JPH05290977A - Element and manufacturing thereof - Google Patents

Abstract

PURPOSE:To provide an EL element having excellent electric characteristic and little luminescent unevenness, and a manufacturing method of the EL element. CONSTITUTION:For an EL element, an aluminium foil 1 is formed, on the surface of which an electric insulating layer including a duplex type positive electrode oxide film 7, an EL luminescent layer formed directly on the insulating layer, and a transparent electrode formed on the EL luminescent layer, are formed. For the film 7, the depth of pores 2a is thinned while a barrier layer 6 is thickened by growing the barrier layer 6 on the surface side primarily after oxidating acid positive electrode, and the thickness of the barrier layer of the film is determined 0.1-0.5mum, while the diameter of the pores is no less than 0.05mum, and the depth of the pores is 0.1-0.5mum, for this element Manufacturing method of the EL element includes a process of forming a first duplex type positive electrode oxide film on the surface of the aluminium foil, a process of forming a second duplex type positive electrode film of thin pores 2a and of thick barrier layer 6, and a process of forming the EL luminescent layer and a transparent electrode layer directly on the oxide film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an EL (electroluminescence) element, and more particularly to an EL element suitable for use as a backlight of a liquid crystal display (LCD) and a method for manufacturing the EL element.

[0002]

2. Description of the Related Art In recent years, electronic devices have been strongly required to be lightweight, thin, low voltage and low power consumption (battery drive), and LCDs (liquid crystal display devices) are increasingly used as display devices. By the way, since the LCD itself does not generate light, a backlight such as an EL element (lamp) has been adopted in order to improve visibility.

Such a light source is thin and lightweight,
There is a strong demand for low prices. The EL element is a surface emitting light source that can be made thinner than, for example, a fluorescent lamp or an incandescent lamp and has low power consumption.

FIG. 5 schematically shows an example of a conventional EL device. Back electrode 21 made of aluminum foil
A resin insulation layer 22 is formed on the above. The resin insulating layer 22 is made of a high dielectric constant organic resin (hereinafter referred to as a binder).
Can be formed by dissolving barium titanate powder in a solvent to form an ink, applying it on the back electrode 21 by a method such as printing, and drying.

The EL light emitting layer 2 is formed on the resin insulating layer 22.
3 and the transparent electrode 24 are formed. EL light emitting layer 2
3 can be formed by dispersing the phosphor powder in the same binder as described above, applying it as an ink, applying it, and then drying.

The transparent electrode 24 is obtained by dispersing ITO (indium tin oxide) powder in the same binder, coating it in the form of ink, and drying. The lead wire 25 is led out from the back electrode 21 and the transparent electrode 24, and the main body portion is packaged with a film having high moisture resistance to form an EL element.

Barium titanate has a large dielectric constant. Therefore, even if a barium titanate layer is formed between the electrodes, the voltage dropped by the barium titanate layer is small. Therefore, a sufficient voltage can be applied to the EL light emitting layer, and high brightness can be easily obtained.

However, in order to form the barium titanate layer on the surface of the aluminum layer, it is necessary to perform a coating process and the like, and there is a limit to the reduction of the thickness of the resin insulating layer. Further, so-called “repellency” occurs due to uneven coating occurring in the coating process, and uneven light emission occurs.

Further, a technique has been proposed in which the surface of an aluminum foil is covered with an alumite film and the barium titanate layer is replaced with the alumite film. JP-A-64-
Japanese Laid-Open Patent Publication No. 10597 discloses an electroluminescence (EL) lamp in which an aluminum foil, which is anodized on an aluminum foil and anodized on one side to form an electrically insulating layer, is used as a back electrode.

Japanese Unexamined Patent Publication (Kokai) No. 1-209693 discloses an aluminum laminate for a dispersion type electroluminescence panel in which an alumite layer and a white coat layer are formed on the surface of an aluminum foil.

Japanese Unexamined Patent Publication No. 1-225097 discloses a dispersion type EL device in which the surface of an aluminum foil is anodized to form a porous oxide film. In these techniques, an aluminum foil, which is a back electrode, is anodized to form an alumite coating on the surface, and the alumite coating is used as an electrical insulating layer.

The alumite film on the surface of the aluminum foil is
An EL element that can be manufactured at a lower cost than an electrically insulating layer of barium titanate and has the same luminous efficiency and brightness can be obtained. Further, the aluminum foil provided with the alumite coating has excellent adhesion.

