JP5024328B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image with a developer obtained by mixing toner particles (developer particles) in a carrier liquid.

  In general, an image forming apparatus that forms an image with a developer obtained by mixing toner particles in a nonvolatile carrier liquid is known (see, for example, Patent Document 1). In such an image forming apparatus, first, by a compaction roller, a corona discharger, or the like, the developer particles carried on the surface of the developing roller are discharged to aggregate toner particles contained in the developing solution on the surface of the developing roller, The developer on the developing roller is separated into a toner particle high concentration layer having a high toner particle concentration and a toner particle low concentration layer having a low toner particle concentration.

  In an image forming apparatus that forms a color image, it is difficult to completely align the characteristics of toner particles (developer) of each color. For this reason, the amount of the developer necessary for producing the same density on the paper may vary depending on the color of the toner particles. Further, since the toner particles of each color may have different charging characteristics, it is necessary to strongly agglomerate the toner particles of a specific color on the surface of the developing roller in order to prevent fogging with a developer containing the toner particles of a specific color. There may be. As a result, the thickness of the low-concentration toner particle layer on the developing roller differs depending on the color of the toner particles.

  The toner particles on the developing roller are supplied from the toner particle high-concentration layer onto the photosensitive drum on which the electrostatic latent image is formed, thereby forming a toner image. The toner image (toner particles) on the photosensitive drum is transferred to an intermediate transfer member, and further transferred from the intermediate transfer member to a sheet and thermally fixed. Thereby, an image is formed on the paper.

  In the image forming process as described above, a part of the carrier liquid contained in the developer moves together with the toner particles from the developing roller to the sheet via the photosensitive drum and the intermediate transfer member. Further, in the process of supplying the developer from the developing roller to the photosensitive drum and the intermediate transfer member, a part of the toner particle high-concentration layer and the toner particle low-concentration layer on the developing roller are partially a photosensitive drum and an intermediate The toner particles move to the transfer member, and a toner particle high concentration layer and a toner particle low concentration layer are formed on the surface of the photosensitive drum and the surface of the intermediate transfer member.

JP2007-121392A

  By the way, since the non-volatile carrier liquid is difficult to volatilize, there is a problem that if the amount of the carrier liquid that moves to the paper is large, the fixability of the toner particles is lowered. To solve this problem, for example, a roller that collects a part of the toner particle low-concentration layer (carrier liquid) on the intermediate transfer member is provided, and the amount of carrier liquid on the intermediate transfer member is reduced and moved to paper. A method of reducing the amount of carrier liquid to be used is conceivable. However, if such a roller is provided, the configuration of the apparatus becomes complicated and the cost increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reducing the amount of carrier liquid on an intermediate transfer member and improving the fixability with a simple configuration.

  As a result of intensive studies in order to achieve the above object, the present inventor has found that the thickness of the low-concentration toner particle layer (developer particle low-concentration layer) formed on the surface of the photoreceptor is determined by the developing roller (developer solution). The thickness of the low-concentration toner particle layer on the carrier is approximately half of the thickness, and the thickness of the low-concentration toner particle layer formed on the surface of the intermediate transfer body after the toner image is transferred is It has been found as an experimental fact that the thickness of the low-concentration layer of toner particles on the intermediate transfer body immediately before the transfer and the thickness of the low-concentration layer of toner particles on the surface of the photosensitive member is about half of the sum. It came to an eggplant.

That is, the image forming apparatus of the present invention is included in a developer carrying member that carries a developer obtained by mixing developer particles in a carrier solution on the surface, and a developer carried on the surface of the developer carrier. Aggregating means for aggregating the developer particles toward the surface of the developer carrying member and separating the developer carried on the surface of the developer carrying member into a developer particle high concentration layer and a developer particle low concentration layer; A plurality of image forming units each having a photosensitive drum on which a developer image is formed by developer particles supplied from the developer carrier, and disposed on the photosensitive drum, facing the photosensitive drum. An intermediate transfer body to which the developer image is transferred, wherein the plurality of image forming units are arranged in order of increasing thickness of the developer particle low-concentration layer on the developer carrier . Transfer the developer image to the intermediate transfer member. Characterized in that the sea urchin arranged.

