WO2017038381A1

WO2017038381A1 - Organic el emission device

Info

Publication number: WO2017038381A1
Application number: PCT/JP2016/073093
Authority: WO
Inventors: 昭徳山谷; 涼子宮里
Original assignee: 株式会社カネカ
Priority date: 2015-09-03
Filing date: 2016-08-05
Publication date: 2017-03-09
Also published as: JP2018174162A

Abstract

Provided is an organic EL emission device that can suppress the occurrence of leak current as a result of an organic functional layer covering the lateral surfaces of a positive electrode layer and the positive electrode layer and a negative electrode layer being near to each other. The present invention includes an organic EL element in which the positive electrode layer, the organic functional layer, and the negative electrode layer are laminated on a substrate, and when the substrate is viewed in plan view, the positive electrode layer, the organic functional layer, and the negative electrode layer are superimposed. The organic functional layer is formed by laminating, from the positive electrode layer side, a hole transport property layer and an emission layer, in that order. The hole transport property layer includes a hole injection layer and a hole transport layer, and is in contact with the positive electrode layer and also with the emission layer. When the organic EL element is viewed in cross section view, at least a portion of the lateral surfaces of the positive electrode layer is covered by the organic functional layer, and the average thickness of the hole transport property layer is 0.5 to 1.5 times the average thickness of the positive electrode layer.

Description

Organic EL light emitting device

The present invention relates to an organic EL light emitting device. In particular, the present invention relates to a highly reliable organic EL light-emitting device in which leakage current is suppressed.

An organic EL element is a semiconductor element that converts electrical energy into light energy.
In recent years, research on organic EL elements aimed at application to display screens of mobile phones and portable displays has been actively conducted.
Further, due to improvements in organic materials and the like constituting the organic EL element, the driving voltage of the element is remarkably lowered and the luminous efficiency is increased. For this reason, sales of organic EL light emitting devices in which high-brightness and high-efficiency organic EL elements are put into practical use as lighting devices have also started.

When this organic EL element is used for illumination, high luminance and efficiency are required.
Generally, in order to obtain high luminance, it is necessary to increase the input current, and it is necessary to increase the current density per light emitting area.
In this way, although high luminance can be obtained, the current density also increases. Therefore, in an element with a large leakage current, the entire element is not turned on or dark spots are increased. Therefore, there is a problem that the element life tends to be short.
Thus, for example, Non-Patent Document 1 reports a stacked organic light-emitting device including a charge generation layer as an improvement method.

Patent Document 1 proposes a measure for suppressing the leak current and suppressing the occurrence of point defects by setting the thickness of the hole transport layer to a value exceeding 150 nm.
That is, according to the manufacturing method described in Patent Document 1, even when dust is mixed in the formation of the organic light emitting layer and a part of the cathode is located on the surface of the hole transport layer, the hole transport layer Can be prevented from breaking down and the occurrence of point defects can be suppressed.

JP 2003-338383 A

The organic EL panel of Patent Document 1 is an organic EL panel for a display in which organic EL elements are arranged in a matrix, and is finely separated from each pixel using a mask on a hole transport layer formed on the entire surface. A light emitting layer is formed. The suppression method of Patent Document 1 focuses on the fact that dust is mixed into the surface of the hole transport layer when this mask is used.

However, in an organic EL light emitting device for illumination, unlike an organic EL panel for display, a high resistance is formed on a light-transmitting metal oxide electrode layer patterned in a rectangular shape so that almost the entire surface is a light emitting region. These organic functional layers are continuously formed using the same mask. Then, it manufactures by forming a metal electrode layer as a reflective electrode layer. That is, in the organic EL light emitting device for illumination, the high resistance organic functional layer is interposed between the translucent metal oxide electrode layer and the reflective electrode layer. The side surface of the translucent metal oxide electrode layer covered with the organic functional layer is formed.
That is, a light emitting layer having a larger area than that of a pixel is formed. In the organic EL light emitting device for illumination that uses the same mask when forming the light emitting layer, dust is hardly mixed into the light emitting layer in the first place. The leakage current suppression method is not suitable.

Therefore, an object of the present invention is to provide an organic EL light emitting device that can suppress the occurrence of leakage current.

In view of such problems, the present inventors have intensively studied, and by controlling the total thickness of the hole transport layer and the hole injection layer with respect to the light-transmitting metal oxide electrode layer, the leakage current is suppressed. As a result, the present invention has been accomplished.

According to one aspect of the present invention, an anode layer, an organic functional layer, and a cathode layer are stacked on a substrate, and the anode layer, the organic functional layer, and the cathode layer overlap when the substrate is viewed in plan. It has an organic EL element, and the organic functional layer is laminated in the order of a hole transporting layer and a light emitting layer from the anode layer side. The hole transporting layer comprises a hole injection layer and a hole transporting layer. A layer that is in contact with the anode layer and in contact with the light-emitting layer, and when the organic EL element is viewed in cross section, at least a part of the side surface of the anode layer is the organic functional layer. The hole transporting layer is an organic EL light emitting device having an average thickness of 0.5 to 1.5 times the average thickness of the anode layer.

According to this aspect, the relationship of the film thickness between the anode layer and the light emitting layer satisfies a predetermined relationship. Therefore, it is possible to increase the distance between the anode layer and the cathode layer, and it is possible to reduce the in-plane charge distribution of the organic EL element. Further, it is possible to reduce the possibility of occurrence of a short circuit due to the formation of a conductive path that does not contribute to light emission between the protrusion on the anode layer and the cathode layer, which cause leakage current, or an unexpected conductive path. Thus, according to this aspect, the leak current generation rate can be reduced.
According to this aspect, the average thickness of the hole transporting layer is not less than 0.5 times and not more than 1.5 times the average thickness of the anode layer, so that sufficient thickness can be secured to reduce the leakage current. In addition, a decrease in luminance and an increase in manufacturing cost can be suppressed.

A preferred aspect is that the hole transporting layer has an average thickness of 60 nm to 180 nm.

According to this aspect, even in a large area, light can be emitted uniformly.

A preferred aspect is that the average thickness of the hole transport layer in the hole transport layer is 1.8 times or more of the average thickness of the hole injection layer.

According to this aspect, since the hole transport layer that is cheaper than the hole injection layer is generally formed thicker, an increase in cost due to the thick film of the hole transport layer can be suppressed.

A preferable aspect is that the hole injection layer contains an electron-accepting compound, is in contact with the anode layer, and the average thickness of the hole injection layer is 15 nm or less.

According to this aspect, the injection barrier in hole injection can be reduced, and the drive voltage can be reduced.

A preferred aspect is that the hole transporting layer extends along an edge of the anode layer when the substrate is viewed in plan, and a part of the anode layer extends from the hole transporting layer. It is that you are.

According to this aspect, it is easy to supply power to the anode layer of the organic EL element from the outside of the organic EL element.

In a preferred aspect, the anode layer has an anode component constituting the organic EL element and a cathode power supply pad separated from other parts, and when the substrate is viewed in plan, the anode layer has the anode layer. The anode component and the cathode power supply pad of the anode layer are divided by a groove, and a part of the organic functional layer enters the groove.

According to this aspect, a groove is formed between the anode component of the anode layer and the cathode power supply pad of the anode layer, and a part of the organic functional layer enters the groove. Therefore, in the groove portion, the organic functional layer sinks to the substrate side, and the cathode layer approaches the anode layer side.
According to this aspect, the average thickness of the hole transporting layer is 0.5 to 1.5 times the average thickness of the anode layer, and the hole transporting layer has a sufficient thickness with respect to the depth of the groove. Therefore, the electrical connection between the anode component and the cathode power supply pad and the electrical connection between the anode component and the cathode layer can be cut off.

A more preferable aspect is that the groove is filled with the organic functional layer.

According to this aspect, since the groove is filled with the organic functional layer, it is possible to more reliably prevent the leakage current from being generated by the groove.

A preferable aspect is that the organic functional layer is formed by laminating one or a plurality of light emitting units, and the light emitting unit is formed by laminating a plurality of layers including one or a plurality of light emitting layers. The maximum wavelength Lk of the light emitted from the second light emitting layer satisfies the following formula 1.

However, the value of p is a positive integer of 1 or more, and the value of q is a decimal number that satisfies −0.2 <q <0.2, and the refractive index at the maximum wavelength L _k of the anode layer is expressed as follows. n _k0 , the average thickness of the anode layer is d ₀ , the refractive index of the x-th layer counted from the anode layer side between the anode layer and the k-th light emitting layer is n _kx , and the thickness is d _x And

According to this aspect, the optical path length between the light emitting layer and the light extraction surface of the substrate is optimized, and q takes 0 or a value close to 0, so that the luminance and power efficiency can be improved as compared with the conventional case. .

In the above aspect, it is preferable that the value of p is a positive integer of 2 or more and the value of q is a decimal that satisfies −0.2 <q <0.2.

