JP3513355B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to an image forming apparatus using the medium between the transfer member, second after especially the toner image formed on the first image bearing member, thereby temporarily transferred to the intermediate transfer member The present invention relates to an image forming apparatus such as a copying machine, a printer or a fax machine, which is further transferred onto an image carrier to obtain an image formed product.

[0002]

2. Description of the Related Art An image forming apparatus using an intermediate transfer member is
A color image forming apparatus, a multicolor image forming apparatus, or a color image that sequentially outputs a plurality of component color images of color image information or multicolor image information by layered transfer and outputs an image formed by combining and reproducing the color image or the multicolor image. It is effective as an image forming apparatus having a forming function and a multicolor image forming function, and it is possible to obtain an image with no misregistration (color misregistration) of each component color image.

FIG. 1 shows a schematic view of an example of an image forming apparatus which is a transfer apparatus using an intermediate transfer member having a roller shape.

FIG. 1 shows a color image forming apparatus (copier or laser beam printer) utilizing an electrophotographic process, which uses an elastic roller 20 having a medium resistance as an intermediate transfer member.

Reference numeral 1 denotes a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) repeatedly used as a first image bearing member, and has a predetermined peripheral speed (process) in a counterclockwise direction indicated by an arrow. It is driven to rotate with speed).

The photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by a primary charger (corona discharger) 2 in the course of its rotation, and then image exposing means (not shown) (color separation of color original image).・ Image forming exposure optical system, scanning exposure system using a laser scanner that outputs a laser beam modulated according to time series electric digital pixel signals of image information)
By receiving the image exposure 3 by, the electrostatic latent image corresponding to the first color component image (for example, magenta component image) of the target color image is formed.

Then, the electrostatic latent image is transferred to the first developing device 41.
The (magenta developing device) develops with the magenta toner M which is the first color. At this time, the second to fourth developing devices 4
2, 43, and 44 (cyan, yellow, and black developing devices) are not operated, and do not act on the photosensitive drum 1. The magenta toner image of the first color is the second to fourth developing images. Not affected by vessels 42-44.

The intermediate transfer member 20 is rotationally driven in the clockwise direction indicated by the arrow at the same peripheral speed as the photosensitive drum 1. The intermediate transfer member 20 of this embodiment includes a pipe-shaped core metal 100,
Elastic body 101 and coating layer 10 formed on the outer peripheral surface thereof
It consists of 2.

The above-mentioned first formed and carried on the photosensitive drum 1.
By the electric field formed by the transfer bias applied to the intermediate transfer body 20 while the color magenta toner image passes through the nip portion between the photosensitive drum 1 and the intermediate transfer body 20,
Intermediate transfer is sequentially performed on the outer peripheral surface of the intermediate transfer body 20. The transfer process from the photosensitive drum to the intermediate transfer body is called a primary transfer process, and the transfer bias is called a primary transfer bias.

The surface of the photosensitive drum 1 on which the transfer of the magenta toner image of the first color corresponding to the intermediate transfer member 20 is completed is cleaned by the cleaning device 14.

Similarly, the second color cyan toner image, the third color yellow toner image, and the fourth color black toner image are sequentially transferred onto the intermediate transfer member 20 in a superimposed manner to form a composite color image corresponding to the target color image. A toner image is formed.

Reference numeral 25 is a transfer roller, which is an intermediate transfer member 20.
Corresponding to, the bearings are arranged in parallel with each other and brought into contact with the lower surface portion.

First from the photosensitive drum 1 to the intermediate transfer body 20
~ The primary transfer bias for the sequential superposition transfer of the toner image of the fourth color is the bias power source 6 with the polarity (+) opposite to that of the toner.
It is applied from 1. The applied voltage is, for example, + 100V-
It is in the range of +3 kV.

First from the photosensitive drum 1 to the intermediate transfer body 20
The transfer roller 25 and the intermediate transfer member cleaning charging member 35 may be separated from the intermediate transfer member 20 in the step of sequentially transferring the fourth color toner image.

A transfer material 24, which is a second image bearing member, of the composite color toner image superposed and transferred on the intermediate transfer member 20.
In the transfer to, the transfer roller 25 is brought into contact with the intermediate transfer body 20, and the transfer material 24 is fed from the sheet feeding cassette 9 to the contact nip between the intermediate transfer body 20 and the transfer roller 25 at a predetermined timing. At the same time, the transfer bias is bias power supply 2
9 is applied to the transfer roller 25. The secondary transfer bias causes the synthetic color toner image to be transferred from the intermediate transfer member 20 to the transfer material 24 which is the second image carrier. This step is called a secondary transfer step, and the transfer bias is called a secondary transfer bias. The transfer material 24 that has received the toner image transfer is the fixing device 1.
Then, it is heated and fixed.

