Development roll for electrophotographic apparatuses

Abstract

The present invention provides a development roll for an electrophotographic apparatus, in which a surface layer has low electric resistance and excellent wear resistance, and which is excellent in uniformity and enables the achievement of excellent images over a long period of time.　This development roll (10) for an electrophotographic apparatus comprises: a shaft body (12); an elastic body layer (14) that is formed on the outer peripheral surface of the shaft body (12); and a surface layer (16) that is formed on the outer peripheral surface of the elastic body layer (14). The elastic body layer (14) is composed of a silicone base material that contains silicone rubber. The surface layer 16 is composed of a crosslinked body of a composition that contains a urethane prepolymer which is composed of the substances (A) and (B) described below, and the substances (C) to (E) described below. The breaking stress of the surface layer (16) is 30 MPa or more. (A) An aromatic isocyanate, (B) A caprolactone-based polyol or a carbonate-based polyol, (C) Carbon black, (D) A (meth)acrylic polymer that contains a hydrophilic group and a silicone group in each molecule, (E) An isocyanurate

Description

Developing rolls for electrophotographic equipment

[0001] The present invention relates to a developing roll for electrophotographic equipment, which is suitably used in electrophotographic equipment such as copying machines, printers, and facsimiles that employ an electrophotographic system.

[0002] A known developing roll for an electrophotographic device has a shaft body made of a core metal or the like, an elastic layer formed on the outer circumferential surface of the shaft body, and a surface layer formed on the outer circumferential surface of the elastic layer. The surface layer is formed of a urethane material or the like containing a conductive agent. Carbon black or the like is used as the conductive agent.

[0003] Japanese Patent Application Laid-Open No. 2001-310998

[0004] When the surface layer of a developing roll contains a large amount of carbon black, the surface layer has low electrical resistance, resulting in a good image. On the other hand, the surface layer becomes brittle and prone to wear, resulting in poor durability. For this reason, achieving both low electrical resistance and strength in the surface layer is a challenge. Furthermore, the electrical resistance of the surface layer is also affected by the uniformity of the surface layer. A uniform surface layer stabilizes the electrical resistance and chargeability of the surface layer, resulting in a good image. Therefore, the uniformity of the surface layer is also important.

[0005] The problem to be solved by the present invention is to provide a developing roll for electrophotographic equipment, which has a surface layer with low electrical resistance, excellent wear resistance, and excellent uniformity, and which provides excellent images over a long period of time.

[0006] The developing roll for an electrophotographic device according to the present invention comprises a shaft, an elastic layer formed on the outer peripheral surface of the shaft, and a surface layer formed on the outer peripheral surface of the elastic layer, wherein the elastic layer is made of a silicone base material containing silicone rubber, and the surface layer is made of a crosslinked product of a composition containing a urethane prepolymer composed of the following (A) and (B) and the following (C) to (E), and the breaking stress of the surface layer is 30 MPa or more: (A) an aromatic isocyanate, (B) a caprolactone-based polyol or a carbonate-based polyol, (C) carbon black, (D) a (meth)acrylic polymer containing a hydrophilic group and a silicone group in the molecule, and (E) an isocyanurate.

[0007] The weight average molecular weight Mw of the urethane prepolymer is preferably 100,000 or more and 300,000 or less. (A) is preferably diphenylmethane diisocyanate. The content of (C) is preferably 10 parts by mass or more and 35 parts by mass or less per 100 parts by mass of the urethane prepolymer. The content of (D) is preferably 1.0 part by mass or more and 20 parts by mass or less per 100 parts by mass of the urethane prepolymer. The content of (E) is preferably 1.0 part by mass or more and 40 parts by mass or less per 100 parts by mass of the urethane prepolymer. The electrical resistance of the surface layer is preferably 1.0 x 10 ３ Ω or more 1.0×10 ６ The surface layer preferably contains a carbon black dispersant having an aromatic ring.

[0008] (1) A developing roll for an electrophotographic device according to the present invention comprises a shaft, an elastic layer formed on the outer peripheral surface of the shaft, and a surface layer formed on the outer peripheral surface of the elastic layer, wherein the elastic layer is made of a silicone base material containing silicone rubber, and the surface layer is made of a crosslinked product of a composition containing a urethane prepolymer composed of the following (A) and (B) and the following (C) to (E), and the breaking stress of the surface layer is 30 MPa or more: (A) an aromatic isocyanate, (B) a caprolactone-based polyol or a carbonate-based polyol, (C) carbon black, (D) a (meth)acrylic polymer containing a hydrophilic group and a silicone group in the molecule, and (E) an isocyanurate.

[0009] (2) In the above (1), the weight average molecular weight Mw of the urethane prepolymer is preferably 100,000 or more and 300,000 or less.

[0010] (3) In the above (1) or (2), (A) may be diphenylmethane diisocyanate.

[0011] (4) In any one of (1) to (3) above, the content of (C) may be 10 parts by mass or more and 35 parts by mass or less per 100 parts by mass of the urethane prepolymer.

[0012] (5) In any one of the above (1) to (4), the content of (D) may be 1.0 part by mass or more and 20 parts by mass or less per 100 parts by mass of the urethane prepolymer.

[0013] (6) In any one of the above (1) to (5), the content of (E) may be 1.0 part by mass or more and 40 parts by mass or less per 100 parts by mass of the urethane prepolymer.

[0014] (7) In any one of (1) to (6), the electrical resistance of the surface layer is 1.0 × 10 ３ Ω or more 1.0×10 ６ It is preferable that it is Ω or less.

[0015] (8) In any one of the above (1) to (7), the hydrophilic group of (D) may be an amino group or a hydroxy group.

[0016] (9) In any one of the above (1) to (8), the surface layer may further contain a carbon black dispersant having an aromatic ring.

[0017] According to the developing roll for electrophotographic equipment of the present invention, the elastic layer is made of a silicone base material containing silicone rubber, the surface layer is made of a crosslinked product of a composition containing a urethane prepolymer constituted of the above (A) and (B) and the above (C) to (E), and the breaking stress of the surface layer is 30 MPa or more. Therefore, the surface layer has low electrical resistance, excellent abrasion resistance, and excellent uniformity, and provides excellent images over a long period of time.

[0018] When the weight average molecular weight Mw of the urethane prepolymer is 100,000 or more and 300,000 or less, the surface layer has excellent strength and excellent abrasion resistance.

[0019] When the component (A) is diphenylmethane diisocyanate, it is particularly effective in improving strength among aromatic isocyanates, and therefore the abrasion resistance of the surface layer is improved.

