JP2891784B2 - Organic electroluminescence device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent device, and more particularly, to an organic electroluminescent device (hereinafter, referred to as an organic EL device) constituted by using an organic compound as a light emitting body.

[0002]

BACKGROUND ART As shown in FIG. 1, a metal electrode 1 as a cathode and a transparent electrode 2 as an anode are shown in FIG.
And a two-layer structure in which an organic phosphor thin film 3 and an organic hole transport layer 4 which are made of an organic compound and are laminated on each other, or a metal electrode 1 and a transparent electrode 2 as shown in FIG. There is known a three-layer structure in which an organic electron transport layer 5, an organic phosphor thin film 3, and an organic hole transport layer 4 are laminated with each other. Here, the organic hole transport layer 4 has a function of facilitating the injection of holes from the anode and a function of blocking electrons, and the organic electron transport layer 5 has a function of facilitating the injection of electrons from the cathode. I have.

In these organic EL devices, a transparent electrode 2
A glass substrate 6 is disposed outside the substrate, and excitons are generated by recombination of electrons injected from the metal electrode 1 and holes injected from the transparent electrode 2 into the organic phosphor thin film 3. Emits light in the process of radiation deactivation, and this light is emitted outside through the transparent electrode 2 and the glass substrate 6.

Further, an organic EL device which emits stable light by forming a phosphor thin film from an organic host material as a main component and a fluorescent guest material as a sub component has been developed. However, in the conventional organic EL device having the above-described configuration, an organic EL device which emits light at a lower voltage but emits light with higher luminance is desired.

[0005]

An object of the present invention is to satisfy the above-mentioned demands, and an object of the present invention is to provide an organic EL device capable of emitting light with high luminance stably for a long period of time.

[0006]

The organic electroluminescent device according to the present invention is an organic electroluminescent device comprising a phosphor emitting layer and a hole transporting layer comprising an organic compound and laminated on each other, between a cathode and an anode. The phosphor light emitting layer has the following chemical formula 1 or 2

[0007]

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[0008]

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(In the above chemical formulas 1 and 2, L ₁ , L ₂ and L
₃ represents a skeleton represented by the following chemical formula 3, and may be the same.)

[0010]

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(In the above chemical formulas 1, 2 and 3, Q represents a residue of a benzene ring or a naphthalene ring which may have a substituent, and R represents an alkyl group, an aminocarbonylamino group, an aminothiocarbonylamino group, Represents an aralkyl group which may have a substituent or a phenyl group which may have a substituent, and M is Al, Be, Mg, Ca, Zn, Cd, Cr,
Ni, Bi, In, Tl, Ti, Sn, V, Rh, P
b, Fe, Ag, Cu, Sr, Ba, Sc, Ga, Y or Co).

The present invention will be described below with reference to the drawings. The organic EL device of the present invention is the same as the organic EL device having the structure shown in FIG.
Further, the hole transport layer 4 is laminated and formed as a thin film between the pair of electrodes 1 and 2. Furthermore, the organic E according to the invention
In the L element, the above-mentioned chemical formula 1 for forming the phosphor layer 3 is used.
The skeleton represented by the above chemical formula 3 of the electroluminescent compound represented by 2 or 2 is specifically a ligand represented by the following chemical formulas 4 to 6.

[0013]

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[0014]

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[0015]

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The above chemical formula 1 for forming the phosphor thin film 3
Or 2 and the electroluminescent compounds represented by the chemical formulas 4 to 6 are preferably luminescent materials No. EL1 to No. EL40 having a combination of ligands L _{1 to} L ₃ and a central atom M shown in Table 1. L ₁ to l ₂₆ ligand L ₁ ~L ₃ shown in Table 1, Table 2
And the structures of the above Chemical Formulas 4 to 6 and the functional groups R ₁ shown in Table 3.
To R ₆ . In the tables, the symbol-indicates that there is no ligand or functional group.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

For the cathode 1, a metal having a small work function, for example, aluminum, magnesium, indium, silver or an alloy of each having a thickness of about 100 to 5000 ° can be used. The anode 2 is made of a conductive material having a large work function, for example, indium tin oxide (IT) having a thickness of about 1000 to 3000 °.
O) or gold with a thickness of about 800-1500 ° can be used. When gold is used as an electrode material, the electrode is in a translucent state.

