JP7159365B2 - Light-emitting device having a plurality of organic EL elements - Google Patents

Description

The present invention relates to a light-emitting device, a display device, an imaging device, and a moving object having a plurality of organic EL elements.

An organic EL element is an element having a pair of electrodes and an organic compound layer interposed therebetween. A configuration is known in which the pair of electrodes is a reflective electrode having a metal reflective layer and a transparent electrode. In recent years, attention has been focused on organic EL elements driven at a low voltage. These organic EL elements are being put to practical use as light-emitting devices such as thin displays, lighting fixtures, head-mounted displays, and light sources for the printheads of electrophotographic printers, taking advantage of their superior features such as surface-emitting properties, lightness, and visibility. be.

In particular, there is an increasing demand for higher definition of organic EL display devices, and a system using white organic EL elements and color filters (hereinafter referred to as white + CF system) is known. Since the white+CF method is manufactured by vapor-depositing an organic compound layer over the entire surface of the substrate, it has a higher yield than the method using a high-definition metal mask. In addition, since the pixel size and the pitch between pixels are not restricted by the vapor deposition accuracy of the organic compound layer, it is relatively easy to achieve high definition.

On the other hand, when the organic compound layer is provided in common to all the organic EL elements, leakage of drive current is likely to occur between the adjacent organic EL elements via the organic compound layer. As a result, the non-light-emitting pixels slightly emit light due to the influence of the light-emitting pixels, which contributes to the deterioration of the color gamut and efficiency.

Japanese Patent Laid-Open No. 2004-100002 describes that by providing a groove in an insulating layer between pixels, the thickness of the organic compound layer is reduced in that portion. Since the thinned organic compound layer has high resistance, leakage current can be suppressed.

Patent Document 2 describes a configuration in which an end of an insulating partition between pixels is tapered inversely to cut off a portion of an organic compound layer. Leakage current can be suppressed by interrupting the organic compound layer.

JP 2012-216338 A JP 2014-232631 A

The structures described in Patent Documents 1 and 2 have a possibility of deterioration of the sealing layer and a possibility of discontinuity of the upper electrode due to the steep structure.

On the other hand, although it is known that thinning the organic compound layer increases the resistance, if the distance between the reflective electrode and the light-emitting layer is small, optical interference cannot be utilized, resulting in a device with high power consumption. rice field.

An object of the present disclosure is to provide an organic EL element in which leakage current between adjacent organic EL elements is suppressed and power consumption is reduced by utilizing optical interference.

The present invention provides an organic EL device having a reflective electrode, a hole transport region, an electron trapping first light emitting layer, and a light extraction electrode in this order, wherein the thickness of the hole transport region and the first light emitting layer are is an optical distance that intensifies the light emitted from the first light-emitting layer, and the thickness of the hole transport region is smaller than the thickness of the first light-emitting layer. I will provide a.

According to the present invention, it is possible to provide an organic EL element in which leakage current between adjacent organic EL elements is suppressed and power consumption is reduced by utilizing optical interference.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram which shows an example of the light-emitting device which concerns on this invention. A graph showing the relationship between the sheet resistance of the hole transport region and the ratio (I _leak /I _oled ) of the leakage current I _leak to the adjacent organic EL element and the current I _oled flowing through the intended organic EL element. is. 1 is a schematic diagram showing an example of a display device according to an embodiment; FIG. 4 is a graph showing the relationship between hole mobility and the ratio (I _leak /I _oled ) of the leakage current I _leak to an adjacent organic EL element and the current I _oled flowing through the intended organic EL element. Graph showing the relationship between the layer thickness of the first light-emitting layer and the ratio (I _leak /I _oled ) of the leakage current I _leak to the adjacent organic EL element and the current I _oled flowing through the intended organic EL element. be. 1 is a schematic diagram showing an example of a display device according to an embodiment; FIG. It is a mimetic diagram showing an example of an imaging device concerning this embodiment. 1 is a schematic diagram showing an example of a mobile device according to an embodiment; FIG. (a) It is a schematic diagram showing an example of the display apparatus which concerns on this embodiment. (b) It is a schematic diagram showing an example of a foldable display device. It is a schematic diagram which shows an example of the illuminating device which concerns on this embodiment. FIG. 2 is a schematic diagram showing an example of a vehicle having a vehicle lamp according to the present embodiment;

An organic EL device according to the present invention is a device in which leakage current between adjacent organic EL devices is suppressed and power consumption is reduced . , and light extraction electrodes in this order. The sum of the thickness of the hole-transporting region and the thickness of the first light-emitting layer is the optical length that enhances the light emitted by the first light-emitting layer.

By including the thickness of the first emitting layer in the optical length, the thickness of the hole-transporting region can be reduced. As a result, leakage current between the organic EL elements can be reduced.

A sheet resistance in the in-plane direction per pixel of the hole transport region of 4.0×10 ⁷ Ω/□ or more is preferable because leakage current between the organic EL elements can be suppressed. In addition, since the electron trap type light-emitting layer is provided, the optical distance between the reflective electrode and the light-emitting point can be set to a reinforcing distance. The transmissive electrode is also called a light extraction electrode.

FIG. 1 is a schematic cross-sectional view showing the configuration of one embodiment of the light emitting device of the present invention. In the light emitting device of FIG. 1, an organic EL element 10 having a reflective electrode 2, an organic compound layer 4, a light extraction electrode 5, a sealing layer 6, and a color filter 7 is described on a substrate 1. The organic EL element is an RGB light emitting device. Three types are described. The organic compound layer 4 and the light extraction electrode 5 are formed continuously in the in-plane direction of the substrate 1 . An insulating layer 3 is provided in the inter-element region between the three adjacent organic EL elements 10R, 10G, and 10B. More specifically, an insulating layer 3 is provided at the end of the reflective electrode 2 . The insulating layer is for ensuring insulation between the light reflecting electrodes 2B, 2G and 2R and the light extraction electrode 5, and for forming the light emitting region into a desired shape accurately.

