JP6417821B2 - ORGANIC ELECTROLUMINESCENT ELEMENT AND LIGHTING DEVICE - Google Patents

Description

  The present invention relates to an organic electroluminescence element and a lighting device.

  2. Description of the Related Art Organic electroluminescence elements (also referred to as “organic EL elements”) are known as electroluminescent devices that use electroluminescence (EL) of organic light emitting materials. The organic EL element generally includes an anode, a cathode, and a light emitting layer that is laminated between the anode and the cathode and contains an organic light emitting material. In an organic EL element, when an electric field is applied between an anode and a cathode, holes are injected from the anode and electrons are injected from the cathode into the light emitting layer. Then, light emission occurs when excitons generated by recombination of holes and electrons are deactivated. The organic EL element is a thin-film all-solid-state element that is composed of a thin film with a thickness of about a submicron between electrodes, and can emit light at a low voltage of several V to several tens V. It has high luminance and high luminous efficiency. It has many excellent features such as thinness and light weight.

  Since the organic EL element is a self-luminous surface light emitter, it is expected to be used as a backlight, an illumination light source, and the like, and development of a device that emits white light is being promoted. As a method for whitening the light source color of the organic EL element, a plurality of types of organic light emitting materials having different emission colors are contained in a single light emitting layer or a plurality of light emitting layers, and white light is mixed by mixing the plurality of light emitting colors. The method of obtaining is used.

  In such lighting applications, the organic EL elements are required to have particularly high luminous efficiency and durability, low power consumption, and stable white light chromaticity over time and fluctuations in drive current. It is hoped that However, in general, it is difficult to ensure sufficient luminance when the organic EL element is driven at a low voltage, and there is a tendency that the element life is reduced when the luminance is ensured. Therefore, a tandem type (multi-photon emission type) organic EL element in which a plurality of light emitting units each having a light emitting layer are stacked in series has been proposed as a technique for improving luminance efficiency by increasing luminance per current density.

  For example, in Patent Document 1, as a technique for providing a highly efficient white light-emitting element having a spectrum in a wide wavelength region, white chromaticity is less likely to change over time, and the shape of the emission spectrum is less dependent on current density, A first light-emitting element having a first light-emitting layer containing a light-emitting organic compound between the first anode and the first cathode, and a light-emitting property between the second anode and the second cathode A light-emitting element in which a second light-emitting element having a second light-emitting layer containing an organic compound is stacked in series, wherein the first cathode and the second anode are in contact with each other, and the first light-emitting element Either the element or the second light-emitting element shows a first emission spectrum having at least two peaks, and the other shows a second emission spectrum having a peak at a position different from the two peaks, The first emission spectrum and the first emission spectrum; Emitting element showing an emission spectrum of the combined emission spectrum is disclosed in (see claim 1, paragraph 0017, etc.). Further, either one of the first light-emitting element and the second light-emitting element is configured to exhibit an emission spectrum having peaks in both the blue to blue-green wavelength region and the yellow to orange wavelength region. Thus, it is described that two kinds of emission colors having a complementary color relationship are indicated (see claim 3, claim 5, paragraph 0019, paragraph 0023, etc.).

  Patent Document 2 discloses, as a technique for providing a white organic electroluminescent element that has excellent luminous efficiency and durability, and that can suppress chromaticity change and angular dependency of chromaticity, A white organic electroluminescent device having at least an intermediate layer between the cathode and the anode, wherein the intermediate layer has a first unit having at least a first light emitting layer between the anode and the intermediate layer. A second unit having at least a second light emitting layer between the first light emitting layer and the cathode, wherein at least one of the first light emitting layer and the second light emitting layer has a single layer structure, A white organic electroluminescent element in which at least one of the first light-emitting layer and the second light-emitting layer includes at least a light-emitting material and an aggregate of the light-emitting material is disclosed (see claim 1 and the like). ).

JP 2006-012793 A JP 2011-228238 A

  In general, a tandem organic EL element including a plurality of light emitting units as disclosed in Patent Document 1 and Patent Document 2 is superior in luminous efficiency as compared to an element including a single light emitting unit. However, since the luminous efficiency of such a tandem organic EL element is not yet sufficient and the power consumption is at a high level, further improvement of the external extraction quantum efficiency (external quantum efficiency) is desired. In order to improve the external extraction quantum efficiency of the organic EL element, there is a great room for improvement in the light extraction efficiency in that it does not depend greatly on the type of the organic light emitting material.

  In the organic EL element, as a loss in light extraction, the loss caused by the loss of surface plasmon-polaritons caused by interaction of the emitted light generated in the light emitting layer with the free electron group of the metal electrode (hereinafter referred to as plasmon loss). The emitted light generated in the light emitting layer is totally reflected at the interface between the transparent electrode and the transparent substrate, etc., and is confined in the light emitting unit without being emitted to the outside of the organic EL element. There is a loss due to the occurrence of a loss, a loss due to the fact that the emitted light transmitted through the transparent electrode is totally reflected at the interface between the transparent substrate and the air and is not emitted from the main surface side (the emission surface side) of the transparent substrate.

  As a tandem organic EL element, a plurality of light emitting units are provided between an anode that is a transparent electrode and a cathode that is a metal electrode, and a plurality of light emitting units are operated by using the cathode that is a metal electrode as a reflective electrode. The element that takes out the emitted light generated in step 1 from one side is the mainstream. In particular, the plasmon loss caused by the metal electrode is difficult to reduce by the optical design of the light emitting unit, and it is not easy to take out the emitted light confined as surface plasmon-polariton as propagating light again. The light extraction efficiency is greatly impaired, and even when applied to lighting applications, compatibility between high durability and brightness is hindered.

  Then, an object of this invention is to provide the organic EL element which has favorable luminous efficiency and light extraction efficiency, and an illuminating device provided with the same.

  The above object of the present invention is achieved by the following configurations.

1. A transparent electrode, a metal electrode that is a counter electrode of the transparent electrode, and a light emitting layer containing an organic light emitting material, and are stacked in series with an intermediate connector layer between the transparent electrode and the metal electrode An organic electroluminescence element comprising a plurality of light emitting units, wherein the light emitting unit disposed closest to the metal electrode among the plurality of light emitting units emits light among the plurality of light emitting units. It contains an organic light emitting material having the shortest wavelength of light, and in the organic electroluminescence element, two or more types of red phosphorescent light emitting materials exhibiting an emission maximum wavelength in a region of a wavelength of 580 nm or more and less than 830 nm are used. An organic electroluminescence device characterized.

  2. 2. The organic electroluminescent element according to 1 above, wherein the organic light emitting material is composed only of a phosphorescent light emitting material.

  3. The light emitting unit arranged closest to the metal electrode has a plurality of light emitting layers, and the light emitting layer arranged closest to the metal electrode among the plurality of light emitting layers is: 3. The organic electroluminescent element according to 1 or 2 above, which contains an organic light emitting material having the shortest wavelength of emitted light among the plurality of light emitting layers.

  4). 4. The organic electroluminescent material according to any one of 1 to 3 above, wherein the organic light emitting material having the shortest wavelength of emitted light is a blue phosphorescent light emitting material having a light emission maximum wavelength in a region of a wavelength of 400 nm or more and less than 490 nm. Luminescence element.

5 . 5. The organic electroluminescent element according to any one of 1 to 4, wherein the two or more types of red phosphorescent materials are contained in different light emitting units.

6 . Of the two or more types of red phosphorescent materials, the red phosphorescent material having the shortest wavelength of emitted light is included in the light emitting unit closest to the metal electrode among the two or more types of red phosphorescent materials. 6. The organic electroluminescence device as described in 5 above, wherein

7 . Wherein the plurality of respective light-emitting layers emitting unit has an organic electroluminescent device as set forth in the 1 in any of the 6, wherein the concentration of the organic light emitting material is not more than 28 wt%.

8 . 8. An illumination device comprising the organic electroluminescence element according to any one of 1 to 7 above.

  ADVANTAGE OF THE INVENTION According to this invention, the organic EL element which has favorable luminous efficiency and light extraction efficiency, and an illuminating device provided with the same can be provided.

It is sectional drawing which shows typically an example of the layer structure of the organic EL element which concerns on embodiment of this invention. It is a conceptual diagram which shows the emission spectrum in an example of the combination of the organic light emitting material used with the organic EL element which concerns on embodiment of this invention. It is sectional drawing which shows typically the other example of the layer structure of the organic EL element which concerns on embodiment of this invention. It is a perspective view which shows the outline of the organic EL element which concerns on the Example of this invention. It is sectional drawing which shows typically the organic EL element which concerns on the Example of this invention.

  Hereinafter, an organic EL device according to an embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the common part in each figure, and description about the overlapping part is abbreviate | omitted.

  FIG. 1 is a cross-sectional view schematically showing an example of the layer configuration of the organic EL element according to this embodiment.

[Organic EL device]
As shown in FIG. 1, an organic EL element (organic EL element 1) according to an embodiment of the present invention includes a transparent electrode 20, a metal electrode 50 that is a counter electrode of the transparent electrode 20, and a light emission containing an organic light emitting material. A tandem type (multi-photon emission type) including a plurality of light emitting units (30A, 30B) that are stacked in series between the transparent electrode 20 and the metal electrode 50 with the intermediate connector layer 40 interposed therebetween. ) Organic EL element. In this organic EL element 1, among the plurality of light emitting units (30A, 30B), the light emitting unit (30B) disposed closest to the metal electrode 50 is the plurality of light emitting units (30A, 30B). Thus, the plasmon loss is mainly reduced by including an organic light emitting material (also referred to as a dopant compound) having the shortest wavelength of emitted light. In FIG. 1, two light emitting units, a first light emitting unit 30A and a second light emitting unit 30B, are provided, and one intermediate connector layer 40 is provided between the two light emitting units 30A and 30B. A stacked layer configuration is illustrated.

  The transparent electrode 20 and the metal electrode 50 constitute a pair of electrodes. For example, the transparent electrode 20 is an anode and the metal electrode 50 is a cathode. The transparent electrode 20 and the metal electrode 50 are each provided with an extraction electrode portion (not shown) so that an external power supply (not shown) is electrically connected. A predetermined electric field is applied between the transparent electrode 20 and the metal electrode 50 via such an external power source, and charges are injected into the light emitting units 30A and 30B provided between the electrodes.

  As shown in FIG. 1, the transparent electrode 20 is laminated on a light-transmitting substrate 10, and the first light emitting unit 30 </ b> A is laminated on the transparent electrode 20. An intermediate connector layer 40 is laminated on the first light emitting unit 30A, a second light emitting unit 30B is laminated on the intermediate connector layer 40, and a metal electrode 50 is laminated on the second light emitting unit 30B. Has been. A sealing member (not shown) is usually disposed on the upper side of the metal electrode 50 (on the side opposite to the base material 10), and the constituent elements from the transparent electrode 20 to the metal electrode 50 include the base material 10 and the sealing member. Covered and sealed.

  The light emitting units 30A and 30B have light emitting layers 33A and 33B each containing an organic light emitting material. In FIG. 1, each light emitting unit 30A, 30B has a hole injection layer 31, a hole transport layer 32, light emitting layers 33A, 33B, an electron transport layer 34, and an electron injection layer 35, which are laminated in this order from the anode side. Although it has a layer structure, it can be configured by a combination of at least one light-emitting layer or a combination of at least one light-emitting layer and another layer having charge transporting property. It is. The specific layer configuration of the intermediate connector layer 40 and the light emitting units 30A and 30B will be described later.