  According to the image forming apparatus configured as described above, the thickness of the low-concentration toner particle layer on the intermediate transfer body after the toner images are transferred from all the image forming units is changed to the toner particle on the developer carrier. Compared with the case where the image forming unit having the thickest low-density layer is arranged second and later, it can be made thinner.

In addition, the image forming apparatus of the present invention is included in a developer carrying member carrying a developer obtained by mixing developer particles in a carrier solution on the surface, and a developer carried on the surface of the developer carrying member. Aggregating means for aggregating the developer particles toward the surface of the developer carrying member and separating the developer carried on the surface of the developer carrying member into a developer particle high concentration layer and a developer particle low concentration layer; , A photosensitive drum on which a developer image is formed by developer particles supplied from the developer carrier, a reservoir for storing developer, and a developer from the reservoir to the developer carrier. Image forming comprising: a plurality of image forming units having at least one developer supplying member; and an intermediate transfer member that is arranged to face the photosensitive drum and onto which the developer image on the photosensitive drum is transferred. An apparatus, wherein the plurality of image shapes Unit, the order amount is large of the developer per unit is supplied to the developer carrying member time, characterized in that the developer image is arranged to transfer to the intermediate transfer member.

  According to the image forming apparatus configured as described above, the thickness of the low-concentration toner particle layer on the intermediate transfer body after the toner images are transferred from all the image forming units is supplied to the developer carrier. Compared with the case where the image forming unit having the largest amount of developer per unit time is arranged after the second, it can be made thinner.

In addition, the image forming apparatus of the present invention is included in a developer carrying member carrying a developer obtained by mixing developer particles in a carrier solution on the surface, and a developer carried on the surface of the developer carrying member. Aggregating means for aggregating the developer particles toward the surface of the developer carrying member and separating the developer carried on the surface of the developer carrying member into a developer particle high concentration layer and a developer particle low concentration layer; A plurality of image forming units each having a photosensitive drum on which a developer image is formed by developer particles supplied from the developer carrier, and disposed on the photosensitive drum, facing the photosensitive drum. of developer image an image forming apparatus having an intermediate transfer member to be transferred, said plurality of image forming units, aggregation means toward the developer particles on the surface of the developer carrying member agglomerating stronger turn having, before the developer image Characterized in that it is arranged to transfer to the intermediate transfer member.

  According to the image forming apparatus configured as described above, the thickness of the low-concentration toner particle layer on the intermediate transfer body after the toner images are transferred from all the image forming units is set to be the same as that of the developer carrier. Compared with the case where the image forming units having the aggregation means that strongly aggregates toward the surface are arranged at the second and subsequent positions, the thickness can be reduced.

  As described above, by reducing the thickness of the low-concentration toner particle layer on the intermediate transfer body after the toner images are transferred from all the image forming units, the amount of carrier liquid that moves to the paper can be reduced. Therefore, the fixing property of the toner particles can be improved. Further, according to the present invention, the amount of the carrier liquid that moves to the sheet can be reduced depending on the arrangement order of the image forming units, so that the configuration of the image forming apparatus is not complicated.

  According to the image forming apparatus of the present invention, since the amount of carrier liquid on the intermediate transfer member can be reduced with a simple configuration, the amount of carrier liquid that moves to the sheet can be reduced, and as a result, the fixability is improved. Can do.

1 is a cross-sectional view of a color printer as an example of an image forming apparatus according to an embodiment of the present invention. It is an enlarged view of an image forming unit. An explanatory diagram (a) illustrating the aggregation of toner particles contained in the developer, an explanatory diagram (b) when the voltage applied to the discharge wire is larger than (a), and a supply to the developing roller from (a). It is explanatory drawing (c) at the time of increasing the quantity of the developing solution. It is explanatory drawing explaining the movement of a carrier liquid layer.

<Overall configuration of color printer>
Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, the direction will be described based on the user who uses the color printer. That is, the right side in FIG. 1 is “front”, the left side is “rear”, the front side is “left”, and the back side is “right”. Also, the vertical direction in FIG.

