Computer graphics processing and selective visual display system – Single display system having stacked superimposed display... – Diverse display devices
Reexamination Certificate
1997-07-24
2001-01-30
Chow, Dennis-Doon (Department: 2775)
Computer graphics processing and selective visual display system
Single display system having stacked superimposed display...
Diverse display devices
C345S004000, C345S076000
Reexamination Certificate
active
06181301
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims benefit of priority of Japanese Patent Applications No. Hei-8-198022 filed on Jul. 26, 1996 and No. Hei-9-134024 filed on May 23, 1997, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combined display panel for displaying various information thereon, and more particularly to a combined display panel in which a transparent display panel is disposed on a front surface of an instrument panel; the displays on both panels are selectively shown on the combined display panel for use in, for example, an automotive vehicle.
2. Description of Related Art
A combined display panel in which a transparent electroluminescent (EL) display panel is disposed on the front surface of a usual instrument panel has been proposed hitherto. For example, Japanese Utility Model Publication No. Hei-3-17437 discloses a combined display panel which is able to display images on a transparent front panel in addition to images displayed on a conventional panel.
Japanese Patent Laid-Open Publication No. Hei-7-271310 discloses a combined display panel in which a transparent liquid crystal panel is place in front of a back panel, and displays on the front and back panels are selectively switched. In other words, images on the back and the front panels are selectively displayed.
The combined display panel shown in the former Publication is to only add the images on the front panel to the images on the back panel. The combined display panel shown in the latter Publication is able to selectively switch the images on the front panel and on the back panel. It requires, however, a light controller for switching the displays on both panels made of polymer dispersed liquid crystal and a back light for illuminating the transparent liquid crystal panel, thereby making a whole device intricate. It is conceivable to place a transparent electroluminescent panel which does not placing require the light controller in front of the back panel and selectively switching both displays. In this structure of the combined display panel, however, there is a problem that an image of the back panel is vaguely visible through the front EL panel in addition to an image of the front panel when the back panel is turned off and the front panel is turned on. This means that the back panel image, when it is not desired, interferes the front panel image. This problem is caused by the fact that light emitted from the front EL panel also reaches the surface of the back panel and is reflected thereon, and the reflected image becomes visible through the front EL panel. This phenomenon is especially notable when pointers on the back panel are made of a light reflecting body such as a fluorescent tube.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide a combined display panel in which a transparent electroluminescent (EL) display panel as a front panel overlaps and covers a certain part of a back panel. The displays on both panels on the overlapped part are selectively switched so that images reflected from the back panel, vaguely shown on the front panel, when the back panel is turned off and the front panel are turned on, is eliminated. Another object of the present invention is to eliminate an overall luminance imbalance between the overlapped area and the non-overlapped area of the combined display panel.
To eliminate the reflected images, the present invention provides several structures. Inserting a light attenuation filter between the back while front panels is one measure. Light emitted from the electroluminescent display panel overlapped on a part of the instrument panel. In this case, the back panel is turned off, is incident upon the inserted attenuation filter which attenuates intensity of the light. Therefore, the intensity of the reflected light on the surface of the back panel is decreased and the reflected images shown on the front panel are suppressed. A smoked glass plate or a half mirror may be used as the light attenuation filter.
The light attenuator may be included in the transparent electroluminescent panel itself. A light attenuation filter plate may be attached on one of the substrates of the EL panel which faces the back panel. The light emitted backward from the EL panel is attenuated by the filter plate. A light absorbing film which absorbs the light emitted from the EL panel toward the back panel may be disposed on the inner surface of an EL substrate facing the back panel. When the light attenuator is assembled in the EL panel as exemplified above, the combined display panel can be made smaller than the one having a separate light attenuator disposed between the back and front panels.
The light attenuation function may be included in various layers constituting the EL panel or a substrate thereof. For example, one of the transparent electrode layers positioned at the back panel side may be made thicker than the other so that the light emitted backward from a luminescent layer of the EL panel is absorbed thereby. It is also possible to use a smoked or colored glass plate which has the light attenuation function as one of the EL substrates facing the back panel. These elements of the EL panel having the light attenuation function serve to attenuate the light intensity from the luminescent layer of the EL panel directing to the back panel, and thereby to suppress the reflected images shown on the front panel.
Also, a halo phenomenon, which makes vague phantom images on the transparent EL display panel around peripheries of its real images by light scattered on surfaces of various layers in the EL panel, can be suppressed by attenuating light intensity by the light attenuator attached to or included in the EL panel. It is also useful to attach a film for preventing reflection on reflecting surfaces of the back panel including a display plate and pointers.
To eliminate the luminance imbalance on the combined display panel between the overlapped and non-overlapped parts, when the front panel is turned off and the back panel is turned on, a dimming filter, having different transparencies between the two parts, may be disposed to cover a whole surface of the combined display panel. The dimming filter has a higher transparency on the area covering the overlapped part than on the area covering the non-overlapped part and equalizes the overall luminance of the two parts of the combined display panel. The same results may be obtained by disposing a transparency adjustment filter, having the same transparency as the transparent EL panel, only to cover the non-overlapped part. Brightness of the back light illuminating the back panel may be adjusted so that the overall luminance of the combined display panel becomes uniform both on the overlapped and non-overlapped parts.
Other objects and features of the present invention will become readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.
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Inoguchi Kazuhiro
Ishikawa Takeshi
Kameyama Michio
Kotanshi Yoichi
Ogusu Koji
Chow Dennis-Doon
Denso Corporation
Pillsbury Madison & Sutro LLP
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