JP2013238757A - Intermediate transfer belt and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer belt capable of suppressing the occurrence of a developer non-transfer area while maintaining conduction characteristics, and an image forming apparatus capable of forming high-quality images having substantially no developer non-transfer area and uniform density.SOLUTION: Provided is an intermediate transfer belt 1 that contains a polyamide-imide resin as a main component, and has a resistance ratio of the volume resistance value of an outer surface A(Ω cm) to the surface resistance value of an inner surface B(Ω/sq.) of 3 to 1000. Also provided is an image forming apparatus that includes the intermediate transfer belt 1.

Description

  The present invention relates to an intermediate transfer belt and an image forming apparatus. More specifically, the present invention relates to an intermediate transfer belt and a developer non-transfer area that can suppress the occurrence of a developer non-transfer area and maintain current-carrying characteristics. The present invention relates to an image forming apparatus capable of forming a high quality image.

  Various image forming apparatuses using an electrophotographic system are employed in printers such as laser printers and video printers, copiers, facsimiles, and multi-function machines thereof. An image forming apparatus using an electrophotographic method includes a direct transfer method in which a developer image developed on an image carrier is directly transferred to a recording material, and a developer image is transferred to an intermediate transfer belt and then recorded from the intermediate transfer belt. There are intermediate transfer methods that transfer to the body.

  In the direct transfer method, an electrostatic latent image formed on an image carrier such as a photosensitive drum is developed with a developer supplied from a developer carrier provided in the developing unit, and a voltage is applied to the transfer unit. The developed developer image is transferred onto the recording medium that is electrostatically attracted to the transfer conveyance belt and conveyed between the image carrier and the transfer unit, and the recording medium onto which the developer image has been transferred is pressurized. This is a system in which a transferred developer image is fixed as an image or a character on a recording medium by pressing or heat pressing with a roller and a fixing roller.

  In the intermediate transfer method, for example, an electrostatic latent image formed on an image carrier is developed with a developer, and the developed developer image is transferred to an intermediate transfer belt that is in contact with or pressed against the image carrier (primary transfer). Then, the developer image transferred to the intermediate transfer belt is transferred to the recording medium (secondary transfer), and the recording medium on which the developer image has been transferred is pressure-bonded or heat-pressed by a pressure roller and a fixing roller, and transferred. In this method, the developed developer image is fixed on the recording medium as an image or a character.

  An intermediate transfer belt attached to such an intermediate transfer type image forming apparatus is one of the characteristics in which electrical characteristics are important, like other endless belts attached to the image forming apparatus, such as an intermediate transfer belt. Become.

As an endless belt paying attention to electrical characteristics, for example, Patent Document 1 discloses that “the thermoplastic resin is 97 to 75% by weight and carbon black is 3 to 25% by weight, and the surface resistance of the front and back surfaces is 1 × 10 ⁸ to 1”. × 10 ¹² Ω / □, and the volume resistance value after continuously applying a voltage of 0.7 V / μm for 1 hour is 10% or more of the volume resistance value after 10 seconds of application. "Seamless belt" is described (claim 1 etc.).

Patent Document 2 states that “a resin-made annular body satisfying the following formulas (1) to (3).
11.6 LogΩ / □ ≦ ρs ≦ 14.0 LogΩ / □ (1)
10.3 LogΩ · cm ≦ ρv ≦ 14.0 LogΩ · cm (2)
9.8 LogΩ / □ ≦ ρexs ≦ 13.4 LogΩ / □ (3)
(In the above formulas (1) to (3), ρs is the surface resistivity of the outer circumferential surface of the annular body, ρv is the volume resistivity of the outer circumferential surface of the annular body, and ρexs is the creeping resistance of the surface of the circumferential surface of the annular body. The rate is expressed respectively.) "(Claim 1 etc.).

Note that the transfer / conveying belt is related to the transfer / conveying belt but not the intermediate transfer belt. For example, Japanese Patent Application Laid-Open No. H10-260667 discloses that a horizontal black belt-like defect suppresses an elephant (0005). Column), “Image having a transfer conveyance belt that conveys transfer paper to a drum-shaped photoconductor, transfers toner from the photoconductor to the transfer paper by an electric field, and conveys the transfer paper by electrostatic adsorption In the forming apparatus, the volume resistance Rvol of the transfer conveyance belt is in the range of 10 ⁸ to 10 ¹¹ Ω, and the relationship between the volume resistance Rvol and the surface resistance ρsurf of the inner surface layer is (ρsurf) <= 7E + 20 (Rvol) ^{−1. No. 1} is satisfied ”(Claim 1). Incidentally, it is known that the surface resistance value of a general transfer conveyance belt is 10 ¹² to 10 ¹⁵ Ω / □, and the cited document 3 states that “the surface resistance of the transfer conveyance belt is 10 ⁹ to 10 ¹¹ Ω. ”(Claim 2 etc.), but there is no description regarding the actual measurement value, and the basis for this is unknown.

  Further, in order to solve the problems peculiar to the conveying belt for conveying the recording medium, the invention focuses on the resistance value. However, Patent Document 4 discloses that “an inner layer containing a polyimide resin containing a conductive substance, and a surface resistivity”. Is provided with an outer layer that is higher by one digit or more than the surface resistivity of the inner layer, and the overall volume resistivity is a common logarithmic value of 7 to 12 (log Ω · cm). ).

  By the way, in an intermediate transfer type image forming apparatus, when an image is formed on the surface of the recording medium, the developer is not transferred to the 100% printed black solid partial image which is a part of this image, and the surface of the recording medium is transferred. In some cases, a developer non-transfer area (which may be referred to as white spots) is exposed. This developer non-transfer area is particularly in an environment of low temperature and low humidity (for example, 5 to 20% RH at 0 to 10 ° C.) when a high voltage is applied to the intermediate transfer belt when printing paper with high electrical resistance is used. This is likely to occur when a high voltage is applied to the intermediate transfer belt. In addition, a voltage is applied to the intermediate transfer belt at least at the time of primary transfer and secondary transfer of the developer. However, when the voltage is continuously applied, the resistance value increases and the current transfer characteristic that the developer transfer property is deteriorated is deteriorated. There is.

  Such a developer non-transfer area and a decrease in energization characteristics are likely to occur in the “transfer conveyor belt” in Patent Document 3 and the “conveyor belt” in Cited Document 4. Since these belts generally use rubber having a low elastic modulus as a base material, it is highly possible that the belt cannot be used as an intermediate transfer belt due to the possibility that the belt stretches and a transfer image shifts when tension is applied. Inferred with gender.

Japanese Patent Laid-Open No. 7-172613 JP 2009-258708 A JP 2002-268408 A JP 2010-208033 A

  An object of the present invention is to provide an intermediate transfer belt that can suppress the occurrence of a developer non-transfer area and maintain current-carrying characteristics.

  Another object of the present invention is to provide an image forming apparatus capable of forming a high-quality image having substantially no developer non-transfer area and a uniform density.

