JPH0749578A - Electron transferring material made of new diphenoquinone derivative - Google Patents

Abstract

PURPOSE:To provide a new org. electron transferring material useful as an electron transferring material required to form the cell of a photoelectric converter (such as an electrophotographic photoreceptor), an electric field light emitter, etc. CONSTITUTION:A 3,5-dialkyloxy (or dihalogeno)-3',5'-dialkyl-4,4'-diphenoquinone compd. represented by the formula is used as a novel org. electron transferring material. In the formula, R<1> is alkyloxy or halogen and R<2> is alkyl. A positive charge type electrophotographic system fit for environmental protection can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electron transporting material comprising a novel diphenoquinone derivative, and more particularly, it is useful in photoelectric conversion elements (for example, photocells and electrophotographic photoreceptors) and organic thin film electroluminescent elements. , An organic electron transport material comprising a novel diphenoquinone derivative.

[0002]

2. Description of the Related Art As organic charge transporting materials, aromatic amine compounds such as triphenylamine derivatives, conjugated double bond polymer compounds such as polyacetylene, polythiophene, and polyaniline have been well known in the past. The use as a charge transport material in a photoelectric conversion element such as a cell or an electrophotographic photoreceptor or an organic thin film electroluminescent element, or as a conductive polymer material has been studied, but most of them are so-called p-type semiconductors. That is, the hole-transporting charge transport material is a type in which holes (positive holes) move as charge carriers.

On the other hand, there are not many examples of electron transfer type organic charge transporting materials (organic n-type semiconductors), and only a few 2,4.
7-trinitrofluorenone, 9-dicyanomethylenefluorene-4-carboxylate compound, 4-dicyanomethylene-2,6-diphenyl-4H-thiopyran-
1,1-dioxide and its derivatives, 2- (4-biphenylyl) -5- (4-tert-butylphenyl)
-1,3,4-oxadiazole and its derivatives, or 3,5,3 ', 5'-tetraalkyl-4,4'
-Diphenoquinones and the like have only been announced as organic electron transport materials.

Of these, 3,5,3 ', 5'-tetraalkyl-4,4'-diphenoquinones have recently been attracting attention as electron-transporting materials with high mobility found in Japan. (Yasuhiro Yamaguchi, et al .: Journal of the Chemical Society of Canada, vol. 69, p. 759, published 1991). As a specific example in this document, 3,5-dimethyl-3 ′, 5′-di-
Tertiary butyl-4,4'-diphenoquinone is described.

Electron transport materials are useful in electrophotography as charge transport materials where the charge carriers are electrons. That is, a thin layer containing a colored material such as a phthalocyanine as an active ingredient and generating an electric charge by light absorption is provided on a conductive substrate such as a metal, and a layer composed of an organic electron transport material (usually a high layer is formed on the thin layer). When a layered electrophotographic photosensitive material (provided with a molecular binder) is positively charged on the surface and then imagewise exposed, electrons of the electron-hole pairs generated in the colored material layer move in the electron transport layer. Then, it reaches the surface, neutralizes the positive charge imagewise, and forms a latent image due to static electricity. Alternatively, a photosensitive material such as a phthalocyanine compound is mixed with a colored material that generates charges by light absorption such as phthalocyanines, a hole transport material, and an electron transport material (usually with a polymeric binder) to form a photosensitive layer. In the single-layer type electrophotographic photoreceptor,
When image exposure is performed after positively or negatively charging the surface, the electrons of the electron-hole pairs generated in the charge generation material travel through the electron transport material and reach the surface or substrate (holes are positive). It travels through the hole transport material to reach the substrate or surface) and neutralizes the positive or negative charge image-wise, forming a latent image by static electricity. If a colored powder called toner is applied to this, a visible image by electrophotography can be obtained (development).

