Endless belt, intermediate transfer belt, transfer device, and image forming apparatus

Abstract

To provide an endless belt that is excellent in bending resistance during rotation drive.SOLUTION: An endless belt includes resin and conductive particles. The endless belt has pores therein, and the number of pores increases from an outer peripheral surface side toward an inner peripheral surface side. On a cross section along a belt thickness direction, the area ratio Ao of the pores present on the outer peripheral surface side is 0.05% or more and 1.5% or less, the area ratio Am of the pores present in a thickness center part is 1.0% or more and 5.0% or less, and the area ratio Ai of the pores present on the inner peripheral surface side is 2.0% or more and 20.0% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an endless belt, an intermediate transfer belt, a transfer device, and an image forming apparatus. [Background technology]

[0002] In electrophotographic image forming apparatuses (such as copiers, facsimiles, and printers), a toner image formed on the surface of an image carrier is transferred to the surface of a recording medium and fixed on the recording medium to form an image. An intermediate transfer belt, for example, is used to transfer the toner image onto the recording medium. Various endless belts, such as conveyor belts, are used not only in image forming apparatuses but also in other devices.

[0003] For example, Patent Document 1 discloses "an endless belt having at least a cylindrically formed resin base layer, the base layer containing one or more resins selected from polyamideimide and polyimide, and the base layer having a large number of independent spheroidal pores." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-87546 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an endless belt that contains resin and conductive particles, has holes inside, and has excellent bending resistance during rotational driving compared to an endless belt in which there is no change in the proportion of holes on the outer peripheral surface side and the inner peripheral surface side. [Means for solving the problem]

[0006] Means for solving the above problems include the following aspects. <1> resin and conductive particles, An endless belt having holes inside, the number of holes increasing from the outer peripheral surface toward the inner peripheral surface. <2> In the cross section along the belt thickness direction, The area ratio Ao of the holes present on the outer peripheral surface side is 0.05% or more and 1.5% or less, The area ratio Am of the holes present in the thickness central portion is 1.0% or more and 5.0% or less, The area ratio Ai of the holes present on the inner peripheral surface side is 2.0% or more and 20.0% or less. <1> The endless belt described in <3> The ratio Ao / Am of the area ratio Ao of the holes to the area ratio Am of the holes is 0.1 or more and 0.8 or less. The ratio Am / Ai of the area ratio Am of the holes to the area ratio Ai of the holes is 0.1 or more and 0.8 or less. <2> The endless belt described in <4> When observing the outer peripheral surface, the area ratio A of the holes is 0.01% or more and 1.0% or less. <1> ~ <3> 10. The endless belt according to claim 9, <5> In the cross section along the belt thickness direction, The average pore diameter Do of the pores present on the outer peripheral surface side is 0 μm or more and 1.5 μm or less. The average pore diameter Dm of the pores present in the thickness central portion is 0.5 μm or more and 5.0 μm or less, The average pore diameter Di of the pores present on the inner peripheral surface side is 0.6 μm or more and 10.0 μm or less. <1> ~ <4> 10. The endless belt according to claim 9, <6> Contains silicone oil <1> ~ <5> 10. The endless belt according to claim 9, <7> The silicone oil is a polyether-modified silicone oil. <6> The endless belt described in <8> The number average molecular weight of the polyether-modified silicone oil is 300 or more and 10,000 or less. <7> The endless belt described in <9> The resin is a polyimide resin <1> ~ <8> 10. The endless belt according to claim 9, <10> <1> ~ <9> 10. An intermediate transfer belt comprising the endless belt according to any one of claims 1 to 9. <11> An intermediate transfer belt having an outer peripheral surface onto which a toner image is transferred, <1> ~ <9> an intermediate transfer belt having the endless belt according to any one of the above items; a primary transfer device having a primary transfer member that primarily transfers a toner image formed on the surface of an image carrier onto the outer peripheral surface of the intermediate transfer belt; a secondary transfer device that is disposed in contact with the outer peripheral surface of the intermediate transfer belt and has a secondary transfer member that secondarily transfers the toner image transferred onto the outer peripheral surface of the intermediate transfer belt onto a surface of a recording medium; A transfer device comprising: <12> a toner image forming device having an image carrier and forming a toner image on a surface of the image carrier; a transfer device that transfers the toner image formed on the surface of the image carrier to a surface of a recording medium, <11> a transfer device according to the above; An image forming apparatus comprising: [Effects of the Invention]

[0007] <1> According to the present invention, an endless belt containing resin and conductive particles and having holes inside is provided, which has excellent bending resistance during rotational driving compared to an endless belt in which there is no change in the proportion of holes between the outer peripheral surface side and the inner peripheral surface side.

[0008] <2> According to the invention, an endless belt is provided which has excellent bending resistance during rotational driving, compared to an endless belt in which the hole area ratio Ao is less than 0.05% or more than 1.5%, the hole area ratio Am is less than 1.0% or more than 5.0%, or the hole area ratio Ai is less than 2.0% or more than 20.0%. <3> According to the invention, an endless belt is provided which has excellent bending resistance during rotational driving, compared to when the ratio Ao / Am is less than 0.1 or exceeds 0.8, or when the ratio Am / Ai is less than 0.1 or exceeds 0.8. <4> According to the invention, an endless belt having excellent resistance to bending during rotational driving is provided, compared to an endless belt having a hole area ratio A of less than 0.01% or more than 1.0%. <5> According to the invention, an endless belt is provided which has excellent bending resistance during rotational driving, compared to an endless belt in which the average pore diameter Do of the pores exceeds 1.5 μm, the average pore diameter Dm of the pores is less than 0.5 μm or exceeds 5.0 μm, or the average pore diameter Di of the pores is less than 0.6 μm or exceeds 10.0 μm. <6> , or <7> According to the invention, an endless belt is provided which has superior resistance to bending during rotational driving compared to an endless belt which does not contain silicone oil. <8> According to the invention, an endless belt is provided which has excellent resistance to bending during rotational driving, compared to when the number average molecular weight of the polyether-modified silicone oil is less than 300 or more than 10,000. <9> According to the invention, an endless belt is provided which has superior resistance to bending during rotational driving compared to when the resin is a polyamide-imide resin. <10> , <11> , or <12> According to the invention, an intermediate transfer belt, or a transfer device or image forming device equipped with the intermediate transfer belt, is provided, which has excellent bending resistance during rotational driving compared to an endless belt that contains resin and conductive particles and has holes inside, and in which the proportion of holes does not change between the outer surface side and the inner surface side. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 10 is a schematic configuration diagram showing the periphery of a secondary transfer unit in another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present embodiment, which is an example of the present invention, will be described below. These descriptions and examples are for illustrating the embodiment, and do not limit the scope of the embodiment.

[0011] In the numerical ranges described in this embodiment in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this embodiment, the upper or lower limit value of the numerical range may be replaced with the value shown in the examples. In this embodiment, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. When the present embodiment is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these. In this embodiment, each component may contain multiple types of corresponding substances. When referring to the amount of each component in the composition in this embodiment, if multiple types of substances corresponding to each component are present in the composition, the amount refers to the total amount of the multiple types of substances present in the composition, unless otherwise specified.

[0012] [Endless belt] The endless belt according to the present embodiment contains resin and conductive particles, and has pores therein, with the pores being more numerous from the outer circumferential surface side toward the inner circumferential surface side.

[0013] The endless belt according to this embodiment has the above-described structure, and is therefore an endless belt that has excellent bending resistance when rotated. The reason for this is as follows.

[0014] An endless belt having holes therein is known to improve bending resistance. However, there are cases where the bending resistance of an endless belt is insufficient when the endless belt is rotated. This is thought to be because, when the endless belt is rotated, different stresses are applied to the inner peripheral surface and the outer peripheral surface at the bending portions where the endless belt comes into contact with rolls such as a drive roll and a support roll, i.e., compressive stress on the inner peripheral surface and tensile stress on the outer peripheral surface.

