JP4974368B2 - Organic electroluminescence device and method for manufacturing the same - Google Patents

Description

  The present invention relates to an organic electroluminescence element that prevents deterioration of an organic light emitting film due to moisture, oxygen, and the like, and a method for manufacturing the same.

An organic electroluminescence device (organic EL device) has an organic light emitting layer disposed between a pair of electrodes consisting of an anode and a cathode, and holes injected from the anode (hole injection electrode) and the cathode (electron injection electrode). The device emits light by recombining the emitted electrons with the light emitting layer.
Since the light emitting layer is made of an organic substance and easily deteriorates due to oxygen or moisture in the atmosphere, the element surface is usually sealed with a casing called a sealing can or a sealing cap (Patent Document 1). Furthermore, the deterioration of the light emitting layer is suppressed for a long period of time by previously applying a getter agent that adsorbs moisture and oxygen into the sealing can.
In addition, techniques for coating the organic light emitting layer with a protective film made of an inorganic film (silicon nitride film) or a polymer film have been developed (Patent Documents 2 and 3).

JP 2007-141803 A JP-A-8-22891 JP 2005-339828 A

However, when a sealing can is used, since there is an internal space between the sealing can and the element surface, the entire element becomes thicker (1.5 to 3 mm), and there is a problem in reducing the thickness of the organic EL element. is there.
On the other hand, when sealing an element only with a protective film without using a sealing can, it is difficult to suppress deterioration of the light emitting layer for a long period of time. As one of the causes, it is considered that when the inorganic film is coated on the element surface by sputtering or vapor deposition, the film does not sufficiently wrap around the element side surface, and oxygen and moisture enter from the side surface of the organic light emitting layer.

  The present invention has been made to solve the above-described problems, and aims to provide an organic electroluminescence device capable of completely sealing the side surface of an organic light emitting layer, causing little deterioration in light emission characteristics, and capable of reducing the thickness. And

In order to achieve the above object, an organic electroluminescent element of the present invention includes a substrate side electrode formed on a substrate, an organic light emitting layer formed on the upper surface of the substrate side electrode, and an upper surface of the organic light emitting layer. an upper electrode formed on the plurality of partition walls are formed on the upper surface of the substrate side electrode spaced from each other, a first continuously covering the upper and side surfaces and side surfaces of the organic light emitting layer of at least the upper electrode An organic film, a polymer film covering the first inorganic film, and a second inorganic film covering the polymer film, and the organic light emitting layer and the upper electrode are adjacent to each other with the partition as a mask. The first inorganic film is formed between the barrier ribs, and continuously covers the upper surface and the side surface of the upper electrode and the side surface of the organic light emitting layer, and further from the side surface of the organic light emitting layer to the surface of the substrate side electrode. Nitsuna Leads from the substrate side electrode surface on the side surfaces and the upper surface of said partition wall, said polymeric membrane covers said first inorganic film, have further thicker between adjacent said partition wall between said partition wall so as to fill the recess, The first inorganic film is sparser than the second inorganic film.
With such a configuration, the outermost second inorganic film and the relatively thick polymer film prevent external moisture and oxygen from reaching the organic light emitting layer. In addition, the polymer film often contains harmful components that degrade the organic light-emitting layer, but the relatively sparse first inorganic film is formed around the side surface of the organic light-emitting layer due to its characteristics. Since the light emitting layer is completely covered, external moisture, oxygen, and the harmful components are prevented from reaching the organic light emitting layer. As a result, the deterioration of the light emission characteristics is reduced.

In the method for producing an organic electroluminescence element of the present invention, at least the upper surface and the side surface of the upper electrode and the side surface of the organic light emitting layer are continuously covered with a first inorganic film, and the first inorganic film is covered with a polymer film. The polymer film is covered with a second inorganic film, and both the first inorganic film and the second inorganic film are formed by sputtering, and the sputtering pressure of the first inorganic film is set to the second inorganic film. This is higher than the sputtering pressure of the film.
In the method for producing an organic electroluminescent element of the present invention, at least the upper surface and the side surface of the upper electrode and the side surface of the organic light emitting layer are continuously covered with a first inorganic film, and the first inorganic film is a polymer film. The polymer film is covered with a second inorganic film, and the first inorganic film is formed by inductively coupled plasma CVD.

