JPH11329739A - Organic el element and production of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element capable of circumventing saturation phenomenon of emission and serving high-intensity, highly-efficient emission. SOLUTION: This organic electroluminescence element comprises: a charge- injection and recombination area 11 whereto carriers (hole 25 and electron 27) are injected, where an exciton 29 is generated through recombination of injected charge; and a diffusion emission area 13 containing emission center 23 wherein emission is generated through a mechanism that the exciton 29 moves by diffusion to the emission center 23 and transfers its energy to the emission center 23 and the difusion emission area 13 is provided in contact with the charge-injection and recombination area 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (hereinafter simply referred to as "organic EL") device, and more particularly to a material for an organic light emitting layer of an organic EL device.

[0002]

2. Description of the Related Art A light-emitting element (organic EL element) utilizing organic electroluminescence obtained by applying an electric field to an organic material is disclosed in Document 1 (Document 1: "Organic EL").
ectroluminescent diodes '' CWTang and SAVanSlyk
e, Appl. Phys. Lett. vol 51 No.12 pp913-915 (1987)), Tang et al. have been active in research and development since realizing a light-emitting element that can emit light with high luminance at low voltage. Have been done.

The organic EL device of Document 1 is of a two-layer type including an anode, an organic hole transporting layer, an organic electron transporting light emitting layer, and a cathode. A hole injected from the anode and a hole injected from the cathode. The recombined electrons recombine, and the energy generated by the recombination excites the organic compound in the organic electron-transporting light emitting layer, and emits light unique to the compound.
In Reference 1, a DC voltage of about 10 V and a luminance of 1000 c
Surface emission exceeding d / m ² is obtained.

[0004] Further, research on a light emitting material and a charge transporting material, which are materials constituting an organic EL element having such a structure, has been advanced. As a result, in organic EL elements emitting blue light, green light, and orange light, etc. 100 cd / m
Practical elements with excellent durability have been developed such that the luminance half life is tens of thousands of hours when driven continuously at an initial luminance of ² .

[0005] As a red-emitting organic EL element, for example, as described in Document 2, an element using a rare-earth europium (Eu) complex as a light-emitting material has been proposed (Document 2: Kido). Other: Appl. Phys. Le
tt., vol. 65, No. 17, pp. 2124-2126 (1994)).

An organic EL device using an Eu complex as a light emitting material emits red light having a center wavelength of 615 nm due to Eu ions. The full width at half maximum of this emission spectrum is about 5 nm, which is very narrow. On the other hand, the same full-width at half maximum of the emission spectrum of an organic EL element that emits red light and uses a generally well-known dye-based light-emitting material is as wide as 50 to 100 nm. The narrow full width at half maximum of the spectrum indicates that the color purity is good and the chromatic aberration is reduced when the light passes through a lens system. Therefore, it is expected that such an organic EL element is applied as a light emitting element to a flat panel display, an optical print head, and an optical communication module.

Further, the organic E described in the above reference 2
In the L element, the energy of triplet excitons generated by recombination of carriers and not contributing to light emission conventionally can be used for light emission. Therefore, it is considered that the use of such a rare-earth complex as a light-emitting material can greatly improve the light-emitting efficiency as compared with a conventional device.

[0008]

However, when the density of charge injected into the organic EL device is increased in order to increase the luminous brightness of such an organic EL device, there arises a problem that the luminous efficiency is reduced.

Here, an organic EL using a rare-earth complex is used.
The device has a light emission lifetime of several hundred μs to several ms. This value is
The luminescent lifetime of a commonly used dye-based luminescent material is several n
Considering that s to several μs, it can be said that the light emission lifetime is long. This is because light emission of the rare earth complex occurs based on electronic transition between multiplet electronic states of the rare earth ion.

Further, since a certain percentage of the charges injected into the device are recombined to emit light, the injected charge density is proportional to the emission luminance. Therefore, when the injected charge density is increased, the time from light emission caused by one molecule of a luminescent excited molecule to the next light emission involving the molecule (referred to as a light emission time interval) becomes shorter. For example, the thickness of the light emitting layer of the organic EL element is set to 30 nm, the doping amount of the rare earth complex to the light emitting layer is set to 10%, and the ratio of light emitting excitons generated by charge recombination is set to 25%. When all the electrons contribute to light emission, when the injected charge density is 10 mA / cm ² , the light emission time interval per molecule is calculated to be about 20 ms. The light emission time interval when the injected charge density is 1 A / cm ² is calculated to be about 0.2 ms. Therefore, as described above, the emission lifetime of the organic EL device using the rare earth complex is several hundred μs.
In the case of the latter injected charge density, when the energy of the luminescent exciton generated by the recombination of the charge is to excite the rare earth ion which is the luminescence center, it is still in the luminescence state, Rare earth ions are generated that have not returned to the ground state they can. Therefore, when the injected charge density is increased and the light emission time interval becomes shorter than the light emission lifetime, the light emission luminance is saturated.

Conventionally, in a light emitting layer in which charge recombination, generation of excitons, and light emission are performed, the thickness of the light emitting layer is several nm to several tens nm, so that the number of light emitting centers that can be accommodated is limited. In addition, a diffusion region of excitons generated in the light emitting layer cannot be sufficiently provided. For this reason, the number of excitons that transfer energy per light emitting center increases.

