KR20100124205A - Liquid crystal image display device - Google Patents

Abstract

PURPOSE: A liquid crystal image displaying apparatus is provided to prevent light emitting efficiency from being prevented using a rare gas fluorescent lamp as the light source of a backlight unit. CONSTITUTION: A liquid crystal panel includes a pixel group which is capable of converting an optical shielding state and an optical transmitting state. A backlight unit is arranged on the rear side of the liquid crystal panel. Light source includes a pair of external electrodes(14) and three rear gas fluorescent lamps(1,2,3). Driving circuits(71, 72, 73) is in connection with the rear gas fluorescent lamps. Pixels display images using a field sequential mode.

Description

Liquid crystal image display device {LIQUID CRYSTAL IMAGE DISPLAY DEVICE}

The present invention relates to a liquid crystal image display device. In particular, it relates to a liquid crystal image display device which displays a color image in a field sequential manner.

In a liquid crystal image display device using a color filter as a backlight unit, since the color filter absorbs the light of the backlight unit, there is a problem that the utilization efficiency of the light irradiated from the backlight is low.

Therefore, in the liquid crystal drive method of the liquid crystal image display device, the drive method called the field sequential method which displays several primary-color components, such as RGB sequentially by time division, and recognizes a color image to a viewer has been proposed conventionally, and is known. .

In the field sequential liquid crystal image display device, for example, three colors of visible light sources are used as the light source, and the liquid crystal display panel itself does not require a color filter and has the advantage of high light utilization efficiency. Moreover, there exists an advantage that the process of forming a color filter is unnecessary.

8 shows a backlight unit of a conventional field sequential method. 9 is a timing chart which shows the lighting method of the backlight of the conventional field sequential system.

In FIG. 8, the high voltage generating means 184 includes a DC power supply 181, a semiconductor switch 182 using a transistor, and the like, and an inverter 183. 185, 186, and 187 are cold cathode tubes which emit three visible colors of red (R), green (G), and blue (B), respectively, and switch means 188, 189, and 190 of the respective cold cathode tubes. ).

In Fig. 9, when high pressure is supplied in accordance with the opening and closing of the switch 2, the red, green, and blue light sources are sequentially time-divided and turned on to emit light of three colors. Thereby, it can function as a light source for the liquid crystal image display apparatus of a field sequential system.

Japanese Patent Laid-Open No. 11-160675

By the way, in the field sequential liquid crystal image display apparatus, very high speed operation | movement is calculated | required with a liquid crystal and a light source. For example, when the period for displaying one image is 1/30 second, and further dividing it into periods of three colors, the display is switched every 1/90 seconds. In addition, a faster operation than this is actually required.

However, since it is a high-speed operation, the lighting duration is extremely short, and the temperature of the lamp does not sufficiently increase, so that a desired amount of light cannot be obtained unless the vapor pressure of the light-emitting substance encapsulated inside the cold cathode tube, for example, mercury, does not rise, There was a problem that the luminous efficiency with respect to the input power was bad. That is, the effect of power saving which is one of the advantages of field sequential was not enough. In addition, it is expensive to obtain a backlight having the same illuminance using the light source as an LED.

Accordingly, an object of the present invention is to provide a power-saving liquid crystal image display device having a high luminous efficiency and displaying a color image by a field sequential method.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention is the liquid crystal image display apparatus provided with the backlight unit provided with the light source which emits three colors of visible light, a drive circuit, and a liquid crystal display panel, The said liquid crystal display panel displays, A pixel group disposed two-dimensionally with respect to a surface and capable of independently switching a state of shielding / transmitting light, wherein the backlight unit is disposed on a rear surface of the liquid crystal panel, and the light source is displayed on the liquid crystal display panel. The light source is disposed two-dimensionally in correspondence with a surface, and the light source is capacitively coupled to a pair of external electrodes provided with a rare gas inside the light emitting tube and disposed along the tube axis outside the light emitting tube, and the pair of external electrodes. In addition to having a starting electrode made of a conductor provided in the light emitting tube so as to emit light of three colors of visible light by the phosphors coated in the light emitting tube, And a rare gas fluorescent lamp connected to a drive circuit capable of supplying power independently, wherein a frame period for displaying one image on the pixel is divided into three frames based on an image signal. The sub-frame period is configured, and in each of the sub-frame periods, a rare gas fluorescent lamp that emits three colors of visible light is sequentially turned on by varying the time ratio within the sub-frame period according to the required luminance. An image is displayed by a field sequential method, which is driven to transmit light in synchronization with the turning on of the rare gas fluorescent lamp.

