JP2001242656A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrification single layer type electrophotographic photoreceptor which generates a little transfer image memory even when it is used for a reversal developing type image forming device and which has excellent resistance against gas such as ozone and NOX. SOLUTION: In the positive electrification single layer photoreceptor, the charge generating layer of the photosensitive layer contains a phthalocyanine pigment and one kind of compound expressed by general formula (1), (2) or (3) and a terphenyl compound expressed by general formula (4) as an electron transfer agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used for an image forming apparatus such as an electrophotographic copying machine, a facsimile, a laser beam printer, and the like, and an image forming method using the same.

More specifically, a positively charged single-layer type electrophotographic photoreceptor having a very small transfer memory and having excellent resistance to gases such as ozone and NOx, and a reversal developing digital image forming method using the same. It is about.

[0003]

2. Description of the Related Art Organic photoreceptors are easier to manufacture than conventional inorganic photoreceptors, are inexpensive, and have a wide variety of photoreceptor materials such as charge transport agents, charge generators and binder resins. In recent years, it has been widely used because it has an advantage that the degree of freedom in functional design is high.

The organic photoreceptor includes a single-layer type photoreceptor in which a charge transporting agent (a hole transporting agent and an electron transporting agent) is dispersed in the same photosensitive layer together with a charge generating agent, and a charge generating agent containing a charge generating agent. There is a laminated photoconductor in which a layer and a charge transport layer containing a charge transport agent are laminated.

On the other hand, an image forming apparatus using an electrophotographic system charges a photosensitive member (main charging step), forms an electrostatic latent image by exposing the image (exposure step), and develops the electrostatic latent image. The toner is developed with a bias voltage applied (developing step), the formed toner image is transferred onto a transfer sheet (transfer step), and fixed to form an image. Further, the residual toner on the photoconductor is cleaned by a urethane blade or the like (cleaning process), and the residual charge on the photoconductor is erased by an LED or the like (static elimination process).

Image forming apparatuses utilizing the electrophotographic method include digital and analog copying machines, facsimile machines, laser beam printers, and the like. In particular, toner having the same polarity as a charging voltage applied to a photosensitive member in a charging step is used. The reversal developing method of developing by using is widely used in digital image forming apparatuses.

When an electrophotographic photoreceptor is used in a reversal developing digital image forming apparatus, the transfer voltage applied to the photoreceptor in the transfer step is not directly applied to the photoreceptor but via a transfer medium (paper). It is applied and is not applied when the transfer medium does not pass through the transfer process.

However, it is very difficult to turn on and off the transfer voltage, and the front and rear ends of the transfer medium often have portions directly applied to the photosensitive member. That is, before the leading end of the transfer medium covers the transfer device, the transfer voltage starts to be applied, and the transfer voltage continues to be applied even when a part of the transfer device is exposed by the passage of the rear end of the transfer medium. In this portion, a transfer voltage is directly applied to the photosensitive member.

In the case of a positively charged single-layer type electrophotographic photosensitive member, since the polarity of the voltage applied by the transfer device is negative, a negative space charge remains on the surface of the photosensitive member to which the negative voltage is applied, so-called, Transfer memory occurs. In general, since the single-layer type photoconductor has sensitivity to both polarities, negative space charges are erased in the next neutralization step.

However, if the sensitivity of the positively charged single-layer type photoreceptor to the negative polarity is very low (the half-exposure amount is very large), the negative space charge is not sufficiently erased and the next charging step is not performed. However, even if the surface is positively charged, a potential drop is caused by the effect of space charge, and furthermore, it appears as a difference in sensitivity in the developing process, and a so-called transfer memory image occurs in which the portion becomes black in the image. That is, in order to prevent transfer memory from being generated, it is preferable that the difference in positive / negative sensitivity be as small as possible.

On the other hand, a reversal-developing digital image forming apparatus using the positively charged single-layer type photoreceptor generally generates less ozone. However, as described above, since the polarity of the voltage applied in the transfer device is negative, ozone is generated in the vicinity of the transfer device, and is particularly remarkable in a large-sized image forming apparatus. In particular, NOx is frequently generated near the charging device.

