JPH0377299A - Organic electroluminescense element - Google Patents

Abstract

PURPOSE:To obtain the luminescence of high brightness with low drive voltage by providing a luminous layer comprising an inorganic amorphous charge injection and carrier layer and an organic compound, and when necessary, a charge barrier layer between an anode and a cathode. CONSTITUTION:A thin film comprising a desired anode material is so formed on a substrate as to have a thickness, for example, of 10 to 200nm. Then a thin film comprising P type a-Si or the like is formed and an inorganic amorphous layer for hole injection and carrier is thereby formed. Thereafter, a thin film of organic luminous material is formed on the amorphous layer to make a luminous layer and then a thin film comprising a cathode material is so formed thereon as to have a thickness, for example, within the range of 10 to 200nm, thereby forming a cathode. Furthermore, when necessary, an anode and an inorganic amorphous layer for hole injection and carrier is formed, and an organic electron barrier layer is formed thereon via a vapor deposition method or the like. According to this construction, it is possible to obtain the luminescence of high brightness with low drive voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a novel organic electroluminescent device. More specifically, the present invention provides 5v
The present invention relates to an organic electroluminescent device that can emit high-intensity light with the following low driving voltage and good luminous efficiency, and is suitable as a light-emitting device for various display devices.

[Conventional technology]

Recently, electroluminescent elements (hereinafter referred to as EL elements) have been widely used in various display devices because they are self-luminous and have high visibility, and because they are completely solid-state elements, they have excellent impact resistance. Its use as a light emitting device is attracting attention.

There are two types of EL devices: inorganic EL devices that use inorganic compounds in their light-emitting layers, and organic EL devices that use organic compounds. Research on its practical application is actively being conducted.

The structure of the organic EL element is basically an anode/emissive layer/cathode structure, and includes a hole injection transport layer that has a function of efficiently transmitting holes injected from the anode to the emissive layer, and a hole injection transport layer that efficiently transmits holes injected from the anode to the emissive layer. A structure in which an electron injection transport layer having a function of efficiently transmitting injected electrons to a light emitting layer is appropriately provided is known.

Among organic EL devices having such a structure, various devices having a structure consisting of an anode/hole injection/transport layer/emitting layer/cathode have been disclosed as having excellent performance (US Pat. No. 4,539). , No. 507, No. 4,769,292
specification, JP-A-59-194393, JP-A No. 63-
295695). In the organic EL device having this configuration, the total thickness of the hole injection and transport layer and the light emitting layer can be made to be L50 nm or less by using a material with excellent thin film forming properties for the hole injection and transport layer. As a result, we have succeeded in obtaining high-intensity light emission with a drive voltage of 20V or less. Further, a triphenylamine-based hole transport compound that does not transport electrons but can act as a barrier to electrons is used in the hole injection transport layer, and the interface between the hole injection transport layer and the light emitting layer 1; By using an electron barrier, electrons are accumulated at the interface within the luminescent layer, increasing luminous efficiency. For example, by using an aluminum oxine complex as the material of the luminescent layer, 1000 c
d/m” high brightness and color emission with luminous efficiency of 1.5 nm/V
This has been realized through [Applied Physics]
Letters J (A+) pl, Phys.

Lett,) Volume 51, Page 913 (1987 PM)
].

By the way, in the EL element, the light emitting mechanism is the recombination type of electrons and holes, so an inorganic substance is used as the light emitting material,
If a PN junction element configuration is used, it should be possible to drive at a low voltage (approximately 2 to 5 V) comparable to that of a light emitting diode, but as described above, the current driving voltage is 5V or higher. This is an energy barrier to hole injection that exists at the interface between the anode and the hole injection transport layer, or an interface between the hole injection transport layer and the light emitting layer, or an energy barrier to electron injection that exists at the interface between the light emitting layer and the cathode. This is because.

Furthermore, although it is said that the upper limit of the quantum yield of light emission is close to 40%, it is still about 1% in the EL element.

As described above, although the organic EL device with the structure consisting of anode/hole injection/transport layer/light emitting layer/cathode has better performance than EL devices with other structures, the driving pressure and luminous efficiency are It is not always completely satisfactory.

[Problem to be solved by the invention]

Under these circumstances, the present invention was made with the object of providing an organic EL element that can obtain high-intensity light emission with a low driving voltage of 5 V or less and good luminous efficiency.

[Means for Solving the Problem] As a result of intensive research to develop an organic EL device having the above-mentioned excellent characteristics, the present inventors found that at least an inorganic By providing an amorphous charge injecting and transporting layer, the energy barrier for charge injection existing at each interface is relaxed, enabling a lower driving voltage, and the inorganic amorphous material has excellent thin film forming properties.
Moreover, they discovered that it has excellent mechanical strength such as surface hardness, and that the luminous efficiency can be further improved by providing a charge barrier layer if desired.Based on this knowledge, they have completed the present invention. Ta.

That is, the present invention provides a light emitting layer comprising an inorganic amorphous charge injection transport layer and an organic compound between an anode and a cathode,
The present invention provides an organic EL device that is provided with a charge barrier layer that is used as desired.

The present invention will be explained in detail below.

The organic EL device of the present invention is one in which at least an inorganic amorphous charge injection transport layer is provided in the basic structure of an anode/emitting layer/cathode, and the inorganic amorphous charge injection transport layer is made of an inorganic amorphous charge injection transport layer. It may be provided as a hole injection transport layer, an inorganic amorphous electron injection transport layer, or both. Furthermore, in the EL element of the present invention,
In addition to the amorphous charge injection and transport layer, an organic hole injection and transport layer and an organic electron injection and transport layer can be provided as desired.

