JP2003073355A - Metal complex compound and organic electroluminescent device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable phosphorescent compound useful in organic electroluminescent devices and the like. SOLUTION: This phosphorescent compound is a metal complex compound where a bidentate ligand or tridentate ligand of formula (i) or (ii) (Q1 and Q2 are each an aromatic ring or heterocyclic ring or derivative thereof, at least one of them being a benzene ring or derivative thereof; Z, Z1 and Z2 are each C or any atom or atomic group; and W1 to W4 are each C or an atom other than C) is of a cyclic structure, respectively, in which the ortho site with respect to the position where Q1 and Q2 are bound to Z or Z1 and Z2 , also in the case of the tridentate ligand, W1 , are bound to the central transition metal atom M. This compound is stable, having phosphorescent fumction. Since in the above ligands, the ring such as aromatic ring is bound via Z, or Z1 and Z2 , this compound is stable with a wide phosphoresce wavelength spectrum.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a metal complex compound suitable as a light emitting material for an organic electroluminescence device.

[0002]

2. Description of the Related Art Organic electroluminescent devices (hereinafter referred to as organic EL devices) have the characteristics of power saving, a wide viewing angle and high-luminance light emission. It is attracting attention as a light source.

In order to put such an organic EL element into practical use, further improvement in the current luminous efficiency, life (durability), color purity, etc. of the organic layer is required.

Recently, development of a phosphorescent EL device which is used as a phosphorescent light emitting material and has a much higher efficiency than that of a fluorescent light emitting material has been underway. It has been reported that the use of such a phosphorescent light-emitting material exceeds the theoretical limit of 5% in the external quantum efficiency of conventional fluorescent devices and reaches a quantum efficiency of 8% (MABaldo et al; Appl. Phys. Lett.,
75, 4 (1999)).

[0005]

The phosphorescent light-emitting material proposed hitherto includes, for example, the following formula (1):

[Chemical 7] And tris (2-phenylpyridine) iridium (tris (2-phenylpyridine) ir represented by
Idium (III) [Ir (ppy) ₃ ] and the like are known. These proposed Ir (ppy) _{3 and the} like have obtained sufficient luminous efficiency, but have a problem that the stability at high temperature is not yet sufficient. Also, a display device,
For example, for application to a color display device, it is necessary to realize white light emission with high purity.

In order to solve the above-mentioned problems, an object of the present invention is to propose a compound which is excellent in stability and is excellent as a phosphorescent material.

[0007]

In order to achieve the above object, the present invention has the following features.

The metal complex compound according to the present invention has iridium or palladium as the central metal M and has the following formula (i)

[Chemical 8] In the ligand and Q _1, Q ₂ are bonded by Z as represented is, in the ortho-position to the binding position of the Z of the Q ₁ and Q _2, it is bonded to the central metal M.

In the metal complex compound according to another embodiment of the present invention, iridium or palladium is used as the central metal M, and the following formula (ii)

[Chemical 9] And ortho with respect to the binding position of Z ₁ and Z ₂ of the Q ₁ and Q ₂ of ligands represented in, W ₁ in the formula is bound to the central metal M.

In another embodiment of the present invention, the above formula (i)
The ligand represented by is represented by the following formula (a) or (b)

[Chemical 10] In the formula, X ₁ and Y ₁ are bonded to the central metal M, and at least _one of X ₁ and Y ₁ is a nitrogen atom.

In another embodiment of the present invention, the ligand represented by the formula (ii) is represented by the following formula (c) or (d)

[Chemical 11] In the formula, X ₁ , Y ₁ and W ₁ are bonded to the central metal M, and at least one of X ₁ , Y ₁ and W ₁ is a nitrogen atom.

In another embodiment of the present invention, Z, Z ₁
And Z ₂ are, for example, CR ₂ , O, S, NR, SiR
₂ (R is H or any of an alkyl group or an aryl group or a derivative thereof).

