JP3994041B2 - Image forming apparatus - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
    The present invention provides an image formDisguiseMore specifically, an image form for transferring a full color image onto both sides of a sheet at once by providing an intermediate transfer member to which an image from a photosensitive member is transferred.DisguiseRelated to the position.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, a configuration that can form not only a single color but also a multicolor image including a full color is known.
In the case of forming a full-color image, a plurality of developing devices are arranged so as to be able to come into contact with a photosensitive member as one latent image carrier, and a toner image of each color is created for each rotation of the photosensitive member. There is a so-called one-drum system in which a color toner image is created by sequentially transferring the toner from a photoreceptor to a sheet held on an intermediate transfer member or a transfer drum (for example, Non-Patent Document 1).
[0003]
On the other hand, in the case of the one-drum system, the photosensitive member needs to be rotated four times, and therefore, the efficiency is low in terms of productivity. Therefore, the photosensitive member is increased by the number of colors (usually three or four), Correspondingly, an image forming apparatus employing a so-called tandem or in-line configuration in which each developing device is arranged and the paper continuously contacts the photoconductor to obtain a color image has been proposed (for example, Non-Patent Document 2).
[0004]
When forming an image, there is an image forming method called double-sided copying that forms an image on both sides of a single sheet, and a configuration intended for forming the above-described full-color image has also been proposed. The following have been proposed as specific examples.
A photosensitive drum comprising a single drum as a first image carrying means and a transfer belt as a second image carrying means to which a superimposed image on the photosensitive body is transferred opposite thereto, and is transferred from the photoreceptor. The transferred image and the image formed again after the image formation and carried on the photosensitive member are transferred to both sides of the sheet fed toward the transfer position where they face each other (for example, patent document) 1).
A first transfer means for transferring an image from each photoconductor facing a plurality of photoconductors; and a second transfer means for transferring an image in a softened state heated by the first transfer means. And transferring the images carried by both transfer means to both sides of the sheet (for example, Patent Document 2).
An image comprising a transfer belt facing a plurality of photoconductors and a fixing device disposed opposite to the sheet carried on the transfer belt, electrostatically transferred from each photoconductor k and carried on the transfer belt The image from each photoconductor is transferred to one side of the sheet and the other side of the sheet facing each photoconductor, and the image transferred to the sheet surface is heated and softened as it passes through the fixing device. (For example, Patent Document 3).
[0005]
[Non-Patent Document 1]
Electrophotographic Society, “Continuing Fundamentals and Applications of Electrophotographic Technology”, 1996, November 15, first edition, first edition, p34, Fig. 1.23
[Non-Patent Document 2]
Electrophotographic Society, “Continuation of Electrophotographic Technology and Applications”, 1996, November 15, first edition, first edition, p36, Fig. 1.25
[Patent Document 1]
JP-A-9-258518 (“0027” column, FIG. 1)
[Patent Document 2]
JP 2000-250272 A ("0020" column, FIG. 1)
[Patent Document 3]
JP 2000-293065 ("0038" column, FIG. 1)
[0006]
[Problems to be solved by the invention]
Usually, electrostatic transfer is known as a configuration for transferring an image from a photosensitive member to a transfer member, and is also used in Patent Document 1. However, when electrostatic force is used, adhesion in a transfer region or A toner dust phenomenon in which toner in an image is scattered by an electrical action at the time of peeling or an image blur phenomenon in which a part of the image is missing and the edge portion is not clear is likely to occur.
[0007]
On the other hand, when performing thermal transfer that also serves as fixing as disclosed in Patent Document 2 without using electrostatic transfer, toner can be melted and permeated, that is, fixed, at the transfer portion. Therefore, it is necessary to heat the photosensitive member to a high temperature. Therefore, in Patent Document 2, since a configuration for cooling the transfer body is provided, there is a possibility that the size of the apparatus is increased.
[0008]
The configuration shown in Patent Document 3 is a configuration in which electrostatic transfer and thermal transfer are performed, so that the problems in the above-described transfer methods remain.