[0020] When the content of (C) is 10 parts by mass or more and 35 parts by mass or less relative to 100 parts by mass of the urethane prepolymer, low electrical resistance and high abrasion resistance can be simultaneously achieved.

[0021] When the content of (D) is 1.0 part by mass or more and 20 parts by mass or less relative to 100 parts by mass of the urethane prepolymer, the effect of improving the uniformity of the surface layer is excellent.

[0022] When the content of (E) is 1.0 part by mass or more and 40 parts by mass or less per 100 parts by mass of the urethane prepolymer, the strength is improved, and therefore the abrasion resistance of the surface layer is improved.

[0023] The electrical resistance of the surface layer is 1.0×10 ３ Ω or more 1.0×10 ６ When the resistance is Ω or less, the electric resistance is low and an excellent image is obtained.

[0024] When the hydrophilic group of (D) is an amino group or a hydroxy group, the effect of improving the uniformity of the surface layer is excellent.

[0025] If the surface layer further contains a carbon black dispersant having an aromatic ring, the dispersibility of the carbon black is improved.

[0026] 1A is a schematic view of the appearance of a developing roll for an electrophotographic apparatus according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA thereof.

[0027] The developing roll for an electrophotographic device according to the present invention (hereinafter, sometimes simply referred to as the developing roll) will be described in detail. Fig. 1 is a schematic view (a) of the appearance of the developing roll for an electrophotographic device according to one embodiment of the present invention, and Fig. 1 is a cross-sectional view (b) of the developing roll for an electrophotographic device according to the present invention taken along line A-A.

[0028] The developing roll 10 includes a shaft 12, an elastic layer 14 formed on the outer peripheral surface of the shaft 12, and a surface layer 16 formed on the outer peripheral surface of the elastic layer 14. The elastic layer 14 is a layer (base layer) that serves as the base of the developing roll 10. The surface layer 16 is a layer that appears on the surface of the developing roll 10.

[0029] The shaft 12 is not particularly limited as long as it is electrically conductive. Specific examples include a solid or hollow core made of metal such as iron, stainless steel, or aluminum. The surface of the shaft 12 may be coated with an adhesive, primer, or the like, as needed. That is, the elastic layer 14 may be bonded to the shaft 12 via an adhesive layer (primer layer). The adhesive, primer, or the like may be made electrically conductive as needed.

[0030] The elastic layer 14 is made of a silicone base material containing silicone rubber. Silicone rubber is a material with excellent elastic recovery and is resistant to volumetric changes due to environmental changes such as temperature and humidity changes. This reduces fluctuations in the outer diameter of the developing roll 10 due to environmental changes, making it easier to stabilize the amount of toner transport. Silicone rubbers include those prepared by mixing two liquids and those that are thermosetting.

[0031] Various additives such as conductive agents, fillers, extenders, reinforcing agents, processing aids, curing agents, vulcanization accelerators, crosslinking agents, crosslinking aids, antioxidants, plasticizers, UV absorbers, pigments, silicone oils, auxiliaries, surfactants, etc. may be added as needed to the elastic layer 14. As the conductive agent, general conductive agents such as electronic conductive agents such as carbon black and ionic conductive agents such as quaternary ammonium salts may be used.

[0032] The elastic layer 14 may be a foam or a solid body. The thickness of the elastic layer 14 is preferably in the range of 0.1 to 10 mm, and more preferably in the range of 1 to 5 mm.

[0033] The surface layer 16 is composed of a crosslinked composition containing a urethane prepolymer composed of the following (A) and (B) and the following (C) to (E): (A) an aromatic isocyanate, (B) a caprolactone polyol or a carbonate polyol, (C) carbon black, (D) a (meth)acrylic polymer containing a hydrophilic group and a silicone group in the molecule, and (E) an isocyanurate.

[0034] The aromatic isocyanate (A) is an isocyanate in which an isocyanate group is covalently bonded to an aromatic ring. Using an aromatic isocyanate as the isocyanate can impart toughness to the surface layer 16 containing a urethane prepolymer. Examples of aromatic isocyanates include diphenylmethane diisocyanate (MDI), polymethylene polyphenylene polyisocyanate (polymeric MDI), crude MDI (c-MDI), which is a mixture of MDI and polymeric MDI, tolylene diisocyanate (TDI), orthotoluidine diisocyanate (TODI), naphthylene diisocyanate (NDI), and paraphenylene diisocyanate (PDI). Among these, MDI, polymeric MDI, and crude MDI are more preferred from the viewpoint of their superior toughness-enhancing effect.

[0035] The polyol (B) is a caprolactone-based polyol or a carbonate-based polyol. When used as the polyol (B), these can increase the strength of the surface layer 16 containing the urethane prepolymer compared to other polyols such as ether-based polyols and ester-based polyols. These polyols may be used alone or in combination as the polyol (B). Of the caprolactone-based polyols and carbonate-based polyols, caprolactone-based polyols are more preferred from the viewpoint of being more effective in increasing the strength of the surface layer 16.

[0036] The weight-average molecular weight Mw of the urethane prepolymer is preferably 100,000 or more and 300,000 or less. A high molecular weight of 100,000 or more improves toughness, imparting even greater toughness to the surface layer 16 containing the urethane prepolymer. This results in excellent strength and abrasion resistance of the surface layer 16. From this perspective, the molecular weight is more preferably 150,000 or more, and even more preferably 200,000 or more. A molecular weight of 300,000 or less can suppress an increase in the viscosity of the prepolymer and improve moldability. From this perspective, the molecular weight is more preferably 280,000 or less, and even more preferably 250,000 or less. The weight-average molecular weight (Mw) is the weight-average molecular weight converted into standard polystyrene molecular weight and is measured using a GPC measuring device (Shimadzu Corporation, detector: RI, columns: TSKgel GMHxl (2 columns), TSKgel G1000Hxl, mobile phase: THF). The measurement sample is a urethane prepolymer / THF solution (solution concentration: 0.3%).

[0037] The carbon black (C) is used as a conductive agent. There are no particular limitations on the carbon black as long as it has excellent conductivity. As the carbon black, Ketjenblack (registered trademark) and the like are preferred from the viewpoint of excellent conductivity.

[0038] The carbon black (C) contributes to low electrical resistance of the surface layer 16. If the amount of carbon black is too large, the surface layer 16 becomes brittle and prone to wear, resulting in poor durability. From the viewpoint of achieving a high degree of both low electrical resistance and wear resistance, the carbon black content is preferably 10 parts by mass or more and 35 parts by mass or less, more preferably 12 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the urethane prepolymer.

[0039] To improve dispersibility, the carbon black (C) may be dispersed in a solvent and blended into the surface layer-forming composition when forming the surface layer 16. In this case, a carbon black dispersant may be used for the carbon black (C). Examples of carbon black dispersants include ionic surfactants, nonionic surfactants, and transition metal complexes. Among these, carbon black dispersants having an aromatic ring are particularly preferred. These dispersants exhibit excellent dispersibility due to their high adsorption to the surface of carbon black through π-π electron interactions.

[0040] Examples of carbon black dispersants having an aromatic ring include dispersants made of transition metal complexes having an aromatic ring. Examples of dispersants made of transition metal complexes having an aromatic ring include zinc compounds, cobalt compounds, and copper compounds having a porphyrin or phthalocyanine structure. Among these, copper compounds having an aromatic ring are preferred because they are inexpensive and have high dispersing ability.

[0041] From the viewpoint of dispersibility of carbon black, the content of the carbon black dispersant is preferably 1.0 part by mass or more, more preferably 5.0 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the urethane prepolymer. On the other hand, from the viewpoint of suppressing deterioration in physical properties due to an increase in the amount of the carbon black dispersant, the content of the carbon black dispersant is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, per 100 parts by mass of the urethane prepolymer.

[0042] (D) is a (meth)acrylic polymer containing a hydrophilic group and a silicone group in its molecule. The silicone group in (D) contributes to reducing friction on the surface of the surface layer 16. Furthermore, because (D) contains a hydrophilic group, it has affinity with the urethane prepolymer and is therefore easily dispersed within the surface layer 16. Furthermore, by using a high-molecular-weight urethane prepolymer, (D) is more likely to remain within the surface layer 16 and be easily dispersed within the surface layer 16. This also improves the uniformity of the surface layer 16.

[0043] The (meth)acrylic polymer is an acrylic polymer or a methacrylic polymer. The silicone group is a group having a siloxane bond. Examples of siloxane bonds include dimethylsiloxane, methylphenylsiloxane, and diphenylsiloxane. Examples of hydrophilic groups include amino groups, hydroxy groups, ether groups, ester groups, amide groups, imide groups, carboxyl groups, sulfo groups, silanol groups, and mercapto groups. Among these hydrophilic groups, amino groups and hydroxy groups are particularly preferred because of their excellent effect in improving the uniformity of the surface layer 16.

[0044] (D) can be obtained, for example, by copolymerizing a polymerizable (meth)acrylic compound having a hydrophilic group, a polymerizable (meth)acrylic compound having a silicone group, and a polymerizable (meth)acrylic compound having no hydrophilic group or silicone group, which is added as needed. Examples of the polymerizable (meth)acrylic compound include (meth)acrylic monomers and (meth)acrylic oligomers. Examples of the (meth)acrylic monomer include (meth)acrylic acid, (meth)acrylic acid esters, and (meth)acrylamide.

[0045] As the polymerizable (meth)acrylic compound having a hydrophilic group, (meth)acrylic acid esters and (meth)acrylamides are preferred, and (meth)acrylamides are more preferred.

[0046] Examples of the polymerizable (meth)acrylic compound having an amino group as a hydrophilic group include dimethylaminopropyl(meth)acrylamide, dimethylaminomethyl(meth)acrylamide, dimethylaminoethyl(meth)acrylamide, dimethylaminobutyl(meth)acrylamide, dimethylaminohexyl(meth)acrylamide, dimethylaminoheptyl(meth)acrylamide, dimethylaminooctyl(meth)acrylamide, diethylaminopropyl(meth)acrylamide, diphenylaminopropyl(meth)acrylamide, aminopropyldimethyl(meth)acrylamide, hydroxyaminopropyldimethyl(meth)acrylamide, diaminomethyl(meth)acrylamide, triaminopropyl(meth)acrylamide, diethyl(meth)acrylamide, (meth)acrylamide, and isopropyl(meth)acrylamide.

[0047] Examples of polymerizable (meth)acrylic compounds having a silicone group include (meth)acrylic-modified silicone compounds.

[0048] Examples of polymerizable (meth)acrylic compounds that do not have a hydrophilic group or a silicone group include polymerizable (meth)acrylic compounds having a fluorine-containing group, and alkyl (meth)acrylates. Examples of the fluorine-containing group include a fluoroalkyl group, a fluoroalkyl alkylene oxide group, a fluoroalkenyl group, and -F. Compounds having a fluorine-containing group can improve the toner releasability of the surface of the surface layer 16. Alkyl (meth)acrylates make it easy to control the molecular weight of the entire (D).

[0049] Examples of polymerizable (meth)acrylic compounds having a fluorine-containing group include 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluoropropyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 2-(perfluorohexyl)ethyl (meth)acrylate, 2-(perfluorooctyl)ethyl (meth)acrylate, 2-(perfluorodecyl)ethyl (meth)acrylate, 2-(perfluoro-3-methylbutyl)ethyl (meth)acrylate, 2-(perfluoro-5-methylhexyl)ethyl (meth)acrylate, 2-(perfluoro-7-methyloctyl)ethyl (meth)acrylate, 1H,1H,3H-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H, , 7H-dodecafluoroheptyl (meth)acrylate, 1H,1H,9H-hexadecafluorononyl (meth)acrylate, 1H-1-(trifluoromethyl)trifluoroethyl (meth)acrylate, 1H,1H,3H-hexafluorobutyl (meth)acrylate, 3-perfluorobutyl-2-hydroxypropyl (meth)acrylate, 3-perfluorohexyl-2-hydroxypropyl (meth)acrylate, 3-perfluorooctyl-2-hydroxypropyl (meth)acrylate, 3-(perfluoro-3-methylbutyl)-2-hydroxypropyl (meth)acrylate, 3-(perfluoro-5-methylhexyl)-2-hydroxypropyl (meth)acrylate, 3-(perfluoro-7-methyloctyl)-2-hydroxypropyl (meth)acrylate, and the like.

[0050] Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate.

[0051] From the viewpoint of achieving an excellent effect of improving the uniformity of the surface layer 16, the content of (D) is preferably 1.0 part by mass or more per 100 parts by mass of the urethane prepolymer. It is more preferably 2.0 parts by mass or more, and even more preferably 5.0 parts by mass or more. On the other hand, from the viewpoint of suppressing a decrease in physical properties due to an increase in the amount of (D), the content of (D) is preferably 20 parts by mass or less per 100 parts by mass of the urethane prepolymer. It is more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

[0052] The isocyanurate (E) is a compound having an isocyanurate ring. The isocyanurate (E) is composed of a diisocyanate trimer and has three isocyanate functional groups in addition to the isocyanurate ring. The isocyanate functional group of the isocyanurate (E) reacts with the hydrophilic group of the isocyanurate (D), functioning as a crosslinking agent for the isocyanurate (D). This allows the isocyanurate (D) to remain more easily inside the surface layer 16, contributing to the uniformity of the surface layer 16 together with the isocyanurate (D). Furthermore, the crosslinking of the isocyanurate (D) contributes to improving and maintaining the strength of the surface layer 16. Furthermore, the nitrogen atom in the ring structure of the isocyanurate ring improves the toner charging property.

[0053] The isocyanurate (E) is not particularly limited as long as it is composed of a diisocyanate trimer. The diisocyanate constituting the isocyanurate (E) may be an aliphatic isocyanate or an aromatic isocyanate. The diisocyanate constituting the isocyanurate (E) is preferably an aliphatic isocyanate not containing an aromatic ring.

[0054] Examples of diisocyanates constituting the isocyanurate (E) include diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (hydrogenated MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), isophorone diisocyanate (IPDI), orthotoluidine diisocyanate (TODI), naphthylene diisocyanate (NDI), xylylene diisocyanate (XDI), paraphenylene diisocyanate (PDI), lysine diisocyanate methyl ester (LDI), and dimethyl diisocyanate (DDI). Among these, dicyclohexylmethane diisocyanate (hydrogenated MDI), hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), dimethyl diisocyanate (DDI), etc. are preferred.

[0055] Examples of aliphatic isocyanurates include 1,3,5-tris(6-isocyanatohex-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(6-isocyanatotetra-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1,3,5-tris(6-isocyanatododec-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

[0056] The content of the isocyanurate (E) is preferably 1.0 part by mass or more per 100 parts by mass of the urethane prepolymer, from the viewpoints of contributing to the uniformity of the surface layer 16, contributing to improving and maintaining strength, and improving toner chargeability. It is more preferably 5.0 parts by mass or more, and even more preferably 10 parts by mass or more. On the other hand, from the viewpoint of preventing a decrease in physical properties due to an increase in the amount of the isocyanurate (E), the content of the isocyanurate (E) is preferably 40 parts by mass or less per 100 parts by mass of the urethane prepolymer, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[0057] The surface layer 16 may also contain various additives, as needed, such as a urethane reaction catalyst, a urethane crosslinking agent, a urethane extender, a filler (inorganic or organic), a silane coupling agent, a dispersant, a leveling agent, a crosslinking agent, a crosslinking aid, a plasticizer, a flame retardant, an antifoaming agent, roughness-imparting particles, a conductive agent, etc. These may be used alone or in combination of two or more.

[0058] The conductive agent may be an electronic conductive agent or an ionic conductive agent other than carbon black. The conductive agent may be an electronic conductive agent alone, an ionic conductive agent alone, or a combination of an electronic conductive agent and an ionic conductive agent.

[0059] Examples of the electron conductive agent include conductive oxides such as graphite, conductive titanium oxide, conductive zinc oxide, and conductive tin oxide. Although not particularly limited, these may be used alone or in combination of two or more as the electron conductive agent.

[0060] The ionic conductive agent is not particularly limited. Any agent used in the field of electrophotographic equipment may be used. Examples of the ionic conductive agent include quaternary ammonium salts, quaternary phosphonium salts, imidazolium salts, borates, surfactants, etc. Among these, quaternary ammonium salts, quaternary phosphonium salts, and imidazolium salts are preferred, with imidazolium salts being particularly preferred.

[0061] Examples of the cation of the quaternary ammonium salt include those having one or more alkyl or aryl groups having about 1 to 18 carbon atoms (e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, phenyl, xylyl, etc.). The alkyl or aryl group of the cation of the quaternary ammonium salt preferably has 1 to 10 carbon atoms. Examples of the anion of the quaternary ammonium salt include F － , Cl － ,Br － , I － halogen ions such as ClO ４ － , B.F. ４ － , P.F. ６－ , S.O. ４ ２－ , HSO ４ － , C ２ H ５ SO ４ － , C.F. ３ COO － , C.F. ３ SO ３ － , (CF ３ SO ２ ) ２ N － , (CF ３ CF ２ SO ２ ) ２ N － , C.F. ３ (CF ２ ) ３ SO ３ － , (CF ３ SO ２ ) ３ C － , C.F. ３ (CF ２ ) ２ COO － Examples of the anion of the quaternary ammonium salt include ClO ４ － , P.F. ６ － , (CF ３ SO ２ ) ２ N － , C.F. ３ SO ３ － etc. are more preferable.

[0062] Examples of the cation of the quaternary phosphonium salt include those having one or more alkyl or aryl groups having about 1 to 18 carbon atoms (e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, phenyl, xylyl, etc.). The alkyl or aryl group of the cation of the quaternary phosphonium salt preferably has 1 to 10 carbon atoms. Examples of the anion of the quaternary phosphonium salt include F － , Cl － ,Br －, I － halogen ions such as ClO ４ － , B.F. ４ － , P.F. ６ － , S.O. ４ ２－ , HSO ４ － , C ２ H ５ SO ４ － , C.F. ３ COO － , C.F. ３ SO ３ － , (CF ３ SO ２ ) ２ N － , (CF ３ CF ２ SO ２ ) ２ N － , C.F. ３ (CF ２ ) ３ SO ３ － , (CF ３ SO ２ ) ３ C － , C.F. ３ (CF ２ ) ２ COO － Examples of the anion of the quaternary phosphonium salt include ClO ４ － , P.F. ６ － , (CF ３ SO ２ ) ２ N － , C.F. ３ SO ３ － etc. are more preferable.

[0063] Examples of the imidazolium salt include unsubstituted imidazolium salts, 1-alkylimidazolium salts, 3-alkylimidazolium salts, 1,3-dialkylimidazolium salts, and 1,2,3-trialkylimidazolium salts. More specifically, examples of the imidazolium salt include 1-methylimidazolium salt, 1,3-dimethylimidazolium salt, 1,3-diethylimidazolium salt, 1,3-dipropylimidazolium salt, 1,3-dibutylimidazolium salt, 1,3-dicyclohexylimidazolium salt, 1-ethyl-3-methylimidazolium salt, 1-propyl-3-methylimidazolium salt, 1-butyl-3-methylimidazolium salt, 1-hexyl-3-methylimidazolium salt, 1-ethyl-2,3-dimethylimidazolium salt, 1-propyl-2,3-dimethylimidazolium salt, and 1-butyl-2,3-dimethylimidazolium salt. Examples of the anion of the imidazolium salt include F － , Cl － ,Br － , I － halogen ions such as ClO ４ － , B.F. ４ － , P.F. ６ － , S.O. ４ ２－ , HSO ４ － , C ２ H ５ SO ４ － , C.F. ３ COO － , C.F. ３ SO ３ － , (CF ３ SO ２ ) ２ N － , (CF ３ CF ２ SO ２ ) ２ N － , C.F. ３ (CF ２ ) ３ SO ３ － , (CF ３ SO ２ )３ C － , C.F. ３ (CF ２ ) ２ COO － Examples of the anion of the imidazolium salt include ClO ４ － , P.F. ６ － , (CF ３ SO ２ ) ２ N － , C.F. ３ SO ３ － etc. are more preferable.

[0064] Examples of borates include those having one or more alkyl or aryl groups having about 1 to 18 carbon atoms (e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, phenyl, xylyl, etc.), and containing alkali metal ions or alkaline earth metal ions such as lithium ions, sodium ions, potassium ions, and calcium ions.

[0065] From the viewpoint of low electrical resistance, the content of the ionic conductive agent is preferably 0.1 parts by mass or more per 100 parts by mass of the urethane prepolymer. It is more preferably 0.5 parts by mass or more, and even more preferably 1.0 part by mass or more. Furthermore, from the viewpoint of easily suppressing bleeding of the ionic conductive agent, it is preferably 20 parts by mass or less per 100 parts by mass of the urethane prepolymer. It is more preferably 15 parts by mass or less, and even more preferably 13 parts by mass or less.

[0066] Examples of the silane coupling agent include mercapto-based silane coupling agents, sulfide-based silane coupling agents, amine-based silane coupling agents, epoxy-based silane coupling agents, vinyl-based silane coupling agents, etc. Among these, mercapto-based silane coupling agents are more preferred from the viewpoints of improving the adhesive strength between the elastic layer 14 containing a silicone polymer and the surface layer 16 containing a urethane prepolymer, and being able to form a bond with the isocyanurate (E).

[0067] Examples of mercapto-based silane coupling agents include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane. Examples of sulfide-based silane coupling agents include bis-(3-(triethoxysilyl)-propyl)-disulfide and bis(3-triethoxysilylpropyl)trisulfide. Examples of amine-based silane coupling agents include 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane. Examples of epoxy-based silane coupling agents include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane. Examples of vinyl-based silane coupling agents include vinyltriethoxysilane and vinyltrimethoxysilane.

[0068] The content of the silane coupling agent is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.5 parts by mass or more and 8.0 parts by mass or less, and even more preferably 1.0 parts by mass or more and 5.0 parts by mass or less, relative to 100 parts by mass of the urethane prepolymer.

[0069] The roughness-forming particles are particles for imparting roughness to the surface of the surface layer 16. In other words, they are particles for imparting irregularities to the surface of the surface layer 16. The surface irregularities of the surface layer 16 can improve toner adhesion and the amount of toner transport.

[0070] Examples of the material of the roughness-forming particles include urethane resin, polyamide resin, (meth)acrylic resin, (meth)acrylic silicone resin, silicone-grafted (meth)acrylic polymer, (meth)acrylic-grafted silicone polymer, urethane rubber, silica, etc. Of these, urethane resin and urethane rubber are more preferred.

[0071] The size of the roughness-forming particles is not particularly limited, but from the viewpoint of easily ensuring uniform developability, an average particle diameter of 3.0 μm or more and 50 μm or less is preferable. An average particle diameter of 5.0 μm or more and 30 μm or less is more preferable. The average particle diameter of the roughness-forming particles is expressed as the average of 20 arbitrary points when the surface of the surface layer 16 is observed with a laser microscope, and the diameter of the roughness-forming particles visible during surface observation is taken as the particle size.

[0072] From the viewpoint of easily ensuring uniform developability, the content of the roughness-forming particles is preferably 3.0 parts by mass or more and 50 parts by mass or less, and more preferably 5.0 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the urethane prepolymer.

[0073] The surface layer 16 has a breaking stress of 30 MPa from the viewpoint of ensuring excellent abrasion resistance. If the breaking stress is less than 30 MPa, the abrasion resistance will not be satisfactory and durability will decrease. From the above viewpoints, the breaking stress of the surface layer 16 is more preferably 35 MPa or more, and even more preferably 40 MPa or more. On the other hand, from the viewpoint of ease of manufacture, the breaking stress of the surface layer 16 is preferably 60 MPa or less, more preferably 55 MPa or less, and even more preferably 50 MPa or less. The breaking stress of the surface layer 16 is affected by the molecular weight of the urethane prepolymer, the amount of carbon black, the amount of acrylic polymer, the amount of isocyanurate, and the like. For example, the greater the molecular weight of the urethane prepolymer, the greater the breaking stress of the surface layer 16. If the amount of carbon black, the amount of acrylic polymer, the amount of isocyanurate, and the like is too high, the physical properties will decrease and the breaking stress of the surface layer 16 will decrease. The breaking stress of the surface layer 16 can be adjusted taking these factors into consideration. The breaking stress of the surface layer 16 can be measured by performing a tensile test on a test piece in which the elastic layer 14 and the surface layer 16 are laminated together.

[0074] The thickness of the surface layer 16 is not particularly limited, but is preferably 1.0 μm or more and 20 μm or less, and more preferably 3.0 μm or more and 15 μm or less.

[0075] The electrical resistance of the surface layer 16 is set to 1.0×10 ３ Ω or more 1.0×10 ６It is preferably 1.0×10 Ω or less, and more preferably 1.0×10 ３ Ω or more 1.0×10 ５ The electrical resistance of the surface layer 16 can be adjusted by adjusting the amount of carbon black or ionic conductive agent blended.

[0076] The developing roll 10 can be produced by forming an elastic layer 14 on the outer peripheral surface of a shaft 12 and then forming a surface layer 16 on the outer peripheral surface of the elastic layer 14 .

[0077] The elastic layer 14 can be formed, for example, as follows: First, the shaft 12 is placed coaxially in the hollow portion of a roll-forming die, and an uncrosslinked elastic layer-forming material is injected and heated and cured (crosslinked), and then the die is demolded, or the uncrosslinked elastic layer-forming material is extruded onto the surface of the shaft 12, thereby forming the elastic layer 14 on the outer periphery of the shaft 12.

[0078] A surface layer forming composition is used to form the surface layer 16. The surface layer forming composition may contain an appropriate solvent, such as an organic solvent such as methyl ethyl ketone, toluene, acetone, ethyl acetate, butyl acetate, methyl isobutyl ketone (MIBK), THF, or DMF, or a water-soluble solvent such as methanol or ethanol, in order to adjust the viscosity.

[0079] The surface layer 16 can be formed by a method such as coating a surface layer-forming composition onto the outer peripheral surface of the elastic layer 14. As the coating method, various coating methods such as roll coating, dipping, and spray coating can be applied. The coated surface layer 16 may be subjected to ultraviolet irradiation or heat treatment, if necessary.

[0080] According to the developing roll 10 having the above-described configuration, the elastic layer 14 is made of a silicone base material containing silicone rubber, and the surface layer 16 is made of a crosslinked body of a composition containing a urethane prepolymer composed of the above-described (A) and (B) and the above-described (C) to (E). The breaking stress of the surface layer 16 is 30 MPa or more. Therefore, the surface layer 16 has low electrical resistance, excellent abrasion resistance, and excellent uniformity, and produces excellent images over a long period of time.

[0081] The present invention will be described in detail below using examples and comparative examples.

[0082] Example 1 Preparation of Elastic Layer-Forming Material A material for forming an elastic layer was prepared by mixing conductive silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd., "X-34-264A / B, mixing mass ratio A / B = 1 / 1") using a static mixer.

[0083] <Preparation of Elastic Layer> A solid cylindrical iron rod with a diameter of 6 mm was prepared as a shaft, and an adhesive was applied to the outer surface. After this shaft was set in the hollow space of a roll-forming mold, the prepared elastic layer-forming material was injected into the hollow space, heated at 190°C for 30 minutes to harden, and then demolded. This resulted in a roll-shaped elastic layer (thickness 3 mm) made of conductive silicone rubber formed along the outer surface of the shaft.

[0084] <Preparation of Surface Layer-Forming Material> 18 parts by mass of roughness-forming particles were blended into THF as a solvent and stirred for 10 minutes. Next, 100 parts by mass of urethane prepolymer, 40 parts by mass of carbon black dispersed in a carbon black dispersant (containing 21 parts by mass of carbon black), 13 parts by mass of ion conductive agent, 8.0 parts by mass of acrylic polymer, 15 parts by mass of isocyanurate, and 5.0 parts by mass of silane coupling agent were blended and thoroughly mixed and dispersed using a triple roll mill to prepare a surface layer-forming material (solid content concentration 10.8% by mass).

[0085] <Preparation of Surface Layer> A surface layer forming material was applied to the outer peripheral surface of the elastic layer by roll coating, and then heated at 155°C for 50 minutes to harden, thereby forming a surface layer (thickness 14 µm). In this way, a developing roll was prepared.

[0086] Examples 2 to 3 and 7 Developing rolls were produced in the same manner as in Example 1, except that the urethane prepolymer was changed in the preparation of the surface layer forming material.

[0087] Examples 4 and 5 Developing rolls were produced in the same manner as in Example 1, except that the blending amount of the acrylic polymer was changed in the preparation of the surface layer forming material.

[0088] Example 6 A developing roll was produced in the same manner as in Example 1, except that carbon black containing no dispersant was used in preparing the surface layer forming material.

[0089] Examples 8 and 9 Developing rolls were produced in the same manner as in Example 1, except that the amount of carbon black added was changed in the preparation of the surface layer forming material.

[0090] Examples 10 and 11 Developing rolls were produced in the same manner as in Example 1, except that the amount of isocyanurate added was changed in the preparation of the surface layer forming material.

[0091] Comparative Examples 1 to 3 Developing rolls were produced in the same manner as in Example 1, except that the urethane prepolymer was changed in the preparation of the surface layer forming material.

[0092] Comparative Example 4 A developing roll was produced in the same manner as in Example 1, except that the acrylic polymer was not blended in the preparation of the surface layer forming material.

[0093] Comparative Example 5 A developing roll was produced in the same manner as in Example 1, except that in the preparation of the surface layer forming material, no isocyanurate was used and another crosslinking agent was used.

[0094] The materials used are as follows: Urethane prepolymer <1>: "Miractran E590" manufactured by Nippon Miractoran Industry Co., Ltd. (thermoplastic polyurethane of aromatic isocyanate and caprolactone-based polyol, weight-average molecular weight Mw 250,000, melt viscosity 2,000 to 3,000 Pa·s) Urethane prepolymer <2>: "Miractran E590" manufactured by Nippon Miractoran Industry Co., Ltd. (thermoplastic polyurethane of aromatic isocyanate and caprolactone-based polyol, weight-average molecular weight Mw 300,000, melt viscosity 3,000 Pa·s or more) Urethane prepolymer <3>: "Miractran E590" manufactured by Nippon Miractoran Industry Co., Ltd. (thermoplastic polyurethane of aromatic isocyanate and caprolactone-based polyol, weight-average molecular weight Mw 200,000, melt viscosity less than 2,000 Pa·s) Urethane prepolymer <4>: the following synthetic product (thermoplastic polyurethane of aromatic isocyanate and caprolactone-based polyol, weight-average molecular weight Mw 50,000) Urethane prepolymer <5>: the synthetic product below (thermoplastic polyurethane of non-aromatic isocyanate and caprolactone-based polyol, weight-average molecular weight Mw 250,000) Urethane prepolymer <6>: "Miractran E985" manufactured by Nippon Miractoran Kogyo Co., Ltd. (thermoplastic polyurethane of aromatic isocyanate and carbonate-based polyol, weight-average molecular weight Mw 250,000) Urethane prepolymer <7>: "Miractran E385" manufactured by Nippon Miractoran Kogyo Co., Ltd. (thermoplastic polyurethane of aromatic isocyanate and ether-based polyol, weight-average molecular weight Mw 250,000) Carbon black <1>: "MHI Black #273" manufactured by Mikuni Colorants Co., Ltd. (dispersant: copper compound having an aromatic ring), carbon black:dispersant = 9.5:8.5 (mass ratio) Carbon black <2>: "VULCAN 7HJ" manufactured by CABOT (no dispersant) Ion conductive agent: "Tetramethylammonium chloride" manufactured by Tokyo Chemical Industry Co., Ltd. Acrylic polymer: the synthetic product below Isocyanurate: DIC's "Burnoc DB980K" Other crosslinking agents: Isocyanate-based crosslinking agents (TMP-modified TDI, Mitsui Takeda Chemical's "Takenate B830") Silane coupling agent: Momentive Performance Materials Japan's "SILQUEST A-189" Roughness-forming particles: Negami Chemical Industries' "Art Pearl C800"

