Light-emitting element

Abstract

To provide a light-emitting element with high luminescence efficiency, which has a fluorescent material. Alternatively, to provide a light-emitting element in which the proportion of the delayed fluorescence component due to TTA is high among the luminescent components. Alternatively, to provide a novel light-emitting device with high luminous efficiency and reduced power consumption. [Solution] The system has an anode, a cathode, and an EL layer sandwiched between the anode and the cathode, and the EL layer is It has an emissive layer and an electron transport layer in contact with the emissive layer, the emissive layer has a host material and electron transport The layer has a first material, and the LUMO level of the first material is higher than the LUMO level of the host material. Low, and the proportion of the delayed fluorescence component due to TTA in the emission exhibited by the EL layer is 1% of the total. A light-emitting element that is 0% or more. In one embodiment of the present invention, the light emitted by the EL layer The proportion of the delayed fluorescence component due to TTA may be 15% or more of the total.

Description

[Technical Field]

[0001] One aspect of the present invention is a light-emitting element, a display module, a lighting module, a display device, This invention relates to optical devices, electronic devices, and lighting devices. One aspect of the present invention is not limited to the above-mentioned technical field. Not specified. The technical field of one aspect of the invention disclosed herein, etc., relates to a product, method, or manufacturing. This relates to a method. Alternatively, one aspect of the present invention relates to a process, machine, or manufacture. This relates to tea, or composition of matter. More specifically, the technical field of one aspect of the present invention disclosed herein includes semiconductor devices, and Display devices, liquid crystal display devices, light-emitting devices, lighting devices, energy storage devices, memory devices, imaging devices, and their Driving methods, or methods for manufacturing them, can be given as examples. [Background technology]

[0002] In recent years, electroluminescence (EL) Research and development of the light-emitting elements used are actively underway. The basic configuration of these light-emitting elements is as follows: This device has a layer containing a light-emitting material (EL layer) sandwiched between a pair of electrodes. By applying a voltage, light emission can be obtained from the light-emitting material.

[0003] Since the aforementioned light-emitting element is self-illuminating, the display device using it has excellent visibility and backlighting. It has advantages such as not requiring a light and consuming little power. Furthermore, it can be manufactured to be thin and lightweight. It also has advantages such as a high response speed.

[0004] An organic material is used as the light-emitting material, and an EL layer containing the light-emitting organic material is provided between a pair of electrodes. In the case of a light-emitting element (for example, an organic EL element), by applying a voltage between a pair of electrodes... Electrons are injected from the cathode and holes from the anode into the light-emitting EL layer. A flow occurs. Then, the injected electrons and holes recombine to produce a luminescent organic material. The material enters an excited state, and light emission can be obtained from the excited, luminescent organic material.

[0005] The types of excited states that organic materials can form include singlet excited states (S * ) and triplet excited state (T * ) and the emission from the singlet excited state is fluorescence, and the emission from the triplet excited state is phosphorescence. It is called. Also, the statistical generation ratio of these in light-emitting elements is S * :T * =1: The answer is 3. Therefore, instead of using a light-emitting element that uses a fluorescent material, use a phosphorescent material. This type of light-emitting element can achieve higher luminescence efficiency. Therefore, the triplet excited state In recent years, there has been a great deal of activity in developing light-emitting devices using phosphorescent materials that can convert light into light. ru.

[0006] Among light-emitting elements using phosphorescent materials, in particular, light-emitting elements that emit blue light have a high three Because it is difficult to develop stable materials with multiplet excitation energy levels, practical applications have not yet been achieved. Therefore, in light-emitting devices that emit blue light, more stable fluorescent materials are used. The development of light-emitting devices is underway, and methods are being developed to improve the luminescence efficiency of light-emitting devices using fluorescent materials. It is being searched for.

[0007] As a light emission mechanism capable of converting a portion of the triplet excited state into light emission, triplet-triplet emission is used. Triplet-triplet annihilation (TTA) is known Yes. TTA is when two triplet excitons come into close proximity, and the excitation energy is transferred. This involves the transfer and exchange of spin angular momentum, and as a result, singlet excitons It is said to be generated.

[0008] Anthracene compounds are known to produce TTA. Non-patent document 1 states that By using anthracene compounds as the host material for light-emitting elements, a light-emitting element that exhibits blue light emission can be produced. In this case, it has been reported to exhibit an external quantum efficiency of more than 10%. Of the luminescence components exhibited, the proportion of the delayed fluorescence component due to the anthracene compound TTA is... It has been reported that this figure is around 10%.

[0009] Furthermore, tetracene compounds are known to be compounds with a high proportion of delayed fluorescence components due to TTA. Non-patent document 2 describes the delayed emission from tetracene compounds, specifically focusing on TTA-induced fluorescence. The proportion of photo-components has been reported to be higher than that of anthracene compounds.

[0010] Furthermore, if TTA occurs, the fluorescence lifetime of the fluorescent material will be compared to the fluorescence lifetime of the fluorescent material when TTA does not occur. Remarkably long-lived luminescence (delayed fluorescence) is being produced. Such delayed fluorescence occurs in the light-emitting element. When steady-state carrier injection is interrupted at a certain point, the attenuation of luminescence after the interruption can be observed. This can be confirmed by measurement. In this case, the delayed fluorescence spectrum and the stationary fluorescence spectrum are measured. The shape of the emission spectrum during carrier injection is consistent. [Prior art documents] [Non-patent literature]

[0011] [Non-Patent Document 1] Tsunenori Suzuki, et al., Japanese Journal of Applied Physics, vol. 53, 052102 (2014) [Non-Patent Document 2] DYKondakov, et al., Journal of Applied Physics, vol. 106, 124510 (2009) [Overview of the project] [Problems that the invention aims to solve]

[0012] In a light-emitting device having a fluorescent material, in order to increase the luminescence efficiency, triple elements that do not contribute to luminescence are used. Converting the energy of a singlet exciton into the energy of a luminescent singlet exciton, and It is important to increase the conversion efficiency of triplet excitons. In other words, TTA is important for increasing the energy of triplet excitons. It is important to convert energy into the energy of singlet excitons. To do this, the emission element Increasing the proportion of the delayed fluorescence component based on TTA among the luminescence components exhibited by the child is particularly important. This is important because a high proportion of delayed fluorescence components based on TTA indicates luminescence. This is because it means that the rate of singlet exciton generation is increasing.

[0013] Therefore, in one aspect of the present invention, a light-emitting element having a fluorescent material has high luminescence efficiency. One objective is to provide a light-emitting element. Alternatively, in one aspect of the present invention, the light-emitting component is One of the objectives is to provide a light-emitting element with a high proportion of delayed fluorescence components due to TTA. Alternatively, in one aspect of the present invention, a novel light-emitting device is provided that has high luminous efficiency and reduced power consumption. One of the objectives is to provide a novel display device. Alternatively, in one aspect of the present invention, a novel display device is provided. This will be one of the challenges.

[0014] Furthermore, the description of the above problems does not preclude the existence of other problems. It is not necessary to solve all of these problems. Other issues are addressed in the specification. This becomes clear from the descriptions, and we will extract any issues other than those mentioned above from the descriptions in the specifications, etc. It is possible to do so. [Means for solving the problem]

[0015] One aspect of the present invention comprises an anode, a cathode, and an EL layer sandwiched between the anode and the cathode, and E The L layer has an emissive layer and an electron transport layer in contact with the emissive layer, and the emissive layer has a host material and an electron transport layer. The sub-transport layer has a first material, and the LUMO level of the first material is equal to the LUMO level of the host material. At a lower level, the luminescence exhibited by the EL layer is occupied by delayed fluorescence components due to triplet-triplet annihilation. This light-emitting element is characterized by having a proportion of 10% or more of the total.

[0016] Another aspect of the present invention comprises an anode, a cathode, and an EL layer sandwiched between the anode and the cathode. The EL layer has an emissive layer and an electron transport layer in contact with the emissive layer, and the emissive layer is made of a host material The electron transport layer has a first material, and the LUMO level of the first material is L of the host material. The emission exhibited by the EL layer is 0.05 eV or more lower than the UMO level, and is triplet-triplet. A light-emitting element characterized by having a delayed fluorescence component account for 10% or more of the total due to annihilation. He is a child.

[0017] In one embodiment of the present invention, in the luminescence exhibited by the EL layer, triplet-triplet annihilation occurs. The proportion of the delayed fluorescence component may be 15% or more of the total. Also, the first material is The substance may also include a condensed heteroaromatic ring skeleton having an azine skeleton or a triazine skeleton. Furthermore, the first material may be a substance having a pyrazine skeleton or a pyrimidine skeleton. The triplet excitation energy of the first material is the highest among the materials contained in the light-emitting layer. The triplet excitation energy may be 0.2 eV or more greater than that of a high-energy material.

[0018] Furthermore, one aspect of the present invention has a hole transport layer in contact with the light-emitting layer, wherein the hole transport layer is a second material It is characterized by the fact that the LUMO level of the second material is greater than that of the host material. It may be a light-emitting element having a hole transport layer in contact with the light-emitting layer, and the hole transport layer is The material has a second material, and the triplet excitation energy of the second material is among the materials contained in the light-emitting layer. Compared to the triplet excitation energy of the material with the highest triplet excitation energy, it is more than 0.2 eV higher. It may also be a light-emitting element characterized by its size.

[0019] Furthermore, in one embodiment of the present invention, the light-emitting layer may further contain a fluorescent material to form a light-emitting element. The triplet excitation energy of the fluorescent material is greater than the triplet excitation energy of the host material. A light-emitting element characterized by the above may also be used. Furthermore, the LUMO level of the fluorescent material is the same as that of the host material. The light-emitting element may be characterized by having a LUMO level that is the same as or greater than the LUMO level. Alternatively, the light-emitting layer may be a light-emitting element that emits blue light.

[0020] Another aspect of the present invention relates to a light-emitting element and a transistor or substrate. It is a light device. Furthermore, in addition to the light-emitting device, it also has a sensor, an operation button, a speaker, or a microphone. It may also be an electronic device having a cu and a . Furthermore, in addition to the light-emitting device, it may have a housing and a lighting fixture having a cu and a . It can also be used as a device. [Effects of the Invention]

[0021] According to one aspect of the present invention, a light-emitting element having a fluorescent material has a high luminescence efficiency. It can be provided. Or, according to one aspect of the present invention, the luminescent component can be delayed by TTA. A light-emitting element with a high proportion of the prolonged fluorescence component can be provided. Alternatively, according to one aspect of the present invention... This allows us to provide a novel light-emitting device with high luminous efficiency and reduced power consumption. Alternatively, according to one aspect of the present invention, a novel display device can be provided.

[0022] Furthermore, the description of these effects does not preclude the existence of other effects. The embodiment does not necessarily have to have all of these effects. Furthermore, other effects are... This will become clear from the description in the specification, drawings, claims, etc., and the specification, drawings Furthermore, it is possible to extract other effects from the descriptions in the claims and other documents. [Brief explanation of the drawing]

[0023] [Figure 1] A schematic cross-sectional view of a light-emitting element according to one embodiment of the present invention, and a schematic diagram illustrating the correlation of energy levels. [Figure 2] A diagram illustrating energy barriers and recombination regions. [Figure 3] A diagram illustrating the components of the transition dipole moment. [Figure 4] A schematic diagram illustrating the method for measuring molecular orientation. [Figure 5] A schematic cross-sectional view of a light-emitting element according to one embodiment of the present invention. [Figure 6] A schematic cross-sectional view of a light-emitting element according to one embodiment of the present invention. [Figure 7] A schematic cross-sectional view of a light-emitting element according to one embodiment of the present invention, and a schematic diagram illustrating the correlation of energy levels. [Figure 8] A schematic cross-sectional view of a light-emitting element according to one embodiment of the present invention, and a schematic diagram illustrating the correlation of energy levels. [Figure 9] A block diagram and a circuit diagram illustrating a display device according to one embodiment of the present invention. [Figure 10] A perspective view showing an example of a touch panel according to one aspect of the present invention. [Figure 11] A cross-sectional view showing an example of a display device and a touch sensor according to one embodiment of the present invention. [Figure 12] A cross-sectional view showing an example of a touch panel according to one aspect of the present invention. [Figure 13] A block diagram and timing chart diagram of a touch sensor according to one aspect of the present invention. [Figure 14] A circuit diagram of a touch sensor according to one aspect of the present invention. [Figure 15] A perspective view illustrating a display module according to one embodiment of the present invention. [Figure 16] A diagram illustrating an electronic device according to one embodiment of the present invention. [Figure 17] A diagram illustrating a lighting device according to one embodiment of the present invention. [Figure 18] A diagram explaining light-emitting elements. [Figure 19] The ratio of delayed fluorescence components to the LUMO levels of light-emitting elements 1 to 8. [Figure 20] External quantum efficiency with respect to the delayed fluorescence component ratio of light-emitting elements 1 to 8. [Figure 21] A diagram showing the current density-luminance characteristics of the light-emitting element 4-2. [Figure 22] A diagram showing the voltage-luminance characteristics of light-emitting element 4-2. [Figure 23] A diagram showing the brightness-current efficiency characteristics of the light-emitting element 4-2. [Figure 24] A diagram showing the voltage-current characteristics of the light-emitting element 4-2. [Figure 25] A diagram showing the luminance-external quantum efficiency characteristics of light-emitting element 4-2. [Figure 26] A diagram showing the emission spectrum of light-emitting element 4-2. [Figure 27] This figure shows the decay curve illustrating the transient fluorescence characteristics of light-emitting element 4-2. [Figure 28] A diagram showing the reliability of the light-emitting element 4-2. [Figure 29] Angle-dependent characteristics and calculation results of the light-emitting element 9. [Modes for carrying out the invention]

[0024] Embodiments of the present invention will be described below. However, the present invention can be implemented in many different forms. It is possible to make such a form and details without departing from the spirit and scope of the present invention. Those skilled in the art will readily understand that the details can be changed in various ways. Therefore, the details of this embodiment The interpretation is not limited to the content stated herein.

[0025] In the figures described herein, the size and thickness of the anode, EL layer, intermediate layer, cathode, etc. Some aspects may be exaggerated for the sake of clarity in their explanations. Therefore, each component may not necessarily be... An element is not limited by its own size, nor by the relative size between its constituent elements.

[0026] Furthermore, in this specification, the ordinal numbers used as "1st," "2nd," "3rd," etc., are used for convenience. It is something that indicates the order of processes or the relative positions of things. Therefore, for example The phrase "the first" can be replaced with "the second" or "the third" as appropriate in the explanation. Furthermore, the ordinal numbers described herein and used to specify one aspect of the present invention The ordinal numbers "ru" may not always agree.

[0027] Furthermore, in the configuration of the present invention as described herein, parts that are the same or have similar functions The same symbols are used consistently across different drawings, and explanations of their repetition are omitted. When referring to parts with similar functions, the hatch pattern is the same, and no special designation is given. There are cases where this is not the case.

[0028] Furthermore, in this specification, color refers to hue (corresponding to the wavelength of monochromatic light) and saturation (vividness, i.e., whiteness). It is defined by three elements: the degree to which it is not tinged with light, and lightness (the intensity of light). In this specification, color refers to any one of the three elements mentioned above. Only one element, or any two elements of your choice, may be shown. Also, in this specification, 2 Two lights having different colors means that at least one of the three elements mentioned above is different. Furthermore, the shapes of the two light spectra or the distribution of the relative intensity ratio of each peak are different. This also includes that.

[0029] Note that the words "membrane" and "layer" may differ in some cases or depending on the situation. Therefore, they can be interchanged. For example, the term "conductive layer" can be replaced with "conductive film." In some cases, it may be possible to change the term to "insulating film". Alternatively, for example, the term "insulating film" may be used. In some cases, it may be possible to change the term to "insulating layer."

[0030] Furthermore, in this specification, etc., singlet excited state (S * ) is a singlet with excitation energy It refers to a state. Among singlet excited states, the excited state with the lowest energy is called the lowest. This is called a low-excited singlet state. Furthermore, the singlet excitation energy level is the energy level of the singlet excited state. This refers to the Ghee level. It is the lowest excitation energy level among the singlet excitation energy levels. This is called the lowest excited singlet energy (S1) level. In this specification, the term "S1" is used simply to refer to the lowest singlet energy level. Even when expressed as multiplet excited states and singlet excited energy levels, the lowest excited singlet This may represent a term state or an S1 level.

[0031] Furthermore, in this specification, etc., the triplet excited state (T * ) is a triplet with excitation energy This refers to a state. Among the triplet excited states, the excited state with the lowest energy is called the lowest. This is called a low-excited triplet state. Furthermore, the triplet excitation energy level is the energy level of the triplet excited state. This refers to the Ghee level. It is the lowest excitation energy level among the triplet excitation energy levels. This is called the lowest excited triplet energy (T1) level. In this specification, the term "triplet energy" is sometimes used simply to refer to the triplet energy level. Even when referred to as multiplet excited states and triplet excited energy levels, the lowest excited triple This may represent a term state or a T1 level.

[0032] Furthermore, in this specification, the term "fluorescent material" refers to a material that can relax from a singlet excited state to a ground state. These are materials that emit light in the visible light region. Phosphorescent materials are those that relax from a triplet excited state to a ground state. In other words, phosphorescent materials are materials that emit light in the visible light region at room temperature. It is one of the materials capable of converting triplet excitation energy into visible light.

[0033] In this specification, room temperature refers to any temperature between 0°C and 40°C.

[0034] Furthermore, in this specification, the blue wavelength range refers to the wavelength range of 400 nm to 550 nm. Therefore, blue emission refers to emission having at least one emission spectral peak in that band. That is the case.

[0035] (Embodiment 1) <Example of light-emitting element configuration> First, regarding the configuration of a light-emitting element according to one aspect of the present invention, using Figures 1(A), (B), and (C) The following explains further.

[0036] Figure 1(A) is a schematic cross-sectional view of a light-emitting element 150 according to one embodiment of the present invention.

[0037] The light-emitting element 150 has an EL layer 10 provided between a pair of electrodes (electrode 101 and electrode 102) It has 0. The EL layer 100 has at least an emissive layer 130. In this embodiment, In this explanation, electrode 101 is described as the anode and electrode 102 as the cathode. However, the configuration of the light-emitting element 150 can be reversed.

[0038] Furthermore, the EL layer 100 shown in Figure 1(A) has a functional layer in addition to the light-emitting layer 130. Functional layer The hole injection layer 111, hole transport layer 112, electron transport layer 118, and electron injection layer 119 It has. Note that the configuration of the EL layer 100 is not limited to the configuration shown in Figure 1(A), and the hole injection layer Selected from among 111, hole transport layer 112, electron transport layer 118, and electron injection layer 119 The configuration should have at least one of the following: Alternatively, the EL layer 100 may be a hole or an electron To reduce the injection barrier, improve hole or electron transport, or hinder hole or electron transport. A functional layer having functions such as being able to harm or suppress the quenching phenomenon caused by electrodes. It may also be a configuration that includes these features.

[0039] Furthermore, Figure 1(B) is a schematic cross-sectional view showing an example of the light-emitting layer 130 shown in Figure 1(A). The light-emitting layer 130 shown in 1(B) comprises at least a host material 131 and a guest material 132, It holds.

[0040] The host material 131 converts the triplet excitation energy to the singlet excitation energy by TTA. It is preferable that it has a function to exchange. By doing so, the triplet excited energy generated in the light-emitting layer 130 A portion of the energy is converted into singlet excitation energy by TTA in the host material 131. This allows for the transfer of the singlet excitation energy generated by TTA to the guest material 132. By moving it, it becomes possible to extract it as fluorescence emission. To do this, host material 1 The lowest excited singlet energy (S1) level of material 31 is higher than the S1 level of guest material 132. This is preferable. Also, the lowest excited triplet excitation energy (T1) level of the host material 131 It is preferable that this is lower than the T1 level of guest material 132.

[0041] The host material 131 may be composed of a single compound or multiple compounds. It is acceptable if it is done that way. Also, as guest material 132, any luminescent organic material can be used. The luminescent organic material is a material capable of emitting fluorescence (hereinafter also called a fluorescent material). (u) is preferable. In the following description, a fluorescent material is used as the guest material 132. The configuration used will be explained. Note that guest material 132 can be interpreted as a fluorescent material. stomach.

[0042] <Light-emitting mechanism of light-emitting element> First, the light-emitting mechanism of the light-emitting element 150 will be explained below.

[0043] In one embodiment of the present invention, a light-emitting element 150 comprises a pair of electrodes (electrode 101 and electrode 102) By applying a voltage between them, electrons are released from the cathode and holes from the anode. The electrons and holes are injected into the EL layer 100, and an electric current flows. Then, the injected electrons and holes recombine. This leads to the formation of excitons. Of the excitons produced by carrier recombination, one The ratio of multiplet excitons to triplet excitons is statistically 1:3. Therefore, singlet The probability of generating a term exciton is 25%.

[0044] An exciton is a pair of carriers (electron and hole). An exciton has an excitation energy. Because it possesses this property, the material on which excitons are formed enters an excited state.

[0045] Furthermore, singlet excitons are generated in the EL layer 100 through the following two processes, and the guest material Light emission is obtained from material 132. (α) Direct generation process (β)TTA process

[0046] ≪(α) Direct generation process≫ First, carriers (electrons or holes) recombine in the light-emitting layer 130 of the EL layer 100. Next, we will explain the case in which singlet excitons are formed.

[0047] When carriers recombine in the host material 131, excitons are generated, which contribute to the host material 131 excited states (singlet excited state or triplet excited state) are formed. At this time, When the excited state of host material 131 is a singlet excited state, the S1 level of host material 131 is Then, the singlet excitation energy is transferred to the S1 level of guest material 132, and the guest A singlet excited state is formed in material 132. Note that the excited state of host material 131 is triplet. When it is in an excited state, it will be explained in the (β)TTA process described later.

[0048] Furthermore, when carriers recombine in guest material 132, exciton generation occurs. An excited state (singlet excited state or triplet excited state) is formed in the material 132.

[0049] When the excited state of the formed guest material 132 is a singlet excited state, guest material 132 Light emission is obtained from the singlet excited state. In this case, to obtain high luminescence efficiency, guest The fluorescence quantum yield of material 132 is preferably high.

[0050] On the other hand, when a triplet excited state is formed in guest material 132, guest material 132 becomes a fluorescent material. Because it is a material, the triplet excited state of guest material 132 is thermally deactivated and does not contribute to luminescence. However, if the T1 level of the host material 131 is lower than the T1 level of the guest material 132, The triplet excitation energy of guest material 132 is obtained from the T1 level of guest material 132. Energy transfer to the T1 level of host material 131, which is present in a much larger quantity than material 132. This becomes possible. In that case, the (β)TTA process described later will generate triplet excitation energy. This allows for the conversion from ghee to singlet excitation energy. Therefore, the probability of TTA generation is For the level to be increased, the T1 level of the host material 131 must be lower than the T1 level of the guest material 132. This is important.

