JP2019080044A - Light-emitting device with plurality of organic el element - Google Patents

Abstract

To provide a light-emitting device capable of suppressing generation of a leak current between adjacent organic EL elements and suppressing power consumption by utilizing optical interference.SOLUTION: The light-emitting device includes a plurality of organic EL elements. Each of the organic EL elements includes a reflector 2, hole transport regions 41, 42, an electron trap type light-emitting layer 43 and light extraction electrode 5 in this order. The sheet resistance of the hole transport region is at least 4.0×10Ω/* at an electric current of 0.1 nA/pixel, and a total of a thickness of the hole transport region and a thickness of the electron trap type light-emitting layer is an optical distance for combining and intensifying the light emitted by the electron trap type light-emitting layer.SELECTED DRAWING: Figure 1

Description

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

  The organic EL element is an element having a pair of electrodes and an organic compound layer disposed therebetween. It is known that the pair of electrodes are a reflective electrode having a metal reflective layer and a transparent electrode. In recent years, organic EL elements driven at low voltage have attracted attention. This organic EL element is being put into practical use as a light emitting device such as a thin display, a luminaire, a head mounted display, a light source for a print head of an electrophotographic printer, and the like while making use of excellent features such as surface light emission characteristics, light weight and visibility. is there.

  In particular, the demand for higher definition of the organic EL display device is increasing, and a method using a white organic EL element and a color filter (hereinafter, white + CF method) is known. The white + CF method is manufactured by vapor-depositing the organic compound layer on the entire surface of the substrate, so the yield is high compared to the method using a high definition metal mask. In addition, since the pixel size and the pitch between the pixels are not limited by the deposition accuracy of the organic compound layer, high definition is relatively easy.

  On the other hand, when the organic compound layer is provided in common to all the organic EL elements, a leak 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 pixel slightly emits light due to the influence of the light emitting pixel, which contributes to the reduction of the color gamut and the reduction of the efficiency.

  Patent Document 1 describes that, by providing a groove in an insulating layer between pixels, thinning of the organic compound layer at that portion is described. Since the thinned organic compound layer has high resistance, leakage current can be suppressed.

  Patent Document 2 describes a configuration in which a part of an organic compound layer is interrupted by forming an end of an insulating partition between pixels into a reverse taper shape. Leakage current can be suppressed by interrupting the organic compound layer.

JP 2012-216338 A JP, 2014-223631, A

  With the structures described in Patent Document 1 and Patent Document 2, there is a possibility that the sealing layer may be deteriorated or the upper electrode may be broken due to the steep structure.

  On the other hand, although it is known that the resistance is increased by thinning the organic compound layer, optical interference can not be utilized when the distance between the reflective electrode and the light emitting layer is small, and therefore, the element has high power consumption. The

  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 is a light emitting device having a plurality of organic EL elements, wherein the organic EL element has a reflective electrode, a hole transport region, an electron trap type light emitting layer, and a transmissive electrode in this order, and the hole transport The sheet resistance of the region is 4.0 × 10 ⁷ Ω / □ at a current of 0.1 nA / pixel, and the sum of the thickness of the hole transport region and the thickness of the electron trap type light emitting layer is the above Provided is a light emitting device characterized in that it is an optical distance to reinforce light emitted from an electron trap type light emitting layer.

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

It is a cross-sectional schematic diagram which shows an example of the light-emitting device which concerns on this invention. Graph showing the relationship between the sheet resistance in the hole transport region and the ratio (I _leak / I _oled ) between the leakage current I _leak to the adjacent organic EL element and the current I _oled flowing to the intended organic EL element It is. It is a schematic diagram which shows an example of the display apparatus which concerns on this embodiment. It is the graph which showed the relationship between a hole mobility and ratio (I _leak / I _oled ) of the leak current I _leak to the adjacent organic EL element, and the electric current I _oled flowed to the intended organic EL element. The graph _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 to the intended organic EL element is there. It is a schematic diagram showing an example of the display apparatus which concerns on this embodiment. It is a schematic diagram showing an example of the imaging device concerning this embodiment. It is a schematic diagram showing an example of the portable apparatus which concerns on this embodiment. (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 bendable display. It is a schematic diagram which shows an example of the illuminating device which concerns on this embodiment. It is a schematic diagram which shows an example of the motor vehicle which has a lamp for vehicles concerning this embodiment form etc.

