JP2000267435A - Developing device and image forming device - Google Patents

Abstract

[PROBLEMS] To provide a developing device capable of satisfactorily charging a toner and having excellent durability, and an image forming apparatus including the developing device. A pressing portion (38) of a layer thickness regulating blade (23) for pressing on a developing roller (22) is formed of silicone rubber.
2 is set so as to be 15 to 30 gf / cm. As a result, the non-magnetic one-component toner is sufficiently charged because it is pressed by the silicone rubber having particularly good chargeability, and the pressing force is 15 to 30 g.
Since it is extremely weak at f / cm, embedding of the external additive into the toner base particles at the time of pressing can be significantly reduced, and abrasion of the silicone rubber can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, and more particularly, to a developing device provided in an image forming apparatus such as a facsimile or a laser printer, and an image forming apparatus provided with the developing device.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a laser printer using a non-magnetic one-component toner, a developing roller for carrying the toner and a side of the developing roller are provided.
A developing device including a layer thickness regulating blade that forms a thin layer of toner on the developing roller and a photosensitive drum that is disposed to face the developing roller and forms an electrostatic latent image is mounted.

[0003] The layer thickness regulating blade is pressed against the surface of the developing roller, and the toner supplied to the developing roller is rubbed between the layer thickness regulating blade and the developing roller, and is sufficiently charged. Is carried on the developing roller as a thin layer having a constant thickness. On the other hand, the electrostatic latent image is formed by uniformly charging the surface of the photosensitive drum with a charger and then irradiating the surface with a laser beam based on predetermined image data by a laser light emitting device by high-speed scanning. ing. Then, development is performed by selectively transferring the charged toner when the charged toner is opposed to the electrostatic latent image.

[0004]

However, when developing such a non-magnetic one-component toner, most of the charging of the toner is performed by frictional contact between the layer thickness regulating blade and the developing roller. Therefore, in order to uniformly charge the toner, it is necessary to strongly press the layer thickness regulating blade against the developing roller and rub the toner to some extent. On the other hand, in order to improve the fluidity and charge stability of the toner, an external additive made of fine powder such as silica, alumina, and titanium oxide is externally added. Such external additives are embedded in the base particles of the toner, resulting in a decrease in fluidity or a decrease in chargeability. Therefore, it is conceivable that the pressing portion of the layer thickness regulating blade that presses the photosensitive drum is made of a rubber member to reduce the embedding of the external additive into the toner base particles during the frictional contact of the layer thickness regulating blade.

However, in recent years, reduction of waste and reduction of running cost have been strictly required in consideration of environmental considerations, and it has been demanded to extend the life of consumables as much as possible. In particular, regarding the life of the developing device,
There is a need to extend its life by a factor of about two. For this reason, if the pressing portion of the layer thickness regulating blade is formed of a rubber member, the embedding of the external additive into the toner base particles during frictional contact of the layer thickness regulating blade can be reduced, but this alone is not sufficient. not,
On the other hand, the abrasion of the rubber member of the pressing portion is large, and the above-mentioned demand cannot be satisfied at all.

According to the present invention, there is provided a developing device capable of satisfactorily charging a toner and having excellent durability, and
An object of the present invention is to provide an image forming apparatus including the developing device.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a developer carrying member for carrying a non-magnetic one-component developer, and pressing on the developer carrying member. A layer thickness regulating member for forming a thin layer of the developer, and a photoconductor on which an electrostatic latent image is formed, wherein the developer formed on the developer carrier by the layer thickness regulating member In a developing device configured to form a visible image by making the thin layer of the photoconductive member face the photosensitive member on which an electrostatic latent image is formed, The pressing portion for pressing is formed of silicone rubber, and the pressing force on the developer carrier at the pressing portion is 15 to 30 gf / cm.

According to such a configuration, the developer is pressed on the developer carrier by the pressing portion of the layer thickness regulating member formed of silicone rubber with a pressing force of 15 to 30 gf / cm. While being charged by friction, it is carried in a thin layer on the developer carrying member.