In addition, the present invention provides a driving circuit in which the rare gas fluorescent lamp has a plurality of divided external electrodes divided such that at least one of the pair of external electrodes is spaced apart in the tube axis direction, and is capable of supplying power independently to each of the divided external electrodes. Is connected, and the starting electrode is provided for each of the divided external electrodes.

According to the present invention, in the field sequential liquid crystal image display device, a rare gas fluorescent lamp is used for the backlight light source, so that the luminous efficiency does not decrease even if the lighting is extremely short. In addition, these rare gas fluorescent lamps are disposed two-dimensionally in correspondence with the display surface of the liquid crystal display panel to form a direct backlight, and can be illuminated in each area, so that they can be turned on as necessary and are power-saving. . Moreover, since all the rare gas fluorescent lamps are provided with a starting electrode and easy to start lighting, they are suitable as a light source of a field sequential method.

In addition, since a driving circuit is connected to each lamp that emits three colors of visible light and can be independently dimmed and controlled, it is a power-saving type and the contrast ratio can be improved.

Further, according to the present invention, since the dividing external electrodes divided in the tube axis direction are provided and the drive circuits are connected to each of them, selective dimming in the tube axis direction is possible, so that the backlight unit can be constituted by a small number of lamps and economically. to be. Moreover, since all the divided external electrodes are provided with the starting electrode, it is easy to start the lighting and is suitable as a field sequential light source.

1 (a) is a cross-sectional view showing a rare gas fluorescent lamp according to the first embodiment of the present invention, (b) is a cross-sectional view along the line A-A ', and (c) is a cross-sectional view along the line B-B'.
FIG. 2A is an enlarged cross-sectional view for explaining the starting electrode, and FIG. 2B is an enlarged cross-sectional view seen from different viewpoints.
3 is a block diagram for explaining a lighting circuit of a three-color light source according to the present invention.
4 is a front view of a backlight unit in which three color light sources according to the present invention are arranged.
5 is a perspective view showing the configuration of a liquid crystal image display device according to the present invention.
6 is a timing chart for explaining a display method of a liquid crystal image according to the present invention.
Fig. 7A is a sectional view showing a rare gas fluorescent lamp according to a second embodiment of the present invention, and Fig. 7B is a front view of a backlight unit using the same.
8 is a diagram illustrating a conventional backlight unit.
9 is a timing chart showing a lighting method of a conventional backlight unit.

A description is given below with reference to the drawings. Fig.1 (a) is sectional drawing of the rare gas fluorescent lamp which concerns on 1st Embodiment of this invention, (b) is sectional drawing of the A-A 'line, and (c) is sectional drawing of the B-B' line.

In FIG. 1, the rare gas fluorescent lamp 1 includes a light emitting tube 11 made of a light-transmissive dielectric material such as glass, and the light emitting tube 11 is disposed on an outer surface of the light emitting tube 11. A pair of band-shaped external electrodes 13 and 14 are provided along the tube axis direction of the light emitting tube 11. On the inner surface of the light emitting tube, there is formed a phosphor layer 12 in which phosphors which emit visible light of any one of three primary colors (RGB) of red, green and blue are applied over almost the entire inner surface of the light emitting tube.

