Illumination – Revolving
Reexamination Certificate
2003-05-08
2004-06-01
Dunn, Drew (Department: 2872)
Illumination
Revolving
C362S561000, C349S063000
Reexamination Certificate
active
06742907
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an illumination device and display device using this wherein a light-guide plate is arranged at the front face of an illuminated object and this illuminated object is two-dimensionally surface-illuminated, and more particularly relates to an illumination device and display device using this wherein properties such as illumination function, recognisability, contrast and energy-saving that are based on the optical diffusion characteristic of this light-guide plate are greatly improved.
2. Description of Related Art
Conventionally, various types of illumination device are employed that exhibit the function of surface illumination in respect of a display device that requires planar illumination, such as a liquid crystal display device.
For example there is known a display device that is arranged at the back face of the object to be illuminated, such as a liquid crystal display panel; normally such an illumination device is arranged to be constantly lit. An illumination device is also known mounted on a liquid crystal display device having a reflective function. In the case of such an illumination device, a reflective plate is arranged at the back face of the liquid crystal display panel and the device is employed by illumination provided by external light. Furthermore, an illumination device is also known that is arranged together with a semi-transparent reflective plate at the back face of a liquid crystal display panel; this illumination device is used for reflection when the environment is brighter and to provide back lighting illumination when the environment is dark (for such devices, for example Early Japanese Patent Publication No. SHO.57-049271, Early Japanese Patent Publication No. SH0.57-054926 and Early Japanese Patent Publication No. SH0.58-095780 may be referred to).
However, conventional illumination devices having solely an illumination function suffered from the problem that power consumption in order to keep the light source constantly lit was large; for example, they could not be used over a long time to provide illumination for portable equipment. Also, in the case where a conventional display device having solely a reflective function was mounted on a liquid crystal display device or the like, there was the problem that contrast of the display screen was low, making it impossible to employ them in a dark environment. Furthermore, illumination devices that are employed with a semi-transparent reflective plate inevitably have the problem that the display is dark both when used with reflection and when used with back lit illumination; this technique represents an unsatisfactory compromise and has not become popular at all.
In these circumstances there has recently been proposed for example in Early Japanese Patent Publication No. H.6-324331 an illumination device that is arranged at the front face of a display device such as a liquid crystal display device. The illumination device of this proposal is incorporated in a thin liquid crystal display device and has the object of ensuring high contrast of illumination both when lit and when not lit. Specifically, a thin illumination device is arranged at the top face (front face) of a liquid crystal display and a reflective plate is arranged at the back face of the liquid crystal display. The illumination device comprises a light-guide plate and a light source that is arranged at the end face of this light-guide plate or in its vicinity. At the optical output face of the light-guide plate, there is formed an indented shape comprising faces practically parallel with this face and faces approximately perpendicular thereto. The indented shape may be formed for example of a plurality of ribs or projections of cylindrical or prismatic shape.
However, the illumination devices arranged at the front face of these publications are adapted to light sources of rod or linear shape. For such light sources, fluorescent tubes, which are of high light-emitting efficiency are generally employed; however, fluorescent tubes need power of at least a certain level and suffer from the problem that their power consumption cannot be reduced below this. Also, if point light sources such as LEDs or electric light bulbs were employed, there was the problem that, since the lines of intersection at the root sections forming the ribs or prismatic projections and optical output faces are straight lines, the quality of illumination tends to be adversely affected by regular reflection. Furthermore, in the case of point light sources, there was the problem that unevenness of brightness could not be eliminated by one-dimensional distribution control of the pattern of the projections. Also, illumination devices arranged at the front face in this way were subject to the problem of being easily affected by external damage to the light-guide plate, causing light to be emitted by dispersive reflection of optical flux from such damaged portions, lowering the contrast of the illuminated object such as the liquid crystal display when lit.
Also, with such illumination devices of the type that were arranged at the front face, since the light source is arranged at the end face of the light-guide plate, a space needs to be provided at the end of the light-guide plate sufficient to screen the light source from the observer; if they are employed as illumination for a liquid crystal display or the like, a border is therefore necessary around the periphery of the display area. This resulted in waste of space and imposed considerable design limitations.
In one aspect, the present invention was made in order to solve the various problems of a conventional illumination device as described above.
An object of the present invention is to provide an illumination device using a point light source of low power consumption and high quality, and a display device such as a liquid crystal display device using this.
Also, a further object of the present invention is to provide an illumination device of low power consumption and high quality by employing as light source a light emitting diode (LED), and a display device such as a liquid crystal display device using this. Yet a further object of the present invention is to provide an illumination device whereby illumination can be achieved without loss of reflective function and a display device such as a notice board device or liquid crystal display device using this, and a device such as an electronic device or mobile telephone using this liquid crystal display device.
Yet a further object of the present invention is to provide an illumination device with little deterioration of illumination function by low-cost, convenient means, and a display device such as a liquid crystal display device with little deterioration of display quality.
Yet a further object of the present invention is to provide an illumination device whereby rays of light can be efficiently directed into the interior of a light-guide plate from a light source positioned remote from the light-guide plate end, which is space-saving, and has excellent design characteristics, a display device such as a liquid crystal display device, and a device such as an electronic device or mobile telephone using this liquid crystal display device.
Furthermore, from the point of view of display devices in which an illumination device is mounted, in view of conventional reflective type liquid crystal display devices for the aforesaid display devices, it is an object to provide various types of electronic device such as liquid crystal display devices, portable telephone devices; timepieces, cameras or data terminal devices wherein the production of a bright line which is annoying to the observer can be prevented, wherein unevenness of brightness can be eliminated, which are of a type in which power consumption can be reduced and furthermore which afford an illumination function of high quality.
Furthermore, conventionally, notice board devices having an illumination function were of a construction in wh
Funamoto Tatsuaki
Kubota Kanemitsu
Miyashita Satoru
Yokoyama Osamu
Boutsikaris Leo
Dunn Drew
Oliff & Berridg,e PLC
Seiko Epson Corporation
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