JPH05281772A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image forming device having a stable electrifying characteristic even under high speed and high durability by composing a member to be electrified of a paper tube supporting body, and a conductive layer and a photosensitive layer, which are successively laminated on the paper supporting body. CONSTITUTION:The member to be electrified 1 as a photosensitive body, has the paper tube supporting body 1a and the photosensitive layer 1b. In other words, the conductive layer and the photosensitive layer 1b are laminated on the surface of the paper tube supporting body 1a. On the other hand, an electrifying device 2 coming into contact with the member to be electrified 1 to electrify it, is composed of a core metal 2a, an elastic layer 2b, and a resistant layer 2c. Then, it is preferable that rigidity is imparted to a paper so as not to deform the photosensitive layer 1b at the time of pressurizing, because the electrifying device 2 is contact with the photosensitive body. Therefore, the paper tube has 1-10mm thickness, preferably, 2-8mm thickness. Thus, the member to be electrostatified 1 is constituted of the paper tube supporting body 1a, and the conductive layer and the photosensitive layer 1b, which are laminated thereon, so that the propagation of a vibration to the member to be electrified 1 as the photosensitive body is reduced, and the occurrence of an electrifying noise can suppressed to a level free from problems in practical use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more specifically, charging is performed by contact charging in which a charging device is pressed against a member to be charged such as an electrostatic latent image carrier, which is a photoconductor, to charge the member. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Recently, a contact charging device for directly contacting and charging a photosensitive member has been proposed as disclosed in, for example, Japanese Patent Laid-Open No. 63-167380, and compared with a corona charging method which has been conventionally used. It has been recognized that it has advantages such as the ability to use low applied voltage and low ozone generation.

An example of this type of contact charging system is shown in FIG. 1, in which the electrophotographic photosensitive drum (1) is shown.
The charging roller (2), which is a charging member, is contact driven to apply an _AC voltage V _AC and a DC voltage V _DC to uniformly charge the photosensitive drum. As can be understood from the above, the charging roller needs to maintain conductivity, and the core (2a) is surrounded by the elastic body (2b) to keep the contact portion uniform.
Must be configured by

Conventionally, the conductivity is adjusted by adding a conductive material such as conductive carbon black into the elastic layer.
The elasticity is adjusted by additives such as process oil and plasticizer added to the elastic layer.

In order to improve these characteristics, the elastic layer is further covered with a member having a volume resistance value of 4.0 × 10 ⁹ Ωcm or more, as described in JP-A-1-191161. Contact charging devices have been proposed.

However, in a contact type charging device for charging by applying an electric field in which an alternating electric field is superimposed on a direct current electric field to the contact type charging device, mechanical vibration occurs due to the alternating electric field in the charging device, which is uncomfortable as a charging sound. It is recognized that there is a problem of giving an environment, and especially when the frequency of the alternating electric field is as high as several hundreds Hz, the charging noise becomes remarkable due to the problem of tone color.

In this phenomenon, when an AC electric field is applied to the charging device, the electric field strength causes vibration in the charging device, and the vibration propagates to the photoconductor. At this time, when the support of the photoconductor is composed of a metal cylinder as conventionally used, it is recognized that the propagated vibration causes resonance without being attenuated and a remarkable charging sound is generated. Further, since the generated charging sound mainly contains the AC frequency and its overtone component, the discomfort of the charging sound is remarkable when the frequency is in the audible range for humans of several hundred Hz and is easily heard. Will be things.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus which solves the above drawbacks. A further object of the present invention is to use a contact charging device for charging by an electric field in which an alternating electric field is superimposed on a direct current electric field,
An object of the present invention is to provide an image forming apparatus that generates less charging noise.

A further object of the present invention is to provide an image forming apparatus having stable charging characteristics even under high speed and high durability.

[0010]

In order to achieve the above object, an image forming apparatus according to the present invention is a contact type apparatus in which a charging device is brought into contact with a member to be charged and an AC electric field and a DC electric field are applied to the charging device. In the image forming apparatus for charging, the member to be charged is composed of a paper tube support, and a conductive layer and a photosensitive layer sequentially laminated on the paper tube support.