  The organic EL element 1 is a bottom emission type light emission format. That is, the emitted light generated in the light emitting layer 33 </ b> A included in the first light emitting unit 30 </ b> A is transmitted through the first light emitting unit, the transparent electrode 20, and the base material 10, and the organic EL element 1 from the emission surface on one end side of the base material 10. It is taken out outside. The emitted light generated in the light emitting layer 33B of the second light emitting unit 30B is transmitted through the second light emitting unit, the intermediate connector layer 40, the first light emitting unit, the transparent electrode 20, and the base material 10, and It is taken out from the organic EL element 1 from the emission surface on one end side. Further, the emitted light generated in each of the light emitting layers 33A and 33B is reflected by the metal electrode 50, and the reflected light is also taken out of the organic EL element 1 from the emission surface on one end side of the substrate 10. The emitted light extracted outside the organic EL element 1 exhibits a predetermined light source color by the color mixture of the emitted light generated in the respective light emitting layers 33A and 33B of the respective light emitting units 30A and 30B. The light emission form of the organic EL element 1 may be a top emission type. In such a case, the anode is a “metal electrode”, and the cathode is also a “transparent electrode” even when a metal or alloy having a relatively small work function is laminated on the surface.

  The light emitting unit provided in the organic EL element 1 may have a configuration in which three or more light emitting units are connected in series instead of the two configurations shown in FIG. When the number of light emitting units increases, it is possible to improve both the luminance of emitted light and the light emission lifetime for a predetermined current density. However, when the number of the light emitting units is excessively increased, the thickness of the organic EL element increases to increase the driving voltage, or the productivity may be impaired. Therefore, the number of light emitting units is preferably 2 or more and 3 or less.

  In the organic EL element 1, two or more kinds of organic light emitting materials exhibiting different emission spectra are used. That is, the light emitting layers 33A and 33B respectively included in the two light emitting units 30A and 30B are configured so as to include organic light emitting materials that exhibit different emission spectra. Therefore, in each of the light emitting layers 33A and 33B, when an electric field is applied between the transparent electrode 20 and the metal electrode 50, excitons generated by recombination of injected holes and electrons are deactivated. In this case, emitted light of different emission colors is generated. For example, by using two types of organic light-emitting materials that emit light that has a complementary color relationship with each other, or three types that emit light that has a relationship of three primary colors. The emitted light from the organic EL element 1 can be white light. As a combination of organic light emitting materials whose emission colors are complementary to each other, a combination of blue to blue-green emission light and yellow to orange emission light is preferable. Note that when three or more light emitting units are provided, it is only necessary that the light emitting layers of at least two light emitting units include organic light emitting materials exhibiting different emission spectra.

  In the organic EL element 1, among the plurality of light emitting units (30A, 30B), the light emitting unit (30B) disposed closest to the metal electrode 50 is among the plurality of light emitting units (30A, 30B). It is comprised so that the organic light emitting material with the shortest wavelength of emitted light may be contained. On the surface of the metal electrode 50, the collective vibration of free electrons on the metal surface and the emitted light satisfying the reflection condition are coupled to excite surface plasmon-polaritons, and a part of the emitted light is localized in the vicinity of the metal surface. Turn into. The optical loss (plasmon loss) generated in this way generally ranges from about 30% to 40%. Plasmon loss shows emission wavelength dependency, and tends to be smaller as the wavelength of the emitted light is shorter and larger as the wavelength of the emitted light is longer. Moreover, the property also depends on the distance from the light emitting point, and tends to be smaller as the distance between the light emitting point and the metal surface is longer and larger as the distance between the light emitting point and the metal surface is shorter. Therefore, the organic light emitting material having the shortest wavelength of the emitted light among the organic light emitting materials used is contained in the light emitting unit disposed closest to the metal electrode 50, thereby the same kind of organic light emitting material. The light extraction efficiency can be improved and high external extraction quantum efficiency can be realized as compared with the case where is contained in a different light emitting unit.

  Moreover, in the organic EL element 1, among the plurality of light emitting units (30A, 30B), the light emitting unit (30A) disposed farthest from the metal electrode 50 is the plurality of light emitting units (30A, 30B). Among them, it is preferable to contain an organic light emitting material having the longest wavelength of emitted light. The organic light emitting material having the longest wavelength of the emitted light among the organic light emitting materials used is contained in the light emitting unit (30A) disposed farthest from the metal electrode 50, so that the same kind of organic light emission Compared with the case where the material is contained in different light emitting units, the light extraction efficiency can be further improved. In contrast, among the plurality of light emitting units (30A, 30B), the light emitting unit (30A) disposed farthest from the metal electrode 50 is the most among the plurality of light emitting units (30A, 30B). It is preferable not to contain an organic light emitting material having a short wavelength of emitted light.

  Two or more types of organic light emitting materials used in the organic EL element 1 are blue light emitting organic light emitting materials in which the organic light emitting material having the shortest wavelength of emitted light exhibits a light emission maximum wavelength in a region of a wavelength of 400 nm or more and less than 490 nm ( It is preferably used in a combination of blue light emitting material). If the organic light emitting material having the shortest wavelength of emitted light is a blue light emitting material, it is advantageous because the degree of improvement in light extraction efficiency is increased. In addition, as such a blue light emitting material, a blue phosphorescent light emitting material which is phosphorescent is particularly preferable.

  As the organic light emitting material, it is preferable to use three or more types showing different emission spectra, and it is more preferable to use four or more types showing different emission spectra. When multiple types of organic light emitting materials are used, the emitted light with a broad spectrum can be obtained by synthesizing each emitted light, and high color rendering properties (average color rendering index (Ra)) can be realized. become. Further, even if some of the organic light-emitting materials are deteriorated or the current density to the organic EL element 1 is fluctuated, the chromaticity of the emitted light is changed, Color unevenness on the exit surface or viewing angle can be suppressed to a low level. Such a plurality of types of organic light emitting materials may be included in one light emitting layer, or may be included in two or more types.

  As a combination of organic light-emitting materials exhibiting different emission spectra, as an example, when the light source color of the organic EL element is white, blue light-emitting organic light emission that exhibits a light emission maximum wavelength in a region of a wavelength of 400 nm or more and less than 490 nm is an example. A combination of a material (blue light emitting material) and a yellow light emitting or orange light emitting organic light emitting material (yellow to orange light emitting material) exhibiting a light emission maximum wavelength in a wavelength region of 550 nm or more and less than 600 nm, or a wavelength of 400 nm or more and less than 490 nm A blue light-emitting organic light-emitting material (blue light-emitting material) that exhibits a light emission maximum wavelength in a region, a green light-emitting organic light-emitting material (green light-emitting material) that exhibits a light emission maximum wavelength in a region of wavelengths from 510 nm to less than 580 nm, and a wavelength of 580 nm Red light-emitting organic light-emitting material (red light-emitting material) exhibiting a light emission maximum wavelength in a region of less than 830 nm It is possible to use a combination of.

  As the organic light-emitting material, it is preferable to use two or more types of organic light-emitting materials (two or more types of red light-emitting materials) exhibiting a maximum light emission wavelength in a wavelength region of 580 nm or more and less than 830 nm. When two or more kinds of red light emitting materials exhibiting different emission spectra are used, the color rendering property (special color rendering index (R9) in test color No. 9) of the red light emission color can be enhanced. As the red light emitting material, either a red fluorescent material that is fluorescent or a red phosphorescent material that is phosphorescent, or a combination thereof may be used, but a red phosphorescent material that is phosphorescent. More preferably, two or more materials are used. Further, from the viewpoint of improving the visibility, it is more preferable to use a red light emitting material exhibiting a light emission maximum wavelength in a region from a short wave having a wavelength of 580 nm or more and less than 650 nm.

  FIG. 2 is a conceptual diagram showing an emission spectrum in an example of a combination of organic light emitting materials used in the organic EL element according to this embodiment.

  In the example shown in FIG. 2, a red light-emitting organic light-emitting material (first red light-emitting material) having a light emission maximum wavelength at a wavelength of 616 nm and a red light-emitting organic light-emitting material (second red light having a light emission maximum wavelength at a wavelength of 594 nm). Light-emitting material), green light-emitting organic light-emitting material (green light-emitting material) having a light emission maximum wavelength at a wavelength of 560 nm, and blue light-emitting organic light-emitting material (blue light-emitting material) having a light emission maximum wavelength at a wavelength of 475 nm An example of a spectrum is shown. In addition, the spectrum shown by FIG. 2 is an emission spectrum when each organic luminescent material is light-emitted independently.

  As shown in FIG. 2, when two kinds of red light emitting materials having different emission spectra are used together with a blue light emitting material and a green light emitting material, the light source color of the emitted light of the organic EL element is changed to an average color rendering index (Ra ) And the special color rendering index (R9) are both high values, and white light excellent in color rendering can be obtained. In addition, when an emission spectrum having a maximum emission wavelength in such a wavelength region is synthesized, a spectrum having a high emission intensity in the vicinity of a wavelength of 550 nm is generated. Therefore, the visibility of the emitted light is increased, and the light can be suitably used for applications such as a lighting device that emits a light bulb color or warm white.

  FIG. 3 is a cross-sectional view schematically showing another example of the layer configuration of the organic EL element according to the embodiment of the present invention.

  The organic EL element according to the present invention may have a configuration in which the light emitting unit has a plurality of light emitting layers instead of the configuration having one light emitting layer shown in FIG. For example, as shown in FIG. 3, each of the plurality of light emitting layers (30A, 30B) may include a plurality of light emitting layers (33A1, 33A2, 33B1, 33B2), or a plurality of light emitting units (30A, 30B). 30B), a part of the light emitting layers may have a plurality of light emitting layers, and the other light emitting layer may have a single light emitting layer. When a plurality of light emitting layers are laminated in this manner, the tendency of recombination of injected charges to occur near the interface between the light emitting layers becomes strong. For this reason, even when an electric field is applied, the position variation of the emission light generation position (light emission point) due to the organic light emitting material is suppressed, and the chromaticity variation of the emitted light can be reduced. Moreover, since the generated excitons are hardly diffused to other adjacent layers by suppressing the positional variation of the light emitting point, higher light emission efficiency can be realized.

  Of the plurality of light emitting units (30A, 30B), the light emitting unit (30B) disposed closest to the metal electrode 50 has a plurality of light emitting layers (33B1, 33B2). In this way, in the light emitting unit (30B) that includes an organic light emitting material having a short wavelength of emitted light, if the positional fluctuation of the position where the emitted light is generated is suppressed, high energy that generates emitted light of a short wavelength is obtained. The exciton is effectively confined, and the decrease in luminous efficiency is further suppressed.

  In addition, among the plurality of light emitting layers (33B1, 33B2) included in the light emitting unit (30B) disposed closest to the metal electrode 50, the light emitting layer (33B1, 33B2) disposed closest to the metal electrode 50 ( 33B2) preferably contains an organic light emitting material having the shortest wavelength of emitted light among the plurality of light emitting layers (33B1, 33B2). The organic light-emitting material having the shortest wavelength of emitted light among the organic light-emitting materials used is contained in the light-emitting layer (33B2) disposed closest to the metal electrode 50, so that the same type of organic light emission Compared with the case where the materials are contained in different light emitting layers, the light extraction efficiency can be further improved, and a higher external extraction quantum efficiency can be realized.