The invention described in claim 2 is the first invention.
In the invention described in (1), the developer carrying member is formed of a conductive elastic body.

According to such a configuration, the developer is pressed between the pressing portion of the layer thickness regulating member formed of silicone rubber and the developer carrier formed of the conductive elastic body. While being charged, it is carried on the developer carrying member as a thin layer.

[0011] The invention according to claim 3 is based on claim 1.
In the invention described in Item 2, the developer is a polymerized toner obtained by polymerizing a polymerizable monomer.

When the developer is a polymerized toner obtained by polymerizing a polymerizable monomer, the flowability becomes extremely good because the shape of the particles is closer to a true sphere than a pulverized toner. Therefore, it is possible to reduce frictional resistance when pressed and rubbed between the pressing portion of the layer thickness regulating member and the developer carrying member.

The invention described in claim 4 is the first invention.
4. The invention according to any one of Items 3 to 3, wherein at least the surface of the developer carrier contains fluorine.

By including fluorine having a small frictional resistance on at least the surface of the developer carrying member, the frictional resistance when the developer is pressed and rubbed between the pressing portion of the layer thickness regulating member and the developer carrying member. Can be further reduced.

According to a fifth aspect of the present invention, in the first aspect of the invention, the surface roughness of the surface of the developer carrier is smaller than the average particle diameter of the developer. It is characterized by.

For example, when the surface roughness of the surface of the developer carrying member is larger than the average particle diameter of the developer, the developer gets into the unevenness of the surface of the developer carrying member and is moved from the layer thickness regulating member. However, if the surface roughness of the surface of the developer carrier is made smaller than the average particle diameter of the developer as in the present invention, such a problem may occur. The developer is always pressed by a constant pressing force on the surface of the developer carrying member without generation of the toner.

The invention described in claim 6 is the first invention.
The image forming apparatus according to any one of the first to fifth aspects is provided with a developing device.

By providing the image forming apparatus with the developing device according to any one of claims 1 to 5, a stable image can be obtained without causing an image forming defect such as fogging due to poor charging. Can be formed.

[0019]

FIG. 1 is a side sectional view showing a main part of an embodiment of a laser printer as an image forming apparatus according to the present invention. In FIG. 1, a laser printer 1 includes a feeder unit 4 for supplying paper 3 and an image forming unit 5 for forming a predetermined image on the supplied paper 3 in a main body casing 2. .

The feeder unit 4 includes the main casing 2.
Paper tray 100 detachably mounted on the bottom of the paper tray
A sheet pressing plate 6 provided in the sheet feeding tray 100;
Paper feed roller 7 and paper feed pad 8 provided above one end of paper feed tray 100, and registration roller 9 provided downstream of paper feed roller 7 in the transport direction of paper 3.
And

The sheet pressing plate 6 is capable of stacking the sheets 3 in a stacked manner, and the end farther from the sheet feed roller 7 is swingably supported, and the end closer to the sheet feeding roller 7 is vertically movable. And is urged upward by a spring (not shown) from the back side. Therefore, as the stacking amount of the sheet 3 increases, the sheet pressing plate 6 is rotated downward against the urging force of the spring with the end remote from the sheet feeding roller 7 as a fulcrum. The paper feed roller 7 and the paper feed pad 8 are disposed to face each other, and the paper feed pad 8 is moved by a spring 10 disposed on the back side of the paper feed pad 8.
Is pressed toward the paper feed roller 7. The uppermost sheet 3 on the sheet pressing plate 6 is pressed from the back side of the sheet pressing plate 6 toward the sheet feeding roller 7 by a spring (not shown), and the sheet feeding roller 7 is rotated by the rotation of the sheet feeding roller 7. After being sandwiched between the pads 8, the sheet is fed one by one. The registration roller 9 includes two rollers on the driving side and the driven side. The registration roller 9 sends the sheet 3 sent from the sheet feeding roller 7 to the image forming unit 5 after a predetermined registration.

