JPS63132249A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To afford spectral sensitivity in the range from visible region to near infrared region, high sensitivity and superior electric characteristics to an electrophotographic sensitive body by providing a photosensitive layer contg. a specified asymmetric squarylium compd. CONSTITUTION:A photosensitive layer 4 comprising a layer-built body constituted of a charge generating layer 2 contg. an asymmetric squarylium compd. expressed by the formula and a charge transfer layer 3 contg. a charge transfer material is formed on an electroconductive substrate 1. In the formula, each R1 and R2 is alkyl, phenyl group, etc.; R3 is H atom, OH group, etc.; R4 is alkyl or OH group; n is zero or an integer 1-3; The charge generating layer may be formed of the squarylium compd. alone, but it may be formed also by the use of binder resin in combination. By this constitution, the electrophotographic sensitive body can acquire spectral sensitivity in the range from visible region to near infrared region, high sensitivity, and superior electric characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrophotographic photoreceptors used in electrophotographic processes. More specifically, the present invention relates to an electrophotographic photoreceptor containing a novel square aryllium compound in a photoconductive layer.

Conventional technology Traditionally, as electrophotographic photoreceptors, filterless photosensitive materials such as amorphous selenium, selenium alloys, cadmium sulfide, and zinc oxide, as well as organic photosensitive materials typified by polyvinyl carbazole and polyvinyl carbazole derivatives, have been widely used. Are known.

It is well known that amorphous selenium or selenium alloy has extremely excellent properties as an electrophotographic photoreceptor and is used in practical use. However, its production requires a complicated step of vapor deposition, and the produced vapor-deposited film has the disadvantage of not being flexible. When zinc oxide is used, it is used as a dispersion type photosensitive material in which zinc oxide is dispersed in a resin, but such a photosensitive material has a drawback in mechanical strength, and cannot withstand repeated use as it is.

Polyvinylcarbazole, which is widely known as an organic photoconductive material, has excellent advantages in terms of transparency, film-forming properties, and flexibility, but polyvinylcarbazole itself does not have sensitivity in the visible light range. Therefore, it cannot be put to practical use as it is, and therefore various sensitization methods have been proposed.

However, when polyvinylcarbazole is spectrally sensitized using a dye sensitizer, the spectral sensitivity range is extended to the visible light range, but it still does not have sufficient sensitivity as an electrophotographic photoreceptor and suffers from photofatigue. It has a serious drawback. or,
When chemically sensitized using an electron-accepting compound, a photoreceptor with sufficient sensitivity as an electrophotographic photoreceptor can be obtained, and some of them have been put into practical use. There are still some problems.

In recent years, various types of organic electrophotographic photoreceptors have been studied, and it has been reported that, in particular, a laminated type photoreceptor having a charge generation layer and a charge transport layer has electrical properties superior to those of conventional photoreceptors. Known charge generating materials used in these electrophotographic photoreceptors include bisazos, trisazos, phthalocyanines, pyryliums, square lyliums, and the like. Phthalocyanines, trisazo compounds, and squareylium compounds have been reported to have sensitivity from the visible region to the near-infrared region.
9-105536@ and Japanese Patent Application Laid-Open No. 58-21416.

Problems to be Solved by the Invention However, phthalocyanines have disadvantages in that their spectral sensitivity is biased toward long wavelengths and poor red color reproducibility, and trisazo compounds do not have excellent electrical properties and sufficient sensitivity. .

Furthermore, the square aryllium compound shown in JP-A No. 58-214162 does not have sufficient sensitivity, and the square aryllium compound shown in JP-A 49-105536 etc. has relatively high sensitivity. It has drawbacks in chargeability, dark decay, etc., and has not been able to achieve both high sensitivity and low dark decay.

Therefore, an object of the present invention is to provide an electrophotographic photoreceptor having spectral sensitivity from the visible region to the near-infrared region, high sensitivity, and excellent electrical properties, eliminating the above-mentioned shortcomings.

Means for Solving the Problems The above objects of the present invention can be achieved by using an asymmetric square lylium compound represented by the following general formula (I) as a photosensitive material for an electrophotographic photoreceptor. Therefore, the electrophotographic photoreceptor of the present invention is characterized by having a photosensitive layer containing an asymmetric square aryllium compound represented by the following general formula (I).

(In the formula, R1 and R2 each represent an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted benzyl group, and R3 is a hydrogen atom, a hydroxyl group, a methyl group, a fluoromethyl group, halogen atom, carboxyl group, alkylcarbonylamino group or alkylsulfonylamino group, R4 represents an alkyl group or hydroxyl group, n represents O or an integer from 1 to 3) Specific examples of squareylium compounds used in the body include the following.

These squaryllium compounds are produced by, for example, a Friedel-Crach-type reaction between squarium chloride and an aniline derivative represented by the general formula (II) (wherein R1-R3 have the same meanings as described above). After reacting and hydrolyzing the obtained cyclobutenedione derivative, heating it with a phenol derivative represented by general formula (III) (wherein R4 and n have the same meanings as above) in an organic solvent, It can be synthesized by reaction.

