JPH0558032B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to disazo compounds. Prior Art Conventionally, certain disazo compounds have been used in laminated photoreceptors, which are one form of electrophotographic photoreceptor.
It is known to be effective as a charge-generating pigment used in a charge-generating layer. The laminated photoreceptor referred to herein means that a charge-generating pigment having the ability to generate charge carriers by light is applied onto a conductive support by an appropriate method such as vacuum evaporation, coating with a pigment solution, or adding a pigment to a resin solution. A charge generation layer is formed as a thin layer by coating a dispersion liquid containing fine particles dispersed therein, and the charge carriers generated in the charge generation layer can be efficiently injected onto the charge generation layer, and the charge carriers can be transferred. It is a photoreceptor on which a transport layer (usually, this charge transport layer consists of a charge transport substance and a binder resin) is formed. Disazo compounds conventionally used in this type of photoreceptor include, for example, JP-A-47-37543;
and benzidine-based disazo compounds described in JP-A No. 52-55643, etc.
Stilbene-based disazo compounds described in Japanese Patent No. 52-8832 are known. However, conventional laminated photoreceptors using disazo compounds generally have low sensitivity, and the visible wavelength range extends from approximately 450 to 700 nm.
Considering this photosensitive wavelength characteristic, the image reproducibility of red originals was poor. Therefore, when this photoreceptor is mounted, there is a disadvantage in the design of the copying machine because it is necessary to use a filter that cuts out red light. Purpose An object of the present invention is to provide a disazo compound that is effective in electrophotographic photoreceptors, particularly in the above-mentioned laminated photoreceptor, and the laminated photoreceptor using the disazo compound of the present invention is Its sensitivity is higher than that of conventional photoreceptors using disazo compounds, and its sensitivity wavelength range is only on the short wavelength side of the visible range (approximately 450 to 600 nm), so it has excellent reproduction of red original images. It is something. Structure That is, the present invention is a disazo compound represented by the general formula (). [In the formula, A is (wherein R represents an alkyl group such as methyl, ethyl, propyl, butyl, an alkoxy group, a nitro group, a halogen, a cyano group or a halomethyl group, and n is an integer of 0, 1, 2 or 3, When n is an integer of 2 or 3, R may be the same or different groups. ] Furthermore, the disazo compound represented by the formula () of the present invention is represented by the formula () The diamino compound represented by is diazotized to form the general formula () (In the formula, X represents an anionic functional group.) Then, this tetrazonium salt and the general formula () The compound represented by (hereinafter referred to as Katsupura)
It can be produced by reacting with. The tetrazonium salt compound represented by the formula is a useful intermediate for disazo compounds, and by combining it with an appropriate coupler, a wide range of disazo compounds having a thioxanthone skeleton and azo groups at the 2- and 8-positions can be synthesized. can do. This disazo compound is expected to be used as a photoconductive material for electrophotographic photoreceptors, particularly as a charge generating material. Typical examples of anionic functional groups in the tetrazonium salt compound of general formula () are CI, Br,
I, BF ₄ , PF ₆ ,

[Formula] CIO ₄ , SO ² ₄ ,

[Formula] AsF ₆ and SbF ₆ are mentioned, and BF ₄ is preferable. The disazo compound represented by the formula () of the present invention is useful as a charge-generating substance for a laminated electrophotographic photoreceptor as described above, but it is also useful as a charge-transporting substance as a charge-generating substance in the resin. It is useful as a charge-generating material in an electrophotographic photoreceptor having a single-layer type photosensitive layer, and as a photoconductive material in an electrophotographic photoreceptor having a photosensitive layer in which a photoconductive substance is dispersed in a resin. The tetrazonium salt represented by the general formula () which is an intermediate of the general formula () of the present invention, for example, reduces 2,8-dinitrothioxanthone,
It can then be obtained by diazotization. 2,8-dinitrothioxanthone and 2,
The production of 8-diaminothioxanthone is described, for example, by EDAmstutz and CRNeumoyer, Journal
of American Chemical Society, 69 1925
(1947). Diazotization of 2,8-diaminothioxanthone is carried out by adding sodium nitrite in an inorganic acid such as hydrochloric acid or sulfuric acid at -10°C to 20°C. This diazotization reaction is completed in approximately 30 minutes to 3 hours. Furthermore, a tetrazonium salt can be obtained by adding, for example, hydroborofluoric acid or an aqueous sodium borofluoride solution to this diazotization reaction solution. The production of the disazo compound of the general formula () of the present invention can be carried out by directly allowing the above diazotization reaction solution to act on a coupler, or by adding, for example, hydrogen borofluoride to the diazotization reaction solution. It can also be obtained by adding an acid or an aqueous sodium borofluoride solution to precipitate the tetrazonium salt of general formula (), isolating the tetrazonium salt, and then reacting the tetrazonium salt with a coupler. In practice, this reaction is performed using N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO).
Mix and dissolve the tetrazonium salt and coupler in an organic solvent such as
This is carried out by dropping an aqueous alkaline solution such as an aqueous sodium acetate solution at 40°C. This reaction is complete in approximately 5 minutes to 3 hours. After the reaction is completed, the precipitated crystals are collected and purified by an appropriate method (for example, washing with water and/or an organic solvent, recrystallization method, etc.) to complete the production of the dizazo compound. The dizuazo compound of the present invention is a colored crystal at room temperature, and specific examples thereof are shown in Table 1 below along with melting point, elemental analysis value, and infrared absorption spectrum data.