That is, if there is a useful electron-transporting material, a positive charging type or positive / negative charging type electrophotographic photoconductor can be obtained. Since the negative charging type electrophotography has been the mainstream, the corona at the time of negative charging is obtained. Generation of ozone due to discharge is remarkable,
As a result, there have been problems of equipment corrosion and environmental pollution. However, in the case of positive charging, the generation of ozone is extremely small, so it becomes a method particularly suitable for environmental protection, and positive charging type electrophotography must become the mainstream in the future, and in that sense electron transport materials are urgent. It is a necessary material.

In addition to electrophotography, electron transport materials are important materials in organic electroluminescent devices. That is, as described in Shogo Saito, et al .: Chemistry and Industry (Chemical Society of Japan), Vol. 42, p. 2023, published in 1989, fluorescent molecules emit fluorescence by energy generated by recombination of holes and electrons. An electron transport material is necessary because of the cell structure of the thin film electroluminescent device.

[0008]

The object of the present invention is to provide a high-performance material by synthesizing a novel compound of an organic electron transporting material (n-type organic semiconductor), which has not been known many times, as much as possible. is there. In particular, unsynthesized derivatives of 3,5,3 ', 5'-tetra-substituted-4,4'-diphenoquinones found and attracting attention in Japan are successively synthesized to obtain higher performance materials. Is to provide.

[0009]

The object of the present invention is to provide a novel 3,5-dialkyloxy (or dihalogeno) -3 ', 5'-dialkyl-group represented by the above formula (1).
Progress was made in the solution by employing 4,4'-diphenoquinones as organic electron transport materials. Formula 1
In the above, R ¹ represents an alkyloxy group or a halogen group, and R ² represents an alkyl group.

In the present invention, the diphenoquinone skeleton 3,5 is used.
By substituting an alkyloxy group or a halogen group at the − position, localization of conjugated double bond system π-electrons of diphenoquinone was promoted and asymmetry was enhanced. It is considered that this is the reason why the electron transport material has higher performance.

In the present invention, 3,5-dialkyloxy (or dihalogeno) -3 ', 5'-dialkyl-4,4'-diphenoquinones newly provided as an electron transport material are described in the literature (FM Menger, Other: Journal
Of Organic Chemistry, 1985 , 50,
3927-3928), that is, a method of oxidizing 2,6-disubstituted phenol with potassium permanganate in chloroform.

In the present invention, however, two different phenol derivatives, 2,6-dialkyloxy (or dihalogeno) phenol and 2,6-dialkylphenol, are used in order to synthesize highly soluble diphenoquinones, that is, asymmetric diphenoquinones. Charged as raw material,
The target asymmetric diphenoquinones must be isolated from the three types of diphenoquinone derivatives produced after the completion of the oxidation reaction. Column chromatography is the most robust isolation method, but it is difficult to obtain a large amount of the desired product. However, in the present invention, paying attention to the difference in solubility of the three kinds of diphenoquinone derivatives produced, it is possible to separate as a single product crystal colored in red by carefully selecting the solvent that selectively dissolves only the target compound. did it.

These crystals are particularly useful materials as an electron transport material in an electrophotographic photoreceptor, and if a layer is formed together with a polymer binder such as polyester or polycarbonate, higher performance is achieved. It has been found to function as an electron transport material.

Representative examples of 3,5-dialkyloxy (or dihalogeno) -3 ', 5'-dialkyl-4,4'-diphenoquinones newly provided as organic electron transporting materials in the present invention are shown below. However, the present invention is not limited to these.

[0015]

[Chemical 2]

[0016]

[Chemical 3]

[0017]

[Chemical 4]

[0018]

[Chemical 5]

Since the novel organic electron transporting material according to the present invention is particularly useful in the electrophotographic photoreceptor, especially in the above-mentioned single-layer type electrophotographic photoreceptor, the following description will be focused on it.

[0020]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The parts and% shown below are based on weight unless otherwise specified.

