JP2002182481A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which the deterioration of an image carrier is suppressed while preventing the increase of the cost of a device and nonconformity such as the occurrence of an abnormal image at the time of using cardboard. SOLUTION: In the image forming device provided with an endless transfer feeding means 6 to transfer a toner image on the image carrier 3 to a transfer material S while feeding the transfer material S and a driving means not shown in a figure to impart driving force to the endless transfer feeding means 6, the endless transfer feeding means 6 is constituted of a member consisting of at least two or more layers such as a surface layer 6a and a surface coating layer 6b formed on the surface layer, and is arranged so as to come into contact with the image carrier 3 at a fixed position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
More specifically, the present invention relates to an image forming apparatus using an electrostatic transfer system such as a facsimile apparatus, and more particularly, to an endless transfer / transporting means for transferring a toner image on an image carrier onto a transfer material while conveying a transfer material; The present invention relates to an image forming apparatus including a transfer unit that applies a driving force to a transfer conveyance unit.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrostatic transfer system, such as a copying machine, a printer, a facsimile machine, etc., a photoreceptor (image carrier) uniformly charged in advance is reflected on an original in a dark place. An electrostatic latent image is formed by exposing with optical image information such as light, and a toner image obtained by developing the electrostatic latent image with toner from a developing device is transferred onto a transfer material by a transfer device. After fixing, image formation is performed. By the way, as the transfer device, a bias roller as a transfer unit is opposed to a photoreceptor via a transfer belt (endless transfer transfer unit) made of a certain electric resistance material or the like, and a transfer material carried by the transfer belt is provided. A contact transfer method is known in which a transfer bias is applied to transfer a toner image onto a transfer material when is transferred to a transfer position. In a contact type transfer method using a transfer belt, a transfer nip is formed by bringing a transfer belt into contact with a photoconductor, and a toner image is transferred from the photoconductor to the transfer material by passing the transfer material through the transfer nip. Transcription is performed.

[0003]

However, when the transfer belt is made of an elastic material, substances such as a sulfur component for accelerating vulcanization and a plasticizer for giving plasticity are formed from the elastic material. These substances are deposited, and these substances adhere to the photoconductor as the image carrier. When substances such as the sulfur component and the plasticizer adhere to the photoconductor, there is a problem that the photoconductor is deteriorated and an abnormal image such as white spots is generated in the image. Therefore, the transfer belt is configured to be able to contact and separate from the photoconductor, and when transferring the toner image of the photoconductor to the transfer material, the transfer belt is brought into contact with the photoconductor to form a transfer nip. . On the other hand, when the transfer is not performed, the transfer belt is separated from the photoconductor. As a configuration for moving the transfer belt toward and away from the photoconductor,
For example, there is a roller provided with a contact / separation mechanism that pivotally supports one of the stretching rollers that stretches the transfer belt as a swing fulcrum and swings the transfer belt by a driving unit such as a solenoid.

However, when the above-mentioned contact / separation mechanism is provided, the structure is complicated and the cost is increased, and the size of the apparatus is increased in order to secure the installation space. Further, the reliability of the device may be impaired due to the failure of the contact / separation mechanism. When thick paper is used as the transfer material,
Since the thickness of the transfer material is thicker than that of a commonly used transfer material, the driving force of a drive unit such as a solenoid is lost to the paper thickness, so that the transfer nip becomes unstable. As a result, good transfer cannot be performed and an abnormal image may be generated. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the cost of an apparatus and to prevent problems such as the occurrence of an abnormal image when using thick paper while maintaining the image holding capacity. An object of the present invention is to provide an image forming apparatus capable of suppressing body deterioration.

[0006]

In order to achieve the above object, an invention according to claim 1 is an endless transfer / transporting means for transferring a toner image on an image carrier onto a transfer material while transporting the transfer material. And an endless transfer / conveying means, the driving means for applying a driving force to the endless transfer / conveying means, wherein the endless transfer / conveying means comprises at least two layers of a base layer and a surface coat layer formed on the base layer. It is characterized by being constituted by the above-mentioned members, and being arranged in contact with a fixed position with respect to the image carrier.

In this image forming apparatus, the endless transfer / transporting means is composed of at least two layers of a base layer and a surface coat layer formed on the base layer. Even when a substance that degrades the image carrier when adhered to the surface is deposited, the surface coat layer can block the substance and prevent the substance from adhering to the image carrier. Therefore, the deterioration of the image carrier can be suppressed, and abnormal images such as white spots on the image can be reduced. Further, by arranging the endless transfer / transporting means in contact with a fixed position with respect to the image carrier, the endless transfer / transport means as described in the related art can be moved toward and away from the image carrier. It is not necessary to provide a contact / separation mechanism for the transfer, and the endless transfer / transfer means can be simply configured.
Therefore, the cost and size of the endless transfer / transport unit can be reduced. Further, since there is no need to provide the contact / separation mechanism, there is no trouble that may occur in the contact / separation mechanism, and the reliability of the apparatus can be improved. Furthermore, as compared with the conventional configuration having the contact / separation mechanism, the positioning between the endless transfer / transporting means and the image carrier can be performed accurately, and a stable transfer nip area is secured, thereby improving transferability. Can be done. In particular, even when thick paper is used as the transfer material, the transfer nip can be stabilized, and occurrence of an abnormal image can be prevented.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the base layer is made of an elastic material, and an elongation ratio of the surface coat layer when cracks occur is set to 50% or more. It is a feature.