The organic hole transport layer 4 further has a CTM (Carrier Transporting Mat) represented by the following chemical formulas 7 to 18.
The compounds known as erials) can be used alone or as a mixture.

[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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[0033]

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In FIG. 1, the organic phosphor thin film 3 and the organic hole transport layer 4 are arranged between the cathode 1 and the anode 2 to form a two-layer structure. In addition, the same effect can be obtained as an organic EL element having a three-layer structure in which an organic electron transport layer 5 made of, for example, an oxadiazole derivative is disposed. Further, as a three-layer structure as shown in FIG.
The phosphor thin film is formed as a so-called mixture of a host and a guest substance. For example, a compound represented by the above formulas 4 to 6 is formed as a fluorescent guest substance as an auxiliary component using a tetraphenylbutadiene derivative as an organic host substance as a main component. The same effect may be obtained.

[0035]

As described above, in the organic EL device according to the present invention, the organic EL device having the constitution in which the phosphor emitting layer and the hole transport layer made of the organic compound are laminated between the cathode and the anode. In the device, since the phosphor light emitting layer is made of a phosphor thin film containing the electroluminescent compound represented by the above chemical formula 1 or 2, light can be efficiently emitted with high luminance at a low voltage.

[0036]

【Example】

[Example (1)] N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'- as a hole transport layer on ITO glass
Biphenyl-4,4'-diamine is 1.5 × 10 ⁵ To
Heated under vacuum of rr and deposited to a thickness of 500 mm. Next, a compound represented by the following chemical formula 19 was used as a light emitting layer at 2.0 ×
Was heated under vacuum at 10¯ ⁵ Torr, it was deposited to a thickness of 500 Å. Next, magnesium and aluminum were deposited as a cathode through a metal mask at a deposition rate of 10 ° / sec and 1 °, respectively.
/ Sec under a vacuum of 1.3 × 10 ⁵ Torr to form a device with a thickness of 1000 °.

When a DC voltage of 20 V was applied to the device thus fabricated using the ITO electrode as an anode, 125 mA / cm
To obtain a luminance of 210 cd / m ² at a ^second current density. The emission spectrum of this device had a peak at 450 nm, and emitted blue light.

[0038]

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[Example (2)] Until the light emitting layer of Example (1) was formed, a film was formed by the same method, and then, as an electron transport layer, 2- (4′-t-butylphenyl) -5 was used. -(4 ″ -biphenyl) -1,3,4-oxadiazole was heated under a vacuum of 1.2 × 10 ⁵ Torr to a thickness of 300 °. Next, a cathode was formed by the same method as in Example (1) to prepare an element.

When a DC voltage of 23 V was applied to the device thus prepared using the ITO electrode as an anode, 75 mA /
A luminance of 185 cd / m ² was obtained at a current density of cm ² . The emission spectrum of this device had a peak at 490 nm and emitted blue-green light. [Example (3)] Up to the hole transport layer, a film was formed by the same method as in Example (1), and then a tetraphenylbutadiene derivative represented by the following chemical formula 20 was added to the light emitting layer of Example (1). The used compounds were used at a deposition rate of 10 ° / sec and 0.1 ° / sec, respectively.
Vacuum is deposited to a thickness of 400 ° under a vacuum of 0 × 10 ⁵ Torr to form a light emitting layer, and then an electron transport layer is formed in the same manner as in Example (2).
After forming the film at 0 °, a cathode was formed to form a device.

