TWI427581B - Color liquid crystal display device and display method thereof - Google Patents

Description

Color liquid crystal display device and display method thereof

The present invention relates to a color liquid crystal display device using a field sequential driving liquid crystal display element and a display method thereof.

As a method of coloring a liquid crystal display element, there is a method of using a color filter. However, in this state, there is a problem that a cost increases. Further, in this method, there is also a problem that only one display area can display a color corresponding to the color of the color filter of the portion.

In order to solve such problems, a liquid crystal display element having a field sequential mode is proposed. In the method, the light source is sequentially illuminated by a plurality of light sources respectively emitting different colors, and the liquid crystal display element is turned ON in accordance with the timing of the light source illumination. OFF, and using the integration ability for the time of the human eye, various display colors are displayed with one display pixel.

A display method for driving a liquid crystal display element in the aforementioned field order using three color light sources of red (R), green (G), and blue (B) will be described in more detail using the timing chart of FIG. These three-color light sources repeat the action of emitting light in the order of RGB as shown in the figure. Since there is a period in which no light source emits light between the respective illuminating colors, this is because the liquid crystal display element is turned ON during this period. The reason for the OFF action.

As shown in (a), (b), and (c) of FIG. 1, if the liquid crystal display element is made transparent only during the period corresponding to any one of the three color light sources, red, green, and blue colors can be displayed. Any one of the colors, as shown in (d), (e), and (f) of the drawing, if the liquid crystal display element is made transparent only during the period corresponding to any two colors in the three-color light source, the two colors are performed. Adding color, it can display any color of cyan (C), magenta (M), yellow (Y). Further, as shown in (g) of the figure, when the liquid crystal display element is made to be in a transmissive state during the period corresponding to all of the three color light sources, the three colors are added and mixed, so that white (W) can be displayed, and, for example, As shown in (h) of the figure, if the liquid crystal display element is kept in a light-shielded state during any of the three-color light sources, black (BK) can be displayed because light of any one of the light sources is not transmitted.

Thus, according to the field sequential rule, color display can be performed without using a color filter. Further, a plurality of color displays can be performed in one area by adjusting the timing of the transmission state.

In the case where a nematic liquid crystal is used as the liquid crystal display element, since the response speed coefficient is milliseconds, the period during which any one of the light sources in the timing chart of FIG. 1 emits light (the period during which the liquid crystal is turned ON and OFF) is a millisecond, and the representative value It is 2~5 milliseconds. In order to perform additive color mixing on a plurality of light sources, the period during which the plurality of light sources are sequentially illuminated (1 frame) must be very short, specifically 20 milliseconds or less, preferably 50 Hz at the frame frequency. the above. In the case where the frame frequency is 50 Hz, as shown in Fig. 1, the allocation time (secondary frame) of each color when using the three-color light source is about 6.67 msec. Therefore, the time for each light source to illuminate is 4.67~1.67 milliseconds.

When the display capacity of the liquid crystal display element is increased, in the so-called static driving in which one terminal is displayed for one display segment, the number of terminals is increased and the display segment is connected to the terminal. Wrap around. Therefore, a so-called multiplex drive that displays two or more display segments for one terminal and displays them by time is used. In the segment type liquid crystal display element, the TN mode is generally used, and the multiplex drive is performed from about 1/2 to 1/16 power (duty) in accordance with the increase in the number of segments. In the dot matrix form of the liquid crystal display element, the number of display segments (points) becomes larger than that of the segment form, so the STN mode is used, and the multiplex drive from about 1/32 to 1/480 power is applied. .

A liquid crystal display device that uses the above-described field sequential driving liquid crystal display device has been proposed to employ an optical shutter element (gate cell) (see, for example, Patent Document 1). (Patent Document 1) Japanese Patent Laid-Open Publication No. 2002-221700

However, it is known that even when a liquid crystal display element fabricated under generally the same conditions is used, the response speed at the time of multiplex driving is more sluggish than when it is statically driven. This tendency becomes remarkable particularly when the time discrimination becomes large, and the STN-LCD driven at 1/480 of a power will become a response speed of several hundred milliseconds.

Therefore, it is theoretically impossible to use a field sequential driving system of a liquid crystal display element having a slow response speed, and it is impossible to perform field sequential driving of such a slow response liquid crystal display element by the above-mentioned frame frequency of 50 Hz, even if it is completely It is also thin and very difficult to see without display or display. If the frame frequency is lowered in accordance with the response speed of the liquid crystal display element, the color can be made thicker and any display or the like can be confirmed. However, in this case, the color change itself is recognized as flickering and is still difficult to see.

