JP5532695B2 - Image forming apparatus and double-sided image forming method - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus and a double-sided image forming method.

  Recently, in an electrophotographic image forming apparatus, double-sided printing is electronically performed using a so-called electronic RDH (Recirculating Document Handler). This double-sided printing by the electronic RDH is different from the method of performing double-sided printing by a conventional analog copying machine, and the printed matter is immediately put on the other side of the image forming support without stocking what is printed on one side of the image forming support. Can print continuously. That is, based on the image information converted into the digital signal, a first electrostatic latent image is formed on the electrostatic latent image carrier, and a toner image is formed based on the electrostatic latent image. After the transfer and fixing process on one surface of the image forming support, the second image formed on the electrostatic latent image carrier on the other surface of the image forming support immediately without stocking the image forming support. Double-sided printing is performed by transferring and fixing the toner image formed based on the electrostatic latent image.

In the double-sided image forming method using the electronic RDH, the fixing process is generally performed by a heating method. In such a case, the image forming support on which the visible image based on the first electrostatic latent image is formed on one side is in a high temperature state that retains heat from the fixing process. Since the toner image based on the second electrostatic latent image formed on the electrostatic latent image carrier is transferred, in this toner image transfer process, the image forming support and the electrostatic latent image carrier are Due to the close contact, the heat held by the image forming support is transferred to the electrostatic latent image carrier, which causes the electrostatic latent image carrier to be heated to a high temperature. There is a problem that heat deterioration or the like occurs.
In addition, when the electrostatic latent image bearing member becomes high temperature, the developer used when the fixing process is performed by a heating method has a softening point temperature and a glass transition point temperature as toner constituting the developer. Since the resin contains a relatively low binder resin, there is a problem that a cleaning defect or the like is caused due to the fusion of the toner onto the electrostatic latent image carrier.

On the other hand, in an image forming apparatus, it has been proposed to use a heat storage material for cooling or heating components constituting the image forming apparatus (for example, see Patent Documents 1 to 4).
In Patent Document 1, in the fixing device, a heat storage member made of a heat storage material is disposed so as to be in contact with the heating roller, and the heat storage member is disposed through the radiant heat or air from the heating roller in a state of being separated from the heating roller. It is disclosed that the heat is stored by the heat conduction and the heat roller is heated by contacting the heat storage member when the temperature of the heat roller is lower than the expected temperature.
Japanese Patent Application Laid-Open No. H10-260260 discloses that a component of an image forming apparatus that rises in temperature due to its own heat generation or heat received from surroundings such as a developing device or a fixing device is cooled by using a heat storage material.
In Patent Document 3, heat generated in components such as a fixing device or a document illumination lamp is stored in a heat storage material through a heat transporting means including a duct, a heat pipe, or a metal member, and the heat is stored in an image forming support. It is disclosed that it is used for dehumidification.
In Patent Document 4, heat generated in a fixing device is stored in a heat storage material through a heat transport unit including a heat pipe, and the heat is used for dehumidification of an image forming support or for prevention of dew condensation on a document reading device. It is disclosed.

JP 2008-225256 A JP 2008-116681 A JP 2006-154673 A JP 2004-061580 A

  The present invention has been made based on the circumstances as described above, and the purpose thereof is to form a visible image by thermal fixing on each of both surfaces of an image forming support using electronic RDH. It is an object of the present invention to provide an image forming apparatus and a double-sided image forming method capable of stably obtaining a good visible image and reducing the amount of heat to be supplied from a heat source for heat fixing.

The image forming apparatus of the present invention develops an electrostatic latent image formed on an electrostatic latent image carrier with a toner containing a binder resin and a colorant to form a toner image. An image forming unit that transfers the image onto a forming support and heat-fixes the transferred toner image to form a visible image on the image forming support, and an image forming support that passes through the image forming unit. An image forming support reversing section comprising an image forming support reversing transport path for supplying the image forming support again to the image forming section in a state where the image forming support having a visible image formed on one surface thereof is reversed. In an image forming apparatus having
A heat circulation mechanism made of a heat storage material having a heat absorbing portion provided inside the electrostatic latent image carrier and a heat radiating portion that heats the image forming support that has not been processed on both sides by the heat absorbed in the heat absorbing portion. Is provided,
The thermal circulation mechanism forms a visible image on the entire surface of the image forming unit by the heat absorbing unit, and changes the surface temperature of the image forming support supplied to the image forming unit again through the image forming support reversing unit to the glass transition of the toner. It cools to a temperature within the point temperature (Tg) + 10 ° C. and preheats the unprocessed double-sided image forming support supplied to the image forming unit without passing through the image forming support reversing unit by the heat radiating unit. The
The heat storage material has a melting point of 32.4 ° C. or higher and 58 ° C. or lower .
In the image forming apparatus of the present invention, the toner preferably has a glass transition temperature (Tg) of 38 ° C. or higher and 54 ° C. or lower.

In the double-sided image forming method of the present invention, the electrostatic latent image formed on the electrostatic latent image carrier is developed with a toner containing a binder resin and a colorant to form a toner image, and then the toner The first visible image forming process is performed in which the image is transferred onto one surface of the image forming support, and the transferred toner image is heat-fixed on the one surface of the image forming support to form a visible image. After that, a toner image is formed on the electrostatic latent image carrier, and then the toner image is transferred onto the other surface of the image forming support, and the image forming support is transferred to the transferred toner image. In the double-sided image forming method for performing a second visible image forming process for forming a visible image by performing a heat fixing process on the other surface,
By a heat circulation mechanism made of a heat storage material having a heat absorbing portion provided inside the electrostatic latent image carrier and a heat radiating portion that heats the image forming support that has not been processed on both sides by the heat absorbed in the heat absorbing portion. The surface temperature of the image forming support on which a visible image is formed only on one surface by the first visible image forming process is cooled to a temperature within the glass transition point temperature (Tg) of the toner + 10 ° C. The image forming support subjected to the first visible image forming process is preheated by the heat radiating unit ,
The heat storage material has a melting point of 32.4 ° C. or higher and 58 ° C. or lower .
In the double-sided image forming method of the present invention, the toner preferably has a glass transition temperature (Tg) of 38 ° C. or higher and 54 ° C. or lower.

