JP2007121567A - Developing device and image forming apparatus using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of suppressing the occurrence of a ghost due to the developing hysteresis of a developer carrier by noticing the surface of the developer carrier that holds and carries toner as one-component developer, and to provide an image forming apparatus using the developing device. <P>SOLUTION: The developing device includes a developing housing 2 with an opening formed facing an image carrier 1 on which an electrostatic latent image is carried, capable of storing the toner, and the developer carrier 3 arranged facing the opening of the developing housing 2 and also, capable of holding and carrying the toner on the outer peripheral surface. Regarding the surface roughness of the developer carrier 3, the arithmetic mean roughness (Ra) is ≥1.5μm, and also, the arithmetic mean slope (Δa) is ≥0.1 and ≤0.4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and more particularly, to a developing device using a one-component developer (toner) and an image forming apparatus using the developing device.

  In general, in a one-component developing method using only toner as a developing device used in an image forming apparatus such as an electrophotographic method, the toner is carried and conveyed by the developing roll, and then on the developing roll in the developing area facing the photoreceptor. A system is employed in which toner is allowed to fly to the photoreceptor, and the electrostatic latent image formed on the photoreceptor is visualized (development process). At this time, a portion where the toner is consumed and a portion where the toner is not consumed are generated corresponding to the electrostatic latent image (development history) on the developing roll after passing through such a developing step. Such a development history is usually eliminated in the next toner supplying step and the toner layer regulating step, and a uniform toner layer is formed again on the developing roll, and the next developing step is performed. Image defects caused by development history such as ghosts are not caused.

On the other hand, due to the recent demand for higher speed and higher image quality required for image forming apparatuses, magnetic toners using polyester resin with good low-temperature fixability have been proposed as the toner to be used, and the toner diameter is also becoming smaller. It is in.
Such a magnetic toner using a polyester resin or a toner having a reduced diameter has, for example, a strong cohesiveness due to the action of the polar group of the polyester resin or the action of reducing the diameter, and is easily fixed on the developing roll. Therefore, after development, in the portion where the toner is not consumed (corresponding to the non-image portion), the toner is easily fixed on the developing roll, and only a part of the toner on the surface layer is replaced with the next new toner, and the toner is consumed. In the portion (corresponding to the image portion), almost the entire amount of toner is replaced with the next new toner. When a toner layer having a partially replaced amount on the developing roll reaches the next developing step, the developing efficiency becomes higher at the portion where almost all of the toner has been replaced with new toner, and the ghost (the density due to the development history) (In particular, this ghost is noticeable when a halftone image is formed after a solid image is formed).

JP-A-10-90995 (Examples, Table 1)

In order to solve such a problem, a proposal has been made to reduce the ghost by applying a predetermined surface treatment to the circumferential surface of the developing roll (see Patent Document 1). In this Patent Document 1, a resin layer is coated on the circumferential surface of the developing roll, and the resin layer is composed of irregularities larger and smaller than the toner diameter, and the large irregularities have an arithmetic average roughness Ra of 1.3 to 1. It is shown that the effective line length SRlr is 104% or less for small irregularities of .8 μm. However, in the effective line length SRlr of the unevenness, for example, in the roughness curve of the surface roughness, the same numerical value may be calculated even if the unevenness interval and each peak height are different. It is difficult to express an appropriate value for the surface roughness.
Therefore, in order to express the surface roughness of the developing roll in Japanese Patent Application No. 2005-089915, the present inventors newly focused on the root mean square roughness Rq as the roughness parameter of the minute area, and calculated the arithmetic average roughness. If Ra is 1.3 μm or more and the root mean square roughness Rq is 0.08 μm or less, it has been proposed that ghosts can be prevented.

In this proposal, since the focus was on the roughness of a minute area, it was confirmed that ghosting could be prevented even with a toner having strong cohesiveness. However, the root mean square roughness Rq is equivalent to the square of the roughness curve. In addition, since the surface shape of the minute area is not directly evaluated, there is a possibility that it is insufficient.
The present invention is for solving such technical problems, and pays attention to the surface of the developer carrying member carrying and transporting the toner of the one-component developer, and the ghosting due to the development history in the developer carrying member. It is an object of the present invention to provide a developing device in which generation is suppressed and an image forming apparatus using the developing device.