As described above, when electrostatic transfer is used, it is difficult to obtain an appropriate transfer image due to an electrical adverse effect, and a cooling mechanism is required for thermal transfer, which leads to complicated equipment and large size. .
[0009]
On the other hand, toner scattered due to a toner dust phenomenon caused by an electrical influence or toner that has escaped from a part of an image due to a bleeding phenomenon of an image causes background stains when adhered to the sheet surface by an electrostatic field during transfer. In particular, when the toner roughness is rougher than the sheet roughness or when there is a toner group that has aggregated, the situation is easily recognized as background stain.
[0010]
It is an object of the present invention to provide toner dust and phenomenon, image bleeding phenomenon, and complicated and large-sized equipment, assuming the above-described conventional image forming apparatus, in particular, a configuration that performs batch transfer of full-color images on both sides of a sheet. It is an object of the present invention to provide an image forming apparatus having a configuration capable of preventing background contamination and preventing contamination.
[0011]
[Means for Solving the Problems]
  According to a first aspect of the present invention, a primary transfer body to which an image visualized using toner on a latent image carrier is transferred, and the primary transfer body is provided so as to be opposed to the primary transfer body. A secondary transfer body on which an image carried on the primary transfer body is thermally transferred;
  The image transferred to the primary transfer member again after the image transfer to the secondary transfer member and the image carried on the secondary transfer member were collectively transferred to both surfaces of the recording medium by heating and pressing. After that, the image transferred on both sides of the recording medium is fixed by heating and pressing.CraftAboutExecuteImage formationIn the device
  The toner used for the visible image has a particle size smaller than the surface roughness (Rz) of the recording medium, and the surface roughness of the primary transfer body, the secondary transfer body, and the recording medium is reduced. That the recording medium is rougher than the secondary transfer member than the secondary transfer member.It is a feature.
[0012]
  The invention according to claim 2 is the claim of claim1Image formationapparatusInA plurality of the latent image carriers are provided so as to face the primary transfer body, and have an arrangement capable of sequentially transferring images of different colors on the primary transfer body.It is a feature.
[0013]
  The invention according to claim 3 is the claim1 or 2Image formation describedapparatusInThe temperature of each transfer member at the time of thermal transfer from the primary transfer member to the secondary transfer member is set to be equal to or lower than the melting / penetration temperature to the recording medium in the range of the glass transition temperature of the toner to the softening temperature.It is a feature.
[0014]
  The invention according to claim 44. The image forming apparatus according to claim 1, wherein the pressure at the time of thermal transfer from the primary transfer body to the secondary transfer body is 2 to 10 N / cm. ² Is set toIt is a feature.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a schematic diagram showing a main configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 shown in FIG. 1 is a color printer capable of forming a full-color image. The present invention can be applied not only to a color printer but also to a facsimile machine, a copying machine, or a printing machine that can use an electrostatic recording system or an electrophotographic system.
[0021]
In FIG. 1, the image forming apparatus 1 is provided with a paper feeding unit B on the lower side and a paper discharging unit C on the upper side, with an image forming processing unit A installed in the center in the vertical direction.
In the image forming processing section A, a plurality of image forming units 2A, 2B, 2C, and 2D are juxtaposed in the horizontal direction, and each of the image forming units 2A to 2D is in contact with a photoconductor included in these image forming units. It faces the primary transfer belt 3 which is a primary transfer body having a possible stretched surface.
[0022]
The image forming units 2A to 2D are units capable of forming yellow, magenta, cyan, and black images used to form full-color images. Now, one of them will be described in detail. It is as follows. Of course, other image forming units have the same configuration.
[0023]
In the image forming unit 2A, a photosensitive member 4 is disposed as a latent image carrier using a drum that can rotate while contacting the primary transfer belt 3. Around the photosensitive member 4, the photosensitive member 4 is disposed. A charging device 5, a writing device 6, a developing device 7, a primary transfer device 8, a cleaning device 9 including a blade 9A and a charge eliminating lamp 9B for performing image forming processing in the rotation process are arranged.
