JP6776309B2 - Organic light emitting element, display device, imaging device and lighting device - Google Patents

Description

The present invention relates to an organic light emitting element, a display device, an imaging device and a lighting device.

The organic light emitting element is driven by installing a thin film containing a luminescent organic compound between the anode and the cathode, applying a voltage between the electrodes, and injecting holes and electrons. The holes and electrons are recombined in the element, and the light emitted when the excited state (exciton) of the organic compound returns to the ground state is used.

Recent advances in organic light-emitting devices have been remarkable, and their features are high brightness at low applied voltage, variety of light-emitting wavelengths, high-speed responsiveness, thin and lightweight light-emitting devices, and therefore development of a wide range of applications. Is being done.

A full-color display using an organic light emitting element is known. The method includes a method of emitting different emission colors by creating a light emitting layer for each pixel (element), and a method of emitting white light emission, and a color filter is used to extract a different emission color for each pixel. There are methods and so on. As for the white light emitting layer, it is known that two or more kinds of light emitting materials are used and two or more light emitting layers are used.

Patent Document 1 describes an organic light emitting device in which two light emitting layers are laminated, and the light emitting layer on the cathode side has a blue light emitting dopant, and the light emitting layer on the anode side has a 0.5 wt% red light emitting dopant and a green light emitting dopant. Is described.

Patent Document 2 describes an organic light emitting device having a 0.3 wt% light blue light emitting dopant and a 0.3 wt% yellow light emitting dopant in one light emitting layer.

Japanese Unexamined Patent Publication No. 2014-022205 Japanese Unexamined Patent Publication No. 2008-270557

X. Y. Zheng et al. , "A White OLED based on DPVBi blue light emerging host and DCJTB red dopant", Display, 2003, Volume 24, 3, p. 121-124

Since the organic light emitting device of Patent Document 1 has a high dopant concentration of red light emission, excitons are likely to be deactivated by the dopant, and further improvement in luminous efficiency is desired.

In the organic light emitting device of Patent Document 2, since the light blue light emitting dopant and the yellow light emitting dopant are contained in the same layer, excitons are likely to be trapped in the yellow light emitting dopant in the same layer as the light blue light emitting dopant. Therefore, since the concentration of excitons present in the layer of the light blue light emitting dopant is not relatively low, material deterioration is likely to occur, and the continuous drive life cannot be practically sufficient.

An object of the present invention is to provide an organic light emitting device having high luminous efficiency and long drive life.

The present invention has a first electrode, a first light emitting layer, a second light emitting layer, and a second electrode in this order, and the first light emitting layer has a first host material and a first dopant that emits fluorescence. The second light emitting layer has a second host material and a second dopant material, and the lowest excited triplet energy of the first host material is higher than the lowest excited triplet energy of the first dopant material. The minimum singlet energy of the first dopant material is smaller than the lowest excited singlet energy of the second dopant material, and the weight of the first light emitting layer is 100 wt%. Provided is an organic light emitting element characterized in that the weight ratio of the first dopant material is 0.3 wt% or less.

According to the present invention, it is possible to provide an organic light emitting device having high luminous efficiency and a long drive life.

It is the schematic sectional drawing which shows one Embodiment of this invention. It is a schematic diagram explaining one Embodiment of this invention. It is a schematic diagram explaining one Embodiment of this invention. It is a schematic diagram explaining the material deterioration mechanism of an organic light emitting element. It is the schematic sectional drawing of an example of the display device using the organic light emitting element which concerns on one Embodiment of this invention. It is a figure which shows the data analysis result of the TTA emission ratio. It is a schematic diagram which shows an example of the display device which concerns on one Embodiment of this invention. (A) It is a schematic diagram which shows an example of the image pickup apparatus which concerns on one Embodiment of this invention. (B) It is a schematic diagram which shows an example of the electronic device which concerns on one Embodiment of this invention. (A) It is a schematic diagram which shows an example of the display device which concerns on one Embodiment of this invention. (B) It is a schematic diagram which shows an example of the foldable display device. (A) It is a schematic diagram which shows an example of the lighting apparatus which concerns on one Embodiment of this invention. (B) It is a schematic diagram which shows an example of the automobile which has the lighting equipment for a vehicle which concerns on one Embodiment of this invention.

The organic light emitting element according to the embodiment of the present invention has a first electrode, a first light emitting layer, a second light emitting layer, and a second electrode in this order, and the first light emitting layer is the first host. It has a material and a first dopant material that emits fluorescence, the second light emitting layer has a second host material and a second dopant material, and the lowest excited triplet energy of the first host material is the first higher than the lowest excited triplet energy of the dopant material, the lowest excited singlet energy of the first dopant material is a small organic light-emitting device than the lowest excited singlet energy of said second dopant material, said first luminous The organic light emitting element is characterized in that the weight ratio of the first dopant material is 0.3 wt% or less when the weight of the layer is 100 wt%.

When the minimum triplet energy of the first dopant material is smaller than the minimum excited triplet energy of the host material, the life of the organic light emitting device tends to be extended, but the luminous efficiency due to Triplet-Triplet Animation (hereinafter, TTA) is improved. The effect of improvement is small.

In the present embodiment, when the lowest excited triplet energy of the first dopant is smaller than the lowest excited triplet energy of the host material, the lowest excited triplet energy trapped in the first dopant material is the weight ratio of the first dopant material. Control with. As a result, both the long life of the organic light emitting element and the improvement of the luminous efficiency by TTA can be achieved.

In the present embodiment, appropriately setting the weight ratio of the first dopant material in the first light emitting layer leads to an increase in the efficiency of TTA. TTA is a phenomenon in which two triplet excitons collide with each other to generate singlet excitons. In an organic light emitting element that emits fluorescence, in order to obtain an organic light emitting element having high luminous efficiency, it is preferable to efficiently generate light emission by TTA. TTA occurs when triplet excitons collide with the host material, which is the main component of the light emitting layer. However, when the minimum triplet energy of the dopant material is smaller than the minimum excited triplet energy of the host material, the minimum excited triplet energy is likely to be trapped in the dopant material, which may hinder the generation of TTA in the host material. is there.

It has been found that when the weight ratio of the first dopant material is 0.3 wt% or less, triplet excitons that are not appropriately trapped by the first dopant material are generated, and as a result, TTA is efficiently generated. If the weight ratio of the first dopant material is larger than this, the probability that triplet excitons are trapped in the first dopant material increases significantly, and the efficiency of TTA decreases.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the present invention. FIG. 1A has an anode 2, a hole transport layer 3, a first light emitting layer 4, an electron transport layer 6, and a cathode 7 on a substrate 1 in this order from the substrate side. The first light emitting layer has a first dopant, and its weight ratio is 0.3 wt% or less when the weight of the first light emitting layer is 100 wt%.

FIG. 1B has an anode 2, a hole transport layer 3, a first light emitting layer 4, a second light emitting layer 5, an electron transport layer 6, and a cathode 7 on the substrate 1 in this order from the substrate side. The first electrode may be an anode or a cathode. The first light emitting layer 4 and the second light emitting layer 5 each have a dopant of a different light emitting color. The present invention is not limited to such a configuration, and may have a hole injection layer, an electron block layer, a hole block layer, and an electron injection layer. The hole injection layer may be arranged between the anode 2 and the hole transport layer 3. The electron block layer may be arranged between the hole transport layer 3 and the second light emitting layer 5 .

The hole block layer may be arranged between the second light emitting layer 5 and the electron transport layer 6. The electron injection layer may be arranged between the electron transport layer 6 and the cathode 7. These hole injection layer, electron block layer, hole block layer, and electron injection layer are appropriately used in the present invention as needed.

The energy of the organic compound layer is determined by the material that occupies a large proportion of its weight. If it is one material, it is the physical property of the material, and if it is a plurality of materials, it is the physical property of the material having the largest weight ratio. In the case of 1: 1 it may be the average value.

In the organic light emitting device according to the present embodiment, the first light emitting layer is a light emitting layer having a first host material and a first dopant material. The second light emitting layer is a light emitting layer having a second host material and a second dopant material. The first light emitting layer and the second light emitting layer may be in contact with each other.

In the organic light emitting device according to the present embodiment, the first host material is the material having the largest weight ratio in the first light emitting layer. The second host material is the material having the largest weight ratio in the second light emitting layer. It can also be said that the host material is a substrate material for the light emitting layer.

The first dopant material may be a material having a smaller energy gap than the second dopant material. That is, the emission wavelength of the first dopant material is longer than the emission wavelength of the second dopant material.

In the organic light emitting device according to the present embodiment, the first dopant material may be a light emitting material that emits light having the longest wavelength in the light emitting layer. The second dopant material may be a light emitting material that emits light having the shortest wavelength in the light emitting layer. In this case, the lowest excited triplet energy of the second dopant is preferably higher than the lowest excited triplet energy of the first dopant because the second light emitting layer that emits light of a short wavelength is more likely to be deteriorated. Since the density of triplet excitons in the second light emitting layer is reduced and the triplet excitons are retained in the first light emitting layer, the device life can be extended. A luminescent material is a material that emits light. The first dopant material and the second dopant material may be light emitting materials. The long and short emission wavelengths of the light emitting material may be compared using the wavelength of the peak having the highest intensity in the emission spectrum of the light emitting material.

The light emitting material of the organic light emitting device according to the present embodiment may be a light emitting material that emits fluorescence. This is because the TTA causes the singlet excitons generated from the triplet excitons to emit light.

The difference between the lowest excited trinomial energy T1 (H1) of the first host material and the lowest excited triplet energy T1 (D1) of the first dopant material may be 0.3 eV or less. When the difference is 0.3 eV or less, the lowest excited triplet energy trapped in the first dopant material is reduced, so that the lowest excited triplet energy is likely to be present in the first host material. As a result, the TTA efficiency is improved, which is preferable.

On the other hand, in the organic light emitting device according to the present embodiment, the lowest excited trinomial energy T1 (H1) of the first host material and the lowest excited triplet energy T1 (D1) of the first dopant material have the following formula (1). It is preferable to satisfy the relationship of.
T1 (H1) -T1 (D1) ≥ 0.3eV (1)

That is, the difference between the lowest excited triplet energy of the first host material and the lowest excited triplet energy of the first dopant material may be 0.3 eV or more. This has the effect of extending the life of the organic light emitting element. Since the second light emitting layer having the dopant of shorter wavelength emission than the first light emitting layer is more likely to deteriorate in material than the first light emitting layer, it is preferable to reduce the density of triplet excitons. By using the energy relationship of the formula (1), the triplet excitons can be retained in the first light emitting layer, and the triplet exciton density of the second light emitting layer can be reduced.

