JP2016197196A - Intermediate transfer belt and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer belt that can provide good dispersibility of metal oxide fine particles in a coating liquid for surface layer formation, and thereby suppressing a variation in output of an optical sensor reading the density of a toner; and an image forming apparatus including the same.SOLUTION: The present intermediate transfer belt is an intermediate transfer belt that is included in an image forming apparatus of an electrophotographic system and has a surface layer on a substrate. The surface layer is obtained by irradiating a coating film of a coating liquid for surface layer formation with an activation energy ray to cure the coating film, the coating liquid for surface layer formation containing metal oxide fine particles (A), a (meth)acrylate monomer (B) having a refraction index nD from 1.6 to 1.8, and an activation energy ray curable composition containing a polyfunctional (meth)acrylate (C) other than the (meth)acrylate monomer (B).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrophotographic image forming apparatus and an intermediate transfer belt provided therein.

  In an electrophotographic image forming apparatus, for example, a latent image formed on a photoreceptor is developed with toner, and the obtained toner image is temporarily held on an endless belt-shaped image carrier (intermediate transfer belt). The toner image on the intermediate transfer belt is transferred onto an image support such as paper.

  Examples of the intermediate transfer belt include a belt in which a surface layer made of a photocured film obtained by curing an acrylic monomer or the like by a polymerization reaction is laminated on a substrate. In such an intermediate transfer belt, metal oxide fine particles are added to the surface layer for the purpose of improving durability by controlling resistance and improving hardness, improving transferability, and the like.

  However, in the coating solution for forming the surface layer, the coating failure occurs due to the aggregation of the metal oxide fine particles, and the resulting surface layer is disturbed, thereby reflecting the surface layer. There is a problem that in-plane variation occurs in the rate, and as a result, output variation of the optical sensor that reads the toner density on the intermediate transfer belt occurs.

  As means for solving such problems, Patent Documents 1 to 3 disclose that the dispersibility is improved by using a surface-treated metal oxide fine particle. It cannot be said that sex is obtained.

JP 2007-179013 A JP 2006-189805 A JP 2005-338246 A

  The present invention has been made in consideration of the above-mentioned circumstances, and the object thereof is to obtain good dispersibility of the metal oxide fine particles in the coating solution for forming the surface layer. An object of the present invention is to provide an intermediate transfer belt capable of suppressing variations in output of an optical sensor to be read and an image forming apparatus including the intermediate transfer belt.

The intermediate transfer belt of the present invention is an intermediate transfer belt provided in an electrophotographic image forming apparatus,
A surface layer is formed on the substrate;
The surface layer is other than the metal oxide fine particles (A), the (meth) acrylate monomer (B) having a refractive index nD in the range of 1.6 to 1.8, and the (meth) acrylate monomer (B). It is obtained by irradiating a coating film of a coating solution for forming a surface layer containing an active energy ray-curable composition containing a polyfunctional (meth) acrylate (C) with an active energy ray and curing it. It is characterized by that.

  In the intermediate transfer belt of the present invention, the (meth) acrylate monomer (B) having a refractive index nD in the range of 1.6 to 1.8 is a compound represented by the following formulas (a) to (g). It is preferable that it is at least 1 or more types chosen from.

  In the intermediate transfer belt of the present invention, the structural unit derived from the metal oxide fine particles (A) in the surface layer, the (meth) acrylate monomer (B) having a refractive index nD in the range of 1.6 to 1.8, and In the total of structural units derived from the polyfunctional (meth) acrylate (C) other than the (meth) acrylate monomer (B), the content of the metal oxide fine particles (A) is 5 to 30% by mass, (meth) acrylate The content ratio of the structural unit derived from the monomer (B) is preferably 20 to 50% by mass, and the content ratio of the structural unit derived from the polyfunctional (meth) acrylate (C) is preferably 40 to 75% by mass.

  In the intermediate transfer belt of the present invention, the metal oxide fine particles (A) are preferably composed of metal oxide fine particles subjected to surface treatment.

The image forming apparatus of the present invention comprises an endless belt-shaped image carrier, toner image forming means for forming a toner image on the surface of the image carrier, and the density of the toner image formed on the surface of the image carrier. An image forming apparatus including an optical sensor for reading,
The endless belt-shaped image carrier is the intermediate transfer belt described above.

  According to the intermediate transfer belt of the present invention, the surface layer is formed using the (meth) acrylate monomer (B) having a refractive index nD in the range of 1.6 to 1.8. Good dispersibility of the metal oxide fine particles (A) in the liquid can be obtained, and therefore, output variation of the optical sensor that reads the toner concentration can be suppressed.

  Since the image forming apparatus of the present invention includes the above-described intermediate transfer belt, output variations of the optical sensor that reads the toner density can be suppressed.

FIG. 3 is an explanatory cross-sectional view illustrating an example of a configuration of an image forming apparatus including the intermediate transfer belt of the present invention.

  Hereinafter, the present invention will be described in detail.

[Intermediate transfer belt]
The intermediate transfer belt of the present invention is provided in an electrophotographic image forming apparatus, for example, an endless belt-like belt. Specifically, a surface layer is formed on a substrate. However, the metal oxide fine particles (A) and the (meth) acrylate monomer (B) having a refractive index nD in the range of 1.6 to 1.8 (hereinafter also referred to as “high refractive index acrylic monomer (B)”). ) And a polyfunctional (meth) acrylate (C) other than the (meth) acrylate monomer (B) (hereinafter also referred to as “polyfunctional acrylic monomer (C)”). It contains the cured resin obtained by irradiating and hardening | curing an active energy ray to the coating film of the coating liquid for surface layer formation containing these.

[Substrate]
The substrate constituting the intermediate transfer belt of the present invention has, for example, an endless belt shape, and may have a single-layer configuration or a multi-layer configuration of two or more layers.
The constituent material of the substrate is not particularly limited. For example, polyalkylene terephthalate resin such as polyimide resin (PI), polyamideimide resin, polycarbonate resin, polyphenylene sulfide resin (PPS), polyvinylidene fluoride resin, polybutylene terephthalate, poly It is preferable to use an ether resin, a polyether ketone resin, a polyether ether ketone resin or the like having high strength and high durability, and a polyphenylene sulfide resin, a polycarbonate resin, and a polyalkylene terephthalate that can be formed by extrusion. It is more preferable to use a resin, a polyether ether ketone resin, or the like. Moreover, it is preferable that the base has conductivity by dispersing a conductive agent in the resin as described above.
As the conductive agent, carbon black, carbon nanotube, or the like can be used.

  The layer thickness of the substrate is preferably 50 to 250 μm in consideration of mechanical strength, image quality, and the like.

[Surface layer]
The surface layer constituting the intermediate transfer belt of the present invention comprises a metal oxide in a cured resin containing a structural unit derived from a high refractive index acrylic monomer (B) and a structural unit derived from a polyfunctional acrylic monomer (C). Fine particles (A) are dispersed. By containing the metal oxide fine particles (A) in the surface layer, toughness is obtained in the surface layer, and high durability is obtained.

[Metal oxide fine particles (A)]
As the metal oxide fine particles (A) contained in the surface layer, various metal oxide fine particles including transition metals can be used.
Examples of the metal oxide constituting the metal oxide fine particles include silica (silicon oxide), magnesium oxide, zinc oxide, lead oxide, aluminum oxide, tin oxide, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, and cobalt oxide. , Copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, titanium oxide, niobium oxide, molybdenum oxide, vanadium oxide, etc. Among these, titanium oxide, aluminum oxide, zinc oxide, tin oxide It is preferable to use aluminum oxide or tin oxide.

  As these metal oxide fine particles, those produced by a general production method such as a gas phase method, a chlorine method, a sulfuric acid method, a plasma method, or an electrolytic method are used.

  The number average primary particle size of the metal oxide fine particles (A) is preferably in the range of 1 nm to 300 nm. Especially preferably, they are 3 nm or more and 50 nm or less. If the particle size is excessively small, sufficient wear resistance may not be obtained on the surface layer. On the other hand, if the particle size is excessively large, the metal oxide fine particles inhibit photocuring, and the surface There is a possibility that sufficient abrasion resistance cannot be obtained in the layer.

  The number average primary particle size of the metal oxide fine particles (A) is a photographic image (aggregated particles) obtained by taking a magnified photograph 10,000 times with a scanning electron microscope (manufactured by JEOL Ltd.) and randomly capturing 300 particles with a scanner. Automatic image processing analyzer LUZEX AP (Nireco Corporation) software version Ver. The number average primary particle size is calculated using 1.32.

As the metal oxide fine particles (A), it is particularly preferable to use those subjected to surface treatment.
The surface-treated metal oxide fine particles can be obtained by surface-treating untreated metal oxide fine particles (hereinafter referred to as “untreated metal oxide fine particles”) with a surface treatment agent.

Examples of the surface treatment agent used for the surface treatment of the untreated metal oxide fine particles include compounds having a radical polymerizable functional group. Examples of the radical polymerizable functional group include an acryloyl group and a methacryloyl group.
Moreover, in order to provide low surface energy property, a silicone oil, the compound which has a polyfluoroalkyl group, etc. can also be used as a surface treating agent. As the silicone oil, straight silicone oil (for example, methyl hydrogen polysiloxane (MHPS)), modified silicone oil, or the like can be used.
In the present invention, it is preferable that the metal oxide fine particles have at least one of a radical polymerizable functional group and a low surface energy functional group introduced on the surface thereof. Here, the low surface energy functional group is a functional group introduced by a surface treatment agent used for imparting low surface energy, for example, a silane-coupled silicone oil group or polyfluoroalkyl group. Etc. When both are introduced, the ratio of the radical polymerizable functional group to the low surface energy functional group is preferably 2: 1 to 1: 2.

  The surface treatment agent having a radical polymerizable functional group used for the surface treatment of untreated metal oxide fine particles includes a functional group having a carbon / carbon double bond and an alkoxy that couples with the hydroxyl group on the untreated metal oxide fine particle surface. A compound having a polar group such as a group in the same molecule is preferred.

  The surface treatment agent having a radical polymerizable functional group is preferably a compound having a functional group that is polymerized (cured) by irradiation with active energy rays such as ultraviolet rays or electron beams to become a resin such as polystyrene or polyacrylate. A silane compound having a reactive acryloyl group or a methacryloyl group is particularly preferred because it can be cured in a small amount of light or in a short time.

  Examples of the surface treatment agent having a radical polymerizable functional group include a compound represented by the following general formula (1).

[In general formula (1), R ¹ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aralkyl group having 1 to 10 carbon atoms, R ² is an organic group having a reactive double bond, X is a halogen atom, An alkoxy group, an acyloxy group, an aminoxy group, or a phenoxy group is shown, and m is an integer of 1 to 3. ]
Examples of the compound represented by the general formula (1) include the following S-1 to S-30.

_{S-1 CH 2 = CHSi (} CH 3) (OCH 3) 2
_{S-2 CH 2 = CHSi (} OCH 3) 3
S-3 CH ₂ ═CHSiCl _{3
S-4 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-5 CH 2 = CHCOO (} CH 2) 2 Si (OCH 3) 3
_{S-6 CH 2 = CHCOO (} CH 2) 2 Si (OC 2 H 5) (OCH 3) 2
_{S-7 CH 2 = CHCOO (} CH 2) 3 Si (OCH 3) 3
_{S-8 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) Cl 2
_{S-9 CH 2 = CHCOO (} CH 2) 2 SiCl 3
_{S-10 CH 2 = CHCOO (} CH 2) 3 Si (CH 3) Cl 2
S-11 CH ₂ ═CHCOO (CH ₂ ) ₃ SiCl _{3
S-12 CH 2 = C (} CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-13 CH 2 = C (} CH 3) COO (CH 2) 2 Si (OCH 3) 3
_{S-14 CH 2 = C (} CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-15 CH 2 = C (} CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-16 CH 2 = C (} CH 3) COO (CH 2) 2 Si (CH 3) Cl 2
_{S-17 CH 2 = C (} CH 3) COO (CH 2) 2 SiCl 3
_{S-18 CH 2 = C (} CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
_{S-19 CH 2 = C (} CH 3) COO (CH 2) 3 SiCl 3
_{S-20 CH 2 = CHSi (} C 2 H 5) (OCH 3) 2
S-21 CH ₂ ═C (CH ₃ ) Si (OCH ₃ ) _{3
S-22 CH 2 = C (} CH 3) Si (OC 2 H 5) 3
_{S-23 CH 2 = CHSi (} OCH 3) 3
_{S-24 CH 2 = C (} CH 3) Si (CH 3) (OCH 3) 2
_{S-25 CH 2 = CHSi (} CH 3) Cl 2
_{S-26 CH 2 = CHCOOSi (} OCH 3) 3
_{S-27 CH 2 = CHCOOSi (} OC 2 H 5) 3
_{S-28 CH 2 = C (} CH 3) COOSi (OCH 3) 3
_{S-29 CH 2 = C (} CH 3) COOSi (OC 2 H 5) 3
_{S-30 CH 2 = C (} CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3
In addition to the compound represented by the general formula (1), the following S-31 to S-33 may be used as the compound having a radical polymerizable functional group.

  The said compound can be used individually or in mixture of 2 or more types.

  Moreover, the epoxy compound shown by following S-35-S-37 can also be used as a surface treating agent.

  As a manufacturing method of surface-treated metal oxide fine particles (A), for example, 0.1 to 200 parts by mass of a surface treatment agent and 50 to 5000 parts by mass of a solvent are used with respect to 100 parts by mass of untreated metal oxide fine particles. And a method using a wet media dispersion type apparatus.

  Also, the slurry containing the untreated metal oxide fine particles and the surface treatment agent (suspension of solid particles) is wet-dispersed to break up the aggregates of the untreated metal oxide fine particles and at the same time untreated metal oxide fine particles The surface treatment proceeds. Thereafter, the solvent is removed to form powder, so that metal oxide fine particles surface-treated with a uniform and finer surface treatment agent can also be obtained.

  The surface treatment amount of the surface treatment agent (the surface treatment agent coating amount) is preferably 0.1% by mass or more and 60% by mass or less with respect to the metal oxide fine particles. Especially preferably, it is 5 mass% or more and 40 mass% or less.

  The surface treatment amount of the surface treatment agent was obtained by heat-treating the metal oxide fine particles after the surface treatment at 550 ° C. for 3 hours, quantitatively analyzing the ignition residue with fluorescent X-ray, and obtaining the molecular weight conversion from the Si amount. Is.

  The wet media dispersion type device is filled with beads as media in a container, and further agitation discs mounted perpendicular to the rotation axis are rotated at high speed to crush and disperse the aggregated particles of metal oxide fine particles. It is an apparatus having a process, and as its configuration, there is no problem as long as it is a type that can sufficiently disperse the untreated metal oxide fine particles when performing the surface treatment on the untreated metal oxide fine particles and can perform the surface treatment. Various styles such as vertical, horizontal, continuous, batch, etc. can be adopted. Specifically, a sand mill, ultra visco mill, pearl mill, glen mill, dyno mill, agitator mill, dynamic mill and the like can be used. These dispersion-type devices are pulverized and dispersed by impact crushing, friction, shearing, shear stress, etc., using a grinding medium such as balls and beads. As beads used in the dispersion type apparatus, balls made of glass, alumina, zircon, zirconia, steel, flint stone and the like can be used, but those made of zirconia or zircon are particularly preferable. Further, as the size of the beads, those having a diameter of about 1 mm to 2 mm are usually used, but in the present invention, those having a diameter of about 0.3 mm to 1.0 mm are preferably used.

  Various materials such as stainless steel, nylon and ceramic can be used for the disk and container inner wall used in the wet media dispersion type apparatus. In the present invention, the disk and container inner wall made of ceramic such as zirconia or silicon carbide are particularly used. Is preferred.

  By the wet treatment as described above, metal oxide fine particles surface-treated with the surface treatment agent can be obtained.

  The metal oxide fine particles (A) are preferably contained in the surface layer in a proportion of 5 to 30% by mass.

[High refractive index acrylic monomer (B)]
The high refractive index acrylic monomer (B) constituting the active energy ray-curable composition for forming the cured resin is a (meth) acrylate monomer having a refractive index nD in the range of 1.6 to 1.8. Specific examples include compounds represented by the above formulas (a) to (g). These can be used individually by 1 type or in mixture of 2 or more types.

  In the surface layer, the structural unit derived from the high refractive index acrylic monomer (B) is preferably contained in a proportion of 5 to 30% by mass.

[Polyfunctional acrylic monomer (C)]
The polyfunctional acrylic monomer (C) constituting the active energy ray-curable composition for forming the cured resin has two or more (meth) acryloyloxy groups (acryloyloxy group or methacryloyloxy group) in one molecule. It is used to develop the wear resistance, toughness, and adhesion of the surface layer of the intermediate transfer belt. Specifically, bis (2-acryloxyethyl) -hydroxyethyl-isocyanurate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol Bifunctional monomers such as diacrylate, hydroxypivalate neopentyl glycol diacrylate, urethane acrylate; trimethylolpropane triacrylate, pentaerythritol triacrylate, tris (acryloxyethyl) isocyanurate, ditrimethylolpropane tetraacrylate, penta Erythritol tetraacrylate (PETTA), dipentaerythritol hexaacrylate (DPHA), urethane acrylate, polyhydric alcohol and polybasic acid, and (meth ) Ester compound synthesized from acrylic acid, for example a polyfunctional monomer of trifunctional or more such as trimethylol ethane / succinic acid / acrylic acid = 2/1/4 mole esters compounds synthesized from, and the like. In order to give the coating film a hard coat property, it is desirable to use a polyfunctional acrylate having three or more functions. These can be used individually by 1 type or in combination of 2 or more types.

The polyfunctional acrylic monomer (C) preferably has a number average molecular weight of 1,000 or less, more preferably 200 or more and 600 or less.
When the number average molecular weight of the polyfunctional acrylic monomer (C) is in the above range, the density of the cured resin can be improved and high strength can be obtained.

  In the present invention, the number average molecular weight of the polyfunctional acrylic monomer (C) is a value measured by a gel permeation chromatography (Gel Permeation Chromatography) method using the polyfunctional acrylic monomer (C) as a measurement sample.

  In the surface layer, the structural unit derived from the polyfunctional acrylic monomer (C) is preferably contained in a proportion of 40 to 75% by mass.

[Other additives]
In the active energy ray-curable composition, an organic solvent, a light stabilizer, an ultraviolet absorber, a catalyst, a colorant, an antistatic agent, a lubricant, a leveling agent, an antifoaming agent, a polymerization accelerator, and an antioxidant are added as necessary. Additive components such as an agent, a flame retardant, an infrared absorber, a surfactant, and a surface modifier can be included.

  The organic solvent is contained in the active energy ray-curable composition from the standpoints of uniform solubility and dispersion stability of the active energy ray-curable composition, as well as adhesion to the endless belt-like substrate and smoothness and uniformity of the coating. The organic solvent is not particularly limited as long as it satisfies the above performance. Specific examples include organic solvents such as alcohols, hydrocarbons, halogenated hydrocarbons, ethers, ketones, esters, and polyhydric alcohol derivatives.

  The thickness of the surface layer is preferably 1 to 5 μm in consideration of mechanical strength, image quality, and the like.

[Method of manufacturing intermediate transfer belt]
The intermediate transfer belt of the present invention is formed by, for example, applying a surface layer forming coating solution for forming a surface layer on a substrate to form a coating film, and irradiating the coating film with an active energy ray to cure. By doing so, a surface layer made of a curable resin can be formed, and thereby manufactured.

In the solid content constituting the coating solution for forming the surface layer, the content of the metal oxide fine particles (A) is 5 to 30% by mass, the content of the high refractive index acrylic monomer (B) is 20 to 50% by mass, polyfunctional The content ratio of the acrylic monomer (C) is preferably 40 to 75% by mass.
In the surface layer forming coating solution, the solid content is an active energy ray-curable composition containing metal oxide fine particles (A), and a high refractive index acrylic monomer (B) and a polyfunctional acrylic monomer (C). It is said.

  In the case of using a polyimide resin as a constituent material, for example, a method of immersing a polyamic acid solution in an outer peripheral surface of a cylindrical mold, a method of applying to a peripheral surface, a method of further centrifuging, Alternatively, it is developed into a ring shape by an appropriate method such as a method of filling a casting mold, the developed layer is dried and formed into a bell-shaped shape, and the molded product is heat-treated to convert the polyamic acid into an imide. Then, it can be carried out by an appropriate method according to the conventional method such as a method of recovering from a mold (JP-A 61-95361, JP-A 64-22514, JP-A 3-180309, etc.). In manufacturing the endless belt-like substrate, an appropriate treatment such as mold release treatment or defoaming treatment can be performed.

  The surface layer forming coating solution comprises an active energy ray-curable composition containing a high refractive index acrylic monomer (B) and a polyfunctional acrylic monomer (C), metal oxide fine particles (A), a polymerization initiator, It contains other components such as a solvent as necessary.

  As a method for preparing the coating liquid for forming the surface layer, for example, the active energy ray-curable composition and the metal oxide fine particles (A) are added to the solvent at a solid content concentration of 3 to 10% by mass, for example, wet media dispersion There is a method of dispersing by a mold apparatus. As the wet media dispersion type apparatus, for example, various types such as a vertical type, a horizontal type, a continuous type, and a batch type can be adopted. Specifically, a sand mill, ultra visco mill, pearl mill, glen mill, dyno mill, agitator mill, dynamic mill and the like can be used. These dispersion-type devices are pulverized and dispersed by impact crushing, friction, shearing, shear stress, etc., using a grinding medium such as balls and beads.

  As beads used in the dispersion type apparatus, balls made of glass, alumina, zircon, zirconia, steel, flint stone and the like can be used, but those made of zirconia or zircon are particularly preferable. Further, as the size of the beads, those having a diameter of about 0.03 mm to 2 mm are usually used, but in the present invention, those having a diameter of about 0.3 mm to 1.0 mm are preferably used.

  Various materials such as stainless steel, nylon and ceramic can be used for the disk and container inner wall used in the wet media dispersion type apparatus. In the present invention, the disk and container inner wall made of ceramic such as zirconia or silicon carbide are particularly used. Is preferred.

The end point of the dispersion is preferably a dispersion state in which the rate of change of the light transmittance at 405 nm from 1 hour before becomes 3% or less after the solution obtained by coating the dispersion with a wire bar on the PET film is naturally dried. More desirably, it is preferably 1% or less.
By the dispersion treatment as described above, a coating solution for forming the surface layer can be obtained.

The polymerization initiator contained in the coating solution for forming the surface layer can be used without particular limitation as long as it can polymerize the active energy ray-curable composition with active energy rays such as light.
As the polymerization initiator, for example, a photopolymerization initiator such as an acetophenone compound, a benzoin ether compound, a benzophenone compound, a sulfur compound, an azo compound, a peroxide compound, or a phosphine oxide compound can be used.
Specifically, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, acetoin, butyroin, toluoin, benzyl, benzophenone, p-methoxybenzophenone, diethoxyacetophenone, α, α-dimethoxy-α-phenylacetophenone , Methylphenylglyoxylate, ethylphenylglyoxylate, 4,4′-bis (dimethylaminobenzophenone), 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-1, Carbonyl compounds such as 2-diphenylethane-1-one and 1-hydroxycyclohexyl phenyl ketone; sulfur compounds such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; Azo compounds such as sobutyronitrile and azobis-2,4-dimethylvalero; peroxide compounds such as benzoyl peroxide and di-t-butyl peroxide, and the like. These may be used alone or in combination of two or more. Can be used.

  Of these, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy are preferred from the viewpoint that light stability, high efficiency of photocleavage, surface curability, compatibility with cured resin, low volatility and low odor are obtained. It is preferable to use 2-methyl-1-phenylpropan-1-one or 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one.

  The content of the polymerization initiator in the coating solution for forming the surface layer is preferably 1 to 10% by mass, is excellent in curability, and can be applied to the elastic layer while obtaining sufficient hardness for the specific surface layer to be obtained. From the reason that high adhesion can be obtained, it is more preferably 2 to 8% by mass, and further preferably 3 to 6% by mass.

The coating solution for forming the surface layer preferably contains a solvent because the coating property (workability) is good.
Specific examples of the solvent include ethanol, isopropanol, butanol, toluene, xylene, acetone, methyl ethyl ketone, ethyl acetate, and butyl acetate.

The viscosity of the surface layer forming coating solution is preferably 10 to 100 cP.
The solid concentration of the surface layer forming coating solution is preferably 3 to 10% by mass.

  Examples of a method for applying the surface layer forming coating solution include spray coating.

Examples of the curing method of the active energy ray-curable composition include a method of irradiating active energy rays.
The active energy ray can be used without limitation as long as it is an energy source that activates the formed active energy ray-curable composition with ultraviolet rays, electron beams, γ rays, etc., but ultraviolet rays and electron beams are preferred. In particular, ultraviolet rays are preferable because they are easy to handle and high energy can be easily obtained. As the ultraviolet light source, any light source that generates ultraviolet light can be used. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. An ArF excimer laser, a KrF excimer laser, an excimer lamp, synchrotron radiation, or the like can also be used. In order to irradiate the spot-like active energy rays, it is preferable to use an ultraviolet laser.

  Moreover, an electron beam can be used similarly. The electron beam is from 50 keV to 1000 keV, preferably from 100 keV emitted from various electron beam accelerators such as cockroft walton type, bandegraph type, resonant transformer type, insulated core transformer type, linear type, dynamitron type, and high frequency type. An electron beam having an energy of 300 keV can be given.

The irradiation conditions vary depending on individual light sources, illuminance, curing unevenness, hardness, curing time, taking into account the cure rate, 50 mW / cm ² or more, and more preferably from 80~200mW / cm ^2. Illuminance indicates a value measured with UIT250 (USHIO INC.).

  The irradiation time of the active energy ray is preferably from 0.5 seconds to 5 minutes, and more preferably from 3 seconds to 2 minutes from the viewpoint of curing efficiency and work efficiency.

The atmosphere at the time of irradiation with active energy rays can be cured without problems in an air atmosphere. However, in consideration of curing unevenness and curing time, the oxygen concentration in the atmosphere is preferably 5% or less, particularly preferably 1% or less. In order to obtain this atmosphere, it is effective to introduce nitrogen gas or the like.
The oxygen concentration indicates a value measured with an oxygen concentration meter “OX100” (manufactured by Yokogawa Electric Corporation) for atmospheric gas management.

It is preferable to dry the coating solution for forming the surface layer after coating on the substrate. This removes the solvent.
The coating film may be dried before or after the polymerization of the monomer constituting the active energy ray-curable composition, and during the polymerization, and can be appropriately selected by combining these. In order to make the amount of volatile substances in the surface layer to a specified amount after polymerizing the monomers constituting the active energy ray-curable composition after primary drying to such an extent that the fluidity of the coating film is lost. It is preferable to perform secondary drying.
The method for drying the coating film can be appropriately selected depending on the type of solvent, the layer thickness of the surface layer to be formed, etc. The drying temperature is preferably 40 to 100 ° C., more preferably about 60 ° C. It is. The drying time is preferably, for example, 1 to 5 minutes, and more preferably about 3 minutes.

According to the intermediate transfer belt as described above, the surface layer is formed using the surface layer forming coating liquid in which the high refractive index acrylic monomer (B) is blended. It is possible to obtain a good dispersibility of the oxide fine particles (A), and thus it is possible to suppress the occurrence of disturbance of the surface layer due to poor application of the coating liquid for forming the surface layer, and an optical sensor for reading the toner concentration. Output variation can be suppressed.
The reason why the dispersion stability of the metal oxide fine particles (A) in the surface layer forming coating liquid is improved by blending the high refractive index acrylic monomer (B) in the surface layer forming coating liquid is unknown. However, since the high refractive index of the polymer is achieved by introducing a substituent having high molecular refraction into the molecule, the high refractive index acrylic monomer (B) includes sulfur, phosphorus-containing substituents, aromatic rings, fluorine Substituents with halogen elements other than atoms are considered to have been introduced, and therefore the molecular density is high, resulting in a compound having a higher specific gravity than general (meth) acrylic monomers, resulting in surface layer formation. It is presumed that the dispersion stability of metal oxide fine particles having a high specific gravity in the coating solution can be improved.
In addition, it is estimated that the reason why the variation in the output of the optical sensor that reads the toner density can be suppressed by suppressing the occurrence of the disturbance of the surface layer is that the amount of transmitted light in the surface layer is stabilized. The

[Image forming apparatus]
The intermediate transfer belt as described above is used in various known electrophotographic image forming apparatuses such as a monochrome image forming apparatus and a full color image forming apparatus.

  FIG. 1 is an explanatory sectional view showing an example of the configuration of an image forming apparatus provided with the intermediate transfer belt of the present invention.

  In this image forming apparatus, a plurality of sets of image forming units 20Y, 20M, 20C, and 20Bk, which are toner image forming means, and toner images formed in these image forming units 20Y, 20M, 20C, and 20Bk are displayed on an image support P. The image forming apparatus includes an intermediate transfer unit 10 that transfers the toner image onto the image support P, and a fixing device 30 that performs a fixing process for fixing the toner image by heating and fixing the image to obtain a toner layer.

  The image forming unit 20Y forms a yellow toner image, the image forming unit 20M forms a magenta toner image, and the image forming unit 20C forms a cyan toner image. At 20 Bk, a black toner image is formed.

  The image forming units 20Y, 20M, 20C, and 20Bk are photoconductors 11Y, 11M, 11C, and 11Bk that are rotating image carriers, and charging that applies a uniform potential to the surfaces of the photoconductors 11Y, 11M, 11C, and 11Bk. Means 23Y, 23M, 23C, 23Bk, exposure means 22Y, 22M, 22C, 22Bk for forming electrostatic latent images of a desired shape on the uniformly charged photoreceptors 11Y, 11M, 11C, 11Bk, and the respective colors Development means 21Y, 21M, 21C, and 21Bk that develops the electrostatic latent image by conveying the toner on the photoreceptors 11Y, 11M, 11C, and 11Bk, and the photoreceptors 11Y, 11M, 11C, and 11Bk after the primary transfer. And cleaning means 25Y, 25M, 25C, and 25Bk for collecting residual toner remaining in the toner.

The intermediate transfer unit 10 transfers the toner image formed by the intermediate transfer belt 16 of the present invention, which is an image carrier that circulates and the image forming units 20Y, 20M, 20C, and 20Bk, to the intermediate transfer belt 16, and performs primary transfer. Secondary transfer is performed such that the toner images transferred onto the intermediate transfer belt 16 by the primary transfer rollers 13Y, 13M, 13C, and 13Bk and the primary transfer rollers 13Y, 13M, 13C, and 13Bk are transferred onto the image support P. A secondary transfer roller 13 </ b> A as a unit and a cleaning unit 12 that collects residual toner remaining on the intermediate transfer belt 16 are included.
The intermediate transfer belt 16 is an endless belt that is stretched by a plurality of support rollers 16a to 16d and is rotatably supported.

The intermediate transfer unit 10 detects toner density (toner adhesion amount) of the toner image on the intermediate transfer belt 16, and is an optical sensor using infrared light, for example, an IDC sensor (Image Density Control Sensor). Means (not shown) are provided.
Specifically, the IDC sensors are provided on the near side and the far side in the direction perpendicular to the paper surface on the downstream side of the primary transfer roller 13Bk and the upstream side of the secondary transfer roller 13A, respectively. The amount of toner adhesion on the part and the back part is detected.

The color toner images formed by the image forming units 20Y, 20M, 20C, and 20Bk are sequentially transferred onto the rotating intermediate transfer belt 16 by the primary transfer rollers 13Y, 13M, 13C, and 13Bk, and superimposed color. A toner image is formed. The image support P accommodated in the paper feed cassette 41 is fed by the paper feed / conveyance means 42, passes through a plurality of intermediate rollers 44a to 44d, and a registration roller 46, and then a secondary transfer roller 13A as a secondary transfer means. And the color toner images are collectively transferred onto the image support P.
The image support P to which the color toner image has been transferred is fixed by a fixing device 30 equipped with a heat roller fixing device, and is sandwiched between paper discharge rollers and placed on a paper discharge tray outside the apparatus.
On the other hand, after the color toner image is transferred to the image support P by the secondary transfer roller 13 </ b> A, the residual toner is removed by the cleaning unit 12 from the intermediate transfer belt 16 from which the image support P is separated by curvature.

  According to the image forming apparatus as described above, since the intermediate transfer belt of the present invention is provided, the output variation of the optical sensor that reads the toner density can be suppressed.

(Developer)
The developer used in the image forming apparatus of the present invention may be a one-component developer using magnetic or non-magnetic toner, or may be a two-component developer in which a toner and a carrier are mixed.
The toner constituting the developer is not particularly limited, and various known toners can be used. For example, a so-called polymerized toner obtained by a polymerization method having a volume-based median diameter of 3 to 9 μm can be used. It is preferable to use it. By using the polymerized toner, a high resolution and a stable image density can be obtained in the formed image, and the occurrence of image fog is extremely suppressed.

  The carrier in the case of constituting the two-component developer is not particularly limited, and various known ones can be used. For example, the volume-based median diameter is 30 to 65 μm, and the magnetization is 20 to 70 emu. A ferrite carrier comprising / g of magnetic particles is preferred. When a carrier with a volume-based median diameter of less than 30 μm is used, carrier adhesion may occur and a white-out image may be generated. When a carrier with a volume-based median diameter of greater than 65 μm is used, There may occur a case where an image having a uniform image density is not formed.

(Image support)
As the image support P used in the image forming apparatus of the present invention, coated paper such as plain paper, fine paper, art paper or coated paper from thin paper to thick paper, commercially available Japanese paper or postcard paper Various types of plastic films, cloths, etc. for OHP can be mentioned, but are not limited thereto.

  As mentioned above, although embodiment of this invention was described concretely, embodiment of this invention is not limited to said example, A various change can be added.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

[Example 1 of production of endless belt-shaped substrate]
100 parts by mass of polyphenylene sulfide resin “E2180” (manufactured by Toray Industries, Inc.), 16 parts by mass of conductive filler “Furness # 3030B” (manufactured by Mitsubishi Chemical), 1 part by mass of graft copolymer “Modiper A4400” (manufactured by NOF Corporation) And 0.2 part by mass of calcium montanate was put into a single screw extruder and melt kneaded to obtain a resin mixture.
This resin mixture is extruded into a seamless belt shape from an annular die having a seamless belt-shaped slit-like discharge port attached to the tip of a single-screw extruder, and then a cylindrical cooling provided at the tip of the discharge port. An endless belt-like substrate [1] having a thickness of 150 μm is produced by extrapolating the tube (ratio D / d between the diameter D of the annular die and the diameter d of the cooling tube is 1.00), cooling, and solidifying. did.
The ten-point average roughness Rzjis in the circumferential direction of the endless belt-shaped substrate [1] was measured in accordance with JIS B0601: '94 (measurement reference length 20 μm), and Rz = 1.4 μm.

[Example 2 of production of endless belt-shaped substrate]
N-methyl-2-pyrrolidone (NMP) solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) “Uwanis S (solid 18 mass%) ”(manufactured by Ube Industries) and 23% of the oxidized carbon black“ SPECIAL BLACK4 ”(Degussa, pH 3.0, volatile content: 14.0%) with respect to 100 mass parts of the polyamic acid. Add to mass part, use collision type disperser "GeanusPY" (manufactured by Sinaus), pressure 200 MPa, minimum area 1.4 mm ² , collide after 2 divisions, and again pass through 2 divisions 5 times To obtain a polyamic acid solution containing carbon black.
After applying this polyamic acid solution containing carbon black to the inner peripheral surface of the cylindrical mold to a thickness of 0.5 mm via a dispenser, and rotating for 15 minutes at 1500 rpm to form a spread layer having a uniform thickness, While rotating at 250 rpm, hot air at 60 ° C. was applied for 30 minutes from the outside of the mold, and then heated at 150 ° C. for 60 minutes. Thereafter, the temperature was increased to 360 ° C. at a rate of 2 ° C./min, and further heated at 360 ° C. for 30 minutes to remove the solvent, dehydrated ring closure, water removal, and complete the imide conversion reaction. Thereafter, the temperature was returned to room temperature, and the substrate was peeled off from the cylindrical mold to produce an endless belt-shaped substrate [2] having a thickness of 0.1 mm.

[Example 1: Production Example 1 of Intermediate Transfer Belt]
(1) Preparation of surface layer-forming composition / multifunctional acrylic monomer (C): dipentaerythritol hexaacrylate (DPHA) (refractive index = 1.490) 50 parts by mass / high refractive index acrylic monomer (B): formula Compound represented by (a) (bisacryloyloxyethoxyphenylfluorene “A-BPEF” (manufactured by Shin-Nakamura Chemical Co., Ltd., refractive index nD = 1.62)) 30 parts by mass / metal oxide fine particles (A): 3- Alumina fine particles (particle size = 20 nm) surface-treated with methacryloxypropyltrimethoxysilane [A1] 20 parts by mass in a solvent: propylene glycol monomethyl ether acetate (PMA) so that the solid content concentration becomes 20% by mass By dissolving and dispersing, a composition for forming a surface layer [1] was prepared.

(2) Preparation of surface layer forming coating solution / surface layer forming composition [1] 500 parts by mass (100 parts by mass in terms of solid content)
Polymerization initiator: “Irgacure 184” (manufactured by Ciba Specialty Chemicals)
5 parts by mass / leveling agent: “KF-54” (manufactured by Shin-Etsu Silicone) 0.5 parts by mass / solvent: 300 parts by mass of propylene glycol monomethyl ether acetate (PMA) for mixing and stirring for surface layer formation A coating solution [1] was prepared.
The surface layer-forming coating solution [1] is applied onto the outer peripheral surface of the endless belt-shaped substrate [1] by spray coating, and after primary drying at 40 ° C. for 30 minutes, The surface layer having a film thickness of 4 μm is formed by irradiating ultraviolet rays with a mercury lamp having an ultraviolet intensity of 1 kw / cm ² to obtain an integrated light amount of 600 mJ / cm ² , thereby forming a surface layer having a thickness of 4 μm. ] Was obtained.
The refractive index of the surface of the intermediate transfer belt [1] was 1.55. The refractive index of the surface of the intermediate transfer belt [1] is determined based on an automatic refractometer “KPR-200” (Kalnew) on the surface of a cured product having a thickness of 3 mm obtained by curing a coating film composed only of the surface layer forming coating solution [1]. It is a refractive index at a wavelength of 588 nm measured at 20 ° C. using an optical industry company).

[Examples 2-11, Comparative Examples 1-2: Production Examples 2-13 of Intermediate Transfer Belt]
In the intermediate transfer belt production example 1, using the substrate according to Table 1, the surface layer forming compositions [2] to [13] were prepared according to the formulation of Table 1, and the surface layer was formed using this. Other than the above, intermediate transfer belts [2] to [13] were produced in the same manner.
In Table 1, A2 is tin oxide fine particles (particle size = 30 nm) surface-treated with vinyltrimethoxysilane, and TMPT is trimethylolpropane trimethacrylate (refractive index = 1.471).
Moreover, the compound represented by Formula (h) used by a comparative example is the following compound.

(1) Stability of coating solution for surface layer formation About the composition [1] to [13] for surface layer formation, a polymerization initiator, a leveling agent and a solvent immediately after or after 3 days and 7 days after storage in a cool and dark place Was added in a predetermined amount to prepare a coating solution (surface layer forming coating solution), and the stability when this was coated on a substrate was evaluated according to the following evaluation criteria. The results are shown in Table 2.
-Evaluation criteria-
A: No coating film defects occur in the coating liquid after storage for 7 days (pass)
B: Coating film defects occurred due to aggregation of metal oxide fine particles in the coating liquid after storage for 7 days, but no coating film defects occurred in the coating liquid after storage for 3 days (pass)
C: Coating defects caused by aggregation of metal oxide fine particles also occurred in the coating solution after storage for 3 days (failed)
D: A coating film defect occurred in the coating solution immediately after preparation (failed)

(2) Stability of sensor output A full-color copying machine “Bizhub C454e” (manufactured by Konica Minolta) equipped with intermediate transfer belts [1] to [13] was used as an evaluation machine. In this evaluation machine, a solid image toner patch of each color (yellow, magenta, cyan, and black) is created and transferred to the intermediate transfer belt, and the potential in the region immediately before forming the solid image toner patch and the solid image The potential of each toner patch was measured as the output of an optical sensor for detecting the toner density, and the measured potential difference was calculated. This was performed for 100 sheets, and the fluctuation range of the first measured potential difference and the 100th measured potential difference was calculated. The variation in the measured potential difference was considered to be accompanied by a change in the surface state of the intermediate transfer belt, and was evaluated according to the following evaluation criteria. The results are shown in Table 2.
-Evaluation criteria-
A: The fluctuation range of the sensor output is less than 1%, and there is no hindrance to the concentration measurement (pass)
B: The fluctuation range of the sensor output is 1% or more, but it is less than 5% and there is no problem in concentration measurement in actual use (pass)
C: The fluctuation range of the sensor output is 5% or more, and the image density cannot be adjusted based on the output result (failed).

DESCRIPTION OF SYMBOLS 10 Intermediate transfer part 11Y, 11M, 11C, 11Bk Photoconductor 12 Cleaning means 13Y, 13M, 13C, 13Bk Primary transfer roller 13A Secondary transfer roller 16 Intermediate transfer belts 16a to 16d Support rollers 20Y, 20M, 20C, 20Bk Image forming unit 21Y, 21M, 21C, 21Bk Developing means 22Y, 22M, 22C, 22Bk Exposure means 23Y, 23M, 23C, 23Bk Charging means 25Y, 25M, 25C, 25Bk Cleaning means 30 Fixing device 41 Paper feed cassette 42 Paper feed transport means 44a, 44b, 44c, 44d Intermediate roller 46 Registration roller P Image support

Claims (5)

An intermediate transfer belt provided in an electrophotographic image forming apparatus,
A surface layer is formed on the substrate;
The surface layer is other than the metal oxide fine particles (A), the (meth) acrylate monomer (B) having a refractive index nD in the range of 1.6 to 1.8, and the (meth) acrylate monomer (B). It is obtained by irradiating a coating film of a coating solution for forming a surface layer containing an active energy ray-curable composition containing a polyfunctional (meth) acrylate (C) with an active energy ray and curing it. An intermediate transfer belt characterized by that. The (meth) acrylate monomer (B) having the refractive index nD in the range of 1.6 to 1.8 is at least one selected from compounds represented by the following formulas (a) to (g). The intermediate transfer belt according to claim 1.

  The metal oxide fine particles (A) in the surface layer, the structural unit derived from the (meth) acrylate monomer (B) having a refractive index nD in the range of 1.6 to 1.8, and the (meth) acrylate monomer (B) In the total of structural units derived from polyfunctional (meth) acrylate (C) other than the above, the content ratio of metal oxide fine particles (A) is 5 to 30% by mass, and the structural unit derived from (meth) acrylate monomer (B) The content ratio of 20 to 50% by mass and the content rate of structural units derived from polyfunctional (meth) acrylate (C) is 40 to 75% by mass, according to claim 1 or 2. Intermediate transfer belt.   The intermediate transfer belt according to any one of claims 1 to 3, wherein the metal oxide fine particles (A) are made of metal oxide fine particles subjected to surface treatment. An image comprising an endless belt-shaped image carrier, toner image forming means for forming a toner image on the surface of the image carrier, and an optical sensor for reading the density of the toner image formed on the surface of the image carrier A forming device,
An image forming apparatus, wherein the endless belt-shaped image carrier is the intermediate transfer belt according to any one of claims 1 to 4.

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