As means for solving the problems,
Claim 1 contains a polyamideimide resin as a main component, and the resistance ratio (A / B) of the volume resistance value A (Ω · cm) of the outer surface to the surface resistance value B (Ω / □) of the inner surface is 3 An intermediate transfer belt of ~ 1000,
Claim 2 is the intermediate transfer belt according to claim 1, wherein the intermediate transfer belt contains a conductivity imparting agent so that the outer surface side has a lower content than the inner surface side.
Claim 3 is the intermediate transfer belt according to claim 2, wherein the conductivity-imparting agent has a difference between the content of the outer surface and the content of the inner surface of 2 to 8% by mass.
According to a fourth aspect of the present invention, the conductivity imparting agent is contained in the outer surface side in an amount of 10 to 20% by mass when the total mass of the polyamideimide resin and the conductivity imparting agent is 100% by mass, and on the inner surface side. The intermediate transfer belt according to claim 2, which is contained in an amount of 15 to 25% by mass,
The volume resistance value A (Ω · cm) is in a range of 1 × 10 ⁸ to 1 × 10 ¹³ and the surface resistance value B (Ω / □) is 1 × 10 ⁹ to 1 ×. an intermediate transfer belt according to any one of claims 1 to 4 in 10 ¹² in the range of,
6. The intermediate transfer belt according to claim 1, wherein the intermediate transfer belt has a multilayer structure including an outer layer including the outer surface and an inner layer including the inner surface, which are directly or indirectly laminated. Yes,
Claim 7 is the intermediate transfer belt according to claim 6, wherein both the outer layer and the inner layer are mainly composed of a polyamideimide resin.
An eighth aspect of the present invention is an image forming apparatus including the intermediate transfer belt according to any one of the first to seventh aspects.

  The intermediate transfer belt according to the present invention contains a polyamide-imide resin as a main component, and the resistance ratio (A / cm) of the volume resistance value A (Ω · cm) of the outer surface to the surface resistance value B (Ω / □) of the inner surface. Since B) is 3 to 1000, even if a high voltage is applied in a low temperature and low humidity environment, it is difficult to generate a developer non-transfer area, and the resistance value increases even if the voltage is applied for a long time. Therefore, the initial energization characteristics can be maintained. As described above, the intermediate transfer belt according to the present invention can suppress abnormal discharge from the outer surface even when a high voltage is applied by setting the volume resistance value A of the outer surface high. Therefore, according to the present invention, it is possible to provide an intermediate transfer belt that can suppress the occurrence of a developer non-transfer area and maintain current-carrying characteristics when mounted on an image forming apparatus.

  The image forming apparatus according to the present invention includes the intermediate transfer belt according to the present invention. Therefore, according to the present invention, it is possible to provide an image forming apparatus capable of forming a high-quality image having substantially no developer non-transfer area and a uniform density.

FIG. 1 is a schematic side view showing an intermediate transfer belt which is an embodiment of an intermediate transfer belt according to the present invention. FIG. 2 is a schematic view of a tandem type color image forming apparatus which is an example of the image forming apparatus according to the present invention. FIG. 3 is a schematic view of a multi-pass color image forming apparatus which is an example of the image forming apparatus according to the present invention.

  An intermediate transfer belt which is an embodiment of an intermediate transfer belt according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the intermediate transfer belt 1 includes an inner layer 2 as a belt base and an outer layer 3 that is directly laminated on the outer peripheral surface of the inner layer 2. In this invention, the “outer layer” is an “outer surface, that is, a layer including the outermost periphery” and is a layer on the side to which the developer is transferred when the intermediate transfer belt is mounted on the image forming apparatus. Is an “inner surface, ie, a layer including the innermost circumference”, and is a layer on the side that comes into contact with the intermediate transfer support roller without transferring the developer when the intermediate transfer belt is mounted on the image forming apparatus.

  The intermediate transfer belt 1 has a resistance ratio (A) of the volume resistance value A (Ω · cm) of the outer surface, that is, the outer surface of the outer layer 3, to the surface resistance value B (Ω / □) of the inner surface, that is, the inner surface of the inner layer 2. / B) (Ω · cm / (Ω / □)) is 3 to 1000. In the present invention, the reason why the resistance ratio (A / B) is adopted is that the volume resistance value A of the outer layer 3 and the volume resistance value A ′ of the inner layer 2 show different values, and in addition to the surface resistance value B. It has been found that when a resistance ratio (A / B) that defines the volume resistance value A with respect to the surface resistance value B is adopted instead of the volume resistance value A ′, a direct and reliable relationship with the problem of the present invention can be defined. In particular.

  In the intermediate transfer belt 1, when the resistance ratio (A / B) between the volume resistance value A and the surface resistance value B exceeds 1000, the resistance value of the intermediate transfer belt 1 is applied when a voltage is applied to the intermediate transfer belt 1 for a long time. May gradually increase with the application time, resulting in inferior developer transferability and reduced energization characteristics. On the other hand, when the resistance ratio (A / B) is less than 3, when a high voltage is applied, particularly when a high voltage is applied in a low temperature and low humidity environment, a developer non-transfer area is likely to occur. A high-quality image may not be formed. It is preferable that the resistance ratio (A / B) is 10 to 100 in that the maintenance of the current-carrying characteristics and the suppression of the occurrence of the developer non-transfer area can be balanced at a high level.

  As shown in FIG. 1, the intermediate transfer belt 1 has a two-layer structure in which an inner layer 2 and an outer layer 3 are laminated, but the intermediate transfer belt according to the present invention may have a single-layer structure. It may be a multilayer structure of three or more layers. In particular, since both the inner layer 2 and the outer layer 3 of the intermediate transfer belt 1 contain a polyamideimide resin as a main component, if the boundary between them is not clear, a substantially two-layer structure can be used. Sometimes it looks like a layered structure. Therefore, the layer configuration of the intermediate transfer belt according to the present invention is not particularly limited as long as it satisfies the relational expression described later. In the present invention, when the intermediate transfer belt 1 has a multilayer structure, the resistance ratio (A / B) can be easily satisfied and the folding resistance of the intermediate transfer belt is improved. The reason for this is that a difference occurs in the stretchability of each layer by adopting a multilayer structure, and the polyamideimide resin contained in each layer and the conductivity imparting agent contained as desired, for example, carbon black and polyamideimide resin have a synergistic effect. The inventor of the present invention speculates that the molecular structure is improved in a straight chain by the generation. “Containing polyamideimide resin as a main component” means that the polyamideimide resin is contained at the maximum content in the intermediate transfer belt, that is, the matrix resin forming the inner layer and the outer layer.

  The width, the inner peripheral diameter, and the total thickness of the intermediate transfer belt 1 are appropriately set according to the characteristics of the intermediate transfer belt 1 and the like. As an example, for example, the width of the intermediate transfer belt 1 is 200 to 350 mm, and the inner peripheral diameter is 200 to 2,500 mm. Further, the overall thickness of the intermediate transfer belt 1 is usually preferably 50 to 300 μm, more preferably 60 to 200 μm, and particularly preferably 70 to 100 μm, for example. When the overall thickness of the intermediate transfer belt 1 is within the above range, mechanical strength and flexibility can be ensured, and the durability is excellent. The thickness of the intermediate transfer belt 1 is measured in the same manner as the inner layer 2.

  The intermediate transfer belt 1 contains a conductivity-imparting agent, and the content on the outer surface side of the conductivity-imparting agent is lower than the content on the inner surface side. Thus, when the content rate of the electroconductivity imparting agent is set, the resistance ratio (A / B) can be satisfied. Here, the “outer surface side” refers to the outer layer when the intermediate transfer belt 1 has a multilayer structure, and in the region from the outer surface to a depth of 20 μm when the intermediate transfer belt 1 has a single layer structure. “Inner surface side” means an inner layer when the intermediate transfer belt 1 has a multi-layer structure, and an area from the inner surface to a depth of 20 μm when the intermediate transfer belt 1 has a single-layer structure. . By having the resistance ratio (A / B) within the above range, the intermediate transfer belt 1 can be obtained by combining the conductivity imparting agent between the content ratio on the outer surface side and the content ratio on the inner surface side. It is preferable to contain so that a difference may be 2-8 mass%, and it is especially preferable to contain so that it may become 2-7 mass%.

