JP2024062919A - Intermediate transfer belt, transfer device, and image forming apparatus - Google Patents

Abstract

[Problem] To provide an intermediate transfer belt that has excellent toner transfer retention on uneven paper. [Solution] An intermediate transfer belt having metal oxide particles as a solid lubricant on its surface, with the average spacing between the metal oxide particles on the surface being 1000 nm or less, and the average height of the metal oxide particles from the surface being 15 nm to 320 nm. [Selected Figures] None

Description

The present invention relates to an intermediate transfer belt, a transfer device, and an image forming device.

In electrophotographic image forming devices (copiers, facsimiles, printers, etc.), 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 roller, for example, is used to transfer the toner image to the recording medium.

For example, Patent Document 1 discloses an intermediate transfer belt for use in an electrophotographic image forming apparatus, the intermediate transfer belt having a base layer and a surface layer, the surface layer being made of a coating layer formed of a material containing at least a binder resin and inorganic fine particles having a volume average particle diameter of 30 nm to 200 nm, the inorganic fine particles being unevenly distributed and fixed on the surface of the coating layer.

Patent document 2 discloses an elastic transfer belt in which "an elastic layer is laminated on a base layer containing a polyimide resin or a polyamide-imide resin, and the elastic layer is covered with spherical particles having an average particle size of 0.5 to 4 μm and a refractive index at a wavelength of 900 nm that is larger than that of the elastic layer."

Patent Document 3 discloses a method for producing an electrophotographic photoreceptor in which an intermediate layer is formed on a conductive support and a photosensitive layer is formed on the intermediate layer, the method comprising the steps of: obtaining metal oxide fine particles by subjecting a metal oxide fine particle raw material to a hydrophobic treatment with an organic compound; preparing a coating liquid for forming an intermediate layer containing the metal oxide fine particles and a binder resin; and applying the coating liquid for forming an intermediate layer to the outer peripheral surface of the conductive support to form an intermediate layer, the method comprising the steps of: forming an intermediate layer on the electrophotographic photoreceptor; and the metal oxide fine particle raw material subjected to the hydrophobic treatment has an electrolyte content of 20 μS/cm or more and 500 μS/cm or less.

JP 2011-039430 A JP 2011-242724 A JP 2015-141316 A

The object of the present invention is to provide an intermediate transfer belt that is superior in transfer retention of toner onto uneven paper compared to an intermediate transfer belt that satisfies at least one of the following conditions: the average distance between metal oxide particles on the surface exceeds 1000 nm, and the average height of the metal oxide particles from the surface is less than 15 nm or more than 320 nm, and a transfer device and an image forming device that include the intermediate transfer belt.

Means for solving the above problems include the following aspects.
<1>
An intermediate transfer belt comprising metal oxide particles as a solid lubricant on a surface thereof, the metal oxide particles having an average distance between adjacent ones of the metal oxide particles on the surface of the intermediate transfer belt being 1000 nm or less, and an average height of the metal oxide particles from the surface of the intermediate transfer belt being 15 nm or more and 320 nm or less.
＜2＞
The intermediate transfer belt according to <1>, wherein the average distance between the metal oxide particles on the surface is from 3 nm to 200 nm.
＜3＞
The intermediate transfer belt according to <1>, wherein the metal oxide particles have an average height from the surface of the intermediate transfer belt of 30 nm to 150 nm.
＜4＞
The intermediate transfer belt according to <1>, wherein the metal oxide particles have an aspect ratio of 1 or more and 1.8 or less.
＜5＞
The intermediate transfer belt according to <4>, wherein the metal oxide particles have an aspect ratio of 1 or more and 1.4 or less.
＜6＞
The intermediate transfer belt according to <1>, wherein the metal oxide particles have surfaces that have been subjected to a hydrophobic treatment.
＜７＞
The intermediate transfer belt according to <6>, wherein the metal oxide particles are surface-hydrophobized with at least one hydrophobizing agent selected from the group consisting of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane, octyltriethoxysilane, hexamethyldisilazane, and tetramethyldisilazane.
＜8＞
The intermediate transfer belt according to <1>, wherein the metal oxide particles are at least one type of particles selected from the group consisting of silica particles, titania particles, alumina particles, cerium oxide particles, magnesium oxide particles, zinc oxide particles, and zirconia particles.
＜9＞
The intermediate transfer belt according to <8>, wherein the metal oxide particles are silica particles.
＜10＞
The intermediate transfer belt according to <1>, wherein the metal oxide particles have a surface free energy of 54 mJ/m ² or less.
<11>
The intermediate transfer belt according to item <1>, having a surface onto which a toner image is transferred;
a primary transfer device having a primary transfer member for primarily transferring a toner image formed on a surface of an image carrier onto a surface of the intermediate transfer belt;
a secondary transfer device that is disposed in contact with a surface of the intermediate transfer belt and has a secondary transfer member that secondarily transfers the toner image transferred onto the surface of the intermediate transfer belt onto a surface of a recording medium;
a cleaning device having a cleaning blade for cleaning the surface of the intermediate transfer belt;
a metal oxide particle supplying device provided in contact with a surface of the intermediate transfer belt and configured to supply metal oxide particles as a solid lubricant to the surface of the intermediate transfer belt;
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 comprising:
An image forming apparatus comprising:

According to the invention related to <1>, <8>, or <9>, there is provided an intermediate transfer belt which is excellent in toner transfer retention onto paper having irregularities, as compared with an intermediate transfer belt which satisfies at least one of the following: an average distance between metal oxide particles on the surface exceeds 1,000 nm, and an average height of the metal oxide particles from the surface is less than 15 nm or exceeds 320 nm.
According to the second aspect of the present invention, there is provided an intermediate transfer belt which is superior in transfer retention of toner to paper having projections and recesses, as compared with an intermediate transfer belt having metal oxide particles on the surface with an average spacing of less than 3 nm.
According to the third aspect of the present invention, there is provided an intermediate transfer belt that is superior in transfer retention of toner to paper having irregularities, as compared with an intermediate transfer belt in which the average height from the surface of metal oxide particles is less than 30 nm or exceeds 150 nm.
According to the fourth aspect of the present invention, there is provided an intermediate transfer belt which is superior in transfer retention of toner to paper having projections and recesses, as compared with an intermediate transfer belt in which the aspect ratio of metal oxide particles exceeds 1.8.
According to the fifth aspect of the present invention, there is provided an intermediate transfer belt which is excellent in transfer retention of toner to paper having irregularities, as compared with an intermediate transfer belt in which the aspect ratio of metal oxide particles exceeds 1.4.
According to the sixth aspect of the present invention, there is provided an intermediate transfer belt which is excellent in transfer retention of toner onto paper having irregularities, as compared with an intermediate transfer belt in which the metal oxide particles are not subjected to a surface hydrophobic treatment.
According to the seventh aspect of the present invention, there is provided an intermediate transfer belt which is superior in transfer retention of toner to paper having irregularities, as compared with an intermediate transfer belt in which metal oxide particles have been surface-hydrophobized with polydimethylsiloxane.
According to the invention related to item <10>, there is provided an intermediate transfer belt which is excellent in transfer retention of toner to paper having unevenness, as compared with an intermediate transfer belt in which the surface free energy of metal oxide particles exceeds ⁵⁴ mJ/m2.