[0013]

However, the alumite processing, which has been used for a long time for the surface treatment of aluminum sashes, aluminum wheels, etc., is also described in "Aluminum Handbook", Light Metal Society, Showa 38, pp. 820-821. As described above, it is a method of anodizing in an acidic aqueous solution such as sulfuric acid to form a porous film (duplex type anodic oxide film) of 6 μm to several hundred μm. The duplex type anodized film has a porous layer on the surface side and a barrier layer on the inner side, but the thickness of the barrier layer is thin.

Therefore, the alumite layer has a low withstand voltage, and the leakage current increases as the electric field strength increases. Therefore, there is a problem in practical use unless the withstand voltage of the EL element is low and the luminous efficiency cannot be increased.

Further, the present inventors have used an anodized film (hereinafter simply referred to as a barrier type film) formed by anodization in a neutral electrolytic solution as an electrically insulating layer, whereby a resin or anodized film is used. It has been found that an EL element having improved electrical characteristics can be manufactured as compared with a conventional EL element having an electrically insulating layer formed, and a patent application has already been filed for this EL element and its manufacturing method (Japanese Patent Application No. Hei 10 (1999) -135242). 2-416782). Although this EL element has excellent electrical characteristics, it is still desired to improve its performance and uneven light emission.

An object of the present invention is to provide an EL element having excellent electric characteristics and less unevenness in light emission. Another object of the present invention is to provide a method for manufacturing an EL element, which can obtain an EL element having excellent electric characteristics and less unevenness in light emission.

[0017]

The present invention proposes an EL device having the following points. That is, an aluminum foil, an electrical insulating layer including a duplex type anodic oxide film formed on the surface of the aluminum foil, an EL light emitting layer directly formed on the electrical insulating layer, and an EL light emitting layer on the EL light emitting layer. An EL device having a transparent electrode formed on the substrate, wherein the duplex type anodic oxide film is a film having a shallow pore depth and a thick barrier layer by mainly growing a barrier layer on the surface side after acidic anodic oxidation. The thickness of the barrier layer of this film is 0.1 to 0.5 μm, the pore diameter is 0.05 μm or more, and the pore depth is 0.1 to 0.5 μm.
An EL device is provided.

As a manufacturing method for providing such an EL device, an aluminum foil is anodized in an acidic electrolytic solution to form a duplex type anodic oxide film (hereinafter referred to as a first anodized film on the surface of the aluminum foil. A step of forming a duplex type anodized film), and the aluminum foil on which the first duplex type anodized film is formed is further anodized in a neutral electrolytic solution to mainly form the first duplex type oxidized film. A barrier layer constituting the film is grown on the surface side, and the duplex depth type anodic oxide film having a shallow pore depth and a thick barrier layer (hereinafter referred to as the second
Of the second duplex type anodic oxide coating), and E directly on the second duplex type anodic oxide coating.
Provided is a method for manufacturing an EL device, which comprises the step of forming an L light emitting layer and a transparent electrode layer.

[0019]

The second duplex type anodic oxide film formed by the method of the present invention is obtained by growing the barrier layer of the first duplex type anodic oxide film formed by acidic anodic oxidation mainly on the surface side. Therefore, the thickness of the barrier layer forming the second duplex type anodic oxide coating is large, and the barrier layer is a dense layer. Therefore, the second duplex type anodic oxide film is
It can be an electrically insulating layer having excellent electrically insulating properties.

The pore depth of the porous layer forming the second duplex type anodic oxide film is shallower than the pore depth of the first duplex type anodic oxide film, but is smaller than that of the second duplex type anodic oxide film. Still has pores. Therefore, the surface layer of the second duplex type anodic oxide film is rich in undulations as compared with the anodic oxide film formed only by the barrier type film (without pores). For this reason, the wettability of the binder and the like during the formation of the EL light emitting layer is improved, and the cissing can be prevented. By preventing repelling at the time of forming the EL light emitting layer, it is possible to reduce light emission unevenness of the EL element.

As described above, according to the method of the present invention, it is possible to form an electrically insulating layer having excellent electrically insulating characteristics and to reduce unevenness in light emission of the obtained EL element. It is possible to manufacture an EL element which has at least one of the electrical characteristics improved, and which has less unevenness in light emission.

In short, in the method of manufacturing an EL element of the present invention, a duplex type anodic oxide film (acidic anodizing treatment)
It is possible to manufacture an EL device having the advantages of both the barrier type anodized film (neutral anodizing treatment).

