JP2010182531A - Backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit equipped with a rare-gas fluorescent lamp with less electric power consumption and capable of improving a contrast ratio of a liquid crystal display. <P>SOLUTION: In the backlight unit in which the rare-gas fluorescent lamp having a pair of external electrodes arranged along a tube axis is arranged in parallel outside a light-emitting tube, and which is equipped with a driving circuit to light on the rare-gas fluorescent lamp, and a control signal generating circuit to send out a light-adjustment signal to the driving circuit, this is equipped with the driving circuit in which at least one electrode of the external electrodes of the rare-gas fluorescent lamp is divided in a tube axial direction, and connected separately and independently at every divided external electrode, and a starting electrode formed at the inner face of a tube wall in which the external electrode positioned at least at one end of the rare-gas fluorescent lamp is formed. The control signal generating circuit feeds all the external electrodes divided when the rare-gas fluorescent lamp started lighting on against the driving circuit, and after a lapse of a certain period, sends out the light-adjustment signal to dim at every divided external electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a backlight unit including a fluorescent lamp, and more particularly, to a backlight unit including a fluorescent lamp having an external electrode disposed on the outer peripheral surface of an arc tube in which a rare gas is sealed as a discharge gas. In addition, the present invention relates to a backlight lighting method.

  Conventionally, as a fluorescent lamp used for a light source of an OA device, a backlight of a liquid crystal display device, etc., a pair of strip-like external electrodes are disposed on the outer surface of the arc tube, and a high frequency voltage is applied to light the lamp. Noble gas fluorescent lamps are known. A backlight unit of a liquid crystal display device that lights a plurality of these rare gas fluorescent lamps side by side is known.

8A is a cross-sectional view showing a conventional rare gas fluorescent lamp described in, for example, Patent Document 1, FIG. 8B is a cross-sectional view taken along the line ZZ ′, and FIG. 9 shows a conventional rare gas fluorescent lamp. A backlight unit provided.
In FIG. 8A, a rare gas fluorescent lamp 8 includes an arc tube 81 made of a translucent dielectric material, and a pair of strip-shaped external parts spaced apart by sandwiching the arc tube 81 on the outer surface of the arc tube 81. Electrodes 83 and 84 are disposed along the tube axis direction of the arc tube 81. A fluorescent material is applied to the entire inner surface of the arc tube 81, and a luminous gas made of a rare gas such as Xe gas is sealed inside.
When a high frequency voltage is applied between the external electrodes 83 and 84, an excimer discharge is generated in the discharge space S through the arc tube 81 which is a dielectric material, and the phosphor is excited by the vacuum ultraviolet light generated by the excimer discharge. In order to convert the light into visible light, visible light is emitted outside the arc tube 81.

In FIG. 9, the backlight unit 800 includes a plurality of rare gas fluorescent lamps 8 arranged in parallel in a box-shaped casing 95, and a reflection sheet 91 is provided on the back of the rare gas fluorescent lamp 8. ing. Further, a power source (not shown) is disposed on the back surface of the reflection sheet 91, and power can be supplied to each rare gas fluorescent lamp 8.
On the light emission side of the rare gas fluorescent lamp 8, a diffusion plate 92 for emitting light in a planar shape, a diffusion sheet 93, and a directivity control sheet 94 are disposed so as to overlap each other. As described above, a backlight unit including a rare gas fluorescent lamp can provide a planar visible light source suitable for a liquid crystal display device.

JP 2008-243415 A

  In recent years, demand for energy saving in large-sized liquid crystal display devices such as flat-screen televisions has increased, and a backlight unit as a light source is also required to have low power consumption. In addition, the liquid crystal display device is also required to improve the contrast ratio in order to display an image beautifully.

