JP2021189235A - Developing roller and image forming apparatus - Google Patents

Abstract

To provide a developing roller and an image forming apparatus that can prevent fogging in a high temperature and high humidity condition and provide a high-quality image.SOLUTION: A developing roller comprises: a shaft body 2; an elastic layer 3 that is provided on an outer surface of the shaft body 2; and a coating layer 4 that is provided on the outside of the elastic layer 3. In the developing roller 1, the coating layer 4 contains a base resin and a conductivity imparting agent; the base resin in the coating layer 4 is a silicone modified urethane resin; the conductivity imparting agent is zinc oxide particles.SELECTED DRAWING: Figure 1

Description

The present invention relates to a developing roller and an image forming apparatus.

A developing roller used in an image forming apparatus such as a copying machine, a printer, or a facsimile that employs an electrophotographic method has a function of imparting a uniform frictional charge to toner and stably transporting a predetermined amount of toner to a developing region. Has. In recent years, the characteristics of toner have been improved in the process of increasing the speed, life, and image quality of electrophotographic devices, and along with this, the electrical characteristics of various materials that make up the developing roller have been adjusted for development. It is also being considered to improve the developer transportability of the roller.

In an image forming apparatus that employs an electrophotographic method, polyurethane is used for the surface layer (also referred to as a coating layer) of a developing roller because it does not contaminate the photosensitive drum. However, in particular, when a large amount of image is output from the initial stage, a high temperature and high humidity environment occurs, insufficient charging occurs on the surface of the developing roller, and the developer is developed on the white background of the image. Also called) may occur.

Therefore, for the purpose of preventing the generation of afterimages or improving fog, for example, Patent Document 1 discloses a developing roller containing at least a quaternary ammonium base-containing copolymer in a material constituting the surface. There is. According to this developing roller, excellent negative chargeability can be imparted to the toner, and the surface resistance of the developing roller can be reduced.

Japanese Unexamined Patent Publication No. 2001-31136

However, there is still room for improvement in preventing fogging under high temperature and high humidity conditions in order to cope with high speed and high image quality of the electrophotographic apparatus.
The present invention has been made in view of the above circumstances, and an image forming apparatus including a developing roller capable of suppressing fogging under high temperature and high humidity conditions and providing a high-quality image and a developing roller thereof. The purpose is to provide.

The present inventors have made further studies to solve the above-mentioned problems caused by polyurethane. As a result, by dispersing the zinc oxide particles in the coating layer containing the silicone-modified polyurethane according to the present invention as the base resin, the capacitance of the developing roller is reduced, and in addition to the effect of suppressing the decay of the toner charge, oxidation is performed. We have found that the ability to apply charge to the toner by zinc particles can be improved, and have reached the present invention.

That is, the present invention is a developing roller including a shaft body, an elastic layer provided on the outer surface of the shaft body, and a coating layer provided outside the elastic layer, and the coating layer imparts conductivity to the base resin. The base resin is a silicone-modified urethane resin, and the conductivity-imparting agent is a developing roller which is zinc oxide particles.

The coating layer may further contain a roughnessing agent.

The resistance value on the surface of the developing roller ^{is preferably 1 × 10 6} Ω or more and 9 × 10 ⁹ Ω or less.

The hexadecane contact angle on the surface of the developing roller is preferably 30 ° or more.

The image forming apparatus of the present invention includes the developing roller of the present invention.

According to the developing roller and the image forming apparatus of the present invention, it is possible to suppress the occurrence of fog under high temperature and high humidity conditions and provide a high quality image.

It is a perspective view which shows one Embodiment of the development roller of this invention. It is a schematic sectional drawing which shows one Embodiment of the image forming apparatus of this invention. It is a schematic front view which shows the apparatus which measures the resistance of the surface of a developing roller. It is a graph which shows the CF characteristic of a developing roller.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Developing roller]
As shown in FIG. 1, the developing roller 1 of the present invention includes a shaft body 2, an elastic layer 3 provided on the outer surface of the shaft body 2, and a coating layer 4 provided outside the elastic layer 3.
The coating layer 4 contains a base resin and a conductivity-imparting agent. The base resin is a silicone-modified urethane resin, and the conductivity-imparting agent is zinc oxide particles.
The details of each configuration will be described below.

