JP5243763B2 - Developing roll - Google Patents

Description

The present invention relates to a developing roll used in an electrophotographic apparatus such as a copying machine, a printer, or a facsimile.

In a conventional developing roll, a conductive elastic layer (base layer) is formed on a concentric circle of a metal shaft body such as SUS, and a binder, a conductive agent, and other additives (roughness formation) are formed on the conductive elastic layer. A single layer or a plurality of resin layers including an agent or the like. As the outermost resin layer, a forming material in which a conductive agent such as carbon black is blended with a binder polymer such as acrylic resin, polycarbonate urethane, or ether urethane is used (for example, Patent Document 1, Patent Document 1). 2).
JP 2003-3032 A JP 2002-363426 A

In the developing roll in which the outermost layer is formed of a forming material using an electronic conductive agent such as carbon black as the conductive agent, the middle level (semiconductive region) electric resistance (5
If it is going to obtain (x10 < ⁵ > -5x10 < ⁶ > (omega | ohm)), in an electronic electrically conductive agent which can obtain desired electrical resistance with a small quantity of mixing | blending, electrical resistance will fluctuate and variation will arise. In addition, in an electronic conductive agent with good dispersibility, as the blending amount of the electronic conductive agent increases, toner and external additives adhere to the surface of the developing roll (filming), and the surface roughness increases. As a result, the amount of toner transport increases,
The toner chargeability is deteriorated due to the change of the roll surface, and a problem of image defects (fogging, roughness, density unevenness, etc.) occurs.

Furthermore, when trying to obtain a moderate electrical resistance using an electronic conductive agent capable of obtaining a desired electrical resistance with a small amount of the above composition, the dependence of the electronic conductive agent on the electrical resistance is usually large. In addition, since the dispersibility with the binder is greatly affected, it is easily affected by various factors such as mixing and shear (shear stress) by a pump. Moreover, when it is going to obtain a moderate electrical resistance using the said electronic conductive agent with favorable dispersibility, it is necessary to increase the compounding quantity of an electronic conductive agent, and the compounding quantity of a dispersing agent also increases in connection with it. When the amount of the dispersant increases, naturally, the active group of the dispersant also remains, and this binds to the toner, resulting in a problem that the toner adheres to the surface of the developing roll (filming).

The present invention has been made in view of such circumstances, and provides a developing roll capable of obtaining excellent images by suppressing toner adhesion (filming) and toner accumulation by improving the dispersibility of the conductive agent. For that purpose.

In order to achieve the above object, a developing roll of the present invention is a developing roll in which at least one layer is formed on a shaft body and an outer peripheral surface of the shaft body, and the outermost layer has the following conductive composition. It is configured to be formed using the object (α).
(Α) The following (A) to (E) are essential components, and the content of (B) is in the range of 20 to 60 parts by weight with respect to 100 parts by weight of (A ). The content is in the range of 10 to 30 parts by weight with respect to 100 parts by weight of (A), and the blending amount of (E) is 1.5 to 15.9 parts by weight with respect to 100 parts by weight of (A). A conductive composition set in a range .
(A) Acrylic resin.
(B) Silicone component.
(C) An electronic conductive agent having an average primary particle size of 27 nm or less and a conductivity index of 70 or more.
(D) Diisocyanate.
(E) Polymeric dispersant (hereinafter, sometimes simply referred to as “dispersant”) .

