JPH11329727A - Rgb light emitting organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an RGB light-emitting organic EL element capable of emitting only monochromatic light and having high luminous efficiency. SOLUTION: This EL element is composed of: an organic EL (electroluminescence) layer which further consists of a transparent substrate 1, a transparent first electrode layer 3, an organic light emitting layer 4 for emitting ultraviolet light, and a transparent second electrode layer 5; and three kinds of fluorescent materials 6 each emitting one of the three primary colors of R, G, and B. Since full-color display can be performed using the fluorescent materials 6 emitting light by irradiation of ultraviolet light from the light emitting layer 4, this structure makes it easy to form a minute pattern of the organic EL layer without using color conversion filters or the like and hence the luminous efficiency is high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an organic EL device using an organic material for a light emitting layer.
The present invention relates to a structure of an organic EL device that emits visible light of primary colors and can be used as a full-color display.

[0002]

2. Description of the Related Art Display devices for display include:
CRT (Cathode Ray Tube), LCD (Liquid Cryst)
al), plasma (Plasma), light emitting diode (Light Em)
It has been known from the related art such as itting Diode) and EL (Electro Luminescence), and is widely used for various displays such as TVs and personal computers.

[0003] Among them, EL is a self-luminous type, and is expected to be a thin display element because it can use a thin film. And, as a thin film type DC EL, an organic thin film E
L has attracted attention in recent years. For example, in order to form a full-color display, an element that efficiently emits the three primary colors of red, green, and blue is required. However, in inorganic EL, there is only a material with low emission efficiency for blue. However, according to the organic EL, an element capable of efficiently emitting blue light has been developed.

As an organic EL device usable as a full-color display, for example, one having a structure shown in FIG. 3 is known. This organic EL element is a glass substrate 100
And a transparent electrode film 101 formed on a glass substrate 100,
A hole transport layer 102 formed on the transparent electrode film 101 and R, G and B formed separately on the hole transport layer 102 from each other.
Three types of light emitting layers 103 emitting the three primary colors, and light emitting layer 1
And a back electrode layer 105 formed on the electron transport layer 104, respectively. The hole transport layer 102, the light emitting layer 103, and the electron transport layer
The light emitting layer 200 is formed at 104.

In this organic EL device, recombination light emission is caused by injection of holes into the electron transport layer 104 or injection of electrons into the hole transport layer 102. As described above, the light emission voltage is as low as about 10 V because of the injection light emission similar to the light emitting diode. The electron transport layer 104 and the hole transport layer 1
By separating the functions by interposing the light emitting layer 103 between the layers 02, the material of the light emitting layer 103 can be selected from a wide range.

[0006] In the above-mentioned organic EL device configured to emit three primary colors of R, G and B by selecting the material of the light emitting layer 103, the three types of light emitting layers 200 emit light from the glass substrate 100. Viewed through. Therefore, full-color light emission can be achieved by selecting voltage application to the three types of light-emitting layers 103, and this organic EL element can be used as a pixel of a full-color display.

In the organic EL device shown in FIG. 4, the light emitting layer 200 is configured to emit only one type of blue light.
The three types of color conversion layers 300 convert blue light into red light, green light and blue light, respectively. If you do this,
The number of times the light-emitting layer 200 that is weak to water or chemicals is processed can be reduced. Further, in the organic EL device shown in FIG. 5, the light emitting layer 200 is configured to emit only white light by one kind,
Red light, green light and blue light are respectively extracted from white light by three types of filters 400. Also in this case, the number of times of processing the light emitting layer 200 that is vulnerable to water and chemicals can be reduced.

[0008]

By the way, in order to form three kinds of light emitting layers 200 having different light emitting materials on the same substrate as shown in FIG. 3, first, a red layer is formed and processed.
Next, a process of forming and processing a green layer and further forming and processing a blue layer is required, and the light emitting layer must be processed at least three times. However, the light emitting layer 200, which is an organic layer, is weak to moisture and has poor durability to organic solvents and chemicals. Therefore, there is a problem that it is difficult to process the light emitting layer 200 into a fine pattern. There is also a problem that the driving voltage differs for each color.

In this regard, as shown in FIGS.
If only the monochromatic light of blue light or white light is emitted from 00, it becomes easy to process the light emitting layer 200 into a fine pattern, and there is no problem of the driving voltage. However, in the method using the color conversion layer 300, there is a problem that the light emission efficiency is reduced due to the loss generated at the time of color conversion. There is a problem.

Further, in the above-mentioned organic EL devices, since the light in the light emitting layer is directly visually recognized, there is a problem that dark spots due to pinholes in the light emitting layer are conspicuous. The present invention has been made in view of such circumstances, and an object of the present invention is to provide an RGB light emitting organic EL element that emits only monochromatic light and has high luminous efficiency.

