JP5418376B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, an LED printer, and a facsimile.

  2. Description of the Related Art Conventionally, there has been known an image forming apparatus provided with a plurality of image forming units that correspond to each of a plurality of colors including black and that form an image of a corresponding color on an image carrier that the image forming apparatus has (see Patent Document 1, for example). .

The image forming apparatus described in Patent Document 1 includes a direct transfer position for directly transferring a black image formed by a black image forming unit onto a recording medium, and a primary image from the remaining other color image forming units onto an intermediate transfer member. There is a secondary transfer position where the transferred other color image is secondarily transferred from the intermediate transfer member to the recording medium. This secondary transfer position is located upstream of the direct transfer position in the recording medium conveyance direction. The intermediate transfer member is rotatably stretched by a plurality of roller members, and the intermediate transfer member is rotated by a driving roller that is one of the plurality of roller members. Further, there is provided a transfer conveyance belt that is rotatably stretched by a plurality of roller members and carries the recording medium so as to pass through the direct transfer position and the secondary transfer position.
In the image forming apparatus described in Patent Document 1, the recording medium is passed directly between the transfer position and the secondary transfer position by the transfer conveyance belt, and directly transferred to the other color image transferred from the secondary transfer position onto the recording medium. The black image transferred onto the recording medium from the position is superimposed on the recording medium to form a full-color image on the recording medium.

  Looking at the operation status of image forming apparatuses in the market, the proportion of monochrome images is about 70 to 80%, and considering that black toner is consumed when forming full-color images, resource saving and In view of cost and the like, it is desirable to suppress the consumption of black toner during image formation.

  As in the image forming apparatus described in Patent Document 1, the black image formed on the image carrier by the black image forming unit is directly transferred onto the recording medium, so that the intermediate transfer is performed like the other color image forming unit. The transfer efficiency is higher than when a black image is transferred from the image carrier to the recording medium via the body. Therefore, transferring the black image directly from the image carrier onto the recording medium is more effective at the black image forming unit than transferring the black image from the image carrier onto the recording medium via the intermediate transfer member. It is possible to suppress the consumption of black toner when forming a black image on the top.

  Patent Document 2 discloses a configuration for detecting misalignment on paper.

  In the image forming apparatus described in Patent Document 1, since each image is transferred directly onto the recording medium carried and transferred by the transfer conveyance belt at the transfer position and the secondary transfer position, the transfer position of each image is different. There arises a problem that misalignment tends to occur between the images transferred onto the recording medium.

  In the image forming apparatus described in Patent Document 1, the secondary transfer position is located upstream of the direct transfer position in the recording medium conveyance direction, but the secondary transfer position is in the recording medium conveyance direction from the direct transfer position. Even if it is located on the downstream side, the same problem as described above occurs.

  Further, the recording medium is passed through a direct transfer position where the image is directly transferred from the second image carrier onto the recording medium and a secondary transfer position where the image is secondarily transferred onto the paper via the intermediate transfer body. In the case of an image forming apparatus that uses a recording medium conveying belt that is carried and conveyed and is rotatably stretched by a plurality of roller members, there is a problem that the apparatus is easily increased in size and cost.

  Furthermore, in the configuration of the above-mentioned Patent Document 1 or the like, the image position may be slightly shifted depending on the thickness of the recording medium such as paper.

  Further, in the positional deviation detection on paper described in Patent Document 2, it is necessary to create a four-color positional deviation detection pattern on the paper, and there is a problem that the positional deviation detection pattern is drawn on a part of the paper.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of suppressing misalignment of an image transferred on a recording medium while saving resources and reducing costs. It is.

  According to the first aspect of the present invention, a plurality of first image carriers on which a first toner image corresponding to each color is formed, and a plurality of first image carriers are provided opposite to each other. An intermediate transfer body on which the first toner image is primarily transferred, secondary transfer means for secondary transfer of the toner image on the intermediate transfer body onto the recording medium, and an image from the intermediate transfer body onto the recording medium. A second image carrier provided on the upstream side or downstream side in the recording medium conveyance direction from the secondary transfer position to be transferred next, on which a toner image is formed, and a second toner image on the second image carrier. A direct transfer means for transferring directly onto the recording medium, wherein a first detection means is provided on the intermediate transfer member, and a second detection means is provided on the recording medium conveyance path or on the intermediate transfer member, and a plurality of first toners Detects image misalignment with the first detector and transfers it to the first toner image and recording medium The image forming condition is controlled so that the positional deviation between the images is detected based on the detection results of the first detecting means and the second detecting means. An image forming apparatus comprising a control means for controlling the image forming apparatus.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the second detection means is provided on the recording medium conveyance path.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the second detection means is located downstream of the secondary transfer position by the secondary transfer means and the direct transfer position by the direct transfer means. It is provided between the transfer position and the discharge position of the recording medium.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the second detection means is provided at a position downstream of the fixing means for fixing the image on the recording medium in the recording medium conveyance direction. And

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the second detection means is provided on the intermediate transfer member.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the second detection means is provided in common with the first detection means.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the first toner image detected by the second detection means is a yellow toner image. And

  According to an eighth aspect of the present invention, in the image forming apparatus according to the second, fifth or sixth aspect, the first detection means or the second detection means is transferred onto the recording medium with the density of the plurality of first toner images. And detecting the density of the second toner image, and the control means controls the image forming conditions so as to adjust the density of each image based on the detection result of the first detection means or the second detection means. To do.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, a third detection unit is further provided on the second image carrier, and the density of the second toner image can be detected by the third detection unit. Then, the control means controls the image forming conditions so as to adjust the density of each image based on the detection result of the first detection means, the second detection means, or the third detection means.

  According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, both the secondary transfer unit and the direct transfer unit are roll-shaped members.

  According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, the intermediate transfer member is an intermediate transfer belt stretched around a plurality of rollers.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect, the intermediate transfer belt is an elastic belt.

  According to a thirteenth aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect, the detecting means detects the positional deviation or density of the first toner image or the positional deviation or density of the second toner image. Is switched according to the type of the recording medium.

  According to a fourteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the detection means for detecting the positional deviation or density of the first toner image or the positional deviation or density of the second toner image is provided. Switching is performed according to the color of the recording medium.

  According to a fifteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the detection means for detecting the positional deviation or density of the first toner image or the positional deviation or density of the second toner image is provided. Switching is performed according to the unevenness of the recording medium.

  According to the present invention, it is possible to suppress displacement of an image transferred onto a recording medium while saving resources and reducing costs.

1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to an embodiment of the present invention. It is a pattern image for resist skew detection in an embodiment of the present invention. It is a schematic block diagram which shows other embodiment of the image forming apparatus which concerns on embodiment of this invention. It is a figure explaining the sensor after fixing in an embodiment of the invention. FIG. 4 is a diagram for explaining contact / separation between an intermediate transfer member and a transfer conveyance belt or transfer roller according to an embodiment of the present invention. FIG. 4 is a diagram for explaining contact / separation between an intermediate transfer member and a transfer conveyance belt or transfer roller according to an embodiment of the present invention. FIG. 3 is a diagram schematically illustrating a toner shape in the embodiment of the present invention. FIG. 3 is a schematic diagram illustrating an outer shape of a toner according to an embodiment of the present invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. In the image forming apparatus shown in FIG. 1, three image forming units 30 Y, C, and M of yellow, cyan, and magenta (hereinafter abbreviated as Y, C, and M) are arranged in series along the intermediate transfer body 6. A color image forming apparatus (color digital multi-function peripheral) in which a black (hereinafter abbreviated as “B”) image forming unit 30B is provided independently at an upstream position in the recording sheet moving direction from the tandem arrangement. However, in the present embodiment, the black image formed by the image forming unit 30B is arranged to be directly transferred onto the recording paper.

