JP3099983B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device which uses light emitted from a phosphor excited by infrared light as a backlight.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display device equipped with a backlight is often used as a display of a laptop or a notebook computer. At present, two types of backlights, a fluorescent lamp represented by a cold-cathode tube and an electroluminescence (EL) lamp, have been put into practical use. Conditions required for the backlight include (1) high brightness, (2) low power consumption, and (3) thin type.
One is. In particular, recently, the importance of portable and thin notebook personal computers has been increasing, and a backlight that satisfies the above-mentioned conditions is required for the practical use of such computers. However, although the EL lamp is a thin surface light source, it has problems in luminance and power consumption. On the other hand, fluorescent lamps have high luminance and relatively low power consumption, but they are line light sources and have a certain thickness. On the other hand, besides the method described above, Japanese Patent Application Laid-Open Nos. 59-5094, 59-213175, 60
-346, 60-149028, and 61-254978 using a method using a phosphor. However, most of the phosphor materials disclosed therein emit light when excited by ultraviolet light. There are several candidates for ultraviolet light sources, all of which have basically the same shape as fluorescent lamps, and cannot solve the above-mentioned disadvantages of the prior art. Ultraviolet light can also cause ozone generation, which results in air pollution.

[0003]

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a liquid crystal display device having a compact, low power consumption and safe backlight.

[0004]

The present invention relates to a light-transmitting liquid crystal display device using light emitted from a phosphor layer using infrared light as a light source as a backlight, wherein the phosphor layer is provided on the front side of the display side, and the infrared light is supplied to the liquid crystal display device. The present invention relates to a light-transmitting liquid crystal display device characterized in that an arbitrary two-dimensional pattern is formed by using the method, and the two-dimensional pattern can be displayed by the fluorescence of the phosphor layer by irradiating the phosphor layer with the pattern.

FIG. 1 shows a light transmitting type liquid crystal display device 1 in which a phosphor layer 2 is formed on the display side. The phosphor layer 2
Emits light from the infrared light source 3. Since the phosphor layer 2 emits light by infrared rays, there is no generation of ozone, which is a disadvantage of the conventional technology, and there is no fear of air pollution. As such a phosphor material, a material utilizing an infrared stimulating effect, a material utilizing a quantum counting effect, a material utilizing multi-stage energy transmission, and the like are known. Of these, those utilizing the infrared stimulating effect require that the phosphor be irradiated with short-wavelength light in advance to excite it to a metastable state. As the short-wavelength light, so-called external light such as room light emitted from the display side of the element can be used. If adopted separately (see FIG. 3), a stable display can be realized irrespective of the external light and the state of the liquid crystal display element. As the liquid crystal display element 1, a liquid crystal display element which is generally used in a light transmission type liquid crystal display device can be employed. The method for forming the phosphor layer is not particularly limited. However, when the phosphor layer is formed directly on the surface of the liquid crystal display element, it is necessary to adopt a method that does not damage the liquid crystal display element. When the liquid crystal display element has a transparent substrate, the phosphor layer may be provided on the transparent substrate.

FIG. 1 is a view showing one example of a light transmission type liquid crystal display device of the present invention. In the case of FIG. 1, a similar two-dimensional pattern is formed by transmitting infrared light through the liquid crystal display element 1 showing an arbitrary two-dimensional pattern, and the phosphor layer 2 excited by the pattern emits light to display. I do. In this case, since an image is displayed using the light emission of the phosphor layer 2, there is no polarization. As a result, excellent display with a wide viewing angle is possible, but since the phosphor material is exposed to form the phosphor layer 2 on the display side, it is necessary to prevent mechanical or chemical damage from the outside. It is necessary to employ appropriate protective means such as providing a transparent protective film accordingly.

As the infrared light source 3, a light emitting diode (LED) or a semiconductor laser (LD) can be used. Since these are all point light sources, it is necessary to use a plurality of light sources or to use a magnifying optical system in order to uniformly illuminate the front surface on the display element side. The most desirable method is a method in which a plurality of light sources are used as a line light source, and the line light is uniformly applied to the entire display element using an optical means. In this case, an optical system when a fluorescent lamp, which is a line light source, is used for the backlight can be similarly used. Since both the LED and the LD are semiconductor elements, they have a longer life than conventional fluorescent lamps and EL lamps, and can be made compact even if a plurality of them are used. Since the power consumption is proportional to the number of elements used, it cannot be said unconditionally. However, since the power consumption per unit is very small, it can be reduced by optimizing the design of the optical system and the luminous efficiency of the phosphor. It is possible to achieve power consumption. As the wavelength of the infrared light, one included in the wavelength region of the excitation spectrum of the phosphor material used is adopted.

