JPH04276715A - Multigradation display method for matrix type display device - Google Patents

Abstract

PURPOSE:To decrease the number of electrodes per piece of display dots and to allow displaying of multiple gradations at a high degree without lowering the ratio of the line width of the electrodes of the min. line width to the electrodes of the max. line width so much. CONSTITUTION:Time-divided display electric powers are supplied to at least one piece of the display picture elements constituting one piece of the display dots of the liquid crystal matrix type display device in which plural pieces of the display picture elements 10a, 10b are formed of scanning electrodes 3 and signal electrodes 6a, 6b and one piece of the display dot is constituted of >=2 pieces of the adjacent display picture elements 10a, 10b varying in light transmittance and having the same light transparent area or varying in the light transmittance and light transparent area.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-gradation display method for a matrix type display device.

0002

2. Description of the Related Art As a liquid crystal matrix type display device capable of expressing halftones, Japanese Patent Application Laid-Open No. 1-267519 discloses a matrix electrode in which a plurality of intersections are formed between crossed scanning electrodes and signal electrodes, and a scanning electrode and a signal electrode. In a display device having a ferroelectric liquid crystal disposed between electrodes, a display device in which a plurality of intersection points subdivided into a plurality of groups from a plurality of intersection points is used as one pixel is shown. And specifically,
By narrowing the line width of the electrodes to a ratio of 1:1/2:1/4:..., the intersection area of the above intersection points becomes 1:1/2:
By adjusting the ratio to 1/4:... and controlling the ON/OFF of power to these multiple intersections,
A mode that enables halftone expression is described.

[0003] Although it is possible to display a certain degree of multiple gradations using the display device described in Japanese Patent Application Laid-Open No. 1-267519 using the easy and reliable method of turning the power ON/OFF, it is desirable to increase the level of gradation to a very high level. This makes manufacturing the display device extremely difficult. In the display device described in JP-A-1-267519, for example, the line width of the electrode is 1
If one pixel is composed of four segment electrode groups and one common electrode group with a ratio of :1/2:1/4:1/8, it is possible to express 16 gradations in calculation. , by adding segment electrodes with thinner line widths,
Although it is computationally possible to further increase the degree of gradation,
In order to increase the degree of gradation, the line width of the electrodes must be made narrower. However, patterning is extremely difficult to reduce the line width of the electrode to ⅛ or more than that of the reference electrode, and it is extremely difficult to stably manufacture such thin electrodes industrially. Furthermore, in order to increase the degree of gradation, the number of signal electrodes must be increased, resulting in a problem that the display device becomes complicated. Incidentally, the above publication merely states that 16 gradation levels are possible in combination with dividing the common electrode.

Furthermore, in Japanese Patent Application Laid-Open No. 2-166419, one display unit is composed of n adjacent pixels, and a light transmittance control layer is provided for each pixel to control the light transmittance of that pixel. , a liquid crystal display device is disclosed in which the ratio of the light transmittance of the light transmittance control layer of n pixels in one display unit is 1:2:4...2n-1. Japanese Patent Publication No. 2-1664
As an example, Japanese Patent No. 19 discloses a display unit composed of four pixels having different light transmittances as shown in FIG. 2 of the same publication. In Figure 2 of the same publication, pixel T1
, T2 , T3 and T4 have a light transmittance ratio of 1:2.
:4:8, and it is explained with reference to FIG. 3 of the publication that 16 gradations can be obtained by a liquid crystal display device having this display unit.

According to the method described in Japanese Patent Application Laid-open No. 2-166419, in order to obtain even higher gradations, it is necessary to increase the number of pixels constituting one display unit (
For example, in order to obtain 128 gradations, one display unit must be composed of 7 pixels with a light transmittance ratio of 1:2:4:8:16:32:64) If the size of the display unit is the same, the size of the pixel must necessarily be made smaller, and accordingly, the line width of the electrode must be made thinner. In addition, in order to subdivide the ratio of light transmittance of pixels into many subdivisions, it is necessary to create a light transmittance control layer in which the absolute value of light transmittance is adjusted extremely accurately, and a circuit is required to control each pixel. The problem is that it becomes complicated.

[0006]

[Problem to be Solved by the Invention] It is possible to industrially easily manufacture a display with a high degree of multi-gradation, which is required for applications such as liquid crystal television panels, and to produce a display with a small number of gradations per display dot. This is possible using a matrix type display device with display pixels.

[0007]

[Means for Solving the Problems] In the present invention, a plurality of display pixels are formed by scanning electrodes and signal electrodes, and two or more adjacent display pixels having different light transmittances and the same light transmitting area A multi-level matrix type display device characterized in that time-divided display signal power is supplied to at least one display pixel constituting one display dot of a liquid crystal matrix type display device configured with one display dot. This is the display method.

