CN101196633A - Field sequential driving liquid crystal display device and driving method thereof - Google Patents

Abstract

The invention discloses a liquid crystal display device with improved visual recognition and a driving method thereof. The liquid crystal display device comprises: a first liquid crystal unit; a second liquid crystal unit; two orthogonal polarizers arranged on both sides of a double-layer structure panel including the first and second liquid crystal units along the normal direction of the substrate; a light source, capable of emitting light of a plurality of colors; and a control circuit that time-sequentially divides one frame into a plurality of subframes, emits light of a predetermined color in each subframe, and controls the light including the first and second The state of light transmission and light shielding of multiple display areas of the double-layer structure panel of two liquid crystal units, wherein the first and second liquid crystal units are configured to be in a mutual optical compensation relationship in both the driving state and the non-driving state.

Description

Field sequential driving liquid crystal display device and driving method thereof

Cross References to Related Applications

This application is based on and claims Japanese Patent Application No. 2006-274730 filed on October 6, 2006, Japanese Patent Application No. 2007-066255 filed on March 15, 2007, and Japanese Patent Application No. 2007-066255 filed on March 29, 2007 Priority of No. 2007-087912, the entire contents of which are hereby incorporated by reference.

Background technique

A) technical field

The invention relates to a liquid crystal display device, more specifically to a field sequentially driven liquid crystal display device with a double-layer structure liquid crystal unit.

B) Relevant technical description

Generally, in a liquid crystal display device, displaying white characters and numbers on a black background is called a negative display, and displaying black characters and numbers on a white background is called a positive display.

The field sequential (FS) driving method is known as a method of driving a color liquid crystal display device displaying colors other than white on a black background and a color liquid crystal display device displaying colors other than black on a white background.

According to the FS driving method, a light source capable of emitting light of various colors is prepared, and while the liquid crystal display device is turned on and off in synchronization with the light emission timing of the light source, color light is sequentially repeated, thereby utilizing the temporal integration ability of the human eye Various colored lights are displayed on the display pixels.

A color liquid crystal display device driven by the FS driving method is already known.

JP-A-2004-29154 (the entire contents of which are incorporated herein by reference) discloses a color liquid crystal display device that drives a negative display liquid crystal cell using an antiferroelectric liquid crystal FS.

JP-A-2004-294824 (the entire contents of which are incorporated herein by reference) discloses a negative display FS liquid crystal display device using a twisted nematic (TN) liquid crystal cell.

JP-A-2002-303846 (the entire contents of which are incorporated herein by reference) discloses a positive display FS liquid crystal display device using a uniform alignment liquid crystal cell.

Contents of the invention

It is an object of the present invention to provide a FS liquid crystal display device with improved visual recognition.

According to one aspect of the present invention, there is provided a liquid crystal display device, comprising: a first liquid crystal unit including a first pair of opposing substrates and a first liquid crystal layer held between the first pair of substrates, the first pair of substrates at least There is a first pair of pixel electrodes for displaying predetermined characters and numbers, and the alignment state of the first liquid crystal layer can be controlled by adjusting the voltage applied between the first pair of pixel electrodes; the second liquid crystal unit includes a second pair of opposing substrates and a second liquid crystal layer held between the second pair of substrates, the second pair of substrates having a second pair of pixel electrodes for completely covering areas of predetermined characters and numerals, and the second liquid crystal layer The alignment state can be controlled by adjusting the voltage applied between the second pair of pixel electrodes; two orthogonal polarizers are arranged in the double-layer structure panel including the first and second liquid crystal cells along the normal direction of the substrate The two sides of the light source, capable of emitting multiple colors of light; and the control circuit, time sequentially divides a frame into a plurality of sub-frames, emits light of a predetermined color in each sub-frame, and synchronously with the light emission, controls including the first The state of light transmission and light shielding of multiple display areas of the double-layer structure panel of the first and second liquid crystal cells, wherein the first and second liquid crystal cells constitute a relationship of mutual optical compensation in both the driving state and the non-driving state .

According to another aspect of the present invention, there is provided a method for driving a liquid crystal display device, the liquid crystal display device comprising: a first liquid crystal unit including a first pair of opposing substrates and a first liquid crystal held between the first pair of substrates layer, the first pair of substrates has at least a first pair of pixel electrodes for displaying predetermined characters and numbers, and the alignment state of the first liquid crystal layer can be controlled by adjusting the voltage applied between the first pair of pixel electrodes; Two liquid crystal cells comprising a second pair of opposing substrates and a second liquid crystal layer held between the second pair of substrates, the second pair of substrates having a second pair for completely covering the area of the predetermined characters and numbers The alignment state of the pixel electrode and the second liquid crystal layer can be controlled by adjusting the voltage applied between the second pair of pixel electrodes; two orthogonal polarizers are arranged along the normal direction of the substrate including the first and The two sides of the double-layer structure panel of the second liquid crystal unit; the light source, capable of emitting multiple colors of light; and the control circuit, time-sequentially dividing one frame into a plurality of sub-frames, emitting light of a predetermined color in each sub-frame, Synchronously with light emission, controlling the states of light transmission and light shielding of a plurality of display areas of the double-layer structure panel including the first and second liquid crystal cells, wherein the driving method is controlled in such a manner that in one subframe The display area that enters the light shielding state enters another subframe.

