JPH06202442A - Image forming device - Google Patents

Abstract

PURPOSE:To always obtain a stable and high-quality image by preventing toner and the additive agent of toner from adhering to the surface of an image carrier. CONSTITUTION:In an image forming device, a photosensitive drum 1 is uniformly electrostatically charged by using a roller electrostatic charger 2 being a contact electrostatic charging device, and then a latent image is formed and developed with a developer, thereby forming a visible image. The charger 2 is constituted by providing an elastic layer 24 consisting of a conductive urethane sponge on a core bar 21 such as a metallic roller, etc., and further providing an urethane rubber layer 23 whose volume resistivity is about 10<5>OMEGA.cm by dispersing carbon on the elastic layer 24. One-component developer using toner whose glass transition temperature Tg is 50 deg.C to 70 deg.C is used as the developer. Furthermore, the number of foaming cells of the elastic layer 24 of the charger 2 is selected and set to the range of 20 cells/inch to 50 cells/inch, desirably, 20 cells/ inch to 40 cells/inch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer such as an electrophotographic system or an electrostatic recording system,
In particular, it relates to an image forming apparatus using a contact charging method.

[0002]

2. Description of the Related Art Conventionally, developers (toners) of different colors
A plurality of developing devices for accommodating each of them are provided, and the steps of charging, exposing, developing, and transferring are sequentially performed by using an electrophotographic method.
A color image forming apparatus that forms a full-color or multi-color multi-color image in a plurality of recording cycles is widely used. Among such conventional electrophotographic color image forming apparatuses, a schematic configuration example of a color image forming apparatus that includes a transfer drum and forms a multicolor image by a plurality of recording cycles is shown in FIG.

In FIG. 8, for example, an organic photoconductor (OPC) or A-Si, CdS, S is formed on the outer peripheral surface of an aluminum cylinder.
The photoconductor drum 1 as an image bearing member formed by applying a photoconductor made of e or the like is rotationally driven in the direction of the arrow in the drawing by a driving unit (not shown). A roller-type contact charging device (hereinafter, abbreviated as a roller charger) 2 for uniformly charging the photoconductor drum 1 along the rotation direction of the photoconductor drum 1, and developing a latent image after exposure. A plurality of developing devices 4 for separately storing different color developing agents, for example, yellow (Y), magenta (M), cyan (C), and black (BK) color developing agents (toners).
A rotary developing device 4 that rotatably supports a, 4b, 4c, and 4d by a support 5, and a recording material carrier that carries and conveys a recording material (paper) onto which a developed visible image (toner image) is transferred. A transfer drum 6, a cleaning device 7 for removing residual toner and the like on the photosensitive drum 1, and the like are provided.

Further, in this example, the optical signal E emitted from the exposure device 3 having a light source such as a laser is, for example, a rotating mirror,
An electrostatic latent image is formed on the photosensitive drum 1 by raster-scanning the photosensitive drum 1 through an imaging lens, a reflecting lens, and the like. The optical signal E enters the exposure position between the roller charger 2 and the developing device 4.

The developing device 4 corresponds to the electrostatic latent image formed on the photosensitive drum 1 by the optical signal E, and electrostatically develops the developer, that is, the developer from the selected developing devices 4a to 4d. The toner is caused to fly and the electrostatic latent image is developed to form a toner image of the selected color. This toner image is transferred onto the recording material carried on the transfer drum 6 at the image transfer position (image transfer portion).

The transfer drum 6 is rotatably supported at the center thereof in the direction of the arrow shown in the drawing, and the photosensitive drum 1
The surface of the photosensitive drum 1 is in contact with or slightly separated from the surface of the photosensitive drum 1. This transfer drum 6 is shown in FIG.
As shown in FIG. 2, a dielectric sheet 6b of PET, PVdF or the like is stretched in a substantially cylindrical shape in a notch portion of a drum casing 6a having a notch structure in which the outer peripheral surface of a hollow drum casing is notched only in the transfer region. It has (hereinafter, abbreviated as a notch-structured transfer drum), and rotates in the arrow direction at substantially the same speed as the photosensitive drum 1. Further, a gripper 66 that holds the leading end of the recording material is provided on a part of the support 6a.

As a means for electrostatically adsorbing the recording material fed from the inside of the paper feed cassette 10 by the pickup roller 9 to the dielectric sheet of the transfer drum 6 inside and outside the transfer drum 6 along the rotation direction thereof. Suction roller 67
a, a suction charger 67b, and a transfer charger 6 as a means for transferring the toner image formed on the photosensitive drum 1.
9. A pair of separating chargers 64a and 64b for separating the recording material held on the transfer drum 6, and guiding the recording material after separation to the fixing device 8 for guiding the separated recording material to the fixing device 8. A separating claw 65 for removing the recording material, a transfer drum cleaning device 68 for removing the toner and the like adhering to the surface of the transfer drum 6 after the recording material is separated, and the like are provided.

Next, an image forming process of the color image forming apparatus having the above structure will be described. First, the photoconductor drum 1 is uniformly charged to a predetermined potential by the roller charger 2, and then the photoconductor drum 1 is subjected to the optical signal E modulated by the image signal of the first color, for example, yellow input to the exposure device 3. A first color electrostatic latent image of yellow is formed on the upper surface. The yellow electrostatic latent image is developed into a visible image by the developing device 4a containing the yellow (Y) developer which is previously placed at the developing position by the rotation of the support 5 of the developing device 4.

In parallel with this process, the transfer drum 6 holds the leading end of the recording material supplied in synchronization with the formation of an image by a gripper 66, and a suction roller 67a which can be brought into contact with and separated from the transfer drum 6 is used. The recording material is sandwiched between the attraction roller and the transfer drum 6, and at the same time, the recording material is electrostatically attracted to the surface of the transfer drum by applying an electric charge to the dielectric sheet forming the surface of the transfer drum by the attraction charger 67b.

The recording material held on the transfer drum 6 is conveyed by the rotation of the transfer drum 6 to an image transfer portion located at a position facing the photoconductor drum 1, and a yellow toner image formed on the photoconductor drum 1 is conveyed. Is transferred onto the recording material by the action of the transfer charger 69. After that, the developer or the like remaining on the surface of the photosensitive drum 1 is removed by a cleaning device 7 such as a known blade means, and is uniformly charged again by the roller charger 2, and then the photosensitive device 1 is exposed by the exposure device 3. An electrostatic latent image based on the image signal of the second color, for example, magenta, is formed on the upper side. The electrostatic latent image of the second color is developed by the developing device 4b containing the magenta (M) developer corresponding to the image signal of the second color, and becomes a magenta toner image. The magenta toner image of the second color is transferred onto the recording material carried and conveyed by the transfer drum 6 again by the action of the transfer charger 69. As a result, the second-color magenta toner image is superimposed on the first-color yellow toner image that was previously transferred.