The external electrodes 13 and 14 are not particularly limited as long as they are conductive. For example, gold, silver, nickel, carbon, gold palladium, silver palladium, platinum, aluminum, and the like can be suitably used. It is formed by attaching a tape-like metal to the outer surface of the sheet or by screen printing and firing the conductive paste. Except the power supply part of an external electrode, it coat | covers with the insulating film which baked the glass paste.

The glass constituting the light emitting tube 11 is, for example, barium glass. Alternatively, copal glass, tungsten glass, soda-lime glass, borosilicate glass, aluminosilicate glass, or the like may be used.

The rare gas enclosed in the light emitting tube 11 is, for example, xenon, krypton, argon, neon or a mixed gas thereof, and is encapsulated in about 10 to 300 Torr.

The phosphor 12 coated on the inner surface of the light emitting tube 11 is, for example, a phosphor emitting red (R) is a europium-activated yttrium oxide phosphor (Y ₂ O ₃ : Eu) or (Y, Gd) BO ₃ : Eu, phosphor emitting green (G), cerium terbium-activated phosphate lantern phosphor (LaPO ₄ : Ce, Tb), phosphor emitting blue (B) is europium-activated barium aluminate magnesium phosphor ( BaMgAl ₁₀ O ₁₇ : Eu).

When a high frequency voltage is applied between the external electrodes 13 and 14, excimer discharge is generated in the discharge space S through the light emitting tube 11, which is a dielectric material, and the phosphor is excited by the vacuum ultraviolet light generated by the excimer discharge. The visible light of any one of red, green, and blue is emitted to the outside of the light emitting tube 11.

According to such an external electrode type rare gas fluorescent lamp, since the rare gas is mainly sealed inside the light emitting tube and emits light by excimer discharge, the light emission principle for exciting the phosphor is also different from that of the cold cathode tube, and there is no need to consider temperature rise. It is also equipped with sufficient responsiveness for driving in a field sequential manner.

As shown in Fig. 1 (c), the external electrodes 13 and 14 are disposed with the light emitting tube interposed therebetween, and the surface thereof is covered with the insulating film 15. When looking at the circumferential direction of the light emitting tube 11, when the surface other than the part in which the external electrode is provided, and the surface, the left and right are opened, and this becomes a light output part and emits visible light. This opening is large enough compared with the width | variety in the circumferential direction of an external electrode, and has a structure with high light utilization efficiency.

As shown in FIG. 1 (b), on the inner surface side of the light emitting tube 11 corresponding to the ends of the external electrode 13 and the external electrode 14, the starting electrode 21 is arranged in the circumferential direction of the light emitting tube 11. It is formed in C shape over half or more of a circumference. This starting electrode 21 generates longitudinal discharge for improving startability.

FIG. 2A is an enlarged cross sectional view for explaining the starting electrode, and FIG.

In Fig. 2A, the starter electrode 21 is capacitively coupled to the external electrodes 13 and 14 via a pipe wall of the light emitting tube 11, which is a dielectric. The starting electrode 21 is, for example, a conductor made of carbon paste, and is formed by drying and firing. The starting electrode 21 is provided continuously in the circumferential direction with respect to the tube axis direction, and is, for example, C-shaped or the like as shown in Fig. 1B.

In addition, the starter electrode 21 is provided so as to intersect the external electrode 14 when viewed from the time point C, as shown in FIG. . Let this be the intersection 23. This is for minimizing the distance between the starting electrode 21 and the external electrode 14 to facilitate the generation of vertical discharge, and is formed so as to have the same relationship with the external electrode 13. The vertical discharge mainly occurs near the intersection 23.

In the vicinity of the intersection 23, the phosphor layer 12 is not provided and is exposed. In the intersecting portion 23, when the starter electrode 21 is covered with the phosphor layer 12, the starter voltage is increased by the phosphor, so that this is partially removed, so as to increase the light emitting area for the other regions. The phosphor layer 12 is provided.

