JP4914711B2 - Developing roll - Google Patents

Description

  The present invention relates to a developing roll, and more particularly to a developing roll suitable for an electrophotographic apparatus.

  In recent years, electrophotographic apparatuses such as copying machines, printers, and facsimiles that employ an electrophotographic system have been widely used. In these electrophotographic apparatuses, a photosensitive drum is usually incorporated. Various conductive rolls such as a developing roll, a charging roll, a toner supply roll, and a transfer roll are disposed around the photosensitive drum.

  As a developing method in this type of electrophotographic apparatus, a non-magnetic one-component developing method has recently become mainstream. In the above developing method, a toner layer is formed on the surface of the developing roll using a layer forming blade, and the surface of the photosensitive drum surface is brought into direct contact or non-contact with the surface of the photosensitive drum. Toner is adhered to the surface.

  Therefore, the developing roll is required to have good toner transportability. Conventionally, toner transportability has been imparted by forming irregularities on the surface of a developing roll.

  For example, in Patent Document 1, an elastic body layer having an uneven portion formed around a conductive shaft is provided, and the load length ratio tp (c) (c: cutting level%) of the surface of the elastic body layer is A developing roll satisfying 50 <tp (50%) <100 is disclosed.

  Moreover, the point which coats the coating agent which added fillers, such as a spherical silica and bridge | crosslinking polymethyl methacrylate, on the elastic-body layer surface, and forms the said uneven | corrugated | grooved part is disclosed.

JP 2001-317539 A

  However, the conventionally known developing rolls have a problem that, when used for a long period of time, the toner conveyance amount is reduced, and the image density is likely to be lowered. This is considered to be due to the following reason.

  That is, as the usage amount of the developing roll increases, the roll surface is worn by the layer forming blade. In the case where there are uneven portions on the roll surface, the above wear occurs preferentially at the tips of the convex portions.

  For this reason, it is considered that the height of the convex portion is lowered and the toner conveyance amount is reduced, and as a result, the image density is lowered.

  In particular, when the height of the convex portion varies, the stress due to the layer forming blade concentrates on the higher convex portion. For this reason, the convex portions are likely to be worn unevenly, and the above-described problems are likely to occur.

  Therefore, the problem to be solved by the present invention is to provide a developing roll having a good image density even when used for a long time.

In order to solve the above-mentioned problems, the developing roll according to the present invention has a concavo-convex portion on the roll surface, and the concavo-convex portion has a ten-point average roughness Rz of 8 to 16 μm and a load length ratio tp (20%). The gist is that 5% or more and 10% or less and the load length ratio tp (50%) is 10% or more and 45% or less .

  Here, the uneven portion is preferably formed on the surface of the surface layer.

  The surface layer preferably contains a urethane polymer or an epoxy polymer.

  The surface layer may be formed by coating.

  The developing roll according to the present invention has an uneven portion on the roll surface, and the ten-point average roughness Rz, load length rate tp (20%), load length rate tp (50%) of the uneven portion. Is within a specific range. Therefore, the developing roll according to the present invention hardly deteriorates in image density even when used for a long period of time, and is excellent in durability.

  This is because, in the developing roll according to the present invention, the height of the convex portion is relatively uniform, whereby the stress due to the layer forming blade is evenly distributed, the wear of the convex portion is alleviated, and the toner conveyance amount is reduced. It is assumed that the decrease can be suppressed.

  Here, when the concavo-convex part is formed on the surface of the surface layer, the production of the layer below the surface layer is performed in the same manner as in the past, and the concavo-convex part can be formed simply by changing the surface layer forming method, formation conditions, etc. . Therefore, there is an advantage that the degree of freedom of rough surface control is increased.

  Moreover, when the said surface layer contains a urethane type polymer or an epoxy-type polymer, the abrasion resistance of a surface layer improves. Therefore, there exists an advantage which becomes easy to acquire the said effect.

  Moreover, when the said surface layer is formed by coating, there exists an advantage which is easy to form the said uneven | corrugated | grooved part comparatively.

  Hereinafter, the developing roll according to this embodiment (hereinafter, also referred to as “main roll”) will be described in detail.

  This roll has an uneven part on the roll surface. If this roll has an uneven | corrugated | grooved part on the roll surface, the roll structure will not be specifically limited.

