JP2002091186A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of eliminating the faulty attraction of recording material to a transfer belt and preventing the deterioration of a transfer member caused by the unevenness of surface free energy on the inner surface of the transfer belt and preventing an image defect because of the deterioration thereof. SOLUTION: In this image forming device, a recording material carrying means for carrying the recording material on a recording material carrier has an electrifying pressing member for applying charge while holding the recording material in such pressure distribution that pressure is higher at a center part than at an end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus, and more particularly, to a four-drum type full-color image forming apparatus.

[0002]

2. Description of the Related Art In recent years, multifunction peripherals having all output terminals such as copiers, printers, and faxes have been widely accepted in the market. The electrophotographic system has been widely accepted as such a network-compatible output terminal, but one of the major problems is the DutyCycle of the main body. This is the limit number of sheets that the main body can continue to operate normally without service maintenance, but one of the biggest limiting factors of Duty Cycle is the longevity of the photosensitive drum. Also, from the viewpoint of ecology, eliminating waste, that is, reducing consumables, extending the life of consumables, and increasing reliability have become our absolute issues. Digitization has progressed from conventional analog devices, and it has become an absolute issue for us to reduce the cost of the main unit to be equal to or less than the analog. Further, in recent years, black-and-white machines have conventionally been the mainstream in copying machines and printers, but in offices, the use of originals or output files in full color has been rapidly increasing. Not only the analog equivalent digital machine, but also the main body cost and the running cost black and white equivalent full color printer are becoming our absolute issues. For that purpose, a technology capable of dramatically reducing the TCO (total required cost as viewed from the user) is desired.

Under these circumstances, in recent years, a plurality of photoconductors and a transfer belt that carries and conveys a recording material have been provided, and the recording material carried on the transfer belt has different colors formed on the respective photoconductors. Among color image forming apparatuses that obtain a color image by sequentially superimposing and transferring toner images,
A continuous tandem type color image forming apparatus has become mainstream.

In the above-described image forming apparatus, the toner scattered from the photosensitive drum or the toner transferred from the photosensitive drum at the time of a jam or a paper interval is formed on a recording material carrier (hereinafter, referred to as a “transfer belt”). Further, when an image is formed on the second surface of the recording material after the toner image is fixed on the first surface of the recording material, the release agent oil adhered to the recording material when the toner image is fixed on the first surface, etc. Therefore, it has been proposed to provide a counter blade system, a fur brush system, and an oil cleaner roller and an oil cleaner web for removing the release agent oil from the transfer belt as cleaning means. Further, there has been proposed a toner produced by a polymerization method in which such a release agent oil does not need to be used and oil is internally added.

An image forming apparatus that adsorbs and conveys a recording material such as paper on an endless belt and forms an image has been commercialized. An example of such an image forming apparatus will be briefly described with reference to FIG.

[0006] Inside the image forming apparatus, a photosensitive drum 105 as an image carrier is provided, and a toner image is formed. Recording material carrier (transfer belt) adjacent to photosensitive drum 105
The toner image formed on the photosensitive drum is transferred onto the recording material P carried and conveyed on the transfer belt 106. The recording material P to which the toner image has been transferred is fixed to the fixing device 109 by heating and pressing to fix the toner image, and then is discharged outside the apparatus as a recording image.

On the outer periphery of the photosensitive drum 105, an exposure lamp 101, a photosensitive drum charger 102 as a charging unit, an exposure device 103, a developing unit 104 as a developing unit, a transfer charger 107 as a transfer charging unit, and a cleaner 108
Is provided in the upper part of the apparatus, not shown,
Further, a light source device and a polygon mirror are provided.

[0008] The laser beam emitted from the light source device is scanned by rotating the polygon mirror, the light beam of the scanning light is changed by the reflection mirror, and is condensed on the generatrix of the photosensitive drum 5 by the fθ lens and exposed. The photosensitive drum 10
An electrostatic latent image corresponding to the image signal is formed on 5.

The developing device 104 is filled with a predetermined amount of toner by a toner supply device (not shown). Developing unit 104
Develops the latent image on the photosensitive drum 105 and visualizes it as a toner image.

The recording material P is accommodated in a recording material cassette (not shown), is supplied to the transfer belt 106 through a plurality of conveyance rollers and registration rollers 113, and faces the photosensitive drum 5 by conveyance by the transfer belt 106. It is sequentially sent to the transfer unit.

The transfer belt 106 is made of a polycarbonate resin sheet or a polyethylene terephthalate resin sheet (P
(ET resin), or a dielectric resin sheet such as a polyvinylidene fluoride resin sheet, a polyurethane resin sheet, a polyamide resin sheet, or a polyimide resin sheet, in which a conductive filler such as carbon black is dispersed. It is made of a material adjusted to a low value of about ⁷ to 10 ¹¹ Ω · cm, and its both end portions are joined together to form an endless shape, or a seamless (seamless) belt is used.

In order to improve the life and reliability of the transfer belt in consideration of TOC, a tensile strength of at least 1000 kg / cm ² such as a polyimide resin sheet and a Young's modulus of at least 2.5 × 10 ⁴ kg / cm ² are required. High strength, low wear members are being used.

The transfer belt 1 is driven by a driving roller 111.
When 06 rotates and reaches a certain speed, the recording material P is sent out from the registration roller 113 to the transfer belt 106, and the recording material P is conveyed toward the transfer unit. At the same time, the image writing signal is turned ON, and an image is formed on the photosensitive drum 105 at a certain timing based on the signal. Then, a transfer charger 10 is provided at a transfer portion below the photosensitive drum 105.
The toner image formed on the photosensitive drum 105 is transferred to the recording material P by applying an electric field or charge to the recording material P. The recording material P is transferred from the registration roller 113 to the transfer belt 1.
As soon as it is sent out onto the transfer belt 06, it is electrostatically held on the transfer belt 106 and conveyed by being applied with an electric field or charge by the attraction charger 114.

