JP7094822B2 - Intermediate transfer belt, image forming device, and method for manufacturing the intermediate transfer belt - Google Patents

Description

The present invention relates to an intermediate transfer belt for electrophotographic, an image forming apparatus including the intermediate transfer belt, and a method for manufacturing the intermediate transfer belt.

The electrophotographic image forming apparatus is an intermediate transfer method in which the toner image formed on the surface of the photoconductor is primaryly transferred to the intermediate transfer belt, and the toner image carried on the intermediate transfer belt is secondarily transferred to the recording material. It has been known. As the intermediate transfer belt, a resin endless belt to which appropriate conductivity is imparted is widely used.

Since the intermediate transfer belt comes into contact with a cleaning blade, a photoconductor, a transfer roller, a recording material, etc. that clean the belt surface, high wear resistance is required. Patent Document 1 describes a laminated belt for an image forming apparatus in which a coat layer containing a heat-crosslinkable resin is formed on a base material layer and the surface hardness of the coat layer is 250 N / mm ² or more and 700 N / mm ² or less. Have been described.

Japanese Unexamined Patent Publication No. 2017-40871

By the way, the manufacturing process of the intermediate transfer belt includes a step of cutting the side portion of the belt-shaped work piece with a metal blade and forming the belt into a predetermined belt width. However, when an attempt is made to manufacture an intermediate transfer belt having a layer having a high hardness on the surface like the belt member described in the above document, damage is accumulated on the metal blade during repeated cutting and deterioration progresses. Then, it becomes necessary to replace the metal blade frequently, which may lead to a decrease in productivity at the time of manufacturing.

Therefore, an object of the present invention is to improve the productivity at the time of manufacturing while ensuring the wear resistance of the intermediate transfer belt.

One aspect of the present invention is an intermediate transfer belt for electrophotographic, which has a base layer and a surface layer formed on the outer peripheral side of the base layer, and has a surface hardness of the surface layer measured by a nanoindentation method. However, in the belt width direction, it is 160 N / mm ² or more and 340 N / mm ² or less in the first region including the entire area of the maximum image forming region, and is outside the first region in the belt width direction and the intermediate transfer. The second region including the end of the belt is characterized by being 70 N / mm ² or more and 120 N / mm ² or less.

Further, another aspect of the present invention is a method for manufacturing an intermediate transfer belt for electrophotographic, in which a base layer forming step of forming a base layer in a belt shape and a photocurable resin material are applied to the outer peripheral side of the base layer. A coating step of applying the coating liquid containing the coating liquid, an irradiation step of irradiating the surface of the belt-shaped workpiece coated with the coating liquid with light, and a belt-shaped workpiece irradiated with light in the belt width direction. The surface hardness of the intermediate transfer belt measured by the nanoindentation method, including the cutting step of cutting the side portion, is 160 N / mm ² or more and 340 N / in the first region including the maximum image forming region in the belt width direction. In the irradiation step, the thickness is ^{2 or less, and 70 N / mm 2 or more and 120 N / mm 2 or less} in the second region which is outside the first region in the belt width direction and includes the cutting position in the cutting step. It is characterized in that the amount of light radiated to the second region of the belt-shaped processed product is set to a value smaller than the amount of light radiated to the first region.

According to the present invention, it is possible to improve the productivity at the time of manufacturing while ensuring the wear resistance of the intermediate transfer belt.

The schematic diagram of the image forming apparatus which concerns on this disclosure. Sectional drawing of the intermediate transfer belt. The figure for demonstrating the curing method of the surface layer at the time of manufacturing an intermediate transfer belt. The figure for demonstrating the dimension of an intermediate transfer belt.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 is a full-color printer provided with a so-called tandem type intermediate transfer type image forming engine in which four image forming portions PY, PM, PC, and PK are arranged along the rotation direction of the intermediate transfer belt 7.

