JPH05266978A - End surface light emitting type thin film electroluminescence element - Google Patents

Abstract

PURPOSE:To enhance performance, as an optical wave guide, of a pixel in a light emitting portion by forming a plurality of grooves on an insulating substrate, embedding electroluminescence constitution layers in the grooves, and disposing second electrode layers perpendicularly to the grooves. CONSTITUTION:Electroluminescence constitution layers 16 each comprising a first electrode layer 13a, a first insulating film 14a, a second insulating film 14b and a light emitting layer 15 are embedded in a plurality of grooves 11 formed on a glass substrate 12. Stripe-like second electrode layers 13b perpendicular to the grooves 11 are laid on the glass substrate 12. The glass substrate 12 provided with the electroluminescence constitution layers 16 and the like thereon is cut along dashed lines 17. Ends including exposed portions of the electroluminescence constitution layers 16 of the obtained cut pieces 181, 182, 183 are covered with a glass film, thus manufacturing an end surface light emitting type thin film electroluminescence element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge emitting thin film electroluminescent element (edge emitting thin film EL element) used for a light source of a printer.

[0002]

2. Description of the Related Art Lasers, LEDs and the like are generally used as light sources for electrophotographic printers, but recently thin film EL elements have been receiving attention.

A thin film EL element has a structure in which a transparent electrode, an insulating layer, a light emitting layer, an insulating layer and an electrode are sequentially laminated on a transparent glass substrate. In such a thin film EL element, by applying a voltage between the electrodes, electroluminescent light is extracted from the transparent electrode, so-called surface emission occurs. On the other hand, when an opaque electrode made of metal or the like is used instead of the transparent electrode to apply a voltage to cause electroluminescence, light is extracted in a direction perpendicular to the facing direction of the electrode, so-called edge emission is performed. .. D. Leksel et al., “Proc
Seeding of the SID ", Vol. 29.
/ 2, p. 145 to 150, Y ₂ O as an insulating layer
₃ (thickness 3000A) as Mn-activated ZnS as a light emitting layer
Edge of double insulation structure using (thickness 10000A)
Has announced the emitter.

Z. K. Kun et al., “Proceedi
ng of the SID ", Vol. 28/1
p. 81-85, 1987, edge emitters have announced that the value of edge emission is several tens of times the light output per unit area of surface emission. For this reason,
The edge-emitting type thin film EL element can be used as a light source for a printer. In such a thin film EL element, it is preferable that the light emitted in the pixel emits edge light as efficiently as possible, and the function as an optical waveguide of the light emitting portion becomes important.

The structure and manufacturing method of the edge emitting thin film EL element are basically the same as those of the conventional surface emitting thin film EL element except that an opaque electrode such as a metal electrode is used instead of the transparent electrode. In such a thin film EL edge emitting device, in order to improve the edge emission efficiency, selection of an insulating film having a refractive index smaller than that of the light emitting layer, selection of a metal electrode having a large reflectance for a predetermined emission wavelength, etc. Attempts have been made to improve by selection and from the viewpoint of the structure in which the pixels of the light emitting portion are optically separated from each other by etching the portions other than the pixels of the light emitting layer.

By the way, a conventional edge emitting type thin film EL element having a structure shown in FIG. 5 is known. Glass substrate 1
One metal electrode 2a is formed on the top. The light emitting layer 4 disposed between the pair of insulating films 3a and 3b is formed on the metal electrode 2a. The other metal electrode 2
b is formed on the upper insulating film 3b. The power supply 5 is connected to the pair of metal electrodes 2a and 2b. In such a thin film EL edge emitting device, the power source 5
Light is emitted from the end face of the light emitting layer 4 by applying a predetermined voltage to the metal electrodes 2a, 2b to drive the metal electrodes 2a, 2b.

The metal electrodes 2a, 2b, the pair of insulating films 3a, 3b and the light emitting layer 4 in the edge emitting thin film EL element are wet-etched or dry-etched by masking a resist pattern formed by photo-etching. Sputter etching). However, when each of the above-mentioned constituent members (particularly the insulating films 3a and 3b, the light emitting layer 4) is formed by patterning using such etching, it is affected by contamination, ion damage, etc., and the life is reduced due to a decrease in light output and dielectric breakdown. There is a problem of causing a decrease.

Moreover, it is necessary to fill the side surface of the light emitting layer 4 after patterning with an insulator having a low refractive index. For this purpose, as shown in FIG. 5, the lower insulating film 3a, the light emitting layer 4, and the upper insulating film 3b are formed by etching using different resist patterns as masks. It is necessary to adopt a method of covering the side surface of the light emitting layer 4. As a result, there is a problem that the manufacturing process becomes complicated.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an edge emitting thin film EL device having improved performance as an optical waveguide of a pixel of a light emitting portion.

[0010]

An edge emitting thin film EL element according to the present invention is an insulating substrate having a plurality of grooves, a first electrode layer, first and second insulating films embedded in the grooves, and An electroluminescent constituent layer including a light emitting layer,
The insulating substrate is provided with a second electrode layer formed so as to be orthogonal to the groove. As the insulating substrate, it is desirable to use a glass substrate having a refractive index of about 1.5 to 1.6, for example. / The electrode layer is formed of, for example, Al, Cu, ITO or the like.

The insulating film is made of, for example, Ta ₂ O ₅ or Y ₂ O.
₃ , Al ₂ O ₃ , Si ₃ N ₄ , SiAlON, SiO
It is formed of N, SiO ₂ or Ta ₂ O ₅ —SiO ₂ composite or the like.

The light emitting layer is made of, for example, ZnS as a matrix.
ZnSe, SrS, CaS or the like is used, and as the emission center, Mn or a lanthanide element such as Eu, Tm, Sm or Ce is used.

[0013]

In general, in the edge emission type thin film EL element, the refractive index n ₁ of the core which is a light emitting portion and the refractive index n _{2 of the} clad surrounding the optical waveguide have a relationship of n ₁ > n _2. This is important for improving the light output characteristics.

According to the present invention, by embedding an EL component layer including an electrode layer, an insulating film and a light emitting layer in a plurality of groove portions of an insulating substrate, the insulating layer is provided above and below the light emitting layer and the light emitting layer is provided above and below the light emitting layer. The side surface can be covered with the insulating substrate. In such a structure, when the matrix of the light emitting layer is ZnS, the refractive index thereof is 2.2 to 2.4, and the insulating substrate is made of non-alkali glass (for example, HOYA trade name; NA-4.
0), the refractive index is 1.57, so
By the action of the optical waveguide formed by the light emitting layer, the insulating layer and the glass substrate, the light output from the end surface of the light emitting layer can be remarkably improved. Further, by embedding the EL constituent layer in the plurality of groove portions of the insulating substrate, it is possible to reduce the etching step at the time of fine processing, and in particular, since it is possible to avoid the etching processing of the light emitting layer and the insulating film, these light emitting layers,
The influence of contamination, ion damage, etc. on the insulating film can be suppressed. Therefore, it is possible to obtain an edge emitting thin film EL element having excellent light output characteristics, good dielectric breakdown resistance characteristics, and a long life.

[0015]

Embodiments of the present invention will now be described in detail with reference to the manufacturing steps shown in FIGS. Example 1

