JP2001034076A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent image defect caused by faulty transfer or retransfer and to stably attract and carry recording material by making the volume resistivity of the area of a carrying and feeding means where the recording material is held higher than that of the area thereof on a transfer electrifying means side. SOLUTION: A feeding belt 8 is constituted of two layers being a surface layer as a 1st area on a side where the recording material is carried and a base layer as a 2nd area on a side where transfer electrifying blades 4a to 4b abut on. For example, the surface layer is formed of thermosetting polyimide resin whose volume resistivity is 1015 to 1018 Θcm so that its thickness may be about 40 μm, and the base layer whose base resin is the same thermosetting polyimide resin as the surface layer and whose film thickness is about 40 μm uses the resin whose volume resistivity is adjusted to be 1010 to 1013 Θcm by mixing carbon as resistance adjusting material. As the coating film method of two-layer belt, polyimide whose resistance is not adjusted is formed as coating film on the inner surface of a cylinder having the inside diameter nearly as long as the outer periphery length of the belt 8 and polyimide whose resistance is adjusted is formed as the coating film on its surface further.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic system, an electrostatic recording system, etc., and more particularly to a carrying means for carrying a recording material in a color image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a plurality of image forming units are provided, toner images of different colors are formed in each image forming unit, and the toner images are sequentially superimposed and transferred on the same recording material.
Various color image forming apparatuses for obtaining a color image have been proposed, and among them, a color copying apparatus based on a multicolor electrophotographic system is widely used.

An example of such a color electrophotographic copying apparatus will be briefly described with reference to the drawings. As shown in FIG. 6, the color electrophotographic copying machine includes a pair of rollers 211 and 211.
It has a transport belt 208 suspended in between and driven by a drive source (not shown) in the direction of arrow F. Four image forming units Pe, Pf, Pg and Ph are disposed above the transport belt 208. . Since each image forming unit has the same configuration, the configuration will be schematically described below taking the first color image forming unit Pe as an example.

In the image forming section Pe, a cylindrical image carrier, that is, a photosensitive drum 201a, which rotates in the direction of arrow D near the conveyor belt 208, is disposed.
After the photosensitive layer on the surface 01a is uniformly charged by the primary charger 215a, the yellow component light image 216a of the original image is exposed to this, and an electrostatic latent image is formed on the photosensitive drum 201a.

The latent image is moved by the rotation of the photosensitive drum 201a and reaches the position of the developing device 203a, where the latent image is developed by yellow toner supplied from the developing device 203a, and the latent image is visualized as a yellow toner image. .

The above yellow toner image is transferred to the photosensitive drum 20
With the rotation of 1a, it reaches a transfer site where a blade-shaped transfer charger 204a having a conductive blade is arranged. At this time, a recording material (not shown) is supplied from the conveyance path 212 onto the conveyance belt 208 and conveyed to the transfer site by the conveyance belt 208.

Then, a transfer bias is applied to the transfer charger 204a, and the yellow toner image on the photosensitive drum 201a is transferred onto the recording material.

After that, the photosensitive drum 201a is removed from the residual toner remaining thereon by the cleaning blade 230 of the cleaning device, and is ready for the next image forming process.

On the other hand, the recording material on which the yellow toner image has been transferred advances to the next second color image forming section Pf by conveyance by the conveyance belt 208. Second color image forming unit Pf
Has the same configuration as the first color image forming portion Pe, and in the same manner as described above, the latent image is formed on the photosensitive drum 201b and the latent image is developed with magenta toner. The toner image is transferred onto the recording material at the transfer portion so as to overlap the yellow toner image.

Similarly, in the image forming units Pg and Ph,
A cyan toner image and a black toner image are formed on the photosensitive drums 201c and 201d, respectively.
The color images 04c and 204d are sequentially superimposed and transferred onto the recording material, and a color image in which four color toner images are superimposed on the recording material is obtained.

The recording material to which the four color toner images have been transferred is discharged by the separation charge eliminator 261 to be separated from the conveyor belt 208, and a pair of fixing roller 207a and pressure roller 207b
The fixing is carried out by applying pressure and heat to the nip portion of the rollers 207a and 207b which are usually heated to a predetermined temperature.

As a result, the recording material is mixed with the toner images of the respective colors and fixed to the recording material to form a full-color permanent image, and then discharged outside the copying apparatus.