Each of the image forming units PY to PK includes a photosensitive drum 1, which is a photoconductor, a charging device 2, a developing device 4, an exposure device 3, and a drum cleaner 6, respectively, by executing an electrophotographic process. It forms a yellow, magenta, cyan, and black toner image. That is, the surface of the photosensitive drum 1 is uniformly charged by the charging device 2, and the photosensitive drum 1 is exposed by the laser beam irradiated by the exposure device 3. At this time, the laser beam is modulated and output based on the data obtained by decomposing the image to be output into a monochromatic image, and an electrostatic latent image corresponding to the monochromatic image is formed on the surface of the photosensitive drum 1. The developing apparatus 4 agitates the developing agent containing toner inside the container, supports the charged toner particles on a developing agent carrier such as a developing sleeve, and supplies the charged toner particles to the photosensitive drum 1. The electrostatic latent image supported on the photosensitive drum 1 is developed by the toner supplied from the developing device 4, and the toner image is visualized.

The toner images formed by the image forming portions PY to PK are transferred to the recording material P via the intermediate transfer unit 15. The intermediate transfer unit 15 is configured such that an intermediate transfer belt 7, which is an intermediate transfer body, is stretched on a drive roller 8, a tension roller 9, and a driven roller 10. The drive roller 8 is rotationally driven by a drive source to rotate the intermediate transfer belt 7 in a direction along the rotation direction of the photosensitive drum 1 (counterclockwise in the figure). The tension roller 9 applies an appropriate tension to the intermediate transfer belt 7 and tilts its own rotation axis with respect to the rotation axis of the drive roller 8 to shift the intermediate transfer belt 7 (bias in the belt width direction). It also serves as a correction roller for correction.

On the inner peripheral side of the intermediate transfer belt 7, a primary transfer roller 5 is arranged at a position corresponding to each photosensitive drum 1 with the intermediate transfer belt 7 interposed therebetween, as a nip portion between the photosensitive drum 1 and the intermediate transfer belt 7. The primary transfer portion T1 is formed. The toner image carried on the photosensitive drum 1 is primarily transferred by the primary transfer roller 5 to the intermediate transfer belt 7 so as to overlap each other in the primary transfer unit T1. Adhesions such as primary transfer residual toner remaining on the photosensitive drum 1 without being transferred to the intermediate transfer belt 7 are removed by the drum cleaner 6.

The secondary transfer roller 12 is arranged at a position facing the drive roller 8 with the intermediate transfer belt 7 interposed therebetween, and the secondary transfer portion T2 is formed as a nip portion between the intermediate transfer belt 7 and the secondary transfer roller 12. ing. The secondary transfer roller 12 is a transfer means of the present embodiment for transferring a toner image from the intermediate transfer belt 7 to the recording material P. The recording material P supplied from the storage unit such as a cassette or tray is subjected to secondary transfer at the timing when the toner image supported on the intermediate transfer belt 7 reaches the secondary transfer unit T2 by the registration roller pair 13. It is sent to the unit T2. In the secondary transfer unit T2, the toner image is secondarily transferred from the intermediate transfer belt 7 to the recording material P by the secondary transfer roller 12.

The intermediate transfer unit 15 includes a belt cleaner 16 that cleans the surface of the intermediate transfer belt 7. The belt cleaner 16 is the cleaning means of the present embodiment. The belt cleaner 16 is made of an elastic material such as urethane rubber, has a cleaning blade 11 which is a blade member that abuts on the intermediate transfer belt 7 at the tip portion, and cleans the belt surface as the intermediate transfer belt 7 rotates. .. Adhesions such as secondary transfer residual toner remaining on the intermediate transfer belt 7 without being transferred to the recording material P are scraped off by the cleaning blade 11 and collected in a collection container.

The recording material P to which the toner image is transferred is then conveyed to the fixing device. The fixing device has a roller pair that sandwiches and conveys the recording material P and a heat source such as a halogen lamp, and applies heat and pressure to the toner image. As a result, the toner melts and mixes colors and adheres to the recording material P, so that a fixed image fixed on the recording material P can be obtained. The recording material P that has passed through the fixing device is discharged to the outside of the image forming device 100.

