JPH05331459A - Organic electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain an organic electroluminescent element capable of making an organic fluorescencer efficiently emit light in high brightness by successively laminating an anode, a hole transport layer, a luminescent layer, an electron transport layer and a cathode and constituting the electron transport layer from a specific organic compound. CONSTITUTION:The element is obtained by successively laminating an anode, a hole transport layer consisting of an organic compound, a luminescent layer consisting of an organic compound, an electron transport layer consisting of a phenanthroline derivative of formula I (R1 to R8 are H, alkyl, aryl, etc.) and a cathode. Furthermore, as the organic compound constituting the hole transport layer, e.g. a triphenylamine derivative of formula II is used. As the luminescent layer, a thin film of a fluorescent substance containing a triphenylamine derivative is used. Further, as the cathode, e.g. aluminum is used and as the anode, e.g. indium tin oxide is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescence device, and more particularly to an organic electroluminescent device in which an anode, a hole transport layer made of an organic compound, a light emitting layer made of an organic compound, an electron transport layer made of an organic compound, and a cathode are sequentially laminated. It relates to a luminescence element.

[0002]

2. Description of the Related Art As an organic electroluminescence device of this type, as shown in FIG.
There is known a two-layer structure in which an organic phosphor thin film (light emitting layer) 3 and an organic hole transporting layer 4 which are laminated on each other are disposed between a transparent electrode 2 which is an anode and a transparent electrode 2. Also, as shown in FIG. 2, a three-layer structure in which an organic electron transport layer 5, a light emitting layer 3 and an organic hole transport layer 4 which are laminated between a metal electrode 1 and a transparent electrode 2 are arranged is also available. Known Here, the organic hole transport layer 4 has a function of facilitating injection of holes from the anode and a function of blocking electrons, and the organic electron transport layer 5 has a function of facilitating injection of electrons from the cathode. There is.

In these organic electroluminescent elements, a glass substrate 6 is arranged outside the transparent electrode 2. Excitons are generated by recombination of electrons injected from the metal electrode 1 and holes injected from the transparent electrode 2,
The excitons emit light in the process of radiation deactivation, and the light is emitted to the outside through the transparent electrode 2 and the glass plate 6.

[0004]

However, even an organic electroluminescence device capable of emitting light at a relatively high brightness is not sufficiently satisfactory in brightness. The present invention has been made to satisfy the above-mentioned conventional demands, and an object of the present invention is to provide an organic electroluminescence device capable of efficiently emitting light with high brightness from an organic phosphor.

[0005]

The electroluminescence device according to the present invention is an organic luminescent device in which an anode, a hole transport layer made of an organic compound, a light emitting layer made of an organic compound, an electron transport layer made of an organic compound, and a cathode are sequentially stacked. An electroluminescence device, wherein the electron transport layer is a phenanthroline derivative represented by the following chemical formula 1.

[0006]

[Chemical 1]

(In the chemical formula 1, R _{1 to} R ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group or a cyano group. Represents a group or a hydroxyl group). The electroluminescence device according to the present invention is an organic electroluminescence device in which an anode, a hole transport layer made of an organic compound, a light emitting layer made of an organic compound, an electron transport layer made of an organic compound, and a cathode are sequentially laminated, The transport layer is a 1,7-phenanthroline derivative represented by the following chemical formula 83

[0008]

[Chemical 83]

(In the chemical formula 83, R _{1 to} R ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group or a cyano group. Represents a group or a hydroxyl group). The electroluminescence device according to the present invention is an organic electroluminescence device in which an anode, a hole transport layer made of an organic compound, a light emitting layer made of an organic compound, an electron transport layer made of an organic compound, and a cathode are sequentially laminated, The transport layer is a 4,7-phenanthroline derivative represented by the following chemical formula 84.