  Around each of the photoreceptors 1Y, 1C, 1M, and 1B, which are latent image carriers for each color shown in FIG. 1, charging devices 2Y, 2C, 2M, and 2B for charging the surfaces of the photoreceptors 1Y, 1C, 1M, 1B, A toner image is formed by supplying toner to the latent image on the photoreceptors 1Y, 1C, 1M, 1B, the exposure device 5 that forms a latent image on the surface of the charged photoreceptors 1Y, 1C, 1M, and 1B with a laser. Developing devices 3Y, C, M, and B, and photoreceptors 1Y, C, M, and B are provided with cleaning devices 4Y, M, C, and B that remove deposits such as toner that adhere to the surface of the photoreceptors. Although the cleaning devices 4Y, 4C, 4M, and 4B used in the present embodiment are of a blade type, the present invention is not limited to this, and a fur brush roller and a magnetic brush cleaning system are used. Also good. Further, the exposure apparatus 5 is not limited to the laser system, and may be a system such as an LED system. Further, the photosensitive members 1Y, 1C, 1M, 1B, the charging devices 2Y, 2C, 2M, 3B, the developing devices 3Y, 3C, 3M, 3B, and the cleaning devices 4Y, 4C, 4M, 4B M and B are integrally formed.

  Document data read by a scanner, received data such as a facsimile, or color image information transmitted from a computer is color-separated into Y, C, M, and B colors to form plate data for each color, and the exposure device 5 Sent to. The uniformly charged photoconductors 1Y, 1C, 1M, and 1B are exposed on the image portion by the exposure device 5, and toner images are formed by the developing devices 3Y, 3C, and M, B.

  The color toner images formed on the photoconductors 1Y, 1C, and 1M are transferred to the intermediate transfer body 6 that is an intermediate transfer body at the same timing, and a color-superposed toner image is formed.

  The black toner image formed on the photoreceptor 1B is directly transferred onto the recording paper conveyed by the transfer conveyance belt 8, and then the YCM toner image superimposed on the intermediate transfer body 6 is transferred onto the recording paper. .

  In addition, recording paper, which is a recording medium on which an output image is formed, is set in the paper feed tray 40, and the recording paper is directed from the paper feed tray 40 to the transfer conveyance belt 8 by a paper feed roller or the like (not shown). And is carried on the front surface which is the outer surface of the loop of the transfer / conveyance belt 8.

  A direct transfer roller 15 is provided at a position facing the photoconductor 1B via the transfer conveyance belt 8, and a direct transfer nip is formed by the photoconductor 1B and the direct transfer roller 15 via the transfer conveyance belt 8. Yes.

  A voltage having a polarity opposite to that of the toner is applied to the direct transfer roller 15, and black is formed on the photosensitive member 1B on the recording paper sandwiched between the photosensitive member 1B and the transfer conveyance belt 8 at the direct transfer nip by this voltage. The toner image is transferred.

  In FIG. 1, three image forming units 30Y, 30C, and 30M are arranged in series along the intermediate transfer body 6. The primary transfer rollers 14Y, 14C, 14M are respectively opposed to the photoconductors 1Y, C, M provided in the image forming units 30Y, 30C, 30M via the intermediate transfer body 6 and slightly downstream in the rotation direction of the intermediate transfer body. It is provided corresponding to the photoreceptors 1Y, 1C, 1M.

  A high voltage having a polarity opposite to that of the toner is applied to the primary transfer rollers 14Y, 14C, and 14M, and each color toner image on the photoreceptors 1Y, 1C, and 1M is transferred onto the intermediate transfer body 6 by the electric field generated by this voltage. Are sequentially transferred so as to overlap each other, and a color image composed of three colors Y, M, and C is formed on the intermediate transfer member 6.

  The color image on the intermediate transfer member 6 is applied between the secondary transfer roller 16 and the counter roller 17 at a secondary transfer nip formed by the secondary transfer roller 16 and the counter roller 17 via the intermediate transfer member 6. Is transferred to the recording paper conveyed to the secondary transfer nip by the transfer conveying belt 8. At this time, a high voltage having a polarity opposite to the charging polarity of the toner may be applied to the secondary transfer roller 16, or a voltage having the same polarity as the charging polarity of the toner may be applied to the counter roller 17.

  When a high voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 16, it is possible to use a high voltage power source for directly applying a voltage to the transfer roller 15. Since it is not necessary to provide a dedicated power source for applying a voltage, cost reduction and size reduction of the image forming apparatus can be achieved. On the other hand, when a voltage having the same polarity as the charging polarity of the toner is applied to the opposing roller 17, a voltage is applied to the toner through the intermediate transfer member 6, so that it is good even if the recording paper absorbs moisture and the resistance is lowered. Transcription becomes possible. Further, the secondary transfer roller 16, the counter roller 17, and a power source (not shown) for applying a high voltage thereto constitute a secondary transfer device.

  In this way, the recording paper on which the toner images of Y, C, M, and B are transferred depends on the curvature of the roller member that stretches the transfer conveyance belt 8 downstream of the secondary transfer nip in the transfer conveyance belt rotation direction. At the bent portion where the rotation direction of the transfer / conveyance belt 8 changes suddenly, the curvature of the recording paper is separated from the transfer / conveyance belt 8 by the waist of the recording paper and reaches the fixing device 10, and Y, C, M, B toner images on the recording paper. Is finally fixed by the fixing device 10, and a color image is formed on the recording paper.

  The transfer of the black toner image used in this embodiment is a direct transfer onto a recording sheet. This direct transfer reduces the number of components and the laser writing image of the black image exposed from the exposure device 5. There is an advantage that writing can be performed in the same direction as laser writing images of Y, C and M images. Further, the black image formed on the photosensitive member 1B by the black image forming unit is directly transferred onto the recording paper, so that the Y, M, and C images are transferred from the photosensitive member 1B to the recording paper via the intermediate transfer member. The transfer efficiency is higher than when a black image is transferred. For this reason, transferring the black image directly from the photoreceptor 1B onto the recording paper is more likely to transfer the black image from the photoreceptor 1B to the recording paper via the intermediate transfer member on the photoreceptor 1B at the black image forming portion. It is possible to suppress the consumption of black toner when forming a black image. However, the present invention is not limited to the configuration in which the black image is directly transferred from the photosensitive member 1B onto the recording paper, and an intermediate transfer member such as an intermediate transfer member or an intermediate transfer drum different from the intermediate transfer member 6 from the photosensitive member 1B. The configuration may be such that the black image is transferred to the recording paper via a transfer member. However, in this case, the laser writing image of the black image exposed from the exposure device 5 becomes a mirror image of the laser writing image of the YCM image, and the writing control becomes complicated.

  So far, the full color mode for creating a full color image composed of Y, C, M, and B toner images on the recording paper has been described. However, in the image forming apparatus of the present embodiment, only the B toner image is formed on the recording paper. It also has a monochrome mode for creating monochrome images. At the time of monochrome image creation in the monochrome mode, the exposure device 5 uses the data of a black image formed based on received data such as a document read by a scanner, a facsimile, or image information transmitted from a computer. The image portion on the photoconductor 1B is exposed, a black toner image is formed by the developing device 3B, the black toner image is directly transferred from the photoconductor 1B onto the recording paper conveyed by the transfer conveyance belt 8, and the black on the recording paper The toner image is fixed on the recording paper by the fixing device 10 to form a monochrome image.