[0015] Therefore, in the endless belt according to this embodiment, the number of holes is increased from the outer peripheral surface side to the inner peripheral surface side. As a result, the inner peripheral surface side has more holes, which alleviates compressive stress. On the other hand, the outer peripheral surface side has fewer holes and more resin, which increases resistance to tensile stress.

[0016] Therefore, it is presumed that the endless belt according to this embodiment is an endless belt that has excellent bending resistance when rotated.

[0017] The endless belt according to this embodiment will be described in detail below.

[0018] (pore structure) The endless belt according to this embodiment has pores (that is, air bubbles) inside, and has a porous structure in which the pores are more numerous from the outer circumferential surface side toward the inner circumferential surface side. Here, the term "porous structure in which the number of pores increases from the outer peripheral surface side to the inner peripheral surface side" refers to a structure in which the pore area ratio Ao, the pore area ratio Am, and the pore area ratio Ai increase in this order, as will be described later. However, if the difference between the pore area ratio Ao, the pore area ratio Am, and the pore area ratio Ai is within the range of ±10%, the amount of pores present is considered to be the same from the outer peripheral surface side to the inner peripheral surface side.

[0019] -Hole area ratio- In a cross section along the belt thickness direction, for example, the area ratio Ao of holes present on the outer surface side is 0% or more and 2.0% or less, the area ratio Am of holes present in the central part of the thickness is 0.5% or more and 8.5% or less, and the area ratio Ai of holes present on the inner surface side is 1.5% or more and 21.5% or less. This structure increases the compressive stress relaxation force on the inner peripheral surface due to the holes, and increases the resistance to tensile stress on the outer peripheral surface due to the resin, resulting in improved bending resistance during rotational driving.

[0020] The area ratio Ao of the pores present on the outer peripheral surface side is preferably 0.05% or more and 1.5% or less, and more preferably 0.3% or more and 1.3% or less. The area ratio Am of pores present in the central part of the thickness is preferably 1.0% or more and 5.0% or less, and more preferably 1.0% or more and 4.5% or less. The area ratio Ai of the holes present on the inner peripheral surface side is preferably 2.0% or more and 20.0% or less, and more preferably 10% or more and 20% or less.

[0021] From the viewpoint of improving bending resistance during rotational driving, the ratio Ao / Am of the pore area ratio Ao to the pore area ratio Am is preferably 0 or more and 0.9 or less, more preferably 0.1 or more and 0.8 or less, and even more preferably 0.1 or more and 0.4 or less. From the same viewpoint, the ratio Am / Ai of the pore area ratio Am to the pore area ratio Ai is preferably 0 or more and 0.9 or less, more preferably 0.1 or more and 0.8 or less, and even more preferably 0.1 or more and 0.6 or less.

[0022] From the viewpoint of improving resistance to bending during rotational driving, the area ratio A of holes when observing the outer peripheral surface is preferably 0.01% to 1.2%, more preferably 0.01% to 1.0%, and even more preferably 0.05% to 0.6%. In particular, when the hole area ratio A is within the above range, the number of holes exposed on the outer peripheral surface of the belt is reduced, and the outer peripheral surface of the belt is made flatter, which has the advantage of suppressing deterioration in the transferability of toner images when the endless belt is used as an intermediate transfer belt or the like.

[0023] The area ratios of the holes present on the outer peripheral surface side, the thickness central portion, and the inner peripheral surface side of the endless belt are measured as follows. A sample piece is taken from the target endless belt by cutting it along the thickness direction. Next, the cut surface of the sample piece is used as the observation surface and observed with a scanning electron microscope (SEM). Specifically, a 30 μm × 40 μm area, with one side corresponding to the outer circumferential surface of the belt, is observed at a magnification of 3000 times, and the pore area ratio relative to the observed area is determined. This procedure is performed for five sample pieces, and the arithmetic average of the pore area ratios is taken as the pore area ratio Ao present on the outer circumferential surface. Also, a 30 μm × 40 μm area centered at the half-thickness position of the belt is observed at a magnification of 3000 times, and the pore area ratio relative to the observed area is determined. This procedure is performed for five sample pieces, and the arithmetic average of the pore area ratios is taken as the pore area ratio Am of the pores present in the central thickness portion. Also, a 30 μm × 40 μm area, with one side corresponding to the inner peripheral surface of the belt, is observed at a magnification of 3000 times to determine the area ratio of holes to the observed area. This procedure is performed for five sample pieces, and the arithmetic average value of the area ratios of holes present on the inner peripheral surface side is taken as the area ratio Ai of holes present on the inner peripheral surface side.

[0024] On the other hand, the method for measuring the area ratio A of holes when observing the outer peripheral surface of the endless belt is as follows. A sample piece including the outer circumferential surface of the belt is taken from the target endless belt. Next, the outer peripheral surface of the belt of the sample piece is used as the observation surface and observed with a scanning electron microscope (SEM). Specifically, an area of ​​30 μm × 40 μm is observed at a magnification of 3000 times, and the pore area ratio relative to the observed area is determined. This procedure is performed for five sample pieces, and the arithmetic average of the pore area ratios is defined as the pore area ratio A when the outer peripheral surface of the endless belt is observed.

[0025] -Average pore size- In the endless belt according to the present embodiment, it is preferable that the diameter of the pores (that is, air bubbles) present inside the belt increases from the outer circumferential surface side toward the inner circumferential surface side. Here, "the pore diameter increases from the outer peripheral surface side to the inner peripheral surface side" refers to a structure in which the average pore diameter Do of the pores, the average pore diameter Dm of the pores, and the average pore diameter Di of the pores increase in this order, as will be described later. However, if the difference between the average pore diameter Do, the average pore diameter Dm, and the average pore diameter Di is within a range of ±0.01%, the pore diameters are considered to be the same from the outer peripheral surface side to the inner peripheral surface side. Specifically, for example, in a cross section along the belt thickness direction, it is preferable that the porous structure has an average pore diameter Do of pores present on the outer surface side of 0 μm or more and 2.5 μm or less, an average pore diameter Dm of pores present in the central part of the thickness of 0.1 μm or more and 6.0 μm or less, and an average pore diameter Di of pores present on the inner surface side of 0.3 μm or more and 11.0 μm or less. This structure increases the compressive stress relaxation force on the inner peripheral surface due to the holes, and increases the resistance to tensile stress on the outer peripheral surface due to the resin, resulting in improved bending resistance during rotational driving.

[0026] In a cross section along the belt thickness direction, the average pore diameter Do of the pores present on the outer peripheral surface side is more preferably 0 μm or more and 1.5 μm or less, and even more preferably 0 μm or more and 1.2 μm or less. The average pore diameter Dm of the pores present in the central part of the thickness is more preferably 0.5 μm or more and 5.0 μm or less. The average pore diameter Di of the pores present on the inner circumferential surface side is more preferably 0.6 μm or more and 10.0 μm or less.

[0027] From the viewpoint of improving bending resistance during rotational driving, the ratio Do / Dm of the average pore diameter Do to the average pore diameter Dm is preferably 0 or more and 1.5 or less, more preferably 0 or more and 1.0 or less, and even more preferably 0.1 or more and 0.5 or less. From the same viewpoint, the ratio Dm / Di of the average pore diameter Dm to the average pore diameter Di is preferably 0.1 or more and 2.0 or less, more preferably 0.2 or more and 1.4 or less, and even more preferably 0.2 or more and 0.5 or less.