[0051] Furthermore, if the T1 level of the host material 131 is higher than the T1 level of the guest material 132, In the weight ratio of the host material 131 to the guest material 132, the weight of the guest material 132 By lowering the quantity ratio, the probability of carrier recombination with guest material 132 is reduced. This is possible. Also, the energy from the T1 level of the host material 131 to the T1 level of the guest material 132 The probability of energy transfer occurring can be reduced. Specifically, the host material 131 is 1 The weight ratio of guest material 132 to the total weight is preferably greater than 0 and 0.05 or less.

[0052] ≪(β)TTA process≫ Next, triplet excitons formed in the carrier recombination process in the light-emitting layer 130 The case where a singlet exciton is formed will be described.

[0053] Here, the case where the T1 level of the host material 131 is lower than the T1 level of the guest material 132 will be described. A schematic diagram showing the energy level correlation at this time is shown in Fig. 1(C). Also, the notations and symbols in Fig. 1(C) are as follows. Note that the T1 level of the host material 131 may be higher than the T1 level of the guest material 132. ·Host(131): Host material 131 ·Guest(132): Guest material 132 (fluorescent material) ·Host(131): Host material 131 ·Guest(132): Guest material 132 (fluorescent material) ·S FH : S1 level of the host material 131 ·T FH : T1 level of the host material 131 ·S FG : S1 level of the guest material 132 (fluorescent material) ·T FG : T1 level of the guest material 132 (fluorescent material)

[0054] Carriers recombine in the host material 131, and an excited state of the host material 131 is formed by the generation of excitons. At this time, when the generated exciton is a triplet exciton, a reaction may occur in which one of the two generated triplet excitons is converted into a singlet exciton having the energy of the S1 level (S ) of the host material 131 due to the proximity of the two triplet excitons (see Fig. 1(C) TTA). This is a reaction in which the number of triplet excitons decreases while generating singlet excitons, which can be expressed by the following general formula (G1) or (G2). FH * ) of the host material 131 due to the proximity of the two triplet excitons (see Fig. 1(C) TTA). This is a reaction in which the number of triplet excitons decreases while generating singlet excitons, which can be expressed by the following general formula (G1) or (G2). See Fig. 1(C) TTA). This is a reaction in which the number of triplet excitons decreases while generating singlet excitons, which can be expressed by the following general formula (G1) or (G2). This is a reaction in which the number of triplet excitons decreases while generating singlet excitons, which can be expressed by the following general formula (G1) or (G2).

[0055] 3 H * + 3 H * → 1 (HH) * →1 H ** +H → 1 H * +H (G1) 3 H * + 3 H * → 3 (HH) * → 3 H ** +H → 3 H * +H (G2)

[0056] The general formula (G1) is given by two triangular ions in the host material 131 whose sum of spin quantum numbers is 0. Multiplet exciton ( 3 H * ) but exciton pairs whose sum of spin quantum numbers is 0 ( 1 (HH) * ) form , higher-order singlet excitons excited electronically or vibrationally ( 1 H ** ) via singlet excitation child( 1 H * This is a reaction that produces ). Also, the general formula (G2) is used when the host material 131 is So, two triplet excitons whose sum of spin quantum numbers is 1 (atomic unit) ( 3 H * ) but, exciton pairs whose sum of quantum numbers is 1 ( 3 (HH) * ) forms and is excited electronically or vibrationally A higher-order triplet exciton ( 3 H ** ) then the triplet exciton ( 3 H * ) is produced in the reaction Yes. In general formulas (G1) and (G2), H represents the ground state in the host material 131. .

[0057] In general formulas (G1) and (G2), the sum of the spin quantum numbers is 1 (atomic unit) in the triple There are three times more pairs of term excitons than pairs with a sum of 0 spin quantum numbers. Of the excitons produced from the two triplet excitons, the newly produced singlet exciton and the triplet exciton are... The ratio of multiplet excitons is 1:3 by statistical probability. Also, in the light-emitting layer 130, triple When the density of term excitons is sufficiently high (for example, 1 × 10⁻⁶ 12 cm -3 (The above) shows triple excitation By ignoring the deactivation of individual excitons and considering only the reaction involving two closely spaced triplet excitons, Cut.

[0058] Therefore, one reaction in general formula (G1) and three reactions in general formula (G2) As in general formula (G3), 8 triplet excitons ( 3 H * ) from one singlet exciton ( 1 H * ) and three electronically or vibrationally excited higher-order triplet excitons ( 3 H ** ) generates This will happen.

[0059] 8 3 H * → 1 H * +3 3 H ** +4H→ 1 H * +3 3 H * +4H (G3)

[0060] Higher-order triplet excitons generated electronically or vibrationally by the general formula (G3) 3 H * * ) is rapidly relaxed, resulting in a triplet exciton ( 3 H * ) and then another triplet excitation The reaction between the initiator and the general formula (G3) is repeated. Therefore, in the general formula (G3), triplet excitation occurs. Kishi( 3 H * All of them are singlet excitons ( 1 H * If it is converted to ), then there are 5 triplet excitations Kishi( 3 H * ) from one singlet exciton ( 1 H * ) will be generated (general formula (G4 ))

[0061] 5 3 H → 1 H * +4H (G4)

[0062] On the other hand, singlet excitons are directly generated by the recombination of carriers injected from a pair of electrodes. 1 H * ) and triplet exciton ( 3 H * The statistical generation rate of ) is, 1 H * : 3 H * = 1:3 That is, singlet excitons are directly produced by the recombination of carriers injected from a pair of electrodes. The probability of success is 25%.

[0063] Therefore, singlet excitations directly generated by the recombination of carriers injected from a pair of electrodes By combining the exciton with the singlet exciton generated by TTA, it is injected from a pair of electrodes. Twenty excitons (singlet excitons and triplet excitons) were directly generated by the recombination of carriers. From the total of the children, eight singlet excitons can be generated (general formula (G5)). That is, T TA increases the singlet exciton generation probability from the conventional 25% to a maximum of 40% (= 8 excitons / 20%). It becomes possible to improve the quality up to (1).

[0064] 5 1 H * +15 3 H * → 5 1 H * +(3 1 H * +12H) (G5)

[0065] In the singlet excited state formed by the singlet excitons generated through the above process, energy transfer occurs from the S1 level (S ) of the host material 131 to the S1 level (S FH ) of the guest material 132, which is a lower energy level (see Fig. 1 (C) Route A). Then, the guest material 132 in the singlet excited state emits fluorescence. FG ) (see Fig. 1(C) Route A). Then, the guest material 132 in the singlet excited state emits fluorescence. (C) Route A). Then, the guest material 132 in the singlet excited state emits fluorescence.

[0066] Note that when carriers recombine in the guest material 132 and the generated excited state formed by the excitons is a triplet excited state, if the T1 level (T ) of the host material 131 is lower than the T1 level (T FH ) of the guest material 132, the triplet excitation energy of T will transfer to T FG without being deactivated (see Fig. 1(C) Route B) and is utilized in TTA FG . FH

[0067] Also, when the T1 level (T FG ) of the guest material 132 is lower than the T1 level (T FH ) of the host material 131 , the weight ratio of the host material 131 to the guest material 132 is preferably lower for the guest material 132. Specifically, the weight ratio of the host material 131 to the guest material 132 is preferably greater than 0 and 0.05 or less. By doing so This can reduce the probability of recombination of carriers with the guest material 132. Also, the T1 level (T FH ) of the host material 131 to the T1 level (T FG ) of the guest material 132 can reduce the probability of energy transfer occurring.

[0068] As described above, by TTA, the triplet excitons formed in the light-emitting layer 130 are converted into singlet excitons, so that efficient light emission from the guest material 132 can be obtained.

[0069] <Regarding the generation probability of TTA> As described above, by TTA, the generation probability of singlet excitons can be improved, and the luminous efficiency of the light-emitting device can be improved. However, in order to obtain a high luminous efficiency, it is important to increase the probability of TTA occurring (also referred to as TTA efficiency). That is, it is important that the ratio of the delayed fluorescence component due to TTA in the light emission exhibited by the light-emitting device is high.

[0070] As described above, by the TTA process, it is possible to improve the generation probability of singlet excitons. Together with the 25% of singlet excitons generated by the direct recombination of carriers injected from a pair of electrodes, the singlet exciton generation probability can be improved up to 40% at most. That is, the proportion of the delayed fluorescence component due to TTA in the light emission exhibited by the light-emitting device can be improved up to (40% - 25%) / 40% = 37.5%.

[0071] <Improvement of luminous efficiency due to increase in delayed fluorescence component of light emission> For example, a blue light-emitting device having an anthracene compound generally used as a host material ​​​​​​In a light-emitting device, the proportion of the light emitted by the delayed fluorescence component due to TTA is 10 It is approximately %. In this specification, delayed fluorescence is defined as steady-state carrier injection into the emissive layer. Even after blocking, the luminescence intensity remains 0.01 or higher compared to when carriers are being injected steadily. The strength ratio is 1 × 10 -6 The luminescence should be such that it lasts for more than 1 second.

[0072] In a light-emitting element that emits blue light, in order to improve the luminescence efficiency of the light-emitting element, The proportion of the delayed fluorescence component due to TTA needs to be increased.

[0073] As described above, the TTA process is formed in the carrier recombination process in the light-emitting layer 130. This is the process by which a singlet exciton is formed by a triplet exciton. However, the carrier regeneration If the triplet exciton formed during the coupling process is deactivated by another process, the singlet exciton It does not contribute to formation, and the delayed fluorescence component of the light emission exhibited by the light-emitting element due to TTA is reduced, which is a problem. ru.

[0074] There are various possible factors that can cause the deactivation of the formed triplet exciton, but one of them is There is an action of carrier electrons in the light layer 130. Triplet excitons formed in the light-emitting layer 130 and When carrier electrons interact with triplet excitons, the triplet excitons may be deactivated.

[0075] Therefore, in a light-emitting element according to one aspect of the present invention, carriers present in the light-emitting layer 130 The electron density was appropriately adjusted to reduce the deactivation of triplet excitons. (Emitting layer 130) The carrier electrons present are mainly supplied from the electron transport layer 118, therefore, The movement of carrier electrons from the transport layer 118 to the light-emitting layer 130 can be appropriately adjusted, and therefore Therefore, the LUMO levels of the material used in the electron transport layer 118 and the host material of the light-emitting layer 130 An energy barrier can be established between the LUMO level of material 131 and the LUMO level.

[0076] In a light-emitting element according to one aspect of the present invention, the material used for the electron transport layer 118 is LUM By lowering the O level to a level lower than the LUMO level of the host material 131 that the light-emitting layer 130 has This forms an energy barrier against the movement of carrier electrons. When electron movement is suppressed, the carrier recombination region in the light-emitting layer 130 becomes the electron transport layer 118 As a result, the densities of both triplet excitons and carrier electrons in the recombination region are As the threshold decreases, the probability of triplet exciton deactivation also decreases. It is possible that if the density decreases, TTA itself may become less likely to occur. However, in reality, three The negative effects of reducing electron density are greater than the negative effects of reducing the multiplet exciton density, which lead to triplet excitation. The effect of inhibiting the inactivation of the offspring is far greater, and the above configuration actually makes TTA more likely to occur. The inventors have discovered this.

[0077] Figure 2 shows that the LUMO level of the material used in the electron transport layer 118 is the same as that of the light-emitting layer 130. Figure 2 shows the energy diagrams for the case where the LUMO level of material 131 is higher and lower than the LUMO level. This creates an energy barrier between the electron transport layer 118 (ETL) and the light-emitting layer 130 (EmL). When an energy barrier is formed, a recombination region is formed. The ion region extends towards the electron transport layer 118 (ETL), and triplet excitons (tr The density of iplet excitation and electrons decreases, leading to triplet excitation. It is understood that the probability of quenching of the starter decreases. When the rate is reduced, the TTA process will produce singlet excitons from triplet excitons. This is achieved, and the delayed fluorescence component due to TTA of the light-emitting element increases. Therefore, the present invention In one embodiment, the luminescence efficiency of the light-emitting element can be improved.

[0078] For example, according to one aspect of the present invention, the delayed fluorescence component of the light emitted by the light-emitting element is occupied by TTA. The proportion of material that can be added can be 10% or more. Furthermore, material having a relatively deep LUMO level By using the material in the electron transport layer 118, the delayed fluorescence emission of the light-emitting element by TTA is achieved. The proportion of this can also be 15% or more. To obtain such an effect, electrons The LUMO levels of the material used in the transport layer 118 and the host material 13 of the light-emitting layer 130 It is preferable to provide an appropriate energy barrier between the LUMO level 1 and the other energy level. The Ghee difference is preferably 0.05 eV or greater.

[0079] Here, if the LUMO level of the material used in the electron transport layer 118 is extremely deep, electron transport The movement of carrier electrons from layer 118 to the light-emitting layer 130 becomes less likely, and the light-emitting layer 130 Because the carrier balance decreases, the luminescence efficiency of the light-emitting element may decrease. Therefore, in order to appropriately suppress the movement of carrier electrons from the electron transport layer 118 to the light-emitting layer 130 The above energy barrier must be moderately large. Therefore, the electron transport layer 118 The LUMO levels of the materials used and the LUMO levels of the host material 131 of the light-emitting layer 130 The difference from the position is preferably between 0.05 eV and 0.3 eV.

[0080] Furthermore, as described above, in one embodiment of the present invention, the light-emitting element is connected from the electron transport layer 118 to the light-emitting layer 130. This device moderately suppresses the movement of carrier electrons in the light-emitting layer 130. And the guest material 132, which is present in a smaller quantity than the host material 131, traps carrier electrons. If this happens, even electron transfer within the light-emitting layer 130 will become less likely to occur, and unnecessary The drive voltage becomes high. From this perspective, the LUMO level of the guest material is It is preferable that the level is higher than the LUMO level of the material.

[0081] In addition to TTA, other factors that cause delayed fluorescence in light-emitting devices include Thermal activation delay due to reverse intersystem crossing from triplet excited state to singlet excited state Light is possible. For reverse intersystem crossing to occur efficiently, the energy between the S1 level and the T1 level is - Preferably the difference is 0.2 eV or less. In other words, the energy difference between the S1 level and the T1 level When the energy difference is greater than 0.2 eV, inverse interterm crossing becomes less likely. Therefore, TTA For TTA to be efficiently generated, the compound in which TTA is generated must have the lowest excitation singlet energy The energy difference between the energy level and the lowest excited triplet energy level is greater than 0.2 eV. This is preferable, and more preferably 0.5 eV or higher.

[0082] The lowest excited singlet energy level is the lowest excited singlet energy level of an organic compound from its ground state. It can be observed from the absorption spectrum during the transition to [a specific state]. Alternatively, the fluorescence of organic compounds can be observed. The lowest excited singlet energy level can also be estimated from the peak wavelength of the emission spectrum. The lowest excited triplet energy level is the energy level to which an organic compound transitions from the ground state to the lowest excited triplet state. Although this can be observed from the absorption spectrum during the transition, since this transition is forbidden, Observation can sometimes be difficult. In such cases, the phosphorescence spectrum of organic compounds is used. The lowest excited triplet energy level can also be estimated from the wavelength. Therefore, organic compounds In this case, the peak wavelength of the fluorescence emission spectrum and the peak wavelength of the phosphorescence emission spectrum are A difference in energy equivalent value of 0.2 eV is preferable, and 0.5 eV or more is even preferable. preferable.

[0083] <Improved hole transport layer and luminous efficiency> The relationship between the material of the electron transport layer 118 and its luminous efficiency is as described above. Next, The relationship between the material of the pore transport layer 112 and its luminescence efficiency will be explained.

[0084] The material of the hole transport layer 112 has a higher LUMO level compared to the host material 131. Preferably, the material of the hole transport layer 112 and the host material 131 have equivalent LUMOs. In some cases, carrier electrons that reach the light-emitting layer 130 do not remain in the light-emitting layer 130, but instead reach the hole transport layer Carrier electrons are lost in layer 112. Then, in the hole transport layer 112, the carriers Because recombination occurs, the carrier recombination efficiency in the light-emitting layer 130 decreases. Of course, the excitons generated in the hole transport layer 112 transfer energy to the light-emitting material in the light-emitting layer 130. If energy transfer is possible, there is no problem, but otherwise, the luminescence efficiency will be low.

[0085] Therefore, the material of the hole transport layer 112, compared to the host material 131, has a LUMO level It is preferable that the value is high. The LUMO level of the material in the hole transport layer 112 is the host It is more preferable that the LUMO level is 0.3 eV or higher than that of material 131. (Luminescent layer 130) This is because it can effectively suppress the movement of carrier electrons from to the hole transport layer 112. ru.

[0086] <Suppression of triplet excitation energy transfer> Next, the triplet excitation energy generated in the light-emitting layer 130 is retained in the light-emitting layer 130. This section explains how to prevent movement outside of the designated area.

[0087] When the triplet excitation energy generated in the light-emitting layer 130 is transferred to the outside, the TTA of the light-emitting layer 130 The probability of this occurring decreases. Therefore, suppressing the transfer of triplet excitation energy reduces the luminescent layer This allows for maintaining a high probability of TTA occurrence and high luminescence efficiency of the light-emitting element. It is possible.

[0088] First, to suppress the transfer of triplet excitation energy from the light-emitting layer 130 to the hole transport layer 112, For this purpose, the T1 level of the material in the hole transport layer 112 is used by the host material in the light-emitting layer 130. It should be higher than T1 of 131. More preferably, the material of the hole transport layer 112 The T1 level is set to be 0.2 eV or more higher than the T1 level of the host material 131 in the light-emitting layer 130. You should do that.

[0089] Similarly, the transfer of triplet excitation energy from the light-emitting layer 130 to the electron transport layer 118 is suppressed. To achieve this, the T1 level of the material in the electron transport layer 118 is determined by the host material in the light-emitting layer 130. It is sufficient to make it higher than the T1 level of material 131. More preferably, the electron transport layer 118 has The T1 level of the material is set to be 0.2 eV higher than the T1 level of the host material 131 in the light-emitting layer 130. That's all you need to do.

[0090] By suppressing the transfer of triplet excitation energy and retaining it in the light-emitting layer 130, other than TTA the triplet excitation energy is less likely to be lost, and the generation probability of TTA in the light-emitting layer 130 can be maintained at a high level, and the luminous efficiency of the light-emitting device can be maintained at a high level.

[0091] <Measurement of Delayed Fluorescence Component> An example of a method for evaluating the delayed fluorescence component in the light emission from the light-emitting layer will be described.

[0092] In a state where carriers are constantly injected into the light-emitting layer, the light emission from the light-emitting layer has an intensity having a delayed fluorescence component and other components. When carriers are injected into the light-emitting layer for a sufficient time the emission intensity related to delayed fluorescence saturates. Therefore, the proportion occupied by the delayed fluorescence component in the light emission refers to the value in a state where carriers are constantly injected into the light-emitting layer.

[0093] To evaluate the proportion occupied by the delayed fluorescence component in the light emission, the injection of carriers into the light-emitting layer can be stopped and the decaying light emission can be measured. The lifetime from when the injection of carriers is stopped until the light emission extinguishes is such that the lifetime of the delayed fluorescence is several μs, while the lifetime of normal fluorescence emission is several ns Therefore, the delayed fluorescence can be evaluated by measuring the component that extinguishes in a time of several μs.

[0094] When the decay of the light emission is observed with a streak camera in a time of several μs after the injection of carriers into the light-emitting layer is stopped an exponential decay curve can be obtained. The light emission when the injection of carriers into the light-emitting layer is stopped has a delayed fluorescence component and other components, but after several ns have elapsed substantially only the delayed fluorescence component remains. Therefore, for the decay curve, an exponential function is fitted​​ By doing so, an equation of a decay curve with time as a parameter can be obtained.

[0095] By applying time 0 s to the equation of the decay curve, the value of the intensity of the delayed fluorescence component when carrier injection is stopped can be estimated. At the moment when carrier injection into the light-emitting layer is stopped Since the carriers are being injected steadily, it can be said that the estimated intensity of the delayed fluorescence component is the intensity of the delayed fluorescence component in the state where carriers are being injected steadily. Since the carriers are being injected steadily, it can be said that the estimated intensity of the delayed fluorescence component is the intensity of the delayed fluorescence component in the state where carriers are being injected steadily. The ratio of the delayed fluorescence component in the light emission can be calculated from the light emission intensity of the light-emitting layer in the state where carriers are being injected steadily and the intensity of the obtained delayed fluorescence component. In addition, the delayed fluorescence component in the light emission of the light-emitting layer includes not only delayed fluorescence derived from the TTA process including intermolecular interaction, but also thermally activated delayed fluorescence (TADF) derived from energy transfer from the triplet excited energy level of the molecule to the singlet excited energy level. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process.

[0096] In addition, the delayed fluorescence component in the light emission of the light-emitting layer includes not only delayed fluorescence derived from the TTA process including intermolecular interaction, but also thermally activated delayed fluorescence (TADF) derived from energy transfer from the triplet excited energy level of the molecule to the singlet excited energy level. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process. There is a possibility that it is included. However, for TADF to occur, conditions that enable reverse energy transfer from the triplet excited energy level to the singlet excited energy level are necessary. The condition is that the energy levels of both are close to each other, and if the energy gap between the two is about 0.2 eV or less, TADF can occur, but the molecules that satisfy the condition among the molecules used in the light-emitting layer are limited. Therefore, when molecules with a relatively large energy gap are used in the light-emitting layer, there is no need to consider TADF, and it can be said that the delayed fluorescence component in the light emission exhibited by the light-emitting layer is substantially delayed fluorescence derived from the TTA process.

[0097] For specific measurement details, please refer to the examples.

[0098] <Molecular orientation and light extraction efficiency> In organic EL, carriers are supplied to the light-emitting layer, and carrier recombination occurs within the light-emitting layer. Although light emission occurs from the guest material contained in the light-emitting layer, if this light emission is not isotropic, In other words, the emission intensity may be angle-dependent. This emission is due to the transition dipole motor of the guest material. It occurs perpendicular to the moment. Therefore, the direction of the transition dipole moment depends on the angle of emission. This will affect the properties. The direction of the transition dipole moment of an organic molecule is determined by the organic molecule's properties. Because it is affected by molecular orientation, the emission from the guest material is due to the molecular orientation of the guest molecule. It may exhibit anisotropy.