The organic compound layer 4 may be formed as a common layer for a plurality of organic EL elements. The common layer is arranged across a plurality of organic EL elements, and can be formed by applying a coating method such as spin coating or a vapor deposition method to the entire surface of the substrate. The fact that the organic compound layer is a common layer can also be said to mean that one organic compound layer is provided with a plurality of reflective electrodes.

In this embodiment, the reflective electrode 2 is an anode, and the light extraction electrode 5 is a cathode.

In this embodiment, the organic compound layer 4 is composed of a plurality of layers. The organic compound layer has a hole transport layer 41 , an electron block layer 42 , a first light emitting layer 43 , a second light emitting layer 44 and an electron transport layer 45 . It may have an organic compound layer other than this. The organic compound layer disposed between the reflective electrode and the first light-emitting layer can be collectively referred to as a hole transport region. The hole-transporting region may have a hole-injecting layer, a hole-transporting layer, an electron-blocking layer, and the like.

The organic EL element is electrically connected to adjacent organic EL elements through the hole transport region. In the organic EL element according to this embodiment, the sheet resistance of the hole transport region is 4.0×10 ⁷ at a current of 0.1 nA/pixel in order to suppress leakage current between adjacent organic EL elements. Ω/□ or more. More preferably. It is more preferably 6.0×10 ⁷ Ω/□ or more.

FIG. 2 shows the relationship between the sheet resistance of the hole transport region and the ratio (I _leak /I _oled ) of the leakage current I _leak to the adjacent organic EL element and the current I _oled flowing through the intended organic EL element. is a graph showing A method for measuring I _oled and I _leak will be described by taking a red organic EL device as an example. The R pixel is energized while the adjacent green organic EL element (also called G pixel) and blue organic EL element (also called B pixel) are short-circuited (potential=0V, that is, short-circuited). At this time, the current flowing from the reflective electrode of the R pixel to the light extraction electrode of the R pixel is I _oled ), and the sum of the currents flowing from the reflective electrode of the R pixel to the reflective electrode of the G or B pixel is I _leak . Note that the sheet resistance in the in-plane direction per pixel was calculated by the method of formula (1), and was calculated using the potential value at which _Ioled was 0.1 nA/pixel.
Rs = dI _leak /dV*W/L (Formula 1)
Here, W is the sum of the widths of adjacent pixels, L is the distance to the adjacent pixels, and V is the voltage applied to the pixels. dI _leak /dV is the differential resistance.

The hole-transporting region may be composed of multiple organic compound layers. The hole-transporting region may be composed of a hole-injecting layer, a hole-transporting layer, an electron-blocking layer, and the like. Each of them may be used alone or may be used in combination. Further, each layer may be composed of a single compound, or may be composed of a plurality of types of compounds. That is, the organic compound layer may have one type of compound, or may have a plurality of types of compounds.

When the hole-transporting region has a hole-transporting layer, the layer thickness of the hole-transporting layer is preferably less than 10 nm. This is because the thinner the layer thickness of the hole transport layer with high mobility, the thinner the layer thickness of the hole transport layer on the side wall of the insulating layer, and the greater the resistance value between the organic EL elements. In particular, the layer thickness of the hole transport layer is preferably 7 nm or less, more preferably 5 nm or less.

Further, from the viewpoint of in-plane resistance, the hole mobility in the in-plane direction of the substrate of the hole transport layer is preferably 2.5×10 ⁻³ cm ² /V*sec or less, and 1.0 More preferably, it is x10 ^-3 cm ² /V*sec or less.

FIG. 4 is a graph showing the relationship between the hole mobility and the ratio (I _leak /I _oled ) of the leakage current I _leak to the adjacent organic EL element and the current I _oled flowing through the intended organic EL element. is.

When the hole-transporting region further has an electron-blocking layer, in order to suppress hole accumulation at the interface between the hole-transporting layer and the electron-blocking layer and the interface between the electron-blocking layer and the first light-emitting layer, It is preferable that the ionization potential difference is small.

It is preferable to form a stepwise energy structure in which the ionization potential increases in this order from the work function of the reflective electrode to the first light-emitting layer. That is, it is preferable that the ionization potential of the hole-transporting layer is positioned between the work function of the reflective electrode and the ionization potential of the first light-emitting layer. Moreover, it is preferable that the ionization potential of the electron blocking layer is positioned between the ionization potential of the hole transport layer and the ionization potential of the first light-emitting layer.

The ionization potential of an organic compound layer composed of multiple types of compounds can be estimated by photoelectron yield spectroscopy, photoelectron spectroscopy, and the like.

By forming the hole transport layer as a mixed layer of two or more kinds of hole transport materials, properties such as hole mobility and ionization potential can be controlled. Furthermore, since the effective distance of the hopping site is increased, the side wall of the insulating layer tends to have a higher resistance. When the hole-transporting layer contains the electron-blocking layer compound, the ionization potential approaches that of the electron-blocking layer, and hole accumulation at the interface between the hole-transporting layer and the electron-blocking layer can be suppressed. Further, it is more preferable if the compound used for the electron blocking layer has a high resistance, since the resistance value of the hole transporting layer increases.

The hole transport layer may have a first compound and a second compound. The hole mobility of the first compound is preferably 1.0×10 ⁻³ cm ² /V*sec or less, more preferably 5.0×10 ⁻⁴ cm ² /V*sec or less. .

The HOMO of the first compound may be lower than the HOMO of the second compound. The HOMO of the first compound may be at least 0.1 eV lower than the HOMO of the second compound.

When the sum of the weight of the first compound and the weight of the second compound is 100 wt%, the weight ratio of the first compound is preferably 50 wt% or more and 95 wt% or less, and 75 wt% or more and 95 wt% or less. is more preferred.

When the hole-transporting region has a hole-injecting layer, the hole-injecting layer is an organic compound layer disposed between the reflective electrode and the hole-transporting layer. The hole injection layer may comprise a compound with an electron affinity of 5.0 eV or greater. The layer thickness of the hole injection layer is preferably 10 nm or less in order to suppress leakage current between adjacent organic EL elements.

Examples of compounds having an electron affinity of 5.0 eV or more include hexaazatriphenylene derivatives and tetracyanoquinodimethane derivatives, with hexaazatriphenylene hexacyano compounds being preferred. The organic compound contained in the hole injection layer may have a LUMO of −5.0 eV or less.

When the material of the organic compound layer is analyzed and the material changes, it can be said that it is another organic compound layer. A change in material indicates an increase or decrease in the type of material, and does not indicate that only the weight ratio is changed.

The organic EL device according to this embodiment has a light-emitting layer. The number of light-emitting layers may be singular or plural. When there is more than one, it may have a first light-emitting layer and a second light-emitting layer, and may have another organic compound layer between the first light-emitting layer and the second light-emitting layer.

The first light-emitting layer and the second light-emitting layer may emit any emission wavelength. For example, the first emitting layer may emit blue and the second emitting layer may emit green and red to emit white. Alternatively, the first light-emitting layer may emit green and red to emit white. Further, white light may be emitted by setting complementary colors such as blue and yellow between the first light-emitting layer and the second light-emitting layer. Among them, a structure in which the first light-emitting layer does not emit blue light, that is, a structure in which the first light-emitting layer emits light other than blue is preferable. When the light-emitting layer emitting blue light is close to the metal electrode, the surface plasmon loss is large and the power consumption is increased. Note that the fact that the light-emitting layer emits blue light means that it has a light-emitting material that emits blue light.

In order to reduce the power consumption of a light-emitting device, it is preferable to increase the luminous efficiency of the light-emitting device by optical interference.

In this embodiment, by using an electron-trapping-type light-emitting layer as the light-emitting layer, it is possible to maintain an optical distance for intensifying light emission even when the hole-transporting region is made thin. Since the electron-trapping light-emitting layer mainly emits light from the cathode-side interface, the distance from the light-emitting point to the reflective electrode is the sum of the thickness of the hole-transporting region and the thickness of the light-emitting layer. That is, even when the thickness of the hole transport region is reduced, the distance of optical interference can be maintained by adopting a structure in which the thickness of the light-emitting layer compensates for it.

The first light emitting layer is an electron trap type light emitting layer. The term "electron trapping type" means that the light-emitting layer has a first compound and a second compound, and the electron affinity of the compound having a higher weight ratio among the two is smaller than the electron affinity of the other compound. Electron affinity can also be estimated by the lowest unoccupied molecular orbital (LUMO) of a molecule. When estimating by LUMO, the electron-trapping emissive layer shows that the LUMO of the compound having a larger weight ratio between the two is higher than the LUMO of the other compound. A higher LUMO indicates closer to the vacuum level, which can be rephrased as a shallow LUMO and a small absolute value of the LUMO. Electron affinity is generally represented by an absolute value, and LUMO is generally represented by a real number. Specifically, electron affinity is represented by a positive number and LUMO is represented by a negative number.

A pyrene derivative, an anthracene derivative, a fluorene derivative, a naphthalene derivative, or the like may be used as the first compound to constitute the electron-trapping light-emitting layer. When the first compound is the compound with the highest weight ratio in the light-emitting layer, the first compound is called a host material or host.

Examples of the second compound include pyrene derivatives, fluoranthene derivatives, fluorene derivatives, chrysene derivatives, anthracene derivatives and the like. In the first compound and the second compound, a derivative refers to a state in which the basic skeleton has a substituent or a condensed ring. For example, fluoranthene derivatives include benzofluoranthene, dibenzofluoranthene, indenobenzo[k]fluoranthene, and the like. When the first compound is called host, the second compound is called dopant or guest.

The substituent contained in the derivative may include an alkyl group, an aryl group having 6 to 60 carbon atoms, a heteroaryl group having 6 to 60 carbon atoms, and the like.

The distance between the first light-emitting layer and the reflective electrode preferably satisfies the following formula in order to enhance the light emitted from the first light-emitting layer. Although the layer thickness of the first light-emitting layer is preferably small, the layer thickness of the light-emitting layer has little effect on leakage current. can be done.
(0.12-(φr/4π))<L/λ1<(0.18-(φr/4π)) (2)
Here, λ1 is the minimum wavelength of the peaks of the emission spectrum emitted by the first light-emitting layer, and φr is the phase shift at the reflective electrode. By satisfying Expression (2), surface plasmon loss can be suppressed and power consumption can be reduced.

Moreover, when the hole-transporting region has a hole-transporting layer and an electron-blocking layer, the first light-emitting layer more preferably satisfies the following formula (3).
d(1st−EML)>d(HTL)+d(EBL) (3)
Here, d(1st-EML) is the layer thickness of the first light-emitting layer. Also, d(HTL) and d(EBL) are the layer thicknesses of the hole-transporting layer and the electron-blocking layer, respectively.

The first emissive layer may be 35 nm or less. A thickness of 35 nm or less is preferable because leakage current between adjacent organic EL elements is further suppressed. This verification will be described later.