[Intermediate transfer belt]
The configuration of the intermediate transfer belt 7 for electrophotographic will be described. As shown in FIG. 2, the intermediate transfer belt 7 according to the present embodiment has a layer structure formed by two layers, a base layer 31 and a surface layer 32 (coat layer) formed on the outer peripheral side of the base layer 31. The surface 7a of the surface layer 32 is an outer peripheral surface of the intermediate transfer belt 7 that carries the toner image or is in contact with the photosensitive drum 1, the secondary transfer roller 12, the cleaning blade 11, and the recording material P (see FIG. 1).

(Base layer)
As the material constituting the base layer 31, a resin having mechanical strength and bending resistance as an intermediate transfer body is preferable. Specifically, polyamide, polyacetal, polyarylate, polycarbonate, polyphenylene ether, polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polysulphon, polyether sulfone, polyphenyl sulfide, polybutylene terephthalate, polyether ether ketone, polyfluoride. Vinylidene, polyvinyl fluoride, polyetheramide copolymer, polyurethane copolymer, polyimide, polyamideimide and the like. It is formed from one of these resins or a mixture thereof. Further, as the base layer 31, a material whose hardness does not change (or the change can be ignored) in response to the curing method of the surface layer 32 (ultraviolet rays in this embodiment) is used.

A conductive substance can be added to the base layer 31 in order to impart conductivity. As the conductive substance, carbon-based inorganic conductive particles such as carbon black, carbon fiber, and carbon nanotube, and conductive particles such as metal oxides such as zinc antimonate, zinc oxide, tin oxide, and titanium oxide are used. By adding such a conductive substance as needed, the volume resistance value of the base layer 31 is adjusted to the range of 10 ⁸ to 10 ¹² [Ω · cm]. If this volume resistance value is too large, the primary transferability or secondary transferability due to the application of a predetermined transfer bias may decrease, and if it is too small, resistance unevenness tends to be noticeable and transfer unevenness tends to be noticeable. Etc., and image defects are likely to occur. The thickness of the base layer 31 is preferably 40 μm or more and 200 μm or less from the viewpoint of mechanical strength and bending resistance.

(surface)
The surface layer 32 is mainly composed of a photocurable resin material, a photopolymerization initiator, a conductive substance and the like. Further, in order to improve the releasability, a fluororesin or the like may be added. Examples of the photocurable resin material include ultraviolet curable resins such as urethane resin, acrylic resin, epoxy resin, polyester resin, methacrylic resin, maleimide resin, oxetane resin, polyether resin, and polyvinyl ether resin. Above all, considering that the surface layer 32 rubs against other members such as a photoconductor and a cleaning blade, an acrylic resin having a high hardness is particularly preferable. Such an ultraviolet curable resin can be obtained by curing an ultraviolet curable monomer, oligomer, prepolymer, or the like.

Examples of the photopolymerization initiator include benzophenone, thioxanthone-based compound, benzyldimethylketal, α-hydroxyketone, α-hydroxyalkylphenone, α-aminoketone, α-aminoalkylphenone, monoacylphosphine oxide, and bisacylphosphinoxide. Examples thereof include radical generation type photopolymerization initiators such as hydroxybenzophenone, aminobenzophenone, titanosen-based, oxime ester, and oxyphenyl acetate.

Examples of the conductive substance include carbon-based inorganic conductive particles such as carbon black, carbon fiber and carbon nanotube, and metal oxides such as zinc antimonate, zinc oxide, tin oxide and titanium oxide.

The thickness of the surface layer 32 is preferably 1 μm or more and 20 μm or less. If the thickness of the surface layer 32 is less than 1 μm, the surface layer 32 may be worn due to the increase in the cumulative usage time due to friction with the cleaning blade 11 or the like, and the original performance of the intermediate transfer belt 7 may be impaired. There is. If the thickness of the surface layer 32 is larger than 20 μm, the flexibility of the intermediate transfer belt 7 is insufficient, and the surface layer 32 may be cracked and the bending resistance may not be satisfied.