  In the intermediate transfer belt 1, the conductivity imparting agent is preferably contained in the outer surface side in an amount of 10 to 20% by mass when the total mass of the polyamideimide resin and the conductivity imparting agent is 100% by mass. It is particularly preferable that it is contained in an amount of ˜19% by mass. On the other hand, it is preferably contained in an amount of 15-25% by mass on the inner surface side, and particularly preferably contained in an amount of 16-24% by mass. When the conductivity imparting agent is contained in the outer surface side and the inner surface side at the above-described content, in addition to the improvement in elongation and tear strength, there is an effect that high folding resistance is also exhibited.

The conductivity imparting agent may be any component that imparts conductivity to the intermediate transfer belt 1, and examples thereof include conductive powder. As the conductive powder, for example, in addition to conductive carbon such as ketjen black and acetylene black, rubber carbons such as SAF, ISAF, HAF, FEF, GPF, SRF, FT and MT, titanium oxide, and oxidation Examples thereof include metals such as zinc, nickel, copper, silver, germanium, metal oxides, conductive polymers such as polyaniline, polypyrrole, and polyacetylene, and nanoparticles. Moreover, the said ion conductive agent can also be used as an electroconductivity imparting agent. Among these, conductive carbon and carbon for rubber are preferable, and carbon black is particularly preferable. As the conductivity-imparting agent, one of these various substances can be used alone, or two or more of them can be used in combination. A preferable shape of the conductivity-imparting agent is spherical or irregular. The size of the particles of the conductivity-imparting agent having a spherical or irregular shape is preferably about 0.01 to 10 μm as the primary particle diameter. If conductive agent is carbon black, the BET specific surface area, strong correlation between the primary particle diameter is preferably ^{50~300m 2 / g, 100~200m 2 /} g is more preferable.

  The intermediate transfer belt 1 will be described in detail. The inner layer 2 is formed by curing a resin composition for an inner layer, which will be described later, and has a single-layer structure containing a polyamideimide resin, a conductivity imparting agent, and various additives as required. The inner layer 2 has an appropriate width, inner peripheral diameter, and thickness appropriately set according to the characteristics of the intermediate transfer belt 1 and the like, and may be the same thickness as the outer layer 3 described later, or may be thinner or thicker than the outer layer 3. May be. As thickness of the inner layer 2, it is preferable that it is 20-200 micrometers, for example, it is more preferable that it is 25-170 micrometers, and it is especially preferable that it is 30-90 micrometers. When the thickness of the inner layer 2 is within the above range, the mechanical strength and flexibility of the intermediate transfer belt 1 can be ensured, and the durability of the intermediate transfer belt 1 is excellent. The thickness of the inner layer 2 is measured or calculated as follows. First, the total thickness of the intermediate transfer belt 1 is measured using a contact-type film thickness meter or a non-contact-type film thickness meter such as an overcurrent film thickness meter (trade name “CTR-1500E”, manufactured by Sanko Electronics Co., Ltd.) taking measurement. Next, the cross section of the intermediate transfer belt 1 is observed with, for example, a laser microscope, the boundary between the inner layer 2 and the outer layer 3 is specified, the thickness ratio of each layer is calculated, and the inner layer 2 is calculated from this thickness ratio and the total thickness. Measure or calculate thickness. In addition, when the boundary between the inner layer 2 and the outer layer 3 cannot be specified, the inner layer 2 and the outer layer 3 have the same thickness for convenience.

The inner layer 2 has a surface resistance value B (Ω / □) of its inner surface, that is, a surface resistance value B (Ω / □) measured from its inner surface, at a temperature of 24 ° C. and a relative humidity of 50%. It is preferably in the range of 10 ⁹ to 10 ¹² , particularly preferably in the range of 10 ⁹ to 10 ¹¹ . If the inner layer 2 has a surface resistance value within the above range, the resistance ratio (A / B) can be easily adjusted within the above range, and the resistance can be stabilized and the image quality can be improved. The surface resistance value of the inner layer 2 is determined by using a high resistivity meter “Hiresta-UP” (trade name, manufactured by Mitsubishi Chemical Corporation, URS probe) in a state where the URS probe is in contact with the inner surface of the inner layer 2. According to K6911, it can be obtained by measuring the surface resistance value when a voltage of 500 V is applied for 10 seconds. In the present invention, the reason why the surface resistance value B (Ω / □) of the inner surface is measured is that measurement is easy and variation in measured values is small.

The inner layer 2 has a volume resistance value A ′ (Ω · cm) of its inner surface, that is, a volume resistance value A ′ (Ω · cm) as measured from its inner surface, at a temperature of 24 ° C. and a relative humidity of 50%. Is preferably in the range of 10 ⁷ to 10 ¹² , particularly preferably in the range of 10 ⁸ to 10 ¹¹ . When the inner layer 2 has a volume resistance value in the above range, there is an effect that resistance is stabilized and image quality is improved. The volume resistance value of the inner layer 2 is measured in a state where the URS probe is brought into contact with the inner surface of the inner layer 2 using a high resistivity meter “Hiresta-UP” (trade name, manufactured by Mitsubishi Chemical Corporation, URS probe). A rubber sheet (140 mm × 240 mm × 1 mm (thickness), volume resistance value 10 ¹ Ω · cm or less, JIS A hardness 61) is placed on the metal surface of a register table ULF (product name, manufactured by Mitsubishi Chemical Corporation), It can be determined by measuring the surface resistance value when a voltage of 100 V is applied for 10 seconds. Specifically, a registration table ULF is connected to a switch box U type (product name, manufactured by Mitsubishi Chemical Corporation), and a conductive rubber sheet, an intermediate transfer belt, and a URS probe are arranged in this order on the metal surface of the registration table ULF for measurement. . The URS probe and the high resistivity meter are connected to the switch box U type.

  The outer layer 3 is formed by curing a resin composition for an outer layer, which will be described later, and has a single-layer structure containing a polyamideimide resin, a conductivity imparting agent, and various additives as required. In the intermediate transfer belt 1 in which the relationship with the developer is important and the relationship with the developer is important because the relationship with the recording material is hardly required because the recording material is not held or conveyed when mounted on the image forming apparatus. If it contains a polyamideimide resin, the developer can be transferred and carried as desired on the outer surface thereof, and the function as the intermediate transfer belt 1 can be sufficiently exhibited. Specifically, the outer layer 3 is formed of polyamide-imide resin assuming the electrical characteristics required for the intermediate transfer belt 1, and the electrical characteristics sufficiently satisfy the required characteristics, for example, with fluororesin or silicone rubber. I can't.

  The outer layer 3 has an appropriate width, inner peripheral diameter, and thickness appropriately set according to the characteristics of the intermediate transfer belt 1, and may be the same thickness as the inner layer 2, or may be thinner or thicker than the inner layer 2. Good. As thickness of the outer layer 3, it is preferable that it is 20-200 micrometers, for example, it is more preferable that it is 25-170 micrometers, and it is especially preferable that it is 30-90 micrometers. When the thickness of the outer layer 3 is within the above range, the mechanical strength and flexibility of the intermediate transfer belt 1 can be ensured, and the durability of the intermediate transfer belt 1 is excellent. The thickness of the outer layer 3 can be measured or calculated in the same manner as the inner layer 2.