The organic light emitting device according to the present embodiment may be a white organic light emitting device having a red light emitting material, a green light emitting material, and a blue light emitting material. In this case, the red light emitting material may be the first dopant material and the blue light emitting material may be the second dopant material. Further, the organic light emitting device according to the present embodiment may be a white organic light emitting device having two types of light emitting materials related to complementary colors. For example, the yellow light emitting material is the first dopant material and the light blue light emitting material is the second dopant material.

FIG. 2 is a diagram showing triplet energy transfer in the first light emitting layer and the second light emitting layer of the organic light emitting device according to the present embodiment. It represents the triplet energy transfer from the first host material to the second dopant. Hereinafter, they may be referred to as triplet energy, triplet excitons, etc., but they refer to the same ones.

Since triplet excitons move in the light emitting layer while repeating Dexter-type energy transfer between adjacent molecules, they cannot move between dopant materials discretely arranged in the light emitting layer. Therefore, the host material will be moved.

In FIG. 2, the triplet excitons generated in the second host material move to the first host material and become singlet excitons via TTA (TTA in FIG. 2) and move to the first dopant material. It is divided into those that do (ET2 in FIG. 2). In the present embodiment, the weight ratio of the first dopant is 0.3 wt% or less, and the number of triplet excitons that move to the first dopant material is small, so that the amount of ET2 is reduced and the excitons become singlet excitons via TTA. You can do a lot of things. That is, the luminous efficiency of the first light emitting layer can be increased.

If the light emitting layer in the organic light emitting device is only the first light emitting layer, the luminous efficiency can be improved by adjusting the weight ratio of the first dopant material.

The first dopant material of the organic light emitting device according to the present embodiment is preferably a fluorescent light emitting material. This is because when a phosphorescent material is used, triplet excitons of the dopant material are consumed by light emission and the like, and ET2 in FIG. 2 becomes large. When the triplet excitons are consumed by light emission, the amount of the host triplet excitons moving to the dopant material, that is, ET2, increases. As a result, the number of triplet excitons in the host decreases, and the number of triplet excitons that contribute to TTA decreases. Therefore, in order to improve the luminous efficiency of the first light emitting layer, the first dopant material is preferably a fluorescent light emitting material.

Further, the organic light emitting device having a fluorescent light emitting material has a longer device life than the organic light emitting device having a phosphorescent light emitting material, which is also a reason why the first dopant material is preferably a fluorescent light emitting material. More preferably, all the light emitting materials in the light emitting layer are fluorescent light emitting materials.

On the other hand, when the light emitting layer has a first light emitting layer and a second light emitting layer, it is preferable to configure the triplet excitons so that they can easily move from the second host material to the first host material. If there is no energy barrier from the second host material to the first host material, it is possible to smoothly move from the second host material to the first host material as shown in ET1 of FIG. Therefore, it is preferable that there is no energy barrier in the path from the second light emitting layer to the first light emitting layer.

The energy barrier refers to a state in which the energy state to be moved is higher than that before the movement. In the organic light emitting device, a configuration having an energy barrier may include a layer having a higher minimum excited triplet energy than the second light emitting layer. As an energy barrier of triplet energy from the second light emitting layer, an intermediate layer arranged between the second light emitting layer and the first light emitting layer can be mentioned. Even if there is an energy barrier, if the energy barrier is small, it may have an energy barrier of, for example, less than 0.3 eV.

More preferably, there is no energy barrier. Specifically, this facilitates the smoother movement of triplet excitons from the second host material to the first host material. That is, in the organic light emitting element according to the present embodiment, the lowest excited triplet energy of the material of the main component of each layer contained in the region from the first light emitting layer to the second light emitting layer is on the second electrode side of each layer. It is preferably less than or equal to the minimum excited triplet energy of the material of the main component of the adjacent layer. The material of the main component of the organic compound layer is a material having the largest weight ratio among the organic compound layers, and if the organic compound layer is a light emitting layer, it is a host material. When the weight ratio of the material of the organic compound layer is 1: 1, the lowest excited triplet energy of the average value is defined as the lowest excited triplet energy of the organic compound layer. As a result, the triplet excitons are smoothly moved from the second light emitting layer to the first light emitting layer, so that a long continuous drive life can be realized.

In the organic light emitting device according to the present embodiment, the minimum excitation triplet energy of the second host material is preferably higher than the minimum excitation triplet energy of the first host material. As a result, the triplet excitons transferred from the second host material to the first host material serve as an energy barrier when returning to the second host material, so that the triplet exciton density of the second light emitting layer tends to decrease. Therefore, a long continuous drive life can be realized.

In the organic light emitting device according to the present embodiment, it is preferable that the first light emitting layer and the second light emitting layer are in contact with each other. As a result, the triplet excitons can be smoothly moved from the second light emitting layer to the first light emitting layer, and a long continuous drive life can be realized.

In the organic light emitting device according to the present embodiment, it is preferable that the first host material and the second host material are the same material. This is because the transfer efficiency of triplet excitons between the same materials is superior to the transfer efficiency of triplet excitons between different materials. By smoothly moving the triplet excitons from the second light emitting layer to the first light emitting layer, a long continuous drive life can be realized.

The organic light emitting device according to the present embodiment may have an energy transfer path of the lowest excited triplet in the direction from the second electrode to the first electrode. This means that the lowest excited triplet energy of the second light emitting layer easily reaches the first dopant material by energy transfer. In other words, there is no energy barrier of the lowest excited triplet from the second light emitting layer to the first dopant material.

When moving from the second light emitting layer to the first dopant material, if the energy is within 0.3 eV, the energy after the movement is high, that is, there may be an energy barrier. A small energy barrier within 0.3 eV does not significantly impede energy transfer.

Further, in the region from the second light emitting layer to the first light emitting layer, the first dopant material is preferably an organic compound having the smallest minimum excited triplet energy. This is because the efficiency of energy transfer is higher than in the presence of an organic compound having a higher minimum excited triplet energy than the first dopant material.

It can be said that an energy path exists even when there is an energy barrier of less than 0.3 eV.

The first light emitting layer and the second light emitting layer may be in contact with each other, or other layers may be arranged between them. Examples of the other layer include a layer called an intermediate layer of the light emitting layer, an energy transfer suppression layer, and the like. Even when an energy transfer suppression layer or the like is present, the layer may be configured so that the lowest excited triplet energy can be transferred from the second light emitting layer to the first dopant material.

FIG. 3 is a diagram showing energy transfer from the second light emitting layer to the first light emitting layer. FIG. 3A is an example in which the first light emitting layer and the second light emitting layer are in contact with each other. In FIG. 3A, the lowest excited triplet energy T1 (H1) of the first host material and the lowest excited triplet energy T1 (H2) of the second host material satisfy the relationship of the following equation (2).

T1 (H1) ≤ T1 (H2) (2)
By satisfying the equation (2), the lowest excited triplet energy is easily transferred from the second light emitting layer to the first light emitting layer. As a result, the triplet exciton density of the second light emitting layer, in which the constituent material is liable to deteriorate, decreases, so that the device life can be extended. Further, the luminous efficiency can be improved by the TTA in the first light emitting layer.

In FIG. 3B, an intermediate layer arranged between the first light emitting layer and the second light emitting layer is shown. The relationship between the lowest excited triplet energy T1 (HM), T1 (H1), and T1 (H2) of the host material of the intermediate layer satisfies the following equation (3).
T1 (H1) ≤ T1 (HM) ≤ T1 (H2) (3)

The organic light emitting device according to the present embodiment may have a plurality of intermediate layers. Even if it has a plurality of intermediate layers, it has an energy path of minimum triplet energy from the second light emitting layer to the first light emitting layer. That is, the minimum excited triplet energy of each intermediate layer is equal to or less than the minimum excited triplet energy of the layer adjacent to the second light emitting layer side of the intermediate layer, and is equal to or greater than the minimum excited triplet energy of the first host material. .. The intermediate layer may be a light emitting layer, a charge transport layer, or the like. The intermediate layer may be the same material as the first host material or the second host material, or may be another material.

The organic light emitting device according to the present embodiment can realize a long continuous drive life by having the above configuration. This is because the triplet excitons are smoothly transferred from the second light emitting layer to the first light emitting layer, and moreover, many triplet excitons are present in the first host material in the first light emitting layer. This is because the weight ratio of the first dopant material is small, so that there are few triplet excitons trapped in the first dopant material. As a result, in the first host material, TTA is likely to occur, and the effect that the luminous efficiency of the organic light emitting element is high can be obtained.

In the organic light emitting device according to the present embodiment, the second lowest excited triplet energy of the host material T1 (H2) and the lowest excited triplet energy T1 of the second dopant material (D2) satisfies the relationship of formula (4) Is preferable.
T1 (H2) ≤ T1 (D2) (4)

This reduces the trapping of triplet excitons in the second dopant material in the second light emitting layer. Further, by satisfying the equation (2), the triplet excitons can be easily moved to the first light emitting layer.

In the organic light emitting device according to the present embodiment, the first emitting layer has a third dopant material, the lowest excited triplet energy of the lowest excited triplet energy T1 (H1) and the third dopant material of the first host material It is preferable that T1 (D3) satisfies the relationship of the formula (5). When the third dopant material is contained in the second light emitting layer, it is preferable that the same relationship is satisfied for the second light emitting layer. Specifically, the same relationship satisfies the following equation (6).
0eV <T1 (H1) -T1 (D3) <0.3eV (5)
0eV <T1 (H2) -T1 (D3) <0.3eV (6)

When the formula (5) is satisfied, T1 (D3) has a lower energy than T1 (H1), and is therefore effective for retaining triplet excitons in the first light emitting layer. The triplet excitons of the third dopant material have enough energy to move to the host material. Since triplet excitons are less likely to be trapped by the third dopant, TTA can occur efficiently. The same effect can be said for equation (6). As a result, the continuous drive life can be extended without impairing the luminous efficiency.