In the above metal complex compounds, the ligand has a structure in which an aromatic ring or a hetero ring is bridged by C represented by Z, Z ₁ and Z ₂ or another atom or atomic group. It has a high degree of freedom in the structure that can be adopted as a ligand, and the molecule can be designed so that the emission wavelength is broadened.

Further, since Z, or Z ₁ and Z ₂ are provided in the above-mentioned ligand, it is possible to reduce the strain in the orbits of the atoms binding to the central metal M and to enhance the chemical stability of the complex. . Furthermore, such a metal complex compound can realize phosphorescent emission with high emission efficiency due to the heavy atom effect of the central metal.

Further, in the tridentate ligand represented by the above formula (ii) or more specific formulas (c) and (d), three atoms are bonded to the central metal M, Central metal M
A strong complex can be obtained because the binding force between the ligand and the ligand is strong.

According to another aspect of the present invention, in the organic electroluminescent device, a transition metal such as Ir, Pt, or Pd is used as the central metal M, and the above formula (i) or, as a specific example, the formula (a) or the formula (b). ) as shown in, such as the ligand and Q _1, Q ₂ ring structures joined by Z is, Z ₁ of the Q ₁ and Q ₂ and Z ₂
The metal complex compound bonded to the central metal M at the ortho position with respect to the bonding position with is used as a light emitting material.

According to another aspect of the present invention, in the organic electroluminescent device, a transition metal such as Ir, Pt, or Pd is used as the central metal M, and the above formula (ii) or, as a specific example, the formula (c) or the formula (d). ) Etc., Z of Q ₁ and Q ₂ of the ring structure
₁ and the ortho position with respect to the bonding position with Z ₂ and W _{1 in} the formula
A metal complex compound whose position is bonded to the central metal M is used as a light emitting material.

The metal complex compound having a ligand represented by the above formulas (i) and (ii) can emit phosphorescence, and these are used as a light emitting material of an organic electroluminescence device. As a result, a display device and a light source with high luminous efficiency can be obtained. Further, by using the metal complex compound according to the present invention, light emission with a wide wavelength range can be easily obtained, and white phosphorescent light emission can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION [Embodiment 1] A metal complex compound according to an embodiment of the present invention has the general formula (i)

[Chemical 12] And a ligand in which Q ₁ and Q ₂ are bound by Z is
At each ortho position with respect to the bonding position of Q ₁ and Q ₂ with Z, it is bonded to a central metal M made of a transition metal such as Ir or Pd.

As Z in the ligand,

[Chemical 13] Such an atom or atomic group can be adopted. Where R
When there are two groups, R may be an independent group or may form a ring with each other.

Among the above-mentioned ligands, the bidentate ligand which forms a coordinate bond with the central metal M at two positions is exemplified by the following formula (a) or (b).

[Chemical 14] The structure is as shown in. In this ligand, X ₁ and Y _2, which are the ortho positions with respect to the bonding positions of Q ₁ and Q ₂ of the formula (i) composed of an aromatic ring with Z, are bonded to the central metal M. As a matter of course, in the formula (b), the bonding relationship between the five-membered ring and the six-membered ring with respect to Z includes a structure that is the left-right opposite to the structure of the formula (b). In formulas (a) and (b), X _{1 to} X ₅
In addition to C, N, O, S, P, and the like can be adopted as Y _{1 to} Y ₅ , and the bond to these atoms is not limited to H, but a substituent such as an alkyl group or an aryl group. May be At least _one of X ₁ and Y ₁ which forms a coordinate bond with the central metal is more preferably an N atom. More specific examples of these ligands are shown below.

[Chemical 15] Examples of such ligands are:

The general structure of the metal complex compound having the bidentate ligand as described above is, for example, the following formula (A) or (B):

[Chemical 16] It is represented by.