[0024]
The photoreceptor 4 has a configuration in which an organic photosensitive layer that is a photoconductive substance is provided on the surface of an aluminum cylinder having a diameter of about 30 to 100 mm. The photosensitive member 4 may be formed with an amorphous silicon layer on the surface.
The writing device 5 is provided for the photosensitive member included in each of the image forming units 2A to 2D, and includes a laser light source (not shown), a deflecting member using a rotating polygon mirror, and an imaging optical system. On the basis of the image forming timing at (2), the photosensitive member is irradiated with scanning light by a signal from an image formation control unit (not shown).
[0025]
In the image forming units 2A to 2D, a charging process, a writing process, and a developing process are performed on the photosensitive member at a predetermined image forming timing, and an electrostatic latent image formed in the writing process is a visible image in the developing process. When processed into an image, the image is sequentially transferred to the primary transfer belt 3. At the time of transfer, electrostatic transfer is performed by a primary transfer device 8 facing the photoconductor 4 with the primary transfer belt 3 interposed therebetween. The primary transfer device 8 uses a roller that generates less ozone as it discharges by contacting the back surface of the primary transfer belt 3, and is relatively low in polarity opposite to the charge polarity of the toner used in the development process. By applying a voltage transfer bias, the toner carried on the photoconductor 4 is electrostatically transferred to the primary transfer belt 3.
[0026]
Details of the toner used in the development process will be described later.
After the primary transfer, the residual toner and the residual charge on the photosensitive member are removed from the photosensitive member 4 by the blade 8A and the charge removal lamp 8B included in the cleaning device 8, and are prepared for the next image forming process.
[0027]
The primary transfer belt 3 is a heat-resistant seamless belt based on a resin film or rubber having a thickness of about 20 μm to 600 μm, and is wound around a plurality of rollers 3A to 3C so as to be movable in the direction indicated by the arrow. It has become.
Among the rollers around which the primary transfer belt 3 is wound, a roller denoted by reference numeral 3A is a heating roller that faces a secondary transfer member described later. The roller 3A used as a heating roller is configured to set the temperature of the primary transfer belt 3 below the melting / penetrating temperature of the toner in the range of the glass transition temperature of the toner to the softening temperature. Reference numeral 10 denotes a tension roller of the primary transfer belt 3. Reference numeral 11 denotes a cleaning device. The cleaning device 11 can rotate in contact with the primary transfer belt 3 and has thermal conductivity such as a motion whose surface roughness is rougher than that of the primary transfer belt 3. The cleaning roller 11A is made of a good material, the blade 11B is in contact with the cleaning roller 11A, and the recovery member 11C. The cleaning roller 11A is provided with a heat source. In the cleaning device 11, the primary transfer belt 3 to the residual toner are wiped off by the cleaning roller 11A depending on the surface roughness, and the recovery member 11C is scraped off by the blade 11B after being melted by the heating source having the wiped toner inside. It can be transported toward the accommodating portion (not shown).
[0028]
In the image forming processing section A, a secondary transfer belt 12 that forms a secondary transfer member is provided facing the primary transfer belt 3.
The secondary transfer belt 12 is a heat-resistant seamless belt based on a resin film or rubber having a thickness of about 20 μm to 600 μm, and is wound around a plurality of rollers 112A to 12D so as to be movable in the direction indicated by the arrow. It has become.
Inside the secondary transfer belt 12, a heating roller 13 is provided in contact with the roller 3A on the side of the primary transfer belt 3, and the temperature of the secondary transfer belt 12 is set to the glass transition temperature of the toner. The temperature is set to be equal to or lower than the melting / penetrating temperature of the toner within the range of the softening temperature.
[0029]
The heating roller 13 forms a transfer nip portion in cooperation with the roller 3A on the primary transfer belt 3 side. For this reason, both rollers are set to have an outer diameter of about 40 to 60 mm and the transfer nip width is set. Can be set to about 5 to 10 mm. In order to set this transfer nip portion, both rollers have a surface layer portion made of heat-resistant rubber, and the transfer nip width can be appropriately set by selectively setting the thickness of the rubber.
