JPH05339565A - Compound for organic el element and organic el element - Google Patents

Abstract

PURPOSE:To obtain an org. EL element having high reliability and luminous efficiency by using an indole deriv. having a specific backbone as a compd. for the element. CONSTITUTION:An indole deriv. having a backbone of formula I or a compd. having a backbone of fomrula II is used as a compd. for an org. EL element. In those formulas, R<1> to R<7> are each H, halogen, OH, carboxyl, cyano, nitro, amino, alkyl, alkenyl, aryl, aryloxy, alkyloxy, arylcarbonyl, or alkylcarbonyl provided that two adjacent groups of them may combine with each other to form a ring; R R<42>, and R<43> are each alkoxy, alkyl, dialkylamino, or nitro; and p, q, and r are each 0-3 provided that p+q+r>=1. The compd. is used for a luminescent layer, a hole injection and transport layer, and an electron injection and transport layer to give an org. EL element giving a stable and high luminance.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an organic EL (electroluminescence).
More specifically, the present invention relates to an element and a compound used therein, which emits light by applying an electric field to a single-layer or laminated-structure thin film made of an organic compound.

[0002]

2. Description of the Related Art An organic EL device has a structure in which a thin film containing a fluorescent organic compound is sandwiched between a cathode and an anode, and electrons and holes are injected into the thin film to recombine to generate excitons (exciton). ) Is generated and light is emitted by utilizing the emission of light (phosphorescence, fluorescence) when the exciton is deactivated.

The characteristic of the organic EL element is that it can emit a surface with a high luminance of about 1000 cd / m ² at a low voltage of about 10 V, and it emits light from blue to red by selecting the type of fluorescent substance. Is possible.

On the other hand, a problem with the organic EL device is that it has a short lifetime and therefore has low reliability. The cause of this is a physical change of the organic compound (film change / peeling due to crystallization, etc.) Oxidation of the cathode ( Metals with low work function (Mg, Li, Na, etc. are used for electron injection) Low luminous efficiency (~ 1%) and large heat generation Photochemical and electrochemical changes of organic compounds And so on.

[0005]

In particular, the present invention realizes an organic EL device having high reliability and high luminous efficiency by using the above-mentioned organic compound having less physical changes, photochemical changes, and electrochemical changes. The purpose is to do.

[0006]

The above objects are achieved by the present invention described in (1) to (7) below.

(1) A compound for an organic EL device, which is an indole derivative having a skeleton represented by the following chemical formula 3.

[0008]

[Chemical 3]

(In the above chemical formula 3, R ^{1 to} R ⁷ are hydrogen atom, halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, amino group, alkyl group, alkenyl group,
It is an aryl group, an aryloxy group, an alkyloxy group, an arylcarbonyl group or an alkylcarbonyl group, and those adjacent to each other may combine with each other to form a ring. )

(2) The compound for organic EL device of the above (1), which has a skeleton represented by the following chemical formula 4.

[0011]

[Chemical 4]

(In the above chemical formula 4, R ⁴¹ , R ⁴² and R
⁴³ is an alkoxy group, an alkyl group, a dialkylamino group or a nitro group, p, q, and r are integers of 0 to 3, and p + q + r ≧ 1. )

(3) An organic EL device having at least one organic compound layer, wherein at least one organic compound layer contains the compound for organic EL device of the above (1) or (2). ..

(4) Organic EL of (1) or (2) above
The organic EL device according to (3) above, wherein the organic compound layer containing the device compound is a light emitting layer.

(5) The organic EL device according to (4), wherein the light emitting layer further contains at least one fluorescent substance.

(6) Organic EL of (1) or (2) above
The organic EL device according to any one of the above (3) to (5), wherein the organic compound layer containing the device compound is a hole injecting and transporting layer.

(7) Organic EL of (1) or (2) above
The organic EL device according to any one of (3) to (6) above, wherein the organic compound layer containing the device compound is an electron injecting and transporting layer.

[0018]

FUNCTION AND EFFECT The organic EL device of the present invention has the above chemical formula 3.
Since the compound of the present invention shown in is used for the light emitting layer, the hole injecting and transporting layer, and the electron injecting and transporting layer, high brightness can be stably obtained, and depending on the wavelength, about 100 cd / m ² or more,
In particular, a high brightness of about 1000 cd / m ² or more can be stably obtained.

Further, since the thin film of the above compound is substantially amorphous and has a good film quality, uniform surface emission is possible without unevenness.

Further, E using the compound of the present invention in the light emitting layer
The L element is capable of stable emission of purple and blue. Since the emission wavelength can be changed by selecting a substituent or doping various compounds, it is possible to cope with a wide wavelength range from blue / purple to red (maximum emission wavelength of 400 to 700 nm).

[0021]

[Specific Structure] The specific structure of the present invention will be described in detail below.

The compound for organic EL device of the present invention is an indole derivative having the skeleton shown in Chemical formula 3 above.

In the above chemical formula 3, R ^{1 to} R ⁷ are hydrogen atom, halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, amino group, alkyl group (for example, methyl group, ethyl group, propyl group, butyl group). Group, etc.), alkenyl group (eg, ethynyl group, etc.), aryl group (eg, phenyl group, biphenyl group, terphenyl group, etc.), aryloxy group (eg, phenyloxy group, etc.), alkyloxy group (eg, methoxy group) Group, ethoxy group, etc.), arylcarbonyl group (eg, phenylcarbonyl group, etc.)
Or an alkylcarbonyl group (for example, an acetyl group, a propionyl group, etc.), wherein each group has one substituent such as an alkyloxy group, an alkyl group, an aryl group, a nitro group, a cyano group, an amino group or a halogen atom. Or you may have two or more.

At least one of R ^{1 to} R ³ is preferably an aryl group or a group having an aryl group, more preferably all of them are aryl groups.

For example, a compound having a skeleton represented by the following chemical formula 5 is preferable.

[0026]

[Chemical 5]

In the above Chemical Formula 5, R ⁴¹ , R ⁴² and R ⁴³
Is an alkoxy group (preferably having 1 to 5 carbon atoms, particularly 1 carbon atom), an alkyl group (preferably having 1 to 5 carbon atoms),
Dialkylamino group (preferably alkyl having 1 carbon atom)
~ 5) or a nitro group. p, q, and r are integers of 0 to 3, and p + q + r ≧ 1, preferably p + q + r ≦ 6.
Is. R ⁴¹ , R ⁴² and R ⁴³ are usually bonded to the para position, but may be bonded to the ortho position.

The adjacent ones of R ^{1 to} R ⁷ may be bonded to each other to form a 5- or 6-membered, especially 6-membered condensed ring.

The alkyl group and alkenyl group are
It is preferable that the carbon number is 1 to 5. Further, the aryl group is preferably a phenyl group.

Specifically, the compounds exemplified in Tables 1 and 2 below are preferable.

[0031]

[Table 1]

[0032]

[Table 2]

Further, compounds in which the substituents are bonded to each other to form a condensed ring include compounds represented by the following chemical formulas 6 and 7. A compound having a skeleton represented by the following chemical formula 8 is also preferable.

[0034]

[Chemical 6]

In the chemical formula 6, R ¹¹ , R ¹² , R ¹³ , R
¹⁴ is preferably selected from the same as the above R ^{1 to} R ^7, and specifically, for example, R ^{1 to} R ³ and R ¹¹ to
It is preferable that all of R ¹⁴ and R ^{6 to} R ⁷ are hydrogen atoms.

[0036]

[Chemical 7]

In the chemical formula 7, R ²¹ , R ²² , R ²³ , R
²⁴ is preferably selected from the same as the above R ^{1 to} R ^7, and specifically, for example, R ^{1 to} R ⁵ and R ²¹ to
It is preferred that all of R ²⁴ are hydrogen atoms.

[0038]

[Chemical 8]

In the chemical formula 8, R ³¹ , R ³² , R ³³ , R ³⁴ ,
R ³⁵ and R ³⁶ are preferably selected from the same as R ^{1 to} R ⁷ . X is a bond, 1,4-phenylene, 4,4′-biphenylene, or the like, and specifically, X is a bond, 1,4-phenylene, or 4,
4′-biphenylene, R ^{2 to} R ⁷ , R ^{31 to} R ³⁶
Those in which all of are hydrogen atoms are preferred.

The structures of the compounds of the present invention are NMR, IR,
It can be confirmed by elemental analysis, mass spectrometry, liquid chromatography, fluorescence spectrum analysis and the like. Further, the melting point of the compound of the present invention varies depending on the substituents and the like,
Usually, it is about 100 to 300 ° C.

The compound of the present invention can be obtained, for example, by the Fisher method (E,
Fisher, O.Hess; Ber., 17,559 (1883)) and Bischer method (AB
ischer; Ber., 25,2860 (1892)), and particularly useful is a reaction from an aromatic amine and a benzoin derivative (MBRichards; J.Chem.Soc., 97,977).
(1910)). Further, the production method is not limited to these, and can be produced by various other synthetic methods.