According to yet another embodiment of the present invention, there is provided a driving method of a liquid crystal display device, the liquid crystal display device comprising: a first liquid crystal unit including a first pair of opposing substrates and a first pair of substrates held between the first pair of substrates A liquid crystal layer, the first pair of substrates has at least a first pair of pixel electrodes for displaying predetermined characters and numbers, and the alignment state of the first liquid crystal layer can be controlled by adjusting the voltage applied between the first pair of pixel electrodes; A second liquid crystal cell comprising a second pair of opposing substrates and a second liquid crystal layer held between the second pair of substrates, the second pair of substrates having a second pair for completely covering the area of the predetermined characters and numbers The pixel electrodes, and the alignment state of the second liquid crystal layer can be controlled by adjusting the voltage applied between the second pair of pixel electrodes; two orthogonal polarizers are arranged along the normal direction of the substrate including the first and the two sides of the double-layer structure panel of the second liquid crystal unit; a light source capable of emitting light of various colors; and a control circuit time-sequentially dividing one frame into a plurality of sub-frames, and emitting light of a predetermined color in each sub-frame , synchronously with light emission, controlling states of light transmission and light shielding of a plurality of display regions of the double-layer structure panel including first and second liquid crystal cells, wherein the driving method is controlled in such a manner that by controlling the first The alignment state of the liquid crystals of at least one of the first and second liquid crystal cells implements gradation display in an intermediate state between a driven state and a non-driven state.

According to the FS liquid crystal display device of the present invention, visual recognition can be improved.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a liquid crystal display unit having a double-layer structure.

FIG. 2 is a diagram showing a transmission axis direction of a polarizing plate of a liquid crystal display cell and a rubbing direction of a liquid crystal cell.

Fig. 3 is a schematic block diagram of a FS liquid crystal display device equipped with a liquid crystal display unit.

4A is a diagram showing a transparent electrode installed on a rear liquid crystal cell of a liquid crystal display unit, and FIG. 4B is a diagram showing a transparent electrode installed on a front liquid crystal cell of a liquid crystal display unit.

5A is an explanatory diagram of a transparent electrode of a rear liquid crystal cell serving as a segment display electrode, and FIG. 5B is an explanatory diagram of a transparent electrode of a front liquid crystal cell serving as a background electrode.

Fig. 6 is an explanatory diagram showing a color display state.

7 is a table illustrating a driving method of the liquid crystal display device according to Embodiment 1-1.

FIG. 8 is a table illustrating a driving method of the liquid crystal display device according to Embodiment 1-2.

FIG. 9 is a table illustrating a driving method of the liquid crystal display device according to Embodiments 1-3.

FIG. 10 is a table illustrating a driving method of the liquid crystal display device according to Embodiments 1-4.

FIG. 11 is a table illustrating a driving method of the liquid crystal display device according to Embodiments 1-5.

FIG. 12 is a table illustrating a driving method of the liquid crystal display device according to Embodiments 1-5.

13A and 13B are diagrams showing examples of electrode patterns of a double liquid crystal cell.

FIG. 14 is a table illustrating a driving method of the liquid crystal display device according to Embodiment 2-1.

Fig. 15 is an explanatory diagram showing a color display state.

FIG. 16 is a table illustrating a driving method of the liquid crystal display device according to Embodiment 2-2.

Fig. 17 is an explanatory diagram showing a color display state.

FIG. 18 is a table illustrating a driving method of the liquid crystal display device according to Embodiment 2-3.

Fig. 19 is an explanatory diagram showing a color display state.

20A and 20B are diagrams showing examples of electrode patterns of a double liquid crystal cell.

Fig. 21 is a diagram illustrating grayscale display.

Fig. 22 shows a display example according to Embodiment 3-1.

FIG. 23 is a table illustrating a driving method of the liquid crystal display device according to Embodiment 3-1.

Fig. 24 shows a display example according to Embodiment 3-2.

FIG. 25 is a table illustrating a driving method of the liquid crystal display device according to Embodiment 3-2.

26A and 26B show an example of a projection type display device employing the embodiment.

27 is a diagram showing the direction of the transmission axis of the polarizer and the rubbing direction of the liquid crystal cell of a liquid crystal display cell utilizing a double-layer structure of a vertically aligned liquid crystal cell.

Detailed ways

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

Example 1

FIG. 1 is a schematic cross-sectional view showing an example of the structure of a liquid crystal display unit incorporated in a liquid crystal display device.

The liquid crystal display device is composed of a front liquid crystal display unit 1b, a rear liquid crystal display unit 1a, a front polarizing plate (polarizer) 2b, and a rear polarizing plate 2a.

A spacer is provided between the front liquid crystal cell 1b and the rear liquid crystal cell 1a to connect them together. A front polarizer 2b is attached to the front liquid crystal cell 1b, and a rear polarizer 2a is attached to the rear front liquid crystal cell 1a. We call the double-TN liquid crystal unit connected together as a double-layer structure panel SP.

As shown, the front liquid crystal cell 1b sandwiches a liquid crystal 6b through a pair of transparent substrates 3b1 and 3b2 (eg, glass substrates) on which transparent electrodes 5b1 and 5b2 are formed.

The transparent electrodes 5b1 and 5b2 have alignment films 7b1 and 7b2 on opposite surfaces of the electrodes.

The sealing member 4b bonds the peripheral areas of the transparent substrates 3b1 and 3b2 using an adhesive, thereby sealing the liquid crystal 6b in the space between the transparent substrates 3b1 and 3b2.