  As shown in FIG. 1, a color printer 1 as an example of an image forming apparatus includes a paper feeding unit 30, four LED units 40, four image forming units 50, and a transfer unit 60 in a main body housing 10. And a fixing unit 70.

  The paper feed unit 30 is provided in the lower part of the main body housing 10, and a paper feed tray 31 that accommodates the paper S, and a transfer position P (intermediate transfer belt 63 and secondary transfer roller 65 from the paper feed tray 31. The paper feeding mechanism 32 is mainly provided. The sheets S in the sheet feeding tray 31 are separated one by one by the sheet feeding mechanism 32 and conveyed to the transfer position P.

  The LED unit 40 is arranged to face the lower side of the photosensitive drum 51, and a plurality of light emitting units (LEDs) (not shown) are arranged at the tip in the axial direction (left-right direction) of the photosensitive drum 51. The LED unit 40 blinks the light emitting portion based on the image data to expose the surface of the photosensitive drum 51 that is uniformly charged by the charger 52, and the static electricity based on the image data is exposed on the photosensitive drum 51. An electrostatic latent image is formed.

  The image forming unit 50 is arranged side by side above the sheet feeding unit 30 and is an example of a photosensitive drum 51, a charger 52, a reservoir 53 for storing the developer DL, and a developer supply member. The apparatus mainly includes a supply roller 54 and an intermediate roller 55, a developing roller 56 as an example of a developer carrier, and a corona discharger 57 as an example of aggregating means.

  The developer DL in the reservoir 53 is supplied to the developing roller 56 via the supply roller 54 and the intermediate roller 55 and is carried on the surface of the developing roller 56. The developer DL (toner particles T) carried on the surface of the developing roller 56 is supplied from the developing roller 56 to the electrostatic latent image on the photosensitive drum 51. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 51.

  The developer DL of the present embodiment is a mixture of positively charged toner particles T (developer particles) and a non-volatile carrier liquid C (see FIG. 3). Each image forming unit 50 is different in only the color of the toner particles T in the developer DL stored in the storage unit 53, and the configuration is substantially the same. Details of each part of the image forming unit 50 will be described later.

  The transfer unit 60 is provided above the image forming unit 50, is stretched between the driving roller 61, the driven roller 62, and the driving roller 61 and the driven roller 62, and is disposed so as to face each photosensitive drum 51. The endless intermediate transfer belt 63 (intermediate transfer member), four primary transfer rollers 64 arranged to face the photosensitive drum 51 with the intermediate transfer belt 63 interposed therebetween, and a driving roller 61 with the intermediate transfer belt 63 interposed therebetween. And a secondary transfer roller 65 disposed to face each other.

  The toner images of the respective colors formed on the photosensitive drums 51 are sequentially superimposed and transferred onto the intermediate transfer belt 63. The sheet S conveyed from the sheet feeding unit 30 passes between the intermediate transfer belt 63 and the secondary transfer roller 65 (transfer position P), so that the toner image on the intermediate transfer belt 63 is transferred to the sheet S. Transcribed.

  The fixing unit 70 is provided on the upper rear side of the transfer unit 60 and mainly includes a heating roller 71 and a pressure roller 72 that is disposed to face the heating roller 71 and presses the heating roller 71. The sheet S on which the toner image has been transferred passes between the heating roller 71 and the pressure roller 72 to thermally fix the toner image, and is discharged onto the paper discharge tray 12 by the discharge roller 73.

<Details of each part of image forming unit>
Next, details of each part of the image forming unit 50 will be described with reference to FIG.
The photosensitive drum 51 is configured by forming a photosensitive layer on the surface (outer peripheral surface) of a cylindrical drum body having conductivity. The cleaning blade 51B is in sliding contact with the downstream side of the position in contact with the intermediate transfer belt 63 in the rotation direction of the photosensitive drum 51. The developer DL remaining without being supplied to the intermediate transfer belt 63 is scraped off and collected by the cleaning blade 51B and stored in a waste developer tank (not shown).