The image forming unit 5 includes a scanner unit 11, a developing unit 12 as a developing device, a fixing unit 13, and the like.

The scanner unit 11 is provided at an upper part in the main body casing 2 and has a laser emitting unit (not shown),
It includes a polygon mirror 14, which is driven to rotate, lenses 15 and 16, reflection mirrors 17, 18 and 19, and the like.
A laser beam based on predetermined image data emitted from the laser emitting section is indicated by a chain line as shown by a polygon mirror 14, a lens 15, reflection mirrors 17 and 18, and a lens 1
6. The light passes through or is reflected by the reflecting mirror 19 in this order to irradiate the surface of the photosensitive drum 21 of the developing unit 12 described later by high-speed scanning.

FIG. 2 is a side sectional view showing the developing unit 12 in an enlarged manner. Next, based on FIG.
2 will be described. In FIG. 2, a developing unit 12 is disposed below the scanner unit 11 and is detachably mounted on the main body casing 2.
0, a photosensitive drum 21 as a photosensitive member, a developing cartridge 36, a scorotron type charger 25, and a transfer roller 26
And so on. The developing cartridge 36 is detachably attached to the drum cartridge 20 and includes a developing roller 22 as a developer carrier, a layer thickness regulating blade 23 as a layer thickness regulating member, a supply roller 24, a toner box 27, and the like. Have.

In the toner box 27, a positively chargeable non-magnetic one-component toner having an electrical insulation property is accommodated as a developer. If you use positively charged toner,
The image can be developed on the positively charged photosensitive drum 21 by reversal development. That is, when a negatively chargeable toner is used, the photosensitive drum 21 needs to be negatively charged.
For example, when the photosensitive drum 21 is negatively charged in a non-contact state using the scorotron charger 25,
If a large amount of ozone is generated, and charging is performed in a state of contact using a conductive roller, brush, or the like in order to prevent this, uneven charging occurs on the photosensitive drum 21. Sometimes. On the other hand, the photosensitive drum 21
Is positively charged, even if it is charged in a non-contact state using the scorotron charger 25, the generation of ozone is extremely small and the charging can be performed uniformly without charging. Therefore, by using a positively charged toner, generation of ozone is small and uniform development can be achieved.

The toner may be a polymerizable monomer, for example, a styrene monomer such as styrene, or an acrylic resin such as acrylic acid, alkyl (C1 to C4) acrylate, or alkyl (C1 to C4) methacrylate. To a styrene-acrylic spherical resin obtained by copolymerizing a monomer by a known polymerization method such as suspension polymerization, a coloring agent such as carbon black, a charge control agent such as nigrosine, and a wax are added. A polymerized toner is used which has as a main component the toner base particles obtained as described above and to which an external additive composed of a fine powder such as silica, alumina or titanium oxide is added. Such a polymerized toner has extremely good fluidity because the shape of the particles is closer to a true sphere than a pulverized toner. Further, in this toner, fluidity and charge stability are improved by externally adding an external additive such as silica. The average particle size of the polymerized toner is about 7 to 10 μm. In the present embodiment, two types of silica to be externally added, one having a BET specific surface area of 200 and the other having a BET specific surface area of 50, are used. While increasing the fluidity of the toner with silica,
The silica having a large BET specific surface area of 50 prevents the small particles from being embedded in the base particles.

The toner in the toner box 27 is rotated by a rotating shaft 28 provided at the center of the toner box 27.
The toner is agitated by the agitator 29 supported by the toner box 27 and is discharged from the toner supply port 30 opened on the side of the toner box 27. A window 40 for detecting the remaining amount of toner is provided on a side wall of the toner box 27.
0 is always cleaned by the cleaner 39 which rotates together with the agitator 29.