Similar to the front liquid crystal unit 1b, the rear liquid crystal unit 1a is composed of a pair of transparent substrates 3a1 and 3a2 (eg, glass substrates), transparent electrodes 5a1 and 5a2 formed on the transparent substrates 3a1 and 3a2, and transparent electrodes 5a1 and 5a2 formed on the transparent electrodes 5a1 and 5a2. The alignment films 7a1 and 7a2 on the opposite surfaces are composed, wherein the transparent substrates 3a1 and 3a2 are bonded together through the sealing member 4a using a tape adhesive and seal the liquid crystal 6a therebetween.

FIG. 2 is a diagram showing the direction of the transmission axis of the polarizing plate of the liquid crystal display cell and the rubbing direction of the liquid crystal cell.

That is, the rubbing direction 9b2 is used to represent the front alignment film 7b2 of the front liquid crystal cell 1b, and the rubbing direction 9b1 is used to represent the rear alignment film 7b1 of the front liquid crystal cell 1b. The rubbing direction 9a2 in FIG. 2 is used to represent the front alignment film 7a2 of the rear liquid crystal cell 1a, and the rubbing direction 9a1 in FIG. 2 is used to represent the rear alignment film 7a1 of the rear liquid crystal cell 1a.

The front liquid crystal cell 1b is formed as a TN type liquid crystal cell. The alignment films 7b1 and 7b2 are made of horizontal alignment film SE410 produced by Nissan Chemical Industries, Ltd. The pretilt angle was obtained by rubbing the alignment film in the direction of FIG. 2 with a rubbing cloth made of rayon.

The transparent substrates 3b1 and 3b2 were stacked and bonded together with an adhesive, with a gap control member having a diameter of 5 μm interposed therebetween. The liquid crystal 6b sealed in the space between the transparent substrates 3b1 and 3b2 is made of a liquid crystal material having a positive dielectric constant anisotropy (liquid crystal molecules rise from a horizontal twisted alignment when a voltage is applied) and a birefringence Δn of 0.95, which The liquid crystal material is produced by Merck Ltd with the addition of a chiral material used to determine the direction of the twist.

The rear LC cell 1a has similarities to the front LC cell 1b except that for the front LC cell 1b, the chiral material is used to set the clockwise twist direction, while for the rear LC cell 1a, the chiral material is used to set the counterclockwise twist direction. Structure.

Because the front liquid crystal cell 1b has the opposite twist direction to the rear liquid crystal cell 1a, and the rubbing direction 9b1 of the rear alignment film 7b1 of the front liquid crystal cell 1b is perpendicular to the rubbing direction 9a2 of the front alignment film 7a1 of the rear liquid crystal cell 1a, the front liquid crystal cell 1b and the rear liquid crystal unit 1a have a relationship of mutual optical compensation, as shown in FIG. 2 .

Fig. 3 is a block diagram showing the FS liquid crystal display device of the embodiment. In FIG. 3, the front and rear polarizing plates 2b and 2a are not shown.

As shown in FIG. 3, a backlight LS that sequentially emits red (R), green (G), and blue (B) is disposed on the rear side of the rear liquid crystal cell 1a.

The driver 10b for the backlight LS works synchronously with the drivers 10a of the two liquid crystal units 1b and 1a under the control of the synchronous controller 20 .

The backlight LS may be a known light source composed of a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), or the like. The FS driving method may be the methods described in JP-A-2004-29154, JP-A-2004-294824, and JP-A-2002-303846, in addition to using a liquid crystal cell of a double-layer structure. Similar to the liquid crystal display devices described in these laid-open applications, one frame period is time-sequentially divided into a plurality of subframes, the backlight LS is driven to emit light in each subframe, and in synchronization with the light emission, the front liquid crystal unit 1b and The electrodes of the rear liquid crystal cell 1a are turned on and off.

The front liquid crystal cell 1b and the rear liquid crystal cell 1a have transparent electrodes as shown in FIGS. 4A and 4B.

That is, the transparent electrodes 5a1 and 5a2 of the rear liquid crystal cell 1a are segment electrodes as shown in FIG. 4A.

More specifically, the transparent electrodes 5a1 and 5a2 are general display electrodes for displaying characters and numerals.

The transparent electrodes 5b1 and 5b2 are background display electrodes shown in FIG. 4B.

More specifically, the transparent electrodes 5b1 and 5b2 of the front liquid crystal cell 1b are background display electrodes for display, so-called stereoscopic display, of the entire effective display area inside the sealing member 4b.

A segment electrode may be formed on the front liquid crystal cell 1b, and a background display electrode may be formed on the rear liquid crystal cell 1a.

Next, a color display example of a liquid crystal display device is described.

For simplicity of description, it is assumed that the transparent electrodes 5b1 and 5b2 of the front liquid crystal cell 1b are background display electrodes, and the transparent electrodes 5a1 and 5a2 of the rear liquid crystal cell 1a are seven-segment electrodes. The electrodes in the seven-segment electrode are appended with letters a1 to h1 as shown in FIGS. 5A and 5B .

The backlight LS for emitting light of three colors R, G, and B can emit eight color lights including white and black if intermediate luminance is not considered. Therefore, a display example in which seven colors of light are distributed to the seven-segment electrodes a1 to g1 and one color of light is distributed to the background display electrode h1 will be described.

