JPH07152265A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of obtaining a high quality image which is stable at all times by solving various problems resulting from heating toner when carrying out image formation by means of an intermediate transfer body. CONSTITUTION:A toner image, formed on an image carrier (photoreceptor 1), is transferred to the intermediate transfer body 5 by means of a primary transfer device 6, and then the toner is plastically deformed in contact with a transfer body 9, such as a sheet of plain paper, by the application of pressure by means of a secondary transfer device 7, thereby transferring and fixing the image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using electrophotography or electrostatic recording.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic method or an electrostatic recording method is widely used as a copying machine or a printer because of its high recording speed and the ability to record on plain paper. In particular, the use of dry toner facilitates handling. In such an image forming apparatus, technical development aimed at higher quality images has been made, but it has been pointed out that when dry toner is used, the maximum image deterioration occurs in transfer of plain paper ( For example, Horie et al .: The Electrophotographic Society, Vol. 26, No. 1 (198
7) p. 48 "Higher image quality of electronic photography").

Further, as is well known, in the electrophotographic system (Carlson process), a photoconductive photoconductor is uniformly charged and imagewise exposed to form an electrostatic latent image, which is charged. Develop with a toner that is a particle and a coloring material. After that, the toner image is transferred onto a transfer body such as plain paper, and the toner image is fixed onto the transfer body to form a recorded matter.

[0004]

By the way, of the above-mentioned image forming processes, in the transfer process, generally, electrostatic transfer is performed using a corona charger or a bias roller. This has the advantage that the mechanical structure is simple and the transfer efficiency is relatively high, but before the contact between the image bearing member and the transfer member, the toner flies due to the potential difference between the image carrier and the transfer member. May occur, or the Coulomb repulsion between the toner particles may cause the toner to scatter and reduce the remodeling power.

As a technique for eliminating such defects and aiming at higher image quality, toner is transferred from an image carrier to an intermediate transfer member by adhesive force to perform transfer (primary transfer), and further transfer of plain paper or the like. A method has been proposed in which a toner is melted and transferred to a transfer body while being pressed against the body to be heated and simultaneously fixed (secondary transfer) (for example, JP-A-49).
-78559 publication). With this method, the system configuration is complicated, but since the toner is not electrostatically transferred, image deterioration is less and image quality can be greatly improved.

However, on the other hand, this method has many problems due to the use of heat in the secondary transfer. (1) Since the intermediate transfer member serves as a heat dissipation member, the thermal efficiency is lower than that of general heat roller fixing. (2) The temperature of the photoconductor rises via the intermediate transfer member, which affects the characteristics. (3) The temperature inside the apparatus rises via the intermediate transfer member, which affects the function of the apparatus. As a result, this method has a problem that the device becomes large and complicated.

The present invention has been made in view of the above points, and an object thereof is to solve various problems caused by heating toner when forming an image by using an intermediate transfer member, and always stabilize the toner. An object of the present invention is to provide an image forming apparatus capable of obtaining a high quality image.

[0008]

In order to solve the above-mentioned problems, the present invention provides, in claim 1, a drum- or belt-shaped image bearing member, and a drum- or belt-shaped intermediate transfer member.
A latent image forming device that forms an electrostatic latent image on the image carrier, a developing device that develops the electrostatic latent image on the image carrier with dry toner, and the image carrier on the intermediate transfer member. A structure having a primary transfer device for transferring the toner image on the holding member, and a secondary transfer device for transferring and fixing the toner image on the transfer member by superposing the transfer member on the intermediate transfer member and applying pressure thereto, To do.

Further, in claim 2, a drum or belt-shaped image carrier, a drum or belt-shaped intermediate transfer member, and a latent image forming apparatus for forming an electrostatic latent image on the image carrier. A plurality of developing devices for developing the electrostatic latent image on the image carrier with dry toner, a primary transfer device for transferring the toner image on the image carrier to the intermediate transfer member, and the intermediate transfer device In an image forming apparatus equipped with a secondary transfer device that transfers a toner image to a transfer body and fixes the toner image at the same time by stacking the transfer body on the body and applying a pressure to the image carrier while switching the developing device to be used. The step of forming a toner image on the intermediate transfer body and repeating the step of forming a toner image on the intermediate transfer body is repeated to form a superimposed toner image on the intermediate transfer body. Transfer the combined toner image A structure for fixing and simultaneously transferred to.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention. This device, as shown in FIG.
It comprises a charging device 2, an image exposure device 3, a developing device 4, an intermediate transfer member 5, a primary transfer device 6, a secondary transfer device 7, a cleaning device 8 and the like.