The outer layer 3 has a surface resistance value B ′ (Ω / □) of its outer surface under conditions of a temperature of 24 ° C. and a relative humidity of 50%, that is, a surface resistance value B ′ (Ω / □) measured from its inner surface. Is preferably in the range of 10 ⁹ to 10 ¹³ , particularly preferably in the range of 10 ⁹ to 10 ¹² . When the outer layer 3 has a surface resistance value B ′ within the above range, it has an effect of stabilizing the resistance and improving the image quality. The surface resistance value of the outer layer 3 is determined by using a high resistivity meter “Hiresta-UP” (trade name, manufactured by Mitsubishi Chemical Corporation, URS probe) in a state where the URS probe is brought into contact with the front surface of the outer layer 3. According to K6911, it can be obtained by measuring the surface resistance value when a voltage of 500 V is applied for 10 seconds.

The outer layer 3 has a volume resistance value A (Ω · cm) of its outer surface at a temperature of 24 ° C. and a relative humidity of 50%, that is, a volume resistance value A (Ω · cm) of 10 measured from its outer surface. ^It is preferably in the range of ⁸ to 10 ¹³ , particularly preferably in the range of 10 ⁹ to 10 ¹² . When the outer layer 3 has a volume resistance value in the above range, the resistance ratio (A / B) can be easily adjusted within the above range, and the resistance can be stabilized and the image quality can be improved. The volume resistance value A of the outer layer 3 is a state in which the URS probe is brought into contact with the front surface of the outer layer 3 using a high resistivity meter “Hiresta-UP” (trade name, manufactured by Mitsubishi Chemical Corporation, URS probe). A conductive rubber sheet (140 mm × 240 mm × 1 mm (thickness), volume resistance value 10 ¹ Ω · cm or less, JIS A hardness 61) is placed on the metal surface of a register table ULF (product name, manufactured by Mitsubishi Chemical Corporation). , By measuring the surface resistance value when a voltage of 100 V is applied for 10 seconds. Specifically, a registration table ULF is connected to a switch box U type (product name, manufactured by Mitsubishi Chemical Corporation), and a conductive rubber sheet, an intermediate transfer belt, and a URS probe are arranged in this order on the metal surface of the registration table ULF for measurement. . This URS probe and high resistivity meter are connected to a switch box U type. In the present invention, the reason why the volume resistance value A (Ω · cm) of the outer surface is measured is that measurement is easy and variation in measured values is small.

  The surface resistance value and volume resistance value of the inner layer 2 and the outer layer 3 can be adjusted by, for example, the type and content of the conductivity-imparting agent and / or the molding conditions of the inner layer 2 or the outer layer 3.

  As shown in FIG. 1, the intermediate transfer belt 1 has a two-layer structure in which an outer layer 3 having the same thickness as the inner layer 2 is directly laminated on the outer peripheral surface of the inner layer 2. Therefore, the outer layer 3 has the same inner diameter as the outer diameter of the inner layer 2, and has the same width as the width of the inner layer 2.

  A method for manufacturing the intermediate transfer belt according to the present invention will be described. The intermediate transfer belt according to the present invention only needs to have a resistance ratio (A / B) in the above range. For example, the resistance ratio (A / B) indicates the content of the conductivity-imparting agent on the outer surface side and the inner side. It can be adjusted by making it different from the surface side. As described above, as a method of making the content of the conductivity imparting agent different between the outer surface side and the inner surface side, specifically, two types of polyamideimide compositions having different content rates of the conductivity imparting agent are successively used. Examples thereof include a method of forming an endless shape, a method of laminating an endless molded product formed of each polyamideimide composition, and the like. Hereinafter, as a method for producing an intermediate transfer belt according to the present invention, a method of continuously molding two kinds of polyamideimide compositions in an endless manner (hereinafter referred to as one production method) will be described. .

  In one manufacturing method, two types of polyamideimide compositions, that is, an inner layer resin composition that forms the inner surface side and an outer layer resin composition that forms the outer surface side are prepared. Each of these resin compositions contains a polyamideimide resin, a conductivity imparting agent, and various additives as desired. Among the polyamide-imide resins, aromatic polyamide-imide resins are preferable because they have excellent mechanical properties such as strength, flexibility, dimensional stability, and heat resistance.

  The aromatic polyamideimide resin can be produced by a diisocyanate method in which a tricarboxylic acid anhydride and a diisocyanate compound are reacted, and the diisocyanate method is excellent in terms of availability of raw materials, reactivity, and a small amount of byproducts. In addition to the aromatic polyamideimide resin produced by the diisocyanate method, an aromatic polyamideimide resin produced using a diamine compound instead of the diisocyanate compound can be used as long as the polycondensation reaction can be suitably advanced. preferable. An aromatic polyamideimide resin obtained using a diamine compound has a high Young's modulus and is suitable as a resin contained in a resin composition forming an endless belt. Moreover, the aromatic polyamide-imide resin in which part of the tricarboxylic acid anhydride is replaced with tetracarboxylic dianhydride to increase the imide bond is excellent in moisture resistance. The aromatic polyamideimide resin can be easily synthesized by reacting in an appropriate solvent under normal pressure and at normal temperature or under heating.

  The tricarboxylic acid anhydride is preferably an aromatic tricarboxylic acid anhydride, such as trimellitic acid anhydride, 3,4,4′-diphenyl ether tricarboxylic acid anhydride, 3,4,4′-benzophenone tricarboxylic acid anhydride. 2,3,5-pyridinetricarboxylic acid anhydride, naphthalenetricarboxylic acid anhydride, and derivatives thereof. These acid anhydrides can be used alone or in combination of two or more.

  Examples of the tetracarboxylic dianhydride used in place of a part of the tricarboxylic acid anhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3, 3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2, 2'-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) sulfonic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride Bis (3,4-dicarboxyphenyl) ether dianhydride, ethylenetetracarboxylic dianhydride, and derivatives thereof. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  Preferred examples of the diisocyanate compound include aromatic diisocyanate compounds. In addition, as the diisocyanate compound, an aliphatic diisocyanate compound and / or an alicyclic diisocyanate compound, or amines that are derivatives thereof can be used together with or in place of the aromatic diisocyanate compound.

  Examples of the aromatic diisocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, diphenylmethane-4,4′-diisocyanate, 4,4′-diisocyanate diphenyl ether, 4,4′-diisocyanate diphenyl sulfone, and 4,4′-diisocyanate. Biphenyl, 3,3′-dimethyl-4,4′-diisocyanate biphenyl, 2,4-toluene diisocyanate, xylylene diisocyanate and the like can be mentioned. Diamines that are derivatives of these aromatic diisocyanate compounds can also be used as raw materials. Examples of the aliphatic diisocyanate compound include ethylene diisocyanate, propylene diisocyanate, and hexamethylene diisocyanate. Examples of the alicyclic diisocyanate compound include 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like. Among these diisocyanate compounds, considering the heat resistance, mechanical properties, solubility, and the like of the endless belt, 60% by mass or more, preferably 70% by mass or more of all the diisocyanate compounds used is diphenylmethane-4,4 ′. -Diisocyanate, 2,4-toluene diisocyanate, 3,3'-dimethyl-4,4'-diisocyanate biphenyl, isophorone diisocyanate or a diamine which is a derivative thereof is preferable. Furthermore, considering the dimensional stability of the endless belt 1, 70% by mass or more of all diisocyanate compounds used may be diphenylmethane-4,4′-diisocyanate or its derivative 4,4′-diaminodiphenylmethane. preferable.