The above aspect is preferably a decimal in which the value of q in Equation 1 is −0.1 <q <0.1.

A preferable aspect is that the hole transporting layer has a hole transporting material whose hole mobility is 1.0 × 10 ⁻³ cm ² / V · s or more as a main component.

“Main component” as used herein refers to a component occupying 50% or more of all components.

According to this aspect, the amount of voltage increase caused by the hole transporting layer can be suppressed to be small, and an organic EL light emitting device with high power efficiency can be obtained.

A preferable aspect is that when the drive voltage at a luminance of 1 cd / m ² is a threshold voltage (V _th ) V, the applied voltage is minus (V _th −1.0) V or more and plus (V _th −0.5) V or less. In this range, the absolute value of the current density is less than 1.0 × 10 ⁻⁴ mA / cm ² .

According to this aspect, a highly reliable organic EL light emitting device is obtained.

A preferable aspect is that the organic EL element is covered with a sealing film, and the organic EL element is sealed with the substrate and the sealing film.

According to this aspect, since the organic EL element is film-sealed, the generation of leakage current can be further suppressed.

In a preferred aspect, the organic functional layer includes a phosphorescent second light emitting layer, the hole transporting layer has an average thickness of 60 nm or more and 120 nm or less, and a power efficiency of 20 lm / W or more during lighting. It is possible to emit white light.

According to this aspect, the light from the phosphorescent second light emitting layer is amplified by the light interference effect, and the light emission intensity is increased. Therefore, it becomes a high-intensity organic EL light emitting device.

In a preferred aspect, the light emitting layer emits blue light when lit, the organic functional layer includes a phosphorescent second light emitting layer, and the average thickness of the hole transporting layer is 80 nm or more. It is 140 nm or less, and can emit white light at a color temperature of 4000 K or more when lit.

According to this aspect, the light from the light emitting layer emitting blue light is amplified by the light interference effect and the light emission intensity is increased, so that the organic EL light emitting device with a high color temperature is obtained.

In a preferred aspect, the light emitting layer emits blue light when lit, the organic functional layer includes a phosphorescent second light emitting layer, and the average thickness of the hole transporting layer is 80 nm or more. It is 120 nm or less, and can emit white light with a power efficiency of 20 lm / W or more at a color temperature of 4000 K or more when lit.

According to this aspect, both the above-described phosphorescent light-emitting second light-emitting layer and blue light-emitting layer exhibit the light interference effect, and the organic EL light-emitting device has high luminance and high color temperature.

An aspect related to the present invention is an organic EL light-emitting device including an organic EL element formed on a light-transmitting insulating substrate, and the organic EL element is in contact with the light-transmitting insulating substrate from the light-transmitting insulating substrate side. A first hole transporting layer in contact with the light-transmitting metal oxide electrode layer from the light-transmitting metal oxide electrode layer side, comprising a light-sensitive metal oxide electrode layer, an organic functional layer, and a reflective electrode layer; A first light-emitting layer in contact with the first hole-transporting layer, wherein at least a part of a side surface of the translucent metal oxide electrode layer included in the organic EL element is covered with the organic functional layer; Furthermore, in the organic EL light emitting device, the average thickness of the first hole transporting layer is not less than 0.5 times and not more than 1.5 times the average thickness of the translucent metal oxide electrode layer.

According to the organic EL light emitting device of the present invention, the organic functional layer covers the side surface of the anode layer, and the generation of leakage current due to the close distance between the anode layer and the cathode layer can be suppressed.

It is a perspective view of one embodiment of an organic EL light emitting device of the present invention. It is a cross-sectional schematic diagram of one Embodiment of the organic EL element which concerns on this invention. 1 is a plan view of an organic EL light emitting device according to a first embodiment of the present invention. It is a cross-sectional perspective view of the organic EL light-emitting device of FIG. FIG. 4 is a cross-sectional view showing each cross section of the organic EL light emitting device of FIG. 3, wherein (a) shows an AA cross section and (b) shows a BB cross section. It is explanatory drawing of the organic electroluminescent light emitting device of FIG. 3, and is a perspective view which shows the state which peeled the reflective electrode layer from the organic EL element. It is sectional drawing of the organic EL element of FIG. It is a figure which shows the voltage dependence of the current density and brightness | luminance in the forward bias state before and behind the light emission start voltage of the organic EL element of FIG. 3, and a reverse bias state, (a) is a graph of the current density with respect to a drive voltage, ( b) is a graph of luminance against drive voltage. 1 is a cross-sectional configuration diagram of an organic EL element of Example 1. FIG. It is a top view which shows the formation procedure of the organic EL element of Example 1, and (a), (b), (c) in order, and also through the formation region of the lower layer covered with the upper layer so that each layer formation region can be understood. Yes. It is a figure which shows the voltage dependence of the current density in the forward bias state before and behind the light emission start voltage of the organic EL element of Example 1, and a reverse bias state. 5 is a graph showing emission spectra of organic EL light emitting devices of Example 1 and Comparative Example 1. It is a graph which shows the emission spectrum of the organic EL light-emitting device of Example 2 and Example 3. FIG.

Hereinafter, embodiments of the present invention will be described in detail. The vertical direction is based on FIG. That is, the substrate 1 side is the lower side and the sealing film 11 side is the upper side.

(Organic EL light emitting device 100)
The organic EL light emitting device 100 according to the first embodiment of the present invention is a lighting device, and is an organic EL panel having a light emitting surface and a back surface as both main surfaces as shown in FIG. That is, the surface of the organic EL light emitting device 100 is a light emitting surface, and the opposite surface is a back surface.
The organic EL light emitting device 100 is a light emitting device that emits light from the light emitting region 20 on the light emitting surface side based on light emission of the organic EL element 10 included therein. The organic EL light emitting device 100 preferably emits white light from the light emitting region 20 on the light emitting surface side.
The organic EL light emitting device 100 is a member having a planar shape, and is preferably a plate member.
The organic EL light emitting device 100 includes an organic EL element 10 formed on a translucent insulating substrate 1 (hereinafter, also simply referred to as “substrate 1”), and is a bottom emission type organic EL light emitting device that extracts light from the substrate 1 side. Device.

The organic EL light-emitting device 100 includes a specific organic EL element 10 and suppresses leakage current.

When the driving voltage at the luminance of 1 cd / m ² shown in FIG. 8B is the threshold voltage (V _th ) V, the organic EL light emitting device 100 has a minus (V _th − The absolute value of the current density is preferably less than 1.0 × 10 ⁻⁴ mA / cm ² at a voltage of 1.0) V or more and plus (V _th −0.5) V or less. That is, the organic EL light emitting device 100 has an absolute value of current density of 1.0 × 10 ⁻⁴ mA / cm in a voltage range of − (V _th −1.0) V to (V _th −0.5) V. Preferably it is less than ² .
Hereinafter, in the present specification, when the applied voltage is increased from 0 V, the light emission start voltage of the organic EL element 10 is the voltage when the luminance is 1 cd / m ^2, and the value is the threshold voltage ( V _th ). That is, the threshold voltage (V _th ) is a voltage when the voltage is increased from 0 V and the luminance becomes 1 cd / m ² .

In the case of a normal organic EL element, the organic EL element 10 itself has a diode characteristic. For this reason, until the threshold voltage (V _th ), the characteristic is essentially close to an insulator.
However, in an organic EL element in which a leak current is generated, there is an abnormal portion where electricity tends to flow in a part thereof, and the film itself is more likely to deteriorate compared to other portions.
When the deterioration of the organic EL element 10 is promoted, it becomes difficult for current to flow through the portion, and a region that does not emit light is generated and becomes a dark spot. Therefore, in order to provide an organic EL light emitting device that does not substantially generate a dark spot, it is necessary to use the organic EL element 10 in which leakage current is suppressed.

Therefore, in the organic EL light emitting device 100 according to the first embodiment of the present invention, the thickness of the translucent metal oxide electrode layer 2 of the organic EL element 10 and the thickness of the first hole transporting layer 4 of the organic functional layer 3. One of the characteristics is that generation of a leakage current generated in the light-transmitting metal oxide electrode layer 2 is suppressed by optimizing the ratio of the above.

Hereinafter, the organic EL light emitting device 100 according to the first embodiment of the present invention will be described based on this fact.

As can be seen from FIGS. 1 and 2, the organic EL light emitting device 100 has a light emitting region 20 corresponding to the organic EL element 10 on its light emitting surface.
The organic EL light emitting device 100 preferably includes a sealing region 70 including a sealing film 11 that covers the entire surface of the light emitting region 20 on the back surface when viewed in plan. By doing so, it is possible to prevent moisture from entering the organic EL element 10 and to suppress the generation of dark spots.
More preferably, the sealing film 11 has at least an inorganic sealing layer having a thickness of 1 μm or more and 10 μm or less in contact with the organic EL element 10 and an adhesive layer in contact with the inorganic sealing layer. That is, it is more preferable that the sealing film 11 includes an inorganic sealing layer that covers the organic EL element 10 and an adhesive layer that covers the outer side of the inorganic sealing layer in the thickness direction. More preferably, the organic EL light emitting device 100 includes a soaking film or an exterior film on the sealing film 11.