An example is shown below.

(Synthesis example) Square phosphate chloride 15. 'EJ (0,10 mol) and boron trifluoride ethyl ether complex 13ml (0,1
0 mole) was dissolved in methylene chloride 60d, mixed with N,N-dimethylaniline 63rfIi (0.50 mole), and the reaction was carried out by stirring at room temperature for 5 hours. After the reaction was completed, the mixture was diluted with dilute hydrochloric acid and then with water. Wash and separate and purify using column chromatography to obtain 3-chloro-4-(4
,”-dimethylaminophenyl)-3-cyclobutene-
19.0 g (yield: 81%) of 1,2-dione was obtained.

Next, 75 ml of acetic acid and 25 ml of water were added to the obtained compound 19.09 (0,081 mol), and the mixture was heated under reflux for 1 hour. After cooling, the precipitate was filtered off and washed with water to give 3-( 4--dimethylaminophenyl)-4-
Hydroxy-3-cyclobutene-1,2-dione 17
．． 2 g (yield 98%) was obtained.

The obtained 4-hydroxycyclobutene derivative was 1.07!
? (4,9 mmol) and phloroglucinol (2-elongate >0.80y (4,9 mmol)) in butanol 25
ml and heated under reflux for 6 hours. Let the mixture cool;
The precipitate was separated by filtration, washed with butanol, and extracted with exemplified compound Nα1.
1.51y (yield 94%) S- was obtained.

Melting point: 320° C. or higher Infrared absorption spectrum: Figure 3 Elemental analysis "18" l Other square lylium compounds exemplified above as 5NO5 can also be synthesized in the same manner as above.

In the present invention, the square lium compound represented by the general formula (I>) is included in the photosensitive layer of the electrophotographic photoreceptor,
It is preferable to use it in an electrophotographic photoreceptor in which the photosensitive layer has a multilayer structure. That is, in an electrophotographic photoreceptor including a photosensitive layer with a two-layer structure consisting of a charge generation layer and a charge transport layer,
By providing a charge generation M containing a square aryllium pigment and a known charge transport layer, an electrophotographic photoreceptor with high sensitivity and improved electrical properties such as chargeability and dark decay can be obtained.

A case where the electrophotographic photoreceptor of the present invention has the above-mentioned two-layered photosensitive layer will be explained with reference to the drawings. As shown in FIGS. 1 and 2, square lyllium A photosensitive layer 4 is provided, which is a laminate of a charge generation layer 2 containing a compound and a charge transport layer 3 containing a charge transport substance. The stacking order of the charge generation layer 2 and the charge transport layer 3 is arbitrary.

In this case, a protective layer may be provided on the photosensitive layer 4, or an intermediate layer may be provided between the photosensitive layer 4 and the conductive support 1.

The charge generation layer may be formed of the square aryllium compound alone, but it can also be formed using the square aryllium compound in combination with a binder resin.

In the latter case, the ratio of the squarelillium compound to the binder resin is from 10% to 90% by weight, preferably from 20% to 70% by weight.

When using a binder resin, the binder resin itself may or may not have photoconductivity. Examples of the photoconductive binder resin include photoconductive polymers such as polyvinylcarbazole, polyvinylcarbazole derivatives, polyvinylnaphthalene, polyvinylanthracene, and polyvinylpyrene;
Alternatively, other organic matrix materials having charge transport ability may be used.

Furthermore, as the binder resin that does not have photoconductivity, a known insulating resin can be used.

Examples of these known insulating resins include polystyrene, polyester, polyvinyltoluene, polyvinylanisole, polychlorostyrene, polyvinyl butyral, polyvinyl acetate, polyvinyl butyl methacrylate, copolystyrene-butadiene, polysulfone, copolystyrene-methyl methacrylate, and polycarbonate. It will be done.

At this time, in order to further improve the mechanical strength of the resulting electrophotographic photoreceptor, a plasticizer can be used in the same manner as in general polymeric materials. As the plasticizer, for example, chlorinated paraffin, chlorinated biphenyl, phosphate plasticizer, phthalate plasticizer, etc. can be used, and it is added in an amount of 0 to 10% by weight to the binder resin to improve the sensitivity of the electrophotographic photoreceptor. It is possible to further improve its mechanical strength without deteriorating its electrical properties.

The thickness of the charge generation layer is 0.05 to 3μ, preferably 0.1μ.
~1μ.

The charge generation layer is formed by a well-known method. That is, when forming a charge generation layer using a square aryllium compound alone without using a binder resin, solvent coating and vacuum evaporation methods can be used.

Furthermore, when a binder resin is used in combination, the square aryllium compound is pulverized and then dispersed in the binder resin. As the pulverization method, known methods such as SPEX IILL, ball mill, l
, RED DEVIL (trade name), etc. can be used.

The binder resin in which the squareylium compound is dispersed is coated on the charge transport layer or the conductive support. Coating methods include a dipping method, a spray method, a bar coater method, and an applicator method, and a good charge generation layer can be formed by any of these methods.