After the transfer of the image to the transfer material 24, the transfer residual toner on the intermediate transfer body 20 is made to have a polarity (+) opposite to that of the photosensitive drum by the charging member 35 for cleaning the intermediate transfer body connected to the bias power source 36. It is charged and returned onto the photosensitive drum 1 by electrostatic force. After that, the surface of the photosensitive drum 1 is cleaned by the cleaning device 14.

In a color electrophotographic apparatus having an image forming apparatus using the above-mentioned intermediate transfer member, a second image support is attached or adsorbed onto a transfer drum which is a conventional technique,
A color electrophotographic apparatus having an image forming apparatus for transferring an image from the first image support thereto is disclosed in, for example, JP-A-63-63.
It is superior to the transfer method described in Japanese Patent No. 301960 in the following points.

That is, there is little color shift when the toner images of the respective colors are superposed. Then, as shown in FIG.
Since it is possible to transfer an image from the intermediate transfer member without requiring any processing or control (eg, gripping by a gripper, adsorbing, giving a curvature, etc.) to the second image supporting member, A wide variety can be selected, for example, envelopes, postcards and the like.

Further, since the intermediate transfer member is excellent in rigidity, it is unlikely that the dimensional accuracy such as dents, strains, and deformations will be changed by repeated use, so that the frequency of replacement of the intermediate transfer member can be increased.

[0020]

As described above, because of the advantage of using the intermediate transfer member, a color copying machine, a color printer or the like using this image forming apparatus has already started to operate in the market. When the image forming apparatus using the intermediate transfer member is actually used repeatedly in various environments, it still has the following problems to be overcome.

The transfer efficiency from the first image carrier, for example, the photosensitive drum to the intermediate transfer member, and the transfer efficiency from the intermediate transfer member to the second image carrier, such as paper or OHP sheet, are
It is known that a sufficiently high product cannot be obtained, and the transfer efficiency deteriorates particularly in a low temperature and low humidity environment. for that reason,
A cleaning device, which should be provided on the photosensitive drum and the intermediate transfer member, is indispensable, and the load on the device is increased due to cleaning with a large amount of transfer residual toner, which makes the cleaning device considerably complicated in structure and expensive. turn into.

All of these phenomena are caused by the fact that sufficient transfer efficiency is not obtained, but as a means for improving the transfer efficiency, as shown in FIG. 2, as shown in FIG. An image forming apparatus for charging the toner after the primary transfer on the intermediate transfer member is provided with a pre-transfer charger 23) and has been partially put into practical use. 2, the same parts as those shown in FIG. 1 are designated by the same reference numerals.

In such a conventional configuration, the amount of charge of the toner (hereinafter referred to as tribo) on the intermediately transferred intermediate transfer member is different for each color, and the optimum bias condition at the time of secondary transfer is different for each color. Although it was difficult to obtain sufficient transfer efficiency, the toner layer on the intermediate transfer member was corona charged (discharged) using the pre-transfer charger to raise the tribo of the toner of each color and make it an appropriate charge. As a result, the transfer efficiency can be improved. Here, the voltage applied to the pre-transfer charger is a high voltage having the same polarity as the toner, that is, a high voltage having the opposite polarity to the voltage applied to the transfer roller. Further, by using the pre-transfer charger, the environmental stability of the transfer efficiency was improved, and it became possible to always maintain the stable transfer efficiency regardless of the environment.

However, when the toner layer on the intermediate transfer member is corona-charged (discharged) in order to improve the secondary transfer efficiency by providing a pre-transfer charger, the toner layer slips through the toner layer and the surface of the intermediate transfer member also becomes strong. Since the transfer material is charged and electrostatic energy on the surface increases, a transfer material may generate a suction force to wind around the intermediate transfer body, which may cause so-called imperfect separation of the transfer material. This phenomenon occurs particularly remarkably when used in a low temperature and low humidity environment (15 ° C./10%) and when a paper having low rigidity such as thin paper or Japanese paper is used as a transfer material.

The present invention, the kind of the transfer material, regardless of the size, and to provide a stable transfer performance, that obtained without depending separation performance to a use environment images forming device.

[0026]

[Means for Solving the Problems]Image forming device
Is an intermediate transfer member for the image formed on the first image carrier.
Secondary transfer to the second image carrier after primary transfer to
And is primarily transferred onto the intermediate transfer member.
Image type with a charger that charges the recorded image before secondary transfer
To the equipmentIn advance, The intermediate transfer member is at least an elastic layer,
The outermost surface layer, and the charger of the intermediate transfer member.
Surface potential rise by 300V or less, and the intermediate transfer
The JIS-A hardness of the body is 70 degrees or less, and the intermediate transfer body
Characterized by the thickness of the elastic layer being 0.5 mm or more
It

The intermediate transfer member used in the present invention may have a roller shape, and preferably has a two-layer structure of a surface layer and an elastic layer.