Example 1 (Synthesis Example 1) 15.4 parts of 2,6-dimethoxyphenol and 17.8 parts of 2,6-diisopropylphenol were mixed with 50 parts of chloroform.
It was dissolved in 0 volume part, 126.4 parts of potassium permanganate was added, and the mixture was heated to reflux for 6 hours with vigorous stirring.
The insoluble matter was removed by filtration while hot, and the filtrate was concentrated under reduced pressure to dryness. 1,500 parts by volume of methanol was added to the solid residue, and the mixture was vigorously stirred at room temperature for one day and night, insoluble matter was removed by filtration, and the filtrate was concentrated under reduced pressure to dryness. The thus obtained crude crystal mainly composed of 3,5-dimethoxy-3 ', 5'-diisopropyl-4,4'-diphenoquinone was recrystallized from ethanol and further recrystallized from a 1: 1 mixed solvent of cyclohexane and toluene. As a result of crystallization and purification, 5.2 parts could be obtained as a reddish brown scaly crystal of a pure diphenoquinone derivative of interest (single spot by thin layer chromatography). Melting point
195-196 ° C (decomposition). Mass spectrometry (FD method) m /
z = 328 (calc _{C 20 H 24 O 4 = 328.41} ).
There was obtained 3,5-dimethoxy-3 ', 5'-diisopropyl-4,4'-diphenoquinone (compound of formula 2).

Example 2 (Synthesis Example 2) 15.4 parts of 2,6-dimethoxyphenol and 20.6 parts of 2,6-di-tert-butylphenol were dissolved in 500 parts by volume of chloroform and potassium permanganate 12 was added.
6.4 parts was added, and the mixture was heated to reflux for 6 hours with vigorous stirring. The insoluble matter was removed by filtration while hot, and the filtrate was concentrated under reduced pressure to dryness. 1,500 parts by volume of methanol was added to the solid residue, and the mixture was vigorously stirred at room temperature for one day and night, insoluble matter was removed by filtration, and the filtrate was concentrated under reduced pressure to dryness. 3,5-dimethoxy-3 ', 5' thus obtained
-Di-tert-butyl-4,4'-diphenoquinone-based crude crystals were recrystallized from ethanol.
When the purification was repeated, 3.1 parts could be obtained as dark red prismatic crystals that sparkle the pure product of the diphenoquinone derivative. Melting point 225-226 [deg.] C (decomposition). Mass spectrometry (FD method) m / z = 356 (calculated value C ₂₂ H ₂₈ O
₄ = 356.47).

FT-infrared spectrum (KBr tablet method)
Is shown in FIG. In Figure 1, 2,960cm ^-1 characteristic absorption band alkanes present several back and forth, the 1,643cm ^-1 C = O stretching vibration of the ex-tended quinones, 1,11
At 0 cm ⁻¹ , characteristic absorption bands of the C—O—C antisymmetric stretching vibration are observed, respectively. Therefore, here, 3,5-dimethoxy-3 ', 5'-di-tert-butyl-4,4'
-It can be seen that diphenoquinone (compound of formula 3) was obtained.

Example 3 (Synthesis Example 3) 5.0 parts of 2,6-difluorophenol and 2,6-di-
7.9 parts of tertiary butylphenol is dissolved in 100 parts by volume of chloroform, and potassium permanganate 48.5 is added.
Parts were added, and the mixture was heated to reflux with vigorous stirring for 7 hours. The insoluble matter was removed by filtration while hot, and the filtrate was concentrated under reduced pressure to dryness. 300 volume parts of methanol was added to the solid residue, and the mixture was vigorously stirred at room temperature for one day and night, insoluble matter was removed by filtration, and the filtrate was concentrated under reduced pressure to dryness. The thus obtained crude crystals mainly composed of 3,5-difluoro-3 ′, 5′-di-tert-butyl-4,4′-diphenoquinone were recrystallized and purified from ethanol and then methanol, It was possible to obtain 1.1 parts of a pure product of the diphenoquinone derivative as dark red crystals that sparkle. Melting point 109-111 [deg.] C (decomposition). Mass spectrometry (FD method) m / z = 332 (calculated value C ₂₀ H ₂₂ F
₂ O ₂ = 332.39).

FT-infrared spectrum (KBr tablet method)
Is shown in FIG. In FIG. 2, 2,960cm ^-1 characteristic absorption band alkanes present several back and forth, the 1,645cm ^-1 C = O stretching vibration of the ex-tended quinone, 1, 22
Characteristic absorption bands of CF stretching vibration are observed at 7 cm ⁻¹ . Therefore, here, 3,5-difluoro-3
It can be seen that ', 5'-di-tert-butyl-4,4'-diphenoquinone (compound of formula 5) was obtained.

Example 4 (Performance Test on Electrophotographic Photoreceptor) 1 part of α-type oxytitanium phthalocyanine as a charge generating agent, 70 parts of p-dibenzylaminobenzaldehyde diphenylhydrazone as a hole transporting material, and 70% as an electron transporting material. 30 parts of diphenoquinone derivative, polyester as polymer binder (Vylon-200 manufactured by Toyobo)
100 parts and dichloromethane as solvent 1,500
The parts were mixed, placed in a closed container together with glass beads, shaken and dispersed for 2 hours using a paint conditioner device, and then the glass beads were removed by sieving to obtain a coating liquid for a single-layer type electrophotographic photoreceptor. As a control (blank), a coating solution containing 100 parts of p-dibenzylaminobenzaldehyde = diphenylhydrazone as a hole transport material and no electron transport material was prepared by the same method.

These coating liquids were applied onto an aluminum plate using an applicator so that the thickness of the coating layer after drying was 20 ± 3 μm.
The coating solution was applied so as to have a thickness of m, dried in an air dryer at 80 ° C. for 1 hour, then placed in a black bag and left at room temperature overnight or more.

The electrostatic recording test apparatus (SP-42 manufactured by Kawaguchi Electric Co., Ltd.) was used for the single-layer type electrophotographic photosensitive member thus prepared.
The electrophotographic characteristics were evaluated according to 8). Measurement conditions: Applied voltage + 6.0kV, Static N
o. 3 (Turntable rotation speed mode) Light source Tungsten lamp White light, sample surface illuminance 10
looks

The measurement results are shown in Table 1, and V _{0 in} Table 1
Indicates an initial surface potential when a voltage is applied to positively charge the photoconductor and exposure is started, V ₁ indicates a surface potential after 1 second from the start of exposure, and the difference V ₀ − V ₁
Represents photosensitivity, and the larger the number, the higher the sensitivity.

[0030]

[Table 1]

From Table 1, sample No. 1 using only the hole transport material as the charge transport material. Even with 0 (control), it has a slight light attenuation 4 (light sensitivity), probably because it has some electron transporting ability.
Samples with addition of diphenoquinone derivative as electron transport material
NO. In Nos. 1 to 4, the light attenuation (light sensitivity) was remarkably increased. 2-4 optical attenuation (optical sensitivity)
The increase of Comparative Example NO. It turns out that it greatly exceeds 1.
That is, it can be said that the novel diphenoquinone derivative proposed by the present invention has an electron transporting capacity higher than that of known compounds.

[0032]

As is apparent from the examples, the novel diphenoquinone derivative proposed by the present invention has a higher electron transporting capacity than known compounds, and thus is a better electron transporting material, for example, charge transporting material for electrophotographic photoreceptors. When used as a material, it is possible to contribute to the realization of a positively charged electrophotographic system suitable for environmental protection.

[Brief description of drawings]

FIG. 1 is a novel diphenoquinone derivative, 3,5-dimethoxy-3, which is an electron transport material provided by the present invention.
FT-infrared spectrum of ', 5'-di-tert-butyl-4,4'-diphenoquinone (compound of formula 3) (KBr tablet method).

FIG. 2 shows one of the novel diphenoquinone derivatives, 3,5-difluoro-3, which is an electron transport material provided by the present invention.
FT-infrared spectrum of ', 5'-di-tert-butyl-4,4'-diphenoquinone (compound of formula 5) (KBr tablet method).

Claims (1)

[Claims] 1. An electron transport material comprising a diphenoquinone derivative represented by the following formula 1. [Chemical 1] (In Formula 1, R ¹ represents an alkyloxy group or a halogen group, and R ² represents an alkyl group.)