JP2004020766A - LCD display - Google Patents

Abstract

Provided is a liquid crystal display that uses a cold-cathode tube as a backlight and performs dimming in a two-stage configuration of high luminance and low luminance while reducing luminance loss on the high luminance side.
A liquid crystal display is provided on an LCD, a first diffusion plate provided on a back surface of the LCD to improve luminance unevenness, and provided on a back surface of the first diffusion plate to absorb ultraviolet light and emit visible light. A phosphor film that emits fluorescent light, a high-intensity lamp provided on the back surface of the phosphor film, a wavelength-selective film provided on the back surface of the high-intensity lamp, and transmitting ultraviolet light, and a back surface of the wavelength-selective film. And a second diffuser plate for improving brightness unevenness, provided on the back surface of the second diffuser plate, a low-intensity lamp UV cold cathode lamp, and provided on the back surface of the UV cold cathode lamp to reflect ultraviolet light. Reflective sheet.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display in which a backlight used in an aircraft liquid crystal display requiring a high dimming ratio is improved.
[0002]
[Prior art]
2. Description of the Related Art In a conventional liquid crystal display for an aircraft, a dimming ratio of 3000: 1 or more is required in order to secure anti-glare properties during night flight. On the other hand, in a cold cathode lamp, the discharge voltage is high because the tube voltage is very high, and only a dimming ratio of 500: 1 can be obtained at the maximum. For this reason, dimming at the time of high luminance and low luminance is performed by separate lamps, and light emission is switched to satisfy the dimming request.
[0003]
FIG. 3 shows the configuration of the liquid crystal display, wherein the upper side is the front of the panel and the lower side is the back. On the back surface of the LCD 13 protected by the transparent protective plate 12, a first diffusion plate 14 for improving luminance unevenness and a high-luminance lamp 16 which is a cold-cathode lamp for high luminance are arranged. Further, a second diffusion plate 18, a low-intensity lamp 25 as a low-intensity cold-cathode lamp, and a reflection sheet 20 are provided on a substrate 21 on the back of the high-intensity lamp 16 with a reflective film 17 interposed therebetween. .
[0004]
For the high-brightness lamp 16, a small-diameter lamp having a high tube brightness and advantageous for high brightness is used to satisfy the maximum brightness requirement, and for the low-brightness lamp 25, a large-diameter lamp having a low driving impedance and advantageous for dimming is used. You are using a lamp.
[0005]
At the time of high-intensity lighting, only the high-intensity lamp 16 is turned on, and dimming of about 100: 1 is performed. At the time of low-brightness lighting, only the low-brightness lamp 25 is turned on, and similarly, dimming of about 100: 1 is performed. In the case of the luminance corresponding to the lamp switching, the operation is performed in such a manner that the lights are overlapped and the discontinuity of the luminance is avoided.
[0006]
[Problems to be solved by the invention]
However, in the liquid crystal display described in the related art, the dimming ratio can be increased, but the reflection film on the back of the high-intensity lamp does not increase the reflectivity, and becomes a leakage light at the time of high-intensity lighting. Lose. As a result, there is a problem that the luminance of high luminance is reduced by about 10%.
[0007]
Therefore, there is a problem that it is necessary to solve the problem of reducing the luminance loss on the high luminance side while using a cold cathode tube for the backlight and performing dimming in a two-stage configuration of high luminance and low luminance.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a liquid crystal display according to the present invention has the following configuration.
[0009]
(1) The liquid crystal display is provided on an LCD, a back surface of the LCD, a first diffusion plate for improving luminance unevenness, and a back surface of the first diffusion plate, and absorbs ultraviolet light to emit visible light. A phosphor film that emits fluorescence, a high-intensity lamp provided on the back surface of the phosphor film, a wavelength-selective film provided on the back surface of the high-intensity lamp, and transmitting ultraviolet light, and a back surface of the wavelength-selective film. A second diffuser for improving brightness unevenness; a UV cold-cathode lamp of a low-intensity lamp; and a UV diffuser provided on the back of the UV cold-cathode lamp for reflecting ultraviolet light. And a reflection sheet.
[0010]
(2) In addition, the liquid crystal display is provided on the LCD, a first diffusion plate provided on the back surface of the LCD to improve luminance unevenness, and provided on the back surface of the first diffusion plate to absorb ultraviolet light and become visible. A phosphor film that emits fluorescence of light, a high-intensity lamp provided on the back surface of the phosphor film, a silver-evaporated reflector provided on the back surface of the high-intensity lamp, and transmitting ultraviolet light having a wavelength of 300 to 320 nm; A second diffusion plate provided on the back of the silver vapor-deposited reflection plate to improve luminance unevenness, provided on the back of the second diffusion plate, a low-intensity lamp UV cold cathode lamp, and a back surface of the UV cold cathode lamp; And a reflection sheet for reflecting ultraviolet light.
[0011]
As described above, by using a UV lamp as the low-brightness lamp in a liquid crystal display that performs desired dimming by switching between a high-brightness lamp and a low-brightness lamp, it is possible to reduce the brightness loss on the high-brightness side. Becomes possible.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of a liquid crystal display according to the present invention will be described with reference to the drawings. The same components as those described in the related art will be described with the same reference numerals.
[0013]
