JP2017156396A - Charging roll for electrophotographic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging roll for an electrophotographic apparatus that suppresses adhesion of toner and is excellent in uniform chargeability.SOLUTION: There is provided a charging roll for an electrophotographic apparatus 10 comprising: a shaft body 12; an elastic body layer 14 that is formed on an outer periphery of the shaft body 12; and a surface layer 16 that is formed on an outer periphery of the elastic body layer 14, where the surface layer 16 contains a binder polymer (a), a melamine resin (b), and a fluorine modifier (c) including a hydroxyl group. The amount of (b) is preferably within a range of 20 to 200 parts by mass relative to 100 parts by mass of (a), and the amount of (c) is preferably within a range of 0.1 to 10 parts by mass. The amount of (c) is preferably within a range of 0.0005 to 0.5 parts by mass relative to 100 parts by mass of (b).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a charging roll for an electrophotographic apparatus that is suitably used in an electrophotographic apparatus such as a copying machine, a printer, and a facsimile that employs an electrophotographic system.

  For charging rolls in electrophotographic equipment, the contact surface between the charging roll and the photosensitive drum can be improved by adding fine irregularities to the product surface by adding particles to the surface layer or scraping the surface to improve antifouling properties. Has been devised to reduce toner and to prevent the toner and external additives from being rubbed into the roll surface (Patent Document 1). In addition, in order to improve toner adhesion, a contrivance has been made to blend a melamine resin in the surface layer (Patent Document 2).

JP 2008-116869 A JP 2006-163059 A

  The toner carried from the toner BOX inside the electrophotographic apparatus is usually used for printing, but the toner not used for printing is carried to the waste toner BOX by a cleaning blade in close contact with the photosensitive drum. However, waste toner and toner external additives are submicron fine particles, and the charging roller scrapes the surface of the photosensitive drum with use over time, leaving a gap between the cleaning blade and the photosensitive drum. There may occur a situation in which toner or toner external additive that should be transported to the BOX slips through and is transported to the charging roll. When toner or an external toner additive adheres to the charging roll, the charging ability is reduced, streaks are generated in the output image, and this causes image defects.

  The problem to be solved by the present invention is to provide a charging roll for an electrophotographic apparatus that suppresses toner adhesion and is excellent in uniform chargeability.

  In order to solve the above problems, a charging roll for an electrophotographic apparatus according to the present invention comprises: a shaft body; an elastic body layer formed on an outer periphery of the shaft body; and a surface layer formed on the outer periphery of the elastic body layer. And the surface layer comprises a binder polymer (a), a melamine resin (b), and a fluorine-based modifier (c) having a hydroxyl group.

  The amount of (c) is preferably in the range of 0.0005 to 0.5 parts by mass with respect to 100 parts by mass of (b). The amount of (c) is preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of (a). It is preferable that the amount of (b) is in the range of 20 to 200 parts by mass with respect to 100 parts by mass of (a).

  According to the charging roll for electrophotographic equipment according to the present invention, it is possible to suppress the adhesion of slipped toner and toner external additives, thereby suppressing image defects. Moreover, it is excellent in uniform chargeability.

It is the external appearance schematic diagram (a) of the charging roll for electrophotographic apparatuses which concerns on 1st embodiment of this invention, and its AA sectional view (b). It is a photograph of the AFM surface resistance distribution of the charging roll which concerns on an Example and a comparative example.

  The charging roll for electrophotographic equipment according to the present invention (hereinafter sometimes simply referred to as a charging roll) will be described in detail. FIG. 1A is a schematic external view of a charging roll for an electrophotographic apparatus according to the first embodiment of the present invention, and FIG.

  The charging roll 10 includes a shaft body 12, an elastic body layer 14 formed on the outer periphery of the shaft body 12, and a surface layer 16 formed on the outer periphery of the elastic body layer 14. The elastic body layer 14 is a layer serving as a base of the charging roll 10. The surface layer 16 is a layer that appears on the surface of the charging roll 10.

  The surface layer 16 includes a binder polymer (a), a melamine resin (b), and a fluorine-based modifier (c) having a hydroxyl group.

  The binder polymer (a) is not particularly limited, and a suitable material may be selected according to required characteristics. Examples of the binder polymer (a) include acrylic resins, methacrylic resins, fluorine resins, silicone resins, polycarbonate resins, urethane resins, and polyamide resins. The binder polymer (a) does not include a melamine resin. These may be used individually by 1 type as a binder polymer of the surface layer 16, and may be used in combination of 2 or more type. Of these, fluororesins are preferred from the viewpoint of being difficult to oxidize and difficult to absorb water.

  The melamine-based resin (b) makes the surface layer 16 containing the binder polymer harder so that the toner and the toner external additive are not embedded or pierced on the surface. As a result, it is easy to suppress the adhesion of the slipped-out toner or toner external additive. Melamine resin (b) can also be used as a crosslinking agent for binder polymer (a). The melamine resin (b) reacts formaldehyde with a material having a polyfunctional amino group such as melamine, melamine derivative, urea, urea derivative, thiourea, thiourea derivative, guanidine, guanidine derivative, guanamine, and guanamine derivative. Examples thereof include trimethylol melamine, hexamethylol melamine, dimethylol urea, dimethylol guanidine, and one or more polycondensates thereof. These may be used individually by 1 type as a melamine-type resin (b) of the surface layer 16, and may be used in combination of 2 or more type.

  The melamine-based resin (b) is 20 parts by mass with respect to (a) 100 parts by mass from the viewpoint of making the surface layer 16 containing the binder polymer high in hardness and facilitating the adhesion of toner and toner external additives. The above is preferable. More preferably, it is 50 mass parts or more, More preferably, it is 100 mass parts or more. When the amount of the melamine resin (b) is 100 parts by mass or more with respect to 100 parts by mass of (a), the effect of suppressing the adhesion of toner and toner external additives is particularly excellent, and the generation of streak images can be suppressed even after durability. . Moreover, it is preferable that a melamine-type resin (b) is 200 mass parts or less with respect to said (a) 100 mass parts from a viewpoint of ensuring the surface characteristic of the surface layer 16 by a binder polymer easily. More preferably, it is 180 mass parts or less, More preferably, it is 150 mass parts or less.

  Since the fluorine-based modifier (c) having a hydroxyl group is a fluorine-based modifier, tackiness on the surface of the surface layer 16 can be suppressed. As a result, it is easy to suppress the adhesion of the slipped-out toner or toner external additive. Moreover, it becomes easy to remove even if it adheres. Moreover, by having a hydroxyl group, even if it is a fluorine-type modifier, compatibility with a melamine-type resin (b) becomes high, and uniform charging property is ensured. Examples of the fluorine-based modifier include fluorine-based surfactants. Examples of the fluorine-based modifier include DIC's Megafac series.

  The fluorine-based modifier (c) having a hydroxyl group is preferably 0.1 parts by mass or more with respect to 100 parts by mass of (a) from the viewpoint of easily suppressing tackiness. More preferably, it is 0.3 mass part or more, More preferably, it is 0.5 mass part or more. Moreover, it is preferable that it is 10 mass parts or less with respect to said (a) 100 mass parts from a viewpoint of ensuring excellent compatibility with said (b) and being easy to ensure uniform charging property. More preferably, it is 8 mass parts or less, More preferably, it is 7 mass parts or less. When (c) is 7 parts by mass or less with respect to 100 parts by mass of (a), excellent compatibility with (b) above can be secured and particularly excellent uniform chargeability can be exhibited.

  And from a viewpoint of exhibiting the effect by said (b) and (c) with sufficient balance, the quantity of said (c) is 0.0005-0.5 mass part with respect to 100 mass parts of said (b). It is preferable to be within the range. More preferably, it exists in the range of 0.001-0.3 mass part, More preferably, it exists in the range of 0.005-0.1 mass part.

  The surface layer 16 can be formed by using a composition for forming a surface layer, coating this on the outer peripheral surface of the elastic body layer 14, and appropriately performing drying, heating, and crosslinking treatment. The composition for surface layer formation contains the above (a) to (c) as essential components. The composition for forming a surface layer may contain one or more kinds of various additives added to the surface layer in addition to the above (a) to (c). Examples of such additives include conductive agents such as ionic conductive agents (such as quaternary ammonium salts) and electronic conductive agents (such as carbon black), roughness forming particles for forming roughness on the surface layer 16, filling Agents, stabilizers, ultraviolet absorbers, lubricants, mold release agents, dyes, pigments, flame retardants and the like. The composition for forming a surface layer may contain a solvent in consideration of applicability.

  Resin particles or the like are used as the roughness forming particles. The material for the roughness forming particles is not particularly limited, and acrylic particles, silicone particles, urethane particles and the like are used.

  In the composition for forming a surface layer, the melamine-based resin (b) and the fluorine-based modifier (c) having a hydroxyl group are excellent in compatibility with each other by hydrogen bonding. The binder polymer (a) and the melamine resin (b), and the binder polymer (a) and the fluorine-containing modifier (c) having a hydroxyl group are excellent in compatibility with each other. As a result, in the composition for forming the surface layer, the melamine resin (b) and the fluorine-containing modifier (c) having a hydroxyl group are uniformly dispersed. The melamine resin (b) works as a crosslinking agent depending on the type of the binder polymer. Moreover, it becomes a crosslinked body by self-crosslinking reaction.

The surface layer 16 can be adjusted to a predetermined volume resistivity by a material type, a blending of a conductive agent, and the like. The volume resistivity of the surface layer 16 may be appropriately set in the range of 10 ⁵ to 10 ¹¹ Ω · cm, 10 ⁸ to ¹⁰ 10 Ω · cm, and the like depending on the application. The thickness of the surface layer 16 is not particularly limited, and may be set as appropriate within a range of 10 to 30 μm depending on the application.

  The elastic body layer 14 contains a crosslinked rubber. The elastic body layer 14 is formed of a conductive rubber composition containing uncrosslinked rubber. The crosslinked rubber is obtained by crosslinking uncrosslinked rubber. The uncrosslinked rubber may be a polar rubber or a nonpolar rubber. From the viewpoint of excellent conductivity, the uncrosslinked rubber is more preferably a polar rubber.

  The polar rubber is a rubber having a polar group, and examples of the polar group include a chloro group, a nitrile group, a carboxyl group, and an epoxy group. Specific examples of polar rubbers include hydrin rubber, nitrile rubber (NBR), urethane rubber (U), acrylic rubber (a copolymer of acrylic ester and 2-chloroethyl vinyl ether, ACM), and chloroprene rubber (CR). And epoxidized natural rubber (ENR). Among polar rubbers, hydrin rubber and nitrile rubber (NBR) are more preferable from the viewpoint that the volume resistivity tends to be particularly low.

  Examples of hydrin rubber include epichlorohydrin homopolymer (CO), epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-allyl glycidyl ether binary copolymer (GCO), epichlorohydrin-ethylene oxide-allyl glycidyl ether ternary. A copolymer (GECO) etc. can be mentioned.

  Examples of the urethane rubber include polyether type urethane rubber having an ether bond in the molecule. A polyether type urethane rubber can be produced by a reaction between a polyether having hydroxyl groups at both ends and a diisocyanate. The polyether is not particularly limited, and examples thereof include polyethylene glycol and polypropylene glycol. Although it does not specifically limit as diisocyanate, Tolylene diisocyanate, diphenylmethane diisocyanate, etc. can be mentioned.

  Examples of the nonpolar rubber include isoprene rubber (IR), natural rubber (NR), styrene butadiene rubber (SBR), and butadiene rubber (BR).

  Examples of the crosslinking agent include a sulfur crosslinking agent, a peroxide crosslinking agent, and a dechlorination crosslinking agent. These crosslinking agents may be used alone or in combination of two or more.

  Examples of the sulfur crosslinking agent include conventionally known sulfur crosslinking agents such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, sulfur chloride, thiuram vulcanization accelerator, and polymer polysulfide. it can.

  Examples of peroxide crosslinking agents include conventionally known peroxide crosslinking agents such as peroxyketals, dialkyl peroxides, peroxyesters, ketone peroxides, peroxydicarbonates, diacyl peroxides and hydroperoxides. Can do.

  Examples of the dechlorination crosslinking agent include dithiocarbonate compounds. More specifically, quinoxaline-2,3-dithiocarbonate, 6-methylquinoxaline-2,3-dithiocarbonate, 6-isopropylquinoxaline-2,3-dithiocarbonate, 5,8-dimethylquinoxaline-2,3- A dithiocarbonate etc. can be mentioned.

  The blending amount of the crosslinking agent is preferably within a range of 0.1 to 2 parts by mass, more preferably 0.3 to 1.8 parts by mass with respect to 100 parts by mass of the uncrosslinked rubber from the viewpoint of difficulty in bleeding. In the range of parts, more preferably in the range of 0.5 to 1.5 parts by weight.

  When a dechlorination crosslinking agent is used as the crosslinking agent, a dechlorination crosslinking accelerator may be used in combination. Examples of the dechlorination crosslinking accelerator include 1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter abbreviated as DBU) or a weak acid salt thereof. Although the dechlorination crosslinking accelerator may be used in the form of DBU, it is preferably used in the form of its weak acid salt from the viewpoint of handling. Examples of weak acid salts of DBU include carbonate, stearate, 2-ethylhexylate, benzoate, salicylate, 3-hydroxy-2-naphthoate, phenol resin salt, 2-mercaptobenzothiazole salt, 2- Examples include mercaptobenzimidazole salts.

  The content of the dechlorination crosslinking accelerator is preferably in the range of 0.1 to 2 parts by mass with respect to 100 parts by mass of the uncrosslinked rubber from the viewpoint of difficulty in bleeding. More preferably, it is in the range of 0.3 to 1.8 parts by mass, and still more preferably in the range of 0.5 to 1.5 parts by mass.

The elastic layer 14, for imparting conductivity, carbon black, _{graphite, c-TiO 2, c-} ZnO, c-SnO 2 (c- means conductive.), Ion conductive agent (quaternary Conventionally known conductive agents such as ammonium salts, borates, surfactants, etc.) can be appropriately added. Moreover, you may add various additives suitably as needed. Additives include lubricants, vulcanization accelerators, anti-aging agents, light stabilizers, viscosity modifiers, processing aids, flame retardants, plasticizers, foaming agents, fillers, dispersants, antifoaming agents, pigments, release agents. Examples include molds.

The elastic body layer 14 can be adjusted to a predetermined volume resistivity by the kind of the crosslinked rubber, the blending amount of the ionic conductive agent, the blending of the electronic conductive agent and the like. The volume resistivity of the elastic body layer 14 may be set as appropriate in the range of 10 ² to 10 ¹⁰ Ω · cm, 10 ³ to 10 ⁹ Ω · cm, 10 ⁴ to 10 ⁸ Ω · cm, and the like depending on the application. .

  The thickness of the elastic layer 14 is not particularly limited, and may be set as appropriate within a range of 0.1 to 10 mm depending on the application.

  The elastic body layer 14 can be manufactured as follows, for example. First, the shaft body 12 is coaxially installed in the hollow part of the roll molding die, injected with an uncrosslinked conductive rubber composition, heated and cured (crosslinked), and then demolded, or The elastic body layer 14 is formed on the outer periphery of the shaft body 12 by, for example, extruding an uncrosslinked conductive rubber composition on the surface of the shaft body 12.

  The shaft body 12 is not particularly limited as long as it has conductivity. Specific examples include solid bodies made of metal such as iron, stainless steel, and aluminum, and a cored bar made of a hollow body. You may apply | coat an adhesive agent, a primer, etc. to the surface of the shaft body 12 as needed. That is, the elastic body layer 14 may be bonded to the shaft body 12 via the adhesive layer (primer layer). The adhesive, primer, etc. may be made conductive as necessary.

  According to the charging roll 10 having the above-described configuration, the surface layer 16 has a higher hardness due to the melamine resin (b) and a lower tack due to the fluorine-based modifier (c) having a hydroxyl group. Adhesive adhesion is suppressed, and image defects due to this are suppressed. Adherence of toner and toner external additives cannot be sufficiently suppressed only by either increasing the hardness with the melamine resin (b) or reducing the tack with the fluorine-based modifier (c) having a hydroxyl group. By combining these two technologies, it is possible to effectively suppress adhesion of toner and toner external additives. Melamine-based resins and fluorine-based modifiers have a problem in compatibility, but the compatibility problem is solved by using a fluorine-based modifier (c) having a hydroxyl group as the fluorine-based modifier. As well as satisfying uniform chargeability.

The hardness of the roll surface is preferably a Martens hardness of 50 N / mm ² or more from the viewpoint of suppressing adhesion of toner and toner external additives. More preferably, it is 60 N / mm ² or more, and still more preferably 80 N / mm ² or more. On the other hand, 120 N / mm ² or less is preferable from the viewpoint of suppressing the abrasion of the photosensitive drum. More preferably, it is 110 N / mm < ² > or less, More preferably, it is 100 N / mm < ² > or less. According to the configuration of the present invention, the hardness of the roll surface can be adjusted within the preferred range.

  The tackiness of the roll surface is preferably 20 mN or less from the viewpoint of suppressing adhesion of toner and toner external additives. More preferably, it is 18 mN or less, More preferably, it is 15 mN or less. On the other hand, the lower limit is not particularly limited, but is preferably 0.03 mN or more. More preferably, it is 0.1 mN or more. The roll surface tackiness can be expressed by the maximum stress obtained from the probe tack method. According to the configuration of the present invention, the tackiness of the roll surface can be adjusted within the preferred range.

  The configuration of the charging roll according to the present invention is not limited to the configuration shown in FIG. For example, the charging roll 10 shown in FIG. 1 may have a configuration in which another elastic body layer is provided between the shaft body 12 and the elastic body layer 14. In this case, the other elastic body layer is a layer serving as a base of the charging roll, and the elastic body layer 14 functions as a resistance adjusting layer for adjusting the resistance of the charging roll. Another elastic body layer can be comprised by either of the materials mentioned as a material which comprises the elastic body layer 14, for example. For example, the charging roll 10 shown in FIG. 1 may have a configuration in which another elastic layer is provided between the elastic layer 14 and the surface layer 16. In this case, the elastic body layer 14 is a layer serving as a base of the charging roll, and the other elastic body layer functions as a resistance adjusting layer for adjusting the resistance of the charging roll.

  Hereinafter, the present invention will be described in detail using Examples and Comparative Examples.

(Examples 1-5)
<Preparation of conductive rubber composition>
For 100 parts by mass of hydrin rubber (ECO, “Epichromer CG102” manufactured by Daiso), 5 parts by mass of vulcanization aid (Zinc oxide, “Zinc oxide type 2” manufactured by Mitsui Metals), carbon (“Ketjen” manufactured by Ketjen Black International) 10 parts by weight of black EC300J "), 0.5 parts by weight of vulcanization accelerator (2-mercaptobenzothiazole," Noxeller MP "manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.), sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., 2 parts by mass of Sulfax PTC ") and 50 parts by mass of a filler (calcium carbonate," Shiroka Hana CC "manufactured by Shiroishi Kogyo Co., Ltd.) were added, and these were stirred and mixed with a stirrer to prepare a conductive rubber composition.

<Preparation of elastic layer>
Set a core metal (shaft body, diameter 6 mm) in the molding die, inject the conductive rubber composition described above, heat at 170 ° C. for 30 minutes, cool and demold, and thicken the outer periphery of the core metal A 1.5 mm elastic layer was formed.

<Preparation of surface layer forming composition>
Binder polymer 1 (acrylic / fluorine resin mixture, DIC “TK300”), melamine resin (Beckamine M-3), and fluorine-containing modifier 1 having a hydroxyl group (manufactured by DIC) so as to have the composition shown in Table 1. "Megafuck F561"), carbon ("MS-55" manufactured by Mikuni Dye), and roughness forming particles (acrylic particles, "MX-800S" manufactured by Soken Chemical Co., Ltd.) are added so that the solid content concentration becomes 20% by mass. The concentration was adjusted with MEK.

<Production of surface layer>
The surface layer-forming composition was roll-coated on the surface of the elastic layer and heated at 120 ° C. for 50 minutes to form a surface layer having a thickness of 10 μm on the outer periphery of the elastic layer. Thereby, the charging roll which concerns on Examples 1-5 was produced.

(Examples 6 to 10)
In the preparation of the composition for forming the surface layer, the binder polymer 2 (urethane resin, “Adekabon titer HUX-350” manufactured by Asahi Denka Kogyo Co., Ltd.) is used in place of the binder polymer 1 (acrylic / fluorine resin mixed, “DIC300” TK300). A charging roll according to Examples 6 to 10 was produced in the same manner as in Examples 1 to 5 except that methanol was used as the solvent.

(Examples 11 to 15)
In the preparation of the composition for forming the surface layer, a fluorine-containing modifier 1 having a hydroxyl group (“Megafac F477” manufactured by DIC) is used in place of the fluorine-containing modifier 1 having a hydroxyl group (“Megafac F561” manufactured by DIC). A charging roll according to Examples 11 to 15 was produced in the same manner as in Examples 6 to 10 except that.

(Comparative Example 1)
A charging roll according to Comparative Example 1 was prepared in the same manner as in Example 8 except that in the preparation of the surface layer forming composition, the melamine resin and the fluorine-based modifier having a hydroxyl group were not blended.

(Comparative Example 2)
A charging roll according to Comparative Example 2 was produced in the same manner as in Example 8 except that a fluorine-based modifier having a hydroxyl group was not blended in the preparation of the surface layer forming composition.

(Comparative Example 3)
In the preparation of the composition for forming the surface layer, a charging roll according to Comparative Example 3 was produced in the same manner as in Example 8 except that the melamine-based resin was not blended.

(Comparative Examples 4-5)
Comparative Example 4 was carried out in the same manner as in Example 8 except that in the preparation of the surface layer forming composition, the fluorine-containing modifiers 3 and 4 having no hydroxyl group were used instead of the fluorine-containing modifier having a hydroxyl group. A charging roll according to ˜5 was produced.
・ Fluorine-based modifier 3: Neos “Factent 710FL”, no hydroxyl group ・ Fluorine-based modifier 4: Seimi Chemical “Surflon S-386”, no hydroxyl group

(Comparative Example 6)
In the preparation of the surface layer forming composition, a charging roll according to Comparative Example 6 was prepared in the same manner as in Example 8 except that the non-fluorine-based modifier 5 having a hydroxyl group was used instead of the fluorine-based modifier having a hydroxyl group. Was made.
Non-fluorine modifier 5: Acrylic / silicone mixed resin, “US270” manufactured by Toa Gosei, with hydroxyl group

  For each of the produced charging rolls, the adhesion of the toner or the toner external additive was evaluated by the influence on the image (post-endurance streak image), and the uniform chargeability was evaluated by the influence on the image (uneven image). Further, the surface hardness and the surface tackiness of each manufactured charging roll were examined. The evaluation results and the composition (parts by mass) of the composition for forming the surface layer are shown in the following table.

(Stripe image after endurance)
The produced charging roll was attached to an actual machine (“iR3245” manufactured by Canon), and a printing test (printing rate 5%) of 5000 sheets was performed in an environment of 32.5 ° C. × 83% RH (endurance test). Thereafter, the charging roll was taken out from the actual machine, and the fixing state of the toner or the toner external additive on the surface thereof was visually observed. When the toner or toner external additive is not fixed on the surface of the charging roll and no image abnormality is observed, the adhesion prevention property is particularly good. “◎”, and the toner or toner external additive is slightly fixed on the surface of the charging roll. In the case where the streak image due to the stain appears, but the tolerance is good, the adhesion preventing property is good, and the toner or toner external additive is often fixed on the surface of the charging roll. When the streak image was in an unacceptable range, the anti-adhesion property was judged as “x”.

(Uneven image)
In the image after the durability test, when the uneven image due to the resistance unevenness was not observed, the uniform charging property was particularly good “◎”, and the uneven image due to the resistance unevenness was slightly observed, but within the allowable range. The uniform chargeability was good “◯”, and the uneven charge due to resistance unevenness was in an unacceptable range.

(surface hardness)
Martens hardness was measured in accordance with ISO 14577-1. Specifically, it was measured using a micro hardness meter (Fischer “Microscope HS100”). The numerical value of Martens hardness showed the average value when arbitrary 5 points | pieces were measured.
<Measurement conditions>
Indenter: Square-angled diamond indenter with a face angle of 136 ° Initial load: 0 mN
Maximum indentation load: 20mN (constant load)
Maximum load arrival time: 5 sec
Maximum load holding time: 30 sec
Desorption time: 5 sec
Measurement temperature: 25 ° C

(Tackiness)
It was measured by the maximum stress (ASTM-D-2979) obtained from the probe tack method. Specifically, it measured using the adhesive force meter ("Fusing Simulator FSR-1000" by Rhesca). The maximum stress was calculated from the stress-strain curve when a smooth probe end face was attached to the object to be measured and then pulled apart. The value showed the average value when arbitrary 5 points | pieces were measured.
<Measurement conditions>
Indenter: Square pillar type diamond indenter with a contact area of 78.5 mm ² Initial load: 0 mN
Maximum indentation load: 200mN (constant load)
Maximum load arrival time: 10 sec
Maximum load holding time: 10 sec
Desorption time: 10 sec
Measurement temperature: 25 ° C

  In Comparative Example 1, the surface layer forming composition does not contain a melamine-based resin and a fluorine-based modifier having a hydroxyl group. For this reason, toner adhesion could not be suppressed, and streak image defects occurred after durability. In Comparative Example 2, the fluorine-based modifier having a hydroxyl group is not blended in the surface layer forming composition. For this reason, toner adhesion could not be suppressed, and streak image defects occurred after durability. In Comparative Example 3, the melamine-based resin is not blended in the surface layer forming composition. For this reason, toner adhesion could not be suppressed, and streak image defects occurred after durability. Comparative Examples 4 and 5 are fluorine-based modifiers that have a melamine-based resin and a fluorine-based modifier in the surface layer-forming composition, but do not have a hydroxyl group. For this reason, it is inferior to uniform chargeability. Comparative Example 6 is a non-fluorine-based modifier, although a melamine-based resin and a modifier are blended in the surface layer forming composition. For this reason, toner adhesion could not be suppressed, and streak image defects occurred after durability. In contrast, in the examples, in the surface layer forming composition, a melamine-based resin and a fluorine-based modifier having a hydroxyl group were blended, toner adhesion was suppressed, and no defects in streak images were observed after durability. . Moreover, it is excellent in uniform chargeability. From these, in the composition for forming the surface layer, in addition to the binder polymer, the melamine resin and the fluorine-based modifier having a hydroxyl group are blended, so that toner adhesion is effectively suppressed, and image defects due to this can be suppressed. I understand that.

  In the comparison of Examples, it can be seen that when the blending amount of the melamine resin is 100 parts by mass or more with respect to 100 parts by mass of the binder polymer, the effect of suppressing toner adhesion is improved. Moreover, it turns out that uniform charging property improves that the compounding quantity of the fluorine-type modifier which has a hydroxyl group is 7 mass parts or less with respect to 100 mass parts of binder polymers.

  Next, the result of observing uneven resistance on the surface of the charging roll with an AFM (Atomic Force Microscope) is shown. The observation was performed on Example 8, Comparative Example 1, Comparative Example 4, and Comparative Example 6. FIG. 2 shows the results of the surface resistance distribution. 2A is Comparative Example 1, FIG. 2B is Example 8, FIG. 2C is Comparative Example 6, and FIG. 2D is Comparative Example 4. FIG. Moreover, about Example 8, the comparative example 1, the comparative example 4, and the comparative example 6, the solution state (appearance) of the composition for surface layer formation was observed, and the presence or absence of turbidity was investigated. Moreover, about these, the hardness nonuniformity of the charging roll surface and tack nonuniformity were also investigated. The results are shown in Table 5.

(Hardness unevenness)
The Martens hardness was calculated from the difference between the maximum value and the minimum value when any five points were measured.

(Tack unevenness)
The tackiness was calculated from the difference between the maximum value and the minimum value when any five points were measured.

  As shown in FIG. 2, from Example 8 (FIG. 2 (b)), by adding a melamine-based resin and a fluorine-based modifier having a hydroxyl group to the binder polymer, there is almost no resistance unevenness. You can see (the color difference is small). Similarly, Comparative Example 1 (FIG. 2A) and Comparative Example 6 (FIG. 2C) have small resistance unevenness. However, Comparative Example 4 (FIG. 2 (d)) is a mixture of a melamine-based resin and a fluorine-based modifier having no hydroxyl group with respect to the binder polymer. (Color density difference is large). And from Table 5, in the comparative example 4, white turbidity was observed in the solution, and it was confirmed that dispersibility is bad. Other than this, it was confirmed that the solution was transparent and excellent in dispersibility. In Comparative Example 4, it was confirmed that hardness unevenness and tack unevenness were also large. Other than this, it was confirmed that hardness unevenness and tack unevenness were small.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the present invention. .

10 Charging roll 12 Shaft body 14 Elastic body layer 16 Surface layer

Claims (4)

A shaft body, an elastic body layer formed on the outer periphery of the shaft body, and a surface layer formed on the outer periphery of the elastic body layer,
The charging roll for electrophotographic apparatus, wherein the surface layer comprises a binder polymer (a), a melamine resin (b), and a fluorine-based modifier (c) having a hydroxyl group.   2. The charging roll for an electrophotographic apparatus according to claim 1, wherein the amount of (c) is in the range of 0.0005 to 0.5 parts by mass with respect to 100 parts by mass of (b).   The charging roll for electrophotographic equipment according to claim 1 or 2, wherein the amount of (c) is in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of (a).   4. The charging for an electrophotographic apparatus according to claim 1, wherein the amount of (b) is in the range of 20 to 200 parts by mass with respect to 100 parts by mass of (a). roll.