By the way, in the liquid crystal display device, since the liquid crystal itself does not emit light, a backlight such as a rare gas fluorescent lamp or a light emitting diode is required. These backlights supply a constant brightness over the entire screen to be displayed, and the brightness of the image is controlled by the operation of the liquid crystal panel. Therefore, even when the image is dark, power is consumed by providing illumination unnecessarily. In addition, there is a limit to the adjustment of light and dark by the liquid crystal panel, and it is difficult to improve the contrast ratio of light and dark if the backlight is always lit constantly.
Even if the lighting state is controlled for each lamp, the backlight unit using a conventional rare gas fluorescent lamp or a cold cathode fluorescent lamp (hereinafter referred to as CCFL) having an electrode inside the arc tube has only one direction. Only dimming is possible. In particular, since CCFL discharges only in the tube axis direction, it is difficult to adjust light in two directions in a planar shape. In addition, it is uneconomical to increase the number of lamps and drive circuits and to arrange a plurality of lamps in a vertical and horizontal array.

  Accordingly, it is an object of the present invention to provide a backlight unit including a rare gas fluorescent lamp and a method for lighting the backlight unit, which can reduce the power consumption and increase the contrast ratio of the liquid crystal display device.

  In order to solve the above-described problems, the present invention provides a drive circuit for arranging a rare gas fluorescent lamp having a pair of external electrodes arranged along the tube axis outside the arc tube in parallel and lighting the rare gas fluorescent lamp. In the backlight unit including a control signal generation circuit for sending a dimming signal to the drive circuit, at least one of the external electrodes of the rare gas fluorescent lamp is divided in the tube axis direction, and the divided external electrodes A drive circuit that is independently connected to each other, and a starting electrode formed on an inner surface of a tube wall on which an external electrode located at at least one end of the rare gas fluorescent lamp is formed, and the control signal generation circuit includes: The drive circuit is supplied with power to all the divided external electrodes at the start of lighting of the rare gas fluorescent lamp, and is adjusted for each of the divided external electrodes after a certain period of time has elapsed. Characterized by sending a dimming signal.

  Further, according to the present invention, the control signal generation circuit is configured such that, based on the image signal, the start of each frame display period of the image signal is set to the start of lighting, and the light is adjusted for each frame display period. An optical signal is transmitted.

  Further, the present invention is characterized in that the dimming signal is a duty dimming signal for adjusting a duty ratio of an on period and an off period of lighting of the rare gas fluorescent lamp by the driving circuit.

  According to the present invention, even when the external electrodes divided in the tube axis direction of the rare gas fluorescent lamp and in which the starting electrode is not formed need to be flashed and dimmed, the external electrode where the starting electrode is formed is provided. By starting the discharge for all the divided external electrodes at the same time as the electrodes, a discharge is quickly generated in the entire arc tube, and then the light can be adjusted for each external electrode. That is, discharge can be started easily from a low voltage, and light control can be performed for each area of the screen, so that power consumption is small and the contrast ratio can be improved.

  According to the present invention, on the basis of the image signal, at every frame start timing of the image signal, the start-up lighting is performed for all the divided external electrodes for a certain period, and then the light is adjusted. For each frame, dimming can be performed for each area of the screen.

  According to the present invention, since the light control method is duty light control, light control can be performed in a wide range.

(A) is sectional drawing of the noble gas fluorescent lamp used for the backlight unit of this invention, (b) is A-A 'sectional view, (c) is B-B' sectional view. (A) is the partial explanatory view for demonstrating the starting part of the noble gas fluorescent lamp used for the backlight unit of this invention, (b) is the partial explanatory view seen from the viewpoint C. It is a figure for demonstrating the backlight unit of this invention. It is a block diagram for demonstrating the lighting circuit of the backlight unit of this invention. It is a timing chart for demonstrating the lighting method of the backlight unit of this invention. It is a block diagram for demonstrating the lighting circuit of the backlight unit of this invention. It is a figure for demonstrating the structure of the backlight unit of this invention, (a) is a block diagram explaining the arrangement | positioning of a noble gas fluorescent lamp, (b) is a block diagram explaining the whole structure of a backlight unit. . (A) It is sectional drawing of the noble gas fluorescent lamp used for the conventional backlight unit, (b) is a Z-Z 'sectional view. It is a perspective view for demonstrating the structure of the conventional backlight unit.