In any case, the image formation according to the present invention
The surface potential of the intermediate transfer member in the apparatus rises by 5 V or more and 300 V or less, and the JI of the intermediate transfer member.
It is more preferable that the S-A hardness is 10 degrees or more and 70 degrees or less, and the thickness of the elastic layer of the intermediate transfer body is 0.5 mm or more and 10 mm or less.

[0029]

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

In the image forming apparatus, a photosensitive drum, which is a first image carrier, a pre-transfer charger, a transfer roller (or transfer belt), and a charging member, which is a cleaning device for the intermediate transfer member, are provided around the intermediate transfer member. Are arranged. As described above, a voltage of about 100 V to 3 kV is applied to the intermediate transfer member, but in addition, from the peripheral portion of the intermediate transfer member,
It is easily affected by electrostatic current due to current flow. The main purpose of the corona charger, which is the pre-transfer charger, is to increase the tribo of the toner of each color on the intermediate transfer member so that the charge is adjusted to an appropriate charge, but the applied voltage is sufficiently large (1 kV to Since it is 5 kV), the toner on the intermediate transfer member slips through and the surface of the intermediate transfer member is also strongly charged. If the charge on the surface of the intermediate transfer body that has been charged by the pre-transfer charger passes through the secondary transfer process and remains on the surface of the intermediate transfer body even during the separation step, strong electrostatic energy is applied to the surface of the intermediate transfer body. Accumulated. This electrostatic energy is
The transfer material generates a suction force to wind around the intermediate transfer body, and the transfer material winds around the intermediate transfer body, which causes a separation failure of the transfer material.

The improper separation of the transfer material is particularly remarkable when a paper having a small rigidity such as thin paper or Japanese paper is used as the transfer material or in a low temperature and low humidity environment. The reason for this is considered to be that paper with low rigidity tends to be mechanically wrapped around the intermediate transfer body, and in a low temperature and low humidity environment, the electric potential and electrostatic energy on the surface of the intermediate transfer body rise significantly compared to the normal environment. Therefore, it is considered that the separation failure is likely to occur due to the reason described above.

Therefore, the surface potential of the intermediate transfer member does not increase due to the corona charger, which is the pre-transfer charger, or the charge on the intermediate transfer member generated by the pre-transfer charger is generated by the secondary transfer. It is important that they are sufficiently removed during the process and separation process, and it is necessary to always maintain a stable low potential regardless of the environment.

That is, in the image forming apparatus according to the present invention ,
In addition, the potential increase on the surface of the intermediate transfer member by the pre-transfer charger is 300 V or less. The potential increase on the surface of the intermediate transfer member is measured by the following method.

<Measurement Method of Surface Potential of Intermediate Transfer Body> (1) As shown in FIG. 3, the intermediate transfer body 2 is arranged so that both axes of the intermediate transfer body 20 and the corona charger 200 are parallel to each other.
Distance between the 0 surface and the wire of the corona charger 200 is 7 mm
Then, the bias power source 201 is connected. (2) The linear velocity on the surface of the intermediate transfer member 20 is 120 mm / se.
The intermediate transfer member 20 is driven so as to be c. (3) A surface electrometer (MODEL 344A, manufactured by Trek) 202 is arranged on the downstream side of the position where the corona charger 200 is arranged. In addition, from the corona charger 200 to the surface potential meter 2
The distance to 02 is set to be equal to the distance from the pre-transfer charger to the position where the secondary transfer process is performed. (4) DC voltage +3.0 kV from the bias power source 201,
A superimposed voltage (constant voltage) having an AC peak-to-peak voltage of 5 kV and a frequency of 500 Hz is applied to the circuit, and the surface potential meter measures the potential increase on the surface of the intermediate transfer member 20. The atmosphere during measurement is 23 ° C./40% RH.

Further, as a result of intensive studies by the present inventors, in order to maintain the stable separation performance of the transfer material, in addition to the electrostatic factors described above, sufficient elastic force of the intermediate transfer member is required. We have come to the conclusion that it is necessary. This is because if the elastic force of the intermediate transfer body is sufficiently large, the transfer material is easily attracted to the transfer roller (or transfer belt) side, which is a transfer member,
Conversely, if the elastic force of the intermediate transfer body is small, the transfer material is easily adsorbed to the intermediate transfer body side.
Therefore, the intermediate transfer member must have sufficient elastic force to maintain the stable separation performance of the transfer material even when used in a low temperature and low humidity environment and when using thin paper or paper with small rigidity. In the direction in which the hardness of the intermediate transfer body is small and the elastic layer has a large thickness, the separation failure can be improved.

That is, J of the intermediate transfer member used in the present invention is used.
The IS-A hardness is 70 degrees or less, and the thickness of the elastic layer of the intermediate transfer member is 0.5 mm or more. More preferably, the JIS-A hardness of the intermediate transfer member is 10 degrees or more and 70 degrees or less,
Moreover, the thickness of the elastic layer of the intermediate transfer member is 0.5 mm or more, 10
It is in the range of mm or less.