As the transfer charger 107, a non-contact charger such as a corona discharge or a contact charger using a charging member such as a charging roller, a charging brush or a charging blade is used.
The non-contact charger has problems that ozone is generated, and the image is not formed stably because it is vulnerable to environmental changes in the temperature and humidity of the atmosphere because it is charged via air. On the other hand, the contact charger has advantages such as ozonelessness and resistance to temperature and humidity environmental fluctuations.

Next, the recording material P on which the toner image has been transferred is neutralized by the separation charger 116 at a downstream portion of the transfer belt 106 in the conveying direction to attenuate the electrostatic attraction force.
The transfer belt 106 is separated from the end. Particularly in a low humidity environment, the recording material also dries and the electric resistance increases, so that the electrostatic attraction between the recording material and the transfer belt increases, and the effect of the separation charger increases. Normally, a non-contact charging device is used for the separation charging device because the recording material P is de-charged in a state where the toner image is not fixed. The output of the separation charger 16 is Vpp = 10 kV, 500
An AC voltage of about Hz is used. In addition, in order to prevent image defects such as toner scattering, in addition to the AC output, +1
A plus or minus DC component of about 00 μA may be superimposed.

The detached recording material P is conveyed to the fixing device 109. The fixing device 109 includes a fixing roller, a pressure roller, a heat-resistant cleaning member that cleans each of the rollers, a heating heater installed in each roller, and an application roller that applies a release agent oil such as dimethyl silicone oil to the fixing roller. And a thermistor that detects the surface temperature of the pressure roller and controls the fixing temperature. The recording material P on which the toner image is formed is fixed to the recording material P by fixing, a copy image is formed, and the copy image is discharged to a discharge tray.

After the transfer, the photosensitive drum 105 is cleaned and removed of residual toner by a cleaner 108, and is ready for the next latent image formation.

After the recording material P is separated, the transfer belt 106 is connected to the conductive fur brush 110 installed on the recording material carrier side and the drive roller 1 grounded as opposed to the conductive fur brush 110.
By contacting the transfer belt 11, toner and other foreign matters remaining on the transfer belt 106 are cleaned, and at the same time, accumulated charges are removed (discharge). As the conductive fur brush, a conductive web (nonwoven fabric) can be used.

In the conventional image forming apparatus as described above, as a means for electrostatically adsorbing the recording material P, an adsorption charger 114 is used.
And a pair of rollers consisting of an opposing roller and a suction charger. Of course, a non-contact charger such as a corona discharge, or a charging roller, a charging brush, and a charging blade as the electrostatic charging means are used as the electrostatic suction means. Contact chargers using such a charging member are also used. However, when a non-contact system is used, the contact state between the recording material P and the transfer belt 106 cannot be guaranteed. Therefore, it is necessary to provide a separate pressing member to secure the adhesion between the recording material P and the transfer belt 106. is there.

In order to stably transport the recording material P by electrostatic attraction as described above, it is needless to say that the entire width of the recording material P is attracted and charged with respect to the paper width.

However, in the image forming apparatus according to the prior art as described above, first, a recording material left undisturbed in a humid or low humidity environment, a recording material used as a second surface during double-sided printing with an image on the back side, and the like are used. If used, the image quality may be significantly reduced. The reason for this is that these recording materials are deformed and the flatness is impaired, so that there are places where the contact state with the transfer belt 106 is not improved.

For example, paper as a recording material loaded in a paper feed cassette absorbs or discharges moisture depending on the temperature and humidity of the outside air. In the process, the paper is deformed into a shape almost like a part of a spherical surface. Such paper is the transfer belt 1
When the paper is fed onto the transfer belt 106 and passes through a pair of rollers of the attraction charger 114 and the attraction charger opposing roller 115, it is squeezed by the roller pair and is formed into the transfer belt 106 having a high flatness. The deformation is accumulated as the sheet passes, and as a result, the deformation is carried in the center of the rear end portion while floating from the transfer belt 106. Since the floating portion has a gap even in the transfer portion, the image on the photosensitive drum 105 cannot be transferred, which may result in an image defect. Second, when a member having a rubber material on its surface layer is brought into contact with the inner surface of the transfer belt, process oil or the like internally added to the rubber material migrates, and the surface free energy of the inner surface of the transfer belt is extremely increased. Has been newly found in our diligent examination.

The transfer belt has a tensile strength of 1000 kg / cm ² or more and a Young's modulus of 2.5 × 10 ⁴ kg, such as a polyimide resin sheet having improved life and reliability of the transfer belt.
/ Cm ² or higher strength, low wear, low surface roughness, and when used as a charging member, it was found to be even more remarkable. As a result, unevenness in the surface free energy of the inner surface of the transfer belt at the downstream transfer portion promotes image defects, deterioration of the transfer blade, and the like, leading to a reduction in reliability.

[0024]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to stably perform electrostatic adsorption and conveyance of a recording material. An object of the present invention is to provide an image forming apparatus in which occurrence of an image defect is prevented.

[0025]

According to the present invention, there is provided a recording material holding means for holding a recording material, comprising a charge pressing member for holding the recording material with an uneven pressure distribution and applying a charge. Can be solved, and the present invention has been achieved.

