JP2000206829A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower a noise level and also to prevent the phenomenon of a heat by suppressing electrifying sound in an image forming device by the improvement of an image holding member represented by a photoreceptive drum. SOLUTION: This is an image forming device having the image holding member to which electrification processing is applied by being brought into contact with an electrifying member to which voltage is applied, and also is an image forming device at which a vibrating electric field is formed by applying vibration voltage obtained by superposing DC voltage and AC voltage between the electrifying member and the image holding member. In this case, the thickness of an aluminum pipe stock constituting the image holding member is set to be >=1.5 mm, and also the thickness of a pipe stock is set so that the characteristic frequency of the image holding member is prevented from being within the range of the integral multiple of the frequency of applied voltage ±100 Hz.

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 provided with an image holding member or a process cartridge using the same, and more particularly, a charging process (including a static elimination process) by contact of a charging member to which a voltage is applied. The present invention relates to an image forming apparatus provided with an image holding member to be applied or a process cartridge using the same.

[0002]

2. Description of the Related Art Conventionally, a laser beam printer (hereinafter, referred to as an electrophotographic process or an electrostatic recording process) has been used.
In image forming apparatuses such as "LBP") and copying machines, a charging device for charging an image holding member such as an electrophotographic photosensitive member or an electrostatic recording dielectric is generally a non-contact type. A corona discharge device was employed.

However, recently, since the power supply voltage can be reduced and the generation of ozone is extremely small, the roller type charging member to which a voltage is applied is advantageous. A contact charging device for charging an image holding member by using a charging device is being adopted.

The voltage applied to the charging roller as the charging member may be only a DC voltage, but for uniform charging, it is preferable to apply an oscillating voltage obtained by superimposing a DC voltage and an AC voltage. In particular, an oscillating voltage obtained by superimposing a DC voltage and an AC voltage having a peak-to-peak voltage that is at least twice the charging start voltage of the image holding member when only a DC voltage is applied to the charging member is applied to the charging member. Improving the chargeability is suitably performed.

[0005]

However, the above-described vibration voltage is applied to the charging roller as described above, and a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a "photosensitive drum") as a cylindrical image holding member. ), The frequency of the AC voltage applied to the charging roller must be increased in order to ensure uniform charging of the photosensitive drum surface. In this case, if this frequency exceeds approximately 200 Hz, There is a problem that the so-called "charging noise" caused by the vibration of the charging roller and the charging roller increases.

[0006] It is considered that the cause of the generation of the "charging noise" is that the photosensitive drum and the charging roller repeatedly stick and separate due to electrostatic attraction and vibrate.

Accordingly, an object of the present invention is to improve the image holding member typified by the photosensitive drum to suppress the "charging noise" in the image forming apparatus and reduce the noise level.
Another object of the present invention is to prevent the "buzz" phenomenon.

[0008]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that such "charging noise"
Have been found to occur due to the occurrence of a resonance phenomenon at a natural frequency of the vibration voltage applied to the contact-type charging member, which is the natural frequency of the image holding member, and have completed the present invention. Was.

That is, an image forming apparatus according to a first aspect of the present invention is an image forming apparatus including an image holding member to which a charging process is performed by contact of a charging member to which a voltage is applied. In an image forming apparatus which forms an oscillating electric field by applying an oscillating voltage obtained by superimposing a DC voltage and an AC voltage between the image holding member and an image forming member, the thickness of an aluminum tube constituting the image holding member is 1.5 mm. This is characterized in that the base tube has such a thickness that the natural frequency of the image holding member does not fall within a range of an integral multiple of the frequency of the applied voltage ± 100 Hz.

The image forming apparatus according to a second aspect of the present invention is an image forming apparatus including an image holding member to which a charging process is performed by contact of a charging member to which a voltage is applied, wherein the charging member and the charging member are provided. In an image forming apparatus formed by applying an oscillating voltage in which a DC voltage and an AC voltage are superimposed on an image holding member to form an oscillating electric field, the thickness of the aluminum tube constituting the image holding member is 0.9 mm. In addition to the above, an aluminum anodic oxide film subjected to pure water sealing treatment on the surface of the raw tube is formed to a thickness of 7 μm or more, and the natural frequency of the image holding member is adjusted by applying an applied voltage. Integer multiple of frequency ±
The thickness is set so as not to be in the range of 100 Hz.

