JP5649922B2 - Conductive elastomer member for electrophotographic apparatus - Google Patents

Description

  The present invention relates to a conductive elastomer member for an electrophotographic apparatus.

2. Description of the Related Art Conventionally, electrophotographic apparatuses such as printers, copiers, and facsimiles are provided with a conductive elastomer member made of a conductive elastomer composition.
Specific examples of the conductive elastomer member include a roller-shaped, belt-shaped or sheet-shaped developing member, a charging member, a transfer member, and the like. For example, a conductive material for charging the surface-supported toner. The developing roller, which is an elastomer member, has an elastic body layer with a predetermined thickness on the outer periphery of the core metal, and an elastomer containing a conductive filler such as carbon black in order to impart conductivity to the elastic body layer. The elastic layer is formed with a composition.

Such a conductive elastomer member is such that conductivity is expressed by forming a chain-like aggregate in the elastic layer of a conductive filler such as carbon black blended in the elastomer composition. It is considered.
However, such a conductive elastomer member has a problem that its conductivity gradually decreases when voltage is continuously applied, that is, its electric resistance increases.
In particular, in a conductive elastomer member that plays a role of controlling the movement of toner as charged particles, such as a developing roller for an electrophotographic apparatus (hereinafter also simply referred to as “developing roller”), the electric resistance of the elastic layer is low. When it rises, it becomes difficult to control the movement of the toner, and there is a risk of deteriorating image quality such as a decrease in image density.

  By the way, as shown in the following Patent Document 1, as the developing roller, one having a surface layer on the outer periphery of the elastic body layer is known.

JP 2003-223046 A

The surface layer of the developing roller is intended to improve the wear resistance and prolong the life of the developing roller, improve the releasability of the surface to improve the cleaning property, and improve the image quality due to unnecessary toner adhesion. For example, it is made of a fluororesin having a low surface free energy for the purpose of preventing the deterioration.
However, in general resins, the required electrical characteristics can be obtained relatively easily by adjusting the content of the conductive filler, whereas in the case of fluororesins, it is more conductive than other general resins. Since it is difficult to control the property, if the surface layer is formed of a fluororesin, there is a possibility that a change in electrical characteristics due to continuous voltage application will be more noticeable.

  In the developing roller, since the toner carried on the surface from the core metal through the elastic layer and the surface layer needs to be in a desired charged state, the electrical characteristics of the surface layer are not stable. Even if the electrical characteristics of the elastic layer are stabilized, the performance required for the developing roller is not exhibited.

For this reason, the formation of the surface layer with a fluororesin can prevent the deterioration of the image quality from the viewpoint of releasability, but it may cause the deterioration of the image quality rather from the viewpoint of electrical characteristics.
Such a problem is a problem common not only to the developing roller but also to other conductive elastomer members for electrophotographic apparatuses.
Then, since such a problem is caused when the surface layer is formed by the fluororesin, since little attention has been paid so far, the solution has hardly been studied so far.

  In view of the above problems, an object of the present invention is to provide a conductive elastomer member for an electrophotographic apparatus having a surface layer made of a fluororesin and having stable electrical characteristics.

  As a result of diligent studies to solve the above problems, the present inventor has replaced a part or all of the conventionally widely used conductive filler such as carbon black with a predetermined amount of graphite as an elastomer or fluororesin. It has been found that the change in the electrical characteristics associated with the application of voltage can be suppressed by the inclusion, and the present invention has been completed.

  That is, the present invention relating to the electroconductive elastomer member for electrophotographic apparatus for solving the above-mentioned problems has an elastic layer inside the surface layer made of fluororesin, and the elastic layer is composed of graphite and carbon An electroconductive elastomer member for an electrophotographic apparatus formed of an elastomer composition containing black and an elastomer, wherein the surface layer contains 4% by mass or more and 20% by mass or less of graphite, and the surface layer The average particle size of the graphite contained in is 8 μm or less.

  According to the present invention, graphite is contained in both the elastic layer and the surface layer, and the surface layer using the fluororesin contains a predetermined size of graphite in a predetermined ratio. For this reason, it is possible to suppress changes in electrical characteristics through the surface layer and the elastic body layer with the lapse of the power application time.