Another aspect of the present invention is that a plurality of display pixels are formed by scanning electrodes and signal electrodes, and one display dot is formed by two or more adjacent display pixels having different light transmittances and light transmitting areas. This is a multi-gradation display method for a matrix type display device, characterized in that time-divided display signal power is supplied to at least one display pixel constituting one display dot of the liquid crystal matrix type display device.

Preferred embodiments of the present invention are as follows. (1) The multi-gradation display method described above, characterized in that the light transmittance of the display pixels of the liquid crystal matrix type display device is changed by providing the display device with filters having different light transmittances.

(2) The above matrix type display device is characterized in that at least one of a scanning electrode and a signal electrode constituting one display dot is composed of a plurality of electrodes having different line widths. Multi-gradation display method.

(3) The liquid crystal matrix type display device includes:
The multi-gradation display method described above is characterized in that a mask is provided at a position corresponding to a display pixel having a smaller light-transmitting area, the mask having a window smaller in size than the electrode crossing area of the display pixel.

(4) In the matrix type display device, two or more adjacent display pixels having different light transmittances and the same light transmitting area constitute one display dot, and the one display dot is constituted by two or more adjacent display pixels having different light transmittances and the same light transmitting area. The light transmittance of a plurality of display pixels is 1:
1/m: 1/m2 :...1/m(n-1) (However, m is the time-division gradation of the power supplied to the display pixel with the maximum light transmittance, and n is the gradation level of one display dot. The above multi-gradation display method is characterized in that the display device has a ratio of (the number of display pixels constituting).

(5) The above-mentioned matrix type display device constitutes one display dot by two or more adjacent display pixels having different light transmittances and light-transmitting areas, and a plurality of display pixels constituting the one display dot. The light transmittance of the display pixel is 1:1/t:
1/t2:...1/t(n-1) (where t is a number of 1.5 or more, and n is the number of display pixels constituting one display dot), The light transmission area of the plurality of display pixels constituting one display dot is 1:1/s:
1/s2:...1/s(n-1) [However, s=m/
t (where m is the time-division gradation of the power supplied to the display pixel with the maximum light transmittance, and n has the same meaning as above). The above multi-gradation display method.

The present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows the steps used in the multi-gradation display method of the present invention.
FIG. 2 is a partially enlarged sectional view of an example of a matrix display device;
FIG. 2 is a partially enlarged plan view of the example device shown in FIG. 1 and 2, a matrix display device 1 includes a scanning electrode 3 provided on a glass substrate 2, and a signal electrode provided on the glass substrate 4 via a filter 5 so as to face the scanning electrode 3. 6 are provided, and the scanning electrode 3 and the signal electrode 6 are orthogonal to each other to form a matrix. An alignment film 7 is provided on the scanning electrode 3, and the alignment film 7 is provided on the signal electrode 6 (lower side in FIG. 1). is provided with an alignment film 8, and the alignment film 7 and the alignment film 8
A ferroelectric liquid crystal 9 is filled in the gap between the two. The signal electrodes 6a and 6b have the same line width, and the signal electrodes 6a and 6b intersect with the scanning electrode 3 to form display pixels 10a and 10b, respectively. Therefore,
The electrode crossing areas of display pixels 10a and 10b are the same. Furthermore, circuits 11a and 11b for applying signal voltages to the signal electrodes 6a and 6b, and a circuit 12 for applying a scanning voltage to the scanning electrode 3 are provided.

The filter 5 is provided with a window for transmitting light from outside the glass substrate 2 at a position corresponding to the display pixel, and the portion of the filter 5 other than the window does not transmit light. A window 5a is provided at a position corresponding to the display pixel 10a, a window 5b is provided at a position corresponding to the display pixel 10b, and the windows 5a and 5
The size of b is substantially the same as the electrode crossing area of display pixels 10a and 10b, respectively. In FIG. 2, the window is shown to be slightly smaller than the display pixel in order to distinguish between the window and the display pixel, but both have substantially the same size.

The window 5a and the window 5b are formed to have different light transmittances, that is, the ratio of the light transmittance of the window 5a to the light transmittance of the window 5b is 1:1/8. There is. Therefore, the ratio of the amount of light transmitted through the window 5a and the amount of light transmitted through the window 5b is also 1:1/8.