That is, the present invention is as follows. (1) A recording material carrier that carries and conveys a recording material, an image forming unit that forms a visible image with toner on the recording material carried by the recording material carrier, and a cleaning unit that cleans the recording material carrier An image forming apparatus comprising: a recording material supporting means for supporting a recording material on the recording material supporting body; An image forming apparatus, comprising: a charge pressing member for holding a material and applying a charge. (2) The charging and pressing member is a contact type charger, a central portion of the charging and pressing member is formed of an elastic body made of a conductive material, and an end of the charging and pressing member is formed of a conductive fiber. (1) The image forming apparatus according to (1). (3) The image forming apparatus according to (2), wherein the elastic body made of the conductive material includes a fluororesin layer. (4) The image forming apparatus according to (2), wherein the elastic body made of a conductive material contains a polyamide elastomer resin. (5) The elastic body made of the conductive material has at least 2
(2) The roller is formed in the shape of a roller having at least two layers, wherein the charging pressing member rotates and its peripheral speed follows the moving speed of the member to be charged.
The image forming apparatus according to any one of (1) to (4). (6) The recording material carrier has a Young's modulus of 2.5 kg / cm ^2.
As described above, the image forming apparatus according to any one of (1) to (5), comprising a material having a tensile strength of 1000 kg / cm ² or more. (7) The image according to any one of (1) to (6), wherein the amount of wear of the recording material carrier when the image forming apparatus is operated is 1.0 μm / 100,000 rotations or less. Forming equipment. (8) The toner is a non-magnetic toner, has a weight average particle diameter of 6 to 10 μm, and has a shape factor S
F-1 is 100 to 140 and SF-2 is 100 to 120
The image forming apparatus according to any one of (1) to (7), wherein the toner is a substantially spherical toner produced by a polymerization method falling within the range of (1). (9) The image forming means is an image carrier for carrying an electrostatic latent image, a charging means for applying a voltage to the surface of the image carrier and charging the surface of the image carrier, and charged by the charging means. An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the image carrier; a developing means for forming a visible image by attaching toner to the electrostatic charge image formed on the surface of the image carrier; Transfer charging means for transferring the visible image formed on the surface of the carrier to a recording material, wherein the image forming means is provided for each of the first to fourth color toners. The image forming apparatus according to any one of (1) to (8), wherein the toner images of each color are sequentially superimposed and transferred onto the recording material carried on the material carrier.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. <1> Recording Material Carrier and Recording Material Carrier in the Present Invention The recording material carrier in the present invention is for supporting the recording material on the recording material carrier, and has a charge pressing member.

As a recording material holding means, specifically, in FIG. 1, a pair of suction chargers (adsorption roller 11a and suction roller 11a) for sucking and conveying the recording material P to a transfer belt 71 as a recording material carrier. Charging device 11b).

The suction charger 11b of the suction charger pair is a charging pressing member.

The charge pressing member according to the present invention has a configuration in which the central portion sandwiches the recording material with a pressure distribution higher than that of the end portion and applies a charge. With such a configuration, it is possible to eliminate poor adsorption of the recording material to the recording carrier.

In the present invention, the charging / pressing member is preferably a contact-type charger. The central portion of the charging / pressing member is formed of an elastic body made of a conductive material, and the ends are formed of conductive fibers. Is preferred.

The elastic body made of a conductive material constituting the central portion has a rubber layer formed of rubber such as acrylic rubber (ACM), butadiene rubber (BR), and ethylene propylene rubber (EPDM). The elastic body has a hardness of 40 to 90 ° and a volume resistivity of 10 ⁵ to 10 ¹⁰ Ω.
・ Cm is preferred. The elastic body made of a conductive material is formed into a roller having two or more layers having a surface layer on the rubber layer so as to prevent transfer of an internal additive such as process oil internally added to the rubber layer to the belt. Preferably, it is formed. Such an elastic body formed in a roller shape having two or more layers preferably has a fluororesin layer or a polyamide elastomer resin layer as a surface layer, and particularly preferably has a fluororesin layer.

Further, as the fluororesin layer, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF),
Group consisting of polyvinyl fluoride (PVF), tetrafluoroethylene-hexafluoropropylene copolymer (PFEP), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA) and tetrafluoroethylene-ethylene copolymer (PETFE) And one or more fluororesins selected from the group consisting of:

Further, the end of the charging pressing member is composed of conductive fibers, as the conductive fiber, 10 ³ to 10 ⁹
Conductive fibers (trade name, Kainol, etc.) with an electrical resistance of Ω · cm, made by dispersing conductive carbon in fibers such as rayon or nylon, are 10 to 50 fibers /
A brush-like body (brush) bundled at a density of mm ² may be used. Further, it is preferable that the charging pressing member in the present invention makes a rotational movement, and its peripheral speed is substantially equal to the moving speed of the transfer belt.

As the charging pressing member in the present invention, specifically, an adsorption charger 11b as shown in FIG. 2 is preferably mentioned, but the present invention is not limited to this.

The suction charger 11b shown in FIG. 2 has a 150 mm width in the central portion in the longitudinal direction covered with conductive rubber, and a conductive fur brush is planted at 80 mm on both ends.

More specifically, the center portion is made of a conductive rubber material made of EPDM (hardness 50 degrees, volume resistivity 10 ⁸ Ω · cm).
The thickness is 1.0 mm, and both ends are conductive rayon hair (volume resistivity: 10 ⁶ Ω · cm, density: 80 / mm ² ) hair length: 3.0 mm (including base cloth) The conductive rubber layer has a surface layer covered with a polyamide elastomer (hereinafter referred to as “PAE”) tube. The PAE tube contains carbon and has a surface resistance of 3 × 10 ⁶ Ω · c.
m, a Young's modulus of 130 (Mpa), a surface roughness Rz of 2.3 μm, and a thickness of 100 μm. In the present invention, the method for measuring the surface resistance value is JIS K691.
Perform based on 1.

The penetration amount of the fur brushes at both ends in the state where the transfer belt 71 is in contact is expected to be 1.0 mm. As shown in FIG. 3A, a pair of attraction charging rollers 11 is used, and the attraction charger 11b is used as an attraction charger opposing roller 11a.
By holding the transfer belt 71 together with (grounding), a strong holding force is applied to the conductive rubber portion at the center, and the fur brush bristles at both ends are weakly pressed by the fur brush bristles. A negligibly small holding force is applied to the recording material P and the transfer belt 71 as compared with FIG. 3B shows the pressure distribution of the suction charging roller pair 11.