The tridentate ligand coordinated to the central metal M at three positions is represented by the following general formula (ii)

[Chemical 17] Z ₁ of Q ₁ and Q _{2 in} the formula having a structure as shown in
And the ortho position with respect to the bonding position with Z ₂ and W _{1 in} the formula bond with the central metal M to form a metal complex compound. Specifically, the structure of this ligand has the following formula (c) and formula (d):

[Chemical 18] Can be expressed as Here, of course, the positional relationship between the five-membered ring and the six-membered ring of the formula (d) with respect to the ring having W ₁ includes the structure of the formula (d) and the left-right structure. In the formulas (c) and (d), X _{1 to} X ₅ , Y _{1 to} Y ₅ and W _{1 to} W.
_In addition to C, N, O, S, P and the like can be adopted as 4, and the atom bonded to these atoms is not limited to H but may be a substituent such as an alkyl group or an aryl group. . It is more preferable that at least one of X _1, Y ₁ and W _{1 which} form a coordinate bond with the central metal be an N atom.

As for Z ₁ and Z ₂ of the tridentate ligand, the same atom or atomic group as Z of the bidentate ligand can be adopted.

More specific examples of these ligands are shown below.

[Chemical 19] There is a structure like this.

The general structure of the metal complex compound having the above-mentioned tridentate ligand bonded thereto is, for example, the following formula (C) or (D):

[Chemical 20] It is represented by. In the metal complex compound having such a tridentate ligand, three atoms in the ligand are bonded to the central metal M, so that the binding force between the ligand and the metal becomes strong and a stable complex is obtained. Will be realized.

Such a metal complex compound has a central metal M
Due to the heavy atom effect, the phosphorescent function capable of highly efficient light emission can be exerted. In addition, since rings such as Q ₁ and Q ₂ are bonded via Z or Z ₁ and Z ₂ and the ring structures are not directly bonded to each other, the degree of freedom in the molecular design of the ligand is high and various Such a function can be easily imparted to the metal complex compound, the distortion of the orbital of the coordination bond to the central metal M can be reduced, and a chemically stable complex can be obtained.

The metal complex compound described above is
It suffices that at least one ligand represented by the general formula (i) or (ii) is coordinate-bonded to the central metal, and different ligands coordinate with the same metal as the central metal. May be. For example, a ligand represented by the above formula (i) or formula (ii),
A metal complex compound to which a ligand different from this has a complex structure with low symmetry, and can be designed to include many wavelength components when light is emitted due to such an asymmetric structure. Can be widened.

[Embodiment 2] FIG. 1 shows a schematic cross-sectional structure of an organic electroluminescence device using a phosphorescent light emitting material.
On the transparent substrate 10 such as glass, ITO (Indium Tin O
xide) or the like is used here to form the transparent electrode 12 that functions as an anode, and the organic layer 20 having a laminated structure is formed on the transparent electrode 12. The organic layer 20 includes at least the light emitting layer 24 and has a different layer structure depending on the function of the organic compound used. In addition to the light emitting layer single layer structure, a multilayer structure such as a hole transporting layer / light emitting layer, a light emitting layer / electron transporting layer, and a hole transporting layer / light emitting layer / electron transporting layer can be adopted. In the second embodiment, the hole transport layer 22, the light emitting layer (phosphorescent light emitting layer) 24, the hole blocking layer 26, and the electron transport layer 28 are stacked in this order from the transparent electrode 12 side. A metal electrode 14 which functions as a cathode here is formed on the organic layer 20. For example, the metal electrode 14 is composed of a laminated body of a LiF layer (electron injection layer) and an Al electrode as shown in the figure. can do. Alternatively, the metal electrode 14 may be formed of a single Al electrode layer. In addition to Al, for example, Mg-A
A g alloy, an Al-Li alloy, or the like can be used.
Although not shown, CuPc, starburst amine, vanadium oxide, or the like may be inserted as a hole injection layer between the transparent electrode 12 and the hole transport layer 22.

The organic electroluminescent device having the above-mentioned structure is
In the second embodiment, a phosphorescent light emitting material having a phosphorescent type light emitting function and having high efficiency and high stability is used as the light emitting layer material of the organic layer 20. Then, as the phosphorescent material, a metal complex compound in which the bidentate ligand of the general formula (i) described in Embodiment 1 is coordinate-bonded to the central metal M, or the tridentate coordination of the general formula (ii). A metal complex compound in which the child is coordinate-bonded to the central metal M is used. Specific structures of the metal complex compound that can be adopted in the second embodiment are as follows.
(D) can be mentioned.