The organic EL device according to this embodiment may have an electron transport layer between the light emitting layer and the transmissive electrode. The electron transport layer is selected in consideration of the balance with the hole mobility of the hole transport layer. The electron transport layer is composed of aromatic hydrocarbon compounds such as chrysene derivatives, fluoranthene derivatives and anthracene derivatives; heterocyclic compounds such as phenanthroline derivatives, diazafluoranthene derivatives and azaanthracene derivatives; It can be selected from metal complexes.

In this embodiment, the RGB sub-pixels may be arranged in any of the stripe arrangement, square arrangement, delta arrangement, and Bayer arrangement.

The reflective electrode of the organic EL element according to this embodiment is preferably made of a metal material having a reflectance of 80% or more. Specifically, metals such as Al and Ag, and alloys obtained by adding Si, Cu, Ni, Nd, Ti, and the like thereto can be used. Reflectance refers to the reflectance at the emission wavelength emitted from the light-emitting layer. Moreover, the reflective electrode may have a barrier layer on the surface on the light extraction side. Metals such as Ti, W, Mo and Au and their alloys are preferable as materials for the barrier layer.

The insulating layer of the organic EL element according to the present embodiment is a silicon nitride (SiN) layer, a silicon oxynitride (SiON) layer, or a silicon oxide (SiN) layer formed using a chemical vapor deposition method (CVD method). SiO) layer.

In order to increase the resistance of the organic compound layer between the organic EL elements, the layer thickness of the organic compound layer is preferably formed thinner on the sidewalls of the insulating layer than on the region of the organic EL element. Specifically, by increasing the angle between the side wall of the insulating layer and the substrate and the thickness of the insulating layer, the thickness of the side wall can be reduced. The angle between the side wall of the insulating layer and the substrate can also be called the taper angle of the insulating layer. The region of the organic EL element is the region where the reflective electrode is provided.

The angle formed by the insulating layer and the substrate is preferably 60 degrees or more and 90 degrees or less. Also, the thickness of the insulating layer is preferably 40 nm or more and 150 nm or less. The insulating layer may have grooves in the regions between the reflective electrodes. By providing the groove, the layer thickness of the organic compound layer can be reduced and the resistance can be increased. A groove can also be described as a depression in the planarization layer between the reflective electrodes.

The light extraction electrode of the organic EL device according to the present embodiment is a semi-transmissive reflective layer having a property of transmitting part of the light reaching its surface and reflecting the other part (that is, semi-transmissive reflectivity). It's okay. The light extraction electrode is made of, for example, a single metal such as magnesium or silver, an alloy containing magnesium or silver as a main component, or an alloy material containing alkali metal or alkaline earth metal. The light extraction electrode may have a laminated structure as long as it has a preferable transmittance.

The sealing layer of the organic EL element according to this embodiment can be formed using a chemical vapor deposition method (CVD method) or an atomic layer deposition method (ALD method). The encapsulation layer is made of a material with extremely low permeability to oxygen and moisture from the outside, such as a silicon nitride (SiN) layer, a silicon oxynitride (SiON) layer, an aluminum oxide layer, a silicon oxide layer, and a titanium oxide layer. may be In addition, it may be in the form of a single layer or a laminate as long as it has sufficient moisture blocking performance. When taking the form of lamination, it is preferable to use a combination of SiN and aluminum oxide. When laminating, it may be a lamination of three or more layers.

The hole-transporting region of the organic EL device according to this embodiment may be composed of compounds shown in HT-1 to HT-38 below.

The compound used for the hole-transporting region may be a compound represented by the following general formula [1] or general formula [2].

In general formula [1], Ar ₁ to Ar ₃ are each independently selected from a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic group. The aryl group includes a phenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, a naphthyl group and a spirofluorenyl group. Heterocyclic groups include dibenzofuranyl, dibenzothiophenyl, thiophenyl, furanyl, and carbazolyl groups.

In general formula [2], Ar ₄ is a substituted or unsubstituted aryl group. The aryl group is any one of a phenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, a dibenzofuranyl group, a dibenzothiophenyl group and a naphthyl group.

Ar ₅ to Ar ₈ are each independently selected from substituted or unsubstituted aryl groups and substituted or unsubstituted heterocyclic groups. Aryl groups are each independently selected from phenyl, biphenyl, terphenyl, fluorenyl, phenanthrenyl and pyrenyl groups. Heterocyclic groups include dibenzofuranyl, dibenzothiophenyl, thiophenyl, furanyl, and carbazolyl groups.

A light-emitting device according to the present invention may be a display device having active elements such as transistors. The display device has a horizontal driving circuit, a vertical driving circuit, and a display portion, and the display portion has the light emitting device according to the present invention.

FIG. 3 is a schematic diagram showing an example of the display device according to this embodiment. The display device 15 has a display area 11 , a horizontal drive circuit 12 , a vertical drive circuit 13 and a connection section 14 . The display area may have a light emitting device according to the present invention.

The display device according to this embodiment may be used in the display section of an image forming apparatus such as a multifunction printer or an inkjet printer. In that case, it may have both a display function and an operation function.

The display device according to the present embodiment may be used in the display section of an imaging device, such as a camera, having an optical system having a plurality of lenses and an imaging device that receives light that has passed through the optical system. The imaging device may have a display unit that displays information acquired by the imaging element. Further, the display section may be a display section exposed to the outside of the imaging device, or may be a display section arranged within the viewfinder.

The display device according to this embodiment may have color filters having red, green, and blue colors. The color filters may be arranged in a delta arrangement of said red, green and blue.

The display device according to this embodiment may be used in the display section of a mobile terminal. In that case, it may have both a display function and an operation function.

Next, the organic EL element of this embodiment will be described.