The light emitting device according to the present invention is a light emitting device in which the leakage current between adjacent organic EL elements is suppressed and the power consumption is reduced. The organic EL element has a reflective electrode, a hole transport region, an electron trap type light emitting layer, and a transmissive electrode, and the sheet resistance in the in-plane direction per pixel of the hole transport region is 4.0 × 10 ⁷ Ω /. Since it is □ or more, the leak current between 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 a distance of reinforcement. The transmission electrode is also called a light extraction electrode.

  FIG. 1 is a schematic cross-sectional view showing the configuration of an embodiment of a light emitting device according to the present invention. In the light emitting device shown in 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 on a substrate 1 is described. Three types are described. The organic compound layer 4 and the light extraction electrode 5 are continuously formed in the in-plane direction of the substrate 1. In addition, an insulating layer 3 is provided in an inter-element region between three adjacent organic EL elements 10R, 10G, and 10B. More specifically, the insulating layer 3 is provided at the end of the reflective electrode 2. The insulating layer is intended to ensure the insulation between the light reflective electrodes 2B, 2G and 2R and the light extraction electrode 5 and to make the light emitting region into a desired shape accurately.

  The organic compound layer 4 may be formed as a common layer of a plurality of organic EL elements. The common layer is disposed across a plurality of organic EL elements, and can be formed by performing a coating method such as spin coating or an evaporation method on the entire surface of the substrate. The fact that the organic compound layer is a common layer can also be said that a single organic compound layer is provided with a plurality of reflective electrodes.

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

  In the present 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. You 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 transport region may have a hole injection layer, a hole transport layer, an electron block layer, and the like.

The organic EL element is electrically connected to the adjacent organic EL element 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 the leak current between the adjacent organic EL elements. It is considered as Ω / □ or more. More preferably. More preferably, it is 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 ) between the leakage current I _leak to the adjacent organic EL element and the current I _oled flowing to the intended organic EL element Is a graph showing The measuring method of I _oled and I _leak is illustrated and illustrated with a red organic EL element. The R pixel is energized in a state where the adjacent green organic EL element (also referred to as G pixel) and the blue organic EL element (also referred to as B pixel) are shorted (potential = 0 V, that is, shorted). 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 current sum flowing from the reflective electrode of the R pixel to the reflective electrode of the G pixel or B pixel is I _leak . The sheet resistance in the in-plane direction per pixel was calculated by the method of equation (1), and the sheet resistance was calculated using the value of the potential at which I _oled is 0.1 nA / pixel.
Rs = dI _leak / dV * W / L (equation 1)

Here, W is the sum of the widths of the adjacent pixels, L is the distance to the adjacent pixels, and V is the voltage applied to the pixels. dI _leak / dV is a differential resistance.

  The hole transport region may be composed of a plurality of organic compound layers. The hole transport region may be composed of a hole injection layer, a hole transport layer, an electron block layer, and the like. Each of them may be used alone, or a plurality of them may be used in combination. Each layer may be composed of a single compound or a plurality of compounds. That is, the organic compound layer may have one type of compound or more than one type of compound.

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

Further, from the viewpoint of in-plane direction resistance, the hole mobility in the in-plane direction of the substrate of the hole transport layer is desirably 2.5 × 10 ⁻³ cm ² / V * sec or less, and 1.0 × it is more preferably not more than ^{10 -3 cm 2 / V * sec} .

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

  When the hole transport region further has an electron block layer, in order to suppress hole accumulation at the interface between the hole transport layer and the electron block layer and at the interface between the electron block layer and the first light emitting layer, The difference in ionization potential is preferably small.

  It is preferable to form a step-like energy structure in which the ionization potential is sequentially increased 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 transport layer be disposed between the work function of the reflective electrode and the ionization potential of the first light emitting layer. In addition, it is preferable that the ionization potential of the electron block layer be disposed between the ionization potential of the hole transport layer and the ionization potential of the first light emitting layer.

  The ionization potential of the organic compound layer composed of a plurality of types of compounds can be estimated by photoelectron spectroscopy and photoelectron spectroscopy.

  The hole transport layer can control characteristics such as hole mobility and ionization potential by forming a mixed layer of two or more types of hole transport materials. Furthermore, since the effective distance of the hopping site is increased, the resistance of the side wall of the insulating layer can be increased. When the hole transport layer contains the compound of the electron block layer, the ionization potential approaches the electron block layer, so that the accumulation of holes at the interface between the hole transport layer and the electron block layer can be suppressed. If the compound used for the electron blocking layer is a high-resistance compound, the resistance value of the hole transport layer is further increased, which is more preferable.