  The present inventors have further studied the case where the toner carried and conveyed by the developer carrying member has a small diameter, and the surface roughness of the peripheral surface of the developer carrying member is a predetermined value for ensuring toner conveyance. Large irregularities within the range are required, and these irregularities need to have an irregular shape that makes it difficult for the toner to adhere to the toner. Under the expectation that the toner is likely to remain when it becomes steep, the present invention has been found by focusing on the arithmetic average slope Δa as a new roughness parameter.

  That is, as shown in FIG. 1, the present invention faces a developing housing 2 that opens opposite to an image carrier 1 on which an electrostatic latent image is carried and can store toner, and faces the opening of the developing housing 2. And a developer carrier 3 capable of carrying and transporting toner on the outer peripheral surface. The developer carrier 3 has an arithmetic average roughness (Ra) of 1.5 μm or more and an arithmetic average. The inclination (Δa) has a surface roughness of 0.1 or more and 0.4 or less.

  In such technical means, the developer carrier 3 may be any material that can carry toner. For example, in a mode in which the toner has magnetism, the developer carrier 3 has a magnetic field inside the non-magnetic sleeve. The structure provided with the generating means is mentioned. Further, the developer carrier 3 and the image carrier 1 may be in contact with each other, or may be arranged in a non-contact manner, and the rotation directions of the developer carrier 3 and the image carrier 1 are the same direction (With direction) at the opposite portion in the contact arrangement. In the non-contact arrangement, the opposite direction may be the same direction (With direction) or the opposite direction (Against direction).

  Further, the arithmetic average roughness (Ra) referred to in the present invention is calculated in accordance with JIS B0601-1994, while the arithmetic average slope (Δa) indicates the surface roughness of a minute region. The absolute value of the slope (angle) of the line segment of the roughness measurement curve is obtained and calculated as an average of the values. In particular, the arithmetic average slope Δa is measured by measuring the surface roughness measurement pitch of 0.15 μm and the height direction resolution of 0.01 μm, and subjecting the obtained waveform to Fourier transform to obtain the toner particle size. The above long frequency component was cut, and each point was calculated for a weighted average of 5 points.

Here, the difference in the designation regarding the surface roughness will be described. 2A to 2C illustrate (a) the arithmetic average roughness Ra, (b) the arithmetic average slope Δa, and (c) the root mean square roughness Rq. (A) Shows that the arithmetic average roughness Ra is a value obtained by averaging the absolute value of the roughness measurement curve y = f (x) over a reference length. Further, (b) shows a minute slope (Δy / Δx) of the roughness measurement curve y = f (x), and the arithmetic average slope Δa is obtained by averaging the absolute value of this minute slope over a reference length. It is the value. Further, in (c), a value obtained by averaging y = f ² (x) obtained by squaring the roughness measurement curve y = f (x) over the reference length is a square value of the root mean square roughness Rq ( Rq ² ).
As described above, the roughness parameter representing the surface roughness does not necessarily represent a uniform tendency, and an appropriate surface roughness can be represented on the contrary by appropriately selecting and using.

  In the present invention, as the surface roughness of the developer carrier 3, the arithmetic average roughness Ra is 1.5 μm or more and the arithmetic average slope Δa is 0.1 or more and 0.4 or less. The transportability of the toner by the carrier 3 is good, the toner sticking to the developer carrier 3 can be suppressed, and the occurrence of ghost can be suppressed even when the toner having a high aggregation property is used. It becomes like this.

  Furthermore, in the present invention, the developer carrier 3 preferably has an average interval (Sm) of irregularities on the peripheral surface of 150 μm or more and 300 μm or less. According to this, the arithmetic average roughness Ra and the irregularities described above More appropriate toner conveyance performance is ensured by the average interval Sm. In addition, the average interval Sm of the unevenness is measured according to JIS B0601-1994, similarly to the arithmetic average roughness Ra described above.

In the present invention, in order to form the above-described surface roughness, it is preferable that the peripheral surface of the developer carrier 3 is roughened by blasting and a metal plating layer is laminated. Thus, by appropriately roughening the peripheral surface, it is possible to ensure an appropriate surface roughness and improve the adhesion of the plating layer. At this time, although it does not specifically limit as a metal plating layer, For example, when step coverage is also considered, electroless nickel plating is suitable. The plating is not limited to the chemical plating method and may be based on a physical plating method.
The blasting material is not limited to glass, ceramics, metal, resin-based media, etc., but particle size # 40 to # 100 (particle size 500 μm to 150 μm) from the viewpoint of obtaining a desired surface roughness (uneven surface). Equivalent spherical particles are preferred.

  Further, in the present invention, as shown in FIG. 1, the developer carrier 3 is disposed away from the developer carrier 3 on the upstream side in the rotation direction of the developer carrier 3 from the facing portion between the developer carrier 3 and the image carrier 1. And a layer regulating member 4 for regulating the toner layer on the developer carrier 3, and the layer regulating member 4 has a pressing pressure against the developer carrier 3 of 0.59 N / cm (60 gf / cm) or less. In this case, by reducing the pressing pressure by the layer regulating member 4, it is possible to prevent toner deterioration and suppress the surface roughness of the peripheral surface of the developer carrier 3. Good toner conveyance can be realized.

Further, the toner carried and conveyed by the developer carrier 3 is preferably one having magnetism from the viewpoint of improving the conveyance force of the developer carrier 3 and applying it to a high-speed process. Further, from the viewpoint of achieving high image quality, the toner is preferably a spherical toner produced by a polymerization method. In particular, the present invention is suitable when spherical toner is used because the surface roughness of the peripheral surface of the developer carrier 3 is adjusted.
The present invention is not limited to the above-described developing device, but also targets an image forming apparatus using these developing devices.

  According to the present invention, there is provided a developing housing that can store toner, and a developer carrying member that faces the opening of the developing housing and that can carry and carry toner on the outer peripheral surface thereof. Since the arithmetic average roughness (Ra) is 1.5 μm or more as the surface roughness and the arithmetic average inclination (Δa) is in the range of 0.1 to 0.4, it depends on the developer carrier. In addition to ensuring good toner transportability, it is possible to prevent toner from sticking even when toner having high cohesiveness is used, and to suppress occurrence of image defects such as ghosts.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 3 shows an embodiment of an image forming apparatus including a developing device to which the present invention is applied. In the figure, reference numeral 21 denotes a photosensitive drum that rotates in the direction of the arrow and includes an organic photoconductive layer on the surface. The photosensitive drum 21 is charged by a charging device 22 such as a corotron, and the like. An electrostatic latent image is formed by the exposure device 23. This electrostatic latent image is formed as a potential image based on a contrast with a high potential portion not exposed to light because the surface potential of the portion of the photosensitive drum 21 exposed to light is lowered. Further, the developing device 30 stores toner, which is colored particles, in the developing housing 31, carries the toner on the developing roll 32, and applies a developing bias from the bias power source 25 to the developing roll 32, thereby developing the developing roll. The side 32 is held at an intermediate potential between the high potential portion and the low potential portion of the electrostatic latent image, and the image portion of the electrostatic latent image on the photosensitive drum 21 is developed with charged toner. is there. Further, the transfer device 26 is configured by, for example, a transfer roll disposed in contact with the photoconductive drum 21, and a transfer bias in a direction in which the toner image on the photoconductive drum 21 is attracted by the bias power source 27 is applied. The toner image on the photosensitive drum 21 is transferred to the recording material 28. The toner remaining on the photosensitive drum 21 is removed by, for example, a doctor blade type cleaning device 29.

  In this embodiment, the recording material 28 onto which the toner image on the photosensitive drum 21 is transferred is conveyed to the fixing device 50, and the toner image is fixed to the recording material 28 by the fixing device 50. The fixing device 50 employs, for example, a heat roll method, and includes a heating roll 51 and a pressure roll 52, and a toner image is obtained by passing the recording material 28 between the heating roll 51 and the pressure roll 52. It is fixed on the recording material 28.

  As shown in FIG. 4, the developing device 30 in the present embodiment has a developing housing 31 that opens toward the photosensitive drum 21, and a developing roll 32 is disposed facing the opening of the developing housing 31. A layer regulating member 33 that regulates the toner layer on the surface of the developing roll 32 is provided on the upper edge of the opening of the developing housing 31. The developing housing 31 has a developing wall 34 in which a developing roll 32 is accommodated, and a toner chamber 35 in which toner is accommodated behind the developing chamber 34, with a partition wall 31 a formed as a part of the developing housing 31 as a boundary. It is divided into and. The toner chamber 35 has an agitator 36 in which the contained toner is agitated. The agitator 36 has a flexible film attached to a part of a rotating body, for example, and develops toner in the toner chamber 35. This is scraped to the chamber 34 side.

  In this embodiment, since the polyester resin magnetic toner that can be fixed at low temperature is used, the developing roll 32 includes a magnet body 32b in which a plurality of magnetic poles are fixedly disposed, and a magnet body 32b around the magnet body 32b. The non-magnetic sleeve 32a is rotatably provided, so that the toner is conveyed along the circumferential surface of the sleeve 32a. In the present embodiment, the developing roll 32 and the photosensitive drum 21 are disposed so as to rotate in contact with each other in the same direction (with direction) at opposing portions. As for the magnetic pole arrangement of the magnet body 32b, the number and arrangement of the magnetic poles may be appropriately selected as long as the toner in the developing chamber 34 is conveyed on the sleeve 32a.

  Further, the layer regulating member 33 includes a leaf spring material 33a having one end fixed to the developing housing 31 and a rubber member 33b attached to the free end side of the leaf spring material 33a. The pressure applied to the roll 32 is adjusted so that the linear pressure is 0.59 N / cm (60 gf / cm) or less, and a predetermined charge amount is applied to the toner on the sleeve 32a and a predetermined toner thin layer is formed. It is supposed to do. At this time, as the rubber member 33b, for example, urethane rubber or silicone rubber is used. The layer regulating member 33 is not limited to such a configuration, and may be appropriately selected as long as it can apply a predetermined charge amount to the toner on the sleeve 32a and form a predetermined toner layer thickness. .

In particular, the sleeve 32a in the present embodiment is obtained by performing a blasting process on the surface of the aluminum base material to obtain a predetermined surface roughness and then performing nickel plating as a metal plating layer.
In the blasting process, spherical glass beads to be blown are used in a size equivalent to particle size # 40 to # 100 (particle size 500 μm to 150 μm), and arithmetic average roughness Ra (based on JIS B0601-1994) is 1.5 μm. That's it.
In addition, for example, after nickel replacement, nickel plating is performed by electroless bright nickel plating with good surface step coverage, and the arithmetic average slope Δa (details) as a predetermined surface roughness (surface roughness of a minute area) Is adjusted to be within the range of 0.1 to 0.4. At this time, for example, by adjusting the P content and the like, the deposited film exhibits nonmagnetic properties. In this embodiment, the nickel plating layer is used as the surface treatment of the sleeve 32a. However, the present invention is not limited to this, and any other metal plating layer may be used as long as it is nonmagnetic and has a predetermined surface property. There is no problem.

Next, the surface roughness of the sleeve 32a after the plating process will be described. In the present embodiment, the surface roughness of the sleeve 32a after the plating treatment is such that the arithmetic average roughness Ra based on the above-mentioned JIS B0601-1994 is 1.5 μm or more, and the average interval Sm of the irregularities is 150 to 150 μm. It is in the range of 300 μm. Further, the arithmetic average slope Δa is set within the range of 0.1 to 0.4, and the arithmetic average slope Δa is obtained as follows.
A profile of the surface of the sleeve 32a (corresponding to a roughness measurement curve) is obtained at a magnification of 2000 with a laser microscope VK-8500 manufactured by KEYENCE. Then, the absolute value of the slope of the line segment was obtained and averaged to obtain the arithmetic average slope Δa. Specifically, the surface roughness measurement pitch is 0.15 μm, the height resolution is 0.01 μm, and the obtained waveform (corresponding to the roughness measurement curve) is Fourier transformed to obtain the toner particle size. After the above long frequency component was cut and the undulation component was removed, each point was further obtained by averaging five points. The slope at each sampling point was calculated with reference to the formula (dZ _i / dx) for obtaining the local slope of JIS B0601-2001.
At this time, the Fourier transform was performed as the removal of the undulation component, which is necessary for extracting only the fine irregularities on the surface, and the five-point weighted average does not reduce the measurement accuracy too much, and the detection variation of the measurement apparatus. The purpose was to correct.

Next, the operation of the image forming apparatus in the present embodiment will be described with a focus on the developing device 30.
In FIG. 4, the toner scraped from the toner chamber 35 by the agitator 36 is guided into the developing chamber 34. The toner in the developing chamber 34 is attracted by the magnetic poles of the magnet body 32b of the developing roll 32, and is attracted and conveyed to the developing roll 32 side as it is rotated by the sleeve 32a. Then, the toner on the sleeve 32 a is adjusted to a predetermined layer thickness and charge amount by the layer regulating member 33, and then developed by the bias power source 25 in the developing region at the opposite portion between the developing roll 32 and the photosensitive drum 21. The electrostatic latent image on the photosensitive drum 21 is visualized (developed) by the action of the bias. The development cycle is performed as described above.

  In the present embodiment, the sleeve 32a on the surface of the developing roll 32 has an arithmetic average roughness Ra of 1.5 μm or more and an average interval Sm between 150 to 300 μm as described above. Since the arithmetic average inclination Δa is adjusted to be in the range of 0.1 to 0.4, the toner conveying force by the developing roll 32 is ensured, and the toner easily slips on the sleeve 32a when forming the layer. Even when a toner having strong cohesion is used, the toner is hardly fixed on the sleeve 32a. Therefore, even if a portion where the toner is consumed (corresponding to the image portion) and a portion where the toner is not consumed (corresponding to the non-image portion) are mixed in the development, the toner is rubbed with the toner in the developing chamber 34. It is easily scraped off from the surface of the sleeve 32a, and a state where a uniform thin toner layer is formed is maintained at the next development. Therefore, it is possible to suppress the occurrence of ghost due to the development history.

  FIGS. 5A and 5B show an example of a formed image in the present embodiment. After outputting a vertical image along the traveling direction as shown in FIG. 5A, the entire surface as shown in FIG. Even if an image having a halftone is output, since the occurrence of ghost is suppressed, a uniform image is obtained as the halftone image, and no image defect such as a ghost occurs.

On the other hand, in the conventional developing device in which the sleeve 32a has a surface roughness different from that of the present embodiment in which the arithmetic average inclination Δa exceeds 0.4, the following phenomenon occurs.
That is, since the layer regulating member is pressed against the developing roll (the pressing pressure is larger than that in the present embodiment), the toner on the circumferential surface of the developing roll is regulated in a thin layer. At this time, the toner layer is pressed against the developing roll side by the layer regulating member and is difficult to fly. In the toner layer, there are a portion where the toner is easy to move and a portion where the toner is difficult to move. For example, when the toner passes through the layer regulating member many times (for example, when the toner is not consumed corresponding to the non-image portion), the toner near the surface of the developing roll, which is the lower layer of the toner layer, It stays without being replaced, and is packed by repeated pressurization and adhesion to the developing roll.
On the other hand, when the toner is continuously consumed in the development area (corresponding to the image portion), the toner in the upper layer of the toner layer is consumed by the development, and the aggregation of the lower layer of the toner layer is gradually broken down. The toner can fly easily.
Due to such behavior of the toner, a difference in development amount appears between a portion where the toner is continuously consumed and a portion where the toner is not consumed, and an image defect called a ghost occurs.

FIGS. 6 (a) and 6 (b) show this ghost. If a halftone as shown in (b) is output after a vertical image as shown in (a) is output, the vertical image as shown in (a) is developed. On the developing roll after this, the toner is consumed in the vertical image portion and the toner is not consumed in the non-image portion. At this time, the toner tends to aggregate near the surface of the developing roll corresponding to the non-image portion, so that only the upper layer of the toner layer is replaced during the next development. For this reason, the development amount differs between the portion where the toner is consumed and the portion where the toner is not consumed, and when a full-tone halftone image as shown in FIG.
When the arithmetic average inclination Δa becomes less than 0.1, the toner slips too much on the surface of the developing roll, so that a predetermined amount of toner cannot be supplied to the developing area, and the stability of development is impaired. Negative ghosts will also be generated.

  In order to prevent such a ghost, it is conceivable to reduce the difference in the development amount between the image portion and the non-image portion by forming an excessive amount of toner on the developing roll. The charge amount is likely to be non-uniform, which causes image quality deterioration such as image unevenness. In addition, a method of forcibly forming a toner thin layer by increasing the pressing force of the layer regulating member to increase the scraping effect of the toner layer on the developing roll is conceivable. For example, toner external additives are buried and it becomes difficult to obtain a stable image over a long period of time.

As described above, in the present embodiment, regarding the surface roughness of the developing roll 32, the arithmetic average roughness Ra is set to 1.5 μm or more, and a fine region in which the swell component on the surface corresponding to the toner particle size or more is removed. Since the arithmetic average inclination Δa is in the range of 0.1 to 0.4, the various binding forces between the developing roll 32 and the toner can be weakened, and the surface of the developing roll 32 can be reduced. Nearby toner also becomes easy to move, and toner aggregation can be suppressed. For this reason, it is possible to prevent the occurrence of ghost accompanying toner aggregation.
Further, by using the developing roll 32 having such a surface shape, a uniform toner thin layer can be formed even when the pressing pressure of the layer regulating member 33 is 0.59 N / cm (60 gf / cm) or less. The stress applied to the toner can be greatly reduced. Therefore, a stable image can be formed over a long period.
Furthermore, a good image can be formed even when a toner having a small particle diameter is used, and a good image can be formed also when a so-called spherical toner obtained by a polymerization method is used.
Furthermore, since the surface of the developing roll 32 is formed of a metal plating layer, for example, unlike a conventional resin layer, the amount of deformation of the surface shape due to frictional wear is small, and the surface shape is maintained for a long time. As a result, for example, by combining the photosensitive drum 21 with amorphous silicon formed, the mechanical life is extended, and the frequency of parts replacement can be greatly reduced.
In this embodiment, attention is paid to the surface roughness of a minute area. However, in the method according to JIS B0601, for example, measurement is performed with a stylus on the measurement surface, and therefore the tip diameter of the measurement needle is several μm. Therefore, it should be noted that the arithmetic average slope Δa in the present embodiment cannot be measured.

In the present embodiment, magnetic toner is used as the toner. However, for example, non-magnetic toner can be used instead of magnetic toner. In this case, for example, a toner supply roll disposed opposite to the developing roll 32 in the developing chamber 34 may be provided, and a supply bias for supplying toner may be applied between the toner supply roll and the developing roll 32.
Thus, it goes without saying that the same effects as those of the present embodiment can be obtained when the nonmagnetic toner is used.

Example 1
In this example, the arithmetic average slope Δa was measured for the three types of sleeves using the method described in the above embodiment. FIGS. 7A to 7C show examples of three specific roughness measurement curves (profiles). The measured arithmetic average inclination Δa is 0.11 μm, 0.44 μm, and 0.58 μm, respectively, and a curve before Fourier transformation (shown as a surface shape before Fourier transformation) and a curve after Fourier transformation (after Fourier transformation). It is shown as a surface shape). In the present embodiment, the three types of sleeves were similarly processed up to the blasting process. However, the subsequent processing methods were different, and those having Δa of 0.11 μm were the same as in the embodiment. Others depended on other methods.
The measurement is performed over the sleeve surface over a length of 150 μm. As a result, the roughness in the micro area is greatly different in all three types although the large undulation component is not so different. That is, it can be seen that the surface is rougher when Δa is 0.44 μm and 0.58 μm than when Δa is 0.11 μm. For this reason, it has been understood that such a rough surface tends to catch toner, particularly toner having a small particle diameter, and toner sticking easily occurs.

Example 2
In the present embodiment, the relationship between the arithmetic average slope Δa and the ghost grade is evaluated. Specifically, two vertical lines (density 100%, reflection density 1.4) as shown in FIG. 5A are arranged. Two images were output by A4 vertical feeding, and then a full-tone halftone image having a reflection density of 0.4 was continuously output to check the occurrence of ghosts. Here, the reason why two horizontal images are output is that ghost is more likely to occur than when only one image is output.
The ghost grade is ghost grade ± 0.5 when the image density difference between the ghost generation area (the portion corresponding to the image portion) and the portion corresponding to the non-image portion is 0.1, and ± 0.2 when the image density difference is 0.2. It was set to ± 1.5 when 1, 0.3 and ± 2 when 0.4. The range in which the ghost grade is good is within ± 0.5.

As a result, as shown in FIG. 8, the arithmetic average slope Δa and the ghost grade have a substantially linear relationship, and according to this, the ghost grade is within a range of ± 0.5 (halftone with a reflection density of 0.4). In the image, the arithmetic average slope Δa that falls within the range of the image density difference between the portion corresponding to the vertical and the portion other than that is 0.1 or less was 0.1 to 0.4.
When the arithmetic average inclination Δa exceeds 0.4, the toner is easily restrained by the sleeve surface, resulting in a ghost. On the other hand, when Δa is less than 0.1, the toner restraining force on the sleeve surface is insufficient and the negative ghost It was thought to lead to outbreak.
For this reason, it has been found that the occurrence of image defects due to ghosts can be suppressed by setting the arithmetic average slope Δa to 0.1 to 0.4. At this time, the reason why the ghost grade is indicated by ± is that there are so-called positive ghost and negative ghost.

Example 3
In this example, the relationship between the pressing pressure by the layer regulating member and the toner life was evaluated and confirmed. The pressing pressure was changed by changing the thickness of the leaf spring material. At this time, the linear pressure is set to 25 to 120 gf / cm, and the toner life repeats the output of a standard image (image with an image area ratio of about 5%), and the output image has an image defect (image unevenness) due to toner deterioration. Etc.) was visually confirmed and evaluated.
As a result, as shown in FIG. 9, it was confirmed that the pressing pressure should be 0.59 N / cm (60 gf / cm) or less in order to obtain an output of 20000 sheets or more.
For this reason, conventionally, since the binding force to the toner by the developing roll surface is strong, it has been necessary to increase the pressing pressure by the layer regulating member, but in this example, it is possible to reduce it, and as a result, It was found that the toner life was also improved.

Example 4
In this example, the relationship between the arithmetic average slope Δa and the arithmetic average roughness Ra is evaluated and confirmed with respect to the surface roughness of the developing roll. As the sleeve of the developing roll, the arithmetic average roughness Ra was changed by changing the blasting material, and evaluation was made including those subjected to various plating treatments and those not. The evaluation criteria were determined as in Example 2, and determined by determining whether the ghost grade of the output image was within ± 0.5.
The result was as shown in FIG. In the figure, ○ indicates that the ghost grade is good within ± 0.5, and ● indicates that the ghost grade exceeds ± 0.5 and is not good.
From the results of FIG. 10, it was confirmed that those having a good ghost grade have an arithmetic average roughness Ra of 1.5 μm or more and an arithmetic average slope Δa of 0.4 or less.
In FIG. 10, good results are shown even when Δa is less than 0.1, but when combined with the results of FIG. 8, it was determined that 0.1 to 0.4 is preferable as the range of Δa.

Example 5
In this example, the relationship between the arithmetic average inclination Δa and the average interval Sm of the unevenness was evaluated and confirmed with respect to the surface roughness of the developing roll. As the sleeve of the developing roll, the average interval Sm of the unevenness was changed by changing the blasting material, and evaluation was made including those subjected to various plating treatments and those not. The evaluation criteria were determined as in Example 2, and determined by determining whether the ghost grade of the output image was within ± 0.5.
The result was as shown in FIG. In the figure, ○ indicates that the ghost grade is good within ± 0.5, and ● indicates that the ghost grade exceeds ± 0.5 and is not good.
From the results of FIG. 11, it was confirmed that those having a good ghost grade have an average interval Sm of unevenness of 150 μm or more and an arithmetic average slope Δa of 0.4 or less.

Comparative Example In this comparative example, the relationship between the arithmetic average inclination Δa and the effective line length SRlr of the unevenness was evaluated and confirmed using the developing roll used in the above-described example, as shown in FIG. Results were obtained. As a result, a correlation that can be approximated by a first order was found between the two, and when a linear approximation line was obtained, y = 73.796x + 90.586 was obtained.
This means that the effective line length SRlr of 104% or less corresponds to the arithmetic average slope Δa of 0.18 or less. However, as shown in Examples and the like, in the present invention, the arithmetic average slope Δa may be 0.1 to 0.4, and from this, the expression of the surface roughness by the effective line length SRlr is It was understood that this does not represent a preferable surface roughness as a developing roll.
In addition, when the present inventors examined what coated the binder resin containing electroconductive fine particles on the image development roll surface, SRlr is 122-172 and (DELTA) a becomes a value of 0.48-1.1. I will add that.

◎ Comparative Example 2
In this comparative example, the relationship between the arithmetic average slope Δa and the root mean square roughness Rq was evaluated and confirmed, and the results shown in FIG. 13 were obtained. As a result, there is no clear correlation between Rq and Δa. For example, when Rq is 0.08 or less, Δa varies within a range of about 0.1 to about 1.1, and Δa is 0.4. It turned out that the area | region shown by the B area | region in the following figures and the area | region shown by A area | region are included. Among the A region and the B region, the region having excellent ghost grade is the B region. Therefore, it was understood that the expression of the surface roughness by Rq does not represent the actual behavior.

It is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. (A) is arithmetic average roughness, (b) is arithmetic average inclination (DELTA) a, (c) is explanatory drawing which shows the root mean square roughness Rq. 1 is an explanatory diagram showing an embodiment of an image forming apparatus to which the present invention is applied. It is explanatory drawing which shows the developing device of embodiment. (A) (b) is explanatory drawing which shows an image without a ghost. (A) (b) is explanatory drawing which shows the image at the time of ghost occurrence. (A)-(c) is a graph which shows the result of Example 1. FIG. 10 is a graph showing the results of Example 2. 10 is a graph showing the results of Example 3. It is a graph which shows the result of Example 4. 10 is a graph showing the results of Example 5. 6 is a graph showing the results of Comparative Example 1. 10 is a graph showing the results of Comparative Example 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Developing housing, 3 ... Developer carrier, 4 ... Layer control member

Claims (8)

A developing housing that opens opposite to an image carrier on which an electrostatic latent image is carried and can store toner;
A developer carrying member disposed facing the opening of the developing housing and capable of carrying and transporting toner on the outer peripheral surface;
The developer carrying member has a surface roughness with an arithmetic average roughness (Ra) of 1.5 μm or more and an arithmetic average slope (Δa) of 0.1 to 0.4. Development device. The developing device according to claim 1,
The developing apparatus, wherein the developer carrying member has an average interval (Sm) of irregularities on the peripheral surface of 150 μm or more and 300 μm or less. The developing device according to claim 1,
The developing device according to claim 1, wherein the peripheral surface of the developer carrying member is roughened by blasting and a metal plating layer is laminated thereon. The developing device according to claim 3.
The developing device, wherein the blasting material used for the blasting process is a spherical particle having a particle size of # 40 to # 100 (particle size: 500 μm to 150 μm). The developing device according to claim 1,
A layer regulating member that is spaced apart from the developer carrying body and upstream of the facing portion between the developer carrying body and the image carrying body and that regulates the toner layer on the developer carrying body. With
The developing device, wherein the layer regulating member is set so that a pressure applied to the developer carrying member is 0.59 N / cm (60 gf / cm) or less. The developing device according to claim 1,
2. A developing device according to claim 1, wherein the toner carried and conveyed by the developer carrying member has magnetism. The developing device according to claim 1,
2. A developing apparatus according to claim 1, wherein the toner carried and conveyed by the developer carrying member is a spherical toner produced by a polymerization method. An image carrier on which an electrostatic latent image is carried;
An image forming apparatus comprising: the developing device according to claim 1.

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