JPH075432A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To simplify an external circuit and reduce a flicker on a screen by decreasing a data signal for liquid crystal driving when a gradational display is made with ferroelectric liquid crystal. CONSTITUTION:Vertical electrodes 4a and 4b, and 5a and 5b and horizontal electrodes 6(7) made of transparent electrodes are formed inside glass substrates 2 and 3 while crossing one another in a matrix shape. Respective pixels, e.g. a pixel 4 consists of vertical electrodes 4a and 4b which differ in area and their area ratio is 1:2. For the gradational display, an unillustrated driving circuit performs the selective ON/OFF driving of electrodes of area corresponding to gradations displayed on respective pixels among the vertical and horizontal electrodes and for gradations which can not be displayed only with an area ratio by the selection of electrodes, one pixel is blinked at a specific inversion period to vary the mean transmissivity of light, thereby enabling the gradational display.

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,
More specifically, the present invention relates to a liquid crystal display device that performs gradation display using a liquid crystal composition exhibiting ferroelectricity.

[0002]

2. Description of the Related Art In recent years, along with the miniaturization of electronic equipment,
A liquid crystal display (LCD) has been attracting attention as a display replacing a CRT (Cathode Ray Tube). This LCD has an advantage that it consumes much less power than a CRT and can be miniaturized.

Since this LCD has no color in the liquid crystal itself and does not emit light by itself, initially, only binary display such as white and blue or white and black was performed.

However, with the increase in the amount of information, there is a demand for an LCD capable of clearly drawing out halftones such as photographs. Therefore, at present, for example, a thin film transistor (TFT) having a semiconductor layer such as amorphous silicon or polysilicon on a glass substrate.
er) is formed and the amount of light transmission is controlled by controlling the electric field value applied to the liquid crystal, and there is a display that displays a halftone.

Further, in the case of a liquid crystal display device using a simple matrix, halftone display is realized by applying different voltage values to each intersection of the electrodes.

However, in order to realize halftone display with the above-mentioned TFT, there is a problem of high cost, and in order to realize halftone display with the above-mentioned simple matrix, there is a problem of deterioration of contrast and viewing angle. .

For this reason, recently, it has a display performance comparable to that of an active matrix type display device in terms of viewing angle and contrast, and it is possible to form a screen with a simple matrix, and to reduce the cost, and thus the ferroelectricity. Liquid crystal display devices are attracting attention. However, this ferroelectric liquid crystal display device has memory characteristics because it exhibits spontaneous polarization, but when an electric field is applied to the liquid crystal, the liquid crystal molecules have only two alignment states, a light transmission state and a light blocking state. For the time being, it was very difficult to display halftone even though binary display was possible.

Therefore, in the conventional ferroelectric liquid crystal display device, for example, each pixel is divided into areas (area ratio of 1 :).
Eight gradation display is performed by changing the combination of the electrodes to be driven by using the electrodes which have a ratio of 2: 4).
Further, each pixel is composed of a pair of counter electrodes, and the electrodes are driven in a time division manner. For example, in the case of displaying a moving image, 30 screens are displayed per second, and when each pixel is rewritten a plurality of times for each screen, by blinking each pixel according to the display gradation, There is a display in which gradation is displayed by changing the average transmittance.

[0009]

However, in such a conventional liquid crystal display device, in the case of the above conventional example, three or more kinds of electrodes having different area ratios must be prepared for each pixel. , The connection with the external circuit becomes complicated and the reliability is deteriorated, and when driving these electrodes, it is necessary to add three or more data signals to one unit pixel, which makes the external circuit very complicated. There was a problem of becoming.

Further, in the case of the above-mentioned conventional example, the electrodes of each pixel are turned ON / OF at high speed in accordance with the gradation displayed by each pixel.
By operating F and changing the average transmittance of light,
The gradation is displayed. This ON / OFF operation speed is
Since the blinking is repeated at high speed, the flicker of the screen called flicker can be made inconspicuous to some extent by utilizing the afterimage phenomenon of human eyes. However, in the case of the above-mentioned conventional example, although it is fast, the blinking operation is repeated in all the pixels, so that there is a problem that flicker becomes a concern.

Therefore, the present invention has been made in view of the above problems, and when performing gradation display using a ferroelectric liquid crystal, the data signal for driving the liquid crystal is reduced as much as possible to simplify the external circuit. In addition, it is an object of the present invention to provide a liquid crystal display device which can realize proper gradation display with less flicker.