According to the image forming apparatus of the present invention, since the natural frequency of the image holding member is away from the integral multiple of the frequency of the applied voltage, the resonance phenomenon due to the applied voltage does not occur and the "charging noise" is suppressed. can do.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image holding member according to the present invention will be described by taking a photosensitive drum as an embodiment thereof as an example.
This will be described with reference to the drawings. The photosensitive drum generally includes a negatively-charged function-separated laminated photosensitive drum, a positively-charged function-separated laminated photosensitive drum, and a positively-charged single-layer photosensitive drum. A specific description will be given by taking a separation and lamination type photosensitive drum as an example.

FIG. 1 is a schematic sectional view of a photosensitive drum according to an embodiment of the present invention. An undercoat layer 2 and a laminated photosensitive layer 5 including a charge generation layer 3 and a charge transport layer 4 are sequentially laminated on a conductive substrate 1.

The conductive substrate 1 functions not only as an electrode of the photosensitive drum but also as a support for the other layers. The conductive substrate 1 may be cylindrical, plate-like or film-like. In the present invention, an aluminum substrate is used.

In the first aspect of the present invention, the thickness of the tube of the photosensitive drum is 1.5 mm or more, and preferably around 1.5 mm from the viewpoint of cost. With such a thickness, the resonance phenomenon due to the applied voltage does not occur, and “charging noise” can be reduced. In the second aspect of the present invention, the wall thickness of the raw tube is 0.9 mm or more.

The undercoat layer 2 is provided for the purpose of preventing injection of unnecessary charges from the conductive substrate to the photosensitive layer, covering defects on the surface of the substrate, improving the adhesiveness of the photosensitive drum, and the like. It can be classified into a type in which a layer as a component is formed and a type in which an anodic oxide film (hereinafter also referred to as “film”) is formed on the surface of an aluminum substrate. In the first invention of the present invention, any of the above-mentioned types may be used, and they may be provided as necessary. In the second invention, the latter is used. FIG. 2 is a schematic cross-sectional view of the photosensitive drum in this case. An anodic oxide film 6 is formed as a subbing layer on the conductive substrate 1, and a laminated photosensitive layer 5 composed of the charge generation layer 3 and the charge transport layer 4 is laminated thereon.

The resin binder used in the former case includes polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin,
Polyurethane resin, epoxy resin, polyester resin,
Melamine resin, silicone resin, polybutyral resin,
It is possible to use a polyamide resin and a copolymer thereof as appropriate in combination. Further, in the above resin binder, SiO ₂ , TiO ₂ , In ₂ O ₃ , ZrO
Metal oxide fine particles such as ₂ may be contained. The thickness of the resin layer depends on its composition, but can be arbitrarily set within a range that does not cause an adverse effect such as an increase in residual potential when used repeatedly and continuously.

When the latter aluminum anodic oxide film is formed, a sealing treatment is performed as the final step of film formation. The sealing treatment is a treatment for closing pores of about 100 mm existing on the aluminum surface immediately after the anodizing treatment, and a pure water sealing for closing the coating by swelling by hydration reaction in boiling water or steam. There is a method using pores or vapor sealing, or nickel acetate sealing using a nickel acetate solution to block the hydration of the film and filling with nickel hydroxide by hydrolysis of nickel acetate.

In the second invention of the present invention, the sealing treatment is performed by pure water sealing, and the film thickness is formed in a range of 7 μm or more, preferably 7 μm to 10 μm.
Further, preferably, a pore-forming treatment is performed by adding a phosphate ester-based surfactant, a naphthalenesulfonic acid-based formaldehyde condensate, a bisphenol A sulfonic acid-based formaldehyde condensate, or the like as a surfactant to the pore-sealing agent. . By forming a film subjected to the pure water sealing treatment as described above on the thick tube, the resonance phenomenon due to the applied voltage does not occur, and the "charging noise" can be reduced.

