Azo compounds having a triarylamine and a method for producing the same

Abstract

To provide an azo compound having triaryl amine that is useful as an organic photoconductor in a positive-charged monolayer photoreceptor, has high sensitivity, and also has high solubility in organic solvent.SOLUTION: The foregoing problem is solved by an azo compound having, for example, the following structure.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an azo compound having a novel triarylamine useful as an organic photoconductor and a method for producing the same.

Background Art

[0002] Most of the practical electrophotographic photoreceptors are functional separation type electrophotographic photoreceptors in which a charge generation layer and a charge transport layer are laminated on a conductive substrate, and a hole transport material is used as the charge transport substance contained in the charge transport layer. These are exclusively used in the negatively charged electrophotographic process.

[0003] In addition, a highly reliable charging method in the electrophotographic process is by corona discharge, and most copiers and printers adopt this method. However, as is well known, negative corona discharge is more unstable than positive corona discharge. For this reason, a charging method using a scorotron is adopted, which is one of the factors contributing to cost increase. Negative corona discharge is accompanied by a larger amount of generation of ozone, which is a substance that causes chemical damage. Therefore, by using it for a long time, oxidation degradation of the binder resin and charge transfer material due to ozone generated during charging, and ionic compounds generated during charging, for example, nitrogen oxide ions, sulfur oxide ions, ammonium ions, etc. accumulate on the surface of the photoreceptor, resulting in image quality deterioration, which becomes a problem. For this reason, in order to prevent external discharge of ozone, ozone filters are often used in negatively charged copiers and printers, which is also a factor contributing to cost increase of the apparatus. In addition, a large amount of generated ozone also causes environmental pollution problems.

[0004] In order to solve these problems, the development of a positive charge type single-layer electrophotographic photoreceptor is in progress. In the case of the positive charging method, the generation amount of ozone, nitrogen oxide ions, etc. can be suppressed. Furthermore, in the use of the two-component developer widely used at present, when the electrophotographic photoreceptor is positively charged, less environmental variation and a more stable image can be obtained. From this aspect as well, a positive charge type electrophotographic photoreceptor is desirable. However, in order to achieve high-speed printing or miniaturization of the apparatus due to the reduction in the diameter of the photoreceptor, the sensitivity and durability are still not sufficient. Therefore, there is still a long-awaited need for a charge transport material that has excellent charge transport ability and durability in a positively charged single-layer electrophotographic photoreceptor.

[0005] Patent Document 1 proposes using a diphenoquinone derivative as an electron transport material for a single-layer electrophotographic photoreceptor. Further, Non-Patent Document 1 describes a semiconducting material composed of a naphthalene tetracarboxylic diimide derivative, and Patent Documents 2 and 3 propose naphthalene tetracarboxylic diimide derivatives. Additionally, Patent Document 4 discloses an azo compound useful as an organic photoconductor.

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide an azo compound having a triarylamine that is useful as an organic photoconductor in an electrophotographic photoreceptor for high-speed copiers and laser printers, particularly a positively charged single-layer photoreceptor, and that has high sensitivity and excellent solubility in organic solvents.

Means for Solving the Problems

[0007] The above problems are solved by the following configuration 1). 1) An azo compound having a triarylamine represented by the following general formula (I).

[0008]

Chemical Formula

[0009] [In general formula (I), A is a residue of an azo pigment represented by the following general formula (II),

[0010]

Chemical Formula

[0011] (In the general formula (II), B represents the main skeleton of the azo pigment, represented by the following general formula (III) or the following general formula (IV), Cp 1 , Cp 2 represents a coupler moiety residue having an -OH group and a -CONH- group, Cp 1 is represented by the following general formula (V), Cp 2 is represented by the following general formula (VI), Ar 1 , Ar 2 and Ar 3 are each independently aromatic represents a monovalent or divalent group of a hydrocarbon ring, X represents an ethylene group or a vinylene group, l represents an integer of 1 to 3, and m represents an integer of 0 to 2. E is the Cp of the coupler moiety residue 1 , Cp 2 It bonds to replace the hydrogen atoms of the -OH and -CONH- groups in the carboxylate, and E is a carboester group: -C(=O)-OR 1 (R in the formula 1 represents a substituted or unsubstituted alkyl group having 4 to 10 carbon atoms.) and n represents an integer of 1 to 6.] Note that general formulas (III) to (VI) are shown in the column of embodiments. Effect of the Invention

[0012] According to the present invention, it is possible to provide an azo compound having a triarylamine which is useful as an organic photoconductor in electrophotographic photoreceptors for high-speed copying machines and laser printers, particularly in positively charged single-layer type photoreceptors, and which has high sensitivity and excellent solubility in organic solvents. [Brief description of the drawings]

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be further described.

