JP2004259545A - Manufacturing method of inorganic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to manufacture an inorganic EL element having high brightness at low cost. <P>SOLUTION: A first adhesive layer 2a is formed on a transparent electrode 1b by a wet spray method, on which, luminous body powder 2b is formed by a dry spray method. A second adhesive layer 3a is formed on the luminous body powder 2b by the wet spray method, on which, nano-sized high-dielectric ultrafine particle powder 3b is sprayed by the dry spray method, and on the high-dielectric powder layer 2, a back electrode 4 is formed by the wet spray method. Thus, by manufacturing the inorganic EL element by the spray method without using a screen printing technology, the high-brightness inorganic EL element can be provided at low cost. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an inorganic EL device in which a light emitting layer and an insulating layer are interposed between a transparent electrode and a back electrode.
[0002]
[Prior art]
Dispersion type thick film electroluminescent elements (hereinafter referred to as “inorganic EL elements”) have the excellent feature of emitting thin and elegant light like paper, and therefore have been required to have a high decorative effect. Widely used in certain areas. For example, as described in Japanese Patent Publication No. 7-58636, “Electroluminescent Lamp”, this inorganic EL element includes a light emitting layer, an insulating layer, and a light emitting layer formed on a transparent electrode formed on a transparent film such as polyethylene terephthalate (PET). The light emitting layer, the insulating layer, and the rear electrode were manufactured by sequentially laminating a light emitting ink, an insulating ink, and a conductive ink in a film shape using a screen printing technique.
The characteristics of the luminescent powder and the high-dielectric powder contained in the luminescent layer and the insulating layer greatly affect the emission luminance of the inorganic EL element. As the luminescent powder, zinc sulfide (ZnS) is used. As a body powder, a combination using barium titanate (BaTiO ₃ ) is typically adopted as one of the best combinations.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 7-58636
[Problems to be solved by the invention]
However, the conventional inorganic EL element still has a problem that the emission luminance is still insufficient.
In order to increase the luminance of the EL element, it is of course important to improve the characteristics of the phosphor powder itself and the high dielectric powder itself, but it is also important to fill the phosphor powder and the high dielectric powder as densely as possible. is there. However, in conventional inorganic EL devices, the packing density of the luminescent powder and the high dielectric powder is not sufficiently high.
This is related to the following specific screen printing manufacturing process of the inorganic EL element. The above-described luminescent ink, insulating ink and conductive ink are obtained by dispersing a luminescent powder, a high dielectric powder or a conductive powder by stirring and mixing, respectively, in a resin binder dissolved in a solvent. It is required to adjust the viscosity to be suitable for screen printing.
[0005]
In other words, from the viewpoint of screen printing, it is preferred that the luminous ink and the insulating ink have a viscosity suitable for screen printing, so that these luminescent powders and high dielectric powders are used up to the originally required filling rate. Difficult to mix. In particular, with respect to the insulating layer, even if the dielectric constant of the high dielectric powder itself is sufficiently high, the filling factor is insufficient, so that the dielectric constant of the entire insulating layer is considerably reduced. In addition, because of screen printing, the light emitting layer and the insulating layer have to be unnecessarily thick. For this reason, the emission luminance of the inorganic EL element could not be sufficiently increased.
[0006]
The second problem is that the viscosity of each ink fluctuates not only with the filling rate but also with the particle size of each powder, the temperature and humidity of the printing atmosphere, so that the ratio of the solvent is finely adjusted or used for printing. A great deal of labor and management have been required to adjust the viscosity of the ink, such as maintaining the previous ink temperature constant.
[0007]
The third problem is that screen printing requires a large and expensive screen printing apparatus and requires skilled printing know-how. Furthermore, it was difficult to waste expensive ink and to establish a consistent production line. For this reason, it has been difficult to reduce the manufacturing cost of the EL element.
[0008]
Also, as a general theory, it is recognized that reducing the particle size of the luminescent powder or the high dielectric powder improves the emission luminance. However, if the particle size is too small, the resin binder is uniformly kneaded. It will be difficult.
On the other hand, an attempt to use high-dielectric ultra-fine particle powder for the purpose of increasing the brightness has been proposed in Japanese Patent Application Laid-Open No. 9-23076 "EL lamp" or the like. The high-dielectric ultra-fine particle powder is dispersed therein, and the fact that the ink is a dispersion type ink is the same as the known art, and does not solve the above first to third problems.
