JP2022012917A - Developing roller - Google Patents

Abstract

To provide a developing roller that can satisfactorily prevent toner releasability and filming properties and provide a high-quality image, and an image forming apparatus.SOLUTION: A developing roller 1 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. The elastic layer 3 includes silicone rubber. The coating layer 4 contains a base resin and a roughness agent but does not contain a conductivity imparting agent. The base resin is a silicone modified urethane resin. The roughness agent is composed of particles having a siloxane bond or a urethane bond. The value of resistance of the developing roller 1 is 1×106 Ω or more and 9×109 Ω or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a developing roller.

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.

A developing roller used in an electrophotographic image forming apparatus generally includes an elastic layer and a coating layer on the outer periphery of a shaft body. As the material of the coating layer, for example, a material containing a binder for paint such as a polycarbonate-based, ether-based, or polyester-based polyurethane resin as a main component is used. Among the materials of the coating layer, those in which conductive carbon black is dispersed in order to impart conductivity are widely known (see Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 2003-3032 Japanese Patent Application Laid-Open No. 2002-363426

In recent years, the melting point of toner used for printing has been lowered for the purpose of suppressing power consumption and high-speed printing in electrophotographic copying machines. However, such low melting point toner tends to melt due to frictional heat generated by pressing the developing roller and other regulating members, and in a high humidity environment, the chargeability of the toner itself tends to decrease due to the influence of moisture. Therefore, in a high temperature and high humidity environment, the toner melts and adheres to the developing roller (hereinafter referred to as filming). When filming occurs, the charging performance of the developing roller deteriorates, causing a deterioration in the chargeability of the toner, and as a result, there is a problem that image defects such as fog and roughness occur.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a developing roller which is excellent in toner releasability, filming resistance, etc. and can obtain a good image for a long period of time. ..

The present inventors have made further studies to solve the above-mentioned problems caused by polyurethane. As a result, the base resin is a silicone-modified polyurethane resin, does not contain a conductivity-imparting agent such as carbon black or an ionic conductive material, and the roughness agent is a material equivalent to that of the base resin. We have found that it is possible to provide a high-quality image with low and stable toner releasability and good filming property, which led to the present invention.

That is, the developing roller of 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 elastic layer is a silicone rubber. Particles containing, the coating layer contains a base resin and a roughening agent, but does not contain a conductivity-imparting agent, the base resin is a silicone-modified urethane resin, and the roughening agent has a siloxane bond or a urethane bond. The resistance value of the developing roller is 1 × 10 ⁶ Ω or more and 9 × 10 ⁹ Ω or less.

The average particle size of the coarsening agent is preferably 2 μm or more and 10 μm or less.

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

According to the developing roller of the present invention, the toner releasability and the filming resistance are improved, and a high-quality image can be provided.

It is a perspective view which shows one Embodiment of the development roller 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.
[Development 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 elastic layer 3 contains silicone rubber, and the coating layer 4 contains a base resin and a roughening agent, but does not contain a conductivity-imparting agent. The base resin is a silicone-modified urethane resin, and the roughness agent is composed of particles having a siloxane bond or a urethane bond. The resistance value of the developing roller is 1 × 10 ⁶ Ω or more and 9 × 10 ⁹ Ω or less.
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 properties.

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. The elastic layer 3 contains silicone rubber. Silicone rubber has the advantage that the compressive stress strain due to pressing is small. Examples of the silicone rubber include polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polyphenylvinylsiloxane, and copolymers of these siloxanes.

By blending a conductivity-imparting agent such as an electron 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 roughening agent, but does not contain a conductivity-imparting agent. The base resin is a silicone-modified urethane resin. The coating layer 4 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) a roughening agent. 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 used in the synthesis of the silicone-modified polyol 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, and 2 parts by mass. It is more preferable that the amount is 8 parts by mass or more and 8 parts by mass or less. By keeping 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 composition 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) Roughing agent The roughening agent used for the coating layer 4 is particles having a siloxane bond or a urethane bond. Examples of such a roughness agent include silicone rubber particles, polyurethane particles, and acrylic particles having a urethane bond. Heat-resistant and flexible silicone rubber particles, polyurethane particles, and acrylic particles having a urethane bond are preferable, and silicone rubber particles and acrylic particles having a urethane bond are more preferable.

The silicone rubber particles and acrylic particles having a urethane bond used in the present invention preferably have heat resistance that does not deform or melt even at a temperature of 100 ° C. or higher, and more preferably have heat resistance at 130 ° C. to 180 ° C. .. As a result, it is possible to prevent the silicone rubber particles and the acrylic particles having a urethane bond from being deformed even at the crosslinking temperature of the coating layer 4. For the heat resistance of the silicone rubber particles and the acrylic particles having the urethane bond, confirm in the melt flow indexer that the silicone rubber particles and the acrylic particles having the urethane bond do not melt and flow out even when pressure and heat are applied. Can be evaluated by.

The hardness of the silicone rubber particles and the acrylic particles having a urethane bond is preferably 20 degrees or more and 80 degrees or less, preferably 50 degrees or more and 75 degrees or less, as measured by a durometer A (instantaneous) (JIS K 6253: 1997). Is more preferable. When the hardness of the silicone rubber particles and the acrylic particles having the urethane bond is within the above range, the friction coefficient of the coating layer 4 may increase due to the destruction or deformation of the silicone rubber particles and the acrylic particles having the urethane bond. It is possible to effectively prevent the occurrence of adhesion, prevent the occurrence of cracks and cracks in the coating layer 4 due to the excessively high hardness of the coating layer 4, and prevent excessive stress on the toner.

Silicone rubber particles and acrylic particles may be present (buried) in the coating layer 4, may be unevenly dispersed in the coating layer 4, and may be unevenly distributed on the surface side of the coating layer 4. May be good.

Among the silicone rubber particles and the acrylic particles having a urethane bond, the silicone rubber particles preferably have a structure in which organopolysiloxane and polyorganosilces oxane such as dimethylpolysiloxane are crosslinked, and the acrylic particles having a urethane bond are selected. Commercially available acrylic particles can be used.

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 Powder", "9701 Cosmetic Powder" and the like can be used.

The amount of the silicone rubber particles and / or the acrylic particles having a urethane bond is preferably 15 parts by mass or more and 50 parts by mass or less, and 20 parts by mass or more and 45 parts by mass with respect to 100 parts by mass of the (A) silicone-modified polyol. More preferably, it is less than or equal to a part. By setting the amount of the silicone rubber particles and / or the acrylic particles having the urethane bond within the above range, the surface roughness of the elastic roller 1 is appropriately maintained and the developer transportability is good. While being maintained, the resolution can be maintained at a high level to prevent deterioration of image quality.
The coating layer 4 may contain only one type of roughening agent, or may contain two or more types of the roughening agent.

The particle size of the silicone rubber particles and the acrylic particles having a urethane bond is preferably 0.2 μm or more and 10 μm or less, and more preferably 0.8 μm or more and 5 μm or less. By keeping the particle diameters of the silicone rubber particles and the acrylic particles having the urethane bond within the above range, the surface roughness of the elastic roller 1 is appropriately maintained, and the developer transportability is kept good. , It is possible to maintain a high level of resolution and prevent deterioration of image quality. The particle size of the silicone rubber particles and the acrylic particles having a urethane bond can be measured by observing the cross section with a microscope after cutting the elastic roller 1.

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 value of the surface of the developing roller 1 of the present invention is preferably 1 × 10 ⁶ Ω or more and 9 × 10 ⁹ Ω or less, and more preferably 1 × 10 ⁶ Ω or more and 1 × 10 ⁹ Ω or less. If the resistance value exceeds 9 × 10 ⁹ Ω, the image quality deteriorates, and the lower limit is the limit resistance value that can be realized without a conductive agent.
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 a reactive ether-modified silicone oil.
The resistance value on the surface of the developing roller is a value measured by the method described in Examples described later.

(Capacitance of developing roller)
The low frequency capacitance of the developing roller is preferably low, particularly preferably less than 10 nF at 0.1 Hz.
A conductivity-imparting agent such as carbon or an ionic conductive material is not used in the coating layer 4 because the toner releasability is inferior as a result of the increase in capacitance.

(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.).

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 7.5 mm, length 274.1 mm) subjected to electroless nickel plating is washed with ethanol, and a silicone-based primer (trade name "Primer No. 16", Shin-Etsu Chemical) is used on the surface thereof. (Made by Kogyo Co., Ltd.) 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 4.25 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 types 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

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)
・ Roughing agent (trade name "EP-2601", manufactured by Toray Dow Corning Co., Ltd.)
-Roughness agent Highly restorative acrylic fine particles XX-4316Z (average particle diameter 3 μm) Sekisui Plastics Co., Ltd. A catalyst and thinner are appropriately added to the composition for the upper coating layer.

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 a coating layer was formed by blending the number of parts by mass shown in Table 2.
MA100 (manufactured by Mitsubishi Chemical Corporation) was used as the carbon of Comparative Example 1.

[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. 2 shows a schematic front view of the measuring device.
As shown in FIG. 2, 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 toner releasability)
A monochrome image forming apparatus (trade name "HL-L2360DN", manufactured by Brother Industries, Ltd.) is used to mount the developing rollers of the above Examples and Comparative Examples on the cartridge, and the cartridge electrodes are mounted in a low temperature and low humidity environment (10 ° C. 20% RH). The print density was measured when the voltage was changed by connecting to an external power supply. The print density was measured by measuring the solid print portion with an X-Rite 504 spectrodensitometer manufactured by X-Rite.
The print density was judged according to the following evaluation criteria. It was judged that the toner releasability is better as the concentration becomes higher even at a low voltage.
A: 1.4 or more B: 1.35 or more C: less than 1.35

(Filming evaluation)
The filming condition after printing 4000 sheets with a monochrome image forming apparatus (trade name "HL-L2360DN", manufactured by Brother Industries, Ltd.) was evaluated.
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 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. Capacitance was measured with an LCR meter. The CF characteristics are shown in FIG.

1 Develop roller 2 Shaft body 3 Elastic layer 4 Coating layer 51 Gold-plated plate 52 Weight 53 Shaft 54 Ultra-high resistance / micro ammeter

Claims (3)

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 elastic layer contains silicone rubber and contains
The coating layer contains a base resin and a roughening agent, but does not contain a conductivity-imparting agent.
The base resin is a silicone-modified urethane resin.
The coarsening agent is a particle having a siloxane bond or a urethane bond.
A developing roller having a resistance value of 1 × 10 ⁶ Ω or more and 9 × 10 ⁹ Ω or less. The developing roller according to claim 1, wherein the average particle size of the roughness agent is 2 μm or more and 10 μm or less. The developing roller according to claim 1 or 2, wherein the hexadecane contact angle on the surface of the developing roller is 30 ° or more.

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