Accordingly, the number of luminescent excitons that cannot participate in light emission increases, and as a result, luminous efficiency decreases. Such a phenomenon is referred to herein as a light emission saturation phenomenon.

Therefore, the organic EL device can avoid the saturation phenomenon of light emission, and can emit light with high luminance and high efficiency.
The advent of devices and methods for their manufacture has been desired.

[0014]

For this reason, the inventors of the present invention have conducted intensive studies and, as a result, have paid attention to the property that the diffusion transfer distance of triplet excitons involved in light emission of rare earth complexes is long, and this property has been studied. The present inventors have found out the structure of an organic EL device that can provide high-luminance and high-efficiency light emission by utilizing the method described above.

According to the organic EL device of the present invention, a charge injection / recombination region where charges are injected and excitons are generated by recombination of the injected charges, and a light emitting center are provided.
And a diffused light emitting region in which the exciton diffuses and moves to the light emitting center and transfers energy to the light emitting center to generate light emission. The diffused light emitting region is in contact with the charge injection / recombination region. Features.

This makes it possible to separate the region where excitons are generated from the region where light is emitted. Therefore, a desired number of light-emitting centers can be present at an appropriate density in a region where light is emitted. Also,
The diffusion movement distance of the triplet exciton can be sufficiently set. As a result, even if the injected charge density is increased, the number of excitons per light emission center does not change much. For this reason, even if the injected charge density is increased, there is no possibility that the light emission time interval per one light emission center becomes shorter than the light emission lifetime. Therefore, the phenomenon of saturation of light emission can be avoided, and high-luminance light emission can be achieved in accordance with an increase in light emission efficiency and an increase in injected charge density.

Preferably, the charge injection / recombination region includes an anode, an organic layer and a cathode, and the diffused light emitting region includes a host material and a rare earth complex as a light emitting center. .

The charge injection / recombination region is formed by a conventional organic E
It has the same structure as the L element. That is, this region has an anode, an organic layer and a cathode. Holes are injected from the anode and electrons are injected from the cathode into the organic layer, and the holes and electrons are recombined in the organic layer to generate excitons. The organic layer preferably includes at least a layer that recombines electric charges to generate excitons (here, referred to as a recombination layer). This recombination layer is a layer corresponding to a light emitting layer of a conventional organic EL element, and here is a layer that particularly generates triplet excitons. The organic layer may include a recombination layer and a hole transport layer. At this time, the hole transport layer is provided between the anode and the recombination layer. Thereby, the efficiency of injecting holes into the recombination layer can be improved. The organic layer may include a recombination layer and an electron transport layer. At this time, the electron transport layer is provided between the cathode and the recombination layer. Thereby, the efficiency of injecting electrons into the recombination layer can be improved. Further, the organic layer may be configured such that a hole transport layer, a recombination layer, and an electron transport layer are included in this order from the anode side. Thereby, the efficiency of charge injection into the recombination layer can be improved. In addition, a hole injection layer may be interposed between the anode and the hole transport layer in order to improve the efficiency of charge injection into the recombination layer, or the cathode and the electron transport layer may be used for the same purpose. And an electron injection layer may be interposed therebetween.

The diffuse light emitting region is a region in which triplet excitons generated in the organic layer move by diffusion and generate light emission due to the triplet excitons. For this reason, this region preferably contains a host material and a rare earth complex. The triplet exciton that diffuses and moves in the diffusion light emitting region collides with the rare earth complex. At that time, the energy of the triplet exciton is transferred to the rare earth complex, and finally light is emitted from the rare earth ion. This light is emitted from the organic EL device of the present invention.

Preferably, the material molecules constituting the organic layer have a triplet level higher than the triplet energy level of the host material, and the host material is composed of a triplet of the rare earth complex. It is preferable to have a triplet level higher than the energy level.

Thus, the energy of the triplet exciton generated in the organic layer can be efficiently transferred to the triplet level of the rare-earth complex as the light-emitting center via the triplet energy level of the host material. it can.

Preferably, the charge injection / recombination region is a region narrower than a range in which triplet excitons diffuse.

Thus, the generated triplet exciton does not return to the ground state in the charge injection / recombination region before diffusing to the diffusion light emitting region. Can be diffused and moved to the diffused light emitting region provided. Considering the diffusion movement distance of the triplet exciton, it is preferable that the structure be such that the triplet exciton can reach the diffused light emitting region from any position in the charge injection / recombination region at a distance of 1 μm or less.

Preferably, the diffused light-emitting region is a region wider than a range in which triplet excitons are diffused.

Thus, a desired number of light emitting centers can be provided in the diffuse light emitting region at an appropriate density. Further, a sufficient diffusion region for triplet excitons can be secured. Therefore, there is no possibility that the light emission time interval per light emission center becomes shorter than the light emission life, and the light emission saturation phenomenon can be avoided. Considering the diffusion movement distance of the triplet exciton of about 10 μm, it is preferable that the diffused light emitting region is provided over a region at least several μm away from a portion in contact with the charge injection / recombination region.

Further, in the organic EL device of the present invention,
Preferably, an organic layer and a cathode are provided on the anode in this order, and a diffused light emitting region is provided so as to cover the entire surface of the cathode and the upper surface of the anode.