  In the monochrome mode, the contact portion (secondary transfer nip) between the intermediate transfer member 6 and the transfer conveyance belt 8 is released and separated by a mechanism (not shown). As a result, even if the image forming units 30Y, 30C, and 30M and the intermediate transfer body 6 are not operated, there is no influence on the formation of a monochrome image. Therefore, unless the image forming units 30Y, 30C, and M and the intermediate transfer body 6 are operated in the monochrome mode, the deterioration of the image forming units 30Y, 30C, and M and the intermediate transfer body 6 can be suppressed correspondingly, and the image forming unit. 30, Y, C, M and the advantage that the life of the intermediate transfer body 6 can be extended.

  In this embodiment, among the four color toner images, the Y, C, and M images transferred onto the recording paper via the intermediate transfer member 6 are aligned on the intermediate transfer member, and among these three colors, Color matching (position shift) on the recording paper is detected using a color image obtained by transferring one color onto the recording paper. If the device is equipped with a scanner, this color misregistration is detected by scanning this color image with a scanner to detect misregistration between the images, and based on the detection results, adjustment of each image forming position and adjustment of image forming conditions. By performing the above, it is possible to align the images of Y, C, M, and B. It is possible to reduce the number of colors when outputting a color image and detecting misregistration on the paper, and the number of patterns on the paper is reduced compared to transferring and aligning all four colors on the paper. However, it is possible to correct the misalignment without feeling uncomfortable. Also, when a normal output image is read, even if the image is not always four colors, it is possible to perform color matching for all colors if B + 1 colors or more are used.

  At this time, it is preferable to use Y for the detection pattern. Since yellow is not easily recognized by human eyes, color matching can be performed more comfortably.

  By performing these operations when the type of recording medium to be used (such as paper type) is changed, it is possible to minimize color misregistration that occurs when the type of recording paper changes.

  For these misregistration detections, a misregistration detection pattern may be additionally formed on the paper or may be corrected from normal color output image data.

  Regarding the positional deviation detection method, the positional deviation can be detected using a color image output by the user. The output image is read by a sensor such as a scanner, the signal is color-separated into YMCB, and the amount of positional deviation is detected for each color by comparison with the output original image information, and image formation is performed based on the detection result. Conditions can be corrected. In this method, as long as the apparatus is equipped with a scanner, it is possible to detect misalignment without adding special parts. On the other hand, as a disadvantage, an operation of reading an image output by the user with a scanner occurs.

  On the other hand, when creating a misregistration detection pattern regarding the misregistration detection method, for example, a resist skew detection pattern image as shown in FIG. 2 is formed near both ends and the center in the width direction. These three pattern images formed near both ends and near the center are respectively composed of four Y, C, M, and B reference toner images Sy, Sc, Sm, and Sb arranged at a predetermined interval in the sub-scanning direction. The reference toner images are formed so as to be aligned in the main scanning direction.

  In FIG. 2, each reference toner image in the pattern image formed near the front end in the main scanning direction is detected by the first end optical sensor 111. Each reference toner image in the pattern image formed near the center in the belt width direction is detected by the central light sensor 112. Each reference toner image in the pattern image formed in the vicinity of the back end in the belt width direction is detected by the second end photosensor 113.

If the formation timings of the reference toner images of the respective colors are appropriate, the detection intervals of the reference toner images are equal to each other, but if they are inappropriate, the formation intervals of the reference toner images of the respective colors are not equal. Also, the detection intervals are not equal. If there is no optical writing skew in the optical system, the same color reference toner images are detected at the same timing among the three pattern images. However, if the skew is generated, the detection timing differs. come. A control unit (not shown) provided in the image forming apparatus main body performs optical writing on the photosensitive member by the optical writing device based on the detection interval and detection timing of each color toner image in the main scanning direction and the sub-scanning direction. The start timing is adjusted and the tilt of the optical mirror is adjusted to suppress misalignment of each color and image skew.
In this method, an optical sensor for reading is separately required. However, in many cases, the conventional apparatus is also mounted as a standard and can be used. Further, there is a merit that no user misalignment correction work occurs.

  In the present embodiment, three image forming units 30Y, 30C, and 30M are arranged in series along the intermediate transfer body 6, and the image forming unit 30B is located upstream of the tandem arrangement in the recording sheet moving direction. An image forming apparatus provided independently is employed.

  In the image forming apparatus of the present embodiment, the image forming unit 30B is arranged independently of the image forming units 30Y, 30C, and 30M, so that Y, C, and M reverse transfer toners are mixed in the black image forming process. There is nothing to do. Therefore, the toner collected from the photoreceptor 1B is carried to the developing device 3B through a black toner collection path (not shown) and reused. In the middle of the black toner collection path, an apparatus for removing paper dust or an apparatus capable of switching to a path for discarding toner may be provided.

  In FIG. 1, reference numeral 7 denotes an intermediate transfer body cleaning device that removes deposits such as toner attached to the front surface of the intermediate transfer body 6, and reference numeral 9 denotes a front surface of the transfer conveyance belt 8. Reference numeral 12 denotes a transfer / conveying belt cleaning device for removing deposits such as toner.

  In the image forming apparatus according to the present embodiment, the secondary transfer nip is positioned downstream of the direct transfer nip in the recording paper conveyance direction. However, the black toner as described above is mixed with other color toners. However, the secondary transfer nip may be positioned upstream of the direct transfer nip in the recording sheet conveyance direction.

  In the image forming apparatus of the present embodiment, as shown in FIG. 1, an optical sensor 11 is arranged between the secondary transfer and the paper discharge position. Then, a pattern image as described above is created on the photoconductors 1Y, CM, and B, the pattern images of each color are finally transferred onto a recording sheet, and the pattern image is detected by the optical sensor 11.

By doing so, it is possible for the user to perform color matching automatically without performing color matching work with the scanner, thereby improving user convenience.
At this time, the optical sensor is not contaminated with unfixed toner by installing the sensor between the fixing position and the paper discharge position. Therefore, a shutter for preventing contamination by the toner of the sensor and a cleaning member when it becomes dirty are not required, and the sensor can be used for a long time with a smaller and less expensive configuration.

  Further, the present invention is a transfer / conveying belt that is rotatably supported by a plurality of roller members and carries a recording medium so as to pass through the direct transfer position and the secondary transfer position as shown in FIG. The transfer rollers 15 and 16 may be opposed to the latent image carrier 30 </ b> B and the intermediate transfer body 6, respectively, without using 8.

  This is because, in the conventional technique, since the alignment is performed on the belt, the conveyance belt is necessary. However, in the present invention, the alignment is performed on the paper, so that the conveyance belt is not necessary. Furthermore, since it is not necessary to create a misregistration detection pattern on the transport belt, the cleaning mechanism is not required. As a result, there is no need for a waste toner conveyance path, and the apparatus can be significantly downsized, the number of parts can be reduced, and the cost can be reduced.

  Further, when the transfer rollers 15 and 16 are used, the optical sensor 11 also serves as a density detecting means. By doing so, the cost can be reduced and the size can be reduced as compared with the case where the density detecting means is provided separately. Further, since the density on the paper is directly detected, there may be a case where the density can be detected more accurately than the detection on the image carrier.

  Further, the density detecting means may be installed facing the second image carrier. When the reflection characteristics of paper and toner are close, it is possible to detect the toner adhesion amount more accurately than when detecting on paper.

  Further, the positional deviation correction and density detection may be performed on the intermediate transfer body by transferring the density detection pattern transferred onto the paper again onto the intermediate transfer body. Similar to the case of using an optical sensor for detecting the positional deviation on the paper, the density can be detected without the need for a new density detection sensor, and at the same time, the density can be detected even when the reflection characteristic of the paper is close to the toner pattern.