The organic EL element of this embodiment has at least an anode and a cathode, which are a pair of electrodes, and an organic compound layer disposed between these electrodes. In the organic EL device of the present embodiment, the organic compound layer may be a single layer or a multilayer structure as long as it has a light-emitting layer.

Here, in the case where the organic compound layer is a laminate composed of a plurality of layers, the organic compound layer includes, in addition to the light emitting layer, a hole injection layer, a hole transport layer, an electron blocking layer, a charge generation layer, a hole/exciton blocking layer, an electron It may have a transport layer, an electron injection layer, and the like. Also, the light-emitting layer may be a single layer, or may be a laminate composed of a plurality of layers.

In the organic EL device of the present embodiment, the light-emitting layer may consist of a light-emitting material alone, or may be a mixed layer with other compounds. Here, when the light-emitting layer is a layer composed of a light-emitting material and another compound, the other compound may be a host and may have an assist.

Here, the host is a compound having the largest weight ratio among the compounds constituting the light-emitting layer. A guest, a dopant, or a light-emitting material is a compound whose weight ratio is smaller than that of the host among the compounds constituting the light-emitting layer, and is responsible for the main light emission. The assist is a compound that has a weight ratio smaller than that of the host among the compounds constituting the light-emitting layer and assists the light emission of the guest. Note that the assistant may be called a second host. When the composition of the light-emitting layer of the organic EL element is assumed to be uniform, the composition of the entire light-emitting layer can be determined by analyzing a portion of the light-emitting layer.

Here, the concentration of the guest in the light-emitting layer is preferably 0.01% by weight or more and 20% by weight or less, more preferably 0.1% by weight or more and 5.0% by weight or less, relative to the entire light-emitting layer. preferable.

As the host used together with the guest, it is preferable to use a host with a high LUMO (a material whose LUMO is closer to the vacuum level). When an electron-trapping light-emitting material is used, the LUMO of the light-emitting material is low. Therefore, by using a material with a high LUMO as a host, the guest in the light-emitting layer can receive more electrons supplied to the host in the light-emitting layer. Because you can.

The light-emitting layer according to this embodiment may be a single layer or multiple layers, and it is possible to mix red light emission, which is the light emission color of this embodiment, by including a light-emitting material having another emission color. A multi-layer means a state in which a light-emitting layer and another light-emitting layer are laminated. In this case, the emission color of the organic EL element is not limited. More specifically, it may be white or a neutral color. In the case of white, when one light-emitting layer emits red light, another light-emitting layer emits a color other than red, ie, blue or green.

The organic EL device according to this embodiment can be formed by vapor deposition or coating film formation. Vapor deposition is preferably carried out in a high vacuum. A known coating method can be used for the coating film formation, and the coating may be applied together with an arbitrary organic solvent.

The organic compound according to this embodiment can be used as a constituent material of an organic compound layer other than the light-emitting layer that constitutes the organic EL element of this embodiment. Specifically, it may be used as a constituent material for an electron transport layer, an electron injection layer, a hole transport layer, a hole injection layer, a hole blocking layer, and the like. In this case, the emission color of the organic EL element is not particularly limited. More specifically, it may be white or a neutral color.

Here, in addition to the organic compound according to the present embodiment, conventionally known low-molecular-weight and high-molecular-weight hole-injecting compounds or hole-transporting compounds, host compounds, light-emitting compounds, and electron-injecting compounds can be used as necessary. A polarizing compound or an electron-transporting compound or the like can be used together.

Examples of these compounds are given below. As the hole-injecting and transporting material, a material having high hole mobility is preferable so that holes can be easily injected from the anode and the injected holes can be transported to the light-emitting layer. In order to suppress deterioration of film quality such as crystallization in the organic EL device, a material having a high glass transition temperature is preferred. Low-molecular-weight and high-molecular-weight materials with hole injection and transport properties include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly(vinylcarbazole), poly(thiophene), and others. A conductive polymer can be mentioned. Furthermore, the above hole injection transport materials are also suitably used for the electron blocking layer.

The electron-transporting material can be arbitrarily selected from those capable of transporting electrons injected from the cathode to the light-emitting layer, and is selected in consideration of the balance with the hole mobility of the hole-transporting material. . Materials having electron transport properties include oxadiazole derivatives, oxazole derivatives, pyrazine derivatives, triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, organoaluminum complexes, condensed ring compounds (e.g., fluorene derivatives, naphthalene derivatives, chrysene derivatives, anthracene derivatives, etc.). Furthermore, the above electron-transporting materials are also suitably used for the hole blocking layer.

[Use of organic EL element]
FIG. 6 is a schematic diagram showing an example of the display device according to this embodiment. Display device 1000 may have touch panel 1003 , display panel 1005 , frame 1006 , circuit board 1007 , and battery 1008 between upper cover 1001 and lower cover 1009 . The touch panel 1003 and display panel 1005 are connected to flexible printed circuits FPC 1002 and 1004 . Circuits including transistors are arranged on the circuit board 1007 . The battery 1008 may not be provided unless the display device is a portable device, and even if the display device is a portable device, it is not necessary to be provided at this position.

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

FIG. 7 is a schematic diagram showing an example of an imaging device according to this embodiment. The imaging device 1100 may have a viewfinder 1101 , a rear display 1102 , an operation unit 1103 and a housing 1104 . The viewfinder 1101 may have a display device according to this embodiment. In that case, the display device may display not only the image to be captured, but also environmental information, imaging instructions, and the like. The environmental information may include the intensity of outside light, the direction of outside light, the moving speed of the subject, the possibility of the subject being blocked by an obstacle, and the like.

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

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

The display device according to this embodiment may have color filters having red, green, and blue colors. The color filters may be arranged in a delta arrangement of said red, green and blue.

The display device according to this embodiment may be used in the display section of a mobile terminal. In that case, it may have both a display function and an operation function. Mobile terminals include mobile phones such as smart phones, tablets, head-mounted displays, and the like.

FIG. 8 is a schematic diagram showing an example of a mobile device according to this embodiment. Electronic device 1200 includes display portion 1201 , operation portion 1202 , and housing 1203 . The housing 1203 may include a circuit, a printed board including the circuit, a battery, and a communication portion. The operation unit 1202 may be a button or a touch panel type reaction unit. The operation unit may be a biometric recognition unit that recognizes a fingerprint and performs unlocking or the like. A mobile device having a communication unit can also be called a communication device.

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

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

Also, the frame 1301 and the display portion 1302 may be curved. Its radius of curvature may be between 5000 mm and 6000 mm.

FIG. 9B is a schematic diagram showing another example of the display device according to this embodiment. A display device 1310 in FIG. 9B is configured to be foldable, and is a so-called foldable display device. The display device 1310 has a first display portion 1311 , a second display portion 1312 , a housing 1313 and a bending point 1314 . The first display unit 1311 and the second display unit 1312 may have the light emitting device according to this embodiment. The first display portion 1311 and the second display portion 1312 may be a seamless display device. The first display portion 1311 and the second display portion 1312 can be separated at a bending point. The first display unit 1311 and the second display unit 1312 may display different images, or the first and second display units may display one image.

FIG. 10 is a schematic diagram showing an example of a lighting device according to this embodiment. The illumination device 1400 may have a housing 1401 , a light source 1402 , a circuit board 1403 , an optical film 1404 and a light diffusion section 1405 . The light source may have the organic EL element according to this embodiment. The optical filter may be a filter that enhances the color rendering of the light source. The light diffusing portion can effectively diffuse the light from the light source such as lighting up and deliver the light over a wide range. If necessary, a cover may be provided on the outermost part.

The illuminating device may have its light emitting position divided into areas. The light emitting device according to this embodiment is effective in suppressing light emission in an unintended area.

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

Moreover, the lighting device according to the present embodiment may have a heat dissipation section. The heat radiating part is for radiating the heat inside the device to the outside of the device, and may be made of metal, liquid silicon, or the like, which has a high specific heat.

FIG. 11 is a schematic diagram of an automobile, which is an example of a mobile object according to the present embodiment. The automobile has a tail lamp, which is an example of a lamp. The automobile 1500 may have a tail lamp 1501, and may be configured to turn on the tail lamp when a brake operation or the like is performed.

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

Automobile 1500 may have a body 1503 and a window 1502 attached thereto. The window may be a transparent display unless it is a window for checking the front and rear of the automobile. The transparent display may have an organic EL element according to this embodiment. In this case, constituent materials such as electrodes of the organic EL element are made of transparent members.

A mobile object according to the present embodiment may be a ship, an aircraft, a drone, or the like. The moving body may have a body and a lamp provided on the body. The lighting device may emit light to indicate the position of the aircraft. The lamp has the organic EL element according to this embodiment.

The organic EL element according to the present embodiment is controlled in light emission luminance by a TFT, which is an example of a switching element, and an image can be displayed by each light emission luminance by providing the organic EL elements in a plurality of planes. The switching elements according to the present embodiment are not limited to TFTs, and may be transistors made of low-temperature polysilicon or active matrix drivers formed on a substrate such as a Si substrate. On the substrate can also mean inside the substrate. This is selected depending on the definition. For example, in the case of a definition of about QVGA at 1 inch, it is preferable to provide the organic EL element on the Si substrate. By driving the display device using the organic EL element according to the present embodiment, it is possible to stably display images with good image quality even for a long period of time.

(Example 1)
Device D100 was constructed as follows. Panel characteristics such as leakage between pixels and power consumption of the manufactured light emitting device were evaluated.

As shown in FIG. 1, a reflective electrode 2 is patterned on the substrate to form an insulating layer between pixels. Here, the insulating layer is formed of a silicon oxide film, and the thickness of the insulating layer is set to 65 nm. The taper angles of the sidewalls of the insulating layer were 80° and 75° on the pixel opening side and the inter-pixel side, respectively. Further, the pixel array was a delta array, the distance between pixel openings was 1.4 μm, and the distance between reflective electrodes was 0.6 μm. A film of the following compound 1 was formed to a thickness of 3 nm as a hole injection layer on the reflective electrode.

Exemplified Compound HT-9 was deposited to a thickness of 15 nm as a hole transport layer, and Exemplified Compound HT-27 was deposited to a thickness of 10 nm as an electron blocking layer. The first light-emitting layer was formed with a thickness of 10 nm by using the following compound 2 as a host material at a weight ratio of 97% and the following compound 3 as a light-emitting dopant at a weight ratio of 3%. The hole mobilities of exemplified compounds HT-9, HT-27, and compound 2 were measured to be 2×10 ⁻³ cm ² /V*sec, 5×10 ⁻⁴ cm ² /V*sec, and 1 It was ×10 ⁻³ cm ² /V*sec.

The second light-emitting layer was formed by using Compound 2 as a host material at a weight ratio of 99% and Compound 4 below as a light-emitting dopant at a weight ratio of 1%.

The electron transport layer was formed by forming a film of the following compound 5 to a thickness of 110 nm. The electron injection layer was formed by depositing LiF to a thickness of 0.5 nm. A film of MgAg alloy with a thickness of 10 nm was formed as a light extraction electrode. The ratio of Mg and Ag was 1:1. Thereafter, a SiN film of 1.5 μm was formed as a sealing layer by the CVD method.

Table 1 shows the specifications of the display device, which are the prerequisites for power consumption calculation in this embodiment. The pixel aperture ratio was set to 50%, and the aperture ratio of the sub-pixels was set to 16.7%, which is the same for R, G, and B. In this study, the display device with the specifications shown in Table 1 emits white light with a color temperature of 6500 K (CIE (x, y) = (0.313, 0.329)) and a luminance of 500 cd/ ^cm2 . Calculated power required. Specifically, the currents required for the R, G, and B pixels were calculated from the measured luminous efficiency. In this analysis, the driving voltage was assumed to be 10.0 V, and the power consumption was calculated from the required current value.

Here, the ratio I _leak /I _oled of the current I _leak between pixels to I _oled when the current I _oled flowing through the pixel is 0.1 [nA/pixel] is used as an index of inter-pixel leakage.

D101 to D108 were produced in the same manner as D100 except that the layer thickness of each organic compound layer was set as shown in Table 2. Table 2 shows the layer thicknesses and evaluation results of D100 to D108.

As for the inter-pixel leak ratio, 0.35 or less is indicated by ◯, and a larger value is indicated by x. Power consumption of 400 mW or less was evaluated as ◯, and power consumption greater than 400 mW was evaluated as x.

(Example 2)
D109 to D114 of this example are the same as D108 except that the hole transport layer is a mixed layer of Exemplified Compound HT37 and Exemplified Compound HT27. Table 3 is a table showing the mixed concentration of the hole transport layer and the mobility measurement results. By using a mixed layer as the hole transport layer, it is possible not only to control the mobility, but also to dramatically increase the in-plane resistance by increasing the concentration of the material with low mobility, that is, HT27. Become.

FIG. 4 is a graph showing the relationship between the hole mobility and the inter-pixel leak ratio. Here, since the elements in Table 3 have the same layer thickness, the power consumption determined by the optical interference conditions is the same. From FIG. 4, it can be seen that as the mobility of the hole transport layer increases, the inter-pixel leakage ratio tends to increase. In particular, it can be seen that the slope increases when the hole mobility exceeds 2.5×10 ⁻³ cm ² /V*sec.

As a result of this study, it was found that the mobility of the hole transport layer is preferably 2.5×10 ⁻³ cm ² /V*sec or less. Moreover, when the mobility of the hole transport layer is low like D114, the layer thickness of the hole transport region can be increased. However, if the mobility is too low, the driving voltage will increase, so the layer thickness may be increased within a range in which this is taken into account. The layer thickness of the hole transport layer is preferably 10 nm or less.

(Example 3)
In this example, D112 was compared with D115 and D116. As shown in Table 4, D115 and D116 are the same as D112 except that the structure of the hole transport layer is different.

It is known that inserting a mixed layer of a hole-transporting layer and an electron-blocking layer between the hole-transporting layer and the electron-blocking layer reduces the energy barrier and reduces the accumulation of holes.

This reduction in hole accumulation can be a factor in lowering the resistance in the in-plane direction. Therefore, in order to confirm the effect of the mixed layer, devices D112, D115 and D116 were compared. Device D115 is the same as D112 except that after forming a film of HT-37 as a hole transport material to a thickness of 5 nm, a mixed layer of HT-37 and HT-27 of 50:50 is formed to a thickness of 5 nm. Device D116 is the same as device D112, except that HT-37 is formed as a hole transport material to a thickness of 5 nm and the mixed hole transport layer is not formed.

Looking at Table 4, D116 having H37 with high hole mobility has a high inter-pixel leakage ratio of 1.32. D115, in which a mixed layer of these was provided between the hole transport layer and the electron blocking layer, had a leak ratio of 1.81.

From this, the resistance component of inter-pixel leakage is not due to the decrease in hole accumulation due to the decrease in the energy barrier due to the mixed layer, but the bulk component of the hole transport layer and the electron block layer, that is, the layer thickness, mainly contributes. It can be seen that

FIG. 5 shows the relationship between the layer thickness of the first light-emitting layer and the ratio (I _leak /I _oled ) of the leakage current I _leak to the adjacent organic EL element and the current I _OLED flowing through the intended organic EL element. It is a graph showing Based on the evaluation of the leakage current described above, when the threshold at which I _leak /I _oled is 0.35 or less is estimated, it is found that the thickness of the first light emitting layer is preferably 35 nm or less.

As described above, according to the present invention, it is possible to provide an organic EL element in which leakage current between adjacent organic EL elements is suppressed and power consumption is reduced by utilizing optical interference.

REFERENCE SIGNS LIST 1 substrate 2 reflective electrode 3 insulating layer 4 organic compound layer 5 light extraction electrode 6 sealing layer 7 color filter 10 light emitting element 1000 display device 1001 upper cover 1002 flexible printed circuit 1003 touch panel 1004 flexible printed circuit 1005 display panel 1006 frame 1007 circuit board 1008 Battery 1009 Lower Cover 1100 Imaging Device 1101 Viewfinder 1102 Rear Display 1103 Operation Unit 1104 Housing 1200 Electronic Device 1201 Display Unit 1202 Operation Unit 1203 Housing 1300 Display Device 1301 Frame 1302 Display Unit 1303 Base 1310 First Display Device 1311 1312 second display unit 1313 housing 1314 bending point 1500 automobile 1501 tail lamp 1502 window 1503 vehicle body

Claims (27)

An organic EL device having a reflective electrode, a hole transport region, an electron trapping first light emitting layer, and a light extraction electrode in this order,
the sum of the thickness of the hole-transporting region and the thickness of the first light-emitting layer is an optical length that enhances the light emitted by the first light-emitting layer;
The organic EL device , wherein the thickness of the hole transport region is smaller than the thickness of the first light emitting layer . The sheet resistance of the hole transport region is 4.0×10 at 0.1 nA/pixel ⁷ 2. The organic EL element according to claim 1, which is Ω/□. the hole-transporting region has a hole-transporting layer and an electron-blocking layer,
2. The organic EL device according to claim 1 , wherein the hole transport layer has a hole mobility of 2.5×10 ⁻³ cm ² /V*sec or less. the hole-transporting region has a hole-transporting layer and an electron-blocking layer,
When the layer thickness of the first emitting layer is d (1st-EML), the layer thickness of the hole transport layer is d (HTL), and the layer thickness of the electron blocking layer is d (EBL), the following formula (3 ), the organic EL element according to any one of claims 1 to 3 .
d(1st-EML) > d(HTL) + d(EBL) (3)
In formula (3), d(1st-EML) is the layer thickness of the first light-emitting layer, and d(HTL) and d(EBL) are the layer thicknesses of the hole-transporting layer and the electron-blocking layer, respectively. the hole-transporting region has a hole-transporting layer and an electron-blocking layer,
The hole transport layer has a mixed layer of a first compound and a second compound,
The hole mobility of the first compound is lower than the hole mobility of the second compound,
1 to 1, wherein the weight ratio of the first compound is equal to or greater than the weight ratio of the second compound when the sum of the weight of the first compound and the weight of the second compound is 100 wt % . 5. The organic EL device according to any one of 4 . 6. The organic EL device according to claim 5 , wherein the weight ratio of said first compound is 50 wt % or more and 95 wt % or less. 7. The organic EL device according to claim 5 , wherein said first compound has a hole mobility of 1×10 ⁻³ cm ² /V*sec or less. 8. The organic EL according to any one of claims 5 to 7 , wherein the electron blocking layer is disposed between the hole transport layer and the first light-emitting layer and contains the first compound. element. 9. The mixed layer according to any one of claims 5 to 8, wherein two types selected from compounds represented by the following general formula [1] or the following general formula [2] are mixed. organic EL element.

In general formula [1], Ar ₁ to Ar ₃ are each independently selected from a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic group. The aryl group is selected from phenyl group, biphenyl group, terphenyl group, fluorenyl group, naphthyl group and spirofluorenyl group, and the heterocyclic group is dibenzofuranyl group, dibenzothiophenyl group, thiophenyl group and furanyl group. group, carbazolyl group.

In general formula [2], Ar ₄ is a substituted or unsubstituted aryl group. The aryl group is any one of a phenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, a dibenzofuranyl group, a dibenzothiophenyl group and a naphthyl group.
Ar ₅ to Ar ₈ are each independently selected from substituted or unsubstituted aryl groups and substituted or unsubstituted heterocyclic groups. The aryl group is selected from a phenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, a phenanthrenyl group and a pyrenyl group. The heterocyclic group is selected from a dibenzofuranyl group, a dibenzothiophenyl group, a thiophenyl group, a furanyl group and a carbazolyl group. 10. The organic EL element according to claim 9 , wherein the mixed layer has two kinds of compounds represented by the general formula [2]. 6. The organic EL device according to claim 5 , wherein the mixed layer has a layer thickness of less than 10 nm. 12. The organic EL device according to claim 11 , wherein the mixed layer has a layer thickness of 5 nm or less. 13. The method according to any one of claims 1 to 12 , further comprising a hole injection layer in contact with the reflective electrode, wherein the hole injection layer contains a compound having an electron affinity of 5.0 eV or more. Organic EL device. 14. The organic EL element according to any one of claims 1 to 13 , further comprising a second light emitting layer arranged between the first light emitting layer and the light extraction electrode. Having another organic EL element different from the organic EL element,
15. The organic EL element according to any one of claims 1 to 14, wherein the hole transport region is arranged continuously from the organic EL element to the other organic EL element. An organic EL device having a reflective electrode, a hole transport region, an electron trapping first light emitting layer, and a light extraction electrode in this order,
the distance between the reflective electrode and the end portion of the first light-emitting layer on the side of the light extraction electrode is a distance that enhances the light emitted by the first light-emitting layer ;
The organic EL device , wherein the thickness of the hole transport region is smaller than the thickness of the first light emitting layer . the hole-transporting region has a hole-transporting layer;
17. The organic EL device according to claim 16 , wherein the hole transport layer comprises a first compound and a second compound having a higher HOMO than the first compound. 18. The organic EL device according to claim 17 , wherein the hole transport layer is a mixed layer of the first compound and the second compound. 19. When the sum of the weight of the first compound and the weight of the second compound is 100 wt %, the weight ratio of the first compound is equal to or greater than the weight ratio of the second compound. The described organic EL device. 20. The organic EL device according to claim 19 , wherein the weight ratio of said first compound is 50 wt% or more and 95 wt% or less. 21. The organic EL element according to any one of claims 18 to 20 , wherein the mixed layer has a layer thickness of 5 nm or less. Having another organic EL element different from the organic EL element,
22. The organic EL element according to any one of claims 17 to 21 , wherein the hole transport layer is arranged continuously from the organic EL element to the other organic EL element. 23. The organic EL element according to any one of claims 16 to 22 , further comprising a second light emitting layer arranged between said first light emitting layer and said light extraction electrode. 24. A display device comprising a light emitting device according to any one of claims 1 to 23 and an active element connected to the light emitting device. An imaging device having an optical system having a plurality of lenses and an imaging device that receives light that has passed through the optical system,
24. An imaging apparatus, comprising: a display section for displaying information acquired by an imaging device, the display section comprising the light emitting device according to claim 1 . A moving object comprising: a lamp having the light emitting device according to any one of claims 1 to 23 ; and a body provided with the lamp. 24. An illumination device comprising: a light source having the light emitting device according to claim 1 ; and an optical film provided on a light extraction side of the light source.

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