According to the invention related to <11> or <12>, a transfer device and an image forming device are provided that are superior in transfer retention of toner to paper having irregularities, compared to an intermediate transfer belt that satisfies at least one of the following: the average distance between metal oxide particles on the surface is less than 50 nm, and the average height of the metal oxide particles from the surface is less than 30 nm.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. FIG. 11 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.

The present embodiment, which is an example of the present invention, will be described below. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the embodiment.

In the numerical ranges described in the present embodiment, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in the present embodiment. In addition, in the numerical ranges described in the present embodiment, the upper or lower limit of the numerical range may be replaced with a 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 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 size of the members in each drawing is conceptual, and the relative relationship between the sizes of the members is not limited to this.
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 substances corresponding to each component are present in the composition, the amount refers to the total amount of the multiple substances present in the composition, unless otherwise specified.

[Intermediate transfer belt]
The intermediate transfer belt according to this embodiment has metal oxide particles as a solid lubricant on its surface, the average distance between the metal oxide particles on the surface is 1000 nm or less, and the average height of the metal oxide particles from the surface is 15 nm or more and 320 nm or less.

The intermediate transfer belt according to this embodiment has the above-mentioned configuration, which allows it to maintain the transfer of toner to paper having unevenness. The reason for this is unclear, but is presumed to be as follows.

In the field of electrophotographic devices, in a transfer device that cleans the outer peripheral surface of an intermediate transfer belt with a cleaning blade, the transfer retention of a toner image onto paper with irregularities (i.e., a recording medium with an irregular surface such as embossed paper; hereafter also referred to simply as "irregular paper") decreases. This is because, as image formation is repeated, discharge products generated from the image carrier and the like accumulate on the surface of the intermediate transfer belt, gradually increasing the adhesive force between the intermediate transfer belt and the toner. In particular, in the region at the edge of the recess in the irregular paper, the pressing force of the irregular paper onto the intermediate transfer belt at the transfer position of the toner image from the intermediate transfer belt (i.e., the secondary transfer section) decreases, so the transfer retention of the toner decreases.

In contrast, the intermediate transfer belt according to this embodiment has metal oxide particles on its surface as a solid lubricant. The metal oxide particles present on the surface of the intermediate transfer belt accumulate at the contact point with the cleaning blade to form a particle dam, and this particle dam serves to scrape off (polish) deposits (e.g., discharge products) on the surface of the intermediate transfer belt. This prevents the adhesion between the intermediate transfer belt and toner from increasing due to deposits, and the transferability of the toner to the textured paper is maintained even after repeated image formation.

In addition, the intermediate transfer belt according to this embodiment has an average distance between metal oxide particles on the surface (hereinafter also simply referred to as "particle distance") of 1000 nm or less, and an average height from the surface of the metal oxide particles (hereinafter also simply referred to as "particle height") of 15 nm to 320 nm. When toner is transferred to an intermediate transfer belt having metal oxide particles on its surface, the metal oxide particles are interposed between the toner and the intermediate transfer belt. When the particle distance and particle height are within the above ranges, the interposed metal oxide particles form an appropriate gap between the toner and the intermediate transfer belt, reducing the van der Waals force between the two. Therefore, the increase in adhesion between the intermediate transfer belt and the toner due to deposits is suppressed, and the transferability of the toner to the textured paper is maintained even after repeated image formation.

However, if the number of metal oxide particles is small and the particle spacing exceeds 1000 nm, the amount of toner that comes into direct contact with the intermediate transfer belt increases without the metal oxide particles being interposed between the intermediate transfer belt and the toner. In that case, the adhesion force between the intermediate transfer belt and the toner increases due to the deposits, and the transfer retention of the toner to the textured paper after repeated image formation decreases. Also, if the particle height of the metal oxide particles is high and exceeds 320 nm, the contact area between the toner and the metal oxide particles increases, and the van der Waals force between the toner and the metal oxide particles increases, resulting in a strong adhesion force, and the transfer retention of the toner to the textured paper after repeated image formation decreases. Also, if the particle height of the metal oxide particles is low and less than 15 nm, an appropriate gap is not formed between the toner and the intermediate transfer belt, and the van der Waals force between the toner and the intermediate transfer belt increases. Therefore, the adhesion force between the intermediate transfer belt and the toner increases due to the deposits, and the transfer retention of the toner to the textured paper after repeated image formation decreases.

As a result, the intermediate transfer belt according to this embodiment has excellent toner transfer retention onto textured paper.

The intermediate transfer belt according to this embodiment is described in detail below.

(Metal oxide particles)
The intermediate transfer belt has metal oxide particles on its surface as a solid lubricant.

-Particle spacing-
The average spacing (particle spacing) between metal oxide particles on the surface is 1000 nm or less.
If the particle spacing exceeds 1000 nm, the transfer retention of the toner onto the textured paper after repeated image formation decreases.
From the viewpoint of improving the initial toner transferability, the lower limit of the particle interval is preferably 3 nm or more.
From the viewpoint of toner transfer retention and initial toner transferability, the particle interval is preferably 3 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less.

The particle spacing is controlled by adjusting the amount of metal oxide particles supplied to the surface of the intermediate transfer belt, adjusting the degree of aggregation of the metal oxide particles, etc.

The average spacing between metal oxide particles (particle spacing) refers to the average spacing between adjacent metal oxide particles. Note that the spacing refers to the distance between the apex of a particle (the point farthest from the surface of the intermediate transfer belt) and the apex of the particle adjacent to that particle. When the metal oxide particles are aggregated, the aggregated particles are considered to be one particle.

The particle spacing is measured by the following method.
The surface of the intermediate transfer belt on which metal oxide particles exist is photographed as an SEM image, and 10 straight lines are drawn randomly on the binary image of this image. The lengths of the areas that are not metal oxide particles are measured, and an arithmetic average value is calculated from the lengths.

