JPH077710B2 - Method of manufacturing thin film EL device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] This is an improvement in the method of manufacturing a thin film EL element, and is an improvement in improving the luminous efficiency and luminance characteristics of the thin film EL element.

Emission of a thin film EL device using zinc sulfide as a base material and a halide of a rare earth element as a luminescent center by controlling the composition ratio of a rare earth element and a halogen element added as a luminescent center in zinc sulfide forming a base material. Utilizing the newly discovered property that the efficiency and brightness can be controlled, the composition ratio of the rare earth element and the halogen element is increased relative to the stoichiometric composition ratio, and the composition ratio of the rare earth element is increased to improve the luminous efficiency. A method of manufacturing a thin film EL device having improved luminance characteristics, which is a sputtering method using zinc sulfide, a rare earth element sulfide such as terbium sulfide, and a zinc halide such as zinc fluoride as independent sources. Alternatively, it is a method of manufacturing a thin film EL device, which is characterized in that an EL film is formed by using a vacuum deposition method.

[Industrial application field]

TECHNICAL FIELD The present invention relates to an improvement in a method for manufacturing a thin film EL element, which makes it possible to improve the luminous efficiency and luminance characteristics of the thin film EL element. In particular, the present invention relates to an improvement in a method for manufacturing a thin film EL element in which the composition ratio of a rare earth element and a halogen element is increased to increase the composition ratio of a rare earth element in comparison with a stoichiometric composition ratio.

[Conventional technology]

A thin film EL element is a rare earth element such as terbium, samarium, thulium, praseodymium, etc., which functions as a luminescence center, and a halogen element such as fluorine or chlorine. It is a light-emitting element that emits light based on the luminescence phenomenon, and conventionally known are a DC drive type as shown in FIG. 2 and an AC drive type as shown in FIG.

See Fig. 2. In the DC drive type thin film EL device, a transparent electrode 2 made of ITO or the like and having a thickness of about 2,000 Å is formed on a glass substrate 1 and the rare earth element that functions as an emission center is formed on the transparent electrode 2. An EL film 4 made of zinc sulfide or the like containing an element such as terbium and a halogen element such as fluorine is formed, and a counter electrode 6 made of aluminum or the like is further formed thereon.

See FIG. 3. In the AC drive type thin film EL device, in addition to the layer structure shown in FIG. 2, the EL film 4 is sandwiched between silicon oxynitride, aluminum oxide, yttrium oxide, etc. A first insulating film 3 and a second insulating film 5 having a thickness of about 2,000 Å are formed.

By the way, of the rare earth elements that function as emission centers,
Terbium emits green light, samarium emits red light, thulium emits blue light, and praseodium emits white light, but their luminous efficiency and brightness are not satisfactory except for terbium. Even in the best terbium, the luminous efficiency is 0.1-0.2 lumen.
It is / W, and the brightness is 30 foot transvers, so it is hard to say that each is sufficiently satisfactory, and the reproducibility is poor.

As a means for solving this problem, the inventor of the present invention has
There is a correlation between the composition ratio of the rare earth element contained in the film and the halogen element and the luminous efficiency / luminance characteristics, and the best luminous efficiency is obtained when the number of atoms of the rare earth element and the number of atoms of the halogen element are the same.・ It is effective to realize brightness and it is effective to increase the composition ratio of the rare earth element and the halogen element contained in the EL film to at least the stoichiometric composition ratio. By discovering this, we completed the invention of a method for manufacturing a thin film EL device with excellent luminous efficiency and brightness characteristics.

[Problems to be solved by the invention]

As one of the methods for manufacturing the thin film EL element according to the invention described above, a sputtering method using a composite target having zinc, sulfur, a rare earth element and a halogen element in a desired mixing ratio can be used. For example, a sputtering method using a composite target containing zinc sulfide, terbium, and zinc difluoride in a 100: 3: 1 weight ratio can be used.

Even with this manufacturing method, it is possible to manufacture a thin film EL element having the same composition ratio of a rare earth element and a halogen element and excellent light emission efficiency and brightness characteristics, but the composite target (zinc, sulfur, rare earth element and It is complicated and not easy to produce a composite target having a halogen element in a desired mixing ratio, and the sputter rate of zinc sulfide, the sputter rate of a rare earth element, and the sputter rate of a halogen element are significantly increased. Because of the difference, the composition ratio of zinc sulfide, rare earth element, and halogen element contained in the EL film becomes non-uniform in the thickness direction, and if necessary, it is easy to manufacture an EL film of sufficient thickness with good reproducibility. In addition, there is a drawback that the luminous efficiency and the brightness may not be improved as expected.

The present invention eliminates these drawbacks, and its purpose is to eliminate the need to use a special source, to provide excellent luminous efficiency and luminance characteristics, and to have sufficient thickness (driving voltage) with good reproducibility. Thin film that can produce EL film of sufficient thickness to make the brightness extremely large)
It is to provide a manufacturing method of an EL element.

