JP2004274389A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To resolve the problem that a liquid crystal display device cannot be operated with a remote controller or causes malfunction just after turning on a back light. <P>SOLUTION: In the liquid crystal display device provided with a liquid crystal panel, the back light, and a light reception part for receiving the operation signals from a remote controller, a light shielding means for limiting the field angle on the lower side is provided to a remote control signal light reception part of a remote controller, so that infrared rays emitted from the liquid crystal panel just after turning on the back light are prevented from being made incident on the light reception part of the remote controller. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention mainly relates to a panel-type display device, and more particularly to a means for satisfactorily receiving a signal of a remote controller for remotely controlling a liquid crystal display.
[0002]
[Prior art]
FIG. 6 shows the configuration of the liquid crystal display device. The liquid crystal display includes a liquid crystal panel 120, a backlight unit 100, a video signal processing unit, a system control unit, and a light receiving unit 130 for remote control signals. A video signal obtained directly or externally and received by a tuner is input to the liquid crystal display device. The input video signal is converted into a drive signal for the liquid crystal panel by the video signal processing unit, and drives the liquid crystal panel. A viewer can watch a video by viewing light from the backlight unit 100 provided behind the liquid crystal panel through opening and closing of the liquid crystal panel 120.
[0003]
The viewer can control the entire liquid crystal display device from outside using a remote controller. For example, this is the case where the power is turned on / off or the channel is changed.
[0004]
The backlight included in the backlight unit is a cold-cathode light source, and is mainly configured by enclosing neon, argon, mercury, and the like. A voltage is applied to the backlight by inverter control, and the backlight is internally discharged. At this time, ultraviolet light emitted by the excitation of gaseous mercury hits the phosphor coated on the inner wall of the backlight tube and emits light.
[0005]
[Problems to be solved by the invention]
However, since the vapor pressure of mercury is low, excitation of neon and argon becomes dominant when the temperature of the backlight tube is low, such as when starting up a liquid crystal display device. That is, in this case, the light emitted from the backlight is dominated by infrared rays to near infrared rays.
[0006]
FIG. 7 shows a state of emitted light when the liquid crystal display device is activated. When the liquid crystal display device is activated, it mainly emits infrared or near-infrared light as emitted light 200 from the backlight. The emitted light 200 hits the floor in front of the liquid crystal display device, and becomes reflected light 210 that is irregularly reflected. Some of the reflected light 210 enters the light receiving unit 130 of the remote controller. The reflected light 220 incident on the light receiving unit 130 becomes noise with respect to the signal of the remote controller.
[0007]
That is, the liquid crystal display device has a problem in that the remote control becomes less effective or malfunctions until the backlight tube reaches a relatively high temperature at which light emission due to mercury excitation becomes dominant at the time of startup.
[0008]
[Means for Solving the Problems]
The present invention provides means for solving the above problems. That is, the light receiving section 130 of the remote control signal has a light blocking means for reducing the viewing angle with respect to the lower side. Thereby, the intensity of the reflected light 220 shown in FIG. 7 is significantly attenuated at the position of the light receiving element in the light receiving section. As a result, the above problem at the time of starting the liquid crystal display device can be solved.
[0009]
Further, in the present invention, a preheating step for warming the backlight is included in a backlight lighting procedure at the time of startup (hereinafter, referred to as a “lighting sequence”). The lighting sequence according to this application warms the backlight tube before outputting an image. As a result, an excited state by mercury is immediately generated inside the tube of the backlight, and the above-mentioned problem is solved.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
FIG. 1 shows a light receiving section 130 of a remote control signal according to the present embodiment. The figure is a cross-sectional view of the light receiving unit 130 as viewed from the side. The escutcheon 13 is directed downward of the liquid crystal device.
[0011]
The light receiving section 130 of the remote control signal includes the light receiving window 10, the light guide plate 14, and the light receiving element 16. The light receiving window 10 is a window opened in escutchees 12 and 13 which are external housings of the liquid crystal display device. The light receiving window 10 may be covered with a cover through which an infrared signal from a remote controller (hereinafter, the “infrared signal” includes a signal based on infrared light and near infrared light).
[0012]
The light guide plate 14 is made of a material that transmits infrared light, and has a role of guiding an infrared signal from the light receiving window 10 to the light receiving element 16. The light receiving element 16 converts an infrared signal from the remote controller into an electric signal and outputs the electric signal. The center line 90 indicates the center line of the optical axis of the light guide plate 14 and the light receiving element 16.
[0013]
Here, the liquid crystal display device of the present invention has means for limiting the lower viewing angle of the light receiving unit 130. In the present embodiment, the reflected light 220 is blocked by providing the light shielding portion 1 on the light receiving window side of the light guide plate 14. The light-shielding portion 1 is provided by painting black ink below the center line 90 on the light receiving window side of the light guide plate 14.
[0014]
Further, on the light receiving element 16 side of the light guide plate 14, the light shielding unit 2 and the light shielding unit 3 are provided above the center line 90. By providing the light shielding portions 2 and 3, the reflected light 220 could be further blocked. The light-shielding portions 2 and 3 were also provided by applying black ink like the light-shielding portion 1.
[0015]
In the present embodiment, the light-shielding portion is configured by painting with black ink, but is not limited to painting with black as long as the reflected light 220 from below is blocked. The escutcheon 13 may be extended to the light shielding portion 1.