  When two or more types of red light emitting materials are used as the organic light emitting material, each red light emitting material may be contained in the same light emitting layer, but is preferably contained in different light emitting layers. . Each red light emitting material may be contained in the same light emitting unit, but is preferably contained in different light emitting units. In general, red light-emitting materials tend to have low charge transport performance, but it is possible to ensure charge transport performance per single light-emitting layer by including two or more red light-emitting materials in different light-emitting layers. Therefore, it is possible to prevent an increase in driving voltage and a decrease in luminance.

  When two or more kinds of red light emitting materials are used in different light emitting layers, it is preferable that each red light emitting material is contained together with the green light emitting material or the blue light emitting material in the same light emitting layer. More preferably, it is contained together with the green light emitting material. Since the green light emitting material and the blue light emitting material tend to have higher charge transport performance than the red light emitting material, it is possible to supplement the charge transport by including the red light emitting material together with the green light emitting material and the blue light emitting material. In particular, green light-emitting materials generally tend to have a HOMO level or LUMO level that is close to that of red light-emitting materials. Therefore, by including a red light-emitting material together with a green light-emitting material, it is possible to drive at a low voltage. Become.

  When two or more types of red light emitting materials are used as the organic light emitting material, among the two or more types of red light emitting materials, the red light emitting material having the shortest wavelength of emitted light is one of the two or more types of red light emitting materials. It is preferable to be included in the light emitting unit closest to the metal electrode 50, and to be included in the light emitting layer closest to the metal electrode 50 among the plurality of light emitting layers including the red light emitting material. It is preferable. The red light emitting material having the shortest wavelength of emitted light among the red light emitting materials used is included in the light emitting unit or light emitting layer closer to the metal electrode 50, so that the same type of red light emitting material can be used in different light emitting units or light emitting units. Compared with the case where it is contained in the light emitting layer, the light extraction efficiency can be further improved, and higher external extraction quantum efficiency can be realized. On the other hand, the red light emitting material having the longest wavelength of emitted light among the two or more types of red light emitting materials is the light emitting unit farthest from the metal electrode 50 among the plurality of light emitting layers containing the red light emitting material. Or in the light emitting layer.

  Specifically, the arrangement of the light emitting layer containing each organic light emitting material in the organic EL element can be exemplified by the following configuration. In addition, the structure illustrated below attaches | subjects the number from the transparent electrode 20 side to the light emitting layer of each light emitting unit in the organic EL element with which the 1st light emitting unit 30A and the 2nd light emitting unit 30B are provided. . For example, the light emitting layers 33A and 33B in FIG. 1 correspond to the first light emitting layer and the second light emitting layer in this order, and the light emitting layers 33A1, 33A2, 33B1 and 33B2 in FIG. It corresponds to 3 light emitting layers and 4th light emitting layer. In addition, when the first light emitting unit 30A has a single light emitting layer and the second light emitting unit has two light emitting layers, the first light emitting layer, the second light emitting layer, and the third light emitting layer are sequentially formed. Will respond. The first red light emitting material is a red light emitting material having a wavelength longer than that of the second red light emitting material.

(1) First light emitting unit [first light emitting layer: first red light emitting material + green light emitting material] / second light emitting unit [second light emitting layer: second red light emitting material + blue light emitting material]
(2) First light emitting unit [first light emitting layer: first red light emitting material + second red light emitting material] / second light emitting unit [second light emitting layer: green light emitting material + blue light emitting material]
(3) First light emitting unit [first light emitting layer: first red light emitting material + green light emitting material] / second light emitting unit [second light emitting layer: blue light emitting material / third light emitting layer: second red light emitting material]
(4) First light emitting unit [first light emitting layer: first red light emitting material + green light emitting material] / second light emitting unit [second light emitting layer: second red light emitting material / third light emitting layer: blue light emitting material]
(5) First light emitting unit [light emitting layer: first red light emitting material + second red light emitting material] / second light emitting unit [first light emitting layer: blue light emitting material / second light emitting layer: green light emitting material]
(6) First light emitting unit [light emitting layer: first red light emitting material + second red light emitting material] / second light emitting unit [first light emitting layer: green light emitting material / second light emitting layer: blue light emitting material]
(7) First light emitting unit [first light emitting layer: first red light emitting material / second light emitting layer: green light emitting material] / second light emitting unit [third light emitting layer: blue light emitting material / fourth light emitting layer: second Red light emitting material]
(8) First light emitting unit [first light emitting layer: green light emitting material / second light emitting layer: first red light emitting material] / second light emitting unit [third light emitting layer: blue light emitting material / fourth light emitting layer: second Red light emitting material]
(9) First light emitting unit [first light emitting layer: first red light emitting material / second light emitting layer: green light emitting material] / second light emitting unit [third light emitting layer: second red light emitting material / fourth light emitting layer: Blue light emitting material]
(10) First light emitting unit [first light emitting layer: green light emitting material / second light emitting layer: first red light emitting material] / second light emitting unit [third light emitting layer: second red light emitting material / fourth light emitting layer: Blue light emitting material]
(11) First light emitting unit [first light emitting layer: second red light emitting material / second light emitting layer: green light emitting material] / second light emitting unit [third light emitting layer: blue light emitting material / fourth light emitting layer: first Red light emitting material]
(12) First light emitting unit [first light emitting layer: green light emitting material / second light emitting layer: second red light emitting material] / second light emitting unit [third light emitting layer: blue light emitting material / fourth light emitting layer: first Red light emitting material]
(13) First light emitting unit [first light emitting layer: second red light emitting material / second light emitting layer: green light emitting material] / second light emitting unit [third light emitting layer: first red light emitting material / fourth light emitting layer: Blue light emitting material]
(14) First light emitting unit [first light emitting layer: green light emitting material / second light emitting layer: second red light emitting material] / second light emitting unit [third light emitting layer: first red light emitting material / fourth light emitting layer: Blue light emitting material]
(15) First light emitting unit [first light emitting layer: first red light emitting material / second light emitting layer: second red light emitting material] / second light emitting unit [third light emitting layer: blue light emitting material / fourth light emitting layer: Green luminescent material]
(16) First light emitting unit [first light emitting layer: second red light emitting material / second light emitting layer: first red light emitting material] / second light emitting unit [third light emitting layer: blue light emitting material / fourth light emitting layer: Green luminescent material]
(17) First light emitting unit [first light emitting layer: first red light emitting material / second light emitting layer / second red light emitting material] / second light emitting unit [third light emitting layer: green light emitting material / fourth light emitting layer: Blue light emitting material]
(18) First light emitting unit [first light emitting layer: second red light emitting material / second light emitting layer / first red light emitting material] / second light emitting unit [third light emitting layer: green light emitting material / fourth light emitting layer: Blue light emitting material]
(19) First light emitting unit [first light emitting layer: first red light emitting material + green light emitting material] / second light emitting unit [second light emitting layer: second red light emitting material + green light emitting material / third light emitting layer: blue Luminescent material]
(20) First light emitting unit [first light emitting layer: second red light emitting material + green light emitting material] / second light emitting unit [second light emitting layer: first red light emitting material + green light emitting material / third light emitting layer: blue Luminescent material]

  Among these, a preferable embodiment is that the first light emitting unit has a first light emitting layer containing a green light emitting material and a second light emitting layer containing a red light emitting material in this order from the transparent electrode side, and the second light emitting unit has The third light emitting layer containing a red light emitting material and the fourth light emitting layer containing a blue light emitting material are provided in this order from the transparent electrode side (13). Alternatively, the first light emitting unit has a first light emitting layer containing a green light emitting material and a red light emitting material, and the second light emitting unit is a second light emitting layer containing a green light emitting material and a red light emitting material and blue. It has (22) which has the 3rd light emitting layer containing a luminescent material in this order from the transparent electrode side. According to such a form, the plasmon loss is minimized and a high light extraction efficiency is obtained while organic light emitting materials of a plurality of colors are used. Further, the light source color of the emitted light of the organic EL element can be white light having both a high average color rendering index (Ra) and a special color rendering index (R9), thereby reducing chromaticity variation. In particular, in the case where the first light emitting unit has only the first light emitting layer (22), the film forming process of the light emitting layer is reduced, and even if the current density fluctuates, other light emitting layers adjacent to the charge recombination region. Therefore, it is easy to stabilize the chromaticity of the emitted light against current density fluctuations.

  In each of the light emitting layers included in the plurality of light emitting units, the concentration of the organic light emitting material is preferably 28% by mass or less based on the total mass of the compounds contained in the light emitting layer. When the concentration of the organic light-emitting material contained in the light-emitting layer is limited to 28% by mass or less, aggregation of molecules of the organic light-emitting material is suppressed and concentration quenching hardly occurs, so that a high quantum yield can be ensured.

  The organic light-emitting material used in the organic EL element is a fluorescent light-emitting material (fluorescent light emission) as long as it is a light-emitting material exhibiting a maximum emission wavelength in the visible light wavelength region (wavelength region of approximately 360 nm or more and 830 nm or less). Material) and phosphorescent light-emitting material (phosphorescent material) may be used, or a combination thereof may be used, but all kinds of organic light-emitting materials used are composed of only phosphorescent materials. Is more preferable. Since the quantum yield can be maximized by using a phosphorescent material, it is possible to improve the external extraction quantum efficiency compared to the case of using a fluorescent material, and to easily realize high luminance. It is.

  Next, the detail of each element which comprises an organic EL element is demonstrated.

≪Base material≫
As a base material, there is no limitation in particular in kind, such as glass and a plastics. When taking out light from the base material side, it is preferable that the base material is transparent. Specifically as a transparent base material, glass, quartz, a transparent resin film etc. are mentioned, for example. A particularly preferable substrate is a resin film that can give flexibility to the organic EL element. Examples of the resin film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester such as modified polyester, polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate pro Cellulose esters such as pionate (CAP), cellulose acetate phthalate, cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, polystyrene, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, Polyetherketone, polyimide, polyethersulfone (PES), polypheny Sulfide, polysulfones, polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, arton (trade name, manufactured by JSR) or appel (trade name, manufactured by Mitsui Chemicals) And the like. Alternatively, when making the base material opaque, for example, a metal plate such as aluminum or stainless steel, a metal film, a resin substrate, a ceramic substrate, or the like can be used.

The substrate may be an inorganic material, an organic material, or a substrate on which a barrier film made of a hybrid thereof is formed. Specifically, the water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992 is 0.01 g / (m ² · 24 h. ) Oxygen permeability measured by the following barrier film or a method according to JIS K 7126-1987 is 10 ⁻³ cm ³ / (m ² · 24 h · atm) or less, and water vapor permeability is 10 ^−5. A high barrier film of g / (m ² · 24 h) or less is preferable.

  The material for forming the barrier film may be any material that has a function of suppressing the intrusion of moisture, oxygen, or the like that degrades the element. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Furthermore, it is preferable that the barrier coating film has a laminated structure in order to improve brittleness. The laminated structure can be formed, for example, by alternately laminating inorganic layers and organic layers a plurality of times.

  Examples of the method for forming a barrier film include a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, an ion plating method, a plasma polymerization method, an atmospheric pressure plasma polymerization method, Examples thereof include a plasma CVD method, a laser CVD method, a thermal CVD method, and a coating method. Among these, it is particularly preferable to form by an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143.

