JPH10142828A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming of a reversible development system low in cost and ozone conc. without needing an electrifier for discharge and capable of forming a good electrostatic image by incorporating a charge generating material(CGM) into an overcoating layer(OCL) and irradiating the layer with pre-exposure light after transfer. SOLUTION: This device is equipped with an electrophotographic photoreceptor having a layer (CGL) containing a material which generates charges by absorption of light, a layer (CTL) containing a material (CTM) which transfers the charges produced in the CGL, and OCL containing both of CTM and CGM successively formed in this order on a conductive base body. The device is equipped with an electrifying device 15 for transfer having opposite polarity to the electrification polarity to give photosensitivity and with a discharging part 12 with light (pre-exposure part). Namely, the toner is transferred by the transfer electrifier 15 in the opposite polarity to that of the main electrifier 11, the toner is completely discharged by the discharging part 12 with light to return to the main electrifier. Thus, the electrifier for discharge is unnecessitated in the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a transfer charging means having a polarity opposite to the charging property for imparting photosensitivity to a photosensitive member.

[0002]

2. Description of the Related Art In recent years, as an electrophotographic image forming apparatus for a digital copying machine, a laser printer, a plain paper facsimile, etc., in order to form a toner image on an image exposed portion,
A so-called reversal development system using a transfer charger having a polarity opposite to that of the main charging has come to be used.

A photoreceptor used in an image forming apparatus using the above-described reversal developing method is a function-separated type in which CGL and CTL are laminated on a conductive substrate in this order from the viewpoint of high sensitivity and durability. Electrophotographic photoreceptors are mainly used.

However, a photoreceptor having such a layer structure has high sensitivity only at a single polarity and hardly has photosensitivity at a reverse polarity because of the above-mentioned layer structure. In the reversal development method, the main charge → image exposure → development by toner having the same polarity as the main charge → transfer charge of the opposite polarity to the main charge is repeatedly performed. Due to the influence, the charge is unevenly charged to a polarity opposite to that of the main charge. This non-uniform charging is of the opposite polarity to the main charging polarity,
Since the photoreceptor shows almost no sensitivity to this polarity, it is impossible to uniformly remove the light from the photosensitive member, and the charge becomes apparently non-uniform at the time of the next main charging, leading to an image defect. This phenomenon is more remarkable in a high-humidity environment where the resistance of the transfer paper decreases due to the moisture absorption of the transfer paper.

[0005] Therefore, various methods have been disclosed in the prior art in order to uniformly remove static electricity in an electrophotographic image forming apparatus using a reversal development system.

In JP-A-57-176087 and JP-A-58-80656, photocarriers are generated on the CTL surface by using static elimination light absorbed by the CTL surface layer, and the photosensitivity at the opposite polarity is utilized. I have. However, the CTL absorption light requires only a small light sensitivity and requires a large amount of charge removal.

[0007] Further, the light absorption of the CTL tends to form a charge trap at the same time as the generation of photocarriers, and causes a decrease in sensitivity at the residual potential and main charging polarity.

[0008] JP-A-58-90651 and JP-A-5-90651
JP-A-9-95582, JP-A-59-180575, JP-A-61-20081, JP-A-61-26
No. 4,370, JP-A-63-169684 and JP-A-64-25183, in order to make the polarity after transfer the same as that of the main charge, the same polarity as the main charge between the transfer and the light removal. Is provided.

[0009] However, the increase in the number of chargers for static elimination not only increases the size and cost of the image forming apparatus, but also causes electrical fatigue of the photoreceptor and ozone and nitrogen oxides generated by corona discharge of the charger. , The durability of the photoconductor is reduced.

The same applies to Japanese Patent Application Laid-Open No. 1-170974.

In the method disclosed in Japanese Patent Application Laid-Open No. 6-51538, it is possible to remove transfer charges of the opposite polarity by static elimination light in a photoreceptor obtained by adding CGM to CTL. There is an adverse effect such that the charge formed on the surface of the photoreceptor due to charging for imparting photosensitivity increases dark decay of the charge.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic image forming apparatus using a so-called reversal developing system using a transfer means having a polarity opposite to the charging (main charging) polarity for imparting photosensitivity. An object of the present invention is to provide a new image forming apparatus for solving the above-mentioned problems.