[0099] The luminescent layer has multiple molecules, and the guest material is dispersed in the host material. Fabrication of the luminescent layer Depending on the case, the guest molecule may not be randomly oriented within the host material, but rather the guest The molecules are oriented in a certain direction, that is, there is a bias in the molecular orientation of the guest molecule. Therefore, the guest material in the light-emitting layer is arranged in a way that makes it easy to extract light to the outside of the light-emitting element. If the light source has directionality, the light extraction efficiency of the light source will increase. Specifically, relative to the substrate surface Then, the guest molecule is oriented so that its transition dipole moment is in the horizontal direction. It's preferable to have them around.

[0100] When evaluating molecular orientation, the molecules of the light-emitting layer within the actual light-emitting element, especially the transition dipoles of the guest material, are important. It is not easy to directly observe the orientation of the moment. Therefore, The light emitted from the light-emitting layer is linearly polarized to extract the p-polarized light component, and the resulting visible light The p-polarized emission spectrum over wavelengths from the visible region to the near-infrared region (from 440 nm to 956 nm) The angular dependence of the area intensity of the torque was measured, and the result was analyzed by calculation (simulation) By doing so, a method for deriving the molecular orientation of the luminescent material in the light-emitting layer was conceived. Hereinafter, the method for deriving the molecular orientation will be described.

[0101] Here, the state where the guest molecules are randomly oriented in the host molecules will be described. When the guest molecules are randomly oriented in the host molecules, the sum of the transition dipole moments of all the molecules has equal components in the x, y, and z directions that are orthogonal to each other. Here, for example, when there is a layer in a plane extending in the x and y directions, if the molecules in the layer are isotropically oriented the transition dipole moment has two dimensions for the component parallel to the layer, so the overall is two-thirds (67%) and the component perpendicular to the layer is one-third (33%) of the whole.

[0102] Next, the measurement will be described. When measuring the intensity of the light emission of the light-emitting layer with a measuring device, before the light enters the detector, the light is made to enter and pass through a Glan-Taylor polarizing prism. Then at the detector, only the polarization component in a specific direction can be detected.

[0103] Here, three types of components shown in FIG. 3 are defined for the transition dipole moment related to the light emission That is, A) the component 181 of the transition dipole moment in the direction parallel to the observation direction 180 of the detector among the components parallel to the light-emitting layer 130, B) among the components parallel to the light-emitting layer 130 the component 182 of the transition dipole moment in the direction perpendicular to the observation direction 180 of the detector, C ) the component 183 of the transition dipole moment in the direction perpendicular to the light-emitting layer 130. Then, for B ) the component 182 of the transition dipole moment in the direction perpendicular to the observation direction 180 of the detector, C The components cannot pass through the Grand-Taylor polarizing prism between the detector and the light-emitting layer 130. Therefore, component B is not detected by the detector. In other words, in this measurement, A and We are observing p-polarized light consisting of the C component.

[0104] Next, in order to evaluate the angle dependence of the light emission, the detector 185 is positioned perpendicular to the light-emitting layer 130. A certain state is taken as the initial position, and the light-emitting layer 130 is tilted. The initial state is shown in Figure 4(A). Figure 4(B) shows the state in which the light-emitting layer 130 is tilted (tilt angle θ). In the initial state (tilt angle 0°) Therefore, since the detector 185 is facing the front of the light-emitting layer 130, the emission originates from the C component mentioned above. Light is not observed, but component A is observed. As the tilt angle of the light-emitting layer 130 is increased, Detector 185 observes not only component A, but also component C depending on the tilt angle. This allows us to evaluate the angle dependence of light.

[0105] Here, of the light emitted outside the element, the component perpendicular to the light-emitting layer 130 is the light-emitting layer 13 Because its intensity is extremely small compared to the component parallel to 0, it is not possible to evaluate the C component in this state. That is difficult. Therefore, by adjusting the thickness of each layer of the light-emitting element in advance and utilizing optical interference... Therefore, the emission intensity of the component parallel to the light-emitting layer 130 is reduced. That is, from the light-emitting element The light extracted in the forward direction consists of a component directly extracted from the light-emitting layer 130 and a component from the light-emitting layer 130. The light generated once enters the electrode, is reflected, and is extracted as a component, but each layer of the light-emitting element By adjusting the thickness of the two, their phases are reversed and they cancel each other out. Then, component A This allows us to weaken the C component, making it easier to observe.

[0106] By doing so, the angle dependence of light emission from the light-emitting layer can be measured. (Horizontal axis) The tilt angle from the initial state of the light-emitting layer 130, the area intensity of the normalized emission spectrum on the vertical axis, and The shape of the graph obtained by plotting the measurement results is the relationship between component A and component C during emission. It changes depending on the ratio. Here, when the ratio of component A and component C during emission is changed... The shape of each graph can be obtained through calculation (simulation). Therefore, conversely The graph obtained through calculation is fitted to the shape of the graph obtained from the measurement results. This allows us to obtain the ratio of component A to component C during emission. Transition dipole moment The orientation of the particles is specific to the molecule (in this case, the guest material), therefore, the components of A and C Information regarding the orientation of the guest material can be obtained from the ratio.

[0107] If component A exceeds 67%, then the component of the transition dipole moment parallel to the light-emitting layer is It means that the amount increases, and simply put, if component A is 100%, it means perfect horizontal orientation. Light is emitted perpendicular to the transition dipole moment, therefore the transition dipole moment The more parallel the beam is to the light-emitting layer, the higher the light extraction efficiency. In other words, when A reaches 100% The closer you get, the higher the light-emitting efficiency of the element becomes.

[0108] Furthermore, by observing the light extracted from the light-emitting element according to one aspect of the present invention based on the above measurements, The guest material is not randomly oriented, but rather in a specific orientation state, and transition dipole moment It can be seen that the luminescence is tilted significantly from the vertical direction of the light-emitting layer. The transition dipole moment is emitted. When the light layer is tilted from the vertical direction, the light emission in the vertical direction of the light-emitting layer is strengthened, thus, in one aspect of the present invention It can be seen that the orientation state of the guest material contributes to the high luminous efficiency of the light-emitting element.

[0109] For details on measurement and calculation, please also refer to the description in the examples.

[0110] <Material> Next, the details of the components of a light-emitting element according to one aspect of the present invention will be described below.

[0111] ≪Luminous layer≫ In the light-emitting layer 130, the host material 131 is at least more abundant by weight than the guest material 132. The guest material 132 (fluorescent material) is present and dispersed in the host material 131. Emitting layer 1 In 30, the materials that can be used as the host material 131 are, among the luminescence exhibited Organic compounds with a high proportion of delayed fluorescence components due to triplet-triplet annihilation (TTA) are preferred. Specifically, organic compounds in which the delayed fluorescence component due to TTA accounts for 20% or more. A material is preferred. In addition, in the light-emitting layer 130, the host material 131 is composed of a type of compound. It may be composed of multiple compounds, or it may be a single compound.

[0112] Furthermore, in the luminescent layer 130, there are no particular limitations on the guest material 132, but anthracite is also an option. Cene derivatives, tetracene derivatives, chrysene derivatives, phenanthrene derivatives, pyrene derivatives Perylene derivatives, stilbene derivatives, acridone derivatives, coumarin derivatives, phenoxa Zin derivatives, phenothiazine derivatives, etc. are preferred, and for example, the following materials can be used. Cut.

[0113] 5,6-Bis[4-(10-phenyl-9-antryl)phenyl]-2,2'-bipyri Zin (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-antri [Lu)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N, N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl] )phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bi (3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluorene- 9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn) ), N,N'-bis[4-(9H-carbazole-9-yl)phenyl]-N,N'-di Phenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazo (Abbreviated) 4'-(10-phenyl-9-anthryl)triphenylamine ( Name: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-dife Nyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl Nyl-N-[4-(10-phenyl-9-antryl)phenyl]-9H-carbazole -3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert- Butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-antryl)-4'- (9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA) PA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4, 1-Phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (Abbreviation: DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2 -Anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: 2PCAPPA) , N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'- Triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N', N',N'',N'',N''',N'''-Octaphenyldibenzo[g,p]Crystal N-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N-(9, 10-Diphenyl-2-anthryl)-N,9-Diphenyl-9H-carbazole-3- Amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-i [Lu)-2-anthryl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviation) :2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N',N '-Triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,1 0-Bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-to Riphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis (1,1'-biphenyl-2-yl)-N-[4-(9H-carbazole-9-yl) [phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N ,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 6, Coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-Bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (Abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}- 6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2 -{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i j]Quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinite Lyl (abbreviation: DCM2), N,N,N',N'-tetrakis(4-methylphenyl)teto Spiral-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N ,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluorane Ten-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6- [2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H- Benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}pro Pandinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1, 1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij ]Quinolysin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitol (Abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl ]Ethenyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM) ), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3 ,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl ]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), 5 ,10,15,20-tetraphenylbisbenzo[5,6]indeno[1,2,3-cd Examples include perylene [1',2',3'-lm].

[0114] Furthermore, the light-emitting layer 130 contains materials other than the host material 131 and the guest material 132. It's okay to do so.

[0115] There are no particular limitations on the materials that can be used for the light-emitting layer 130, but for example, Ris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methicone) Aluminum (III) (abbreviation: Almq3), Bis (10-H) Droxybenzo[h]quinolinate)beryllium(II) (abbreviation: BeBq2), bis(2 -methyl-8-quinolinolate)(4-phenylphenolate)aluminum(III)(abbreviated) Name: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2- (2-benzoxazolyl)phenolate]zinc(II) (abbreviation: ZnPBO), bis[2 -(2-benzothiazolyl)phenolate]zinc(II) (abbreviation: ZnBTZ) and other metals Complex, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4 -Oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenate) [Nyl]-1,3,4-oxadiazole-2-yl]benzene (abbreviation: OXD-7), 3 -(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1, 2,4-Triazole (abbreviation: TAZ), 2,2',2''-(1,3,5-Benzene) Tris(1-phenyl-1H-benzoimidazole) (abbreviation: TPBI), Baso Phenanthroline (abbreviation: BPhen), vasocuproin (abbreviation: BCP), 9-[4 -(5-phenyl-1,3,4-oxadiazole-2-yl)phenyl]-9H-cal Heterocyclic compounds such as bazole (abbreviated as CO11), 4,4'-bis[N-(1-naphthyl )-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylf (phenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviated) Name: TPD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)- Examples include aromatic amine compounds such as N-phenylaminobiphenyl (abbreviated as BSPB). Furthermore, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, and chrysene derivatives are also used. Examples include condensed polycyclic aromatic compounds such as dibenzo[g,p]chrysene derivatives, and specifically , is 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl- 9-[4-(10-phenyl-9-antryl)phenyl]-9H-carbazole-3- Amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenyl Amine (abbreviation: DPhPA), 4-(9H-carbazole-9-yl)-4'-(10- Phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), N,9-diphenyl Nyl-N-[4-(10-phenyl-9-antryl)phenyl]-9H-carbazole -3-amine (abbreviation: PCAPA), N,9-diphenyl-N-{4-[4-(10-f Phenyl-9-antryl)phenyl]phenyl}-9H-carbazole-3-amine (abbreviated) Name: PCAPBA), N,9-diphenyl-N-(9,10-diphenyl-2-antri 2PCAPA)-9H-carbazole-3-amine, 6,12-dimethoxy -5,11-diphenylchrysene, N,N,N',N',N'',N'',N''',N '''-Octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine n (abbreviation: DBC1), 9-[4-(10-phenyl-9-antryl)phenyl]-9 H-carbazole (abbreviation: CzPA), 3,6-diphenyl-9-[4-(10-phenyl Lu-9-antryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 9,1 0-Bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10- Di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10- di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-biantril ( Abbreviation: BANT), 9,9'-(Stilben-3,3'-diyl)diphenanthrene (abbreviation) Name: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation) Examples include DPNS2, 1,3,5-tri(1-pyrenyl)benzene (abbreviated as TPB3), etc. It can be listed. In addition, from among these and known substances, the guest material 132 is Select one or more materials that have an energy gap larger than the energy gap. You can choose and use them as you see fit.

[0116] The light-emitting layer 130 can also be composed of two or more layers. For example, the first When the light-emitting layer and the second light-emitting layer are stacked in order from the hole transport layer side to form the light-emitting layer 130, the first A material with hole transport properties is used as the host material for the light-emitting layer, and the host material for the second light-emitting layer is This configuration uses a material that has electron transport properties. Furthermore, the light-emitting layer 130 is a host material. And it may also have a first region having guest material and a second region having host material. stomach.

[0117] Next, the details of the other components of the light-emitting element 150 shown in Figure 1(A) will be described below.

[0118] ≪A pair of electrodes≫ Electrodes 101 and 102 have the function of injecting holes and electrons into the light-emitting layer 130. 101 and electrode 102 are made of metals, alloys, conductive compounds, and mixtures or laminates thereof. It can be formed using various materials. Aluminum is a typical example of a metal, but others include Silver, tungsten, chromium, molybdenum, copper, titanium, and other transition metals, lithium and cesium Alkali metals such as um, and Group 2 metals such as calcium and magnesium can be used. Rare earth metals such as ytterbium (Yb) may be used as the transition metal. In this case, alloys containing the above metals can be used, such as MgAg and AlLi. It can be used. Conductive compounds include indium tin oxide (Indium Tin O) Examples include metal oxides such as xide. Conductive compounds include inorganic carbon such as graphene. Elementary materials may also be used. As mentioned above, by stacking multiple of these materials... Electrode 101 and electrode 102 may be formed, or both may be formed.

[0119] Furthermore, the light emitted from the light-emitting layer 130 is emitted from one or both of the electrodes 101 and 102. It is extracted through. Therefore, at least one of electrode 101 and electrode 102 is exposed to visible light. It transmits light. When using a material with low light transmittance, such as metal or alloy, for the electrode that extracts light. Electrode 10 is provided with a thickness sufficient to transmit visible light (for example, a thickness of 1 nm to 10 nm). One or both of electrode 1 and electrode 102 may be formed.

[0120] ≪Hole Injection Layer≫ The hole injection layer 111 receives hole injections from one of the pair of electrodes (electrode 101 or electrode 102). It has the function of promoting hole injection by reducing the entry barrier, for example, transition metal oxides, lids It is formed by cyanine derivatives or aromatic amines, etc. as a transition metal oxide. For example, molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, Examples include manganese oxides. Phthalocyanine derivatives include phthalocyanine and gold Examples include phthalocyanines. Aromatic amines include benzidine derivatives and phenyl Examples include diamine derivatives. Also, polymer compounds such as polythiophenes and polyanilines. It is also possible to use self-doped polythiophenes such as poly(ethylenediol) Typical examples include xythiophene / poly(styrene sulfonic acid).

[0121] The hole injection layer 111 is a composite of a hole transport material and a material that exhibits electron-accepting properties in relation to it. A layer containing a material can also be used. Alternatively, a layer containing an electron-accepting material and holes can be used. A lamination of layers containing transportable materials may also be used. A steady state or an electric field may exist between these materials. Charge transfer is possible in its presence. Quinodymethane is an example of a material that exhibits electron-accepting properties. Organic acceptors such as derivatives, chloranil derivatives, and hexaazatriphenylene derivatives It can be listed. Specifically, 7,7,8,8-tetracyano-2,3,5,6-te Trafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,1 0,11-Hexacyano-1,4,5,8,9,12-Hexazatriphenylene (abbreviation) These are compounds that have electron-withdrawing groups (halogen groups or cyano groups), such as HAT-CN. Transition metal oxides, such as oxides of Group 4 to Group 8 metals, can be used. It contains vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, and oxide These include tungsten, manganese oxide, and rhenium oxide. Among them, molybdenum oxide is present in the atmosphere. However, it is preferable because it is stable, has low hygroscopicity, and is easy to handle.

[0122] As a hole-transporting material, a material with higher hole transport capabilities than electron transport can be used, 1× 10 -6 cm 2 It is preferable that the material has a hole mobility of / Vs or greater. Specifically, Aromatic amines, carbazole derivatives, aromatic hydrocarbons, stilbene derivatives, etc. are used. This is possible. Furthermore, the hole-transporting material may be a polymer compound.

[0123] Examples of materials with high hole transport capabilities include, for example, aromatic amine compounds such as N,N'- Di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPP) A) 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino] Biphenyl (abbreviation: DPAB), N,N'-bis{4-[bis(3-methylphenyl)a [Mino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-dia Min (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl Examples include )-N-phenylaminobenzene (abbreviation: DPA3B).

[0124] Furthermore, as a carbazole derivative, specifically, 3-[N-(9-phenylcarbazole [Lu-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPC) A1) 3,6-bis[N-(9-phenylcarbazole-3-yl)-N-phenyl Mino]-9-phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl [Lu)-N-(9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole Lu (abbreviation: PCzPCN1), 3-[4-(9-phenanthryl)-phenyl]-9-F Examples include enyl-9H-carbazole (abbreviated as PCPPn).

[0125] In addition, other carbazole derivatives include 4,4'-di(N-carbazolyl)bipheni (abbreviated as CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzyl n (abbreviation: TCPB), 9-[4-(10-phenyl-9-antryl)phenyl]-9 H-carbazole (abbreviation: CzPA), 1,4-bis[4-(N-carbazolyl)phenyl [L]-2,3,5,6-tetraphenylbenzene, etc., can be used.

[0126] Furthermore, examples of aromatic hydrocarbons include 2-tert-butyl-9,10-di(2-na Phthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di (1-Naphthyl)anthracene, 9,10-Bis(3,5-diphenylphenyl)ant Spiral (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenyl phenyl Nyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene Cene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2 -tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl) Chil-1-naphthyl)anthracene (abbreviation: DMNA), 2-tert-butyl-9,1 0-Bis[2-(1-naphthyl)phenyl]anthracene, 9,10-Bis[2-(1- Naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1 -Naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl Anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bi Anthrill, 10,10'-bis(2-phenylphenyl)-9,9'-biantrill, 10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'- Bianthril, anthracene, tetracene, lubren, perylene, 2,5,8,11-te Examples include tert-butyl perylene. In addition, pentacene, cornet Other types of utensils can also be used. In this way, 1 × 10 -6 cm 2 Hole mobility of / Vs or greater It is more preferable to use aromatic hydrocarbons having 14 to 42 carbon atoms.

[0127] Furthermore, aromatic hydrocarbons may have a vinyl skeleton. Aromatic hydrocarbons having a vinyl group Examples of hydrocarbons include 4,4'-bis(2,2-diphenylvinyl)biphenyl( Abbreviation: DPVBi), 9,10-bis[4-(2,2-diphenylvinyl)phenyl] Examples include tranthene (abbreviated as DPVPA).

[0128] Also, poly(N-vinylcarbazole) (abbreviation: PVK) and poly(4-vinyltriphenyl PVTPA (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamine) [Phenylamino(Mino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide](abbreviated) Name: PTPDMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bis( High molecular weight compounds such as phenyl(benzidine) (abbreviated as Poly-TPD) can also be used. Cut.

[0129] ≪Hole transport layer≫ The hole transport layer 112 is a layer containing a hole transportable material, and is exemplified as the material for the hole injection layer 111. The material can be used. The hole transport layer 112 is the hole that is injected into the hole injection layer 111. Because it has the function of transporting holes to the light-emitting layer 130, the highest occupied orbital (Hi) of the hole injection layer 111 The most Occupied Molecular Orbital, also known as HOMO (u) It is preferable to have the same or close HOMO level as the level.

[0130] In addition to the materials exemplified as the material for the hole injection layer 111, other hole transportable materials include... Examples of highly transportable substances include 4,4'-bis[N-(1-naphthyl)-N-pheny [Nuaminobiphenyl (abbreviation: NPB) and N,N'-bis(3-methylphenyl)-N, N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4''-Tris(N,N-diphenylamino)triphenylamine (abbreviation: T) DATA), 4,4',4''-Tris[N-(3-methylphenyl)-N-phenyl Minotriphenylamine (abbreviation: MTDATA), 4,4'-bis[N-(spiro-9 ,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB) ), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine ( Aromatic amine compounds such as (abbreviated as BPAFLP) can be used. Matter is mainly 1 × 10 -6 cm 2 It is a substance having a hole mobility of / Vs or greater. However, Other substances may be used if they have higher hole transport capabilities than the positive ones. Layers containing substances with high pore transport properties include not only single layers, but also two or more layers made of the aforementioned substances. It may also be made into a stacked structure.

[0131] Furthermore, the hole transport material of the hole transport layer 112 is compared with the host material 131 of the light-emitting layer. It is preferable that the LUMO level and the lowest excited triplet energy (T1) level are high. If the material of the transport layer 112 and the host material 131 have equivalent LUMO levels, Carrier electrons that reach the light layer 130 do not remain in the light-emitting layer 130, but instead transport to the hole transport layer 112. Rear electrons are removed. As a result, exciton recombination within the light-emitting layer 130 decreases, and light emission occurs. Efficiency decreases. Also, if the lowest excitation triplet energy (T1) level is the same, luminescence occurs. Triplet excitons generated in layer 130 do not produce TTA within the light-emitting layer 130, and hole transport layer 112 Triplet energy diffusion occurs, resulting in lower luminescence efficiency.

[0132] For example, as a hole transport material of the hole transport layer 112, 3-[4-(9-phenant Use lyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn). It is preferable that PCPPn is at the LUMO level and the lowest excited triplet energy (T1) level. The ratio is moderately high, moderately suppressing the diffusion of carrier electrons from the light-emitting layer 130 to the hole transport layer 112. This increases the probability of TTA generation in the light-emitting layer 130 and improves the luminescence efficiency of the light-emitting element. can.

[0133] ≪Electron transport layer≫ The electron transport layer 118 passes through the electron injection layer 119 to the other of the pair of electrodes (electrode 101 or electrode 101 or electrode 101). It has the function of transporting electrons injected from 102) to the light-emitting layer 130. Therefore, it is possible to use materials that have higher electron transport capabilities than holes, 1 × 10 -6 cm 2 / It is preferable that the material has an electron mobility of Vs or higher. Specifically, a quinoline ligand. , metals having a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand Complex, oxadiazole derivative, triazole derivative, phenanthroline derivative, pyrid Examples include derivatives of ions, bipyridine derivatives, and pyrimidine derivatives.

[0134] For example, tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris (4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis (10-Hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2) , bis(2-methyl-8-quinolinolate)(4-phenylphenolate)aluminum(I II) Metal complexes having a quinoline skeleton or a benzoquinoline skeleton, such as (abbreviation: BAlq) It is a layer consisting of bodies, etc. In addition, bis[2-(2-hydroxyphenyl)benzoxy Sazolato]zinc(II) (abbreviation: Zn(BOX)2), bis[2-(2-hydroxyphosphate) Oxazoles such as [Nyl]benzothiazolat]zinc(II) (abbreviation: Zn(BTZ)2) Metal complexes having thiazole ligands can also be used. In addition, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3 ,4-oxadiazole (abbreviation: PBD) and 1,3-bis[5-(p-tert-butyric acid) [Oxadiazole-2-yl]benzene (abbreviation: OXD-7) ), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl) -1,2,4-triazole (abbreviation: TAZ), vasophenanthroline (abbreviation: BPhe n) Vasocuproine (abbreviated as BCP) can also be used. It is mainly 1 x 10 -6cm 2 It is a substance with an electron mobility of / Vs or higher. The transport layer 118 may be a single layer, or a layer consisting of two or more layers of the above material stacked together. That's fine.

