Charging roll for electrophotographic equipment and method for producing the charging roll for electrophotographic equipment

Abstract

To provide an electrophotographic instrument-purpose charging roll, and electrophotographic instrument-purpose charging roll manufacturing method that exert an excellent charging performance, not relying upon surface roughness, and are excellent in charging uniformity.SOLUTION: An electrophotographic instrument-purpose charging roll 10 comprises: a shaft body 12; and an elastic body layer 14 that is formed on an outer peripheral surface of the shaft body 12. The elastic body layer 14 contains an acrylonitrile butadiene rubber, in which an amount of acrylonitrile is more than 30 mass% and less than 41 mass% in 100 pts.mass of a polymer component, more than 5 pts.mass and less than 95 pts.mass. In the electrophotographic instrument-purpose charging roll, surface roughness Ra of the elastic body layer 14 is more than 0.2 μm and less than 1.5 μm, and in a surface of the elastic body layer 14, a carbonyl group exists in an orientated state, and a ratio of a maximum detection peak of an extension / construction of the carbonyl group to a maximum detection peak of the extension / construction oscillation of a methine group of a butadiene group in an infrared split spectrum by a high-sensitivity reflection measurement method is more than 1.5 and less than 5.3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a charging roll for electrophotographic equipment that is suitably used in electrophotographic equipment such as copying machines, printers, and facsimiles that employ an electrophotographic system, and to a method for manufacturing the charging roll for electrophotographic equipment. [Background technology]

[0002] 2. Description of the Related Art In a charging roll for an electrophotographic device, in order to ensure a sufficient amount of charge, roughness is imparted to the surface by adding roughness-imparting particles to the surface layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-083711 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is difficult to make the roughness of the charging roll surface, which is imparted by roughness-forming particles, uniform over the entire circumference, and uneven surface roughness can cause uneven discharge, which can lead to uneven charge on the photoconductor. On the other hand, until now, there has been a problem that without surface roughness, a sufficient amount of charge cannot be secured.

[0005] The problem to be solved by the present invention is to provide a charging roll for an electrophotographic device which exhibits excellent charging properties without relying on surface roughness and which also exhibits excellent charging uniformity, and a method for manufacturing a charging roll for an electrophotographic device. [Means for solving the problem]

[0006] The electrostatic charging roll for electrophotographic equipment according to the present invention comprises a shaft and an elastic layer formed on the outer peripheral surface of the shaft, the elastic layer contains 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of a polymer component, the surface roughness Ra of the elastic layer is 0.2 μm or more and 1.5 μm or less, carbonyl groups are oriented on the surface of the elastic layer, and the ratio of the maximum detection peak of the stretching vibration of the carbonyl group to the maximum detection peak of the stretching vibration of the methine group of the butadiene skeleton in an infrared spectrum measured by a high sensitivity reflectance measurement method is 1.5 to 5.3.

[0007] The elastic layer may contain isoprene rubber as a polymer component. The elastic layer may not contain roughness-forming particles that form surface roughness. The elastic layer may have a DBP absorption of 70 cm 3 / 100g or more 160cm 3 The elastic layer preferably contains carbon black having a dielectric constant of 180 or more and 830 or less when 1 V·1 kHz is applied. The carbonyl groups on the surface of the elastic layer preferably exist in an oriented state by subjecting the surface of the elastic layer to a corona treatment at a temperature of 43° C. or more and 92° C. or less.

[0008] The method for producing a charging roll for an electrophotographic device according to the present invention includes the steps of: forming an elastic layer on the outer peripheral surface of a shaft, the elastic layer containing 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of a polymer component and having a surface roughness Ra of 0.2 μm or more and 1.5 μm or less; and performing a corona treatment on the surface of the elastic layer at a temperature of 43° C. or more and 92° C. or less to orient and present carbonyl groups. Effect of the Invention

[0009] According to the charging roll for electrophotographic equipment of the present invention, the charging roll comprises a shaft and an elastic layer formed on the outer peripheral surface of the shaft, the elastic layer contains 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of a polymer component, the surface roughness Ra of the elastic layer is 0.2 μm or more and 1.5 μm or less, carbonyl groups are present in an oriented state on the surface of the elastic layer, and the ratio of the maximum detection peak of the stretching vibration of the carbonyl group to the maximum detection peak of the stretching vibration of the methine group of the butadiene skeleton in an infrared spectrum measured by a high sensitivity reflectance measurement method is 1.5 to 5.3, and therefore the charging roll exhibits excellent charging properties without relying on surface roughness and also has excellent charging uniformity.

[0010] Here, when the elastic layer contains isoprene rubber as a polymer component, the elasticity is good, and distortion is less likely to remain even when left in a compressed state in a high-temperature, high-humidity environment, and the occurrence of streak images due to distortion is suppressed.

[0011] Furthermore, if the elastic layer does not contain roughness-forming particles that form surface roughness, the surface roughness Ra of the elastic layer can be kept small, making it easier to suppress uneven discharge due to non-uniformity in the surface roughness.

[0012] The elastic layer has a DBP absorption capacity of 70 cm 3 / 100g or more 160cm 3 When the elastic layer contains carbon black having a density of 100 g / 100 g or less, the elastic layer can exhibit low resistance and high capacitance.

[0013] If the dielectric constant of the elastic layer is 180 or more and 830 or less when 1 V·1 kHz is applied, the electrostatic capacitance is large, and therefore the electrostatic property is excellent.

[0014] The carbonyl groups on the surface of the elastic layer can be oriented by subjecting the surface of the elastic layer to a corona treatment at a temperature of 43° C. or higher and 92° C. or lower.

[0015] The method for producing a charging roll for electrophotographic equipment according to the present invention includes the steps of forming an elastic layer on the outer peripheral surface of a shaft, the elastic layer containing 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of polymer components and having a surface roughness Ra of 0.2 μm or more and 1.5 μm or less, and performing a corona treatment on the surface of the elastic layer at a temperature of 43° C. or more and 92° C. or less to orient and present carbonyl groups, so that a charging roll for electrophotographic equipment that exhibits excellent charging properties without relying on surface roughness and also has excellent charging uniformity can be produced. [Brief description of the drawings]

[0016] [Figure 1] 1A is a schematic external view of a charging roll for an electrophotographic device according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The charging roll for electrophotographic equipment according to the present invention (hereinafter, simply referred to as the charging roll) will be described in detail. Fig. 1 is a schematic external view (a) of the charging roll for electrophotographic equipment according to one embodiment of the present invention, and its AA line cross-sectional view (b).

[0018] The electrostatic charge roll 10 includes a shaft 12 and an elastic layer 14 formed on the outer peripheral surface of the shaft 12. The elastic layer 14 is a layer (base layer) that serves as the base of the electrostatic charge roll 10. The elastic layer 14 is a layer that appears on the surface of the electrostatic charge roll 10.

[0019] The shaft body 12 is not particularly limited as long as it is conductive. Specific examples include a core bar made of a solid or hollow body made of a metal such as iron, stainless steel, or aluminum. An adhesive, primer, or the like may be applied to the surface of the shaft body 12 as needed. In other words, the elastic layer 14 may be bonded to the shaft body 12 via an adhesive layer (primer layer). The adhesive, primer, or the like may be made conductive as needed.

[0020] The elastic layer 14 contains a polymer component. The elastic layer 14 contains 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber (NBR) having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of the polymer component.

[0021] The elastic layer 14 contains NBR as a polymer component, and therefore can have low resistance. In addition, a carbonyl group can be formed on the surface of the elastic layer 14 by a corona treatment described later. By orienting the carbonyl groups on the surface of the elastic layer 14, the electrostatic capacitance can be increased due to the dipole effect of the carbonyl group, and the chargeability can be improved. In the elastic layer 14, the amount of NBR and the amount of acrylonitrile in NBR affect the amount of carbonyl groups generated by the corona treatment described later.

[0022] If the amount of NBR in the elastic layer 14 is too small, the amount of carbonyl groups generated by the corona treatment described later will be insufficient, and the effect of improving the chargeability will not be sufficiently obtained. Therefore, the content of NBR in the elastic layer 14 is set to 5 parts by mass or more in 100 parts by mass of the polymer component. From this viewpoint, the content of NBR is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more in 100 parts by mass of the polymer component. On the other hand, if the amount of NBR in the elastic layer 14 is too large, the amount of carbonyl groups generated by the corona treatment described later will be too large, and the image will deteriorate (white stripes will occur) due to excessive charging under high temperature and high humidity conditions. Therefore, the content of NBR in the elastic layer 14 is set to 95 parts by mass or less in 100 parts by mass of the polymer component. From this viewpoint, the content of NBR is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less in 100 parts by mass of the polymer component.

[0023] In addition, in the elastic layer 14, if the amount of acrylonitrile in the NBR is too small, the amount of carbonyl groups generated by the corona treatment described later becomes too large, and the image deteriorates (white stripes occur) due to excessive charging under high temperature and high humidity conditions. For this reason, the amount of acrylonitrile in the NBR is set to 30% by mass or more. From this viewpoint, the amount of acrylonitrile in the NBR is preferably 33% by mass or more. On the other hand, if the amount of acrylonitrile in the NBR is too large, the amount of carbonyl groups generated by the corona treatment described later becomes insufficient, and the effect of improving the chargeability cannot be sufficiently obtained. In addition, the rebound resilience is likely to decrease, and the compression set decreases. For this reason, the amount of acrylonitrile in the NBR is set to 41% by mass or less. From this viewpoint, the amount of acrylonitrile in the NBR is preferably 40% by mass or less, more preferably 38% by mass or less.

[0024] As described above, the elastic layer 14 can increase the electrostatic capacitance and improve the chargeability by orienting a predetermined amount of carbonyl groups on the surface of the elastic layer 14, so that it can exhibit excellent chargeability without relying on surface roughness as in the past. Therefore, it is not necessary to actively impart surface roughness to the elastic layer 14. Since the surface roughness of the elastic layer 14 is small, discharge unevenness is suppressed, so that the chargeability of the elastic layer 14 can be made more uniform. From this viewpoint, the surface roughness Ra of the elastic layer 14 is preferably 1.5 μm or less. More preferably, it is 1.0 μm or less, and even more preferably, it is 0.7 μm or less. On the other hand, if the surface of the elastic layer 14 is too smooth, the contact area with the photoconductor becomes too large, so that the surface is easily scraped by rubbing against the photoconductor, and the carbonyl groups generated by the corona treatment described later disappear due to wear, and the chargeability decreases. From this viewpoint, the surface roughness Ra of the elastic layer 14 is preferably 0.2 μm or more. More preferably, it is 0.3 μm or more.

[0025] From the viewpoint of reducing the surface roughness of the elastic layer 14, it is preferable that the elastic layer 14 does not contain roughness-forming particles that form surface roughness. From the viewpoint of reducing the surface roughness of the roll surface, it is also not preferable to form a separate surface layer on the outer circumferential surface of the elastic layer 14 and to contain roughness-forming particles that form surface roughness in the surface layer.

[0026] A predetermined amount of carbonyl groups are oriented and present on the surface of the elastic layer 14. The amount of carbonyl groups present on the surface of the elastic layer 14 can be quantified by infrared spectroscopy (IR analysis). The oriented presence of carbonyl groups can be confirmed by infrared spectroscopy using a high sensitivity reflectance measurement method (IR-RAS analysis).

[0027] The ratio of the maximum detection peak of the stretching vibration of the carbonyl group to the maximum detection peak of the stretching vibration of the methine group of the butadiene skeleton in the infrared spectrum by the high sensitivity reflection measurement method is preferably 1.5 or more. When the peak ratio is 1.5 or more, both the amount and the orientation of the carbonyl group are sufficient, and the electrostatic capacitance can be increased by the dipole effect of the carbonyl group, and the charging property can be improved. From this viewpoint, the peak ratio is more preferably 1.7 or more, and even more preferably 2.0 or more. On the other hand, when the peak ratio is too large, the amount of carbonyl group is excessive, and the image is deteriorated (white stripes occur) due to excessive charging under high temperature and high humidity conditions. Therefore, from this viewpoint, the peak ratio is preferably 5.3 or less. More preferably, it is 5.0 or less, and even more preferably, it is 4.0 or less.

[0028] The dielectric constant of the elastic layer 14 increases due to the presence of a predetermined amount of carbonyl groups oriented on the surface of the elastic layer 14. The dielectric constant of the elastic layer 14 is preferably 180 or more. The dielectric constant of the elastic layer 14 is preferably 200 or more, more preferably 250 or more, and even more preferably 300 or more. On the other hand, as the amount of oriented carbonyl groups on the surface of the elastic layer 14 increases, the dielectric constant of the elastic layer 14 also increases. In order to prevent excessive charging under high temperature and high humidity conditions, from the viewpoint of a predetermined amount of carbonyl groups, the dielectric constant of the elastic layer 14 is preferably 830 or less. The dielectric constant of the elastic layer 14 is preferably 800 or less, more preferably 700 or less, and even more preferably 600 or less. The dielectric constant of the elastic layer 14 can be expressed as a value when 1 V·1 kHz is applied.

[0029] The carbonyl groups on the surface of the elastic layer 14 can be oriented and present by subjecting the surface of the elastic layer containing a specific amount of NBR containing a specific amount of acrylonitrile to corona treatment within a specific temperature range. The corona treatment is preferably performed at a temperature equal to or higher than the glass transition temperature (Tg) of the polymer component of the elastic layer 14. If the set temperature (ambient temperature) in the corona treatment is lower than the glass transition temperature (Tg) of the polymer component of the elastic layer 14, the carbonyl groups can be generated on the surface of the elastic layer 14, but the generated carbonyl groups cannot be oriented. From this viewpoint, the set temperature in the corona treatment is preferably 43°C or higher, more preferably 50°C or higher. On the other hand, if the set temperature in the corona treatment is too high, the generated carbonyl groups cannot be oriented due to the effect of relaxation caused by thermal energy. From this viewpoint, the set temperature in the corona treatment is preferably 92°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower.

[0030] The elastic layer 14 may further contain isoprene rubber (IR) as a polymer component. When the elastic layer 14 contains isoprene rubber as a polymer component, the elastic layer 14 has good resilience, and distortion is unlikely to remain even when left in a compressed state in a high-temperature, high-humidity environment, and the occurrence of streak images due to distortion is suppressed. The content of isoprene rubber (IR) is preferably 5 parts by mass or more and 95 parts by mass or less in 100 parts by mass of the polymer component of the elastic layer 14.

[0031] From the viewpoint of low resistance, the elastic layer 14 preferably contains a conductive agent. Examples of the conductive agent include an electronic conductive agent and an ionic conductive agent. The conductive agent is preferably an electronic conductive agent. Among electronic conductive agents, carbon black is particularly preferable.

[0032] The elastic layer 14 may contain only one type of carbon black, or may contain two or more types of carbon black. When the elastic layer 14 contains only one type of carbon black, the uniformity of the resistance is improved.

[0033] In the elastic layer 14, it is preferable that the carbon black has a relatively large DBP absorption. Carbon black with a large DBP absorption has the function of storing electric charge as a dielectric. This makes it easy to improve the charging property. On the other hand, if the DBP absorption is too large, the discharge property is likely to decrease. From this viewpoint, the DBP absorption of carbon black is set to be 70 cm 3 / 100g or more 160cm 3 The DBP absorption amount of carbon black is calculated based on the amount of DBP (dibutyl phthalate) absorbed by 100 g of carbon black in accordance with JIS K6221.

[0034] From the viewpoint of improving capacitance, the DBP absorption amount of carbon black is preferably 120 cm 3 From the viewpoint of improving dischargeability, it is more preferable that the discharge rate is 150 cm 3 / 100g or less, more preferably 140cm 3 / 100g or less.

[0035] Carbon black with a high DBP absorption amount is preferably relatively high resistance from the viewpoint of excellent function of storing electric charge as a dielectric. From this viewpoint, carbon black with a relatively small specific surface area and large particle size is preferable. Specifically, carbon black with a specific surface area of ​​25 m 2 / g or more 75m 2 / g or less. The average particle size is preferably 35 nm or more and 75 nm or less. The specific surface area of ​​the carbon black is more preferably 30 m 2 / g or more 70m 2 / g or less, more preferably 30m 2 / g or more 60m 2 / g or less. The average particle size of the carbon black is more preferably 40 nm or more and 70 nm or less, and further preferably 40 nm or more and 60 nm or less. When the average particle size of the carbon black is 35 nm or more and 75 nm or less, it is easy to set the specific surface area of ​​the carbon black in a suitable range, and it is easy to make the carbon black have high resistance.

[0036] The specific surface area of ​​carbon black is a value measured by the BET method. The average particle size of carbon black is expressed as the arithmetic mean diameter obtained by observing carbon black under an electron microscope.

[0037] From the viewpoint of easily ensuring capacitance, the carbon black content is preferably 5 parts by mass or more relative to 100 parts by mass of the polymer component contained in the elastic layer 14. More preferably, it is 10 parts by mass or more, and even more preferably, it is 20 parts by mass or more. Moreover, from the viewpoint of easily suppressing insufficient discharge, the carbon black content is preferably 75 parts by mass or less relative to 100 parts by mass of the polymer component contained in the elastic layer 14. More preferably, it is 70 parts by mass or less, and even more preferably, it is 60 parts by mass or less. And, when the carbon black content is 5 parts by mass or more and 75 parts by mass or less relative to 100 parts by mass of the polymer component contained in the elastic layer 14, it is easy to maintain the capacitance within a suitable range.

[0038] If necessary, various additives may be appropriately added to the elastic layer 14. Examples of the additives include a lubricant, a vulcanization accelerator, an antioxidant, a light stabilizer, a viscosity modifier, a processing aid, a flame retardant, a plasticizer, a foaming agent, a filler, a dispersant, an antifoaming agent, a pigment, and a mold release agent.

[0039] The thickness of the elastic layer 14 is not particularly limited, and may be appropriately set within a range of 0.1 to 10 mm depending on the application.

[0040] Since the charging roll 10 does not cover the carbonyl groups formed on the outer peripheral surface of the elastic layer, it is preferable not to form a layer (surface layer, protective layer) separate from the elastic layer on the outer peripheral surface of the elastic layer.

[0041] The charging roll 10 can be manufactured by forming the elastic layer 14 on the outer circumferential surface of a shaft body, and subjecting the outer circumferential surface of the shaft body to corona treatment under a predetermined temperature condition.

[0042] The elastic layer 14 can be formed as follows: First, a shaft is coaxially placed in the hollow portion of a roll molding die, and an uncrosslinked composition for forming an elastic layer is injected and heated and cured (crosslinked), and then the composition is demolded, or the uncrosslinked composition for forming an elastic layer is extruded onto the surface of the shaft to form the elastic layer 14 on the outer periphery of the shaft.

[0043] The composition for forming the elastic layer is composed of a composition containing 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of a polymer component.

[0044] The elastic layer 14 is molded to have a small surface roughness Ra in order to prevent a decrease in uniformity due to the influence of surface roughness. Specifically, the surface roughness Ra is set to be 0.2 μm or more and 1.5 μm or less.

[0045] As described above, the corona treatment is preferably carried out at a temperature equal to or higher than the glass transition temperature (Tg) of the polymer component of the elastic layer 14. The temperature set in the corona treatment is preferably 43° C. or higher, and more preferably 50° C. or higher. The temperature set in the corona treatment is preferably 92° C. or lower, and more preferably 90° C. or lower, and even more preferably 80° C. or lower.

[0046] According to the charging roll 10 having the above configuration, the elastic layer 14 contains 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber having an acrylonitrile amount of 30% by mass or more and 41% by mass or less per 100 parts by mass of the polymer component, the surface roughness Ra of the elastic layer 14 is 0.2 μm or more and 1.5 μm or less, carbonyl groups are oriented and present on the surface of the elastic layer 14, and the ratio of the maximum detection peak of the stretching vibration of the carbonyl group to the maximum detection peak of the stretching vibration of the methine group of the butadiene skeleton in an infrared spectroscopic spectrum measured by a high sensitivity reflectance measurement method is 1.5 to 5.3, and therefore, excellent charging properties are exhibited without relying on surface roughness, and charging uniformity is also excellent. EXAMPLES

[0047] The present invention will be described in detail below using examples and comparative examples.

[0048] Example 1 <Preparation of Composition for Forming Elastic Layer> NBR <2> 5 parts by weight of carbon black (CB) <1> Then, 95 parts by mass of isoprene rubber (IR), 5 parts by mass of peroxide crosslinking agent, 3 parts by mass of vulcanization aid, and 3 parts by mass of catalyst were blended and stirred and mixed by a stirrer to prepare a composition for forming an elastic layer.

[0049] <Preparation of Elastic Layer> A core bar (diameter 8 mm) was set in a molding die (pipe-shaped), the composition for forming the elastic layer was injected, and the die was heated at 180°C for 30 minutes. The die was then cooled and demolded to form an elastic layer 1.9 mm thick around the outer periphery of the core bar.

[0050] <Corona treatment> The outer peripheral surface of the produced elastic layer was subjected to corona treatment at a set temperature (ambient temperature) of 55°C (output: 20 kHz·10 kV, treatment time: 30 seconds). In this manner, the electrostatic charge roll of Example 1 was produced. The electrostatic charge roll of Example 1 has an elastic layer on the outer peripheral surface of a shaft (core metal), and the outer peripheral surface of the elastic layer is subjected to corona treatment at a predetermined temperature. The elastic layer is the layer that appears on the surface. A normal surface layer (protective layer) is not formed on the outer peripheral surface of the elastic layer.

[0051] (Examples 2 to 4, 7 to 11) A charging roll was produced in the same manner as in Example 1, except that the composition for forming the elastic layer was changed to the composition shown in Table 1.

[0052] (Examples 5 to 6) A charging roll was produced in the same manner as in Example 1, except that the composition for forming the elastic layer was changed to the composition shown in Table 1, and the corona treatment temperature was changed to the set temperature shown in Table 1.

[0053] (Examples 12 to 13) A charging roll was produced in the same manner as in Example 1, except that an elastic layer having the composition shown in Table 1 was molded and then polished to give a predetermined surface roughness.

[0054] (Comparative Examples 1 to 4) A charging roll was produced in the same manner as in Example 1, except that the composition for forming the elastic layer was changed to the composition shown in Table 2. In Comparative Example 1, the polymer component of the elastic layer was composed only of NBR, and in Comparative Example 2, the polymer component of the elastic layer was composed only of IR.

[0055] Comparative Example 5 After forming an elastic layer having the composition shown in Table 2, a surface layer having a thickness of 1.0 μm and the composition shown below was formed on the outer peripheral surface of the elastic layer without performing a corona treatment on the outer peripheral surface of the elastic layer. In this manner, the charging roll of Comparative Example 5 was produced.

[0056] <Preparation of Composition for Forming Surface Layer> The roughness-forming particles and the binder polymer were mixed, 200 parts by mass of methyl ethyl ketone (MEK) was added, and the mixture was mixed and stirred at a predetermined stirring speed to prepare a composition for forming a surface layer. Binder polymer (acrylic): DIC "Acrydic A-1300" Particles for roughening (PU): Negami Chemical Industries' "Art Pearl C-600 transparent" average particle size 10μm

[0057] (Comparative Examples 6 to 8) A charging roll was produced in the same manner as in Example 1, except that the composition for forming the elastic layer was changed to the composition shown in Table 2, and the corona treatment temperature was changed to the set temperature shown in Table 2.

[0058] Comparative Example 9 After forming an elastic layer having the composition shown in Table 2, the outer peripheral surface of the elastic layer was not subjected to corona treatment, and no surface layer was formed on the outer peripheral surface of the elastic layer, to obtain the charging roll of Comparative Example 9.

[0059] (Comparative Examples 10 to 11) A charging roll was produced in the same manner as in Example 1, except that an elastic layer having the composition shown in Table 2 was molded and then polished to give it a predetermined surface roughness.

[0060] As materials for the elastic layer forming composition, the following materials were prepared. (Base polymer) ·NBR <1> (AN content 33% by mass): "Nipol DN101L" manufactured by Nippon Zeon ·NBR <2> (AN content 40% by mass): "Nipol DN3350" manufactured by Nippon Zeon ·NBR <3> (AN content 28% by mass): "Nipol DN2880" manufactured by Nippon Zeon ·NBR <4> (AN content 42.5% by mass): "Nipol DN4050" manufactured by Nippon Zeon IR: Nippon Zeon "Nipol IR2200" (Carbon Black) ·CB <1> (DBP absorption capacity 70ml / 100g, BET specific surface area 180m 2 / g, average particle size 25nm): Orion Engineered Carbons "Special Black4" ·CB <2> (DBP absorption capacity 160ml / 100g, BET specific surface area 75m 2 / g, average particle size 35 nm): Denka "Denka Black" ·CB <3> (DBP absorption capacity 58ml / 100g, BET specific surface area 180m 2 / g, average particle size 18 nm): Mitsubishi Chemical “#1000” ·CB <4> (DBP absorption capacity 175ml / 100g, BET specific surface area 165m 2 / g, average particle size 21 nm): Mitsubishi Chemical "#3400B"

[0061] The surface roughness Ra and dielectric constant of the elastic layer of the produced charging roll were measured. In addition, infrared spectroscopy (IR) was performed to investigate the amount and orientation of carbonyl groups on the outer peripheral surface of the elastic layer of the produced charging roll. The charging performance (LL charging property, HH charging property, charging uniformity) of the produced charging roll was also evaluated. Furthermore, a compression set test was performed on the elastic layer of the produced charging roll. These results are shown in the table below.

[0062] (Surface roughness Ra) The arithmetic mean roughness (Ra) was measured at three arbitrary points on the circumference at positions 5 mm inward in the axial direction from both ends of the elastic layer and at three positions in the axial center using a surface roughness meter (Tokyo Seimitsu's "Surfcom 1400D"). The average value of the arithmetic mean roughness (Ra) at a total of nine points (3 points x 3 positions) was calculated and used as the surface roughness Ra.

[0063] (Dielectric constant) Aluminum electrodes were deposited on the surface of the elastic layer, and measurements were made using an LCR meter ZM2353 manufactured by NF Corporation. Measurement conditions: Voltage 1V / Frequency 1kHz Measurement environment: 25℃ 50% RH

[0064] (Infrared spectroscopy) The outer surface of the elastic layer of the charging roll was measured by a high-sensitivity reflection measurement method (IR-RAS method) using a Fourier transform infrared spectrophotometer consisting of a JASCO "FT / IR-6800" equipped with a JASCO "RAS PRO 410-H". The maximum detection peak (2800-3200 cm) of the stretching vibration of the methine group of the butadiene skeleton was -1 ) for the maximum detected peak of the stretching vibration of the carbonyl group (1650-1780 cm -1 ) ratio was calculated.

[0065] (LL chargeability) The conductive roll thus produced was incorporated into a "CLJ4525dn" manufactured by HP, and 150k sheets (150,000 sheets) of halftone images were output in a low temperature, low humidity environment (LL environment) of 10°C x 10% RH (relative humidity). If no black streaks due to insufficient electrostatic charge occurred in the image, or if the occurrence was extremely slight and did not pose a problem in practical use, it was marked as "O", and if the above-mentioned black streaks occurred in part or the entire image, causing image problems, it was marked as "X".

[0066] (HH chargeability) The conductive roll thus produced was incorporated into a HP "CLJ4525dn" and 150k (150,000) halftone images were output in a high temperature and high humidity environment (HH environment) of 40°C x 90% RH (relative humidity). If no white streaks due to overcharging were observed in the image or if the occurrence was extremely slight and did not pose a problem in practical use, it was marked as "○", and if the above-mentioned white streaks occurred in part or the entire image, causing image problems, it was marked as "×".

[0067] (Charging uniformity) The conductive roll thus produced was incorporated into a "CLJ4525dn" manufactured by HP, and 150k sheets (150,000 sheets) of halftone images were output in a low temperature, low humidity environment (LL environment) of 10°C x 10% RH (relative humidity). If no black spots due to insufficient charging uniformity occurred in the image, or if the occurrence was extremely minor and did not pose a problem in practical use, it was marked as "O", and if the above-mentioned black spots occurred in part or the entire image, causing image problems, it was marked as "X".

[0068] (Compression set) The conductive roll thus prepared was incorporated into a HP CLJ4525dn K-color cartridge, and a compression set test was performed by leaving the cartridge in a high temperature and high humidity environment (HH environment) of 40°C x 90% RH (relative humidity) for 5 days. The cartridge with the conductive roll still incorporated was then incorporated into a HP CLJ4525dn, and a halftone image was output in a low temperature and low humidity environment (LL environment) of 10°C x 10% RH (relative humidity). When no uniaxial streak images were generated due to the distortion of the conductive roll, or when the generation was extremely slight and did not pose any practical problems, the result was marked as "○", and when the above streaks were generated in part or the entire image, causing image problems, the result was marked as "×".

[0069] [Table 1]

[0070] [Table 2]

[0071] Comparative Example 5 is a charging roll having a surface layer containing roughness-forming particles on the outer peripheral surface of an elastic layer. In Comparative Example 5, the surface roughness caused by the roughness-forming particles is not uniform over the entire outer peripheral surface of the surface layer, so that uneven discharge occurs, charging uniformity is poor, and black spots occur in image evaluation.

[0072] Comparative Example 9 is a charging roll in which the outer peripheral surface of the elastic layer is not subjected to corona treatment, and the outer peripheral surface of the elastic layer does not have a surface layer containing roughness-forming particles. In Comparative Example 9, since the outer peripheral surface of the elastic layer is not subjected to corona treatment, no carbonyl group is generated on the outer peripheral surface of the elastic layer, and the IR-RAS spectrum peak ratio is a small value. Therefore, the effect of increasing the electrostatic capacitance due to the dipole of the carbonyl group cannot be expected on the outer peripheral surface of the elastic layer, and since the contact area with the photoconductor is large, the charging property in the LL environment is poor, and black streaks occur in the image evaluation.

[0073] In Comparative Examples 6 to 8, the corona treatment was performed on the outer peripheral surface of the elastic layer, but the temperature was outside the predetermined range. In Comparative Examples 6 and 8, the set temperature of the corona treatment was low, so that although carbonyl groups were generated on the outer peripheral surface of the elastic layer, the carbonyl groups were difficult to orient on the outer peripheral surface of the elastic layer, and the IR-RAS spectrum peak ratio was small. Therefore, the effect of increasing the capacitance due to the dipole of the carbonyl group could not be expected, and the contact area with the photoconductor was large, so that the charging property was poor in the LL environment, and black streaks occurred in the image evaluation. On the other hand, in Comparative Example 7, the set temperature of the corona treatment was high, so that although carbonyl groups were generated on the outer peripheral surface of the elastic layer, the thermal energy was large, so that the carbonyl groups were relaxed, and the IR-RAS spectrum peak ratio was small. Therefore, the effect of increasing the capacitance due to the dipole of the carbonyl group could not be expected, and the contact area with the photoconductor was large, so that the charging property was poor in the LL environment, and black streaks occurred in the image evaluation.

[0074] In contrast, in the examples, the outer peripheral surface of the elastic layer is subjected to corona treatment within a specified temperature range. As a result, the carbonyl groups are oriented on the outer peripheral surface of the elastic layer, and the IR-RAS spectrum peak ratio is large. According to the examples, excellent charging performance can be achieved even without surface roughness, and it can be seen that excellent charging performance can be achieved without relying on surface roughness.

[0075] In Comparative Examples 1 and 2, the amount of NBR in the elastic layer is not satisfactory. In Comparative Example 1, the polymer component of the elastic layer is composed only of NBR, so the amount of carbonyl groups is too large, and the elastic layer is charged too much under high temperature and high humidity conditions, resulting in white streaks in the image evaluation. In addition, NBR is soft in a high temperature and high humidity environment, resulting in set streaks. On the other hand, in Comparative Example 2, the polymer component of the elastic layer is composed only of IR and does not contain NBR, so the effect of increasing the electrostatic capacitance due to the dipole of the carbonyl group cannot be expected, and the contact area with the photoconductor is large, resulting in poor charging properties in an LL environment, resulting in black streaks in the image evaluation.

[0076] In Comparative Examples 3 and 4, the amount of acrylonitrile in the NBR of the elastic layer is not satisfactory. In Comparative Example 3, the amount of acrylonitrile in the NBR is small, so the amount of carbonyl groups is too large, and the toner is charged too much under high temperature and high humidity conditions, resulting in white streaks in the image evaluation. On the other hand, in Comparative Example 4, the amount of acrylonitrile in the NBR is large, so the effect of increasing the capacitance due to the dipole of the carbonyl groups cannot be expected, and the contact area with the photoconductor is large, so the charging property in the LL environment is poor, resulting in black streaks in the image evaluation.

[0077] In contrast, in the examples, the elastic layer contains a specific amount of NBR having a specific amount of acrylonitrile, and therefore it is understood that excellent charging performance can be exhibited.

[0078] In Comparative Examples 10 and 11, the outer peripheral surface of the elastic layer was subjected to corona treatment, but the surface roughness Ra of the outer peripheral surface of the elastic layer was outside the specific range. In Comparative Example 10, the roughness Ra of the outer peripheral surface of the elastic layer was too small, so that the contact area with the photoconductor was large, and the surface was scraped by rubbing with the photoconductor, resulting in the loss of carbonyl groups, and thus the charging property was deteriorated. In Comparative Example 11, the roughness Ra of the outer peripheral surface of the elastic layer was too large, so that uneven discharge occurred, charging uniformity was poor, and black spots occurred in the image evaluation.

[0079] In contrast, in the examples, the surface roughness Ra of the outer peripheral surface of the elastic layer is within a specific range, so there is no deterioration in charging due to the influence of the contact area with the photoconductor, and there is no influence of uneven discharge due to the surface roughness Ra.

[0080] In the charging roll of the embodiment, the elastic layer contains 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of the polymer component, the surface roughness Ra of the elastic layer is 0.2 μm or more and 1.5 μm or less, and a predetermined amount of carbonyl groups are oriented and present on the surface of the elastic layer. According to the embodiment, since the surface roughness Ra of the elastic layer is small, discharge unevenness is suppressed, charging uniformity is excellent, and black spots are suppressed in image evaluation. In addition, charging properties are also excellent. Therefore, it can be seen that excellent charging performance is exhibited without relying on surface roughness, and charging uniformity is also excellent.

[0081] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments and examples, and various modifications are possible without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0082] 10. Charging roll 12 Axial body 14 Elastic layer

Claims

1. A shaft body and an elastic layer formed on an outer circumferential surface of the shaft body, The elastic layer contains 5 parts by mass or more and 95 parts by mass or less of an acrylonitrile-butadiene rubber having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of a polymer component, The surface roughness Ra of the elastic layer is 0.2 μm or more and 1.5 μm or less, a charging roll for an electrophotographic device, wherein carbonyl groups are oriented on the surface of the elastic layer, and a ratio of a maximum detection peak of stretching vibration of the carbonyl groups to a maximum detection peak of stretching vibration of a methine group of a butadiene skeleton in an infrared spectrum measured by a high sensitivity reflectance measurement method is 1.5 or more and 5.3 or less.

2. 2. The charging roll for an electrophotographic device according to claim 1, wherein said elastic layer contains isoprene rubber as a polymer component.

3. 3. The charging roll for an electrophotographic device according to claim 1, wherein said elastic layer does not contain roughness-forming particles that form a surface roughness.

4. The elastic layer has a DBP absorption of 70 cm ３ / 100g or more 160cm ３ 4. The charging roll for an electrophotographic apparatus according to claim 1, further comprising carbon black having a particle size of 100 g / m2 or less.

5. 5. The charging roll for an electrophotographic device according to claim 1, wherein the elastic layer has a dielectric constant of 180 or more and 830 or less when a voltage of 1 V·1 kHz is applied thereto.

6. 6. The charging roll for an electrophotographic device according to claim 1, wherein the carbonyl groups on the surface of the elastic layer are oriented and present by subjecting the surface of the elastic layer to a corona treatment at a temperature of 43° C. or higher and 92° C. or lower.

7. forming an elastic layer on the outer peripheral surface of the shaft, the elastic layer containing 5 parts by mass or more and 95 parts by mass or less of acrylonitrile-butadiene rubber having an acrylonitrile content of 30% by mass or more and 41% by mass or less per 100 parts by mass of a polymer component, and having a surface roughness Ra of 0.2 μm or more and 1.5 μm or less; and performing corona treatment on the surface of the elastic layer at a temperature of 43° C. to 92° C. to orient and cause carbonyl groups to be present.

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