JPH08199161A - Organic electroluminescent device - Google Patents

Abstract

(57) [Summary] [Object] To provide an organic electroluminescent device capable of maintaining stable light emitting characteristics for a long period of time and suppressing an increase in driving voltage. An organic electroluminescent device having at least a hole injection layer, a hole transport layer and an electron transport layer between an anode and a cathode, wherein the hole injection layer is treated with an organic solvent represented by the following general formula (2) ) Or the like, which is composed of a porphyrin compound and has a hole transport layer and an electron transport layer formed by a dry method. Embedded image (In the formula, R ³ and R ⁴ are each independently hydrogen, a halogen atom, a hydroxyl group, a saturated or unsaturated aliphatic hydrocarbon group,
Represents an aromatic hydrocarbon group, or R ³ and R ⁴
And may combine with each other to form a ring structure. Y represents a nitrogen atom or a CH group, and M represents a central ion such as a transition metal or a metal oxide. )

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device, and more particularly, to a thin film type device which emits light by applying an electric field to a light emitting layer made of an organic compound.

[0002]

2. Description of the Related Art Conventionally, as a thin film type electroluminescence (EL) element, Zn which is an inorganic material 〓-〓 group compound semiconductor is used.
It is general that S, CaS, SrS, etc. are doped with Mn or a rare earth element (Eu, Ce, Tb, Sm, etc.), which is the emission center, but the EL element made from the above inorganic material is 1). AC drive is required (50 to 1000 Hz), 2) high drive voltage (up to 200 V), 3) full colorization is difficult (especially blue is a problem), and 4) peripheral drive circuit costs are high. ing.

However, in recent years, in order to improve the above problems,
EL devices using organic thin films have been developed. In particular, the electrode type was optimized for the purpose of improving the efficiency of carrier injection from the electrode in order to increase the light emission efficiency, and the organic hole transport layer made of an aromatic diamine and the organic light emission made of an aluminum complex of 8-hydroxyquinoline. Of an organic electroluminescent device having a layer (Appl. Phy
s. Lett. , 51, p. 913, 1987), the luminous efficiency has been greatly improved as compared with the conventional EL device using a single crystal such as anthracene, and is close to practical characteristics.

However, the materials used in these devices are
Since the molecular weight is small, the stability of the film after film formation is poor, and there are drawbacks such that aggregation occurs in a few days to a few weeks, and the glass transition temperature is low, resulting in lack of thermal stability. Therefore, an attempt has been made to further stabilize the device by further inserting a porphyrin compound having a stable hole-transporting property between the anode and the hole-transporting layer (JP-A-63-295695). However, the drive voltage when the device is driven at a constant current density rises from 7 V to 11 V in 500 hours, and the rise of the drive voltage has not been suppressed yet.

On the other hand, in an attempt to stabilize the film by increasing the molecular weight of the element-constituting substance, for example, 1,3,5-tris (4-carbazolyl) phenyl) benzene as a starburst type substance (see JP-A-6- No. 312979),
Development of 4,4 ′, 4 ″ -tri (N-phenoxazinyl) triphenylamine (JP-A-6-312981) and the like can be mentioned.

In addition to the above low molecular weight materials, poly (p-phenylene vinylene) is used as a material for the organic light emitting layer.
(Nature, 347, 539, 1990),
Poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene] (Appl.Ph
ys. Lett. , 58, 1982, 1991)
And the like, and a device in which a low molecular weight light emitting material and an electron transfer material are mixed with a polymer such as polyvinylcarbazole (Applied Physics, Vol. 61, page 1044, 1992) are being developed.

[0007]

However, in the organic electroluminescent elements disclosed so far, the life of the element is extremely short, and the driving voltage increases when the element is driven at a constant current density. However, there is a drawback that stable driving characteristics cannot be obtained.

[0008]

In view of the above situation, the inventors of the present invention provide an organic electroluminescent device capable of maintaining stable light emitting characteristics for a long period of time and suppressing an increase in driving voltage. As a result of repeated intensive studies for the purpose, a layer composed of a specific porphyrin compound was used as the hole injection layer, the hole injection layer was treated with an organic solvent, and the hole transport layer and the electron transport layer were treated by a dry method. The present invention has been completed by finding that the above problems can be solved by forming a film by.

That is, the gist of the present invention is an organic electroluminescent device having at least a hole injection layer, a hole transport layer and an electron transport layer between an anode and a cathode, wherein the hole injection layer is an organic solvent. An organic electric field comprising a treated porphyrin compound represented by the following general formula (1) or (2), wherein the hole transport layer and the electron transport layer are formed by a dry method. It exists in the light emitting element.

[0010]

Embedded image

(In the formula, R ¹ and R ² are each independently hydrogen,
Halogen atom, hydroxyl group, saturated or unsaturated aliphatic hydrocarbon group which may have a substituent, aromatic hydrocarbon group which may have a substituent, alkoxy which may have a substituent Group, an aryloxy group which may have a substituent, a dialkylamino group which may have a substituent,
Or represents a diarylamino group which may have a substituent, or R ¹ and R ² are bonded to each other to form a ring structure,
It represents an aromatic hydrocarbon ring which may have a substituent or a heterocyclic ring which may have a substituent. X represents a nitrogen atom or a CH group. )

[0012]

[Chemical 4]

(In the formula, R ³ and R ⁴ are each independently hydrogen,
Halogen atom, hydroxyl group, saturated or unsaturated aliphatic hydrocarbon group which may have a substituent, aromatic hydrocarbon group which may have a substituent, alkoxy which may have a substituent Group, an aryloxy group which may have a substituent, a dialkylamino group which may have a substituent,
Or represents a diarylamino group which may have a substituent, or R ³ and R ⁴ are bonded to each other to form a ring structure,
It represents an aromatic hydrocarbon ring which may have a substituent or a heterocyclic ring which may have a substituent. Y represents a nitrogen atom or a CH group, and M represents an ion of a transition metal, a transition metal oxide or a transition metal halide. ) Hereinafter, the organic electroluminescent element of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view schematically showing a constitutional example of the organic electroluminescent device of the present invention, in which 1 is a substrate, 2 is an anode, and 3 is.
Is a hole injection layer, 4 is a hole transport layer, 5 is an electron transport layer, and 6 is a cathode. The substrate 1 is used as a support of the organic electroluminescent element of the present invention, and a plate of quartz or glass, a metal plate or metal foil, a plastic film or sheet, etc. is used. A glass plate and a transparent synthetic resin plate such as polyester, polymethylmethacrylate, polycarbonate, and polysulfone are particularly preferable.

An anode 2 is provided on the substrate 1. Anode 2
Plays a role of injecting holes into the organic light emitting layer.
This anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium, or tellurium, a metal oxide such as an oxide of indium and / or tin, copper iodide, carbon black, or poly (3-). (Methylthiophene), a conductive polymer such as polyaniline. The anode 2 is usually formed by a sputtering method, a vacuum vapor deposition method or the like, but fine particles of a metal such as silver or copper iodide, carbon black, fine particles of a conductive metal oxide, or a conductive polymer. In the case of fine powder or the like, it can also be formed by dispersing it in an appropriate binder resin solution and applying it on a substrate. Further, in the case of a conductive polymer, a thin film can be directly formed on the substrate by electrolytic polymerization, or can be formed by coating on the substrate (App.
l. Phys. Lett. , 60, 2711, 19
1992). The anode 2 may be a laminate of different materials. The thickness of the anode 2 varies depending on the required transparency, but when the transparency is required, it is desirable that the visible light transmittance is 60% or more, preferably 80% or more. Is usually 5 to 1000 n
m, preferably about 10 to 500 nm.

When it is opaque, the anode 2 may be made of the same material as the substrate 1, and the substrate 1 can also serve as the anode 2.
It is also possible to stack different conductive materials on the above-mentioned anode. A hole injection layer 3 is provided on the anode 2. It is required for the material of the hole injection layer 3 that holes are easily injected from the anode, it is difficult to form a trap at the interface, and the film is stable. In the present invention, the porphyrin compound represented by the general formula (1) or (2) is used as the hole injection layer 3. Examples of preferred porphyrin compounds
1, shown in Table-2, but not limited thereto.

[0017]

[Table 1]

[0018]

[Table 2]

The upper limit of the thickness of the hole injection layer 3 is determined by the light transmittance, and the lower limit is determined by the anode coverage. The lower limit of film thickness is
It is not less than the center line average roughness (Ra) of the surface of the anode 2, preferably not less than twice the center line average roughness. For example, indium tin oxide (hereinafter referred to as “I
"TO") is generally a stylus type surface roughness tester (Taylor ST manufactured by Taylor Hobson).
When measured by EP), the center line average roughness (Ra) in the surface roughness of JIS B0601 is 0.7 nm to 1.5.
It has a value of about nm. Therefore, when ITO is used as the anode 2, the thickness of the hole injection layer is 1.5 nm or more, preferably 3 nm or more, and particularly preferably 5 nm or more. The upper limit of the film thickness is usually 300 nm or less, preferably 200 nm or less.

In the present invention, it is necessary to treat these hole injection layers with an organic solvent. Solvents used for the treatment are generally aromatic hydrocarbons such as toluene, xylene and benzene, alcohols such as methanol, ethanol and isopropyl alcohol, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, ethyl ether, 1 , 4-dioxane, tetrahydrofuran (TH
F) and the like ethers, carbon tetrachloride, halogenated hydrocarbons such as chloroform, nitro compounds such as nitrobenzene and nitromethane, methylaniline, dimethylaniline, pyridine, picoline, pyrazine, biperidine, methylamine, dimethylamine, trimethylamine, Examples include amines such as diethylamine and n-hexylamine, and other solvents such as aprotic polar solvents such as dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF) N-methylpyrrolidone.

As the method of treatment, there are a method of exposing to a solvent vapor, a method of directly immersing in a solvent, and the like. The treatment time is generally 1 second or more and 10 hours or less, preferably 30 minutes or more and 10 hours or less in the method of exposing to solvent vapor, and 10 seconds or more and 30 minutes or less in the method of directly dipping in the solvent. It is preferable to remove the solvent quickly after the treatment. Although the film is crystallized by the solvent treatment, the crystal is extremely stable, and a stabilized hole injection layer can be formed.

The hole transport layer 4 is formed on the hole injection layer 3. The material for the hole-transporting layer is required to have high hole mobility, excellent stability, and resistance to generation of impurities serving as traps during production or use. As such a hole transport material, for example, 1,1-bis (4
-Di-p-tolylaminophenyl) cyclohexane and other aromatic diamine compounds linked to a tertiary aromatic amine unit (JP-A-59-194393), 4,4'-
Aromatic amines containing two or more tertiary amines represented by bis [N- (1-naphthyl) -N-phenylamino] biphenyl and having two or more fused aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-312058). -234681), an aromatic triamine having a starburst structure with a derivative of triphenylbenzene (US Pat. No. 4,923,774), N, N '.
-Diphenyl-N, N'-bis (3-methylphenyl)
-Aromatic diamines such as biphenyl-4,4'-diamine (US Pat. No. 4,764,625), α, α, α ′,
α'-Tetramethyl-α, α'-bis (4-di-p-tolylaminophenyl) -p-xylene (JP-A-3-26)
9084), a triphenylamine derivative which is sterically asymmetric as a whole molecule (JP-A-4-12927), a compound in which a plurality of aromatic diamino groups are substituted on a pyrenyl group (JP-A-4-175395), Aromatic diamines in which tertiary aromatic amine units are linked by ethylene groups (JP-A-4-264189), aromatic diamines having a styryl structure (JP-A-4-290851), and aromatic tertiary amines with thiophene groups. One in which units are linked (JP-A-4-304466), a starburst type aromatic triamine (JP-A-4-308688), and a benzylphenyl compound (JP-A-4-3641).
53), those in which a tertiary amine is linked by a fluorene group (JP-A-5-25473), triamine compounds (JP-A-5-239455), bisdipyridylaminobiphenyl (JP-A-5-320634). ,
N, N, N-triphenylamine derivative (Japanese Patent Laid-Open No. 6-1
972), an aromatic diamine having a phenoxazine structure (Japanese Patent Application No. 5-290728), and a diaminophenylphenanthridine derivative (Japanese Patent Application No. 6-45669).
Aromatic amine compound, hydrazone compound (JP-A-2-311591), silazane compound (US Pat. No. 4,950,950), silanamin derivative (JP-A-6-49079), phosphamine derivative (JP-A-6-25659), quinacridone compounds and the like. These compounds may be used alone or in combination.