【table】

[Table] Production examples are shown below. Production example 1 (Production of tetrazonium salt) 2,8 into hydrochloric acid consisting of 62 ml of water and 62 ml of concentrated hydrochloric acid.
-Add 8.68g of diaminothioxanthone, approx. 60℃
After heating for 1 hour, cool to 0℃,
Next, add 5.35g of sodium nitrite to this and 10ml of water.
was added dropwise over 5 minutes at a temperature of 0°C to 1°C. After stirring at the same temperature for 1 hour, 10 ml of 42% borofluoric acid was added to the reaction solution, and the precipitated crystals were separated, washed with methanol, and dried to give 8.45 g (yield 53.7%). Yellowish brown crystals of tetrazonium bistetrafluoroborate were obtained. Infrared absorption spectrum of this (KBr tablet method)
As shown in FIG. 1, an absorption band based on N ₂ was observed at 2260 cm ^-1 and an absorption band based on >C=0 was observed at 1660 cm ^-1 . Production Example 2 (Production of Disazo Compound No. 1) 1.10 g of the tetrazonium salt obtained in Production Example 1 and 1.32 g of 2-hydroxy-3-naphthoic acid anilide as a coupling component were added in 150 ml of cooled N,N-dimethylformamide. to which a solution consisting of 0.82 g of sodium acetate and 7 ml of water was added.
The mixture was added dropwise over 5 minutes at a temperature of 10°C, and after cooling was stopped, the mixture was further stirred at room temperature for 3 hours. After that, the formed precipitate was collected and heated to 80°C.
Wash 3 times with 200 ml of N-dimethylformamide,
Next, it was washed twice with 200 ml of water and dried at 80° C. under a reduced pressure of 2 mmHg to obtain 1.50 g (yield 75.6%) of the disazo compound No. 1 in Table 1. This disazo compound appeared as an orange-red powder, and its infrared absorption spectrum (KBr tablet method) was shown in FIG. Production Examples 3 to 17 (Production of Disazo Compounds No. 2 to 16) Same as Production Example 1 except that the compound in Table 2 below was used as a coupling component in the production of the disazo compound of Compound No. 1 of Production Example 2. Table 1 by method
Disazo compounds of Compound Nos. 2 to 16 shown in 1 were produced. In addition, among the disazo compounds of the present invention, the infrared absorption spectra of typical ones are
It is shown in Figure 8. Figure 3... Compound No. 8 Figure 4... Compound No.
9 Figure 5...Compound No.10 Figure 6...Compound No.11 Figure 7...Compound No.12 Figure 8...Compound No.13