<Axis body>
As the shaft body 2, preferably, a shaft body having conductive properties and used for a conventionally known developing roller can be used. The shaft body 2 is preferably made of at least one metal selected from the group consisting of, for example, iron, aluminum, stainless steel, and brass. It should be noted that such a shaft body 2 is also generally known by the name of "core metal".

The shaft body 2 may contain an insulating resin. The insulating resin may be, for example, a thermoplastic resin or a thermosetting resin. The shaft body 2 may include, for example, a core body made of an insulating resin and a plating layer provided on the core body. Such a shaft body 2 can be obtained, for example, by plating a core body made of an insulating resin to make it conductive.
The shaft body 2 is preferably a core metal in order to obtain good conductive characteristics.

The shape of the shaft body 2 is preferably, for example, a rod shape, a tubular shape, or the like. The cross-sectional shape of the shaft body 2 may be, for example, a circular shape, an elliptical shape, or a non-circular shape such as a polygon. The outer peripheral surface of the shaft body 2 may be subjected to a treatment such as a cleaning treatment, a degreasing treatment, and a primer treatment.

The length of the shaft body 2 in the axial direction is not particularly limited, and may be appropriately adjusted according to the form of the image forming apparatus to be installed. Further, the diameter of the shaft body 2 (diameter of the circumscribed circle) is not particularly limited, and may be appropriately adjusted according to the form of the image forming apparatus to be installed.

<Elastic layer>
The elastic layer 3 develops hardness and elasticity that can be pressed against the photoconductor with an appropriate nip width and nip pressure so that toner can be supplied to the electrostatic latent image formed on the surface of the photoconductor in just proportion. It is provided to be applied to the roller 1. Various rubber materials can be used for the elastic layer 3. The rubber used for the rubber material includes ethylene-propylene-diene copolymer rubber (EPDM), acrylic nitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), and styrene-. Examples thereof include butadiene rubber (SBR), fluororubber, silicone rubber, epichlorohydrin rubber, hydride of NBR, and urethane rubber. These can be used alone or in combination of two or more. Among these, silicone rubber having a small compressive stress strain due to pressing is preferable. Examples of the silicone rubber include polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polyphenylvinylsiloxane, and copolymers of these siloxanes.

By blending a conductivity-imparting agent such as an electronically conductive substance or an ionic conductive substance in the elastic layer 3, the conductivity thereof can be appropriately adjusted. Examples of the electronically conductive substance include conductive carbon such as Ketjen Black EC and acetylene black, carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT, and an oxidation-treated color (ink). Examples thereof include metals such as carbon, copper, silver and germanium, and metal oxides thereof. Among these, carbon black (conductive carbon, carbon for rubber, carbon for color (ink)) is preferable because it is easy to control the conductivity with a small amount. The ion conductive substances include inorganic ion conductive substances such as sodium perchlorate, lithium perchlorate, calcium perchlorate, lithium chloride, lithium bisimide, and potassium bisimide, modified aliphatic dimethylammonium etosulfate, and the like. Examples thereof include organic ion conductive substances such as stearyl ammonium acetate. Reactive ether-modified silicone oil may be added to the elastic layer 3.

<Coating layer>
The coating layer 4 contains a base resin and a conductivity-imparting agent. The base resin is (A) a silicone-modified urethane resin, and the conductivity-imparting agent is (B) zinc oxide particles.
The coating layer 4 of the present invention can be formed by heating and curing a composition for a coating layer containing (a) a silicone-modified polyol, (b) an isocyanate compound, and (c) zinc oxide particles. The details of the coating layer composition will be described below.

(A) Silicone-modified polyol The silicone-modified polyol is a prepolymerized product obtained by polymerizing a composition composed of a modified silicone oil and an isocyanate compound.
Details of the modified silicone oil and the isocyanate compound will be described below. Examples of the modified silicone oil include both-ended modified silicone oil and one-ended modified silicone oil.

-Both ends modified silicone oil-
The bi-terminal modified silicone oil is a kind of so-called reactive silicone oil and has a property of polymerizing with an isocyanate compound. Therefore, it is preferable that both ends of the silicone chain of the modified silicone oil are modified by an ether group, an amino group (primary or secondary amino group), a mercapto group, or a hydroxyl group. These two-ended modified silicone oils are both-ended ether-modified silicone oil, both-ended amino-modified silicone oil, both-ended mercapto-modified silicone oil, both-ended carboxyl-modified silicone oil, both-ended phenol-modified silicone oil, and both-ended carbinol-modified silicone. It is commercially available as an oil.