The EL device of the present invention has at least one organic compound layer, and at least one organic compound layer contains the compound of the present invention. FIG. 1 shows a configuration example of the EL element of the present invention. The EL device 1 shown in the figure has an anode 3, a hole injecting and transporting layer 4, a light emitting layer 5, an electron injecting and transporting layer 6, and a cathode 7 in this order on a substrate 2.

The light emitting layer has a function of injecting holes and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. The hole injecting and transporting layer has a function of facilitating injection of holes from the anode, a function of transporting holes and a function of hindering electrons, and the electron injecting and transporting layer facilitates injection of electrons from the cathode. These layers have the function of transporting electrons and the function of transporting electrons, and these layers improve the luminous efficiency by increasing the holes and electrons injected into the light emitting layer. The electron injecting and transporting layer and the hole injecting and transporting layer are provided as necessary in consideration of the functions of the compound used in the light emitting layer for electron injecting, electron transporting, hole injecting, and hole transporting. For example, when the compound used for the light emitting layer has a high hole injecting / transporting function or an electron injecting / transporting function, the light emitting layer is not provided with the hole injecting / transporting layer or the electron injecting / transporting layer. It can be configured to also serve as a transport layer.
In some cases, neither the hole injecting / transporting layer nor the electron injecting / transporting layer may be provided.

The compound of the present invention can be applied to any of a hole injecting / transporting layer, a light emitting layer and an electron injecting / transporting layer. The compound of the present invention can change its properties from hole injection / transport properties to electron injection / transport properties by selecting a substituent. Further, by selecting a substituent, the emitted light can have a short wavelength of 400 nm or less. Therefore, when the compound of the present invention is used for the hole injecting and transporting layer or the electron injecting and transporting layer and the fluorescent substance having the fluorescence on the long wavelength side having a smaller energy gap than that is used for the light emitting layer, any emission color can be obtained. It is possible.

Of the above-exemplified compounds, those preferable as the hole injecting and transporting compound are No. 102 and 1 in Table 1.
05, 106, 111 and the like, and those in which R ^{41 to} R ⁴³ in the above Chemical Formula 5 are alkoxy groups are also preferable as the hole injecting and transporting compound. No. 101, 127, 128 and the like are preferable as the electron injecting and transporting compound, and compounds in which all the substituents exemplified in the above Chemical Formulas 6 to 8 are hydrogen atoms are also as the electron injecting and transporting compound. Can be used. The hole injecting / transporting compound and the electron injecting / transporting compound can also be applied to the light emitting layer.

The case where the compound of the present invention is used in the light emitting layer will be described. In this case, the light emitting layer may contain other fluorescent substances. Examples of the other fluorescent substance include at least one compound selected from compounds such as those disclosed in JP-A-63-264692, such as coumarin, quinacridone, rubrene, and styryl dyes. Be done. The content of such a fluorescent substance is preferably 5 mol% or less of the compound of the present invention. The emission light can be shifted to the long wavelength side by appropriately selecting and adding such a compound.

Further, the light emitting layer may contain a singlet oxygen quencher. Examples of such a quencher include nickel complex, rubrene, diphenylisobenzofuran, and tertiary amine. The content of such a quencher is preferably 10 mol% or less of the compound of the present invention.

When the compound of the present invention is used in the light emitting layer, the hole injecting / transporting layer and the electron injecting / transporting layer may be formed in a conventional organic E layer.
Various organic compounds used in the L element, for example, JP-A-63-295695 and JP-A-2-191694.
Various organic compounds described in, for example, Japanese Patent Laid-Open No. 3-792 can be used. For example, an aromatic tertiary amine, a hydrazone derivative, a carbazole derivative or the like can be used for the hole injecting / transporting layer, and an oxadiazole derivative or the like can be used for the electron injecting / transporting layer.

The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited and may vary depending on the forming method, but are usually about 10 to 1000 nm, particularly 50 to 200 nm. Preferably.

The thickness of the hole injecting and transporting layer and the thickness of the electron injecting and transporting layer may be approximately the same as the thickness of the light emitting layer.

When the compound of the present invention is used in the hole injecting / transporting layer or the electron injecting / transporting layer, the fluorescent substance used in the light emitting layer may be selected from those having a longer wavelength fluorescence as described above. It may be appropriately selected from one or more of the above-mentioned fluorescent substances used in combination with the compound of the present invention in the light emitting layer. In such a case, the compound of the present invention can be used for the light emitting layer.

For the cathode, it is preferable to use a material having a small work function, for example, Li, Na, Mg, Al, Ag, In or an alloy containing at least one of these. The cathode preferably has fine crystal grains, and particularly preferably is in an amorphous state. The thickness of the cathode is 10
It is preferably about 1000 nm.

At least one of the electrodes must be transparent or semi-transparent in order to make the EL element emit light in a plane.
Since the material of the cathode is limited as described above, it is preferable to determine the material and thickness of the anode so that the transmittance of emitted light is 80% or more. In particular,
For example, ITO, SnO ₂ , Ni, Au, Pt, Pd,
It is preferable to use polythiophene, polypyrrole or the like for the anode. The thickness of the anode is preferably about 10-500 nm.

The substrate material is not particularly limited, but in the illustrated example, a transparent or semitransparent material such as glass or resin is used in order to take out emitted light from the substrate side.

When an opaque material is used for the substrate, the stacking order shown in FIG. 1 may be reversed.

Next, a method for manufacturing the EL device of the present invention will be described.

The cathode and anode are preferably formed by vapor phase growth method such as vapor deposition method and sputtering method.

For forming the hole injecting and transporting layer, the light emitting layer and the electron injecting and transporting layer, it is preferable to use the vacuum deposition method because a uniform thin film can be formed. When the vacuum vapor deposition method is used, an amorphous state or a homogeneous thin film having a crystal grain size of 0.1 μm or less can be obtained. If the crystal grain size exceeds 0.1 μm, the driving voltage of the device must be increased, and the charge injection efficiency also decreases.

The conditions of vacuum vapor deposition are not particularly limited, but 1
The degree of vacuum is 0 ^-5 Torr or less, and the deposition rate is 0.1 to 1 nm /
It is preferably about sec. Moreover, it is preferable to form each layer continuously in a vacuum. If they are continuously formed in vacuum, impurities can be prevented from adsorbing to the interface of each layer, so that high characteristics can be obtained. Further, the driving voltage of the element can be lowered.

When a vacuum vapor deposition method is used to form each of these layers, when a plurality of compounds are contained in one layer, it is preferable to co-evaporate the boats containing the compounds by individually controlling the temperature, but mixing them in advance. You may vapor-deposit after that.

In addition to this, a solution coating method (spin coating, dipping, casting, etc.), Langmuir-Blodgett (LB) method, or the like can be used. In the solution coating method, the compound of the present invention may be dispersed in a matrix substance such as a polymer.

The EL element of the present invention is usually used as a DC drive type EL element, but it can also be AC drive or pulse drive. The applied voltage is usually about 5 to 20V.

[0063]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Example 1 Compound N shown in Table 1 above
o. 103 was synthesized by the following method. First, J (4
-Methoxyphenyl) amine 3.3 g, benzoin 3.
0 g and 2.0 g of zinc chloride were reacted at 180 ° C. for 2 hours. After cooling, water was added, the mixture was extracted with chloroform, dried, and the solvent was distilled off to obtain 5.6 g of an oily reaction product. The reaction product is passed through a silica gel column for 1.2
White crystals of g were obtained. Further, the crystals were recrystallized from acetonitrile and ethanol to obtain 0.9 g of white crystals.
When this compound was analyzed by IR, NMR and mass spectrometry, it was confirmed to be compound No. 103 in the above Table 1. The melting point of this compound was 138 to 139 ° C.

Example 2 A glass substrate having an ITO transparent electrode (anode) having a thickness of 100 nm was ultrasonically cleaned with a neutral detergent, acetone, and ethanol, and was pulled up from boiling ethanol and dried to obtain a vapor deposition apparatus. After fixing to the substrate holder of No. 1, the pressure was reduced to 1 × 10 ⁻⁶ Torr.

Next, the compound represented by the following chemical formula 9 was vapor-deposited at a vapor deposition rate of 0.2 nm / sec. To a thickness of 50 nm to form a hole injecting and transporting layer. This compound was synthesized according to the method of Example 1. The melting point of this compound was 132 to 134 ° C.

[0067]

[Chemical 9]

Then, while maintaining the reduced pressure, tris (8-quinolinol) aluminum was deposited at a deposition rate of 0.2 nm.
It was vapor-deposited to a thickness of 50 nm at a time of 10 sec to obtain a light emitting layer having a strong electron injecting and transporting function.

Furthermore, while maintaining the reduced pressure, MgAg
(Weight ratio 10: 1) 200 at a deposition rate of 0.2 nm / sec
An EL device was obtained by vapor deposition to a thickness of nm to form a cathode.

When a voltage was applied to this EL element and a current was passed through it, a yellow-green (light emission maximum wavelength λ max = 495 nm) emission of 1500 cd / m ² was confirmed at 12 V · 50 mA / cm ² , and this emission was 100 It was stable for more than an hour.