Due to the action of the pressure distribution of the pair of charging and attracting rollers as shown in FIG. 3B, for example, the sheet is left unattended for a long period of time, or a printed image already exists on the back side, so that it deforms and the flatness is significantly reduced. Even when the recording material P is used,
By passing through the suction section formed by the pair of charging and suction rollers, an effect is produced in which the recording material P is deformed from the center line parallel to the transport direction to the outside while being along the transfer belt 71 (FIG. 1)). If the pressure distribution as shown in FIG. 4B is used, for example, when the recording material P that has been left unattended for a long period of time, or has a printed image already present on the back surface, and has been deformed and significantly reduced in flatness is used, A floating portion occurs at the rear end of the recording material P, and an image defect occurs. Although the example using the adsorption charger has been described above, it is needless to say that the present invention can be applied to the case where the image is simultaneously adsorbed in the transfer unit without performing the adsorption charging.

The recording material carrier of the present invention carries and conveys the recording material, and may have a belt shape, a drum shape, or the like.

The recording material carrier has a Young's modulus of 2.5 kg.
/ Cm ² or more and a material having a tensile strength of 1000 kg / cm ² or more (JIS K7113).

If the Young's modulus is less than 2.5 kg / cm ² or the tensile strength is less than 1000 kg / cm ² , the belt may break, and the belt circumference may change in durability. The recording material carrier satisfying the above physical properties can be obtained by appropriately selecting and using a commercially available polyimide resin. Specifically, the transfer belt as a recording material carrier is made of a sheet obtained by dispersing a conductive filler such as carbon black in a dielectric resin and performing resistance adjustment.
For example, a material made of a polyimide resin having a volume resistivity of 10 ¹² Ω · cm and a film thickness of 75 μm is used, and both ends are overlapped and joined together to form an endless shape or have no seams (seamless). ) A belt can be used.

The amount of wear of the transfer belt when the image forming apparatus is operated is preferably 1.0 μm / 100,000 revolutions or less, and more preferably 0.5 μm / 10
More preferably, the rotation is not more than 000 revolutions.

When the amount of wear of the recording material carrier when the image forming apparatus is operated is 1.0 μm / 100,000 revolutions or less, the life of the transfer belt becomes 1,000,000 sheets or more. The amount of wear of the recording material carrier was set to 1.0 μm / 100,0
In order to reduce the rotation to less than 00 revolutions, the Young's modulus of the recording material carrier is 2.5 kg / cm ² or more and the tensile strength is
m ² or more, and the initial coefficient of friction is set to 0.
It is preferred to be 5 or less. Further, after the endurance, it is possible to prevent the transfer of the process oil or the like internally added to the rubber material to the belt, so that it is possible to prevent a rise in μ (mew) on the surface and to reduce the amount of wear. In the present invention, the wear amount of the recording material carrier is measured as follows. In addition, the same measurement was performed in Examples described later. Measuring method: Laser displacement meter Measured using KEYENCE LT-8010. The coefficient of friction of the recording material carrier is measured using HEIDON Tribogear Muse TYPE: 94B (trade name). <2> Toner in the Present Invention The toner in the present invention is preferably a non-magnetic toner, has a weight average particle diameter of 6 to 10 μm, and has a shape factor SF-1 of 100 to 140 and SF-
2 is more preferably a substantially spherical toner produced by a polymerization method in the range of 100 to 120.

The toner having the above-mentioned weight average particle diameter and shape factor in the present invention is obtained by a polymerization method for producing a toner by polymerizing a polymerizable monomer composition having at least a polymerizable monomer and a colorant. It is particularly preferable to manufacture the toner using a suspension polymerization method in which the polymerizable monomer composition is subjected to suspension polymerization in an aqueous medium to manufacture the toner. When producing a toner by this suspension polymerization method, by appropriately changing the stirring speed of a stirrer in an aqueous medium, the weight average particle size of the toner is controlled by controlling the particle size of the granulated particles. It is also possible to change the shape factor of the toner by changing the polymerization conditions such as the selection of the composition of the toner material to be contained in the polymerizable monomer composition and the polymerization temperature during polymerization, and the pH of the aqueous medium. It is possible to control. The toner in the present invention can be used as a non-magnetic toner for a two-component developer.

By using a non-magnetic toner having a weight average particle diameter of 6 to 10 μm, a high-resolution and high-quality image can be obtained. In the present invention, the method for measuring the average particle size of the toner is as follows. The particle size distribution of the toner is measured using a Coulter Counter TA-II or a Coulter Multisizer (manufactured by Coulter). As the electrolytic solution, a 1% NaCl aqueous solution is prepared using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter Scientific Japan) can be used. As a measurement method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and the measurement sample is added to 2 to 50 ml.
Add ~ 20 mg. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the volume and the number of toner particles having a size of 2 μm or more are measured by using the measuring device using a 100 μm aperture as the aperture. Calculate the number distribution. As non-magnetic polymerized toner,
It is preferable that the shape factor SF-1 is within the range of 100 to 140 and SF-2 is within the range of 100 to 120.

In the present invention, the shape factors SF-1 and S
F-2 was replaced with a scanning electron microscope FE- manufactured by Hitachi, Ltd.
Using a SEM (S-800), 100 toner particles are randomly sampled, and the image information is obtained through an interface through an image analyzer (Luzex) manufactured by Nireco Corporation.
The value is calculated by the following equation and defined as shape factors SF-1 and SF-2.

[0048]

(Equation 1) (AREA: toner projection area, MXLNG: absolute maximum length, PERI: circumference) By using such a spherical toner, transfer efficiency is 95%.
The above can always be secured, which is an essential component of the cleaningless system. As the two-component developer, it is preferable to use a mixture of the polymerized toner and a resin magnetic carrier produced by a polymerization method.

As the magnetic carrier, the specific gravity is 2.5 to
4.5, especially 2.5-4.0, 79.58 kA
/ M (1000 Oe) in a magnetic field of 15 to 60 Am ² / kg, especially 25
６０60 Am ² / kg, remanent magnetization (σr) 0.1-20
Am ² / kg, particularly preferably in 0.1~10Am ² / kg. Further, it is preferable to use one having a number average particle size of 15 to 60 μm and a specific resistance of 1 × 10 ⁴ to 1 × 10 ⁹ Ω · cm.

