JP2013156491A - On-vehicle liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle liquid crystal display device which automatically selects and adjusts a built-in light source and an external light source as a light source of a backlight unit of a liquid crystal display device in accordance with the illuminance around the arrangement position of a liquid crystal panel, adjusts brightness of the liquid crystal panel, thereby obtains excellent visibility, and has low power consumption.SOLUTION: The on-vehicle liquid crystal display device includes: a transmission type liquid crystal panel 2 including a display observation surface; a backlight unit 7 including a light guide plate 8 arranged so as to face an opposite display observation surface of the liquid crystal panel 2, a built-in light source 9 and an external light source 10 which emit light to the light guide plate 8, and dimming means 16 for adjusting the quantity of light of the external light source 10 and/or dimming means 15 for adjusting the quantity of light of the built-in light source 9; an illuminance detector 17 for measuring ambient illuminance on the display observation surface of the liquid crystal panel 2; a panel brightness detector 18 for measuring brightness of the liquid crystal panel 2; and control means 20 for controlling the dimming means 15 and 16 of the backlight unit 7 by a detection result of the illuminance detector 17 and the panel brightness detector 18, and being capable of adjusting the quantity of illumination light.

Description

  The present invention relates to a liquid crystal display device, and in particular, a vehicle-mounted liquid crystal display device including a backlight unit capable of automatically adjusting the brightness of a display screen of a liquid crystal panel according to ambient brightness in order to ensure visibility. About.

  2. Description of the Related Art Conventionally, a liquid crystal display device in which a backlight unit is disposed on the back side of a liquid crystal panel has been used as a display unit for various instruments and navigation systems disposed on an automobile console.

  In the backlight unit, a light guide plate is disposed on the back surface of the liquid crystal panel, and a plurality of LEDs (Light Emitting Diodes) as light sources are disposed on a side end surface of the light guide plate, and the emitted light of the LEDs is guided. The light guide plate is guided into the light plate and emitted from the surface of the light guide plate to the liquid crystal panel as illumination light.

  Incidentally, there has been a demand for liquid crystal display devices to reduce power consumption. In order to simply reduce the power consumption, the power consumption of the power supply can be reduced by reducing the luminance of the backlight. However, in a transmissive liquid crystal display device, if the backlight luminance is lowered, the display quality such as luminance and contrast on the display screen of the liquid crystal panel is directly affected. Therefore, in the current situation where display quality must be maintained or further improved, the amount of light cannot simply be reduced in order to reduce power consumption.

  In view of this, a configuration has been proposed for enabling a bright display while keeping power consumption low by adding a light collecting function to the liquid crystal display device and supplementing the amount of light of the backlight of the LED (see Patent Document 1). .

  The liquid crystal display device disclosed in Patent Document 1 exemplifies a liquid crystal display device used in a small photographic device, and the amount of sunlight taken in by the user through the light collecting function is on the display screen of the liquid crystal display device. When it is determined that the amount of light is more than a level at which an object to be photographed can be recognized and there is no practical problem, the backlight is turned off to reduce power consumption.

Japanese Patent Laid-Open No. 10-68948

  However, in an in-vehicle liquid crystal display device, when a vehicle passes through a tunnel, the user (driver) determines whether or not display using sunlight is possible, and the light source of the backlight unit is an LED or the like. It is not realistic to perform the operation of switching between the backlight and the outside light, and it is also unsuitable from the viewpoint of safety of the driving operation of the automobile.

  In addition, in-vehicle liquid crystal display devices, it is necessary to perform liquid crystal display with sufficient quality even in a bright place. For this purpose, a backlight having sufficient luminance is required.

  That is, in the in-vehicle liquid crystal display device, it is assumed that the display screen is irradiated with very bright illuminance of about 100,000 lux. In that case, the brightness of the display screen of the liquid crystal panel is relatively low, and the display screen is very difficult to see. As countermeasures, conventionally, it has been proposed to increase the amount of light incident on the light guide plate by increasing the LED current of the backlight unit or increasing the number of LEDs arranged in advance. The increase in power consumption was against the demand for low power consumption.