When the JIS-A hardness of the intermediate transfer member is 10 degrees or less, or when the elastic layer of the intermediate transfer member has a thickness of 10 mm or more, the photosensitive drum, which is the first image bearing member, is contacted for a long time. The elastic layer is distorted and easily causes image defects,
There is a problem. Further, when the elastic layer of the intermediate transfer body is formed to have a thickness of 10 mm or more, the cost of the intermediate transfer body is increased.

In the present invention, the JIS-A hardness is measured by the following method. In the case of an intermediate transfer body in which the elastic layer is formed on a rigid cylinder and has a thickness of 5 mm or more, it is a measured value when a JIS-A hardness meter is pressed against the intermediate transfer body with a load of 1 kg. If the thickness is less than 5 mm, cut out the elastic layer, stack the sections of the elastic layer to 5 mm, place the object to be measured on a metal plate with sufficient rigidity, and press the hardness meter with a load of 1 kg. The value when applied.
Even when the intermediate transfer member is a belt or the like, a part of the intermediate transfer member is cut out and then measured in the same manner as above.

Further, the image forming apparatus of the present invention is an intermediate transfer member for cleaning the intermediate transfer member by applying an electric charge to the transfer residual developer not secondarily transferred from the intermediate transfer member by using a charging member. Additional charging member for cleaning
In this case, the developer is transferred from the first image carrier to the intermediate transfer member, and at the same time, the transfer residual developer on the intermediate transfer member is collected in the first image carrier. Therefore, since the primary transfer simultaneous cleaning is possible,
Since it is not necessary to enter the step of cleaning the intermediate transfer member each time one sheet is printed out, for example, in the case of continuous printing with a color laser printer, a color copying machine or the like, a significant improvement in throughput can be realized.

Further, since the intermediate transfer member can be cleaned only by the charger, the structure is very simple and a low cost cleaning means can be provided.

Further, as compared with blade cleaning, fur brush cleaning, etc., mechanical damage to the parts used is eliminated, so that it is possible to provide a stable intermediate transfer member cleaning means that can withstand long-term use.

When the above-mentioned intermediate transfer body whose potential rise of the intermediate transfer body is 300 V or more is used in the image forming apparatus having this cleaning device, the surface potential of the intermediate transfer body is raised by the cleaning charger. In some cases, the secondary transfer residual developer cannot be recovered by the first image carrier, which is the secondary transfer residual developer recovery member, and so-called cleaning failure may occur.

This is because the surface potential of the intermediate transfer member is a discharge difference in which the potential difference between the intermediate transfer member and the first image carrier, which is the secondary transfer residual developer collecting member, in the vicinity of the nip portion is indicated by the Paschen's law. When the voltage is higher than the voltage, it is considered that discharge occurs near the nip portion, disturbs the charge of the secondary transfer residual developer charged to an appropriate charge, and causes cleaning failure. Therefore, by suppressing the increase in the potential of the surface of the intermediate transfer member by the pre-transfer charger to 300 V or less, the occurrence of cleaning failure can be prevented.

Further, when the intermediate transfer member whose surface potential rise by the pre-transfer charger is 5 V or less is used, the secondary transfer residual developer on the intermediate transfer member is effectively charged with sufficient charge for cleaning. May not be granted to.
Therefore, in order to improve the cleaning property on the intermediate transfer member, it is more preferable that the potential increase of the surface of the intermediate transfer member by the pre-transfer charger is 5 V or more and 300 V or less.

The intermediate transfer member used in the present invention has at least an elastic layer and a surface layer serving as an outermost layer, and has a multilayer structure of two layers or two or more layers.

Specifically, the intermediate transfer member used in the present invention is preferably in the shape of a roller and has a structure in which an elastic layer and a surface layer are sequentially laminated on a cylindrical conductive support. For example, as shown in FIG. 4, a structure in which an elastic layer 101 is provided on the peripheral surface of a cylindrical conductive support 100 that is a rigid body, or as shown in FIG. 5, a coating layer 102 is provided on a surface layer 101. Alternatively, as shown in FIG. 6, a coating layer 103 may be further provided on the coating layer 102. However, in terms of cost, a two-layer structure including an elastic layer and a surface layer is preferable.

When the intermediate transfer member has a roller shape, it is possible to prevent color misregistration due to superposition of images. Good durability due to repeated use. And so on.