  ADVANTAGE OF THE INVENTION According to this invention, the organic electroluminescent element in which the side surface of an organic light emitting layer is completely sealed, there is little deterioration of a light emission characteristic, and thickness reduction is obtained.

FIG. 1 shows an example of a cross-sectional structure of an organic electroluminescence element according to the first embodiment of the present invention. In this figure, a transparent substrate side electrode (transparent conductive film; ITO film) 2 is formed on a transparent substrate 30. An organic light emitting layer 4 is formed on the upper surface of the substrate side electrode 2, and an upper electrode 6 is formed on the upper surface of the organic light emitting layer 4.
The organic light emitting layer 4 is a layer that emits light by recombining holes injected from the anode and electrons injected from the cathode. In this embodiment, light from the organic light emitting layer 4 is emitted to the lower surface side of the transparent substrate 30 to constitute a bottom emission type organic electroluminescence element. Further, in this embodiment, the substrate-side electrode 2 extends in a strip shape in the left-right direction in FIG. 1, while the organic light emitting layer 4 and the upper electrode 6 extend in a strip shape in a direction perpendicular to the substrate-side electrode 2. The overlapping portion of 2 and the upper electrode 6 is a passive matrix system that constitutes a pixel.
In the present invention, in order to prevent the deterioration of the organic light emitting film, the bottom emission type is used instead of the top emission type that emits to the upper surface of the organic light emitting film in that a three-layer film described later is formed on the organic light emitting film. Is preferred.

  In this embodiment, after the substrate-side electrode 2 is formed, a plurality of barrier ribs 40 are formed in a strip shape in a direction perpendicular to the substrate-side electrode 2 by photolithography or the like. An upper electrode 6 is formed. Thereby, the organic light emitting layer 4 and the upper electrode 6 can be formed in a strip shape with the partition 40 itself as a mask.

As the transparent substrate 30, for example, glass, quartz glass, synthetic resin (for example, polyethylene terephthalate, polycarbonate, PMMA (polymethyl methacrylate), etc.) can be used, but is not particularly limited thereto. Further, it may be a translucent substrate.
As the substrate-side electrode 2, for example, a conductive transparent film made of gold; polyaniline; ITO (InO ₃ —SnO ₂ ), tin oxide such as SnO: Sb, or zinc oxide such as ZnO: Al can be used. The polarity of the substrate side electrode 2 may be an anode (hole injection electrode) or a cathode, but in the case of an ITO film, it functions as an anode.
As the upper electrode 6, for example, a metal or alloy film such as aluminum, magnesium, Al—Li alloy, Al—Mg alloy, Al—Nd alloy, or Al—Mg alloy can be used. When the substrate-side electrode 2 is used as an anode, the counter electrode serves as a cathode. Therefore, it is preferable to use a metal or alloy having a low work function as the upper electrode 6.

The organic light emitting layer 4 may have a single layer structure or a multilayer structure, and a conventionally known organic light emitting layer used for an organic EL element can be used. Examples of the multilayer structure include a two-layer structure of a light-emitting layer and a hole transport layer, a two-layer structure of a light-emitting layer and an electron transport layer, and a three-layer structure of an electron transport layer, a light-emitting layer, and a hole transport layer. Furthermore, the thing of the five-layer structure of an electron injection layer, an electron carrying layer, a light emitting layer, a hole transport layer, and a hole injection layer is also mentioned.
As the composition of the organic light emitting layer 4, a conventionally known composition used for the organic EL element (for example, an organic compound such as a low molecular fluorescent dye, an organometallic complex, or a polymer material) can be used. Specific examples of the organic light emitting layer 4 include 8-hydroxyquinoline aluminum (Alq ₃ ). When the organic light emitting layer 4 has a multilayer structure, for example, a triphenylamine derivative can be used as the hole transport layer, and Alq ₃ can be used as the light emitting layer and the electron transport layer.