(Production method)
The intermediate transfer belt 7 can be manufactured by the following procedure.
(A) First, a belt-shaped processed product obtained by molding the above-mentioned constituent material of the base layer 31 into an endless belt-shaped film is obtained (base layer forming step). As the molding method of the base layer 31, a known method such as an extrusion molding, an inflation method, or a centrifugal molding method can be used.
(B) Next, a surface layer coating liquid in which the above-mentioned constituent material of the surface layer 32 is dissolved and dispersed in an appropriate organic solvent is subjected to a base layer 31 by any method such as ring coating, dip coating, or spray coating. It is applied to the outer peripheral surface of the belt-shaped work piece having (coating step).
(C) The belt-shaped work piece coated with the surface coating liquid is dried for the purpose of removing the organic solvent. The drying step can be performed in an environment of about 30 to 60 ° C. so as not to induce a radical reaction.
(D) The belt-shaped work piece is irradiated with ultraviolet rays using an ultraviolet irradiation machine to cure the resin material, and a belt-shaped work piece on which the surface layer 32 is formed is obtained (irradiation step).
(E) The belt-shaped workpiece is cut to a predetermined length in the belt width direction, and the cut pieces are removed to obtain an intermediate transfer belt 7 (cutting step).

Here, in the above-mentioned cutting step, the side portion of the belt-shaped workpiece in the belt width direction is cut by a metal blade such as tungsten steel. However, when the surface layer 32 is made of a high-hardness resin as in the present embodiment, the metal blade needs to be replaced frequently because damage is accumulated on the cutting edge by repeating the cutting process, which causes a decrease in productivity. I will be there.

Therefore, in the present embodiment, by setting the surface hardness of the end positions on both sides of the surface layer 32 in the belt width direction to be smaller than the surface hardness of the central position, the merit of using the high hardness surface layer 32 is not impaired. We are trying to improve productivity. The "end position" here is the end position of the intermediate transfer belt 7 obtained by the cutting step, and refers to a position adjacent to the cut surface.

[Structure example of intermediate transfer belt and its evaluation]
Hereinafter, the configuration example (Example) of the intermediate transfer belt 7 according to the present embodiment, and the results of the evaluation test conducted using the Example and the comparative example will be described. The method for producing the intermediate transfer belt 7 used in the evaluation test is as follows.

(Base layer forming step)
The base layer 31 is made of a polyether ether ketone resin containing a conductive substance having a thickness of 100 μm, a volume resistivity of ρv = 5 × 10 ⁹ [Ω · cm], and a surface resistivity of ρs = 5 × 10 ¹² [Ω / □]. A tubular film was used. This tubular film was prepared by tubular extrusion molding, and a tubular endless belt was obtained by cutting the film to a desired length.

(Applying process)
The coating liquid for forming the surface layer 32 was prepared according to the formulation shown below.
Dipentaerythritol hexaacrylate 8.0 parts by mass Pentaerythritol tetraacrylate 17.0 parts by mass Pentaerythritol triacrylate 5.0 parts by mass Methylethylketone 47.0 parts by mass Ethylene glycol 15.0 parts by mass Antimony-doped tin oxide fine particles (Ishihara Sangyo Co., Ltd.) Made by SN-100P)
6.0 parts by mass Photopolymerization initiator (Irgacure 184 manufactured by Ciba Geigy)
2.0 parts by mass

These materials were mixed and dispersed with a stirring homogenizer, and then further dispersed with a disperser nanomizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.) to obtain a mixed and dispersed liquid. This mixed dispersion was applied to the cylindrical endless belt by the ring coating method. The belt-shaped work piece coated with the coating liquid was put into a drying oven at 80 ° C. for 1 minute to volatilize the solvent.

(Irradiation process)
Then, as shown in FIG. 3, the belt-shaped workpiece W was fitted and held in the core 41, and the core 41 was irradiated with ultraviolet rays while rotating in the circumferential direction D1 to be cured. At this time, the integrated value (integrated light amount) of the amount of ultraviolet rays irradiated to the low hardness regions 21 and 21 of the belt-shaped work piece W is set to be smaller than the integrated light amount in the high hardness region 22. However, the low hardness regions 21 and 21 are regions on both sides of the belt-shaped workpiece W in the belt width direction D2, and include cutting positions in the cutting step. The high hardness region 22 is a region located between the low hardness regions 21 and 21 and serving as a supporting surface for supporting the toner image in a state of being mounted on the image forming apparatus. The larger the integrated amount of ultraviolet rays, the more the cross-linking reaction of the resin material progresses, and the higher the surface hardness.

