JP2004246341A - Image forming apparatus and its transferring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which performs stable transferring regardless of surface roughness of a recording material, and also to provide its transferring method. <P>SOLUTION: In the image forming apparatus which transfers a toner image from an intermediate transferring body 130 moving while carrying the toner image to the recording material P, information on surface roughness of the recording material P is inputted, bias of intermediate transferring body top charger (a post charger) 90 is controlled based on the information on surface roughness of the recording material P and toner triboelectricity of the toner image is controlled. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus for transferring a toner image on an image carrier (photoconductor or intermediate transfer body) to a recording material, and more particularly to an improvement in the transfer operation.

  As a conventional image forming apparatus, primary transfer in which a toner image of each color is formed on each of a plurality of image carriers, and the toner images are sequentially transferred to an intermediate transfer member, and toner images of a plurality of colors are transferred to the intermediate transfer member from There is an apparatus capable of obtaining a color image by forming a color image and then performing secondary transfer in which the color image is collectively transferred onto a recording material.

Such an intermediate transfer type image forming apparatus has various types of recording materials, for example, because the intermediate transfer member is less likely to be scratched than the photosensitive drum and is easy to clean dirt such as paper dust. There is an advantage that it can handle thick paper having a basis weight of about 300 g / m ² .

  Furthermore, with the improvement of image quality not only on plain paper but also on image forming apparatuses, recording with improved surface smoothness (small surface roughness) such as art paper and coated paper as conventionally used in printing machines. Emphasis has also been placed on handling wood.

  However, such an image forming apparatus has a problem in that good transfer cannot be performed on thick paper (recording material) having a surface with irregularities such as embossed paper or embossed paper.

As a conventional technique for preventing a transfer failure due to the surface roughness of a recording material, for example, Japanese Patent Application Laid-Open No. H11-163,199 discloses an electrostatic force acting on a toner image during a transfer operation from an image carrier to a recording material. It describes a configuration in which electrostatic attraction or electrostatic repulsion is selected according to the surface roughness of a recording material.
JP-A-11-24443

  However, with this technique, it was not possible to obtain a sufficient effect with respect to transfer failure caused by surface roughness.

  That is, transfer failure due to surface roughness is caused by, for example, a gap between the toner image and the recording material when a transfer current is applied in a state where the toner image on the intermediate transfer member and the recording material are not sufficiently adhered. This is caused by a phenomenon that abnormal discharge occurs and toner cannot be transferred normally.

  Therefore, simply changing the method of applying the transfer electric field does not lead to a fundamental solution.

  The present invention has been made under such circumstances, and it is an object of the present invention to provide an image forming apparatus capable of performing stable transfer regardless of the surface roughness of a recording material, and a transfer method thereof. .

  In order to solve the above problems, in the present invention, the image forming apparatus is configured as in the following (1) to (8), and the transfer method in the image forming apparatus is configured as in the following (9).

(1) an image carrier that carries a toner image and moves;
Image forming means for forming a toner image on the image carrier,
Transfer means for electrostatically transferring the toner image on the image carrier formed by the image forming means to a recording material at a transfer position;
Charging means for charging the toner image on the image carrier before reaching the transfer position,
Bias applying means for applying a bias to the charging means,
Control means for controlling the output of the bias applying means according to information on the surface roughness of the recording material;
An image forming apparatus comprising:

(2) In the image forming apparatus according to (1),
An information input unit for inputting information on the surface roughness of the recording material,
The image forming apparatus, wherein the control unit controls an output of the bias applying unit according to information input to the information input unit.

(3) In the image forming apparatus according to (1),
A surface roughness detection unit for detecting the surface roughness of the recording material,
The image forming apparatus, wherein the control unit controls an output of the bias applying unit in accordance with information detected by the surface roughness detecting unit.

(4) The image forming apparatus according to any one of (1) to (3),
The image forming apparatus, wherein the control unit controls the bias applying unit such that the larger the surface roughness of the recording material, the smaller the charge of the toner image on the image carrier.

(5) In the image forming apparatus according to any one of (1) to (3),
The image forming apparatus, wherein the control unit controls the absolute value of the DC component of the output of the bias applying unit to decrease as the surface roughness of the recording material increases.