As the material used for the elastic layer, rubber or elastomer is mainly used from the viewpoint of stabilizing the nip width between the photosensitive drum and the transfer roller, but when forming the intermediate transfer member by the elastic layer alone. Several problems occur. One is the problem of contamination of the photosensitive drum. An amorphous resin such as an acrylic resin or a polycarbonate resin is used on the surface of the photosensitive drum, which is the first image bearing member, which is in contact with the intermediate transfer member in order to secure light transmittance. The bleeding of the components may contaminate or alter the surface of the photosensitive drum to cause image defects such as horizontal stripes at the pitch of the circumferential length of the photosensitive drum. Further, when the above-mentioned material is used for the elastic layer, sufficient lubricity cannot be given to the surface of the intermediate transfer member, and the adhesive force of the toner increases due to deterioration of the surface lubricity of the intermediate transfer member. Transfer efficiency cannot be obtained. Therefore, as the structure of the intermediate transfer member, by forming the surface layer on the elastic layer, the elastic layer component is prevented from leaking to the surface of the intermediate transfer member to suppress the contamination on the photosensitive drum, and the toner adhesion amount is reduced to reduce the transfer efficiency. It becomes possible to improve.

As the cylindrical conductive support used in the present invention, a metal or alloy such as aluminum, iron, copper and stainless, a conductive resin having carbon or metal particles dispersed therein, or the like can be used. Examples thereof include the above-mentioned cylindrical shape, a cylinder having a shaft penetrating the center thereof, and a cylinder having a reinforced interior.

As described above, the elastic layer of the intermediate transfer member used in the present invention needs to satisfy the stabilization of the nip width with the first image bearing member, for example, the photosensitive drum. Take the configuration used. The layer (surface-containing layer) forming the outer circumference of the elastic layer is made of rubber, elastomer or resin. As rubber, elastomer and resin used, for example, as rubber and elastomer, styrene-butadiene rubber, high styrene rubber,
Examples thereof include butadiene rubber, isoprene rubber, ethylene-propylene copolymer, nitrile butadiene rubber, chloroprene rubber, butyl rubber, silicone rubber, fluororubber, nitrile rubber, urethane rubber, acrylic rubber, epichlorohydrin rubber and norbornene rubber.

As the resins, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer are used. Copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene-acrylic Acid phenyl copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α- Methyl chloroacrylate copolymer, styrene-acryloni Styrene resins such as tolyl-acrylic acid ester copolymers (styrene or styrene-substituted homopolymers or copolymers), vinyl chloride resins, styrene-vinyl acetate copolymers, rosin-modified maleic acid resins, phenol resins , Epoxy resin, polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, fluororesin, polycarbonate,
Examples thereof include polyamide resin, polyvinyl butyral resin, and copolymers and mixtures thereof.

The volume resistivity of the intermediate transfer member used in the present invention is preferably 10 ¹ to 10 ¹³ Ω · cm, more preferably 10 ² to 10 ¹⁰ Ω · cm. Furthermore, at least the volume resistivity of the surface layer is preferably within these ranges.

In order to control the resistance as described above, a conductive agent can be added at appropriate times within a range that does not impair the object of the present invention. For example, various conductive inorganic particles and carbon black, ionic conductive agents, conductive resins, conductive particle-dispersed resins and the like can be mentioned. Specifically, titanium oxide, tin oxide, barium sulfate, aluminum oxide, strontium titanate, magnesium oxide, as conductive inorganic particles,
Particles of silicon oxide, silicon carbide, silicon nitride, etc., which have been subjected to surface treatment with tin oxide, antimony oxide, carbon, etc. as necessary, and these shapes are also spherical, fibrous, plate-like,
Any shape such as an irregular shape may be used. The ionic conductive agent is an ammonium salt, an alkyl sulfonate, a phosphate ester salt, a perchlorate, or the like, and the conductive resin is a quaternary ammonium salt-containing polymethylmethacrylate, polyvinylaniline, polyvinylpyrrole, polydiacetylene. And polyethyleneimine. Further, as the conductive particle-dispersed resin, carbon, aluminum, conductive particles of nickel or the like dispersed in a resin such as urethane, polyester, vinyl acetate-vinyl chloride copolymer and polymethylmethacrylate may be mentioned. Although not limited to these, conductive inorganic particles are preferable as the conductive agent for the surface layer from the viewpoint of controlling the conductivity among them.

A specific amount of highly lubricious powder may be added to the surface layer in order to impart high lubricity to the surface of the intermediate transfer member. As described above, when high lubricity is given to the surface of the intermediate transfer member, the adhesive force with the toner is reduced,
It has an advantage that the transfer efficiency can be further improved. The substance to be added to the surface layer is preferable to use a high lubricity of the powder, for example, fluorine rubber, full Tsu-containing elastomer,
Powders of graphite, fluorocarbons in which fluorine is bonded to graphite, and fluorine compound powders of resins such as PTFE, PVDF, ETFE, and PFA, silicone-based powders such as silicone resin particles, silicone rubber, and silicone elastomer. PE, PP, PS, acrylic resin, nylon resin,
Resins such as phenolic resins and epoxy resins and their compounds, powders of mixtures, granular carbon such as spherical graphite, inorganic powders such as silica, alumina, titanium oxide, magnesium oxide, tin oxide, iron oxide, etc. These may be used alone or in combination of two or more.

The present invention will be described in detail below with reference to examples.