[0041]

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When a DC voltage of 18.5 V was applied to the device thus prepared using the ITO electrode as an anode, a current of 5 mA /
Blue light emission having a luminance of 1 cd / m ² was obtained at a current density of cm ² . Example (4) A device was prepared in the same manner as in Example (1) except that a compound represented by the following chemical formula 21 was used for the light emitting layer.

When a DC voltage of 25.2 V was applied to the device fabricated in this manner using the ITO electrode as an anode,
A luminance of 195 cd / m ² was obtained at a current density of cm ² . The emission spectrum of this device had a peak at 465 nm, and emitted blue light.

[0044]

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Example (5) A device was prepared in the same manner as in Example (2), except that the compound used for the light emitting layer of Example (4) was used for the light emitting layer. When a DC voltage of 29.4 V was applied to the device thus prepared using ITO as an anode, a current density of 270 mA / cm ² was 476 cd / m 2.
A luminance of ² was obtained. The emission spectrum of this device had a peak at 465 nm, and emitted blue light.

Example (6) Example (3) was the same as Example (3) except that the luminescent material of Example (1) used in the luminescent layer was changed to the luminescent material of Example (4). A device was prepared in the same manner. When a DC voltage of 27.1 V was applied to the device thus prepared using the ITO electrode as an anode, a luminance of 563 cd / m ² was obtained at a current density of 275 mA / cm ² . The emission spectrum of this device had a peak at 455 nm and emitted blue light.

Example (7) A device was prepared in the same manner as in Example (1) except that a compound represented by the following chemical formula 22 was used for the light emitting layer. When a DC voltage of 23.7 V was applied to the device thus prepared using the ITO electrode as an anode, a current density of 75 mA / cm ² and 49 cd / m ^{2 were obtained.}
Blue light having a luminance of.

[0048]

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Example (8) A device was prepared in the same manner as in Example (2), except that the compound used for the light emitting layer of Example (7) was used for the light emitting layer. 29.5 V using the ITO electrode as a cathode
When a DC voltage of 37.5 mA / cm ² was applied, 38
Blue light with a luminance of cd / m ² was obtained.

Example (9) Example (3) was the same as Example (3) except that the luminescent material of Example (1) used in the light emitting layer was changed to the luminescent material of Example (7). A device was prepared in the same manner. When a DC voltage of 28.9 V was applied to the device thus prepared using the ITO electrode as an anode, a luminance of 776 cd / m ² was obtained at a current density of 475 mA / cm ² . The emission spectrum of this device had a peak at 445 nm, and emitted blue light.

Example (10) A device was prepared in the same manner as in Example (1) except that a compound represented by the following chemical formula 23 was used for the light emitting layer. When a DC voltage of 23.5 V was applied to the device thus prepared using the ITO electrode as an anode, the current density of 87.5 mA / cm ² was 189 cd / cm ^2.
Blue light emission with m ² brightness was obtained.

[0052]

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Example (11) A device was prepared in the same manner as in Example (2), except that the compound used in the light emitting layer of Example (10) was used for the light emitting layer. Blue light was emitted from the device thus prepared. Example (12) In Example (3), the same method as in Example (3) was used, except that the luminescent material of Example (1) used in the light emitting layer was changed to the luminescent material of Example (10). A device was created.

When a DC voltage of 21.9 V was applied to the device thus prepared using the ITO electrode as an anode,
A luminance of 65 cd / m ² was obtained at a current density of A / cm ² . The emission spectrum of this device had a peak at 465 nm and emitted blue light. Example (13) A device was prepared in the same manner as in Example (1), except that a compound represented by the following chemical formula 24 was used for the light emitting layer.

When a DC voltage of 18.9 V was applied to the device thus prepared using the ITO electrode as an anode, a current of 75 mA / cm ^{2 was obtained.}
At a current density of 8 cd / m ² .

[0056]

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Example (14) A device was prepared in the same manner as in Example (2), except that the compound used for the light emitting layer of Example (13) was used for the light emitting layer. The ITO electrode was used as a cathode for the device fabricated in this way.
When a DC voltage of 10 V was applied, a current density of 10 mA / cm ²
Blue light with a luminance of cd / m ² was obtained.