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, and 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 0.1 eV or more lower than the HOMO of the second compound.

  When the total 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 is 75 wt% or more and 95 wt% or less Is more preferred.

  When the hole transport region has a hole injection layer, the hole injection layer is an organic compound layer disposed between the reflective electrode and the hole transport layer. The hole injection layer may have a compound having an electron affinity of 5.0 eV or more. The layer thickness of the hole injection layer is preferably 10 nm or less in order to suppress the leak current between the adjacent organic EL elements.

  Examples of the compound having an electron affinity of 5.0 eV or more include a hexaazatriphenylene derivative and a tetracyanoquinodimethane derivative, and a hexaazatriphenylene nylene hexacyano compound is preferable. The organic compound of the hole injection layer may have a LUMO of -5.0 eV or less.

  If the material of the organic compound layer is analyzed and the material changes, it can be called 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 changes.

  The organic EL element according to the present embodiment has a light emitting layer. The light emitting layer may be singular or plural. When it is plural, 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 light emission wavelength. For example, the first light emitting layer may emit blue and the second light emitting layer may emit white by emitting green and red. In addition, the first light emitting layer may emit white by emitting green and red. In addition, white may be emitted by setting the relationship between complementary colors such as blue and yellow in the first light emitting layer and the second light emitting layer. Among them, a configuration in which the first light emitting layer does not emit blue, that is, a configuration in which the first light emitting layer emits other than blue is preferable. When the light emitting layer emitting blue light approaches the metal electrode, the surface plasmon loss is large and the power consumption is increased. In addition, that a light emitting layer emits blue means having a light emitting material which emits blue light.

  In order to reduce the power consumption of the light emitting device, it is preferable to enhance the light emission efficiency of the light emitting device by optical interference.

  In this embodiment, by forming the light emitting layer as the electron trap type light emitting layer, even when the hole transporting region is thinned, it is possible to maintain an optical distance to strengthen light emission. Since the electron trap type light emitting layer mainly emits light at the interface on the cathode side, the distance from the light emitting point to the reflective electrode is the sum of the thickness of the hole transport 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 the optical interference can be maintained by compensating the thickness of the light emitting layer.

  The first light emitting layer is an electron trap type light emitting layer. The electron trap type indicates that the light emitting layer has the first compound and the second compound, and the electron affinity of the compound having a large weight ratio of 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 it estimates by LUMO, an electron trap type light emitting layer represents that LUMO of the compound with a large weight ratio of both is higher than LUMO of the other compound. The fact that LUMO is high indicates that it is closer to the vacuum level, and it can be rephrased that LUMO is shallow and the absolute value of LUMO is small. Generally, electron affinity is represented by an absolute value, and LUMO is represented by a real number. Specifically, electron affinity is represented by a positive number, and LUMO is represented by a negative number.

  In order to form an electron trap type light emitting layer, a pyrene derivative, an anthracene derivative, a fluorene derivative, a naphthalene derivative or the like may be included as the first compound. When the first compound is the compound having the largest weight ratio in the light emitting layer, the first compound is called 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, the derivative means a state having a substituent or a fused ring with respect to the basic skeleton. For example, fluoranthene derivatives include benzofluoranthene, dibenzofluoranthene, indenobenzo [k] fluoranthene and the like. When the first compound is called a host, the second compound is called a dopant or a 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 equation in order to intensify the light emitted by the first light emitting layer. Although it is preferable that the layer thickness of the first light emitting layer is small, the light emitting layer should be a light emitting device in which the leak current is suppressed even when the layer thickness is large because the size of the layer has little influence on the leak current. Can.
(0.12− (φr / 4π)) <L / λ1 <(0.18− (φr / 4π)) (2)
Here, λ 1 is the minimum wavelength of the peaks of the emission spectrum emitted by the first light emitting layer, and φ r is the phase shift at the reflective electrode. By satisfying the equation (2), surface plasmon loss can be suppressed and power consumption can be reduced.

In the case where the first light emitting layer 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 transport layer and the electron block layer, respectively.

  The first light emitting layer may be 35 nm or less. If the thickness is 35 nm or less, the leakage current between adjacent organic EL elements is further suppressed, which is preferable. This verification will be described later.

  The organic EL device according to the present embodiment may have an electron transport layer between the light emitting layer and the transmission electrode. The electron transport layer is selected in consideration of the balance of the hole mobility of the hole transport layer. The electron transport layer is formed of an aromatic hydrocarbon compound such as chrysene derivative, fluoranthene derivative or anthracene derivative, a phenanthroline derivative, a heterocyclic compound such as diazafluoranthene derivative or azaanthracene derivative, an organic compound such as Alq3, beryllium complex or magnesium complex It can be selected from metal complexes.