≪Anode≫
Examples of the anode include an electrode using a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) as an electrode material. Specific examples of such an electrode substance include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) that can form a transparent conductive film can be used.

  The anode may be formed as a thin film using a method such as vapor deposition or sputtering after forming these electrode materials, and then a pattern having a desired shape may be formed by a photolithography method. When pattern accuracy is not required (about 100 μm or more) ), A pattern may be formed by forming a film by a method such as vapor deposition or sputtering through a mask having a desired shape. Or when using the electrode substance which can be apply | coated like an organic electroconductivity compound, wet application methods, such as a printing system and a coating system, can also be used.

  The film thickness of the anode can be appropriately determined according to the electrode substance used as a material, but is 10 to 1000 nm, preferably 10 to 200 nm. When light emission is extracted from the anode side, it is desirable that the transmittance be greater than 10%. The sheet resistance of the anode is preferably several hundred Ω / □ or less.

≪Cathode≫
Examples of the cathode include an electrode using a metal, an alloy, an electrically conductive compound, or a mixture thereof having a small work function (4 eV or less) as an electrode material. Specific examples of such electrode materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, and aluminum / aluminum oxides. (Al ₂ O ₃ ) mixtures, indium, lithium / aluminum mixtures, aluminum, silver, alloys based on silver, aluminum / silver mixtures, rare earth metals, and the like.

  The cathode can be formed as a thin film using a method such as vapor deposition or sputtering of these electrode materials. In addition, when light emission is taken out from the cathode, the cathode is a transparent electrode having optical transparency. A light-transmitting cathode can be formed into a transparent or translucent cathode by forming a cathode with a film thickness of 1 to 20 nm and then covering a conductive transparent material known as an anode electrode material on the cathode. it can.

  The film thickness of the cathode can be set appropriately according to the electrode substance used as the material, but is in the range of 10 nm to 5 μm, preferably 50 to 200 nm. The sheet resistance of the cathode is preferably several hundred Ω / □ or less.

≪Light emitting unit≫
As a layer structure of the light emitting unit, an appropriate layer structure employed in a general organic EL element can be adopted. Specifically, the following configuration can be exemplified.
(1) Hole injection transport layer / light emitting layer / electron injection transport layer (2) Hole injection transport layer / first light emitting layer / second light emitting layer / electron injection transport layer (3) Hole injection transport layer / first Light emitting layer / intermediate layer / second light emitting layer / electron injection transport layer (4) hole injection transport layer / light emission layer / hole blocking layer / electron injection transport layer (5) hole injection transport layer / electron blocking layer / light emission Layer / hole blocking layer / electron injection transport layer (6) hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer (7) hole injection layer / hole transport layer / first light emission Layer / second light emitting layer / electron transport layer / electron injection layer (8) hole injection layer / hole transport layer / first light emitting layer / intermediate layer / second light emitting layer / electron transport layer / electron injection layer (9) Hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer (10) hole injection layer / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / Electron transport layer / electric Injection layer

≪Luminescent layer≫
The light emitting layer is a layer that emits light by recombination of electrons and holes injected from the electrodes and the intermediate connector layer. The light emitting layer contains an organic light emitting material that emits light. The organic light emitting material preferably contains a host compound and a dopant compound. Note that the light emitting portion may be in the light emitting layer or at the interface between the light emitting layer and the adjacent layer.

  Each light emitting layer may contain a plurality of host compounds and dopant compounds. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient.

  As the dopant compound, a phosphorescent dopant compound or a fluorescent dopant compound can be used. Further, the dopant compound may be contained at a uniform concentration with respect to the film thickness direction of the light emitting layer, or may have a concentration distribution.

<Phosphorescent dopant compound>
A phosphorescent dopant compound is a compound in which light emission from an excited triplet is observed. Specifically, it is a compound that emits phosphorescence at room temperature (25 ° C.), and is defined as a compound having a phosphorescence quantum yield of 0.01 or more at 25 ° C. The phosphorescent quantum yield of the phosphorescent dopant compound is preferably 0.1 or more.

  The phosphorescent quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. The phosphorescence quantum yield in the solution can be measured using various solvents, and the phosphorescent dopant compound may be any phosphorescent dopant compound as long as the phosphorescence quantum yield is achieved in any solvent.

  There are two types of light emission principles of the phosphorescent dopant compound. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is used as the phosphorescent dopant. It is an energy transfer type in which light emission from a phosphorescent dopant compound is obtained by transferring to a compound. The other is a carrier trap type in which a phosphorescent dopant compound becomes a carrier trap, and recombination of carriers occurs on the phosphorescent dopant compound, and light emission from the phosphorescent dopant compound is obtained. In any case, it is a condition that the excited state energy of the phosphorescent dopant compound is lower than the excited state energy of the host compound.

  As the phosphorescent dopant compound, a known compound used for a light emitting layer of a general organic EL device can be used. For example, compounds represented by general formulas (4) to (6) described in JP2013-4245A, and exemplified compounds (Pt-1 to Pt-3, Os-1, Ir-1 to Ir-45) ), And exemplary compounds (Ir-46, Ir-47, Ir-48) represented by the following chemical formulas are preferable.

  Other specific examples of the phosphorescent dopant compound include, for example, Nature 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17, 1059 (2005), International Publication No. 2009100991, International Publication No. 2008101842, International Publication No. 2003030257, United States Patent Publication No. 200006835469, United States Patent Publication No. 2006060202194, United States Patent Publication No. 20070087321, United States Patent Publication No. And the compounds described in JP20050244673.

  Inorg. Chem. 40, 1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chem. lnt. Ed. 2006, 45, 7800, Appl. Phys. Lett. 86, 153505 (2005), Chem. Lett. 34, 592 (2005), Chem. Commun. 2906 (2005), Inorg. Chem. 42, 1248 (2003), International Publication No. 2009050290, International Publication No. 20022015645, International Publication No. 2009000673, United States Patent Publication No. 20020034656, United States Patent No. 7332232, United States Patent Publication No. 20090108737, United States Patent Publication No. 200900397776. , U.S. Patent No. 6921915, U.S. Patent No. 6,687,266, U.S. Patent Publication No. 20070190359, U.S. Patent Publication No. 2006060008670, U.S. Patent Publication No. 20090165846, U.S. Patent Publication No. 20080015355, U.S. Patent No. 7250226, U.S. Patent No. 7396598, U.S. Patent Publication No. 20060263635, U.S. Patent Publication No. 200301368657, U.S. Patent Publication No. 2003015280 2 and the compounds described in US Pat. No. 7,090,928.

  Also, Angew. Chem. lnt. Ed. 47, 1 (2008), Chem. Mater. 18, 5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics 23, 3745 (2004), Appl. Phys. Lett. 74, 1361 (1999), International Publication No. 2002002714, International Publication No. 2006009024, International Publication No. 200606056418, International Publication No. 2005019373, International Publication No. 20050051873, International Publication No. 200500513873, International Publication No. 2007004380, International Publication No. U.S. Patent Publication No. 2006082742, U.S. Patent Publication No. 20060251923, U.S. Patent Publication No. 20050260441, U.S. Patent No. 7393599, U.S. Patent No. 7,534,505, U.S. Patent No. 7,445,855, U.S. Patent Publication No. 20070190359, U.S. Patent Publication No. 20080297033. U.S. Pat. No. 7,338,722, U.S. Pat. Publication No. 200201334984, U.S. Pat. No. 7,279,704, U.S. Pat. No. 98120 and compounds described in US Patent Publication No. 2006103874.

  In addition, International Publication No. 2005076380, International Publication No. 201303663, International Publication No. 2008140115, International Publication No. 2007052431, International Publication No. 201111334013, International Publication No. 2011157339, International Publication No. 20100086089, International Publication No. 20101314646. International Publication No. 201212020327, International Publication No. 20111051404, International Publication No. 2011004639, International Publication No. 20111073149, US Patent Publication No. 20122228583, US Patent Publication No. 201212212126, Japanese Patent Application Laid-Open No. 2012-069737, Japanese Unexamined Patent Application Publication No. 2012. JP-A-195554, JP-A-2009-114086, JP-A-2003-81988, JP-A-2002-302671, JP-A-2. Compounds described in 02-363552 JP, and the like.

<Fluorescent luminescent dopant compound>
As the fluorescent light emitting dopant compound, a known compound used for a light emitting layer of a general organic EL device can be used. Specifically, for example, coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes. System dyes, polythiophene dyes, rare earth complex phosphors, and the like.

  In addition, a delayed fluorescent compound can be used as the fluorescent dopant compound. Examples of the delayed fluorescent light-emitting fluorescent compound include compounds described in International Publication No. 2011/156793, Japanese Patent Application Laid-Open No. 2011-213643, Japanese Patent Application Laid-Open No. 2010-93181, and the like.

  The thickness of the light emitting layer is preferably 5 nm to 200 nm, more preferably 10 nm to 100 nm. When the thickness of the light emitting layer is in such a range, the uniformity of the formed light emitting layer is easily ensured, and the possibility that the driving voltage becomes excessively high is reduced.

<Host compound>
The host compound is a compound mainly responsible for charge transport in the light emitting layer. As a host compound, the compound whose phosphorescence quantum yield of phosphorescence emission in room temperature (25 degreeC) is less than 0.1 is preferable, and the compound less than 0.01 is more preferable. Moreover, it is preferable that the mass ratio in the layer is 20% or more among the compounds contained in a light emitting layer as a host compound.

  As a host compound, the well-known compound used for the light emitting layer of a general organic EL element can be used. Specifically, for example, compounds having a basic skeleton such as carbazole derivatives, triarylamine derivatives, aromatic derivatives, nitrogen-containing heterocyclic compounds, thiophene derivatives, furan derivatives, oligoarylene compounds, carboline derivatives, diazacarbazole Derivatives (wherein at least one carbon atom of the hydrocarbon ring constituting the carboline ring of the carboline derivative is substituted with a nitrogen atom), and the like. The host compound may be a low molecular compound, a high molecular compound having a repeating unit, or a compound having a reactive group such as a vinyl group or an epoxy group. As the host compound, a compound having a hole transporting ability or an electron transporting ability, preventing emission light from being long-wavelength, and having a high glass transition temperature (Tg) is preferable. The Tg of the host compound is preferably 90 ° C. or higher, more preferably 120 ° C. or higher. In addition, Tg is a value calculated | required by the method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry: Differential scanning calorimetry).

  One type of host compound may be used per single light emitting layer, or a plurality of types may be used. By using a plurality of types of host compounds, the movement of charges can be adjusted, and the efficiency of the organic EL element can be increased. Moreover, when using a multiple types of dopant compound together, each emitted light can be generated appropriately.

  Specific examples of the host compound include, for example, JP-A Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, and 2002-334786. Gazette, 2002-8860 gazette, 2002-334787 gazette, 2002-15871 gazette, 2002-334788 gazette, 2002-43056 gazette, 2002-334789 gazette, 2002-75645 gazette. Publication No. 2002-338579 Publication No. 2002-105445 Publication No. 2002-343568 Publication No. 2002-141173 Publication No. 2002-352957 Publication No. 2002-203683 Publication No. 2002-363227 Publication No. 2002-363227 Publication No. 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, Examples thereof include compounds described in JP-A Nos. 2002-299060, 2002-302516, 2002-305083, 2002-305084, 2002-308837 and the like.

