JPS6113278A - Transmission type liquid crystal display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a transmissive liquid crystal display device having a backlight source.

(Prior art and its problems) Liquid crystal display devices have the advantage of low operating voltage and significantly lower power consumption than other display devices. Because of these characteristics, it has excellent compatibility with integrated circuits, and is often used as a display device for various numbers, characters, graphics, etc. In recent years, monochrome or full-color LCD televisions have been developed.

The problem with liquid crystal display devices is that the contrast is low and the viewing angle is limited, making it difficult to see the display clearly.

The clarity of such display can be greatly improved by using a transmissive liquid crystal display device that utilizes light from the back side.

In particular, in the case of a color display device combined with a color filter, the reflective type does not provide enough light and requires a high-brightness backlight source. However, problems associated with backlight sources arise in transmissive liquid crystal display devices. The brightness is insufficient for use in bright places, and the power consumption of the light source is extremely large, and the volume required for the light source system is large. Heat-generating light bulbs, fluorescent lamps, cathode ray tubes, etc. are used as light sources, and although these tubes can provide a certain level of illumination brightness, their power consumption and occupied space are lower than those of liquid crystal display panels. Therefore, it is extremely large, and the characteristics of low power consumption, light weight, and thinness, which are characteristics of liquid crystal display devices, are significantly impaired. In addition to the above-mentioned tube-type light source, there is an electroluminescent plate as a thin plate-shaped light source, but it is currently used in low brightness areas, so it is not possible to use the electroluminescent plate as the back light source of a transmissive liquid crystal display device in bright places. At times, the contrast is extremely low, and color display devices that employ color filters are unable to provide good display, especially due to insufficient light intensity.

As described above, it is desired to improve the back light source and illumination method of transmissive liquid crystal panels in order to realize clear display.

(Object of the Invention) An object of the present invention is to provide an ultra-thin transmissive liquid crystal display device with effectively low power consumption, which improves the problems associated with the back light source of the transmissive liquid crystal display device as described above. It is in.

(Structure of the Invention) According to the present invention, a transmission type liquid crystal display device is characterized in that an electroluminescent plate that can transmit part or most of external light from behind is installed on the back side of a liquid crystal display panel. is obtained.

(Detailed explanation of the configuration) - The device of the present invention can effectively reduce the power consumption required for illumination because it can use both back illumination from outside light and back illumination from the electroluminescent plate, and the electroluminescent plate is thin. Therefore, the entire display device can also be made thinner.

The translucent electroluminescent material of the present invention can be easily manufactured. An electroluminescent plate emits light by applying a voltage to an electroluminescent phosphor layer, such as zinc sulfide, to which an activator is attached. The dielectric materials currently used in AC, electroluminescent, and AC-driven electroluminescent plates all have translucent properties. Therefore, by constructing the electrode for voltage application with a transparent electrode such as ITO or a thin gold film, an electroluminescent plate whose entire surface is transparent can be obtained.

Furthermore, as a second method, the electrode on the liquid crystal panel side is made of a transparent electrode, but the electrode on the back side is made of a metal electrode such as aluminum that also serves as a reflective layer, and this metal electrode is made into a thin stripe electrode. , external light may be transmitted through the gap between the electrodes.

In the second method, external light is introduced only through the opening of the metal electrode, which reduces the utilization rate of external light. It has the advantage of efficiently extracting light. FIG. 1 shows a display device of the present invention using a translucent electroluminescent plate, and FIG. 2 shows a display device of the present invention using an electroluminescent plate having a back striped metal electrode. 1 is a liquid crystal display panel, 2, 3
is an electroluminescent plate.

(Example 1) An electroluminescent plate having a structure in which BaTiQ3 powder, Zn8 phosphor powder, and ■TO powder were laminated between sheets with an ITO thin film formed on a polymer film was prepared. ITO
By applying an alternating voltage between the electrodes, 400 cd/-
Emission brightness of about 100% was obtained. In addition, this electroluminescent plate has a white color because it is composed of powder, but by paying attention to the powder particle size and the solvent of the polymer material, and making the layer as thin as possible, the J45% or more It has transmittance.

This electroluminescent plate is placed over the liquid crystal display panel, and the pole is 1.
The AI electrode has a stripe shape with a width of 0.97β at a parrot period.
．． It is patterned into stripes of 0.19 width with a period of 2 parrots.

This electrode shape provides an electroluminescent plate that transmits about 45+% of external light. This electroluminescent plate was installed behind the liquid crystal display panel. Note that if you are concerned about the appearance of striped light emission or transmission of external light, a thin diffuser plate may be inserted between the liquid crystal panel and the electroluminescent plate.

(Effects of the Invention) When the outside light is bright, the liquid crystal display device of the present invention uses the outside light as backlighting, so there is no power consumption of the backlight source, and it can be used without impairing the low power consumption of the liquid crystal. When the electroluminescent plate is lit, visibility can be further improved. It is also possible to use it in a dark place. As described above, optimal visibility is achieved by turning on and off the electroluminescent plate according to the surrounding brightness, or by adjusting the brightness by adjusting the driving voltage and driving frequency, and also by making use of external light. Therefore, less power consumption is achieved. In addition, the electroluminescent plate is 2′
Since the display device is as thin as 1.3 mm or less, the entire display device can also be made thinner.

Note that in order to effectively utilize external light, it is better to arrange the display panel so that the external light is incident perpendicularly to the rear surface of the display panel. usually,
External light often enters from the front upper part, so it is also effective to use a mirror to view the panel.

As described above, the display device of the present invention has great industrial value.

[Brief explanation of drawings]

FIGS. 1 and 2 schematically show the cross-sectional structure of the display device of the present invention. Liquid crystal display panel...1. Electroluminescent plate...
2. 3￥1 Figure 2 + ” - Light

Claims (1)

[Claims] 1. A transmissive liquid crystal display device, characterized in that a translucent electroluminescent plate is installed behind a liquid crystal display panel so that external light and electroluminescent light can be used as back illumination.