First, a 36 mm × 36 mm × 1 mm non-alkali glass substrate (trade name: NA-4, manufactured by HOYA Co.) in which a plurality of groove portions 11 each having a width of 4 mm and a depth of 1.8 μm are processed.
0) 2 was prepared, and an Al film having a thickness of 2000 angstrom (A) was formed on the glass substrate 12 by the RF magnetron sputtering method. Next, Ta ₂ O ₅ -S
A Ta ₂ O ₅ —SiO ₂ film having a thickness of 3000 A was formed on the Al film by performing sputtering using a sintering target composed of an iO ₂ composite and a sputtering gas of Ar—O ₂ . Continued, Tb activated ZnS sintering target, Ar
Sputtering is performed using the sputtering gas of
ZnS: T with a thickness of 1.0 μm on the a ₂ O ₅ —SiO ₂ film
The b layer was formed. Further, Ta ₂ O ₅ -SiO ₂ sintered target consisting of composite, the performing sputtering using a sputtering gas Ar-O ₂ ZnS: Ta having a thickness of 3000A on the Tb layer ₂ O ₅ -SiO ₂ film Was deposited.
Each of these materials was formed into a film in a region surrounded by a chain double-dashed line in FIG. Next, the Al film other than the groove 11 and T
a ₂ O ₅ —SiO ₂ film, ZnS: Tb layer and Ta ₂ O
By removing the _5- SiO ₂ film, the first electrode layer 13 a made of Al and the first insulating layer made of Ta ₂ O ₅ —SiO ₂ are formed in the groove 11 of the glass substrate 12 as shown in FIGS. The EL component layer 16 composed of the film 14a, the light emitting layer 15 made of ZnS: Tb, and the second insulating film 14b made of Ta ₂ O ₅ —SiO ₂ was buried. After that, the thickness is 1.0 μm on the entire surface by the RF magnetron sputtering method.
Al film was formed and patterned to form a stripe-shaped second electrode layer 13b orthogonal to the groove 11.

Next, the glass substrate 12 on which the EL constituting layer 16 and the like are formed is cut along the chain line 17 in FIG. 1 to obtain the cut piece (eg 18 ₁ ) of the EL constituting layer 1.
The end face including the exposed portion of No. 6 was covered with the glass film 19 to manufacture the end face light emitting type thin film EL device 20 shown in FIG. Reference numeral 21 in FIG. 4 is a drive power source connected to the first and second electrode layers 13a and 13b.

Edge emitting thin film EL device 20 of the first embodiment
At the drive power source 21, the first and second electrode layers 13
An AC pulse voltage of 5 kHz was applied to a and 13b, and the output of the light 22 from the end face was measured. As a result, 22.5m
W / cm ² It came out. Example 2 A thickness of 2000 A was used instead of the first electrode layer made of Al.
A thin film EL light emitting device having the same structure as in Example 1 was manufactured except that the electrode layer made of ITO was used.

With respect to the light emitting device of Example 2, an AC pulse voltage of 5 kHz was applied from the driving power source to the first and second electrode layers. As a result, the end face light output is 21.0 mW / cm.
² , Surface light output is 510 μW / cm ² Met.

[0020]

As described in detail above, according to the edge emitting thin film EL device of the present invention, the performance of the pixel of the light emitting portion as the optical waveguide can be improved and the edge light output can be improved. As shown in FIG.

[Brief description of drawings]

FIG. 1 is an edge-emitting thin film EL according to Example 1 of the present invention.
FIG. 4 is a plan view showing a state in which the element is being manufactured.

FIG. 2 is a sectional view of FIG.

FIG. 3 is an enlarged cross-sectional view of a main part of FIG.

FIG. 4 is a sectional view showing an edge emission type thin film EL element manufactured according to Example 1 of the present invention.

FIG. 5 is a cross-sectional view showing a conventional edge emitting thin film EL element.

[Explanation of symbols]

11 ... Groove part, 12 ... Glass substrate, 13a, 13b ... Electrode layer, 14a, 14b ... Insulating film, 15 ... Light emitting layer, 16 ... E
L constituent layer, 20 ... Edge emitting thin film EL element, 21 ... Driving power source.

Claims (1)

[Claims] 1. An insulating substrate having a plurality of groove portions, an electroluminescent component layer embedded in the groove portions and including a first electrode layer, first and second insulating films and a light emitting layer, and the groove portions in the insulating substrate. And a second electrode layer formed so as to be orthogonal to the edge emitting type thin film electroluminescence element.