Since the start discharge 21 spreads the vertical discharge generated at a low voltage into the light emitting tube as preliminary ionization discharge, the startup from the voltage application to the excimer discharge is performed quickly. That is, it is easy to start lighting and it is preferable to perform blinking lighting for a short time in a field sequential system.

Next, the three-color light source formed using said rare gas fluorescent lamp is demonstrated. 3 is a block diagram for explaining a lighting circuit of a three-color light source.

In FIG. 3, since the rare gas fluorescent lamps 1, 2, and 3 arranged in parallel are the same as the rare gas fluorescent lamp 1 shown in FIG. 1, description is abbreviate | omitted. In these rare gas fluorescent lamps 1, 2, and 3, phosphors for emitting visible light of three colors of red, green, and blue are coated on the inner surface of the light emitting tube. For example, a phosphor for emitting visible light of red (R), (2) green (G), and (3) blue (B) is applied to the rare gas fluorescent lamp 1.

These three rare gas fluorescent lamps constitute one tricolor light source, each of which emits visible light by one color. This tricolor light source becomes tricolor light source TC11 arrange | positioned two-dimensionally as a part of backlight unit.

The external electrode 14 provided outside the light emitting tubes of the rare gas fluorescent lamps 1, 2, and 3 is a ground electrode, and the external electrode 13 is an electrode for supplying a high voltage. Here, although the external electrode 14 is grounded by common wiring, it may be separately.

The drive circuits 71, 72, and 73 are connected to the external electrodes 13 of the rare gas fluorescent lamps 1, 2, and 3.

What constitutes each drive circuit 71, 72, and 73 is the transformer 41, 42, and 43, the DC power supply 31, 32, and 33, the switching element circuits 51, 52, and 53, a switching operation. Signal generating circuits 61, 62, and 63; The switching element circuit is comprised of a push-pull circuit system, a half bridge circuit system, a full bridge circuit system, etc., for example, is a half bridge circuit system.

A control signal generation circuit 80 is connected to each drive circuit, and an image signal processing circuit 81 is connected to the control signal generation circuit 80.

The DC voltage supplied from the DC power supply is converted into an AC voltage by the switching element circuit, stepped up by a transformer, and supplied to each external electrode as lighting power. The switching operation signal generation circuit generates a PWM signal which is a dimming signal for turning on and off the switching element of the switching element circuit.

When the image signal processing circuit 81 receives an image signal, the control signal generation circuit 80 switches a dimming signal for discharging each of the rare gas fluorescent lamps determined on the basis of the image signal. To be sent.

When the switching operation signal generating circuits 61, 62, and 63 receive the dimming signal, the switching operation signal generating circuits 61, 62, and 63 transmit an operation signal for operating the switching element circuits 51, 52, and 53 based on the dimming signal, and the DC power supply 31 The direct current voltage supplied from the circuit 1) is converted into an alternating voltage by the switching element circuits 51, 52, and 53 to light each lamp.

Dimming is performed by so-called duty dimming which turns on a rare gas fluorescent lamp by varying the time ratio of lighting time within a certain period by a PWM signal.

4 is a front view of the backlight unit in which the three color light source groups are arranged.

The backlight unit 100 is disposed on the rear surface of the liquid crystal display panel described later, and functions as a so-called direct light source. The three-color light sources TC11 to TC34 constituted by the noble gas fluorescent lamps arranged in parallel are two-dimensionally arranged corresponding to the display surface of the liquid crystal display panel, and the three color light sources are independently fed and dimmed, so that the display surface of the image The brightness can be controlled by controlling the luminance for each region within the region, and unnecessary lighting can be saved. Moreover, since contrast can be added regardless of control of a liquid crystal, contrast ratio also improves.

FIG. 5 is a perspective view showing the configuration of a liquid crystal image display device using the backlight unit shown in FIG. 4.

In FIG. 5, the backlight unit 100 is disposed on the rear surface of the liquid crystal display panel 200.

Between the backlight unit 100 and the liquid crystal display panel 200, a diffusion plate 92, a diffusion sheet 93, and a directivity control sheet 94 are provided to make light uniform in the emission direction. Is installed.

