JP2024008365A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device which can reduce an influence of paper powder and a transfer residual toner without increasing manufacturing cost, can suppress an abnormal image such as lateral black stripes, and has high temporal durability.

SOLUTION: An image formation device has: an image carrier 10; a charging member 20 which is arranged so as to be brought into contact with the image carrier and charges the image carrier; development means 200 which supplies a toner to the image carrier, and forms a toner image on the image carrier; and transfer means 62 for transferring the toner image on the image carrier onto a recording medium or an intermediate transfer body. The development means recovers a transfer residual toner remaining on the image carrier after the transfer. Surface roughness Rz of the charging member is 5 μm or more and 16 μm or less and an electric resistance value of the charging member is 0.1 MΩ or more and 1.6 MΩ or less, or surface roughness Rz of the charging member is 5 μm or more and 18 μm or less and an electric resistance value of the charging member is 0.1 MΩ or more and 1.4 MΩ or less.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art Conventionally, image forming apparatuses are known that use a method of charging an image carrier by bringing a charging member such as a charging roller to which a voltage is applied into contact with the surface of a photoreceptor (image carrier).

In such an image forming apparatus, there is a technique for cleaning toner adhering to the surfaces of the photoreceptor and the charging roller. In the prior art, it is known that, for example, toner adhering to a photoreceptor is cleaned using a cleaning means such as a cleaning blade. In recent years, from the viewpoint of downsizing the apparatus, a so-called cleaner-less method, which does not include a dedicated cleaning means for cleaning the photoreceptor, has been proposed.

In a cleanerless image forming apparatus, if printing is continued with paper containing a lot of paper dust, not only residual toner after transfer but also a lot of paper dust will adhere to the charging member. When a large amount of paper dust adheres to the charging member, the electrical resistance of the paper dust causes uneven charging from the charging member to the photoreceptor, resulting in abnormal images such as horizontal black lines. In order to avoid such abnormal images, for example, the following Patent Documents 1 and 2 have been proposed.

In Patent Document 1, in an image forming apparatus using a cleanerless system in which developer remaining on the surface of an image carrier is collected by the developing device, a non-image forming area in a contact area between a contact charging member and an image carrier is disclosed. It is disclosed that the treatment of the surface of the corresponding contact charging member portion is different from the treatment of the surface of the contact charging member portion corresponding to the imaging area. Further, Patent Document 1 discloses that the ten-point average roughness Rz of the surface of the contact charging member portion is different between the non-image forming area and the image forming area, and that the Rz of the non-image forming area is 3 μm or more and 12 μm or less. ing.

Patent Document 2 discloses a paper dust removing means for removing paper dust by contacting the surface of an image carrier, and a paper dust removing means for forming a potential difference between the paper dust removing means and the image carrier. It is disclosed that the image forming apparatus includes a bias applying means for applying a bias of 1, and a control means for controlling the bias applying means so as to change the potential difference according to the amount of image formation.

However, in an image forming apparatus using a cleanerless system, as in Patent Document 1, when the charging member has different roughness Rz between the non-image forming area and the image forming area, the manufacturing process increases and the manufacturing cost increases. will increase. Further, if a paper dust removing means, a bias applying means, and a control means are provided as in Patent Document 2, the number of parts increases, resulting in an increase in manufacturing cost.
Additionally, if the charging member continues to operate with a large amount of paper dust attached to the charging member, the electrical resistance of the charging roller will vary locally depending on the amount of paper dust attached to the surface of the charging roller. It becomes impossible to uniformly charge the entire member. In order to avoid this, if a paper dust removing means is provided as described above, the manufacturing cost will increase.
Further, in the case of a cleanerless image forming apparatus, it is necessary to maintain the charging roller to be well charged even over time, and for this purpose, it is required to reduce the influence of paper dust and transfer residual toner. When the influence of paper dust and transfer residual toner increases, for example, the life of a process unit in a cleanerless system becomes short, and its durability over time becomes low.

Therefore, the present invention provides an image forming apparatus that can reduce the effects of paper dust and transfer residual toner, suppress abnormal images such as horizontal black lines, and have high durability over time without increasing manufacturing costs. The purpose is to

In order to solve the above problems, an image forming apparatus of the present invention includes an image bearing member, a charging member that is arranged to come into contact with the image bearing member and charges the image bearing member, and a charging member that charges the image bearing member. a developing device that supplies toner to form a toner image on the image carrier; and a transfer device that transfers the toner image on the image carrier to a recording medium or an intermediate transfer body, and the developing device includes: Transfer residual toner remaining on the image carrier after the transfer is collected, and the charging member has a surface roughness Rz of 5 μm or more and 16 μm or less, and an electrical resistance value of 0.1 MΩ or more and 1 .6 MΩ or less, or the surface roughness Rz of the charging member is 5 μm or more and 18 μm or less, and the electrical resistance value of the charging member is 0.1 MΩ or more and 1.4 MΩ or less. .

According to the present invention, it is possible to reduce the influence of paper dust and transfer residual toner without increasing manufacturing costs, suppress abnormal images such as horizontal black lines, and provide an image forming apparatus that has high durability over time. can be provided.

1 is a diagram for explaining an embodiment of an image forming apparatus of the present invention. FIG. 3 is a diagram for explaining another embodiment of the image forming apparatus of the present invention. FIG. 3 is a diagram for explaining another embodiment of the image forming apparatus of the present invention. FIG. 3 is a diagram for explaining another embodiment of the image forming apparatus of the present invention. FIG. 6 is a diagram showing an example of the occurrence of an abnormal image in the relationship between the surface roughness Rz of the charging roller and the electrical resistance value. FIG. 2 is a diagram for explaining one embodiment of a process cartridge.

An image forming apparatus according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments shown below, and may be modified within the scope of those skilled in the art, such as other embodiments, additions, modifications, deletions, etc. These are also included within the scope of the present invention as long as they exhibit the functions and effects of the present invention.

The image forming apparatus of the present embodiment includes an image carrier, a charging member that is arranged to come into contact with the image carrier and charges the image carrier, and a charging member that supplies toner to the image carrier and that charges the image carrier. a developing device that forms a toner image on the image carrier; and a transfer device that transfers the toner image on the image carrier to a recording medium or an intermediate transfer body; Collect the transfer residual toner remaining on the body, and the surface roughness Rz of the charging member is 5 μm or more and 16 μm or less, and the electrical resistance value of the charging member is 0.1 MΩ or more and 1.6 MΩ or less, Alternatively, the surface roughness Rz of the charging member is 5 μm or more and 18 μm or less, and the electrical resistance value of the charging member is 0.1 MΩ or more and 1.4 MΩ or less.

In the image forming apparatus of this embodiment, the transfer residual toner remaining on the image carrier is collected by the developing means. The image forming apparatus of this embodiment is configured without using a cleaning means (for example, a cleaning blade) for cleaning an image carrier (also referred to as an electrostatic latent image carrier, a photoreceptor, etc.). In this case, there are advantages such as miniaturization of the device.

Hereinafter, a method that does not use a cleaning means for cleaning the image carrier will be referred to as a cleaner-less method, a cleaner-less configuration, or the like. Further, as the charging member, for example, a charging roller can be used, and in the following description, the charging roller is taken as an example.

FIG. 1 is a diagram illustrating an example of an image forming apparatus according to the present embodiment, and is a diagram illustrating an example of a process for forming an image in a cleanerless type image forming apparatus.