Typical examples of such device configurations include (1) anode/inorganic amorphous hole injection transport layer/light emitting layer/cathode (2) anode/inorganic amorphous hole injection transport layer/organic hole injection transport Layer/Emissive layer/Cathode (3) Anode/Inorganic amorphous hole injection transport layer/Emissive layer/Organic electron injection transport layer/Cathode (4) Anode/Emissive layer/Inorganic amorphous electron injection transport layer/Cathode (5) ! Pole/Emissive layer/Organic electron injection/transport layer/Inorganic amorphous electron injection/transport layer/Cathode (6) Anode/Organic hole injection/transport layer/Emissive layer/Inorganic amorphous electron injection/transport layer/Cathode (7) Anode/Inorganic Examples include an amorphous hole injection transport layer/light emitting layer/inorganic amorphous electron injection transport layer/cathode.

In the organic EL device of the present invention, a charge barrier layer can be further provided as desired. This charge barrier layer may be provided as an electron barrier layer, a hole barrier layer, or both. Regarding the location where the charge barrier layer is provided, when the charge barrier layer is an electron barrier layer, it is provided between the light emitting layer and the anode, preferably in contact with the anode side surface of the light emitting layer; In this case, it is provided between the light-emitting layer and the cathode, preferably in contact with the cathode-side surface of the light-emitting layer.

Typical examples of such device configurations include (8) anode/inorganic amorphous hole injection transport layer/electron barrier layer/emissive layer/cathode (9) anode/emissive layer/hole blocking layer/inorganic amorphous Examples include a solid electron injection transport layer/cathode (10) anode/inorganic amorphous hole injection transport layer/electron barrier layer/light emitting layer/hole barrier layer/inorganic amorphous electron injection transport layer/cathode.

In the device having the above structure, it is preferable that each device is supported by a substrate, and the substrate is not particularly limited, but may be made of a material conventionally used in organic EL devices, such as glass, transparent plastic, quartz, etc. can be used.

Next, to explain each component, the inorganic amorphous hole injection transport layer (hereinafter abbreviated as 1aHTL) is:
It is an amorphous thin film made of an inorganic substance, and has the function of transmitting holes injected from the anode to a light emitting layer or an organic hole injection transport layer. This layer may be a single layer or a stack of multiple layers made of different materials, but the hole mobility is 10-"crs"/
It is desirable that it be equal to or higher than V·S, and most hydrogenated amorphous films satisfy this requirement. This IaH
The material of the TL is a P-type semiconductor with hole carriers, and its ionization energy is determined by the work function of the metal forming the anode facing the IaHTL and the ionization energy of the light emitting layer or the organic hole injection transport layer. A P-type semiconductor whose ionization energy satisfies this condition and whose electrical conductivity is greater than 10-'S/cm is particularly preferred.

An example of such a material is P-type a-8i.

Examples include P-type a-5iC, a-5i, N, %aC, etc. Among these, P type which can control valence electrons and has electrical conductivity of 10-'S/cm or more Type a-3i and P type a-5tC are preferred [Energy J Vol. 1, p. 125 (198
2pm) “Solid Stiso Communication (
Solid State Commun, ) J vol. 17, p. 1193 (1975)]. This P type a-S
i and P type a-5iC have ionization energy of 5.3
eV, which is located between the work function of the metal forming the anode facing the IaHTL and the ionization energy of the light emitting layer or organic hole injection transport layer (1986 Society of Applied Physics Conference Proceedings 27a- 8-1).

A device using such IaHTL can inject more holes into a light emitting layer or an organic hole injection transport layer at a lower voltage than a device that does not use IaHTL. This is due to the following reasons. In other words, there is an energy barrier when injecting holes from the anode into the light emitting layer, and
An energy barrier also exists when injecting from the anode into the organic hole injection transport layer, but in this case, the barrier is reduced compared to direct injection into the light emitting layer. IaHTL has the same effect as such an organic hole injection transport layer, but the contact resistance can be reduced by making the resistance of the IaHTL near the anode particularly low, and by using an ohmic contact metal for the anode. It exhibits an effect that holes can be injected into the IaHTL in a state that is impossible with an insulator or an organic hole injection transport layer similar thereto. Furthermore, IaH
Holes transported within the TL by the electric field reach the interface with the light emitting layer or the organic hole injection transport layer. An energy barrier also exists at this interface, but when using an IaHTLimP-type semiconductor, voltage drop hardly occurs in Ia and HTL, but occurs in the light emitting layer or organic hole injection transport layer, which is a high resistance layer. It becomes easier to release a high electric field at the interface, improving hole injection efficiency and lowering the driving voltage.

In this way, the device using IaHTL can inject more holes into the light emitting layer or the organic hole injection transport layer at a lower driving voltage than the device not using IaHTL. As P type a-3t and P type a-3i
When using C and I, the effect is significant. Furthermore, since the inorganic amorphous material used in the IaHTL has excellent thin film forming properties, it is difficult to generate pinholes in f;Iaf(TLI), and even in large-area devices, undesirable situations caused by pinholes can be prevented. It has the advantage of not only being able to suppress the occurrence of corrosion, but also having excellent mechanical strength such as surface hardness.

On the other hand, the electron barrier layer has the role of keeping electrons that try to exit from the light emitting layer to the anode side within the light emitting layer, and the electron barrier layer is preferably placed between the light emitting layer and the IaHTL. By providing it in contact with the anode side surface of the layer, the light emitting efficiency of the device is improved. This electron barrier layer is preferably a layer whose electron mobility is inferior to that of the light-emitting layer, or a layer having an electron affinity smaller than that of the light-emitting layer.

Preferred examples of such an electron barrier layer include a layer made of a triphenyldiamine compound and [Applied Phys.
t,) J Vol. 51, page 913 (1987 noon)],
Hole injecting and transporting layers made of aromatic tertiary amine compounds (Japanese Patent Application Laid-open Nos. 59-194393 and 63-295695) have been disclosed.

