JP2517629B2 - Thin film EL panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a thin film used in a flat display device.
Regarding EL panel.

<< Prior art and its problems >> In recent years, various thin films have been used to realize flat display devices.
EL panels (electroluminescence panels) are in practical use.

An example of this will now be described with reference to FIG. 7. A transparent front electrode 2 made of In ₂ O ₃ , SnO ₂ or the like is laminated on a glass substrate 1, and a small amount of Mn is contained on the transparent front electrode 2. Through the phosphor film 4 made of ZnS, Si ₃ N ₄ or Ta ₂ O ₅
A first dielectric film 3 and a second dielectric film 5 made of, for example, are laminated and formed, and a back electrode 6 is further formed on the second dielectric film 5.
Are laminated and formed.

As the above-mentioned laminating method, a method of sequentially laminating the transparent front electrode 2 and the like on the glass substrate 1 by the sputtering vapor deposition method or the electron beam vapor deposition method is used, and the electrodes 2 and 6 are formed by photolithography. It is patterned into an arbitrary shape by the technique.

Here, when an AC voltage is applied between the electrodes 2 and 6 (for example, the electric field in the phosphor film 4 is 1 to 2 × 10 ⁶ V / cm), the region part sandwiched between the electrodes 2 and 6 is It will emit light.
Therefore, if the shapes of the electrodes 2 and 6 are patterned into a desired shape, it is possible to obtain a light-emitting display having an arbitrary shape.

By the way, in the EL panel, each film is very thin, and the total film thickness is very thin, less than 2 μm.

Therefore, the surface area of the panel is large compared to its volume, and it is sensitive to the surrounding environment. For example, when dust or the like is mixed in the thin film in the manufacturing process, local defects of film quality occur in the thin film. In such a case, when a voltage is applied to this defective portion, Joule heat causes dielectric breakdown,
Furthermore, it may spread to a size that allows the dielectric breakdown portion to be visually recognized due to a propagating breakdown. Here, the term “propagative breakdown” means that a dielectric breakdown that occurs in a certain minute area (about 1 μm) does not end with the breakdown only in that area, but propagates to the periphery and spreads to a size that can be visually recognized. When you do.

For this reason, the larger the display surface area of the panel, the more easily the above-mentioned propagating breakdown due to the inclusion of dust,
There is a problem that the larger the display panel, the lower the manufacturing yield and the manufacturing cost.

Incidentally, the dielectric breakdown includes self-healing type dielectric breakdown as well as the above-mentioned propagation type. Here, the self-healing type dielectric breakdown means that the dielectric breakdown generated in a minute area does not propagate to the periphery and is self-healing and ends with the dielectric breakdown in a maximum area of about 3 μm. Indicates the case where the dielectric breakdown does not proceed.

Therefore, it is needless to say that a self-healing type in which even if a local defect is caused by the inclusion of dust or the like, the breakdown type of the dielectric breakdown is limited to only one breakdown point, no matter how excellent the pressure resistance is, A dielectric film having transmissivity cannot be used as an insulating film for EL.

<Object of the Invention> In view of the above problems, the present invention is intended for manufacturing a large-sized display panel by preventing the propagation of dielectric breakdown due to dust contamination or the like and ending the self-healing dielectric breakdown. Even if it exists, it aims at providing the thin film EL panel which can be manufactured at low cost by improving the manufacturing yield.

<< Means for Solving the Problems >> In order to achieve the above object, the present invention comprises: a first dielectric layer formed by laminating a plurality of dielectric films on a glass substrate with a transparent entire surface electrode interposed therebetween; A second dielectric layer formed by stacking a plurality of dielectric films on the first dielectric layer via a phosphor film, and a back surface using Al or an Al-containing alloy as a constituent material on the second dielectric layer. In a thin-film EL panel provided with electrodes, the melting point of the dielectric film on the back electrode side forming the second dielectric layer and the boiling point of the back electrode constituent substance are on the back electrode side forming the second dielectric layer. It is characterized in that it is configured by increasing the melting point of the dielectric film.

<< Operation >> In the present invention, the melting point of the back electrode-side dielectric film forming the second dielectric layer and the boiling point of the back electrode constituent substance are the back electrode side dielectric film forming the second dielectric layer. Has a higher melting point, which prevents the growth of dielectric breakdown.

