JP2003295661A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus by which a transfer material is collected without being caught by each endless belt shape intermediate transfer body or each fixing roller when a toner image on each endless belt intermediate transfer body corresponding to two image forming parts arranged in parallel is simultaneously transferred or simultaneously fixed onto the both surfaces of the transfer material, simultaneous transferring and fixing are stably performed, a difference in a brilliancy degree is eliminated between the front and rear images, and the images are efficiently formed with high image quality. <P>SOLUTION: In the image forming apparatus having a heat roller type fixing device by which the transfer material with the non-fixed toner image carried on the both front and rear surfaces is carried while being held between a first fixing roller positioned above and a second fixing roller positioned below, and simultaneously fixed the product hardness (Asker-C) A of the first fixing roller is smaller than the product hardness (Asker-C) B of the second fixing roller. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a heat roller type fixing device for fixing each unfixed toner image formed on both surfaces of a transfer material to the transfer material at the same time, or to both surfaces of the transfer material. The present invention relates to an image forming apparatus that simultaneously transfers and fixes a toner image.

[0002]

2. Description of the Related Art In a thermal fixing device composed of two rotating bodies in contact with each other, peeling of a transfer material from the rotating body is an important issue. The releasability of the transfer material from the rotating body is affected by the adhesive force between the transfer material and the rotating body, the rigidity of the paper, and the like. In a conventional image forming apparatus for fixing a transfer material carrying unfixed toner on one side, the surface of the transfer material carrying the unfixed toner and the adhesive force Fh of the heating rotator in contact with the surface of the transfer material and the unfixed toner are carried. Assuming that the adhesive force Fp between the non-transferred material and the pressure rotator in contact with it is Fh> Fp,
It is known that even if the effect of gravity on the paper is taken into consideration (when considering only the effect of gravity, the paper is likely to be wrapped around the pressure rotating body on the lower side), the paper is likely to be wrapped around the heating rotating body. ing.

Therefore, in the conventional heat roller type fixing device, Japanese Patent Application Laid-Open Nos. 55-17108 and 5-2653 are used.
No. 44, JP-A-2000-98777, etc., the hardness of the pressure roller which is not in contact with the unfixed toner image on the lower side is higher than the hardness of the heating roller which is on the upper side and is in contact with the unfixed toner image. It is so-called self-set so that the ejection direction of the nip outlet is set to the pressure roller side so that the unfixed toner image surface and the heating roller surface can be peeled off without setting a forced peeling means such as a contact separation claw. It is known to ensure stripping properties. By eliminating the means such as the contact separation claw, it is possible to suppress scratches on the heating roller and uneven glossiness of the solid image due to the scratches. Also, as in Japanese Patent Nos. 3084692 and 3087663, the relationship between the surface distortion amount of the heating roller and the surface distortion amount of the heating roller and the pressure roller is regulated to secure the self-stripping property. There is also.

On the other hand, in the conventional electrophotographic image forming apparatus, when a double-sided image is formed on a transfer material, an unfixed toner image is once formed on one surface (transferred from the image forming portion) and heat-fixed, and then another image is formed. BACKGROUND ART A toner image is formed on one surface (transferred from an image forming unit) and heat fixing is performed. in this case,
The following problems have been pointed out for offset printing systems. Productivity is poor during double-sided image formation.
The image position accuracy on the front and back is poor. Since the paper is curled, the water content and the electric resistance are changed by the first heat fixing, 2
It affects the transfer of the first time and the image quality is different on the front and back.
Since one side is heat-fixed once while the other side is heat-fixed twice, the gloss image quality on the front and back sides is different.

Therefore, in recent years, KONICA TECHN
ICAL REPORT Vol. 12 JAN. 19
99 p. 35 and Japan Hard Copy 2
Various double-sided simultaneous image forming apparatuses have been proposed as described in p.

[0006]

When fixing a transfer material carrying unfixed toner on both sides in this way, the unfixed toner is deposited on both surfaces of the transfer material entering the heat roller type fixing device. The known relationship between the size of the adhesive force between the rotating body and the transfer material does not apply, and the transfer material easily winds around the lower rotating body due to paper strain or gravity. The phenomenon that it easily winds around one rotating body is not desirable not only because it deteriorates the feeding property, but also because it tends to cause a difference in gloss and uneven gloss. When such wrapping occurs, the image forming apparatus naturally becomes unstable, it takes time to restore, and the operation rate and the yield decrease, which is not preferable at all. The present invention eliminates such disadvantages,
In addition to eliminating the winding of the transfer material, there is no difference in gloss on both sides, the image quality of each image on the front and back of the transfer material is uniform and stable, and simultaneous fixing of the front and back is possible, and further transfer It is an object of the present invention to provide an image forming apparatus capable of simultaneously fixing and fixing the front and back sides.

[0007]

This object is achieved by any of the following technical means (1) to (20).

(1) A transfer material carrying unfixed toner images on both front and back sides is nipped and conveyed between a first fixing roller provided on the upper side and a second fixing roller provided on the lower side, and simultaneously fixed. An image forming apparatus including a heat roller type fixing device, wherein the product hardness of the second fixing roller is smaller than the product hardness of the first fixing roller.

(2) The product hardness is As under a predetermined load.
The image forming apparatus according to item (1), which is a hardness measured when a ker-C hardness meter is used.

(3) The product hardness is a hardness measured when a type A or a type C of a micro hardness meter MD-1 manufactured by Kobunshi Keiki Co., Ltd. is used. Image forming apparatus.

(4) The hardness of the heat-resistant elastic layer of the second fixing roller is made smaller than the hardness of the heat-resistant elastic layer of the first fixing roller, and the outer diameter of the first fixing roller, the thickness of the core metal, The thickness and thermal conductivity of the heat resistant elastic layer are made substantially equal to the outer diameter and core thickness of the second fixing roller, and the thickness and thermal conductivity of the heat resistant elastic layer are made substantially equal to each other, and the core of each of the first and second fixing rollers is set. At least one heating source is provided inside or on the surface of the gold, and the power of the heating source inside or on the surface of the core of the first fixing roller and the power of the heating source on or inside the core of the second fixing roller are set. The image forming apparatus according to any one of (1) to (3), characterized in that and are substantially equal to each other.

(5) The first fixing roller and the second fixing roller each have a heat resistant elastic layer on a core metal and a fluorine resin layer containing at least PFA resin on the outermost layer. A release agent is not applied to the first and second fixing rollers, and a fixed object such as a transfer material peeling claw is not brought into contact with the image-corresponding areas of the first and second fixing rollers for use. The image forming apparatus according to any one of items (1) to (4), wherein the toner contains wax.

(6) The unfixed toner image corresponding to the front surface of the transfer material is provided on the first endless belt-shaped intermediate transfer member, and the unfixed toner image corresponding to the back surface is provided on the lower side. The first backup roller is formed on each of the second endless belt-shaped intermediate transfer members provided inside the first endless belt-shaped intermediate transfer member and the inside of the second endless belt-shaped intermediate transfer member. An image formation in which the first and second endless belt-shaped intermediate transfer bodies are pressed against each other by a certain second backup roller to form a nip portion, and a transfer material is passed through the nip portion to perform transfer and fixing at the same time. In the apparatus, the materials and thicknesses of the first and second endless belt-shaped intermediate transfer members are set to be substantially the same, and the product hardness of the second backup roller is set to be higher than the product hardness of the first backup roller. small An image forming apparatus characterized by being formed.

(7) The product hardness is As under a predetermined load.
The image forming apparatus according to item (6), which is a hardness measured when a ker-C hardness meter is used.

(8) The product hardness is a hardness measured when a type A or a type C of Micro Hardness Meter MD-1 manufactured by Kobunshi Keiki Co., Ltd. is used. Image forming apparatus.

