JPH07129059A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an inexpensive image forming device which can form an image of high definition and high quality. CONSTITUTION:This image forming device using a belt-like photoreceptor is provided. The belt-like photoreceptor 2 is traveled by three or more rollers including a large-diameter roller 10. It has >=50mm diameter and is used as a driving roller for traveling the belt-like photoreceptor 2. One of rollers is used as a tension roller adjusting tension added to the belt-like photoreceptor 2. An image forming process part having an electrifying part 3, an exposure part 4 and a developing part 5 is disposed on the circumference of the large- diameter roller 10. A color image forming process part may be used as the image forming process part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to improvement of an image forming apparatus using a belt-shaped photoreceptor.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic process (so-called Carlson process) has been widely adopted as a method for image formation in various printers, copying machines and the like. This electrophotographic process forms an image on recording paper through an image forming process such as charging, exposure, development (dry development or wet development), transfer, and fixing. For example, according to the wet development method, silver salt photography is used. It is possible to obtain resolution and gradation comparable to

By the way, in the image forming apparatus for forming an image by the above-mentioned electrophotographic process, in order to continuously perform a series of image forming processes, a drum system in which the photoconductor is drum-shaped and a belt in which the photoconductor is belt-shaped are used. The type is known.

The former uses, as a photosensitive member, an aluminum drum having an Se-based photosensitive material (for example, Se-Te) vapor-deposited on its surface, an aluminum drum coated with an organic photoconductor, and the like. The photosensitive drum is driven to rotate. Then, steps such as charging, exposure, development, and transfer are performed. On the other hand, the latter uses a belt made of an organic photoconductor or the like, and performs the same steps on a photosensitive belt run by rollers.

[0005]

However, these drum-type and belt-type image forming apparatuses have respective advantages and disadvantages, and their improvement is awaited.

For example, in the drum type, the shape and size of the photosensitive drum are required to be highly accurate, the manufacturing cost thereof is very high, and the apparatus becomes expensive.

On the other hand, the belt system is advantageous in terms of manufacturing cost, but it is a system in which the photosensitive belt is stretched and driven by rollers, so that the running state of the belt is stable. difficult. For example, depending on the position of the driving roller, the photosensitive belt may be loosened, or the cleaning blade may become a load to make the running state unstable, which may cause a significant deterioration in image quality.

Further, the applicant of the present application has previously mentioned that Japanese Patent Laid-Open No. 2-6
In 966 and Japanese Patent Laid-Open No. 2-6967,
We have proposed a wet development method using a solidified developer, but when applying such a development method to the above belt type image forming apparatus, it is necessary to dispose a backing plate with a built-in heater in the developing section or to perform cleaning. It is necessary to add a heating roller near the blade, which makes the structure very complicated.

Therefore, the present invention has been proposed in order to solve the drawbacks of the conventional image forming apparatus, and an object thereof is to provide an image forming apparatus capable of high-definition and high-quality image formation. Further, it is an object of the present invention to provide an inexpensive image forming apparatus that can simplify the apparatus configuration.

[0010]

In order to achieve the above object, an image forming apparatus of the present invention comprises a belt-shaped photoconductor and three or more rollers including a large-diameter roller, and the belt-shaped photoconductor runs. It is characterized by comprising a group of rollers forming a path and an image forming process section having at least a charging section, an exposing section and a developing section, wherein the image forming process section is arranged in the vicinity of the large diameter roller. It is a thing.

That is, although the image forming apparatus of the present invention basically adopts the belt system, the belt-shaped photosensitive member which runs along the peripheral surface of the large-diameter roller in processes such as charging, exposure and development. By performing this on the body, the image formation is stabilized and the image quality equal to or higher than that of the drum system is secured.

Therefore, the large-diameter roller needs to have a size enough to dispose at least the charging section, the exposing section, and the developing section on the periphery, and specifically, the diameter needs to be 50 mm or more. In this case, it is not necessary to increase the diameter of the large-diameter roller more than necessary, but in order to secure sufficient torque and smoothly feed the belt-shaped photoconductor when the large-diameter roller is used as the drive roller, It is preferably about 100 mm.

