Radiation imagery chemistry: process – composition – or product th – Plural exposure steps
Reexamination Certificate
1999-04-09
2001-09-18
Wu, Shean C. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Plural exposure steps
C349S064000, C349S113000
Reexamination Certificate
active
06291146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The instant invention relates to an apparatus for diffusing reflected light, such as that from a reflective TFT-LCD (Thin Film Transistor-Liquid crystal display), into a desired solid angle which can be deviated from the unpleasant high intensity specular ray usually produced by the covering glass.
2. Description of the Related Art
To facilitate later discussion, we first define the optics terms and variables that shall be used, as shown in FIG.
1
. An incident plane is the plane containing the incident ray and the normal direction of the reflection point. A specular ray is defined as the reflected light ray on the incident plane whose reflected angle is equal to the incident angle. The light cone subtended by the diffused light is called a diffused light cone. Define the distribution angle of the diffused light cone in the incident plane as the vertical diffusion angle, &thgr;
S
, and that perpendicular to the incident plane as the horizontal diffusion angle, &thgr;
T
. A deviation angle &thgr;
0
is the angle between the specular ray and the central ray in the diffused light cone.
Traditional reflective light diffusing elements, such as diffusive films (e.g., the Poloroid Holographic Reflector and Sumitomo Lumisty) or bump reflectors (e.g., U.S. Pat. No. 5,610,741 and R.O.C. Patent No. 255,019), can not simultaneously achieve the goals of controlling the size of the diffused light cone, directing the reflected light distribution away from the specular ray, keeping the resolution power, and preventing from color dispersion. However, for certain applications the specular ray reflected by the covering glass is undesired because it is glare of the virtual image of the light source, and also, owing to the user's viewing angle, one side of the usual diffused light cone around the specular ray will be useless. Since the efficiency of usual reflective TFT-LCDs is already as low as 10%, extra waste of diffused light will demand a stronger light source and thus cause further increase in the cost. Therefore, effectively controlling and smoothly distributing diffused light within specific solid angle to yield higher intensity and more thorough use of reflected light from a reflective liquid crystal display (LCD) will be of great practical value.
One way to improve the above situation is by combining a diffusive film with a slant reflector structure. Although a diffused reflective light away from the specular ray can be achieved in this way, yet this method obviously increases the structure cost and, as a drawback of usual diffusive films, decreases the resolution of the LCD and causes the color dispersion problem.
SUMMARY OF THE INVENTION
An object of the invention is to provide a reflection-type light diffuser which can reflect and diffuse incident light to a desired solid angle with required intensity uniformity and has no degradation of display quality.
The invention provides a reflection-type light diffuser for scattering incident light into a desired angular area away from the specular ray, said reflector comprises:
a substrate;
a plurality of bumpy elements connected onto said substrate according to a pattern to form a nonplanar surface; and
a layer of reflective material uniformly coating onto said plurality of bumpy elements and uncovered said substrate, whereby a nonplanar reflecting surface is formed for reflecting and diffusing incident light from above;
wherein each of said plurality of bumpy elements has a first surface and a second surface, with said first surface having a longer slant than said second surface and the normal direction of said first surface being pointing to a predetermined direction.
As described above, according to the invention each of the first longer surfaces has a monotonically convex and/or concave curve in the incident plane for scattering incident light into a desired angular area in the incident plane with specific intensity uniformity.
Further, as described above, according to the invention each of the first longer slants has an irregular curve in the incident plane. Although the curve is irregular, the incident light will still be scattered into a certain angular area in the incident plane, yet the intensity uniformity is not guaranteed because of the irregular surface.
Yet further, according to the invention, each of the first longer slants has a wavy curve in the horizontal plane for scattering light into a desired solid angle with specific intensity uniformity.
Further according to the invention, each of the first longer slants has an irregular curve in the horizontal plane. Again, in spite of the irregularity, the incident light will be scattered into a certain solid angle without the guarantee of intensity uniformity.
Further, the invention provides a mask for the photo-exposure procedures for making a reflection-type light diffuser according to the instant invention, wherein said mask comprises an opaque plate with a plurality of parallel straight slits with each of said slits further comprises bumpy punctures and/or dented patches along one side of it.
Yet further, the invention provides a mask for the photo-exposure procedures for making a reflection-type light diffuser according to the instant invention, wherein said mask comprises an opaque plate with a plurality of regular wavy slits with fixed separation or irregular wavy slits with fixed separation.
REFERENCES:
patent: 5365354 (1994-11-01), Jannson et al.
patent: 5610741 (1997-03-01), Kimura
patent: 5945967 (1999-08-01), Rallison et al.
Chang Wei-Chih
Liu Chung-Yuan
Shiu Jyh-Wen
Ting Dai-Liang
Industrial Technology Research Institute
McDermott & Will & Emery
Wu Shean C.
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