This will be described below with reference to the drawings. 1A is a cross-sectional view of a rare gas fluorescent lamp of the present invention, FIG. 1B is a cross-sectional view taken along the line AA ′, and FIG. 1C is a cross-sectional view taken along the line BB ′.
In FIG. 1, a rare gas fluorescent lamp 1 includes an arc tube 11 made of a light-transmitting dielectric material such as glass, and a pair of strip-like external electrodes 130 sandwiching the arc tube 11 on the outer surface of the arc tube 11. 131, 132, 133, and 14 are disposed along the tube axis direction of the arc tube 11. A phosphor layer 12 is formed on the inner surface of the arc tube 11 and is coated with a phosphor that emits visible light over the entire area.

These external electrodes 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, and light emission This can be realized by sticking a tape-like metal on the outer surface of the tube 11 or screen-printing and baking a conductive paste. Except for the power feeding portion of the external electrode, it is covered with a protective film obtained by baking glass paste.
The glass constituting the arc tube is, for example, barium glass, and other materials such as kovar glass, tungsten glass, soda lime glass, borosilicate glass, and aluminosilicate glass may be used.
The rare gas sealed in the arc tube 11 is, for example, xenon, krypton, argon, neon, or a mixed gas thereof, and is sealed at about 10 to 300 Torr.

As the phosphor 12 applied to the inner surface of the arc tube 11, for example, as a phosphor emitting visible light, a red phosphor is europium-activated yttrium oxide phosphor (Y ₂ O ₃ : Eu) or (Y, Gd). BO ₃ : Eu, green phosphor is cerium / terbium activated lanthanum phosphate phosphor (LaPO ₄ : Ce, Tb), blue phosphor is europium activated barium magnesium aluminate phosphor (BaMgAl ₁₀ O ₁₇ : Eu ).
When a high frequency voltage is applied between the external electrodes, an excimer discharge is generated in the discharge space S through the arc tube 11 that is a dielectric material, and the phosphor is excited by the vacuum ultraviolet light generated by the excimer discharge to emit light. Visible light is emitted to the outside of the tube 11.

  The external electrodes 130, 131, 132, and 133 are all electrodes of the same polarity that are connected to the high voltage side, but are divided and arranged so as to be separated from each other in the tube axis direction. In contrast, the external electrode 14 having a different polarity is a common ground electrode for the external electrodes 130, 131, 132, and 133. These are collectively called a pair of external electrodes. The external electrode 14 may be divided into a plurality of parts in the tube axis direction.

Thus, in the rare gas fluorescent lamp of the present invention, one of the electrodes 130, 131, 132, and 133 is divided into a plurality of parts along the tube axis direction. By separately connecting drive circuits capable of supplying high-frequency power independently to each of the plurality of electrodes, it is possible to supply power differently between the electrodes.
In addition, when a voltage is applied to the external electrode 131, discharge is performed only between the external electrode 131 and the external electrode 14, and therefore, discharge occurs in a region where other electrodes such as the external electrode 132 are disposed. Absent.
That is, since light can be emitted for each external electrode pair, it is possible to emit light between the external electrode 131 and the external electrode 14 and not to emit light between the external electrode 132 and the external electrode 14.
Further, when the phase of the high-frequency voltage supplied between the external electrodes is synchronized with each other, creeping discharge between the external electrodes can be less likely to occur.

