Illumination – Plural light sources – With modifier
Reexamination Certificate
2001-12-19
2003-11-11
Cariaso, Alan (Department: 2875)
Illumination
Plural light sources
With modifier
C362S561000, C313S500000, C313S498000, C313S499000
Reexamination Certificate
active
06644832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an illumination device and a manufacturing method therefor, a display device, and an electronic instrument and, in particular, to an illumination device that is advantageous when formed as a front light placed on the viewing side of a display device, and to a display device whose viewing side is provided with this illumination device, as well as to an electronic instrument provided with this display device.
2. Description of the Related Art
Conventionally, a reflective type of liquid crystal display device (electro-optical device) is known in which exterior light such as sunlight shines into the viewing side of a liquid crystal display panel, is reflected inside the liquid crystal display panel, and is then transmitted to the viewer's side. However, because reflective type liquid crystal display devices are difficult to view in dark locations, a reflective type of liquid crystal display device provided with a front light (illumination device) on the viewer's side of the liquid crystal display panel has been proposed.
Broadly speaking, a conventional front light is constructed from a light source disposed on one edge of the viewing side of the liquid crystal display panel, and a light guide plate that is disposed on the viewing side of the liquid crystal display panel and that guides light from the light source toward the liquid crystal display panel.
However, the problem when using the above conventional front light is that a part of the light emitted from the light source does not travel towards the liquid crystal display panel, but instead travel from the surface of the light guide plate on the viewer's side directly towards the viewer (leakage light). As a result, the illumination efficiency is reduced and the leakage light causes the low contrast ratio of the liquid crystal display device leading to deterioration in the quality of the display.
SUMMARY OF THE INVENTION
The present invention was conceived in view of the above circumstances and it is an aim thereof to provide an illumination device that is capable of reducing the amount of light leaked that does not travel towards a display device but travels directly towards a viewer and that can thereby improve the illumination efficiency, and a manufacturing method for the illumination device, as well as a display device whose viewing side is provided with this illumination device, and an electronic instrument provided with this display device.
The illumination device of the present invention is provided with a transparent substrate having light emitting elements which are disposed on a surface thereof and which emit light, and the light emitting elements are provided with at least a transparent electrode, a light emitting layer, and a reflective electrode, in that order, from the outgoing surface of the transparent substrate.
That is, in the illumination device of the present invention, a reflective electrode functioning as a cathode electrode of the light emitting element reflects light emitted from the light emitting layer of a light emitting element, and then the reflected light travels towards a transparent electrode that functions as an anode electrode. As a result, light travels from one surface of a transparent substrate. Note that the illumination device of the present invention is provided on one side of the display device.
By employing a structure in which light that travels from the light emitting layer of a light emitting element is reflected by a reflective electrode and travels towards the opposite side of the reflective electrode in this way, when the illumination device of the present invention is provided in a display device, it is possible to reduce the amount of light leaked that does not travel towards the display device but travels from the illumination device directly towards the viewer. As a result, it is possible to obtain high contrast ratio. In addition, it is possible to illuminate efficiently towards the display device. As a result, the illumination efficiency is improved, and therefore power consumption can be reduced.
Furthermore, in the illumination device of the first aspect of the present invention, at least the reflective electrode of each light emitting element is formed in concavities that are formed having a pattern on one surface of the transparent substrate.
By forming at least the reflective electrode of each light emitting element inside the concavities that are formed on the transparent substrate, it is not necessary to perform a patterning process for at least the reflective electrodes of the light emitting elements. Accordingly, it is possible to simplify the patterning process.
It is also desirable that at least the reflective electrode and the light emitting layer of each light emitting element be formed in the concavities. By forming the light emitting layer inside the concavities in this way, the light emitting layer is wrapped with the transparent substrate, the reflective electrode, and the transparent electrode. Therefore, it is possible to prevent the light emitting layer from degradation. In particular, since the transparent substrate is made from a glass substrate or the like that has a low gas permeability, it is possible to prevent water vapor or the like from penetrating into the light emitting layer from the outside of the illumination device. Therefore, it is possible to prevent the light emitting layer from deteriorating.
Moreover, in the illumination device according to the first aspect of the present invention, it is desirable that the light emitting layer of the light emitting element consist of an organic electroluminescent material. Since the light emitting layer consists of an organic electroluminescent material that is capable of light emission at low voltages and that has a high level brightness, it is possible to reduce power consumption and to improve the illumination efficiency.
In the illumination device according to the first aspect of the present invention, it is also desirable that the concavities be formed on the outgoing surface of the transparent substrate; that the concavities have a concave curved bottom; and that at least the reflective electrode of each light emitting element be formed on the concave curved bottom of the concavities.
By forming concavities having a concave curved bottom on the outgoing surface of the transparent substrate and forming at least the reflective electrode of each light emitting element on the concave curved bottom of the concavities, it is possible to use the curved reflective electrode to condense the emitted light. Therefore, it is possible to reduce light leaking from the side of the light emitting elements and also to reduce the total reflected light within the transparent electrode and at the boundary between the transparent electrode and the light emitting layer. Accordingly, the light emitting element can emit light more efficiently, and the illumination efficiency can be improved.
It is also desirable that a protective layer be provided over the surface of the transparent substrate on which the concavities are formed so as to protect the light emitting elements.
The illumination device according to the first aspect of the present invention may be manufactured using a method in which, after the concavities have been formed on one surface of the transparent substrate with a pattern, at least the reflective electrode of the light emitting elements can be formed in the concavities.
Moreover, the illumination device may be manufactured using a method in which the concavities having a concave curved bottom are formed on one surface of the transparent substrate by isotropically etching after forming the resist in the pattern.
Furthermore, it is desirable that the light emitting elements have a layer structure which the transparent electrode, the light emitting layer, and the reflective electrode are sequentially formed in the concavities on the surface of the transparent substrate. Because the light emitting el
Iisaka Hidehito
Sakata Hidefumi
Takeuchi Tetsuhiko
Yoshida Shohei
Cariaso Alan
Negron Ismael
Seiko Epson Corporation
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