JPS6016078B2 - thin film light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides EL (ElectroL) by applying an alternating electric field.
The present invention relates to a thin film light emitting device that emits light.

A thin film light emitting device obtains EL light emission by applying an alternating current electric field to a semiconductor light emitting layer made of ZnS, ZnSe, etc. doped with impurities such as Mn, C, AI, or ThF3 as an active substance that forms a light emitting center. In order to obtain high brightness light emission, both royal surfaces of the light emitting layer are Y203, Ti02, Sj3N.
A three-layer structure thin film light emitting device coated with a dielectric thin film such as No. 4 is generally used.

As an example of this thin film light emitting device, the basic structure of a ZnS:Mh thin film light emitting device is shown in FIG. The structure of the thin film light emitting device will be explained in detail based on FIG.
A first dielectric layer 3 made of Si02 or the like is formed in an overlapping manner by sputtering or electron beam evaporation. 1st
A ZnS light-emitting layer 4 is formed on the dielectric layer 3, which is obtained by performing crab beam evaporation of a ZnS:Mn pellet. At this time, the ZnS:Mh bonding pellet used for deposition is a pellet in which Mn, which is an active substance, is set at a concentration depending on the purpose. A second dielectric layer 5 made of the same material as the first dielectric layer 3 is laminated on the Z-light emitting layer 4, and a back electrode 6 made of a mountain or the like is further formed by vapor deposition thereon. The transparent electrode 2 and the back electrode 6 are connected to an AC power source 7 to drive the thin film light emitting device. A between electrodes 2 and 6
When the C voltage is applied, the AC voltage will be exceeded between the dielectric layers 3 and 5 on both sides of the ZnS light emitting layer 4, and therefore the electric field generated in the ZnS light emitting layer 4 will excite the conductor and An electron that has been accelerated and has gained enough energy,
The Mh luminescent center is directly excited, and when the excited Mn luminescent center returns to the ground state, it emits yellow light.

That is, when the electrons accelerated in the Goryeo region excite the electrons of the Mn atoms that have entered the Zn site, which is the luminescence center in the ZnS luminescent layer 4, and fall to the ground state, the electrons emit light in a wide wavelength range with a peak of about 50A. Exhibits strong luminescence. The thin film EL element having the above structure can be used as a flat thin display device that takes advantage of the advantages of a space factor, and can be used to display characters, symbols, static images, etc. It can be used as a display means for images, work images, etc.

In a thin film light emitting device used as a display device, a matrix electrode structure is adopted in which the transparent electrode 2 and the back electrode 6 are formed into a strip shape, and a plurality of them are arranged perpendicularly to each other. When viewed from a plan view, the crossing position corresponds to one pixel on the display screen. Thin-film light emitting display devices have a lower operating voltage than conventional cathode ray tubes (CRTs), and are heavier and stronger than plasma display panels (PDPs), which are similar flat display devices. It has many advantages over liquid crystals (LCDs), such as a wider operating temperature range and faster response speed.

In addition, since it is a pure mass matrix type panel, its operating life is long, and its address accuracy makes it extremely effective as an input/output display means for computers, etc. In a display device using the above-mentioned thin film light emitting device, "in order to improve the contrast ratio of the light emitting pattern,"
A structure in which a blackened area is formed on the background side as shown in FIGS. 4 and 5 has been proposed.