-Particle height-
The average height (particle height) from the surface of the metal oxide particles is 15 nm or more and 320 nm or less.
If the particle height exceeds 320 nm, the initial toner transferability is degraded, whereas if the particle height is less than 15 nm, the transferability of the toner to the textured paper after repeated image formation is degraded.
From the viewpoint of toner transfer retention and initial toner transferability, the particle height is preferably 30 nm or more and 150 nm or less, and more preferably 40 nm or more and 130 nm or less.

The particle height is controlled by adjusting the particle size of the metal oxide particles, adjusting the degree of aggregation of the metal oxide particles, etc.

The average height of metal oxide particles from the surface (particle height) means the average value of the height of metal oxide particles present on the surface of the intermediate transfer belt from the surface. Here, the height means the distance to the apex of the particle (the point farthest from the surface of the intermediate transfer belt). When the metal oxide particles are aggregated, the aggregated particles are regarded as one particle.

The particle height is measured by the following method.
A cross section of the belt formed by the ion beam in the thickness direction is photographed by SEM, and the cross-sectional image is binarized to measure the particle height.

- Particle aspect ratio -
The aspect ratio of the metal oxide particles is preferably from 1 to 1.8, in other words, the metal oxide particles are preferably close to spherical.
By making the aspect ratio 1.8 or less, an appropriate gap is formed between the toner and the intermediate transfer belt by the intervening metal oxide particles, making it easier to maintain the transferability of the toner to the textured paper even after repeated image formation.
From the viewpoint of toner transfer maintenance and initial toner transferability, the aspect ratio is more preferably 1 or more and 1.4 or less.

The aspect ratio of a metal oxide particle means the ratio of the long axis length to the short axis length (long axis length/short axis length). The long axis length of a metal oxide particle means the maximum length of the metal oxide particle. The short axis length of a metal oxide particle means the maximum length among the lengths in the direction perpendicular to the extension line of the long axis length of the metal oxide particle.
The aspect ratio of the metal oxide particles is the average value obtained by determining the aspect ratios of 100 metal oxide particles using a scanning electron microscope.

- Hydrophobization of particles -
The metal oxide particles are preferably subjected to a surface hydrophobic treatment.
By using metal oxide particles that have been surface-treated to be hydrophobic, the adhesive force between the toner and the metal oxide particles is reduced, making it more likely that the initial toner transferability and the transfer retention of the toner to the textured paper after repeated image formation will decrease.

Hydrophobizing agents used in surface hydrophobic treatment include, for example, known organosilicon compounds having an alkyl group (e.g., methyl, ethyl, propyl, butyl, etc.), and specific examples include silazane compounds (e.g., silane compounds such as methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane, octyltriethoxysilane, hexamethyldisilazane, tetramethyldisilazane, etc.). One type of hydrophobizing agent may be used alone, or two or more types may be used in combination.

The metal oxide particles preferably have a surface free energy of 54 mJ/ ^m2 or less. When the surface free energy of the metal oxide particles is in the above range, the adhesion of the toner to the intermediate transfer belt is reduced, and excellent transfer retention of the toner to paper having unevenness is obtained, particularly in a high-speed compatible image forming apparatus, excellent transfer retention of the toner to paper having unevenness is obtained. The surface free energy is adjusted by the degree of surface hydrophobic treatment of the metal oxide particles, the selection of the hydrophobic treatment agent used, etc.
The surface free energy of the metal oxide particles is more preferably 45 mJ/ ^m2 or less, and even more preferably 30 mJ/ ^m2 or less.

The surface free energy of the metal oxide particles is measured by the following method.
Based on the OWRK method, using water and diiodomethane, whose surface free energies are known, water is dropped onto the surface of a powder compact of metal oxide particles to measure the contact angle of the water, and further diiodomethane is dropped onto the surface of the powder compact of metal oxide to measure the contact angle of the diiodomethane, and the surface free energy (mJ/ ^m2 ) is calculated.

-Types of metal oxide particles-
Examples of metal oxide particles include silica particles (SiO ₂ ), titania particles (TiO ₂ ), alumina particles (Al ₂ O ₃ ), cerium oxide particles, magnesium oxide particles, zinc oxide particles, and zirconia particles (ZrO ₂ ).
Among these, silica particles are preferred as the metal oxide particles.

By using silica particles as metal oxide particles, the ability (abrasive ability) to scrape off deposits (e.g. discharge products) when the silica particles accumulate at the contact area between the intermediate transfer belt and the cleaning blade and form a particle dam can be improved. Therefore, the transferability of the toner to the textured paper is more easily maintained even after repeated image formation.

(Configuration of intermediate transfer belt)
The intermediate transfer belt according to this embodiment has a belt body and metal oxide particles as a solid lubricant present on the surface (that is, the outer circumferential surface) of the belt body.
The belt body may be a single layer body including a resin substrate layer, or a laminate body including a resin substrate layer.
Examples of the laminate including a resin substrate layer include a laminate having an elastic layer provided on the outer peripheral surface of the resin substrate layer, a laminate having a resin layer provided on the inner peripheral surface of the resin substrate layer, and a laminate having an elastic layer provided on the outer peripheral surface of the resin substrate layer and a resin layer provided on the inner peripheral surface of the resin substrate layer.
The elastic layer provided on the outer peripheral surface of the resin substrate layer and the resin layer on the inner peripheral surface of the resin substrate layer are well-known layers that are used in intermediate transfer belts.

--Resin substrate layer--
The resin substrate layer contains, for example, a resin and a conductive agent. The resin substrate layer may contain other well-known components as necessary.

Resin Examples of the resin include polyimide resin (PI resin), polyamideimide resin (PAI resin), aromatic polyether ketone resin (e.g., aromatic polyether ether ketone resin, etc.), polyphenylene sulfide resin (PPS resin), polyetherimide resin (PEI resin), polyester resin, polyamide resin, and polycarbonate resin.
From the viewpoints of mechanical strength and dispersibility of the conductive agent, the resin is preferably a polyimide-based 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.

Examples of polyimide resins include imidized products of polyamic acids (precursors of polyimide resins), which are polymers of tetracarboxylic dianhydrides and diamine compounds.
The polyimide resin may, for example, be a resin having a structural unit represented by the following general formula (I).