≪Hole transport layer≫
The hole transport layer is a layer having a function of transporting injected holes to the light emitting layer side.

  Examples of materials applicable to the hole transport layer include porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, Polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives, indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, polyvinylcarbazole, aromatic amines in the main chain or side chain Introduced polymer material or oligomer, polysilane, conductive polymer or oligomer (for example, PEDOT: PSS, aniline copolymer, polyaniline) Polythiophene, etc.) and the like.

  Examples of the triarylamine derivative include a benzidine type typified by α-NPD, a starburst type typified by MTDATA, and a compound having fluorene or anthracene in the triarylamine linking core part. In addition, hexaazatriphenylene derivatives such as those described in JP-A-2003-519432 and JP-A-2006-135145 can be used.

  As specific examples of the hole transport material, Appl. Phys. Lett. 69, 2160 (1996), J. MoI. Lumin. 72-74, 985 (1997), Appl. Phys. Lett. 78, 673 (2001), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 51, 913 (1987), Synth. Met. 87, 171 (1997), Synth. Met. 91, 209 (1997), Synth. Met. 111, 421 (2000), SID Symposium Digest, 37, 923 (2006), J. Am. Mater. Chem. 3, 319 (1993), Adv. Mater. 6, 677 (1994), Chem. Mater. 15,3148 (2003), U.S. Patent Publication No. 20030162053, U.S. Patent Publication No. 200201558242, U.S. Patent Publication No. 20060240279, U.S. Patent Publication No. 20080220265, U.S. Patent No. 5061569, International Publication No. 2007002683, and International Publication No. 2007002683. 2008018009, EP650955, U.S. Patent Publication No. 20080124572, U.S. Patent Publication No. 200707078938, U.S. Patent Publication No. 200880106190, U.S. Patent Publication No. 20080018221, International Publication No. 201212115034, Japanese Patent Publication No. 2003-519432, JP-A-2006 -135145, US Patent Application No. 13/585981 and the like.

JP-A-11-251067, J. Org. Huang et. al. It is also possible to use a p-type hole transport material as described in the literature (Applied Physics Letters 80 (2002), p. 139). Alternatively, an inorganic compound such as p-type-Si or p-type-SiC, or an orthometalated organometallic complex having Ir, Pt, or the like as a central metal represented by Ir (ppy) ₃ can also be used.

  The thickness of the hole transport layer is not particularly limited, but is usually 5 nm to 5 μm, preferably 2 nm to 500 nm, more preferably 5 nm to 200 nm.

≪Electron transport layer≫
The electron transport layer is a layer having a function of transporting injected electrons to the light emitting layer side. The electron transport layer may be a single layer or a plurality of layers.

  Examples of materials applicable to the electron transport layer include nitrogen-containing aromatic heterocyclic derivatives, aromatic hydrocarbon ring derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, silole derivatives, and the like. Examples of the nitrogen-containing aromatic heterocyclic derivative include carbazole derivatives, azacarbazole derivatives (one or more carbon atoms constituting the carbazole ring are substituted with nitrogen atoms), pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, pyridazine derivatives, triazines. Derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, azatriphenylene derivatives, oxazole derivatives, thiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, and the like. Examples of the aromatic hydrocarbon ring derivative include naphthalene derivatives, anthracene derivatives, and triphenylene derivatives.

In addition, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, for example, tris (8-quinolinol) aluminum (Alq ₃ ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7 -Dibromo-8-quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and metal complexes thereof A metal complex in which the central metal is replaced with In, Mg, Cu, Ca, Sn, Ga, or Pb can be used. In addition, metal-free or metal phthalocyanine, or those having a terminal substituted with an alkyl group or a sulfonic acid group can be used. Moreover, inorganic compounds such as n-type-Si and n-type-SiC can also be used.

  Other specific examples of the electron transporting material include US Pat. No. 6,528,187, US Pat. No. 7,230,107, US Patent Publication No. 20050025993, US Patent Publication No. 2004036077, US Patent Publication No. 200901115316, US Patent Publication No. 200901870. U.S. Patent Publication No. 20090179554, International Publication No. 20030609556, International Publication No. 20080832085, Appl. Phys. Lett. 75, 4 (1999), Appl. Phys. Lett. 79, 449 (2001), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 79, 156 (2001), U.S. Pat.No. 7,964,293, U.S. Patent Publication No. 2009030202, International Publication No. 20040980975, International Publication No. 2004063159, International Publication No. 2005085387, International Publication No. 20060606731, International Publication No. 2007086552. International Publication No. WO 200814690, International Publication No. 2009090442, International Publication No. 200909066779, International Publication No. 200905253, International Publication No. 20110869935, International Publication No. 2010150593, International Publication No. 20110047707, EP23111826, JP2010-251675A JP, 2009-209133, JP 2009-124114, JP 2008-277810, JP 2 006-156445, JP-A-2005-340122, JP-A-2003-45662, JP-A-2003-31367, JP-A-2003-282270, International Publication No. 201212115034, etc. Is mentioned.

The film thickness of the electron transport layer is not particularly limited, but is 2 nm to 5 μm, preferably 2 nm to 500 nm, and more preferably 5 nm to 200 nm. Further, the electron mobility of the electron transport layer is preferably 10 ⁻⁵ cm ² / Vs or more.

≪Hole injection layer≫
The hole injection layer is a layer provided between the anode and the light emitting layer in order to lower the driving voltage and improve the light emission luminance. The hole injection layer can be interposed, for example, between the anode and the light emitting layer or between the anode and the hole transport layer. For the hole injection layer, see “Organic EL devices and their forefront of industrialization” (November 30, 1998, issued by NTT), Chapter 2, Chapter 2, “Electrode materials” (pages 123-166). It is described in detail. Details are also described in, for example, JP-A-9-45479, JP-A-9-260062, and JP-A-8-288069.

  Examples of materials applicable to the hole injection layer include phthalocyanine derivatives represented by copper phthalocyanine, hexaazatriphenylene derivatives as described in JP-T-2003-519432, JP-A-2006-135145, and the like, oxidation Oxides represented by vanadium, amorphous carbon, conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometalated complexes represented by tris (2-phenylpyridine) iridium complex, triarylamine derivatives, etc. Can be mentioned.

≪Electron injection layer≫
The electron injection layer is a layer provided between the cathode and the light emitting layer in order to lower the driving voltage and improve the light emission luminance. The electron injection layer can be interposed, for example, between the cathode and the light emitting layer, or between the cathode and the electron transport layer. The details of the electron injection layer are described in Volume 2, Chapter 2, “Electrode Materials” (pages 123-166) of “Organic EL devices and their industrialization front line (issued by NTT Corporation on November 30, 1998)”. It is described in. Details thereof are also described in, for example, JP-A-6-325871, JP-A-9-17574, and JP-A-10-74586.

  As a material applicable to the electron injection layer, specifically, a metal represented by strontium or aluminum, an alkali metal compound represented by lithium fluoride, an alkaline earth metal compound represented by magnesium fluoride, Examples thereof include oxides typified by aluminum oxide, metal complexes typified by lithium 8-hydroxyquinolate (Liq), and the like.

  The thickness of the electron injection layer is not particularly limited, but is preferably 0.1 nm to 5 μm.

≪Hole blocking layer≫
The hole blocking layer has a function of an electron transport layer in a broad sense, and has a function of transporting electrons while having a very small ability to transport holes. By blocking holes while transporting electrons, the recombination probability of electrons and holes can be improved.

  Examples of the hole blocking material applicable to the hole blocking layer include compounds listed as materials applicable to the electron transport layer, compounds listed as host compounds, and the like.

  The thickness of the hole blocking layer is preferably 3 nm to 100 nm, more preferably 5 nm to 30 nm.

≪Electron blocking layer≫
The electron blocking layer has a function of a hole transport layer in a broad sense, and has a function of transporting holes while having a remarkably small ability to transport electrons. By blocking electrons while transporting holes, the probability of recombination of electrons and holes can be improved.

  As an electron blocking material applicable to the electron blocking layer, for example, the same species as the hole transporting material can be used. Examples thereof include compounds listed as materials applicable to the hole transport layer, compounds listed as host compounds, and the like.

  The thickness of the electron blocking layer is preferably 3 nm to 100 nm, more preferably 5 nm to 30 nm.

  Each of these layers forming the light emitting unit is, for example, a known method such as a vacuum deposition method, a spin coating method, a casting method, an LB method (Langmuir-Blodget method), an ink jet method, a spray method, a printing method, a slot type coater method, etc. It can be formed by depositing each material by a thin film forming method.

  Examples of the liquid medium for dissolving or dispersing the organic material include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, mesitylene, cyclohexyl benzene, and the like. Aromatic hydrocarbon rings, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used.

  In film formation, patterning may be performed by a metal mask, an inkjet printing method, or the like as necessary. When patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire element layer may be patterned.

≪Intermediate connector layer≫
The intermediate connector layer is a non-light emitting layer, and is provided so as to be sandwiched between a plurality of light emitting units. The intermediate connector layer can be either a metal single layer or a charge generation layer. A metal single layer consists of a metal or an alloy, and is comprised by the thin layer with a thickness of 0.1 nm-10 nm. The charge generation layer is a layer having a function of injecting holes on the cathode side or electrons on the anode side when an electric field is applied. The intermediate connector layer preferably has a charge generation layer configuration in that plasmon loss can be further reduced.

<Single metal layer>
The metal single layer can be formed using a material similar to that of the anode or the cathode or a material having lower conductivity than the anode or the cathode. The metal single layer has almost no metal material deposited on some of its fine areas, so-called pinholes are formed, or it is formed in a net shape in the in-plane direction, or distributed in islands (spots). It may be formed so as to.

Examples of materials applicable to the metal single layer include metals such as calcium, lithium, sodium, potassium, cesium, rubidium, barium, strontium, aluminum, silver, alloys based on these metals, CuI, and indium tin. Examples thereof include conductive transparent materials such as oxide (ITO), SnO ₂ , and ZnO.

  The film thickness of the metal single layer is preferably 0.6 nm to 5 nm, more preferably 0.8 nm to 3 nm, and still more preferably 0.8 nm to 2 nm. When the thickness of the metal single layer is 0.6 nm or more, it is easy to ensure the performance stability of the organic EL element, and in particular, it is possible to reduce the fluctuation of the initial performance immediately after manufacture. Further, when the thickness of the metal single layer is 5 nm or less, absorption of transmitted light can be suppressed, so that light emission efficiency, storage stability, and drive stability can be increased.

  It is preferable that the layer adjacent to the metal single layer has a function of easily transferring charges to and from the metal single layer. Specifically, the layer adjacent to the metal single layer includes, for example, a charge transporting organic material having a high charge transporting property, and an inorganic material or an organometallic complex capable of oxidizing or reducing the charge transporting organic material, or Preferably, the charge transporting organic material is formed as a mixed layer doped with an inorganic material or an organometallic complex capable of forming a charge transfer complex.

  The metal single layer can be formed by a known method such as resistance heating evaporation, electron beam evaporation, ion plating, or ion beam sputtering.