In the organic light emitting layer element according to the present embodiment, the material constituting the light emitting layer preferably has a difference between the lowest excited singlet energy and the lowest excited triplet energy of 0.2 eV or more. In this case, intersystem crossing due to thermal excitation from the lowest excited triplet state to the lowest excited singlet state can be suppressed. Emission through intersystem crossing due to thermal excitation is called thermoactive delayed fluorescence.

The emission lifetime of general fluorescence used in organic light emitting elements is on the order of nanoseconds, whereas the emission lifetime of thermally activated delayed fluorescence is on the order of microseconds. Therefore, the energy of the singlet excitons of the light emitting dopant is transferred to the triplet excitons of the neighboring host molecule before being emitted as light emission. Then, the formation of triplet excitons having an energy Tn (H) higher than the lowest excited triplet energy is likely to cause the cleavage of a single bond of an organic molecule.

Further, since it is necessary to set the minimum excited triplet energy of the thermally active delayed fluorescent material to be high, deterioration via the higher energy Tn (H) is likely to be promoted in that respect as well.

In the organic light emitting device according to the present embodiment, it is preferable that the first host material and the second host material are the same material. As a result, triplet excitons can be smoothly moved from the first light emitting layer to the second light emitting layer, and an organic light emitting device having a longer continuous drive life can be provided.

In the organic light emitting device according to the present embodiment, the weight ratio of the first dopant material is preferably 0.05 wt% or more. If it is less than 0.05 wt%, the doping concentration is too low and the Felster-type energy transfer of the singlet excitons from the first host material to the first dopant material does not occur efficiently, and the first dopant material The emission intensity may be significantly reduced.

Non-Patent Document 1 shows an emission spectrum of an organic light emitting device having a light emitting layer in which DCJTB is mixed as a red light emitting material with DPVBi as a host material. When the red light emitting material is 0.08 wt%, the emission peak derived from the red light emitting material can be confirmed, but when the red light emitting material is 0.03 wt%, the emission intensity derived from the red light emitting material is significantly reduced. , It is stated that the emission peak could not be confirmed.

Therefore, in the organic light emitting device according to the present embodiment, the concentration of the first dopant material is preferably 0.05 wt% or more and 0.30 wt% or less. This makes it possible to provide an organic light emitting element having both continuous drive life and luminous efficiency.

The first host material contained in the organic light emitting device according to the embodiment of the present invention is preferably a low molecular weight organic compound. Organic compounds are roughly classified into small molecules, oligomer molecules, and polymers depending on the molecule. Polymers and oligomer molecules are defined by the International Association of Genuine Applied Chemistry (IUPAC) Polymer Naming Methods Committee as follows.

Polymer, polymer molecule (macromolecule, polymer molecule): A molecule having a large molecular weight and having a structure composed of a number of repetitions of a unit obtained substantially or conceptually from a molecule having a small relative molecular weight. ..

Oligomer molecule: A molecule with a medium relative molecular weight and having a structure composed of a small number of repetitions of units substantially or conceptually obtained from a molecule with a small relative molecular weight. To say.

A low-molecular-weight organic compound is a molecule that does not meet the above definitions of polymer, polymer molecule, and oligomer molecule. That is, it is a molecule in which the number of repetitions of the repeating unit is a small number, preferably 3 or less, and more preferably 1.

In addition, there are two types of macromolecules: synthetic macromolecules obtained by chemical synthesis and natural macromolecules existing in nature. Natural polymers include polymers with a monodisperse of molecular weight, but synthetic polymers generally have molecular weight dispersibility due to differences in repeating units. On the other hand, organic low molecular weight compounds do not exist in nature and are molecules obtained by synthesis, but they do not have molecular weight dispersibility due to differences in repeating units.

The presence or absence of such dispersibility makes an important difference when used in the light emitting layer of an organic light emitting device. When a dispersible polymer compound is used in the light emitting layer, the energy spread of the state density of the lowest excited triplet energy of the compound contained in the light emitting layer becomes large, and it is difficult to control the triplet exciter in the light emitting layer. It is thought that the effect will be reduced.
Further, it is more preferable that all the light emitting layers of the organic light emitting device according to the embodiment of the present invention are composed of a low molecular weight organic compound.

In the organic light emitting device according to the present embodiment, the second dopant material is preferably a hydrocarbon compound. A hydrocarbon compound is a compound composed of carbon and hydrogen. Generally, a hydrocarbon compound is a material having a high binding energy for a single bond and is less likely to undergo bond cleavage deterioration. For example, the dissociation energy required for the single bond of C atom-C atom between aromatic hydrocarbons (CC single bond) and the dissociation of CC single bond between aromatic hydrocarbon and alkyl group is about 4 to 5 eV. is there. On the contrary, for example, the dissociation energy of a C-N single bond (CN single bond) of an amino group and an aromatic hydrocarbon or a C-N single bond such as a heterocycle and an aromatic hydrocarbon is 3 to 3. It is about 4 eV. Since the CN single bond has a smaller dissociation energy than the CC single bond, the bond is likely to be dissociated via the excited state.

The first dopant according to this embodiment has a low minimum excitation triplet energy and is less likely to deteriorate than the first host material, but when a triplet excitator is trapped, it receives energy transfer from a neighboring molecule and is excited at a higher order. There is a possibility of triplet state. Therefore, by using a hydrocarbon compound as the first dopant material, it is possible to provide an organic light emitting device having a longer continuous drive life.

In the organic light emitting element according to the present embodiment, when the second dopant material is a blue light emitting material, it is a hydrocarbon compound that does not contain a CN single bond between an amino group or an aromatic hydrocarbon and a heterocycle in the molecule. Is more preferable. The first dopant material is considered to contribute less to deterioration via the excited state than the first host material, but when it contains a CN single bond, the bond is cleaved only in the lowest excited singlet state. This is because there is a possibility of doing so.

In the present invention, it is preferable that the second dopant material is a blue light emitting material, the first dopant material is a red light emitting material, and the third dopant material is a green light emitting material. This makes it possible to provide an organic light emitting device that displays a good white color. In the present specification, the blue light emitting material refers to a light emitting material having a maximum peak wavelength of the light emitting spectrum of 430 nm to 480 nm. Further, the green light emitting material refers to a light emitting material having a maximum peak wavelength of a light emitting spectrum of 500 nm to 570 nm, and the red light emitting material refers to a material having a maximum peak wavelength of a light emitting spectrum of 580 nm to 680 nm. The maximum peak wavelength can also be said to be the shortest peak wavelength in the spectrum.

The measurement of the lowest excited singlet energy can be obtained from the visible light-ultraviolet absorption spectrum. To measure the lowest excited singlet energy is to measure the energy gap. In the present embodiment, it can be obtained from the absorption edge of the thin film formed on the glass substrate. As the device, for example, a spectrophotometer U-3010 manufactured by Hitachi can be used.

The maximum occupied orbital (HOMO) energy can be measured for ionization potential using atmospheric photoelectron spectroscopy (measuring instrument name AC-2 manufactured by RIKEN).

The lowest unoccupied orbital (LUMO) energy can be calculated from the energy gap measurement and the ionization potential. That is, electron affinity = ionization potential-energy gap.

The lowest excited triplet energy can be obtained from the phosphorescence spectrum of the organic material of interest. Specifically, the phosphorescence spectrum is measured at a low temperature such as liquid nitrogen temperature (77K), and T1 energy can be obtained from the first emission peak (shortest wavelength peak) of the measured phosphorescence spectrum.

If phosphorescence cannot be obtained, energy transfer from the triplet sensitizer is used. This method can also be applied to those with weak phosphorescence that cannot be measured.

Further, if the phosphorescence cannot be measured by the above method because the phosphorescence efficiency is very low, there is a method in which the minimum excited triplet energy can be obtained by using triplet-triplet energy transfer to the acceptor.

If phosphorescence is not obtained even after the above measurements, the lowest excited triplet energy can be obtained by the following calculation method by molecular orbital calculation.

Molecular orbital calculations are currently widely used in Gaussian 09 (Gaussian 09, Revision A.02, MJ Frisch, GW Tracks, WB Schlegel, GE Scusseria, MA. Robb, JR Cheeseman, G. Scalmani, V. Barone, B. Mennici, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, HP Hratchan, A. F. Izma. , J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.K. , H. Nakai, T. Vreven, JA Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, JJ Heed, E. Brothers, K.N. Kudin, V.I. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavacari, A. Rendell, J.C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. M. Klene, J.E.Knox, J.B.Cross, V.Bakken, C.Adamo, J.Jaramillo, R.Goperts, R.E.Stratmann, O.Yazyev, A.J.Austin, R. Cammi, C. Pomelli, JW Ochterski, RL Martin, K. Morokuma, VG Zakrzewski, GA Voth, P. Salvador, JJ Dannenberg, S. Dapprich, A.M. It can be carried out by D. Daniels, O. Farkas, JB Foresman, JV Ortiz, J. Cioslowski, and D.J. Fox, Gaussian, Inc., Wallingford CT, 2009.). The following methods, which are currently widely used, can be used as the calculation method. First, the structural optimization of the ground state is calculated by the density functional theory (DFT) using B3LYP for the functional and 6-31G * for the basis function.

Next, in the optimized structure, the minimum excited triplet (absorption) energy is calculated by the time-dependent density functional theory (TDDFT) using B3LYP for the functional and 6-31G ^* for the basis set. Note that computational chemistry software having the same function may be used instead for the calculation of DFT and TDDFT.

When comparing the lowest excited triplet energies of multiple materials, the measurement method or calculation method shall be unified.

Further, the lowest excited singlet energy can be obtained by the same method as the above-mentioned calculation method of the lowest excited triplet energy except that the lowest excited singlet energy is obtained as a result. When comparing the lowest excited singlet energy and the lowest excited triplet energy of a compound, the methods shall be unified and compared, such as between measured values or calculated values.

FIG. 4 is a diagram showing a deterioration mechanism of an organic light emitting element that emits fluorescence. The energy S1 (D) of the singlet exciton of the light emitting dopant is transferred to the lowest excited triplet energy T1 (H) of the host material. As a result, triplet excitons with higher energy Tn (H) are formed. A mechanism is known in which the single bond of an organic molecule is cleaved by deactivating the energy of Tn (H) having a high energy in the light emitting layer (Japanese Patent Laid-Open No. 2011-216640). Since triplet excitons have a long excitation lifetime, they have a high density in the membrane, and it is presumed that the above energy transfer process occurs at a relatively high frequency.