As a method of reducing the integrated light amount of the low hardness regions 21 and 21 as compared with the integrated light amount of the high hardness region 22, any of the following two can be used.
(1) By adjusting the installation position and angle of the mirror constituting the optical system that guides the ultraviolet rays radiated from the light source toward the belt-shaped workpiece W, the distribution of the ultraviolet rays irradiation amount in the belt width direction is made non-uniform. how to.
(2) A method in which a filter is arranged between the light source and the belt-shaped workpiece W so as to cover the low hardness region 21, and the proportion of ultraviolet rays reaching the low hardness region 21 is reduced as compared with the high hardness region 22.

In Example 1, the amount of light applied to the belt-shaped workpiece is made non-uniform by arranging the mirrors, the integrated light amount of the high hardness region 22 is 2.8 J / cm ² , and the integrated light amount of the low hardness region 21 is 1. It was set to .3 J / cm ² . At this time, the surface hardness of the obtained intermediate transfer belt 7 was 160 N / mm ^{2 at the center position in the belt width direction and 120 N / mm 2 at} the end position. The method for measuring the surface hardness will be described later.

In Example 2, the integrated light amount of the high hardness region 22 was set to 3.5 J / cm ² , and the integrated light amount of the low hardness region 21 was set to 0.5 J / cm ² . At this time, the surface hardness of the obtained intermediate transfer belt 7 was 340 N / mm ² at the center position in the belt width direction and 70 N / mm ² at the end position.

In Comparative Examples 1 to 3, unlike Examples 1 and 2, the belt-shaped workpiece W was optically designed so as to be uniformly irradiated with ultraviolet rays in the belt width direction. In Comparative Example 1, the integrated light intensity was set to 1.3 J / cm ² , and an intermediate transfer belt having a surface hardness of 120 N / mm ² was obtained. In Comparative Example 2, the integrated light intensity was set to 2.8 J / cm ² , and an intermediate transfer belt having a surface hardness of 160 N / mm ² was obtained. In Comparative Example 3, the integrated light intensity was set to 4.0 J / cm ² , and an intermediate transfer belt having a surface hardness of 480 N / mm ² was obtained.

(Cutting process)
The belt-shaped workpiece obtained by the irradiation process is fitted to the core, and while the core is rotated at 2 rpm, both ends of the belt-shaped workpiece are inserted by inserting a tungsten steel circular blade with a blade thickness of 0.3 mm. I disconnected. Then, the cut pieces were removed to obtain an intermediate transfer belt.

Common to each sample, the dimensions at the time of manufacture were set as follows (see FIG. 4). Here, a sample having medium hardness regions 23 and 23 in which the integrated light amount is adjusted so that the surface hardness between the low hardness regions 21 and 21 and the high hardness region 22 is moderate between the two is used. There is.
Width of belt-shaped work piece before cutting L ・ ・ ・ 410mm
Width of intermediate transfer belt after cutting Lb ・ ・ ・ 360 mm
Cutting width (cutting allowance) of belt-shaped workpiece La ・ ・ ・ 25 mm
Width of high hardness area Lm ・ ・ ・ 312mm
Width of low hardness region Lr ・ ・ ・ 31mm
Width of medium hardness area Ls ・ ・ ・ 18mm
Maximum image width Li ・ ・ ・ 298mm
Width of non-image area Ln ・ ・ ・ 31mm
Cleaning blade width Lc ・ ・ ・ 328mm

However, the maximum image width Li refers to the maximum length in the belt width direction of the toner image that can be formed by the image forming portions PY to PK, that is, the width of the maximum image forming region that can form an image on the intermediate transfer belt. The non-image region refers to a region on the surface of the intermediate transfer belt that does not carry the toner image (that is, an region outside the range of the maximum image width). Further, the width Lc of the cleaning blade refers to the length of the tip portion of the cleaning blade 11 that abuts on the intermediate transfer belt.