In the present invention, the ratio of the carrier of the developer to the developer is preferably 4 to 12% in T / D. <3> Image Forming Apparatus According to the Present Invention The image forming apparatus according to the present invention includes a recording material carrier that carries and conveys a recording material, and an image forming unit that forms a toner image on the recording material carried by the recording material carrier. Cleaning means for cleaning the recording material carrier, and further comprising the recording material carrying means for carrying the recording material on the recording material carrier.

Further, the image forming means of the present invention comprises: an image carrier for carrying an electrostatic latent image; a charging means for applying a voltage to the surface of the image carrier to charge the surface of the image carrier; Latent image forming means for forming an electrostatic latent image on the surface of the image carrier charged by the above, and development for forming a visible image by attaching toner to the electrostatic charge image formed on the surface of the image carrier Means for transferring a visible image formed on the surface of the image carrier to a recording material.

The image forming apparatus of the present invention has a feature in the recording material holding means, and other than that, those used in ordinary image forming apparatuses can be used. However, it is preferable to use the above-described recording material carrier and toner. Hereinafter, one embodiment of the image forming apparatus of the present invention will be described with reference to FIG. 1, but the present invention is not limited to this.

In the apparatus, Pa, Pb, Pc, and Pd are provided side by side as first, second, third, and fourth image forming means. It is formed through a transfer process.

Image forming means Pa, Pb, Pc and Pd
In FIG. 1, electrophotographic photosensitive drums 3a, 3b, 3c and 3d are provided as dedicated image carriers, and toner images of respective colors are formed on the photosensitive drums 3a, 3b, 3c and 3d. You. A transfer belt 71 as a recording material carrier is installed adjacent to each of the photosensitive drums 3a to 3d, and toner images of respective colors formed on the photosensitive drums 3a, 3b, 3c and 3d are carried on the transfer belt 71. The image is transferred onto the conveyed recording material P. Further, the recording material P on which the toner images of the respective colors have been transferred is heated and pressed by the fixing device 9 to fix the toner images, and then discharged out of the apparatus as a recorded image.

The image formation will be described with reference to the photosensitive drum 3a.

First, the original G is set on the original table 10 with the surface to be copied facing downward. Next, copying is started by pressing the copy button. The original illumination lamp, short focus lens array, and CCD sensor (not shown) form an integrated unit and scan while irradiating the original.
The reflected light of the illumination scanning light on the document surface is imaged by the short focus lens array and is incident on the CCD sensor. CCD
The sensor includes a light receiving unit, a transfer unit, and an output unit.
The light signal is converted into a charge signal in the CCD light receiving unit, and the transfer unit sequentially transfers the light signal to the output unit in synchronization with the clock pulse. The output unit converts the charge signal into a voltage signal, amplifies the signal, reduces the impedance, and outputs the voltage signal. The analog signal thus obtained is subjected to image processing by a well-known method, converted into a digital signal, and sent to a printer unit. The printer unit receives the image signal and forms an electrostatic latent image as follows. Photosensitive drums 3a to 3d
Is rotated in the direction of arrow A at a predetermined peripheral speed about the center support shaft, and during the rotation process, is uniformly charged with a negative polarity by the magnetic brush charger 2a serving as a charging means that is driven to rotate in the direction of arrow B. After receiving the processing, the light of the solid-state laser element, which is turned on and off in response to the image signal on the uniformly charged surface, is scanned by a rotating polygon mirror that rotates at a high speed, so that the surface of the photosensitive drum can be used for the original image. The formed electrostatic latent images are sequentially formed.

As the photosensitive drum 3 used in the present invention, a commonly used organic photosensitive member or the like can be used. Preferably, the resistance is 10 ^-9 to 1 on the organic photosensitive member.
0 and one with a surface layer having a material of ¹⁴ Omega · cm, the use of such amorphous silicon photosensitive member, can be realized charge injection charging, the prevention of ozone generation, and is effective in reducing power consumption. Further, the chargeability can be improved.

More specifically, the following first photosensitive member is formed on a 30 mm-diameter aluminum drum substrate made of a negatively charged organic photosensitive member.
To the fifth five layers are provided in order from the bottom.

The first layer is a subbing layer, and is a conductive layer having a thickness of 20 μm provided to smooth defects or the like of an aluminum substrate (hereinafter referred to as “aluminum substrate”).

The second layer is a positive charge injection preventing layer, which functions to prevent the positive charge injected from the aluminum substrate from canceling out the negative charge charged on the surface of the photoreceptor. 1x by methoxymethylated nylon
This is a medium-resistance layer having a thickness of 1 μm and a resistance adjusted to about 10 ⁻⁶ Ω · cm.

The third layer is a charge generating layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs upon exposure.

The fourth layer is a charge transport layer, in which hydrazone is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, the negative charges charged on the photoreceptor surface cannot move through this layer, and only the positive charges generated in the charge generation layer can be transported to the photoreceptor surface.

The fifth layer is a charge injection layer, which is a coating layer of a material in which SnO ₂ ultrafine particles are dispersed in a binder of an insulating resin. Specifically, doping the insulating resin with antimony, which is a light-transmitting insulating filler, reduces the resistance (makes it conductive)
This is a coating layer of a material in which SnO ₂ particles having a particle size of about 0.03 μm are dispersed in a resin by 70% by mass. The thus prepared coating liquid is applied to a thickness of about 3 μm by a suitable coating method such as dipping coating method, spray coating method, roll coating method, beam coating method, etc. to form a charge injection layer. In the present invention, the charging means is not particularly limited, for example,
A magnetic brush charging type charger (magnetic brush charger) can be used. The magnetic brush charger 2a used in the image forming apparatus of FIG. 1 is provided on a rotatable non-magnetic sleeve having an outer diameter of 16 mm and a fixed magnet provided therein.
Magnetic particles are formed in a brush shape by a magnetic field, and the magnetic particles are transported as the non-magnetic sleeve rotates. Preferably, the non-magnetic sleeve rotates counterclockwise with respect to the photosensitive drum. By applying a charging voltage to the non-magnetic sleeve, a charge is given from the magnetic particles onto the photosensitive drum 3a, and charged to a potential corresponding to the charging voltage. The higher the rotation speed, the better the charging uniformity tends to be.

