JPH02132791A - Thin-film el element - Google Patents

Abstract

PURPOSE:To attempt shortening time necessary to form insulating films and to attempt reducing the manufacturing cost of the thinfilm EL element in the title, by composing insulating layers of an organic insulating layer formed through a coating process and an inorganic insulating layer formed through a sol-gel process which is a kind of the coating process, and then forming one portion of the insulating layers, in contact with an EL luminous layer, out of the inorganic insulating layer. CONSTITUTION:The thin-film EL element in the title is composed of a glass substrate 1, a transference electrode 2, a lower-part insulating layer 3 made of a titanium dioxide film formed through a sol-gel process, a luminous layer 4, an upper-part insulating layer 5 made of a titanium dioxide film 5a formed through the sol-gel process and a cyanoethylcellulose film 5b formed through a coating process, and back electrodes 6. Then, at least one portion of the insulating layers, in contact with the electroluminescence(EL) luminous layer 4 is formed out of the inorganic insulating layer 5a which surpasses the organic insulating layer 5b in insulating-property whereby the gradient of brightness-voltage characteristic in the thin-film EL element becomes steep to reduce power consumption. Because, the organic insulating layer 5b and the inorganic insulating layers 3, 5a, all are also formed through the coating process, they make any vacuum space unnecessary. This permits to attempt shortening time necessary to form the insulating layers and to attempt reducing the manufacturing cost of the thin-film EL element.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a thin film EL (electroluminescence) device, and particularly to a thin film EL device that can achieve cost reduction.

<Conventional technology> Conventionally, thin-film EL elements have been manufactured using an I/O film on a transparent substrate such as glass.
Transparent electrodes made of ntOs, Sno=, etc., SiOz.
SiaN4, AQtOs. TagOs+ YtO3T
A lower insulating layer made of an inorganic material such as ie, a luminescent layer made of a matrix such as ZnS doped with Mn or the like as a luminescent center,
Upper insulating layer and AQ made of the same material as the lower insulating layer
It has a so-called double insulation structure in which the back electrodes are sequentially laminated.

The insulating layer is formed by sputtering.

Problems to be Solved by the Invention> However, the above-mentioned conventional thin film EL device has a slow film formation rate, and the insulating layer must be formed by a spatter method that requires a vacuum, so it takes a long time to manufacture it. This method has the disadvantage that the manufacturing cost increases as a result.

Therefore, an object of the present invention is to form an insulating film in a short time.
It is an object of the present invention to provide a thin film EL element that is inexpensive to manufacture.

Means for Solving the Problems> In order to achieve the above object, the thin film EL element of the present invention has the following features:
The insulating layer provided between the electrodes consists of an organic insulating layer formed by a coating method and an inorganic insulating layer formed by a sol-gel method, which is a type of coating method, and at least the above EL of the insulating layer is formed. The portion that contacts the light emitting layer is characterized by being the above-mentioned inorganic insulating layer.

<Function> The inorganic insulating layer in contact with the EL light-emitting layer has better insulating properties than the organic insulating layer, and the brightness of the thin film El and the device is lower than in the case where the organic insulating layer is in contact with the EL light-emitting layer. The slope of the voltage characteristic becomes steeper, reducing power consumption.

In addition, since the organic insulating layer and inorganic insulating layer are formed by a coating method, a vacuum space is not required, and the film formation speed is fast.
The manufacturing cost of thin-film EL devices is reduced, and since there is an organic insulating layer, which is faster to form than an inorganic insulating layer, in areas other than the parts that contact the EL emitting layer, the entire insulating layer is formed of an inorganic insulating layer. The film formation speed becomes faster than when

Example The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 is a sectional view of one embodiment of the thin film EL element of the present invention. In FIG. 1, l is a glass substrate, 2 is a transparent electrode,
3 is a lower insulating layer made of a TiOt film formed by a sol-gel method, 4 is a light emitting layer, and 5 is a TiOt film 5a formed by a sol-gel method and a cyanoethylcellulose film 5b formed by a coating method. 6 is a back electrode.

This thin film EL element is manufactured by the method described below.

■ First, a glass substrate! A transparent electrode (ITO (tin-doped indium oxide) film) 2 is deposited on the top by sputtering to a thickness of about 2,000 yen.
It is formed to a human thickness and etched into stripes.

■ Next, tetrapropoxytitanium Ti (O C 3
I{7)a, water H, O, ethyl alcohol C 2 1-
A solution of { 50 1-1 mixed at a molar ratio of 1:1:100 was applied using a spinner, and the lower insulating layer 3 was baked at 150°C for 1 hour and then at 600°C for 1 hour in air. A film with a thickness of approximately 2,000 layers is formed. That is, the lower insulating layer is formed by a sol-gel method, which is a type of coating method.