(Measurement of surface hardness)
The surface hardness of the intermediate transfer belt manufactured by the above steps was measured by a nanoindentation method compliant with ISO14577 using a microhardness meter (product name: HM2000) manufactured by Fisherscope. The measurement conditions were a maximum pushing load of 0.2 mN and a pushing time of 5 seconds. Further, in consideration of the variation in the measurement results, the measurement was performed three times at the same location, and the average value was adopted as the measurement value of the hardness.

(Evaluation method)
In order to evaluate each sample of the intermediate transfer belt, evaluation was performed from the viewpoints of ease of cutting (cuttability), wear resistance, and coat cracking.

The cutability was evaluated by measuring the cut step and straightness of the obtained intermediate transfer belt each time the belt-shaped workpiece W was cut by the cutting step, and evaluated according to the following criteria. However, the cut step indicates the presence or absence of a step on the cut surface, and when the cut position (the position of the cut surface in the belt width direction) at a predetermined number of measurement points arranged at equal intervals in the circumferential direction is measured. , Refers to the absolute value of the difference between the measured values for adjacent measurement points. Further, the straightness refers to the degree of variation in the cutting position when the cutting positions at a predetermined number of measurement points arranged at equal intervals in the circumferential direction are measured.
◯: When less than 30 samples have a cut step or straightness that does not meet the standard value when 100 intermediate transfer belts are cut ×: When 100 intermediate transfer belts are cut, the cut step or straightness is the standard value. When 30 or more samples that do not meet the requirements are generated

The standard values in the evaluation test shown in Table 1 are as follows. Regarding the cut step, the number of measurement points was set to 3100, and the standard value was satisfied when the cut step between adjacent measurement points was 100 μm or less (the maximum cut step was 100 μm or less). Regarding the straightness, the number of measurement points is 31,300, and the variation of the cutting position in the belt width direction is 150 μm or less (the difference between the maximum value and the minimum value of the cutting position is 150 μm for the coordinate axis extending in one direction in the belt width direction). The following) is assumed to satisfy the standard value.

The wear resistance was evaluated by attaching each sample of the intermediate transfer belt to the evaluation device and performing a durability test in which an image was formed on a large number of recording materials. The evaluation environment was a high temperature and high humidity (32.5 ° C / 85% RH) environment. As an evaluation device, a Canon color multifunction device (product name iRC2620) was used, and the intermediate transfer belt of the present embodiment was attached instead of the polyimide intermediate transfer belt attached to the device. After outputting 100,000 images, the scraping of the surface layer 32 of the intermediate transfer belt was evaluated according to the following criteria.
◯: The amount of decrease in the film thickness of the surface layer 32 is less than 1 μm compared to before the durability test ×: The amount of decrease in the film thickness of the surface layer 32 is 1 μm or more compared to before the durability test.

The pressing force (linear pressure) per unit length in the longitudinal direction (belt width direction) at the contact portion between the intermediate transfer belt 7 and the urethane rubber cleaning blade 11 is set to 580 mN / cm. did. Further, the cleaning blade 11 was not coated with the lubricant as in iRC2620. The weight average particle size of the toner used was 5.0 μm, and the average circularity was 0.985.

In the evaluation of coat cracks, the surface of the intermediate transfer belt obtained by the cutting step was visually observed, and the case where the cracks on the surface layer 32 could not be visually recognized was evaluated as ◯, and the case where the cracks could be visually observed was evaluated as x. The evaluation results of each sample are summarized in Table 1.