  The object of the present invention is to automatically select and adjust the built-in light source and the external light source as the light source of the backlight unit of the liquid crystal display device according to the illuminance around the arrangement of the liquid crystal panel, thereby adjusting the brightness of the liquid crystal panel. An object of the present invention is to provide an in-vehicle liquid crystal display device capable of adjusting and performing display capable of obtaining good visibility and meeting the demand for low power consumption.

  In order to solve the above problems, an in-vehicle liquid crystal display device of the present invention includes a transmissive liquid crystal panel provided with a display observation surface, and a light guide plate disposed to face the opposite display observation surface of the liquid crystal panel, A built-in light source and an external light source that emit light that is illumination light of the liquid crystal panel to the light guide plate, a dimming unit that adjusts the amount of light of the external light source, and / or a dimming unit that adjusts the amount of light of the built-in light source. A backlight unit, an illuminance detector that measures the ambient illuminance on the display observation surface of the liquid crystal panel, a panel luminance detector that measures the luminance of the liquid crystal panel, and the detection results of the illuminance detector and the panel luminance detector And a control means capable of adjusting the light quantity of the illumination light by controlling the light control means of the backlight unit.

  Further, when the control means detects that the detection result of the panel luminance detector is inappropriate as the luminance corresponding to the illuminance detected by the illuminance detector, the light amount and / or external light of the built-in light source of the backlight unit Control is performed to adjust the light amount of the light source so that the luminance of the liquid crystal panel is appropriate.

  Furthermore, when the control means performs adjustment to increase the amount of light used as illumination light of the liquid crystal panel, the brightness of the liquid crystal panel is made to correspond to the illuminance detected by the illuminance detector only by adjusting the external light source. When the brightness of the built-in light source cannot be adjusted and the light intensity of the liquid crystal panel is adjusted to reduce the light quantity of the illumination light, the brightness of the liquid crystal panel can be adjusted only by adjusting the built-in light source. Control is performed to adjust the amount of light from the external light source when the luminance cannot be set to an appropriate luminance corresponding to the illuminance detected by the illuminance detector.

  According to the in-vehicle liquid crystal display device of the present invention, it is possible to ensure optimal brightness and always display with good visibility according to the change in ambient illuminance. In addition, the configuration in which the external light source is given priority and used as illumination light emitted from the backlight unit has an excellent effect that power consumption can be reduced.

The block diagram which shows the structure of the vehicle-mounted liquid crystal display device of this invention

  A vehicle-mounted liquid crystal display device (hereinafter simply referred to as a liquid crystal display device) 1 according to the present embodiment includes a transmissive liquid crystal panel 2 having a known configuration. That is, the liquid crystal panel 2 has a pair of transparent substrates 3 (3A, 3B) that are pressure-bonded via a peripheral sealing material 4, and is disposed on the display observation surface side of the pair of transparent substrates 3. A transparent electrode (not shown) is formed on the inner surface of the transparent substrate 3A. In addition, a color filter layer, a smoothing layer, and a transparent electrode (none of which are shown) are sequentially stacked on the inner surface of the transparent substrate 3B disposed on the side opposite to the observation surface. An alignment film (not shown) is provided on the transparent electrodes formed on the transparent substrates 3A and 3B. Further, the peripheral sealing material 4 is disposed in the peripheral portion of the surfaces of the transparent substrates 3A and 3B facing each other, and liquid crystal (not shown) is disposed in the space surrounded by the peripheral sealing material 4. ) And a plurality of spacers (not shown).

  The liquid crystal display device 1 includes a backlight unit 7 that is disposed on the side opposite to the display viewing surface of the liquid crystal panel 2 and that irradiates the liquid crystal panel 2 with light from a light source, which will be described later.