[0016]
FIG. 2 shows another method for limiting the lower viewing angle of the light receiving unit 130. FIG. 2 shows a state where the light guide plate 14 and the light receiving element 16 are inclined upward with respect to the horizontal line 95 of the light receiving window 10. By tilting the light receiving element upward in this manner, the lower viewing angle of the light receiving unit 10 can also be limited.
[0017]
(Embodiment 2)
FIG. 3 illustrates an embodiment in which the lower viewing angle of the light receiving unit 130 is not limited, but is increased to a position where the light emitting point 85 of the reflected light 210 does not enter the lower viewing angle of the light receiving unit 130. . Instead of limiting the lower viewing angle of the light receiving unit 130, the light emitting point 85 that reflects the reflected light 220 that interferes with the remote control signal may be removed from the lower viewing angle of the light receiving unit 130. Can be avoided.
[0018]
In other words, if the light emitting point 85 on the floor in front of the liquid crystal panel is located before the lower viewing angle of the light receiving unit 130, the reflected light 220 from the issuing point 85 does not enter the light receiving unit 130.
[0019]
Further, the infrared radiation light 200 emitted from the liquid crystal panel becomes weaker as the distance from the liquid crystal panel becomes longer. Therefore, the intensity of the reflected light from the light emitting point where the reflected light enters the lower viewing angle of the light receiving unit 130 (to the left of the light emitting point 85 in the figure) is weakened and does not interfere with the remote control signal.
[0020]
(Embodiment 3)
Next, a description will be given of means for solving the above-mentioned problem by operating a lighting sequence of the backlight. FIG. 4 shows a configuration of the backlight unit 100. The backlight unit 100 includes a microcomputer 20, a tube current control unit 22, a PWM dimming unit 24, an inverter 26, and a backlight 28. The backlight emits light with a drive current DI including an AC current portion of several tens of KHz and a non-signal portion. The tube current control unit 22 controls the amplitude of the AC portion. The PWM dimmer 24 controls the ratio between the AC portion and the no-signal portion.
[0021]
The microcomputer sends a control signal Ci to the tube current control unit 22 for control. In addition, the control signal Cp is sent to the PWM dimming unit 24 to control. The tube current control unit 22 and the PWM dimming unit 24 send the drive signals DCi and DCp to the inverter 26. The inverter 26 receives these signals and drives the backlight with the drive current DI.
[0022]
FIG. 5 shows a lighting sequence of the present invention. In FIG. 5, the vertical axis indicates the tube current value, and the horizontal axis indicates time. The time T0 indicates the time when the power of the liquid crystal display device is turned on. A period from time T0 to time T1 is a time for initialization of the liquid crystal display device. Specifically, data loading to the device and the like are performed. The time t1 from the time T1 to the time T2 is a time during which the first applied current is applied to the backlight.
[0023]
When the lamp tube of the backlight is cold, excitation of mercury hardly occurs, and infrared rays mainly emitted by argon are emitted. Therefore, by flowing a current larger than the normal steady-state current value during the time t1, the temperature in the tube of the backlight is increased. When the temperature in the tube rises, discharge by excitation of mercury starts, and light emission of the phosphor can be obtained.
[0024]
Next, at time T2, a video signal is sent to the liquid crystal panel to display a video. At this time, at time t2 between times T2 and T3, the second applied current is applied to the backlight. The second applied current is smaller than a normal steady-state current value. When the applied current is reduced, the discharge by argon is weakened, and the generation of infrared rays is reduced. That is, after the temperature is increased by the first applied current and light emission by mercury starts, the backlight is heated while the current is once decreased to suppress the emission of infrared light by argon.
[0025]
Next, at t3 from time T3 to T4, the applied current is gradually increased to a steady current value. At this time, the temperature in the tube of the backlight also rises, and light emission excited by mercury is mainly performed, and light emission of infrared rays is reduced.
[0026]
By doing so, after the time T2 at which an image is projected, the amount of infrared rays generated from the backlight is reduced, and malfunction of the remote controller can be avoided.
[0027]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the malfunction etc. of the remote control which arises at the time of starting of a liquid crystal display device can be avoided.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a remote control signal receiving unit of the liquid crystal display device of the present invention; FIG. 2 is a diagram showing an embodiment of a remote control signal receiving unit of the liquid crystal display device of the present invention; FIG. FIG. 4 is a diagram showing an embodiment of a remote control signal receiving unit of the liquid crystal display device of FIG. 4. FIG. 4 is a diagram showing a configuration of a backlight unit of the present invention. FIG. 5 is a diagram showing a starting sequence of the backlight of the present invention. FIG. 7 is a diagram showing an overview of a liquid crystal display device. FIG. 7 is a diagram for explaining a malfunction of a remote controller that occurs when the liquid crystal display device is started.
DESCRIPTION OF SYMBOLS 10 Receiving window 12 Escutcheon 13 Escutcheon 14 Light guide plate 16 Light receiving element 20 Microcomputer 22 Tube current control unit 24 PWM dimming unit 26 Inverter 28 Backlight

Claims (2)

A liquid crystal display device having a liquid crystal panel, a backlight, and a light receiving unit that receives an operation signal from a remote controller,
The light receiving unit includes a light receiving window provided in a housing body, a light receiving element, and a light guide plate provided between the light receiving element and the light receiving window and provided with a light blocking unit below an optical axis of the light receiving element. A liquid crystal display device comprising: 2. The liquid crystal according to claim 1, wherein a first applied current larger than a steady current value is applied to the backlight when the backlight is started, and a second applied current smaller than the steady current value is applied to the backlight. Display device.

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