JP3432093B2 - Image forming device - Google Patents

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 that of a charging property for imparting photosensitivity to a photoconductor.

[0002]

2. Description of the Related Art Recently, 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 method using a transfer charger having a polarity opposite to that of the main charging has come to be used.

The photosensitive member used in the image forming apparatus using the reversal development method is of a function separation type in which CGL and CTL are laminated in this order on a conductive substrate in terms of high sensitivity and durability. Electrophotographic photoreceptors are mainly used.

However, since the photoconductor having this kind of layer structure has the above-mentioned layer structure, it has high sensitivity only with a single polarity and almost no photosensitivity with the opposite polarity. In the reversal development method, main charging → image exposure → development by a toner having the same polarity as main charging → transfer charging with a polarity opposite to the main charging is repeatedly performed, so that the surface of the photosensitive member passing through the transfer portion is not covered by the image pattern. Due to the influence, it is unevenly charged with the opposite polarity to the main charge. This non-uniform charging has a polarity opposite to the main charging polarity,
Since the photosensitive member shows almost no sensitivity to this polarity, uniform photo-discharging cannot be performed, resulting in apparently non-uniform charging during the next main charging, leading to image defects. This phenomenon is more remarkable in a high humidity environment in which the resistance of the transfer paper decreases due to the moisture absorption of the transfer paper.

In view of this, various methods have been disclosed in the prior art for uniformly removing static electricity in an electrophotographic image forming apparatus using the reversal development method.

In JP-A-57-176087 and JP-A-58-80656, charge-eliminating light absorbed in the CTL surface layer is used to generate photo carriers on the CTL surface, and photosensitivity in reverse polarity is utilized. There is. However, with CTL absorbed light, only a small photosensitivity can be expected, and a large amount of static elimination light is required.

Further, the light absorption of CTL easily forms charge traps at the same time as the generation of photocarriers, resulting in a decrease in sensitivity in the residual potential and the main charging polarity.

Japanese Unexamined Patent Publication Nos. 58-90651 and 5
9-95582, JP-A-59-180575, JP-A-61-20081, JP-A-61-26.
In Japanese Patent Laid-Open No. 4370, Japanese Patent Application Laid-Open No. 63-169684, and Japanese Patent Application Laid-Open No. 64-25183, in order to make the polarity after transfer the same as the main charging, the same polarity as the main charging is provided between the transfer and the photo-electrification. Is equipped with a charger for static elimination.

However, the addition of a charger for removing static electricity not only increases the size of the image forming apparatus and raises the cost, but also ozone and nitrogen oxides generated by electrical fatigue of the photoconductor and corona discharge of the charger. The durability of the photoconductor is deteriorated due to the influence of.

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

Further, according to the method disclosed in Japanese Patent Laid-Open No. 6-51538, it is possible to remove transfer charges of opposite polarity in a photoconductor in which CGM is added to CTL by removing charge, but black spots and Due to the charging for imparting photosensitivity, the dark decay of the charges formed on the surface of the photoconductor becomes large, which causes a problem.

[0012]

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

[0013]

SUMMARY OF THE INVENTION The present invention is an electrophotographic photosensitive material.
The electrophotographic photosensitive member is provided with a body, and
Main charger or main charger for main charging the sub-photoreceptor
Roller, exposure with toner of the same polarity as the main charge
The electrostatic latent image on the electrophotographic photosensitive member obtained by
Developing device for image, transfer charging of the opposite polarity to the main charging
Transfer the image developed by the toner to the transfer material
The transfer charger and the light
This is the order in which the light neutralization unit for neutralizing the charges on the true photoconductor is removed.
In the image forming apparatus provided for, the electrophotographic photoreceptor
On a conductive substrate, a layer (CGL) containing a material (CGM) that absorbs light to generate an electric charge and a layer (CC) containing a material (CTM) that conveys an electric charge generated in the CGL.
TL) and a surface coating layer (OCL) containing both CTM and CGM in this order.
In addition, between the transfer charging device and the light charge eliminating portion, there is no charge removing charger for making the polarity of the electrophotographic photosensitive member after the transfer charging the same as the main charging. It is composed of a characteristic image forming apparatus.