[0011]

The feature of the RGB light emitting organic EL device of the present invention which solves the above problems is that a transparent substrate,
An organic EL layer formed of a transparent first electrode layer formed on a substrate, a light emitting layer formed on the first electrode layer, made of an organic material that emits ultraviolet light by applying a voltage, and a transparent second electrode layer;
A phosphor that is formed on the organic EL layer and emits light by ultraviolet light from the light emitting layer. The organic EL layer is divided into at least two second electrode layers separated from each other.
And B are provided corresponding to the divisions of the organic EL layers, each of which emits visible light of three primary colors, so that visible light from the phosphor can be visually recognized from the front surface side of the substrate.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the RGB light emitting organic EL device of the present invention, three kinds of phosphors respectively emit light by ultraviolet light emitted from the organic EL layer, and a full color display by three primary colors of R, G and B is displayed. Is done. Therefore, since the organic EL layer emits monochromatic light, it is easy to process the organic EL layer into a fine pattern, and since the driving voltage can be kept constant, the circuit can be simplified. Further, since the phosphor is generally an inorganic substance, it has excellent durability and can be used as a long-life full-color display.

Further, since the indirect light due to the fluorescent material is visually recognized, a dark spot generated by a pinhole or the like of the organic EL layer is less conspicuous as compared with the case where the direct light from the organic EL layer is visually recognized. Is improved. As the substrate, a transparent substrate such as a glass substrate and a resin substrate is used. In addition, between the substrate and the first electrode layer, or between the first electrode layer and the light emitting layer, visible light is transmitted and ultraviolet light is reflected so that ultraviolet light is transmitted through the substrate and is not visually recognized. It is desirable to provide a layer. Examples of the material of such an ultraviolet reflective layer include ZnO and TiO ₂ .

The first electrode layer is made of an IT
A transparent thin film such as O, AZO (Al-added ZnO), or SnO ₂ can be used. Since a film may be formed on the substrate, a film forming method in which a high temperature acts, such as a high frequency sputtering method, may be used. The thickness of the first electrode layer is generally preferably in the range of 10 to 300 nm, but is not particularly limited.

The light emitting layer can be composed of a hole transporting layer, a light emitting layer formed on the hole transporting layer, and an electron transporting layer formed on the light emitting layer, as in the prior art. Among them, the hole transport layer is formed of a tertiary amine derivative such as a triphenyldiamine derivative, a di (tri) azole such as a (di) styrylbenzene (pyrazine) derivative, a diolefin derivative, or an oxadiazole derivative, as in the related art. Derivatives, quinosaline derivatives, furan compounds, hydrazone compounds, naphthacene derivatives, coumarin compounds, quinacridone derivatives, indole compounds, pyrene compounds,
Examples include anthracene-based compounds.

The light emitting layer emits ultraviolet light when a voltage is applied, and examples thereof include polysilane. Examples of the electron transport layer include polysilane, oxadiazole derivatives, and trisquinolino aluminum complexes. The thickness of the hole transport layer is the same as before.
It is desirable to set it to 10 to 100 nm. When the thickness is smaller than this range, the number of pinholes increases and dark spots frequently occur. When the thickness is larger than this range, the luminous efficiency decreases. The thickness of the luminous body layer is desirably 10 to 100 nm as in the conventional case. When the thickness is smaller than this range, the number of pinholes increases and dark spots frequently occur. When the thickness is larger than this range, the luminous efficiency decreases. And the thickness of the electron transport layer is
It is desirable to set the thickness to 10 to 100 nm as in the conventional case. When the thickness is smaller than this range, the number of pinholes increases and dark spots frequently occur. When the thickness is larger than this range, the luminous efficiency decreases.

In the light emitting layer, whichever of the hole transport layer and the electron transport layer may be located on the first electrode layer side. However, the electron transport layer side must be brought into contact with a metal electrode having a small work function. Each layer constituting the light emitting layer can be formed by a vacuum evaporation method, a Langmuir-Blodgett evaporation method, a dip coating method, a spin coating method, a vacuum gas evaporation method, an organic molecular beam epitaxy method, or the like.

As the second electrode layer, a transparent thin film of ITO, AZO (Al-added ZnO), SnO ₂ or the like can be used. However, if the second electrode layer is formed from ITO, AZO, or the like, a thin film forming method such as high frequency sputtering must be used, and the light emitting layer is damaged by the action of high temperature or high energy of evaporated atoms. So the second
The electrode layer is preferably composed of a transparent conductive metal layer and a transparent anodic oxide film formed on the surface of the conductive metal layer. In other words, a relatively thick conductive metal layer is formed by vapor deposition, etc., which is anodized to form a transparent anodic oxide film, and thereby the thickness of the conductive metal layer itself is reduced to make it transparent. It is desirable to form a second electrode layer. With this configuration, the second electrode layer can be easily controlled in film thickness.
Å or more, and the occurrence of pinholes can be prevented. Furthermore, since the anodic oxide film is dense and transparent, it can protect the second electrode layer itself, protect the light-emitting layer that is mechanically and thermally weak, and can also function as a barrier layer against moisture. . The anodic oxide film is easy to print the phosphor.

