JP2002268408A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of setting the volume resistivity and the surface resistivity of a transfercarrying belt within a certain extent as for the transfer/carrying belt using rubber as base materials. SOLUTION: The image forming device is provided with the transfer belt 6 for carrying a transfer paper to a drum type photoreceptor 3, transferring toner from the photoreceptor 3 to the transfer paper by an electrical field, and then, carrying the transfer paper while electrostatically attracting the transfer paper. The volume resistivity Rvol of the transfer belt 6 is within the extent of 10<8> to 10<11> Ω, and the relation between the volume resistivity Rvol and the surface resistivity ρsurf of the inside layer satisfies (ρsurf )<=7E+20(Rvol )<-1.1> . The surface resistivity of the surface layer of the transfer belt 6 is 10<9> to 10<11> Ω.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and the like, and more particularly to an apparatus for forming a monochrome image.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, a transfer failure occurs when toner is transferred from a photosensitive drum depending on the electric resistance of a transfer / transport belt, and an abnormal image occurs. Sometimes. However, depending on the output image, it is difficult to understand the abnormality,
Or it may be at a level without any problems. On the other hand, there are images in which an abnormal image is likely to appear. For example, a problem does not occur in a text-based original or a solid image, but an abnormal image often occurs in an image used as a graphic image.

For example, a two-dot horizontal line image is easily recognized when a transfer failure occurs, as in the sample image shown in FIG. 5, and poses a problem because the image quality is significantly reduced. The horizontal black belt-shaped abnormal image also changes depending on the set value of the transfer current, and appears remarkably when the transfer current is low, and a problem remains in terms of variation in product quality.

Transfer / transport belts (mainly used in color copying machines, etc.)
Excluding the intermediate transfer belt. About) Bell
Conventional technology that mentions the relationship between the electrical characteristics of the
Is shown below. (1) In the technology disclosed in Japanese Patent Application Laid-Open No.
The volume resistance value of the inner layer and the surface layer of
Transfer, even if there is a deposit on the inner layer of the belt, transfer is not possible.
I try not to cause goodness. The volume resistance of the inner layer is
10¹³Ω · cm or less, volume resistivity of the surface layer is 10¹²Ω ・ c
Two types of substances that are not less than m. However
Only the volume resistance is specified, and the occurrence of a horizontal black band as shown in FIG.
Has not been suppressed. (2) Japanese Patent Application Laid-Open No. H03-100579 discloses a belt table.
Characterized in that the surface resistance of the layer is lower than the volume resistance
A belt is disclosed. Volume resistance of 10^Ten-10 ¹⁴Ω
cm and the surface resistance of the surface layer is lower than this.
Stipulates. However, volume resistance and surface resistance of surface layer
With just the relationship, the occurrence of the horizontal black belt can be completely suppressed.
I can't. (3) In the technology disclosed in JP-A-10-213974,
Specify the surface resistance of each of the inner and outer layers of the
Thus, white spots on the image are prevented. Inner layer
Surface resistance is 10⁹-10¹⁴Ω, surface layer is 10⁸-10¹⁴Ω
Range, but only for surface resistance.
It is not possible to control the occurrence of the horizontal black belt. (4) In Japanese Patent Application Laid-Open No. 08-227238,
By defining the volume resistance, the transfer paper separates from the belt.
Technology to prevent exfoliation discharge when
I have. Volume resistance is 5 × 10⁸~ 5 × 10^TenΩ ・ cm range
It is designed to use an enclosed belt. But volume resistance
It is only a provision of anti-power, and also suppresses the occurrence of horizontal black belt
Can not. (4) In the technology disclosed in JP-A-08-185068,
By specifying the volume resistance of the default, transfer omission and image disorder
Try to prevent. Volume resistance of 10⁹Ω · cm
It is stipulated below, but only for volume resistance,
It is not possible to suppress the occurrence of the beam horizontal black belt. (5) JP-A-08-030109 discloses a belt table.
The surface resistance of the layer is higher than that of the inner layer,
The sheet resistance is 10⁸-10¹²Ω, inner layer is 10^Five-10 ^TenΩ
Specified in the range. However, only the surface resistance is specified.
Similarly, the occurrence of a horizontal black belt cannot be suppressed.

[0005] In these prior arts, the resistance value of the belt is specified in order to prevent a transfer failure such as image omission, image disorder, and white omission. However, none of the "horizontal black bands" shown in FIG. Experiments conducted by the inventors of the present application have revealed that it is necessary to define both the surface resistance of the transfer belt inner layer and the volume resistance in the belt thickness direction in order to suppress the horizontal black band. Therefore, the above conventional technology
Only the volume resistance of the belt, only the surface resistance,
Neither does the definition of the surface resistance and the volume resistance satisfies the conditions required for the "horizontal black belt" -like defect to suppress the occurrence of elephants.

Accordingly, an object of the present invention is to provide an image forming apparatus which solves the above-mentioned problems by setting the volume resistance and surface resistance of a transfer / transport belt using rubber as a base material within a certain range. I do.