(9) The hardness of the heat-resistant elastic layer of the second backup roller is made smaller than the hardness of the heat-resistant elastic layer of the first backup roller, and the outer diameter of the first backup roller, the substrate thickness, and the heat resistance of the first backup roller are reduced. The thickness and thermal conductivity of the elastic layer are made substantially equal to the outer diameter of the second backup roller, the substrate thickness, the thickness of the heat resistant elastic layer and the thermal conductivity, and the outer diameter of the first endless belt-shaped intermediate transfer member. , Substrate thickness,
The thickness, thermal conductivity, and hardness of the heat-resistant elastic layer are set to be substantially equal to the outer diameter of the second endless belt-shaped intermediate transfer member, the substrate thickness, the thickness of the heat-resistant elastic layer, the thermal conductivity, and the hardness. 2. At least one heating source is installed inside the core metal of each backup roller, or on the surface or the inner surface of the endless belt-shaped intermediate transfer member, and is arranged inside the core metal of the first backup roller or the first endless belt. The electric power of the heating source in contact with the intermediate transfer member and the electric power of the heating source arranged in the core of the second backup roller or in contact with the second endless belt-shaped intermediate transfer member are substantially equal to each other ( 6)
The image forming apparatus according to any one of items (8) to (8).

(10) In each of the first endless belt-shaped intermediate transfer member and the second endless belt-shaped intermediate transfer member, a heat resistant elastic layer is provided on a substrate and a fluororesin layer containing at least a PFA resin is provided as an outermost layer. In addition, a release agent is not applied to each of the first and second endless belt-shaped intermediate transfer bodies, and the toner used is a wax-containing toner (6). ) To (9), the image forming apparatus according to any one of items.

(11) A transfer material carrying unfixed toner images on both front and back sides is nipped and conveyed between a first fixing roller provided on the upper side and a second fixing roller provided on the lower side, and simultaneously fixed. In an image forming apparatus equipped with a heat roller type fixing device, a solid image on the front and back sides of the first fixing roller and the second fixing roller is changed while the surface roughness of the first fixing roller is changed. The image forming apparatus is characterized in that the difference in glossiness is less than 5.

(12) The outer diameter of the first fixing roller,
The thickness of the core metal, the thickness and thermal conductivity of the heat resistant elastic layer, and the hardness are made substantially equal to the outer diameter of the second fixing roller, the thickness of the core metal, the thickness of the heat resistant elastic layer, and the thermal conductivity and hardness of the first fixing roller. At least one heating source is installed inside or on the surface of the core of each of the second fixing rollers, and the electric power of the heating source inside or on the surface of the core of the first fixing roller and the core of the second fixing roller are installed. The image forming apparatus according to item (11) is characterized in that the electric power of the heating source on the inside or on the surface is made substantially equal.

(13) The first fixing roller and the second fixing roller have a heat resistant elastic layer on a core metal and a fluorine resin layer containing at least PFA resin on the outermost layer. A release agent is not applied to the first and second fixing rollers, and a fixed object such as a transfer material peeling claw is not brought into contact with the image-corresponding areas of the first and second fixing rollers for use. The image forming apparatus according to item (11) or (12) is characterized in that the toner is a wax-containing toner.

(14) The unfixed toner image corresponding to the front side surface of the transfer material is provided on the first endless belt-shaped intermediate transfer member, and the unfixed toner image corresponding to the back surface is provided on the lower side. The first backup roller is formed on each of the second endless belt-shaped intermediate transfer members provided inside the first endless belt-shaped intermediate transfer member and the inside of the second endless belt-shaped intermediate transfer member. An image formation in which the first and second endless belt-shaped intermediate transfer bodies are pressed against each other by a certain second backup roller to form a nip portion, and a transfer material is passed through the nip portion to perform transfer and fixing at the same time. In the apparatus, the surface roughness of the first endless belt-shaped intermediate transfer member and the surface roughness of the second endless belt-shaped intermediate transfer member are changed, and the glossiness of the solid images on the front and back sides during simultaneous double-sided image formation The difference is 10 or less An image forming apparatus having the following roughness.

(15) Outer diameter, substrate thickness, heat-resistant elastic layer thickness and thermal conductivity of the first endless belt-shaped intermediate transfer member,
The hardness is set to be substantially equal to the outer diameter of the second endless belt-shaped intermediate transfer member, the substrate thickness, the thickness of the heat-resistant elastic layer and the thermal conductivity, and the hardness of the core metal of each of the first and second backup rollers. Alternatively, at least one heating source is installed on the surface or the inner surface of the endless belt-shaped intermediate transfer member, and is arranged inside the core metal of the first backup roller or the electric power of the heating source in contact with the first endless belt-shaped intermediate transfer member. The image forming apparatus according to item (14), wherein the electric power of a heating source arranged inside the core of the second backup roller or in contact with the second endless belt-shaped intermediate transfer member is made substantially equal.

(16) In each of the first endless belt-shaped intermediate transfer member and the second endless belt-shaped intermediate transfer member, a heat resistant elastic layer is provided on a substrate and a fluororesin layer containing at least a PFA resin is provided as an outermost layer. A release agent is not applied to each of the first and second endless belt-shaped intermediate transfer members, and the toner to be used is one containing wax (14). ) Or (15) the image forming apparatus.

(17) A transfer material carrying unfixed toner images on both front and back sides is nipped and conveyed between a first fixing roller provided on the upper side and a second fixing roller provided on the lower side, and simultaneously fixed. An image forming apparatus including a heat roller type fixing device, wherein the surface distortion amount of the second fixing roller is larger than the surface distortion amount of the first fixing roller.

(18) In the first fixing roller and the second fixing roller, a heat resistant elastic layer is provided on a core metal, and a fluorine resin layer containing at least PFA resin is provided on the outermost layer. A release agent is not applied to the first and second fixing rollers, and a fixed object such as a transfer material peeling claw is not brought into contact with the image-corresponding areas of the first and second fixing rollers for use. The toner according to item (17) is characterized in that the toner contains wax.

(19) The unfixed toner image corresponding to the front surface of the transfer material is provided on the first endless belt-shaped intermediate transfer member, and the unfixed toner image corresponding to the back surface is provided on the lower side. The first backup roller is formed on each of the second endless belt-shaped intermediate transfer members provided inside the first endless belt-shaped intermediate transfer member and the inside of the second endless belt-shaped intermediate transfer member. An image formation in which the first and second endless belt-shaped intermediate transfer bodies are pressed against each other by a certain second backup roller to form a nip portion, and a transfer material is passed through the nip portion to perform transfer and fixing at the same time. In the device, the first and second endless belt-shaped intermediate transfer members are configured to have at least an elastic layer, and the second endless belt is more than the surface strain amount of the first endless belt-shaped intermediate transfer member. Intermediate transfer An image forming apparatus characterized by increasing a surface distortion amount of an object.

(20) In each of the first endless belt-shaped intermediate transfer member and the second endless belt-shaped intermediate transfer member, a heat resistant elastic layer is provided on a substrate, and an outermost layer is a fluororesin layer containing at least PFA resin. In addition, a release agent is not applied to each of the first and second endless belt-shaped intermediate transfer members, and the toner used is a wax-containing toner (19). The image forming apparatus according to the item (1).

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment according to the present invention will be described below with reference to the drawings.

The description in the embodiments of the present invention does not limit the technical scope by the terms used.

FIG. 1 is a schematic view showing a color image forming apparatus 100 which is one of the image forming apparatuses according to the present invention.

In the present embodiment, two sets of color image forming units A and B are provided above and below the transfer material conveyance path 55. In the secondary transfer area, the two endless belt-shaped intermediate transfer bodies 20 and 40 have two backup rollers 26,
They are provided so as to be pressed against each other by 46 to form a nip portion. The toner image is transferred by the backup rollers 26 and 46 acting as secondary transfer rollers to the front and back of the transfer material P nipped and conveyed in the nip portion of the two endless belt-shaped intermediate transfer bodies 20 and 40. .

In the figure, 10 and 30 are photoconductors, 11, and
31 is a charging roller, 12 and 32 are exposure optical systems as image writing means, 13 and 33 are developing units, 14 and 34 are cleaning units, 20 and 40 are first and second endless belt-shaped intermediate transfer members, and 21. , 41 are drive rollers, 22, 2
3, 42 and 43 are guide rollers, 24 and 44 are tension rollers, 25 and 45 are primary transfer rollers, 26 and 46 are first and second backup rollers serving as secondary transfer rollers, and 27 and 47 are cleaning rollers. A device, 48 is a scorotron electrode which is an auxiliary means, 60 is a fixing device, and 55 is a transfer material conveyance path. A color image forming section A is arranged on the upper side and a color image forming section B is arranged on the lower side. ing.