Next, the film structure covering the organic light emitting layer will be described. This film structure is composed of three layers of a first inorganic film 12, a polymer film 14 and a second inorganic film 16.
The first inorganic film 12 continuously and completely covers the upper surface and side surface of the upper electrode 6 and the side surface of the organic light emitting layer 4, and is further connected to the surface of the substrate side electrode 2 from the side surface of the organic light emitting layer 4. The surface is connected to the surface (side surface and upper surface) of the partition wall 40. The polymer film 14 covers the first inorganic film 12 and is particularly thick between the partition walls 40 and 40 so as to fill the recesses between the adjacent partition walls 40 and 40. The second inorganic film 16 covers the polymer film 14.

The first inorganic film 12 is sparser (porous) than the second inorganic film 16. As the degree of sparseness, for example, the refractive index can be raised, the refractive index of the first inorganic film 12 can be about 1.5 to 1.55, and the refractive index of the second inorganic film 16 can be about 1.6 to 1.65.
By making the first inorganic film 12 relatively porous, the wraparound of the film forming material is improved and the step coverage is excellent. Therefore, the first inorganic film 12 is formed continuously on the upper surface and side surface of the upper electrode 6 and the side surface of the organic light emitting layer 4, and the side surface of the organic light emitting layer 4 can be completely sealed.
Further, the organic light emitting film 4 is shielded from moisture and oxygen by covering the outer side of the first inorganic film 12 with the polymer film 14 relatively thick. Furthermore, the barrier performance can be improved by covering the second inorganic film 16 outside the polymer film 14. This is because the barrier performance of the inorganic film is improved by forming the inorganic film on the surface flattened by the polymer film.

As the first inorganic film 12 and the second inorganic film 16, for example, an inorganic oxide or inorganic nitride layer can be used. Specifically, for example, B, Al, Si, Ga, Ge, In, Examples thereof include one or more oxides or nitrides selected from the group consisting of Sn, Zn, Ti, Y, Zr, Nb, Mo, W, Hf, Ta, and Ce, or a plurality of layers thereof. The first inorganic film and the second inorganic film, and these inorganic oxides or inorganic nitrides are obtained by film formation by a PVD (physical vapor deposition) method or a CVD (chemical vapor deposition) method. Examples of the PVD method include a sputtering method.
Examples of the first inorganic film 12 and the second inorganic film 16 include Al ₂ O ₃ , Si ₃ N ₄ , SiO ₂ , SiO _x N _{y and the} like (x and y are predetermined composition ratios). .

In particular, the first inorganic film 12 is preferably formed by a sputtering method in which the sputtering pressure is set higher than the sputtering pressure of the second inorganic film, or inductively coupled plasma CVD. The reason is as follows.
In the sputtering method, when the sputtering pressure (pressure in the sputtering atmosphere) is increased, the mean free path of the sputtering material (film forming material) decreases in inverse proportion to the pressure. Therefore, the wraparound of the particles is improved and the side surface of the organic light emitting layer 4 can be completely covered. At this time, the coating becomes porous.
Inductive-Coupling Plasma (ICP) In the case of plasma CVD, the reaction pressure is several Pa to several hundred Pa, which is more than two orders of magnitude higher than that of PVD such as ordinary vapor deposition and sputtering, so the mean free The process is further reduced, and the particles are better circulated.

As the polymer film 14, a known resin can be used, and the polymer film 14 may be formed by applying a monomer by spin coating or the like and then curing it. As a known resin, for example, a photo-curing resin or a thermosetting resin having an acrylate-based or methacrylate-based functional group can be used. The polymer film 14 may be transparent, and examples of the transparent resin include polyvinyl chloride resin, melamine resin, phenol resin, alkyd resin, epoxy resin, polyurethane resin, polyester resin, maleic acid resin, and polyamide resin.
As the method for curing the resin, ultraviolet irradiation can be employed in the case of a photocurable resin, and thermosetting can be employed in the case of a thermosetting resin.

