WO2006080235A1

WO2006080235A1 - Display apparatus

Info

Publication number: WO2006080235A1
Application number: PCT/JP2006/300746
Authority: WO
Inventors: Shinya Tanaka; Hisashi Oyama; Nobuyuki Takahashi
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2005-01-25
Filing date: 2006-01-19
Publication date: 2006-08-03

Abstract

A display apparatus suitable for use with an instrument panel. The display panel comprises a display panel, which has a plurality of pixels each of which modulates a light, and a directly underlying backlight that is disposed on the rear side of the display panel. The backlight has a plurality of light sources (1A,1B,1C,1D) and a control circuit (30A) that controls the brightness of the plurality of light sources. The control circuit can cause at least two of the plurality of light sources (1A,1B,1C,1D) to exhibit mutually different brightness.

Description

Specification

Display device

Technical field

TECHNICAL FIELD [0001] The present invention relates to a display device, and particularly to a display device including a direct type backlight.

Background art

[0002] Conventionally, the instrument panel of an automobile has been provided with various instruments such as a speedometer. Instead of these instruments, a display device such as a liquid crystal display device or a CRT is provided. It has been proposed to display information necessary for driving with this display device (see, for example, Patent Document 1).

[0003] Among various display devices, the liquid crystal display device has a feature that it is thin and has low power consumption, so that it is expected to be used for an instrument panel. Unlike CRT (CRT) and EL (electric mouth luminescence) display devices, liquid crystal display devices are not self-luminous display devices that emit light themselves. Therefore, the liquid crystal display device includes an illumination device (called a backlight) provided on the back side of the liquid crystal display panel, and performs display using light from the backlight.

[0004] The backlight is a “direct type” in which a plurality of light sources are arranged directly below the liquid crystal display panel, and a light source is arranged at the end of the light guide plate, and the light from the light source is guided to the liquid crystal display panel by the light guide plate Broadly divided into “edge light type”.

[0005] The general structure of a direct type backlight is schematically shown in Figs. 6 (a) and (b). The knock light 60 is provided on the back side of the transmissive liquid crystal display panel 70, and includes a plurality of cold cathode tubes 61 arranged at a predetermined interval, a case 63 for accommodating the cold cathode tubes 61, and a cold cathode. An optical sheet (for example, a diffusion sheet or a prism sheet) 65 disposed between the tube 61 and the liquid crystal display panel 70 is provided. The direct-type backlight 60 can be easily adjusted in brightness by adjusting the number of cold-cathode tubes 61 as light sources. Therefore, the direct-type backlight 60 is widely used in large liquid crystal display devices that easily achieve high brightness. Yes.

Patent Document 1: Japanese Patent Laid-Open No. 9-123848 Disclosure of the invention

Problems to be solved by the invention

[0006] However, the inventor of the present application made various studies for actually using the liquid crystal display device in the instrument panel. As shown in Figs. 6 (a) and 6 (b), It was found that liquid crystal display devices equipped with a direct-type knocklight of V may not be used suitably for instrument panels.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a display device suitably used for an instrument panel.

Means for solving the problem

[0008] A display device according to the present invention includes a display panel having a plurality of pixels each of which modulates light, and a backlight provided on the back side of the display panel.

A plurality of light sources and a control circuit for controlling the luminance of the plurality of light sources, the control circuit can control at least two of the plurality of light sources to different luminances, This achieves the above object.

[0009] In a preferred embodiment, the backlight is a direct type knock light.

[0010] In a preferred embodiment, the control circuit may supply currents of different strengths to the at least two light sources.

[0011] In a preferred embodiment, the control circuit changes the brightness of the plurality of light sources between a first brightness and a second brightness corresponding to 60% of the first brightness. obtain.

[0012] In a preferred embodiment, the control circuit supplies a plurality of lighting circuits each connected to at least one light source of the plurality of light sources, and each of the plurality of lighting circuits. A control signal generating circuit that generates a control signal for controlling the intensity of the generated current and outputs the control signal individually to each of the plurality of lighting circuits.

[0013] In a preferred embodiment, the control circuit may supply pulse currents having different pulse widths to the at least two light sources.

[0014] In a preferred embodiment, the control circuit sets the luminance of the plurality of light sources between a first luminance and a second luminance corresponding to 90% of the first luminance. It can be changed with. In a preferred embodiment, the control circuit supplies a plurality of lighting circuits each connected to at least one light source of the plurality of light sources, and each of the plurality of lighting circuits. A control signal generating circuit for generating a control signal for controlling a pulse width of the pulse current to be output and individually outputting the control signal to each of the plurality of lighting circuits.