[0010]

[Chemical 84]

(In the chemical formula 84, R _{1 to} R ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group or a cyano group. Represents a group or a hydroxyl group). The electroluminescence device according to the present invention is an organic electroluminescence device in which an anode, a hole transport layer made of an organic compound, a light emitting layer made of an organic compound, an electron transport layer made of an organic compound, and a cathode are sequentially laminated, Phenanthroline derivative having a transport layer having a dihydro form of dibenzophenanthroline represented by the chemical formula 87 as a skeleton

[0012]

[Chemical 87]

(In the chemical formula 87, R _{1 to} R ₁₀ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group or a cyano group. Represents a group or a hydroxyl group).

[0014]

According to the present invention, it is possible to obtain an organic electroluminescence device capable of efficiently emitting light with high brightness.

[0015]

The present invention will be described in detail below with reference to the drawings. The organic electroluminescence device of the present invention is similar to the organic electroluminescence device having the structure shown in FIG. 2, and as shown in FIG. 2, the electron transport layer 5 is provided between the pair of metal cathode 1 and transparent anode 2. The light emitting layer 3 and the hole transport layer 4 are sequentially formed. In this case, one of the electrodes 1 and 2 may be transparent. For example, the cathode 1 may be made of a metal having a small work function, such as aluminum, magnesium, indium, silver, or an alloy of each, and having a thickness of about 100 to 5000 Å. Further, for example, the anode 2 is made of a conductive material having a large work function, such as indium tin oxide (hereinafter, also referred to as ITO), and has a thickness.
It is possible to use gold with a thickness of about 1000 to 3000Å, or gold with a thickness of about 800 to 1500Å. When gold is used as the electrode material, the electrode becomes semitransparent.

As shown in FIG. 2, the organic hole transport layer 4 is composed of
For example, a triphenylamine derivative represented by the chemical formula 2 below, and a CTM (Carrier Transport Mate) represented by the chemical formulas 3 to 13 below.
Compounds known as rials) can be used.

[0017]

[Chemical 2]

[0018]

[Chemical 3]

[0019]

[Chemical 4]

[0020]

[Chemical 5]

[0021]

[Chemical 6]

[0022]

[Chemical 7]

[0023]

[Chemical 8]

[0024]

[Chemical 9]

[0025]

[Chemical 10]

[0026]

[Chemical 11]

[0027]

[Chemical formula 12]

[0028]

[Chemical 13]

As shown in FIG. 2, as the light emitting layer 3, a phosphor thin film containing a tetraphenylbutadiene compound represented by the following chemical formulas 14 to 16 and 85 is preferably used.

[0030]

[Chemical 14]

[0031]

[Chemical 15]

[0032]

[Chemical 16]

[0033]

[Chemical 85]

Further, as the light emitting layer 3, compounds represented by the chemical formulas 17 to 25 are also used. The thickness of these light emitting layers 3 is set to 1 μm or less.

[0035]

[Chemical 17]

[0036]

[Chemical 18]

[0037]

[Chemical 19]

[0038]

[Chemical 20]

[0039]

[Chemical 21]

[0040]

[Chemical formula 22]

[0041]

[Chemical formula 23]

[0042]

[Chemical formula 24]

[0043]

[Chemical 25]

As shown in FIG. 2, the electron transport layer 5 includes:
A compound represented by the general formula 1 is used.

[0045]

[Chemical 1]

(In the chemical formula 1, R _{1 to} R ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group or a cyano group. Represents a group or a hydroxyl group). Hereinafter, specific examples of the phenanthroline derivative used in the present invention are shown in chemical formulas 26 to 82, but the present invention is not limited thereto.

[0047]

[Chemical formula 26]

[0048]

[Chemical 27]

[0049]

[Chemical 28]

[0050]

[Chemical 29]

[0051]

[Chemical 30]

[0052]

[Chemical 31]

[0053]

[Chemical 32]

[0054]

[Chemical 33]

[0055]

[Chemical 34]

[0056]

[Chemical 35]

[0057]

[Chemical 36]

[0058]

[Chemical 37]

[0059]

[Chemical 38]

[0060]

[Chemical Formula 39]

[0061]

[Chemical 40]

[0062]

[Chemical 41]

[0063]

[Chemical 42]

[0064]

[Chemical 43]

[0065]

[Chemical 44]

[0066]

[Chemical 45]

[0067]