The present invention has been made in order to solve the aforementioned problems, and an object thereof is to obtain a liquid crystal display element having a large display capacity even at a low cost and requiring high power driving, and having the characteristics of field sequential driving and A color liquid crystal display element in which one segment (dot) performs multicolor display and a display method thereof.

The color liquid crystal display device of the present invention is composed of a liquid crystal display element capable of performing monochrome display and a field sequential drive liquid crystal display element capable of color display.

Further, the field sequential driving liquid crystal display device has one segment or dot region of a liquid crystal display element capable of monochrome display, or a plurality of display regions corresponding to regions in which two or more segments or dots are integrated. In addition, the liquid crystal display element capable of performing monochrome display is a liquid crystal display element in the form of a segment driven by multiplex, or a liquid crystal display element in the form of an omnipot matrix driven by multiplex, or a liquid crystal display element. The combination of the components.

The display method of the color liquid crystal display device of the present invention is a liquid crystal display element capable of performing monochrome display, and a segment or a dot region having the liquid crystal display element or an area in which two or more segments or points are integrated. a field sequential driving liquid crystal display element corresponding to a plurality of display areas, combined to perform color display, and a liquid crystal display element in the form of a multiplexed driving, or a liquid crystal in the form of a full dot matrix driven by multiplex A display element or a liquid crystal display element capable of performing monochrome display in combination with such liquid crystal display elements is combined with a field sequential drive liquid crystal display element for color display.

According to the present invention, even a liquid crystal display element which is low in cost and requires a large display capacity driven by a high power has the characteristics of field sequential driving and can be performed by one segment (dot). The effect of the color display.

Specifically, the color liquid crystal display device of the present invention combines a liquid crystal display element which is driven at a high power with a field sequential driving liquid crystal display element which is divided into a plurality of regions and which is independent of each region and can be multicolor displayed.

According to the present mode, even if it is impossible to make all the segments (points) individually perform multicolor display, for example, when the characters are displayed by the liquid crystal display elements of the full dot matrix, a plurality of dots are made as one cluster (for example, 16×). 16 o'clock) indicates a text in which the display color can be changed in each cluster without controlling every point in the cluster. Further, in the segment display, for example, 8 words (7 segments) are displayed in a more connected manner, and in the case of dots, the display color can be changed in every 7 segments of one cluster.

If the contrary is used, the present invention is not suitable for the purpose of performing multi-color display of all segments (points) individually, for example, by displaying the picturer by the liquid crystal display element of the full dot matrix, or even in the form of a segment. For each of the segments, the meaning is independent. For such applications, miniature color filters are suitable for use, and high quality displays have been achieved by a combination with active matrix driving. However, such liquid crystal display elements are very expensive.

That is, the present invention imposes a certain degree of limitation on color display, but is a novel method of realizing color display at a very low cost. The present invention will be more specifically described below using Figs. 2 and 3.

Fig. 2 is an exploded perspective view showing the structure of a liquid crystal display device in the case where the present invention is applied to a liquid crystal display element in which a segment display and a dot matrix display are mixed. The liquid crystal display device is a liquid crystal display device which can perform monochrome display (black and white display) in a normal segment form + dot matrix form, and a field sequential drive liquid crystal display device which can be color-displayed into a plurality of clusters. 2 layers of structure are established. Here, the division into a plurality of clusters refers to one or two or more regions corresponding to the segments of the respective independent colors in which the display elements of the normal segment type are to be displayed.

Generally, the liquid crystal display element 1 of the segment + dot type has no limitation in the response speed, so various modes can be used, as shown in FIG. 2, which may be a normally black mode or a normally white mode. However, it is preferable to use a normally black mode because the naked eye cannot see the seam of the color displayed by the field sequential liquid crystal display. Of course, it is also possible to use a mode in which a black mask is applied outside the display portion. In this case, the display mode may be either black or white. In addition, the driving method is also unlimited.

On the other hand, since the necessary condition for driving the liquid crystal display element 2 in the field order is a high-speed response, the mode of the liquid crystal is also limited, and the driving is also driven by the low power of the static driving up to 1/3 of the power. The display mode can be any of long black or white, and any one can be selected according to design. 3 is an RGB backlight unit having a surface light source of red, green, and blue light.