  In addition, although there is a tradeoff with cost, it is also possible to provide a plurality of these positional deviation detection means and density detection means and select them appropriately according to the situation of use.

  The following FIG. 4 and Tables 1 to 3 show the cases where the alignment / density detection of each color is performed. Here, as shown in FIG. 4, a sensor 101 after fixing is a sensor 101, a sensor on the intermediate transfer member is a sensor 102, and a sensor on the B unit as a second image carrier is a sensor 103. These combinations are four types of patterns A, B, C, and D as shown in Table 1.

  Patterns A and B are patterns in which three colors of Y, M, and C are detected on the intermediate transfer member, and the remaining one color (here, Y) and the B image are detected on the paper. . Patterns C and D are patterns in which the B misregistration detection image is transferred again to the intermediate transfer member via the recording paper and the misregistration detection is performed on the intermediate transfer member. The patterns C and D are provided in common for detecting misalignment of three colors Y, M, and C, and detecting misalignment of one of Y, M, and C (Y here) and the B image. With a single sensor 102 provided. That is, in the patterns C and D, only one sensor is used for detecting misalignment.

  Further, in each case, the cases shown in Table 2 can be further divided depending on which color is used for position shift detection and density detection.

  That is, all the points for aligning the CMY colors on the intermediate transfer member are common (in Table 2, the point where ymc is aligned by the sensor 102 is common). (Black) alignment, “ymc density control”, and “k density control” are performed at each of the three positions.

  Furthermore, Table 3 shows these advantages and disadvantages.

In order to leave as little toner as possible in the user's output image, by selecting patterns C and D, correction can be performed without leaving a misregistration detection pattern or density detection pattern on the paper.
When the smoothness of the paper is low (the unevenness is large), the density detection pattern is likely to be uneven in the distribution of adhesion amount due to the transfer. Therefore, pattern B-1, pattern B-2, and D are desirable when using paper with large unevenness.
In addition, when the misregistration detection pattern is detected by the sensor 102, in order to retransfer the B image from the recording paper to the intermediate transfer member, it is necessary to apply a bias having a polarity opposite to the normal transfer bias. It is necessary to create a pattern in a blank area that has not been created. In this case, the number of patterns that can be created is reduced, and the positional deviation detection accuracy is lowered. Conversely, if the B image is not re-transferred from the recording paper to the intermediate transfer member, it is not necessary to apply a reverse bias to the normal transfer bias. Deviation detection patterns can be created.
This also applies to the density detection pattern. Since the density detection pattern generally requires a larger pattern area than the misregistration detection pattern, it is necessary to set more margins.
Of course, the cost can be reduced if the number of sensors is small, and can be reduced by selecting the pattern C.

  The combination of misregistration detection and density detection can be changed according to the color of the recording paper. Usually, the combination of pattern B-2 is used to detect misregistration and density. However, if the paper color is close to the toner color (for example, yellow paper), it is difficult to detect Y toner misregistration on the paper. Thus, by detecting the pattern D without using the sensor A, it is possible to detect the positional deviation without the influence of the paper color.

  Further, the combination of positional deviation detection and density detection can be changed according to the unevenness of the paper. Usually, detection is performed with a combination of the pattern B-2. However, when the unevenness of the paper is very smooth like the coated paper and the light reflection characteristics are known, the image carrier is as shown in B-3. It is possible to obtain a more accurate density because the density detection on the paper detects the density on the paper after the actual fixing rather than the density detection on the upper or intermediate transfer body.

  Further, in this configuration example, a contact / separation device 20 is provided to contact and separate the intermediate transfer body 6 from the transfer conveyance belt 8 or the transfer roller 16 in the area of the secondary transfer device. The contact / separation device 20 may be in various known forms. For example, as shown in FIG. 5, the shaft 19 of the secondary transfer roller 16 is inserted into a groove 21 formed in a wall portion in the image forming apparatus main body, and a spring 21 is inserted. The intermediate transfer body 6 and the transfer conveyance belt 8 can be brought into contact with and separated from each other by pressing against the cam 23 and rotating the cam 23 with a pulse motor (not shown).

  In order to separate the intermediate transfer body 6 in contact with the area of the secondary transfer device from the transfer conveyance belt 8 or the transfer roller 16, the cam 23 is rotated clockwise in FIG. The secondary transfer roller 16 that is in contact with the intermediate transfer body 6 via the transfer conveyance belt 8 is moved by moving in the groove 21 against the urging force and displacing the secondary transfer roller 16 away from the opposing roller 17. And the opposed roller 17. By separating the secondary transfer roller 16 and the opposing roller 17 in this way, the transfer conveying belt 8 is displaced in a direction away from the intermediate transfer body 6 in conjunction with the displacement of the opposing roller 17 by its own tension. As shown, the intermediate transfer member 6 and the transfer conveyance belt 8 or the transfer roller 16 are separated from each other.

  Further, when the intermediate transfer body 6 and the transfer conveyance belt 8 which are separated in the region of the secondary transfer device are brought into contact with each other, the cam 23 is rotated counterclockwise in FIG. The inside of the groove 21 is moved in the urging direction, and the secondary transfer roller 16 is displaced in a direction approaching the opposing roller 17. By displacing the secondary transfer roller 16 in the direction approaching the counter roller 17 in this way, the transfer conveyance belt 8 is also displaced in the direction approaching the intermediate transfer body 6 in conjunction with the displacement of the secondary transfer roller 16. Therefore, by bringing the secondary transfer roller 16 and the counter roller 17 into contact with each other via the intermediate transfer body 6, the intermediate transfer body 6 and the transfer conveyance belt 8 or the transfer roller 16 come into contact with each other.

  In the present configuration example, when the monochrome mode is executed, the intermediate transfer member 6 and the transfer conveyance belt 8 or the transfer roller 16 are separated from each other by the secondary transfer separation device, and thereafter, monochrome image formation is started. Here, in this configuration example, Y, C, and M correction pattern images are created on the intermediate transfer body 6 during monochrome image formation, and positions between color images (Y, C, and M images) are determined. Controls deviation adjustment and density adjustment. Such color image adjustment control does not need to be performed every time the monochrome mode is executed, and a control unit (not shown) provided in the image forming apparatus main body indicates whether a predetermined number of prints have been made since the previous color image adjustment control. This may be performed when a predetermined number of sheets have been printed since the previous color image adjustment control.

  Further, it is preferable that the separation distance between the intermediate transfer member 6 and the transfer conveyance belt 8 or the transfer roller 16 by the separation device is small because the change in the conveyance path of the recording paper is small. However, if the separation distance between the intermediate transfer member 6 and the transfer conveyance belt 8 or the transfer roller 16 is small, a color image (Y, M) created on the intermediate transfer member 6 for color image adjustment control as described above. , C pattern image) is a monochrome image (black toner image) on the recording paper, so that the color image on the intermediate transfer body 6 on the recording paper on which the monochrome image is placed or the secondary image in the area of the secondary transfer device. There is a risk of moving onto the transfer roller 16. For this reason, the secondary transfer device is biased so that an electric field is applied so that the color image (Y, M, C pattern image) created on the intermediate transfer member 6 is attracted to the intermediate transfer member by electrostatic force. Is preferably applied. For example, a high voltage having a polarity opposite to the toner charging polarity may be applied to the counter roller 17 of the secondary transfer device. As a result, the color image (Y, M, C pattern image) on the intermediate transfer member 6 is prevented from moving onto the recording paper on which the monochrome image is placed or onto the transfer conveyance belt 8 in the area of the secondary transfer device. be able to.

  Next, since the intermediate transfer member 6 used in the present embodiment corresponds to various recording papers, in other words, the surface of the intermediate transfer member 6 is elastically deformed following the irregularities on the surface of the recording paper, and the intermediate transfer member. 6 is preferably an elastic belt formed of an elastic body so that occurrence of poor transfer of a color image from the top to the recording paper can be suppressed. As the elastic body, urethane rubber, silicone rubber, acrylonitrile butadiene rubber (NBR), ethylene propylene rubber (EPM, EPDM) or the like is used.

The toner is composed of at least a binder resin and a colorant, and a lubricant for reducing friction is externally added to the toner surface. In addition, a charge control agent for controlling the chargeability of the toner and releasability to the fixing device. It may contain an external additive that contains a release agent or the like that improves fluidity and imparts fluidity.
The binder resin is an ester resin, a vinyl resin, an amide resin, an epoxy resin, a silicone resin, or the like, and a vinyl resin is particularly preferable. Specifically, styrene such as polystyrene, poly P-chlorostyrene, polyvinyltoluene, and the like Homopolymer of the substituted product, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate Copolymer, styrene-ethyl acrylate copolymer, styrene-butyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-butadiene copolymer, styrene-meta Use methyl acrylate-butyl acrylate copolymer, etc. Rukoto can.

  As the colorant, all dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, yellow Lead, titanium yellow, polyazo yellow, bengara, red lead, lead vermilion, cadmium red, cadmium mercurial red, antimony vermilion, permanent red 4R, para red, phise red, parachlor ortho nitroaniline red, risor fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Per Nent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polyazo Red, Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean blue, alkali blue rake, peacock blue rake, Victoria blue rake, metal-free phthalocyanine blue, phthalocyanine blue, indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone Violet, chrome green, zinc green, pigment green B, naphthol green B, green Ngorudo, titanium oxide, zinc white, lithopone and mixtures thereof can be used. The content of the colorant is usually 1 to 15% by mass, preferably 3 to 10% by mass with respect to the toner.

As the charge control agent, for example, a salicylic acid compound, a nigrosine dye, a quaternary ammonium salt compound, an alkylpyridinium compound, or the like can be used. The content is usually from 0.1 to 5% by weight, preferably from 1 to 3% by weight, based on the toner.
As the release agent, for example, polyolefin wax such as low molecular weight polyethylene, low molecular weight polypropylene, low molecular weight polyethylene-polypropylene copolymer, ester wax such as fatty acid lower alcohol ester, fatty acid higher alcohol ester, fatty acid polyhydric alcohol ester, An amide wax or the like can be used. The content is usually 0.5 to 10% by mass, preferably 1 to 5% by mass, based on the toner.
Furthermore, a fluidity imparting agent may be added to the toner. Examples of the fluidity-imparting agent include fine particles of metal oxides such as silica, titania, alumina, magnesia, zirconia, ferrite, and magnetite, and metal oxides obtained by treating these fine particles with a silane coupling agent, titanate coupling agent, or zircoaluminate. Fine particles. Silica and titania hydrophobized with a coupling agent are preferred. Since the primary particle size of silica is small, the effect of imparting fluidity is large. Further, titania can control the toner charge amount. It is more preferable to add these in combination.
Further, the amount of lubricant added externally to the toner is preferably in the range of 0.1 to 2.0% by mass. If the addition amount of the lubricant is less than 0.1% by mass, the amount supplied to the photoreceptor 1 is small and it is difficult to reduce the friction coefficient of the photoreceptor 1. It may adhere to the charging device 2 and cause abnormal images.

  In the present invention, the toner preferably has a circularity of 0.92 or more. Circularity SR = (peripheral length of a circle having the same area as the particle projection area / perimeter length of the particle projection image) × 100%. The closer the toner is to a true sphere, the closer to 100%. In the conventional image forming apparatus, when such toner is used, there is a case where the cleaning apparatus 4 such as a cleaning blade cannot be sufficiently scraped off. This is because the toner easily rolls on the photoreceptor 1. In this case, as a countermeasure, it is conceivable that the cleaning blade is brought into contact with the photosensitive member 1 with a stronger force, but this affects the rotation or movement accuracy of the photosensitive member 1 and causes banding. On the other hand, a lubricant is applied to the surface of the photoreceptor 1 from both a coating means (not shown) and toner to reduce the friction coefficient of the surface of the photoreceptor 1, thereby increasing the transfer rate during transfer and remaining toner. It is possible to reduce the burden of cleaning by the cleaning blade and to perform cleaning without banding even if the cleaning blade comes into contact with a strong force.

  This degree of circularity is thermally or mechanically spheroidized with toner produced by dry grinding. Thermally, for example, the spheronization treatment can be performed by spraying toner base particles together with a hot air stream on an atomizer or the like. In addition, a spheroidizing treatment can be performed by mechanically charging the mixture into a mixer such as a ball mill together with a mixed medium such as glass having a low specific gravity and stirring. However, in the thermal spheronization process, toner base particles that are aggregated and have a large particle size or fine particles are generated in the mechanical spheronization process, and thus a second classification step is required. In addition, in a toner manufactured in an aqueous solvent, the shape can be controlled by applying strong stirring in the process of removing the solvent.

Further, since the toner having a smaller volume average particle diameter Dv can improve the reproducibility of fine lines, a toner having a maximum particle size of 8 μm or less is used. However, since the developing property and the cleaning property are lowered when the particle size is small, at least 3 μm is preferable. Further, if the particle size is less than 3 μm, the toner having a small particle diameter that is difficult to be developed on the surface of the carrier or the developing roller increases. This is not preferable because an abnormal image such as fogging is formed.
Moreover, it is preferable that the particle size distribution represented by ratio (Dv / Dn) of volume average particle diameter Dv and number average particle diameter Dn is the range of 1.05-1.40. By sharpening the particle size distribution, the toner charge amount distribution can be made uniform. When Dv / Dn exceeds 1.40, the toner charge amount distribution is wide and the amount of the reversely charged toner T1 increases, making it difficult to obtain a high-quality image. If Dv / Dn is less than 1.05, it is difficult to produce and it is not practical. The particle size of the toner is 50,000 by using a Coulter Counter Multisizer (manufactured by Coulter Co., Ltd.) and selecting an aperture having a measurement hole size of 50 μm corresponding to the particle size of the toner to be measured. It is obtained by measuring the average particle size of the particles.

The toner preferably has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180 in the circularity. 7A and 7B are diagrams schematically illustrating the shape of the toner. FIG. 7A is a diagram for explaining the shape factor SF-1, and FIG. 7B is a diagram for explaining the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) 2 / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) 2 / AREA} × (100 / 4π) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.
Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.
When the shape of the toner is close to a sphere, the contact between the toner and the toner or the photoreceptor 1 becomes a point contact, so that the adsorbing force between the toners is weakened, resulting in an increase in fluidity. 1 is weakened, the transfer rate is increased, and the reversely charged toner is easily collected by the temporary holding device.
The shape factors SF-1 and SF-2 of the toner are preferably 100 or more. Further, when SF-1 and SF-2 are increased, the amount of the reversely charged toner T1 is increased, the toner charge amount distribution is broadened, and the load on the temporary holding device is increased. For this reason, SF-1 preferably does not exceed 180, and SF-2 also preferably does not exceed 180.

