JP6802970B2 - Semi-conductive roller and its manufacturing method - Google Patents

Description

The present invention relates to a semi-conductive roller used as a developing roller or the like in an image forming apparatus using an electrophotographic method, and a method for manufacturing the same.

In the above image forming apparatus, a charging member that uniformly charges the surface of the photoconductor, a developing member that develops an electrostatic latent image formed by exposing the surface of the charged photoconductor into a toner image, and a formed toner image are used. A semi-conductive roller is used as a transfer member for transferring to paper or the like, a cleaning member for removing toner remaining on the surface of a photoconductor after transferring a toner image, and the like.
Further, as the semi-conductive roller, the semi-conductive rubber composition is molded into a tubular shape in order to secure a sufficient contact nip with the photoconductor and to satisfactorily exhibit the functions of the above-mentioned members. A roller body provided with a cross-linked roller body and a shaft made of metal or the like inserted and fixed through a through hole in the center of the roller body is generally used.

As the rubber forming the rubber composition, for example, epichlorohydrin rubber is used to impart semiconductivity to the roller body and reduce the roller resistance value of the semiconductive roller to a range suitable for use as, for example, a developing roller. Ion conductive rubber such as is used.
As the rubber, a diene rubber is used together with the ion conductive rubber in order to impart the characteristics of a rubber to the roller body, that is, the characteristics of being flexible, having a small compression set and less likely to cause settling.

Further, when the semi-conductive roller is used as a developing roller in particular, the image durability is lowered, and when the image formation is repeated, the toner adheres to the margin portion of the formed image, so-called fog defect is likely to occur. There is a tendency, and in order to prevent this, the roller body is required to have high flexibility.
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, if the roller body of the developing roller provided in the developing unit is not sufficiently flexible, the toner is likely to be damaged by repeated contact with the roller body when image formation is repeated.
Then, the rate at which the toner is crushed due to damage increases, and the crushed toner generated by the damage has a large deviation in charging characteristics and the like as compared with normal toner, so that it adheres to the margin portion of the formed image and causes fog. It is easy to occur.

Therefore, it is required that the roller body of the developing roller is provided with good flexibility, the image durability is improved, and fog defects are less likely to occur.
In order to increase flexibility, in ordinary rubber products, a plasticizer such as oil may be added to the rubber composition on which the rubber product is based.
However, in the case of a semi-conductive roller, when a plasticizer is added to the rubber composition that is the basis of the roller body, the plasticizer bleeds to the outer peripheral surface of the roller body over time and transfers to a mating member such as a photoconductor. However, there is a problem that the mating member is contaminated and causes an image defect.

Further, when a plasticizer is added to the rubber composition to impart flexibility particularly suitable for the roller body of the developing roller, there is a problem that the compression set of the roller body becomes large and settling is likely to occur.
Therefore, it has been considered to add liquid rubber such as liquid NBR and liquid BR and liquid polymer such as liquid poly (meth) acrylate to the rubber composition which is the base of the roller body, which are all liquid at room temperature. (Patent Document 1 etc.).

Since liquid rubber and liquid polymer are less likely to bleed on the outer peripheral surface of the roller body than plasticizers, it is possible to suppress the occurrence of image defects due to the bleeding. However, when liquid rubber or liquid polymer is blended to give the roller body flexibility suitable for a developing roller, there is a problem that the compression set of the roller body becomes large and settling easily occurs. is there.

Japanese Unexamined Patent Publication No. 2005-148467 Japanese Unexamined Patent Publication No. 2011-53536

An object of the present invention is to provide a semi-conductive roller provided with a roller body which is flexible, has excellent image durability, and is less likely to cause image defects and settling due to bleeding, and a method for manufacturing the same.

The present invention comprises a tubular roller body comprising a rubber containing epichlorohydrin rubber and a diene rubber, a cross-linking component for cross-linking the rubber, and a cross-linked product of a rubber composition containing an ultraviolet curable resin. Is provided with an oxide film on the outer peripheral surface, a substantially tubular cured region containing a cured product of the ultraviolet curable resin in the vicinity of the outer peripheral surface, and the ultraviolet curable tree in the radial inward of the cured region. It has an uncured area where the fat is left in an uncured state without being cured, and the type A durometer hardness of the roller body specified in Japanese Industrial Standard JIS K6253-3: 2012 is 45 or less. It is a conductive roller.

Further, the present invention is the method for producing a semi-conductive roller of the present invention, wherein the rubber composition is formed into a tubular shape and crosslinked to form a roller body, and ultraviolet rays are applied to the outer peripheral surface of the roller body. Is irradiated to selectively cure the ultraviolet curable resin contained in the vicinity of the outer peripheral surface, thereby leaving the uncured region inward in the radial direction of the roller body and in the vicinity of the outer peripheral surface. This is a method for manufacturing a semi-conductive roller, which comprises a step of forming the cured region.

According to the present invention, it is possible to provide a semi-conductive roller provided with a roller body which is flexible, has excellent image durability, and is less likely to cause image defects and settling due to bleeding, and a method for manufacturing the same.

FIG. (A) is a perspective view showing the appearance of an example of the embodiment of the semi-conductive roller of the present invention, and FIG. (B) is a schematic diagram of the internal structure of the roller body among the semi-conductive rollers of the above example. It is sectional drawing shown in.