Example (15) Example (3) was the same as Example (3) except that the luminescent material of Example (1) used in the luminescent layer was replaced with the luminescent material of Example (13). A device was prepared in the same manner. The device produced in this way, where the ITO electrode by applying a DC voltage of 22.9V as the anode, 432cd / m ² at a current density of 500mA / cm ²
Was obtained. The emission spectrum of this device had a peak at 465 nm, and emitted blue light.

Example (16) A device was prepared in the same manner as in Example (1) except that a compound represented by the following chemical formula 25 was used for the light emitting layer. When a DC voltage of 19.9 V was applied to the device thus prepared using the ITO electrode as an anode, the current density of 125 mA / cm ² was 145 cd / m 2.
A blue light with a luminance of ² was obtained.

[0060]

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Example (17) An element was prepared in the same manner as in Example (2), except that the compound used in the light emitting layer of Example (16) was used for the light emitting layer. The ITO electrode was used as a cathode for the element fabricated in
At a current density of 85mA / cm ² was applied a DC voltage of V 90
A luminance of 4 cd / m ² was obtained. The emission spectrum of this device is 500n
It has a peak at m and emits blue-green light.

Example (18) Example (3) was the same as Example (3) except that the luminescent material of Example (1) used in the luminescent layer was changed to the luminescent material of Example (16). A device was prepared in the same manner. When a DC voltage of 18.6 V was applied to the device thus prepared using the ITO electrode as an anode, the current density of 250 mA / cm ² was 258 cd / m ^2.
Was obtained. The emission spectrum of this device had a peak at 465 nm, and emitted blue light.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing an organic EL device having a two-layer structure.

FIG. 2 is a structural diagram showing an organic EL element having a three-layer structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Metal electrode (cathode) 2 ... Transparent electrode (anode) 3 ... Organic phosphor thin film 4 ... Organic hole transport layer 5 ... Organic electron transport layer 6 ... Glass substrate

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Nakata 6-1, 1-1 Fujimi, Tsurugashima-cho, Iruma-gun, Saitama Prefecture Pioneer Corporation (72) Inventor Yoshikazu Sato 3-26-8 Shimo, Kita-ku, Tokyo No. (72) Inventor Masaharu Nomura 3-26-8 Shimo, Kita-ku, Tokyo (58) Field surveyed (Int. Cl. ⁶ , DB name) C09K 11/06 CA (STN) REGISTRY (STN) WPI (DIALOG) )

Claims (3)

(57) [Claims] An organic electroluminescent device comprising a phosphor light-emitting layer and a hole transport layer, which are made of an organic compound and are stacked on each other, are disposed between a cathode and an anode, wherein the phosphor light-emitting layer is represented by the following chemical formula 1 or 2 Embedded image Embedded image (In the above chemical formulas 1 and 2, L ₁ , L ₂ and L ₃ each represent a skeleton represented by the following chemical formula 3 and may be the same.) (In the chemical formulas 1, 2 and 3, Q represents a benzene ring or naphthalene ring residue which may have a substituent, and R represents an alkyl group, an aminocarbonylamino group, an aminothiocarbonylamino group, or a substituent. Represents an aralkyl group which may be substituted or a phenyl group which may be substituted;
1, Be, Mg, Ca, Zn, Cd, Cr, Ni, B
i, In, Tl, Ti, Sn, V, Rh, Pb, Fe,
Ag, Cu, Sr, Ba, Sc, Ga, Y or Co). 2. The organic electroluminescence device according to claim 1, wherein an organic electron transport layer is disposed between the cathode and the phosphor layer. 3. The phosphor light-emitting layer includes a second electroluminescent compound different from the electroluminescent compound, and a content ratio of the second electroluminescent compound is larger than a content ratio of the electroluminescent compound. The organic electroluminescence device according to claim 2, wherein