As the film forming method of the above organic hole transporting material, there are roughly classified two kinds of film forming methods such as a wet film forming method and a dry film forming method, but a wet method such as a spin coat method or a dip method is known. When a laminated film is formed by the film formation method, the interfaces of the hole injection layer and the hole transport layer are mixed with each other, and a clear layer structure cannot be formed. Therefore, it is difficult to control the state of the interface and the device is manufactured with good reproducibility. Is difficult. Therefore, in the present invention, the hole transport layer 4 is formed by a dry film forming method. Examples of the dry film forming method of the organic hole transporting material include a vacuum vapor deposition method and an ionization vapor deposition method, and the vacuum vapor deposition method is usually used.

When the hole transport layer 4 is formed, a metal complex and / or a metal salt of an aromatic carboxylic acid is further used as an acceptor (JP-A-4-320484),
A benzophenone derivative and a thiobenzophenone derivative (JP-A-5-295361) and fullerenes (JP-A-5-331458) are doped at a concentration of 10 ⁻³ to 10% by weight to generate holes as free carriers. Therefore, it is possible to drive at a low voltage.

The thickness of the hole transport layer 4 is usually 10 to 30.
It is 0 nm, preferably 30 to 100 nm. As the material of the hole transport layer 4, it is possible to use an inorganic material instead of an organic compound. The conditions required for the inorganic material are the same as those for the organic hole transport material. Examples of the inorganic material used for the hole transport layer 4 include p-type hydrogenated amorphous silicon, p-type hydrogenated amorphous silicon carbide, p-type hydrogenated microcrystalline silicon carbide, p-type zinc sulfide, and p-type zinc sulfide. Examples include type zinc selenide. These inorganic hole transport layers are CV
It is formed by the D method, plasma CVD method, vacuum deposition method, sputtering method, or the like.

The thickness of the inorganic hole transporting layer is usually 10 to 300 nm, preferably 30 to 1 like the organic hole transporting layer.
00 nm. An electron transport layer 5 is provided on the hole transport layer 4. The electron transport layer 5 is formed of a compound capable of efficiently transporting electrons from the cathode toward the hole transport layer 4 between the electrodes to which an electric field is applied.

The electron transport material must be a compound that has a high electron injection efficiency from the cathode 6 and can efficiently transport the injected electrons. For this purpose, it is required that the compound has a high electron affinity, a high electron mobility, excellent stability, and is unlikely to generate impurities serving as traps during production or use.

As materials satisfying such conditions, aromatic compounds such as tetraphenyl butadiene (Japanese Patent Laid-Open No. Sho 5)
7-51781), a metal complex such as an aluminum complex of 8-hydroxyquinoline (JP-A-59-1943).
93), a cyclopentadiene derivative (JP-A-2-
289675), perinone derivatives (JP-A-2-2)
No. 89676), an oxadiazole derivative (JP-A-2-216791), and a bisstyrylbenzene derivative (JP-A 1-245087, 2-222248).
4), perylene derivative (JP-A-2-189890).
JP-A No. 3-791, JP), coumarin compound (JP-A-2-191694-, JP-A-3-792), rare earth complex (JP-A-1-256584), distyrylpyrazine derivative (JP-A-2). -252793),
p-phenylene compound (JP-A-3-33183), thiadiazolopyridine derivative (JP-A-3-372)
92), a pyrrolopyridine derivative (JP-A-3-37).
293), naphthyridine derivatives (JP-A-3-20).
3982).

The electron transport layer 5 using these compounds is
It simultaneously plays a role of transporting electrons and a role of causing light emission upon recombination of holes and electrons. When the hole transport layer 4 has a light emitting function, the electron transport layer 5 serves only to transport electrons. Examples of the dry film forming method of the electron transport layer include a vacuum evaporation method and an ionization evaporation method.

For the purpose of improving the luminous efficiency of the device and changing the luminescent color, for example, a fluorescent dye for laser such as coumarin is doped with an aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. Ph.
ys. , 65, 3610, 1989). Also in the present invention, the emission characteristics of the device can be further improved by doping the above-mentioned electron transport material as a host material with various fluorescent dyes at 10 ⁻³ to 10 mol%. The thickness of the electron transport layer 5 is usually 10 to 200.
nm, preferably 30-100 nm.