《Semi-conductive roller》
FIG. 1 (a) is a perspective view showing an appearance of an example of an embodiment of the semi-conductive roller of the present invention, and FIG. 1 (b) shows an internal structure of a roller body among the semi-conductive rollers of the above example. It is sectional drawing which shows typically.
With reference to FIGS. 1 (a) and 1 (b), the semi-conductive roller 1 of this example includes a rubber containing epichlorohydrin rubber and a diene-based rubber as described above, a cross-linking component for cross-linking the rubber, and UV curing. A non-porous and single-layered tubular roller body 2 is provided by a crosslinked product of a rubber composition containing a mold resin, and a shaft 4 is inserted into a through hole 3 at the center of the roller body 2. It is fixed.

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

A substantially tubular cured region 2a containing a cured product of an ultraviolet curable resin is provided in the vicinity of the outer peripheral surface 5 of the roller body 2 in the roller body 2, and is within the radial direction of the cured region 2a. On the other side, an uncured region 2b containing an uncured product of the ultraviolet curable resin is provided.
When the roller main body 2 has the above configuration, the uncured ultraviolet curable resin contained in the uncured region 2b can function as a softener or a plasticizer for rubber to impart high flexibility to the roller main body 2. Specifically, the image durability of the roller body 2 can be improved by setting the hardness of the type A durometer specified in Japanese Industrial Standards JIS K6253-3: 2012 to 45 or less.

Further, the uncured ultraviolet curable resin contained in the uncured region 2b bleeds to the outer peripheral surface 5 of the roller main body 2 so as to surround the uncured region 2b in the vicinity of the outer peripheral surface 5 in a substantially tubular shape. It can be suppressed by the cured region 2a containing the cured product of the ultraviolet curable resin provided in. Therefore, coupled with the fact that the cured region 2a contains almost no uncured ultraviolet curable resin, it is possible to suppress the occurrence of image defects due to bleeding of the uncured ultraviolet curable resin.

Moreover, in order to impart high flexibility to the roller body 2 and improve image durability, even if the type A durometer hardness of the roller body 2 is set to 45 or less as described above, conventional products such as plasticizers and liquid rubbers are used. It is also possible to reduce the compression set to make it less likely to cause settling as compared with the roller body which has the same rubber hardness by blending. The reason for this is not clear, but it is considered that the substantially tubular hardened region 2a provided in the vicinity of the outer peripheral surface 5 of the roller main body 2 functions as a shell for suppressing settling.

Therefore, with the above configuration, it is possible to configure a semi-conductive roller 1 provided with a roller body 2 that is flexible, has excellent image durability, and is less likely to cause image defects or settling due to bleeding.
On the outer peripheral surface 5 of the furnace over La body 2 to form an oxide film 6, as shown enlarged in FIG.

By forming the oxide film 6, the oxide film 6 functions as a dielectric layer, and the dielectric loss tangent of the semiconductive roller 1 can be reduced. Further, the oxide film 6 functions as a low friction layer, and the adhesion of toner can be satisfactorily suppressed.
The "single-layer structure" of the semi-conductive roller 1 described above means that the number of layers made of crosslinked rubber is a single layer, and the cured region 2a and the uncured region 2b are integrally continuous rubber. Since it is composed of the crosslinked product of the above, it is counted as one layer, and the oxide film 6 is not included in the number of layers.

As described above, the roller body 2 needs to have a type A durometer hardness of 45 or less as specified in Japanese Industrial Standards JIS K6253-3: 2012.
If the hardness of the Type A durometer exceeds this range, the roller body 2 becomes hard and sufficient flexibility cannot be obtained, so that the image durability is lowered especially when the semi-conductive roller 1 is used as a developing roller. As a result, fog defects are likely to occur.

On the other hand, by setting the hardness of the type A durometer of the roller body 2 within the above range, it is possible to impart good flexibility to the roller body 2, improve image durability, and prevent fog defects from occurring.
Considering that the effect is further improved, the hardness of the type A durometer of the roller body 2 is preferably 43 or less, particularly 40 or less, even in the above range.

Further, the hardness of the type A durometer of the roller body 2 is preferably 30 or more, particularly 35 or more, even in the above range.
If the hardness of the Type A durometer is less than this range, even if the hardening region 2a is provided in the vicinity of the outer peripheral surface 5, the compression set of the roller body 2 may become large and settling may easily occur.

To adjust the type A durometer hardness of the roller body 2 to the above range, adjust the blending ratio of the ultraviolet curable resin per 100 parts by mass of rubber, and especially the type and blending ratio of diene rubber among rubbers. Alternatively, as will be described later, the thickness and the like of the cured region 2a formed may be adjusted by manipulating the intensity of the ultraviolet rays irradiating the outer peripheral surface 5 of the roller body 2 and the irradiation time.

Incidentally, in Patent Document 2, a rubber composition containing a curable monoma is formed into a tubular shape, and the rubber is crosslinked by heating to form a roller body, and at the same time, the solubility constant of the rubber and the curable monoma ( Based on the difference in SP value), the curable monoma is intentionally subjected to a curing reaction while bleeding on the outer peripheral surface of the roller body, or after being bleeded, further irradiated with an electron beam or the like to cause a curing reaction to cause the outer peripheral surface. It is described that a charged roller or the like having a surface layer made of a cured product of a curable monoma formed on the surface is manufactured.

However, in such a configuration, most of the curable monoma is spent on bleeding on the outer peripheral surface of the roller body to form a surface layer, and in the uncrosslinked state, almost no residue remains inside the roller body. Since a large amount of carbon is blended as the charging roller, the hardness of the type A durometer as a whole of the roller body cannot satisfy the range of 45 or less specified in the present invention. Therefore, the problem that the image durability is lowered and fog defects are likely to occur is still not solved.

In the present invention, the hardness of the type A durometer of the roller body 2 is expressed by a value measured by the following method under a normal temperature and humidity environment with a temperature of 23 ± 2 ° C. and a relative humidity of 55 ± 2%.
<Type A durometer hardness measurement>
With both ends of the shaft 4 protruding from both ends of the roller body 2 fixed to the support base, the center of the roller body 2 in the width direction complies with the provisions of Japanese Industrial Standards JIS K6253-3: 2012 from above. The hardness of the type A durometer of the roller body 2 is determined by the value measured under the conditions of a load of 1 kg and a measurement time of 3 seconds (standard measurement time of vulcanized rubber) by applying the push needle of the type A durometer.

<< Manufacturing method of semi-conductive roller >>
In order to manufacture the semi-conductive roller 1, first, the prepared rubber composition is extruded into a tubular shape using an extrusion molding machine, then cut into a predetermined length, pressurized and heated in a vulcanization can. And crosslink.
Next, the crosslinked tubular body is heated using an oven or the like for secondary cross-linking, cooled, and then polished to have a predetermined outer diameter to form the roller body 2.

As the polishing method, various polishing methods such as dry traverse grinding can be adopted.
Moreover, you may finish by mirror polishing at the end of a polishing process. In that case, the releasability of the outer peripheral surface 5 is further improved, and the synergistic effect of forming the oxide film 6 makes it possible to further better suppress the adhesion of toner. In addition, contamination of the photoconductor or the like can be effectively prevented.
The shaft 4 can be inserted into and fixed in the through hole 3 at any time from after cutting the tubular body to after polishing.

However, after cutting, it is preferable to first perform secondary cross-linking and polishing with the shaft 4 inserted through the through hole 3. As a result, warpage 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, the workability of the polishing can be improved, and the deflection of the outer peripheral surface 5 can be suppressed.
As described above, the shaft 4 is press-fitted into the through hole 3 having an outer diameter larger than the inner diameter of the through hole 3, or is placed before the secondary cross-linking via a conductive thermosetting adhesive. It may be inserted into the through hole 3 of the tubular body of.

In the former case, electrical joining and mechanical fixing are completed at the same time as the shaft 4 is press-fitted.
In the latter 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 at the same time. It is fixed mechanically.
Next, the outer peripheral surface 5 of the roller body 2 is irradiated with ultraviolet rays having a predetermined wavelength for a predetermined time. Then, the ultraviolet curable resin in the vicinity of the outer peripheral surface 5 and in the roller main body 2 from the outer peripheral surface 5 and contained at least in the range where the ultraviolet rays reach is selectively cured to form the cured region 2a. At the same time, the ultraviolet curable resin is left in an uncured state without being cured in the radial direction of the roller body 2 from the cured region 2a, and becomes an uncured region 2b.

Further, when the irradiation of the ultraviolet rays is carried out in a particularly oxidizing atmosphere, the diene-based rubber exposed on the outer peripheral surface 5 of the roller body 2 is oxidized, and at the same time as the curing region 2a is formed, the outer peripheral surface 5 is oxidized. The film 6 is formed. That is, the oxide film 6 can be formed only by irradiating the outer peripheral surface 5 of the roller body 2 with ultraviolet rays having a predetermined wavelength for a predetermined time to oxidize the diene-based rubber or the like in the rubber composition exposed on the outer peripheral surface 5. Easy and efficient.

Moreover, the oxide film 6 formed by irradiation with ultraviolet rays does not cause problems like the conventional coating film formed by applying a coating agent, and has a uniform thickness and the roller body 2. It is also excellent in adhesion of.
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 15 minutes or shorter.

However, the oxide film 6 but it may also be formed in other ways.
《Rubber composition》
<Epichlorohydrin rubber>
As the epichlorohydrin rubber, various polymers containing epichlorohydrin as a repeating unit and having ionic conductivity can be used.

Examples of such epichlorohydrin rubber include epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allylglycidyl ether binary copolymer, and epichlorohydrin-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, etc. The above can be mentioned.

Among them, copolymers containing ethylene oxide, especially ECO and others, are effective in reducing the roller resistance value of the semi-conductive roller 1 to a range suitable for use as a developing roller or the like when used in combination with a diene rubber. / Or GECO is preferred.
The ethylene oxide content of both of the above copolymers is preferably 30 mol% or more, particularly preferably 50 mol% or more, and preferably 80 mol% or less.

Ethylene oxide works to lower the roller resistance value of the semi-conductive roller 1. However, if the ethylene oxide content is less than this range, such an action cannot be sufficiently obtained, so that the roller resistance value 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 semi-conductive roller 1 tends to increase. Further, the roller body 2 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 and the workability may decrease.

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 semi-conductive roller 1. 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 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. On the contrary, the roller resistance value 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, the epichlorohydrin-ethylene oxide copolymer (ECO) is modified with allylglycidyl ether. Those are also known, and any of these GECOs can be used in the present invention.

One or more of these epichlorohydrin rubbers can be used.
<Diene rubber>
Examples of the diene rubber include one or more of natural rubber, isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and the like. Can be mentioned.

Of these, it is preferable to use NBR and CR together, or NBR, CR and BR together. As each rubber, two or more kinds of rubbers of the same type and different grades may be used in combination.
(NBR)
Since the dissolution parameter (SP value) of NBR is close to that of epichlorohydrin rubber, BR, and CR, NBR functions as a so-called compatibilizer for these rubbers, assists in fine dispersion between each rubber, and is a rubber composition. It functions to increase the fluidity during heating, to ensure good processability even in a formulation that does not contain a processing aid, and to further improve the flexibility of the roller body 2.

Further, since NBR is a polar rubber, it also functions to finely adjust the roller resistance value of the semi-conductive roller 1.
Further, NBR is also a material that is oxidized by ultraviolet irradiation in an oxidizing atmosphere to form an oxide film 6 on the outer peripheral surface 5 of the semi-conductive roller 1.
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%, high nitrile NBR having 36 to 42%, and 43% or more. Any of the highest nitrile NBRs may be used.

Further, as the NBR, there are an oil-extended type in which the flexibility is adjusted by adding extenuating oil and a non-oil-extended type in which no extensibility oil is added. In the present invention, bleeding is performed 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 substance.
One or more of these NBRs can be used.
(CR)
The CR functions particularly to improve the flexibility of the roller body 2.

Further, since CR is also a polar rubber, it also functions to finely adjust the roller resistance value of the semi-conductive roller 1.
Further, CR is also a material that is oxidized by ultraviolet irradiation in an oxidizing atmosphere to form an oxide film 6 on the outer peripheral surface 5 of the semi-conductive roller 1.
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 the 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 the 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. Examples of such other copolymerization components include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylic nitrile, isoprene, butadiene, acrylic acid, and acrylic acid ester. , Methacrylic acid, and methacrylic acid ester and the like.

Further, there are two types of CR, one is an oil-extending type in which the flexibility is adjusted by adding spreading oil, and the other is a non-oil-extending type in which extension oil is not added. , It is preferable to use a non-oil spread type CR.
One or more of these CRs can be used.
(BR)
The BR functions in particular to impart good properties as rubber to the semi-conductive roller 1, that is, properties that are flexible, have low compression set, and are less likely to cause settling.

Further, BR is also a material that is oxidized by ultraviolet irradiation in an oxidizing atmosphere to form an oxide film 6 on the outer peripheral surface 5 of the semi-conductive roller 1.
As the BR, various BRs having a polybutadiene structure in the molecule and having crosslinkability can be used.
In particular, a high cis BR having a cis-1,4 bond content of 95% or more, which can exhibit good properties as a rubber in a wide temperature range from high temperature to low temperature, is preferable.

Further, there are two types of BR, one is an oil-extending type in which extensibility oil is added to adjust the flexibility, and the other is a non-oil-extending type in which no spreading oil is added. , Non-oil spread type BR is preferable.
One or more of these BRs can be used.
(Rubber mixing ratio)
The mixing ratio of the rubber can be arbitrarily set according to various characteristics required for the semi-conductive roller 1, particularly the roller resistance value, the flexibility of the roller body 2, and the like.

For example, the blending ratio of epichlorohydrin rubber is preferably 25 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 45 parts by mass or less, particularly 40 parts by mass or less, based on 100 parts by mass of the total amount of rubber.
If the blending ratio of epichlorohydrin rubber is less than this range, the roller resistance value of the semi-conductive roller 1 may not be sufficiently lowered to a range suitable for use as a developing roller or the like.

On the other hand, when the blending ratio of epichlorohydrin rubber exceeds the above range, the ratio of diene-based rubber is relatively small, which imparts good processability to the rubber composition or provides the roller body 2 as rubber. It may not be possible to impart good characteristics, that is, characteristics that are flexible, have a small compression set, and are less likely to cause settling. Further, when the semi-conductive roller 1 is used particularly as a developing roller, toner tends to adhere to the semi-conductive roller 1, and the image density of the formed image may decrease.

On the other hand, by setting the blending ratio of epichlorohydrin rubber in the above range, the roller resistance value of the semi-conductive roller 1 can be used as a developing roller or the like while maintaining the effect of using the diene rubber together. It can be sufficiently lowered to a suitable range.
The blending ratio of CR is preferably 5 parts by mass or more, and preferably 15 parts by mass or less based on 100 parts by mass of the total amount of rubber.

If the blending ratio of CR is less than this range, good flexibility may not be imparted to the roller body 2.
On the other hand, when the compounding ratio of CR exceeds the above range, the ratio of epichlorohydrin rubber becomes relatively small, and the roller resistance value of the semi-conductive roller 1 reaches a range suitable for use as a developing roller or the like. It may not be lowered sufficiently. Further, the ratio of NBR and BR becomes small, and there is a possibility that the effect of using these rubbers in combination cannot be sufficiently obtained.

In the combined system of three types of rubber, epichlorohydrin rubber, CR, and NBR, the blending ratio of NBR is basically the remaining amount of the other two types of rubber. That is, epichlorohydrin rubber and CR may be blended in the above-mentioned predetermined ratios, and NBR may be further added to make the total amount of rubber 100 parts by mass.
On the other hand, in the combined system of four types of rubber, epichlorohydrin rubber, CR, NBR, and BR, the blending ratio of NBR is preferably 5 parts by mass or more, preferably 15 parts by mass or less, based on 100 parts by mass of the total amount of rubber. It is preferable to have it.

If the blending ratio of NBR is less than this range, it may not be possible to impart good processability to the rubber composition or impart good flexibility to the roller body 2.
On the other hand, when the blending ratio of NBR exceeds the above range, the proportion of epichlorohydrin rubber becomes relatively small, and the roller resistance value of the semi-conductive roller 1 reaches a range suitable for use as a developing roller or the like. It may not be lowered sufficiently. In addition, the ratio of CR and BR may decrease, and the effect of using these rubbers in combination may not be sufficiently obtained.

In the combined system of the above four types of rubber, the blending ratio of BR is basically the remaining amount of the other three types of rubber. That is, epichlorohydrin rubber, CR, and NBR may be blended in the above-mentioned predetermined ratios, and BR may be further added to make the total amount of rubber 100 parts by mass.
<Crossing component>
As the cross-linking component, it is preferable to use a thiourea-based cross-linking agent and a sulfur-based cross-linking component in combination .

(Chiolea cross-linking agent)
As the thiourea-based cross-linking agent, various thiourea compounds having a thiourea structure in the molecule and capable of mainly functioning as a cross-linking agent for epichlorohydrin rubber can be used.
Examples of the thiourea-based cross-linking agent include one or more of ethylene thiourea (also known as 2-mercaptoimidazoline), diethyl thiourea, and dibutyl thiourea. Ethylenethiourea is particularly preferable.

The blending ratio of the thiourea-based cross-linking agent is preferably 0.2 parts by mass or more per 100 parts by mass of the total amount of rubber, and preferably 1 part by mass or less.
If the blending ratio of the thiourea-based cross-linking agent is less than this range, the cross-linking of the epichlorohydrin rubber becomes insufficient, and the compression set of the roller main body 2 may become large and settling may easily occur.

On the other hand, when the blending ratio of the thiourea-based cross-linking agent exceeds the above range, the roller main body 2 after cross-linking becomes too hard, so that the image durability may decrease and fog defects may easily occur. Further, the excess thiourea-based cross-linking agent may bloom on the outer peripheral surface 5 of the roller body 2, hinder the formation of the cured region 2a and the oxide film 6 by irradiation with ultraviolet rays, or contaminate the photoconductor or the like.

(Crosslink accelerator)
As the thiourea-based cross-linking agent, various cross-linking accelerators that promote the cross-linking reaction of epichlorohydrin rubber by the thiourea-based cross-linking agent may be used in combination.
Examples of such a cross-linking accelerator include guanidine-based accelerators such as 1,3-diphenylguanidine (D), 1,3-di-o-tolylguanidine (DT), and 1-o-tolylbiguanide (BG). Species or two or more species are mentioned.

The blending ratio of the cross-linking accelerator is preferably 0.2 parts by mass or more per 100 parts by mass of the total amount of rubber, preferably 1 part by mass or less, considering that the effect of promoting the cross-linking of epichlorohydrin rubber is sufficiently exhibited. It is preferable to have it.
(Sulfur-based cross-linking component)
As the sulfur-based cross-linking component for mainly cross-linking the diene-based rubber, it is preferable to use a sulfur-based cross-linking agent and a sulfur-containing cross-linking accelerator in combination.

Among these, sulfur-based cross-linking agents include, for example, sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, or organic sulfur-containing agents such as tetramethylthium disulfide and N, N-dithiobismorpholine. Examples thereof include compounds, and sulfur is particularly preferable.
The blending ratio of sulfur is preferably 0.5 parts by mass or more and preferably 2 parts by mass or less per 100 parts by mass of the total amount of rubber.

If the sulfur content is less than this range, the diene rubber cannot be crosslinked satisfactorily to impart good rubber properties, that is, flexibility, low compression set, and less settling. There is a risk.
On the other hand, when the blending ratio of sulfur exceeds the above range, excess sulfur blooms on the outer peripheral surface 5 of the roller body 2 and hinders the formation of the cured region 2a and the oxide film 6 by irradiation with ultraviolet rays or the like. There is a risk of contaminating the photoconductor and the like.

When, for example, oil-treated powdered sulfur, dispersible sulfur, or the like is used as sulfur, the above-mentioned compounding 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 blending 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.

Examples of the sulfur-containing cross-linking accelerator include one or more types such as a thiazole-based accelerator, a thiuram-based accelerator, a sulfenamide-based accelerator, and a dithiocarbamate-based accelerator. Of these, it is preferable to use a thiuram-based accelerator and a thiazole-based accelerator in combination.
Examples of the thiuram-based accelerator include tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), dipentamethylene thiuram tetrasulfide (DPTT) and the like. 1 type or 2 or more types of.

Examples of the thiazole-based accelerator include 2-mercaptobenzothiazole (MBT), di-2-benzothiazolyl disulfide (MBTS), 2-mercaptobenzothiazole zinc salt (ZnMBT), and 2-mercaptobenzothiazole cyclohexyl. One or more kinds such as amine salt (CMBT), 2- (4'-morpholinodithio) benzothiazole (MDB) and the like can be mentioned.

Considering that the effect of promoting the cross-linking of the diene rubber is sufficiently exhibited in the combined system of the two types of cross-linking accelerators, the blending ratio of the thiuram-based accelerator is 0.3 per 100 parts by mass of the total amount of rubber. It is preferably parts by mass or more and 2 parts by mass or less. The blending ratio of the thiazole-based accelerator is preferably 0.3 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the total amount of rubber.

<UV curable resin>
As an ultraviolet curable resin, it has compatibility with rubber, and in an uncured state, it functions as a softener and plasticizer for rubber as described above, and is cured in a crosslinked product of rubber by irradiation with ultraviolet rays. Any of the various monomas or oligomas that can react to form the cured region 2a can be used.

In particular, in terms of compatibility with each of the above-mentioned rubbers, one or more of acrylate monoma, urethane acrylate, polyester acrylate, epoxy acrylate and the like can be mentioned, and among them, aliphatic urethane acrylate, aromatic urethane acrylate and the like can be mentioned. Urethane acrylate is preferred.
The blending ratio of the ultraviolet curable resin is preferably 2 parts by mass or more and preferably 10 parts by mass or less per 100 parts by mass of the total amount of rubber.

Further, in the above-mentioned combination system of three types of rubbers, epichlorohydrin rubber, CR, and NBR, the blending ratio of the ultraviolet curable resin is preferably 5 parts by mass or more even in the above range.
On the other hand, in the combined system of four types of rubber, epichlorohydrin rubber, CR, NBR, and BR, the blending ratio of the ultraviolet curable resin is preferably 5 parts by mass or more, preferably 8 parts by mass or more, even in the above range. Is even more preferable.

When the blending ratio of the ultraviolet curable resin is less than this range, the uncured ultraviolet curable resin functions as a softener and a plasticizer for rubber to improve the overall flexibility of the roller body 2 and to improve the overall flexibility of the roller body 2. Type A plasticizer There is a possibility that the effect of setting the hardness to 45 or less cannot be obtained.
On the other hand, when the compounding ratio of the ultraviolet curable resin exceeds the above range, the roller body 2 becomes too soft and the type A durometer hardness of the roller body 2 becomes less than 30, even if it is in the vicinity of the outer peripheral surface 5. Even if the hardening region 2a is provided, the compression set may become large and settling may easily occur.

<Others>
Various additives may be further added to the rubber composition, if necessary. Examples of the additive include a cross-linking accelerator, an acid receiver, a filler, a processing aid and the like.
Among these, as the cross-linking accelerator, for example, a metal compound such as zinc oxide (zinc oxide); fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and one or more of conventionally known cross-linking accelerators. Can be mentioned.

The mixing ratio of the cross-linking accelerator is preferably 0.1 part by mass or more, and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.
The antacid functions to prevent the chlorine-based gas generated from the epichlorohydrin rubber, CR, etc. at the time of cross-linking from remaining in the roller main body 2 and thereby inhibiting cross-linking and contaminating the photoconductor and the like.

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 more reliably.

The compounding ratio of the acid receiving agent is preferably 0.1 part by mass or more, and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.
If the blending ratio of the antacid is less than this range, the effect of blending the antacid may not be sufficiently obtained. Further, when the compounding ratio of the antacid exceeds the above range, the roller body 2 after cross-linking becomes too hard, so that the image durability may be lowered and fog defects may be likely to occur.

Examples of the filler include one or more of zinc oxide, silica, carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide and the like.
By blending the filler, the mechanical strength of the semi-conductive roller 1 and the like can be improved.
Further, when conductive carbon black is used as the filler, electronic conductivity can be imparted to the roller body 2.

As the conductive carbon black, granular acetylene black is particularly preferable. Since the granular acetylene black is easy to handle and can be uniformly dispersed in the rubber composition, it is possible to impart as uniform electron conductivity as possible to the roller body 2.
The blending ratio of the conductive carbon black is preferably 1 part by mass or more, and preferably 10 parts by mass or less per 100 parts by mass of the total amount of rubber.

Examples of the processing aid include fatty acid metal salts such as zinc stearate.
The mixing ratio of the processing aid is preferably 0.1 part by mass or more and preferably 2 parts by mass or less per 100 parts by mass of the total amount of rubber.
Further, as the additive, various additives such as deterioration inhibitor, scorch inhibitor, plasticizer, lubricant, pigment, antistatic agent, flame retardant, neutralizing agent, nucleating agent, co-crosslinking agent, etc. May be blended with.

The semi-conductive roller 1 of the present invention is suitably used as a developing roller in an image forming apparatus using an electrophotographic method, such as a laser printer, an electrostatic copier, a plain paper facsimile machine, and a combination machine thereof. In addition, it can also be used as, for example, a charging roller, a transfer roller, a cleaning roller, or the like.

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.
<Example 1-1>
(Preparation of rubber composition)
As rubber, 30 parts by mass of GECO [HYDRIN (registered trademark) T3108 manufactured by Nippon Zeon Co., Ltd.], 10 parts by mass of CR [SHOPPREN (registered trademark) WRT manufactured by Showa Denko Corporation, non-oil exhibition], and NBR [ JSR N250 SL manufactured by JSR Corporation, low nitrile NBR, acrylonitrile content: 20%, non-oil-extended] 60 parts by mass was blended.

While kneading the above three types of rubber using a Bambali mixer, the following components were mixed and kneaded.

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.
Ultraviolet curable resin: aliphatic urethane acrylate [EBECRYL (registered trademark) 8465 manufactured by Daicel Ornex Co., Ltd., solvent-free, number of functional groups: 3, average molecular weight Mn: 1400]
Carbon Black: Acetylene Black [Denka Black (registered trademark) granular manufactured by Denki Kagaku Kogyo Co., Ltd.]
Cross-linking accelerator: Zinc oxide 2 types [Mitsui Mining & Smelting Co., Ltd.]
Antacid: Hydrotalcites [DHT-4A (registered trademark) -2 manufactured by Kyowa Chemical Industry Co., Ltd.]
Processing aid: Zinc stearate [SZ-2000 manufactured by Sakai Chemical Industry Co., Ltd.]
Then, while continuing kneading, the following cross-linking components were blended and further kneaded to prepare a rubber composition. The compounding ratio of the ultraviolet curable resin was 2 parts by mass per 100 parts by mass of the total amount of rubber.

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.
Sulfur: Dispersive sulfur [Tsurumi Chemical Industry Co., Ltd. trade name Sarfax PS, sulfur content: 99.5%]
Thiram-based accelerator: Tetramethyl thiuram monosulfide [TMTM, Sunseller (registered trademark) TS manufactured by Sanshin Chemical Industry Co., Ltd.]
Thiazole Accelerator: Di-2-benzothiazil disulfide [MBTS, Shandong Shanxian Chemical Co., Inc. Ltd. Product name SUNSINE MBTS]
Thiourea-based cross-linking agent: Ethylene thiourea [2-mercaptoimidazoline, EU, Axel (registered trademark) 22-S manufactured by Kawaguchi Chemical Industry Co., Ltd.]
Guanidine-based accelerator: 1,3-di-o-tolylguanidine [DOTG, Sunseller DT manufactured by Sanshin Chemical Industry Co., Ltd.]
(Manufacturing of semi-conductive roller 1)
The rubber composition was supplied to an extruder, extruded into a tubular shape having an outer diameter of φ20 mm and an inner diameter of φ7.0 mm, mounted on a temporary shaft for cross-linking, and cross-linked in a vulcanization can at 160 ° C. for 1 hour. ..

Next, the crosslinked tubular body was reattached to a shaft having an outer diameter of φ7.5 mm coated with a conductive thermosetting adhesive on the outer peripheral surface, and heated to 160 ° C. in an oven to adhere to the shaft. ..
Next, both ends of the tubular body are cut and shaped, and the outer peripheral surface is traverse-polished using a cylindrical grinder and then mirror-polished as a finish so that the outer diameter is φ20.00 mm (tolerance 0.05). Finished to form the roller body 2. A # 2000 wrapping film [Mirror film manufactured by Sankyo Rikagaku Co., Ltd. (registered trademark)] was used for mirror polishing.

Next, after washing the outer peripheral surface 5 of the roller body 2 after mirror polishing with water, the distance from the outer peripheral surface 5 to the UV lamp is set to be 5 cm, and the ultraviolet irradiation device [PL21-manufactured by Sen Special Light Source Co., Ltd.] 200] was set, and ultraviolet rays having wavelengths of 184.9 nm and 253.7 nm were irradiated for 15 minutes each while rotating 90 ° about the shaft.
Then, by this irradiation, the ultraviolet curable resin contained in the roller main body 2 in the vicinity of the outer peripheral surface 5 is selectively cured while leaving the uncured region 2b inward in the radial direction of the roller main body 2, and the said. A semi-conductive roller 1 was manufactured by forming a cured region 2a in the vicinity of the outer peripheral surface 5 and oxidizing the rubber exposed on the outer peripheral surface 5 of the roller body 2 to form an oxide film 6 on the outer peripheral surface 5. ..

<Comparative Example 1-1>
A rubber composition was prepared in the same manner as in Example 1-1 except that the ultraviolet curable resin was not blended, and the semi-conductive roller 1 was manufactured.
<Examples 1-2 to 1-4, Comparative Example 1-2>
The mixing ratio of the ultraviolet curable resin is 1 part by mass (Comparative Example 1-2), 5 parts by mass (Example 1-2), 8 parts by mass (Example 1-3), and 1 part by mass per 100 parts by mass of the total amount of rubber. A rubber composition was prepared in the same manner as in Example 1-1 except that the portion was 10 parts by mass (Examples 1-4), and the semi-conductive roller 1 was manufactured.

<Type A durometer hardness measurement>
The type A durometer hardness of the roller body 2 of the semi-conductive roller 1 manufactured in Examples and Comparative Examples was described above in a normal temperature and humidity environment with a temperature of 23 ± 2 ° C. and a relative humidity of 55 ± 2%. It was measured by the measuring method.
The type A durometer hardness was evaluated as good (◯) when it was 45 or less, and poor (x) when it exceeded 45.

<Actual machine test>
A new cartridge for a commercially available laser printer (a toner container containing toner, a photoconductor, and a developing roller in contact with the photoconductor) of the semi-conductive rollers manufactured in Examples and Comparative Examples. In place of the existing development roller, it was incorporated as a development roller.
The laser printer uses a positively charged crushing type non-magnetic one-component toner, and the recommended number of printed toners is 12,000.

(Image durability evaluation)
The cartridge is mounted on a laser printer in the initial state, and images with a density of 5% are continuously printed up to the recommended number of prints of the toner (12000 sheets) in a high temperature and high humidity environment with a temperature of 30 ± 1 ° C. and a relative humidity of 80 ± 1%. The image was formed, and it was confirmed whether or not fog was generated in the margin portion of the final formed image, and the image durability was evaluated according to the following criteria.

⊚: No fog was seen. The image durability was extremely good.
◯: Although there was slight fog that could not be visually observed, the image durability was good.
Δ: Although there was a slight amount of fog on the edge of the paper that could be visually observed, the image durability was at a practical level.

X: Clear fog was observed at the edge of the paper. The image durability was poor.
(Evaluation)
Separately prepared cartridges incorporating the semi-conductive rollers manufactured in the examples and comparative examples, which were used in the image durability evaluation, under a high temperature and high humidity environment with a temperature of 30 ± 1 ° C and a relative humidity of 80 ± 1%. After storing for 5 days, it was attached to a laser printer to form an image, and the presence or absence of settling was evaluated according to the following criteria.

◯: No image defects such as fading due to settling of the semi-conductive roller were observed in the formed image. No settling.
X: The above image defect was observed. There is a settling.
The above results are shown in Table 3.

From the results of Examples 1-1 to 1-4 and Comparative Examples 1-1 and 1-2 in Table 3, three types of rubber, epichlorohydrin rubber, CR, and NBR, are used in combination, and a rubber containing an ultraviolet curable resin is blended. The outer peripheral surface 5 of the roller body 2 made of the composition is irradiated with ultraviolet rays to form a cured region 2a in the vicinity of the outer peripheral surface 5 while leaving an uncured region 2b inward in the radial direction of the roller body 2. It was found that by setting the overall type A durometer hardness to 45 or less, it is possible to construct a semi-conductive roller 1 provided with a roller body 2 that is flexible, has excellent image durability, and is less likely to cause image defects and settling due to bleeding. ..

Further, from the results of Examples 1-1 to 1-4, considering that the above effect is further improved, the type A durometer hardness of the roller body 2 is 43 or less, particularly 40 or less even in the above range. It was found that 30 or more, particularly 35 or more is preferable.
<Example 2-1>
As rubber, GECO [HYDRIN (registered trademark) T3108 manufactured by Nippon Zeon Co., Ltd.] 40 parts by mass, CR [Showpren (registered trademark) WRT manufactured by Showa Denko Co., Ltd., non-oil exhibition] 10 parts by mass, NBR [JSR] JSR N250 SL manufactured by JSR Corporation, low nitrile NBR, acrylonitrile content: 20%, non-oil spread] 10 parts by mass, and BR [JSR BR01 manufactured by JSR Corporation, cis-1,4 bond content: 95 mass %, Mooney viscosity ML _{1 + 4} (100 ° C.): 45, non-oil spread] A rubber composition was prepared in the same manner as in Example 1-1 except that 40 parts by mass was blended to produce a semi-conductive roller 1. ..

<Comparative Example 2-1>
A rubber composition was prepared in the same manner as in Example 2-1 except that the ultraviolet curable resin was not blended, to produce the semi-conductive roller 1.
<Examples 2-2-2-4, Comparative Example 2-2>
The mixing ratio of the ultraviolet curable resin is 1 part by mass (Comparative Example 1-2), 5 parts by mass (Example 1-2), 8 parts by mass (Example 1-3), and 1 part by mass per 100 parts by mass of the total amount of rubber. A rubber composition was prepared in the same manner as in Example 2-1 except that the amount was 10 parts by mass (Examples 1-4), and the semi-conductive roller 1 was manufactured.

The semi-conductive rollers of the above Examples and Comparative Examples were subjected to the above-mentioned tests to evaluate their characteristics. The results are shown in Table 4.

From the results of Examples 2-1 to 2-4 and Comparative Examples 2-1 and 2-2 in Table 4, similar results were obtained in a system in which four types of rubber, epichlorohydrin rubber, CR, NBR, and BR were used in combination. It turned out to be obtained.
That is, the outer peripheral surface 5 of the roller body 2 made of a rubber composition obtained by blending the above four types of rubber with an ultraviolet curable resin is irradiated with ultraviolet rays, leaving an uncured region 2b inward in the radial direction of the roller body 2. At the same time, by forming a cured region 2a in the vicinity of the outer peripheral surface 5 and setting the overall type A durometer hardness to 45 or less, the roller is flexible and has excellent image durability, and is less likely to cause image defects and settling due to bleeding. It was found that the semi-conductive roller 1 provided with the main body 2 can be configured.

Further, from the results of Examples 2-1 to 2-4, considering that the above effect is further improved, the type A durometer hardness of the roller body 2 is 43 or less, particularly 40 or less even in the above range. It was found that 30 or more, particularly 35 or more is preferable.

1 Semi-conductive roller 2 Roller body 2a Hardened area 2b Unhardened area 3 Through hole 4 Shaft 5 Outer peripheral surface 6 Oxidized film

Claims (5)

A tubular roller body composed of a rubber containing epichlorohydrin rubber and a diene rubber, a cross-linking component for cross-linking the rubber, and a cross-linked product of a rubber composition containing an ultraviolet curable resin, and the roller body has an outer peripheral surface. provided with a oxide film, in the vicinity of the outer circumferential surface, substantially cylindrical hardened zone comprising a cured product of the ultraviolet curable resin, radially inward of the curing zone, the ultraviolet-curable resins are cured reaction A semi-conductive roller having an uncured region left in an uncured state without being cured, and having a type A durometer hardness of 45 or less specified in the Japanese Industrial Standard JIS K6253-3: 2012 of the roller body. The semi-conductive roller according to claim 1, wherein the compounding ratio of the ultraviolet curable resin is 2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the total amount of the rubber. The semi-conductive roller according to claim 1 or 2 , which is incorporated into an image forming apparatus using an electrophotographic method and used as a developing roller for developing an electrostatic latent image formed on the surface of a photoconductor into a toner image. The method for manufacturing a semi-conductive roller according to any one of claims 1 to 3 , wherein the rubber composition is formed into a tubular shape and crosslinked to form a roller body, and the roller body. By irradiating the outer peripheral surface of the roller with ultraviolet rays and selectively curing the ultraviolet curable resin contained in the vicinity of the outer peripheral surface, the uncured region is left inward in the radial direction of the roller body. A method for manufacturing a semi-conductive roller, which comprises a step of forming the cured region in the vicinity of the outer peripheral surface. The fourth aspect of the present invention is to irradiate the ultraviolet rays in an oxidizing atmosphere to cure the ultraviolet curable resin and oxidize the rubber exposed on the outer peripheral surface of the roller body to form an oxide film on the outer peripheral surface. The method for manufacturing a semi-conductive roller according to the description.

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