JP5986472B2 - Electrophotographic materials - Google Patents

Description

  The present invention relates to an electrophotographic member.

  Conventionally, electrophotographic apparatuses such as electrophotographic copying machines, printers, and facsimiles are known. These electrophotographic apparatuses form an image through processes such as latent image formation by image data exposure on a charged photoreceptor, development, transfer to a transfer medium, and fixing. Therefore, various electrophotographic members are incorporated in the apparatus in order to realize these processes.

  For example, a roll-shaped charging member is incorporated to charge the surface of the photoreceptor. In addition, a roll-shaped developing member is incorporated in order to attach a toner to the electrostatic latent image formed on the surface of the photosensitive member to form a visible image. Also, recently, each toner image formed by a plurality of photoconductors by color is primarily transferred onto the belt surface, and the toner images of each color are superimposed and transferred onto a sheet of paper. It is used.

  These electrophotographic members may be provided with a surface layer for the purpose of improving durability on the surface of the member. As a method for improving the durability of the surface layer, a method of reinforcing the bonding between molecules by cross-linking the polymers forming the surface layer to a network structure, or a method using a polymer having a rigid skeleton as the above-mentioned polymer, etc. It is.

  As the surface layer, a urethane polymer or an acrylic polymer is used as a base polymer, and a mixture of various additives such as a conductive agent is often used. For example, Patent Document 1 discloses a developing roll having a cross-linked structure in which thermoplastic polyurethane as a base polymer is cross-linked with an isocyanate and having a surface layer to which a conductive agent is added.

JP-A-11-267583

  However, the method of cross-linking the polymers forming the surface layer into a network structure tends to produce a portion having a high cross-linking density, and when deformed by an external force, stress concentrates on the cross-linking point, and is easily broken, resulting in poor durability. Moreover, the method of cross-linking between the polymers forming the surface layer into a network structure or the method using a polymer having a rigid skeleton tends to make the surface layer hard. Therefore, these methods are disadvantageous as an electrophotographic member because a hard surface layer gives stress to the toner, and toner filming in which the surface of the surface layer is covered with the toner tends to occur.

  As another method for improving the durability of the surface layer, it is conceivable to reinforce the surface layer by adding a filler to the surface layer. However, in order to obtain a reinforcing effect by this method, it is necessary to add a large amount of filler to the surface layer, which is not realistic because the hardness of the surface layer tends to increase.

  Moreover, the method of cross-linking between the polymers forming the surface layer into a network structure tends to shift the glass transition point of the cross-linked polymer to the high temperature side. Therefore, there is a problem that the temperature dependency of the storage elastic modulus of the surface layer increases in the operating temperature range of the electrophotographic member, and as a result, the temperature dependency of the hardness of the surface layer increases.

  The present invention has been made in view of the above-described background, and provides an electrophotographic member having a surface layer that can exhibit better durability than conventional ones and has a low hardness and a low temperature dependence of hardness in the operating temperature range. It was obtained by trying.

One aspect of the present invention is a member for electrophotography having a surface layer and used for an electrophotographic apparatus,
The above surface layer is
Containing ionic conductive agent,
A cyclic molecule having a functional group that reacts with an isocyanate group, a linear molecular chain penetrating through the ring of the cyclic molecule, and a terminal that is arranged at both ends of the linear molecular chain to prevent the elimination of the cyclic molecule The polyrotaxane having a group has a crosslinked structure crosslinked by an isocyanate compound having an isocyanate group at least at both ends;
The crosslinked structure is
The first cross-linked portion formed by the reaction of the reactive group of the cyclic molecule in one of the polyrotaxanes forming a crosslink and the one isocyanate group in the isocyanate compound, and the cyclic in the other polyrotaxane forming a crosslink Ru electrophotographic member near which comprises a second bridge portion formed by the reaction of the other of the isocyanate group in the reactive group and the isocyanate compound having a molecular.

  In the electrophotographic member, the surface layer has the specific cross-linking structure described above. Compared with the surface layer having a crosslinked structure crosslinked in a network structure, the surface layer is less likely to have a portion with a high crosslinking density. In the surface layer, since the cyclic molecule crosslinked with the isocyanate compound can move like a pulley, the polyrotaxane can move flexibly. For this reason, when the surface layer is deformed by an external force, it is difficult for stress to concentrate at the cross-linking point, and it is difficult to break. Therefore, the said surface layer can express favorable durability compared with the past.

  Further, the surface layer does not need to use a polymer having a rigid skeleton in order to improve durability, and a flexible polymer chain can be selected as a linear molecular chain constituting the polyrotaxane. Therefore, the surface layer can be reduced in hardness in the operating temperature range. Furthermore, since the surface layer can reduce the temperature dependence of the storage elastic modulus, the temperature dependence of the hardness can be reduced.