Fig. 3 is an exploded perspective view showing the configuration of a liquid crystal display device 11 in the form of a full dot matrix, in which the liquid crystal display device of the present invention is applied. In principle, it is identical to the state of FIG. 2, and only the liquid crystal display element 1 of the normal segment + dot form of FIG. 2 is replaced, and the liquid crystal display element 11 of the full dot matrix form is used. That is, it is established by the liquid crystal display element 11 of the usual full dot matrix type and the two-layer structure of the liquid crystal display element 12 which is divided into a plurality of field sequential driving liquid crystal display elements 12. Here, the division into a plurality of clusters refers to an area corresponding to two or more points of various independent colors of a display element to be displayed in a usual dot matrix form.

Generally, the liquid crystal display element 11 of the full dot matrix type is not limited in response speed, and various modes can be used. As shown in FIG. 3, it can be a normally black mode or a normally white mode. However, it is preferable to use the normally black mode for the reason that the seam of the color displayed by the field sequential liquid crystal display is not visible to the naked eye. In addition, the driving method is also unlimited.

On the other hand, since the necessary condition for driving the liquid crystal display element 12 in the field order is a high-speed response, the mode of the liquid crystal is also limited, and the driving is also driven by the low power of the static driving up to 1/3 of the power. The display mode can be either black or white, and any one can be selected according to the design. 13 is an RGB backlight unit having a surface light source of red, green, and blue light.

Next, the present invention will be described in more detail by way of examples.

(Example 1)

A liquid crystal display element in which a segment display and a dot matrix display are mixed as shown in Fig. 2 will be described, and an embodiment of the present invention is applied.

A liquid crystal display element in the form of a normal segment + dot matrix is a 90 degree twisted TN-LCD in a normally black mode. Basically, it is the same as the conventional TN-LCD, but the transmittance is made smaller by emphasizing the black color of the substrate. Therefore, the product of the birefringence and the cell thickness of the liquid crystal is set, that is, the retardation value is 2.5 μm. The liquid crystal has a birefringence of 0.2 and a cell thickness of 12.5 μm. The liquid crystal display element is driven by multiplex driving of 1/8 power. The response speed at this time is very slow due to the thick cell thickness, and the rise and fall times are about 250 ms.

On the other hand, as a field sequential liquid crystal display, a 90 degree twisted TN-LCD of a normally white mode is used. These lines are also substantially the same as the conventional TN-LCD, but in order to give priority to high-speed responsiveness, the cell thickness is set as thin as possible. Specifically, the cell thickness is 2.0 μm, and a liquid crystal having a birefringence of 0.25 is combined here. Thus, the retardation value of the liquid crystal cell is 0.5 μm.

The driving of the liquid crystal cell is performed by static driving, and similarly to the normal field sequential liquid crystal display element, driving is performed while using the light-emitting timing of the RGB three-color LED as a backlight. By the way, if the response speed is measured by the liquid crystal cell, the rise and fall are both 2ms.

When the two liquid crystal display elements and the backlight unit are superimposed and the target display element is produced and observed, the display of changing the color at each segment as desired is obtained. The image image to be displayed is shown in Fig. 4. In (a) and (b) of the same figure, the colors of the characters or numbers are different.

Further, a polarizing plate is attached to each of two liquid crystal display elements, and the liquid crystal display elements are in a state in which the polarization axes of the opposite polarizing plates are in common, even if there is no liquid crystal display element on either side. The polarizing plate on the opposite side can also perform the same display. Since it is actually shown in the present embodiment that the polarizing plate is provided by such conditions, it is possible to confirm that there is no problem at all.

(Example 2)

An embodiment of the present invention will be described with respect to a liquid crystal display element of the full dot matrix type shown in FIG.

As a liquid crystal display element of a normal full dot matrix type, a film compensation type 240-degree torsion STN-LCD of a normally black mode is used. Basically the same as the usual STN-LCD. The product of the birefringence of the liquid crystal and the cell thickness, i.e., the retardation value, was set to 0.9 μm. The liquid crystal display element is driven by multiplex driving of 1/240 power. At this time, the response speed is about 200 ms for the rise and fall times.

On the other hand, as the field sequential liquid crystal display, the same cell condition as in Example 1 was used. The difference from the first embodiment is only the difference in the shape of the pattern when the points are clustered. Here, the display of the horizontal direction 480 × 240 points in the vertical direction is made into one cluster at 60 × 60 dots, that is, the total area of the horizontal region is 8 regions × 4 regions. In this case, all the clusters have the same shape, but of course, the shape can be arbitrarily matched with the design.

When the two display liquid crystal display elements and the backlight unit are superimposed and the target display element is produced and observed, the display of the color can be freely changed in each area as desired. The image image to be displayed is shown in Fig. 5. In (a) and (b) of the same figure, the colors of the respective characters are different.