On the other hand, the remaining rollers have no meaning if they are made too large, and rather the size of the apparatus is increased. Therefore, the diameter of the remaining rollers is made smaller than that of the large rollers. Therefore, the diameter of this small diameter roller is preferably 50 mm or less.
It is desirable to set it to about 0 mm.

In the image forming apparatus of the present invention, any of the rollers constituting the roller group may be used as the driving roller, but the large diameter roller described above is used as the driving roller and the remaining small diameter rollers are used as the driven rollers. By doing
The running state of the belt-shaped photosensitive member becomes the most stable, and the image forming process is stabilized. Further, if one of the rollers forming the roller group is a tension roller and a predetermined tension is applied to the belt-shaped photoconductor stretched between these roller groups, the tensioned state is stable. And the image quality is further improved.

In the image forming apparatus of the present invention, as the developing method, either a dry developing method or a wet developing method can be adopted, and further, the wet developing method using the solidified developer described above is also applicable. However, when the wet development method using this solidified developer is used, it is necessary to heat the developing section to melt the solidified developer. Therefore, in this case, it is preferable that the large-diameter roller is made of aluminum and the heating means is provided inside. With such a configuration, it is not necessary to add a backing plate, a heating roller, or the like separately, and the device can be simplified.

The image forming process in the image forming apparatus of the present invention may be a single color (so-called monochrome) image forming process or a color image forming process for forming a color image. In the latter case, for example, a developing section for developing with magenta, cyan, and yellow developers may be arranged around the large-diameter roll.

[0017]

Since the image forming apparatus of the present invention is basically of the belt type, it has the advantage of the belt type. That is,
It can easily cope with large-sized images and can reduce the manufacturing cost compared to the drum system.

Further, in the image forming apparatus of the present invention, the steps of charging, exposing, developing and the like are performed on the belt-shaped photosensitive member which runs along the peripheral surface of the large diameter roller. It also has advantages, and the running state of the belt-shaped photosensitive member becomes stable, so that high definition and high quality of the image can be achieved.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of a monochrome laser printer device to which the present invention is applied. This printer device is an image forming process including a photoconductor belt 2, a charging charger (charging unit) 3, a laser optical system (exposure unit) 4, and a developing device (developing unit) 5 in a printer body 1 which is an outer casing. Unit, a charge removing lamp 6, a cleaning mechanism including a cleaning blade 7, and a transfer mechanism unit.

The printer body 1 is detachably loaded with one or a plurality of paper feed cassettes, in this example, two paper feed cassettes 8 and 9 having different paper sizes, and is set in each paper feed cassette 8 and 9. A developer image is formed on the transfer sheet.

Here, the material that can be used as the transfer sheet is preferably one having a large adhesive force to the developer, and can be appropriately selected according to the application. For example, various kinds of paper such as natural paper and synthetic paper, cloth or non-woven fabric composed of vegetable fibers such as cotton and hemp, and animal fibers such as silk and wool, organic synthetic fibers such as polyamide, polyester, polyacetal and polyurethane. Or a cloth or non-woven fabric made of inorganic fibers such as ceramics or carbon, a mesh of metal or organic polymer, or a polymer foam such as polyurethane foam. In order to save in the form of an ordinary document, it is preferable to use a white background paper or the like as the transfer target from the viewpoint of enhancing the visibility, but it is not limited to this.

The transfer sheet may have a resin layer on its surface, which is compatible with the dispersion medium of the developer, for the purpose of securing the adhesive force to the developer. Thereby, the transfer of the developer image can be made more reliable.

The resin constituting the resin layer formed on the surface of the transfer sheet may be any resin as long as it is compatible with the dispersion medium, for example, thermoplastic elastomer, low density polyolefin, ionomer resin, Vinyl acetate copolymer polyolefin, low molecular weight polyolefin,
A hot melt adhesive or the like can be used. These are commercially available under the trade name Chemipearl (A type, M type, S type, V type, W type) (all manufactured by Mitsui Petrochemical Co., Ltd.) and the trade name Acryft (manufactured by Sumitomo Chemical Co., Ltd.). In this example, a sheet coated with vinyl acetate copolymer polyolefin (Vicat softening point: 40 ° C.) was used.