A supply roller 24 is disposed at a position lateral to the toner supply port 30 so as to be rotatable in the direction of the arrow (counterclockwise), and a developing roller 22 is opposed to the supply roller 24. It is arranged to be rotatable in the direction of the arrow (counterclockwise). The supply roller 24 and the developing roller 22 are in contact with each other so that each of them is compressed to some extent.

The supply roller 24 has a metal roller shaft,
A roller made of a conductive foam material is covered. Ma
Further, the developing roller 22 has a conductive roller on a metal roller shaft.
A roller made of an elastic material is covered. More specifically
Indicates that the roller portion of the developing roller 22 is made of carbon fine particles.
Conductive urethane rubber or silicone rubber containing
The surface of the roller body consisting of
Coated with a coating layer of urethane rubber or silicone rubber
ing. The surface roughness of the surface of this coat layer is
The ten-point average roughness R is smaller than the average particle size._zTo
3 to 5. Note that the developing roller 22
Is a bias that causes a potential difference with the photosensitive drum 21.
Resistance is applied, and the resistance value from the axis to the surface
But about 10 ^Four-10⁸It is configured to be Ω.

In the vicinity of the developing roller 22, a layer thickness regulating blade 23 is provided. The layer thickness regulating blade 23 has a blade body 37 made of a metal leaf spring material.
And a pressing portion 38 provided at the tip of the blade main body 37 and having a semicircular cross section made of insulating silicone rubber. An end of the blade main body 37 opposite to the pressing portion 38 is provided with a developing roller. The pressing unit 38 is configured to be pressed on the developing roller 22 by the elastic force of the blade body 37 while being supported by the developing cartridge 36 near the developing roller 22.

The toner discharged from the toner supply port 30 is supplied to the developing roller 2 by the rotation of the supply roller 24.
2, the supply roller 24 and the developing roller 2
2 is positively triboelectrically charged, and the developing roller 22
The toner supplied above is pressed by the pressing portion 38 of the layer thickness regulating blade 23 and the developing roller 2 with the rotation of the developing roller 22.
2 where the thickness regulating blade 23
Of the developing roller 22 is rubbed between the pressing portion 38 of the developing roller 22 and the developing roller 22 so as to be sufficiently triboelectrically charged and formed as a thin layer having a constant thickness.
Carried on top.

On the other hand, the photosensitive drum 21 is
At the side position of the developing roller 22, it is rotatable in the direction of the arrow (clockwise) so as to face the developing roller 22. The photosensitive drum 21 has a drum main body grounded and a surface formed of a positively chargeable material such as an organic photoreceptor containing polycarbonate as a main component. Further, the scorotron type charger 25 is connected to the photosensitive drum 2.
Above 1, they are arranged at predetermined intervals. The scorotron charger 25 is a scorotron charger for positive charging that generates corona discharge from a charging wire such as tungsten, and is configured to uniformly positively charge the surface of the photosensitive drum 21. Have been.

The surface of the photosensitive drum 21 is uniformly positively charged by the scorotron charger 25, and is then exposed by high-speed scanning of a laser beam from the scanner unit 11 to form an electrostatic latent image based on predetermined image data. An image is formed. Then, by the rotation of the developing roller 22, the toner that is carried on the developing roller 22 and is positively charged,
When the photosensitive drum 21 faces and contacts the photosensitive drum 21, the photosensitive drum 2
1 is selectively transferred to a portion of the electrostatic latent image formed on the surface of the photosensitive drum 21, that is, a portion of the uniformly positively charged photosensitive drum 21, which is exposed to a laser beam and has a reduced potential. Thus, a visible image is formed, whereby development (reversal development) is achieved.

Below the photosensitive drum 21, a transfer roller 26 facing the photosensitive drum 21 is disposed rotatably in the direction of the arrow (counterclockwise). Transfer roller 26
In FIG. 1, a metal roller shaft is covered with a roller made of a conductive rubber material, and a predetermined transfer bias is applied. Therefore, the toner developed on the photosensitive drum 21 is transferred to the sheet 3 while the sheet 3 passes between the photosensitive drum 21 and the transfer roller 26.