The inventors of the present invention have made extensive studies in order to obtain a developing roll capable of obtaining an excellent image by improving the dispersibility of the electronic conductive agent and suppressing the adhesion of the toner. As a result, acrylic resin (component A), silicone component (component B), specific electronic conductive agent (component C), diisocyanate (component D), and dispersant (component E) are essential components, and The content of the silicone component (component B) is in the range of 20 to 60 parts by weight with respect to 100 parts by weight of the acrylic resin (component A), and the content of the specific electronic conductive agent (component C) is acrylic. In the range of 10 to 30 parts by weight with respect to 100 parts by weight of the resin (component A), the blending amount of the dispersant (component E) is 1.5 to 15 with respect to 100 parts by weight of the acrylic resin (component A). It was found that when the outermost layer (surface layer) of the developing roll was formed using a conductive composition set in a range of 9.9 parts by weight , the intended purpose could be achieved, and the present invention was achieved. That is, by using the specific amount of the silicone component (component B) and the specific electronic conductive agent (component C), the dispersibility of the electronic conductive agent is improved, so that a desired electrical resistance can be obtained with an appropriate blending amount. The amount of the dispersant (E component) used can be reduced, and accordingly, the active group of the dispersant (E component) is reduced, so that the binding portion with the toner is reduced. It is possible to suppress toner adhesion on the roll surface and to suppress image deterioration due to this. Moreover, since the compounding amount of the electronic conductive agent can be easily increased by improving the dispersibility of the electronic conductive agent, the residual charge on the roll can easily escape and the residual charge can be suppressed.

Thus, the present invention includes an acrylic resin (component A), a silicone component (component B), a specific electronic conductive agent (component C), a diisocyanate (component D), and a dispersant (component E). An essential component, and the content of the silicone component (component B) is within a range of 20 to 60 parts by weight with respect to 100 parts by weight of the acrylic resin (component A), and the specific electronic conductive agent (component C). The content is within the range of 10 to 30 parts by weight with respect to 100 parts by weight of the acrylic resin (component A), and the blending amount of the dispersant (E component) is with respect to 100 parts by weight of the acrylic resin (component A). The outermost layer of the developing roll is formed using a conductive composition set in the range of 1.5 to 15.9 parts by weight . For this reason, since the dispersibility of an electronic conductive agent (C component) improves, the roll provided with the desired electrical resistance is obtained easily. In addition, since the amount of the dispersant (E component) can be reduced by improving the dispersibility, the occurrence of toner adhesion due to the dispersant (E component) formulation can be suppressed. Furthermore, since the amount of the electronic conductive agent used can be increased by improving the dispersibility, it is difficult for residual charges to remain, and thus toner accumulation on the roll surface can be suppressed. Thus, toner adhesion (filming) and accumulation due to various factors are suppressed, and as a result, an excellent image can be obtained.

When the acrylic resin (component A) is a silicone-grafted acrylic resin, a high releasability is obtained, which acts more advantageously on toner adhesion.

And when the said silicone component (B component) is an acrylic silicone resin, compatibility with acrylic resin (A component) is good, and the effect that a uniform coating film without a sea-island structure can be produced is acquired.

  Next, an embodiment of the present invention will be described.

An example of the developing roll of the present invention is shown in FIG. This developing roll normally exhibits a function in contact with the photosensitive drum, and an elastic layer 2 is formed along the outer peripheral surface of the shaft body 1, and an intermediate layer 3 is formed on the outer peripheral surface of the elastic layer 2. Furthermore, an outermost layer (surface layer) 4 is formed on the outer peripheral surface of the intermediate layer 3. In the developing roll of the present invention, the most characteristic feature is that the outermost layer (surface layer) 4 is formed using a special conductive composition.

The shaft body 1 is not particularly limited, and for example, a metal core made of a metal solid body, a metal cylinder body hollowed out inside, or the like is used. Examples of the material include stainless steel, aluminum, and iron plated. If necessary,
An adhesive, a primer, or the like may be applied on the shaft body 1, and the adhesive, the primer, or the like may be made conductive as necessary.

Next, the material (elastic layer material) used for forming the elastic layer 2 is not particularly limited, but silicone rubber is preferably used because it has low hardness and little sag.

Furthermore, a conductive agent may be appropriately added to the elastic layer material. As the conductive agent,
Carbon black, graphite, potassium titanate, iron _{oxide, c-TiO 2, c-} Zn
Examples thereof include electronic conductive agents such as O and c-SnO ₂ , and ionic conductive agents such as quaternary ammonium salts, borates, lithium salts, and surfactants. In addition, the above “c−” means having conductivity. These may be used alone or in combination of two or more.

Further, the material (interlayer material) used for forming the intermediate layer 3 is not particularly limited. For example, acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), Examples thereof include rubber-based materials such as polyurethane-based elastomer, chloroprene rubber (CR), natural rubber, butadiene rubber (BR), butyl rubber (IIR), hydrin rubber (ECO, CO), and resin-based materials such as urethane resin. Among these, H-NBR is preferably used from the viewpoint of adhesiveness and stability of the coating liquid and the like.

In addition, it is also possible to mix | blend a conductive agent, a crosslinking agent, a crosslinking accelerator, a stearic acid, ZnO (zinc white), a softening agent, etc. in the said intermediate layer material as needed. As the conductive agent,
The thing similar to what was illustrated by the said material for elastic layers can be used.

Next, as described above, the special conductive composition is used as a material (outermost layer material) used for forming the outermost layer 4, which is a feature of the present invention. The special conductive composition includes an acrylic resin (component A), a silicone component (component B),
It is obtained by using a specific electronic conductive agent (C component), diisocyanate (D component), and a dispersant (E component) as essential components.

Examples of the acrylic resin (component A) include polymers and copolymers such as acrylic acid and esters thereof, acrylamide, acrylonitrile, methacrylic acid and esters thereof, and specific examples include acrylic resins. . Furthermore, the block copolymer which has the structural unit (A) induced | guided | derived from a silicone polymer and the structural unit (B) induced | guided | derived from an acrylic polymer as a structural component is mention | raise | lifted. The order of the block arrangement of the structural units in such a block copolymer is not particularly limited. An example of the block copolymer is a silicone block acrylic resin that is a block copolymer of a silicone portion and an acrylic portion. Furthermore, a high molecular weight silicone graft acrylic resin is mentioned. The silicone graft acrylic resin is a polymer having a structure in which a silicone component is connected as a side chain in a pendant form to a main chain made of an acrylic polymer. The high molecular weight silicone graft acrylic resin has a number average molecular weight (Mn) of 250,000 to
Those in the range of 450,000 are preferably used. Particularly preferably, the number average molecular weight (Mn) = 3
It is 100,000 to 400,000. These may be used alone or in combination of two or more. Among these, high molecular weight silicone graft acrylic resins and acrylic resins are preferably used from the viewpoint of toner chargeability. In particular, from the viewpoint of toner releasability, a high molecular weight silicone graft acrylic resin is preferably used.

The silicone component (B component) used together with the A component is not particularly limited as long as it is a compound having a siloxane skeleton. For example, an acrylic silicone resin,
Examples thereof include urethane silicone resin and silicone oil. These may be alone or 2
Used in combination with more than seeds. Among these, acrylic silicone resins are preferably used from the viewpoint of dispersibility of the filler.

Examples of the acrylic silicone resin include a silicone-modified acrylic resin. More specifically, there is a silicone graft acrylic resin, and this silicone graft acrylic resin has a structure part derived from siloxane in a main chain which is a linear structure part derived from an acrylic monomer. Some side chains are grafted. And
Among such silicone graft acrylic resins, those having a low molecular weight are preferably used. By using such a low molecular weight material, it becomes possible to form an outermost layer that is uniform and has good releasability with respect to the toner. In addition, the low molecular weight specifically refers to
The number average molecular weight (Mn) is in the range of 3000 to 10,000. Particularly preferably, Mn = 500
It is in the range of 0 to 10,000. That is, when Mn is less than 3000, bleeding tends to occur on the outermost layer surface, and the image is adversely affected.
Compatibility with acrylic resin (component A), which is the base polymer, decreases, making it difficult to form a uniform coating film when forming the outermost layer, increasing resistance unevenness and adversely affecting images. This is because there is a tendency. The low molecular weight is a number average molecular weight (M
n) refers to the range of 2000 to 4000. In addition, all the number average molecular weights (Mn) in this invention including the number average molecular weight (Mn) of the said silicone graft acrylic resin are the number average molecular weights of polystyrene conversion by a gel permeation chromatography (GPC) method.

The blending amount of the silicone component (component B) needs to be set in the range of 20 to 60 parts with respect to 100 parts by weight (hereinafter abbreviated as “part”) of the acrylic resin (component A). Particularly preferred is 35 to 45 parts. That is, when the blending amount of the silicone component (component B) is less than 20 parts, filming occurs when it exceeds a certain friction coefficient, and conversely when it exceeds 60 parts,
This is because the adhesion with the intermediate layer 3 is reduced and the outermost layer 4 is easily peeled off.

The specific electronic conductive agent (C component) used together with the A component and the B component is not particularly limited as the material, for example, the same as exemplified in the elastic layer material,
Carbon black, graphite, potassium titanate, iron _{oxide, c-TiO 2, c-} Zn
Examples thereof include electronic conductive agents such as O, c-SnO ₂ . In addition, the above “c−” means having conductivity. These may be used alone or in combination of two or more.

And as said specific electronic conductive agent (C component), a conductivity index | exponent must be 70 or more. Especially preferably, it is 80 or more. In general, the upper limit of the conductivity index is 600.
It is. If this conductivity index is low, such as less than 70, the following problems arise. That is, if the conductivity index is low, the desired medium electrical resistance cannot be obtained unless the blending amount of the electronic conducting agent is increased. However, if the blending amount of the electronic conducting agent is increased, the dispersing agent is increased accordingly. The amount must also be increased. When the blending amount of the dispersant is increased, the active group of the dispersant also increases, so that the binding portion with the toner (or external additive) increases. As a result, the toner (or external additive) of the roll surface is increased. Adhesion (filming) occurs and image degradation due to this occurs. The conductivity index is a value calculated using the following mathematical formula (1).

In the above formula (1), the specific surface area (X) of the electronic conductive agent refers to a nitrogen adsorption specific surface area, which is a method for measuring the total specific surface area of particles such as so-called carbon black. Then, it is measured and calculated as follows. That is, the value obtained by immersing degassed carbon black in liquid nitrogen, measuring the amount of nitrogen adsorbed on the carbon black surface at equilibrium, and calculating the specific surface area (m ² / g) from this measured value. is there.

In the above formula (1), the DBP absorption amount (Y) of the electronic conductive agent is JIS K
6217 is a value measured by (A method), the absorption amount of dibutyl phthalate (cm ^3/1
00 g).

In the above formula (1), the volatile content (Z) of the electronic conductive agent is a value measured and calculated as follows, taking carbon black as an example. That is, the ratio of the surface functional groups of carbon black desorbed in the form of CO, CO ₂ , H ₂ O, etc. The weight loss ratio when carbon black is introduced into a crucible and heated at 950 ° C. for 7 minutes ( %).

Furthermore, the specific electron conductive agent (component C) has an average primary particle size of 27 nm.
Must be: Preferably it is 20 nm or less, and a general lower limit is 8 nm. That is, when the average particle size of the primary particles exceeds 27 nm, the average particle size is large.
Dispersibility in the coating material used as the material for the outermost layer is poor, and a low-resistance outermost layer is formed. Also,
This is because if the blending amount of the electronic conductive agent is decreased in order to improve the dispersibility in order to obtain an electric resistance of medium resistance, the residual potential of the developing roll is reduced and the residual potential is deteriorated.

The average particle diameter of the primary particles of the electronic conductive agent (C component) is measured and calculated as follows, taking carbon black as an example. That is, it is a value obtained by measuring the diameter of a small spherical component (a state that has a fine crystal outline and cannot be separated any more) constituting the carbon black aggregate using an electron microscope and calculating an average value thereof. is there. In the present invention, the average particle diameter of the primary particles of the electronic conductive agent is, for example, arbitrarily extracted from the population which is the “small spherical component constituting the carbon black aggregate” and measured. This is the average value obtained.

Content of the said specific electronic conductive agent (C component) needs to be set in the range of 10-30 parts with respect to 100 parts of acrylic resins (A component). That is, when the blending amount of the electronic conductive agent (component C) is less than 10 parts, for example, the filling amount of carbon black is small, the conduction path is small, and the residual charge tends to accumulate. This is because, if the amount exceeds 50 parts, the amount of the unreacted carbon black dispersant in the coating film increases, so that the toner adhesion to the roll tends to deteriorate.

Next, the diisocyanate (D component) used together with the components A to C is not particularly limited. For example, 4,4′-diphenylmethane diisocyanate (MD
I), 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 3,3'-bitrylene-4,4'-diisocyanate,
3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 2,4-tolylene diisocyanate uretidinedione (dimer of 2,4-TDI), 1,5-naphthylene diisocyanate, metaphenylene diisocyanate, hexa Methylene diisocyanate (
HDI), isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), carbodiimide-modified MDI, orthotoluidine diisocyanate, xylene diisocyanate, paraphenylene diisocyanate, lysine diisocyanate methyl ester and the like. These may be used alone or in combination of two or more.
Among these, MDI, TDI, H in terms of expressing mechanical properties (elongation, elastic modulus)
DI is preferably used.

The blending amount of the diisocyanate (component D) is preferably in the range of 20 to 120 parts, particularly preferably in the range of 65 to 100 parts, with respect to 100 parts of the acrylic resin (component A). That is, when the blending amount of the diisocyanate (component D) is less than 20 parts, the crosslinking point is reduced, the crosslinking of the acrylic resin is sweet on the developing roll surface, and the coating film is peeled off.
This is because there is a tendency to cause image defects, and conversely, if it exceeds 120 parts, the surface of the developing roll becomes hard and stress with the toner and the contact member occurs, so that the toner adhesion tends to deteriorate.

And the dispersing agent (E component) used with the said AD component has an effect | action which prevents aggregation of electronic conductive agents (C component) by distributing around the said electronic conductive agent (C component). It is. Such dispersant component (E) had a liquid, positive Riakuriru acid derivatives For example, polymethacrylic acid derivatives, maleic anhydride copolymer (diisobutylene - maleic anhydride, styrene - maleic anhydride polycarboxylates) such as condensed naphthalene sulfonate, nonionic water-soluble polymer (polyvinylpyrrolidone, polymeric dispersants typified by polyether derivatives) and the like. These may be used alone or in combination.

The blending amount of the dispersant (component E) is {electron conducting agent (component C) blending amount × [[electronic conducting agent (
The BET specific surface area (m ² / g)] / 500]} of component (C) is preferably set to a value (blending amount) calculated. That is, when there is too little compounding quantity of a dispersing agent (E component), the tendency for the dispersibility of an electronic conductive agent (C component) to deteriorate is seen. Further, when the amount of the dispersant (E component) is too large, the active group of the dispersant (E component) is excessive and the binding portion with the toner increases, and the toner (
This is because there is a tendency that adhesion (filming) of the external additive) occurs.

In addition to the components A to E, the conductive composition as the outermost layer material includes a chain extender, a filler such as calcium carbonate, mica, silica, and graphite, a plasticizer, a crosslinking accelerator, and a crosslinking agent. Other additives such as a retarder, an anti-aging agent, and a colorant such as zinc oxide and titanium oxide may be appropriately blended.

The chain extender is not particularly limited as long as it has two or more functional groups. For example, 1,4-butanediol (1,4-BD), ethylene glycol, diethylene glycol, propylene glycol, dipropylene Glycol, hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylene glycol, triethylene glycol, trimethylolpropane (TMP), glycerin, pentaerythritol, sorbitol, 1,2,6-hexanetriol, etc. Has a number average molecular weight (Mn) of 3
00 or less polyol, 4,4'-diamino-3,3'-dichlorodiphenylmethane (
MOCA) and the like. These may be used alone or in combination of two or more. Among these, 1,4-BD and MOCA are preferable in terms of expressing reactivity and mechanical properties.

The amount of the chain extender is 1 with respect to 100 parts of the acrylic resin (component A).
Within the range of -20 parts is preferred, particularly preferably within the range of 3-10 parts.

The developing roll of the present invention can be produced, for example, as follows. That is,
First, each component of the elastic layer material is kneaded using a kneader such as a kneader or a roll to prepare an elastic layer material. Moreover, the coating solution used as the material for intermediate | middle layers is prepared by mix | blending each component of the said material for intermediate | middle layers in an organic solvent, and melt | dissolving. Further, the components A to E and other components as necessary are blended in an organic solvent and dissolved to prepare a solution of a special conductive composition that is the material for the outermost layer.

The organic solvent used in preparing the intermediate layer material and the outermost layer material is not particularly limited, and examples thereof include methyl ethyl ketone (MEK), toluene, acetone, methyl isobutyl ketone, and tetrahydrofuran. These may be used alone or in combination of two or more.

And as a coating solution which is the said material for intermediate | middle layers, it is preferable to set so that the ratio of a compounding component may become a density | concentration of about 20 weight% of the whole solution. In addition, as a solution of the conductive composition that is the material for the outermost layer, the ratio of the components A to E and other additives used as necessary is a concentration of about 20% by weight of the whole solution. It is preferable to set so that

Next, the elastic layer material is filled in a mold in which a core metal to be the shaft body 1 is set, and heat crosslinking is performed under a predetermined condition (for example, 180 to 200 ° C. × 15 minutes). Thereafter, the base roll in which the elastic layer 2 is formed along the outer peripheral surface of the shaft 1 is manufactured by removing the mold. Next, the intermediate layer material is formed on the outer peripheral surface of the elastic layer 2 by applying the intermediate layer material. Further, the intermediate layer 3
The outermost layer 4 is formed by applying a special conductive composition solution, which is the material for the outermost layer, to the outer peripheral surface of the outermost layer. And by heating on predetermined conditions (for example, 170-180 degreeC * 1 hour), the intermediate | middle layer 3 was formed in the outer peripheral surface of the elastic layer 2, and also the outermost layer 4 was formed in the outer peripheral surface 3
A developing roll having a layer structure (see FIG. 1) can be produced.

In addition, the molding method of the elastic layer 2 is not limited to the cast molding method, and may be manufactured by an injection molding method, a method of polishing after press molding, or the like. The method for applying the material for each layer is not particularly limited, and conventionally known dipping method, spray coating method, roll coating method and the like can be mentioned.

The thickness of each layer in the developing roll of the present invention is not particularly limited, but the thickness of the elastic layer 2 is 0.
. It is preferable to set within a range of 5 to 10 mm, and particularly preferably within a range of 3 to 6 mm. Further, the thickness of the intermediate layer 3 is usually set in the range of 1 to 90 μm, preferably 3
The thickness of the outermost layer 4 is usually set in the range of 0.5 to 100 μm, and preferably in the range of 1 to 50 μm.

The developing roll of the present invention is not limited to the three-layer structure as shown in FIG. 1, but may be a single layer or a two-layer structure, or a multilayer structure having four or more layers. That is,
For example, the two-layer structure may be a two-layer structure including an elastic layer in which no intermediate layer is formed and an outermost layer. Moreover, in the multilayer structure of four or more layers, for example, a structure of four or more layers including an elastic layer, an outermost layer, and two or more intermediate layers may be used. However, the outermost layer (surface layer) of the layers constituting the developing roll needs to be formed using the special conductive composition. In the case of a single layer structure, the layer is formed using the special conductive composition.

Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

First, prior to the examples and comparative examples, materials shown below were prepared as materials for the outermost layer of the developing roll.

[Acrylic resin A]
Acrylic resin (Nakage Kogyo Co., Ltd., Balaklon W-248E)

[Acrylic resin B]
A silicone-grafted acrylic polymer represented by the following formula (10) was produced. That is, the (Y ₁ ) _k1 portion, the (Y ₂ ) _k2 portion, the (X) _m portion, and the (Z) _n1 portion are combined in the presence of azobisisobutyronitrile (AIBN) that is an azo polymerization initiator, It was prepared by radical polymerization (polymerization conditions: 60 to 100 ° C. × 5 to 10 hours) by a solution polymerization method. In addition, the number average molecular weight (Mn) of the produced silicone graft acrylic polymer was 360,000.

[Silicone component]
Acrylic silicone resin (number average molecular weight Mn: 5000, manufactured by Toagosei Co., Ltd., Aaron J20
)

[Electronic conductive agent A]
Carbon black (manufactured by Tegusa, Printex L6: average particle diameter of primary particles 18 nm, conductivity index 81, BET specific surface area 265 m ² / g)

[Electronic conductive agent B]
Carbon black (manufactured by Showa Cabot, N234: average primary particle size of 22 nm,
Conductivity index 62, BET specific surface area 123m ² / g)

[Electronic conductive agent C]
Carbon black (manufactured by Denki Kagaku Kogyo Co., Ltd., HS-100: average particle diameter of primary particles 48 nm
, Conductivity index 74, BET specific surface area 39 m ² / g)

[Electronic conductive agent D]
Carbon black (manufactured by Tegusa, Special Black 4: average particle diameter of primary particles 25 nm,
Conductivity index 8, BET specific surface area 180m ² / g)

[Electronic conductive agent E]
Carbon black (manufactured by Tegusa, Printex L: average primary particle size 23 nm, conductivity index 73, BET specific surface area 150 m ² / g)

[Diisocyanate]
Tolylene diisocyanate (TDI) (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate T-6
5)

[Dispersant]
Polymeric dispersant (Lubrisol, Solsperse 24000)

[Example 1]
(Preparation of elastic layer material)
Conductive silicone rubber (X34-270A / B, manufactured by Shin-Etsu Chemical Co., Ltd.) was kneaded with a kneader to prepare an elastic layer (base rubber layer) forming material.

(Preparation of intermediate layer material)
H-NBR (acrylonitrile amount: 50% by weight, iodine value: 23 mg / 100 mg) 1
00 parts, 0.5 parts of stearic acid, 5 parts of zinc white (ZnO), 40 parts of carbon black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.), dithiocarbamate-based crosslinking accelerator (BZ) 1 part, 2 parts of a sulfenamide-based crosslinking accelerator (CZ), and 1 part of sulfur were kneaded using a roll, and these were mixed into a mixed organic solvent of MEK and toluene [MEK: toluene (weight ratio) = 2: 1] and dissolved therein to prepare a coating solution to be an intermediate layer forming material having a concentration of 20% by weight.

(Preparation of outermost layer material)
The components shown in Table 1 below were blended in the proportions shown in the table, and these were blended and dissolved in an organic solvent (MEK) to prepare a material for the outermost layer, which was a 20 wt% concentration coating solution.

(1) Preparation of base roll First, an aluminum cored bar (diameter 9 mm) was prepared as a cored bar, and an adhesive was applied to the outer peripheral surface of the cored bar. Next, the core metal is set in the hollow part of the cylindrical mold, and a silicone rubber compound is poured into the gap between the cylindrical mold and the core metal, and then the mold is covered and heated. (180 ° C. × 5 minutes), the silicone rubber compound was vulcanized, and then demolded to produce a cored bar (base roll) with an elastic layer (base rubber layer).

(2) Production of Development Roll After the intermediate layer forming solution is applied to the outer peripheral surface of the base roll by a roll coating method, drying and heat treatment (200 ° C. × 60 minutes) are performed, and an elastic layer (base rubber) An intermediate layer was formed on the outer peripheral surface of the layer. Further, the outermost layer forming solution is applied to the outer peripheral surface of the intermediate layer by a roll coating method, and then dried and heated (200 ° C. × 60 minutes) to form the outermost layer on the outer peripheral surface of the intermediate layer. did. In this way, a developing roll having a three-layer structure was produced (see FIG. 1). In addition, the thickness of the elastic layer (base rubber layer) of this roll is 5 mm, the thickness of the intermediate layer is 10 μm, and the thickness of the outermost layer is 1 μm.

[Examples 2 to 24, Comparative Examples 1 to 14]
A developing roll was produced in the same manner as in Example 1 except that the outermost layer material obtained by blending the components shown in Tables 1 to 6 below in the proportions shown in the same table was used.

Using the developing rolls of Examples and Comparative Examples thus obtained, measurements and evaluations on filming resistance, residual potential and adhesion were performed according to the following criteria. These results are shown in Tables 1 to 6 below.

[Film resistance]
Each developing roll was incorporated in an electrophotographic copying machine, and images were actually printed out. After 6000 copies were printed, a solid black copy was taken. The density of the copy (filming portion and normal portion) was measured using a Macbeth densitometer (Gretag Macbeth, reflection densitometer RD914). Evaluation is that the density difference of the measured value by Macbeth densitometer is less than 0.08.
, 0.08 or more was taken as x.

[Residual potential]
The residual potential was determined as follows. That is, as shown in FIG. 2, 23 ° C. × 53%
Under the RH environment, the surface of the developing roll 31 was charged by applying a corona current of 100 μA using the corona discharge wire 32 while rotating the developing roll 31 in the direction of the arrow at a rotational speed of 64 rpm. Then, a residual potential on the surface of the developing roll 31 was measured with a surface potential meter 33. As a result, the obtained residual potential was 50 V or less, and the case where it exceeded 50 V was rated as x.

[Adhesion]
Using a feather blade on the surface of each developing roll, put a feather blade in a grid pattern (cut into 5 x 5 squares, 1 square size: 2 mm x 2 mm) to reach the elastic layer, and attach adhesive tape ( Teraoka Polyester Film Co., Ltd., No. 648 # 50, size: 25 mm × 30 mm) was attached. Subsequently, this tape was peeled off, and it was visually evaluated whether or not the layer portion of the roll cut into a grid pattern was peeled off when the tape was peeled off and adhered to the tape adhesive surface. And what is not attached to the tape adhesive surface is ○ (If the attached is caused by rubber breakage of the elastic layer at the interface with the elastic layer, ○), the layer portion of the roll is peeled off What stuck on the adhesive surface was set as x.

From the results in the above table, it can be seen that the product of the example has good filming resistance and a low residual potential, and a good copy image can be obtained. Moreover, it is clear that a highly reliable developing roll having excellent adhesion was obtained.

On the other hand, the products of Comparative Examples 1 and 8 use carbon black having a low conductivity index as the material for the outermost layer. Therefore, the amount of the dispersant increases because the amount of carbon black needs to be increased. The filming property was inferior. In Comparative Examples 2 and 9, carbon black with a large average particle size of primary particles is used as the material for the outermost layer, so that only a small amount of carbon black and a small amount of dispersant are required. Although the filming property was good, the residual potential was high. Further, Comparative Examples 3 and 10 using carbon black having a very low conductivity index as the outermost layer material were inferior in filming resistance. And the comparative example 4, in which the blending amount of the acrylic silicone resin in the material for the outermost layer was less than the specific range
Since 6,11,13 products had a small amount of silicone component as a release component, the adhered toner was difficult to peel off and the filming resistance was poor. In Comparative Examples 5, 7, 12, and 14 in which the blending amount of the acrylic silicone resin was often out of the specific range, the silicone component was too much.
The adhesion with the lower layer was reduced, and the outermost layer was peeled off.

The developing roll of the present invention can be suitably used for electrophotographic apparatuses such as copying machines, printers and facsimiles.

It is sectional drawing which shows an example of the image development roll of this invention. It is a schematic diagram showing a method for measuring the residual potential on the surface of the developing roll.

Explanation of symbols

1 shaft body 2 elastic layer 3 intermediate layer 4 outermost layer

Claims (4)

A shaft and a developing roll having at least one layer formed on the outer peripheral surface of the shaft, wherein the outermost layer is formed using the following conductive composition (α). Developing roll.
(Α) The following (A) to (E) are essential components, and the content of (B) is in the range of 20 to 60 parts by weight with respect to 100 parts by weight of (A ). The content is in the range of 10 to 30 parts by weight with respect to 100 parts by weight of (A), and the blending amount of (E) is 1.5 to 15.9 parts by weight with respect to 100 parts by weight of (A). A conductive composition set in a range .
(A) Acrylic resin.
(B) Silicone component.
(C) An electronic conductive agent having an average primary particle size of 27 nm or less and a conductivity index of 70 or more.
(D) Diisocyanate.
(E) A polymeric dispersant.   The developing roll according to claim 1, wherein the acrylic resin as the component (A) is a silicone graft acrylic resin.   The developing roll includes a shaft body, an elastic layer formed on the outer peripheral surface of the shaft body, an intermediate layer formed on the outer peripheral surface of the elastic layer, and an outermost layer formed on the outer peripheral surface of the intermediate layer. The developing roll according to claim 1 or 2, comprising a layer structure.   The developing roll according to any one of claims 1 to 3, wherein the silicone component (B) is an acrylic silicone resin.

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