[0135] Furthermore, as an electron transport material with a particularly deep LUMO, 2,2'-(pyridine-2,6-di (Lu)bis(4,6-diphenylpyrimidine) (abbreviation: 2,6(P2Pm)2Py), 2, 9-Bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (Abbreviation: NBPhen), 2,2'-(pyridine-2,6-diyl)bis(4-phenyl) It is preferable to use benzo[h]quinazoline) (abbreviation: 2,6(P-Bqn)2Py), etc. stomach.

[0136] Furthermore, as a deep electron transport material, LUMO has a diazine skeleton or triazine in its molecular structure. It is preferable to use a substance containing a condensed heteroaromatic ring skeleton having a rib skeleton. It is also preferable to use a substance that contains a pyrazine skeleton or a pyrimidine skeleton.

[0137] The host material 1 has the LUMO level of the material used in the electron transport layer 118, and the light-emitting layer 130 has the same level. Below LUMO levels 31, an energy barrier is formed against the movement of carrier electrons. This is preferable because it allows for the transfer of carrier electrons to the light-emitting layer 130. This suppresses movement and expands the carrier recombination region in the light-emitting layer 130 toward the electron transport layer 118, and recombination In order to lower the density of triplet excitons and carrier electrons in the combined region, the triplet excitons are converted into carrier electrons. This can reduce the deactivation of excitons caused by the injection of rear electrons.

[0138] Furthermore, a layer for controlling the movement of electron carriers is provided between the electron transport layer 118 and the light-emitting layer 130. This is also possible. This involves using a material with high electron transport properties, as described above, and a material with high electron trapping properties. A layer with a small amount of additive suppresses the movement of electron carriers, thereby improving the carrier balance. This configuration allows for adjustment of the light emission layer. This has a significant effect in suppressing problems that arise from this (for example, a decrease in the lifespan of the element).

[0139] ≪Electron injection layer≫ The electron injection layer 119 promotes electron injection by reducing the electron injection barrier from the electrode 102. Having a function, for example, Group 1 metals, Group 2 metals, or their oxides, halides, Carbonates and the like can be used. Also, the electron transport material shown above, and electrons Composite materials exhibiting electron-donating properties can also be used. Examples of electron-donating materials include: Examples include Group 1 metals, Group 2 metals, or oxides thereof.

[0140] Furthermore, the light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer mentioned above are Each method includes vapor deposition (including vacuum deposition), inkjet printing, coating, gravure printing, etc. It can be formed by the method. In addition, the above-mentioned light-emitting layer, hole injection layer, hole transport layer, electron transport layer In addition to the materials mentioned above, the electron injection layer and electron transport layer may also contain inorganic compounds or polymer compounds (oligonucleotides). Mers, dendrimers, polymers, etc. may also be used.

[0141] Circuit board Furthermore, the light-emitting element 150 can be fabricated on a substrate made of glass, plastic, or the like. Regarding the order in which the components are fabricated on the substrate, whether you start stacking from the electrode 101 side or from the electrode 102 side... It can also be stacked.

[0142] The substrate on which the light-emitting element 150 can be formed can be, for example, glass, quartz, or plastic. Materials such as can be used. Flexible substrates may also be used. Flexible substrates are those that can be bent. A flexible substrate is a substrate that can be modified, such as polycarbonate or polyal. Examples include plastic substrates made of a specific material. Also, films, inorganic vapor-deposited films, etc. Other materials can also be used. Furthermore, in the manufacturing process of light-emitting elements and optical elements, the support material can be used. Other materials are also acceptable as long as they function as such. Alternatively, light-emitting elements and optical elements Any device that has the function of protecting the child will suffice.

[0143] For example, the light-emitting element 150 can be formed using various substrates. It is not limited to a specific type. One example of such a substrate is a semiconductor substrate (for example, a single crystal). Substrates (or silicon substrates), SOI substrates, glass substrates, quartz substrates, plastic substrates, metal Substrates, stainless steel substrates, substrates with stainless steel foil, tungsten Substrate, substrate having tungsten foil, flexible substrate, laminated film, fibrous Examples include paper or substrate films containing the material. An example of a glass substrate is barium phosphate. Examples include borosilicate glass, aluminoborsilicate glass, or soda-lime glass. Flexible Examples of substrates, laminated films, and base films include the following: For example, polyethylene terephthalate (PET), polyethylene naphthalate (PE N), polyethersulfone (PES), and polytetrafluoroethylene (PTFE) are used as substitutes. There are plastics that are represented. For example, there are resins such as acrylic. For example, polypropylene, polyester, polyvinyl fluoride, or polychlorinated Examples include vinyl. Alternatively, polyamide, polyimide, aramid, and epoxy. Examples include inorganic vapor-deposited films or paper products.

[0144] Alternatively, a flexible substrate may be used as the substrate, and light-emitting elements may be formed directly on the flexible substrate. Alternatively, a release layer may be provided between the substrate and the light-emitting element. The release layer is placed on top of the light-emitting element. After partially or completely completing the process, it is separated from the circuit board and used for transfer to another circuit board. This allows for the transfer of light-emitting elements to substrates with poor heat resistance or flexible substrates. The aforementioned delamination layer has, for example, a laminated structure of inorganic films consisting of a tungsten film and a silicon oxide film. Configurations such as those in which a resin film such as polyimide is formed on the substrate can be used.

[0145] In other words, a light-emitting element is formed using one substrate, and then the light-emitting element is transferred to another substrate. A light-emitting element may be placed on the substrate. An example of a substrate on which the light-emitting element is placed is the one described above. In addition to the substrates mentioned above, we also offer cellophane substrates, stone substrates, wood substrates, and fabric substrates (made from natural fibers such as silk, cotton, and hemp). ), synthetic fibers (nylon, polyurethane, polyester) or regenerated fibers (acetate) (including cupro, rayon, recycled polyester, etc.), leather substrate, or rubber substrate, etc. These substrates allow for the creation of light-emitting elements that are less prone to breakage and have high heat resistance. This allows for lighter or thinner light-emitting elements.

[0146] Furthermore, a field-effect transistor (FET), for example, is formed on the aforementioned substrate, and the FET and electricity A light-emitting element 150 may be fabricated on electrodes that are electrically connected. This allows the FET to This allows for the fabrication of an active-matrix type display device that controls the driving of the light-emitting element 150.

[0147] In this embodiment, one aspect of the present invention has been described. Or, other embodiments may be described. In this section, one aspect of the present invention will be described. However, this aspect of the present invention is not limited to these. It is not possible. For example, in one aspect of the present invention, the light emitted by the EL layer is delayed fluorescence due to TTA The proportion of is 10% or more, and the LUMO level of the material in the electron transport layer is Although an example was shown where the luminescent layer has a level lower than the LUMO level of the host material, the present invention One embodiment is not limited thereto. Depending on the circumstances, or depending on the situation, one embodiment of the present invention may be... For example, the luminescence exhibited by the EL layer is such that the proportion of delayed fluorescence components is 10% or more. Alternatively, the LUMO level of the material in the electron transport layer may be the LUMO level of the host material. It may be higher than the level of . Or, for example, in one aspect of the present invention, the electron transport layer has The LUMO level of the material is 0.05e higher than the LUMO level of the host material in the emissive layer. Although an example for cases lower than V has been shown, the present invention is not limited to this. Or, depending on the situation, in one aspect of the present invention, for example, the material L of the electron transport layer The UMO level is 0.05 eV or more lower than the LUMO level of the host material in the emissive layer. It doesn't have to be.

[0148] The configuration shown in this embodiment can be used in appropriate combination with other embodiments. ru.

[0149] (Embodiment 2) In this embodiment, the configuration example of a light-emitting element according to one aspect of the present invention described in Embodiment 1 is described below. This will be explained below using Figures 5 to 7.

[0150] <Example of light-emitting element configuration 1> An example of the configuration of a light-emitting element according to one aspect of the present invention will be described below with reference to Figure 5. Figure 5 This is a cross-sectional view showing a light-emitting element according to one embodiment of the present invention.

[0151] The light-emitting element 250 shown in Figure 5 is a bottom-emitting element that extracts light from the substrate 200 side. It is a light-emitting element of type n). However, one aspect of the present invention is not limited thereto, and the light-emitting element exhibits This is a top-emission type light-emitting device that extracts light in the opposite direction from the substrate 200. Bilateral radiation is extracted from both above and below the substrate 200 on which the element or light-emitting element is formed. It may also be a dual-emission type light-emitting element.

[0152] The light-emitting element 250 has electrodes 101 and 102 on the substrate 200. Between 01 and electrode 102, there is an emissive layer 123B, an emissive layer 123G, and an emissive layer 123R. It also has a hole injection layer 111, a hole transport layer 112, an electron transport layer 118, and an electron It has an injection layer 119.

[0153] If the light-emitting element is of the bottom emission type, the electrode 101 has the function of transmitting light. It is preferable that the electrode 102 has the function of reflecting light.

[0154] The light-emitting element 250 shown in Figure 5 has a region 221B sandwiched between electrodes 101 and 102, and A partition wall 140 is provided between region 221G and region 221R. The partition wall 140 is insulating. The partition wall 140 covers the end of the electrode 101 and has an opening that overlaps with the electrode. By providing the wall 140, the electrodes 101 on the substrate 200 in each region are arranged in island-like formations. It becomes possible to separate them.

[0155] The light-emitting layers 123B, 123G, and 123R each have the function of exhibiting different colors. It is preferable to have a light-emitting material. For example, the light-emitting layer 123B is blue, and the light-emitting layer 12 If the luminescent material has the function of exhibiting green light at 3G and red light at the luminescent layer 123R, then the light emission will be emitted. Element 250 can be used in a display device capable of full-color display. The film thickness of the light-emitting layer may be the same or different.

[0156] Furthermore, as shown in Embodiment 1, the LUMO level of the material used in the electron transport layer 118 This lowers the LUMO level of the host material in the light-emitting layer 123B to a lower level. Among the light emitted by the light-emitting layer 123B, the delayed fluorescence component accounts for a relatively large proportion of the light emission. It can produce offspring.

[0157] Note that one or more of the light-emitting layers 123B, 123G, and 123R may be used. The light-emitting layer may be configured with two or more layers stacked on top of each other.

[0158] <Example of light-emitting element configuration 2> Next, regarding a configuration example different from the light-emitting element shown in Figure 5, we will explain the following using Figures 6(A) and (B). To perform a clearing.

[0159] Figures 6(A) and 6(B) are cross-sectional views showing a light-emitting element according to one embodiment of the present invention. In (B), the same hatching pattern is used for areas that have the same function as the symbols shown in Figure 5. In some cases, the symbols may be omitted. Also, the same symbols are used for parts with similar functions. And, the detailed explanation may be omitted.

[0160] Figures 6(A) and 6(B) show that multiple light-emitting layers are stacked between a pair of electrodes via a charge-generating layer 115. This is an example of the configuration of a tandem type light-emitting element. The light-emitting element 252 shown in Figure 6(A) is on the substrate 20 A top-emission type light-emitting element that extracts light in the opposite direction to 0, Figure 6(B The light-emitting element 254 shown in the image is a bottom-emission element that extracts light towards the substrate 200. ) type light-emitting element. However, one aspect of the present invention is not limited thereto, and the light-emitting element exhibits Double-sided emission (Duo) emission captures light from both above and below the substrate 200 on which the light-emitting element is formed. It may also be an alpha emission type.

[0161] The light-emitting element 252 and the light-emitting element 254 have an electrode 101 and an electrode 102 on the substrate 200, and It has pole 103 and electrode 104. Also, between electrode 101 and electrode 102, and electrode 1 Between 02 and electrode 103, and between electrode 102 and electrode 104, there is a light-emitting layer 160 and charge It has a generation layer 115 and a light-emitting layer 170. It also has a hole injection layer 111 and a hole transport layer 1 12, electron transport layer 113, electron injection layer 114, hole injection layer 116, hole transport layer 1 It has 17, an electron transport layer 118, and an electron injection layer 119.

[0162] Furthermore, the electrode 101 comprises a conductive layer 101a and a conductive layer 101b in contact with the conductive layer 101a. It has a conductive layer 103a and a conductive layer 1 in contact with the conductive layer 103a. 03b and , the electrode 104 has a conductive layer 104a and a conductive layer in contact with the conductive layer 104a It has layer 104b and

[0163] The light-emitting element 252 shown in Figure 6(A) and the light-emitting element 254 shown in Figure 6(B) are connected to electrode 101 Region 222B sandwiched between electrode 102 and electrode 103, region sandwiched between electrode 102 and electrode 103 Between 222G and the region 222R sandwiched between electrodes 102 and 104, there is a partition wall 14 It has 0. The partition wall 140 is insulating. The partition wall 140 has electrodes 101, 103, and has an opening that covers the end of the electrode 104 and overlaps with the electrode. A partition wall 140 is provided. This makes it possible to separate the electrodes on the substrate 200 in each region into island-like structures. ru.

[0164] Furthermore, the light-emitting element 252 and the light-emitting element 254 are located in region 222B, region 222G, and region 2 Optical element 224B and optical element 22 are positioned in the direction from which the light emitted from 22R is extracted. The substrate 220 has 4G and optical elements 224R. The light emitted from each region is It is emitted to the outside of the light-emitting element via the optical element. That is, the light emitted from region 222B The light emitted from region 222G, which is emitted through optical element 224B, is directed towards optical element 224 The light emitted via G and emanating from region 222R is emitted via optical element 224R. It can be done.

[0165] Furthermore, optical elements 224B, 224G, and 224R are connected to the incident light. It has the function of selectively transmitting light exhibiting a specific color. For example, via the optical element 224B The light emitted from region 222B is blue light, and optical element 224 The light emitted from region 222G, which is transmitted via G, becomes green light, and the optical element The light emitted from region 222R via 224R is red in color.

[0166] In Figures 6(A) and 6(B), the light emitted from each region through each optical element is referred to as blue. Light exhibiting (B), light exhibiting green (G), and light exhibiting red (R) are used to break down This is schematically illustrated with lines and arrows.

[0167] Furthermore, a light-shielding layer 223 is provided between each optical element. The light-shielding layer 223 is provided from adjacent regions It has the function of blocking emitted light. Alternatively, the light-blocking layer 223 may be omitted. .

[0168] <<Microcavity>> Furthermore, the light-emitting elements 252 and 254 have a microcavity structure.

[0169] The light emitted from the light-emitting layer 160 and the light-emitting layer 170 is directed towards a pair of electrodes (for example, electrode 101 and Resonance occurs between electrodes 102). In light-emitting elements 252 and 254, each region The thickness of the conductive layers (conductive layer 101b, conductive layer 103b, and conductive layer 104b) can be adjusted. This makes it possible to enhance the wavelength of light emitted from the light-emitting layer 160 and the light-emitting layer 170. In each region, at least one of the hole injection layer 111 and the hole transport layer 112 has a different thickness. By doing so, the wavelength of light emitted from the light-emitting layer 160 and the light-emitting layer 170 may be strengthened.

[0170] For example, in electrodes 101 to 104, the refractive index of a conductive material having the function of reflecting light If the refractive index is smaller than the refractive index of the light-emitting layer 160 or the light-emitting layer 170, then electrode 1 The thickness of the conductive layer 101b on 01 is determined by the optical distance between electrode 101 and electrode 102 being m B λ B / 2(m B λ is a natural number, B(These represent the wavelengths of light that are strengthened in region 222B.) Adjust so that it is the same as the thickness of the conductive layer 103b of electrode 103. The optical distance between pole 102 is m G λ G / 2(m G λ is a natural number, G It is strengthened in region 222G. The wavelengths of light are adjusted to be as shown. Furthermore, the conductive layer 1 of the electrode 104 The film thickness of 04b is such that the optical distance between electrode 104 and electrode 102 is m R λ R / 2(m R is natural number, λ R The wavelengths of light that are strengthened in region 222R are adjusted accordingly.

[0171] As described above, a microcavity structure is provided to adjust the optical distance between pairs of electrodes in each region. This suppresses light scattering and absorption near each electrode, resulting in high light extraction efficiency. This can be achieved. In the above configuration, conductive layer 101b, conductive layer 103b Preferably, the conductive layer 104b has the function of transmitting light. Also, conductive layer 101b The materials constituting conductive layer 103b and conductive layer 104b may be the same as each other. They may be different. Also, conductive layer 101b, conductive layer 103b, conductive layer 104b are Each layer may have a configuration consisting of two or more layers stacked on top of each other.

[0172] Note that the light-emitting element 252 shown in Figure 6(A) is a top-export type light-emitting element, therefore the electrode 10 The conductive layer 101a of 1, the conductive layer 103a of electrode 103, and the conductive layer 104 of electrode 104 The conductive layer 104a preferably has the function of reflecting light. Also, the electrode 102 is It is preferable that the material has both the function of transmitting light and the function of reflecting light.

[0173] Furthermore, since the light-emitting element 254 shown in Figure 6(B) is a bottom-extrusion type light-emitting element, the electrode 10 The conductive layer 101a of 1, the conductive layer 103a of electrode 103, and the conductive layer of electrode 104 Preferably, the electrolytic layer 104a has both the function of transmitting light and the function of reflecting light. Furthermore, it is preferable that the electrode 102 has the function of reflecting light.

[0174] Furthermore, in the light-emitting element 252 and the light-emitting element 254, conductive layer 101a, conductive layer 103a, Alternatively, the same material may be used for the conductive layer 104a, or a different material may be used. When the same material is used for layer 101a, conductive layer 103a, and conductive layer 104a, the light-emitting element 25 The manufacturing costs of 2 and the light-emitting element 254 can be reduced. Note that conductive layer 101a, conductive layer 103 a. The conductive layer 104a may have a configuration in which two or more layers are stacked.

[0175] Furthermore, as shown in Embodiment 1, the LUMO level of the material used in the electron transport layer 113 The electron transport layer is made lower than the LUMO level of the host material in the light-emitting layer 170. The LUMO level of the material used in 118 is the LUMO level of the host material having the LUMO level of the luminescent layer 160 Lower the position below. By doing so, the proportion of the delayed fluorescence component in the emission exhibited by the light-emitting layer It is possible to fabricate light-emitting elements with a relatively large proportion of light emission.

[0176] Furthermore, the light-emitting layer 160 and the light-emitting layer 170 are, for example, light-emitting layer 170a and light-emitting layer 170b Each can be configured with two layers stacked together. The two light-emitting layers are combined with the first compound Two types of light-emitting materials, a substance and a second compound, each having the function of exhibiting different colors. By using this method, multiple light sources can be obtained simultaneously. In particular, the light-emitting layer 160 and the light-emitting layer 17 It is preferable to select the light-emitting material used in each light-emitting layer so that the light emitted by 0 and results in a white color. It seems so.

[0177] Furthermore, the light-emitting layer 160 or light-emitting layer 170 may also be configured with three or more layers stacked together. It is also acceptable for the material to include layers that do not contain luminescent material.

[0178] The configuration shown in this embodiment may be used in appropriate combination with the configurations shown in other embodiments. It is possible.

[0179] (Embodiment 3) In this embodiment, a configuration different from the configurations shown in Embodiments 1 and 2 is generated. The optical element and the light-emitting mechanism of the said light-emitting element will be explained below with reference to Figures 7 and 8. .

[0180] <Example of light-emitting element configuration 1> Figure 7(A) is a schematic cross-sectional view of the light-emitting element 450.

[0181] The light-emitting element 450 shown in Figure 7(A) has a pair of electrodes (electrode 401 and electrode 402) between them. Multiple light-emitting units (in Figure 7(A), light-emitting unit 441 and light-emitting unit 44 2) It has a configuration similar to the EL layer 100 shown in Figure 1(A). In other words, the light-emitting element 150 shown in Figure 1(A) has one light-emitting unit and emits light. The element 450 has multiple light-emitting units. In the light-emitting element 450, the electrode 40 Assuming that electrode 1 functions as the anode and electrode 402 functions as the cathode, the following explanation will be given, but light emission The configuration of element 450 can be reversed.

[0182] Furthermore, in the light-emitting element 450 shown in Figure 7(A), the light-emitting unit 441 and the light-emitting unit 4 42 is stacked, and charge generation occurs between light-emitting unit 441 and light-emitting unit 442. A layer 445 is provided. Note that the light-emitting unit 441 and the light-emitting unit 442 have the same configuration. The configuration may also be different. For example, the light-emitting unit 441 may have the EL layer 100 shown in Figure 1(A) It is preferable to use this.

[0183] In other words, the light-emitting element 450 has a light-emitting layer 420 and a light-emitting layer 430. In addition to the light-emitting layer 420, unit 441 includes a hole injection layer 411, a hole transport layer 412, and an electron transport layer. It has a transmission layer 413 and an electron injection layer 414. The light-emitting unit 442 has a light-emitting layer 43 In addition to 0, there are hole injection layer 416, hole transport layer 417, electron transport layer 418, and electron injection layer 4 It has 19.

[0184] The charge generation layer 445 contains a composite material of an organic compound and an acceptor substance. The composite material used is one that can be used in the hole injection layer 111 shown in Embodiment 1. It is sufficient if they are present. As for organic compounds, aromatic amine compounds, carbazole compounds, aromatic carbon Various compounds such as hydrogenated compounds and polymer compounds (oligomers, dendrimers, polymers, etc.) It can be used. Note that the organic compound must have a hole mobility of 1 × 10⁻⁶. -6 cm 2 / V It is preferable to use one that is s or greater. However, a material that has higher hole transport than electron transport. Other materials may be used if quality is important. A composite of organic compounds and acceptor substances. The material exhibits excellent carrier injection and carrier transport properties, enabling low-voltage and low-current operation. This can be achieved. Note that, as with the light-emitting unit 442, the anode side of the light-emitting unit If it is in contact with the charge generation layer 445, the charge generation layer 445 is the hole injection layer of the light-emitting unit. Alternatively, it can also serve as a hole transport layer, so the light-emitting unit may have a hole injection layer or A hole transport layer is not required.

[0185] Furthermore, the charge generation layer 445 includes a layer containing a composite material of an organic compound and an acceptor substance, and other It may be formed as a laminated structure by combining layers composed of different materials. For example, organic A layer containing a composite material of a compound and an acceptor substance, and one selected from among electron-donating substances A layer containing a compound and a compound with high electron transport properties may be formed by combining them. A layer containing a composite material of an organic compound and an acceptor substance is combined with a layer containing a transparent conductive film. They may be formed in this way.