[Means for solving problems]

The means adopted by the present invention to achieve the above-mentioned object is deposition using three kinds of substances, zinc sulfide, rare earth element sulfide, and zinc halide, as three independent sources. Method to independently control the deposition rates of these three sources to form the EL film. As the deposition method, a vacuum vapor deposition method or a sputtering method is suitable. In other words, the three most readily available materials, zinc sulfide, rare earth element sulfides such as diterbium trisulfide, and zinc halides such as zinc difluoride, were separated into three independent substances. Used as a source, control the power applied to each source independently to control the deposition rate of each source, and if necessary, shield flying objects such as slits between each source and the substrate to be deposited. A means is provided to enable fine control of the deposition rate so that the constituent materials of each source are deposited in a desired amount so that the number of atoms of the rare earth element and the number of atoms of the halogen element contained in the EL film are the same. It is a thing.

The present invention is also applicable to a DC drive type thin film EL element in which the EL film 4 is not sandwiched between the upper and lower insulating films 3 and 5, and the AC drive in which the EL film 4 is sandwiched between the upper and lower insulating films 3 and 5. Type thin film EL device can be realized.

[Action]

The basic idea of the present invention is an EL device in which zinc sulfide is used as a base material and a rare earth element and a halogen element are added as emission centers.
The composition ratio of the rare earth element and the halogen element contained in the film is 1:
There is to be 1.

In order to control the composition ratio of the rare earth element and the halogen element to 1: 1, it is clear that it is effective to be able to control each independently. Moreover, since the sulfur content is apt to be too small, a compound of a rare earth element sulfide, a halogen element and zinc, and zinc sulfide are used as three independent sources and their respective deposition rates ( Applied voltage)
Is to be controlled independently. Further, a rare earth element sulfide has a large sulfur content, such as diterbium trisulfide, while a compound of a halogen element and zinc has a low zinc content, such as zinc difluoride. It is also possible to prevent the above-mentioned drawbacks, and these functions comprehensively, and the composition ratio of the rare earth element and the halogen element is 1: 1 and an EL film of good film quality can be manufactured.

The luminance of the thin film EL element manufactured by using the method for manufacturing a thin film EL element according to the present invention (luminance for a voltage exceeding the light emission threshold voltage by 30 V when driven at 1 KHz) is shown in FIGS. 4 and 5. As shown, it is about 20 times higher than the conventional technology.
It is 0 foot lambert.

〔Example〕

Hereinafter, with reference to the drawings, a method for manufacturing a thin film EL device according to two embodiments of the present invention will be further described.

Example 1 AC-driven thin-film EL that forms an EL film by using a vacuum deposition method using three independent sources of three kinds of substances, zinc sulfide, diterbium trisulfide, and zinc difluoride. A method of manufacturing the device will be described.

See Fig. 1a. Sputtering method is used to deposit a thickness of approximately 2,000 on the glass substrate 1.
A transparent electrode 2 made of Å ITO film and a first insulating film 3 made of aluminum oxide and having a thickness of about 2,000 Å are formed.

Subsequently, a film having a thickness of about 6,000Å is vacuum-deposited using the above source. At this time, the power applied to each source is controlled to control the respective deposition rates so that the number of terbium atoms and the number of fluorine atoms introduced into the EL film are the same. That is, for example, the deposition rate of zinc sulfide is 300Å / min, the deposition rate of diterbium disulfide is 5Å / min, and the deposition rate of zinc difluoride is 3Å / min.
Minutes. A suitable substrate temperature is about 230 ° C. afterwards,
The EL film 4 is formed by heat treatment at about 450 ° C. for about 1 hour.

Next, the second insulating film 5 made of yttrium oxide and having a thickness of about 2,000Å is formed by using the electron beam evaporation method, and further, the counter electrode made of aluminum is formed by using the evaporation method or the sputtering method. (Back electrode) 6 is formed.

The number of atoms of terbium and the number of atoms of fluorine contained in the EL film 4 of the thin film EL element manufactured through the above steps are approximately the same. The brightness (brightness with respect to the voltage exceeding the light emission threshold voltage of 30 V when driven at 1 KHz) is shown in FIG. 4 (the brightness-voltage relationship of the AC drive type thin film EL element manufactured by carrying out the present embodiment is the same as that of the conventional technology). This is significantly improved as shown in the graph (comparing the brightness vs. voltage relationship) in comparison with the related art. In the figure, A indicates the value of this embodiment, and B indicates the value of the prior art. As is clear from the figure, the luminous efficiency and the luminance (luminance for a voltage exceeding the light emission threshold voltage of 30 V when driven at 1 KHz) are improved to 1 lumen / W and 200 foot transversal, respectively.

Second example AC drive type thin film EL element for forming EL film by using sputtering method with three independent targets of three kinds of substances of zinc sulfide, diterbium trisulfide and zinc difluoride The case of manufacturing is described.

See Fig. 1b As in the case of the first example, a transparent electrode 2 made of an ITO film having a thickness of about 2,000Å is formed on the glass substrate 1 by using the sputtering method.
And a first insulating film 3 made of aluminum oxide and having a thickness of about 2,000 Å is formed.