[0013]

SUMMARY OF THE INVENTION The present invention provides a layer (CGL) containing a material (CGM) that absorbs light and absorbs light on a conductive substrate and a material (CTM) that transports the charge generated in the CGL. ) Containing layer (CTL) and CTM
And a surface coating layer (OCL) containing both CGM and CGM, in this order, an electrophotographic photosensitive member, a transfer charging unit having a polarity opposite to the charging polarity for imparting photosensitivity, and a charge removing unit using light. And an image forming apparatus characterized by having:

In the present invention, a layer (CGL) containing a material (CGM) for absorbing light and generating a charge and a material (CTM) for transporting the charge generated in the CGL are included on a conductive substrate. Layer (CTL) and CTM and CG
By using an electrophotographic photoreceptor obtained by laminating a surface coating layer (OCL) containing both M in this order,
The above object has been achieved.

OCL has a spectral sensitivity corresponding to the spectral absorption of the contained CGM by containing CGM, and has a light sensitivity of the opposite polarity to that of main charging. However,
The spectral sensitivity at the main charging polarity of the photoconductor is CG in OCL.
Desensitized by the spectral absorption of M. Therefore, CGM contained as a main component in CGL and CGM contained in OCL
It is desirable that the spectral absorption differs from that of GM.

However, in order to remove the main charge and to remove the reverse charge due to the transfer, the CGM contained in the CGL and the CGM contained in the OCL need to have both sensitivity to irradiation light for light removal. There is.

As CGM in OCL and CGL, azo pigments, phthalocyanine pigments,
Examples include polycyclic quinone pigments, perylene pigments, squarium salt pigments, and trigonal crystalline selenium pigments.

In the OCL, CTM and CTM are simultaneously performed.
Must be contained. This is because if the OCL does not contain CTM when the carrier generated by CGL is transported to the CTL surface in a series of electrophotographic processes,
This is because carriers are trapped at the boundary between CTL and OCL, causing an increase in residual potential.

As the CTM in OCL and CTL, pyrene compounds, carbazole compounds,
Examples include hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, pyrazoline compounds, styryl compounds, stilbene compounds, and the like.

The OCL may further contain an antioxidant, a nitric acid-resistant compound, an ultraviolet absorber, a photodeterioration inhibitor, a radical trapping agent, a leveling agent, a lubricant and the like in order to improve the function of the photoreceptor. In particular, by adding a lubricant such as polytetrafluoroethylene to the OCL, the amount of abrasion of the photosensitive layer during a series of copying processes can be reduced to maintain the effect of the present invention.

FIG. 1 and FIG. 2 are schematic cross-sectional views for explaining the structure of a specific example of a photosensitive member suitable for use in the image forming apparatus of the present invention. is there.

FIG. 1 shows a CGL 3 and a CT on a conductive substrate 4.
This is an example of a photoconductor in which an OCL1 containing CGM7 is provided on L2.

FIG. 2 shows an example in which the conductive substrate 4 and the CGL 3
This is an example in which an undercoat layer 5 is provided therebetween, and the structure of other portions is the same as the example shown in FIG.

On the other hand, FIGS. 3 and 4 show examples of a conventional photosensitive member, FIG. 3 shows an example in which the OCL 1 is not provided in the example of FIG. 1, and FIG. 4 shows an example in which the OCL 1 is provided in the example of FIG. This is an example that is not provided.

FIGS. 5 and 6 show an example of a photoreceptor provided with CTL6 containing CGM7 instead of CTL2 in the examples shown in FIGS.

FIG. 7 shows an image forming apparatus using a conventional photoconductor, in which a main charger 1 is provided around a cylindrical photoconductor 10.
1, an image exposure light source 9, a light removing unit 12, a cleaning device 13, a removing charger 14, a transfer charger 15, a separation charger 16, and a developing unit 18.

Photoreceptor 10 main charged by main charger 11
Is to obtain an electrostatic latent image by exposure 9 corresponding to the image pattern,
The developing unit 18 develops the toner by toner having the same polarity as the main charge. Then, the toner is transferred by the transfer charge 15 having the opposite polarity to the main charge.
Is transferred to a transfer material, and in order to facilitate the removal of the charge on the photoreceptor 10 unevenly charged by the transfer charge, a charge 14 for static elimination having the same polarity as the main charge is performed. After the charge is removed, the flow returns to the main charge 11 again.