(2) Next, a light-emitting layer 4 doped with ZnS as a base material and Mn as a light-emitting center is formed on the lower insulating layer 3 to a thickness of about 7,000 layers by electron beam evaporation.

(2) Furthermore, as part of the upper insulating layer 5, a TiOt film 5a is formed on it by the same sol-gel method as the lower insulating layer 3.
Formed with a thickness of about 500 people.

(2) Next, cyanoethylcellulose is dissolved in dimethylpolamide to form a 2% solution, which is applied using a spinner and dried at 150° C. for 1 hour to form the cyanoethylcellulose film 5b. In this way, the upper insulating layer 5 is formed by forming both the T i O t film 5a, which is an inorganic insulating layer, and the anoethylcellulose film 5b, which is an organic insulating layer, by a coating method.

(2) Finally, the AQ back electrode 6 is formed in a stripe shape so as to be orthogonal to the transparent electrode 2, thereby completing the production of the thin film EL element.

The inorganic insulating layer formed by the sol-gel method or the organic insulating layer formed by the coating method are not limited to the TiOt film and the cyanoethyl cellulose film, respectively. In the case of an inorganic insulating film, for example, tetraethoxysilane Si(O
C d{ s)-, }ributoxyaluminum A
If I2(OC4H11)3, bentabutoxytantalum Ta(Oc4t-to)s, tripropoxyyttrium Y(OC.1-17)3, etc. are selected as starting materials, SiOt, AQxO3. TatOs. YzO
An inorganic insulating film a can be formed. Further, by mixing solutions, these mixed films can be easily created, and the composition ratio can be freely selected. In the case of organic insulating film,
A polyimide-based or epoxy-based organic insulating film can be used.

When the above-mentioned upper insulating layer and lower insulating layer are composed only of inorganic insulating films made by sol-gel method, the required film thickness is 200 mm.
If 0 to 3000 people are to be formed at once, relatively thin films of about 500 people must be laminated several times because cracks are likely to occur during the firing process. The disadvantage is that it requires a large number of steps to achieve the required film thickness. On the other hand, in the case of only an organic insulating film formed by coating, several thousand
Even if the thickness of the film is formed at once, the above-mentioned cracks will not occur. However, if the light-emitting layer and the organic insulating film are in direct contact, the slope of the brightness-voltage characteristic of the thin-film EL element becomes gentle, resulting in an increase in power consumption during driving. Therefore, in this embodiment, the portion of the upper insulating layer 5 that is in contact with the EL light emitting layer 4 is replaced with an inorganic insulating layer 5a made of a Tidy film.
By doing so, the above-mentioned disadvantages are prevented.

FIG. 2 is a cross-sectional view of another embodiment of the invention.

In this embodiment, the lower insulating layer 13 is composed of an inorganic insulating layer 13a made of a T r O x film formed by a sol-gel method and a cyanoethyl cellulose film 13 formed by a coating method.
It is constructed of a laminated film with b.

Moreover, the above-mentioned upper insulating layer and lower insulating layer can each be constructed from a laminated film of three or more layers formed by a sol-gel method. Furthermore, the present invention can also be applied to a thin film EL element having an MIS (metal-insulator semiconductor) structure in which either the upper insulating layer or the lower insulating layer is omitted.

Effects of the Invention> As is clear from the above, the thin film EL element of the present invention has the following effects:
Since the insulating layer is formed by a coating method, the insulating layer can be formed in a short time, and manufacturing costs can be reduced. Furthermore, the thin film EL element of the present invention is
Since the area other than the part that contacts the EL light emitting layer has an organic insulating layer formed by a coating method, it is possible to form an insulating layer in a shorter time than when the entire structure is made of an inorganic insulating layer. It is possible to reduce costs.

In addition, in the thin film EL cable of the present invention, at least the portion of the insulating layer that is in contact with the EL light emitting layer is composed of an inorganic insulating layer. The brightness-voltage characteristic of the thin-film EL element becomes steeper than that in the case where the thin-film EL element is used, and power consumption can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional structural diagram of one embodiment of the present invention, and FIG. 2 is a cross-sectional structural diagram of another embodiment of the present invention. 1.1 1... Temporary glass base, 2.12... Transparent electrode, 3, l3... Lower insulating layer, 5a, I 3a, I 5a... TiO2 film, 4.14.
...Light emitting layer, 5.15...Jiro insulating layer, 5b, l 31). I 5b...cyanoedil cellulose membrane, 6.16... back electrode.

Claims (1)

[Claims] (1) In a thin film EL device in which a light-emitting layer and an insulating layer are provided between electrodes, the insulating layer is an organic insulating layer formed by a coating method and an inorganic insulating layer formed by a sol-gel method, which is a type of coating method. and of the insulating layer, at least the above E
A thin film EL device characterized in that a portion in contact with the L-emitting layer is the above-mentioned inorganic insulating layer.