In particular, when the porous layer forming the second duplex type anodic oxide film has a pore diameter of 0.05 μm or more and a pore depth of 0.1 to 0.5 μm, the EL light emitting layer is formed. It is possible to allow the binder to sufficiently enter the pores. When the binder sufficiently enters the pores, the space inside the pores is reduced, and the adhesion between the EL light emitting layer and the second duplex type anodic oxide film is improved. Due to this improvement in adhesion, unevenness in light emission is improved and brightness is improved.

[0024]

EXAMPLES Examples of the present invention will be described below. First, a solution in which 150 g of sodium carbonate and 50 g of sodium phosphate were dissolved in 1 liter of pure water, an aluminum foil having a purity of 99.99% whose one surface was masked with an organic film coated with an adhesive was used as an anode, and a carbon plate was used as a cathode. Was used as an electrolytic solution, and electrolytic polishing was performed for 2 minutes at a current density of 12 A / dm ² and an electrolytic solution temperature of 90 ° C. to obtain an aluminum foil having one surface electrolytically polished.

Next, an electrolytically polished aluminum foil was used as an anode, an aluminum plate having a purity of 99.99% was used as a cathode, and a 4% phosphoric acid aqueous solution was used as an acidic electrolytic solution. The current density was 0.8 A / dm ² , and the electrolytic solution temperature was Acid anodic oxidation was performed by conducting constant current electrolysis for 5 minutes under the condition of about 25 ° C.

As a result of this acidic anodic oxidation, as shown in FIG. 1, on the surface of the aluminum foil 1 which has been electropolished, a porous layer 3 having pores 2 having a pore diameter of about 0.1 μm (thickness of about 0.55 μm) is formed. ) And a barrier layer 4 (thickness of about 0.05μ
first duplex type anodized film 5 including
(Thickness of about 0.6 μm) was formed.

Next, the aluminum foil on which the first duplex type anodic oxide film was formed was used as an anode, and the purity was 99.
Using 99% aluminum plate as the cathode, 0.05 mol /
Using a liter of ammonium adipate solution as a neutral electrolyte, constant current electrolysis was performed until the voltage reached 250 V under conditions of current density 0.8 A / dm ² and electrolyte temperature of about 60 ° C. Constant-voltage electrolysis was performed until it became 1/10, and neutral anodization was performed.

As a result of the neutral anodic oxidation, as shown in FIG. 2, a porous layer having pores 2a having a pore diameter of about 0.1 μm and a pore depth of about 0.3 μm, which is shallower than the pores 2 is formed. A second duplex type anodic oxide film 7 including the barrier layer 6 and the barrier layer 6 was formed. The barrier layer 6 is thicker than the barrier layer 4 by about 0.3 μm, and the second duplex type anodic oxide film 7 is formed.
Since the total thickness is about 0.7 μm,
It is considered that the barrier layer also grew at the interface between the aluminum substrate and the oxide film. 2 that are common to those in FIG. 1 are assigned the same reference numerals as in FIG. 1 and their explanations are omitted.

The growth of the barrier layer is considered to be due to the following reaction. As shown in FIG. 3, ionic conduction of Al ³⁺ ions occurs from the side of the aluminum foil 1 which is the base of the anodic oxide coating 5, by performing anodic oxidation in an acidic aqueous solution and then neutral anodic oxidation, so that the electrolytic solution From the side, it is considered that ionic conduction of O ²⁻ ions occurs. Then, Al ₂ O ₃ is formed where Al ³⁺ ions and O ²⁻ ions collide. At this time, while forming a new anodic oxide film, the first duplex type anodic oxide film 5 is formed.
The film quality is improved to be more precise. 3 that are common to FIG. 1 are assigned the same reference numerals as in FIG.

Since other anions such as O ²⁻ ions can also penetrate into the film from the electrolytic solution, strictly speaking, an oxide film formed by acidic anodization and an oxide film formed by neutral anodization after that. The film quality is different from the film. For example, when a phosphoric acid type is used as the acidic electrolyte, phosphorus is mixed in the film.

As a result, the barrier layer 4 forming the first duplex type anodic oxide film 5 grows mainly on the surface side of the oxide film, and a film having an increased thickness of the barrier layer is formed. This state is shown in FIG. The two-dot chain line in FIG. 2 indicates the boundary between the aluminum and the oxide film when the aluminum foil is anodized in an acidic aqueous solution. As can be seen from FIG. 2, the oxide film grows even at the interface between the aluminum substrate and the oxide film.