[0011]

According to the present invention, since the main body of the support of the member to be charged is constituted by the paper tube, the propagation of vibration to the photosensitive member is reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a conceptual diagram of the present invention. In the figure, the member to be charged 1 which is a photoconductor has a paper tube support 1a and a photoconductive layer 1b. Although not shown, the paper tube support 1
A conductive layer is laminated on the surface of the above, which will be described later. A core metal (not shown) is inserted into the support 1. The charging device 2 that contacts and charges the member to be charged 1 includes a cored bar 2a, an elastic layer 2b, and a resistance layer 2c. In the figure, other exposure devices, developing devices, transfer devices, cleaning devices, etc. are omitted from the drawing.

In the above structure, since the support of the photoconductor is composed of the paper tube support, that is, paper, when the photosensitive layer is formed on the surface of the support, heating or the like is performed, so that volatile components are generated from the paper. It needs to be prevented. Therefore, a sealing layer is provided on the surface of the paper tube to prevent air bubbles and floating of the photosensitive layer due to volatile components from the paper. Further, in order to form a photosensitive layer on the surface, the unevenness on the surface is preferably R _Z 5.0 μ or less.

As a method for realizing this, fine paper fibers may be used on the surface when the paper tube is finished, or calendered paper may be used. Further, a coated paper whose surface is coated with a resin or the like may be used, and it is preferable to coat the surface with a resin in order to have smoothness. Resins such as melamine and epoxy can be used as the resin. The smooth layer may also serve as a sealing layer provided on the surface layer of the paper tube.

In the present invention, since the charging device is brought into contact with the photosensitive member, it is preferable that the paper has rigidity so that the photosensitive layer is not deformed when pressure is applied. Therefore, the paper tube is 1-10m
m preferably has a wall thickness of 2 to 8 mm.

In the present invention, it is necessary to impart conductivity to the surface of the paper tube, and this is because an electrode is required on the back surface when forming the photosensitive layer on the surface layer.

The conductive layer forming this electrode is preferably composed of a resin in which a pigment is dispersed, and this layer may also serve as the sealing layer / smoothing layer and serve as an undercoat layer. As the resin material used for this layer, thermosetting resins such as phenol, polyester, melamine and epoxy are preferably used.

The conductive pigment added is preferably a white or light-colored pigment because it is used as a photosensitive layer.
For example, metal oxide-based conductive pigments such as titanium oxide, tin oxide, zinc oxide, and metal powder are used.

The conductive layer is adjusted to have a volume resistivity of 10 ⁷ Ωcm or less, preferably 10 ⁶ Ωcm or less. Further, as the film thickness of the electrode layer, a thickness of 10 to 1000 μm is preferably used also from the viewpoint of reducing irregularities on the surface of the paper tube.

The photosensitive layer used in the present invention is α-Si.
Photosensitive layers including commonly used photoconductors such as selenium and OPC can be used. In particular, the OPC photosensitive member is preferable because of the simplicity of the manufacturing method. The OPC photosensitive member may be of a single layer type in which a charge generating material (hereinafter, CG material) and a charge transporting material (hereinafter, CT material) are mixed, or a laminated type in which a CG layer and a CT layer are stacked.

CG materials include pyrylium / thiopyrylium dyes, phthalocyanine pigments, perylene pigments,
Organic dyes such as dibenzpyrenequino pigment, pyranthrone pigment, azo pigment, indigo pigment, and quinacridone pigment are used alone or in a mixture.

As the CT material, a pyrazoline compound, a hydrazone compound, a stilbene compound, a triphenylamine compound, a benzidine compound, an oxazole compound, an indole compound, a carbazole compound, etc. are used alone or in a mixed form. ..

The CG material / CT material is dissolved in a resin having film-forming properties to form a photosensitive layer. This is because the CG material / CT material generally has a low molecular weight and is poor in film-forming property by itself.

As the film-forming resin, insulating resins such as polyester, polyvinyl butyral, cellulosic resin, polyarylate, polyacrylamide resin, polyurethane resin, casein, phenoxy resin, acrylic resin, polysulfone, polycarbonate, polystyrene and carbazole are used. A photoconductive resin such as polyvinyl anthracene or polyvinyl anthracene is used alone or in a mixture.

In the case of a single layer type photosensitive layer, the above CG material and C
The T material and an appropriate resin component are dissolved and mixed with a solvent or the like and coated to form a photosensitive layer on the support.