According to the organic EL device having such a structure,
First, when a DC voltage is applied between the anode and the cathode, excitons are generated in the organic layer sandwiched between the cathode and the anode, and the excitons diffuse into the diffused light emitting region in contact with the organic layer. Among these excitons, triplet excitons diffuse and move in the diffused light emission region, reach the light emission center, and transfer energy. Then, light is emitted from the light emitting center. Therefore, the organic layer is used as a layer for generating excitons, and by utilizing the characteristics of triplet excitons having a long diffusion movement distance, light emission is performed in a diffused light emitting region that can be formed as a wider region than a conventional light emitting layer. This can be done by moving the child. Therefore, when the charge density injected into the organic EL element having such a structure is increased, light emission efficiency is improved and light emission with high luminance is obtained.

Preferably, a hole is formed in the cathode, and the organic layer and the diffused light emitting region are in contact with each other through the hole.

The charge injection / recombination region needs to be a region narrower than the range in which the triplet exciton diffuses and moves. Here, the charge injection / recombination region is composed of an anode, an organic layer, and a cathode. For this reason, if at least the hole is formed in the cathode, the triplet exciton generated in the charge injection / recombination region around the hole can be diffused and moved to the diffusion light emitting region through the hole. . If a plurality of holes are formed in the cathode, the charge injection / recombination region can be made substantially smaller than the diffusion movement range. That is, the triplet exciton can reach the diffusion light emitting region from any position of the charge injection / recombination region at a short distance.
Further, even if the hole is formed, the remaining cathode is not cut but is electrically connected, so that charge injection into the charge injection / recombination region is easy.

In manufacturing an organic EL device including a charge injection / recombination region including an anode, an organic layer and a cathode, and a diffused light emitting region in contact with the charge injection / recombination region, After stacking the cathode in this order,
At least partially removing the cathode to form a charge-injecting recombination region with the remaining cathode portion, the organic layer portion and the anode portion located below the cathode portion, and exposed by the removal. Forming a diffused light emitting layer over the portion and the charge injection recombination region.

It is preferable that the removal performed at least partially on the cathode is performed using a physical method.

As a physical method, it is preferable to use, for example, a sputtering method. After forming an organic layer and a cathode on the anode, for example, a SiO
_Two films are formed to a thickness of 0.1 nm. As a result, a mesh-like SiO ₂ film having a large number of hole shapes is formed. Then, by performing sputtering using this SiO ₂ film as a sputtering mask, the portion of the cathode exposed from the holes of the SiO ₂ film is removed. It is preferable that the depth of the hole formed by sputtering is a depth that reaches the surface of the organic layer even if it is shallow, and is preferably a depth at which a cross section of the organic layer is exposed.

As a physical method, a mechanical method may be used. For example, a sand blast method is preferably used. Further, for example, a fibrous body immersed in an adhesive containing an epoxy resin or the like may be attached to the surface of the cathode, and the fibrous body may be peeled off to partially remove the cathode or the cathode and the organic layer.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an organic EL device using the light emitting material of the present invention will be described below with reference to the drawings. It should be noted that the drawings merely schematically show the shapes, sizes, and arrangements of the components so that the present invention can be understood, and thus the present invention is not limited to the illustrated examples.

FIG. 1 is a diagram showing a schematic configuration image of an organic EL device for describing an embodiment of the present invention.

The organic EL device of the present invention has a charge injection / recombination region 11 and a diffused light emitting region 13 in contact with the charge injection / recombination region 11. The charge injection / recombination region 11 is a region of the organic layer 17 where both the anode 15 and the cathode 19 are in contact with each other. The diffused light emitting region 13 includes a host material 21 and a rare earth complex serving as a light emitting center 23.

The principle of light emission of this organic EL device will be described.

First, when a DC voltage is applied between the anode 15 and the cathode 19, the holes 25 and the cathode 1
From 9, electrons 27 are respectively injected into the organic layer 17. In the organic layer 17, these charges (holes 25 and electrons 27)
Are recombined to generate excitons 29. In the present invention, the energy of triplet excitons among the generated excitons 29 is used for light emission. The triplet excitons 29 diffuse and move from the organic layer 17 to the diffused light emitting region 13 in contact with the organic layer 17. The triplet exciton 29 collides with the light emitting center 23 in the diffuse light emitting region 13. At this time, the triplet exciton 29 transfers energy to the rare earth complex which is the light emission center 23. In the rare earth complex 23, this energy is transferred to the emission energy level of the rare earth ion, and light emission is generated from the rare earth ion. This light emission is light emission obtained from the organic EL device of the present invention (FIG. 1).

Therefore, a region for generating excitons (charge injection / recombination region 11) and a region for generating light emission (diffused light emitting region 13) can be separated. As a result, a desired number of light-emitting centers 23 can be provided at an appropriate density in the diffuse light-emitting region 13 that is a region where light emission occurs. Further, the moving distance of the triplet exciton 29 can be sufficiently secured. As a result, even if the charge density injected into the device is increased, the number of excitons colliding per light emitting center is not significantly changed. Therefore, even if the injected charge density is increased, there is no possibility that the light emission time interval per one light emission center becomes shorter than the light emission lifetime. Therefore, the saturation phenomenon of light emission can be avoided,
It is possible to achieve high-luminance light emission in accordance with an increase in luminous efficiency and an increase in injected charge density.

