JPH06324306A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display device capable of displaying gradation with a simple driving power source. CONSTITUTION:This liquid crystal display device has a liquid crystal cell 1 holding a crystal layer 6 between two sheets of substrates 3 and 5 in which plural pixel electrodes 4 are formed in one side and a driving power source 18 impressing voltages to electrodes 4. Each pixel electrode 4 of the liquid crystal cell is composed of plural divided electrodes 41 to 45 having different dimensions and divided electrode parts are driven independently by the driving power source 18.

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 capable of displaying gradations of light and shade.

[0002]

2. Description of the Related Art Conventionally, in order to display gray scales in a liquid crystal display device, taking an active matrix type as an example, an electric field which causes a transmittance of a liquid crystal display portion to have a desired value as shown in a conceptual diagram of FIG. The potential of the pixel electrode was applied so as to be applied to the liquid crystal layer. That is, each pixel electrode 4 is
The signal line 12 is connected to the gate line 11 and the signal line 12.
4 through the signal line switch TFT 14 connected to
The analog voltages V1 and V2 shown in are input. However, the relationship between the applied voltage and the transmittance of the liquid crystal is not linear as shown in FIG. 4, and the change from opaque to transparent is sensitive to the applied voltage. Therefore, in order to display accurate gradation, a so-called gamma correction circuit 17 for correcting non-linearity and a driving power supply 18 for accurately applying an applied voltage were indispensable.

Further, depending on the liquid crystal material, there is a so-called hysteresis in which the transmittance is different depending on the intermediate value from transmission to non-transmission and from non-transmission to transmission, and the response speed is significantly slowed under the condition that the applied voltage has an intermediate value. There are some drawbacks.

[0004]

SUMMARY OF THE INVENTION The present invention provides a liquid crystal display device capable of natural gradation display while omitting a complicated correction circuit and a highly accurate drive circuit for generating an accurate output voltage. It is in.

[0005]

According to the present invention, there is provided a first substrate having electrodes, a plurality of pixel electrodes, and the electrodes of the first substrate and the pixels at a predetermined interval from each other. A liquid crystal display cell including a second substrate arranged so that the electrodes face each other, a liquid crystal layer sandwiched between the first and second substrates, and a driving power supply for applying a voltage to the electrodes. In the liquid crystal display device provided, each pixel electrode is composed of a plurality of divided electrode portions having different areas, and each divided electrode portion can be independently driven by the drive power source. A device is provided.

Further, the driving power supply includes means for selectively applying a binary voltage to each divided electrode portion of the plurality of divided electrode portions of the pixel electrode, and a plurality of areas of the pixel electrode forming one pixel are provided. The present invention provides a liquid crystal display device characterized by being variable as follows.

Further, the present invention provides a liquid crystal display device characterized in that the size of each area of a plurality of divided electrode portions having different areas constituting one pixel electrode is different by a ratio of a geometric progression of approximately 2. .

[0008]

In the conventional gray scale display, the voltage applied to the pixel electrode is adjusted by the voltage corresponding to the gray scale, whereas in the present invention, the pixel electrode is divided into a plurality of divided electrode portions having different areas. The display is so-called binary display in which either one of the voltage corresponding to transmission and the voltage corresponding to non-transmission is applied to each divided electrode portion. The gradation display is performed with the total area of a plurality of pixel electrodes in a transmissive state.

That is, in the present invention, gradation display of luminance (transmittance) is conventionally performed by controlling the applied voltage, but in the present invention, only transparent or non-transparent is selected, and instead the pixel electrode in the transparent state is selected. The average brightness (average transmissivity) is equivalently controlled by the total area, and gradation display is visually performed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic plan view for explaining an embodiment of the present invention, and FIG. 2 is a schematic sectional view taken along the line AA of FIG. Incidentally, the parts having the same reference numerals as those in FIG. 3 showing the conventional device indicate the same parts.

