JP2000112255A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable transfer electrification over a long period by decreasing the friction or the like with a recording material carrying body by a low friction thin film layer and preventing the crack or the like of the low friction thin film layer as of the transfer member of a transfer means. SOLUTION: A transfer member 40 is composed of a blade base body 44 composed of rectangular plate like conductive rubber and an electrode 42 provided by projecting the base body 44 and the blade base body 44 is used by abutting it on a photosensitive drum 1 through a transfer sheet 5f of a transfer drum 5. A low friction thin film layer 46 having a lower coefficient of friction than that of the base body 44 is provided on the surface of the base body 44 by coating. The low friction thin film layer 46 is provided at least on the surface of the blade base body 44 in the adjacent position of the side opposed to the photosensitive drum 1. The low friction thin film layer 46 is formed by dispersing lubricant fine particles in a binder resin such as nylon and fluorinated graphite expressed by chemical formula, (CF)1-xCx (where, 0.6<=X<=0.8), is used as the lubricant fine particles.

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 for electrostatically forming an image on a recording material such as paper, such as a laser beam printer.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine or a laser beam printer includes an image carrier, and a recording material carrier for carrying a recording material such as paper and transporting the recording material to the image carrier. Are known.

As an example of such an image forming apparatus, FIG. 5 shows a multi-transfer four-color full-color copying machine.

In this copying machine, a photosensitive drum 1 as an image carrier is used.
Around the charger 2, the optical scanning device 3, and yellow, magenta, cyan, and black developing units 4Y, 4M,
4C, 4K, a transfer drum 5, a transfer charger 5b, and an image forming means such as a cleaner 6.

The image forming process for forming a color image on a recording material will be described. First, the surface of the photosensitive drum 1 is charged to a predetermined potential by the charger 2 and the first document of the original sent from the reader unit 30 is charged. The color information, for example, yellow image information, is irradiated with a laser beam by the scanning optical device 3,
A latent image is formed on the surface of the photosensitive drum 1. Next, the latent image on the photosensitive drum 1 is developed by the developing device 4Y to form a first color yellow toner image. The toner image is transferred from the paper feed cassette 7a, 7b or 7c and transferred onto the surface of the recording material P carried on the transfer drum 5 at the transfer section facing the photosensitive drum 1 by the action of the transfer charger 5b.
The residual toner on the surface of the photosensitive drum 1 is removed, and the photosensitive drum 1 is again used for transferring the next toner image of the second color.

The above steps are performed for the remaining magenta, cyan, and black, and the yellow,
A full-color image is formed by superimposing four color toner images of magenta, cyan, and black. When the transfer of the four color toner images is completed, the recording material P is set to the separation charger 5h and the separation claw 8a.
The toner is separated from the transfer drum 5 by the action of the separation push-up roller 8 b, fixed by the fixing device 9, and then discharged to the tray 10.

The fixing device 9 includes a fixing roller 9b containing a heater 9a as a heat source and a pressing roller 9c pressed against the fixing roller 9b.
The recording material is heated and pressed while nipping and transporting the recording material at the nip portion between the rollers 9b and 9c, and the toner image is melted and fixed to the recording material and fixed.

The transfer drum 5 from which the recording material has been separated is cleaned and removed by a fur brush 16 and a backup brush 17 of unnecessary toner and the like adhering to the surface, and is used for the next image formation.

As shown in FIG. 6, the transfer drum 5 has a frame on which a transfer sheet 5f is wound in a cylindrical shape.
The front and rear ends of f are attached to the connecting member of the frame,
The photosensitive drum 1 comes into contact with the photosensitive drum 1 and is rotated in the direction of arrow C. In the case of this example, the transfer sheet 5f is a PC (polycarbonate) film having a thickness of 150 μm and a volume resistivity of 10 ¹⁵ Ωcm or more.