<< Description of Embodiments >> Next, embodiments of the thin film EL panel according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of the present invention. First, a transparent front electrode 1 made of In ₂ O ₃ or SnO ₂ is first formed on a glass substrate 11.
2 is patterned into a desired shape and laminated.

A first dielectric layer 13 is laminated and formed on the transparent front electrode 12, and the first dielectric layer 13 is further provided with a phosphor film 14 made of ZnS containing a small amount of Mn via a first dielectric layer 13. The second dielectric layer 15 is formed by stacking two dielectric layers 15.
Similar to the transparent front electrode 12, a back electrode 16 made of Al patterned into a desired shape is laminated and formed thereon.

Here, in the present embodiment, the first dielectric layer 13 is sequentially formed on the transparent front electrode 12 by an Al ₂ O ₃ film 13c (film thickness 100Å to 3000).
Å), Si ₃ N ₄ film 13b (same 500 Å ~ 3000 Å) and Al ₂ O ₃ film 14
The second dielectric layer 15 is provided by laminating the respective dielectric films of a (50 Å to 1000 Å), and the second dielectric layer 15 is sequentially formed on the phosphor film 14 by the Al ₂ O ₃ film 15a (film pressure). 50Å ~ 1000
Å), Si ₃ N ₄ film 15b (500 Å to 3000 Å) and BeO film 15c
It is provided by laminating each dielectric film (100 Å to 3000 Å).

Thus, in the present embodiment, the boiling point of Al forming the back electrode 16 is 2060 ° C., while the melting point of the BeO film 15c which is the back electrode side dielectric film forming the second dielectric layer 15 is 2570 ° C.
Therefore, the melting point of the dielectric film on the back electrode side forming the second dielectric layer is higher.

In order to sequentially form the transparent front electrode 12 and the like on the glass substrate 11, a sputtering vapor deposition method, an electron beam vapor deposition method, a CVD method (chemical vapor deposition method) and the like are used, and the transparent front electrode is also used. The patterning of 12 and the back electrode 16 is performed by photolithography as in the conventional example to form an arbitrary shape.

As described above, the thin film EL panel of this embodiment uses the Al film having a boiling point of 2060 ° C. as the constituent material of the back electrode 16, and the dielectric film 15c on the back electrode side forming the second dielectric layer 15 has a melting point of 2570. By using BeO at ℃, the melting point of the dielectric film on the side of the back electrode forming the second dielectric layer and the boiling point of the above-mentioned substance forming the back electrode are the dielectric on the side of the back electrode forming the second dielectric layer. It is configured by increasing the melting point of the film.

Next, FIG. 2 shows the experimental results of the emission luminance characteristics and the distribution of the withstand voltage of the EL panel of this example, and FIG. 3 shows the experimental results of the emission luminance characteristics and the distribution of the withstand voltage of the EL panel in the conventional example. Show. Here, in the case of the present embodiment in FIG. ₂ , Al ₂ O ₃ having a film thickness of 500 Å is sequentially formed on the phosphor film 1.
Film 15a, 1500 Å thickness Si ₃ N ₄ film 15b, and 1000 Å thickness BeO
The second dielectric layer 15 is formed by stacking the dielectric films of the film 15c.
In the case of the conventional example shown in FIG. 3,
Sequentially 500 Å Al ₂ O ₃ film and 1500 Å film thickness on phosphor film
_This is the case of stacking ₃ N ₄ . The driving conditions in the above experiment were that the pulse width was 50 μS and pulse driving was performed at 1 KHz.

Here, 20A and 20B in FIG. 2 and FIG. 3 show the light emission luminance (cd / m ² ) with respect to the respective applied voltages (Vo-p), and 30A and 30B are the respective applied voltages. Self-healing withstand voltage 40 and propagation withstand voltage 50 against voltage
2 shows the distribution of the withstand voltage.

As is apparent from FIGS. 2 and 3, the emission luminance characteristics 20A and 20B are not so different from each other, but there is a large difference in the withstand voltage distributions 30A and 30B (in the drawings). The white part 40 shows a self-healing type withstand voltage, and the shaded part 50 shows a propagation type withstand voltage).