It is known that when the surface of the photoreceptor is exposed to the above-mentioned gases such as ozone and NOx, the charged potential of the portion is reduced, which causes image fogging and black streaks.

[0013]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reversible development type digital image forming apparatus which has a very small transfer memory and excellent resistance to gas such as ozone and NOx. An object of the present invention is to provide a charged single-layer type electrophotographic photosensitive member.

Still another object of the present invention is to provide a reversal-developing digital image forming apparatus using the positively charged single-layer type electrophotographic photosensitive member of the present invention.

[0015]

Means for Solving the Problems As a result of intensive studies, the present inventors have formed a photosensitive layer on a conductive substrate to achieve the above object, and the photosensitive layer is a phthalocyanine compound as a charge generating agent. General formula (1) as an electron transport agent,
At least one compound represented by (2) or (3)
The positively-charged single-layer type electrophotographic photoreceptor, which is characterized by containing a seed and a terphenyl compound represented by the general formula (4), has a very small transfer memory and is resistant to gas such as ozone. I found the fact that it is excellent.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A positively charged single-layer type electrophotographic photosensitive member has a single photosensitive layer provided on a conductive substrate. This photosensitive layer is formed by dissolving or dispersing a charge generating agent, a hole transporting agent, an electron transporting agent, a binder resin, and the like in an appropriate solvent, applying the obtained coating solution on a conductive substrate, and drying. You.

Next, various materials used for the positively charged single-layer type electrophotographic photosensitive member of the present invention will be described in detail.

<Charge Generating Agent> At present, LEDs and semiconductor lasers are used as the light source of the digital image forming apparatus, but the oscillation wavelength thereof is about 740 nm or more and is limited to the infrared region. Therefore, at least 700-8
An organic photoreceptor having sensitivity in a wavelength region around 50 nm is required.

As the charge generator used in the organic photoreceptor satisfying the above requirements, for example, polycyclic quinone compounds, pyrylium compounds, squarium compounds, phthalocyanine compounds, azo compounds and the like are proposed or put into practical use. However, various phthalocyanine compounds are used in the positively charged single-layer type electrophotographic photoreceptor of the present invention.

In general, phthalosinine-based compounds include metal-free phthalosinins having no central metal (CGM-
1) and aluminum phthalocyanine, vanadium phthalosinine, cadmium phthalocyanine, antimony phthalosinine, chromium phthalosinine, copper 4-phthalosinine, germanium phthalosinine, iron phthalosinine, chloroaluminum phthalosinine, titanyl Phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalosinine, magnesium phthalosinine, dialkylphthalosinine, tetramethylphthalosinine, metal phthalocyanines having a central metal such as tetraphenylphthalosinine, and α-type, β
There are various crystal types such as type, γ-type, δ-type, ε-type, σ-type, and x-type, and any of them can be used. These phthalocyanine compounds can be used alone or as a blend of two or more.

(CGM-1)

Embedded image

The phthalocyanine compound is used in an amount of 0.1 to 20% by weight, especially 0.5 to 20% by weight, based on the weight of the binder resin.
It is preferable to contain 10 wt%.

<Electron transporting agent> The electron transporting agent used in the single-layer type electrophotographic photoreceptor of the present invention has a high electron mobility to reduce transfer memory, and has the general formula (1) according to claim 1, The compound represented by (2) or (3) is used.

When the above compounds are used as the electron transporting agent, they may be used alone or in at least one kind. That is, various electron transporting agents may be contained together with the compound.

Examples of various electron transporting agents include pyrene compounds, carbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, tetraphenylmethane compounds, Cyanoethyl, tetracyanoquinodimethane, chloranil, bromoanil, 2,
4,7-trinitro-9-fluorenone, 2,4,5,7-
Tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7
And electron-withdrawing substances such as -tetranitroxanthone, 2,4,8-trinitrothioxanthone, and those obtained by polymerizing these electron-withdrawing substances.

The content of the electron transporting agent is 5 to 100% by weight, more preferably 10 to 80% by weight based on the weight of the binder resin.
Is preferred.