The above-mentioned charging, exposing, developing and transferring steps are repeated for the third color cyan (C) and the fourth color black (BK) image formation. When the color toner images are transferred in an overlapping manner, the separation charging device 64a disposed inside and outside the transfer drum 6 to face each other,
64b operates to remove the electrostatic attraction force between the recording material conveyed by the transfer drum 6 and the surface of the transfer drum 6. Further, the gripper 66 holding the leading end of the recording material is released. At the same time, the separation claw 65 is operated to separate the recording material from the transfer drum 6 and send it to the recording material conveying means. The recording material is sent to the known heating and pressure type fixing device 8 by the recording material conveying means, and the toner images multiple-transferred by the fixing device 8 are fused and fixed on the recording material to obtain a color image. Thus, the desired full-color print can be obtained.

After the recording material is separated, the transfer drum 6 after separation of the recording material is removed by operation of a transfer drum cleaning device 68 such as a fur brush or a web to remove the toner and the like adhering to the surface thereof, and prepares for the next transfer step. .

FIG. 10 is a sectional view of the roller charger 2, for example, Japanese Patent Laid-Open No. 63-149668 and Japanese Patent Laid-Open No. 6-96868.
It is disclosed in Japanese Patent Laid-Open No. 3-149669. The roller charger 2 has an advantage that ozone, which is harmful to the human body, is extremely less than the conventional corona charger, and has been put into practical use in recent years.

As shown in FIG. 10, this roller charger 2
Is provided with a conductive elastic layer 22 made of EPDM, NBR, silicon rubber or the like on a cored bar 21 such as a metal roller, and further, on the elastic layer 22, for example, a urethane rubber layer 23 in which carbon is dispersed (volume resistance). It has a structure in which a ~10 ⁵ Ω · cm), urethane rubber layer 23 is in contact with the photosensitive drum 1, 2 or more times the peak voltage of the charge starting voltage from a power source (not shown) to the core 21 ( The photosensitive drum 1 is uniformly charged by applying a pulsating voltage having V _PP ).

Further, as shown in FIG. 11, the roller charger 2 is formed in a shape called a crown, for example, the diameter of the end portion is 12 mm, while the diameter of the central portion is 100 μm or more. There are many cases. With such a shape, the photosensitive drum 1 can be charged more uniformly.

As another example of the contact type charging device, as shown in FIG. 12, a blade type contact type charging device 3 is used.
0 (hereinafter, simply referred to as a blade charger) has also been proposed and put into practical use in recent years. In this blade charger 30, the tip end of a conductive elastic blade 31 is, for example, a urethane rubber layer 32 in which carbon is dispersed (volume resistance: 10 ⁵ Ω · cm).
The urethane rubber layer 32 is in contact with the photosensitive drum 1, and a pulsating voltage having a peak-to-peak voltage (V _PP ) that is at least twice the charging start voltage is applied to the elastic blade 31 from a power source (not shown). By doing so, the photosensitive drum 1 is uniformly charged.

On the other hand, as for the transfer drum 6, as shown in FIG. 13, an elastic layer 6d of urethane foam, silicone rubber foam or the like is provided on a conductive drum housing 6c having no notch, and further, this elastic layer 6d. A transfer drum 6A having a structure in which the surface thereof is covered with the dielectric sheet 6b as described above (hereinafter, abbreviated as solid-state transfer drum) is also in practical use, and an appropriate bias voltage is applied to the drum housing 6c during transfer. As a result, the toner image formed on the photosensitive drum 1 can be transferred in the same manner as the cutout-structure transfer drum 6.

[0018]

However, in the above-mentioned conventional example, there is a problem that a so-called filming phenomenon occurs in which the toner or the external additive of the toner adheres to the surface of the photosensitive layer of the photosensitive drum 1. . Particularly, in the case of the crown-shaped roller charger as shown in FIG.
The diameter at the center of the roller charger 2 is 10 more than the diameter at the end.
Since it is larger than 0 μm, the peripheral speed at the center of the roller becomes higher than the peripheral speed at the end. As a result, the toner and its external additives that have slipped through the cleaning blade of the cleaning device 7 are strongly rubbed against the photosensitive drum 1 at the center of the roller having a high peripheral speed, and adhere to the surface of the photosensitive layer of the photosensitive drum 1. . Therefore, when a crown-shaped roller charger is used, more filming phenomenon occurs.

When this filming occurs, the charge of the photosensitive layer in the portion where the toner or the external additive of the toner adheres is not attenuated even when exposed, so that a normal latent image is not formed and the image quality is remarkably deteriorated. . In particular, in a color image forming apparatus, a toner having a glass transition temperature Tg of about 50 ° C. to 70 ° C. is used in order to improve color mixture color development of the toner at the time of fixing. It is easy for problems to occur.

When the central portion of the surface of the photosensitive drum is strongly rubbed by the roller charger, the photosensitive layer at that portion is scraped off, and the central portion and the end portion of the photosensitive layer have different thicknesses. Will end up. As a result, the latent image potentials formed on the photoconductor drums are different, resulting in uneven image density. This was not a problem in the conventional black and white image forming apparatus,
The color image forming apparatus has a problem that the color balance is lost.

Further, when the above-mentioned solid-state transfer drum 6A is used as the transfer drum and the contact type charging device is used, the toner is fused on the photosensitive drum, and the normal charging is performed on the photosensitive drum. There is a problem in that the photosensitive drum must be replaced because black spots and white spots are generated on the image without exposure and the image quality is significantly impaired.

This is because the photosensitive drum is pressed by the bias voltage applied by the roller charger or the blade charger,
Fine particles of silica or the like that have slipped through the cleaning blade of the cleaning device 7 are embedded in the photosensitive layer on the photosensitive drum, and the toner adheres to the embedded fine particles and is fused on the photosensitive drum. it is conceivable that. Further, since the solid constitution transfer drum 6A is in contact with the photosensitive drum via the elastic layer 6d, its pressure is higher than that of the cutout constitution transfer drum 6, so that the fine particles are embedded in the photosensitive layer and the toner is melted. It encourages wearing.
In particular, when a color image is formed, a sharp melt toner is used in order to improve the color-mixing and coloring property of the toner at the time of fixing, so that there is a drawback that the fusion of the toner is more likely to occur.