<Charge generation layer>
The charge generation layer is a layer having a function of injecting holes on the cathode side and electrons on the anode side when an electric field is applied. The position of charge generation may be within the charge generation layer or at the interface between the charge generation layer and another adjacent layer. Alternatively, it may be in the vicinity of such an interface.

  The charge generation layer may be formed of a single layer or a plurality of layers. The charge generation layer preferably includes any one of a bipolar layer, a p-type layer, and an n-type layer, more preferably includes any one of a p-type layer and an n-type layer, and both the p-type layer and the n-type layer. It is further preferable that it contains.

  The bipolar layer is a layer that can generate and transport holes and electrons inside the layer by an external electric field. The p-type layer is a charge transport layer in which majority carriers are holes, and the n-type layer is a charge transport layer in which majority carriers are electrons. The p-type layer and the n-type layer preferably have a conductivity higher than that of a semiconductor.

Examples of the layer configuration of the charge generation layer include the following configurations.
(1) Light-emitting unit / bipolar layer (one layer) / light-emitting unit (2) Light-emitting unit / n-type layer / p-type layer / light-emitting unit (3) Light-emitting unit / n-type layer / intermediate layer / p-type layer / light-emitting unit The intermediate layer includes, for example, an n-type layer and a p-type diffusion prevention layer, a pn reaction suppression layer, a level adjustment layer that adjusts the charge level between the p-type layer and the n-type layer, and the like. It is a layer provided to improve the charge generation ability and long-term stability.

  When the charge generation layer is formed of a plurality of layers, the interface between the plurality of layers may have an interface (heterointerface, homointerface), multidimensional such as bulk heterostructure, island shape, phase separation, etc. A typical interface may be formed.

  The film thickness of each layer forming the charge generation layer is not particularly limited, but is preferably 1 nm to 100 nm, more preferably 10 nm to 50 nm.

  The charge generation layer preferably has a high light transmittance for the light emitted from the light emitting layer. Specifically, the transmittance at a wavelength of 550 nm is preferably 50% or more, and more preferably 80% or more.

More specifically, examples of the layer for forming the charge generation layer include the following layers.
(1) Electron transporting material layer (2) Electron extraction layer (organic acceptor material / inorganic acceptor material)
(3) Mixed layer of electron transport material and alkali (earth) metal salt (or alkali (earth) metal precursor) (4) n-type semiconductor layer (organic material, inorganic material)
(5) n-type conductive polymer layer (6) single hole injection / transport material layer (7) multiple types of hole injection / transport material mixed layer (8) organometallic complex layer (9) hole Mixed layer of transportable material and metal oxide (10) p-type semiconductor layer (organic material, inorganic material)
(11) p-type conductive polymer layer

  As a material constituting the charge generation layer, an inorganic material or an organic material having a work function of 3.0 eV or less can be used for the electron injecting layer (n-type layer). In addition, an inorganic material or an organic material having a work function of 4.0 eV or more can be used for the hole injecting layer (p-type layer). An appropriate material can be used as the inorganic material or the organic material constituting the layer as exemplified in the above (1) to (11). It is also possible to use materials applicable to the hole injection layer, hole transport layer, electron injection layer, and electron transport layer.

  The electron injecting layer preferably contains an electron donating material. The hole injecting layer preferably contains an electron accepting material. These electron donating materials and electron accepting materials may form a layer alone, or may be formed by mixing with a binder or other charge transporting material.

  As the electron-donating material, for example, an alkali metal, an alkaline earth metal, a rare earth metal, or a metal belonging to Group 13 of the periodic table, or an oxide, halide, salt, or the like containing these metals is used. be able to. Specifically, lithium, cesium, magnesium, calcium, ytterbium, indium, lithium fluoride, sodium fluoride, potassium fluoride, lithium oxide, cesium carbonate, and the like can be given. Further, as described in JP2012-014905A, phthalocyanine derivatives, porphyrin derivatives, tetrathiafulvalene (TTF) derivatives, tetrathiatetracene (TTT) derivatives, metallocene derivatives, thiophene derivatives, imidazole radical derivatives, condensed poly Ring aromatic hydrocarbons, arylamine derivatives, azine derivatives, transition metal coordination complex derivatives, and the like can also be used.

  Examples of the electron-accepting material include metal oxides such as molybdenum oxide, vanadium oxide, rhenium oxide, ruthenium oxide, and tungsten oxide, ferric chloride, ferric iodide, aluminum chloride, aluminum iodide, and indium chloride. Further, halides such as indium iodide, gallium chloride, gallium iodide, antimony pentachloride, and boron trifluoride can be used. Hexaazatriphenylenehexacarbonitrile (HATCN), dicyano-dichloroquinone (DDQ), trinitrofluorenone (TNF), tetracyanoquinodimethane (TCNQ), tetrafluoro-tetracyanoquinodimethane (F4TCNQ), etc. As other electron-accepting materials, quinone derivatives, polycyano derivatives, tetracynoquinodimethane derivatives, DCNQI derivatives, polynitro derivatives, as described in JP2011-086442A and JP2012-014905A, Use transition metal coordination complex derivatives, phenanthroline derivatives, azacarbazole derivatives, quinolinol metal complex derivatives, heteroaromatic hydrocarbon compounds, fullerene derivatives, phthalocyanine derivatives, porphyrin derivatives, fluorinated heterocyclic derivatives Rukoto can also.

  For the formation of the layer constituting the charge generation layer, for example, vacuum deposition method, spin coating method, casting method, LB method (Langmuir-Blodget method), ink jet method, spray method, printing method, slot type coater method, etc. A known thin film forming method can be used. As another method, when the layer constituting the charge generation layer is formed of an inorganic material, a fine particle dispersion, a precursor fine particle dispersion or a precursor solution, or a solution is wet-coated, and if necessary, It can also be formed by supplying energy from the outside.

  As the external energy source, heat, light (ultraviolet, visible, infrared, etc.), electromagnetic wave (microwave, etc.), plasma, discharge, etc. can be selected. By applying external energy, a film having higher conductivity can be formed. In addition, the conduction band, valence band, and Fermi level of the formed layer can be changed by external energy.

  As the fine particle dispersion, a dispersion in which fine particles are dispersed with water or an organic solvent is used. The fine particles preferably have an average particle size of 10 μm or less, more preferably an average particle size of 100 nm or less, and still more preferably particles having an average particle size of 20 nm or less.

Examples of the fine particle dispersion of the inorganic material include a fine particle metal dispersion in which fine particles of a metal such as gold, silver, copper, aluminum, nickel, iron, and zinc or an alloy containing these as a main component are dispersed, titanium oxide, oxidation Fine particle inorganic oxide in which fine particles such as zirconium, niobium oxide, zinc oxide, tin oxide, iron oxide, molybdenum oxide, vanadium oxide, lithium oxide, calcium oxide, magnesium oxide, ITO, IZO, In-Ga-Zn-Oxide are dispersed Dispersions, copper metal salts (such as CuI), silver metal salts (such as AgI), iron salts (such as FeCl ₃ ), compound semiconductors (such as gallium-arsenic, cadmium-selenium), titanates (SrTiO ₃ , BaTiO ₃₎ And the like, and fine particle inorganic salt dispersion liquid in which fine particles are dispersed.

  Examples of the precursor fine particle dispersion or precursor solution of the inorganic material include a dispersion or solution that forms a layer constituting the charge generation layer by a sol-gel reaction, an oxidation-reduction reaction, or the like. That is, a precursor of a sol-gel reaction in which a metal halide salt such as titanium, zirconium, zinc, tin, niobium, molybdenum, vanadium, a metal alkoxide, a metal acetate, or the like is dispersed or dissolved, or a precursor of a redox reaction A reductive metal compound such as AgI is dispersed or dissolved.

≪Sealing≫
For sealing the organic EL element, for example, a method in which a sealing member is bonded to an electrode or a substrate with an adhesive can be used. The sealing member should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and concave plate shape or flat plate shape may be sufficient as it. The transparency and electrical insulation of the sealing member are not particularly limited.

  As a sealing member, a glass plate, a polymer plate, a polymer film, a metal plate, a metal film etc. are mentioned, for example. Specific examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Specific examples of the polymer plate and polymer film include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Specifically, as the metal plate and metal film, one or more metals selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum, or these The thing which consists of these alloys is mentioned. In order to process the sealing member into a concave shape, sandblasting, chemical etching, or the like can be used.

The polymer film preferably has an oxygen permeability measured by a method according to JIS K 7126-1987 of 1 × 10 ⁻³ cm 3 / (m 2 · 24 h · atm) or less. The water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992 is 1 × 10 ⁻³ g / (m 2 · 24 h. It is preferable that

  As an adhesive for adhering the sealing member, a photo-curing or thermosetting adhesive having a reactive vinyl group such as an acrylic acid oligomer or a methacrylic acid oligomer, or a moisture curing type such as 2-cyanoacrylate Adhesives, epoxy-based thermosetting or chemical-curing (two-component mixed) adhesives, hot-melt polyamide-based, polyester-based, polyolefin-based adhesives, and cationic-curing UV-curable epoxy A resin adhesive is mentioned.

  The adhesive is preferably one that can be adhesively cured from room temperature to 80 ° C. The adhesive may be applied using a commercially available dispenser or screen printing.

  In the gap between the sealing member and the display area of the organic EL element, in the case of a gas phase and a liquid phase, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil is used. It is preferable to inject. Alternatively, a vacuum may be used. Further, a hygroscopic compound may be enclosed in the gap. Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide etc.), perchloric acids (eg perchloric acid) Barium, magnesium perchlorate, etc.). In sulfates, metal halides and perchloric acids, anhydrous salts are preferably used.

  In addition, for sealing an organic EL element, an electrode and a light emitting unit are coated on the outer side of the electrode facing the substrate, and the barrier property by an inorganic material, an organic material, or a hybrid thereof is used in contact with the substrate. A method of forming a coating film to form a sealing film can also be used.

≪Protective film, protective plate≫
A protective film or a protective plate for physically protecting the organic EL element may be provided outside the sealing member or the sealing film. In particular, since the mechanical strength of the sealing film is not necessarily high, it is preferable to provide a protective film or a protective plate when the organic EL is sealed with the sealing film. Examples of the material that can be used for this include the same glass plate, polymer plate, polymer film, metal plate, and metal film that can be used for sealing. Among these, a polymer film is preferable in that it is lightweight and can be thinned.

≪Light extraction≫
An organic EL element emits light inside a layer having a higher refractive index than air (a layer having a refractive index of about 1.6 to 2.1), and only 15% to 20% of the generated light can be extracted. It is generally said. This is because light incident on the interface (transparent substrate-air interface) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the element, or a transparent electrode or light emitting layer and the transparent substrate. This causes the total reflection of the light, the light is guided through the transparent electrode, the light emitting unit and the like, and as a result, the light escapes in the direction of the element side surface.

  As a method for reducing such light loss, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the interface between the transparent substrate and the air (US Pat. No. 4,774,435), substrate A method of improving efficiency by providing light condensing properties (Japanese Patent Laid-Open No. 63-314795), a method of forming a reflective surface on the side surface of an element (Japanese Patent Laid-Open No. 1-220394), a substrate and a light emitter A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between them (Japanese Patent Laid-Open No. 62-172691), a flat layer having a lower refractive index than the substrate between the substrate and the light emitter Of introducing a diffraction grating (Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any one of a substrate, a transparent electrode layer and a light emitting layer (including between the substrate and the outside) (Japanese Patent Laid-Open No. 11-283951) ) Etc. can also be used .