  As the solvent used in the polycondensation reaction for synthesizing the aromatic polyamideimide resin, a polar solvent is preferable in terms of solubility, and an aprotic polar solvent is particularly preferable in consideration of reactivity. Examples of aprotic polar solvents include N, N-dialkylamides, and examples of N, N-dialkylamides include N, N-dimethylformamide, N, N-dimethylacetamide, N, N- Examples include diethylformamide, N, N-diethylacetamide, and N, N-dimethylmethoxyacetamide. Further, as a polar solvent, N-methyl-2-pyrrolidone, pyridine, dimethyl sulfoxide, tetramethylene sulfone, dimethyltetramethylene sulfone, and the like are also preferable. These solvents can be used alone or in combination of two or more.

  These resin compositions are polyamideimide resin compositions containing a polyamideimide resin as a main component, and may contain a resin other than the polyamideimide resin if desired.

  The conductivity imparting agent is as described above. The resin composition for the inner layer and the resin composition for the outer layer have the resistance ratio (A / B) when the intermediate transfer belt is used due to the conductivity and particle size of the conductivity-imparting agent and the conductivity characteristics required for the endless belt. As long as the content of the conductivity-imparting agent is appropriately adjusted so as to be within the above range, the volume resistance value and the surface resistance value of the inner layer resin composition and the outer layer resin composition are not particularly limited. In order to adjust the resistance ratio (A / B) to the above range, the content of the conductivity imparting agent in the outer layer resin composition is adjusted to be higher than the content of the conductivity imparting agent in the inner layer resin composition. Specifically, the content of the conductivity imparting agent is preferably such that the difference between the content of the outer layer resin composition and the content of the inner layer resin composition is 2 to 8 parts by mass. The content of the conductivity-imparting agent in the resin composition for the outer layer is preferably 10 to 20% by mass, when the total mass of the polyamideimide resin and the conductivity-imparting agent is 100% by mass, and 11 to 19 masses. % Is particularly preferred. The content of the conductivity-imparting agent in the resin composition for the inner layer is preferably 15 to 25% by mass when the total mass of the polyamideimide resin and the conductivity-imparting agent is 100% by mass, and 16 to It is particularly preferably 24% by mass. In each composition, when the content of the conductivity-imparting agent is less than the lower limit, the distance between the conductive materials is too far away, and the expression of conductivity in the endless belt may be deteriorated. The mechanical strength of the endless belt substrate, whose content exceeds the upper limit, may be lowered.

  Various additives are not particularly limited as long as they do not hinder the object of the present invention. For example, silicone compounds, fluorine organic compounds, coupling agents, lubricants, antioxidants, plasticizers, colorants, antistatic agents, Various additives such as anti-aging agent, reinforcing filler, reaction aid, reaction inhibitor and the like can be mentioned. These various additives can be determined as appropriate according to the characteristics developed by the addition of these additives.

  When the endless belt is molded by centrifugal molding, the inner layer resin composition and the outer layer resin composition preferably have a viscosity of 50,000 mPa · s or less during molding. For the viscosity of these compositions, a solvent, for example, a solvent used in a polycondensation reaction for synthesizing an aromatic polyamideimide resin is used.

  The resin composition for the inner layer and the resin composition for the outer layer include a polyamideimide resin, a conductivity imparting agent, various additives as required, and a solvent as required, for example, a mixing roll, a pressure kneader, an extruder, a three-roll, a homogenizer, It is prepared by mixing using a ball mill, a pot mill, a bead mill or the like.

  Next, the prepared resin composition for the outer layer is formed into a ring shape by a known molding method to form the outer surface side, that is, the outer layer 3. Then, it is preferable to perform the solvent removal process which consists of a primary solvent removal process and a secondary solvent removal process. For example, the outer layer resin composition is poured into a cylindrical mold, the mold is rotated, and the outer layer resin composition layer is uniformly spread on the inner peripheral surface of the mold by centrifugal force. The solvent is dried and removed from the composition layer through a primary solvent removal step and a secondary solvent removal step, and a film-like molded body of the outer layer resin composition is formed. The primary solvent removing step is performed, for example, by passing hot air of 40 to 150 ° C. through the mold for 5 to 60 minutes while the mold is rotated. The secondary solvent removal step is performed, for example, by heating in a heater at 200 to 300 ° C. for 1 to 3 hours or by heating with superheated steam at 200 to 260 ° C. for 0.5 to 3 hours. . In addition, at least one of the primary solvent removal step and the secondary solvent removal step when molding the film-shaped molded body of the resin composition for the outer layer is omitted, and the primary when molding the film-shaped molded body of the resin composition for the inner layer It can also be carried out by a solvent removal step and a secondary solvent removal step.

  On the inner peripheral surface of the film-shaped molded body of the outer layer resin composition thus molded, the prepared inner layer resin composition is molded into an annular shape by a known molding method to form the inner surface side, that is, the inner layer 2. Then, it is preferable to perform the solvent removal process which consists of a primary solvent removal process and a secondary solvent removal process. For example, the resin composition for the inner layer is poured into a cylindrical mold in which the film-shaped molded body of the resin composition for the outer layer is molded, and the film-shaped molded body of the resin composition for the outer layer is rotated by centrifugal force. The outer layer resin composition layer is uniformly spread in the inner peripheral surface of the outer layer, and the solvent is dried and removed from the outer layer resin composition layer through the primary solvent removal step and the secondary solvent removal step. An endless belt molded body in which a film-shaped molded body of the product and a film-shaped molded body of the resin composition for the inner layer are laminated is molded. The primary solvent removal step and the secondary solvent removal step are as described above.

  In this way, the endless belt molded body is removed, both end portions of the annular endless belt molded body are removed, and the intermediate transfer belt is manufactured by cutting to a predetermined width. The cutting machine that cuts the endless belt molded body may be an apparatus that can cut the endless belt molded body so that the cutting start point and the cutting end point substantially coincide with each other.

  The intermediate transfer belt thus produced contains a polyamideimide resin as a main component, and the resistance ratio of the volume resistance value A (Ω · cm) of the outer surface to the surface resistance value B (Ω / □) of the inner surface. Since (A / B) is 3 to 1000, it is possible to suppress the occurrence of the developer non-transfer area when the image forming apparatus is mounted, and to maintain the energization characteristics.

  Since the intermediate transfer belt has such characteristics, when the intermediate transfer belt is attached to the image forming apparatus as an intermediate transfer belt, it can contribute to forming a high-quality image.

  The intermediate transfer belt according to the present invention is not limited to the above-described embodiments, and various modifications can be made within a range in which the object of the present invention can be achieved. For example, the outer layer 3 and the inner layer 2 of the endless belt 1 both have a single layer structure, but in the present invention, the outer layer and / or the inner layer of the endless belt may have a multilayer structure in which two or more layers are laminated. .

  In the endless belt 1, the outer layer 3 is directly laminated on the outer peripheral surface of the inner layer 2, but in this invention, after the adhesive layer or the primer layer is formed on the outer peripheral surface of the inner layer 2, this adhesion is performed. The outer layer 3 may be formed on the outer peripheral surface such as the agent layer or the primer layer. Further, the endless belt 1 includes an inner layer 2 and an outer layer 3. In the present invention, the endless belt has a surface layer or the like formed of a fluororesin or the like on the outer peripheral surface of the outer layer as desired. In addition, fine particles such as fluororesin may adhere to the outer peripheral surface of the outer layer.

  Further, in the intermediate transfer belt 1, both the inner layer 2 and the outer layer 3 contain only a polyamideimide resin as a matrix resin. In this invention, the inner layer and the outer layer are made of other resins in addition to the polyamideimide resin as a matrix resin. May be contained. Examples of such other resins include polyamide resins, polyimide resins, epoxy resins, and phenol resins.

  The endless belt 1 includes an inner layer 2 and an outer layer 3. In the present invention, the endless belt is an inner peripheral surface of the inner layer 2 and at least one end of the inner layer 2 in the axial direction, if desired. An elongated guide member having a string shape or a band shape made of an elastic material may be provided. This guide member functions as a guide for preventing side shake while the endless belt is running. Examples of the material for the guide member include elastic materials having appropriate rubber elasticity and wear resistance, such as urethane elastomers, silicone elastomers, fluororesin elastomers, and styrene elastomers. Among these, urethane-based elastomers having an A hardness of 30 or more and 95 or less according to JIS K 6253-1997, which is excellent in wear resistance, are preferable. The guide member is preferably provided so as to make a round of the inner peripheral surface of the inner layer at both end portions in the axial direction of the inner layer.

  Next, an example of an image forming apparatus provided with the intermediate transfer belt 1 according to the present invention (hereinafter sometimes referred to as an image forming apparatus according to the present invention) will be described with reference to FIG. The image forming apparatus 10 is an intermediate transfer type tandem color image forming apparatus. An intermediate transfer tandem color image forming apparatus 10 is basically configured in the same manner as a conventionally known image forming apparatus, but an endless belt 1 according to the present invention is mounted as an intermediate transfer belt 1.

  As shown in FIG. 2, the endless belt 1 is stretched around two support rollers 42, a tension roller 43 and a counter roller 44 as the intermediate transfer belt 1. In the vicinity of the position where the counter roller 44 is installed, a secondary transfer unit 40 including a counter roller 44, a secondary transfer roller 45, and an electrode roller 46 is disposed.

  As shown in FIG. 2, in the image forming apparatus 10, four types of developing units B, C, M, and Y are arranged in series on the intermediate transfer belt 1. The developing unit B includes an image carrier 11B such as a photoconductor, a charging roller 12B, an exposure unit 13B, a developing roller 23B, a developing unit 20B including a housing 21B, a transfer roller 14B, and a cleaning blade 15B. The developing unit B contains a black developer. The developing units C, M, and Y are configured in the same manner as the developing unit B, and contain a cyan developer 22C, a magenta developer 22M, and a yellow developer 22Y.

  As shown in FIG. 2, a fixing unit 30 having an endless belt 35 as a fixing belt is disposed downstream in the conveyance direction of the recording medium 16 in the image forming apparatus 10. The fixing device 30 is a pressure heat fixing device including a fixing roller 31, a support roller 33, a fixing belt 35, and a pressure roller 32 in a housing 34 having an opening. The fixing unit 30 may be a heat roller fixing device, a heat fixing device, a pressure fixing device, or the like.

  The image forming apparatus 10 forms an image as follows. First, the developing unit B visualizes the electrostatic latent image on the surface of the image carrier 11B as a developer image with the black developer 22B, and the developer image is transferred onto the intermediate transfer belt 1 (primary transfer). Subsequently, the developer images are transferred to the intermediate transfer belt 1 by the developing units C, M, and Y, and a color image is formed. The color image reaches the secondary transfer unit 40 by the rotation of the intermediate transfer belt 1 and is transferred onto the recording medium 16 conveyed to the secondary transfer unit 40 (secondary transfer). Next, the recording medium 16 in which the color image is visualized is conveyed to the fixing unit 30 and the color image is fixed as a permanent image. In this way, a color image is formed on the recording medium 16. Although the case where a color image is formed using the image forming apparatus 10 has been described, in the case of forming a monochrome image, the developer image primary-transferred to the intermediate transfer belt 1 is immediately secondary-transferred to the recording medium 16. Then, it may be conveyed to the fixing means 30.

  Another example of an image forming apparatus provided with the endless belt 1 according to the present invention (hereinafter sometimes referred to as an image forming apparatus according to the present invention) will be described with reference to FIG. The image forming apparatus 50 is an intermediate transfer type multi-pass color image forming apparatus. The intermediate transfer type multi-pass color image forming apparatus 50 is basically configured in the same manner as a conventionally known image forming apparatus, but an endless belt 1 according to the present invention is mounted as the intermediate transfer belt 1.

  As shown in FIG. 3, the endless belt 1 is stretched around two support rollers 42, a tension roller 43 and a counter roller 44 as the intermediate transfer belt 1. In the vicinity of the position where the counter roller 44 is installed, a secondary transfer unit 40 including a counter roller 44, a secondary transfer roller 45, and an electrode roller 46 is disposed.

  As shown in FIG. 3, the image forming apparatus 50 includes a developing unit 20 including four types of developing units B, C, M, and Y. The developing units B, C, M, and Y built in the developing unit 20 include a charging unit, an exposure unit, and the like, and store a black developer, a cyan developer, a magenta developer, and a yellow developer, respectively. The developing unit 20 may include a charging unit, an exposing unit, and the like outside the developing unit 20 and in the vicinity of the image carrier 11.

  As shown in FIG. 3, a fixing unit 30 is disposed downstream in the conveyance direction of the recording body 16 in the image forming apparatus 50. The fixing device 30 is configured in the same manner as the fixing device 30 of the image forming apparatus 10.

  The image forming apparatus 50 forms an image as follows. First, an electrostatic latent image is visualized as a developer image with the black developer 22B on the surface of the image carrier 11 by the developing unit B of the developing means 20, and transferred onto the intermediate transfer belt 1 (primary transfer). Subsequently, the image carrier 11 and the intermediate transfer belt 1 rotate once, and each developer image is superimposed and transferred to the intermediate transfer belt 1 by the developing units C, M, and Y, thereby forming a color image. The color image reaches the secondary transfer unit 40 by the rotation of the intermediate transfer belt 1 and is transferred onto the recording medium 16 conveyed to the secondary transfer unit 40 (secondary transfer). Next, the recording medium 16 in which the color image is visualized is conveyed to the fixing unit 30 and the color image is fixed as a permanent image. In this way, a color image is formed on the recording medium 16. Although the case where a color image is formed using the image forming apparatus 50 has been described, in the case of forming a monochrome image, the developer image primarily transferred to the intermediate transfer belt 1 is immediately secondary transferred to the recording medium 16. Then, it may be conveyed to the fixing means 30.

  According to these image forming apparatuses 10 and 50, since the endless belt 1 is used as the intermediate transfer belt 1, it is possible to form a high-quality image having substantially no developer non-transfer area and a uniform density.