(6) In the image forming apparatus according to (5),
The image forming apparatus is capable of outputting a bias in which a DC component and an AC component are superimposed on each other.

(7) The image forming apparatus according to any one of (1) to (6),
The image forming unit includes a photoconductor on which an electrostatic latent image is formed, a developing unit that develops the electrostatic latent image with toner, and a transfer unit that transfers a toner image on the photoconductor to an intermediate transfer body. Have
The image forming apparatus, wherein the image carrier is the intermediate transfer body.

(8) In the image forming apparatus according to any one of (1) to (6),
An image forming apparatus, wherein the image carrier is a photoconductor on which an electrostatic latent image is formed.

(9) A transfer method in an image forming apparatus for transferring a toner image from a moving image bearing member carrying a toner image to a recording material,
A step A of inputting information on the surface roughness of the recording material;
A step B of controlling the toner tribo of the toner image based on the information on the surface roughness of the recording material input in the step A;
Transfer method in an image forming apparatus provided with:

  ADVANTAGE OF THE INVENTION According to this invention, the abnormal discharge in the space | gap of a toner image and a recording material resulting from the unevenness | corrugation of a recording material surface can be prevented effectively, and stable transferability can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to embodiments of an image forming apparatus.

  FIG. 1 is a cross-sectional view illustrating a configuration of an “image forming apparatus” according to the first embodiment.

  This image forming apparatus is a four-color full-color laser printer, and includes an intermediate transfer belt 130 as an intermediate transfer member (corresponding to an image carrier in the claims) on which toner images are superimposed once, and a moving direction thereof (arrows in the drawing). Direction), four image forming sections arranged in order from the upstream side, that is, a first (yellow) image forming section Pa, a second (magenta) image forming section Pb, and a third (cyan) image forming section Pb. An image forming unit Pc and a fourth (black) image forming unit Pd are provided.

  The first to fourth image forming units Pa, Pb, Pc, and Pd are dedicated image carriers, in this embodiment, drum-type electrophotographic photosensitive members (hereinafter, referred to as “photosensitive drums”) 3a, 3b, and 3d. 3c, 3d, and toner images of respective colors are formed on the photosensitive drums 3a, 3b, 3c, 3d.

  Around the photosensitive drums 3a, 3b, 3c, 3d, pre-exposure lamps 111a, 111b, 111c, 111d, drum chargers (primary chargers) 2a, 2b, 2c, 2d, potential sensors 113a, 113b, 113c, respectively. , 113d, developing units 1a, 1b, 1c, 1d, transfer chargers 24a, 24b, 24c, 24d, and cleaners 4a, 4b, 4c, 4d, and a light source device (not shown) is provided above the image forming apparatus main body. (Shown) and a polygon mirror 117 are provided.

  The laser light emitted from the light source device is scanned by rotating the polygon mirror 117, the light beam of the scanning light is deflected by the reflection mirror, and is condensed on the generatrix of the photosensitive drums 3a, 3b, 3c, 3d by the fθ lens. And exposure, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drums 3a, 3b, 3c, 3d.

  The developing devices 1a, 1b, 1c, and 1d are filled with a predetermined amount of yellow, magenta, cyan, and black toners as developers by a supply device (not shown). The developing devices 1a, 1b, 1c, 1d develop the electrostatic latent images on the photosensitive drums 3a, 3b, 3c, 3d, respectively, and develop them as yellow toner image, magenta toner image, cyan toner image and black toner image ( Visualization). The toner images formed on the photosensitive drum are sequentially transferred onto the intermediate transfer belt 130 by the primary transfer blades 24a, 24b, 24c, 24d. The toner image superimposed on the intermediate transfer belt 130 is transferred onto a recording material by the secondary transfer roller 41.

  The recording material P is stored in a recording material cassette 10, and is supplied to a secondary transfer unit from the recording material cassette 10 via a paper feed roller, a plurality of conveyance rollers, and a registration roller 12.

  The intermediate transfer belt 130 is made of a dielectric resin sheet such as a polyethylene terephthalate resin sheet (PET resin sheet), a polyvinylidene fluoride resin sheet, or a polyurethane resin sheet, and its both ends are overlapped and joined. Endless or seamless (seamless) belts are used.

  The recording material P to which the toner image has been transferred is transported to the fixing device 9 by the transport unit 62. The separation guide 64 stabilizes the leading end behavior of the recording material P.

  The fixing device 9 includes a fixing roller 51 and a pressure roller 52, heat-resistant cleaning members 54 and 55 for cleaning them, and roller heaters 56 and 57 disposed in the fixing roller 51 and the pressure roller 52. An application roller 50 for applying a release agent oil such as dimethyl silicone oil to the fixing roller 51; a reservoir 53 of the oil; and a thermistor 58 for detecting the temperature of the surface of the pressure roller 52 and controlling the fixing temperature. And

  The recording material P to which the four color toner images have been transferred is mixed with the toner image by fixing and fixed to the recording material P, and a full-color image is formed, and is discharged onto the discharge tray 63.

  The transfer-completed photosensitive drums 3a, 3b, 3c, and 3d are cleaned and removed of transfer residual toner by the cleaners 4a, 4b, 4c, and 4d, respectively, and are subsequently provided for the next image formation. Toner and other foreign matters remaining on the intermediate transfer belt 130 are wiped on the surface of the intermediate transfer belt 130 by the cleaning blade 20.

The intermediate transfer belt 130 used in the image forming apparatus having the above-described configuration is a dielectric sheet such as a PET sheet, a polyvinylidene fluoride sheet, or a polyurethane sheet as described above, and has a volume resistivity of 10 ⁹ to 10 ^15. Ω · cm is common.

  Next, the smoothness (surface roughness) of the recording material will be described.

  In general, the paper becomes rough in the order of art paper <coated paper <plain paper <embossed paper, and has irregularities of about 1 to 3 μm, 3 to 5 μm, 3 to 8 μm, and 15 μm in ten-point average roughness Rz (JIS B 0601), respectively. There is.

  Now, in such an image forming apparatus, when a secondary transfer current applied to the secondary transfer roller 41 was set to 45 μA to form an image of a full-color image, an image defect occurred on embossed paper.

  More specifically, there are various types of embossed paper, for example, in the order of trade names “Rezac 80 Tsumugi”, “Rezac 66”, and “Rezac 75 Momigami” manufactured by Tokuseki Paper Co., Ltd. The image level was getting worse. This can be said to be worse in the order of poor paper smoothness. In other words, it was found that the larger the surface roughness of the paper, the worse the image level due to transfer failure.

  At this time, the toner tribo (the amount of charge per unit weight of the toner) before the secondary transfer was measured to be about −31 μC / g.

  Thus, a similar experiment was conducted by using the intermediate transfer body charger (post-charger) 90 shown in FIG. 1 to remove the toner tribo from about −31 μC / g to about −25 μC / g. , Image defects were greatly reduced.

  As the charger 90, a corona charger that generates a charge by applying a bias to a charging wire by a bias applying unit (power supply) 150 is used, but the present invention is not limited to this method.

  The output of the post charger 90 is controlled by the control unit 100.

  FIG. 2 shows the relationship between the current applied to the intermediate transfer member upper charger 90 and the toner tribo. In this embodiment, a 12 kVpp alternating current (AC) component (voltage) is superimposed and output in addition to the direct current (DC) component (current) shown in FIG. According to this embodiment, it is understood that the toner tribo can be changed by changing the DC component. For example, if the absolute value of the DC component is reduced, the toner tribo can be reduced accordingly.

  By repeating such an experiment and determining the output of the charger 90 on the intermediate transfer member corresponding to each embossed paper having different surface roughness, image defects did not occur.

  In the present embodiment, the charging method of the constant current control is used because the corona discharge is stabilized and the toner tribo can be easily adjusted.However, the charging method is not limited to this. The relationship between the output of the container and the toner tribo can be changed.

  Needless to say, the relationship between the output of the charger and the toner tribo is not limited to this.

  On the other hand, if transfer is performed on paper having a surface roughness smaller than that of plain paper, for example, cast-coated paper manufactured by Nippon Paper Co., Ltd., with the same setting as that of plain paper, scattering of images (characters) occurs. Was. Then, the toner tribo was increased from about -31 [mu] C / g before the secondary transfer to about -38 [mu] C / g using the post-charging device 90, and scattering was eliminated.

  As described above, for paper having poor surface smoothness (large surface roughness), the toner tribo can be reduced to reduce the mirroring power with the image carrier, so that the paper is easily transferred, and recording is performed. Excellent transfer is performed because abnormal discharge due to transfer current application does not occur even in a portion having a wide gap with the material.

  On the other hand, in the case of coated paper or art paper having a high surface smoothness (small surface roughness), the adhesion between the image bearing member and the recording material becomes high, and the above-described abnormal discharge does not occur. If the size is small, another image defect called scattering tends to occur. Therefore, for a recording material having a high surface smoothness, the toner tribo on the image carrier is increased so that this image defect does not occur. At this time, scattering can be more effectively prevented by increasing the value of the transfer current.

  In this embodiment, a portion for inputting the value of the surface roughness of the paper is formed on the operation panel 110 so that the user can input a value suitable for the paper to be used, and the intermediate transfer according to the input value is performed. The output of the on-body charger 90 is output.

  Alternatively, a paper type (such as a product name) is input from the operation panel 110, and the control unit 100 outputs an appropriate output according to the input paper type information based on a table prepared in advance. The charger 90 may be controlled on condition.

  Since the toner tribo changes depending on the environment in which the apparatus is used, the toner characteristics, the endurance state of the developer, and the like, the detector 120 that detects the temperature and humidity of the environment inside the main body is used. More preferably, the output of the charger 90 is controlled.

  In this embodiment, the post-charger 90 is applied with a bias in which the AC output and the DC output are superimposed, but the post-charger 90 may be operated by applying only the DC component.

  With the configuration described above, it was possible to provide an image forming apparatus capable of performing stable transfer even on a recording material having irregularities such as embossed paper.

  Second Embodiment An “image forming apparatus” according to a second embodiment will be described. The basic configuration of the image forming apparatus of the present embodiment is the same as that of the above-described first embodiment.

  The present embodiment is characterized in that the toner tribo before the primary transfer is changed by the on-drum charger 45 shown in FIG. 3 in order to change the toner tribo before the secondary transfer. That is, in this embodiment, the potential of the drum charger 45 before the intermediate transfer member 130 is controlled in order to improve the transfer operation between the intermediate transfer member and the recording material. FIG. 3 shows a part of the image forming apparatus described in the first embodiment. The configuration other than the charger 45 is the same as that in the first embodiment. Further, in the figure, the bias applying means 150 connected to the charger 45a is similarly connected to the other chargers 45b to 45d.

  Although the target toner tribo is almost the same as that of the first embodiment, the optimal output of the on-drum charger 45 is adjusted in order to adjust the toner tribo on the photosensitive drum.

  With the configuration described above, it was possible to provide an image forming apparatus capable of performing stable transfer even on a recording material having irregularities such as embossed paper.

  Third Embodiment An “image forming apparatus” according to a third embodiment will be described. In the first and second embodiments, the device configuration for transferring the image from the photosensitive drum 3 to the intermediate transfer belt 130 has been described. This embodiment is an example of an apparatus for directly transferring a photosensitive drum to paper. That is, this is an example in which the output of the post-charging device for charging the toner image before transfer on the photosensitive drum is controlled according to the surface roughness of the paper. In this embodiment, the same effects as those of the first and second embodiments can be obtained.

  FIG. 4 is a cross-sectional view illustrating the configuration of the present embodiment. In the figure, the same reference numerals are used for the same configurations of the first and second embodiments. In this embodiment, toner images formed on a plurality of photoconductors (corresponding to an image carrier in the claims) 3a to 3d are sequentially transferred to a recording material conveyed by a recording material conveying belt 160. It has a configuration. Then, the chargers 24a to 24d are arranged to charge the toner image on the photoconductor before being transferred to the recording material.

  As described in the first and second embodiments, the control unit 100 controls the operation of the chargers 24a to 24d so that an output corresponding to the surface roughness of the recording material is obtained.

  With the configuration described above, it was possible to provide an image forming apparatus capable of performing stable transfer even on a recording material having irregularities such as embossed paper.

  FIG. 5 is a sectional view illustrating a configuration of an “image forming apparatus” according to the fourth embodiment. This embodiment is an example in which a surface sensor 95 for measuring the surface roughness of a recording material is provided in the image forming apparatus of the first embodiment.

  The surface sensor 95 includes, for example, a light emitting element and a light receiving element (not shown). The light emitting element includes an LED that emits near-infrared light, and the light receiving element includes a CCD. Light emitted from the light emitting element is reflected on the surface of the recording material being conveyed toward the secondary transfer unit, and the reflected light enters the light receiving element. Then, utilizing the property that the light reflection state varies depending on the surface roughness of the recording material, the depth of the irregularities on the surface of the recording material is analyzed from the output of the light receiving element (CCD), and the output corresponding to the surface roughness is obtained. Obtainable.

  Then, the control unit 100 determines the output of the charger 90 on the intermediate transfer member (corresponding to the image carrier in the claims) based on the detection result, so that the image defect does not occur.

  Although the present embodiment uses such a surface sensor, the present invention is not limited to such a sensor, and the same applies to a device such as a surface roughness meter using a sensing lever using a mechanical needle. Needless to say, the effect is obtained.

  With the configuration described above, it was possible to provide an image forming apparatus capable of performing stable transfer even on a recording material having irregularities such as embossed paper.

Longitudinal sectional view showing the configuration of the first embodiment. Diagram showing the relationship between the output of the post charger and the toner tribo Longitudinal sectional view showing the configuration of the second embodiment. Longitudinal sectional view showing the configuration of the third embodiment. Longitudinal sectional view showing the configuration of the fourth embodiment.

Explanation of reference numerals

90 Intermediate transfer body charger 100 Control means 130 Intermediate transfer belt 150 Bias applying means

Claims (9)

An image carrier that carries the toner image and moves;
Image forming means for forming a toner image on the image carrier,
Transfer means for electrostatically transferring the toner image on the image carrier formed by the image forming means to a recording material at a transfer position;
Charging means for charging the toner image on the image carrier before reaching the transfer position,
Bias applying means for applying a bias to the charging means,
Control means for controlling the output of the bias applying means according to information on the surface roughness of the recording material;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
An information input unit for inputting information on the surface roughness of the recording material,
The image forming apparatus according to claim 1, wherein the control unit controls an output of the bias applying unit in accordance with information input to the information input unit. The image forming apparatus according to claim 1,
A surface roughness detection unit for detecting the surface roughness of the recording material,
The image forming apparatus according to claim 1, wherein the control unit controls an output of the bias applying unit in accordance with information detected by the surface roughness detecting unit. The image forming apparatus according to claim 1, wherein
The image forming apparatus according to claim 1, wherein the control unit controls the bias applying unit such that as the surface roughness of the recording material increases, the charge of the toner image on the image carrier decreases. The image forming apparatus according to claim 1, wherein
The image forming apparatus according to claim 1, wherein the control unit controls the absolute value of the DC component of the output of the bias applying unit to decrease as the surface roughness of the recording material increases. The image forming apparatus according to claim 5,
The image forming apparatus according to claim 1, wherein the bias applying unit is capable of outputting a bias in which a DC component and an AC component are superimposed. The image forming apparatus according to claim 1, wherein
The image forming unit includes a photoconductor on which an electrostatic latent image is formed, a developing unit that develops the electrostatic latent image with toner, and a transfer unit that transfers a toner image on the photoconductor to an intermediate transfer body. Have
The image forming apparatus, wherein the image carrier is the intermediate transfer body. The image forming apparatus according to claim 1, wherein
The image forming apparatus is characterized in that the image carrier is a photoconductor on which an electrostatic latent image is formed. A transfer method in an image forming apparatus for transferring a toner image from a moving image bearing member carrying a toner image to a recording material, comprising:
A step A of inputting information on the surface roughness of the recording material;
A step B of controlling the toner tribo of the toner image based on the information on the surface roughness of the recording material input in the step A;
A transfer method in an image forming apparatus, comprising:

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