JPH0511715A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To enhance an apparent display speed of a LED. CONSTITUTION:A liquid crystal layer is divided into a first liquid crystal layer and a second liquid crystal layer, the display surface of a LCD is constituted from first display dots and second display dots arranged to each other. Namely, the first display dots and the second display dots in the X or Y direction respectively, alternately or every other dot, constitute first surface display dots and second surface display dots. Whereby, supplied data are separated into two systems of signals every two layers of liquid crystals, every halves of one screen are simultaneously displayed in parallel.

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 used for a display device such as a personal computer, a copying machine, a facsimile device, a printer, and a measuring machine.

[0002]

2. Description of the Related Art FIG. 12 shows an appearance of a conventionally used simple matrix type LCD (liquid crystal display), in which one display dot which is a unit for displaying an image is arranged in a matrix. Figure 13 shows this LCD
The transparent electrode 2 is arranged with the liquid crystal layer 1 interposed therebetween, the glass substrate 3 is arranged on the outer side thereof, and the upper polarizing plate 4 and the lower polarizing plate 5 are arranged on the outer side thereof. Has been done. In the conventional LCD thus configured, one dot of display is displayed by writing the image data to be displayed on the system side into an image memory (not shown) and then controlling the electrode 2 corresponding to each pixel. In addition, there is a display device using a conventional LCD in which a backlight is arranged behind the LCD in order to make the screen easy to see. In such a liquid crystal display device, a cold cathode tube which is advantageous in terms of brightness, power consumption and life is often used.

[0003]

However, in the conventional liquid crystal display device of the simple matrix system, the transmittance of the image data is written in the image memory until it is actually displayed, that is, the transmittance is applied after the pulse is applied to the electrodes. The time it takes for the liquid crystal to reach a steady state is several hundred mse due to the characteristics of the liquid crystal itself.
c. I needed a degree. Then, the scanning is repeated many times until the transmittance reaches the steady state, but there is a problem that the driving voltage, the viewing angle, etc. are affected when the number of display dots increases. Also, because the next image cannot be displayed before the displayed image is visually recognized, until the transmittance reaches a steady state as a system,
Processing such as displaying a new image cannot be performed, which may affect the overall processing performance. on the other hand,
Liquid crystal display device having two liquid crystal layers (two-layer TN (twisted
nematic) liquid crystal display devices, etc.) are used for improving display quality but not for improving display speed. Therefore, a first object of the present invention is to increase the apparent display speed of the LCD.

On the other hand, in a liquid crystal display device using a cold cathode tube backlight, heat generation in the tube causes unevenness in contrast and unevenness in brightness. FIG. 14 and FIG. 15 show examples of unevenness due to the cold cathode tubes that actually occur. As shown in the figure, in addition to the fact that the contrast near the tube is lowered due to heat generation of the tube, the light uniformity of the backlight unit itself is poor, and the area near the tube becomes brighter than other areas. Then, due to the uneven contrast due to heat generation and the uneven brightness due to the arrangement of the tubes, the vicinity of the tubes became thin and bright. As described above, the liquid crystal display device using the cold cathode tube as the backlight of the LCD has a drawback that the heat generation is high and the light emission is not uniform when viewed as a display surface. For this reason, the contrast of the display screen in the vicinity of the cold cathode tube is lowered due to heat generation of the tube. Furthermore, the uneven brightness, which is the original drawback of the cold cathode tube backlight, becomes more noticeable as the uneven contrast.
The display quality was degraded. In contrast to this problem, in the active matrix LCD, the uneven contrast can be eliminated, but the uneven brightness has been a problem. Therefore, a second object of the present invention is to provide a liquid crystal display device having a display surface which is easy to see by correcting the unevenness due to the cold cathode tube backlight.

[0005]

According to a first aspect of the present invention, in a simple matrix type liquid crystal display device, two liquid crystal layers for dot display including transparent electrodes are stacked and electrodes are alternately arranged in upper and lower layers. And simultaneously display each layer to achieve the first object. Thus, in the invention according to claim 1, the liquid crystal layer is divided into two layers and half of one screen is simultaneously displayed in parallel, thereby increasing the apparent display speed and reducing the load on the display on the system side. Is reduced to improve the processing capacity as a whole.

According to a second aspect of the present invention, the image data supplied to the liquid crystal display device according to the first aspect is divided into two data to be displayed on each liquid crystal layer, and among the dots arranged in each line direction, the Nth dot is arranged. Th (N = 1, 3, 5, 7, ...) and N +
The first dot is displayed simultaneously to achieve the first object. That is, the liquid crystal display device according to claim 1 requires two systems of signals for each of the two liquid crystal layers.
For that reason, the conventional signal input is possible without changing the signal output format on the system side or requiring a dedicated interface.
In the liquid crystal display device, the versatility is improved by separating the signals of two systems for each of the two liquid crystal layers.

According to the third aspect of the present invention, the liquid crystal display panel, the cold cathode tube backlight arranged on the back surface of the liquid crystal display panel, and the temperature detection for detecting the temperature of each part arranged on the back surface of the liquid crystal display panel. Means and level setting means for setting the gradation level of each part of the liquid crystal display panel according to the temperature of each part detected by the temperature detecting means are provided in the liquid crystal display device to achieve the second object. . In the invention according to claim 4, two liquid crystal layers for dot display including transparent electrodes are superposed, electrodes are alternately arranged in upper and lower layers, and a liquid crystal display panel for displaying simultaneously in each layer is provided. A cold-cathode tube backlight arranged, temperature detecting means arranged on the back surface of the liquid crystal display panel to detect the temperature of each part, and each part of the liquid crystal display panel according to the temperature of each part detected by the temperature detecting means. The liquid crystal display device is provided with a gradation level setting means for setting the gradation level of 1) to achieve the first and second objects.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the liquid crystal display device of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows the arrangement of display dots on the LCD.
The display surface of the LCD is composed of first surface display dots and second surface display dots which are alternately arranged. FIG. 2 shows a cross section of this LCD. The LCD includes a first display layer 13 composed of a first liquid crystal layer 11 and first electrodes 12 arranged on both surfaces thereof, and a second display layer composed of a second liquid crystal layer 14 and second electrodes 15 arranged on both surfaces thereof. 16 is provided.
The first and second display layers 13 and 16 are provided with a transparent substrate 17 made of glass or the like between and between them, and further, an upper polarizing plate 18 and a lower polarizing plate 19 are disposed outside thereof. . As shown in FIG. 3, the first liquid crystal layer 11 and the second liquid crystal layer 14 are alternately (1) in the X and Y directions.
The first surface display dots and the second surface display dots are formed every other dot.

FIG. 4 shows the configuration of a drive circuit for driving an LCD of 640 × 400 dots. This LC
In the D drive circuit, the data signal line of the image data expanded in the image memory (not shown) is used as the upper screen data (first
Liquid crystal layer data) and lower screen data (second liquid crystal layer data), and an independent X driver for each liquid crystal layer,
It is designed to be driven by both line drivers of the Y driver. To these line drivers, as a timing signal, a clock and a latch pulse are supplied to the X driver, and a latch pulse and a frame pulse are supplied to the Y driver. FIG. 5 shows a timing chart of these timing signals and data signals. The dots indicated by ,, and in FIG. 6 are on / off controlled at the same time. That is, of the dots arranged in the X-axis direction, the Nth (N = 1, 2, 3, ...)
The + 1st dot is displayed at the same time.

According to the embodiment described above, the time required to display the screen can be reduced to half that of the conventional one, and the processing performance on the system side can be improved. In addition, the same control method as the conventional liquid crystal display device can be used, and the circuit on the system side,
Since there is no need to change the timing, versatility can be secured.

Next, the second liquid crystal display device of the present invention
The embodiment will be described in detail with reference to FIGS. 7 to 11. FIG. 7 shows the configuration of the liquid crystal display device.
The liquid crystal display device includes an LCD 21. This LCD
Image data expanded in an image memory (not shown) is supplied to the CPU 21 from the CPU 22 via the LCD controller 23, and the image data is displayed. A cold cathode tube backlight 24 is arranged on the back surface of the LCD 21. The cold cathode tube backlight 24 is adapted to be turned on by a power source supplied from a backlight power source section 25.

The liquid crystal display device further includes a temperature detecting section 6 on the back surface of the LCD 21. This temperature detector 26
Has a plurality of temperature sensors (not shown),
They are arranged on the back surface of 21 at regular intervals. For example, they are arranged at regular intervals in the direction perpendicular to the longitudinal direction of the cold cathode tube backlight 24, or are arranged on the entire back surface of the LCD 21. The temperature of each part detected by the temperature detection unit 26 is supplied to the contrast correction judgment unit 27, and the contrast correction judgment unit 27 judges whether or not the correction is necessary. As a result, a gradation display command is output from the CPU 22 to the LCD controller 23, and gradation display is performed. As a result, gradation is added to a portion where the contrast is lowered due to heat generation of the cold cathode tube, and unevenness is corrected.

Next, the correction performed by the contrast correction judging section 27 of the liquid crystal display device will be described. Figure 8 now
As shown in, in the sidelight type liquid crystal display device, it is assumed that the temperature of each part of the LCD 21 is a, b, and c. FIG. 9 shows the relationship between the temperature of the LCD 21 and the liquid crystal drive voltage that provides the optimum contrast. As shown in this figure, the liquid crystal drive voltage that gives the optimum contrast between 0 ° C. and 40 ° C. changes as a straight line P, becomes thin in the range above the straight line P, and becomes thin in the range below the straight line P. It becomes dark in the range. This is because the contrast of the liquid crystal changes by changing the liquid crystal drive voltage. Therefore, the liquid crystal drive voltages that give the optimum contrast at the temperatures of the respective portions shown in FIG. 8 are x, y, and z, respectively. However, if the liquid crystal drive voltage is set to the voltage of the optimum contrast at the temperature a, the contrast becomes lower (thinner) by the voltage of (xy) in the area of the temperature b, and In the area c, the contrast is reduced by the voltage of (x−z) and the image is displayed.

