JP7083440B2 - Conductive roller - Google Patents

Description

The present invention relates to a conductive roller.

In an electrophotographic machine such as a copying machine, a printer, or a facsimile that employs an electrophotographic method, conductive rollers such as a charging roller, a developing roller, a transfer roller, and a toner supply roller are arranged around the photoconductor.
It is important that these conductive rollers have resistance suitable for each application and have uniform chargeability, and various methods for improving charge uniformity have been reported.
Patent Document 1 describes a charging member that charges a charged body by abutting on the charged body and applying a voltage, and the conductive elastic layer is at least in a charging member having a conductive elastic layer. , A charged member comprising a conductive pigment having a nitrogen adsorption specific surface area of 45 to 300 [m ² / g] and a DBP oil absorption of 50 to 250 [ml / 100 g] is described.
Further, in Patent Document 2, in a charging member provided with a surface resistance layer containing conductive composite particles whose surface is coated with a conductive material, the specific surface area of the conductive composite particles is 80 m ² / g or more. A charging member having a DBP oil absorption amount of 300 m ² / g or less and a DBP oil absorption amount of 50 cm ^3/100 g or more and 250 cm ^3/100 g or less of the conductive composite particles is described.

Japanese Unexamined Patent Publication No. 7-134469 Japanese Unexamined Patent Publication No. 2006-133591

An object of the present invention is to provide a conductive roller that is less likely to cause image defects when applied to an image forming apparatus and can obtain a high-quality image. A further object of the present invention is to provide an image forming apparatus having the conductive roller.

As a result of diligent studies, the present inventors used carbon black having a specific DBP oil absorption as a conductive agent and an ionic conductive agent having a specific content in the conductive roller having an elastic layer formed on the outer periphery of the shaft. By doing so, it was found that the above-mentioned problems could be solved.
That is, the present invention relates to the following <1> to <7>.
<1> The shaft is provided with an elastic layer formed on the outer periphery of the shaft, the elastic layer contains polyurethane formed by reacting polyisocyanate and a polyol, and the elastic layer has a DBP oil absorption of 20 ml / 100 g or more and 120 ml /. A conductive roller containing 100 g or less of carbon black, and the elastic layer containing 0.1 to 10 parts by mass of an ionic conductive agent with respect to 100 parts by mass of polyisocyanate.
<2> The conductive roller according to <1>, wherein the elastic layer contains 1 to 25 parts by mass of the carbon black with respect to 100 parts by mass of polyisocyanate.
<3> The conductive roller according to <1> or <2>, wherein the volume resistance value of the elastic layer is ¹⁰⁴ Ω or more and ¹⁰⁹ Ω or less.
<4> The conductive roller according to any one of <1> to <3>, wherein the polyurethane contained in the elastic layer is foamed polyurethane.
<5> The conductive roller according to any one of <1> to <4>, wherein the conductive roller further includes a surface layer formed on the surface of the elastic layer.
<6> The conductive roller according to any one of <1> to <5>, wherein the conductive roller is a developing roller.
<7> An image forming apparatus comprising the conductive roller according to any one of <1> to <6>.

According to the present invention, it is possible to provide a conductive roller that is less likely to cause image defects when applied to an image forming apparatus and can obtain a high-quality image. Further, according to the present invention, it is possible to provide an image forming apparatus having the conductive roller.

It is sectional drawing in the direction orthogonal to the axial direction of the conductive roller which shows one embodiment of the conductive roller of this invention. It is a schematic block diagram which shows an example of an electrophotographic image forming apparatus.

Hereinafter, the present invention will be illustrated in detail based on the embodiments thereof. In the following description, the description of "A to B" indicating the numerical range represents a numerical range including the end points A and B, and in the case of A <B, it represents "A or more and B or less", and A>. In the case of B, it represents "A or less and B or more".
Further, parts by mass and% by mass are synonymous with parts by weight and% by weight, respectively.

[Conductive roller]
The conductive roller of the present invention includes a shaft and an elastic layer formed on the outer periphery of the shaft, the elastic layer contains polyurethane formed by reacting polyisocyanate and a polyol, and the elastic layer has a DBP oil absorption of 20 ml. It is characterized by containing carbon black of 100 g or more and 120 ml / 100 g or less, and the elastic layer containing 0.1 to 10 parts by mass of an ionic conductive agent with respect to 100 parts by mass of polyisocyanate.