  The image forming apparatus according to the present invention is not limited to the above-described example, and various modifications can be made within a range in which the object of the present invention can be achieved. For example, the image forming apparatuses 10 and 50 are electrophotographic image forming apparatuses. However, in the present invention, the image forming apparatus is not limited to the electrophotographic system. For example, the electrostatic image forming apparatus. It may be. The image forming apparatuses 10 and 50 are intermediate transfer type image forming apparatuses. However, in the present invention, the image forming apparatus may be a direct transfer type image forming apparatus. It may be a tandem type image forming apparatus in which a plurality of image carriers having units are arranged in series on a transfer conveyance belt, or a monochrome type image forming apparatus having a single developing unit. The image forming apparatus according to the present invention is suitably used as an image forming apparatus such as a copying machine, a facsimile, or a printer.

Example 1
In a reaction vessel, N-methyl-2-pyrrolidone, trimellitic anhydride, an equivalent amount of diphenylmethane-4,4′-diisocyanate, and reaction raw materials (trimellitic anhydride and diphenylmethane-4,4′- 2 mol% of potassium fluoride (catalyst) is added to the total number of moles of diisocyanate), and the temperature is raised from room temperature to 150 ° C. over 30 minutes with stirring. (Substantially fully ring-closed polyamideimide resin) A 20% by mass aromatic polyamideimide solution was obtained. N-methyl-2-pyrrolidone was further added to this solution to prepare a polyamideimide solution having a reactant concentration of 15% by mass. To the obtained polyamideimide solution, an oxidation-treated carbon black (trade name “Printex 150T”, manufactured by Degussa, pH 4.0, volatile content 10.0%) is added to a total of 100 masses of the polyamideimide resin and the oxidation-treated carbon black. The resin composition for the inner layer was prepared by mixing and dispersing in a pot mill for 24 hours in a proportion of 20% by mass with respect to% (indicated as CB content in Table 1).

  Further, in the reaction vessel, N-methyl-2-pyrrolidone, trimellitic anhydride, equivalent diphenylmethane-4,4′-diisocyanate, and reaction raw materials (trimellitic anhydride and diphenylmethane-4,4) 2 mol% of potassium fluoride (catalyst) is added to the total number of moles of '-diisocyanate), the temperature is raised from room temperature to 150 ° C. over 30 minutes with stirring, and the temperature is maintained for 5 hours. An aromatic polyamideimide solution having an object concentration (substantially fully ring-closed polyamideimide resin) of 20% by mass was obtained. N-methyl-2-pyrrolidone was further added to this solution to prepare a polyamideimide solution having a reactant concentration of 15% by mass. To the obtained polyamideimide solution, an oxidation-treated carbon black (trade name “Printex 150T”, manufactured by Degussa, pH 4.0, volatile content 10.0%) is added to a total of 100 masses of the polyamideimide resin and the oxidation-treated carbon black. The resin composition for outer layers was prepared by mixing at 15% by mass with respect to% (indicated as CB content in Table 1) and mixing and dispersing in a pot mill for 24 hours.

  The mold used for molding has an inner diameter of 226 mm, an outer diameter of 246 mm, and a length of 400 mm, and the inner surface of the mold is mirror-polished by polishing. Next, ring-shaped lids (inner diameter 170 mm, outer diameter 250 mm) are fitted into the openings at both ends of the mold, respectively, the mold is closed, and the outer layer resin composition is rotated at a speed of 1,000 rpm. 76 g was injected into the inner periphery of the mold. Next, the mold was rotated at the same speed for 30 minutes to uniformly spread the resin composition layer on the inner peripheral surface of the mold. Next, while rotating the mold at the same speed, the temperature around the mold was maintained at 80 ° C. with a hot air dryer, and this state was maintained for 30 minutes to form a film-shaped molded body. Thereafter, the rotation of the mold was stopped, the film-shaped molded body was taken out from the centrifugal molding machine together with the mold, and was subjected to superheated steam treatment in a superheated steam furnace at 150 ° C. for 25 minutes, and then the mold was cooled to 80 ° C. Then, after mounting the mold holding the film-shaped molded body of the resin composition for the outer layer on a centrifugal molding machine, the resin composition for the inner layer 2 is held on the mold rotating at a speed of 1,000 rpm. 76 g was injected into the inner periphery of the film-shaped molded product of the resin composition. Next, the mold was rotated at the same speed for 30 minutes to uniformly spread the resin composition layer on the inner peripheral surface of the mold. Next, while rotating the mold at the same speed, the temperature around the mold is maintained at 80 ° C. by a hot air dryer, and this state is maintained for 30 minutes, and a film shape of the outer layer resin composition and the inner layer resin composition is obtained. A laminated molded body was molded. Thereafter, the rotation of the mold is stopped, the film-shaped laminated molded body is taken out from the centrifugal molding machine together with the mold, subjected to superheated steam treatment in a superheated steam furnace adjusted to 250 ° C. for 2 hours, and then allowed to cool at room temperature. An endless belt molded body was obtained. The endless belt molded body was cooled together with the mold, the endless belt molded body was peeled off due to the difference in thermal expansion coefficient between the mold and the endless belt molded body, and the endless belt molded body was removed from the mold. Both end portions of this endless belt molded body were cut and cut into a size having a peripheral length of about 226 mm, a width of 240 mm, and a thickness of 80 μm, and the intermediate transfer belt 1 was produced.

  In the intermediate transfer belt 1 thus manufactured, it is clear that the thicknesses of the inner layer 2 and the outer layer 3 are both 40 μm from the amount of the outer layer resin composition and the inner layer resin composition. The boundary between 2 and the outer layer 3 could not be clearly distinguished.

(Example 2)
In the resin composition for the inner layer, the content of the oxidized carbon black with respect to 100% by mass in total of the polyamideimide resin and the oxidized carbon black is changed from 20% by mass to 16% by mass, and the polyamideimide resin is changed in the outer layer resin composition. An intermediate transfer belt was produced basically in the same manner as in Example 1 except that the content of the oxidized carbon black was changed from 15% by mass to 11% by mass with respect to the total of 100% by mass of the oxidized carbon black.

(Example 3)
In the resin composition for the inner layer, the content of the oxidized carbon black is changed from 20% by mass to 24% by mass with respect to a total of 100% by mass of the polyamideimide resin and the oxidized carbon black, and the polyamideimide resin is changed in the outer layer resin composition. An intermediate transfer belt was produced basically in the same manner as in Example 1 except that the content of the oxidized carbon black was changed from 15% by mass to 19% by mass with respect to the total of 100% by mass of the oxidized carbon black.

Example 4
Basically the same as Example 1 except that the content of the oxidized carbon black in the resin composition for the inner layer was changed from 20% by mass to 17% by mass with respect to 100% by mass in total of the polyamideimide resin and the oxidized carbon black. Thus, an intermediate transfer belt was produced.

(Example 5)
Basically the same as Example 1 except that the content of the oxidized carbon black in the resin composition for the inner layer was changed from 20% by mass to 23% by mass with respect to 100% by mass in total of the polyamideimide resin and the oxidized carbon black. Thus, an intermediate transfer belt was produced.

(Example 6)
Basically the same as Example 1 except that the content of the oxidized carbon black in the resin composition for outer layers was changed from 15% by mass to 11% by mass with respect to 100% by mass in total of the polyamideimide resin and the oxidized carbon black. Thus, an intermediate transfer belt was produced.

(Example 7)
Basically the same as Example 1 except that the content of the oxidized carbon black in the resin composition for the outer layer was changed from 15% by mass to 18% by mass with respect to 100% by mass in total of the polyamideimide resin and the oxidized carbon black. Thus, an intermediate transfer belt was produced.

(Example 8)
An intermediate transfer belt was manufactured basically in the same manner as in Example 1 except that the thickness of the inner layer 2 was changed to 20 μm.

Example 9
An intermediate transfer belt was manufactured basically in the same manner as in Example 1 except that the thickness of the outer layer 3 was changed to 20 μm.

(Comparative Example 1)
In the resin composition for the inner layer, the content of the oxidized carbon black with respect to a total of 100% by mass of the polyamideimide resin and the oxidized carbon black is changed from 20% by mass to 13% by mass, and in the outer layer resin composition, the polyamideimide resin is changed. An intermediate transfer belt was produced basically in the same manner as in Example 1 except that the content of the oxidized carbon black with respect to the total of 100% by mass of the oxidized carbon black was changed from 15% by mass to 8% by mass.

(Comparative Example 2)
In the resin composition for the inner layer, the content of the oxidized carbon black with respect to 100% by mass in total of the polyamideimide resin and the oxidized carbon black is changed from 20% by mass to 26% by mass. An intermediate transfer belt was produced basically in the same manner as in Example 1 except that the content of the oxidized carbon black relative to 100% by mass of the resin and the oxidized carbon black was changed from 15% by mass to 21% by mass. .

  The volume resistance value A (Ω · cm), the volume resistance value A ′ (Ω · cm), the surface resistance value B (Ω / □) and the surface resistance value B ′ (Ω / □) of each of the produced intermediate transfer belts are described above. The resistance ratio (A / B) of the volume resistance value A (Ω · cm) to the surface resistance value B (Ω / □) was calculated. The results are shown in Table 1 together with the content of the conductivity imparting agent in each layer.

(Presence or absence of developer non-transfer area)
The ease of occurrence of the developer non-transfer area was evaluated using the produced intermediate transfer belt. Specifically, a secondary current of a developing bias applied to the intermediate transfer belt and the photosensitive member surface potential in a state where the intermediate transfer belt manufactured in an evaluation machine (product name “image Neo Neo271”, manufactured by Ricoh Co., Ltd.) is mounted. In order to increase this, a constant voltage control related to the photosensitive member and the charging roller was performed to form a belt-like solid pattern on a copy paper (PPC paper). Thus, when constant voltage control is performed on the photosensitive member and the charging roller, the secondary current of the developing bias applied to the intermediate transfer belt and the photosensitive member surface potential is increased by controlling the transfer roller and the toner charge amount. In addition, when constant voltage control is performed on the photosensitive member and the charging roller, the secondary current of the developing bias applied to the intermediate transfer belt and the photosensitive member surface potential is increased by controlling the transfer roller and the toner charge amount. In addition, constant voltage control of the photoconductor and charging roller prevents overcurrent, obtains stable charge, and achieves appropriate transfer efficiency, so that the belt-like solid pattern is always constant regardless of the setting of the exposure means. Formed. In this constant voltage control, a case where three or more developer non-transfer areas exist in an arbitrary area of 25 mm × 25 mm in the belt-like solid pattern formed on the copy paper (PPC paper) is set to “Yes”. A case where two or less developer non-transfer areas exist or a case where no developer non-transfer areas exist does not indicate “no”. The results are shown in Table 1.

(Electrical characteristics evaluation)
The energization characteristics were evaluated as follows using the manufactured intermediate transfer belt. Specifically, using a high resistivity meter “Hiresta-UP” (trade name, manufactured by Mitsubishi Chemical Corporation, URS probe), a voltage of 500 V is applied in accordance with JIS K6911 with the URS probe in contact with the outer layer 3. The surface resistance value over time when applied for 8 hours was measured. The voltage application time and the rate of increase of the surface resistance value in the measured surface resistance value over time are confirmed, and the surface resistance values after 10 seconds (10 seconds after the start of voltage application) and 8 hours after the voltage application time are obtained. Confirmed, change ratio of surface resistance value after 8 hours of voltage application to surface resistance value after 10 seconds of voltage application [surface resistance value after 8 hours of voltage application / surface resistance value after 10 seconds of voltage application] Was calculated. The range in which this change ratio is 1 to 100 times is a practically acceptable range. The results are shown in Table 1.

(Folding resistance)
Using a MIT folding fatigue tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., tip R0.38 mm), a test piece having a width of 15 mm cut out from each manufactured intermediate transfer belt was subjected to conditions of speed 175 cpm, angle 90 °, and load 0.5 kg. Then, the number of bending until the test piece broke was measured according to JIS-P8115. The results are shown in Table 1.

  As shown in Table 1, Examples 1 to 9 satisfying claim 1 are adjusted with an optimal balance of resistance values satisfying the resistance ratio (A / B), and changes in the evaluation of the energization characteristics An image formed by an image forming apparatus mounted as an intermediate transfer belt is “developer non-developing” because the ratio of 1 to 100 times exhibits good current-carrying characteristics, and the number of bendings is 1300 or more and exhibits good folding resistance. It is presumed that there is substantially no “transfer area”, the density is uniform, and the quality is high.

DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 2 Inner layer 3 Outer layer 10, 50 Image forming apparatus 11, 11B, 11C, 11M, 11Y Image carrier 12B, 12C, 12M, 12Y Charging unit 13B, 13C, 13M, 13Y Exposure unit 14, 14B, 14C, 14M, 14Y Transfer means 15B, 15C, 15M, 15Y Cleaning means 16 Recording medium 20, 20B, 20C, 20M, 20Y Developing means 21B, 21C, 21M, 21Y, 34 Housing 22B, 22C, 22M, 22Y Developer 23B, 23C, 23M, 23Y Developer carrier 30 Fixing device 31 Fixing roller 32 Pressure roller 33 Fixing belt support roller 35 Endless belt (fixing belt)
40 Secondary transfer section 42 Support roller 43 Tension roller 44 Opposite roller 45 Secondary transfer roller 46 Electrode rollers B, C, M, Y Development unit

Claims (8)

  An intermediate containing a polyamideimide resin as a main component and having a resistance ratio (A / B) of the volume resistance value A (Ω · cm) of the outer surface to the surface resistance value B (Ω / □) of the inner surface is 3 to 1000 Transfer belt.   The intermediate transfer belt according to claim 1, wherein the intermediate transfer belt contains a conductivity-imparting agent such that the outer surface side has a lower content than the inner surface side.   3. The intermediate transfer belt according to claim 2, wherein the conductivity imparting agent has a difference of 2 to 8 mass% between the content on the outer surface side and the content on the inner surface side.   The conductivity imparting agent is contained in an amount of 10 to 20% by mass on the outer surface side and 15 to 25 on the inner surface side when the total mass of the polyamideimide resin and the conductivity imparting agent is 100% by mass. The intermediate transfer belt according to claim 2, wherein the intermediate transfer belt is contained by mass%. The volume resistance value A (Ω · cm) is in the range of 1 × 10 ⁸ to 1 × 10 ¹³ , and the surface resistance value B (Ω / □) is in the range of 1 × 10 ⁹ to 1 × 10 ¹² . The intermediate transfer belt according to any one of claims 1 to 4, wherein   The intermediate transfer belt according to claim 1, wherein the intermediate transfer belt has a multilayer structure having an outer layer including the outer surface and an inner layer including the inner surface, which are directly or indirectly laminated.   The intermediate transfer belt according to claim 6, wherein each of the outer layer and the inner layer includes a polyamideimide resin as a main component.   An image forming apparatus comprising the intermediate transfer belt according to claim 1.

Images