[0186] The charge generation layer 445, sandwiched between the light-emitting unit 441 and the light-emitting unit 442, is an electrode. When a voltage is applied to electrode 401 and electrode 402, electrons are injected into one light-emitting unit, and the other Any method that injects holes into the light-emitting unit is acceptable. For example, in Figure 7(A), When a voltage is applied such that the potential of electrode 401 is higher than the potential of electrode 402, the charge The generation layer 445 injects electrons into the light-emitting unit 441 and holes into the light-emitting unit 442. do.

[0187] Furthermore, Figure 7(A) describes a light-emitting element having two light-emitting units. The same can be applied to light-emitting elements that stack three or more light-emitting units. Yes. As shown in the light-emitting element 450, multiple light-emitting units are placed between a pair of electrodes in a charge generation layer. By arranging them in partitions, high-brightness light emission is possible while maintaining a low current density, and furthermore, This enables the creation of light-emitting elements with a long lifespan. Furthermore, it enables the creation of light-emitting elements with low power consumption.

[0188] Furthermore, the light-emitting layer 420 has a host material 421 and a guest material 422. Layer 430 has a host material 431 and a guest material 432. Also, the host material 43 Compound 1 comprises organic compound 431_1 and organic compound 431_2.

[0189] Furthermore, in this embodiment, the light-emitting layer 420 is similar to the light-emitting layer 130 shown in Figure 1(A). The structure consists of a host material 421 and a guest material 422 in the light-emitting layer 420. These correspond to the host material 131 and guest material 132 of the light-emitting layer 130, respectively. Furthermore, the guest material 432 of the light-emitting layer 430 is described below as a phosphorescent material. Oh, electrode 401, electrode 402, hole injection layer 411, hole injection layer 416, hole transport layer 412 , hole transport layer 417, electron transport layer 413, electron transport layer 418, electron injection layer 414, and The sub-injection layer 419 consists of the electrode 101, electrode 102, hole injection layer 111, as shown in Embodiment 1. These correspond to the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119, respectively. Therefore, a detailed explanation of this embodiment will be omitted.

[0190] Furthermore, as shown in Embodiment 1, the LUMO level of the material used in the electron transport layer 413 The electron transport layer is made lower than the LUMO level of the host material in the light-emitting layer 420. The LUMO level of the material used in 418 is the LUMO level of the host material having the LUMO level of the luminescent layer 430 Lower the position below. By doing so, the proportion of the delayed fluorescence component in the emission exhibited by the light-emitting layer It is possible to fabricate light-emitting elements with a relatively large proportion of light emission.

[0191] ≪Light-emitting mechanism of light-emitting layer 420≫ The light-emitting mechanism of the light-emitting layer 420 is the same as that of the light-emitting layer 130 shown in Figure 1(A). ru.

[0192] ≪Light-emitting mechanism of light-emitting layer 430≫ Next, the light-emitting mechanism of the light-emitting layer 430 will be explained below.

[0193] The organic compound 431_1 and organic compound 431_2 in the light-emitting layer 430 form an excited complex. Formation is carried out. Here, organic compound 431_1 is used as the host material, and organic compound 431_2 This will be explained using the following as supporting material.

[0194] In the light-emitting layer 430, organic compound 431_1 and organic compound 431_ form an excitation complex. The combination with 2 can be any combination that can form an excited complex, but on the other hand It is preferable that one material has hole transport properties and the other has electron transport properties. It seems so.

[0195] Organic compound 431_1, organic compound 431_2, and guest material 4 in the light-emitting layer 430 The correlation of energy levels with 32 is shown in Figure 7(B). Note that the notation in Figure 7(B) and The symbols are as follows: ·Host(431_1): Organic compound 431_1 (host material) · Assist(431_2): Organic compound 431_2 (assist material) • Guest (432): Guest material 432 (phosphorescent material) • Exciplex: Excited complex ·S PH : The lowest level of the singlet excited state of organic compound 431_1 ·TPH : The lowest level of the triplet excited state of organic compound 431_1 ·T PG : The lowest level of the triplet excited state of guest material 432 (phosphorescent material) ·S E : The lowest level of the singlet excited state of the excited complex ·T E : The lowest level of the triplet excited state of the excited complex

[0196] Singlet excitation of an excited complex formed by organic compound 431_1 and organic compound 431_2 The lowest energy level of the initial state (S E ) and the lowest level of the triplet excited state of the excited complex (T E ) They will be adjacent to each other (see Figure 7(B) Route C).

[0197] And the excited complex (S E ) and (T E The energy of both ) is used by guest material 432 (phosphorescent By shifting to the lowest level of the triplet excited state of the material, luminescence can be obtained (Figure 7(B)Rou (see te D).

[0198] Furthermore, the processes of Route C and Route D described above are referred to as Ex in this specification, etc. This is called TET (Exciplex-Triplet Energy Transfer). It may happen.

[0199] Furthermore, organic compound 431_1 and organic compound 431_2 have holes in one and electrons in the other. They receive and, by being in close proximity, rapidly form an excited complex. Alternatively, one of them is excited When it enters the initial state, it quickly interacts with the other to form an excited complex. Therefore, Most of the excitons in the light-emitting layer 430 exist as excited complexes. Excited complexes are organically formed. The band gap is smaller than that of both compound 431_1 and organic compound 431_2. Therefore, the driving voltage is increased by the formation of an excited complex from the recombination of one hole and the other electron. It can be lowered.

[0200] By configuring the light-emitting layer 430 as described above, the guest material 432 (phosphorescent material) of the light-emitting layer 430 This makes it possible to efficiently obtain light emission from the source.

[0201] Furthermore, the emission from the light-emitting layer 420 has a shorter wavelength peak than the emission from the light-emitting layer 430. It is preferable to have a configuration that includes a cubic element. A light-emitting element using a phosphorescent material that exhibits short-wavelength emission. This tends to degrade in brightness quickly. Therefore, by using short-wavelength emission as fluorescence emission, the brightness can be reduced. This makes it possible to provide light-emitting elements with low degradation.

[0202] Furthermore, by obtaining light of different emission wavelengths from the light-emitting layer 420 and the light-emitting layer 430, multicolor emission is achieved. It can be used as an optical element. In this case, the emission spectrum will have different emission peaks. Since the light is synthesized, the resulting emission spectrum has at least two maximum values.

[0203] Furthermore, the above configuration is also suitable for obtaining white light emission. The light-emitting layer 420 and the light-emitting layer 430 By making the light sources complementary to each other, white light emission can be obtained.

[0204] Furthermore, one or both of the light-emitting layers 420 and 430 may have multiple emission wavelengths. By using light-emitting materials, it is possible to produce white light with high color rendering, consisting of the three primary colors or four or more light-emitting colors. It is also possible to obtain colored light emission. In this case, either the light-emitting layer 420 or the light-emitting layer 430 Alternatively, both are further divided into layers, and each divided layer contains a different light-emitting material. That's fine.

[0205] <Examples of materials that can be used for the light-emitting layer> Next, the materials that can be used for the light-emitting layer 420 and the light-emitting layer 430 will be described below. .

[0206] <<Materials that can be used for the light-emitting layer 420>> The material that can be used for the light-emitting layer 420 is the light-emitting layer 130 shown in Embodiment 1 above. You can use materials that can be used for that purpose.

[0207] <<Materials that can be used for the light-emitting layer 430>> In the light-emitting layer 430, organic compound 431_1 (host material) is present in the largest amount by weight. The guest material 432 (phosphorescent material) is dispersed in the organic compound 431_1 (host material). .

[0208] Organic compound 431_1 (host material) includes zinc and aluminum-based metal complexes, as well as Xadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline Derivatives, dibenzoquinoxaline derivatives, dibenzothiophene derivatives, dibenzofuran derivatives Body, pyrimidine derivatives, triazine derivatives, pyridine derivatives, bipyridine derivatives, phena Examples include anttroline derivatives. Other examples include aromatic amines and carbazole derivatives. Examples include the body, etc.

[0209] Guest material 432 (phosphorescent material) includes iridium, rhodium, or platinum-based organic gold. Examples include genus complexes or metal complexes, among which are organoiridium complexes, such as iridium-based complexes. Orthometallic complexes are preferred. 4H-triazole ligands are preferred as ligands for orthometallation. Ligand, 1H-triazole ligand, imidazole ligand, pyridine ligand, pyrimidine ligand Examples include ligands, pyrazine ligands, or isoquinoline ligands. As metal complexes... Examples include platinum complexes having porphyrin ligands.

[0210] As organic compound 431_2 (assist material), an excited complex is formed with organic compound 431_1. This combination is considered to be possible. In this case, the emission peak of the excited complex is guest material 432 (phosphorescent). Triplet MLCT (Metal to Ligand Charge Trans The organic compound is designed to overlap with the absorption band of the fer) transition, more specifically, with the absorption band on the longest wavelength side. Select material 431_1, organic compound 431_2, and guest material 432 (phosphorescent material). This is preferable. This makes it possible to create a light-emitting element with dramatically improved luminous efficiency. However, when using thermally activated delayed fluorescence materials instead of phosphorescent materials, the longest wavelength The absorption band on the side is preferably a singlet absorption band.

[0211] The light-emitting material included in the light-emitting layer 430 is a material that can convert triplet excitation energy into light emission. Any material will do. A material that can convert the triplet excitation energy into light emission is a phosphorescent material. In addition, there is thermally activated delayed fluorescence. Examples include fluorescence (TADF) materials. Therefore, they are described as phosphorescent materials. The part indicated can be interpreted as a thermally activated delayed fluorescence material. Fluorescent materials are those that can be excited from a triplet excited state to a singlet excited state with only a small amount of thermal energy. It allows for reverse intersystem crossing and efficiently exhibits luminescence (fluorescence) from the singlet excited state. It refers to the material that does this. Also, the conditions under which thermally activated delayed fluorescence can be efficiently obtained are triple The energy difference between the singlet excitation energy level and the singlet excitation energy level is preferably 0 eV. It is more preferably greater than 0.2 eV and less than or equal to 0.1 eV. These are some examples.

[0212] Furthermore, materials exhibiting thermally activated delayed fluorescence can undergo reverse intersystem crossing from a triplet excited state on their own. It may be a material that can generate excited states, or an excited complex (excyplex, or It may also be a combination of two materials that form an exciplex.

[0213] Furthermore, the emission color of the light-emitting material contained in the light-emitting layer 420 and the light-emitting material contained in the light-emitting layer 430 is limited There is no fixed rule; they can be the same or different. The light emitted from each is mixed and taken out of the element. Therefore, if the light-emitting colors of both are complementary colors, the light-emitting element will emit white light. It can emit light. Considering the reliability of the light-emitting element, the light-emitting layer 420 contains light The emission peak wavelength of the material is preferably shorter than that of the light-emitting material contained in the emission layer 430. It's nice.

[0214] <Example of light-emitting element configuration 2> Next, regarding a configuration example different from the light-emitting element shown in Figure 7, we will explain the following using Figures 8(A) and (B). To perform a clearing.

[0215] Figure 8(A) is a schematic cross-sectional view of the light-emitting element 452.

[0216] The light-emitting element 452 shown in Figure 8(A) has an E between a pair of electrodes (electrode 401 and electrode 402). The structure has an L layer 400 sandwiched in between. In the light-emitting element 452, the electrode 401 is the anode and It functions in this way, with electrode 402 acting as the cathode.

[0217] Furthermore, the EL layer 400 has a light-emitting layer 420 and a light-emitting layer 430. Also, the light-emitting element 4 In 52, the EL layer 400 includes, in addition to the light-emitting layer 420 and the light-emitting layer 430, a hole injection layer 4 11. The hole transport layer 412, electron transport layer 418, and electron injection layer 419 are shown in the diagram. These stacked structures are just examples, and the configuration of the EL layer 400 in the light-emitting element 452 is one example of these. It is not limited to this. For example, the stacking order of the above layers may be changed in the EL layer 400. Alternatively, functional layers other than those described above may be provided in the EL layer 400. These functional layers may include For example, the function of injecting carriers (electrons or holes), the function of transporting carriers, The system should have a configuration that includes functions to suppress carriers and functions to generate carriers.

[0218] Furthermore, the light-emitting layer 420 has a host material 421 and a guest material 422. Layer 430 has a host material 431 and a guest material 432. The host material 431 is It has organic compound 431_1 and organic compound 431_2. Note that guest material 422 is The fluorescent material, guest material 432, is described below as a phosphorescent material.

[0219] ≪Light-emitting mechanism of light-emitting layer 420≫ The light-emitting mechanism of the light-emitting layer 420 is the same as that of the light-emitting layer 130 shown in Figure 1(A). ru.

[0220] ≪Light-emitting mechanism of light-emitting layer 430≫ The light-emitting mechanism of the light-emitting layer 430 is the same as that of the light-emitting layer 430 shown in Figure 7(A). ru.

[0221] <<Light-emitting mechanism of light-emitting layer 420 and light-emitting layer 430>> The light-emitting mechanisms of the light-emitting layer 420 and the light-emitting layer 430 have already been explained, but the light-emitting element As shown in sub-image 452, the light-emitting layer 420 and the light-emitting layer 430 are in contact with each other. In addition, at the interface between the light-emitting layer 420 and the light-emitting layer 430, the excited complex releases host material from the light-emitting layer 420. Assuming that energy transfer to material 421 (especially energy transfer of the triplet excitation level) has occurred However, the triplet excitation energy can be converted into light emission in the light-emitting layer 420.

[0222] Furthermore, the T1 level of the host material 421 of the light-emitting layer 420 is the organic compound present in the light-emitting layer 430. It is preferable that the T1 level is lower than that of 431_1 and organic compound 431_2. Also, the light-emitting layer 4 In 20, the S1 level of the host material 421 is equal to the S1 level of the guest material 422 (fluorescent material). It is higher than the T1 level of the host material 421, and the T1 level of the guest material 422 (fluorescent material) is higher than the T1 level of the guest material 422 (fluorescent material). A level lower than the current level is preferable.

[0223] Specifically, when TTA is used for the light-emitting layer 420 and ExTET is used for the light-emitting layer 430, The correlation of energy levels is shown in Figure 8(B). Note that the notation and symbols in Figure 8(B) are as follows: It is as follows: • Fluorescence EML (420): Fluorescent Emission Layer (Emission Layer 420) • Phosphorescence EML (430): Phosphorescent layer (Emitting layer 430) ·S FH : The lowest level of the singlet excited state of host material 421 ·T FH : The lowest level of the triplet excited state of host material 421 ·S FG : The lowest level of the singlet excited state of guest material 422 (fluorescent material) ·T FG : The lowest level of the triplet excited state of guest material 422 (fluorescent material) ·S PH : The lowest level of the singlet excited state of the host material (organic compound 431_1) ·T PH : The lowest level of the triplet excited state of the host material (organic compound 431_1) ·T PG : The lowest level of the triplet excited state of guest material 432 (phosphorescent material) ·S E : The lowest level of the singlet excited state of the excited complex ·T E : The lowest level of the triplet excited state of the excited complex

[0224] As shown in Figure 8(B), since the excited complex exists only in the excited state, the excited complex and the excited complex Exciton diffusion between the body and the excited state is unlikely to occur. Also, the excited level of the excited complex (S E , T E ) is luminescent Excited level (S) of organic compound 431_1 in layer 430 (i.e., host material of phosphorescent material) P H , T PH Since it is lower than ), energy diffusion from the excited complex to organic compound 431_1. Neither occurs. Similarly, energy diffusion from the excited complex to organic compound 431_2 also occurs. No. In other words, within the phosphorescent layer (luminescent layer 430), the exciton diffusion distance of the excited complex is Because it is short, it is possible to maintain the efficiency of the phosphorescent layer (emissive layer 430). At the interface between the layer (light-emitting layer 420) and the phosphorescent light-emitting layer (light-emitting layer 430), the phosphorescent light-emitting layer (light-emitting layer A portion of the triplet excitation energy of the excited complex (430) is transmitted to the fluorescence emission layer (emission layer 420). Even if it disperses, the triplet excitation energy of the fluorescent emission layer (emission layer 420) generated by that diffusion Since energy is emitted through TTA, energy loss can be reduced. .

[0225] As described above, the light-emitting element 452 utilizes ExTET in the light-emitting layer 430, and the light-emitting layer 42 By using TTA in 0, energy loss is reduced, resulting in a light-emitting element with high luminescence efficiency. It can be made into a child. Also, as shown in the light-emitting element 452, the light-emitting layer 420 and the light-emitting layer 4 When the 30 is in contact with each other, the above energy loss is reduced, and EL The number of layers can be reduced to 400. Therefore, a light-emitting element with lower manufacturing costs can be produced. It is possible.

[0226] Furthermore, the light-emitting layer 420 and the light-emitting layer 430 may not be in contact with each other. In combination, organic compound 431_1, organic compound 431_2, or are generated in the light-emitting layer 430. From the excited state of guest material 432 (phosphorescent material), the host material 421 in the light-emitting layer 420, This involves energy transfer to guest material 422 (fluorescent material) via the Dexter mechanism (especially the triplet energy transfer). Energy transfer can be prevented. Therefore, between the light-emitting layer 420 and the light-emitting layer 430 The layer to be added only needs to be a few nanometers thick.

[0227] The layer provided between the light-emitting layer 420 and the light-emitting layer 430 may be made of a single material, but It may contain pore transport materials and electron transport materials. When composed of a single material, Bipolar materials may be used. Here, a bipolar material refers to a material with high electron-hole mobility. This refers to materials where the ratio is 100 or less. It also includes hole-transporting materials or electron-transporting materials, etc. It may be used. Or, at least one of them may be the host material of the light-emitting layer 430. It may also be formed from the same material as organic compound 431_1 or organic compound 431_2). This makes it easier to fabricate light-emitting elements and reduces the driving voltage. Furthermore, hole injection An excitation complex may be formed between the electron-transporting material and the electron-transporting material, thereby enabling the diffusion of excitons. This can be effectively prevented. Specifically, the host material of the light-emitting layer 430 (organic compound 431 _1 or the excited state of organic compound 431_2) or guest material 432 (phosphorescent material) Then, the energy of the light-emitting layer 420 to the host material 421 or guest material 422 (fluorescent material) This can prevent the movement of ghee.

[0228] In addition, in the light-emitting element 452, the carrier recombination region is formed with a certain degree of distribution. This is preferable. For this reason, in the light-emitting layer 420 or light-emitting layer 430, an appropriate amount of carriers is provided. It is preferable that the guest material 432 (phosphorescent) of the light-emitting layer 430 is trapping, and in particular the guest material 432 (phosphorescent) It is preferable that the material has electron trapping properties. Also, the luminescent layer 420 has It is preferable that the material 422 (fluorescent material) has hole-trapping properties.

[0229] Furthermore, the emission from the light-emitting layer 420 has a shorter wavelength peak than the emission from the light-emitting layer 430. It is preferable to have a configuration that includes a cubic element. A light-emitting element using a phosphorescent material that exhibits short-wavelength emission. This tends to degrade in brightness quickly. Therefore, by using short-wavelength emission as fluorescence emission, the brightness can be reduced. This makes it possible to provide light-emitting elements with low degradation.

[0230] Furthermore, by obtaining light of different emission wavelengths from the light-emitting layer 420 and the light-emitting layer 430, multicolor emission is achieved. It can be used as an optical element. In this case, the emission spectrum will have different emission peaks. Since the light is synthesized, the resulting emission spectrum has at least two maximum values.

[0231] Furthermore, the above configuration is also suitable for obtaining white light emission. The light-emitting layer 420 and the light-emitting layer 430 By making the light sources complementary to each other, white light emission can be obtained.

[0232] Furthermore, by using multiple light-emitting materials with different emission wavelengths in the light-emitting layer 420, the three primary colors and It is also possible to obtain highly color-rendering white light emission consisting of four or more emission colors. In this case, the emission The layer 420 is further divided into layers, and each divided layer contains a different light-emitting material. That's fine.

[0233] <Materials that can be used for the light-emitting layer> Next, the materials that can be used for the light-emitting layer 420 and the light-emitting layer 430 will be described below. .

[0234] <<Materials that can be used for the light-emitting layer 420>> In the light-emitting layer 420, the host material 421 is present in the largest amount by weight, and the guest material 422 ( The fluorescent material is dispersed in the host material 421. The S1 level of the host material 421 is gestic. The S1 level of host material 422 (fluorescent material) is higher than that of host material 421, and the T1 level of host material 421 is higher than that of host material 422. It is preferable that the T1 level is lower than that of material 422 (fluorescent material).

[0235] <<Materials that can be used for the light-emitting layer 430>> In the light-emitting layer 430, the host material (organic compound 431_1 or organic compound 431_2) It is the most abundant by weight, and guest material 432 (phosphorescent material) is the host material (organic compound Dispersed in 431_1 and organic compound 431_2). Host material of luminescent layer 430 ( The T1 levels of the organic compound 431_1 and organic compound 431_2 are guest materials of the luminescent layer 420. It is preferable that the T1 level is higher than that of material 422 (fluorescent material).

[0236] Host material (organic compound 431_1 and organic compound 431_2), guest material 432 ( As for phosphorescent materials, the organic compound 431_1 explained in Figure 7 above as the light-emitting element 450, organic Compound 431_2 and guest material 432 can be used.

[0237] The light-emitting layers 420 and 430 are produced by vapor deposition (including vacuum deposition) and inkjet printing. It can be formed by methods such as coating, gravure printing, etc.

[0238] The configuration shown in this embodiment may be used in appropriate combination with the configurations shown in other embodiments. It is possible.

[0239] (Embodiment 4) In this embodiment, a display device having an light-emitting element according to one aspect of the present invention is described using Figure 9. Give an explanation.

[0240] Figure 9(A) is a block diagram illustrating a display device according to one embodiment of the present invention, and Figure 9(B) is a block diagram illustrating a display device according to one embodiment of the present invention. ) is a circuit diagram illustrating the pixel circuit of a display device according to one aspect of the present invention.

[0241] <Explanation regarding display devices> The display device shown in Figure 9(A) has a region having pixels of the display element (hereinafter referred to as the pixel portion 802). ) and a circuit section (hereinafter) located outside the pixel section 802 and having a circuit for driving the pixels The drive circuit section 804 and the circuit that has a function to protect the element (hereinafter referred to as the protection circuit 806) It has a terminal section 807 and a protection circuit 806. good.

[0242] A portion or all of the drive circuit section 804 is formed on the same substrate as the pixel section 802. This is desirable. This makes it possible to reduce the number of parts and terminals. Drive circuit section 804 If part or all of the pixel section 802 is not formed on the same substrate, the drive circuit Part or all of section 804 is COG or TAB (Tape Automated Bo It can be implemented by (nding).

[0243] The pixel units 802 are arranged in X rows (where X is a natural number greater than or equal to 2) and Y columns (where Y is a natural number greater than or equal to 2). It has a circuit for driving multiple display elements (hereinafter referred to as the pixel circuit 801), and the drive circuit Section 804 is a circuit that outputs a signal (scan signal) for selecting pixels (hereinafter referred to as the scan line drive circuit 804). 04a) is for supplying signals (data signals) to drive the display elements of a pixel. It has a drive circuit such as a circuit (hereinafter referred to as the signal line drive circuit 804b).

[0244] The scan line driving circuit 804a has a shift register and the like. The scan line driving circuit 804a is terminal The sub-unit 807 receives a signal to drive the shift register and outputs a signal. For example, the scan line drive circuit 804a receives a start pulse signal, a clock signal, etc. , outputs a pulse signal. The scan line drive circuit 804a is connected to the wiring to which the scan signal is supplied (hereinafter It has the function of controlling the potential of the scan lines (referred to as GL_1 to GL_X). Multiple drive circuits 804a are provided, and multiple scan line drive circuits 804a drive scan lines GL_1 to GL_X may be divided and controlled. Alternatively, the scan line drive circuit 804a may control the initialization signal It has the function of supplying, however, it is not limited to the scan line drive circuit 804 'a' can also supply another signal.

[0245] The signal line drive circuit 804b has a shift register, etc. The signal line drive circuit 804b is terminal Through sub-unit 807, in addition to signals for driving the shift register, the source of data signals A signal (image signal) is input. The signal line drive circuit 804b uses the image signal to drive the pixel circuit 8 It has the function of generating a data signal to write to 01. Furthermore, the signal line drive circuit 804b, The data signal is generated according to the pulse signal obtained by inputting a start pulse, clock signal, etc. It has a function to control the output. In addition, the signal line drive circuit 804b is provided with a data signal. It has the function of controlling the potential of the wiring (hereinafter referred to as data lines DL_1 to DL_Y). Alternatively, the signal line drive circuit 804b may have the function of supplying an initialization signal. However, the signal line drive circuit 804b is not limited to this and may also supply other signals. It is Noh.

[0246] The signal line drive circuit 804b is configured using, for example, multiple analog switches. The line drive circuit 804b sequentially turns on multiple analog switches, thereby controlling the image. The image signal can be time-division multiplexed and output as a data signal. Furthermore, a shift register can be used. The signal line drive circuit 804b may be configured in this way.

[0247] Each of the multiple pixel circuits 801 is supplied with a scan signal via one of the multiple scan lines GL. A pulse signal is input, and a data signal is given via one of several data lines DL. A data signal is input. In addition, each of the multiple pixel circuits 801 is controlled by a scan line drive circuit 8 04a controls the writing and retention of data in the data signal. For example, row m, column n The pixel circuit 801 is connected to the scan line drive circuit 8 via the scan line GL_m (where m is a natural number less than or equal to X). A pulse signal is input from 04a, and the data line DL_n(n) is controlled according to the potential of the scan line GL_m. A data signal is input from the signal line drive circuit 804b via (where Y is a natural number less than or equal to Y).

[0248] The protection circuit 806 shown in Figure 9(A) is, for example, a combination of the scan line drive circuit 804a and the pixel circuit 801 It is connected to the scan line GL, which is the wiring between them. Alternatively, the protection circuit 806 is connected to the signal line drive circuit It is connected to the data line DL, which is the wiring between 804b and the pixel circuit 801. Alternatively, it is connected to the protection circuit. The path 806 can be connected to the wiring between the scan line drive circuit 804a and the terminal section 807. Alternatively, the protection circuit 806 is connected to the wiring between the signal line drive circuit 804b and the terminal section 807. It can be connected. The terminal 807 is used to supply power and control to the display device from an external circuit. This refers to the part equipped with terminals for inputting signals and image signals.

[0249] The protection circuit 806, when a potential outside a certain range is applied to the wiring to which it is connected, This is a circuit that creates a conductive state between one wire and another wire.

[0250] As shown in Figure 9(A), protection circuits 806 are provided for the pixel section 802 and the drive circuit section 804, respectively. By providing it, ESD (Electrostatic Discharge) This can improve the resistance of the display device to overcurrents generated by gas discharge, etc. Furthermore, the configuration of the protection circuit 806 is not limited to this, and for example, the scan line drive circuit 804a may be protected Configuration with circuit 806 connected, or with protection circuit 806 connected to signal line drive circuit 804b. It can also be configured as follows. Alternatively, it can be configured by connecting the protection circuit 806 to the terminal 807. It is also possible to do so.

[0251] Furthermore, in Figure 9(A), the scan line drive circuit 804a and the signal line drive circuit 804b are used. The example shown illustrates the formation of the drive circuit section 804, but the configuration is not limited to this. , a base that forms only the scan line drive circuit 804a and has a separately prepared signal line drive circuit formed A structure for mounting a plate (for example, a drive circuit board formed from a single-crystal semiconductor film or a polycrystalline semiconductor film). It's fine to accept it.

[0252] <Example of pixel circuit configuration> The multiple pixel circuits 801 shown in Figure 9(A) can be configured, for example, as shown in Figure 9(B). can.

[0253] The pixel circuit 801 shown in Figure 9(B) consists of transistors 852 and 854, and a capacitive element 862. It has a light-emitting element 872 and

[0254] One of the source and drain electrodes of transistor 852 is connected to the circuit to which the data signal is applied. It is electrically connected to the line (data line DL_n). Furthermore, the gate voltage of transistor 852 The poles are electrically connected to the wiring (scan line GL_m) to which the gate signal is supplied.

[0255] Transistor 852 has the function of controlling the writing of data to the data signal.

[0256] One of the pair of electrodes of the capacitive element 862 is connected to a wiring to which a potential is supplied (hereinafter referred to as the potential supply line VL_ It is electrically connected to (a), and the other is connected to the source electrode and drain of transistor 852. It is electrically connected to the other electrode.

[0257] The capacitive element 862 functions as a holding capacitor to retain the written data.

[0258] One of the source and drain electrodes of transistor 854 is electrically connected to the potential supply line VL_a. They are connected precisely. Furthermore, the gate electrode of transistor 854 is connected to the socket of transistor 852. The other electrode is electrically connected to the drain electrode.

[0259] One of the anodes and cathodes of the light-emitting element 872 is electrically connected to the potential supply line VL_b. The other end is electrically connected to the source electrode and drain electrode of transistor 854. It can be done.

[0260] As the light-emitting element 872, the light-emitting elements shown in Embodiments 1 to 3 may be used. can.

[0261] Furthermore, a high power supply potential VDD is supplied to one of the potential supply lines VL_a and VL_b. On the other hand, a low power supply potential VSS is applied.

[0262] In a display device having the pixel circuit 801 shown in Figure 9(B), for example, the scan line drive shown in Figure 9(A) The motion circuit 804a sequentially selects the pixel circuit 801 for each row and turns on the transistor 852. The data signal is written in this state.

[0263] The pixel circuit 801, on which data has been written, is maintained by the transistor 852 being turned off. It enters a state of holding. Furthermore, the transistor 854's so The amount of current flowing between the drain electrode and the light-emitting element 872 is controlled by the current flowing through it. It emits light with brightness corresponding to the amount of light. By doing this sequentially for each row, an image can be displayed.

[0264] Furthermore, a light-emitting element according to one aspect of the present invention is an active matrix having an active element in the pixels of a display device. The RIX system, or the passive matrix system in which the pixels of the display device do not have active elements. It can be applied to each method.

[0265] In the active matrix system, the active elements (active elements, nonlinear elements) are, In addition to transistors, various active elements (active elements, nonlinear elements) are used. This is possible. For example, MIM (Metal Insulator Metal) or TF It is also possible to use elements such as D (Thin Film Diode). Because the manufacturing process is simplified, it is possible to reduce manufacturing costs or improve yield. Alternatively, these elements can improve the aperture ratio due to their small size. This allows for lower power consumption and higher brightness.

[0266] Other than the active matrix method, there are active elements (active elements, nonlinear elements). It is also possible to use a passive matrix type that does not use active elements. Because it does not use nonlinear elements, the manufacturing process is simpler, resulting in reduced manufacturing costs or lower yield. This can improve performance. Alternatively, by using active elements (active elements, nonlinear elements) Therefore, the aperture ratio can be improved, leading to lower power consumption or higher brightness. It is possible.

[0267] The configuration shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments. can.

[0268] (Embodiment 5) In this embodiment, a display device having a light-emitting element according to one aspect of the present invention, and the display device An electronic device with an input device attached will be explained using Figures 10 to 14.

[0269] <Explanation regarding the touch panel 1> In this embodiment, as an example of electronic equipment, a display device and an input device are combined. This document describes the Touch Panel 2000. It also explains a touch sensor as an example of an input device. This section explains when to use this method.

[0270] Figures 10(A) and 10(B) are perspective views of the Touch Panel 2000. For clarity, the following shows typical components of the Touch Panel 2000.

[0271] The touch panel 2000 has a display device 2501 and a touch sensor 2595 (Figure 10). (See (B)). Also, the touch panel 2000 consists of circuit board 2510, circuit board 2570, and circuit board It has 2590. Note that substrates 2510, 2570, and 2590 are all acceptable. It has flexibility. However, any one of substrates 2510, 2570, and 2590. Alternatively, the entire structure may be non-flexible.

[0272] The display device 2501 has multiple pixels on the substrate 2510 and can supply signals to these pixels. It has multiple wirings 2511 that extend to the outer periphery of the substrate 2510. It is routed, and a part of it forms terminal 2519. Terminal 2519 is FPC2509( 1) Connect electrically to it.

[0273] The circuit board 2590 has a touch sensor 2595 and multiple connections electrically connected to the touch sensor 2595. It has several wires 2598. Multiple wires 2598 are routed around the outer periphery of the substrate 2590. A portion of it forms a terminal. This terminal is then electrically connected to FPC2509(2). This is done. Note that in Figure 10(B), for clarity, the back side of substrate 2590 (substrate 2510 and The electrodes and wiring of the touch sensor 2595, which is located on the opposite side, are shown with solid lines.

[0274] For example, a capacitive touch sensor can be used as the touch sensor 2595. Quantitative methods include surface capacitance and projected capacitance.

[0275] Projected capacitance systems are mainly categorized into self-capacitance systems and mutual-capacitance systems, based on differences in their driving methods. There is a mutual capacitance method, which is preferable because it enables simultaneous multi-point detection.

[0276] Note that the touch sensor 2595 shown in Figure 10(B) is a projected capacitive touch sensor. This configuration applies the following:

[0277] Furthermore, the touch sensor 2595 can detect the proximity or contact of an object to be detected, such as a finger. It can be used to apply various sensors.

[0278] The projected capacitive touch sensor 2595 has electrodes 2591 and 2592. Electrode 2591 is electrically connected to one of the multiple wires 2598, and electrode 2592 is multiple Connect electrically to any of the other wires 2598.

[0279] As shown in Figures 10(A) and 10(B), the electrode 2592 consists of multiple electrodes arranged repeatedly in one direction. It has a shape in which quadrilaterals are connected at their corners.

[0280] Electrode 2591 is quadrilateral and is repeatedly arranged in a direction intersecting the direction in which electrode 2592 extends. It is placed there.

[0281] Wiring 2594 is electrically connected to the two electrodes 2591 that sandwich electrode 2592. A shape that minimizes the area of ​​the intersection between electrode 2592 and wiring 2594 is preferable. This reduces the area where electrodes are not provided, thereby reducing variations in transmittance. This reduces variations in the brightness of light transmitted through the touch sensor 2595. can.

[0282] The shapes of electrodes 2591 and 2592 are not limited to these and can take on various shapes. For example, multiple electrodes 2591 are arranged so that there are as few gaps as possible, and an insulating layer is used to connect them. The electrode 2592 is provided in multiple locations spaced apart so that there is a region that does not overlap with the electrode 2591. It may be set as follows. In this case, between the two adjacent electrodes 2592, there is an electrical isolation between them. Providing a bordered dummy electrode is preferable because it reduces the area of ​​regions with different transmittances.

[0283] <Explanation regarding display devices> Next, the details of the display device 2501 will be explained using Figure 11(A). Figure 11(A) This corresponds to the cross-sectional view between the dashed line X1 and X2 shown in Figure 10(B).

[0284] The display device 2501 has a plurality of pixels arranged in a matrix. These pixels are display elements. It also includes a pixel circuit that drives the display element.

[0285] The following explanation applies to the case where a light-emitting element that emits white light is applied to the display element. To explain further, the display elements are not limited to these. For example, the color of light emitted from each adjacent pixel. You may use light-emitting elements with different emission colors so that they differ.

[0286] For example, substrates 2510 and 2570 have a water vapor transmission rate of 1 × 10⁻⁶ -5 g·m -2 ·day -1 The following is preferably 1 × 10 -6 g·m -2 ·day -1 The following flexible Materials having the properties can be suitably used. Alternatively, the thermal expansion coefficient of the substrate 2510 and the substrate It is preferable to use a material with a thermal expansion coefficient approximately equal to 2570. For example, a material with a linear expansion coefficient 1 x 10 -3 / K or less, preferably 5 × 10 -5 / K or less, more comfortable 1×10 -5 Materials with a temperature of 1 / K or less can be suitably used.

[0287] The substrate 2510 includes an insulating layer 2510a that prevents the diffusion of impurities to the light-emitting element, and a flexible group Adhesive layer 25 for bonding plate 2510b, insulating layer 2510a, and flexible substrate 2510b It is a laminate having 10c. In addition, the substrate 2570 prevents the diffusion of impurities to the light-emitting element. A protective insulating layer 2570a, a flexible substrate 2570b, and insulating layer 2570a and flexible substrate 2 It is a laminate having an adhesive layer 2570c to bond 570b together.

[0288] Examples of adhesive layers 2510c and 2570c include polyester, polyolefin, etc. Polyamide (nylon, aramid, etc.), polyimide, polycarbonate, or acrylic Polyurethane, epoxy resin, or silicone can be used. Materials containing resins having siloxane bonds can be used.

[0289] Furthermore, a sealing layer 2560 is provided between substrate 2510 and substrate 2570. The sealing layer 2560 is It is preferable that it has a refractive index greater than that of air. Also, as shown in Figure 11(A), the sealing layer If light is to be extracted to the 2560 side, the sealing layer 2560 can also serve as an optical bonding layer. ru.

[0290] Furthermore, a sealing material may be formed on the outer periphery of the sealing layer 2560. As a result, the area surrounded by substrate 2510, substrate 2570, sealing layer 2560, and sealing material The configuration may include a light-emitting element 2550R. Furthermore, the sealing layer 2560 may be made of an unspecified material. The container may be filled with an active gas (such as nitrogen or argon). Furthermore, a desiccant may be placed inside the inert gas. It may also be provided to adsorb moisture, etc. Alternatively, UV-curing resin or thermosetting resin may be used. It may be filled with, for example, PVC (polyvinyl chloride) resin, acrylic resin, Polyimide resins, epoxy resins, silicone resins, PVB (polyvinyl butyral) A resin based on the EVA (ethylene vinyl acetate) system can be used. As for the sealing material mentioned above, it is preferable to use, for example, epoxy resin or glass frit. It is preferable to use a material that does not allow moisture or oxygen to pass through when using a sealing material. It is suitable.

[0291] Furthermore, the display device 2501 has a pixel 2502R. The pixel 2502R is a light-emitting module. It has a 2580R liter.

[0292] Pixel 2502R is connected to the light-emitting element 2550R, and is powered by the light-emitting element 2550R. It has a transistor 2502t that can do so. Note that transistor 2502t is a pixel circuit It functions as part of the light-emitting module 2580R and the light-emitting element 2550R. It has a color layer 2567R.

[0293] The light-emitting element 2550R has a lower electrode, an upper electrode, and an EL layer between the lower electrode and the upper electrode. It has. As the light-emitting element 2550R, for example, the light-emitting elements shown in Embodiments 1 to 4 The element can be applied.

[0294] Furthermore, a microcavity structure is employed between the lower electrode and the upper electrode, allowing for specific wavelengths. The light intensity may be increased.

[0295] Furthermore, if the sealing layer 2560 is provided on the side from which light is extracted, the sealing layer 2560 emits light. It is in contact with element 2550R and the colored layer 2567R.

[0296] The colored layer 2567R is located in a position that overlaps with the light-emitting element 2550R. As a result, the light-emitting element 2 A portion of the light emitted by 550R passes through the colored layer 2567R, resulting in light emission in the direction of the arrows shown in the diagram. It is ejected to the outside of module 2580R.

[0297] Furthermore, the display device 2501 is provided with a light-shielding layer 2567BM in the direction from which light is emitted. The light layer 2567BM is provided so as to surround the colored layer 2567R.

[0298] The colored layer 2567R only needs to have the function of transmitting light in a specific wavelength range, for example For example, a color filter that transmits light in the red wavelength range, and a color filter that transmits light in the green wavelength range. Filters, color filters that transmit light in the blue wavelength range, color filters that transmit light in the yellow wavelength range - Filters can be used. Each color filter is printed using various materials. Formed by methods such as inkjet etching and photolithography. It is possible.

[0299] Furthermore, the display device 2501 is provided with an insulating layer 2521. The insulating layer 2521 is transient It covers the st 2502t. The insulating layer 2521 flattens the irregularities caused by the pixel circuit. It has the function of having the insulating layer 2521 capable of suppressing the diffusion of impurities. This is also good. This suppresses the decrease in reliability of transistors such as the 2502t due to the diffusion of impurities. It can be controlled.

[0300] Furthermore, the light-emitting element 2550R is formed above the insulating layer 2521. The lower electrode of 50R is provided with a partition wall 2528 that overlaps the end of the lower electrode. Oh, a spacer that controls the distance between substrate 2510 and substrate 2570 is formed on the partition wall 2528. It is permissible.

[0301] The scan line drive circuit 2503g(1) consists of a transistor 2503t and a capacitive element 2503c. It has the following features. Furthermore, the drive circuit can be formed on the same substrate using the same process as the pixel circuit. .

[0302] Furthermore, wiring 2511, which can supply signals, is provided on the circuit board 2510. Furthermore, terminal 2519 is provided on wiring 2511. Also, FPC is provided on terminal 2519. 2509(1) is electrically connected. Also, FPC2509(1) receives video signals, etc. It has the function of supplying lock signals, start signals, reset signals, etc. (Note: FPC25) 09(1) is a printed wiring board (PWB: Printed Wiring Board) ) may be attached.

[0303] Furthermore, transistors of various structures can be applied to the display device 2501. Figure 1 In 1(A), the case where a bottom-gate type transistor is applied is illustrated as an example. However, it is not limited to this, for example, the top gate type transistor shown in Figure 11(B) The data may also be applied to the display device 2501.

[0304] Furthermore, the polarity of transistors 2502t and 2503t is not particularly limited. There is no structure having N-channel and P-channel transistors, N-channel type Using a structure consisting of either a transistor or a P-channel transistor The crystallinity of the semiconductor film used in transistors 2502t and 2503t may also be considered. There are no particular limitations on this either. For example, amorphous semiconductor films and crystalline semiconductor films can be used. It is possible. Also, as a semiconductor material, Group 13 semiconductors (for example, semiconductors containing gallium) Semiconductors of Group 14 (e.g., semiconductors containing silicon), compound semiconductors (including oxide semiconductors) (m), organic semiconductors, etc. can be used. Transistor 2502t and Transistor 2 In either or both of the 503t, the energy gap is 2 eV or more, preferably 2 By using an oxide semiconductor with a voltage of 0.5eV or higher, and more preferably 3eV or higher, the transient This is preferable because it can reduce the off-current of the transistor. As the oxide semiconductor, In- Ga oxide, In-M-Zn oxide (where M is aluminum (Al), gallium (Ga)), Yttrium (Y), Zirconium (Zr), Lanthanum (La), Cerium (Ce), S Examples include s(Sn), hafnium (Hf), or neodymium (Nd).

[0305] <Explanation regarding touch sensors> Next, we will explain the details of the touch sensor 2595 using Figure 11(C). C) corresponds to the cross-sectional view between the dashed line X3 and X4 shown in Figure 10(B).

[0306] The touch sensor 2595 has electrodes 2591 and 2591 arranged in a staggered pattern on the substrate 2590. 592, the insulating layer 2593 covering electrode 2591 and electrode 2592, and adjacent electrode 259 It has wiring 2594 that electrically connects 1.

[0307] Electrodes 2591 and 2592 are formed using a light-transmitting conductive material. The conductive materials include indium oxide, indium tin oxide, and indium zinc oxide. Conductive oxides such as zinc oxide, zinc oxide with added gallium, etc., can be used. Furthermore, a film containing graphene can also be used. A film containing graphene can be, for example, in the form of a film. The formed graphene oxide-containing film can be reduced to form the new film. The reduction method is as follows: For example, methods involving the application of heat can be cited.

[0308] For example, a light-transmitting conductive material was deposited on a substrate 2590 by sputtering. Then, unwanted parts are removed using various pattern formation techniques such as photolithography. Electrodes 2591 and 2592 can be formed.

[0309] Furthermore, the materials used for the insulating layer 2593 include, for example, resins such as acrylic and epoxy. In addition to resins containing siloxane bonds such as silicone, silicon oxide, silicon oxide nitride, Inorganic insulating materials such as aluminum oxide can also be used.

[0310] Furthermore, an opening reaching the electrode 2591 is provided in the insulating layer 2593, and the wiring 2594 is adjacent to it. It is electrically connected to electrode 2591. The translucent conductive material increases the aperture ratio of the touch panel. Because it can be done, it can be suitably used for wiring 2594. Also, electrode 2591 and A material with higher conductivity than electrode 2592 is suitable for wiring 2594 because it can reduce electrical resistance. It can be used for this purpose.

[0311] The electrode 2592 extends in one direction, and multiple electrodes 2592 are arranged in a stripe pattern. Furthermore, the wiring 2594 is provided intersecting with the electrode 2592.

[0312] A pair of electrodes 2591 are provided flanking one electrode 2592. Also, the wiring 2594 is The pair of electrodes 2591 are electrically connected.

[0313] Note that the multiple electrodes 2591 are not necessarily arranged in a direction perpendicular to that of a single electrode 2592. It is not necessary, and they may be positioned to form an angle greater than 0 degrees but less than 90 degrees.

[0314] Furthermore, wiring 2598 is electrically connected to electrode 2591 or electrode 2592. A portion of the wiring 2598 functions as a terminal. Wiring 2598 can be, for example, aluminum. Um, gold, platinum, silver, nickel, titanium, tungsten, chromium, molybdenum, iron, koba Metallic materials such as copper, palladium, or other metallic materials, or alloy materials containing such metallic materials, may be used. can.

