Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2002-03-08
2004-09-14
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S112000, C313S113000, C359S577000, C359S584000, C359S885000
Reexamination Certificate
active
06791261
ABSTRACT:
This invention relates to improvements in a light emitting device capable of emitting multiple colors suitable for application for example in organic electro-luminescence(=EL) devices.
The art of combining a reflective layer with a multi-layer dielectric film wherein layers having differing refractive indexes are alternately stacked, and therewith reflecting light of specific wavelengths is known. In Shingaku Gihou, OME 94-79 (March, 1995), pp 7-12, the concept is set forth of using very small resonance structures based on such multi-layer dielectric films to emit multiple light colors. According to this literature, by adjusting the positions of the light emission layer and the reflective surface where reflection occurs in these very small resonance structures, resonant light can be output having any of the wavelengths contained in the light output by the emission layers.
In Japanese Patent Laid-open No. 275381/1994, for example, a light emitting device having the layer structure illustrated in
FIG. 13
is disclosed. This light emitting device comprises a transparent substrate
100
, a very small resonance structure
102
, a positive electrode
103
, a hole transport layer
106
, an organic EL layer
104
, and negative electrodes
105
. The wavelengths are selected by altering each of the thicknesses of the positive electrodes
103
.
In the article written by members of Bell laboratory, J. Appl. Phys. 80(12), Dec. 15, 1996, a light emitting device having the layer structure illustrated in
FIG. 14
is disclosed. This light emitting device comprises a transparent substrate
100
, a very small resonance structure
102
, SiO
2
film
108
, a positive electrode
103
, a hole transport layer
106
, an organic EL layer
104
, and negative electrodes
105
. The thicknesses of the negative electrodes
103
are the same, but the optical path lengths are altered, respectively, by an SiO
2
layer, to select the resonant light wavelength.
With light emitting devices having the structure set forth in the publicized literature noted above, however, there is a problem in that it is very difficult to design light emitting devices optimized for all of a plurality of wavelengths. In other words, the very small resonance structure and gap adjustment materials are optimized for a specific wavelength dispersion. Wherefore, with a very small resonance structure designed so that it is compatible with one of the plurality of light colors having a range of wavelengths, adequate reflectance cannot be achieved relative to other wavelength dispersions. In a color display apparatus, for example, it is necessary to balance the resonance intensity and color purity of each of the colors R (red), G (green), and B (blue) according to the characteristics of human vision. Such balancing adjustments are difficult with conventional light emitting devices.
That having been said, it is nevertheless very difficult in actual manufacturing practice to make the structure of the multi-layer dielectric film different for each pixel (light emission region) unit, therefor this is a difficult method to realise industrially, and hence an expensive process.
Thereupon, a first object of the present invention is to provide a multiple wavelength light emitting device that is balanced and optimized for a plurality of wavelengths.
A second object of the present invention is to provide a multiple wavelength light emitting device wherewith optimization for a plurality of wavelengths is easy, and the manufacture thereof is easy.
A third object of the present invention is to provide an electronic apparatus capable of emitting light of a plurality of optimized wavelengths.
A fourth object of the present invention is to provide an interference mirror capable of sharpening and emitting a multiple wavelength light spectrum.
An invention that realizes the first object noted above is a multiple wavelength light emitting device for emitting multiple light beams having differing wavelengths, comprising:
1) light emission means for emitting light containing the wavelength components to be output;
2) a reflecting layer positioned in proximity to the light emission means; and
3) a semi-reflecting layer group that is positioned so as to be in opposition with the reflecting layer with the light emission means sandwiched therebetween, wherein semi-reflecting layers that reflect some of the light emitted from the light emission means having specific wavelengths, while transmitting the remainder, are stacked up in order in the direction of light travel corresponding to the light wavelengths to be output.
The present invention is also a multiple wavelength light emitting device that comprises at least two but possibly more light emission regions such that the wavelengths of the output light differ, structured so that the distance between a reflecting surface for light from the light emission means side on the semi-reflecting layers that reflect some of the light output from one of the plurality of light emission regions and a point that exists in the interval from the end of the light emission means on the semi-reflecting layer group side to the reflecting layer is adjusted so that it becomes an optical path length at which light of the wavelength output from that light emission region resonates.
Based on the structure described above, the semi-reflecting layer group is optimized for all light wavelengths that are to be emitted, in any of the light emission regions. By adjusting the distance between the reflecting surface of the semi-reflecting layers for the light from the light emission means side and the point existing in the interval from the end of the semi-reflecting layer group side of the light emission means to the reflecting layer, and preferably the distance between the light emission points within the light emission means and the surface (reflecting surface) on the light emission means side of the reflecting layer, according to the light emission means and reflecting layer used, which optimized light is output is determined. The semi-reflecting layers other than those optimized for light of wavelengths other than those output merely function commonly as semitransparent layers exhibiting a certain attenuation factor, wherefore it is possible to maintain balance between light of multiple wavelengths.
There is no limitation on the “light emission means,” as used here, but it is at least necessary that the wavelength component be generated for the light that one wishes to output. The “reflective layer” should form a flat surface, but it does not necessarily have to have a uniform flat surface. The language “in proximity to” includes cases where there is contact with the light emission means, and cases where the positioning results in a slight gap therebetween. So long as a reflective action is exhibited, this may be something that is not closely and indivisibly connected to the light emission means. The “light emission region” is a domain for outputting light having some wavelength dispersion, and signifies that light of different wavelengths is output in each light emission region. “Wavelength” is inclusive of a wide range of wavelengths, including ultraviolet and infrared radiation in addition to wavelengths in the visible light region. “Semi-reflecting layers” include structures such as half mirrors or polarizing panels in addition to interfering laminar structures wherein multiple film layers having different refractive indexes are stacked in layers. In the case of a very small dielectric-based resonating structure, “reflecting surface” refers to the surface on the side toward the light emission means. “Optical path length” corresponds to the product of the medium's refractive index and thickness.
The specification of the “point existing in the interval from the semi-reflecting layer group side of the light emission means to the surface of the reflecting layer” is for the purpose of adjusting the position in the thickness direction where resonance conditions will be satisfied by the light emission means configuration. Here, th
Burroughes Jeremy Henley
Kaneko Takeo
Koyama Tomoko
Shimoda Tatsuya
Oliff & Berridg,e PLC
Patel Ashok
Seiko Epson Corporation
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