The light emitted from the light emitting region 20 when the organic EL light emitting device 100 is turned on has a spectrum with one emission peak in the range of 500 nm to 580 nm and one emission in the range of 590 nm to 650 nm. White light having a peak is preferable. More preferably, the white light further has an emission peak in the range of 450 nm to 480 nm.
The organic EL light emitting device 100 of the present embodiment includes one emission peak in each of the ranges of light irradiated from the light emitting region 20 in the range of 450 nm to 480 nm, 500 nm to 580 nm, and 590 nm to 650 nm. ing.

The color of light emitted from the light emitting region 20 of the organic EL light emitting device 100 is preferably 2700K to 5000K, more preferably 3000K or higher, and further preferably 4000K or higher.

(Translucent insulating substrate 1)
The light-transmitting insulating substrate 1 (hereinafter simply referred to as the substrate 1) is a base material that has a planar shape and is made of a light-transmitting insulating material.
The board | substrate 1 of this embodiment is a plate-shaped body or film-shaped body provided with translucency and insulation, for example, can use a glass substrate and a resin film board | substrate.
The substrate 1 is preferably a glass substrate from the viewpoint of suppressing moisture intrusion into the organic EL element 10 that causes performance degradation.
In addition, the board | substrate 1 can also be used as a flexible board | substrate by making an average thickness thin or using a flexible material.

(Organic EL element 10)
The organic EL element 10 is an element composed of a multilayer film formed on the substrate 1.
As shown in FIG. 2, the multilayer film includes, in order from the translucent insulating substrate 1 side, a translucent metal oxide electrode layer 2 (hereinafter also referred to as a TCO layer 2), an organic functional layer 3, In addition, the overlapping portion of all these films is the organic EL element 10 including the reflective electrode layer 6.
This overlapping portion coincides with the light emitting region 20 when viewed in plan. That is, the organic EL element 10 is a part where the TCO layer 2, the organic functional layer 3, and the reflective electrode layer 6 are superimposed when the substrate 1 is viewed in plan, and is a part constituting the light emitting region 20.

In the organic EL element 10, at least a part of the side surface of the TCO layer 2 included therein is covered with the organic functional layer 3.
Specifically, the organic EL element 10 is covered with a first hole transporting layer 4 that is a part of the organic functional layer 3. Therefore, since the side surface of the TCO layer 2 can be covered with the first hole transporting layer 4 in the process of depositing the organic functional layer 3 without changing the mask pattern, the organic EL light emitting device 100 for illumination is provided at low cost. it can.
More specifically, the portion indicated by the thick line in FIG. 10B ′ is the side surface of the TCO layer 2 included in the organic EL element 10 and is the side surface covered with the organic functional layer 3.
That is, the TCO layer 2 constituting a part of the organic EL element 10 is an organic layer continuous from the organic functional layer 3 constituting a part of the organic EL element 10 when the substrate 1 is viewed in cross section as shown in FIG. The first hole transporting layer 4 of the functional layer 3 covers the side surface.

The average thickness of the first hole transporting layer 4 is not less than 0.5 times and not more than 1.5 times the average thickness of the TCO layer 2. As a result, the organic EL light emitting device 100 in which the leakage current is suppressed is obtained.

The organic EL element 10 preferably emits white light with a power efficiency of 20 lm / W or more at a luminance of 3000 cd / m ² at the time of lighting.
The organic EL element 10 more preferably has a power efficiency of 30 lmW or more at a luminance of 3000 cd / m ² at the time of lighting. More preferably, the organic EL element 10 emits white light at a color temperature of 4000 K or higher.
The organic EL element 10 more preferably has a power efficiency of 250 lmW or less at a luminance of 3000 cd / m ² at the time of lighting.

Here, the hole transport layer 15 on the TCO layer 2 side generally has a relatively high carrier mobility, and even when the thickness is increased, the increase in driving voltage is small, and the manufacturing cost is low.
Therefore, in the organic EL light emitting device 100 of the present embodiment, the hole transport layer 15 on the TCO layer 2 side (ITO side) is selected as a thickening target as a measure for reducing the leakage current. As a result, according to the organic EL light emitting device 100, the leak current generation rate can be more effectively reduced, and at the same time, the optical path length is optimized and the luminance and power efficiency can be improved.

It is preferable that the film thickness (optical path length) from the interface between the substrate 1 and the TCO layer 2 to the interface on the substrate 1 side of the light emitting layer satisfies the light emission intensity enhancement condition of the following formula 1. That is, the thickness from the interface between the substrate 1 and the TCO layer 2 to the interface on the TCO layer 2 side of the kth light emitting layer satisfies (L _k / 2) × (p + q) = Σn _kx d _x . It is preferable.
By doing so, the light emission intensity from each light emitting layer is enhanced, and the luminance of the organic EL element 10 can be improved.

(However, the value of p is a positive integer of 1 or more, and
The value of q is −0.2 <q <0.2,
More preferably, the decimal number is −0.1 <q <0.1. )
Here, the maximum wavelength of light emitted from the k-th light-emitting layer and L _k counted from the light transmission metal oxide electrode layer 2, a refractive index at a maximum wavelength L _k of the transparent metal oxide electrode layer 2 N _k0 , film thickness d ₀ , between the translucent metal oxide electrode layer 2 and the kth light emitting layer, and the refractive index of the xth layer counted from the translucent metal oxide electrode layer 2 side _Is n _kx and the average film thickness is d _x .

That is, p + q = (2Σn _kx d _x ) / L _k is satisfied, −0.2 <q <0.2 is preferably satisfied, and −0.1 <q <0.1 is more preferable.

(Translucent metal oxide electrode layer 2)
The translucent metal oxide electrode layer 2 (TCO layer 2) is a translucent conductive layer having translucency and conductivity, and is a layer constituting the anode layer of the organic EL element 10.
As the material main component of the TCO layer 2, transparent conductive metal oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), and zinc oxide (ZnO) can be adopted.
The material main component of the TCO layer 2 is preferably highly transparent ITO or IZO from the viewpoint of a high performance element.
From the viewpoint of improving the luminance distribution, the TCO layer 2 preferably contains fine metal wires in these materials. The diameter of the fine metal wire is preferably 1 μm to 100 μm.

The average thickness of the TCO layer 2 is preferably 50 nm or more, and more preferably 70 nm or more.
The average thickness of the TCO layer 2 is preferably 200 nm or less, and more preferably 160 nm or less.

(Organic functional layer 3)
As shown in FIG. 2, the organic functional layer 3 includes at least a first hole transporting layer 4 in contact with the TCO layer 2 and a first light emitting layer 5 (light emitting layer) in contact with the first hole transporting layer 4. .
The organic functional layer 3 preferably further includes a phosphorescent second light emitting layer 52. That is, the organic functional layer 3 preferably has a plurality of light emitting

layers

5 and 52.
The average thickness of the organic functional layer 3 is preferably twice or more the average thickness of the TCO layer 2, and more preferably 2.3 times or more.

(First hole transporting layer 4)
The first hole transporting layer 4 is preferably formed of a material mainly composed of a hole transporting material. The hole mobility of the hole transporting material is preferably 1.0 × 10 ⁻³ cm ² / V · s or more.
As shown in FIG. 7, the first hole-transporting layer 4 preferably includes a first hole-injecting layer 41 that is in contact with the TCO layer 2 and contains an electron-accepting dopant that is an electron-accepting compound.
The average thickness of the first hole injection layer 41 is more preferably 15 nm or less.
The layers other than the first hole injection layer 41 in the first hole transporting layer 4 are in contact with the first light emitting layer 5 and are hole transporting layers having hole transporting properties.
Hereinafter, in the present specification, the first hole transport layer 4 other than the first hole injection layer 41 may be referred to as a “first hole transport layer 15”.

Here, in the prior art, a conductive polymer material such as PEDOT: PSS can be given as a representative example of the hole injection layer material. However, since this polymer material is laminated by a coating method, its lifetime is inferior to that of an organic EL element produced by a vapor deposition method. Therefore, in order to be a highly reliable organic EL element, it is preferable that the hole injection layer 41 is also laminated with a low molecule by a vapor deposition method.

In addition, examples of the hole injection layer material include metal oxides such as molybdenum oxide (MoO ₃ ). Generally, metal oxides that are inorganic compounds have a high vapor deposition temperature. Therefore, it is currently difficult to use these compounds in mass production facilities.

In order to obtain an organic EL device 10 that is highly reliable and can be mass-produced at low cost, a deep LUMO organic material such as HATCN, or a p-type such as F4-TCNQ using a triarylamine-based hole transport material as a host. It is appropriate to use a charge transfer complex co-deposited with a dopant material for the hole injection layer.
However, these materials are generally more expensive than hole transporting materials, and the material cost increases as the film thickness increases. Therefore, in order to obtain the organic EL element 10 that can be mass-produced inexpensively, it is desirable that the hole injection layer material be as thin as possible.