On the other hand, the photosensitive belt 2 is formed by molding a negatively charged phthalocyanine-based organic photosensitive material into a belt shape. In addition to the phthalocyanine-based organic photosensitive material, well-known organic photoconductors are used. Can be used. Specifically, poly-N-vinylcarbazole and 2,
Electrophotographic photosensitive base material composed of 4,7-trinitrofluoren-9-one, poly-N-vinylcarbazole sensitized with pyrylium salt dye, and poly-N-vinylcarbazole sensitized with cyanine dye. Examples thereof include an electrophotographic photosensitive substrate containing an organic pigment as a main component, an electrophotographic photosensitive substrate containing a eutectic complex composed of a dye and a resin as a main component, and the like.

The photosensitive belt 2 is wound around a plurality of rollers, in this example, a roller group consisting of three rollers, a large diameter roller 10, a pressure contact roller 11 and a peeling roller 12, to form a closed loop. Then, the large-diameter roller 10 is used as a driving roller to run counterclockwise in the drawing.

Here, the large-diameter roller 10 has a larger diameter than the other rollers (the pressing roller 11 and the peeling roller 12), and has a diameter of 100 mm in this example. On the other hand, the pressing roller 11 and the peeling roller 12 are constituted by a small diameter roller having a diameter of about 30 mm. Also, in this example,
The pressure roller 11 is a tension roller, and the photosensitive belt 2 is made to travel while applying a constant tension. However, the present invention is not limited to this.
It may be provided separately from. In this case, from the viewpoint of running stability, the tension roller is the large-diameter roller 10
It is preferable to provide it between the press roller 11 and

In this example, a sensor 19 is provided between the developing device 5 and the pressure contact roller 11 at an arbitrary position of the traveling system of the photosensitive sheet 2, so that the seam of the photosensitive belt 2 can be detected. Then, the image forming start position is controlled.

In the traveling system having the above-mentioned structure, the photosensitive belt 2 travels along the peripheral surface of the large-diameter roller 10 and then passes through the pressing roller 11 and the peeling roller 12.
It runs on the large diameter roller 10 again. When traveling along the peripheral surface of the large-diameter roller 10, the back side of the photosensitive belt 2 is supported by the large-diameter roller 10, so that the photosensitive belt 2 is loosened, There is no risk of unstable driving.

Therefore, in this embodiment, the image forming process unit and the cleaning mechanism are arranged along the peripheral surface of the large-diameter roller 10, and the photosensitive belt running along the peripheral surface of the large-diameter roller 10 is arranged. The image forming process is performed for 2. That is, the static elimination lamp 6, the cleaning blade 7, the charging charger 3, the laser optical system 4, and the developing device 5 are arranged so as to surround the large diameter roller 10.
A series of image forming processes (static elimination → cleaning → charging → exposure → development → ...) Is continuously performed. Therefore, the stability of the imaging process is comparable to the drum system. Regarding the static elimination lamp 6,
It is not always necessary to arrange around the large diameter roller 10,
It is also possible to install it at an arbitrary position between the peeling roller 12 and the large diameter roller 10.

The charging charger 3, the laser optical system 4, and the developing device 5 constituting the above-mentioned image forming process section may be of a normal electrophotographic type, and the type thereof is not limited, but in this example, charging is performed. A scorotron was used as the charger 3. This charging charger (scorotron) 3
The discharge wire 31 and the mesh 32 provided on the opening surface and functioning as a grid electrode enable uniform charging without unevenness.

The laser optical system 4 is composed of a laser light source 41, a polygon mirror (not shown) for scanning the laser beam on the photoconductor belt 2, a reflection mirror 42, and the like. Depending on the photoconductor belt 2
Selective exposure.