As the central metal M, transition metals such as Ir, Pt and Pd are adopted. By using such a transition metal, the heavy electron effect is likely to occur, and the metal complex compound is likely to exhibit the phosphorescence emission function.

Z of the ligand, Z₁, Z₂Hired about
The atom or atomic group is the same as in Embodiment 1.
It That is, for bidentate ligands, aromatic rings and hetero
Rings or derivatives thereof Q₁And Q₂Is basically Z
About a tridentate ligand that is bound through one atom represented by
Is W₁~ W_FourWith a ring, Q₁And Q₂And Z respectively
₁, Z₂Are bonded through one atom represented by. This
Sea urchin ligand is Z or Z₁And Z₂Aromatic ring, etc. are linked via
By combining, the degree of freedom regarding the possible structure of the ligand
High brightness, wide emission wavelength range, and white light emitting device realized
It will be very advantageous to do. Also, for the central metal M
Ortho (X₁And Y₁) Bond angle is Q ₁And Q₂And
Less strain and chemically stable than directly bonded structures
It becomes a bond and the stability of the metal complex compound is enhanced. Furthermore
In the tridentate ligand, there are three bonds with the central metal M.
Since the binding force is stronger, the stability as a complex is better.
Get higher Therefore, when used as a light-emitting material for the device
In addition, it is particularly useful for improving the heat resistance of the light-emitting layer and improving the life of the device.
Can contribute to.

The bidentate ligand or tridentate ligand as described above is, for example, diarylmethane, ether, thioether or the like, and when one or more of these are bonded to the central metal M, phosphorescence is emitted. Exert function. A plurality of the same ligands may be bonded to the same central metal M, or different ligands may be bonded. However, since these metal complex compounds are used as the light emitting material of the organic electroluminescent device as in the second embodiment, it is very important that they are chemically stable, and that H is different from the central metal M. The chemically bonded and unstable hydride complex directly bonded is not suitable as the metal complex compound used for the light emitting material of the organic electroluminescent device according to the second embodiment.

The ligands X _{1 to} X ₅ , Y _{1 to} Y ₅ and the tridentate ligands W _{1 to} W ₄ are the same as in the first embodiment except for C,
N, O, S, P and the like can be adopted, and the bond to these atoms is not limited to H but may be a substituent such as an alkyl group or an aryl group. Bond with central metal M 2
The bidentate ligand, any of X ₁ and Y _1, at least one of X ₁ and Y ₁ and W ₁ for tridentate ligand N
More preferably, it is an atom.

Specific examples of the metal complex compound as described above include the following formula (2)

[Chemical 21] Ir (Bnpy) ₂ acac as shown in FIG.

In the organic electroluminescent device according to the second embodiment, the phosphorescent emitting layer 24 can be formed by using the above metal complex compound alone, but the metal complex compound is used as a dopant (guest). The material) is doped in a predetermined host material. As a host material,
A compound containing a carbazole group can be used, and for example, a compound represented by the following formula (3)

[Chemical formula 22] 4,4'-N, N'-dicarbazole-biphenyl (4,4'-N, N'-dic
Arbazole-biphenyl; CBP) can be used. Also, the following formula (4)

[Chemical formula 23] It is also possible to use 4,4 ′, 4 ″ -tris (carbazolyl) -triphenylamine (TCTA) having a hole-transporting property as shown in the above.
Since A has higher heat resistance, it is particularly useful for an organic electroluminescent device that is more easily exposed to higher temperatures.

The hole-transporting layer 22 is not particularly limited as long as it has a hole-transporting function. For example, a polymer of triphenylamine can be adopted, and one example is represented by the following formula (5).

[Chemical formula 24] The α-NPD shown in can be used.