The liquid crystal display panel 200 is a monochrome liquid crystal display in which each pixel is arranged two-dimensionally in a matrix form and displays a black and white image (monochrome gray scale image) which can switch a state where each light is shielded / transmitted independently. It is a panel and does not have a color filter. In addition, although not shown in figure, the liquid crystal display panel 200 consists of a polarizing plate and a liquid crystal display element, for example, and a liquid crystal display element consists of a glass substrate, a liquid crystal layer, a transparent electrode, etc. That is, the liquid crystal display panel 200 plays only the role of the shutter which switches the shielding / transmission of the light emitted from the backlight unit 100 which is a group of three color light sources.

The liquid crystal display panel 200 is connected to the liquid crystal display panel drive circuit 83. The liquid crystal panel drive circuit 83 is connected to the control signal generation circuit 82, receives information from the image signal, and independently drives each pixel of the liquid crystal display panel 200 in synchronization with light emission of the backlight unit. Can be.

FIG. 6A is a timing chart for explaining a display method of any one pixel in the liquid crystal image display device shown in FIG. 5, and FIG. 6B shows another example. The timing of turning on the rare gas fluorescent lamps for displaying red, green, and blue, respectively, is shown. In addition, in the timing chart, during the period indicated as "ON", the lamp as the light source is turned on and the liquid crystal display panel as the shutter is also driven in synchronization with the light. . In the period when it is "off", an image may not be displayed, for example, a lamp may not be lit or liquid crystal may shield light. In addition, although liquid crystal response time, such as what is called a rising and falling, is actually considered in order to change the state of a liquid crystal, it focuses only on the lighting timing of a lamp, and is not shown here.

Here, the frame period FS1 shown in Fig. 6A shows a period in which one image is displayed. When the next frame period FS2 is started, the next image is displayed. One frame period is constituted by sub frame periods SFS11, SFS12, and SFS13 that are equally time-divided into three periods.

In one frame period, for example, FS1 shown in FIG. 6, in the first sub frame period SFS11, only a lamp corresponding to red lights up, and red is displayed on the liquid crystal display panel. In the next sub frame period SFS12, only a lamp corresponding to green lights up, and green is displayed on the liquid crystal display panel. In the next sub frame period SFS13, only a lamp corresponding to blue is lit, and blue is displayed on the liquid crystal display panel.

Thus, according to the field sequential method, the subframe period SFS1 corresponding to the display of the red component, the sub frame period SFS2 corresponding to the display of the green component, and the sub frame period SFS3 corresponding to the display of the blue component are sequentially displayed. The color image is displayed by overlapping the colors of the respective sub frame periods.

In each sub frame period, the lighting time ratio of the rare gas fluorescent lamp can be adjusted by adjusting the lighting time ratio (hereinafter referred to as a duty ratio) within a predetermined period according to the dimming signal. For example, the duty ratio is increased when the luminance is brightened, and the duty ratio is reduced when the luminance is darkened. In this way, the components of each color can be adjusted and mixed, the desired color can be expressed based on the image signal, and the luminance can also be adjusted.

Since the rare gas fluorescent lamp is a light source, the temperature rise is not sufficient even if it is flashing for a short time, so that the luminous efficiency does not decrease. As a result, the duty ratio can be reduced as needed, the light can be reduced, and power can be saved.

As shown in the second frame period FS2, in the last sub frame period SFS23 of the frame period FS2, the blue component and the red component are set to be turned on at the same time. When two or more colors are turned on at the same time as described above, the display can be displayed at high luminance in addition to the color of the screen to be displayed as compared with when the display is divided into three and lit. Since this is according to the visibility characteristic of each color component, the green component has the highest visibility, and then uses what becomes a red component and a blue component.

In addition, as shown in Fig. 6B, three colors may be simultaneously turned on in any period as in the lighting state within the period of SFS13. In this case, the color displayed by mixing of three colors is white. The lighting of two or more colors simultaneously may be in any subframe period, and for example, as shown in SFS21, red and green may be simultaneously lit in the first subframe period.