As shown in FIG. 2, the liquid crystal display cell 1 has an IT
Glass upper substrate 3 having transparent common electrode 2 made of O
And a glass lower substrate 5 having a plurality of pixel electrodes 4 and 4 made of ITO so that each of the electrodes 2 and 4 faces each other by about 5
The liquid crystal layer 6 is filled with the liquid crystal layer 6 sandwiched therebetween with a space of μm. Each pixel electrode 4 forms one pixel of the liquid crystal display cell 1, and as shown in FIG. 1, a plurality of divided electrode portions having different areas, that is, a rectangular divided electrode portion 4 is formed.
1, a hook-shaped divided electrode portion 42, 43, 44, 45, which has a minimum area of 300 μm square pixel area 4
The layout is such that the area increases from 1 to areas S1, S2, S3, S4 and S5. The minimum divided electrode area S1 is about 54 .mu.m square.

Further, the divided electrode portions 41 to 45 are electrically insulated from each other so that an independent voltage is applied thereto, and the pixel switching elements 131 to 1 each of which is a TFT.
Signal lines 121 to 125 through this element.
Connected to. The signal lines 121 to 125 are connected to the input signal line 15 via the signal line switch TFT elements 141 to 145. TFT elements for signal line switches 141 to 14
The gate electrode of 5 is commonly connected to the scanning shift register circuit 16. Further, the pixel switching elements 131 to 13
The gate electrodes of 5 are commonly connected to the scanning line 11.

As described above, in this embodiment, the pixel electrodes constituting one pixel have divided electrode portions 41, 42 having different areas.
It is composed of 43, 44, 45. The voltage applied from the driving power supply 18 to the divided electrode portion is either a sufficiently low voltage that allows light to pass through the cell or a sufficiently high voltage that does not allow light to pass through the cell.

Next, the area distribution of the divided pixel electrodes will be described. Since the brightness (transmittance) is controlled by the total area of the pixel electrodes in the transmissive state, the area ratio of each pixel electrode is determined by the following equation (n is an integer). Sn = S0.multidot.2n ^-1 (1) In this embodiment, 32 gradations can be displayed. In this case, the pixel electrodes are S1 (= S0), S2 (= 2S0) and S3.
It can be realized by a combination of 5 pixels of (= 4S0), S4 (= 8S0) and S5 (= 16S0). The maximum brightness is 31S0 in the total area of the transmissive pixels in the transmissive state of all pixels.

As an example, with respect to the brightness corresponding to 5S0, the divided electrode portions 41 and 43 of S1 and S3 are in a transmissive state, and S2 and S3 are
This is realized by selectively controlling the divided electrode portions 41, 44, 45 having an area of 4, S5 so as to be in an opaque state. Similarly, other gradations can be realized by selectively driving the divided electrode portions.

As described above, an arbitrary gradation is realized by the number of divisions of the pixel electrode of the number of digits when displayed in binary number, and each luminance corresponds to the number of digits where 1 is displayed when displayed in binary number. It can be controlled by selecting the pixel electrode in the transmissive state. When the display signal is a digital signal, generally, a digital signal of 1 or 0 is input in parallel for each digit. Conventionally, a digital signal is converted into an analog signal in the peripheral circuit or the driving circuit, but in this embodiment, the potential corresponding to the digital signal of 1 or 0 of each digit is directly applied to the pixel electrode as shown in FIG. To enter.

In practice, the area of the pixel electrode and the amount of transmitted light are not necessarily in a proportional relationship, such as a slight semi-transmission even with an applied voltage that makes the peripheral portion of the pixel electrode non-transmissive. In consideration of the fact that the sensitivity of brightness in 1 is not in a linear relationship, the distribution of the pixel area needs to be corrected by the equation (1), but the correction based on the experimental data is easy.