The electron transport layer 28 is not particularly limited as long as it has an electron transport function, but as an example, the following formula (6)

[Chemical 25] Where an aluminum quinolinol complex (Alq ₃ ) such as that shown in FIG. 2 can be used, as described above, as a host material of the phosphorescent emitting layer 24, bipolar CBP or hole transporting TCTA is used.
When a compound such as the above is used, it is preferable to form the hole blocking layer 26 between the light emitting layer 24 and the electron transport layer 28 in order to prevent holes from flowing out from the light emitting layer 24 to the electron transport layer 28. Is. As described above, the electron transport layer 28
When Alq ₃ or the like is used for the above, problems such as the emission of Alq ₃ due to the holes flowing into the electron transport layer or the inability to confine the holes in the light emitting layer to lower the light emission efficiency are prevented. can do. Hole blocking layer 2
As an example of the material of 6, the following formula (7) is used.

[Chemical formula 26] Bathocuproine (BCP) as shown in can be used.

Next, the light emitting principle of the organic electroluminescent device according to the second embodiment, which uses the above-mentioned metal complex compound as a dopant for phosphorescence, will be described.

When holes and electrons are injected into the organic layer 20 from the transparent electrode 12 as the anode and the metal electrode 14 as the cathode, the holes pass through the hole transport layer 22 and the electrons pass through the electron transport layer 2.
8 and the hole blocking layer 26, and the light emitting layer 2
Reach 4 and rejoin. Due to the recombination of the electrons and holes, the host material of the light emitting layer 24 first becomes in an excited state.
Here, the excited states of the molecule include a singlet excited state in which the electron spin directions are antiparallel and a triplet excited state in which the electron spin directions are parallel, and from simple quantum mechanical reasoning,
The production ratio of the singlet excited state and the triplet excited state is 1: 3. Fluorescence is a luminescent form in which only the singlet excited state contributes, whereas in phosphorescence, the triplet excited state, including those transitioned from the singlet excited state, contributes to light emission. The excited state of the host material is 25% in the singlet excited state and 75% in the triplet excited state. The excitation energy of the host material in such a ratio is transferred to the above-mentioned metal complex compound according to the present invention, and the metal complex compound is in a singlet excited state and a triplet excited state, respectively. The singlet excited state of the metal complex compound further moves to the triplet excited state, and finally, all phosphorescence emission from the triplet excited state results. by this,
Almost all of the generated excited state energy is used as the emission energy. In the second embodiment, the phosphorescence caused by the above-mentioned metal complex compound has a ligand of Z or Z ₁ when the ligand of the metal complex compound is Z or Z ₁ regardless of using any of the exemplified CBP and TCTA as the host material. And Z ₂ are provided, the degree of freedom of the ligand is high, and the emission wavelength range thereof is wide, and white is exhibited.

As described above, the organic electroluminescent device according to the second embodiment realizes highly efficient light emission and white light emission by using phosphorescence. Further, since the metal complex compound having a phosphorescent function is chemically stable, the durability of the device can be improved.

[0042]

EXAMPLES Next, specific examples of the above-described embodiment will be described as examples.

[Synthesis of Ir (Bnpy) ₂ acac]

[Chemical 27] I, which is the metal complex compound of the present invention having a phosphorescent function
The r (Bnpy) ₂ acac was performed by first synthesizing the compound E shown in the above reaction formula and further reacting this compound E.

First, iridium trichloride hydrate (0.02
56 g; 0.070 mmol) and 2-benzylpyridine (0.0711 g; 0.420 mmol) were placed in a flask, the inside of the reaction vessel was replaced with nitrogen, and 2-methoxyethanol (2.8 mL) was added to the flask under a nitrogen atmosphere. 2 at ℃
Stir for 0 hours. After distilling off the reaction solvent under reduced pressure, the residue was dissolved in a small amount of methylene chloride, ether was added, and the precipitated crystals were filtered to obtain the desired Chloro-bridged dimer (Compound E) (0.0286 g; 0 0.0254 mmo
1; 73%).

