JPH11256148A - Luminous material and organic el element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a material for an organic luminous layer favorable for utilizing energy transferred to a triplet exciton for light emission by including a phosphorescent substance having a specific value or above of phosphorescent luminous intensity and a triplet level and a rare earth complex therein. SOLUTION: This material comprises a phosphorescent substance having a phosphorescent luminous intensity of that of benzophenone or above and a rare earth complex (e.g. a europium complex having a β-diketone ligand), and the phosphorescent substance has a triplet level of that of a ligand in the rare earth complex or above. The phosphorescent substance preferably contains a benzoyl group represented by formula I (R1 is an alkyl, a cycloalkyl, an acyl or an aryl; R2 to R6 are each H, an alkyl, a cycloalkyl, an acyl or an aryl) or its complex group and is especially preferably a benzophenone derivative represented by formula II (R1 to R10 are each H, hydroxyl group, an alkyl, a cycloalkyl, an acyl, amino, nitro, an alkoxy, cyano or an aryl) or its derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (hereinafter simply referred to as "organic EL") device, and more particularly to a material for an organic light emitting layer of an organic EL device.

[0002]

2. Description of the Related Art A light-emitting element (organic EL element) utilizing organic electroluminescence obtained by applying an electric field to an organic material is disclosed in Document 1 (Document 1: "Organic EL").
ectroluminescent diodes '' CWTang and SAVanSlyk
e, Appl. Phys. Lett. vol 51 No.12 pp913-915 (1987)), Tang et al. have been active in research and development since realizing a light-emitting element that can emit light with high luminance at low voltage. Have been done.

The organic EL device of Document 1 is of a two-layer type including an anode, a hole transport layer, an organic light emitting layer and a cathode, in which holes injected from the anode and electrons injected from the cathode are used. Recombination causes the energy generated by the recombination to excite the organic compound in the organic light emitting layer. Then, upon deactivation from the excited state, light emission specific to the compound is emitted. In Document 1, surface light with a luminance exceeding 1000 cd / m ² is obtained at a DC voltage of about 10 V.

[0004]

However, in the conventional organic EL device, most of the energy generated by recombination of holes and electrons is consumed as heat. More specifically, recombination of holes and electrons generates electrically neutral molecular excitons. Light emission occurs via this molecular exciton. The generated molecular exciton is a mixture of a singlet exciton and a triplet exciton, and the singlet exciton and the triplet exciton generally have a triplet excitation ratio of 1: 3. It is said that more children are created. In addition, excitons that contribute to light emission are singlet excitons, and triplet excitons are non-emissive. Therefore, the triplet exciton is eventually consumed as heat, and light emission is generated from the singlet exciton having a low generation rate. Therefore, in the organic EL element, of the energy generated by the recombination of holes and electrons, the energy transferred to the triplet exciton has a large loss.

Therefore, in recent years, researches have been made to effectively utilize the energy transferred to triplet excitons for light emission.

For example, as described in Document 2,
A material system called a rare earth complex emits light via a triplet level of a ligand (Reference 2: “Relations between Intr”).
amolecular Energy Transfer Efficiencies and Triple
t State Energies in Rare Earth β-diketone Chelate
s '' S.Sato and M.Wada: Bull.Chem.Soc.Jpn.vol.43pp
1955-1962 (1970)). In addition, since the transfer of energy from a triplet level to another triplet level is easily performed without inversion of electron spin, as described in Reference 3, carrier recombination occurs. It is considered that the energy of the generated triplet exciton is transferred to the triplet level of the rare-earth complex and is extracted as light emission of rare-earth ions in the rare-earth complex. Thereby, the luminous efficiency of the organic EL element can be dramatically improved (Reference 3: Japanese Patent Application Laid-Open No. 8-319482). Furthermore, in order to obtain light emission from the rare-earth complex, each material is selected such that the triplet level of the host material doped with the rare-earth complex is higher than the triplet level of the ligand of the rare-earth complex. Thin-film EL
In forming an element, it is necessary to select the material of each layer so that the triplet level of the host material doped with the rare earth complex is lower than the triplet level of the material forming another thin film layer.

However, it has been difficult to specifically specify a host material that satisfies the above conditions from among materials having many triplet levels.

For this reason, there has been a demand for the appearance of a preferable material for the organic light emitting layer for utilizing the energy transferred to the triplet exciton for light emission.

[0009]

According to the present invention, there is provided a light-emitting material comprising a phosphorescent substance having a phosphorescence intensity higher than that of benzophenone and a rare-earth complex. The phosphorescent substance is a substance having a triplet level equal to or higher than the triplet level of the ligand of the rare earth complex.

[0010] Here, a phosphorescent substance is a substance whose emission intensity based on a transition from a triplet energy state to a ground singlet state is higher than other substances.

When this light emitting material is used as a material for an organic light emitting layer of an organic EL device, the energy of triplet excitons generated by recombination of carriers injected from a cathode and an anode is more triplet than that of a phosphorescent substance. It can be transferred to the triplet level of a rare earth complex having a low level. Then, the transferred energy can be extracted as light emission of rare earth ions in the rare earth complex. Also, if a phosphorescent substance having a phosphorescence intensity equal to or higher than that of benzophenone is used,
Light emission with sufficient intensity as an organic EL element can be obtained. In addition, strong phosphorescence means having a clear triplet level, and energy is not easily deactivated by heat due to the presence of an unknown level due to impurities or the like. That means.
Therefore, energy can be efficiently transferred from the triplet level to the rare earth complex before the energy is thermally deactivated.

The phosphor preferably contains a benzoyl group or a complex group of a benzoyl group represented by the following formula (1).

[0013]

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R1 in the above formula (1) is a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted aryl group. Also, R2
To R6 each consist of hydrogen, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted acyl group, or a substituted or unsubstituted aryl group. Is good. These R2 to R6 may be the same group, may be partially different, or may be entirely composed of different groups.

Here, the substituted alkyl group is, for example, a trifluoromethyl group or a trichloromethyl group.
An unsubstituted alkyl group refers to, for example, a methyl group or an ethyl group. Further, the substituted cycloalkyl group is, for example, a cyclopropyl group or a cyclobutyl hydroxide group, and the unsubstituted cycloalkyl group is a cyclobutyl group or a cyclohexyl group. The substituted acyl group is, for example, a trifluoroacetyl group and the like, and the unsubstituted acyl group is an acetyl group and the like. The substituted aryl group is, for example, a chlorophenyl group or a phenylhydroxide group, and the unsubstituted aryl group is, for example, a phenyl group, a naphthyl group, or the like.

For example, when all of R2 to R6 are hydrogen, the above formula (1) is a benzoyl group.

The phosphorescent substance is preferably benzophenone or a benzophenone derivative represented by the following formula (2).

[0018]

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Each of R1 to R10 in the above formula (2) is hydrogen, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted acyl group, or A substituted or unsubstituted amino group, or a nitro group, or a substituted or unsubstituted alkoxy group, or a cyano group,
Alternatively, it is a substituted or unsubstituted aryl group. R1 to R10 may be the same group, may be partially different, or may be entirely different groups. The benzophenone or benzophenone derivative represented by the above formula (2) contains the benzoyl group (or a benzoyl group composite group) represented by the above formula (1). By using benzophenone (or a derivative of benzophenone) in which R1 of the benzoyl group is a phenyl group as a light-emitting material in an organic EL device,
High intensity light emission is obtained.