Therefore, an object of the present invention is to use the contact type charging means which can prevent the toner, the external additive of the toner and the like from adhering to the surface of the image bearing member and can always obtain a stable and high quality image. Another object of the present invention is to provide the image forming apparatus.

[0024]

The above object is achieved by the image forming apparatus according to the present invention. In summary, in the first aspect of the present invention, a latent image is formed after the image carrier is uniformly charged by a contact type charging means, and the latent image is developed with a developer to form a visible image. In the image forming apparatus, the developer has a glass transition temperature of 50 ° C. to 70 ° C., and the contact type charging unit is a roller charging unit having at least a foam layer on a roller-shaped conductive support, The image forming apparatus is characterized in that the number of foam cells of the foam is 20 cells / inch to 50 cells / inch.

Further, in the second aspect, the present invention provides
In an image forming apparatus for forming a latent image after uniformly charging an image carrier by a contact type charging means and developing the latent image with a developer, a glass transition temperature of the developer is 50 ° C. The image forming apparatus is characterized in that the contact type charging means is a brush charging means.

Further, in a third aspect, the present invention provides
In an image forming apparatus for forming a latent image after uniformly charging an image carrier by a contact type charging means and developing the latent image with a developer, a glass transition temperature of the developer is 50 ° C. ˜70 ° C., and the contact type charging means is a roller-shaped charging means, and the difference between the portion having the highest peripheral speed and the portion having the slowest peripheral speed of the roller-shaped charging means is 0.08% to 0.
The image forming apparatus is 8%, preferably 0.16% to 0.5%.

Further, in the fourth aspect of the present invention, a latent image is formed after the image carrier is uniformly charged by the contact type charging means, and the latent image is developed with a developer to form a visible image. In the image forming apparatus capable of forming a color image by repeating the step of transferring the visible image to a recording material, the image forming method is characterized in that a glass transition temperature of the developer is 60 ° C to 70 ° C. It is a device.

[0028]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view showing the overall construction of a first embodiment in which the present invention is applied to an electrophotographic color image forming apparatus. In the color image forming apparatus of this embodiment, the solid-state transfer drum 6A as shown in FIG. 13 is used as the transfer drum, and accordingly, the recording material adsorbing means, the toner image transferring means, the recording material separating means, etc. The configuration is the same as that of the conventional color image forming apparatus shown in FIG. 8 except that is slightly changed. Therefore, corresponding elements, members, parts and the like are designated by the same reference numerals unless necessary. Will be omitted.

Also in this embodiment, for example, an organic photoreceptor (OPC) or A-Si, Cd is formed on the outer peripheral surface of an aluminum cylinder.
The photoconductor drum 1 having a photoconductor made of S, Se or the like applied is used as an image carrier and is rotationally driven in the direction of the arrow in the figure. A roller charger (roller type contact type charging device) 2 that uniformly charges the photosensitive drum 1 along the rotation direction of the photosensitive drum 1, and develops different colors for developing latent images after exposure. A plurality of developing devices 4a, 4b, 4c and 4d, which separately store color developing agents (toners) such as yellow (Y), magenta (M), cyan (C) and black (BK), are provided by the support 5. A rotary developing device 4 that rotatably supports, carrying a recording material (paper) onto which a developed visible image (toner image) is transferred,
A transfer drum 6A as a recording material carrier to be conveyed, a cleaning device 7 for removing residual toner and the like on the photosensitive drum 1, and the like are provided.

The developing device 4 is a so-called rotary type in which one of the plurality of developing devices 4a to 4d supported by the support 5 is fixed in advance at the developing position by the rotation of the support 5. This is a developing device, and the developing opening surfaces 44a, 44 of the developing devices are formed on the same cylinder centered on the rotation axis of the support.
b, 44c and 44d are set. Support 5
The developing devices 4a to 4d attached to are driven so that their developing opening surfaces 44a to 44d always face the surface of the photosensitive drum 1.

One means of this driving method is disclosed in, for example, Japanese Patent Laid-Open No.
It is described in detail in JP-A-0-93437. Here, each of the developing devices 4a to 4d is replaced with a two-component developing system using a mixture of a non-magnetic toner and a magnetic carrier as a developer,
A one-component developing method using only non-magnetic toner has been proposed. Compared to the two-component developing method, this method does not require a developer mixing means, a means for maintaining a constant mixing ratio, a magnet for carrying and carrying the developer, and the like, and thus it is possible to provide a smaller and lower cost apparatus. It has the advantage of being possible.

Yellow toner, magenta toner, cyan toner, and black toner are contained in the developing devices 4a, 4b, 4c, and 4d, respectively, and further, coating rollers 42a, 42b, 42c, and 42d,
And toner regulation members 43a, 43b, 43c, and 4
3d are provided, and the developing rollers 41a, 41b, 4 are provided.
1c and 41d, the toner applying roller 4
The toner on 2a to 42d is applied to the developing rollers 41a to 41d, and necessary toner is applied to the toner by the toner regulating members 43a to 43d.

The material of the regulating members 43a to 43d is preferably nylon or the like when the toner has a negative polarity and silicon rubber or the like when the toner is positively charged. In short, the polarity is opposite to the polarity of the toner. A material that is electrostatically charged is preferable. Further, it is preferable to select the peripheral speed in the range of 1.0 to 2.0 times the peripheral speed of the photosensitive drum 1.

At the time of development, an alternating electric field is preferably applied to the developing rollers 41a to 41d from a power source (not shown) to perform development. The developing rollers 41a to 41d are opposed to the surface of the photosensitive drum 1 with a gap of 150 to 450 μm, and a contact member for holding the gap coaxially with the developing rollers 41a to 41d is provided. It is provided and brought into contact with the photosensitive drum 1 to maintain accuracy.

On the other hand, in the transfer drum 6A, as described above, the elastic layer 6d such as urethane foam or silicone rubber foam is provided on the conductive drum housing 6c having no notch, and the surface of the elastic layer 6d is further covered. It is a solid-state transfer drum having a structure covered with a dielectric sheet 6b, and transfers by applying a transfer bias to the conductive drum housing 6c.

FIG. 2 is a schematic sectional view showing the structure of the roller charger 2 used in this embodiment. The roller charger 2 is made of a conductive urethane sponge on a metal core 21 such as a metal roller. The elastic layer 24 is provided, and the urethane sponge elastic layer 24 is further provided with the urethane rubber layer 23 in which, for example, carbon is dispersed to have a volume resistance of about 10 ⁵ Ω · cm. The rubber layer 23 is brought into contact with the photosensitive drum 1, and a pulsating voltage having a peak-to-peak voltage (V _PP ) that is at least twice the charging start voltage is applied to the core metal 21 from a power source (not shown). Is uniformly charged.

In the image forming apparatus of this embodiment described above, the glass transition temperature Tg of the toner is preferably 50 to 50.
It is set to 70 ° C. The glass transition temperature Tg of the toner and the permanent image after fixing have a close relationship, and specifically, a good color image can be obtained when the glass transition temperature Tg is in the range of 50 to 70 ° C.

This will be described. In the electrophotographic process, toners of different colors are melt-mixed in the fixing process to develop a desired color. Glass transition temperature Tg is 70 ° C
When the value exceeds the above range, the colors are not sufficiently mixed at the time of fixing and only an image with a dull hue can be obtained. On the other hand, when the temperature is 50 ° C. or lower, a so-called offset phenomenon occurs in which the melted toner adheres to the fixing roller. Here, the glass transition temperature Tg was measured by the method described below.

That is, the measurement is carried out using a differential thermal analysis measuring device (DSC measuring device), DSC-7 (manufactured by Perkin Elmer Co.). Measurement data is 5-20mg, preferably 10mg
Weigh accurately. Put this in an aluminum pan,
Using an empty aluminum pan as a reference, first perform the following operation to erase the previous history.

From room temperature to 200 ° C. under N ₂ atmosphere 10
The temperature is raised at a rate of ° C / min and the temperature is kept at 200 ° C for 10 minutes. afterwards,
Quench to reduce temperature to 10 ° C and hold at 10 ° C for 10 minutes. Then, the temperature is raised to 200 ° C. at a temperature rising rate of 10 ° C./min. In this temperature rising process, an endothermic peak of the main peak in the temperature range of 40 to 100 ° C. is obtained. At this time, the intersection of the line at the midpoint of the pace line before and after the appearance of the endothermic peak and the differential heat curve is taken as the glass transition temperature Tg in the present invention.

Four types of toners, the glass transition temperature Tg of which was measured by the method described above, namely toner A (glass transition temperature Tg 50 ° C.) and toner B (glass transition temperature Tg 60).
C.), toner C (glass transition temperature Tg 70.degree. C.), and toner D (glass transition temperature Tg 80.degree. C.) are prepared, and the number of foam cells in the urethane sponge elastic layer 24 of the roller charger 2 used in the above-described embodiment is determined. 20 cells / inch,
30 cells / inch, 40 cells / inch, and 50 cells / inch
Inch and E on the conventional cored bar 21 as a comparative example
Using the charging roller having the structure shown in FIG. 6 in which the elastic layer 22 of the PDM is provided and the resistance layer 23 is provided thereon, a toner image is formed by the image forming apparatus shown in FIG. After fixing, a print image was obtained, and the state of filming was observed (use conditions: temperature 30 ° C., relative humidity 80%, 2000
Sheet printing). The results are shown in Table 1 below.

[0043]

[Table 1]

When the roller charger 2 of the present embodiment is used, the urethane sponge elastic layer 24 has two foam cells.
For 0, 30, and 40 cells / inch, filming is performed using any of toners A, B, C, and D having glass transition temperatures Tg of 50 ° C., 60 ° C., 70 ° C., and 80 ° C., respectively. Did not occur (indicated by ◯ in Table 1). Further, when the number of foam cells is 50 cells / inch, only the toner A having a glass transition temperature Tg of 50 ° C. is 20
A slight filming occurs at the time of printing 00 sheets, which is not visible as a defect on the printed recording paper, but when the photosensitive layer of the photosensitive drum is observed with a microscope, the toner is fused. It was observed that the toner did not form (represented by Δ in Table 1), and filming did not occur with respect to the other toners (that is, ◯).

On the other hand, when the conventional roller charger is used, the toners A and B having the glass transition temperatures Tg of 50 ° C. and 60 ° C. are filmed and printed at the time of printing 2000 sheets. In the image on the recording paper, white spots were found in the black part, and the image quality was remarkably impaired (X in Table 1)
). Toner C having a glass transition temperature Tg of 70 ° C.
In regard to the above, as to the toner D having a glass transition temperature Tg of 80 ° C., no filming was observed at the time of printing 2000 sheets. Further, in all cases, the toner D having a glass transition temperature Tg of 80 ° C. had a poor color mixture color-developing property, and only an image having a dull hue was obtained.

When the number of foam cells is 20 cells / inch or less, when the roller charger 2 is brought into contact with the photosensitive drum 1, the number of foam cells is too small and the roller charger 2 is deformed. No charging was done. Therefore, the number of foam cells of the elastic layer 24 of the roller charger 2 is 20 cells / inch to 50 cells / inch, and preferably 20 cells / inch.
A range of 40 cells / inch is good. Further, similar results were obtained when a sponge other than urethane, such as EPDM or silicon rubber, was used as the sponge for the elastic layer 24.

As a mechanism of occurrence of filming by the roller charger 2, fine particle toner that has slipped through the cleaning blade, external additive, toner scattered from the developing device 4 or the like adheres to the roller charger 2, and the adhered toner. It is considered that the above phenomenon is generated by being stressed at the nip portion between the roller charger 2 and the photosensitive drum 1 and being rubbed against the photosensitive layer. Therefore, the lower the glass transition temperature Tg of the toner is, the lower the viscosity is, and the more the filming is likely to occur.

As in this embodiment, a sponge is used as the elastic layer 24 of the roller charger 2 and the number of foam cells is 20 to 20.
It is considered that the setting of 50 cells / inch reduces the stress applied to the toner and the like at the nip portion between the roller charger 2 and the photosensitive drum 1, and filming does not occur.

Although the roller charger 2 is used as the contact type charging device in the first embodiment, the present invention is not limited to the roller charger. Next, a second embodiment of the present invention in which the brush charger 40 as shown in FIG. 3 is used as a contact type charging device will be described. The color image forming apparatus of this embodiment has the same configuration as that of the first embodiment except that the contact type charging device is the brush charger 40 as shown in FIG. The same reference numerals are given to the parts and the like, and the description thereof will be omitted unless necessary.

