Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
1999-10-01
2001-11-27
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
Reexamination Certificate
active
06323919
ABSTRACT:
This application is based on Japanese patent application HEI 10-281678, filed on Oct. 2, 1998, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a reflection type display, and more particularly to a reflection type display with a front light.
b) Description of the Related Art
A liquid crystal display will now be described as an example of a display using electro-optical material which changes optical characteristics in accordance with electric field, however, the present invention is not limited to that.
Reflection type liquid crystal displays have been known as one type of the liquid crystal displays. A reflection type liquid crystal display is expected as a suitable display for an information terminal or the like because of low power consumption.
However, images displayed on the reflection type liquid crystal display are invisible in dark environment because the display has no light source. To overcome this disadvantage, a reflection type liquid crystal display having a front light on its viewer's side has been proposed. For example, such the reflection type liquid crystal display comprises a wedge-shaped light guide plate having a light source on its side. The light guide plate is placed on the viewer's side of the display panel. The wedge-shaped light guide plate has a planar bottom surface and a prismatic top surface comprising planar surfaces and slanted (oblique) surfaces which are arranged alternately.
The lights are introduced into the light guide plate from the light source which is placed on the side of the light guide plate. The slanted surfaces of the light guide plate reflect the introduced lights toward the liquid crystal display. A reflection plate of the liquid crystal display reflects the lights toward the viewer's eyes through the light guide plate. That is, the wedge-shaped light guide plate works as a reflector and a light transmitter.
To work as an ideal light transmitter, the planar surfaces of the prismatic top surface of the light guide plate must be almost parallel to the bottom surface. If each of the planar surfaces of the prismatic top surface is formed at a large angle with the bottom surface, the reflected lights from the liquid crystal display are refracted by the light guide plate because it works as a prism. Such the refraction influences the display quality of the liquid crystal display.
In order to reflect lateral lights in the light guide plate so as to incident upon the liquid crystal display at almost right angle, each of the slanted surfaces is required to be formed at an angle of approximately 45 degrees with the bottom surface.
The light guide plate having such the slanted surfaces and planar surfaces arranged alternately will become tapered, that is, wedge shaped. For example, the height around the light incident side of such the wedge-shaped light guide plate differs from the height around the light outgoing side, and the difference is approximately 2 to 3 mm. Such the wedge-shaped light guide plate may deteriorate the display quality of the liquid crystal display. In a case where a touch panel is disposed on the liquid crystal display, for example, a wedge-shaped gap appears between the liquid crystal display and the touch panel because of the wedge shaped light guide. This gap causes parallax.
As stated above, the reflection type liquid crystal display with the front light can be driven with low power consumption because the light source is activated only when the user needs it. However, employing the front light also brings several disadvantageous matters.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a reflection type display with a front light which has less disadvantages caused by the front light.
According to one aspect of the present invention, it is provided a reflection type display comprising a panel which comprises a first transparent substrate arranged to face external incident lights, a second substrate opposing to and coupled with said first substrate through a gap therebetween, electro-optical material retained in the gap, and electrodes formed on at least one of said first and second substrates in order to apply electric field to said electro-optical material, said electrodes forming pixels arranged repeatedly in the first direction at a first pitch; a light guide plate disposed outside of said first substrate on the light incident side, comprising a light incident portion to which the lights are introduced, and a pair of major surfaces including a planar surface facing to said first substrate and a prismatic surface on other side, said prismatic surface comprising pseudo-planar surfaces which are formed at an angle of approximately 0.5 to 3.5 degrees with said planar surface and are raised greater as being distanced away from said light incident portion and slanted surfaces which are formed at an angle of approximately 40 to 60 degrees with said planar surface and are descended greater as being distanced away from said light incident portion, said pseudo-planar surfaces and said slanted surfaces are arranged alternately to form multiple prisms arranged repeatedly at a second pitch which is different from said first pitch; and a combination of a linear polarizing plate and a quarter wavelength plate disposed on said planar surface of said light guide plate.
Modifying the shape of the light guide plate can reduce disadvantageous matters caused by employing the front light.
The top surface of the light guide plate is prismatic. The prismatic surface comprises the pseudo-planar surfaces and the slanted surfaces which are arranged alternately. The pseudo-planar surfaces are raised greater as being distanced away from the light source. The slanted surfaces are descended greater as being distanced away from the light source. Thus, the heights of the apex lines of the prisms are almost uniformed, and the completed light guide plate has a pseudo-planar shape.
To obtain uniform brightness from the light guide plate, the reflection rate of the prisms should be increased as being distanced away from the light source. This adjustment is accomplished by adjusting depths of the prisms (that is, the difference between the apex line of the prism and the bottom line of the prism).
REFERENCES:
patent: 4811507 (1989-03-01), Blanchet
patent: 5584556 (1996-12-01), Yokoyama et al.
patent: 5727107 (1998-03-01), Umemoto et al.
patent: 6088074 (2000-07-01), Suzuki
patent: 6108059 (2000-08-01), Yang
patent: 6151089 (2000-11-01), Yang et al.
patent: 6196692 (2001-03-01), Umemoto et al.
patent: 6199995 (2001-03-01), Umemoto et al.
patent: 8-94844-A (1996-04-01), None
Ishige Osamu
Oki Yoji
Yang Ying Bao
Dudek James A.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Schechter Andrew
Sony Corporation
LandOfFree
Reflection type display with front light does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reflection type display with front light, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reflection type display with front light will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2569768