In formula (I), R ¹ represents a tetravalent organic group, and R ² represents a divalent organic group.
The tetravalent organic group represented by R ¹ may be an aromatic group, an aliphatic group, a cyclic aliphatic group, a group in which an aromatic group and an aliphatic group are combined, or a group in which these groups are substituted. Specific examples of the tetravalent organic group include residues of tetracarboxylic dianhydrides, which will be described later.
The divalent organic group represented by ^R2 may be an aromatic group, an aliphatic group, a cyclic aliphatic group, a group in which an aromatic group and an aliphatic group are combined, or a group in which these groups are substituted. Specific examples of the divalent organic group include residues of diamine compounds described below.

Specific examples of tetracarboxylic dianhydrides used as raw materials for polyimide resins include pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,3,3',4-biphenyl tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)sulfonic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, and ethylene tetracarboxylic dianhydride.

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, 3,3'-dimethylbenzidine, 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, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane Examples of the amino groups include 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 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, _H2N ( _{CH2 ) 3O} ( _CH2 ) _2O ( _CH2 )NH2, _H2N ( _CH2 ) _3S ( _CH2 ) _3NH2 , and _H2N ( _CH2 ) _3N (CH3 _{) 2} ( _{CH2 ) 3NH2} .

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.

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.

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.

Here, the resin content in the resin substrate layer 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, from the viewpoints of mechanical strength and volume resistivity adjustment, etc.

Conductive Agent Examples of the conductive agent include conductive (for example, volume resistivity less than 10 ⁷ Ω·cm, the same applies below) or semi-conductive (for example, volume resistivity 10 ⁷ Ω·cm or more and 10 ¹³ Ω·cm or less, the same applies below) powders.
Specifically, the conductive agent is not particularly limited, but examples thereof include carbon black, metals (e.g., aluminum, nickel, etc.), metal oxides (e.g., yttrium oxide, tin oxide, etc.), and ion-conductive substances (e.g., potassium titanate, LiCl, etc.).

The conductive agent is selected depending on the purpose of use, but carbon black is preferred.
Examples of carbon black include ketjen black, oil furnace black, channel black, acetylene black, etc. As the carbon black, surface-treated carbon black (hereinafter also referred to as "surface-treated carbon black") may be used.
Surface-treated carbon black can be obtained by imparting, for example, a carboxy group, a quinone group, a lactone group, a hydroxy group, etc. to its surface. Examples of the surface treatment method 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.

From the viewpoints of dispersibility, mechanical strength, volume resistivity, film-forming properties, etc., the average particle size of carbon black 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.

The average particle size of the conductive agent (particularly carbon black) is measured by the following method.
First, a measurement sample having a thickness of 100 nm is taken from the resin substrate layer using a microtome, and the measurement sample is observed using a TEM (transmission electron microscope). Then, the diameter of a circle equal to the projected area of each of 50 conductive particles (i.e., the equivalent circle diameter) is taken as the particle diameter, and the average value of the diameters is taken as the average particle diameter.

From the viewpoint of mechanical strength and volume resistivity, the content of the conductive agent 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, relative to the resin substrate layer.

-Other ingredients-
Examples of other components include a filler for improving mechanical strength, an antioxidant for preventing thermal deterioration of the belt, a surfactant for improving fluidity, and a heat-resistant anti-aging agent.
When other components are contained, the content of the other components is preferably more than 0 mass% and not more than 10 mass%, more preferably more than 0 mass% and not more than 5 mass%, and even more preferably more than 0 mass% and not more than 1 mass%, relative to the resin substrate layer.

--Thickness of resin substrate layer--
From the viewpoint of mechanical strength, the thickness of the resin substrate layer is preferably 60 μm or more and 120 μm or less, and more preferably 80 μm or more and 120 μm or less.

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

(Volume resistivity of intermediate transfer belt)
From the viewpoint of transferability, the common logarithm of the volume resistivity of the intermediate transfer belt when a voltage of 500 V is applied for 10 seconds is preferably 9.0 (log Ω·cm) or more and 13.5 (log Ω·cm) or less, more preferably 9.5 (log Ω·cm) or more and 13.2 (log Ω·cm) or less, and particularly preferably 10.0 (log Ω·cm) or more and 12.5 (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 (R8430A manufactured by Advantest) is used as the resistance measuring device, and a UR probe (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) is used as the probe, and the volume resistivity (log Ω cm) is measured at 6 points at equal intervals in the circumferential direction of the intermediate transfer belt, and 3 points at the center and both ends in the width direction, for a total of 18 points, 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 of a temperature of 22° C. and a humidity of 55% RH.

(Surface resistivity of intermediate transfer belt)
From the viewpoint of transferability to textured paper, the common logarithm of the surface resistivity when a voltage of 500 V is applied to the outer peripheral surface of the intermediate transfer belt for 10 seconds is preferably 10.0 (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/suc, is a logarithmic value of the resistance per unit area, and is also expressed as log(Ω/suc), log Ω/suc, log Ω/□, etc.
The surface resistivity when a voltage of 500 V is applied to the outer peripheral surface of the intermediate transfer belt for 10 seconds is measured by the following method.
A microcurrent meter (R8430A manufactured by Advantest) is used as the resistance measuring device, and a UR probe (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) is used as the probe, and the surface resistivity (log Ω/suc) of the outer peripheral surface of the endless belt is measured at 6 points at equal intervals in the circumferential direction of the outer peripheral surface of the intermediate transfer belt, and 3 points at the center and both ends in the width direction, for a total of 18 points, 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 of a temperature of 22° C. and a humidity of 55% RH.

<Method of Manufacturing Intermediate Transfer Belt>
The method for producing the intermediate transfer belt according to this embodiment includes, for example, a step of preparing a belt body, and a step of applying metal oxide particles as a solid lubricant to the outer circumferential surface of the belt body.

In the process of preparing the belt body, the belt body is obtained using a well-known manufacturing method for intermediate transfer belts.

The step of applying metal oxide particles may be, for example, the following modes (1), (2), and (3), with mode (1) being preferred.
(1) A mode in which a supply member is brought into contact with a molded product of metal oxide particles to scrape off the metal oxide particles, and the scraped off metal oxide particles are supplied to the surface of the belt main body. (2) A mode in which a molded product of metal oxide particles is pressed directly against the intermediate transfer belt (i.e., the belt main body) and worn down to supply the metal oxide particles to the surface of the belt main body. (3) A mode in which an appropriate amount of powdered metal oxide particles is placed on a supply member such as a roll, and the powder is supplied from the supply member to the surface of the belt main body.