[0012]

A liquid crystal display device according to claim 1, wherein electrodes for applying an electric field to a liquid crystal composition exhibiting ferroelectricity are arranged to face each other inside a pair of parallel substrates, and a drive signal is applied to the electrodes. In a liquid crystal display device provided with a liquid crystal drive circuit that applies a voltage to change the molecular orientation of the liquid crystal composition provided between the substrates, each pixel constituting the liquid crystal display surface is composed of a plurality of electrodes having different areas, The drive control circuit selects and drives an electrode having an area corresponding to the gradation of an image signal to be displayed for each pixel, and when displaying a halftone that cannot be displayed only by selecting the drive electrode. Only by driving any one of the plurality of electrodes to blink to display a desired gradation, the above object is achieved.

In this case, each pixel has, for example, an area ratio of 1: 2, as described in claim 2.
The above object is achieved by being composed of one counter electrode.

Further, for example, as described in claim 3, the electrode for driving the blinking has an inversion driving period of 30H.
It may be configured to drive at z or higher.

[0015]

According to the present invention, each pixel forming the liquid crystal display surface is composed of a plurality of electrodes having different areas, and the drive control circuit forms an electrode having an area corresponding to the gradation to be displayed for each pixel. Only when selecting and driving, and displaying halftones that cannot be expressed simply by selecting drive electrodes,
Any one of the plurality of electrodes is driven to blink to display a desired gradation. Therefore, each pixel can be configured with a small number of divided electrodes, the number of data signals for driving the liquid crystal is reduced, the external circuit can be simplified, and the transmittance of light can be increased by blinking any one electrode. Can be adjusted to display a finer gradation. Therefore, basically, gradation display can be performed by selectively driving the electrodes, and intermediate gradation can be displayed by supplementarily driving any one electrode forming the pixel to blink. The flicker can be made inconspicuous by reducing the blinking pixel area. According to the second aspect of the present invention, since each pixel is composed of two electrodes having an area ratio of 1: 2, the number of data signals required for selectively driving the electrodes is smaller than in the conventional example, and one pixel is used. When the total transmissive state of is set to “3”, the area of the transmissive state can be set to “2”, “1”, and “0” by selecting each electrode. The gradation can be displayed. Further, according to the present invention, even when performing gradation display between each of the four gradations, by driving any one electrode to blink at a predetermined rate, the light transmittance can be easily changed. The number of gradations can be increased (for example, 7 gradations). As described above, according to the present invention, only when any one of the electrodes in one pixel blinks only when it is necessary to blink the electrodes for gradation display,
Since the entire pixel is not driven to blink as in the conventional example, flicker can be made even less noticeable.

According to the third aspect of the present invention, for example, when the electrodes are driven to blink, the reversal driving cycle of the electrodes is set to 30 Hz or more. Therefore, when the electrodes are blinked by utilizing the afterimage phenomenon of human eyes. The flicker of can be made inconspicuous.

[0017]

EXAMPLES The present invention will be described below based on examples.

1 to 7 are views for explaining the liquid crystal display device of the present invention.

First, the structure will be described.

FIG. 1 is a sectional view of a liquid crystal cell of the liquid crystal display device of this embodiment.

In FIG. 1, a liquid crystal cell 1 has a pair of rectangular glass substrates 2 and 3 formed of low-alkali soda glass or the like. The glass substrate 2 and the glass substrate 3 are provided.
Are opposed to each other at a predetermined interval. On the inner surfaces of the glass substrate 2 and the glass substrate 3 which face each other, IT
Transparent electrodes (for example, 640 vertical electrodes and 480 horizontal electrodes) are patterned and formed into a predetermined shape by an O (Indium Tin Oxide) film using a photolithography technique. As shown in FIG. 1, one pixel 4 is composed of a vertical electrode 4a and a vertical electrode 4b on the surface of a glass substrate 2, and another adjacent pixel 5 is composed of a vertical electrode 5a and a vertical electrode 5b. . And here, the vertical electrodes 4a, 5a
And the vertical electrodes 4b and 5b are formed with an electrode width of 1: 2. On the surface of the other glass substrate 3, a horizontal electrode 6 having a pixel width is formed by the same ITO film as the vertical electrode.
(7) are arranged and formed at equal intervals.

In this way, the glass substrate 2 on which the transparent electrodes are formed and the glass substrate 3 are crossed with the transparent electrodes facing each other to form a simple matrix liquid crystal cell 1.