≪Condensation≫
The surface on the light extraction side of the organic EL element can be processed to provide, for example, a microlens array-like structure, or a condensing sheet can be attached thereto. Thus, the brightness | luminance in a specific direction can be raised by condensing emitted light to a specific direction, for example, a front direction with respect to an element light emission surface.

  Specific examples of the microlens array-like structure include a structure in which quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged. If one side is 10 μm to 100 μm, there is a low possibility that the effect of diffraction will be generated and coloring will occur or the thickness of the structure will be excessively thick. Moreover, the structure in which the triangle-shaped stripe was formed may be sufficient, and the shape where the apex angle was rounded, the shape which changed the pitch at random, etc. may be sufficient.

  As the condensing sheet, for example, a sheet that is put into practical use in an LED backlight of a liquid crystal display device can be used. Specifically, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. Moreover, in order to control a light radiation angle, you may use a light-diffusion plate and a light-diffusion film together with a condensing sheet. As the light diffusion film, for example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

≪Usage≫
The organic EL element according to the present invention described above can be used as a display device, a display, and various light sources. Examples of light emission sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light sensors Examples include a light source. The organic EL element may have a resonator structure or may be used by causing laser oscillation. As an application of the organic EL element according to the present invention, an application as a backlight of a display device and a light source of an illumination device is particularly preferable, and it is suitable for a device in which emitted light is white light.

  The emission color of the organic light emitting material and the color of the emitted light of the organic EL element are shown in FIG. 4.16 on page 108 of “New Color Science Handbook” (edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with the total CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates.

  Further, in this specification, light whose deviation Duv from the black body radiation locus of light color is in the range of −20 to +20 within the range of the correlated color temperature of 2500 to 7500 K is referred to as white light. To do. The definition of Duv (= 1000 duv) is based on JIS Z 8725: 1999 “Light Source Distribution Temperature and Color Temperature / Correlated Color Temperature Measurement Method”.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using the Example of this invention, the technical scope of this invention is not limited to this.

  As an example of the present invention, a white light emitting organic EL device including two light emitting units was manufactured. In addition, as an organic EL element which concerns on an Example, the light emitting unit arrange | positioned nearest to a metal electrode among several light emitting units is organic with the shortest wavelength of emitted light among several light emitting units. Samples 101 to 109 containing the light emitting material were manufactured by changing the configuration of the light emitting layer and the type of the organic light emitting material in the light emitting unit, respectively. Moreover, as a control sample (organic EL element according to the comparative example), among the plurality of light emitting units, the light emitting unit disposed closest to the metal electrode is the light emitting light of the plurality of light emitting units. Samples 110 to 112 containing no organic light emitting material having the shortest wavelength were produced.

  FIG. 4 is a perspective view showing an outline of the organic EL element according to the embodiment of the present invention. FIG. 5 is a cross-sectional view schematically showing an organic EL element according to an example of the present invention.

  As shown in FIG. 4, the organic EL element 100 according to the example has a structure in which a glass substrate 101 is covered with a glass cover 102. The sealing operation with the glass cover 102 was performed in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) without bringing the organic EL element into contact with the atmosphere.

  As shown in FIG. 5, an anode 103 that is a transparent electrode, an interelectrode component 104 that includes a plurality of light emitting units, and a cathode 105 that is a metal electrode are stacked on a glass substrate 101. The glass cover 102 is filled with nitrogen gas, and a water catching agent 107 is provided.

<< Production of Sample 101 >>
<Formation of transparent electrode>
A glass transparent substrate having a size of 30 mm × 30 mm and a thickness of 0.7 mm was prepared as a base material for the organic EL element. On this transparent substrate, ITO (indium tin oxide) was patterned to a thickness of 150 nm to form a film, thereby forming an anode as a transparent electrode. Next, the transparent substrate on which the anode was formed was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and then subjected to UV ozone cleaning for 5 minutes.

<Formation of first light emitting unit>
Then, the 1st light emission unit was formed in the following procedures using the vacuum evaporation system. First, the transparent substrate on which the anode was formed was fixed to the substrate holder of the vacuum deposition apparatus, and each deposition crucible of the vacuum deposition apparatus was filled with the material of each layer constituting the first light emitting unit. As the crucible, a resistance heating crucible made of molybdenum or tungsten was used.

Subsequently, the chamber of the vacuum deposition apparatus was depressurized to a vacuum degree of 1 × 10 ⁻⁴ Pa, and the compound M-1 (MTDATA) represented by the following structural formula was deposited on the anode at a deposition rate of 0.1 nm / second. Then, a hole injection layer having a film thickness of 15 nm was formed.

  Next, a compound M-2 (α-NPD) represented by the following structural formula was deposited on the hole injection layer to form a hole transport layer having a thickness of 50 nm.

  Subsequently, the compound GD-1 (green light emitting material) and the compound H-1 (host compound) represented by the following structural formula were deposited at a deposition rate of 0.1 nm / second so that the compound GD-1 was 15% by mass. And co-evaporated on the hole transport layer to form a first light-emitting layer having a thickness of 30 nm.

  Subsequently, the compound RD-1 (red light emitting material) and the compound H-1 (host compound) represented by the following structural formula are deposited at a deposition rate of 0.1 nm / second so that the compound RD-1 is 15% by mass. Co-evaporation was performed on the first light-emitting layer to form a second light-emitting layer having a thickness of 30 nm. Note that Compound RD-1 is a phosphorescent red light-emitting material (red phosphorescent light-emitting material) that exhibits an emission maximum wavelength in a region near a wavelength of 620 nm.

  Subsequently, Compound E-1 (ET-100) represented by the following structural formula was deposited on the second light-emitting layer at a deposition rate of 0.1 nm / second to form an electron transport layer having a thickness of 20 nm.

<Formation of intermediate connector layer>
Subsequently, an n-type dopant material “NDN-26” (manufactured by Novaled) and Compound E-1 were deposited on the first light emitting unit at a deposition rate of 0.1 nm / second so that NDN-26 was 5 mass%. Co-evaporated to form an n-type layer having a thickness of 20 nm.

  Subsequently, a p-type dopant material “NDP-9” (manufactured by Novaled) and compound M-2 are co-deposited on the n-type layer at a deposition rate of 0.1 nm / second so that NDP-9 is 50% by volume. Then, a p-type layer having a thickness of 10 nm was formed.

<Formation of second light emitting unit>
Subsequently, Compound M-2 was deposited on the p-type layer at a deposition rate of 0.1 nm / second to form a 50 nm-thick hole transport layer.

  Subsequently, the compound BD-1 (blue light-emitting material), the compound RD-1 and the compound H-1 (host compound) represented by the following structural formula, the compound BD-1 being 15% by mass, and the compound RD-1 being Co-evaporation was performed on the hole transport layer at a deposition rate of 0.1 nm / second so as to be 1.5% by mass, thereby forming a third light emitting layer having a thickness of 30 nm.

  Subsequently, Compound E-1 was deposited on the third light-emitting layer at a deposition rate of 0.1 nm / second to form an electron transport layer having a thickness of 35 nm.

  Subsequently, LiF was vapor-deposited on the electron carrying layer, and the 1.5-nm-thick electron injection layer was formed.

<Formation of metal electrode>
On this transparent substrate, aluminum was deposited to a thickness of 110 nm to form a cathode that is a metal electrode.

  Subsequently, the non-light-emitting surface opposite to the transparent electrode side of the cathode is sealed with a glass case, and a light-collecting sheet is attached to the light-emitting surface opposite to the anode of the transparent substrate, so that the organic EL of the sample 101 is obtained. It was set as the element.

<< Production of Sample 102 >>
The organic EL element of sample 102 was manufactured in the same manner as the organic EL element of sample 101 except that the configuration of the second light emitting unit was changed as follows.

<Formation of second light emitting unit>
In the formation of the second light emitting unit, Compound M-2 was deposited on the p-type hole transport layer at a deposition rate of 0.1 nm / second to form a 50 nm-thick hole transport layer.

  Subsequently, the compound BD-1 (blue light emitting material) and the compound H-1 (host compound) are deposited on the hole transport layer at a deposition rate of 0.1 nm / second so that the compound BD-1 is 15% by mass. Co-evaporation was performed to form a third light emitting layer having a thickness of 30 nm.

  Next, Compound RD-1 (red light emitting material) and Compound H-1 (host compound) were co-deposited on the third light emitting layer at a deposition rate of 0.1 nm / second so that Compound RD-1 was 15% by mass. Evaporation was performed to form a fourth light emitting layer having a thickness of 30 nm.

  Subsequently, Compound E-1 was deposited on the fourth light emitting layer at a deposition rate of 0.1 nm / second to form an electron transport layer having a thickness of 35 nm.

  Subsequently, LiF was vapor-deposited on the electron carrying layer, and the 1.5-nm-thick electron injection layer was formed.

<< Production of Sample 103 >>
In the organic EL element of Sample 103, the type of the organic light emitting material to be contained in each light emitting layer is changed as shown in the table below, and vapor deposition is performed so that the compound BD-1 (blue light emitting material) is 30% by mass. It was manufactured in the same manner as the organic EL element of Sample 102 except that the light emitting layer was formed.

<< Preparation of Sample 104 to Sample 107 >>
The organic EL elements of Sample 104 to Sample 107 were manufactured in the same manner as the organic EL element of Sample 102 except that the type of organic light emitting material to be contained in each light emitting layer was changed as shown in the table below. Compound RD-2 is a phosphorescent red light-emitting material (red phosphorescent light-emitting material) that exhibits a light emission maximum wavelength in a region near a wavelength of 605 nm.

<< Production of Sample 108 >>
The organic EL element of sample 108 was manufactured in the same manner as the organic EL element of sample 101 except that the configuration of the first light emitting unit and the second light emitting unit was changed as follows.

<Formation of first light emitting unit>
In the formation of the first light emitting unit, Compound M-1 was deposited on the anode at a deposition rate of 0.1 nm / second to form a 15 nm thick hole injection layer.

  Next, Compound M-2 was deposited on the hole injection layer to form a 50 nm-thick hole transport layer.

  Subsequently, the compound GD-1, the compound RD-2, and the compound H-1 were deposited at a deposition rate of 0.1 nm / second so that the compound GD-1 was 15% by mass and the compound RD-2 was 1.5% by mass. And co-evaporated on the hole transport layer to form a first light-emitting layer having a thickness of 30 nm.

<Formation of second light emitting unit>
In the formation of the second light emitting unit, Compound M-2 was deposited on the p-type hole transport layer at a deposition rate of 0.1 nm / second to form a 50 nm-thick hole transport layer.

  Subsequently, the compound GD-1, the compound RD-1, and the compound H-1 were positive at a deposition rate of 0.1 nm / second so that the compound GD-1 was 15 mass% and the compound RD-1 was 5 mass%. Co-evaporation was performed on the hole transport layer to form a third light-emitting layer having a thickness of 30 nm.

  Next, Compound BD-1 and Compound H-1 were co-deposited on the third light-emitting layer at a deposition rate of 0.1 nm / second so that Compound BD-1 would be 15% by mass. A light emitting layer was formed.

  Subsequently, Compound E-1 was deposited on the fourth light emitting layer at a deposition rate of 0.1 nm / second to form an electron transport layer having a thickness of 35 nm.