Example 3 A glass substrate having an ITO transparent electrode (anode) with a thickness of 100 nm was ultrasonically washed with a neutral detergent, acetone, and ethanol, and was pulled up from boiling ethanol and dried to obtain a vapor deposition apparatus. After fixing to the substrate holder of No. 1, the pressure was reduced to 1 × 10 ⁻⁶ Torr.

Next, the compound represented by the above chemical formula 9 was vapor-deposited at a vapor deposition rate of 0.2 nm / sec. To a thickness of 50 nm to obtain a light emitting layer having a strong hole injecting and transporting function.

Then, while maintaining the reduced pressure state, 1,3-
Bis (5-t-butylphenyl-1,3,4-oxadiazol-2-yl) benzene (OXD-7) was deposited at a deposition rate of 0.2 nm / sec to a thickness of 50 nm to form an electron injecting and transporting layer. And

Further, while maintaining the reduced pressure, MgAg
(Weight ratio 10: 1) 200 at a deposition rate of 0.2 nm / sec
An EL device was obtained by vapor deposition to a thickness of nm to form a cathode.

When a voltage was applied to this EL element and a current was passed through it, it was confirmed that 150 cd / m ² blue light (λmax = 470 nm) was emitted at 18 V · 25 mA / cm ² , and this emission was 1
It was stable for more than 0 hours.

Example 4 A glass substrate having an ITO transparent electrode (anode) having a thickness of 100 nm was ultrasonically washed with a neutral detergent, acetone, and ethanol, and was pulled up from boiling ethanol and dried to obtain a vapor deposition apparatus. After fixing to the substrate holder of No. 1, the pressure was reduced to 1 × 10 ⁻⁶ Torr.

Then, N, N'-diphenyl-di (3-
Methylphenyl) -4,4'-diaminobiphenyl (T
PD) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 50 nm to form a hole injecting and transporting layer.

Then, while maintaining the reduced pressure, the following chemical formula 1
Compound of No. 0 at 50 nm at a deposition rate of 0.2 nm / sec
Was evaporated to a light emitting layer having a strong electron injecting and transporting function. This compound was synthesized according to the method of Example 1. The melting point of this compound was 186 to 187 ° C.

[0079]

[Chemical 10]

Further, while maintaining the reduced pressure state, MgAg
(Weight ratio 10: 1) 200 at a deposition rate of 0.2 nm / sec
An EL device was obtained by vapor deposition to a thickness of nm to form a cathode.

When a voltage was applied to this EL element and a current was passed through it, it was confirmed that 15 cd / m ² bluish purple (λmax = 400 nm) was emitted at 15 V · 250 mA / cm ² , and this emission was stable for 20 hours or more. Was.

The effects of the present invention are apparent from the above examples.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration example of an EL element of the present invention.

[Explanation of symbols]

 1 EL element 2 substrate 3 anode 4 hole injecting and transporting layer 5 light emitting layer 6 electron injecting and transporting layer 7 cathode

Claims (7)

[Claims] 1. A compound for an organic EL device, which is an indole derivative having a skeleton represented by the following chemical formula 1. [Chemical 1] (In the above chemical formula ¹ , R ^{1 to} R ⁷ are hydrogen atom, halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, amino group, alkyl group, alkenyl group, aryl group, aryloxy group, alkyloxy group, An arylcarbonyl group or an alkylcarbonyl group, which are adjacent to each other, may combine with each other to form a ring.) 2. The compound for an organic EL device according to claim 1, which has a skeleton represented by the following chemical formula 2. [Chemical 2] (In the above Chemical Formula 2, R ⁴¹ , R ⁴² and R ⁴³ are an alkoxy group, an alkyl group, a dialkylamino group or a nitro group, p, q and r are integers of 0 to 3, and p + q +
r ≧ 1. ) 3. Having at least one organic compound layer,
At least one organic compound layer contains the compound for organic EL device according to claim 1 or 2.
L element. 4. The organic EL device according to claim 3, wherein the organic compound layer containing the compound for organic EL device according to claim 1 or 2 is a light emitting layer. 5. The organic EL device according to claim 4, wherein the light emitting layer further contains at least one fluorescent substance. 6. The organic EL device according to claim 3, wherein the organic compound layer containing the compound for organic EL device according to claim 1 or 2 is a hole injecting and transporting layer. 7. The organic EL device according to claim 3, wherein the organic compound layer containing the compound for organic EL device according to claim 1 or 2 is an electron injecting and transporting layer.