Incidentally, a substituted or unsubstituted alkyl group,
The substituted or unsubstituted cycloalkyl group, the substituted or unsubstituted acyl group, and the substituted or unsubstituted aryl group are specifically the groups described above. The substituted amino group is, for example, a dimethylamino group. The substituted alkoxy group is, for example, a chloromethoxy group and the like, and the unsubstituted alkoxy group is, for example, a methoxy group and an ethoxy group.

The derivative is a compound obtained by partially modifying the compound represented by the above formula (2) within a range that does not impair the object of the present invention. For example, a derivative of this benzophenone is represented by 2-amino-5-nitrobenzophenone, 4,4′-dimethoxybenzophenone,
One or two or more substances selected from the group of benzoylbiphenyl, 4,4'-bis (dimethylamino) benzophenone, and 4-morpholinobenzophenone are preferable. These substances have higher phosphorescence emission intensity than benzophenone. When these substances are used as a light emitting material in an organic EL device, light emission with higher intensity can be obtained.

Further, triphenylacetophenone or a derivative thereof represented by the following formula (3) may be used as the phosphorescent substance.

[0023]

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In the formula (3), each of R1 to R20 is hydrogen, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted acyl group. Or a substituted or unsubstituted aryl group. Further, R1 to R20 may be the same group, may be partially different, or may be entirely composed of different groups.
If all of R1 to R20 are hydrogen, it becomes 2,2,2-triphenylacetophenone (see the following formula (4)).
The substituted or unsubstituted alkyl group, the substituted or unsubstituted cycloalkyl group, the substituted or unsubstituted acyl group, and the substituted or unsubstituted aryl group are specifically the groups described above. Is good.

[0025]

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When this is used as a phosphorescent material and a light emitting material is formed in combination with a rare earth complex, the energy of the triplet exciton generated in triphenylacetophenone is converted to the triplet level of the ligand of the rare earth complex. It can be efficiently transferred and extracted as emission of rare earth ions. Thereby, the luminous efficiency can be improved as compared with the related art.

Further, methyl derivatives of triphenyl acetophenone, and the R2 and R15 in the formula (3) as a methyl group (-CH ₃₎ [2,2-diphenyl-2
(2-Methylphenyl)] ethyl-2-methylphenone (hereinafter referred to as Me-TPAP) (see formula (5) below) may be used as the phosphorescent substance.

[0028]

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The rare earth complex of the light emitting material is preferably a europium complex having a β-diketone ligand. When such a rare-earth complex is excited to emit light, light emission having a higher intensity and a longer life than other materials can be obtained. This is described in detail in, for example, Reference 4 (Reference 4: Fluorescense Enhancementby).
Electron-Withdrawing Groups onβ-Diketones in Eu
(III) -β-diketonato-topo Ternary Complexes, Analyti
cal Sciences vol.12 pp31-36 (1996), J.Yuan and K.Mat
sumoto).

[0030] In compounds and rare earth complex which is composed of a rare earth element ion, a ligand, generally, RE _n
(L1) _m (L2) _l . Here, RE is a rare earth element ion, L1 is a main ligand, and L2 is a second ligand. Further, n and m are positive integers, and l is 0 or a positive integer. The rare earth elements include scandium (Sc), yttrium (Y), and yttrium (Y) belonging to Group IIIa subgroup of the periodic table.
And lanthanoids (15 elements from lanthanum (La) to lutetium (Lu)). Among them, elemental ions involved in light emission include europium ion (Eu ³⁺ ) that emits red light and terbium ion (Tu) that emits green light.
b ³⁺ ) and cerium ion (Ce ³⁺ ) which emits blue light. In addition, the main ligand has a negative charge, and the charge of the molecule is neutralized by coordinating with the positively charged rare earth element ion. As the main ligand, β
-Diketones and quinolinols. The second ligand is generally an electrically neutral ligand. By coordinating to the rare earth element together with the main ligand, the second ligand satisfies the coordination number of the complex and stabilizes the compound. It works to make it in a good state. Examples of the second ligand include 1,10-phenanthroline, dipyridyl, terpyridyl and the like.

In an organic EL device having an anode, an organic light emitting layer, and a cathode, it is preferable to use the above-mentioned light emitting material as a material for the organic light emitting layer.

This luminescent material comprises a phosphor having a phosphorescence intensity equal to or higher than that of benzophenone and a rare earth complex. This phosphorescent substance is a substance having a triplet level equal to or higher than the triplet level of the ligand of the rare earth complex. For this reason, among the molecular excitons generated in the organic light emitting layer by the recombination of carriers, the energy of the triplet exciton that has not conventionally contributed to light emission can be extracted as light emission. Specifically, the energy of the triplet exciton generated in the phosphor is transferred to the triplet level of the ligand of the rare earth complex whose triplet level is lower than that of the phosphor, and finally the emission of rare earth element ions Take out as. By using a phosphorescent substance having a phosphorescence emission intensity equal to or higher than that of benzophenone, light emission with an intensity which can be used as an organic EL element can be obtained. Further, since the energy of the triplet exciton, which has conventionally been an energy loss, can be taken out as luminescence, luminous efficiency can be greatly improved.

The phosphor preferably contains a benzoyl group of the formula (1) or a complex group of a benzoyl group. Among them, benzophenone represented by the formula (2) or a derivative thereof is preferable. Further, among the substances represented by the formula (2), 2-amino-
One or more substances selected from the group consisting of 5-nitrobenzophenone, 4,4'-dimethoxybenzophenone, 4-benzoylbiphenyl, 4,4'-bis (dimethylamino) benzophenone, and 4-morpholinobenzophenone Is preferred. Further, the phosphorescent substance may be triphenylacetophenone represented by the above formula (3) or a derivative thereof. Among them, for example, 2,2,2-triphenylacetophenone or Me-TPAP is preferably used.

The rare earth complex used as a material for the organic light emitting layer is preferably a europium complex having a β-diketone ligand. From this complex,
Light emission of rare earth element ions having high intensity and long life can be obtained.

As the organic EL device, preferably,
Preferably, a hole transport layer is provided between the anode and the organic light emitting layer. By providing the hole transport layer, holes can be efficiently injected from the anode to the organic light emitting layer, so that the luminous efficiency can be further improved.

Further, an electron transport layer may be provided between the cathode and the organic light emitting layer. Thereby, the efficiency of injecting electrons from the cathode into the organic light emitting layer is improved, so that the luminous efficiency can be further improved.

In the organic EL device, preferably, a hole transport layer is provided between the anode and the organic light emitting layer, and an electron transport layer is preferably provided between the organic light emitting layer and the cathode. Thereby, the efficiency of injecting holes from the anode into the organic light emitting layer and the efficiency of injecting electrons from the cathode into the organic light emitting layer can be improved. Therefore, the luminous efficiency can be further improved.

The anode of the organic EL device of the present invention is
As in the conventional case, a transparent electrode that transmits EL light is used.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an organic EL device using the light emitting material of the present invention will be described below with reference to the drawings. It should be noted that the drawings merely schematically show the shapes, sizes, and arrangements of the components so that the present invention can be understood, and thus the present invention is not limited to the illustrated examples.