On the other hand, the image forming apparatus using the photoreceptor of the present invention has the same structure as shown in FIG. 8 except that the charge removing charger 14 shown in FIG. 7 is eliminated. .

FIG. 9 further includes a main charging roller 20 in place of the main charger 11 shown in FIG.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An undercoat layer is formed on a conductive substrate having a conductive layer provided on an aluminum cylinder, and then a C layer is formed.
Poly (vinyl acetate-)
A dispersion obtained by dispersing together with vinyl alcohol-vinyl benzal) and cyclohexanone was dip-coated on the undercoat layer to form CGL.

Next, a dispersion obtained by dispersing a triphenylamine compound as a CTM together with a polycarbonate resin, monochlorobenzene and dichloromethane was used for the above-mentioned CG.
The CTL was formed by dip coating on L.

Next, a dispersion obtained by dispersing the triphenylamine compound as CTM, polycarbonate resin, disazo pigment as CGM, monochlorobenzene and dichloromethane was spray-coated on the CTL. An OCL was formed to prepare an electrophotographic photosensitive member.

The electrophotographic photoreceptor thus produced has the same polarity as the main charge installed in front of a cleaning device of a digital copying machine (trade name: CLC-550) manufactured by Canon Inc. as schematically shown in FIG. An image forming apparatus of the present invention was obtained by combining the apparatus with the charge removing device 4 for charging, which was removed (schematically shown in FIG. 8).

[0034]

【Example】

Example 1 Conductive titanium oxide (tin oxide, antimony oxide,
5 parts by weight of an average primary particle size of 0.4 μm, 5 parts by weight of high-resistance titanium oxide (alumina coat, average particle size of 0.4 μm), 10 parts by weight of a phenol resin precursor (resole type),
After 10 parts by weight of methanol and 10 parts by weight of butanol are dispersed in a sand mill, they are dip-coated on an aluminum cylinder having an outer diameter of 80 mm and a length of 360 mm, and then heat-cured to have a volume resistance of 5 × 10 ⁹ Ωcm and a thickness of 20 μm. A conductive layer was formed.

Next, 3 parts by weight of a methoxymethylated nylon (methoxymethylation degree: about 30%) represented by the following compound 1,

Embedded image After mixing and dissolving 9 parts by weight of 6/66/610/12 quaternary copolymer nylon and 150 parts by weight of isopropanol,
By dip coating on the conductive layer, an undercoat layer of 1 μm was formed.

Next, 10 parts by weight of a disazo pigment of the following compound 2

Embedded image

The poly (vinyl acetate) of the following compound 3
Vinyl alcohol-vinyl benzal (molecular weight: 8,000
0) 5 parts by weight, compound 3

Embedded image And 700 parts by weight of cyclohexanone were sand-mill-dispersed, and the resulting dispersion was dip-coated on the undercoat layer.
A 05 μm CGL was formed.

Next, 10 parts by weight of a triphenylamine compound of the following compound 4, compound 4

Embedded image

10 parts by weight of a polycarbonate resin (Bisphenol Z, molecular weight Mw 25000) of the following compound 5,

Embedded image Monochlorobenzene 50 parts by weight and dichloromethane 25
Parts by weight were dispersed in a sand mill, and this dispersion was applied onto the CGL by dip coating and dried with hot air to form a 20 μm CTL.

Next, 8 parts by weight of the triphenylamine compound of the compound 4, 16 parts by weight of a polycarbonate resin (bisphenol Z, molecular weight of 80,000) of the compound 5, and 0.1 part by weight of a disazo pigment of the compound 2 Then, 600 parts by weight of monochlorobenzene and 400 parts by weight of dichloromethane were dispersed in a sand mill, and this dispersion was spray-coated on the CTL and dried with hot air to form an OCL of 5 μm to prepare an electrophotographic photosensitive member.

Example 2 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the CGM contained in the OCL was replaced by a disazo pigment of the following compound 6. Compound 6

Embedded image

Example 3 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the CGM contained in the OCL was replaced by a disazo pigment of the following compound 7. Compound 7

Embedded image

Example 4 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that CGL was formed by the following method.