The image forming process of this apparatus is executed as follows. In FIG. 1, the charging device 2 uniformly charges the photoconductor 1 to, for example, about −800 V, and the image exposure device 3 performs exposure according to image data.
Form an electrostatic latent image on top. By the developing device 4,
For example, development is performed with a negatively charged toner having a particle size of about 5 to 10 μm. Next, the primary transfer device 6 electrostatically transfers the toner image onto the intermediate transfer member 5 by the action of the bias while pressing the intermediate transfer member 5 against the photosensitive member 1. Further, the transfer body 9
Is superposed on the intermediate transfer body 5 and pressure is applied by the secondary transfer device 7 to make the toner viscous and generate a binding force with the transfer body 9, and transfer and fixing to the transfer body 9 are performed. After the toner image is transferred to the transfer body 9 as described above, the toner image may be fixed to the transfer body 9 by the fixing device after that.

Next, a specific configuration example of this embodiment will be described. The photoreceptor 1 is usually Se, OPC, a-Si.
The OPC drum is used here because of its stable characteristics, cost, ease of disposal, safety and the like. As the charging device 2, a corona charger using a scorotron is often used, but a charging roller is used here in order to reduce ozone. As the image exposure device 3, a combination of a semiconductor laser and a polygon mirror is often used, but the adoption of a fixed scanning element such as an LED array which leads to downsizing of the device is also increasing. Here, the LED array is used. As the developing device 4, a device suitable for the developer used is used. For example, when a two-component developer including a magnetic carrier and toner or a magnetic toner is used, a developing sleeve having a magnet roller inside holds the developer and rotates the developer to the surface of the photoreceptor 1. A developing device for transportation is used. When a non-magnetic one-component toner is used, a developing device is used in which a toner layer is formed on an elastic sleeve made of metal or rubber and the toner layer is conveyed to the developing area of the photoconductor 1. Here, in both magnetic and non-magnetic cases, the conveyed developer is used as the photosensitive member 1.
In addition to the method of developing by contacting with the toner, there is also a method of causing the toner to fly and developing while leaving the photoreceptor 1 and the toner in a non-contact state. In this embodiment, two-component contact development is performed. The intermediate transfer member 5 has a function of temporarily holding the toner image during the process of transferring the toner image from the photosensitive member 1 to the transfer member 9. The intermediate transfer member 5 may be a drum-shaped member or a belt-shaped member, but the latter is used here. The primary transfer device 6 is a device that transfers a toner image from the photoconductor 1 to the intermediate transfer member 5, and brings the photoconductor 1 and the intermediate transfer member 5 into contact with each other at a predetermined pressure and applies a bias to electrostatically transfer the toner image. Similarly, there is a method in which the photoreceptor 1 and the intermediate transfer body 5 are brought into contact with each other at a predetermined pressure to perform adhesive transfer by utilizing the adhesiveness of the surface of the intermediate transfer body 5, and a method in which corona transfer is performed by a corotron or the like. Here, a roller (primary transfer roller) that performs electrostatic transfer by applying a bias is used. The secondary transfer device 7 is a device that transfers a toner image from the intermediate transfer member 5 to a transfer member 9 such as plain paper. In this apparatus, the transfer member 9 is brought into contact with the intermediate transfer member 5 at the correct position, and the pressure is applied by sandwiching them to make the toner on the intermediate transfer member 5 viscous and generate a binding force with the transfer member 9. Transfer is performed. This apparatus can also fix the toner image on the transfer body 9 simultaneously with the transfer, and here, a pair of rollers (secondary transfer rollers) are used. The cleaning device 8 cleans untransferred toner and impurities on the photoconductor 1 after transfer. As this device, a rubber blade,
There is a fur brush, a magnetic brush, or the like, but here, a device in which a blade and a fur brush are combined is used.

The toner used in the above process retains the required fluidity and charge amount until the primary transfer, and the adhesive force with the transfer body 9 is increased by applying a relatively small pressure during the secondary transfer. It is necessary to have such characteristics. It is also important that this toner does not cause an offset with respect to the intermediate transfer member 5. For that purpose, (1) the surface tension is relatively small, (2) it is softened at a low temperature, and the melt viscosity is low, (3)
The core material is a soft material having characteristics such as plastic deformation under a predetermined pressure, (1) has an appropriate hardness, (2) has good triboelectric chargeability, (3) has good powder fluidity, A capsule toner having a hard material having the above properties as a shell material is preferable.