As shown in FIG. 1, the liquid crystal display according to the first embodiment of the present invention performs dimming at high luminance and low luminance with separate lamps, and performs desired dimming by switching light emission. An LCD 13 provided inside a display 11 covered with a transparent protective plate 12, a first diffusion plate 14 provided on the back of the LCD 13 to improve luminance unevenness, and a first diffusion plate 14 A fluorescent film 15 that absorbs ultraviolet light and emits visible light fluorescence, a high-intensity lamp 16 that is provided on the back of the fluorescent film 15, and a fluorescent film 15 that is provided on the back of the high-intensity lamp 16. A wavelength-selective film 17 for transmitting light, a second diffuser 18 provided on the back of the wavelength-selective film 17 to improve brightness unevenness, and a low-luminance lamp provided on the back of the second diffuser 18 UV cold cathode lamp 19 Provided on the rear surface of the pole lamp 19, a reflection sheet 20 that reflects ultraviolet light and has a structure in which on the substrate 21.
[0014]
As the high-intensity lamp 16, a small-diameter lamp having a high tube luminance and advantageous for high luminance is used to satisfy the maximum luminance requirement.
[0015]
As a UV (Ultra Violet) cold cathode lamp 19, which is a low-intensity lamp, a large-diameter lamp having a low driving impedance and advantageous for dimming is used.
[0016]
The wavelength-selective film 17 is composed of a dielectric multilayer film, and is designed to have a very high reflectance in the visible light region and to transmit in the ultraviolet region. In the dielectric multilayer film, a filter having arbitrary characteristics can be manufactured using the refractive index, the film thickness, and the number of layers of the dielectric material as parameters. For example, the resonator reflection surface of a He—Ne laser is formed of a dielectric multilayer film, and has a reflectance of 99% or more. It is very high even when compared with about 90% reflectance of an aluminum-deposited surface which is generally used as a reflection surface.
[0017]
In the liquid crystal display 11 having such a configuration, at the time of high-brightness lighting, only the high-brightness lamp is lit, and dimming of about 100: 1 is performed.
At the time of lighting at a low luminance point, only the UV cold cathode lamp 19 is turned on, and dimming of about 100: 1 is similarly performed. The UV cold-cathode lamp 19 is also a kind of cold-cathode lamp, and the lamp characteristics including dimming are the same as those of the low-luminance lamp described in the related art.
[0018]
Ultraviolet light output from the UV cold cathode lamp 19 passes through the wavelength-selective film 17 and is absorbed by the phosphor film 15 to emit visible light fluorescence.
This fluorescent property depends on the physical properties of the phosphor. As a phosphor that absorbs ultraviolet light and emits white light, for example, calcium halophosphate is well known. This is a phosphor widely used in general fluorescent lamps.
[0019]
In the embodiment, it seems that the following three problems (phosphor efficiency, color rendering property, and phosphor transmittance at the time of high-luminance light emission) are considered to be new. Not be.
(1) The light emission by the phosphor is used at the time of low luminance dimming, and the light emission efficiency does not necessarily have to be high. In some cases, the second diffusion plate 18 on the front surface of the UV cold cathode lamp 19 may be omitted.
(2) Since the color sensitivity of the human eye becomes dull at low luminance, the color rendering is not a major problem. It is necessary to make the fluorescent characteristics as close as possible to a high-intensity lamp.
(3) Due to the above-mentioned efficiency, the phosphor is extremely thin or only needs to be applied to spots, and the transmittance of visible light can be increased. In addition, since the phosphor itself has a diffusion function, the efficiency of the first diffusion plate 14 on the rear surface of the LCD 13 can be increased.
[0020]
Next, a liquid crystal display according to a second embodiment of the present invention will be described with reference to the drawings.
[0021]
As shown in FIG. 2, the liquid crystal display of the second embodiment performs dimming at high luminance and low luminance by different lamps, and performs desired dimming by switching light emission. And
An LCD 13 covered with a transparent protective plate 12, a first diffusion plate 14 provided on the back of the LCD 13 to improve luminance unevenness, and a first diffusion plate 14 provided on the back of the first diffusion plate 14 to absorb ultraviolet light. A phosphor film 15 that emits visible light fluorescence, a high-intensity lamp 16 provided on the back surface of the phosphor film 15, and a silver deposition provided on the back surface of the high-intensity 16 lamp and transmitting ultraviolet light having a wavelength of 300 to 320 nm. A reflection plate 22, a second diffusion plate 18 provided on the back surface of the silver-deposited reflection plate 22 to improve luminance unevenness, and a UV cold cathode lamp 19 of a low-intensity lamp provided on the back surface of the second diffusion plate 18. And a reflection sheet provided on the substrate 21 at the back of the UV cold cathode lamp 19 and reflecting ultraviolet light.
[0022]
The silver deposited reflector 22 is replaced with the wavelength-selective film of the first embodiment. The reflectance characteristic of the silver-deposited surface greatly depends on the wavelength, and is as high as about 98% for visible light, but almost transparent at 5 to 10% for ultraviolet light with a wavelength of 300 to 320 nm. Therefore, if the emission wavelength of the UV cold cathode lamp 19 is selected to be ultraviolet light, the operation is basically the same as that described in the first embodiment.
[0023]
【The invention's effect】
As described above, the liquid crystal display according to the present invention has a very high reflectance with respect to visible light on the rear side of the high-intensity lamp. There is an effect that it can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an internal structure of a liquid crystal display according to the present invention.
FIG. 2 is a schematic cross-sectional view showing an application example of the liquid crystal display.
FIG. 3 is a schematic cross-sectional view showing an internal structure of a liquid crystal display according to the related art.
[Explanation of symbols]
11 LCD display 12 Protective plate 13 LCD
14 First Diffusion Plate 15 Phosphor Film 16 High Brightness Lamp 17 Wavelength Selective Film 18 Second Diffusion Plate 19 UV Cold Cathode Lamp 20 Reflection Sheet 21 Substrate 22 Silver Evaporated Reflection Plate

Claims (2)

LCD and
A first diffusion plate provided on the back of the LCD to improve luminance unevenness;
A phosphor film that is provided on the back surface of the first diffusion plate and absorbs ultraviolet light and emits visible light fluorescence;
A high-intensity lamp provided on the back of the phosphor film,
A wavelength-selective film that is provided on the back of the high-intensity lamp and transmits ultraviolet light,
A second diffusion plate provided on the back surface of the wavelength-selective film to improve luminance unevenness;
A UV cold cathode lamp of a low-intensity lamp, provided on the back of the second diffuser;
A reflection sheet provided on the back of the UV cold cathode lamp and reflecting ultraviolet light;
LCD consisting of LCD and
A first diffusion plate provided on the back of the LCD to improve luminance unevenness;
A phosphor film that is provided on the back surface of the first diffusion plate and absorbs ultraviolet light and emits visible light fluorescence;
A high-intensity lamp provided on the back of the phosphor film,
A silver-evaporated reflector provided on the back of the high-intensity lamp and transmitting ultraviolet light having a wavelength of 300 to 320 nm,
A second diffusion plate provided on the back surface of the silver vapor-deposited reflection plate to improve luminance unevenness;
A UV cold cathode lamp of a low-intensity lamp, provided on the back of the second diffuser;
A reflection sheet provided on the back of the UV cold cathode lamp and reflecting ultraviolet light;
LCD consisting of

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