Here, as the preferable two-ended modified silicone oil used in the present invention, both-ended modified silicone oil represented by the following general formula (1) can be mentioned.

In the general formula (1), R represents −C ₃ H ₆ OC ₂ H ₄ OH or −C ₃ H ₆ OCH ₂ −C (CH ₂ OH) ₂ C ₂ H ₅ , and n is 20 or less. Represents an integer.

_{Among the two-ended} modified silicone oils represented by the general formula (1), it is particularly preferable to use a silicone oil in which R at both ends is −C 3 H ₆ OC ₂ H _{4 OH and n is about 10.} .. As for such a silicone oil, a commercially available one can be appropriately obtained.

In the general formula (1), the functional group bonded to the silicon atom is a methyl group, but both-ended modified silicone oil in which this methyl group is substituted with a hydrogen atom may be used.

By containing the modified silicone oil at both ends in the composition for forming the coating layer 4, it is possible to impart appropriate elasticity to the coating layer 4 and to adjust the electrical characteristics of the coating layer 4. , The occurrence of filming can be effectively suppressed.

-One-ended diol-modified silicone oil-
The one-ended diol-modified silicone oil is a reactive silicone oil like the two-ended modified silicone oil, but has two hydroxyl groups bonded to one end of the silicone chain. Normally, when a double-ended silicone oil and an isocyanate compound are polymerized, a linear polyurethane is produced. However, by using a single-ended diol-modified silicone oil in combination, a branched chain is introduced into the polyurethane, and the developing roller 1 is used. It is possible to improve the nano-level fine roughness of.

Examples of the one-ended diol-modified silicone oil include one-ended modified silicone oil represented by the following general formula (2).

In the general formula (2), R'represents _{−C 3} H _{6 OCH 2} −C (CH ₂ OH) ₂ C ₂ H ₅ , and n represents an integer of 20 or less.

Among the one-terminal diol-modified silicone oils represented by the general formula (2), it is particularly preferable to use silicone oil having n of about 10. In the general formula (2), the functional group bonded to the silicon atom is a methyl group, but a silicone oil in which this methyl group is substituted with a hydrogen atom may be used.

In the present invention, the one-terminal diol-modified silicone oil used for preparing the silicone-modified polyol is preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the two-ended modified silicone oil. It is more preferable that the amount is 8 parts by mass or more and 8 parts by mass or less. By adjusting the amount of the one-ended diol-modified silicone oil used with respect to the two-ended modified silicone oil within the above range and adjusting the surface roughness of the coating layer 4, the development performance is maintained well while maintaining good development performance. Filming can be effectively prevented.

-Isocyanate compound-
In the present invention, the isocyanate compound used for prepolymerizing the silicone-modified polyol is not particularly limited as long as it has reactivity with the reactive group introduced into the silicone oil, but for example. , Diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and other diisocyanates, and modified forms of these isocyanates, such as adduct type, bullet type, isocyanurate type and allophanate type. Can be done. Among these isocyanate compounds, bifunctional isocyanate compounds, isocyanurate-type isocyanate compounds and adduct-type isocyanate compounds are preferable, and these may be used alone or in combination. The longer the molecular chain of an isocyanate compound, the more flexible polyurethane can be produced.

(B) Isocyanate compound As the isocyanate compound for curing the silicone-modified polyol, various isocyanate compounds usually used for preparing polyurethane, for example, aromatic isocyanate compounds, aliphatic isocyanate compounds, and alicyclic isocyanate compounds are used. Can be done.
Examples of the aromatic isocyanate compound include 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), and 4,4'-diphenylmethane diisocyanate (4,4). '-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylenedi isocyanate, polymethylene polyphenylene polyisocyanate, trizine diisocyanate (TODI), 1,5-naphthalenedi isocyanate (NDI), Examples thereof include 3,3'-dimethylbiphenyl-4,4'-diisocyanate.
Examples of the aliphatic isocyanate compound include hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornene diisocyanatomethyl (NBDI), xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate. (TMXDI) and the like can be mentioned.
Further, examples of the alicyclic polyisocyanate include transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), H12MDI (hydrogenated MDI), and 4,4'-dicyclohexylmethane. Diisocyanate and the like can be mentioned.

In the present invention, the amount of the isocyanate compound used in the mixed solution used to form the coating layer 4 is such that the reaction rate of the isocyanate compound is 80% or more and 126% or less, preferably 95% or more and 112% or less. It is preferable to be done.

(C) Zinc Oxide Particles The zinc oxide particles preferably have an average particle diameter of 20 nm or more and 750 nm or less in consideration of dispersibility and conductivity in the resin composition for a coating layer.

(Other ingredients)
-Roughness agent-
Examples of the roughening agent include inorganic particles such as silica (including surface-treated silica) and resin particles such as acrylic, urethane, nylon, acrylonitrile, silicone, silicone rubber, and benzoguanamine. Only one type of roughness agent may be contained in the coating layer 4, or two or more types may be contained.

The size of the roughness agent is an average particle diameter of 2 μm or more, preferably 3 μm or more and 15 μm or less. By setting the average particle size of the roughness agent in the above range, the surface roughness of the developing roller 1 is appropriately maintained, the developer transportability is maintained well, and the resolution is maintained at a high level. It is possible to prevent deterioration of image quality. When the average particle size is 2 μm, it is easy to aggregate and it is not completely dispersed before coating.
The average particle size (secondary particles) of the roughness agent can be measured with a particle size distribution measuring device (manufactured by Beckman Coulter).

The roughness agent used in the present invention preferably has heat resistance that does not deform or melt even at a temperature of 100 ° C. or higher, and more preferably has heat resistance at 130 ° C. to 180 ° C. This makes it possible to prevent the roughness agent from being deformed even at the crosslinking temperature of the coating layer 4. The heat resistance of the roughness agent can be evaluated by applying pressure and heat to the melt flow indexer to confirm that the roughness agent does not melt and flow out.

The roughness agent may be present (buried) in the coating layer 4, may be unevenly dispersed in the coating layer 4, or may be unevenly distributed on the surface side of the coating layer 4.

The roughness agent is preferably silicone rubber particles, which have similar material components to the base resin and are flexible. As the silicone rubber particles, a structure in which organopolysiloxane or polyorganosylces oxane such as dimethylpolysiloxane is crosslinked is preferable.

Regarding the silicone rubber particles, as the organic group, an alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group; an aryl group such as a phenyl group and a trill group; an alkenyl group such as a vinyl group and an allyl group; β- Aralkyl groups such as phenylethyl group and β-phenylpropyl group; monovalent halogenated hydrocarbon groups such as chloromethyl group and 3,3,3-trifluoropropyl group; epoxy group, amino group, mercapto group, acryloxy group, Organopolysiloxane or organopolysilsesquioxane having a group selected from one or more kinds of monovalent organic groups having 1 or more and 20 or less carbon atoms selected from reactive group-containing organic groups such as methacryloxy groups. It is preferable to prepare from, and particles prepared from these organopolysiloxanes or organopolysilsesquioxane may be surface-treated with organoalkoxysilanes. Examples of such silicone rubber particles include "KMP-597" manufactured by Shin-Etsu Chemical Co., Ltd. and "EP-5500", "EP-2600", and "EP-2601" manufactured by Toray Dow Corning Co., Ltd. , "E-2720", "DY 33-430M", "EP-2720", "EP-9215 Cosmetic Particle", "9701 Cosmetic Powder" and the like can be used.

The content of the roughness agent is preferably 1 part by mass or more and 40 parts by mass or less, and more preferably 3 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the silicone-modified polyol. By keeping the amount of the roughener used within the above range, the surface roughness of the developing roller 1 is appropriately maintained, the developer transportability is kept good, and the resolution is high. It is possible to maintain the standard and prevent deterioration of image quality.

The thickness of the coating layer 4 is preferably 5 μm or more and 13 μm or less, and more preferably 6 μm or more and 11 μm or less.

(Other configurations)
The developing roller 1 of the present invention may include an adhesive layer between the shaft body 2 and the elastic layer 3 and between the elastic layer 3 and the coating layer 4. An adhesive layer may be provided between the elastic layer 3 and the coating layer 4 by irradiating the surface modification of the elastic layer 3 with UV light or the like and performing a primer treatment, and surface modification and adhesion by plasma coating. The agent layer may be provided at the same time.

In the developing roller 1 of the present invention, the electrical characteristics can be adjusted, and in particular, the developing performance can be satisfactorily adjusted by adjusting the coating layer. The resistance value and capacitance can be adjusted by combining the isocyanurate type and the adduct type of the isocyanate compound.

(Resistance value on the surface of the developing roller)
The resistance of the surface of the developing roller 1 of the present invention, 1 is preferably × or less 10 ⁶ Omega than 9 × 10 ⁹ Omega, and more preferably less 1 × 10 ⁶ Omega least 1 × 10 ⁹ Omega. The resistance value on the surface of the developing roller 1 can be adjusted by the combination of the type of the silicone-modified polyol and the isocyanate compound of the coating layer 4. If necessary, the resistance value can be controlled by adding reactive ether-modified silicone oil or zinc oxide particles.
However, basically, the electron conductivity due to carbon is not used because the resistance value varies and it is difficult to control. In addition, ionic conductive materials are not used because they are affected by environmental changes.
The resistance value on the surface of the developing roller is a value measured by the method described in Examples described later.

(Hexadecane contact angle)
The hexadecane contact angle on the surface of the developing roller 1 is preferably 30 ° or more, more preferably 45 ° or more, and further preferably 50 ° or more. When the temperature is 30 ° or more, the occurrence of filming can be satisfactorily suppressed. By suppressing filming, the life of the developing roller 1 is extended, which leads to stabilization of image quality. In addition, fog generation due to filming can be suppressed.
The hexadecane contact angle can be measured using a portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.).

In the developing roller of the present invention, the coating layer uses a silicone-modified urethane resin as a base resin and contains zinc oxide particles as a conductivity-imparting agent, so that fogging under high temperature and high humidity conditions can be suppressed. By changing the urethane resin to a silicone-modified urethane resin, the capacitance of the coating layer can be reduced, and in addition to the effect of suppressing the attenuation of the toner charge, the charge imparting performance to the toner by the zinc oxide particles is improved. As a result, fog can be effectively and remarkably suppressed.

[Developer and image forming device]
The developing roller 1 of the present invention can be suitably used as a developer carrier in a developing apparatus and an image forming apparatus. In the present embodiment, the configuration other than the developing roller 1 in the image forming apparatus is not particularly limited. An example of the developing apparatus and the image forming apparatus 10 provided with the developing roller 1 of the present invention will be described with reference to FIG.

The image forming apparatus 10 connects a plurality of image carriers 11B, 11C, 11M and 11Y mounted on the developing units B, C, M and Y of each color (black, cyan, magenta, yellow) in series on the transfer transfer belt 6. It is a tandem type color image forming apparatus arranged in the above, and the developing units B, C, M and Y are arranged in series on the transfer transfer belt 6. The developing unit B carries an image via an image carrier 11B, for example, a photosensitive member (also referred to as a photosensitive drum), a charging means 12B, for example, a charging roller, an exposure means 13B, a developing device 20B, and a transfer transfer belt 6. A transfer means 14B that comes into contact with the body 11B, for example, a transfer roller and a cleaning means 15B are provided.

The developing device 20B is an example of the developing device of the present invention, and includes the developing roller 1 of the present invention and the developing agent 22B as shown in FIG. Therefore, in the image forming apparatus 10, the developing roller 1 is mounted as the developing agent carriers 23B, 23C, 23M and 23Y. Specifically, the developing apparatus 20B includes a housing 21B accommodating a one-component non-magnetic developer 22B, a developing agent carrier 23B for supplying the developing agent 22B to the image carrier 11B, and a developing agent carrier 23B. A toner supply roller 25B for supplying the developer 22B and a developer amount adjusting means 24B for adjusting the thickness of the developer 22B, for example, a blade are provided. In the developing apparatus 20B, the developing agent amount adjusting means 24B is in contact with or pressed against the outer peripheral surface of the developing agent carrier 23B as shown in FIG. That is, the developing device 20B is a "contact developing device". The developing units C, M and Y are basically configured in the same manner as the developing unit B, and the same elements are designated by the same reference numerals and the symbols C, M or Y indicating each unit, and the description thereof will be omitted. ..

In the image forming apparatus 10, the developer carrier 23B of the developing apparatus 20B is arranged so that its surface is in contact with or pressed against the surface of the image carrier 11B. Similar to the developing device 20B, the developing devices 20C, 20M and 20Y are also arranged so that the surface of the developing devices 23C, 23M and 23Y is in contact with or pressed against the surfaces of the image carriers 11C, 11M and 11Y. .. That is, the image forming apparatus 10 is a "contact type image forming apparatus".

The fixing means 30 is arranged on the downstream side of the developing unit Y. The fixing means 30 includes a fixing roller 31, an endless belt support roller 33 arranged in the vicinity of the fixing roller 31, a fixing roller 31, and an endless belt in a housing 34 having an opening 35 through which the recording body 16 is passed. An endless belt 36 wound around the support roller 33 and a pressure roller 32 arranged to face the fixing roller 31 are provided, and the fixing roller 31 and the pressure roller 32 are in contact with each other or pressure-welded to each other via the endless belt 36. It is a pressure heat fixing device that is rotatably supported so as to be. A cassette 41 for accommodating the recording body 16 is installed at the bottom of the image forming apparatus 10. The transfer transfer belt 6 is wound around a plurality of support rollers 42.

The developers 22B, 22C, 22M and 22Y used in the image forming apparatus 10 may be a dry developer or a wet developer as long as they can be charged by friction, and may be a non-magnetic developer or magnetic developer. It may be an agent. In the housings 21B, 21C, 21M and 21Y of the developing units B, C, M and Y, one component non-magnetic black developer 22B, cyan developer 22C, magenta developer 22M and yellow developer 22Y are contained. Each is stored.

The image forming apparatus 10 forms a color image on the recording body 16 as follows. First, in the developing unit B, an electrostatic latent image is formed on the surface of the image carrier 11B charged by the charging means 12B by the exposure means 13B, and a black electrostatic latent image is formed by the developer 22B supplied by the developer carrier 23B. The image is developed. Then, when the recording body 16 passes between the transfer means 14B and the image carrier 11B, the black electrostatic latent image is transferred to the surface of the recording body 16. Next, in the same manner as in the developing unit B, the cyan image, the magenta image, and the yellow image are superimposed on the recording body 16 in which the electrostatic latent image is visualized as a black image by the developing units C, M, and Y, respectively. A color image is visualized. Next, in the recording body 16 in which the color image is visualized, the color image is fixed to the recording body 16 as a permanent image by the fixing means 30. In this way, a color image can be formed on the recording body 16.

The developing apparatus 20B includes a developing roller 1, which is excellent in developer transportability and suppresses the occurrence of toner filming, and can contribute to forming a high-density, high-quality image for a long period of time. Further, the image forming apparatus provided with the developing apparatus 20B can form a high-density and high-quality image for a long period of time.

The developing apparatus and the image forming apparatus of the present invention are not limited to those described above, and various modifications can be made as long as the object of the present invention can be achieved.

In the present invention, the image forming apparatus 10 is not limited to the electrophotographic system, and may be, for example, an electrostatic image forming apparatus. Further, the image forming apparatus 10 in which the developing roller 1 of the present invention is arranged is not limited to the tandem type color image forming apparatus in which a plurality of image carriers having development units of each color are arranged in series on a transfer transfer belt. For example, a monochrome image forming apparatus provided with a single developing unit, a 4-cycle color image forming apparatus that sequentially repeats primary transfer of a developer image carried on an image carrier onto an endless belt, or the like may be used. Further, the developer used in the image forming apparatus is a one-component non-magnetic developer, but in the present invention, it may be a one-component magnetic developer or a two-component non-magnetic developer. Alternatively, it may be a two-component magnetic developer.

The image forming apparatus is a contact type image forming apparatus in which the surface of the developing roller is arranged in contact with or in pressure contact with the surface of the image carrier, but the image forming apparatus of the present invention is a non-contact type image forming apparatus. You may.

Since the image forming apparatus 10 of the present invention includes the developing roller 1 of the present invention, the generation of fog under high temperature and high humidity conditions is suppressed, and a high quality image can be provided.

Although the present invention has been described above with reference to the embodiments, it goes without saying that the technical scope of the present invention is not limited to the scope of the invention described in the above embodiments. It will be apparent to those skilled in the art that improvements can be made. It is also clear from the description of the claims that the invention with such changes or improvements may be included in the technical scope of the present invention.

Hereinafter, the present invention will be described in detail with reference to examples. The present invention is not limited to the examples shown below.

[Example 1]
The developing roller of Example 1 was produced by the following procedure.
(Formation of primer layer)
The shaft body (made by SUM23, diameter 10 mm, length 274.2 mm) subjected to electroless nickel plating is washed with ethanol, and a silicone-based primer (trade name "Primer No. 16", Shin-Etsu Chemical Co., Ltd.) is used on the surface thereof. Made by the company) was applied. The primer-treated shaft was fired at a temperature of 150 ° C. for 10 minutes using a gear oven, and then cooled at room temperature for 30 minutes or more to form a primer layer on the outer peripheral surface of the shaft.

(Formation of elastic layer)
An elastic body made of a rubber material was formed on the outer peripheral surface of the shaft by extrusion molding using a mirable rubber composition formed of silicone rubber. In extrusion molding, a rubber composition formed of silicone rubber is heated at 270 ° C. for 5 minutes using an external wire heating furnace (IR furnace), and further heated at 200 ° C. for 4 hours using a gear oven. And cured. As a result, an elastic layer made of a cured product of the rubber composition was formed on the outer peripheral surface of the primer-treated shaft. The elastic layer was a solid layer, and the thickness of the elastic layer was 3 mm.

(Formation of coating layer)
First, the compounds shown below were kept at 100 ° C. to 120 ° C. for 4 to 6 hours with the compounding of the mass parts shown in Table 1 to synthesize two kinds of silicone-modified polyols A and B.
a1 Double-ended hydroxyl group-modified dimethyl silicone oil a2 Single-ended diol-modified silicone oil a3 Isocyanurate compound Isocyanurate type a4 Isocyanate compound Adduct type

Next, using the following materials, a composition for a coating layer was prepared by blending the number of parts by mass shown in Table 2. The base resin was a silicone-modified urethane resin formed of the following silicone-modified polyol and isocyanate.
-The above silicone-modified polyols A and B
・ Isocyanate (trade name "TPA-100", manufactured by Asahi Kasei Corporation)
-Roughness agent (trade name "EP-2601", manufactured by Toray Dow Corning Co., Ltd.)
・ Roughness agent (trade name "ACEMAT OK412, made by Evonik Japan)"
・ Catalyst (trade name "Neostan U-100", manufactured by Nitto Kasei Co., Ltd.)
-Zinc oxide particles (Sakai Chemical Industry Co., Ltd., class I average particle diameter for rubber 0.75 μm)

Next, the outer peripheral surface of the elastic layer was UV-treated. Then, the composition for a coating layer was applied onto the UV-treated elastic layer by a spray method. The applied composition was heated at 150 ° C. to 160 ° C. for 30 minutes to obtain a developing roller.
The thickness of the coating layer after drying was 9 μm.

[Examples 2 and 3 and Comparative Example 1]
A developing roller was produced in the same manner as in Example 1 except that the coating layer was formed with the formulations shown in Table 2.

[evaluation]
The following evaluations were performed on the above-mentioned Examples and Comparative Examples. The evaluation results are shown in Table 2.

(Resistance value on the surface of the developing roller)
The resistance values on the surfaces of the developing rollers of the above Examples and Comparative Examples were measured. FIG. 3 shows a schematic front view of the measuring device.
As shown in FIG. 3, a developing roller 1 is placed on a gold-plated plate 51, a weight 52 weighing 500 g is hung on both ends, and the resistance value between the shaft 53 and the gold-plated plate 51 is set to an ultra-high resistance at an applied voltage of 100 V. / Measurement was performed using a micro ammeter "5450" (manufactured by ADC Co., Ltd.) 54.

(Hexadecane contact angle)
Hexadecane was set in the device, droplets of hexadecane were dropped on the developing roller, and the hexadecane contact angle was measured using a portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.).

(Evaluation of fog under high temperature and high humidity conditions)
A color image forming apparatus (trade name "C610dn2", manufactured by Oki Data Corporation) was used to mount the developing rollers of the above Examples and Comparative Examples on a magenta color cartridge, and fog under high temperature and high humidity conditions and filming after printing 4000 sheets. Evaluated the situation.
Perform 10 sheets of 0.3% duty printing, stop the white solid printing with a momentary interruption, attach the tape to the photosensitive drum, and transfer it to white paper. A tape was attached to the reference paper, and the color difference ΔE between the reference value and the transferred portion was measured. Under the same conditions, the color difference Δ after printing 4000 sheets was also measured. The color difference ΔE was measured with a color difference meter (trade name “CR-241”, manufactured by Konica Minolta Co., Ltd.).
The color difference Δ after printing 4000 sheets was evaluated according to the following evaluation criteria.
A: ΔE is less than 1 B: ΔE is 1 or more and less than 1.5 C: 1.5 or more

(Filming evaluation)
Filming was evaluated by the amount of the developer adhered. Specifically, after sucking the developer adhering to the surface of the developing roller after printing 4000 sheets, the mass transferred to the filming weight measuring jig was measured. For the filming evaluation, the mass of the transferred developer was evaluated according to the following evaluation criteria. The filming evaluation is passed if it is A.
A: 0 mg or more and 0.003 mg or less B: More than 0.003 mg and 0.006 mg or less C: More than 0.006 mg

(CF characteristics)
Moreover, the capacitance measurement of the developing roller was measured as follows.
Using an LCR meter (manufactured by NF Circuit Design Block Co., Ltd.), an electrode is made with a conductive paste on the surface of the coating layer forming development roller at a measurement environment temperature of 23 ° C and a humidity of 55% RH, and between the conductive paste and the core metal. The capacitance was measured with an LCR meter. The CF characteristics are shown in FIG. In FIG. 4, E1, E2 and E3 show Examples 1, 2 and 3, respectively, and CE1 shows Comparative Example 1.

From Table 2, the developing roller of the present invention uses silicone-modified polyurethane as the base resin of the coating layer and disperses zinc oxide particles as a conductivity-imparting agent in the coating layer to evaluate fog and film under high temperature and high humidity conditions. It turned out to be excellent in characteristics.
Further, as shown in FIG. 4, it can be seen that the capacitance of the developing roller of the present invention is smaller than that of the comparative example. The developing roller of the present invention is excellent in the above-mentioned characteristics because the capacitance can be reduced, so that the attenuation of the toner charge can be suppressed, and the charge applying performance to the toner by the zinc oxide particles is improved.

1 Develop roller 2 Shaft body 3 Elastic layer 4 Coating layer 6 Transfer transfer belt 7 Second surface roughness agent 8 First surface roughness agent 10 Image forming device 11B, 11C, 11M, 11Y Image carrier 12B, 12C, 12M, 12Y Charging means 13B, 13C, 13M, 13Y Exposure means 14B, 14C, 14M, 14Y Transfer means 15B, 15C, 15M, 15Y Cleaning means 16 Recorder 20B, 20C, 20M, 20Y Developer 21B, 21C, 21M, 21Y,
22B, 22C, 22M, 22Y Developer 23B, 23C, 23M, 23Y Developer carrier 24B, 24C, 24M, 24Y Developer amount adjusting means 25B, 25C, 25M, 25Y Toner supply roller 30 Fixing means 31 Fixing roller 32 Pressure roller 33 Endless belt support roller 34 Housing 35 Opening 36 Endless belt 41 Cassette 42 Support roller B, C, M, Y Development unit 51 Gold-plated plate 52 Weight 53 Shaft 54 Ultra-high resistance / micro ammeter

Claims (5)

A developing roller including a shaft body, an elastic layer provided on the outer surface of the shaft body, and a coating layer provided outside the elastic layer.
The coating layer contains a base resin and a conductivity-imparting agent.
The base resin is a silicone-modified urethane resin.
A developing roller in which the conductivity-imparting agent is zinc oxide particles. The developing roller according to claim 1, wherein the coating layer further contains a roughnessing agent. The developing roller according to claim 1 or 2, wherein the resistance value on the surface of the developing roller is 1 × 10 ⁶ Ω or more and 9 × 10 ^{9 Ω or less.} The developing roller according to any one of claims 1 to 3, wherein the hexadecane contact angle on the surface of the developing roller is 30 ° or more. An image forming apparatus comprising the developing roller according to any one of claims 1 to 4.

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