In the liquid crystal display device of the present invention, when performing color display, three kinds of phosphor materials which respectively emit red, green and blue light, which are the three primary colors of light, are used and arranged in a two-dimensional pattern. Form. The arrangement of the pattern is the same as the arrangement of the color filters conventionally used for color liquid crystals. As a method for forming a phosphor pattern, a method similar to a phosphor forming method conventionally used for a color CRT is used. In the liquid crystal display device of the present invention, when performing color display, it is possible to omit a color filter which is required in the related art. As a result, the manufacturing cost is reduced, and the intensity of light is increased by an amount that has been attenuated by passing through the color filter, and the brightness of image display is improved. Color display can be realized without using a color filter.

[0009]

Embodiments of the present invention will be described below.

Example 1 In this example, a liquid crystal display device as shown in FIG. 2 was manufactured. On a transparent glass substrate, a stimulable phosphor material C
aS: A uniform film was formed using Ce and Sm by using a coating method. This was adhered to the display side of the display element 1 as a phosphor layer 2. As the infrared light source 3, CaS: Ce,
Oscillation wavelength 1.2 included in the wavelength region of Sm photostimulated excitation light
A plurality of μm semiconductor lasers formed in a line were used. In this way, the infrared light that was the line light was converted into surface light using the edge light method known as the prior art. By irradiating the phosphor layer 2 with the infrared surface light emission thus formed, Ca emitting green light is emitted.
S: A liquid crystal display device was obtained using Ce, Sm as a backlight. In this embodiment, the phosphor material is CaS:
Although Ce and Sm were used, the effect of the present invention is not limited to this, and similar operations were obtained with other phosphor materials. In this embodiment, the edge light method is used as the method of forming the surface light source, but the same effect can be obtained by using another backlight method.

Example 2 In this example, a liquid crystal display device as shown in FIG. 3 was manufactured. The configuration of the element is the same as that of Example 1 except that a white fluorescent lamp 6 is provided as a stimulating excitation light source on the side opposite to the display side of the liquid crystal display element 1. With such a configuration, a display element having a more stable image display than that of the first embodiment can be realized. In particular, the effect of this example was remarkable when the stimulable phosphor layer was used.

Example 3 In this example, a display element showing a color display was manufactured.
On a transparent glass substrate, light 3 of the stimulable phosphor material
CaS: Eu, Sm (red), Ca whose primary colors are shown by photostimulated light
S: Ce, Sm (green), SrS: Ce, Sm (blue)
Was formed in a pattern arrangement as shown in FIG. 4 using a coating method. Using this as a phosphor layer, a display element using the same element configuration as in Example 1 was produced. As a result, a display element exhibiting good color display was realized. Next, using the same phosphor layer, a display element having the same element configuration as in Example 2 was produced. As a result, Example 2
In addition to the effects obtained in the above, a display element exhibiting good color display was realized.

[0013]

(1) Effect on Claim 1 A liquid crystal display device which is compact, consumes less power, and has a small viewing angle dependence is obtained. (2) Effect on Claim 2 In addition to the effect of Claim 1, a liquid crystal display device with stable display quality was realized. (3) Effect on Claim 3 A color display liquid crystal display device capable of omitting a color filter was obtained.

[Brief description of the drawings]

FIG. 1 shows a backlight type liquid crystal display device of the present invention.
FIG. 3 is a schematic diagram of an example.

FIG. 2 is a diagram showing an edge-light type liquid crystal display device of the present invention.

FIG. 3 is a diagram showing a liquid crystal display device of the present invention similar to that shown in FIG. 2, except that a white fluorescent lamp is provided as a stimulating excitation light source.

FIG. 4 is a view showing a pattern arrangement of stimulable phosphor layers of three primary colors in a color liquid crystal display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display element 2 Phosphor layer 3 Infrared light source 4 Reflector 5 Diffusion plate 6 White fluorescent lamp

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1335 G02F 1/13 505 G02F 1/1347 G09F 9/00-9/46

Claims (3)

(57) [Claims] 1. A light-transmitting liquid crystal display device using, as a backlight, light emitted from a phosphor layer using infrared light as a light source, wherein the phosphor layer is provided on the front side of the display side, and the liquid crystal display device uses infrared light. A light-transmitting liquid crystal display device, wherein an arbitrary two-dimensional pattern is formed by irradiating the phosphor layer with the pattern, and the two-dimensional pattern can be displayed by the fluorescence of the phosphor layer. 2. The phosphor layer is formed by using an infrared stimulable phosphor material. In addition to the infrared light source,
The light transmission type liquid crystal display device according to claim 1, further comprising a stimulating light source. 3. The light transmission type color liquid crystal display device according to claim 1, wherein the phosphor layer is constituted by a pattern layer formed by using three kinds of phosphor materials which respectively emit light of three primary colors. .