The average thickness of the first hole transporting layer 4 is preferably 60 nm or more and 180 nm or less. The average thickness of the first hole transporting layer 4 is more preferably 60 nm or more and 120 nm or less from the viewpoint of the organic EL element 10 including the phosphorescent second light emitting layer 52 and having improved luminance. The average thickness of the first hole transporting layer 4 is more preferably 80 nm or more and 140 nm or less from the viewpoint of including the phosphorescent second light emitting layer 52 and the organic EL element 10 having a high color temperature. The average thickness of the first hole transporting layer 4 is 80 nm or more and 120 nm or less from the viewpoint that the luminance is improved including the phosphorescent second light emitting layer 52 and the organic EL element 10 has a high color temperature. More preferably.

When the thickness of the hole transporting layer such as the first hole transporting layer 4 is increased, in particular, the thickness of the hole transporting layer 15 included in the hole transporting layer 4 is generally increased, Since the resistance increases as compared with the case where the hole injection layer 41 is thickened, there is a concern that the driving voltage increases.

The voltage increase width V (V) of the drive voltage caused by the resistance of these layers can be estimated using the space charge limited current (SCLC) formula shown by the following formula 2.

Here, J is a current density flowing through the organic EL element 10, and this value is assumed to be 5 mA / cm ² as a general rated current density, and the mobility μ of the hole transport material is 1.0 × 10 ^−3. Assuming that cm ² / V · s, relative dielectric constant ε is 1, and vacuum dielectric constant ε ₀ is 8.854 × 10 ⁻¹² c / V · m, the thickness L of the hole transport layer 15 is 100 nm. In this case, the increase amount V of the drive voltage is about 0.2V. It can be said that this voltage increase width is sufficiently smaller than the driving voltage (for example, 6.9 V in Example 1 described later).

(First light emitting layer 5)
The first light emitting layer 5 is a phosphorescent or fluorescent light emitting layer and is a light emitting layer in contact with the first hole transporting layer 4.
When the phosphorescent second light emitting layer 52 having a high color temperature is included as in the organic EL element 10 of the present embodiment, the first light emitting layer 5 is preferably a light emitting layer that emits blue light.

(Second light emitting layer 52)
The second light emitting layer 52 is a phosphorescent light emitting layer, and is preferably a light emitting layer that emits red and green light.
The second light-emitting layer 52 may have a structure in which a red sub-light-emitting layer that emits light of each color and a green sub-light-emitting layer are stacked, but a single light-emitting layer including a red phosphorescent material, a green phosphorescent material, and a phosphorescent light-emitting layer host material It is preferable that
When the second light emitting layer 52 is a single light emitting layer, it is more preferable that the second light emitting layer 52 uniformly includes a red phosphorescent material, a green phosphorescent material, and a phosphorescent layer host material. That is, the second light emitting layer 52 is preferably a red-green light emitting layer containing a red phosphorescent material, a green phosphorescent material, and a phosphorescent light emitting layer host material.

The maximum emission peak wavelength of the red phosphorescent material is preferably separated from the maximum emission peak wavelength of the green phosphorescent material by 50 nm or more. By doing so, it becomes possible to irradiate light with high color rendering properties.
In the organic EL light-emitting device 100 of the present embodiment, it can emit light with high color-rendering index R _a and the special color rendering index R _9. Specifically, in the organic EL light emitting device 100, the average color rendering index R _a and the special color rendering index R ₉ pursuant to JIS Z 8726 are both enables emission of 90 or more.

(Reflective electrode layer 6)
The reflective electrode layer 6 is a layer having conductivity and light reflectivity. The reflective electrode layer 6 is a back electrode layer formed on the back surface side, and is a layer constituting the cathode layer of the organic EL element 10.
The reflective electrode layer 6 can be formed using a material capable of forming a thin film, for example, a metal material. From the viewpoint of making the organic EL light emitting device 100 with high brightness, the reflective electrode layer 6 is preferably a white glossy metal layer among various metal materials, among which silver (Ag) and aluminum (Al) are preferable. More preferred.

(Organic functional layer 3)
The organic functional layer 3 has a first light emitting layer 5 in contact with at least the first hole transporting layer 4. The organic functional layer 3 preferably has a phosphorescent second light emitting layer 52 in addition to the first light emitting layer 5.
The organic functional layer 3 may include other light emitting layers in addition to these light emitting layers, and it is preferable that a connection layer described later is interposed between these light emitting layers.
A unit interposed between the connection layer and each of the electrode layers 2 and 6 and including the light emitting layer is referred to as a “light emitting unit” in the present specification.
As shown in FIG. 7, the organic functional layer 3 of the present embodiment includes a first light emitting unit 30 including the first light emitting layer 5, a second light emitting unit 31 including the second light emitting layer 52, and the first A connection layer 32 for connecting the light emitting unit 30 and the second light emitting unit 31 is provided.

In the organic EL element 10, the

light emitting units

30 and 31 are composed of a plurality of organic layers mainly made of an organic compound.
As such an organic compound, known materials such as low molecular dye materials and conjugated polymer materials generally used in organic EL elements can be used.
As long as each

light emitting unit

30 and 31 has

light emitting layers

5 and 52 that actually emit light in the layer, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, etc. A plurality of layers can be included, and these layers other than the light emitting layer mainly have a function of promoting light emission in the light emitting layer.

Here, each of the hole injection layer and the electron injection layer can be replaced with a hole injection surface layer or an electron injection surface layer of a connection layer described later.

These layers are formed by a known method such as a vacuum deposition method, a sputtering method, a CVD method, a dipping method, a roll coating method (printing method), a spin coating method, a bar coating method, a spray method, a die coating method, or a flow coating method. I can make a film. These layers are preferably formed by vacuum deposition from the viewpoint of the high-performance organic EL element 10.

(First light emitting unit 30)
As shown in FIG. 7, the first light emitting unit 30 includes a first hole transporting layer 4, a first light emitting layer 5, an electron transporting layer 17, and an electron injection layer 18.
In the first hole transporting layer 4, a first hole injection layer 41 and a first hole transporting layer 15 are laminated from the TCO layer 2 side. That is, in the organic EL light emitting device 100, the first hole transporting layer 4 is arranged between the TCO layer 2 and the first light emitting layer 5, and the first hole injection layer 41 is in contact with the TCO layer 2. The first hole transport layer 15 is in contact with the first light emitting layer 5.

(Connection layer 32)
The connection layer 32 injects electrons into the first light emitting unit 30 on the TCO layer 2 side serving as an anode when the organic EL element 10 is energized, and holes to the second light emitting unit 31 on the reflective electrode layer 6 side serving as a cathode. It is a layer having a function of injecting.
If the connection layer 32 has such a function, it can be formed of various materials. The connection layer 32 can be formed by using, for example, a single organic material or a combination of a plurality of types of organic materials.

The connection layer 32 is preferably used in combination with each charge injection layer from the viewpoint of improving the transparency and improving the luminance and the viewpoint of improving the injection property of each charge and improving the electrical characteristics.

More preferably, the connection layer 32 is a layer in which each charge transporting material is doped with a corresponding electron accepting or electron donating dopant. The connection layer 32 can be configured, for example, by laminating a hole injection layer in which a hole transporting material is doped with an electron accepting dopant and an electron injection layer in which an electron transporting material is doped with an electron donating dopant. . The connection layer 32 can also be comprised only with an organic material.

(Second light emitting unit 31)
As shown in FIG. 7, the second light emitting unit 31 includes a second hole injection layer 50, a second hole transport layer 51, a second hole transport layer 51, and a second hole transport layer 51 from the connection layer 32 side toward the reflective electrode layer 6 side. The light emitting layer 52, the second electron transport layer 53, and the second electron injection layer 55 are laminated in this order.

(Light extraction layer 7)
As shown in FIG. 2, the organic EL light emitting device 100 has a light extraction layer 7 on the outermost surface of the region including at least the light emitting region 20 on the light emitting surface side from the viewpoint of improving the luminance, color, and angle-dependent optical characteristics. It is preferable to provide.
In the organic EL light emitting device 100 of the present embodiment, the light extraction layer 7 is provided on the light emission side surface of the glass substrate as the substrate 1. That is, in the organic EL light emitting device 100, the light extraction layer 7 overlaps the light emitting region 20 when viewed in plan.

As a method of forming the light extraction layer 7, for example, when the substrate 1 is a glass substrate, a surface of the glass substrate that is the substrate 1 is coated with a resin made of acrylic or the like and nanoimprinted, or a resin containing glass beads is sprayed. There are methods of coating and slit coating. It is preferable to stick a resin film (optical film) having a minute uneven structure on one surface and having an adhesive on the other surface to the surface of the glass substrate as the substrate 1 so that the one surface becomes the outermost surface.

