JPH02226692A - Manufacture of thin-film el panel - Google Patents

Abstract

PURPOSE:To obtain a panel without unevenness in its luminous characteristic by depositing an insulating layer, a luminous layer, etc., with the potentials of plural electrodes kept at an equipotential level. CONSTITUTION:Transference electrodes 2 are formed on a glass substrate 1, and then an insulating layer, a luminous layer, etc., are deposited thereon by the use of a mask. At this time, an insulating ceramic mask 3a is used as the mask, or a metal foil 5 formed into the shape of irregularities is sandwiched between a ceramic or metal mask 3b and the electrodes 2, both of which are formed on the substrate 2. On this account, all of the transference electrodes 2 are insurated or short-circuited for keeping their potentials at an equipotential level. Accordingly, unevenness in the quality and thickness of part of insulating film, caused on each transference electrode is reduced so that a panel can be obtained without unevenness in its luminous characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of preventing the influence of a pattern of a transparent electrode formed on an underlying layer in a method of forming an insulating layer of a two-film EL by electron beam evaporation.

1. The direct thin-film EL panel has a variety of structures depending on the voltage application method, but it is an AC drive type with a double insulation structure that is currently in practical use, and each electrode is arranged in stripes in a direction perpendicular to each other. A so-called dot matrix type display panel will be described as an example. FIG. 7 shows its cross-sectional structure. First, a glass substrate! A transparent electrode 101 (
For example, ITO) first insulating layer 102a, light emitting 74103
(for example, ZnS:Mn), the second insulating layer 102b
, and a back electrode 104 (for example, M) are sequentially laminated. When an AC voltage is externally applied between the transparent electrode 101 and the back electrode 104, the light emitting layer 103 at the intersection of the picture electrodes emits light.

Next, the insulating layer will be described in detail. Various conditions are required for the insulating layer, and it is rarely formed from a single material (generally, a multilayer film is used.The material and manufacturing method, etc.
It is selected according to the requirements depending on which part of the element it is used for. A material with high insulation and high dielectric constant is selected for the main insulating layer, and a stable material is selected for the side in contact with the electrode, with low reactivity with the electrode, low diffusion, and moisture resistance. On the other hand, factors such as adhesion to the light-emitting layer and carrier injection effect into the light-emitting layer are important factors in selection. (Owaki et al. “High Definition A4 Size 1000X700 Don’t Thin Film EL Panel” Television Sciron Society Journal 42-101097-003
(1988)) Taking these points into consideration, the inventor of the present application has disclosed the structure shown below in another application, Japanese Patent Application No. 83-258038. Its structure is shown in FIG. Luminous layer I
An insulator layer 15a made of oxide is formed on both sides of 6 by electron beam evaporation.

t5b 1 Thousands of insulating layers 14a and 14b made of tantalum pentoxide are formed on the outside thereof, and an insulating layer made of oxide formed by sputtering to suppress charge injection from the electrode is further formed on the outside thereof. ! 3a and 13b are formed. However, although it has been confirmed that the thin-film EL panel with this configuration has excellent performance in terms of brightness, luminous efficiency, and dielectric strength characteristics, the dot matrix type thin MEL display panel with this configuration has It was found that variations in light emission characteristics occur between electrodes.

Furthermore, it was confirmed through experiments that the oxide layer formed by electron beam evaporation was strongly involved in this variation in luminescent characteristics.

Originally, the electron beam evaporation method is a method in which a thin film is formed by heating an evaporation material with an electron beam, evaporating or sublimating it, and physically depositing it on a substrate. However, it is considered that the evaporated particles are not all neutral particles but are ionized to some extent by the electron beam irradiation. When such particles are deposited on a transparent electrode or a thin film on a transparent electrode, the amount of charge-up will vary depending on whether the transparent electrode is grounded or not, and naturally the properties of the film will also differ. However, in order to connect the transparent electrode and the drive circuit, an insulating layer,
A part of the light-emitting layer, etc. must be partially masked during vapor deposition, and a metal mask is conventionally used for this method. Therefore, it is impossible to uniformly contact the metal mask and hold the substrate so that it is grounded through the metal mask and the substrate holder. This is the cause of variations in the quality and thickness of the insulating film that occur between individual transparent electrodes, and this phenomenon becomes more pronounced as the substrate becomes larger and the pattern of the transparent electrode becomes more precise. Become.