[0015] The diphenoquinone derivative of Patent Document 1 has a slightly low charge mobility, so the photosensitive body sensitivity characteristics are not sufficient when considering the high speed and miniaturization of copiers and printers. In addition, the diphenoquinone derivative of Patent Document 1 has low compatibility with the resin binder for forming the photosensitive body, and sufficient characteristics cannot be obtained. The naphthalene tetracarboxylic diimide derivatives of Patent Documents 2 and 3 have a complicated structure and problems in production. In addition, the naphthalene tetracarboxylic diimide derivative of Non-Patent Document 1 has a problem that its electron transporting property is low and it does not have practical characteristics. Furthermore, although the azo compound of Patent Document 4 has excellent electron transporting property, it has almost no hole transporting property and is not yet sufficient in terms of sensitivity and durability. The present invention solves the problems of these conventional technologies and provides a highly sensitive azo compound having a triarylamine that is useful as an organic photoconductor in electrophotographic photoreceptors for high-speed copiers and laser printers, particularly in positive charge single-layer photoreceptors, and has excellent solubility in organic solvents, and a method for producing the same.

[0016] The azo compound having a triarylamine of the present invention is as shown in the above Configuration 1), but the following Configurations 2) to 5) are also included in the embodiments of the present invention.

[0017] 2) The azo compound having a triarylamine according to 1), wherein B in the general formula (II) is represented by the following general formula (III).

[0018]

Chemical formula

[0019] (In general formula (III), R 11 , R 12 each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a carboxyl group or an ester thereof.)

[0020] 3) An azo compound having the triarylamine according to 1), wherein B in the general formula (II) is represented by the following general formula (IV).

[0021] [Chemical formula]

[0022] (In general formula (IV), R 13 , R 14 , and R 15 each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a carboxyl group or an ester thereof.)

[0023] 4) An azo compound having the triarylamine according to 1), wherein Cp 1 in the general formula (II) is represented by the following general formula (V), and Cp 2 is represented by the following general formula (VI).

[0024] [Chemical formula]

[0025] [Chemical formula]

[0026] (In general formulas (V) and (VI), Z represents a condensed ring of a hydrocarbon ring or a heterocyclic ring, and Y represents a monovalent or divalent group of a hydrocarbon ring. The linking group X in the general formula (II) is linked to Y.)

[0027] 5) A method for producing an azo compound having a triarylamine represented by the general formula (I), characterized in that an azo pigment represented by the general formula (II) is reacted with a pyrophosphoric acid diester represented by the following general formula (VII) in the presence of a base.

[0028]

Chemical formula

[0029] R 1 represents a substituted or unsubstituted alkyl group having 4 to 10 carbon atoms such as a butyl group, a pentyl group, or a hexyl group.

[0030] Further, examples of the hydrocarbon rings of Ar 1 , Ar 2 , Ar 3 , Z, and Y include a benzene ring, a naphthalene ring, an anthracene ring, a pyrene ring, etc. Examples of the heterocyclic rings include an indole ring, a carbazole ring, a benzoxazole ring, a dibenzofuran ring, etc. Examples of the substituents of these hydrocarbon rings and heterocyclic rings include alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group; alkoxy groups such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group; halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; dialkylamino groups such as a dimethylamino group and a diethylamino group; halomethyl groups such as a trifluoromethyl group; a nitro group, a cyano group, a carboxy group or its ester, a hydroxyl group, -SO 3 sulfonate groups such as Na, etc.

[0031] Further, examples of the halogen atoms of R 11 to R 15 include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc., examples of the alkyl groups include a methyl group, an ethyl group, a propyl group, a butyl group, etc., and examples of the alkoxy groups include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, etc.

[0032] Examples of compounds are shown below. <Examples of compounds in which the main skeleton B of the azo pigment is represented by the general formula (III)>

[0033] (III)-1

[0034] [Chemical formula]

[0035] (III)-2

[0036] [Chemical formula]

[0037] (III)-3

[0038] [Chemical formula]

[0039] <Examples of compounds in which the main skeleton B of the azo pigment is represented by the general formula (IV)>

[0040] (IV)-1

[0041] [Chemical formula]

[0042] (IV)-2

[0043] [Chemical formula]

[0044] (IV)-3

[0045] [Chemical formula]

[0046] (IV)-4

[0047] [Chemical formula]

[0048] The azo compound having the triarylamine represented by the general formula (I) of the present invention can be produced by reacting the azo pigment represented by the general formula (II) with a pyrophosphoric acid diester represented by the following general formula (VII) in the presence of a base.