The magnetic particles used as the charging member have a volume average particle diameter of 10 to 100 μm and a saturation magnetization of 20 μm.
00 to 25000 kA / m ² (20 to 250 emu / c
m ³ ) and a resistance of 1 × 10 ⁻² to 1 × 10 ¹⁰ Ω · cm is preferable. Considering that an insulating defect such as a pinhole is present on the photosensitive drum, 1 × 10 ⁻⁶ to 1 ×. 10 ^-8
It is more preferable to use one having a resistance of ~ Ω · cm.

Here, the resistance value of the magnetic particles is such that the bottom area is 2
After putting 2 g of magnetic particles into a 28 mm ² metal cell, 6.
The weight can be measured at 6 kg / mm ² ) and a voltage of 100 V can be applied for measurement.

As the magnetic particles, those obtained by adjusting the resistance by oxidizing or reducing the surface of a single magnetite such as ferrite or adjusting the resistance by coating the surface of a single magnetite such as ferrite with a resin can be used. .

It is preferable to adjust the nip width of the magnetic brush charger with respect to the photosensitive drum 3 so as to be 2.0 to 10.0 mm. Next, the amplitude of the applied bias and the charging potential in the first cycle when a rectangular alternating voltage having a frequency of 1000 Hz is applied to the charger will be described.

By increasing the amplitude, the difference between the DC component of the applied bias and the charged potential in the first cycle becomes smaller. More specifically, DC of the bias applied to the charger is described.
If the component is Vdc and the surface potential on the charged photosensitive drum 1 at this time is Vs, the difference between them is ΔV = |
When Vdc−Vs | is approximately 40 V or less, the uniformity of charging is improved.

Therefore, for example, it is preferable to apply a bias in which a rectangular alternating voltage of 1000 Hz and 800 V is superimposed on a DC voltage of -700 V to the charger to obtain good charging properties.

The developing means that can be used in the present invention will be described.

The developing means in the present invention may be any developing means used in an ordinary image forming apparatus, and examples thereof include a developing apparatus for developing a two-component magnetic brush for a color developer shown in FIG.

The developing device 1a includes a developing sleeve 41 and a magnet roller 4 fixedly arranged in the developing sleeve 41.
2. It has stirring screws 43 and 44, a regulating blade 45 arranged to form a thin layer of developer on the surface of the developing sleeve 41, and a developing container 46.

The developing sleeve 41 has a region closest to the photosensitive drum 3a by about 500 at least during development.
μm, and is preferably set so that development can be performed in a state where the developer contacts the photosensitive drum 3a.

In the present invention, it is preferable to use a developer using the above-mentioned toner. The developing step of visualizing the electrostatic latent image by a two-component magnetic brush method using the above-described developing device and a circulation system for the developer will be described below. First, the developer pumped by the N2 pole with the rotation of the developing sleeve 41 is regulated by the regulating blade 45 arranged perpendicular to the developing sleeve 41 in the process of being transported from the S2 pole to the N1 pole. Sleeve 41
A thin layer is formed thereon. Here, the developer formed as a thin layer is
When conveyed to the developing main pole S1, poles are formed by magnetic force. The electrostatic latent image is developed by the spike-shaped developer, and then the developer on the developing sleeve 41 is moved by the repelling magnetic field of the N3 pole and the N2 pole to the developing container 4.
Returned to 6. A DC voltage and an AC voltage are applied to the developing sleeve 41 from a power supply (not shown). In general, in the two-component developing method, when an AC voltage is applied, the developing efficiency is increased, and the quality of an image is high. On the contrary, there is a risk that fogging is likely to occur. For this reason, fog is generally prevented by providing a potential difference between the DC voltage applied to the developing device and the surface potential of the photosensitive drum.

The developing devices 1a, 1b, 1c and 1d shown in FIG.
Are filled with a predetermined amount of cyan, magenta, yellow, and black toners, respectively, as a developer by a supply device (not shown). Developing units 1a, 1b, 1c and 1
d develops the latent images on the photosensitive drums 3a, 3b, 3c, and 3d, respectively, and visualizes them as a cyan toner image, a magenta toner image, a yellow toner image, and a black toner image.

This toner image is then transferred to the recording material P by the transfer device 7. The transfer device 7 suspends an endless transfer belt 71 between a driving roller 72 and a driven roller 73, and is rotated in the direction of arrow D in FIG. Further, the transfer device 7
A transfer charging blade 74 as a transfer charging unit is provided therein. The transfer charging blade generates a pressing force from the inside of the transfer belt 71 in the direction of the photosensitive drum 3a, and is supplied with power from a high-voltage power supply to supply the recording material P. The toner image on the photosensitive drum 3a is sequentially transferred to the upper surface of the recording material P by performing charging of a polarity opposite to that of the toner from the back side. Here, the recording material P is conveyed from the paper feeding and conveying device to a transfer section formed by the photosensitive drum 3a and the belt 71 at an appropriate timing in synchronization with the rotation of the photosensitive drum 3a. Hereinafter, similarly, image formation and transfer are performed in the second image forming unit Pb to the fourth image forming unit Pd.

As the transfer charging blade 74, for example,
Resistance in ^{1 × 10- 5 ~1 × 10 7} Ω · cm, plate thickness 2m
m and a length of 306 mm are used. Transfer is performed by applying a bias of +15 μA to the transfer charging blade 74 by constant current control.

The toner images formed on the photosensitive drums 3a to 3d are electrostatically transferred onto the recording material by the transfer charging blade 74. Next, the recording material P to which the toner image has been transferred is removed from the end of the transfer belt 71 by being discharged by the separation charger 16 at a downstream portion of the transfer belt 71 in the transport direction and attenuating the electrostatic attraction force. Particularly in a low humidity environment, the recording material also dries and the electric resistance increases, so that the electrostatic attraction force between the transfer belt 71 and the separation belt increases, and the effect of the separation charger increases. A non-contact charging device is used as the separation charging device because the recording material P is de-charged in a state where the toner image is not fixed. The output of the separation charger 16 is, for example, V
pp = 10 kV, an AC voltage of about 500 Hz is used. Also, to prevent image defects such as toner scattering,
It is preferable to superimpose a plus or minus DC component of about 100 μA in addition to the AC output.