In the image forming apparatus of the present invention, since the fixing process is performed by a heating method, when a visible image is formed on both sides of the image forming support, the image forming support on which the visible image is formed on one side, In the process of forming a visible image on the other side, the image forming support is brought into close contact with the electrostatic latent image carrier on which the toner image is formed in a high temperature state that retains heat from the heat fixing process. Although it will be transferred to the latent image carrier, the heat absorption part provided inside the electrostatic latent image carrier and the heat radiation that heats the unprocessed image forming support on both sides by the heat absorbed in the heat absorption part A heat circulation mechanism made of a heat storage material is provided, and heat transferred from the image forming support having a visible image formed on one surface to the electrostatic latent image carrier is absorbed by the heat circulation mechanism. The heat storage material receives heat in The surface temperature of the imaging support is cooled to a particular temperature. In this way, by cooling the image forming support on which the visible image is formed on one surface by the thermal circulation mechanism through the electrostatic latent image carrier, the image forming support from the image forming support on which the visible image is formed on one surface is cooled. Since the temperature increase of the electrostatic latent image carrier due to the transfer of heat is suppressed, thermal degradation of the electrostatic latent image carrier can be suppressed, and toner on the electrostatic latent image carrier can be suppressed. The occurrence of adverse effects such as toner fusion on the electrostatic latent image carrier and thermal deterioration of the toner due to excessive heating of the toner can be suppressed. Moreover, the heat absorbed in the heat-absorbing part of the thermal circulation mechanism is effectively used without being discarded, and the double-sided unprocessed image formation is supplied to the image-forming part by the heat-radiating part without passing through the image-forming support reversing part. Since the support is preheated, it is possible to reduce the amount of heat required to be supplied from a heat source in the heat fixing process on one surface of the image forming support.
Therefore, according to the image forming apparatus of the present invention, it is possible to stably obtain a good visible image even when a visible image is formed on each of both surfaces of an image forming support by thermal fixing using electronic RDH. In addition, the amount of heat to be supplied from the heat source for heat fixing can be reduced.

According to the double-sided image forming method of the present invention, a heat absorbing portion provided inside the electrostatic latent image carrier, and a heat radiating portion for heating the image forming support that has not been processed on both sides by the heat absorbed in the heat absorbing portion. The surface temperature of the image forming support on which the visible image is formed only on one surface by the first visible image forming process is cooled by the heat absorbing part, and the heat radiating part is used to Since the image forming support to be subjected to the visible image forming process is preheated, even when a visible image is formed by heat fixing on both sides of the image forming support using electronic RDH, the image forming support is stable and good. A visible image can be obtained, and the amount of heat to be supplied from a heat source for heat fixing can be reduced.
In other words, the image forming support on which a visible image is formed on one side by the first visible image forming process has a toner image formed in a high temperature state that retains heat from the heat fixing process during the second visible image forming process. The heat absorbing portion provided inside the electrostatic latent image carrier is in a state of being in close contact with the electrostatic latent image carrier and the heat of the image forming support is transferred to the electrostatic latent image carrier. And a heat-circulating mechanism comprising a heat storage material that heats the image forming support that has not been processed on both sides by the heat absorbed by the heat absorbing portion. Since the heat transferred to the electrostatic latent image carrier is transferred to the heat absorbing portion and is received by the heat storage material in the heat absorbing portion, thereby the surface temperature of the image forming support is cooled to a specific temperature, A visible image is formed on one side Since the temperature rise of the electrostatic latent image carrier caused by the transfer of heat from the image forming support is suppressed, thermal deterioration of the electrostatic latent image carrier is suppressed and the electrostatic latent image carrier Occurrence of adverse effects such as toner fusion on the electrostatic latent image bearing member and thermal deterioration of the toner due to excessive heating of the toner on the body is suppressed. Moreover, the heat absorbed in the heat-absorbing part of the heat circulation mechanism is effectively used without being discarded, and the double-sided unprocessed image forming support used for the first visible image forming process is preheated by the heat dissipating part. Therefore, in the heat fixing process in the first visible image forming process, the amount of heat required to be supplied from the heat source can be reduced.

1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus of the present invention. FIG. 2 is an explanatory schematic diagram illustrating an example of a configuration of a thermal circulation mechanism of the image forming apparatus in FIG. 1.

  The double-sided image forming apparatus and double-sided image forming method of the present invention will be described below.

FIG. 1 is an explanatory diagram showing the overall configuration of the image forming apparatus of the present invention.
The double-sided image forming apparatus 10 is a digital copying machine that forms visible images on both sides of an image forming support using electronic RDH, and includes an image reading unit A, an image processing unit B, an image storage unit C, and an image forming unit. D and the image forming support body reversing portion E.

  In the image reading unit A, the original 121 placed on the original table glass 122 is irradiated with light by a halogen light source 123 provided on a carriage (not shown) that moves on the guide rail. The reflected light from the original 121, that is, the optical image corresponding to the image on the original 121 has a mirror 127 provided on the carriage together with the halogen light source 123, and a pair of mirrors 124 and 125 that move on the guide rail. The light is guided to the lens reading unit 128 via the movable mirror unit 126. The lens reading unit 128 includes an imaging lens 129 and a CCD line sensor 130, and an optical image introduced into the lens reading unit 128 is converged by the imaging lens 129 and is stored in the CCD line sensor 130. An image is formed on the light receiving surface, and the optical image on the line is sequentially photoelectrically converted into an electric signal by the CCD line sensor 130.

  Specifically, the halogen light source 123, the mirror 127, and the movable mirror unit 126 are driven by a motor (not shown), and the image information of one page of document is read by the CCD line sensor 130 as image data. The image data of the document 121 read by the image reading unit A is subjected to various image processing such as density conversion, filter processing, scaling processing, and γ correction in the image processing unit B, and then the image storage unit C. Stored in

Reference numeral 81 denotes an automatic document feeder that automatically conveys the read document 121 on the document table glass 122. When a plurality of read documents 121 are set on the document setting table 82 and the copy button on the operation panel 80 is pressed, 81 is set. Then, each page of the original 121 is taken out one by one by the paper feed roller 83, and the original 121 is driven by the driving roller 84, the driven roller 92, and the belt 86 that is circulated and moved by the driving roller 84 and the driven roller 92. In addition to being automatically automatically conveyed to a predetermined position on the glass 122, the page that has been read is removed from the platen glass 122 and discharged onto the document discharge tray 94 via the document discharge roller 87.
The automatic document feeder 81 can also automatically read both sides of one double-sided document. That is, after a double-sided original is automatically conveyed onto the platen glass 122 and image data on one side is read, the double-sided original is switched by a guide plate 89, a reverse roller 90, and a switching guide 88 driven by a solenoid (not shown). The direction can be changed in a state where the double-sided document is reversed by the reversing mechanism provided, and it is automatically conveyed again to a predetermined position on the document table glass 122, and the image data on the back side of the document can be read.

In the image forming unit D, a visible image is formed on the image forming support in accordance with the image data output via the image storage unit C.
That is, in the image forming unit D, a laser beam generated by a semiconductor laser (not shown) is modulated based on image data, and the modulated laser beam is rotated by a polygon mirror 142 rotated by a drive motor 141. An organic electrostatic latent image carrier (scanned), in which a charge generation layer 22 and a charge transport layer 23 are formed on the outer peripheral surface of a cylindrical substrate 21 via an fθ lens (not shown) and a reflection mirror 143. The surface of the electrostatic latent image carrier 20 is rotated clockwise by power from a driving source (not shown) and is uniformly charged in advance by a charger 152 made of, for example, a scorotron charger. An electrostatic latent image is formed by image exposure on the electrostatic latent image carrier 20, and the toner is transferred onto the developing sleeve 153A rotated by the developing unit 153. Is conveyed to the surface of the electrostatic latent image carrier 20 to form a toner image, and this toner image is supplied from the cassette 171 at the same timing and is conveyed through the image forming support processing path 174. A transfer roller 157 is transferred onto a forming support, and after being separated from the electrostatic latent image carrier 20 by a separation pole 158, a heating roller 31 and a pressure roller 32 containing a heat source such as a heater 31A are provided. In the heating type fixing device 30, heat fixing is performed, whereby a visible image is formed. Note that the developing device 153 may be of either a contact type or a non-contact type.
In FIG. 1, reference numeral 159 denotes a cleaning device. The cleaning device 159 may be either a blade type or a brush type cleaning type.

In the image forming support reversing unit E, a visible image should be formed on the other side of the image forming support on which the visible image is formed only on one surface in the image forming unit D by the image forming support reversing conveyance path. The kimono is inverted, and the image forming support in the inverted state is fed toward the image forming portion D again.
That is, in the image forming support body reversing unit E, the image forming support that has been formed on one surface and has been ejected from the fixing device 30 has the first switching claw 177 extending in the upper right direction and the image forming support. The entrance of the duplex copying conveyance path 184 continuous with the body processing conveyance path 174 is opened, and the sheet is conveyed downward, and the second switching claw 180 of the duplex copying conveyance path 184 extends in the lower left direction to double-side. When the exit of the copying conveyance path 184 is opened, the conveying roller 181 is conveyed to the reversing roller 181. The reversing roller 181 is further reversed and the second switching claw 180 extends in the upper left direction so that the duplex copying conveying path 184 is conveyed. In this state, the paper is conveyed through the reverse conveyance path 183 toward the image forming unit D in a state where the front and back are reversed by closing the outlet.
In the example of this figure, the image forming support reversing conveyance path is formed by the duplex copying conveying path 184 and the reversing conveying path 183.

In the double-sided image forming apparatus using electronic RDH in which the image forming operation is performed as described above, the double-sided image forming process is performed as follows.
That is, when a copy button provided on the operation panel 80 is pressed, first, image data on both sides of the document 121 is obtained by the image reading unit A as described above, and the image forming support stocked from the cassette 171 is taken out. The image forming support processing path 174 is fed to the image forming section D by the image forming support transport path 175 having a plurality of transport rollers and transport belts, and passes through the image forming section D. The toner image corresponding to the image data on the surface of the original is formed on one surface of the image forming support by carrying out the above image forming operation, and the fixing device 30 relates to one surface of the image forming support. A heat fixing process is performed to form a visible image. In this way, the first visible image forming process is performed.
Next, when the image forming support on which the visible image is formed on only one surface is discharged from the fixing device 30, the image forming support supports the image forming support reversing portion E including the image forming support reversing conveyance path. After having been reversed by passing, the image forming supporter transport path 175 feeds it again to the image forming portion D in the same manner as when it is supplied from the cassette 171, and the image forming supporter processing transport path 174. The toner image corresponding to the image data on the back side of the document is formed on the other side of the image forming support by carrying out the above image forming operation, and the other side of the image forming support in the fixing device 30. The heat fixing process is performed to form a visible image. In this way, the second visible image forming process is performed following the first visible image forming process.
Then, the first switching claw 177 extends in the lower right direction and the entrance of the duplex copying conveyance path 184 is closed, whereby an image forming support on which images are formed on both sides from the image forming support discharge tray 176 is formed. Is discharged out of the machine.

  As shown in FIG. 2, the double-sided image forming apparatus 10 includes a heat absorbing portion 13 provided inside the latent electrostatic image bearing member 20 and heat that has been absorbed by the heat absorbing portion 13. The heat circulation mechanism which consists of a thermal storage material which has the thermal radiation part 14 which heats the image formation support body is provided. The thermal circulation mechanism has a configuration in which the heat storage material is continuously circulated between the heat absorbing portion 13 and the heat radiating portion 14.

According to the thermal circulation mechanism, a visible image is formed only on one surface by the first visible image forming process in the heat absorbing unit 13, and image formation in a state in which heat is retained by the fixing process related to the first visible image forming process. Heat is received from the support via the electrostatic latent image carrier 20, whereby the surface temperature of the image forming support, specifically, the electrostatic latent image carrier 20 is separated, and the image forming support The surface temperature of one surface of the image forming support at a position passing through the separation electrode 158 on the processing conveyance path 174, that is, one surface of the image forming support having a visible image formed on one surface and a toner image transferred on the other surface. Is cooled to a temperature within the glass transition temperature (Tg) of the toner + 10 ° C., preferably within the glass transition temperature (Tg).
Here, the glass transition temperature (Tg) of the toner is a value measured by DSC, and the intersection of the baseline and the endothermic peak slope is defined as the glass transition temperature.
Specifically, using a differential scanning calorimeter (DSC), the temperature is raised to 100 ° C., left at that temperature for 3 minutes, and then cooled to room temperature at a drop temperature of 10 ° C./min. Next, when this sample was measured at a heating rate of 10 ° C./min, an extension of the baseline below the glass transition point and a tangent line indicating the maximum slope from the peak rising portion to the peak apex. The intersection point is shown as the glass transition point. Here, as a measuring device, DSC-7 manufactured by PerkinElmer, Inc. can be used.

  The image forming support on which the visible image is formed on only one surface is cooled by the thermal circulation mechanism, and the surface temperature is set to the above temperature range, so that the visible image can be formed on the entire surface during the second visible image forming process. Since the temperature rise of the electrostatic latent image carrier 20 due to the transfer of heat from the formed image forming support is sufficiently suppressed, the thermal degradation of the electrostatic latent image carrier 20 is prevented. It is possible to suppress the toner from being excessively heated on the electrostatic latent image carrier 20 in relation to the glass transition temperature (Tg) of the toner. It is possible to suppress the occurrence of adverse effects such as toner fusion on the electrostatic latent image carrier 20 and thermal degradation of the toner.

  On the other hand, in the heat radiating unit 14, the heat absorbed in the heat absorbing unit 13 is released, and this heat causes the double-sided unprocessed image forming support to be supplied to the image forming unit D without passing through the image forming support reversing unit E. That is, the image forming support to be subjected to the first visible image forming process is preheated.

  As a heat storage material constituting such a heat circulation mechanism 10, a visible image is formed only on one surface in the heat absorbing portion 13, and image formation in a state in which heat is retained by the fixing process related to the first visible image forming process. The surface temperature of the support may be any material that can be cooled to a desired temperature range by utilizing the characteristic of the heat storage material that maintains a constant temperature during the phase change. The material and thickness of the substrate 21, the charge generation layer 22 and the charge transport layer 23 constituting the electrostatic latent image carrier 20 according to the glass transition temperature (Tg) of the toner constituting the developer to be developed or as necessary. An appropriate one can be used in consideration of the rotational speed of the electrostatic latent image carrier 20, the heat fixing conditions in the fixing device 30, and the like.

Specifically, examples of the heat storage material include sodium acetate hydrate (melting point: 58 ° C., heat of fusion: 264 kJ / kg), sodium thiosulfate hydrate (melting point: 48 ° C., heat of fusion: 197 kJ / kg), sulfuric acid Inorganic hydrate salts such as sodium hydrate (melting point: 32.4 ° C., heat of fusion: 251 kJ / kg); C ₂₀ H ₄₂ (melting point: 36.4 ° C., heat of fusion: 247 kJ / kg), C ₂₂ H ₄₆ (Melting point: 44 ° C., heat of fusion: 251 kJ / kg), n-paraffin such as C ₂₄ H ₅₀ (melting point: 51 ° C., heat of fusion: 255 kJ / kg) and the like.

Specifically, as the heat circulation mechanism that constitutes the double-sided image forming apparatus 10, for example, the heat storage material itself, or a material in which the heat storage material is microencapsulated by an appropriate technique, and the microencapsulated heat storage material are dispersed in water. In the heat storage material container 16, the end of the state is made of a circulation pipe-like body 15 configured to be continuously circulated by the circulation transfer means in the heat storage material container 16. A part of the circulation pipe 15 is disposed inside the electrostatic latent image carrier 20 to form the heat absorbing portion 13, and the other part of the image forming support stocked in the cassette 171. In contact with the image forming support that is to be used for the first visible image forming process earliest in the cassette 171, Rui can be used as the heat radiation portion 14 formed by constituted by being arranged to close.
In the heat circulation mechanism having such a configuration, when the heat radiating portion 14 is in a state of being close to the image forming support, the separation distance (proximity distance) is preferably 1 mm or less, and more preferably 0. 5 mm or less.

Here, the endothermic part 13 constituting the heat circulation mechanism is an electrostatic latent image from the viewpoint of heat transfer from the electrostatic latent image carrier 20 to the endothermic part 13 and drivability of the electrostatic latent image carrier 20. The inside of the carrier 20 is preferably in a state of being very close to the electrostatic latent image carrier 20. Specifically, the state in which the heat absorption unit 13 and the electrostatic latent image carrier 20 are close to each other preferably has a proximity distance (separation distance) of 1 mm or less, and more preferably 0.5 mm or less.
Further, when the heat absorption unit 13 is in contact with the electrostatic latent image carrier 20, a large amount of driving energy is required to drive the electrostatic latent image carrier 20, so It is preferable to provide a mechanism for applying a lubricant between the electrostatic latent image carrier 20 and the heat absorbing portion 13.
As the lubricant, for example, so-called silicon grease or metal soap can be used.
In addition, the material of the heat storage material container 16 is not particularly limited, and a material made of a material that can hold the heat storage material and has a relatively excellent heat transfer property is used as, for example, the heat storage material container 16. It can be appropriately used in consideration of the workability to the required shape in relation to the required arrangement position.
Specific examples of the material constituting the heat storage material container 16 include, for example, polyethylene, polypropylene, and aluminum. These materials are preferable because they have relatively excellent heat transfer properties, good moldability and workability, and can ensure accuracy in the holding state. The heat storage material container 16 made of such a material preferably has a thickness of 0.1 to 2 mm from the viewpoint of strength and heat conduction.

In the example of this figure, the circulation pipe-like body 15 constituting the heat circulation mechanism is provided with a resin heat storage material container 16, and its external shape is U-shaped, and one end portion related to the U-shape is The electrostatic latent image carrier 20 is inserted into the cylindrical body of the base 21, and one end inserted into the base 21 is in a state of being very close to the inner peripheral surface of the base 21. As a result, the heat absorbing portion 13 is formed, and the other end extending parallel to the one end is in contact with the uppermost one of the image forming supports stocked in the cassette 171. Thus, the heat radiating portion 14 is formed. In addition, the circulation pipe-like body 15 is circulated by a pump in a flow path in a U-shaped connecting portion 19 extending perpendicularly to one end constituting the heat absorbing portion 13 and the other end constituting the heat radiating portion 14. Transfer means (not shown) is provided, and the heat storage material is continuously circulated in the direction of the arrow in FIG. 2 by this pump.
The electrostatic latent image carrier 20 provided with the heat absorption part 13 is formed on a cylindrical outer peripheral surface of a 2 mm-thick base 21 made of, for example, aluminum, for example, a charge generating layer 22 having a thickness of 0.8 μm, and for example having a thickness of 25 μm. The charge transport layer 23 is formed in this order, and is configured to rotate clockwise, for example, at a rotational speed of 200 to 500 mm / sec.

The heat circulation mechanism configured as described above is in a state in which the heat storage material continuously circulates at least during the double-sided image forming process in which double-sided image formation is performed. The image forming support on which a visible image is formed on one surface by the forming process is cooled, and the image forming support to be subjected to the first visible image forming process by the heat radiating unit 14 is preheated.
That is, according to the thermal circulation mechanism composed of the circulation pipe 15, the toner image based on the electrostatic latent image formed on the electrostatic latent image carrier 20 in the second visible image forming process is placed on the image forming support. During the transfer process, a visible image is formed on one surface by the first visible image forming process, and a toner image is formed on the image forming support in a state where heat is retained by the fixing process related to the first visible image forming process. The electrostatic latent image carrier 20 is brought into a close contact state, and the heat of the image forming support is transferred to the electrostatic latent image carrier 20. The generated heat is transferred to the heat storage material in the heat absorption part 13 and is finally absorbed into the heat storage material by the phase change of the heat storage material, whereby the electrostatic latent image carrier 20 is brought to a high temperature state. There was no visible image on only one side Surface temperature on the surface of the one of the imaging support is the desired temperature range imaging support is cooled.
Further, the heat stored in the heat storage material in the heat absorption part 13 in this way is transferred to the heat radiation part 14 by the circulation transfer means or by the phase change of the heat storage material, and the heat radiation part 14 contacts the heat radiation part 14. The image forming support is preheated by being released from the heat storage material by the phase change of the heat storage material, that is, transferred to the image forming support located at the uppermost portion of the cassette 171 in the finished state. The

(Image forming support)
The image forming support used in the present invention is a support for holding a toner image, and specifically, coated with plain paper, fine paper, art paper or coated paper from thin paper to thick paper. Various kinds of paper such as printing paper, commercially available Japanese paper and postcard paper, plastic films for OHP, cloth, and the like can be exemplified, but the invention is not limited thereto.

(Developer)
The developer used in the present invention is composed of a toner containing at least a binder resin and a colorant. Even if it is a magnetic or non-magnetic one-component developer composed only of toner, a carrier described later is mixed. It may be a two-component developer.

〔toner〕
Specifically, the toner constituting the developer is, for example, a capsule-type toner in which colorant fine particles and, if necessary, fine particles of an internal additive such as a release agent or a charge control agent are contained in a binder resin It is preferable that
The toner is preferably configured as a low-temperature fixing type.

  The method for producing such a toner is not particularly limited, and is known as a pulverization method, a suspension polymerization method, a miniemulsion polymerization aggregation method, an emulsion polymerization aggregation method, a dissolution suspension method, a polyester molecular extension method, or the like. The method of etc. can be mentioned.

[Crushing method]
The pulverization method is performed as follows. That is, the binder resin and the colorant are mixed sufficiently by a mixer such as a Henschel mixer and a ball mill together with toner constituents such as a release agent and a charge control agent as necessary, and heated by a heating roll, a kneader, an extruder, etc. Toner particles can be obtained by melt-kneading using a kneader, cooling and solidifying, pulverizing and classifying.

(Suspension polymerization method)
The suspension polymerization method is performed as follows. That is, a toner constituent component such as a release agent or a colorant and a radical polymerization initiator are added to the radical polymerizable monomer, and then these are dissolved or dispersed in the radical polymerizable monomer by a sand grinder or the like. Then, a uniform monomer dispersion is prepared, and then the monomer dispersion is added to an aqueous medium to which a dispersion stabilizer has been added in advance, and the monomer dispersion is prepared by homomixer or ultrasonic dispersion. Disperse in an aqueous medium to form oil droplets. Since the particle size of the oil droplets finally becomes the particle size of the toner, the oil droplets are controlled and dispersed so as to have a desired particle size. The size of the oil droplets to be dispersed is preferably 3 to 10 μm in volume-based median diameter. Thereafter, the mixture is heated and polymerized, and after completion of the polymerization reaction, the dispersion stabilizer is removed, washed and dried to obtain colored particles, and external additives are added and mixed as necessary to obtain toner particles. Can do.

[Binder resin]
When the toner particles constituting the toner are produced by a pulverization method, a dissolution suspension method or the like, the binder resin constituting the toner is polystyrene; styrene-substituted products such as poly-p-chlorostyrene and polyvinyltoluene. Polymer: Styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α -Chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, Styrene-isoprene copolymer, styrene-acrylo Styrene copolymers such as tolyl-indene copolymer; polyvinyl chloride, phenol resin, natural modified phenol resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane Examples thereof include resins, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral resins, terpene resins, coumarone indene resins, and petroleum resins. Moreover, as a preferable binder resin, a styrene resin in which one part or all of the resin is crosslinked can be exemplified. These can be used alone or in combination of two or more.

  On the other hand, when the toner particles constituting the toner are produced by suspension polymerization method, miniemulsion polymerization aggregation method, emulsion polymerization aggregation method, etc., as a polymerizable monomer for obtaining each resin constituting the toner, For example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethyl Styrene or styrene derivatives such as styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene; Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, Methacrylate derivatives such as isobutyl tacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, acrylic Acrylic acid ester derivatives such as phenyl acid; olefins such as ethylene, propylene, isobutylene; vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, vinyl fluoride Vinyl halides such as vinyl; vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone N-vinyl compounds such as N-vinylcarbazole, N-vinylindole and N-vinylpyrrolidone; Vinyl compounds such as vinylnaphthalene and vinylpyridine; Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide And vinyl monomers such as These vinyl monomers can be used alone or in combination of two or more.

Moreover, it is preferable to use combining what has an ionic dissociation group as a polymerizable monomer. The polymerizable monomer having an ionic dissociation group has, for example, a substituent such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group as a constituent group, and specifically includes acrylic acid, methacrylic acid, maleic acid. Acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate And 3-chloro-2-acid phosphooxypropyl methacrylate.
Furthermore, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene as crosslinking agents; ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl A binder resin having a crosslinked structure can also be obtained by using polyfunctional vinyls such as glycol dimethacrylate, neopentyl glycol diacrylate, divinyl aniline, divinyl ether, divinyl sulfide, divinyl sulfone and the like as a polymerizable monomer. These crosslinking agents can be used alone or in combination of two or more.

The binder resin contained in the toner of the developer used in the present invention preferably has a glass transition temperature (Tg) of less than 55 ° C. from the viewpoint of fixability and storage stability.
When the toner is of a low-temperature fixing type, it is preferable that a so-called core-shell structure is formed by two kinds of resins having different glass transition temperatures (Tg). The core layer may be formed of a resin having a glass transition temperature (Tg) of less than 50 ° C., and the shell layer covering the core layer may be formed of a resin having a glass transition temperature (Tg) of 55 ° C. or higher. preferable.
In such a core-shell toner, the entire toner, that is, the glass transition temperature (Tg) of the toner is preferably less than 55 ° C., and preferably 30 to 50 ° C.
When the glass transition temperature (Tg) of the toner is less than 30 ° C., depending on the storage conditions, even if a resin having a high glass transition temperature (Tg) is used as the resin constituting the shell layer, the toner There is a possibility that a problem of blocking between particles, that is, so-called aggregation occurs.

Here, the glass transition temperature (Tg) of the binder resin refers to a value measured by DSC, and the intersection of the baseline and the endothermic peak slope is defined as the glass transition temperature.
Specifically, similarly to the glass transition temperature of the toner, using a differential scanning calorimeter (DSC), the temperature is raised to 100 ° C., left at that temperature for 3 minutes, and then cooled to room temperature at a drop temperature of 10 ° C./min. To do. Next, when this sample was measured at a heating rate of 10 ° C./min, an extension of the baseline below the glass transition point and a tangent line indicating the maximum slope from the peak rising portion to the peak apex. The intersection point is shown as the glass transition point. Here, as a measuring device, DSC-7 manufactured by PerkinElmer, Inc. can be used.

  In addition, the binder resin has a peak or shoulder in the range of 600 to 50,000 in the molecular weight distribution based on the styrene equivalent molecular weight measured by gel permeation chromatography (GPC), and in particular, the peak of the low molecular weight component. Or it is preferable that a shoulder exists in the range of 3,000-15,000, and also the value of the ratio (Mw / Mn) of a weight average molecular weight (Mw) and a number average molecular weight (Mn) is 2-100. preferable.

  Here, the measuring method of the molecular weight of the binder resin by GPC is as follows. That is, 1 cc of tetrahydrofuran (THF) is added to 0.5 to 5 mg of a measurement sample, for example, 1 mg, and the mixture is sufficiently dissolved by stirring using a magnetic stirrer at room temperature. After treatment with a 50 μm membrane filter, inject onto a GPC column. Measurement of GPC is performed by stabilizing the column at a temperature of 40 ° C., flowing THF at a flow rate of 1 cc / min, and injecting about 100 μL of a sample having a concentration of 1 mg / cc. The column is preferably used in combination with a commercially available polystyrene gel column. For example, combinations of Shodex GPC KF-801, 802, 803, 804, 805, 806, 807 manufactured by Showa Denko KK, TSKgel G1000H, G2000H, G3000H, G4000H, G5000H, G6000H, G7000H, TSK guard column manufactured by Tosoh Corporation And so on. As the detector, a refractive index detector (IR detector) or a UV detector can be used. The molecular weight of the sample is calculated using a calibration curve created using monodisperse polystyrene standard particles based on the molecular weight distribution of the sample. About 10 points may be used as polystyrene for preparing a calibration curve.

[Surfactant]
The surfactant used to obtain the binder resin when the toner particles constituting the toner are produced by suspension polymerization, miniemulsion polymerization aggregation or emulsion polymerization aggregation is not particularly limited. Are sulfonates (sodium dodecylbenzene sulfonate, sodium arylalkyl polyether sulfonates), sulfate esters (sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc.), fatty acid salts (sodium oleate, Ionic surfactants such as sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, calcium oleate, etc.) can be exemplified as suitable ones. Also, polyethylene oxide, polypropylene oxide, combination of polypropylene oxide and polyethylene oxide, ester of polyethylene glycol and higher fatty acid, alkylphenol polyethylene oxide, ester of higher fatty acid and polyethylene glycol, ester of higher fatty acid and polypropylene oxide, sorbitan ester, etc. Nonionic surfactants can also be used. These surfactants are used as an emulsifier when a toner is obtained by an emulsion polymerization method, but may be used for other processes or purposes.

(Dispersion stabilizer)
When the toner particles constituting the toner are produced by suspension polymerization, a dispersion stabilizer made of an inorganic compound that can be easily removed can be used. Examples of the dispersion stabilizer include tricalcium phosphate, magnesium hydroxide, hydrophilic colloidal silica and the like, and tricalcium phosphate is particularly preferable. Since this dispersion stabilizer is easily decomposed by an acid such as hydrochloric acid, it can be easily removed from the surface of the toner particles.

(Polymerization initiator)
When the toner particles constituting the toner are produced by a suspension polymerization method, a miniemulsion polymerization aggregation method or an emulsion polymerization aggregation method, the binder resin can be polymerized using a radical polymerization initiator.
In the case of using the suspension polymerization method, an oil-soluble radical polymerization initiator can be used. Examples of the oil-soluble polymerization initiator include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2 ′. -Azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, etc. Azo or diazo polymerization initiator, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4- Dichlorobenzoyl peroxide, lauroyl peroxide, 2,2- Examples include peroxide polymerization initiators such as bis- (4,4-t-butylperoxycyclohexyl) propane and tris- (t-butylperoxy) triazine, and polymer initiators having a peroxide in the side chain. Can do.

[Chain transfer agent]
For the purpose of adjusting the molecular weight of the binder resin when the toner particles constituting the toner are produced by suspension polymerization, miniemulsion polymerization aggregation or emulsion polymerization aggregation, a commonly used chain transfer agent is used. Can be used.
The chain transfer agent is not particularly limited. For example, mercaptans such as n-octyl mercaptan, n-decyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionate, terpinolene, carbon tetrabromide And α-methylstyrene dimer and the like are used.

[Colorant]
As the colorant constituting the toner, known inorganic or organic colorants can be used. Specific colorants are shown below.
Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black and lamp black, and magnetic powder such as magnetite and ferrite.
Examples of the colorant for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.
Examples of the colorant for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, and the like.
Examples of the colorant for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66, C.I. I. And CI Pigment Green 7.

The above colorants can be used alone or in combination of two or more.
The addition amount of the colorant is in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

  As the colorant, a surface-modified one can also be used. As the surface modifier, conventionally known ones can be used, and specifically, silane coupling agents, titanium coupling agents, aluminum coupling agents and the like can be preferably used.

[Charge control agent]
The toner particles constituting the toner may contain a charge control agent as necessary. Various known compounds can be used as the charge control agent.

〔Release agent〕
The toner particles constituting the toner may contain a release agent as necessary. Examples of the mold release agent include paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyolefin wax, carnauba wax, and derivatives thereof. Examples of the derivatives include block copolymers with oxides and vinyl monomers, and graft modified products. In some cases, long chain alcohols, long chain fatty acids, acid amides, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes, animal waxes, mineral waxes, petrolactams, and the like may be used.

[Particle size of toner particles]
The toner particles preferably have a volume-based median diameter of 3 to 8 μm, particularly 3 to 7 μm.
This particle diameter can be controlled by adjusting the dispersion diameter of the oil droplets when toner particles are formed by suspension polymerization.
When the volume-based median diameter is 3 to 8 μm, the reproducibility of fine lines and high image quality of photographic images can be achieved, and the amount of toner consumption can be reduced compared to the case of using a large particle size toner. be able to.
The volume-based median diameter of the toner particles can be measured using a Coulter Multisizer (manufactured by Coulter Inc.) with a 50 μm aperture and a particle size distribution in the range of 2.0 to 40 μm.

  The toner can be used with so-called external additives added for the purpose of improving fluidity and chargeability and improving cleaning properties. These external additives are not particularly limited, and various inorganic fine particles, organic fine particles and lubricants can be used. In addition, various external additives may be used in combination.

[Carrier]
The carrier constituting the two-component developer is not particularly limited. For example, a magnetic material made of a known material such as a metal such as iron, ferrite, or magnetite, or an alloy of the metal with a metal such as aluminum or lead. Particles can be used, and it is particularly preferable to use ferrite particles.

The carrier preferably has a volume average particle size of 15 to 100 μm, more preferably 25 to 60 μm.
The volume average particle diameter of the carrier can be measured by, for example, a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

Further, it is preferable to use a carrier in which magnetic particles are coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin.
The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, ester resin, or fluorine-containing polymer resin is used.
The resin for constituting the resin-dispersed carrier is not particularly limited, and known resins can be used. Specifically, for example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, and the like can be used. Can be used.

  The mixing ratio of toner and carrier in the two-component developer used in the present invention is such that the toner concentration in the two-component developer is 3 to 20% by mass, preferably 4 to 15% by mass.

As described above, when the double-sided image forming apparatus 10 performs the double-sided image forming process for forming visible images on both sides of the image forming support, the fixing device 30 performs the fixing process by the heating method. The toner image was formed on the image forming support on which the visible image was formed on one side by the first visible image forming process in a high temperature state in which the heat from the heat fixing process was retained during the second visible image forming process. Although it is in a state of being in close contact with the electrostatic latent image carrier 20, the heat absorbing portion 13 provided in the electrostatic latent image carrier 20 and the double-side unprocessed image forming support stocked in the cassette 171 Is transferred to the electrostatic latent image carrier 20 from the image forming support on which a visible image is formed on one surface by a heat circulation mechanism including a circulation pipe 15 having a heat radiating portion 14 provided so as to be in contact with the electrostatic latent image. The received heat is received by the heat storage material circulating in the heat storage material container 16 in the circulation pipe-shaped body 15 in the heat absorbing section 13, whereby the electrostatic latent image carrier 20 has a visible image formed on one side. Because it is heated by the heat transferred from the forming support and does not become a high temperature state, and while the phase change occurs, temperature control is performed using the characteristics of the heat storage material to maintain a constant temperature, The surface temperature of the image forming support is cooled to a specific temperature. In this way, since the temperature rise of the electrostatic latent image carrier 20 due to the transfer of heat from the image forming support on which a visible image is formed on one surface is suppressed, the electrostatic latent image carrier 20 is suppressed due to excessive heating of the toner on the electrostatic latent image carrier 20 due to the relationship with the glass transition temperature (Tg) of the toner. It is possible to suppress the occurrence of adverse effects such as toner fusion and toner thermal degradation on the electrostatic latent image carrier.
Moreover, the heat absorbed in the heat absorption part 13 of the heat circulation mechanism is transferred to the heat dissipation part 14 by the heat storage material circulating in the heat storage material container 16 and is effectively used without being discarded in the heat dissipation part 14. Specifically, the double-sided unprocessed image forming support provided for the first visible image forming process is preheated by the heat radiating unit 14, and thus the heat fixing process in the first visible image forming process is performed. The amount of heat required to be supplied from the heat source, that is, the heater 31 </ b> A constituting the heating roller 31 in the fixing device 30 can be reduced.

