JP2891783B2 - 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.

[0007]

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(In the above chemical formula 1, Q and Q ′ each represent a residue of a benzene ring or a naphthalene ring which may have a substituent, and A represents — (CH ₂ ) _n -0- (CH ₂ ) _n -(n represents an integer of 1 to 2) or a linear or branched alkylene having 2 to 8 carbon atoms, and M represents Be, Mg, Ca, Zn, Cd, Cr, N
i, Ti, Sn, V, Pb, Fe, Cu, Sr, Ba,
(Representing Ga 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 specific structure of the electroluminescent compound represented by is represented by the following chemical formulas 2 to 7.

[0010]

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[0011]

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[0012]

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[0013]

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[0014]

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[0015]

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(In the above chemical formulas 2 to 7, A is-(CH ₂ ) _n-
0- (CH ₂ ) _n- (n represents an integer of 1 to 2) or 2 to 2 carbon atoms
8 represents a linear or branched alkylene, and M is Be, M
g, Ca, Zn, Cd, Cr, Ni, Ti, Sn, V,
Represents Pb, Fe, Cu, Sr, Ba, Ga or Co, and R _{1 to} R ₁₂ each represent hydrogen, an alkyl group, an alkoxy group, a nitro group or a halogen. The electroluminescent compounds represented by the above chemical formulas 2 to 7 that form the phosphor thin film 3 are luminescent materials having a combination of functional groups R _{1 to} R ₁₂ , a crosslinking group A and a central atom M shown in Tables 1 and 2. No.
L1 to No. L38 are preferred. In the table, the symbol-indicates that there is no functional group.

[0017]

[Table 1]

[0018]

[Table 2]

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 transporting layer 4 further has a CTM (Carrier Transporting Mat) represented by the following chemical formulas 8 to 19.
The compounds known as erials) can be used alone or as a mixture.

[0021]

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[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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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 mixture of a so-called host and a guest substance. For example, a compound represented by the above Chemical Formulas 2 to 7 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.

[0034]

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, light can be efficiently emitted with high luminance at a low voltage.

[0035]

【Example】

[Example (1)] N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine was used as a hole transport layer on ITO glass. It was heated under a vacuum of 0.5 × 10 ⁵ Torr and deposited to a thickness of 500 °. Next, the compound represented by the following chemical formula 20 was heated under a vacuum of 2.0 × 10 ⁵ Torr as a light emitting layer,
Evaporated to a thickness of 00 °. Next, magnesium and aluminum were each deposited as a cathode through a metal mask at a deposition rate of 1.
1.3 × 10¯ ⁵ Torr in the 0Å / sec and 1Å / sec
Vacuum was deposited to a thickness of 1000 mm under vacuum to produce a device.

When a DC voltage of 28 V was applied to the device thus prepared using the ITO electrode as an anode, 650 mA / cm
To obtain a luminance of 116cd / m ² in ² current density. The emission spectrum of this device had a peak at 550 nm, and yellow-green to yellow light was emitted.

[0037]

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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 added to 1.2 ×
Was heated under vacuum at 10¯ ⁵ Torr, it was deposited to a thickness of 300 Å. Next, a cathode was formed by the same method as in Example (1) to prepare an element.

When a DC voltage of 29 V was applied to the device thus prepared using the ITO electrode as an anode, 425 mA
A luminance of 234 cd / m ² was obtained at a current density of / cm ² . The light emission spectrum of this device had a peak at 560 nm, and yellow light was emitted. [Example (3)] Up to the hole transport layer, a film was formed in the same manner as in Example (1), and then a tetraphenylbutadiene derivative represented by the following chemical formula 21 was added to the light emitting layer of Example (1). The compounds used were deposited at a deposition rate of 10 ° / sec and 0.1 ° respectively.
/ Sec under a vacuum of 1.0 × 10 ⁵ Torr to a thickness of 400 ° to form a light emitting layer, and then form an electron transporting layer 200 ° in the same manner as in Example (2), and then form a cathode. Films were formed to form devices.

[0040]

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When a DC voltage of 25.7 V was applied to the device thus prepared with the ITO electrode serving as an anode, 167.5 mA
A luminance of 626 cd / m ² was obtained at a current density of / cm ² . The emission spectrum of this device peaked at 455 nm and emitted blue light. Example (4) An element was prepared in the same manner as in Example (1) except that the compound represented by the following chemical formula 22 was used for the light emitting layer.

When a DC voltage of 30 V was applied to the device thus prepared using the ITO electrode as an anode, a voltage of 525 mA / cm ²
At a current density of 83 cd / m ² . The light emission spectrum of this device had a peak at 565 nm, and yellow light was emitted.

[0043]

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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 32 V was applied to the device thus prepared using ITO as an anode, 10
A luminance of 125 cd / m ² was obtained at a current density of 7.5 mA / cm ² . The light emission spectrum of this device had a peak at 575 nm, and yellow to orange light was emitted.

[Embodiment (6)] In the embodiment (3),
The luminescent material of Example (1) used in the luminescent layer was used in Example (4).
A device was prepared in the same manner as in Example (3), except that the luminescent material was replaced by When a DC voltage of 26 V was applied to the device thus prepared using the ITO electrode as an anode, 125 mA / c
to obtain a luminance of 455cd / m ² at a current density of m ^2. The emission spectrum of this device had a peak at 460 nm, and emitted blue light.

[Example (7)] The light emitting layer had the following chemical formula 2
A device was prepared in the same manner as in Example (1) except that the compound shown in No. 3 was used. The device created in this way has IT
When a DC voltage of 24 V was applied using the O electrode as an anode, 40
Blue light with a luminance of 19 cd / m ² was obtained at a current density of 0 mA / cm ² .

[0047]

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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. When a DC voltage of 23 V was applied to the device thus prepared using the ITO electrode as a cathode, a luminance of 116 cd / m ² was obtained at a current density of 325 mA / cm ² . The emission spectrum of this device emitted a blue light with a peak at 485 nm.

[Embodiment (9)] In the embodiment (3),
The luminescent material of Example (1) used in the luminescent layer was used in Example (7).
A device was prepared in the same manner as in Example (3), except that the luminescent material was replaced by When a DC voltage of 25.4 V was applied to the device thus prepared using the ITO electrode as an anode, 750 m
A luminance of 267 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 (10) 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. Blue light was emitted from the device thus prepared.

[0051]

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[Embodiment (11)] The embodiment (10) was applied to the light emitting layer.
Example (2) except that the compound used for the light-emitting layer was used.
A device was prepared in the same manner as described above. Blue light was emitted from the device thus prepared. [Example (12)] In the same manner as in Example (3), except that the luminescent material of Example (1) used in the luminescent layer in Example (3) was changed to the luminescent material of Example (10). A device was created.

When a DC voltage of 23.7 V was applied to the device thus prepared using the ITO electrode as an anode, 775 m
A luminance of 210 cd / m ² was obtained at a current density of A / cm ² . The emission spectrum of this device had a peak at 480 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 Continuation of the front page (72) Inventor Hitoshi Nakata 6-1, 1-1, Fujimi, Tsurugashima-cho, Iruma-gun, Saitama Pref. 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 (56) References JP-A-2-8290 (JP, A) JP-A-2-8287 (JP, A) JP-A-1 -297490 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09K 11/06 CA (STN) REGISTRY (STN) WPI (DIALOG)

Claims (3)

(57) [Claims] 1. An organic electroluminescent device comprising a phosphor light-emitting layer and a hole transport layer, which are made of an organic compound and are laminated on each other, are disposed between a cathode and an anode, wherein the phosphor light-emitting layer has the following chemical formula 1. 1) (In the above Chemical Formula 1, Q and Q ′ each represent a residue of a benzene ring or a naphthalene ring which may have a substituent;
Represents-(CH ₂ ) _n -0- (CH ₂ ) _n- (n represents an integer of 1 to 2) or a linear or branched alkylene having 2 to 8 carbon atoms, and M represents Be, Mg, Ca, Zn, Cd, Cr, Ni, Ti, S
n, V, Pb, Fe, Cu, Sr, Ba, Ga or Co
An organic electroluminescent device comprising an electroluminescent compound represented by the following formula: 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