JPS5961837A - Electrophotographic receptor - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic receptor which has high sensitivity, small residual potential and excellent durability by incorporating a bisazo compd. having an excellent carrier generating power in a photosensitive layer. CONSTITUTION:A photosensitive layer contg. the bisazo compd. (e.g.; the compd., etc. of the formula III, formula IV) wherein at least a part forms aggregate and the absorption max. of the visible absorption spectrum of said aggregate is on the longer wavelength side by >=60nm as compared to the absorption spectrum in a uniformly dissolved state and which is expressed by the formula I [Ar1 and R2 are (substd.) phenylene, (substd.) naphthylene, these substituents are halogen, (substd.) alkyl, (substd.) alkoxy; A is the formula II, Ar3 is a (substd.) aroma. carbon ring, (substd.) aromatic heterocycle; Z is an atom group necessary for constituting a (substd.) arom. carbon ring or (substd.) arom. heterocycle] is provided. An electrophotographic receptor having high sensitivity, small residual potential and excellent durability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor containing a bisazo compound formed in a specific agglomerated state.

Traditionally, inorganic photoconductive compounds such as selenium, zinc oxide, and cadmium sulfide have been used in the photosensitive layer of electrophotographic photoreceptors, but in recent years organic photoconductive compounds have been used due to issues such as thermal stability, moisture resistance, and safety. Photoconductive compounds attracted attention, and the development of organic photoreceptors,
Research began to be actively conducted. However, the reality is that an organic photoconductive compound with satisfactory performance has not yet been obtained, and so-called functionally separated electrophotographic photoreceptors, in which the carrier generation function and carrier transport function are shared by different substances, have not yet been obtained. There is a lot of research aimed at improving performance.

Many proposals have been made to use organic dyes or organic pigments as carrier-generating substances in such functionally separated electrophotographic photoreceptors, but it is difficult to find compounds that can exhibit sufficient performance; Small changes in the crystalline state, aggregation state, impurities, etc. of a compound can cause large differences in electrophotographic properties, so many studies are required to form a photosensitive layer in the optimal state for each compound. It can be said that it includes the points that should be done.

Among organic pigments useful as carrier-generating substances, azo pigments have attracted particular attention in recent years. Examples of such pigments include bisazo compounds described in Japanese Patent Application No. 56-69175; Even when compounds are used, it is still difficult to consistently obtain sufficient electrophotographic sensitivity.

As a result of intensive research, the present inventors have found that a significant improvement in sensitivity can be obtained with bisazo compounds formed into specific aggregates, and have completed the present invention.

An object of the present invention is to provide an electrophotographic photoreceptor containing a bisazo compound having excellent carrier generation ability, which has high sensitivity, low residual potential, and excellent durability. This object is achieved by forming a photosensitive layer containing a specific aggregate of a bisazo compound represented by the following general formula [I].

A-N=N Ar, -C>c Ar2 N-N
In formula A, Ar and Ar are substituted or unsubstituted (
7) A phenyl group represents a substituted or unsubstituted naphthyl group, and examples of these substituents include a halogen atom, a substituted or terminally substituted alkyl group, or a substituted or unsubstituted alkoxy group.

A represents, Ars is a substituted/unsubstituted aromatic carbocyclic group,
Alternatively, it represents a substituted or unsubstituted aromatic heterocyclic group. Z
represents an atomic group necessary to constitute a substituted/unsubstituted aromatic carbocycle or a substituted/unsubstituted aromatic heterocycle.

Preferred substituents for Ar, % Ar, Ars include fluorine atom, chlorine atom, bromine atom, alkyl group having 1 to 4 carbon atoms, alkoxy group having 1 to 4 carbon atoms, trifluoromethyl More preferred alkyl groups include methyl and ethyl groups, and more preferred alkoxy groups include methoxy and ethoxy groups.

Here, the specific aggregate means that the bisazo compound has an absorption maximum of at least 5
It is characterized by having an absorption maximum on the long wavelength side of Qnm or more.

The bisazo compound is N,N-dimethylformamide,
■When completely dissolved in a solvent such as 2-dichloroethane or 0-dichlorobenzene, it has a reddish color.
Generally, the absorption maximum of the visible absorption spectrum is shown in the wavelength range of 500 to 600 nm.

This is considered to be absorption by compound molecules that are in a monomolecular state or in a state close to it.