The material molecules constituting the organic layer have a triplet level higher than the triplet level of the host material in the diffused light emitting region. The host material has a triplet level equal to or higher than the triplet level of the rare earth complex. For this reason, triplet excitons generated in the organic layer diffuse and move to a diffused light emitting region having a low energy level. In addition, triplet excitons collide with rare earth complexes with lower energy levels in the diffuse emission region. Thereby, energy can be efficiently transferred to the rare earth complex.

The charge injection / recombination region is a region narrower than a region where triplet excitons are diffused. The diffused light emitting region is a region wider than the range in which triplet excitons are diffused. Thereby, the generated triplet exciton does not return to the ground state in the charge injection / recombination region before diffusing to the diffusion light emitting region, and is provided from the charge injection / recombination region in contact with this region. Can be diffused to the diffused light emitting region. In addition, a desired number of light emitting centers can be provided in the diffuse light emitting region at an appropriate density, and the diffusion region of triplet excitons can be sufficiently secured. Therefore, there is no possibility that the light emission time interval per one light emission center becomes shorter than the light emission life,
The saturation phenomenon of light emission can be avoided.

Further, the organic layer preferably includes a recombination layer for recombining electrons and holes. In order to improve the efficiency of charge injection into the recombination layer, the organic layer may be configured to include a recombination layer and a hole layer transport layer,
It may be configured to include a recombination layer and an electron transport layer. Further, the hole transport layer, the recombination layer, and the electron transport layer may be included in this order from the anode side. In addition, a hole injection layer may be interposed between the anode and the hole transport layer in order to improve the efficiency of charge injection into the recombination layer, or the cathode and the electron transport layer may be used for the same purpose. And an electron injection layer may be interposed therebetween.

The anode is usually provided on a substrate. This substrate typically comprises a transparent substrate. For example, it can be composed of a glass substrate.

For the anode, a metal or an electrically conductive material that transmits EL light emission and has a large work function (about 4.0 eV or more) is used. Generally, indium tin oxide (IT
O) is used.

In addition, for example, magnesium,
Alternatively, an alloy of magnesium and silver or an alloy of aluminum and lithium is used.

For the recombination layer, an oxadiazole derivative (PBD) or the like conventionally used as a material for the light emitting layer is used.

The thickness of each of the anode and cathode layers is set to a suitable value according to the design.

The hole transport layer 19 provided between the anode and the recombination layer is made of, for example, N, N'-diphenyl-N,
N ′-(3-methylphenyl) -1,1′-biphenyl-4,4′-diamine (hereinafter, TPD), N, N′-
Diphenyl-N, N '-(1-naphthyl) -1,1'-
It is composed of a diamine derivative such as biphenyl-4,4'-diamine (hereinafter referred to as NPD) or an organic or inorganic material such as a triphenylamine-based, triphenylmethane-based, pyrazoline-based, hydrazone-based, or amorphous silicon-based material. Is done.

The electron transport layer provided between the cathode and the recombination layer may be formed of a metal such as a quinolinol complex such as tris (8-hydroxyquinolinol) aluminum (hereinafter referred to as Alq) or a porphyrin complex. Complexes,
Oxadiazole derivatives, cyclopentadiene derivatives,
A perylene derivative or the like can be used.

[0050]

EXAMPLES Next, the organic EL device of the present invention will be described more specifically with reference to examples. However, the amounts of chemicals used, numerical conditions such as processing temperature and processing time, and chemicals used in the following description are merely examples within the scope of the present invention.

<First Embodiment> In the first embodiment, FIG.
Using an organic EL device having a structure as shown in FIG. 1, it is confirmed that triplet excitons diffuse from the charge injection / recombination region to the diffused light emitting region to emit light.

FIG. 2 is a schematic diagram showing the structure of the organic EL device of the first embodiment, which is shown by a cross-section.

In this example, an organic EL device is manufactured as follows.

First, a 200 nm-thick ITO film is formed on the glass substrate 31 by using an electron beam evaporation method. The sheet resistance of this ITO film was 10Ω / □ (square). Next, the well-known photolithography and subsequent etching are performed to process the ITO film into a stripe shape having a width of 2 mm to form the anode 15. Thereafter, the glass substrate 31 on which the anode 15 was formed was washed with acetone and 2
-Washing and drying with propanol and transfer into a vacuum deposition apparatus for organic film formation;

Next, an organic layer 17 is formed on the anode 15. In this example, the organic layer 17 includes a hole transport layer 33, a recombination layer 35, and an electron transport layer 37.

First, the hole transport layer 33 is formed on the anode 15.

In this example, N, N′-diphenyl-N, N′-bis (3-methylphenyl) 1,1′-biphenyl-4,4′-diamine (hereinafter, referred to as N) -N-diphenyl-N, N′-bis (3-methylphenyl) TPD) is used. The TPD is put into a crucible in a vacuum evaporation apparatus, and the crucible is heated by resistance wire. In this example, the temperature of the crucible is controlled so that the deposition rate becomes 0.3 nm / sec. A contact mask corresponding to a desired shape of the organic layer 17 is provided on the substrate 31 including the anode 15, and a shutter between the crucible and the substrate 31 is opened to deposit TPD on the substrate 31. The hole transport layer 33 having a thickness of 40 nm is formed on the display of the crystal resonator type film thickness meter.