In the color image forming section A, the photoconductor 1
0, the charging roller 11, the exposure optical system 12, the developing device 13, and the cleaning unit 14 constitute one set, and the first image forming unit 1 for each color is configured, and yellow (Y), magenta (M), and cyan ( The image forming means 1 of each color of C) and black (K) are arranged facing the stretched surface (S) of the endless belt-shaped intermediate transfer member 20 in the order of Y, M, C, K from the right. is there. The image forming means 1 for each color has the same configuration in all four sets, and therefore, only one set of components is designated by a reference numeral, and the others are omitted.

Also in the color image forming section B, the second image forming means 3 includes the photosensitive drum 30, the charging roller 31, the exposure optical system 32, the developing device 33, and the cleaning unit 3.
4 as one set, and the image forming means 3 of each color of yellow (Y), magenta (M), cyan (C) and black (K) is attached to the intermediate transfer body 40 (T). Are arranged in the order of Y, M, C, K from the right. Since the image forming means 3 for each color have the same structure in all four groups, the reference numerals are given only to one group and the others are omitted.

The charging roller 11 is a conductive roller that comes into contact with the photosensitive member 10 and has a negative voltage (-0.5 to-) having the same polarity as the toner.
-1.0 kV is preferred). It is also possible to use a brush or a belt instead of the roller, or use a scorotron charger or the like.

The exposure optical system 12 is arranged downstream of the charging roller 11 in the rotation direction of the photoconductor 10. The exposure optical system 12 includes, for example, an exposure element in which a plurality of LEDs (light emitting diodes) are arranged in an array in parallel with the drum axis of the photoconductor 10 in the main scanning direction, and a light focusing property as an imaging element. It is an exposure unit composed of an optical transmitter (trade name: SELFOC lens array). Other laser optical systems can be used as the exposure optical system 12. The exposure optical system 12 imagewise exposes the photosensitive layer of the photoconductor 10 according to the image data of each color read by an image reading device provided separately and recorded in the memory, and forms an electrostatic latent image for each color. .

The developing device 13 is a developing device formed of a cylindrical non-magnetic stainless steel or aluminum material which keeps a predetermined gap with respect to the peripheral surface of the photoconductor 10 and rotates in the forward direction of the photoconductor 10. It has a sleeve 131 and contains one-component or two-component developers of yellow (Y), magenta (M), cyan (C), and black (K) according to the development color of each color. In the embodiment, the developing device 13 containing the two-component developer is provided with a not-shown abutting roller or the like so as to have a predetermined gap with the photoreceptor 10, for example, 100 to 500 μm.
The developing sleeve 131 is kept in a non-contact state with a distance of m.
By applying a developing bias in which a DC voltage and an AC voltage are superimposed on each other, non-contact reversal development is performed and a toner image is formed on the photoconductor 10.

The endless belt-shaped intermediate transfer members 20 and 40 have a volume resistivity of 10 ⁶ to 10 ¹² Ω · cm. For example, modified polyimide, thermosetting polyimide, polyamide imide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, A conductive filler such as carbon is dispersed in an engineering plastic such as nylon alloy or polycarbonate, or an ionic conductive material is contained.
A seamless belt having a one-layer or two-layer structure in which a semi-conductive film substrate having a thickness of 0.04 to 0.20 mm is coated with fluorine at a thickness of 5 to 50 μm, preferably as a toner filming prevention layer, on the outer side. . It is preferable that the fluorine coating also has semiconductivity so that the surface is not unnecessarily charged. As the base material of the belt, in addition to this, silicon rubber or urethane rubber, ethylene propylene butadiene terpolymer rubber, chloroprene rubber, nitrile rubber or the like is dispersed with a conductive filler such as carbon or contains an ionic conductive material. It is also possible to use a semiconductive rubber belt having a thickness of 0.1 to 1.0 mm.

Each of the rollers follows the rotation direction of the first endless belt-shaped intermediate transfer member 20, and includes a drive roller 21, a guide roller 22, a backup roller 26 which also functions as a secondary transfer roller, a guide roller 23, a tension roller 24, Four
The primary transfer rollers 25 are arranged in this order inscribed in the tensioned first endless belt-shaped intermediate transfer body 20.

The backup roller serving as the primary transfer roller and the secondary transfer roller is made of polyurethane, ethylene propylene butadiene terpolymer, silicone, etc. on the peripheral surface of a conductive core metal (a voltage is applied) such as stainless steel. Disperse conductive filler such as carbon in the rubber material of
Volume resistivity 1 by including ionic conductive material
Solid state of 0 ⁵ to 10 ⁹ Ω · cm or foam sponge, thickness 0.2 to 7 mm, rubber hardness 20 to 90
It is formed by lining a semiconductive elastic rubber having a degree (Asker-C).

The cleaning device 27 is provided so as to face the guide roller 23 with the first endless belt-shaped intermediate transfer member 20 interposed therebetween.

The first endless belt-shaped intermediate transfer body 20 is driven by the rotation of the drive roller 21 by a drive motor (not shown). The guide roller 22, the secondary transfer roller 26, the guide roller 23, the tension roller 24, and the primary transfer roller 25 are driven to rotate by the rotation of the first endless belt-shaped intermediate transfer body 20. The belt slack of the rotating intermediate transfer member 20 is tensioned by the tension roller 24.

The primary transfer roller 25 is provided so as to face the photoconductor 10 with the intermediate transfer body 20 sandwiched therebetween, and is subjected to a predetermined load (total load is preferably about 4.9 to 49 N).
Pressed in the 0 direction. A DC voltage (preferably 0.5 kV to 5 kV) having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied to the primary transfer roller 25,
A transfer area W is formed between the first endless belt-shaped intermediate transfer body 20 and the photoconductor 10. By the transfer electric field in the transfer area W,
The toner images of the respective colors formed on the photoconductor 10 are transferred onto the intermediate transfer body 20.

Further, by applying a high load (a total load of about 19.6 to 196 N) to the primary transfer roller 25 in the direction of the photosensitive member 10 via the first endless belt-shaped intermediate transfer member 20, the load is lower than the above. The toner image can also be transferred to the endless belt-shaped intermediate transfer member 20 (so-called pressure transfer) by applying a voltage.

In order to realize such pressure transfer,
It is preferable that the relationship between the adhesion force F1 of the surface of the photoconductor and the toner, the adhesion force F2 of the surface of the endless belt-shaped intermediate transfer body and the adhesion force F3 of the toner and the transfer material is F1 <F2 <F3.

The color image forming section B is arranged symmetrically to the color image forming section A, and the functions of the respective units are the same.

In the color image forming section B, 3 is a photoconductor 30, a charging roller 31, an exposure optical system 32, a developing device 33,
This is a second image forming unit including a cleaning unit 34 and the like.

The image forming means 3 of each color of yellow (Y), magenta (M), cyan (C) and black (K) are opposed to the stretched surface T of the intermediate transfer member 40 from the right to Y, M ,. C,
They are arranged in the order of K. The image forming means 1 for each color has the same configuration in all four sets, and therefore, only one set of components is designated by a reference numeral, and the others are omitted. However, the color image forming section B is provided with the scorotron electrode 48 which is an auxiliary means for changing the polarity of the toner on the intermediate transfer member 40. As a result, the photosensitive member, the developer, and the primary transfer roller of the color image forming unit A and the color image forming unit B can be shared, and the toner on the intermediate transfer member 20 in front of the secondary transfer region V can be used. While the polarity is negative,
Since the polarity of the toner on the intermediate transfer body 40 can be made positive, it is possible to perform the double-sided transfer on the transfer material at once in the secondary transfer area V. Specifically, the backup roller 26
The conductive core metal is grounded or a negative voltage is applied, and a positive voltage is applied to the conductive core metal of the backup roller 46. A negative voltage may be applied to the conductive core metal of the backup roller 26, and the conductive core metal of the backup roller 46 may be grounded or a positive voltage may be applied.