In this manner, each lamp of the three-color light source is independently turned on, and only one color or two colors can be turned on within one sub frame period.

Usually, in the field sequential method, lighting of two or more colors at the same time is not performed, but in the present invention, in any one image, in one sub frame period obtained by dividing one frame period for displaying the same by three times, In addition to matching the color of the display screen, the luminance can be improved by using the visibility characteristics by simultaneously lighting two or more light sources to improve the luminance entirely. Therefore, it is possible to make high brightness with little power, and to make high brightness according to the request of an image signal.

Since the display method of the image with respect to one pixel is performed in all the pixels provided in the matrix form in the liquid crystal display panel, luminous efficiency is high and a very power-saving liquid crystal image display device can be implement | achieved.

FIG. 7A is a diagram for explaining the rare gas fluorescent lamp according to the second embodiment of the present invention. FIG. The configuration of the rare gas fluorescent lamp other than the external electrode is the same as that of the rare gas fluorescent lamp shown in Fig. 1 (a). In this figure, the same reference numerals as those in Fig. 1 (a) are omitted.

In FIG. 7A, the external electrodes 131, 132, 133, and 134 are electrodes connected to, for example, the high voltage side, but are divided to be spaced apart from each other in the tube axis direction. In contrast, the external electrode 14 is a shared ground electrode with respect to the external electrodes 131, 132, 133, and 134. The external electrodes 131, 132, 133, and 133 divided in the tube axis direction are also referred to as divided external electrodes, and are collectively referred to as divided external electrode groups. These 131, 132, 133, 134, and 14 are collectively referred to as a pair of external electrodes. In addition, you may divide and install the external electrode 14 in multiple numbers in a tube axis direction.

In addition, for each of the divided external electrodes 131, 132, 133, and 134, the same starting electrode 21 as shown in FIG. 2 is provided. This is because, even if the start electrode 21 is provided only at the end of the lamp, if the distance between each divided external electrode and the start electrode 21 is far from each other, it cannot serve as a moving part. When the external electrodes are divided in this manner, it is necessary to provide a starting electrode for each of the divided external electrodes.

In addition, although the part where the starting electrode is provided becomes a dark part, as shown in FIG.2 (b), the fluorescent substance layer 12 is formed so that only the vicinity of the intersection part 23 of an external electrode and a starting electrode may be exposed. As a result, the light emitting area can be increased.

By separately connecting each of the divided external electrode groups with a drive circuit capable of independently feeding high frequency power, different power can be supplied to each divided external electrode.

For example, when a voltage is applied to the external electrode 131, since discharge is performed only between the external electrode 131 and the external electrode 14, other electrodes such as the external electrode 132 are lit. In the region, no discharge occurs. Since light can be emitted for each of the divided external electrodes in this manner, even one lamp can select and illuminate the lighting region in the tube axis direction, thereby saving unnecessary power.

In addition, although a plurality of external electrodes are formed in one lamp, since the discharge spaces communicate with each other, these external electrodes can be used as preliminary ionization discharges when the divided external electrodes adjacent in the tube axis direction are discharged. , The startability can be improved.

Next, the backlight unit by the three-color light source group formed using the rare gas fluorescent lamp which has this divided external electrode is demonstrated. FIG.7 (b) is a front view of the backlight unit by the three-color light source group which comprised the backlight unit shown in FIG. 4 using the rare gas fluorescent lamp mentioned above.

In FIG.7 (b), the backlight unit 100 arrange | positions three above-mentioned rare gas fluorescent lamps in parallel, and comprises three color light sources, and the red (R), green (G), and blue (B) visible light, respectively is shown. A phosphor layer for emitting light is formed inside the light emitting tube.

In addition, a drive circuit is connected to each divided external electrode divided into four in the tube axis direction of these three lamps. Thereby, substantially the same structure as four tricolor light sources arrange | positioned along the tube axis direction is provided.