[0028] Here, the average pore diameter of the pores present on the outer peripheral surface side, the thickness central portion, and the inner peripheral surface side of the endless belt is measured as follows. A sample piece is taken from the target endless belt by cutting it along the thickness direction. Next, the cut surface of the sample piece is used as the observation surface and observed with a scanning electron microscope (SEM). Specifically, a 9 μm × 12 μm area, with one side corresponding to the outer circumferential surface of the belt, is observed at a magnification of 10,000 times to determine the equivalent circle diameter of the pores present in the observation field. This procedure is performed for 10 sample pieces, and the arithmetic mean value of the equivalent circle diameters of the pores is taken as the average pore diameter Do of the pores present on the outer circumferential surface. Also, a 9 μm × 12 μm area centered at the half-thickness position of the belt is observed at a magnification of 10,000 times to determine the equivalent circle diameter of the pores present in the observation field. This procedure is performed for 10 sample pieces, and the arithmetic mean value of the equivalent circle diameters of the pores is defined as the average pore diameter Dm of the pores present in the center of the thickness. Also, a 9 μm × 12 μm area, with one side corresponding to the inner peripheral surface of the belt, is observed at a magnification of 10,000 times to determine the equivalent circle diameter of the pores present in the observation field. This procedure is performed for 10 sample pieces, and the arithmetic mean value of the equivalent circle diameters of the pores is taken as the average pore diameter Di of the pores present on the inner peripheral surface side.

[0029] (composition) The endless belt according to the present embodiment contains a resin and conductive particles. Specifically, for example, the endless belt is made of a single layer of resin containing conductive particles. In particular, the endless belt (the resin layer constituting the endless belt) preferably contains silicone oil from the viewpoint of improving bending resistance during rotational driving. The endless belt (the resin layer constituting the endless belt) may contain other well-known components as needed.

[0030] -resin- Examples of resins include polyimide resins (PI resins), polyamideimide resins (PAI resins), aromatic polyether ketone resins (e.g., aromatic polyether ether ketone resins), polyphenylene sulfide resins (PPS resins), polyetherimide resins (PEI resins), polyester resins, polyamide resins, and polycarbonate resins. From the viewpoint of improving bending resistance during rotational driving, the resin is preferably a polyimide resin (that is, a resin containing a structural unit having an imide bond), more preferably a polyimide resin or a polyamideimide resin, and most preferably a polyimide resin.

[0031] Examples of polyimide resins include imidized products of polyamic acids (precursors of polyimide resins), which are polymers of tetracarboxylic dianhydrides and diamine compounds. An example of the polyimide resin is a resin having a structural unit represented by the following general formula (I).

[0032] [ka]

[0033] In general formula (I), R 1 represents a tetravalent organic group, and R 2 represents a divalent organic group. R 1 Examples of the tetravalent organic group represented by the formula (1) include an aromatic group, an aliphatic group, a cyclic aliphatic group, a group in which an aromatic group and an aliphatic group are combined, and groups in which these groups are substituted. Specific examples of the tetravalent organic group include residues of tetracarboxylic dianhydrides, which will be described later. R 2 Examples of the divalent organic group represented by the formula (I) include an aromatic group, an aliphatic group, a cyclic aliphatic group, a group combining an aromatic group and an aliphatic group, and a group obtained by substituting any of these. Specific examples of the divalent organic group include residues of diamine compounds described below.

[0034] Specific examples of tetracarboxylic dianhydrides used as raw materials for polyimide resins include pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)sulfonic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, and ethylenetetracarboxylic dianhydride.

[0035] Specific examples of diamine compounds used as raw materials for polyimide resins include 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3'-dimethyl 4,4'-biphenyldiamine, benzidine, and 3,3'-dimethyl Benzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylpropane, 2,4-bis(β-amino-tert-butyl)toluene, bis(p-β-amino-tert-butylphenyl)ether, bis(p-β-methyl-δ-aminophenyl)benzene, bis-p-(1,1-dimethyl-5-amino-pentyl)benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di(p -aminocyclohexyl)methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetradiamine, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylheptamethylenediamine, Examples include 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 12-diaminooctadecane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, piperazine, HN(CH)O(CH)O(CH)NH, HN(CH)S(CH)NH, and HN(CH)N(CH)(CH)NH.

[0036] The polyamide-imide resin may be a resin having an imide bond and an amide bond in the repeating unit. More specifically, the polyamide-imide resin may be a polymer of a trivalent carboxylic acid compound (also called tricarboxylic acid) having an acid anhydride group and a diisocyanate compound or a diamine compound.

[0037] As the tricarboxylic acid, trimellitic anhydride and its derivatives are preferred. In addition to the tricarboxylic acid, tetracarboxylic dianhydride, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, etc. may be used in combination.

[0038] Examples of the diisocyanate compound include 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 2,2'-dimethylbiphenyl-4,4'-diisocyanate, biphenyl-4,4'-diisocyanate, biphenyl-3,3'-diisocyanate, biphenyl-3,4'-diisocyanate, 3,3'-diethylbiphenyl-4,4'-diisocyanate, 2,2'-diethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, 2,2'-dimethoxybiphenyl-4,4'-diisocyanate, naphthalene-1,5-diisocyanate, and naphthalene-2,6-diisocyanate. The diamine compound may be a compound having a structure similar to that of the above-mentioned isocyanate, but having an amino group instead of the isocyanato group.

[0039] Here, the resin content of the endless belt (the resin layer constituting it) is preferably 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and even more preferably 75% by mass or more and 90% by mass or less.

[0040] -Conductive particles- The conductive particles are conductive (for example, a volume resistivity of 10 7 Ω·cm or less, and so on below) or semi-conductive (e.g., volume resistivity 10 7 Ω cm or more 10 13 Examples include powders with a resistivity of Ω·cm or less, and the same applies below. Specifically, examples of the conductive particles include conductive carbon particles and metal oxide particles.

[0041] An example of the conductive carbon particles is carbon black. Examples of carbon black include ketjen black, oil furnace black, channel black, acetylene black, etc. Surface-treated carbon black (hereinafter also referred to as "surface-treated carbon black") may also be used as the carbon black. Surface-treated carbon black can be obtained by adding, for example, a carboxy group, a quinone group, a lactone group, a hydroxy group, etc. to its surface. Examples of surface treatment methods include an air oxidation method in which the carbon black is reacted with air in a high-temperature atmosphere, a method in which the carbon black is reacted with nitrogen oxides or ozone at room temperature (e.g., 22°C), and a method in which the carbon black is oxidized with air in a high-temperature atmosphere and then oxidized with ozone at a low temperature.

[0042] Examples of the metal oxide particles include tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles.

[0043] Examples of conductive particles include metal particles (e.g., aluminum particles, nickel particles, etc.), ion-conductive particles (e.g., potassium titanate particles, LiCl particles, etc.), etc.

[0044] Among these, carbon black is preferred as the conductive particles from the viewpoint of improving electrical properties.

[0045] The average primary particle size of the conductive particles is preferably 2 nm or more and 40 nm or less, more preferably 8 nm or more and 20 nm or less, and even more preferably 10 nm or more and 15 nm or less.

[0046] The method for measuring the average primary particle size of the conductive particles is as follows. First, a 100 nm diameter film was cut from the endless belt (the resin layer that makes up the belt) using a microtome. A sample for measuring the thickness is taken and observed using a TEM (transmission electron microscope).The diameter of a circle equal to the projected area of ​​each of 50 primary particles of the conductive particles (i.e., the equivalent circle diameter) is taken as the particle size, and the average value is taken as the average primary particle size of the conductive particles.

[0047] The content of the conductive particles is preferably 10% by mass or more and 50% by mass or less, more preferably 12% by mass or more and 40% by mass or less, and more preferably 15% by mass or more and 30% by mass or less, of the endless belt (the resin layer that constitutes it).

