Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Patent
1996-11-04
1999-10-12
Sikes, William L.
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
349 64, 349 65, 362 31, G02F 1133, F21V 704
Patent
active
059661925
DESCRIPTION:
BRIEF SUMMARY
SPECIFICATION
1. Technical Field
The present invention relates to a surface light source device and a liquid crystal display, and more specifically, to a surface light source device utilizing an optical element that shows a light scattering effect and a light guiding effect, i.e., "light scattering guide," and a planar element that has a prismatic effect, i.e., "prism sheet," and a liquid crystal display using the same for backlighting.
2. Background Art
A surface light source device utilizing a light scattering guide and a prism sheet is proposed and used for backlighting of a liquid crystal display and the like. The prism sheet is formed of a platelike optical material having a surface (i.e., "prismatic surface") that is formed with V-shaped repetitive corrugated rows.
It is known that the prism sheet functions to modify the propagation direction properties of light fluxes. In the conventional surface light source device, therefore, the prism sheet is located solely on the exit-surface side of the light scattering guide.
FIG. 1 shows an arrangement of the principal part of a conventional surface light source device that employs a prism sheet. Referring to FIG. 1, numeral 1 denotes a light scattering guide having a wedge-shaped profile. The light scattering guide 1 is composed of a matrix of, for example, polymethyl methacrylate (PMMA) and particles uniformly dispersed therein, the particles having a refractive index different from that of the matrix. These particles will be referred to as "particles of different refractive index" hereinafter. A relatively thick end surface of the light scattering guide 1 provides an incidence surface 2. A light source element (e.g., fluorescent lamp) L is located in the vicinity of the incidence surface 2.
A reflector 3 is arranged along one surface (back surface) 6 of the light scattering guide 1. A specular silver foil or diffusive white sheet is used as the reflector 3. An illumination light is emitted from the other surface, i.e., an exit surface 5, of the light scattering guide 1. The prism sheet 4 is located outside the exit surface 5.
For ease of illustration, the distance between the light scattering guide 1 and the prism sheet 4 and the pitch of prismatic rows are exaggerated. One surface of the prism sheet 4 is composed of V-shaped prismatic surfaces 4a and 4b, while the other surface is a flat surface (bright surface) 4e from which an illumination flux 4f is emitted. The liquid crystal display is constructed by locating a conventional liquid crystal display device (i.e., "liquid crystal display panel") outside the prism sheet 4.
Since the thickness of the light scattering guide 1 is reduced with distance from the incidence surface 2, reflection repeatedly occurs between the exit surface 5 and the slanting back surface 6 in the light scattering guide 1. In consequence, a uniform high luminance can be obtained.
The light introduced from the light source element L into the light scattering guide 1 is subjected to scattering and reflecting actions as it is guided toward a relatively thin end surface 7. In this process, light emission from the exit surface 5 occurs gradually.
The light emitted from the exit surface 5 is provided with directivity and parallelized, depending on the diameter (correlation distance of a nonuniform-refraction structure, in general) of the particles of different refractive index dispersed in the light scattering guide 1. In other words, the illumination light taken out of the exit surface 5 has a tendency to propagate preferentially in a specific direction.
The greater the diameter of the particles of different refractive index (the greater the correlation distance of the nonuniform-refraction structure, in general), the more positively the light emitted from the exit surface 5 is parallelized. Usually, the preferential propagation direction (main propagation direction of the illumination flux) is raised at an angle of about 25.degree. to 30.degree. to the exit surface as viewed from the side of the incidence surface 2.
Thus, the functio
REFERENCES:
patent: 4642736 (1987-02-01), Masuzawa et al.
patent: 5046826 (1991-09-01), Iwamoto et al.
patent: 5303322 (1994-04-01), Winston et al.
patent: 5414599 (1995-05-01), Kaneko et al.
patent: 5485354 (1996-01-01), Ciupke et al.
patent: 5600455 (1997-02-01), Ishikawa et al.
patent: 5659410 (1997-08-01), Koike et al.
patent: 5704703 (1998-01-01), Yamada et al.
Higuchi Eizaburo
Koike Yasuhiro
Nitto Jushi Kogyo Kabushiki kaisha
Sikes William L.
Ton Toan
LandOfFree
Surface light source device and a liquid crystal display does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Surface light source device and a liquid crystal display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Surface light source device and a liquid crystal display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-657531