Specific examples of such toner include Japanese Patent Publication No. 1-45912, Japanese Patent Publication No. 1-40354, Japanese Patent Application Laid-Open No. 2-61647 and Japanese Patent Application Laid-Open No. 1-1836.
Those described in Japanese Patent No. 67, etc. are used. That is, as the core material of the toner, a wax compound, an ethylene acrylic copolymer ethylene vinyl acetate copolymer,
There are styrene resins, acrylic resins, styrene acrylic resins, styrene diene resins, epoxy resins, polyester resins, polyamide resins, higher fatty acids and their derivatives, polyolefins, chlorinated polyethylene resins, etc., which are used alone or in combination. . As a method for producing the capsule toner, there are various polymerization methods such as suspension polymerization, a phase separation method, and a spray dry method.

The particle size produced in this way is 5-10.
A toner having a particle size of about 30 μm is mixed with a ferrite particle having a particle size of about 30 to 70 μm, and a carrier coated with an appropriate resin in consideration of contact charging and durability of the toner is used as a developer. When this developer is sufficiently stirred, the charge amount of the toner becomes about -10 to -40 μc / g.

The secondary transfer roller is preferably made of a rigid material such as metal in order to bring the intermediate transfer body 5 and the transfer body 9 into contact with each other with a high pressure.

The intermediate transfer member 5 is required to be flexible, durable against the pressure of the primary transfer and the secondary transfer, and releasable from the toner whose surface is made viscous or molten. In addition, the intermediate transfer member 5 includes the photosensitive member 1 and the transfer member 9.
It is necessary to determine the resistance value so as not to affect transferability by being charged by contacting and separating with. Therefore, as the intermediate transfer member 5, it is suitable to use a metal film of nickel or the like, a resin film of PET or the like as a base, and a surface layer of silicone rubber or the like in which conductive particles such as carbon are dispersed. Here, when the toner image is transferred from the photoconductor 1, a transfer bias may be directly applied to the surface layer as described above.

The primary transfer roller has a low resistance in order to efficiently generate a transfer bias and is made of a material having rubber elasticity in order to widen the contact area between the photoconductor 1 and the intermediate transfer member 5. desirable. Between the intermediate transfer body 5 and the transfer body 9 by the secondary transfer roller, 10 to 200 kg /
A pressure of about cm ² is applied. As a result, the outer shell of the toner is destroyed and the core material adheres strongly to the transfer body 9. At this time, since the intermediate transfer body 5 has releasability from the toner, offset does not occur and the intermediate transfer body 5 is completely transferred and fixed on the transfer body 9. At this time, heat may be supplementarily applied to the secondary transfer roller. By doing so, the adhesion of the toner to the transfer body 9 is improved. However, if the heating temperature of the secondary transfer roller is too high, the temperature inside the apparatus will rise and the power consumption will increase, so this heating temperature is preferably 100 ° C. or less.

In this apparatus, the intermediate transfer member 5 to the transfer member 9 are
Since the heat is not mainly used when transferring the toner image to, the temperature of the intermediate transfer body 5 rises, and as a result, the photoconductor 1 is heated or the heat is radiated through the intermediate transfer body 5. As a result, the temperature inside the apparatus is not increased and large power consumption is not required, and a high quality image can always be obtained.

FIG. 2 is a schematic configuration diagram of an image forming apparatus according to the second embodiment of the present invention. Descriptions of parts of this embodiment that are the same as those of the first embodiment will be omitted. The principle part of the image forming process of this embodiment is the same as that of the first embodiment, but the specific means are partially different as follows.

The intermediate transfer member of this embodiment is composed of a roller (intermediate transfer roller 10) in which an elastic material such as silicone rubber is laminated on a metallic core material such as aluminum, the surface of which is powdered toner. On the other hand, it is configured to have adhesiveness and releasability from viscous toner. The intermediate transfer roller 10 also has the function of a primary transfer device. That is, this intermediate transfer roller 10
Is brought into pressure contact with the photoconductor 1 at a predetermined pressure, and the toner image is adhesively transferred by utilizing the adhesiveness of the surface thereof. Here, a bias may be applied to the intermediate transfer roller 10 to electrostatically transfer the toner image.

The secondary transfer device of the present embodiment has a pressure roller 11
The transfer member 9 such as plain paper is sandwiched and pressed against the intermediate transfer roller 10. As a result, the toner becomes viscous when it receives pressure, and a binding force with the transfer body 9 is generated to transfer the toner. It is also possible to perform fixing at the same time as this transfer.

In this apparatus, in order to maintain the function of the intermediate transfer roller 10 for a long time, it is desirable to provide a means for cleaning the intermediate transfer roller 10. The cleaning of the intermediate transfer roller 10 having rubber elasticity as in the present embodiment is highly reliable when performed with a scraper made of an elastic plate made of metal or urethane resin.