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

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

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

  In order to increase the resistance of the organic compound layer between the organic EL elements, it is preferable that the layer thickness of the organic compound layer be thinner on the side wall of the insulating layer than in the region of the organic EL element. Specifically, the thickness of the side wall can be reduced by increasing the angle between the side wall of the insulating layer and the substrate and the thickness of the insulating layer. The angle between the side wall of the insulating layer and the substrate may be referred to as the taper angle of the insulating layer. The area of the organic EL element is an area where the reflective electrode is provided.

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

  The light extraction electrode of the organic EL element according to this embodiment is a semi-transmissive reflective layer having a property of transmitting part of the light reaching the surface and reflecting the other part (i.e., transflective property). May be there. The light extraction electrode is formed 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 an alkali metal or an alkaline earth metal. The light extraction electrode may have a laminated configuration 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 sealing layer is made of a material having extremely low permeability to external oxygen and moisture, such as a silicon nitride (SiN) layer, a silicon oxynitride (SiON) layer, an aluminum oxide layer, a silicon oxide, and a titanium oxide. May be done. Moreover, if there is sufficient water blocking performance, it may be in the form of a single layer or a laminate. In the case of the form of lamination, it is preferable to use SiN and aluminum oxide in combination. When laminating, three or more layers may be laminated.

  The hole transport region of the organic EL element according to the present embodiment may be composed of the following compounds represented by HT-1 to HT-38.

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

In the 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. Examples of the aryl group include phenyl group, biphenyl group, terphenyl group, fluorenyl group, naphthyl group and spirofluorenyl group. The heterocyclic group includes dibenzofuranyl group, dibenzothiophenyl group, thiophenyl group, furanyl group and carbazolyl group.

In the general formula [2], Ar ₄ is a substituted or unsubstituted aryl group. The aryl group is any 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 a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic group. The aryl group is independently selected from a phenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, a phenanthrenyl group and a pyrenyl group. The heterocyclic group includes dibenzofuranyl group, dibenzothiophenyl group, thiophenyl group, furanyl group and carbazolyl group.

  The light emitting device according to the present invention may be a display device having an active element such as a transistor. The display device includes a horizontal drive circuit, a vertical drive circuit, and a display unit, and the display unit includes the light emitting device according to the present invention.

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

  The display device according to the present embodiment may be used in a display unit of an image forming apparatus such as a multi-function printer and an inkjet printer. In that case, both the display function and the operation function may be provided.

  The display device according to the present embodiment may be used in a display unit of an imaging device including an optical system having a plurality of lenses, such as a camera, and an imaging device that receives light passing through the optical system. The imaging device may have a display unit that displays information acquired by the imaging device. Further, the display unit may be a display unit exposed to the outside of the imaging device or a display unit disposed in the finder.

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

  The display device according to the present embodiment may be used in a display unit of a portable terminal. In that case, both the display function and the operation function may be provided.

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

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

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

  In the organic EL device of the present embodiment, the light emitting layer may be made of only a light emitting material, or may be a mixed layer with another compound. 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 further have an assist.

  Here, the host is a compound having the largest weight ratio among the compounds constituting the light emitting layer. Further, the guest, the dopant or the light emitting material is a compound having a weight ratio smaller than that of the host among the compounds constituting the light emitting layer, and is a compound responsible for main light emission. The assist is a compound which has a smaller weight ratio than the host among the compounds constituting the light emitting layer and assists the light emission of the guest. The assist may be called a second host. When the composition of the light emitting layer of the organic EL element is regarded as uniform, it can be regarded as the composition of the whole light emitting layer by analyzing a part 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 with respect to the whole light emitting layer, and more preferably 0.1% by weight or more and 5.0% by weight or less preferable.

  In addition, as a host used with a guest, it is preferable to use a host with a high LUMO (a material with a LUMO closer to a vacuum level). When an electron trap type light emitting material is used, the guest of the light emitting layer receives more electrons supplied to the host of the light emitting layer by using a material having a high LUMO as the host because the LUMO of the light emitting material is low. It is because it can.