Crystal powder of oxotitanylphthaloshanine of the following compound 8 (Bragg angles 2θ ± 0.2 ° in CuKα characteristic X-ray diffraction are 9.0 °, 14.2 ° and 27.
4 parts by weight having a strong peak at 1 °) Compound 8

Embedded image 2 parts by weight of a butyral resin (trade name: SREC BM-2, manufactured by Sekisui Chemical Co., Ltd.) and 135 parts by weight of cyclohexanone are dispersed in a sand mill, and the dispersion is diluted with ethyl acetate. The CGL having a film thickness of 0.15 μm was formed by dip coating and hot-air drying on the undercoat layer.

Example 5 In Example 4, CGM contained in OCL was replaced with Compound 6.
An electrophotographic photoreceptor was prepared in the same manner except that the disazo pigment was used.

Example 6 In Example 4, CGM contained in OCL was replaced with Compound 7.
An electrophotographic photoreceptor was prepared in the same manner except that the disazo pigment was used.

Example 7 In Example 1, 8 parts by weight of the triphenylamine compound of compound 4 and the polycarbonate solution of compound 5 were used as the OCL coating solution.
Bone resin (Bisphenol Z, molecular weight 80000)
16 parts by weight, 0.1 part by weight of a disazo pigment of Compound 2, fine powder of polytetrafluoroethylene (average primary particle size of 0.2
An electrophotographic photoreceptor was prepared in the same manner except that 6 parts by weight of 0 μm, molecular weight Mw 400,000, 6 parts by weight of an emulsion polymerization product, 650 parts by weight of monochlorobenzene and 450 parts by weight of dichloromethane were subjected to sand mill dispersion, and this dispersion was used.

Example 8 Digital copier manufactured by Canon Inc., trade name: CLC-55
The charger for static elimination (corresponding to 14 shown in FIG. 7) installed in front of the cleaning device 0 was removed to form an image forming apparatus (schematic diagram shown in FIG. 8).

Comparative Example 1 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the thickness of the CTL was 25 μm and no OCL was provided.

Comparative Example 2 In Example 1, as a CTL coating solution, 10 parts by weight of a triphenylamine compound of Compound 4 and a polycarbonate resin of Compound 5 (bisphenol Z, molecular weight Mw 250)
00) 10 parts by weight, 0.1 part by weight of the disazo pigment of compound 2, 50 parts by weight of monochlorobenzene and 25 parts by weight of dichloromethane were subjected to sand mill dispersion, and the electrophotographic photoreceptor was prepared in the same manner except that this dispersion was used. Created.

Comparative Example 3 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that a liquid containing no disazo pigment of Compound 2 was used as the OCL coating liquid.

Comparative Example 4 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that a liquid not containing the triphenylamine compound of Compound 4 was used as a coating liquid for OCL.

Comparative Example 5 Digital copier manufactured by Canon Inc., trade name: CLC-55
0 was used as an image forming apparatus for a comparative example.

Image Evaluation Image evaluation was performed in an environment of 30 ° C. and a relative humidity of 80%. The electrophotographic photoreceptors prepared in Example 1 and Comparative Example 1 were installed in the image forming apparatus of Example 8, respectively. The negative charging main charging current was 570 μA, the charging voltage was −450 V, and the positive charging transfer current was 200 μm. A halftone image is formed using four color toners of cyan, magenta, yellow and black so that the toner density on the transfer paper after setting, transferring and fixing is 0.3 in reflection density. I put it out.

As a result, when the electrophotographic photosensitive member of Example 1 was used, a uniform halftone image was obtained.
In the case where the electrophotographic photosensitive member of Comparative Example 1 was used, the photosensitive member was placed at a position corresponding to a portion which was once subjected to transfer charge on the photosensitive member.
The toner density after the color tone increased, and the image density became non-uniform.

The same image evaluation was performed in Examples 2, 3, 4, 5,
6 and 7 and the electrophotographic photosensitive members prepared in Comparative Examples 2 and 3.

As a result, in the photosensitive member of Comparative Example 3, Comparative Example 1
Although non-uniformity in image density was observed as in the case of the photoconductor of Example 2, it was not observed in the photoconductors of Examples 2, 3, 4, 5, 6, 7 and Comparative Example 2. However, in the case of the photoreceptor of Comparative Example 2, a black-spotted image defect was observed on the entire surface of the image.