The conductive metal layer is made of In-Sn, Z
It can be formed from a conductive metal such as n, Sn, or Sn-Sb. Ti, Al, Al-Li, Mg, Mg
-A metal such as Ag or Si can also be used. This conductive metal layer can be formed by a method in which high temperature does not act, such as a vapor deposition method. Since the electron transport layer must be brought into contact with a metal electrode having a small work function, Al, Al—Li, Mg—Ag are first placed on the electron transport layer.
And the like, on which In-Sn, Zn, Sn, and Sn which are transparent by anodic oxidation and whose oxide film is conductive
It is desirable to form by depositing -Sb or the like.

The thickness of the anodic oxide film is preferably in the range of 100 to 300 nm. When the thickness exceeds 1000 nm, the transparency is reduced, and the emission luminance of the organic EL element is reduced. Since the anodic oxide film has high strength, the presence thereof can protect the organic EL element mechanically or from moisture. Therefore, the thickness of the anodic oxide film is
It is desirable to form as thick as possible within the above range.

The thickness of the conductive metal layer after forming the anodic oxide film is preferably in the range of 10 to 100 nm. When the thickness exceeds 150 nm, the transparency is reduced, and the luminous efficiency of the organic EL device is reduced. The formation of the anodic oxide film can be performed by ordinary anodic oxidation treatment. According to the anodic oxidation treatment, a current flows to a portion where no anodic oxide film is formed, and oxidation proceeds, so that a uniform oxide film without defects such as pinholes can be formed. Further, since the thickness of the anodic oxide film can be controlled by the applied voltage, the thickness can be easily and extremely accurately controlled.

In the organic EL device of the present invention, at least the second electrode layer is divided into three sections separated from each other. Second
Only the electrode layer may be divided into three, or the light emitting layer thereunder may be divided into three. Only 3 for the second electrode layer
If it is divided into two, the display quality is slightly reduced, but it is easy to process it into a fine pattern. As the phosphor, one that emits three primary colors of R, G and B upon irradiation with ultraviolet light is used. As a phosphor that emits red light, an yttrium oxide phosphor (Y ₂ O ₃ ; Eu), an yttrium oxysulfide phosphor (Y ₂ O ₂ S; Eu), or the like can be used. Zinc sulfide phosphor (ZnS; Cu, ZnS; Cu, Al),
Cadmium sulfide phosphor ((ZN, Cd) S; Cu, A
1) can be used. As the phosphor that emits blue light, zinc sulfide phosphor (ZnS; Ag), calcium tungstate (CaWO ₄ ), or the like can be used.

The thickness of the phosphor is preferably in the range of 1 to several μm, but is not particularly limited. The thicker the effect, the greater the effect of protecting the light emitting layer. The phosphor can be provided on the second electrode layer, but may be provided between the light emitting layer and the second electrode layer as long as the phosphor is conductive.

[0024]

The present invention will be described below in detail with reference to examples. (Example 1) FIG. 1 is a schematic sectional view of an organic EL device of this example. This organic EL element has a glass substrate 1 and a thickness of 150 to 3 made of TiO ₂ formed on the glass substrate 1.
A reflective layer 2 having a thickness of 00 nm, a first electrode layer 3 having a thickness of 300 nm made of ITO and formed on the reflective layer 2, a light emitting layer 4 formed on the first electrode layer 3, and a light emitting layer formed on the light emitting layer 4; And a phosphor 6 formed on the second electrode layer 5.

In the above structure, the light emitting layer 4 comprises the first electrode layer 3
A hole transport layer 40 formed thereon, a light-emitting layer 41 formed on the hole transport layer 40 and separated from each other into three,
And an electron transport layer formed on each of the light emitting layers 41. The hole transport layer 40 is formed at 700 nm from a triphenyldiamine derivative (TPD),
41 is formed at 700 nm from polydimethylsilane, and the electron transport layer 42 is formed at 500 nm from Alq (aluminum triquinolinol complex) containing 0.1% by volume of quinacridone.

The second electrode layer 5 includes a conductive metal layer 50 formed on each electron transport layer 42 and a conductive metal layer 50
And an anodic oxide film 51 formed thereon. Then, as shown in FIG. 2, the conductive metal layer 50
An Al-Li alloy layer 52 having a thickness of 500 ° formed on 42;
500-mm thick In- formed on the Al-Li alloy layer 52
The anodic oxide film 51 is composed of ITO and the Sn alloy layer 53.