[Transfer device]
--First embodiment--
The transfer device according to the first embodiment includes an intermediate transfer belt onto whose surface (i.e., outer peripheral surface) a toner image is transferred, a primary transfer device having a primary transfer member which primarily transfers a toner image formed on the surface of an image carrier onto the surface of the intermediate transfer belt, a secondary transfer device which is disposed in contact with the surface of the intermediate transfer belt and has a secondary transfer member which secondarily transfers the toner image transferred onto the surface of the intermediate transfer belt onto the surface of a recording medium, and a cleaning device having a cleaning blade which cleans the surface of the intermediate transfer belt.The intermediate transfer belt according to the above embodiment is applied as the intermediate transfer belt.

The transfer device according to the first embodiment has excellent transfer retention of toner onto paper with unevenness due to the above configuration.

In the primary transfer device, the primary transfer member is disposed opposite the image carrier with the intermediate transfer belt in between. In the primary transfer device, the primary transfer member applies a voltage of the opposite polarity to the charge polarity of the toner to the intermediate transfer belt, thereby primarily transferring the toner image onto the surface of the intermediate transfer belt.

In the secondary transfer device, the secondary transfer member is disposed on the toner image carrying 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 carrying side together with the secondary transfer member. In the secondary transfer device, the intermediate transfer belt and the recording medium are sandwiched between the secondary transfer member and the backing member to form a transfer electric field, whereby the toner image on the intermediate transfer belt is secondarily transferred 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.

In the cleaning device, the cleaning blade is disposed on the toner image carrying side of the intermediate transfer belt. The cleaning device further includes, for example, a cleaning blade and a backing member disposed on the side of the intermediate transfer belt opposite the toner image carrying side. In the cleaning device, for example, the intermediate transfer belt is sandwiched between the cleaning blade and the backing member, and the surface of the intermediate transfer belt is cleaned by the cleaning blade.

The transfer device according to the present embodiment may be a transfer device that transfers a toner image onto a surface of a recording medium via a plurality of intermediate transfer belts. In other words, 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 belt, secondary transfer of the toner image from the first intermediate transfer belt to a second intermediate transfer belt, and then tertiary transfer of the toner image from the second intermediate transfer belt to a recording medium.
A transfer device applies the intermediate transfer belt according to the present embodiment to at least one of a plurality of intermediate transfer belts.

--Second embodiment--
The transfer device according to the second embodiment includes an intermediate transfer belt having a surface onto which a toner image is transferred, a primary transfer device having a primary transfer member which performs primary transfer of the toner image formed on the surface of an image carrier onto the surface of the intermediate transfer belt, a secondary transfer device arranged in contact with the surface of the intermediate transfer belt and having a secondary transfer member which performs secondary transfer of the toner image transferred onto the surface of the intermediate transfer belt onto the surface of a recording medium, a cleaning device having a cleaning blade which cleans the surface of the intermediate transfer belt, and a metal oxide particle supplying device arranged in contact with the surface of the intermediate transfer belt and which supplies metal oxide particles as a solid lubricant to the surface of the intermediate transfer belt.

The transfer device according to the second embodiment has excellent transfer retention of toner onto uneven paper due to the above configuration.

In the transfer device according to the second embodiment, the metal oxide particle supply device is provided, for example, downstream of the secondary transfer device in the rotation direction of the intermediate transfer belt and upstream of the cleaning device in the rotation direction of the intermediate transfer belt.

The metal oxide particle supplying device may, for example, have a molded product of metal oxide particles as a solid lubricant, and a metal oxide particle supplying member (the above-mentioned embodiment (1)).
Examples of the molded product of metal oxide particles include metal oxide particles solidified together with a binder resin, and molded products obtained by compression molding of metal oxide particles. The shape of the molded product may be a rod shape, a plate shape (i.e., a blade shape), etc.
Examples of the metal oxide particle supplying member include a rotating brush and a rubber roll, among which a rotating brush is preferred. The rotating brush and the rubber roll come into contact with the molded product of the metal oxide particles while rotating, scraping off the metal oxide particles, and supplying the scraped off metal oxide particles to the surface of the intermediate transfer belt.

Another example of the metal oxide particle supplying device is one in which a molded product of metal oxide particles is pressed directly against the intermediate transfer belt (i.e., the belt body) (the above-mentioned (2) embodiment). The molded product of metal oxide particles pressed against the intermediate transfer belt wears away, and the metal oxide particles are supplied to the surface of the belt body.

In the transfer device according to the second embodiment, the configuration other than the metal oxide particle supply device is the same as that described in the transfer device according to the first embodiment above.

[Image forming apparatus]
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 to the surface of a recording medium. The transfer device is the transfer device according to the first embodiment or the transfer device according to the second embodiment.

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 with a developer containing toner to form a toner image.

The image forming apparatus according to this embodiment may be any of the well-known image forming apparatuses, such as an apparatus equipped with a fixing unit that fixes a toner image transferred onto the surface of a recording medium; an apparatus equipped with a cleaning unit that cleans the surface of an image carrier before charging after the toner image is transferred; an apparatus equipped with a discharging unit that irradiates the surface of an image carrier with discharging light to discharge the surface before charging after the toner image is transferred; and an apparatus equipped with an image carrier heating member that increases the temperature of the image carrier and reduces the relative temperature.

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 method using a liquid developer).

In the image forming apparatus according to this embodiment, for example, the portion including the image carrier may be 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.

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 the description of the rest will be omitted.
Here, an example of an image forming apparatus to be described with reference to the drawings is an image forming apparatus in which the transfer device according to the second embodiment is applied as a transfer device. In an image forming apparatus in which the transfer device according to the first embodiment is applied as a transfer device, the transfer device may or may not be provided with a solid lubricant supply device.

(Image forming apparatus)
FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to the present embodiment.

As shown in FIG. 1, the 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, 1K (an example of a toner image forming apparatus) in which toner images of each color component are formed by an electrophotographic method, a primary transfer section 10 that sequentially transfers (primary transfer) each color component toner image formed by each image forming unit 1Y, 1M, 1C, 1K to an intermediate transfer belt 15, a secondary transfer section 20 that collectively transfers (secondary transfer) the superimposed toner images transferred onto the intermediate transfer belt 15 to a recording medium, paper K, and a fixing device 60 that fixes the secondary transferred image onto the paper K. The image forming apparatus 100 also has a control section 40 that controls the operation of each device (each section).

Each image forming unit 1Y, 1M, 1C, and 1K of the image forming device 100 is equipped with a photoconductor 11 (an example of an image carrier) that rotates in the direction of arrow A and holds a toner image formed on its surface.

Around the photoconductor 11, there is provided a charger 12 that charges the photoconductor 11 as an example of a charging means, and a laser exposure device 13 (the exposure beam is indicated by the symbol Bm in the figure) that writes an electrostatic latent image on the photoconductor 11 as an example of a latent image forming means.