At this time, as the emission wavelength of the emission dopant is shorter, the energy S1 (D) of the higher singlet exciton moves to the triplet exciton, so that the total energy Tn (H) increases and the material deteriorates. Easy to cause. Therefore, the second light emitting layer having the second dopant having a shorter emission wavelength than the first dopant is more likely to cause material deterioration. Therefore, it is advantageous in terms of continuous drive life to collect triplet excitons in the first light emitting layer having the first dopant having a longer emission wavelength than the second dopant.

[Structure of an organic light emitting device according to an embodiment of the present invention]
(substrate)
The substrate of the organic light emitting device according to this embodiment may be a Si substrate, a glass substrate, or a resin substrate. In the case of a Si substrate, a micro display device can be obtained by forming a transistor on the Si itself. In the case of a glass substrate, a TFT may be provided as a display device. The resin substrate can also be called a flexible substrate. In the case of a flexible substrate, it may be a foldable or rollable display device. As long as it does not interfere with the light emitting direction of the light emitting device, it does not matter whether it is transmitted or not transmitted.

(electrode)
In the present embodiment, the first electrode is an anode and the second electrode is a cathode, but the first electrode may be a cathode and the second electrode may be an anode. When light is taken out from the second electrode side, the first electrode may be a reflective electrode.

The first electrode of the organic light emitting device according to the present embodiment is preferably a metal material having a reflectance of 80% or more. Specifically, metals such as Al and Ag, and alloys obtained by adding Si, Cu, Ni, Nd, Ti and the like to them can be used. As the alloy, AgMg, AlCu, TiN and the like can be used. Reflectance refers to the reflectance at the emission wavelength emitted from the light emitting layer. Further, the reflective electrode may have a barrier layer on the surface on the light extraction side. As the material of the barrier layer, metals of Ti, W, Mo, and Au and alloys thereof are preferable. The alloy may include the above-mentioned alloy.

The second electrode of the organic light emitting device according to the present embodiment is a semi-transmissive reflective layer having a property of transmitting a part of the light reaching its surface and reflecting the other part (that is, semi-transmissive reflectivity). It may be there. The upper electrode is formed of, for example, a simple substance metal such as magnesium or silver, an alloy containing magnesium or silver as a main component, or an alloy material containing an alkali metal or an alkaline earth metal.

When the second electrode is an alloy, for example, an alloy of magnesium and silver can be mentioned. In the case of an alloy of magnesium and silver, the alloy may be 1: 1 or may have a large amount of either atomic%. If any atomic% is to be increased, it may be silver. When the atomic% of silver is increased, the transmittance is high, which is preferable. Further, when increasing any atomic%, magnesium may be used. When the atomic% of magnesium is increased, the film property is high and it is difficult to cut, which is preferable.

The second electrode may have a laminated structure as long as it has a preferable transmittance.

(Organic compound layer)
The organic compound layer according to the present embodiment may be formed as a common layer of a plurality of organic light emitting devices. The common layer is arranged across a plurality of organic light emitting elements, and can be formed by performing a coating method such as spin coating or a thin film deposition method on the entire surface of the substrate.

The organic compound layer according to the present embodiment is a layer including at least a light emitting layer, and may be composed of a plurality of layers. Examples of the plurality of layers include a hole injection layer, a hole transport layer, an electron block layer, a light emitting layer, a hole block layer, and an electron transport layer. Each organic compound layer may be composed of a plurality of materials. In that case, the weight ratio may be 1: 1 to 4. The organic compound layer emits light when holes injected from the anode and electrons injected from the cathode recombine in the light emitting layer.

The light emitting layer may be composed of a plurality of layers, and each light emitting layer may have a red light emitting material, a green light emitting material, and a blue light emitting material, and by mixing each light emitting color, white light is emitted. Can be done. Further, white may be emitted by having a light emitting material having a relationship between complementary colors such as a blue light emitting material and a yellow light emitting material in any of the light emitting layers. The number of light emitting layers may be two, three, or more. The plurality of light emitting layers may emit light of different colors. Further, there may be a light emitting layer that emits light of the same color as other light emitting layers.

When white is emitted from a plurality of light emitting layers, for example, a first light emitting layer and a second light emitting layer, the organic light emitting element may have a color filter on the light emitting side thereof. By combining the white emission and the color filter, it is possible to obtain a required emission color such as RGB.

The compound contained in the light emitting layer is not particularly limited, and may be an anthracene derivative, a fluorene derivative, a pyrene derivative, a fluoranthene derivative, a chrysene derivative, a triphenylene derivative, or an iridium complex. These compounds may be hosts or guests.

The first dopant may be any one of a fluorene derivative, a fluoranthene derivative, a pyrene derivative, a rubrene derivative, a perylene derivative, and a boron complex.

Hereinafter, specific examples of the organic compound used in the organic compound layer will be shown. The present invention is not limited to these exemplary compounds.

Examples of the host material for the organic light emitting device according to the present embodiment include the following compounds. The host material may be a first host, a second host, or a host of a light emitting layer further provided.

The compounds of EM1 to 21 to 22 are preferable because they have a pyrene skeleton in their partial structure. In a compound having a pyrene skeleton, pyrene skeletons having a wide flatness are easily stacked, and triplet excitons are easily moved. As a result, TTA can be efficiently generated. EM1 can be synthesized by the method described in JP-A-2007-063285, EM23 can be synthesized by the method described in JP-A-2011-249754, and EM25 can be synthesized by the method described in JP-A-2012-102020. It can be synthesized by the method described in the publication, and EM26 can be synthesized by the method described in International Publication No. 2005/040302. The synthetic method described in each publication may be appropriately changed in consideration of the amount of compound synthesized and the type of substituent provided in the basic skeleton. For example, the halogen atom used in the coupling reaction may be changed to another type of halogen atom. Further, a dehalogenation step may be provided in order to reduce the halogen used in the coupling reaction from the final product. Further, in the synthesis step, the boronic acid derivative and the pinacol borane derivative used, the halogen species of the halogen compound, the Pd catalyst used in the Suzuki coupling reaction, and the like may be changed. Examples of the Pd catalyst to be modified include (Pd (PPh ₃ ) ₄ , Pd (PPh ₃ ) ₂ Cl ₂ , Pd (OAc) ₂ , Pd (dba) ₂ , Pd (dba) _{3 and the} like. S-Phos, X-Phos, triortotrilphosphine, tricyclohexylphosphine and the like may be added to the catalyst as phosphorus ligands, and a triflate form may be used instead of the halogen form. Suzuki Coupling Negishi coupling using organic zinc or still coupling using organic tin may be used instead of.

Examples of the blue light emitting material of the organic light emitting device according to the present embodiment include the following compounds.

BDs 8 to 30 are preferable because the single bonds constituting the compound are limited to CC bonds and CH bonds having high binding energies. However, since the bond between C and N of the cyano group is a triple bond and has a higher bond energy than a single bond, it may be regarded as a hydrocarbon compound although it has a C—N bond. The concentration of the blue light emitting material in the light emitting layer is preferably in the range of 0.1 or more and 10 wt% or less. More preferably, it is in the range of 0.3 or more and 2.0 wt% or less. BD1 can be synthesized by the method described in JP-A-9-241629, BD9 can be synthesized by the method described in JP-A-2008-297535, and BD16 can be synthesized by the method described in JP-A-2010-143879. BD23 can be synthesized by the method described in JP2012-246258, and BD25 can be synthesized by the method described in JP2009-221180. BD28 can be synthesized by the method described in JP-A-2011-011994. The synthesis method described in each publication may be appropriately changed in consideration of the amount of compound synthesized and the type of substituent provided in the basic skeleton. For example, the halogen atom used in the coupling reaction may be changed to another type of halogen atom. Further, a dehalogenation step may be provided in order to reduce the halogen used in the coupling reaction from the final product. Further, in the synthesis step, the boronic acid derivative and the pinacol borane derivative used, the halogen species of the halogen compound, the Pd catalyst used in the Suzuki coupling reaction, and the like may be changed. Examples of the Pd catalyst to be modified include (Pd (PPh ₃ ) ₄ , Pd (PPh ₃ ) ₂ Cl ₂ , Pd (OAc) ₂ , Pd (dba) ₂ , Pd (dba) _{3 and the} like. S-Phos, X-Phos, triortotrilphosphine, tricyclohexylphosphine and the like may be added to the catalyst as phosphorus ligands, and a triflate form may be used instead of the halogen form. Suzuki Coupling Negishi coupling using organic zinc or still coupling using organic tin may be used instead of.

Examples of the green light emitting material of the organic light emitting device according to the present embodiment include the following compounds.

GD8 to 31 are hydrocarbon compounds, which are preferable in achieving a long continuous drive life. The concentration of the green light emitting material in the light emitting layer is preferably in the range of 0.1 or more and 10.0 wt% or less. More preferably, it is in the range of 0.5 or more and 5.0 wt% or less. GD5 can be synthesized by the synthesis method described in JP-A-2006-176493, GD13 can be synthesized by the synthesis method described in JP-A-2008-255095, and GD16 can be synthesized by the synthesis method described in JP-A-2011-256113. GD21 can be synthesized by the synthesis method described in JP2012-001514, and GD29 can be synthesized by the synthesis method described in JP2013-0675886. The synthesis method described in each publication may be appropriately changed in consideration of the amount of synthesis and the type of substituent provided in the basic skeleton. For example, the halogen atom used in the coupling reaction may be changed to another type of halogen atom. Further, a dehalogenation step may be provided in order to reduce the halogen used in the coupling reaction from the final product. Further, in the synthesis step, the boronic acid derivative and the pinacol borane derivative used, the halogen species of the halogen compound, the Pd catalyst used in the Suzuki coupling reaction, and the like may be changed. Examples of the Pd catalyst to be modified include (Pd (PPh ₃ ) ₄ , Pd (PPh ₃ ) ₂ Cl ₂ , Pd (OAc) ₂ , Pd (dba) ₂ , Pd (dba) _{3 and the} like. S-Phos, X-Phos, triortotrilphosphine, tricyclohexylphosphine and the like may be added to the catalyst as phosphorus ligands, and a triflate form may be used instead of the halogen form. Suzuki Coupling Negishi coupling using organic zinc or still coupling using organic tin may be used instead of the above. Examples of the red light emitting material of the organic light emitting element according to the present embodiment include the following compounds.