On the other hand, the charge transport layer includes he-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, p-diethylaminobenzaldehyde=N,N-diphenylhydrazone, p-diethylaminobenzaldehyde-he-α-naphthyl-N-phenyl Hydrazones such as hydrazone, 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[quinolyl(2>]-3-(p-diethylaminostyryl)-5-( Pyrazolines such as p-diethylaminophenyl) pyrazoline, oxazole compounds such as 2-(p-diethylaminostyryl)-6-dinithylaminobenzoxazole, and thoria such as bis(4-diethylamino-2-methylphenyl)-phenylmethane. Rylmethane compound, N,N”-diphenyl-N,N
-Binder resin containing a diamine compound such as -bis-(3-methylphenyl)-(I,1-biphenyl)-4,4''-diamine, or poly-N-
Photoconductive polymers such as vinyl carbazole and polyvinylanthracene are used.

Further, as the conductive support, metal, paper treated with conductivity, a polymer film having a conductive layer, glass, etc. can be used.

Example Next, the present invention will be explained by examples.

Example 1 Exemplary compound No.1' 1 part by weight of polyester resin (manufactured by DuPont, Adhesive 49000) 1 part by weight,
Add 10 parts by weight of tetrahydrofuran and mill with a ball mill.
The time-pulverized and mixed dispersion was applied to a polyester film [manufactured by Toshi,
Metal Me (registered trademark)] and dried at 70''C for 5 hours to form a charge generation layer with a thickness of 1 μm.

On this charge generation layer, N,N--diphenyl-N,N-
-bis-(3-methylphenyl)-[1゜1'-biphenyl]-4.4-diamine 1 part by weight, polycarbonate resin (manufactured by Ondai, Panlite (registered trademark)) 11 parts by weight, and tetrahydra A homogeneous solution consisting of 10 parts by weight of Rowalan was applied using an applicator and dried at 70° C. for 16 hours to form a charge transport layer with a thickness of 22 μm, thereby producing an electrophotographic photoreceptor.

Next, using an electrostatic copying paper testing device (manufactured by Kawaguchi Electric, Electrostatic Paper Analyzer 5P-428), after being negatively charged by applying a -6 kV corona discharge, it was left in a dark place for 2 seconds, and then Using a tungsten lamp, the photosensitive layer was irradiated with light so that the surface illuminance was 10 lux, and the exposure amount E1/2 was set so that the surface potential was 1/2 of the surface potential VD after being left in the dark. The results were as follows: initial charging potential Vo=-830V, potential after being left in the dark for 2 seconds) VDDP--800V, E1/2=3.5 lux·sec, and residual potential Rp=OV.

In addition, the following measurements were performed to demonstrate that the material has extremely excellent sensitivity to long wavelength light. After charging the above photoreceptor by corona discharge in a dark place, 1 μW was obtained using a monochromator at 800 nm.
/ctA monochromatic light was irradiated onto the photoreceptor. Then, the time required for the surface potential to decrease to 1/2 was measured, and the exposure element was determined. The result was 15.5 erg/c screen.

Examples 2 to 8 In Example 1, as shown in Table 1, Exemplary Compounds No. 2.8.11.13.14.21 and 29 were used instead of Exemplary Compound NQ2 as the squarelylium compound.
Electrophotographic photoreceptors were produced in the same manner as in Example 1 except that (Examples 2 to 8, respectively) were used, and the characteristics thereof were evaluated. The results obtained are shown in Table 1.

Table 1 Effects of the Invention The electrophotographic photoreceptor of the present invention has a photosensitive layer containing a square aryllium compound that has spectral sensitivity from the visible region to the near-infrared region and has high sensitivity and excellent electrical properties. It has excellent electrical properties such as chargeability and dark decay, and can be widely used not only in copying machines but also in semiconductor laser printers and the like.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams showing cross-sectional views of the electrophotographic photoreceptor of the present invention, and FIG. 3 is an infrared absorption spectrum of an example of the square aryllium compound used in the present invention. DESCRIPTION OF SYMBOLS 1... Conductive support, 2... Charge generation layer, 3...
Charge transport layer, 4... photosensitive layer.

Claims (1)

[Claims] General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1 and R_2 each have 1 to 20 carbon atoms.
represents an alkyl group, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted benzyl group, and R_3 is a hydrogen atom, a hydroxyl group, a methyl group, a trifluoromethyl group, a halogen atom, a carboxyl group, an alkylcarbonylamino group, or an alkylsulfonyl group. represents an amino group, R_4 represents an alkyl group or a hydroxyl group, and n is 0 or 1 to 3
represents an integer. ) An electrophotographic photoreceptor comprising a photosensitive layer containing an asymmetric squarium compound. (2) The squarerium compound has the above general formula (I)
, R_1 and R_2 each represent a lower alkyl group or a benzyl group, R_3 represents a hydrogen atom, a hydroxyl group, a methyl group, or a halogen atom, R_4 represents an alkyl group or a hydroxyl group, and n represents 0 or 1. An electrophotographic photoreceptor according to claim 1.