In actual display, not only numbers including "8" are displayed in seven colors, but also various color images are displayed in a plurality of segments.

Example 1-1

In the first display configuration example, color display is implemented on a black back screen, which is an example of a typical negative display. In Figure 6, the background display electrode h1 is used for black display, the segment electrode a1 is used for white display, the segment electrode b1 is used for yellow display, the segment electrode c1 is used for magenta display, and the segment electrode d1 is used for red display , the segment electrode e1 is used for cyan display, the segment electrode f1 is used for green display, and the segment electrode g1 is used for blue display.

In this display configuration example, the color display is implemented by driving the segment electrodes and the background electrodes on and off at the lighting sequence of the R, G and B light-emitting diodes of the backlight LS, as shown in FIG. 7 .

The characteristic of the first display configuration example is that even at each R, G, and B LED lighting timing, the background is maintained in black by setting the background display electrode h1 in an off state, and is driven synchronously with each LED lighting timing The conduction and disconnection of each segment electrode implements the display of seven colors.

The conduction state of each electrode is the state in which the effective voltage for white display is applied to the liquid crystals of the dual liquid crystal cells 1b and 1a, each of which acts as a general TN cell with parallel Nicol polarizers on both sides thereof Work. The off state of each electrode is a state where no voltage is applied in the case of static driving and an effective voltage for black display is applied to the liquid crystals of the dual liquid crystal cells 1b and 1a in the case of multiple driving, each of the liquid crystal cells 1b and 1a Works as a normal TN cell with parallel Nicol polarizers on both sides of it.

Example 1-2

In the second display configuration example, color display is implemented on a white background, which is a typical example of positive display. In Figure 6, the background display electrode h1 is used for white display, the segment electrode a1 is used for black display, the segment electrode b1 is used for blue display, the segment electrode c1 is used for green display, and the segment electrode d1 is used for cyan display , the segment electrode e1 is used for red display, the segment electrode f1 is used for magenta display, and the segment electrode g1 is used for yellow display.

In this display configuration example, in the lighting sequence of the R, G and B light-emitting diodes of the backlight LS, color display is implemented by driving the segment electrodes and the background electrodes on and off, as shown in FIG. 8 .

The second display configuration example is characterized in that even at each R, G, and B LED lighting timing, the background is maintained white by setting the background display electrode h1 in a conductive state, and is driven synchronously with each LED lighting timing The conduction and disconnection of the segment electrodes realize the display of seven colors. The definition of the on and off states of each electrode is the same as the first display configuration example.

It is often considered that color display cannot be realized because the segment electrodes a1-g1 are affected by the background display electrodes in the on-state. However, if the segment electrodes are driven to be turned on while the background display electrodes are driven to be turned on, black display can be realized due to the mutual optical compensation of the dual liquid crystal cells 1b and 1a.

For example, with respect to the background display electrode h1 , the segment electrode a1 is driven to conduct at each light emitting sequence of the R, G and B light-emitting diodes.

Similarly, if the segment electrode is in the same state as the background display electrode h1 in the light emitting sequence, that is, the conduction state, then the emitted light of each other segment electrode is blocked, and if the segment electrode is in the same state as the background display electrode h1 in emitting light The states with different timings, ie, the off state, transmit the emitted light of each of the other segment electrodes. The display of seven colors on a white background is realized in this way.

Example 1-3

In the third display configuration example, the background color is a color other than white and black, and is one of R, G, and B of the backlight LS.

For example, assuming that the turn-on and turn-off timings of the backlight LS and the electrodes a1~h1 are set as shown in Figure 9, the background display electrode h1 in Figure 6 is used for blue display, the segment electrode a1 is used for yellow display, and the segment electrode Electrode b1 is used for white display, segment electrode c1 is used for red display, segment electrode d1 is used for purple display, segment electrode e1 is used for green display, segment electrode f1 is used for cyan display, and segment electrode g1 is used for Do black display.

Example 1-4

In the fourth display configuration example, the background color is a mixed color of two colors of R, G, and B.

For example, assuming that the turn-on and turn-off timings of the backlight LS and electrodes a1~h1 are set as shown in Figure 10, the background display electrode h1 in Figure 6 is used for magenta display, the segment electrode a1 is used for red display, and the segment electrode Electrode b1 is used for purple-red display, segment electrode c1 is used for yellow display, segment electrode d1 is used for white display, segment electrode e1 is used for black display, segment electrode f1 is used for blue display, and segment electrode g1 is used for green display.

Example 1-5

In the fifth display configuration example, the background color can be changed without changing the display color by the segment electrodes.

For example, assuming that the backlight LS and the turn-on and turn-off timing of the electrodes a1~h1 are set as shown in Figure 11, the background display electrode h1 in Figure 6 is used for white display, and all the segment electrodes a1~g1 are used for red display , that is, the segment display is a red number "9". Assuming that the turn-on and turn-off timings of the backlight 31 and the electrodes a1 - h1 are set as shown in FIG. 12 , the background can be changed to blue without changing the red segment display.

As shown in FIG. 11 and FIG. 12 , the segment electrodes a1-g1 and the background display electrode h1 only work in sequence when the color LEDs to be displayed emit light to provide different display states.

Example 2

The inventor has created a liquid crystal display in which the so-called color break phenomenon does not occur by changing the FS driving method.

FIG. 13 shows an example of an electrode pattern of a double liquid crystal cell in Embodiment 2. FIG. The liquid crystal cells 1a and 1b have transparent electrodes for displaying according to voltage applied to the liquid crystal layer. One unit (called display unit) has segment electrodes, such as electrodes a2-d2 shown in Figure 13 for segment display, and the other unit (called background display unit) has electrodes for displaying the entire effective display area. The rigid electrode e2. Or a display unit or a background display unit may be provided at the upper portion (at the rear side).

An embodiment in which one frame of driving voltage is divided into three subframes will be described.

Example 2-1

FIG. 14 shows a table illustrating a driving method of the liquid crystal display device of the first embodiment. In Example 2-1, color segment display is realized on a black background, which is a typical negative display. Figure 14 shows the conduction/disconnection (ON/OFF) state of each R, G and B light-emitting diodes in each subframe, the segment electrodes a2-d2 on the display unit and the rigidity on the background display unit. The on/off state of the electrodes e2, and each color displayed in the display area defined by each electrode. The rigid electrode e2 is larger than the segment electrodes a2-d2 and is formed to cover almost the entire display area, so that the segment electrodes a2-d2 overlap on the display area. The display color of the electrode e2 is the background display color rather than the segment electrode color.

The on-state of the light-emitting diode corresponds to a light-emitting state, and the off-state corresponds to a non-light-emitting state. The definitions of the on state and the off state are similar to those in Embodiment 1.

Fig. 15 shows an example of actual display. In the embodiment 2-1, the rigid electrode e2 is set in an off state in all subframes to realize a black display of the background (not superimposed on the segment electrodes a2-d2). The on or off state of the segment electrodes a2 - d2 is set according to each subframe. In the display area where the rigid electrode e2 of the background display unit is superimposed on each segment electrode a2~d2 of the display unit, if one of the units is turned on, the liquid crystal display unit enters a light transmission state, and if both units are When it is turned on or off, the liquid crystal display unit enters into a light-shielding state.

In each subframe, the LED emits light of its displayed color. Various colors of light can be emitted by adjusting on/off and R, G and B luminous intensity. In the table shown in FIG. 14, the on/off of the voltage is controlled so that electrode a is used for white (W) display, electrode b is used for red (R) display, electrode c is used for yellow (Y) display, and Electrode d is used for black (BK) display, as shown in FIG. 15 .

Example 2-2

FIG. 16 shows a table illustrating a driving method of the liquid crystal display device of the second embodiment. In embodiment 2-2, a color segment display is realized on a white background, which is a typical positive display. The definition of on/off of light emitting diodes and on/off of each electrode is similar to that of embodiment 2-1.

Fig. 17 shows an example of actual display. In the second embodiment, in the sub-frame when the backlight emits white light, the rigid electrode e2 is set to be in the conduction state to realize the white display of the background. The method of controlling the light transmission/light shielding of the liquid crystal display unit is similar to that of Embodiment 2-1.

If the rigid electrode (e2) is in the conduction state, it should be considered that due to the influence of the display of the electrode (e2), in the display area where the rigid electrode e2 is superimposed on any of the segment electrodes a2~d2, the color mutation phenomenon of the segment display may occur . The inventors have found that in the sub-frame when the electrode e is set to the on state, by setting the electrodes in the segment electrodes a~d to the on state to display a color light different from white, the superimposed electrode area is shaded The emitted light from the backlight can prevent color mutation. For example, since the electrode a2 has the same ON/OFF state as the electrode e in all subframes, black display (light shielding state) is realized.

If it is desired to display another color, the driving voltage is set to a state different from that of the electrode e2 (one of which is an on state and the other is an off state) in a sub-frame when light of that color is emitted by the backlight.

In the table shown in FIG. 16, the on/off of the control voltage is used so that the electrode a2 is used for black (BK) display, the electrode b2 is used for red (R) display, the electrode c2 is used for yellow (Y) display, and Electrode d2 is used for white (W) display, as shown in FIG. 17 . Similar to the first embodiment, by adjusting the on/off and luminous intensity of the R, G, and B light-emitting diodes, it is possible to emit light of various colors other than those shown in the table.

Example 2-3

FIG. 19 shows a table illustrating a driving method of the liquid crystal display device according to the third embodiment. In embodiments 2-3, a color segment display is realized on a desired color background. The definitions of on/off of the light emitting diode and on/off of each electrode are similar to those in Embodiment 2-1.

Fig. 19 shows an example of actual display. In Fig. 19, the blue display is used as the background color. In the sub-frame when the backlight emits blue light, the electrode e is set to be in a conduction state. The control method of the light transmission/light shielding state of the liquid crystal display unit is similar to that of Embodiment 2-1.

The color shift phenomenon can be prevented in a similar manner to Example 2-2.

In the table shown in FIG. 18, the on/off of the voltage is controlled so that the electrode a2 is used for white (W) display, the electrode b2 is used for red (R) display, the electrode c2 is used for black (BK) display, and Electrode d2 is displayed in blue (B), as shown in FIG. 19 . Similar to the first embodiment, by adjusting the on/off and luminous intensity of the R, G, and B light-emitting diodes, it is possible to emit light of various colors other than those shown in the table.