1 is a schematic perspective view showing a conductive elastomer member (developing roller) for an electrophotographic apparatus according to one embodiment. The graph which shows the electrical property of the electroconductive elastomer member (roller) for electrophotographic apparatuses of an Example. The graph which shows the electrical property of the electroconductive elastomer member (roller) for electrophotographic apparatuses of an Example. The graph which shows the electrical property of the electroconductive elastomer member (roller) for electrophotographic apparatuses of a comparative example.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings while illustrating a developing roller as a conductive elastomer member for an electrophotographic apparatus.

FIG. 1 is a perspective view showing a developing roller, and as shown in this perspective view, the developing roller 1 has a metal at the center to be provided in the electrophotographic apparatus in a state of being rotatable around an axis. A cored bar 2 made of a round bar is provided.
The developing roller 1 in this embodiment has an elastic body layer 3 provided on the outer periphery of the metal core 2 with a substantially constant thickness, and a surface layer 4 that covers the surface of the elastic body layer 3.
The elastic layer 3 is provided so that the developing roller 1 exhibits desired elastic deformation by contact with another member, and the surface layer 4 is provided with a surface wear resistance and separation. It is provided on the outermost surface side of the developing roller 1 in order to improve moldability.

  Although the thickness of the elastic layer 3 and the thickness of the surface layer 4 vary depending on the electrophotographic apparatus in which the developing roller 1 of the present embodiment is incorporated, the thickness of the elastic layer 3 is usually as follows. The surface layer 4 has a thickness of 1 μm to 100 μm.

The electrical conductivity required for the developing roller of the present embodiment is not particularly limited, but is usually required to be formed to have an electric resistance value of about 10 ³ to 10 ⁶ Ω. The hardness is usually preferably about 30 to 60 °, particularly preferably 30 to 50 °.
The electrical resistance value of the developing roller can be obtained by the method described in the examples.

In the developing roller 1 of the present embodiment, it is important to form the surface layer 4 with a fluororesin from the viewpoints of wear resistance, releasability (surface cleaning properties), and the like.
Moreover, it is important that the surface layer 4 contains 4% by mass or more and 20% by mass or less of graphite in order to suppress a change in electrical characteristics over time.
In particular, it is preferable to contain graphite in the surface layer 4 so as to have a ratio of 5% by mass to 10% by mass.

Carbon black usually has a size of 1 μm or less (several tens of nanometers), whereas graphite is also called graphite (graphite) and usually has a size exceeding 1 μm. The particle size is one order or more larger than that of carbon black, and the crystal structure is developed as compared with carbon black.
Therefore, graphite has a semi-metallic electronic state, and the conductivity of the particles themselves is usually superior to that of carbon black.

In addition, since the development of conductivity by carbon black is greatly affected by the formation of the structure, for example, when conductivity is imparted to the surface layer with only carbon black, the content of carbon black and the electrical It is difficult to recognize the interrelation between the characteristics and the electrical characteristics are suddenly changed with a certain content as a boundary.
On the other hand, since graphite is excellent in the conductivity of the particles themselves, it is easier to adjust the electrical properties depending on the content compared to carbon black.

Furthermore, when a voltage is continuously applied to a developing roller in which only carbon black is employed as the conductive filler, a change occurs in the tunnel effect in the structure of the carbon black formed in the surface layer and the elastic layer, In addition, since such a change occurs in a relatively short period after the voltage is applied, the electric characteristics of the developing roller may change immediately.
On the other hand, when graphite is used, since it is difficult to be affected by this, even if continuous power application to the developing roller 1 is performed, the electrical characteristics of the surface layer 4 and the elastic layer 3 are changed. It is hard to let you.

When the size of graphite is excessively large, the surface of the developing roller 1 tends to be rough, which may cause problems in the surface wear resistance and cleaning performance by a cleaning blade, There is a possibility that the merit of using the fluororesin for forming the surface layer 4 may be lost.
Therefore, in order to stabilize the electrical characteristics while suppressing the effect of using the fluororesin for the formation of the surface layer 4, the average particle diameter of the graphite contained in the surface layer 4 is not more than a predetermined value. In particular, it is an important requirement that the average particle diameter of graphite is 8 μm or less.
Furthermore, it is preferable that the graphite contained in the surface layer 4 has an average particle diameter of 3 to 5 μm.

The term “average particle size” used for the size of graphite and the like is intended to be a D50 value measured by a particle size distribution analyzer using a laser diffraction scattering method.
The particle size of carbon black is usually determined by direct observation with an electron microscope and is represented by an arithmetic average value of measured values obtained by measuring the size of a plurality of particles.