Next, a recombination layer 35 is formed on the hole transport layer 33.

In this example, as the material of the recombination layer 35,
An oxadiazole derivative (hereinafter, referred to as PBD) is used. The recombination layer 35 having a thickness of 30 nm is formed on the hole transport layer 33 by a vacuum deposition method using a contact mask similarly to the hole transport layer 33 described above.

Subsequently, the electron transport layer 37 is formed on the recombination layer 35.
To form

In this example, tris (8-hydroxyquinolinol) aluminum (referred to as Alq) is used as the material of the electron transport layer 37. The above-described hole transport layer 3
Similarly to 3 and the recombination layer 35, an electron transport layer 37 having a thickness of 20 nm is formed on the recombination layer 35 at a deposition rate of 0.2 nm / sec by a vacuum deposition method using a contact mask.

After that, the substrate 31 on which the anode 15 and the organic layer 17 are formed is transferred to a vacuum deposition apparatus for depositing a metal film, and a cathode 19 is formed on the organic layer 17.

In this example, an alloy of magnesium and silver (Mg: Ag = 10: 1) is used as the material of the cathode 19. 10 by vacuum evaporation using a contact mask
The cathode 19 having a thickness of 0 nm is formed on the electron transport layer 37. The planar shape of the cathode 19 when viewed from above is substantially the same as that of the electron transport layer 37. However, the planar shape of the cathode 19 should not be larger than that of the electron transport layer 37 so that portions other than the electron transport layer 37 do not contact the cathode 19. The edge 37a of the electron transport layer 37 and the corresponding edge 19a of the cathode 19 are formed as close as possible. In this example, the edge 37a of the electron transport layer 37 is formed.
The position of the contact mask is adjusted so that the distance between the contact mask and the edge 19a of the cathode is 2 μm or less.

Thereafter, the substrate 31 on which the anode 15, the organic layer 17 and the cathode 19 are formed is transferred to a vacuum deposition apparatus for depositing an organic film, and a diffused light emitting region 13 is formed on the entire upper surface of the substrate 31 including on the cathode 19. I do.

In this example, the diffused light emitting region 13 is composed of a host material and a rare earth complex serving as a light emitting center.
Here, the rare earth complex is a europium (Eu) complex represented by the following formula (1) (hereinafter referred to as Eu (DBM) ₃ Phen), and the host material is a gadolinium (Gd) complex represented by the following formula (2) (hereinafter referred to as Eu). , Gd (DBM) ₃ Phen
Called. ). This Gd (DBM) ₃ Phen has a triplet level equivalent to Eu (DBM) ₃ Phen and is a non-light emitting material.

[0066]

Embedded image

Eu (DBM) ₃ Phen and Gd (DB
M) ₃ Phen and a separate crucible in a vacuum evaporation apparatus, and heat the crucible by resistance wire. Here, Eu (DB
M) ₃ Phen and Gd (DBM) ₃ ratio of deposition rate of the Phen is so 1:10, to control the temperature of each crucible. When the ratio of the deposition rates is 1:10 (Eu (D
BM) ₃ Phen: After confirming that it was constant at Gd (DBM) ₃ Phen), the shutter between the substrate 31 and the crucible was opened, and the diffused light emitting region 1 was placed above the substrate 31.
3 material is deposited. 10 on the crystal oscillator type thickness gauge display
μm thick Eu (DBM) ₃ Phen and Gd (DB
M) A diffused light emitting region 13 which is a co-deposited film with ₃ Phen is formed. In the diffuse light emitting region 13, Gd
(DBM) ₃ Phen to Eu (DBM) ₃ Phen is uniformly dispersed about 10%. Thus, the organic EL device of the first embodiment is obtained (FIG. 2).

When a DC voltage was applied to the device so that the anode 15 was positive and the cathode 19 was negative, emission of two colors of blue-green light and red light was observed. Blue-green light is emitted from both electrodes (anode 15 and cathode 1).
9), that is, in the charge injection / recombination region 11, the red light emission is generated in the charge injection / recombination region 1.
1 from the edge of the organic layer 17
It occurs to spread to three. Light emission becomes weaker as the distance from the edge of the organic layer 17 increases, but occurs over a region several μm away from the edge. The diffuse light emitting region 13 where red light emission occurs is a region where no electric field is applied. Therefore, since the electrically neutral excitons spread from the organic layer 17 in all directions of the diffused light emitting region 13, light emission surrounding the charge injection / recombination region 11 can be obtained.

The blue-green light emission is light emission based on the transition from the excited singlet of oxadiazole to the ground state. Then, in red emission, triplet excitons generated by recombination of electric charges diffuse and move to the diffused light emitting region 13, and Eu (DB)
M) ₃ Phen collides and its energy is Eu (DB)
It is speculated that M) ₃ Phen was propagated to the triplet level of the ligand having the β-diketone and was obtained as a characteristic red emission of Eu ions.

Thus, it was confirmed that the triplet exciton diffused and moved from the charge injection / recombination region 11 to the diffused light emitting region 13 to emit light.