As shown in FIG. 1B, in the cross-sectional view taken along the line AA ′ of the rare gas fluorescent lamp 1, the inner surface side of the tube wall where the leftmost external electrode 130 is provided is made of, for example, carbon paste. The starter electrode 21 is formed in a C shape over a half circumference in the circumferential direction of the arc tube 11. This starting electrode 21 generates a seed discharge for improving the starting performance, and is provided so as to intersect the external electrodes 131 and 14 through the tube wall of the arc tube 11 which is a dielectric material, and is capacitively coupled. Has been. This will be described in detail below. The starting electrode 21 is a conductive material, and the material is not limited as long as it has a high sputtering resistance.
A region where the external electrode 130 and the starting electrode 21 are provided at the end of the arc tube 11 is referred to as a starting unit 20. In addition, an area other than the starting unit 20 is referred to as a light emitting unit 22 in the sense that it bears main light emission as a backlight.

2A is a partial explanatory view for explaining the starting unit 20 of the rare gas fluorescent lamp 1 of the backlight unit of the present invention, and FIG. 2B is a partial explanatory view seen from the viewpoint C. FIG.
In FIG. 2 (a), the voltage on the high voltage side electrode 130 disposed on the outer surface of the tube wall where the starting electrode 21 is formed on the inner surface of the arc tube 11 is higher than that between the external electrodes. By applying a low appropriate high-frequency voltage, direct discharge between the external electrode 130 and the external electrode 14 is not caused between the external electrode 130 and the start electrode 21 or between the external electrode 14 and the start electrode 21. In between, a small-scale seed discharge ID can be generated.

As shown in FIG. 2B, when the inside of the arc tube 11 is observed from the viewpoint C in the direction of the arrow shown in FIG. 2A, the starting electrode 21 and the outside are connected via the tube wall of the arc tube 11. A seed discharge ID is generated between the electrodes 14.
When such a seed fire discharge ID is generated, the light emitting unit 22 adjacent to the starter unit 20 can easily start the discharge from a low voltage by using the seed fire discharge ID as a preliminary ionization discharge.
In the case of a lamp in which the external electrode is divided in the tube axis direction as in the present invention, if easy starting means such as the starting electrode 21 is provided on the external electrode constituting the light emitting unit 22, the emitted light is hindered. As an alternative, a starter 20 is provided. As a result, even the external electrodes 131, 132, 133, and 134 that do not include easy-starting means can start discharging from a low voltage.
Moreover, since the seed discharge ID is generated only in a narrow region as shown in the figure, the power consumption is very small even if the discharge is maintained.
The starter 20 is preferably provided at the end of the arc tube 11. Further, the starter 20 may be provided at both ends of the arc tube. This is because startability is further improved by starting from both ends.
As shown in the figure, the starting electrode 21 is provided on the inner surface of the tube wall to which no phosphor is applied. Therefore, the light emitted by the seed fire discharge ID is emitted as it is without being converted, and is thus shielded by the light shielding means described later so as not to affect the displayed image.

FIG. 3 is an explanatory diagram for explaining the operation of the rare gas fluorescent lamp of the present invention shown in FIG.
In FIG. 3, between the external electrodes 131, 132, 133, and 134 provided in the rare gas fluorescent lamp 1 and the external electrode 14, a drive circuit capable of independently supplying a high-frequency voltage (not shown) is connected. Is powered independently. As described above, by adjusting the voltage and timing supplied from the high-frequency power source, it is possible to blink the region where each external electrode is provided or to adjust the light emission amount.
The areas that can be dimmed and blinked independently are the lighting areas LD1, LD2, LD3, and LD4, and their locations are shown in FIG.
The light emission from the lighting regions LD1, LD2, LD3, and LD4 in the rare gas fluorescent lamp 1 with respect to the screen 200 on which an image or video is displayed with the rare gas fluorescent lamp as a backlight, LD1, LD2, and LD3 illustrated for the screen 200 is illustrated. , Reflected as the brightness of the LD4 region.
That is, it is possible to perform dimming such that, in an image or video displayed on the screen, the light emission amount is set to 30% for a dark region and the light emission amount is set to 70% for a bright region.
As a result, compared with the case where a constant light emission amount is output for the entire area of the screen, the necessary amount of light is emitted according to the luminance required for each area of the displayed image or video. Since power is output, power consumption can be saved.
Further, in the case of a backlight of a liquid crystal image device, a dark portion and a bright portion in the screen can be created regardless of the light transmittance control by the liquid crystal panel, so that the contrast ratio of the image can be improved. it can.

Here, the starting lighting when the rare gas fluorescent lamp and the backlight are turned on as shown in FIG. 3 will be described.
As described above, in the rare gas fluorescent lamp 1 of the present invention, at least one external electrode is disposed so as to be separated in the tube axis direction, and each of the divided external electrodes is shown in FIG. Since there is no easy starting part like the starting electrode 21, it cannot start discharge easily by itself. Therefore, a starter 20 having a starter electrode 21 on the inner surface of the arc tube 11 is provided at the end of the arc tube for improving startability.
However, if the starting unit 20 and the lighting region to be lit are separated from each other and no discharge is generated in the lighting region between them, the starting becomes difficult. In order to solve this problem, the following lighting circuit and lighting method are used.

The lighting circuit and lighting method of the backlight unit of the present invention will be described.
FIG. 4 is a block diagram for explaining the lighting circuit of the backlight unit of the present invention, and FIG. 5 is a timing chart for explaining the lighting method. FIG. 6 shows an example of the lighting circuit of the backlight unit when a plurality of rare gas fluorescent lamps are used.
In FIG. 4, the rare gas fluorescent lamp 1 is the same as the rare gas fluorescent lamp 1 shown in FIG. The external electrode 14 provided outside the arc tube is a ground electrode, and external electrodes 130, 131, 132, 133, and 134 are provided as electrodes on the high voltage side so as to be separated in the tube axis direction. A starting electrode (not shown) is provided on the inner wall of the arc tube at the position where the external electrode 130 is provided, and constitutes the starting unit 20.
A separate independent drive circuit is connected to each of the lighting regions LD1, LD2, LD3, and LD4 that emit light by discharge between the external electrodes 131, 132, 133, and 134 and the external electrode 14. Also, another drive circuit is connected to the starting unit 20.
Each drive circuit is composed of transformers 40, 41, 42, 43 and 44, DC power supplies 30, 31, 32, 33 and 34, switching element circuits 50, 51, 52, 53 and 54, and switching operation signal generation. Circuits 60, 61, 62, 63 and 64. The switching element circuit is configured by a push-pull circuit method, a half bridge circuit method, a full bridge circuit method, and the like, for example, a half bridge circuit method.
A control signal generation circuit 70 is connected to each drive circuit, and an image signal processing circuit 71 is connected to the control signal generation circuit 70.

The DC voltage supplied from the DC power source is converted into an AC voltage by the switching element circuit, boosted by a transformer, and supplied to each external electrode as lighting power. The switching operation signal generation circuit generates a PWM signal for ON / OFF control of the switching element of the switching element circuit.
Regarding the operation of each drive circuit, the transformer 41 connected to the external electrode 131 for causing the lighting region LD1 to emit light, the switching element circuit 51, the DC power supply 31, the switching operation signal generation circuit 61, the control signal generation circuit 70, the image signal processing This will be described using the circuit 71.
When the image signal processing circuit 71 receives the image signal, the dimming signal for performing discharge between the external electrodes 131 and 14 determined by the control signal generation circuit 70 based on the image signal is subjected to switching operation. It is sent to the signal generation circuit 61.
When the switching operation signal generation circuit 61 receives the dimming signal, the switching operation signal generation circuit 61 sends an operation signal for operating the switching element circuit 51 based on the dimming signal, and the DC voltage supplied from the DC power supply 31 is used as the switching element circuit 51. The lamp is turned on by converting to AC voltage.
Such an operation is similarly performed for each of the lighting regions LD2, LD3, and LD4.
Dimming is performed by adjusting the duty ratio of the on period and the off period in which the period in which the rare gas fluorescent lamp is turned on is turned on and the period in which the rare gas fluorescent lamp is turned off is turned off. Details are described below.

FIG. 5 is a timing chart for explaining a lighting method of the backlight unit of the present invention shown in FIG. (A) is a frame of an image signal, (b) is a starting electrode, (c) is a lighting region LD1, (d) is a lighting region LD2, (e) is a lighting region LD3, (f) is a lighting region LD4, This is an on / off switching element operation signal.
For example, in a liquid crystal display device that displays a moving image, an image displayed on the screen is periodically rewritten (for example, 1/60 seconds) to display the moving image. Here, the frame display period _TF shown in FIG. 5A indicates a period during which the frame signal is turned on and one image is displayed. That is, when the next frame display period _TF is started, a different image is displayed (of course, the image may not change).
FIG. 5B is a switching element operation signal (hereinafter simply referred to as an operation signal) for a high frequency voltage applied to the external electrode 130 constituting the starter 20 in FIG. It will be substantially supplied to the combined starter electrode 20 (shown in FIG. 1) and is therefore shown as a starter electrode operating signal. Further, when the operation signal of each lighting region LD1, LD2, LD3, LD4 is turned on, a high frequency voltage is applied to the external electrode provided at the corresponding position, and the lighting region emits light. As described above, the brightness is adjusted by changing the duty ratio by ON / OFF control of the operation signal within the frame display period as described above, so the duty ratio is increased when darkening, and the duty ratio when brightening. Make it smaller.

First, before the frame signal is turned on, that is, before the frame display period is started, the operation signal of the start electrode is turned on to generate a seed discharge that facilitates starting in each lighting region.
Simultaneously when the operation signal of the start electrode is turned on, or at least before the start of frame display, the operation signals of all the lighting regions LD1, LD2, LD3, and LD4 are also turned on simultaneously to start discharging. In this way, when the starter discharge is generated at the same time or has already occurred by the starting electrode, the discharge spreads in order from the lighting region adjacent to the starting portion, and the discharge can be quickly generated in the entire arc tube. After the discharge spreads over the entire arc tube, power consumption can be saved by turning off the starting electrode.
This, and turns on the operation signal starting electrode, discharge is the starting period T _S for any given period until the off after spread throughout the light emitting tube. In other words, after the start of the frame display period, the operation signal is turned on at least simultaneously for the start electrode and each of the lighting regions LD1, LD2, LD3, and LD4.
In this way, by simultaneously turning on the operation signal for a certain period of time for the starting electrode and all the lighting areas in synchronization with the start of the frame display period, discharge can be started quickly even in the lighting area away from the starting electrode. Can do.
Further, start-up period T _S may in a very short period until discharge occurs in all of the external electrodes, even when discharged at all external electrodes, also the contrast ratio is lowered by subsequent performing dimming Absent.
Note that the starting electrode may be discharged maintained as also on post-start period T _S ends, in that case it is necessary to light the pilot discharge is shielded so as not to affect the image. Always operating signal during the starting period T _S even if discharge sustain is turned on.

After the start-up period _{T S,} so that each lighting region LD1, LD2, LD3, LD4 intact sustaining operation signal is turned depending on the required luminance in each area of the screen. So to speak after the start-up period T _S, the process proceeds to the dimming period, the duty dimming is performed by the on / off period according to the respective illumination regions.
The operation signal for the duty dimming is to time the dimming period T _D which is turned. Dimming period T _D for each lighting region is determined based on the image signal. Thereby, dimming of each lighting area is performed for each frame.
For example, in the first frame shown in FIG. 5, in the lighting region LD1 and lighting area LD2, it is long dimming period T _D towards the lighting region LD1, brighter. Moreover, it is not necessary T _D period dimming period, as the lighting region LD3 of the frames exist at all.

As described above, when starting the lighting of the rare gas fluorescent lamp, the operation signal is turned on simultaneously for an arbitrary fixed period to the starting electrode and all the external electrodes divided in the tube axis direction corresponding to each lighting region. As a result, a discharge is generated in the entire arc tube, and then lighting according to the dimming signal is performed for each external electrode of each divided lighting region.
As a result, even in a lighting region corresponding to an external electrode that is divided in the tube axis direction and is not provided with a starting electrode, each region in the screen can be discharged quickly from a low voltage. Dimming can be performed. For this reason, it is possible to provide illumination as necessary for each region, as compared with the case where illumination is constantly provided for the entire screen, so that power consumption is reduced and the contrast ratio can be improved.

  Furthermore, by performing the lighting method in synchronization with the start timing of each frame of the image signal, it is possible to perform the dimming for each frame of images that are continuously displayed.

  Further, since the light control method is duty light control, a wide range of light control can be performed and the contrast ratio can be improved.

FIG. 6 is a block diagram for explaining a lighting circuit in a case where one lighting region is configured by using a plurality of rare gas fluorescent lamps in the backlight unit of the present invention.
6 is the same in configuration except that the number of rare gas fluorescent lamps is different from that in FIG.
In FIG. 6, the external electrodes corresponding to the same position in the tube axis direction of the plurality of rare gas fluorescent lamps 1, 2, and 3 divided in the tube axis direction constitute one lighting region. Yes. That is, the external electrodes 131, 231 and 331 are connected to the switching element circuit 51 through the same transformer 41 and operate in the same way when lit. Therefore, the region where the external electrodes 131, 231 and 331 are provided is a single region. It can be regarded as the lighting region LD1. Similarly, the lighting region LD2 includes external electrodes 132, 232, and 332, the lighting region LD3 includes external electrodes 133, 233, and 333, and the lighting region LD4 includes external electrodes 134, 234, and 334.
A grounded external electrode 14 is provided on the outer surface of the arc tube of the rare gas fluorescent lamps 1, 2 and 3. As described above, the external electrode 14 may be divided and provided in the tube axis direction.

  The backlight lighting method shown in FIG. 6 is the same as that described with reference to FIGS.

In this way, if a plurality of rare gas fluorescent lamps are arranged in parallel and the divided external electrodes corresponding to the same position in the tube axis direction of adjacent lamps are combined into one lighting region, dimming can be performed. One lighting region, which is a unit to be performed, can be configured with an arbitrary size.
Furthermore, even in a region where the starting electrode is not provided, discharge can be easily started from a low voltage due to the effect of the starting portion, so even if a plurality of lamps are arranged, the external electrode and the external electrode of the adjacent lamps Undesirable discharge does not occur between the two.

  Note that the external electrodes 130, 230, and 330, which are located at the end of the rare gas fluorescent lamp and serve as the starter, are discharged all at the same time when turned on, as described above, and may all be driven by the same drive circuit.

  Even when one drive circuit is connected to a plurality of divided external electrodes corresponding to the same position in the tube axis direction of a plurality of adjacent lamps in this way, the operation is the same, so the divided lamps are divided. This is synonymous with connecting the drive circuit separately for each external electrode.

FIG. 7 is a configuration diagram of a backlight unit including the rare gas fluorescent lamp of the present invention, (a) is a configuration diagram showing the arrangement of the lamp, and (b) is an overall configuration diagram of the backlight unit including a casing. is there. The rare gas fluorescent lamp 1 is the same as that described in FIG.
As shown in FIG. 7A, for example, nine rare gas fluorescent lamps 1 are arranged in parallel, and the external electrode is divided into four in the tube axis direction (excluding the external electrode provided with the starting electrode). For each lamp, a single lighting region is formed by combining external electrodes corresponding to the same position in the tube axis direction, and power is supplied. Therefore, in this case, the screen is divided into 12 by 4 horizontal by 3 vertical, and the 12 lighting regions LD11, LD12, LD13, LD14, LD21, LD22, LD23, LD24, LD31, LD32, LD33, and LD34 Individual flashing and dimming can be performed in two vertical and horizontal directions.
Note that the number of lighting regions is not limited to the number shown, and can be set as appropriate according to the number of divided external electrodes and the number of drive circuits.

.
In FIG. 7B, the backlight unit 100 includes a plurality of rare gas fluorescent lamps 1 arranged in a row in parallel with each other in a box-shaped casing 95 having one surface opened as a light emitting surface. It is stored. The light from the backlight unit 100 is emitted toward the opening side of the casing 95. Each of the rare gas fluorescent lamps 1 is arranged so as to face the front so that the directions of the light emitting portions thereof coincide with each other. A plurality of drive circuits (not shown) are installed on the back surface of the casing 95.
The casing 95 is provided with a light shielding portion 96 for shielding light emitted by the starter discharge of the starting portion 20 provided in the rare gas fluorescent lamp 1. Thereby, even when the seed discharge is maintained while the lamp is lit, the emitted light does not leak.
A lead wire led out from a power supply terminal (not shown) provided on the divided external electrode of the rare gas fluorescent lamp is introduced to the back side through a small hole provided on the back side of the casing 95 and connected to the connector for driving. Connected to the circuit.
A reflective sheet 91 is provided between the rare gas fluorescent lamp 1 and the casing 95. On the light emission side of the rare gas fluorescent lamp 1, a diffusion plate 92, a diffusion sheet 93, and a directivity control sheet 94 for emitting light in a planar shape are arranged to overlap each other.

DESCRIPTION OF SYMBOLS 1 Noble gas fluorescent lamp 11 Luminescent tube 12 Phosphor layer 130 External electrode 131 External electrode 132 External electrode 133 External electrode 12 Phosphor layer 14 External electrode 15 Protective film 20 Starting part 21 Starting electrode 22 Light emitting part 31 DC power supply 41 Transformer 51 Switching Element circuit 61 Switching operation signal generation circuit 70 Control signal generation circuit 71 Image signal processing circuit 8 Noble gas fluorescent lamp 81 Luminescent tube 82 Phosphor layer 83 External electrode 84 External electrode 85 Protective film 78 Drive circuit 91 Reflective sheet 92 Diffusion plate 93 Diffusion Sheet 94 Directivity control sheet 95 Casing 96 Light shielding unit 200 Screen LD1 Lighting area LD11 Lighting area ID Fire discharge TF Frame display period T _S start period T _D dimming period

Claims (3)

A rare gas fluorescent lamp having a pair of external electrodes arranged along the tube axis is arranged in parallel outside the arc tube, and a driving circuit for lighting the rare gas fluorescent lamp and a dimming signal are sent to the driving circuit. In a backlight unit equipped with a control signal generation circuit,
At least one of the external electrodes of the rare gas fluorescent lamp is divided in the tube axis direction;
A drive circuit connected separately and independently for each of the divided external electrodes;
A starting electrode formed on the inner surface of the tube wall on which the external electrode located at least one end of the rare gas fluorescent lamp is formed,
The control signal generation circuit supplies power to all of the divided external electrodes when starting the lighting of the rare gas fluorescent lamp with respect to the drive circuit, and after a certain period of time, dimming is performed for each of the divided external electrodes. A backlight unit that transmits a dimming signal.   The control signal generation circuit transmits the dimming signal based on the image signal, wherein the start time of each frame display period of the image signal is set as the lighting start time, and the dimming is performed for each frame display period. The backlight unit according to claim 1.   3. The back according to claim 1, wherein the dimming signal is a duty dimming signal that adjusts a duty ratio between an on period and an off period of lighting of the rare gas fluorescent lamp by the driving circuit. Light unit.

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