Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified... – With bonding or intermediate layer of specified composition
Reexamination Certificate
2000-02-22
2003-09-23
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
With bonding or intermediate layer of specified composition
C428S001100, C428S001330, C428S001550, C428S349000, C428S112000, C428S113000, C428S359000, C428S599000, C428S362000, C428S307700
Reexamination Certificate
active
06623812
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reflector for liquid crystal devices, a method for fabrication of the reflector, and a reflective liquid crystal display device incorporating the reflector.
2. Description of Related Art
Transmission type or transmissive liquid crystal display (“LCD”) devices have been conventionally used which have a flat-type light source, called a backlight, behind a liquid crystal panel. However, the backlight used in this type of LCD devices consumes a large amount of electric power. The incorporation of such an LCD device in rechargeable battery-operated, portable information terminal equipments, so-called “mobile terminals”, has accordingly led to the shortened service lives thereof, which has been a problem.
As a solution to such a problem, a reflection-type or reflective LCD device has been proposed which incorporates a reflector for reflecting the incident light that has passed through a liquid crystal layer. Display images are created by reflecting ambient light at the reflector surface toward a front side of the device. Elimination of the backlight results in the marked reduction of power consumption and extension of service lives of portable information terminal equipments incorporating the reflective LCD device.
A conventional reflector for use in such reflective LCD devices utilizes a thin metal film formed by depositing a metal, such as aluminum or silver, by various techniques, including vacuum evaporation, sputtering and ion-plating.
However, the thin metal film such deposited generally has a specular surface which provides the high-intensity reflected light with the angle equal to the angle of incidence, and accordingly, its use problematically results in a narrow angle of view.
In order to obtain a wider angle of view, the intensity of light scattered in a direction perpendicular to a display screen must be increased for incident light that enters from all directions. For this purpose, a method has been proposed which provides microscopic projections and depressions over an entire surface of a reflector to assure diffuse reflection. This method improves the problem of narrow angle of view, since diffusion reflection occurs at the entire surface of the reflector due to the presence of the microscopic projections and depressions provided thereon.
The techniques used to provide such microscopic roughness on a reflector surface are broadly classified into two types. A first type of techniques treats a reflector substrate itself, as by polishing with abrasive or etching with chemicals. However, the practice of this type of techniques results in poor reproducibility of the shapes of microscopic projections and depressions, and accordingly in the difficulty to control microscopic light diffusion at the reflector surface.
A second type of techniques utilizes a photosensitive resin which, after being applied to a reflector substrate, is etched, as by a photolithographic process, to form a mat surface of microscopic roughness that is subsequently covered with a reflection layer. However, this type of techniques requires a number of steps, increasing the complexity of a reflector-forming process. Also, it has been difficult to provide an even distribution of uniformly shaped projections and depressions over a wide area such as of a display part of LCD devices. These deficiencies have led the display part to exhibit reflective characteristics largely varied from location to location.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a reflector, suitable for use in liquid crystal display devices, which performs uniform light diffusion enabling a wide angle of view and which can be efficiently fabricated by a simple process, a method for fabrication thereof and a reflective liquid crystal display device incorporating the reflector.
The reflector of the present invention is particularly suitable for use in reflective liquid crystal display devices which display images by reflecting at a reflector surface the incident light that has passed through a liquid crystal layer. The reflector includes a resin layer having at its surface microscopic projections and depressions, or alternatively, a light diffusion layer, respectively formed by application of a coating composition containing a binder resin and crosslinked resin particles.
In accordance with a first aspect of the present invention, the reflector includes a resin layer having at its surface microscopic projections and depressions and formed by application of a coating composition containing a binder resin and crosslinked resin particles, and a reflection layer provided on the resin layer so as to follow the shapes of microscopic projections and depressions of the resin layer.
In the reflector according to the first aspect, the reflection layer thereof follows the surface profile of the underlying resin layer to have microscopic projections and depressions. Accordingly, diffusion reflection of incident light occurs at a surface of the reflection layer in such a fashion that the reflected light can be scattered in a direction perpendicular to a display screen.
In accordance with a second aspect of the present invention, the reflector has a reflection layer and a light diffusion layer formed on the reflection layer by application of a coating composition containing a binder resin and crosslinked resin particles.
In the reflector according to the second aspect, light incident thereupon passes through the light diffusion layer and arrives at a surface of the reflection layer where it is reflected. The reflected light, when it passes through the light diffusion layer, is scattered in a direction perpendicular to a display screen.
In the first aspect of the present invention, the incorporation of the crosslinked resin particles in the coating composition imparts the microscopic surface roughness to the resin layer. Such use of the crosslinked resin particle is based on the ground that they can be manufactured in the form of very fine particles showing a sharp particle size distribution curve. For example, the crosslinked resin particles can be manufactured having a particle size distribution which permits particles in the 10 nm-1,000 nm size range to account for at least 90%, preferably at least 95% of the particles. The use of such crosslinked resin particles assures an even distribution of uniformly-shaped microscopic projections and depressions over an entire surface of the resin layer. The crosslinked resin particles for use in the present invention preferably have an average particle size in the range of 50 nm-600 nm. The particle size distribution of the crosslinked resin particles can be determined as by a laser diffraction type particle size distribution measuring apparatus. Although having fine particle sizes, the crosslinked resin particles are dispersed in a uniform fashion throughout the resin layer, which further assures the even distribution of uniformly-shaped microscopic projections and depressions over an entire surface of the resin layer.
In the second aspect of the present invention, the inclusion of the aforementioned crosslinked resin particles in the coating composition results in the formation of the light diffusion layer having desired light diffusivity on the reflection layer. In the second aspect, such use of crosslinked resin particles serves to impart uniform and satisfactory light diffusion characteristics to the light diffusion layer. Those crosslinked resin particles have the reduced refractive index and are less affected by optical interference compared to inorganic particles, and the use thereof results in the reduced occurrence of problematic white spots and the like on displayed images.
The crosslinked resin particles used in the present invention can be prepared by various polymerization techniques, including emulsion polymerization, soap-free emulsion polymerization using no emulsifier, and dispersion polymerization using a polar organic solvent as a medium.
The particularly preferred, crossli
Kaji Hirokazu
Minamino Hiromasa
Ohata Masashi
Seio Mamoru
Tanaka Hideto
Hon Sow-Fun
Olson & Hierl Ltd.
Pyon Harold
LandOfFree
Reflector, method for fabrication thereof and reflective... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reflector, method for fabrication thereof and reflective..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reflector, method for fabrication thereof and reflective... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3098758