However, when a photosensitive layer is prepared by coating the bisazo compound on a suitable support, an absorption maximum due to newly formed aggregates appears on the long wavelength side depending on the conditions at the time of preparation. The maximum wavelength differs depending on the compound, but it is at least 60 nm higher than the absorption maximum when dissolved in a solvent.
It is characterized by its appearance on the long wavelength side of nm or more.

For example, in the case of a bisazo compound of the following structural formula (II),
The visible absorption spectrum is shown in Figure 1.

Structural Formula [11] In FIG. 1, curve B is an absorption spectrum of an N,N-dimethylformamide solution, and shows an absorption maximum at 575 nm. Curve A is the absorption spectrum of the coating layer on the polyester film, which is the spectrum when the aggregate of the present invention is formed.

In curve A, there is a shoulder at 560 nm as610
A maximum C appears at 660 nm, and in this case, it is thought that the maximum appearing at a longer wavelength is due to an aggregate having a larger cohesive energy. In this case, the specific aggregate in the present invention is an aggregate corresponding to the maximum C, and compared to curve B, 85n
It appears on the m long wavelength side.

As for the body side, the following can be mentioned. e
16 − to ω
＋eP ri
0 too ■ δ 9 8d
d d8
9 36
8 d8
in;
(5ε ku5t
S heart g 1
3 5 & 5 g 3 B, 9 98
9 9 6 3 98
Q Q3,
．． 3 3
9 6;
3 Yuji; Wind pod δ
8 The bisazo dye in the present invention is prepared by diazotizing the corresponding diamino compound by a known method as a raw material, and combining the obtained tetrazonium salt and Kabuchi with, for example, N,
It can be easily synthesized by a known method of coupling in the presence of a base in a solvent such as N-dimethylformamide.

When forming a photosensitive layer using the bisazo dye obtained in this way, it is treated as necessary to adjust the degree of crystallinity, and then pulverized using a ball mill, homomixer, etc. A method of dispersing in a dispersion medium and applying a dispersion liquid with a binder added if necessary. Alternatively, a method can be used in which the solution is dissolved in an appropriate solvent, or a binder is added if necessary, and the mixed and dissolved solution is applied. At that time, in the dispersion coating method, the absorption spectrum of the bisazo dye changes depending on the grinding and dispersion conditions, and in the dispersion coating method, the solvent, drying conditions, and even the solvent used to form the upper layer Since the absorption spectrum changes depending on the conditions, it is necessary to select appropriate conditions in each case.

Examples of the solvent or dispersion medium used for forming the photosensitive layer include n-butylamine, diethylamine, ethylenediamine, inpropaturamine, triethanolamyl,
Triethylenediamine, N.

N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, l,2-dichloroethane, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, isoprohafur, ethyl acetate, butyl acetate, dimethyl sulfoxide, etc. It will be done.

In the case of dispersion coating, an advantageous method for forming the aggregates of the present invention is to synthesize pigment particles with good dispersibility, and then thoroughly grind them into fine particles using a ball mill or the like. The reason why the desired aggregates are advantageously formed by micronization is unknown, but if the pulverization is insufficient, the desired aggregates cannot be sufficiently obtained. In addition, in the case of dissolving and coating, if the coating is left untreated after coating, the target aggregates will hardly be formed and the appearance will be reddish-purple. In this case, the coating layer is
The desired aggregate can be formed by treatment with a solvent with high affinity, for example, a halogenated hydrocarbon such as 1,2-dichloroethane, or N,N-dimethylformamide.

The electrophotographic photoreceptor of the present invention obtained as described above is
Since carrier generation ability is significantly improved, it has high sensitivity, low residual potential, and excellent durability.

Specific examples of the present invention will be described below, but the embodiments of the present invention are not limited thereby.

Example 1 A conductive support made of a polyester film laminated with aluminum is coated with a 0.0 mm thick film made of vinyl chloride-vinyl acetate-maleic anhydride copolymer "S-LEC MF-10j (manufactured by Tanezu Kagaku Co., Ltd.)". Provided with an intermediate layer of 0.05 μm,
On top of that, exemplified compound (1) 2y was added to ethylenediamine 2
A solution dissolved in a mixed solution of d and tetrahydrofuran ioo m was applied so that the film thickness after drying was 0.5 μm,
A carrier generation layer was formed. The carrier generation layer thus obtained had a reddish-purple appearance, and 1,2-dichloroethane was then applied to its surface to change the color of the carrier generation layer from reddish-purple to blue. Then, on top of this, tri(p-)lyl)amine 6.9
and polycarbonate resin “Panlite L-1250J1
A carrier transport layer was formed by coating a solution obtained by dissolving 0 g of 0 g in 100 rL of tetrahydrofuran so that the film thickness after drying was 10 μm, thereby producing an electrophotographic photoreceptor of the present invention.