  The graphite used for forming the surface layer 4 may be either natural graphite or artificial graphite. However, artificial graphite is preferable in that it is easily available and the quality is more stable.

  Moreover, you may contain electroconductive fillers other than graphite as a component for providing electroconductivity with respect to the said surface layer 4, and it is preferable to use carbon black together with graphite especially.

This carbon black includes furnace black produced by a furnace method that incompletely burns oil and gas in a high-temperature gas, acetylene black produced by thermally decomposing hydrocarbons such as acetylene, and channel black. Can be adopted.
In addition, when adopting furnace black, carbon black of FEF type, ISAF type, HAF type and the like classified by general names can be used.
When carbon black is contained in the surface layer 4, it is preferably set in any proportion within the range of more than 0% by mass and not more than 8% by mass.

As the fluororesin for forming the surface layer 4 by containing these graphite and carbon black, those that easily disperse graphite and carbon black and those that easily adjust the surface layer to a desired film thickness are suitable. It is.
For this reason, a varnish type material in which a fluororesin or a precursor of a fluororesin such as an oligomer is dispersed in a solvent, which can be cured by heat or chemical reaction, is used as a material for forming the surface layer 4 It is preferable to adopt.
Examples of the fluororesin used in such a varnish type include a copolymer of ethylene tetrafluoride / vinyl monomer, which can be cured by an isocyanate or a melamine curing agent. Specifically, Commercially available products such as “Zeffle GK500”, “Zeffle GK510”, “Zeffle GK550”, “Zeffle GK570”, and “Zeffle GK580” from Daikin can be used.

Although the surface layer 4 is formed in this way, the electrical stability of the surface layer itself is ensured, but the elastic body layer 3 provided inside the surface layer 4 also has electrical stability. If it is not secured, the characteristics as the developing roller 1 are impaired.
Therefore, it is an important requirement for securing the electrical stability of the developing roller 1 that the elastic body layer 3 is also formed of an elastomer composition containing graphite, carbon black, and an elastomer.

As the elastomer for forming the elastic body layer 3, for example, a thermoplastic elastomer or the like can be used. However, in terms of thermal and chemical stability, a thermosetting type reaction reactive type elastomer is used. Is preferred.
Preferred elastomers include ethylene-propylene rubber (EPM, EPDM), butadiene rubber (BR), natural rubber (NR), styrene-butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile- Examples include butadiene rubber (NBR, NIR, etc.), silicon rubber, epichlorohydrin rubber, polyurethane and the like.

Among these, polyurethane is preferably used as the elastomer.
By adopting polyurethane as the elastomer, it is possible to make the developing roller 1 of the present embodiment have a relatively low surface hardness and hardly cause permanent deformation.

  The polyurethane is usually obtained by reacting a polyol and a polyisocyanate.

The polyol is a compound having a plurality of hydroxyl groups in the molecule.
Although it does not specifically limit as said polyol, For example, polyester type polyol, polyolefin type polyol, polyether type polyol, polycarbonate type polyol, polyacrylic type polyol, polyether ester type polyol etc. are mentioned.
These polyols can be used singly or in combination of two or more.

Although it does not specifically limit as a hydroxyl value (OHV) of the said polyol, 50-160 are preferable at the point which can form the hardened | cured material which has moderate hardness.
In addition, the said hydroxyl value is a value calculated | required by the method according to JISK0070.

Although it does not specifically limit as an average functional group number of the said polyol, 2-3 are preferable at the point which can comprise the polyurethane which has moderate hardness.
In addition, the said average functional group number means the theoretical functional group number determined by the number of active hydrogen groups of the initiator molecule | numerator used for manufacture of a polyol.
However, the actual number of functional groups may be different due to the influence of side reactions during polymerization.

Examples of the polyester polyol include compounds having 2 or more ester bonds and 2 or more hydroxyl groups in the molecule.
Specifically, for example, ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, glycerin, 1,1,1-trimethylolpropane, and one or two other low molecular polyols A condensation polymer of at least one species with one or more of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, other low molecular carboxylic acid and oligomeric acid, Alternatively, ring-opening polymers such as propionlactone, valerolactone, and caprolactone are exemplified.

Examples of the polyolefin-based polyol include compounds having 4 or more olefins and 2 or more hydroxyl groups in the molecule.
Specifically, for example, after polymerizing a diene compound such as butadiene and isoprene and optionally styrene and acrylonitrile in the presence of an anionic polymerization catalyst such as metal lithium, metal potassium and metal sodium, ethylene oxide, A polyol obtained by addition polymerization of alkylene oxide such as propylene oxide, or a polyol obtained by radical polymerization of the diene compound with a radical initiator having a hydroxyl group such as hydrogen peroxide, or hydrogenating these And the like.

Examples of the polyether polyol include compounds having two or more ether bonds and two or more hydroxyl groups in the molecule.
Specifically, for example, ethylene oxide, propylene oxide, propylene oxide, butylene oxide, or an alkylene oxide such as a mixture thereof in ethylene glycol, diethylene glycol, propylene glycol, glycerin, trimethylolpropane, or the like in the presence of an alkali catalyst or the like. Examples include polyalkylene polyols obtained by addition polymerization, polytetramethylene glycol obtained by polymerizing tetrahydrofuran under a cationic catalyst, or a mixture thereof.

  Examples of the polycarbonate polyol include 1,6-hexanediol polycarbonate polyol, 1,6-hexanediol and 1,4-butanediol polycarbonate polyol, 1,6-hexanediol and 1,5-pentanediol. Examples include polycarbonate polyol, polycarbonate polyol of 1,6-hexanediol and 3-methyl-1,5-pentanediol.

The polyacrylic polyol has a hydroxyl group at the end of a polymer compound obtained by polymerizing an acrylic acid derivative monomer or a polymer compound obtained by copolymerizing an acrylic acid derivative monomer and other monomers. Things.
Among them, those obtained by polymerizing acrylic acid derivative monomers such as ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate alone, and acrylic polyols copolymerized by adding other monomers such as styrene are preferably used. .

Examples of the polyether ester-based polyol include compounds having two or more ether bonds, two or more ester bonds, and two or more hydroxyl groups in the molecule.
Specifically, for example, one or more of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, other low molecular carboxylic acid and oligomeric acid, and ethylene Glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, glycerin, 1,1,1-trimethylolpropane, and one or more other low molecular polyols are conventionally known methods And those obtained by polycondensation with.
Specifically, for example, a polycondensate of adipic acid, diethylene glycol, and trimethylolpropane can be used.

The polyether ester-based polyol preferably has a hydroxyl value (OHV) of 50 to 160 and an average functional group number of 2 to 3 in that the elastic layer 3 having an appropriate hardness can be formed. .
Specifically, the polyether ester polyol has a hydroxyl value (OHV) of 57 to 64 and a polyether ester polyol having an average functional group number of 2 to 3, and a hydroxyl value (OHV) of 150. It is more preferable that it is used for forming the elastic body layer 3 by mixing with a polyether ester polyol having an average functional group number of 2 to 160.
The polyether ester-based polyol having a hydroxyl value (OHV) of 150 to 160 and an average functional group number of 2 to 3 is a polyether having a hydroxyl value (OHV) of 57 to 64 and an average functional group number of 2 to 3. It has a function of reducing the viscosity of the mixture with the ester-based polyol, and can be expected to improve workability when the elastic body layer 3 is formed.
More specifically, the polyetherester polyol is preferably a polycondensate of adipic acid, diethylene glycol, and trimethylolpropane.

In the polyether ester polyol mixture, the polyether ester polyol having a hydroxyl value (OHV) of 150 to 160 and the average functional group number of 2 to 3 is 10 to 30% by mass in the polyol. It is preferably included.
The polyether ester-based polyol having a hydroxyl value (OHV) of 150 to 160 and an average functional group number of 2 to 3 is contained in an amount of 10 to 30% by mass in all polyols. Appropriate hardness required for the developing roller can be imparted to the elastic layer.

The polyisocyanate is a compound having a plurality of isocyanate groups in the molecule.
The polyisocyanate is not particularly limited. Specifically, for example, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4, 4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, tolidine diisocyanate (TODI), 1 , 5-Naphthalene diisocyanate (NDI) and other polyisocyanates, hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornene diisocyanate methyl (NBDI), key Aliphatic polyisocyanates such as silylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), H12MDI (hydrogenated MDI), etc. Alicyclic polyisocyanate, carbodiimide-modified polyisocyanate of each of the above-mentioned polyisocyanates, or isocyanurate-modified polyisocyanate thereof.
These polyisocyanates are used singly or in combination of two or more. Preferably, a mixture of 2,4-TDI and 2,6-TDI (2,4-TDI / 2 , 6-TDI = 80/20 mass ratio) can be used.

The elastic layer 3 is not necessarily formed in a solid (non-foamed) state, and may be formed of a foam made of an elastomer composition.
Therefore, an elastic body layer can also be formed with foamed polyurethane.

The elastic layer 3 preferably contains carbon black in any proportion within the range of 1% by mass to 4% by mass.
As said carbon black, the thing similar to what was described in the said surface layer 4 is employable as a component of the elastomer resin composition for forming the elastic body layer 3. FIG.
That is, the elastic layer 3 can contain furnace black, acetylene black, channel black, and the like.
For furnace black, carbon black such as FEF, ISAF, or HAF can be used.

It is preferable to include the carbon black in the elastomer composition in an amount of 1 to 4% by mass. By adding the carbon black to the elastomer composition in an amount of 1% by mass or more, the elastic layer 3 has appropriate conductivity. This is because it can be given.
The graphite has a surface area smaller than that of the carbon black, and it is difficult to form a dense chain aggregate (structure) in the elastomer composition with the graphite alone. The formation of is supplemented with carbon black, so that the elastic layer 3 exhibits appropriate conductivity.
Therefore, the combined use of carbon black and graphite makes the continuity of the chain aggregate more reliable and makes it difficult for charge accumulation to occur even when a voltage is continuously applied. The performance that resistance value hardly changes can be expressed.

Moreover, since the carbon black also functions as a reinforcing material, an appropriate hardness can be imparted to the elastic layer 3 made of the elastomer composition by containing 1% by mass or more in the elastomer composition.
Even if the carbon black is excessively contained, it is difficult not only to improve the complementary effect of the structure beyond a certain level, but also the dispersion in the elastomer composition becomes non-uniform, or the fluidity of the elastomer composition is extremely high. There is a possibility that the formation of the elastic layer becomes difficult due to loss.
For example, when a large amount of carbon black is contained in the polyol, the viscosity of the mixed liquid of the polyol and polyisocyanate becomes high, and the workability in the case of forming an elastic body layer by casting is reduced. Or agglomerates of the carbon black may be formed in the polyol.
In this respect, carbon black is preferably contained in the elastic layer at a ratio of 4% by mass or less.

The carbon black includes, but is not DBP oil absorption amount is particularly limited, but is preferably a 71~168cm ³ / 100g.
By DBP oil absorption of the carbon black is 71cm ^3/100 g or more, has the advantage be ongoing voltage application to the developing roller 1 becomes difficult to further change the electrical resistance of the elastic layer 3, by DBP oil absorption amount is less than 168cm ^3/100 g, giving a good Naru fluidity polyurethane before curing, capable of facilitating the formation of the elastic layer.

The DBP oil absorption amount is obtained by substituting the void volume in carbon black having a constant mass with a liquid and using the capacity as an index.
Specifically, it refers to the amount of oil (cm ³ ) that can be included per 100 g of carbon black, and is a value measured by a method based on ASTM D3493-85a.
The DBP oil absorption can be an index representing the three-dimensional state of the aggregate of primary particles of the carbon black.
That is, it is considered that carbon black tends to form a chain-like aggregate (structure) in the elastomer composition when the DBP oil absorption amount is large. Therefore, the one where the DBP oil absorption amount is larger can exhibit conductivity with a smaller content, and can further suppress the change in the electric resistance value due to continuous voltage application.

As the graphite used for forming the elastic body layer 3, those described in the surface layer 4 can be used.
In addition, it is preferable that content of the graphite in the said elastomer composition shall be 3 mass% or more and 6 mass% or less.
By including 3% by mass or more of the graphite in the elastomer composition, there is an advantage that the electric resistance value is hardly changed even when the developing roller 1 is continuously charged, and 6% by mass or less is included. Thus, there is an advantage that the hardness of the elastomer composition can be made more appropriate.

Further, the graphite used for forming the elastic body layer 3 also preferably has an average particle diameter of 3 to 5 μm, like the graphite used for forming the surface layer 2.
By setting the average particle diameter of the graphite to 3 μm or more, there is an advantage that it is easy to impart good fluidity to the polyurethane composition before curing and the formation of the elastic body layer 3 can be made easier. By making it below, the hardness of the polyurethane composition (polyurethane elastic body) after curing can be made more appropriate.
In the present embodiment, a polyurethane composition is exemplified as the elastomer composition for forming the elastic body layer 3, but the elastic body layer 3 may not necessarily be formed of a polyurethane elastic body.

  For example, if it is a polymer substance that has rubber-like elasticity at room temperature and changes easily when an external force is applied, but is an elastic polymer substance that immediately recovers to its original shape when the external force is removed, it is particularly a type of elastomer. It is not intended to limit.

The composition for forming the surface layer 4 and the elastic body layer 3 may further contain a filler (filler).
Examples of the filler include inorganic fillers such as silica, clay, talc, and calcium carbonate, and organic fillers such as polytetrafluoroethylene (PTFE) fine particles.
If such an filler is contained in the elastomer composition for forming the elastic layer 3, the total content of the carbon black and the conductive filler such as graphite is 10 mass in the elastomer composition. It is preferable to make it contain so that it may become% or less.
By making the total amount of the filler in the elastomer composition 10% by mass or less, the processability before curing of the elastomer composition can be improved and the hardness after curing is appropriate for the developing roller 1. Can be.

In addition, the surface layer and the elastic layer may include additives other than fillers such as wax, hydrolysis inhibitor, silane coupling agent, surfactant, anti-aging agent, antioxidant, pigment, UV absorption Agents, antistatic agents, and the like may be included.
The specific compound name is not described in detail here, but as the additive, general ones used for rubber, plastics and the like can be appropriately employed, and their blending amounts are not particularly limited, and are arbitrary. Can be selected.

The developing roller 1 of this embodiment can be manufactured as follows.
Specifically, when polyurethane is employed as the elastomer, it can be produced as follows.

  For example, the core metal 2 is set at the center of a mold having a cylindrical cavity slightly larger than the outer diameter of the elastic layer 3 to be produced, and the polyol, the polyisocyanate, and the carbon black described above are set. Prepare the graphite and knead them using, for example, a mixer or a bead mill, pour the kneaded material into the mold, cross-link in the mold by heating, demold, and further heat to post-crosslink the polyurethane Then, the outer diameter is adjusted by surface polishing to produce a semi-finished product in which up to the elastic body layer 3 is provided around the cored bar.

  Next, for example, a fluororesin varnish in which a copolymer of ethylene tetrafluoride / vinyl monomer is dispersed in a solvent, and a dispersion in which graphite and carbon black are dispersed in a solvent highly compatible with the solvent are prepared. Then, by mixing them, the liquid mixture is adjusted so that the fluororesin, graphite, and carbon black have a predetermined ratio as a solid liquid, and an isocyanate or a melamine curing agent is added to the liquid mixture. A fluororesin coating solution for forming the surface layer is prepared.

  Then, the developing roller can be manufactured by applying the fluororesin coating liquid on the surface of the semi-finished product, drying it, and curing the coating film to form the surface layer 4.

The developing roller thus obtained is preferably formed so as to be able to suppress an increase in electrical resistance value when voltage is continuously applied by constant current control. For example, a current value control of 100 μA is possible. When the voltage is continuously applied, the time for the electric resistance value to reach 5 times the initial value is preferably 100 hours or more.
Furthermore, it is preferable that the voltage after 200 hours is -30 to 30% of the initial voltage.

Since the developing roller is in such an electrically stable state, the printing quality of the electrophotographic apparatus using the developing roller is also stabilized, and a good printing state can be maintained over a long period of time. it can.
Specific examples of the electrophotographic apparatus in which the electroconductive elastomer member for an electrophotographic apparatus of the present invention is used include a printer such as a laser beam printer, a copying machine, and a facsimile.

The electroconductive elastomer member for an electrophotographic apparatus of the present invention is not limited to a member (developing member) such as a developing roller for adhering toner to a photoreceptor, and the conductivity changes by light irradiation. Examples thereof include a charging member such as a charging roller for charging the photoconductor, and a transfer member such as a transfer roller for transferring the toner adhering to the photoconductor to a transfer medium.
Examples of the shape include a roller shape, a belt shape, and a sheet shape.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

<Manufacture of conductive roller>
The following roller was manufactured as a conductive elastomer member for an electrophotographic apparatus.

(Elastic layer)
For the formation of the elastic body layer, two kinds of blends shown in Table 1 below were used.

(Surface layer)
For the formation of the surface layer, the formulations shown in Table 2 below were used.

(Production of rollers: Examples 1 to 9)
An elastic layer was formed by the blend A in Table 1 so that the thickness of the core metal with a diameter of 6 mm was 3 mm and the length in the axial direction was 220 cm.
The surface of this elastic layer is coated with a fluororesin coating solution of Formulas 1 to 9 in Table 2 above, and this coating film is dried and cured to form a surface layer having a thickness of 30 μm. Produced.

(Electric resistance value)
This roller (electroconductive elastomer member for electrophotographic apparatus) is placed horizontally on a SUS plate, and a load of 4.9 N is applied to both ends of the roller so that the surface of the roller is pressed against the SUS plate. Connect the grounding electrode of the device (manufactured by Trek, model name “610C”) to the SUS plate and connect the high-voltage electrode to the cored bar. Applied to the roller.
And the change with the passage of time of the voltage value which this high voltage power supply device is generating was monitored.
The resistance value of the roller was obtained by dividing the observed voltage value by the current value (100 μA).
In the measurement of the electrical resistance value, the initial resistance value (R0) at the start of energization, the resistance value (R50) after 50 hours of energization, and the resistance value (R100) after 100 hours of energization are obtained, and the energization start is started. The values of resistivity change (R50 / R0) after 50 hours of energization with respect to time and resistivity change (R100 / R0) after 100 hours of energization with respect to the start of energization were calculated.

(Surface roughness)
In addition, Table 3 shows the results of measuring the surface roughness (ten-point average surface roughness: RzJIS) of the surface layer.

(Comparative Examples 1-5)
Rollers in the same manner as in the Examples except that the surface layers were formed using Formulations 10 to 12 shown in Table 4 below and that some of the rollers were formed with an elastic layer with Formulation B that did not contain graphite. The same evaluation was carried out.
The results are shown in Table 5 below.

(Comparative Examples 6 and 7)
A roller was prepared in the same manner as in the example except that the formulations 13 and 14 shown in the following Table 6 containing coarse graphite were used for forming the surface layer, and the same evaluation was performed.
The results are shown in Table 7 below.

  The results of observing how the resistance value changes with the passage of voltage application time (energization time) for the rollers of this example and comparative examples are shown in FIGS.

  From these figures, it can be seen that according to the present invention, a conductive elastomer member for an electrophotographic apparatus having a stable electric resistance value can be provided.

  1: developing roller (conductive elastomer member for electrophotographic apparatus), 2: cored bar, 3: elastic layer, 4: surface layer

Claims (8)

A conductive elastomer member for an electrophotographic apparatus, having an elastic layer inside a surface layer using a fluororesin, wherein the elastic layer is formed of an elastomer composition containing graphite, carbon black, and an elastomer. Because
The surface layer contains 4% by mass or more and 20% by mass or less of graphite, the average particle diameter of the graphite contained in the surface layer is 8 μm or less, and the surface layer further contains carbon black. A conductive elastomer member for an electrophotographic apparatus, characterized by being contained in an amount exceeding 0% by mass and not more than 8% by mass . Claim 1 for an electrophotographic apparatus conductive elastomer member according graphite content is 10 mass% or more and 5 mass% or less of the surface layer. Wherein the elastomeric composition for an electrophotographic apparatus conductive elastomer member according to claim 1 or 2 graphite is contained 3 wt% or more 6 wt% or less. The electroconductive elastomer member for an electrophotographic apparatus according to any one of claims 1 to 3 , which is a developing roller for an electrophotographic apparatus. A conductive elastomer member for an electrophotographic apparatus, having an elastic layer inside a surface layer using a fluororesin, wherein the elastic layer is formed of an elastomer composition containing graphite, carbon black, and an elastomer. Because
Characterized in that said elastomer Ri polyurethane der, in the surface layer of graphite are contained 20 wt% or less than 4 wt%, average particle diameter of the graphite contained in the surface layer is 8μm or less A conductive elastomer member for an electrophotographic apparatus. The conductive elastomer member for an electrophotographic apparatus according to claim 5, wherein the surface layer has a graphite content of 5 mass% to 10 mass%. The conductive elastomer member for an electrophotographic apparatus according to claim 5 or 6, wherein the elastomer composition contains 3% by mass to 6% by mass of graphite. The electroconductive elastomer member for an electrophotographic apparatus according to claim 5, which is a developing roller for an electrophotographic apparatus.

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