As in the above-mentioned embodiment 2, in the region where the electrodes of the two liquid crystal cells of the liquid crystal display device 101 overlap, even if the driving voltages of the two liquid crystal cells are not only in the off state but also in the on state, the light from the backlight can be shielded. . Therefore, it is possible to provide a multi-color liquid crystal display device capable of preventing sudden color changes and display drift and improving display quality.

Since the display brightness can be adjusted by the backlight, the voltage applied to the liquid crystal cell can be determined under the condition (all on/all off) under which the response speed becomes the maximum, and there is an advantage that it is not necessary to implement a method that significantly reduces the response speed of the liquid crystal Gradation display.

Example 3

The inventor has created a liquid crystal display capable of realizing multi-color display without color mutation phenomenon.

20A and 20B show examples of electrode patterns of a double liquid crystal cell. The liquid crystal cells 1a and 1b have transparent electrodes for displaying according to voltage applied to the liquid crystal layer. One unit (called display unit) has segment electrodes for segment display, such as electrodes a3~d3 and e3-1~e3-7 shown in Figure 3A, and the other unit (called background display unit) has segment electrodes for segment display. Rigid electrode f for displaying the entire active display area. Or a display unit or a background display unit may be provided at the upper portion (at the rear side).

Fig. 21 is a conceptual diagram illustrating grayscale display. An example of simple control is used in this embodiment, in which when the background display unit is set in a driving state or a non-driving state, the voltage applied to the display unit is controlled to achieve a grayscale display of a desired tone. If grayscale display is not implemented, the liquid crystal display unit enters a light-transmissive state by setting the background display unit 1b to an on (or off) state and setting the display unit to an off (or on) state. In this embodiment, the light transmission of the backlight unit is adjusted by adjusting the voltage applied to the display unit, thereby realizing gray scale display. In the example shown in FIG. 21 , in order to transmit half of the light of the backlight, the background display unit is set to an on (or off) state and the display unit is set to an on (or off) state. In this embodiment, the voltage application state of gradation display is represented by O/O ON (O/O is the tone ratio of gradation display). An embodiment in which one frame of driving voltage is divided into three subframes will be described.

Example 3-1

Fig. 22 shows a display example. In Embodiment 3-1, segment display is realized on a white background. In Example 3-1, a color segment display is realized on a white background, which is a typical positive display. The rigid electrode f3 is larger than the segment electrode and formed to cover almost the entire display area. The segment electrodes in the watch shown in FIG. 7 constitute the display area. The display color of the electrode f3 in the table is different from the color of the background display area of the display area defined by the segment electrodes. For example, color intensity is indicated by prepending a fractional value to the color name, for example, 1/2 blue if the blue intensity is half the normal intensity. The settings in Example 3-1 are: a3-cyan, b3-purple (display intensity may be consistent with temperature), c3-cyan, d3-purple, e3-1-cyan, e3-2-2/3 Cyan, e3-3-1/3 cyan, e3-4-black, e3-5-1/3 magenta, e3-6-2/3 magenta, e3-7-magenta, and f3-white.

FIG. 23 shows a table illustrating a driving method of the liquid crystal display device of the second embodiment. Figure 23 shows the on/off state of each R, G and B light-emitting diode in each subframe, the segment electrodes a3～d3 and e3-1～e3-7 on the display unit and the background display The on/off status of the rigid electrodes f3 on the unit, and each color displayed in the display area defined by each electrode. The on-state of the light-emitting diode corresponds to a light-emitting state, and the off-state corresponds to a non-light-emitting state. The on state of each electrode corresponds to a driving state, and the off state corresponds to a non-driving state.

Example 3-1 uses a TN liquid crystal cell. If the dual TN LC cells with opposite twist directions are both in the off state, both cells cancel the light twist, so that the LC display cell with crossed polarizers enters a light-blocking state. If both cells are in the on state, the liquid crystal molecules in the cell rise vertically so that light passes through the liquid crystal cell without any distortion, and the liquid crystal display cell with crossed polarizers enters a light-blocking state. If one of the cells is in the on state, the light passes through the cell in the on state without any twist, and the light is twisted by 90° in the cell in the off state. The liquid crystal display unit thus enters a light-transmitting state. In this embodiment, although relative twist directions are used to obtain the best viewing angle properties, it is contemplated that the same twist directions could also be used.

In each subframe, the LEDs emit light of the corresponding color. Various colors of light can be emitted by adjusting the on/off state and luminous intensity of each of the R, G, and B light-emitting diodes.

In the sub-frame when the backlight emits white light, all the segment electrodes and the rigid electrodes f are set to conduction state, thus realizing the white display of the background (areas not superimposed on the segment electrodes). According to each subframe, each segment electrode is determined to be in an on or off state. In the display area where the rigid electrode f of the background display unit is superimposed on each segment electrode of the display unit, if one of the units is in a conduction state, the liquid crystal display unit enters a light-transmissive state. If both units are in the on or off state, the liquid crystal display unit enters the light-shielding state. If the color intensity of electrodes b3, e3-2, e3-3, e3-5, e3-6, etc. is to be set (for example, if the air conditioner temperature is represented by color intensity), then there will be a drive waveform with an effective voltage capable of gray scale display Applied across segmented electrodes. The effective voltage of the driving waveform can be controlled by adjusting the turn-on voltage, by sequentially driving the pulse timing of the turn-on waveform, or other methods.