Further, a polarizing plate is attached to each of the two liquid crystal display elements and used, but the two liquid crystal display elements are in a state in which the polarization axes of the opposite polarizing plates are in common, even if there is no side. The liquid crystal display element is a polarizing plate on the opposite side, and the same display can be performed. In fact, in this embodiment, the STN-LCD sold in the market is used. Therefore, the transmission axis direction of the polarizing plate is deviated from the transmission axis direction of the polarizing plate of the TN-LCD on the field side, so that it cannot be surely confirmed, but in the rotation STN- When the polarizing plate on the opposite side was removed in the state in which the LCD was aligned with the polarization axis, it was confirmed that no problem occurred at all.

As described in the above embodiments, the liquid crystal display element of the usual black-and-white display and the field sequential liquid crystal display element of each of the appropriate regions are used, and the field sequential liquid crystal display element can be repeatedly combined and sequentially used. With a combination of backlight systems of a plurality of light sources, color display can be obtained simply and at low cost.

Further, the description has been made in the embodiment for the segment + dot matrix form and the full dot matrix form, but of course, the present invention can also be applied only to the segment display.

Further, in the embodiment, the normally black mode is used as the liquid crystal display element of the usual black and white display, and the normally white mode is used as the field sequential liquid crystal display element. However, the present invention is not limited to such a combination, and any combination can be realized.

Further, in the embodiment, the liquid crystal display element as a black-and-white display is a TN-LCD and an STN-LCD, and the field-sequential liquid crystal display element is a TN-LCD. However, the present invention is not limited to such a combination, and is displayed as a black-and-white display. In addition to the liquid crystal display element, of course, it is also possible to use an LCD of all modes such as a vertical alignment type LCD or a guest main type LCD, or even a ferroelectric type LCD, even as a field sequential liquid crystal display element, even by a so-called high speed response. From the point of view, it is not suitable for the STN-LCD, and various types of LCDs such as a ferroelectric LCD can also be used.

1. . . Conventional segment + dot matrix liquid crystal display element

2. . . Field order

3. . . RGB backlight unit

11. . . Full dot matrix liquid crystal display element

12. . . Field order

13. . . RGB backlight unit

Figure 1 is a driving sequence diagram of the field sequential mode.

Fig. 2 is an exploded perspective view showing the configuration of a liquid crystal display device to which the present invention is applied, in a liquid crystal display device in which a segment display and a dot matrix display are mixed.

Fig. 3 is an exploded perspective view showing the configuration of a liquid crystal display device to which the present invention is applied in a liquid crystal display element of a full dot matrix type.

Fig. 4 is a view showing a display example of the embodiment 1 of the present invention.

Fig. 5 is a view showing a display example of the embodiment 2 of the present invention.

1. . . Conventional segment + dot matrix liquid crystal display element

2. . . Field order

3. . . RGB backlight unit

Claims (5)

A color liquid crystal display device characterized by combining a liquid crystal display element capable of monochrome display and a field sequential drive liquid crystal display element capable of color display; and the field sequential drive liquid crystal display element has liquid crystal capable of monochrome display One segment or dot region of the display element, or a plurality of display regions corresponding to regions in which two or more segments or dots are integrated. The color liquid crystal display device of claim 1, wherein the liquid crystal display element capable of performing monochrome display is a liquid crystal display element in the form of a segment driven by multiplexing, or an omnipotent matrix form driven by multiplex A liquid crystal display element or a combination of such liquid crystal display elements. The color liquid crystal display device of the first or second aspect of the invention, wherein the liquid crystal display element capable of performing monochrome display, the color-displayable field sequential driving liquid crystal display element side polarizing plate, and the color-developable color The field sequential driving liquid crystal display element is a polarizing plate on the liquid crystal display element side capable of performing monochrome display, and is a single polarizing plate. A display method of a color liquid crystal display device, characterized in that a liquid crystal display element capable of performing monochrome display, and a segment or a dot area having the liquid crystal display element or integrating two or more segments or points A field sequential drive liquid crystal display element capable of color display of a plurality of display areas corresponding to the area is combined for color display. A display method of a color liquid crystal display device, characterized in that a liquid crystal display element in the form of a segment driven by multiplex, or a liquid crystal display element in the form of an omnipot matrix driven by multiplex, or a combination of such liquid crystal display elements Liquid crystal display element capable of monochrome display and field for color display The sequential driving liquid crystal display elements are combined for color display.