FIG. 1 is a diagram showing an example in which the present invention is applied to an organic EL device 10 having an anode 13, an organic light emitting layer 15 and a cathode 17 on a substrate 11 in this order. It is a schematic sectional drawing of 10.

The substrate 11 is typically constituted by a transparent substrate. For example, it can be composed of a glass substrate.

The anode 13 is made of a metal or an electric conductive material that transmits EL light emission and has a large work function (generally, 4.0 eV or more). Generally, indium tin oxide (I
TO) is used.

For the cathode 17, for example, magnesium, an alloy of magnesium and silver, or an alloy of aluminum and lithium is used.

The organic light emitting layer 15 is formed using the light emitting material of the present invention. The light emitting material includes a phosphorescent substance having a phosphorescence intensity higher than that of benzophenone and a rare earth complex. The organic light emitting layer 15 is formed by adding a rare earth complex to a phosphorescent substance.

The thickness of each of the anode 13, the organic light emitting layer 15, and the cathode 17 is a suitable value according to the design.

FIG. 2 shows that an anode 13,
FIG. 3 is a diagram in which the present invention is applied to an organic EL device 20 including a hole transport layer 19, an organic light emitting layer 15, and a cathode 17 in this order, and is a schematic sectional view of the organic EL device.

The hole transport layer 19 is made of, for example, N, N′-diphenyl-N, N ′-(3-methylphenyl) -1,
1'-biphenyl-4,4'-diamine (hereinafter referred to as TP
D), diamine derivatives such as N, N′-diphenyl-N, N ′-(1-naphthyl) -1,1′-biphenyl-4,4′-diamine (hereinafter, NPD), and triphenylamine-based , Triphenylmethane, pyrazoline, hydrazone, or amorphous silicon materials. Other components 11, 13, 15, and 17 can be the same as the organic EL device described with reference to FIG.

FIG. 3 shows that an anode 13,
FIG. 2 is a diagram in which the present invention is applied to an organic EL device 30 including an organic light emitting layer 15, an electron transport layer 21, and a cathode 17 in this order, and is a schematic sectional view of the organic EL device.

In the electron transport layer 21, for example, tris (8
-Hydroxyquinolinol) aluminum (hereinafter referred to as Al
Called q. ), A metal complex such as a porphyrin complex, an oxadiazole derivative, a cyclopentadiene derivative, a perylene derivative, or the like. Other components 11, 13, 15, 17
Are the organic ELs described with reference to FIGS. 1 and 2, respectively.
It can be the same as the element.

FIG. 4 shows that an anode 13,
FIG. 3 is a diagram in which the present invention is applied to an organic EL device 40 including a hole transport layer 19, an organic light emitting layer 15, an electron transport layer 21, and a cathode 17 in this order, and is a schematic cross-sectional view of the organic EL device. .

Each component 11, 13, 15,
17, 19, and 21 can be the same as the organic EL elements described with reference to FIGS.

FIG. 5 shows that an anode 13,
FIG. 2 is a diagram in which the present invention is applied to an organic EL device 50 including a phosphorescent material layer 23, an organic light emitting layer 15, and a cathode 17 in this order, and is a schematic sectional view of the organic EL device.

The phosphor layer 23 is a layer composed of a phosphor, but functions as a hole transport layer. Further, for example, if the phosphor constituting the phosphor layer 23 is a substance having a triplet level equal to or higher than the triplet level of the phosphor of the material of the organic light emitting layer 15, the phosphor is generated in the organic light emitting layer 15. Since the effect of confining the triplet excitons in the organic light emitting layer 15 is increased, the intensity of light emission from the element 50 can be improved.

The components 11, 13,
Reference numerals 15 and 17 can be the same as the organic EL elements described with reference to FIGS.

The organic EL device 10 described with reference to FIG.
The organic EL element 20 described with reference to FIG. 2, the organic EL element 30 described with reference to FIG. 3, the organic EL element 40 described with reference to FIG. 4, and the organic EL element 50 described with reference to FIG. Also, the organic light-emitting layer is formed using a light-emitting material including a phosphorescent substance having a phosphorescence intensity higher than that of benzophenone and a rare-earth complex. Note that the triplet level of the phosphor is equal to or higher than the triplet level of the ligand of the rare earth complex. Therefore, the energy of the triplet exciton generated in the phosphor by the recombination of carriers can be transferred to the triplet level of the rare earth complex which is lower than or equal to the triplet level of the phosphor. The transferred energy can be extracted as light emission of rare earth ions in the rare earth complex.

[0056]

EXAMPLES Next, the luminescent material and the organic EL device of the present invention will be described more specifically with reference to examples.
However, the amounts of chemicals used, numerical conditions such as processing temperature and processing time, and chemicals used in the following description are merely examples within the scope of the present invention.

<First Embodiment> An example of an organic EL device using the light emitting material of the present invention as a material for an organic light emitting layer will be described as a first embodiment.

In this example, the organic EL device 10 already described with reference to FIG. 1 is manufactured as follows.

First, a film of ITO is formed on the glass substrate 11 as the anode 13 to a thickness of 200 nm by using an electron beam evaporation method. The sheet resistance of this ITO film was 10Ω / □ (square). Next, well-known photolithography and subsequent etching are performed to reduce the ITO film to 2 m.
The anode 13 is formed by processing into an m-width stripe shape.
Thereafter, the glass substrate 11 on which the anode 13 is formed is washed and dried using acetone and 2-propanol, and is moved into a vacuum evaporation apparatus for forming an organic film.

Next, an organic light emitting layer 15 is formed on the substrate 11 provided with the anode 13.

In this example, a phosphorescent substance 2,2,2-triphenylacetophenone (hereinafter referred to as TPAP) represented by the following formula (4) is used as a material of the organic light emitting layer 15.
And a europium (Eu) complex which is a rare earth complex. Here, as the europium complex, europium (tridibenzoylmethane) phenanthroline (hereinafter referred to as Eu (DBM) ₃ Phen) represented by the following formula (6) is used.

[0062]

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In a separate crucible in a vacuum evaporation apparatus,
Add P and Eu (DBM) ₃ Phen, and heat the crucible by resistance wire. In this example, TPAP and Eu (DBM)
The temperature of each crucible is controlled so that the ratio of the ₃ Phen evaporation rates is 10: 1. After confirming that the ratio of the evaporation rates was constant at 10: 1 (TPAP: Eu (DBM) ₃ Phen), the shutter between the substrate 11 and the crucible was opened, and organic light emission was performed on the substrate 11. Deposit the material of the layer. The organic light-emitting layer 15 having a thickness of 50 nm is formed on the display of the quartz crystal film thickness meter. This organic light emitting layer 15
Inside, Eu (DBM) ₃ Phen is uniformly dispersed in TPAP by about 10%.

Thereafter, the substrate 11 on which the organic light emitting layer 15 is formed is transferred to a vacuum evaporation apparatus for metal film evaporation, and a magnesium (Mg) film is formed on the organic light emitting layer 15 as a cathode 17 by vacuum evaporation. To a thickness of 200 nm. The formation of the cathode 17 is performed by covering the organic light emitting layer 15 with a metal mask provided with a slit having a width of 2 mm and vapor-depositing Mg. As a result, a cathode 17 in the form of a stripe having a width of 2 mm is formed. The cathode 17 is formed so as to be orthogonal to the anode 13. Thereby, the organic EL device of the first embodiment is obtained.

(Comparative Example 1) Here, as Comparative Example 1,
An example in which an organic light emitting layer is formed using only the u complex will be described. Here, the material of the organic light emitting layer is Eu complex E
The steps other than using only u (DBM) ₃ Phen
This is performed in the same manner as in the first embodiment. Here, Eu (DBM) ₃ is formed on the substrate on which the anode is formed by using a vacuum evaporation method.
Phen is deposited to a thickness of 50 nm to form an organic light emitting layer. Thereafter, a cathode is formed of Mg on the organic light emitting layer in the same manner as in the first embodiment, and an organic EL device of Comparative Example 1 is obtained.

(Comparative Example 2) As Comparative Example 2, the first
The organic light-emitting layer of the organic EL element of the embodiment of the present invention is formed by using TPD instead of TPAP to obtain the TPD and Eu (DBM) ₃
It is composed of a co-evaporated film with Phen. Eu (DBM) ₃ Phe is formed on the substrate on which the anode is formed by using a vacuum deposition method.
n is approximately 10% evenly dispersed in the TPD,
While keeping the evaporation rate constant, TPD and Eu (DB
M) film is formed comprising a ₃ Phen. At this time, the film thickness is 50 nm. Thereafter, an anode of Mg is formed on this film in the same manner as in the first embodiment, and the device of Comparative Example 2 is obtained.

As a result, when a voltage was applied between the anode and the cathode of the organic EL device of the first embodiment, light emission was generated from the overlapping portion of the two orthogonal electrodes, and the light was observed from the glass substrate side. Was. FIG. 6 shows an emission spectrum characteristic diagram of the organic EL device of the first embodiment. The horizontal axis indicates wavelength (nm), and the vertical axis indicates EL emission intensity (arbitrary unit). According to FIG. 6, red light emission having a sharp peak near a wavelength of 612 nm is obtained.

On the other hand, the devices of Comparative Examples 1 and 2 also
A voltage was applied in the same manner as in Example 1, but no light emission was observed.

As a result, in the first embodiment, the holes injected from the anode and the electrons injected from the cathode are recombined in the organic light emitting layer, and triplet excitons of TPAP are generated. The energy of this triplet exciton is Eu (DBM)
It is speculated that this was propagated to the triplet level of the ligand having a β-diketone of ₃ Phen and was obtained as a characteristic red emission of Eu ions.

Therefore, in order to confirm this estimation, first, the triplet level of TPAP is measured. TPAP to EP
A solution (solution mixed with diethyl ether: isopentane: ethanol = 5: 5: 2 (volume ratio)) at a concentration of 10 ^-4 M was dissolved in solution A, and the solution was frozen in liquid nitrogen to measure the photoexcitation spectrum. I do. This EPA solution has less light scattering because the solution freezes into a homogeneous glass in liquid nitrogen. Therefore, it is suitable for measurement of a light excitation spectrum that dislikes light scattering.

FIG. 7 shows the measurement results of the emission spectrum obtained when excitation is performed with monochromatic light having a wavelength of 350 nm. In FIG. 7, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). According to FIG. 7, 400 nm (25000 cm ⁻¹ ), 429 nm (2
3310 cm ^-1 ), and 461 nm (21690 cm ^-1 )
There is a peak near the wavelength of ^-1 ). Here, a peak at a wavelength of 400 nm is a first peak, a peak at a wavelength of 429 nm is a second peak, and a peak at a wavelength of 461 nm is a third peak.
, The first peak is considered to be light emission due to the transition from the triplet level to the ground state. The second peak is considered to be light emission due to a transition from the triplet level to a vibration level one level higher than the ground state. The third peak is considered to be light emission due to a transition from a triplet level to a vibration level two above the ground state. Therefore, the triplet level of TPAP is 2500 points higher than the first peak.
0 cm ^-1 .

Next, the triplet level of Eu (DBM) ₃ Phen is measured. As a result of measurement in the same manner as TPAP,
Only a peak at a wavelength of 612 nm, which is the emission peak of Eu ions, was obtained. This means that singlet excitation of the ligand occurs by photoexcitation, and energy is transferred to triplets by intersystem crossing. However, it is considered that the energy transfer from this triplet level to Eu ³⁺ which is the central metal ion occurs very efficiently, so that light emission from the triplet level is not observed.

Therefore, the following experiment was conducted.

The gadolinium (Gd) complex Gd, which is considered to be the same rare earth and the same chemical properties as Eu,
(DBM) ₃ Phen is synthesized. This Gd (DBM)
_{Since 3} Phen has an atomic level higher than the triplet level of the ligand, energy transfer to the Gd ion does not occur.
Therefore, it is non-luminous. When a photoexcitation spectrum was measured using this Gd complex, a phosphorescence spectrum was observed. Then, the triplet level of 20490 cm ^{−1 of} the ligand was determined.

As a result, in the organic EL device of the first embodiment, the organic light emitting layer is formed of TPAP and Eu (DBM) ₃
The energy of the triplet exciton (energy level 25000 cm ⁻¹ ) generated in TPAP by the recombination of carriers is lower than the energy level (20490 cm ⁻¹ ) of Eu (Phen). DBM) ₃
After moving to the triplet level of Phen, it is considered that energy is quickly transferred to Eu ions, and light emission is obtained from the Eu ions.

The phosphorescence intensity of TPAP was 1.8 times the phosphorescence intensity of benzophenone represented by the following formula (7).

[0077]

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In the device of Comparative Example 1, triplet excitons are not generated because the material of the organic light emitting layer is only Eu (DBM) ₃ Phen. It is considered that no light emission was obtained. In the device of Comparative Example 2, the triplet level of TPD, which is the host material of the organic light emitting layer, was 19610 cm ^-1 , and Eu (DBM) ₃ Phe
No energy transfer occurs because it is lower than the n triplet level of 20490 cm ^-1 . Therefore, it is considered that light emission was not obtained.

In this embodiment, the deposition rate ratio between TPAP and Eu (DBM) ₃ Phen in the organic light emitting layer is set to 10: 1, but the ratio is not limited to this value. In order to further improve the luminous efficiency of the organic EL element, the value of this ratio is optimized according to each condition.

<Second Embodiment> As a second embodiment, a derivative of benzophenone is used as a phosphorescent substance instead of TPAP which is a material of the organic light emitting layer of the first embodiment, as shown in the following formula (8). An example in which 2-amino-5-nitrobenzophenone is used will be described.

[0081]

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Here, differences from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

In the same manner as in the first embodiment, the IT
An anode is formed with an O film, and then, on a substrate on which the anode is formed, 2-amino-5-nitrobenzophenone and Eu (DBM) ₃ P are formed as an organic light emitting layer by using a vacuum evaporation method.
A co-evaporated film with hen is formed. As in the first example, 2-amino-5-nitrobenzophenone and Eu (D
BM) ₃ Phen at a deposition rate ratio of 10: 1. Thereafter, an Mg cathode is formed on the organic light emitting layer to obtain the organic EL device of the second embodiment.

When a voltage was applied between the anode and the cathode of the organic EL device, red light emission characteristic of Eu ions having a peak at a wavelength of 612 nm was observed.

When the photoexcitation spectrum was measured in the same manner as in the first example, the triplet level of 2-amino-5-nitrobenzophenone was 20575 cm ^-1 . This value is higher than the triplet level of Eu (DBM) ₃ Phen.

As a result, the recombination of carriers causes 2
The energy of the triplet exciton generated in -amino-5-nitrobenzophenone is transferred to the triplet level of the Eu complex,
Thereafter, it is considered that the ions move to Eu ions, and light emission of Eu ions is obtained.

The phosphorescence intensity of 2-amino-5-nitrobenzophenone was five times that of benzophenone.

<Third Embodiment> As a third embodiment, a derivative of benzophenone as a phosphorescent substance instead of TPAP which is a material of the organic light emitting layer of the first embodiment is shown by the following formula (9). An example in which 4,4′-dimethoxybenzophenone is used will be described.

[0089]

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Here, differences from the first and second embodiments will be described, and detailed description of similar points will be omitted.

In this example, an organic EL element having a substrate, an anode, an organic light emitting layer and a cathode in this order is formed through the same steps as in the first and second embodiments. Here, 4,4′-dimethoxybenzophenone and Eu (DBM) ₃ Phen represented by the above formula (9) are used as the material of the organic light emitting layer formed by using the vacuum evaporation method.

When a voltage is applied between the anode and the cathode of the organic EL device of the third embodiment formed as described above, 61
Red light emission specific to Eu ions is obtained at a wavelength of 2 nm.

When the triplet level of 4,4′-dimethoxybenzophenone was measured in the same manner as in the first and second examples, the value was 24390 cm ⁻¹ .

The phosphorescent emission intensity of 4,4′-dimethoxybenzophenone was 110 times that of benzophenone.

<Fourth Embodiment> As a fourth embodiment, a derivative of benzophenone as a phosphorescent substance instead of TPAP which is a material of the organic light emitting layer of the first embodiment is represented by the following formula (10). An example using 4-benzoylbiphenyl will be described.

[0096]

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Here, points different from the first and second embodiments will be described, and detailed description of the same points will be omitted.

In this example, an organic EL element having a substrate, an anode, an organic light emitting layer, and a cathode in this order is formed through the same steps as in the first and second embodiments. Here, as the material of the organic light emitting layer formed by using the vacuum evaporation method, 4-benzoylbiphenyl represented by the above formula (10) and E
u (DBM) ₃ Phen.

When a voltage is applied between the anode and the cathode of the organic EL device of the fourth embodiment formed as described above, 61
Red light emission specific to Eu ions is obtained at a wavelength of 2 nm.

In addition, as in the first and second embodiments, 4
When the triplet level of -benzoylbiphenyl was measured, the value was 21505 cm ^-1 .

The phosphorescent emission intensity of 4-benzoylbiphenyl was 12 times that of benzophenone.

<Fifth Embodiment> As a fifth embodiment, a benzophenone derivative is used as a phosphorescent substance instead of TPAP, which is the material of the organic light emitting layer of the first embodiment, as shown in the following formula (11). An example using 4,4′-bis (dimethylamino) benzophenone will be described.

[0103]

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Here, points different from the first and second embodiments will be described, and detailed description of the same points will be omitted.

In this example, an organic EL element having a substrate, an anode, an organic light emitting layer and a cathode in this order is formed through the same steps as in the first and second embodiments. Here, 4,4′-bis (dimethylamino) benzophenone and Eu (DBM) ₃ Phen represented by the above formula (11) are used as the material of the organic light emitting layer formed by using the vacuum evaporation method.

When a voltage is applied between the anode and the cathode of the organic EL device of the fifth embodiment formed as described above, 61
Red light emission specific to Eu ions is obtained at a wavelength of 2 nm.

When the triplet level of 4,4′-bis (dimethylamino) benzophenone was measured in the same manner as in the first and second examples, the value was 21,280 cm ⁻¹ .

Further, 4,4′-bis (dimethylamino)
The phosphorescent emission intensity of benzophenone is 1
It was 00 times.

<Sixth Embodiment> As a sixth embodiment, a derivative of benzophenone as a phosphorescent substance instead of TPAP which is a material of the organic light emitting layer of the first embodiment is represented by the following formula (12). An example in which 4-morpholinobenzophenone is used will be described.

[0110]

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Here, differences from the first and second embodiments will be described, and detailed description of the same points will be omitted.

In this example, an organic EL element having a substrate, an anode, an organic light emitting layer and a cathode in this order is formed through the same steps as in the first and second embodiments. Here, 4-morpholinobenzophenone and Eu (DBM) ₃ Phen represented by the above formula (12) are used as the material of the organic light emitting layer formed by using the vacuum evaporation method.

When a voltage is applied between the anode and the cathode of the organic EL device of the sixth embodiment formed as described above, 61
Red light emission specific to Eu ions is obtained at a wavelength of 2 nm.

Further, similar to the first and second embodiments, 4
When the triplet level of morpholino benzophenone was measured, the value was 21740 cm ^-1 .

The phosphorescent emission intensity of 4-morpholinobenzophenone was 100 times that of benzophenone.

(Comparative Example 3) As Comparative Example 3, 9-fluorenone represented by the following formula (13) was used as a phosphorescent substance instead of TPAP which is the material of the organic light emitting layer of the first embodiment. An example of use will be given.

[0117]

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The triplet level of this 9-fluorenone is 21
740 cm ⁻¹ , which is higher than the triplet level of the Eu complex. However, the phosphorescence intensity is 0.7 times the phosphorescence intensity of benzophenone measured under the same conditions.

This 9-fluorenone and Eu (DBM) ₃
An organic light-emitting layer is formed with Phen, and the other conditions are the same as in the first embodiment to form an element of Comparative Example 3.

(Comparative Example 4) Also, 4-nitrobenzophenone represented by the following formula (14), which is a derivative of benzophenone, is used as a phosphorescent material which is a material of the organic light emitting layer.

[0121]

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The triplet level of this 4-nitrobenzophenone is higher than the triplet level of the Eu complex.
m ⁻¹ . The phosphorescence intensity is 0.1 times the phosphorescence intensity of benzophenone.

The 4-nitrobenzophenone and Eu (D
BM) ₃ Phen to form an organic light-emitting layer, and otherwise, form the element of Comparative Example 4 in the same manner as in the first embodiment.

Comparative Example 5 Further, D-tryptophan represented by the following formula (15) is used as a phosphorescent substance.

[0125]

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The triplet level of this D-tryptophan is
At 21275 cm ⁻¹ , higher than the triplet level of the Eu complex. The phosphorescence intensity is 0.1 times the phosphorescence intensity of benzophenone.

This D-tryptophan and Eu (DBM)
_An organic light emitting layer is formed with ₃ Phen, and the other elements are formed in the same manner as in the first embodiment to form an element of Comparative Example 5.

When a voltage was applied between the anode and the cathode of each of the devices of Comparative Examples 3 to 5, the obtained light emission intensity was 1/10 of that of the first embodiment.
0 or less. This level of emission intensity is insufficient for use as an organic EL device.

As described above, in the devices of the first embodiment to the sixth embodiment in which light emission that can be used as an organic EL device is obtained, the phosphorescence emission intensity of benzophenone is as described above. 1.8 to 100 times.

Accordingly, it is desirable that the phosphorescent substance, which is the material of the organic light emitting layer, has a phosphorescence intensity higher than that of benzophenone.

The reason why benzophenone is used as a reference is that benzophenone is a representative substance which has a relatively simple structure and is frequently used among phosphorescent substances as shown in the above formula (7). It is.

<Seventh Embodiment> A seventh embodiment is represented by the following formula (5), which is a methyl derivative of TPAP instead of TPAP which is the material of the organic light emitting layer of the first embodiment. An example using Me-TPAP will be described.

[0133]

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Here, points different from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

First, this Me-TPAP is synthesized.

In this example, 2-methylbenzophenone 2
g (0.01 mol) and zinc powder 0.06 g (0.00
1 mol) in 100 ml of acetonitrile, and 5.4 g (0.04 mol) of aluminum chloride are further added to the solution. Thereafter, this solution is reacted by applying ultrasonic waves in a nitrogen atmosphere at a temperature of 35 ° C. for 10 hours.

Next, 100 ml of water is added to the reaction solution, and 100 ml of an aqueous ammonium chloride solution is further added. Thereafter, the mixture is separated into an organic layer and an aqueous layer with a separating funnel using water and chloroform.

The organic layer is dried over anhydrous sodium sulfate and then purified by sublimation to obtain Me-TPAP.

In this example, 0.2 g of Me-TP was used.
AP (see formula (5) above) was obtained, and the yield was 5%.
It was about.

Next, using the obtained Me-TPAP,
An organic EL device is formed in the same manner as in the first embodiment.

Here, an anode is formed of an ITO film on the substrate, and then, on the substrate on which the anode is formed, Me-TPAP and Eu are formed as an organic light emitting layer by using a vacuum deposition method.
(DBM) A co-deposited film with ₃ Phen is formed. Similar to the first embodiment, Me-TPAP and Eu (DBM) ₃ P
The deposition rate ratio is set to 10: 1 with hen. Thereafter, an Mg cathode is formed on the organic light emitting layer to obtain the organic EL device of the seventh embodiment.

When a voltage was applied between the anode and the cathode of the organic EL device, when a voltage of 10 V was applied,
Strong red emission characteristic of Eu ions having a peak at a wavelength of 612 nm was observed.

The intensity of the light emission obtained was about three times higher than that of the first embodiment. Further, even when the organic EL element was continuously driven at the same current density, a decrease in emission intensity could be further suppressed. Further, in the organic EL device of this example, generation of a leak current not involved in light emission was also able to be suppressed.

As a result, the emission intensity, the durability of the device, and the leakage current can be reduced as compared with the organic EL device of the first embodiment.

This is because the introduction of a methyl group into the TPAP molecule causes the molecule to become more asymmetrical, which results in a film of this material produced by evaporation, which is more amorphous, in other words, more homogeneous. It is considered that this was because an improved film was obtained.

This effect is expected in a derivative of triphenylacetophenone represented by the following formula (3). However, in this case, R1 to R2 in the formula (3)
At least one group represented by 0 is a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted acyl group, or a substituted or unsubstituted aryl group; Hydrogen is preferred.

[0147]

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<Eighth Embodiment> As an eighth embodiment, here, the organic EL element 20 already described with reference to FIG.
Is manufactured as follows.

Hereinafter, points different from the first embodiment will be described, and detailed description of the same points will be omitted.

In this example, similar to the first embodiment,
After a film of ITO was formed to a thickness of 200 nm on the glass substrate 11, photolithography and etching were performed to obtain a 2 m
An m-width stripe-shaped anode 13 is formed. afterwards,
After washing and drying the substrate 11 on which the anode 13 is formed, the substrate 11 is set in a vacuum evaporation apparatus for forming an organic film. Thereafter, the substrate 1 on which the anode 13 is formed is formed by using a vacuum evaporation method.
On top of this, a TPD film is deposited to a thickness of 50 nm on the substrate 1 to form a hole transport layer 19. Subsequently, on the hole transport layer 19, TP
Using the AP and the Eu complex as materials, the same process as in the first embodiment is performed to form the organic light emitting layer 15 which is a co-deposited film of these two materials. The substance used as the Eu complex in this example is europium (tri-2-fluorenecarbonylmethylheptafluoropropyl ketone) phenanthroline (hereinafter referred to as Eu (F
1HA) ₃ Phen. ).

[0151]

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In this organic light emitting layer 15, TPA
Eu (FlHA) ₃ Phen is uniformly dispersed in P by about 10%.

Thereafter, a cathode 17 orthogonal to the anode 13 in a stripe shape of 2 mm width is formed on the organic light emitting layer in the same manner as in the first embodiment. Thus, the organic EL device according to the eighth embodiment is obtained.

When a voltage was applied between the anode and the cathode of the organic EL device, light emission was generated from the overlapping portion of the two orthogonal electrodes, and observed from the glass substrate side. This emission was red emission unique to Eu ions having a peak near the wavelength of 612 nm. Also, this light emission is the first
The intensity was about twice as high as that of the device of Example 1.

In the organic EL device according to the eighth embodiment,
Since the hole transport layer 19 is provided between the anode 13 and the organic light emitting layer 15, the efficiency of injecting holes from the anode to the organic light emitting layer 15 is improved. For this reason, it is considered that the emission intensity was higher than that of the device of the first embodiment.

The hole transport layer is not limited to the material of this embodiment. A triphenylamine-based, triphenylmethane-based, pyrazoline-based, amorphous silicon-based, or the like can be used.

The phosphor used as the material of the organic light emitting layer of this embodiment may be the phosphor used in the above-described second to seventh embodiments.

Although Eu (FlHA) ₃ Phen, which is an Eu complex, was used here as the rare earth complex, Eu (DBM) ₃ Phen used in the above-described examples and the rare earth disclosed in Reference 4 were used. A complex may be used.

<Ninth Embodiment> As a ninth embodiment, here, the organic EL element 50 already described with reference to FIG.
Is manufactured as follows.

Hereinafter, points different from the first embodiment will be described, and detailed description of the same points will be omitted.

In this example, similar to the first embodiment,
An anode 13 made of ITO is formed on a glass substrate 11. Thereafter, TPAP, which is a phosphor, is formed as a phosphor layer 23 having a thickness of 50 nm on the substrate 11 on which the anode 13 is formed, using a vacuum deposition method. Subsequently, the organic light emitting layer 15 is formed on the phosphor layer 23 by using a vacuum evaporation method.
It is formed to a thickness of nm. The material of the organic light emitting layer 15 is
Here, the second was used in Example, Eu (FlHA) ₃ Phen represented by 2-amino-5-nitro-benzophenone and Equation (16) represented by the following equation (8).

[0162]

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Next, in the same manner as in the first embodiment, a cathode 17 orthogonal to the anode 13 in a stripe shape of 2 mm width is formed on the organic light emitting layer 15 by a vacuum evaporation method. Thereby, the organic EL device of the ninth embodiment is obtained.

When a voltage is applied between the anode and the cathode of this organic EL device, an E having a peak at a wavelength of 612 nm is obtained.
Red light emission characteristic of u ions was obtained. This light emission showed about four times the intensity of the light emission obtained from the device of the first embodiment.

The phosphor layer 23 of this embodiment is a layer having a role as a hole transport layer. Here, the triplet level of TPD which is the material of the hole transport layer of the eighth embodiment is 19
610 cm ^-1 . This is lower than the triplet level of 25,000 cm ^{−1 of} TPAP, which is the material of the organic light emitting layer. On the other hand, the triplet level of TPAP which is the material of the phosphor layer of this example is 25000 cm ^-1 , and the triplet level of 2-amino-5-nitrobenzophenone which is the material of the organic light emitting layer is 20575 cm ^{-1. -1} . Therefore, the material of the phosphor layer is configured to have a higher triplet level than the material of the organic light emitting layer. As a result, in the organic EL device of the ninth embodiment, the effect of confining triplet excitons generated in the organic light emitting layer in the organic light emitting layer can be enhanced, so that the emission intensity is increased. it is conceivable that.

The rare earth complex Eu (FlHA)
_The triplet level of ₃ Phen is 20620 cm ⁻¹ ,
It is slightly larger than the triplet level of amino-5-nitrobenzophenone. Nevertheless, the red emission characteristic of Eu ions is obtained because the two energy levels are considered to be substantially the same height, and 2-amino-
From the triplet level of 5-nitrobenzophenone, Eu (Fl
It is considered that this did not hinder the energy transfer to the triplet level of HA) ₃ Phen.

<Tenth Embodiment> As a tenth embodiment, the organic EL element 30 described above with reference to FIG. 3 is manufactured as follows.

In this example, as the material of the organic light emitting layer 15, Me-TPAP represented by the following formula (5), which is the same methyl derivative of TPAP as in the seventh embodiment, and Eu (FlH
A) ₃ Phen is used.

[0169]

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Hereinafter, points different from the seventh embodiment will be described, and detailed description of the same points will be omitted.

First, a stripe-shaped anode 13 made of ITO and having a width of 2 mm is formed on a glass substrate 11.
Thereafter, the organic light-emitting layer 15 is formed on the substrate 11 on which the anode 13 is formed by vacuum evaporation in the same manner as in the seventh embodiment.
It is formed to a thickness of 0 nm. Thereafter, the electron transport layer 21 is formed to a thickness of 50 nm on the organic light emitting layer 15 using Alq as a material by a vacuum evaporation method. Thereafter, a cathode 17 orthogonal to the anode 13 is formed on the electron transport layer 21 in a stripe shape with a width of 2 mm using a vacuum evaporation method. Thus, the organic EL device according to the tenth embodiment is obtained.

When a voltage is applied between the anode and the cathode of this organic EL device, an E having a peak at a wavelength of 612 nm is obtained.
Red light emission characteristic of u ions was observed. This light emission showed about twice the intensity of the light emission obtained from the device of the seventh embodiment.

In the organic EL device of the tenth embodiment, the electron transport layer 21 is provided between the organic light emitting layer 15 and the cathode 17.
Is provided, the efficiency of electron injection from the cathode 17 to the organic light emitting layer 15 is improved. For this reason, it is considered that the emission intensity was higher than that of the device of the seventh embodiment.

The material of the electron transport layer is not limited to the material of this embodiment, but may be an oxadiazole-based material. The phosphor used as the material of the organic light emitting layer may be the phosphor used in the first to sixth embodiments. As the rare earth complex, Eu (DBM) ₃ Phen or a substance disclosed in Reference 4 may be used.

<Eleventh Embodiment> As an eleventh embodiment, here, the organic EL element 40 already described with reference to FIG. 4 is manufactured as follows.

Hereinafter, points different from the first to tenth embodiments will be described, and detailed description of the same points will be omitted.

In this example, as materials of the organic light emitting layer 15, Me-TPAP represented by the above formula (5) and Eu (F
lHA) ₃ Phen.

First, a stripe-shaped anode 13 made of ITO and having a width of 2 mm is formed on a glass substrate 11.
After that, a hole transport layer 19 is formed on the substrate 11 on which the anode 13 is formed by using a vacuum evaporation method. This hole transport layer 1
The material No. 9 is TPD and is formed to a thickness of 50 nm. Next, Me is formed on the hole transport layer 19 by using a vacuum evaporation method.
The -TPAP and Eu (FlHA) ₃ organic light-emitting layer 15 is a co-deposited film of Phen formed to a thickness of 30 nm. Subsequently, the electron transport layer 21 is formed to a thickness of 30 nm on the organic light emitting layer 15 by using a vacuum evaporation method. This electron transport layer 2
The material of No. 1 is Alq. Thereafter, the electron transport layer 21
A cathode 17 orthogonal to the anode 13 is formed in a stripe shape having a width of 2 mm on the top using a vacuum evaporation method. Thus, the organic EL device according to the eleventh embodiment is obtained.

When a voltage is applied between the anode and the cathode of the organic EL device, an E having a peak at a wavelength of 612 nm is obtained.
Red light emission characteristic of u ions was observed. Further, comparing the light emission of the device of the seventh embodiment with the light emission of the device of this embodiment using the same Me-TPAP as the phosphorescent material as the material of the organic light emitting layer, The light emission obtained is about twice the intensity of the device of the seventh embodiment.

The luminous intensity is higher than that of the device of the eleventh embodiment because a hole transport layer is provided between the anode and the organic luminescent layer.
Also, this is because an electron transport layer is provided between the cathode and the organic light emitting layer. As a result, the efficiency of injection of carriers into the organic light emitting layer is improved, so that the luminous efficiency is considered to be improved.

The material of the hole transport layer and the material of the electron transport layer are not limited to the materials described in this embodiment, and the materials described in the above embodiments can be used.

Also, in the present invention, a phosphorescent substance not containing a benzoyl group, which has a higher phosphorescent emission intensity than benzophenone and has a higher triplet level than the triplet level of the rare earth complex used in the above embodiment. Α-naphthoflavones (triplet level 21740 cm ⁻¹ , phosphorescence intensity: 35 times that of benzophenone) represented by the following formula (17) and phenanthridine (triple) represented by the following formula (18) Term level 21980 cm ^-1 , phosphorescence intensity:
(5 times benzophenone) is used as a phosphorescent material that is a material of the organic light emitting layer.

[0183]

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In forming an organic EL device using these materials, a stable vapor-deposited film could not be obtained when forming an organic light emitting layer. As a result, no light emission was obtained from the formed device. Therefore, when an organic light-emitting layer is formed by an evaporation method such as a vacuum evaporation method, these materials having low film-forming properties cannot be used. However, it is considered that if these materials are dispersed in a polymer such as polyvinyl carbazole to form a thin film by a spin coating method or the like, an organic light emitting layer having good film quality can be obtained. If an organic light emitting layer having good film quality is obtained, it is expected that light can be obtained also in the organic EL device using the above-mentioned α-naphthoflavones and phenanthridine.

[0185]

As is clear from the above description, the luminescent material of the present invention comprises a phosphorescent substance having a phosphorescence intensity higher than that of benzophenone and a rare earth complex. A phosphorescent substance is a substance having a triplet level equal to or higher than a triplet level of a ligand of a rare earth complex.

Therefore, if this light emitting material is used as a material for an organic light emitting layer of an organic EL device, the energy of triplet excitons generated by recombination of carriers injected from a cathode and an anode is reduced to the triplet of a phosphorescent substance. Transfer to the triplet level of a rare earth complex that is at or below the singlet level. Then, the transferred energy can be extracted as light emission of rare earth ions in the rare earth complex. In addition, when a phosphorescent substance having a phosphorescence intensity equal to or higher than that of benzophenone is used, light emission with sufficient intensity as an organic EL element can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an organic EL element for describing an embodiment of the present invention and a first example.

FIG. 2 is a schematic cross-sectional view of an organic EL device for describing an embodiment and an eighth example.

FIG. 3 is a schematic cross-sectional view of an organic EL element for describing an embodiment and a tenth example.

FIG. 4 is a schematic cross-sectional view of an organic EL device for describing an embodiment and an eleventh example.

FIG. 5 is a schematic cross-sectional view of an organic EL device for describing an embodiment and a ninth example.

FIG. 6 is an emission spectrum characteristic diagram of the organic EL device according to the first embodiment.

FIG. 7 provides a description of an organic EL device according to a first embodiment;
It is a light excitation spectrum characteristic view of TPAP.

[Explanation of symbols]

 10: organic EL element, organic EL element of the first embodiment 11: glass substrate 13: anode 15: organic light emitting layer 17: cathode 19: hole transport layer 20: organic EL element, organic EL element of the eighth embodiment 21: Electron transport layer 23: Phosphorescent material layer 30: Organic EL device, organic EL device of tenth embodiment 40: Organic EL device, organic EL device of eleventh embodiment 50: Organic EL device, ninth embodiment Example organic EL device

Claims (19)

[Claims] 1. A phosphor having a phosphorescence intensity equal to or higher than that of benzophenone and a rare earth complex, and wherein the phosphor has a triplet or higher triplet level of a ligand of the rare earth complex. A light-emitting material, which is a substance having a term level. 2. The light emitting material according to claim 1, wherein the phosphorescent substance contains a benzoyl group or a benzoyl group composite group represented by the following formula (1) (provided that the following formula (1) is used). R1 is a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group,
Or a substituted or unsubstituted acyl group or a substituted or unsubstituted aryl group, each of R2 to R6 is hydrogen, or a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group, or
A substituted or unsubstituted acyl group or a substituted or unsubstituted aryl group, which may be the same, partially different, or entirely different. A light-emitting material characterized by the above-mentioned). Embedded image 3. The light emitting material according to claim 1, wherein the phosphorescent substance is benzophenone or a benzophenone derivative represented by the following formula (2) (wherein R1 to R10 of the following formula (2) are each Is hydrogen, or a hydroxyl group, or a substituted or unsubstituted alkyl group,
Or a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted acyl group, or a substituted or unsubstituted amino group, or a nitro group, or a substituted or unsubstituted alkoxy group, or a cyano group, or a substituted or unsubstituted group And may be the same, partially different, or all different. A light-emitting material characterized by the above-mentioned). Embedded image 4. The light emitting material according to claim 3, wherein the benzophenone derivative is 2-amino-5-nitrobenzophenone, 4,4′-dimethoxybenzophenone, 4-benzoylbiphenyl, 4,4′-bis. A light-emitting material comprising one or more derivatives selected from the group consisting of (dimethylamino) benzophenone and 4-morpholinobenzophenone. 5. The light emitting material according to claim 1, wherein the phosphorescent substance is triphenylacetophenone represented by the following formula (3) or a derivative thereof (provided that each of R1 to R20 in the following formula (3)) Is hydrogen, a hydroxyl group, or a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted acyl group, or a substituted or unsubstituted aryl group. , Even if some are different,
All may be different. A light-emitting material characterized by the above-mentioned). Embedded image 6. The light emitting material according to claim 5, wherein the phosphor is 2,2,2-triphenylacetophenone represented by the following formula (4). Embedded image 7. The light emitting material according to claim 5, wherein the phosphorescent substance is [2,2-diphenyl-2- (2-methylphenyl)] ethyl-2- represented by the following formula (5).
A material for light emission, which is methylphenone. Embedded image 8. The light emitting material according to claim 1, wherein the rare earth complex is a europium complex having a β-diketone ligand. 9. An organic EL device comprising an anode, an organic light emitting layer, and a cathode, wherein the organic light emitting layer comprises a phosphorescent substance having a phosphorescence intensity equal to or higher than that of benzophenone, and a rare earth complex, and The organic EL device is characterized in that the substance is formed of a light emitting material which is a substance having a triplet level equal to or higher than a triplet level of a ligand of the rare earth complex.
element. 10. The organic EL device according to claim 9, wherein the phosphorescent substance contains a benzoyl group or a complex group of a benzoyl group represented by the following formula (1) (provided that the following formula (1) is satisfied). R1 is a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group,
Or a substituted or unsubstituted acyl group or a substituted or unsubstituted aryl group, each of R2 to R6 is hydrogen, or a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group, or
A substituted or unsubstituted acyl group or a substituted or unsubstituted aryl group, which may be the same, partially different, or entirely different. An organic EL device characterized by the above-mentioned). Embedded image 11. The organic EL device according to claim 9, wherein the phosphorescent substance is benzophenone or a derivative of benzophenone represented by the following formula (2) (provided that R1 to R10 of the following formula (2) are respectively Is hydrogen, or a hydroxyl group, or a substituted or unsubstituted alkyl group,
Or a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted acyl group, or a substituted or unsubstituted amino group, or a nitro group, or a substituted or unsubstituted alkoxy group, or a cyano group, or a substituted or unsubstituted group And may be the same, partially different, or all different. 2. An organic EL device according to claim 1, Embedded image 12. The organic EL device according to claim 11, wherein the benzophenone derivative is 2-amino-5-nitrobenzophenone, 4,4′-dimethoxybenzophenone, 4-benzoylbiphenyl, 4,4′-bis An organic EL device comprising one or more derivatives selected from the group consisting of (dimethylamino) benzophenone and 4-morpholinobenzophenone. 13. The organic EL device according to claim 9, wherein the phosphorescent substance is triphenylacetophenone represented by the following formula (3) or a derivative thereof (provided that each of R1 to R20 in the following formula (3)) Is hydrogen, a hydroxyl group, or a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted acyl group, or a substituted or unsubstituted aryl group. , Even if some are different,
All may be different. An organic EL device characterized by the above-mentioned). Embedded image 14. The organic EL device according to claim 13, wherein the phosphor is 2,2,2-triphenylacetophenone represented by the following formula (4). Embedded image 15. The organic EL device according to claim 13, wherein the phosphor is [2,2-diphenyl-2- (2-methylphenyl)] ethyl-2- represented by the following formula (5).
An organic EL device comprising methylphenone. Embedded image 16. The organic EL device according to claim 9, wherein the rare earth complex is a europium complex having a β-diketone ligand. 17. The organic EL device according to claim 9, further comprising a hole transport layer between the anode and the organic light emitting layer. . 18. The organic EL device according to claim 9, further comprising an electron transport layer between the cathode and the organic light emitting layer. 19. The organic EL device according to claim 9, further comprising a hole transporting layer between the anode and the organic light emitting layer.
An organic EL device comprising an electron transport layer between the organic light emitting layer and the cathode.