Further, the polymer film 14 can be formed by evaporating and vapor-depositing a predetermined monomer or oligomer, followed by polymerization and curing (vacuum deposition method). As the polymerization method, thermal polymerization or ultraviolet polymerization can be appropriately used depending on the thermal decomposition temperature of the monomer. As a monomer used in this method, for example, a monomer described in US Pat. No. 4,499,520 can be used.

  The coating thickness of the polymer film 14 can be set to, for example, 0.5 to 5 μm, but when the film thickness is 1 μm or more, a desired thickness can be ensured by a plurality of coatings.

  The substrate-side electrode 2, the organic light emitting layer 4, and the upper electrode 6 constituting the organic EL element have a larger upper surface area than the side surface, but harmful components enter from the upper surface by the first inorganic film 12. Can be prevented.

According to the present invention, the outermost second inorganic film 16 and the relatively thick polymer film 14 prevent external moisture and oxygen from reaching the organic light emitting layer 4. Further, the polymer film 14 often contains harmful components that degrade the organic light emitting layer 4, but the surface (including side surfaces) of the organic light emitting layer 4 is completely covered by the first inorganic film 12. Therefore, external moisture, oxygen, and the harmful components are prevented from reaching the organic light emitting layer 4. As a result, the deterioration of the light emission characteristics is reduced.
Further, according to the present invention, it is possible to reliably prevent moisture and oxygen from reaching the organic light emitting layer 4 without using a sealing can as described above, so that the device can be thinned.

A substrate side electrode 2 made of an ITO film is formed on a transparent substrate 30, an organic light emitting layer 4 is formed on the upper surface of the substrate side electrode 2, an upper electrode 6 is formed on the upper surface of the organic light emitting layer 4, and a partition 40 is further formed. The organic EL element having the structure shown in FIG. 1 was used. Note that Alq ₃ was used as the organic light emitting layer 4 and Al was used as the upper electrode 6.
This organic EL element was installed in a sputtering apparatus, and opposed to the Al target through a mesh (a porosity of 30 to 70%). Ar gas was used as a carrier gas, and oxygen was flowed toward the surface of the organic EL element at a flow rate of 10 to 20 sccm. A total pressure of Ar gas and oxygen in the sputtering apparatus was set to 1 to ₂ Pa, and Al ₂ O ₃ was sputtered to a thickness of 100 nm on the surface of the organic EL element to form a first inorganic film 12.

Next, the polymer film 14 was formed into a film having a thickness of 4 μm by the vacuum vapor deposition method (because the partition wall height was 4 μm), and was subjected to ultraviolet curing to form the polymer film 14 on the surface of the first inorganic film 12.
Further, the organic EL element after the polymer film 14 was formed was placed in the sputtering apparatus. A 100 nm-thick Al ₂ O ₃ film is formed on the surface of the polymer film 14 in the same manner as the first inorganic film 12 except that the total pressure is reduced to 0.2 to 0.5 Pa by reducing the flow rate of the carrier gas. Thus, the second inorganic film 16 was formed.
When the refractive indexes of the first inorganic film 12 and the second inorganic film 16 are measured by spectroscopic ellipsometry, they are 1.5 to 1.55 and 1.6 to 1.65, respectively, and the first inorganic film 12 is sparser (porous). I found out that
The SEM (scanning electron microscope) image confirmed that the first inorganic film 12 was formed around the side surface of the organic EL element (the organic light emitting layer 4 and the upper electrode 6).