FIG. 2 is a plan view of a state where the vertical electrodes and the horizontal electrodes intersect with each other. As shown in FIG.
For example, the pixel 4 is divided into an A region shown by hatching where the vertical electrodes 4a and the horizontal electrodes 6 intersect and a B region where the vertical electrodes 4b and the horizontal electrode 6 intersect. The A region and the B region are regions in which the vertical electrodes and the horizontal electrodes are arranged to face each other with the liquid crystal layer in between, and by selectively applying an electric field to the predetermined vertical electrodes and horizontal electrodes ( (ON state), it is possible to change the alignment of the liquid crystal in the A region or the B region of a predetermined pixel so that the ON controlled region is in the light transmitting state and the OFF controlled region is in the light shielding state.

Returning to FIG. 1 again, alignment films 8 and 9 made of a polyimide resin are formed on the transparent electrodes of the glass substrates 2 and 3, respectively, by using, for example, an offset method, and then baked.

Next, the alignment film 8 is aligned in a predetermined direction by forming fine grooves on the surface of the alignment film 8 in a certain direction by using a rubbing method.

Next, an epoxy resin adhesive is printed on the outer peripheral edge of the glass substrate 3 by a screen method to form a sealing material 10, and then, on the orientation film 9 of the glass substrate 3, inside the sealing material, a diameter of 3 μm is formed. The polystyrene particles to be the spacers 11 are evenly dispersed so as to be about 350 particles / mm ² .

Then, the glass substrate 2 and the glass substrate 3 formed as described above are overlapped as shown in FIG. 1, and pressed at a pressure of 2.5 Kg / cm ² from above and below the substrates at 40 ° C. at 150 ° C. Leave for 10 minutes and seal 10
The epoxy resin adhesive is heat-cured to form the liquid crystal cell 1.

Then, the ferroelectric liquid crystal composition 12 is injected through a liquid crystal injection port (not shown) by a liquid crystal injection process using a vacuum method, and then the injection port is closed using a UV curable resin. Then, the polarizing plate 1 is provided outside the glass substrates 2 and 3.
By pasting Nos. 3 and 14 in a crossed Nicol state, a liquid crystal display device as shown in FIG. 1 is obtained.

FIG. 3 is a block diagram showing an example of a drive circuit of the liquid crystal display device of this embodiment. As shown in FIG.
The liquid crystal display device 15 includes a liquid crystal display panel 16, drive circuits 17 and 18 that drive the vertical electrodes and horizontal electrodes of the liquid crystal display panel 16 to perform dot matrix display, and display each pixel in gray scale based on an image signal. In addition, a liquid crystal controller 19 for driving the drive circuits 17 and 18 by converting into ON / OFF control signals for selecting electrodes of each pixel and driving the electrodes to blink, and the liquid crystal controller 1 thereof.
It is composed of a CPU 20 for transmitting an image signal to 9, and a driving power source 21 for supplying electric power for driving the above-mentioned respective parts.

4A and 4B are views for explaining the driving operation of the liquid crystal display device of the present embodiment, in which FIG. 4A is a plan view and FIG. 4B is a sectional view taken along the line bb of FIG.

As shown in FIG. 3A, when the liquid crystal display panel 16 is driven, each signal corresponding to each pixel on each of the scanned vertical electrodes is sequentially scanned by scanning the vertical electrode side. Line-sequential scanning in which a voltage is applied simultaneously from the horizontal electrode side is used.

FIG. 5 is a diagram showing a drive voltage waveform applied to each pixel of FIG.

FIGS. 5A and 5B show a state in which a voltage waveform of V _X1 is applied from the scanning electrode (vertical electrode) side and a voltage waveform of V _Y1 is applied from the signal electrode (horizontal electrode) side. There is. The time required to scan all the vertical electrodes once is called one field. The voltage waveform of FIG. 5C is the sum of the voltage waveforms of the vertical electrode and the horizontal electrode (V ₁ + V ₂ ), and the applied voltage when the pixel at which the vertical electrode and the horizontal electrode intersect is turned on. It is a waveform.

The voltage waveform of FIG. 5 (d) is obtained by subtracting the voltage waveform of the horizontal electrode from the voltage waveform of the vertical electrode (V
₁ -V _2), the applied voltage waveform in the case of OFF pixels that intersects the vertical electrode and the horizontal electrode.

Therefore, for example, as shown in FIG. 4, V _X1
By applying a voltage waveform for ON-controlling the pixel to V _Y1 and V _Y1 , the pixel shown by hatching where the vertical electrode and the horizontal electrode intersect in FIG. 4 is brought into a light transmitting state. Similarly, by applying a voltage waveform to V _X1 and V _Y1 when the pixel is OFF-controlled, the pixel shown by the hatching in FIG. 4 can be brought into a light shielding state.