Further, the electrophotographic photosensitive members of Examples 1, 2, 3, 4, 5, 6, and 7 and Comparative Examples 1 and 2 were installed in the image forming apparatus of Example 8, respectively, and 1,000 sheets were continuously printed. A paper durability test was performed. At this time, the dark portion potential (Vd) on the photoreceptor immediately after the main charging after the end of the durability test and after the 1000-sheet run, the residual potential (Vr) after the durability test, and the ozone concentration near the photoconductor after the durability test were measured.

As a result, Examples 1, 2, 3, 4, 5,
In the photoconductors of Comparative Examples 2 and 7, before and after the durability test, no potential fluctuation which was a problem in the electrophotographic process was observed, but in the photoconductor of Comparative Example 2, Vd before the durability test was observed.
Was -460 V, whereas Vd after the durability test was -3.
It had changed to 95V. The ozone concentration was 0.1 ppm or less in each case.

Next, the image forming apparatus of Comparative Example 5 was used in Example 1
And installing the electrophotographic photosensitive members of Comparative Examples 1, 2, 3, and 4,
The settings were the same as in Example 8 above, except that the current of the negatively charged charger for discharging was set to 100 μA.

As a result, with respect to the image quality, a uniform halftone image was obtained with the photoconductors of Example 1 and Comparative Examples 1 and 3, but a black spot-like image defect was obtained with the photoconductor of Comparative Example 2. Was seen. Further, with respect to the photoreceptor of Comparative Example 4, a halftone image could not be obtained due to an increase in residual potential.

Further, in the same manner as in the case of using the image forming apparatus of the eighth embodiment, 10
A paper passing durability test was performed on 00 sheets. When the ozone concentration near the photoreceptor after the durability test was measured, all were 1.5 pp.
m or more.

Tables 1 and 2 show the above-described image evaluation, potential characteristics, and measured values of ozone concentration.

[Table 1]

[Table 2]

[0064]

According to the image forming apparatus of the present invention, the C
Since it contains GM and irradiates pre-exposure after transfer, it is an image forming apparatus of the reversal development type, and does not require a charger for static elimination. It has a remarkable effect that it can be obtained repeatedly.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of each specific example of an electrophotographic photosensitive member used in the present invention.

FIG. 2 is a schematic cross-sectional view showing a configuration of each specific example of an electrophotographic photosensitive member used in the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of the configuration of a conventional electrophotographic photosensitive member.

FIG. 4 is a schematic cross-sectional view showing an example of the configuration of a conventional electrophotographic photosensitive member.

FIG. 5 is a schematic cross-sectional view showing an example of the configuration of a conventional electrophotographic photosensitive member.

FIG. 6 is a schematic cross-sectional view showing an example of the configuration of a conventional electrophotographic photosensitive member.

FIG. 7 is a schematic diagram illustrating an example of a configuration of a conventional image forming apparatus.

FIG. 8 is a schematic diagram showing a configuration of each specific example of the image forming apparatus of the present invention.

FIG. 9 is a schematic diagram showing a configuration of each specific example of the image forming apparatus of the present invention.

[Explanation of symbols]

 1: OCL containing CGM 2: CTL 3: CGL 4: conductive substrate 5: undercoat layer 6: CTL containing CGM 7: dispersed CGM 8: original 9: image exposure light source 10: photoconductor 11: Main charger 12: Light eliminator (pre-exposure) 13: Cleaning device 14: Charger for static elimination 15: Transfer charger 16: Separation charger 17: Paper feed 18: Developing device 19: Fixing device 20: Contact charging vessel

Claims (2)

[Claims] 1. A layer (CGL) containing a material (CGM) that absorbs light and generates a charge on a conductive substrate, and a CGL
An electrophotographic photoreceptor obtained by laminating a layer (CTL) containing a material (CTM) for transporting charges generated in the above and a surface coating layer (OCL) containing both CTM and CGM in this order; An image forming apparatus comprising: a transfer charging unit having a polarity opposite to a charging polarity for applying a charge; 2. The method according to claim 1, wherein the irradiating light for the charge elimination is CG
2. The image forming apparatus according to claim 1, wherein both CGM included in L and CGM included in OCL have sensitivity.