[0049] [Chemical formula]

[0050] (In the formula, R 1 represents a substituted or unsubstituted alkyl group having 4 to 10 carbon atoms.)

[0051] Specifically, in an aprotic organic solvent, in the presence of a base as a catalyst, at a temperature of 0 to 150 ° C, preferably 10 to 100 ° C, for 30 minutes to 20 hours, the azo pigment represented by the general formula (II) and the following general formula (VII) A method of reacting a pyrophosphoric acid diester represented by the formula in an appropriate molar ratio can be mentioned. The molar ratio depends on the number of Es introduced. Preferably, it is suitable to use a slightly excessive amount of the pyrophosphoric acid diester. In addition, for example, the methods described in European Patent No. 0648770, European Patent No. 0648817, Japanese Patent Publication No. 2001-513119, etc. can be referred to. The azo pigment represented by the general formula (II) is disclosed in Japanese Patent No. 3573829.

[0052] Suitable aprotic organic solvents include, for example, ether solvents such as tetrahydrofuran or dioxane, glycol ether solvents such as ethylene glycol methyl ether or ethylene glycol ethyl ether, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, toluene, xylene, nitrobenzene, pyridine, picoline, or quinoline. Preferred solvents are pyridine, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0053] Suitable bases as catalysts include, for example, hydroxides, carbonates of alkali metals such as sodium or potassium, or their amides (e.g., sodium amide, potassium amides), alkali metal hydrides (e.g., lithium hydride), etc. Also, organic aliphatic and aromatic bases can be used, for example, heterocyclic N-bases such as diazabicyclooctene, diazabicycloundecene, 4-dimethylaminopyridine, dimethylpyridine, pyridine, or triethylamine. Among them, 4-dimethylaminopyridine, dimethylpyridine, and pyridine are preferred.

[0054] The pyrophosphoric acid diester represented by the general formula (VII) can be produced by known methods and is also commercially available. R 1 represents the above, but a branched alkyl group is preferred in terms of a surprisingly improved solubility.

[0055] The compound obtained after completion of the reaction in the above production method can be isolated by ordinary methods. In particular, the azo compound having the triarylamine represented by the general formula (I) of the present invention has excellent solubility in organic solvents, so purification by recrystallization, column chromatography, etc. is easy for further purity improvement.

[0056] The azo compound having the triarylamine represented by the general formula (I) of the present invention can be utilized, for example, in the following manner as an organic photoconductor, particularly as a charge generating material, in various electrophotographic photoreceptors. (1) A single-layer photoreceptor is formed by providing a photoconductive layer mainly composed of the azo compound, a binder resin, and, if necessary, a sensitizer on a conductive support. (2) A charge transport material is further added to the system of (1) to form a single-layer photoreceptor in the same manner. (3) A charge generation layer mainly composed of the azo compound is provided on a conductive support, and further a charge transport layer mainly composed of a charge transport material and a binder resin is provided thereon to form a laminated photoreceptor. (4) A photoreceptor having a layer structure in which the charge generation layer and the charge transport layer of (3) are laminated in reverse is formed. In addition, since the azo compound having the triarylamine of the present invention has excellent solubility in organic solvents, it can also be used in other color materials, for example, materials for recording media, color filters, and the like.

Examples

[0057] The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples.

[0058] <Example 1> · Production of Compound (III-1) 1.09 g (1.00 mmol) of the precursor (E = H) of Compound (III-1) was added to a solution of 2.18 g (10.0 mmol) of di-tert-butyl pyromellitate and 50 ml of dehydrated pyridine. After stirring at room temperature for 30 minutes, the mixture was further heated and stirred at about 60 °C for 2 hours. It gradually became reddish, and a uniform solution was obtained. After returning to room temperature, the solvent was removed under reduced pressure, about 20 ml of methanol was added, and the precipitated solid was collected by filtration and dried under reduced pressure by heating at 60 °C for 1 day to obtain 1.48 g (yield 99.3%) of an azo compound having a triarylamine in the form of a red powder represented by the following structural formula.

[0059]

Chemical formula

[0060] Elemental analysis (as C89H82ClN7O13) (all E as C5H9O2) was as follows. The instrument used for elemental analysis in this example and the following examples was vario MICRO cube manufactured by Elementar.

[0061]

Table 1

[0062] The infrared absorption spectrum (KBr tablet method) of this product is shown in Figure 1. From the results of the above elemental analysis and the infrared absorption spectrum, it was confirmed that the compound (III-1) was synthesized.