It should be noted that, as in the present invention, the light and shade of pixels are transmitted,
It is possible to naturally display a combination of opaque areas when the original pixel pitch is 300 μm or less, and at a pitch higher than that, the shape of the pixel after division is reflected in the visual sense. It becomes impossible to express light and shade.

(Embodiment 2) The number of divided electrode portions forming one pixel can be reduced by setting the applied voltage to three values. If the selection voltage (transmission) in FIG. 4 is V1 and the non-selection voltage (non-transmission) is V2, the intermediate voltage is selected as the semi-transmission voltage. In the conventional device, in case of 8 gradations, V1
Although -V2 is divided into 7 to perform gradation display, in the case of this embodiment, a very simple ternary structure is used.
As shown in FIG. 5, the number of divided electrode portions of one pixel electrode is made up of two electrode portions 21 and 22 having an area ratio of 1: 2, and by selectively applying a ternary voltage to them. 8 gradation display is possible. The cell configuration and the driving power supply are simple, and there are advantages including manufacturing and operation.

[0021]

As described above, according to the binary driving structure of the multi-split electrode section of the present invention, the voltage applied to the pixel electrode may be a binary value which gives a transparent state or an opaque state. It is clear that the nonlinearity of the applied electric field versus the liquid crystal, the hysteresis, the characteristic that the response speed is slow at an intermediate value, and the like are significantly improved. Furthermore, the influence of the signal wraparound (crosstalk) with the adjacent pixel and the signal line does not affect the transmission and non-transmission of the liquid crystal because they are minute potential changes. Similarly, it is clear that a minute change in the output voltage of the drive circuit does not affect the display.

Further, in the case of gradation display, signals are inputted digitally, but so-called A from digital to analog is used.
The D conversion is unnecessary in the present invention, and the peripheral circuit is greatly simplified.

According to the structure of three-value driving of the plurality of divided electrode portions, it is possible to achieve a relatively large number of gray scale displays with a minimum number of divided electrodes and without imposing a heavy load on the driving power source.

[Brief description of drawings]

FIG. 1 is a schematic partial plan view illustrating an embodiment of the configuration of the present invention.

FIG. 2 is a schematic cross-sectional view of FIG. 1 taken along the line AA and seen in the direction of the arrow.

FIG. 3 is a schematic partial plan view showing a conventional liquid crystal display device.

FIG. 4 is a curve diagram showing a transmittance-applied voltage characteristic of a conventional liquid crystal display device.

FIG. 5 is a schematic partial plan view showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display cell 2 ... Electrode 3 ... Upper substrate 4 ... Pixel electrode 41, 42, 43, 44, 45 ... Divided electrode part 5 ... Lower substrate 6 ... Liquid crystal layer 11 ... Gate line 121 ~ 125 ... Signal line 131 ~ 135 ... Pixel TFTs 141 to 145 ... Signal line switch TFT 15 ... Input signal line 16 ... Scan shift register circuit 18 ... Drive power supply

Claims (3)

[Claims] 1. A first substrate having an electrode and a plurality of pixel electrodes arranged at a predetermined distance from the first substrate so that the electrode of the first substrate and the pixel electrode face each other. A liquid crystal display device comprising a liquid crystal display cell comprising a second substrate, a liquid crystal layer sandwiched between the first and second substrates, and a driving power supply for applying a voltage to the electrodes. The liquid crystal display device, wherein each of the pixel electrodes is composed of a plurality of divided electrode portions having different areas, and each of the divided electrode portions can be independently driven by the driving power source. 2. The driving power source comprises means for selectively applying a binary voltage to each of the plurality of divided electrode portions of the pixel electrode, and a plurality of areas of the pixel electrodes forming one pixel are provided. The liquid crystal display device according to claim 1, wherein the liquid crystal display device can be varied as follows. 3. A liquid crystal display device according to claim 1, wherein the size of each area of the plurality of divided electrode portions having different areas forming one pixel electrode is different by a ratio of geometrical series of approximately 2.