JP4577530B2 - Developing roller, developing device, image forming apparatus, and developing roller manufacturing method - Google Patents

Description

  The present invention relates to a technical field of a developing roller having a concavo-convex portion on an outer peripheral surface and conveying toner to a latent image carrier, a developing device having the developing roller, an image forming apparatus including the developing device, and a method of manufacturing the developing roller. .

Conventionally, in a developing device that develops an electrostatic latent image with a non-magnetic one-component toner, a charge is imparted to the toner by frictional charging on the developing roller. As this developing roller, there is known a developing roller having a concavo-convex portion on the outer peripheral surface and a flat or substantially flat surface of the convex portion (for example, see Patent Document 1). The toner is effectively frictionally charged on the developing roller by the uneven portion. As shown in FIG. 10A, the developing roller a includes a base material b and a surface layer c obtained by coating the surface of the base material b with plating or the like.
JP2007-121948A.

  In general, a toner supply roller and a toner regulating member are in contact with the developing roller a (not shown). Further, silica having high hardness is used as one of external additives for coating the toner base particles. On the other hand, on the outer peripheral surface of the base material b, a plurality of base material concavo-convex portions including base material concave portions d and base material convex portions e are formed. And the surface layer c is also formed with a plurality of substrate irregularities consisting of recesses f and projections g corresponding to these substrate recesses d and substrate projections e.

  By the way, the surface layer c is worn by the toner supply roller, the toner regulating member or the toner particles by the image formation. On the other hand, in recent years, there has been a demand for higher image quality and a reduction in toner usage, and as a result, the diameter of toner has become smaller. When image formation is performed for a long period of time using this small particle size toner, the surface layer of the concave portion f hardly wears as shown in FIG. 10B, whereas the surface layer of the top portion h of the convex portion g It wears relatively large and almost flat. As described above, when the wear state and the wear amount are different between the concave portion f and the convex portion g, the depth of the concave and convex portions is reduced by long-term image formation. For this reason, the amount of toner conveyed by the developing roller decreases, and it becomes difficult to maintain the image density, and it is difficult to perform good development over a long period of time.

  The present invention has been made in view of such circumstances. The object of the present invention is to perform good development over a long period of time by suppressing the decrease in the depth of the uneven portions as much as possible even when an image is formed over a long period of time. The present invention provides a developing roller, a developing device, an image forming apparatus, and a method for manufacturing the developing roller.

To attain the above object, according to the developing low la according to the present invention, a flat in the axial direction together is formed between the substrate recess and the substrate recess consists formed continuously inclined substrate groove A base material having a base material convex portion having a flat portion, a concave portion formed of an inclined groove corresponding to the base material concave portion and continuously formed on the outer peripheral surface of the base material, and a base material convexity on the outer peripheral surface of the base material. At least a surface layer having a convex portion having a flat top portion in the axial direction, and the surface hardness of the flat top portion of the convex portion is larger than the surface hardness of the concave portion. Therefore, it is possible to suppress the abrasion of the surface layer at the flat top portion of the convex portion that is relatively easily worn during long-term image formation. As a result, the difference in wear between the surface layer of the concave portion with relatively little wear and the surface layer at the flat top portion of the convex portion can be reduced as compared with the conventional developing roller. That is, even if image formation is performed over a long period of time, it is possible to suppress a change in the depth of the uneven portion of the developing roller. As a result, the amount of toner conveyed by the developing roller hardly changes, and the image density can be maintained substantially constant over a long period of time. Therefore, good development can be performed over a long period of time.

In addition, by reducing the surface hardness of the concave portion of the developing roller so that the surface layer can be actively scraped, filming caused by deteriorating toner staying in the concave portion having poor resetability of the toner supply roller can be prevented. . Furthermore, the recess the toner charging property because the distance from the toner regulating blade is far away tends to deteriorate, to maintain the recess in the amorphous, it is possible to suppress the reduction of the toner chargeability. As a result, toner fog and toner scattering can be suppressed, and good development characteristics can be obtained.
In the toner transport method in which the toner is not transported to the surface of the convex portion by the toner regulating member, the function of the concave portion for ensuring the toner chargeability on the surface of the concave portion and the wear resistance on the surface of the convex portion (the depth of the concave and convex portion). It is possible to achieve both functions by separating the function of the convex part (maintain).

  In addition, the toner chargeability at the top can be reduced by crystallizing the top of the convex portion. On the contrary, since the toner charging property is not good, it is possible to prevent excessive charging (charge-up) due to rubbing between the toner regulating blade and the convex portion of the developing roller, and it is possible to improve development debris. Also, in the method of using toner having a particle size smaller than the unevenness of the developing roller, applying the tip of the toner regulating blade to the developing roller, conveying the toner to the concave portion of the developing roller, and not conveying the toner to the convex portion This makes it possible to more effectively suppress toner on the convex portion, and to prevent toner filming and excessive charging on the convex flat surface.

Further, the convex and concave portions of the surface layer are made of the same material, and the convex portions and the concave portions are made to have different crystallization degrees (for example, the crystallization degree of the convex portions is made higher than the crystallization degree of the concave portions). And the surface hardness and electrical resistance of the recess can be controlled. In that case, each surface layer of a convex part and a recessed part is made not to crystallize completely. Thereby, the surface composition of the developing roller can be easily created. In particular, if the hardness of the convex portion is increased and the wear is reduced too much, filming in which the toner is fused occurs, but the occurrence of this filming can be suppressed by controlling the degree of crystallization.
Furthermore, the surface layer of the convex portion is locally heated so that it hardly affects the crystallization of the base material. Accordingly, it is possible to prevent the base material from being warped or bent due to stress release of the base material or a change in crystallinity.