In the present invention, a layer (CGL) containing a material (CGM) that absorbs light to generate charges and a material (CTM) that transports charges generated in CGL are contained on a conductive substrate. Layer (CTL) and CTM and CG
By using an electrophotographic photoreceptor formed by laminating a surface coating layer (OCL) containing both M in this order,
The above object is achieved.

By containing CGM, OCL has a spectral sensitivity corresponding to the spectral absorption of the contained CGM and has a photosensitivity opposite to that of the main charge. However,
The spectral sensitivity of the main charging polarity of the photoconductor is CG in OCL.
It is desensitized by the spectral absorption of M. Therefore, CGM contained as a main component in CGL and C contained in OCL
It is desirable to have different spectral absorption from GM.

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

Azo pigments, phthalocyanine pigments, which are conventionally known as CGM in OCL and CGL,
Examples thereof include polycyclic quinone pigments, perylene pigments, squalium salt pigments, and trigonal crystal selenium pigments.

Also, during OCL, CTM and CTM
Must be included. This is because if CGL is not contained in OCL when the carrier generated in CGL in a series of electrophotographic processes is transported to the CTL surface,
This is because carriers are trapped at the boundary between CTL and OCL and the residual potential increases.

A pyrene compound, a carbazole compound, which is conventionally known as CTM in OCL and CTL,
Examples thereof include hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, pyrazoline compounds, styryl compounds and stilbene compounds.

Further, the OCL may contain an antioxidant, a nitric acid resistant compound agent, an ultraviolet absorber, a photodegradation inhibitor, a radical trap agent, a leveling agent, a lubricant and the like in order to improve the function of the photoreceptor. In particular, the effect of the present invention can be sustained by adding a lubricant such as polytetrafluoroethylene to OCL to reduce the amount of abrasion of the photosensitive layer during a series of copy processes.

1 and 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 CGL3, CT on a conductive substrate 4.
It is an example of a photoconductor in which OCL1 containing CGM7 is provided on L2.

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

On the other hand, FIGS. 3 and 4 show an example of a conventional photoconductor, FIG. 3 shows an example in which OCL1 is not provided in the example of FIG. 1, and FIG. 4 shows OCL1 in the example of FIG. This is an example not provided.

Further, FIGS. 5 and 6 are examples of the photoconductor in which CTL6 containing CGM7 is provided in place of CTL2 in the examples of FIGS. 3 and 4.

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

Photoreceptor 10 main charged by main charger 11.
Obtains an electrostatic latent image by exposure 9 according to the image pattern,
In the developing section 18, the toner is developed by a toner having the same polarity as the main charge. Then, the toner is transferred by the transfer charging 15 having a polarity opposite to that of the main charging.
After being transferred to a transfer material, in order to make it easier to remove the charges on the photoconductor 10 that are non-uniformly charged by the transfer charging, the discharging 14 having the same polarity as the main charging is performed, and the charge is completely removed by the optical discharging 12. The charge is removed, and the main charging 11 is resumed.

On the other hand, as shown in FIG. 8, the image forming apparatus using the photoconductor of the present invention has a similar structure except that the charge eliminating charger 14 shown in FIG. 7 is omitted. .

Further, FIG. 9 is provided with a main charging roller 20 in place of the main charger 11 shown in FIG.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An undercoat layer is formed on a conductive substrate provided with a conductive layer on an aluminum cylinder, and then C
The disazo pigment as GM is poly (vinyl acetate)
CGL was formed by dip-coating the dispersion obtained by dispersing together with vinyl alcohol-vinyl benzal) and cyclohexanone on the undercoat layer.

Next, the dispersion obtained by dispersing the triphenylamine compound as the CTM together with the polycarbonate resin, monochlorobenzene and dichloromethane was used as the CG.
D was dip-coated on L to form CTL.

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

The electrophotographic photosensitive member thus prepared is schematically shown in FIG. 7, and has the same polarity as the main charging installed in front of the cleaning device of the digital copying machine (trade name CLC-550) manufactured by Canon Inc. An image forming apparatus of the present invention was obtained by combining with an apparatus (schematic shown in FIG. 8) from which the discharging charger 4 for charging is removed.

[0034]

【Example】

Example 1 Conductive titanium oxide (tin oxide, antimony oxide coat,
5 parts by weight of average primary particle size of 0.4 μm, 5 parts by weight of high resistance titanium oxide (alumina coat, 0.4 μm of average primary particle size), 10 parts by weight of phenol resin precursor (resor type),
After 10 parts by weight of methanol and 10 parts by weight of butanol were dispersed in a sand mill, the aluminum cylinder having an outer diameter of 80 mm and a length of 360 mm was dip-coated and 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 methoxymethylated nylon represented by the following compound 1 (degree of methoxymethylation of about 30%), compound 1

[Chemical 1] 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, compound 2

[Chemical 2]

Poly (vinyl acetate) of the following compound 3
Vinyl alcohol-vinyl benzal (molecular weight 8000
0) 5 parts by weight, compound 3

[Chemical 3] And 700 parts by weight of cyclohexanone are dispersed in a sand mill, and the dispersion is 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

[Chemical 4]

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

[Chemical 5] 50 parts by weight of monochlorobenzene and 25 parts of dichloromethane
Parts by weight were dispersed in a sand mill, and the dispersion was dip-coated on the CGL 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 the polycarbonate resin of the compound 5 (bisphenol Z, molecular weight 80000), 0.1 part by weight of the 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 the dispersion was spray-coated on the CTL and dried with hot air to form an OCL of 5 μm to prepare an electrophotographic photoreceptor.

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

[Chemical 6]

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

[Chemical 7]

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.

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

[Chemical 8] 2 parts by weight of butyral resin (trade name: S-REC BM-2, manufactured by Sekisui Chemical Co., Ltd.) and 135 parts by weight of cyclohexanone were dispersed in a sand mill, and the dispersion was diluted with ethyl acetate, and then formed in the same manner as in Example 1. Dip coating and hot air drying were performed on the formed undercoat layer to form a CGL having a film thickness of 0.15 μm.

Example 5 In Example 4, the CGM contained in OCL was treated with the compound 6
An electrophotographic photosensitive member was prepared in the same manner except that the disazo pigment of 1 was replaced.

Example 6 In Example 4, CGM contained in OCL was treated with compound 7
An electrophotographic photosensitive member was prepared in the same manner except that the disazo pigment of 1 was replaced.

Example 7 In Example 1, as the OCL coating liquid, 8 parts by weight of the triphenylamine compound of the compound 4 and the polycarbonate of the compound 5 were used.
Bone resin (bisphenol Z, molecular weight 80,000)
16 parts by weight, 0.1 part by weight of the disazo pigment of Compound 2, polytetrafluoroethylene fine powder (average primary particle size 0.2
0 μm, molecular weight Mw 400000, emulsion polymerization product) 6 parts by weight, monochlorobenzene 650 parts by weight and dichloromethane 450 parts by weight were sand mill dispersed, and an electrophotographic photosensitive member was prepared in the same manner except that this dispersion was used.

Example 8 Canon Co., Ltd. digital copying machine, trade name CLC-55
The charge eliminating charger (corresponding to 14 shown in FIG. 7) installed in front of the cleaning device No. 0 was detached and used as an image forming apparatus (shown schematically in FIG. 8).

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

Comparative Example 2 In Example 1, as a CTL coating liquid, 10 parts by weight of a triphenylamine compound of Compound 4, a polycarbonate resin of Compound 5 (bisphenol Z, molecular weight Mw 250) were used.
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 dispersed in a sand mill, and an electrophotographic photosensitive member was obtained 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 the OCL coating liquid did not contain the compound 2 disazo pigment.

Comparative Example 4 An electrophotographic photosensitive member was prepared in the same manner as in Example 1, except that the coating liquid for OCL did not contain the triphenylamine compound of Compound 4.

Comparative Example 5 Canon Co., Ltd. digital copying machine, trade name CLC-55
0 was used as the image forming apparatus for the comparative example.

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

As a result, when the electrophotographic photoreceptor of Example 1 was used, a uniform halftone image was obtained.
When the electrophotographic photosensitive member of Comparative Example 1 was used, 2
The toner density after the color increases and the image density becomes non-uniform.

Similar image evaluations were carried out in Examples 2, 3, 4, 5,
The electrophotographic photoconductors prepared in Examples 6 and 7 and Comparative Examples 2 and 3 were used.

As a result, in the photoconductor of Comparative Example 3, Comparative Example 1
The non-uniformity in image density as seen with the photoconductor of Example 1 was observed, but not with the photoconductors of Examples 2, 3, 4, 5, 6, 7 and Comparative Example 2. However, in the photoconductor of Comparative Example 2, black spot-like image defects were observed on the entire surface of the image.