The detached recording material P is conveyed to the fixing device 9. The fixing device 9 includes a fixing roller, a pressure roller, a heat-resistant cleaning member for cleaning each of them, and a thermistor for detecting a surface temperature of a heater installed in each roller to control a fixing temperature. The recording material P on which the toner image is formed is fixed to the recording material P by fixing, and a full-color copy image is formed and discharged to a paper discharge tray.

The transfer belt 71 after the recording material P is separated is brought into contact with the conductive fur brush 8 grounded on the recording material carrying side and the driving roller 72 grounded opposite to the conductive fur brush 8. The toner and other foreign matters remaining on the transfer belt 71 are cleaned, and the accumulated charge is removed (static elimination).

The toner remaining on the transfer belt 71 is wiped off by bringing the cleaning blade 5 as cleaning means into contact with the surface of the transfer belt 71. The cleaning blade as a cleaning member of the transfer belt 71 has a rubber hardness of 7, for example.
Those having a 7 ° (JISA), a rebound resilience of 45% (23 ° C.), a plate thickness of 2 mm, and a free length of 8 mm are used. The cleaning unit has a swing angle of 0 °, a contact angle of 25 °, and a total pressure on the transfer belt of 4.5 kgf, but is not limited to this.

[0082]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments.

[0083]

Example 1 The same image forming apparatus as that shown in FIG. 1 described in the above embodiment was used.

The charging pressing member is shown in the above embodiment.
The same adsorption charger 11b as in FIG. 2 was used. Specifically
The adsorption charger 11b is a SU having a diameter of 16 mm and a length of 310 mm.
M23L-D core metal has 150mm width at the center in the longitudinal direction.
Covered with conductive rubber, 8
At 0 mm, a conductive fur brush was planted. In detail
In the center, conductive rubber material made of EPDM (hardness 50 degrees,
Volume resistivity 10 ⁸Ω · cm) 1.0mm thick, both ends
The part is made of conductive rayon hair (volume resistivity 10 ⁶Ω · cm, dense
50,000 / inch^Two= 7750 lines / cm^Two) Hair length
3.0 mm (including the base cloth) and the center conductive rubber layer
The surface layer is further covered with a PAE tube. P
AE tube contains carbon and has a surface resistance value
Is 3 × 10⁶Ω · cm, Young's modulus 1200kg / c
m^TwoWith a surface roughness Rz of 2.3 μm and a thickness of 100 μm
Using.

The penetration amount of the fur brushes at both ends in the state where the transfer belt 71 is in contact is 1.0 mm.

In Example 1, other respective means were prepared as follows.

As the magnetic particles used in the magnetic brush charger, it is better to use particles having as small a resistance as possible in order to improve the charging performance. Therefore, in this embodiment, the volume average particle diameter is 25 μm, and the saturation magnetization is 20,000 kA / m 2. ² (20
0 emu / cm ³ ) and magnetic particles having a resistance of 5 × 10 ⁻⁶ Ω · cm. Further, the magnetic brush charger is a photosensitive drum 3
Was adjusted to be approximately 6 mm. The magnetic brush charger rotates at 150 mm / sec with respect to the rotation speed of the photosensitive drum 3a of 100 mm / sec. The magnetic brush charger of this embodiment has a DC voltage of -70.
A rectangular alternating voltage of 1000 Hz and 800 V with respect to 0 V
By applying a bias superimposed on the charging device to the charger, good charging properties could be obtained.

The developing sleeve has a DC voltage of -500.
V, Vpp = 1500 V, Vf = 200 as an AC voltage
0 Hz was applied.

The T / D ratio of the obtained developer was 8%. As a magnetic carrier, the amount of magnetization in a magnetic field of 1 kOe is 10,000 kA / m ² (100 emu / c
m ³ ), and the number average particle size is 40 μm,
Further, one having a specific resistance of 10 ¹³ Ω · cm was used. Further, as the non-magnetic polymerized toner, the shape factor SF-1 is 115,
A substantially spherical toner having a smooth surface of SF-2 of 110, a weight average particle diameter of 8 μm, and a specific gravity of 1.
The average charge per unit mass of 05 g / cm ³ is 25 μ
c / g of toner was used. Further, the transfer belt 71 of the present embodiment is made of a sheet in which a conductive filler such as carbon black is dispersed in a dielectric resin to adjust the resistance, and has a volume resistivity of 10 ¹² Ω · cm and a film thickness of 75 μm. An endless shape or a seamless (seamless) belt was used.

The transfer belt 71 has a tensile strength of 3200 kg.
/ Cm ² , Young's modulus 6.0 × 10 ⁴ kg / cm ² , surface roughness Rz 0.92 μm (measured using SE-30 manufactured by Kosaka Seisakusho under conditions of length 0.8 and cutoff 0.08)
The physical property value of was used.

In the actual machine, the wear amount of the transfer belt is 0.5 μm.
m / 100,000 revolutions.

The following evaluations were made in the above configuration. An actual machine durability test was performed. The durability test was performed using an intermittent A4 (recycled paper) single sheet mode / image Duty 5% to 30% original. As a result, there was no occurrence of poor adhesion of the recording material to the transfer belt, deterioration of the transfer member due to uneven surface free energy on the inner surface of the transfer belt, and hence, no image defect. As a result of the image endurance test, the transfer belt was 1
For a million sheets and a transfer blade of 500,000 sheets, a high-quality image was stably maintained without any problem that appeared on the image for a long period of time.