As shown in Table 1, in Examples 1 and 2, the cuttability at the time of manufacture and the wear resistance at the time of use were good, and the coat crack on the surface did not occur. On the other hand, the intermediate transfer belt of Comparative Example 1 having a surface hardness of less than 160 N / mm ² at the center position has good cutability, but the amount of decrease in the film thickness of the surface layer 32 is large, and Examples 1 and 2 have a large decrease in film thickness. The wear resistance was inferior to that of. Further, although the intermediate transfer belt of Comparative Example 2 having a surface hardness at the end position exceeding 120 N / mm ² has high wear resistance, the deterioration of the metal blade progresses quickly, and compared with Examples 1 and 2. The productivity at the time of manufacture was inferior. Further, the intermediate transfer belt of Comparative Example 3 having a surface hardness of more than 340 N / mm ² had coat cracks. It should be noted that the wear resistance of Comparative Example 3 has not been evaluated because the one in which the coat is cracked is not suitable for use as an intermediate transfer belt.

From the above, the surface hardness of the first region including the maximum image forming region of the intermediate transfer belt is set to 160 N / mm ² or more and 340 N / mm ² or less, and the surface hardness of the second region including the end portion of the intermediate transfer belt is set. It can be seen that it should be set to 70 N / mm ² or more and 120 N / mm ² or less. With such a setting, it becomes possible to provide an intermediate transfer belt capable of improving productivity at the time of manufacturing while ensuring wear resistance.

Further, it is preferable to set the average value of the surface hardness within the range of the maximum image width Li of the toner image carried by the intermediate transfer belt to 160 N / mm ² or more and 340 N / mm ² or less. In Examples 1 and 2, the hardness is set to be constant (160 N / mm ² or 340 N / mm ² ) over the high hardness region 22 having a width Lm wider than the maximum image width Li, and thus this condition is satisfied. ing. In the present embodiment, the variation in hardness (standard deviation of the measured value of hardness) in the high hardness region 22 is set to 30 N / mm ² or less. Further, the variation in hardness is preferably 20 N / mm ² or less, and more preferably the variation in hardness is 10 N / mm ² or less. With such a setting, the wear of the intermediate transfer belt 7 is reduced by the surface layer 32 having a high hardness, at least in the region serving as the supporting surface of the toner image, so that the performance of the intermediate transfer belt 7 is maintained for a long period of time. Is possible.

Further, the intermediate transfer belt of the present embodiment is located in the first region (high hardness region 22) including the central position in the belt width direction and outside the first region, and the end position of the belt (cutting position in the cutting step). ) Is included in the second region (low hardness regions 21 and 21). The hardness of the surface of the first region can be regarded as constant except for the tolerance at the time of manufacturing. At this time, the ratio of the area occupied by the first region is set to be more than half of the surface of the entire intermediate transfer belt (Lm / L ≧ 1/2). This makes it possible to provide an intermediate transfer belt which has high wear resistance and secures a first region suitable as a surface for supporting a toner image. It is more preferable to set the length (Lm) of the first region in the belt width direction to a size widely used as a recording material (for example, 297 mm, which is the length of the long side of A4).

Further, in the present embodiment, the width Lb of the intermediate transfer belt> the width Lc of the cleaning blade, and the end position of the intermediate transfer belt 7 is located outside the cleaning blade 11 in the belt width direction (see FIG. 4). .. Usually, the hardness is distributed with a gradient from the set hardness of the high hardness region 22 to the set hardness of the low hardness region 21. Therefore, it is preferable that the range of contact with the cleaning blade 11 is set to at least a region having a higher hardness than the low hardness region 21. That is, both ends of the tip of the cleaning blade 11 in the belt width direction are arranged inside the inner ends of the low hardness regions 21 and 21, and the low hardness region 21 does not come into contact with the cleaning blade 11. Is preferable.

In the present embodiment, the medium hardness region 23 is provided between the high hardness region 22 and the low hardness region 21, and the end portion of the cleaning blade 11 abuts on the medium hardness region 23. The hardness of the medium hardness region 23 is set so as to satisfy the relationship of "hardness of the low hardness region 21 <hardness of the medium hardness region 23 <hardness of the high hardness region 22". However, the range of the medium hardness region may be narrower than the range shown in the figure. Further, the high hardness region 22 may be extended without providing the medium hardness region 23 so that the end portion of the cleaning blade 11 comes into contact with the high hardness region 22.

In this embodiment, the target hardnesses of the low hardness region 21 and the high hardness region 22 are set respectively, and a configuration is adopted in which the variation of the measured value of the hardness is allowed within a range of a predetermined value or less with respect to the target hardness. However, the hardness of the belt surface may be continuously changed. That is, when the hardness of the belt surface is measured along the belt width direction, the graph may have a smooth curve instead of a stepped shape. In this case, the first region refers to a region including the entire area of the maximum image forming region and having a measured hardness of 160 N / mm ² or more and 340 N / mm ² or less. Further, the second region refers to a region including the end portion of the intermediate transfer belt and having a measured hardness of 70 N / mm ² or more and 120 N / mm ² or less.

Further, in the present embodiment, the photocurable resin is used as the constituent material of the surface layer 32, but the present invention is not limited to this, and for example, a thermosetting resin may be used as the constituent material of the surface layer 32. In this case, by controlling the temperature distribution in the curing reaction, the surface hardness of the cutting position of the belt-shaped workpiece can be set lower than that of the central position.

1 ... Photoreceptor / 7 ... Intermediate transfer belt / 11 ... Blade member (cleaning blade) / 12 ... Transfer means (secondary transfer roller) / 16 ... Cleaning means (belt cleaner) / 21 ... Second region (low hardness region) / 22 ... 1st region (high hardness region) / 31 ... Base layer / 32 ... Surface layer / 100 ... Image forming apparatus / Li ... Maximum image width / PY, PM, PC, PK ... Image forming part / W ... Belt-shaped work piece

Claims (6)

An intermediate transfer belt for electrophotographic
With the base layer,
It has a surface layer formed on the outer peripheral side of the base layer, and has.
The hardness of the surface of the surface layer measured by the nanoindentation method is
In the belt width direction, it is 160 N / mm ² or more and 340 N / mm ² or less in the first region including the entire area of the maximum image forming region, and is outside the first region in the belt width direction and of the intermediate transfer belt. In the second region including the end, it is 70 N / mm ² or more and 120 N / mm ² or less.
An intermediate transfer belt characterized by that. The surface layer contains a photocurable resin material.
The intermediate transfer belt according to claim 1. The surface layer has a variation in surface hardness of 30 N / mm ² or less in the first region.
The intermediate transfer belt according to claim 1 or 2. An image forming portion having a photoconductor and forming a toner image on the surface of the photoconductor,
The intermediate transfer belt according to any one of claims 1 to 3, wherein the toner image formed by the image forming unit is transferred.
A transfer means for transferring a toner image supported on the intermediate transfer belt to a recording material is provided.
The average hardness of the surface of the surface layer in the maximum image forming region is 160 N / mm ² or more and 340 N / mm ² or less.
An image forming apparatus characterized in that. It has a blade member that abuts on the intermediate transfer belt at the tip portion, and further comprises a cleaning means for cleaning the surface of the intermediate transfer belt as the intermediate transfer belt rotates.
In the belt width direction, both ends of the tip portion of the blade member are arranged inside the inner end portion of the second region.
The image forming apparatus according to claim 4. A method for manufacturing intermediate transfer belts for electrophotographic photography.
The base layer forming step of forming the base layer in a belt shape,
A coating step of applying a coating liquid containing a photocurable resin material to the outer peripheral side of the base layer, and
An irradiation step of irradiating the surface of the belt-shaped work piece coated with the coating liquid with light, and
Including a cutting step of cutting the side portion of the belt-shaped workpiece irradiated with light in the belt width direction.
The hardness of the surface of the intermediate transfer belt measured by the nanoindentation method is 160 N / mm ² or more and 340 N / mm ² or less in the first region including the maximum image forming region in the belt width direction, and the first in the belt width direction. Irradiate the second region of the belt-shaped work piece in the irradiation step so that the second region outside the first region and including the cutting position in the cutting step is 70 N / mm ² or more and 120 N / mm ² or less. The amount of light to be applied is set to a value smaller than the amount of light emitted to the first region.
A method for manufacturing an intermediate transfer belt.

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