Then, the obtained compound E (0.0225
g; 0.0200 mmol) and sodium carbonate (0.
0212 g; 0.200 mmol) in a flask,
After replacing the inside of the reaction vessel with nitrogen, acetylacetone (0.
0050 g; 0.0500 mmol) and 2-ethoxyethanol (2 mL) were added, and 2 at 80 ° C. under a nitrogen atmosphere.
Stir for 0 hours. After distilling off the reaction solvent under reduced pressure, the residue was purified by silica gel column chromatography (20% ethyl acetate-hexane) to give the desired Ir (Bn).
py) ₂ acac was obtained (0.0194 g; 0.030).
9 mmol; 77%). Further, when the melting point of the synthesized metal complex compound represented by the chemical formula (2) was examined, it was 330 ° C. (the melting point of the conventional metal complex compound of the chemical formula (1) is 3
28 ° C).

[Production of White Phosphorescent Organic Electroluminescent Device] (Example 1) Ir (Bnp) synthesized as described above.
y) An organic electroluminescent device was prepared by using ₂ acac as a phosphorescent material. This element will be described with reference to FIG. The transparent electrode 12 of ITO is formed on the glass substrate 10 in advance by vacuum deposition (degree of vacuum: 5 ×
10 ^-7 Torr; 1 Torr ≈ 133 Pa), α-NP
D was deposited to a thickness of 40 nm to form the hole transport layer 22. Next, the bipolar CBP is used as a host material of the light emitting layer 24 and the Ir (Bnpy) is used as a dopant.
_The light emitting layer 24 was formed to a thickness of 20 nm by co-evaporating ₂ acac and 6 wt% of the dopant. Further, the hole blocking layer 26 is formed by using BCP.
With a thickness of 10 nm and Alq ₃ of 3 as the electron transport layer 28.
It was vapor-deposited at 0 nm. Further, after this, a LiF layer is added to 0.5 n.
m and Al are vapor-deposited to a thickness of 150 nm to form the metal electrode 14,
The element part was obtained as described above.

The substrate on which such an element portion is formed is transferred to a chamber evacuated to a high vacuum, the inside of the chamber is replaced with nitrogen at 1 atm, and the end portion of the sealing glass is removed by using an ultraviolet curing resin. The transparent electrode 12 was adhered to the terminal portion, and the surface other than the terminal portion was adhered to the surface of the glass substrate 10 on which the element was formed, and the resin portion was irradiated with ultraviolet rays using a UV lamp to seal the element portion.

A direct current voltage is applied between the transparent electrode 12 and the metal electrode 14 of the organic electroluminescence device manufactured as described above to cause a current to flow through the device to continuously drive the device. It was measured.

The device according to Example 1 was manufactured with a current density of 0.1 mA.
The emission spectrum obtained by driving under the condition of / cm ² is
As shown in FIG. 2A, the wavelength is 500 to 600 nm.
A peak due to the metal complex compound as the doping material of the light emitting layer is observed in a wide range in the vicinity. Further, in Example 1, since the bipolar CBP is used as the host material of the light emitting layer 24 as described above, electrons are emitted from the light emitting layer 24.
Reaching the hole transport layer 22 from the α-NPD of the hole transport layer.
Also emits light. The light caused by this α-NPD is 447 nm.
It is a peak in the vicinity. In Example 1, light from the metal complex compound that emits phosphorescence and α- of the hole transport layer were used.
A very wide emission wavelength range is realized by adding color with light from NPD, and white light close to natural white is obtained.

This device has the above current density of 0.1 mA / c.
A maximum luminous efficiency of 2.5 cd / A was obtained at m ² . FIG. 3 shows the relationship between the drive voltage (V) and the emission luminance (cd / m ² ) of the elements of Example 1 and Example 2 described later. Element of Example 1, the luminance 189.1cd / m ² at a current density of 11 mA / cm ^2, the driving voltage is 6.7V
Met. FIG. 4A shows the relationship between the current density (mA / cm ² ) and the external quantum efficiency (%) [after correction of angular distribution] of the device of Example 1. The maximum external quantum efficiency is 1.
It reaches 5%, which shows that high-efficiency light emission is realized.