First, the charging roller 20 uniformly charges the photosensitive drum 10 as an image carrier. The charging roller 20 of this example is arranged so as to be in contact with the photoreceptor drum 10, and applies, for example, a DC voltage to the photoreceptor drum 10. Charging in this example is a contact DC charging method.

The exposure device 21 exposes the photoreceptor drum 10 with exposure light L to form an electrostatic latent image on the photoreceptor drum 10 . Although the exposure device 21 is not particularly limited, for example, an LED is used.

The developing roller 72 is an example of a developer carrier included in the developing device 61. A developing bias is applied to the developing roller 72 by an applying means, and the developing roller 72 supplies the toner 200 to the photoreceptor drum 10 . As a result, a toner image (also referred to as a visible image) is formed on the photoreceptor drum 10.

The developing device 61 includes, for example, a stirring roller 73, and may stir the toner within the developing device 61. The rotation direction of the stirring roller 73 can be selected as appropriate, and the stirring roller 73 may be in contact with the developing roller 72 or may be in non-contact.

Transfer roller 62 transfers the toner image on photosensitive drum 10 onto recording paper 105 .
The static elimination lamp 64 eliminates the potential of the photoreceptor drum 10 . For example, the static electricity is removed by irradiating the static electricity removal light QL.

The above configuration is the basic configuration of a cleanerless type image forming apparatus. Such an apparatus does not include cleaning means such as a cleaning grade for cleaning the photosensitive drum 10 after the transfer process.

Although not particularly limited, in the example shown in FIG. 1, for example, -300V is applied to the developing roller 72, and -1200V is applied to the charging roller 20. For example, the surface of the photoreceptor drum 10 becomes about -50V when electricity is removed, and about -500V when it is charged.

The image forming apparatus of this embodiment preferably includes a cleaning brush 161 (brush member) for scraping dirt on the charging roller 160. In this case, image quality stability over time is improved.

Here, an example of the flow of toner in the example shown in FIG. 1 will be described. For the sake of explanation, the symbols of the toners in the drawings are changed depending on the position and state of the toner.
The developing roller 72 carries toner 200, and the toner 200 carried by the developing roller 72 is supplied to the photosensitive drum 10. The toner supplied to the photoreceptor drum 10 forms a toner image (visible image) according to the electrostatic latent image (toner 201). The toner 201 on the photosensitive drum 10 is transferred onto the recording paper 105. The toner 202 transferred to the recording paper 105 is fixed on the recording paper 105 in a later process.

The toner that has not been transferred in the transfer process remains on the photosensitive drum 10 as transfer residual toner 203. After the static elimination step, the transfer residual toner 203 adheres to the charging roller 20 at (or near) the contact point between the photoreceptor drum 10 and the charging roller 20 . Among the transfer residual toner 203, some toner 206 does not adhere to the charging roller 20, and this toner 206 remains on the photoreceptor drum 10. This toner 206 is collected by the developing roller 72 as described later.

Next, an example of a method for recovering transfer residual toner in a cleanerless image forming apparatus will be described with reference to FIGS. 2, 3A, and 3B.

FIG. 2 is a schematic diagram for explaining a state after FIG. 1, and is a diagram schematically showing a state during printing. "During printing" here means a state in which the apparatus is in operation, and includes not only the process of transferring toner onto the recording paper but also the process of preparing to transfer the toner onto the recording paper. FIG. 3 is a diagram illustrating processing performed between transfer to the previous recording paper and transfer to the next recording paper.

As described with reference to FIG. 1, toner that has not been transferred in the transfer process remains on the photoreceptor drum 10 as transfer residual toner 203. In FIG. 2, it is shown that transfer residual toner 203 remains on the photosensitive drum 10 on the downstream side of the transfer roller 62.

After the transfer is performed on the previous recording paper 105, the surface of the photoreceptor drum 10 is neutralized by the static eliminating lamp 64. This widens the potential difference between the charging roller 20 and the photoreceptor drum 10, and discharge occurs between the charging roller 20 and the photoreceptor drum 10 before charging. In the figure, discharge is schematically illustrated.

Due to the discharge before charging, the transfer residual toner 203 is negatively charged (not shown in FIG. 2). In the transfer residual toner 203, due to discharge before charging, for example, there is some that is negatively charged and some that remains slightly positively charged. The transfer residual toner 203, which remains slightly positive, adheres to the charging roller 20 at (or near) the location where the charging roller 20 and the photoreceptor drum 10 come into contact. The toner attached to the charging roller 20 is illustrated as toner 204.

Note that an arrow a in the figure schematically indicates that the transfer residual toner 203 on the photoreceptor drum 10 adheres to the charging roller 20. The fact that the transfer residual toner 203 on the photosensitive drum 10 adheres to the charging roller 20 may also be referred to as moving.

The image forming apparatus of this example includes a cleaning brush 161 that collects toner adhering to the charging roller 20. The positive toner 204 adhering to the charging roller 20 is collected by the cleaning brush 161. An arrow b in the figure schematically indicates that the toner 204 on the charging roller 20 is collected by the cleaning brush 161. Collecting the toner 204 on the charging roller 20 by the cleaning brush 161 may also be referred to as moving.

A collection bias is applied to the cleaning brush 161. The value of the recovery bias is not particularly limited and can be selected as appropriate.

Of the transfer residual toner 203 on the photoreceptor drum 10 , negatively charged toner does not adhere to the charging roller 20 and remains on the photoreceptor drum 10 . This toner is illustrated as toner 206. Note that both the toner 203 and the toner 206 are residual toner after transfer.

The toner 206 remaining on the photosensitive drum 10 is collected by the developing roller 72. The toner collected by the developing roller 72 is illustrated as toner 208. Collecting by the developing roller 72 may also be referred to as moving. The toner 206 passing between the photoreceptor drum 10 and the developing roller 72 moves toward the developing roller 72 due to the potential difference between the photoreceptor drum 10 and the developing roller 72 . An arrow c in the figure schematically indicates that the toner 206 on the photosensitive drum 10 is collected by the developing roller 72.

Although there are no particular restrictions on how to collect the toner with the developing roller 72 as described above, for example, a method of adjusting the potential of each member may be used. For example, the surface of the photoreceptor drum 10 after static elimination is -50V, the charging roller 20 is −1100V, the cleaning brush 161 is −1300V, the surface of the photoreceptor drum 10 after charging is −500V, and the developing roller 72 is −50V. One example is to set the voltage to 300V. Although the potentials are illustrated in FIG. 2 as an example, the potentials are not limited to this.

Next, with reference to FIGS. 3A and 3B, an example of the movement of toner when the apparatus is stopped and toner collection will be described.

As described with reference to FIG. 2, the positive transferred residual toner 203 (the same applies to the toner 206) that has become negative during the discharge before charging, adheres to the charging roller 20 and is collected by the cleaning brush 161. During printing, since this collection is repeated, the positively charged toner 207 accumulates on the cleaning brush 161.

When the apparatus is shut down, the potential difference between the cleaning brush 161 and the charging roller 20 is adjusted, and the slightly positively charged toner 207 is moved to the charging roller 20 side. This is shown by arrow d in the figure.

