description is omitted.

FIG. 1 shows a partial schematic sectional view taken along the line BB of FIG. 2, a potential distribution during voltage application, and an orientation direction of the liquid crystal at that time. Thus, the operation and effect in the column direction of the present embodiment will be described.

As shown in FIG. 1A, a buried electrode 33 is provided below the reflective electrode 8 and an adjacent buried electrode 3 is provided.
A voltage of the opposite polarity is applied to 3 'to give a liquid crystal on the reflective electrode 8 a potential gradient independent of an image signal. Further, in order to keep the potential gradient constant, the polarity of the voltage applied to the embedded electrode 33 is inverted for each frame in which the polarity of writing to the reflective electrode 8 is reversed.

Since the potential gradient on the reflective electrode 8 is constant, the alignment direction of the liquid crystal does not change from black display where a low voltage is applied to white display where a high voltage is applied. As a result, not only during the period during which the same image is displayed, but also when the image display shifts from the monochrome display of FIG. 1A to the white display of FIG. No nation line occurs.

Further, since there is no other electrode or any other element on the reflective electrode 8 that generates an electric field concentrated portion, the embedded electrode 33
There is no danger of causing a secondary display failure due to the provision of the display.

In the white display, between the reflective electrodes (the embedded electrodes 3
3), a disclination line is generated. However, as a characteristic of the reflective display device, the distance between the reflective electrodes can be made very small, and the reflectance between the reflective electrodes in the white display is low. No effect.

In order not to generate an unnecessary horizontal electric field between the electrodes in the row direction, a light-shielding layer or conductor (not shown) under the buried electrode is connected to the midpoint of the signal voltage or the opposite substrate (transparent electrode 9). Is desirably kept at the same potential as the potential of. Especially,
It is conceivable that the influence of the electrode provided below the buried electrode 33 may affect the pixel electrode when displaying uniform luminance, but the influence is completely removed by setting the potential as described above. can do.

FIG. 3 shows a comparison of display characteristics between the case where the row inversion driving method is combined with the structure of this embodiment and the case where the dot inversion driving method is combined with the conventional structure.

In the present embodiment, in particular, the occurrence of disclination lines on the reflective electrode 8 which significantly reduces the luminance in white display is eliminated in the column direction, and the white luminance (reflectance ) Can be greatly improved.

FIG. 4 shows an equivalent circuit of the liquid crystal display of this embodiment. The basic configuration is the same as that of the conventional liquid crystal display device, except that an embedded electrode 33 and an embedded electrode drive circuit 34 for generating a predetermined voltage are newly provided to provide a uniform potential gradient on the reflective electrode. It is characterized in that a built-in electrode drive circuit 34 is provided.

The buried electrode drive circuit 34 provides a desired voltage to the buried electrode 33 by applying a higher voltage to the positive polarity and a lower voltage to the negative polarity than any voltage applied to the reflective electrode 8 and the transparent electrode 9. Is realized.

[0062] As a specific circuit configuration of the embedded electrode driving circuit 34 is the positive polarity and negative polarity of the voltage + V _BE and -
When V _BE is given as a fixed potential as shown in FIG.
Each time the polarity of the write voltage applied to the pixel is inverted for each frame, the direction of the potential gradient changes. For this reason, the liquid crystal molecules on the pixel electrodes are tilted in different directions for each frame, resulting in an unstable display.

In order to prevent this, the scanning side driving circuit 20
Prior to the image writing by the above method, a countermeasure was provided by providing an embedded electrode drive circuit 34 for inverting the polarity of the embedded electrode 33. The circuit configuration of the embedded electrode drive circuit 34 includes a line selection unit such as a shift register and a selector, and a voltage switch unit that applies a desired voltage to the selected embedded electrode.

FIG. 17 is a timing chart of the outputs of the embedded electrode driving circuit 34 and the scanning side driving circuit 20. By setting the polarity inversion timing of the output of the embedded electrode drive circuit 34 ahead of the scan signal VGn of the scanning side drive circuit 20, the influence of the polarity inversion of the output of the embedded electrode drive circuit 34 can be prevented. .