[Chemical 46]

[0068]

[Chemical 47]

[0069]

[Chemical 48]

[0070]

[Chemical 49]

[0071]

[Chemical 50]

[0072]

[Chemical 51]

[0073]

[Chemical 52]

[0074]

[Chemical 53]

[0075]

[Chemical 54]

[0076]

[Chemical 55]

[0077]

[Chemical 56]

[0078]

[Chemical 57]

[0079]

[Chemical 58]

[0080]

[Chemical 59]

[0081]

[Chemical 60]

[0082]

[Chemical formula 61]

[0083]

[Chemical formula 62]

[0084]

[Chemical 63]

[0085]

[Chemical 64]

[0086]

[Chemical 65]

[0087]

[Chemical 66]

[0088]

[Chemical 67]

[0089]

[Chemical 68]

[0090]

[Chemical 69]

[0091]

[Chemical 70]

[0092]

[Chemical 71]

[0093]

[Chemical 72]

[0094]

[Chemical 73]

[0095]

[Chemical 74]

[0096]

[Chemical 75]

[0097]

[Chemical 76]

[0098]

[Chemical 77]

[0099]

[Chemical 78]

[0100]

[Chemical 79]

[0101]

[Chemical 80]

[0102]

[Chemical 81]

[0103]

[Chemical formula 82]

Further, in the above-mentioned Examples, the electron transport layer 5 in the organic electroluminescence device is formed of the derivative having the skeleton of 1,10-phenanthroline represented by the above Chemical Formula 1, but the following Chemical Formula 83 or 84 is used.
A thin film formed from 1,7-phenanthroline or a phenanthroline derivative having 4,7-phenanthroline as a skeleton may be used.

[0105]

[Chemical 83]

[0106]

[Chemical 84]

In Chemical Formulas 83 and 84, R _{1 to} R ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group, Represents a cyano group or a hydroxyl group. Furthermore, in addition to the phenanthroline derivative having 1,7-phenanthroline or 4,7-phenanthroline as the skeleton, the electron transport layer 5 in the organic electroluminescence device has the dihydro form of dibenzophenanthroline represented by the following chemical formula 87 as the skeleton. It may be a thin film formed from a phenanthroline derivative.

[0108]

[Chemical 87]

In the chemical formula 87, R _{1 to} R ₁₀ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group or a cyano group. Or represents a hydroxyl group. Specific examples of the dihydro derivative of dibenzophenanthroline are shown in Chemical Formulas 88 to 91, but the present invention is not limited thereto.

[0110]

[Chemical 88]

[0111]

[Chemical 89]

[0112]

[Chemical 90]

[0113]

[Chemical Formula 91]

Example 1 A glass substrate on which an ITO thin film having a thickness of 1500 Å was formed was ultrasonically cleaned in ethanol for 5 minutes and then air-dried. Chemical formula 2 on this glass substrate
Compound shown by

[0115]

[Chemical 2]

[0116] was deposited from a tantalum boat at a vapor deposition rate of 3Å / sec to a film thickness of 500Å to form a hole transport layer. The degree of vacuum during vapor deposition was 5 × 10 ⁻⁶ Torr. Next, a tetraphenyl butadiene derivative represented by the chemical formula 15 is formed on the hole transport layer as a light emitting substance.

[0117]

[Chemical 15]

[0118] was deposited to a film thickness of 200Å at a vapor deposition rate of 4Å / sec to form a light emitting layer. Next, the chemical formula 3 is formed on the light emitting layer.
Phenanthroline compound represented by 9

[0119]

[Chemical Formula 39]

[0120] was deposited at a vapor deposition rate of 3Å / sec to a film thickness of 500Å to form an electron transport layer. Finally, a Mg-Ag alloy metal layer having a film thickness of 1500 Å was deposited on the electron transport layer from different boats at a vapor deposition rate of 10 Å / sec for Mg and a vapor deposition rate of 1 for Ag.
A film was formed at a rate of Å / second, an electrode layer was formed, and an organic electroluminescence device was prepared. The ITO thin film of the organic electroluminescence device thus created is used as an anode,
When a voltage was applied using the Mg-Ag alloy layer as a cathode,
Blue light emission with a luminance of 25 cd / m ² was obtained at 5V. At this time, the luminous efficiency was 0.7 lm / W.