<Hole transporting agent> The hole transporting agent used in the single-layer type electrophotographic photoreceptor of the present invention is preferably a compound represented by the general formula (6) or (7) according to claim 2 for reducing transfer memory. The compounds shown are preferably used.

When the above compounds are used as the hole transporting agent, they may be used alone or in at least one kind. That is, various hole transporting agents may be contained together with the compound.

Oxadiazole compounds such as 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, styryl compounds such as 9-4 (-diethylaminostyryl) anthracene, Carbazole compounds such as polyvinyl carbazole, organic polysilane compounds, pyrazoline compounds such as 1-phenyl-3 (p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds, indole compounds, oxazole compounds, iso Examples thereof include nitrogen-containing cyclic compounds such as oxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds. These hole transporting agents can be used alone or as a blend of two or more.

The content of the hole transporting agent is 5 to 500 wt% based on the weight of the binder resin, and more preferably 25 to 200 watts.
t% is preferred.

<Binder Resin> As the binder resin for dispersing the above components, various resins conventionally used in the photosensitive layer can be used.

For example, styrene-butadiene copolymer,
Styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, ionomer, Thermoplastic resin such as vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, silicone resin, epoxy resin , Phenolic resin,
Resins such as urea resins, melamine resins, other cross-linkable thermosetting resins, and photo-curing resins such as epoxy acrylate and urethane-acrylate can be used. These binder resins can be used alone or as a blend of two or more.

Particularly preferred resins are bisphenol Z-type polycarbonates derived from bisphenol Z-type monomers and phosgene, such as Panlite manufactured by Teijin Chemicals Limited and PCZ manufactured by Mitsubishi Gas Chemical Company, Ltd.

The weight average molecular weight of the binder resin of the above example is from 5,000 to 200,000, and more preferably from 15,000 to
100,000 is preferred.

<Additive> The positively charged single-layer type electrophotographic photoreceptor of the present invention is characterized in that the terphenyl compound according to claim 1 is particularly contained for the purpose of improving gas resistance such as ozone. I do. Although the details are not clear, it is considered that when the terphenyl compound is contained, molecules enter into fine voids on the surface of the photosensitive layer and hinder gas from entering the surface of the photosensitive layer.

The content of the terphenyl compound is 0.5 to 30% by weight, more preferably 1 to 30% by weight, based on the weight of the binder resin.
-10 wt% is preferred.

The thickness of the positively charged single-layer type electrophotographic photosensitive member of the present invention is preferably 5 to 50 μm, particularly preferably 15 to 35 μm.

In the positively charged single-layer type electrophotographic photosensitive member of the present invention, a barrier layer may be formed between the conductive substrate and the photosensitive layer as long as the characteristics of the photosensitive member are not impaired.

As the conductive base on which the photosensitive layer is formed, various conductive materials can be used.
For example, simple metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass, and plastic materials on which the above metals are deposited or laminated , Aluminum iodide, tin oxide,
Glass coated with indium oxide or the like can be given.

The conductive substrate may be in the form of a sheet, a drum, or the like, depending on the structure of the image forming apparatus to be used. The substrate itself has conductivity or the surface of the substrate is conductive. What is necessary is just to have the property. The conductive substrate preferably has a sufficient mechanical strength when used.

When the photosensitive layer is formed by a coating method, the above-described hole transporting agent, charge generating agent, electron acceptor, binder resin, etc., together with a suitable solvent, may be used in a known method.
For example, a dispersion may be prepared by dispersing and mixing using a roll mill, a ball mill, an attritor, a paint shaker, an ultrasonic disperser, or the like, and the dispersion may be applied by a known means and dried.

Various organic solvents can be used as a solvent for preparing the dispersion, for example, alcohols such as methanol, ethanol, isopropanol and butanol, and aliphatic solvents such as n-hexane, octane and cyclohexane. Hydrocarbons, aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, and chlorobenzene; dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether. Ethers, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and methyl acetate, dimethylformaldehyde, dimethylformamide, dimethyls Rufoxide and the like. These solvents are used alone or in combination of two or more.

Further, in order to improve the smoothness of the surface of the photosensitive layer, a leveling agent such as silicone oil may be used.