The developing device 5 may be of a dry type or a wet type, but in this example, it is melted by heating or cooling,
The developing device uses a solidified wet developer that is repeatedly solidified. That is, the developing device 5 includes a developer container 51 containing a solidified developer, a supply roll 52, and a developing roll 5.
3, the molten solidified wet developer is supplied to the surface of the developing roll 53 via the supply roll 52,
It is used for developing an electrostatic latent image on the surface of the photosensitive belt 2. In this example, the developing roller 53 is in a so-called pseudo contact state in which the developing roller 53 is in contact with the photosensitive belt 2 at a position slightly separated from the large diameter roller 10 to the pressure contact roller 11 side. You may make it contact with the body belt 2.

The dispersion medium used in the solidified wet developer is an electrically insulating organic substance, and its melting point is set to 30 ° C. or higher, more preferably 40 ° C. or higher in consideration of the normal use environment and handleability. . Although the upper limit of the melting point is not particularly specified, it is practically about 100 ° C., more preferably 80 ° C. or lower. This is because even if the melting point is too high, extra energy is consumed for heating, and when it is used by holding it on a support, it must not exceed the heat resistant temperature of the material generally used as a support. In consideration. In this example, the melting point of the developer is set to 46 ° C.

Examples of materials for the dispersion medium which satisfy these requirements include paraffins, waxes, and mixtures thereof. First, as paraffins, various normal paraffins having 19 to 60 carbon atoms from nonadecane to hexacontane are available. As waxes, carnauba wax,
Examples thereof include vegetable waxes such as cotton wax, animal waxes such as beeswax, ozokerite, and petroleum waxes such as paraffin wax, microcrystalline wax, petrolatum and the like. These materials are generally dielectric materials having a dielectric constant ε of about 1.9 to 2.3. In addition, an ethylene vinyl acetate copolymer or the like may be added in order to increase the cohesive force of the dispersion medium.

Furthermore, polyethylene, polyacrylamide, poly-n-stearyl acrylate, poly-n
-A crystalline polymer having a long alkyl group in the side chain such as a homopolymer or a copolymer of polyacrylate such as stearyl methacrylate (for example, copoly-n-stearyl acrylate-ethyl methacrylate) can be used, but the viscosity upon heating Considering the above, the above paraffins and waxes are preferable.

As the colorant particles dispersed in the electrically insulating organic material, conventionally known inorganic pigments, organic pigments,
Dyes and mixtures of these can be used. Examples of the inorganic pigment include chrome-based pigments, cadmium-based pigments, iron-based pigments, cobalt-based pigments, ultramarine blue and navy blue. As an organic pigment or dye, Hansa Yellow (CI11
680), Benzidine Yellow G (CI21090), Benzidine Orange (CI21110), Fast Red (CI3708)
5), Brilliant Carmine 3B (CI16015-Lake), Phthalocyanine Blue (CI74160), Victoria Blue
(CI42595-Lake), Spirit Black (CI50415)
, Oil blue (CI74350), alkali blue (CI4
2770A), First Scarlet (CI12315), Rhodamine 6B (CI45160), Rhodamine Rake (CI4516)
0-Lake), Fast Sky Blue (CI74200-Lake)
Nigrosine (CI50415), carbon black and the like. These may be used alone or as a mixture of two or more kinds, and those having a desired color development may be selected and used.

In addition to these electrically insulating organic substances and colorant particles, a resin may be used in combination with the developer for the purpose of improving the dispersibility and the chargeability of the colorant. As such a resin, known materials can be appropriately selected and used. For example, rubbers such as butadiene rubber, styrene-butadiene rubber, cyclized rubber, natural rubber, styrene resin, vinyltoluene resin, acrylic resin can be used. -Based resins, methacrylic-based resins, polyester-based resins, polycarbonate-based resins, polyvinyl acetate-based resins and other synthetic resins, rosin-based resins, hydrogenated rosin-based resins, alkyd resins including modified alkyds such as linseed oil-modified alkyd resins , Natural resins such as polyterpenes, and the like. In addition, modified phenol resins such as phenol resins and phenol formalin resins, pentaerythritol phthalate, coumarone-indene resins, ester gum resins and vegetable oil polyamide resins are also useful, and polyvinyl chloride and chlorinated Halogenated hydrocarbon polymers such as polypropylene, synthetic rubbers such as vinyltoluene-butadiene, butadiene-isoprene, 2
-Polymers of acrylic monomers having a long chain alkyl group such as ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, lauryl acrylate, octyl acrylate or copolymers thereof with other polymerizable monomers (for example, styrene-lauryl methacrylate) Copolymers, acrylic acid-lauryl methacrylate copolymers, etc.), polyolefins such as polyethylene, and polyterpenes can also be used.