[0057]

【Example】

(Example 1) Diameter 182 mm, length 320 mm, thickness 5
mm cylindrical aluminum roller is coated in advance with a rubber compound of the following composition extruded into a tube shape, and vulcanized at 150 ° C for 1 hour to give a wall thickness of 5 m.
m elastic layer was obtained. Then, the elastic layer was polished by the following method. A belt-shaped abrasive paper corresponding to # 800 was wound around the obtained elastic layer halfway, and a tension of 10 Kg was applied, and then the elastic layer was rotated at a speed of 500 rpm to rotate the belt from end to end of 50 mm / min. Moved at the speed of. At this time, the polishing belt is also 50 mm / sec by the feeding device.
It was sent at the speed of to remove the polishing dust. After that, the same surface polishing was further performed using a polishing paper corresponding to # 1000 to obtain a roller (1).

[0058]   Rubber compound epichlorohydrin rubber 70 parts by weight             NBR 30 parts by weight             Paraffin oil 25 parts by weight             Vulcanizing agent 3 parts by weight             Vulcanization aid 2 parts by weight             Vulcanization accelerator 3 parts by weight             Filler 10 parts by weight Next, a paint having the following formulation was prepared as an upper layer.

Paint formulation Polyurethane prepolymer 100 parts by weight Curing agent (including solvent) 10 parts by weight PTFE particles (particle size 0.3 μm) 200 parts by weight Dispersion aid 10 parts by weight DMF 540 parts by weight (1) A surface layer having a thickness of 15 μm is formed on the surface, then pre-dried at 80 ° C. for 30 minutes, and further heated at 130 ° C. for 2 hours to remove the residual solvent and complete the reaction, and the intermediate transfer member (1). Got The surface potential and JIS-A hardness of the obtained intermediate transfer member were measured by the above-mentioned measuring methods. The surface potential was 17 V and the JIS-A hardness was 32 degrees.

The intermediate transfer member (1) was mounted on the full-color electrophotographic apparatus having the organic photosensitive drum 1 having a protective layer as a photosensitive member and having the structure shown in FIG. 7 and using the transfer belt 26 as a transfer member. The transfer belt 26 is supported by a bias roller 27 and a drive roller 28 so as to bear parallel to the intermediate transfer member and to be in contact with the lower surface. A desired secondary transfer bias is applied to the bias roller 27 by a secondary transfer bias source 29,
The drive roller 28 is grounded. 4, the same parts as those shown in FIGS. 1 and 2 are designated by the same reference numerals.

Using this full-color electrophotographic apparatus, a low temperature and low humidity environment (temperature 15 ° C., humidity 10%, hereinafter L / L environment) and a high temperature and high humidity environment (temperature 32.5 ° C., humidity 80)
%, Hereinafter H / H environment), an endurance test was performed on 5000 full-color image prints. Two types of transfer paper were used: 75 g / m ² paper, which is plain paper for printers, and 40 g / m ² paper.

As a result, in both the L / L environment and the H / H environment, with two types of paper, no defective separation of the transfer material to the intermediate transfer body occurred, and good images were obtained at the initial stage and after the durability test of 5,000 sheets. Was obtained.

The image forming conditions of this embodiment are shown below.

Photosensitive member: Organic photosensitive drum photosensitive member having protective layer in which PTFE particles are dispersed Surface potential: -750V Color developer (for all four colors): Non-magnetic one-component toner Primary transfer voltage: + 1.0kV Secondary transfer voltage : +5.5 kV Process speed: 120 mm / sec Development bias: -550 V Intermediate transfer member cleaning charging bias: AC peak-to-peak voltage 3.0 kV, frequency 2.0 kHz, DC voltage +1.
The superimposed voltage of 0 kV. Also, bring the organic photosensitive drum into contact with this intermediate transfer member, and
After the drum was left to stand for 1 month in an environment of 0 ° C./95% RH and a drum contamination test was conducted, the surface of this organic photosensitive drum was observed, and no surface fogging or cracking was observed.
A full-color image print was performed using this organic photosensitive drum, and it was found that a uniform image was obtained in a solid image and the barrier property of the elastic layer component of the surface layer against bleeding was high.

Example 2 An intermediate transfer member (2) was prepared in the same manner as in Example 1 except that the coating composition used for the surface layer was changed to the following composition and the thickness of the surface layer was changed to 20 μm. . When the surface potential and JIS-A hardness of the obtained intermediate transfer member were measured by the above-mentioned measuring method,
The surface potential rise was 280 V and the JIS-A hardness was 34 degrees.

Fluorine resin (including solvent) 100 parts by weight (fluoroolefin-vinyl ether copolymer) Curing agent 20 parts by weight DMF 300 parts by weight This intermediate transfer member (2) was used in Example 1 in a full-color electrophotographic apparatus. Then, 5000 sheets of full-color image prints were subjected to a durability test under the same conditions as in Example 1.