  Therefore, according to the double-sided image forming apparatus 10, the first visible image forming process and the second visible image forming process in which the fixing process by the heating method is performed on each of both surfaces of the image forming support using the electronic RDH. Even when a visible image is formed, a stable and good visible image can be obtained, and the amount of heat to be supplied from a heat source for heat fixing can be reduced.

  Further, in the double-sided image forming apparatus 10, since the temperature rise of the electrostatic latent image carrier 20 is suppressed, the toner caused by excessive heating of the toner on the electrostatic latent image carrier 20. Since thermal degradation is suppressed, a so-called toner recycling system in which the toner remaining on the electrostatic latent image carrier 20 is collected by the cleaning device 159 and returned to the developing unit 153 for reuse can be suitably employed.

As mentioned above, although this invention was demonstrated, this invention is not limited to this, A various change can be added.
For example, the thermal circulation mechanism includes a heat absorption part provided inside the electrostatic latent image carrier, and a heat dissipation part that heats the unprocessed image forming support by the heat absorbed in the heat absorption part. As long as it is made of a heat storage material, it is not limited to the above, but is made of a long sheet-like body obtained by processing or processing the heat storage material, and one end portion of the sheet body is an electrostatic latent image. It is inserted into the columnar shape of the substrate constituting the carrier, and the other end is disposed so as to contact the uppermost one of the image forming supports stocked in the cassette. The thing of the structure which is may be sufficient.
Here, as the sheet-like body, for example, a heat storage material itself, or a material in which the heat storage material is microencapsulated by an appropriate technique and a material in which the microencapsulated heat storage material is dispersed in water, for example, a laminate A structure that is enclosed in a sheet-like heat storage material container made of a film or the like, for example, a structure that is filled in a substrate made of a sheet-like porous material such as paper, nonwoven fabric, fiber, or film. Can be used.

  The image forming apparatus is not limited to the formation of a monochrome image as described above, and can be applied to the formation of a color image. At this time, a four-cycle double-sided image forming apparatus comprising four types of color developing devices for yellow, magenta, cyan, and black and one electrostatic latent image carrier, and color development for each color. The image forming unit having a container and an electrostatic latent image carrier may be of any configuration, such as a tandem double-sided image forming apparatus in which each image forming unit is mounted for each color.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

(Toner Production Example 1)
100 parts by mass of styrene acrylic resin (glass transition temperature (Tg) 56 ° C.), 8 parts by mass of carbon black and 4 parts by mass of pentaerythritol behenate are kneaded using a twin screw extruder, solidified, and then pulverized Further, 1.2 parts by mass of hydrophobic silica and 0.3 parts by mass of hydrophobic titania are further externally mixed to obtain a particle diameter of 6.3 μm in terms of volume-based median diameter and a glass transition temperature ( A toner having a Tg) of 54 ° C. (hereinafter referred to as “toner (1)”) was obtained.

(Toner Production Example 2)
In the toner production example 1, in the same manner as in the toner production example 1 except that a polyester resin (glass transition temperature (Tg) 50 ° C.) is used instead of the styrene acrylic resin, the median particle size is based on volume. A toner (hereinafter referred to as “toner (2)”) having a diameter of 6.1 μm and a glass transition temperature (Tg) of 49 ° C. was obtained.

(Toner Production Example 3)
100 parts by mass of a polyester resin (glass transition temperature (Tg) 36 ° C.), 8 parts by mass of carbon black, and 4 parts by mass of pentaerythritol behenate are kneaded using a twin screw extruder, and then freeze-pulverized and cooled. Thus, colored resin particles having a particle diameter of 5.3 μm in terms of volume-based median diameter and a glass transition temperature (Tg) of 34 ° C. were obtained.
The obtained colored resin particles are dispersed in an aqueous medium containing a surfactant. In this system, a resin particle having a glass transition temperature (Tg) of 55 ° C. and a number average primary particle diameter of 120 nm is obtained. The dispersion was added, and the resin particles were aggregated on the surface of the colored resin particles by salting out, and then the resin particles were coated on the surface of the colored resin particles by heating to 90 ° C. Thereafter, the system is cooled, filtered and washed. Further, 1.2 parts by mass of hydrophobic silica and 0.3 parts by mass of hydrophobic titania are added and mixed, thereby having a core-shell structure and a particle size of volume. A toner (hereinafter referred to as “toner (3)”) having a standard median diameter of 5.7 μm and a glass transition temperature (Tg) of 42 ° C. was obtained.

(Toner Production Example 4)
In Toner Production Example 3, a core-shell structure was provided in the same manner as in Toner Production Example 3 except that polyester resin having a glass transition temperature of 30 ° C. was used instead of polyester resin having a glass transition temperature of 36 ° C. A toner (hereinafter referred to as “toner (4)”) having a particle diameter of 5.7 μm in terms of volume-based median and a glass transition temperature (Tg) of 38 ° C. was obtained.

[Example 1]
By remodeling the image forming apparatus “bizhub 750” using electronic RDH (manufactured by Konica Minolta Business Technologies, Inc .; 75PPM (75 sheets / minute); adopting an automatic double-sided mechanism), a heat storage material container made of aluminum and having a thickness of 1 mm is obtained. An image forming apparatus equipped with a thermal circulation mechanism using sodium acetate hydrate as a heat storage material was prepared. An image forming apparatus provided with this thermal circulation mechanism basically has a structure as shown in FIGS.
In the image forming apparatus provided with the produced thermal circulation mechanism, the electrostatic latent image carrier has a charge generation layer having a thickness of 0.8 μm and a charge transport layer having a thickness of 25 μm on the outer peripheral surface of a 2 mm-thick aluminum substrate. In this state, the inner peripheral surface of the substrate of the electrostatic latent image carrier and the heat absorbing portion are close to each other (specifically, the distance between the inner peripheral surface of the substrate and the heat absorbing portion is 0.1 mm).