【table】

【table】

【table】

[Table] Effects As mentioned above, the disazo compound of the present invention is effective as a photosensitive material for electrophotographic photoreceptors, especially as a charge-generating material for laminated photoreceptors. A specific usage example is shown.
Furthermore, in order to clarify the inventive step of the present invention, a comparison with conventional disazo compounds is also shown. Application example A tetrahydrofuran solution (solid content concentration 2%) of 76 parts by weight of disazo compound No. 10 of the present invention and polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) 1260
parts by weight and 3,700 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto the aluminum surface of an aluminum-deposited polyester base (conductive support) using a doctor blade, and air-dried. , a charge generation layer with a thickness of about 1 μm was formed. Separately, 2 parts by weight of 4'-diphenylamino-α-phenylstilbene, 2 parts by weight of polycarbonate resin (Panlite K1300, manufactured by Teijin Kasei Co., Ltd.) and 16 parts by weight of tetrahydrofuran were mixed and dissolved to form a solution. The layer was coated with a doctor blade at 80°C for 2 minutes and then dried at 100°C for 5 minutes to form a charge transport layer with a thickness of about 20 μm, forming the laminated photoreceptor (A) shown in Figure 9. Created. For comparison, in accordance with the above procedure for producing the photoreceptor, instead of the disazo compound of the present invention, the benzidine-based disazo compound disclosed in JP-A-45-37543 and JP-A-52-55643 was used. The compound 4,4'-bis(2-
Hydroxy-3-phenylcarbamoyl-1-
naphthylazo)-3,3'-dichlorodiphenyl and 4,4'-bis(2-hydroxy-3-phenylcarbamoyl-), which is a stilbene-based disazo compound described in JP-A-52-8832. Laminated photoreceptors (B) and photoreceptors (C) were prepared in exactly the same manner except that 1-naphthylazo)stilbene was used. The photoreceptors (A), (B), and (C) thus prepared were tested using a commercially available electrostatic copying paper tester (manufactured by Kawaguchi Electric Seisakusho Co., Ltd., model SP-428).
Its electrostatic properties were measured. That is, first, a -6KV corona discharge was applied to the photoreceptor for 20 seconds to make it negatively charged, and the photoreceptor was left to decay in the dark for 20 seconds, and the surface potential at that time was measured and expressed as Vpo (volts).
Next, the photosensitive layer was irradiated with light from a tungsten lamp so that the surface had an illumination intensity of 20 lux.
Time (seconds) until the surface potential becomes 1/2 of Vpo
was determined and set as the exposure amount E1/2 (lux seconds).
The results are shown in Table 3.

[Table] In order to investigate the sensitive wavelength range of the photoreceptor (A) according to the present invention, spectral sensitivity was measured using the following measurement procedure. First, the photoreceptor is charged to a surface potential of -800 volts or more by corona discharge in a dark place, and dark decayed until the surface potential reaches -800 volts.When the surface potential reaches -800 volts, a monochromator is turned on. The photoreceptor was irradiated with monochromatic light of 1 μW/cm ² using a spectrometer. Then, the time (seconds) until the surface potential attenuated to -400V was determined, and the half-reduced exposure amount (μW·sec/cm ² ) was calculated. On the other hand, the potential difference actually obtained by exposure is determined by subtracting the potential attenuation due to dark decay from the apparent potential difference of 400 volts obtained by exposure, and the light decay rate is calculated from this potential difference and the above-mentioned halved exposure amount. (Volt・^cm2・
μW ^-1・sec ^-1 ) was calculated and defined as the sensitivity. This spectral sensitivity curve is shown in FIG. As is clear from the results in Table 3, photoreceptor (A) using the disazo compound of the present invention has extremely high sensitivity compared to photoreceptors (B) and (C) using conventional disazo compounds. I understand. Moreover, from FIG. 10, it is found that the photoreceptor (A) using the disazo compound of the present invention has a sensitivity wavelength range of approximately 450 to 600 nm, and from this,
It can be seen that the image reproducibility of red originals is good.

[Brief explanation of the drawing]

FIG. 1 is an infrared absorption spectrum diagram (KBr tablet method) of the tetrazonium salt compound of Example.
Figures 2 to 8 are infrared absorption spectra of typical disazo compounds of the present invention (KBr tablet method).
It is. FIG. 9 is an enlarged sectional view of an electrophotographic photoreceptor according to the present invention, in which 11 is a polyester base, 2 is a
2 is an aluminum vapor deposited film, 33 is a charge generation layer, 4
4 represents a charge transport layer. FIG. 10 is a spectral sensitivity curve of the electrophotographic photoreceptor according to the present invention.

Claims (1)

[Claims] 1 General formula () [In the formula, A is (wherein, R represents an alkyl group, an alkoxy group, a nitro group, a halogen, a cyano group, or a halomethyl group, and n is an integer of 0, 1, 2, or 3, and n is an integer of 2 or 3. in case of,
R may be the same or different groups. )
represents. ] A disazo compound represented by: