Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2001-12-13
2003-12-30
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
Reexamination Certificate
active
06671014
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 Related Art
As the light sources employed is 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 miniaturization of the liquid-crystal projection device.
In particular in the case of a liquid-crystal projection device for color display, further miniaturization 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 colors constituting the color 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 is 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 miniaturization 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 in which a brighter image than conventionally is 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 where light of good optical emission directionality is emitted.
A second task of the present invention is to provide a miniature liquid-crystal projection device in which a brighter image than conventionally is projected by increasing the amount of light that can be transmitted through a polarizing plate of the liquid crystal panel by using a polarization conversion element that can convert a 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 in which a brighter image than conventionally is projected, by increasing the amount of light that is transmitted through the polarizing plate of the liquid crystal panel by employing a polarization conversion element that functions in a specified wavelength band in projecting a color image.
A fourth task of the present invention is to provide a miniature liquid-crystal projection device in which a brighter image than conventionally is projected by increasing the amount of light that is transmitted through the aperture of a pixel and miniaturizing 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 in which a clear image is projected by raising the purity of the light that is projected and the brightness compared with conventional devices, by increasing the amount of light consisting of light of only a specified wavelength by employing miniature luminescent elements that emit light of only a specified wavelength, due to optical resonance, in projection of a color image.
A liquid-crystal projection device includes a liquid crystal display element. The liquid crystal element includes 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 lights; and a transparent liquid crystal panel that controls the transmission of light emitted from a face of the organic electroluminescent element.
The liquid-crystal projection device may include an organic thin-film layer formed from as a white luminescent layer that emits white light.
The organic thin-film layer may be formed by successively stacking primary color luminescent layers that respectively emit light of respective wavelength regions of a plurality of primary colors necessary for color display.
The organic electroluminescent may be formed of a transparent electrode layer overlying a transparent substrate, the organic thin-film layer overlying the transparent electrode layer and an electrode layer overlying the organic thin-film layer and that reflects light emitted by the organic thin-film layer.
The organic electroluminescent element may include 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 the electrode layer; and a half-mirror layer provided on the optical output side from the 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 the light; and the distance between the half-mirror layer and the electrode layer is set to an optical distance that produces resonance of the light.
Between the organic electroluminescent element and the transparent liquid crystal panel there maybe further provided a polarization conversion element that converts the polarization condition of emitted light from the organic electroluminescent element, and the transparent liquid crystal panel maybe provided with a polarizing plate that transmits light of a specified polarization, of the light emitted alter passing through the polarization conversion element.
The polarization conversion element may include a circular polarization selective reflection filter arranged on the organic electroluminescent element side and that reflects one circularly polarized component of right-handed circularly polarized light and left-handed circularly polarized light and that transmits the other circularly polarized component, and a ¼ wavelength plate that converts circularly polarized light to linearly polarized light and that converts linearly polarized light to circularly polarized light.
The polarization conversion element may include a linearly polarized light selective reflection filter arranged on the transparent liquid crystal panel side and that, of two perpendicular linearly polarized components, reflects one linearly polarized component and transmits the other linearly polarized component, and a ¼ wavelength plate that converts circularly polarized l
Miyashita Satoru
Shimoda Tatsuya
Yokoyama Osamu
Dudek James
Oliff & Berridge, plc
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