After the second duplex type anodic oxide film 7 is formed in this way, DMF (dimethylformamide) is added to a binder such as cyanoethyl-4,4,6-triglucan (cyanoethyl pullulan) in which the phosphor powder is dispersed. ) Is added to form an ink-emitting EL luminescent agent directly on the second duplex type anodic oxide coating 7 and dried,
An EL light emitting layer was formed.

Further, a transparent electrode film on which ITO was vapor-deposited and a lead wire was attached was attached by thermocompression bonding. After that, the film attached to one surface of the aluminum foil was removed, and the lead wire was led out from the surface of the aluminum foil on the side where the film was removed to obtain an EL device having a structure as shown in FIG.

The EL element 10 shown in the figure has an aluminum foil 1 as a back electrode, and a second duplex type anodic oxide film 7 formed on one surface of the aluminum foil 1.
An (electrically insulating layer), an EL light emitting layer 11 formed on the second duplex type anodic oxide film 7, and a transparent electrode film 12 formed on the EL light emitting layer 11. Then, the lead wire 13a is provided from the transparent electrode film 12, and the lead wire 13b is provided from the aluminum foil 1.
Has been derived.

The performance of the EL element (Sample 1) manufactured in this manner was evaluated by applying an applied voltage of 100 V (AC 400 Hz).
It was measured under the conditions. The results are shown in Table 1.

Comparative Example 1 First, in the same manner as in Sample 1, one surface of the aluminum foil was electrolytically polished.

Next, a high dielectric constant organic resin is dissolved in a solvent and barium titanate powder is dispersed in the solvent to form an ink, which is applied to the electrolytically polished surface of the aluminum foil by a printing method and dried. Then, an electrical insulating layer (resin insulating layer) having a thickness of about 40 μm was formed.

After that, an EL light emitting layer and a transparent electrode were formed on the resin insulating layer in the same manner as in Sample 1, and lead wires were led out to obtain an EL element (Sample 2). For comparison, the performance of this EL device was measured in the same manner as in Sample 1. The results are also shown in Table 1.

Comparative Example 2 After electrolytically polishing one surface of an aluminum foil in the same manner as in Sample 1, the electrolytically polished aluminum foil was used as an anode, an aluminum plate having a purity of 99.99% was used as a cathode, and 0 was used. Using a 0.055 mol / liter ammonium adipate solution as a neutral electrolyte, a current density of 0.8 A /
After constant current electrolysis was performed under conditions of dm ² and electrolyte temperature of about 60 ° C. until the voltage reached 250 V, constant voltage electrolysis was performed until the current value became 1/10, and neutral anodization was performed. By this neutral anodic oxidation, a barrier type anodic oxide film having a thickness similar to that of Sample 1 was formed on the electrolytically polished surface of the aluminum foil.

Then, an EL light emitting layer and a transparent electrode were formed on the barrier type anodic oxide film in the same manner as in Sample 1, and lead wires were led out to obtain an EL device (Sample 3).

For comparison, the performance of this EL device was measured in the same manner as in Sample 1. The results are also shown in Table 1.

[0042]

[Table 1]

As is clear from Table 1, sample 1 is
The brightness and luminous efficiency were improved and the power consumption was reduced as compared with Samples 2 and 3. Further, it was confirmed that the electrical insulating layer was not destroyed even when an overvoltage was applied, and it was also confirmed that the unevenness of light emission was small.

It was also confirmed that Sample 1 has a higher electrostatic capacity and a smaller equivalent series resistance (ESR) than Sample 3. From these facts, the second duplex type anodic oxide film used as the electrical insulating layer in Sample 1 has different film quality from the barrier type anodic oxide film by neutral anodic oxidation, and is considered as a capacitor. It is considered to have excellent characteristics.

From the above results, it is considered that when neutral anodic oxidation is performed after acidic anodic oxidation, a denser anodic oxide coating can be obtained than the barrier type anodic oxide coating obtained by only neutral anodic oxidation.

According to the above-described embodiment, it is possible to manufacture an EL element having the same or higher characteristics without using a coating process for forming the electrically insulating layer. The manufacturing method of the EL element of the present invention is not limited to the above-mentioned method, and includes various modifications and applications.

For example, the thickness of the grown barrier layer (reference numeral 6 in FIG. 2) in the second duplex type anodic oxide film was about 0.3 μm in the above-mentioned embodiment,
It can be appropriately changed within a range of about 0.1 to 0.5 μm. When it exceeds 0.5 μm, the voltage drop in the second duplex type anodic oxide film becomes large, and the brightness of the obtained EL element is likely to be lowered. On the other hand, when the thickness is less than 0.1 μm, the withstand voltage of the obtained EL element is likely to decrease.

The pore depth of the porous layer in the second duplex type anodic oxide film is 0.1 to 0.5 μm.
About m is preferable. If the pores are too shallow, the adhesion to the EL light emitting layer deteriorates, the brightness of the obtained EL element decreases, and uneven light emission also increases. On the other hand, if it is too deep, the pores are not filled with the binder and a gap is formed, so that the brightness of the obtained EL element is lowered.

The pore diameter may be 0.05 μm or more, but is preferably about 0.05 to 0.5 μm. 0.05μ
If it is less than m, the pore size is too small to be practically effective. From the relationship between the thickness of the barrier layer and the pore depth described above, the thickness of the second duplex type anodic oxide film (reference numeral 7 in FIG. 2) is preferably in the range of 0.2 to 1.0 μm.

To obtain such a second duplex type anodic oxide film, an acidic aqueous solution of an inorganic or organic acid such as sulfuric acid, chromic acid, oxalic acid or phosphoric acid is used as an electrolytic solution for acidic anodic oxidation. You can Regardless of which acidic electrolytic solution is used, the first duplex type anodic oxide coating including the porous layer and the barrier layer can be formed on the surface of the aluminum foil.

The current density during acidic anodization is 0.1 to 3 A.
It is preferably within the range of / dm ² . Electrolysis bath temperature is room temperature to 4
0 ° C is preferred. However, these conditions are not restrictive.

By appropriately selecting conditions such as the type of acidic electrolyte, the current density, the amount of current drop after constant voltage transfer, and the temperature of the electrolytic bath, the porous layer constituting the first duplex type anodic oxide film can be formed. It is possible to control the pore diameter, the pore depth, the film thickness of the barrier layer forming the first duplex type anodic oxide coating, and the like.

After the first duplex type anodic oxide film is obtained, an electrolytic solution for neutral anodic oxidation for growing a barrier layer in the anodic oxide film is an ammonium borate aqueous solution or an ammonium phosphate aqueous solution. A neutral aqueous solution of an inorganic or organic acid or a salt thereof having a pH of 5 to 8 such as an ammonium adipate-based aqueous solution can be used. Regardless of which electrolytic solution is used, the barrier layer in the first duplex type anodic oxide film is grown to form the second duplex type anodic oxide film including the porous layer and the grown barrier layer. You can

The current density during neutral anodic oxidation is 0.1 to 5 A.
/ Dm ² and the falling current value after the constant voltage shift is preferably 0.01 to 5 A / dm ² .
The temperature of the electrolytic bath is preferably room temperature to 90 ° C. However, these conditions are not restrictive.

In the method of the present invention, the EL is directly formed on the second duplex type anodic oxide film formed as described above.
A light emitting layer can be formed. The method for forming the EL light emitting layer is not particularly limited. For example, the phosphor powder is dispersed in a binder having a high dielectric constant such as cyanoethyl-4,4,6-triglucan or cyanoethylpolyvinyl alcohol, and DMF ( It is possible to apply a method known in the art, such as applying an ink-like material dissolved in a solvent such as dimethylformamide) and drying it.

Further, the method for forming the transparent electrode on the EL light emitting layer is not particularly limited, and other than the method of thermocompression bonding the transparent electrode film having ITO deposited on the polyester film surface, for example, A method known in the art, such as a method in which ITO powder is dissolved in a solvent such as DMF together with a binder such as cyanoethyl-4,4,6-triglucan to form an ink, which is applied onto the EL light emitting layer and dried. Can be applied.

A mechanism for applying a voltage is generally provided for the structure in which the transparent electrode is formed in this manner. The mechanism for applying the voltage is, for example, as shown in FIG.
However, the present invention is not limited to this structure. Furthermore, E
It is preferable to seal the L element body by a method such as housing it in a moisture-proof film package.

In the EL device manufactured as described above, since the second duplex type anodic oxide film including the grown barrier layer functions as an electrical insulating layer, the withstand voltage property is improved, and at the same time, the brightness and light emission are improved. The electrical characteristics such as efficiency can be improved. Further, the presence of the porous layer improves the wettability of the binder and the like when forming the EL light emitting layer, and can reduce the light emission unevenness of the obtained EL element.

Although the surface of the aluminum foil is electrolytically polished prior to the acid anodic oxidation in the above-mentioned embodiment, the surface polishing may or may not be performed. As the surface polishing method, a method such as a chemical polishing method or a mechanical polishing method can be applied in addition to the electrolytic polishing method.

Although the modified examples and application examples of the present invention have been described above, other various changes, improvements, combinations, etc., such as an aluminum plate or a member having an aluminum layer on the surface instead of the aluminum foil, are possible. It will be obvious to those skilled in the art.

The method of the present invention can be applied, for example, to the manufacture of EL elements for various uses other than the light source for the backlight of LCD devices.

[0062]

As described above, according to the present invention,
It is possible to provide an EL element with reduced unevenness in light emission.

Further, an EL element having high withstand voltage and excellent electrical characteristics can be manufactured by a simple process.

[Brief description of drawings]

FIG. 1 is a cross-sectional sketch of a first duplex type anodized film.

FIG. 2 is a cross-sectional sketch of a second duplex type anodized film.

FIG. 3 is a cross-sectional view for explaining the principle that the barrier type anodic oxide film forming the first duplex type anodic oxide film grows on the surface side by neutral anodization.

FIG. 4 is a schematic sectional view of an EL device obtained in an example.

FIG. 5 is a schematic cross-sectional view of an EL device according to the related art.

[Explanation of symbols]

1 Aluminum foil (back electrode) 2, 2a Pore 3, 3a Porous anodized film 4 Barrier type anodized film (by acidic anodization) 5 First duplex type anodized film 6 Grown barrier type anodized film 7 Second duplex type anodic oxide film (electrical insulating layer) 10 EL element 11 EL light emitting layer 12 Transparent electrode film 13a, 13b Lead wire

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisashi Takahashi 5-9-6 Tokodai, Tsukuba, Ibaraki Pref., Tsukuba Research Laboratories, Nippon Heavy Industries, Ltd. (72) Takeshi Tonomura 5-Tokodai, Tsukuba, Ibaraki 9-6 Nippon Heavy Chemical Industry Co., Ltd. Tsukuba Research Laboratory (72) Inventor Takeyuki Fujii 5-9-6 Tokodai, Tsukuba City, Ibaraki Prefecture Japan Heavy Chemical Industry Co., Ltd. Tsukuba Research Laboratory (72) Inventor Kenichi Kondo Setagaya-ku, Tokyo 2-3-3 Chitosedai (72) Inventor Takahiro Saida 1-2-22-15 Fujigaoka, Midori-ku, Yokohama-shi, Kanagawa Synergy Fujigaoka 201 (72) Inventor Shuichi Taya 2-17-8, Minami-ku, Midori-ku, Yokohama-shi, Kanagawa Shimura Mansion No.405 (72) Inventor Sadayoshi Yamakawa 1-1 Sachimachi, Nagai City, Yamagata Prefecture Marcon Electronics Co., Ltd. (72) Inventor Shunichi Osawa, Mayor of Yamagata Prefecture Shiko-cho, No. 1 No. 1 Marcon in the Electronics Co., Ltd.

Claims (2)

[Claims] 1. An aluminum foil, an electrical insulating layer including a duplex type anodic oxide film formed on a surface of the aluminum foil, an EL light emitting layer directly formed on the electrical insulating layer, and the EL. An EL device having a transparent electrode formed on a light emitting layer, wherein the duplex type anodized film has a shallow pore depth by mainly growing a barrier layer on the surface side after acidic anodization, thereby forming a barrier layer. An EL device having a thickened film, in which the barrier layer of the film has a thickness of 0.1 to 0.5 μm, a pore diameter of 0.05 μm or more, and a pore depth of 0.1 to 0.5 μm. 2. A step of forming a first duplex type anodic oxide film on the surface of the aluminum foil by anodizing an aluminum foil in an acidic electrolyte, and forming the first duplex type anodic oxide film. By further anodizing the formed aluminum foil in a neutral electrolytic solution, a barrier layer which mainly constitutes the first duplex type oxide film is grown on the surface side, and the pore depth is shallow and the barrier layer is thick. A method for manufacturing an EL device, comprising: a step of forming a second duplex type anodic oxide film; and a step of directly forming an EL light emitting layer and a transparent electrode layer on the second duplex type anodic oxide film.