In this image forming apparatus, the extension rate of the surface coat layer provided on the surface of the endless transfer / transporting means when a crack occurs (when the endless transfer / transporting means is extended until cracks occur on the surface). Elongation rate of the surface coat layer)
Is set to 50% or more. It has been confirmed by experiments that if the elongation percentage of the surface coat layer is 50% or more, the substance deposited from the base layer does not adhere to the image carrier and the image carrier does not deteriorate. Further, it was confirmed by an experiment that if the elongation percentage of the surface coat layer was less than 50%, the substance deposited from the base layer adhered to the image carrier and the image carrier deteriorated. Therefore, by setting the elongation percentage of the surface coat layer to 50% or more, it is possible to prevent the image carrier from deteriorating due to the substance precipitated from the base layer, and to prevent the occurrence of an abnormal image.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the relationship between the extension rate of the surface coating layer of the endless transfer transfer means when a crack occurs and the extension rate when the belt is stretched is: Elongation rate when cracks occur in surface coat layer ≧
(Elongation ratio when belt is stretched) × 10.

According to the present invention, for example, even when the transfer belt as the endless transfer transfer means is stretched around a roller, the material of the surface coat layer of the transfer belt has good elongation (the ability to follow the rubber base material). It is another object of the present invention to prevent the generation of more effective cracks by using a coating material having good (i.e., good). In this image forming apparatus, the extension rate of the surface coat layer of the endless transfer / transport means when a crack occurs is determined by the extension rate of the endless transfer / transport means at the time of mounting and stretching (the endless transfer / transport means is attached to the image forming apparatus main body). (Extension rate of the endless transfer / transporting means when mounted and stretched)
It is set to 0 times or more. As described above, the extension rate at the time of occurrence of a crack in the surface coat layer of the endless transfer / transporting means is not limited to the property as the material of the endless transfer / transport means, but is defined based on the characteristics of the mounted state. Thus, it is possible to prevent the occurrence of an appropriate crack during the operation of the endless transfer transfer means.

According to a fourth aspect of the present invention, in the image forming apparatus of the first, second or third aspect, a lubricant applying means for applying a lubricant to the surface of the surface coat layer is provided. .

[0013] In this image forming apparatus, the surface of the surface coat layer is coated with the lubricant, so that the toner hardly adheres to the surface, and the cleaning property of the surface coat layer surface is better than when the surface is not coated with the lubricant. Can be up. Further, when a fine crack occurs in the surface coat layer, the photoconductor deteriorating substance of the base layer may be precipitated from the fine crack, but the lubricant blocks the photoconductor deteriorating substance by filling the fine crack, It is possible to prevent the photoconductor deteriorating substance from adhering to the image carrier. In addition, as the above-mentioned lubricant, relatively high-order fatty acids such as zinc stearate, barium stearate, calcium stearate, zinc oleate, and manganese oleate can be mentioned.

According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third or fourth aspect, an amorphous silicon-based photosensitive member is used as the image carrier.

An amorphous silicon-based photoreceptor has a higher surface hardness than, for example, an organic photoreceptor, and in particular, is excellent in moisture resistance, continuous repeated use characteristics, electrical pressure resistance, use environment characteristics, and durability. In this image forming apparatus, since the image carrier is an amorphous silicon-based photoconductor, the life of the image carrier can be extended, and the durability and life of the entire apparatus can be increased.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a transfer and conveyance device using a transfer belt as a transfer material carrier of the image forming apparatus according to the present embodiment, FIG. 2 is a plan view showing a schematic configuration of the transfer and conveyance device, and FIG. FIG. 2 is a schematic configuration diagram of a forming apparatus.

A transfer unit 1 shown in FIG. 1 supports a belt unit 2 detachably from a main body 1A. The belt unit 2 includes a transfer belt 6 as a belt-shaped transfer material carrier to which a toner image formed on a drum-shaped photoconductor 3 as an image carrier shown in FIG. 3 is transferred. The transfer belt 6 is stretched around a driving roller 5 and a driven roller 4 as support members. Further, the belt unit 2 includes a bias roller 11 as a transfer charge applying unit that applies a transfer bias to the transfer belt 6 to apply a transfer charge, a contact plate 13 that removes the charge of the transfer belt 6,
A belt cleaning device 16 for removing the toner and paper dust attached to the surface of the transfer belt 6 and cleaning the transfer belt 6 is provided. Bias roller 11
The high-voltage power supply 12 for applying a voltage to the main body 1A shown in FIG.
It is provided in. As shown in FIGS. 1 and 2, the drive roller 5 has a gear 5b connected to a drive motor (not shown) at one end thereof, and is driven to rotate.

In FIG. 3, the transfer belt 6 can follow the rotation of the drive roller 5 and move in the direction of conveyance of the transfer paper S as a transfer material (in the direction of arrow A) at a position facing the photosensitive member 3. It has become.

The driven roller 4 and the driving roller 5 are rotatably supported by a support 7 as shown in FIGS. When the transfer belt 6 comes into contact with the photoconductor 3, a transfer nip portion B is formed at which the transfer paper S can be conveyed while being in contact with the photoconductor 3 at a position facing the photoconductor 3. This transfer nip portion B
Has a length (nip width) of about 4 to 8 [mm] along the transport direction A.

Among the rollers 4 and 5, the roller 4 located on the photoconductor 3 side is configured as a driven roller to the roller 5 on the driving side. As shown in FIG. 2, the surface shape of the driven roller 4 has both ends 4a,
4a is formed in a tapered shape, and the transfer belt 6
To prevent biasing. The driven roller 4 shown is a conductive roller made of metal or the like, but only supports the transfer belt 6 having the electric resistance as described above, and is electrically directly connected to other conductive members. Not shown. The driven roller 4 can be fed back to the high-voltage power supply 12 and grounded as in a contact plate 13 described later (see FIG. 4). Drive roller 5
It is preferable to select a material such as EPDM rubber, chloroprene rubber, or silicone rubber from the viewpoint of a function of increasing the gripping force on the transfer belt 6 at the time of driving. Etc. can also be used. Further, the feedback current from the driving roller 5 can be returned to the high voltage power supply 12.