  Furthermore, by setting the range in which the crystallization of the convex portion proceeds to be within the average particle diameter of the toner to be used from the upper surface of the convex portion, the toner conveyed to the concave portion where chargeability is likely to be lowered is made amorphous. It can be made to contact a certain recessed part. Accordingly, it is possible to prevent a decrease in toner charge. That is, the toner can be charged more effectively by making the toner chargeability of the concave portion higher than the chargeability of the convex portion.

  Furthermore, by forming a surface layer on the substrate by electroless plating before forming the uneven portion on the base material, even if a material that is relatively difficult to process is used for the base material, The shape stability of can be improved. Thereby, the smoothness of the surface of the concavo-convex portion can be improved, the rolling properties of the toner particles are improved, and the toner filming at the concavo-convex portion can be suppressed. Therefore, the toner transportability and the toner chargeability can be maintained better over a long period of time.

On the other hand, according to the developing device having the developing roller of the present invention, the electrostatic latent image on the latent image carrier can be developed satisfactorily over a long period of time. Furthermore, an image forming apparatus provided with this developing device can form a stable and good image quality over a long period of time.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram schematically illustrating an example of an embodiment of an image forming apparatus according to the present invention.
As shown in FIG. 1, the image forming apparatus 1 of this example basically has the same configuration as the conventional image forming apparatus 1 described in Patent Document 1 described above. First, the same configuration as that of the conventional image forming apparatus 1 will be described.

  The apparatus main body 2 is provided with a photoreceptor 3 which is a latent image carrier provided so as to be rotatable in the clockwise rotation direction α in FIG. A charging device 4 is provided in the vicinity of the outer periphery of the photoreceptor 3. Further, in the vicinity of the outer periphery of the photoconductor 3, a rotary developing unit 5, a primary transfer device 6, and a cleaning device 7, which are developing devices, are arranged in this order from the charging device 4 toward the rotation direction α of the photoconductor 3. Has been. The rotary developing unit 5 includes a developing device 5Y for yellow, a developing device 5M for magenta, a developing device 5C for cyan, and a developing device 5K for black. Each of these developing devices 5Y, 5M, 5C, and 5K is detachably supported by a rotary 5a that is provided to be rotatable about a central axis in a rotation direction β (counterclockwise in FIG. 1). Further, an exposure device 8 is disposed below the charging device 4 and the cleaning device 7.

  Further, the image forming apparatus 1 includes an endless belt-shaped intermediate transfer belt 9 that is an intermediate transfer medium. The intermediate transfer belt 9 is stretched around a belt driving roller 10 and a driven roller 11. A rotational driving force of a motor (not shown) is transmitted to the belt driving roller 10. The intermediate transfer belt 9 is rotated in the rotation direction γ (counterclockwise in FIG. 1) while being pressed against the photoreceptor 2 by the primary transfer device 6 by the belt driving roller 10.

  A secondary transfer device 12 is provided on the belt driving roller 10 side of the intermediate transfer belt 9. A transfer material cassette 13 in which a sheet-like transfer material such as transfer paper (not shown; corresponding to the transfer medium of the present invention) is stored is provided below the exposure device 8. Further, a pickup roller 15 and a gate roller pair 16 are provided in the vicinity of the secondary transfer device 12 in the transfer material conveyance path 14 from the transfer material cassette 13 to the secondary transfer device 12.

  A fixing device 17 is provided above the secondary transfer device 12. The fixing device 17 includes a heating roller 18 and a pressure roller 19 that is pressed against the heating roller. Further, a waste transfer material tray 20 is provided on the upper portion of the apparatus main body 2. Further, a pair of discharge transfer material rollers 21 is provided between the fixing device 17 and the discharge transfer material tray 20.

  In the image forming apparatus 1 of this example configured as described above, for example, a yellow electrostatic latent image is first applied to the photoreceptor 3 uniformly charged by the charging device 4 by, for example, the laser light L of the exposure device 8. Formed. The yellow electrostatic latent image on the photoreceptor 3 is developed by yellow toner of the yellow developing device 5Y positioned at the development position shown in the figure by the rotation of the rotary 5a. Thus, a yellow toner image is formed on the photoreceptor 3. This yellow toner image is transferred to the intermediate transfer belt 9 by the primary transfer device 6. The toner remaining on the photoreceptor 3 after the transfer is scraped off by a cleaning blade of the cleaning device 7 and collected.

  Next, a magenta electrostatic latent image is formed by the exposure device 8 on the photoconductor 3 uniformly charged again by the charging device 4 as described above. The magenta electrostatic latent image is developed with magenta toner of the magenta developing device 5M positioned at the development position. The magenta toner image on the photoreceptor 3 is transferred onto the intermediate transfer belt 9 by the primary transfer device 6 while being superimposed on the yellow toner image. The toner remaining on the photoreceptor 3 after the transfer is collected by the cleaning device 7. Thereafter, similarly for cyan and black, toner images are sequentially formed on the photosensitive member 3, and these toner images are sequentially transferred onto the intermediate transfer belt 9 while being superimposed on the previously transferred toner image. Thus, a full-color toner image is formed on the intermediate transfer belt 9. Similarly, each toner remaining on the photoreceptor 3 after the transfer is collected by the cleaning device 7.

  The full-color toner image transferred to the intermediate transfer belt 9 is transferred by the secondary transfer device 12 to the transfer material conveyed from the transfer material cassette 13 through the transfer material conveyance path 14. At this time, the transfer material is conveyed to the secondary transfer device 12 by the gate roller pair 16 at the timing of the full color toner image on the intermediate transfer belt 9.

  The toner image fixed on the transfer material is heated and pressure-fixed by the heating roller 18 and the pressure roller 19 of the fixing device 12. The transfer material on which the image is formed in this way is conveyed through the transfer material conveyance path 14 and is discharged and stored in the waste transfer material tray 20 by the waste transfer material roller pair 21.

Next, the structure of the characteristic part of the image forming apparatus 1 of this example will be described.
The developing devices 5Y, 5M, 5C, and 5K for the respective colors in the image forming apparatus 1 of this example all have the same configuration. Therefore, in the following description of the developing devices 5Y, 5M, 5C, and 5K, the reference numerals Y, M, C, and K of each color are omitted. In this case, the developing device is denoted by reference numeral 5 ′ so as to be distinguished from the rotary developing unit 5.

FIG. 2 is a cross-sectional view taken along a direction orthogonal to the longitudinal direction of the developing device according to the embodiment of the present example.
The developing device 5 'in this example is formed in a long container shape. As shown in FIG. 2, the developing device 5 ′ includes a toner housing portion 23, a toner supply roller 24, a developing roller 25, and a toner regulating member in a long housing 22 like the developing device described in Patent Document 1 described above. 26. The toner container 23, the toner supply roller 24, the developing roller 25, and the toner regulating member 26 are extended along the longitudinal direction of the developing device 5 ′ (direction perpendicular to the paper surface in FIG. 2).

  The toner storage unit 23 is divided into two first and second toner storage units 23 a and 23 b by a partition wall 27. In that case, the toner accommodating portion 23 is formed as a communicating portion 23c in which the upper portions of the first and second toner accommodating portions 23a and 23b in FIG. 2 communicate with each other. In this state, the movement of the toner 28 between the first and second toner accommodating portions 23a and 23b is suppressed by the partition wall 27. When the rotary 5a of the rotary developing unit 5 rotates and the developing device 5 'is turned upside down as shown in FIG. 2, the toner 28 accommodated in the first and second toner accommodating portions 23a and 23b is connected to the communicating portion. Move to the 23c side. When the rotary 5a further rotates and the developing device 5 'is in the state shown in FIG. 2, the toner 28 moves again to the first and second toner accommodating portions 23a and 23b. As a result, a part of the toner 28 previously stored in the first toner storage portion 23a moves into the second toner storage portion 23b, and the toner 28 previously stored in the second toner storage portion 23b. A part of the toner moves into the first toner container 23a, and the toner 28 in the toner container 23 is mixed and stirred. The toner 28 is a non-magnetic one-component toner whose toner base particles are coated with an external additive. In that case, at least silica is used as an external additive in the present invention.

  A toner supply roller 24 is provided at the lower portion of the first toner storage portion 23a in FIG. 2 so as to be rotated clockwise in FIG. Further, a developing roller 25 is provided outside the handling 22 so as to be able to rotate counterclockwise in FIG. The developing roller 25 is provided close to the photoconductor 3 (without contact). The developing roller 25 is in contact with the toner supply roller 24 through the opening 22a of the housing 22 with a predetermined contact pressure. Further, a toner regulating member 26 is provided on the housing 22. The toner regulating member 26 is in contact with the developing roller 25 at a position downstream of the developing roller 25 in the rotation direction with respect to the nip portion (contacting portion) between the developing roller 25 and the toner supply roller 24. Thus, the toner regulating member 26 regulates the layer thickness of the toner 28 supplied from the toner supply roller 24 to the developing roller 25. Therefore, the toner 28 regulated by the toner regulating member 26 is conveyed toward the photosensitive member 3 by the developing roller 25. Then, the electrostatic latent image on the photoreceptor 3 is developed in a non-contact manner by the toner 28 conveyed by the developing roller 25, and a toner image of each color is formed on the photoreceptor 3.

  As shown in FIG. 3A, a net-like uneven pattern is formed on the outer peripheral surface of the developing roller 25 as in the developing roller described in Patent Document 1 described above. In the developing roller 25 of this example, a groove 29 is formed over the entire circumference as a concave / convex pattern at a predetermined position in the axial direction of the outer peripheral surface. In that case, the groove 29 is formed continuously in a spiral shape with a predetermined angle (45 ° in the illustrated example, but not limited to this) with respect to the axial direction of the developing roller 25, and a predetermined number having regularity. The first inclined grooves 29a, and the first inclined grooves 29a and a predetermined number of second inclined grooves 29b that are continuously spirally inclined in the opposite direction. These first and second inclined grooves 29a and 29b are each formed with a predetermined pitch interval p in the inclined direction and a predetermined width W in the axial direction. Note that the inclination angles and the pitches of the first and second inclined grooves 29a and 29b may be different from each other.

  As shown in FIG. 3B, the developing roller 25 includes a base material 25a and a surface layer 25b formed on the outer peripheral surface of the base material 25a. The substrate 25a is made of a sleeve made of a metal material such as an aluminum-based material such as 5056 aluminum alloy or 6063 aluminum alloy, or an iron-based material such as STKM. The surface layer 25b is made of a plating layer such as nickel plating or chrome plating applied on the substrate 25a.

  As shown in FIG. 3C, on the outer peripheral surface of the base material 25a of the developing roller 25, there are first and second inclined base material grooves 29a 'for forming first and second inclined grooves 29a, 29b. 29b 'is formed by rolling. As the processing method of the first and second inclined base material grooves 29a ′ and 29b ′ in this base material, a conventionally known processing method can be adopted. Therefore, description of this processing method is omitted. A predetermined number of island-shaped base material protrusions 30 ′ surrounded by the first and second inclined base material grooves 29 a ′ and 29 b ′ are formed on the outer peripheral surface of the base material 25 a. In the present invention, the base material concave portion refers to the base material 25a side from the half of the depth of the first and second inclined base material grooves 29a 'and 29b', and the base material convex portion 30 'is the first and second base material grooves 30'. The side which protrudes outside the base material 25a from the half of the depth of 2nd inclination base material groove | channels 29a 'and 29b' is said.

  As shown in FIG. 3C and FIG. 4, the top of the base material protrusion 30 ′ is formed on the base material flat portion 30 a ′. The shape of the substrate flat portion 30a ′ of each substrate protrusion 30 ′ is such that the inclination angles of the first and second inclined substrate grooves 29a ′ and 29b ′ are 45 ° and the pitch p thereof is the same. In the case where the first and second inclined base grooves 29a 'and 29b' are inclined at angles other than 45 ° and their pitches p are set to be equal to each other, the rhombus is formed. Presents. Further, the shape of the substrate flat portion 30a ′ of each substrate protrusion 30 ′ is such that the inclination angles of the first and second inclined substrate grooves 29a ′ and 29b ′ are 45 ° and their pitches p are different from each other. Is set to be rectangular, and the inclination angles of the first and second inclined substrate grooves 29a 'and 29b' are other than 45 ° and their pitches p are set to be different from each other. Exhibits a parallelogram shape. The base flat part 30a ′ is formed in a truncated quadrangular truncated pyramid shape with the four side walls being inclined on the base flat part 30a ′ side of the base convex part 30 ′ in any quadrilateral shape. Yes.

  The portions constituting the substrate recesses of the first and second inclined substrate grooves 29a ′ and 29b ′ are respectively formed in the curved recesses of the sinusoidal concave surface along the tilt direction. Then, the four side walls of the truncated quadrangular pyramid shape of the base material convex portion 30 ′ are continuously formed on the four side walls of the sinusoidal curved concave portion of the base material concave portion. At this time, the point at which the four side walls of the truncated quadrangular pyramid shape of the base material convex portion 30 ′ and the four side walls of the base material concave portion of the sine wave shape are continuous is half the depth of the concave and convex portions. .

  Applying plating such as nickel-based electroless plating to the outer peripheral surface of the substrate 25a on which the first and second inclined substrate grooves 29a 'and 29b' and the substrate flat portion 30a 'of the substrate protrusion 30' are formed. Thus, the surface layer 25b is formed on the surface of the substrate 25a. The surface layer 25b has concave and convex portions of the first and second inclined grooves 29a and 29b having the same shape as the concave and convex portions of the first and second inclined base grooves 29a 'and 29b'. 30 is formed.

  The convex portion 30 has a quadrilateral flat top portion 30a. Further, in the state where the surface layer 25b is formed on the base material 25a, the top 30a side of the first and second inclined grooves 29a, 29b is formed in a truncated quadrangular pyramid shape with the four side walls inclined. Yes. And the four side walls of the truncated quadrangular frustum shape are formed continuously to the four side walls of the sine wave shape on the recess side of the first and second inclined grooves 29a and 29b, respectively.

  Furthermore, in the developing roller 25 of this example, the surface hardness of the surface layer 25b at the top 30a of the convex portion 30 is formed in a high hardness portion 30a ″ that is larger than the surface hardness of other portions. The range of the protrusion 30 where 30a ″ is formed (depth t from the top surface of the protrusion 30) is set within the average particle diameter of the toner used. Further, the toner chargeability of the surface layer 25b other than the high hardness portion 30a ″ including the concave portions of the first and second inclined grooves 29a and 29b is higher than the toner chargeability of the high hardness portion 30a ″.

  On the other hand, the present inventor has shown that the surface layer 25b of the convex portion 30 of the developing roller 25 wears relatively large and flat as shown in FIG. The phenomenon in which the surface layer 25b of the concave portions 29a and 29 is almost worn was examined through further durability experiments. The wear shape was measured with Keyence VK-9500, which is a three-dimensional measurement laser microscope. The image forming apparatus used in the experiment is an LP9000C printer manufactured by Seiko Epson Corporation. Then, instead of the developing roller used in this printer, the following developing roller 25 was used. In that case, in order to make this developing roller 25 usable, a printer of Seiko Epson LP9000C was modified. The image forming conditions in the durability experiment are standard image forming conditions for the LP9000C printer.

  Using a STKM material for the base material 25a of the developing roller 25, the surface finish of the base material 25a was performed by centerless processing before processing the concavo-convex portion on the base material 25a. Next, first and second inclined base material grooves 29a 'and 29b' were formed in the base material 25a by rolling. Next, as the surface layer 25b, a plating layer having a thickness of 3 μm was formed on the substrate surface by electroless nickel-phosphorus (Ni—P) plating. At this time, as shown in FIG. 5A, the uneven portion of the developing roller 25 has an uneven depth (height from the bottom of the grooves 29a and 29b to the upper surface of the protruded portion 30) of 6 μm, an uneven pitch of 100 μm, and an uneven depth. The width of the convex portion 30 at a half line was 60 μm, and the width of the concave portions (grooves 29a and 29b) at a half line of the concave / convex depth was 40 μm.

  Further, the toner supply roller 24 is formed of a urethane foam roller and is installed with a biting amount of 1.5 mm with respect to the developing roller 25. Further, the toner regulating member 26 is constituted by a blade made of urethane rubber, and is installed at a contact pressure of 40 g / cm against the developing roller 25.

  Further, two types of toner are used. One of these toners is composed of polyester particles produced by a pulverization method with appropriate amounts of CCA, WAX, and pigment added therein to form toner mother particles. The toner mother particles have 20 nm small particle size silica and 40 nm medium particles. This is a small-diameter toner having an average particle diameter D50 of 4.5 μm and an unevenness depth of less than 6 μm by externally adding diameter silica, 100 nm large particle diameter silica, and 30 nm titania. In another toner, WAX and a pigment are added in appropriate amounts to styrene acrylic particles produced by a polymerization method to form toner mother particles, and the toner mother particles have 20 nm small particle size silica and 40 nm medium particles. This is a small-diameter toner having an average particle diameter D50 of 4.5 μm, which is the same as that of the toner described above, by externally adding diameter silica, 100 nm large particle diameter silica, and 30 nm titania.

  Then, an endurance image formation experiment was conducted on a standard pattern image formation of LP9000C with a monochrome character pattern having a monochrome image occupation ratio of 5% on A4 plain paper. As a result of this experiment, the top portion 30a of the surface layer 25b of the convex portion 30 having the initial profile shown by the solid line in FIG. 5B is flat as shown by the one-dot chain line as the number of image formation increases. The profile tended to wear out. Such a flat wear profile of the convex portion 30 tended to wear to a similar curved profile even when the second small particle size toner described above was used.

  The reason is considered as follows. In FIG. 6A, the toner particles positioned on the flat surface 30a of the convex portion 30 are first and first moved by the toner supply roller 24 and the toner regulating member 26 that are pressed against the developing roller 25 as the developing roller 25 rotates. 2 respectively move into the inclined grooves 29a, 29b. At this time, as the developing roller 25 rotates in FIG. 6A, the toner particles located at the top 30a of the convex portion 30 move into the first and second inclined grooves 29a and 29b, respectively. At this time, since the average particle diameter (D50 particle diameter) of the toner particles is smaller than the depth of the concavo-convex portion, the particles of the toner 28 moved into the first and second inclined grooves 29a and 29b become a plurality of layers. Further, as the developing roller 25 rotates, the toner particles located in the first and second inclined grooves 29 a and 29 b move to the top portion 30 a of the convex portion 30. At this time, since the position of the toner particles in the uppermost layer is substantially the same height as the top portion 30a of the convex portion 30, among the particles of the toner 28 located in the first and second inclined grooves 29a and 29b, Mainly, the toner particles in the uppermost layer move substantially laterally, and the toner particles in the lower layer hardly move. By the lateral movement of the toner particles of the uppermost layer, the surface of the surface layer 25b is gradually worn over a long period of time by a relatively hard external additive on the surface of the toner particles.

  6A and 6B are cross-sectional views along the inclination direction of the first and second inclined grooves 29a and 29b, similarly to FIG. 3B. For this reason, the partial cross sections of these developing rollers 25 are different from the rotation direction of the developing rollers 25. Therefore, the toner particles located in the first inclined groove 29a move onto the top portion 30a of the convex portion 30, and the toner on the top portion 30a thereafter moves to any of the first and second inclined grooves 29a, 29b adjacent to the top portion 30a. Will also move to. Further, the toner particles located in the second inclined groove 29a move onto the top portion 30a of the convex portion 30, and the toner on the top portion 30a then moves to any of the first and second inclined grooves 29a, 29b adjacent to the top portion 30a. Will also move to. The same applies to the description of other examples below.

An example of a method for manufacturing the developing roller 25 configured as described above will be described.
As shown in FIG. 7A, first and second inclined base material grooves 29a 'and 29b' are formed on the base material 25a by rolling. Next, as shown in FIG. 7B, an amorphous surface layer 25b is formed by electroless plating on the surface of the substrate 25a on which the first and second inclined substrate grooves 29a 'and 29b' are formed. Form. Thereby, the first and second inclined grooves 29a and 29b are formed corresponding to the first and second inclined base grooves 29a 'and 29b'. At this time, the top 30a side is a convex portion 30 from one half of the depth of the first and second inclined grooves 29a, 29b, and is more than half of the depth of the first and second inclined grooves 29a, 29b. The material 25a side (opposite side from the top 30a) is a recess. In this case, the hardness of the surface layer 25b is set higher than the hardness of the base material 25a.

  Next, as shown in FIG. 7C, the surface layer 25b at the apex 30a of the convex portion 30 is heated by an ion beam or local heating to cause surface crystallization. At this time, the depth t from the top surface of the top portion 30a in the surface crystallized portion (high hardness portion 30a ″) of the surface layer 25b is the average particle diameter (D50) of the toner used in the developing device 5 ′ having the developing roller 25. The surface hardness of the surface crystallized portion (high hardness portion 30a ″) of the surface layer 25b is the surface layer of the other portion including the concave portions of the first and second inclined grooves 29a, 29b. It is larger than the surface hardness of 25b. Further, the toner chargeability of the surface layer 25b other than the surface crystallized portion (high hardness portion 30a ″) of the surface layer 25b including the concave portions of the first and second inclined grooves 29a, 29b is the high hardness portion 30a. It is higher than the toner chargeability of ″.

Furthermore, another example of the manufacturing method of the developing roller 25 of this example will be described.
As shown in FIG. 8A, an amorphous surface layer 25b is formed on the surface of the substrate 25a by electroless plating. In this case, the hardness of the surface layer 25b is set higher than the hardness of the base material 25a. Next, as shown in FIG. 8B, the amorphous surface layer 25b is completely crystallized by annealing. The annealing temperature at this time is, for example, 300 ° C. or more, but is not more than the heat treatment temperature of the substrate 25a. Next, as shown in FIG. 8C, first and second inclined grooves 29a and 29b are formed on the surface of the base material 25a having the crystallized surface layer 25b by rolling. At this time, the top 30a side is a convex portion 30 from one half of the depth of the first and second inclined grooves 29a, 29b, and is more than half of the depth of the first and second inclined grooves 29a, 29b. The material 25a side (opposite side from the top 30a) is a recess. And the formation part of the 1st and 2nd inclination groove | channels 29a and 29b in the crystallized surface layer 25b becomes amorphous again by the rolling by a rolling process. Therefore, the surface hardness of the crystallized surface layer 25b of the top portion 30a is greater than the surface hardness of the re-amorphized surface layer 25b. Thus, the developing roller 25 of this example is formed.

Next, a specific example of the developing roller 25 of the present invention will be described.
Using a STKM material having a hardness of Hv of 150 for the base material 25a of the developing roller 25, the surface finish of the base material 25a was performed by centerless processing before processing the uneven portion on the base material 25a. Next, a substrate uneven portion having a depth of 6 μm was formed on the surface of the substrate 25a by rolling. In that case, base material recessed part 29a ', 29b' (the bottom part side of the base material recessed part of base material convex part 30 ') is formed in a sine wave shape. Further, the top 30a ′ side of the base convex portion 30 ′ was formed in a truncated quadrangular pyramid shape. Then, the four side walls of the truncated quadrangular pyramid shape were continuously formed on the four side walls of the sinusoidal curved concave portions 29a ′ and 29b ′, respectively. At this time, the point where the four side walls of the truncated quadrangular truncated pyramid shape and the four side walls of the sine wave shape of the base material convex portion 30 ′ is a half point of the depth of the base material uneven portion. .

  As the surface layer 25b, a plating layer having a thickness t of 3 μm was formed on the substrate surface by electroless nickel-phosphorus (Ni—P) plating. At this time, the surface hardness of the surface layer 25b was 550 in Hv. Next, the surface layer 25b portion of the top portion 30a is heated by irradiating with an ion beam in a range where the depth t from the top surface of the convex portion 30 is 1.5 μm, thereby crystallizing the surface layer 25b portion. Turned into. At this time, the surface hardness of the crystallized surface layer 25b was 1000 in Hv. That is, the high hardness portion 30a ″ of the top portion 30a is larger than the surface hardness of the portion of the surface layer 25b other than the high hardness portion 30a ″.

  Next, an experiment was conducted on the toner chargeability and the surface potential of the developing roller in the developing roller of the present invention. The experiment is a toner charge amount measurement by a toner rubbing test and a surface potential test of the toner conveying surface of the developing roller.

  In the toner rubbing test, a sample plate in which a surface layer having a thickness of 3 μm was formed on an STKM material by electroless nickel-phosphorus (Ni—P) plating as a sample of the developing roller. The surface hardness of this sample plate was 550 in Hv. Further, another same sample plate was produced, and the surface layer of this sample plate was annealed at 400 ° C. for 2 hours to crystallize the surface layer. The surface hardness of this sample plate was 1000 in Hv. Accordingly, it was found that the hardness of the surface layer was increased by the annealing treatment.

  As the toner, the first toner described above was used. Further, a blade made of urethane rubber used for the toner regulating member 26 was prepared. Then, each sample plate was sprayed with toner, and the toner on each sample plate was rubbed with a urethane rubber blade. Thereafter, the charge amount of the rubbed toner was measured with a charge amount measuring device. After the number of rubbing was increased and rubbed every predetermined number of times, the charge amount of the toner was measured with a charge amount measuring device. The toner rubbing test result at this time is shown in FIG. As shown in FIG. 9A, it was found that the toner chargeability is better when the surface layer of the plating layer is not annealed.

  On the other hand, in the surface potential test on the toner conveying surface of the developing roller, an experimental developing cartridge that uses the above-described LP9000C printer as a driving experimental machine was used. In that case, the driving experimental machine and the experimental developing cartridge were modified so that the surface of the developing roller could be seen. Further, a sample developing roller in which a surface layer having a thickness of 3 μm is formed by electroless nickel-phosphorus (Ni—P) plating of the STKM material, and a sample developing roller in which the surface layer is annealed at 400 ° C. for 2 hours in the same manner as described above. One developing roller was prepared.

  As the toner, the first toner described above was used. Then, the experimental developing cartridge was set in the driving experimental machine, and the driving experimental machine was idled. Then, a part of the toner on the peripheral surface of the developing roller was removed to expose a part of the surface of the developing roller. Further, a surface potential meter was set on the developing roller. In this state, the developing roller was rotated to measure the potential difference between the toner removal unit and the toner viewing removal unit, and the recovery rate was observed in the surface transmission. The surface potential test at this time is shown in FIGS. 9B and 9C. As shown in FIGS. 9B and 9C, the surface potential of the developing roller is improved by starting the driving of the developing roller (DR). In that case, in each of the experimental results shown in FIGS. 9B and 9C, a peak value having a bad surface potential periodically appears periodically when the developing roller (DR) is driven. These portions having a bad peak value of the surface potential are portions where the toner is removed from the conveying surface. As a whole, the surface potential was better when the annealing treatment shown in FIG. 9B was not performed than when the annealing treatment shown in FIG. 9C was performed. That is, it was found that the surface potential recoverability of the toner conveying surface of the developing roller after toner development is deteriorated by the annealing treatment.

  Through these experiments, the surface of the top of the convex part is crystallized by annealing treatment, and its hardness is increased, and the surface of the concave part is not annealed and becomes amorphous, resulting in good toner chargeability. I understood.

  According to the developing roller 25 of these examples, the surface hardness of the high hardness portion 30a ″ of the top portion 30a of the convex portion 30 of the developing roller 25 is the portion constituting the concave portions of the first and second inclined grooves 29a and 29b. It is set to be larger than the surface hardness of the portion other than the high hardness portion 30a ″. Therefore, the wear of the surface layer 25a of the top portion 30a, which is relatively easily worn during long-term image formation, is suppressed, and the wear of the surface layer 25a of the recess is small. Therefore, the difference in wear between the convex portion and the concave portion can be reduced as compared with the conventional developing roller. Thereby, even if image formation is performed over a long period of time, the depth of the uneven portion of the developing roller 25 does not change much. As a result, the amount of toner conveyed by the developing roller 25 hardly changes, and the image density can be maintained substantially constant over a long period of time. Therefore, good development can be performed over a long period of time.

In addition, since the surface hardness of the concave portion of the developing roller 25 is small, it is possible to prevent filming that occurs in the concave portion having poor resetability. In addition, the toner chargeability tends to be deteriorated because the distance from the toner regulating blade 26 is long in the concave portion, but it is possible to suppress a decrease in toner chargeability by maintaining the concave portion in an amorphous state. That is, the toner can be charged more effectively by making the toner chargeability of the concave portion higher than the chargeability of the convex portion. As a result, toner fog and toner scattering can be suppressed, and good development characteristics can be obtained.
In the toner transport method in which toner is not transported to the surface of the convex portion 30 by the toner regulating member 26, the function of the concave portion for ensuring the toner charging property on the surface of the concave portion and the wear resistance on the surface of the convex portion (the depth of the concave and convex portion). Both functions can be achieved by separating the function of the convex part (maintenance of the thickness).

  Further, by crystallizing the top portion 30a of the convex portion 30, the toner chargeability at the top portion 30a is not so good. However, since the toner charging property is not good, it is possible to prevent excessive charging (charge-up) due to rubbing between the toner regulating blade 26 and the convex portion 30 of the developing roller 25, and to improve development rubble. be able to. Also, in the method of using toner having a particle size smaller than the unevenness of the developing roller, applying the tip of the toner regulating blade to the developing roller, conveying the toner to the concave portion of the developing roller, and not conveying the toner to the convex portion This makes it possible to more effectively suppress toner on the convex portion, and to prevent toner filming and excessive charging on the convex flat surface.

The concavo-convex part of the surface layer 25b is made of the same material, and the crystallization degree of the convex part and the concave part is made different (for example, the crystallization degree of the convex part is made higher than the crystallization degree of the concave part). It becomes possible to control the surface hardness and electrical resistance with the recess. In that case, each surface layer 25b of the convex portion and the concave portion is not completely crystallized (whether or not it is completely crystallized can be known by XRD analysis). Thereby, the surface composition of the developing roller can be easily created. In particular, when the hardness of the convex portion 30 is increased and the wear is reduced too much, filming in which the toner is fused occurs, but the occurrence of filming can be suppressed by controlling the degree of crystallization.
Furthermore, by locally heating the surface layer 25b of the convex part 30, there is almost no influence on the crystallization of the base material 25a. Therefore, the base material 25a can be prevented from warping or bending due to stress release from the base material 25a or a change in crystallinity.

  Furthermore, the range in which the crystallization of the convex portion 30 proceeds is within the average particle diameter (D50 particle diameter) of the toner used from the upper surface of the convex portion 30, so that it is conveyed to the concave portion where the chargeability tends to decrease. The toner can be brought into contact with a recess that is amorphous. Accordingly, it is possible to prevent a decrease in toner charge.

  Further, by forming the surface layer 25b on the base material 25a by electroless plating before forming the uneven portion on the base material 25a, even if a material that is relatively difficult to process is used for the base material 25a, the surface layer by this plating is used. The shape stability of the concavo-convex portion can be improved by 25b. Thereby, the smoothness of the surface of the concavo-convex portion can be improved, the rolling property of the toner particles is improved, and the toner filming at the concavo-convex portion can be suppressed. Therefore, the toner transportability and the toner chargeability can be maintained better over a long period of time.

  According to the developing device 5 ′ having the developing roller 25, the electrostatic latent image on the photoreceptor 3 can be favorably developed over a long period. On the other hand, the image forming apparatus 1 provided with the developing device 5 ′ can form an image with a good image quality having a stable density over a long period of time.

  In the present invention, the axial interval and the number of the second inclined grooves 29b are not necessarily the same as those of the first inclined grooves 29a and may be different. Further, the number of the first and second inclined grooves 29a and 22b can be one or more and an arbitrary number.

  In addition, when a toner using relatively hard silica as an external additive and having a silica coverage of 100% or more on the toner base particles, a large amount of silica is present on the surface of the toner base particles. Therefore, the wear rate of the surface layer 25b of the convex portion 30 becomes relatively faster. Therefore, even if the developing roller 25 of this example is used in the developing device 5 ′ using toner having a silica coverage of 100% or more, the durability of the developing roller 25 can be more effectively improved.

  Furthermore, the base material recess formed by the first and second inclined base material grooves 29a ′ and 29b ′ is not necessarily formed in a sine wave shape. The substrate recess can be formed with another curved surface, or can be formed in a reverse truncated quadrangular pyramid shape with a flat bottom. In that case, it forms so that it may continue to the truncated quadrangular frustum shape of a base-material convex part in the above-mentioned inflection point (position of about 1/2 of the depth of a base-material uneven part).

  Furthermore, in the above-described example, the present invention is applied to the image forming apparatus 1 having the rotary developing unit 5, but the present invention is not limited to this. In the present invention, for example, an image forming apparatus in which image forming units are arranged in tandem, a four-cycle image forming apparatus, a monochromatic image forming apparatus, or a toner image from a latent image carrier to a transfer material (to the transfer medium of the present invention). The present invention can be applied to any image forming apparatus including a developing device having a developing roller having at least a concavo-convex portion, such as an image forming apparatus that directly transfers to an equivalent) (that is, an image forming apparatus that does not include an intermediate transfer medium). it can. In short, the present invention can be applied to any image forming apparatus within the scope of the matters described in the claims.

1 is a diagram schematically illustrating an example of an embodiment of an image forming apparatus according to the present invention. It is sectional drawing which shows typically the image development apparatus shown in FIG. (A) is a figure which shows a developing roller, a toner supply roller, and a toner control member typically, (b) is a fragmentary sectional view which follows the IIIB-IIIB line in (a), (c) is a base material in (b) It is a fragmentary sectional view which shows only. It is a partial expanded sectional view in Drawing 3 (b) of a development roller. (A) The figure which shows the size of the uneven | corrugated | grooved part of a developing roller, (b) is a figure explaining the process of abrasion of a developing roller in case a toner particle size is larger than the depth of the uneven | corrugated | grooved part of a developing roller. (A) is a diagram for explaining the behavior of toner particles on the developing roller when the toner particle size is smaller than the depth of the uneven portion of the developing roller, and (b) is a diagram showing the state of wear of the developing roller in (a). . (A) thru | or (c) is a figure explaining an example of the manufacturing method of the developing roller shown in FIG.3 and FIG.4. (A) thru | or (c) is a figure explaining the other example of the manufacturing method of the developing roller shown in FIG.3 and FIG.4. (A) is a figure which shows a toner rubbing test result, (b) and (c) are figures which show a surface potential test result. (A) is a fragmentary sectional view of the uneven | corrugated | grooved part in the conventional developing roller, (b) is a fragmentary sectional view explaining abrasion of the convex part in (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 3 ... Photoconductor, 5 ... Rotary developing unit, 5Y, 5M, 5C, 5K, 5 '... Developing apparatus, 24 ... Toner supply roller, 25 ... Developing roller, 25a ... Base material, 25b ... Surface 26, toner regulating member, 28 ... toner, 29 ... groove, 29a ... first inclined groove, 29b ... second inclined groove, 29a '... first inclined substrate groove, 29b' ... second inclined substrate groove, 30 ... convex part, 30 ... top part, 30 '... base material convex part, 30a "... high hardness part

Claims (9)

A base material having a base material concave portion formed of an inclined base material groove formed continuously in a predetermined region of the outer peripheral surface and a base material convex portion formed between the base material concave portions and having a flat portion flat in the axial direction. And a recess formed of an inclined groove corresponding to the base material recess and continuously formed on the outer peripheral surface of the base material, and an axial direction formed on the outer peripheral surface of the base material corresponding to the base material convex portion. And at least a surface layer having a convex portion having a flat top,
The developing roller characterized in that the surface hardness at the flat top of the convex portion is larger than the surface hardness of the concave portion.   2. The developing roller according to claim 1, wherein in the toner charging property of the uneven portion, the charging property of the concave portion is higher than the charging property of the convex portion.   The developing roller according to claim 1, wherein the surface layer is formed by electroless plating.   The crystallization degree of the surface layer of the convex part is higher than the crystallization degree of the surface layer of the concave part among the surface layer of the concave part and the surface layer of the convex part. 2. The developing roller according to 1.   5. The developing roller according to claim 1, wherein neither the surface layer of the concave portion nor the surface layer of the convex portion is completely crystallized.   6. The development according to claim 1, wherein a range in a depth direction of the convex portion having a surface hardness larger than a surface hardness of the concave portion is within an average particle diameter of a toner to be used. roller. A developing roller that conveys toner to the latent image carrier, a toner supply roller that contacts the developing roller to supply the toner, and a toner amount that contacts the developing roller and conveys the toner to the latent image carrier are regulated. And at least a toner regulating member that
The developing roller is the developing roller according to any one of claims 1 to 6,
The developing device, wherein an average particle diameter of the toner is smaller than a depth of the concave portion of the developing roller. A developing roller that conveys toner to the latent image carrier, a toner supply roller that contacts the developing roller to supply the toner, and a toner amount that contacts the developing roller and conveys the toner to the latent image carrier are regulated. And at least a toner regulating member that
The developing roller is the developing roller according to any one of claims 1 to 6,
The average particle diameter of the toner is smaller than the depth of the concave portion of the developing roller, the toner regulating blade is an elastic body, and the tip of the toner regulating blade is in contact with the developing roller, or the toner is in the regulating nip. A developing device having a tip of a regulating blade. A latent image carrier on which at least an electrostatic latent image is formed; a developing device for developing the electrostatic latent image with toner by non-contact development to form a toner image on the latent image carrier; and the latent image carrier At least a transfer device for transferring the toner image to a transfer medium,
Imaging equipment, wherein the developing device is a developing device according to claim 8.

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