  The charger 52 is arranged to be opposed to the photosensitive drum 51 at a predetermined interval so as not to contact the photosensitive drum 51, and is configured to uniformly charge the surface of the photosensitive drum 51 by discharging electric charges to the photosensitive drum 51. Has been.

  The reservoir 53 stores the developer DL supplied from a known concentration adjusting unit 80 that adjusts the concentration of the developer DL (weight ratio of the toner particles T to the carrier liquid C).

  The supply roller 54 is a metal roller that rotates to carry the developer DL stored in the storage unit 53 on the surface and supply the developer DL to the intermediate roller 55.

  The intermediate roller 55 (also called an anilox roller) is a metal roller configured to be able to carry a predetermined amount of developer DL in a groove formed on the surface. By supplying the developer DL to the developing roller 56 via the intermediate roller 55, the supply amount of the developer DL to the developing roller 56 can be kept uniform. A liquid amount regulating blade 55B that scrapes off the developer DL adhering to the surface of the intermediate roller 55 is in sliding contact with the downstream side of the position in contact with the supply roller 54 in the rotation direction of the intermediate roller 55.

  The developing roller 56 is a roller that rotates while carrying the developer DL supplied from the intermediate roller 55 on its surface, and supplies the developer DL (toner particles T) to the photosensitive drum 51. The cleaning blade 56B is in sliding contact with the downstream side of the position in contact with the photosensitive drum 51 in the rotation direction of the developing roller 56. The developer DL remaining without being supplied to the photosensitive drum 51 is scraped off and collected by the cleaning blade 56B, returned to the density adjusting unit 80, and reused.

  As shown in FIG. 3A, the corona discharger 57 is disposed to face the developing roller 56 at a predetermined interval so as not to contact the developing roller 56, and is stretched along the axial direction (left-right direction) of the developing roller 56. The discharge wire 57A is mainly provided. The corona discharger 57 applies a voltage to the discharge wire 57 </ b> A to generate corona discharge, thereby discharging electric charge to the developer carried on the surface of the developing roller 56.

  As a result, the toner particles T contained in the developer are aggregated so as to be pressed toward the surface of the developing roller 56, and the developer carried on the surface of the developing roller 56 has a high concentration (weight ratio) of the toner particles T. The toner particles are separated into a high concentration layer of toner particles and a low concentration layer of toner particles having a low concentration of toner particles T.

  In the following, for convenience of explanation, the toner particle high-concentration layer is referred to as a toner particle layer TL, and the toner particle low-concentration layer is referred to as a carrier liquid layer CL. The toner particles T are mixed with the carrier liquid C only by the difference (the carrier liquid layer CL in FIGS. 3A to 3C does not show the toner particles T).

<Order of image forming units>
Next, the arrangement order of the plurality of image forming units 50, which is a feature of the present invention, will be described. In the following description, the arrangement order of the plurality of image forming units 50 is the image formation in which the toner image is first transferred after the intermediate transfer belt 63 rotating in the direction of the arrow shown in FIG. Assume that the units 50 (50A) are counted in order.

  Accordingly, in the present embodiment, the image forming unit 50A disposed at the foremost side in FIG. 1 is the first, and hereinafter, the image forming unit 50B is the second along the rotation direction of the intermediate transfer belt 63, and the image forming unit. 50C is the third, and the image forming unit 50D arranged on the rearmost side is the fourth.

  In the four image forming units 50 (50A to 50D), the image forming unit 50A having the thickest carrier liquid layer CL on the developing roller 56 is the first (first) intermediate toner image on the photosensitive drum 51. It arrange | positions so that it may transfer to the transfer belt 63. FIG.

  Specifically, in the present embodiment, among the image forming units 50 </ b> A to 50 </ b> D, the image forming unit 50 </ b> A having the corona discharger 57 that strongly aggregates the toner particles T toward the surface of the developing roller 56 is the first toner. It is arranged on the foremost side so as to transfer the image to the intermediate transfer belt 63.

  In the image forming unit 50A, the voltage (absolute value) applied to the corona discharger 57 (discharge wire 57A) is set to be the largest. The image forming units 50B to 50D are set such that voltages applied to the discharge wire 57A are substantially equal to each other and smaller than the image forming unit 50A. Thus, by setting the voltage applied to the discharge wire 57A of the image forming unit 50A to be larger than that of the image forming units 50B to 50D, the thickness of the carrier liquid layer CL on the developing roller 56 of the image forming unit 50A can be adjusted. It becomes thicker than the thickness of the carrier liquid layer CL on the developing roller 56 of the forming units 50B to 50D.

  Specifically, as shown in FIG. 3B, by increasing the voltage applied to the discharge wire 57A, the amount of charge given to the developer DL carried on the surface of the developing roller 56 increases, and the toner The particles T are strongly aggregated toward the surface of the developing roller 56. Accordingly, the thickness of the toner particle layer TL is reduced as compared with the case of FIG. 3A, and as a result, the thickness of the carrier liquid layer CL on the developing roller 56 is increased.

  In this embodiment, as a result of the aggregation of the toner particles T by the corona discharger 57, the thickness of the carrier liquid layer CL on the developing roller 56 is approximately 4.0 μm in the image forming unit 50A, and the developing is performed in the image forming units 50B to 50D. The thickness of the carrier liquid layer CL on the roller 56 is about 3.0 μm.

<Operation and effect of the color printer 1>
Next, functions and effects of the color printer 1 will be described with reference to FIG.
In FIG. 4, for convenience of explanation, the toner particle layer TL is not shown, but the toner particle layer TL (toner particle T) is exposed from the developing roller 56 to the exposed portion (on the photosensitive drum 51). It is transferred to the portion exposed by the laser beam.

  More specifically, on the photosensitive drum 51, a toner particle layer TL (toner image) and a carrier liquid layer CL are formed in order from the surface side on the exposed portion exposed by the laser beam, and the carrier liquid layer CL is formed on the non-exposed portion. Only formed.

  Table 1 shows the arrangement order of the image forming units 50 </ b> A to 50 </ b> D and the thickness of the carrier liquid layer CL formed on the developing roller 56, the photosensitive drum 51, and the intermediate transfer belt 63, and FIG. FIG. 4B shows the result of arrangement of the image forming units 50A to 50D, and FIG. 5B shows the result when the order of the image forming units 50A and 50D is reversed (comparative example).

The conditions in Tables 1 (A) and (B) are as follows.
(1) Developing roller Developer thickness: 6 μm
Development bias: 750V (image forming unit 50A)
600V (image forming units 50B to 50D)
(In order to equalize the density of the toner images transferred to the paper S.)
(2) Discharge wire Applied voltage: 4.0 kV (image forming unit 50A)
3.7 kV (image forming units 50B to 50D)
(3) Photosensitive drum surface potential: 1000 V (unexposed portion)
140V (exposure section)
(4) Transfer roller Transfer bias: -1000V

  As shown in FIG. 4 and Table 1 (A), the thickness of the carrier liquid layer CL1 on the developing roller 56 of the image forming unit 50A is 4.0 μm. Half of the carrier liquid layer CL1 moves to the surface of the photosensitive drum 51 as an experimental fact to form a carrier liquid layer CL2 having a thickness of 2.0 μm. At this time, a toner particle layer TL (toner image) moved from above the developing roller 56 is also formed on the exposed portion of the photosensitive drum 51 (not shown).

  The remaining half of the carrier liquid layer CL1 on the developing roller 56 of the image forming unit 50A remains as the carrier liquid layer CL3 on the developing roller 56, and is scraped and collected by the cleaning blade 56B.

  A part of the carrier liquid layer CL2 formed on the photoconductive drum 51 of the image forming unit 50A is transferred to the surface of the intermediate transfer belt 63 together with the toner particle layer TL (toner image) of the exposure portion, and the carrier liquid layer CL4. Form.

  At this time, the thickness of the carrier liquid layer CL formed on the intermediate transfer belt 63 after the carrier liquid layer CL (toner image) is transferred is formed on the intermediate transfer belt 63 just before the toner image is transferred. It is known from experimental facts that it is half the sum of the thickness of the carrier liquid layer CL and the thickness of the carrier liquid layer CL on the photosensitive drum 51.

  Accordingly, the thickness of the carrier liquid layer CL4 is equal to the thickness (0 μm) of the carrier liquid layer CL on the intermediate transfer belt 63 just before the toner image is transferred from the image forming unit 50A and the carrier liquid on the photosensitive drum 51. It becomes 1.00 μm which is a half of the sum of the thickness of the layer CL2 (2.0 μm).

  The remainder of the carrier liquid layer CL2 on the photosensitive drum 51 of the image forming unit 50A remains on the photosensitive drum 51 as the carrier liquid layer CL5, and is scraped and collected by the cleaning blade 51B.

  The thickness of the carrier liquid layer CL6 on the developing roller 56 of the image forming unit 50B (the same applies to the image forming units 50C and 50D) is 3.0 μm. Half of the carrier liquid layer CL6 moves to the surface of the photosensitive drum 51 to form a carrier liquid layer CL7 having a thickness of 1.5 μm, and the other half remains on the developing roller 56 as the carrier liquid layer CL8. It is collected by the blade 56B.

  A part of the carrier liquid layer CL7 on the photosensitive drum 51 of the image forming unit 50B is transferred to the surface of the intermediate transfer belt 63 together with the toner image to form a carrier liquid layer CL9. At this time, the thickness of the carrier liquid layer CL9 is the same as the thickness (1.00 μm) of the carrier liquid layer CL4 on the intermediate transfer belt 63 before the toner image is transferred from the image forming unit 50B, and on the photosensitive drum 51. The thickness of the carrier liquid layer CL7 is 1.25 μm, which is half the sum of the thickness (1.5 μm).

  The remaining carrier liquid layer CL7 on the photosensitive drum 51 of the image forming unit 50B remains as the carrier liquid layer CL10 on the photosensitive drum 51 and is collected by the cleaning blade 51B, as in the case of the image forming unit 50A. The

  Hereinafter, the thickness of the carrier liquid layer CL on the intermediate transfer belt 63 after the carrier liquid layer CL (toner image) on the photosensitive drum 51 of the image forming unit 50C is transferred is determined by the thickness of the toner image from the image forming unit 50C. The thickness (1.25 μm) of the carrier liquid layer CL9 on the intermediate transfer belt 63 before transfer and the thickness (1.5 μm) of the carrier liquid layer CL on the photosensitive drum 51 of the image forming unit 50C. It is 1.38 μm which is half of the sum.

  Further, after the carrier liquid layer CL (toner image) on the photosensitive drum 51 of the image forming unit 50D is transferred, that is, after all the toner images are transferred, the carrier liquid layer CL on the intermediate transfer belt 63 is transferred. The thickness is the thickness (1.38 μm) of the carrier liquid layer CL on the intermediate transfer belt 63 before the toner image is transferred from the image forming unit 50D, and the carrier liquid on the photosensitive drum 51 of the image forming unit 50D. It becomes 1.44 μm, which is half of the sum of the thickness of the layer CL (1.5 μm).

  On the other hand, as shown in Table 1 (B), when the order of the image forming units 50A and 50D is reversed, that is, when the image forming unit 50A is arranged in the fourth (last) position, all the toner images are transferred. The thickness of the carrier liquid layer CL on the intermediate transfer belt 63 is 1.66 μm.

  In this manner, by arranging the image forming unit 50A first, the thickness of the carrier liquid layer CL on the intermediate transfer belt 63 after all the toner images are transferred is arranged at the end of the image forming unit 50A. Compared to the case, the thickness can be reduced by about 13%. Thereby, the amount of the carrier liquid C on the intermediate transfer belt can be reduced.

  The carrier liquid C on the intermediate transfer belt 63 after all the toner images are transferred moves to the paper S at the transfer position P (see FIG. 1). Therefore, by reducing the amount of the carrier liquid C on the intermediate transfer belt after all the toner images have been transferred, the amount of the carrier liquid C that moves to the paper S can be reduced. Fixability of the toner image (toner particles T) can be improved.

  In the present embodiment, the amount of the carrier liquid C that moves to the paper S can be reduced simply by arranging the image forming unit 50A first, so that the configuration of the color printer 1 is not complicated.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention.

  In the above embodiment, the configuration in which the image forming unit 50A having the highest voltage applied to the corona discharger 57 (discharge wire 57A) is first arranged is exemplified, but the present invention is not limited to this. For example, an image forming unit having the largest amount of developer DL per unit time (hereinafter referred to as supply amount) supplied to the developing roller 56 may be arranged first. The thickness of the carrier liquid layer CL on the developing roller 56 of the image forming unit having the largest supply amount is thicker than the thickness of the carrier liquid layer CL on the developing roller 56 of another image forming unit.

  Specifically, as shown in FIG. 3 (c), since the thickness of the developer DL carried on the developing roller 56 is increased by increasing the supply amount, the toner particle layer after the charge is applied. Even if the thickness of TL is the same as that in FIG. 3A, the thickness of the carrier liquid layer CL is relatively large. Therefore, the fixing property of the toner particles T transferred to the paper S can be improved by arranging the image forming unit having the largest supply amount first, as in the embodiment.

  Note that the amount (supply amount) of the developer DL per unit time supplied to the developing roller 56 is applied to the intermediate roller 55 by changing the depth of a groove formed on the surface of the intermediate roller 55, for example. It changes by changing the bias.

  Further, depending on the type (color, etc.) of the toner particles T to be used, even if the voltage applied to the corona discharger 57 is the same, the toner particles T are more strongly aggregated on the surface of the developing roller 56 than the other toner particles T, so The thickness of the carrier liquid layer CL on 56 may increase. Therefore, the toner particles T transferred to the paper S can also be arranged by first arranging an image forming unit that uses the developer DL containing the toner particles T that are more strongly aggregated than the other as described above. The fixing property can be improved.

  In the above embodiment, the arrangement order of the second and subsequent image forming units 50B to 50D is not particularly described. However, in the image forming units 50A to 50D, the carrier liquid layer CL on the developing roller 56 is thick. In order, it is desirable to arrange the toner images so as to be transferred onto the intermediate transfer belt 63.

  Tables 2 (A) to (C) below show the order of arrangement of the image forming units 50A to 50D and the thickness of the carrier liquid layer CL formed on the developing roller 56, the photosensitive drum 51, and the intermediate transfer belt 63. (A) shows the case where the carrier liquid layer CL is arranged in order from the thickest, and (B) shows the case where the second and subsequent layers are arranged in order from the thinnest carrier liquid layer CL (Comparative Example). (C) is a case where the second and third of (A) are interchanged (comparative example).

  As shown in Tables 2 (A) and 2 (B), the carrier liquid layer on the intermediate transfer belt 63 after all the toner images are transferred by arranging the carrier liquid layer CL in order from the thickest one. The thickness of CL (1.58 μm) should be reduced compared to the case where the second and subsequent image forming units 50B to 50D are arranged in order from the smallest carrier liquid layer CL (1.77 μm). Can do.

  Further, as shown in Tables 2 (A) and 2 (C), by arranging the carrier liquid layer CL in order from the thickest one, the carrier on the intermediate transfer belt 63 after all the toner images are transferred. The thickness (1.58 μm) of the liquid layer CL can be made thinner than when the second and third image forming units 50B and 50C are exchanged (1.61 μm).

  Thus, by arranging the carrier liquid layer CL in order from the thickest one, the thickness of the carrier liquid layer CL on the intermediate transfer belt 63 after all the toner images are transferred can be reduced. The amount of carrier liquid C on the intermediate transfer belt after the toner image is transferred can be reduced. As a result, the amount of the carrier liquid C that moves to the paper S can also be reduced, so that the fixability of the toner particles T transferred to the paper S can be improved.

  As a specific method of arranging the image forming units 50A to 50D in order from the thickest carrier liquid layer CL on the developing roller 56, for example, on the developing roller 56 of each of the image forming units 50A to 50D in advance. The thickness of the carrier liquid layer CL may be measured, and may be arranged in order based on the result.

  Further, the image forming units 50A to 50D have a corona discharger 57 (a corona discharger 57 with a large voltage applied to the discharge wire 57A) that causes the toner particles T to aggregate more strongly toward the surface of the developing roller 56. You may arrange in order. Furthermore, the image forming units 50 </ b> A to 50 </ b> D may be arranged in order from the largest amount of the developer DL per unit time supplied to the developing roller 56.

  In the above-described embodiment, the corona discharger 57 is illustrated as the aggregating unit and is disposed to face the developing roller 56 (developer carrying member) with a predetermined interval therebetween, but the present invention is not limited thereto. It is not something. For example, it may be a roller that rotates while being in contact with the developer carrying member and discharges electric charges to the developer carried on the surface of the developer carrying member by applying a voltage.

  In the embodiment, the two developer supplying rollers (the supply roller 54 and the intermediate roller 55) are exemplified as the developer supplying member. However, the present invention is not limited to this, and for example, one or three or more developing members It is good also as a structure which consists of a roller for liquid supply.

In the embodiment, the intermediate transfer belt 63 is exemplified as the intermediate transfer member. However, the present invention is not limited to this, and may be, for example, a roller-shaped intermediate transfer member.
In the above embodiment, the color printer 1 is exemplified as the image forming apparatus. However, the present invention is not limited to this, and may be, for example, a copying machine or a multifunction machine.

DESCRIPTION OF SYMBOLS 1 Color printer 50 Image forming unit 50A Image forming unit 51 Photosensitive drum 53 Storage part 54 Supply roller 55 Intermediate roller 56 Developing roller 57 Corona discharger 63 Intermediate transfer belt C Carrier liquid CL Carrier liquid layer DL Developer liquid T Toner particle TL Toner Particle layer

Claims (3)

A developer carrying body carrying a developer obtained by mixing developer particles in a carrier liquid on the surface, and developer particles contained in the developer carried on the surface of the developer carrying body are formed on the developer carrying body. Aggregating means for aggregating toward the surface and separating the developer carried on the surface of the developer carrying member into a developer particle high concentration layer and a developer particle low concentration layer, and supplied from the developer carrying member A plurality of image forming units having a photosensitive drum on which a developer image is formed by developer particles;
An image forming apparatus provided with an intermediate transfer member that is disposed to face the photosensitive drum and onto which a developer image on the photosensitive drum is transferred;
The plurality of image forming units are arranged so as to transfer developer images to the intermediate transfer member in order of increasing thickness of the developer particle low-concentration layer on the developer carrier. Forming equipment. A developer carrying body carrying a developer obtained by mixing developer particles in a carrier liquid on the surface, and developer particles contained in the developer carried on the surface of the developer carrying body are formed on the developer carrying body. Aggregating means for aggregating toward the surface and separating the developer carried on the surface of the developer carrying member into a developer particle high concentration layer and a developer particle low concentration layer, and supplied from the developer carrying member A photosensitive drum on which a developer image is formed by developer particles; a reservoir for storing developer; and at least one developer supply member for supplying developer from the reservoir to the developer carrier. A plurality of image forming units;
An image forming apparatus provided with an intermediate transfer member that is disposed to face the photosensitive drum and onto which a developer image on the photosensitive drum is transferred;
The plurality of image forming units are arranged to transfer developer images to the intermediate transfer member in descending order of the amount of developer supplied per unit time to the developer carrier. Image forming apparatus. A developer carrying body carrying a developer obtained by mixing developer particles in a carrier liquid on the surface, and developer particles contained in the developer carried on the surface of the developer carrying body are formed on the developer carrying body. Aggregating means for aggregating toward the surface and separating the developer carried on the surface of the developer carrying member into a developer particle high concentration layer and a developer particle low concentration layer, and supplied from the developer carrying member A plurality of image forming units having a photosensitive drum on which a developer image is formed by developer particles;
An image forming apparatus provided with an intermediate transfer member that is disposed to face the photosensitive drum and onto which a developer image on the photosensitive drum is transferred;
The plurality of image forming units are arranged so as to transfer the developer images to the intermediate transfer member in order of aggregation means for causing the developer particles to aggregate more strongly toward the surface of the developer carrier. An image forming apparatus.

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