Next, using the above target, the thickness is about 6,000Å
Is formed by sputtering. At this time, the power applied to each target is controlled to control the respective deposition rates so that the number of terbium atoms and the number of fluorine atoms introduced into the EL film are the same. That is, for example, the deposition rate of zinc sulfide is 400 Å / min, the deposition rate of diterbium trisulfide is 6 Å / min, and the deposition rate of zinc difluoride is 4 Å / min. A suitable substrate temperature is about 300 ° C. After that, heat treatment is performed at about 450 ° C for about 1 hour E
The L film 4 is formed.

Next, as in the case of the first example, the second insulating film 5 made of yttrium oxide and having a thickness of about 2,000Å is formed by using the electron beam evaporation method, and further, the evaporation method or the sputtering method is used. Is used to form a counter electrode (back electrode) 6 made of aluminum.

The number of atoms of terbium and the number of fluorine atoms contained in the EL film 4 of the thin film EL device manufactured through the above steps are almost the same. The luminance (luminance for a voltage exceeding the light emission threshold voltage of 30 V when driven at 1 KHz) is shown in FIG. 5 (the luminance-voltage relationship of the AC drive type thin film EL element manufactured by carrying out the present embodiment is the same as that of the conventional technique). This is significantly improved as shown in the graph (comparing the brightness vs. voltage relationship) in comparison with the related art. In the figure, A indicates the value of this embodiment, and B indicates the value of the prior art. As can be seen from the figure, the luminous efficiency and the luminance (luminance for a voltage exceeding 30V of the light emission threshold voltage driven at 1KHz) are improved to 1.0 lumen / W and 200 foot transversal, respectively.

〔The invention's effect〕

As described above, in the method for manufacturing a thin film EL element according to the present invention, three kinds of substances, zinc sulfide, rare earth element sulfide, and zinc halide, are used as three independent sources. Since the EL film is formed by using the eggplant deposition method and independently controlling the deposition rates of these three sources, the number of atoms of rare earth elements contained in the EL film and the halogen element It is almost the same as the number of atoms,
It is possible to manufacture a thin film EL device with excellent luminous efficiency and brightness characteristics. The method for manufacturing a thin film EL device according to the present invention can control the light emission efficiency and the brightness characteristics of the EL film to desired values to some extent, which is effective for realizing a color image. Also, without the need for special sources,
An EL film having a sufficient thickness can be manufactured.

[Brief description of drawings]

FIG. 1a is a structural diagram of an AC drive type thin film EL element manufactured by using the method for manufacturing a thin film EL element according to the first embodiment of the present invention. FIG. 1b is a structural diagram of an AC drive type thin film EL element manufactured by using the method of manufacturing a thin film EL element according to the second embodiment of the present invention. FIG. 2 is a structural diagram of a DC drive type thin film EL element according to the prior art. FIG. 3 is a structural diagram of an AC drive type thin film EL element according to the prior art. FIG. 4 shows the luminance (1K
The luminance (voltage for a voltage exceeding the light emission threshold voltage of 30 V) when driven at Hz is compared with the voltage relationship of the prior art (the luminance for a voltage exceeding the light emission threshold voltage of 30 V when driven at 1 KHz) for the voltage. Is a graph represented by. FIG. 5 shows the brightness of an AC-driven thin film EL device manufactured by the method for manufacturing a thin film EL device according to another embodiment of the present invention (for a voltage exceeding the light emission threshold voltage of 30 V when driven at 1 KHz). 6 is a graph showing a relationship between luminance) and voltage with respect to the luminance of the related art (luminance for a voltage exceeding a light emission threshold voltage by 30 V when driven at 1 KHz) versus voltage. 1 ... Translucent substrate (glass substrate), 2 ... Translucent electrode (ITO electrode), 3 ... First insulating film (silicon oxynitride, aluminum oxide, yttrium oxide), 4 ... EL film (Composition of zinc sulfide, rare earth element and halogen element), 5 ... Second insulating film (silicon oxynitride, aluminum oxide, yttrium oxide), 6 ... Counter electrode (back electrode).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seito Sato 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (56) References JP 62-140394 (JP, A) JP 61- 253797 (JP, A) JP 61-34890 (JP, A) JP 59-141192 (JP, A)

Claims (5)

[Claims] 1. A transparent electrode (2) is formed on a transparent substrate (1), an EL film (4) is formed on the transparent electrode (2), and the EL film (4) is formed. ) In the method for manufacturing a thin film EL element, which has a counter electrode (6) formed thereon, the EL film (4) uses zinc sulfide, a rare earth element sulfide, and a zinc halide as independent sources. A method for manufacturing a thin film EL element, which is characterized by forming using a deposition method. 2. The method according to claim 1, further comprising the step of forming a first insulating film (3) and a second insulating film (5) with the EL film (4) interposed therebetween. A method for producing the thin film EL element described in the above. 3. The thin film according to claim 1, wherein the sulfide of the rare earth element is diterbium trisulfide and the halide of zinc is zinc difluoride. EL element manufacturing method. 4. The method according to claim 1, wherein the deposition method is a sputtering method.
A method of manufacturing a thin film EL element according to the item. 5. The method of manufacturing a thin film EL element according to claim 1, 2, or 3, wherein the deposition method is a vacuum vapor deposition method.