In this embodiment, although not shown in detail in FIG. 4, as shown in FIG. 1, the vertical electrode is composed of two electrodes having different area ratios for one pixel, and each electrode is described above. By applying the ON / OFF control signal, the pixels are selectively driven.

When a DC voltage is applied to the above-mentioned liquid crystal drive electrode, an electrochemical reaction occurs. Therefore, when driving the liquid crystal, an AC voltage waveform is always used as described above. For this reason, the polarity of the waveform is inverted to reduce the DC component.

As described above, in each pixel of the dot matrix, the above-mentioned ON / OFF control is performed to selectively drive the area A or the area B of a predetermined pixel, and blinking is driven at a predetermined inversion cycle. be able to.

In the case of displaying a moving image in this embodiment,
Since 30 screens are displayed in 1 second and the rewriting operation is performed 4 times during the display of each screen, 120 rewriting operations are performed in 1 second.

FIG. 6 is a diagram showing a specific drive control state for each electrode when gradation display is performed in each pixel.

In this embodiment, A of each electrode forming one pixel is
Since the area ratio of the region to the B region is configured to be 1: 2, the gradation levels “1”, “3”, “5” shown in FIG. 6 can be obtained only by selectively driving each electrode. , "7" can be displayed. That is, at the gradation level “1”, the light transmittance is 0% in the OFF control state in both the area A and the area B.

At the gradation level "3", the area A is ON-controlled and the area B is OFF-controlled, and the light transmittance is 33.3% from the area ratio thereof.

At the gradation level "5", the area A is OFF-controlled and the area B is ON-controlled, and the light transmittance becomes 66.7% from the area ratio.

At the gradation level "7", since the areas A and B are ON-controlled, the light transmittance is 100%.

Further, by driving one of the electrodes constituting each pixel to blink, three gradations of "2", "4" and "6" shown in the gradation levels shown in FIG. 6 are displayed. This makes it possible to display a total of 7 gradations.

That is, at the gradation level "2", since the ON control is performed only twice while the area A is being rewritten four times on each screen, an average transmittance of 50% is obtained in the area A,
Since the B region is OFF-controlled, the average transmittance for one pixel is 16.7%.

At the gradation level "4", the area A is controlled to be OFF, and the area B is turned off only three times while rewriting four times on each screen.
Since the N control is performed and the average transmittance of 75% is obtained in the B region, the average transmittance of one pixel becomes 50%.

At the gradation level "6", the ON control is performed only twice while the area A is rewritten four times on each screen.
50% average transmittance is obtained in the region,
Since the area B is ON-controlled, the average transmittance in one pixel is 83.3%.

Of course, the number of gray scales that can be displayed is not limited to the above-mentioned seven gray scales, and the number of rewrites can be increased by shortening the inversion cycle of the electrodes to be driven to blink, and further display is possible. The number of gradations can be increased.

As described above, the liquid crystal display device of this embodiment is
Since one pixel is composed of two electrodes having different area ratios, it is possible to reduce the number of data signals driving the electrodes as compared with the conventional example, and the external circuit can be simplified. In the case of intermediate gray scale display that cannot be displayed only by selecting electrodes having different area ratios, only one of the two electrodes is made to blink, and only a part of some pixels is made to blink. Therefore, it is possible to obtain a liquid crystal display device in which flicker is less noticeable.

Therefore, with respect to the gradation level that one pixel is composed of a plurality of electrodes having different area ratios and cannot be displayed only by selecting the electrode, the electrodes are time-division driven to enable a large number of gradation display, and By limiting the blinking electrode to any one of the plurality of electrodes, the pixel area for blinking drive is reduced and flicker is less noticeable. Further, in this embodiment, since the ferroelectric liquid crystal is driven by using the simple matrix method, the structure is simple and the manufacturing can be performed at low cost.

FIG. 7 is a schematic constitutional view of a liquid crystal display device using a micro color filter according to another embodiment, in which (a) is a plan view and (b) is a sectional view taken along line bb of (a). It is a figure. As shown in FIG. 7, here, a liquid crystal display device capable of gradation display using a ferroelectric liquid crystal composition is colorized by using a micro color filter. As shown in FIG. 7B, in the structure of the liquid crystal cell 22, the glass substrates 23 and 24 are arranged to face each other vertically, and the horizontal electrodes 25 and the vertical electrodes 26 are provided inside the glass substrates 23 and 24.
R is formed on the vertical electrode 26 for each pixel.
A colored layer 27 made of (red), G (green), and B (blue) micro color filters is formed. Therefore, one picture element is formed by utilizing the intersections of the matrix of three pixels. And, as described above, in FIG.
Although not shown in detail, the vertical electrode 26 that is a scanning electrode
As shown in FIG. 2, one pixel is composed of two types of electrodes having an area ratio of 1: 2. As in the above-described embodiment, two electrodes are selectively driven, When gradation display is not possible only by selecting the electrode, either one of the electrodes is driven to blink, and gradation display is performed so as to make flicker as inconspicuous as possible. In this example, R, G,
It is possible to display 7 gradations for each of B.