RDs 5 to 23 are hydrocarbon compounds, which are preferable in achieving a long continuous drive life. RD5 can be synthesized by the synthesis method described in JP-A No. 10-330295, RD9 can be synthesized by the synthesis method described in JP-A-2013-0433846, and RD12 can be synthesized by the synthesis method described in JP-A-2013-0433846. It can be synthesized by the synthesis method described in Japanese Patent Application Laid-Open No. 2012-149012, RD13 can be synthesized by the synthetic method described in JP-A-2013-0496663, and RD20 can be synthesized by the synthetic method described in JP-A-2013-1394426. It can be synthesized by the synthesis method described in the publication. The synthesis method described in each publication may be appropriately changed in consideration of the amount of synthesis and the type of substituent provided in the basic skeleton. For example, the halogen atom used in the coupling reaction may be changed to another type of halogen atom. Further, a dehalogenation step may be provided in order to reduce the halogen used in the coupling reaction from the final product. Further, in the synthesis step, the boronic acid derivative and the pinacol borane derivative used, the halogen species of the halogen compound, the Pd catalyst used in the Suzuki coupling reaction, and the like may be changed. Examples of the Pd catalyst to be modified include (Pd (PPh ₃ ) ₄ , Pd (PPh ₃ ) ₂ Cl ₂ , Pd (OAc) ₂ , Pd (dba) ₂ , Pd (dba) _{3 and the} like. S-Phos, X-Phos, triortotrilphosphine, tricyclohexylphosphine and the like may be added to the catalyst as phosphorus ligands, and a triflate form may be used instead of the halogen form. Suzuki Coupling Negishi coupling using organic zinc or still coupling using organic tin may be used instead of.

Examples of the material used for the hole injection layer, the hole transport layer, and the electron block layer of the organic light emitting device according to the present embodiment include the following compounds. The hole injection layer, the hole transport layer, and the electron block layer are organic compound layers arranged between the anode and the light emitting layer. The electron block layer preferably has a lower LUMO than the light emitting layer host.

Examples of the material used for the electron transport layer and the hole block layer of the organic light emitting device according to the present embodiment include the following compounds. The electron transport layer and the hole block layer are organic compound layers arranged between the cathode and the light emitting layer. The hole block layer preferably has a lower HOMO than the host of the light emitting layer.

The material constituting the hole block layer or the electron block layer used in the organic light emitting device according to the present embodiment preferably has a higher minimum excited triplet energy than the host material of the adjacent light emitting layer. As a result, triplet excitons can be confined in the light emitting layer, and TTA can be efficiently generated.

As the electron injection layer of the organic light emitting device according to the present embodiment, a mixture of an electron donating dopant and an electron transporting material may be used. As the electron donating dopant, an alkali metal, an alkaline earth metal, a rare earth metal, or a compound thereof can be used. The electron injection layer is formed by containing 0.1 to 25 wt% of an alkali metal compound in the electron transporting material. More preferably, the alkali metal compound is a cesium compound. Further, more preferably, the cesium compound is a substance derived from cesium carbonate and cesium carbonate. A preferred method for forming an electron-injected layer in the present invention is to co-deposit cesium carbonate and an electron-transporting material. In order to ensure good electron injection properties, the thickness of the electron injection layer is preferably 10 nm to 100 nm. In addition, cesium carbonate is decomposed at the time of co-evaporation, and suboxides such as (Cs ₁₁ O ₃ ) Cs ₁₀ and (Cs ₁₁ O ₃ ) Cs and Cs ₁₁ O ₃ derived from cesium carbonate are formed in the electron injection layer. May be done. Further, a coordination compound may be formed between the cesium and the organic compound.

(Protective layer)
The protective layer of the organic light emitting element according to the present embodiment is a silicon nitride (SiN) layer, a silicon oxynitride (SiON) layer, or an atomic layer deposition method (SiON) formed by using a chemical vapor deposition method (CVD method). It is composed of an aluminum oxide layer formed using the ALD method), a material with extremely low permeability of oxygen and moisture from the outside, such as silicon oxide and titanium oxide, and if it has sufficient moisture blocking performance, it can be a single layer or It may have multiple layers. In the case of a plurality of layers, different materials may be laminated or the same material may be laminated at different densities. The protective layer is preferably configured in consideration of the refractive index so that the light emitted from the organic light emitting element can be easily taken out of the device. The protective layer can also be called a sealing layer.

(Flat layer)
The flattening layer of the organic light emitting device according to the present embodiment is for filling the unevenness of the protective layer, and is preferably arranged on the protective layer. As a result, scattered light due to the inclined portion of the unevenness of the protective film can be reduced, and color mixing can be suppressed. The flattening layer is composed of a resin layer or the like formed by coating. The flattening layer may be provided with an arbitrary thickness, and may be, for example, 10 nm or more and 1000 nm or less.

(Color filter)
The color filter of the organic light emitting device according to the present embodiment may be patterned by applying a color resist on the flattening layer and performing lithography. Further, a color filter may be provided on the facing substrate described later and laminated on the flattening layer. In this case, the above-mentioned flattening layer may be 10 nm or more and 1000 nm or less.

The color resist is made of, for example, a photocurable resin, and a pattern can be formed by curing a portion irradiated with ultraviolet rays or the like.

In the present embodiment, the color filter may have an RGB color filter. The RGB color filters may be arranged in any of a stripe arrangement, a square arrangement, a delta arrangement, and a Bayer arrangement.

The packed layer of the organic light emitting device according to the present embodiment is arranged between the color filter and the facing substrate. The packed bed is made of an organic material such as an acrylic resin, an epoxy resin, or a silicone resin. Further, a flattening layer may be formed between the color filter and the packing layer. The flattening layer may be the same as or different from the flattening layer arranged between the color filter and the protective layer. When the two flattening layers are made of the same material, it is preferable because the flattening layers have high adhesion outside the display area.

The outside of the display area is an area where the EL element at the end of the substrate is not arranged and an area that does not contribute to the display.

(Opposite board)
The facing substrate of the organic light emitting device according to the present embodiment is preferably a transparent substrate. The facing substrate may be composed of, for example, a transparent glass substrate, a transparent plastic substrate, or the like.

The organic light emitting device may have a binder resin. Examples of the binder resin include polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, urea resin and the like. However, it is not limited to these. Further, these binder resins may be used alone as a homopolymer or a copolymer, or may be used as a mixture of two or more. Further, if necessary, known additives such as plasticizers, antioxidants, and ultraviolet absorbers may be used in combination.

(Application of organic light emitting device according to one embodiment of the present invention)
The organic light emitting element according to the present embodiment can be used as a constituent member of a display device or a lighting device. In addition, there are applications such as an exposure light source of an electrophotographic image forming apparatus, a backlight of a liquid crystal display device, and a light emitting device having a color filter as a white light source.

The display device has an image input unit for inputting image information from an area CCD, a linear CCD, a memory card, etc., has an information processing unit for processing the input information, and displays the input image on the display unit. It may be an image information processing device.

Further, the display unit of the image pickup device or the inkjet printer may have a touch panel function. The drive method of this touch panel function may be an infrared method, a capacitance method, a resistance film method, or an electromagnetic induction method, and is not particularly limited. Further, the display device may be used as a display unit of a multifunction printer.

Next, the display device according to the present embodiment will be described with reference to the drawings. FIG. 5 is a schematic cross-sectional view showing an example of a display device having an organic light emitting element and a TFT element connected to the organic light emitting element. The TFT element is an example of an active element.

The display device of FIG. 5 is provided with a substrate 10 such as glass and a moisture-proof film 11 for protecting the TFT element or the organic compound layer on the substrate 10 . Reference numeral 12 is a metal gate electrode 12 . Reference numeral 13 is a gate insulating film 13 , and reference numeral 14 is a semiconductor layer.

The TFT element 17 has a semiconductor layer 14 , a drain electrode 15, and a source electrode 16 . An insulating film 18 is provided on the upper part of the TFT element 17 . The anode 20 and the source electrode 16 constituting the organic light emitting element are connected via the contact hole 19 .

The method of electrical connection between the electrodes (anode, cathode) included in the organic light emitting element and the electrodes (source electrode, drain electrode) included in the TFT is not limited to the mode shown in FIG. That is, either one of the anode and the cathode and either one of the TFT element source electrode or the drain electrode may be electrically connected.

Although the organic compound layer is shown as one layer in the display device of FIG. 5, the organic compound layer 21 may be a plurality of layers. A first protective layer 23 and a second protective layer 24 for suppressing deterioration of the organic light emitting element are provided on the cathode 22 .

Although the display device of FIG. 5 uses a transistor as a switching element, a MIM element may be used as the switching element instead.

The transistor used in the display device of FIG. 5 is not limited to a transistor using a single crystal silicon wafer, and may be a thin film transistor having an active layer on the insulating surface of the substrate. Examples of the active layer include non-single crystal silicon such as single crystal silicon, amorphous silicon and microcrystalline silicon, and non-single crystal oxide semiconductors such as indium zinc oxide and indium gallium zinc oxide. The thin film transistor is also called a TFT element.

The transistor included in the display device of FIG. 5 may be formed in a substrate such as a Si substrate. Here, being formed in the substrate means that the substrate itself such as a Si substrate is processed to manufacture a transistor. That is, having a transistor in the substrate can also be seen as the substrate and the transistor being integrally formed.

In the organic light emitting element according to the present embodiment, the emission brightness is controlled by a TFT which is an example of a switching element, and by providing the organic light emitting element in a plurality of planes, an image can be displayed by each emission brightness. The switching element according to this embodiment is not limited to the TFT, and may be an active matrix driver formed on a substrate such as a transistor formed of low-temperature polysilicon or a Si substrate. On a substrate can also be said to be inside the substrate. Whether to provide a transistor in the substrate or to use a TFT is selected depending on the size of the display unit. For example, if the size is about 0.5 inch, it is preferable to provide an organic light emitting element on the Si substrate.

FIG. 7 is a schematic view showing an example of the display device according to the present embodiment. The display device 1000 may have a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 1007, and a battery 1008 between the upper cover 1001 and the lower cover 1009. Flexible print circuits FPC1002 and 1004 are connected to the touch panel 1003 and the display panel 1005. A transistor is printed on the circuit board 1007. The battery 1008 may not be provided if the display device is not a portable device, or may be provided at a different position even if it is a portable device.

The display device according to the present embodiment may be used as a display unit of an image pickup device having an optical unit having a plurality of lenses and an image pickup element that receives light that has passed through the optical unit. The image pickup device may have a display unit that displays the information acquired by the image pickup device. Further, the display unit may be a display unit exposed to the outside of the image pickup apparatus or a display unit arranged in the finder. The image pickup device may be a digital camera or a digital video camera.

FIG. 8A is a schematic view showing an example of the image pickup apparatus according to the present embodiment. The image pickup apparatus 1100 may include a viewfinder 1101, a rear display 1102, an operation unit 1103, and a housing 1104. The viewfinder 1101 may have a display device according to the present embodiment. In that case, the display device may display not only the image to be captured but also environmental information, imaging instructions, and the like. The environmental information may include the intensity of the outside light, the direction of the outside light, the moving speed of the subject, the possibility that the subject is shielded by a shield, and the like.

Since the optimum timing for imaging is a short time, it is better to display the information as soon as possible. Therefore, it is preferable to use a display device using the organic light emitting element of the present invention. This is because the organic light emitting element has a high response speed. A display device using an organic light emitting element can be more preferably used than these devices and liquid crystal display devices, which require a display speed.

The image pickup apparatus 1100 has an optical unit (not shown). The optical unit has a plurality of lenses and forms an image on an image pickup element housed in the housing 1104. The focus of a plurality of lenses can be adjusted by adjusting their relative positions. This operation can also be performed automatically.

The display device according to the present embodiment may have a color filter having red, green, and blue. In the color filter, the red, green, and blue may be arranged in a delta arrangement.

The display device according to the present embodiment may be used as a display unit of a mobile terminal. In that case, it may have both a display function and an operation function. Examples of mobile terminals include mobile phones such as smartphones, tablets, and head-mounted displays.

FIG. 8B is a schematic view showing an example of the electronic device according to the present embodiment. The electronic device 1200 has a display unit 1201, an operation unit 1202, and a housing 1203. The housing 1203 may include a circuit, a printed circuit board having the circuit, a battery, and a communication unit. The operation unit 1202 may be a button or a touch panel type reaction unit. The operation unit may be a biometric recognition unit that recognizes a fingerprint and releases the lock. An electronic device having a communication unit can also be called a communication device.

FIG. 9 is a schematic view showing an example of the display device according to the present embodiment. FIG. 9A is a display device such as a television monitor or a PC monitor. The display device 1300 has a frame 1301 and a display unit 1302. The light emitting device according to the present embodiment may be used for the display unit 1302.

It has a frame 1301 and a base 1303 that supports the display unit 1302. The base 1303 is not limited to the form shown in FIG. 9A. The lower side of the frame 1301 may also serve as the base.

Further, the frame 1301 and the display unit 1302 may be bent. The radius of curvature may be 5000 mm or more and 6000 mm or less.

FIG. 9B is a schematic view showing another example of the display device according to the present embodiment. The display device 1310 of FIG. 9B is a foldable display device, which is a so-called foldable display device. The display device 1310 has a first display unit 1311, a second display unit 1312, a housing 1313, and a bending point 1314. The first display unit 1311 and the second display unit 1312 may have a light emitting device according to the present embodiment. The first display unit 1311 and the second display unit 1312 may be a single display device having no joints. The first display unit 1311 and the second display unit 1312 can be separated by a bending point. The first display unit 1311 and the second display unit 1312 may display different images, or the first and second display units may display one image.

FIG. 10A is a schematic view showing an example of the lighting device according to the present embodiment. The lighting device 1400 may include a housing 1401, a light source 1402, a circuit board 1403, an optical film 1404, and a light diffusing unit 1405. The light source may have the organic light emitting element according to the present embodiment. The optical filter may be a filter that improves the color rendering property of the light source. The light diffusing unit can effectively diffuse the light of the light source such as lighting up and deliver the light to a wide range. The optical filter and the light diffusing portion may be provided on the light emitting side of the illumination. If necessary, a cover may be provided on the outermost side.

The lighting device is, for example, a device that illuminates a room. The illuminating device may emit white, neutral white, or any other color from blue to red. It may have a dimming circuit for dimming them. The lighting device may have an organic light emitting element according to an embodiment of the present invention and a power supply circuit connected thereto. The power supply circuit is a circuit that converts an AC voltage into a DC voltage. Further, white has a color temperature of 4200 K, and neutral white has a color temperature of 5000 K. The illuminator may have a color filter.

Further, the lighting device according to the present embodiment may have a heat radiating unit. The heat radiating unit releases the heat inside the device to the outside of the device, and examples thereof include metals and liquid silicon having a high specific heat.

FIG. 10B is a schematic view of an automobile which is an example of a moving body according to the present embodiment. The vehicle has a tail lamp, which is an example of a lamp. The automobile 1500 may have a tail lamp 1501 and may be in a form in which the tail lamp is turned on when a brake operation or the like is performed.

The tail lamp 1501 may have the organic light emitting element according to the present embodiment. The tail lamp may have a protective member that protects the organic EL element. The protective member has a certain degree of high strength and may be made of any material as long as it is transparent, but it is preferably made of polycarbonate or the like. A flange carboxylic acid derivative, an acrylonitrile derivative, or the like may be mixed with the polycarbonate.

The automobile 1500 may have a vehicle body 1503 and a window 1502 attached to the vehicle body 1503. The window may be a transparent display as long as it is not a window for checking the front and rear of the vehicle. The transparent display may have the organic light emitting element according to the present embodiment. In this case, the constituent material such as the electrode of the organic light emitting element is composed of a transparent member.

The moving body according to the present embodiment may be a ship, an aircraft, a drone, or the like. The moving body may have an airframe and a lamp provided on the airframe. The lamp may emit light to indicate the position of the aircraft. The lamp has an organic light emitting element according to the present embodiment.

As described above, by using the apparatus using the organic light emitting element according to the present embodiment, it is possible to perform stable display even for a long time display with good image quality.

(Example 1)
The procedure for manufacturing the organic light emitting device having the top emission type structure shown in FIG. 1 is shown below.

A 40 nm film of Ti was formed on the substrate by a sputtering method and patterned using a known photolithography technique to form an anode. At this time, the electrode area of the opposing electrodes (metal electrode layer, cathode) was set to 3 mm ² .

Subsequently, the substrate and material on which the cleaned electrodes were formed were attached to a vacuum vapor deposition apparatus (manufactured by ULVAC), and after exhausting to 1.33 × 10 ^-4 Pa (1 × ^10-6 Torr), UV / ozone was used. It was washed. Then, each layer was formed with the following layer structure.

Then, after forming the electron transport layer, lithium fluoride was formed into a film of 0.5 nm as an electron injection layer. Then, a 10 nm film of MgAg alloy was formed as a cathode. The ratio of Mg and Ag was 1: 1. Then, 1.5 μm of SiN was formed as a sealing layer by a CVD method.

On the other hand, the lowest excited triplet energies of the host and dopant of each light emitting layer were obtained. Since the material contained in which phosphorescence emission could not be observed by the above-mentioned measurement method, the minimum excited triplet energy of each compound was obtained by using the above-mentioned calculation method in a unified manner.

The lowest excited triplet of EM1 which is the first and second host material, RD21 which is the red light emitting material which is the first dopant, BD24 which is the blue light emitting material which is the second dopant material, and GD11 which is the green light emitting material which is the third dopant. The energies were T1 (H1) = T1 (H2) = 2.04 eV, T1 (D1) = 1.24 eV, T1 (D2) = 2.15 eV, and T1 (D3) = 1.88 eV, respectively. Therefore, the following equations (1), (4), and (5) are satisfied.
T1 (H1) -T1 (D1) ≥ 0.3eV (1)
T1 (H2) ≤ T1 (D2) (4)
0eV <T1 (H1) -T1 (D3) <0.3eV (5)

Further, since the first and second hosts are made of the same material and the first and second light emitting layers are adjacent to each other, there is a migration path of triplet excitons from the first light emitting layer to the second light emitting layer. doing.

Furthermore, the lowest excited singlet energies of the host and dopant of each light emitting layer were obtained by the above-mentioned calculation method. The lowest excited singlet of EM1 which is the first and second host material, RD21 which is the red light emitting material which is the first dopant, BD24 which is the blue light emitting material which is the second dopant material, and GD11 which is the green light emitting material which is the third dopant. The energies were S1 (H1) = S1 (H2) = 3.15 eV, S1 (D1) = 2.13 eV, S1 (D2) = 2.98 eV, and S1 (D3) = 2.67 eV, respectively.

The difference between the lowest excited singlet energy and the lowest excited triplet energy of each compound is 0.2 eV or more, which is not a delayed fluorescence compound.

A voltage application device (not shown) was connected to the obtained white organic light emitting device, and its characteristics were evaluated.

The current-voltage characteristics were measured with a micro ammeter 4140B manufactured by Hewlett-Packard Co., Ltd., and the chromaticity was evaluated using "SR-3" manufactured by Topcon. The emission brightness was measured with a BM7 manufactured by Topcon Corporation. The efficiency, voltage, and CIE chromaticity coordinates in the u'v'space at 1000 cd / m ² display are 4.0 cd / A, 4.0 V, and CIE (u', v') = (0.196, 0. It was 386). Here, the amount of color shift Δu'v'represented by the following equation (6) with respect to the CIE chromaticity coordinates (0.198, 0.468) in the u'v'space of white light having a reference color temperature of 6400K. Was 0.047, which was a good white organic light emitting element.

Further, when a continuous drive test was conducted at an initial brightness of 4000 cd / m ² , the brightness half-time was 3500 h and the durability characteristics were also good.

Next, the TTA emission ratio of the obtained white element was measured for light emission derived from the red light emitting material, light emission derived from the green light emitting material, and light emission derived from the blue light emitting material, respectively.

The TTA ratio was determined by performing transient response measurement and analyzing the measurement results.

In transient response measurement, a square wave voltage is applied to an organic light emitting element by a voltage pulse generator, and the emission intensity from the organic light emitting element is time-resolved and detected by an oscilloscope via a photomultiplier tube in synchronization with the voltage. Do by. Specifically, a positive voltage having a desired current density is applied to the organic light emitting element for a sufficient time until the light emission intensity reaches a steady state. After that, a negative voltage is applied to discharge the electric charge from the device.

In this embodiment, 33250A manufactured by Azilent Co., Ltd. was used as the voltage pulse generator, and the square wave voltage was applied with a voltage equivalent to a frequency of 100 Hz, a positive voltage of 10 mA / cm ² , and a pulse width of 1 ms, and a negative voltage of -10 V. .. The oscilloscope used was TDS5054 manufactured by Tektronix.

FIG. 6A is an example of the transient response measurement result, and shows the time change of the emission intensity obtained in synchronization with the voltage. The positive voltage is switched to the negative voltage at 0 s, and the emission intensity in the steady state when the positive voltage is applied is set to 1.

The breakdown of the emission intensity when a positive voltage is applied is the sum of the emission from the singlet excitons generated by the recombination of electric charges and the emission from the singlet excitons generated by TTA.

On the other hand, when a negative voltage is applied, light emission by TTA is observed. The observed luminescence is a transient response characteristic. The TTA emission ratio is determined by analyzing the transient response characteristics of the emission by TTA.

It is known that if the transient response characteristic of light emission when a negative voltage is applied is based on TTA, the reciprocal of the square root of the light emission intensity can be expressed by linear approximation.

Therefore, as shown in FIG. 6B, the time change of the reciprocal of the square root of the emission intensity is plotted, and the transient response characteristic is fitted by Equation 2 to obtain the constant B. In the formula (7), _ITTA indicates the emission intensity when a negative voltage is applied, A and B indicate constants, and t indicates time.

At this time, the emission intensity 1 / B ^{2 at} the time t = 0 when the positive voltage is switched to the negative voltage is defined as the ratio of the emission by TTA to the total emission. For example, since B = 1.72 in FIG. 6B, 1 / B ² = 0.338, and the TTA emission ratio is 33.8%.

The organic light emitting device of this embodiment is a white light emitting device having a blue light emitting material, a green light emitting material, and a red light emitting material. Therefore, optical interference filters having peak wavelengths of transmitted light of 460 nm, 560 nm, and 640 nm are installed between the organic light emitting element and the photomultiplier tube, respectively, and are derived from a blue light emitting material, a green light emitting material, and a red light emitting material. The TTA emission ratio of the emission was measured.

In the organic light emitting device of this example, the TTA emission ratio of the light emitted from the blue light emitting material is 8%, the TTA emission ratio of the light emitted from the green light emitting material is 18%, and the TTA emission ratio of the light emitted from the red light emitting material is 37%. In particular, the TTA emission ratio of the emission derived from the red light emitting material was good. The fact that the TTA ratio of luminescence derived from the blue luminescent material is lower than that of G and R is evidence that triplet excitons are efficiently migrating from the first luminescent layer to the second luminescent layer, which results in long continuous driving. It is considered that the life has been realized.

(Examples 2 to 4, Comparative Examples 1 to 3)
The white organic light emitting devices of Examples 2 to 3 and Comparative Examples 1 and 2 were produced in the same manner as in Example 1 except that the weight ratio of the red light emitting material which is the first dopant of Example 1 was appropriately changed. .. The characteristics of the obtained organic light emitting device were measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

When the TTA emission ratio derived from the red light emitting material is 38% or more, it is A, when it is 35% or more and less than 38%, it is B, when it is 31% or more and less than 35%, it is C, and when it is 27% or more and less than 31%, it is D. , If it is less than 27%, it is indicated as E.

If Δu'v'is less than 0.06, it is A, if it is 0.06 or more and less than 0.07, it is B, and if it is 0.07 or more and less than 0.08, it is C, 0.08 or more and 0.09. If it is less than, it is written as D, and if it is 0.09 or more, it is written as E.

In each of the organic light emitting devices of Examples 1 to 4, Comparative Examples 1 and 2, and the reference example, the TTA emission ratio derived from the blue light emitting material is about 7 to 9%, and the TTA emission ratio derived from the green light emitting material is about 17 to 19. It was almost the same as%. On the other hand, when the red light emitting material which is the first dopant is 0.3 wt% or less, the TTA emission ratio derived from the red light emitting material is higher than that when the red light emitting material which is the first dopant is 0.5 wt% or more. , The proportion of TTA derived from the red light emitting material is high, and it can be seen that TTA occurs satisfactorily.

However, in the organic light emitting device of the reference example in which the first dopant is less than 0.05 wt%, the light emitting intensity derived from the red light emitting material was lowered. Considering the red emission brightness, the weight ratio of the first dopant is preferably 0.05 wt% or more and 0.3 wt% or less when the weight of the first light emitting layer is 100 wt%.

Further, the organic light emitting devices of Examples 1 to 4, which were able to display a good TTA light emission ratio and a good white color, were also subjected to a continuous drive test at an initial brightness of 4000 cd / m ² , and the brightness half time was obtained. The durability characteristics were also good at 2500 to 3500 h.

From the results of Examples 1 to 4 and Comparative Examples 1 and 2, it can be seen that a particularly preferable first dopant concentration is 0.1% or more and 0.2% or less. As a result, a particularly good organic light emitting device can be obtained in terms of the TTA light emitting ratio and the white display.

(Examples 5 to 10, Comparative Examples 4 to 9)
The material and weight ratio of the hole transport layer, the electron blocking layer, the hole blocking layer, the electron transport layer, the first host, the second host, the first dopant, the second dopant, and the third dopant of Example 1 are appropriately changed. The white organic light emitting devices of Examples 2 to 3 and Comparative Examples 1 and 2 were produced in the same manner as in Example 1. The characteristics of the obtained organic light emitting device were measured and evaluated in the same manner as in Example 1. The results are shown in Table 3. When the TTA emission ratio derived from the red light emitting material is 38% or more, it is A, when it is 35% or more and less than 38%, it is B, when it is 31% or more and less than 35%, it is C, and when it is 27% or more and less than 31%, it is D. , If it is less than 27%, it is indicated as E. Further, the luminance half time is described as A when it is 3000 h or more, B when it is 2000 h or more and less than 3000 h, and C when it is less than 2000 h.

The organic light emitting devices of Examples 5 to 10 have a weight ratio of the red light emitting material which is the first dopant of 0.3 wt%, whereas the organic light emitting elements of Comparative Examples 3 to 8 have the red light which is the first dopant. The weight ratio of the light emitting material is 0.5 wt%. In each of the organic light emitting devices of Examples 5 to 10 and Comparative Examples 3 to 8, the TTA light emitting ratio derived from the blue light emitting material is about 7 to 9%, and the TTA light emitting ratio derived from the green light emitting material is about 17 to 19%. It was almost the same.

On the other hand, when the red light emitting material which is the first dopant is 0.3 wt% or less, the TTA emission ratio derived from the red light emitting material is higher than that when the red light emitting material which is the first dopant is 0.5 wt% or more. , The proportion of TTA derived from the red light emitting material is high, and it can be seen that TTA occurs satisfactorily.

The brightness half-life was good in all of the organic light emitting devices of Examples 5 to 10 and Comparative Examples 3 to 8.

However, it is the first dopant material RD1 or the third dopant material GD6 that the organic light emitting devices of Examples 7 and 10 are inferior in the brightness half life to the organic light emitting devices of Examples 5, 6, 8 and 9. It is considered that this is because the compound is not a hydrocarbon compound.

Table 4 shows the values of the lowest excited singlet energy and the lowest excited triplet energy of each material used for the light emitting layer.

(Comparative Example 9)
A white organic light emitting device similar to that of Example 1 was prepared except that HT7 was inserted at 5 nm as an intermediate layer between the first light emitting layer and the second light emitting layer of Example 1. As a result of measuring and evaluating the characteristics in the same manner as in Example 1, the luminance half time was 1600 hours, which was significantly lower than that in Example 1.

The minimum excited triplet energy of HT7 obtained by the same calculation method as in Example 1 is 2.69 eV, which is higher than the excited triplet energy of 2.04 eV of EM1 which is the first host and the second host. It was. Therefore, since the movement path of the triplet excitons from the first light emitting layer to the second light emitting layer was blocked by the intermediate layer, the triplet excitons were retained in the first light emitting layer, and material deterioration was likely to occur. Conceivable.

(Comparative Example 10)
An organic light emitting device was produced in the same manner as in Example 1 except that the configurations of the first light emitting layer and the second light emitting layer of Example 1 were as follows. The first light emitting layer has 99.1 wt% of EM1 as the first host, 0.3 wt% of the red light emitting material RD21 as the first dopant, and 0.6 wt% of the blue light emitting material BD24 as the second dopant. The second light emitting layer had 98.0 wt% of EM1 as the second host and 2.0 wt% of the green light emitting material GD11 as the third dopant. That is, the first dopant and the second dopant are contained in the same layer. As a result of measuring and evaluating the characteristics in the same manner as in Example 1, the luminance half time was 1700 hours, which was significantly lower than that in Example 1.

This is because the triplet excitons are trapped in the first light emitting layer by the first dopant, so that the triplet excitons are retained in the first light emitting layer, and the exciton of the first light emitting layer in which the second dopant is present It is considered that the material deterioration is likely to occur because the concentration does not become relatively low.

(Reference example 2)
An organic light emitting device having the configuration shown in FIG. 1A was produced. The host and dopant materials of the first light emitting layer are as shown in Table 5 below. The weight ratio of the dopant was 0.6 wt%.

When the dopant concentration is larger than 0.3 wt% and the barrier of the minimum excited triplet energy from the dopant to the host is 0.3 eV or more, the triplet excitons are likely to be localized in the dopant material. It was confirmed that TTA was less likely to occur.

The lowest excited triplet energy T1 (H) of the host of each organic light emitting device and the lowest excited triplet energy T1 (D) of the dopant are calculated by the same calculation method as in Example 1, and are calculated by the following equation (8). , ΔT1 was obtained.
ΔT1 = T1 (H) -T1 (D) (8)

Further, the TTA emission ratio of each organic light emitting element was measured and measured in the same manner as in Example 1 except that the desired wavelength was not extracted by the optical interference filter because it was a monochromatic element.

The above results are shown in Table 5. The TTA emission ratio is A when 30% or more, B when 25% or more and less than 30%, C when 20% or more and less than 25%, D when 15% or more and less than 20%, 10% or more 15 If it is less than%, it is expressed as E, and if it is less than 10%, it is expressed as F. From this, it was confirmed that when the dopant concentration is larger than 0.3 wt% and the barrier of the minimum excited triplet energy from the dopant to the host is 0.3 eV or more, TTA is less likely to occur. ..

(Example 11)
An organic light emitting device was produced in the same manner as in Example 2 except that the first dopant material was changed to RD20.

(Example 12)
An organic light emitting device was produced in the same manner as in Example 11 except that the second dopant material was changed to GD29.

(Example 13)
An organic light emitting device was produced in the same manner as in Example 12 except that the third dopant was changed to BD23.

(Example 14)
An organic light emitting device was produced in the same manner as in Example 13 except that the material of HTL was changed to HT3.

(Example 15)
An organic light emitting device was produced in the same manner as in Example 14 except that the ETL material was changed to ET7.

(Example 16)
An organic light emitting device was hard-made in the same manner as in Example 15 except that the material of EBL was changed to HT10.

(Example 17)
An organic light emitting device was produced in the same manner as in Example 16 except that the material of HBL was changed to ET12.

(Example 18)
An organic light emitting device was produced in the same manner as in Example 17 except that the phenyl group, which is a substituent of ET12, was changed to a naphthyl group.

(Example 19)
An organic light emitting device was produced in the same manner as in Example 18 except that the EBL was a mixed layer of HT10 and HT3.

(Example 20)
An organic light emitting element was produced in the same manner as in Example 18 except that the EBL was a mixed layer of HT2 and HT3.

(Example 21)
The film thickness of HIL is 8.4 nm, the film thickness of HTL is 8.0 nm, the film thickness of EBL is 10.0 nm, the film thickness of the first light emitting layer is 20.4 nm, and the film thickness of the second light emitting layer is 9.2 nm. An organic light emitting device was produced in the same manner as in Example 20 except that the film thickness of HBL was 80 nm, the film thickness of ETL was 30 nm, and the film thickness of LiF was 0.45 nm.

(Example 22)
The film thickness of HIL is 3.0 nm, the film thickness of HTL is 11.0 nm, the film thickness of EBL is 12.0 nm, the film thickness of the first light emitting layer is 17.4 nm, and the film thickness of the second light emitting layer is 10.8 nm. An organic light emitting element was produced in the same manner as in Example 20 except that the film thickness of HBL was 100 nm, the film thickness of ETL was 32 nm, and the film thickness of LiF was 0.45 nm.

(Example 23)
The film thickness of HIL is 3.0 nm, the film thickness of HTL is 8.0 nm, the film thickness of EBL is 10.0 nm, the film thickness of the first light emitting layer is 20.4 nm, and the film thickness of the second light emitting layer is 9.2 nm. An organic light emitting device was produced in the same manner as in Example 19 except that the film thickness of HBL was 80 nm, the film thickness of ETL was 30 nm, and the film thickness of LiF was 0.45 nm.

(Example 24)
The film thickness of HIL is 8.4 nm, the film thickness of HTL is 5.5 nm, the film thickness of EBL is 9.5 nm, the film thickness of the first light emitting layer is 17.2 nm, and the film thickness of the second light emitting layer is 8.6 nm. An organic light emitting element was produced in the same manner as in Example 19 except that the film thickness of HBL was 110 nm, the film thickness of ETL was 32 nm, and the film thickness of LiF was 0.45 nm.

(Example 25)
The film thickness of HIL is 8.4 nm, the film thickness of HTL is 5.5 nm, the film thickness of EBL is 12.0 nm, the film thickness of the first light emitting layer is 20.4 nm, and the film thickness of the second light emitting layer is 5.0 nm. An organic light emitting element was produced in the same manner as in Example 19 except that the film thickness of HBL was 80 nm, the film thickness of ETL was 26 nm, and the film thickness of LiF was 0.45 nm.

(Example 26)
An organic light emitting device was produced in the same manner as in Example 24 except that the mixing ratio of HT10 and HT3 in EBL was 1: 2.

(Example 27)
An organic light emitting device was produced in the same manner as in Example 24 except that the mixing ratio of HT10 and HT3 in EBL was 1: 3.

(Example 28)
An organic light emitting device was produced in the same manner as in Example 21 except that the mixing ratio of HT2 and HT3 in EBL was 1: 2.

(Example 29)
An organic light emitting device was produced in the same manner as in Example 21 except that the mixing ratio of HT2 and HT3 in EBL was 1: 3.

In Examples 11 to 29, it was confirmed that the TTA efficiency was high and the drive life was long, as in Examples 1 to 10.

As described above, the organic light emitting device according to the embodiment of the present invention is an organic light emitting device having high luminous efficiency and long drive life.

1 Substrate 2 First electrode 3 Hole transport layer 4 First light emitting layer 5 Second light emitting layer 6 Electron transport layer 7 Second electrode 10 Glass substrate 11 Moisture-proof film 11
12 Gate electrode 13 Gate insulating film 14 Semiconductor layer 15 Drain electrode 16 Source electrode 17 Thin film transistor 18 Insulation film 19 Contact hole 20 Anode 21 Organic compound layer 22 Cathode 23 First protective layer 24 Second protective layer 1000 Display device 1001 Top cover 1002 Flexible print circuit 1003 Touch panel 1004 Flexible print circuit 1005 Display panel 1006 Frame 1007 Circuit board 1008 Battery 1009 Bottom cover 1100 Imaging device 1101 Viewfinder 1102 Rear display 1103 Operation unit 1104 housing 1200 Electronic device 1201 Display unit 1202 Operation unit 1203 1300 Display device 1301 Frame 1302 Display unit 1303 Base 1310 Display device 1311 First display unit 1312 Second display unit 1313 Housing 1314 Bending point 1400 Lighting device 1401 Housing 1402 Light source 1403 Circuit board 1404 Optical film 1405 Light diffusing unit 1500 Tail lamp 1502 Window 1503 Body

Claims (22)

It has a first electrode, a first light emitting layer, a second light emitting layer, and a second electrode in this order, and the first light emitting layer has a first host material and a first dopant material that emits fluorescence. The second light emitting layer has a second host material and a second dopant material.
The lowest excited triplet energy of the first host material is higher than the lowest excited triplet energy of the first dopant material.
The lowest excited singlet energy of the first dopant material is an organic light emitting device smaller than the lowest excited singlet energy of the second dopant material.
An organic light emitting device characterized in that the weight ratio of the first dopant material is 0.3 wt% or less when the weight of the first light emitting layer is 100 wt%. The organic light emitting device according to claim 1, wherein the emission wavelength of the first dopant is longer than the emission wavelength of the second dopant material. The organic light emitting device according to claim 1 or 2, wherein the first dopant material is a red light emitting material, and the second dopant material is a blue light emitting material. Any one of claims 1 to 3, wherein the difference between the lowest excited triplet energy of the first host material and the lowest excited triplet energy of the first dopant material is 0.3 eV or more. The organic light emitting device according to. The lowest excited triplet energy of the main component of the organic compound layer contained in the region from the first light emitting layer to the second light emitting layer is the main component of the organic compound layer adjacent to the second electrode side of the organic compound layer. The organic light emitting element according to any one of claims 1 to 4, wherein the component has a minimum excitation triplet energy or less. The organic light emitting device according to any one of claims 1 to 5, wherein the lowest excited triplet energy of the second host material is higher than the lowest excited triplet energy of the first host material. The organic light emitting device according to any one of claims 1 to 6, wherein the lowest excited triplet energy of the second host material is smaller than the lowest excited triplet energy of the second dopant material. The first light emitting layer further comprises a third dopant material.
Claims 1 to 7 are characterized in that the lowest excited triplet energy T1 (H1) of the first host material and the lowest excited triplet energy T1 (D3) of the third dopant material satisfy the following formula (4). The organic light emitting device according to any one of the above.
0eV <T1 (H1) -T1 (D3) <0.3eV (4) The second light emitting layer further comprises a third dopant material.
Claims 1 to 7 are characterized in that the lowest excited triplet energy T1 (H2) of the second host material and the lowest excited triplet energy T1 (D3) of the third dopant material satisfy the following formula (5). The organic light emitting device according to any one of the above.
0eV <T1 (H2) -T1 (D3) <0.3eV (5) The organic light emitting material according to claim 8 or 9, wherein the first dopant material is a red light emitting material, the second dopant material is a blue light emitting material, and the third dopant material is a green light emitting material. element. A claim that the material contained in the first light emitting layer and the material contained in the second light emitting layer have a difference between the lowest excited singlet energy and the lowest excited triplet energy of 0.2 eV or more. The organic light emitting element according to any one of 1 to 10. The organic light emitting device according to any one of claims 1 to 11, wherein the first host material and the second host material are the same material. The organic light emitting device according to any one of claims 1 to 12, wherein the first light emitting layer and the second light emitting layer are in contact with each other. Any of claims 1 to 13, wherein the weight ratio of the first dopant material is 0.05 wt% or more and 0.3 wt% or less when the weight of the first light emitting layer is 100 wt%. The organic light emitting device according to item 1. It further has an intermediate layer arranged between the first light emitting layer and the second light emitting layer, and the lowest excited triplet energy T1 (HM) of the intermediate layer is the lowest excited triplet of the second host material. The organic light emitting element according to any one of claims 1 to 14, wherein the energy is equal to or less than the term energy and equal to or higher than the minimum excited triplet energy of the first host material. The organic light emitting device according to any one of claims 1 to 15, wherein the first host material is a low molecular weight organic compound. The first light emitting layer and the second light emitting layer are light emitting layers that emit white light from the first light emitting layer and the second light emitting layer.
The organic light emitting element according to any one of claims 1 to 16, wherein the organic light emitting element has a color filter on the light emitting side. A display device having a plurality of pixels, wherein the pixel has the organic light emitting element according to any one of claims 1 to 17 and an active element connected to the organic light emitting element. Display device. An image pickup apparatus having an optical unit having a plurality of lenses, an image pickup element that receives light that has passed through the optical unit, and a display unit that displays an image.
The display unit is a display unit that displays an image captured by the image pickup device, and the display unit includes the organic light emitting element according to any one of claims 1 to 17. It is characterized by having a display unit having the organic light emitting element according to any one of claims 1 to 17, a housing provided with the display unit, and a communication unit provided in the housing. Electronics. A lighting device comprising a light source having the organic light emitting element according to any one of claims 1 to 17 and a light diffusing unit or an optical film that transmits light emitted by the light source. A mobile body having a lamp having the organic light emitting element according to any one of claims 1 to 17 and an airframe provided with the lamp.

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