[0063] <Example 2> · Production of compound (III-2) To a solution of 437 mg (2.00 mmol) of di-tert-butyl pyromellitate and 10 ml of dehydrated pyridine, 241 mg (0.200 mmol) of the precursor (E = H) of compound (III-2) was added, and the mixture was heated and stirred at about 60 °C for 2 hours. It gradually turned reddish, and a uniform solution was obtained. After returning to room temperature, the solvent was removed under reduced pressure, methanol was added, and the precipitated solid was collected by filtration and dried under reduced pressure by heating at 60 °C for 1 day to obtain 333 mg (yield 103.7%) of an azo compound having a triarylamine of a red powder represented by the following structural formula.

[0064]

Chemical formula

[0065] Elemental analysis (as C98H84ClN7O13) (all E as C5H9O2) was as follows.

[0066]

Table 2

[0067] The infrared absorption spectrum (KBr tablet method) of this product is shown in Figure 2. From the results of the elemental analysis and the infrared absorption spectrum, it was confirmed that compound (III-2) was synthesized.

[0068] <Example 3> · Production of compound (III-3) 0.679 g (0.500 mmol) of the precursor (E = H) of compound (III-3) was added to a solution of 1.09 g (5.00 mmol) of di-tert-butyl pyromellitate and 30 ml of dehydrated pyridine. After stirring at room temperature for 30 minutes, the mixture was heated and stirred at about 60 °C for 2 hours. It gradually became reddish, and a uniform solution was obtained. After returning to room temperature, the solvent was removed under reduced pressure, 10 ml of methanol was added, and the precipitated solid was collected by filtration and dried under reduced pressure by heating at 60 °C for 1 day to obtain 0.874 g (yield 99.4%) of an azo compound having a red powder of triarylamine represented by the following structural formula.

[0069]

Chemical formula

[0070] Elemental analysis (as C111H104N8O13) (all E as C5H9O2) was as follows.

[0071]

Table 3

[0072] The infrared absorption spectrum (KBr tablet method) of this product is shown in Figure 3. From the results of the elemental analysis and the infrared absorption spectrum, it was confirmed that compound (III-3) was synthesized.

[0073] <Example 4> · Production of compound (IV-1) To a solution of 0.327 g (1.50 mmol) of di-tert-butyl pyromellitate and 10 ml of dehydrated pyridine was added 0.173 g (0.100 mmol) of the precursor (E = H) of compound (IV-1), and the mixture was heated with stirring at about 60 °C for 2.5 hours. It gradually took on a deep purple color, and a homogeneous solution was obtained. After returning to room temperature, the solvent was removed under reduced pressure, methanol was added, and the precipitated solid was collected by filtration and dried under reduced pressure by heating at 60 °C for 1 day to obtain 0.133 g (yield 48.5%) of an azo compound having a triarylamine as a deep purple powder represented by the following structural formula.

[0074] [Chemical formula]

[0075] Elemental analysis (as C143H132N14O18) (all E as C5H9O2) was as follows.

[0076] [Table 4]

[0077] The infrared absorption spectrum (KBr tablet method) of this product is shown in Figure 4. From the results of the above elemental analysis and the above infrared absorption spectrum, it was confirmed that compound (IV-1) was synthesized.

[0078] [Example 5] ·Production of compound (IV-2) To a solution of 0.437 g (2.00 mmol) of di-tert-butyl pyromellitate and 10 ml of dehydrated pyridine was added 0.390 g (0.200 mmol) of the precursor (E = H) of compound (IV-2), and the mixture was heated with stirring at about 60 °C for 3 hours. It gradually took on a deep purple color, and a homogeneous solution was obtained. After returning to room temperature, the solvent was removed under reduced pressure, methanol was added, and the precipitated solid was collected by filtration and dried under reduced pressure by heating at 60 °C for 1 day to obtain 0.483 g (yield 94.7%) of an azo compound having a triarylamine as a deep purple powder represented by the following structural formula.

[0079] [Chemical formula]

[0080] Elemental analysis (as C159H143N15O18) (all as E: C5H9O2) was as follows.

[0081] [Table 5]

[0082] The infrared absorption spectrum (KBr tablet method) of this product is shown in Fig. 5. From the results of the above elemental analysis and the infrared absorption spectrum, it was confirmed that the compound (IV-2) was synthesized.