The transfer material P onto which the toner image has been transferred from the endless belt-shaped intermediate transfer bodies 20 and 40 is sent to the conveying section 56.
The transport unit 56 is provided between the backup rollers 26 and 46, which also function as secondary transfer rollers, and the fixing device 60. The transport unit 56 has a spur 561 that is a spur member, and has a spur 5
Reference numeral 61 has a plurality of protrusions on its peripheral surface, and is provided rotatably around a rotation spindle. The spur 561 guides the back surface side of the transfer material P to convey the transfer material P, prevent the back surface toner image of the transfer material P having toner images on both sides from being disturbed, and fix the transfer material P to the fixing device 60. The transfer material P is conveyed to the fixing device 60 while keeping the entering direction constant. The distance between the secondary transfer position and the nip formed by the two rollers of the fixing device is preferably smaller than the length of the minimum length transfer material that can be passed by the apparatus. When the distance between the secondary transfer position and the nip formed by the two rollers of the fixing device is longer than the minimum length of the transfer material that can be passed by the apparatus, the spur 561 is driven to stabilize the transfer material. Therefore, a means for transporting is required.

Another embodiment of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a method of collectively performing secondary transfer and fixing.

In FIG. 2A, the toner images formed on the color image forming portions A and B on the first and second endless belt-shaped intermediate transfer bodies 20 and 40 are synchronized with the conveyance of the transfer material P. The first and second backup rollers 26 and 46 are taken
Acts as a secondary transfer roller, and the transfer material P sandwiched between both endless belt-shaped intermediate transfer bodies is collectively pressed by the pressure applied between the secondary transfer rollers by a pressure mechanism (not shown). Transfer and fixing are performed simultaneously. The total load applied to the secondary transfer roller is preferably 98 to 980N.

The transfer material P on which the fixing process is completed is guided by the guide 57.
And is discharged from the paper discharge roller 58.

In FIG. 2B, the toner images formed on the color image forming portions A and B on the first and second endless belt-shaped intermediate transfer bodies 20 and 40 are synchronized with the conveyance of the transfer material P. The transfer material P is sandwiched between the secondary transfer rollers 26 and 46, which are heat rollers, and the heat and heat of the rollers simultaneously transfer and fix the transfer material P collectively. In this case, the first and second endless belt-shaped intermediate transfer bodies 20 and 40 use a heat resistant belt made of a material such as polyimide resin or silicone rubber as a base material, and suppress toner offset to the belt. As described above, the surface is coated with fluorine such as PFA (the fluorine coating is also preferably provided with semiconductivity so that the surface is not unnecessarily charged), and is present on the photoreceptor 10 or its surroundings. The cooling plate 65 needs to be provided in consideration of the adverse effect of heat on the developer.

The first and second backup rollers 26 and 46, which are heat rollers in the structure of FIG. 2B, are secondary transfer rollers, and pressure is applied between the secondary transfer rollers by a pressure mechanism (not shown). In this method, the transfer and the fixing are simultaneously performed by the pressure and heat applied.

It is desirable that the toner used in the system in which the transfer and the fixing are performed at the same time contains a releasing agent such as wax (natural wax such as carnauba wax or synthetic wax such as ester wax). When heat is applied to the secondary transfer rollers 26 and 46 that indirectly heat the intermediate transfer bodies 20 and 40 by that method, the material of the secondary transfer rollers (backup rollers) 26 and 46 is heat resistant. Therefore, the use of silicone rubber is limited.

The transfer material P on which the fixing process is completed is guided by the guide 57.
And is discharged from the paper discharge roller 58. In this case, since the transfer and fixing are performed, the image is not disturbed even if the surface of the transfer material comes into contact with the conveyor belt after the secondary transfer position.
Therefore, the distance between the secondary transfer position and the nip formed by the two rollers of the fixing device can be set arbitrarily.

As described above, the advantages of the present invention are that the color toner images on the intermediate transfer member can be simultaneously transferred to the front and back surfaces of the transfer material at the same time. The fixing process is sufficient and the image position accuracy can be secured.

Next, the image forming process (image forming step) will be described with reference to FIG. When the image recording is started, the driving motor (not shown) of the photoconductor drum is started to rotate the photoconductors 10 and 30 of the yellow (Y) image forming means 1 and 3 in the image forming units A and B in the directions indicated by arrows. At the same time, the photoconductors 10 and 30 are charged by the charging action of the charging rollers 11 and 31.
Application of electric potential is started.

After the photoconductors 10 and 30 have been given a potential, the exposure optical systems 12 and 32 start the image writing by the electric signals corresponding to the first color signal, that is, the Y image data, and the photoconductors 10 and 30 are started. An electrostatic latent image corresponding to the Y image of the original image is formed on the surface of 30.

The latent image is reversely developed by the developing units 13 and 33 in a non-contact state, and a yellow (Y) toner image is formed in accordance with the rotation of the photoconductor 10.

In the transfer area W, the toner image of Y formed on the photoconductors 10 and 30 as image forming bodies by the above image forming process is transferred by the primary transfer rollers 25 and 45 to the endless belt-shaped intermediate transfer body 20. 40 is transferred.

Next, endless belt-shaped intermediate transfer members 20, 40
Is synchronized with the Y toner image, a potential is given by the charging action of the charging rollers 11 and 31 by the magenta (M) image forming means 1 and 3, and the M color signal is obtained by the exposure optical systems 12 and 32. That is, the image writing is performed by the electric signal corresponding to the image data of M, and the toner image of M formed on the photoconductors 10 and 30 by the non-contact reversal development by the developing devices 13 and 33 is the transfer area of M. At W, the toner images of Y are superposed on each other by the primary transfer rollers 25 and 45.

By a similar process, the Y and M superimposed toner images are synchronized with each other, and C formed on the photoconductors 10 and 30 by the cyan (C) image forming means 1 and 3 is used.
In the C transfer area W, the C toner image corresponding to the C image data based on the C color signal is transferred to the primary transfer rollers 25 and 45.
Is formed by superimposing the toner images of Y, M, and C, and synchronized with the superimposed toner images of Y, M, C by the black (K) image forming means 1, 3.
K based on the K color signals formed on the photoconductors 10 and 30.
K toner image corresponding to the image data of
In the above, the Y, M, and
The toner images of K are superposed on the toner images of C, and the superposed color toner images of Y, M, C, and K are formed on the endless belt-shaped intermediate transfer bodies 20 and 40, respectively.

Further, the photoconductors 10 and 3 of each color after the primary transfer
The residual toner remaining on the upper surface of 0 is removed by the cleaning units 14 and 34, and the history of the photoconductors 10 and 30 in the previous image formation is eliminated by a uniform exposure device (not shown) before charging, and the next Enter the image forming cycle.

The endless belt-shaped intermediate transfer members 20 and 40 carrying the superimposed toner image are fed in the direction of arrow F, and the transfer material P is fed from the paper feeding cassette 54 which is the transfer material storing means. The toner image on the intermediate transfer bodies 20 and 40 is synchronized with the toner images on the endless belt-shaped intermediate transfer bodies 20 and 40 by being driven by the secondary transfer roller. It is fed to the transfer area V of the backup rollers 26 and 46 that play the role of.

At this time, in the case of electrostatic transfer, in the transfer area V, an electric field such that the toner images on the endless belt-shaped intermediate transfer bodies 20 and 40 are transferred to the transfer material P is generated by the secondary transfer roller. A voltage is applied to each backup roller 26,46 as occurs with the backup rollers 26,46 also serving. In the case of pressure transfer, the secondary transfer roller 2
A total load of 19.6 to 196N is applied between 6 and 46.

Transfer material P having toner images transferred on both front and back surfaces
As described above, it is possible to adopt a system in which fixing is performed at the same time as the transfer, or the fixing roller 61, which passes through the conveyance section 56 having a spur 561 for preventing image distortion, and which is located above and below the fixing device 60 at different positions. It is also possible to adopt a system in which the front and back are simultaneously fixed at 62 and the paper is discharged by the paper discharge roller 58.