On the other hand, the image forming apparatus of the present invention has the following features.
Using the positively charged single-layer type electrophotographic photoreceptor described in the above, and including at least a main charging step, an exposure step, a development step, a transfer step, a charge removal step, and a cleaning step along a traveling direction of the photoreceptor; The voltage applied in the process is a reversal-developed digital image forming apparatus, which has a polarity opposite to that of the voltage applied in the charging process, and examples thereof include a digital copying machine, a facsimile, and a laser beam printer. Can be

The positively charged single-layer type electrophotographic photoreceptor of the present invention comprises:
As described above, since the transfer memory is very small, no memory image is generated even when used in the image forming apparatus. Further, since it has excellent resistance to gases such as ozone and NOx, even in a large-sized image forming apparatus in which a large amount of the gas is generated, image fogging and black stripes do not occur.

[0046]

The present invention will be described below with reference to examples and comparative examples. Note that the following embodiments are merely examples embodying the present invention, and do not limit the technical scope of the present invention.

<Examples 1 to 12> 2.2 parts by weight of an X-type metal-free phthalocyanine (CGM-1) as a charge generating agent and the general formula (1) [ET-101, -10] as an electron transporting agent
2), one kind (30 parts by weight) selected from general formulas (2) [ET-201, -202] and general formula (3) [ET-301, -302]; 5)
[HT-501], one kind (60 parts by weight) selected from the general formula (6) [HT-601], and a terphenyl compound selected from the general formula (4) [AD-401, -402] One type (3 parts by weight), 100 parts by weight of a bis-Z type polycarbonate resin having a weight average molecular weight of 50,000 as a binder resin, and 750 parts by weight of tetrahydrofuran are dispersed or dissolved in a ball mill for 20 hours to obtain a single-layer type photosensitive material. A coating solution for a layer was prepared. Then, this coating solution is applied on an aluminum tube as a support by a dip coating method, and dried with hot air at 130 ° C. for 45 minutes to obtain a positively charged unit having a single photosensitive layer having a thickness of 22.5 μm. A layer type photoreceptor was prepared.

Tables 1 to 3 show the structural formulas of the compounds used in the examples.

<Electron transport agent>

[Table 1]

<Hole transport agent>

[Table 2]

<Terphenyl compound>

[Table 3]

<Comparative Examples 1 and 2> ET- as an electron transporting agent
A positively charged single-layer type photoreceptor was produced in the same manner as in Examples 1 to 12, except that Examples 1 and 2 were used.

<Comparative Examples 3 to 14> Positively charged single-layer type photoconductors were prepared in the same manner as in Examples 1 to 12, except that no terphenyl compound was added.

Table 4 shows the structural formulas of the compounds used in Comparative Examples 1 and 2.

<Electron transport agent>

[Table 4]

The following characteristics were evaluated for the positively charged single-layer type electrophotographic photoreceptors of the above Examples and Comparative Examples. The evaluation results are shown in Tables 5 and 6.

<Evaluation of Light Sensitivity>
C) Drum sensitivity tester (Gentec Cynthia 3)
0M), an applied voltage was applied to the photoreceptors of the examples and comparative examples to charge the surfaces thereof to +700 V.

Next, monochromatic light having a wavelength of 780 nm (half-width 20 nm, extracted from white light of a halogen lamp, which is an exposure light source of the tester, using a band-pass filter).
A light intensity of 15 μW) was applied to the charged surface of the photoreceptor (exposure time: 40 msec). Then, the surface potential at the point when 330 msec had elapsed from the start of exposure was measured as the post-exposure potential VL (V). That is, the smaller the potential after exposure, the higher the sensitivity of the photoconductor.

<Evaluation of Transfer Memory> Using a digital copying machine CREAGE630 manufactured by Kyocera Mita Co., Ltd., the photoconductors of the respective examples and comparative examples were uniformly charged to +850 V by a main charger, and the reflection optical density was reduced. After outputting a halftone of about 0.5 and performing image exposure, a developing bias of +650 V was applied, and reversal development was performed with a two-component developer using positively charged toner. Then, the image was transferred to a transfer sheet at a transfer output of 6 kV, and after fixing, an image for evaluation was obtained.