Around the photoconductor 11, there is provided a developer 14, which is an example of a developing means and contains toner of each color component, and visualizes the electrostatic latent image on the photoconductor 11 with the toner. There is also provided a primary transfer roll 16, which transfers the toner image of each color component formed on the photoconductor 11 to the intermediate transfer belt 15 at the primary transfer section 10.

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

The intermediate transfer belt 15 is driven (rotated) in a circular manner in the direction B shown in FIG. 1 by various rolls at a speed suited to the purpose. These rolls include a drive roll 31 driven by a motor (not shown) with excellent constant speed performance 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 to prevent the intermediate transfer belt 15 from meandering, a back roll 25 provided in the secondary transfer section 20, and a cleaning back roll 34 provided in a cleaning section that scrapes off residual toner on the intermediate transfer belt 15.

The primary transfer section 10 is composed of a primary transfer roll 16 arranged opposite the photoconductor 11 with the intermediate transfer belt 15 in between. The primary transfer roll 16 is arranged in pressure contact with the photoconductor 11 with the intermediate transfer belt 15 in between, 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 each photoconductor 11 are electrostatically attracted to the intermediate transfer belt 15 in sequence, and superimposed toner images are formed on the intermediate transfer belt 15.

The secondary transfer unit 20 is configured with a back roll 25 and a secondary transfer roll 22 that is arranged on the toner image bearing surface side of the intermediate transfer belt 15.

The back roll 25 is formed so that the surface resistivity is 1× ¹⁰ Ω/□ or more and 1× ¹⁰ Ω/□ or less, and the hardness is set to, for example, 70° (Asker C: manufactured by Kobunshi Keiki Co., Ltd., the same applies below.) This back roll 25 is disposed on the back side of the intermediate transfer belt 15 to constitute an opposing electrode of the secondary transfer roll 22, and is disposed in contact with a metallic power supply roll 26 to which a secondary transfer bias is stably applied.

On the other hand, the secondary transfer roll 22 is a cylindrical roll having a volume resistivity of 10 ^7.5 Ωcm or more and 10 ^8.5 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 further grounded to form a secondary transfer bias between the secondary transfer roll 22 and the back roll 25, and performs a second transfer of the toner image onto the paper K transported to the secondary transfer unit 20.

Further, an intermediate transfer belt cleaning member 35 is provided so as to be freely contactable and detachable on the downstream side of the secondary transfer unit 20 of the intermediate transfer belt 15, which removes residual toner and paper powder remaining on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15. An example of the intermediate transfer belt cleaning member 35 is a cleaning roll. However, it may also be a cleaning blade.
Further, downstream of the secondary transfer section 20 of the secondary transfer roll 22, a secondary transfer roll cleaning member 22A is provided to remove residual toner and paper powder on the secondary transfer roll 22 after secondary transfer and clean the surface of the secondary transfer roll 22. The secondary transfer roll cleaning member 22A is exemplified by a cleaning blade, but may also be a cleaning roll.

Further, a metal oxide particle supplying device 70 that supplies metal oxide particles as a solid lubricant is provided on the intermediate transfer belt 15 downstream of the secondary transfer unit 20 and upstream of the intermediate transfer belt cleaning member 35 .
The metal oxide particle supplying device 70 has a metal oxide particle molded product 71, a metal oxide particle supplying member 72 that scrapes off the metal oxide particle molded product and supplies the metal oxide particles to the surface of the intermediate transfer belt 15, and a sliding member 73 that rubs the metal oxide particles against the surface of the intermediate transfer belt 15 by sliding, thereby forming a coating of metal oxide particles.

The configuration including the intermediate transfer belt 15, the primary transfer roll 16, the secondary transfer roll 22, the intermediate transfer belt cleaning member 35, and the metal oxide particle supplying device 70 corresponds 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.

On the other hand, upstream of the yellow image forming unit 1Y, there is provided a reference sensor (home position sensor) 42 that generates a reference signal that serves as a reference for timing image formation in each of the image forming units 1Y, 1M, 1C, and 1K. In addition, downstream of the black image forming unit 1K, there is provided an image density sensor 43 for adjusting image quality. This reference sensor 42 generates a reference signal by recognizing a mark 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 recognition of this reference signal.

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

Next, a 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.

The image processing device performs image processing on the input reflectance data, such as shading correction, positional deviation correction, brightness/color space conversion, gamma correction, and various image editing processes 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 the four colors Y, M, C, and K, and is output to the laser exposure device 13.

In the laser exposure device 13, an exposure beam Bm emitted from, for example, a semiconductor laser is irradiated onto the photoconductor 11 of each of the image forming units 1Y, 1M, 1C, and 1K in accordance with the input color material gradation data. In each of the photoconductors 11 of the image forming units 1Y, 1M, 1C, and 1K, the surface is charged by the charger 12, and then 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.

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 toner's charging polarity (negative polarity) is applied to the substrate of the intermediate transfer belt 15 by the primary transfer roll 16, and the toner images are sequentially superimposed on the surface of the intermediate transfer belt 15 to perform the primary transfer.

After the toner images are sequentially transferred to the surface of the intermediate transfer belt 15, the intermediate transfer belt 15 moves to transport the toner images 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 accordance 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 the positioning roll (not shown) rotates in accordance with the movement timing 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.

In the secondary transfer section 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 transported 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 image held on the intermediate transfer belt 15 is electrostatically transferred onto the paper K in one go in the secondary transfer section 20, which is pressed by the secondary transfer roll 22 and the back roll 25.

Then, the paper 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 the transport belt 55 provided downstream of the secondary transfer roll 22 in the paper transport direction. The transport belt 55 transports the paper K to the fixing device 60 at an optimal transport speed for the fixing device 60. The unfixed toner image on the paper K transported to the fixing device 60 is fixed onto the paper K by being subjected to a fixing process using heat and pressure by the fixing device 60. The paper K on which the fixed image has been formed is then transported to a discharged paper storage section (not shown) provided in the discharge section of the image forming device.

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.

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

The following describes examples of the present invention, but the present invention is not limited to the following examples. In the following description, all "parts" and "%" are by weight unless otherwise specified.