Further, a charge-donor agent is usually added to the above-mentioned developer, and the developer used here is no exception. Examples of the charge donor used include metal salts of fatty acids such as naphthenic acid, octenoic acid, oleic acid, stearic acid, isostearic acid and lauric acid, metal salts of sulfosuccinic acid esters, oil-soluble sulfonic acid metal salts and phosphoric acid. Ester metal salts, metal salts such as abietic acid, aromatic carboxylic acid metal salts, aromatic sulfonic acid metal salts and the like.

Further, in order to improve the charge of the colorant particles (6), SiO ₂ , Al ₂ O ₃ , TiO ₂ , Zn
O, Ga ₂ O _3, In ₂ O ₃ , GeO ₂ , SnO ₂ , P
Fine particles of metal oxide such as bO ₂ and MgO, or a mixture thereof may be added as a charge enhancer.

In the developing method using such a solidified wet type developer, it is necessary to heat the photosensitive belt 2 in order to melt the developer in the developing process and the cleaning process. For this reason, in this embodiment, the large-diameter roller 10 is made of aluminum having good thermal conductivity, and a heating means (for example, a resistor) 13 is provided inside to transfer the heat to the photosensitive belt 2. There is.

On the other hand, the transfer mechanism comprises a pressure roller 14 and a pressure contact roller 11, and the pressure roller 14 and the pressure contact roller 11 sandwich the photosensitive belt 2. Of these rollers, the pressure contact roller 11 also serves as a guide roller for the photoconductor belt 2, and the pressure roller 14 serves to superpose the transfer sheet 15 on the developed photoconductor belt 2. However, if the transfer sheet 15 itself is sufficiently pressed, the pressure roller 14 may be omitted.

Further, the transfer sheet 15 is transferred from the photosensitive belt 2.
A peeling roller 12 is provided at a position where the peeling roller 1 comes in contact with the back surface side of the photosensitive belt 2.
2 functions as a guide roller, and the traveling direction of the photosensitive belt 2 is changed. A cooling plate 16 is provided immediately in front of the peeling roller 12 so as to come into contact with the back surface side of the photoconductor belt 2.
Alternatively, the transfer sheet 15 is configured to be heated or cooled.

A fixing device 17 and a discharging unit 18 are arranged in the traveling direction of the peeled transfer sheet 15, so that the transfer sheet 15 can be smoothly discharged. The fixing device 17 provided in front of the discharge unit 18 is composed of a heat roll, a heat oven, or the like, and heats the transfer sheet 15 after transfer to a predetermined temperature (for example, 60 ° C.) to form a developer image. It is structured so that it can be fixed.

In the present embodiment, the transfer sheet 15 is conveyed in a substantially horizontal direction from the pressure contact with the photosensitive belt 2 to the peeling. The transfer sheets 15 can be arranged in a straight line, and the transfer sheet 15 can be stabilized in a conveyed state. Although the transfer path of the transfer sheet 15 is set to the horizontal direction here, it goes without saying that the transfer path can be set in any direction depending on the configuration of the apparatus.

In the printer device described above, an electrostatic latent image is formed on the photoconductor belt 2 and developed using a solidified wet developer. That is, the photosensitive belt 2 is rotationally driven in the counterclockwise direction in the figure, the surface is charged by the charging charger 3, and then laser light from the laser optical system 4 is irradiated to form an electrostatic latent image. This electrostatic latent image is visualized by the developer when passing through the developing device 5.