  The backlight unit 7 includes a light guide plate 8 disposed so as to face an opposite display observation surface that is the back surface of the liquid crystal panel 2. In this embodiment, the backlight unit 7 includes two types of light sources: a built-in light source 9 and an external light source 10 as light sources to be emitted from the surface of the light guide plate 8 to the liquid crystal panel 2 as illumination light. It has a light source.

  The built-in light source 9 includes a plurality of LEDs (Light Emitting Diodes) 11 disposed on the side end surface of the light guide plate 8, and the light emitted from the LEDs 11 is guided into the light guide plate 8. The light is emitted from the surface to the liquid crystal panel 2 as illumination light. The built-in light source 9 is not limited to the LED 11, and there is no particular limitation on the type such as an incandescent bulb or a fluorescent tube, and the arrangement position is not limited to the side end of the light guide plate.

  The external light source 10 includes a lighting port 12 for taking in external light and a light transmission means 13 for guiding external light incident from the lighting port 12 to the light guide plate 8. The outside light introduced from the light is guided into the light guide plate 8 and emitted from the surface of the light guide plate 8 to the liquid crystal panel 2 as illumination light. The light transmission means 13 can be exemplified by a light guide tube, a mirror, a prism, an optical fiber and the like that connect the lighting port 12 and the light guide plate 8, but there is no particular limitation on the type thereof.

  Further, the backlight unit 7 includes a first dimming unit 15 (control circuit) for adjusting the light amount of the built-in light source 9 and a first dimming unit for adjusting the light amount of the external light source 10 as the dimming unit 14. And the brightness of the built-in light source 9 is controlled by the first light control means 15, and the brightness of the external light source 10 is controlled by the second light control means 16. It is configured.

  For example, the first dimming unit 15 may be a voltage adjustment driver disposed in the electric circuit of the light source, or may be a switch that simply turns on and off the built-in light source 9.

  Various modes can be considered as the second light control means 16. For example, when a light guide tube is used as the light transmission means 13, is the second dimming means 16 having a shutter-type mechanism capable of opening and closing the light guide tube, and is the external light source 10 used simply as the external light source 10 Or not. When a mirror or prism is used as the light transmission means 13, a single external light adjustment liquid crystal panel is interposed on the optical path from the lighting port 12 to the light guide plate 8 as the second light adjustment means 16. Then, a driver for adjusting the voltage is disposed in the driving electric circuit of the liquid crystal panel for adjusting the external light, and the light transmittance of the liquid crystal panel for adjusting the external light is changed by the voltage (electric signal). Can be adjusted. Similarly, when an optical fiber is used as the optical transmission means 13, the amount of light can be reduced using an electrical signal.

  Furthermore, the liquid crystal display device 1 includes an illuminance detector 17 that measures the illuminance of the display observation surface of the liquid crystal panel 2, a panel luminance detector 18 that measures the luminance of the display observation surface of the liquid crystal panel 2, and the illuminance detector 17. In addition, a control unit (controller) 20 is provided that can control the light control unit 14 of the backlight unit 7 in consideration of the detection result of the panel luminance detector 18.

  The illuminance detector 17 is a sensor such as a photodiode that measures the illuminance (ambient illuminance) of external light irradiated around the display observation surface on the display observation surface side of the liquid crystal panel 2.

  The panel luminance detector 18 is a sensor such as a photodiode that measures the luminance of light emitted through the liquid crystal panel 2 on the display observation surface side of the liquid crystal panel 2. In the transmissive liquid crystal panel 2, the transmissive liquid crystal panel 2 may be disposed between the reverse display observation surface of the liquid crystal panel 2 and the backlight unit 7.

  The control means 20 is connected to the illuminance detector 17 and the panel luminance detector 18 via electric circuits. Then, the luminance detected by the panel luminance detector 18 and the illuminance detected by the illuminance detector 17 are referred to, and based on the result, the dimming means 14 of the backlight unit 7 is controlled to display the liquid crystal panel 2. It is configured to make it easier to see.