In FIG. 2, a blackening film layer 8 is formed between the light emitting layer 4 and the second dielectric layer 5 on the upper side. However, this structure has drawbacks such as the emission starting voltage shifts to a higher voltage side due to the insertion of the black purulent layer 8, and the voltage-emission brightness characteristic changes, and the black purulent layer 8 has a low resistance. This causes a problem of crosstalk, and the dielectric strength of the element becomes unstable. In FIG. 3, a blackened film layer 8 is formed between the second dielectric layer 5 and the back electrode 6, but it is difficult to obtain a blackened purulent layer 8 with a high resistance value, and the resistance value of the blackened film is In some cases, crosstalk problems may occur. Further, a problem arises in that the light emission starting voltage shifts to the high voltage side. In FIG. 4, in order to prevent the problem of crosstalk caused by the structure shown in FIG. Inferior to those in Figures 2 and 3. In Figure 5, after forming the back electrode 6, the background side surface is covered with a blackened film layer 8.
It is coated with In this case, if the back electrode 6 is made of a transparent electrode, there will be no problem in terms of contrast, but in general, the back electrode 6 is made of a metal such as AI in consideration of the electrode resistance value and the charging/discharging time constant. It is formed. Therefore, external light that has entered the element is reflected at the interface of this back electrode 6, resulting in a decrease in contrast ratio. In view of the above-mentioned problems, an object of the present invention is to provide a new and useful thin film light-emitting element that improves the contrast ratio and eliminates problems such as crosstalk and high voltage ratio of emission start voltage.

Hereinafter, the present invention will be explained in detail according to embodiments with reference to the drawings.

FIG. 6, FIG. 7, and FIG. 8 are block diagrams of thin film light emitting devices showing one embodiment of the present invention, respectively.

In the figure, the same reference numerals as in FIG. 1 indicate the same contents, and the explanation will be omitted. In the configuration shown in FIG. 6, a blackened film layer 9 is formed at the junction between the second dielectric layer 5 on the upper side and the back electrode 6.

As for the characteristics of the blackened film layer 9 required in this structure, as explained in the structure of FIG. 4, there is no need to consider the problem of crosstalk, so the lower the resistance, the better. PbTe, PbSe, HgTe, H bag e, S which has a small band gap that absorbs all the light of
i, snake, etc. are used. Further, as a means of lowering the resistance value, there is a method of doping each substance with impurities that serve as donors and acceptors so as to lower the resistance value. Blackened film layer 9
After forming, the back electrode 6 is formed using AI or the like, and patterning may be performed by simultaneously forming the blackened film layer 9 and the back electrode 6 by a photo-etching method or a lift-off method. Next, black resin 10 has a passivation effect on the entire rear surface.
The surface is coated with black to make the entire back surface black. The configuration in FIG. 7 is almost the same as the configuration in FIG. 6, but after coating the back side surface with a resin 11 or a vapor deposited film having a passivation effect, a black paint 12 is applied to the surface of the resin 11 or the vapor deposited film. By doing so, the entire back side is made black.

The configuration shown in FIG. 8 is one in which a thin film light emitting element is housed in an external enclosure.A sealed envelope is constructed by bonding a back glass plate 13 to a glass substrate 1, and the thin film light emitting element is housed in this external enclosure. A protective fluid 14 such as silicone oil is further injected into the space of the envelope.

The protective fluid 14 is for preventing moisture and the like from entering into the thin film light emitting device from the outside. In this embodiment, the entire background side is made black by mixing black paint into the protective fluid 14. According to the above configuration,
By making the background color black, the contrast can be improved, and the problems of crosstalk and an increase in the emission starting voltage can also be solved.

In addition, various excellent effects such as high contrast display can be obtained without changing the voltage-emission brightness characteristics.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic structure of a thin film light emitting device. FIG. 2, FIG. 3, FIG. 4, and FIG. 5 are block diagrams of a thin film light emitting device in which the background of the subordinate column is blackened, respectively. Figure 6,
FIGS. 7 and 8 are configuration diagrams of thin film light emitting devices showing one embodiment of the present invention, respectively. 9...Blackening film layer, 1
0, 11... Resin, 12... Black paint, 14... Protective fluid. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. In a thin-film light-emitting element in which a thin-film light-emitting layer that emits EL light when a voltage is applied is interposed between a display electrode and a back electrode, a blackened film layer having a low resistance value is interposed on the interface of the back electrode on the display surface side. 1. A thin film light emitting device characterized in that a black background film is formed on the rear surface of the thin film light emitting device.