Further, the toner used in the image forming apparatus of the present invention may be substantially spherical. FIG. 8 is a schematic view showing the outer shape of the toner, FIG. 8A is an appearance of the toner, and FIG. 8B is a cross-sectional view of the toner. In FIG. 8A, the X axis represents the longest axis r1 of the longest axis of the toner, the Y axis represents the shortest axis r2 of the next longest axis, and the Z axis represents the shortest axis thickness r3. ≧ Short axis r2 ≧ Thickness r3
The toner has a major axis / minor axis ratio (r2 / r1) of 0.5 to 1.0 and a thickness / minor axis ratio (r3 / r2) of 0.7 to 1.0. It has a substantially spherical shape. When the ratio of the major axis to the minor axis (r2 / r1) is less than 0.5, the charge amount distribution becomes wide because it approaches an indefinite shape.
When the ratio of the thickness to the short axis (r3 / r2) is less than 0.7, the charge amount distribution becomes wide because the shape approaches an indefinite shape. In particular, when the ratio of the thickness to the short axis (r3 / r2) is 1.0, the charge amount distribution becomes narrow because of the substantially spherical shape.
The size of the toner so far was measured with a scanning electron microscope (SEM) while changing the angle of the field of view and observing in situ.

The shape of the toner can be controlled by the manufacturing method. For example, the toner by the dry pulverization method has an irregular shape in which the toner surface is uneven and the toner shape is not constant. Even this dry pulverized toner can be made into a nearly spherical toner by applying mechanical or thermal treatment. In many cases, a toner produced by forming droplets by a suspension polymerization method or an emulsion polymerization method has a smooth surface and a nearly spherical shape. Moreover, it can be made into an ellipse by stirring in the middle of the reaction in a solvent and applying a shearing force.
In addition, as such a substantially spherical toner, a toner composition containing a polyester prepolymer having a functional group containing a nitrogen atom, a polyester, a colorant, and a release agent in an aqueous medium in the presence of fine resin particles. A toner that undergoes crosslinking and / or elongation reaction is preferred.

Hereinafter, the constituent material of the toner and a suitable manufacturing method will be described. (polyester)
The polyester is obtained by a polycondensation reaction between a polyhydric alcohol compound and a polycarboxylic acid compound.
Examples of the polyhydric alcohol compound (PO) include a dihydric alcohol (DIO) and a trihydric or higher polyhydric alcohol (TO). (DIO) alone or a mixture of (DIO) and a small amount of (TO) preferable. Examples of the dihydric alcohol (DIO) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide bisphenol (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among these, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use. The trihydric or higher polyhydric alcohol (TO) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.

Examples of the polyvalent carboxylic acid (PC) include divalent carboxylic acid (DIC) and trivalent or higher polyvalent carboxylic acid (TC). (DIC) alone and (DIC) and a small amount of (TC) Mixtures are preferred. Divalent carboxylic acids (DIC) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms. Examples of the trivalent or higher polyvalent carboxylic acid (TC) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polyhydric carboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the above-mentioned acid anhydride or lower alkyl ester (Methyl ester, ethyl ester, isopropyl ester, etc.).
The ratio of the polyhydric alcohol (PO) to the polycarboxylic acid (PC) is usually 2/1 to 1/1, preferably as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. Is 1.5 / 1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1.

The polycondensation reaction between a polyhydric alcohol (PO) and a polycarboxylic acid (PC) is carried out in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, and heated to 150 to 280 ° C. while reducing the pressure as necessary. The produced water is distilled off to obtain a polyester having a hydroxyl group. The hydroxyl value of the polyester is preferably 5 or more, and the acid value of the polyester is usually 1 to 30, preferably 5 to 20. By giving an acid value, it tends to be negatively charged, and furthermore, when fixing to a recording paper, the affinity between the recording paper and the toner is good and the low-temperature fixability is improved. However, when the acid value exceeds 30, there is a tendency to deteriorate with respect to the stability of charging, particularly environmental fluctuation.
The weight average molecular weight is 10,000 to 400,000, preferably 20,000 to 200,000. A weight average molecular weight of less than 10,000 is not preferable because offset resistance deteriorates. On the other hand, if it exceeds 400,000, the low-temperature fixability is deteriorated.
In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting a terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of the amine with amines.

Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; the above polyisocyanates with phenol derivatives, oximes, Those blocked with caprolactam or the like; and combinations of two or more of these.
The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5, low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1, when a urea-modified polyester is used, the urea content in the ester is lowered and hot offset resistance is deteriorated.

The content of the polyvalent isocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40% by mass, preferably 1 to 30% by mass, more preferably 2 to 20% by mass. %is there. If it is less than 0.5% by mass, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40% by mass, the low-temperature fixability deteriorates.
The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester will be low, and the hot offset resistance will deteriorate.

Next, as amines (B) to be reacted with the polyester prepolymer (A), a divalent amine compound (B1), a trivalent or higher polyvalent amine compound (B2), an amino alcohol (B3), an amino mercaptan (B4) ), Amino acid (B5), and amino acids B1 to B5 blocked (B6).
Examples of the divalent amine compound (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′-diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′-dimethyldicyclohexyl). Methane, diamine cyclohexane, isophorone diamine, etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine, etc.). Examples of the trivalent or higher polyvalent amine compound (B2) include diethylenetriamine and triethylenetetramine. Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan. Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid. Examples of the block (B6) in which the amino group of B1 to B5 is blocked include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

The ratio of amines (B) is equivalent to the equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is usually 1/2 to 2/1, preferably 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2. When [NCO] / [NHx] is more than 2 or less or less than 1/2, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance is deteriorated.
The urea-modified polyester may contain a urethane bond together with a urea bond. The molar ratio of the urea bond content to the urethane bond content is usually 100/0 to 10/90, preferably 80/20 to 20/80, and more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance is deteriorated. The urea-modified polyester is produced by a one-shot method or the like. Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) are heated to 150-280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate, dibutyltin oxide, etc., and water generated while reducing the pressure as necessary. Distill off to obtain a polyester having a hydroxyl group. Subsequently, at 40-140 degreeC, this is made to react with polyvalent isocyanate (PIC), and the polyester prepolymer (A) which has an isocyanate group is obtained. Further, this (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a urea-modified polyester.

When reacting the polyvalent isocyanate compound (PIC) and when reacting (A) and (B), a solvent may be used as necessary. Usable solvents include aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide, etc.) and ethers And those inert to isocyanates (PIC), such as tetrahydrofuran (such as tetrahydrofuran).
In addition, in the crosslinking and / or extension reaction between the polyester prepolymer (A) and the amines (B), a reaction terminator can be used as necessary to adjust the molecular weight of the resulting urea-modified polyester. Examples of the reaction terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), and those blocked (ketimine compounds).

The weight average molecular weight of the urea-modified polyester is usually 10,000 or more, preferably 20,000 to 10,000,000, and more preferably 30,000 to 1,000,000. If it is less than 10,000, the hot offset resistance deteriorates. The number average molecular weight of the urea-modified polyester is not particularly limited when the above-mentioned unmodified polyester is used, and may be a number average molecular weight that can be easily obtained to obtain the above weight average molecular weight. When the urea-modified polyester is used alone, its number average molecular weight is usually 2000-15000, preferably 2000-10000, more preferably 2000-8000. When it exceeds 20000, the low-temperature fixability and the glossiness when used in a full-color device are deteriorated.
By using the unmodified polyester and the urea-modified polyester in combination, the low-temperature fixability and the gloss when used in the full-color image forming apparatus 100 are improved. Therefore, it is preferable to use the urea-modified polyester alone. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond.
The unmodified polyester and the urea-modified polyester are preferably at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance. Therefore, it is preferable that the unmodified polyester and the urea-modified polyester have a similar composition.

The mass ratio of unmodified polyester and urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, and particularly preferably 80 /. 20-93 / 7. When the weight ratio of the urea-modified polyester is less than 5%, the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.
The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 ° C, preferably 45 to 60 ° C. If it is less than 45 ° C., the heat resistance of the toner deteriorates, and if it exceeds 65 ° C., the low-temperature fixability becomes insufficient.
In addition, since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.
Here, the aforementioned substances can be used as the colorant, charge control agent, release agent, external additive and the like.

Next, a toner manufacturing method will be described. Here, although a preferable manufacturing method is shown, it is not limited to this.
(Toner production method)
1) A toner material solution is prepared by dispersing a colorant, unmodified polyester, a polyester prepolymer having an isocyanate group, and a release agent in an organic solvent. The organic solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal after toner base particle formation. Specifically, toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, methyl ethyl ketone, Methyl isobutyl ketone and the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform and carbon tetrachloride are preferred. The usage-amount of an organic solvent is 0-300 mass parts normally with respect to 100 mass parts of polyester prepolymers, Preferably it is 0-100 mass parts, More preferably, it is 25-70 mass parts.

2) The toner material liquid is emulsified in an aqueous medium in the presence of a surfactant and resin fine particles. The aqueous medium may be water alone or an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be included.
The amount of the aqueous medium used relative to 100 parts by mass of the toner material liquid is usually 50 to 2000 parts by mass, preferably 100 to 1000 parts by mass. If the amount is less than 50 parts by mass, the dispersion state of the toner material liquid is poor and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 20000 parts by mass, it is not economical.
Further, in order to improve the dispersion in the aqueous medium, a dispersant such as a surfactant and resin fine particles is appropriately added.
As surfactants, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, Quaternary ammonium salt type cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, fatty acid amide derivatives, polyhydric alcohols Nonionic surfactants such as derivatives, for example, amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine And the like.

  Further, by using a surfactant having a fluoroalkyl group, the effect can be obtained in a very small amount. Preferred anionic surfactants having a fluoroalkyl group include fluoroalkyl carboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3- [ω-fluoroalkyl (C6-C11 ) Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [ω-fluoroalkanoyl (C6-C8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (C11-C20) carvone Acids and metal salts, perfluoroalkylcarboxylic acids (C7 to C13) and metal salts thereof, perfluoroalkyl (C4 to C12) sulfonic acids and metal salts thereof, perfluorooctanesulfonic acid diethanolamide, N-propyl-N- ( 2-Hydroxyethyl) Perful Olooctanesulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. Can be mentioned.

Product names include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.), Florard FC-93, FC-95, FC-98, FC-129 (Sumitomo 3M Co., Ltd.), Unidyne DS-101. DS-102 (manufactured by Daikin Industries, Ltd.), Megafac F-110, F-120, F-113, F-191, F-812, F-833 (manufactured by Dainippon Ink, Inc.), Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products), and Fgentent F-100, F150 (manufactured by Neos).
Further, as the cationic surfactant, aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amine acids having a fluoroalkyl group, and perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salts. , Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (manufactured by Asahi Glass), Florard FC-135 (manufactured by Sumitomo 3M), Unidyne DS-202 (Daikin Industries) Manufactured), MegaFuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products), Footgent F-300 (Neos), and the like.

The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage existing on the surface of the toner base particles is in the range of 10 to 90%. For example, polymethyl methacrylate fine particles 1 μm and 3 μm, polystyrene fine particles 0.5 μm and 2 μm, poly (styrene-acrylonitrile) fine particles 1 μm, trade names are PB-200H (manufactured by Kao), SGP (manufactured by Soken), Techno Examples include polymer SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), and micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.).
In addition, inorganic compound dispersants such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite can also be used.

  As a dispersant that can be used in combination with the above resin fine particles and inorganic compound dispersant, the dispersed droplets may be stabilized by a polymer protective colloid. For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups Bodies such as acrylic acid-β-hydroxyethyl, methacrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxypropyl, methacrylic acid-β-hydroxypropyl, acrylic acid-γ-hydroxypropyl, methacrylic acid-γ-hydroxy Propyl, acrylic acid-3-chloro-2-hydroxypropyl, methacrylic acid-3-chloro-2-hydroxypropyl, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate Luric acid esters, N-methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, or compounds containing vinyl alcohol and a carboxyl group Esters such as vinyl acetate, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, vinyl pyridine, vinyl pyrrolidone, vinyl Nitrogen compounds such as imidazole and ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, poly Xoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonyl phenyl ether, polyoxyethylene, lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, poly Polyoxyethylenes such as oxyethylene nonylphenyl ester, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

  The dispersion method is not particularly limited, and known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied. Among these, the high-speed shearing method is preferable in order to make the particle size of the dispersion 2 to 20 μm. When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 40 to 98 ° C.

3) At the same time as the preparation of the emulsion, the amines (B) are added to cause a reaction with the polyester prepolymer (A) having an isocyanate group.
This reaction involves molecular chain crosslinking and / or elongation. The reaction time is selected depending on the reactivity of the isocyanate group structure of the polyester prepolymer (A) with the amines (B), but is usually 10 minutes to 40 hours, preferably 2 to 24 hours. The reaction temperature is generally 0 to 150 ° C, preferably 40 to 98 ° C. Moreover, a well-known catalyst can be used as needed. Specific examples include dibutyltin laurate and dioctyltin laurate.

4) After completion of the reaction, the organic solvent is removed from the emulsified dispersion (reactant), washed and dried to obtain toner base particles.
In order to remove the organic solvent, the temperature of the entire system is gradually raised in a laminar stirring state, and after giving strong stirring in a certain temperature range, the solvent base is removed to produce spindle-shaped toner base particles. . Further, when an acid such as calcium phosphate salt or an alkali-soluble material is used as the dispersion stabilizer, the calcium phosphate salt is dissolved from the toner base particles by a method such as dissolving the calcium phosphate salt with an acid such as hydrochloric acid and washing with water. Remove. It can also be removed by operations such as enzymatic degradation.

  5) A charge control agent is injected into the toner base particles obtained above, and then inorganic fine particles such as silica fine particles and titanium oxide fine particles are externally added to obtain a toner. When preparing a developer by adding external additives and lubricants, these may be added simultaneously or separately and mixed. For mixing external additives and the like, a general powder mixer is used, but it is preferable to equip a jacket or the like to adjust the internal temperature. Examples of the mixing equipment that can be used include a V-type mixer, a rocking mixer, a Ladige mixer, a Nauter mixer, a Henschel mixer, and the like. It is preferable to prevent the embedding of the external additive and the formation of a thin film on the toner surface of the lubricant by changing the mixing conditions such as the rotation speed, rolling speed, time, and temperature. Thereby, a toner having a small particle size and a sharp particle size distribution can be easily obtained. Furthermore, by giving strong agitation in the process of removing the organic solvent, the shape between the spherical shape and the spindle shape can be controlled, and the surface morphology is also controlled between the smooth shape and the umeboshi shape. Can do.

The toner according to the present invention can be mixed with a magnetic carrier and used as a two-component developer. In this case, the toner concentration of the carrier and the toner in the developer is preferably 1 to 10 parts by mass of the toner with respect to 100 parts by mass of the carrier. The toner according to the present invention can also be used as a one-component magnetic toner that does not use a carrier or a non-magnetic toner.
In the image forming unit 30 of this embodiment, the photosensitive member 1 (image carrier) that forms a latent image and one or more devices selected from the charging device 2, the developing device 3, and the cleaning device 4 are integrated. Therefore, the process cartridge can be attached to and detached from the image forming apparatus. Therefore, when maintenance is required, the process cartridge can be replaced, and convenience is improved.

  In the process cartridge of the present invention, the image carrier that carries the color toner image of each color is disposed in contact with the intermediate transfer member, and the image carrier of the developing device that visualizes the black toner image is the intermediate transfer member. Since it is provided independently at a position upstream of the body in the recording medium moving direction, the same effect as the image forming apparatus of the present invention can be obtained.

