JP2019215422A - Developing roller - Google Patents

Abstract

To provide a developing roller that simultaneously improves both black solid density and two-dot density, is excellent in both contrast and thin line reproducibility, can form a good image without unevenness in density depending on the density of images adjacent thereto in the transverse direction, and eliminates the possibility that an image density of a black solid part in particular is gradually reduced even when image formation is repeated.SOLUTION: A developing roller 1 comprises a roller body 5 including a cylindrical inner layer 2 that is formed of a cross-linked product of a rubber composition containing rubber containing NBR and an ion conductive agent, and an outer layer 4 that is formed of an elastic material. The roller resistance value of the roller body 5 as a whole R(Ω, upon application of 400 V) and the roller resistance value of the inner layer 2 alone R(Ω, upon application of 400 V) satisfy both the formula (1): 0.1≤logR-logR≤1.0 (1) and the formula (2): 6.5≤logR≤8.5 (2).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a developing roller used in an image forming apparatus using an electrophotographic method.

As the developing roller, for example, a developing roller having a single-layer roller main body formed by forming a rubber composition containing a diene rubber and an ion conductive rubber into a cylinder and then crosslinking the rubber composition is known.
In some cases, an oxide film is formed by, for example, irradiating the outer peripheral surface of a single-layer roller body with ultraviolet rays (see Patent Document 1).

Examples of the image forming apparatus incorporating the developing roller include a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a composite machine thereof.
As one of image evaluation criteria of an image forming apparatus such as a laser printer, a solid black density and a 2-dot density are known.
The black solid density is the density of a so-called black solid image in which the entire surface of the paper is black, and the higher the black solid density, the higher the contrast can be formed.

The 2dot density is the density of an image called an isolated 2dot, in which circles are arranged on a square lattice with a grid length of about 80 μm. The higher the 2dot density, the better the reproducibility of fine lines in the image, and No image can be formed.
However, these two image densities are in a reciprocal relationship, and it is difficult to achieve both.
That is, the black solid density increases as the roller resistance value of the developing roller decreases, but the 2-dot density tends to increase as the roller resistance value of the developing roller increases, and in a conventional developing roller having a single-layer structure, It is difficult to balance these two conflicting characteristics.

The roller body of the developing roller has a structure including two layers of a cylindrical inner layer made of an elastic material and an outer layer made of an elastic material laminated on the outer peripheral surface of the inner layer, and adjusting the resistance values of both layers. It has been studied to achieve both of the above-mentioned two contradictory characteristics (see Patent Document 2 and the like).
That is, the black solid density is related to the resistance value near the surface of the roller body, and the black solid density can be improved by lowering the resistance value near the surface.

On the other hand, the 2dot density is related to the roller resistance value of the entire roller body, and the higher the overall roller resistance value, the higher the 2dot density can be.
for that reason,
The roller body has a structure including two layers, an inner layer and an outer layer, both of which are made of an elastic material;
・ The outer layer has a low resistance state in order to adjust the resistance value near the surface of the roller body to a range where the solid black density can be improved. ・ The inner layer under the outer layer is the same as the outer layer. If the overall roller resistance value is set to a high resistance state in order to adjust the roller resistance to a range where the 2dot density can be improved,
Both black solid density and 2 dot density can be achieved.

However, in the invention and the like described in Patent Document 2, since the setting of the resistance value range of the inner layer and the outer layer is not yet appropriate, the density of the image adjacent to the image to be formed in the horizontal direction orthogonal to the paper passing direction. In some cases, may cause density unevenness depending on the density.
According to the study of the inventor, the problem is to change the setting of the resistance value range of the inner layer and the outer layer, and to change the inner layer from the electronic conductive compound described in Patent Document 2 by using epichlorohydrin rubber as the rubber. By changing to a conductive composition, it can be reduced to some extent.

  However, it has been found that such a configuration causes a new problem that the image density particularly in the black solid portion gradually decreases while image formation is repeated.

JP 2014-80456 A JP-A-2006-95455

  An object of the present invention is to improve both the solid black density and the 2-dot density at the same time, to achieve excellent contrast and fine line reproducibility, and to obtain a good image without unevenness in density depending on the density of horizontally adjacent images. An object of the present invention is to provide a developing roller that can form an image and that does not cause the image density of a solid black portion to gradually decrease even when image formation is repeated.

The present invention includes a roller main body, the roller main body includes a cylindrical inner layer made of an elastic material, and an outer layer made of an elastic material laminated on the outer peripheral surface of the inner layer,
The inner layer is made of a rubber composition containing acrylonitrile butadiene rubber (NBR) and a crosslinked product of a rubber composition containing an ion conductive agent,
The roller roller resistance value _{R 1} of the entire body (Omega, at 400V applied), and the roller resistance value _{R 2} (Omega, at 400V applied) in a state of the inner layer only of the formula (1):
0.1 ≦ logR ₂ −logR ₁ ≦ 1.0 (1)
And equation (2):
6.5 ≦ logR ₂ ≦ 8.5 (2)
Is a developing roller that satisfies both conditions.

  According to the present invention, both the solid black density and the 2-dot density are simultaneously improved, so that both the contrast and the reproducibility of fine lines are excellent, and there is no unevenness in density depending on the density of the image adjacent in the horizontal direction. It is possible to provide a developing roller that can form an image and that does not cause the image density of a solid black portion to gradually decrease even when image formation is repeated.

FIG. 1A is a perspective view showing the overall appearance of an example of the developing roller of the present invention, and FIG. 1B is an end view of the developing roller of the above example. FIG. 7 is a diagram illustrating a method for measuring the roller resistance value of the entire roller body and the inner layer.

As described above, the developing roller of the present invention includes a roller main body, the roller main body includes a cylindrical inner layer made of an elastic material, and an outer layer made of an elastic material laminated on the outer peripheral surface of the inner layer,
The inner layer is made of a crosslinked product of a rubber composition containing a rubber containing NBR and an ion conductive agent,
Roller resistance value _{R 1} of the entire roller body (Omega, at 400V applied), and the roller resistance _{R 2} in the state of the inner layer only (Omega, at 400V applied) have the formula (1):
0.1 ≦ logR ₂ −logR ₁ ≦ 1.0 (1)
And equation (2):
6.5 ≦ logR ₂ ≦ 8.5 (2)
Are satisfied.

According to the developing roller of the present invention, as described above, the roller body has a two-layer structure of an inner layer and an outer layer, and the inner layer contains NBR, which is a polar rubber, and an ionic conductive agent, thereby imparting ionic conductivity. Layer that does not contain (except) epichlorohydrin rubber.
Therefore, in combination with setting the roller resistance values R ₁ and R ₂ in a range that satisfies the expressions (1) and (2), both the black solid density and the 2-dot density are simultaneously improved, and the reproducibility of the contrast and the fine line is improved. A good image excellent in both can be formed.

In addition, it is possible to suppress the occurrence of density unevenness depending on the density of the image adjacent in the horizontal direction in the image, and it is possible to prevent the image density of the solid black portion from gradually decreasing even when image formation is repeated. It can also be suppressed.
These facts are clear from the results of Examples, Comparative Examples and Conventional Examples described later.
FIG. 1A is a perspective view showing an overall appearance of an example of a developing roller of the present invention, and FIG. 1B is an end view of the developing roller of the above example.

Referring to FIGS. 1A and 1B, a developing roller 1 of this example has an outer layer 4 made of an elastic material directly laminated on an outer peripheral surface 3 of a cylindrical inner layer 2 made of an elastic material. A roller body 5 having a two-layer structure is provided.
A shaft 7 is inserted into and fixed to the through hole 6 at the center of the inner layer 2.
The shaft 7 is integrally formed of a highly conductive material, for example, a metal such as iron, aluminum, an aluminum alloy, and stainless steel.