[0315] Furthermore, an insulating layer is provided to cover the insulating layer 2593 and the wiring 2594, and the touch sensor 2595 It may be protected.

[0316] Furthermore, the connection layer 2599 electrically connects the wiring 2598 and the FPC 2509(2).

[0317] The connecting layer 2599 is an anisotropic conductive film (ACF: Anisotropic Co (Inductive Film) and anisotropic conductive paste (ACP: Anisotropic You can use things like (c) Conductive Paste.

[0318] <Explanation regarding the touch panel 2> Next, we will explain the details of the touch panel 2000 using Figure 12(A). Figure 12( A) corresponds to the cross-sectional view between the dashed line X5 and X6 shown in Figure 10(A).

[0319] The touch panel 2000 shown in Figure 12(A) is the same as the display device 2501 described in Figure 11(A). This configuration involves bonding the touch sensor 2595, as explained in Figure 11(C), to the other component.

[0320] Furthermore, the touch panel 2000 shown in Figure 12(A) is explained in Figures 11(A) and 11(C). In addition to the configuration described above, it also includes an adhesive layer 2597 and an anti-reflective layer 2567p.

[0321] The adhesive layer 2597 is provided in contact with the wiring 2594. Attach the circuit board 2590 to the circuit board 2570 so that the sensor 2595 overlaps the display device 2501. They are combined. Furthermore, it is preferable that the adhesive layer 2597 is translucent. Also, adhesive layer 25 For 97, a thermosetting resin or an ultraviolet curing resin can be used. For example, A Use acrylic resin, urethane resin, epoxy resin, or siloxane resin. It is possible.

[0322] The anti-reflective layer 2567p is provided in a position that overlaps with the pixel. For example, a circular polarizer can be used.

[0323] Next, for a touch panel with a configuration different from that shown in Figure 12(A), Figure 12(B) is used. I will explain.

[0324] Figure 12(B) is a cross-sectional view of the touch panel 2001. The 2001 is a combination of the touch panel 2000 and the display device 2501 shown in Figure 12(A). The position of the touch sensor 2595 is different. Here, we will describe the different configurations in detail, and similarly Where the configuration can be used, refer to the description of Touch Panel 2000.

[0325] The colored layer 2567R is located in a position that overlaps with the light-emitting element 2550R. Also shown in Figure 12(B). The light-emitting element 2550R emits light towards the side where the transistor 2502t is located. As a result, some of the light emitted by the light-emitting element 2550R passes through the colored layer 2567R, as shown in Figure The light is emitted to the outside of the light-emitting module 2580R in the direction of the arrow shown inside.

[0326] Furthermore, the touch sensor 2595 is located on the circuit board 2510 side of the display device 2501.

[0327] The adhesive layer 2597 is located between substrates 2510 and 2590 and touches the display device 2501. Attach sensor 2595.

[0328] As shown in Figures 12(A) and 12(B), the light emitted from the light-emitting element is directed towards the substrate 2510 and the substrate It is sufficient for the injection to occur through either or both of the 2570 components.

[0329] <Explanation of how the touch panel is operated> Next, an example of a touch panel driving method will be explained using Figure 13.

[0330] Figure 13(A) is a block diagram showing the configuration of a mutual capacitive touch sensor. Figure A shows the pulse voltage output circuit 2601 and the current detection circuit 2602. In 13(A), the electrodes 2621 to which the pulse voltage is applied are X1-X6, and the change in current is observed. The electrodes 2622 that detect the signal are designated as Y1-Y6, and each is illustrated with six wires. Figure 13(A) shows the capacitance 2 formed by the superposition of electrode 2621 and electrode 2622. This indicates 603. Note that electrodes 2621 and 2622 have interchangeable functions. That's fine.

[0331] The pulse voltage output circuit 2601 is a circuit for sequentially applying pulses to the X1-X6 wiring. Yes. When a pulse voltage is applied to the wiring of X1-X6, the electrodes form capacitance 2603. An electric field is generated between electrode 2621 and electrode 2622. This electric field generated between the electrodes is shielded, etc. By causing a change in the mutual capacitance of a capacitance of 2603, the proximity or contact of the detected object is detected. It can detect touch.

[0332] The current detection circuit 2602 detects changes in the mutual capacitance of capacitor 2603 in the wiring Y1-Y6. This is a circuit for detecting changes in current. In the wiring of Y1-Y6, proximity of the object to be detected, If there is no contact, the detected current value does not change, but if the object being detected is nearby, or if there is contact When contact reduces the mutual capacitance, a change in the current value is detected. This can be done using an integrating circuit or similar.

[0333] Next, Figure 13(B) shows the input and output of the mutual capacitive touch sensor shown in Figure 13(A). The timing chart of the force waveform is shown. Figure 13(B) shows the impact of each matrix over a 1-frame period. The system will detect the object to be detected. Also, in Figure 13(B), the case where the object to be detected is not detected ( This shows two cases: one where the object to be detected is not touched, and another where the object to be detected is touched. Regarding the wiring of Y1-Y6, the waveforms shown represent the voltage values ​​corresponding to the detected current values. Yes, they are.

[0334] A pulse voltage is applied sequentially to the wiring of X1-X6, and according to this pulse voltage, Y1-Y The waveform changes in wiring 6. If there is no proximity or contact with the object to be detected, X1-X6 The waveforms of Y1-Y6 change uniformly in response to changes in the wiring voltage. On the other hand, when the object to be detected is in close proximity... At the point of contact, the current value decreases, and therefore the waveform of the corresponding voltage value also changes. .

[0335] In this way, by detecting changes in mutual capacitance, the proximity or contact of the object being detected can be detected. It is possible.

[0336] <Explanation regarding the sensor circuit> Furthermore, in Figure 13(A), only a capacitor 2603 is provided at the wiring intersection as a touch sensor. The configuration of a symmetric matrix type touch sensor is shown, but it has transistors and capacitors. It may also be an active matrix type touch sensor. An example of a sensor circuit included in the sensor is shown in Figure 14.

[0337] The sensor circuit shown in Figure 14 consists of capacitor 2603, transistor 2611, and transistor 2 It has 612 and transistor 2613.

[0338] Transistor 2613 receives a signal G2 at its gate, and an electric current is applied to either its source or drain. A pressure VRES is given, and the other is one electrode of capacitance 2603 and transistor 2611. The gate is electrically connected. Transistor 2611 has either the source or the drain connected to the gate. Electrically connect either the source or drain of the 2612 transistor, and connect the other to the voltage VSS. A signal G1 is given to the gate of transistor 2612, and the source or The other end of the rain wire is electrically connected to the wiring ML. The other electrode of the capacitance 2603 has a voltage VSS. It is given.

[0339] Next, the operation of the sensor circuit shown in Figure 14 will be explained. First, the signal G2 is a transient When a potential is applied that turns on transistor 2613, the gate of transistor 2611 is activated. A potential corresponding to the voltage VRES is applied to node n to which it is connected. Next, the signal G2 is By applying a potential that turns off transistor 2613, the potential at node n is maintained. It is held.

[0340] Next, the mutual capacitance of capacitance 2603 changes due to the proximity or contact of a detected object such as a finger. Consequently, the potential of node n changes from VRES.

[0341] The read operation applies a potential to signal G1 that turns on transistor 2612. The current flowing through transistor 2611, i.e., the current flowing through wiring ML, in accordance with the potential of do n. The current changes. By detecting this current, the proximity or contact of the object to be detected can be detected. It is possible.

[0342] As transistors 2611, 2612, and 2613, acid It is preferable to use a synthetic semiconductor layer in the semiconductor layer in which the channel region is formed. In particular, By applying such a transistor to the 2613, the potential of node n can be extended. This makes it possible to retain the data over a period of time, and the operation of resupplying VRES to node n (lift This can reduce the frequency of the reshuffling action.

[0343] The configuration shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments. can.

[0344] (Embodiment 6) In this embodiment, a display module and electronic device having a light-emitting element according to one aspect of the present invention Next, we will explain using Figures 15 and 16.

[0345] <Explanation regarding the display module> The display module 8000 shown in Figure 15 consists of an upper cover 8001 and a lower cover 8002. In between, touch sensor 8004 connected to FPC8003, and FPC8005 connected It comprises a display device 8006, a frame 8009, a printed circuit board 8010, and a battery 8011. ru.

[0346] A light-emitting element according to one aspect of the present invention can be used, for example, in a display device 8006.

[0347] The upper cover 8001 and the lower cover 8002 are the touch sensor 8004 and the display device 80 The shape and dimensions can be appropriately modified to match the size of 06.

[0348] The touch sensor 8004 is a resistive or capacitive touch sensor connected to the display device 80 It can be used superimposed on 06. Also, on the opposing substrate (encapsulation substrate) of the display device 8006 It is also possible to give it a touch sensor function. It is also possible to install a light sensor within each pixel to create an optical touch sensor.

[0349] Frame 8009 provides protection for the display device 8006, as well as control the operation of the printed circuit board 8010. It functions as an electromagnetic shield to block the electromagnetic waves generated. 8009 may also function as a heat sink.

[0350] Printed circuit board 8010 contains power supply circuits and signal outputs for video signals and clock signals. It has a processing circuit. The power supply that provides power to the power supply circuit may be an external commercial power supply. That's fine, or it could be powered by a separately provided battery 8011. Battery 8011 is, This can be omitted when using commercial power.

[0351] Furthermore, the display module 8000 includes additional components such as polarizing plates, phase difference plates, and prism sheets. They may be provided as such.

[0352] <Explanation regarding electronic equipment> Figures 16(A) to 16(G) show electronic devices. These electronic devices are enclosed in a housing. 9000, display unit 9001, speaker 9003, operation key 9005 (power switch, or (including operating switch), connection terminal 9006, sensor 9007 (force, displacement, position, velocity, acceleration) Speed, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field A device that measures electric current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared radiation. It may have a microphone (including a 9008), etc.

[0353] The electronic devices shown in Figures 16(A) to 16(G) can have various functions. Example For example, a function to display various information (still images, videos, text images, etc.) on the display unit, touch Sensor functions, calendar, date or time display functions, various software ( A function that controls processing by program, wireless communication function, and various functions using wireless communication function. Features include the ability to connect to a computer network, and the ability to transmit various types of data using wireless communication. It has the function of receiving data, reading programs or data recorded on a recording medium and displaying them. It can have functions such as displaying information in the section. The functions that electronic devices can have are not limited to these, and they can have a variety of functions. Yes, it is possible. Also, although not shown in Figures 16(A) to 16(G), electronic devices have multiple The device may also be configured to have a numerical display unit. Furthermore, a camera or the like may be provided to the electronic device to capture still images. Shadow recording function, video recording function, and recording medium for captured images (external or built into the camera). It may also have functions such as saving to a storage device and displaying the captured image on a display unit.

[0354] Details of the electronic equipment shown in Figures 16(A) to 16(G) will be explained below.

[0355] Figure 16(A) is a perspective view showing the personal digital assistant 9100. The display unit 9001 is flexible. Therefore, it conforms to the curved surface of the curved housing 9000. It is possible to incorporate the display unit 9001. Furthermore, the display unit 9001 is a touch sensor. It is equipped with a mechanism that allows operation by touching the screen with a finger or stylus. For example, display You can launch the application by touching the icon displayed in section 9001. Cut.

[0356] Figure 16(B) is a perspective view showing the personal digital assistant (PDA) 9101. The PDA 9101 is a personal digital assistant (PDA). For example, it has one or more functions selected from a telephone, a notebook, or an information viewing device. In terms of functionality, it can be used as a smartphone. Note that the mobile information terminal 9101 is a smartphone. Although the speaker 9003, connection terminal 9006, sensor 9007, etc. are omitted in the illustration, Figure 1 It can be installed in the same position as the portable information terminal 9100 shown in 6(A). The information terminal 9101 can display text and image information on multiple sides. For example, 3 Two operation buttons 9050 (also called operation icons or simply icons) are displayed on the display unit 9001 It can be displayed on one side. Also, the information 9051 shown by the dashed rectangle is displayed on the display unit 900. It can be displayed on other sides of 1. For example, information 9051 can be sent via email or A display that notifies you of incoming calls from social networking services (SNS) or phone calls. Subject of emails and social media posts, sender's name, date, time, and timestamp. This includes things like remaining battery power and antenna reception strength. Or, information 9051 is displayed. Instead of displaying information 9051, you may also display operation button 9050 or the like.

[0357] Figure 16(C) is a perspective view showing the personal digital assistant (PDA) 9102. The PDA 9102 is a personal digital assistant (PDA). The display unit 9001 has the function of displaying information on three or more sides. Here, information 9052, information This shows an example where Report 9053 and Information 9054 are displayed on different sides. For example, mobile The user of the information terminal 9102 has the portable information terminal 9102 stored in the breast pocket of their clothing. Then you can check that display (information 9053 in this case). Specifically, the incoming call A position from which the caller's phone number or name can be observed from above the mobile information terminal 9102. The information is displayed on the device. The user can view the information without taking the portable information terminal 9102 out of their pocket. You can check and decide whether or not to answer the call.

[0358] Figure 16(D) is a perspective view showing the wristwatch-type personal information terminal 9200. Personal information terminal 9 200 includes mobile phone, email, document viewing and creation, music playback, and internet communication. It can run various applications such as computer games. The display surface of part 9001 is curved, and the display is made along the curved display surface. Yes, it is possible. Furthermore, the personal digital information terminal 9200 can perform standardized short-range wireless communication. This is possible. For example, by communicating with a wireless headset, hands It is also possible to make free calls. In addition, the mobile information terminal 9200 has a connection terminal 9006. Furthermore, it can directly exchange data with other information terminals via connectors. Charging can also be performed via connection terminal 9006. Note that the charging operation is performed via connection terminal 9006. This may also be done by wireless power transfer without the need for an intermediary.

[0359] Figure 16(E),(F),(G) is a perspective view showing a foldable portable information terminal 9201. Furthermore, Figure 16(E) is a perspective view of the mobile information terminal 9201 in an unfolded state, and Figure 16( F) The mobile information terminal 9201 changes from one state to the other, either unfolded or folded. This is a perspective view of the device in the process of being folded, with Figure 16(G) showing the mobile information terminal 9201 in the folded state. This is a perspective view. The 9201 personal digital information terminal offers excellent portability when folded, and when unfolded... In this state, the seamless, wide display area provides excellent readability. (Portable Information Terminal 920) The display unit 9001 of unit 1 is connected to three housings 9000 by a hinge 9055. It is supported by bending the two housings 9000 via the hinge 9055. The ability to reversibly transform the mobile information terminal 9201 from an unfolded state to a folded state. This is possible. For example, the mobile information terminal 9201 can be bent with a radius of curvature of 1 mm or more and 150 mm or less. It is possible.

[0360] The electronic device described in this embodiment has a display unit for displaying some kind of information. The present invention is characterized by the fact that, in one aspect of the present invention, the light-emitting element does not have a display unit. It can also be applied to devices. Furthermore, in the display section of the electronic device described in this embodiment... In the case of a flexible display surface, the configuration allows for display along a curved display surface, or a folding display surface. While examples of foldable display unit configurations have been given, the system is not limited to these, and may also include configurations that are not flexible and flat. The display may be placed on the surface.

[0361] The configuration shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments. can.

[0362] (Embodiment 7) In this embodiment, an example of a lighting device using a light-emitting element, which is one aspect of the present invention, is described below. This will be explained using Figure 17.

[0363] Figure 17 shows an example in which the light-emitting element is used as an indoor lighting device 8501. Because it can be scaled up to a large area, it is also possible to create large-area lighting devices. In addition, curved surfaces By using the housing, it is also possible to form a lighting device 8502 in which the light-emitting area has a curved surface. Yes, it is possible. The light-emitting element shown in this embodiment is a thin film, which allows for greater design flexibility in the housing. Therefore, lighting fixtures with various elaborate designs can be created. Furthermore, the interior walls A large lighting device 8503 may be provided on the surface. Also, lighting devices 8501, 8502, 85 A touch sensor may be provided at 03 to turn the power on or off.

[0364] Furthermore, by using the light-emitting element on the surface side of the table, it is equipped with the functionality of a table. This can be made into a lighting device 8504. Furthermore, light-emitting elements can be used in some other furniture. This allows the lighting device to function as a piece of furniture.

[0365] As described above, various lighting devices can be obtained by applying light-emitting elements. This is included in one aspect of the present invention.

[0366] Furthermore, the configuration shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments. It is possible. [Examples]

[0367] In this embodiment, eight types of light-emitting elements with different element configurations were fabricated. This includes four types of light-emitting elements that use different materials in their electron transport layers, and these four types of light-emitting elements are Four types of light-emitting elements were used, differing only in the material used for the hole transport layer. The fabrication of the light-emitting element 8 will be explained using Figure 18. Furthermore, the materials used in this embodiment... The chemical formula is shown below.

[0368] [ka]

[0369] <<Fabrication of light-emitting elements 1 to 8>> First, indium tin oxide (ITO) containing silicon dioxide is spat onto a glass substrate 900. A first electrode 901, which functions as an anode, was formed by depositing a film using the taring method. The film thickness was set to 70 nm, and the electrode area to 2 mm × 2 mm.

[0370] Next, as a pretreatment for forming light-emitting elements on the substrate 900, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0371] Then, 1 × 10 -4 A substrate is introduced into a vacuum deposition apparatus where the internal pressure is reduced to approximately Pa, and then vacuum After vacuum firing at 170°C for 30 minutes in the heating chamber of the deposition apparatus, the substrate 900 It was left to cool for about 30 minutes.

[0372] Next, the substrate 900 is placed in the vacuum deposition apparatus so that the surface on which the first electrode 901 is formed faces downwards. It was fixed in a holder provided inside. In this embodiment, the EL layer 902 was deposited by vacuum deposition. The constituent elements are a hole injection layer 911, a hole transport layer 912, a light-emitting layer 913, an electron transport layer 914, and an electron The injection layers 915 are formed sequentially.

[0373] 1 × 10 inside the vacuum chamber -4 After reducing the pressure to Pa, in the case of light-emitting elements 1 to 4, 3- [4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation) PCPPn and molybdenum oxide are used in a ratio of PCPPn:molybdenum oxide = 4:2 (by weight). Co-deposition was carried out in such a manner, and a hole injection layer 911 was formed on the first electrode 901. The film thickness was 10 The value was set to nm. Also, in the case of light-emitting elements 5 to 8, 9-phenyl-3-[4-(1 0-phenyl-9-antryl)phenyl]-9H-carbazole (abbreviation: PCzPA) Combine PCzPA and molybdenum oxide in a ratio of PCzPA:molybdenum oxide = 4:2 (by weight). A hole injection layer 911 was formed on the first electrode 901 by deposition. The film thickness was set to 10 nm. Co-evaporation is a vapor deposition method in which multiple different substances are evaporated simultaneously from different evaporation sources. That is the case.

[0374] Next, in the case of light-emitting elements 1 to 4, PCPPn is injected onto the hole injection layer 911 at a rate of 30 nm. A hole transport layer 912 was formed by deposition. In the case of light-emitting elements 5 to 8, holes A 30 nm layer of PCzPA was deposited on the injection layer 911 to form a hole transport layer 912.

[0375] Next, 7-[4-(10-phenyl-9-antryl)phenyl] onto hole transport layer 912 -7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), N,N'-bis (3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluorene-9) -yl)phenyl]-pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn) ) is cgDBCzPA:1,6mMemFLPAPrn=1:0.03 (weight ratio) A co-deposited layer 913 was formed. The film thickness was set to 25 nm.

[0376] Next, in the case of light-emitting elements 1 and 5, bathophenanthroline is placed on the light-emitting layer 913. A 25nm layer of BPhen (abbreviated as BPhen) was deposited to form an electron transport layer 914. Furthermore, a light-emitting element 2 And in the case of the light-emitting element 6, 2,2'-(pyridine-2,6-diyl) is placed on the light-emitting layer 913. Bis(4,6-diphenylpyrimidine) (abbreviation: 2,6(P2Pm)2Py) at 25 nm A vapor deposition was performed to form an electron transport layer 914. In the case of light-emitting elements 3 and 7, On the photolayer 913, 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10 - A 25nm layer of phenanthroline (abbreviated as NBPhen) is deposited to form an electron transport layer 914. In addition, in the case of light-emitting elements 4 and 8, 2,2'-(pyrite) was added to the light-emitting layer 913. Zin-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 2,6( A 25nm layer of P-Bqn)2Py) was deposited to form an electron transport layer 914.

[0377] Furthermore, lithium fluoride is deposited at a 1 nm thickness on the electron transport layer 914 to form an electron injection layer 915. did.

[0378] Finally, aluminum is deposited onto the electron injection layer 915 to a thickness of 200 nm, and the shadow A second electrode 903, which serves as a pole, was formed to obtain light-emitting elements 1 to 8. In the vapor deposition process, resistance heating was used for all deposition steps.

[0379] Table 1 shows the element structures of the light-emitting elements 1 to 8 obtained as described above.

[0380] [Table 1]

[0381] Furthermore, the fabricated light-emitting elements 1 to 8 are stored in a nitrogen atmosphere to prevent exposure to the air. The device was sealed inside a light box (a sealing material was applied around the element, and UV treatment was performed during sealing). (and heat treatment at 80°C for 1 hour). Note that four of each light-emitting element were prepared for the following measurements. It was made.

[0382] ≪Characteristics of Light-Emitting Elements 1 to 8≫ For the fabricated light-emitting elements 1 through 8 (four of each), a picosecond fluorescence lifetime measurement system was used for the measurement. A stem (manufactured by Hamamatsu Photonics) was used. In this measurement, the fluorescence emission lifetime of the light-emitting element was measured. To measure this, a rectangular pulse voltage is applied to the light-emitting element, and the attenuation from the falling edge of that voltage is measured. The light emission was measured with time resolution using a streak camera. A pulsed voltage was applied with a period of 10 Hz. Furthermore, by integrating the repeatedly measured data, we obtained data with a high signal-to-noise ratio. The measurement was performed at room temperature (300K), with an applied pulse voltage of approximately 3V and an applied pulse duration of 100μF. The measurement was performed under the following conditions: negative bias voltage of -5V, and measurement time range of 50μsec.

[0383] The decay curve showing the transient fluorescence characteristics obtained by measurement is calculated using the following equation (f1). We performed the fitting.

[0384]

number

[0385] However, in formula (f1), L represents the normalized luminescence intensity and t represents the elapsed time.