After the separation of the recording material, the transport belt 108 removes the charge received during the transfer by the inner charge remover 213 and the outer charge remover 214, and further includes a cleaning blade 220 and a backup roller 22 provided on the downstream side in the traveling direction.
As a result, fog toner, scattered toner, dust such as paper dust, and the like attached to the surface are removed, and the surface is cleaned in preparation for the next image formation.

In the image forming apparatus for forming a color image by multiple transfer as described above, the transfer / conveying belt has a high resistance, specifically 10 ¹⁴ , for the purpose of firmly adsorbing the recording material. A single layer resin made of polyethylene terephthalate resin or polycarbonate resin having a volume resistance of 10 ¹⁶ Ω · cm has been used for the belt.

As the transfer charging member, Japanese Patent Laid-Open No. 6-342
As disclosed in JP-A-243-243 and JP-A-6-342245, a transfer blade capable of reducing a transfer electric field in a transfer area to reduce image defects such as scattering at the time of transfer is used. It has become to.

[0016]

However, in the case of the above-described prior art, the following problems have occurred.

When a transfer belt with high resistance is used for the purpose of firmly adsorbing the recording material, it has an excellent function in terms of adsorbing the recording material, but in a low humidity environment, specifically, the absolute water content. Is 1.0 g / kg or less, especially 0.8 g / kg.
g / kg or less, or when an attempt is made to form images on both sides, which has been increasing from the viewpoint of ecology in recent years, the resistance value of the recording material due to a decrease in the moisture content of the recording material is reduced. When the recording material rises, both the recording material and the transfer conveyance belt have high resistance, so that when transferring the toner image formed on the photosensitive drum to the recording material, a very large transfer electric field is required in the transfer portion. When a transfer electric field is applied, there is a problem that a local abnormal discharge occurs and transfer failure occurs.

Further, in a system in which a large transfer electric field needs to be applied, not only poor transfer occurs at the time of transfer from the photosensitive drum to the recording material, but also the toner image once transferred to the recording material is transferred to the next color. There was also a problem that the image was easily retransferred onto the photosensitive drum.

It has also been proposed to use a transfer conveyance belt having a lower resistance than the above in order to reduce an image defect caused by an increase in the resistance value of the recording material. In this case, the recording material cannot be sufficiently adsorbed in a high-humidity environment or the like, resulting in poor conveyance or electrical interference between adjacent transfer members, resulting in poor transfer.

Further, when a recording material having a short dimension in the direction perpendicular to the traveling direction of the transfer conveyance belt, that is, in the width direction of the belt, specifically, when a JIS standard A4 size paper is passed in the vertical direction, recording is performed. If the resistance of the conveyance belt is lower than that of the material, most of the transfer current generated by the transfer charging member flows not only to the recording material but only to the transfer conveyance belt portion having no recording material. There were various problems such as occurrence of transfer failure.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to prevent the occurrence of image defects due to transfer failure and retransfer and to stably adsorb a recording material. It is an object of the present invention to provide an image forming apparatus which can convey and continuously obtain high-quality images on recording materials of various sizes.

[0022]

In order to achieve the above object, according to the present invention, there is provided an image carrier on which an electrostatic latent image is formed, and an electrostatic latent image formed on the image carrier. Developing means for developing, a transfer charging means disposed on the recording material carried and conveyed by the carrying means, with the carrying means interposed therebetween, and transferring a developed image developed by the developing means to the recording material; and Fixing means for fixing the unfixed developed image transferred to the recording material, wherein the carrying and conveying means includes at least two regions having different volume resistivity, and the recording material is The first region to be carried has a higher volume resistivity than the second region on the transfer charging unit side.

The volume resistivity of the first region is 1
0 is ^{15 ~10 18 Ω} · cm, the volume resistivity of the second region, it is preferable is ^{10 10} ~10 ¹³ Ω · cm.

It is also preferable that the carrying means is made of an aromatic polyimide resin.

It is also preferable that the carrying means has a two-layer structure.

It is also preferable that the carrying / transporting means has a two-layer structure by forming the second region after forming the first region.

[0027]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, the shape, and the relative arrangement thereof should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, and are not intended to limit the scope of the invention to the following embodiments.

(Embodiment 1) FIG. 1 shows an example of an image forming apparatus to which the present invention is applied. The image forming apparatus shown in FIG. 1 is a four-color full-color laser beam printer, and FIG. 2 is a longitudinal sectional view showing a schematic configuration thereof.