Therefore, in FIG. 7B, by using a relatively long lamp and a split external electrode, the same operation as that shown in FIG. 4 is possible as the backlight unit, and the three-color light sources TC11 to TC34 are independent. It can be fed and controlled to light.

According to the backlight unit using the rare gas fluorescent lamp described above, since a plurality of lighting regions can be formed in the tube axis direction using a long rare gas fluorescent lamp, three lamps of each color can be prepared for each of the three color light source groups. It is not necessary and economical because the number of lamps is reduced.

Since the conventional cold cathode tube discharges in the tube axis direction, the lighting region in the tube axis direction cannot be selected to emit light, but this rare gas fluorescent lamp enables selective dimming in the tube axis direction.

Moreover, since a starting electrode is provided for every divided external electrode, it is easy to start and is suitable as a light source for the field sequential system which operates at high speed.

In addition, since the structure and the image display method of the liquid crystal image display apparatus using the backlight unit shown in FIG.7 (b) are the same as that of the backlight unit shown in FIG. 4, it abbreviate | omits description.

1: rare gas fluorescent lamp 2: rare gas fluorescent lamp
3: rare gas fluorescent lamp 11: light emitting tube
12 phosphor layer 13 external electrode
14 external electrode 15 insulating film
21: starting electrode 23: intersection
24: exposed part 31: DC power
32: DC power 33: DC power
41: trance 42: trance
43: transformer 51: switching element circuit
52: switching element circuit 53: switching element circuit
61: switching operation signal generation circuit 62: switching operation signal generation circuit
63: switching operation signal generation circuit 71: driving circuit
72: driving circuit 73: driving circuit
80: control signal generation circuit 81: image signal processing circuit
83 liquid crystal display panel drive circuit 92 diffuser plate
93: diffusion sheet 94: directivity control sheet
95 casing 100 backlight unit
131: external electrode 132: external electrode
133: external electrode 134: external electrode
181: DC power supply 182: semiconductor switch
183: inverter 184: high voltage generating means
185: cold cathode tube 186: cold cathode tube
187: cold cathode tube 188 switch means
189: switch means 190: switch means
200: liquid crystal image display device S: discharge space
TC11 ~ TC34: 3 color light source

Claims (2)

A liquid crystal image display device comprising a backlight unit including a light source for emitting three colors of visible light, a driving circuit, and a liquid crystal display panel,
The liquid crystal display panel is disposed two-dimensionally with respect to the display surface, and includes a pixel group that can switch a state of independently shielding / transmitting light,
The backlight unit is disposed on the rear surface of the liquid crystal panel, the light source is two-dimensionally disposed corresponding to the display surface of the liquid crystal display panel,
The light source includes a pair of external electrodes in which a rare gas is sealed inside the light emitting tube, the pair of external electrodes provided along the tube axis outside the light emitting tube, and a conductor provided in the light emitting tube to capacitively couple the pair of external electrodes. In addition, each of the three rare gas fluorescent lamps for emitting three colors of visible light by the phosphors applied in the light emitting tube,
The rare gas fluorescent lamp is connected to a drive circuit capable of feeding independently,
Based on the image signal, the frame period for displaying one image in the pixel is constituted by three sub frame periods obtained by dividing the frame period into three,
In each of the sub frame periods, a rare gas fluorescent lamp that emits three colors of visible light is sequentially turned on by varying the time ratio within the sub frame period, according to the required luminance.
And the pixel is configured to display an image by a field sequential method, which is driven to transmit light in synchronism with the lighting of the rare gas fluorescent lamp. The method according to claim 1,
The rare gas fluorescent lamp has a plurality of divided external electrodes divided such that at least one of the pair of external electrodes is spaced apart in the tube axis direction, and a drive circuit capable of supplying power independently to each of the divided external electrodes is connected.
And the starting electrode is provided for each of the divided external electrodes.

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