  In the image forming apparatus of the present invention, in the color image forming process, the toner collected from the latent image carrier of the black developing device can be reused without being mixed with YCM toner. It can contribute to resource saving and cost reduction without causing deterioration. In addition, if the direct transfer method is used for transferring the black image, the number of components can be reduced, and the black image written by the exposure device is written in the same direction as the YCM image. This makes it possible to provide an image forming apparatus that contributes to cost reduction because the writing control is not complicated.

Below, it describes about the effect | action and effect for every claim.
According to the first aspect of the present invention, when the positional deviation is detected only on the belt, the position of each color on the belt may be misaligned depending on the type of the recording medium. Therefore, it is possible to perform exact alignment for matching. In addition, since the plurality of first toner images are subjected to positional deviation control on the intermediate transfer body, if positional deviation control is performed on the recording medium with the second toner image and at least one first toner image, It is possible to control the positional deviation of all toner images. It is possible to reduce the toner image transferred from the intermediate transfer member onto the recording medium.

  Claim 2> Since the detection pattern is read on the conveyance path, it is not necessary to apply a reverse polarity bias to the normal transfer bias and reverse transfer from the recording paper to the intermediate transfer member, and in parallel with the usual image creation. The detection pattern can be transferred and read.

  According to the third aspect of the present invention, a work for correcting misalignment is separately required for the scanner. However, the incorporation of the detecting means eliminates the trouble and improves the convenience for the user.

  According to the fourth aspect of the present invention, since the detection is performed after the fixing, there is no fear that the detecting means is stained with unfixed toner. Therefore, a cleaning member for the detection means and a member for preventing contamination are not required, and it is possible to reduce the size and cost.

  Claim 5> Since no detection pattern is left on the recording medium, it is not necessary to leave toner in the user's output image. In addition, alignment and density control can be performed without giving the user a sense of incongruity.

  (6) In the configuration of (5), since the number of detection means (sensors) is small, the cost can be reduced.

  According to the seventh aspect of the present invention, when yellow is drawn on paper, it is difficult for human eyes to recognize it, and it is possible to detect and correct misalignment without feeling uncomfortable.

  According to the present invention, since the positional deviation and the density are detected by the same detecting means, the cost can be reduced and the size can be reduced as compared with the case where the density detecting means is provided separately. In addition, since the density of the second toner image transferred onto the recording medium is detected, it may be possible to detect the density more accurately than when detected on the image carrier.

  Claim 9> Even when the reflection characteristics of paper and toner are close and the accuracy of density detection on the recording medium cannot be expected, the toner adhesion amount can be detected more accurately by enabling density detection on the second image carrier. It becomes possible to do.

  Claim 10> The structure is simpler than using a belt-shaped member, and it is possible to reduce the size and cost.

  Claims 11 and 12> By using an elastic belt as the intermediate transfer member, it is possible to prevent an image with low granularity caused by uneven transfer or a so-called hollow image in which a part of the toner of the line image is lost. It becomes possible.

  Claim 13> Depending on the type of recording medium, image detection on the recording medium is affected. In that case, switching the detection means enables accurate image detection without being affected by the type of the recording medium.

  Claim 14> When the color of the recording medium is close to the color of the toner (for example, yellow paper) and it is difficult to detect the toner image on the medium, an accurate image can be obtained without switching the detection means. Detection is possible.

  Claim 15> When the recording medium is very smooth coated paper, the reflection characteristics of the recording medium and the toner layer are greatly different, so that detection on the recording medium is possible, but the recording medium has irregularities. In this case, even if there is no toner, the light is scattered as in the case where the toner is present, and it is difficult to accurately detect. By switching the detection means when there is unevenness, accurate detection can be performed without the influence of unevenness of the recording medium.

  Each embodiment described above is a preferred embodiment of the present invention, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging apparatus 3 Developing apparatus 4 Cleaning apparatus 5 Exposure apparatus 6 Intermediate transfer body 7 Intermediate transfer body cleaning apparatus 8 Transfer conveyance belt 9 Transfer conveyance belt cleaning apparatus 10 Fixing apparatus 11 Optical sensor 12 Toner container 14 Primary transfer roller 15 Direct transfer roller 16 Secondary transfer roller 17 Opposing roller 18 Optical sensor 19 Axis 20 Contacting / separating device 21 Groove 22 Spring 23 Cam 30 Image forming unit 40 Paper feed tray 111 First end optical sensor 112 Central optical sensor 113 Second end Optical sensor

JP 2006-201743 A JP 9-314911 A

Claims (15)

A plurality of first image carriers on which a first toner image corresponding to each color is formed;
An intermediate transfer member provided opposite to the plurality of first image carriers, to which a first toner image on the first image carrier is primarily transferred;
Secondary transfer means for secondary transfer of the toner image on the intermediate transfer member onto a recording medium;
A second image carrier on which a toner image is formed, provided on the upstream side or the downstream side in the recording medium conveyance direction from the secondary transfer position where the image is secondarily transferred from the intermediate transfer body onto the recording medium;
Direct transfer means for directly transferring the second toner image on the second image carrier onto the recording medium;
A first detection means;
A second detection means;
With
The first detecting means is provided on the intermediate transfer member;
The first detection means detects a positional shift of the plurality of first toner images,
The second detecting means detects a positional deviation between the first toner image and the second toner image transferred onto the recording medium;
An image forming apparatus comprising: control means for controlling image forming conditions so as to suppress positional deviation between images based on detection results of the first detection means and the second detection means.   The image forming apparatus according to claim 1, wherein the second detection unit is provided on the recording medium conveyance path.   The second detecting means is a portion between a secondary transfer position by the secondary transfer means and a direct transfer position by the direct transfer means and a position from the downstream transfer position to the discharge position of the recording medium. The image forming apparatus according to claim 2, wherein the image forming apparatus is provided.   4. The image forming apparatus according to claim 3, wherein the second detection unit is provided at a position downstream of the fixing unit that fixes the image on the recording medium in the recording medium conveyance direction.   The image forming apparatus according to claim 1, wherein the second detection unit is provided on the intermediate transfer member.   The image forming apparatus according to claim 5, wherein the second detection unit is provided in common with the first detection unit.   The image forming apparatus according to claim 1, wherein the first toner image detected by the second detection unit is a yellow toner image. The first detection means or the second detection means detects a density of the plurality of first toner images and a density of the second toner image transferred onto the recording medium;
7. The image forming condition is controlled by the control unit so as to adjust the density of each image based on a detection result of the first detection unit or the second detection unit. Image forming apparatus. Third detection means is further provided on the second image carrier,
The density of the second toner image can be detected also by the third detection means,
The image forming condition is controlled by the control means so as to adjust the density of each image based on a detection result of the first detection means, the second detection means, or the third detection means. 9. The image forming apparatus according to 8.   The image forming apparatus according to claim 1, wherein both the secondary transfer unit and the direct transfer unit are roll-shaped members.   The image forming apparatus according to claim 1, wherein the intermediate transfer member is an intermediate transfer belt stretched around a plurality of rollers.   12. The image forming apparatus according to claim 11, wherein the intermediate transfer belt is an elastic belt.   The detection means for detecting the positional deviation or density of the first toner image or the positional deviation or density of the second toner image is switched according to the type of the recording medium. The image forming apparatus according to 8 or 9.   The detection means for detecting the positional deviation or density of the first toner image or the positional deviation or density of the second toner image is switched according to the color of the recording medium. 14. The image forming apparatus according to 13.   The detection means for detecting the positional deviation or density of the first toner image or the positional deviation or density of the second toner image is switched according to the unevenness of the recording medium. 14. The image forming apparatus according to 13.

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