JPH11338311A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device which has a structure capable of restricting base soil on an image carrier and establishing uniform solid development characteristic. SOLUTION: An image is formed in such a manner that onto the latent-image carrier 1 uniformly electrified in advance an electrostatic latent image is formed by optical writing, a developer carrier 2B with developer held on it is brought into contact with the electrostatic latent image, thereby rendering the electrostatic latent image visible, the image is transferred to a transfer medium and the transferred image is fixed. In the case, the friction coefficient (μ) of the latent- image carrier 1 is set to 0.1<=μ<=0.4.

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, and more particularly, to an image forming apparatus using an electrophotographic process for controlling developer adhesion between a latent image carrier and a developer carrier. Regarding the configuration.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic process such as a printer, a copying machine or a facsimile machine, an electrostatic latent image formed on a latent image carrier such as a photosensitive drum is supplied from a developing device. A visible image is processed by a developer such as toner, and the visible image is electrostatically transferred to a transfer material such as recording paper to obtain a copy.

When the developer is supplied from the developing device to the latent image carrier, the developer carried on the surface of developer supplying means such as a developing roller provided in the developing device is used. The toner layer in the toner layer is electrostatically attracted by the electrostatic force from the electrostatic latent image and adheres to the electrostatic latent image. However, in actuality, the non-electrostatic force generated by the contact state between the toner layer and the latent image carrier causes the toner to be applied to the surface of the latent image carrier, particularly, to the background portion where the electrostatic attraction of the latent image does not act on the toner. May adhere. For this reason, the occurrence of background contamination on the latent image carrier may be significant.

Therefore, conventionally, the degree of background contamination is detected by detecting the toner density outside the image area of the latent image carrier, and the amount of lubricant applied to the surface of the latent image carrier according to the degree of background contamination. (For example, Japanese Patent Application Laid-Open No. 8-254933) to improve the cleaning effect performed after image transfer by controlling the supply of toner by adjusting the contact pressure of the lubricant application means, or a toner layer made of a one-component developer. The relative linear velocity ratio when the developing roller of the developing material supply means carrying the image bearing member is rotated while being in contact with the photosensitive member as the latent image carrying member is set to 1.2 to 3.0 times. 0.5-2.5
Configuration to double (for example, JP-A-9-73299)
Has been proposed.

[0005]

However, the contact pressure of the lubricant applying means against a latent image carrier such as a photoreceptor and the linear velocity ratio between the latent image carrier and the developing roller provided in the developer supplying means are reduced. When changing, there were the following problems.

That is, if the contact pressure of the lubricant applying means is increased, the load on the driving means for setting the contact pressure is increased, so that an abnormal image due to rotational unevenness called banding is likely to occur, and When the linear velocity ratio relative to the latent image carrier is increased, a state where the image density is non-uniform, which is referred to as "toner", is likely to occur. If the linear velocity ratio exceeds 1.2 times, the toner tends to approach the rear end of the image and the occurrence of an abnormal image becomes remarkable.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus having a configuration capable of suppressing the problem of the above-described conventional image forming apparatus, particularly, a background stain on an image carrier and establishing a uniform solid development characteristic. It is in.

[0008]

In order to achieve this object, according to the first aspect of the present invention, an electrostatic latent image is formed on a previously charged latent image carrier by light writing, and the electrostatic latent image is formed. In an image forming apparatus for forming an image by causing a developer carrying member carrying a developer to come into contact with an image to visually present the electrostatic latent image and transferring the image to a transfer medium and fixing the transferred image. , The coefficient of friction (μ) of the latent image carrier is set to 0.
It is characterized in that 1 ≦ μ ≦ 0.4.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the hardness (HS) of at least one of the latent image carrier and the developer carrier is set to 10 ≦
(HS) ≦ 60 ° (JIS-A).

According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the substrate hardness (HS) of at least one of the latent image carrier and the developer carrier is set to 10%.
≦ (HS) ≦ 60 ° (JIS-A).