  Subsequently, LiF was vapor-deposited on the electron carrying layer, and the 1.5-nm-thick electron injection layer was formed.

<< Production of Sample 109 >>
The organic EL element of Sample 109 was manufactured in the same manner as the organic EL element of Sample 108, except that the type of organic light emitting material contained in each light emitting layer was changed as shown in the table below.

<< Production of Samples 110 to 111 >>
The organic EL elements of Samples 110 to 111 were manufactured in the same manner as the organic EL element of Sample 101 except that the types of organic light emitting materials to be contained in each light emitting layer were changed as shown in the table below.

<< Production of Sample 112 >>
The organic EL element of Sample 112 was manufactured in the same manner as the organic EL element of Sample 101 except that the configuration of the light emitting unit was changed as follows.

<Formation of light emitting unit>
In the formation of the light emitting unit, Compound M-1 was deposited on the anode at a deposition rate of 0.1 nm / second to form a 15 nm thick hole injection layer.

  Next, Compound M-2 was deposited on the hole injection layer to form a 50 nm-thick hole transport layer.

  Subsequently, the compound GD-1, the compound RD-2, and the compound H-1 were deposited at a deposition rate of 0.1 nm / second so that the compound GD-1 was 15% by mass and the compound RD-2 was 1.5% by mass. And co-evaporated on the hole transport layer to form a first light-emitting layer having a thickness of 30 nm.

  Next, Compound BD-1 and Compound H-1 are co-deposited on the first light-emitting layer at a deposition rate of 0.1 nm / second so that Compound BD-1 is 15% by mass, and a second film having a thickness of 30 nm is formed. A light emitting layer was formed.

  Subsequently, Compound E-1 was deposited on the second light emitting layer at a deposition rate of 0.1 nm / second to form an electron transport layer having a thickness of 35 nm.

  Subsequently, LiF was vapor-deposited on the electron carrying layer, and the 1.5-nm-thick electron injection layer was formed.

<Formation of metal electrode>
On this transparent substrate, aluminum was deposited to a thickness of 110 nm to form a cathode that is a metal electrode.

  Subsequently, the non-light-emitting surface opposite to the transparent electrode side of the cathode is sealed with a glass case, and a condensing sheet is attached to the light-emitting surface opposite to the anode of the transparent substrate, so that the organic EL of the sample 112 is obtained. It was set as the element.

  The arrangement of the organic light emitting material used in the organic EL elements of the produced samples 101 to 112 and the concentration (mass%) of the organic light emitting material (BD-1) having the shortest wavelength of the emitted light are shown in the following table. It is as follows. The light emitting unit disposed closest to the metal electrode is the second light emitting unit, and the light emitting layer disposed closest to the metal electrode is the light emitting layer 4.

≪Sample evaluation≫
Next, for the manufactured organic EL elements of Sample 101 to Sample 112, the external extraction quantum efficiency, drive voltage, power efficiency, color rendering properties (average color rendering index (Ra) and special color rendering index (R9)), current density The chromaticity stability against fluctuations, the light emission lifetime, and the chromaticity stability against driving time were evaluated.

<Spectral luminance evaluation>
Spectral radiance meter CS-2000 (manufactured by Konica Minolta Sensing Co., Ltd.) is used for the external extraction quantum efficiency, driving voltage, power efficiency, average color rendering index (Ra) and special color rendering index (R9) of the organic EL element of the sample. And measured. The sample organic EL elements were each driven with a constant current of ^2.5 mA / cm ² . These results are shown in Table 2. The results for each sample are shown as relative values with the measured value of the sample 101 as 100.

<Chromaticity stability evaluation against current density fluctuation>
The chromaticity stability with respect to the variation of the current density of the organic EL element of the sample is the chromaticity variation (chromaticity difference (ΔEE) of the emitted light when the current density of each sample is increased from 1 mA / cm ² to ² mA / cm ^2. )). The chromaticity difference (ΔE) is obtained by measuring the chromaticity coordinates (x, y) in the CIE1931 color system chromaticity diagram for the emitted light at each current density, and from the displacement (Δx, Δy) of the chromaticity coordinates, Calculation was performed according to Equation 1. Note that a spectral radiance meter CS-2000 (manufactured by Konica Minolta Sensing) was used for measurement of chromaticity (chromaticity coordinates). The results are shown in Table 2.
ΔE = (Δx ² + Δy ² ) ^1/2 (Equation 1)

<Emission life evaluation>
The light emission lifetime of the sample organic EL element was evaluated by the half-life of the initial luminance. Specifically, each sample organic EL element was continuously driven at a constant current with a front luminance of 4000 cd / m ^2, and the time required for the front luminance to decrease to 2000 cd / m ² was measured. The emission lifetime was assumed. The results are shown in Table 2. The results for each sample are shown as relative values with the measured value of the sample 101 as 100.

<Chromaticity stability evaluation with respect to driving time>
The chromaticity stability of the sample with respect to the driving time of the organic EL element was evaluated by the chromaticity variation (chromaticity difference (ΔE)) of the emitted light when each sample was continuously driven to the half life of the initial luminance. The chromaticity difference (ΔE) is determined by measuring the chromaticity coordinates (x, y) in the CIE 1931 color system chromaticity diagram for the emitted light having the initial luminance and the emitted light having a half-life, and the displacement (Δx, Δy) was calculated according to Equation 1. The results are shown in Table 2.

<Evaluation results>
As shown in Table 2, the light emitting unit disposed closest to the metal electrode among the plurality of light emitting units contains an organic light emitting material having the shortest wavelength of emitted light among the plurality of light emitting units. In the sample 101 to the sample 109, the light emitting unit arranged closest to the metal electrode among the plurality of light emitting units is an organic light emitting material having the shortest wavelength of emitted light among the plurality of light emitting units. High external extraction quantum efficiency is realized as compared with the samples 110 to 111 which are not contained and the sample 112 which is not a tandem type.

  In addition, among the plurality of light emitting layers, the light emitting layer disposed closest to the metal electrode includes an organic light emitting material having the shortest wavelength of emitted light among the plurality of light emitting layers. In sample 109, the light emitting layer disposed closest to the metal electrode among the plurality of light emitting layers does not contain an organic light emitting material having the shortest wavelength of emitted light among the plurality of light emitting layers. Compared to 102, high external extraction quantum efficiency is realized, and power efficiency is excellent. Therefore, by including an organic light emitting material having the shortest wavelength of emitted light in the light emitting layer disposed near the metal electrode, plasmon loss can be reduced and the external extraction quantum efficiency of the organic EL element can be improved. Is recognized.

  Further, when comparing the sample 101 with the sample 103 and the sample 104, the sample 103 and the sample 104 having a plurality of light emitting layers in which the light emitting unit arranged closest to the metal electrode has a plurality of light emitting layers. Compared with the sample 101 which is not, the chromaticity stability with respect to the fluctuation of the current density and the chromaticity stability with respect to the driving time are excellent. Therefore, it can be seen that by using a plurality of light emitting layers per light emitting unit, fluctuations in the light emitting position of the organic light emitting material are suppressed and the chromaticity of the emitted light is stabilized.

  Further, when comparing the sample 103 and the sample 104, the sample 104 in which the concentration of the organic light emitting material is 28% by mass or less is compared with the sample 103 in which the concentration of the organic light emitting material is 30% by mass. And the light emission life is improved. Therefore, if the concentration of the organic light emitting material is 28% by mass or less, it can be said that the occurrence of concentration quenching is suppressed and the luminance is improved.

  Further, comparing Samples 101 to 104 with Samples 105 to 107, Sample 105 to Sample 107 in which two types of red light emitting materials are used Sample 101 in which two or more types of red light emitting materials are not used. -The average color rendering index (Ra) and the special color rendering index (R9) are higher than those of the sample 104. Thus, it can be seen that by using two kinds of red light emitting materials, the color rendering properties of the emitted light can be enhanced, and white light with a low color temperature can be realized.

  Further, when comparing the sample 105 and the sample 106 to the sample 107, in the sample 106 to the sample 107 in which two types of red light emitting materials are included in different light emitting units, two or more types of red light emitting materials are the same light emitting unit. Compared with the sample 105 contained in the battery, the driving voltage is low and the power efficiency is improved. Therefore, it is recognized that the influence of the red light emitting material having low charge transportability can be reduced by including two kinds of red light emitting materials in different light emitting units.

  Further, when the sample 108 and the sample 109 are compared, the red light emitting material having the shortest wavelength of emitted light among the two or more types of red light emitting materials is the most relative to the metal electrode among the two or more types of red light emitting materials. In the sample 109 included in the near light emitting unit, the red light emitting material having the shortest wavelength of emitted light among the two or more types of red light emitting materials is the most relative to the metal electrode among the two or more types of red light emitting materials. Compared with the sample 108 not included in the near light emitting unit, a high external extraction quantum efficiency is realized, and power efficiency is excellent. Therefore, by including the red light emitting material having the shortest wavelength of emitted light in the light emitting unit arranged close to the metal electrode, plasmon loss is reduced and the external extraction quantum efficiency of the organic EL element is improved. I understand that.

1 Organic EL element 10 Base material 20 Anode (transparent electrode)
30A, 30B Light emitting unit 31 Hole injection layer 32 Hole transport layer 33A, 33B Light emitting layer 34 Electron transport layer 35 Electron injection layer 40 Intermediate connector layer 50 Cathode (metal electrode)

Claims (8)

A transparent electrode;
A metal electrode as a counter electrode of the transparent electrode;
An organic electroluminescence device comprising a light emitting layer containing an organic light emitting material, and comprising a plurality of light emitting units stacked in series with an intermediate connector layer interposed between the transparent electrode and the metal electrode. ,
Among the plurality of light emitting units, the light emitting unit arranged closest to the metal electrode contains an organic light emitting material having the shortest wavelength of emitted light among the plurality of light emitting units ,
In the organic electroluminescence element, two or more kinds of red phosphorescent materials exhibiting a maximum emission wavelength in a region of a wavelength of 580 nm or more and less than 830 nm are used . The organic electroluminescent element according to claim 1, wherein the organic light emitting material is made only of a phosphorescent light emitting material. The light emitting unit disposed closest to the metal electrode has a plurality of light emitting layers,
The light emitting layer disposed closest to the metal electrode among the plurality of light emitting layers contains an organic light emitting material having the shortest wavelength of emitted light among the plurality of light emitting layers. The organic electroluminescence device according to claim 1 or 2, wherein the organic electroluminescence device is characterized. The organic phosphorescent material having the shortest wavelength of emitted light is a blue phosphorescent material exhibiting a maximum emission wavelength in a region of a wavelength of 400 nm or more and less than 490 nm. The organic electroluminescent element of description. The organic electroluminescent element according to any one of claims 1 to 4, wherein the two or more kinds of red phosphorescent materials are contained in different light emitting units. Of the two or more types of red phosphorescent materials, the red phosphorescent material having the shortest wavelength of emitted light is included in the light emitting unit closest to the metal electrode among the two or more types of red phosphorescent materials. The organic electroluminescence element according to claim 5 , wherein Wherein the plurality of respective light-emitting layers emitting unit has an organic electroluminescent device according to any one of claims 1 to 6, wherein the concentration of the organic light emitting material is not more than 28 wt%. An illuminating device comprising the organic electroluminescence element according to any one of claims 1 to 7 .

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