Color display device with one light source on one side and...

Liquid crystal cells – elements and systems – Particular structure – Particular illumination

Reexamination Certificate

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C362S027000, C362S035000

Reexamination Certificate

active

06181391

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a color display device.
Recently, color liquid crystal display devices are used in OA devices such as computers and displays of domestic electrified products such as televisions. As this type of color liquid crystal display device, there is widely known a color liquid display device of a TFT system. The color liquid crystal display device of a TFT system comprises color filters corresponding to three primary with thin film transistors (TFT), and a backlight having white color light sources. In this display device, liquid crystals corresponding to the respective color filters are made open by a drive circuit and light is transmitted through the liquid crystal made open, thereby obtaining a mosaic color mixture based on the combination of red, green and blue.
The above-described color liquid crystal display device of a TFT system enables the procurement of a clear full color image. However, on the other hand, the minute color filters of red, green and blue are needed for the respective pixel. Since the color filters are expensive parts in the color liquid display device.
Under the above-described circumstances, recently, there is proposed a color-filterless color liquid crystal display device which a three primary color backlight is combined with a monochromatic liquid crystal cell without the use of color filter and thin film transistor (see, for example, Japanese Patent Application Laid-Open Publication No. 6-138459). In this display device, pulse luminescence is caused of the three primary color light sources sequentially on a periodic basis, and the liquid crystal is made open with the same timing as that with which color light is given forth by such pulse luminescence to thereby green and blue.
Also, there is known a display device wherein three light guiding means are sequentially piled up, and any one of three primary color light sources is disposed in each of the light guiding means to thereby control the color distribution of each of the light sources through the on and off operation of respective switches, namely so-called electrically ornamented signboard.
However, in the above-described filterless color liquid crystal display device or electrically ornamented signboard, although many proposals concerning the control of the liquid crystal cell have hitherto bean made, there are not so many practical proposals concerning a backlight. For example, this type of backlight has three light sources. Therefore, miniaturization thereof is difficult. On the other hand, a color filter is provided on a light source side so as to obtain a pure color having a high degree of chromaticness. This raises the specific problem of being accompanied by an increase in the number of the parts used, with the result that the light utilization efficiency becomes inferior. No practical solution to this specific problem has hitherto existed.
SUMMERY OF THE INVENTION
The present invention has been made in view of the above-described conventional techniques and has an object to provide a structure which can solve the specific problem for the color-filterless color display device.
The present invention provides a color display device, which is equipped with singular light guiding means that faces a liquid crystal cell and first, second and third light sources that respectively independently exhibit three primary colors. The first and second light sources are disposed on a one-end surface side of the light guiding means. The third light source is disposed on the other-end surface side.
According to this construction, since the light guiding means is only one in number, the structure can be simplified and miniaturized. Also, since of the three light sources exhibiting the primary colors the first and second light sources exhibiting respectively two primary colors are disposed on one-end surface side of he light guiding means and the third light source exhibiting the remaining one primary color is disposed on the other-end surface of the light guiding means, the probability decreases that the light which enters from one light source to the light guiding means is hardened by the other light sources. This decreases the light loss and increases the amount of outgoing light.
Reflecting means for directing the light from the light sources toward the light guiding means may be disposed on one-end surface and the other-end surface of the light guiding means.
According to this construction, the lights from the light sources can be efficiently condensed by the reflecting means on to one-end and the other-end surface of the light guiding means. Therefore, there increases the luminance of the light guiding means.
The light sources may be caused to make their pulse luminescence in synchronism with the drive timing with which the liquid of the liquid crystal cell is driven.
According to this construction, by sequentially periodically causing pulse luminescence of the primary color light sources and opening the liquid crystal with the same timing at which this pulse luminescence is made, a residual color mixture is obtained based on the combination of red, green, and blue colors.
Diffusing means may be provided on one surface of the light guiding means facing the liquid crystal cell, dots may be provided on the other surface of the light guiding means, and a reflecting member that covers the other surface of the light guiding means may be provided.
According to this construction, since the diffusing means, dots, and reflecting member are provided, the light that has entered into the light guiding means is made to go out toward the liquid crystal cell side by being diffused. Therefore, the light sources and dots are not seen, with the result that the luminance can be made uniform.
The diffusing means may be constructed using a diffusion sheet.
According to this construction, the diffusing means is constituted by a freely demountable sheet-like member. Therefore, the operation of tuning the diffusing means at the developing time becomes easy to perform. This results in a decrease in the developing cost and thus becomes one factor causing a decrease in the manufacturing cost.
The first light source may consists of a transparent color-developing tube and may be located nearer to the light guiding means than the second light source.
According to this construction, the whole or a part of light from the second light source enters into the light guiding means by passing through the first light source. At this time, since the first light source is a transparent color-developing tube and, in the condition of its being lit out, is transparent, the light from the second light source passes sufficiently through the first light source and enters into the light guiding means. For this reason, the loss of the light from the second light source due to the effect of the light source is suppressed to being kept small, with the result that the amount of light emission increases.
The transparent color-developing tube may be constructed of a transparent glass tube having neon gas sealed therein.
According to this construction, the transparent color-developing tube is transparent when lit out and, when lit up, turns red and therefore can construct the three primary colors together whit the other light sources.
The second light source may be constructed using a cold-athode tube that exhibits a blue color.
According to this construction, the second light source that emits a blue color light is located more remote from the light guiding means than the first light source. However, the white balance luminance of the blue color (second light source) is higher than that of each of the red and green colors (first and third light sources) that are located closer to the light guiding means. Therefore, the emission of the three primary color lights falls under a so-called “white color region”.
The dots may include a complementary color dot that is colored to the complementary color of one of the light sources.
According to this construction, in even a case where no uniform plane luminesce

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