  In the present embodiment, when the control means 20 detects that the detection result of the panel luminance detector 18 is inappropriate as the luminance corresponding to the illuminance detected by the illuminance detector 17, the built-in light source of the backlight unit 7 The light quantity of 9 and / or the light quantity of the external light source 10 is adjusted to control the liquid crystal panel 2 to have an appropriate brightness. Specifically, the control means 20 obtains an allowable luminance range (hereinafter referred to as an ideal luminance range) of the liquid crystal panel 2 corresponding to the illuminance of the display observation surface for obtaining good visibility, and detects the panel luminance. It is determined whether the detection result of the detector 18 is in the ideal luminance range corresponding to the illuminance detected by the illuminance detector 17, and based on the result, the brightness of the built-in light source 9 is adjusted to the first dimming. The brightness of the external light source 10 can be controlled by the second light control means 16.

  At that time, the ideal luminance range is stored and managed in advance so that it can be referred to as a data table, and each time the illuminance detector 17 detects illuminance, this data table is referred to and the detection result of the panel luminance detector 18 is collated. Then, the brightness of the built-in light source 9 and / or the brightness of the external light source 10 may be appropriately controlled by the first light control means 15 and / or the second light control means 16.

  In this way, by taking into account the relationship with the illuminance of the display observation surface of the liquid crystal panel 2, it is possible to always ensure good visibility of the liquid crystal panel 2 by adjusting the luminance of the display observation surface of the liquid crystal panel 2. it can.

  Further, in the present embodiment, the control means 20 performs control to use the external light source 10 in preference to the built-in light source 9 as light emitted from the backlight unit 7 to the liquid crystal panel 2.

  In other words, the illuminance detector 17 detects the luminance of the liquid crystal panel 2 only by adjusting the external light source 10 when the control means 20 performs adjustment to increase the amount of light used as illumination light of the liquid crystal panel 2. When it is not possible to obtain an appropriate luminance corresponding to the illuminance, the light amount of the built-in light source 9 is adjusted. On the contrary, when performing adjustment to reduce the amount of light that becomes the illumination light of the liquid crystal panel 2, the brightness of the liquid crystal panel 2 is made to correspond to the illuminance detected by the illuminance detector 17 only by adjusting the built-in light source 9. When it is not possible to obtain a sufficient luminance, control is performed to adjust the light quantity of the external light source 10.

  Specifically, if the second dimming means 16 is a mechanism for switching whether or not to use external light as the external light source 10, it switches to use external light.

  Moreover, if the light quantity of external light can be adjusted, all the light taken in from the lighting port 12 is utilized. The brightness of the display observation surface of the liquid crystal panel 2 is sufficient to obtain good visibility in relation to the illuminance of the display observation surface of the liquid crystal panel 2 using only the external light source 10. If not, the built-in light source 9 is driven supplementarily.

  As described above, the configuration in which the external light source 10 is prioritized and used in the backlight unit 7 can meet the demand for low power consumption.

  Then, the illuminance detector 17 measures the ambient illuminance of the liquid crystal panel 2 that changes every moment, and the control means 20 determines that the luminance of the liquid crystal panel 2 measured by the panel luminance detector 18 is the ambient illuminance of the liquid crystal panel 2. As the brightness of the corresponding liquid crystal panel 2, it is determined whether or not the brightness is appropriate for obtaining good visibility. If the brightness is inappropriate, the light control means 14 of the backlight unit 7 is controlled. The amount of illumination light is adjusted, the result of the light amount adjustment is fed back to the control means 20 as the luminance of the liquid crystal panel 2 measured by the luminance detector, and the ambient illuminance of the liquid crystal panel 2 measured by the illuminance detector 17 The vehicle-mounted liquid crystal display device according to the present embodiment is performed by repeatedly performing control management such as determining whether the luminance is appropriate for obtaining good visibility as the luminance of the liquid crystal panel 2 corresponding to the above. , In response to changes in the ambient illumination, to ensure optimum luminance can always perform good visibility of the display.