According to this embodiment, the embedded electrode 33 which is electrically insulated from the reflective electrode is disposed below the reflective electrode 8 between the pixel electrodes, and the embedded electrode 33 has two or more different voltages. Is applied to the liquid crystal 10 on the reflective electrode 8 to give a potential gradient independent of an image signal. With this potential gradient, the liquid crystal can be oriented stably to improve the image quality, and the luminance in white display can be greatly improved without formation of the disclination line on the reflective electrode.

Embodiment 2 FIGS. 5 to 8 show an example in which the present invention is applied to a reflection type liquid crystal display device by a frame inversion driving method. Note that the same liquid crystal material, alignment film, and the like as in Example 1 were used.

Although the basic configuration is almost the same as that of the first embodiment,
A shield electrode 35 is provided between the reflective electrode 8 and the buried electrode 33, and the potential of the shield electrode 35 is changed to the transparent electrode 9.
Set equal to the potential of Then, through holes 36 are provided at lattice points in the spaces between the pixels, and the potential of the embedded electrode 33 can be applied to the liquid crystal through the through holes 36.

As shown in FIG. 5, the through holes 36 are arranged in a staggered manner, and the through holes 3 on the diagonal of the pixel are formed.
By setting 6 to the opposite polarity, the liquid crystal on reflective electrode 8
A potential gradient in the direction of 5 degrees can be given.

FIG. 6 is a schematic cross-sectional view taken along the line AA in FIG. 5, in which the potential distribution during voltage application and the orientation direction of the liquid crystal at that time are displayed in an overlapping manner.

The behavior of the liquid crystal molecules is almost the same as that of the first embodiment except that the angle is not the column direction but the 45-degree direction. Therefore, the description is omitted. Since it can be formed, no disclination line is formed on the reflective electrode.

Further, even if the image changes as shown in FIGS. 6A and 6B, the orientation direction does not change, and the response speed does not decrease even in the frame inversion driving. The polarization axis of the polarizing beam splitter (not shown) is preferably horizontal or vertical in order to reduce the size of the optical system. In this case, the orientation axis is 45 degrees from horizontal or vertical.
It is necessary to incline by degrees. In such a case, the configuration of the present embodiment is suitable.

FIG. 7 is a graph showing a comparison of display characteristics between the case where the row inversion driving method is combined with the structure of the present embodiment and the case where the dot inversion driving method is combined with the conventional structure.

In the present embodiment, in particular, the occurrence of disclination lines on the reflective electrode, which significantly reduces the luminance in white display, is eliminated in both the row and column directions. Further, the white luminance can be greatly improved.

FIG. 8 shows an equivalent circuit of the liquid crystal display of this embodiment. The basic configuration is the same as that of the liquid crystal display device of the first embodiment, but is characterized in that a shield electrode 35 and a shield electrode voltage 38 are newly provided in the first embodiment.

The above-mentioned shield electrode voltage 38 is applied to the transparent electrode 9 on the opposite side which has the least influence on the liquid crystal on the reflective electrode 8.
Was applied. Except for this, driving is performed in exactly the same manner as in the first embodiment, and a description thereof will be omitted.

According to this embodiment, the embedded electrode 33 electrically insulated from the reflective electrode 8 is disposed below the reflective electrode 8 between the pixel electrodes. By disposing the shield electrode 35 having a through hole between them, the liquid crystal on the reflective electrode 8 does not depend on the image signal.
It is possible to give a potential gradient in the direction of 5 degrees.

Since the liquid crystal is stably aligned by the potential gradient, the image quality is improved, and there is no formation of a disclination line on the reflective electrode. In the frame inversion driving method, the luminance in white display is greatly improved. Can be.

Further, even if the image changes, the orientation direction does not change, so that the response speed of the frame inversion drive does not decrease.

[Embodiment 3] FIGS. 15 and 16 show modifications of Embodiments 1 and 2. FIG.

FIG. 15 shows a modification of the first embodiment, in which a staggered auxiliary electrode 3 is provided every other pixel on a stripe embedded electrode 33.
9 are arranged. By the electric field generated by the auxiliary electrode 39 and the buried electrode 33, the liquid crystal molecules on the pixel electrode 11
It can be controlled stably from the direction.