Although not shown in FIG. 2A,
The emission spectrum of the organic electroluminescent element according to Example 1 is
When the amount of current supplied to the device is relatively small, that is, when the emission brightness is low, the light becomes nearly white, and when the brightness is high, the spectrum on the long wavelength side becomes small. Therefore, it can be seen that the element of Example 1 is suitable not only for applications such as a light source that is always driven at the maximum luminance but also for applications such as a white display device that is driven in a region less than the maximum luminance for many times. However, the use is not particularly limited to the display device.

Example 2 An organic electroluminescent device according to Example 2 was produced in the same procedure as in Example 1 above. Example 1
Is that the above-mentioned TCTA having a hole transporting property is used as the host material of the light emitting layer 24. The light-emitting layer 24 of this device is made of TCT which is a host material.
Ir (Bnpy) ₂ ac as a dopant for A
It was formed by co-evaporating ac at a ratio of 5 wt%.

A direct current voltage was applied to the obtained organic electroluminescent device and the organic electroluminescent device was continuously driven to measure its emission spectrum, emission efficiency, and half-life of luminance. FIG. 2B shows the second embodiment.
3 shows an emission spectrum of the device according to (1) when driven under the condition of a current density of 0.33 mA / cm ² . As shown in the drawing, also in Example 2, the device emitted light in a wide wavelength range, and the obtained emission color was white light. The difference from the emission spectrum of the device of Example 1 shown in FIG.
In (b), the emission peak due to α-NPD of the hole transport layer 22 is small. However, such characteristics do not apply under all driving conditions. Contrary to Example 1 described above, the element of Example 2 has a relatively small wavelength spectrum intensity as shown in FIG. 2B when the amount of current supplied to the element is relatively small, that is, when the emission brightness is low. However, in the region of maximum emission luminance (when high voltage is applied or supply current is large), the emission intensity on the short wavelength side due to α-NPD becomes sufficiently high as in FIG. 2A,
It was found that the emission color was very close to white under the maximum emission luminance condition. Therefore, it can be seen that the device of Example 2 is particularly excellent for applications such as white light sources that are often driven under the maximum light emission condition. However, of course, the application is not limited to the light source.

The device of Example 2 has a current density of 0.33 mA.
A maximum luminous efficiency of 2.6 cd / A was achieved at / cm ² . Element of the second embodiment, a luminance 236.7cd / m ² at a current density of 11 mA / cm ^2, the driving voltage is 4.9V
Met. As shown in FIG. 3, the device of Example 2 was
It can be seen that even when compared with the element of Example 1, the light emission luminance on the low voltage side of the driving voltage is very high, low voltage driving is possible, that is, the light emission efficiency is high.

FIG. 4B shows the relationship between the current density (mA / cm ² ) and the external quantum efficiency (%) [after correction of angular distribution] of the device of Example 2, and the device of Example 2 Also, the external quantum efficiency reaches 1.5% at the maximum, and it can be seen that highly efficient light emission is realized. Example 2
The current density is 0.1 mA / cm ^{2 to} 10 mA.
The external quantum efficiency is high and shows a substantially constant value in a wide range of / cm ² , indicating that stable emission characteristics are achieved.

It is considered that such a difference in characteristics between the devices of Example 1 and Example 2 is due to the difference in the host material. That is, by using the above-mentioned TCTA having a hole transporting property but a low electron transporting property as the host material, the hole transporting layer 22 (α
The amount of electrons injected into -NPD) is small, and the light emission rate is increased as a whole. Further, in the device of Example 2, contrary to Example 1, under the high-luminance emission condition, electrons are injected into the hole transport layer 22 and α-NPD also emits light, and at this time, the wavelength is very wide. Light emission in the region occurs stably, and white light emission with high brightness and long life is achieved.