  As described above, according to the present invention, it is possible to provide an electrophotographic member having a surface layer that can exhibit better durability than conventional ones and has a low hardness and a small temperature dependence of hardness in the use temperature range.

1 is a diagram schematically illustrating an electrophotographic member of Example 1. FIG. It is the figure which showed the II-II cross section in FIG. It is the figure which showed the structure of the surface layer typically. 6 is a diagram schematically showing an electrophotographic member of Example 2. FIG. It is the figure which showed the VV cross section in FIG.

  The electrophotographic member is a member used in an electrophotographic apparatus. Specific examples of the electrophotographic apparatus include an image forming apparatus such as a copying machine, a printer, a facsimile, a multifunction peripheral, and a POD (Print On Demand) apparatus that employs an electrophotographic system using a charged image.

The electrophotographic member, the conductive member is incorporated in an electrophotographic image forming apparatus, for example, a developing member, the charging member, Ru can be a transfer member. Since the surface layer of the conductive member is in contact with the toner, it is required to have a low hardness in order to reduce toner stress. On the other hand, since the surface layer of the conductive member is often used in contact with a mating member such as a blade member or a latent image carrier in the process of forming an image, durability is required. Furthermore, since the conductive member is used in a wide temperature range of about 0 ° C. to 40 ° C., it is desired that the temperature dependence of hardness is small within the temperature range. Therefore, in the above case, the above-described effects can be sufficiently exhibited. As the transfer member, specifically, a toner image carried on the photoconductor is primarily transferred to an intermediate transfer member, and then this toner image is secondarily transferred from the intermediate transfer member to a transfer material such as paper. The intermediate transfer member can be exemplified.

  Here, the polyrotaxane in the cross-linked structure of the surface layer is arranged at both ends of the cyclic molecule having a functional group that reacts with an isocyanate group, a linear molecular chain penetrating the ring of the cyclic molecule, and the linear molecular chain. And a terminal group that prevents the elimination of the cyclic molecule.

  It is sufficient that the cyclic molecule of the polyrotaxane is substantially cyclic. If the polyrotaxane can move freely along a linear molecular chain like a pulley, it is not necessarily completely like a “C” shape. There is no need for a closed ring. Specific examples of the cyclic molecule include various cyclodextrins such as α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, dimethylcyclodextrin, glucosylcyclodextrin, and derivatives and modified forms thereof, crowns. Examples include ethers, benzocrowns, dibenzocrowns, dicyclohexanocrowns, and derivatives and modified products thereof. One or more of these may be contained. Of these cyclic molecules, α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, and derivatives and modified forms thereof are preferable from the viewpoint of reactivity and the like, and particularly preferably α-cyclodextrin, And derivatives or modified products thereof.

  Specific examples of the functional group that reacts with the isocyanate group included in the cyclic molecule include a hydroxyl group and an amino group.

  The linear molecular chain of the polyrotaxane can be composed of a linear polymer. Specific examples of the linear polymer include polyethers such as polyethylene glycol, polypropylene glycol, polyalkylene glycol such as polytetramethylene glycol, polyesters such as polycaprolactone, polyethylene adipate, polybutylene adipate, polyethylene, and the like. Examples thereof include polyalkylenes such as polypropylene. Among the linear polymers, the above-described polyalkylene glycol can be preferably used from the viewpoint of reducing the hardness of the surface layer.

Also, the linear molecule chains, have good as having an ether bond in the molecule. In this case, it becomes easy to reduce the volume electrical resistance of the surface layer. Therefore, this case is suitable as the conductive member. Specifically, the linear molecular chain having an ether bond in the molecule can be composed of the above-described polyethers such as polyalkylene glycol.

  The terminal group of the polyrotaxane is not particularly limited as long as it has such a high bulkiness that it can function as a stopper for preventing the detachment of the cyclic molecule from the linear molecular chain. Specific examples of the terminal group include a dinitrophenyl group such as an adamantane group, 2,4-dinitrophenyl group, and 3,5-dinitrophenyl group, a trityl group, a fluorescein, and a pyrene. Can do.

  As the polyrotaxane, a cyclic molecule is a cyclodextrin (reacted with an isocyanate group) from the viewpoint of surface layer durability, low hardness, low temperature dependence of hardness, low volume electric resistance, reactivity with the isocyanate compound, and the like. A polyrotaxane having a hydroxyl group as a functional group) or a derivative thereof or a modified form thereof, a linear molecular chain being a polyethylene glycol chain, and a terminal group being an adamantane group can be particularly preferably used. .

  On the other hand, the isocyanate compound in the crosslinked structure of the surface layer can be specifically composed of an isocyanate prepolymer. Moreover, the said isocyanate compound can also have an isocyanate group and another functional group in the part in the middle of a molecule | numerator other than both terminals, as long as it has an isocyanate group at both terminals. The isocyanate compound is preferably a diisocyanate compound such as a diisocyanate prepolymer having isocyanate groups at both ends. The isocyanate group includes an isocyanate group in the isocyanurate group.

The isocyanate compound is not good as having an ether bond in the molecule. In this case, since the molecules move easily, the volume electric resistance of the surface layer is easily lowered. Therefore, this case is suitable as the conductive member. In particular, when the linear molecular chain has an ether bond in the molecule and the isocyanate compound has an ether bond in the molecule, the volumetric electric power of the surface layer is increased due to the synergistic effect of the combination of the two. It is easy to make resistance lower. Therefore, this case is particularly suitable as the conductive member.

The molecular weight of the isocyanate compound, Ru can be in the range of 300 to 3000. In addition, the said molecular weight means the number average molecular weight computed from the quantity of NCO contained in the isocyanate obtained by titration etc., and the number of functional groups obtained from structural analysis by thermal decomposition CG-MS, NMR, etc. In this case, the surface layer is flexible and easily stretched, which is advantageous for reducing the hardness of the surface layer. Further, in this case, at the time of cross-linking with the polyrotaxane, the polyrotaxane is rich in reactivity with the functional group of the cyclic molecule, so that it is easy to form an appropriate amount of cross-linking points for obtaining the pulley effect. In addition, since stress concentration is unlikely to occur at the cross-linking point, it is more difficult to break down, and durability can be easily improved.

  The molecular weight is preferably 150 or more, more preferably 200 or more, and still more preferably 250 or more, from the viewpoint of reducing the hardness of the surface layer, flexibility, and the like. The molecular weight is preferably 4000 or less, more preferably 3500 or less, and even more preferably 3200 or less, from the viewpoints of reactivity at the time of crosslinking and durability improvement.

  Specific examples of the isocyanate compound include polyether polyols having isocyanate groups at both ends and polyester polyols having isocyanate groups at both ends. Of these, polyether polyols having isocyanate groups at both ends are preferable from the viewpoint of reducing the volume electrical resistance of the surface layer. More specifically, examples of the isocyanate compound include compounds represented by the following formula (1).

_{OCN-X 2 - (X 1} - (C p H 2p O) q -X 1 -X 2) r -NCO ··· Equation (1)

However, in Formula (1), p, q, and r are positive integers. p is preferably about 1 to 20, more preferably about 1 to 5. q is preferably about 1 to 30, more preferably about 1 to 20. r is preferably about 1 to 10, more preferably about 1 to 5. X ₁ is a urethane bond or a urea bond, and preferably a urethane bond. X ₂ is the main skeleton of diisocyanate. That is, X ₂ is a portion obtained by removing an isocyanate group from diisocyanate, for example, a tolylene group in the case of tolylene diisocyanate. Specific examples of the diisocyanate include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), naphthalene diisocyanate (NDI), and hydrogenated xylene diisocyanate (H6XDI). And isophorone diisocyanate (IPDI). The two X ₂ in the formula (1) may be the same type of diisocyanate main skeleton or different types of diisocyanate main skeleton.

  As said isocyanate compound, the compound of following formula (2) can be used conveniently. In this case, there are advantages such as low volume electric resistance and excellent mechanical properties.

  However, in formula (2), n is preferably about 1 to 40, more preferably about 1 to 20.

  The cross-linked structure of the surface layer includes the first cross-linked portion and the second cross-linked portion. Specifically, for example, when the functional group is a hydroxyl group, a urethane bond is formed by reaction with the isocyanate group of the isocyanate compound. That is, the cyclic molecules of the adjacent polyrotaxane are cross-linked by the isocyanate compound via the urethane bond. Therefore, in this case, the first cross-linking part and the second cross-linking part are constituted by urethane bonds. Further, when the functional group is an amino group, a urea bond is formed by reaction with the isocyanate group of the isocyanate compound. That is, the cyclic molecules of the adjacent polyrotaxane are cross-linked by the isocyanate compound via the urea bond. Therefore, in this case, the first cross-linking part and the second cross-linking part are composed of urea bonds.

  In the cross-linked structure, it is not necessary that all the cyclic molecules are cross-linked, and cyclic molecules that are not involved in cross-linking may be included as long as the pulley effect is obtained.

It said surface layer, Ru can contain a polyurethane-based thermoplastic elastomer. This is advantageous for improving the mechanical properties of the surface layer. Specific examples of the polyurethane-based thermoplastic elastomer include those formed by combinations of various isocyanates and polyols, modified products thereof, and the like. Specific examples of the isocyanate include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), naphthalene diisocyanate (NDI), and hydrogenated xylene diisocyanate (H6XDI). ), Isophorone diisocyanate (IPDI), and the like. Specific examples of the polyol include polyethers such as polyalkylene glycol such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and polyesters such as polycaprolactone, polyethylene adipate, polybutylene adipate, and polycarbonate diol. Examples can be given. The surface layer preferably contains a carbonate-based thermoplastic polyurethane elastomer from the viewpoint of improving mechanical properties.

  The surface layer may contain a polyurethane-based thermoplastic elastomer, for example, about 1% to 30% by mass, preferably about 5% to 15% by mass.

It said surface layer, contains the ionic conductive agent as the conductive agent. Therefore, the electrophotographic member, without compromising the temperature dependence of the surface hardness, not easy to lower the surface layer of the volume resistivity. In addition, when the linear molecular chain and / or the isocyanate compound has an ether bond in the molecule, the number of polar sites in the cross-linked structure increases, which is advantageous for lowering the volume resistivity of the surface layer.

  Specific examples of the ionic conductive agent include quaternary ammonium salts, borates, perchlorates, ionic liquids, and the like. These can be used alone or in combination of two or more. The surface layer can contain about 1 to 10 parts by mass, more preferably about 1 to 5 parts by mass of the ionic conductive agent with respect to 100 parts by mass of the polymer component contained in the surface layer.

  Moreover, the said surface layer can contain an electronic conductive agent as a electrically conductive agent, if it is in the range which does not impair the temperature dependence of the hardness of a surface layer. In this case, since the surface layer can be reinforced at the same time as imparting conductivity to the surface layer, it is advantageous in improving durability.

Specific examples of the electronic conductive agent include carbon-based conductive materials such as carbon black, carbon nanotube, and graphite, barium titanate, c-TiO ₂ , c-ZnO, and c-SnO ₂ (where c- is conductive). It means sex.) And the like. These can be used alone or in combination of two or more. The surface layer can contain about 1 to 30 parts by mass, more preferably about 5 to 20 parts by mass of the electronic conductive agent with respect to 100 parts by mass of the polymer component contained in the surface layer.

  In addition to the above, the above surface layer may optionally be a reaction catalyst, a filler, a coupling agent, a dispersant, a leveling agent, a crosslinking agent, a crosslinking aid, a particle for forming roughness, a flame retardant, a plasticizer, a softening agent. Various additives such as an agent, a lubricant and an antioxidant can be contained. These can be used alone or in combination of two or more.

  The thickness of the said surface layer is not specifically limited, It can be set as optimal thickness according to the kind of member for electrophotography. For example, in the case of the surface layer in the developing member or the charging member, the thickness can be set to about 1 to 20 μm from the viewpoints of securing an optimum hardness and suppressing an excessive increase in hardness. Further, for example, in the case of the surface layer of the transfer member, the thickness can be set to about 10 to 100 μm from the viewpoint of securing an optimum hardness and suppressing an excessive increase in hardness.

  In the electrophotographic member, the configuration below the surface layer is not particularly limited. However, considering the ease of application to an electrophotographic apparatus, the electrophotographic member is preferably in the form of a roll or a belt. In this case, the electrophotographic member specifically includes, for example, a shaft, an elastic layer made of a conductive rubber elastic body formed along the outer peripheral surface of the shaft, and an outer peripheral surface of the elastic layer. A conductive roll having the surface layer formed along the surface, a cylindrical base layer formed from a resin material having conductivity, and the surface layer having rubber elasticity formed along the outer peripheral surface of the base layer. An electrically conductive belt, a cylindrical base layer formed of a conductive resin material, an elastic layer made of a conductive rubber elastic body formed along the outer peripheral surface of the base layer, and an outer peripheral surface of the elastic layer It can be configured as a conductive belt having the surface layer formed along the surface.

  As the shaft body, one having conductivity can be suitably used. Specifically, for example, solid bodies (core metal) and hollow bodies made of metals (including alloys) such as stainless steel, aluminum, and iron, solid bodies and hollow bodies made of conductive plastics, conductive or non-conductive plastics Examples of the solid body or hollow body of which metal plating is applied can be given.

  Examples of the rubber material constituting the elastic layer include various rubbers such as silicone rubber, urethane rubber, butadiene rubber, hydrin rubber, nitrile rubber, fluorine rubber, chloroprene rubber, isoprene rubber, and natural rubber. The rubber material includes the conductive agent, filler, extender, reinforcing material, processing aid, curing agent, vulcanization accelerator, crosslinking agent, crosslinking aid, antioxidant, plasticizer, ultraviolet absorber, Various additives such as pigments, silicone oils, auxiliaries, and surfactants can be appropriately added. The thickness of the elastic layer can be, for example, about 0.1 to 10 mm, preferably about 1 to 5 mm.

  Examples of the resin material constituting the base layer include various resins such as polyamideimide resin, polyimide resin, polyethersulfone resin, fluorine resin, and polycarbonate resin. Various additives such as a flame retardant (inorganic flame retardant, organic flame retardant), a filler (calcium carbonate, etc.), and a leveling agent can be appropriately added to the resin material. The thickness of the base layer can be about 50 μm to 200 μm.

  The electrophotographic member according to the example will be specifically described with reference to the drawings.

Example 1
A schematic configuration of the electrophotographic member according to the first embodiment will be described with reference to FIGS. As shown in FIGS. 1 and 2, the electrophotographic member R is used in an electrophotographic apparatus. Specifically, the electrophotographic member R of this example is a roll-like conductive member incorporated in an electrophotographic image forming apparatus, and is used as a developing member (developing roll) or a charging member (charging roll). Can do.

  The electrophotographic member R has a surface layer 1. Specifically, the electrophotographic member R of the present example includes a conductive shaft body 2 and an elastic layer 3 made of a conductive rubber elastic body formed along the outer peripheral surface of the shaft body 2. In addition. However, both end portions of the shaft body 2 are projected from both end surfaces of the elastic layer 3. In this example, specifically, the shaft body 2 is a metal cored bar, and the rubber elastic body is silicone rubber.

  As schematically shown in FIG. 3, the surface layer 1 has a crosslinked structure in which a polyrotaxane 10 is crosslinked by an isocyanate compound 11. The polyrotaxane 10 used for cross-linking is composed of a cyclic molecule 101 having a functional group that reacts with an isocyanate group, a linear molecular chain 102 penetrating through the ring of the cyclic molecule 101, and both ends of the linear molecular chain 102. And a terminal group 103 that is arranged to prevent the elimination of the cyclic molecule. Specifically, the cyclic molecule 101 is a cyclodextrin grafted with polycaprolactone and has a hydroxyl group as a functional group that reacts with an isocyanate group. The linear molecular chain 102 is a polyethylene glycol chain. The end group is an adamantane group 103. On the other hand, the isocyanate compound 11 used for cross-linking is an isocyanate compound having isocyanate groups at least at both ends. Specifically, it is an ether type polyol having isocyanate groups at both ends.

  The cross-linked structure includes the first cross-linked portion 12 formed by the reaction of the reactive group of the cyclic molecule 101 in one polyrotaxane 10 forming the cross-linkage and one isocyanate group in the isocyanate compound 11, and the other polyrotaxane forming the cross-link. 10 and the second cross-linking portion 13 formed by the reaction between the reactive group of the cyclic molecule 101 in the group 10 and the other isocyanate group in the isocyanate compound 11. Specifically, the 1st bridge | crosslinking part 12 and the 2nd bridge | crosslinking part 13 are comprised from the urethane bond. In addition, the crosslinked structure in the surface layer 1 of FIG. 3 has shown the example containing the cyclic molecule which is not concerned in bridge | crosslinking.

  Although the surface layer 1 is mainly comprised from the crosslinked polymer which has the said crosslinked structure, the surface layer 1 contains the other component. In this example, the surface layer 1 contains a polyurethane-based thermoplastic elastomer. Moreover, the surface layer 1 contains the ionic conductive agent and the electronic conductive agent as a conductive agent.

(Example 2)
A schematic configuration of the electrophotographic member according to Example 2 will be described with reference to FIGS. As shown in FIGS. 4 and 5, the electrophotographic member B is used in an electrophotographic apparatus. Specifically, the electrophotographic member B of this example is an endless belt-like conductive member incorporated in an electrophotographic image forming apparatus, and can be used as a transfer member (intermediate transfer belt).

  The electrophotographic member B has a surface layer 5. Specifically, the electrophotographic member B of this example further includes a cylindrical base layer 6 formed of a conductive resin material. A surface layer 5 is formed along the outer peripheral surface of the base layer 6. Since the surface layer 5 has the same crosslinked structure as the surface layer 1 of Example 1, description is abbreviate | omitted. The electrophotographic member B may have a rubber elastic layer formed of a conductive rubber material between the base layer 6 and the surface layer 5.

  Next, a plurality of conductive roll samples to be incorporated into an electrophotographic image forming apparatus were prepared and evaluated. Each conductive roll sample has a different type of surface layer. Hereinafter, the experimental example will be described.

(Experimental example)
<Preparation of compound material for surface layer>
The following surface layer compounding materials were prepared.
-Polyrotaxane (1) [manufactured by Advanced Soft Materials, "Celum Superpolymer A1000"]
The cyclic molecule is a cyclodextrin grafted with polycaprolactone and has a hydroxyl group as a functional group that reacts with an isocyanate group. The linear molecular chain is a polyethylene glycol chain. The terminal group is an adamantane group. In addition, the weight average molecular weight Mw of a polyrotaxane (1) is about 600,000, and a hydroxyl value is 72 mgKOH / g.
Polyol (1) [manufactured by Sanyo Chemical Industries, "Sanniks GP-1500"]
The main component is polyoxypropylene glyceryl ether. The number average molecular weight determined from the hydroxyl value of 109 mgKOH / g is 1500.
Polyol (2) [manufactured by Sanyo Chemical Industries, "Sanniks PP-1000"]
The main component is polyoxypropylene glycol. The number average molecular weight determined from the hydroxyl value of 109 mgKOH / g is 1000.
Isocyanate compound (1) [Nippon Polyurethane Industry Co., Ltd., “Coronate HX”]
Isocyanurate of hexamethylene diisocyanate. The NCO content is 21%. The molecular weight is 600.
Isocyanate compound (2) [Nippon Polyurethane Industry Co., Ltd., “Coronate C2510”]
The isocyanate compound (2) is a polyether polyol having isocyanate groups at both ends, and specifically, is a compound that falls under the formula (1) described above. The NCO content is 5%. The molecular weight is 1680.
・ Isocyanate compound (3) [Synthetic product]
Adipate polyol [manufactured by Sanyo Chemical Industries, “San Ester No. 22”, Mn = 1000] (hereinafter referred to as material A), isocyanate [manufactured by Nippon Polyurethane Co., Ltd., “Coronate T100” (2,4TDI) , Mn = 174.16] (hereinafter referred to as material B). Next, 76.33 g (0.076 mol) of material A was weighed into a 500 ml flask, and was stirred for 10 minutes at 70 ° C. under a nitrogen purge. Further, 23.66 g (0.139 mol) of the material B was added little by little, followed by stirring and reaction at 70 ° C. for 2 hours after the completion of the dropping. As a result, a polyester polyol having isocyanate groups at both ends was obtained. The NCO content is 5%. The molecular weight is 1680. The molecular weight was calculated from NCO% obtained from NCO titration and the number of functional groups.
Isocyanate compound (4) [manufactured by Sumika Bayer Urethane Co., Ltd., “Desmodur BL1100”]
The isocyanate compound (4) is a polyether polyol having isocyanate groups at both ends, and specifically, a compound that falls under the above-described formula (1). The NCO content is 3%. The molecular weight is 2800.
・ Polyurethane thermoplastic elastomer [Nipporan N5196, manufactured by Nippon Polyurethane Industry Co., Ltd.]
・ Ionic conductive agent (quaternary ammonium salt: tetramethylene ammonium chloride)
・ Electronic conductive agent (carbon black) [manufactured by Lion Corporation, “Ketjen EC300J”]

<Preparation of surface layer forming material>
After blending each of the above-prepared blended materials at the blending ratio (parts by mass) shown in Table 1 to be described later, and dissolving this in MEK so as to have a concentration of 20% by mass, it is sufficiently mixed using three rolls, Dispersed. Thereby, each surface layer forming material used for preparation of the conductive roll samples 1-9 was prepared.

<Preparation of conductive roll sample>
By mixing a conductive silicone rubber [manufactured by Shin-Etsu Chemical Co., Ltd., “X-34-264A / B, mixing mass ratio A / B = 1/1”] with a static mixer, an elastic layer forming material is obtained. Prepared.

  A solid cylindrical iron bar with a diameter of 6 mm was prepared as a shaft, and an adhesive was applied to the outer peripheral surface. After this shaft body was set in the hollow space of the roll molding die, the prepared elastic layer forming material was poured into the hollow space, heated and cured at 190 ° C. for 30 minutes, and demolded. Thereby, a roll-shaped elastic layer (thickness 3 mm) made of conductive silicone rubber was formed along the outer peripheral surface of the shaft body.

  Next, each of the prepared surface layer forming materials was applied to the outer peripheral surface of the elastic layer by a roll coating method, and then subjected to a crosslinking treatment at 170 ° C. for 30 minutes to form a surface layer (thickness 15 μm). Thereby, the conductive roll samples 1-9 were produced.

  Test pieces were prepared using each surface layer forming material, and the durability of the surface layer, the hardness of the surface layer and its temperature dependency, and the volumetric electrical resistance of the surface layer were investigated. In addition, the crosslinking treatment conditions at the time of preparing the test piece were the same as the crosslinking treatment conditions at the time of producing the conductive roll sample described above.

−Durability of surface layer−
In accordance with JISK7311, the load value and elongation at break when a dumbbell test piece prepared from each surface layer forming material was pulled at a pulling speed of 100 mm / min were measured, and the breaking stress and breaking elongation were calculated. Further, the breaking energy was calculated by multiplying the breaking stress obtained from the tensile test and the breaking elongation. The case where the value of the fracture energy was 1000 (MJ / m ³ ) or more was designated as “A” because the durability of the surface layer was excellent. The case where the value of the fracture energy was 450 (MJ / m ³ ) or more and less than 1000 (MJ / m ³ ) was designated as “B” because the durability of the surface layer was good. The case where the value of the fracture energy was less than 450 (MJ / m ³ ) was designated as “C” because the surface layer was inferior in durability.

-Surface hardness and its temperature dependence-
Based on JISK7244, the storage elastic modulus in each temperature when the sinusoidal vibration was given to the test piece produced from each said surface layer forming material in the tension mode was read. The measurement temperature range was -10 ° C to 50 ° C. Then, the storage elastic modulus digit change rate (= LOG (storage elastic modulus at 0 ° C.) − LOG (storage elastic modulus at 40 ° C.)) was calculated from the storage elastic modulus at 0 ° C. and 40 ° C. When the storage elastic modulus was 1 × 10 ⁸ MPa or less in the range of 0 ° C. to 40 ° C., the surface layer was judged to have low hardness. Moreover, when the storage elastic modulus digit change rate was 0.1 or less, it was judged that there was almost no temperature dependence of the hardness of a surface layer. When the storage modulus digit change rate was larger than 0.1 and 0.3 or less, it was judged that the temperature dependence of the hardness of the surface layer was small. When the storage modulus digit change rate was larger than 0.3, it was judged that the temperature dependence of the hardness of the surface layer was large.

In Table 1 to be described later, the case where the storage elastic modulus is 1 × 10 ⁸ MPa or less within the range of 0 ° C. to 40 ° C. and the storage elastic modulus digit change rate is 0.1 or less is referred to as “A”. did. In this case, it has excellent filming resistance when used as the surface layer of the developing roll. Further, the case where the storage elastic modulus is 1 × 10 ⁸ MPa or less within the range of 0 ° C. to 40 ° C. and the storage elastic modulus digit change rate is larger than 0.1 and not larger than 0.3 is expressed as “B " In this case, it has good filming resistance when used as the surface layer of the developing roll. In addition, the case where the storage elastic modulus was 1 × 10 ⁸ MPa or less in the range of 0 ° C. to 40 ° C. and the change rate of the storage elastic modulus digit was larger than 0.3 was defined as “C”. In this case, the filming resistance is inferior when used as the surface layer of the developing roll.

-Volumetric electrical resistance of surface layer-
In accordance with SRIS2304, a voltage of 10 V was applied to a test piece of length 100 mm × width 100 mm × thickness 15 μm made from each surface layer forming material using an electrode (“SME-8411” manufactured by Toa Denpa Kogyo Co., Ltd.). The volume electric resistance (Ω · cm) was measured. The measurement temperature was 23 ° C. The case where the volume electric resistance was less than 5 × 10 ⁸ (Ω · cm) was designated as “A” because it was a low volume electric resistance and could exhibit excellent conductivity. The case where the volume electrical resistance is 5 × 10 ⁸ (Ω · cm) or more and less than 1 × 10 ⁹ (Ω · cm) is considered to be “B” because it has a relatively low volume electrical resistance and can exhibit good conductivity. " The case where the volume electrical resistance was 1 × 10 ⁹ (Ω · cm) or more was designated as “C” because the volume electrical resistance was high and the conductivity was inferior.

  Table 1 summarizes the surface layer composition and evaluation results of the produced conductive roll samples.

  According to Table 1, the following can be understood. That is, the surface layer of Sample 7 is obtained by crosslinking a polyol that is not a polyrotaxane with a trifunctional isocyanate compound, and the crosslinked structure of the crosslinked polymer is a network structure. Therefore, the surface layer of the sample 7 is likely to have a portion having a high crosslink density, and when deformed by an external force, stress concentration is easily generated at the crosslink point of the portion, resulting in poor durability. Moreover, the surface layer of the sample 7 has a large temperature dependence of the storage elastic modulus within the temperature range of 0 ° C. to 40 ° C. that is the assumed use temperature of this example, as can be seen from the large digit change rate of the storage elastic modulus. . Therefore, it can be said that the surface layer of the sample 7 has a large temperature dependence of hardness.

  The surface layer of Sample 8 uses the isocyanate compound (2) having a smaller number of isocyanate groups than the isocyanate compound (1). Therefore, compared with the surface layer of the sample 7, a part with a high crosslinking density relatively decreases, and the durability of the surface layer is improved. However, like the surface layer of Sample 7, the temperature dependence of the storage elastic modulus is large and the temperature dependence of the hardness is large within the temperature range of 0 ° C. to 40 ° C.

  In the surface layer of Sample 9, since the number of functional groups of the used polyol (2) is smaller than the molecular weight of the polyol (1), the portion having a higher cross-linking density is relatively decreased as compared with the surface layer of Sample 8, and the durability of the surface layer is reduced. Improved. However, like the surface layer of Sample 7, the temperature dependence of the storage elastic modulus is large and the temperature dependence of the hardness is large within the temperature range of 0 ° C. to 40 ° C.

  On the other hand, the surface layers of Sample 1 to Sample 6 have a crosslinked structure in which the polyrotaxane (1) is crosslinked by the isocyanate compounds (1) to (4). This cross-linked structure is composed of a urethane bond formed by a reaction between a hydroxyl group of a cyclic molecule in one polyrotaxane (1) forming a cross-link and one isocyanate group in the isocyanate compounds (1) to (4), and a cross-link. It includes a hydroxyl group of a cyclic molecule in the other polyrotaxane (1) to be formed and a urethane bond formed by a reaction between the other isocyanate group different from the one isocyanate group in the isocyanate compounds (1) to (4). .

  Therefore, the surface layers of Sample 1 to Sample 6 are less likely to have a portion with a higher crosslinking density than the surface layers of Sample 7 to Sample 9 having a crosslinked structure crosslinked in a network structure. Moreover, since the cyclic molecule bridge | crosslinked by isocyanate compound (1)-(4) can move like a pulley in the surface layer of sample 1-sample 6, polyrotaxane (1) can move flexibly. Therefore, when the surface layers of Sample 1 to Sample 6 are deformed by an external force, it is difficult for stress to concentrate on the cross-linking point and it is difficult to break. Therefore, the surface layers of Sample 1 to Sample 6 can exhibit better durability than conventional ones. In particular, since the surface layers of Sample 2 to Sample 6 are crosslinked by a bifunctional isocyanate compound having isocyanate groups at both ends, the fracture energy is large and excellent durability can be expressed.

  The surface layers of Samples 1 to 6 are polyethylene glycol chains in which the linear molecular chain constituting the polyrotaxane is flexible. Therefore, the surface layers of Sample 1 to Sample 6 can be reduced in hardness in the operating temperature range as compared with the surface layers of Sample 7 to Sample 9. Furthermore, since the surface layers of Sample 1 to Sample 6 can reduce the temperature dependence of the storage elastic modulus, the temperature dependence of the hardness can be reduced.

  In particular, in the surface layers of Sample 2 to Sample 4 and Sample 6, since the linear molecular chain has an ether bond in the molecule and the isocyanate compound has an ether bond in the molecule, Sample 1 Compared to the surface layer of 5, the volumetric electrical resistance of the surface layer is lower due to the synergistic effect of the combination of both.

  As mentioned above, although the Example of this invention was described in detail, this invention is not limited to the said Example, A various change is possible within the range which does not impair the meaning of this invention.

R, B Electrophotographic member 1 Surface layer 10 Polyrotaxane 101 Cyclic molecule 102 Linear molecular chain 103 End group 11 Isocyanate compound 12 First cross-linked part 13 Second cross-linked part 2 Shaft 3 Elastic layer 5 Surface layer 6 Base layer

Claims (6)

An electrophotographic member having a surface layer and used in an electrophotographic apparatus,
The above surface layer is
Containing ionic conductive agent,
A cyclic molecule having a functional group that reacts with an isocyanate group, a linear molecular chain penetrating through the ring of the cyclic molecule, and a terminal that is arranged at both ends of the linear molecular chain to prevent the elimination of the cyclic molecule The polyrotaxane having a group has a crosslinked structure crosslinked by an isocyanate compound having an isocyanate group at least at both ends;
The crosslinked structure is
The first cross-linked portion formed by the reaction of the reactive group of the cyclic molecule in one of the polyrotaxanes forming a crosslink and the one isocyanate group in the isocyanate compound, and the cyclic in the other polyrotaxane forming a crosslink An electrophotographic member comprising: a second cross-linked portion formed by a reaction between the reactive group of a molecule and the other isocyanate group in the isocyanate compound. The electrophotographic member according to claim 1,
The member for electrophotography, wherein the linear molecular chain in the polyrotaxane has an ether bond in the molecule. The electrophotographic member according to claim 1, wherein
The above-mentioned isocyanate compound has an ether bond in the molecule, and is a member for electrophotography. It is the member for electrophotography of any one of Claims 1-3,
The molecular weight of the said isocyanate compound exists in the range of 300-3000, The member for electrophotography characterized by the above-mentioned. The member for electrophotography according to any one of claims 1 to 4 ,
The electrophotographic member, wherein the surface layer contains a polyurethane-based thermoplastic elastomer. The member for electrophotography according to any one of claims 1 to 5 ,
An electrophotographic member, which is a conductive member incorporated in an electrophotographic image forming apparatus.

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