[0016] In a preferred embodiment, the plurality of light sources includes a plurality of rod-shaped light sources.

[0017] In a preferred embodiment, the plurality of rod-shaped light sources are arranged substantially parallel to each other at a predetermined interval.

[0018] In a preferred embodiment, the plurality of bar-shaped light sources arranged substantially parallel to each other at a predetermined interval are divided into a plurality of blocks to which at least one bar-shaped light source belongs. The control circuit can control the brightness of the plurality of rod-shaped light sources independently for each of the plurality of blocks.

In a preferred embodiment, the plurality of rod-shaped light sources are arranged such that the longitudinal direction of the display panel and the longitudinal direction of the plurality of rod-shaped light sources are substantially orthogonal.

[0020] In a preferred embodiment, the plurality of light sources includes a plurality of point light sources.

[0021] In a preferred embodiment, the plurality of point light sources are arranged in a matrix.

In a preferred embodiment, the plurality of point light sources arranged in a matrix are divided into a plurality of blocks to which at least one point light source belongs, and the control circuit includes the control circuit The brightness of the plurality of point light sources can be controlled independently for each of the plurality of blocks.

[0023] In a preferred embodiment, the plurality of light sources includes a plurality of cold cathode tubes.

[0024] In a preferred embodiment, the plurality of light sources includes a plurality of xenon tubes.

[0025] In a preferred embodiment, the plurality of light sources includes a plurality of light emitting diodes.

[0026] In a preferred embodiment, the plurality of light sources include at least one cold cathode tube and at least one xenon tube.

The invention's effect [0027] In the display device according to the present invention, the control circuit can control at least two light sources of the plurality of light sources to have different luminances, so that the emission luminance of the knocklight can be partially changed. it can. Therefore, the display device according to the present invention is suitably used for an instrument panel mounted on a motor vehicle.

Brief Description of Drawings

FIG. 1 (a) is a cross-sectional view schematically showing a liquid crystal display device 100 according to a preferred embodiment of the present invention, and (b) is a schematic view of a backlight 10 provided in the liquid crystal display device 100. FIG.

FIG. 2 is a diagram schematically showing a control circuit 30A included in the knocklight 10.

FIG. 3 is a diagram schematically showing another control circuit 30B included in the backlight 10.

FIG. 4 is a diagram showing an example in which the liquid crystal display device 100 is used for an instrument panel of a four-wheeled vehicle.

FIG. 5 (a) is a cross-sectional view schematically showing a liquid crystal display device 200 in another preferred embodiment of the present invention, and FIG. 5 (b) schematically shows a backlight 10 ′ included in the liquid crystal display device 200. FIG.

[FIG. 6] (a) and (b) schematically show a conventional direct backlight 60, (a) is a cross-sectional view, and (b) is a top view.

Explanation of symbols

[0029] 1 Bar light source

1 'point light source

1A, 1B, 1C, ID light source block

3 cases

5 Optical sheet

10, 10 'backlight (lighting device)

20 LCD panel

21 and 22 substrates

23 Liquid crystal layer

30A ゝ 30B Control circuit 32A, 32B lighting circuit

34A, 34B control signal generation circuit

40 Power supply

100, 200 LCD

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments.

[0031] (Embodiment 1)

A liquid crystal display device 100 according to the present embodiment will be described with reference to FIGS. 1 (a) and 1 (b). FIG. 1A is a cross-sectional view schematically showing the liquid crystal display device 100, and FIG. 1B is a top view schematically showing the backlight 10 included in the liquid crystal display device 100. FIG.

As shown in FIG. 1 (a), the liquid crystal display device 100 includes a liquid crystal display panel 20 and a backlight (illumination device) 10 provided on the back side of the liquid crystal display panel 20.

The liquid crystal display panel 20 includes a pair of substrates (for example, glass substrates) 21 and 22 and a liquid crystal layer 23 provided therebetween, and each has a plurality of pixels that modulate light. . As the liquid crystal display panel 20, a transmissive display panel having various known structures can be used. Further, a transflective display panel may be used as the liquid crystal display panel 20. Typically, on each liquid crystal layer 23 side of the pair of substrates 21 and 22, an electrode for applying a voltage to the liquid crystal layer 23 and an alignment direction of the liquid crystal molecules contained in the liquid crystal layer 23 are defined. An alignment film (both not shown) is provided.

The knock light 10 is a direct type backlight having a plurality of light sources 1 arranged immediately below the display area of the liquid crystal display panel 20 as shown in FIGS. 1 (a) and 1 (b). The light source 1 in the present embodiment is a rod-shaped light source having a rod-shaped outer shape. As the rod-shaped light source 1, for example, a cold cathode tube (CCFT) can be used. As shown in FIG. 1 (b), these rod-like light sources 1 are arranged substantially parallel to each other at a predetermined interval, and further, the longitudinal direction thereof is substantially orthogonal to the longitudinal direction of the liquid crystal display panel 20. Arranged.

The rod-shaped light source 1 is accommodated in the case 3, and the optical sheet 5 is disposed between the rod-shaped light source 1 and the liquid crystal display panel 20. The optical sheet 5 is, for example, a diffusion sheet Sheet. In FIG. 1, a force showing one optical sheet 5 In practice, a diffusion sheet or prism sheet is used in appropriate combination. In order to increase the light utilization efficiency, typically, the force with which a member with high light reflectance (light reflecting sheet) is provided on the surface of the case 3 on the rod-like light source 1 side, or the case 3 itself It is made of a material with high light reflectivity.

The backlight 10 in the present embodiment further has a control circuit that controls the luminance of the plurality of rod-like light sources 1. FIG. 2 shows a control circuit 30A in the present embodiment. As shown in FIG. 2, the control circuit 30A includes a plurality of lighting circuits 32A and a control signal generation circuit 34A that generates a control signal for controlling the lighting circuits 32A.

[0037] Each lighting circuit 32A is connected to three rod-like light sources 1 and a power source 40, and supplies a drive current to the rod-like light source 1 based on a control signal from the control signal generating circuit 34A. In the present embodiment, the control circuit 30A has four lighting circuits 32A, and the rod-shaped light source 1 is divided into four blocks 1A to 1D. The number of rod-shaped light sources 1 belonging to each block (that is, connected to each lighting circuit 32A) is not limited to the three exemplified here. It is sufficient if at least one rod-shaped light source 1 belongs to each lighting circuit 32 A, and at least one rod-shaped light source 1 belongs to each block.

[0038] The control signal generation circuit 34A generates a control signal (current intensity control signal) for controlling the intensity of the current supplied from the lighting circuit 32A to the rod-shaped light source 1, and generates the generated control signal for each lighting circuit. Output individually to 32A. The lighting circuit 32A supplies a current having a strength corresponding to the input control signal to the rod-shaped light source 1, and the rod-shaped light source 1 emits light with a light emission intensity corresponding to the strength of the supplied current.

[0039] Since the control signal generation circuit 34A individually outputs the control signal to each lighting circuit 32A, the intensity of the current supplied to the rod-shaped light source 1 can be made different for each of the blocks 1A to: LD. . Therefore, the control circuit 30A can cause each of the blocks 1A to 1D to emit light with different brightness. What kind of control signal power is output from the control signal generation circuit 34A to each lighting circuit 32A, that is, what brightness of each of the blocks 1A to 1D is to be emitted at what part of the liquid crystal display panel 20? It may be set in advance according to whether to display the correct information. FIG. 2 shows a control circuit 30A that adjusts the luminance of the rod-shaped light source 1 by controlling the current intensity (current intensity control system), but the present invention is not limited to this. FIG. 3 shows another control circuit 30B used in the display device of the present invention. The control circuit 30B shown in FIG. 3 is a control circuit of a method (pulse width modulation method) that adjusts the luminance of the rod-shaped light source 1 by modulating the pulse width of the pulse current.

[0041] The control signal generation circuit 34B included in the control circuit 30B generates and generates a control signal (pulse width control signal) for controlling the pulse width of the pulse current supplied from the lighting circuit 32B to the rod-shaped light source 1 A control signal is individually output to each lighting circuit 32B. The lighting circuit 32B supplies a pulse current having a pulse width corresponding to the input control signal to the rod-shaped light source 1, and the rod-shaped light source 1 emits light for a lighting time corresponding to the pulse width of the supplied pulse current.

[0042] Since the control signal generation circuit 34B outputs the control signal to each lighting circuit 32B individually, the pulse width of the Norse current supplied to the rod-shaped light source 1 should be different for each of the blocks 1A to 1D. Can do. Therefore, the control circuit 30B can cause each of the blocks 1A to 1D to emit light with different luminances.

If a pulse width modulation method as shown in FIG. 3 is used, it is easy to widen the dimming width. However, when the pulse width modulation method is used, a flickering force may be generated due to interference between the driving frequency of the liquid crystal display panel 20 and the pulse current frequency. When the method of controlling the current intensity as shown in Fig. 2 is used, no such flicker force is generated. Using a method that controls the current intensity, the luminance of the rod-shaped light source 1 can be changed between a typical luminance and a luminance equivalent to 60% of the typical luminance, and a pulse width modulation method can be used. When used, the luminance of the rod-shaped light source 1 can be changed between a typical luminance and a luminance equivalent to 90% of the typical luminance.

As already described, since the liquid crystal display device 100 can partially change the brightness of the knocklight 10, as will be described later, a display device for an instrument panel mounted on a motor vehicle. Is preferably used. “Automobile” refers to an auto-propelled vehicle or machine that can be used to transport passengers and goods!

FIG. 4 shows an example in which the liquid crystal display device 100 is used for an instrument panel of a four-wheeled vehicle. The In Fig. 4, the speed of the motor vehicle, shift lever position, remaining battery level, water temperature, and remaining fuel level are displayed on the right side of the display area, and car navigation information is displayed on the left side of the display area. is doing. Car navigation information is information that informs the driving driver of the current location and the route to the destination.

[0046] Since the liquid crystal display device 100 in the present embodiment can partially change the luminance of the backlight 10, when displaying a plurality of pieces of information on the liquid crystal display panel 20, each of the portions displaying each piece of information is displayed. Can be illuminated with a desired brightness. For example, it is possible to illuminate the left area displaying the car navigation information with a relatively high luminance and illuminate the display area of the right area displaying the vehicle speed or the like with a relatively low luminance. Therefore, it is easy to display information in various layouts in the display area, and the design panel design diversity can be increased. In addition, since the brightness of the knocklight 10 can be partially lower than typical brightness, it is possible to reduce power consumption. For example, when black display is performed on a part of the liquid crystal display panel 20, the power consumption without affecting the display is reduced by setting the light emission luminance of the area corresponding to that part to zero (or lowering). can do.

In addition, as in the present embodiment, the configuration in which the longitudinal direction of the rod-shaped light source 1 and the longitudinal direction of the liquid crystal display panel 20 are substantially orthogonal changes the luminance along the longitudinal direction of the liquid crystal display panel 20. Therefore, the display panel is particularly preferably used for a display device having a shape with a large aspect ratio, such as a display device for an instrument panel.

In the present embodiment, a cold cathode tube is illustrated as the rod-shaped light source 1, but the rod-shaped light source 1 is not limited to this. From the viewpoint of manufacturing cost, a cold cathode tube may be used, or a xenon tube that does not contain mercury may be used in combination from the viewpoint of environmental impact.

[Embodiment 2]

A liquid crystal display device 200 according to this embodiment will be described with reference to FIGS. 5 (a) and 5 (b). FIG. 5 (a) is a cross-sectional view schematically showing the liquid crystal display device 200, and FIG. 5 (b) is a top view schematically showing the backlight 10 ′ included in the liquid crystal display device 200.

As shown in FIG. 5 (a), the liquid crystal display device 200 includes a liquid crystal display panel 20 and a liquid crystal display panel. And a direct-type backlight (illumination device) 10 'provided on the back side of the lamp 20.

[0051] As shown in Fig. 5 (b), the backlight 10 'in the present embodiment has a plurality of point light sources 1' arranged in a matrix. As the point light source 1 ′, for example, an LED (light emitting diode) can be used.

[0052] A plurality of point light sources 1 'arranged in a matrix are divided into a plurality of blocks.

In FIG. 5 (b), each block is indicated by a broken line. Here, the number of force blocks exemplifying 12 blocks to which each of the six point light sources 1 ′ belongs, and the number of point light sources 1 ′ belonging to each block can be arbitrarily set. Multiple point light sources 1 ′ should be divided into at least two blocks, and each block should have at least one point light source 1 ′.

Although not shown here, the knocklight 10 has a control circuit that can control the luminance of the plurality of point light sources 1 independently for each block. Therefore, the liquid crystal display device 200 in the present embodiment can also partially change the brightness of the knocklight 10 ′ and can be suitably used as a display device for an instrument panel.

As the control circuit, for example, a control circuit having a configuration similar to that of the control circuit 30A shown in FIG. 2 can be used. By preparing the same number of lighting circuits 32A as the blocks and connecting the point light sources 1 'to each lighting circuit 3 2A, it becomes possible to control the brightness of multiple point light sources 1' for each block. . Alternatively, a control circuit having the same configuration as the control circuit 30B shown in FIG. 3 may be used as the control circuit.

[0055] In the first embodiment, the backlight 10 having the rod-shaped light source 1 is illustrated, and in the second embodiment, the backlight 10 'having the point-shaped light source 1' is illustrated. As a light source that may have both light sources, the illustrated cold cathode tube, xenon tube, and LED may be used in appropriate combination!

In addition, in Embodiments 1 and 2, the power exemplified by the direct type knock light The present invention is also suitably used for a display device including an edge light type knock light. For example, it is also used in a display device including an edge light type backlight having a plurality of LEDs and a light guide plate that guides light from these LEDs to the display panel.

Industrial applicability According to the present invention, a display device suitably used for an instrument panel is provided. The instrument panel according to the present invention is suitably used for various automatic vehicles such as passenger cars, motorcycles, buses, trucks, tractors, airplanes, motor boats, civil engineering vehicles, and trains.

Claims

The scope of the claims

[1] A display panel having a plurality of pixels each of which modulates light, and a backlight provided on the back side of the display panel,

The backlight includes a plurality of light sources, and a control circuit that controls luminance of the plurality of light sources,

The display device capable of controlling at least two light sources of the plurality of light sources to different brightnesses from each other.

2. The display device according to claim 1, wherein the backlight is a direct type backlight.

3. The display device according to claim 1, wherein the control circuit can supply currents having different strengths to the at least two light sources.

[4] The control circuit determines the luminance of the plurality of light sources from the first luminance and the first luminance.

4. The display device according to claim 3, wherein the display device can be changed between the second luminance corresponding to%.

[5] The control circuit controls a plurality of lighting circuits each connected to at least one of the plurality of light sources, and a current intensity supplied from each of the plurality of lighting circuits. 5. A display device according to claim 3, further comprising: a control signal generation circuit that generates a control signal for output and outputs the control signal individually to each of the plurality of lighting circuits.

6. The display device according to claim 1, wherein the control circuit can supply pulse currents having different pulse widths to the at least two light sources.

7. The control circuit according to claim 6, wherein the control circuit can change the brightness of the plurality of light sources between a first brightness and a second brightness corresponding to 90% of the first brightness. Display device.

[8] The control circuit controls a plurality of lighting circuits each connected to at least one of the plurality of light sources, and a pulse width of a pulse current supplied from each of the plurality of lighting circuits. The display device according to claim 6, further comprising: a control signal generation circuit that generates a control signal to output the control signal and outputs the control signal individually to each of the plurality of lighting circuits.

[9] The display device according to any one of claims 1 to 8, wherein the plurality of light sources include a plurality of rod-shaped light sources.

10. The display device according to claim 9, wherein the plurality of rod-shaped light sources are disposed substantially parallel to each other at a predetermined interval.

[11] The plurality of rod-shaped light sources arranged substantially parallel to each other at a predetermined interval are divided into a plurality of blocks to which at least one rod-shaped light source belongs,

11. The display device according to claim 10, wherein the control circuit is capable of independently controlling brightness of the plurality of rod-shaped light sources for each of the plurality of blocks.

[12] The plurality of rod-shaped light sources are arranged so that the longitudinal direction of the display panel and the longitudinal direction of the plurality of rod-shaped light sources are substantially orthogonal to each other! 12. A display device according to claim 10 or 11.

13. The display device according to claim 1, wherein the plurality of light sources include a plurality of point light sources.

14. The display device according to claim 13, wherein the plurality of point light sources are arranged in a matrix.

[15] The plurality of point light sources arranged in a matrix is divided into a plurality of blocks to which at least one point light source belongs,

15. The display device according to claim 14, wherein the control circuit is capable of independently controlling brightness of the plurality of point light sources for each of the plurality of blocks.

16. The display device according to claim 1, wherein the plurality of light sources include a plurality of cold cathode tubes.

17. The display device according to claim 1, wherein the plurality of light sources include a plurality of xenon tubes.

18. The display device according to any one of claims 1 to 8 and 13 to 15, wherein the plurality of light sources include a plurality of light emitting diodes.

19. The display device according to claim 1, wherein the plurality of light sources include at least one cold cathode tube and at least one xenon tube.