As a method for further improving the luminous efficiency of the organic electroluminescence device, another electron transport layer 5b may be laminated on the electron transport layer 5 as shown in FIG.
The compound used for the electron transport layer 5b is required to be capable of easily injecting electrons from the cathode and having a further high electron transporting ability. As such an electron transport material, for example,

[0032]

Embedded image

[0033]

[Chemical 6]

Oxadiazole derivatives such as (App
l. Phys. Lett. , 55, 1489, 19
1989; Jpn. J. Appl. Phys. , 31 volumes,
1812, 1992) or a system in which they are dispersed in a resin such as polymethylmethacrylate (Appl. Phys.
Lett. , 61, 2793, 1992), or n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n
Examples include type zinc selenide. The thickness of the electron transport layer 5b is usually 5 to 200 nm, preferably 10 to 100 n.
m.

An interface layer 5 is provided between the electron transport layer and the cathode 6.
It is also possible to provide c (see FIGS. 2-3). The role of the interface layer is that it has an affinity with the electron transport layer and at the same time has good adhesiveness with the cathode, and is chemically stable, so that the reaction between the electron transport layer and the cathode during and / or after the formation of the cathode can be performed. It has a suppressing effect. It is also important to provide a uniform thin film shape from the viewpoint of adhesion with the cathode.
As a material that plays such a role, an aromatic amine compound (Japanese Patent Application No. 5-290728), a compound having a phenylcarbazole skeleton (Japanese Patent Application No. 6-199562), and a poly-vinylcarbazole derivative (Japanese Patent Application No. 6-
20092) and the like.

When forming the above-mentioned interface layer, these compounds may be mixed and used. Further, for the purpose of improving the stability of the film of the interface layer, other fluorescent dyes, light emitting materials and the like can be mixed. Examples of the materials to be mixed include compounds consisting of aromatic amines, laser dyes such as coumarin derivatives, polycyclic aromatic dyes such as perylene and rubrene, organic pigments such as quinacridone, and 8-hydroxyquinoline metal complexes. Can be mentioned.

A cathode 6 is provided on the electron transport layer or the interface layer. The film thickness of the cathode 6 is usually the same as that of the anode 2. Although not shown in FIG. 1, a substrate similar to the substrate 1 may be further provided on the cathode 6. However, it is required that at least one of the anode 2 and the cathode 6 has good transparency.
It is necessary as an L element. From this, one of the anode 2 and the cathode 6 preferably has a film thickness of 10 to 500 nm and is desired to have good transparency.

In the organic electroluminescent device of the present invention, a protective film may be formed, if necessary, and the entire device may be sealed. The material of the protective film is Al, Ni, Au, Ag
And other metals (JP-A-3-141588, JP-A-4-141588)
6795, JP 4-19993, US Pat. No. 5,059,862, JP 4-363896, JP 5-315078), and metal oxides (JP 4-212284). Japanese Patent Laid-Open No. 4-7388
6, JP-A-5-335080), metal fluoride (JP-A-4-212284), metal sulfide (JP-A-4-212284), metal nitride (JP-A-4-212284). No. 73886), polymer (JP-A-4-
Japanese Patent No. 137483, Japanese Patent Laid-Open No. 4-206386,
JP-A-4-233192, JP-A-4-26709
No. 7, JP-A-4-355096), plasma polymerized film (JP-A-5-101886) and the like. As a sealing method, the element is placed in an airtight case and an oxygen adsorbent or a water adsorbent is placed inside (Japanese Patent Laid-Open No. 3-3).
7991, JP-A-3-261091), a method of putting an element in an inert liquid or oil (JP-A-4-3).
No. 63890, No. 5-36475, No. 5-41281, No. 5-114486, No. 5-129080, and a method using a photocurable resin (No. 4-267097). Japanese Patent Laid-Open Publication No. Hei 5
No. 182759, JP-A No. 5-290976) and the like.

Further, the organic electroluminescent device of the present invention can be subjected to aging in order to stabilize the initial light emitting characteristics at an early stage. The aging method is not particularly limited, and it can be performed, for example, by previously driving with a current density of 1 to 1000 times the current density when actually driving the element.

In general, the emission luminance required practically as a display device or a light source is 50 to 100 cd / m ² . In order to achieve this brightness, the organic electroluminescent device of the present invention is usually driven at a current density in the range of 0.1 to 100 mA / cm ² . Here, the current density is a value obtained by dividing the current flowing in each pixel by the area of the pixel in the case of a panel, and is a value obtained by dividing the total current by the area of the light emitting portion in the case of a light source.