In a conductive roller having an elastic layer, the present inventors have applied it to an image forming apparatus by containing carbon black having a specific DBP oil absorption amount in the elastic layer and further containing a specific amount of an ionic conductive agent. At that time, it was found that image defects are less likely to occur and a high-quality image can be obtained, and the present invention has been completed. In the present invention, the high-quality image means an image having at least excellent dot reproducibility, and an image in which uneven image density is suppressed is preferable.
The detailed mechanism by which the above effects are obtained is unknown, but some are thought to be as follows.
Although a desired resistance value has been required for a conductive roller applied to an image forming apparatus, the present inventors have made that the resistance value and the resistance value of the elastic layer are particularly high in the conductive roller having an elastic layer. We have found that uniformity is important for obtaining high quality images.
It is considered that the desired resistance value is achieved by the elastic layer containing carbon black having a specific DBP oil absorption amount. In addition, by containing the ionic conductive agent in a specific range, the uniformity of the resistance value in the conductive roller is improved, and the uniformity of the resistance value between the conductive rollers is also improved, resulting in higher image quality. It is considered that the image can be obtained and the productivity of the conductive roller can be improved.
Hereinafter, the present invention will be described in detail.

Hereinafter, embodiments of the conductive roller of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the conductive roller 10 of the present invention in a direction orthogonal to the axial direction of the conductive roller 10.
In FIG. 1, the conductive roller 10 is preferably used in an image forming apparatus such as a copying machine or a printer, and is used for a developing roller, a toner supply roller, a charging roller, and the like. Among these, the conductive roller of the present invention is preferably a developing roller because it has a resistance value particularly suitable for a developing roller and is excellent in resistance uniformity.
As shown in FIG. 1, the conductive roller 10 of the present invention has a shaft 12 and at least an elastic layer 13 from the shaft 12 side. In the present invention, the conductive roller 10 preferably has at least an elastic layer 13 formed on the outer periphery of the shaft 12, and further preferably has a surface layer 14 formed on the outer peripheral side of the elastic layer 13. In the present invention, the conductive roller 10 may have a lower layer (not shown) between the elastic layer 13 and the surface layer 14, and an adhesive layer may be provided between the elastic layer 13 and the lower layer. (Not shown) may be provided, and the present invention is not particularly limited.
Among these, the conductive roller of the present invention preferably has at least the elastic layer 13 and the surface layer 14 formed on the outer periphery of the shaft 12, and is composed of the elastic layer 13 and the surface layer 14 formed on the outer periphery of the shaft 12. Is more preferable.

<Shaft>
The shaft 12 serves as the shaft of the conductive roller 10, and is not particularly limited as long as it has good conductivity. For example, a steel material such as sulfur free-cutting steel is plated with nickel or zinc. It can be made of material or metal such as iron, stainless steel, and aluminum. Further, the shape of the shaft 12 is not particularly limited as long as it has sufficient rigidity, and examples thereof include a medium substance or a cylindrical body in which the inside thereof is hollowed out.

<Elastic layer>
In the present invention, the elastic layer 13 is a layer having conductivity and elasticity formed on the outer peripheral side of the shaft 12, in FIG. 1, on the outer periphery of the shaft 12, and the conductive roller 10 is in contact with the charged body. It is a layer that absorbs the pressure and energizes the current from the shaft 12 to the surface of the conductive roller 10.
In the present invention, the elastic layer 13 contains polyurethane obtained by reacting polyisocyanate and a polyol, and further contains carbon black having a DBP oil absorption of 20 ml / 100 g or more and 120 ml / 100 g or less.

(Polyurethane)
In the present invention, the elastic layer contains polyurethane obtained by reacting polyisocyanate and a polyol.
As the polyisocyanate constituting polyurethane, aromatic isocyanate or its derivative, aliphatic isocyanate or its derivative, alicyclic isocyanate or its derivative is used. Among these, aromatic isocyanates or derivatives thereof are preferable, and toluene diisocyanate (TDI) or its derivatives, diphenylmethane diisocyanate (MDI) or its derivatives are particularly preferably used.

Examples of the tolylene diisocyanate or a derivative thereof include crude tolylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. Urea modified products, bullet modified products, carbodiimide modified products, urethane modified products modified with polyols, etc. are used.
As the diphenylmethane diisocyanate or its derivative, for example, diphenylmethane diisocyanate or its derivative obtained by phosgenating diaminodiphenylmethane or its derivative is used. Examples of the derivative of diaminodiphenylmethane include a polynuclear body, and pure diphenylmethane diisocyanate obtained from diaminodiphenylmethane, polymeric diphenylmethane diisocyanate obtained from a polynuclear body of diaminodiphenylmethane, and the like can be used. As for the number of functional groups of the polypeptide diphenylmethane diisocyanate, a mixture of pure diphenylmethane diisocyanate and a polypeptide having various functional groups is usually used, and the average number of functional groups is preferably 2.05 to 4.00, more preferably 2. .50 to 3.50 are used. Further, a derivative obtained by modifying these diphenylmethane diisocyanate or a derivative thereof, for example, a urethane modified product modified with a polyol or the like, a dimer by uretidine formation, an isocyanurate modified product, a carbodiimide / uretonimine modified product, an alohanate modified product. , Urea modified product, Bullet modified product and the like can also be used. Further, several kinds of diphenylmethane diisocyanate and its derivatives can be blended and used.

Further, the polyisocyanate may be prepolymerized with a polyol, and as a method thereof, the polyisocyanate and the polyol are kept warm at preferably 40 to 70 ° C., preferably 6 to 240 hours, more preferably 24 to 72 hours. There is a way to do it. In this case, the ratio of the blending amount of the polyol and the polyisocyanate is preferably adjusted so that the polyisocyanate content of the obtained prepolymer is 4 to 30% by mass, and more preferably 6 to 15% by mass. .. If the isocyanate content is less than 4% by mass, the stability of the prepolymer may be impaired and the prepolymer may be cured during storage, making it unusable. Further, when the isocyanate content exceeds 30% by mass, the content of the non-prepolymerized isocyanate increases, and this polyisocyanate undergoes a prepolymerization reaction with the polyol component used in the subsequent polyurethane curing reaction. The effect of using the prepolymer method is diminished because it is cured by a reaction mechanism similar to that of the one-shot method. When an isocyanate component obtained by prepolymerizing isocyanate with a polyol is used, the polyol component includes diols such as ethylene glycol and butanediol, polyols such as trimethylolpropane and sorbitol, and theirs, in addition to the polyol component described later. Derivatives can also be used.

Examples of the polyol component include a polyether polyol obtained by addition polymerization of ethylene oxide and propylene oxide, a polytetramethylene ether glycol, a polyester polyol obtained by condensing an acid component and a glycol component, a polyester polyol obtained by ring-opening polymerization of caprolactone, and a polycarbonate diol. Can be used.

Examples of the polyether polyol obtained by addition-polymerizing ethylene oxide and propylene oxide include water, propylene glycol, ethylene glycol, glycerin, trimethylolpropane, hexanetriol, triethanolamine, diglycerin, pentaerythritol, ethylenediamine, and methylglucogit. , Aromatic diamine, sorbitol, sucrose, phosphoric acid and the like as starting materials, and addition polymerization of ethylene oxide and propylene oxide can be mentioned. , Glyceroltriol as a starting material is preferable. Regarding the ratio of ethylene oxide to propylene oxide and the microstructure to be added, the ratio of ethylene oxide is preferably 2 to 95% by mass, more preferably 5 to 90% by mass, and those having ethylene oxide added to the ends are preferable. Further, the arrangement of ethylene oxide and propylene oxide in the molecular chain is preferably random.

The molecular weight of the polyether polyol is bifunctional when water, propylene glycol, or ethylene glycol is used as a starting material, and the weight average molecular weight is preferably in the range of 300 to 6,000, preferably 400 to 3,000. Those in the range of are more preferable. When glycerin, trimethylolpropane, or hexanetriol is used as a starting material, the starting material is trifunctional, and the weight average molecular weight is preferably in the range of 900 to 9,000, more preferably in the range of 1,500 to 6,000. preferable. Further, a bifunctional polyol and a trifunctional polyol can be appropriately blended and used.

Further, the polytetramethylene ether glycol can be obtained, for example, by cationic polymerization of tetrahydrofuran, and the weight average molecular weight is preferably in the range of 400 to 4,000, more preferably in the range of 650 to 3,000. It is also preferable to blend polytetramethylene ether glycols having different molecular weights. Further, polytetramethylene ether glycol obtained by copolymerizing an alkylene oxide such as ethylene oxide or propylene oxide can also be used.
Further, it is also preferable to use a blend of polytetramethylene ether glycol and a polyether polyol obtained by addition-polymerizing ethylene oxide and propylene oxide. In this case, these blend ratios are preferably in the range of 95: 5 to 20:80, more preferably in the range of 90:10 to 50:50 in terms of mass ratio.
Further, together with the above-mentioned polyol component, a polymer polyol obtained by modifying a polyol with acrylonitrile, a polyol obtained by adding melamine to a polyol, diols such as butanediol, polyols such as trimethylolpropane, and derivatives thereof can also be used in combination.

In the present invention, the polyurethane contained in the elastic layer may be in the form of unexpanded rubber or in the form of foamed foam, but from the viewpoint of obtaining an elastic layer having more excellent elasticity, it may be foamed polyurethane (polyurethane foam). preferable.

(Carbon black)
In the present invention, the elastic layer contains carbon black having a DBP oil absorption of 20 ml / 100 g or more and 120 ml / 100 g or less. When the DBP oil absorption amount of carbon black is 20 ml / 100 g or more and 120 ml / 100 g or less, a desired volume resistance value can be obtained.
The DBP oil absorption amount of carbon black contained in the elastic layer is preferably 30 ml / 100 g or more, more preferably 40 ml / 100 g or more, still more preferably 50 ml / 100 g or more, and more preferably 50 ml / 100 g or more, from the viewpoint of obtaining a desired volume resistance value. It is preferably 110 ml / 100 g or less, more preferably 100 ml / 100 g or less, and further preferably 90 ml / 100 g or less.
Here, the amount of DBP (dibutyl phthalate) oil absorbed can be measured according to JIS K 6217: 2017.
The elastic layer may contain carbon black having a DBP oil absorption of less than 20 ml / 100 g or more than 120 ml / 100 g, but the content thereof is carbon having a DBP oil absorption of 20 ml / 100 g or more and 120 ml / 100 g or less. When the content of black is 100 parts by mass, it is preferably 100 parts by mass or less, more preferably 30 parts by mass or less, further preferably 10 parts by mass or less, still more preferably 3 parts by mass or less, still more preferably 1 part by mass. It is not contained in a portion or less, more preferably.
The carbon black may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black contained in the elastic layer is preferably 20 m ² / g or more, more preferably 40 m ² / g or more, and further, from the viewpoint of obtaining a conductive roller having a desired resistance. It is preferably 60 m ² / g or more, more preferably 70 m ² / g or more, and preferably 400 m ² / g or less, more preferably 300 m ² / g or less, still more preferably 250 m ² / g or less, still more. It is preferably 200 m ² / g or less.
Here, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black can be measured according to JIS K 6217: 2017.

The content of carbon black in the elastic layer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 25 parts by mass or less, more preferably 20 parts by mass with respect to 100 parts by mass of polyisocyanate. It is not less than parts by mass, more preferably 15 parts by mass or less, and even more preferably 8 parts by mass or less.
When the content of carbon black in the elastic layer is within the above range, it is easy to obtain a desired resistance value.

(Ion conductive agent)
In the present invention, the elastic layer contains 0.1 to 10 parts by mass of an ionic conductive agent with respect to 100 parts by mass of polyisocyanate. When the elastic layer contains the ionic conductive agent in the above-mentioned content, the uniformity of resistance in the conductive roll is improved, and a high-quality image can be obtained.
The content of the ionic conductive agent is preferably 8 parts by mass or less, and more preferably 4 parts by mass or less with respect to 100 parts by mass of polyisocyanate.

The ionic conductive agent includes, but is not limited to, tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (for example, lauryltrimethylammonium), hexadecyltrimethylammonium, octadecyltrimethylammonium (for example, stearyltrimethylammonium), and benzyltrimethyl. Ammonium salts with ammonium, modified fatty acid dimethylethylammonium, etc. and perchloric acid, chloric acid, hydrochloric acid, bromine acid, iodic acid, borohydrophobic acid, sulfuric acid, ethyl sulfate, carboxylic acid, sulfonic acid, etc .; lithium, sodium, potassium Alkali metal salts or alkaline soils of alkali metals such as calcium and magnesium and alkaline earth metals with perchloric acid, chloric acid, hydrochloric acid, bromic acid, iodic acid, borohydrofluoric acid, trifluoromethylsulfate, sulfonic acid and the like. Kind of metal salt;

As the ion conductive agent, a lithium salt is preferable. When the ion conductive agent is a lithium salt, a conductive roller having more excellent resistance uniformity can be obtained.
The lithium salt may be a salt of an organic acid such as sulfonic acid or trifluoromethanesulfonic acid, or a salt of an inorganic acid such as perchloric acid or tetrafluoroboric acid. Here, the lithium salts include Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, lithium perchlorate (LiClO ₄ ), lithium chloride (LiCl), and lithium bromide (LiCl). LiBr), LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₂ , LiCF ₃ SO ₃ , LiAsF ₆ , LiC ₄ F ₉ SO _3, LiC ₆ H ₅ SO ₃ , and the like.
Further, as the lithium salt, a lithium salt polyol may be used. Examples of the lithium salt polyol include one kind or two or more kinds of complexes in which a lithium salt is dissolved in a polyol, coordinated and ionized (Li ⁺ ). Specific examples of the lithium salt polyol include Sanconol (registered trademark) PEO-20R manufactured by Toei Chemical Co., Ltd.
One of these lithium salts may be used alone, or two or more thereof may be used in combination. The lithium salt may be dissolved in various solvents and mixed with the raw material for the elastic layer.

(Other additives)
In the raw material of the elastic layer, in addition to the above-mentioned polyisocyanate and polyol, carbon black, and ionic conductive agent, if desired, a foaming agent (water, low boiling point, gas body, etc.), a cross-linking agent, a surfactant, etc. , A catalyst, a foaming agent, and other other additives can be added, whereby an elastic layer can be obtained as desired.
Monoamines such as triethylamine and dimethylcyclohexylamine; diamines such as tetramethylethylenediamine, tetramethylpropanediamine and tetramethylhexanediamine; pentamethyldiethylenetriamine, pentamethyldipropylenetriamine and tetra Triamines such as methylguanidine; cyclic amines such as triethylenediamine, dimethylpiperazine, methylethylpiperazine, methylmorpholin, dimethylaminoethylmorpholin, dimethylimidazole; dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethylethanolamine, methylhydroxy Alcohol amines such as ethyl piperazine and hydroxyethyl morpholine; ether amines such as bis (dimethylaminoethyl) ether, ethylene glycol bis (dimethyl) aminopropyl ether; stannous Octanoate, dibutyltin diacetate, dibutyl Examples thereof include organic metal compounds such as tin dilaurate, dibutyltin mercaptide, dibutyltin thiocarboxylate, dibutyltin dimalate, dioctyltin markaptide, dioctyltin thiocarboxylate, phenylmercury propionate, and lead octate. .. These catalysts may be used alone or in combination of two or more.

Examples of the foaming agent include water, a polydimethylsiloxane-polyethylene oxide copolymer, a polydimethylsiloxane-polypropylene oxide copolymer, and a polydimethylsiloxane-polyethylene adipate copolymer.

In the present invention, when the polyurethane is foamed polyurethane (polyurethane foam), it is preferable to add a silicone foam stabilizer or various surfactants to the polyurethane foam in order to stabilize the cells of the foam material.
As the silicone defoaming agent, a dimethylpolysiloxane-polyoxyalkylene copolymer or the like is preferably used, and is composed of a dimethylpolysiloxane moiety having a molecular weight of 350 to 15,000 and a polyoxyalkylene moiety having a molecular weight of 200 to 4,000. The one is particularly preferable. The molecular structure of the polyoxyalkylene moiety is preferably an addition polymer of ethylene oxide or a co-addition polymerization of ethylene oxide and propylene oxide, and it is also preferable that the molecular end thereof is ethylene oxide.
Examples of the surfactant include cationic surfactants, anionic surfactants, ionic surfactants such as amphoteric and nonionic surfactants such as various polyethers and various polyesters.
These foam stabilizers and surfactants may be used alone or in combination of two or more. The blending amount of the silicone foam stabilizer and various surfactants is preferably 0.1 to 10 parts by mass, and 0.5 to 5 parts by mass with respect to 100 parts by mass of the total amount of the polyisocyanate and the polyol. Is more preferable.

In the present invention, when the polyurethane contained in the elastic layer is foamed polyurethane (polyurethane foam), the foaming method of the polyurethane foam raw material includes the conventionally used mechanical floss method, water foaming method, foaming agent floss method and the like. Although a method can be used, it is particularly preferable to use a mechanical floss method in which foaming is performed by mechanical stirring while mixing an inert gas.
Here, the inert gas used in the mechanical floss method may be any gas that is inert in the polyurethane reaction, and is not only an inert gas in a narrow sense such as helium, argon, xenone, radon, and krypton, but also nitrogen, carbon dioxide, and drying. Examples thereof include gases that do not react with urethane foam raw materials such as air. In the present invention, the molding conditions of the elastic layer made of the polyurethane foam raw material are not particularly limited, and normal conditions may be followed.

When the polyurethane contained in the elastic layer is foamed polyurethane, the foaming ratio thereof is preferably 1 to 20 times, more preferably 1 to 10 times, still more preferably 1 from the viewpoint of achieving both appropriate elasticity and strength. ~ 5 times.

The volume resistance value of the elastic layer is preferably 104 Ω or more, more preferably ^{10 4.5} Ω or more, still more preferably ¹⁰⁵ Ω or more, from the viewpoint of obtaining a high-quality image when applied to an image forming apparatus. Even more preferably 10 ⁶ Ω or more, still more preferably 10 ⁷ Ω or more, preferably 10 ¹⁰ Ω or less, more preferably 10 ^9.5 Ω or less, still more preferably 10 ⁹ Ω or less, still more preferably 10 It is ^8.5 Ω or less, more preferably ¹⁰⁸ or less.
The volume resistance value of the elastic layer is measured by the method described in Examples.

The thickness of the elastic layer also depends on the radius of the conductive roller. For example, when the conductive roller has a radius of 3 to 10 mm, the thickness of the elastic layer is preferably 2 to 10 mm, more preferably 2 to 10 mm. Is 2 to 8 mm, more preferably 3 to 6 mm.
The Asker C hardness of the elastic layer is preferably 45 to 70 °, more preferably 50 to 70 °, and even more preferably 58 to 62 °. Asker C hardness is a value measured according to JIS K 7312: 1996. When the Asker C hardness is within the above range, for example, when the conductive roller is a developing roller, the hardness range is optimum for contact with the photoconductor, and the toner mass is broken while suppressing the deterioration of the toner. It is considered that uneven development can be eliminated and an image with higher image quality can be obtained.

<Surface layer>
The conductive roller 10 of the present invention preferably has a surface layer 14 formed directly or indirectly on the outer periphery of the elastic layer 13. As described above, an adhesive layer or a lower layer may be provided between the elastic layer 13 and the surface layer 14, but it is preferable that the surface layer 14 is directly formed on the surface of the elastic layer 13.
The surface layer 14 forms the surface of the conductive roller 10, and is a layer that comes into contact with the photoconductor when the conductive roller 10 is used as a developing roller.
The surface layer can be formed of various solvent-based paints such as urethane-based, acrylic-based, acrylic urethane-based, and fluorine-based paints. Among these, the surface layer preferably contains polyurethane as a resin component.
Further, the surface roughness may be adjusted by containing fine particles made of urethane, acrylic, silica or the like.
A conductive agent (electron conductive agent such as carbon black and ionic conductive agent), a vulcanization agent, a vulcanization accelerator, an antiaging agent, and the like may be appropriately added to the surface layer. Among these, in order to further enhance the conductivity of the surface layer, it is preferable to contain a conductive agent, whereby a higher image quality image can be obtained. As the conductive agent, at least one selected from an ionic conductive agent and an electronic conductive agent may be used, and two or more thereof may be used in combination. Examples of the ion conductive agent include the ion conductive agent exemplified in the elastic layer. Examples of the electronic conductive agent include fine particles of metal oxides such as ITO, tin oxide, titanium oxide, and zinc oxide; fine particles of metals such as nickel, copper, silver, and germanium: developed titanium oxide whiskers, developed barium titanate whiskers, and the like. Development whiskers and the like. Further, as the electronic conductive agent, developed carbon such as Ketjen black and acetylene black, carbon black for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT and MT, and carbon for color subjected to oxidation treatment and the like. Black, pyrolysis carbon black, natural graphite, artificial graphite and the like can be used.
The surface layer is formed by applying a predetermined solvent-based paint to the elastic layer using a known method such as dip coating, spray coating, roll coater coating, drying, and heat-curing as desired. It is possible.

When the surface layer contains polyurethane, the surface layer composition for forming the surface layer preferably contains a polyisocyanate and a polyol, and in addition, contains the above-mentioned conductive agent, antiaging agent and the like. Is preferable. Further, in order to promote the reaction between the polyisocyanate and the polyol, it is preferable to contain a catalyst, and examples of the catalyst include the urethanization catalyst exemplified in the elastic layer.
Examples of the polyisocyanate and the polyol include the compounds exemplified in the elastic layer.
When the surface layer contains polyurethane, the polyurethane is preferably rubber-like rather than foam-like.

The layer thickness of the surface layer also depends on the radius of the conductive roller. For example, when the conductive roller has a radius of 3 to 10 mm, the layer thickness of the surface layer is preferably 1 to 50 μm, more preferably 2 It is ~ 30 μm, more preferably 10 to 30 μm.

The conductive roller of the present invention preferably has a volume resistance value of ^{105 Ω or more, more preferably 10 5.5 Ω} , from the viewpoint of obtaining a high-quality image when applied to an image forming apparatus. The above is more preferably ^{106 Ω or more, still more preferably 10 7 Ω} or more, still more preferably 10 ⁸ Ω or more, preferably 10 ¹¹ Ω or less, more preferably 10 ^10.5 Ω or less, still more preferably. It is 10 ¹⁰ Ω or less, more preferably 10 ^9.5 Ω or less, still more preferably 10 ⁹ or less.
When the volume resistance value of the conductive roller is within the above range, the characteristics as a developing roller are particularly excellent.

[Image forming device]
The conductive roller of the present invention is preferably applied to an image forming apparatus such as a copier, a printer, or a facsimile that employs an electrophotographic method. That is, it is preferable that the conductive roller of the present invention is arranged in the image forming apparatus.
The conductive roller of the present invention is suitable as a conductive roller such as a charging roller, a developing roller, a transfer roller, and a toner supply roller arranged around the photoconductor, and is particularly preferably used as a developing roller. ..
FIG. 2 is a schematic configuration diagram showing an example of an electrophotographic non-magnetic one-component developed image forming apparatus to which the conductive roller of the present invention is applied. In FIG. 2, the image forming apparatus according to the present embodiment has a photoconductor drum 1 as an image holder that rotates in a predetermined direction, and the photoconductor drum 1 is charged around the photoconductor drum 1. The charging roller 7 is to be used, an exposure device as a latent image forming device for forming an electrostatic latent image on the photoconductor drum 1, and an electrostatic latent image formed on the photoconductor drum 1 are visualized. The developing roller 2, the transfer roller 5 that transfers the toner image visualized on the photoconductor drum 1 to the recording medium 8 that is the transfer target, and the cleaning roller 6 that cleans the residual toner on the photoconductor drum 1. And are sequentially arranged. The developer supply roller 3 is arranged in contact with the developing roller 2.

The photoconductor 1 is in contact with the transfer roller 5 via the recording medium 8. When the recording medium 8 does not pass through, the transfer roller 5 is in direct contact with the photoconductor 1. By rotating the developer supply roller 3, the developing roller 2 and the photoconductor 1 in the direction of the arrow, the developer is supplied to the surface of the developing roller 2 by the developing agent supply roller 3, and a uniform thin layer is supplied by the layer regulating blade 4. After being arranged in, it adheres to the electrostatic latent image on the photoconductor 1, and the latent image is visualized. Then, by generating an electric field between the photoconductor 1 and the transfer roller 5, the developer image on the photoconductor 1 is transferred to the recording medium 8. Further, the cleaning roller 6 removes the developer remaining on the surface of the photoconductor 1 after transfer.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[Preparation of elastic layer]
<Example 1>
Prepolymerized TDI (manufactured by Asahi Glass Co., Ltd., 800 BP) 100 parts by mass and conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) 25 mass 12.5 parts by mass of an isocyanate component containing parts and an ester-based polyol (manufactured by Kuraray Co., Ltd., F510), 12.5 parts by mass of an ester-based polyol (manufactured by Kuraray Co., Ltd., F1010), and an ether-based 25 parts by mass of polyol (manufactured by Sanyo Kasei Kogyo Co., Ltd., FA951), 3 parts by mass of foam stabilizer (manufactured by Tohredo Corning Co., Ltd., SF2937F), and catalyst (manufactured by Nitto Kasei Co., Ltd., U-100) 0 .05 parts by mass, 2 parts by mass of aliphatic quaternary ammonium sulfate (manufactured by Kao Co., Ltd., KS-48) and 0.3 parts by mass of sodium perchlorate (manufactured by Showa Kagaku Kogyo Co., Ltd., MP-100) The polyol component mixed with the portion was mixed, foamed by a mechanical floss method, and injected into a mold in which a metal shaft (φ8 mm) was set. Then, this mixture was heat-cured at 120 ° C. for 30 minutes to form an elastic layer having a thickness of 6 mm on the outer periphery of the metal shaft.

<Example 2>
The same as in Example 1 except that the conductive carbon black used (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) was changed to 16 parts by mass. An elastic layer was formed.

<Example 3>
The same as in Example 1 except that the conductive carbon black used (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) was changed to 8 parts by mass. An elastic layer was formed.

<Example 4>
The same as in Example 1 except that the conductive carbon black used (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) was changed to 4 parts by mass. An elastic layer was formed.

<Example 5>
The same as in Example 1 except that the conductive carbon black used (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) was changed to 1 part by mass. An elastic layer was formed.

<Example 6>
Conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) Instead of 8 parts by mass, conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB605, DBP oil absorption = 77 ml / 100 g, N ₂ SA = 85 m ² / g) An elastic layer was formed in the same manner as in Example 1 except that 8 parts by mass was used.

<Example 7>
Conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) Instead of 8 parts by mass, conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB285, DBP oil absorption = 111 ml / 100 g, N ₂ SA = 77 m ² / g) An elastic layer was formed in the same manner as in Example 1 except that 8 parts by mass was used.

<Example 8>
Conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) Instead of 8 parts by mass, conductive carbon black (manufactured by Asahi Carbon Co., Ltd., Asahi Thermal FT, DBP oil absorption = 28 ml / 100 g, N ₂ SA = 24 m ² / g) An elastic layer was formed in the same manner as in Example 1 except that 8 parts by mass was used.

<Example 9>
Except for changing the aliphatic quaternary ammonium sulfate (KS-48 manufactured by Kao Corporation) to 4 parts by mass and adding 2 parts by mass of a lithium salt (Sanconol manufactured by Sanko Chemical Industry Co., Ltd.) to the polyol component. Formed an elastic layer in the same manner as in Example 3.

<Example 10>
An elastic layer was formed in the same manner as in Example 3 except that sodium perchlorate (MP-100, manufactured by Showa Chemical Industry Co., Ltd.) was not used.

<Example 11>
Except for using 2 parts by mass of sodium perchlorate (MP-100, manufactured by Showa Chemical Industry Co., Ltd.) instead of 2 parts by mass of aliphatic quaternary ammonium sulfate (KS-48, manufactured by Kao Corporation). , An elastic layer was formed in the same manner as in Example 10.

<Example 12>
Example 10 except that 2 parts by mass of a lithium salt (Sanconol, manufactured by Sanko Chemical Industry Co., Ltd.) was used instead of 2 parts by mass of an aliphatic quaternary ammonium sulfate (KAO Corporation, KS-48). The elastic layer was formed in the same manner as in the above.

<Comparative Example 1>
Examples except that the ionic conductive agent aliphatic quaternary ammonium sulfate (Kao Corporation, KS-48) and sodium perchlorate (Showa Chemical Industry Co., Ltd., MP-100) are not used. An elastic layer was formed in the same manner as in 3.

<Comparative Example 2>
Use of 6 parts by mass of aliphatic quaternary ammonium sulfate (KS-48 manufactured by Kao Co., Ltd.), which is an ionic conductive agent, and use of sodium perchlorate (MP-100 manufactured by Showa Chemical Industry Co., Ltd.). An elastic layer was formed in the same manner as in Example 3 except that the amount was changed to 2 parts by mass and 4 parts by mass of a lithium salt (Sanconol manufactured by Sanko Chemical Industry Co., Ltd.) was used.

<Comparative Example 3>
Conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) Instead of 8 parts by mass, conductive carbon black (manufactured by Electrochemical Industry Co., Ltd.) , Denka black, DBP oil absorption = 125 ml / 100 g, N ₂ SA = 61 m ² / g) An elastic layer was formed in the same manner as in Example 3 except that 8 parts by mass was used.

<Comparative Example 4>
Conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB805, DBP oil absorption = 58 ml / 100 g, N ₂ SA = 198 m ² / g) Instead of 8 parts by mass, conductive carbon black (manufactured by Asahi Carbon Co., Ltd., SB305, DBP oil absorption = 136 ml / 100 g, N ₂ SA = 147 m ² / g) An elastic layer was formed in the same manner as in Example 3 except that 8 parts by mass was used.

[Preparation of surface layer]
Polytetramethylene glycol ether polyol (manufactured by Hodoya Chemical Industry Co., Ltd., PTG1000SN: OH value 112 mgKOH / g) 100 parts by mass, carbon black (Mitsubishi Chemical Co., Ltd. carbon black, MA600) 5 parts by mass, methyl ethyl ketone (MEK) Disperse in 350 parts by mass, then add 40 parts by mass of isocyanate curing agent (Coronate Hx: NCO% = 21%, manufactured by Toso Co., Ltd.), and stir with a stirring motor for 30 minutes to apply the surface paint. Prepared.
The above-mentioned surface layer paint was applied to the shafts with elastic layers obtained in Examples 1 to 12 and Comparative Examples 1 to 4 by the dipping method, and dried at 105 ° C. for 120 minutes. A surface layer having a thickness of 20 μm was formed to form a conductive roller.

[evaluation]
The elastic layer or the conductive roller obtained in Examples and Comparative Examples was evaluated as follows.
<Volume resistance value of elastic layer>
The volume resistance value of the elastic layer was measured by the following method.
That is, the roller is placed on a metal plate, a load of 500 g is applied to both ends of the roller, 100 V is applied between the shaft 12 and the metal plate, and the resistance after 5 seconds is measured by a resistance measuring machine (manufactured by ADVANTEST). It was measured by R8340).
The results are shown in the table below.

<Dot reproducibility>
The obtained conductive roller was incorporated into a cartridge as a developing roller, and an initial image was formed by a monochrome MS812dn manufactured by Lexmark in a 25 ° C. and 50% RH environment. The microdot printing part was enlarged and observed, and visually judged according to the following criteria. The results are shown in the table below.
◎: Very good dot reproducibility 〇: Good dot reproducibility △: Poor dot reproducibility ×: Very poor dot reproducibility

From the results of Tables 1 and 2, in Examples 1 to 12 in which the elastic layer meets the requirements of the present invention, a desired volume resistance value can be obtained, and further, when applied to an image forming apparatus, the dot reproducibility is excellent. A conductive roller was obtained.
On the other hand, in Comparative Example 1 containing no ionic conductive agent and Comparative Example 2 in which the content of the ionic conductive agent exceeded 10 parts by mass with respect to 100 parts by mass of polyisocyanate, the dot reproducibility was poor. Further, in Comparative Examples 3 and 4 containing carbon black having a DBP oil absorption amount of more than 120 ml / 100 g, the volume resistance value of the elastic layer did not fall within the desired range, and the dot reproducibility was also the worst.

According to the present invention, it is possible to provide a conductive roller that is less likely to cause image defects when applied to an image forming apparatus and can obtain a high-quality image, and is particularly expected to be applied as a developing roller. ..

1 Photoconductor 2 Developing roller 3 Developing agent supply roller 4 Layer regulation blade 5 Transfer roller 6 Cleaning roller 7 Charging roller 8 Recording medium 10: Conductive roller 12: Shaft 13: Elastic layer 14: Surface layer

Claims (6)

With a shaft and an elastic layer formed on the outer circumference of the shaft,
The elastic layer contains polyurethane formed by reacting polyisocyanate and polyol.
The elastic layer contains carbon black having a DBP oil absorption of 20 ml / 100 g or more and 120 ml / 100 g or less.
The elastic layer is a conductive roller containing 0.1 to 10 parts by mass of an ionic conductive agent with respect to 100 parts by mass of polyisocyanate.
The conductive roller further comprises a surface layer formed on the surface of the elastic layer.
The surface layer is a conductive roller containing polyurethane and carbon black as a conductive agent . The conductive roller according to claim 1, wherein the elastic layer contains 1 to 25 parts by mass of the carbon black with respect to 100 parts by mass of polyisocyanate. The conductive roller according to claim 1 or 2, wherein the elastic layer has a volume resistance value of ¹⁰⁴ Ω or more and ¹⁰⁹ Ω or less. The conductive roller according to any one of claims 1 to 3, wherein the polyurethane contained in the elastic layer is foamed polyurethane. The conductive roller according to any one of claims 1 to 4, wherein the conductive roller is a developing roller. An image forming apparatus comprising the conductive roller according to any one of claims 1 to 5.

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