[0009]
[Patent Document 2]
JP-A-9-232076
Therefore, a first object of the present invention is to provide a method for manufacturing an inorganic EL element which can be manufactured at low cost without using a screen printing technique.
A second object of the present invention is to facilitate the adoption of nano-sized high-dielectric ultrafine particles and to achieve high brightness.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a first feature of the method for manufacturing an inorganic EL device according to the present invention resides in that a luminescent powder and a high dielectric powder are sprayed and formed by a dry spray method. That is, a first step of spraying a first adhesive layer on a transparent electrode supported by a base material by a wet spray method, and before the first adhesive layer is solidified, a phosphor powder is applied on the first adhesive layer. A second step of spraying by a dry spray method, a third step of spraying a second adhesive layer on the phosphor powder by a wet spray method, and a step of coating the second adhesive layer on the second adhesive layer before the second adhesive layer solidifies. A fourth step of spraying the high dielectric powder by a dry spray method and a fifth step of forming a back electrode on the high dielectric powder.
[0012]
According to the manufacturing method of the present invention, the following effects can be obtained.
First, it is not necessary to use the conventional dispersion type luminescent ink and insulating ink to form the luminescent layer and the insulating layer, and a sufficient filling ratio of the luminescent powder and the high dielectric powder is secured. Thus, the luminescent powder and the high dielectric powder can be filled and formed at a high density with almost no gap between the powder particles. In addition, the thickness of the light emitting layer and the insulating layer can be reduced as much as possible, and the electric field applied to the light emitting layer increases. Therefore, the light emission luminance of the EL element can be greatly improved.
[0013]
Second, since the dispersion type ink is not used as in the related art, a great deal of labor and management for appropriately adjusting the viscosity of each ink is not required, and the quality can be easily secured.
[0014]
Third, since a large-sized, expensive, and screen printing apparatus requiring skilled printing know-how is not required, the manufacturing cost of the EL element can be significantly reduced.
[0015]
Fourth, since both expensive luminescent powder and high dielectric powder are dry-sprayed, it is possible to collect and reuse the extra powder that has not adhered to the adhesive layer, which also reduces the manufacturing cost. Contribute to reduction.
[0016]
A second feature of the method for manufacturing an inorganic EL device according to the present invention is that the first to fourth steps are arranged in one line.
With this configuration, it is easy to form a consistent manufacturing line, and it is possible to efficiently mass-produce EL elements having uniform quality.
[0017]
A third feature of the method for manufacturing an inorganic EL device according to the present invention is that, between the spray means used in the first to fourth steps and the object to be sprayed, a predetermined area of the object to be sprayed is provided. It is to arrange each mask for spraying.
This makes it possible to form a pattern in which a light emitting powder layer, a high dielectric powder layer, and the like are formed in a necessary region in accordance with a required graphic pattern such as a symbol or figure.
[0018]
A fourth feature of the method for manufacturing an inorganic EL device according to the present invention resides in that nano-sized high dielectric ultrafine powder is used. Barium titanate (BaTiO ₃ ) powder is suitable for the high-dielectric ultrafine particle powder, and the size thereof is desirably 50 to 90 nm. With such a configuration, the dielectric constant of the insulating layer is improved, and the light emission luminance is improved.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the method for producing an inorganic EL device according to the present invention will be described.
FIG. 1 shows a completed state of an inorganic EL device manufactured by the method of the present invention. This inorganic EL element has a light-emitting layer 2, a high dielectric layer 3, and a back electrode layer 4 sequentially formed on a transparent electrode 1b of a so-called ITO film 1, and has a known thick-film inorganic EL element. Is substantially the same as The ITO film 1 has a known structure in which a transparent electrode 1b is formed on a transparent substrate (transparent film) 1a by a method such as vapor deposition. As the transparent substrate 1a, polyethylene terephthalate (PET) or the like is used. For example, indium-tin oxide (ITO) or the like is typically employed. As an example, the thickness of the transparent substrate 1a is about 75 μm, and the thickness of the transparent electrode 1b is about 30 to 50 nm.
[0020]
Next, each manufacturing process of the inorganic EL device will be described with reference to FIGS.