In this apparatus, since electrostatic force is not used for transfer, there is almost no image deterioration due to flying of toner,
A very high quality image can be obtained.

In the first and second embodiments, it is possible to eliminate the cleaning device 8 for the photoconductor 1 and give the developing device 4 its function to achieve the toner recycling. In this case, the toner not transferred to the intermediate transfer body 5 or the intermediate transfer roller 10 is collected by the developing device 4. Further, in the case of this apparatus, since the photoconductor 1 and the transfer body 9 are not in direct contact with each other, the paper dust which is a problem when using plain paper as the transfer body 9 is greatly reduced.

FIG. 3 is a schematic configuration diagram of a multicolor image forming apparatus according to the third embodiment of the present invention. This apparatus includes a charging device 2, an image exposing device 3, four developing devices 12 for supplying toner of each color (yellow, magenta, cyan, black) around the photoconductor 1, an intermediate transfer belt 13, and a cleaning device 8. And the primary transfer roller 14 is located at a position where the intermediate transfer belt 13 and the photoconductor 1 come into contact with each other, and the secondary transfer is performed at a position until the transfer body 9 such as plain paper is separated from the intermediate transfer belt 13 and discharged. There is a roller 15.

Desirable conditions for the toner in this embodiment are the same as those in the first embodiment. The image formation in this embodiment is performed as follows. First, a toner image is formed according to image data of a certain color component (for example, yellow). That is, in FIG.
It is uniformly charged to about 0 V and an electrostatic latent image is formed by imagewise exposure. Thereby, for example, the potential of the background portion is -600 to
-800V, potential of image part (toner adhesion part) is -100
It becomes about -500V.

Subsequently, a bias of about -500 to -700 V is applied to the sleeve of the yellow developing device Y, and the developer is supplied to the developing area of the photoconductor 1 while rotating the sleeve. For example, the particle size is 5 to 10 μm. Develop with a degree of negatively charged toner. At this time, the other developing devices are retracted so as not to respond to the electrostatic latent image.

Thereafter, while the primary transfer roller 14 presses the intermediate transfer belt 13 against the photosensitive member 1, +0.5 to 3.
A toner image is electrostatically transferred onto the intermediate transfer belt 13 by applying a bias of about 0 kV.

Next, a toner image is similarly formed according to the image data of the second color (for example, magenta), and this toner image is transferred onto the intermediate transfer belt 13 in an overlapping manner. At this time,
The transfer bias applied to the primary transfer roller 14 is preferably set to be larger than that of the first color.

Similarly, toner images of the third and fourth colors are formed, and a multicolor toner image is formed on the intermediate transfer belt 13.

Next, the transfer member 9 such as plain paper is placed on the intermediate transfer belt 13, and the secondary transfer roller 15 is set to 10 to 20.
By applying a pressure of about 0 kg / cm ^2, the outer shell of the toner on the intermediate transfer belt 13 is destroyed and the core material is plastically deformed, and the toners or the toner and the transfer body 9 are strongly bonded and fixed. It

Here, heat may be supplementarily applied to the secondary transfer roller 15. By doing so, the adhesion of the toner to the transfer body 9 is improved. However, if this temperature is too high, the temperature inside the machine will rise and the power consumption will increase, so it is desirable to keep this temperature below 100 ° C.

The final fixed image thus obtained is obtained without the main use of heat. Further, the graininess of each toner is lost, and a state in which a melted material or a plastically deformed material is laminated is obtained. Therefore, the light transmittance of the color toner is improved and the color reproducibility is improved.

FIG. 4 is a schematic configuration diagram of another multicolor image forming apparatus according to the fourth embodiment of the present invention. This apparatus includes a charging device 2, an image exposure device 3, four developing devices 12 for supplying toners of respective colors (yellow, magenta, cyan, black) around the photoconductor 1, an intermediate transfer roller 10,
A cleaning device 8 is arranged. Further, a pressure roller 11 is provided which presses a transfer body 9 such as plain paper between the intermediate transfer roller 10 and presses it. The transfer body 9 is cyclically conveyed to the pressure contact position of the pressure roller 11 through the circulation conveyance path 16.

The other components are the same as those in the first embodiment. The image formation in this embodiment is performed as follows. First, a toner image is formed according to image data of a certain color component (for example, yellow). That is, in FIG. 4, the photoreceptor 1 is uniformly charged to about -800V,
An electrostatic latent image is formed by imagewise exposure. Thereby, for example, the potential of the background portion is −600 to −800V, and the potential of the image portion (toner adhered portion) is about −100 to −500V.