From the table shown in Figure 23, it can be seen that the liquid crystal display device with controlled liquid crystal cells and backlight without color mutation can emit light of multiple colors more than the number of sub-frame divisions, and can eliminate the problems caused by parallax and ghosting. Display problems such as color loss and discoloration, at most when grayscale display cannot be achieved.

Example 3-2

Fig. 24 shows a display example. In Example 3-2, color segment display is realized on a black background, which is a typical positive display. The definition of the on/off state of the light emitting diode and the on/off state of each segment electrode is the same as that in Embodiment 3-1. In Embodiment 3-2, a greater number of colors can be displayed than in the first embodiment by the time-sequential division color mixing method. It should be noted, however, that this embodiment is used under the condition that the color shift phenomenon is allowed.

FIG. 25 shows a table illustrating a driving method of the liquid crystal display device of the second embodiment. As shown in Figure 9, the settings in the second embodiment are: a3-blue, b3-red or blue (the display intensity may be consistent with the temperature), c3-blue, d3-red, e3-1-blue , e3-2-cyan, e3-3-1/2 cyan, e3-4-black, e3-5-1/2 fuchsia, e3-6-fuchsia, e3-7-red, and f-white. The number of colors that can be displayed is larger than that of Example 3-1.

As mentioned above, when the driving voltage of the liquid crystal display unit is not only in the off state but also in the off state, the liquid crystal display unit 101 can shield the light from the backlight in the display area where the electrodes of the two liquid crystal units overlap. Therefore, it is possible to provide a multi-color liquid crystal display device capable of preventing display drift and the like and improving display quality.

By controlling the liquid crystal cells to enable grayscale display, it is also possible to provide a liquid crystal display device capable of displaying various colors.

Another display device capable of employing the present invention may be a projection type display device. 26A and 26B show examples of projection-type display devices.

The projection type display device shown in FIG. 26A has a structure in which a light source LS for emitting parallel light, a polarizer X1, a double-layer structure panel SP, a polarizer X2, and a screen SC are sequentially arranged in this order along the light propagation direction. Polarizers X1 and X2 are arranged in a cross-Nicol relationship.

The structure of the projection type display device shown in FIG. 26B is that a light source LS such as a point light source, a polarizer X1, a double-layer structure panel SP, a polarizer X2, a Fresnel prism FL and Screen SC.

Using such a projection system to project an image on a screen SC, the observer sees a light image projected onto the screen and generally perpendicular to the substrate so that there is no discernible difference between the viewing angles.

The present invention has been described with reference to the embodiments. The present invention is not limited thereto. For example, the liquid crystal unit using the double-layer structure panel SP is not limited to the TN liquid crystal unit, but for those of ordinary skill in the art, as long as the two liquid crystal units meet the conditions of shielding light from the backlight in the on and off states, this It is obvious that the invention can also be applied to vertical alignment type cells, STN cells, ferroelectric liquid crystal cells, and the like.

FIG. 27 shows an example of a transmission axis of a polarizer and a rubbing direction of a liquid crystal cell of a display device using a vertically aligned liquid crystal cell as a double-layer structure panel. In order from the left, the four coordinate axes correspond to the polarizer X1, the vertical alignment liquid crystal display unit VC1, the vertical alignment liquid crystal display unit VC2, and the polarizer X2. As shown, rubbing treatment is performed so that the direction in which the liquid crystal molecules fall becomes vertical when a voltage is applied to the double vertically aligned liquid crystal cell.

If a chiral material is added to the liquid crystal cell so that the liquid crystal molecules are twisted while the voltage is applied down, it is set in such a way that the liquid crystal layers of the liquid crystal cell have the same chiral pitch and opposite twist directions.

Although a segment type electrode is used for a display unit, a dot matrix type liquid crystal unit in which a plurality of pixels (dots) are provided may also be used.

Furthermore, in the embodiment, the rigid electrode f is used to display the entire effective display area of the background display unit. The background display unit may have a plurality of display areas. In this case, among the plurality of display areas of the background display unit, there is a display area where the liquid crystal molecules are not driven. In typical examples, these areas appear to be displayed in black. This black display can be achieved by mask printing. Mask printing may use a black mask, or may use a color that matches the decorative color of the peripheral outline of the display device.

The invention has been described in connection with the preferred embodiments. The present invention is not limited to the above-described embodiments. It is obvious to those skilled in the art that other various modifications, improvements, combinations, etc. can be made.

Claims (17)