A pair of display pixels 10a and 10b constitute one display dot D. Each display pixel 10a
and 10b are supplied with time-divided display signal power. The supply of time-divided display signal power to display pixels is as follows:
For example, this is carried out by applying time-divided signal voltages to the signal electrodes 6a and 6b and time-divided (or non-time-divided) scanning voltages to the scanning electrodes. The supply of time-divided display signal power itself is well known and is described, for example, in "Liquid Crystal" (published by Baifukan, July 1985), co-edited by Mitsuharu Okano and Shunsuke Kobayashi. For example, as shown in Figure 3,
Eight types of gradations can be obtained by combining applying seven types of time-divided power (a) to (g) to display pixels and not applying power (h). In this case, the time division gradation level is 8.

Now, when time-divided display signal power (including the case where the power is 0) with a gradation level of 8 is applied independently to the display pixel 10a and the display pixel 10b, the display pixel 10a and the display pixel 10b The ratio of the amount of light transmitted is 1:1/8
Therefore, one display dot D provides 64 (=8×8
) Gradation display is possible. The ability to achieve a very high degree of multi-gradation as described above with only two display pixels having the same light-transmitting area is a significantly superior effect of the present invention. Moreover, according to the multi-gradation display method of the present invention, multiple gradations are possible by turning ON/OFF the display signal power to the display pixels, so control is easy and highly accurate multi-gradation display is possible. be. Since the display pixel described above can be formed by combining two signal electrodes and scanning electrodes having the same line width, it is extremely advantageous in manufacturing a liquid crystal matrix type display device.

Filters with different light transmittances can be made by, for example, using a liquid raw material of transparent synthetic resin (for example, acrylic resin), carbon black, a dye or dye mixture with a controlled wavelength balance of transmitted light, or a mixture of dyes or dye mixtures with a controlled wavelength balance of transmitted light. It can be manufactured by adding controlled pigments or pigment mixtures to form a film and polymerizing it, or it can be manufactured by adding carbon black, dyes, pigments, etc. to such synthetic resin itself. By adjusting the amount of carbon black, dye, pigment, etc. mixed in, the transmittance can be controlled (taking into consideration the wavelength distribution of light used in the display device).

Furthermore, in the case of a color display device using RGB color filters, RGB color filters may be additionally provided in addition to the filters with different light transmittances as described above. G and B
For each of display pixel 10a and display pixel 10b
Color filters having different light transmittances may be used depending on the color filter.

The time-divided gradation level of the display signal power may be any number greater than or equal to 2, and it is possible to supply the time-divided display signal power with a gradation level of 2 to 64 using a technique known per se. Although it is possible, it is generally preferable to use 2 to 16 gradations in terms of high precision and ease of control.

In the display device shown in FIGS. 1 and 2, the light transmittance of two or more adjacent display pixels constituting one display dot may be in any ratio, but as much as possible with a small number of display pixels. In order to obtain a large number of gradations, the light transmittance of the plurality of adjacent display pixels is set to 1:1/m:1.
/m2:...1/m(n-1) (where, m is the time-division gradation of the power supplied to the display pixel with the maximum light transmittance, and n is the display pixel constituting one display dot. It is preferable to have a ratio of . At this time, the error range of the light transmittance of each display pixel is preferably -40 to +40%, particularly -30 to +30%, and even more particularly -20 to +20%. The smaller the absolute value of the light transmittance of the display pixel, the greater the effect of the reduction in the amount of light transmitted at the edge, so the smaller the absolute value of the light transmittance of the display pixel, the larger the above-mentioned light transmittance is than the above ratio. It is preferable. Further, n is preferably 8 or less, particularly 4 or less, and even more particularly 3 or less. As described above, the display device used in the present invention is capable of displaying extremely high gradations even if the number of two or more adjacent display pixels constituting one display dot is reduced, so the structure is It is simple and easy to manufacture and control.

For example, in the matrix type display device shown in FIGS. 1 and 2, a display device formed such that the ratio of the light transmittance of the window 5a to the light transmittance of the window 5b is 1:1/16 is used. However, if time-divided display signal power with 16 gradations is supplied, 256 gradations can be displayed.

FIG. 4 is a partially enlarged sectional view of an example of a matrix type display device used in another multi-gradation display method of the present invention, and FIG. 5 is a partially enlarged sectional view of the example of the device shown in FIG. FIG. In FIGS. 4 and 5, a matrix display device 21
A scanning electrode 23 is provided on a glass substrate 22, and a signal electrode 26 is provided on a glass substrate 24 via a filter 25 so as to face the scanning electrode 23.
The scanning electrodes 23 and the signal electrodes 26 are orthogonal to form a matrix, and an alignment film 27 is provided on the scanning electrodes 23.
An alignment film 2 is placed above the signal electrode 26 (lower side in FIG. 4).
8 is provided, and the gap between the alignment film 27 and the alignment film 28 is filled with ferroelectric liquid crystal 29. The signal electrodes 26a and 26b have line widths at a ratio of 1:1/4, and the signal electrodes 26a and 26b intersect with the scanning electrode 23 to form display pixels 30a and 30b, respectively. Therefore, the ratio of the electrode crossing areas of the display pixels 30a and 30b is 1:1/4. Further, circuits 31a and 31 for applying signal voltages to the signal electrodes 26a and 26b
b, and a circuit 32 for applying a scanning voltage to the scanning electrodes 23.