In the case of a laminated type photosensitive layer, CG is provided on a support.
The layers and the CT layers may be laminated in this order, or the CT layers and the CG layers may be laminated in this order, which is determined by the application.

The thickness of the CG layer is preferably 0.01 to 15 μm, and the mixing ratio of the CG material and the resin is preferably 10: 1 to 1:20. The thickness of the CT layer is preferably 5 to 50 μ, and the mixing ratio of the CT material and the resin is preferably 5: 1 to 1: 5.

Furthermore, an intermediate layer may be interposed between the conductive layer and the photosensitive layer for the purpose of preventing the leakage of charges from the conductive layer and improving the adhesiveness. Casein / PVA /
Nitrocellulose, polyamide, polyurethane, gelatin, etc. are used. The film thickness of the intermediate layer is 5 μm or less, preferably 0.5 to 3 μm. Further, the resistance value of the intermediate layer is preferably 10 ⁷ Ωcm or less.

As a film forming method for each layer, the constituent materials are dissolved and mixed in an organic solvent selected according to dispersibility and solubility to form a coating, and then a dip coating method, a spray coating method, a wire bar coating method, a blade coating method. Etc. Examples of the contact type charging device used in the present invention include a charging device in which a coating layer is arranged on the surface of an elastic layer. Further, since the electric current is applied in the diameter direction, both the elastic layer and the coating layer need to have specific resistance in the medium resistance region.

FIG. 2 shows a method of measuring the resistance value according to the present invention. An electrode made of a 50 μ aluminum sheet is wound around the charging device 2, a voltage is applied to the core metal 2 a by a power source 4, and a current is measured by a direct current ammeter 6 to measure a resistance value.

The resistance value in the present invention is 1 in the elastic layer.
It is preferably 0 ³ to 10 ⁶ Ω, and 10 ⁴ to 10 ⁹ Ω with the coating layer provided, and the elastic layer has a hardness of 20 to 80 ° at a hardness defined by a JIS K6301 A-type hardness tester. Is preferred.

As a constituent material of the charging device used in the present invention, a resin material used for the elastic layer is, for example, E
Synthetic rubber such as PDM, EPT, EPM, NBR, BR, BR, CR, etc. Thermosetting elastomer such as natural rubber or thermoplastic elastomer such as vinyl chloride, vinyl acetate polyester, PVA etc. is used, and conductivity is given to the elastic layer. The conductive particles added to achieve carbon black
Conductive particles such as zinc oxide, titanium oxide, and metal powder are used.

As the resin material used for the resistance layer disposed on the surface of the charger, a material having flexibility at room temperature such as polyamide, polyimide, fluororesin, silicon resin, PVA, polyester is used. As the conductive particles added to impart conductivity, the conductive particles such as carbon black, zinc oxide, titanium oxide and metal powder mentioned above are used.

In the present invention, the elastic body is preferably used for supporting the electrode, and therefore it is preferable that the elastic body has a flame retardancy of 94 HB or more in accordance with UL-94 standard. It is preferable that the film thickness of 1 to 3 mm and the resistance layer to be 1 to 500 μm.

As the electric field used in the present invention, an electric field obtained by superimposing an AC electric field on a DC electric field is used. The AC electric field is V _PP which is more than twice the charging start electric field, and the DC electric field is determined by the potential required for the image forming apparatus. The charging start electric field refers to the minimum electric field at which a member to be charged is charged when a contact type charging device is attached in a used state and only a DC electric field is applied to perform charging.

Specific examples of the present invention are shown below, but the invention is not limited thereto. Specific Example 1 (Photoreceptor) Support Body A paper tube having a diameter of 30 mm, a length of 260 mm and a thickness of 3 mm is prepared as a support body for the photoreceptor. To do. The unevenness on the paper tube was 100 μm at the joint, but as a lower layer combining the sealing layer, the smooth layer, and the conductive layer on the paper tube, 100 parts by weight of a phenolic resin (Priauchen), conductive oxide A coating film having a thickness of 200 μm was formed by roll coating using a coating material prepared by dispersing and dissolving 100 parts by weight of titanium (ECT-62) in methyl alcohol. This is 130 ℃ / 20m
In-crosslinking was carried out to obtain a support. At this time, the unevenness of the joint was reduced, and R _Z was 3.0 μ.