[0048] -Silicone oil- The silicone oil has the function of partially volatilizing during the formation of the endless belt (the resin layer that constitutes it), forming pores (i.e., air bubbles) inside the belt and forming a porous structure with the above-mentioned pore area ratio and average pore size.

[0049] Examples of silicone oils include straight silicones such as dimethyl silicone oil, methyl hydrogen silicone oil, diphenyl silicone oil, methyl phenyl silicone oil, and chlorophenyl silicone oil; and modified silicone oils such as alkyl-modified silicone oil, aralkyl-modified silicone oil, polyether-modified silicone oil, polyester-modified silicone oil, fluoroalkyl-modified silicone oil, amino-modified silicone oil, alkoxy-modified silicone oil, epoxy-modified silicone oil, and carboxyl group-modified silicone oil.

[0050] Among these, polyether-modified silicone oil is preferred as the silicone oil from the viewpoint of forming a porous structure having the above-mentioned pore area ratio and average pore size.

[0051] Examples of polyether-modified silicone oils include silicone oils in which at least one of the side chains and terminals of a polysiloxane chain is modified with polyalkylene oxide.

[0052] In particular, from the viewpoint of forming a porous structure having the above-mentioned pore area ratio and average pore size, the number average molecular weight of the polyether-modified silicone oil is preferably 300 or more and 20,000 or less, more preferably 300 or more and 10,000 or less, and even more preferably 500 or more and 10,000 or less. The number average molecular weight of silicone oil is measured by gel permeation chromatography (GPC). Molecular weight measurement by GPC is performed using a Tosoh GPC HLC-8120GPC measuring device, a Tosoh TSKgel SuperHM-M (15 cm) column, and tetrahydrofuran (THF) as the solvent. The number average molecular weight is calculated from the measurement results using a molecular weight calibration curve created with monodisperse polystyrene standard samples.

[0053] -Other ingredients- Examples of other components include fillers for improving mechanical strength, antioxidants for preventing thermal deterioration of the belt, surfactants for improving fluidity, and heat-resistant anti-aging agents. When other components are contained, the content of the other components is preferably more than 0% by mass and not more than 10% by mass, more preferably more than 0% by mass and not more than 5% by mass, and even more preferably more than 0% by mass and not more than 1% by mass, relative to the endless belt (the resin layer constituting the endless belt).

[0054] (thickness of endless belt) The thickness of the endless belt (the resin layer constituting the endless belt) according to this embodiment is, for example, preferably 60 μm or more and 120 μm or less, and more preferably 60 μm or more and 110 μm or less.

[0055] The thickness of the endless belt is measured as follows. That is, the cross section of the endless belt in the thickness direction is observed with an optical microscope or a scanning electron microscope, the thickness of the endless belt to be measured is measured at 10 points, and the average value is taken as the thickness.

[0056] (Young's modulus) The Young's modulus of the endless belt according to the present embodiment is preferably 2900 MPa or more and 5500 or less, and more preferably 3000 MPa or more and 3600 or less, from the viewpoint of improving the bending resistance during rotational driving. The Young's modulus of the endless belt is adjusted by, for example, the type of resin and the weight average molecular weight of the resin.

[0057] The Young's modulus of the endless belt is measured as follows. Using a tensile testing machine (Model-1605N, manufactured by Aiko Engineering Co., Ltd.), the endless belt is cut into a piece of 80 mm x 5 mm so that the circumferential direction is long, and the test is carried out at a tensile speed of 20 mm / min with the test piece length between the chuck jigs set to 40 mm.Young's modulus is calculated from the slope of the linear region of the SS curve (strain 10 N-38 N).

[0058] (Manufacturing method of endless belt) A method for manufacturing an endless belt according to the present embodiment includes, for example, a step of applying a resin solution containing a resin or a precursor thereof and conductive particles onto a surface of a mold to form a coating film; a step of heating and drying the coating film, and optionally reacting the precursor (e.g., imidizing in the case of a polyimide resin precursor) to form a resin film; A step of releasing the resin film from the mold; It has. Then, the resin film is removed from the mold to form an endless belt.

[0059] Here, the mold is not particularly limited, but a cylindrical mold is preferably used. The substrate may be a metal substrate. Furthermore, instead of a metal mold, a mold made of other materials such as resin, glass, or ceramic may be used. Furthermore, the surface of the mold may be provided with a glass coat, a ceramic coat, or the like, or may be coated with a release agent such as a silicone-based or fluorine-based release agent.

[0060] Examples of methods for applying the resin solution include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0061] In the method for manufacturing an endless belt according to this embodiment, a resin solution containing silicone oil is applied, and the evaporation state of the silicone oil can be varied in the thickness direction of the belt by adjusting the heating and drying conditions of the coating (drying temperature, drying air speed), thereby obtaining an endless belt having a porous structure with the above-mentioned pore area ratio and average pore size.

[0062] (Endless belt applications) The endless belt according to the present embodiment can be used, for example, as an endless belt for an electrophotographic image forming apparatus. Examples of the endless belt for an electrophotographic image forming apparatus include an intermediate transfer belt, a transfer belt (i.e., a recording medium transport belt), a fixing belt (e.g., a heating belt, a pressure belt), and a transport belt (i.e., a recording medium transport belt). The endless belt according to the present embodiment can be used not only as an endless belt for an image forming apparatus, but also as a belt-like member such as a conveyor belt, a drive belt, a laminate belt, an electrical insulating material, a pipe covering material, an electromagnetic wave insulating material, a heat source insulator, and an electromagnetic wave absorbing film. The endless belt according to the present embodiment may have a functional layer on the outer peripheral surface side or the inner peripheral surface side depending on the application. However, the endless belt according to the present embodiment is preferably applied as a resin substrate layer.

[0063] [Transfer device] The transfer device according to this embodiment includes an intermediate transfer belt onto whose outer peripheral surface a toner image is transferred, a primary transfer device having a primary transfer member that performs primary transfer of the toner image formed on the surface of an image carrier onto the outer peripheral surface of the intermediate transfer belt, and a secondary transfer device that is arranged in contact with the outer peripheral surface of the intermediate transfer belt and has a secondary transfer member that performs secondary transfer of the toner image transferred onto the outer peripheral surface of the intermediate transfer belt onto the surface of a recording medium. As the intermediate transfer belt, an intermediate transfer belt having the endless belt according to the present embodiment is applied. The transfer device according to this embodiment may include a known device such as a cleaning device having a cleaning member that cleans the outer peripheral surface of the intermediate transfer belt.

[0064] (Intermediate transfer belt) The intermediate transfer belt has the endless belt according to the present embodiment. The intermediate transfer belt may be a single-layer endless belt or a laminate having an endless belt as a resin substrate layer. The laminate may be, for example, a laminate having a resin substrate layer, an elastic layer provided on the resin substrate layer, and a release layer provided on the elastic layer, or a laminate having a resin substrate layer and a release layer provided on the resin substrate layer.

[0065] The elastic layer will now be described. The elastic layer is made of a heat-resistant elastic material. Examples of heat-resistant elastic materials include silicone rubber and fluororubber. Examples of silicone rubber include RTV (Room Temperature Vulcanizing) silicone rubber, HTV (High Temperature Vulcanizing) silicone rubber, and liquid silicone rubber, and specific examples include polydimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, and fluorosilicone rubber. Examples of fluororubbers include vinylidene fluoride rubber, tetrafluoroethylene / propylene rubber, tetrafluoroethylene / perfluoromethylvinyl ether rubber, phosphazene rubber, and fluoropolyether.

[0066] The elastic layer may contain other components, such as fillers, conductive agents, softeners (paraffin-based, etc.), processing aids (stearic acid, etc.), antioxidants (amine-based, etc.), vulcanizing agents (sulfur, metal oxides, peroxides, etc.), and functional fillers (alumina, etc.).

