JP2021089369A - Developing roller and manufacturing method therefor - Google Patents

Abstract

To provide a developing roller capable of forming an image superior in image quality than a current state while maintaining a simple structure omitting a coating film, and to provide a method for manufacturing the same.SOLUTION: In a developing roller 1, an arithmetic mean height Sa is made to be 0.6 μm or less, which defines a surface shape of an outer peripheral surface 5 of a roller body 2, and a direction Std of the surface property when the peripheral direction of the outer peripheral surface is 0° is made to be 20°or more. A manufacturing method includes a step of further performing the wet-polishing on the polished outer peripheral surface 5 to finish the arithmetic average height Sa and the direction Std of the surface property in the above-mentioned range.SELECTED DRAWING: Figure 1

Description

The present invention relates to a developing roller and a method for manufacturing the same.

In an image forming apparatus using an electrophotographic method, a developing roller including a roller body made of a crosslinked rubber product is used. Regarding the developing roller, various surface shapes of the outer peripheral surface of the roller body have been studied (Patent Documents 1, 2, etc.).

Japanese Unexamined Patent Publication No. 2013-066144

An object of the present invention is to provide a developing roller capable of forming an image having a higher image quality than the current state, and a method for manufacturing the same.

The present invention includes a tubular roller body, and the outer peripheral surface of the roller body has an arithmetic mean height Sa of 0.6 μm or less and the outer peripheral surface specified in the International Organization for Standardization ISO25178-2: 2012. This is a developing roller having a surface texture direction Std of 20 ° or more when the circumferential direction is 0 °.
Further, the present invention is a method for manufacturing such a developing roller, in which a step of polishing the outer peripheral surface of the roller body and the polished outer peripheral surface of the roller body are further wet-polished to obtain the arithmetic mean height Sa. It is characterized by including a step of finishing the surface texture direction Std within the above range.

According to the present invention, it is possible to provide a developing roller capable of forming an image having a higher image quality than the current state, and a method for manufacturing the same.

It is a perspective view which shows an example of embodiment of the developing roller of this invention. It is a micrograph which enlarges and shows a part of the outer peripheral surface of the roller body of the developing roller of Example 1 of this invention. It is a micrograph which enlarges and shows a part of the outer peripheral surface of the roller body of the developing roller of the comparative example 1 of this invention. It is a micrograph which enlarges and shows a part of the outer peripheral surface of the roller body of the developing roller of the comparative example 2 of this invention. It is a micrograph which shows a part of the outer peripheral surface of the roller body of the developing roller of the comparative example 3 of this invention in an enlarged manner. It is a micrograph which shows a part of the outer peripheral surface of the roller body of the developing roller of the comparative example 4 of this invention in an enlarged manner. It is a micrograph which shows a part of the outer peripheral surface of the roller body of the developing roller of the comparative example 5 of this invention in an enlarged manner.

In development using a developing roller, a developing roller is provided in a developing unit containing toner of an image forming apparatus, and the tip of a quantity regulating blade (charged blade) is brought into contact with the outer peripheral surface of the roller body of the developing roller. In this state, rotate the developing roller.
Then, the toner in the developing unit is charged and adheres to the outer peripheral surface of the roller body, and when the adhered toner passes through the nip portion between the outer peripheral surface of the roller body and the tip portion of the amount control blade, the adhered toner is attached. The amount is regulated and a toner layer is formed on the outer peripheral surface.

Further, an electrostatic latent image is formed on the surface of the photoconductor by uniformly charging and then exposing the photoconductor in parallel.
Next, when the developing roller is further rotated in this state to convey the toner layer to the vicinity of the surface of the photoconductor, the toner forming the toner layer is subjected to the electrostatic latent image formed on the surface of the photoconductor. It selectively moves to the surface of the photoconductor and the electrostatic latent image is developed into a toner image.

The outer peripheral surface of the roller body is generally coated with a coating film in order to adjust the surface shape.
The coating film is formed by applying a liquid coating agent, which is the basis thereof, to the outer peripheral surface of the roller body by a coating method such as a spray method or a dipping method, and then drying the coating film.
However, the coating film has a problem that various defects such as foreign matter such as dust and uneven thickness are likely to occur in the formation process.

In addition, an organic solvent is required to prepare the coating agent, but the use of the organic solvent has a large burden on the environment and goes against the recent trend toward low VOC (volatile organic compounds).
In the invention described in Patent Document 1, it is proposed that the outer peripheral surface of a roller body made of a crosslinked rubber product is polished to have a predetermined surface shape, and according to such a configuration, the coating film is omitted. , It is considered that the above-mentioned problems caused by the coating film can be solved.

On the other hand, in order to improve the image quality of the formed image, it has recently become common to use a grain-shaped toner or a toner having a smaller diameter.
In order to form an image with good image quality corresponding to these toners, it is desirable that an appropriate amount of toner is uniformly supported on the outer peripheral surface of the roller body to form a toner layer. Ideally, the outer peripheral surface should be finished in the finest possible surface shape.

In order to finish the outer peripheral surface of the roller body into a finer surface shape, for example, wet polishing or the like may be adopted as the polishing method, and the polishing count of the abrasive material used for polishing may be increased to make the polishing grain finer. Conceivable.
However, the finer the grain size, that is, the smaller the surface roughness of the outer peripheral surface, the smaller the amount of toner carried on the outer peripheral surface of the roller body, and the density of the formed image tends to decrease.

The outer peripheral surface of the roller body finished by polishing has a surface shape including a large number of fine irregularities, and according to the inventor's examination, it is possible to control the shape of these numerous irregularities by the roller of the developing roller. It is important for optimizing the amount of toner carried on the outer peripheral surface of the main body.
Therefore, the inventor stipulates as a new index of surface roughness in the International Organization for Standardization Standard ISO25178-2: 2012 "Geometric Characteristic Specifications (GPS) of Products-Surface Properties-Part 2: Terms, Definitions and Surface Texture Parameters". The arithmetic mean height Sa, which is represented by the average value of the absolute value of the difference in height of each point constituting the unevenness with respect to the average surface of the outer peripheral surface of the roller body, and the angle spectrum f APS (S). ) Is the value of the angle s that maximizes the surface texture direction Std, which represents the direction of the surface texture streaks.
We considered defining the range of.

That is, the arithmetic mean height Sa defines the size of the unevenness, and the outer peripheral surface of the roller body is finished into a finer surface shape so as to be compatible with the above-mentioned grain-shaped toner and small-diameter toner. For that purpose, the arithmetic mean height Sa may be reduced.
Specifically, by setting the arithmetic mean height Sa to 0.6 μm or less, the outer peripheral surface of the roller body can be finished into a finer surface shape, and even if the toner is grain-shaped or has a small diameter, the outer peripheral surface is concerned. It can be uniformly supported on the surface without variation.

Therefore, it is possible to suppress the occurrence of uneven density in the formed image.
Further, if the arithmetic mean height Sa is set to this range, it is possible to suppress the excessive toner from being supported on the outer peripheral surface of the roller body and to prevent fog and the like from occurring in the formed image.
However, when only the arithmetic mean height Sa is simply set in the above range, as described above, the amount of toner carried per unit area on the outer peripheral surface of the roller body, that is, the amount of toner conveyed becomes small. , The density of the formed image may decrease.

This is because, according to the inventor's examination, the directionality of the unevenness is not added to the arithmetic mean height Sa.
On the other hand, the unevenness of the outer peripheral surface defined by the direction Std of the surface texture is 20 ° or more with the circumferential direction as 0 °, so that the unevenness has the same arithmetic mean height Sa. However, the amount of toner carried on the outer peripheral surface can be increased.

For example, as shown in FIG. 2, the unevenness of the outer peripheral surface of the roller body is set to intersect the circumferential direction, and the unevenness is generated in the circumferential direction, so that the unevenness is generated in the circumferential direction, as shown in FIG. The amount of toner carried on the outer peripheral surface can be increased by promoting the adhesion of the toner to the outer peripheral surface due to the rotation of the roller body, as compared with the case where the direction is along the circumferential direction.
Then, it is possible to support an appropriate amount of toner on the outer peripheral surface to suppress a decrease in the density of the formed image.

These things are clear from the results of Examples and Comparative Examples described later.
The angle of inclination in the direction of the uneven streaks is the same on the left and right, and the surface-like direction Std of 20 ° or more means that the inclination is 20 ° or more in either the left direction or the right direction with respect to the circumferential direction. Also includes.
The arithmetic mean height Sa is preferably 0.5 μm or less even in the above range, considering that the above effect is further improved.

Although the lower limit of the arithmetic mean height Sa is not particularly limited, it is preferably 0.2 μm or more, particularly 0.3 μm or more.
When the arithmetic mean height Sa is less than this range, the amount of toner carried on the outer peripheral surface is 20 ° or more even if the surface-like direction Std that defines the direction of the uneven streaks is set to 20 ° or more with the circumferential direction as 0 °. May be insufficient and the density of the formed image may decrease.

On the other hand, by setting the arithmetic mean height Sa in the above range, an appropriate amount of toner that is neither too much nor too little is supported on the outer peripheral surface of the roller body, and there is no fog or decrease in the density of the formed image. A good image can be formed.
Further, the maximum value of the surface texture direction Std is 90 ° when the circumferential direction is defined as 0 °, and in the present invention, the surface texture direction Std is 20 ° or more and 90 ° in any of the left and right directions. Can include ranges up to °.
However, the direction Std of the surface texture is preferably 60 ° or more, particularly 70 ° or more, even in the above range, in consideration of further improving the above-mentioned effect.

<< Development roller and its manufacturing method >>
FIG. 1 is a perspective view showing an example of an embodiment of the developing roller 1 of the present invention.
With reference to FIG. 1, the developing roller 1 of this example includes a roller body 2 formed in a non-porous and single-layer tubular shape by a rubber composition imparted with conductivity. A shaft 4 is inserted and fixed in a through hole 3 at the center of the roller body 2.

The shaft 4 is integrally formed of a material having good conductivity, for example, a metal such as iron, aluminum, an aluminum alloy, or stainless steel.
The shaft 4 is, for example, electrically joined to the roller body 2 via a conductive adhesive and mechanically fixed, or a through hole having an outer diameter larger than the inner diameter of the through hole 3. By press-fitting into 3, it is electrically joined to the roller body 2 and mechanically fixed.

Further, the shaft 4 may be electrically joined to the roller main body 2 and mechanically fixed by using both methods in combination.
The outer peripheral surface 5 of the roller body 2 is covered with an oxide film 6 as shown in an enlarged manner in the drawing.
When the outer peripheral surface 5 is covered with the oxide film 6, the oxide film 6 can function as a dielectric layer to reduce the dielectric loss tangent of the developing roller 1.

Further, the oxide film 6 can be made to function as a low friction layer to satisfactorily suppress the adhesion of toner.
Moreover, since the oxide film 6 can be easily formed by simply oxidizing the rubber in the vicinity of the outer peripheral surface 5 by, for example, irradiating the outer peripheral surface 5 with ultraviolet rays, the productivity of the developing roller 1 may decrease. It is also possible to suppress the high manufacturing cost.

However, the oxide film 6 may be omitted.
The "single layer" of the roller body 2 means that the number of layers made of rubber or the like is a single layer, and the extremely thin oxide film 6 formed by irradiation with ultraviolet rays or the like is not included in the number of layers. To do.
To produce the developing roller 1, for example, the prepared rubber composition is extruded into a tubular shape using an extruder, then cut to a predetermined length, pressurized and heated in a vulcanization can. Crosslink the rubber.