The photoreceptor obtained as described above was subjected to the following characteristic evaluations using an electrostatic paper tester model SP-428 manufactured by Nichidenki Seisakusho. Surface potential VA when charged at a charging voltage of -5kv for 5 seconds.Next, exposure required to attenuate the surface potential VA by half by irradiating halogen lamp light so that the illuminance on the photoreceptor surface becomes 351ux. Amount (half-reduced exposure amount) E3A was determined.

In addition, the surface potential (residual potential) VR after exposure with an exposure amount of 301 ux-see was determined. As a result, VA=-t
too (V) E3'i = 2.2 (1ux-sec) VR=
It was O(V).

Comparative Example l Regarding the carrier generation layer obtained in Example 1, 1.2-
A carrier transport layer was formed thereon in the same manner as in Example 1 without performing the treatment with dichloroethane, and the reddish-purple state was maintained, thereby producing an electrophotographic photoreceptor for comparison.

The same measurements as in Example 1 were performed on the comparative photoreceptor thus obtained. As a result, VA=-1210 (V) E34 = 8.9 (tux-sec) VR=
-20 (V). It is clear that the photoreceptor of Example 1 has significantly higher sensitivity than the photoreceptor of Comparative Example 1.

Next, regarding the photoconductor of Example 1 and the photoconductor of Comparative Example 1,
Absorption spectra were measured using reflected light using an integrating sphere. On the other hand, the absorption spectra of the solution of Exemplified Compound (1) obtained in Example 1 was coated on a transparent polyester film and were and were not sprayed with l,2-dichloroethane using transmitted light. When measured, it was 500
In the wavelength region longer than nm, the photoreceptor 3, Example 1, and Comparative Example 1 showed almost the same spectra as the photoreceptor 3, Example 1, and Comparative Example 1, respectively, which were measured using the reflected light described above, so the transmission was less affected by light scattering. A comparison was made using light absorption spectra.

FIG. 2 shows the absorption spectrum of a carrier generation layer coated on a transparent polyester film in the same manner as in Example 1 and Comparative Example 1. In the figure, the track MA indicates the coating layer corresponding to Example 1; Curve B is the spectrum of the coating layer corresponding to Comparative Example 1.

As is clear from the above results, in the absorption spectrum of the dye corresponding to the photoreceptor of Example 1, the aggregate absorption at 66° nm is strong and the absorbance at 660 nm is 86°.
The ratio of absorbance ε610 at 60 and 610 nm is ε6
60/εago = 1.07, but in the absorption spectrum of the dye corresponding to the photoreceptor of Comparative Example 1, 660 nm
It can be seen that no maximum appears at 660 nm, and the aggregates corresponding to the absorption maximum at 660 nm greatly contribute to the electrophotographic properties.

Example 2 An electrophotographic photoreceptor of the present invention was produced in the same manner as in Example 1, except that exemplified compound Ql) was used instead of exemplified compound (1). Then, when the same measurement as in Example 1 was performed, VA=-1030 (V) Ey6= 2.1 (lux-sec) VR=
Off).

Comparative Example 2 A comparative electrophotographic photoreceptor was prepared in the same manner as in Comparative Example 1, except that exemplified compound Q1) was used instead of exemplified compound (1), and the same measurements as in Example 1 were carried out. Then, VA=-tloo (V) Ey6= 9.4 (lux-sec) VR
=-ao (V).

Next, coating layers of dyes corresponding to Example 2 and Comparative Example 2 were formed on transparent polyester films as described above, and absorption spectra were measured using transmitted light. The result! !
Shown in Figure 3. In the figure, curve A is the absorption spectrum of the coating layer corresponding to Example 2, and curve B is the absorption spectrum of the coating layer corresponding to Comparative Example 2. The electrophotographic photoreceptor of Example 2 has strong absorption at 670 rm, and the absorbance at 670 nm is ε6? Absorbance at 620 nm with 662o
The ratio is ε67o/ε620-1.02, giving excellent electrophotographic properties.

