JP2009109745A - Conductive roller, electrophotographic process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roller, electrophotographic process cartridge and an image forming apparatus for which resistance can be freely set, with little variation in resistance even when high voltage is applied and with stable resistance from an initial period of use to end of service life for a product. <P>SOLUTION: The conductive roller contains (a) silicone rubber with a dimethyl polysiloxane skeleton, (b) carbon black with flocculation unit size of 230 nm or more and 380 nm or less, (c) carbon black or inorganic filler with flocculation unit size of 590 nm or more and 210 nm or less. The ratio of occupied area of component (a) and component (b) is 1:1 or more and 1:4 or less. In addition, regarding a curve differentiated from a thermogravimetric reduction curve which is obtained when the temperature of the elastic layer is raised from 25° at 20°C/min under a nitrogen environment, the displacement of the carbon black when high voltage is applied is reduced without losing flexibility of the silicone rubber by using the conductive silicone rubber composite with a minimum value and a maximum value provided with a specific relationship. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a conductive roller, an electrophotographic process cartridge, and an image forming apparatus used in an electrophotographic image forming apparatus such as an electrophotographic copying apparatus, a printer, and an electrostatic recording apparatus.

  As an image formation of an electrophotographic apparatus such as a copying machine or a laser beam printer, a method using the following process is known. Specifically, first, a rotatable photosensitive drum is uniformly charged by a charging means such as a charging roller, and an electrostatic latent image is formed on the charged photosensitive drum surface by exposure with a laser beam or the like. Next, the photosensitive drum and the developing roller are rotated with each other while the developer formed in a thin film on the surface of the developing roller is brought into contact with the photosensitive drum carrying the electrostatic latent image. At this time, when a developing bias is applied to the developing roller, the developer (toner) moves from the developing roller to the electrostatic latent image on the photosensitive drum, and the electrostatic latent image is developed (visualized) as a toner image. Thereafter, the toner image on the photosensitive drum is transferred to the recording material by a transfer roller, and fixed on the recording material by heating, pressurizing, or the like in the fixing unit, whereby the image formation on the recording material is completed, and the image forming apparatus It is discharged outside.

For the developing roller, charging roller, and transfer roller used in the developing device, a conductive roller having an electrical resistance in a semiconductive region with a volume resistivity of 1 × 10 ³ to 1 × 10 ¹⁰ Ω · cm is mainly used. The However, in recent years, needs for colorization and high image quality of electrophotography have increased, and further resistance stability of these conductive rollers has been strictly demanded. As an issue regarding resistance stability, first of all, it is necessary for an electrophotographic apparatus to cope with a wide range of temperature and humidity, and one of the important issues is that resistance is stable even when the environment changes. Can be mentioned. Next, in the conductive roller to which a high voltage is applied, the resistance may fluctuate with the course from the initial use to the product life, and the temporal stability of the resistance during the application of a high voltage is also important. If the resistance stability of the conductive roller is poor, in the case of the developing roller, the toner charge amount changes and image defects such as fogging occur.

In order to solve the above required characteristics, a method of adjusting the composition of the silicone rubber composition used for the elastic layer is known. In order to reduce the environmental dependency of the conductive roller, it is proposed to add carbon black and acetylene black or ketjen black having a particle size, DBP oil absorption and sulfur content within a specific range to the silicone rubber composition. (See Patent Document 1). Further, as a means for reducing the time-dependent change in resistance during high voltage application, there is a method of filling silicone rubber with MT carbon having a specific range of nitrogen adsorption specific surface area, DBP oil absorption, and average particle diameter (Patent Literature). 2).
JP 2005-132969 A JP 2001-158856 A

  However, the method of filling resistance resistance by filling a specific carbon black has limitations such as the resistance cannot be set arbitrarily in a wide range according to the application of the product because there are restrictions on the type and filling amount of carbon black that can be used. was there.

  SUMMARY OF THE INVENTION The present invention has been made in view of these problems of the prior art, and can be set freely, and the conductive roller, the electrophotographic process cartridge, and the image forming apparatus have little resistance variation from the initial use to the product life. The purpose is to provide.

In order to achieve the above object, the conductive roller of the present invention comprises:
A shaft core,
In a conductive roller having a conductive elastic layer made of a cured product of a silicone rubber composition formed around the shaft core body,
The elastic layer is
(A) a silicone rubber containing a dimethylpolysiloxane skeleton;
(B) carbon black having a size of aggregated unit of 230 nm or more and 380 nm or less;
(C) carbon black or an inorganic filler having an aggregate unit size of 590 nm to 1210 nm,
Including
The ratio of the occupied area of the component (b) and the component (c) is 1: 1 or more and 1: 4 or less,
And about a curve obtained by differentiating the thermogravimetric decrease curve obtained when the elastic layer is heated from 25 ° C. to 20 ° C./min in a nitrogen atmosphere, within a low temperature range of 360 ° C. or more and 520 ° C. or less, Having at least one peak in each of the high temperature side temperature range of 580 ° C. or more and 650 ° C. or less,
The peak height of the maximum temperature within the low temperature range is P1max (wt% / ° C),
P2min (wt% / ° C) as the peak height of the lowest temperature within the high temperature range.
When P1max and P2min have a low peak height of P3 (wt% / ° C), and a minimum portion between 520 ° C and 580 ° C is P4 (wt% / ° C),
0.0 ≦ P4 / P3 ≦ 0.9
It is characterized by being.

  The electrophotographic process cartridge of the present invention is provided with a developing roller, a thin layer of toner is formed on the surface of the developing roller, the developer roller is brought into contact with the photosensitive drum, and the toner is formed on the surface of the photosensitive drum. In the electrophotographic process cartridge in which a toner image is formed on the surface of the photosensitive drum by supplying the developing roller, the developing roller is composed of a conductive roller having the above-described configuration.

  In the image forming apparatus of the present invention, a developing roller is mounted, a thin layer of toner is formed on the surface of the developing roller, and the toner is supplied to the surface of the photosensitive drum by bringing the developing roller into contact with the photosensitive drum. Thus, in the image forming apparatus for forming a toner image on the surface of the photosensitive drum, the developing roller is composed of the conductive roller having the above-described configuration.

  According to the present invention, it is possible to provide a conductive roller in which the resistance of the conductive roller can be freely set and the resistance variation is small from the initial use to the product life.

The conductive roller according to the present invention has a shaft core and a conductive elastic layer formed around the shaft core and made of a cured product of the silicone rubber composition. The elastic layer contains the following components (a) to (c):
(A) a silicone rubber containing a dimethylpolysiloxane skeleton,
(B) carbon black having an aggregate unit size of 230 nm or more and 380 nm or less,
(C) Carbon black or an inorganic filler having an aggregate unit size of 590 nm to 1210 nm.

  And the ratio of the occupied area in the elastic layer of the said component (b) and the said component (c) is 1: 1 or more and 1: 4 or less.

In addition, a curve obtained by differentiating the thermogravimetric decrease curve obtained when the elastic layer is heated from 25 ° C. to 20 ° C./min in a nitrogen atmosphere is within a low temperature range of 360 ° C. to 520 ° C. and 580 ° C. Each having at least one peak in the high temperature side temperature range of from ℃ to 650 ℃,
The peak height of the maximum temperature within the low temperature range is P1max (wt% / ° C),
P2min (wt% / ° C) as the peak height of the lowest temperature within the high temperature range.
When P1max and P2min have a low peak height of P3 (wt% / ° C), and a minimum portion between 520 ° C and 580 ° C is P4 (wt% / ° C),
0.0 ≦ P4 / P3 ≦ 0.9
It is.

  FIG. 1 shows a schematic cross-sectional view in a plane orthogonal to the shaft core of the conductive roller according to the preferred embodiment, and FIG. 2 shows a schematic perspective view thereof. As shown in FIGS. 1 and 2, the elastic roller includes a shaft core body 1 and an elastic layer 2 formed concentrically on the outer periphery of the shaft core body 1. Moreover, the coating layer 3 is formed in the single | mono layer or the multilayer on the outer periphery of the formed elastic layer 2 according to a use.

  Examples of the material constituting the shaft core 1 include the following materials.

  Alloys of iron, steel, aluminum, titanium, copper and nickel, stainless steel containing these metals, alloys of duralumin, brass and bronze, as well as composite materials in which carbon black and carbon fibers are solidified with plastic are known to exhibit rigidity and conductivity. Material.

  Further, the shape of the shaft core may be a columnar shape or a cylindrical shape having a hollow at the center.

As a rubber component contained in the rubber composition forming the elastic layer 2, an addition reaction type silicone rubber is used for the following reasons.
・ Low compression set despite low hardness compared to other general-purpose rubber.
・ Excellent workability.
-Good dimensional stability due to the absence of by-products associated with the curing reaction.
-The physical properties after curing are stable.

  Furthermore, the temperature difference between P1max and P2min is preferably 90 ° C. or higher and 290 ° C. or lower.

  The means for obtaining the thermogravimetric reduction curve is not particularly limited as long as the temperature of the sample can be raised from 25 ° C. to 20 ° C./min in a nitrogen atmosphere and the weight loss of the sample at that time can be measured. A differential thermo-thermogravimetric simultaneous measurement device (TG / DTA) that is easy to obtain and easy to handle is suitable. Moreover, the curve obtained by differentiating the thermogravimetric decrease curve is a change in weight (wt%) per unit time (second), and can be obtained using software attached to the thermogravimetric simultaneous measurement apparatus.

  The silicone rubber having a dimethylpolysiloxane skeleton as the component (a) has a structure in which an alkenyl group-containing polysiloxane and a hydrosilyl group-containing hydrogen polysiloxane are subjected to an addition reaction and crosslinked. Since the Si-O bond of polysiloxane has a larger bond energy than the C-C bond formed by crosslinking, when the silicone rubber is heated, the C-C bond at the crosslinking point is first cleaved, and the molecule before crosslinking A polysiloxane with chains is reformed. The peak that appears in the low temperature range of 360 ° C. or more and 520 ° C. or less in the derivative of the thermogravimetric reduction curve is a peak indicating that the polysiloxane having a short molecular chain is reduced among the polysiloxanes regenerated by thermal decomposition. It is. In the present invention, the presence of this polysiloxane having a short molecular chain improves the resistance stability when a high voltage is applied. In the first place, it is estimated that one of the causes of the resistance fluctuation at the time of applying a high voltage is that the charged carbon black is moved by the Coulomb force and the dispersion state is changed. Therefore, as shown in FIG. 3, by cross-linking polysiloxane having a short molecular chain to reduce the network structure, the carbon black is fixed to the network structure, and the movement of the carbon black can be reduced.

  On the other hand, the peak appearing in the high temperature side temperature range of 580 ° C. or higher and 650 ° C. or lower is a peak indicating that polysiloxane having a long molecular chain is reduced among polysiloxanes re-formed by thermal decomposition. A polysiloxane having a long molecular chain has a high degree of freedom of movement of the polysiloxane and is related to the flexibility characteristic of silicone rubber.

  If all of the polysiloxane network structure is made smaller in order to further increase the stability of resistance, the flexibility of the silicone rubber is lost, and toner deterioration is accelerated when used as a developing roller. The deterioration of the toner disturbs the charge amount of the toner, and defects on the image different from the initial stage such as fogging and ghost are likely to occur. Polysiloxane optimizes the balance between polysiloxanes with short molecular chains and polysiloxanes with long molecular chains, reducing resistance fluctuations when high voltage is applied and maintaining the flexibility of silicone rubber. High-precision images can be obtained until the end of the product life.

In the present invention, as described above, P3 and P4 based on P1max and P2min defined above are:
0.0 ≦ P4 / P3 ≦ 0.9
Meet the relationship. The relationship from P1max to P4 will be described with reference to FIG. 4 showing a case where there is one peak in each temperature range. P1max is the height (wt% / ° C) of the peak closest to 520 ° C (including the peak at 520 ° C) among the peaks in the range of 360 ° C or more and 520 ° C or less. P2min is the height (wt% / ° C) of the peak located closest to 580 ° C (including the peak at 580 ° C) among the peaks in the range of 580 ° C to 650 ° C. P3 has a lower peak height (wt% / ° C.) when P1max and P2min are compared, and is P1max in FIG. Further, P4 is the position where the differential curve is the smallest (wt% / ° C.) in the range of 520 ° C. and 580 ° C., and in FIG. 4, is the valley portion sandwiched between the P1max peak and the P1max peak.

  If there is a peak in a region higher than 520 ° C. and lower than 580 ° C. in a derivative of the thermogravimetric decrease curve, the effect of the present invention may not be exhibited. That is, the blending ratio of the polysiloxane that contributes to resistance stability at 360 ° C. to 520 ° C. and the polysiloxane that contributes to flexibility at 580 ° C. to 650 ° C. becomes small. P4 / P3 needs to be 0.9 or less in order to obtain each effect sufficiently.

  The temperature difference between P1max and P2min is preferably 90 ° C. or higher and 290 ° C. or lower. If the temperature is lower than 90 ° C, the effect of achieving both resistance stability and flexibility is weakened. If the temperature is wider than 290 ° C, the distribution of the size of the network structure becomes extreme, which may adversely affect normal rubber properties. It is not preferable.

The silicone rubber component in the silicone rubber composition, which is a material for forming the elastic layer, preferably contains the following components (A) and (B) in a mass ratio of 1: 1 to 19: 1.
(A) A first polysiloxane having at least one alkenyl group at the terminal and having a weight average molecular weight of 60,000 to 100,000, wherein 99 mol% or more of the main chain is a repeating unit of dimethylsiloxane.
(B) A second polysiloxane having at least one alkenyl group at the terminal and having a weight average molecular weight of 900,000 to 2,000,000, wherein 99 mol% or more of the main chain is a repeating unit of dimethylsiloxane.

  Since the first polysiloxane has a small network structure after crosslinking, it plays a role of resistance stability of the silicone rubber. Even if the weight average molecular weight is less than 60,000, the resistance stability does not change so much. When the weight average molecular weight is more than 100,000, the resistance stability is lost, which is not preferable.

  On the other hand, the second polysiloxane has a network structure that becomes larger after crosslinking, and plays a role in expressing the flexibility of silicone rubber. Therefore, when the weight average molecular weight is less than 900,000, the flexibility of the silicone rubber may be lost. Conversely, when the weight average molecular weight is greater than 2 million, the elastic modulus of the silicone rubber decreases, so that the compression set is deteriorated, and there is a possibility that image defects due to deformation occur. Further, in the first and second polysiloxanes, it is desirable that at least one alkenyl group is present at the terminal, and the type thereof is not particularly limited. However, for reasons such as high reactivity with active hydrogen, vinyl It is preferably at least one of a group and an allyl group, and a vinyl group is particularly preferable.

  In the first and second polysiloxanes, 99 mol% or more of the main chain is a repeating unit of dimethylsiloxane means that the following repeating unit X:

Means that 99 mol% or more of the unit represented by X in the main chain structure in which is repeated is dimethylsiloxane.

  In addition, the weight average molecular weight in this invention was measured by the gel permeation chromatography (GPC). That is, toluene as a solvent was allowed to flow through a column stabilized in a 40 ° C. heat chamber at a flow rate of 0.5 ml per minute, and 50 to 200 μl of a sample solution adjusted to 0.05 to 0.60 mass% was injected. And the weight average molecular weight of the sample was computed from the calibration curve created with several types of monodisperse polystyrene standard samples.

  The blending ratio of the polysiloxane having a larger network structure after crosslinking and the polysiloxane having a smaller network structure is, as described above, from 1: 1 to 19: 1 in terms of mass ratio from the optimum balance of resistance stability and flexibility. It is preferable to cure in the following.

  For the purpose of imparting conductivity to the elastic layer 2, carbon black (component (b)) is blended as a conductive agent in the silicone rubber composition. As the carbon black as the component (b), those having an aggregate unit size of 230 nm or more and 380 nm or less in the elastic layer are used. When the size of the aggregated unit of carbon black is less than 230 nm, it is difficult to fix the carbon black to the polysiloxane network structure, so that sufficient resistance stability cannot be obtained. Carbon black with agglomeration unit size larger than 380 nm also has a large particle size and weak formation of a conductive network. Therefore, a large amount of carbon black is required to achieve conductivity, and low compression set of silicone rubber, etc. Cause the loss of characteristics.

  The size of the aggregated unit of carbon black here was determined as follows. First, a sample is collected by cutting with a sharp blade so that the cross section of the central portion in the longitudinal direction of the conductive roller can be observed. From this sample, a frozen section cutting device (Leica EM FCS manufactured by Leica Microsystems) was used, and a diamond knife (Cryo dry 35 ° manufactured by Diatome) was used in an atmosphere of −120 to −50 ° C. Make ultra-thin sections. The obtained ultra-thin sections were taken with a scanning transmission electron microscope (S-4800 manufactured by Hitachi), and TEM images were taken at 100,000 to 300,000 times, and randomly selected carbon black as shown in FIG. The length of the long side is determined from the circumscribed square of one aggregation unit. Similarly, the average of the long sides of 100 circumscribed squares of randomly selected carbon black agglomeration units was defined as the carbon black agglomeration unit size.

  In addition to carbon black as the component (b), at least one of carbon black having an aggregate unit size of 590 nm to 1210 nm and an inorganic filler is blended as the component (c). The size of the aggregation unit of the inorganic filler can also be measured by the same method as described above. Since component (c) is fixed to the network structure of the polysiloxane skeleton and fills the network space, the movement of carbon black as component (b) contributing to the conductivity of the silicone rubber is further reduced, and the resistance is stabilized. Can be increased. Accordingly, when a component (c) having a cohesive unit size of less than 230 nm is used, the size is insufficient to fill the space of the network structure. Even if the size of the aggregation unit of component (c) is larger than 380 nm, there is no difference in the stability of resistance, and the mechanical strength of the silicone rubber may be lowered.

  The inorganic filler is not particularly limited as long as the size of the aggregation unit in the above range can be supplied into the elastic layer and the intended effect can be obtained. As such an inorganic filler, silica, alumina, calcium carbonate, celite, quartz powder, and zinc white can be used. These 1 type (s) or 2 or more types can be used in combination.

  In the present invention, the ratio of the area occupied by component (b) and component (c) is 1: 1 or more and 1: 4 or less. The occupied area here was calculated | required as follows.

  First, it cut | disconnected and extract | collected with the sharp blade so that the cross-section observation of the center part of the longitudinal direction of an electroconductive roller was carried out, and the SEM image was image | photographed 10,000 times using the electron microscope (Hitachi S-4800). The obtained SEM image was binarized and classified according to the size of the aggregated unit, and the total area was taken as the occupied area in the size of each aggregated unit.

  When the ratio of occupied area is less than 1: 1, the amount of carbon black or inorganic filler of 590 nm to 1210 nm is less than the amount of carbon black of 230 nm or more and 380 nm or less. There are times when it does not improve. On the other hand, even if the occupied area ratio is larger than 1: 4, the resistance stability effect is not improved as expected, and the amount of carbon black and inorganic filler is increased, so that the flexibility of the silicone rubber is lost. This is not preferable.

  In this invention, a component (b) and a component (c) are 12 to 18 mass parts in total with respect to 100 mass parts of components (a). By setting the total mass part of the component (b) and the component (c) within the above numerical range, the volume resistivity required for the conductive roller can be adjusted. Further, it is possible to avoid the deterioration of the toner due to the increase in the hardness of the silicone rubber, the fogging or ghosting of the electrophotographic image.

  The method for forming the elastic layer 2 on the surface of the shaft core 1 is not particularly limited, and conventionally known methods for forming various rollers can be used. Examples thereof include a method of forming an elastic layer on the surface of the shaft core body 1 by molding by various molding methods such as extrusion molding, press molding, injection molding, liquid injection molding, and cast molding. In particular, there is a method of obtaining an elastic layer by applying a coating liquid containing a conductive silicone resin composition for forming an elastic layer around a shaft core by using a ring-shaped coating head, followed by heat curing. preferable. According to this method, when the coating liquid passes through the slit in the ring-shaped coating head, high shear stress is applied to the coating liquid, and the dispersion state of carbon black in the coating liquid coated on the shaft core body Is always preferable because it is constant.

  A schematic explanatory diagram of a ring coater having a ring-shaped coating head that can be preferably used here is shown in FIG. In the coating apparatus shown in FIG. 6, a column 5 is attached substantially vertically on the gantry 4, and a precision ball screw 6 is attached substantially vertically on the gantry 4 and the column 5. Two linear guides 7 are attached to the column 5 in parallel with the precision ball screw 6. The LM guide 8 is connected to the linear guide 7 and the precision ball screw 6 so that the rotary motion is transmitted from the servo motor 9 via the pulley 10 so that the LM guide 8 can be moved up and down. A ring-shaped coating head 11 that discharges the coating liquid is attached to the column 5 on the outer peripheral surface of the cylindrical shaft core body 1. Further, a bracket 12 is attached on the LM guide 8, and a work lower holder 13 for holding and fixing the shaft core 1 is attached to the bracket 12 substantially vertically. Further, the central axis of the on-work holder 14 that holds the shaft core 1 on the opposite side is attached to the upper part of the bracket 12. The workpiece upper holder is arranged so as to be substantially concentric with the workpiece lower holder 13 to hold the shaft core body 1.

  The central axis of the ring-shaped coating head 11 is supported so as to be parallel to the moving direction of the workpiece lower holder 13 and the workpiece upper holder 14. Further, when the workpiece lower holding tool 13 and the workpiece upper holding tool 14 are moved up and down, the central axis of the discharge port that is an annular slit opened inside the coating head 11, the workpiece lower holding tool 13 and the workpiece upper holding tool 14 are held. The center axis of the tool 14 is adjusted to be substantially concentric. With such a configuration, the central axis of the discharge port that is an annular slit of the coating head 11 can be aligned with the central axis of the shaft core 1, and the inner peripheral surface of the ring-shaped coating head A uniform gap is formed between the outer peripheral surface of the shaft core body 1.

  The coating solution supply port 15 is connected to a supply valve 17 via a coating solution conveying pipe 16. The coating liquid supply valve 17 is provided with a mixing mixer, a supply pump, a quantitative discharge device, a tank, and the like in front of it, and is capable of discharging a fixed amount (a constant amount per unit time) of the coating liquid. A coating solution containing unvulcanized silicone rubber is weighed from a tank by a fixed discharge device and mixed by a mixing mixer. Thereafter, the coating liquid mixed by the supply pump is sent from the supply valve 17 to the supply port 15 via the pipe 16.

  The coating liquid fed from the supply port 15 passes through the flow path in the ring type coating head 11 and is discharged from the nozzle of the ring type coating head 11. In order to make the thickness of the elastic layer constant, the discharge amount from the ring-shaped coating head nozzle and the supply amount from the supply pump are made constant. By moving the held shaft core body 1 upward in the vertical direction (the central axis direction of the shaft core body), the shaft core body 1 moves relative to the coating head 11 in the axial direction. A cylindrical (roll-shaped) layer 2 made of an unvulcanized conductive silicone rubber composition is formed on the outer periphery of the core body 1.

  The layer of the unvulcanized conductive silicone rubber composition formed on the outer periphery of the shaft core is heat-treated to form a conductive roller. As the heat source, a far-infrared ceramic heater, a near-infrared heater, a lamp heater, a UV heater, or a micro heater that can heat the coating layer in a non-contact manner is desirable.

  The coating layer 3 can be provided on the outer periphery of the elastic layer 2 formed as described above depending on the application. Examples of the material for forming the coating layer 3 include various polyamides, fluororesins, hydrogenated styrene-butylene resins, urethane resins, silicone resins, polyester resins, phenol resins, imide resins, and olefin resins. In the coating layer 3, fine particles having a volume average particle diameter of 1 to 20 μm can be dispersed according to individual applications. Examples of such fine particles include polymethyl methyl methacrylate fine particles, silicone rubber fine particles, polyurethane fine particles, polystyrene fine particles, amino resin fine particles, and phenol resin fine particles.

  The covering layer 3 can also be blended with a conductive agent in order to adjust the electrical resistance of the entire conductive roller. Conductive agents include carbon black, graphite, conductive metal oxides, copper, aluminum, nickel, iron powder, or alkali metal salts that are ionic conductive agents, and ammonium salts, which are conductive agents having various electron conduction mechanisms. Can be used.

  The coating layer 3 is formed by applying a coating liquid in which the above-mentioned resin component and additives such as fine particles and conductive agent added as necessary are mixed using a solvent as necessary. A construction method is preferred. For the preparation of the coating solution, the additive can be suitably dispersed in the coating solution by using a conventionally known dispersing device using sand mill, paint shaker, dyno mill, or pearl mill beads. The obtained coating liquid as a dispersion liquid is applied to the surface of the elastic layer 2 by a spray coating method or a dipping method.

  Next, an example of an image forming apparatus having the conductive roller of the present invention will be described with reference to FIG. The image forming apparatus shown in FIG. 7 has four electrophotographic process cartridges 18 for forming yellow, cyan, magenta and black images, respectively, and these are provided in a tandem manner. Each electrophotographic process cartridge 18 includes a photosensitive drum 19, a charging device (charging roller 20 in FIG. 4), an image exposure device 21 (writing beam in the drawing), a developing device 22, a cleaning device 23, and the like. The specification of each part has a slight difference in adjustment according to the characteristics of each color toner, but these four electrophotographic process cartridges 18 are the same in the basic configuration.

  The developing device 22 includes a developing roller 27 disposed opposite to the photosensitive drum 19 and a developing container 26 containing toner 25. That is, the conductive roller according to the present invention is mounted on the electrophotographic process cartridge 18 as a developing roller. Further, the toner 25 is supplied to the developing roller 27, and the toner 25 that is not used for development and scrapes off the toner 25 remaining on the developing roller 27 is regulated. A developing blade 29 for charging is provided.

  The photosensitive drum 19 is uniformly charged to a predetermined polarity and potential by the charging device 20. Image information is irradiated from the image exposure device 21 onto the surface of the photosensitive drum 19 charged as a beam, and an electrostatic latent image is formed. Next, toner 25 is supplied from a thin layer of toner on the developing roller 27 onto the formed electrostatic latent image, and a toner image is formed on the surface of the photosensitive drum 19.

  In the image transfer device 24, the transfer conveyance belt 31 is stretched around a drive roller 32, a tension roller 33 and a driven roller 34, and a transfer roller 36 is installed inside the transfer conveyance belt 31 at a position facing the photosensitive drum 19. Yes. Then, by applying a bias to the electrostatic adsorption roller 35, the transfer material 30 is electrostatically adsorbed to the outer peripheral surface of the transfer conveyance belt 31, and the transfer material 30 is conveyed. When the transfer material 30 is conveyed to the transfer position, a bias having a polarity opposite to that of the toner image on the surface of the photosensitive drum 19 is applied to the transfer roller 36. As a result, the toner image is transferred to the transfer material 30.

  The transfer material 30 onto which the toner image has been transferred is sent from the transfer conveyance belt 31 to the fixing device 37, where the toner image is fixed on the transfer material 30 and printing is completed. On the other hand, the photosensitive drum 19 after the transfer of the toner image to the transfer material 30 is further rotated, and the surface of the photosensitive drum 19 is cleaned by the cleaning device 23.

  The conductive roller of the present invention can be used for the above-described developing roller, charging roller, and transfer roller. In addition to the image forming apparatus described above, the image forming apparatus can be used for an intermediate transfer type image forming apparatus.

The present invention will be described more specifically with reference to the following examples. The present invention is not limited to the following examples. First, various measurement methods and evaluation methods performed in Examples and Comparative Examples will be described.
[Thermal weight reduction curve of conductive roller]
A thermogravimetric decrease curve of the conductive roller was measured using a differential thermothermal weight simultaneous measurement apparatus (trade name: Thermo Plus TG8120; manufactured by Rigaku). Measurement conditions are as follows: a sample is cut from a conductive roller in an amount of 15 mg to 20 mg and set in a TG device, and after flowing nitrogen gas for 15 minutes or more, the temperature is raised to 800 ° C. at a heating rate of 20 ° C./min. It was. The obtained thermogravimetric decrease curve was differentiated using the software attached to the differential thermothermogravimetric simultaneous measurement apparatus, and a curve obtained by differentiating the thermogravimetric decrease curve was obtained.

  Of the peaks in the range of 360 ° C. or more and 520 ° C. or less of the obtained differential curve, the peak height that is the most from 520 ° C. is P1 (wt% / ° C.), the peak in the range of 580 ° C. or more and 650 ° C. or less. Among them, the height of the peak at 580 ° C. at the most was defined as P2 (wt% / ° C.). Further, when P1 and P2 are compared, the lower peak height (wt% / ° C) is P3, and the position where the differential curve is the smallest (wt% / ° C) in the range of 520 ° C and 580 ° C is P4. It was.

[Resistance stability of conductive roller when high voltage is applied]
As shown in FIG. 8, in an environment of a temperature of 23 ° C. and a humidity of 50% RH, the conductive roller before forming the coating layer is pressed against a metal roller for electrodes having a diameter of 30 mm with a load of 1000 g for each side of 500 g. The conductive roller was driven to rotate by rotating the metal roller at 28 rpm. In this state, the fluctuation rate of the current after 10 minutes with respect to the initial current when a voltage of 100 V was applied between the shaft core and the metal roller from the DC power source for 10 minutes was obtained by the following equation.
Current fluctuation rate (%) = (initial current−current after 10 minutes) / initial current × 100
[Flexibility of conductive roller]
The hardness of the conductive roller was measured using an ASKER C-type hardness meter (manufactured by Kobunshi Keiki). Details of the measurement method are given in JIS K6253 5. The test was carried out in accordance with (Durometer Hardness Test).

[Image damage of conductive roller]
In order to evaluate the effect of resistance stability and flexibility upon application of a high voltage on the image, the fog was measured when the conductive roller was used as a developing roller. Fog is an image detrimental effect caused by the change in the toner charge amount over time when the resistance fluctuation of the developing roller is large or when the hardness is high, and the resistance stability and flexibility when a high voltage is applied to the conductive roller. Ideal for evaluating sex.

  A conductive roller having a coating layer was incorporated in an electrophotographic process cartridge of a laser beam printer (HP Color LaserJet 3600 manufactured by Hewlett-Packard). A solid white image was output after outputting 10,000 continuous images at a printing rate of 1% in an environment of 30 ° C. and 80% RH. Using the reflection densitometer (TC-6DS / A manufactured by Tokyo Denshoku Co., Ltd.), the solid white image is measured for the reflection density of the white background portion, and the average value of 10 points measured on the image is defined as Ds. Then, the difference (Dr−Ds) between the reflection density of the paper before outputting the solid white image (the average value thereof is Dr) and Ds was obtained and used as the fogging amount. A fogging amount of 0% or more and less than 1.0% was designated as “A”, a fogging amount of 1.0% or more and less than 3.0% was designated as “B”, and a fogging amount of 3.0% or more was designated as “C”.

(Example 1)
[Preparation of elastic layer]
A primer (trade name: DY39-051; manufactured by Toray Dow Corning Co., Ltd.) is applied to a shaft body made of free-cutting steel having a diameter of 8 mm and a length of 250 mm for the purpose of improving the adhesion to silicone rubber. Baking was performed at 150 ° C. for 30 minutes.

A liquid silicone rubber base material A containing the following (1-1) to (1-5) was prepared.
(1-1) Dimethylpolysiloxane having a weight average molecular weight of 10,000, in which vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 50 parts by mass
(1-2) dimethylpolysiloxane having a weight average molecular weight of 2 million, in which vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 50 parts by mass;
(1-3) Carbon black (Raven 890 manufactured by Columbian Chemical): 6 parts by mass
(1-4) Carbon black (Asahi Carbon Asahi 50H): 24 parts by mass,
(1-5) Isopropanol solution of 2% by mass of chloroplatinic acid as a curing catalyst: 10 ppm with respect to (1-1) and (1-2) above.

  Moreover, the base material B of the liquid silicone rubber which mix | blended said (1-1)-(1-4) and the following (1-6) was prepared.

  (1-6) Methyl hydrogen polysiloxane (prepared so that SiH group is 1.1 mol with respect to 1 mol of vinyl group contained in dimethylpolysiloxane substituted with vinyl group): 3 parts by mass .

  Next, the base material A and the base material B of the liquid silicone rubber were mixed at a mass ratio of 1: 1 to prepare an unvulcanized silicone rubber.

  A shaft core body having an outer diameter of φ6 mm was vertically set by the shaft core body holding shafts (shaft core upper holding shaft 10 and shaft core lower holding shaft 9) of the ring coater having the ring-shaped coating head shown in FIG. . The shaft core body was moved by vertically raising the shaft core body holding shaft at 60 mm / s. In accordance therewith, the unvulcanized silicone rubber prepared above was discharged at 5.0 ml / s to form an unvulcanized silicone rubber layer on the outer periphery of the shaft core.

  The shaft body on which the unvulcanized silicone rubber layer was formed was irradiated with an infrared heating lamp (HYL25, manufactured by Hybek) at an output of 1000 W for 4 minutes while rotating at 60 rpm to cure the unvulcanized silicone rubber layer. To obtain a silicone rubber layer. Then, it heated at 200 degreeC for 4 hours in order to remove the reaction residue and unreacted low molecule in a silicone rubber layer. A conductive roller having a silicone rubber layer with a thickness of 3 mm was obtained.

  When the ratio of the aggregated unit of carbon black and the occupied area was measured from the obtained conductive roller, 230 nm and 590 nm were present at 1: 4. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had peaks of P1 and P2 at 360 ° C. and 650 ° C., the temperature difference between P1 and P2 was 290 ° C., and P4 / P3 was 0.7. . Further, the hardness of the conductive roller was 62 °, and the resistance variation rate when a high voltage was applied was 63%. These results are summarized in Table 1.

[Preparation of coating layer]
100 parts by mass of polyurethane polyol prepolymer (trade name: Takelac TE5060; manufactured by Mitsui Takeda Chemical Co., Ltd.), 77 parts by mass of isocyanate (trade name: Coronate 2521; manufactured by Nippon Polyurethane Co., Ltd.), and carbon black (trade name: MA-100; Mitsubishi) MEK was added to 20 parts by mass of Chemicals). After 5 hours of dispersion and rotation with a ball mill, 6 parts of urethane fine particles (trade name: Art Pearl C-400 transparent; manufactured by Negami Kogyo Co., Ltd.) were added and the dispersion was rotated again for 1 hour. The obtained conductive roller was immersed in this solution to form a coating film, and after air drying, a coating layer having a thickness of 30 μm was formed by heat treatment at 140 ° C. for 4 hours. The thickness of the coating layer was obtained by cutting a part of the conductive roller and photographing with a digital microscope VHX-200 manufactured by Keyence. The thickness of the portion where no urethane fine particles were present was defined as the thickness of the coating layer.

  When this was incorporated into an electrophotographic process cartridge of a laser beam printer (trade name: HP Color LaserJet 3600; manufactured by Hewlett Packard) as a developing roller, the amount of fogging of a solid white image after printing 10,000 sheets was measured. It was 2.1%. The results are shown in Table 1.

(Example 2)
A conductive roller was prepared in the same manner as in Example 1 except that (1-1) and (1-2) in Example 1 were changed to the following (2-1) and (2-2). .
(2-1) Dimethylpolysiloxane having a weight-average molecular weight of 160,000, wherein vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 86 parts by mass,
(2-2) Dimethylpolysiloxane having a weight average molecular weight of 740,000 wherein vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 14 parts by mass.

  When the ratio of the aggregated unit of carbon black and the occupied area was measured from the obtained conductive roller, 230 nm and 590 nm were present at 1: 4. Moreover, the curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 490 ° C. and 580 ° C., the temperature difference between P1 and P2 was 90 ° C., and P4 / P3 was 0.9. . Further, the hardness of the conductive roller was 58 °, and the resistance variation rate when a high voltage was applied was 74%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was 2.5%. . These results are summarized in Table 1.

(Example 3)
A conductive roller was produced in the same manner as in Example 1 except that (1-1) and (1-2) in Example 1 were changed to the following (3-1) and (3-2). .
(3-1) Dimethylpolysiloxane having a weight-average molecular weight of 270,000, in which vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 90 parts by mass,
(3-2) Dimethylpolysiloxane having a weight average molecular weight of 900,000, wherein vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 10 parts by mass.

  When the ratio of the aggregated unit of carbon black and the occupied area was measured from the obtained conductive roller, 230 nm and 590 nm were present at 1: 4. Moreover, the curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 520 ° C. and 590 ° C., the temperature difference between P1 and P2 was 70 ° C., and P4 / P3 was 0.9. . Further, the hardness of the conductive roller was 55 °, and the rate of change in resistance when a high voltage was applied was 76%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 2.6%. . These results are summarized in Table 1.

Example 4
A conductive roller was produced in the same manner as in Example 1 except that (1-1) and (1-2) in Example 1 were changed to the following (4-1) and (4-2). .
(4-1) Dimethylpolysiloxane having a weight average molecular weight of 100,000, in which 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane, with 95% by mass,
(4-2) Dimethylpolysiloxane having a weight average molecular weight of 2 million in which vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 5 parts by mass.

  When the ratio of the aggregated unit of carbon black and the occupied area was measured from the obtained conductive roller, 230 nm and 590 nm were present at 1: 4. Moreover, the curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 460 ° C. and 650 ° C., the temperature difference between P1 and P2 was 190 ° C., and P4 / P3 was 0.8. . Further, the hardness of the conductive roller was 58 °, and the resistance variation rate when a high voltage was applied was 74%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 2.7%. . These results are summarized in Table 1.

(Example 5)
A conductive roller was produced in the same manner as in Example 1 except that (1-1) to (1-4) in Example 1 were changed to the following (5-1) and (5-2).
(5-1) Dimethylpolysiloxane having a weight average molecular weight of 60,000, wherein vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 80 parts by mass,
(5-2) Dimethylpolysiloxane having a vinyl group substituted at both ends and having a weight average molecular weight of 900,000, wherein 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 20 parts by mass, (5-3) carbon Black (Raven 890 manufactured by Columbia Chemical): 6 parts by mass,
(5-4) Carbon black (Asahi Carbon Asahi 50H): 24 parts by mass.

  When the ratio of the aggregated unit of carbon black and the occupied area was measured from the obtained conductive roller, 230 nm and 590 nm were present at 1: 4. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 440 ° C. and 590 ° C., the temperature difference between P1 and P2 was 150 ° C., and P4 / P3 was 0.8. . Further, the hardness of the conductive roller was 62 °, and the resistance variation rate when a high voltage was applied was 63%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was 2.1%. . These results are summarized in Table 1.

(Example 6)
A conductive roller was prepared in the same manner as in Example 5 except that (5-3) and (5-4) in Example 5 were changed to the following (6-3) and (6-4). .
(6-3) Carbon black (Raven 860 Ultra manufactured by Columbia Chemical): 6 parts by mass,
(6-4) Carbon black (Asahi Carbon Asahi 50H): 6 parts by mass.

  When the size of the aggregated unit of carbon black and the ratio of the occupied area were measured from the obtained conductive roller, 380 nm and 590 nm were present at 1: 1. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 440 ° C. and 590 ° C., the temperature difference between P1 and P2 was 150 ° C., and P4 / P3 was 0.8. . The hardness of the conductive roller was 58 °, and the resistance variation rate when a high voltage was applied was 60%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 0.7%. . These results are summarized in Table 1.

(Example 7)
A conductive roller was prepared in the same manner as in Example 5 except that (5-3) and (5-4) in Example 5 were changed to the following (7-3) and (7-4). .
(7-3) Carbon black (Raven 860 Ultra manufactured by Columbia Chemical): 6 parts by mass,
(7-4) Carbon black (thermal carbon black N990 manufactured by Engineered Carbons): 12 parts by mass.

  When the ratio of the aggregated unit of carbon black and the occupied area was measured from the obtained conductive roller, 380 nm and 1210 nm were present at 1: 2. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 440 ° C. and 590 ° C., the temperature difference between P1 and P2 was 150 ° C., and P4 / P3 was 0.8. . Further, the hardness of the conductive roller was 59 °, and the rate of change in resistance when a high voltage was applied was 57%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 0.8%. . These results are summarized in Table 1.

(Example 8)
A conductive roller was prepared in the same manner as in Example 5 except that (5-3) and (5-4) in Example 5 were changed to the following (8-3) and (8-4). .
(8-3) Carbon black (Raven 860 Ultra manufactured by Columbia Chemical): 6 parts by mass,
(8-4) Silica (Admatechs Admafine SO-C3): 12 parts by mass.

  When the ratio of the aggregated unit of carbon black to the occupied area was measured from the obtained conductive roller, 380 nm and 900 nm were present at 1: 2. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 440 ° C. and 590 ° C., the temperature difference between P1 and P2 was 150 ° C., and P4 / P3 was 0.8. . Further, the hardness of the conductive roller was 59 °, and the rate of change in resistance when a high voltage was applied was 59%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 0.9%. . These results are summarized in Table 1.

Example 9
A conductive roller was produced in the same manner as in Example 1 except that (1-1) to (1-4) in Example 1 were changed to (9-1) to (9-4) below.
(9-1) Dimethylpolysiloxane having a weight average molecular weight of 10,000, in which vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 33 parts by mass,
(9-2) dimethylpolysiloxane having a weight average molecular weight of 740,000 wherein vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 67 parts by mass, (9-3) carbon Black (Raven 890 manufactured by Columbia Chemical): 6 parts by mass,
(9-4) Carbon black (Asahi Carbon Asahi 50H): 24 parts by mass.

  When the ratio of the aggregated unit of carbon black and the occupied area was measured from the obtained conductive roller, 230 nm and 590 nm were present at 1: 4. Moreover, the curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller has peaks of P1 and P2 at 360 ° C. and 580 ° C., the temperature difference between P1 and P2 is 220 ° C., and P4 / P3 is 0.7. . The hardness of the conductive roller was 60 °, and the rate of change in resistance when a high voltage was applied was 75%. Further, after a coating layer was formed in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the amount of fogging of a solid white image after outputting 10,000 sheets was measured to be 2.9%. . These results are summarized in Table 1.

(Comparative Example 1)
A conductive roller was produced in the same manner as in Example 1 except that (1-1) to (1-4) in Example 1 were changed to (Ratio 1-1) to (Ratio 1-2) below. .
(Ratio 1-1) Dimethylpolysiloxane having a weight average molecular weight of 10,000, in which vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 100 parts by mass,
(Ratio 1-2) Carbon black (Raven 860 Ultra manufactured by Columbia Chemical): 6 parts by mass.

  When the size of the aggregated unit of carbon black was measured from the obtained conductive roller, it was 380 nm. In the curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller, P1 was 360 ° C., but P2 was not present, and P4 / P3 was 0.0. The hardness of the conductive roller was 70 °, and the rate of change in resistance when a high voltage was applied was 74%. Further, after a coating layer was formed in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 4.3%. . These results are summarized in Table 2.

(Comparative Example 2)
In Comparative Example 1, a conductive roller was produced in the same manner as Comparative Example 1 except that (Ratio 1-1) was changed to (Ratio 2-1) below.
(Ratio 2-1) Dimethylpolysiloxane having a weight average molecular weight of 900,000: 100 parts by mass with vinyl groups substituted at both ends and 99 mol% or more of the main chain being a repeating unit of dimethylpolysiloxane.

  When the size of the aggregated unit of carbon black was measured from the obtained conductive roller, it was 380 nm. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had no P1, P2 was 590 ° C., and P4 / P3 was 0.1. The hardness of the conductive roller was 48 °, and the rate of change in resistance when a high voltage was applied was 92%. Further, after a coating layer was formed in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 6.0%. . These results are summarized in Table 2.

(Comparative Example 3)
In Comparative Example 1, a conductive roller was produced in the same manner as Comparative Example 1 except that (Ratio 1-1) was changed to (Ratio 3-1) below.
(Ratio 3-1) Dimethylpolysiloxane having a weight-average molecular weight of 500,000, wherein vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 100 parts by mass.

  When the size of the aggregated unit of carbon black was measured from the obtained conductive roller, it was 380 nm. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had neither P1 nor P2, and had a peak at 550 ° C. When this peak was P3, P4 / P3 was 0.2. The hardness of the conductive roller was 50 °, and the rate of change in resistance when a high voltage was applied was 85%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated into an electrophotographic process cartridge as a developing roller, and the amount of fogging of a solid white image after outputting 10,000 sheets was measured to be 5.1%. . These results are summarized in Table 2.

(Comparative Example 4)
In Comparative Example 1, a conductive roller was produced in the same manner as Comparative Example 1 except that (Ratio 1-1) was changed to (Ratio 4-1) to (Ratio 4-2) below.
(Ratio 4-1) Dimethylpolysiloxane having a weight average molecular weight of 100,000, in which a vinyl group is substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 95 parts by mass
(Ratio 4-2) Dimethylpolysiloxane having a weight average molecular weight of 2 million, in which vinyl groups are substituted at both ends and 99 mol% or more of the main chain is a repeating unit of dimethylpolysiloxane: 5 parts by mass.

  When the size of the aggregated unit of carbon black was measured from the obtained conductive roller, it was 380 nm. Moreover, the curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 460 ° C. and 650 ° C., the temperature difference between P1 and P2 was 190 ° C., and P4 / P3 was 0.8. . Further, the hardness of the conductive roller was 54 °, and the rate of change in resistance when a high voltage was applied was 82%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was 4.5%. . These results are summarized in Table 2.

(Comparative Example 5)
In Example 5, the conductive rollers were the same as Example 5 except that (5-3) and (5-4) were changed to the following (Ratio 5-1) and (Ratio 5-2), respectively. Was made.
(Ratio 5-1) Carbon black (Raven 890 manufactured by Columbia Chemical): 12 parts by mass,
(Ratio 5-2) Carbon black (Asahi Carbon Asahi 50H): 6 parts by mass.

  When the size of the aggregated unit of carbon black and the ratio of the occupied area were measured from the obtained conductive roller, 230 nm and 590 nm were present at 2: 1. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 440 ° C. and 590 ° C., the temperature difference between P1 and P2 was 150 ° C., and P4 / P3 was 0.8. . Further, the hardness of the conductive roller was 60 °, and the rate of change in resistance when a high voltage was applied was 78%. Further, after forming a coating layer in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 4.4%. . These results are summarized in Table 2.

(Comparative Example 6)
In Example 5, the conductive rollers were the same as Example 5 except that (5-3) and (5-4) were changed to the following (Ratio 6-1) and (Ratio 6-2), respectively. Was made.
(Ratio 6-1) Carbon black (Raven 3600 Ultra manufactured by Columbia Chemical): 6 parts by mass,
(Comparative 6-2) Carbon black (Asahi Carbon Asahi 50H): 24 parts by mass.

  When the ratio of the aggregated unit of carbon black to the occupied area was measured from the obtained conductive roller, 180 nm and 590 nm were present at 1: 4. The curve obtained by differentiating the thermogravimetric decrease curve of the conductive roller had P1 and P2 peaks at 440 ° C. and 590 ° C., the temperature difference between P1 and P2 was 150 ° C., and P4 / P3 was 0.8. . The hardness of the conductive roller was 69 °, and the rate of change in resistance when a high voltage was applied was 69%. Further, after a coating layer was formed in the same manner as in Example 1, it was incorporated in an electrophotographic process cartridge as a developing roller, and the fogging amount of a solid white image after outputting 10,000 sheets was measured to be 4.0%. . These results are summarized in Table 2.

It is a schematic sectional drawing which shows an example of the electroconductive roller of this invention. It is a schematic perspective view which shows an example of the electroconductive roller of this invention. It is the schematic by which carbon black is fixed to the network structure of polysiloxane. It is explanatory drawing which shows the relationship of each peak in this invention. It is explanatory drawing of the method of measuring the magnitude | size of the aggregation unit in this invention. It is a schematic block diagram which shows an example of the manufacturing apparatus applied to formation of the elastic layer of this invention. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention. It is the schematic which shows the evaluation method of the resistance stability of the electroconductive roller in the Example of this invention.

Explanation of symbols

1: shaft core body 2: elastic layer 3: coating layer 4: mount 5: column 6: precision ball screw 7: linear guide 8: LM guide 9: servo motor 10: pulley 11: coating head 12: bracket 13: under the work Holder 14: Workpiece holder 15: Supply port 16: Pipe 17: Material supply port 18: Electrophotographic process cartridge 19: Photoconductive drum 20: Charging roller 21: Image exposure device 22: Developing device 23: Cleaning device 24: Image Transfer device 25: toner 26: developing container 27: developing roller 28: toner supply roller 29: developing blade 30: transfer material 31: transfer conveying belt 32: driving roller 33: tension roller 34: driven roller 35: electrostatic adsorption roller 36 : Transfer roller 37: Fixing device

Claims (8)

A shaft core,
In a conductive roller having a conductive elastic layer made of a cured product of a silicone rubber composition formed around the shaft core body,
The elastic layer is
(A) a silicone rubber containing a dimethylpolysiloxane skeleton;
(B) carbon black having a size of aggregated unit of 230 nm or more and 380 nm or less;
(C) carbon black or an inorganic filler having an aggregate unit size of 590 nm to 1210 nm,
Including
The ratio of the occupied area of the component (b) and the component (c) is 1: 1 or more and 1: 4 or less,
And about a curve obtained by differentiating the thermogravimetric decrease curve obtained when the elastic layer is heated from 25 ° C. to 20 ° C./min in a nitrogen atmosphere, within a low temperature range of 360 ° C. or more and 520 ° C. or less, Having at least one peak in each of the high temperature side temperature range of 580 ° C. or more and 650 ° C. or less,
The peak height of the maximum temperature within the low temperature range is P1max (wt% / ° C),
P2min (wt% / ° C) as the peak height of the lowest temperature within the high temperature range.
When P1max and P2min have a low peak height of P3 (wt% / ° C), and a minimum portion between 520 ° C and 580 ° C is P4 (wt% / ° C),
0.0 ≦ P4 / P3 ≦ 0.9
A conductive roller characterized by the above.   The conductive roller according to claim 1, wherein a temperature difference between the P1max and the P2min is 90 ° C or higher and 290 ° C or lower.   The total content of the component (b) and the component (c) in the elastic layer is 12 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the component (a). The conductive roller according to claim 1 or 2. The silicone rubber composition is
A first polysiloxane having at least one alkenyl group at the end and having a weight average molecular weight of 60,000 to 100,000, wherein 99 mol% or more of the main chain is a repeating unit of dimethylsiloxane;
The second polysiloxane having at least one alkenyl group at the terminal and having a weight average molecular weight of 900,000 to 2,000,000 and having a repeating unit of dimethylsiloxane of 99 mol% or more of the main chain is in a mass ratio of 1: The conductive roller according to any one of claims 1 to 3, wherein the conductive roller is contained in a ratio of 1 to 19: 1.   The elastic layer is obtained by applying a coating liquid for forming the elastic layer using a ring-shaped coating head to the periphery of the shaft core, followed by heat curing. The conductive roller according to any one of 1 to 4.   The conductive roller according to claim 1, wherein the conductive roller is a developing roller.   A developing roller is mounted, a thin layer of toner is formed on the surface of the developing roller, the toner is supplied to the surface of the photosensitive drum by bringing the developing roller into contact with the photosensitive drum, and the surface of the photosensitive drum An electrophotographic process cartridge for forming a toner image on an electrophotographic process cartridge, wherein the developing roller is the developing roller according to claim 6.   A developing roller is mounted, a thin layer of toner is formed on the surface of the developing roller, the toner is supplied to the surface of the photosensitive drum by bringing the developing roller into contact with the photosensitive drum, and the surface of the photosensitive drum An image forming apparatus for forming a toner image on the image forming apparatus, wherein the developing roller is the developing roller according to claim 6.

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