The system for transferring the unfixed toner images on both the front and back sides is not limited to the above.
As described in JP-A-2000-315031, a toner image formed on a photoconductor is directly transferred to a transfer material, or KONICA TECHNICAL REPORT
Vol. 12 JAN. 1999 p. 35, etc., the toner image once transferred onto the intermediate transfer member and the toner image on the photosensitive member may be transferred onto the front and back surfaces of the transfer material.

Further, the heating source is arranged not only when it is arranged inside the core metal of the fixing roller or the backup roller as shown, but also when the heating roller is brought into contact with the inner or outer surface of the fixing roller or the intermediate transfer member. And so on.

The endless belt-shaped intermediate transfer members 20, 40 which have undergone the secondary transfer process are put into the next image forming process after being cleaned by the cleaning devices 27, 47.

The upper and lower fixing rollers 6 in the fixing device 60.
Separation of the transfer material P at the exit of the fixing nip portion by 1, 62 is achieved by the adhesive force between the transfer material P and the fixing rollers 61, 62.
The stiffness and the fixing rollers 61, 62 related to the rigidity of the transfer material P
The quality is determined by the centrifugal force due to the rotation of the roller and the own weight of the transfer material P. From this point of view, in the double-sided simultaneous fixing method, the fixing roller 62 on the lower side is affected by the own weight of the transfer material P.
It has been found that the separation of the transfer material P from the sheet becomes difficult, and the hardness relationship between the upper and lower two fixing rollers 61 and 62 that determines the shape of the fixing nip is set to the configuration according to claims 1 to 3.
As shown in the schematic diagram of FIG. 3, the nip surface of the nip forming portion is in the state of a convex cylindrical surface downward, and the transfer material P after fixing is set in the advancing direction of the transfer material P by a cutting line at the exit from the convex cylindrical surface. In this way, it is possible to improve the balance between the separability from the fixing roller 62 on the lower side and the separability from the fixing roller 61 on the upper side by directing it in the direction, that is, upward.
For product hardness, use an Asker-C hardness tester,
A micro hardness meter may be used especially when the elastic layer is thin.

The same holds true for the image forming apparatus according to any one of claims 6 to 8 in which, as shown in FIG. 4, the toner images formed on the two intermediate transfer members are simultaneously transferred and fixed. You can think about it.

Further, in order to improve the separation balance, it is also effective to define the surface roughness relationship as described in claims 11 and 14. The relationship between the surface roughness and the separability is good or bad.For example, toner with high viscoelasticity has better roughness and separability is better, and toner with low viscoelasticity has poorer separability. Although it depends on the physical properties, the tendency that the surface roughness greatly contributes to the separability is found in any toner. Further, it is necessary to determine the set value for the surface roughness in consideration of the gloss. If there is a large difference in glossiness between the two images fixed on the front and back sides of the transfer material, the image quality will vary and will not be stable. Therefore, it is necessary to make the difference inconspicuous. The difference in glossiness is within 20 and more preferably within 10. Therefore, the fixing roller 61, 62 and the endless belt-shaped intermediate transfer member 2 are also taken into consideration in consideration of the condition.
A surface roughness of 0, 40 was set.

In order to improve the separation balance, it is also effective to define the surface strain relationship as described in claim 17. The larger the surface strain, the more the adhesive force between the transfer material P and the fixing roller can be reduced. Therefore, in the double-sided simultaneous fixing method, separation of the transfer material P from the lower fixing roller 62 becomes difficult due to the influence of the weight of the transfer material P, but the surface distortion of the fixing roller 62 should be larger than that of the fixing roller 61. Can improve the separation balance. This concept can be similarly considered in the image forming apparatus according to claim 19 in which the toner images formed on the two intermediate transfer bodies are simultaneously transferred and fixed.

Further, in these apparatuses, as described in claims 5, 10, 13, 16, 18, and 20, a fluorine resin containing PFA having good releasability is attached to a portion in contact with the toner. It is used and mixed with low melting point wax such as carnauba wax or ester wax in the toner, so that the oilless structure (do not apply the release agent such as dimethyl silicone oil to the fixing roller. Low cost, oil It has a high merit in that it does not deteriorate the image quality such as streaks and there is no problem in the writing property on the transfer material.) It is possible to use no contact peeling member such as a separating claw (no problem such as uneven gloss due to scratches on the fixing roller). It will be possible. Note that the terms "upper side" and "lower side" used herein are also valid in various systems in which the line a (shown in FIGS. 3 and 4) connecting the centers of the upper and lower fixing rollers does not coincide with the vertical line, where a is the horizontal line. Includes all ranges that do not match.

When the toner contains about 10% or more of carnauba wax or ester wax,
It is possible to handle without an oil application member and without a contact peeling member.

Further, in these devices, as described in claims 4, 9, 12, and 15, the upper and lower heating source powers, the heat capacity of the heating material such as the fixing roller in contact with the transfer material, and the heat transfer physical properties. Since the temperatures of the portions in contact with the upper and lower transfer materials can be made the same by making the above values the same, it is possible to prevent the difference in gloss on both sides from occurring easily.

[0078]

Embodiment 1 As shown in FIG. 1, the structure of the entire apparatus is such that the secondary transfer portion can perform simultaneous front and back fixing at different positions after transfer.

The upper first fixing roller 61 has an outer diameter of 50
mm / core material A5056TD / core thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 m
m / silicone rubber hardness 15 ° (JIS-A) / silicone rubber thermal conductivity 0.50 W / m · ° C./roll surface PF
A coating 30 μm / Asker-C (measurement load 9.8 N) product hardness 78 ° / micro A hardness 72 °, the second fixing roller 62 on the lower side has an outer diameter of 50 mm / core material A5056TD / core thickness 5mm / Elastic layer material LT
V silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 10 ° (JIS-A) / silicone rubber thermal conductivity 0.50 W / m ° C / roll surface PFA coating 30 μm / Asker-C (measurement load 9.8 N )
The product hardness is 73 ° / micro A hardness is 62 °.

Inside the core of the first fixing roller 61 on the upper side, one or two halogen lamps are arranged so that the total power is about 500 to 1250W. Inside the core of the lower second fixing roller 62, a halogen lamp having the same structure as the inside of the core of the first fixing roller is arranged (not shown). A sensor (not shown) for detecting the surface temperature in a non-contact manner is arranged close to the surfaces of the first fixing roller 61 and the second fixing roller 62 (ON / OFF) or PID control of the halogen heater is performed according to the detected temperature. . The surface temperatures of the two fixing rollers are controlled to be the same.

The toner is an ester wax of about 10-15.
The main material was St-Ac mixed with mass%, and the release agent was not applied to the surface of the fixing roller.

As the separating member, a baffle plate on which a fluorine sheet such as PTFE is attached is provided in the vicinity of the nip outlet in a non-contact manner with the fixing rollers 61 and 62.

The size, material and hardness of the lower second fixing roller 62 are made the same as those of the upper first fixing roller 61, and the upper and lower fixing rollers are replaced to make a copy. If done, 56-80 g / m ²
The PPC paper having a small weight and the coated paper having a weight of about 81 to 105 g / m ² caused a problem of winding around the fixing roller 62, but there was no winding problem in the above-described embodiment.

Example 2 As shown in FIG. 2, the structure of the entire apparatus was such that the secondary transfer portion was capable of simultaneous transfer and fixing.

Upper first endless belt-shaped intermediate transfer member 20
The backup roller 26 has an outer diameter of 50 mm / core metal material A5056TD / core metal thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 15 ° (JIS-A) / silicone rubber thermal conductivity 0.50W / m ・ ° C / Asker-C product hardness 62 °
The backup roller 46 of the lower second endless belt-shaped intermediate transfer member 40 has an outer diameter of 50 mm / core metal material A5.
056TD / core metal thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 10 ° (JIS-A) / silicone rubber thermal conductivity 0.50 W / m · ° C./Asker-C product hardness 55 °, and the first and second endless belt-shaped intermediate transfer bodies 20, 40
(Common to both) is a semi-conductive polyimide base material coated with semi-conductive silicone rubber, and the surface layer is made of PF.
It was coated with resin A and had the same structure.