As shown in FIG. 3, the brush charger 40 used in this embodiment has a conductive support 41 in which rayon, nylon or the like is dispersed with carbon, metal oxides such as TiO ₂ or ZnO. A large number of brushes 42 made of the electrically conductive fibers are planted. Then, the conductive brush 42 is brought into contact with the photoconductor drum 1 and a predetermined bias voltage is applied to the support 41 to uniformly charge the photoconductor drum 1 to a desired potential. The bias voltage to be applied may be only a DC voltage, or a peak-to-peak voltage that is at least twice the charging start voltage may be superimposed, as in the roller charger described above.

According to this embodiment, since the brush charger 40 is used as the contact type charging device, the photosensitive drum 1
Filming was able to be prevented even when a toner having a low glass contact temperature Tg of 50 ° C. to 70 ° C., which had a low contact pressure with the toner and had a glass transition temperature Tg of 50 ° C. to 70 ° C., which was good in color mixing and color development, was used as in the first embodiment.

FIG. 4 is a schematic sectional view showing the overall construction of a third embodiment in which the present invention is also applied to an electrophotographic color image forming apparatus. The color image forming apparatus according to the present exemplary embodiment includes a process cartridge 1 in which a photosensitive drum 1 and at least a roller charger 2 arranged around the photosensitive drum 1 are integrated.
Other than 1 (the cleaning device 7 is also integrated in this embodiment), the configuration is the same as in the first embodiment, so the corresponding elements, members, parts, etc. are given the same reference numerals. The description thereof will be omitted unless necessary.

In this example, the glass transition temperature Tg
Of 50 ° C. to 70 ° C. and the number of foam cells of the elastic layer 24 of the roller charger 2 is set to 20 to 50 cells / inch, filming can be prevented and the photosensitive drum 1
It has become possible to provide an image forming apparatus capable of achieving a longer life, lowering running costs, and obtaining high-quality images.

The roller charger 2 used in this embodiment has the same structure as that shown in FIG. 2, and a conductive urethane sponge layer 24 as an elastic layer is provided on a cored bar 21 such as a metal roller.
Further, carbon is dispersed on the urethane sponge elastic layer 24 to have a volume resistance of 10 ⁵ Ω.
-It has a configuration in which a urethane rubber layer 23 having a size of about cm is provided, and the number of foam cells is 20 cells / inch to 50 cells /
Inches.

As described above, by setting the roller charger 2 to have a low number of foam cells, filming on the photosensitive drum 1 can be prevented as described above, and as a result, the life of the photosensitive drum 1 is extended. Further, since the process cartridge 11 in which the photosensitive drum 1, the roller charger 2 around the photosensitive drum 1, and the cleaning device 7 are integrated is used, the replacement of the photosensitive drum 1 and the waste toner removal which are conventionally performed by a service person are performed. Maintenance such as processing can be performed by the user by exchanging the process cartridge 11.

Conventionally, when filming occurs on the photosensitive drum 1 and a defect occurs on the image, a serviceman replaces only the photosensitive drum 1, but the process cartridge 11 is used. In the case, the photosensitive drum 1
In addition to the roller charger 2 and the cleaning device 7,
Since there is no choice but to replace items that can still be used, this leads to a rise in running costs.

However, according to the present embodiment, since filming can be prevented, even if the process cartridge 11 is constructed, the parts in the cartridge 11 can be effectively used for the life of the process cartridge 11 and the image with low running cost can be obtained. A forming device can be provided. Further, since a toner having a glass transition temperature Tg of 50 ° C. to 70 ° C. can be used, a high quality print can be obtained.

Next, a fourth embodiment of the present invention will be described.

[0059] This example difference in the color image forming apparatus of the first embodiment shown in FIG. 1, as the roller charger 2, an outer diameter R _E of the outer diameter R _C and end of the central portion _RC- R
_{Since E} uses a charging roller having an A4 vertical width of 10 to 150 μm and the other structure is the same as that of the first embodiment, corresponding elements, members, parts and the like are designated by the same reference numerals. The description thereof will be omitted unless necessary.

In the color image forming apparatus using the roller charger 2 having the structure of the present embodiment, four kinds of toners, the toner A (toner A () of which the glass transition temperature Tg was measured by the same method as in the first embodiment, were used. Glass transition temperature Tg50 ° C.), toner B (glass transition temperature Tg60 ° C.), toner C (glass transition temperature Tg70 ° C.), and toner D (glass transition temperature Tg80 ° C.) are prepared and a toner image is formed on the recording paper. After transfer and fixing, a print image was obtained, and the appearance of filming was observed (use conditions: temperature 30 ° C., relative humidity 80
%, 2000 sheets printed). The results are shown in Table 2 below.

[0061]

[Table 2]

In Table 2 above, ◯ indicates that filming did not occur, and Δ indicates that slight filming occurred, but at this time, it was observed as a defect on the printed recording paper. Although it is not visible, the toner is fused when the photosensitive layer of the photosensitive drum is observed with a microscope. Further, x indicates that filming has occurred, and at this time, the image on the printed recording paper has white spots in the black portion, and the image quality is significantly impaired.

From the above results, in the roller charger of the present embodiment, the toner having the glass transition temperatures Tg of 50 ° C., 60 ° C., 70 ° C., and 80 ° C. is R _C −R _{E of 10} to 60 μm. It can be seen that filming does not occur with any of the toners B, C, and D. Also,
For the toner A, the R _C -R _E is 70-100 △, × is above 110 [mu] m, with respect to toner B is, R
In _C -R _E is 90 to 120 △, × is above 130 .mu.m, with respect to the toner C, and R _C -R _E 110~14
It can be seen that Δ is 0 μm and x is 150 μm or more.

[0064] Further, the toner D glass transition temperature Tg of 80 ° C., it can be seen R _C -R _E is the degree to which minor filming seen in 130～150Myuemu.
However, in the present embodiment, the fixed image of Toner D had a poor color mixture color-developing property, and only a dull color was obtained.

If R _C -R _E is 10 μm or less, the central portion of the charging roller floats from the photosensitive drum 1 when the roller charger 2 is brought into contact with the photosensitive drum 1. However, uniform charging was not performed. Therefore, R _C -R _E of the roller charger 2 is 10 to 100 μm,
The range of 20 to 60 μm is preferable. Since the diameter of the roller charger 2 used in this embodiment is 12 mm, when the peripheral speed difference is obtained using this, the peripheral speed difference without filming is 0.08% to 0.8%, preferably 0. 16% ~
It becomes 0.5%.

Other diameters (10 mm to 30 mm)
It has been confirmed that filming can be suppressed even when the roller charger of (1) is used within the above range of the peripheral speed difference.

Further, in general, even at a process speed of 10 to 200 mm / sec in which a roller charger is used, filming can be effectively suppressed within the range of the above peripheral speed difference.

As described above, by reducing the difference between the portion having the highest peripheral speed and the portion having the slowest peripheral speed of the roller charger,
The stress applied to the toner or the like is reduced in the portion of the roller charger having a high peripheral speed, and the occurrence of filming can be suppressed.

Next, a fifth embodiment of the present invention will be described.

In this embodiment, in the color image forming apparatus of the third embodiment using the process cartridge 11 shown in FIG. 4, the roller charger 2 is used as the outer diameter R _C of the central portion and the outer portion of the end portion. the difference R _C -R _E of the diameter R _E 10 to 150
Since a charging roller having an A4 vertical width of .mu.m is used and the other structure is the same as that of the third embodiment, corresponding elements, members, parts and the like need not be designated by the same reference numerals. As long as they are omitted.

In this example, the glass transition temperature Tg
Of 50 ° C. to 70 ° C. is used, and the difference between the highest peripheral speed portion and the lowest peripheral speed portion of the roller charger 2 is 0.0.
By setting it to 8% to 0.8%, preferably 0.16% to 0.5%, filming can be prevented, the life of the photosensitive drum 1 can be extended, the running cost can be reduced, and high image quality can be achieved. It has become possible to provide an image forming apparatus capable of obtaining various images.

The roller charger 2 used in this embodiment has the same structure as that shown in FIG. 2, and a conductive urethane sponge layer 24 as an elastic layer is provided on a core metal 21 such as a metal roller.
Further, carbon is dispersed on the urethane sponge elastic layer 24 to have a volume resistance of 10 ⁵ Ω.
-It has the structure which provided the urethane rubber layer 23 about cm.

By setting the peripheral speed difference of each part of the roller charger 2 as described above, filming on the photosensitive drum 1 can be prevented as described above, and as a result, the life of the photosensitive drum 1 is extended. Further, since the process cartridge 11 in which the photosensitive drum 1, the roller charger 2 around the photosensitive drum 1, and the cleaning device 7 are integrated is used, the replacement of the photosensitive drum 1 and the waste toner removal which are conventionally performed by a service person are performed. Maintenance such as processing can be performed by the user by exchanging the process cartridge 11.

Conventionally, when filming occurs on the photosensitive drum 1 and a defect occurs on the image, a serviceman replaces only the photosensitive drum 1, but the process cartridge 11 is used. In the case, the photosensitive drum 1
In addition to the roller charger 2 and the cleaning device 7,
Since there is no choice but to replace items that can still be used, this leads to a rise in running costs.

However, according to the present embodiment, since filming can be prevented, even if the process cartridge 11 is constructed, the parts in the cartridge 11 can be effectively used for the life of the process cartridge 11, so that an image with low running cost can be obtained. A forming device can be provided. Further, since a toner having a glass transition temperature Tg of 50 ° C. to 70 ° C. can be used, a high quality print can be obtained.

In the above embodiment, the case where an image is formed using the process cartridge has been described.
Needless to say, even if the present invention is applied to a non-cartridge type image forming apparatus, the same operational effect can be obtained.

Next, a sixth embodiment of the present invention will be described.

In this embodiment, the present invention is applied to the color image forming apparatus of the first embodiment shown in FIG. 1, and the overall structure of the color image forming apparatus is the same as that of the first embodiment. Since they are the same, corresponding elements, members, parts and the like are designated by the same reference numerals and the description thereof will be omitted unless necessary.

In this embodiment, four kinds of toners whose glass transition temperatures Tg were measured by the same method as in the first embodiment, namely, toner A (glass transition temperature Tg 50 ° C.) and toner B (glass transition temperature Tg 60) were used. C.), toner C (glass transition temperature Tg 70.degree. C.), and toner D (glass transition temperature Tg 80.degree. C.) are prepared, and a low temperature and low humidity environment (15.degree. C., 10.degree.
% Rh), normal environment (23 ° C., 60% Rh), and high temperature and high humidity environment (32.5 ° C., 85% Rh) to form a toner image, transfer it to recording paper, fix it, and print the image. Obtained and observed the state of filming. The results are shown in Tables 3 and 4 below. In addition, as a comparative example, Table 5 shows the case where a corona charger and a notched transfer drum are used.

[0080]

[Table 3]

[0081]

[Table 4]

[0082]

[Table 5]

As can be seen from Table 3 above, toner A having a glass transition temperature Tg of 50 ° C., toner B having a glass transition temperature Tg of 60 ° C. and toner C having a glass transition temperature Tg of 70 ° C. showed good color development.
Toner D at 80 ° C. gave only a dull shade. Further, as can be seen from Table 5 above, in the comparative examples, no toner fusion was observed under any environment. However, as can be seen from Table 4 above, when the image forming apparatus of this embodiment is used,
Toner A did not show fusion under low temperature and low humidity environment, but toner fusion occurred under normal environment and high temperature and high humidity environment. On the other hand, in toners B, C and D, no toner fusion was observed in any environment.

As described above, by setting the glass transition temperature of the toner to be used to 60 ° C. to 70 ° C., even in the image forming apparatus using the roller charger and the solid constitution transfer drum,
It has become possible to prevent toner fusion while maintaining high image quality.

In this embodiment, the case where the roller charger is used has been described, but the present invention can be applied to the case where the blade charger 30 shown in FIG. 12 is used, and the same effects can be obtained. Needless to say. Further, it goes without saying that the transfer drum is not limited to the configuration of this embodiment, and various modifications and changes can be considered.

FIG. 5 is a schematic sectional view showing the overall construction of a seventh embodiment in which the present invention is applied to an electrophotographic color image forming apparatus. The color image forming apparatus of the present embodiment is the same as the above-described first embodiment except that the photosensitive drum 1 and at least the roller charger 2, the developing device 4, and the cleaning device 7 arranged around the photosensitive drum 1 are integrated into the process cartridge 51. Since the configuration is the same as that of the first embodiment, the corresponding elements, members, parts, etc. are designated by the same reference numerals and the description thereof will be omitted unless necessary.

Also in this embodiment, the roller charging device 2 which is a contact type charging device is used as the charging means, and the solid constitution transfer drum 6A as shown in FIG. 13 is used as the transfer drum. Of course, the structure of the image forming apparatus is simplified and the amount of ozone generated is reduced.
Furthermore, maintenance such as cleaning of the corona wire, which was necessary in the corona charger, is no longer necessary. Further, since the dielectric sheet 6b of the transfer drum 6A is supported by the elastic layer 6d, the dielectric sheet 6 of the cutout-structured transfer drum 6 is formed.
While b had to be replaced after every tens of thousands of prints, it could withstand hundreds of thousands to 1,000,000 prints and did not need to be replaced until the life of the device body. No need to replace. Further, according to this embodiment, the glass transition temperature Tg of the toner used is 60
By setting the temperature to 70 ° C., the toner fusion on the photosensitive drum 1 can be prevented, and each developing device 4 in the process cartridge 51 can be prevented.
Despite the toner remaining in a to 4d, there is no inconvenience that the cartridge has to be replaced because the toner is fused on the photosensitive drum 1.

In the above embodiment, the case where an image is formed using the process cartridge has been described.
Needless to say, even if the present invention is applied to a non-cartridge type image forming apparatus, the same operational effect can be obtained.

FIG. 6 is a schematic sectional view showing the overall construction of an eighth embodiment in which the present invention is applied to an electrophotographic color image forming apparatus. In the color image forming apparatus of this embodiment, as in the case of the seventh embodiment, the photosensitive drum 1 and at least the roller charger 2, the developing device 4, and the cleaning device 7 arranged around the photosensitive drum 1 are integrated. Although it has the structure of the process cartridge 51, the structure of the developing device 4 is slightly different from that of the seventh embodiment. That is, each developing device 4a
4d, in this embodiment, like the developing device of the first embodiment, a one-component developing device using only toner as a developer is used. Since the other construction is the same as that of the seventh embodiment, the corresponding elements, members, parts and the like are designated by the same reference numerals and the description thereof will be omitted unless necessary.

Further, the developing devices 4a to 4d of this embodiment have a glass transition temperature Tg of 60 to 70 ° C. and an aggregation degree of 3% to.
30% toner is used.

In recent years, instead of the two-component developing method using a mixture of non-magnetic toner and magnetic particles as a developer,
A one-component developing method using only non-magnetic toner has been proposed,
It has been put to practical use.

Also in this embodiment, the developing devices 4a, 4
In b, 4c, and 4d, yellow toner,
It contains magenta toner, cyan toner, and black toner, and these non-magnetic toners are sent to the toner applying rollers 42a, 42b, 42c, and 42d by toner sending members 45a, 45b, 45c, and 45d. These coating rollers 42a to 42d are the developing roller 41.
a, 41b, 41c, and 41d rotate in the direction of the arrow so as to have a relative speed difference, and apply rollers 42a-4
The toner on 2d is applied onto the developing rollers 41a to 41d. The coating rollers 42a to 42d are preferably sponge, knurled, brush or the like in order to coat the toner well. The toner applied on the developing rollers 41a to 41d is conveyed by the developing rollers 41a to 41d rotating in the direction of the arrow in the figure, and the toner regulating member formed of an elastic body such as phosphor bronze, urethane rubber, or silicon rubber ( Blades 43a, 43b, 43c, and 43d are used for thin layer coating and development.

Compared to the two-component developing method, the one-component developing method using only the non-magnetic toner has advantages such as a simple developing device configuration and no need to control the mixing ratio of the toner and the magnetic particles. However, it is particularly effective when used for a process cartridge. However, it is inferior in uniformity of image quality as compared with the two-component developing method, and it is fatal particularly in a color image which requires high image quality.

The reason why a uniform image cannot be obtained in the one-component developing method as compared with the two-component developing method is that the two-component developing method sufficiently loosens and homogenizes the toner when stirring and mixing with the magnetic particles. While the toner is sufficiently charged, the toner is not uniformly applied in the one-component developing method and is applied on the developing roller. As a result, insufficiently charged toner is generated, and when developing the latent image, as shown in FIG. As shown, a part of the area image has uneven density, resulting in a non-uniform image.

Analysis of this phenomenon has revealed that there is a close relationship between image uniformity and toner cohesion.
That is, by using a toner having a low cohesiveness and excellent fluidity, the developer is conveyed, coated on the developing roller by the coating roller, and uniformized in the process of being regulated by the toner regulating blade, so that the toner is sufficiently charged. However, an image with excellent uniformity can be obtained.

Next, the method of measuring the toner aggregation degree will be described.

Using a powder tester (manufactured by Hosokawa Micron Corporation), (1) after leaving the toner for 12 hours in an environment of 23 ° C. and 60% Rh, 5.0 g is accurately measured. (2) 100 mesh (opening 150 mesh)
μm), 200 mesh (opening 75 μm), and 400 mesh (opening 38 μm) sieves are stacked and set. (3) Sift the precisely weighed 5.0 g toner (10
(0 mesh) and vibrate for 15 seconds with an amplitude of 1 mm. (4) Gently weigh accurately the amount of toner remaining on each sieve.

[0098]

[Equation 1]

[0099]

[Equation 2]

[0100]

[Equation 3]

Printing was performed by the image forming apparatus shown in FIG. 6 using toners having different agglutination measured by the above-mentioned measuring method, and the uniformity of the image was observed. The results are shown in Table 6 below. The glass transition temperature of each toner is 60.
The toner fusion on the photosensitive drum 1 was not observed.

[0102]

[Table 6]

As can be seen from Table 6 above, the toners E, F, G, H, I and J, which are toners having a cohesion degree of 2%, 3%, 5%, 10%, 20% and 30%, are A uniform image was obtained, but the toners K and L, which are toners having a cohesion of 40% and 50%, can obtain only a non-uniform image with uneven density in a part of the area image as shown in FIG. It was Also,
The toner E having a cohesion degree of 2% produced a uniform image as described above, but the toner was heavily scattered from the developing devices 4a to 4d, and was not suitable for practical use.

As described above, by using a toner having a cohesion degree of 3% to 30%, a high-quality image with good uniformity was obtained even when a one-component developing device was used. . Further, the glass transition temperature Tg of the toner is 60 ° C.
By setting the temperature to ˜70 ° C., it is possible to prevent toner from sticking to the developing roller, coating roller, etc. of the developing device, and to extend the life of the developing device.

In the above embodiment, the case where an image is formed using the process cartridge has been described.
Needless to say, even if the present invention is applied to a non-cartridge type image forming apparatus, the same operational effect can be obtained.

Although the present invention is applied to the electrophotographic color image forming apparatus in each of the above-described embodiments, the present invention is also applicable to an apparatus for forming a black and white image or an image forming apparatus other than the electrophotographic method. It goes without saying that the same effect can be obtained.

Further, the constitution of the image forming apparatus, the constitution of the contact type charging device, the transfer drum, etc., the shape, the materials used, etc. are not limited to those in the above embodiment, and can be variously changed and modified as required. It is a thing.

[0108]

As described above, according to the present invention,
In an image forming apparatus using a toner having a glass transition temperature Tg of 50 ° C. to 70 ° C. in a developing device, as a charging unit for uniformly charging an image carrier, a conductive material is formed on a roller-shaped conductor such as a metal roller. Since a sponge layer is provided and a contact type charging device in which the number of foam cells of the sponge layer is 20 cells / inch to 50 cells / inch or a contact type charging device using a conductive brush is used, There is an effect that it is possible to effectively prevent the image forming, the life of the image carrier can be extended, the running cost can be reduced, and a high quality printed image can be obtained.

Further, according to the present invention, the glass transition temperature T
In an image forming apparatus using a toner whose g is 50 ° C. to 70 ° C. in a developing device, a conductive sponge layer is formed on a roller-shaped conductor such as a metal roller as a charging unit for uniformly charging the image carrier. By using the provided contact type charging device, the peripheral speed difference of each part in the axial direction of the charging device is 0.08% to
Since it is 0.8%, preferably 0.16% to 0.5%, filming can be effectively prevented,
This has the effects of extending the life of the image carrier, reducing the running cost, and obtaining a high-quality printed image.

Further, according to the present invention, in the image forming apparatus using the contact type charging device as the charging means for uniformly charging the image carrier, the glass transition temperature Tg is 60 ° C. to 70 ° C.
Since a toner having a temperature of ℃ and a cohesion of 3% to 30% is used in the developing device, a high-quality printed image with good uniformity can be obtained even when a one-component developing device is used. Moreover, since filming can be effectively prevented, the life of the image carrier can be extended and the running cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a first embodiment in which the present invention is applied to an electrophotographic color image forming apparatus.

2 is a schematic cross-sectional view showing a configuration of a roller charger used in the color image forming apparatus of FIG.

FIG. 3 is a schematic sectional view showing a configuration of a brush charger used in the color image forming apparatus according to the second embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a third embodiment in which the present invention is applied to an electrophotographic color image forming apparatus.

FIG. 5 is a schematic sectional view showing a seventh embodiment in which the present invention is applied to an electrophotographic color image forming apparatus.

FIG. 6 is a schematic cross section showing an eighth embodiment in which the present invention is applied to an electrophotographic color image forming apparatus.

FIG. 7 is a schematic view showing an example of a non-uniform image obtained when a one-component developing method is used.

FIG. 8 is a schematic sectional view showing an example of an electrophotographic color image forming apparatus using a conventional roller charger.

FIG. 9 is a schematic perspective view showing an example of a notched transfer drum.

10 is a schematic cross-sectional view showing the configuration of a roller charger used in the color image forming apparatus of FIG.

FIG. 11 is a schematic plan view showing an example of the outer shape of a roller charger.

FIG. 12 is a schematic sectional view showing a blade charger which is another example of the contact type charging device.

FIG. 13 is a schematic sectional view showing an example of a solid configuration transfer drum.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Roller charger 4 Developing device 4a-4d Developing device 6 Notch-structure transfer drum 6A Solid-state transfer drum 7 Cleaning device 11 Process cartridge 21 Core metal 23 Urethane rubber layer 24 Conductive urethane sponge elastic layer 30 Blade Charger 40 Brush Charger 41 Conductive Support 42 Conductive Brush 51 Process Cartridge

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mashiro Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Naoki Enomoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Hiroshi Sasame 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hajime Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Toshiaki Miyashiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Haruo Fujii 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (11)

[Claims] 1. An image forming apparatus for forming a latent image after uniformly charging an image carrier by a contact type charging means, and developing the latent image with a developer to form a visible image. The transition temperature is 50 ° C. to 70 ° C., and the contact type charging means is a roller charging means having at least a foam layer on a roller-shaped conductive support, and the number of foam cells of the foam is 20 cells / An image forming apparatus having a size of from inch to 50 cells / inch. 2. An image forming apparatus for forming a visible image by forming a latent image after uniformly charging an image carrier by a contact type charging means, and developing the latent image with a developer to form a visible image. An image forming apparatus having a transition temperature of 50 ° C. to 70 ° C. and the contact type charging means being brush charging means. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is a color image forming apparatus capable of forming a color image by repeating steps of charging, exposing and developing. apparatus. 4. A process cartridge which is detachably mountable to the apparatus main body by integrally supporting at least the image carrier, the contact type charging means, and the cleaning means for the image carrier. The image forming apparatus according to any one of 1 to 3. 5. An image forming apparatus for forming a latent image after uniformly charging an image carrier by a contact type charging means and developing the latent image with a developer to form a visible image, wherein the glass of the developer is used. The transition temperature is 50 ° C. to 70 ° C., the contact-type charging means is a roller-shaped charging means, and the difference between the highest peripheral speed portion and the lowest peripheral speed portion of the roller-shaped charging means is 0.08. % -0.8%, preferably 0.16% -0.5
%, The image forming apparatus. 6. The image forming apparatus according to claim 5, wherein the image forming apparatus is a color image forming apparatus capable of forming a color image by repeating steps of charging, exposing and developing. 7. A process cartridge which is detachably mountable to the apparatus main body by integrally supporting at least the image carrier, the contact type charging means, and the cleaning means for the image carrier. Or the image forming apparatus according to item 6. 8. A latent image is formed after the image carrier is uniformly charged by a contact type charging means, the latent image is developed with a developer to form a visible image, and the visible image is transferred to a recording material. In an image forming apparatus capable of forming a color image by repeating the steps, the glass transition temperature of the developer is 60 ° C to 7 ° C.
An image forming apparatus having a temperature of 0 ° C. 9. A recording material carrying means for holding and transporting the recording material comprises a conductive support, an elastic layer provided on the support, and a dielectric layer provided on the elastic layer. The image forming apparatus according to claim 8, which is provided. 10. A process cartridge which is detachably attached to the apparatus main body by integrally supporting at least the image bearing member, the contact type charging unit, and the cleaning unit for the image bearing member. Or the image forming apparatus according to item 9. 11. The developing method for developing the latent image is a one-component developing method using only toner as a developer, and the degree of toner aggregation is 3% to 30%. Image forming apparatus.