JPS59228397A - Thin film light emitting element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thin film light emitting device that emits electroluminescence.

Conventional structure and its problems A thin film EL (electroluminescence) element that emits light by applying an alternating current electric field has a dielectric thin film layer on one side or both sides of a phosphor thin film layer, and this is connected with two electrode layers. The sandwiching structure provides high brightness. A device with a single dielectric thin film layer is characterized by a simple structure and low driving voltage. A device with two dielectric thin film layers is characterized by being less prone to dielectric breakdown and having particularly high brightness. ZnS, Zn5e, ZnF2, etc. to which active materials are added are known as fluorescent materials used here, and in particular, elements with ZnS as a matrix and Mn as a luminescent center have a maximum temperature of 3,400 to 5,000C.
d/m" brightness has been achieved. Dielectric materials include Y2O3, S10.Si3N4.Al2O3, Ta
205 etc. are typical ones. ZnS has a thickness of 500
The dielectric thin film has a thickness of 400 to 800 nm and a relative dielectric constant of 4 to 25.

When driving with AC, the voltage applied to the element is divided between the ZnS layer and the dielectric thin film layer, and the former has a voltage of 4 to 6 of the total applied voltage.
It only costs a small amount. The voltage required for light emission is surprisingly high. In a device with 19 dielectric layers on both sides of a ZnS layer, 200V can be achieved with several kll+ pulse drive.
Currently, higher voltages are being applied. This high voltage has many negative consequences on the drive circuit, requiring a special high voltage IP and increasing costs. Motsu PbT 103 and Pb
It has been proposed to use a thin film mainly composed of (T11-xZrX)03 or the like as a dielectric thin film layer. These thin films have a dielectric constant (hereinafter referred to as εE) of 160 or more, but a dielectric breakdown electric field strength (hereinafter referred to as Eb) of 0.5-○.
, eMV/crn, and therefore the film thickness needs to be significantly thicker than that of conventionally used dielectric materials. In the case of a high-brightness device, the thickness of the ZnS layer is required to be about 0.6 μm, and from the aspect of device reliability, the thickness of the dielectric thin film layer is required to be 1.5 μm or more. , particles in the film grow due to the high substrate temperature. This is no good,
The film becomes cloudy and the light permittivity decreases. When an EL element using such a cloudy film is applied to an XY matrix device or the like, there is a problem in that even non-emitting segments scatter light emitted from other segments, thereby causing crosstalk.

OBJECTS OF THE INVENTION The object of the present invention is to realize a thin film light emitting device that can be stably driven at a low driving voltage and without crosstalk by using a dielectric film with large ε1 and Eb for the dielectric layer.

Structure of the Invention The present invention is intended to solve the above-mentioned problems, and is characterized in that a dielectric layer containing SrTiO3 as a main component is used as the dielectric layer.

In an AC driven thin film EL element, the voltage applied to the dielectric layer is the product 1i·E of the film thickness t of the dielectric thin film layer and the electric field strength E. The smaller the value of ti·E, the more effectively the voltage is applied to the phosphor thin film layer. In order for the device to operate stably without causing dielectric breakdown, t may be considered to be inversely proportional to Eb of the dielectric thin film layer. Eo has the relationship E02E7·ε2/ε from the electric field strength E2 in the phosphor thin film layer, relative dielectric constant ε2, and ε1 of the dielectric thin film layer.・E7. And if ε2 is set constant, Ei becomes ε
is inversely proportional to 1.

Therefore, it can be said that t,·Ei is almost inversely proportional to Eb·ε. The smaller Eb·ε is, the better the dielectric thin film layer is.

The thin film mainly composed of 5rTf○3 used in the present invention has a thicker Eb·ε than conventional materials (it is excellent as a dielectric thin film for EL elements). S r T on the substrate of
By depositing zO3, a film with ε1 of more than 100 or more can be produced. If the substrate temperature is about 500°C, ε ranges from 200 to 250. Furthermore, since the S r TiOs film thus obtained has an ε1 of 1×1o 6 /Cm or more, the device is stable and difficult to cause dielectric breakdown. The higher the substrate temperature, the larger ε1 becomes, but Eb gradually decreases, so the substrate temperature should be 350 to 4.
A range of 60°C is most preferred. In this temperature range,
EbΦε is as large as approximately 150 x 106V 7cm 0 Eb·ε of conventionally used materials is approximately 50 x 106V /l:m for Y2O3, for example.
AIJ203 is 30X 106V/cm.

For Si3N4, 7o×106V/Crn, PbTiO2
When compared with 90×10 6 v/Cm, it can be seen that the thin film containing 5rTi○3 as a main component of the present invention is superior. Furthermore, since the S r TiOs thin film has a large Eb, the EL element stably emits light even if it is not formed too thick. Therefore, clouding of the thin film does not occur.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.
It was deposited to a thickness of 0.5 μm using the F sputtering method.

A mixed gas of O2 and Ar is used as the sputtering gas, and the gas pressure is 5×10 Pa. A sintered body of S r T 10s was used as a target.

The substrate temperature was 400°C. Thereon, ZnS and film were simultaneously deposited by resistance heating to form a ZnS:Mn phosphor layer 4 having a thickness of 0.6 μm. The heat treatment is carried out in vacuum at 6
After heating at 20'C for 1 hour, a Ta205 film 6 with a thickness of 4Q was deposited by electron beam evaporation to protect the ZnS film.
nm was deposited. On top of that, a PbNb2O6 film 6 is deposited to a thickness of 0.1 μm using the magnetron RF snoring method.
Attached. A mixed gas of 02 and Ar is used as the sputtering gas, and the gas pressure is 3 Pa. A sintered body of PbNb2O6 was used as a target. The board temperature is 380
It is ℃. As an upper electrode, an AI film 7 was deposited to a thickness of 0.1 μm by resistance heating vapor deposition.

The S r T z O3 film made under the above conditions has a dielectric constant of 140 and a dielectric strength voltage of 1.6×10 V/leakage. Also,
The PbNb2O6 film has a dielectric constant of 60. Insulation voltage 2.0X1
06V/cTn.

The thus obtained thin film light emitting device, whose dielectric film was mainly formed of a 5rTi○3 film, was driven by an AC pulse with a repetition frequency of 5.
0Cd/n? brightness was obtained. The luminescence was stable and showed almost no change over time.

Effects of the Invention As described above, according to the present invention, since the dielectric thin film layer of the thin film light emitting device is composed of a dielectric whose main component is SrTiO3, the driving voltage can be significantly reduced without crosstalk. I can do it.

[Brief explanation of the drawing]

The figure is a cross-sectional view of a thin film light emitting device that is an embodiment of the present invention. 1...Glass substrate, 2...Transparent electrode,
3...SrTiO3 film, 4-...=ZnS:
Mn film, 5... Ta205 film, 6281. Pb
Nb2O6 film, 7...AI electrode.

Claims (1)

[Claims] A dielectric thin film layer is provided on at least one surface of the phosphor thin film layer, and a voltage is applied to the thin film layer through two electrode layers, at least one of which is optically transparent. A thin film light emitting device characterized in that the dielectric thin film layer is made of a dielectric material containing S r T 103 as a real component.