On the other hand, the transfer sheet 15 is fed from the paper feed cassette 8 or the paper feed cassette 9 and is conveyed to the latent image carrier composed of the photoconductor belt 2 at a timing. Then, the visible image formed of the developer is transferred from the photosensitive belt 2 to the transfer sheet 15, and the transfer sheet 15 that is in close contact with the photosensitive belt 2 is mechanically separated.

For the transfer, the photosensitive belt 2 is run while holding the developed image, and the pressing roller 11 makes contact with the transfer sheet 15 at the same timing and pressurization and heating (pressing heating: temperature 48 ° C.). By doing. As described above, the transfer mechanism is configured to sandwich the photosensitive belt 2 between the pressure roller 14 and the pressure contact roller 11.
The developer image is melted or softened by the pressure and heat of the pressure roller 14 and the pressure roller 11, and the image is transferred onto the transfer sheet 15.

After pressure contact by the transfer mechanism, the photosensitive belt 2 and the transfer sheet 15 are conveyed in a close contact state and separated by the curvature separation on the separation roller 12. At the time of peeling, the peeling roller 12 may be heated and the photosensitive belt 2 may be slightly heated from the back side so that the visible image is easily peeled from the photosensitive belt 2. In this example, the peeling temperature was 30 ° C.

Thereafter, the transfer sheet 15 is fixed to the fixing device 17
The visible image on the transfer sheet 15 is fixed by the fixing device 17 and is discharged to the discharge portion 18.

On the other hand, the photosensitive belt 2 after the visible image transfer is
The static elimination lamp 6 removes the charged electric charge, and the cleaning blade 7 removes the residual developer, so that the developer is repeatedly used. The cleaning blade 7
When the residual developer is removed by the method, the photoconductor belt 2 is heated by the large-diameter roller 10 and the residual developer is melted.
Will be quickly removed by.

In the case of a color printer, as shown in FIG. 2, yellow (Y), magenta (M), cyan (C), and further necessary instead of the image forming process unit in the apparatus shown in FIG. The black (K) color developing units 21, 22, 23, 24 may be arranged around the large-diameter roller 10 in accordance with the above. In FIG. 2, the same members as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

In the case of a color printer, Y,
A method of performing color transfer of M, C, and K to perform batch transfer, and Y,
There is a system in which M, C, and K images are transferred every time and color is superposed on the recording paper, and any of them may be adopted.

The specific embodiments to which the present invention is applied have been described above, but it goes without saying that the present invention is not limited to these embodiments.

[0055]

As is apparent from the above description, in the present invention, the belt system is adopted and charging,
Since image forming processes such as exposure and development are performed on the peripheral surface of the large-diameter roller, it is possible to easily deal with large-sized images, simplify the device configuration, reduce the size of the device, and reduce manufacturing costs. Can be reduced.

Further, since the running state of the belt-shaped photosensitive member can be made stable, it is possible to obtain a high-definition and high-quality image comparable to the drum system.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a monochrome printer device to which the present invention is applied.

FIG. 2 is a schematic diagram showing a configuration example applied to a color printer.

[Explanation of symbols]

 2 ... Photosensitive belt 3 ... Charging charger (charging part) 4 ... Laser optical system (exposure part) 5 ... Developing device (developing part) 10 ... Large diameter roller 11 ... Pressure contact Roller 12 ... Peeling roller

Claims (5)

[Claims] 1. A belt-shaped photoreceptor and a roller including a large-diameter roller.
It is provided with a group of rollers which form the traveling path of the belt-shaped photosensitive member, and an image forming process section having at least a charging section, an exposing section and a developing section, and the image forming process section is a large diameter roller. An image forming apparatus, which is arranged in a vicinity position. 2. The image forming apparatus according to claim 1, wherein the large-diameter roller is a driving roller for running the belt-shaped photosensitive member. 3. The image forming apparatus according to claim 1, wherein the large-diameter roller is made of aluminum and a heating means is provided inside. 4. The image forming apparatus according to claim 1, wherein at least one of the rollers forming the roller group is a tension roller for adjusting the tension applied to the belt-shaped photosensitive member. 5. The image forming apparatus according to claim 1, wherein the image forming process unit is a color image forming process unit.