These act as barriers by not transporting electrons.

In addition, the present inventors have discovered that a-3, which is an inorganic amorphous material,
it-, C, (0,5<x<1) or a-S t +-
A layer consisting of wN++ (0,4<x), which can be obtained by determining the value of X so that the electron affinity of this layer is smaller than that of the light emitting layer, or by determining the range of production conditions. is preferable as an electron barrier layer, and when the inorganic amorphous material is a-5rl-Nw,
Particularly preferred values of X are greater than 0.47 and 0.5
It was found that it exists in a range of less than 7. Note that the inorganic amorphous material used for this electron barrier layer does not need to be a P-type semiconductor.

The electron barrier layer made of such an inorganic amorphous material is
The ionization energy of the ionization energy is between (1) the ionization energy of IaHTL and the ionization energy of a layer such as a light-emitting layer facing an electron barrier layer other than IaHTL, and (2) electrons other than IaHTL. It can be divided into two types: those having a value larger than the ionization energy of the layer such as the light-emitting layer facing the barrier layer.

In the electron barrier layer of type (1), the i-pole/IaHT
Ionization energy increases in the order of L/electron barrier layer/light emitting layer, etc., and holes are likely to be injected, but the hole mobility of the electron barrier layer may be greater than 10 cm/V-5. preferable.

This kind of electron barrier layer can also be considered as part of the IaHTL. On the other hand, in the electron barrier layer of type (2),
It is desirable to set the film thickness so that holes tunnel through this layer, and the film thickness is particularly preferably 20 nm or less.

The inorganic amorphous electron injection transport layer (hereinafter abbreviated as IaETL) in the above device configuration is an amorphous thin film made of an inorganic material, and transmits electrons injected from the electrode to the light emitting layer or the organic electron injection transport layer. It has the function of This layer may be a single layer or may be a stack of multiple layers made of different materials, but the electron mobility must be IQ-"c1/V-S or higher. is desirable, and most hydrogenated amorphous films satisfy this requirement.

The material of this IaETL is an N-type semiconductor with electron carriers, and its electron affinity is between the work function of the metal pin that forms the cathode facing the IaETL and the electron affinity of the light-emitting layer or the organic electron injection and transport layer. An N-type semiconductor whose electron affinity satisfies this condition and whose electrical conductivity is greater than 10''lS/crR is particularly preferable.

An example of such a material is N-type a-5i.

Examples include N-type a-5iC, a-5i, N, a-C, among which valence electron control is particularly possible and electrical conductivity of 10-'S/cm or more is possible. N type a-
5i and N-type a-5iC are preferred [“Energy (
Energy) J Vol. 1, p. 125 (1982) "Solid Stiso Communication (S
solidState Commun, ) J Volume 17,
Page 1193 (1975 noon)]. This N type a-3i
and N-type a-3iC has an electron affinity of 3.4 to 3.7e
V, and is located between the work function of the metal forming the cathode facing the IaETL and the electron affinity of the light-emitting layer or the organic electron injection transport layer (19J36, Proceedings of the Japan Society of Applied Physics Conference 27a-3 -1).

An element used in such an IaETL can inject more electrons into a light emitting layer or an organic electron injection transport layer at a lower voltage than an element that is not used. This is due to the following reasons. That is, an energy barrier exists when electrons are injected from the cathode into the emissive layer, and an energy barrier also exists when injected from the cathode into the organic electron injection transport layer. The barrier is reduced compared to direct injection. IaETL has the same effect as such an organic electron injection transport layer, but in addition, the resistance of the IaETL near the cathode can be particularly reduced, or IaETL can be applied to the cathode.
By using a metal that makes an ohmic contact with the aETL, electrons can be injected into the IaETL with low contact resistance, an effect that is impossible with an insulator or an organic electron injection transport layer similar thereto. Furthermore, I
Electrons are transported within the aETL by an electric field and reach the interface with the light-emitting layer or the organic electron injection and transport layer. An energy barrier also exists at this interface, but when an N-type semiconductor is used for the IaETL, voltage drop hardly occurs in the IaETL, but occurs in the light-emitting layer or organic electron injection transport layer, which is a high resistance layer. It becomes easier to form a high electric field at the interface, improving electron injection efficiency.

In this way, a device using IaETL can inject more electrons into the light emitting layer or organic electron injection transport layer at a lower driving voltage than a device not using IaETL. Type a-5i and N type a-Si
When C is used, the effect is remarkable. Furthermore, N+ type a-8i may be used as the IaETL of the low resistance portion, and Ail may be used as the ohmic electrode for this. Furthermore, since the inorganic amorphous material used in the 1aETL has excellent thin film forming properties, the IaETL using this
L has the advantage of being able to prevent pinholes from occurring even in large-area devices, as well as being superior in mechanical strength such as surface hardness.

On the other hand, the hole blocking layer has a role of retaining holes in the light emitting layer that try to exit from the light emitting layer to the cathode side, and the hole blocking layer is preferably placed somewhere between the light emitting layer and the IaETL. By providing it in contact with the cathode side surface of the light emitting layer, the light emitting efficiency of the device is improved. This hole blocking layer is preferably a layer whose hole mobility is inferior to that of the light-emitting layer, or a layer whose ionization energy is lower than that of the light-emitting layer.

The present inventors have found that N-type a-5iC, which is an inorganic amorphous material, is preferable as such a hole blocking layer because it has low hole mobility. Mat:
a-5it□N1(o, 4 (x < 0, 57
), in which the value of X is determined or the range of manufacturing conditions is determined so that the ionization energy of the hole blocking layer is greater than the ionization energy of the light emitting layer. I also found that things are preferable.

Note that the inorganic amorphous material used for this type of hole blocking layer does not need to be an N-type semiconductor.

A hole blocking layer made of such an inorganic amorphous material is
As for its electron affinity, (1) one having a value between the electron affinity of IaETL and the electron affinity of a layer such as a light emitting layer facing a hole blocking layer other than IaETL, and (2) IaETL.
It can be divided into two types: those having a value smaller than the electron affinity of a layer such as a light emitting layer facing a hole blocking layer other than aETL. In the hole blocking layer of type (1), the electron affinity decreases in the order of cathode/IaETL/hole blocking layer/light emitting layer, etc., and electrons are easily injected, but the movement of electrons in the hole blocking layer It is preferable that the degree L O-"c is larger than /V·S.

This kind of hole blocking layer can also be considered as part of the IaETL. On the other hand, in the hole blocking layer of type (2),
It is desirable to set the film thickness so that electrons tunnel through this layer, and the film thickness is particularly preferably 20 nm or less.

The method for producing the inorganic amorphous thin film is a known method such as plasma CVD method, ECR plasma CVD method, etc.
Hl, StHCl (,
, C,)i, ,N)i, and the like can be used. For example, a-5iC is H2, Si
It can be produced using the above method from HCHa gas, and when controlling the electrical conductivity by controlling the valence electrons with a-5iC or a-8t, it is usually produced using BAHCHa gas.
A thin film is formed by adding a gas such as a-SiC or a-
A method of doping B, P, etc. into the SiC film is used. In the case of B-dope, a P-type semiconductor is obtained, and in the case of P-doped, an N-type semiconductor is obtained.

Usually, the SiH, CH, CtHhN Hs gases mentioned above are used diluted to about 10% with hydrogen gas, and B, H, and PH3 are used diluted to about 500 ppm. 70 - Through the controller,
The mixture ratio, pressure, etc. of the raw material gas mixture are adjusted and introduced into the CVD furnace.

After that, energy is applied using radio frequency, light, electric discharge, etc. to decompose the gas in the furnace, and a thin film is formed on the substrate. At this time, the substrate is set at an appropriate substrate temperature, and the thin film production rate varies depending on the production method, type of raw material, production conditions, etc., but is usually selected in the range of 0.1 to 10 nm/min.

As the anode in the organic EL device of the present invention, an electrode material containing a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function (4 eV or more) is preferably used. A specific example of such an electrode material is Au.
Examples include metals such as Cu, ITO, SnO, and conductive transparent materials such as ZnO. The anode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. When emitting light from this electrode, it is desirable that the transmittance be greater than 10%, and the sheet resistance of the electrode is preferably several hundred 0/port or less.

Furthermore, although the film thickness depends on the material, it is usually 500 nm or less,
Preferably it is selected within the range of 10 to 200 nm.

On the other hand, as a cathode, it has a small work function (4 eV or less).
Electrode materials made of metals, alloys, electrically conductive compounds, and mixtures thereof are used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium/#4 mixture, All A no z, ytterbium, indium, and the like. The cathode can be manufactured by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. Further, the sheet resistance of the electrode is preferably several hundreds of nanometers or less, and the film thickness is usually selected to be 500 nm or less, preferably in the range of 10 to 200 nm. In the element of the present invention, it is preferable that either the anode or the cathode be transparent or semi-transparent, since this allows light to pass through and extract the light with good efficiency.

The light-emitting layer in the organic EL device of the present invention is made of an organic compound that has fluorescence in a solid state and has a thickness of 5 nm to 5 μm.
It is a thin film of about m, and when (1) is applied with a field,
Injection function that can inject holes from the anode or hole injection transport layer and electrons from the cathode or electron injection transport layer, (2) Injected charges (electrons and holes)
(3) provides a field for recombination of electrons and holes, which leads to light emission; and (3) a light-emitting function. Note that there may be a difference in the ease with which holes are injected and the ease with which electrons are injected, and there may be differences in the transport function expressed by the mobility of holes and electrons.
It is preferable to move one of the charges.

In the above-mentioned injection function, the ionization energy of the light emitting layer is 6. from the point that it is relatively easy to inject holes if an appropriate anode material is selected. It is preferable that the electron affinity is OeV or less, while the electron affinity is preferably 2.5 eV or more because it is relatively easy to inject electrons if an appropriate cathode material is selected. Further, regarding the light emitting function, it is desirable that solid state fluorescence is strong. This is because such a light-emitting layer has a large ability to convert the excited state of the compound itself, an aggregate of compounds, or a crystal forming the layer into light.

The organic compound used in the light emitting layer of the organic EL device of the present invention is not particularly limited as long as it has the properties described above and is capable of forming a thin film, and any compound may be selected from conventionally known compounds. Can be used. Examples of the organic compound that can be used include polycyclic fused aromatic compounds, benzothiazole-based, benzimidazole-based, benzoxazole-based fluorescent brighteners, metal chelated oxinoid compounds, styrylbenzene-based compounds, and the like.

Examples of the polycyclic fused aromatic compound include anthracene, naphthalene, phenanthrene, pyrene, chrysene,
Examples include fused ring luminescent substances containing a perylene skeleton and other fused ring luminescent substances containing about 8 fused rings.