  The light emitting layer according to the present embodiment may be a single layer or a plurality of layers, and by including a light emitting material having another light emitting color, it is possible to mix the light emission with red light which is the light emitting color of the present embodiment. The term "multilayer" means a state in which a light emitting layer and another light emitting layer are stacked. In this case, the luminescent color of the organic EL element is not limited. More specifically, it may be white or neutral. In the case of white, when one light emitting layer emits red light, another light emitting layer emits a color other than red, that is, blue or green.

  The organic EL element which concerns on this embodiment can perform film forming by vapor deposition or application | coating film forming. The deposition is preferably performed in high vacuum. The coating film formation can be performed using a known coating method, and may be coated with any organic solvent.

  The organic compound which concerns on this embodiment can be used as a constituent material of organic compound layers other than the light emitting layer which comprises the organic EL element of this embodiment. Specifically, it may be used as a constituent material of 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 luminescent color of the organic EL element is not particularly limited. More specifically, it may be white or neutral.

  Here, in addition to the organic compound according to the present embodiment, if necessary, a hole injecting compound or hole transporting compound of a low molecular weight system or a polymer system which is conventionally known, a compound serving as a host, a light emitting compound, an electron injection The organic compound or the electron transporting compound can be used together.

  Examples of these compounds are given below. As the hole injecting and transporting material, a material having a high hole mobility so as to facilitate the injection of holes from the anode and transport the injected holes to the light emitting layer is preferable. Moreover, in order to suppress deterioration of film quality, such as crystallization, in the organic EL element, a material having a high glass transition temperature is preferable. Examples of low molecular weight and high molecular weight materials having hole injection transport capability include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly (vinylcarbazole), poly (thiophene), and the like A conductive polymer is mentioned. Furthermore, the above-mentioned hole injecting and transporting material is 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, etc. . Materials having electron transport performance include oxadiazole derivatives, oxazole derivatives, pyrazine derivatives, triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, organoaluminum complexes, condensed ring compounds (for example, fluorene derivatives, naphthalene derivatives, Chrysene derivatives, anthracene derivatives and the like). Furthermore, the above-mentioned electron transporting material is suitably used also for the hole blocking layer.

[Use of organic EL element]
FIG. 6 is a schematic view showing an example of a display device according to the present embodiment. The display device 1000 may include a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 1007, and a battery 1008 between the upper cover 1001 and the lower cover 1009. The flexible printed circuit FPCs 1002 and 1004 are connected to the touch panel 1003 and the display panel 1005. A circuit including a transistor is disposed on the circuit board 1007. The battery 1008 may not be provided if the display device is not a portable device, and even if it 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 a display portion of an imaging device including an optical unit having a plurality of lenses and an imaging element that receives light passing through the optical unit. The imaging device may have a display unit that displays information acquired by the imaging device. Further, the display unit may be a display unit exposed to the outside of the imaging device or a display unit disposed in the finder. The imaging device may be a digital camera or a digital video camera.

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

  Since the timing suitable for imaging is a short time, it is better to display 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 more suitably used than these devices and liquid crystal display devices for which display speed is required.

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

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

  The display device according to the present embodiment may be used in a display unit of a portable terminal. In that case, both the display function and the operation function may be provided. As a mobile terminal, mobile phones, such as a smart phone, a tablet, a head mounted display, etc. are mentioned.

  FIG. 8 is a schematic view showing an example of a portable device according to the present embodiment. The electronic device 1200 includes a display portion 1201, an operation portion 1202, and a housing 1203. The housing 1203 may include a circuit, a printed circuit board including the circuit, a battery, and a communication unit. The operation unit 1202 may be a button or a touch panel type reaction unit. The operation unit may be a biometric recognition unit that recognizes a fingerprint and performs lock release or the like. A portable device having a communication unit can also be referred to as a communication device.

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

  A frame 1301 and a base 1303 for supporting the display portion 1302 are provided. The base 1303 is not limited to the form shown in FIG. The lower side of the frame 1301 may double as a base.

  In addition, the frame 1301 and the display portion 1302 may be bent. The curvature radius may be 5000 mm or more and 6000 mm or less.

  FIG. 9B is a schematic view showing another example of the display device according to the present embodiment. The display device 1310 in FIG. 9B is configured to be foldable, and is a so-called foldable display device. The display device 1310 includes 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 the present embodiment. The first display portion 1311 and the second display portion 1312 may be one display device without a joint. The first display portion 1311 and the second display portion 1312 can be divided at a bending point. The first display unit 1311 and the second display unit 1312 may display different images, or one image may be displayed by the first and second display units.

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

  The lighting device may have its light emitting position divided into areas. The light emitting device according to the present embodiment is effective in suppressing light emission in an unintended region.

  The lighting device is, for example, a device that lights a room. The illumination 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. The power supply circuit is a circuit that converts an alternating voltage into a direct voltage. Also, white means color temperature 4200K and neutral white means color temperature 5000K. The lighting device may have a color filter.

  Moreover, the illuminating device which concerns on this embodiment may have a thermal radiation part. The heat radiating portion is for releasing the heat in the apparatus to the outside of the apparatus, and examples thereof include metals with high specific heat, liquid silicon and the like.

  FIG. 11 is a schematic view of an automobile which is an example of a mobile object according to the present embodiment. The said motor vehicle 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 light the tail lamp when a brake operation or the like is performed.

  The tail lamp 1501 may have the organic EL element according to the present embodiment. The tail lamp may have a protective member that protects the organic EL element. The protective member has high strength to a certain extent, and the material is not limited as long as it is transparent, but is preferably made of polycarbonate or the like. The polycarbonate may be mixed with a flange carboxylic acid derivative, an acrylonitrile derivative or the like.

  The car 1500 may have a car body 1503 and a window 1502 attached thereto. The window may be a transparent display if it is not a window for checking the front and back of the car. The transparent display may have the organic EL element according to the present embodiment. In this case, the constituent material such as the electrode of the organic EL element is formed of a transparent member.

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

  In the organic EL element according to the present embodiment, the light emission luminance is controlled by a TFT which is an example of a switching element, and by providing the organic EL elements in a plurality of planes, an image can be displayed by each light emission luminance. The switching element according to this embodiment is not limited to the TFT, and may be an active matrix driver formed on a substrate such as a transistor formed of low temperature polysilicon or a Si substrate. The substrate can also be said to be in the substrate. This is selected according to the definition. For example, in the case of 1 inch and a definition of about QVGA, 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, stable display can be achieved with good image quality and long-term display.

Example 1
The element D100 was configured as follows. Panel characteristics such as leak between pixels of the manufactured light emitting device and power consumption were evaluated.

  As shown in FIG. 1, the reflective electrode 2 is pattern-formed on the substrate, and an insulating layer is formed between the pixels. Here, the insulating layer is formed of a silicon oxide film, and the thickness of the insulating layer is 65 nm. The taper angles of the side walls of the insulating layer were 80 ° and 75 °, respectively, on the pixel opening side and between the pixels. The pixel arrangement was a delta arrangement, in which the distance between pixel apertures was 1.4 μm and the distance between reflective electrodes was 0.6 μm. The following compound 1 was deposited to a thickness of 3 nm as a hole injection layer on the reflective electrode.

As the hole transport layer, the exemplified compound HT-9 was deposited to 15 nm, and as the electron blocking layer, the exemplified compound HT-27 to 10 nm. The first light emitting layer was formed to a thickness of 10 nm so that the weight ratio of the following compound 2 as a host material was 97% and the weight of the following compound 3 as a light emitting dopant was 3%. The hole mobility of this exemplified compound HT-9, HT-27, and compound 2 was measured respectively 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 to have the compound 2 as a host material in a weight ratio of 99% and the following compound 4 as a light emitting dopant in a weight ratio of 1%.

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

Table 1 shows display device specifications as a premise of power consumption calculation in this example. The aperture ratio of the pixel is 50%, and the aperture ratio of the sub-pixel is 16.7% which is uniform for R, G, and B. In this study, a display having the specifications shown in Table 1 emits white light (CIE (x, y) = (0.313, 0.329)) with a color temperature of 6500 K and a luminance of 500 cd / cm ^2. The required power was calculated. Specifically, the required current of R pixel, G pixel, and B pixel was calculated from the luminous efficiency obtained by the measurement. In this analysis, power consumption was calculated from the required current value, assuming that the drive voltage is 10.0V.

Here, the ratio I _leak / I _oled of the current I _leak between the pixels to I _oled when the current I _oled flowing to the pixel is 0.1 [nA / pixel] is adopted as the index of the _leak between the pixels.

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

  The inter-pixel leak rate was 0.35 or less as よ り 大 き い, and the larger one was as x. The power consumption was 400 mW or less and よ り 大 き い was larger.

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

FIG. 4 is a graph showing the relationship between the hole mobility and the inter-pixel leak rate. Here, since the elements in Table 3 have the same layer thickness, the power consumption determined under the optical interference condition is equal. It can be seen from FIG. 4 that the inter-pixel leak ratio tends to increase as the mobility of the hole transport layer increases. In particular, it can be seen that the slope increases as the hole mobility becomes larger than 2.5 × 10 ⁻³ cm ² / V * sec.

As a result of this examination, it was found that the mobility of the hole transport layer is preferably 2.5 × 10 ⁻³ cm ² / V * sec or less. When the mobility of the hole transport layer is small as in D114, the layer thickness of the hole transport region can be increased. However, if the mobility is too low, the drive voltage increases, so the layer thickness may be increased as long as it is taken into consideration. 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 configuration of the hole transport layer is different.

  It is known that by inserting a mixed layer of a hole transport layer and an electron block layer between the hole transport layer and the electron block layer, the energy barrier becomes smaller and the hole accumulation becomes smaller.

  The decrease in the accumulation of holes can be a cause of the in-plane resistance decrease. Therefore, in order to confirm the effect of the mixed layer, comparison of elements D112, D115 and D116 was performed. The element D115 is the same as D112 except that a 50:50 mixed layer of HT-37 and HT-27 is formed 5 nm after forming 5 nm HT-37 as a hole transport material. The device D116 is the same as D112 except that HT-37 as a hole transport material is deposited to a thickness of 5 nm and the mixed hole transport layer is not deposited.

  Referring to Table 4, D116 having H37 with high hole mobility has a high inter-pixel leak ratio of 1.32. In addition, in the case of D115 in which the mixed layer thereof was provided between the hole transport layer and the electron block layer, the leak ratio was 1.81.

  From this, the resistance component of the inter-pixel leak is mainly due to the bulk components of the hole transport layer and the electron block layer, that is, the layer thickness, not due to the reduction of the hole accumulation due to the reduction of the energy barrier by the mixed layer. Know that

FIG. 5 shows the relationship between the layer thickness of the first light emitting layer and the ratio (I _leak / I _oled ) between the leakage current I _leak to the adjacent organic EL element and the current I _OLED flowing to the intended organic EL element Is a graph representing It is understood that the layer thickness of the first light emitting layer is preferably 35 nm or less when the threshold value at which I _leak / I _oled is 0.35 or less is estimated based on the above evaluation of the leak current.

  As described above, according to the present invention, it is possible to provide an organic EL element in which power consumption is reduced by suppressing leakage current between adjacent organic EL elements and 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 view finder 1102 rear display 1103 operation unit 1104 housing 1200 electronic device 1201 display 1202 operation unit 1203 housing 1300 display device 1301 frame 1302 display unit 1303 base 1310 display device 1311 first display unit 1312 second display unit 1313 housing 1314 bending point 1500 automobile 1501 tail lamp 1502 window 503 body

Claims (25)

