Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
1998-01-09
2003-01-14
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S096000
Reexamination Certificate
active
06507379
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid-crystal projection device i.e. what is known as a projector and in particular relates to improvements in the light source and peripheral optical system of a small-size liquid-crystal projection device.
2. Description of the Relate Art
As the light sources employed in conventional liquid-crystal projection devices, light sources using a fluorescent tube or light-guide plate or electrical discharge-type light sources such as metal halide lamps have come to be employed.
In particular, Japanese Patent Laid-Open number Sho.51-119243 discloses a flat plate-shaped light source. This specification states that the flat plate-shaped light source employs electroluminescence i.e. electroluminescent elements.
However, in the case of a light source employing a fluorescent tube or light-guide plate, it is difficult to make the diameter of the fluorescent tube etc. small. There was therefore the problem that miniaturization of a liquid-crystal projection device was difficult, since the thickness of the light source itself could not be reduced below the diameter of the fluorescent tube.
Also, in the case of an electric discharge-type light source such as a metal halide lamp, the reflector of large aperture that was considered necessary to direct the light diverging from the light source parallel to the liquid crystal panel was a factor impeding miniaturisation of the liquid-crystal projection device.
In particular in the came of a liquid-crystal projection device for colour display, further miniaturisation of the liquid-crystal projection device was difficult owing to the need to provide liquid crystal display elements consisting of a light source as aforementioned and liquid crystal panel for each of the primary colours constituting the colour image.
Also, Japanese Patent Laid-Open number Sho.51-119243 does not clearly disclose a material constituting a luminescent layer of an electroluminescent element. When the conventional inorganic electroluminescent material is employed as material for this luminescent layer, light from the electroluminescent element in light of a highly divergent character. This therefore suffered from the problem that projection of a bright image could not be achieved since the light could not be effectively directed into the aperture of the projection lens.
A further problem was that the drive voltage required for an electroluminescent element using inorganic material is at least 100 volts, which is comparatively high.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid-crystal projection device wherein, in order to solve the above problems, greater miniaturisation than conventionally can be achieved and in which a bright image can be projected with low voltage.
In more detail, a first task of the present invention is to provide a miniature liquid-crystal projection device that can be driven with lower voltage than conventionally and whereby a brighter image than conventionally can be projected by preventing the diminution in the amount of light produced by divergence of the light, by employing an organic electroluminescent element having a resonator structure whereby light of good optical emission directionality is emitted.
A second task of the present invention is to provide a miniature liquid-crystal projection device whereby a brighter image than conventionally can be projected by increasing the amount of light that can be transmitted through the polarizing plate of the liquid crystal panel by using a polarization conversion element that can convert the condition of polarization of the emitted light from the light source.
A third task of the present invention is to provide a miniature liquid-crystal projection device whereby a brighter image than conventionally can be projected, by increasing the amount of light that can be transmitted through the polarizing plate of the liquid crystal panel by employing a polarisation conversion element that functions in a specified wavelength band in projecting a colour image.
A fourth task of the present invention is to provide a miniature liquid-crystal projection device whereby a brighter image than conventionally can be projected by increasing the amount of light that can be transmitted through the aperture of a pixel and miniaturising the device itself by employing a miniature luminescent element comprising a microlens array element that focuses the light on to pixel apertures of the liquid crystal panel.
A fifth task of the present invention is to provide a miniature liquid-crystal projection device whereby a clear image can be projected by raising the purity of the light that is projected and the brightness compared with conventionally, by increasing the amount of light consisting of light of only a specified wavelength by employing miniature lumuinescent elements that emit light of only a specified wavelength, due to optical resonance, in projection of a colour image.
A liquid-crystal projection device according to claim
1
consists in a liquid-crystal projection device having a liquid crystal display element comprising: an organic electroluminescent element constructed by sandwiching an organic thin-film element between an electrode layer that reflects light and an electrode layer that transmits light; and a transparent liquid crystal panel that controls the transmission of light emitted from a face of the organic electroluminescent element.
A liquid-crystal projection device according to claim
2
consists in a liquid-crystal projection device according to claim
1
wherein the organic thin-film layer is constituted as a white luminescent layer that emits white light.
A liquid-crystal projection device according to claim
3
consists in a liquid-crystal projection device according to claim
1
wherein the organic thin-film layer is constituted by successively stacking primary colour luminescent layers that respectively emit light of respective wavelength regions of a plurality of primary colours necessary for colour display.
A liquid-crystal projection device according to claim
4
consists in a liquid-crystal projection device according to claim
1
wherein the organic electroluninescent element in constituted of a transparent electrode layer overlying a transparent substrate, the organic thin-film layer overlying this transparent electrode layer and an electrode layer overlying the organic thin-film layer and that reflects light emitted by the organic thin-film layer.
A liquid-crystal projection device according to claim
5
consists in a liquid-crystal projection device according to claim
1
wherein the organic electroluminescent element comprises: an electrode layer that reflects light emitted from the organic thin-film layer; a transparent electrode layer that sandwiches the organic thin-film layer between itself and this electrode layer; and a half-mirror layer provided on the optical output side from this transparent electrode layer and that reflects some of the incoming light through the transparent electrode layer into the electrode layer, while transmitting the rest of this light; and the distance between this half-mirror layer and the electrode layer is set to an optical distance that produces resonance of the light in question.
A liquid-crystal projection device according to claim
6
consists in a liquid-crystal projection device according to any one of claims
1
to
5
wherein, between the organic electroluminescent element and the transparent liquid crystal panel there is further provided a polarization conversion element that converts the polarization condition of emitted light from the organic electroluimnescent element, and the transparent liquid crystal panel is provided with a polarizing plate that transmits light of specified polarization condition, of the light emitted after passing through the polarization conversion element.
A liquid-crystal projection device according to claim
7
consists in a liquid-crystal projection device according to claim
6
wherein the pola
Miyashita Satoru
Shimoda Tatsuya
Yokoyama Osamu
Dudek James
Oliff & Berridg,e PLC
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