[0093]

Example 2 In Example 2, a PFA conductive tube of 100 μm was formed on the surface layer of the central conductive rubber layer made of EPDM.
The evaluation was performed using the same configuration as in Example 1 except that a charging pressing member covered with was used. With the above-described configuration, there was no occurrence of poor adhesion of the recording material to the transfer belt, deterioration of the transfer member due to uneven surface free energy on the inner surface of the transfer belt, and therefore, poor image quality. As a result of the image endurance test, the transfer belt was 1 million sheets, and the transfer blade was
Over a long period of 500,000 sheets, high quality images were stably maintained without any defects appearing on the images.

[0094]

Embodiment 3 In Embodiment 3, a film-shaped porous PTFE having a thickness of 200 μm was formed on the metal part of the core metal as in Embodiment 1 as the surface layer of the central conductive layer of the charging / pressing member. Evaluation was performed in the same configuration as in Example 1 except that the coated product was used.

With the above configuration, there was no occurrence of poor adhesion of the recording material to the transfer belt, deterioration of the transfer member due to uneven surface free energy on the inner surface of the transfer belt, and hence, no image defect. As a result of performing an image endurance test, over 1 million sheets of the transfer belt and 500,000 sheets of the transfer blade, a high-quality image was stably maintained over a long period of time without any problem that appeared on the image.

[0096]

REFERENCE EXAMPLE 1 The same procedure as in Example 1 was repeated except that the central conductive layer of the charging / pressing member was coated with only the surface layer rubber layer on the metal part of the cored bar as in Example 1. The evaluation was performed using the same configuration as that described above.

In the above-described configuration, poor adhesion of the recording material to the transfer belt, deterioration of the transfer member due to uneven surface free energy on the inner surface of the transfer belt, and therefore, image failure occurred. As a result of performing an image endurance test, over 100,000 sheets of the transfer belt and 10,000 sheets of the transfer blade, a high-quality image was stably maintained without any problem that appeared on the image for a long period of time.

[0098]

COMPARATIVE EXAMPLE 1 In Comparative Example 1, a charge pressing member was used in which the metal portion of the metal core was the same as that of Example 1 of the central conductive layer and no coating was applied. Other than that, it carried out by the structure similar to Example 1.

As a result of performing an image output durability test with the above-described configuration, about 150,000 sheets of the transfer belt were rubbed and scratched on the inner surface, causing a problem that the transfer belt became apparent.

[0100]

According to the present invention, it is possible to eliminate poor adhesion of a recording material to a transfer belt and to prevent deterioration of a transfer member due to uneven surface free energy on the inner surface of the transfer belt, and hence, occurrence of an image defect. It becomes possible. Also, T
The CO can be reduced as much as possible, and the service life of the transfer belt and the transfer portion can be improved by one digit compared with the related art.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus according to the present invention.

FIG. 2 (a) is a front view of one embodiment of a charging pressing member according to the present invention. (B) The perspective view of one form of the charging press member in this invention is shown.

FIG. 3 (a) is a schematic configuration diagram of one embodiment of a recording material holding unit in the present invention. (B) shows the pressure distribution of the recording material carrying means shown in (a).

FIG. 4 shows (1) a pressure distribution of a charging pressing member in the present invention. (2) shows a pressure distribution of the charging pressing member in the conventional example.

FIG. 5 is a cross-sectional view around a photosensitive drum in one embodiment of the image forming apparatus of the present invention.

FIG. 6 shows a conventional image forming apparatus.

[Explanation of symbols]

 1a to 1d Developing device 2a to 2d Magnetic brush charger 3a to 3d Photosensitive drum 5 Cleaner 6a to 6d Transfer charging blade 7 Transfer device 9 Fixing device 11 Adsorption charger pair 11a Adsorption roller facing roller 11b Adsorption charger 71 Transfer belt P Recording material

Claims (9)

[Claims] A recording material carrier that carries and conveys the recording material;
Image forming means for forming a visible image by toner on a recording material carried by the recording material carrier, cleaning means for cleaning the recording material carrier, and a recording material carried on the recording material carrier. An image forming apparatus comprising: a recording material supporting unit; wherein the recording material supporting unit has a charging pressing member that clamps the recording material with a pressure distribution higher than an end portion and applies a charge. An image forming apparatus comprising: 2. The charge pressing member is a contact-type charger, a central portion of the charge pressing member is made of an elastic body made of a conductive material, and an end of the charge pressing member is made of a conductive fiber. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 2, wherein the elastic body made of a conductive material includes a fluororesin layer. 4. The image forming apparatus according to claim 2, wherein the elastic body made of a conductive material includes a polyamide elastomer resin layer. 5. The elastic body made of a conductive material is formed as a roller having at least two layers.
The image forming apparatus according to claim 2, wherein the charging pressing member performs a rotational movement, and a peripheral speed of the charging pressing member follows a moving speed of the member to be charged. 6. The recording material carrier has a Young's modulus of 2.5 kg.
/ Cm ² or more, the image forming apparatus according to any one of claims 1 to 5, characterized in that it consists of tensile strength 1000 kg / cm ² or more materials. 7. The apparatus according to claim 1, wherein an amount of wear of the recording material carrier when the image forming apparatus is operated is 1.0 μm / 100,000 rotations or less. Image forming apparatus. 8. The non-magnetic toner has a weight average particle diameter of 6 to 10 μm, and the non-magnetic toner has a shape factor SF-1 of 100 to 140 and an SF-2 of 100.
The image forming apparatus according to any one of claims 1 to 7, wherein the toner is a substantially spherical toner generated by a polymerization method in a range of from -120. 9. An image carrier for carrying an electrostatic latent image, a charging unit for applying a voltage to the surface of the image carrier and charging the surface of the image carrier, and charging by the charging unit. Electrostatic latent image forming means for forming an electrostatic latent image on the surface of the formed image carrier, and developing means for forming a visible image by attaching toner to the electrostatic charge image formed on the image carrier surface. Transfer charging means for transferring a visible image formed on the surface of the image carrier to a recording material, wherein the image forming means is provided for each of the first to fourth color toners; 9. The image forming apparatus according to claim 1, wherein toner images of respective colors are sequentially transferred onto the recording material carried on the recording material carrier in a superimposed manner.