JPS6343880B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] - Industrial Application Field - The present invention can be advantageously utilized in a matrix-driven thin film EL panel having a double insulating film structure and a method for manufacturing the same.

-Prior art- Fig. 3 is a side cross-sectional view of an EL panel manufactured by a conventional manufacturing method, in which 1 is a transparent glass substrate, 2 is a stripe-like structure made of, for example, In ₂ O ₂ formed on the glass substrate 1. A SiO ₂ film 3a is formed on the substrate surface 1a of the glass substrate 1 by reactive sputtering using Si as a target in a mixed gas of Ar gas and abundant O ₂ gas.

Next, while the O ₂ gas is gradually reduced, N ₂ gas is injected to form a Si, N, and O compound thin film 4a.

Next, all O ₂ gas is exhausted and Ar gas and abundant
A Si ₃ N ₄ film 5a with excellent insulation properties is formed in N ₂ gas.

The SiO ₂ film 3a, the compound thin film 4a, and the Si ₃ N ₄ film 5a, which are thus sequentially laminated, constitute a first insulating layer.

ZnS is deposited on this first insulating layer, that is, on the Si ₃ N ₄ film 5a.
A light-emitting layer 6 is formed using Mn as a matrix and Mn as a light-emitting center.

Next, the Si ₃ N ₄ film 5b, the compound thin film 4b, and the SiO ₂ film 3b having excellent insulating properties are sequentially formed on the light emitting layer 6 in the reverse order of the formation of the films described above. These three layers are the second insulating layer.

Then, on this second insulating layer, that is, the SiO ₂ film 3b
A striped back electrode 7 made of Al is formed on the transparent electrode 2 and arranged so as to intersect with the transparent electrode 2 at right angles.

In this type of EL panel, for example, when performing a matrix display by sequentially scanning multiple back electrodes 7, the change in luminance due to small voltage changes must be made large. In other words, the luminance vs. applied voltage characteristic (hereinafter referred to as the BV characteristic) If the slope of the curve is not steep, even if the applied voltage is lowered, the applied voltage will gradually decrease due to a transient phenomenon, during which time the EL panel will also emit light, causing so-called crosstalk. Put it away. It is known that for this reason, it is not possible to increase the number of scanning electrodes, that is, to increase the number of display pixels.

-Problems to be Solved by the Invention- However, the EL panel manufactured by the conventional method as described above has a structure in which the light emitting layer 6 is sandwiched between Si ₃ N ₄ films 5a and 5b with excellent insulation properties. Because of this, an interface state with a shallow energy level is formed at the interface with the Si ₃ N ₄ films 5a and 5b of the light-emitting layer 6, so that fewer electrons are injected from the Si ₃ N ₄ film 5a or 5b, resulting in gradual avalanche. Showing the phenomenon, B-
There was a drawback that the slope of the V characteristic curve could not be made steeper.

Figure 2 shows the B-V characteristics of an EL panel, and an EL panel with a conventional structure starts emitting light at an applied voltage Va, as shown by curve I in the figure, and as the applied voltage V increases, the brightness B gradually increases. The brightness is almost saturated at voltage Vb. In this way, the conventional BV curve has a gentle slope like curve I.

In the display method of this type of display panel, a voltage Vb is applied when displaying, and when not displaying, the voltage is lowered only to Va in order to shorten the application time and increase the number of display pixels instead of reducing the voltage to zero.

However, as mentioned above, conventional EL panels have B-
Since the V curve is gentle, that is, the difference between Va and Vb is large, it takes time to boost the voltage from Va to Vb, and the number of scanning electrodes cannot be increased.

[Structure of the invention]

-Means for Solving the Problem- In order to solve the above problem, the present invention provides a method of forming a deep layer at the interface between the light emitting layer and the insulating layer between both sides of the light emitting layer and the Si ₃ N ₄ film having excellent insulating properties. A Si ₃ N ₄ film in a nitrogen-deficient state (hereinafter referred to as
Si ₃ N _4-x film) is added to the structure.
In order to improve the adhesion to each of the Si ₃ N _4-x film, the Si ₃ N ₄ film with excellent insulating properties, the transparent electrode made of In ₂ O ₃ , etc., and the back electrode made of Al, etc.
The SiO ₂ film is formed continuously in the same vacuum chamber by the reactive sputtering method without exposing it to the atmosphere by simply changing the amount of gas supplied.

- Effect - As mentioned in the above means, a deep energy level can be formed at the interface between the light-emitting layer and the insulating layer due to the presence of the Si ₃ N _4-x film, so that the BV characteristic curve has a steep slope. EL panels can be manufactured, and the first insulating layer and the second insulating layer can be formed continuously in the same vacuum chamber.

-Example- Hereinafter, an example of the present invention will be described based on the drawings.

Note that the same reference numerals are used for the same components as in the conventional example.

FIG. 1 is a side cross-sectional view of an EL panel manufactured by the method according to the present invention, in which a plurality of striped transparent electrodes 2 made of, for example, In ₂ O ₃ are formed on a transparent glass substrate 1. First, each film constituting the first insulating layer 9a is successively formed in the same vacuum chamber on the substrate surface 1a having the transparent electrode 2 by reactive sputtering using Si as a target.

In this method, Ar gas and abundant
The SiO ₂ film 3a is formed in a mixed gas atmosphere of O ₂ gas. This SiO ₂ film 3a is the above-mentioned transparent electrode 2 and the Si ₃ N ₄ film 5a with excellent insulating properties formed afterwards.
The film thickness may be 1000 Å or less since it is intended to improve adhesion with the film.

Next, a compound thin film 4a of Si, O, and N is formed on this SiO ₂ film 3a while gradually decreasing the amount of O ₂ gas and simultaneously increasing the injection of N ₂ gas. In this case, if the Si ₃ N ₄ film 5a is formed directly on the SiO ₂ film 3a, there is a risk that the Si ₃ N ₄ film 5a will peel off.
Since the compound thin film 4a is provided to alleviate these rapid changes in film composition, it goes without saying that the film thickness may be 1000 Å or less.
In some cases, this thin compound film 4a may be substantially removed.

Subsequently, O ₂ gas is completely eliminated and a Si ₃ N ₄ film 8a with excellent insulation properties is formed on this compound thin film 4a in a mixed gas atmosphere of Ar gas and abundant N ₂ gas.
form. This Si ₃ N ₄ film 5a has the function of insulating the EL panel, and therefore has a thickness of 1000 to 3000 Å.
It is preferable to set the film thickness to an appropriate level.

Further, a large amount of N ₂ gas is evacuated to create a mixed gas atmosphere of Ar gas and a small amount of N ₂ gas in the vacuum chamber, thereby forming a nitrogen-deficient Si ₃ N _4-x film 8a.
This Si ₃ N _4-x film 8a is stoichiometrically stable.
In a state where Si ₃ N ₄ is deficient in nitrogen, more electrons are generated, and more electrons are injected into the light emitting layer 6 that is subsequently formed on this Si ₃ N _4-x film 8a. The film thickness is 500~
The thickness is preferably about 3000 Å.

As described above, the SiO ₂ film 3a, the compound thin film 4a, the Si ₃ N ₄ film 5a, and the Si ₃ N _4-x film 8a, which are laminated in sequence, are the first
This is an insulating layer 9a.

The method of changing the amounts of Ar gas, N ₂ gas, and O ₂ gas in forming each film constituting the first insulating layer 9a is to constantly evacuate the inside of the vacuum chamber using the exhaust device of the reactive sputtering device. However, the required gas is injected into the vacuum chamber while changing the mixing ratio of Ar gas, N ₂ gas, and O ₂ gas using a separately provided gas mixer. Therefore, the SiO ₂ film 3a on the glass substrate 1 side, the compound thin film 4a of Si, N, and O,
The Si ₃ N ₄ film 5a and the Si ₃ N _4-x film 8a can be successively formed in the same vacuum chamber without being exposed to the atmosphere.

The sample on which the first insulating layer 9a was formed in this way was taken out from the vacuum chamber and Si ₃ N _4-x in a nitrogen-deficient state was removed.
A light emitting layer 6 is formed on the film 8a by electron beam evaporation in a separate vacuum chamber. This light emitting layer 6 is made of, for example, ZnS.
doped with 0.3 to 0.7% by weight of Mn as the luminescent center, and when an electric field of 10 ⁶ V/cm or more is applied, it emits horizontal orange, but is not limited to this, and can emit other colors. It's okay if it's something.

Next, a second insulating layer is continuously formed on this light emitting layer 6 in the same vacuum chamber by the same sputtering method as described above.

In this method, the first insulating layer 9a is formed in the reverse order so as to be arranged symmetrically with each film of the first insulating layer 9a.

First, a nitrogen-deficient state is chemically quantitatively formed on the light-emitting layer 6 in a mixed gas atmosphere of Ar gas and a small amount of _N2 gas.
A Si ₃ N _4-x film 8b is formed.

Next, the amount of N ₂ gas is increased to form a Si ₃ N ₄ film 5b with excellent insulation properties on this Si ₃ N _4-x film 8b in a mixed gas atmosphere of Ar gas and rich N ₂ gas. .

Furthermore, while gradually reducing _N2 gas,
O ₂ gas is injected to form a compound thin film 4b of Si, N, and O on this Si ₃ N ₄ film 5b as required.

Finally, in an atmosphere of Ar gas and rich O ₂ gas, on this compound thin film 4b, or when this compound thin film 4b is not formed,
A SiO ₂ film 3b on the back electrode side is formed on the Si ₃ N ₄ film 5b.

This Si ₃ N _4-x film 8b formed in a sequential manner,
Si ₃ N _4-x film 8b, Si ₃ N ₄ film 5b, compound thin film 4b,
The SiO ₂ film 3b is the second insulating layer 9b, and each film is formed in the same vacuum chamber by sputtering in the same manner as the first insulating layer 9a, so that they can be formed under the same conditions. However, as described above, the steps of the method are reversed and the films are arranged symmetrically with the light emitting layer 6 in between.

The sample thus obtained is taken out of the vacuum chamber, and a plurality of striped back electrodes 7 made of, for example, Al are deposited on the SiO ₂ film 3b so as to cross the transparent electrode 2 at right angles. Thereafter, necessary processing is performed as required to obtain an EL panel having a structure as shown in FIG.

In addition, Al, which is the material of the back electrode 7, and the SiO ₂ film 3
If you want to further increase the adhesion with b, use SiO ₂ film 3b
An Al ₂ O ₃ film may be further formed thereon, or an Al ₂ O ₃ film may be used in place of the SiO ₂ film 3b.

The EL panel having the structure obtained by the above method has nitrogen-deficient Si ₃ N _4-x films 8a and 8b on both sides of the light-emitting layer 6, that is, a state in which nitrogen is deficient from the Si ₃ N ₄ film having excellent insulating properties. This Si ₃ N _4-x film 8a,
Since the layer 8b forms a so-called donor level that supplies conduction electrons, the Si ₃ N _4-x films 8a, 8b and the light emitting layer 6
An interface state with a deep energy level is formed at the interface between the Si ₃ N _4-x films 8a and 8b, and electron injection from the Si 3 N 4-x film 8a or 8b into the light-emitting layer 6 occurs between the Si ₃ N _4-x films 8a and 8b. When the potential difference reaches a certain value, it shows a so-called avalanche phenomenon in which it increases rapidly, and the slope of the BV curve also becomes steep.

Next, we will explain with reference to Figure 2, which shows the BV characteristics of the EL panel. In addition, curve I is the conventional B-V
The curve shows the BV characteristics of the present invention.

As shown in the figure, the BV characteristic curve according to the present invention starts emitting light at an applied voltage of V ₁ and reaches saturation brightness at a voltage of V ₂ , and the slope of the so-called BV curve becomes steep and the voltage V ₁ Since the difference between and V ₂ becomes smaller,
This has the advantage that the number of scanning electrodes, that is, the number of display pixels can be increased, and crosstalk does not occur.

Further, even in the low voltage range, many electrons are injected into the light emitting layer, so as shown in FIG. 2, light is emitted at a voltage lower than the light emission starting voltage Va of the conventional EL panel. Of course, the saturation brightness voltage _V2 can also be much lower than that of conventional EL panels.

These voltages differ depending on the film thickness of the light emitting layer 6, the first insulating layer 9a, and the second insulating layer 9b. When the film thickness was set to 3000 Å, a reduction of approximately 50 V was achieved compared to the conventional method.

Since the Si ₃ N 4 films 5a and 5b with excellent insulation properties are formed on the outside of the Si ₃ N _{4 -x} films 8a and 8b, no current from the drive circuit flows, that is, no direct current flows. Since the components are cut out, there is no problem of damage to the EL panel due to Joule heat, and an EL panel with a long life can be obtained.

〔Effect of the invention〕

As explained above, this invention provides nitrogen-deficient Si ₃ N _4-x films for the first and second insulating layers, and the first and second insulating layers are sandwiched between the Si ₃ N _4-x films so that the light emitting layer is sandwiched between them. Since two insulating layers are provided, the interface level in the light-emitting layer can be made deeper than that of conventional ones, making it possible to obtain an EL panel with a steep BV characteristic curve, thereby increasing the number of display pixels, and This has the effect of extending the life of the EL panel.

In addition, since the first and second insulating layers are formed by changing the mixing ratio of the mixed gas using the reactive sputtering method, each film can be formed successively in the same separate vacuum chamber. Each of the first and second insulating layers can be easily formed under the same conditions.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of an EL panel manufactured by the method according to the present invention, Fig. 2 is a graph showing the BV characteristics of the EL panel, and Fig. 3 is a graph showing the EL panel manufactured by the conventional manufacturing method.
FIG. 3 is a side sectional view of the EL panel. 1...Glass substrate, 2...Transparent electrode, 3a, 3b...
SiO ₂ film, 4a, 4b... Compound thin film, 5a, 5b
... _{Si3N4 film} , 6...light emitting layer, 7...back electrode, 8a,
8b...Si ₃ N _4-x film.

Claims (1)

[Claims] 1. In an EL panel formed by sequentially laminating a transparent electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a back electrode on a glass substrate, the first insulating layer is made of at least Si ₃ . _N4 membrane,
A nitrogen-deficient Si ₃ N _4-x film is sequentially laminated, and the second insulating layer is formed by sequentially laminating at least a nitrogen-deficient Si ₃ N _4-x film and a Si ₃ N ₄ film. An EL panel characterized by: 2. A transparent substrate with a transparent electrode formed thereon is placed in a vacuum chamber, and a SiO ₂ film is formed in a mixed gas of Ar gas and abundant O ₂ by reactive sputtering using Si on the transparent substrate as a target. Gradually reduce the amount of O ₂ gas and increase N ₂ gas at the same time to form a compound thin film of Si, O, and N as required, and finally Si in a mixed gas of only Ar gas and abundant N ₂ gas. ₃ N ₄ film is formed, and a large amount of N ₂ gas is rapidly exhausted to form a nitrogen-deficient Si ₃ N _4-x film, which is taken out of the vacuum chamber and nitrogen-deficient
A light-emitting layer is formed on the surface of the Si ₃ N _4-x film, and then a nitrogen-deficient state is formed on the surface of the light-emitting layer in a mixed gas of Ar gas and a small amount of N ₂ gas in another vacuum chamber.
Form a Si ₃ N _4-x film, then rapidly increase N ₂ gas to form a Si ₃ N ₄ film in a mixed gas of Ar gas and rich N ₂ gas, then gradually reduce N ₂ gas. At the same time, while increasing O ₂ gas, a thin compound film of Si, O, and N is formed in a mixed gas of Ar gas, N ₂ gas, and O ₂ gas, and finally in a mixed gas of Ar gas and O ₂ gas only.
1. A method for manufacturing an EL panel, comprising forming a SiO ₂ film and forming a back electrode on the surface of the SiO ₂ film.