The phosphor 6 comprises an R phosphor 60 for emitting red light, a G phosphor 61 for emitting green light, and a B phosphor 62 for emitting blue light. 5 are each formed to a thickness of 50 μm. Hereinafter, a method for manufacturing the organic EL device will be described, and the detailed description of the configuration will be substituted. First, a glass substrate 1 was prepared, and a reflection layer 2 was formed from ZnO on the surface thereof by high frequency sputtering. Then, the surface of the reflective layer 2 is subjected to IT by high frequency sputtering.
The first electrode layer 3 was formed from O.

Next, a hole transport layer 40 is formed on the first electrode layer 3 by using a vacuum evaporation method, and then a luminous layer 41 and an electron transport layer 42 are formed in this order using a mask. The light emitting layer 4 divided into three was formed, respectively. Then, A is formed on the surface of the electron transport layer 42 of the light emitting layer 4 by using a similar mask.
An l-Li alloy layer 52 was formed, and then an In-Sn alloy layer was formed.

The device thus manufactured was immersed in an electrolytic solution consisting of a 1% by weight aqueous solution of phosphoric acid, and a DC voltage of 100 V was applied using the device as an anode and an Al plate having substantially the same area as the device as a cathode. Then, anodic oxidation was performed. The thickness of the anodic oxide film formed here is determined according to the applied voltage. If the applied voltage is 100 V, the thickness of the formed anodic oxide film is 150 nm. Therefore, the element thickness 200n
The conductive metal layer having a thickness of 150 nm from the surface is anodized to form an anodized film made of ITO,
A transparent second electrode layer 5 was formed.

Further, Y ₂ O ₂ S; Eu, ZnS; C
u, Al and ZnS; using Ag, and using a mask on each of the second electrode layers 5 to form R phosphors 60, G phosphors 61 and B
Each of the phosphors 62 was formed by printing. In the obtained organic EL device, ultraviolet light is emitted from the light emitting layer 4 by applying a DC voltage to the first electrode layer 2 and the second electrode layer 5. The ultraviolet light passes through the transparent second electrode layer 5 and irradiates the phosphor 6, and the phosphor 6 emits fluorescence. The fluorescent light is visually recognized through the second electrode layer 5, the light emitting layer 4, the first electrode layer 3, the reflective layer 2, and the glass substrate 1.

The ultraviolet light directed toward the glass substrate 1 is
The light is reflected by the reflection layer 2 and passes through the second electrode layer 5 to cause the phosphor 6 to emit light. Thereby, in the RGB light emitting organic EL device of this embodiment, high luminous efficiency can be obtained. Further, the anodic oxide film 51 has high strength and excellent adhesion to the In—Sn alloy layer 53. Further, since the adhesion between the anodic oxide film 51 and the phosphor 6 which is an inorganic substance is excellent, the light emitting layer 4 is protected by the anodic oxide film 51 and the phosphor 6 and has excellent durability.

[0032]

According to the RGB light emitting organic EL device of the present invention, since the organic EL layer only needs to emit monochromatic ultraviolet light, it is easy to process the light emitting layer into a fine pattern. The occurrence of pinholes and the like is also prevented. Therefore, the number of manufacturing steps is small, and a dark spot is unlikely to occur, so that the display quality is improved.

Further, since the organic layer is protected by the phosphor, the durability is improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an RGB light emitting organic EL device according to one embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a schematic sectional view of a conventional organic EL element.

FIG. 4 is a schematic sectional view of a conventional organic EL element.

FIG. 5 is a schematic sectional view of a conventional organic EL element.

[Explanation of symbols]

1: glass substrate 2: reflective layer 3: first electrode layer 4: light-emitting layer 5: second electrode layer 6: phosphor 40: hole transport layer 41: light-emitting layer 42: electron transport layer 50: conductive metal layer 51: Anodized film

Claims (1)

[Claims] 1. A transparent substrate, a transparent first electrode layer formed on the substrate, and a light emitting layer formed on the first electrode layer and formed of an organic material that emits ultraviolet light by applying a voltage, and a transparent first electrode layer. An organic EL layer composed of two electrode layers; and a phosphor formed on the organic EL layer and emitting light by ultraviolet light from the light emitting layer, wherein the organic EL layer has at least the second electrode layer separated from each other. The phosphors are composed of three types that emit visible light of three primary colors of R, G and B, respectively, and are provided corresponding to the sections of the organic EL layer, respectively. An RGB light-emitting organic EL device, which is configured to be visible from the front side of the substrate.