<Second Embodiment> In the organic EL device according to the present invention having the charge injection / recombination region and the diffused light emitting region, in order to further improve the luminous efficiency, the position of the charge injection / recombination region from Also, the structure must be such that triplet excitons can reach the diffused light emitting region at a distance of 1 μm or less. Further, the diffused light emitting region needs to be formed to have a size extending to a region separated from the charge injection / recombination region by several μm or more. This is because the triplet exciton generated in the charge injection / recombination region diffuses and moves by about 10 μm.

Therefore, as a second embodiment, an example of a method of manufacturing an organic EL device having a charge injection / recombination region and a diffused light emitting region having the above-described structure will be described with reference to FIGS. .

FIG. 3 is a schematic manufacturing process diagram of the organic EL device of this embodiment, which is shown by a cross-section. FIG. 4 is a plan view of the cathode of the organic EL element of this embodiment as viewed from above.

Here, only points different from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

The organic EL device according to the second embodiment is manufactured as follows.

First, the charge injection / recombination region 11 is formed. The charge injection / recombination region 11 includes an anode 15, an organic layer 17 and a cathode 19.

Here, the anode 15 made of ITO is formed on the glass substrate 31 in the same manner as in the first embodiment.

Next, an organic layer 17 is formed on the anode 15.
In this example, the organic layer 17 is composed of the hole transport layer 33 and the recombination layer 3.
5 and the electron transport layer 37.

The hole transport layer 33 is formed on the entire surface of the glass substrate 31 including the anode 15 by using a vacuum evaporation method.
TPD is formed to a thickness of 40 nm. At this time, the TPD is placed in a crucible in the vacuum evaporation apparatus, and the crucible is heated by resistance wire. The temperature of the crucible is controlled so that the vapor deposition rate of TPD becomes 0.3 nm / sec. Subsequently, a recombination layer 35 is formed on the hole transport layer 33. Recombination layer 35
Is a co-deposited layer of PBD and Eu (DBM) ₃ Phen. Here, the hole transport layer 3 is set such that the ratio of the deposition rates of Eu (DBM) ₃ Phen and PBD is 1: 3.
A recombination layer 35 having a thickness of 20 nm is formed on the substrate 3 by vacuum deposition. Next, an electron transport layer 37 is formed on the recombination layer 35. In this example, the material of the electron transport layer 37 is A
Use lq. An electron transport layer 37 having a thickness of 20 nm is formed on the recombination layer 35 at a deposition rate of 0.2 nm / sec by using a vacuum deposition method.

Thereafter, the substrate 31 on which the anode 15 and the organic layer 17 are formed is transferred to a vacuum evaporation apparatus for metal film evaporation, and a cathode 19 is formed on the organic layer 17.

In this example, magnesium is used as the material of the cathode 19. The cathode 19 having a thickness of 100 nm is formed on the electron transport layer 37 by a vacuum deposition method.

On the upper surface of the cathode 19, SiO
_{The two} films 41 are formed to a thickness of 0.1 nm. This film thickness is measured by a quartz oscillator film thickness meter, and the SiO ₂ film 41 having a thickness of 0.1 nm measured by this film thickness meter has a large number of holes 4.
It is a mesh-like film on which 1a is formed. The cathode 19 is exposed from the hole 41a (FIG. 3).
(A)).

Next, the substrate 31 on which the anode 15, the organic layer 17, the cathode 19, and the SiO ₂ film 41 are formed is put in a magnetron sputtering apparatus, and sputtering is performed by argon ions. The sputtering conditions are such that the gas pressure is 5 milliTorr and the sputtering power is 100W. When this sputtering is performed, the Si provided on the cathode 19
The O ₂ film 41 functions as a mask, and the holes 41a of the SiO ₂ film
The cathode 19 exposed from is etched. The etching depth may be such that a hole 43 penetrating the cathode 19 is formed and the organic layer 17 is exposed from the hole 43. Preferably, the cross section 35a of the recombination layer 35 is removed until the organic layer 17 under the cathode 19 is removed.
3 is preferably etched to a depth such that it is exposed. In this example, the anode 15 is deep enough to expose the anode 15 from the hole 43 (FIG. 3B).

Here, reference is made to FIG. FIG. 4 shows a state of the cathode after the sputtering. The average value of the planar width of the removed portion 19x was approximately 10 μm, and the average value of the planar width of the remaining portion 19y was approximately 0.5 μm.

The cathode must not be cut by sputtering. The remaining portion 19y has a mesh-like structure and is electrically connected (FIG. 4).

Thereafter, the substrate 31 on which the anode 15, the organic layer 17 and the cathode 19 are formed is transferred to a vacuum deposition apparatus for depositing an organic film. The diffusion light emitting region 13 is formed.

In this example, as in the first embodiment, the diffused light emitting region 13 is formed by Eu (DBM) ₃ Phen and Gd (DB
M) It is composed of a co-deposited film with ₃ Phen. Eu (DBM) ₃ Phen and Gd (DBM) ₃ P
The co-deposition film 13 is formed to a thickness of 10 μm with the ratio of the deposition rate to hen being 1:10 (FIG. 3C).

Thus, the organic EL device of the second embodiment is obtained. The size of the plane of this element as viewed from above is 2
mm × 2 mm.

When a DC voltage was applied to the device so that the anode 15 became positive and the cathode 19y became negative, light emission started when the applied voltage was 6 V, and
The highest luminance was obtained when a voltage of V was applied. Also,
Light emission was red light having a peak at a wavelength of 615 nm from the entire surface of the device.