The toner 205 that has moved to the charging roller 20 is moved to the photosensitive drum 10 due to the potential difference between the charging roller 20 and the photosensitive drum 10 . This is shown by arrow e in the figure. This moved toner is shown as toner 209 in the figure. Note that when the apparatus is shut down, the charge removal lamp 64 does not remove the charge from the photoreceptor drum 10, so the potential difference between the charging roller 20 and the photoreceptor drum 10 is adjusted in consideration of this.

The positively charged toner 209 on the photosensitive drum 10 is not collected by the developing roller 72 but passes through the developing roller 72 as it is. Furthermore, the toner 209 passes through the transfer roller 62. In this manner, positively charged toner 209 is present on the photoreceptor drum 10 when the apparatus is shut down.

2, 3A, and 3B, toners 203, 206, and 209 are shown on the photosensitive drum 10. As shown in FIG. All of these are considered as transfer residual toner. The toner 209 is the one that has moved onto the photosensitive drum 10 again after the transfer residual toner 203 is collected by the cleaning brush 161, but such toner may also be included in the transfer residual toner.

Although there are no particular limitations on how to move the toner as in the example shown in FIG. 3A, for example, there is a method of adjusting the potential of each member. For example, the potential of the cleaning brush 161 is set to -150V, the potential of the charging roller 20 is set to -350V, the potential of the surface of the photosensitive drum 10 is set to 500V, and the potential of the developing roller 72 is set to +250V. Although the potentials are illustrated in FIG. 3A as an example, the present invention is not limited to this.

Next, how the toner on the photosensitive drum 10 is collected when the apparatus is shut down will be described with reference to FIG. 3B. FIG. 3B is a continuation of FIG. 3A.

As shown in the figure, the charge removal lamp 64 removes the charge from the photoreceptor drum 10 at a predetermined timing. By removing the charge, the potential difference between the charging roller 20 and the photoreceptor drum 10 widens, and discharge occurs between the charging roller 20 and the photoreceptor drum 10. In the figure, discharge is schematically illustrated. Note that the illustrated static elimination is not static elimination performed for image formation, but static elimination performed for toner recovery.

Due to the above discharge, the toner 209 is negatively charged. Note that, similarly to FIG. 2, among the toner 209, toner that is not negatively charged but remains positively charged adheres to the charging roller 20 and is collected by the cleaning brush 161 (arrow g in the figure, h).

The toner 209 negatively charged by the above discharge does not move to the charging roller 20 but remains on the photoreceptor drum 10 . The negatively charged toner 209 is collected by the developing roller 72 to which a developing bias is applied (arrow i in the figure). The toner collected by the developing roller 72 is shown as toner 208 in the figure.

Toner movement as in the example shown in FIG. 3B can be achieved by, for example, a method of adjusting the potential of each member, although this is not particularly limited. For example, the potential of the cleaning brush 161 is -1300V, the potential of the charging roller 20 is -1100V, the surface potential of the photoreceptor drum 10 after static elimination is -50V, the potential of the surface of the photoreceptor drum 10 is 500V, and the potential of the developing roller 72 is -1100V. One example is to set it to -300V. Although the potentials are illustrated in FIG. 3B as an example, the present invention is not limited to this.

The image forming apparatus of this embodiment can employ the cleanerless method as described above. The cleanerless method described above is a method in which the charging characteristics of toner are controlled and the toner is moved and collected using an electric field in each process. This removes transfer residual toner on the photoreceptor drum 10.

By using a cleanerless type image forming apparatus as described above, there is no need to provide a cleaning blade for cleaning the photoreceptor, and advantages such as miniaturization of the apparatus and omission of parts can be obtained. However, in a cleanerless image forming apparatus, as printing continues, paper dust adheres to the charging roller, and as a large amount of paper dust adheres, the electric resistance of the paper dust causes the charging roller to charge the photoreceptor drum 10. is not uniform. This results in abnormal images such as horizontal black lines. In contrast, in the prior art, it has been proposed to provide a paper dust removal brush and to provide different surface treatments between the image forming area and the non-image forming area of the charging member. However, when doing so, there is a problem that manufacturing costs increase. In addition, if a large amount of paper dust adheres to the charging roller, the charging performance of the charging roller will locally decrease and the life of the cleanerless unit will be shortened. Costs will increase.

Therefore, the inventors of the present invention conducted extensive studies and decided to specify the characteristic values of the charging member, especially electric resistance and surface roughness Rz in combination, thereby creating a surface treatment for the charging member without adding new members. It has been found that it is possible to reduce the influence of paper dust and transfer residual toner at a lower cost without separating the toner, and to avoid horizontal black streaks.

Furthermore, according to this embodiment, durability over time can be increased without increasing manufacturing costs. According to this embodiment, the influence of paper dust and transfer residual toner can be reduced, and the state in which the charging member can be charged satisfactorily can be maintained even over time. Therefore, even when using a cleanerless method, the life of the process unit including the charging member can be extended.

Note that the process unit is a part that includes an image carrier, a charging member, a developing means, etc., and the process unit may also be called an image forming unit, etc., and an example of the process unit is a process cartridge described below. .

In this embodiment, the surface roughness Rz of the charging member is 5 μm or more and 16 μm or less, and the electrical resistance value of the charging member is 0.1 MΩ or more and 1.6 MΩ or less, or The roughness Rz is 5 μm or more and 18 μm or less, and the electrical resistance value of the charging member is 0.1 MΩ or more and 1.4 MΩ or less. A detailed example will be explained below.

<Evaluation (1): Test when both surface roughness Rz and electrical resistance value are changed>
Using the image forming apparatus having the configuration shown in FIG. 1, a test was conducted in which both the surface roughness Rz and the electrical resistance value of the charging roller were changed. In evaluation (1), using a device in which the surface roughness Rz and electrical resistance of the charging roller were changed, an image was formed after carrying out the durability process as described below, and it was evaluated whether horizontal black streaks occurred. . Furthermore, in evaluation (1), paper containing a large amount of paper dust (for example, High White) was used as the recording medium. The image forming apparatus used in evaluation (1) was equipped with a cleanerless process cartridge, and a charging rubber roller was used as the charging roller.

The durability process is an acceleration condition for generating horizontal black streaks due to paper dust when a large amount of paper dust adheres to the charging roller, and is configured in two steps here. The first step is a paper passing durability process, and the second step is a humidity conditioning process. After performing the durability process, an image is formed and evaluated to confirm the durability against horizontal black streaks in the cleanerless method.

In the first step in the durability process (paper passing durability process), a large amount of paper powder and transfer residual toner adheres to the charging member by passing 8,000 sheets at a temperature of 27° C. and a humidity of 80%. Specifically, 1,000 sheets were passed per day in an environment where paper dust and transfer residual toner easily adhered to the charging member (temperature: 27° C., humidity: 80%), for a total of 8 days of paper passing durability.
In the second step (humidity conditioning step) in the durability process, after the first step, humidity conditioning was performed in a low temperature, low humidity environment (temperature 10° C., humidity 15%) where the electrical resistance of the charging roller is highest. Specifically, the device was left in a low temperature, low humidity environment for 8 hours or more.

After controlling the humidity, images (blank paper, halftone images) were output in a low-temperature, low-humidity environment, and the output images were visually checked to see if horizontal black lines occurred at the intervals between the charging rollers.