[0067] The release layer will now be described. The release layer includes, for example, a heat-resistant release material. Examples of heat-resistant release materials include fluororubber, fluororesin, silicone resin, and polyimide resin. Among these, fluororesins are preferred as the heat-resistant release material. Specific examples of fluororesins include tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polyethylene / tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and polyvinyl fluoride (PVF).

[0068] The intermediate transfer belt may have a known structure, except for the endless belt according to the present embodiment.

[0069] -Volume resistivity of intermediate transfer belt- The common logarithm of the volume resistivity of the intermediate transfer belt when a voltage of 100 V is applied for 10 seconds is preferably 8.0 (log Ω·cm) or more and 13.5 (log Ω·cm) or less, and more preferably 8.5 (log Ω·cm) or more and 13.2 (log Ω·cm) or less. The volume resistivity of the intermediate transfer belt when a voltage of 500 V is applied for 10 seconds is measured by the following method. A microcurrent meter (Advantest R8430A) is used as the resistance measuring device, and a UR probe (Mitsubishi Chemical Analytech Co., Ltd.) is used as the probe. The volume resistivity (log Ω cm) is measured at 18 points in total (6 points at equal intervals around the circumference of the intermediate transfer belt, and 3 points at the center and both ends in the width direction) at a voltage of 500 V, an application time of 10 seconds, and a pressure of 1 kgf, and the average value is calculated. The measurements are also performed in an environment with a temperature of 22°C and a humidity of 55% RH.

[0070] (Surface resistivity of intermediate transfer belt) The common logarithm of the surface resistivity when a voltage of 100 V is applied to the outer peripheral surface of the intermediate transfer belt for 10 seconds is preferably 9.5 (log Ω / suq.) or more and 15.0 (log Ω / suq.) or less, more preferably 10.5 (log Ω / suq.) or more and 14.0 (log Ω / suq.) or less, and particularly preferably 11.0 (log Ω / suq.) or more and 13.5 (log Ω / suq.) or less. The unit of surface resistivity, log Ω / suq., is a logarithmic value of the resistance per unit area, and is also expressed as log(Ω / suq.), log Ω / suquare, log Ω / □, etc. The surface resistivity when a voltage of 100 V is applied to the outer peripheral surface of the intermediate transfer belt for 10 seconds is measured by the following method. Using a microcurrent meter (Advantest R8430A) as the resistance measuring device and a UR probe (Mitsubishi Chemical Analytech Co., Ltd.) as the probe, the surface resistivity (log Ω / suq.) of the outer surface of the endless belt is measured at 18 points in total (6 points equally spaced circumferentially and 3 points at the center and both ends in the width direction) at a voltage of 500 V for 10 seconds and a pressure of 1 kgf, and the average value is calculated. The measurements are also performed in an environment of 22°C temperature and 55% RH humidity.

[0071] (Primary transfer device) In the primary transfer device, the primary transfer member is disposed opposite to the image carrier with the intermediate transfer belt sandwiched therebetween, and the toner image is primarily transferred onto the outer peripheral surface of the intermediate transfer belt by applying a voltage of a polarity opposite to the charge polarity of the toner to the intermediate transfer belt by the primary transfer member.

[0072] (Secondary transfer device) In the secondary transfer device, the secondary transfer member is disposed on the toner image bearing side of the intermediate transfer belt. The secondary transfer device includes, for example, a backing member disposed on the opposite side of the intermediate transfer belt from the toner image bearing side, along with the secondary transfer member. In the secondary transfer device, the intermediate transfer belt and recording medium are sandwiched between the secondary transfer member and the backing member to form a transfer electric field, thereby secondarily transferring the toner image on the intermediate transfer belt to the recording medium. The secondary transfer member may be a secondary transfer roll or a secondary transfer belt. The backing member may be, for example, a backing roll.

[0073] (cleaning device) In the cleaning device, the cleaning member is disposed on the toner image bearing side of the intermediate transfer belt. The cleaning device further includes, for example, the cleaning member and a backing member disposed on the opposite side of the intermediate transfer belt from the toner image bearing side. In the cleaning device, for example, the cleaning member cleans the outer peripheral surface of the intermediate transfer belt while sandwiching the intermediate transfer belt between the cleaning member and the backing member. Examples of the cleaning member include a cleaning blade and a cleaning brush.

[0074] The transfer device according to the present embodiment may be a transfer device that transfers a toner image onto the surface of a recording medium via multiple intermediate transfer bodies. That is, the transfer device may be, for example, a transfer device that performs primary transfer of a toner image from an image carrier to a first intermediate transfer body, secondary transfer of the toner image from the first intermediate transfer body to a second intermediate transfer body, and then tertiary transfer of the toner image from the second intermediate transfer body to a recording medium. The transfer device applies an intermediate transfer belt having the endless belt according to the present embodiment to at least one of a plurality of intermediate transfer bodies.

[0075] [Image forming device] The image forming apparatus according to the present embodiment includes a toner image forming device that forms a toner image on the surface of an image carrier, and a transfer device that transfers the toner image formed on the surface of the image carrier onto the surface of a recording medium. The transfer device according to the present embodiment is applied to the transfer device.

[0076] An example of a toner image forming device is a device that includes an image carrier, a charging device that charges the surface of the image carrier, an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged image carrier, and a developing device that develops the electrostatic latent image formed on the surface of the image carrier using a developer containing toner to form a toner image.

[0077] The image forming apparatus according to this embodiment may be any known image forming apparatus, such as an apparatus equipped with a fixing device that fixes a toner image transferred onto the surface of a recording medium; an apparatus equipped with a cleaning device that cleans the surface of an image carrier after the toner image is transferred and before the image carrier is charged; an apparatus equipped with a static elimination device that irradiates the surface of an image carrier with static elimination light to eliminate static electricity after the toner image is transferred and before the image carrier is charged; or an apparatus equipped with an image carrier heating member that increases the temperature of the image carrier and reduces the relative temperature.

[0078] The image forming apparatus according to this embodiment may be either a dry development type image forming apparatus or a wet development type image forming apparatus (a development type using a liquid developer).

[0079] In the image forming apparatus according to the present embodiment, for example, the portion including the image carrier may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge including a toner image forming device and a transfer device is preferably used.

[0080] An example of an image forming apparatus according to the present embodiment will be described below with reference to the drawings. However, the image forming apparatus according to the present embodiment is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0081] (Image forming device) FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to this embodiment.

[0082] 1, image forming apparatus 100 according to this embodiment is, for example, an intermediate transfer type image forming apparatus generally called a tandem type, and includes a plurality of image forming units 1Y, 1M, 1C, and 1K (an example of a toner image forming device) that form toner images of each color component by electrophotography, a primary transfer unit 10 that sequentially transfers (primary transfer) the toner images of each color component formed by each image forming unit 1Y, 1M, 1C, and 1K onto an intermediate transfer belt 15, a secondary transfer unit 20 that collectively transfers (secondary transfer) the superimposed toner images transferred onto intermediate transfer belt 15 onto paper K, which is a recording medium, and a fixing device 60 that fixes the secondarily transferred images onto paper K. Image forming apparatus 100 also has a control unit 40 that controls the operation of each device (each unit).

[0083] Each of the image forming units 1Y, 1M, 1C, and 1K of the image forming apparatus 100 includes a photoconductor 11 (an example of an image carrier) that rotates in the direction of arrow A and carries a toner image formed on its surface.

[0084] Around the photosensitive member 11, there is provided a charger 12 as an example of a charging means for charging the photosensitive member 11, and there is provided a laser exposure device 13 (the exposure beam is indicated by the symbol Bm in the figure) as an example of an electrostatic latent image forming device for writing an electrostatic latent image on the photosensitive member 11.