  For example, in the liquid crystal display device 1 of the present embodiment, when the illuminance on the display observation surface of the liquid crystal panel 2 is low, that is, when the surrounding environment of the liquid crystal panel 2 is dark, the amount of available external light is limited. The built-in light source 9 compensates only for the brightness (light quantity) that is insufficient to obtain the brightness necessary to visually recognize the display on the liquid crystal panel 2, thereby ensuring good visibility without using excessive power. can do.

  Further, when the illuminance on the display observation surface of the liquid crystal panel 2 is extremely high, that is, when the surrounding environment of the liquid crystal panel 2 is bright enough to be dazzling, good visibility is ensured unless the display screen of the liquid crystal panel 2 is also set to high luminance. However, it is assumed that only the amount of external light taken from the lighting port 12 is insufficient, but in that case too much brightness is necessary to obtain the luminance necessary for visually recognizing the display on the liquid crystal panel 2. By supplementing the thickness (light quantity) with the built-in light source 9, good visibility can be secured without using excessive power. And the light which is radiate | emitted from the backlight unit 7, and permeate | transmits the inside of the liquid crystal panel 2 can make it easy to visually recognize the display of a display observation surface by surpassing the light which irradiates a display observation surface.

Further, for example, the display observation surface of the liquid crystal panel 2 is in the shade, and the illuminance detected by the illuminance detector 17 is low, but direct light is inserted into the lighting port 12, which is sufficient for the external light source 10. If the brightness of the external light source 10 is controlled by the second light control means 16 to reduce the amount of light, an appropriate luminance (about 200 cd / m ² ) can be obtained. Good visibility can be ensured without using the light source 9 at all.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Liquid crystal panel 3 Transparent substrate 3A (Display observation surface side) Transparent substrate 3B (Non-display observation surface side) Transparent substrate 4 Peripheral sealing material 7 Backlight unit 8 Light guide plate 9 Built-in light source 10 External light source 11 LED
DESCRIPTION OF SYMBOLS 12 Light aperture 13 Light transmission means 14 Light control means 15 1st light control means 16 2nd light control means 17 Illuminance detector
18 Panel brightness detector 20 Control means

Claims (3)

A transmissive liquid crystal panel with a display observation surface;
A light guide plate disposed facing the non-display viewing surface of the liquid crystal panel, a built-in light source and an external light source that emits light serving as illumination light of the liquid crystal panel to the light guide plate, and an amount of light of the external light source A backlight unit comprising a dimming means for adjusting and / or a dimming means for adjusting the amount of light of the built-in light source;
An illuminance detector for measuring the ambient illuminance on the display observation surface of the liquid crystal panel;
A panel brightness detector for measuring the brightness of the liquid crystal panel;
According to the detection results of the illuminance detector and the panel luminance detector, control means capable of adjusting the light quantity of the illumination light by controlling the light control means of the backlight unit;
An in-vehicle liquid crystal display device comprising:   When the control means detects that the detection result of the panel luminance detector is inappropriate as the luminance corresponding to the illuminance detected by the illuminance detector, the light amount of the internal light source of the backlight unit and / or the external light source The in-vehicle liquid crystal display device according to claim 1, wherein control is performed to adjust the amount of light so that the luminance of the liquid crystal panel is appropriate.   When the control means performs adjustment to increase the amount of light that is the illumination light of the liquid crystal panel, the control means appropriately adjusts the brightness of the liquid crystal panel to the illuminance detected by the illuminance detector only by adjusting the external light source. When the brightness cannot be adjusted, the amount of light from the built-in light source is adjusted, and when adjusting to reduce the amount of light used as illumination light for the liquid crystal panel, the brightness of the liquid crystal panel is detected by adjusting the built-in light source only. The vehicle-mounted liquid crystal display device according to claim 2, wherein control is performed to adjust a light amount of the external light source when an appropriate luminance corresponding to the illuminance detected by the device cannot be achieved.

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