One or two halogen lamps are arranged inside the core of the upper first backup roller 26 so that the total power is about 500 to 1250W. A halogen lamp having the same structure as the inside of the core metal of the first backup roller is arranged inside the core metal of the lower second backup roller 46 (not shown). First
A sensor (not shown) for detecting the surface temperature is arranged in contact with or close to the surfaces of the backup roller 26 and the second backup roller 46, and the halogen heater is turned on / off or PID controlled according to the detected temperature. Two
The surface temperatures of the two backup rollers are controlled to be the same.

The toner is an ester wax of about 10-15.
A material containing St-Ac mixed in a mass% as a main material was used, and the release agent was not applied to the surface of the intermediate transfer member.

The separating member is in the vicinity of the nip outlet and is in non-contact with the endless belt-shaped intermediate transfer member 20, 40 by PTFE.
A baffle plate with a fluorine sheet attached was installed.

The size, material, hardness, etc. of the lower second fixing roller 62 are made the same as those of the upper first fixing roller 61, or the upper and lower fixing rollers are replaced to make a copy. If done, 56-80 g / m ²
The PPC paper having a small weight and the coated paper having a weight of about 81 to 105 g / m ² caused a problem of winding around the fixing roller 62, but there was no winding problem in the above-described embodiment.

However, the first backup roller 26 of the upper first endless belt-shaped intermediate transfer member 20 may be the same as the second backup roller 46 of the lower second endless belt-shaped intermediate transfer member 40. , If the upper and lower backup rollers are exchanged for copying, 56-80g / m
^{The second} endless belt-shaped intermediate transfer member 40 is made of PPC paper having a weight of about ² or coated paper having a weight of about 81 to 105 g / m ^2.
There was a problem of winding around, but there was no winding problem in the above example.

Embodiment 3 As shown in FIG. 1, the structure of the entire apparatus is such that the secondary transfer portion can simultaneously fix the front and back sides at different positions after the transfer.

The upper first fixing roller 61 has an outer diameter of 50
mm / core material A5056TD / core thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 m
m / silicone rubber hardness 15 ° (JIS-A) / silicone rubber thermal conductivity 0.50 W / m · ° C./roll surface PF
A coating 30 μm / Asker-C (measurement load 1
Kgf) product hardness 78 ° / surface roughness Rz 2 μm,
The second fixing roller 62 on the lower side has an outer diameter of 50 mm / core metal material A5056TD / core metal thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 15 ° (JIS-A) / Silicone rubber thermal conductivity 0.50 W / m · ° C./roll surface PFA coating 30 μm / Asker-C (measurement load 9.8 N) product hardness 78 ° / surface roughness Rz 1 μm. The surface roughness is different because the post-treatment conditions such as polishing after PFA firing are changed.

Inside the core of the first fixing roller 61 on the upper side, one or two halogen lamps are arranged so that the total power is about 500 to 1250 W. Inside the core of the lower second fixing roller 62, a halogen lamp having the same structure as the inside of the core of the first fixing roller is arranged (not shown). A sensor (not shown) for detecting the surface temperature in a non-contact manner is arranged close to the surfaces of the first fixing roller 61 and the second fixing roller 62 (ON / OFF) or PID control of the halogen heater is performed according to the detected temperature. . The surface temperatures of the two fixing rollers are controlled to be the same.

The toner is an ester wax of about 10-15.
The main material was St-Ac mixed with mass%, and the release agent was not applied to the surface of the fixing roller.

As the separating member, a baffle plate on which a fluorine sheet such as PTFE is attached is provided in the vicinity of the nip outlet in a non-contact manner with the fixing rollers 61 and 62.

If the surface roughness of the lower second fixing roller 62 is made the same as the surface roughness of the upper first fixing roller 61, or if the upper and lower fixing rollers are replaced, copying is performed. PPC paper with a weight of about 80 g / m ² or 8
With the coated paper having a weight of about 1 to 105 g / m ^2, there was a problem of wrapping around the fixing roller 62, but there was no wrapping problem in the above embodiment. Further, the difference in gloss on both sides could be suppressed within 10 and there was no visual problem.

Embodiment 4 As shown in FIG. 2, the overall construction of the image forming apparatus 1 is such that simultaneous transfer and fixing can be carried out at the secondary transfer portion.

Upper first endless belt-shaped intermediate transfer member 20
The backup roller 26 has an outer diameter of 50 mm / core metal material A5056TD / core metal thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 15 ° (JIS-A) / silicone rubber thermal conductivity 0.50W / m ・ ° C / Asker-C product hardness 62 °
The backup roller 46 of the lower second endless belt-shaped intermediate transfer member 40 has an outer diameter of 50 mm / core metal material A5.
056TD / core metal thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 15 ° (JIS-A) / silicone rubber thermal conductivity 0.50 W / m · ° C./Asker-C product hardness 62 °, and the first and second endless belt-shaped intermediate transfer members 20, 40
(Common to both) is a semi-conductive polyimide base material coated with semi-conductive silicone rubber, and the surface layer is made of PF.
The surface roughness of the first endless belt-shaped intermediate transfer member 20 was Rz 2 μm, and the surface roughness of the second endless belt-shaped intermediate transfer member 40 was Rz 1 μm. The surface roughness is different because the post-treatment conditions such as polishing after PFA firing are changed.

Inside the core metal of the upper first backup roller 26, one or two halogen lamps are arranged so that the total power is about 500 to 1250W. A halogen lamp having the same structure as the inside of the core metal of the first backup roller is arranged inside the core metal of the lower second backup roller 46 (not shown). First
A sensor (not shown) for detecting the surface temperature is arranged in contact with or close to the surfaces of the backup roller 26 and the second backup roller 46, and the halogen heater is turned on / off or PID controlled according to the detected temperature. Two
The surface temperatures of the two backup rollers are controlled to be the same.

The toner is an ester wax of about 10-15.
A material containing St-Ac mixed in a mass% as a main material was used, and the release agent was not applied to the surface of the intermediate transfer member.

The separating member is in the vicinity of the nip outlet and is in non-contact with the endless belt-shaped intermediate transfer member 20, 40 by PTFE.
A baffle plate with a fluorine sheet attached was installed.

Lower second endless belt-shaped intermediate transfer member 40
The surface roughness of the upper end of the first endless belt-shaped intermediate transfer member 20.
56 to 80 g when the same surface roughness as above is used or when the upper and lower endless belt-like intermediate transfer bodies are replaced for copying.
PPC paper with a weight of about / m ² or 81-105 g / m ²
The coated paper having a small weight causes a problem of wrapping around the fixing roller 62, but there is no wrapping problem in the above embodiment. Further, the difference in gloss on both sides could be suppressed within 10 and there was no visual problem. The smaller the surface roughness of the toner used in this study was, the more advantageous the separability was.

Example 5 As shown in FIG. 1, the structure of the entire apparatus was such that simultaneous transfer on the front and back sides can be carried out at different positions after transfer at the secondary transfer portion.

The upper first fixing roller 61 has an outer diameter of 50.
mm / core material A5056TD / core thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1 mm /
Silicone rubber hardness 15 ° (JIS-A) / silicone rubber thermal conductivity 0.50 W / m · ° C./roll surface PFA coating 30 μm / Asker-C (measurement load 9.8
N) The second fixing roller 6 on the lower side has a product hardness of 86 °
2 is outer diameter 50 mm / core material A5056TD / core thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 10 ° (JIS
-A) / Silicone rubber thermal conductivity 0.50 W / m · ° C /
Roll surface PFA coating 30 μm / Asker-
C (measurement load 9.8N) Product hardness is 78 ° /. In this case, since the conditions other than the rubber thickness are all the same, the ratio of the amount of surface strain is also inversely proportional to the rubber thickness, and the upper strain: lower strain = 1.5: 1.

Halogen lamps are arranged inside the core of the upper first fixing roller 61 and inside the core of the lower second fixing roller 62 (not shown). A sensor (not shown) for detecting the surface temperature in a non-contact manner is arranged close to the surfaces of the first fixing roller 61 and the second fixing roller 62 (ON / OFF) or PID control of the halogen heater is performed according to the detected temperature. . The surface temperatures of the two fixing rollers are controlled to be the same.

The toner is an ester wax of about 10-15.
The main material was St-Ac mixed with mass%, and the release agent was not applied to the surface of the fixing roller.

As the separating member, a baffle plate on which a fluorine sheet such as PTFE is attached is provided in the vicinity of the nip outlet in a non-contact manner with the fixing rollers 61 and 62.

When the silicone rubber thickness of the lower second fixing roller 62 is made to be exactly the same as the size, material and hardness of the upper first fixing roller 61, or the upper and lower fixing rollers are exchanged for copying. Is a PPC paper having a weight of about 56 to 80 g / m ² or coated paper having a weight of about 81 to 105 g / m ² , and the trouble of winding around the fixing roller 62 occurred. There was no problem.

Embodiment 6 As shown in FIG. 2, the structure of the entire apparatus is such that the secondary transfer portion can perform simultaneous transfer and fixing.

Upper first endless belt-shaped intermediate transfer member 20
The backup roller 26 has an outer diameter of 50 mm / core metal material A5056TD / core metal thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 15 ° (JIS-A) / silicone rubber thermal conductivity 0.50W / m ・ ° C / Asker-C product hardness 62 °
The backup roller 46 of the lower second endless belt-shaped intermediate transfer member 40 has an outer diameter of 50 mm / core metal material A5.
056TD / core metal thickness 5 mm / elastic layer material LTV silicone rubber / silicone rubber thickness 1.5 mm / silicone rubber hardness 15 ° (JIS-A) / silicone rubber thermal conductivity 0.50 W / m · ° C./Asker-C product hardness 62 °, and the first and second endless belt-shaped intermediate transfer members 20, 40
(Common to both) is a semi-conductive polyimide base material coated with semi-conductive silicone rubber, and the surface layer is made of PF.
The resin was coated with resin A and had the same structure except the thickness of the silicone rubber. The rubber thickness of the first endless belt-shaped intermediate transfer member 20 was set to 2/3 times the rubber thickness of the second endless belt-shaped intermediate transfer member 40. Since all the conditions except the rubber thickness are the same, the surface strain ratio is also inversely proportional to the rubber thickness, and the upper strain:
The lower distortion is 1.5: 1.

Inside the core metal of the upper first backup roller 26, one or two halogen lamps are arranged so that the total power is about 500 to 1250W. A halogen lamp having the same structure as the inside of the core metal of the first backup roller is arranged inside the core metal of the lower second backup roller 46 (not shown). First
A sensor (not shown) for detecting the surface temperature is arranged in contact with or close to the surfaces of the backup roller 26 and the second backup roller 46, and the halogen heater is turned on / off or PID controlled according to the detected temperature. Two
The surface temperatures of the two backup rollers are controlled to be the same.

The toner is an ester wax of about 10-15.
A material containing St-Ac mixed in a mass% as a main material was used, and the release agent was not applied to the surface of the intermediate transfer member.

The separating member is in the vicinity of the nip outlet and is in non-contact with the endless belt-shaped intermediate transfer member 20, 40 by PTFE.
A baffle plate with a fluorine sheet attached was installed.

Lower second endless belt-shaped intermediate transfer member 40
If the silicone rubber thickness of the above is exactly the same as the rubber thickness of the first upper endless belt-shaped intermediate transfer member 20, or if the upper and lower endless belt-shaped intermediate transfer members are replaced, copying is performed.
PPC paper with a weight of 6 to 80 g / m ² or 81 to 1
The coated paper having a weight of about 05 g / m ² caused a problem of winding around the fixing roller 62, but there was no winding problem in the above embodiment.

[0115]

According to the present invention, the toner images on the endless belt-shaped intermediate transfer bodies corresponding to the two image forming portions arranged in parallel are simultaneously and simultaneously transferred to both surfaces of the transfer material, and are simultaneously and simultaneously fixed. When this is done, the transfer material is collected without being caught in each endless belt-shaped intermediate transfer body or each fixing roller,
It has become possible to stably perform simultaneous transfer and simultaneous fixing, eliminate the difference in glossiness between front and back images, and provide an image forming apparatus capable of efficiently printing high-quality images.

[Brief description of drawings]

FIG. 1 is a schematic view showing a color image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a method of collectively performing secondary transfer and fixing.

FIG. 3 is a schematic view showing a formation state of a nip portion between fixing rollers in a fixing device.

FIG. 4 is a schematic diagram showing a formation state of a nip portion between first and second endless belt-shaped intermediate transfer bodies in a secondary transfer portion.

[Explanation of symbols]

1,3 image forming means 10 photoconductor 11,31 Charging roller 20 First endless belt-shaped intermediate transfer member 25,45 Primary transfer roller 26 First backup roller (secondary transfer roller) 40 Second endless belt-shaped intermediate transfer member 46 Second backup roller (secondary transfer roller) 48 Scorotron electrode 60 fixing device 61 First Fixing Roller 62 Second fixing roller 100 color image forming apparatus

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) H05B 3/00 335 H05B 3/00 335 F term (reference) 2H028 BA16 BC01 BC03 2H033 AA10 AA16 AA46 BA11 BA25 BA29 BA58 BB05 BB06 BB14 BB15 BB23 BB29 BB30 BB34 BE09 2H078 AA21 BB01 CC06 DD39 DD53 DD57 EE27 EE35 2H200 FA06 GA12 GA14 GA23 GA33 GA45 GA47 GA54 GA57 GA59 GB12 JA25 JA08 JA23 JA08 JA23 JA28 H47H27HA45 HB12 HB43 HB43 HB43 HB43 H02 JC04 JC13 JC15 JC16 JC17 KA03 KA20 LA18 LA31 LB09 LB13 MA03 MA04 MA08 MA14 MA20 MB04 MC02 MC06 NA02 NA09 3K058 AA61 AA71 BA18 DA26 GA03 GA06

Claims (20)

[Claims] 1. A transfer material carrying unfixed toner images on both front and back sides is nipped and conveyed between a first fixing roller provided on the upper side and a second fixing roller provided on the lower side, and simultaneously fixed. In an image forming apparatus equipped with a heat roller type fixing device, the second fixing device may have a hardness higher than that of the first fixing roller.
An image forming apparatus characterized by reducing the product hardness of the fixing roller. 2. The product hardness is Asker at a predetermined load.
The image forming apparatus according to claim 1, wherein the hardness is measured when a -C hardness meter is used. 3. The image forming according to claim 1, wherein the product hardness is a hardness measured when a type A or a type C of Micro Hardness Meter MD-1 manufactured by Kobunshi Keiki Co., Ltd. is used. apparatus. 4. The hardness of the heat resistant elastic layer of the second fixing roller is made smaller than the hardness of the heat resistant elastic layer of the first fixing roller, and the outer diameter of the first fixing roller, the thickness of the core metal, and the heat resistance of the first fixing roller. The thickness and thermal conductivity of the elastic layer are made substantially equal to the outer diameter and core thickness of the second fixing roller, and the thickness and thermal conductivity of the heat-resistant elastic layer are made substantially equal to each other, and the core metal of each of the first and second fixing rollers is set. At least one heating source is installed inside or on the surface, and the first
2. The electric power of the heating source inside or on the surface of the core metal of the fixing roller is substantially equal to the electric power of the heating source on the inside or surface of the core metal of the second fixing roller.
The image forming apparatus according to any one of 3 above. 5. The first fixing roller and the second fixing roller have a heat resistant elastic layer on a cored bar and a fluorine resin layer containing at least PFA resin on the outermost layer. A release agent is not applied to the first and second fixing rollers, and a fixed object such as a transfer material peeling claw is not brought into contact with the image corresponding area of the first and second fixing rollers and used. The image forming apparatus according to claim 1, wherein the toner contains wax. 6. An unfixed toner image corresponding to the back surface is provided on the lower side of the first endless belt-shaped intermediate transfer member having an unfixed toner image corresponding to the front surface of the transfer material provided on the upper side. Formed on the second endless belt-shaped intermediate transfer member,
By a first backup roller inside the first endless belt-shaped intermediate transfer member and a second backup roller inside the second endless belt-shaped intermediate transfer member,
In the image forming apparatus, in which the first and second endless belt-shaped intermediate transfer members are brought into pressure contact with each other to form a nip portion, and a transfer material is passed through the nip portion to perform transfer and fixing at the same time, 2, the material of the endless belt-shaped intermediate transfer member,
An image forming apparatus, wherein the thickness is set to be substantially the same, and the product hardness of the second backup roller is smaller than the product hardness of the first backup roller. 7. The product hardness is Asker at a predetermined load.
The image forming apparatus according to claim 6, wherein the hardness is measured when a -C hardness meter is used. 8. The image forming according to claim 6, wherein the product hardness is a hardness measured when using a type A or a type C of a micro hardness meter MD-1 manufactured by Kobunshi Keiki Co., Ltd. apparatus. 9. The hardness of the heat-resistant elastic layer of the second backup roller is made smaller than the hardness of the heat-resistant elastic layer of the first backup roller, and the outer diameter of the first backup roller, the substrate thickness, and the heat-resistant elasticity of the first backup roller. The layer thickness and thermal conductivity are made substantially equal to the outer diameter of the second backup roller, the substrate thickness, and the heat resistant elastic layer thickness and thermal conductivity, and
The outer diameter of the endless belt-shaped intermediate transfer member, the substrate thickness, the thickness and thermal conductivity of the heat-resistant elastic layer, and the hardness of the second endless belt-shaped intermediate transfer member are determined by At least one heating source is provided inside the core metal of each of the first and second backup rollers, or on the surface or the inner surface of the endless belt-shaped intermediate transfer member, which has substantially the same conductivity and hardness.
The electric power of the heating source arranged inside the core metal of the first backup roller or in contact with the first endless belt-shaped intermediate transfer member and the electric power of the heating source arranged inside the core metal of the second backup roller or the second endless belt-shaped intermediate transfer member The image forming apparatus according to any one of claims 6 to 8, wherein the electric power of the heating source in contact with the body is made substantially equal. 10. The first endless belt-shaped intermediate transfer member and the second endless belt-shaped intermediate transfer member are provided with a heat resistant elastic layer on a substrate and a fluororesin layer containing at least a PFA resin as an outermost layer. And the first and second
10. The image forming apparatus according to claim 6, wherein a release agent is not applied to each of the endless belt-shaped intermediate transfer members and the toner to be used contains a wax. apparatus. 11. A transfer material having unfixed toner images on both front and back sides thereof is nipped and conveyed between a first fixing roller provided on the upper side and a second fixing roller provided on the lower side, and simultaneously fixed. In an image forming apparatus provided with a heat roller type fixing device, the surface roughness of the first fixing roller and the surface roughness of the second fixing roller are changed, and a solid image on the front and back sides at the time of double-sided simultaneous image formation is formed. An image forming apparatus having a roughness such that a difference in glossiness is 5 or less. 12. The outer diameter of the first fixing roller, the thickness of the core metal, the thickness and thermal conductivity of the heat-resistant elastic layer, and the hardness of the outer diameter of the second fixing roller, the thickness of the core metal, and the thickness of the heat-resistant elastic layer. And heat conductivity and hardness are substantially equal to each other, and at least one heating source is provided inside or on the surface of the core metal of each of the first and second fixing rollers.
In one aspect, the power of the heating source inside or on the surface of the core of the first fixing roller is made substantially equal to the power of the heating source inside or on the surface of the core of the second fixing roller. Item 12. The image forming apparatus according to Item 11. 13. The first fixing roller and the second fixing roller are provided with a heat resistant elastic layer on a cored bar and a fluorine resin layer containing at least PFA resin on the outermost layer. A release agent is not applied to the first and second fixing rollers, and a fixed object such as a transfer material peeling claw is not brought into contact with the image corresponding area of the first and second fixing rollers and used. 13. The image forming apparatus according to claim 11, wherein the toner contains wax. 14. An unfixed toner image corresponding to the back surface is provided on the lower side of the first endless belt-shaped intermediate transfer member having an unfixed toner image corresponding to the front surface of the transfer material provided on the upper side. Formed on the second endless belt-shaped intermediate transfer body, respectively, inside the first endless belt-shaped intermediate transfer body, and inside the second endless belt-shaped intermediate transfer body. An image forming apparatus that presses the first and second endless belt-shaped intermediate transfer members by a second backup roller to form a nip portion, and allows a transfer material to pass through the nip portion to perform transfer and fixing at the same time. In, the surface roughness of the first endless belt-shaped intermediate transfer member and the surface roughness of the second endless belt-shaped intermediate transfer member are changed, and the glossiness difference between the front and back solid images during simultaneous double-sided image formation Is less than 10 An image forming apparatus characterized by: 15. The outer diameter of the first endless belt-shaped intermediate transfer member, the substrate thickness, the thickness and thermal conductivity of the heat resistant elastic layer, and the hardness are the outer diameter of the second endless belt-shaped intermediate transfer member and the substrate thickness. ,
At least one heat source is provided inside the core metal of each of the first and second backup rollers, or on the surface or the inner surface of the endless belt-shaped intermediate transfer member, with the thickness, thermal conductivity and hardness of the heat resistant elastic layer being substantially equal. Installed and arranged inside the core of the first backup roller or the electric power of a heating source in contact with the first endless belt-shaped intermediate transfer member and arranged inside the core of the second backup roller or the second endless belt. 15. The image forming apparatus according to claim 14, wherein the electric power of the heating source in contact with the intermediate transfer member is made substantially equal. 16. The first endless belt-shaped intermediate transfer member and the second endless belt-shaped intermediate transfer member are provided with a heat resistant elastic layer on a substrate and a fluororesin layer containing at least a PFA resin as an outermost layer. And the first and second
16. The image forming apparatus according to claim 14, wherein a release agent is not applied to each of the endless belt-shaped intermediate transfer members and the toner used contains wax. 17. A transfer material carrying unfixed toner images on both front and back sides is nipped and conveyed between a first fixing roller provided on the upper side and a second fixing roller provided on the lower side, and simultaneously fixed. An image forming apparatus including a heat roller type fixing device, wherein the surface distortion amount of the second fixing roller is larger than the surface distortion amount of the first fixing roller. 18. The first fixing roller and the second fixing roller are provided with a heat resistant elastic layer on a cored bar and a fluorine resin layer containing at least PFA resin on the outermost layer. A release agent is not applied to the first and second fixing rollers, and a fixed object such as a transfer material peeling claw is not brought into contact with the image corresponding area of the first and second fixing rollers and used. The image forming apparatus according to claim 17, wherein the toner contains wax. 19. An unfixed toner image corresponding to a back side surface is provided on a first endless belt-shaped intermediate transfer member having an unfixed toner image corresponding to a front side surface of a transfer material provided on an upper side. Formed on the second endless belt-shaped intermediate transfer body, respectively, inside the first endless belt-shaped intermediate transfer body, and inside the second endless belt-shaped intermediate transfer body. An image forming apparatus that presses the first and second endless belt-shaped intermediate transfer members with each other by a second backup roller to form a nip portion, and allows a transfer material to pass through the nip portion to perform transfer and fixing at the same time. In the above, the first and second endless belt-shaped intermediate transfer bodies are configured to have at least an elastic layer, and the second endless belt-shaped intermediate transfer body is more than the surface strain amount of the first endless belt-shaped intermediate transfer body. Of intermediate transfer body An image forming apparatus having a large surface strain amount. 20. The first endless belt-shaped intermediate transfer member and the second endless belt-shaped intermediate transfer member have a heat resistant elastic layer provided on a substrate and a fluororesin layer containing at least a PFA resin as an outermost layer. And the first and second
20. The image forming apparatus according to claim 19, wherein a release agent is not applied to each of the endless belt-shaped intermediate transfer members and the toner used contains wax.