The bias roller 11 is provided on the downstream side (the left side in FIG. 3) of the driven roller 4 in the moving direction of the transfer belt 6 so as to contact the inside of the transfer belt 6. The bias roller 11 constitutes a contact electrode for applying a charge having a polarity opposite to the charge polarity of the toner T on the photoconductor 3 to the transfer belt 6.
It is connected to the. In this embodiment, since the toner T having a positive polarity is used, the polarity of the transfer bias is negative. Although the bias roller 11 is used as the transfer charge applying means, the present invention is not limited to this, and a corona charger or a brush may be used. The installation position of the transfer charge applying means is not limited to the downstream side of the transfer nip B in the transfer paper transport direction, but may be installed on the upstream side in the transport direction.

The contact plate 13 is disposed in contact with the inner surface of the belt near the driven roller 4 on the lower side of the transfer belt 6 which is not the transfer paper transfer surface. Thereby, a transfer nip portion B described later
The injection of charges into the transfer paper S on the upstream side is suppressed. The contact plate 13 is for detecting a current flowing on the transfer belt 6 as a feedback current, and a current supplied from the bias roller 11 is controlled by detecting the current. For this reason, a transfer control plate 14 for setting a supply current to the bias roller 11 in accordance with the detected current is connected to the contact plate 13.
Are connected to a high voltage power supply 12.

On the other hand, in the case of an analog type image forming apparatus, the surface of the photoreceptor 3 is charged, for example, to -800 V. As shown in FIG. It moves to the transfer nip B while being electrically attracted. Then, before reaching the transfer nip portion B, the surface potential of the photoconductor 3 is reduced by a pre-transfer static elimination lamp (PTL) 15 arranged near the photoconductor 3 to weaken the charge on the surface of the photoconductor 3. In FIG. 6, the height of the charged charge is represented by the size of a circle, and the charge in a state where the charged charge is reduced by the pre-transfer charge removing lamp 15 is smaller than the circle indicating the charge before the charge is removed. Have been.

In the transfer nip portion B shown in FIG. 3, the toner T on the photosensitive member 3 is transferred onto the transfer paper S by the transfer bias from the bias roller 11 located on the transfer belt 6 side. This transfer bias is -1.5 to -6.5.
The voltage is applied from the high-voltage power supply 12 in the range of [kV] because the transfer bias is variably set as a result of constant voltage control described later. That is, in FIG. 3, the current value output from the high voltage power supply 12 and I _1, the transfer belt 6
If the value at the time of detection of the feedback current flowing through the ground was I ₂ from the contact plate 13 via, between these two, to control the value of I ₁ so that the relation of the following equation is obtained.

I ₁ −I ₂ = Iout (where Iout: constant) This is due to changes in environmental conditions such as temperature and humidity and the transfer belt 6.
This is because the change in transfer efficiency is eliminated by stabilizing the surface potential Vp on the transfer paper S irrespective of the variation in the production quality of the transfer paper. That is, the transfer belt 6
And the current flowing through the transfer paper S to the photoconductor 3 side is Iou
By considering it as t, a change in the ease of current flow to the transfer belt 6 due to a reduction or increase in the surface resistance on the transfer paper S affects the separation performance and transfer performance of the transfer paper S. It is designed to prevent that. In this embodiment, the transfer speed of the transfer belt is 330 [m
m / sec] and the effective bias roller length was 310 [mm], good transfer was obtained when Iout = 35 ± 5 [μA].

When the transfer of the toner image from the photosensitive member 3 is performed, the transfer paper S is also charged at the same time. Therefore, the transfer paper S is electrostatically attracted onto the transfer belt 6 and the transfer paper S is separated from the photoconductor 3 by the relationship between the true charge of the transfer belt 6 and the polarization charge generated on the transfer paper S side. I can do it.
This separation is promoted by the peeling operation of the transfer paper S using its stiffness utilizing the curvature separation of the photoconductor 3. However, such separation of the transfer sheet S by electrostatic attraction is not successful because, for example, in the case of high humidity, a current easily flows through the transfer sheet S due to a change in environmental conditions. For this reason, since the resistance value of the surface coat layer 6b of the transfer belt 6 shown in FIG.
The transfer of the true charges to the transfer paper S at the transfer nip B is delayed, and the bias roller 11 is positioned downstream of the transfer nip B in the transfer paper transport direction. Thus, the transfer of the true charges from the transfer belt 6 to the transfer sheet S is delayed, and the electrostatic attraction between the transfer sheet S and the photoconductor 3 is avoided.

To delay the transfer of the true charge used in this case means that no charge is generated on the transfer sheet S upstream from the transfer sheet S to the transfer nip portion B on the photosensitive member 6 side. I have. This prevents the transfer paper S from being wound around the photoconductor 3 and also prevents the transfer paper S from separating from the photoconductor 3 from being poorly separated.

Further, as the transfer belt 6, it is preferable to select a transfer belt having a small resistance change due to an environmental change. As a conductive material for controlling the resistance, a suitable amount of carbon, zinc oxide or the like is added. When an elastic belt (rubber belt) is used, it is desirable to select a material having a low hygroscopicity and a stable resistance value, such as chloroprene rubber, EPDM rubber, silicone rubber, and epichlorohydrin rubber. Note that the value of the current Iout flowing to the photoconductor 3 is not unique, and can be reduced, for example, when the transport speed is low. If not used, increase it.

On the other hand, the transfer paper S passing through the transfer nip portion B
Is transported electrostatically in accordance with the movement of the transfer belt 6,
Curvature separation at the driving roller 5 is performed. For this reason,
The diameter of the driving roller 5 is set to 16 [mm] or less. Furthermore, in the case of using such a drive roller 5, fine 45K paper (stiffness: horizontal 21 [cm ^3/100]) experimental result that separation is possible of is obtained.

The transfer paper S separated from the transfer belt at the outer peripheral position of the drive roller 5 is guided by a guide plate to form a heating roller 17a and a pad roller 1 which constitute a fixing section 17.
7b. The fixing unit 17 heats and melts the toner on the transfer paper S and presses the toner on the transfer paper S to fix the toner on the transfer paper S. The surface of the transfer belt 6 on which the image transfer to the transfer paper S and the separation have been completed is cleaned by the cleaning device 16.

The cleaning device 16 is provided with a cleaning blade 16A, and the toner transferred from the surface of the photoreceptor 3 or scattered around the transfer belt 6 without being transferred by rubbing the transfer belt 6. Is scraped off the toner and the paper powder of the transfer paper S when the toner adheres. The transfer belt 6 slid by the cleaning blade 16A has a low friction coefficient to prevent a phenomenon such as an increase in driving force due to an increase in rubbing resistance or a turning-up of the cleaning blade 16A. A material such as polyvinylidene fluoride or tetrafluoroethylene is coated as the surface coat layer 6b. Further, the toner or paper dust that has been picked up from the surface of the transfer belt 6 is collected by the collecting screw 16B.
A is stored in a waste toner collecting container (not shown).

Next, the characteristic parts of the image forming apparatus according to the present embodiment will be described. If the transfer belt 6 is configured to be able to contact and separate from the photoreceptor 3, there is a problem that the configuration of the transfer conveyance device 1 becomes complicated as described above, resulting in an increase in cost. Therefore, as shown in FIG. 3, the transfer belt 6 is always in contact with the photoconductor 3. In the conventional image forming apparatus, the transfer nip is formed by bringing the transfer belt into contact with the photoconductor only when the toner image on the photoconductor is transferred to the transfer paper. However, in the image forming apparatus according to the present embodiment, The transfer nip is always formed. That is, the transfer belt 6 is always in contact with the photoreceptor 3 even when the job is on standby, and the transfer nip B
Is formed.

By keeping the transfer belt 6 in contact with the photoreceptor 3 at all times as described above, the
There is no need to provide a contact / separation mechanism for bringing the transfer belt 6 into and out of contact with the photoconductor 3, and the transfer / conveyance device 1 can be simply configured. Therefore, the cost of the device can be reduced. In addition, since there is no mechanical component or the like for moving the transfer belt 6 toward and away from the photosensitive member 3, there is no initial failure or failure with time that may occur from the contact and separation mechanism, and the reliability of the apparatus can be improved. In addition, the installation space for the transfer / conveyance device 1 can be reduced, and the size of the image forming apparatus main body can be reduced. Also, it is easy to secure a space for taking out the transfer paper when the transfer paper is jammed,
It is also possible to improve the operability of the user and the maintainability of the service person. Furthermore, when the duplex unit is installed, it is easy to secure the installation space for the duplex unit,
The degree of freedom in design can be improved.

Further, since there is no drive source such as a solenoid or a motor for driving the contact / separation mechanism, no heat is generated from this drive source and a rise in temperature inside the apparatus can be suppressed. Therefore, it is possible to suppress a rise in the temperature of the surface of the transfer belt 6, and to reduce the occurrence of toner sticking even when toner adheres to the belt surface of the transfer belt 6.

Further, since there is no contact / separation mechanism, the transfer / transport device 1 and the photosensitive member 3 can be accurately positioned, a stable transfer nip area can be secured, and transferability can be improved. Conventionally, when thick paper is used as the transfer paper, a drive system such as a solenoid or a clutch loses the thickness of the thick paper, so that normal transfer cannot be performed and an abnormal image may be generated. However, the transfer belt 6 is always
By accurately contacting the cardboard and positioning the cardboard, such problems can be avoided, the transfer stability of the thick paper can be achieved, and an abnormal image can be prevented.

As described above, the transfer belt 6 is connected to the photosensitive member 3
There are many advantages of keeping the transfer belt 6
Is composed of an elastic material, a substance such as a sulfur component for accelerating vulcanization or a plasticizer for imparting plasticity (hereinafter, referred to as a “photoconductor deteriorating substance”) is precipitated from the elastic material. May adhere to the photoconductor 3. When the photoconductor deteriorating substance adheres, the photoconductor 3 is degraded, and when an image is formed using the degraded photoconductor 3, there is a problem that an abnormal image such as a white spot occurs. In order to prevent substances deposited from the transfer belt 6 from adhering to the photoreceptor 3, the transfer belt 6 has a two-layer structure of a base layer 6a and a surface coat layer 6b as shown in FIG.

As a material of the base layer 6a of the transfer belt 6, for example, a proper amount of carbon, zinc oxide or the like is added as a conductive material for controlling resistance, and when a rubber belt is used as an elastic belt, chloroprene rubber is used. , EP
It is desirable to select a material that has low hygroscopicity and a stable resistance value, such as DM rubber, silicone rubber, and epichlorohydrin rubber. However, it is not limited to these materials. As a material of the surface coat layer 6b, for example, a fluorine-based coating agent containing fluorine as a main material is used. However, this is an example, and the present invention is not limited to this.

The transfer belt 6 is JISK6911
The surface resistivity of the surface coat layer 6b is from 1 × 10 ⁸ to when the electric resistance is 100 V DC according to the measurement according to
Within the range of 1 × 10 ¹² [Ω], the surface resistivity of the base layer 6a is 1 × 10 ⁷ to 1 × 10 ⁹ [Ω], and the volume resistivity thereof is 5 × 10 ^{8 to} 5 × 10 ¹⁰ [Ω ·]. cm]. The respective values shown as the resistance value of the transfer belt 6 are merely examples, and are not limited thereto, and may be lower than the above range, or conversely, a high resistance region higher than the above range. Is also good.

By using the transfer belt 6 having the two-layer structure, even if the photoreceptor-deteriorating substance precipitates from the base layer 6a, it is blocked by the surface coat layer 6b and can be prevented from adhering to the photoreceptor 3. . The transfer belt 6
Is not limited to the above-described two-layer structure.
A three-layer structure may be provided by providing an intermediate layer between a and the surface coat layer 6b. Alternatively, a structure having four or more layers may be employed. FIG. 5 shows an example of the transfer belt, but the present invention is not limited to the transfer belt, and a transfer roller may be used. In this case, the deterioration of the photoconductor can be blocked by covering the transfer roller with a tube.

[Embodiment 1] In this embodiment, the transfer belt 6
The surface coat layer 6b with good elongation was provided such that the elongation rate of the surface coat layer 6b (hereinafter referred to as "elongation rate at the time of occurrence of cracks") was 50% or more. Here, the extension ratio at the time of occurrence of a crack is the extension ratio of the transfer belt 6 when the transfer belt 6 is extended until a crack occurs on the surface of the transfer belt 6 carrying the transfer paper S. It is an elongation of 6. If this expansion rate is high, the transfer belt 6
Of the transfer belt 6 is less likely to crack. Table 1 shows the results of an experiment in which 500 k runs were performed using the various transfer belts 6 in the above-described image forming apparatus, and the relationship between the elongation ratio when a crack occurred and the photoreceptor deterioration was examined.

[Table 1] In Table 1, "O" in the column of photoreceptor deterioration indicates that no photoreceptor deterioration occurred over time including the initial stage, and "x" indicates the result of photoreceptor deterioration observed.

As can be seen from Table 1, if the elongation rate of the surface coat layer 6b of the transfer belt 6 is 50% or more, the photoconductor does not deteriorate over time including the initial period.
Further, after performing a 500 k endurance run on the transfer belt 6 having an extension ratio of 50%, an evaluation of photoreceptor deterioration was performed (H / H).
(Leave in the environment for 10 days). As a result, no deterioration of the photoreceptor occurred in this evaluation. Therefore, it is desirable that the extension rate of the surface coat layer 6b of the transfer belt 6 when a crack occurs is 50% or more. In this embodiment, since the elongation percentage of the surface coat layer 6b is set to 50% or more, it is possible to prevent the photoconductor 3 from deteriorating even if the photoconductor deteriorating substance is deposited from the base layer 6a. .

When measuring the elongation ratio of the surface coat layer 6b of the transfer belt 6 when a crack occurs, the surface of the transfer belt 6 is observed at a magnification of about 100 to 400 times by a CCD camera. It is difficult to measure a single layer.
Therefore, in practice, with the surface coat layer 6b provided on the base layer 6a as the base material of the transfer belt 6, the base layer 6a is extended, and the extension when a crack occurs in the surface coat layer 6b. I measure the rate. here,
Since the base layer 6a serving as the base material is rich in elasticity, the elongation percentage of the surface coat layer 6b measured in this way when a crack occurs is the same as that measured by the surface coat layer alone.

The characteristic structure of this embodiment is that the transfer belt 6
By using a material having good elongation as the material of the surface coat layer 6b, that is, a material having a high elongation at the time of occurrence of cracks, cracks and deterioration of the photoreceptor are prevented. The elongation rate of the surface coat layer 6b of the transfer belt 6 is adjusted by adding a curing agent to the main material of the fluororesin constituting the surface coat layer 6b. As shown in Table 1, the smaller the numerical value of the elongation ratio, the more brittle the surface coat layer 6b, and when stress is applied by other members when the transfer belt 6 is mounted, cracks occur in the surface coat layer 6b. It will be easier. That is, cracks occur earlier in the surface coat layer 6b with a smaller numerical value of the elongation. Then, if the elongation rate of the surface coat layer 6b is high, the elongation is improved and cracks are less likely to occur. The base layer 6a as a base material of the transfer belt 6 is formed of an elastic body having a sufficiently large elongation.

[Embodiment 2] In Table 1, the characteristics of the transfer belt alone in terms of the material are shown. As shown in FIGS. 1 to 3, the transfer belt 6 uses the driven roller 4 and As the belt unit 2 stretched around the drive roller 5,
Used to some extent in an extended state. Thus, in the present embodiment, the expansion rate of the transfer belt 6 when a crack occurs
The surface coat layer 6b is provided so as to have an extension rate of 10 times or more when used while being stretched over the driven roller 4 and the drive roller 5 (hereinafter, referred to as "stretch rate at the time of stretching"). . Table 2 shows experimental results obtained by measuring the relationship between the ratio of the two elongation ratios (elongation ratio at the time of occurrence of cracks / elongation ratio at the time of stretching) and the deterioration of the photoreceptor in the transfer conveyance device 1. FIG. 7 is a graph showing the experimental results of Table 2. Here, the abscissa indicates the value of (elongation ratio of the surface coat layer when a crack occurs) / (the elongation ratio of the surface coat layer when stretched), and the ordinate indicates the presence and degree of photoreceptor deterioration.

[Table 2]

From Table 2 and FIG. 7, when the deterioration with time, such as the deterioration at the contact portion with the cleaning member 16A, is taken into consideration, the transfer belt 6 having the simply high elongation at the time of the occurrence of the crack is used. It is not sufficient to perform the above-described process, and it has been found that when the extension rate of the transfer belt 6 at the time of occurrence of a crack is 10 times or more the extension rate of the transfer belt 6 at the time of stretching, good characteristics without deterioration of the photoconductor over time can be obtained. . As described above, by defining not only the material properties of the transfer belt 6 but also the expansion rate of the transfer belt 6 when the transfer belt 6 is cracked during mounting, the proper photosensitivity during the operation of the transfer belt 6 can be obtained. It is possible to prevent the occurrence of body deterioration.

That is, the first embodiment relates to a state in which the transfer belt 6 is not mounted on an actual machine, that is, the characteristics of the belt alone in terms of material. In the case of being constructed endlessly as 6 and being used while being stretched over the rollers 4 and 5, when the stretch rate at the time of stretching and the stretch rate at the time of crack generation are appropriate, the stretch rate at the time of proper stretching is obtained. Needs to be calculated. It is clear from Table 2 and FIG. 7 that when the relationship between the two is set so that the elongation ratio at the time of crack occurrence is always 10 times or more the elongation ratio at the time of stretching, photoconductor deterioration occurs. Can be reliably prevented. Therefore, the extension rate at the time of crack occurrence ≧ (the extension rate at the time of belt tension) ×
The material of the surface coat layer 6b,
By setting the extension rate (tension) when the transfer belt is stretched, it is possible to prevent deterioration of the photoconductor. For example, when the extension rate of the surface coat layer 6b of the transfer belt 6 to be used at the time of occurrence of a crack is 50%, the extension rate at the time of stretching the transfer belt that can be set to prevent the photoconductor from deteriorating is:
The range is 5% or less.

It is assumed that the elongation at the time of occurrence of a crack in the second embodiment is 50% or more. However, it is also possible to manufacture the transfer belt 6 by using a material having an elongation ratio of less than 50% when a crack occurs, and put it into practical use.

Embodiment 3 In this embodiment, the transfer belt 6
Is provided with a lubricant applying means for applying a lubricant to the surface of the surface coat layer 6b. FIG. 8A shows the lubricant applying means 20.
FIG. The lubricant applying unit 20 includes an application roller 21 that applies a lubricant to the photoconductor 3, and a lubricant 22.
And an urging spring 23 for urging the lubricant toward the application roller. The application roller 21 is in contact with the surface of the photoconductor 3, and rotates with the photoconductor 3. When the application roller 21 rotates, the lubricant 22 adheres to the surface of the application roller, and this lubricant 2
2 is applied to the surface of the photoconductor 3 at the contact portion with the photoconductor 3.
The lubricant 22 applied to the surface of the photoconductor 3 is applied to the surface of the surface coat layer 6b of the transfer belt 6 which is always in contact at the transfer nip portion. Examples of the lubricant 22 include relatively higher fatty acids such as zinc stearate, barium stearate, calcium stearate, zinc oleate, and manganese oleate. The lubricant 22 can be applied at the time of exchanging the transfer belt 6 or at the time of a process control operation. Further, the lubricant 22 can be always applied.

By applying the lubricant 22 to the surface of the surface coat layer 6b, the surface of the surface coat layer 6b becomes
And the toner hardly adheres to the surface of the surface coat layer 6b, and the cleaning property of the surface coat layer 6b can be improved as compared with the case where the surface coat layer 6b is not coated with the lubricant 22. Further, when a fine crack occurs in the surface coat layer 6b, the photoconductor deteriorating substance of the base layer 6a may precipitate from the fine crack. However, the lubricant 22 blocks the photoconductor deteriorating substance by filling the fine crack, It is possible to prevent the photoconductor deteriorating substance from adhering to the photoconductor 3.

The configuration of the lubricant applying means 20 is not limited to the configuration in which the lubricant 22 is indirectly applied to the transfer belt 6 via the photoreceptor 3 as shown in FIG. Absent. For example, as shown in FIG. 8B, a configuration may be adopted in which a lubricant applying unit 20 is disposed at a position facing the driven roller 4 and the lubricant 22 is applied directly to the transfer belt 6. Further, as shown in FIG. 8C, a configuration may be adopted in which the lubricant 22 is indirectly applied to the transfer belt 6 via a cleaning roller 24 disposed at a position facing the drive roller 5. . The transfer belt 6
In the case of cleaning with a cleaning blade, if the friction coefficient of the surface of the transfer belt 6 is increased due to the application of the lubricant 22, there is a possibility that a problem such as a sharpness may occur. However, in the configuration shown in FIG. 8C, since the cleaning roller 24 is used as the cleaning member, the above-described problem can be prevented.

Embodiment 4 Next, the photosensitive member used in the image forming apparatus according to the present embodiment will be described in detail.
As the photoconductor 3 of the present embodiment, the conductive support is set at 50 ° C.
Heated to 400 ° C., and a vacuum deposition method, a sputtering method, an ion plating method, a thermal CVD method, light C
It is possible to use an amorphous silicon-based photoconductor (hereinafter, referred to as "a-Si-based photoconductor") having a photoconductive layer made of amorphous silicon (a-Si) by a film forming method such as a VD method or a plasma CVD method. it can. Among them, a plasma CVD method, that is, a method in which a raw material gas is decomposed by direct current, high frequency, or microwave glow discharge to form an a-Si deposited film on a support is used as a preferable method.

The layer structure of the a-Si photosensitive member is as follows, for example. FIG. 9 is a schematic configuration diagram for explaining a layer configuration. The a-Si based photoreceptor 500 shown in FIG. 9A has a photoconductive layer 502 made of a-Si: H, X and having photoconductivity provided on a support 501. The a-Si-based photoconductor 500 shown in FIG. 9B has a photoconductive layer 502 made of a-Si: H, X and having photoconductivity, an amorphous silicon-based surface layer 503, and a support 501. It is composed of A- shown in FIG.
The Si-based photoreceptor 500 has an a-S
i: Photoconductive layer 502 made of H and X and having photoconductivity
, An amorphous silicon-based surface layer 503, and an amorphous silicon-based charge injection blocking layer 504. The a-Si-based photoconductor 500 shown in FIG. 9D has a photoconductive layer 502 provided on a support 501.
The photoconductive layer 502 includes a charge generation layer 505 and a charge transport layer 506 made of a-Si: H, X, on which an amorphous silicon-based surface layer 503 is provided.

The support 50 of the a-Si photosensitive member 500
1 may be either conductive or electrically insulating. As the conductive support, Al, Cr, Mo, Au, In,
Examples include metals such as Nb, Te, V, Ti, Pt, Pd, and Fe, and alloys thereof, such as stainless steel.
Further, a film or sheet of a synthetic resin such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polystyrene, polyamide, etc., at least the surface on the side on which the photosensitive layer is formed of an electrically insulating support such as glass, ceramic, etc. A support subjected to a conductive treatment can also be used. The support 501
Can have a cylindrical or plate-like endless belt shape with a smooth surface or an uneven surface, and the thickness thereof is appropriately determined so as to form a desired photoreceptor for an image forming apparatus. When flexibility as a photoconductor for a forming apparatus is required, it can be made as thin as possible as long as the function as the support 501 can be sufficiently exhibited. However, the thickness of the support 501 is usually 10 μm or more in terms of production, handling, mechanical strength, and the like.

The a-Si based photoreceptor 500 is provided between the conductive support 501 and the photoconductive layer 502 if necessary.
It is even more effective to provide a charge injection blocking layer 504 that functions to block charge injection from the conductive support side (FIG. 9C). That is, the charge injection blocking layer 504 has a function of preventing charge from being injected from the support 501 side to the photoconductive layer 502 side when the photosensitive layer is subjected to a charging treatment with a fixed polarity on its free surface. It has a so-called polarity dependency in which such a function is not exerted when it is subjected to charging treatment of the opposite polarity. In order to provide such a function, the charge injection blocking layer 504 contains a relatively large number of atoms for controlling conductivity as compared with the photoconductive layer 502. The thickness of the charge injection blocking layer 504 is preferably 0.1 from the viewpoint of obtaining desired electrophotographic characteristics and economical effects.
It is desirable that the thickness be 5 to 5 μm, more preferably 0.3 to 4 μm, and most preferably 0.5 to 3 μm.

The photoconductive layer 502 is formed on the undercoat layer as required, and the layer thickness of the photoconductive layer 502 is appropriately set as desired from the viewpoint of obtaining desired electrophotographic characteristics and economical effects. Determined, preferably 1-100 μm,
More preferably 20 to 50 μm, optimally 23 to 45 μm
m is desirable.

The charge transport layer 506 comprises a photoconductive layer 502
Is a layer mainly having a function of transporting charge when the function is separated. The charge transport layer 506 contains at least silicon atoms, carbon atoms, and fluorine atoms as its constituent elements, and a-S containing hydrogen atoms and oxygen atoms if necessary.
It is made of iC (H, F, O) and has desired photoconductive properties, in particular, charge retention properties, charge generation properties and charge transport properties. In the present invention, it is particularly preferable to contain an oxygen atom. The layer thickness of the charge transport layer 506 is appropriately determined as desired from the viewpoint of obtaining desired electrophotographic properties and economic effects. The charge transport layer 506 is preferably 5 to 50 μm, more preferably 10 to 50 μm. ~ 4
It is desirable that the thickness be 0 μm, and optimally 20 to 30 μm.

The charge generation layer 505 comprises a photoconductive layer 502
Is a layer mainly having a function of generating a charge when the functions are separated. The charge generation layer 505 is composed of a-Si: H containing at least silicon atoms as constituent elements, containing substantially no carbon atoms and, if necessary, containing hydrogen atoms, and has desired photoconductive properties, in particular, charge generation. It has characteristics and charge transport characteristics. The layer thickness of the charge generation layer 505 is appropriately determined as desired from the viewpoint of obtaining desired electrophotographic characteristics and economic effects, and is preferably 0.5 to 1
5 μm, more preferably 1 to 10 μm, optimally 1 to 5
μm.

The a-Si photoreceptor 500 may be provided with a surface layer on the photoconductive layer 502 formed on the support 501 as described above, if necessary.
It is preferable to form the amorphous silicon-based surface layer 503. This amorphous silicon-based surface layer 503 has a free surface and is mainly characterized by moisture resistance, continuous repeated use characteristics,
It is provided to achieve the object of the present invention in terms of electrical pressure resistance, use environment characteristics, and durability. The thickness of the amorphous silicon-based surface layer 503 is usually 0.01 to
3 μm, preferably 0.05-2 μm, optimally 0.1-
It is desirable that the thickness be 1 μm. Layer thickness is 0.0
If the thickness is less than 1 μm, the surface layer 503 is lost due to abrasion or the like during use of the photoreceptor, and if the thickness exceeds 3 μm, a decrease in electrophotographic characteristics such as an increase in residual potential is observed.

The a-Si-based photoconductor 500 has a high surface hardness, exhibits high sensitivity to long-wavelength light such as a semiconductor laser (770 to 800 nm), and hardly deteriorates due to repeated use. Therefore, it is an electrophotographic photosensitive member suitable for use in high-speed copying machines, laser beam printers (LBP), and the like. In general, the a-Si-based photoconductor is often used by being positively charged. Therefore, in each of the above embodiments, the photoconductor may be used by being positively charged.

[0059]

According to the first to fifth aspects of the present invention, even when a substance that deteriorates the photoreceptor when adhered to the photoreceptor is deposited from the base layer, the surface coat layer blocks the substance. It can be prevented from adhering to the photoreceptor. Therefore, it is possible to suppress the deterioration of the photoreceptor and reduce abnormal images such as white spots in the image. Further, the range of choice of the material constituting the base layer can be expanded.
For example, even when the base layer is formed using a rubber material on which a sulfur component or a plasticizer is deposited, it is possible to suppress the deterioration of the photoconductor and reduce the occurrence of the abnormal image. In addition, since the endless transfer / transfer means is always in contact with the image carrier, the apparatus can be simplified, and the cost, size, and reliability of the apparatus can be reduced. Further, even when thick paper is used as the transfer material, the transfer nip can be stabilized to improve the transferability, and the occurrence of an abnormal image can be prevented. Further, by reducing the size of the endless transfer conveyance means, it is easy to secure a space for taking out the jammed transfer material, and it is possible to improve the operability of the user and the maintenance of the service person. Also,
In the double-sided unit-equipped machine, the installation space for the double-sided unit can be easily secured, and the degree of freedom in design can be improved. Further, since a drive source such as a solenoid or a motor for driving the contact / separation mechanism is not required, no heat is generated from the drive source, and a rise in temperature inside the apparatus can be suppressed. Thus, for example, an increase in the surface temperature of the transfer belt can be reduced, and even when toner adheres to the transfer belt, toner sticking to the transfer belt can be prevented. As described above, it is possible to prevent the image carrier from deteriorating while preventing problems such as an increase in the cost of the apparatus and occurrence of an abnormal image when thick paper is used.

In particular, according to the second and third aspects of the present invention, by defining the characteristics of the surface coat layer, the occurrence of cracks in the surface coat layer can be prevented, and the substances deposited from the base layer pass through the cracks. Adhesion to the photoreceptor can be more stably prevented.

In particular, according to the third aspect of the present invention, even when the transfer belt or the like is stretched over the support roller of the actual machine, the material of the surface coat layer of the transfer belt or the like has good elongation (the rubber base material). By using a coating material having good follow-up properties, it is possible to prevent cracks even better. In particular, by defining the elongation percentage of the surface coat layer after the transfer belt or the like is stretched (after stress relaxation) within a predetermined range, the substance precipitated from the base layer while considering the deterioration of the surface coat layer over time. Can be prevented from adhering to the photoreceptor.

In particular, according to the invention of claim 4, since the surface of the surface coat layer is coated with a lubricant, the cleaning property of the surface coat layer surface can be improved as compared with the case where the surface coat layer is not coated. Has an excellent effect. Further, even when fine cracks occur in the surface coat layer, the lubricant blocks the photoreceptor deteriorating substance deposited from the base layer by filling the fine cracks, so that the photoreceptor deteriorating substance is transferred to the image carrier. There is an excellent effect that the adhesion of the particles can be prevented.

In particular, according to the fifth aspect of the present invention, since the image carrier is an amorphous silicon photosensitive member, the life of the image carrier can be extended, and the durability and life of the entire apparatus can be increased. There is an excellent effect that it becomes possible to achieve.

[Brief description of the drawings]

FIG. 1 is a perspective view of a transfer conveyance device using a transfer belt according to an embodiment of the present invention.

FIG. 2 is a plan view showing a schematic configuration of the transfer / transport device.

FIG. 3 is a schematic configuration diagram of an image forming apparatus using the transfer conveyance device.

FIG. 4 is an explanatory diagram of a configuration in which a driven roller 4 is fed back to a high-voltage power supply 12 and grounded.

FIG. 5 is a cross-sectional view of a transfer belt used in the transfer conveyance device.

FIG. 6 is an explanatory diagram showing a transfer operation of toner particles in the transfer and conveyance device.

FIG. 7 is a graph showing an experimental result obtained by measuring a relationship between an elongation ratio at the time of occurrence of a crack of the transfer belt / an elongation ratio at the time of stretching and photoreceptor deterioration in Example 2.

FIGS. 8A, 8B, and 8C are schematic configuration diagrams of a lubricant applying unit.

FIGS. 9A to 9D are schematic configuration diagrams of a layer configuration of an amorphous silicon photoconductor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transfer / conveyance device 2 belt unit 3 photoreceptor (image carrier) 4 driven roller 5 drive roller 6 transfer belt (endless transfer / conveyance means) 6a base layer 6b surface coat layer 11 bias roller 16 belt cleaning device 16A cleaning member 20 lubrication Agent application means 21 application roller 22 lubricant 23 urging spring 24 cleaning roller 500 amorphous silicon based photoconductor 501 support 502 photoconductive layer 503 amorphous silicon based surface layer 504 charge injection blocking layer 505 charge generation layer 506 charge transport layer S transfer Paper (transfer material)

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Manabu Mochizuki 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H200 FA02 GA04 GA18 GA23 GA66 JA04 JA26 JA29 JA30 JB07 JB15 JB42 JB43 JB45 JB46 JB47 JB49 JB50 KA12 LB02 LB09 MA03 MA12 MA14 MA20 MB02 MB04 MB05 MC03 MC18 NA02 NA09 NA16 NA17 PA06 PA30 PB05

Claims (5)

[Claims] An endless transfer means for transferring a toner image on an image carrier onto the transfer material while transferring the transfer material; and a drive means for applying a driving force to the endless transfer means. In the image forming apparatus, the endless transfer / transporting means is constituted by at least two or more members of a base layer and a surface coat layer formed on the base layer, and is fixed to the image carrier. An image forming apparatus comprising: an image forming apparatus; 2. An image forming apparatus according to claim 1, wherein said base layer is made of an elastic material, and an elongation ratio of said surface coat layer when a crack occurs is set to 50% or more. apparatus. 3. The image forming apparatus according to claim 2, wherein the relationship between the extension rate of the surface coat layer of the endless transfer and transfer means when a crack occurs and the extension rate when the belt is stretched is determined by the crack of the surface coat layer. An image forming apparatus characterized in that it is set so as to satisfy a condition of elongation rate at occurrence ≧ (elongation rate at the time of belt tension) × 10. 4. An image forming apparatus according to claim 1, further comprising a lubricant applying means for applying a lubricant to the surface of said surface coat layer. 5. An image forming apparatus according to claim 1, wherein an amorphous silicon photoconductor is used as said image carrier.