Example 1
-Belt body manufacturing process-
A PI precursor solution was prepared by dissolving polyamic acid, which is a polymer of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether, in N-methyl-2-pyrrolidone (NMP). The PI precursor solution was a solution in which the solid content of the polyimide resin after imidization of the polyamic acid was 18 mass %.
Next, carbon black (FW200: manufactured by Orion Engineered Carbon Corp., average particle size = 13 nm) was added to the PI precursor solution in an amount of 19 parts by mass per 100 parts by mass of the solid content of the polyamic acid, and the mixture was mixed and stirred to prepare a carbon black-dispersed PI precursor solution.
Next, the carbon black-dispersed PI precursor solution was dispensed onto the outer surface of an aluminum cylinder, with the cylinder being rotated, via a dispenser over a width of 500 mm.
Thereafter, the cylinder was heated and dried at 140° C. for 30 minutes while kept horizontal, and then heated for 120 minutes so that the maximum temperature reached 320° C., and the belt body (i.e., a single layer of polyimide resin layer) having a thickness of 80 μm was cut to a width of 363 mm.
Through the above steps, the intermediate transfer belt body was obtained.

- Solid lubricant -
As a solid lubricant, silica particles shown in Table 1 were solidified together with a binder resin to obtain a plate-shaped molded body.
A solid lubricant supplying device was fabricated that supplies a solid lubricant to an intermediate transfer belt by scraping a plate-shaped molded body with a rotating brush.

-Evaluation test-
The toner adhesion and embossed paper transferability were evaluated using a modified image forming apparatus "Versant 180 press (manufactured by Fujifilm Business Innovation Co., Ltd.)" equipped with a solid lubricant supplying device.
The amount of solid lubricant supplied from the solid lubricant supplying device was set to an amount that would result in the particle intervals and particle heights shown in Table 1.

Other Examples and Comparative Examples
The evaluation tests were carried out in the same manner as in Example 1, except that the type of solid lubricant used, particle size, aspect ratio, presence or absence of surface hydrophobic treatment, type of hydrophobic treatment agent (hydrophobic treatment method), and hydrophobicity were changed, and the particle interval and particle height were adjusted by adjusting the supply amount from the solid lubricant supply device, etc.
In Table 1, "TMS" stands for trimethylsilane, "PDMS" stands for polydimethylsiloxane, "OTES" stands for octyltriethoxysilane, and "Amino Silane" stands for aminosilane. "BN" used in Comparative Example 4 stands for boron nitride.

<Evaluation>
(Toner Adhesion)
The toner adhesion to the intermediate transfer belt was measured at the beginning of image formation (when 10 images were formed) and after the passage of time (when 1000 images were formed, maintenance).
The toner adhesion was measured by the following method.
The toner adhesion force indicates the air blowing pressure (unit: MPa) when polyester resin particles having a volume average particle size of 4.7 μm are adhered to the outer peripheral surface of the intermediate transfer belt with a load of 46 g/ ^cm2 , and then air is blown onto the outer peripheral surface from above while increasing the blowing pressure, and all of the polyester resin particles adhered to the outer peripheral surface are separated from the outer peripheral surface.

(Transferability)
A 30% halftone image of blue was printed on 1000 sheets of embossed paper (Boss Snow), and the filling of the recesses was visually confirmed initially (after 10 images were formed) and over time (after 1000 images were formed, maintenance), and the transferability was evaluated by comparing the first and tenth images, and the first and 1000th images. The evaluation criteria were as follows:
A+ (◎+): No white spots in the recesses, same as the first sheet A (◎): No change from the first sheet, slight white spots in the recesses are visible B (◯): White spots in the recesses have slightly worsened compared to the first sheet C (△): White spots in the recesses have worsened significantly more than B (◯) compared to the first sheet, and are unacceptable D (×): White spots in the recesses have worsened even more significantly than C (△) compared to the first sheet

(Transferability when used with high-speed models)
The number of printable sheets per minute (unit: ppm) in the image forming apparatus was set to the upper limit of 120 ppm, and the maintenance was evaluated in the same manner as in the above (transferability). The evaluation criteria were as follows.
A+ (◎+): No white spots in the recesses, same as the first sheet A (◎): No change from the first sheet, slight white spots in the recesses are visible B (◯): White spots in the recesses have slightly worsened compared to the first sheet C (△): White spots in the recesses have worsened significantly more than B (◯) compared to the first sheet, and are unacceptable D (×): White spots in the recesses have worsened even more significantly than C (△) compared to the first sheet

From the above results, it is understood that the intermediate transfer belt of this embodiment is superior in transfer retention of toner to paper having irregularities, as compared with the intermediate transfer belt of the comparative example.
Moreover, Examples 9, 10, and 13 are examples in which the surface free energy exceeds 54 mJ/m ^2. In particular, Example 10 is an example in which the particle interval, particle height, and aspect ratio are the same as those of Example 1, the surface treatment method is different, and the surface free energy exceeds 54 mJ/m ^2. It can be seen that Example 1 has superior embossed paper transferability when used with high-speed models compared to Example 10.

The present embodiment includes the following aspects.
(((1)))
An intermediate transfer belt comprising metal oxide particles on a surface thereof as a solid lubricant, the metal oxide particles having an average distance between adjacent ones of the metal oxide particles on the surface of the intermediate transfer belt being 1000 nm or less, and an average height of the metal oxide particles from the surface of the intermediate transfer belt being 15 nm or more and 320 nm or less.
(((2)))
The intermediate transfer belt according to ((1)), wherein the average distance between the metal oxide particles on the surface is 3 nm or more and 200 nm or less.
(((3)))
The intermediate transfer belt according to ((1))) or ((2)), wherein the metal oxide particles have an average height from the surface of 30 nm or more and 150 nm or less.
(((4)))
The intermediate transfer belt according to any one of ((1))) to ((3)) above, wherein the aspect ratio of the metal oxide particles is 1 or more and 1.8 or less.
(((5)))
The intermediate transfer belt according to ((4)), wherein the aspect ratio of the metal oxide particles is 1 or more and 1.4 or less.
(((6)))
The intermediate transfer belt according to any one of ((1)) to ((5)), wherein the metal oxide particles have been subjected to a surface hydrophobic treatment.
(((7)))
The intermediate transfer belt according to ((6)) above, wherein the metal oxide particles have been subjected to a surface hydrophobic treatment with at least one hydrophobic treatment agent selected from the group consisting of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane, octyltriethoxysilane, hexamethyldisilazane, and tetramethyldisilazane.
(((8)))
The intermediate transfer belt according to any one of ((1))) to (((7))), wherein the metal oxide particles are at least one type of particles selected from the group consisting of silica particles, titania particles, alumina particles, cerium oxide particles, magnesium oxide particles, zinc oxide particles, and zirconia particles.
(((9)))
The intermediate transfer belt according to ((8)), wherein the metal oxide particles are silica particles.
(((10)))
The intermediate transfer belt according to any one of ((1))) to (((9))), wherein the metal oxide particles have a surface free energy of 54 mJ/ ^m2 or less.
(((11)))
An intermediate transfer belt according to any one of ((1))) to (((10))), having a surface onto which a toner image is transferred;
a primary transfer device having a primary transfer member for primarily transferring a toner image formed on a surface of an image carrier onto a surface of the intermediate transfer belt;
a secondary transfer device that is disposed in contact with a surface of the intermediate transfer belt and has a secondary transfer member that secondarily transfers the toner image transferred onto the surface of the intermediate transfer belt onto a surface of a recording medium;
a cleaning device having a cleaning blade for cleaning the surface of the intermediate transfer belt;
a metal oxide particle supplying device provided in contact with a surface of the intermediate transfer belt and configured to supply metal oxide particles as a solid lubricant to the surface of the intermediate transfer belt;
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 comprising:
An image forming apparatus comprising:

The invention according to ((1)), ((8)), or ((9)) provides an intermediate transfer belt that is superior in toner transfer retention to paper having irregularities, compared to an intermediate transfer belt that satisfies at least one of the following: an average distance between metal oxide particles on the surface exceeds 1000 nm, and an average height of the metal oxide particles from the surface is less than 15 nm and exceeds 320 nm.

According to the invention (((2))), an intermediate transfer belt is provided which is superior in toner transfer retention onto paper having irregularities, compared to an intermediate transfer belt having an average spacing of less than 3 nm between metal oxide particles on the surface.
According to the invention related to ((3))), an intermediate transfer belt is provided which is superior in toner transfer retention onto paper having irregularities, compared to an intermediate transfer belt in which the average height from the surface of metal oxide particles is less than 30 nm or more than 150 nm.
According to the invention related to ((4)), an intermediate transfer belt is provided which is superior in toner transfer retention to paper having irregularities, compared to an intermediate transfer belt in which the aspect ratio of metal oxide particles exceeds 1.8.
According to the invention related to ((5)), an intermediate transfer belt is provided which is superior in toner transfer retention onto paper having irregularities, compared to an intermediate transfer belt in which the aspect ratio of metal oxide particles exceeds 1.4.
According to the invention related to ((6)), there is provided an intermediate transfer belt which is superior in transfer retention of toner to paper having irregularities, compared to an intermediate transfer belt in which the metal oxide particles have not been subjected to a surface hydrophobic treatment.
According to the invention ((7)), there is provided an intermediate transfer belt which is superior in toner transfer retention onto paper having irregularities, compared to an intermediate transfer belt in which metal oxide particles have been surface-hydrophobized with polydimethylsiloxane.
According to the invention ((10)), an intermediate transfer belt is provided which is superior in toner transfer retention onto paper having irregularities, compared to an intermediate transfer belt in which the surface free energy of metal oxide particles exceeds 54 mJ/ ^m2 .

The invention according to ((11)) or ((12)) provides a transfer device and an image forming device that are superior in transfer retention of toner to paper having irregularities, compared to an intermediate transfer belt that satisfies at least one of the following: the average distance between metal oxide particles on the surface is less than 50 nm, and the average height of the metal oxide particles from the surface is less than 30 nm.

1Y, 1M, 1C, 1K image forming units 10 primary transfer section 11 photoconductor 12 charger 13 laser exposure device 14 developing device 15 intermediate transfer belt 16 primary transfer roll 17 photoconductor cleaner 20 secondary transfer section 22 secondary transfer roll
Reference Signs List 22A Secondary transfer roll cleaning member 25 Back roll 26 Power supply roll 31 Drive roll 32 Support roll 33 Tension applying roll 34 Cleaning back roll 35 Intermediate transfer belt cleaning member 40 Control unit 42 Reference sensor 43 Image density sensor 50 Paper storage unit 51 Paper supply roll 52 Transport roll 53 Transport guide 55 Transport belt 56 Fixing entrance guide 60 Fixing device 70 Metal oxide particle supply device 71 Metal oxide particle molded product 72 Metal oxide particle supply member 100 Image forming apparatus

Claims (12)

An intermediate transfer belt having metal oxide particles as a solid lubricant on its surface, the average distance between the metal oxide particles on the surface being 1000 nm or less, and the average height of the metal oxide particles from the surface being 15 nm or more and 320 nm or less. The intermediate transfer belt according to claim 1, wherein the average distance between the metal oxide particles on the surface is 3 nm or more and 200 nm or less. The intermediate transfer belt according to claim 1, wherein the average height of the metal oxide particles from the surface is 30 nm or more and 150 nm or less. The intermediate transfer belt according to claim 1, wherein the aspect ratio of the metal oxide particles is 1.0 or more and 1.8 or less. The intermediate transfer belt according to claim 4, wherein the aspect ratio of the metal oxide particles is 1.0 or more and 1.4 or less. The intermediate transfer belt according to claim 1, wherein the metal oxide particles have been subjected to a hydrophobic surface treatment. The intermediate transfer belt according to claim 6, wherein the metal oxide particles are surface-hydrophobized with at least one hydrophobic treatment agent selected from the group consisting of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane, octyltriethoxysilane, hexamethyldisilazane, and tetramethyldisilazane. The intermediate transfer belt according to claim 1, wherein the metal oxide particles are at least one type of particles selected from the group consisting of silica particles, titania particles, alumina particles, cerium oxide particles, magnesium oxide particles, zinc oxide particles, and zirconia particles. The intermediate transfer belt according to claim 8, wherein the metal oxide particles are silica particles. 2. The intermediate transfer belt according to claim 1, wherein the metal oxide particles have a surface free energy of 54 mJ/ ^m2 or less. 2. The intermediate transfer belt according to claim 1, having a toner image transferred onto its surface;
a primary transfer device having a primary transfer member for primarily transferring a toner image formed on a surface of an image carrier onto a surface of the intermediate transfer belt;
a secondary transfer device that is disposed in contact with a surface of the intermediate transfer belt and has a secondary transfer member that secondarily transfers the toner image transferred onto the surface of the intermediate transfer belt onto a surface of a recording medium;
a cleaning device having a cleaning blade for cleaning the surface of the intermediate transfer belt;
a metal oxide particle supplying device provided in contact with a surface of the intermediate transfer belt and configured to supply metal oxide particles as a solid lubricant to the surface of the intermediate transfer belt;
A transfer device comprising: 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 comprising: the transfer device according to claim 11;
An image forming apparatus comprising: