Image forming device

Abstract

The present invention relates to an image forming device, which aims to suppress the occurrence of filming (foreign matter adhesion) in a transfer body to which an image from an image carrier is transferred. The image forming device comprises a plurality of image carriers and a rotatable transfer body to which the images carried by the plurality of image carriers are transferred, and is characterized in that: the elastic deformation rate of the transfer body is greater than the elastic deformation rate of the plurality of image carriers, and the difference in elastic deformation rate between the image carrier on the most upstream side in the rotation direction of the transfer body and the transfer body is smaller than the difference in elastic deformation rate between the image carriers other than the most upstream side and the transfer body.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus. Background Art

[0002] Conventionally, among image forming apparatuses such as printers, facsimile machines, copiers, and their multifunction peripherals, there are known image forming apparatuses that transfer a toner image formed on a photosensitive body to a transfer body such as a transfer belt and then transfer the image to a storage medium.

[0003] For example, Patent Document 1 discloses an electronic photographic apparatus having a photoreceptor, an intermediate transfer belt, a cleaning mechanism for cleaning the photoreceptor, and the like, and discloses making the universal hardness value (HU) and elastic deformation rate of the photoreceptor and the intermediate transfer belt within a specified range. According to Patent Document 1, in an electronic photographic apparatus of an intermediate transfer method equipped with a mechanically strong photoreceptor having a surface with high hardness and high elastic deformation rate, even if characteristic scratches suddenly occur on the surface of the photoreceptor, the adverse effects caused by the scratches can be suppressed and a good image can be continuously formed.

[0004] However, in addition to paper dust, foreign matter such as toner additives such as silica may be attached to the transfer belt, which may hinder high-quality image formation. When pressure from the outside such as contact pressure with the photosensitive body is applied when foreign matter is attached to the transfer belt, so-called filming occurs.

[0005] Patent Document 2 discloses an image forming apparatus having an intermediate transfer belt and a cleaning blade for cleaning the intermediate transfer belt, and discloses a configuration for specifying the Martens hardness and elastic deformation rate of the intermediate transfer belt. According to Patent Document 2, the paper powder filming of the intermediate transfer belt can be well removed, and good cleaning performance can be obtained.

[0006] However, conventional techniques have focused on removing foreign matter on the transfer belt, but suppressing the occurrence of filming on the transfer belt is still insufficient.

[0007] Therefore, an object of the present invention is to provide an image forming apparatus capable of suppressing the occurrence of filming (foreign matter adhesion) on a transfer body to which an image is transferred from an image carrier.

[0008] [Patent Document 1] (Japan) Patent Publication No. 2005-250455

[0009] [Patent Document 2] (Japan) Patent Publication No. 2016-206373 Summary of the invention

[0010] In order to solve the above-mentioned problems, the image forming device of the present invention comprises a plurality of image carriers, and a rotatable transfer body to which the images carried by the plurality of image carriers are transferred, the elastic deformation rate of the transfer body being greater than the elastic deformation rate of the plurality of image carriers, and the difference in elastic deformation rate between the image carrier at the most upstream side in the rotation direction of the transfer body and the transfer body being smaller than the difference in elastic deformation rate between the image carriers other than the most upstream side and the transfer body.

[0011] According to the present invention, it is possible to provide an image forming apparatus capable of suppressing the occurrence of filming (foreign matter adhesion) on a transfer body to which an image is transferred from an image carrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 FIG. 1 is a diagram showing a schematic configuration example of the image forming apparatus of the present invention.

[0013] Figure 2(a) to Figure 2(d) Shown is a schematic cross-sectional view of an example of a photoreceptor.

[0014] Figure 3 The figure shows the results of the investigation into whether filming occurs when the elastic deformation rate [%] of the photoreceptor and the transfer belt is changed. DETAILED DESCRIPTION

[0015] The image forming apparatus of the present invention is described below with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below, and other embodiments, additions, corrections, deletions, etc. can be changed within the scope that can be imagined by those skilled in the art. No matter what the method is, as long as the function and effect of the present invention are achieved, it is within the scope of the present invention.

[0016] (First embodiment)

[0017] The image forming device of this embodiment is an image forming device having multiple image carriers and a rotatable transfer body to which the images carried by the multiple image carriers are transferred, and is characterized in that: the elastic deformation rate of the transfer body is greater than the elastic deformation rate of the multiple image carriers, and the difference in elastic deformation rate between the image carrier on the upstream side in the rotation direction of the transfer body and the transfer body is smaller than the difference in elastic deformation rate between the image carriers other than the upstream side and the transfer body.

[0018] In the image forming apparatus of this embodiment, the transfer body may be a transfer belt to which a visible image (also called a toner image or a toner image) carried by an image carrier (such as a photosensitive body) is transferred. In this embodiment, the transfer body is described by taking the transfer belt as an example.

[0019] Figure 1The figure shows an example of the fixing device according to the present embodiment.

[0020] The image forming apparatus of this embodiment includes a processing unit 10 that integrates a photoreceptor 1, a charger 2, a developer 4, and a photoreceptor cleaning unit 7. Four processing units 10 are provided in parallel, for example, processing units for black, cyan, magenta, and yellow are used. When forming a full-color image, visible images of each color are sequentially transferred to a transfer belt 15 in an overlapping manner.

[0021] The image forming apparatus of this embodiment has four processing units 10, which are represented by reference numerals 10a to 10d. When describing without distinguishing the processing units 10a to 10d, they are described as processing units 10. In addition, the processing units 10a to 10d respectively have a photoreceptor 1, a charger 2, a developer 4, and a photoreceptor cleaning unit 7. For example, the photoreceptors are represented as photoreceptors 1a to 1d. Figure 1 In the figure, the reference numerals of the chargers 2b to 2d, the developers 4b to 4d, and the photoreceptor cleaning units 7b to 7d are omitted. In addition, when not distinguishing them from each other, they are described as the photoreceptor 1, the charger 2, the developer 4, and the photoreceptor cleaning unit 7.

[0022] The photoreceptor 1 as an example of an image carrier is a cylindrical drum-shaped photoreceptor drum, and the photoreceptor 1 rotates in the direction of the arrow.

[0023] Here, an example of the photoreceptor 1 will be described. Figure 2(a) to Figure 2(d) 2 is a schematic cross-sectional view for explaining an example of a photoreceptor 1. FIG. 2(a) shows an example in which a photosensitive layer 92 containing inorganic microparticles is provided near the surface of a conductive support 91. FIG. 2(b) shows an example in which a photosensitive layer 92 and a surface layer 93 containing inorganic microparticles are provided on a conductive support 91. FIG. 2(c) shows an example in which a photosensitive layer 92 and a surface layer 93 containing inorganic microparticles are provided on a conductive support 91, and a charge generating layer 921 and a charge transporting layer 922 are stacked on the photosensitive layer 92. FIG. 2(d) shows an example in which an undercoat layer 94 is provided on a conductive support 91, and a photosensitive layer 92 and a surface layer 93 containing inorganic microparticles are provided thereon, and a charge generating layer 921 and a charge transporting layer 922 are stacked on the photosensitive layer 92.

[0024] As the conductive support 91, a conductive support having a volume resistivity of 1010 [Ω·cm] or less can be used. For example, a material obtained by applying a metal such as aluminum, nickel, chromium, nickel-chromium heat-resistant alloy, copper, gold, silver, platinum, or a metal oxide such as tin oxide or indium oxide to a film-shaped or cylindrical plastic or paper by vacuum evaporation or sputtering can be used. In addition, as the conductive support 91, a conductive powder can be dispersed in a suitable adhesive resin on the above-mentioned support for coating. Furthermore, as the conductive support 91, a conductive layer can be provided on a suitable cylindrical substrate by a heat shrink tube, and the heat shrink tube contains conductive powder in raw materials such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark), etc.

[0025] The photosensitive layer 92 may be a single layer or a stacked layer, but may also be composed of a charge generating layer 921 and a charge transporting layer 922. The charge generating layer 921 is a layer having a charge generating substance as a main component. Well-known charge generating substances may be used in the charge generating layer 921, and as representatives thereof, monoazo pigments, disazo pigments, triazo pigments, perylene pigments, pyrene pigments, quinacridone pigments, quinine condensed polycyclic aromatic hydrocarbon compounds, squaric acid dyes, and other phthalocyanine pigments, naphthalocyanine pigments, azulenium acid dyes, etc. These charge generating substances may be used alone or in combination of two or more.

[0026] The charge generating layer 921 may be formed by dispersing the charge generating layer 921 in a suitable solvent together with a binder resin by ball mill, attritor, sand mill, ultrasonic wave, etc., and applying the dispersed mixture onto a conductive support and drying the dispersed mixture. Examples of the binder resin used in the charge generating layer 921 as required include polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, poly-N-vinyl carbazole, polyacrylamide, polyvinyl styrene, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene ether, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, etc.

[0027] The amount of the binder resin is appropriately 0 to 500 parts by weight, preferably 10 to 300 parts by weight, based on 100 parts by weight of the charge generating material.

[0028] The coating liquid may be applied by dipping, spraying, beating, nozzle, spinner, or ring coating. The thickness of the charge generating layer 921 is preferably about 0.01 to 5 μm, preferably 0.1 to 2 μm.

[0029] The charge transport layer 922 is formed by dissolving or even dispersing the charge transport material and the binding resin in a suitable solvent, and applying it to the charge generating layer 921 and drying it. In addition, a plasticizer, a leveling agent, an antioxidant, etc. may be added as needed. The charge transport material includes an electron transport material and a hole transport material. As the electron transport material and the hole transport material, known materials can be used.

[0030] Examples of the binder resin include thermoplastic or thermosetting resins such as polystyrene, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, styrene-maleic anhydride copolymers, polyesters, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy resins, polycarbonate, cellulose acetate resins, ethyl cellulose resins, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resins, silicone resins, epoxy resins, melamine resins, urethane resins, phenolic resins, and alkyd resins.

[0031] The amount of the charge transport material is preferably 20 to 300 parts by weight, more preferably 40 to 150 parts by weight, relative to 100 parts by weight of the binder resin. In addition, from the viewpoint of resolution and responsiveness, the film thickness of the charge transport layer 922 is preferably less than 25 μm. Regarding the lower limit, although it varies depending on the system used (especially the charged potential, etc.), it is preferably greater than 5 μm. In the photoreceptor 1 of the present embodiment, a plasticizer or a leveling agent may also be added to the charge transport layer 922. As a plasticizer, a plasticizer such as dibutyl phthalate, dioctyl phthalate, etc., which is used as a general resin plasticizer, can be directly used, and its usage amount is preferably about 0 to 30 weight percent relative to the binder resin. As a leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, or polymers or oligomers having a perfluorocarbon group in the side chain are used, and its usage amount is preferably 0 to 1 weight percent relative to the binder resin.

[0032] When the charge transport layer 922 is the outermost layer, inorganic particles are contained in the charge transport layer 922. Examples of the inorganic particles include metal powders of copper, tin, aluminum, indium, and the like, metal oxides of silicon oxide, silicon dioxide, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide, tin-doped indium oxide, and the like, and inorganic materials such as potassium titanate. In particular, metal oxides are preferred, and further, silicon oxide, aluminum oxide, titanium oxide, and the like can also be effectively used.

[0033] Since the average primary particle size of the inorganic fine particles is 0.01 to 0.5 μm, it is preferred from the viewpoint of light transmittance or abrasion resistance of the surface layer 93. When the average primary particle size of the inorganic fine particles is less than 0.01 μm, abrasion resistance and dispersibility may be reduced, while when the average primary particle size is greater than 0.5 μm, the sedimentation of the inorganic fine particles in the dispersion may be promoted or filming of the toner on the surface of the photoreceptor may occur.

[0034] Although the higher the addition amount of inorganic microparticles, the better the wear resistance, when it is too high, it sometimes leads to the side effect of the rise of residual potential and the decrease of the light transmittance of the write light of the protective layer. Therefore, relative to the roughly full solid component, it is preferably less than 30 weight percent, more preferably less than 20 weight percent. Its lower limit is preferably 3 weight percent.

[0035] In addition, these inorganic microparticles may be surface treated with at least one surface treatment agent, which will facilitate the dispersibility of the inorganic microparticles.

[0036] The reduction in the dispersibility of the inorganic fine particles not only causes an increase in the residual potential, but also causes a decrease in the transparency of the coating film or the occurrence of coating film defects, and further causes a decrease in abrasion resistance, which may develop into a problem that hinders high durability or high image quality.

[0037] Next, the case where the photosensitive layer 92 is a single-layer structure is described. A photoreceptor 1 in which the above-mentioned charge generating material is dispersed in a binder resin can be used. The single-layer photosensitive layer 92 can be formed by dissolving or dispersing the charge generating material, the charge transporting material, and the binder resin in an appropriate solvent, and applying and drying.

[0038] In addition, when the single-layer photosensitive layer 92 becomes the surface layer 93, it also contains the above-mentioned inorganic microparticles. Furthermore, the above-mentioned charge transport material is added to the photosensitive layer 92 as a functional separation type, which can also be used well. In addition, plasticizers, leveling agents, antioxidants, etc. can also be added as needed. As a binder resin, in addition to directly using the binder resin listed in the above-mentioned charge transport layer 922, the binder resin listed in the charge generation layer can also be mixed and used.

[0039] The amount of the charge generating material to 100 parts by weight of the binder resin is preferably 5 to 40 parts by weight, and the amount of the charge transporting material is preferably 0 to 190 parts by weight, more preferably 50 to 150 parts by weight. If necessary, the single-layer photosensitive layer 92 can be formed by coating with a coating liquid dispersed by a disperser or the like using a solvent such as tetrahydrofuran, dioxane, dichloroethylene, or cyclohexane together with the charge generating material, the binder resin, and the charge transporting material, by dip coating, spray coating, or bead coating. The film thickness of the single-layer photosensitive layer 92 is preferably about 5 to 25 μm.

[0040] In the photoreceptor 1 of the present embodiment, an undercoat layer 94 may be provided between the conductive support 91 and the photosensitive layer 92. The undercoat layer 94 generally has a resin as a main component, but considering that the photosensitive layer 92 is coated on the resin with a solvent, a resin with high solubility resistance to general organic solvents is preferably used.

[0041] Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethyl nylon, and curable resins that form a three-dimensional network structure such as polyurethane, melamine resin, phenolic resin, alkyd-melamine resin, and epoxy resin.

[0042] In addition, in the primer layer 94, in order to prevent moire, reduce the residual potential, etc., a fine powder pigment of a metal oxide, which can be exemplified by titanium oxide, silicon dioxide, aluminum oxide, zirconium oxide, tin oxide, indium oxide, etc., can also be added. The primer layer 94 can be formed by using a suitable solvent and coating method, similarly to the above-mentioned photosensitive layer 92. Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, etc. can also be used as the primer layer 94. In addition, a known material can also be used. The film thickness of the primer layer 94 is preferably 1 to 5 μm.

[0043] In the photoreceptor 1 of this embodiment, a surface layer 93 containing inorganic fine particles may be provided on the outermost surface of the photosensitive layer 92. The surface layer 93 preferably contains inorganic fine particles and a binder resin. The binder resin may be a thermoplastic resin such as polyarylate resin and polycarbonate resin, or a cross-linked resin such as polyurethane resin and phenolic resin.

[0044] As microparticles, organic microparticles and inorganic microparticles are used. As organic microparticles, fluorine-containing resin microparticles, carbon microparticles, etc. can be cited. Metal powders such as copper, tin, aluminum, and indium, metal oxides such as silicon oxide, silicon dioxide, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide, and tin-doped indium oxide, and inorganic materials such as potassium titanate can be cited. Metal oxides are particularly good, and further, silicon oxide, aluminum oxide, titanium oxide, etc. can also be effectively used.

[0045] Since the average primary particle size of the inorganic fine particles is 0.01 to 0.5 μm, it is preferred from the viewpoint of light transmittance or abrasion resistance of the surface layer 93. When the average primary particle size of the inorganic fine particles is less than 0.01 μm, abrasion resistance and dispersibility may be reduced, while when the average primary particle size is greater than 0.5 μm, the sedimentation of the inorganic fine particles in the dispersion may be promoted or filming of the toner on the surface of the photoreceptor may occur.

[0046] Although the higher the concentration of inorganic particles in the surface layer 93, the better its wear resistance, when it is too high, it sometimes causes the side effect of the rise of residual potential and the decrease of the light transmittance of the write light of the protective layer. Therefore, relative to the roughly all-solid component, it is preferably less than 50 weight percent, more preferably less than 30 weight percent. Its lower limit is preferably 5 weight percent. In addition, these inorganic particles can be surface treated by at least one surface treatment agent, so that the dispersibility of the inorganic particles will be beneficial. Due to the decline in the dispersibility of the inorganic particles, not only the rise of residual potential can be caused, but also the transparency of the coating film can be reduced or the occurrence of coating defects can be caused. Further, it can also cause the reduction of wear resistance, which may hinder high durability or high image quality.

[0047] Although the surface treatment agent used in the past can be used, it is better to use a surface treatment agent that can maintain the insulation of the inorganic microparticles. For example, from the perspective of the dispersibility of the inorganic microparticles and image blur, phthalate coupling agents, aluminate coupling agents, aluminum zirconium coupling agents, higher fatty acids, or a mixture of these and silane coupling agents, or Al2O3, TiO2, ZrO2, silicone resin, aluminum stearate, or a mixture of these are more preferred.

[0048] The treatment with a silane coupling agent may increase the effect of image blurring, but this effect may be suppressed by performing a mixed treatment of the surface treatment agent and the silane coupling agent.

[0049] The surface treatment amount is different due to the average primary particle size of the inorganic microparticles used, preferably 3 to 30wt%, more preferably 5 to 20wt%. When the surface treatment amount is within this range, the dispersion effect of the inorganic microparticles can be obtained, and the significant increase in the residual potential can be suppressed. The materials of these inorganic microparticles can be used alone or in combination of two or more. The thickness of the surface layer 93 is preferably in the range of 1.0 to 8.0μm.

[0050] The photoreceptor 1 that is used repeatedly for a long time preferably has high mechanical durability and is not easy to wear. However, in the image forming device, when ozone and NOx gas are generated from the charger and adhere to the surface of the photoreceptor 1, image flow sometimes occurs. In order to prevent this image flow, it is preferred to make the wear of the photosensitive layer 92 above a certain speed. Considering such long-term repeated use, the surface layer 93 preferably has a film thickness of 1.0μm or more. In addition, the thickness of the surface layer 93 is preferably 8.0μm or less. In this case, the increase in residual potential and the reduction in fine point reproducibility can be suppressed.

[0051] The material of the inorganic fine particles can be dispersed by a suitable disperser. In view of the transmittance of the surface layer 93, the average particle size of the inorganic fine particles in the dispersion is preferably 1 μm or less, and more preferably 0.5 μm or less.

[0052] As a method for providing the surface layer 93 on the photosensitive layer 92, a dip coating method, a ring coating method, a spray coating method, etc. can be used. Among them, as a general film-forming method of the surface layer 93, a spray coating method is used in which a coating is formed by spraying a coating through a nozzle having a micro-opening portion and making the micro-droplets generated by atomization adhere to the photosensitive layer 92. The solvent used here can be exemplified by tetrahydrofuran, dioxane, toluene, methylene chloride, monochlorobenzene, dichloroethane, cyclohexanone, butanone, acetone, etc.

[0053] In order to reduce the residual potential and improve the responsiveness, the surface layer 93 may also contain a charge transport material. The charge transport material may use the material described in the description of the charge transport layer. When a low molecular charge transport material is used as the charge transport material, the surface layer 93 may also have a concentration gradient.

[0054] In addition, a high molecular charge transport material having the function of a charge transport material and a function of a binder resin can also be used well in the surface layer 93. The surface layer 93 composed of these high molecular charge transport materials has excellent wear resistance. As the high molecular charge transport material, known materials can be used, but at least one polymer selected from polycarbonate, polyurethane, polyester, and polyether is preferred. Particularly preferred is a polycarbonate containing a triarylamine structure in the main chain and / or side chain.

[0055] The elastic deformation rate or Martens hardness of the surface layer 93 of the photoreceptor 1 is appropriately controlled by the amount of inorganic particles added or the type of resin. Resins such as polycarbonate and polyarylate increase the elastic deformation rate and Martens hardness by introducing a rigid structure into the resin skeleton. In addition, by using the above-mentioned polymer charge transport material, the elastic deformation rate and Martens hardness are increased.

[0056] Therefore, the method of adjusting the elastic deformation rate in the above-mentioned example of the photosensitive body 1 can be appropriately changed, but as mentioned above, for example, the method of changing the amount of inorganic fine particles added to a certain layer on the outermost surface such as the outermost layer, the type of resin, etc. can be cited.

[0057] The charger 2 is a charging mechanism for charging the photoreceptor 1 and is in the shape of a roller. The charger 2 is pressed against the surface of the photoreceptor 1 and rotates with the rotation of the photoreceptor 1. The charger 2 is used to uniformly charge the photoreceptor 1 by applying a bias voltage of direct current (DC) or alternating current (AC) superimposed on direct current (DC) by a high voltage power source, for example.

[0058] In this example, the charger 2 is a roller-shaped charging method, but the present invention is not limited thereto, and other charging methods, for example, a discharge charging method using a wire-shaped member may be used.

[0059] The exposure unit 3 is a latent image forming mechanism, and an electrostatic latent image is formed by exposing image information to the photoreceptor 1 through the exposure unit 3. The exposure can be performed using, for example, a laser beam scanner such as a laser diode or an LED.

[0060] The developing device 4 is a developing unit that stores toner (developer), and develops the electrostatic latent image on the photoreceptor 1 into a toner image by the developing device 4. The developing device 4 performs development by a predetermined developing bias supplied from, for example, a high voltage power source.

[0061] The photoconductor cleaning unit 7 has a photoconductor cleaning blade 6 therein, and cleans the photoconductor 1. The photoconductor cleaning units 7a to 7d have photoconductor cleaning blades 6a to 6d, respectively, and in this example, reference numerals 6b to 6d are omitted.

[0062] The transfer belt 15 is stretched and arranged by the transfer drive roller 21, the cleaning counter roller 16, the primary transfer roller 5, and the tension roller 20, and is driven and rotated in the direction of the arrow in the figure by the drive motor via the transfer drive roller 21. In addition, as a tensioning mechanism for the transfer belt 15, both sides of the tension roller 20 are pressed by springs.

[0063] The transfer belt 15 (also referred to as an intermediate transfer belt, etc.) may be a multilayer structure or a single-layer structure. As the raw material of the transfer belt 15, for example, PI (polyimide), PAI (polyamide-imide), TPI (thermoplastic polyimide), PVDF (polyvinylidene fluoride), PEEK (polyetheretherketone) may be used. In addition, PC (polycarbonate), PPS (polyphenylene sulfide), etc. may be used.

[0064] Here, thermosetting PI (polyimide) or PAI (polyamide-imide) is formed by centrifugal molding, etc., which cannot be formed continuously, so it takes time and the cost becomes high. On the other hand, thermoplastic TPI, PVDF, PEEK, PC, PPS, etc. can be extrusion-molded continuously, and low cost can be achieved through high production efficiency. As the properties (hardness, elastic deformation rate) of the transfer belt 15, TPI is preferred, which has low cost and high durability and can be used as a transfer belt with a long life.

[0065] In addition, the transfer belt 15 may also contain a conductivity imparting material that imparts conductivity. As the conductivity imparting material, conductive fillers can generally be cited. As conductive fillers, metals, metal oxides, metal coatings, and carbons can be cited. Metals (Ag, Ni, Cu, Zn, Al, stainless steel, etc.) have the highest conductivity, so be careful when high resistance is desired. In addition, it should be noted that, except for expensive Au and Ag, they are sometimes easily oxidized and the resistance value will change. In order to obtain conductivity, metal oxides (SnO2, In2O3, ZnO) are preferably blended in an amount of 10 to 50 mass percent relative to the total of the resin. It should be noted that the mechanical properties of the polymer are sometimes reduced. In addition, it should be noted that it sometimes becomes a high-cost material. Carbon is inexpensive and can also control the medium to high resistance range.

[0066] Generally, conductive carbon, which is relatively cheap and less environmentally dependent, is preferred as the conductivity imparting agent. Carbon includes furnace black, channel black, acetylene black, Ketjen black, etc., depending on the production method. Furnace black or acetylene black are more commonly used in conductive tapes.

[0067] In addition, by containing a semi-aromatic crystalline thermoplastic polyimide having a melting point of 360° C. or less and a conductivity imparting agent, the cost of the transfer belt 15 can be reduced. In particular, the cost of the transfer belt 15 can be reduced by containing a semi-aromatic crystalline thermoplastic polyimide having a melting point of 360° C. or less, at least one selected from the following first group, and a conductivity imparting agent (first group: polyether amide, thermoplastic polyamide-imide, PEEK).

[0068] The hardness and elastic deformation rate of the transfer belt 15 are affected by the composition such as the type and amount of carbon and the molding conditions in addition to the inherent properties of the raw materials of the material. In particular, they are affected by the cooling rate during molding. The slower the cooling rate, the higher the hardness. The cooling rate can be controlled by controlling the temperature of the mandrel, the withdrawal speed of the belt, etc. In addition, the hardness may also increase during the annealing treatment after molding. Therefore, as a method for adjusting the elastic deformation rate of the transfer belt 15, in addition to appropriately selecting the type of material used, methods such as changing the type, amount, and molding conditions of the conductive carbon can also be cited.

[0069] The transfer driving roller 21 is also referred to as a secondary transfer opposing roller, and also functions as an opposing roller when performing secondary transfer.

[0070] In addition, the driving sources of the processing unit 10 and the transfer driving roller 21 may be independent or shared. From the viewpoint of miniaturization and cost reduction of the device body, it is preferred that they be shared. In addition, it is preferred that at least the driving source of the processing unit 10 and the transfer driving roller 21 for black be shared, and it is preferred that they be turned on / off at the same time.

[0071] The transfer belt cleaning unit 32 includes a cleaning blade 31 that abuts against the transfer belt 15 in the reverse direction. The cleaning blade 31 scrapes off the transfer residual toner and the like on the transfer belt 15 to clean the transfer belt 15.

[0072] In addition, the cleaning of the transfer belt 15 is not limited to the scraper cleaning method. In addition, for example, an electrostatic method using a scraper brush or a roller may be used. In the case of the electrostatic method, for example, a cleaning brush or a cleaning roller to which a bias is applied is used instead of the cleaning scraper 31. In the case of the electrostatic method, depending on the use of the image forming device, it is sometimes necessary to transfer a preliminary charge of the residual toner, which leads to problems such as the enlargement of the cleaning unit itself, the need to add 1 to 2 systems of high-voltage power supply, and the need for unnecessary actions for bias cleaning. Therefore, from the perspective of miniaturization, low cost, and cleanability of the device body, the scraper cleaning method is preferred.

[0073] The transfer residual toner scraped off by the cleaning blade 31 passes through the toner conveying path and is collected in the waste toner collection section 33 for the intermediate transfer body.

[0074] The primary transfer rollers 5 are disposed to face each other with the transfer belt 15 interposed therebetween. For example, a predetermined primary transfer bias is applied to the primary transfer rollers 5 by a separate high-voltage power supply, so that the toner image on the photoreceptor 1 is transferred to the transfer belt 15 .

[0075] The image forming apparatus of the present embodiment includes primary transfer rollers 5 a to 5 d , and reference numerals 5 b to 5 d are omitted. When the primary transfer rollers 5 a to 5 d are described without distinguishing them from each other, they are referred to as primary transfer rollers 5 .

[0076] The primary transfer roller 5 can be appropriately changed, and examples thereof include metal rollers (aluminum, SUS, etc.), ion conductive rollers (polyurethane and carbon dispersed, NBR (acrylonitrile-butadiene rubber), epichlorohydrin rubber, etc.), and electron conductive rollers (EPDM (ethylene propylene diene rubber)).

[0077] In the present embodiment, transferring the toner image on the photoreceptor 1 to the transfer belt 15 is referred to as primary transfer, and transferring the toner image on the transfer belt 15 to a transfer material (recording medium) is referred to as secondary transfer.

[0078] The secondary transfer can be performed by a roller method or a belt method, for example. In the present embodiment, the roller method using the secondary transfer roller 25 is illustrated as an example. Examples of the secondary transfer roller 25 include an ion conductive roller (polyurethane and carbon dispersed, NBR (acrylonitrile-butadiene rubber), epichlorohydrin rubber, etc.), an electronic conductive roller (EPDM (ethylene propylene diene rubber), etc.).

[0079] In the case of the belt method, a secondary transfer belt is used and stretched by a roller member or other roller member disposed at the position of the secondary transfer roller 25. The roller member is driven to rotate by a driving motor, so that the secondary transfer belt is driven to rotate.

[0080] In addition, a cleaning mechanism may be used to clean the secondary transfer roller 25. To clean the secondary transfer roller 25, for example, a cleaning blade may be used that contacts the secondary transfer roller 25 in the reverse direction. A cleaning mechanism may be used similarly for the secondary transfer belt.

[0081] The transfer material 26 (storage medium) is placed in the transfer material cartridge 22 or the manual inlet 42. The placed transfer material is fed by the paper feed conveying roller 23, the registration roller pair 24, etc., in alignment with the timing when the leading end of the toner image on the surface of the transfer belt 15 reaches the secondary transfer position. In the secondary transfer, a predetermined secondary transfer bias is applied by, for example, a high voltage power supply, and the toner image on the transfer belt 15 is transferred to the transfer material 26.

[0082] As the secondary transfer bias, an attractive transfer method and a repulsive transfer method can be selected. The attractive transfer method is to apply a positive (+) bias to the secondary transfer roller 25 and to form a secondary transfer electric field by grounding the transfer drive roller 21. The repulsive transfer method is to apply a negative (-) bias to the transfer drive roller 21 and to form a secondary transfer electric field by grounding the secondary transfer roller 25.

[0083] In the present embodiment, the paper feeding is a longitudinal path, but it is not limited thereto and can be changed appropriately. The transfer material 26 is separated from the transfer belt 15 by the curvature of the transfer drive roller 21 and is conveyed to the fixing mechanism 40. After the toner image transferred to the transfer material 26 by the fixing mechanism 40 is fixed, the transfer material 26 is discharged from the discharge port 41.

[0084] As described above, in this embodiment, a visible image is transferred from a photosensitive body (image carrier) to a transfer belt (transfer body), and the visible image on the transfer belt is fixed to a storage medium to form an image.

[0085] In such a transfer belt, foreign matter such as paper dust, silica (an additive contained in the toner), and lubricant adheres to the transfer belt and is fixed to the transfer belt by external pressure on the transfer belt (mainly pressure from contact with the photoreceptor). As a result, filming (foreign matter adhesion) of the transfer belt occurs. When filming occurs, since high-quality image formation is hindered, it is required to suppress filming.

[0086] Therefore, after in-depth research by the inventors, it was found that by focusing on the relationship between the elastic deformation rates of the transfer body and the image carrier and stipulating the specified relationship of the elastic deformation rates, even if there is contact pressure of the image carrier on the transfer body, foreign matter such as paper dust can be prevented from adhering to the transfer body.

[0087] In this embodiment, the elastic deformation rate of the transfer body is set to be larger than the elastic deformation rates of the plurality of image carriers. This relationship can also be expressed by the following equation.

[0088] Elastic deformation rate of transfer body>elastic deformation rate of multiple image carriers…Formula (a)

[0089] In the present invention, the elastic deformation rate is expressed as the ratio of the elastic deformation to the sum of the plastic deformation and the elastic deformation when a load is applied to the transfer body or the image carrier and the transfer body or the image carrier is deformed, and is expressed by the following formula.

[0090] Elastic deformation rate [%] = {deformation amount of elastic deformation / (deformation amount of plastic deformation + deformation amount of elastic deformation)} × 100

[0091] It can also be said that when the elastic deformation rate is large, even if it is dented, it is easy to recover and difficult to plastically deform.

[0092] In the present embodiment, the method for measuring the elastic deformation rate of the transfer body or the image carrier is as follows.

[0093] Measuring instrument: Fischer micro hardness tester H-100

[0094] Measurement conditions: Maximum load 2mN

[0095] Time to reach maximum load: 10 seconds

[0096] Creep time: 10 seconds

[0097] Load reduction time: 10 seconds

[0098] Measurement environment: 23℃, 50%

[0099] Here, the relationship between the elastic deformation rate of the transfer body and the elastic deformation rate of the image carrier and the presence or absence of film formation were tested and evaluated, and the results are shown in Tables 1, Figure 3 Table 1 shows the results of investigating whether filming occurs when the elastic deformation rate [%] of the photoreceptor and the transfer belt is changed. Figure 3 Shown is a plot of Table 1.

[0100] The details of the film formation evaluation method are as follows.

[0101] [Evaluation conditions]

[0102] Machine: MPC3503 manufactured by Ricoh

[0103] Evaluation environment: High temperature and high humidity environment (32°C, 54%)

[0104] Evaluation image: Image density 0.5%

[0105] Image output mode: 3 pages / time, repeated 3000 times

[0106] Image output pages: 9000 pages in total

[0107] [Judgment criteria]

[0108] ○: No adherent matter exists on the photoreceptor.

[0109] ×: There is adhering matter on the photoreceptor.

[0110] In the transfer belt, the elastic deformation rate is adjusted by changing the type of material, the type and amount of the conductive carbon contained, and in the photoreceptor, the elastic deformation rate is adjusted by changing the amount of inorganic fine particles added to the outermost layer on the outermost surface and the type of resin.

[0111] Table 1

[0112]

[0113] As shown in Table 1, Figure 3 As shown, by making the elastic deformation rate of the transfer body larger than the elastic deformation rate of the image carrier, it is possible to suppress adhesion of substances due to pressure on the photoreceptor and reduce filming.

[0114] In addition, in this embodiment, in addition to the above provisions, the relationship between the elastic deformation rates of the plurality of image carriers is also specified. In this embodiment, the difference in elastic deformation rate between the image carrier on the most upstream side in the rotation direction of the transfer body and the transfer body is smaller than the difference in elastic deformation rate between the image carriers other than the most upstream side and the transfer body. Figure 1In the example shown, this corresponds to the photoreceptor 1a.

[0115] The above-mentioned difference can be expressed by the following formula: In the following formula, the unit (%) is omitted.

[0116] Difference = elastic deformation rate of transfer body - elastic deformation rate of image carrier

[0117] In addition, the relationship between the difference value of the image carrier on the most upstream side and the difference value of the image carrier other than the most upstream side can also be expressed by the following formula.

[0118] The difference in elastic deformation rate between the image carrier on the most upstream side and the transfer body is less than the difference in elastic deformation rate between the image carriers other than the image carrier on the most upstream side and the transfer body. Formula (b)

[0119] exist Figure 1 In the example shown, the difference of the photoreceptor 1a (elastic deformation rate of the transfer belt 15 - elastic deformation rate of the photoreceptor 1a) is smaller than the difference of the other photoreceptors 1b to 1d (for example, elastic deformation rate of the transfer belt 15 - elastic deformation rate of the photoreceptor 1b, etc.).

[0120] In addition, the above relationship can also be expressed as follows. That is, the elastic deformation rate of the transfer body is greater than the elastic deformation rate of the plurality of image carriers, and the elastic deformation rate of the image carrier on the most upstream side is greater than the elastic deformation rate of the image carriers other than the image carrier on the most upstream side. In addition, this relationship can also be expressed by the following formula.

[0121] The elastic deformation rate of the transfer body>the elastic deformation rate of the plurality of image carriers, and

[0122] Elastic deformation rate of the image carrier on the most upstream side>elastic deformation rate of image carriers other than the image carrier on the most upstream side

[0123] Foreign matter such as substances contained in the toner will be transferred from the photoreceptor to the transfer belt used in the image forming device, and the amount of transfer to the transfer belt will increase as it moves downstream in the conveying direction of the transfer belt. Therefore, there is a concern that the effect of film formation will become greater as it moves downstream in the conveying direction. Therefore, by satisfying equations (a) and (b), even if the amount of foreign matter on the downstream side increases, it is possible to suppress the foreign matter from sticking due to the pressure from the photoreceptor.

[0124] Cite Figure 1 As described above, the elastic deformation rate indicates the ease / difficulty of elastic deformation and the ease / difficulty of plastic deformation. When the elastic deformation rate is large, it is easy to recover even if it is dented. In this embodiment, the elastic deformation rate of the transfer belt 15 is greater than the elastic working power of the photoreceptors 1a to 1d, and the difference of the photoreceptor 1a is smaller than the difference of the photoreceptors 1b to 1d.

[0125] At the uppermost stream where the difference in elastic deformation rate is small, the degree of elastic deformation (ease of elastic deformation) of the transfer belt 15 and the photoreceptor 1a is close, and when the two are brought into contact at the uppermost stream where there are few foreign matters, the influence of foreign matters is small. On the other hand, at the downstream side where the difference in elastic deformation rate is larger than that at the uppermost stream, the degree of elastic deformation of the transfer belt 15 at the portion facing the photoreceptors 1b to 1d is greater than the degree of elastic deformation of the transfer belt 15 at the portion facing the photoreceptor 1a. Therefore, when the two are brought into contact at the downstream side where there are many foreign matters, a contact method can be adopted in which the transfer belt 15 is easily restored even if it is dented by the influence of foreign matters, and filming can be suppressed.

[0126] As mentioned above, since the amount of foreign matter increases as it goes downstream, the margin for film formation decreases. In addition, the greater the difference between the transfer body and the image carrier, the greater the margin for film formation. Therefore, by forming the above relationship, film formation on the transfer body can be suppressed. On the other hand, when formula (a) is satisfied and formula (b) is not satisfied, film formation will occur in the image carrier on the downstream side, especially in the image carrier at the most downstream side. As a result, it is difficult to obtain good image quality, and it deteriorates over time.

[0127] In this embodiment, the number of image carriers can be changed appropriately as long as it is 2 or more. If the number of image carriers is 2 or more, for example, even if there are 2 image carriers, the relationship between the above equations (a) and (b) can be derived.

[0128] In this embodiment, the difference in elastic deformation rate between the plurality of image carriers and the transfer body is preferably larger toward the downstream side in the rotation direction of the transfer body. Figure 1 In the example shown, the difference of the photoreceptor 1a is preferably the smallest, and as it approaches the downstream side, the difference of the photoreceptor 1b, the difference of the photoreceptor 1c, and the difference of the photoreceptor 1d are preferably increased in the order of the difference. Since the number of times the transfer belt contacts the photoreceptor increases as it moves downstream in the rotation direction (downstream in the conveying direction), the amount of foreign matter also increases accordingly. Therefore, by forming such a structure, the amount of foreign matter adhering to the transfer belt can be further reduced, and filming of the transfer belt can be further suppressed.