Next, the crosslinked tubular body is heated using an oven or the like for secondary cross-linking, cooled, and then the outer peripheral surface 5 is polished to have a predetermined outer diameter (polishing step).
As the polishing method, various polishing methods such as dry traverse polishing can be adopted. Further, it is preferable to finish polish the outer peripheral surface 5 at the end of the polishing step.
Examples of the finish polishing include mirror polishing using a lapping film.

In the mirror polishing, it is preferable to perform two or more steps of mirror polishing while sequentially changing the lapping film from a coarse-grained film having a small count to a fine-grained film having a large count.
In such a polishing method, the type of lapping film used for the mirror polishing of the final stage (the second stage in the case of the second stage, the third stage in the case of the third stage), the conditions of the mirror polishing, and the like are usually selected. Uneven streaks formed along the polishing direction can be formed in other directions.

That is, when the roller body 2 is mirror-polished while rotating around the shaft 4 in the circumferential direction of the outer peripheral surface 5, the surface-like direction Std may be made larger than 0 ° along the circumferential direction of the roller body 2. It is possible.
Then, the arithmetic mean height Sa and the surface texture direction Std can be set to the above-mentioned ranges, respectively.

The types of lapping films include, for example, ordinary lapping films and mirror films classified according to the type of abrasive grains, the difference in the production particle size of each abrasive grain, and the fixed structure of the abrasive grains [registered trademark of Sankyo Rikagaku Co., Ltd.]. ] Differences and the like.
Of these, ordinary lapping films are manufactured by uniformly dispersing abrasive grains in a resin adhesive and coating them on the film, and mirror films are manufactured by electrostatically coating abrasive grains on a film coated with an adhesive layer. Manufactured by fixing with.

Examples of the type of abrasive grains include white oxide arandom (WA), green carbonundum (GC), carbonundum (CC), diamond (D) and the like.
These abrasive grains have different shapes, hardness, and the like.
The shaft 4 can be inserted into the through hole 3 and fixed at any time from after the tubular body is cut to after the finishing process.

However, after cutting, it is preferable to first perform secondary cross-linking, polishing, and finishing with the shaft 4 inserted through the through hole 3.
As a result, warping and deformation of the roller body 2 due to expansion and contraction during secondary cross-linking can be suppressed.
Further, by polishing while rotating around the shaft 4 and then finishing, the workability of the polishing and finishing can be improved, and the deflection of the outer peripheral surface 5 can be suppressed.

As described above, the shaft 4 is inserted into the through hole 3 of the tubular body before the secondary cross-linking via a conductive adhesive, particularly a conductive thermosetting adhesive, and then the secondary cross-linking is performed. Alternatively, a material having an outer diameter larger than the inner diameter of the through hole 3 may be press-fitted into the through hole 3.
In the former case, the tubular body is secondarily crosslinked by heating in the oven, and at the same time, the thermosetting adhesive is cured, and the shaft 4 is electrically bonded to the roller body 2 and mechanically. Is fixed to.

In the latter case, electrical joining and mechanical fixing are completed at the same time as the shaft 4 is press-fitted.
Further, as described above, both methods may be used in combination to electrically join the shaft 4 to the roller body 2 and mechanically fix the shaft 4.
As described above, the oxide film 6 is preferably formed by irradiating the outer peripheral surface 5 of the roller body 2 with ultraviolet rays.

That is, the oxide film 6 can be formed by irradiating the outer peripheral surface 5 after finishing processing such as laser processing with ultraviolet rays having a predetermined wavelength for a predetermined time to oxidize the rubber in the vicinity of the outer peripheral surface 5. ..
Therefore, the process of forming the oxide film 6 is simple and efficient, and it is possible to suppress a decrease in the productivity of the developing roller 1 and a high production cost.

Moreover, the oxide film 6 formed by irradiation with ultraviolet rays does not cause problems like the coating film described above, and is also excellent in thickness uniformity and adhesion to the roller body 2.
The wavelength of the ultraviolet rays to be irradiated is preferably 100 nm or more, preferably 400 nm or less, considering that the diene rubber or the like in the rubber composition is efficiently oxidized to form the oxide film 6 having the above-mentioned excellent function. In particular, it is preferably 300 nm or less.
The irradiation time is preferably 30 seconds or longer, particularly preferably 1 minute or longer, and preferably 30 minutes or shorter, particularly 20 minutes or shorter.
However, the oxide film 6 may or may not be formed by another method.

<< Rubber composition >>
The rubber composition forming the roller body is prepared by blending the rubber with a cross-linking component for cross-linking the rubber and various additives.
In order to impart conductivity to the rubber composition and adjust the roller resistance value of the developing roller to a suitable range, the ionic conductive rubber composition will be described below, but the rubber composition includes ionic conductivity. , An electronically conductive rubber composition may be used.

<Rubber>
As described above, in order to impart ionic conductivity to the rubber composition, it is preferable to use ionic conductive rubber as the rubber.
Further, as the rubber, it is preferable to use a diene rubber together with the ion conductive rubber.
By using a diene rubber in combination, it is possible to impart good workability to the rubber composition and improve the mechanical strength and durability of the roller body.
Further, by using a diene rubber in combination, it is possible to impart good characteristics as rubber, that is, a characteristic that is flexible, has a small compression set, and is less likely to cause settling, to the roller body.

(Ion conductive rubber)
Examples of the ion conductive rubber include epichlorohydrin rubber and polyether rubber.
Among these, epichlorohydrin rubber includes, for example, epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allyl glycidyl ether binary copolymer, epichlorohydrin-. Examples thereof include ethylene oxide-allyl glycidyl ether ternary copolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether ternary copolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer and the like.

Examples of the polyether rubber include an ethylene oxide-allyl glycidyl ether binary copolymer and an ethylene oxide-propylene oxide-allyl glycidyl ether ternary copolymer.
Of these, copolymers containing ethylene oxide, particularly ECO and / or GECO, are preferred.

The ethylene oxide content in ECO and / or GECO is preferably 30 mol% or more, particularly preferably 50 mol% or more, and preferably 80 mol% or less.
Ethylene oxide works to reduce the roller resistance value of the developing roller.
However, if the ethylene oxide content is less than this range, such an action cannot be sufficiently obtained, and therefore the roller resistance value of the developing roller may not be sufficiently reduced.

On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs and the segment movement of the molecular chain is hindered, so that the roller resistance value of the developing roller tends to increase.
In addition, the roller body after cross-linking may become too hard, or the viscosity of the rubber composition before cross-linking at the time of heating and melting may increase, resulting in a decrease in processability of the rubber composition.

The epichlorohydrin content in ECO is the remaining amount of ethylene oxide content.
That is, the epichlorohydrin content is preferably 20 mol% or more, preferably 70 mol% or less, and particularly preferably 50 mol% or less.
The allyl glycidyl ether content in GECO is preferably 0.5 mol% or more, particularly preferably 2 mol% or more, and preferably 10 mol% or less, particularly 5 mol% or less.

The allyl glycidyl ether itself functions as a side chain to secure a free volume, thereby suppressing the crystallization of ethylene oxide and lowering the roller resistance value of the developing roller.
However, if the allyl glycidyl ether content is less than this range, such an action cannot be sufficiently obtained, so that the roller resistance value of the developing roller may not be sufficiently reduced.

On the other hand, allyl glycidyl ether functions as a cross-linking point when cross-linking GECO.
Therefore, when the allyl glycidyl ether content exceeds the above range, the cross-linking density of GECO becomes too high, which hinders the segment movement of the molecular chain, and on the contrary, the roller resistance value of the developing roller tends to increase. ..
The epichlorohydrin content in GECO is the remaining amount of ethylene oxide content and allyl glycidyl ether content.

That is, the epichlorohydrin content is preferably 10 mol% or more, particularly preferably 19.5 mol% or more, and preferably 69.5 mol% or less, particularly 60 mol% or less.
As GECO, in addition to the copolymer in a narrow sense obtained by copolymerizing the three types of monomers described above, modification of epichlorohydrin-ethylene oxide copolymer (ECO) modified with allyl glycidyl ether. Things are also known.
In the present invention, any of these GECOs can be used.
One or more of these ion conductive rubbers can be used.

(Diene rubber)
Examples of the diene rubber include natural rubber, isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (BR), and chloroprene rubber (CR).
In particular, it is preferable to use two types of diene rubber, CR and NBR, in combination.
However, both types of rubber may be used in combination of two or more.

・ CR
The CR functions in particular to improve the flexibility of the roller body and enhance the image durability of the developing roller.
The image durability is an index showing how long the image quality of the formed image can be maintained well by suppressing the deterioration of the toner when the same toner is repeatedly used for image formation.
That is, only a small part of the toner contained in the developing unit of the image forming apparatus is used for one image formation, and most of the remaining toner repeatedly circulates in the developing unit.
Therefore, how much damage the roller body of the developing roller provided in the developing unit and repeatedly contacting with the toner gives or does not give damage to the toner is a big key for improving the image durability.

When the flexibility of the roller body is lowered and the image durability is lowered, the image quality of the formed image tends to be gradually lowered as the image formation is repeated.
Therefore, the developing roller is required to have excellent flexibility of the roller body in order to improve the image durability.
The CR also functions to improve the charging characteristics of the positively charged toner, and to finely adjust the roller resistance value of the developing roller because it is a polar rubber itself.

Further, CR is oxidized by ultraviolet irradiation and also functions as a material for forming an oxide film on the outer peripheral surface of the roller body.
CR is synthesized by emulsion polymerization of chloroprene, and is classified into a sulfur-modified type and a non-sulfur-modified type according to the type of molecular weight modifier used at that time.
Of these, the sulfur-modified type CR is synthesized by plasticizing a polymer obtained by copolymerizing chloroprene and sulfur as a molecular weight modifier with thiuram disulfide or the like to adjust the viscosity to a predetermined value.

Further, the non-sulfur-modified type CR is classified into, for example, a mercaptan-modified type, a xanthate-modified type, and the like.
Of these, the mercaptan-modified type CR is synthesized in the same manner as the sulfur-modified type CR except that alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and octyl mercaptan are used as molecular weight modifiers.

Further, the xanthate-modified type CR is also synthesized in the same manner as the sulfur-modified type CR except that an alkylxanthate compound is used as a molecular weight modifier.
Further, CR is classified into a slow crystallization rate type, a moderate crystallization rate type, and a high crystallization rate type based on the crystallization rate.
In the present invention, any type of CR may be used, but among them, a non-sulfur-modified type CR having a slow crystallization rate is preferable.

Further, as CR, a copolymer of chloroprene and another copolymerization component may be used.
Other copolymerization components include, for example, 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, acrylic acid, acrylic acid ester. , Methacrylic acid, and methacrylic acid ester and the like.
Further, as CR, there are an oil-extending type in which the flexibility is adjusted by adding spreading oil and a non-oil-extending type in which no spreading oil is added. In the present invention, bleeding is performed in order to prevent contamination of the photoconductor. It is preferable to use a non-oil-extending type CR that does not contain spreading oil that can be a substance.
One or more of these CRs can be used.

・ NBR
NBR is also oxidized by ultraviolet irradiation and functions as a material for forming an oxide film on the outer peripheral surface of the roller body. Further, since NBR is a polar rubber, it also functions for finely adjusting the roller resistance value of the developing roller.
The NBR includes low nitrile NBR having an acrylonitrile content of 24% or less, medium nitrile NBR having 25 to 30%, medium and high nitrile NBR having 31 to 35%, and high nitrile NBR having 36 to 42%, and 43% or more. Any ultra-high nitrile NBR can be used.
Further, as NBR, there are an oil-extending type in which extensibility oil is added to adjust the flexibility and a non-oil-extending type in which no spreading oil is added. In the present invention, in order to prevent contamination of the photoconductor and the like. , It is preferable to use a non-oil-extending type NBR that does not contain spreading oil that can be a bleeding substance.
One or more of these NBRs can be used.

(Rubber ratio)
The ratio of rubber can be arbitrarily set according to various characteristics required for the developing roller, particularly the roller resistance value and the flexibility of the roller body.
However, the ratio of the ionic conductive rubber such as epichlorohydrin rubber is preferably 15 parts by mass or more, particularly 30 parts by mass or more, and 80 parts by mass or less, particularly 70 parts by mass or less, based on 100 parts by mass of the total amount of rubber. Is preferable.

When the ratio of the ion conductive rubber is less than the above range or exceeds the above range, the roller resistance value of the developing roller may not be adjusted to a range suitable for the developing roller in any of these cases.
Further, when the ratio of the ion conductive rubber exceeds the above range, the ratio of the diene rubber is relatively small, and it is not possible to impart the above-mentioned good characteristics as the rubber to the roller body. In some cases.

On the other hand, by setting the ratio of the ion conductive rubber in the above range, it is possible to impart good characteristics as rubber to the roller body while adjusting the roller resistance value of the developing roller to a suitable range. ..
The ratio of diene-based rubber is the remaining amount of ionic conductive rubber.
That is, the ratio of the diene-based rubber may be set so that the total amount of rubber is 100 parts by mass when the ratio of the ion conductive rubber is set to a predetermined value within the above range.

<Crosslink component>
As the cross-linking component, it is preferable to use a cross-linking agent for cross-linking the rubber and a so-called cross-linking accelerator having a function of adjusting the cross-linking of the rubber by the cross-linking agent in combination.
Among these, examples of the cross-linking agent include sulfur-based cross-linking agents, thiourea-based cross-linking agents, triazine derivative-based cross-linking agents, peroxide-based cross-linking agents, various monomers, and the like, and sulfur-based cross-linking agents are particularly preferable.

(Sulfur-based cross-linking agent)
Examples of the sulfur-based cross-linking agent include sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, and organic sulfur-containing compounds such as tetramethylthium disulfide and N, N-dithiobismorpholine. Etc., and sulfur is particularly preferable.
The proportion of sulfur is preferably 0.5 parts by mass or more per 100 parts by mass of the total amount of rubber, and preferably 2 parts by mass or less, in consideration of imparting good properties as rubber to the roller body. preferable.

When, for example, oil-treated powdered sulfur, dispersible sulfur, or the like is used as the sulfur, the above ratio is the ratio of sulfur itself as an active ingredient contained therein.
When an organic sulfur-containing compound is used as the cross-linking agent, the ratio thereof is preferably adjusted so that the ratio of sulfur contained in the molecule per 100 parts by mass of the total amount of rubber is within the above range.

(Crosslink accelerator)
Examples of the cross-linking accelerator include one or more of thiuram-based accelerators, thiazole-based accelerators, thiourea-based accelerators, guanidine-based accelerators, sulfenamide-based accelerators, dithiocarbamate-based accelerators, and the like. Can be mentioned.
Of these, it is preferable to use a thiuram-based accelerator, a thiazole-based accelerator, a thiourea-based accelerator, and a guanidine-based accelerator in combination.

Examples of the thiuram-based accelerator include one or more types such as tetramethyl thiuram monosulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrabutyl thiuram disulfide, and dipentamethylene thiuram tetrasulfide, and in particular, tetramethyl. Thiram monosulfide is preferred.
Examples of the thiazole-based accelerator include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2- (4'-). One or more of morpholinodithio) benzothiazole and the like can be mentioned, and di-2-benzothiazolyl disulfide is particularly preferable.

As the thiourea accelerator, various thiourea compounds having a thiourea structure in the molecule can be used.
Examples of the thiourea accelerator include ethylene thiourea, N, N'-diphenyl thiourea, trimethyl thiourea, and formula (1):
(C _n H _{2n + 1} NH) ₂ C = S (1)
[In the formula, n represents an integer of 1-12. ], One or more of thiourea, tetramethylthiourea and the like, and ethylene thiourea is particularly preferable.

Examples of the guanidine-based accelerator include one or more of 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide and the like, and particularly 1,3-. Di-o-tolylguanidine is preferred.
Considering that the effect of adjusting the cross-linking of rubber is sufficiently exhibited in the above four types of combined systems, the ratio of the thiuram-based accelerator is 0.3 parts by mass or more per 100 parts by mass of the total amount of rubber. Is preferable, and it is preferably 1 part by mass or less.

The ratio of the thiazole-based accelerator is preferably 0.3 parts by mass or more and preferably 2 parts by mass or less per 100 parts by mass of the total amount of rubber.
The ratio of the thiourea accelerator is preferably 0.3 parts by mass or more and preferably 1 part by mass or less per 100 parts by mass of the total amount of rubber.
Further, the ratio of the guanidine-based accelerator is preferably 0.3 parts by mass or more and preferably 1 part by mass or less per 100 parts by mass of the total amount of rubber.
The thiourea-based accelerator also functions as an ECO cross-linking agent having no sulfur cross-linking property, and the guanidine-based accelerator also functions as an ECO cross-linking accelerator by the thiourea-based accelerator.

<Conducting agent>
The rubber composition may further contain an ionic conductive agent.
By blending the ionic conductive agent, the ionic conductivity of the rubber composition can be further improved, and the roller resistance value of the developing roller can be further lowered.
As the ionic conductive agent, a salt (ion salt) of an anion having a fluoro group and a sulfonyl group in the molecule and a cation is preferable.
Examples of the anion having a fluoro group and a sulfonyl group in the molecule constituting the ionic salt include one or two such as fluoroalkyl sulfonic acid ion, bis (fluoroalkylsulfonyl) imide ion, and tris (fluoroalkylsulfonyl) methide ion. More than seeds can be mentioned.

Among these, examples of the fluoroalkyl sulfonic acid ion include one or more of _{CF 3} SO ₃ ⁻ , C ₄ F ₉ SO ₃ ^{− and the like.}
Examples of the bis (fluoroalkylsulfonyl) imide ion include (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , and (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) N. ⁻ , (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) N ⁻ , (C ₈ F ₁₇ SO ₂ ) (CF ₃ SO ₂ ) N ⁻ , (CF ₃ CH ₂ OSO ₂ ) ₂ N ⁻ , (CF) ₃ CF ₂ CH ₂ OSO ₂ ) ₂ N ⁻ , (HCF ₂ CF ₂ CH ₂ OSO ₂ ) ₂ N ⁻ , [(CF ₃ ) ₂ CHOSO ₂ ] ₂ N ^−, etc.

Further, as the tris (fluoroalkylsulfonyl) methide ion, for example, one kind or two or more kinds such as _{(CF 3} SO ₂ ) ₃ C ⁻ and (CF ₃ CH ₂ OSO ₂ ) ₃ C ^{− can be mentioned.}
The cations include, for example, alkali metal ions such as sodium, lithium and potassium, Group 2 element ions such as beryllium, magnesium, calcium, strontium and barium, transition element ions, amphoteric element cations and cations. Examples thereof include one or more of quaternary ammonium ions and imidazolium cations.

As the ionic salt, a lithium salt using lithium ion as a cation or a potassium salt using potassium ion is particularly preferable.
_{Among them, (CF 3} SO ₂ ) ₂ NLi [lithium bis (trifluoromethanesulfonyl) imide] and / / in terms of the effect of improving the ionic conductivity of the rubber composition and lowering the roller resistance value of the developing roller. Alternatively, (CF ₃ SO ₂ ) ₂ NK [potassium bis (trifluoromethanesulfonyl) imide] is preferable.

The ratio of the ionic conductive agent such as an ionic salt is preferably 0.5 parts by mass or more and preferably 5 parts by mass or less per 100 parts by mass of the total amount of rubber.
<Others>
Various additives may be further added to the rubber composition, if necessary. Examples of the additive include a cross-linking aid, an acid-receiving agent, a filler, a plasticizer, a processing aid, a deterioration inhibitor and the like.

Among these, examples of the cross-linking aid include metal compounds such as zinc oxide; fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and one or more of conventionally known cross-linking aids.
The proportion of the cross-linking aid is preferably 0.1 part by mass or more, and preferably 7 parts by mass or less, individually per 100 parts by mass of the total amount of rubber.

The antacid function functions to prevent chlorine-based gas generated from epichlorohydrin rubber, CR, or the like during cross-linking from remaining in the roller body, thereby inhibiting cross-linking or contaminating the photoconductor.
As the acid receiving agent, various substances that act as acid receptors can be used, and among them, hydrotalcites or magsalats having excellent dispersibility are preferable, and hydrotalcites are particularly preferable.

Further, when hydrotalcites and the like are used in combination with magnesium oxide and potassium oxide, a higher acid receiving effect can be obtained, and contamination of the photoconductor and the like can be prevented even more reliably.
The ratio of the acid receiving agent is preferably 0.2 parts by mass or more, and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.

Examples of the filler include one or more of zinc oxide, silica, carbon black, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide and the like.
By blending the filler, the mechanical strength of the roller body and the like can be improved.
Further, by using conductive carbon black as the filler, it is possible to impart electronic conductivity to the roller body.

Examples of the conductive carbon black include acetylene black and the like.
The proportion of conductive carbon black is preferably 1 part by mass or more, and preferably 30 parts by mass or less per 100 parts by mass of the total amount of rubber.
Examples of the plasticizer include various plasticizers such as dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate, and various waxes such as polar wax.

Examples of the processing aid include fatty acid metal salts such as zinc stearate.
The ratio of the plasticizer and / or the processing aid is preferably 3 parts by mass or less per 100 parts by mass of the total amount of rubber.
Examples of the deterioration inhibitor include various antioxidants and antioxidants.

Of these, the anti-aging agent works to reduce the environmental dependence of the roller resistance value of the developing roller and suppress the increase in the roller resistance value during continuous energization.
Examples of the anti-aging agent include nickel diethyldithiocarbamate, nickel dibutyldithiocarbamate and the like.
The ratio of the antiaging agent is preferably 0.1 part by mass or more and preferably 1 part by mass or less per 100 parts by mass of the total amount of rubber.

Further, as the additive, various additives such as a scorch inhibitor, a lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizing agent, a nucleating agent, and a co-crosslinking agent may be further added in an arbitrary ratio.
In the example of FIG. 1, the roller main body 2 has a single-layer structure, but the roller main body 2 may have a laminated structure of two or more layers.
Further, the roller body 2 is not limited to the one formed by the rubber composition containing each of the above-mentioned components. For example, a roller resistance value suitable for the developing roller 1 can be imparted, a roller body 2 having excellent mechanical strength and durability can be formed, and the roller body 2 is flexible, has a small compression set, and is less likely to be settled. The roller body 2 can be formed of various materials that can satisfy the requirement that the roller body 2 can be provided.

In either case, by forming the outer peripheral surface 5 of the roller body 2 into the above-mentioned specific surface shape, the density of the formed image is reduced, unevenness, fog, etc. are prevented while maintaining a simple structure in which the coating film is omitted. It is possible to obtain a developing roller 1 that is less likely to occur and can form an image having excellent image quality.
The developing roller 1 of the present invention can be used by being incorporated into an image forming apparatus using an electrophotographic method, such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a multifunction device thereof.

Hereinafter, the present invention will be further described based on Examples and Comparative Examples, but the configuration of the present invention is not necessarily limited to these examples.
The arithmetic average height Sa of the outer peripheral surface of the roller body and the direction Std of the surface texture of the developing rollers manufactured in Examples and Comparative Examples are all shape analysis laser microscopes [VK-X150 manufactured by KEYENCE CORPORATION]. From the measurement result of the surface shape of the outer peripheral surface measured in the range of the ^{observation area: 55625 μm 2} using [/ 160], it was obtained according to the above-mentioned ISO standard.
The arithmetic mean height Sa was evaluated as "◯" when it was 0.6 μm or less, and as "x" when it exceeded 0.6 μm.
Further, the direction Std of the surface texture was evaluated as "◯" when it was 20 ° or more and "x" when it was less than 20 °.

<Example 1>
(Preparation of rubber composition)
As rubber, ECO [Epicroman (registered trademark) D manufactured by Osaka Soda Co., Ltd., EO / EP = 61/39 (molar ratio)] 15 parts by mass, GECO [Epion (registered trademark) manufactured by Osaka Soda Co., Ltd.) 301 (low Vis type), EO / EP / AGE = 73/23/4 (molar ratio)] 45 parts by mass, CR [Showa Denko Corporation Shoprene (registered trademark) WRT, non-oil exhibition] 10 parts by mass , And NBR [JSR N250SL manufactured by JSR Corporation, low nitrile NBR, acrylonitrile content: 20%, non-oil-extended] 30 parts by mass were blended.
Then, 100 parts by mass of the total amount of the above four types of rubber was kneaded by mixing the following components while kneading with a Bambali mixer.

Each component in Table 1 is as follows. The parts by mass in the table are parts by mass per 100 parts by mass of the total amount of rubber.
Ionic salt: Potassium bis (trifluoromethanesulfonyl) imide [K-TFSI, EF-N112 manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd.]
Cross-linking aid: Zinc oxide 2 types [manufactured by Sakai Chemical Industry Co., Ltd.]
Antacid: Hydrotalcites [DHT-4A (registered trademark) -2 manufactured by Kyowa Chemical Industry Co., Ltd.]
Filler: Conductive carbon black [acetylene black, Denka black (registered trademark) manufactured by Denki Kagaku Kogyo Co., Ltd., granular]
Processing aid: Zinc stearate [SZ-2000 manufactured by Sakai Chemical Industry Co., Ltd.]
Anti-aging agent: Nickel dibutyldithiocarbamate [Nocrack (registered trademark) NBC manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.]
Then, while continuing kneading, the following cross-linking components were blended and further kneaded to prepare a rubber composition.

Each component in Table 2 is as follows. The parts by mass in the table are parts by mass per 100 parts by mass of the total amount of rubber.
Dispersible sulfur: Cross-linking agent [trade name Salfax PS manufactured by Tsurumi Chemical Industry Co., Ltd., sulfur content: 99.5%]
Accelerator TS: Tetramethylthiuram Monosulfide [Sunceller (registered trademark) TS manufactured by Sanshin Chemical Industry Co., Ltd., thiuram-based accelerator]
Accelerator DM: Di-2-benzothiazolyl disulfide [Noxeller (registered trademark) DM manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., thiazole-based accelerator]
Accelerator 22: Ethylene thiourea [2-mercaptoimidazoline, Axel (registered trademark) 22-S manufactured by Kawaguchi Chemical Industry Co., Ltd., thiourea accelerator]
Accelerator DT: 1,3-di-o-tolylguanidine [Suncella DT manufactured by Sanshin Chemical Industry Co., Ltd., guanidine-based accelerator]

(Manufacturing of developing rollers)
The prepared rubber composition is supplied to an extruder, extruded into a tubular shape having an outer diameter of φ14.0 mm and an inner diameter of φ6.5 mm, cut and mounted on a temporary shaft for cross-linking, and 160 in a vulcanization can. Cross-linked at ° C. for 1 hour.
Next, the crosslinked tubular body was reattached to a metal shaft having an outer diameter of φ6.0 mm coated with a conductive thermosetting adhesive (polyamide type) on the outer peripheral surface, and heated to 160 ° C. in an oven. After adhering to the metal shaft, both ends were shaped.
Next, the outer peripheral surface of the tubular body was traverse-polished using a cylindrical polishing machine, and then mirror-polished as finish polishing to finish the outer diameter to φ13.00 mm.

Mirror polishing is performed in two stages. The first stage uses a # 1000 wrapping film [Mirror film MCF manufactured by Sankyo Rikagaku Co., Ltd., abrasive grains: CC, manufacturing particle size: # 1000], and the second stage is # 3000. Wrapping film [Wrapping film LGF manufactured by Sankyo Rikagaku Co., Ltd., abrasive grains: GC, production particle size: # 3000] was used.

Next, after wiping the outer peripheral surface after polishing with alcohol, the distance from the UV light source to the outer peripheral surface is set to 50 mm and set in a UV processing device, and an oxide film is formed by irradiating with ultraviolet rays for 15 minutes while rotating at 300 rpm. Manufactured a developing roller.
A part of the outer peripheral surface of the roller body of the manufactured developing roller is enlarged and shown in FIG.
The arithmetic mean height Sa of the outer peripheral surface of the roller body of the developing roller is 0.48 μm (◯), and the surface texture direction Std is 78 ° (◯) when the circumferential direction of the outer peripheral surface is 0 °. It was.

<Comparative example 1>
Same as in Example 1 except that a # 2000 lapping film [mirror film MCF manufactured by Sankyo Rikagaku Co., Ltd., abrasive grains: CC, manufacturing particle size: # 2000] was used in the second stage of the mirror polishing process. Manufactured a developing roller.
A part of the outer peripheral surface of the roller body of the manufactured developing roller is enlarged and shown in FIG.
The arithmetic mean height Sa of the outer peripheral surface of the roller body of the developing roller is 0.65 μm (×), and the surface texture direction Std is 10 ° (×) when the circumferential direction of the outer peripheral surface is 0 °. It was.

<Comparative example 2>
The same as in Example 1 except that the # 1500 wrapping film [wrapping film LGF manufactured by Sankyo Rikagaku Co., Ltd., abrasive grains: GC, production particle size: # 1500] was used in the second stage of the mirror polishing process. Manufactured a developing roller.
A part of the outer peripheral surface of the roller body of the manufactured developing roller is enlarged and shown in FIG.
The arithmetic mean height Sa of the outer peripheral surface of the roller body of the developing roller is 0.49 μm (◯), and the surface texture direction Std is 5 ° (×) when the circumferential direction of the outer peripheral surface is 0 °. It was.

<Comparative example 3>
Same as in Example 1 except that # 2000 lapping film [wrapping film LGF manufactured by Sankyo Rikagaku Co., Ltd., abrasive grains: GC, production particle size: # 2000] was used in the second stage of the mirror polishing process. Manufactured a developing roller.
A part of the outer peripheral surface of the roller body of the manufactured developing roller is enlarged and shown in FIG.
The arithmetic mean height Sa of the outer peripheral surface of the roller body of the developing roller is 0.45 μm (◯), and the surface texture direction Std is 5 ° (×) when the circumferential direction of the outer peripheral surface is 0 °. It was.

<Comparative Example 4>
In the second stage of the mirror polishing process, a # 2000 lapping film [Mirror film MCF manufactured by Sankyo Rikagaku Co., Ltd., abrasive grains: CC, manufacturing particle size: # 2000] was used, and as the third stage, # 2000 A developing roller was manufactured in the same manner as in Example 1 except that polishing was performed using a lapping film [wrapping film LGF manufactured by Sankyo Rikagaku Co., Ltd., abrasive grains: GC, production particle size: # 2000].
A part of the outer peripheral surface of the roller body of the manufactured developing roller is enlarged and shown in FIG.
The arithmetic mean height Sa of the outer peripheral surface of the roller body of the developing roller is 0.33 μm (◯), and the surface texture direction Std is 4 ° (×) when the circumferential direction of the outer peripheral surface is 0 °. It was.

<Comparative Example 5>
Same as in Example 1 except that # 3000 wrapping film [wrapping film LGF manufactured by Sankyo Rikagaku Co., Ltd., abrasive grains: GC, production particle size: # 3000] was used in the second stage of the mirror polishing process. Manufactured a developing roller.
A part of the outer peripheral surface of the roller body of the manufactured developing roller is enlarged and shown in FIG.
The arithmetic mean height Sa of the outer peripheral surface of the roller body of the developing roller is 0.27 μm (◯), and the surface texture direction Std is 12 ° (×) when the circumferential direction of the outer peripheral surface is 0 °. It was.

<Actual machine test>
For new black toner that is equipped with a toner container containing toner, a photoconductor, and a developing roller in contact with the photoconductor, and is removable from the main body of a color laser printer [HL-L8360CDW manufactured by Brother Industries, Ltd.]. Instead of the genuine developing roller of the cartridge, the developing roller manufactured in Examples and Comparative Examples was incorporated.
Then, the assembled cartridge was loaded into the color laser printer to continuously form 30 solid black and halftone (2 spaces per dot) images, and then each image was formed.

(Black solid)
The scanned image of the formed black solid image was converted into brightness, and the black solid density was evaluated according to the following criteria.
◯: The brightness was 45 or less.
X: The brightness was over 45.
As described above, the smaller the brightness, the higher the density of the solid black image.
(Fog)
The formed halftone image was visually observed, and the one in which no fog was observed was evaluated as “◯”, and the one in which fog was observed was evaluated as “x”.

(Toner support state)
The developing roller in the middle of image formation was taken out from the cartridge, and the state of carrying the toner on the outer peripheral surface of the roller body was visually observed, and the state of carrying the toner was evaluated according to the following criteria.
◯: An appropriate amount of toner was supported evenly and evenly.
X: Toner was sparsely supported or excessively supported.
The above results are shown in Table 3.

From the results of Example 1 and Comparative Examples 1 to 5 in Table 3, the coating film was formed by setting the arithmetic average height Sa of the outer peripheral surface of the roller body to 0.6 μm or less and the surface texture direction Std to 20 ° or more. While maintaining a simple structure that omits the above, an appropriate amount of toner can be uniformly supported on the outer peripheral surface of the roller body to form an image with excellent image quality that is less likely to cause a decrease in the density of the formed image, fog, unevenness, etc. It was found that a developing roller could be obtained.

Further, from the result of Example 1, considering that the above effect is further improved, the arithmetic mean height Sa is preferably 0.2 μm or more, particularly 0.3 μm or more even in the above range, and 0. It was found that it is preferably 5 μm or less.
Further, it was found that the surface production direction Std is preferably 60 ° or more, particularly 70 ° or more even in the above range.

1 Development roller 2 Roller body 3 Through hole 4 Shaft 5 Outer peripheral surface 6 Oxidation film

Claims (5)

The outer peripheral surface of the roller body, including the tubular roller body, has an arithmetic mean height Sa of 0.6 μm or less and the circumferential direction of the outer peripheral surface specified in the International Organization for Standardization ISO25178-2: 2012. A developing roller having a surface texture direction Std of 20 ° or more when set to 0 °. The developing roller according to claim 1, wherein the outer peripheral surface includes a large number of irregularities arranged randomly or regularly. The developing roller according to claim 1 or 2, wherein the outer peripheral surface is made of a crosslinked product of rubber and includes an oxide film covering the outer peripheral surface. The method for manufacturing a developing roller according to any one of claims 1 to 3.
A step of polishing the outer peripheral surface of the roller body, and a step of further wet-polishing the polished outer peripheral surface of the roller body to finish the arithmetic mean height Sa and the surface texture direction Std within the above range.
A method for manufacturing a developing roller including. The outer peripheral surface of the roller body is made of a crosslinked rubber, and after the finishing step,
A step of oxidizing the rubber to form the oxide film by irradiating the outer peripheral surface with ultraviolet rays.
The method for manufacturing a developing roller according to claim 4, further comprising.

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