[0095] <Synthesis of urethane prepolymer> (Urethane prepolymer <4>) Polycaprolactone diol (weight average molecular weight Mw 2000) and diphenylmethane diisocyanate were reacted at 80°C to obtain a prepolymer. Subsequently, 1,4-butanediol was added and the reaction was further carried out at 80°C to obtain a urethane polymer <4> with a weight average molecular weight Mw of 50,000. Polycaprolactone diol: "Placcel 220UA" manufactured by Daicel Corporation Diphenylmethane diisocyanate: "Cosmonate PH" manufactured by Mitsui Chemicals Polyurethanes 1,4-butanediol: manufactured by Mitsubishi Chemical Corporation

[0096] (Urethane prepolymer <5>) Polycaprolactone diol (Mw 2000) and 1,3-bis(isocyanatomethyl)cyclohexane were reacted at 80°C to obtain a prepolymer. Subsequently, 1,4-butanediol and an amine catalyst were added, and the reaction was further carried out at 100°C to obtain a urethane polymer <5> with a Mw of 250,000. Polycaprolactone diol: "Placcel 220UA" manufactured by Daicel Corporation 1,3-bis(isocyanatomethyl)cyclohexane: "Cosmonate 600" manufactured by Mitsui Chemicals 1,4-butanediol: manufactured by Mitsubishi Chemical Corporation Amine catalyst: TEDA (manufactured by Tosoh Corporation)

[0097] <Synthesis of Acrylic Polymer> (Acrylic Polymer) A 200 mL reaction flask was charged with 15 g (96 mmol) of dimethylaminopropylacrylamide (manufactured by Kojin Co., Ltd.), 0.92 g (0.2 mmol) of a (meth)acrylate-modified silicone compound (manufactured by Shin-Etsu Chemical Co., Ltd., "X-22-174DX"), 0.38 g (3.8 mmol) of methyl methacrylate (manufactured by Junsei Chemical Industry Co., Ltd.), 1.24 g (4 mmol) of dimethyl 1,1'-azobis(1-cyclohexanecarboxylate) (manufactured by Wako Pure Chemical Industries, Ltd., "VE-73"), and 14.35 g of methyl ethyl ketone (MEK). After bubbling with nitrogen for 5 minutes while stirring, the mixture was polymerized for 7 hours at a temperature of 80 ° C. Then, 26.58 g of MEK was charged to obtain a solution containing 30% acrylic polymer in solids. The acrylic polymer is a (meth)acrylic polymer containing an amino group and a silicone group in the molecule.

[0098] (Initial Fog) Each of the manufactured developing rolls was installed as a developing roll in a non-magnetic one-component electrophotographic printer (trade name "HL-4040CN", manufactured by Brother Industries, Ltd.) and allowed to stand for 24 hours in each environment (HH: 32.5°C x 85% RH, LL: 15°C x 10% RH). This printer was a "contact image forming device," and the installed developing device was a so-called "contact developing device" containing a positively charged developer. Thereafter, the printer's paper settings were set to "thick plain paper," the print quality to "standard," and the color settings to "standard," and 100 solid white images were printed continuously in monochrome mode. Immediately after that, the setting was changed to color mode, and one solid white image was printed. The degree of contamination of the solid white image printed in this color mode was visually evaluated as "fog." The evaluation was made as follows: "Good" means that there was no staining on the entire white image, "Fair" means that there was slight staining on the white image to an extent that was not problematic for practical use, and "Poor" means that there was staining on the white image to an extent that was not acceptable for practical use. These evaluation results are shown as "initial fogging."

[0099] (Initial Halftone Image) The printer (trade name "HL-4040CN", manufactured by Brother Industries, Ltd.) equipped with each of the manufactured developing rolls was connected to a personal computer and allowed to stand for 24 hours under a test environment (23°C, 10% relative humidity). The printer's paper settings were then set to "thick plain paper," the print quality to "standard," the color settings to "standard," and all other settings to "default." A monochrome full-page image with a density equivalent to 18% gray was created on the personal computer screen using the spreadsheet software "Excel" (Microsoft Corporation), and this monochrome full-page image was printed as a halftone image in monochrome mode. The uniformity of the printed halftone image was visually evaluated. The evaluation was based on a "good" rating for a uniform halftone image without density unevenness, a "fair" rating for a slight density unevenness observed in the halftone image to an extent that was not problematic for practical use, and an "unacceptable" rating for a density unevenness observed in the halftone image to an extent that was practically unacceptable. The results of these evaluations are shown in the table as "initial halftone image."

[0100] (Fogging after durability test) Each of the manufactured developing rolls was mounted as a developing roll in the printer (product name "HL-4040CN", manufactured by Brother Industries, Ltd.), and a durability printing test was conducted under the following conditions, after which the image quality was evaluated. That is, after leaving the developing roll to stand for 24 hours in a low-temperature, low-humidity environment, the printer's paper settings were set to "thick plain paper," the print quality to "standard," and the color settings to "standard," and a total of 5,000 sheets (cartridge life) of solid black printing was printed on 5% of the total area of ​​one side of A4 paper. Thereafter, fogging after durability test was evaluated in the same manner as in the initial fogging test.

[0101] (Halftone Image After Durability Test) Each of the manufactured developing rolls was mounted as a developing roll in the printer (product name "HL-4040CN", manufactured by Brother Industries, Ltd.), and a durability printing test was conducted under the following conditions, after which the image quality was evaluated. That is, after leaving the developing roll to stand for 24 hours in a low-temperature, low-humidity environment, the printer's paper settings were set to "thick plain paper," the print quality to "standard," and the color settings to "standard," and a total of 5,000 sheets (cartridge life) of solid black printing was printed on 5% of the total area of ​​one side of A4 paper. Then, the halftone image after durability test was evaluated in the same manner as the initial halftone image evaluation.

[0102] (Wear Resistance) Five of each of the manufactured developing rolls were prepared and mounted as developing rolls in a contact-type color image forming apparatus (trade name "TN-290", manufactured by Brother Industries, Ltd.). The developer and developer regulating member used were those provided with the contact-type color image forming apparatus. The developer had a positive charging characteristic. The environment inside the contact-type color image forming apparatus equipped with each developing roll was adjusted to a high humidity environment, and 5,000 sheets (cartridge life) of solid white images were printed on one side of A4 paper in color printing mode. The image forming apparatus was disassembled and visually inspected for developer leakage from the developing device. The occurrence of toner leakage correlates with wear resistance. The evaluation was made as follows: "Good" if no developer was found outside the developing device for all five developing rolls in each of the Examples and Comparative Examples; "Good" if a very small amount of developer was found adhering to the periphery of the developing device for two of the five developing rolls in each of the Examples and Comparative Examples; and "Poor" if a very small amount of developer was found adhering to the periphery of the developing device for all five developing rolls in each of the Examples and Comparative Examples.

[0103] (Uniformity of Surface Layer) The uniformity of the surface layer was evaluated based on whether or not cissing occurred during roll coating in forming the surface layer. If cissing occurred, it was marked "x", and if not, it was marked "o".

[0104] (Surface Layer Breaking Stress) The elastic layer and the surface layer were scraped off from the developing roll in a combined state, and the scraped-off rubber piece was punched out with a JIS No. 7 punch to prepare a test piece. Before starting the measurement, a notch was made in the elastic layer in advance so that the elastic layer would break first. The pulling speed was set to 10 mm / min, and the stress (MPa) at break was measured.

[0105] (Electrical Resistance Value of Surface Layer) Both ends of the developing roll were pressed against a metal roll (diameter: 30 mm) with a predetermined load, and the metal roll was rotated at a predetermined rotation speed, causing the conductive roll to rotate along with it. While maintaining this state (while rotating both the metal roll and the developing roll), a voltage of 10 V was applied between the ends of the developing roll and the metal roll, and the flowing current value was measured to determine the electrical resistance value (roll electrical resistance: Ω). This was expressed in logarithm.

[0106]

[0107]

[0108]

[0109] In Examples 1 to 11, the surface layer is composed of a crosslinked composition containing a urethane prepolymer composed of an aromatic isocyanate and a caprolactone-based polyol or a carbonate-based polyol, carbon black, a (meth)acrylic polymer containing a hydrophilic group and a silicone group in the molecule, and isocyanurate, and the breaking stress of the surface layer is 30 MPa or more. Furthermore, Examples 1 to 11 demonstrate excellent image quality in evaluations of fog and halftone images at the initial and endurance tests. Furthermore, there is no toner leakage and excellent abrasion resistance. Furthermore, the surface layer also has excellent uniformity. Therefore, it can be seen that the surface layer has low electrical resistance, excellent abrasion resistance, and excellent uniformity, resulting in excellent long-term image quality.

[0110] In contrast, Comparative Example 1 has a small weight-average molecular weight of the urethane prepolymer, resulting in poor breaking stress in the surface layer. This results in poor abrasion resistance. Furthermore, the evaluations of fog and halftone images after durability testing are poor, resulting in poor images. Comparative Example 2 does not use an aromatic isocyanate in the urethane prepolymer, resulting in poor abrasion resistance. Comparative Example 3 uses a polyol in the urethane prepolymer that is neither caprolactone-based nor carbonate-based, resulting in poor abrasion resistance. Comparative Example 4 does not contain a (meth)acrylic polymer containing a hydrophilic group and a silicone group in the molecule in the surface layer, resulting in poor uniformity in the surface layer and poor images from the beginning. Comparative Example 5 does not contain isocyanurate in the surface layer, resulting in poor abrasion resistance. Furthermore, the evaluation of fog after durability testing is poor, resulting in poor images.

[0111] Furthermore, Examples 1, 4, and 5 and Comparative Example 4 show that when the content of the (meth)acrylic polymer containing a hydrophilic group and a silicone group in the molecule is 5.0 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the urethane prepolymer, the uniformity of the surface layer is improved and the image is particularly good. Furthermore, Examples 1 and 6 show that the use of a carbon black dispersant having an aromatic ring results in particularly good images. Furthermore, Examples 1, 8, and 9 show that an increase in the amount of carbon black tends to decrease abrasion resistance, while a decrease in the amount of carbon black tends to increase electrical resistance and result in poor image quality. Furthermore, Example 1 and Comparative Example 5 show that the use of isocyanurate together with the (meth)acrylic polymer containing a hydrophilic group and a silicone group in the molecule improves chargeability and results in particularly good images.

[0112] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the invention.

[0113] 10 developing roll 12 shaft body 14 elastic layer 16 surface layer

Claims

1. A developing roll for an electrophotographic device, comprising: a shaft, an elastic layer formed on the outer peripheral surface of the shaft, and a surface layer formed on the outer peripheral surface of the elastic layer, wherein the elastic layer is made of a silicone base material containing silicone rubber, and the surface layer is made of a crosslinked product of a composition containing a urethane prepolymer composed of the following (A) and (B) and the following (C) to (E), and the breaking stress of the surface layer is 30 MPa or more: (A) aromatic isocyanate (B) caprolactone-based polyol or carbonate-based polyol (C) carbon black (D) a (meth)acrylic polymer containing a hydrophilic group and a silicone group in the molecule (E) isocyanurate 2. The developing roll for electrophotographic equipment according to claim 1, wherein the weight average molecular weight Mw of said urethane prepolymer is 100,000 or more and 300,000 or less.

3. The developing roll for electrophotographic equipment according to claim 1 or 2, wherein (A) is diphenylmethane diisocyanate.

4. A developing roll for an electrophotographic device according to any one of claims 1 to 3, wherein the content of (C) is 10 parts by mass or more and 35 parts by mass or less per 100 parts by mass of the urethane prepolymer.

5. A developing roll for an electrophotographic device according to any one of claims 1 to 4, wherein the content of (D) is 1.0 part by mass or more and 20 parts by mass or less per 100 parts by mass of the urethane prepolymer.

6. A developing roll for an electrophotographic device according to any one of claims 1 to 5, wherein the content of (E) is 1.0 part by mass or more and 40 parts by mass or less per 100 parts by mass of the urethane prepolymer.

7. The electrical resistance of the surface layer is 1.0 x 10 ３ Ω or more 1.0×10 ６ The developing roll for an electrophotographic apparatus according to any one of claims 1 to 6, having a surface roughness of Ω or less.

8. The developing roll for an electrophotographic device according to any one of claims 1 to 7, wherein the hydrophilic group of (D) is an amino group or a hydroxy group.

9. The developing roll for an electrophotographic device according to any one of claims 1 to 8, wherein the surface layer further contains a carbon black dispersant having an aromatic ring.

Images