According to a fourth aspect of the present invention, in the image forming apparatus of the first aspect, the contact pressure (P) of the developer carrier with respect to the latent image carrier is set to 3 ≦ P ≦ 16 g · f / mm. It is characterized by having been set.

According to a fifth aspect of the present invention, in the image forming apparatus of the first aspect, a nip width between the latent image carrier and the developer carrier is set to 2 mm or less.

According to a sixth aspect of the present invention, in the image forming apparatus of the first aspect, the diameters D and d of the latent image carrier and the developer carrier are set to satisfy the relationship of (D / d) <6. It is characterized by having been set to.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

FIG. 1 is a schematic diagram for explaining a relational structure between a photosensitive drum 1 corresponding to an image carrier and a developing device 2 corresponding to a developer supply unit in an image forming apparatus according to an embodiment of the present invention. In FIG. 1, the photosensitive drum 1 is made of an inorganic or organic photosensitive member, and has a surface friction coefficient (μ).
Is set to 0.1 ≦ μ ≦ 0.4. This coefficient of friction is based on the experiment shown in FIG. FIG. 2 is a schematic diagram showing an experimental structure for obtaining a friction coefficient by the Euler belt method. In FIG. 2, a measurement sheet (Ricoh PPC TYPE 620) is provided on a part of the peripheral surface of the photosensitive drum 1.
0A4 size T) S is cut into a size of 297 × 30 mm, and the center of the measurement paper S is wound around the photosensitive drum 1 in a range of 90 degrees (π / 2 rad.) In the circumferential direction. Measurement paper S
A constant weight (0.98 N
(100 g)), a digital push-pull gauge DS is attached to the other side, and the measuring paper S is pulled at a constant speed in a state where the weight W is not shaken. The value of the digital push-pull gauge DS at the moment when starts to move is measured. Assuming that the measured value at this time is F (N), the friction coefficient (μ) is μ = In
(F / 0.98) / (π / 2). Among the friction coefficients obtained from the above experimental structure, when the toner is rubbed against the surface of the photosensitive drum 1 by the pressure from the toner layer, the friction coefficient (μ) that can prevent the toner from adhering due to the frictional force due to the rubbing pressure. The values in the above range were obtained as values that can prevent background contamination. The coefficient of friction (μ) in the case where a lubricant or the like is not applied to the surface of the photoconductor drum 1, that is, when it is untreated, is 0.4 to 0.6, but tends to increase with time. On the other hand, the friction coefficient (μ) of the photosensitive drum 1 coated with the lubricant
Obtained a result of 0.1 to 0.6. From these results, the friction coefficient (μ) of the photosensitive drum was set to 0.1 to
By setting the value to 0.4, the toner does not adhere to the surface of the photosensitive drum 1 when the surface is rubbed, and in particular, the toner does not adhere to a background portion other than the portion where the electrostatic latent image is formed. You can do so.

The friction coefficient of such a surface depends on the particle diameter of the toner used for the visible image processing, but when the volume average particle diameter is 4 to 10 μm, the substance which reduces the friction coefficient of the photosensitive drum is used. This is maintained by applying a so-called lubricant. For this purpose, the lubricant is supplied directly for each predetermined number of image forming operations, i.e., every time a copying operation is performed, or the application means carrying the lubricant is applied to the surface of the photosensitive drum 1 constantly or every predetermined number of copying operations. This is done by contact. The photosensitive drum 1 is charged to a predetermined surface potential in advance by a known charging unit, and an electrostatic latent image corresponding to a document image or written information is formed by a known optical writing unit.

The developing device 2 includes a developing roller 2B facing the photosensitive drum 1 in a developing tank 2A, and a developing roller 2B.
B, a supply roller 2C for supplying a toner composed of a one-component developer, a regulating blade 2D for regulating the layer thickness of the toner carried on the developing roller 2B, and an agitator 2
E.

The toner used in the developing device 2 is obtained by mixing a charge control agent (CCA) and a colorant with a resin such as polyester, polyol or styrene acryl, and externally adding a substance such as silica or titanium oxide to the mixture. It is configured. The average particle size of the toner is selected from 3 to 12 μm, and in this embodiment, 7.5 μm is used. As for the particle size, it is possible to satisfy the demand for high resolution and to reduce the particle size.

The developing roller 2B has a hardness (HS) of 10 to 10.
An elastic material such as rubber set to 60 ° (JIS-A) is used, the outer diameter is 10 to 30 mm, and the surface roughness is 1
４4 (μm) RZ. The surface roughness of the developing roller 2B has a relationship of 13 to 80 (%) with respect to the particle diameter of the toner, so that the toner is conveyed without being buried in the surface of the developing roller 2B. The rubber material used for the developing roller 2B includes silicon rubber, butadiene rubber, nitrile-butadiene rubber (NBR) hydrin, ethylene-propylene-diene rubber (EPD).
M). In addition, the surface of the developing roller 2B can be coated with a coating material to stabilize the quality over time.
Teflon-based material is used. The former material has good toner chargeability, and the latter material has excellent releasability. Furthermore, it is also possible to contain a conductive material such as carbon black in order to improve conductivity, and the thickness of the coating layer is set to 5 to 50 μm. Is preferred.

The developing roller 2B has a hardness (HS) of 10
≤ (HS) ≤ 60 ° (JIS-A).
The reason is as follows. If the hardness is lower than the lower limit value, shrinkage / expansion tends to occur during molding, and molding with high dimensional accuracy becomes difficult. In addition, when softening, it is a general process to include an oil component in the base material of the roller, but when such a process is performed, the roller is continuously operated in a pressurized state for visible image processing. Then, the contained oil component oozes out and the developing roller 2
There is a possibility that the toner carried on the surface of B will be contaminated and the developing ability will be significantly reduced. On the other hand, when the hardness is higher than the upper limit, the moldability is improved by the increased hardness, and the content of the oil component can be reduced, so that the contamination of the toner is reduced. Is done.

The developing roller 2B is in contact with the photosensitive drum 1 via a toner layer.
Pressing means such as a coil spring or a leaf spring is used. In this embodiment, the hardness (HS) of the developing roller 2B is 30 ° (J).
IS-A), the contact pressure is 3 to 16 g · f / mm
Is set to The greater the number of pressing means for contact, the smaller the contact unevenness between the opposing surfaces of the developing roller 2B and the photosensitive drum 1; It is preferable to secure Since the contact pressure affects uniform development of a solid image and prevention of background contamination, it is set based on the following reasons. When the inventor conducted an experiment on the contact pressure, the result shown in FIG. 3 was obtained. FIG. 3 is a diagram showing a state of occurrence of a defective image due to the hardness and the contact pressure.
As is evident in the range of the contact pressure indicated by the oblique line inclined downward from the middle, the developing ability is reduced below the lower limit of the range of the contact pressure, and a sufficient development amount cannot be obtained. . If the upper limit is exceeded, the scavenging force of the developing roller 2B increases and the toner transferred to the photosensitive drum 1 is scraped off or condensed due to the toner layer being compressed and condensed. It has been found that the toner image remains on the developing roller 2 and an abnormal image such as density unevenness in a solid image portion easily occurs. Therefore, by setting the contact pressure within the above range on the basis of the hardness of the developing roller 2B, a high-density uniform image can be obtained.

The supply roller 2C of the developing device 2 is made of a flexible material such as urethane foam and has a thickness of 50 to 500 μm.
The structure is such that the toner having a diameter of about 3 mm can easily hold the toner on the surface. Further, the surface hardness is set to a relatively low hardness of 10 to 30 ° (JIS-A) so that the surface can be uniformly contacted with the developing roller 2B, and the amount of biting into the developing roller 2B is 0.5 to 1.5 mm. The linear velocity ratio between the developing roller 2B and the developing roller 2B is set in the range of 0.5 to 1.5, and in this embodiment, the linear velocity ratio is set to 0.9.
(The direction in which the opposing surface moves in the opposite direction). In the case of the present embodiment, the bite amount corresponds to the width of a unit that can be developed by the developing device 2 when the A4 size transfer paper is fed in the vertical direction.
The required torque when targeting 40 mm, 1.5
２．５2.5 kg · fcm is obtained. The biting amount and the above-described linear speed ratio are set to optimal conditions in a wider range because of the dependence on the characteristics of the motor and gear head in the drive system of the developing device 2 and the charging characteristics and supply of the toner. It is also possible.

The toner carried or present on the surface of the supply roller 2C is caused by negative charge induced by frictional charge when receiving forces in opposite directions at the point of contact with the developing roller 2B, and The roller 2B is held on the surface of the developing roller 2B by the transport effect due to the surface roughness of the roller 2B. When the toner layer is transferred from the supply roller 2C to the developing roller 2B, the toner layer does not have a uniform thickness but is in an excessively adhered state (1 to 3 mg / cm ₂ ), and the thickness is made uniform by a regulating blade 2D described later. You. The supply roller 2C can be rotated in a direction opposite to that of the developing roller 2B (a direction in which the facing surface moves in the same direction).

The regulating blade 2D has a distal end extending from a base end supported by the developing tank 2A and a developing roller 2D.
B, which are arranged at an inclination of 10 to 45 ° with respect to the tangential direction at a position facing B, toward the downstream side in the rotation direction of the developing roller 2B, and whose base end is closer to the peripheral surface of the developing roller 2B than the front end. The plate thickness is 0.1 to 0.15 in the contact state.
(Mm) made of a metal blade such as SUS304. Further, the length from the base end to the front end is set to 10 to 15 mm, and the contact pressure with the developing roller 2B is set to 5 to 250 (g · f / cm). In this embodiment, the hardness of the developing roller 2B is 30 ° (JIS-JIS).
In the case of A), SUS having a thickness of 0.1 mm is used, and a contact pressure of 60 (g · f / cm) is selected. The length of the toner layer on the developing roller 2B can be reduced because the size of the apparatus is increased when the length to the front end is too long, and vibration is easily generated when the length to the front end is too long. This prevents the occurrence of uneven toner adhesion due to the inability to make the toner uniform. The uneven toner adhesion causes the occurrence of an abnormal image in which the density due to the uneven toner adhesion becomes noticeable on the developed image. In addition, by regulating the contact pressure, it is possible to prevent an increase in the toner charge amount due to a decrease in the amount of toner attached to the developing roller 2B, which is likely to occur when the upper limit is exceeded, and to prevent the toner from being transferred to the photosensitive drum 1 side. In addition to suppressing the decrease in image density due to insufficient transfer, the phenomenon in which solidified toner, which tends to occur when the density falls below the lower limit, is prevented from passing is prevented, and the occurrence of an abnormal image can be eliminated.

Excess toner carried on the developing roller 2B is scraped off by the regulating blade 2D to form a thin layer having a uniform thickness of about 0.4 to 0.8 mg / cm ₂ per unit area. The charge amount of toner is also -5 to -30μ
C / g is supplied to the electrostatic latent image on the photosensitive drum 1. In this embodiment, the diameter of the photosensitive drum 1 is 5 mm.
The hardness, the contact pressure, and the bite amount to be described later are set so that the development area is 5 to 10 mm when the diameter of the developing roller 2B is 0 mm and the diameter of the developing roller 2B is 16 mm.

Since the present embodiment has the above configuration,
The electrostatic latent image formed on the photosensitive drum 1 by optical writing is subjected to visible image processing by supplying toner from the developing device 2. In the developing device 2, the toner agitated by the agitator 2E is conveyed toward the supply roller 2C and is carried by the supply roller 2C. The toner carried on the supply roller 2C is carried on the surface of the developing roller 2B by the electrostatic force induced by frictional charging when the supply roller 2C rotates while abutting on the developing roller 2B and the surface roughness of the developing roller 2B. As a result, a toner layer is formed. The thickness of the toner layer is regulated by the regulating blade 5E to 0.4 to 0.8 m per unit area.
It is a thin layer having a uniform thickness of about g / cm ₂ , and the charge amount of the toner is set to −5 to −30 μC / g and supplied to the electrostatic latent image on the photosensitive drum 1.

The photosensitive drum 1 in contact with the developing roller 2B has a friction coefficient (μ) on its surface set to 0.1 to 0.4, so that the toner carried on the developing roller 2B Is prevented from being rubbed and adhered by the pressure from the layer, so that adhesion of the toner to portions other than the electrostatic latent image, so-called background portions, is suppressed.

By the way, in the present invention, when the developing roller 2B is in contact with the photosensitive drum 1 via the toner layer, the uniformity of the surface of the developing roller 2B and the uniform We focus on maintaining the contact state. Hereinafter, embodiments of this point will be described. In order to maintain the above-mentioned surface uniformity and uniform contact state, it is necessary to control the amount of bite between the developing roller 2B and the photosensitive drum 1, that is, to control the amount of close contact between the opposing peripheral surfaces, and Contact pressure management becomes important. The bite amount affects the supply performance corresponding to the transferability of the toner, and depends on the outer diameter tolerance of the developing roller 2B, the deviation of the rotation center, and the like. Further, the contact pressure affects the amount of toner adhering to the background portion of the photosensitive drum 1 due to the pressure of the toner layer carried on the developing roller 2B and the above-mentioned bite amount,
Although relatively easy to obtain due to the mechanical elements of the developing roller 2B, the apparatus may be complicated to obtain good contact pressure.

FIG. 3 shows the image characteristics in the relationship between the contact pressure and the hardness, that is, the results obtained by experiments on the state of occurrence of a defective image. In FIG. 3, the development in the case of a hardness of 40 ° (JIS-A) Roller (tentatively referred to as developing roller A) and a developing roller having a hardness of 20 ° (JIS-A) (temporarily developing roller B).
With respect to the handling pressure at which a defective image does not occur, the developing roller A applies an applied contact pressure of 3 to 8
gf / mm, and 3 for the developing roller B.
It can be seen that a state in which a defective image does not occur is obtained in the range of up to 16 gf / mm.

FIG. 4 is a diagram showing the relationship between the hardness and the amount of bite when the contact pressure is changed. In FIG. 4, the contact pressure is changed to the values of the developing rollers A and B described above. When trying to set, the variation width of the bite amount is 0.02 mm for the developing roller A and 0.105 mm for the developing roller B.
In the case of the developing roller A, it is necessary to increase the dimensional accuracy by a factor of five as compared with the developing roller B.

Therefore, in the present embodiment, the coating layer described in the above embodiment is provided on the surface layer of the developing roller 2B, and the material for forming the coating layer has flexibility in selection. The coating layer has a charging property of the toner and a carrying property during conveyance,
Further, the toner is provided with the releasability from the toner and the abrasion resistance as a function. However, in the case of a material having a relatively low hardness, the abrasion resistance is often inferior. By using a relatively high-grade material as the coating layer and by setting the hardness of the developing roller 2B to be soft depending on the hardness of the roller base material, the entire developing roller 2B can be made of one material having a low hardness. The above-mentioned contact pressure is obtained by eliminating the above-mentioned problems. As a result, the surface layer of the developing roller 2B is made of a relatively high material, and the overall hardness of the developing roller 2B is reduced when the roller base material is made of a relatively low-hardness material. The same result as that in which a defective image hardly occurs is obtained.

In the present invention, attention is paid to the point that the nip width at the contact position between the photosensitive drum 1 and the developing roller 2B affects the developing characteristics of a solid image. Hereinafter, FIGS. 5 and 6
An embodiment in this regard will be described below. Experiments have shown that if the nip width at the contact position between the photosensitive drum 1 and the developing roller 2B exceeds 2 mm, a uniform density cannot be obtained for solid image development. this is,
This is because the scavenging effect, which is the performance of scraping the toner from the photosensitive drum 1 by the developing roller 2B, is increased. As shown in FIG. 5, the hardness of the developing roller 2B and the contact state (contact pressure) are reduced. Dependent. The nip width shown in FIG. 5 is a half of the contact length in the circumferential direction at a contact position between the photosensitive drum 1 and the developing roller 2B with respect to a line connecting the center points of the two. Indicates the nip width,
The actual nip width corresponds to twice this value. FIG.
Indicates the relationship between the bite amount and the one-side nip width when the hardness of the developing roller 2B is 20 ° (JIS-A). In FIG. Experiments have confirmed that an image having a uniform and sufficient density can be obtained by selecting the contact pressure.

Therefore, in this embodiment, a hardness of 20 ° (JI
By setting the bite amount at which the one-side nip width is 1 mm or less in the case of SA) to 0.19 mm or less, the nip width of 2 mm or less can be obtained, so that the above-described problem can be prevented. . Further, from the results shown in FIG. 5, the contact pressure at which the nip width becomes 2 mm or less is 12 gf / m when the hardness is 20 ° (JIS-A).
20gf / m in the case of hardness 40 ° (JIS-A)
mm.

By setting such characteristics, density unevenness in a solid image can be prevented and a solid image with a uniform density can be obtained.

The present invention focuses on the nip width described above, which can be set by the diameter ratio between the photosensitive roller 1 and the developing roller 2B. Hereinafter, an embodiment of this point will be described with reference to FIGS. In this embodiment, the diameter (D) of the photosensitive drum 1 and the developing roller 2B
The ratio (R) to the diameter (d) is defined as R = (D / d) <6.

FIGS. 7 and 8 show the change in the one-side nip width depending on the value of the diameter ratio (R). In FIG.
6, when the hardness of the developing roller 2B is 20 ° (JIS-A), the nip width on one side exceeds 1 mm at the contact pressure of 12 gf / mm. Uniformity in density cannot be secured, and image unevenness occurs. However, by setting the diameter of the photosensitive drum 1 to 24 mm and the diameter of the developing roller 2B to 16 mm so that the specific diameter ratio (R) becomes R <6, R = R
In the case of 1.5, as shown in FIG. 8, the nip width can be increased until the contact pressure reaches 16 gf / mm when the hardness is the same as described above. For this reason, it is possible to widen the selection range of the contact pressure and to secure a developing area corresponding to a toner supply range that does not cause image deterioration such as density unevenness on the photosensitive drum 1.

The coating layer provided on the surface layer of the developing roller 2B may contain a conductive material such as carbon black as appropriate in order to obtain conductivity instead of the silicon-based or Teflon-based coating described above. is there.

As a material of the regulating blade 2D,
An elastic rubber material such as polyurethane rubber having a thickness of about 1 to 2 mm, a silicone resin, or a fluororesin having a polarity opposite to the charging characteristic of the toner (for example,
ETFE (ethylene tetrafluoroethylene), PTF
Relatively high materials such as E (polytetrafluoroethylene) and (PVDF (polyvinylidene fluoride)) can also be used. Furthermore, since resistance can be reduced by mixing carbon black or the like other than metal, it is possible to generate an electric field between the developing roller 2B by connecting a bias power supply.

The hardness can be set for the photosensitive drum instead of for the developing roller as shown in the above embodiment. It is also possible to make the relationship opposite to the relationship described above.

[0040]

According to the first aspect of the present invention, by setting the friction coefficient of the latent image carrier within the range of 0.1 ≦ μ ≦ 0.4, the developer can be applied to portions other than the electrostatic latent image. It is possible to surely prevent the latent image carrier from being rubbed and adhered to the background portion of the latent image carrier, thereby eliminating background contamination.

According to the second aspect of the present invention, the hardness (H) of at least one of the latent image carrier and the developer carrier is selected.
By setting S) as 10 ≦ (HS) ≦ 60 ° (JIS-A), contact unevenness between the above-mentioned two carriers is reduced without impairing dimensional accuracy and without causing toner contamination. Thus, the density of the solid image can be made uniform.

According to the third aspect of the invention, the substrate hardness (HS) of at least one of the latent image carrier and the developer carrier is set to 10 ≦ (HS) ≦ 60 ° (JIS-A). By setting, the hardness at the surface layer of the base material is set such that a defective image does not occur, and the hardness of the entire support is made to depend on the hardness of the base material. Accordingly, it is possible to prevent the contact pressure at which a defective image is generated from becoming uneven. This allows
The bite amount is set to an amount that does not generate a defective image, and an image without density unevenness can be formed.

According to the fourth aspect of the present invention, the contact pressure (P) of the developer carrier with respect to the latent image carrier is 3 ≦ P ≦ 16
By setting it to g · f / mm, it is possible to set a biting amount at which a defective image does not occur between the respective carriers.

According to the fifth aspect of the present invention, by setting the nip width between the latent image carrier and the developer carrier to 2 mm or less, one of the image carriers based on the nip width is set. By selecting the hardness and the contact pressure, it is possible to obtain a uniform solid image with sufficient density and no unevenness.

According to the sixth aspect of the present invention, the diameters D and d of the latent image carrier and the developer carrier are respectively expressed by D / D.
By setting d <6, the selection range of the contact pressure that can ensure the uniformity of the density of the solid image without the nip width exceeding the above numerical value can be widened, and the density unevenness with respect to the latent image carrier can be improved. Thus, it is possible to secure a development area corresponding to a toner supply range that does not cause image deterioration.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a relationship between an image carrier and a developer supply unit, which are main components of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining an experimental structure for obtaining a friction coefficient of a latent image carrier used in the image forming apparatus shown in FIG.

FIG. 3 is a diagram showing a state in which a defective image is generated due to the hardness of a developing roller used for a developer supply unit and the contact pressure of the developing roller against a latent image carrier.

FIG. 4 is a diagram showing a relationship between hardness and bite amount when the contact pressure shown in FIG. 3 is changed.

5 is a diagram showing the relationship between the hardness of the developing roller used in the developer supply unit shown in FIG. 1 and the one-side nip according to the contact pressure of the developing roller.

6 is a diagram showing a relationship between a bite amount between a developing roller and a photoconductor as a latent image carrier and a one-side nip width when the hardness of the developing roller shown in FIG. 5 is set to a predetermined hardness. .

FIG. 7 is a diagram illustrating a change in a one-side nip width depending on a value of a diameter ratio (R) between a latent image carrier and a developer carrier.

FIG. 8 is a diagram illustrating a change in nip width with respect to hardness when the diameter ratio is set to a predetermined value.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum as latent image carrier 2 developing device as developer supply means 2B developing roller

Claims (6)

[Claims] An electrostatic latent image is formed on a previously charged latent image carrier by light writing, and a developer carrier carrying a developer is brought into contact with the electrostatic latent image. In an image forming apparatus that forms an image by performing a visual presenting process on an electrostatic latent image, transferring the image to a transfer medium, and fixing the transferred image, the friction coefficient (μ) of the latent image carrier is set to 0.1 ≦ μ. ≦ 0.
An image forming apparatus, wherein the number is set to 4. 2. The image forming apparatus according to claim 1, wherein at least one of the latent image carrier and the developer carrier has a hardness (HS) of 10 ≦ (HS) ≦ 60 ° (JI
An image forming apparatus set in (SA). 3. The image forming apparatus according to claim 1, wherein at least one of the latent image carrier and the developer carrier has a substrate hardness (HS) of 10 ≦ (HS) ≦ 60 ° (JIS-JIS). An image forming apparatus characterized by having been set to A). 4. An image forming apparatus according to claim 1, wherein a contact pressure (P) of said developer carrier with respect to said latent image carrier is provided.
Is set to 3 ≦ P ≦ 16 g · f / mm. 5. The image forming apparatus according to claim 1, wherein a nip width between the latent image carrier and the developer carrier is set to 2 mm or less. 6. An image forming apparatus according to claim 1, wherein each of said latent image carrier and said developer carrier has a diameter D,
An image forming apparatus, wherein d is set to satisfy the relationship of (D / d) <6.