The fixing unit 13 is, as shown in FIG.
A heating roller 32, a pressing roller 31 pressed by the heating roller 32, and a pair of transport rollers 33 provided downstream of the heating roller 32 and the pressing roller 31; It has.
The heating roller 32 is made of metal and includes a halogen lamp for heating. The heating roller 32 transfers the toner transferred onto the sheet 3 in the developing unit 12 while the sheet 3 passes between the heating roller 32 and the pressing roller 31. Then, the sheet 3 is conveyed to a pair of sheet discharge rollers 34 by the conveying rollers 33. A pair of paper discharge rollers 34
Is discharged onto a paper discharge tray 35 by the paper discharge rollers 34.

In the laser printer 1, the toner remaining on the photosensitive drum 21 after the transfer of the visible image is collected by a so-called cleaner-less method. That is, in the cleanerless method, the toner remaining on the photosensitive drum 21 after the visible image is transferred is
First, the photosensitive drum 21 rotates to face the scorotron-type charger 25, and the scorotron-type charger 25 uniformly charges the photosensitive drum 21. Then, the photosensitive drum 21 rotates to face the developing roller 22. Developing roller 2
2, the toner is collected by the developing roller 22 at the same time as the developing is performed.

In this embodiment, in this embodiment, the pressing force of the pressing portion 38 of the layer thickness regulating blade 23 made of silicone rubber on the developing roller 22 is extremely weak, that is, 15 to 30 gf / cm. It is set to be. Such setting of the pressing force can be set by appropriately adjusting the position at which one end of the blade main body 37 is supported by the developing cartridge 36 and the curvature or the amount of bending deformation of the blade main body 37.

As described above, if the pressing force of the pressing portion 38 against the developing roller 22 is set so as to be a very weak pressing force of 15 to 30 gf / cm, the distance between the pressing portion 38 and the developing roller 22 is reduced. When the toner is pressed and rubbed, the embedding of the external additive into the toner base particles can be greatly reduced, and the abrasion of the silicone rubber can be reduced. In addition, even with such an extremely weak pressing force, the toner is pressed by the pressing portion 38 made of silicone rubber, which has a particularly good chargeability, and thus is carried on the developing roller 22 while being sufficiently charged. Therefore, it is possible to improve the durability of the layer-thickness regulating blade 23 and, consequently, the developing unit 12 while reducing the running cost, while making it possible to develop well without developing defects due to defective charging properties.

Since the roller portion of the developing roller 22 is formed of an elastic body made of conductive urethane rubber or silicone rubber, the toner is formed by the pressing portion 38 made of silicone rubber and the conductive elastic body. The toner is pressed between the formed developing roller 22 and the embedding of the external additive into the toner base particles during the pressing is further reduced, and the wear of the silicone rubber is further reduced. Is done.

Further, in this embodiment, since the polymerized toner having extremely good fluidity is used, the toner when the toner is pressed and rubbed between the pressing portion 38 of the layer thickness regulating blade 23 and the developing roller 22 is used. Friction resistance is reduced. That is, when the pressing force of the pressing portion 38 against the developing roller 22 is extremely weak as in the present embodiment, the pressing force between the pressing portion 38 and the developing roller 22 is, for example, various such as variation between apparatuses. May fluctuate based on the change in the frictional force due to the conditions described above.Therefore, stable chargeability may not be ensured.However, if a polymerized toner having extremely good fluidity is used, the frictional force may change. Since the fluctuation of the pressing force can be significantly reduced, stable development can be secured over a long period of time.

Further, in the present embodiment, the surface of the roller portion of the developing roller 22 is coated with a urethane rubber or silicone rubber coating layer containing fluorine having a small frictional resistance so that the layer thickness regulating blade 23 Since the frictional resistance when the toner is pressed and rubbed between the pressing portion 38 and the developing roller 22 is further reduced, the fluctuation of the pressing force based on the change in the frictional force is further stabilized, and the further improvement. This ensures stable development over a long period of time.

In addition, in the present embodiment, the developing roller 22
Is smaller than the average particle diameter of the toner, for example, the surface roughness of the surface of the developing roller 22 is
When the average particle diameter is larger than the average particle diameter of the toner, the toner may be stuck in the irregularities on the surface of the developing roller 22 and the pressing force from the layer thickness regulating blade 23 may not be applied. Therefore, the toner is always pressed by a constant pressing force on the surface of the developing roller 22 and is stably charged, so that stable development can be ensured for a long period of time.

As described above, the laser printer 1 according to the present embodiment includes the developing unit 12 configured as described above.
Because, due to poor charging, for example,
A stable image can always be formed without causing image formation defects such as fogging.

In the description of this embodiment, a positively charged toner is used. However, a negatively charged toner may be used, or a pulverized toner may be used instead of the polymerized toner. .

[0045]

EXPERIMENTAL EXAMPLES The present invention will be described more specifically with reference to the following experimental examples, but the present invention is not limited to the following experimental examples. 1) Image Forming Apparatus A laser printer having the following configuration was used as the image forming apparatus.

The basic configuration is the same as that of the laser printer 1 described above.

Developing roller: Conductive urethane rubber roller on which a fluorine-based surface coat layer is formed Supply roller: Conductive urethane foam rubber Thickness regulating blade: Leaf spring having a semi-cylindrical silicone rubber having a diameter of 3.5 mm Table 1
Toner: Non-magnetic one-component toner, styrene-acrylic copolymer spherical resin obtained by suspension polymerization, nigrosine as a charge control agent, coloring Carbon and other waxes are added as agents, and silicas having BET specific surface areas of 200 and 50 are externally added as external additives.

However, the silica has been subjected to a well-known surface treatment such as a silicone oil and a silane coupling agent.

Printing conditions: At a printing speed of 20 ppm (10 cm / sec as the peripheral speed of the photosensitive drum), intermittent printing of two sheets per minute was performed on the entire surface with a printing area ratio of 4%. 2) Evaluation Beauty when printing 16,000 sheets: 1 under the printing conditions described above.
After printing 6,000 sheets, a zip pattern of 1 dot and 2 spaces on the entire surface was printed, and the beauty was evaluated. Table 1 shows the results.

Number of occurrences of abrasion of the layer thickness regulating blade: Every time 16,000 sheets are printed under the above printing conditions, 400 g of toner is added, and a printing failure occurs due to the occurrence of abrasion of the layer thickness regulating blade. This printing was repeated until the number of generated sheets was measured. Table 1 shows the results. In addition, the printing failure due to the shaving of the layer thickness regulating blade was based on the fact that vertical streaks occurred in the printing, and at this point, a good printing was obtained by replacing it with a new layer thickness regulating blade. Was performed by confirming.

In the above test, the presence or absence of print fog in the initial printing was also determined. Table 1 shows the results.

[0052]

[Table 1]

As is evident from Table 1, the number of abrasions of the layer thickness regulating blade is smaller as the pressing force becomes stronger. Therefore, if the pressing force is reduced, the wear of the silicone rubber is reduced. It can be seen that it can be reduced.

The beauty of printing 16,000 sheets is good when the pressing force is in the range of 15 to 30 gf / cm. That is, when the pressing force is 10 gf / cm, since the pressing force is weak, the charging of the toner becomes insufficient and a printing failure occurs (print fogging has already occurred even in the early stage of use), while 40 gf / cm. / Cm or more, the toner is sufficiently charged, but the pressing force is strong, so that the embedding of the external additive into the toner base particles causes the print quality to deteriorate.

It can be seen that the one having a pressing force in the range of 15 to 30 gf / cm can exhibit twice or more the durability performance as compared with the conventional printing of 16,000 sheets.

[0056]

As described above, according to the first aspect of the present invention, since the developer is pressed on the developer carrier by the silicone rubber having particularly good chargeability, the developer is sufficiently charged. And the pressing force is extremely weak at 15 to 30 gf / cm, so that embedding of the external additive into the toner base particles during pressing can be greatly reduced, and the wear of the silicone rubber can be reduced. Can be reduced. Therefore, it is possible to improve the durability of the developing device and reduce the running cost while developing well without developing defects due to poor charging properties.

According to the second aspect of the present invention, the developer is provided between the pressing portion of the layer thickness regulating member made of silicone rubber and the developer carrier made of a conductive elastic body. Therefore, the embedding of the external additive into the toner base particles at the time of pressing can be further reduced, and the wear of the silicone rubber can be further reduced.

According to the third aspect of the present invention, since the polymerized toner having extremely good fluidity is used as the developer, a pressure is applied between the pressing portion of the layer thickness regulating member and the developer carrier. The frictional resistance at the time of rubbing can be reduced. That is, as in the present invention, when the pressing portion of the layer thickness regulating member against the developer carrying member is extremely weak, the pressing force between the pressing portion of the layer thickness regulating member and the developer carrying member is, for example, an apparatus. It may fluctuate based on a change in frictional force due to various conditions such as variation between them, and therefore, it may not be possible to secure stable charging properties.However, if a polymer toner having extremely good fluidity is used, ,
Fluctuations in the pressing force due to changes in the frictional force can be significantly reduced, whereby stable development can be ensured for a long period of time.

According to the fourth aspect of the present invention, at least the surface of the developer carrying member contains fluorine having a small frictional resistance, so that the pressure between the pressing portion of the layer thickness regulating member and the developer carrying member is reduced. The frictional resistance when the developer is pressed and rubbed can be further reduced. Therefore, it is possible to further stabilize the fluctuation of the pressing force based on the change of the frictional force, and it is possible to secure more stable development for a long period of time.

According to the fifth aspect of the present invention, since the developer is constantly pressed by a constant pressing force on the surface of the developer carrier, the developer is always stably charged. Therefore, stable development can be ensured for a long time.

According to the invention of claim 6, according to claim 1,
By providing the image forming apparatus with the developing device according to any one of the above items 1 to 5, it is possible to always form a stable image without causing an image forming defect such as fog due to poor charging properties. .

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a main part of an embodiment of a laser printer including a developing device of the present invention.

FIG. 2 is an enlarged side sectional view showing a developing unit.

[Explanation of symbols]

 Reference Signs List 1 laser printer 12 developing unit 21 photosensitive drum 22 developing roller 23 layer thickness regulating blade 38 pressing part

Claims (6)

[Claims] 1. A developer carrying member for carrying a non-magnetic one-component developer, a layer thickness regulating member for pressing the developer carrying member to form a thin layer of the developer, and an electrostatic latent image. And a thin layer of the developer formed on the developer carrier by the layer thickness regulating member is opposed to the photoconductor on which an electrostatic latent image is formed. In a developing device configured to form a visible image, a pressing portion of the layer thickness regulating member that presses on the developer carrier is formed of silicone rubber, and the developer in the pressing portion is A developing device, wherein the pressing force on the carrier is 15 to 30 gf / cm. 2. The developing device according to claim 1, wherein the developer carrier is formed of a conductive elastic body. 3. The developing device according to claim 1, wherein the developer is a polymerized toner obtained by polymerizing a polymerizable monomer. 4. At least a surface of the developer carrier,
The developing device according to any one of claims 1 to 3, wherein the developing device contains fluorine. 5. The surface of the developer carrying member has a surface roughness of:
The developing device according to claim 1, wherein the average particle size of the developer is smaller than the average particle size of the developer. 6. An image forming apparatus comprising the developing device according to claim 1.