Next, a process of transferring a toner image onto the recording material P will be described. First, the inner charge remover 5d and the outer charge remover 5e are operated to electrically initialize the transfer sheet 5f.
The recording material P is fed to the transfer drum 5 in a direction indicated by an arrow B by a sheet feeding means (not shown). The suction roller 5g is brought into close contact with the transfer sheet 5f by a driving source (not shown), and the suction current from the positive high-voltage power supply Ea is applied to the transfer sheet 5f by the suction charging member 5c in contact with the opposite back surface of the transfer sheet 5f.
Is injected from the back side of Since the suction roller 5g is electrically grounded, a current (charge of opposite polarity) opposite to the current (charge) injected by the suction charging member 5c is induced (induced), and as a result, the recording material P And the transfer sheet 5f are polarized, and the recording material P and the transfer sheet 5f are electrostatically attracted. Note that the suction roller 5g is used for the transfer drum 5 of the recording material P.
After the end of the suction operation on the transfer drum 5, the operation of detaching from the transfer drum 5 is immediately performed.

Next, a current (charge) from a positive high-voltage power source Et is injected from the back surface of the transfer sheet 5f by the transfer charging member 5b in contact with the back surface of the transfer sheet 5f, and a negative charge formed on the photosensitive drum 1 is formed. Is transferred onto the recording material P.

In this embodiment, an image carrier (OPC drum) having an organic OPC photosensitive member on the surface of the photosensitive drum 1 is provided.
Is adopted. Further, the photosensitive drum 1 is initially charged to the same polarity as the toner, that is, to a negative potential, forms an electrostatic latent image at a portion where the amount of charge is reduced by laser exposure, adheres toner to this, and develops it. A so-called reversal development method is employed. When performing multiple transfer, this transfer operation is repeated for the recording material P a desired number of times, and then the recording material P
From the transfer drum 5.

The inner static eliminator 5d and the outer static eliminator 5e operate before and after the above-described series of suction, transfer, and separation operations to electrically initialize the transfer sheet 5f.

Many types of transfer means have been conventionally used, including a corona charger for injecting electric charge into the transfer sheet 5f without contact, a transfer roller for injecting electric charge while contacting the transfer sheet 5f, and a charging brush. , A transfer blade and the like have been proposed.

In the image forming apparatus, in order to transfer the toner image on the photosensitive drum 1 onto the recording material P in a good condition, it is important that the transfer electric field of the transfer means is regulated so that toner is not scattered. It is. It is also important that a constant amount of charge can be always provided even when the impedance of the recording material P changes depending on the thickness, the material, and the water content of the recording material P.

From this point of view, the transfer means 5b
Is a type in which the charging member contacts the transfer sheet 5f, and it can be said that it is preferable to perform constant current control. In particular, the conductive blade has a clearer boundary between a portion that is in contact with the recording material P or the transfer drum 5 and a portion that is not in contact with the transfer roller or the like, so that the electric field can be easily regulated. In addition, there is an advantage that manufacturing accuracy is easily obtained.

As the transfer blade, a thin metal plate, a conductive resin plate such as PET which has been made conductive, and a conductive rubber plate such as EPDM or urethane which has been made conductive can be considered. It is very convenient to use a conductive rubber plate from the viewpoints of uniformity and small damage to the transfer drum 5 that is a contact partner.

[0018]

However, since the transfer blade made of conductive rubber comes into contact with the recording material P or the transfer drum 5 and rubs, there arises a problem that a large frictional force is generated or worn. there were. Naturally, these frictional forces and abrasion tend to increase as the contact pressure of the blade with the recording material P or the transfer drum 5 or the like, or as the contact area at the contact portion increases.

When the frictional force of the transfer blade with the transfer drum 5 or the like increases, in the above-described image forming apparatus, the contact nip portion between the blade and the transfer drum 5 moves
In the traveling direction, the transfer at a predetermined position cannot be performed, and an image defect occurs.