Example 3 On the conductive support provided with the intermediate layer used in Example 1, a solution obtained by dissolving 2 g of the exemplified compound Cll in a mixed solution of 2 M of ethylenediamine and 100 TIL of TeFhydro7ran was added so that the film thickness after drying was 0. A carrier generation layer was formed by coating to a thickness of .5 μm. Furthermore, 10 g of N,N-ethylaminobenzaldehyde-1,1-diphenylhydrazone 6I and methacrylic resin "Acrivet" (manufactured by Mitsubishi Rayon Co., Ltd.) were added to 1°2-dichloroethane lo
The electrophotographic photoreceptor of the present invention was prepared by applying a solution dissolved in oml to form a carrier transport layer such that the film thickness after drying was 10 μm. When the photoconductor obtained as described above was subjected to the same measurements as in Example 1, ■ A = -1090 (V) E% = 2.0 (Iux-sec, ) VR =
Off).

Comparative Example 3 A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 3, except that methyl ethyl ketone was used instead of 1°2-dichloroethane as the solvent used to form the carrier transport layer. When similar measurements were made, V people = -1220 (V) E% = 8.3 (lux, sec,) V
R=-25 (V). Obviously, the characteristics are inferior to those of the electrophotographic photoreceptor of Example 3.

When the absorption spectra of the photoreceptors of Example 3 and Comparative Example 3 were measured using reflected light, the results were as shown in FIG. In the figure, curve A is the absorption spectrum of the photoreceptor of Example 3, and curve B is the absorption spectrum of the photoreceptor of Comparative Example 3. Measurement using reflected light (7) Only a broad curve can be obtained, but the photoreceptor of Example 3 has an absorption maximum at 660 nm, and the ratio to the absorbance at shorter wavelengths exceeds 1. That is clear.

Example 4 2 g of Exemplified Compound (21) was mixed with ethylenediamine and N,N
- After dissolving in a mixed solvent of dimethylformamide, it was poured into water and reprecipitated, and an amorphous product was obtained.

Next, after grinding this in a ball mill for 15 minutes, 1.
Add 100rrLl of 2-dichloroethane for 2 hours.
Dispersed. Next, the above dispersion was dried on the conductive support provided with an intermediate layer, which was used in Example 1, so that the film thickness was 0.
It was coated to a thickness of 5 μm. Furthermore, on top of that, 4-(
Di(p)tolylamino)-4'-methoxystilbene 6
g and polycarbonate) 1111 fat r Hanlite L-12
10g of 50J and 1001rL of 1,2-dichloroethane
An electrophotographic photoreceptor of the present invention was prepared by applying a solution dissolved in 1.1 to 12 μm to give a film thickness of 12 μm after drying. When the photoconductor obtained as described above was measured in the same manner as in Example 1, VA=-1060 (V) E34= 1.8 (1ux, ·see, ) VR
= O(V).

Comparative Example 4 A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 4, except that the grinding time in the ball mill was changed to 5 minutes, and measurements were performed in the same manner as in Example 1. VA = -1170. (
V) E3A= 4.1 (lux, -5ec, )VR
= 0 (V).

There was no difference in the appearance of the coated surfaces of the carrier generation layer of Example 4 and the carrier generation layer of Comparative Example 4 when viewed under a microscope. However, in the same way as in Example 1 and Comparative Example 1,
A coating layer of the dye corresponding to Example 4 and Comparative Example 4 was prepared on a transparent polyester film, and the absorption spectrum was measured using transmitted light, and the result was as shown in FIG. In the picture, song @
Curve A is the absorption spectrum of the coating layer corresponding to Example 4, and curve B is the absorption spectrum of the coating layer corresponding to Comparative Example 4. In Example 4, the absorbance of maximum absorption at 660 nm is ε660, and the absorbance of maximum absorption at 610 nm is ε61.
The ratio with 0 is εsea/gano=0.96, and in Comparative Example 4, εuo/εe+o=0
．． It was 82. Thus, it is clear that the relative intensity of the absorption maximum at 660 nm has a large effect on the electrophotographic properties.

Subsequently, the electrophotographic photoreceptor obtained in Example 4 was
When the image was copied using an electrophotographic copying machine U-Bix 2000R (manufactured by Konishi Roku Photo Industry Co., Ltd.), a copied image faithful to the original, with high contrast and excellent gradation was obtained. This did not change even after repeating 20,000 times, and a duplicated image similar to the initial one was obtained.

As shown in the above examples, the bisazo compound of the present invention exhibits particularly excellent electrophotographic properties by forming aggregates corresponding to the absorption maximum that appears at a position largely shifted to the long wavelength side. It is something that becomes.