In order to use the organic electroluminescent device as a display panel, a matrix address method (Japanese Patent Laid-Open No. 2-66873; IEICE Technical Report, OME 89-46, 37, 1989) is generally adopted. It In this simple matrix panel, the anode and the cathode form an XY matrix, which corresponds to X data lines and Y scan lines. In the aging of such a simple matrix panel, a method of sequentially turning on the scan lines while all X data are turned on is adopted. In this aging method, each scan line is pulse-driven with a duty corresponding to the number of Y's. In order to perform the aging at a higher speed, a method in which all scan lines are short-circuited externally may be used.

The above-mentioned simple matrix type panel has a problem of crosstalk and a problem that the light emission luminance is lowered because the duty becomes very small when the number of pixels is increased. However, in order to solve these problems, the active matrix is active. Driving with a matrix circuit is conceivable (Japanese Patent Laid-Open No. 2-14
8687, etc.). In the case of the above active matrix type panel, all the data corresponding to each pixel is turned on.
Then just age it.

[0043]

EXAMPLES Next, specific embodiments of the present invention will be further described by way of examples, but the present invention is not limited by the following description of the examples as long as the gist thereof is not exceeded. Example 1 An organic electroluminescent device having the structure shown in FIG. 1 was produced by the following method. 120 transparent ITO conductive film on the glass substrate
After performing ultrasonic cleaning with acetone, water cleaning with pure water, ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen, and UV / ozone cleaning, the product deposited in a vacuum vapor deposition apparatus is installed in the apparatus. It was evacuated using an oil diffusion pump until the degree of vacuum became 2 × 10 ⁻⁶ Torr or less.

As a material for the organic hole injection layer, copper phthalocyanine (Cu) represented by the structural formula of P-2-1 in Table 2 above is used.
Pc) was put in a molybdenum boat and heat vapor deposition was performed. At this time, the degree of vacuum was 5 × 10 ⁻⁵ Torr, and an organic hole injecting layer 3 having a film thickness of 20 nm was obtained in a vapor deposition time of 1 minute. This substrate was taken out into the atmosphere, immersed in a toluene solvent, and subjected to a solvent treatment for 30 seconds. This substrate was set in the vacuum vapor deposition apparatus again, and exhausted using an oil diffusion pump until the degree of vacuum in the apparatus became 2 × 10 ⁻⁶ Torr or less. On this substrate, an aromatic amine compound (H-1) as an organic hole transport layer material

[0045]

[Chemical 7]

[0046] The sample was placed in a ceramic crucible and heated by a tantalum wire heater around the crucible for vapor deposition. The temperature of the crucible at this time was controlled in the range of 190 to 210 ° C. The degree of vacuum during vapor deposition was 4.0 × 10 ⁻⁶ Torr, and an organic hole transport layer 4 having a film thickness of 60 nm was obtained with a vapor deposition time of 1 minute and 30 seconds.
Next, as an organic electron transporting material, an aluminum 8-hydroxyquinoline complex represented by the following structural formula, Al (C ₉ H ₆
NO) ₃ (E-1)

[0047]

Embedded image

The above was vapor-deposited on the organic hole transport layer 4 in the same manner. The temperature of the crucible at this time is 450-46
Control was performed in the range of 0 ° C. The degree of vacuum during vapor deposition is 2.5 x 10
An electron transport layer 5 having a film thickness of 75 nm was obtained with a deposition time of 1 minute and 30 seconds at ^-6 Torr. This layer also serves as a light emitting layer.

Finally, a cathode 6 was formed by depositing an alloy of magnesium and silver with a film thickness of 150 nm by the binary simultaneous vapor deposition method. A molybdenum boat was used for vapor deposition, the degree of vacuum was 1 × 10 ⁻⁵ Torr, and the vapor deposition time was 2 minutes and 30 seconds to obtain a glossy film. The atomic ratio of magnesium to silver is 10: 1.
Met.

Light emission was measured by applying a positive DC voltage to the ITO electrode (anode) and a negative DC voltage to the magnesium-silver alloy electrode (cathode) of the organic electroluminescence device thus produced. With this device, a current density of 6.1 mA / cm ² was obtained when 5 V was applied, and the brightness at that time was 130 cd / m ² . A current density of 253 mA / cm ² was obtained when 10 V was applied, and the luminance at that time was 5412 cd / m ² .

When the surface shape of the CuPc film was observed by SEM before and after the toluene solvent treatment, the surface shape before the treatment was a granular shape affected by the grain boundaries of the substrate, and after the treatment, it was a rod shape. there were. The roughness of each film was Ra, which was 0.9 nm before the treatment and 1.2 nm after the treatment.