The shaft 7 is, for example, electrically connected to the roller body 5 via an adhesive having conductivity and is mechanically fixed, or a shaft having an outer diameter larger than the inner diameter of the through hole 6. By being press-fitted into the roller 6, it is electrically connected to the roller body 5 and is mechanically fixed.
Further, the shaft 7 may be electrically connected to the roller body 5 and mechanically fixed by using both methods.

An oxide film 9 is formed on the surface of the outer layer 4, that is, on the outer peripheral surface 8 of the roller body 5, as shown in an enlarged manner in both figures.
By forming the oxide film 9, the oxide film 9 can function as a dielectric layer to reduce the dielectric loss tangent tan δ of the developing roller 1, and the oxide film 9 can function as a low friction layer to reduce the toner Adhesion can also be satisfactorily suppressed.

Moreover, the oxide film 9 can be easily formed only by oxidizing the rubber near the outer peripheral surface 8 by, for example, irradiating the outer peripheral surface 8 with ultraviolet rays in an oxidizing atmosphere, so that the productivity of the developing roller 1 is improved. It is also possible to suppress a decrease in the cost and an increase in the production cost.
However, the oxide film 9 may be omitted.
Each of the inner layer 2 and the outer layer 4 is preferably formed as a non-porous single layer in order to simplify their structures and improve durability and the like.

The “single layer” of the outer layer 4 indicates that the number of layers made of an elastic material is a single layer.
The “two layers” of the roller body 5 also means that the number of layers of both the inner layer 2 and the outer layer 4 made of an elastic material is two, and in any case, an oxide film formed by irradiation of ultraviolet rays or the like. 9 is not included in the number of layers.
In the present invention, the roller resistance value of the entire roller body 5 _{R 1} (Omega, at 400V applied), and the roller resistance value in the state of only the inner layer 2 _{R 2} (Omega, at 400V applied) were respectively above formula The reason for limiting the range to satisfy (1) and (2) is as follows.

That is, when the difference logR ₂ −logR ₁ between the common logarithmic values logR ₁ and logR ₂ of the roller resistance values R ₁ and R ₂ represented by the formula (1) is less than 0.1, the vicinity of the surface of the roller body 5 is reduced. The resistance value cannot be sufficiently reduced to a range where the solid black density can be improved.
For this reason, the black solid density is insufficient and the contrast of the image is reduced.
If the difference logR ₂ −logR ₁ exceeds 1.0, the resistance near the surface of the roller body 5 becomes too low, and for example, an image is likely to be defective due to an overcurrent in the image.

Further, the roller resistance value _{R 2} in the state of only the inner layer 2 is less than 6.5 expressed in common logarithm logR _2, the roller resistance value _{R 1} of the entire roller body 5 combined with the outer layer 4, 2 dot The density cannot be sufficiently increased to a range where the density can be improved.
As a result, the 2dot density is insufficient, the reproducibility of fine lines in the image is reduced, and the image tends to be blurred.

On the other hand, the image roller resistance value R ₂ in the state of only the inner layer 2, when it exceeds 8.5, expressed in common logarithm logR ₂ causes the image, adjacent to the transverse direction perpendicular to the feed direction of the paper Is likely to be generated depending on the density.
On the other hand, by setting the roller resistance values R ₁ and R ₂ within the ranges satisfying the equations (1) and (2), both the black solid density and the 2 dot density are improved at the same time, and the reproduction of the contrast and the thin line is performed. Sex can be improved.

In addition to the fact that the inner layer 2 is a layer provided with ionic conductivity by including NBR and an ionic conductive agent, unevenness in density depending on the density of an image adjacent in the horizontal direction occurs in an image. It can also be suppressed.
Accordingly, it is possible to form a good image which is excellent in both the contrast and the reproducibility of fine lines and which has no unevenness in density depending on the density of the image adjacent in the horizontal direction.

Further, when the roller resistance values R ₁ and R ₂ are in the ranges satisfying the expressions (1) and (2), respectively, and the inner layer 2 is formed as the above-described layer, the image formation is repeated when the image formation is repeated. It is possible to suppress a decrease in the image density of the solid black portion, that is, a decrease in the durability image density.
<Measurement of roller resistance>
FIG. 2 is a diagram illustrating a method for measuring the roller resistance value of the entire roller body and the inner layer.

Roller resistance value R ₁ of the entire of the roller body _5, and the roller resistance value R ₂ of the inner layer 2, in the present invention, each temperature of 23 ° C., under a relative humidity of 55% normal temperature and normal humidity environment was measured by the following method It is represented by a value.
Referring to FIGS. 1 and 2, first, an aluminum drum 10 that can be rotated at a constant rotation speed is prepared, and an inner layer before forming an outer layer 4 is formed on an outer peripheral surface 11 of the prepared aluminum drum 10 from above. The outer peripheral surface 3 of the roller body 2 or the outer peripheral surface 8 of the roller body 5 is brought into contact with the roller body 5.

Also, a DC power supply 12 and a resistor 13 are connected in series between the shaft 7 and the aluminum drum 10 to form a measuring circuit 14.
In the DC power supply 12, the (−) side is connected to the shaft 7 and the (+) side is connected to the resistor 13, and the resistance value r of the resistor 13 is 100Ω.
Next, a load F of 450 g is applied to both ends of the shaft 7, and the aluminum drum 10 is rotated at 40 rpm while the roller body 5 or the inner layer 2 is pressed against the aluminum drum 10.

Then, while continuing the rotation, when the applied voltage E of 400 V DC is applied from the DC power supply 12 between the roller body 5 or the inner layer 2 and the aluminum drum 10, the detection voltage V applied to the resistor 13 is measured.
From the detection voltage V and the applied voltage E (= 400 V), the roller resistance value R ₁ of the entire roller body 5 or the roller resistance value R ₂ of the inner layer ₂ (collectively referred to as “R” in the following formula) is basically Equation (i '):
R = r × E / V−r (i ′)
Required by However, since the term -r in the formula (i ') can be regarded as minute, in the present invention, the formula (i):
R = r × E / V (i)
The roller resistance value R ₁ of the entire roller body 5 or the roller resistance value R _{2 of the} inner layer 2 is determined by the value obtained by the above.

<< Rubber composition for inner layer 2 >>
As described above, the inner layer 2 is formed by a crosslinked product of a rubber composition provided with ionic conductivity by containing a rubber containing NBR and an ionic conductive agent.
<NBR>
Examples of NBR include low nitrile NBR having an acrylonitrile content of 24% or less, medium nitrile NBR having 25 to 30%, medium high nitrile NBR having 31 to 35%, high nitrile NBR having 36 to 42%, and 43% or more. Any very high nitrile NBR can be used.

As the NBR, there are an oil-extended type in which the flexibility is adjusted by adding an extending oil, and a non-oil-extended type in which the NBR is not added. In the present invention, in order to prevent contamination of the photoreceptor and the like, It is preferable to use a non-oil-extended type NBR that does not contain an extender oil that can be a bleed material.
One or more of these NBRs can be used.
<Other rubber>
As the rubber, other rubbers such as a diene rubber and an ethylene propylene rubber may be used together with the NBR.

(Diene rubber)
The diene rubber containing NBR imparts good processability to the rubber composition, improves the mechanical strength and durability of the inner layer 2, or provides the inner layer 2 with good properties as a rubber, that is, flexibility. In addition, it functions to impart a property that compression set is small and set hardly occurs.