[0083] [Application Example] According to Example 3 described in JP-A-2007-108682, an electrophotographic photoreceptor used in this application example was produced as follows. As a charge generation material, 30 parts by mass of a metal-free phthalocyanine pigment (Dainippon Ink and Chemicals, Inc.: Fastogen Blue 8120B) and 970 parts by mass of cyclohexanone were dispersed in a ball mill apparatus for 2 hours to obtain a charge generation material dispersion. Separately, 49 parts by mass of a polycarbonate resin (Z-polycarbonate, viscosity average molecular weight: 40,000, manufactured by Teijin Chemicals Ltd.), 20 parts by mass of a charge transport material represented by the above-mentioned azo compound (III-2) having a triarylamine, 29.5 parts by mass of a charge transport material represented by the following formula (i), and 0.1 part by mass of a silicone oil (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 340 parts by mass of tetrahydrofuran. To this, 66.6 parts by mass of the above-mentioned charge generation material dispersion was added and stirred to obtain a photosensitive layer coating liquid. Using the above photosensitive layer coating liquid, dip coating was performed on an aluminum drum having a diameter of 30 mm and a length of 340 mm (previously selected ones with a circumferential runout measurement within 20 μm) to form a film, and it was dried at 120 °C for 15 minutes. The photosensitive layer was produced under the condition of a lifting speed such that the thickness was 25 μm. The electrophotographic photoreceptor thus fabricated was mounted on a Ricoh-made IPSio Color 8100 retrofitting machine (with the power pack changed by setting the writing LD wavelength to 780 nm and retrofitted for positive charging polarity), and continuous printing of 100,000 full-color images with a mixture of rectangular patches and characters having an image area ratio of 6% was performed under the following conditions. At that time, evaluations were made on the initial image, the dark potential, the bright potential, and the image quality after printing 100,000 sheets. The results are shown in Table 6. The dark potential, the bright potential, and the image quality were evaluated as follows. · Dark potential: It was defined as the surface potential of the photoreceptor when it moved to the developing unit position after primary charging. The applied voltage of the charger was adjusted so that it was +700 V initially, and then it was set to a constant applied voltage until the end of the test. · Bright potential: After charging, the surface potential of the photoreceptor was measured when it received image exposure (full-surface exposure) and moved to the developing unit position. · Image quality: The presence or absence of background staining due to charging unevenness during full-color image output was examined (〇 was defined as the case where no background staining occurred in the white part, and × was defined as the case where background staining occurred even partially in the white part).

[0084]

Chemical formula

[0085]

Table 6

[0086] As can be understood from the above description, the azo compound having a triarylamine of the present invention exhibits high sensitivity for high-speed copying machines and is extremely useful as an organic photoconductor used in electrophotographic photoreceptors.

Prior art documents

Patent documents

[0087]

Patent Document 1

Patent Document 2

[0088] [Non-Patent Document 1] Chemistry letters (2003), 32(6), 508 - 509

Claims

1. An azo compound having a triarylamine represented by the following general formula (I). 【Chemical 1】 [In the general formula (I), A is a residue of an azo pigment represented by the following general formula (II), [Chemical 2] (In the general formula (II), B represents the main skeleton of the azo pigment, which is represented by the following general formula (III) or the following general formula (IV), Cp 1 , Cp 2 represents a coupler component residue having an -OH group and a -CONH- group, Cp1 is represented by the following general formula (V), Cp2 is represented by the following general formula (VI), Ar 1 , Ar 2 and Ar 3 each independently represents a monovalent or divalent group of an aromatic hydrocarbon ring, X represents an ethylene group or a vinylene group, l represents an integer of 1 to 3, and m represents an integer of 0 to 2.) E is bonded so as to substitute for each hydrogen atom of the -OH group and -CONH- group in the Cp of the coupler component residue 1 , Cp 2 , and is bonded so as to substitute for each hydrogen atom of the -OH group and -CONH- group therein. E is a carbester group: -C(=O)-O-R １ (wherein R １ represents a substituted or unsubstituted alkyl group having 4 to 10 carbon atoms), and n represents an integer of 1 to 6). 【Chemical Formula 3】 (In general formula (III), R 11 , R 12 each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a carboxyl group or an ester thereof.) 【Chemical Formula 4】 (In general formula (IV), R 13 , R 14 , and R 15 each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a carboxyl group or an ester thereof.) 【Chemical Formula 5】 [Chemical Formula 6] (In the general formulas (V) and (VI), Z represents a condensed ring of a hydrocarbon ring or a heterocyclic ring, and Y represents a monovalent or divalent group of a hydrocarbon ring. The linking group X in the general formula (II) is linked to Y.)

2. A method for producing an azo compound for producing the azo compound according to Claim 1, characterized in that an azo pigment represented by the general formula (II) is reacted with a pyrophosphoric acid diester represented by the following general formula (VII) in the presence of a base. [Chemical Formula 7] (wherein R １ represents a substituted or unsubstituted alkyl group having 4 to 10 carbon atoms.)

Images