The same organic EL element as in Example 1 was used. This organic EL device is installed in inductively coupled plasma CVD (ELVESS-PE-CVD equipment manufactured by Tokki), and SiH ₄ , NH ₃ , and N ₂ gases are introduced into the equipment at a molar ratio of 1: 1: 10, respectively. did. Plasma CVD film formation was performed at a pressure of 20 Pa in the apparatus, an RF (Radio Frequency) power of 0.5 W / cm ² , and an RF frequency of 13.56 MHz. The first inorganic film 12 was formed at a deposition rate of 100 nm / min and a deposition thickness of 0.5 μm.
The composition of the first inorganic film 12 was found to be Si ₃ N ₄ by fluorescent X-ray analysis.
The polymer film 14 and the second inorganic film 16 were formed in exactly the same manner as in Example 1.
The refractive index of the first inorganic film 12 was measured and found to be 1.9 to 1.95.
Also in Example 2, it is confirmed by an SEM (scanning electron microscope) image that the first inorganic film 12 is formed around the side surface of the organic EL element (the organic light emitting layer 4 and the upper electrode 6). did.

Using the same organic EL element as in Example 1, a first inorganic film 12 and a polymer film 14 were formed in exactly the same manner as in Example 2.
Next, using inductively coupled plasma CVD (ELVESS-PE-CVD equipment manufactured by Tokki Co., Ltd.), SiH ₄ , NH ₃ , and N ₂ gases were introduced at a molar ratio of 1: 1: 10, respectively. The second inorganic film 16 is formed on the surface of the polymer film 14 by performing plasma CVD film formation with a pressure of 100 Pa, RF (Radio Frequency) power 0.5 W / cm ² , RF frequency 13.56 MHz, film thickness 1.0 μm. Filmed.
The refractive index of the second inorganic film 16 was 1.8 to 1.85.

  The present invention is not limited to passive matrix organic electroluminescent elements, and is not limited to active matrix organic electroluminescent elements or other types of organic electroluminescent elements without departing from the spirit of the present invention. The invention can be applied.

It is a figure which shows an example of the cross-section of the organic electroluminescent element which concerns on embodiment of this invention.

Explanation of symbols

2 substrate side electrode 4 organic light emitting layer 6 upper electrode 12 first inorganic film 14 polymer film 16 second inorganic film 30 substrate

Claims (3)

A substrate-side electrode formed on the substrate; an organic light-emitting layer formed on the upper surface of the substrate-side electrode ; an upper electrode formed on the upper surface of the organic light-emitting layer; and an upper surface of the substrate-side electrode. A plurality of partitions spaced apart from each other, a first inorganic film continuously covering at least the upper surface and side surfaces of the upper electrode and the side surfaces of the organic light emitting layer, a polymer film covering the first inorganic film, A second inorganic film covering the polymer film,
The organic light emitting layer and the upper electrode are formed between adjacent barrier ribs using the barrier ribs as a mask,
The first inorganic film continuously and completely covers the upper surface and side surface of the upper electrode and the side surface of the organic light emitting layer, and is further connected to the substrate side electrode surface from the side surface of the organic light emitting layer. Connected from the surface to the side and top surfaces of the partition,
The polymer film covers the first inorganic film, and is thicker between the partition walls so as to fill the recesses between the adjacent partition walls,
An organic electroluminescence element in which the first inorganic film is sparser than the second inorganic film. It is a manufacturing method of the organic electroluminescent element of Claim 1,
At least the upper and side surfaces of the upper electrode and the side surface of the organic light emitting layer are continuously covered with a first inorganic film, the first inorganic film is covered with a polymer film, and the polymer film is covered with a second inorganic film. And the first inorganic film and the second inorganic film are both formed by sputtering, and the sputtering pressure of the first inorganic film is made higher than the sputtering pressure of the second inorganic film. Production method. It is a manufacturing method of the organic electroluminescent element of Claim 1,
At least the upper and side surfaces of the upper electrode and the side surface of the organic light emitting layer are continuously covered with a first inorganic film, the first inorganic film is covered with a polymer film, and the polymer film is covered with a second inorganic film. And the manufacturing method of the organic electroluminescent element which forms the said 1st inorganic film by inductively coupled plasma CVD.

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