As the multi-filament fluorescent whitening agent, for example, those described in JP-A-59-194393 can be used, and a representative example thereof is 2,5-bis(5,7- di-t-pentyl-2-benzoxasilyl)-1,3,
4-thiadiazole, 4.4'-bis(5,7-t-pentyl-2-benzoxasilyl)stilbene, 4.4
'-Bis[5,7-di(2-methyl-2-butyl)-
2-benzoxasilyl]stilbene, 2,5-bis(
5,7-di-t-pentyl-2-benzoxasilyl)
Thiophene, 2.5-bis(5-(α,σ-dimethylbenzyl 2-benzooxacylylphthiophene, 2.5-
Bis[5,7-di(2-methyl-2-butyl)-2-
benzoxacylyl)-3,4-diphenylthiophene, 2,5-bis(5-methyl-2-benzoxasilyl)thiophene, 4,4'-bis(2-benzoxasilyl)biphenyl, 5-methyl-2 −(2 − [4
-(5-methyl-2-benzoxasilyl)phenyl]
benzoxazole series such as 2-(2-(4-chlorophenyl)vinyl)naphtho(1,2-d)oxazole, 2.2'-(1)-7
benzothiazole series such as (enylene divinylene)-bisbenzothiazole, 2-(2-[4-(2-benzimidazolyl)phenyl]vinyl]penzimitasole, 2-(2-(4-carboxyphenyl)vinyl))
Examples include benzimidazole-based fluorescent brighteners such as benzimidazole.

As the metal chelated oxinoid compound, for example, those described in JP-A-63-295695 can be used. Representative examples include tris(8-quinolitool)aluminum, bis(8-quinolitool)magnesium, bis(benzo[fl-8-quinolitool)
Zinc, bis(2-methyl-8-quinolinolade)aluminum oxide, tris(8-quinolitor)indium, tris(5-methyl-8-quinolitor)aluminum, 8-quinolitorium, tris(5-chloro-8 -quinolitool) gallium, bis(5-chloro-8
Examples include 8-hydroxyquinoline metal complexes such as calcium, poly[zinc (■)-bis(8-hydroxy-5-quinolinonyl)methane], and dilithium evindridione.

Further, as the styrylbenzene-based compound, for example, those described in the specification of the invention titled "Thin Film Electroluminescent Device" filed by the present applicant on February 10, 2016 can be used.

Typical examples thereof include compounds having the structure shown below.

II, C0 CU3 [1,C 'AsCt a.C.O. +13c.

B.C.O. tCt ((U,],C l3C0 OCR.

OCR.

C, [+.

C(CL)s ■ L.C. ■B1 H3 L H3 ■ 3C B, C H,C OC[+.

OC[l.

Furthermore, in addition to the above compounds, for example, 12-7 taloberinone [Journal of Applied Physics J, Appl, Phys. J Vol. 27, L713 (19
1988)], stilbene compounds (patent application 1988-312)
No. 356, No. 63-80257, No. 63-31393
No. 2, No. 63-308859), coumarin compounds (
The invention filed by the present applicant on January 20th, 2017 (named "Thin Film Organic EL Device") can also be used as the light-emitting layer.

The light-emitting layer made of the organic compound may have a laminated structure of two or more layers as desired.
As disclosed in the No. 292 specification, it may be formed from a host material and a fluorescent material. In this case, the host substance is a thin film-like layer, which has some of the functions of the light-emitting layer, including the injection transport function and the light-emitting function. % or less) and plays only part of the light-emitting function of emitting light in response to the combination of electrons and holes. Further, the organic compound used in the light emitting layer may be a compound that does not have thin film forming properties, such as 1,4-diphenyl-1,3-butadiene and 1.
．． 1.4.4-Tetraphenyl-1,3-butadiene and the like can also be used.

Methods for making thin films of these organic light-emitting materials include, for example, the spin-coding method, casting method, LB method, and vapor deposition method. , vapor deposition method is preferred. When this vapor deposition method is used to form a thin film of the luminescent material, the deposition conditions include the sublimation temperature of the organic compound used in the luminescent layer, the desired state of the thin film, such as selection of microcrystalline or amorphous, and crystallinity. Although it varies depending on the orientation of the crystal, etc., generally the boat heating temperature is 50 to 500°C, and the degree of vacuum is 10-' to lO
-'P a, a deposition rate of 0.01 to 50 nm/sec, a substrate temperature of -50 to +300°C, and a film thickness of 5 nm to 5 μm.

In the EL device of the present invention, the organic hole injection transport layer provided as desired is a layer made of an organic hole transport compound, and has a function of transmitting holes injected from the anode to the light emitting layer, By interposing this hole injection transport layer between the anode and the light emitting layer, many holes can be injected into the light emitting layer with a lower electric field, and moreover, more holes can be injected into the light emitting layer from the cathode or the electron injection transport layer. The emitted electrons are accumulated near the interface within the light emitting layer due to the electron barrier existing at the interface between the light emitting layer and the hole injection transport layer, resulting in an element with excellent light emitting performance, such as improved light emitting efficiency.

The organic hole transport compound used in the organic hole injection transport layer is arranged between two electrodes to which an electric field is applied, and when holes are injected from the anode, the organic hole transport compound is used to properly transfer the holes to the light emitting layer. Compounds capable of transmitting, such as those having a mobility of at least 1,0-"cm"/V-5 when an electric field is applied, are preferred.

There are no particular restrictions on such organic hole transport compounds as long as they have the above-mentioned preferable properties.
For photoconductive materials, any material can be selected from those commonly used as hole charge transport materials and known materials used in hole injection and transport layers of EL devices. Examples of the charge transport material include triazole derivatives (described in U.S. Pat. No. 3,112,197, etc.), oxadiazole derivatives (U.S. Pat. No. 3,1
89.447, etc.), imidazole derivatives (described in Japanese Patent Publication No. 37-16096, etc.), polyarylalkane derivatives (US Patent No. 3.
Specification No. 615,402, Specification No. 3,820,989, Specification No. 3,542,544, Japanese Patent Publication No. 45-55
Publication No. 5, Publication No. 51-10983, JP-A-51-9
Publication No. 3224, Publication No. 55-17105, Publication No. 56-
No. 4148, No. 55-108667, No. 55
-156953, US Pat. No. 56-36656), pyrazoline derivatives and pyrazolone derivatives (US Pat. No. 3,180,729, US Pat.
78,746 specification, JP 55-88064, JP 55-88065, JP 49-105537, JP 55-51086, JP 56-80051
Publication No. 56-88141, Publication No. 57-4554
Publication No. 5, Publication No. 54-112637, Publication No. 55-74
546), phenylenediamine derivatives (U.S. Patent No. 3,615,404, Japanese Patent Publication No. 51-10105, Japanese Patent Publication No. 46-3712,
JP 47-25336, JP 54-53435, JP 54-110536, JP 54-1199
25, etc.), arylamine derivatives (U.S. Pat. No. 3,567.450, U.S. Pat. No. 3.18)
Specification No. 0,703, Specification No. 3,240,597,
Specification No. 3,658,520, No. 4.232,103
Specification of No. 4,175,961, No. 4,01
Specification No. 2,376, Japanese Patent Publication No. 49-35702,
Publication No. 39-27577, JP-A-55-144250
No. 56-119132, No. 56-224
No. 37, West German Patent No. 1,110,518, etc.), amino-substituted chalcone derivatives (US Pat. No. 3,526,501, etc.),
Oxazole derivatives (described in U.S. Patent No. 3,257,203, etc.), styryl anthracene derivatives (described in JP-A-56-46234, etc.)
, fluorenone derivatives (described in JP-A-54-110837, etc.), hydrazone derivatives (US Pat. No. 3,717,462, JP-A-54-59143)
No. 55-52063, No. 55-5206
Publication No. 4, Publication No. 55-46760, Publication No. 55-854
Publication No. 95, Publication No. 57-11350, Publication No. 57-14
8749), stilbene derivatives (JP-A-61-210363, JP-A-61-210363, JP-A-61-210-363, etc.)
No. 228451, No. 61-14642, No. 6
No. 1-72255, No. 62-47646, No. 62-36674, No. 62-10652,
62-30255, 60-93445, 60-94462, 60-174749, 60-175052, etc.)
etc. can be mentioned.

In the present invention, these compounds can be used as hole transfer compounds, but the following porphyrin compounds (described in JP-A No. 63-295695 etc.), aromatic tertiary amine compounds and Styrylamine compounds (U.S. Pat. No. 4,127,412, U.S. Pat. Publication No. 55-14425
Publication No. 0, Publication No. 56-119132, Publication No. 61-29
No. 5558, No. 61-98353, No. 63-
It is preferable to use the aromatic tertiary amine compound (described in Japanese Patent No. 295695, etc.), especially the aromatic tertiary amine compound.

Representative examples of the porphyrin compounds include porphine, 1.10,15.20-tetraphenyl-21H,23H-porphine copper(II), 1,10
, 15.20-tetraphenyl-21H,23H-porphine zinc (11), 5.10,15.20-tetrakis(pentafluorophenyl)-218,23H-porphine, silicon phthalocyanine oxide, aluminum 7-thalocyanine chloride, phthalocyanine (metal free)
, dilithium phthalocyanine, copper tetramethyl phthalocyanine, copper 7 talonanine, chromium 7 thalocyanine, zinc 7 thalocyanine, lead 7 thalocyanine, titanium 7 thalocyanine oxide, magnesium phthalocyanine, copper octamethyl phthalocyanine, and the like. Well;
Representative examples of the aromatic tertiary amine compound and styrylamine compound include N,N,N',N'-tetra7enyl-4,4'-diaminobiphenyl, N,N'diphenyl-N,N '-di(3-methylphenyl)-4,4'-
Diaminobiphenyl, 2,2-bisc4-p-tolylaminophenyl)propane, 1,1-bis(4-di-
p-tolylaminophenyl)cyclohexane, N, N,
N',N'-tetra-p-1lylu-4,4'-diaminobiphenyl, l,1-bis(4-di-p-tolylaminophenyl)-4,-phenylcyclohexane, bis(4
-dimethylamino-2-methylphenyl)phenylmethane, bis(4-di-pt-tuluminophenyl)phenylmethane, N,N'-diphenyl-N,N''-di(4
-methoxyphenyl)-4,4'diaminobiphenyl,
N, N, N', N''-tetraphenyl-4,4'-';
Aminodiphenyl ether, 4,4'-bis(diphenylamino)quadrifhenyl, N,N,N-tri(p-tolyl)amine, 4-(di-p-tolylamino)
-4'-(4(di-p-tolylamino)styryl)stilbene, 4-N,N-diphenylamino-(2-diphenylvinyl)benzene, 3-methoxy-4'-N,N
-diphenylaminostilbene, N-7enylcarbasol, and the like.

The organic hole injection transport layer in the device of the present invention may be composed of a single layer composed of one or more of these organic hole transport compounds, or may be composed of a compound different from the above layer. It may also be a stack of organic hole injection transport layers.

On the other hand, the organic electron injection and transport layer provided as desired is made of an organic electron transfer compound and has a function of transferring electrons injected from the cathode to the light emitting layer.

There are no particular limitations on such organic electron transfer compounds, and any one can be selected and used from conventionally known compounds. A preferred example of the organic electron transfer compound is II No.

Nitro-substituted fluorenone derivatives such as J', thiovirane dioxide derivatives such as, diphenylquinone derivatives such as ], or compounds such as 0 [Journal of Agelide Physics (J, Apply, Phys,) J Vol. 27,
L269 (1988)] and anthraquinodimethane derivatives (JP-A No. 57-149259, JP-A No. 58-55450, JP-A No. 61-225151)
No. 61-233750, No. 63-104
081, etc.), fluorenylidene methane derivatives (JP-A-60-69657, JP-A-61-69657, etc.)
143764, 61-148159, etc.), anthrone derivatives (JP-A-61-22
5151, 61-233750, etc.).