For this reason, variations in light emission characteristics mainly appear in the light emission threshold. That is, this variation in light emission characteristics not only significantly deteriorates display quality, but also requires a large modulation voltage when driving, leading to an increase in power consumption. Thin film EL with uniform light emission characteristics
This is an attempt to realize a panel.

In order to solve the above-mentioned problems, the present invention uses a mask made of an insulating material such as ceramic when forming an insulating layer by electron beam evaporation, or a mask made of metal foil with fine irregularities. Either all the multiple transparent electrodes drawn on the substrate are insulated by inserting them between the substrates, or
It is proposed that NM be performed in either short-circuited state.

According to the proposed method of the present invention, a plurality of transparent electrodes drawn on a substrate are either all insulated from other conductors or short-circuited to the same potential. If the substrate is held in this state and an insulating layer is deposited by electron beam evaporation, the charge-up fluorescence will be constant and the film quality will be uniform because all the transparent electrodes are kept at the same potential. Therefore, variations in light emitting characteristics between transparent electrodes are eliminated, and display quality does not deteriorate and electrode consumption does not increase.

The method for manufacturing the thin film EL device used in the present invention will be described in detail step by step with reference to FIG. 6 shown above. In the figure, 11 is a glass substrate, and about 2000 transparent electrodes made of ITO are formed on this glass substrate by electron beam evaporation! 2 is formed.

Thereon, a stable oxide such as 5102 or AeO+ is formed to a thickness of 100 to 500 nm by RF magnetron sputtering as an insulating layer 13a for charge injection suppression, and then Ta205 is formed as a first insulating layer 14a by the same method. 30
Formed to a thickness of 00 to 5000 people. Next, an insulating layer 15a made of an oxide for charge injection is formed by electron beam evaporation, and an oxide with a somewhat high dielectric constant that contains many floating electrons is suitable for this, such as Y2O.
Using materials such as 3 and Ta205, this also has 300 to 50
Form within the range of 0 people. This insulating layer for charge injection +5
1 and 2 show how to hold the substrate when forming a. FIG. 1 shows the positional relationship of the glass substrate 1, the transparent electrode 2, the mask 3, and the substrate holder 4 when viewed from above. As a method of holding the substrate at this time, as shown in Fig. 2, a ceramic mask 3a is used instead of the conventional metal mask.
Use. According to this method, all the transparent electrodes 2 are completely insulated from the holder 4, which is at ground potential, so that the state of the plurality of transparent electrodes 2 becomes uniform. As described above, while holding the substrate, the insulating layer 15a for charge injection is formed by electron beam evaporation. Next, about 5,000 layers of zinc sulfide (ZnS2Mn) containing manganese are formed as the light-emitting layer 16, but since electron beam evaporation or resistance wire heating evaporation is used, an insulating layer 15a for charge injection is formed. After that, it is possible to perform continuous formation without breaking the vacuum. Further, an oxide 15b for charge injection formed thereon is also continuously formed using the same material. After that, the second insulating layer 4b and the insulating layer 3b for suppressing charge injection are sequentially laminated using the same material and the same method as shown above. Finally, a metal such as M is formed as a back electrode 17 to a thickness of about 2000 by electron beam evaporation to form a thin film EL.

Further, 18 is a protective cover made of glass that protects the thin film EL, and the inside thereof is filled with an insulating protective fluid.

Example 11 Section 2 Another example of a method for holding a substrate when forming an insulating layer for charge injection by electron beam evaporation will be described with reference to FIG. The difference from Example 1 is that a metal foil 5 made of AR+ Cu or the like having an uneven shape is inserted between a mask 3b and a glass substrate 1 on which a transparent electrode 2 is formed. By doing so, the plurality of transparent electrodes 2 drawn on the glass substrate 1 are all electrically short-circuited and can be kept at the same potential. Further, the mask 3b in this case may be either the ceramic mask shown in Example 1 or a conventional metal mask. It is only a matter of whether all transparent electrodes are kept at ground potential or insulated from earth, and no potential difference occurs between the plurality of transparent electrodes.