The filter 25 is provided with a window for transmitting light from outside the glass substrate 22 at a position corresponding to the display pixel, and the portion of the filter 25 other than the window does not transmit light. A window 25a is provided at a position corresponding to the display pixel 30a, and a window 25b is provided at a position corresponding to the display pixel 30b, and the sizes of the windows 25a and 25b are substantially equal to the electrode intersection area of the display pixels 30a and 30b, respectively. is the same as In FIG. 5, the window is shown to be slightly smaller than the display pixel in order to distinguish between the window and the display pixel, but both have substantially the same size.

The window 25a and the window 25b have different light transmittances, that is, the ratio of the light transmittance of the window 25a to the light transmittance of the window 25b is 1:1.
/4. Therefore, the ratio of the amount of light transmitted through the window 25a and the amount of light transmitted through the window 25b is 1.
:1/16. Filters and RG with different light transmittance
The B color filter and the like are the same as those described in connection with FIG.

A pair of display pixels 30a and 30b constitute one display dot D. Each display pixel 30a
and 30b are supplied with 16 gray levels of time-divided display signal power in the same manner as described above.

Now, when time-divided display signal power with a gradation level of 16 is independently applied to the display pixel 30a and the display pixel 30b, the display pixel 30a and the display pixel 30b
Since the ratio of the amount of light transmitted to the dot D is 1:1/16, one display dot D can display 256 (=16×16) gradations. The ability to achieve a very high degree of multi-gradation as described above with only two signal electrodes with a line width ratio of 1:1/4 is a particularly excellent effect of the present invention.

As described above, the line width of the signal electrode 26b is only 1/4 of the line width of the signal electrode 26a (reference electrode), which is large enough for industrially stable and accurate manufacturing. It is. Of course, if it is possible in terms of industrial production technology, a signal electrode with a minimum line width having a narrower line width may be additionally provided, thereby making it possible to further increase the degree of gradation.

The window size of the filter 25 may be changed to a size other than the above-mentioned example, and by making all window sizes substantially the same as the electrode crossing area of the display pixel and changing the line width of the signal electrode, the display can be changed. The light transmitting area of the pixel may be changed, or the light transmitting area of the display pixel may be changed by keeping the line width of the signal electrode the same and changing the window size, or both may be changed. For example, as shown in FIG. 6, which is a partially enlarged plan view of another device example (the cross section is similar to FIG. 4), the size of the window 33a is substantially the same as the electrode intersection area of the display pixel 30a. The size of the window 33b may be set to 1/2 of the electrode crossing area of the display pixel 30b. In this case, the ratio of the light transmittance areas of the window 33a and the window 33b is 1:1/8, so by setting the light transmittance ratio of the window 33a and the window 33b to 1:1/2, the window 33a The amount of light transmitted between the window 33b and the window 33b can be set to 1:1/16. Then, in the same manner as described above, by independently supplying time-divided display signal power with 16 gradations to the display pixels 30a and 30b, it is possible to display 256 gradations with one display dot D.

When reducing the light-transmitting area of a display pixel by changing the window size of the filter 25, the window size can be arbitrarily changed within a range of 80% or less of the electrode crossing area. If the window size is made larger than 80% of the electrode crossing area, a large number of display pixels will be required to express a wide range of gradations, resulting in a decrease in efficiency. If the window size of the filter 25 is made smaller, the brightness of the display dots D will be reduced, so the minimum line width of the signal electrode,
It is necessary to determine the window size of the filter 5 by comprehensively considering the brightness of display dots, the degree of gradation, etc.

In the above example, the light transmitting area of the display pixel of the liquid crystal matrix type display device, which has a smaller light transmitting area, is made smaller than the electrode crossing area by using a filter. Alternatively, a black mask or the like may be used to make the light-transmitting area of the display pixel smaller than the electrode crossing area.

In the display device used in the present invention, the number of signal electrodes 6 and 26 constituting one display dot D (two or more) and the line width ratio of each signal electrode may be any value other than the above. It's good to be there. Further, when the size of the window of the filter 25 is made smaller than the electrode crossing area, the window may be positioned at any position corresponding to the display pixel as long as a desired light transmission area is obtained.