Examples of the diene rubber include natural rubber, isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), and chloroprene rubber (CR).
Among them, the diene rubber is preferably a non-polar diene rubber, specifically, at least one of IR, BR, and SBR.
・ IR
As the IR, any of various IRs having a polyisoprene structure, which artificially reproduces the structure of natural rubber, can be used.

As the IR, there are an oil-extended type in which the flexibility is adjusted by adding extender oil and a non-oil-extended type in which the oil is not added. In the present invention, in order to prevent contamination of the photoreceptor as well, It is preferable to use a non-oil-extended type IR that does not contain an extender oil that can be a bleed material.
One or more of these IRs can be used.
・ BR
As the BR, any of 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 a low temperature to a high temperature, is preferable.
As the BR, there are an oil-extended type in which the flexibility is adjusted by adding an extending oil, and a non-oil-extended type in which the BR is not added. In the present invention, in order to prevent contamination of the photoreceptor as well, It is preferable to use a non-oil-extended BR that does not contain an extender oil that can be a bleed material.

One or more of these BRs can be used.
・ SBR
As the SBR, any of various SBRs synthesized by copolymerizing styrene and 1,3-butadiene by various polymerization methods such as an emulsion polymerization method and a solution polymerization method can be used.
As the SBR, there are a high styrene type, a medium styrene type, and a low styrene type SBR classified according to the styrene content, and any of them can be used.

Particularly, SBR having a Mooney viscosity ML _{1 + 4} (100 ° C.) of 60 or less is preferable.
Further, as the SBR, there are an oil-extended type in which the flexibility is adjusted by adding an extending oil, and a non-oil-extended type in which the SBR is not added. It is preferable to use a non-oil-extended SBR that does not contain an extender oil that can be a bleed material.

One or more of these SBRs can be used.
(Ethylene propylene rubber)
Examples of the ethylene propylene rubber include ethylene propylene rubber (EPM), which is a copolymer of ethylene and propylene, and ethylene propylene diene rubber (EPDM), which is a copolymer of ethylene, propylene, and diene. EPDM is particularly preferred. .
・ EPDM
As EPDM, various copolymers obtained by copolymerizing ethylene, propylene, and diene can be used.

Examples of the diene include ethylidene norbornene (ENB) and dicyclopentadiene (DCPD).
EPDM is classified into an oil-extended type in which the flexibility is adjusted by adding an extending oil, and a non-oil-extended type in which the EPDM is not added. It is preferable to use a non-oil-extended type EPDM which does not contain an extender oil which can be a bleed material.

One or more of these EPDMs can be used.
(Ratio of rubber)
When NBR and another rubber are used in combination as the rubber, the proportion of each rubber can be arbitrarily set according to various characteristics required for the inner layer 2, in particular, the roller resistance value R ₂ , the flexibility of the inner layer 2, and the like.
However, for example, when NBR, a non-polar diene rubber and EPDM are used in combination, the ratio of NBR is preferably 30 parts by mass or more in a total amount of rubber of 100 parts by mass, and is preferably 60 parts by mass or less. Preferably it is.

The proportion of NBR is less than this range, the roller resistance value R ₂ in the state of only the inner layer 2 may exceed the scope of formula (2) described above, the image, adjacent to the transverse direction perpendicular to the feed direction of the paper Density unevenness depending on the density of the image to be formed is likely to occur.
On the other hand, when the proportion of NBR exceeds the above range, the proportion of the non-polar, high-resistance diene-based rubber relatively decreases.

Therefore, the roller resistance value R ₂ in the state of only the inner layer 2 becomes less than the range of formula (2) described above, the roller resistance value R ₁ of the entire roller body 5 combined with the outer layer 4, the 2dot concentration In some cases, it cannot be sufficiently increased to the extent that it can be improved.
In addition, the 2dot density may be insufficient, and the reproducibility of the thin line in the image may be reduced, and the image may be easily blurred.

In addition, since the proportion of EPDM excellent in light resistance, ozone resistance, weather resistance, and the like is relatively small, the light resistance, ozone resistance, weather resistance, and the like of the inner layer 2 may be reduced.
In contrast, the proportion of NBR by the above range, while maintaining the above effect of a combination of diene rubber and EPDM, adjusting the resistance value R ₂ of the inner layer 2 on the scope of formula (2) can do.

The proportion of EPDM is preferably at least 20 parts by mass, and more preferably at most 40 parts by mass, in the total amount of rubber of 100 parts by mass.
If the proportion of EPDM is less than this range, the above-mentioned effects of the combined use of EPDM may be insufficient, and the light resistance, ozone resistance, weather resistance, etc. of the inner layer 2 may be reduced.
On the other hand, if the proportion of EPDM is higher than the above range, becomes smaller proportion of relatively NBR is, the roller resistance value R ₂ may exceed the scope of formula (2) described above.

Then, the image tends to have uneven density depending on the density of the image adjacent in the horizontal direction orthogonal to the sheet passing direction.
The ratio of the nonpolar diene rubber is the remaining amount of NBR and EPDM.
That is, the ratio of the nonpolar diene rubber may be set such that the total amount of the rubber is 100 parts by mass when the ratio of NBR and EPDM is set to a predetermined value within the above-described range.

<Ionic conductive agent>
As the ionic conductive agent, a salt (ionic salt) of a cation and an anion having a fluoro group and a sulfonyl group in the molecule is preferable.
By blending ion conductive agent, and ionic conductivity further improvement of the rubber composition may further reduce the roller resistance value R ₂ of the inner layer 2.

Examples of the anion having a fluoro group and a sulfonyl group in the molecule, which constitute the ion salt, include one or two of a fluoroalkylsulfonic acid ion, a bis (fluoroalkylsulfonyl) imide ion, and a tris (fluoroalkylsulfonyl) methide ion. Species or more.
Among these, as the fluoroalkyl sulfonate ion, ^{_{e.g., CF 3 SO 3 -, C}} 4 F 9 SO 3 - 1 , two or more, 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 - include one or more of such ^{_{-, [(CF 3) 2}} CHOSO 2] 2 N.

Further, examples of the tris (fluoroalkylsulfonyl) methide ion include one or more of (CF ₃ SO ₂ ) ₃ C ⁻ , (CF ₃ CH ₂ OSO ₂ ) ₃ C ^{−, and the} like.
Examples of the cation include ions of alkali metals such as sodium, lithium and potassium, ions of Group 2 elements such as beryllium, magnesium, calcium, strontium and barium, ions of transition elements, cations of amphoteric elements, One or more of a quaternary ammonium ion, an imidazolium cation and the like can be mentioned.

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, in terms of the effect of lowering the roller resistance value _{R 2} of the inner layer 2 to improve the ionic conductivity of the rubber composition, _(CF 3 SO _{2) 2} NLi [lithium bis (trifluoromethanesulfonyl) imide Li-TFSI And / or (CF ₃ SO ₂ ) ₂ NK [potassium bis (trifluoromethanesulfonyl) imide, K-TFSI].

The ratio of the ionic conductive agent such as an ionic salt is preferably at least 0.1 part by mass, more preferably at most 1 part by mass, per 100 parts by mass of the total amount of rubber.
Is less than the rate that the range of the ion conductive agent, the roller resistance value R ₂ in the state of only the inner layer 2 may exceed the scope of formula (2) described above, the image, the horizontal direction perpendicular to the feed direction of the paper , The density unevenness depending on the density of the image adjacent to the image tends to occur.

On the other hand, if the proportion of the ion conductive agent is more than the above range, taken roller resistance value R ₂ is less than the range of formula (2) described above, the roller resistance value of the entire roller body 5 combined with the outer layer 4 R ₁ cannot be sufficiently increased to a range where the 2-dot concentration can be improved.
As a result, the 2dot density is insufficient, the reproducibility of fine lines in the image is reduced, and the image tends to be blurred.

In contrast, by the ratio of the ion conductive agent within the above range, it is possible to adjust the resistance value R ₂ of the inner layer 2 on the scope of formula (2).
<Crosslinking component>
The rubber composition for the inner layer 2 contains a crosslinking component for crosslinking the rubber.
As the crosslinking component, it is preferable to use a crosslinking agent for crosslinking the rubber and a crosslinking accelerator for promoting crosslinking of the rubber by the crosslinking agent.

Among them, examples of the crosslinking agent include a sulfur-based crosslinking agent, a thiourea-based crosslinking agent, a triazine derivative-based crosslinking agent, a peroxide-based crosslinking agent, and various monomers, and a sulfur-based crosslinking agent is particularly preferred.
(Sulfur-based crosslinking agent)
Examples of the sulfur-based crosslinking 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 tetramethylthiuram disulfide and N, N-dithiobismorpholine. And the like, with sulfur being particularly preferred.

The 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, in consideration of imparting good properties as rubber to the roller body. preferable.
In the case where, for example, oil-treated powder sulfur, dispersible sulfur, or the like is used as 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 a cross-linking agent, the ratio is preferably adjusted so that the ratio of sulfur contained in the molecule per 100 parts by mass of the total amount of rubber falls within the above range.
(Crosslinking accelerator)
Examples of the crosslinking accelerator for promoting crosslinking of rubber include thiuram-based accelerators, thiazole-based accelerators, thiourea-based accelerators, guanidine-based accelerators, sulfenamide-based accelerators, dithiocarbamate-based accelerators, and the like. Or one or more of these.

Of these, it is preferable to use a thiuram-based accelerator and a thiazole-based accelerator together.
Examples of the thiuram-based accelerator include one or more of tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide and the like. Thiuram monosulfide is preferred.

  Examples of the thiazole accelerator include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, a zinc salt of 2-mercaptobenzothiazole, a cyclohexylamine salt of 2-mercaptobenzothiazole, and 2- (4′- Morpholinodithio) benzothiazole or the like, and di-2-benzothiazolyl disulfide is particularly preferable.

In the above two 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 the rubber in consideration of, for example, sufficiently exhibiting the effect of promoting rubber crosslinking. Is preferably 1 part by mass or less.
Further, the ratio of the thiazole accelerator is preferably at least 0.3 part by mass, more preferably at most 2 parts by mass, per 100 parts by mass of the total amount of rubber.

<Carbon black>
The rubber composition for the inner layer 2 may further contain carbon black as a filler.
By blending carbon black, the mechanical strength and the like of the developing roller can be improved.
Examples of the carbon black include SAF, ISAF, HAF, FEF, and the like.

When conductive carbon black is used as carbon black, electronic conductivity can be imparted to the inner layer 2.
Examples of the conductive carbon black include acetylene black.
The proportion of carbon black is preferably at least 3 parts by mass, more preferably at most 25 parts by mass, per 100 parts by mass of the total amount of rubber.

<Others>
The rubber composition for the inner layer 2 may further contain various additives as necessary.
Examples of the additives include a cross-linking accelerator, a plasticizer, and a processing aid.
Among them, examples of the cross-linking accelerator include one or more of metal compounds such as zinc oxide (zinc white); fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid; Is mentioned.

The ratio of the crosslinking promoting aid is individually preferably 0.1 parts by mass or more, and more preferably 7 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 a polar wax. Examples of the processing aid include fatty acid metals such as zinc stearate. And the like.

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.
Various additives other than carbon black, such as fillers other than carbon black, deterioration inhibitors, scorch inhibitors, lubricants, pigments, antistatic agents, flame retardants, neutralizing agents, nucleating agents, co-crosslinking agents, etc. The agents may be blended in any ratio.

<Preparation of rubber composition>
The rubber composition for the inner layer 2 containing the components described above can be prepared in the same manner as in the related art.
First, the rubber is masticated, and then components other than the crosslinking component are added and kneaded, and finally, the crosslinking component is added and kneaded, whereby a rubber composition for the inner layer 2 is obtained.

For kneading, for example, a kneader, a Banbury mixer, an extruder, or the like can be used.
<< Rubber composition for outer layer 4 >>
The outer layer 4, in combination with the inner layer 2, the roller resistance value R ₁ of the entire of the roller body can be adjusted in the aforementioned range, it can be formed by various elastic materials.
In particular, the outer layer 4 is preferably formed of a crosslinked product of a rubber composition containing epichlorohydrin rubber and diene rubber.

<Epichlorohydrin rubber>
Examples of the epichlorohydrin rubber include epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allyl glycidyl ether binary copolymer, epichlorohydrin-ethylene oxide -Allylic glycidyl ether terpolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer, and the like.

Among them, a copolymer containing ethylene oxide, particularly ECO and / or GECO, is preferable.
The content of ethylene oxide in ECO and / or GECO is preferably at least 30 mol%, particularly preferably at least 50 mol%, and more preferably at most 80 mol%.

Ethylene oxide functions to lower the resistance value of the outer layer 4.
However, if the ethylene oxide content is less than this range, such a function cannot be sufficiently obtained, and the resistance value of the outer layer 4 may not be sufficiently reduced in some cases.
On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs, and the segmental movement of the molecular chain is hindered, so that the resistance value of the outer layer 4 tends to increase.

Further, the outer layer 4 after crosslinking may become too hard, or the viscosity of the rubber composition before crosslinking may increase upon heating and melting, and the processability of the rubber composition may decrease.
The epichlorohydrin content in the ECO is the balance of the ethylene oxide content.
That is, the epichlorohydrin content is preferably at least 20 mol%, more preferably at most 70 mol%, particularly preferably at most 50 mol%.

Further, the content of allyl glycidyl ether in GECO is preferably 0.5 mol% or more, particularly preferably 2 mol% or more, and more preferably 10 mol% or less, particularly preferably 5 mol% or less.
The allyl glycidyl ether itself functions as a side chain to secure a free volume, thereby suppressing crystallization of ethylene oxide and reducing the resistance value of the outer layer 4.

However, when the content of allyl glycidyl ether is less than this range, such a function cannot be sufficiently obtained, and the resistance value of the outer layer 4 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 content of allyl glycidyl ether exceeds the above range, the crosslink density of GECO becomes too high, so that the segmental motion of the molecular chain is hindered, and the resistance of the outer layer 4 tends to increase.

The epichlorohydrin content in GECO is the balance of the ethylene oxide content and the allyl glycidyl ether content.
That is, the epichlorohydrin content is preferably at least 10 mol%, particularly preferably at least 19.5 mol%, more preferably at most 69.5 mol%, particularly preferably at most 60 mol%.
As GECO, in addition to a copolymer in a narrow sense, in which the above-described three types of monomers were copolymerized, epichlorohydrin-ethylene oxide copolymer (ECO) was modified with allyl glycidyl ether. Modified products are also known.

In the present invention, any of these GECOs can be used.
GECO is particularly preferred as the epichlorohydrin rubber.
Since GECO has a double bond in the main chain that functions as a cross-linking point due to allyl glycidyl ether, the compression set after cross-linking can be reduced by cross-linking between main chains.

Therefore, the outer layer 4 can have a small compression set and is unlikely to cause settling.
One or more of these epichlorohydrin rubbers can be used.
<Diene rubber>
The diene rubber is used to impart good processability to the rubber composition, to improve the mechanical strength and durability of the outer layer 4, and to impart good rubber properties to the outer layer 4. Function.

The diene rubber is also oxidized by ultraviolet irradiation, and becomes a material for forming an oxide film 9 on the surface of the outer layer 4, that is, on the outer peripheral surface 8 of the roller body 5.
Examples of the diene rubber include natural rubber, IR, NBR, SBR, BR, CR and the like.
Above all, it is preferable to use a nonpolar diene rubber as the diene rubber, specifically, at least one of IR, BR, and SBR, particularly SBR.

As the SBR, one or more SBRs similar to those used in the inner layer 2 can be used.
Further, CR may be further blended as the diene rubber.
CR are the diene rubber having a polar As described above, the resistance value of the outer layer 4 itself, which functions to fine tune the roller resistance value R ₁ of the entire turn roller body 5.

As the CR, one or more CRs similar to those used in the inner layer 2 can be used.
(Ratio of rubber)
The proportion of the rubber can be arbitrarily set according to various characteristics required for the outer layer 4, such as a resistance value and flexibility.

However, the proportion of epichlorohydrin rubber is preferably at least 15 parts by mass, and more preferably at most 30 parts by mass, in 100 parts by mass of the total amount of rubber.
The proportion of the epichlorohydrin rubber is less than this range, too high resistance of the outer layer 4 itself, tend to roller resistance value R ₁ becomes high in the entire of the roller body 5.
When the difference logR ₂ −logR ₁ falls below the range of the above-described formula (1), the resistance value near the surface of the roller body 5 cannot be sufficiently reduced to a range where the solid black density can be improved. There is a case where the contrast of an image is lowered due to insufficient solid density.

On the other hand, if the proportion of the epichlorohydrin rubber exceeds the above range, the roller resistance value R ₁ of the entire of the roller body 5 tends to be low.
When the difference logR ₂ −logR ₁ exceeds the range of the above-described expression (1), and the resistance value near the surface of the roller body becomes too low, for example, an image is likely to have an image defect due to an overcurrent. There is.

Further, since the proportion of the diene rubber is relatively small, it may not be possible to impart good workability to the rubber composition or to impart good characteristics as a rubber to the outer layer 4.
On the other hand, by setting the proportion of the epichlorohydrin rubber in the above range, the resistance value of the outer layer 4 is reduced while maintaining the above-mentioned effect by using the diene rubber in combination, and the difference logR ₂ −logR ₁ is calculated by the following equation. It can be adjusted to the range of (1).

The ratio of CR is preferably at least 5 parts by mass in the total amount of rubber of 100 parts by mass, and more preferably at most 12 parts by mass.
The proportion of CR is less than this range, the effect described above by blending the CR, namely, the resistance value of the outer layer 4 itself, thus the roller overall roller resistance value obtained effect is sufficiently fine adjustment of the R ₁ of the main body 5 May not be possible.

On the other hand, if the proportion of CR exceeds the above range, relatively epichlorohydrin rubber is reduced, too high resistance of the outer layer 4 itself, higher roller resistance value R ₁ of the entire of the roller body 5 Tend to be.
When the difference logR ₂ −logR ₁ falls below the range of the above-described formula (1), the resistance value near the surface of the roller body 5 cannot be sufficiently reduced to a range where the solid black density can be improved. There is a case where the contrast of an image is lowered due to insufficient solid density.

The ratio of the non-polar diene rubber other than CR is epichlorohydrin rubber or the remaining amount of epichlorohydrin rubber and CR.
That is, the ratio of the non-polar diene rubber may be set so that the total amount of the rubber becomes 100 parts by mass when the ratio of the epichlorohydrin rubber or the epichlorohydrin rubber and CR is set to a predetermined value within the above-described range. .

<Crosslinking component>
As the cross-linking component, a cross-linking agent and a cross-linking accelerator are also preferably used in combination. As the cross-linking agent, a sulfur-based cross-linking agent, particularly sulfur, is preferable, as in the case of the inner layer 2.
It is preferable that the ratio of the sulfur-based crosslinking agent is approximately the same as that of the inner layer 2.
As the crosslinking accelerator to be combined with the sulfur-based crosslinking agent, it is preferable to use four kinds of thiuram-based accelerator, thiazole-based accelerator, thiourea-based accelerator, and guanidine-based accelerator together.

Among them, as the thiuram-based accelerator and the thiazole-based accelerator, the same compounds as those used in the inner layer 2 can be used.
It is preferable that the ratio of both crosslinking accelerators is also approximately the same as that of the inner layer 2.
As the thiourea-based accelerator, various thiourea compounds having a thiourea structure in the molecule can be used.

Examples of the thiourea-based accelerator include ethylene thiourea, N, N'-diphenylthiourea, trimethylthiourea, and formula (3):
_{(C n H 2n + 1 NH} ) 2 C = S (3)
[In the formula, n represents an integer of 1 to 12. And thiourea, tetramethylthiourea, etc. represented by the formula (1), and ethylene thiourea is particularly preferred.

The ratio of the thiourea-based accelerator is preferably at least 0.3 part by mass, more preferably at most 1 part by mass, per 100 parts by mass of the total amount of rubber.
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. Di-o-tolylguanidine is preferred.

The proportion of the guanidine-based accelerator is preferably at least 0.2 part by mass, more preferably at most 1 part by mass, per 100 parts by mass of the total amount of rubber.
The thiourea-based accelerator functions as an ECO crosslinking agent having no sulfur crosslinking property, and the guanidine-based accelerator also functions as an ECO crosslinking accelerator with the thiourea-based accelerator.
<Ionic conductive agent>
The rubber composition for the outer layer 4 may further contain an ionic conductive agent.

By blending ion conductive agent, and further improve the ionic conductivity of the rubber composition, the resistance of the outer layer 4 itself, can be further lowered roller resistance value R ₁ of the entire turn roller body 5.
As the ionic conductive agent, a salt (ionic salt) of a cation and an anion having a fluoro group and a sulfonyl group in the molecule, which is the same as that used in the inner layer 2, is preferable.

The proportion of the ionic conductive agent is preferably at least 0.5 part by mass, and more preferably at most 2 parts by mass, per 100 parts by mass of the total amount of rubber.
<Others>
The rubber composition for the outer layer 4 may further contain various additives as necessary.
Examples of the additive include an acid acceptor and the like.

The acid acceptor functions to prevent chlorine-based gas generated from epichlorohydrin rubber or CR during crosslinking from remaining in the inner layer 2, thereby preventing crosslinking inhibition, contamination of the photoreceptor, and the like.
As the acid acceptor, various substances acting as an acid acceptor can be used. Among them, hydrotalcites or Magsalat having excellent dispersibility are preferable, and hydrotalcites are particularly preferable.

When hydrotalcites and the like are used in combination with magnesium oxide and potassium oxide, a higher acid-accepting effect can be obtained, and contamination of the photoreceptor can be more reliably prevented.
The ratio of the acid acceptor is preferably at least 0.1 part by mass, more preferably at most 7 parts by mass, per 100 parts by mass of the total amount of rubber.
Further, as additives, the same additives as used in the inner layer 2, for example, a crosslinking accelerator, an acid acceptor, a filler, a plasticizer, a processing aid, a deterioration inhibitor, a deterioration inhibitor, a scorch inhibitor , A lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizing agent, a nucleating agent, a co-crosslinking agent and the like.

It is preferable that the ratio of the additive is approximately the same as that of the inner layer 2.
<Preparation of rubber composition>
The rubber composition for the outer layer 4 containing the components described above can be prepared in the same manner as the conventional one.
That is, first, the rubber is masticated, then components other than the crosslinking component are added and kneaded, and finally, the crosslinking component is added and kneaded, whereby a rubber composition for the outer layer 4 is obtained.

For kneading, for example, a kneader, a Banbury mixer, an extruder, or the like can be used.
<< Manufacture of developing roller 1 >>
To produce the developing roller 1 shown in FIGS. 1A and 1B using the rubber compositions for the inner layer 2 and the outer layer 4, for example, both rubber compositions are supplied to a two-layer extruder. Then, after co-extrusion molding into a laminated two-layered cylindrical shape, the whole is crosslinked to form the inner layer 2 and the outer layer 4.

Alternatively, the rubber composition for the inner layer 2 is extruded into a tubular shape and cross-linked to form the inner layer 2, and then a sheet of the rubber composition for the outer layer 4 is wound around the outer peripheral surface 3, and pressed or the like. The outer layer 4 is formed while being formed into a tubular shape and crosslinked, and integrated with the inner layer 2.
Next, the formed laminate of the inner layer 2 and the outer layer 4 is subjected to secondary crosslinking by heating using an oven or the like, cooled, and then polished to a predetermined outer diameter. It is formed.

The thickness of the inner layer 2 can be arbitrarily set according to the structure and dimensions of the image forming apparatus to be incorporated.
Although the thickness of the outer layer 4 can be arbitrarily set, it is preferably 0.1 mm or more, and more preferably 2 mm or less.
The thickness of the outer layer 4 having a predetermined resistance value in this range, when combined with the inner layer 2 having a predetermined roller resistance value R _2, the roller resistance value R ₁ of the entire of the roller body 5, above The range can be adjusted.

Therefore, it is possible to simultaneously improve both the solid black density and the 2-dot density, to provide both excellent contrast and reproducibility of fine lines, and to form a good image without unevenness in density depending on the density of an image adjacent in the horizontal direction. In addition, even when image formation is repeated, the effect of suppressing a gradual decrease in image density, particularly in a solid black portion, can be further improved.
As a polishing method, for example, various polishing methods such as dry traverse polishing can be employed, and mirror polishing may be performed at the end of the polishing step to finish the polishing.

In this case, the releasability of the outer peripheral surface 8 is improved, and the adhesion of the toner is more favorably suppressed without forming the oxide film 9 or by a synergistic effect with the formation of the oxide film 9. In addition, contamination of the photoreceptor and the like can be effectively prevented.
The shaft 7 can be inserted into the through hole 6 and fixed at any time from after the cylindrical body that forms the base of the roller body 5 is cut until after the polishing.

However, after cutting, it is preferable to first perform secondary crosslinking and polishing in a state where the shaft 7 is inserted through the through hole 6. Thereby, warpage and deformation of the roller body 5 due to expansion and contraction at the time of secondary crosslinking can be suppressed.
Further, by polishing while rotating the shaft 7 as a center, the workability of the polishing can be improved, and the deflection of the outer peripheral surface 8 can be suppressed.

As described above, the shaft 7 is inserted into the through-hole 6 of the tubular body before the secondary cross-linking through the conductive adhesive, particularly the conductive thermosetting adhesive, and then subjected to the secondary cross-linking. Alternatively, a material having an outer diameter larger than the inner diameter of the through hole 6 may be pressed into the through hole 6.
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, so that the shaft 7 is electrically connected to the roller body 5 and mechanically. Fixed to.

In the latter case, electrical joining and mechanical fixing are completed simultaneously with press-fitting.
As described above, the shaft 7 may be electrically connected to the roller body 5 and mechanically fixed by using both of the methods.
As described above, the oxide film 9 is preferably formed by irradiating the outer peripheral surface 8 of the roller body 5, which is the surface of the outer layer 4, with ultraviolet rays.

That is, the oxide film 9 can be formed simply by irradiating the outer peripheral surface 8 of the roller main body 5 with ultraviolet light having a predetermined wavelength for a predetermined time and oxidizing the rubber constituting the vicinity of the outer peripheral surface 8, thereby being simple and efficient. .
In addition, the oxide film 9 formed by the irradiation of the ultraviolet rays does not cause a problem such as, for example, a conventional coating film formed by applying a coating agent. Also has excellent adhesion and the like.

The wavelength of the ultraviolet light to be irradiated is preferably 100 nm or more in consideration of efficiently oxidizing the diene rubber in the rubber composition for the outer layer 4 to form the oxide film 9 having the above-described excellent function. , 400 nm or less, particularly preferably 300 nm or less.
The irradiation time is preferably 30 seconds or more, particularly preferably 1 minute or more, and is preferably 30 minutes or less, particularly preferably 20 minutes or less.

However, the oxide film 9 may be formed by another method, or may not be formed in some cases.
One or more optional intermediate layers may be interposed between the inner layer 2 and the outer layer 4.
However, considering the simplification of the structure of the roller body 5, the roller body 5 has a two-layer structure in which the inner layer 2 and the outer layer 4 are directly laminated as shown in FIGS. 1 (a) and 1 (b). Is preferred.

  The developing roller 1 of the present invention can be used by being incorporated in various image forming apparatuses using an electrophotographic method, such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a multifunction machine thereof. .

Hereinafter, the present invention will be further described based on examples, comparative examples, and conventional examples, but the configuration of the present invention is not necessarily limited to these examples.
<Rubber composition (A) for inner layer 2>
Examples of the rubber include NBR (Nipol (registered trademark) DN3335 manufactured by Zeon Corporation, acrylonitrile content: 33.0%, middle and high nitrile NBR) 55 parts by mass, IR [Nipol IR2200 manufactured by Zeon Corporation, non-oil 23 parts by mass, and 22 parts by mass of EPDM [Esprene (registered trademark) EPDM 505A manufactured by Sumitomo Chemical Co., Ltd., ethylene content: 50%, diene content: 9.5%, non-oil extension].

  The following components were blended and kneaded while masticating a total amount of 100 parts by mass of the rubber using a Banbury 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.
Ion salt: potassium bis (trifluoromethanesulfonyl) imide, EF-N112, K-TFSI manufactured by Mitsubishi Materials Electronic Chemicals, Inc.
Crosslinking accelerator: 2 types of zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd. Filler: carbon black FEF, SEAST (registered trademark) SO manufactured by Tokai Carbon Co., Ltd.
Processing aid: zinc stearate, SZ-2000 manufactured by Sakai Chemical Industry Co., Ltd.
Next, while the kneading was continued, the following crosslinking components were blended and further kneaded to prepare a rubber composition (A) for the inner layer 2.

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.
Crosslinking agent: Kanahana 5% oil-containing fine powder sulfur accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. DM: di-2-benzothiazolyl disulfide, Noxeller (registered trademark) DM manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Thiazole accelerator Accelerator TS: tetramethylthiuram monosulfide, Suncellar (registered trademark) TS manufactured by Sanshin Chemical Industry Co., Ltd., thiuram accelerator <Rubber composition (B) for inner layer 2>
A rubber composition (B) for the inner layer 2 was prepared in the same manner as the rubber composition (A) except that the amount of NBR was 35 parts by mass and the amount of IR was 43 parts by mass.

<Rubber composition (C) for inner layer 2>
Rubber composition (A) except that 35 parts by mass of low nitrile NBR [Nipol DN401LL manufactured by Nippon Zeon Co., Ltd., acrylonitrile content: 18.0%] was used as the NBR and the amount of IR was 43 parts by mass. In the same manner as in the above, a rubber composition (C) for the inner layer 2 was prepared.

<Rubber composition (D) for inner layer 2>
A rubber composition (D) for the inner layer 2 was prepared in the same manner as the rubber composition (C) except that the amount of NBR was 55 parts by mass and the amount of IR was 23 parts by mass.
<Rubber composition (E) for inner layer 2>
A rubber composition (E) for the inner layer 2 was prepared in the same manner as the rubber composition (A) except that the amount of the ionic salt was 0.8 parts by mass per 100 parts by mass of the total amount of rubber.

<Rubber composition (F) for inner layer 2>
A rubber composition (F) for the inner layer 2 was prepared in the same manner as the rubber composition (E) except that the same amount of SBR (JSR 1502 manufactured by JSR Corporation, non-oil-extended) was used instead of IR. Was prepared.
<Rubber composition (G) for inner layer 2>
A rubber composition (G) for the inner layer 2 was prepared in the same manner as the rubber composition (A) except that the amount of IR was 10 parts by mass and the amount of EPDM was 35 parts by mass.

<Rubber composition (H) for inner layer 2>
As rubber, 12.5 parts by mass of GECO [Epion (registered trademark) 301L, manufactured by Osaka Soda Co., Ltd., EO / EP / AGE = 73/23/4 (molar ratio)], IR [manufactured by Zeon Corporation) IR2200, non-oil-extended) 41.25 parts by mass, BR [UBEPOL (registered trademark) BR130B manufactured by Ube Industries, Ltd., non-oil-extended] 41.25 parts by mass, and CR [Showa Denko KK] Showrene (registered trademark) WRT, non-oil extended] 5 parts by mass.

  The following components were blended and kneaded while masticating a total amount of 100 parts by mass of the rubber using a Banbury mixer.

Each component in Table 3 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.
Ion salt: potassium bis (trifluoromethanesulfonyl) imide, EF-N112, K-TFSI manufactured by Mitsubishi Materials Electronic Chemicals, Inc.
Crosslinking accelerator: 2 types of zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd. Filler: carbon black FEF, Seat SO manufactured by Tokai Carbon Co., Ltd.
Acid acceptor: 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.
Next, while the kneading was continued, the following crosslinking components were blended and further kneaded to prepare a rubber composition (A) for the inner layer 2.

Each component in Table 4 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.
Crosslinking agent: Kanahana 5% oil-containing fine powder sulfur accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. DM: di-2-benzothiazolyl disulfide, Noxeller DM manufactured by Ouchi Shinko Chemical Industry Co., Ltd., thiazole accelerator Accelerator TS: tetramethylthiuram monosulfide, Suncellar TS manufactured by Sanshin Chemical Industry Co., Ltd., thiuram-based accelerator Accelerator 22: ethylene thiourea [Axel (registered trademark) 22-S manufactured by Kawaguchi Chemical Industry Co., Ltd.] 2-mercaptoimidazoline]
Accelerator DT: 1,3-di-o-tolyl guanidine [Sancellar DT manufactured by Sanshin Chemical Industry Co., Ltd., guanidine-based accelerator]
<Rubber composition for inner layer 2 (J)>
The rubber composition (J) for the inner layer 2 was prepared in the same manner as the rubber composition (H) except that the amount of GECO was 15 parts by mass, the amount of IR was 40 parts by mass, and the amount of BR was 40 parts by mass. Prepared.

<Rubber composition (K) for inner layer 2>
Rubber composition for inner layer 2 in the same manner as rubber composition (H) except that the amount of GECO was 20 parts by mass, the amount of IR was 37.5 parts by mass, and the amount of BR was 37.5 parts by mass. (K) was prepared.
<Rollers measurement of the resistance value _{R 2} of the inner layer 2>
The rubber compositions (A) to (F) for the inner layer 2 are extruded into a cylindrical shape having an outer diameter of 16 mm and an inner diameter of 6.5 mm, mounted on a temporary shaft for cross-linking, and placed in a vulcanizer at 160 ° C. × Crosslinked for 1 hour.

Next, the crosslinked tubular body is applied to a metal shaft 7 having an outer diameter φ7.5 mm, which is the same as that actually used for manufacturing the developing roller 1, having a conductive thermosetting adhesive applied to the outer peripheral surface. It was re-attached and heated to 160 ° C. in an oven to adhere to the shaft 7.
Next, while shaping both ends of the cylindrical body, the outer peripheral surface 3 is traverse-polished using a cylindrical grinder, and then mirror-polished as a finish so as to have an outer diameter of φ16 mm. An integrated sample having only the inner layer 2 was prepared.

Then, the roller resistance value R ₂ (Ω, 400 V applied) of the manufactured sample in the state of only the inner layer 2 was measured by the measurement method described above.
<Rubber composition (I) for outer layer 4>
As the rubber, GECO [Epion 301L manufactured by Osaka Soda Co., Ltd., EO / EP / AGE = 73/23/4 (molar ratio)] 12 parts by mass, SBR [JSR 1502 manufactured by JSR Corporation, Non-Oil Exhibition 78 parts by mass and CR (Showa Denko K.K., Showen WRT, non-oil extended) 10 parts by mass.

  The following components were blended and kneaded while masticating a total amount of 100 parts by mass of the rubber using a Banbury mixer.

Each component in Table 5 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.
Ion salt: potassium bis (trifluoromethanesulfonyl) imide, EF-N112, K-TFSI manufactured by Mitsubishi Materials Electronic Chemicals, Inc.
Crosslinking accelerator: 2 types of zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd. Filler: carbon black (thermal black), Asahi # 15 manufactured by Asahi Carbon Co., Ltd.
Acid acceptor: hydrotalcites, DHT-4A-2 manufactured by Kyowa Chemical Industry Co., Ltd.
Processing aid: zinc stearate, SZ-2000 manufactured by Sakai Chemical Industry Co., Ltd.
Next, while the kneading was continued, the following crosslinking components were blended and further kneaded to prepare a rubber composition (I) for the outer layer 4.

Each component in Table 6 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.
Crosslinking agent: Kanahana 5% oil-containing fine powder sulfur accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. DM: di-2-benzothiazolyl disulfide, Noxeller DM manufactured by Ouchi Shinko Chemical Industry Co., Ltd., thiazole accelerator Accelerator TS: tetramethylthiuram monosulfide, Suncellar TS manufactured by Sanshin Chemical Industry Co., Ltd., thiuram-based accelerator Accelerator 22: ethylenethiourea [Axel 22-S, 2-mercaptoimidazoline manufactured by Kawaguchi Chemical Industry Co., Ltd.] ]
Accelerator DT: 1,3-di-o-tolyl guanidine [Sancellar DT manufactured by Sanshin Chemical Industry Co., Ltd., guanidine-based accelerator]
<Rubber composition (II) for outer layer 4>
A rubber composition (II) for the outer layer 4 was prepared in the same manner as the rubber composition (I) except that the amount of GECO was 30 parts by mass and the amount of SBR was 60 parts by mass.

<Rubber composition (III) for outer layer 4>
A rubber composition (III) for the outer layer 4 was prepared in the same manner as the rubber composition (I) except that the amount of GECO was 20 parts by mass and the amount of SBR was 70 parts by mass.
<Rubber composition (IV) for outer layer 4>
A rubber composition (IV) for the outer layer 4 was prepared in the same manner as the rubber composition (I) except that the amount of GECO was 15 parts by mass and the amount of SBR was 75 parts by mass.

<Rubber composition (V) for outer layer 4>
A rubber composition (V) for the outer layer 4 was prepared in the same manner as the rubber composition (I) except that the amount of GECO was 12 parts by mass and the amount of SBR was 78 parts by mass.
<Examples 1 to 6, Comparative Examples 1 to 8>
The rubber compositions (A) to (K) for the inner layer 2 and the rubber compositions (I) to (V) for the outer layer 4 were supplied to a two-layer extruder in combinations shown in Tables 7 to 9, Extruded into a two-layered cylinder with an outer diameter of 16 mm, an inner diameter of 6.5 mm, and a thickness of 3.5 mm of the cylindrical body from which the inner layer 2 is formed, and mounted on a temporary shaft for cross-linking, a vulcanizing can Crosslinking was performed at 160 ° C. for 1 hour.

Next, the crosslinked tubular body is re-mounted on a metal shaft 7 having an outer diameter of 7.5 mm with a conductive thermosetting adhesive applied to the outer peripheral surface, and heated to 160 ° C. in an oven. It was adhered to the shaft 7.
Next, while shaping both ends of the cylindrical body, the outer peripheral surface 8 is traverse-polished using a cylindrical grinder, and then mirror-polished as a finish so as to have an outer diameter of 16 mm. The roller body 5 having a layer structure and integrated with the shaft 7 was formed.

The thickness of the outer layer 4 was about 0.1 to 2 mm.
Next, after the outer peripheral surface 8 of the formed roller main body 5 is wiped with alcohol, the distance from the outer peripheral surface 8 to the UV lamp is set to 50 mm, and an ultraviolet irradiation device [PL21- manufactured by Sen Special Light Source Co., Ltd.] is used. 200].
Then, the developing roller 1 was manufactured by irradiating ultraviolet rays having wavelengths of 184.9 nm and 253.7 nm for 15 minutes each while rotating the shaft by 90 ° about the shaft, thereby forming the oxide film 9 on the outer peripheral surface 8. .

<Conventional Examples 1-4>
The rubber composition (II) to (V) for the outer layer 4 is used alone and is extruded into a cylindrical shape having an outer diameter of 16 mm and an inner diameter of 6 mm, mounted on a temporary shaft for cross-linking, and placed in a vulcanizing can for 160 hours. C. × 1 hour for crosslinking.
Next, the crosslinked tubular body is re-mounted on a metal shaft 7 having an outer diameter of 7.5 mm with a conductive thermosetting adhesive applied to the outer peripheral surface, and heated to 160 ° C. in an oven. It was adhered to the shaft 7.

Next, while shaping both ends of the cylindrical body, the outer peripheral surface 8 is traverse-polished using a cylindrical grinder, and then mirror-polished as a finish so as to have an outer diameter of 16 mm. And a roller body integrated with the shaft 7 was formed.
Then, after wiping the outer peripheral surface of the formed roller main body with alcohol, the distance from the outer peripheral surface to the UV lamp was set to be 50 mm, and the ultraviolet irradiation device [PL21-200 manufactured by Sen Special Light Source Co., Ltd.] was used. I set it.

Then, while being rotated by 90 ° about the shaft, ultraviolet rays having wavelengths of 184.9 nm and 253.7 nm were irradiated for 15 minutes each to form an oxide film on the outer peripheral surface, thereby manufacturing a developing roller.
With respect to the developing roller 1 manufactured in each of the above Examples, Comparative Examples, and Conventional Examples, the following tests were performed to evaluate the characteristics.

<Rollers measurement of the resistance value R ₃ of the whole of the roller body 5>
The roller resistance value R ₁ (Ω, 400 V applied) of the entire developing roller body 5 of the manufactured developing roller 1 was measured by the above-described measuring method.
<Measurement of solid black density>
The produced developing roller was incorporated in a laser printer [HL-2240D manufactured by Brother Industries, Ltd.], and an image of 1% density was continuously formed on plain paper under an environment of a temperature of 23.5 ° C. and a relative humidity of 55%. Immediately after continuous image formation, one 3 cm square black solid image was formed.

Then, image densities were measured at arbitrary five points on the formed solid black image using a reflection densitometer manufactured by VideoJet X-Rite Co., Ltd., and the average value was obtained as the solid black density. The black solid density was 1.30 or more.
<Measurement of 2dot concentration>
Immediately after forming 4000 continuous 1% density images on plain paper in the same manner as the black solid density, one isolated 2 dot image in which circles are arranged on a square lattice with a lattice length of about 80 μm is immediately obtained. Formed.

Then, image densities were measured at any five points on the formed isolated two-dot image using the same reflection densitometer, and the average value was determined to obtain a two-dot density. Those having a 2dot concentration exceeding 0.02 were accepted.
<Evaluation of density unevenness>
Similar to the solid black density, immediately after 4,000 images of 1% density are continuously formed on plain paper, a half-tone portion of 3 cm width and the paper passing direction of the half-tone portion are determined. One image having a 3 cm square black solid portion was formed by adjoining at a distance of 5 mm in the transverse direction perpendicular to the image.

Then, the halftone portion of the formed image was observed, and those without unevenness were evaluated as good (良好), and those with unevenness were evaluated as poor (x).
<Measurement of durability image density>
The developing roller is incorporated in a laser printer [HL-2240D manufactured by Brother Industries, Ltd.], and 3,000 sheets of 1% density images are continuously printed on plain paper under an environment of a temperature of 23.5 ° C. and a relative humidity of 55%. Immediately after forming an image, one black solid image of 3 cm square was formed.

Then, the image density was measured at any five points on the formed solid black image using a reflection densitometer manufactured by VideoJet X-Rite Co., Ltd., and the average value was obtained to obtain the durability image density. The durability image density was 1.30 or more.
Tables 7 to 9 show the above results.

From the results of Conventional Examples 1 to 4 shown in Table 9, it was found that the black solid density and the 2-dot density were not compatible with the single-layer roller body.
On the other hand, from the results of Examples 1 to 6 and Comparative Examples 1 to 8 in Tables 7 to 9, the roller resistances R ₁ and R ₂ satisfy the equations (1) and (2). It has been found that by combining the above, both the solid black density and the 2-dot density can be simultaneously improved, and an image excellent in both contrast and reproducibility of fine lines can be formed.

It has also been found that unevenness in density depending on the density of the image adjacent in the horizontal direction can be suppressed in the image.
Further, from the results of Examples 1 to 6 and Comparative Examples 3 to 8, even if image formation is repeated, black is obtained especially by forming the inner layer 2 as a layer containing NBR and an ionic conductive agent and given ionic conductivity. It was also found that a decrease in the image density of the solid portion could be suppressed.

DESCRIPTION OF SYMBOLS 1 Developing roller 2 Inner layer 3 Outer surface 4 Outer layer 5 Roller body 6 Through hole 7 Shaft 8 Outer surface 9 Oxide film 10 Aluminum drum 11 Outer surface 12 DC power supply 13 Resistance 14 Measurement circuit F Load V Detection voltage

Claims (3)

Including a roller body, the roller body includes a cylindrical inner layer made of an elastic material, and an outer layer made of an elastic material laminated on the outer peripheral surface of the inner layer,
The inner layer is made of a rubber containing acrylonitrile butadiene rubber, and a crosslinked product of a rubber composition containing an ion conductive agent,
The roller roller resistance value _{R 1} of the entire body (Omega, at 400V applied), and the roller resistance value _{R 2} (Omega, at 400V applied) in a state of the inner layer only of the formula (1):
0.1 ≦ logR ₂ −logR ₁ ≦ 1.0 (1)
And equation (2):
6.5 ≦ logR ₂ ≦ 8.5 (2)
A developing roller that satisfies both.   The developing roller according to claim 1, wherein the rubber further includes at least one selected from the group consisting of isoprene rubber, butadiene rubber, and styrene butadiene rubber, and ethylene propylene diene rubber.   The developing roller according to claim 1, wherein the ionic conductive agent is a salt of a cation and an anion having a fluoro group and a sulfonyl group.

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