[0386] The damping curves obtained from the measurements were fitted, and the results were obtained by fitting n to 1 and 2. We were able to perform the lighting. Also, each of the light-emitting elements 1 to 8 has a fluorescent component. It was found that it also contains delayed fluorescence components. Measurements are taken immediately after the pressure is turned OFF, that is, after the carrier injection into the light-emitting layer is stopped. Fluorescence emission refers to the measurement of delayed fluorescence components in the EL layer of a light-emitting element, specifically in the triplet fluorescence emission. -This is due to the occurrence of triplet annihilation (TTA). Furthermore, the delayed fluorescence component ratio is... The fluorescence emission intensity of the light-emitting element when the pulse voltage is turned ON is compared to the emission immediately after the pulse voltage is turned OFF. This shows the ratio of the fluorescence emission intensity of the element. In other words, carriers are steadily injected into the light-emitting layer. The fluorescence emission intensity of the light-emitting element when the carrier injection is stopped is compared to the fluorescence emission intensity of the light-emitting element immediately after the carrier injection is stopped. This shows the percentage of luminescence intensity. Table 2 below shows the percentage of delayed fluorescence components of light-emitting elements 1 to 8. This indicates.

[0387] Furthermore, the luminescence characteristics of light-emitting elements 1 to 8 were measured, and the external quantum efficiency was determined. The external quantum efficiency of each light-emitting element obtained here is calculated by rotating the substrate from -80 degrees to 80 degrees and observing the light emission. The viewing angle dependence was measured, and values ​​that take into account the light distribution characteristics of EL emission were adopted. The results are as follows: The results are shown in Table 2. The measurements were performed at room temperature (in an atmosphere maintained at 25°C).

[0388] [Table 2]

[0389] Furthermore, Table 3 shows the LUMO levels of the materials used in the electron transport layers of light-emitting elements 1 to 8. The LUMO level is determined in the N,N-dimethylformamide (DMF) solvent of each material. This was estimated from cyclic voltammetry measurements.

[0390] [Table 3]

[0391] Here, Table 3 shows the materials used for the electron transport layer for each of the light-emitting elements 1 to 8. Regarding the percentage of delayed fluorescence component of each light-emitting element relative to the LUMO level (eV) shown, Light-emitting elements 1 to 4 using PCPPn in the pore transport layer, and PCzPA in the hole transport layer The light-emitting elements 5 through 8 used are shown in a common plot in Figure 19.

[0392] As a result, the value differs depending on the material used for the hole transport layer, but the LU value for the electron transport layer is different. A trend was observed where the proportion of delayed fluorescence components increased as the MO level value increased. That is, the LUMO level with the largest value is 2,6(P-Bqn)2Py(LUMO level A light-emitting element using (position: -2.92eV) has the same element configuration as a light-emitting element other than the electron transport layer. In this case, it can be said that the proportion of delayed fluorescence components increases.

[0393] Furthermore, the relationship between the delayed fluorescence component ratio (%) of light-emitting elements 1 to 8 and the external quantum efficiency (%) The relationship is shown in Figure 20.

[0394] As a result, the external quantum efficiency (%) increases as the percentage of delayed fluorescence component (%) increases. The following results were obtained.

[0395] Here, the fluorescence emission intensity due to the direct generation process is I P , fluorescence emission intensity of delayed fluorescence by TTA to I D Therefore, the delayed fluorescence component ratio (X) is expressed by the following formula (f2).

[0396]

number

[0397] Furthermore, from the definition of external quantum efficiency (EQE), I DIf it is 0 (X=0), single term excitation The riser generation rate (α) is 0.25. However, I D When that is added, alpha increases accordingly. Therefore, EQE is I P +I D It is proportional to . Therefore, the following equation (f3) is derived.

[0398]

number

[0399] Since X is equivalent to the x-axis in Figure 20, PCPPn is used in the hole transport layer as shown in Figure 20. The relationship between the delayed fluorescence component ratio (%) and the external quantum efficiency (%) in light-emitting elements 1 to 4. In relation to the hole transport layer, the delayed fluorescence ratio in light-emitting elements 5 to 8 using PCzPA ( The relationship between (%) and external quantum efficiency (%) can be expressed using the above equation (f3). Therefore, there is a correlation between the delayed fluorescence component percentage (%) and the external quantum efficiency (%). Confirmed.

[0400] Furthermore, regarding the light-emitting element 4-2 which has the same element configuration as the light-emitting element 4 shown in Table 1, the element characteristics The current density-luminance characteristics of light-emitting element 4-2 are shown in Figure 21, and the voltage-luminance characteristics are shown in Figure 21. 22. Brightness-current efficiency characteristics (Figure 23), voltage-current characteristics (Figure 24), brightness-external quantum efficiency characteristics. These are shown in Figure 25. Here, the external quantum efficiency of the light-emitting element shown in Figure 25 is as described above. The substrate was rotated from -80 degrees to 80 degrees to measure the viewing angle dependence of the light emission, and the distribution of EL light emission Values ​​that take optical characteristics into consideration were adopted. On the other hand, the characteristic values ​​of the light-emitting element shown in Figures 21 to 24 are color The luminance was determined from the front luminance using a chrominance meter BM-5A (manufactured by TOPCON).

[0401] Also, 1000 cd / m²2 The main initial characteristic values ​​of the light-emitting element 4-2 in the vicinity are shown in Table 4 below. show.

[0402] [Table 4]

[0403] Furthermore, Figure 26 shows that the light-emitting element 4-2 has a current of 12.5 mA / cm². 2 When current flows at this current density, The light spectrum is shown. As shown in Figure 26, the emission spectrum of light-emitting element 4-2 is 464n It has a peak around m, and is used as a guest material (dopant) in the light-emitting layer of light-emitting element 4-2. It is suggested that this originates from the 1,6mMemFLPAPrn used.

[0404] Furthermore, Figure 27 shows the decay curve illustrating the transient fluorescence characteristics of the light-emitting element 4-2. The vertical axis represents the state in which carriers are steadily being injected (when the pulse voltage is ON). The intensity is shown normalized by the luminous intensity. The horizontal axis represents the elapsed time from the falling edge of the pulse voltage. The value in μs is shown. Furthermore, regarding the damping curve shown in Figure 27, the above equation (f1) was used to fit it. The results of the analysis showed that the delayed fluorescence component percentage was 21.5%.

[0405] Next, a reliability test was performed on the light-emitting element 4-2. The results of the reliability test are shown in Figure 28. In Figure 28, the vertical axis represents the normalized luminance (%) when the initial luminance is set to 100%, and the horizontal axis represents This indicates the operating time (h) of the element. Note that the reliability test was conducted with an initial brightness of 5000 cd / m². 2 Set The light-emitting element 4-2 was then driven under the condition of a constant current density.

[0406] As a result, in the light-emitting element 4-2, which is one embodiment of the present invention, a result showing high reliability was obtained. It was done. [Examples]

[0407] In this embodiment, the arrangement of the transition dipole moments of the molecules involved in light emission in the light-emitting layer of the light-emitting element is The directional properties were derived. Specifically, the angular dependence of the spectral intensity of the p-polarized component of the emission was measured. By analyzing the results through calculation (simulation), the transition dipole model of the molecule can be determined. The orientation of the ment was derived. Materials used in this embodiment that are not described in Example 1. The chemical formula is shown below.

[0408] [ka]

[0409] <<Fabrication of the light-emitting element 9>> First, the fabrication of the light-emitting element 9 to be measured will be explained using Figure 18. First, the glass Indium tin oxide (ITO) containing silicon oxide is applied to substrate 900 by sputtering. A film was deposited to form the first electrode 901, which functions as an anode. The film thickness was 70 nm. The electrode area was set to 2 mm x 2 mm.

[0410] Next, as a pretreatment for forming light-emitting elements on the substrate 900, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0411] Then, 1 × 10 -4 A substrate is introduced into a vacuum deposition apparatus where the internal pressure is reduced to approximately Pa, and then vacuum After vacuum firing at 170°C for 30 minutes in the heating chamber of the deposition apparatus, the substrate 900 It was left to cool for about 30 minutes.

[0412] Next, the substrate 900 is placed in the vacuum deposition apparatus so that the surface on which the first electrode 901 is formed faces downwards. It was fixed in a holder provided inside. In this embodiment, the EL layer 902 was deposited by vacuum deposition. The constituent elements are a hole injection layer 911, a hole transport layer 912, a light-emitting layer 913, an electron transport layer 914, and an electron The injection layers 915 are formed sequentially.

[0413] 1 × 10 inside the vacuum chamber -4 After reducing the pressure to Pa, 1,3,5-tri(dibenzothiophen- 4-yl)benzene (abbreviation: DBT3P-II) and molybdenum oxide in a weight ratio (DBT3 The ratio of P-II (molybdenum oxide) is 2:1, and the thickness is 10 nm. A hole injection layer 911 was formed on the first electrode 901 by deposition. Note that co-deposition is different from... This is a vapor deposition method in which multiple substances are simultaneously evaporated from different evaporation sources.

[0414] Next, 30 nm of BPAFLP is deposited on the hole injection layer 911 to form the hole transport layer 912. Ta.

[0415] Next, 7-[4-(10-phenyl-9-antryl)phenyl] onto hole transport layer 912 -7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), N,N'-bis (3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluorene-9) -yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn) This results in cgDBCzPA:1,6mMemFLPAPrn=1:0.03 (weight ratio). The light-emitting layer 913 was formed by co-deposition. The film thickness was set to 15 nm.

[0416] Next, on the light-emitting layer 913, 7-[4-(10-phenyl-9-antryl)phenyl]- 7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA) in a film thickness of 20 nm Form and on top of it, 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1, 10-phenanthroline (abbreviated as NBPhen) is deposited at a 15 nm depth, and the electron transport layer 914 is... It was formed.

[0417] Furthermore, lithium oxide is deposited at a 0.1 nm layer on the electron transport layer 914, and then copper phthalosia is added. A 2nm layer of nin (CuPc) is deposited, and 1,3,5-tri(dibenzothiophene-4) is placed on top of it. -yl)benzene (abbreviation: DBT3P-II) and molybdenum oxide in a weight ratio (DBT3 The ratio of P-II (molybdenum oxide) is 2:1, and the thickness is 60 nm. The electron injection layer 915 was formed by deposition.

[0418] Finally, aluminum is deposited onto the electron injection layer 915 to a thickness of 200 nm, and the shadow A second electrode 903, which will serve as the electrode, was formed to obtain the light-emitting element 9. Therefore, the evaporation process was entirely carried out using the resistance heating method.

[0419] The thickness of each layer of the light-emitting element 9 was determined to minimize the frontal brightness of the light emission. The brightness of the emission originating from the transition dipole moment having a component in the vertical direction is relatively increased. This allows for easy evaluation of the light emission.

[0420] Polarization Measurement Next, we will explain the measurement. The detector used is a Hamamatsu Photonics multi-channel spectrophotometer. A Kuss "PMA-12" was used. Edmund op was used in the optical path from the light-emitting element 9 to the detector. A polarizing prism manufactured by Tics was installed, so that only polarization components parallel to the observation direction reached the detector. It was designed to reach the target. The light that passed through the polarizing prism was "PMA-12" (multichannel spectroscopy). The emission was detected using a photometer (manufactured by Hamamatsu Photonics) and the emission spectrum was obtained. At this time, the substrate emitted light. The front of the surface is defined as 0 degrees, and the substrate is rotated in 1-degree increments from 0 to 80 degrees, and at each angle, The light spectrum was measured and the area intensity of the spectrum was plotted.

[0421] ≪Calculation (Simulation)≫ Next, I will explain the calculations. The calculations are performed using the organic device simulator "" manufactured by CYBERNET Corporation. The `setfos` command was used. The parameters included the stacked structure and film thickness of the element, and the refractive index n of each layer. The extinction coefficient k, emission position, and emission spectrum are set, and the transition dipole mode of the emission molecule is determined. The degree of orientation of the ment was used as a variable parameter for fitting (parameter a described later). ). Note that the emission position was assumed to be near the hole transport layer / emission layer interface. Also, the film thickness of each layer was set to Sun The values ​​of the quartz oscillator (rate monitor) of the deposition machine during pull fabrication, the refractive index n, and the extinction coefficient k are for each layer thickness. The results were obtained from the analysis of the film using spectroscopic ellipsometry. The emission spectrum was obtained from the photoexcitation of the thin film. A spectral analysis (PL) was used.

[0422] We defined a parameter 'a' as representing the degree of orientation of the transition dipole moment. That is, a is Of the sum of the components of the transition dipole moment perpendicular to the light-emitting layer and the components parallel to the light-emitting layer, the perpendicular component This represents the proportion of each component. When a=1, the transition dipole moment is only for the component perpendicular to the light-emitting layer. In this state, when a=0, the transition dipole moment has only the component parallel to the light-emitting layer. It is an existing state. When the orientation state of the molecule is isotropic, the transition dipole moment is Since each component is equal in the perpendicular x, y, and z directions, a = 0. It will be 33.

[0423] ≪Fitting of measurement results and calculations (simulations)≫ Figure 29 shows the measured plot and calculated results of the angle-dependent characteristics. The calculation is performed using a=0 (transition dipole mode). (The moment is perfectly horizontal), a=0.16, a=0.33 (the transition dipole moment is randomly distributed) The results for the direction (direction) and a=1 (transition dipole moment is perfectly perpendicular) are shown in the figure. Angle-dependent characteristics Combining the experimental plot of the sex with the calculation results, 84% of the components of the transition dipole moment are The component is parallel to the light-emitting layer, and 16% is perpendicular to it (a=0.16) The calculation results corresponded well with the measured plot. Therefore, the light-emitting layer 913 of the light-emitting element 9 has The transition dipole moment of the light-emitting molecule is such that 84% of the components are parallel to the light-emitting layer 913. Yes, and many of the transition dipole moments are oriented at an angle from the vertical direction of the luminescent layer. It was estimated.

[0424] Based on these results, the luminescent molecules in the luminescent layer are not randomly oriented, but are strongly oriented. It is understood that the light-emitting element according to one aspect of the present invention has relatively good luminous efficiency. It was suggested that the strong orientation of the luminescent molecules is one of the contributing factors. Therefore, the present invention In one embodiment of a light-emitting element, the transition dipole of the light-emitting material (guest material in this embodiment) When the moment is divided into components parallel and perpendicular to the light-emitting layer, the proportion of the parallel component is 80 It is preferable that the percentage is between % and 100%. [Explanation of symbols]

[0425] 100 EL layer 101 Electrode 101a Conductive layer 101b Conductive layer 102 electrode 103 Electrode 103a Conductive layer 103b Conductive layer 104 Electrode 104a conductive layer 104b Conductive layer 111 Hole injection layer 112 Hole transport layer 113 Electron transport layer 114 Electron injection layer 115 Charge generation layer 116 Hole injection layer 117 Hole transport layer 118 Electron transport layer 119 Electron injection layer 123B Emitting layer 123G emissive layer 123R emissive layer 130 Emitting layer 131 Host Materials 132 Guest Materials 140 Bulkhead 150 light-emitting elements 160 Emitting layer 170 Emitting layer 170a Light-emitting layer 170b Emitting layer 180 Observation direction of the detector 181 Components of the transition dipole moment 182 Components of the transition dipole moment 183 Components of the transition dipole moment 185 detectors 200 circuit boards 220 circuit boards 221B area 221G area 221R area 222B area 222G area 222R area 223 Light blocking layer 224B Optical element 224G optical chip 224R optical element 250 light-emitting elements 252 Light-emitting element 254 Light-emitting element 400 EL layer 401 Electrode 402 Electrode 411 Hole injection layer 412 Hole transport layer 413 Electron transport layer 414 Electron injection layer 416 Hole injection layer 417 Hole transport layer 418 Electron transport layer 419 Electron injection layer 420 Emitting layer 421 Host Materials 422 Guest Materials 430 Emitting layer 431 Host Materials 431_1 Organic compounds 431_2 Organic compounds 432 Guest Materials 441 Light-emitting unit 442 Light-emitting unit 445 Charge generation layer 450 light-emitting elements 452 Light-emitting element 801 Pixel Circuit 802 pixel section 804 Drive Circuit Section 804a Scan line drive circuit 804b Signal line drive circuit 806 protection circuit 807 Terminal section 852 transistors 854 transistors 862 Capacitive elements 872 Light-emitting element 900 circuit boards 901 First electrode 902 EL layer 903 Second electrode 911 Hole injection layer 912 Hole transport layer 913 Emitting layer 914 Electron transport layer 915 Electron injection layer 2000 Touch Panel 2001 Touch Panel 2501 Display device 2502R pixels 2502t Transistor 2503c Capacitive element 2503g Scan line drive circuit 2503t Transistor 2509 FPC 2510 circuit board 2510a Insulating layer 2510b flexible substrate 2510c adhesive layer 2511 Wiring 2519 terminal 2521 Insulating layer 2528 Bulkhead 2550R Light-emitting element 2560 Sealing layer 2567BM light shielding layer 2567p anti-reflection layer 2567R colored layer 2570 circuit board 2570a Insulating layer 2570b flexible substrate 2570c adhesive layer 2580R Light-Emitting Module 2590 circuit board 2591 Electrode 2592 Electrode 2593 Insulating layer 2594 Wiring 2595 Touch Sensor 2597 Adhesive layer 2598 Wiring 2599 Connectivity Layer 2601 Pulse voltage output circuit 2602 Current detection circuit 2603 Capacity 2611 Transistors 2612 transistors 2613 Transistors 2621 Electrode 2622 Electrode 8000 Display Module 8001 Top cover 8002 Lower cover 8003 FPC 8004 Touch Sensor 8005 FPC 8006 Display device 8009 Frame 8010 Printed Circuit Board 8011 Battery 8501 Lighting device 8502 Lighting device 8503 Lighting device 8504 Lighting device 9000 cabinets 9001 Display section 9003 Speaker 9005 Operation Keys 9006 Connection terminal 9007 Sensor 9008 Microphone 9050 Operation Buttons 9051 Information 9052 Information 9053 Information 9054 Information 9055 Hinge 9100 Mobile Information Terminal 9101 Mobile Information Terminal 9102 Mobile Information Terminal 9200 Mobile Information Terminal 9201 Mobile Information Terminal

Claims

1. It comprises a first electrode, a second electrode, a light-emitting layer, and an electron transport layer. The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. Between the first electrode and the light-emitting layer, there is a layer containing a compound having at least one of a halogen group and a cyano group. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer has a first material, The S1 level of the host material is higher than the S1 level of the fluorescent material. The T1 level of the host material is lower than the T1 level of the fluorescent material. The energy difference between the S1 level and the T1 level of the host material is greater than 0.2 eV. The LUMO level of the fluorescent material is higher than that of the host material. A light-emitting element wherein the LUMO level of the first material is lower than the LUMO level of the host material.

2. It comprises a first electrode, a second electrode, a light-emitting layer, and an electron transport layer. The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. A layer containing an acceptor is provided between the first electrode and the light-emitting layer. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer has a first material, The S1 level of the host material is higher than the S1 level of the fluorescent material. The T1 level of the host material is lower than the T1 level of the fluorescent material. The energy difference between the S1 level and the T1 level of the host material is greater than 0.2 eV. The LUMO level of the fluorescent material is higher than that of the host material. A light-emitting element wherein the LUMO level of the first material is lower than the LUMO level of the host material.

3. It comprises a first electrode, a second electrode, a light-emitting layer, and an electron transport layer. The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. Between the first electrode and the light-emitting layer, there is a layer containing a compound having at least one of a halogen group and a cyano group. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer has a first material, The first material is a substance having a pyrimidine skeleton, The S1 level of the host material is higher than the S1 level of the fluorescent material. The T1 level of the host material is lower than the T1 level of the fluorescent material. The energy difference between the S1 level and the T1 level of the host material is greater than 0.2 eV. The LUMO level of the fluorescent material is higher than that of the host material. A light-emitting element wherein the LUMO level of the first material is lower than the LUMO level of the host material.

4. It comprises a first electrode, a second electrode, a light-emitting layer, and an electron transport layer. The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. A layer containing an acceptor is provided between the first electrode and the light-emitting layer. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer has a first material, The first material is a substance having a pyrimidine skeleton, The S1 level of the host material is higher than the S1 level of the fluorescent material. The T1 level of the host material is lower than the T1 level of the fluorescent material. The energy difference between the S1 level and the T1 level of the host material is greater than 0.2 eV. The LUMO level of the fluorescent material is higher than that of the host material. A light-emitting element wherein the LUMO level of the first material is lower than the LUMO level of the host material.

5. It comprises a first electrode, a second electrode, a light-emitting layer, and an electron transport layer. The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. Between the first electrode and the light-emitting layer, there is a layer containing a compound having at least one of a halogen group and a cyano group. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer has a first material, The S1 level of the host material is higher than the S1 level of the fluorescent material. The T1 level of the host material is lower than the T1 level of the fluorescent material. The energy difference between the S1 level and the T1 level of the host material is greater than 0.2 eV. The LUMO level of the fluorescent material is higher than that of the host material. A light-emitting element wherein the LUMO level of the first material is 0.05 eV or more lower than the LUMO level of the host material.

6. It comprises a first electrode, a second electrode, a light-emitting layer, and an electron transport layer. The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. A layer containing an acceptor is provided between the first electrode and the light-emitting layer. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer has a first material, The S1 level of the host material is higher than the S1 level of the fluorescent material. The T1 level of the host material is lower than the T1 level of the fluorescent material. The energy difference between the S1 level and the T1 level of the host material is greater than 0.2 eV. The LUMO level of the fluorescent material is higher than that of the host material. A light-emitting element wherein the LUMO level of the first material is 0.05 eV or more lower than the LUMO level of the host material.

7. It comprises a first electrode, a second electrode, a light-emitting layer, and an electron transport layer. The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. Between the first electrode and the light-emitting layer, there is a layer containing a compound having at least one of a halogen group and a cyano group. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer has a first material, The first material is a substance having a pyrimidine skeleton, The S1 level of the host material is higher than the S1 level of the fluorescent material. The T1 level of the host material is lower than the T1 level of the fluorescent material. The energy difference between the S1 level and the T1 level of the host material is greater than 0.2 eV. The LUMO level of the fluorescent material is higher than that of the host material. A light-emitting element wherein the LUMO level of the first material is 0.05 eV or more lower than the LUMO level of the host material.

8. It comprises a first electrode, a second electrode, a light-emitting layer, and an electron transport layer. The light-emitting layer is located between the first electrode and the electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. A layer containing an acceptor is provided between the first electrode and the light-emitting layer. The light-emitting layer comprises a host material and a fluorescent material. The electron transport layer has a first material, The first material is a substance having a pyrimidine skeleton, The S1 level of the host material is higher than the S1 level of the fluorescent material. The T1 level of the host material is lower than the T1 level of the fluorescent material. The energy difference between the S1 level and the T1 level of the host material is greater than 0.2 eV. The LUMO level of the fluorescent material is higher than that of the host material. A light-emitting element wherein the LUMO level of the first material is 0.05 eV or more lower than the LUMO level of the host material.

9. In any one of claims 1 to 8, A light-emitting element in which the light-emitting layer emits blue light.

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