According to the above, as in the second embodiment, a potential gradient having a 45-degree tilt angle required for downsizing the optical system can be realized. Due to this potential gradient, the liquid crystal is oriented stably, the image quality is improved, and there is no formation of a disclination line on the reflective electrode, so that the white display luminance in the frame inversion driving method can be greatly improved. Also, it is not necessary to use a through hole process.

FIG. 16 is a modification of FIG. 15, in which the embedded electrode 33 in the scanning electrode direction is shielded by the shield electrode 35, and the orientation direction of the liquid crystal molecules is not shown by the potential gradient by the auxiliary electrode 39. They are aligned in the scanning electrode direction.

According to this, as in the first embodiment, the polarity of the embedded electrode 33 can be inverted for each row in synchronization with the writing operation of the scanning electrode.

In particular, when the shape of the pixel is long in the column direction, the auxiliary electrode can be arranged in the scanning electrode direction in which the distance between the pixel electrodes is short, and the electric field is effectively applied to the liquid crystal molecules. can do.

[0085]

According to the present invention, since a disclination line due to a lateral electric field between the reflective electrodes can be prevented, it is possible to provide an excellent liquid crystal display device having high white luminance and no reduction in response speed. it can.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a potential distribution and a behavior of a liquid crystal of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view of the liquid crystal display device according to the embodiment of the present invention.

FIG. 3 is a graph showing characteristics of the liquid crystal display device of the present invention.

FIG. 4 is a diagram showing an electrical configuration of the liquid crystal display device of the present invention.

FIG. 5 is a plan view of a liquid crystal display device according to another embodiment of the present invention.

FIG. 6 is a schematic sectional view showing a potential distribution and a behavior of a liquid crystal of a liquid crystal display device according to another embodiment of the present invention.

FIG. 7 is a graph showing characteristics of another liquid crystal display device of the present invention.

FIG. 8 is a diagram showing an electrical configuration of another liquid crystal display device of the present invention.

FIG. 9 is a configuration diagram of a conventional liquid crystal projector.

FIG. 10 is a schematic sectional view of a conventional liquid crystal display device.

FIG. 11 is a diagram showing an electrical configuration of a conventional liquid crystal display device.

FIG. 12 is a schematic diagram of a driving method of a conventional liquid crystal display device.

FIG. 13 is a schematic cross-sectional view showing a potential distribution and a behavior of a liquid crystal of a conventional liquid crystal display device.

FIG. 14 is a schematic cross-sectional view showing a potential distribution and a behavior of a liquid crystal of a conventional liquid crystal display device.

FIG. 15 is a plan view of a liquid crystal display device according to another embodiment of the present invention.

FIG. 16 is a plan view of a liquid crystal display device according to another embodiment of the present invention.

FIG. 17 is a diagram showing the timing of the driving method of the present invention.

[Explanation of symbols]

1 ... light source, 2 ... lens, 3 ... dichroic prism,
4: liquid crystal panel, 5: screen, 6: projection lens, 7
... polarizing beam splitter, 8 ... reflecting electrode, 9 ... transparent electrode, 10 ... liquid crystal, 11 ... pixel electrode, 12 ... transistor, 13 ... glass substrate, 14 ... alignment film, 15 ... driving element, 16 ... storage capacitor, 17 ... Scanning wiring, 18 signal wiring, 19 display matrix, 20 scanning side driving circuit, 2
DESCRIPTION OF SYMBOLS 1 ... Signal side drive circuit, 22 ... Control circuit, 23 ... Image source,
24 image signal, 25 scanning-side control signal, 26 signal-side control signal, 27 image signal after conversion, 28 transparent electrode voltage, 31 orientation direction, 32 disclination line, 33 embedded electrode , 34 ... embedded electrode drive circuit, 35 ...
Shield electrode, 36: through hole, 37: embedded electrode control signal, 38: shield electrode voltage, 39: auxiliary electrode.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G09G 3/36 G09G 3/36 (72) Inventor Masaya Adachi 7-1-1, Omikamachi, Hitachi City, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Osamu Ito 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory, Ltd. Inside

Claims (19)