Further, the electrophotographic photoconductors of Examples 1, 2, 3, 4, 5, 6, 7 and Comparative Examples 1 and 2 were respectively installed in the image forming apparatus of Example 8 and 1,000 continuous sheets were passed. A paper durability test was conducted. At this time, the dark potential on the photoconductor (Vd) at the initial stage of the durability test and after the 1000-sheet durability and immediately after the main charging, the residual potential after the durability test (Vr), and the ozone concentration near the photoconductor after the durability test were measured.

As a result, Examples 1, 2, 3, 4, 5,
In the photoreceptors of Examples 6 and 7 and Comparative Example 1, no potential fluctuation was observed before and after the durability test, which is a problem in the electrophotographic process, but in the photoreceptors 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 all cases.

Next, in the image forming apparatus of Comparative Example 5, Example 1 is applied.
And the electrophotographic photoconductors of Comparative Examples 1, 2, 3, and 4 are installed,
The setting was performed in the same manner as in Example 8 above, except that the current of the charging charger for negative charge, which was negatively charged, was set to 100 μA.

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

Further, as with the image forming apparatus of Example 8, the image forming apparatus of Comparative Example 5 was used.
A paper passing durability test of 00 sheets was performed. After the durability test, the ozone concentration in the vicinity of the photoconductor was measured and found to be 1.5 pp
It was m or more.

The above image evaluation, potential characteristics and ozone concentration measured values are shown in Tables 1 and 2.

[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 a reversal development type image forming apparatus, but does not require a charge-eliminating charger, and is a low-cost, good electrophotographic image at low ozone concentration. The remarkable effect that it is possible to obtain repeatedly is exhibited.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram of a cross section showing the configuration of each specific example of the electrophotographic photosensitive member used in the present invention.

FIG. 3 is a schematic diagram of a cross section showing an example of the configuration of a conventional electrophotographic photosensitive member.

FIG. 4 is a schematic diagram of a cross section showing an example of the configuration of a conventional electrophotographic photosensitive member.

FIG. 5 is a schematic diagram of a cross section showing an example of the configuration of a conventional electrophotographic photosensitive member.

FIG. 6 is a schematic diagram of a cross section showing an example of the configuration of a conventional electrophotographic photosensitive member.

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

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

FIG. 9 is a schematic diagram showing the 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: Distributed CGM 8: Manuscript 9: Image exposure light source 10: photoconductor 11: Main charger 12: Optical static eliminator (pre-exposure) 13: Cleaning device 14: Charger for static elimination 15: Transfer charger 16: Separation charger 17: Paper feeding 18: Developing device 19: Fixing device 20: Contact charger

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-6-250460 (JP, A) JP-A-6-250414 (JP, A) JP-A-6-138687 (JP, A) JP-A-6- 89034 (JP, A) JP-A-6-83094 (JP, A) JP-A-5-19520 (JP, A) JP-A-4-37862 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/00

Claims (2)

(57) [Claims] 1. A comprising an electrophotographic photosensitive member, and, around the electrophotographic photosensitive member, the main charger for main charging said electrophotographic photosensitive member or
Main charging roller, obtained by exposure with the same polarity toner as the main charging
For developing the electrostatic latent image on the electrophotographic photoreceptor
By the developing device, transfer charging having a polarity opposite to that of the main charging,
Transfer charging to transfer the developed image to the transfer material
To remove the electric charge on the electrophotographic photosensitive member by a container and light.
In the image forming apparatus provided with the light removing unit in this order, the electrophotographic photoreceptor contains a layer (CGL) containing a material (CGM) that absorbs light to generate charges on a conductive substrate.
And materials that carry the charge generated in CGL (CT
An electrophotographic photosensitive member comprising a layer (CTL) containing M) and a surface coating layer (OCL) containing both CTM and CGM in this order , wherein the transfer charger and the light erasing section are provided. The image forming apparatus is characterized in that it does not include a charge eliminating charger for making the polarity of the electrophotographic photosensitive member after the transfer charging the same as that of the main charging. Relative wherein light of said light discharger, the CGL
The image forming apparatus according to claim 1 , wherein both the CGM included in the CGM and the CGM included in the OCL have sensitivity.