Next, FIG. 10 shows the liquid crystal drive voltage and gradation (density).
It is assumed that the display is an 8-gradation display. Therefore, when the optimum contrast is set to gradation 0 and the line at the ambient temperature a is focused, the density corresponds to gradation 0 when the voltage is x, and when the voltages are y and z, the gradations are different. The density becomes 3 and the gradation is 5. That is, at the temperature a, the densities of the areas of the temperatures b and c are reduced by the densities of the gradations 3 and 5. Therefore, if the gradations 3 and 5 are displayed in the areas b and c, the density of the area a can be corrected to be close. In FIG. 11, the liquid crystal drive voltage is changed with a constant width corresponding to each gradation.

[0015]

According to the first and second aspects of the present invention, the apparent display speed of the LCD can be increased. According to the third aspect of the present invention, it is possible to correct the unevenness due to the backlight of the cold-cathode tube and obtain a display surface that is easy to see. According to the fourth aspect of the present invention, the apparent display speed of the LCD can be increased, and unevenness due to the cold cathode tube backlight can be corrected to provide an easily viewable display surface.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an arrangement of display dots of an LCD in a first embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a sectional view of an LCD according to the first embodiment of the same.

FIG. 3 is an explanatory diagram showing an arrangement state of dots of a first liquid crystal layer and a second liquid crystal layer in the first embodiment. .

FIG. 4 is a configuration diagram of a drive circuit for driving an LCD of 640 × 400 dots in the first embodiment.

FIG. 5 is a timing chart of a timing signal and a data signal supplied to the LCD in the first embodiment.

FIG. 6 is an explanatory diagram illustrating dots that are simultaneously displayed on each liquid crystal layer in the first embodiment.

FIG. 7 is a configuration diagram of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a temperature state of each part of the LCD in the second embodiment.

FIG. 9 is a diagram showing the relationship between the temperature of the LCD and the liquid crystal drive voltage that provides the optimum contrast in the second embodiment.

FIG. 10 is a diagram showing a relationship between a liquid crystal drive voltage and gradation (density) in the second embodiment.

FIG. 11 is a diagram showing a case where the liquid crystal drive voltage in the second embodiment is changed in a constant width corresponding to each gradation.

FIG. 12 is an external view of a conventional simple matrix type LCD (liquid crystal display).

FIG. 13 is a sectional view of a conventional LCD as above.

FIG. 14 is an explanatory diagram illustrating a state of unevenness caused by a conventional cold cathode tube.

FIG. 15 is an explanatory diagram illustrating a state of unevenness caused by a conventional cold cathode tube.

[Explanation of symbols]

11 First liquid crystal layer 12 First electrode 14 Second liquid crystal layer 15 Second electrode 17 Transparent substrate 21 LCD 22 CPU 24 Cold cathode tube backlight 26 Temperature detector 27 Contrast correction judgment unit

Claims (4)

[Claims] 1. A liquid crystal display device of a simple matrix type, characterized in that two liquid crystal layers for dot display including transparent electrodes are stacked, and electrodes are alternately arranged in upper and lower layers for simultaneous display in each layer. Display device. 2. The supplied image data is divided into two data to be displayed on each liquid crystal layer, and the Nth dot (N = 1, 3, 5, 7, ...) Of dots arranged in each line direction. 2. The liquid crystal display device according to claim 1, wherein the Nth dot and the (N + 1) th dot are simultaneously displayed. 3. A liquid crystal display panel, a cold-cathode tube backlight arranged on the back surface of the liquid crystal display panel, temperature detecting means arranged on the back surface of the liquid crystal display panel for detecting the temperature of each part, and this temperature detection. 2. A liquid crystal display device comprising: a level setting unit that sets a gradation level of each unit of the liquid crystal display panel according to the temperature of each unit detected by the unit. 4. A liquid crystal display panel in which two layers of liquid crystal layers for dot display including transparent electrodes are stacked, electrodes are alternately arranged in upper and lower layers to display in each layer simultaneously, and a liquid crystal display panel arranged on the back surface of the liquid crystal display panel. A cold-cathode tube backlight, a temperature detecting unit arranged on the back surface of the liquid crystal display panel to detect the temperature of each unit, and a gradation of each unit of the liquid crystal display panel according to the temperature of each unit detected by the temperature detecting unit. A liquid crystal display device comprising: a gradation level setting means for setting a level.