The image forming apparatus shown in FIG. 1 is suspended between a pair of rollers 11, 11 and is driven by an arrow C by a driving source (not shown).
Transport belt 8 serving as a carrying transport unit that travels in the direction, and has four image forming units Pa and P above the transport belt 8.
b, Pc and Pd are provided. Since the image forming units have the same configuration, the configuration of the image forming unit Pa for the first color will be schematically described below as an example.

In the image forming section Pa, a drum-type electrophotographic photosensitive member (hereinafter, referred to as a "photosensitive drum") serving as a cylindrical image carrier which rotates in the direction of arrow A in proximity to the transport belt 8 is provided.
1a is arranged. Around the photosensitive drum 1a, a charging roller 35a, an exposure device 16a, a developing device 3a as a developing device, a transfer charger 4a as a transfer charging device, a cleaning device 30a, and the like are arranged substantially in order along the rotation direction. I have. Further, a fixing device 7 as a fixing unit is disposed downstream of the conveyance belt 8 along the recording material conveyance direction.

In order to form a color image, first, the photosensitive drum 1a is driven to rotate in the direction of arrow A at a predetermined peripheral speed (process speed), in this embodiment, at 200 mm / sec. The surface of the photosensitive drum 1a is primarily charged to a predetermined polarity and a predetermined potential by the charging roller 35a, and to about -550 V in the present embodiment, and the exposure device 16a
Scans and exposes the laser beam L to the photosensitive drum 1a.
An electrostatic latent image of the first color (yellow) is formed thereon, and the electrostatic latent image is developed by the developing device 3a.

As described above, in the case of forming an electrostatic latent image by a digital method, a developing method called a so-called reversal developing method has been widely adopted recently. The reversal development method is, for example, to charge the surface of the photosensitive drum 1a with a negative polarity at the time of the above-described primary charging, and then expose the image area to reduce the charged charge in that area. Developing the toner charged to the same polarity.

The above-mentioned yellow toner image is transferred to the photosensitive drum 1a.
With the rotation of, the transfer device reaches the transfer site where the transfer charger 4a is arranged. The transfer charger 4a is, as shown in FIG.
a, Backup member 40 for backing up this base material
2a, a lubricating coat layer 403a provided on the side of the base material which is in contact with the conveyor belt and in the vicinity of the contact portion.

The material of the substrate 401a is isoprene rubber, styrene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, butyl rubber, silicone rubber,
Rubber material such as chloroprene rubber, chlorosulfonated polyethylene, acrylic rubber, hydrin rubber, urethane rubber, polysulfide rubber, fluorine rubber, or synthetic rubber obtained by synthesizing them, or synthetic resin such as nylon, urethane, polyester, tin oxide, A compound containing a conductive agent such as carbon black can be used.

The thickness of the substrate 401a is about 1.5 to
2.5 mm, the backup member 402a has a thickness of about 50
The coating layer 403a was made of polyethylene terephthalate resin having a thickness of 0 μm, and the fluorine resin having a thickness of about 15 μm.

A recording material (not shown) is supplied from a conveyance path 12 onto a conveyance belt 8 at a time synchronized with a developed image formed on the photosensitive drum 1a, and is conveyed to a transfer portion by the conveyance belt 8. Then, the controller 50 is connected to the transfer charger 4a.
The transfer bias from the transfer bias power supply 51a controlled by the transfer bias is applied to transfer the yellow toner image on the photosensitive drum 1a onto the recording material.

Thereafter, the remaining toner on the photosensitive drum 1a is removed by the cleaning blade 30a of the cleaning device, and the photosensitive drum 1a is ready for the next image forming step. On the other hand, the recording material on which the yellow toner image has been transferred advances to the next second color image forming portion Pb by conveyance by the conveyance belt 8.

The image forming section Pb for the second color has the same configuration as the image forming section Pa for the first color, and forms a latent image on the photosensitive drum 1b and a latent image with magenta toner in the same manner as described above. The image is developed, and the obtained magenta toner image is transferred onto the recording material at the transfer portion so as to overlap the yellow toner image.

Similarly, in the image forming units Pc and Pd,
A cyan toner image and a black toner image are formed on the photosensitive drums 1c and 1d, respectively.
By d, the images are sequentially superimposed and transferred on the recording material, and a color image in which four color toner images are superimposed on the recording material is obtained.

The recording material to which the four color toner images have been transferred is neutralized by the separation neutralizer 61 to be separated from the conveyor belt 8 and sent to the fixing device 7 having a pair of fixing roller 7a and pressure roller 7b. The roller 7 which is usually heated to a predetermined temperature
The fixing is performed by applying pressure and heat at the nip portions a and b.