A dark portion (transfer memory image) of the evaluation image, which appears in a band shape in the longitudinal direction of the photosensitive drum.
And an image density difference (ΔID) between the other portion and the other portion is not allowed to be 0.2 or more.

<Evaluation of Ozone Resistance> The surface potentials of the photoreceptors of the examples and comparative examples were measured using a digital copier CREAGE 7320 manufactured by Kyocera Mita Corporation, and then the photoreceptors were placed in a dark place. Then, it was exposed to an atmosphere having an ozone concentration of 10 ppm at room temperature for 10 hours, and the surface potential immediately after the exposure was measured in the same manner.

(Initial surface potential)-(surface potential immediately after exposure) =. DELTA.V0, and .DELTA.V0 was not allowed to be 60 V or more.

[0063]

[Table 5]

[0064]

[Table 6]

As apparent from Tables 5 and 6, claim 1
It can be understood that the presence of the electron transporting agent greatly affects the difference in image density, that is, memory resistance, and the presence of the terphenyl compound greatly affects ozone resistance.

[0066]

The electrophotographic photoreceptor of the present invention has a very small transfer memory and does not generate a transfer memory image even when used in a digital image forming apparatus of a reversal developing system. Further, because of its excellent gas resistance such as ozone and NOx, even in a large-sized image forming apparatus in which the gas is generated in a large amount,
No image fogging or black streaks occur.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 5/06 315 G03G 5/06 315Z 319 319 5/05 104 5/05 104B F-term (reference) 2H068 AA14 AA19 AA20 AA31 BA12 BA13 BA14 BA16 BA38 BA60 BA63 BA64 BB26 FA02 FC02

Claims (3)

[Claims] 1. A photosensitive layer is formed on a conductive substrate. The photosensitive layer comprises a phthalocyanine compound as an electrification generator and a compound represented by the general formula (1), (2) or (3) as an electron transporting agent. A positively charged single-layer type electrophotographic photoreceptor comprising at least one kind and a terphenyl compound represented by the general formula (4). General formula (1): (In the general formula (1), R ¹ and R ² are the same or different and represent a monovalent hydrocarbon group which may have a substituent.) The general formula (2): (In the general formula (2), R ³ and R ⁴ are the same or different and are an alkyl group, a halogenated alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, an alkoxycarbonyl group. , An aryloxycarbonyl group, an aralkyloxycarbonyl group or a nitro group, and n represents an integer of 0 to 3.) General formula (3): (In the general formula (3), R ⁵ and R ⁶ are the same or different and represent a monovalent hydrocarbon group which may have a substituent.) A general formula (4): (In the general formula (4), R ⁷ , R ⁸ , and R ⁹ are the same or different and each represent a hydrogen atom or an alkyl group, an aryl group, or an amino group which may have a substituent.) 2. A compound represented by the following general formula (5) or (2):
Contains at least one compound represented by (6)
The positively charged single-layer type electrophotographic photosensitive member according to claim 1, wherein
body. General formula (5):(In the general formula (5), R^TenAnd R¹²Are the same or different
An alkyl group which may have a substituent,
Aryl groups, which may have a substituent, aralkyl
A group or an alkoxy group;¹¹And R¹³Is the same
Or differently, a hydrogen atom, which may have a substituent,
Represents a kill group or an alkoxy group. Where R¹¹And R
¹³Is substituted at the para position,¹¹And R¹³Is hydrogen field
I am a child. General formula (6):(In the general formula (6), R14 and R16 are the same or different.
R represents an alkyl group ^Fifteen, R¹⁷Are the same or different
Shows a hydrogen atom or an alkyl group. ) 3. The method according to claim 1, wherein the positively charged single-layer type electrophotographic photoreceptor is used along a traveling direction of the electrophotographic photoreceptor.
It comprises at least a main charging step, an exposure step, a developing step, a transferring step, a discharging step and a cleaning step, wherein the polarity of the voltage applied in the transferring step is negative and the polarity of the voltage applied in the charging step is positive. A reversal-developing digital image forming apparatus.