Figure 4 a and b show the applied voltage vs. brightness of two pixels located close to each other in the thin film EL panel manufactured by the conventional metal mask method and the method shown in Example 1 of the present invention. Show characteristics. a
However, since the conventional metal mask method is used, there is a difference of about +5 V between the emission thresholds of two adjacent pixels due to the potential of the transparent electrode. However, with the ceramic mask method shown in Example 1, the difference in b is about IV, and the effect is clear.

For reference, photos of the light emission state of the thin film EL panel shown in Figures 4a and 4b near the emission threshold are shown in Figures 5a and 5a.
Shown in b. In conventional method a, there is uneven light emission corresponding to the electrodes, but in method b of the present invention, the light emission is similar to -.

As explained above, the thin film EL panel of the present invention has high brightness and
It has high efficiency and high dielectric strength, and does not degrade display quality or increase power consumption.

[Brief explanation of the drawing]

Figure 1 is a plan view of the substrate and holder during vapor deposition, and Figure 2 is a plan view of the substrate and holder during deposition.
FIG. 3 shows the substrate holding method in each case of Embodiment 1 and Embodiment 2 of the present invention, and FIG. 4 shows the conventional method and Embodiment 1 of the present invention.
The applied voltage-luminance characteristics of the thin film EL panel produced by the method described above, FIG. 5 is a photograph of the light emitting state of the panel shown in FIG. 4, and FIG. 6 is a cross-sectional view of the structure of the thin film EL panel used in the present invention. FIG. 7 is a sectional view showing a schematic structure of a thin film EL panel having a general double insulation structure. DESCRIPTION OF SYMBOLS 1... Glass substrate, 2... Transparent electrode, 3... Mask, 3a... Ceramic mask, 3b... Mask, 4... Mask holder 15a, +5b... Electron beam evaporation method Insulating layer formed. 9-B' temporary 7D rotation u=nance (arb, ur+ A Mori Shichien 5th i heart [history, procedural amendment (method) Name of invention Related to the case of a person who amends the manufacturing method of thin film EL panel Patent Applicant: 2-9-1 Seiran, Otsu City, Shiga Prefecture, 520 Kansai NEC Co., Ltd. Subject of amendment: Figure No. 1Q○ 6. Contents of the amendment (1) The detailed description of the invention column is corrected as follows. (1-1) Change “Figure 7” on page 2, line 17 to “Figure 6”
Correct. (1-2) “Figure 6” on page 3, line 20 is changed to “Figure 5”
Correct. (1-3) Correct "Figure 6" in line 6 of page 7 to "Figure 5." (G4) Delete "Also for reference...shown in Figure 5 a+b" in lines 9 to 12 of page 10. (2) Correct the brief description column of the drawing as follows. (2-1) Page 11, line 3 to line 4, “Furthermore,
The figure is a photograph of the light emitting state of the panel shown in Figure 4.'' is deleted. (2-2) "Figure 6" in the 4th line of page 11 is changed to "Figure 5"
Correct. (2-3) Change “Figure 7” in line 5 of page 11 to “Figure 6”
Correct. (3) Correct the drawing as follows. (3-1) Delete Figure 5. The figure number of “Figure 6” is corrected to “Figure 5”. The figure number in “Figure 7” has been corrected to “Figure 6.” Figure Figure

Claims (4)

[Claims] 1. In a thin film EL panel, at least one insulating layer and other layers are formed on a substrate on which a plurality of electrodes made of a transparent conductive film are formed, and at least one of the insulating layers is formed on the substrate surface by electron beam evaporation. 1. A method for manufacturing a thin film EL panel, characterized in that the deposition is carried out by keeping the plurality of electrodes at equal potential, in a manufacturing method in which vapor deposition is carried out partially using a mask placed in a mask. 2. Depending on the material or installation method of the mask, all of the plurality of electrodes are electrically insulated from other conductors,
The manufacturing method according to claim 1, characterized in that the potential states are equal. 3. 2. The manufacturing method according to claim 1, wherein all of the plurality of electrodes are electrically connected to have an equal potential. 4. 2. The manufacturing method according to claim 1, wherein the plurality of electrodes are formed in a connected state in advance, and after the insulating layer is vapor-deposited, the electrodes are separated at the undeposited portions using a mask.