  Specifically, for example, a conductive elastic layer on the outer periphery of a conductive shaft (a metal core made of a metal solid, a metal cylindrical body hollowed inside, or a metal plated body thereof) The surface of the shaft may have an uneven portion, or one or more lower layers (for example, a conductive elastic layer) on the outer periphery of the shaft, and a surface layer on the outer periphery of the lower layer. (For example, a film shape or the like), and an uneven portion may be formed on the surface of the surface layer.

  This roll is preferably the latter roll structure. This is because the lower layer than the surface layer is manufactured in the same manner as in the prior art, and it is easy to form the uneven portion only by changing the surface layer forming method, forming conditions, and the like, so that the degree of freedom of rough surface control is increased.

  Further, the thickness of the surface layer is not particularly limited, but can be appropriately selected in consideration of the ease of forming the uneven portion, the wearability, and the like.

  The upper limit of the thickness of the surface layer is preferably 15 μm or less, more preferably 12 μm or less, and most preferably 10 μm or less from the viewpoint of not increasing the electrical resistance. On the other hand, the lower limit of the thickness of the surface layer is preferably 1 μm or more, more preferably 3 μm or more, and most preferably 5 μm or more from the viewpoint of wear resistance and the like.

  Further, the thickness of the conductive elastic layer is not particularly limited, but it can be generally selected from the range of preferably 0.1 to 10 mm, more preferably 1 to 5 mm.

  Here, in this roll, Rz, tp (20%), and tp (50%), which are the surface roughness parameters of the uneven portions formed on the roll surface, satisfy specific conditions. These surface roughness parameters are values measured in accordance with JIS B 0601-1994 in the roll axis direction.

  In this roll, the ten-point average roughness Rz of the concavo-convex portion is in the range of 8 to 16 μm. This Rz generally corresponds to the height difference of the concavo-convex portions formed on the roll.

  When Rz is larger than 16 μm, the toner is poorly charged and fog is likely to occur. On the other hand, if Rz is smaller than 8 μm, the toner conveyance amount is insufficient and the initial image density tends to be insufficient. In addition, the long-term image density tends to decrease.

  The upper limit of Rz is preferably 15 μm or less, more preferably 14 μm or less, and most preferably 13 μm or less from the viewpoints of appropriate charging of the toner and avoiding an excessive toner conveyance amount.

  On the other hand, the lower limit of Rz is preferably 9 μm or more, more preferably 10 μm or more, and most preferably 11 μm or more from the viewpoint of making the toner transport amount appropriate.

  In this roll, the tp (c%) of the concavo-convex part is a load length ratio (c: cutting level%). Specifically, it can be determined as follows based on the above JIS.

  That is, as shown in FIG. 1, a reference length l is extracted from the roughness curve in the axial direction of the roll surface in the direction of the average line. Then, the ratio of the sum of the cutting lengths (load length ηp = b1 + b2 +... + Bn) obtained when cutting the roughness curve of the extracted portion at a cutting level parallel to the peak line is expressed as a percentage. What is expressed is tp (= ηp / l × 100). The cutting level c is expressed as a percentage when the highest peak is 0% and the lowest valley is 100%.

  In this roll, the load length ratio tp (20%) of the uneven portion is 5% or more. This tp (20%) is generally related to the uniformity of the height of the convex portion.

  When tp (20%) is 5% or more, the stress applied to the convex portion by the layer forming blade is diffused, and the wear of the convex portion is easily relaxed. On the other hand, when tp (20%) is less than 5%, the image density after durability tends to decrease.

  The lower limit of tp (20%) is preferably 6% or more, more preferably 7% or more, and most preferably 8% or more from the viewpoint of wear resistance in contact with the layer forming blade. .

  In addition, since the upper limit of tp (20%) is so favorable that it is large, it is not specifically limited. The upper limit of tp (20%) is preferably 30% or less, more preferably 20% or less from the viewpoint of toner transportability (related to tp (50%)).

  In this roll, the load length ratio tp (50%) of the uneven portion is less than 50%. This tp (50%) is generally related to the distance between adjacent convex portions, that is, the toner holding region.

  When tp (50%) is less than 50%, the toner holding area becomes appropriate, and the toner conveyance amount can be made appropriate. On the other hand, when tp (50%) is 50% or more, it becomes difficult to hold the toner, the toner conveyance amount is insufficient, and the image density after the durability is lowered.

  The upper limit of tp (50%) is preferably 45% or less, more preferably 40% or less, and most preferably 35% or less from the viewpoint of toner transportability.

  In addition, since the minimum of tp (50%) is so favorable that it is small, it is not specifically limited. The lower limit of tp (50%) is preferably 10% or more, and more preferably 25% or more, from the viewpoint of wear resistance in contact with the layer forming blade.

  This roll may be manufactured by any method as long as the surface roughness parameter satisfies a specific condition.

  Specifically, for example, the roll is produced by polishing the surface of the conductive elastic layer formed on the outer periphery of the conductive shaft so as to satisfy the above conditions, or by forming a lower layer (for example, a conductive elastic layer). Examples include a method of coating the outer periphery with a surface layer forming composition and generating an uneven portion that satisfies the above conditions when forming the surface layer.

  The latter method is preferably used. This is because it is relatively easy to generate an uneven portion that satisfies the above conditions.

  In order to form the conductive elastic layer on the outer periphery of the conductive shaft, the conductive elastic layer forming composition is extruded on the surface of the conductive shaft, or the conductive shaft is hollowed in a roll molding die. The conductive elastic layer forming composition is injected coaxially to the part, heated and cured, and then demolded. Further, when a plurality of conductive elastic layers are formed, an operation according to the above method may be repeated.

  Specific examples of the conductive elastic layer forming composition include those containing a conductive agent (an electronic conductive agent and / or an ionic conductive agent) in the following main materials.

  That is, specific examples of the main material include silicone rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), and styrene-butadiene. Rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), acrylic rubber (ACM), chloroprene rubber (CR), urethane rubber, fluorine rubber, hydrin rubber (ECO, CO), urethane elastomer, natural rubber (NR) ) And the like. These may be used alone or in combination.

  From the viewpoints of low sag, conductivity, flexibility, and the like, examples of suitable main materials include silicone rubber, butadiene rubber, hydrin rubber, urethane elastomer, and the like.

  In addition to the conductive agent, the above composition may include a filler, an extender, a reinforcing agent, a processing aid, a curing agent, a vulcanization accelerator, a crosslinking agent, a crosslinking aid, an antioxidant, if necessary. One or two or more kinds of various additives such as plasticizers, ultraviolet absorbers, pigments, silicone oils, lubricants, auxiliaries, and surfactants may be appropriately contained.

  Hereinafter, the case where the surface layer which has an uneven | corrugated | grooved part is formed using coating is demonstrated.

  First, as a first concavo-convex forming method, there is a method in which roughness forming particles are present in the surface layer and a concavo-convex portion that satisfies the above conditions is generated using this.

  Specifically, the surface of the lower layer is coated with a composition containing at least a layer-forming organic component such as a monomer and / or oligomer that can be a polymer that mainly constitutes the surface layer, and roughness-forming particles. Form. Then, by curing the coating layer with heat, a surface layer in which the roughness forming particles are dispersed in the polymer is formed. According to this method, it is possible to form a concavo-convex portion using the particle diameter of the roughness forming particles.

  In this method, conditions such as the average particle size, particle size distribution, and addition amount of the roughness-forming particles may be varied and controlled so as to satisfy the surface roughness parameter.

  Specific examples of the polymer include silicone resins, fluorine resins, polymethyl methacrylate (PMMA), polycarbonate, polyamide resins, urethane resins, nitrile rubber (NBR), epichlorohydrin rubber, and the like. Examples thereof include rubbers, modified products obtained by modifying these resins and rubbers with silicone, fluorine, and the like. These may be contained alone or in combination of two or more.

  Specific examples of the roughness-forming particles include silica particles, urethane particles, crosslinked polymethyl methacrylate particles, urea resin particles, and the like. These may be contained alone or in combination of two or more.

  In the composition, there are 1 additive such as a conductive agent (an electronic conductive agent such as carbon black and / or an ionic conductive agent such as quaternary ammonium salt), a release agent, and a curing agent. You may contain a seed or two or more sorts.

  Next, as a second method for forming unevenness, without forming the roughness forming particles in the surface layer, at the time of forming the surface layer, using the difference in curing shrinkage between the surface layer surface part and the inside of the surface layer, the uneven part satisfying the above conditions is generated. The method of letting it be mentioned.

  Specifically, a composition comprising at least a layer-forming organic component such as a photopolymerizable monomer and / or photopolymerizable oligomer that can be a polymer mainly constituting the surface layer, a photoinitiator, and a light transmission reducing substance. Then, a coating layer is formed by coating the surface of the lower layer. Then, the coating layer is irradiated with light to photocur the layer forming organic component. It is preferable to use ultraviolet rays that are relatively easy to handle.

  According to this method, when the surface of the uncured coating layer is irradiated with light that can cure the layer-forming organic component, it is incident on the coating layer due to the presence of the light transmission reducing substance. The degree of light arrival varies in the layer thickness direction. Therefore, a difference occurs in the curability of the coating layer between the surface layer surface portion and the inside of the surface layer. And due to this, an uneven portion made of a polymer cured product is formed on the surface of the surface layer.

  This method has an advantage that it is easy to obtain a relatively uniform and fine uneven portion and satisfies the surface roughness parameter as compared with the method using the roughness-forming particles. In particular, tp (20%) and tp (50%) can be made relatively high within the above-described range.

  Specific examples of the layer-forming organic component include, for example, urethane monomers; urethane oligomers derived from polyester, PPG, PTMG, polycarbonate, polybutadiene, polycaprolactone, and the like; glycidyl ether, cresol novolac, phenol novolac, and bisphenol. Epoxy oligomers derived from A, etc .; Silicon oligomers derived from silicone polyols, silicone rubbers, etc .; Fluorine oligomers derived from fluorine-containing polyols, fluorine rubbers, etc .; PMMA, polyamide, amideimide, imide, nylon, polysulfone Resin oligomers derived from cellulose, melamine, etc .; butadiene rubber, styrene butadiene rubber, isoprene rubber, silicone rubber, nitrile rubber, acrylic Rugomu, urethane rubber, and the like can be exemplified rubber oligomer derived such from epichlorohydrin rubber. These may be contained alone or in combination of two or more. In addition, the said material can be induced | guided | derived and produced by providing a (meth) acrylate group by the urethanation by reaction with a hydroxyl group, or esterification reaction etc., for example.

  The light transmission-reducing substance is a substance that can exhibit a function of reducing the transmittance of light such as ultraviolet light incident on the composition when it is dispersed in an uncured composition. In order to reduce the light transmittance, the light may be blocked, reflected, scattered, absorbed, or the like.

  The light transmission reducing substance may be conductive or non-conductive as long as it can exhibit the above function. In the case of imparting conductivity to the surface layer, the light transmission reducing substance is preferably conductive because there is an advantage that the necessity of adding another conductive agent is reduced.

Specific examples of the light transmission reducing substance include carbon materials such as carbon black (channel black, furnace black, thermal black, acetylene black, etc.), graphite, carbon fiber, and oxides of indium and tin. (such as ITO), titanium oxide (such as TiO _2), zinc oxide (such as ZnO), oxides of indium and zinc (IZO, etc.), aluminum oxide (such as alumina) metal oxides such or iron powder Examples thereof include metal powders. These may be contained alone or in combination of two or more.

  Of these, carbon black, oxides of indium and tin, and the like can be suitably used from the viewpoints of being excellent in the effect of reducing ultraviolet transmittance and imparting conductivity.

  The content of the light transmission reducing substance may be selected so as to satisfy the surface roughness parameter in consideration of, for example, the light transmission reduction effect of the substance, the layer thickness of the surface layer, and the like. If the light transmission reduction effect is relatively large, the effect can be exhibited with a relatively small content, and if the light transmission reduction effect is relatively small, it is relatively large. It can be said that the effect is more easily achieved when the content is set.

  The photoinitiator is not particularly limited as long as it is selected depending on the type of the layer-forming organic component. The content of the photoinitiator is such that even if a relatively large amount of a light transmission reducing substance is present, the curing reaction by polymerization is promoted, and an uneven portion satisfying the surface roughness parameter is formed. Should be selected.

  In the composition, there are 1 additive such as a conductive agent (an electronic conductive agent such as carbon black and / or an ionic conductive agent such as quaternary ammonium salt), a release agent, and a curing agent. You may contain a seed or two or more sorts.

  Specifically, for example, a roll coating method, a dipping method, a spray coating method, or the like can be applied as a method for coating the surface layer forming composition described above.

  Hereinafter, the present invention will be described in detail using examples. Here, a developing roll was produced in which a conductive elastic layer (thickness: about 4 mm) serving as a base layer and a film-like surface layer (thickness: about 5 μm) were laminated in this order on the outer periphery of the conductive shaft.

In addition, the following test materials were fundamentally used for preparation of a surface layer forming composition.
・ Urethane monomer (Shinakmura Chemical Co., Ltd., “Symac SU28”)
・ Epoxy oligomer (Daicel UCB, “Ebecryl 3700”)
・ Photoinitiator ("Irgacure 187" manufactured by Ciba Specialty Chemicals Co., Ltd.)
Carbon black (acetylene black, average particle size 35 nm) (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.)
・ Release agent (Nippon Yushi Co., Ltd., “FS700”)
・ Curing agent (Nippon Yushi Co., Ltd., “Peroximon F40”)
・ Roughness-forming particles 1 (urethane particles, average particle size 20 μm) (manufactured by Dainippon Ink & Chemicals, “Bernock CFB100”)
Roughness-forming particles 2 (Roughness-forming particles 1 <D10 = 5 μm, D50 = 17 μm, D90 = 26 μm, (D90-D10) /D50=1.24> are classified and treated <D10 = 14 μm, D50 = 18 μm , D90 = 24 μm, (D90−D10) /D50=0.78>)

Example 1
<Preparation of conductive elastic layer forming composition>
Liquid silicone rubber (mixture of 50 parts by weight of “KE1350A” manufactured by Shin-Etsu Chemical Co., Ltd. and 50 parts by weight of “KE1350B” manufactured by Shin-Etsu Chemical Co., Ltd.), carbon black (manufactured by Ketjen Black International Co., Ltd., “ EC300J ") 6 parts by weight was kneaded with a kneader to prepare a conductive elastic layer forming composition.

<Preparation of surface layer forming composition (1)>
Urethane monomer, epoxy oligomer, carbon black, mold release agent, curing agent, and roughness forming particles 2 are blended in the blending ratio shown in Table 1 described later, and a bead mill disperser (manufactured by Shinmaru Enterprises Co., Ltd.). , “Dynomill KDL-Pilot”) was subjected to dispersion treatment (number of rotations 3200 rpm) three times.

  Next, a solvent (MEK: methyl ethyl ketone) was added to the obtained dispersion-treated product so as to have a nonvolatile content concentration of 10% by weight, mixed and stirred to prepare a surface layer forming composition (1).

(Preparation of developing roll)
After injecting the conductive elastic layer forming composition into a roll molding die incorporating a stainless steel core (SUS304) having a diameter of 6 mm and a length of 260 mm by an injection casting machine, the composition is heated at 150 ° C. in an oven. Crosslinked for 45 minutes. Thereby, the roll body which has a conductive elastic layer in the outer periphery of a metal core was produced.

  Next, on the surface of this roll body, after surface treatment by corona discharge (20 seconds at 0.3 kW), the surface layer forming composition (1) was applied by a roll coating method to form a coating layer. .

  Next, heat treatment was performed at 170 ° C. for 40 minutes using an oven to cure the coating layer.

  Thereby, a developing roll according to Example 1 was produced.

(Example 2)
In the preparation of the surface layer forming composition (1) of Example 1, the urethane monomer, the epoxy oligomer, the photoinitiator, the carbon black, and the release agent were blended at the blending ratio shown in Table 1 described later. In substantially the same manner, a surface layer forming composition (2) was prepared. In addition, this surface layer forming composition (2) is an ultraviolet curable composition that does not contain roughness-forming particles.

And in preparation of the image development roll of the said Example 1, it replaced with surface layer formation composition (1), the point which formed the coating layer using surface layer formation composition (2), it replaced with oven, and the ultraviolet irradiation machine (eye) Except for the point that the coating layer was cured by irradiating with UV rays at a UV intensity of 200 mW / cm ² for 30 seconds using “UB031-2” manufactured by Graphics Co., Ltd., and a mercury lamp “H03-L021”. In substantially the same manner, a developing roll according to Example 2 was produced.

(Example 3)
In the preparation of the surface layer forming composition (1) of Example 1, the urethane monomer, the epoxy oligomer, the photoinitiator, the carbon black, and the release agent were blended at the blending ratio shown in Table 1 described later. In substantially the same manner, a surface layer forming composition (3) was prepared. In addition, this surface layer forming composition (3) is an ultraviolet curable composition that does not contain roughness-forming particles.

And in preparation of the image development roll of the said Example 1, it replaced with surface layer formation composition (1), the point which formed the coating layer using surface layer formation composition (3), and replaced with oven using the ultraviolet irradiation machine. A developing roll according to Example 3 was produced in substantially the same manner except that the coating layer was cured by irradiating with ultraviolet rays at an ultraviolet intensity of 200 mW / cm ² for 30 seconds.

(Comparative Example 1)
In the preparation of the surface layer forming composition (1) of Example 1 above, the urethane monomer, epoxy oligomer, carbon black, mold release agent, curing agent, and roughness-forming particles 1 are shown in Table 1 below. A surface layer-forming composition (ratio 1) was prepared in substantially the same manner except that it was blended in step 1.

  And in preparation of the image development roll of the said Example 1, it replaced with surface layer forming composition (1), and it was substantially the same except having formed the coating layer using the surface layer forming composition (ratio 1), and a comparative example 1 was prepared.

(Comparative Example 2)
In the preparation of the surface layer forming composition (1) of Example 1 above, the urethane monomer, epoxy oligomer, carbon black, mold release agent, curing agent, and roughness-forming particles 1 are shown in Table 1 below. A surface layer-forming composition (Ratio 2) was prepared in substantially the same manner except that it was blended in step 1.

  And in preparation of the image development roll of the said Example 1, it replaced with surface layer formation composition (1), and it was substantially the same except having formed the coating layer using the surface layer formation composition (ratio 2), and a comparative example The developing roll which concerns on 2 was produced.

(Comparative Example 3)
In the preparation of the surface layer forming composition (1) of Example 1, the urethane monomer, the epoxy oligomer, the photoinitiator, the carbon black, and the release agent were blended at the blending ratio shown in Table 1 described later. In substantially the same manner, a surface layer forming composition (Ratio 3) was prepared.

And in preparation of the developing roll of the said Example 1, it replaced with surface layer forming composition (1), the point which formed the coating layer using the surface layer forming composition (ratio 3), replaced with oven, and the ultraviolet irradiation machine was used. A developing roll according to Comparative Example 3 was produced in substantially the same manner except that the coating layer was cured by irradiating with ultraviolet rays at an ultraviolet intensity of 200 mW / cm ² for 30 seconds.

(Comparative Example 4)
In the preparation of the surface layer forming composition (1) of Example 1, the urethane monomer, the epoxy oligomer, the photoinitiator, the carbon black, and the release agent were blended at the blending ratio shown in Table 1 described later. In substantially the same manner, a surface layer forming composition (ratio 4) was prepared.

And in preparation of the developing roll of the said Example 1, it replaced with surface layer formation composition (1), the point which formed the coating layer using surface layer formation composition (ratio 4), replaced with oven, and the ultraviolet irradiation machine was used. A developing roll according to Comparative Example 4 was produced in substantially the same manner except that the coating layer was cured by irradiating ultraviolet rays at an ultraviolet intensity of 200 mW / cm ² for 30 seconds.

(Comparative Example 5)
In the preparation of the surface layer forming composition (1) of Example 1, the urethane monomer, the epoxy oligomer, the photoinitiator, the carbon black, and the release agent were blended at the blending ratio shown in Table 1 described later. In substantially the same manner, a surface layer forming composition (ratio 5) was prepared.

And in preparation of the developing roll of the said Example 1, it replaced with surface layer formation composition (1), the point which formed the coating layer using surface layer formation composition (ratio 5), replaced with oven, and the ultraviolet irradiation machine was used. A developing roll according to Comparative Example 5 was produced in substantially the same manner except that the coating layer was cured by irradiating with ultraviolet rays at an ultraviolet intensity of 200 mW / cm ² for 30 seconds.

<Development roll evaluation>
(Measurement of surface roughness parameters)
About the surface layer surface of each produced developing roll, in accordance with JIS B0601, using a contact type surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., “Surfcom 1400D”), ten-point average roughness Rz, load length ratio tp (20%) and load length ratio tp (50%) were measured. Note that tp (20%) and tp (50%) are values calculated from a roughness curve in the roll axis direction.

(Evaluation of initial image density)
Each developing roll is incorporated in a cartridge of a commercially available color laser printer (manufactured by Epson Corp., “LP1500C”), and in an environment of 23 ° C. × 53% RH, 4500 sheets (A4 size, vertical direction) of color 5 An image of a% chart image (5% of the area is printed) was taken out.

  Thereafter, the image density of the obtained image was visually confirmed. As a result, the image density is appropriate (double circle in the table), the image density is slightly thin (triangle in the table), the image density is too low, or fog occurs. The thing was judged to be bad (in the table, x).

(Evaluation of durable image density)
Each developing roll was incorporated in the cartridge of the color laser printer, and 5% chart image of 5000 sheets (A4 size, vertical direction) color was imaged in an environment of 23 ° C. × 53% RH.

  Thereafter, the image density of the image after durability was visually confirmed. As a result, the image density is almost the same as the initial image density (double circle in the table), the image density is slightly reduced but within the allowable range (circle in the table), the image The concentration was greatly reduced, and those outside the allowable range were judged as defective (indicated by X in the table).

  Note that the developing roll having a poor initial image density has not been evaluated for durable image density. Further, as reference data, the 10-point average roughness Rz was determined in the same manner as described above for the surface of the surface layer after the durability test, and the change rate of the 10-point average roughness before and after the durability test was also determined.

  In Table 1, the compounding ratio of the surface layer forming composition of each produced developing roll and the evaluation result of each developing roll are shown together.

  According to Table 1, the following can be understood. That is, in the developing roll according to Comparative Example 1, Rz is too small and tp (20%) is too small. Therefore, the image density is insufficient at the initial stage. This is presumably because the difference in height of the uneven portions on the surface layer was small and the toner transport amount was insufficient in the first place.

  The developing roll according to Comparative Example 2 has an insufficient tp (20%). Therefore, the decrease in image density after endurance was large. This is presumably because the height of the convex portions on the surface layer was relatively varied, and the stress of the layer forming blade was not uniformly dispersed, and the wear of the convex portions was promoted.

  In Comparative Example 3, Rz is too small. For this reason, the initial image density was slightly thin, and the decrease in image density after durability was large. This is presumably because the difference in height of the concavo-convex portions was small and the amount of toner transport was not sufficient.

  In Comparative Example 4, tp (50%) is excessive. For this reason, the initial image density was slightly thin, and the decrease in image density after durability was large. This is presumably because the area of the recess for holding the toner is insufficient and the amount of toner transport is insufficient.

  In Comparative Example 5, Rz is excessive and tp (50%) is excessive. Therefore, fog occurred at an early stage. This is presumably because the toner was not sufficiently charged.

  On the other hand, the developing rolls according to Examples 1 to 3 in which Rz, tp (20%), and tp (50%) satisfy specific conditions have good initial image density, and the image density is lowered after durability. And it had good durability.

  In particular, Example 2 and Example in which Rz, tp (20%) and tp (50%) satisfy specific conditions and the surface layer is formed of an ultraviolet curable composition containing no roughness-forming particles. The developing roll according to No. 3 had excellent durability as compared with the developing roll according to Example 1 in which the surface layer was formed of a composition containing roughness-forming particles.

  For this reason, it is more prominent that the uneven portion of the surface layer is formed using the difference in curing shrinkage between the surface portion of the surface layer and the inside of the surface layer at the time of forming the surface layer, rather than using the roughness forming particles. It was confirmed that the thickness was easy to make uniform and effective in improving the durability.

  While 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.

It is a figure for demonstrating how to obtain tp (20%) and tp (50%) among surface roughness parameters.

Claims (4)

The surface of the roll has uneven portions, and the uneven portions are
Ten-point average roughness Rz is 8 to 16 μm,
The load length ratio tp (20%) is 5% or more and 10% or less ,
A developing roll having a load length ratio tp (50%) of 10% to 45% .
  The developing roll according to claim 1, wherein the uneven portion is formed on a surface of a surface layer.   The developing roll according to claim 2, wherein the surface layer includes a urethane polymer or an epoxy polymer.   The developing roll according to claim 2, wherein the surface layer is formed by coating.

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