[0129] In this embodiment, the elastic deformation rate of the transfer body is preferably 30% or more. In this case, the transfer body can be prevented from being sunken and unable to recover, and foreign matter can be suppressed from being sunken into the transfer body. Thus, filming can be suppressed without foreign matter being sunken.

[0130] In this embodiment, the elastic deformation rate of the transfer body is preferably 70% or less. In this case, the transfer body can be prevented from being easily dented, and foreign matter such as toner can be prevented from leaking when cleaning with a cleaning blade, etc. Therefore, the cleaning performance can be improved.

[0131] (Second embodiment)

[0132] Next, another embodiment of the image forming apparatus according to the present invention will be described. The description of the same matters as those in the above embodiment will be omitted.

[0133] The image forming device of this embodiment is an image forming device having multiple image carriers and a transfer body to which the images carried by the multiple image carriers are transferred, and is characterized in that: the elastic deformation rate of the transfer body is greater than the elastic deformation rate of the multiple image carriers, and the difference in elastic deformation rate between the image carrier carrying the black image and the transfer body is greater than the difference in elastic deformation rate between the image carrier other than the image carrier carrying the black image and the transfer body.

[0134] Generally, in the market, when comparing the color mode and the monochrome mode, the monochrome mode is often used. Therefore, the monochrome mode, which is used frequently, is more susceptible to the influence of paper dust or silica than the color mode. Therefore, in this embodiment, the relationship between the elastic deformation rates of the plurality of image carriers is regulated, especially focusing on the relationship between the elastic deformation rates of the image carriers carrying the black image.

[0135] In this embodiment, similarly to the above embodiment, the elastic deformation rate of the transfer body (eg, transfer belt) is made larger than the elastic deformation rate of the plurality of image carriers. This can be expressed by the following formula similarly to the above embodiment.

[0136] Elastic deformation rate of transfer body>elastic deformation rate of multiple image carriers…Formula (a)

[0137] In addition, similarly to the above-described embodiment, the difference between the elastic deformation rate of the transfer body and the elastic deformation rate of the image carrier can also be expressed by the following equation.

[0138] Difference = elastic deformation rate of transfer body - elastic deformation rate of image carrier

[0139] Then, in this embodiment, the difference in elastic deformation rate between the image carrier carrying the black image and the transfer body is greater than the difference in elastic deformation rate between the image carrier other than the image carrier carrying the black image and the transfer body. This relationship can also be expressed by the following equation.

[0140] The difference of the image carrier carrying the black image>the difference of the image carrier other than the image carrier carrying the black image…Formula (c)

[0141] That is, in the present embodiment, the above-mentioned formula (a) and formula (c) are satisfied. This can suppress filming (foreign matter adhesion) on the transfer body to which an image is transferred from a frequently used image carrier.

[0142] In other words, when the difference of the image carrier carrying the frequently used black image is increased, the degree of elastic deformation of the transfer body in the portion facing the image carrier carrying the black image is greater than the degree of elastic deformation of the transfer body in the portion facing the carrier other than the image carrier carrying the black image. Therefore, when the image carrier carrying the frequently used black image is brought into contact with the transfer body, a contact method can be adopted in which the transfer body is easily restored even if it is depressed by the influence of foreign matter, and filming can be suppressed.

[0143] exist Figure 1 In the example shown, any one of the photoreceptors 1 a to 1 d may be arranged as an image carrier that carries a black image.

[0144] In addition, the above relationship can also be expressed as follows. That is, the elastic deformation rate of the transfer body is greater than the elastic deformation rate of the plurality of image carriers, and the elastic deformation rate of the image carrier carrying the black image is greater than the elastic deformation rate of the image carrier other than the image carrier carrying the black image. In addition, the relationship can also be expressed by the following formula.

[0145] The elastic deformation rate of the transfer body>the elastic deformation rate of the plurality of image carriers, and

[0146] Elastic deformation rate of the image carrier carrying the black image>elastic deformation rate of the image carrier other than the image carrier carrying the black image

[0147] As described above, since the ratio of the black mode is higher than that of the color mode on the market, the filming of the transfer body can be suppressed by making the difference of the image carrier carrying the black image larger than that of the color mode. On the other hand, when formula (a) is satisfied and formula (c) is not satisfied, filming occurs on the image carrier carrying the black image. As a result, it is difficult to obtain good image quality, and the image quality deteriorates over time.

Claims

1. An image forming device comprising a plurality of image carriers and a rotatable transfer body to which images carried by the plurality of image carriers are transferred, characterized in that: The elastic deformation rate of the transfer body is greater than the elastic deformation rate of the plurality of image carriers. The difference in elastic deformation rate between the image carrier on the most upstream side in the rotation direction of the transfer body and the transfer body is smaller than the difference in elastic deformation rate between the image carriers other than the image carrier on the most upstream side and the transfer body, A difference in elastic deformation rate between the plurality of image carriers and the transfer body increases toward a downstream side in a rotation direction of the transfer body.

2. An image forming device comprising a plurality of image carriers and a transfer body to which images carried by the plurality of image carriers are transferred, characterized in that: The elastic deformation rate of the transfer body is greater than the elastic deformation rate of the plurality of image carriers. The difference in elastic deformation rate between the image carrier carrying the black image and the transfer body is greater than the difference in elastic deformation rate between the image carrier other than the image carrier carrying the black image and the transfer body.

3. The image forming device according to claim 1 or 2, characterized in that: The transfer body has an elastic deformation rate of 30% or more.

4. The image forming device according to claim 1 or 2, characterized in that: The transfer body has an elastic deformation rate of 70% or less.

5. The image forming apparatus according to claim 1 or 2, characterized in that: The transfer body is a transfer belt, and the plurality of image carriers are photosensitive bodies.

Images