That is, in this embodiment (that is, FIG. 2), the withstand voltage distribution 30A is all self-recovering type (shown by the white portion 40) when the applied voltage is constant (340Vo-p) or less, When the applied voltage is higher than that, all are of the propagation type (shown by the shaded portion 50). That is, the destruction type control is completely performed at a certain voltage. Therefore, by controlling the applied voltage, the EL panel can be manufactured with an extremely high yield.

On the other hand, in the case of the conventional example (ie, FIG. 3), the withstand voltage distribution 30B shows that the propagation type 50 increases as the applied voltage becomes stronger, but the self-healing type is applied regardless of the strength of the applied voltage.
40 or propagation type 50 dielectric breakdown always occurs in a mixture. Therefore, as compared with the case of this embodiment, it is obvious that the yield of manufacturing the EL panel is low.

As described above, in the thin film EL panel according to the present invention, the melting point of the dielectric film 15c on the back electrode side that constitutes the second dielectric layer 15 and the boiling point of the back electrode 16 constituent material are the back electrode constituent materials. Since it is configured by lowering the boiling point of, even if dust or the like is mixed in during manufacturing of the panel, it can be suppressed by the self-recovery destruction type by controlling the applied voltage.

In this example, BeO is used as the dielectric film on the back electrode side that constitutes the second dielectric layer 15, but the following table shows the dielectric breakdown voltage when other materials are used ( The average value of the breakdown voltage distribution) and the melting points of these materials are shown.

From these experimental results, other than BeO as a dielectric film material, a material having a melting point higher than the boiling point of Al of 2060 ° C., for example,
Other than MgO, Y ₂ O ₃ , CaO, Sc ₂ O ₃ , Cr ₂ O ₃ , Zr
It was also found that the propagation type withstand voltage can be remarkably improved by using O ₂ , lanthanide oxide, HfO ₂ or the like.

The reason why the breakdown type of the dielectric breakdown is the propagation type or the self-healing type is unknown, but it is inferred from the experimental results as follows.

That is, Joule heat generated by local dielectric breakdown heats the dielectric layer and the back electrode near the breakdown point. If the melting point of the dielectric material is reached due to the rise in the temperature, significant heat is generated, and new destruction propagates to surrounding areas one after another, and in this case, propagation-type destruction occurs. However, even if the breakdown point generates heat due to Joule heat, if the dielectric material reaches the melting point and melts, and the Al electrode locally evaporates and opens before forming the conductive path, It is considered to be a recovery type.

By the way, in the present embodiment, the melting point (2570 ° C.) of the BeO film 15c which is the dielectric film on the back electrode side that constitutes the second dielectric layer 15
Is higher than the boiling point (2060 ° C.) of Al forming the back electrode 16, so it is considered that the Al electrode portion above the breaking point easily evaporates to an open state and ends in a self-healing breaking type. Of.

The above-mentioned high-melting-point materials such as BeO have the following properties: resistivity, moisture resistance,
Since it is inferior in chemical resistance and the like, the second dielectric layer 15 cannot be formed by itself, and Si ₃ N ₄ , Al ₂ O ₃ , Ta ₂ O ₅ , S
It is necessary to form a composite layer with one or more membranes selected from iO _{2 and the} like.

In addition, although an example in which Al is used as the back electrode 16 has been shown in the present embodiment, other Mo having a film thickness of 150 Å is formed on the second dielectric layer 15.
A blackened back electrode may be formed by sequentially stacking a film, an Al ₂ O ₃ film having a film thickness of 400 Å, and an Al film having a film thickness of 2000 Å.

By the way, so far, the melting point of the dielectric film on the back electrode side which constitutes the second dielectric layer and the boiling point of the above-mentioned back electrode constituent substance are different from those of the dielectric film on the back electrode side which constitutes the second dielectric layer. In the thin-film EL panel according to the present invention, which is characterized in that it is configured by increasing the height of the other, an example of implementing the present invention by selecting the material of the former dielectric film was shown. A second embodiment for practicing the present invention by selecting the electrode constituent material is shown in FIG.

In this embodiment, unlike the first embodiment, the second dielectric layer 15A has an Al ₂ O ₃ film 15a (film thickness 50Å to 1000 on the phosphor film 14).
Å) and a Si ₃ N ₄ film 15b (film thickness 500 Å to 3000 Å) are laminated and formed, and on the second dielectric layer 15A, Al containing 15% Zn is formed by a sputtering deposition method or the like. A back electrode 16A made of an alloy is laminated.

Here, Al containing 15% of Zn constituting the back electrode 16A.
The boiling point of the alloy is lower than the melting point of the Si ₃ N ₄ film 15b, which is the dielectric film on the back electrode 16A side and which constitutes the second dielectric layer 15A.

As described above, in this embodiment, the melting point of the dielectric film 15b on the back electrode side that constitutes the second dielectric layer 15A and the back electrode 16A
With the boiling point of the constituents of the
By using an Al alloy, the boiling point of the back electrode constituent material is made lower.

FIG. 5 shows the experimental results of the emission luminance characteristics and the distribution of withstand voltage when the alloy of Zn and Al is used as the back electrode 16A (the driving conditions are the same as those of the first embodiment). is there). Then, as is clear from comparison with FIG. 3 showing the experimental results in the conventional example, although there is no significant difference in the emission luminance characteristics 20B and 20C of the two, the breakdown voltage distributions 30B and 30C
It turns out that there is a big difference.

That is, in the present embodiment, the distribution of withstand voltage 30C is all self-recovering type 40 when the applied voltage is constant (260Vo-p) or less (shown by the white line portion 40), but the applied voltage is constant ( Above 320Vo-p), all are propagation type 50 (indicated by shaded area 50). Also in this embodiment, the destruction type can be set to only the self-recovery type by controlling the applied voltage as described above, so that the EL panel can be manufactured with an extremely high yield.

In this example, an example of using an alloy of Zn and Al as a back electrode constituent substance having a low boiling point is shown.
Cu, Pb, Zn or alloys containing them (especially alloys with Al),
Further, an alloy in which Cd, Cs, K, Rb, Se and Te are added in Al can also be used.

Next, FIG. 6 shows the second dielectric layer 15A as the back electrode.
Although it is an example in which the back electrode 16B is formed by sequentially stacking the Zn film 16a and the Al film 16b on top of it, it has been confirmed as a result of an experiment that the propagation type withstand voltage can be remarkably improved as in the above example. .

<< Effects >> As described above, in the thin film EL panel according to the present invention, a back electrode using Al or an Al-containing alloy as a constituent material is provided on the second dielectric layer to form a back electrode forming the second dielectric layer. The melting point of the dielectric film on the side and the boiling point of the constituent material of the back electrode are
Since the dielectric film on the back electrode side of the dielectric layer has a higher boiling point, even if the breakdown point is heated by Joule heat generated by local dielectric breakdown, the second dielectric layer Before the dielectric film on the back electrode side that composes is melted and the back electrode constituent materials are locally evaporated before forming a conductive path, the dielectric breakdown can be limited to self-recovery type dielectric breakdown. In particular, the yield of manufacturing a large-sized EL panel can be remarkably improved, and the manufacturing cost of the thin-film EL panel can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a thin film EL panel according to the present invention, FIG. 2 is an experimental graph showing emission luminance characteristics and distribution of withstand voltage of the panel in the same embodiment, and FIG. The same experimental graph in the example, FIG. 4 shows the second of the present invention.
FIG. 5 is an experimental graph showing the emission luminance characteristics and the distribution of the withstand voltage of the panel in the same embodiment, and FIG. 6 is the back electrode in the second embodiment with a Zn film and an Al film.
FIG. 7 is a cross-sectional view of the case where the film has two layers, and FIG. 11 …… Glass substrate 12 …… Transparent front electrode 13 …… First dielectric layer 14 …… Phosphor film 15 …… Second dielectric layer 16 …… Back electrode

Claims (1)

(57) [Claims] 1. A first dielectric layer formed by laminating a plurality of dielectric films on a glass substrate with a transparent entire surface electrode interposed therebetween, and a plurality of dielectrics having a phosphor film on the first dielectric layer. In a thin film EL panel comprising a second dielectric layer formed by stacking films and a back electrode using Al or an Al-containing alloy as a constituent material on the second dielectric layer, the second dielectric layer is With respect to the melting point of the dielectric film on the back electrode side and the boiling point of the substance forming the back electrode, the melting point of the dielectric film on the back electrode side of the second dielectric layer is set to be higher. Characteristic thin film EL panel.