[0007]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention conveys a transfer sheet to a drum-shaped photoconductor and removes toner from the photoconductor by an electric field. In an image forming apparatus having a transfer conveyance belt for transferring the transfer paper to the transfer paper and electrostatically attracting and transferring the transfer paper, the transfer conveyance belt has a volume resistance R _vol of 10 ⁸ to 1.
0 ¹¹ Ω, and the relationship between the volume resistance R _vol and the surface resistance ρ _surf of the inner surface layer is (ρ _surf ) <= 7E + 20
(R _vol ) ^-1.1 is satisfied.

According to a second aspect of the present invention, in order to achieve the above object, in the image forming apparatus of the first aspect, the surface resistance of the surface layer of the transfer / conveying belt is 10 ⁹ to 10 ¹¹ Ω. I do.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a main part of an image forming apparatus using a transfer / transport belt, and FIG. 2 is a structure of a transfer / transport belt (hereinafter simply referred to as a transfer belt unless otherwise required) used in the apparatus of FIG. FIG. The transfer conveyance device shown in the drawing contacts the transfer belt 6, which is wound around the pair of rollers 4, 5, to transfer the developed image from the drum-shaped photoconductor 3 to the photoconductor 3. DC solenoid 8 to be separated, contact / separation lever 9, transfer belt 6
And a contact plate 13 for removing charges from the transfer belt 6.
Also, a cleaning blade 16 for scraping off paper dust and the like from residual toner and transfer paper adhered to the surface of the transfer belt 6.
A, the cleaning device 16 and the bias roller 1
1 is provided with a high-voltage power supply 12 for applying a voltage.

The roller 5 is connected to a driving motor (not shown) and is driven to rotate. The transfer belt 6
Following the rotation of the roller 5, the roller 5 can move in the transfer paper transport direction (the direction of the arrow A in FIG. 3) at a position facing the photoconductor 3. The rollers 4 and 5 are rotatably supported by a support 7 as shown in FIGS. The support 7 can swing about the support shaft 5 a of the roller 5, which is located downstream of the transfer position with respect to the photoconductor 3, in the transfer paper conveyance direction indicated by the arrow A among the rollers 4 and 5. . The support 7 is operated by a DC solenoid 8 driven on the transfer position side of the transfer belt 6 by a signal from a control plate 8A. That is, a contact / separation lever 9 is connected to the DC solenoid 8, and the contact / separation lever 9 moves the support member 7 to move the transfer belt 6 toward and away from the photosensitive member 3.

The leading edge of the transfer paper conveyed in a state where the control plate 8A is aligned with the leading edge position of the image formed on the photoreceptor 3 by the registration roller 10 serving as the paper transport means approaches the photoreceptor 3. Then, a drive signal is issued to drive the DC solenoid 8. Accordingly, by driving the solenoid 8, the support 7 comes close to the photoconductor 3, and the transfer belt 6 comes into contact with the photoconductor 3, so that the transfer paper is transferred to the photoconductor 3 at a position facing the photoconductor 3. A nip portion that can be conveyed while making contact is formed.

The bias roller 11 is provided on the downstream side of the 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 on the photoconductor 3 to the transfer belt 6, and is connected to a high-voltage power supply 12.

The contact plate 13 is disposed on the inner surface of the transfer belt 6 near the lower driven roller 4 which is not the transfer paper transfer surface, and suppresses charge injection to the transfer paper upstream of the transfer nip. The contact plate 13 is used for the transfer belt 6.
Is for detecting a current flowing through the upper as the feedback current, supply current I ₁ from the I connexion bias roller 11 to the detection of this current is controlled. For this reason, a transfer control plate 14 for setting a supply current to the bias roller 11 according to the detected current is connected to the contact plate 13, and the transfer control plate 14 is connected to the high-voltage power supply 12. I have.

In such a transfer / transport apparatus 1, the support 7 is set so that the transfer belt 6 approaches the photosensitive member 3 in accordance with the transfer of the transfer paper from the registration roller 10, and the photosensitive member 3 A nip portion having a width of about 4 to 8 mm corresponding to the length along the transfer direction of the transfer paper is formed between the two.

On the other hand, in the case of an analog machine, the surface of the photoreceptor 3 is charged to, for example, -800 V, and moves to the nip portion while positively charged toner is electrostatically attracted to the surface. . The photoreceptor 3 is arranged near the photoreceptor 3 before reaching the nip portion, and the surface potential is reduced by a pre-transfer neutralization lamp (PTL) 15 that weakens the charge on the surface of the photoreceptor 3.

The transfer belt 6 has a surface layer 6a as shown in FIG.
An electric field required for transferring the toner is applied from a bias roller 11 or the like in contact with the rubber layer 6b of the transfer belt 6. At this time, the electric characteristics required for the transfer belt 6 are as follows. Is to show conductivity in an appropriate range so that the transfer current flowing through the belt has an appropriate value. Here, a description will be given of the surface resistance of the surface of the rubber layer 6b corresponding to the back side as the transfer belt 6 and the volume resistance measured in the thickness direction of the belt.

FIG. 3 shows an apparatus for measuring the surface resistance and the volume resistance of the transfer belt 6.
This is the same as that disclosed in Japanese Patent No. 85068. That is, a first voltage application electrode A having a diameter of 50 mm, a cylindrical ring electrode B having an inner diameter of 70 mm surrounding the electrode A at an interval of 10 mm, and a ring electrode provided to face the electrode A and the ring electrode B. The transfer belt 6 is arranged between the electrodes A and C as shown in the figure using a resistance measuring device provided with a second voltage application electrode C having a sufficiently larger area than that of the second voltage application electrode C.

<Measurement of Surface Resistance> A current I flowing when a voltage of 100 V is applied between the electrode A and the ring electrode B is measured using the electrode C as a guard electrode, and the surface resistance ρ _surf is calculated by the following equation (1). Was calculated. V is a voltage (100 V). Incidentally, equation (1) is an equation peculiar to the measuring apparatus used this time. ρ _surf = 18.8 × (V / I) (1) <Measurement of volume resistance> The current I flowing when a voltage of 100 V is applied between the electrode A and the electrode C using the ring electrode B as a guard electrode is measured. The volume resistance value R _vol was calculated by the equation (2). V indicates the voltage (100 V), and t indicates the thickness of the belt. Incidentally, the expression (2) is also an expression specific to the measuring device used this time. R _vol = 19.6 × (V / I) × t (2) The surface resistance and the volume resistance were measured at three places in the width direction of the belt, and the average value was obtained.

As described above, it is known that when the electric resistance of the transfer belt 6 is high, the transfer current does not easily flow, and transfer failure occurs. Each environment (10 ° C, 15% RH, 23
At 65 ° C. and at 90% RH at 30 ° C., the volume resistance of the transfer belt 6 and the surface resistance of the inner surface layer were measured, and a 2-dot horizontal line was output to check for image defects.

FIG. 4 is a diagram showing the volume resistance, the surface resistance of the inner layer, and the occurrence of transfer failure in each environment. In each environment, the transfer failure occurred in the transfer belt having a high surface resistance value, and it was found that by defining both the volume resistance and the surface resistance, the occurrence of the horizontal black belt could be prevented. Regarding the volume resistance, a transfer current is difficult to flow through a belt having a resistance value of more than 10 ¹¹ Ω, so that a transfer voltage to be applied is increased. As a result, a horizontal black band is generated regardless of the surface resistance. Conversely, a belt having a volume resistance lower than 10 ⁸ Ω is liable to cause a leakage of the transfer current, resulting in white spots. Therefore the volume resistance is 10 ⁸ to 10 ¹¹ Ω
The transfer failure can be suppressed by defining the range as follows. However, the occurrence of the horizontal black band cannot be completely suppressed only by defining the volume resistance. Therefore, by setting the surface resistance of the belt inner surface layer below the straight line ((surface resistance) = 7E + 20 (volume resistance) ^-1.1 ) shown in FIG. Completely suppress.

If the surface resistance of the surface layer 6a of the transfer belt 6 is too high, a discharge occurs between the photosensitive member 3 and the transfer paper,
Conversely, if it is too low, the transfer paper cannot be held.
Therefore, the surface resistance of the surface layer 6a is specified to be 10 ⁹ to 10 ¹¹ Ω.

[0022]

As described above, the image forming apparatus according to the present invention has the effect of suppressing image defects that occur at the time of transfer by suppressing the volume resistance and surface resistance of the transfer conveyance belt to be low. is there.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main part of an image forming apparatus using a transfer conveyance belt.

FIG. 2 is a diagram illustrating a structure of a transfer conveyance belt used in the apparatus of FIG. 1 and the like.

FIG. 3 is a diagram showing an apparatus for measuring surface resistance and volume resistance of the transfer conveyance belt.

FIG. 4 shows the volume resistance in each environment, the surface resistance of the inner layer,
FIG. 4 is a diagram illustrating occurrence of transfer failure.

FIG. 5 is a view showing an abnormal image in a horizontal black belt shape.

[Explanation of symbols]

 Reference Signs List 3 photoconductor 4, 5 roller 5a roller support shaft 6 transfer belt 6a surface layer 6b rubber layer 7 support 8 DC solenoid 8A control plate 9 contact / separation lever 10 registration roller 11 bias roller 12 high voltage power supply 13 contact plate 14 transfer control plate 15 Pre-transfer neutralization lamp (PTL) 16 Cleaning device 16A Cleaning blade

Claims (2)

[Claims] 1. A transfer paper is transported to a drum-shaped photoconductor, and toner is transferred from the photoconductor to the transfer paper by an electric field.
In an image forming apparatus having a transfer conveyance belt that electrostatically attracts and conveys the transfer paper, a volume resistance R _vol of the transfer conveyance belt is in a range of 10 ⁸ to 10 ¹¹ Ω, and the volume resistance R _vol The relation of the surface resistance ρ _surf of the inner layer is (ρ _surf )
<= 7E + 20 (R _vol ) ^−1.1 An image forming apparatus characterized by satisfying ^-1.1 . 2. The image forming apparatus according to claim 1, wherein a surface resistance of the surface layer of the transfer / conveying belt is 10 ⁹ to 10 ¹¹ Ω.