Next, an example of a suitable method for manufacturing the organic EL device of the present invention will be explained for each device of each structure. First, a method for manufacturing an EL device consisting of an anode/inorganic amorphous hole injection/transport layer/light-emitting layer/cathode will be described. A thin film made of a desired anode material is deposited on a suitable substrate to a thickness of 500 nm or less, preferably 10 to 200 nm. After forming an anode under the above conditions by a method such as vapor deposition or sputtering to have a film thickness in the range of
A thin film made of type a-5i or P-type a-5iC is formed by a method such as plasma CVD to provide an inorganic amorphous hole injection transport layer.

This film thickness is preferably about 5 to 200 nm in order to increase transmittance when emitted light is extracted from the substrate side. Further, film forming conditions cannot be generally determined because they vary depending on the type of material to be thinned, the amount of impurity doped, etc.

Next, on top of this inorganic amorphous hole injection transport layer,
A thin film of an organic light-emitting material is formed under the above conditions by vapor deposition or the like so that the film thickness is in the range of 5 im to 5 μm, and a light-emitting layer is formed, and then a thin film of a cathode material is formed on this layer. , 500 nm or less, preferably 10 to 20
A desired organic EL element can be obtained by forming the film under the above conditions by a method such as vapor deposition or sputtering so as to have a film thickness in the range of 0 nm, and by providing a cathode. In the production of this EL device, the production order was reversed to form a cathode, a light emitting layer, an inorganic amorphous hole injection transport layer,
It is also possible to manufacture the anode in this order.

For the production of an EL device consisting of an anode/inorganic amorphous hole injection transport layer/organic electron barrier layer/emissive layer/cathode, first, the anode and inorganic amorphous hole After sequentially forming the injection transport layer, an organic electron barrier layer is provided thereon by vapor deposition, as in the case of vapor deposition of the light emitting layer, and then, on this,
A desired organic EL device can be obtained by sequentially providing a light emitting layer and a cathode in the same manner as in the case of the EL device described above. In the production of this EL element, the order of production may be reversed, and the cathode, light emitting layer, organic electron barrier layer, inorganic amorphous hole injection and transport layer, and anode may be produced in this order.

Anode/Inorganic amorphous hole injection transport layer/Inorganic electron barrier layer/Emission 1m/For the production of the cathode, first, the anode and the inorganic amorphous hole injection transport layer were sequentially formed in the same manner as in the production of the EL device described above. After this, a thin film of a-sil-1N, a-3i, □C0, etc. is formed thereon by plasma CVD or the like to provide an inorganic amorphous electron barrier layer. When emitting light from the substrate side, the film thickness should be 5 to 20 mm in order to increase the transmittance.
A range of 0 nm is preferred. Regarding the film forming conditions,
It depends on the type of material to be made into a thin film, etc., and cannot be determined generally.

Next, a light-emitting layer and a cathode are sequentially provided thereon in the same manner as in the production of the EL element described above, thereby obtaining a desired EL element. Note that in the production of this EL element, the production order may be reversed and the cathode, light emitting layer, inorganic electron barrier layer, inorganic amorphous hole injection and transport layer, and anode may be produced in this order.

Anode/Inorganic amorphous hole injection transport layer/Inorganic electron barrier layer/Light emitting M/Inorganic amorphous electron injection transport layer/
Regarding the production of the cathode, first, in the same manner as in the production of the EL element described above, an anode, an inorganic amorphous hole injection transport layer, an inorganic electron barrier layer, and a light emitting layer are sequentially formed. A thin film such as a-5i or N-type a-5iC is formed by a plasma CVD method or the like to provide an inorganic amorphous electron injection transport layer, and then a cathode is provided in the same manner as in the production of the EL element described above. In this manner, a desired EL element can be obtained.

In the fabrication of this EL element, the fabrication order was also reversed, and the cathode, inorganic amorphous electron injection and transport layer, light emitting layer, inorganic electron 1jiF wall layer, inorganic amorphous hole injection and transport layer, and anode were fabricated in this order. You may.

When applying a DC voltage to the organic EL device of the present invention obtained in this way, when a voltage of about 1 to 30 V is applied with the anode as + polarity and the cathode as - polarity, the light emission becomes transparent or translucent. It can be observed from the electrode side. Well, even if a voltage with the opposite polarity is applied, no light is emitted at all. Further, when applying an alternating voltage, light is emitted only when the anode is in a positive state and the cathode is in a negative state. Note that the waveform of the applied alternating current may be arbitrary.

[Example J] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 A glass substrate (25rrrm x 75mm x 1.1
mm size, manufactured by HOYA) was used as a transparent support substrate, and this was ultrasonically cleaned with inpropyl alcohol for 30 minutes.
Furthermore, it was washed by immersing it in isopropyl alcohol. This transparent support substrate was dried with dry nitrogen gas, fixed on a substrate holder of a capacitively coupled horizontal RF plasma device, and then treated with 500 pp of SiH4, CH diluted to 10% with hydrogen gas.
The chamber was filled with f:, B, H, diluted to m, through a mass flow controller, and the pressure ITorr was maintained. At this time, the gas flow rate ratio B, H, / (S iH4 + CH
4) was 0.31%, and a high frequency of 50 W and 13.56 MHz was applied to form a P-type a-5iC film with a thickness of 15 nm on the substrate at a substrate temperature of 190° C. to form IaHTL. After 20 days, open the chamber, glass substrate/ITO/P type a
-5iC was taken out and immediately attached to a substrate holder of a vacuum evaporation apparatus.

Coumarin 30 (KU3) on a molybdenum resistance heating boat
0) and attached it to a vacuum evaporation device.

After this, the pressure in the vacuum chamber was reduced to 2xlO-'Pa, and the KU30
Electrification is applied to the port, heated to 230 degrees Celsius, and deposited on the glass substrate/IT at a deposition rate of 0.1 to 0.3 im/s.
A light emitting layer having a thickness of 800 nm was obtained by vapor deposition on O/P type a-5iC. The temperature of the substrate during vapor deposition was room temperature.