The charge generation layer 3 is formed by vacuum-depositing an organic photoconductive substance or applying a material in which particles of the organic photoconductive substance are dispersed in a resin binder. Occurs. The charge generation layer 3 has a high charge generation efficiency and a charge transport layer 4 for generated charges.
It is desirable that the injection property is important, that there is little dependence on the electric field, and that the injection be good even at a low electric field. Specific examples of the charge generation material used in the charge generation layer include the following examples I-1 to I-4, Various phthalocyanine compounds, azo compounds, polycyclic quinone compounds, and derivatives thereof described below can be used.

As the resin binder for the charge generation layer,
Polycarbonate, polyester, polyamide, polyurethane, epoxy, polyvinyl butyral, polyvinyl acetal, phenoxy resin, silicone resin, acrylic resin, vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, formal resin, cellulose resin, or a copolymer thereof, And their halides and cyanoethyl compounds. The thickness of the charge generation layer is 0.1 to 5 μm, preferably 1 μm or less.

The amount of the phthalocyanine compound or the like used as the charge generating substance is 5 parts by weight with respect to 10 parts by weight of the resin binder.
５００500 parts by weight, preferably 10-100 parts by weight.

The charge transport layer 4 is a coating film made of a material in which an organic charge transport material is dispersed in a resin binder. In a dark place, the charge transport layer 4 retains the charge of the photosensitive drum as an insulator layer. It has a function of transporting charges injected from the device. As the charge transport material in the charge transport layer,
Specific examples II-1 to 7 below, Various hydrazones, styryls, diamines, butadienes, indole compounds and mixtures thereof can be used.

As the resin binder for the charge transport layer,
Polycarbonate, polystyrene, polyphenylene ether acrylic resin, and the like have been studied as known materials. However, polycarbonate is currently widely used as the most excellent material system in terms of film strength and printing durability. As such polycarbonates, specific examples III-1 to
2, And bisphenol A-type and bisphenol Z-type polycarbonates, and various copolymers.

The optimum average molecular weight range of such a polycarbonate resin is 10,000 to 100,000. Further, as an antioxidant added to the charge transport layer, the following IV-1 to 4, A single antioxidant or a suitable combination thereof can be used. The thickness of the charge transport layer is 10 to
A range of 50 μm is desirable.

The undercoat layer, the charge generation layer, and the charge transport layer include:
An electron-accepting substance, an antioxidant, a light stabilizer and the like can be added as necessary for the purpose of improving sensitivity, reducing residual potential, or improving environmental resistance and stability against harmful light.

If necessary, on the above-mentioned photosensitive layer,
A surface protective layer may be provided for the purpose of improving environmental resistance and mechanical strength. It is desirable that the surface protective layer does not significantly impede light transmission.

Examples of the charging member that comes into contact with the surface of the above-described electrophotographic photosensitive member include a roller and a brush, and the charging member used in a conventional electrophotographic apparatus can be applied as it is.

By applying an oscillating voltage obtained by superimposing a DC voltage of a specific voltage and an AC voltage having a sine waveform with a peak-to-peak voltage in a specific range to the charging member, an oscillating electric field is generated between the photosensitive member and the charging member. Once formed, the photoconductor can be charged to a predetermined potential.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Comparative Example 1 A thickness of 30 mm and a length of 254 with a thickness of 0.9 mm.
After forming a 3 μm thick film of an organic resin containing metal oxide fine particles as an undercoat layer thereon using an aluminum tube of mm (hereinafter, the diameter and length are all the same). X-type metal-free phthalocyanine having an average particle diameter of 200 nm was added to a vinyl chloride-vinyl acetate copolymer by the following method:
6, and a coating liquid in which a butadiene-based charge transporting agent and a polycarbonate-based resin (molecular weight 30,000) were mixed as the charge transporting layer. By drying for 2 hours,
The photosensitive drum was manufactured by sequentially laminating. After that, the LBP equipped with the photosensitive drum was operated to measure the noise level at the first to fourth natural frequencies. The frequency of the AC applied voltage of this LBP was 700 Hz. In addition, the natural frequency of the manufactured photosensitive drum was also measured. The natural frequency was measured by performing a hammering test with the photosensitive drum mounted on the cartridge in the LBP.