In the organic EL device of the present invention, the charge injection / recombination region 11 includes the cathode 19y, the organic layer 17 and the anode 15
With That is, it is a region where an electric field is generated by applying a voltage between the cathode 19y and the anode 15. The charge injection / recombination region 11 of the organic EL device of the second embodiment is a cathode 19y remaining in a mesh shape, and an organic layer 17 and an anode 15 located below the cathode 19y. The width of the remaining cathode portion 19y is as narrow as about 0.5 μm as described above. Therefore, the triplet exciton can reach the diffused light emitting region 13 only by moving a distance of 1 μm or less from any position of the charge injection / recombination region 11.

Therefore, there is no possibility that the triplet exciton relaxes in the charge injection / recombination region 11 and returns to the ground state. Therefore, the number of triplet excitons moving to the diffusion light emitting region 13 increases, and as a result, triplet excitons colliding with the light emission center increase, so that the luminous efficiency can be improved.

The diffusion light emitting region 13 is formed over the entire surface of the device, and has a sufficient thickness of 10 μm. Therefore, a desired number of rare earth complexes, which are light emission centers, can be included in this region 13. Also,
Since the region 13 has a sufficient size, the light emitting center is not contained at a high density, and the diffusion region of the triplet exciton which diffuses and moves can be sufficiently obtained. For this reason, even if the density of charge injected into the element is increased to achieve high-luminance light emission, the light emission time interval per molecule of the light emission center can be made longer than before. Therefore, the light emission time interval does not become shorter than the light emission lifetime, so that the light emission efficiency can be improved.

The red light emission from the entire surface of the element is due to the fact that the components constituting the charge injection / recombination region 11 are Eu (D
Since BM) ₃ Phen is contained, this Eu complex also functions as a light emission center, and E
This is because light emission from u ions occurred.

Further, the cathode 19 as shown in FIG.
In order to form the structure of y, not only the sputtering method but also a laser ablation method of irradiating a film-shaped cathode surface with a laser and partially removing the cathode with its energy may be used.

<Third Embodiment> As a third embodiment, referring to FIG. 5, 1 μm from the charge injection / recombination region to the diffused light emitting region from any position as described in the second embodiment. Charge injection and recombination regions such that triplet excitons can reach at the following distances, and can contain a desired number of emission centers,
A method of manufacturing an organic EL device having a diffused light emitting region capable of sufficiently securing a triplet exciton diffusion region, which is different from the second embodiment, will be described.

FIG. 5 is a view for explaining a method of manufacturing an organic EL device according to the third embodiment, and schematically shows a cross-section.

Hereinafter, points different from the second embodiment will be described, and detailed description of the same points will be omitted.

The organic EL device according to the third embodiment is manufactured as follows.

First, the anode 15 is formed on the glass substrate 31 in the same manner as in the second embodiment, and then the organic layer 17 is formed by using a vacuum deposition method. The organic layer 17 of this example includes a hole transport layer 33, a recombination layer 35, and an electron transport layer 37 as in the second embodiment. The hole transport layer 33 on the anode 15
Then, a TPD is formed to a thickness of 40 nm, and then a layer of a co-deposited film of PBD and Eu (DBM) ₃ Phen is formed on the hole transport layer 33 to a thickness of 20 nm. This layer is referred to as a recombination layer 35. Subsequently, Alq is formed on the recombination layer 35 as the electron transport layer 37 to a thickness of 20 nm. next,
As in the second embodiment, a magnesium film is deposited on the electron transport layer 37 to a thickness of 100 nm by using a vacuum deposition method.

Thereafter, in this embodiment, a fibrous body 51 impregnated with an adhesive resin made of an epoxy resin is prepared. In this example, for example, Araldite AR-R30 (trade name, manufactured by Showa Polymer Co., Ltd.) is used as the epoxy resin. Further, as the fibrous body, for example, Bencott (trade name: manufactured by Asahi Kasei Corporation) is used.

Then, a fibrous body (Bencott) 51 impregnated with the Araldite AR-R30 is lightly brought into contact with the upper surface of the magnesium film.
Is peeled off (FIG. 5).

As a result, the magnesium film and the organic layer 17 are partially removed, and a large number of holes 53 are formed on the surface of the magnesium film. Then, the remaining magnesium film 49y serves as a cathode.
By the organic layer 17 and the anode 15 located below y
The charge injection / recombination region 11 of this embodiment is configured.

Thereafter, in the same manner as in the second embodiment, the diffused light emitting region 13 is formed on the entire surface of the substrate 31 including the cathode 49y and the inside of the hole 53. E using a vacuum deposition method
A co-deposited film 13 of u (DBM) ₃ Phen and Gd (DBM) ₃ Phen is formed to a thickness of 10 μm.

Thus, the organic EL device of the third embodiment is obtained. The size of a plane of the entire element viewed from above is 2 mm × 2 mm.

When a DC voltage is applied to this device, red light emission is obtained from the entire surface of the device.