1. A liquid crystal display device, comprising: A first liquid crystal unit comprising a first pair of opposing substrates and a first liquid crystal layer held between said first pair of substrates, said first pair of substrates having at least a first pair of pixel electrodes for displaying predetermined characters and numbers , and the alignment state of the first liquid crystal layer can be controlled by adjusting the voltage applied to the first pair of pixel electrodes; A second liquid crystal cell comprising a second pair of opposing substrates having a second liquid crystal layer held between said second pair of substrates, said second pair of substrates having a region for completely covering said predetermined characters and numerals Two pairs of pixel electrodes, and the alignment state of the second liquid crystal layer can be controlled by adjusting the voltage applied to the second pair of pixel electrodes; Two crossed polarizers are arranged on both sides of the double-layer structure panel including the first and second liquid crystal cells along the normal direction of the substrate; a light source capable of emitting light of a plurality of colors; and a control circuit time-sequentially dividing one frame into a plurality of subframes, emitting light of a predetermined color in each subframe, and controlling said double-layer structure panel including said first and second liquid crystal cells in synchronization with light emission The state of light transmission and light occlusion of multiple display areas, Wherein, the first and second liquid crystal units are configured to be in a mutual optical compensation relationship in both the driving state and the non-driving state. 2. The liquid crystal display device according to claim 1, wherein said control circuit controls in such a manner that said plurality of display regions defined by electrodes of said first liquid crystal cell and electrodes of said second liquid crystal cell The light-transmitting state is achieved only in one of the subframes or in all of the subframes. 3. The liquid crystal display device according to claim 2, wherein if the first and second liquid crystal cells defining each of the plurality of display areas are in a driven state or a non-driven state, the display area Each of them enters the light-shielding state. 4. The liquid crystal display device according to claim 3, wherein the light source comprises a light emitting diode. 5. The liquid crystal display device according to claim 3, wherein the light source emits parallel light. 6. The liquid crystal display device according to claim 3, wherein the light source is a point light source emitting radiant light. 7. The liquid crystal display device according to claim 1, wherein the grayscale display has an intermediate alignment state between a driven state and a non-driven state by controlling an alignment state of liquid crystals of at least one of the first and second liquid crystal cells to implement. 8. The liquid crystal display device according to claim 7, wherein said control circuit controls in such a manner that said plurality of display regions defined by electrodes of said first liquid crystal cell and electrodes of said second liquid crystal cell The light-transmitting state is achieved only in one of the subframes or in all of the subframes. 9. The liquid crystal display device according to claim 8, wherein if the first and second liquid crystal cells defining each of the plurality of display areas are in a driven state or a non-driven state, the display area Each of them enters the light-shielding state. 10. The liquid crystal display device according to claim 9, wherein the light source comprises a light emitting diode. 11. The liquid crystal display device according to claim 9, wherein the light source emits parallel light. 12. The liquid crystal display device according to claim 9, wherein the light source is a point light source emitting radiant light. 13. A method for driving a liquid crystal display device, the liquid crystal display device comprising: A first liquid crystal unit comprising a first pair of opposing substrates and a first liquid crystal layer held between said first pair of substrates, said first pair of substrates having at least a first pair of pixel electrodes for displaying predetermined characters and numbers , and the alignment state of the first liquid crystal layer can be controlled by adjusting the voltage applied to the first pair of pixel electrodes; A second liquid crystal cell comprising a second pair of opposing substrates having a second liquid crystal layer held between said second pair of substrates, said second pair of substrates having a region for completely covering said predetermined characters and numerals Two pairs of pixel electrodes, and the alignment state of the second liquid crystal layer can be controlled by adjusting the voltage applied to the second pair of pixel electrodes; Two crossed polarizers are arranged on both sides of the double-layer structure panel including the first and second liquid crystal cells along the normal direction of the substrate; a light source capable of emitting light of a plurality of colors; and a control circuit time-sequentially dividing one frame into a plurality of subframes, emitting light of a predetermined color in each subframe, and controlling said double-layer structure panel including said first and second liquid crystal cells in synchronization with light emission The state of light transmission and light occlusion of multiple display areas, Among them, the driving method is controlled in such a manner that a display area that enters a light-shielded state in one subframe enters another subframe. 14. The driving method of the liquid crystal display device according to claim 13, wherein: Each frame includes a first subframe and a second subframe; The emission color of the light source includes a first color and a second color; and The second color is transmitted in the second subframe in a display area different from the display area in which the first color is transmitted in the first subframe. 15. A method for driving a liquid crystal display device, the liquid crystal display device comprising: A first liquid crystal unit comprising a first pair of opposing substrates and a first liquid crystal layer held between said first pair of substrates, said first pair of substrates having at least a first pair of pixel electrodes for displaying predetermined characters and numbers , and the alignment state of the first liquid crystal layer can be controlled by adjusting the voltage applied to the first pair of pixel electrodes; A second liquid crystal cell comprising a second pair of opposing substrates having a second liquid crystal layer held between said second pair of substrates, said second pair of substrates having a region for completely covering said predetermined characters and numerals Two pairs of pixel electrodes, and the alignment state of the second liquid crystal layer can be controlled by adjusting the voltage applied to the second pair of pixel electrodes; Two crossed polarizers are arranged on both sides of the double-layer structure panel including the first and second liquid crystal cells along the normal direction of the substrate; a light source capable of emitting light of a plurality of colors; and a control circuit time-sequentially dividing one frame into a plurality of subframes, emitting light of a predetermined color in each subframe, and controlling said double-layer structure including said first and second liquid crystal cells in synchronization with light emission the state of light transmission and light occlusion of multiple display areas of the panel, Wherein, the driving method is controlled in such a way that grayscale display is implemented by controlling the alignment state of liquid crystals in at least one of said first and second liquid crystal cells to have an intermediate alignment state between a driven state and a non-driven state. 16. The driving method of the liquid crystal display device according to claim 15, wherein: A display area that enters a light-transmitting state in one subframe is controlled to enter a light-shielding state in another subframe; Each frame includes at least a first subframe and a second subframe; the light source is capable of emitting at least a first color and a second color; and The second color is transmitted in the second subframe in a display area different from the display area in which the first color is transmitted in the first subframe. 17. The driving method of a liquid crystal display device according to claim 15, wherein the mixed color display is implemented by transmitting light of a primary color in each of the subframes and bringing a display area into a light transmission state in a plurality of subframes.

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