[0030]
The pressure set between the roller 3A on the primary transfer belt 3 side and the heating roller 13 on the secondary transfer belt 12 side, which is a member for forming the transfer nip portion, is 2 to 10 N / cm.²Is set to
[0031]
The secondary transfer belt 12 is insulted by residual toner by the cleaning device 14. The cleaning device 14 includes a cleaning roller 14A having a function similar to that of the cleaning device 11 for the primary transfer belt 3, a blade 14B, and a collecting member 14C. A unit in which these members are accommodated is a fulcrum shaft. The cleaning roller 14A can be brought into contact with and separated from the secondary transfer belt 12 by 14D.
[0032]
On the other hand, the sheet feeding unit B includes sheet feeding cassettes 15 and 15 ′ that store sheets that are recording media of a plurality of sizes, and feeding rollers 16 that are arranged on the sheet feeding side of each sheet feeding cassette. 16 'and a registration roller 19 provided at a position where sheets fed out from the respective sheet feeding cassettes join.
[0033]
The paper discharge unit C includes a fixing device 17 and a paper discharge tray 18 that are disposed on the extended line of the extended surface of the secondary transfer belt 12.
In the fixing device 17, a pair of heating rollers 17 </ b> A and 17 </ b> B that are opposed to each other across a sheet conveyance path that is on an extended line of the extended surface of the secondary transfer belt 12 are disposed.
The heating rollers 17A and 17B are devices that fix the toner carried on the sheet by heating and pressing, and are common in temperature, surface property, and releasability between both heating rollers. As a result, when the images are carried on both sides of the sheet, particularly in the case of a full-color image, the glossiness of the image fixed through the melting / penetration stage by heating / pressurizing the sheet is determined. Can be made uniform on both sides. In the present embodiment, the specifications of the heating rollers 17A and 17B are configured such that a silicone rubber layer having a thickness of about 2 to 5 mm is provided on the surface of the core metal, but instead of the silicone rubber layer, a fluororesin It is also possible to use a resin or rubber having high releasability such as, and the heat fixing temperature by the heating roller is set to 160 to 200 ° C. so that the toner is melted and permeated into the sheet.
[0034]
The sheet that has passed through the fixing device 17 is discharged to a discharge tray 18 through a discharge roller pair 19.
In the present embodiment, the sheet is ejected so that the image transferred from the primary transfer belt 3 is on the lower side. In other words, the discharge mode is such that the page order of the sheets stacked on the discharge tray 18 is arranged in order from the lower side, whereby the page alignment after all the sheets are discharged, etc. There is no need for post-processing. An image forming system for the primary transfer belt 3 and the secondary transfer belt 12 is also set so that a discharge form capable of page alignment is obtained. Specifically, from the primary transfer belt 3 to a sheet. The order of image formation on the primary transfer belt 3 is set so that the transferred toner image is an erect image and the toner image transferred from the secondary transfer belt 12 to the sheet is a mirror image. In order for the first page to face downward, the toner image is directly transferred from the primary transfer belt 3 to the sheet.
[0035]
In the image forming apparatus 1 configured as described above, the image forming units 12A to 12D perform image formation in accordance with the image forming order set by the image forming control unit (not shown), and the image forming units 12A to 12D are arranged on the photoconductors of the image forming units. The toner images carried are sequentially transferred to the primary transfer belt 3 and are superimposed and transferred.
[0036]
The superimposed transfer image carried on the primary transfer belt 3 is set in a transfer state with respect to the secondary transfer belt 12 in accordance with the single-sided printing or double-sided printing mode of the sheet.
In the image forming mode on both sides of the sheet, the image superimposed and transferred onto the primary transfer belt 3 is transferred to the secondary transfer belt 12. In this case, the primary transfer belt 3 side and the secondary transfer belt 12 side are below the melting / penetration temperature of the toner with respect to the sheet in the range from the glass transition temperature of the toner to the softening temperature by the roller 3A and the heating roller 13, that is, at the time of fixing. The pressure between both rollers is set to 2-10 N / cm.²Therefore, the toner image on the primary transfer belt 3 is thermally transferred to the secondary transfer belt 12 at the transfer nip portion between the primary and secondary transfer belts via both rollers. In this case, the thermal transfer is a state in which the toner itself undergoes plastic deformation without being affected by electrostatic force, and is also transferred to the uneven surface on the side of the secondary transfer belt 12 using viscoelastic adhesion, that is, transferred by an anchor effect. Means the phenomenon Therefore, in order to obtain the transfer efficiency due to the anchor effect of the toner, in this embodiment, the relationship between the surface roughness between the primary transfer belt 3, the secondary transfer belt 12, and the sheet (recording medium) is 1 A relationship is set in which the surface roughness of the sheet (recording medium) is rougher than that of the secondary transfer belt 12 than that of the secondary transfer belt 3. Regarding the surface roughness, the primary transfer belt 3 has a surface roughness (Rz) set to 1 to 4 μm, the secondary transfer belt 12 has a surface roughness (Rz) set to 5 to 10 μm, and a sheet (recording) Medium) has a surface roughness (Rz) of 8 to 15 μm.
[0037]
When the thermal transfer to the secondary transfer belt 12 is completed, the primary transfer belt 3 can perform image transfer by superimposition again after the toner is removed by the cleaning device 11, and the superimposed transfer image is the primary transfer image. The toner image carried on the secondary transfer belt 12 is transferred together with the toner image carried on the sheet fed from the paper feeding section C while being carried on the transfer belt 3.
[0038]
The sheet on which the toner images are collectively transferred is separated from the secondary transfer belt 12 by the curvature separation when passing through the roller 12C located on the fixing device 17 side among the rollers around which the secondary transfer belt 12 is wound. Then, the toner advances to the fixing device 17, and the toner is melted and permeated by heating and pressurizing by the fixing device 17 to be fixed and discharged to the paper discharge tray 18. When the images transferred on both sides of the sheet are in page order, as described above, the toner images transferred by the primary transfer belt 3 are discharged downward in the discharge tray 18 so that they are aligned in the page order. Will be.
[0039]
On the other hand, in the single-sided printing mode of the sheet, there are a case where the image transferred only to the primary transfer belt 3 is transferred to the sheet and a case where the image transferred to the secondary transfer belt 12 is transferred to one side of the sheet. However, in the case of transferring the image on the primary transfer belt 3 side, the image transferred from the photosensitive member of each image forming unit to the primary transfer belt 3 is heated on the sheet by the roller 3A. Heat transfer. When the sheet carrying the image by thermal transfer is discharged S to the discharge tray 18, the image surface faces downward, and is discharged in a so-called face-down state.
[0040]
When the image forming process as described above is executed, the following characteristics are set so as not to lower the transfer efficiency of the primary transfer belt 3 and the secondary transfer belt 12.
The primary transfer belt 3 does not expand and contract, has an appropriate resistance value (surface resistance, deposition resistance), does not hinder electrostatic transfer of toner from the photoreceptor, and has a releasability with a contact angle of about 110 degrees with the toner. A structure in which a PFA tube (20 to 30 μm) is bonded to a seamless polyimide film having a thickness of 20 to 50 μm that is set to have this characteristic is used.
[0041]
The secondary transfer belt 12 has a releasability with a toner contact angle of about 90 degrees, and a configuration in which a seamless polyimide film having a thickness of 20 to 50 μm, which is set with this property, is coated with 20 to 100 μm of ETFE is used. It is done.
[0042]
Next, the characteristics of the toner used in this embodiment will be described.
Examples of black toner prescriptions and characteristics that are most noticeable on the background as toner prescriptions are presented. For color toner, instead of black toner carbon black, yellow master batch (mixture of yellow pigment Pigment Yellow 180 and polyol resin or polyester resin and water), magenta master batch (Pigment Red 57: 1 and polyol resin or polyester resin). And a mixture of water and a cyan master batch (Pigment Blue 15: 3 and a mixture of a polyol resin or a polyester resin and water) can be obtained by the same production method. In the present invention, since the combination of colors does not have a large meaning, detailed formulations and manufacturing methods are omitted, and the contained components are shown. Evaluations on transferability and fixability in this characteristic are shown in FIG. The result was obtained.