After this, the vacuum chamber was opened, a stainless steel mask was placed on top of the light emitting layer, 3g of magnesium was placed in the molybdenum resistance heating port, copper was placed in the crucible of the electron beam evaporator, and the vacuum chamber was opened again for 1 hour. The pressure was reduced to .2×10-'Pa. Thereafter, the boat containing magnesium was energized to deposit magnesium at a deposition rate of 5 to 8 nm/s. At this time, the copper is heated by an electron beam at the same time to 0.1 to 0.3 i.
Copper was evaporated at m/s and mixed with the magnesium to form a counter electrode. With the above steps, the production of the electroluminescent device was completed. The ITO electrode of this element is the positive electrode, and the Mg
When a direct current of 4 cm was applied using a counter electrode made of a mixture of
A green luminescence was obtained. The maximum emission wavelength at this time is 493n
m, luminance brightness 90cd/m', luminous efficiency O, Q8Lm
/w att;.

Example 2 Glass substrate/ITO/P type a-3 was prepared in the same manner as in Example 1.
iC was produced. Furthermore, without opening the chamber, the residual gas was exhausted, and 5fH4 as in Example 1 and C and H4 diluted with hydrogen to 10% were introduced into the chamber through a mass flow controller, and the pressure was set to LTorr, CzH+
/ (CzH, +S + 84) -0,8 maintained,
A-5iC which is an electron barrier layer is lon with RF output of 40W.
After forming m-shaped holes, KU30/Mg was formed in the same manner as in Example 1.
:Cu was produced, and the production of the electroluminescent device was completed.

When DC 5V was applied using the ITO electrode of this device as the positive electrode and the counter electrode made of a mixture of Mg and copper as the negative electrode, a current with a current density of 50 mA/c+n'' flowed and green light emission was obtained.At this time, the light emission was at its maximum. Wavelength is 493 nm% CIE chromaticity coordinates are x-0,18, y-0,44 Emission brightness 1120 c
d/m2, and the luminous efficiency was 1.4 Ltrl/w, achieving high brightness and high efficiency due to the electron barrier layer.

Example 3 A device was produced in the same manner as in Example 2, but with a-5 in the electron barrier layer.
The difference was that iN was used. At this time, each gas of NHs and SiH4 was introduced using a mass flow controller at a flow rate ratio of NH3/SiH4-5, and the pressure was 0.3 Torr.

Film thickness is 1O under the conditions of RF output 15W and substrate temperature 250°C.
The nm shape was used. The composition of this a-5iN was determined by the Rutherford backscattering method as N/5i-1,2. When 6 V of DC was applied to this element, the same luminous efficiency and brightness as in Example 2 were obtained.

Example 4 After forming up to KU30 in the same manner as Example 2,
-5f was cut into a 20 nm shape. Preparation is H at 3oooppm
3 diluted PH3 and SiH as in Example 1 were flowed into the chamber at a flow rate ratio of PH3/SiH4-0.5%, and the pressure was 0.6 Torr.

The RF output was 20W and the substrate temperature was 60°C.

After this, an AI electrode is formed by vapor deposition, and the El-element fabrication is completed. When a direct current of 4 V was applied using the ITO electrode of this device as the positive electrode and the counter electrode made of AI as the negative electrode, a current with a current density of 60 mA/cm' flowed and green light was emitted.

The maximum emission wavelength at this time is 495 nm *Emission brightness 1
000cd/m2 Luminous efficiency is 1.3L m/w
Met.

Example 5 The ITO-coated substrate was cleaned in the same manner as in Example 1, and the B, H! changed to PH3 and made N-type a-8iC with a film thickness of 20n.
I made it. At this time, the flow rate ratio is 0.55%, and the pressure IT
The conditions were that the substrate temperature was 200°C and the RF output was 35W. Roughly the same a-8 as above as a hole blocking layer
iC was formed with a film thickness of 250 nm. However, the difference was that CH,/(CH4+S i H4)-0,3 at this time. After this, a light emitting layer of KU30 was formed in the same manner as in the example construction, and finally Au'! The poles were formed by vapor deposition.

When the Au electrode of this device was used as the positive electrode and the electrode made of ITO was used as the negative electrode, a DC current of 4 cm was applied, resulting in a current density of 8.3 mA/
A current of cm' was applied, and green light was emitted. The maximum emission wavelength at this time is 502 nm% emission brightness 400 c d /
m'', and the luminous efficiency was x, xLm/w.

Note that coumarin 30 refers to 3-(2″-N-methylbenzimidazolyl)-7-N,N-diethylaminocoumarin and has the following structure.

C.II.

! [Effects of the Invention] According to the present invention, by providing an inorganic amorphous charge injection transport layer and a light emitting layer between an anode and a cathode, and further providing a charge barrier layer as desired, a low driving voltage of about 5 V or less can be achieved. Moreover, an organic EL element capable of outputting high-luminance light with good luminous efficiency can be obtained.

The organic EL device of the present invention has such excellent characteristics,
It is suitably used as a light emitting element in various display devices.

Claims (1)

[Claims] 1. An organic electroluminescent device comprising an inorganic amorphous charge injection transport layer and a light emitting layer made of an organic compound between an anode and a cathode. 2. The organic electroluminescent device according to claim 1, wherein the inorganic amorphous charge injection transport layer is a hole injection transport layer and/or an electron injection transport layer. 3. The organic electroluminescent device according to claim 1 or 2, further comprising a charge barrier layer between the anode and the cathode. 4. The organic electroluminescent device according to claim 3, wherein the charge barrier layer is an electron barrier layer and/or a hole barrier layer.