The results are shown in FIG. 4(A). In FIG. 4A, the horizontal axis represents the electrical resistance value (MΩ), and the vertical axis represents the surface roughness Rz (μm). The broken lines in the figure indicate the electrical resistance value of 0.1 MΩ and the surface roughness Rz of 5 μm. The evaluation criteria are as follows. ● was considered a pass.
[Evaluation criteria]
●: Horizontal black streaks do not occur ▲: Halftone appears (horizontal black streaks do not occur in blank areas (non-image forming areas))
×: Horizontal black streaks occur in both halftone and blank areas.

In evaluation (1), if horizontal black streaks are visible (▲, ×) in blank areas or halftone images under the accelerated conditions of the durability process, it means that the cleaner-less process cartridge has not achieved a long service life. Become.
As in this embodiment, by configuring the charging roller with a combination of surface roughness Rz and electrical resistance MΩ as shown in ●, it is possible to extend the lifespan of a cleanerless type process cartridge and improve durability over time. It can be made higher.

In evaluation (1), the surface roughness Rz and electrical resistance value of the charging roller were measured as follows.
The surface roughness Rz (μm) of the charging roller was measured using a stylus type surface roughness meter under the following measurement conditions.
Measurement method: Rz according to old JIS B0601-1982
Measurement conditions: Axial measurement length: 2.5mm, feed: 0.1mm/sec, cutoff value: 0.8λc, filter method: 2CR, resolution: L/8000 (L: evaluation length)

The electrical resistance value (MΩ) of the charging roller was measured using an electrical resistance measuring device under the following measurement conditions. Through such measurements, it is possible to measure the electrical resistance of the entire charging roller including the shaft and the like.
Measurement environment: 23±3℃, 55±10% (temperature and humidity control time was over 4 hours)
Applied voltage: DC-500V
Rotation speed: 29r/m
Measurement points: 185 locations (circumferential direction)
Measurement time: 6 seconds
Resistance measurement: Average value of measurement points when jig load is 4.9N (500g) on both ends

Looking at the results shown in FIG. 4A, ●▲× occurs in a region where the surface roughness Rz is 18 μm and the electrical resistance value is around 1.6 MΩ. Therefore, it can be seen that there is a threshold value in this area.

FIG. 4(B) is a diagram for explaining the pass area in FIG. 4(A). In the figure, a rectangular region a is a region in which the surface roughness Rz of the charging roller is 5 μm or more and 16 μm or less, and the electrical resistance value of the charging roller is 0.1 MΩ or more and 1.6 MΩ or less. The rectangular region b is a region in which the surface roughness Rz of the charging roller is 5 μm or more and 18 μm or less, and the electrical resistance value of the charging roller is 0.1 MΩ or more and 1.4 MΩ or less.

From the results shown in FIG. 4(A), the surface roughness Rz of the charging roller is 5 μm or more and 16 μm or less, and the electrical resistance value of the charging roller is 0.1 MΩ or more and 1.6 MΩ or less, or When the surface roughness Rz is 5 μm or more and 18 μm or less, and the electrical resistance value of the charging roller is 0.1 MΩ or more and 1.4 MΩ or less, horizontal black streaks can be avoided.

The reason why horizontal black streaks occur when the electrical resistance value of the charging roller is high is considered to be as follows. It is known that when a charging roller has a high electrical resistance, when a certain voltage is applied to the charging roller, the photoreceptor cannot be properly charged, resulting in charging failure. For this reason, even if there is no problem with the electrical resistance of the charging roller alone, charging failures may occur in cleanerless configurations. In the cleanerless configuration, paper dust adheres to the charging roller as printing is repeated, increasing the apparent electrical resistance of the entire charging roller. An increase in the apparent electrical resistance of the entire charging roller causes charging failure to occur locally, resulting in horizontal black lines.

The reason why horizontal black streaks occur when the surface roughness Rz of the charging roller is large is considered to be as follows. When paper dust enters the grooves on the surface of the charging roller, the electric resistance value of the groove itself becomes relatively high compared to other parts, and the ability to charge the surface of the photoreceptor decreases. When the charging ability decreases, charging failure occurs locally, resulting in horizontal black streaks. The larger the groove (Rz) of the charging roller is, the greater the absolute amount of paper dust that can enter the groove, and the more likely horizontal black streaks will occur.
Further, when the surface roughness Rz of the charging roller is large, external additives and paper dust on the photoreceptor are easily scraped off, and the amount of external additives and paper dust that adheres to the charging roller increases. For this reason, horizontal black lines are more likely to occur.

<Evaluation (2): Test when only the electrical resistance value is changed>
Next, a test will be described in which only the electrical resistance value of the charging roller is changed.
A test was conducted using an image forming apparatus having the same configuration as in Evaluation (1) and changing the electrical resistance value of the charging roller. In evaluation (2), the test was conducted with the surface roughness Rz of the charging roller set to 18 μm. In evaluation (2), an image was formed after performing the same durability process as in evaluation (1), and the presence or absence of abnormal images was evaluated. Note that the electrical resistance value was measured in the same manner as in evaluation (1).

The results are shown in Table 1. The evaluation criteria are as follows. ○ was considered a pass.
[Evaluation criteria]
○: No abnormality △: Density decreased, and horizontal black streaks occurred in blank areas (non-image forming areas) (local toner stains)
×: Toner stain (not local but overall charging failure) occurs in blank paper area (non-image forming area)

As shown in Table 1, when the electrical resistance value of the charging roller was high, the photoreceptor was not charged uniformly, resulting in charging failure, resulting in decreased density and toner staining. Furthermore, if the charging roller has a low electrical resistance value, the resistance is too low relative to the voltage applied to the charging roller, resulting in a large current flowing and leakage.

In the cleanerless configuration, since the residual toner passes through the charging roller, external additives and paper powder added to the toner tend to adhere to the charging roller. When external additives and paper powder adhere to the charging roller, the electrical resistance of the charging roller increases, making charging failures more likely to occur. The amount of paper dust adhering to the charging roller is related to horizontal black streaks, and the more paper dust adheres to the charging roller, the more likely horizontal black streaks will occur. On the other hand, by only specifying the electrical resistance value, it is difficult to determine how much paper dust will adhere to the charging roller during durability after printing a large number of sheets. Since it is difficult to ensure quality by specifying the electrical resistance value alone, quality can be ensured by specifying the surface roughness Rz of the charging roller and the electrical resistance value together.

<Evaluation (3): Test when only surface roughness Rz is changed>
Next, a test will be described in which only the surface roughness Rz of the charging roller is changed.
A test was conducted using an image forming apparatus having the same configuration as in Evaluation (1) and changing the electrical resistance value of the charging roller. In evaluation (3), the test was conducted with the electrical resistance value of the charging roller set to 1.4 MΩ. In evaluation (3), an image was formed after performing the same durability process as in evaluation (1), and the presence or absence of abnormal images was evaluated. Note that the surface roughness Rz was measured in the same manner as in evaluation (1).

The results are shown in Table 2. The evaluation criteria are as follows. ○ was considered a pass.
[Evaluation criteria]
○: No abnormality △: Density decrease ×: Toner stain (not local but general charging failure) occurs in blank paper area (non-image forming area)

As shown in Table 2, abnormal images occurred when the surface roughness Rz of the charging roller was large. When the surface roughness Rz of the charging roller is increased, the unevenness becomes larger and a gap is created at the contact surface between the photoreceptor and the charging roller, and the contact is not uniform. For this reason, good charging is not possible and an abnormal image occurs.

Further, in order to reduce the surface roughness of the charging roller, the time and process for polishing the surface of the charging roller increases, which increases manufacturing costs. The smaller the surface roughness Rz of the charging roller is, the more the manufacturing cost increases. As shown in Table 2, when the surface roughness Rz is 2 μm, the manufacturing cost becomes higher than when the surface roughness Rz is 4 μm because it is necessary to increase the types of grindstones.

When paper powder adheres to the charging roller, the apparent electrical resistance of the charging roller increases and horizontal black streaks occur, so the surface roughness Rz of the charging roller is preferably small. However, when specifying only the surface roughness Rz, although it becomes easier to control the amount of paper dust adhering to the charging roller, it becomes difficult to specify how small the surface roughness Rz should be, and the only option is to reduce it as much as possible. Since the allowable surface roughness Rz largely depends on the electric resistance value of the charging roller, the surface roughness Rz is designed to be as small as possible. In order to reduce the surface roughness Rz, the time and process for polishing the surface of the charging roller increases, which increases manufacturing costs.

Further, when the surface roughness Rz of the charging roller is large, in the contact charging method, the charging roller scrapes off a lot of paper dust and external additives on the photoreceptor, and the charging roller becomes easily soiled. Therefore, it is necessary to provide a cleaning blade for cleaning the photoreceptor to prevent the charging roller from getting dirty, which increases the number of parts and increases manufacturing costs.

Considering the above, in a cleaner-less configuration, by specifying the surface roughness Rz and electrical resistance value of the charging roller together, it is possible to create a device configuration that maintains quality and suppresses increases in manufacturing costs. .

<Amount of external additives in toner>
Next, a preferred configuration of the amount of external additives in the toner will be described.
The method for collecting the transfer residual toner explained in FIG. 2 and the like is a method in which the charging polarity of the toner is controlled and the toner is moved and collected by an electric field in each process. This prevents toner staining on the charging roller. However, it is difficult to control the charge polarity of the external additive released from the toner in the same way as the toner. Therefore, movement of the external additive cannot be controlled in the operation of collecting or discharging the toner onto the charging roller after transfer, and the external additive adheres to the charging roller. If printing continues for a long period of time, the adhesion of external additives to the charging roller will accumulate, resulting in density unevenness due to charging failure.

Therefore, in the present embodiment, the toner includes base particles and an external additive, and it is preferable that the external additive is contained in the toner in an amount of 1.8% by mass or less. By using a toner with a small amount of external additive in a cleaner-less configuration, it is possible to suppress staining of the charging roller and suppress density unevenness due to poor charging.

<Evaluation (4): Test when changing the amount of external additives in toner>
Tests were conducted using an image forming apparatus having the same configuration as in Evaluation (1) and varying the amount of external additives in the toner. In evaluation (4), the same durability process as in evaluation (1) was performed, and after conditioning the humidity, an image was formed, and the presence or absence of abnormal images was evaluated.

The results are shown in Table 3. The evaluation criteria are as follows.
[Evaluation criteria]
○: No abnormality △: Density decrease ×: Toner stain (not local but overall charging failure) occurs in blank paper area (non-image forming area)

As shown in Table 3, it can be seen that no abnormal images occur when the amount of external additive is 1.8% by mass or less. When the amount of external additive is 1.8% by mass or less, the amount of external additive released from the toner can be minimized, and the amount of external additive transferred to the charging roller can also be suppressed. It is possible to suppress staining of the charging roller due to additives. On the other hand, when external additives adhere to the charging roller, the apparent electrical resistance of the charging roller increases, charging failure occurs, and the density begins to decrease. As the charging roller becomes more contaminated, toner is developed on the blank paper area, causing horizontal black streaks.

Furthermore, when the amount of external additive is small, it is also effective for adhesion (filming) of the external additive to the developing roller. Although not listed in Table 3 above, when the amount of external additive was 1.8% by mass or less, developing filming tended to improve.

Furthermore, when the amount of external additive is 1.8% by mass or less, the amount of external additive that adheres to the charging roller over time can be reduced, so that durability over time can be improved. Even when a cleaner-less process cartridge is used, the life can be extended.

An example of producing the toner used in the above evaluation will be explained.
-Preparation of toner base particles-
The toner base particles were produced in the following manner using the following raw materials. "Part" represents "part by mass."

Polyester resin 87 parts Rice wax (TOWAX-3F16, manufactured by Toa Kasei Co., Ltd.) 3 parts Carbon black (#44, manufactured by Mitsubishi Chemical Co., Ltd.) 8 parts Azo iron compound (T-77 manufactured by Hodogaya Chemical Co., Ltd.) 2 parts

The toner raw materials having the above formulation were premixed using a Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd., FM20B), and then mixed at 120°C using a twin-screw kneader (manufactured by Ikegai Co., Ltd., PCM-30). The mixture was melted and kneaded at a certain temperature. The obtained kneaded material was rolled to a thickness of 2.7 mm using rollers, cooled to room temperature using a belt cooler, and coarsely ground to 200 μm to 300 μm using a hammer mill. Next, after finely pulverizing using a supersonic jet pulverizer Labojet (manufactured by Nippon Pneumatic Industries Co., Ltd.), the weight average particle size was 5. The particles were classified while appropriately adjusting the louver opening to obtain toner base particles of 8±0.2 μm.

-Preparation of toner-
To 100 parts of the above toner base particles, 1.00 parts of inorganic fine particles 1 and 0.03 parts of inorganic fine particles 2 were added and mixed with stirring using a Henschel mixer to prepare a toner for evaluation.
Note that since 1.03/(100+1.03)=1.03/101.03≈0.01019, the ratio of the external additive to the toner is 1.0% by mass.

Further, the volume average particle diameter of the external additive used in this embodiment is preferably 5 nm or more and 50 nm or less. By setting it within this range, it becomes difficult for the external additive to separate from the base particles, and it is possible to suppress staining of the charging roller due to the external additive.

(toner)
Next, detailed examples of the toner used in the present invention will be described.

<External additives>
The external additive used in the present invention preferably contains inorganic fine particles. The inorganic fine particles have multiple peaks in the particle size range of 5 nm or more and 50 nm or less in the particle size distribution of the primary particles, and among the peaks, the highest peak is n1, the second highest peak is n2, and the peak is When the grain size (nm) at the apex of n1 is n1d, the grain size (nm) at the apex of the peak n2 is n2d, the height of the apex of the peak n1 is n1h, and the height of the apex of the peak n2 is n2h. In addition, it is preferable that all of the following formulas (1) to (3) be satisfied.
n1d>n2d Formula (1)
10<(n1d+n2d) Formula (2)
30≦{(n2h/n1h)×100}<100 Formula (3)

The particle size distribution of inorganic fine particles as used in the present invention refers to the number-based particle size distribution of primary particles thereof, and can be measured by sequentially performing the following steps (1) to (3).
(1) With inorganic fine particles attached to the toner surface, an image of the toner is obtained using a scanning electron microscope SU8200 series (Hitachi High-Technologies Corporation).
(2) The obtained image is binarized using image processing software A-Kun (Asahi Kasei Engineering Co., Ltd.), and the equivalent circle diameter of the inorganic fine particles is calculated. The equivalent circular diameter of inorganic fine particles is measured for 1000 particles.
(3) Next, the number of classes is determined according to the following formula, a histogram is created, and the particle size distribution is obtained.
Number of classes = 1 + log2n (n indicates the number of data of equivalent circle diameter of inorganic fine particles)

As for the inorganic fine particles used in the present invention, n1d, which is the particle diameter (nm) at the apex of the peak n1, is preferably 15 nm to 50 nm, more preferably 20 nm to 40 nm. Further, n2d, which is the particle size (nm) at the apex of the peak n2, is preferably 5 nm to 50 nm, more preferably 10 nm to 20 nm.

Further, the difference between n1d and n2d is preferably 10 nm to 45 nm, more preferably 13 nm to 30 nm.

Further, from the viewpoint of improving the effect of the present invention, more preferable forms of the above formulas (2) and (3) are represented by the following formulas (20) and (30).
20<(n1d+n2d) Formula (20)
40<{(n2h/n1h)×100}<90 Formula (30)

In the present invention, as a means for making the particle size distribution of the primary particles of inorganic fine particles have a plurality of peaks between 5 nm and 50 nm and satisfying all of the above formulas (1) to (3), for example, Examples of such methods include preparing two or more types of inorganic fine particles having different average particle diameters and adjusting their blending amount so as to satisfy the conditions. Note that the inorganic fine particles are preferably of the same type.

The types of inorganic fine particles used in the present invention are not particularly limited, but examples include silica, alumina, titania, barium titanate, magnesium titanate, calcium titanate, strontium titanate, iron oxide, copper oxide, zinc oxide. , tin oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, chromium oxide, cerium oxide, red iron, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride Examples include. Among them, from the viewpoint of improving stress resistance, at least one selected from silica (including hydrophobic silica), alumina, and titania is preferred.

Inorganic fine particles can also be subjected to hydrophobization treatment. The hydrophobic treatment can be obtained, for example, by treating hydrophilic fine particles with a silane coupling agent such as methyltrimethoxysilane, methyltriethoxysilane, or octyltrimethoxysilane. Alternatively, inorganic fine particles can be heat-treated with silicone oil to make them hydrophobic.

Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, chlorphenyl silicone oil, methyl hydrogen silicone oil, alkyl-modified silicone oil, fluorine-modified silicone oil, polyether-modified silicone oil, alcohol-modified silicone oil, amino Examples include modified silicone oil, epoxy-modified silicone oil, epoxy/polyether-modified silicone oil, phenol-modified silicone oil, carboxyl-modified silicone oil, mercapto-modified silicone oil, methacrylic-modified silicone oil, α-methylstyrene-modified silicone oil, and the like.

Commercially available inorganic fine particles can be used. For example, examples of silica include R972, R974, RX200, RY200, R202, R805, and R812 (all manufactured by Nippon Aerosil Co., Ltd.). Examples of titania include P-25 (manufactured by Nippon Aerosil Co., Ltd.), STT-30, STT-65C-S (all manufactured by Titanium Industries Co., Ltd.), TAF-140 (manufactured by Fuji Titanium Industries Co., Ltd.), MT -150W, MT-500B, MT-600B, MT-150A (all manufactured by Teika Co., Ltd.). Examples of hydrophobized titania fine particles include T-805 (manufactured by Nippon Aerosil Co., Ltd.), STT-30A, STT-65S-S (both manufactured by Titanium Kogyo Co., Ltd.), TAF-500T, and TAF-1500T. (all manufactured by Fuji Titanium Industries Co., Ltd.), MT-100S, MT-100T (all manufactured by Teika Co., Ltd.), and IT-S (all manufactured by Ishihara Sangyo Co., Ltd.).

The specific surface area of the inorganic fine particles measured by the BET method is preferably 20 m ² /g to 500 m 2 ^/ g, more preferably 30 m ² /g to 400 m ² /g, from the viewpoint of improving stress resistance.

In addition to the above-mentioned inorganic fine particles, as external additives, for example, fatty acid metal salts (for example, zinc stearate, aluminum stearate, etc.), fluoropolymers, etc. can also be used in combination.

Further, as described above, the content of the external additive is preferably 1.8% by mass or less in the toner. Further, as described above, the volume average particle diameter of the external additive is preferably 5 nm or more and 50 nm or less.

<Toner base particles>
The toner base particles in the present invention include, for example, a binder resin, a colorant, a charge control agent, a release agent, and the like. Known materials can be used for the toner base particles.

[Binder resin]
As the binder resin, polymers of styrene and its substituted products such as polystyrene, polyp-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer Copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methacrylic acid Methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer , styrene-based copolymers such as styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl Methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, aliphatic resin Examples include alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, and paraffin waxes, which can be used alone or in combination.

[Colorant]
As the coloring agent, all known dyes and pigments can be used, such as carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher. , yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), Vulcan fast yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Red Red Red, Lead Red, Lead Vermilion, Cadmium Red, Cadmium Mercury Red, Antimony Vermilion, Permanent Red 4R, Para Red, Phi Cered, Parachlororthonitroaniline Red, Lysole Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmin BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Lysol Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pogment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B , rhodamine lake Y, alizarin lake, thioindigo red B, thioindigo maroon, oil red, quinacridone red, pyrazolone red, polyazole red, chrome vermilion, benzidine orange, perinone orange, oil orange, cobalt blue, cerulean blue, alkali blue Lake, peacock blue lake, Victoria blue lake, metal-free phthalocyanine blue, phthalocyanine blue, fast sky blue, indanthrene blue (RS, BC), indigo, ultramarine, navy blue, anthraquinone blue, fast violet B, methyl violet lake, cobalt Purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment green B, naphthol green B, green gold, acid green lake, malachite green lake, phthalocyanine green, anthraquinone green, Titanium oxide, zinc white, lithobon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight per 100 parts by weight of the binder resin.

[Charge control agent]
Known charge control agents can be used, such as nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified (including quaternary ammonium salts), alkylamides, phosphorus alone or compounds, tungsten alone or compounds, fluorine-based activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives.

The amount of charge control agent used in the present invention is determined by the toner manufacturing method including the type of binder resin, the presence or absence of additives used as necessary, and the dispersion method, and is determined uniformly. However, it is preferably used in an amount of 0.1 to 10 parts by weight, preferably 2 to 5 parts by weight, based on 100 parts by weight of the binder resin. Moreover, if necessary, it may be used in combination with a plurality of charge control agents.

[Release agent]
In the present invention, a release agent may be used to impart release properties to the toner. The softening point of the mold release agent used is preferably 70 to 100°C.

As mold release agents, synthetic waxes such as low molecular weight polyethylene, polypropylene, and their copolymers, vegetable waxes such as candelilla wax, carnauba wax, rice wax, tree wax, and jojoba wax, beeswax, lanolin, and whale wax are used. Examples include animal waxes such as wax, mineral waxes such as montan wax and ozokerite, and fat and oil waxes such as hydrogenated castor oil, hydroxystearic acid, fatty acid amides, and phenol fatty acid esters.

Looking at waxes in terms of chemical structure, hydrocarbon waxes, ester waxes, amide waxes, etc. are known, but ester waxes are the most popular in terms of storage stability, image quality, fixing temperature range, etc. It is suitable for evaluation.

The amount of the release agent is preferably 1 to 6 parts by mass based on the entire toner.

The toner manufacturing method of the present invention may be a conventionally known method, and includes a manufacturing method that involves the steps of mixing, kneading, rolling cooling, pulverizing, and classifying the toner raw materials. For example, after mixing the raw materials, the toner is The toner is obtained by kneading with a kneader, cooling with a belt cooler, pulverizing with a jet mill, and classifying.

The weight average particle diameter of the toner is preferably 4 μm to 10 μm, more preferably 5 μm to 8 μm.

(Developer)
The developer in the present invention contains a toner that can be used in the present invention, and can be used, for example, as a dry one-component developer (one-component developer) or a dry two-component developer (two-component developer). When used as a dry two-component developer, the amount of the carrier and the toner of the present invention to be used is such that the toner particles adhere to the carrier surface of the carrier particles and occupy, for example, 30 to 90% of the surface area of both particles. It is preferable to mix.

As the carrier used, conventionally known carriers such as iron powder, ferrite, glass beads, etc. can be used. Note that these carriers may be coated with resin. In this case, the resin used is polyfluorocarbon, polyvinyl chloride, polyvinylidene chloride, phenol resin, polyvinyl acetal, silicone resin, etc.

In either case, the appropriate mixing ratio of toner and carrier is about 0.5 to 6.0 parts by mass of toner to 100 parts by mass of carrier.

(Other examples of image forming devices)
Next, another example of the image forming apparatus of the present invention will be described.
The image forming apparatus of the present invention also includes a form including a process cartridge.
The process cartridge in this embodiment is one that integrates an image carrier (electrostatic latent image carrier, photoreceptor), a charging member, and a developing means, and stores toner. The process cartridge may further include an exposure means and the like. A process cartridge is an example of a process unit.

In the present invention, when a process cartridge of a cleaning-less type (for example, does not include a cleaning blade for cleaning an image bearing member) is provided, the life of the cleaner-less type process cartridge can be extended, and durability over time can be increased. be able to. According to the present invention, the influence of paper dust and transfer residual toner can be reduced without increasing manufacturing costs, and the charging member can maintain a good charging state even over time.

Next, one embodiment of the process cartridge is shown in FIG. As shown in FIG. 5, the process cartridge of this embodiment incorporates an electrostatic latent image carrier 101, includes a charging device 102, a developing device 104, and further has other means as necessary. In FIG. 5, reference numeral 103 indicates exposure from an exposure device, and reference numeral 105 indicates recording paper.

As the electrostatic latent image carrier 101, for example, those described below can be used. Further, an arbitrary charging member is used for the charging device 102.
An image forming process using the process cartridge shown in FIG. 5 will be described. As the electrostatic latent image carrier 101 rotates clockwise, an electrostatic latent image corresponding to the exposed image is formed on its surface by charging by a charging device 102 and exposure 103 by an exposure means (not shown). .
This electrostatic latent image is developed with toner by a developing device 104, and the developed toner image is transferred onto recording paper 105 by a transfer roller 108 and printed out. Next, the static electricity is further removed by the static eliminating means, and the above operation is repeated again.

The image forming apparatus of the present invention includes an image bearing member, a charging member disposed in contact with the image bearing member to charge the image bearing member, and a charging member configured to supply toner to the image bearing member, It has a developing means for forming a toner image thereon, and a transfer means for transferring the toner image on the image carrier onto a recording medium or an intermediate transfer member. Further, the developing means in this embodiment collects transfer residual toner remaining on the image carrier after the transfer. Furthermore, it has other means selected as appropriate, such as a static elimination means, a recycling means, a control means, and the like.

The image forming method used in the present invention includes a charging step of charging an image carrier, a developing step of supplying toner to the image carrier and forming a toner image on the image carrier, and a development step of supplying toner to the image carrier and forming a toner image on the image carrier. and a transfer step of transferring the toner image to a recording medium or an intermediate transfer member. Furthermore, it has other means selected as appropriate, such as a static elimination means, a control means, etc., as necessary. Furthermore, other processes selected as necessary, such as a static elimination process, a control process, etc., are included.

In the following description, the charging step and the exposure step will be referred to as an electrostatic latent image forming step, and the charging means and the exposing means will be referred to as an electrostatic latent image forming means.

-Electrostatic latent image forming process and electrostatic latent image forming means-
The electrostatic latent image forming step is a step of forming an electrostatic latent image on the electrostatic latent image carrier.
There are no particular restrictions on the material, shape, structure, size, etc. of the electrostatic latent image carrier (sometimes referred to as "electrophotographic photoreceptor", "photoreceptor", or "image carrier"). , can be appropriately selected from known ones. Its shape is preferably a drum shape, and its material includes, for example, an inorganic photoreceptor such as amorphous silicon or selenium, or an organic photoreceptor (OPC) such as polysilane or phthalopolymethine. Among these, organic photoreceptors (OPCs) are preferable because they provide higher definition images.

Formation of the electrostatic latent image can be performed, for example, by uniformly charging the surface of the electrostatic latent image carrier and then imagewise exposing it to light, and may be performed by an electrostatic latent image forming means. Can be done.
The electrostatic latent image forming means includes, for example, a charging means (charger) that uniformly charges the surface of the electrostatic latent image carrier, and an exposure device that imagewise exposes the surface of the electrostatic latent image carrier. means (exposure device).

The charging can be performed, for example, by applying a voltage to the surface of the electrostatic latent image carrier using the charger. The charger may also be referred to as a charging member.
The charger is not particularly limited and can be appropriately selected depending on the purpose, but for example, a contact charger that is known per se and equipped with a conductive or semiconductive roll, brush, film, rubber blade, etc. Examples include utensils. Among them, it is preferable to use a charging roller, and it is more preferable to use a charging rubber roller.
The charger is preferably one that is arranged so as to come into contact with the image carrier and charges the surface of the electrostatic latent image carrier by applying a DC voltage. Direct current and alternating current voltages may be applied in a superimposed manner.

The exposure can be performed, for example, by imagewise exposing the surface of the electrostatic latent image carrier using the exposure device.
The exposure device is not particularly limited as long as it can expose the surface of the electrostatic latent image carrier charged by the charger in the form of an image to be formed, and may be selected as appropriate depending on the purpose. Examples of exposure devices include copying optical systems, rod lens array systems, laser optical systems, liquid crystal shutter optical systems, and the like.
In the present invention, a back-light method may be adopted in which exposure is performed imagewise from the back side of the electrostatic latent image carrier.

-Developing process and developing means-
The developing step is a step of developing the electrostatic latent image using the toner to form a visible image (which may also be referred to as a toner image).
Formation of the visible image can be performed, for example, by developing the electrostatic latent image using the toner, and can be performed by the developing means.
The developing means preferably includes at least a developing device that accommodates the toner and can apply the toner to the electrostatic latent image in a contact or non-contact manner, and the developing device includes a container containing toner. etc. are more preferable.

The developing device may be a single-color developing device or a multi-color developing device, and includes, for example, an agitator that frictionally stirs the toner to charge it and a rotatable magnetic roller. Preferred examples include:
In the developing device, for example, the toner is mixed and stirred, and the toner is charged by friction at that time and held in a spiked state on the surface of a rotating magnet roller, thereby forming a magnetic brush. Since the magnet roller is disposed near the electrostatic latent image carrier (image carrier, photoreceptor), a portion of the toner constituting the magnetic brush formed on the surface of the magnet roller is It moves to the surface of the electrostatic latent image carrier (image carrier, photoreceptor) by electrical attraction. As a result, the electrostatic latent image is developed by the toner, and a visible image is formed by the toner on the surface of the electrostatic latent image carrier (image carrier, photoreceptor).

-Transfer process and transfer means-
The transfer step is a step of transferring the visible image to a recording medium, using an intermediate transfer body, and after first transferring the visible image onto the intermediate transfer body, transferring the visible image onto the recording medium. Preferably, a mode in which secondary transfer is performed is performed, and a primary transfer step in which two or more colors, preferably full-color toners are used as the toner, and a visible image is transferred onto an intermediate transfer body to form a composite transferred image; A more preferred embodiment includes a second transfer step of transferring the transferred image onto a recording medium.
The transfer can be performed, for example, by charging the electrostatic latent image carrier (image carrier, photoreceptor) with the visible image using a transfer charger, and can be performed by the transfer means. . The transfer means includes a primary transfer means for transferring a visible image onto an intermediate transfer body to form a composite transfer image, and a secondary transfer means for transferring the composite transfer image onto a recording medium. Aspects are preferred.
Note that the intermediate transfer body is not particularly limited and can be appropriately selected from known transfer bodies depending on the purpose, and suitable examples include a transfer belt and the like.

The transfer means (the first transfer means, the second transfer means) transfers the visible image formed on the electrostatic latent image carrier (photoreceptor) to the recording medium by peeling and charging it. It is preferable to have at least a container. The number of the transfer means may be one, or two or more.
Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, an adhesive transfer device, and the like.

Note that the recording medium is not particularly limited and can be appropriately selected from known recording media (recording paper). Recording media include cardboard, postcards, envelopes, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, etc. In addition, OHP sheets, OHP films, etc. can be used. is also possible.

-Fixing process and fixing means-
The fixing step is a step of fixing the visible image transferred to the recording medium using a fixing device, and may be performed each time the visible image is transferred to the recording medium for each color developer, or may be performed for each color developer. However, this may be done simultaneously in a laminated state.
The fixing device is not particularly limited and can be appropriately selected depending on the purpose, but known heating and pressing means are suitable. Examples of the heating and pressing means include a combination of a heating roller and a pressure roller, a combination of a heating roller, a pressure roller, and an endless belt, and the like.
The fixing device includes a heating element including a heating element, a film in contact with the heating element, and a pressure member in pressure contact with the heating element via the film, and the film and the pressure member are in contact with each other. Preferably, it is a means for heating and fixing by passing a recording medium on which an unfixed image is formed. The heating in the heating and pressurizing means is usually preferably performed at a temperature of 80°C to 200°C.
In the present invention, for example, a known optical fixing device may be used in addition to or in place of the fixing step and fixing means, depending on the purpose.

-Other processes and other means-
The static elimination step is a process of applying a static elimination bias to the electrostatic latent image carrier to eliminate static electricity, and can be suitably performed by a static elimination means.
The static eliminating means is not particularly limited as long as it can apply a static eliminating bias to the electrostatic latent image carrier, and can be appropriately selected from known static eliminators, such as a static eliminating lamp, etc. Preferred examples include:

It is preferable to include a brush member for scraping dirt off the charging member. As the brush member, for example, the cleaning brush described above can be used. By using such a brush member, image quality stability over time is improved. The brush member may rotate or may be fixed without rotating. Further, such a brush member may collect toner.

In addition to the brush member described above, a collection means for collecting toner remaining on the charging member may be provided. The collecting means is not particularly limited as long as it can remove the toner remaining on the charging member, and can be appropriately selected from known methods, such as magnetic brushes, electrostatic brushes, magnetic brushes, etc. Preferred examples include rollers, blades, webs, and the like.

The control step is a step of controlling each of the steps, and each step can be suitably performed by a control means.
The control means is not particularly limited as long as it can control the movement of each of the means, and can be appropriately selected depending on the purpose, and examples thereof include equipment such as a sequencer and a computer.

Aspects of the present invention are, for example, as follows.
<1> Image carrier;
a charging member that is arranged to come into contact with the image carrier and charges the image carrier;
a developing unit that supplies toner to the image carrier and forms a toner image on the image carrier;
a transfer means for transferring the toner image on the image carrier to a recording medium or an intermediate transfer body;
The developing means collects transfer residual toner remaining on the image carrier after the transfer,
The surface roughness Rz of the charging member is 5 μm or more and 16 μm or less, and the electrical resistance value of the charging member is 0.1 MΩ or more and 1.6 MΩ or less, or
An image forming apparatus characterized in that the charging member has a surface roughness Rz of 5 μm or more and 18 μm or less, and has an electrical resistance value of 0.1 MΩ or more and 1.4 MΩ or less.
<2> The toner includes base particles and an external additive,
The image forming apparatus according to item <1>, wherein the external additive is contained in the toner in an amount of 1.8% by mass or less.
<3> The toner includes base particles and external additives,
The image forming apparatus according to <1> or <2>, wherein the external additive has a volume average particle diameter of 5 nm or more and 50 nm or less.
<4> The image forming apparatus according to any one of <1> to <3>, wherein the image forming apparatus does not include a cleaning blade for cleaning the image carrier.
<5> The image forming apparatus according to any one of <1> to <4>, further comprising a brush member for scraping dirt off the charging member.
<6> The image forming apparatus according to any one of <1> to <5>, wherein the charging member is a charging rubber roller.
<7> A process cartridge in which the image carrier, the charging member, and the developing means are integrated,
The image forming apparatus according to any one of <1> to <6>, wherein the process cartridge does not include a cleaning blade for cleaning the image carrier.

10 Image carrier (photosensitive drum)
20 Charging roller 62 Transfer roller 72 Developing roller 161 Cleaning brush

Japanese Patent Application Publication No. 2004-126104 Patent No. 3596535

Claims (7)

an image carrier;
a charging member that is arranged to come into contact with the image carrier and charges the image carrier;
a developing unit that supplies toner to the image carrier and forms a toner image on the image carrier;
a transfer means for transferring the toner image on the image carrier to a recording medium or an intermediate transfer body;
The developing means collects transfer residual toner remaining on the image carrier after the transfer,
The surface roughness Rz of the charging member is 5 μm or more and 16 μm or less, and the electrical resistance value of the charging member is 0.1 MΩ or more and 1.6 MΩ or less, or
An image forming apparatus characterized in that the charging member has a surface roughness Rz of 5 μm or more and 18 μm or less, and has an electrical resistance value of 0.1 MΩ or more and 1.4 MΩ or less. The toner includes base particles and external additives,
The image forming apparatus according to claim 1, wherein the external additive is contained in the toner in an amount of 1.8% by mass or less. The toner includes base particles and external additives,
The image forming apparatus according to claim 1, wherein the external additive has a volume average particle diameter of 5 nm or more and 50 nm or less. The image forming apparatus according to claim 1, characterized in that the image forming apparatus does not include a cleaning blade for cleaning the image carrier. The image forming apparatus according to claim 1, further comprising a brush member for scraping dirt off the charging member. The image forming apparatus according to claim 1, wherein the charging member is a charging rubber roller. comprising a process cartridge in which the image carrier, the charging member, and the developing means are integrated;
The image forming apparatus according to claim 1, wherein the process cartridge does not include a cleaning blade for cleaning the image carrier.

Images