JPH09249621A - 1,3,5-tris(4-disubstituted aminophenyl)benzene compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new 1,3,5-tris(disubstituted aminophenyl)benzene compound capable of forming an amorphous thin film stable at a normal temperature by a vacuum deposition method and usable as a material for positive hole transportation for an organic electroluminescent element. SOLUTION: This compound is shown by formula I (R<1> is phenyl, etc.; R<2> is naphthyl, etc.). The compound is obtained by heating 1,3,5-tris(4-iodophenyl) benzene, obtained by iodating triphenylbenzene as a well-known compound, as a starting raw material and an amine of formula II in the presence of metal copper and a base such as potassium hydroxide in a high-boiling hydrocarbon- based solvent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is capable of forming a thermally stable amorphous state and forming a thin film by itself.
A novel compound useful as a hole transport material in an organic electroluminescence (EL) device and also useful as a material for a photoelectric conversion device, a thermochromic device, an optical memory device, and the like, more specifically, 1,3,5-tris It relates to a (4-disubstituted aminophenyl) benzene compound.

[0002]

2. Description of the Related Art Inorganic EL elements are used in, for example, a planar light source as a backlight, a display device such as a flat panel display, etc., but a high voltage AC is required to emit light. On the other hand, around 1983 Tan
g. et al. produced an organic EL device having a two-layer structure in which a light emitting layer of an organic fluorescent dye and a hole transport layer made of a triphenylenediamine compound were laminated, and low voltage direct current drive, high efficiency, and high brightness were obtained. An organic EL device has been proposed (JP-A-59-59).
194393, U.S. Pat. No. 4,539,507). Compared with the inorganic EL element, this organic EL element has characteristics that it is driven at a low voltage and has high brightness, and moreover that multicolor emission can be easily obtained. Therefore, many studies have been made thereafter, and the element structure and the organic fluorescent dye, Improvements on organic charge transport compounds have been reported (US Pat. Nos. 4,720,432, 4,769,292, 4,885,211 and 5,061,569, Japanese Journal. Of Applied Physics (Jpn.J.Appl.Phys.), 27
Volume, L 269, 1988, Journal of Applied
Physics (J.Appl.Phys.), Volume 65, Page 3910, 1989
Year).

In considering the application of the organic EL device, the most important problem to be solved is the life (deterioration) of the device. Deterioration of the element appears as 1) deterioration of luminance, 2) generation / increase of non-light emitting part called dark spot, and 3) characteristic deterioration such as voltage rise during constant current driving. Element deterioration factors are classified into internal factors (heat resistance of organic thin film, resistance to electrical conduction, light resistance, etc.) and external factors (water in the environment, oxygen, dust, etc.), but internal factors are It is a problem peculiar to organic materials and a problem related to the essence of organic EL devices. It is said that the most important internal factor is the heat resistance of the organic thin film.

That is, looking at the two-layer structure, there are three interfaces: the interface between the anode and the hole transport layer, the interface between the hole transport layer and the light emitting layer, and the interface between the light emitting layer and the cathode. The thin film shape (uniformity) of the organic layer is extremely important because it has a great influence on the contact surface at these interfaces, and is a major cause of defects in the thin film. If the organic thin film is inferior in heat resistance, the uniformity of the thin film shape will be significantly impaired, resulting in severe deterioration of the device. It can be said that this is the biggest problem in practical use of the organic EL element.

In the organic EL device, the organic layer has an amorphous property to ensure its uniformity, but generally, an organic thin film made of a low molecular weight material by a vacuum deposition method is crystallized with time and heat. Or, they tend to agglomerate, often resulting in loss of uniformity as a thin film.
The material property that greatly affects the heat resistance of the organic thin film is considered to be the glass transition point (hereinafter abbreviated as Tg). As an organic material used for the hole transport layer, TPD (4,4'-bis [N-
Phenyl-N- (3-methylphenyl) amino] diphenyl) has been widely used. However, although TPD shows a considerable hole transporting ability, Tg is as low as 63 ° C., which is considered to be because of this, but the heat resistance of the element using it was insufficient.

Many research results have been reported for the purpose of improving this point (for example, JP-A-6-1972,
No. 6-312979, No. 6-312982, U.S. Pat. No. 5,061,569, Applied Physics.
Letter (Appl. Phys. Lett.), Vol. 65, p. 807, 1994), no organic material has yet been found that can be a decisive hit satisfying heat resistance and hole transport ability.

[0007]

The problem to be solved by the present invention is that the organic EL device is rapidly deteriorated due to insufficient heat resistance of the hole transport material, that is, the present invention is high. It is an object of the present invention to provide a compound having Tg (preferably 125 ° C. or higher, more preferably 130 ° C. or higher) suitable for a hole transport material in which the uniformity of a thin film is less likely to be damaged by heat.

[0008]

As a result of intensive studies, the present inventor has found that a certain triamine compound achieves the above object and is effective in solving the problem. The present invention has been completed based on that finding.

That is, the present invention provides (1) 1,3,5-tris (4) represented by the general formula [I].
-Disubstituted aminophenyl) benzene compound,

[0010]

Embedded image

(In the formula, R ¹ represents a substituted or unsubstituted phenyl group or a substituted or unsubstituted naphthyl group. R ² represents a substituted or unsubstituted naphthyl group.)

(2) 1, 3, 5 represented by the general formula [II]
-Tris (4-disubstituted aminophenyl) benzene compound,

[0013]

Embedded image

(R ³ represents a 1- or 2-naphthyl group.)

(3) 1,3 represented by the general formula [III]
5-tris (4-disubstituted aminophenyl) benzene compound,

[0016]

[Chemical 6]

(R ⁴ and R ⁵ are each 1- or 2
-Represents a naphthyl group. ).

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The substituents R ¹ and R ² of the compound represented by the general formula [I] of the present invention will be described in detail below. R ¹ represents a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group, and R ² represents a substituted or unsubstituted naphthyl group. The substituted or unsubstituted naphthyl group is specifically a substituted or unsubstituted 1- or 2-naphthyl group. Examples of the substituent of the phenyl group and the naphthyl group include an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a disubstituted amino group, a halogen atom, and a silyl group. Specifically, for example, an alkyl group such as methyl, ethyl, butyl, isopropyl, t-butyl or trifluoromethyl, an aryl group such as phenyl or naphthyl, an alkoxy group such as methoxy, ethoxy or isopropoxy, such as a phenoxy or naphthoxy aryloxy group. , For example, dimethylamino, diethylamino, N-methyl-N-
Phenylamino, diphenylamino, dinaphthylamino, N-naphthyl-N-phenylamino, 1-pyrrolyl, 9-carbazolyl, 10-phenoxazyl, 10-
It is a disubstituted amino group of phenothiazyl, 1-morphonino, 1-piperidino or 1-pyrrolidinyl, for example a halogen atom of fluorine, chlorine or bromine, or a silyl group of for example trimethylsilyl, t-butyl-dimethylsilyl or triphenylsilyl. Preferred substituents are alkyl groups, allyloxy groups or disubstituted amino groups, and particularly preferred are alkyl groups or disubstituted amino groups. The number of substituents that may be present is not particularly limited, but in the case of a naphthyl group, it is 1 to 12, and preferably 3
To 6 and, in the case of a phenyl group, preferably 3 to 6.

Preferred R ¹ is an unsubstituted phenyl group or an unsubstituted 1- or 2-naphthyl group. Preferred R ² is an unsubstituted 1- or 2-naphthyl group.

The particularly preferable structure represented by the general formula [I] can be represented by the following general formula [II] and general formula [III].

[0021]

Embedded image

(R ³ represents a 1- or 2-naphthyl group.)

[0023]

Embedded image

(R ⁴ and R ⁵ are each 1- or 2
-Represents a naphthyl group. )

Specific examples of the compounds represented by the general formulas [I], [II] and [III] of the present invention are shown in Tables 1 to 3, but the present invention is not limited thereto.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

A method for synthesizing the compound of the present invention will be described below. A typical synthetic route is shown in (Scheme 1).
This method is a synthetic method based on the Ullmann type reaction using a metal copper catalyst and a base (see US Pat. No. 4,764,625).

[0030]

Embedded image

1,3 which are the starting materials in this synthetic method
5-Tris (4-iodophenyl) benzene is a known compound and can be synthesized by iodination of triphenylbenzene (JP-A-6-305248).

As the base, potassium hydroxide, sodium hydroxide or potassium carbonate is mainly used, and as the reaction solvent, a high boiling hydrocarbon solvent such as decalin is often used. After completion of the reaction, the obtained reaction mixture is cooled to room temperature, extracted with a suitable solvent, and purified by silica gel chromatography and recrystallization, and if necessary, sublimation.

[0033]

The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

Example 1 (Synthesis of Exemplified Compound T-1) 2.5 g (3.65 mmol) of 1,3,5-tris (4-iodophenyl) benzene and 6.0 g of N-phenyl-1-naphthylamine. (27.4 mmol), potassium hydroxide 2.85 g (50.8 mmol) and copper powder 2.
55 g (40.1 mmol) was placed in a flask together with 10 ml of decalin, and reacted under a nitrogen atmosphere at about 200 ° C (external temperature) for about 30 hours. After the reaction is completed, the reaction mixture is mixed with about 50
After cooling to ℃, chloroform and water were added and stirred. After removing unnecessary substances by Celite filtration, the chloroform layer was separated, washed with water and saturated saline, and then filtered and concentrated. Methanol was added to the obtained residue, and the mixture was heated to room temperature and then filtered to remove excess N-phenyl-1-naphthylamine used as much as possible. The obtained solid was separated and purified by silica gel column chromatography, and the obtained crude crystals of Exemplified compound (T-1) were re-crystallized with a chloroform-methanol solvent and then with a tetrahydrofuran (THF) -methanol solvent. Crystallize, 50
Almost T by drying with a vacuum pump at ~ 60 ° C
1.5 g of pure HF-free exemplary compound (T-1)
(43%) could be obtained.

Mass spectrum (FD); M ⁺ = 849 Nuclear magnetic resonance spectrum (300 MHz, CDCl 3) δ 6.96 (3H, t, J = 7.5), 7.05 to 7.
55 (36H, m), 7.61 (3H, s), 7.78
(3H, d, J = 8.0), 7.89 (3H, d, J =
8.0), 7.95 (3H, d, J = 8.0)

<Example 2> (Exemplified compounds T-2 to T-5)
Synthesis of N-phenyl-1-naphthylamine in the reaction of Example 1 in equimolar amounts of N-phenyl-2-naphthylamine, N- (1-naphthyl) -1-naphthylamine, N-
(1-naphthyl) -2-naphthylamine or N- (2
-Naphthyl) -2-naphthylamine except that the corresponding exemplary compound T-2
~ T-5 to 45%, 35%, 36% and 33, respectively.
It could be synthesized with a yield of%.

Reference Example (DSC Measurement of Exemplified Compound T-1) Differential scanning calorimetry of T-1 synthesized in Example 1 (DS
C) was performed (DSC measuring device; RDC-220 manufactured by Seiko Instruments Inc.). First, the DSC measurement result (25 to 350 ° C.) in a crystalline state is shown in FIG. When this heated sample was cooled to 0 ° C. and the temperature of the sample in the glass state was raised, it showed a glass transition at 142 ° C. (Tg) and crystallized at 255 ° C. and melted at 286 ° C. ( (Fig. 2).

The above results are shown in Table 4 together with the measurement results of existing hole transport materials, TPD and α-NPD as comparative compounds. It can be seen that T-1 which is the compound of the present invention has a higher glass transition point (Tg) than any of the comparative examples, and the glass (amorphous) state is more stable. This means forming a stable thin film state in the organic EL material produced by the vacuum deposition method or the like.

[0039]

[Table 4]

[0040]

INDUSTRIAL APPLICABILITY The novel 1,3,5-tris (disubstituted aminophenyl) benzene compound according to the present invention forms a stable amorphous thin film at room temperature by a means such as vacuum deposition, and has a large area by itself. It is possible to make it thin. Moreover, the compound according to the present invention has a high glass transition point, and the amorphous film thereof is excellent in heat resistance and stable. By making such a compound into a thin film and using it as a material for a hole transport layer of an organic EL element, it becomes possible to design an organic EL element having a long life which can endure light emission for a longer time than conventional.

[Brief description of drawings]

FIG. 1 shows a DSC thermogram of Exemplified Compound T-1 in a crystalline state.

FIG. 2 shows a DSC thermogram of an exemplified compound in a glass (amorphous) state.

Claims (3)

[Claims] 1. A 1,3,5-tris (4-disubstituted aminophenyl) benzene compound represented by the general formula [I]. Embedded image (In the formula, R ¹ represents a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group. R ² represents a substituted or unsubstituted naphthyl group.) 2. A 1,3,5-tris (4-disubstituted aminophenyl) benzene compound represented by the general formula [II]. Embedded image (R ³ represents a 1- or 2-naphthyl group.) 3. A compound represented by the general formula [III]: 1,3,5-
Tris (4-disubstituted aminophenyl) benzene compound. Embedded image (R ⁴ and R ⁵ each represent a 1- or 2-naphthyl group.)