[0085] In addition, around the photosensitive member 11, there is provided a developing device 14 as an example of a developing means, which contains toner of each color component and makes the electrostatic latent image on the photosensitive member 11 visible using the toner, and there is provided a primary transfer roll 16 which transfers the toner image of each color component formed on the photosensitive member 11 to an intermediate transfer belt 15 at the primary transfer section 10.

[0086] Furthermore, a photoreceptor cleaner 17 is provided around the photoreceptor 11 to remove residual toner from the photoreceptor 11, and electrophotographic devices including a charger 12, a laser exposure device 13, a developing device 14, a primary transfer roll 16, and the photoreceptor cleaner 17 are arranged in this order along the rotation direction of the photoreceptor 11. These image forming units 1Y, 1M, 1C, and 1K are arranged in a substantially linear fashion from the upstream side of the intermediate transfer belt 15 in the order of yellow (Y), magenta (M), cyan (C), and black (K).

[0087] The intermediate transfer belt 15 is driven (rotated) in a circular manner by various rolls at a speed suited to the purpose in the direction of arrow B shown in Fig. 1. These rolls include a drive roll 31 driven by a motor (not shown) with excellent constant speed characteristics to rotate the intermediate transfer belt 15, a support roll 32 that supports the intermediate transfer belt 15 that extends in a substantially straight line along the arrangement direction of the photoconductors 11, a tensioning roll 33 that applies tension to the intermediate transfer belt 15 and functions as a correction roll that prevents the intermediate transfer belt 15 from meandering, a backing roll 25 provided in the secondary transfer unit 20, and a cleaning backing roll 34 provided in a cleaning unit that scrapes off residual toner on the intermediate transfer belt 15.

[0088] The primary transfer unit 10 is composed of a primary transfer roll 16 disposed opposite the photoconductor 11 with the intermediate transfer belt 15 sandwiched therebetween. The primary transfer roll 16 is disposed in pressure contact with the photoconductor 11 with the intermediate transfer belt 15 sandwiched therebetween, and a voltage (primary transfer bias) of the opposite polarity to the charge polarity of the toner (negative polarity; the same applies below) is applied to the primary transfer roll 16. As a result, the toner images on the photoconductors 11 are electrostatically attracted to the intermediate transfer belt 15 in sequence, and superimposed toner images are formed on the intermediate transfer belt 15.

[0089] The secondary transfer unit 20 is configured to include a back roll 25 and a secondary transfer roll 22 that is disposed on the toner image bearing surface side of the intermediate transfer belt 15 .

[0090] The back roll 25 has a surface resistivity of 1 x 10 7Ω / □ or more 1×10 10 The hardness is set to, for example, 70° (Asker C, manufactured by Kobunshi Keiki Co., Ltd.; the same applies hereinafter.) The back roll 25 is disposed on the back side of the intermediate transfer belt 15 and constitutes an opposing electrode of the secondary transfer roll 22, and is in contact with a metal power supply roll 26 to which a secondary transfer bias is stably applied.

[0091] On the other hand, the secondary transfer roll 22 has a volume resistivity of 10 7.5 Ωcm or more 10 8.5 The secondary transfer roll 22 is a cylindrical roll of Ωcm or less. The secondary transfer roll 22 is arranged in pressure contact with the back roll 25 with the intermediate transfer belt 15 sandwiched therebetween, and the secondary transfer roll 22 is grounded to form a secondary transfer bias between the secondary transfer roll 22 and the back roll 25, thereby performing a second transfer of the toner image onto the paper K being transported to the secondary transfer unit 20.

[0092] In addition, an intermediate transfer belt cleaning member 35 is provided downstream of the secondary transfer section 20 of the intermediate transfer belt 15 so as to be freely movable toward and away from the intermediate transfer belt 15, and removes residual toner and paper dust from the intermediate transfer belt 15 after the secondary transfer and cleans the outer surface of the intermediate transfer belt 15. Further, downstream of the secondary transfer unit 20 of the secondary transfer roll 22, a secondary transfer roll cleaning member 22A is provided to remove residual toner and paper dust from the secondary transfer roll 22 after secondary transfer and clean the outer peripheral surface of the intermediate transfer belt 15. The secondary transfer roll cleaning member 22A is exemplified by a cleaning blade, but may also be a cleaning roll.

[0093] The intermediate transfer belt 15, the primary transfer roll 16, the secondary transfer roll 22, and the intermediate transfer belt cleaning member 35 correspond to an example of a transfer device. Here, the image forming apparatus 100 may be configured to include a secondary transfer belt (an example of a secondary transfer member) instead of the secondary transfer roll 22. Specifically, as shown in Fig. 2, the image forming apparatus 100 may include a secondary transfer device including a secondary transfer belt 23, a drive roll 23A disposed opposite to a back roll 25 with the intermediate transfer belt 15 and the secondary transfer belt 23 interposed therebetween, and an idler roll 23B that stretches the secondary transfer belt 23 together with the drive roll 23A.

[0094] Meanwhile, a reference sensor (home position sensor) 42 is disposed upstream of the yellow image forming unit 1Y, generating a reference signal that serves as a reference for timing image formation in each of the image forming units 1Y, 1M, 1C, and 1K. An image density sensor 43 for adjusting image quality is disposed downstream of the black image forming unit 1K. This reference sensor 42 generates a reference signal by recognizing a mark provided on the back side of the intermediate transfer belt 15, and each of the image forming units 1Y, 1M, 1C, and 1K is configured to start image formation in response to an instruction from the control unit 40 based on the recognition of this reference signal.

[0095] Furthermore, the image forming apparatus according to this embodiment is equipped with a transport means for transporting paper K, which includes a paper storage section 50 for storing paper K, a paper feed roll 51 for taking out and transporting paper K accumulated in the paper storage section 50 at a predetermined timing, a transport roll 52 for transporting paper K unwound by the paper feed roll 51, a transport guide 53 for sending paper K transported by the transport roll 52 to the secondary transfer section 20, a transport belt 55 for transporting paper K transported after secondary transfer by the secondary transfer roll 22 to the fixing device 60, and a fixing entrance guide 56 for guiding paper K to the fixing device 60.

[0096] Next, the basic image forming process of the image forming apparatus according to this embodiment will be described. In the image forming apparatus according to this embodiment, image data output from an image reading device (not shown) or a personal computer (PC) (not shown) is subjected to image processing by an image processing device (not shown), and then image formation is performed by image forming units 1Y, 1M, 1C, and 1K.

[0097] The image processing device performs image processing on the input image data, such as shading correction, positional deviation correction, brightness / color space conversion, gamma correction, and various image editing operations such as frame erasure, color editing, and movement editing. The image data that has undergone image processing is converted into color material gradation data for four colors, Y, M, C, and K, and is output to the laser exposure device 13.

[0098] In accordance with the input color material gradation data, the laser exposure device 13 irradiates the photoconductor 11 of each of the image forming units 1Y, 1M, 1C, and 1K with an exposure beam Bm emitted from, for example, a semiconductor laser. After the surface of the photoconductor 11 of each of the image forming units 1Y, 1M, 1C, and 1K is charged by the charger 12, the surface is scanned and exposed by the laser exposure device 13 to form an electrostatic latent image. The formed electrostatic latent image is developed into a toner image of each color of Y, M, C, and K by each of the image forming units 1Y, 1M, 1C, and 1K.

[0099] The toner images formed on the photoconductors 11 of the image forming units 1Y, 1M, 1C, and 1K are transferred onto the intermediate transfer belt 15 in the primary transfer section 10 where each photoconductor 11 comes into contact with the intermediate transfer belt 15. More specifically, in the primary transfer section 10, a voltage (primary transfer bias) of the opposite polarity to the charge polarity (negative polarity) of the toner is applied to the base material of the intermediate transfer belt 15 by the primary transfer roll 16, and the toner images are sequentially superimposed on the outer peripheral surface of the intermediate transfer belt 15 to perform the primary transfer.