Using the manufactured image forming apparatus equipped with a thermal circulation mechanism, a halftone image with a pixel rate of 15% is printed from the front end of the paper to 1/3 of the original under a temperature / humidity of 30 ° C./50% RH. Using the toner (1) as a one-component developer under the condition that the surface temperature of the heating roller constituting the fixing device is set to 180 ° C. using the A4 image formed in the region, the transfer paper of A4 is used. Double-sided image formation processing was performed, and continuous 50,000 sheets of images were formed by double-sided printing. For the initial image (first image) and the 50,000th image formed, the presence or absence of image fogging (streaks) due to toner filming on the electrostatic latent image carrier was confirmed. The case where no image fog occurred was evaluated as “◯”, and the case where image fog occurred was evaluated as “x”.
In addition, the state of occurrence of toner filming on the electrostatic latent image carrier after 50,000 double-sided continuous image forming processing was visually confirmed. Although the toner filming could be confirmed in the portion, there was no “practical” problem when there was no practical problem, and “x” when the toner filming was remarkable and there was a possibility of causing a practical problem. The results are shown in Table 1.
Further, during the double-sided image forming process, the position where the surface temperature on one side of the transfer paper on which the visible image is formed on one side and the toner image is transferred on the other side passes through the separation pole on the image forming support processing path The temperature was 58 ° C. when measured with a non-contact thermometer.

[Examples 2 to 9 and Comparative Examples 1 and 2]
Example 1 is the same as Example 1 except that the heat storage material shown in Table 1 is used as a heat storage material constituting the heat circulation mechanism, and a one-component developer made of toner shown in Table 1 is used as the developer. Then, double-sided image formation processing was performed to confirm the occurrence of image fogging and toner filming on the electrostatic latent image carrier. The results are shown in Table 1.
Further, during the double-sided image forming process, the surface temperature on one side of the transfer paper on which the visible image was formed on one side and the toner image was transferred on the other side was confirmed by the same method as in Example 1. The results are shown in Table 1.
Here, in Comparative Example 1, an example is shown in which the heat storage material is not enclosed in the heat storage material container disposed in the image forming apparatus and the heat circulation mechanism is not substantially provided.

From the results shown in Table 1, it was confirmed that even when a visible image was formed by thermal fixing on each of both surfaces of the image forming support using electronic RDH, a stable and good visible image could be obtained.
Further, regarding the image forming apparatus according to Examples 1 to 9 and the image forming apparatus according to Comparative Example 1 in which no thermal circulation mechanism is provided, the heating roller constituting the fixing device during the double-sided image forming process. The amount of power supplied to the heater as a heat source was compared. When the electric energy consumed in Comparative Example 1 is 100%, the relative ratio of the electric energy consumed in Examples 1 to 9 is 74% in Example 1 and 85 in Examples 2 to 4, respectively. %, 88% in Examples 5 to 7, 95% in Examples 8 and 9, and the power consumed in the image forming apparatus according to any of the examples compared to the image forming apparatus according to Comparative Example 1. The amount was small. From this, it was confirmed that by providing the thermal circulation mechanism, the amount of electric power used for thermal fixing can be reduced during the double-sided image forming process, and there is an energy saving effect.

A Image reading unit B Image processing unit C Image storage unit D Image forming unit E Image forming support reversing unit 10 Double-sided image forming apparatus 13 Heat absorbing unit 14 Heat radiating unit 15 Circulating pipe-shaped body 16 Heat storage material container 19 Connecting unit 20 Electrostatic latent Image carrier 21 Substrate 22 Charge generation layer 23 Charge transport layer 30 Fixing device 31 Heating roller 31A Heater 32 Pressure roller 80 Operation panel 81 Automatic document feeder 82 Document setting table 83 Paper feed roller 84 Drive roller 86 Belt 87 Document discharge roller 88 switching guide 89 guide plate 90 reversing roller 92 driven roller 94 document discharge tray 121 document 122 document glass plate 123 halogen light source 124 mirror 125 mirror 126 movable mirror unit 127 mirror 128 lens reading unit 129 imaging lens 130 CCD line sensor 141 drive motor 14 Polygon mirror 143 Reflecting mirror 152 Charging unit 153 Developing unit 153A Developing sleeve 157 Transfer pole 158 Separating pole 159 Cleaning device 171 Cassette 174 Image forming support processing transport path 175 Image forming support transport path 176 Image forming support discharge tray 177 1 switching claw 180 2nd switching claw 181 reverse roller 183 reverse transport path 184 transport path for duplex copying

Claims (4)

The electrostatic latent image formed on the electrostatic latent image carrier is developed with a toner containing a binder resin and a colorant to form a toner image, and the toner image is transferred onto an image forming support. An image forming unit that forms a visible image on the image forming support by performing a heat fixing process on the transferred toner image, and an image forming support processing conveyance path that passes through the image forming unit. In an image forming apparatus having an image forming support reversing unit comprising an image forming support reversing conveyance path for supplying again to the image forming unit in a state where the image forming support having a visible image formed thereon is reversed,
A heat circulation mechanism made of a heat storage material having a heat absorbing portion provided inside the electrostatic latent image carrier and a heat radiating portion that heats the image forming support that has not been processed on both sides by the heat absorbed in the heat absorbing portion. Is provided,
The thermal circulation mechanism forms a visible image on the entire surface of the image forming unit by the heat absorbing unit, and changes the surface temperature of the image forming support supplied to the image forming unit again through the image forming support reversing unit to the glass transition of the toner. It cools to a temperature within the point temperature (Tg) + 10 ° C. and preheats the unprocessed double-sided image forming support supplied to the image forming unit without passing through the image forming support reversing unit by the heat radiating unit. The
The image forming apparatus , wherein the heat storage material has a melting point of 32.4 ° C. or higher and 58 ° C. or lower . The image forming apparatus according to claim 1, wherein the toner has a glass transition temperature (Tg) of 38 ° C. or higher and 54 ° C. or lower. The electrostatic latent image formed on the electrostatic latent image carrier is developed with a toner containing a binder resin and a colorant to form a toner image, and then the toner image is formed on one surface of the image forming support. After the first visible image forming process for forming a visible image by performing a heat fixing process on one surface of the image forming support for the transferred toner image, the electrostatic latent image carrying Forming a toner image on the body, then transferring the toner image onto the other surface of the image forming support, and subjecting the transferred toner image to a heat fixing process on the other surface of the image forming support. In the double-sided image forming method for performing a second visible image forming process of forming a visible image by performing:
  By a heat circulation mechanism made of a heat storage material having a heat absorbing portion provided inside the electrostatic latent image carrier and a heat radiating portion that heats the image forming support that has not been processed on both sides by the heat absorbed in the heat absorbing portion. The surface temperature of the image forming support on which a visible image is formed only on one surface by the first visible image forming process is cooled to a temperature within the glass transition point temperature (Tg) of the toner + 10 ° C. The image forming support subjected to the first visible image forming process is preheated by the heat radiating unit,
The double-sided image forming method, wherein the heat storage material has a melting point of 32.4 ° C. or higher and 58 ° C. or lower. The double-sided image forming method according to claim 3, wherein the toner has a glass transition temperature (Tg) of 38 ° C. or higher and 54 ° C. or lower.

Images