Example 2 An organic electroluminescence device was prepared in the same manner as in Example 1 except that the phenanthroline compound represented by the chemical formula 40 was used for the electron transport layer.

[0122]

[Chemical 40]

The ITO thin film of this element was used as an anode and Mg-Ag
When voltage was applied using the alloy layer as a cathode, blue light emission with a luminance of 47 cd / m ² was obtained at 12V. At this time, the luminous efficiency was 0.3 lm / W. [Example 3] An organic electroluminescence device was prepared in the same manner as in Example 1 except that the tetraphenylbutadiene derivative represented by the chemical formula 14 was used for the light emitting layer.

[0124]

[Chemical 14]

The ITO thin film of this device was used as an anode and Mg-Ag.
When a voltage was applied using the alloy layer as a cathode, blue light emission with a brightness of 72 cd / m ² was obtained at 7V. At this time, the luminous efficiency was 0.4 lm / W. [Example 4] 1,1 represented by the chemical formula 85 in the light emitting layer
An organic electroluminescence device was prepared in the same manner as in Example 1 except that 4,4-tetraphenyl-1,3-butadiene was used.

[0126]

[Chemical 85]

The ITO thin film of this device was used as an anode and Mg-Ag.
When a voltage was applied using the alloy layer as a cathode, blue light emission with a brightness of 63 cd / m ² was obtained at 6V. The luminous efficiency at this time was 1.5 lm / W. Furthermore, when a voltage of 13 V was applied to this device, blue light emission with a luminance of 5800 cd / m ² was obtained. [Example 5] Organic material was formed in the same manner as in Example 4 except that a metal layer of Al-Li alloy having a Li concentration of 0.2 wt% and a film thickness of 800 Å was formed as a cathode on the electron transport layer at a deposition rate of 10 Å / sec. An electroluminescence device was created.

The ITO thin film of this element was used as an anode and Al--Li.
When a voltage was applied using the alloy layer as a cathode, blue light emission with a luminance of 82 cd / m ² was obtained at 5V. At this time, the luminous efficiency was 2.4 lm / W. Furthermore, when a voltage of 12 V was applied to this device, blue light emission with a brightness of 9700 cd / m ² was obtained. [Comparative Example 1] An organic electroluminescent device of Comparative Example 1 was prepared in the same manner as in Example 1 except that the electron transport layer was not formed.

The ITO thin film of this device was used as an anode and Mg-Ag.
When a voltage was applied using the alloy layer as an anode, light emission with a brightness of 24 cd / m ² was obtained at 12V. The luminous efficiency at this time is 0.
The value was 02 lm / W, which was one digit smaller than that of the example. [Example 6] The organic electroluminescence device of Example 4 was made to emit light at a brightness of 40 cd / m ² in a vacuum and held at a constant current value. The half-life of the brightness was 4 hours and 45 minutes.

[Comparative Example 2] t-Bu-PBD {2- (4'-tert-butylphenyl) represented by the chemical formula 86 which has been conventionally regarded as one of the most excellent electron transport materials.
Comparative Example 2 was carried out in the same manner as in Example 4 except that -5- (4 "-biphenyl) -1,3,4-oxadiazole} was used as the electron transport layer.
The organic electroluminescence device of was prepared.

[0131]

[Chemical formula 86]

The ITO thin film of this element was used as an anode and Mg-Ag
When a voltage is applied using the alloy layer as an anode, the brightness is 2 at 7V.
A blue light emission of 9 cd / m ² and a luminous efficiency of 1.4 lm / W was obtained, but a luminance of 130 was obtained when a voltage of 13 V was applied to this device.
Only light emission of 0 cd / m ² was obtained. This is Example 4
The maximum brightness is less than one-quarter. Further, when this device was made to emit light at a brightness of 40 cd / m ² in a vacuum and held at a constant current value, the half-life of the brightness was 4 minutes, which was remarkably shorter than that of Example 6 as shown in FIG.