As a result, the recording material is mixed with the toner images of the respective colors and fixed to the recording material to form a full-color permanent image, and then discharged outside the image forming apparatus.

The fixing roller 7a and the pressure roller 7b wipe off the toner by the respective cleaning webs 40 when the toner adheres due to the fixing of the toner image.

On the other hand, after the separation of the recording material, the transport belt 8 discharges the charged charges received at the time of transfer by the inner static eliminator 13 and the outer static eliminator 14, and further includes a cleaning blade 20 and a backup roller provided downstream in the traveling direction. As a result, dust and fogging toner, scattered toner, and dust such as paper dust attached to the surface are removed, and the surface is cleaned in preparation for the next image formation.

Next, the configuration of the transport belt 8 which is a feature of the present invention will be described in detail.

FIG. 2 is a sectional view of the conveyor belt 8 according to the present embodiment. As shown in this cross-sectional view, the transport belt 8
Is a surface layer 8 as a first area on the side where the recording material is carried.
1 and a base layer 82 as a second area on the side where the transfer charging blades 4a, 4b, 4c and 4d are in contact.

The surface layer 81 has a volume resistivity of 10 ¹⁵ to 10 ¹⁸ Ω.
· A thermosetting polyimide resin having a thickness of about 40 μm is formed. The base layer 82 is made of a thermosetting polyimide resin having a thickness of about 40 μm as in the case of the surface layer 81, but is mixed with carbon as a resistance adjusting material.
Those whose volume resistivity was adjusted to 10 ¹⁰ to 10 ¹³ Ω · cm were used.

The measurement of the volume resistance is performed according to JIS K-6911.
The applied voltage of 1 kv and the value of 1 minute were used. As a material of the conveyor belt 8, an aromatic polyimide prepared by a similar manufacturing method may be used.

As a method of forming the two-layer belt, the inner surface of a cylinder having an inner diameter substantially the same as the outer peripheral length of the conveyor belt 8 is provided.
First, after a polyimide film whose resistance has not been adjusted is formed, a polyimide film whose resistance has been adjusted is further formed on the formed polyimide surface.

According to such a method, first, a non-resistance-adjusted polyimide excellent in mechanical properties is formed first, and then a polyimide whose resistance is slightly inferior in mechanical properties is formed. Even if the belt is formed into two layers, a two-layer belt having excellent mechanical properties, particularly, surface accuracy can be obtained.

Here, the polyimide resin will be described. The polyimide resin is obtained, for example, by preparing a polyamic acid by reacting tetracarboxylic dianhydride and a diamine in an organic solvent in substantially equimolar amounts, and imidizing the polyamic acid by heating.

As the above tetracarboxylic dianhydride,
What is represented by the following general formula is mentioned.

[0052]

Embedded image [Wherein, R is a tetravalent organic group, and is an aromatic, aliphatic, cycloaliphatic, combination of aromatic and aliphatic, or a substituted group thereof. ]

For example, pyromellitic dianhydride, 3,
3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,3,3 ', 4-biphenyltetracarboxylic Acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride Anhydride, 2,2'-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-
Dicarboxyphenyl) sulfone dianhydride, perylene-
3,4,9,10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride,
And ethylene tetracarboxylic dianhydride.

Examples of the diamine include 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane,
3'-dichlorobenzidine, 4,4'-aminodiphenylsulfide-3,3'-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3 '-Dimethyl-
4,4'-biphenyldiamine, benzidine, 3,3 '
-Dimethylbenzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminophenylsulfone, 4,4'-
Diaminodiphenyl sulfide, 4,4'-diaminodiphenylpropane, 2,4-bis (β-amino-tert-butyl) toluene, bis (p-β-amino-tert-butylphenyl) ether, bis (p -Β-methyl-δ-aminophenyl) benzene, bis-p- (1,1-dimethyl-
5-amino-pentyl) benzene, 1-isopropyl-
2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di (p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine , Diaminopropyltetramethylene, 3-methylheptamethylenediamine,
4,4-dimethylheptamethylenediamine, 2,11-
Diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-
Methoxyhexamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-
Methylnonamethylenediamine, 2,11-diaminododecane, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10
- diamino-1,10-dimethyl decane, 1,12-diamino-octadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, piperazine, H ₂ N
(CH ₂ ) ₃ O (CH ₂ ) ₂ O (CH ₂ ) NH ₂ , H ₂ N (C
H ₂ ) ₃ S (CH ₂ ) ₃ NH ₂ , H ₂ N (CH ₂ ) ₃ N (C
H ₃ ) (CH ₂ ) ₃ NH _{2 and the} like.

Further, the organic polar solvent used in the synthesis of the polyamic acid has a dipole whose functional group does not react with tetracarboxylic dianhydride or diamine. In addition to being inert to the system and acting as a solvent for the product polyamic acid, it must act as a solvent for at least one of the reaction components, preferably both. In particular, N, N-dialkylamic acid is useful as the organic polar solvent.
Dimethylacetamide, N, N-dimethylacetamide acid and the like can be mentioned. These can be easily removed from the polyamic acids and polyamic acid moldings by evaporation, displacement or diffusion.

Other organic polar solvents other than those described above include:
N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, dimethylsulfone, tetramethylenesulfone, dimethyltetra Methylene sulfone and the like. These may be used alone or in combination.

Further, cresol,
Phenols such as phenol and xylenol, benzonitrile, dioxane, butyrolactone, xylene, cyclohexane, hexane, benzene, and toluene can be used alone or in combination, but addition of water is not preferred. That is, the polyamic acid is hydrolyzed to have a low molecular weight by the presence of water, so that the synthesis of the polyamic acid needs to be performed under substantially anhydrous conditions.

The polyamic acid is obtained by reacting the above tetracarboxylic dianhydride (a) with the diamine (b) in an organic polar solvent.

In this embodiment, a polyimide resin whose repeating unit is represented by the following structural formula is used, but the present invention is not limited to these embodiments.

[0060]

Embedded image

Now, the conveyor belt 8 having the two-layer structure
A description will be given of the results of a study by the applicants of the present application on the transfer characteristics when using the. FIG. 5 shows a low humidity environment, specifically 23 ° C. /
The transfer charging bias (transfer current) applied to the transfer charger 4a and the rate at which the developing toner on the photosensitive drum 1a could be transferred to the recording material under an environment of 5% and an absolute water content of 0.8 g / kg, That is, the relationship of the transfer efficiency was shown.

At this time, the toner developed on the photosensitive drum 1a has a charge amount per unit weight of about -30 mC / kg,
The amount of glue per unit area was 8 g / m ² .

In FIG. 5, a graph plotted by a circle is a transfer efficiency vs. transfer current characteristic when the transport belt 8 having a two-layer structure according to the present invention is used. When the transfer current reaches about 18 μA, the transfer is performed. The efficiency exceeded 95%, and the transfer efficiency saturated. The reason that the transfer efficiency saturates at 95% is that the remaining 5% of toner does not adhere to the photosensitive drum 1a by electrostatic force, but adheres by non-electric force such as van der Waals force. It is thought that it is.

On the other hand, in FIG. 5, a graph plotted with a cross is a transfer efficiency vs. transfer current characteristic when the high-resistance transport belt shown in the prior art is used.
When the transfer efficiency reached 5 μA, the transfer efficiency exceeded 95%, and the transfer efficiency saturated.

Therefore, when comparing the transfer current required for the transfer efficiency to saturate, the transfer belt of the two-layer structure used in the present embodiment is compared with the conventional high-resistance transfer belt. ÷ 25 = 0.72 That is, sufficient toner transfer can be performed with a current output of 72%.

The reason why the necessary transfer current can be reduced in this way is considered to be as follows. Although the transfer charging member used was a blade-shaped transfer charging nip having a very narrow nip, the electrical resistance of the transport belt 8 on the side to which the transfer charger 4a contacts was set to 10 ¹⁰ to 10 ¹³ Ω · c.
This is considered to be because the transfer nip was substantially widened because the medium resistance level was set at a relatively high level of m, so that it was possible to substantially increase the time during which the transfer charging was performed.

As a result, it is possible to suppress the transfer electric field required for transfer even in the low-humidity environment or when forming the image on the second side in the case of forming a double-sided image, thereby suppressing the occurrence of local abnormal discharge. Therefore, good image formation without transfer failure can be performed.

The transfer charger side of the conveyor belt has a medium resistance, but the recording material carrying side has a high resistance. Therefore, there is a problem in adsorption that occurs when the entire conveyance belt has a medium resistance or a low resistance. Also, it is possible to prevent adverse effects such as transfer failure due to occurrence of electrical interference and image failure when a recording material having a short dimension in the width direction of the conveying belt is passed.

(Embodiment 2) FIG. 3 shows a second embodiment. The present invention exerts the same effect as that of the first embodiment even in an image forming apparatus having one photosensitive drum and one transfer drum as shown in FIG.

In FIG. 3, a photosensitive drum 101 is disposed as an image carrier, and a primary charger 102, a light source device (not shown), a developing device 103,
The cleaner 105 is arranged.

The developing device 103 includes a magenta developing device 103a,
It comprises a cyan developing unit 103b, a yellow developing unit 103c, and a black developing unit 103d.

A transfer drum 108 as a recording material carrier is disposed obliquely below the photosensitive drum 101. Inside the transfer drum 108, a charging blade 11 for suction is provided.
2. The charging blade 104 for transfer is provided. The recording material P is conveyed to the transfer drum 108 from a recording material cassette 160 provided at a lower portion of the apparatus main body via a registration roller 113 and the like.

Also in this embodiment, a two-layer resin film made of an aromatic polyimide resin is used for the recording material supporting portion of the transfer drum 108.

The layer structure of this resin film is as follows:
As in the embodiment, the volume resistivity of the recording material carrier side is 1
A high resistance of 0 ¹⁵ to 10 ¹⁸ Ω · cm and a medium resistance on the side in contact with the transfer charger of 10 ¹⁰ to 10 ¹³ Ω · cm. As in the first embodiment, a low humidity environment or double-sided image is formed. It is possible to prevent the occurrence of transfer failure due to local abnormal discharge that occurs during the second-side image formation during the formation, and to achieve good image formation.

[0075]

As described above, according to the present invention,
The carrying / transporting means includes at least two areas having different volume resistivity, and the first area for carrying the recording material has a higher volume resistivity than the second area on the side of the transfer charging means. It is possible to provide a high-quality and highly reliable image forming apparatus capable of preventing image defects due to transfer failure or retransfer and stably carrying and transporting a recording material. It becomes possible.

Further, the carrying / transporting means has a two-layer structure made of an aromatic polyimide resin. The volume resistivity of the first region is as high as 10 ¹⁵ to 10 ¹⁸ Ω · cm, and the volume resistivity of the second region is as follows. By setting the medium resistance to 10 ¹⁰ to 10 ¹³ Ω · cm, it is possible to prevent the occurrence of transfer failure due to a local abnormal discharge that occurs during the formation of the second surface image in a low-humidity environment or in the case of double-sided image formation. Image formation becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a recording material carrier to which the present invention is applied.

FIG. 3 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a configuration of a transfer charger.

FIG. 5 is a diagram showing a relationship between transfer current and transfer efficiency.

FIG. 6 is a schematic configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

 1a, 1b, 1c, 1d Photosensitive drum 3a Developing device 4a, 4b, 4c, 4d Transfer charger 7 Fixing device 8 Conveyor belt 11 Roller 13, 14 Static eliminator 16a Exposure device 20 Cleaning blade 30a Cleaning device 35a Charging roller 40 Cleaning web 50a Controller 51a Transfer bias power supply 81 Surface layer 82 Base layer 401a Base material 402a Backup member 403a Coat layer Pa, Pb, Pc, Pd Image forming unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinya Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H032 AA05 BA18 BA23

Claims (5)

[Claims] An image carrier on which an electrostatic latent image is formed; a developing unit for developing the electrostatic latent image formed on the image carrier; and a recording material carried and conveyed by the carrying unit. A transfer charging unit that is disposed with the carrying / transporting unit interposed therebetween and transfers a developed image developed by the developing unit to the recording material; and a fixing unit that fixes an unfixed developed image transferred to the recording material. And an image forming apparatus comprising: the carrier transporting means having at least two different volume resistivities;
An image forming apparatus, comprising: a first area for carrying the recording material; and a first area having a higher volume resistivity than the second area on the transfer charging unit side. 2. The volume resistivity of the first region is 10 ¹⁵
A ~10 ¹⁸ Ω · cm, the volume resistivity of the second region, the image forming apparatus according to claim 1, characterized in that the ^{10 10} ~10 ¹³ Ω · cm. 3. An image forming apparatus according to claim 1, wherein said carrying means is made of an aromatic polyimide resin. 4. The image forming apparatus according to claim 1, wherein said carrying means has a two-layer structure. 5. The method according to claim 1, wherein the carrying / transporting unit forms the second region after forming the first region.
The image forming apparatus according to claim 4, wherein the image forming apparatus has a layer structure.