As a result, in both the L / L environment and the H / H environment, with two types of paper, no defective separation of the transfer material to the intermediate transfer body occurred, and good images were obtained at the initial stage and after the durability test of 5,000 sheets. Was obtained.

A drum contamination test was conducted on this intermediate transfer member (2) under the same conditions as in Example 1. No fog or cracking on the surface of the organic photosensitive drum was observed.
A full-color image print was performed using this organic photosensitive drum, and it was found that a uniform image was obtained in a solid image and the barrier property of the elastic layer component of the surface layer against bleeding was high.

Example 3 An intermediate transfer member was prepared in the same manner as in Example 1 except that the filler for the elastic layer was changed from 10 parts by weight to 30 parts by weight to obtain an intermediate transfer member (3). It was With respect to the obtained intermediate transfer member, the surface potential rise and JIS-A hardness were measured by the above-described measuring method. The surface potential rise was 19 V and the JIS-A hardness was 68.
It was degree.

The intermediate transfer member (3) was mounted on the full-color electrophotographic apparatus used in Example 1, and 5000 sheets of full-color image prints were subjected to a durability test under the same conditions as in Example 1.

As a result, in both the L / L environment and the H / H environment, with two types of paper, no defective separation of the transfer material to the intermediate transfer body occurred, and good images were obtained at the initial stage and after the durability test of 5,000 sheets. Was obtained.

Further, when a drum contamination test was conducted on this intermediate transfer member (3) under the same conditions as in Example 1, no fog or cracking on the surface of the organic photosensitive drum was observed, and this organic photosensitive drum was also tested. A full-color image print was carried out using the same, and it was found that a uniform image was obtained in a solid image and the barrier property against bleeding of the elastic layer component of the surface layer was high.

Example 4 An intermediate transfer member was prepared in the same manner as in Example 1 except that the thickness of the elastic layer was changed from 5 mm to 0.6 mm to obtain an intermediate transfer member (4). The surface potential increase and JIS-A hardness of the obtained intermediate transfer member were measured by the above-mentioned measuring method,
The surface potential rise was 13 V, and the JIS-A hardness was 36 degrees.

This intermediate transfer member (4) was mounted on the full-color electrophotographic apparatus used in Example 1, and 5000 sheets of full-color image prints were subjected to a durability test under the same conditions as in Example 1.

As a result, in both the L / L environment and the H / H environment, the separation of the transfer material onto the intermediate transfer member did not occur with two types of paper, and good images were obtained at the initial stage and after the durability test of 5000 sheets. Was obtained.

A drum contamination test was conducted on this intermediate transfer member (4) under the same conditions as in Example 1. No fog or cracking on the surface of the organic photosensitive drum was observed. A full-color image print was carried out using the same, and it was found that a uniform image was obtained in a solid image and the barrier property against bleeding of the elastic layer component of the surface layer was high.

Comparative Example 1 An intermediate transfer member (5) was prepared in the same manner as in Example 2 except that the thickness of the surface layer was changed from 20 μm to 30 μm. With respect to the obtained intermediate transfer member (5), the surface potential rise and JIS-A hardness were measured by the above-described measuring methods. The surface potential rise was 320 V and the JIS-A hardness was 34 degrees.

The intermediate transfer member (5) was mounted on the full-color electrophotographic apparatus used in Example 1, and 5000 sheets of full-color image prints were subjected to a durability test under the same conditions as in Example 1.

[0079] As a result, the L / L environment and H / H environments both at 75 g / m ² paper, but did not occur in the separation failure of the transfer material to the intermediate transfer member, in the 40 g / m ² paper, L / L In the environment, separation failure occurred near the 200th sheet, and 43 out of 5000 sheets failed. Also in the H / H environment, separation failure occurred near the 550th sheet, and 19 out of 5000 sheets failed.

Comparative Example 2 An intermediate transfer member (6) was obtained in the same manner as in Example 1, except that the filler for the elastic layer was changed from 10 parts by weight to 50 parts by weight. With respect to the obtained intermediate transfer member (6), the surface potential rise and JIS-A hardness were measured by the above-mentioned measuring methods. The surface potential rise was 18 V and the JIS-A hardness was 74 degrees.

This intermediate transfer member (6) was attached to the full-color electrophotographic apparatus used in Example 1, and 5000 sheets of full-color image prints were subjected to a durability test under the same conditions as in Example 1.

As a result, in the L / L environment and the H / H environment in the 75 g / m ² paper, the separation of the transfer material to the intermediate transfer body did not occur, but in the 40 g / m ² paper, the L / L In the environment, poor separation occurred near the 500th sheet, and 26th of the 5000 sheets failed. Also, in the H / H environment, separation failure occurred near the 750th sheet, and 11 out of 5000 sheets failed.