Comparative Example 1 A device was prepared in the same manner as in Example 1 except that the hole injection layer was not provided and the hole transport layer had a thickness of 60 nm. This device obtained a current density of 4.6 mA / cm ² when a voltage of 14 V was applied, and the luminance at that time was 156 cd / m ² . FIG. 4 shows how the voltage changes when the devices of Example 1 and Comparative Example 1 are driven at a constant current density of 15 mA / cm ² . The device having the CuPc layer subjected to the organic solvent treatment is 9
It was stable even after being driven for 00 hours, and had a voltage increase of about 1 V from the initial stage.

Comparative Example 2 A device was prepared in the same manner as in Example 1 except that the treatment with the organic solvent was omitted. Example 1 and this element are 15 mA /
FIG. 5 shows how the voltage changes when driven at a constant current density of cm ² . The driving voltage of this device increased by 6.5 V after driving for 350 hours.

[0054]

According to the organic electroluminescence device of the present invention, an anode, a hole injection layer, a hole transport layer, an electron transport layer and a cathode are sequentially provided on a substrate, and a porphyrin compound is used for the hole injection layer. In addition, by treating with an organic solvent, the film is more stabilized, a uniform light emitting surface can be obtained over a long period of time, and stable light emitting characteristics can be obtained. Therefore, the EL element of the present invention is a light source (for example, a light source of a copying machine, a liquid crystal display or a backlight of an instrument) that makes use of the characteristics of a flat panel display (for example, for an OA computer or a wall-mounted television) or a surface light emitter. light source),
It can be applied to display boards and marker lights, and its technical value is great.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of an organic electroluminescent element of the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the organic electroluminescent element of the present invention.

FIG. 3 is a schematic cross-sectional view showing still another example of the layer structure of the organic electroluminescent element of the present invention.

FIG. 4 shows the devices of Example 1 and Comparative Example 1 at 15 mA / cm ^2.
Driving voltage characteristics when driven with a constant current density of.

FIG. 5 shows the devices of Example 1 and Comparative Example 2 at 15 mA / cm ^2.
Driving voltage characteristics when driven with a constant current density of.

[Explanation of symbols]

 1 substrate 2 anode 3 hole injection layer 4 hole transport layer 5 electron transport layer 5b electron transport layer 5c composed of a compound different from 5 interface layer 6 cathode

Claims (3)

[Claims] 1. An organic electroluminescent device having at least a hole injection layer, a hole transport layer and an electron transport layer between an anode and a cathode, wherein the hole injection layer is treated with an organic solvent. An organic electroluminescent device comprising a porphyrin compound represented by (1) or (2), wherein the hole transport layer and the electron transport layer are formed by a dry method. Embedded image (In the formula, R ¹ and R ² are each independently hydrogen, a halogen atom, a hydroxyl group, a saturated or unsaturated aliphatic hydrocarbon group which may have a substituent, and an aromatic which may have a substituent. Group hydrocarbon group, optionally substituted alkoxy group, optionally substituted aryloxy group, optionally substituted dialkylamino group, or optionally substituted Optionally represents a diarylamino group, or R ¹ and R ² are bonded to each other to form a ring structure, which may have an aromatic hydrocarbon ring which may have a substituent or which has a substituent. And X represents a nitrogen atom or C
Represents an H group. ) (In the formula, R ³ and R ⁴ are each independently hydrogen, a halogen atom, a hydroxyl group, a saturated or unsaturated aliphatic hydrocarbon group which may have a substituent, and an aromatic which may have a substituent. Group hydrocarbon group, optionally substituted alkoxy group, optionally substituted aryloxy group, optionally substituted dialkylamino group, or optionally substituted Optionally represents a diarylamino group, or R ³ and R ⁴ are bonded to each other to form a ring structure, which may have a substituent, an aromatic hydrocarbon ring, or a substituent. And Y represents a nitrogen atom or C
Represents a H group, and M represents an ion of a transition metal, a transition metal oxide or a transition metal halide. ) 2. The central ion M in the above general formula (2).
The organic electroluminescent device according to claim 1, wherein is a transition metal. 3. The central ion M in the above general formula (2).
The organic electroluminescent device according to claim 1, wherein is TiO or VO.