[0100] After the toner images are sequentially primarily transferred onto the outer peripheral surface of the intermediate transfer belt 15, the intermediate transfer belt 15 moves, and the toner images are transported to the secondary transfer unit 20. When the toner images are transported to the secondary transfer unit 20, the transport means rotates the paper feed roll 51 in synchronization with the timing at which the toner images are transported to the secondary transfer unit 20, and paper K of the desired size is supplied from the paper storage unit 50. The paper K supplied by the paper feed roll 51 is transported by the transport roll 52 and reaches the secondary transfer unit 20 via the transport guide 53. Before reaching the secondary transfer unit 20, the paper K is temporarily stopped, and a positioning roll (not shown) rotates in synchronization with the movement of the intermediate transfer belt 15 on which the toner images are held, thereby aligning the position of the paper K with the position of the toner image.

[0101] In the secondary transfer unit 20, the secondary transfer roll 22 is pressed against the back roll 25 via the intermediate transfer belt 15. At this time, the paper K, which has been conveyed in time, is sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22. At this time, when a voltage (secondary transfer bias) of the same polarity as the charge polarity (negative polarity) of the toner is applied from the power supply roll 26, a transfer electric field is formed between the secondary transfer roll 22 and the back roll 25. Then, the unfixed toner images held on the intermediate transfer belt 15 are electrostatically transferred onto the paper K all at once in the secondary transfer unit 20, which is pressed by the secondary transfer roll 22 and the back roll 25.

[0102] Thereafter, the paper sheet K onto which the toner image has been electrostatically transferred is transported as is after being peeled off from the intermediate transfer belt 15 by the secondary transfer roll 22, and is transported to a transport belt 55 provided downstream of the secondary transfer roll 22 in the paper transport direction. The transport belt 55 transports the paper sheet K to the fixing device 60 at an optimal transport speed for the fixing device 60. The unfixed toner image on the paper sheet K transported to the fixing device 60 is fixed onto the paper sheet K by being subjected to a fixing process using heat and pressure by the fixing device 60. The paper sheet K on which the fixed image has been formed is then transported to an ejected paper storage unit (not shown) provided in the ejection unit of the image forming apparatus.

[0103] On the other hand, after the transfer to the paper K is completed, the residual toner remaining on the intermediate transfer belt 15 is transported to the cleaning section as the intermediate transfer belt 15 rotates, and is removed from the intermediate transfer belt 15 by the cleaning back roll 34 and the intermediate transfer belt cleaning member 35.

[0104] Although the present embodiment has been described above, it should not be construed as being limited to the above embodiment, and various modifications, changes, and improvements are possible. [Example]

[0105] Examples of the present invention will be described below, but the present invention is not limited to the following examples. In the following description, unless otherwise specified, all "parts" and "%" are based on mass.

[0106] Example 1 A solution containing a resin or a resin precursor and conductive particles (hereinafter also referred to as a specific solution) was prepared as follows. A dispersion was obtained by dispersing an N-methyl-2-pyrrolidone solution (solids concentration after imide conversion: 18% by mass) of polyamic acid composed of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether as a solution containing a resin or a resin precursor, carbon black (Special Black 4, manufactured by Orion Engineered Carbons) as conductive particles, and the silicone oil shown in Table 1 using a high-pressure collision disperser. This dispersion and the N-methyl-2-pyrrolidone solution of the polyamic acid were kneaded together, and the amount of carbon black was adjusted to 24 parts by mass per 100 parts by mass of the resin solid content to prepare a specific solution. The amount of silicone oil added to the specific solution was adjusted as shown in Table 1. An aluminum cylinder with an outer diameter of 366 mm and a length of 600 mm was prepared as a cylindrical mold. The coating solution (i.e., the specific solution) was dispensed onto the outer surface of the cylinder via a dispenser over a width of 500 mm to a thickness of 80 μm. The cylinder on which the coating film was formed was kept horizontal, and the coating film was dried by heating under the drying conditions shown in Table 1. Next, the dried coating film was heated to a maximum temperature of 320°C for 120 minutes to form a resin film. The mold was removed by hand to peel off the resin film from the mold. The axial center of the resin film was cut to a width of 363 mm to obtain an endless belt.

[0107] <Examples 2 to 25, Comparative Example 1> The type and amount of silicone oil added and the drying conditions for the coating were changed as shown in Table 1. Except for this operation, an endless belt was obtained in the same manner as in Example 1.

[0108] <Comparative Example 2> The solution containing the resin or resin precursor in Example 1 was changed to a polyamideimide varnish (HPC-9000F-8, solid content 13 mass%, manufactured by Resonac Corporation), which is a solution containing a resin, and the conductive particles were FW-1COLOR BLACK FW1, manufactured by Orion Engineered Carbons Co., Ltd. Except for this operation, an endless belt was obtained in the same manner as in Example 1.

[0109] <Evaluation> (characteristic evaluation) The endless belt of each example was measured for the following properties according to the methods already described. Area ratio Ao of holes on the outer periphery of the belt in the cross section along the belt thickness direction The area ratio Am of holes present in the center of the belt thickness in a cross section along the belt thickness direction Area ratio Ai of holes present on the inner peripheral surface of the belt in the cross section along the belt thickness direction Area ratio A of holes when observing the outer surface The average diameter Do of the pores on the outer periphery of the belt in the cross section along the belt thickness direction The average diameter Dm of the pores at the center of the belt thickness in the cross section along the belt thickness direction The average diameter Di of the pores on the inner surface of the belt in the cross section along the belt thickness direction Young's modulus

[0110] (bending resistance) The bending resistance of each of the endless belts was evaluated as follows. Using a bending tester, the endless belt was repeatedly bent under the following test conditions: bending radius: 0.38 mm, bending angle: 135 degrees, bending speed: 175 reciprocations / minute. The test was performed with the back side of the belt in the compression direction, and the number of times until the endless belt broke was evaluated.

[0111] The results are shown in Table 1. Details of abbreviations etc. in Table 1 are as follows: PI: Polyimide resin PAI: Polyamide-imide resin SB4: Carbon black particles (Special Black 4, manufactured by Orion Engineered Carbons) FW1: Carbon black particles (COLOR BLACK FW1, manufactured by Orion Engineered Carbons) KF-352A: Polyether-modified silicone oil (KF-352A, manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight = 2000) BYK-307: Polyether-modified silicone oil (BYK-307, manufactured by Big Chemie Japan Co., Ltd., number average molecular weight = 1600) KF-6012: Polyether-modified silicone oil (KF-6012, manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight = 1800) KF-6015: Polyether-modified silicone oil (KF-6015, manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight = 300)

[0112] [Table 1]

[0113] From the above results, it can be seen that the endless belt of this example is superior in bending resistance during rotational driving compared to the endless belt of the comparative example.