As described above, the fibrous body 51 impregnated with the adhesive resin is brought into contact with the magnesium film and peeled off to form a mesh-like cathode 49 having a large number of holes 53.
y is formed. At this time, if the fibers in the fibrous body 51 are more densely in contact with the magnesium film, the width of the portion 49y of the magnesium film remaining after the fibrous body 51 is separated can be reduced. Thus, the triplet exciton becomes
From any position of the charge injection / recombination region 11, the diffusion light emission region 13 can be reached only by moving a short distance.

Therefore, the same effects as in the second embodiment can be obtained.

Further, after forming an organic layer and a film-like cathode on the anode, the structure is put in a sandblasting apparatus and sandblasting is performed to form a mesh-like cathode having a large number of holes. can do.

[0109]

As is clear from the above description, the organic EL device of the present invention has a charge injection / recombination region and a diffused light emitting region in contact with the charge injection / recombination region.

Thus, the charge injection / recombination region becomes a region where charges are injected and recombination of charges occurs to generate triplet excitons. The diffused light emitting region is a region in which triplet excitons diffused and moved from the charge injection / recombination region transfer energy to the light emitting center to emit light. In this manner, a region where excitons are generated and a region where light emission is generated can be separated. Therefore, a desired number of light-emitting centers can be present at an appropriate density in a region where light is emitted. Further, the diffusion movement distance of the triplet exciton can be sufficiently secured. As a result, even if the injected charge density is increased, the number of excitons per light emission center does not change much. For this reason,
Even if the injected charge density is increased, there is no possibility that the light emission time interval per one light emission center becomes shorter than the light emission lifetime. Therefore, the phenomenon of saturation of light emission can be avoided, and high-luminance light emission can be achieved in accordance with an increase in light emission efficiency and an increase in injected charge density.

In manufacturing an organic EL device including a charge injection / recombination region including an anode, an organic layer and a cathode, and a diffused light emitting region in contact with the charge injection / recombination region, After stacking the cathode in this order,
At least partially removing the cathode to form a charge-injecting recombination region with the remaining cathode portion, the organic layer portion and the anode portion located below the cathode portion, and exposed by the removal. Forming a diffused light emitting layer over the portion and the charge injection recombination region.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an organic E used for describing an embodiment of the present invention.
It is a schematic structure image figure of L element.

FIG. 2 is a schematic configuration diagram of an organic EL element for describing a first embodiment.

FIGS. 3A to 3C are schematic manufacturing process diagrams of an organic EL device for explaining a second embodiment. FIGS.

FIG. 4 is a top plan view of a cathode of an organic EL element, which is used for describing a second embodiment.

FIG. 5 is a diagram for explaining a method of manufacturing an organic EL device according to a third embodiment.

[Explanation of symbols]

11: charge injection / recombination region 13: diffused light emitting region (co-deposited film) 15: anode 17: organic layer 19: cathode 19a: edge of cathode 19x: removed portion 19y: remaining portion (cathode) 21: host material 23: emission center (rare-earth complex) 25: hole 27: electron 29: exciton (triplet exciton) 31: substrate (glass substrate) 33: hole transport layer 35: recombination layer 35a: cross section of recombination layer 37: electron transport layer 37a: edge of electron transport layer 41: SiO ₂ film 41a: hole 43, 53: hole 49y: remaining magnesium film (cathode) 51: fibrous body

Claims (9)

[Claims] A charge injection / recombination region in which charge is injected and an exciton is generated by recombination of the injected charge; and a light emitting center, wherein the exciton diffuses and moves to the light emitting center. An organic EL device, comprising: a diffused light emitting region that emits light by transferring energy to a light emitting center, wherein the diffused light emitting region is provided in contact with the charge injection / recombination region. 2. The organic EL device according to claim 1, wherein the charge injection / recombination region includes an anode, an organic layer, and a cathode, and the diffusion light emitting region includes a host material and a rare earth as the light emitting center. An organic EL device comprising a complex. 3. The organic EL device according to claim 2, wherein the material molecules forming the organic layer have a triplet level higher than a triplet energy level of the host material, An organic EL device, wherein the host material has a triplet level higher than a triplet energy level of the rare earth complex. 4. The organic EL device according to claim 1, wherein the charge injection / recombination region is a region narrower than a range in which a triplet exciton is diffused. 5. The organic EL device according to claim 1, wherein the diffused light emitting region is a region wider than a range in which a triplet exciton is diffused. 6. The organic EL device according to claim 1, further comprising an organic layer and a cathode on the anode in this order, wherein the diffusion is performed so as to cover the entire surface of the cathode and the upper surface of the anode. Organic E characterized by having a light emitting region
L element. 7. The organic EL device according to claim 6, wherein a hole is formed at least in the cathode, and the organic layer and the diffused light emitting region are in contact with each other through the hole. An organic EL device comprising: 8. When manufacturing an organic EL device having a charge injection / recombination region including an anode, an organic layer and a cathode, and a diffused light emitting region in contact with the charge injection / recombination region, the anode and the organic layer And a step of laminating the cathode in this order, and thereafter, at least partially removing the cathode, the remaining cathode portion, and the organic layer portion and the anode portion located under the cathode portion, A method for manufacturing an organic EL device, comprising: forming a charge injection / recombination region; and forming the diffused light emitting region on a portion exposed by the removal and on the charge injection / recombination region. 9. The method for manufacturing an organic EL device according to claim 8, wherein the removal is performed using a physical method.