Example 1 A photosensitive drum was manufactured and its noise level and natural frequency were measured in the same manner as in Comparative Example 1 except that the thickness of the aluminum tube was set to 1.5 mm.

Comparative Example 2 A photosensitive drum was prepared and the noise level and the natural frequency were measured in the same manner as in Comparative Example 1 except that the thickness of the aluminum tube was set to 1.2 mm.

Example 2 A photosensitive drum was prepared and the noise level and natural frequency were measured in the same manner as in Comparative Example 1 except that the thickness of the aluminum tube was set to 2.0 mm.

The measurement results of Comparative Examples 1 and 2 and Examples 1 and 2 are shown in Table 1 below. The numerical value in parentheses in the column of the natural frequency is the maximum value / minimum value of the noise level at that frequency.

[0035]

[Table 1]

From the above Table 1, it can be seen that the maximum "charge sound" at the second-order natural frequency is greater in the first embodiment with the wall thickness of 1.5 mm than in the second comparison example with the wall thickness of 1.2 mm. It can be seen that it has dropped significantly from 60 dB to 50 dB. Also, compared with Comparative Example 1, the maximum values of the second and fourth orders are 60 dB to 5
It is significantly reduced to 0 dB. Further, as in the second embodiment, the natural frequency shifts as a whole as the thickness increases to 2 mm. In the first and second embodiments, the natural frequency at which the charging noise is particularly large is up to the fourth order. It turns out that there is no. In addition, from the viewpoint of cost, it is more economical to make the wall thickness of the raw tube thin, so practically, it is preferable to be around 1.5 mm rather than 2 mm.

As described above, from Table 1, Examples 1 and 2 are shown.
As shown in the figure, the wall thickness of the raw tube is changed by its natural frequency (from the first order to 4
Next) is an integral multiple of the applied voltage frequency of 700 Hz ± 100H
The thickness (1.5 and 2 mm, respectively) that does not fall within z causes the phenomenon that the charging noise becomes large, particularly 60 dB, at a specific natural frequency as in Comparative Examples 1 and 2. It turns out that it is gone.

COMPARATIVE EXAMPLE 3 A charge generating layer and a charge transporting layer were sequentially laminated on a 0.9 mm thick aluminum tube in the same manner as in Comparative Example 1 except that no undercoating layer was provided, to produce a photosensitive drum. And LBP
Was operated to measure the noise level at the first to fourth natural frequencies. Further, the natural frequency of the manufactured photosensitive drum was measured in the same manner as in Comparative Example 1.

[0039] Example 3 aluminum tube surface, instead of the undercoat layer, except forming an aluminum anodized film 7μm subjected to Junmizufuana treatment (Al 2 _{O 3)} as in Comparative Example 3 Then, a photosensitive drum was manufactured, and the noise level and the natural frequency were measured. The coating was formed as follows.

First, a degreasing agent (Top Alclean 10)
(1) Okuno Pharmaceutical Co., Ltd./60° C./2 minutes), the cutting oil on the surface of the aluminum substrate was degreased and washed with water to sufficiently remove the degreaser. Then, sulfuric acid (180 g / l, 2
0 A) in an electrolytic treatment (1.0 A / dm ² , 12v, 21
Min) to form an anodized film with a film thickness of 7 μm, and washed with water. The pore-sealing treatment was performed by adding a phosphate ester surfactant (Phosphanol RS-610: manufactured by Toho Chemical Industry Co., Ltd.) at 0.1 g / l to pure water at a treatment temperature of 90 ° C. It took 10 minutes.

Comparative Example 4 A photosensitive drum was prepared in the same manner as in Example 3 except that the thickness of the aluminum anodic oxide film was changed to 3 μm, and the noise level and the natural frequency were measured.

Example 4 A photosensitive drum was prepared in the same manner as in Example 3 except that the aluminum anodic oxide film was treated to a thickness of 10 μm, and the noise level and the natural frequency were measured.

The measurement results of Comparative Examples 3 and 4 and Examples 3 and 4 are shown in Table 2 below. The meaning of the numerical value in parentheses in the column of the natural frequency is the same as in Table 1 above.