[Brief explanation of the drawing]

1 to 5 show visible absorption spectra of bisazo compounds. Agent Kuwabara Yoshi Miho l Zume71) Bowl 3 Zu Goru & (η What 2
C Degree & (ηr) Kayachi Figure 11 Figure 11 March 22 +-+ Patent J) Chief Justice Kazuo Wakasugi 1 1982 Patent Application No. 172756 5j2 Title of Invention Electrophotographic Photoreceptor 3 Supplement Relationship with the incident if you stop: Patent 1” 1 (Address: 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name (+27) R1 Representative IN Director, Konishiroku Photo Industry Co., Ltd.
Nobuhiko KawamotoFebruary 2, 1981 (Shipping date:
(February n, 1982) 6. Application and specification to be amended 7. Contents of the amendment An engraving of the application and specification (no change in content) Procedural amendment as attached. 5 u Kazuo Motosugi, Commissioner of the Patent Office 1, Case IJ:/I. 1982 Patent Application No. 172756 2 Name of the invention Electrophotographic photoreceptor: I, Supplementary IL = 8 Relationship to the case Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name (+27) ) Konishiroku Photo Industry Co., Ltd.? ]Representative Director Nobuhikoori Tokoro Higashi)rito II U! f city Sakuramachi 1 city area 6
, Subject of amendment (1) "Claims" column of the typed specification (11) "Detailed description of the invention" of the typed specification
Column 7, Contents of the amendment (1) As per the amended appendix to the claims (1i) Amendment in the specification, page 5, line 1, "phenyl group" and "7L nylene group"
I am corrected. In the first and second lines of the same page, the text "naphthyl group" should be corrected to "naphthylene group." The structure of page 14 has been corrected as follows. @) The 5th and 6th lines of the page say "triethanolamyl" [corrected as triethanolamide d]. Attachment Claim (1) An electrophotographic photoreceptor having a photosensitive layer containing a bisazo compound represented by the following general formula CI), in which a small amount (some of the bisazo compound) forms an aggregate. , the absorption maximum of the visible absorption spectrum of the aggregate is
An electrophotographic photoreceptor characterized in that its absorption spectrum is on the longer wavelength side by at least 60 nm compared to the absorption spectrum in a uniformly dissolved state. General formula [■] N A-N=N-Ar1-CH=C-Ar2-N=NA In the formula, Ar and Ar2 are substituted or unsubstituted phenylene groups, or substituted or unsubstituted naphthylene groups, respectively. These substituents include a halogen atom, a substituted/unsubstituted alkyl group, and a substituted/unsubstituted alkoxy group.゛・2-', Ar3 is a substituted or unsubstituted aromatic carbocyclic group,
Alternatively, 1-0 represents a substituted or unsubstituted aromatic heterocyclic group.
2 represents an atomic group necessary to constitute a substituted/unsubstituted aromatic carbocycle or a substituted/unsubstituted aromatic heterocycle. (2) In the visible absorption spectrum of the bisazo compound, the absorbance of the aggregate is at least 60 nm longer than the absorption maximum in a uniformly dissolved state, and the absorbance of the aggregate is at a shorter wavelength. The ratio of
The electrophotographic photoreceptor according to claim 1, characterized in that the number of electrophotographic photoreceptors is 5 or more.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor having a photosensitive layer containing a bisazo compound represented by the following general formula [I], at least a part of the bisazo compound forms an aggregate, and the visible The absorption maximum of the absorption spectrum is
An electrophotographic photoreceptor characterized in that its absorption spectrum is on the longer wavelength side by at least 60 nm compared to the absorption spectrum in a uniformly dissolved state. A N”=N-Art Ckl=C-Ar2-N=N
In formula -A, Ar and Ar each represent a substituted or unsubstituted phenyl group or a substituted or unsubstituted naphthyl group, and these substituents include a halogen atom, a substituted or
Represents an unsubstituted alkyl group and a substituted/unsubstituted alkoxy group. A represents 1, / Ar is a substituted/unsubstituted aromatic carbocyclic group,
Alternatively, it represents a substituted or unsubstituted aromatic heterocyclic group. Z
represents an atomic group necessary to constitute a substituted/unsubstituted aromatic carbocycle or a substituted/unsubstituted aromatic heterocycle. (2) In the visible absorption spectrum of the bisazo compound, the absorbance of the aggregate absorption maximum which is at least 5Q nm longer than the absorption maximum in a uniformly dissolved state, and the absorbance of the absorption maximum in the shorter wavelength region. The ratio of is 0.8
The electrophotographic photoreceptor according to claim 1, characterized in that the number of electrophotographic photoreceptors is 5 or more.