Such an optical film preferably has light scattering properties. The pasting is preferably after the organic EL element 10 is formed so that the film surface is not scratched.

When the organic EL light emitting device 100 that is an organic EL panel includes such a light extraction layer 7, the color rendering properties, spectrum, and color temperature are those for the organic EL light emitting device 100 including the light extraction layer 7.

Subsequently, the structure of each component of the organic EL light emitting device 100 of the first embodiment will be described in more detail.

As shown in FIG. 5, the organic EL light emitting device 100 has a TCO layer 2, an organic functional layer 3, and a reflective electrode layer 6 laminated on a substrate 1, and the TCO layer 2, the organic functional layer 3, and the like. The reflective electrode layer 6 includes an organic EL element 10 laminated in this order.
The organic EL light emitting device 100 includes a sealing film 11 further outside the reflective electrode layer 6 of the organic EL element 10 with respect to the substrate 1, and the organic EL element 10 is formed by the substrate 1 and the sealing film 11. It is sealed.
As shown in FIG. 3, the organic EL light emitting device 100 is provided with a light emitting region 20 in the center when the substrate 1 is viewed in plan, and a power feeding region 21 is provided so as to surround the light emitting region 20. Yes.
The light emitting region 20 is a region where the TCO layer 2, the organic functional layer 3, and the reflective electrode layer 6 overlap when viewed in plan. The area of the light emitting region 20 occupies 60% or more of the total area of the light emitting surface.
The power feeding region 21 is a region that feeds power to the organic EL elements 10 belonging to the light emitting region 20, and is a non-light emitting region that is continuous in a ring shape. The power supply area 21 extends along each edge of the substrate 1 and is also a frame-shaped frame area.

As shown in FIG. 3, the TCO layer 2 includes an anode component 60, a plurality of anode power supply extension regions 61, and a plurality of cathode power supply pads 62 when viewed in plan.

The anode constituting part 60 is a part that constitutes the organic EL element 10 and is a part that is spread out in a planar shape. The anode constituting unit 60 belongs to the light emitting region 20 when viewed in plan.

As can be seen from FIGS. 4 and 6, the anode power supply extension region 61 is a portion that supplies power to the anode component 60 that is the anode of the organic EL element 10, and is continuous with the anode component 60 when viewed in plan. This is a portion extending outward from the anode component 60.
Each anode power supply extension region 61 belongs to the power supply region 21 and is arranged at a predetermined interval in the circumferential direction.

As can be seen from FIGS. 4, 5, and 6, the cathode power supply pad 62 is an electrode pad portion that supplies power to the reflective electrode layer 6 that is the cathode of the organic EL element 10. This is a site physically separated from the extended region 61. In other words, the cathode power supply pad 62 is a part separated from the other TCO layer 2 by the groove 63 and is an island-like part independent of the other TCO layer 2.

The organic functional layer 3 includes a functional layer constituent unit 65 and an electrode protection unit 66 when viewed in plan.
As shown in FIG. 5, the functional layer constituting portion 65 is a portion that constitutes the organic EL element 10, and is a portion that is formed in a planar shape. The functional layer constituting unit 65 belongs to the light emitting region 20 when viewed in plan.
The electrode protection part 66 is a part that protects the side surface of the functional layer constituting part 65 of the TCO layer 2 when viewed in cross section. That is, the electrode protection portion 66 has a portion extending in the thickness direction when viewed in cross section, and the tip portion in the extending direction of the portion is in contact with the substrate 1.

The reflective electrode layer 6 includes a cathode constituting portion 67 and a pad connecting portion 68 when viewed in plan.
As shown in FIG. 5, the cathode constituting portion 67 is a portion that constitutes the organic EL element 10 and is a portion that is spread out in a planar shape. The cathode constituting portion 67 belongs to the light emitting region 20 when viewed in plan.
The pad connecting portion 68 is a portion that physically and electrically connects the cathode power supply pad 62 and the cathode constituting portion 67, and is a portion that extends outward from the cathode constituting portion 67 when seen in a plan view.

Then, the positional relationship of each component of the organic EL light emitting device 100 of the first embodiment will be described.

As can be seen from FIGS. 4 and 6, most or all of the anode power supply extension region 61 and the cathode power supply pad 62 are located outside the sealing film 11 in the spreading direction of the substrate 1. That is, the anode power supply extension region 61 projects outward from the sealing film 11.
The first hole transporting layer 4 enters the groove 63 between the anode constituent part 60 of the TCO layer 2 and the cathode power supply pad 62 when viewed in cross section, and the electrode protection part 66 of the organic functional layer 3 The groove 63 is filled. That is, the electrical connection between the anode component 60 and the cathode power supply pad 62 is blocked by the organic functional layer 3.
The pad connection portion 68 of the reflective electrode layer 6 is laminated on the electrode protection portion 66 of the organic functional layer 3, and its end portion is connected to the cathode power supply pad 62. Therefore, the anode power supply extension region 61 is electrically connected to the element component of the TCO layer 2 of the organic EL element 10, and the cathode power supply pad 62 is connected to the reflective electrode layer 6 of the organic EL element 10. The cathode component 67 is electrically connected.

Subsequently, each material used for the organic functional layer 3 will be described.

(Hole injection layer 41, 50)
The first hole injection layer 41 is a layer that takes holes from the TCO layer 2 serving as the anode layer or the layer on the TCO layer 2 side and injects holes into the first hole transport layer 15.
The second hole injection layer 50 is a layer that takes holes from the connection layer 32 or the layer on the connection layer 32 side and injects holes into the second hole transport layer 51.
Examples of the material of the hole injection layers 41 and 50 include arylamines, phthalocyanines, vanadium oxide, molybdenum oxide, ruthenium oxide, aluminum oxide, titanium oxide, and other oxides, amorphous carbon, polyaniline, polythiophene, polyphenylene vinylene, In addition, conductive polymers such as derivatives thereof can be employed. The material of the hole injection layers 41 and 50 is preferably a material in which a hole transporting material is doped with an electron accepting dopant from the viewpoint of improving the transparency of the hole injection layers 41 and 50 and improving the luminance.
The average thickness of the hole injection layers 41 and 50 is preferably 0.1 nm or more and 20 nm or less.

(Hole transport layer 15, 51)
The hole transport layers 15 and 51 are layers that restrict the movement of electrons to the TCO layer 2 side while efficiently transporting holes from the hole injection layers 41 and 50 side to the

light emitting layers

5 and 52.
As a material of the hole transport layers 15 and 51, a known hole transport material can be used.
The average thickness of the hole transport layers 15 and 51 is preferably 1 nm or more and 200 nm or less. The average thickness of the first hole transport layer 15 is preferably 1.8 times or more of the average thickness of the first hole injection layer 41, more preferably 2 times or more, and 4.2 times or more. More preferably it is. The average thickness of the first hole transport layer 15 is preferably not more than 8 times the average thickness of the first hole injection layer 41, more preferably not more than 7.2 times, and not more than 5 times. Is more preferable.

(Light emitting layer 5, 52)
The

light emitting layers

5 and 52 are layers in which a host material having a hole transporting property or an electron transporting property is doped with a light emitting material. The

light emitting layers

5 and 52 are layers in which luminescent excitons are generated by combining holes flowing from the hole transport layers 15 and 51 and electrons flowing from the electron transport layers 17 and 53 by applying an electric field.
The thickness of the

light emitting layers

5 and 52 is preferably 1 nm or more and 40 nm or less.

(Electron transport layer 17, 53)
The electron transport layers 17 and 53 are layers that efficiently transport electrons from the electron injection layers 18 and 55 side to the

light emitting layers

5 and 52 and restrict the movement of electrons to the reflective electrode layer 6 side as a cathode. . As a material of the electron transport layers 17 and 53, a known electron transport material can be used.
The average thickness of the electron transport layers 17 and 53 is preferably 1 nm or more and 200 nm or less.

(Electron injection layer 18, 55)
The electron injection layers 18 and 55 are layers that take electrons from the cathode layer (reflective electrode layer 6) or the layer on the cathode side and inject electrons into the electron transport layers 17 and 53.
Examples of the material for the electron injection layers 18 and 55 include alkali metals or alkaline earth metals such as lithium (Li), lithium fluoride (LiF), cesium fluoride (CsF), and calcium fluoride (CaF ₂ ). These compounds can be employed.
The material for the electron injection layers 18 and 55 is preferably a material obtained by doping an electron transporting material with an electron donating dopant from the viewpoint of improving the transparency of the electron injection layers 18 and 55 and improving the luminance.
The average thickness of the electron injection layers 18 and 55 is preferably 0.1 nm or more and 20 nm or less.

(Hole transporting material)
Examples of the hole transporting material include triphenylamine compounds and carbazole compounds.

Examples of triphenylamine compounds include N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD), 4,4′-bis [N- ( Naphthyl) -N-phenyl-amino] biphenyl (α-NPD), 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (MTDATA), 4,4 ′ , 4 "-tris [N, N- (2-naphthyl) phenylamino] triphenylamine (2-TNATA) and the like.

Examples of the carbazole compound include 4,4′-N, N′-dicarbazole biphenyl (CBP), 4,4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine (TCTA), 4,4′-N. , N′-dicarbazole-2,2′-dimethylbiphenyl (CDBP) and the like.

(Electron transportable material)
Examples of the electron transporting material include quinolinolato metal complexes, anthracene compounds, oxadiazole compounds, triazole compounds, phenanthroline compounds, silole compounds, and the like.

Examples of quinolinolato-based metal complexes include tris (8-quinolinolato) aluminum (Alq3), bis (2-methyl-8-quinolinolato) (p-phenylphenolato) aluminum (BAlq), and the like.

Examples of the anthracene compound include 3-t-butyl-9,10-di (2-naphthyl) anthracene (TBADN), 9,10-di (2-naphthyl) anthracene (ADN), and the like.

Examples of the oxadiazole compound include 1,3-bis [(4-t-butylphenyl) -1,3,4-oxadiazole] phenylene (OVTHD-7), 2- (4-biphenylyl) -5 (4-t-butylphenyl) -1,3,4-oxadiazole (PBD), 1,3,5-tris (4-t-butylphenyl-1,3,4-oxadiazolyl) benzene (TPOB), etc. Is mentioned.

Examples of the triazole compound include 3-phenyl-4- (1'-naphthyl) -5-phenyl-1,2,4-triazole (TAZ).

Examples of the phenanthroline-based compound include bathophenanthroline (Bphen) and bathocuproin (BCP).

Examples of silole compounds include 2,5-di- (3-biphenyl) -1,1, -dimethyl-3,4-diphenylsilacyclopentadiene (PPSPP), 1,2-bis (1-methyl-2,3 , 4,5-tetraphenylsilacyclopentadienyl) ethane (2PSP), 2,5-bis- (2,2-bipyridin-6-yl) -1,1-dimethyl-3,4-diphenylsilacyclopentadiene (PyPySPyPy) and the like.

(Luminescent material)
The light emitting material includes a fluorescent material and a phosphorescent material generally having higher luminous efficiency.

Rubrene, DCM, DCM2, DBzR, etc. can be adopted as the red fluorescent material.

As the green fluorescent material, Coumarin 6, C545T, etc. can be adopted.

Examples of blue fluorescent materials include perylene 4,4'-bis (9-ethyl-3-carbazovinylene) -1,1-biphenyl (BCzVBi), 4,4'-bis [4- (di-p-triamino) ) Styryl] biphenyl (DPAVBi) and the like can be employed.

As the red phosphorescent material, iridium complexes such as (bzq) 2Ir (acac), (btp) 2Ir (acac), Ir (bzq) 3, and Ir (piq) 3 can be employed.

As the green phosphorescent material, iridium complexes such as (ppy) 2Ir (acac) and Ir (ppy) 3 can be employed.

As the blue phosphorescent light emitting material, iridium complexes such as FIrpic, FIr6, Ir (Fppy) 3 can be adopted.

(Electron-accepting dopant)
As the electron-accepting dopant, a tetracyanoquinodimethane compound, molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), vanadium oxide (V ₂ O ₅ ), or the like can be employed.

Tetracyanoquinodimethane compounds include tetracyanoquinodimethane (TCNQ).
Examples include 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ).

(Electron donating dopant)
Examples of the electron donating dopant include alkali metals, alkaline earth metals, rare earth metals, compounds of these metals, phthalocyanine complexes having these metals as the central metal, dihydroimidazole compounds, and the like.

Examples of the alkali metal include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and the like.

Examples of alkaline earth metals include magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and the like.

Examples of the dihydroimidazole compound include bis- [1,3 diethyl-2-methyl-1,2-dihydrobenzimidazolyl] tetrathiafulvalene (TTF), tetrathianaphthacene (TTT), and the like.

According to the organic EL element 10 of the present embodiment, the average thickness of the first hole transporting layer 4 is not less than 0.5 times and not more than 1.5 times the average thickness of the TCO layer 2. Even if 63 is formed and unevenness is formed, leakage current and short circuit can be prevented. That is, the organic EL light emitting device 100 according to the present embodiment includes the highly reliable and highly efficient organic EL element 10 with a reduced leakage current generation rate. Therefore, it is possible to prevent the organic EL element 10 from being turned off or a dark spot due to a leak current. Therefore, the yield can be improved with a simple structure.

According to the organic EL light emitting device 100 of the present embodiment, since the optical path length between the light emitting

layers

5 and 52 and the translucent insulating substrate 1 can be easily optimized, high brightness and high color temperature are easily obtained. Moreover, the voltage rise resulting from the 1st hole transportable layer 4 can be suppressed, and it can also be set as high power efficiency.

In the above-described embodiment, the organic functional layer 3 has a structure in which the two light emitting

units

30 and 31 are connected by the connection layer 32, but the present invention is not limited to this. The organic functional layer 3 may have a structure including one light emitting unit 30, or may have a structure in which three or more light emitting units are stacked directly or via a connection layer 32.

Hereinafter, the present invention will be specifically described by way of examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

(Example 1: Light-emitting element 1a)
As Example 1, an organic EL light emitting device 100 as shown in FIGS. 1 and 2 was produced.

Specifically, an ITO film having an average thickness of 120 nm is formed on a glass substrate 1 having an outer shape of 90 mm × 90 mm and a thickness of 0.7 mm. FIGS. 10 (a), 10 (b), and FIG. The organic EL element 10 having the light emitting region 20 of 80.4 mm × 80.4 mm was formed as the organic EL element 10 in the order shown in the order of 10 (c).
Thereafter, when viewed in plan, a sealing region 70 is formed by the sealing film 11 so as to include the light emitting region 20, and an optical film (OCF film) as the light extraction layer 7 is attached to the light emitting side of the substrate 1. did. Thus, the organic EL light emitting device 100 was produced. FIG. 9 shows a cross-sectional configuration diagram of the organic EL element 10 of the first embodiment.

First, an ITO film on the glass substrate 1 was patterned by a wet etching method to prepare an organic EL element forming substrate having the ITO layer 2 shown in FIG.
This substrate for forming an organic EL element is composed of the same ITO film around the central ITO layer 2 to be the organic EL element 10, eight cathode power supply pads 62 at the four corners, and anodes at the four sides. The power supply extension region 61 is provided with four regions.
Normally, after this, the surface of the TCO layer 2 is polished to perform a polishing process for reducing the density of leak defects originating from the surface. However, in Example 1, this polishing process was not performed. . That is, it is in a state where a leak current is intentionally easily generated.

Next, an organic functional layer 3 (FIG. 10B) and an aluminum (Al) layer 6 (FIG. 10) are formed on the organic EL light-emitting element substrate so as to have a cross-sectional configuration diagram shown in FIG. Each of (c)) was laminated by a vacuum deposition method using a predetermined mask to form a light emitting element 1a as the organic EL element 10 of Example 1.
In FIG. 10B ′, the side surface of the TCO layer 2 included in the organic EL element 10 and covered with the organic functional layer 3 is indicated by a bold line.

As shown in FIG. 9, as the first hole transporting layer 4, from the ITO layer 2 side, a hole injection layer (HIL1) which is a first hole injection layer 41 in contact therewith, and a hole transport layer Two layers (HTL1) were formed, and the first light-emitting layer 5 (EML1) was formed in contact with the hole transport layer (HTL1). The organic functional layer 3 including these was further formed to include EML2 as the phosphorescent second light emitting layer 52.

In addition, the specific thickness of each layer at that time was formed so as to have the value shown in the light-emitting element 1a in Table 1. At that time, the degree of vacuum was set to a high vacuum of 2 × 10 ⁻⁵ Pa or more, and vacuum deposition was performed at a predetermined speed. Layers made of two or more materials such as a light emitting layer were co-deposited at a predetermined mixing ratio. The deposition rate of the aluminum (Al) layer 6 was controlled to be 0.5 to 2.0 nm / sec.

In the light emitting device 1a of Example 1, the average thickness of the ITO layer 2 was 120 nm, and the average thickness of the first hole transporting layer 4 was 74 nm (HIL1 (14 nm) + HTL1 (60 nm)). That is, the average thickness of the first hole transporting layer 4 was 0.62 times the average thickness of the ITO layer 2. The average thickness of the organic functional layer 3 is 268 nm, which is 2.23 times the average thickness of the ITO layer 2. That is, the average thickness of the organic functional layer 3 is at least twice the average thickness of the ITO layer 2.

In the light emitting device 1a of Example 1, a blue fluorescent light emitting layer having a light emission maximum wavelength between 450 and 480 nm is used as the first light emitting layer 5 (EML1), and a light emission maximum wavelength is 500 as the second light emitting layer 52 (EML2). A phosphorescent emitting layer between ˜650 nm was used.

In forming the light-emitting element 1a of Example 1, the hole transporting layers 15 and 51 (HTL1, HTL2) have a hole transporting material having a hole mobility of 2.3 × 10 ⁻³ cm ² / V · s. The hole injection layers 41 and 50 (HIL1, HIL2) were formed by co-evaporation of the hole transport layer material and an organic material serving as an electron-accepting dopant.

Next, a silicon nitride film having an average thickness of about 1.6 μm was formed on the organic EL element 10 by a CVD method using a predetermined mask.
Subsequently, polysilazane was applied by a spray method and baked to form a silica conversion layer having an average thickness of about 0.6 μm.
Furthermore, the sealing area | region 70 comprised by the sealing film 11 was formed by affixing the protective film which consists of PET with an adhesive material on this sealed organic EL element 10. FIG.

Finally, the OCF film 7 was pasted on the surface of the glass substrate 1 opposite to the surface on which the elements were formed, to produce the organic EL light emitting device 100 of Example 1.

For the organic EL light emitting device 100 of Example 1 obtained as described above, measurement of current-voltage-luminance characteristics, forward bias before and after the light emission start voltage, and voltage dependency of current density and luminance under reverse bias, leakage An evaluation test and spectrum measurement when a constant current of 3.4 mA / cm ² (corresponding to 220 mA) was applied were performed.
The light emission power efficiency of the organic EL light emitting device 100 of Example 1 when energized with a constant current of 220 mA was 40.75 lm / W.
Table 2 shows voltage, luminance, and emission color when energized with a constant current of 3.4 mA / cm ² (corresponding to 220 mA).
FIG. 11 shows the measurement results of the voltage dependency of current density and luminance under the forward bias state and the reverse bias state before and after the light emission start voltage.
Table 3 shows the results of a leak evaluation test described later.
FIG. 12 shows an emission spectrum in the central portion of the organic EL light emitting device 100.

(Leak evaluation test)
In FIG. 11, when the applied voltage is increased from 0V, the threshold voltage (V _th ), which is the voltage when the luminance becomes 1 cd / m ² , is about 4.8V.

In the organic EL element, when the applied voltage exceeds the emission start voltage, a current starts to flow rapidly. Therefore, when determining the pass / fail of the leak current value, it is necessary to make a determination below the threshold voltage. Therefore, in order to carry out the determination below the threshold voltage, a value 0.5 V lower than the threshold voltage is set as the maximum value of the applied voltage at the time of determining whether the leakage current is acceptable in the forward direction.
The criterion for determining the leakage current value in the forward bias state was set to less than 1.0 × 10 ⁻⁴ mA / cm ² from 0 V to (threshold voltage −0.5) V.
As a criterion for determining the leakage current value in the reverse bias state, the absolute value of the leakage current is 1.0 × 10 ⁻⁴ mA / cm ^{2 in} the reverse bias state from 0 V to (threshold voltage −1.0) V absolute value. Less than. That is, if the leakage current value in the forward bias state is less than 1.0 × 10 ⁻⁴ mA / cm ² in the range of 0 V to (threshold voltage −0.5) V, the leakage current is obtained in the reverse bias state. If the value was less than 1.0 × 10 ⁻⁴ mA / cm ² in the range of 0 V to minus (threshold voltage −1.0) V, the test was accepted.

It is important to ensure the reliability of the organic EL element that the absolute value of the leakage current is smaller than the reference value in this applied voltage range.
In a normal organic EL element with no leakage, the current value increased exponentially with respect to the applied voltage from 0 V to the emission start voltage. The logarithm of the current value was proportional to the voltage, and when the light emission start voltage was exceeded, the charge injection increased rapidly, so that the current value rose vertically and light emission was confirmed.
On the other hand, in the organic EL element having a leak, the current value up to the light emission start voltage is larger than that in a normal organic EL element.

Among the leak defects that will be a problem in the future in the forward bias state, which is the state when the organic EL light emitting device 100 is actually turned on, it cannot be found as a leak defect in the initial leak inspection, and is not detected There is a leak defect. That is, among the leak defects that will be a problem in the future, there are non-exposed leak defects that cannot be detected as leak defects in the initial leak inspection in the forward bias state, and are not detected.

Therefore, in this leak evaluation test, not only the criteria for determining the leak current value in the forward bias state but also the criteria for determining the leak current value in the reverse bias state are set.

As a leak evaluation test, a reverse bias voltage of 3 V was applied to 100 manufactured organic EL elements in order to reveal non-exposed leak defects, and then a forward bias voltage of 3.5 V was applied. Density was defined as leakage current.

Table 3 shows the measurement results of 100 light emitting elements 1a of Example 1 as the number distribution in each range of leakage current. That is, Table 3 shows the result of measurement for 100 light emitting elements 1a of Example 1 as a number distribution according to the leakage current density classification.

When the portion of less than 1.0 × 10 ⁻⁴ mA / cm ² in the forward bias state according to the above-described determination criteria is adopted and judged, 62% of the whole is acceptable in Example 1.

(Comparative Example 1: Light-Emitting Element 1b)
An organic EL light emitting device of Comparative Example 1 was prepared and evaluated in the same manner except that the film thickness of the hole transport layer 15 (HTL1) having a thickness of 60 nm in Example 1 was 24 nm. That is, the specific thickness of each layer was set to the value shown in the light-emitting element 1b in Table 1.

In the light emitting device 1b of Comparative Example 1, the average thickness of the ITO layer 2 was 120 nm, and the average thickness of the first hole transporting layer 4 was 38 nm (HIL1 (14 nm) + HTL1 (24 nm)). That is, the average thickness of the first hole transporting layer 4 was 0.32 times the average thickness of the ITO layer 2. The average thickness of the organic functional layer 3 is 232 nm, which is 1.93 times the average thickness of the ITO layer 2. That is, the average thickness of the organic functional layer 3 is less than twice the average thickness of the ITO layer 2.

For the organic EL light emitting device of Comparative Example 1, measurement of current-voltage-luminance characteristics, leak evaluation test, and spectrum measurement were performed in the same manner as in Example 1. The organic EL light emitting device of Comparative Example 1 had a light emission power efficiency of 38.51 lm / W when a constant current of 220 mA was applied. Compared with the result of Example 1, the result of Comparative Example 1 is shown in Table 2, Table 3, and FIG.

As shown in Table 2, the luminance of the organic EL light emitting device 100 of Example 1 was improved by about 150 cd / m ² as compared with the organic EL light emitting device of Comparative Example 1.
On the other hand, in the element 1a of Example 1, the voltage was almost the same as that of the element 1b of Comparative Example 1 although the hole transport layer (HTL1) was thickened compared to Comparative Example 1.

As shown in Table 3, the element 1a of Example 1 passed 62% of the total, whereas the element 1b of Comparative Example 1 passed only 6%. .
From this, in Example 1, it is thought that the pass rate was greatly improved due to the effect of increasing the thickness of the first hole transporting layer 4.

As shown in FIG. 12, the organic EL light-emitting device 100 of Example 1 has higher emission intensity in almost all wavelength regions than the organic EL light-emitting device of Comparative Example 1, and this is particularly noticeable at 500 nm to 650 nm. It was. This leads to the aforementioned luminance result.

Here, considering the reason, it is considered that the device 100 of Example 1 satisfies the above-described emission intensity enhancement condition, and the device of Comparative Example 1 does not satisfy the emission intensity enhancement condition.
That is, with respect to the optical path length from the interface between the glass substrate 1 and the ITO layer 2 to the HTL2 / EML2 interface that is the interface on the ITO layer 2 side of the phosphorescent second light emitting layer 52, Σn _kx d _{x in} the following formula 1 When the value is obtained, it is 554 nm for the element 1 a of the device 100 of the first embodiment and 491 nm for the element 1 b of the device of the first comparative example.
In the element 1a, when the peak wavelength of green is 560 nm, the value closest to the value of Σn _kx d _x of the element 1a is when p is 2 and q is −0.02, which is 554.4. Is the time.
On the other hand, in the element 1b, when the green peak wavelength is 560 nm, the value closest to the value of Σn _kx d _x of the element 1b is when p is 2 and q is −0.25, which is 490 nm. Is the time.
That is, since the value of q of the element 1a is smaller than that of the element 1b and it matches the emission intensity enhancement condition, it is considered that the element 1a has a high luminance that does not have strong phosphorescence intensity compared to the element 1b. . Here, the values shown in Table 4 were used as the refractive index values of the ITO layer 2 and the organic functional layer 3.

(Example 2: Light-emitting element 2a)
The organic EL light-emitting device 100 of Example 2 was produced and evaluated in the same manner except that the thickness of each layer in Example 1 was set to the value shown in the light-emitting element 2a of Table 1.

In the light-emitting element 2a of Example 2, the average thickness of the ITO layer 2 was 120 nm, and the average thickness of the first hole transporting layer 4 was 114 nm (HIL1 (14 nm) + HTL1 (100 nm)). That is, the average thickness of the first hole transporting layer 4 was 0.95 times the average thickness of the ITO layer 2. The average thickness of the organic functional layer 3 is 314 nm, which is 2.62 times the average thickness of the ITO layer 2.

For the organic EL light emitting device 100 of Example 2, the current-voltage-luminance characteristics were measured in the same manner as in Example 1 except that the current value at the time of measurement was 4.4 mA / cm ² (285 mA), and Spectrum measurement was performed.
The organic EL light emitting device 100 of Example 2 had a light emission power efficiency of 25.11 lm / W when a constant current of 285 mA was applied.

(Example 3: Light-emitting element 3a)
The organic EL light emitting device 100 of Example 3 was produced and evaluated in the same manner except that the film thickness of HTL1 of 100 nm in Example 2 was changed to 60 nm. That is, the specific thickness of each layer was set to the value shown for the light emitting element 3a in Table 1.

In the light emitting element 3a of Example 3, the average thickness of the ITO layer 2 was 120 nm, and the average thickness of the first hole transporting layer 4 was 74 nm (HIL1 (14 nm) + HTL1 (60 nm)). That is, the average thickness of the first hole transporting layer 4 was 0.62 times the average thickness of the ITO layer 2. Moreover, the average thickness of the organic functional layer 3 is 274 nm, which is 2.28 times the average thickness of the ITO layer 2.

The organic EL light emitting device 100 of Example 3 was measured for current-voltage-luminance characteristics and spectrum measurement in the same manner as Example 2. The light emission power efficiency of the organic EL light emitting device 100 of Example 3 when the 285 mA constant current was applied was 25.06 lm / W.

The results of Example 2 and Example 3 are shown in Table 5 and FIG.

In the organic EL light emitting device 100 of Example 2, as shown in FIG. 12, the intensity of the blue light emission peak was improved by about 8% compared to the organic EL light emitting device 100 of Example 3.
Accordingly, as shown in Table 5, in the organic EL light emitting device 100 of Example 2, the color temperature was improved by about 200K compared to the organic EL light emitting device 100 of Example 3.
On the other hand, the element 2a of Example 2 has the same voltage as that of the element 3a of Example 3 although the hole transport layer (HTL1) is thicker than the element 3a of Example 3. It was almost the same.

Considering the reason for improving the blue light emission peak intensity in Example 2, for blue light, the device 100 of Example 2 satisfies the above-described emission intensity enhancement condition, and the device 100 of Example 3 satisfies the above-described emission intensity enhancement condition. It is thought that there is not.
That is, the optical path length from the interface between the glass substrate 1 and the ITO layer 2 to the HTL1 / EML1 interface that is the interface between the first hole transporting layer 4 and the first light emitting layer 5 is the same as described above. The value of Σn _kx d _x in Equation 1 is obtained using the numerical values shown in FIG. The result was 452 nm for the element 2a of the device 100 of Example 2, and 378 nm for the element 3a of the device 100 of Example 3.
In the element 2a, when the peak wavelength of blue is 470 nm, the value closest to the value of Σn _kx d _x of the element 2a is when p is 2 and q is −0.08, which is 451.2. It is. On the other hand, in the element 3a, when the blue peak wavelength is 470 nm, the value closest to the value of Σn _kx d _x of the element 3a is when p is 2 and q is −0.39, which is 378.35. Is the time.
That is, the value of q of the element 2a is smaller than that of the element 3a and the emission intensity enhancement condition is met. Therefore, the element 2a has a higher intensity of blue fluorescent light emission and a higher color temperature than the element 3a. Conceivable.

The above results are summarized as follows.
From the results of Comparative Example 1 and Example 1, the thickness of the HTL 1 is increased, and the total thickness of the first hole transporting layer 4 is 0.5 times or more that of the ITO layer 2, thereby reducing the leakage current. It was found that generation can be suppressed.
From the results of Comparative Example 1 and Example 1, it can be seen that the phosphorescence based on the second light-emitting layer 52 has a low q value and high luminance with no strong phosphorescence intensity by meeting the emission intensity enhancement condition. It was.
From the results of Example 2 and Example 3, it was found that, for the blue light based on the first light-emitting layer 5, when the emission intensity enhancement condition is satisfied, the intensity of blue fluorescent emission is increased and the color temperature is increased.

1. 1. Translucent insulating substrate Translucent metal oxide electrode layer (anode layer)
3. Organic functional layer 4. 4. First hole transporting layer First light emitting layer (light emitting layer)
6). Reflective electrode layer (cathode layer)
7). Light extraction layer 10. Organic EL element 20. Light emitting area 41. First hole injection layer 52. Phosphorescent second light emitting layer 62. Cathode feed pad 63. Groove part 70. Sealing region 100. Organic EL light emitting device

Claims

An anode layer, an organic functional layer, and a cathode layer are laminated on a substrate, and when the substrate is viewed in plan, the organic EL element in which the anode layer, the organic functional layer, and the cathode layer are superimposed,
The organic functional layer is laminated in the order of a hole transporting layer and a light emitting layer from the anode layer side,
The hole transporting layer includes a hole injection layer and a hole transport layer, and is in contact with the light emitting layer as well as in contact with the anode layer,
When the organic EL element is viewed in cross section, at least a part of the side surface of the anode layer is covered with the organic functional layer,
An average thickness of the hole transporting layer is 0.5 times or more and 1.5 times or less of an average thickness of the anode layer.
The organic EL light-emitting device according to claim 1, wherein an average thickness of the hole transporting layer is 60 nm or more and 180 nm or less.
3. The organic EL light emitting device according to claim 1, wherein an average thickness of the hole transport layer in the hole transport layer is 1.8 times or more of an average thickness of the hole injection layer. apparatus.
The hole injection layer contains an electron-accepting compound, and is in contact with the anode layer,
The organic EL light-emitting device according to any one of claims 1 to 3, wherein an average thickness of the hole injection layer is 15 nm or less.
The hole transporting layer extends along an edge of the anode layer when the substrate is viewed in plan view,
5. The organic EL light emitting device according to claim 1, wherein a part of the anode layer protrudes from the hole transporting layer.
The anode layer has an anode constituent part constituting the organic EL element, and a cathode power supply pad separated from other parts,
When the substrate is viewed in plan, the anode component of the anode layer and the cathode power supply pad of the anode layer are divided by a groove,
6. The organic EL light emitting device according to claim 1, wherein a part of the organic functional layer enters the groove.
The organic EL light emitting device according to claim 6, wherein the groove is filled with the organic functional layer.
The organic functional layer has one or more light emitting units stacked,
The light emitting unit is a laminate of a plurality of layers including one or a plurality of light emitting layers,
The organic EL light-emitting device according to any one of claims 1 to 7, wherein the maximum wavelength Lk of light emitted from the kth light-emitting layer from the anode layer satisfies the following formula 1.

However, the value of p is a positive integer of 1 or more, and the value of q is a decimal number that satisfies −0.2 <q <0.2, and the refractive index at the maximum wavelength L k of the anode layer is expressed as follows. n k0 , the average thickness of the anode layer is d 0 , the refractive index of the x-th layer counted from the anode layer side between the anode layer and the k-th light emitting layer is n kx , and the thickness is d x And
The hole transporting layer is mainly composed of a hole transporting material whose hole mobility is 1.0 × 10 −3 cm 2 / V · s or more. The organic EL light-emitting device according to any one of the above.
When the driving voltage at a luminance of 1 cd / m 2 is the threshold voltage (V th ) V, the current is applied in the range where the applied voltage is negative (V th −1.0) V or higher and positive (V th −0.5) V or lower. 10. The organic EL light-emitting device according to claim 1, wherein the absolute value of the density is less than 1.0 × 10 −4 mA / cm 2 .
A sealing film covers the organic EL element,
The organic EL light-emitting device according to any one of claims 1 to 10, wherein the organic EL element is sealed by the substrate and the sealing film.
The organic functional layer includes a phosphorescent second light emitting layer,
The hole transporting layer has an average thickness of 60 nm to 120 nm,
12. The organic EL light-emitting device according to claim 1, wherein the organic EL light-emitting device can emit white light with a power efficiency of 20 lm / W or more when lit.
The light emitting layer emits blue light when lit,
The organic functional layer includes a phosphorescent second light emitting layer,
The hole transporting layer has an average thickness of 80 nm or more and 140 nm or less,
12. The organic EL light-emitting device according to claim 1, wherein the organic EL light-emitting device can emit white light at a color temperature of 4000 K or more when lit.
The light emitting layer emits blue light when lit,
The organic functional layer includes a phosphorescent second light emitting layer,
The hole transporting layer has an average thickness of 80 nm to 120 nm,
The organic EL light-emitting device according to any one of claims 1 to 11, wherein the organic EL light-emitting device can emit white light with a power efficiency of 20 lm / W or more at a color temperature of 4000 K or more when lit.