FIG. 2A shows a first step. First, a first adhesive layer 2a is formed on the transparent electrode 1a by a wet spray method. As the first adhesive layer 2a, a fluorine-based resin is used to ensure moisture resistance. As an example, a material obtained by dissolving a copolymer of viridinene fluoride and propylene hexafluoride in a solvent methyl ethyl ketone is used. The mixing ratio is, for example, a ratio of 10:25 by weight, and the film thickness is determined in consideration of the size of the phosphor powder 2b described later. To about. To form the first adhesive layer 2a by the wet spray method, a spray gun 51 is used as a spray means as shown in FIG.
[0021]
FIG. 2B shows a second step, in which the luminous body powder 2b is sprayed onto the first adhesive layer 2a by a dry spray method to form a layer before the first adhesive layer 2a is solidified. The luminous body powder 2b is made of a powder of zinc sulfide (ZnS) having a thickness of 10 to 20 μm doped with copper (Cu), and the surface of each powder is coated with alumina to ensure moisture resistance. As shown in FIG. 3B, a spray gun 52 is used as a spraying means for forming a layer of the phosphor powder 2b by a dry spray method.
In this embodiment, the light emitting layer 2 is constituted by the first adhesive layer 2a and the light emitting body powder 2b. In this embodiment, the phosphor powder 2b is formed in a single layer. However, it is also possible to form the first adhesive layer 2a and spray the phosphor powder 2b a plurality of times to form a multilayer.
[0022]
FIG. 2C shows a third step, in which a second adhesive layer 3a is formed on the phosphor powder 2 by a wet spray method. As the second adhesive layer 3a, a fluorine-based resin is used to ensure moisture resistance. Specifically, the same material as that of the first adhesive layer 2a is used, and the film thickness is determined in consideration of the size of the high dielectric powder 3b described later. When the nano-sized ultrafine powder is used for the high dielectric powder 3b as described later, the thickness of the second adhesive layer 3a needs to be 100 to 200 times (10 to 20 μm) the particle diameter of the high dielectric powder. is there. In forming the second adhesive layer 3a by the wet spray method, a spray gun 53 is used as a spray means as shown in FIG.
[0023]
FIG. 2 (D) shows a fourth step, in which before the second adhesive layer 3a is solidified, high dielectric powder 3b is sprayed onto the second adhesive layer 3a by a dry spray method to form a layer. As shown in FIG. 3 (D), a spray gun 54 is used as a spraying means for forming a layer of the high dielectric powder 3b. In this embodiment, the high dielectric powder 3b generally has a thickness of 2 to 3 μm. In this embodiment, a high dielectric ultrafine particle powder of BaTiO ₃ having a particle size of 50 to 90 nm is used. ing. Nano-sized high-dielectric ultra-fine particle powder is charged with a high-dielectric substance in a high-temperature plasma atmosphere of 10,000 degrees or more obtained by applying a high-frequency electromagnetic wave to a gas by, for example, an RF plasma method, and is instantaneously heated and vaporized. This vaporized substance rapidly cools and solidifies after leaving the high temperature field, and a spherical nano-sized powder having a uniform particle size is obtained.
In this embodiment, the insulating layer 3 is constituted by the second adhesive layer 3a and the high dielectric powder 3b. The high dielectric powder 3b is not limited to a single layer as in the case of the luminescent powder 2b described above, but may be formed by performing the formation of the second adhesive layer 3a and the layer formation of the high dielectric powder 3b a plurality of times. May be formed in multiple layers.
[0024]
As a final fifth step, carbon ink as a conductive paint is sprayed on the high dielectric powder 3b in FIG. 2D through a spray gun 55 as a spray means shown in FIG. Is formed. Thereby, an inorganic EL device by the spray method according to the method of the present invention is completed. In addition, this carbon ink is formed by mixing carbon powder, which is a conductive powder, with polyester resin, which is a binder, but it is also possible to use silver powder or copper powder instead of carbon powder. It may be a mixture of silver powder or copper powder.
As shown in FIG. 3, the production line for the method of the present invention can be constructed in a line by a transport line (not shown) for transporting the object to be sprayed and a plurality of spray guns 51 to 55. The spray guns 51 to 55 are arranged at predetermined intervals, and the spray target sequentially moves in front of these spray guns, and when the spray object comes to a position facing each spray means, the spray guns are sequentially turned on. Activate. The spray guns 51 to 55 may be mounted on a robot arm (not shown) to perform the spray operation while moving the spray guns 51 to 55 vertically and horizontally in each of the steps (A) to (E).
[0026]
FIG. 4 shows an embodiment of another spray in each of the steps described above. That is, between each of the spray guns 51 to 55 and the target, masks 61 to 65 for spraying a predetermined region of the target at a position close to the target are arranged. The masks 61 to 65 are for patterning the light emitting layer 2, the insulating layer 3, and the back electrode 4 according to a required graphic display.
Not all of the luminescent powder 2b and the high dielectric powder 3b ejected from the spray guns 52 and 54 adhere, and the surplus that does not adhere mainly deposits below and is collected. -Provided for reuse. Therefore, the waste of the expensive phosphor powder 2b and the high dielectric powder 3b can be reduced, and the use of the masks 61 to 65 contributes to the recovery and reuse of the expensive phosphor powder 2b and the high dielectric powder 3b. I do.
[0028]
As for the luminescent powder 2b, nano-sized luminescent ultrafine particles can be used as in the case of the high dielectric powder 3b. The back electrode 4 can also be formed by a combination of a wet spray method and a dry spray method.
[0029]
【The invention's effect】
First, since the luminescent powder and the high dielectric powder are directly sprayed by the dry spray method, there is no need to limit the filling rate for adjusting the viscosity of the ink, and there is almost no gap between the powder particles. Luminous substance powder and high dielectric substance powder can be filled and formed at a high density. In addition, since the light emitting layer and the insulating layer can be formed thinner than those formed by screen printing, the applied electric field to the light emitting layer may be increased, so that the light emission luminance of the EL element can be significantly improved. Second, a great deal of labor and management for proper viscosity adjustment of each ink as in the related art is unnecessary, and quality assurance is facilitated. Third, since a large-sized, expensive, and screen printing apparatus requiring skillful printing know-how is not required, the manufacturing cost of the EL element can be significantly reduced.
[0030]
Fourth, since both the expensive phosphor powder and the high-dielectric powder are dry-sprayed, they can be easily collected and reused. Therefore, these effects make it possible to significantly reduce the manufacturing cost.
[0031]
By making the high dielectric powder at least nano-sized, the high dielectric powder can be filled at a higher density, and the emission luminance can be increased.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view of an inorganic EL device manufactured by the method of the present invention.
FIG. 2 is an enlarged sectional view showing each manufacturing step of the method of the present invention.
FIG. 3 is an explanatory diagram illustrating an example of a production line.
FIG. 4 is an explanatory diagram showing another example of the production line.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 ITO film 1a Transparent substrate 1b Transparent electrode 2 Light emitting layer 2a First adhesive layer 2b Light emitter powder 3 Insulating layer 3a Second adhesive layer 3b High dielectric powder (high dielectric ultrafine powder)
4 Back electrodes 51, 53, 55 Wet spray means 52, 54, Dry spray means 61-65 Mask

Claims (6)

A first step of spraying a first adhesive layer on the transparent electrode supported by the base material by a wet spray method;
A second step of spraying the phosphor powder on the first adhesive layer by a dry spray method before the first adhesive layer is solidified;
A third step of spraying a second adhesive layer on the phosphor powder by a wet spray method;
A fourth step of spraying a high dielectric powder on the second adhesive layer by a dry spray method before the second adhesive layer is solidified;
A fifth step of forming a back electrode on the high dielectric powder. 2. The method according to claim 1, wherein the first to fourth steps are arranged in one line. 3. A mask according to claim 1, wherein a mask for spraying a predetermined area of the object to be sprayed is provided between the spray means used in the first step to the fourth step and the object to be sprayed. A method for manufacturing an inorganic EL device, comprising: 4. The method for manufacturing an inorganic EL device according to claim 1, wherein a nano-sized high-dielectric ultra-fine particle powder is used as the high-dielectric powder. In claim 4, the manufacturing method of an inorganic EL element the high dielectric ultrafine powder which is a powder of barium titanate (BaTiO _3). 6. The method for manufacturing an inorganic EL device according to claim 4, wherein the size of the high-dielectric ultrafine particle powder is 50 to 90 nm.

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