1 2
reduces the life of the device of thin film electrolumi
STRUCTURE OF THIN FILM nescence.
ELECTROLUMINESCENT DEVICE
SUMMARY OF THE INVENTION
FIELD OF THE INVENTION 5 The object of this invention is to provide a displaying
This invention relates to a thin film electrolumines- device of electroluminescence of which life is extended
cent display device and a method for fabricating it, by preventing the adjacent pixels from interfering with
one another owing to leaking current and of which
TECHNICAL BACKGROUND OF THE function is improved by preventing a light from being
INVENTION 10 reflected on a rear electrode by depositing a light ab
Generally an thin film electroluminescent display sorbing layer,
device has a structure wherein a insulating layer is According to the present invention, there is provided
formed on both sides of a fluorescent layer so as to a thin fllm electroluminescent device wherein a first induce a high electrical field around the fluorescent light absorbing layer of SiNx being deposited on a seclayer when a certain voltage is loaded on both sides of ond insulating layer and a rear electrode layer being the fluorescent layer. In a conventional structure of a deposited on the first light absorbing layer. The rear
displaying device of thin film electroluminescence as electrode layer is etched by a wet process at regular
shown in FIG. 1, a transparent substrate 1 laminates a intervals whereby a portion of the First light absorbing
transparent electrode 2, a first insulating layer 3, a fluo- Q layer is exposed and the exposed portion being etched
rescent layer 4, and a second insulating layer 5 sequen- by a ionic reaction process. Thereafter a rear insulating
tially on itself, and a rear electrode 6 is formed on the layer is deposited on the etched surface and the rear
second insulating layer 5 at regular intervals. electrode, and a second light absorbing layer of carbon
The transparent electrode 2 and the rear electrode 6 is deposited on the rear insulating layer, are arrayed in a form of a matrix by line etching at 25 The thin film electroluminescent device of this invenregular intervals and the displaying device of the thin tion comprises a transparent substrate, a transparent film electroluminescence works by an On/Off switch at electrode, a fluorescent layer for emitting a light when cross points of the matrix selectively. A strong electri- being charged with a certain voltage, a first and second cal field is induced by loading an alternative voltage insulating layer deposited on the top and the bottom of between the transparent electrode 2 and the rear elec- 3Q the fluorescent layer to make a dopant be excited and trode 6, which makes the electrons of shallow level or emit a light efficiently, a first light absorbing layer dedeep level of an interfaced surface between the insulat- posited on the second insulating layer to improve the ing layer 3 or 5 and the fluorescent layer 4 to be acceler- function of contrast of a displaying element of electroluated toward an opposite polarity, wherein the acceler- minescence, a rear electrode formed on the first light ated electrons strike Mn2+ of the fluorescent layer 4 35 absorbing layer at regular intervals, a rear insulating composed of zinc sulfide ZnS and Manganese Mn. layer deposited on the rear electrode to prevent the rear After being struck, an electron in valence band of the electrode from leaking current, and a second light abMn2+ excited to the conduction state, is returned to the sorbing layer deposited on the rear insulating layer for valence band, and then a light with a specific wave- preventing blackening of the etched portion of the first length of 585 nm is radiated from the fluorescent layer. 40 light absorbing layer.
By selectively applying a voltage on the transparent The present invention will now be described more
electrode 2 and the rear electrode 6, the light radiates to specifically with reference to the drawings attached
the transparent substrate 1 and the rear electrode 6, and only by way of example.
the light directed to the rear electrode 6 is reflected and T _ , „,„,„„
sent to the transparent substrate 1. 45 BRIEF DESCRIPTION OF DRAWINGS
Accordingly an image is formed on the displaying FIG. 1 and FIG. 2 show sectional views of a conven
device of the thin film electroluminescence by the prin- tional thin film electroluminescence device; and
ciple described above. FIG. 3 shows a sectional view of an inventive thin
However, in a conventional device of electrolumines- film electroluminescence device, cence shown in FIG. 1, it is unable to prevent a light 50 _„or,DTD„T_. T . reflected on the rear electrode of which light received °ETAI^° °^t^PTM^^Ltx^ from the displaying device and the fluorescent layer PREFERRED EMBODIMENT because the fluorescent layer 4 has not a light absorbing Referring to FIG. 3, a transparent electrode 12 is layer on its rear side. Therefore the performance of the laminating on a transparent substrate 11, and a first displaying device is deteriorated because a contrast 55 insulating layer 13 of 200 nm thickness of Si3N4 made among pixels being on and off becomes poor. from Silicon target and N2 gas by radio frequency MagIn another conventional device of electrolumines- netton Sputtering process in a gas reactive furnace is cence shown in FIG. 2, a light absorbing layer 7 made laminating on the transparent electrode 12. of SiNx is introduced to eliminate the above mentioned A fluorescent layer 14 formed on the first insulating problem. And the dielectric condition of the light ab- 60 layer 13 is made from a ZnS pellet doped with 1 mol % sorbing layer 7 is to have a specific resistance of more of Manganese (Mn) by EB process and treated heat than lO'flcm. However it is unable to manufacture the treatment in a vacuum space of 450 C. for 1 hour so as layer 7 of SiNx having light absorbing capacity of more to secure a fine crystallization, a uniform distribution of than 80% and specific resistance of more than 105ftcm doping and a quality adhesiveness to the first insulating by changing the value of 'x' of SiNx. Accordingly the 65 layer 13.
specific resistance being less than 105ficm, the adjacent A second insulating layer of SiON 15 is made from
pixels interfere with one another by leaking electrical Silicon target and 02+N2 gas by radio frequency (RF)
current. And the layer of SiNx which is not close fitting Magnetron Sputtering process in a reactive gas furnace.