In order to prevent such adverse effects, FIG.
The low friction thin film layer 34 made of a high-strength resin such as PET
There is a method of providing a blade 32 made of rubber.
When the frictional force with the contact partner increases, a small vibration called stick-slip occurs, the contact surface of the blade 32 moves, and the surface of the blade 32 in a considerably large area becomes the contact surface. In particular, as shown in FIG. 7, when the boundary between the portion where the low friction thin film layer 34 is formed and the portion where the low friction thin film layer 34 is not formed is in the discharge region of the blade 32 in the direction of the photosensitive drum 1, the low friction thin film layer 34 moves from the boundary. It has been found that it can be destroyed.

SUMMARY OF THE INVENTION The present invention has been made to address the above-mentioned disadvantages. In the transfer member of the transfer means, the frictional force between the transfer member and the recording material carrier is reduced by a low-friction thin-film layer. It is an object of the present invention to provide an image forming apparatus capable of performing stable transfer charging over a long period of time by preventing layer breakage and the like.

[0022]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A rotating image carrier, a recording material carrying the recording material and being conveyed to the image carrier, a recording material carrier rotating in contact with the image carrier, and a conductive substrate carrying the image via the recording material carrier. An image forming apparatus provided with a transfer unit that comes into contact with a body, wherein at least a surface of the surface of the conductive substrate facing the image carrier and a surface at a position close to the image carrier is subjected to friction. An image forming apparatus, wherein a low friction thin film layer having a coefficient lower than that of a conductive substrate is formed. According to the present invention, the low friction thin film layer can be formed on the entire surface of the conductive substrate.

The low friction thin film layer has a particle size of 20
It is formed by dispersing lubricating fine particles of μm or less. Preferably, the lubricating fine particles are fluorinated graphite, and the fluorinated graphite has a composition represented by the following chemical formula: (CF) _1-X C _X (where 0.6 ≦ X ≦ 0.8) Have. The binder resin is nylon. The low friction thin film layer has a volume resistivity of 10 ² Ωc.
m to 10 ¹⁴ Ωcm and a thickness of 50 μm or less.

[0024]

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

Embodiment 1 FIG. 1 is a side view showing a transfer unit in an embodiment of the image forming apparatus of the present invention. The present invention is characterized by the transfer unit, and the mechanical configuration of the image forming apparatus itself is basically the same as that of the conventional image forming apparatus shown in FIG. 5, so that the drawing of the image forming apparatus and its description are omitted.

The transfer means comprises a transfer member (transfer blade) 40 having a rectangular plate-like conductive rubber blade base 44 along the longitudinal direction of the photosensitive drum 1 and an electrode 42 having the base 44 protruding therefrom. The transfer power source E is
t is connected.

According to the present invention, a low friction thin film layer 46 having a smaller coefficient of friction than the substrate 44 is formed on the surface of the substrate 44 by coating. Layer 46 was provided.

The transfer means, that is, the transfer member 40, is used to transfer the blade base 44 provided with the low friction thin film layer 46 to the transfer drum 5
The toner image formed on the photosensitive drum 1 is carried on the transfer drum 5 by the transfer bias supplied from the power source Et to the blade base 44, and is conveyed. It is used to transfer to a recording material.

As a material of the blade base 44, a conductive rubber in which a conductive agent such as tin oxide or carbon is dispersed in rubbers such as isoprene rubber, chloroprene rubber, EPDM, and urethane rubber is used.

When such a conductive rubber blade substrate is brought into contact with and pressed against the transfer sheet 5f, the nip required for stabilizing the discharge is greater than when a conductive metal or conductive resin blade substrate is used. It becomes possible to form a shape stably.

However, since the rubber-like substance is generally liable to wear deformation and has a high coefficient of friction, it is easy to generate minute vibration such as stick-slip with the transfer sheet 5f.
Stabilization of the discharge is hindered by a change in the position of the contact nip.

Therefore, as described above, according to the present invention, the surface of the blade base 44 made of conductive rubber is
The low-friction thin-film layer 46 having a smaller friction coefficient than that of No. 4 was provided. In this embodiment, the low-friction thin-film layer 46 was provided on the entire surface of the blade base 44.

In this embodiment, this low friction thin film layer 46
Among the resins, a nylon resin having a relatively low coefficient of friction was used as a binder resin, and fine particles for improving lubricity were dispersed in the binder resin.

As the lubricating fine particles, fluorine compounds are effective because they have a particularly low coefficient of friction. Further, the lubricating fine particles are preferably indefinite in shape rather than spherical, and a mechanical fixing force due to an anchor effect is applied, so that the adhesive force to the binder resin is dramatically increased, and the lubricating fine particles are reduced to a low friction thin film layer 46. From the vehicle.

From the above, as the lubricating fine particles, fluorinated graphite which is flake-shaped and amorphous and has a low friction coefficient is particularly preferred. For example, (C ₂ F) _n- type Cefbon D
M, (CF) _n- type Cefbon CMA, Cefbon CM
F (manufactured by Central Glass Co., Ltd.), Fluorocarbon # 206
5, # 1030, # 1000 (manufactured by Asahi Glass Co., Ltd.), CF
-100 (manufactured by Nippon Carbon Co., Ltd.) or (CF)
_n- type, fluorocarbon # 2028, # with different fluorination rate
2010 (manufactured by Asahi Glass Co., Ltd.), and those obtained by treating these fluorinated graphite with a base such as an amine to remove fluorine from the surface thereof, but are not limited thereto.

The average particle size of the fluorinated graphite is 20 μm or less, particularly 10 μm, in order to prevent the occurrence of abnormal discharge or the like.
m or less, more preferably in the range of 1 to 8 μm.

In this embodiment, the following chemical formula: (CF) _{1 -X} C _X (where 0.1 ≦ X ≦ 0.9, more preferably 0.6 ≦ X ≦ 0.8) 1) The fluorinated graphite shown by was used.

Since the low friction thin film layer 46 is formed on the surface of the blade base 44, it must not be insulative. According to the study of the present inventors, the volume resistivity is 10 ¹² Ωcm or more,
It turned out that it can be used if the thickness is 10 ¹⁴ Ωcm or less and the thickness is 50 μm or less. According to the fluorinated graphite of the chemical formula (1), when this is dispersed in nylon, it is easy to control to the above-mentioned resistance value.

It is desirable that the thickness of the low-friction thin film layer 46 be equal to or larger than the particle size of the dispersed lubricating fine particles. If the thickness of the thin film layer is extremely thin, the lubricating fine particles are apt to fall off, so that a low friction coefficient is easily maintained.

In this embodiment, as the lubricating fine particles, the fluorinated graphite of the above formula (1) is dispersed in the binder resin nylon resin in the range of 5 to 50 wt%, and is used for forming the low friction thin film layer 46. Was.

In order to form the low friction thin film layer 46, nylon of a type soluble in a solvent such as alcohol, for example, Toresin CM4000, CM8000 (trade name, Toray Industries, Inc.), Platabond (trade name, Nippon Rilsan Co., Ltd.) ) Is dissolved in a solvent such as alcohol, and fluorinated graphite is dispersed to prepare a coating liquid. This is coated on a blade substrate by dipping or spray coating, and then dried to volatilize the solvent. Thereby, a low friction thin film layer 46 using nylon as a binder resin can be obtained.

In this embodiment, as described above, the low-friction thin-film layer 46 is provided on the entire surface of the blade base 44 including the contact nip of the blade base 44 with the transfer sheet 5f. Even if the contact nip changes, the transfer sheet 5 is always kept in a low friction state with the blade base 44.
f, and stable image formation can be performed.

The low friction thin film layer 46 is
4, the entire area of the blade base 44 where the discharge occurs in the direction of the photosensitive drum 1 is the low friction thin film layer 46.
Therefore, there is no boundary between the portion where the low friction thin film layer 46 is formed and the portion where the low friction thin film layer 46 is not formed in the discharge region on the surface of the blade base 44. The phenomenon itself cannot occur.

As described above, in this embodiment, the charging member 40 of the transfer means is a blade base 44 made of conductive rubber.
The low friction thin film layer 46 having a lower coefficient of friction than the blade base 44 is provided on the entire surface of the recording medium, so that the frictional force with the recording material carrier such as the transfer drum 5 can be reduced.
Thus, stable transfer electrification can be maintained over a long period of time by preventing cracks and the like of No. 6.

Embodiment 2 FIG. 2 is a side view showing a transfer unit according to another embodiment of the present invention.

In this embodiment, the transfer member 40 of the transfer means is used.
In order to restrict discharge from the blade base 44 toward the photosensitive drum 1 on the upstream side of the blade base 44 with respect to the moving direction of the transfer sheet 5f of the transfer drum 5, a Mylar-like An insulating member 48 for restricting a strong electric field is provided in proximity.

In the first embodiment, the low-friction thin-film layer 46 having a smaller friction coefficient than the blade base 44 is formed on the entire surface of the blade base 44 of the transfer member 40. Blade base 4
4 may be provided only on the surface at the close position on the side facing the photosensitive drum 1.

However, if there is a boundary between the portion where the low friction thin film layer 46 is formed and the portion where the low friction thin film layer 46 is not formed in the discharge region on the surface of the blade base 44, breakage occurs at the boundary of the low friction thin film layer 46. It is necessary to provide the low friction thin film layer 46 so as to cover the discharge region on the surface of the substrate 44. That is, the blade base 4 that generates the electric lines of force such that the electric lines of force from the surface of the blade base 44 reach the photosensitive drum 1
The low friction thin film layer 46 may be formed so as to cover the surface of No. 4.

Therefore, in this embodiment, the blade base 44
The low-friction thin-film layer 46 was provided in a surface region slightly entering the downstream side through the upper surface of the blade base 44 from the position entering the upper end portion of the insulating member 48 on the upstream side.

According to this, even if the boundary of the low friction thin film layer 46 is located on the surface on the upstream side of the blade base 44, the discharge there is practically not due to the restriction of the electric field by the discharge insulating member 48. There is no crack due to discharge deterioration of the friction thin film layer 46. Further, since the surface on the downstream side of the blade base 44 does not face the photosensitive drum 1 and does not discharge, the blade base 4
The boundary of the low friction thin film layer 46 on the upper surface side of 4 does not exist in the discharge region, and similarly, there is no crack due to the discharge deterioration of the low friction thin film layer 46.

According to the present embodiment, the frictional force between the conductive rubber blade base 44 of the charging member 40 and the recording material carrier such as the transfer drum 5 can be reduced, and the low friction thin film layer 46 can be cracked. And stable transfer electrification can be maintained for a long period of time.

Embodiment 3 FIG. 3 is a side view showing a transfer means according to still another embodiment of the present invention.

In the first and second embodiments, the blade base 44 of the transfer member 40 has a rectangular cross section in the thickness direction of the plate. In the present embodiment, the blade base 44 is formed as shown in FIG. The downstream side has a wedge-shaped cross-sectional shape protruding in the direction of the photosensitive drum 1.

The blade base 44 having such a wedge-shaped cross-section
According to, the discharge area on the downstream side can be enlarged,
Transfer charging can be more stabilized.

In this embodiment, the low friction thin film layer 46 on the surface of the blade base 44 is provided in a surface region from the upper surface on the upstream side of the blade base 44 to the upper surface on the downstream side via the upper surface.

The low friction thin film layer 46 is
4 only needs to be provided on the surface at the close position on the side facing the photosensitive drum 1, that is, from the upper position on the upstream surface of the blade base 44, it slightly enters the downstream side via the upper surface of the blade base 44. What is necessary is just to provide to a surface area.

According to this embodiment, the frictional force between the conductive rubber blade base 44 of the charging member 40 and the recording material carrier can be reduced, and the low friction thin film layer 46 can be prevented from cracking.
It has become possible to maintain stable transfer charging over a long period of time.

In the first to third embodiments described above, the conductive rubber plate is used as the blade base 44 of the transfer member 40. However, the present invention is not limited to this, and the blade base may constitute a contact type transfer member. As a blade base, for example, a metal plate, a conductive resin plate, or the like can be used.

Further, as shown in FIG. 4A, the transfer member 40 may be in the form of a brush made of a brush 50 of conductive fibers 52. The transfer member 40 includes a brush 50
Insulation members 56a and 56b such as Mylar
The insulating member 56b is provided so as to expose the upper portion of the surface on the upstream side.

Similarly, the low-friction thin-film layer 54 is provided at least from the upper portion of the surface on the upstream side of the brush 50 to the surface region slightly entering the downstream side via the upper surface of the brush 50. The low friction thin film layer 54 has a lower friction coefficient than the brush 50. In this case, the brush 50 preferably has a low-friction thin film layer 54 for each of the fibers 52 as shown in FIG.

[0061]

As described above, according to the present invention,
A transfer member, which is a contact-type transfer unit, in which a conductive substrate made of conductive rubber is in contact with an image carrier via a recording material carrier, and at least a side of the surface of the conductive substrate facing the image carrier. The low friction thin film layer having a lower coefficient of friction than the conductive substrate was formed on the surface in a position close to the image carrier, so that the low friction thin film layer formed the conductive substrate with the recording material carrier. The frictional force and the like can be reduced, and the low-friction thin film layer can be prevented from cracking, and stable transfer charging can be performed over a long period of time.

[Brief description of the drawings]

FIG. 1 is a side view showing a transfer unit in an embodiment of the image forming apparatus of the present invention.

FIG. 2 is a side view showing a transfer unit according to another embodiment of the present invention.

FIG. 3 is a side view showing a transfer unit according to still another embodiment of the present invention.

FIG. 4 is a view showing still another example of the transfer member in the transfer unit of the present invention.

FIG. 5 is a schematic diagram illustrating a conventional image forming apparatus.

FIG. 6 is a diagram illustrating the vicinity of a transfer drum installed in the image forming apparatus of FIG. 5;

FIG. 7 is a side view illustrating a transfer unit of the image forming apparatus of FIG. 5;

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 5 transfer drum 5f transfer sheet 40 transfer member 42 electrode 44 blade base 46 low friction thin film layer 48 insulating member

Continued on the front page (72) Inventor Masahiro Inoue 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Rie Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takeshi Tomizawa 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H032 AA05 AA15 BA16 BA17 CA04 DA03 DA12

Claims (7)

[Claims] A rotating image carrier, a recording material carrier that carries a recording material and is conveyed to the image carrier, a recording material carrier that rotates in contact with the image carrier, and a conductive substrate that is a recording material carrier. An image forming apparatus comprising: a transfer unit that is in contact with the image carrier through the image forming apparatus; wherein at least a surface of the surface of the conductive substrate facing the image carrier and a position close to the image carrier. An image forming apparatus, wherein a low-friction thin-film layer having a lower coefficient of friction than a conductive substrate is formed on the surface. 2. The image forming apparatus according to claim 1, wherein said low friction thin film layer is formed on the entire surface of said conductive substrate. 3. The low friction thin film layer has a particle diameter of 2
2. The method according to claim 1, wherein said fine particles are formed by dispersing lubricating fine particles having a size of 0 μm or less.
Or the image forming apparatus of 2. 4. The image forming apparatus according to claim 3, wherein said lubricating fine particles are fluorinated graphite. 5. The image forming apparatus according to claim 4, wherein the fluorinated graphite has a composition represented by the following chemical formula: (CF) _{1 -X} C _X (where 0.6 ≦ X ≦ 0.8). 6. The method according to claim 3, wherein the binder resin is nylon.
The image forming apparatus according to any one of Items 1 to 5, 7. The low friction thin film layer has a volume resistivity of 10
The image forming apparatus according to claim 1, wherein the thickness is not less than ² Ωcm and not more than 10 ¹⁴ Ωcm and not more than 50 μm.