Comparative Example 3 An intermediate transfer member (7) was obtained in the same manner as in Example 1, except that the thickness of the elastic layer was changed from 5 mm to 0.4 mm. With respect to the obtained intermediate transfer member (7), the surface potential rise and JIS-A hardness were measured by the above-described measuring methods. The surface potential rise was 12 V and the JIS-A hardness was 34 degrees.

This intermediate transfer member (7) was mounted on the full-color electrophotographic apparatus used in Example 1, and the durability test of 5000 full-color image prints was conducted under the same conditions as in Example 1.

As a result, in the L / L environment and the H / H environment in the case of 75 g / m ² paper, the separation of the transfer material to the intermediate transfer member did not occur, but in the case of 40 g / m ² paper, the L / L In the environment, poor separation occurred near the 550th sheet, and 16 poor sheets out of 5000 sheets. Further, even in the H / H environment, separation failure occurred near the 700th sheet, and 13 out of 5000 sheets failed.

[0086]

As described above, according to the present invention, after the image formed on the first image carrier is primarily transferred to the intermediate transfer member,
An image forming apparatus for further secondary transfer onto a second image carrier, the image forming apparatus having a charger for charging an image primarily transferred onto the intermediate transfer body before the secondary transfer, the intermediate transfer body Has at least an elastic layer and a surface layer that is the outermost layer, the potential increase of the surface of the intermediate transfer member by the charger is 300 V or less, and the JIS-A hardness of the intermediate transfer member is 70 degrees or less, and By setting the thickness of the elastic layer of the intermediate transfer member to be in the range of 0.5 mm or more, stable transfer performance and separation performance can be obtained regardless of the use environment, regardless of the type and size of the transfer material. Has the advantage.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a color image output device using a roller-shaped intermediate transfer member.

FIG. 2 is an explanatory diagram showing a configuration of a color image output device using a pre-transfer charger.

FIG. 3 is an explanatory diagram illustrating a method for measuring the surface potential of an intermediate transfer member.

FIG. 4 is a cross-sectional view of a roller-shaped intermediate transfer member having an elastic layer used in the present invention.

FIG. 5 is a cross-sectional view of a roller-shaped intermediate transfer member having a coating layer on the elastic layer used in the present invention.

FIG. 6 is a cross-sectional view of a roller-shaped intermediate transfer member having a plurality of coating layers on an elastic layer used in the present invention.

FIG. 7 is an explanatory diagram showing a configuration of a color image output device used in an embodiment of the present invention.

[Explanation of symbols]

1 photosensitive drum 2 Primary charger 3 Image exposure means 9 paper cassettes 14 Photosensitive drum cleaning device 15 Fixer 20 Intermediate transfer body 21 core 22 Elastic layer 23 Pre-transfer charger 24 Transfer material 25 Transfer roller 26 Transfer belt 27 Bias roller 28 Drive roller 29 Secondary transfer bias power supply 35 Charging member for cleaning intermediate transfer member 36 Bias power supply for intermediate transfer member cleaning member 41 Magenta color developing device 42 Cyan color developing device 43 Yellow color developing device 44 Black color developing device 61 Primary transfer bias power supply 100 cores 101 elastic layer 102 coating layer 103 coating layer 200 corona charger 201 Bias power supply 202 surface electrometer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-220902 (JP, A) JP-A-1-92771 (JP, A) JP-A-5-210315 (JP, A) JP-A-8- 63003 (JP, A) JP-A-1-273080 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/16-15/16 103 G03G 15/01-15/01 117

Claims (5)

(57) [Claims] 1. An intermediate transfer member is configured such that an image formed on a first image carrier is primarily transferred to an intermediate transfer member and then secondarily transferred to a second image carrier. a Oite, the intermediate transfer member at least an elastic layer and a surface layer which is the outermost layer to an image forming apparatus having a charger for charging before the secondary transfer of the primary transferred image, the intermediate transfer member The surface potential increase by the charger of 300 V or less, the JIS-A hardness of the intermediate transfer member is 70 degrees or less, and the elastic layer thickness of the intermediate transfer member is 0.5 mm or more. Image forming apparatus . 2. The image forming apparatus according to claim 1 , wherein the intermediate transfer member has a roller shape. 3. The image forming apparatus according to claim 1, wherein the intermediate transfer member has a two-layer structure including a surface layer and an elastic layer.
Place 4. The surface potential rise by the charger is 5V.
The above-mentioned 300V or less, the JIS-A hardness of the intermediate transfer body is 10 degrees or more and 70 degrees or less, and the thickness of the elastic layer of the intermediate transfer body is in the range of 0.5 mm or more and 10 mm or less. The image forming apparatus according to any one of items. 5. The transfer residual developer that has not been secondarily transferred from the intermediate transfer member is charged by using a charging member,
An intermediate transfer member cleaner for cleaning the intermediate transfer member
And a transfer residual developer on the intermediate transfer member, and at the same time, transfer the developer from the first image carrier to the intermediate transfer member. The image forming apparatus according to any one of claims 1 to 4, which is configured as described above.