A light emitting device having a plurality of organic EL elements,
The organic EL device has a reflective electrode, a hole transport region, an electron trap type first light emitting layer, and a light extraction electrode in this order,
The hole transport region is disposed as a common layer to the plurality of organic EL elements,
The sheet resistance of the hole transport region is 4.0 × 10 ⁷ Ω / □ or more at a current of 0.1 nA / pixel,
A light emitting device, wherein the sum of the thickness of the hole transport region and the thickness of the first light emitting layer is an optical distance which enhances the light emitted from the electron trap type light emitting layer. 2. The light emitting device according to claim 1, wherein the sheet resistance of the hole transport region is 6.0 × 10 ⁷ Ω / □ or more at a current of 0.1 nA / pixel.   The light emitting device according to claim 1, wherein a layer thickness of the hole transport region is smaller than a layer thickness of the first light emitting layer.   The light emitting device according to any one of claims 1 to 3, wherein the hole transport region has a hole transport layer and an electron block layer. 5. The light emitting device according to claim 4, wherein the hole mobility of the hole transport layer is 2.5 × 10 ⁻³ cm ² / V * sec or less. When the layer thickness of the first light 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 light emitting device according to claim 5, wherein
d (1st-EML)> d (HTL) + d (EBL) (3)
In Formula (2), d (1st-EML) is a layer thickness of the first light emitting layer, and d (HTL) and d (EBL) are layer thicknesses of the hole transport layer and the electron block layer, respectively. The hole transport layer has a first compound and a second compound,
The hole mobility of the first compound is 1 × 10 ⁻³ cm ² / V * sec or less,
The weight ratio of the first compound is 50 wt% or more and 95 wt% or less when the total of the weight of the first compound and the weight of the second compound is 100 wt%. A light emitting device according to any one of the preceding claims.   The light emitting device according to claim 7, wherein the electron blocking layer comprises a first compound. It further comprises a second light emitting layer disposed between the first light emitting layer and the light extraction electrode,
The light emitting device according to any one of claims 1 to 7, which emits white light. A light emitting device having a plurality of organic EL elements,
The organic EL device has a reflective electrode, an organic compound layer, and a light extraction electrode in this order,
The organic compound layer is disposed as a common layer to the plurality of organic EL elements,
The organic compound layer has a hole transport layer, an electron block layer, and a first light emitting layer in this order,
The first light emitting layer is an electron trap type light emitting layer,
The distance between the reflective electrode and the first light emitting layer is an optical distance that enhances the light emission of the first light emitting layer,
The layer thickness of the hole transport layer is less than 10 nm,
A light emitting device characterized in that the hole mobility of the hole transport layer and the electron block layer is 2.5 × 10 ⁻³ cm ² / V * sec or less. The light emitting device according to any one of claims 1 to 9, wherein the optical distance satisfies the following formula (2).
(0.12− (φr / 4π)) <L / λ1 <(0.18− (φr / 4π)) (2)
Here, λ 1 is the minimum wavelength of the peaks of the emission spectrum emitted by the first light emitting layer, and φ r is the phase shift at the reflective electrode. The hole transport layer has a first compound and a second compound,
The hole mobility of the first compound is 1 × 10 ⁻³ cm ² / V * sec or less,
The weight ratio of the first compound is 50 wt% or more and 95 wt% or less when the total of the weight of the first compound and the weight of the second compound is 100 wt%. The light emitting device as described.   The light emitting device according to claim 12, wherein the weight ratio of the first compound is 75 wt% or more and 95 wt% or less.   The light emitting device according to claim 12, wherein the electron blocking layer comprises a first compound. A light emitting device having a plurality of organic EL elements,
The organic EL device has a reflective electrode, a hole transport region, an electron trap type first light emitting layer, and a light extraction electrode in this order,
The hole transport region is disposed as a common layer to the plurality of organic EL elements,
The distance between the reflective electrode and the first light emitting layer is an optical distance that enhances the light emission of the first light emitting layer,
The layer thickness of the hole transport layer is less than 10 nm,
The light-emitting device, wherein the hole transport layer has a compound represented by the following general formula [1] or general formula [2].

In the 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. Examples of the aryl group include phenyl group, biphenyl group, terphenyl group, fluorenyl group, naphthyl group and spirofluorenyl group. The heterocyclic group includes dibenzofuranyl group, dibenzothiophenyl group, thiophenyl group, furanyl group and carbazolyl group.

In the general formula [2], Ar ₄ is a substituted or unsubstituted aryl group. The aryl group is any 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 a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic group. The aryl group is independently selected from a phenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, a phenanthrenyl group and a pyrenyl group. The heterocyclic group includes dibenzofuranyl group, dibenzothiophenyl group, thiophenyl group, furanyl group and carbazolyl group.   The light emitting device according to claim 15, wherein the hole transport layer has a plurality of types of compounds represented by the general formula [1] or the general formula [2].   The electron injection method according to any one of claims 1 to 16, further comprising a hole injection layer in contact with the reflective electrode, wherein the hole injection layer includes a compound having an electron affinity of 5.0 eV or more. Light emitting device.   The light emitting device according to claim 17, wherein a layer thickness of the hole transport layer is 5 nm or less. A second light emitting layer is provided between the first light emitting layer and the light extraction electrode,
The first light emitting layer is a light emitting layer that emits light other than blue,
The light emitting device according to any one of claims 1 to 18, wherein the second light emitting layer is a light emitting layer which emits blue light.   The light emitting device according to any one of claims 1 to 19, further comprising red, green and blue color filters.   The light emitting device according to claim 20, wherein the color filters are arranged in a delta arrangement of the red color, the green color and the blue color.   A display device comprising the light emitting device according to any one of claims 1 to 21 and an active element connected to the light emitting device. An imaging apparatus comprising: an optical system having a plurality of lenses; and an imaging device for receiving light passing through the optical system,
The imaging device comprises a display unit for displaying information acquired by an imaging device, and the display unit comprises the light emitting device according to any one of claims 1 to 21. A moving body comprising an airframe and a lamp provided to the airframe,
The lamp includes the light emitting device according to any one of claims 1 to 21. An illumination device comprising: a light source; and an optical film provided on a light extraction side of the light source,
22. A lighting device comprising the light emitting device according to any one of claims 1 to 21, wherein the light source.

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