[0114] This embodiment includes the following aspects. (((1))) resin and conductive particles, An endless belt having holes inside, the number of holes increasing from the outer peripheral surface toward the inner peripheral surface. (((2))) In the cross section along the belt thickness direction, The area ratio Ao of the holes present on the outer peripheral surface side is 0.05% or more and 1.5% or less, The area ratio Am of the holes present in the thickness central portion is 1.0% or more and 5.0% or less, The endless belt according to (((1))), wherein the area ratio Ai of the holes present on the inner peripheral surface side is 2.0% or more and 20.0% or less. (((3))) The ratio Ao / Am of the area ratio Ao of the holes to the area ratio Am of the holes is 0.1 or more and 0.8 or less. The endless belt according to (((2))), wherein the ratio Am / Ai of the area ratio Am of the holes to the area ratio Ai of the holes is 0.1 or more and 0.8 or less. (((4))) The endless belt according to any one of (((1))) to (((3))), wherein the area ratio A of the holes when observing the outer peripheral surface is 0.01% or more and 1.0% or less. (((5))) In the cross section along the belt thickness direction, The average pore diameter Do of the pores present on the outer peripheral surface side is 0 μm or more and 1.5 μm or less. The average pore diameter Dm of the pores present in the thickness central portion is 0.5 μm or more and 5.0 μm or less, The endless belt according to any one of (((1))) to (((4))), wherein the average pore diameter Di of the pores present on the inner peripheral surface side is 0.6 μm or more and 10.0 μm or less. (((6))) The endless belt according to any one of (((1))) to (((5))) contains silicone oil. (((7))) The endless belt according to (((6))), wherein the silicone oil is a polyether-modified silicone oil. (((8))) The endless belt according to (((7))), wherein the polyether-modified silicone oil has a number average molecular weight of 300 or more and 10,000 or less. (((9))) The endless belt according to any one of (((1))) to (((8))), wherein the resin is a polyimide resin. (((10))) An intermediate transfer belt having the endless belt according to any one of (((1))) to (((9))). (((11))) an intermediate transfer belt having an outer peripheral surface onto which a toner image is transferred, the intermediate transfer belt having the endless belt according to any one of (((1))) to (((9))); a primary transfer device having a primary transfer member that primarily transfers a toner image formed on the surface of an image carrier onto the outer peripheral surface of the intermediate transfer belt; a secondary transfer device that is disposed in contact with the outer peripheral surface of the intermediate transfer belt and has a secondary transfer member that secondarily transfers the toner image transferred onto the outer peripheral surface of the intermediate transfer belt onto a surface of a recording medium; A transfer device comprising: (((12))) a toner image forming device having an image carrier and forming a toner image on a surface of the image carrier; a transfer device that transfers the toner image formed on the surface of the image carrier to a surface of a recording medium, the transfer device being described in (((11))); An image forming apparatus comprising:

[0115] The effects of the above embodiment are as follows. According to the invention (((1))), there is provided an endless belt that contains a resin and conductive particles and has holes inside, and that has excellent bending resistance during rotational driving, compared to an endless belt in which there is no change in the proportion of holes on the outer peripheral surface side and the inner peripheral surface side.

[0116] The invention according to (((2))) provides an endless belt that has excellent bending resistance during rotational driving, compared to endless belts in which the hole area ratio Ao is less than 0.05% or exceeds 1.5%, the hole area ratio Am is less than 1.0% or exceeds 5.0%, or the hole area ratio Ai is less than 2.0% or exceeds 20.0%. According to the invention related to (((3))), an endless belt is provided which has excellent bending resistance during rotational driving, compared to when the ratio Ao / Am is less than 0.1 or exceeds 0.8, or when the ratio Am / Ai is less than 0.1 or exceeds 0.8. According to the invention related to (((4))), an endless belt is provided which has excellent resistance to bending during rotational driving, compared to when the area ratio A of the holes is less than 0.01% or exceeds 1.0%. The invention according to (((5))) provides an endless belt that has excellent bending resistance during rotational driving, compared to an endless belt in which the average pore diameter Do of the pores exceeds 1.5 μm, the average pore diameter Dm of the pores is less than 0.5 μm or exceeds 5.0 μm, or the average pore diameter Di of the pores is less than 0.6 μm or exceeds 10.0 μm. According to the inventions (((6))) or (((7))), an endless belt is provided which has superior resistance to bending during rotational driving compared to an endless belt which does not contain silicone oil. According to the invention (((8))), an endless belt is provided which has excellent flex resistance during rotational driving, compared to when the number average molecular weight of the polyether-modified silicone oil is less than 300 or more than 10,000. According to the invention (((9))), an endless belt is provided which has excellent resistance to bending during rotational driving, compared to when the resin is a polyamide-imide resin. According to the inventions of (((10))), (((11))), or (((12))), there is provided an intermediate transfer belt, or a transfer device or image forming device including the same, which is an endless belt containing a resin and conductive particles and having holes inside, and which has excellent bending resistance during rotational driving compared to an endless belt in which the proportion of holes does not change between the outer peripheral surface side and the inner peripheral surface side. [Explanation of symbols]

[0117] 1Y, 1M, 1C, 1K Image forming units 10 Primary transfer unit 11 Photoreceptor 12 Charger 13 Laser exposure device 14 Developer 15 Intermediate transfer belt 16 Primary transfer roll 17 Photoconductor cleaner 20 Secondary transfer unit 22 Secondary transfer roll 22A Secondary transfer roll cleaning member 25 Back Roll 26 Power supply roll 31 Drive Roll 32 Support Roll 33 Tensioning roll 34 Cleaning back roll 35 Intermediate transfer belt cleaning member 40 Control Unit 42 Reference Sensor 43 Image density sensor 50 Paper storage section 51 Paper feed roll 52 Transport roll 53 Transport guide 55 Conveyor belt 56 Fixing entrance guide 60 Fixing device 100 Image forming device

Claims

1. resin and conductive particles, An endless belt having holes inside, the number of holes increasing from the outer peripheral surface toward the inner peripheral surface.

2. In the cross section along the belt thickness direction, The area ratio Ao of the holes present on the outer peripheral surface side is 0.05% or more and 1.5% or less, the area ratio Am of the holes present in the thickness central portion is 1.0% or more and 5.0% or less, 2. The endless belt according to claim 1, wherein an area ratio Ai of the holes present on the inner peripheral surface side is 2.0% or more and 20.0% or less.

3. The ratio Ao / Am of the area ratio Ao of the holes to the area ratio Am of the holes is 0.1 or more and 0.8 or less, 3. The endless belt according to claim 2, wherein a ratio Am / Ai of the area ratio Am of the holes to the area ratio Ai of the holes is 0.1 or more and 0.8 or less.

4. 2. The endless belt according to claim 1, wherein an area ratio A of the holes when the outer peripheral surface is observed is 0.01% or more and 1.0% or less.

5. In the cross section along the belt thickness direction, The average pore diameter Do of the pores present on the outer peripheral surface side is 0 μm or more and 1.5 μm or less, The average pore diameter Dm of the pores present in the thickness central portion is 0.5 μm or more and 5.0 μm or less, 2. The endless belt according to claim 1, wherein the average pore diameter Di of the pores present on the inner peripheral surface side is 0.6 μm or more and 10.0 μm or less.

6. 2. The endless belt according to claim 1, further comprising silicone oil.

7. 7. The endless belt according to claim 6, wherein the silicone oil is a polyether-modified silicone oil.

8. 8. The endless belt according to claim 7, wherein the number average molecular weight of the polyether-modified silicone oil is 300 or more and 10,000 or less.

9. 2. The endless belt according to claim 1, wherein the resin is a polyimide resin.

10. An intermediate transfer belt comprising the endless belt according to any one of claims 1 to 9.

11. an intermediate transfer belt having an outer peripheral surface onto which a toner image is transferred, the intermediate transfer belt including the endless belt according to any one of claims 1 to 9; a primary transfer device having a primary transfer member that primarily transfers a toner image formed on the surface of an image carrier onto the outer peripheral surface of the intermediate transfer belt; a secondary transfer device that is disposed in contact with the outer peripheral surface of the intermediate transfer belt and has a secondary transfer member that secondarily transfers the toner image transferred onto the outer peripheral surface of the intermediate transfer belt onto a surface of a recording medium; A transfer device comprising:

12. a toner image forming device having an image carrier and forming a toner image on a surface of the image carrier; A transfer device that transfers the toner image formed on the surface of the image carrier to a surface of a recording medium, comprising: the transfer device according to claim 11; An image forming apparatus comprising:

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