In the above device example, two signal electrodes and one scanning electrode are combined to provide two adjacent display pixels for forming one display dot. In the display device used in the invention, there may be three or more signal electrodes, or one signal electrode and a plurality of scanning electrodes may be combined to provide two or more adjacent display pixels. Alternatively, two or more adjacent display pixels may be provided by using a plurality of both signal electrodes and scanning electrodes.

In the display devices shown in FIGS. 4 to 6, the light transmittance and light-transmitting area of two or more display pixels constituting one display dot may be in any ratio, but a small number of display pixels In order to obtain as many gradations as possible, the light transmittance of the plurality of adjacent display pixels is set to 1:1/t:
1/t2:...1/t(n-1) (where t is 1.
5 or more, n is the number of display pixels constituting one display dot), and the light-transmitting area of the plurality of display pixels constituting one display dot is 1: 1/
s:1/s2 :...1/s(n-1) [However, s=
It is preferable that the display device has a ratio of m/t (where m is the time-division gradation of the power supplied to the display pixel with the maximum light transmittance, and n has the same meaning as above). . At this time, the error range of the amount of light transmitted (light transmittance x light transmitting area) of each display pixel is -40 to +40%, especially -30 to +3
It is preferable to set the light transmittance and the light transmitting area so that it is 0%, more particularly -20 to +20%. Also, n is 8
Below, it is particularly preferably 4 or less, and more particularly 3 or less. As described above, the display device used in the present invention is capable of displaying extremely high gradations even if the number of two or more adjacent display pixels constituting one display dot is reduced. It is simple and easy to manufacture and control.

Further, the display device used in the present invention may be either black and white or color, and RGB as a filter may be used.
By providing color filters on adjacent display dots, a full-color matrix type display device such as a liquid crystal color television panel can be obtained.

[0037] In the display device used in the present invention, the liquid crystal may be of any type, but ferroelectric liquid crystal is particularly preferable, and the liquid crystal is preferably a ferroelectric liquid crystal.
As for other structures of the display device, those known per se can be used. Further, as the method of supplying the time-divided display signal power, the method of driving the display device, etc. in the present invention, methods known per se can be used.

Furthermore, in the method of obtaining multiple gradations using time-divided display signal power, it has been said that flickering is likely to occur, but it is possible to reduce flickering by increasing the frame frequency. In particular, by using a ferroelectric liquid crystal as the liquid crystal, the problem of flickering can be practically solved.

[0039]

Effects of the Invention The multi-gradation display method of the matrix type display device of the present invention provides a matrix type display that uses a small number of electrodes, the line width of the electrodes is not particularly narrow, and can be easily manufactured industrially. Using this device, it is possible to display an extremely high level of multi-gradation, which is a remarkable advantage.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view of an example of a matrix type display device used in the multi-gradation display method of the present invention.

FIG. 2 is a partially enlarged plan view of the example device shown in FIG. 1;

FIG. 3 is a diagram showing an aspect of time-divided display signal power.

FIG. 4 is a partially enlarged sectional view of an example of a matrix type display device used in another multi-gradation display method of the present invention.

FIG. 5 is a partially enlarged plan view of the example device shown in FIG. 4;

FIG. 6 is a partially enlarged plan view of another example of a matrix display device.

[Explanation of symbols]

1, 21 matrix type display device, 2, 22 glass substrate, 3, 23 scanning electrode, 4, 24 glass substrate, 5, 25 filter, 5a, 5b, 25a, 25b window 6, 26
signal electrode, 7, 27 alignment film, 8, 28 alignment film, 9, 29 ferroelectric liquid crystal, 10a, 10b, 30a, 30b display pixel 11a,
11b, 31a, 31b Circuit 12, 32 Circuit 33a, 33b Window D Display dot

Claims (2)

[Claims] [Claim 1] A plurality of display pixels are formed by a scanning electrode and a signal electrode, and one display dot is formed by two or more adjacent display pixels having different light transmittances and the same light transmitting area. 1. A multi-gradation display method for a matrix type display device, characterized in that time-divided display signal power is supplied to at least one display pixel constituting one display dot of the liquid crystal matrix type display device. 2. A liquid crystal matrix type in which a plurality of display pixels are formed by scanning electrodes and signal electrodes, and one display dot is formed by two or more adjacent display pixels having different light transmittances and light transmitting areas. A multi-gradation display method for a matrix type display device, characterized in that time-divided display signal power is supplied to at least one display pixel constituting one display dot of the display device.