[Claims] At least one of two opposing insulating substrates having a light transmitting property, and a liquid crystal layer having dielectric anisotropy and refractive index anisotropy sandwiched between the insulating substrates, At least one of the insulating substrates has a matrix of pixel electrodes, a voltage applying unit that applies an AC voltage according to an image signal to the liquid crystal layer, and the liquid crystal layer on the other insulating substrate facing the same. A liquid crystal display device comprising a light transmissive counter electrode for applying a voltage, and an alignment film formed thereon is not subjected to an alignment process for liquid crystal, and a voltage of an image signal written to the pixel electrode A liquid crystal display device comprising: an electrode for applying a potential gradient independent of a value to a liquid crystal layer on the pixel electrode to provide a potential gradient. 2. The liquid crystal according to claim 1, wherein the direction of the potential gradient of the liquid crystal on the pixel electrode is the same or a combination of the opposite directions in all the pixels in the liquid crystal display device. Display device. 3. At least one of two opposing insulating substrates having optical transparency, and a liquid crystal layer having dielectric anisotropy and refractive index anisotropy sandwiched between the insulating substrates, At least one of the insulating substrates has a matrix of pixel electrodes, a voltage applying unit that applies an AC voltage according to an image signal to the liquid crystal layer, and the liquid crystal layer on the other insulating substrate facing the same. A liquid crystal display device comprising a light-transmitting counter electrode for applying a voltage, and an alignment film formed thereon is not subjected to an alignment process for liquid crystal, and a lower portion between the pixels of the pixel electrode, It has a buried electrode electrically insulated from the pixel electrode, and by applying a predetermined voltage to the buried electrode, a potential gradient on the pixel electrode that does not depend on the voltage value of the image signal written to the pixel electrode is formed. Configured to give to the liquid crystal layer A liquid crystal display device comprising and. 4. A voltage independent of a voltage value of an image signal written to a pixel electrode by applying at least two different voltages to each embedded electrode formed below each pixel of the pixel electrode. 4. The liquid crystal display device according to claim 3, wherein the liquid crystal on the pixel electrode is provided with an inclination. 5. A method according to claim 1, wherein the first voltage is at least a maximum value of a voltage applied to the pixel electrode and the second voltage is at least a maximum value of the voltage applied to the pixel electrode. The liquid crystal display device according to claim 4, wherein the value is equal to or less than the minimum value. 6. A method according to claim 1, wherein said first and second electrodes are provided to each of said embedded electrodes.
6. The liquid crystal display device according to claim 5, further comprising voltage applying means for applying the voltage alternately at a predetermined cycle. 7. A matrix-shaped pixel electrode and voltage applying means for applying an AC voltage to a liquid crystal layer according to an image signal include a scanning electrode and a signal electrode, and each of the embedded electrodes is formed in a stripe shape. 7. The liquid crystal display device according to claim 6, further comprising means for synchronizing or preceding the switching timing of the first and second voltages applied to the embedded electrode with the scanning timing of the scanning electrode. 8. A voltage intermediate between the first and second voltages or a maximum voltage applied to a pixel electrode is applied to the embedded electrode to which the first or second voltage is not applied among the embedded electrodes. 6. The liquid crystal display device according to claim 5, further comprising means for applying a voltage intermediate between the value and the minimum value, or a voltage equal to the counter electrode. 9. The liquid crystal according to claim 5, further comprising: means for applying the first voltage between one pixel electrode between adjacent pixel electrodes and applying the second voltage between the other pixel electrodes. Display device. 10. Among four pixel electrodes (a, b, c, d) surrounding one pixel electrode, one (b) between two other pixel electrodes adjacent to one pixel electrode (a). Or c)
10. The liquid crystal display device according to claim 9, wherein the liquid crystal display devices are configured to have the same voltage. 11. The liquid crystal display device according to claim 3, wherein the matrix-shaped pixel electrode and the embedded electrode are light-transmissive and are of a transmission type for transmitting incident light for display. 12. The pixel electrode in a matrix form is light-reflective, and said buried electrode is light-shielding or light-reflective, and is of a reflection type for reflecting incident light for display.
11. The liquid crystal display device according to any one of items 10 to 10. 13. The liquid crystal is a negative liquid crystal in which the directions of the dielectric anisotropy and the refractive index anisotropy are substantially perpendicular to each other, and the liquid crystal molecules are substantially vertically aligned with the substrate surface when no voltage is applied. Item 1
