Stock material or miscellaneous articles – Composite – Of inorganic material
Patent
1994-10-28
1997-06-24
Ryan, Patrick
Stock material or miscellaneous articles
Composite
Of inorganic material
428697, 428698, 428699, 428917, 313502, 313503, 313509, 257 79, 257 98, 257102, B32B 900
Patent
active
056415826
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a thin-film EL element in which light emitting layers are respectively constituted by thin films.
BACKGROUND ART
Up to this time, various approaches to obtain a newly different color of the emitted light have been made by forming a thin-film EL element in which two or more light emitting layers, each having a different color of emitted light, are laminated together to change the color of the emitted light by the laminated layers.
For example, "Ryozo FUKAO et. al.: Electronic Information Communication Society Technical Study Report, Vol. 86, No. 368, p. 5, 1987" describes such a thin-film EL element as a "two-terminals type tunable color EL", and as a laminate of a green color light emitting layer formed of ZnS:TbF3 and a red color light emitting layer formed of ZnS:SnF3. It is reported herein that, when applying a voltage to such a element, the color of emitted light is changed from red to yellow-green by an increase in the voltage, as shown in FIG. 11.
Also, "S. TANAKA et. al.: Digest 1988 SID Int. Symp., P. 293, 1988" describes another thin-film EL element in which a light emitting layer formed of SrS:Ce,K emitting light of blue-green color and a light emitting layer formed of SrS:Eu emitting light of red color are laminated together. It is also reported therein that a change in the voltage causes the color of the emitted light to change.
However, when making a panel for dot matrix display by using such laminated type of thin-film EL elements mentioned above, the effective voltage applied to the light emitting layer depends on the position in accordance with thickness distributions of the light emitting layer and the insulating layer, so that the color of the emitted light can vary with the location. Also, a voltage drop by line resistance of the electrode causes the color of emitted light to change between the bottom and the tip of the electrode. For these reasons, a problem called "nonuniformity of color" has arisen, so that making a useful panel could not be achieved.
It is considered that the above-mentioned problems are caused by the formation of a high resistant layer where crystallinity is low, also called a "dead layer", between the light emitting layer and the insulating layer with the thickness being from approximately 1000 to approximately 2000 .ANG.. The "dead layer" generally occurs in a light emitting layer formed by conventional light emitting layer forming technique, such as EB (Electron Beam) evaporation method or sputtering method (e.g., see "H. SASAKURA et. al.: J. Appl. Phys. 52 (11), 6901, 1981").
When applying a voltage to a thin-film EL element which includes the conventional laminated type of light emitting layers mentioned above, each respective layer functions as independent thin-film EL elements. Such independent EL elements have "luminance--voltage" characteristics which are different from each other, thus causing the color of the emitted light to change in accordance with a change in the voltage.
For example, when the laminated light emitting strata has two layers, as shown in FIG. 12, it has a structure equivalent to that of a double circuit which includes two pairs of Zener diodes a and b, each pair being connected opposite to each other in series; two capacitors c connected in series, each being connected in parallel with the serially connected Zener diodes; and a capacitor d connected to one end of the two capacitors c.
On the other hand, up to the present, there have been various methods for obtaining full color display with a thin-film EL element. Of these, there are two typical types; one type uses a planar pattern formed of three kinds of materials each of which emits light of a respective one of the three primary colors, red (R), green (G) and blue (B) as shown in FIG. 13; the other type laminates such luminescent materials and decomposes the resulting mixed color emitted light by passing it through filters as shown in FIG. 14.
In FIG. 13, there are provided a glass substrate e, transparent electrodes d patterned on the gl
REFERENCES:
patent: 4727003 (1988-02-01), Ohseto et al.
patent: 4757232 (1988-07-01), Berkstresser et al.
patent: 4800173 (1989-01-01), Kanai et al.
patent: 4983469 (1991-01-01), Huzino et al.
patent: 5087531 (1992-02-01), Terada et al.
patent: 5237182 (1993-08-01), Kitagawa et al.
patent: 5403673 (1995-04-01), Haga et al.
S. Tanda, A. Miyakoshi and T. Nire, Conference Record of the 1988 International Display Research Conference, p. 122.
S. Tanaka et al, Japanese Journal of Applied Physics, vol. 25, No. 3, pp. L225-L227, 1986.
Ryozo Fukao et al, Electronic Information Communication Society Technical Study Report, vol. 86, No. 368, p. 5, 1987.
S. Tanaka et al, Digest 1988 SID Int. Symp., pp. 293-296, 1988.
H. Sasakura et al, J. Appl. Phys., 52 (11), 6901, 1981.
Miyakoshi Atsushi
Nire Takashi
Komatsu Ltd.
Ryan Patrick
Yamnitzky Marie R.
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