As described above, when a liquid crystal display device is constructed by using a ferroelectric liquid crystal composition, gradation display is possible and a large amount of information is obtained by using R, G, B color filters. Color image display can be realized.

In the above embodiments, the electrode structure and the liquid crystal driving method have been described by using the simple matrix method, but the present invention is not limited to this, and other driving methods such as an active matrix method are adopted. It is also possible to carry out.

The area ratio of the plurality of divided electrodes forming one pixel is set to 1: 2 in the above embodiment, but the invention is not limited to this, and other area ratios may be adopted. Further, not only in the case of two divisions, but also in three or four or more divisions depending on the number of gradations to be displayed. In this case, unlike the case of performing the gradation display only by the area ratio, the time division method in which the predetermined electrodes are blink-driven to perform the gradation display is used together, so that it is possible to easily perform the multi-gradation display.

[0056]

According to the liquid crystal display device of the first aspect,
Each pixel is composed of multiple electrodes with different areas, and the drive control circuit selectively drives the electrode of the area corresponding to the gradation displayed by each pixel, and the intermediate gradation that cannot be displayed only by selecting the drive electrode. Only in the case of displaying, any one of the electrodes is supplementarily driven to blink so as to display a desired gradation. Therefore, each pixel can be configured with a small number of divided electrodes, the driving data signal is reduced, the external circuit can be simplified, and any one of the electrodes can be supplementarily blinked to further subdivide. Since the displayed intermediate gradations are displayed, multi-gradation display is possible, and in that case, the pixel area to be blinked can be small, so that flicker such as flicker on the screen can be made inconspicuous.

According to the second aspect of the present invention, for example, the area ratio of the electrodes forming each pixel is 1: 2.
Since it is composed of one electrode, the number of data signals for selectively driving the electrodes can be reduced as compared with the conventional example, and the external circuit can be simplified.

According to the third aspect of the invention, since the inversion driving cycle of the electrodes in the blinking driving is set to 30 Hz or more, the flicker operation of a predetermined electrode is felt by the afterimage phenomenon of human eyes. You can make it difficult and make the flicker inconspicuous.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal cell of a liquid crystal display device of this embodiment.

FIG. 2 is a plan view of a state in which a vertical electrode and a horizontal electrode intersect with each other.

FIG. 3 is a block diagram showing an example of a drive circuit of the liquid crystal display device of the present embodiment.

FIG. 4 is a diagram illustrating a driving operation of the liquid crystal display device of the present embodiment.

5 is a diagram showing a drive voltage waveform applied to each pixel of FIG.

FIG. 6 is a diagram showing a specific drive control state for each electrode when gradation display is performed in each pixel.

FIG. 7 is a schematic configuration diagram of a liquid crystal display device using a micro color filter according to another embodiment.

[Explanation of symbols]

 1 Liquid crystal cell 2, 3 Glass substrate 4, 5 Pixels 4a, 4b, 5a, 5b Vertical electrode 6, 7 Horizontal electrode 8, 9 Alignment film 10 Sealing material 11 Spacer 15 Liquid crystal display device 16 Liquid crystal display panel 17, 18 Drive circuit 19 Liquid crystal controller 20 CPU

Claims (3)

[Claims] 1. An electrode, which is disposed inside a pair of parallel substrates to face each other and applies an electric field to a liquid crystal composition having ferroelectricity, and a liquid crystal composition provided between the substrates by applying a drive signal to the electrodes. In a liquid crystal display device including a liquid crystal drive circuit that changes the molecular orientation, each pixel that constitutes the liquid crystal display surface is composed of a plurality of electrodes having different areas, and the drive control circuit displays an image displayed for each pixel. An electrode having an area corresponding to the gradation of a signal is selected and driven, and only one of the plurality of electrodes is driven to blink only when displaying a halftone that cannot be displayed only by selecting the driving electrode. A liquid crystal display device characterized by displaying a desired gradation. 2. The liquid crystal display device according to claim 1, wherein each pixel is composed of two counter electrodes having an area ratio of 1: 2. 3. The liquid crystal display device according to claim 1, wherein the electrodes for driving the blinking have an inversion driving cycle of 30 Hz or more.