JPH0498790A - Thin film electroluminescence device - Google Patents

Abstract

PURPOSE:To emit a strong and focused light by re-emitting the light emitted from the end surface of a thin film electroluminescence layer in a different direction from that of emission. CONSTITUTION:When a high voltage is applied between each metal electrode 2 and 6, electroluminescence emission is generated in an emission layer due to a strong electric field. The light is reflected by the metal electrode, and is not leaked in the vertical direction, but is emitted from the end surface of an emission layer 4 as indicated by arrows. The light emitted from the end surface is reflected by the surface of a projection 7, and the light is emitted perpendicular to a substrate. Namely, the light generated in the emission layer 4 is reflected by the projection 7, and the light can be effectively extracted vertically and upward to the substrate. Although the projection 7 is provided at an angle of 45 deg. to the substrate in such a way that the emitted light is reflected in the vertical direction, the angle may not be 45 according to purposes.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a thin film electroluminescent device (hereinafter abbreviated as a thin film EL device), which can be used as a light source for general displays and image reading devices. .

[Prior Art] Thin-film EL devices that utilize the light-emitting phenomenon that occurs when a strong electrolyte is applied to a phosphor have come to be used as large-screen flat panel displays with excellent visibility.

A typical structure of a thin film EL element is, for example, as shown in FIG. 4, in which a transparent electrode 20, an insulating layer 2L, a light emitting layer 22, an insulating layer 23, and a metal electrode 24 are laminated on a transparent glass substrate 19. be.

However, the transparent electrode 20 and the transparent glass substrate I9
The light emitted through it is surface-emitting, so there is no directionality.
Image reading cannot extract concentrated light that is suitable as a light source for the device.

[Problem to be solved by the invention] The present invention provides a thin film E that can emit concentrated and strong light.
This is intended to provide an L element.

[Means for Solving Problem R] As described in the claims, the structure of the present invention for achieving the above object is as follows: (1) a substrate on which a metal electrode layer, a thin film electroluminescent layer, and a metal electrode layer are sequentially laminated; (2) A thin film electroluminescent element in which a light reflector is provided on the same substrate and the light emitted from the end face of the thin film electroluminescent layer is emitted in a direction different from the emission direction. The thin film electroluminescent device according to item (1) above, wherein a plurality of thin film electroluminescent layers and electrode layers having different emission wavelength characteristics are alternately laminated, and at least the bottom layer and the top layer are metal electrode layers.

An example of the structure of a thin film EL element for realizing the present invention will be explained in detail with reference to the drawings. In FIG. 1 or 2, 1 is an insulating substrate, 2 and 8 are metal electrodes, and 3 and 5 are insulating layers. , 4 is a light emitting layer. 7 is a protrusion whose at least surface is made of a material that reflects light. These protrusions are formed on the substrate before forming the light emitting layer, insulating layer, and metal electrode, or after forming the films and removing a part of the laminated thin film layer by etching.

When a high voltage is applied between the metal electrodes 2 and 6, electroluminescence occurs within the light emitting layer due to the strong electric field. This light is reflected by the metal electrode and is emitted from the end face of the light emitting layer 4 as shown by the arrow without leaking upward or downward. The light emitted from the end face is reflected by the surface of the protrusion 7, and the light is emitted in a direction perpendicular to the substrate. That is, the light generated in the light emitting layer 4 can be reflected by the protrusion 7 and can be effectively extracted vertically upward relative to the substrate.

This protrusion 7 is provided at an angle of 45'' with respect to the substrate so as to reflect the emitted light in the vertical direction, but this angle is not necessarily limited to 45@ depending on the purpose.
The protrusion 7 may be located at the edge of the substrate as shown in FIG.

In the above configuration, in order to extract light above the substrate,
The substrate does not necessarily have to be transparent, and an opaque substrate such as a ceramic substrate can be used instead of a glass substrate. As the metal electrodes 2 and 6, AI, Ag, Cr, etc. can be used. In addition, the materials for the insulating layers 3 and 5 include oxides such as 5i02, Ta205, Y2O3, and BN.
, AIN, nitrides such as Si3N4, and composite films thereof,
Fluorides such as CaF2, MgF2, or 5rTiOs
, PbTi0a, or other perovskite-type ferroelectric materials can be used. The light-emitting layer is made of ZnS doped with Mn or Tb or a chalcogenide of an alkaline earth element doped with a rare earth element such as Ce5Eu.

The present invention will be explained in more detail below using examples.

Example 1 In the device having the configuration shown in FIG. 1, aluminosilicate glass was used as the glass substrate I. The protrusions 7 are formed by forming a 5i02 thin film on a glass substrate and processing it by a photolithography process so that it has a cross section having a slope inclined at about 45 degrees. The metal electrodes 2 and 6 were formed of Cr, the insulating layer 3 was formed of AIN, the insulating layer 5 was formed of a laminated film of AIN and 5i02, and the light emitting layer 4 was formed of SrS doped with Ce. Next, etching is performed along the protrusion 7 by photolithography so that the Cr electrode at the bottom remains, and the protrusion is used as a mirror surface.

When a voltage is applied between the metal electrodes 2 and B, light is emitted within the light emitting layer 4, and after being reflected multiple times by the upper and lower metal electrodes, it is emitted from the end face, reflected by the mirror surface of the protrusion 7, and emitted toward the substrate. and then taken out vertically. Since the light from the end face is directly reflected, the emitted light is highly directional.

Since this thin film EL element does not have a structure in which light is extracted from the substrate side, it is clear that an opaque ceramic substrate may be used instead of a transparent glass substrate.

Embodiment 2 FIG. 3 shows another embodiment of the present invention, in which Cr metal electrodes 9, 13 and 17, AIN insulating layers lO and 14 are placed on a glass substrate 8 provided with protrusions 18, similar to the embodiment described above. , A.I.N.
and 5i02 insulating layers 12 and 16, Eu
A light emitting layer 11 made of CaS doped with Ce and a light emitting layer 15 made of SrS doped with Ce were formed.

As in Example 1, etching is performed along the protrusions 1B to leave a Cr mirror surface. By appropriately adjusting the voltages applied to the three electrode layers, green-blue, red, and intermediate colors of light are emitted above the substrate.

As described above, according to the present invention, since a transparent electrode is not used, a thin film E with excellent long-term reliability is achieved without increasing the resistance of the electrode.
An L element is obtained.

[Effects of the Invention] As explained above, the thin film EL device of the present invention can emit strong and concentrated light.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of an embodiment of the present invention, FIG. 3 is a cross-sectional view of another embodiment of the present invention, and FIG. 4 is a conventional thin film EL.
A cross-sectional view of the element is shown. 1.8.19...Glass substrate, 2.6,9,13,17.24...Metal electrode, 3.5
, 10, 12, 14, 21.23... insulating layer, 4.1
1,15.22...Light emitting layer, 7,18...Light scattering material, 20...Transparent electrode.

Claims (2)

[Claims] (1) Metal electrode layer, thin film electroluminescent layer,
A light reflector is provided on the same substrate as the one on which the metal electrode layers are sequentially laminated, so that the light emitted from the end face of the thin film electroluminescent layer is emitted in a direction different from the direction in which it is emitted. Thin film electroluminescent device. (2) A plurality of thin film electroluminescent layers and electrode layers having different emission wavelength characteristics are alternately laminated on the substrate,
2. The thin film electroluminescent device according to claim 1, wherein at least the bottom layer and the top layer are metal electrode layers.