A photosensitive layer was provided on this support as follows.

Intermediate Layer A 1 μm intermediate layer is provided by dipping the support in a prepared solution of polyamide resin (CM-8000) in a 5% methanol solution and dipping.

Charge Generation Layer (CG Layer) 10 parts of disazo pigment having the following structural formula

[0040]

[Chemical 1]

Polyvinyl butyral resin (S-REC B
M2) (10 parts) and cyclohexane (120 parts) were dispersed in a sand mill for 10 hours, and 30 parts of methyl ethyl ketone was added to the dispersion to coat the undercoat layer with a CG layer of 0.15 μm.

Charge Transport Layer (CT Layer) 10 parts of a hydrazone compound having the following structural formula,

[0043]

[Chemical 2]

10 parts of a polycarbonate Z resin (manufactured by Mitsubishi Gas Chemical Co., Inc.) was dissolved in monochlorobenzene, and this was coated on the CG layer to form a CT layer of 16 μm. As described above, the photosensitive layer of the invention was obtained.

(Contact charging device) Elastic layer 100 parts by weight of EPDM compound, 5 parts by weight of Ketjen black, 10 parts by weight of paraffin oil, and a mixed resource amount compound for 30 minutes on two rolls cooled to 20 ° C. In the above, 100 parts by weight of the raw material was added with 2 parts by weight of dicumyl peroxide as a vulcanizing agent and further mixed on a roll for 2 hours. The elastic layer is vulcanized and molded so that

Resistive Layer To provide a resistive layer on the elastic layer, 100 parts by weight of methylolated nylon, 2 parts by weight of Ketjen Black,
Silicone oil (molecular weight 2000: 200 ppm) was dissolved in a mixed solvent of methanol / toluene to prepare a coating material for coating, and a 20 μ surface layer was formed on the elastic layer by the dipping method using the coating material. A contact charging device was created.

The photosensitive member and the charging device are attached to the position of the primary charging device of the cartridge used in the laser beam printer, and the DC voltage V _DC =-is applied to the core metal portion 2a of the charging device 2.
700 V, AC voltage V _AC = 2000 V, AC frequency f =
A bias of 500 Hz was applied, and 300 g of one side was applied to both ends of the core bar to stabilize the contact and electrify the core for evaluation.

The evaluation items are as follows.

(1) Image fog (due to poor charging) (2) Charging sound The LBP is placed in an anechoic chamber and the noise during operation is measured. The measurement was performed according to the sixth item of ISO 7779 (operator position).

[0050] Regarding the above items, the paper feed start time (initial)
Also, the measurement was performed at the time of running 10,000 sheets (after running). As a result, stable image properties were shown both at the initial stage and during the durability, and there was no problem of charging property, and the charging sound was good at 50 db at the initial stage and during the durability. It is considered that this is because the paper has a large amount of voids inside so that it has a property of not easily propagating vibration and is less likely to cause resonance.

Comparative Example 1 Evaluation was carried out in the same manner as in Example 1 except that the photosensitive member support was an Al cylinder having a thickness of 1 mm. As a result, although there was no problem in the charging property, the charging noise was as large as 75 db, which was a level that might give an unpleasant feeling to the use environment.

[0052]

As described above, according to the present invention,
In the image forming apparatus that performs contact charging, since the member to be charged is composed of a paper tube support, and a conductive layer and a photosensitive layer laminated on the paper tube support, the member to be charged as a photoreceptor It is possible to reduce the propagation of vibrations to the battery and suppress the generation of charging noise to a level at which there is no practical problem.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an image forming apparatus of the present invention.

FIG. 2 is a diagram showing a method of measuring a resistance value of a charging device in the image forming apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Object to be charged 1a ... Paper tube support 1b ... Photosensitive layer 2 ... Contact charging device 2a ... Core metal part 2b ... Elastic layer 2c ... Resistance layer

Claims (1)

[Claims] 1. An image forming apparatus that performs contact charging by contacting a charging device with a member to be charged and applying an AC electric field and a DC electric field to the charging device, wherein the member to be charged is a paper tube support, An image forming apparatus comprising a conductive layer and a photosensitive layer which are sequentially laminated on the paper tube support.