As described above, in the metal complex compound according to the present invention, the metal complex compound has a phosphorescent function, and the ligand has an aromatic ring or a hetero ring represented by Z, Z ₁ and Z _2. It is possible to realize a stable metal complex compound having a broad emission wavelength and having a structure bridged by C or other atoms or atomic groups.

Further, by using such a metal complex compound as a light emitting material of an organic electroluminescent device, a display device and a light source with high luminous efficiency can be obtained. Further, by using the metal complex compound according to the present invention, light emission with a wide wavelength range can be easily obtained, and white phosphorescent light emission can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an organic electroluminescent element according to a second exemplary embodiment of the present invention.

FIG. 2 is a diagram showing emission spectra of the devices of Example 1 and Example 2.

FIG. 3 is a graph showing the relationship between the applied voltage and the light emission luminance of the devices of Examples 1 and 2.

FIG. 4 is a diagram showing the relationship between the external quantum efficiency and the current density of the devices of Examples 1 and 2.

[Explanation of symbols]

10 transparent substrate, 12 transparent electrode (anode), 14 metal electrode (cathode), 20 organic layer, 22 hole transport layer, 24
Phosphorescent emitting layer, 26 hole blocking layer, 28 electron transporting layer.

Continued front page    (72) Inventor Masamichi Inoki             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Kuki Fujikawa             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. F term (reference) 3K007 AB02 AB03 AB04 CA01 CB01                       DA00 DB03 EB00 FA01                 4C055 AA01 BA02 BA06 BB04 CA01                       DA01 GA02                 4H050 AA01 AA03 AB92 WB11 WB14                       WB17

Claims (8)

[Claims] 1. A central metal M containing iridium or palladium.
And the following formula (i) In the ligand and Q _1, Q ₂ are bonded by Z as represented is, in the ortho-position to the binding position of the Z of the Q ₁ and Q _2, the metal complex compound bound to the central metal M . 2. A central metal M containing iridium or palladium.
And the following formula (ii) A metal complex compound in which the ortho position of the ligand of Q ₁ and Q ₂ with respect to the bonding position with Z ₁ and Z ₂ and W _{1 in} the formula are bonded to the central metal M. 3. In an organic electroluminescence device, a transition metal is used as a central metal M, and the following formula (i): In the ligand and Q _1, Q ₂ are bonded by Z as represented is, in the ortho-position to the binding position of the Z of the Q ₁ and Q _2, the metal complex compound bound to the central metal M Is used as a light emitting material. 4. In an organic electroluminescence device, a transition metal is used as a central metal M, and the following formula (ii): The metal complex compound in which the ortho position of the ligand of the formula Q ₁ and Q ₂ with respect to the bonding position with Z ₁ and Z ₂ and the W ₁ position in the formula is bonded to the central metal M is a light emitting material. An organic electroluminescent device characterized by being used in. 5. The central metal M is any one of Ir, Pt, and Pd, and the central metal M is characterized in that:
The organic electroluminescent element as described in 1. 6. The ligand represented by the formula (i) is represented by the following formula (a) or (b): X ₁ and Y ₁ in the formula are bonded to the central metal M, and X ₁ and Y ₁
At least one is a nitrogen atom, The metal complex compound or organic electroluminescent element of Claim 1 or Claim 3 characterized by the above-mentioned. 7. The ligand represented by the formula (ii) is represented by the following formula (c) or (d): X ₁ , Y ₁ and W ₁ in the formula are bonded to the central metal M, and X ₁ ,
Y ₁ and W ₁ at least one of a metal complex compound or an organic electroluminescent device according to claim 2 or claim 4 characterized in that it is a nitrogen atom. 8. The Z, or Z ₁ and Z ₂ is C
R ₂ , O, S, NR, SiR ₂ (wherein R is H or any of an alkyl group or an aryl group or a derivative thereof)
It is any one of Claim 1- Claim 6 characterized by the above-mentioned.
2. A metal complex compound or an organic electroluminescent device according to any one of 1.