(1) Toner prescription A (black toner)
84 parts by weight of polyester resin
(Weight average molecular weight: 148000, Tg: 53)
Carnauba wax 5 parts by weight (melting point: 81 ° C)
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
After kneading at 100 ° C. using a biaxial extruder with the above formulation, pulverizing and classifying with an airflow pulverizer to obtain a weight average particle size of 7.5 μm (weight average particle size / number average particle size 1.45) Using a Henschel mixer, 0.75% by weight of silica (R-972 Nippon Aerosil) was mixed to obtain toner “A”.
The toner had a softening temperature of 98 ° C. and a loose apparent density of 0.28 g / cc. As a carrier, magnetite particles having an average particle diameter of 50 μm coated with methyl methacrylate resin (MMA) (film thickness: 0.5 μm) were used and mixed with the toner at a toner concentration of 5.0% by weight to obtain developer A. .
(2) Toner Formula B (Black toner)
84 parts by weight of polyester resin
(Weight average molecular weight: 321000, Tg: 68)
Carnauba wax 5 parts by weight (melting point: 81 ° C)
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
After kneading at 150 ° C. using a biaxial extruder with the above formulation, pulverizing and classifying with an airflow pulverizer to obtain a weight average particle size of 8.5 μm (weight average particle size / number average particle size 1.45) Then, using a Henschel mixer, 0.50% by weight of silica (R-972 Nippon Aerosil) was mixed to obtain toner “B”.
The toner had a softening temperature of 145 ° C. and a loose apparent density of 0.27 g / cc.
As a carrier, magnetite particles having an average particle diameter of 50 μm coated with methyl methacrylate resin (MMA) (film thickness 0.5 μm) were used, and mixed with the toner at a toner concentration of 5.0% by weight to obtain developer B.
(3) Toner prescription C (black toner)
84 parts by weight of styrene / butyl acrylate resin
(Weight average molecular weight: 231000, Tg: 68)
Carnauba wax 5 parts by weight (melting point: 81 ° C)
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
After kneading at 140 ° C. using a biaxial extruder with the above formulation, pulverizing and classifying with a mechanical pulverizer to obtain a weight average particle size of 6.5 μm (weight average particle size / number average particle size 1.20) Then, using a Henschel mixer, 1.00 wt% of silica (R-972 Nippon Aerosil) was mixed to obtain toner “C”.
The toner had a softening temperature of 145 ° C. and a loose apparent density of 0.27 g / cc.
As a carrier, magnetite particles having an average particle diameter of 50 μm coated with methyl methacrylate resin (MMA) (film thickness: 0.5 μm) were used, and mixed with the toner at a toner concentration of 5.0% by weight to obtain developer C.
(4) Toner prescription D (black toner)
84 parts by weight of styrene / butyl acrylate resin
(Weight average molecular weight: 181500, Tg: 58)
Carnauba wax 5 parts by weight (melting point: 81 ° C)
Carbon black (Mitsubishi Kasei # 44) 10 parts by weight
Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 1 part by weight
After kneading at 110 ° C. using a biaxial extruder with the above formulation, pulverizing and classifying with a mechanical pulverizer to obtain a weight average particle size of 7.5 μm (weight average particle size / number average particle size 1.20) Then, using a Henschel mixer, 1.25% by weight of silica (R-972 Nippon Aerosil) was mixed to obtain a toner “D”.
The toner had a softening temperature of 125 ° C. and a loose apparent density of 0.35 g / cc.
As a carrier, magnetite particles having an average particle diameter of 50 μm coated with methyl methacrylate resin (MMA) (film thickness: 0.5 μm) were used, and mixed with the toner at a toner concentration of 5.0% by weight to obtain developer D. .
[0043]
From the above results, with respect to transferability and fixability, satisfactory conditions can be obtained by controlling the transfer temperature and pressure.
[0044]
On the other hand, regarding the background stain, two types of patterns can be considered. One is one in which one toner is isolated and adheres to the background, and the other is one in which a plurality of toners aggregate and adhere to the background. When transferring using pressure and heat, the transfer can be performed regardless of the charge amount of the toner.
[0045]
A toner that is stochastically transferred in the gap between the photoreceptor and the sheet (recording medium) (expressed as a gap as the surface roughness (Rz) of the sheet). And a case where toner aggregates are formed and background stains are formed.
Even when the particle size of the toner is small, the probability of soiling increases when an aggregate is formed. This characteristic can be expressed by the loosening density as shown in the above result.
From the above, the toner has a good toner characteristic in which the toner particle size is smaller than the roughness of the transfer paper and it is difficult to form an aggregate of the toners.
[0046]
【The invention's effect】
  According to the first, second, and third aspects of the invention, the toner is transferred not by electrostatic force but by thermal transfer at the time of image transfer to the secondary transfer member constituting one of the members that perform batch transfer onto both sides of the recording medium. The temperature used for the thermal transfer is not higher than the melting / penetration temperature into the recording medium in the range of the glass transition temperature of the toner to the softening temperature, so that the toner dust phenomenon or The image can be transferred while preventing image bleeding. In particular,Since the toner particle size is smaller than the surface roughness (Rz) of the recording medium, even when adhering to the surface of the recording medium, unlike the case of toner larger than the surface roughness of the recording medium, it is difficult to recognize as background stains. Further, the relationship of the surface roughness is such that the surface roughness gradually increases in the transfer process from the primary transfer member to the secondary transfer member, and further from the secondary transfer member to the recording medium. Therefore, it is possible to improve the transfer efficiency to the recording medium using the anchor effect by the softened toner biting into the surface having a rough surface. In addition, as the transfer process shifts to the recording medium side, the biting into the surface is enhanced, so that the toner dust phenomenon is easily suppressed and the occurrence of background stains on the recording medium surface can be prevented.
[0051]
  Claim4According to the described invention, the pressure applied during thermal transfer from the primary transfer member to the secondary transfer member is 2 to 10 N / cm.²Therefore, the toner can be pushed in by effectively utilizing the soft plastic deformation of the toner. Accordingly, it is possible to prevent the occurrence of toner dust phenomenon and image bleeding phenomenon without impairing the toner transfer efficiency, and to eliminate background stains due to the presence of the protruding toner.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a main configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a table showing the results of an evaluation experiment on characteristics of toner used in the image forming apparatus shown in FIG.
[Explanation of symbols]
1 Image forming device
2 Imaging unit
3 Primary transfer belt
3A Roller with built-in heating source
4 Photoconductor
12 Secondary transfer belt
13 Heating roller
17 Fixing device
17A, 17B Heating roller

Claims (4)

A primary transfer member to which an image visualized using toner on a latent image carrier is transferred, and is provided so as to be able to face and contact the primary transfer member, and is carried on the primary transfer member. A secondary transfer body to which an image is thermally transferred,
The image transferred to the primary transfer member again after the image transfer to the secondary transfer member and the image carried on the secondary transfer member were collectively transferred to both surfaces of the recording medium by heating and pressing. after the image forming apparatus to perform more Engineering for fixing by heat and pressure the image transferred to both sides of a recording medium,
The toner used for the visible image has a particle size smaller than the surface roughness (Rz) of the recording medium, and the surface roughness of the primary transfer body, the secondary transfer body, and the recording medium is reduced. An image forming apparatus characterized in that a recording medium is rougher than a secondary transfer body than a secondary transfer body than a primary transfer body . The image forming apparatus according to claim 1 Symbol placement,
An image forming apparatus comprising a plurality of the latent image carriers facing the primary transfer body and capable of sequentially transferring images of different colors on the primary transfer body. . The image forming apparatus according to claim 1 , wherein
The temperature of each transfer member at the time of thermal transfer from the primary transfer member to the secondary transfer member is set to be equal to or lower than the melting / penetration temperature to the recording medium in the range of the glass transition temperature of the toner to the softening temperature. An image forming apparatus . The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, wherein a pressure at the time of thermal transfer from the primary transfer member to the secondary transfer member is set to ² to 10 N / cm ² .

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