Subsequently, a bias of about -500 to -700 V is applied to the sleeve of the yellow developing device Y, and the developer is supplied to the developing area of the photosensitive member 1 while rotating the sleeve, and the particle size is, for example, 5 to 10 μm. Develop with a degree of negatively charged toner. At this time, the other developing devices are retracted so as not to respond to the electrostatic latent image.

The photoreceptor 1 on which the toner image is formed is brought into pressure contact with the intermediate transfer roller 10, and the toner image is transferred to the intermediate transfer roller 10 by the adhesive force of the intermediate transfer roller 10.

Subsequently, the transfer member 9 is supplied between the intermediate transfer roller 10 and the thick roller 11, and 10 to 200 kg /
By applying a pressure of about cm ² , the toner on the intermediate transfer roller 10 is made viscous. That is, this breaks the outer shell of the toner and plastically deforms the core material. As a result, a strong bonding force is generated between the toners or between the toner and the transfer body 9, and transfer / fixing is performed. As a result, on the transfer body 9, a toner layer which is united with each other and loses the graininess is obtained.

Next, a toner image is similarly formed according to the image data of the second color (for example, magenta). This toner image is transferred to the intermediate transfer roller 10 due to the adhesive force, and the error and pressure are applied thereto, and the toner image is transferred onto the transfer body 9 so as to be superimposed on the yellow toner image. As a result, in the overlapped portion, a uniform magenta toner layer is obtained on the yellow toner layer which has no graininess and is uniform.

Similarly, the toner images of the third and fourth colors are formed in the same manner, and are overlaid on the transfer body 9, respectively.

The final image thus obtained is
Since the uniform toner layers in which the granularity of each toner is lost are stacked, the light transmittance of the color toner is improved and the color reproducibility is improved.

Desirable toner conditions are the same as in the first embodiment. Further, as described in the first embodiment, heat may be supplementarily applied to the pressure roller 11. By doing so, the adhesion of the toner to the transfer body 9 is improved. However, if this temperature is too high, the temperature inside the machine will rise and the power consumption will increase, so it is desirable to keep this temperature below 100 ° C.

[0044]

As described above, according to the present invention,
After transferring the toner image formed on the image carrier (photoreceptor) to the intermediate transfer body, contact the transfer body such as plain paper and apply pressure to plastically deform the toner and achieve transfer and fixing. Therefore, various problems caused by mainly using heat can be solved, downsizing of the apparatus can be realized, and a stable image can always be obtained.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram showing another image forming apparatus of the present invention.

FIG. 3 is a schematic configuration diagram showing a multicolor image forming apparatus of the present invention.

FIG. 4 is a schematic configuration diagram showing another multicolor image forming apparatus of the present invention.

[Explanation of reference numerals] 1 photoconductor 2 charging device 3 image exposure device 4, 12 developing device 5 intermediate transfer member 6 primary transfer device 7 secondary transfer device 8 cleaning device 9 transfer member 10 intermediate transfer roller 11 pressure roller 13 intermediate transfer device Belt 14 Primary transfer roller 15 Secondary transfer roller 16 Circulation transport path

Claims (2)

[Claims] 1. A drum or belt-shaped image carrier, a drum or belt-shaped intermediate transfer member, a latent image forming device for forming an electrostatic latent image on the image carrier, and the image carrier. A developing device that develops the electrostatic latent image on the carrier with dry toner, a primary transfer device that transfers the toner image on the image carrier to the intermediate transfer member, and a transfer member on the intermediate transfer member. An image forming apparatus, comprising: a secondary transfer device that transfers a toner image onto a transfer body by applying pressure and fixes the toner image at the same time. 2. A drum or belt-shaped image carrier, a drum or belt-shaped intermediate transfer member, a latent image forming device for forming an electrostatic latent image on the image carrier, and the image carrier. A plurality of developing devices for developing the electrostatic latent image on the carrier with dry toner,
A primary transfer device that transfers the toner image on the image carrier to the intermediate transfer body, and a toner image is transferred to the transfer body and fixed at the same time by applying pressure by overlapping the transfer body on the intermediate transfer body. In an image forming apparatus equipped with a next transfer device, the intermediate transfer member is formed by repeating a step of forming a toner image on the image bearing member and transferring it to the intermediate transfer member while switching a developing device to be used. An image forming apparatus, comprising: forming a superposed toner image on an upper surface of the intermediate transfer member; and thereafter, simultaneously transferring and fixing the superposed toner image on the intermediate transfer member to the transfer member.