13. The liquid crystal display device according to any one of items 12 to 12. 14. At least one of two opposing insulating substrates having a light transmitting property, and a liquid crystal layer having dielectric anisotropy and refractive index anisotropy sandwiched between the insulating substrates, At least one of the insulating substrates has a matrix of pixel electrodes, voltage applying means for applying an AC voltage to the liquid crystal layer according to an image signal, and a voltage applied to the liquid crystal layer on the other insulating substrate facing the same. A liquid crystal display device comprising a light transmissive counter electrode for applying
A buried electrode that is electrically insulated from the pixel electrode, and a first electrode of at least two different voltages applied to the buried electrode;
Wherein a voltage equal to or higher than the voltage applied to the pixel electrode and a second voltage equal to or lower than the voltage applied to the pixel electrode are alternately applied to the embedded electrode in a predetermined cycle. Method. 15. A scanning electrode and a signal electrode for applying an AC voltage according to an image signal to the liquid crystal layer, wherein the embedded electrode is formed in a stripe shape, and a scanning timing of the scanning electrode. The method of driving a liquid crystal display device according to claim 14, wherein the method is performed in synchronization with or in advance of the timing of switching to the first and second voltages applied to the embedded electrode. 16. A voltage intermediate between the first and second voltages or the pixel electrode is applied to the remaining embedded electrodes to which the first and second voltages are not applied among the embedded electrodes. 16. A voltage applied between the maximum value and the minimum value of the voltage or a voltage equal to the counter electrode.
3. The method for driving a liquid crystal display device according to 1. 17. At least one of two opposing insulating substrates having a light transmitting property, and a liquid crystal layer having a dielectric anisotropy and a refractive index anisotropy sandwiched between the insulating substrates, At least one of the insulating substrates has a matrix of pixel electrodes, voltage applying means for applying an AC voltage to the liquid crystal layer according to an image signal, and a voltage applied to the liquid crystal layer on the other insulating substrate facing the same. And a light-transmitting counter electrode for applying the same, and in any one of the row direction and the column direction in the same writing frame, the polarity is inverted for each predetermined pixel, between the pixel electrodes A buried electrode electrically insulated from the pixel electrode is provided at a lower portion, and a predetermined voltage is applied to the buried electrode so that a potential gradient independent of a voltage value of an image signal written to the pixel electrode is obtained. Give to the liquid crystal on the electrodes With a method of driving a liquid crystal display device characterized by the direction of the potential gradient, the direction of polarity reversal of the write polarity of the pixel of the same write frame has to be orthogonal. 18. A light source, a lens that converts light emitted from the light source into parallel light, a polarization beam splitter that reflects one of the polarized lights and transmits the other, and separates the parallel light into three primary colors of red, green, and blue. A color separating / combining means for combining, three reflective liquid crystal display devices for controlling and reflecting the reflectance according to an image signal using each of the three primary color lights as incident light, and reflected by the liquid crystal display device In a liquid crystal projector having a projection unit for projecting an image obtained by combining reflected light by the color separation / combination unit onto a screen, the liquid crystal display device comprises: two insulated substrates, at least one of which is light-transmitting and facing each other; A liquid crystal layer having dielectric anisotropy and refractive index anisotropy is sandwiched between insulating substrates,
At least one of the insulating substrates has a matrix of pixel electrodes, a voltage applying unit that applies an AC voltage according to an image signal to the liquid crystal layer, and a liquid crystal layer on the other insulating substrate facing the same. A liquid crystal display device comprising a light transmissive counter electrode for applying a voltage, and an alignment film formed thereon is not subjected to an alignment process for liquid crystal, and a voltage of an image signal written to the pixel electrode A liquid crystal projector characterized in that an electrode for giving a potential gradient independent of a value to a liquid crystal layer on the pixel electrode is provided to give a potential gradient. 19. A liquid crystal display, comprising a buried electrode electrically insulated from a pixel electrode below a pixel electrode between the pixels, and applying a predetermined voltage to the buried electrode to form a pixel. 19. The liquid crystal projector according to claim 18, wherein a potential gradient independent of a voltage value of an image signal written to the electrode is applied to the liquid crystal layer on the pixel electrode.