[0044]

[Table 2]

From the above Table 2, it can be seen that in Example 3 having an oxide film thickness of 7 μm, compared with Comparative Example 4 having an oxide film thickness of 3 μm,
It can be seen that the “charging noise” at the next natural frequency is significantly reduced. From the above results, it is considered that an appropriate film thickness effective for reducing the charging noise is 7 to 10 μm. Here, since the aluminum anodic oxide film subjected to the pure water sealing treatment has a honeycomb structure, it is conceivable that this structure contributes to absorption of “charging noise”. Table 1
From Comparative Example 1 of Comparative Example 1 and Comparative Example 3 of Table 2, it can be seen that there is almost no sound reduction effect when an organic resin is used as the undercoat layer.

As shown in Table 2, as in Examples 3 and 4, a film was formed on a 0.9 mm thick tube so that the natural frequency of the tube did not fall within an integral multiple of the voltage frequency of 700 Hz ± 100 Hz. It can be seen that the provision of the aluminum anodic oxide film having a thickness of 7 μm or more eliminates the phenomenon of a large charging noise of about 60 dB at a specific frequency.

According to the study of the present inventors, generally, 6
If the dB noise level decreases, many people feel that the noise level has decreased. When the noise level difference between the maximum value and the minimum value is 4 dB or more, a so-called “beat” phenomenon is felt. Therefore, from the above results, it can be said that the noise level of any of the photosensitive drums of the examples was reduced, and the phenomenon of "buzz" was also prevented.

The frequency of the AC voltage applied to the LBP used in this embodiment was measured to be 700 Hz.
Therefore, the frequency of the AC applied voltage of LBP is 700 Hz.
Becomes the fundamental frequency, and when the integral multiple thereof is close to the natural frequency of the photosensitive drum, a so-called resonance phenomenon occurs,
It is considered that "charging noise" was generated. Examples 1-4
According to the photosensitive drum described above, the "electrification noise" could be reduced because the photosensitive drum had a natural frequency that was not an integral multiple of this frequency 700 Hz ± 100 Hz.

[0049]

As described above, according to the image forming apparatus of the present invention, in a contact charging type electrophotographic apparatus,
The thickness of the tube of the image holding member is a predetermined range, or an anodic oxide film of a predetermined thickness is formed on the tube having the predetermined thickness, and the frequency of the vibration voltage at which the natural frequency is applied By using an image holding member that is not within an integral multiple of ± 100 Hz, the “charging noise” is suppressed to reduce the noise level,
It is effective in preventing the phenomenon of "buzz".

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a photosensitive drum in an embodiment.

FIG. 2 is a schematic sectional view of a photosensitive drum according to another embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 undercoat layer 3 charge generation layer 4 charge transport layer 5 laminated photosensitive layer 6 anodized film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H003 AA00 CC04 2H035 CB03 CG01 2H068 AA42 AA54 AA58 CA32 CA33 FC01

Claims (2)

[Claims] 1. An image forming apparatus comprising an image holding member to which a charging process is performed by contact of a charging member to which a voltage is applied, wherein a DC voltage and an AC voltage are applied between the charging member and the image holding member. In the image forming apparatus formed by applying an oscillating voltage superimposed with the above to form an oscillating electric field, the thickness of the aluminum tube constituting the image holding member is 1.
5 mm or more, and the natural frequency of the image holding member is an integral multiple of the frequency of the applied voltage ± 100 Hz.
An image forming apparatus characterized in that the thickness is set so as not to fall within the range of (1). 2. An image forming apparatus comprising an image holding member to which a charging process is performed by contact of a charging member to which a voltage is applied, wherein a DC voltage and an AC voltage are applied between the charging member and the image holding member. In the image forming apparatus which forms an oscillating electric field by applying an oscillating voltage superimposed with the above, the thickness of the aluminum tube constituting the image holding member is set to 0.
An aluminum anodic oxide film having a thickness of 7 μm or more formed by subjecting the surface of the base tube to pure water sealing treatment to a thickness of 9 μm or more, and applying a natural frequency of the image holding member to the base tube. An image forming apparatus characterized in that the thickness is set so as not to fall within a range of an integral multiple of the voltage frequency ± 100 Hz.