Example 7 An organic electroluminescent device was prepared in the same manner as in Example 4, except that the phenanthroline compound represented by the chemical formula 40 was used for the electron transport layer.

[0134]

[Chemical 40]

When this device was made to emit light in a vacuum and held at a constant current value, the half-life of brightness from blue light emission with an initial brightness of 200 cd / m ² was 4 hours and 45 minutes, and an initial brightness of 40 cd.
The half-life of luminance from blue emission of / m ² is 35 hours,
The half-life of luminance from blue light emission with an initial luminance of 10 cd / m ² is 1
This was 00 hours, and the half-life of luminance was significantly extended in this device as compared with Comparative Example 2.

Example 8 An organic electroluminescent device was prepared in the same manner as in Example 1 except that the dihydro derivative of dibenzophenanthroline represented by the chemical formula 88 was used in the electron transport layer.

[0137]

[Chemical 88]

This device was subjected to a vacuum in an initial luminance of 40 cd / m ²
When it was made to emit blue light and was held at a constant current value, the half-life of brightness was 33 hours, and the half-life of brightness was remarkably extended as compared with Comparative Example 2.

[0139]

As described above, in the organic electroluminescence device according to the present invention, the electron transport layer, the light emitting layer and the hole transport layer, which are made of organic compounds and are laminated on each other, are arranged between the cathode and the anode. In the organic electroluminescent device of (1), since the electron transport layer is made of a thin film containing the phenanthroline derivative, it is possible to efficiently emit light with high brightness and for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of an organic electroluminescence element.

FIG. 2 is a schematic structural diagram of an organic electroluminescence device.

FIG. 3 is a graph showing changes with time in luminance of organic electroluminescent elements of Example 6 and Comparative Example 2.

[Explanation of symbols]

 1 Metal Electrode (Cathode) 2 Transparent Electrode (Anode) 3 Light Emitting Layer 4 Organic Hole Transport Layer 5 Organic Electron Transport Layer 6 Glass Substrate

Claims (4)

[Claims] 1. A positive electrode, a hole transport layer comprising an organic compound,
What is claimed is: 1. An organic electroluminescence device comprising a light emitting layer made of an organic compound, an electron transporting layer made of an organic compound, and a cathode, which are sequentially stacked, wherein the electron transporting layer is a phenanthroline derivative represented by the following chemical formula 1. (In the chemical formula 1, R _{1 to} R ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group, a cyano group or a hydroxyl group. The organic electroluminescence device is characterized by comprising: 2. A positive electrode, a hole transport layer made of an organic compound,
An organic electroluminescence device in which a light emitting layer made of an organic compound, an electron transporting layer made of an organic compound, and a cathode are laminated in this order, and the electron transporting layer is represented by the following chemical formula 83:
1,7-phenanthroline derivative represented by: (In Chemical Formula 83, R _{1 to} R ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group, a cyano group or a hydroxyl group. The organic electroluminescence device is characterized by comprising: 3. A positive electrode, a hole transport layer comprising an organic compound,
An organic electroluminescence device in which a light emitting layer made of an organic compound, an electron transporting layer made of an organic compound, and a cathode are sequentially laminated, wherein the electron transporting layer is represented by the following chemical formula 84:
4,7-phenanthroline derivative represented by: (In the chemical formula 84, R _{1 to} R ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group, a cyano group or a hydroxyl group. The organic electroluminescent element is characterized by comprising: 4. A positive electrode, a hole transport layer comprising an organic compound,
An organic electroluminescent device in which a light emitting layer made of an organic compound, an electron transporting layer made of an organic compound, and a cathode are laminated in this order, and the electron transporting layer is a phenanthroline derivative having a dihydro form of dibenzophenanthroline represented by the chemical formula 87 as a skeleton. [Chemical 87] (In the chemical formula 87, R _{1 to} R ₁₀ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted amino group, a halogen atom, a nitro group, a cyano group or a hydroxyl group. The organic electroluminescent element is characterized by comprising: