JP6819747B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

In Patent Document 1, after a toner image formed of golden toner is transferred to an intermediate transfer body, a toner image formed of at least one color of toner other than the golden toner is superimposed and transferred on the golden toner image. An image forming apparatus for transferring a superposed toner image onto paper is disclosed.

Japanese Unexamined Patent Publication No. 2006-317633

As an image forming apparatus, the first image is formed with a first toner containing a flat pigment formed of a metal or a metal oxide, and the maximum of the first toner does not contain a flat pigment formed of a metal or a metal oxide. There is a device that forms a second image with a second toner whose maximum length is smaller than its length.

In this apparatus, since the flat pigment has conductivity, when the first image is transferred from the forming portion including the photoconductor or the like to a medium such as an intermediate transfer body, charge injection may occur in the flat pigment. When charge injection occurs in the pigment, the flat toner may be reversed polarity and retransferred to the forming portion. In this case, the transfer rate when the first image is transferred from the forming portion to the medium is reduced.

In particular, in an image forming apparatus that transfers the first image and the second image to a medium in this order, charge injection may occur in the flat pigment during the transfer of the first image and the transfer of the second image. , The transfer rate when the first image is transferred from the forming part to the medium can be further reduced.

An object of the present invention is to suppress a decrease in the transfer rate when the first image is transferred from the forming portion to the medium as compared with the case where the first image and the second image are transferred to the medium in this order.

The invention of claim 1 forms a first image with a first toner containing a flat pigment formed of a metal or a metal oxide, and does not contain a flat pigment formed of a metal or a metal oxide and the first toner. A second image is formed with a second toner having a maximum length smaller than the maximum length of the second toner, and a third image is formed with a third toner containing no flat pigment and having a maximum length smaller than the maximum length of the second toner. An image forming apparatus including a forming unit and a transfer unit that transfers the third image, the second image, and the first image to a medium in this order.

The invention of claim 2 is the image forming apparatus according to claim 1, wherein the forming portion forms the second image with the second toner containing a spherical pigment formed of a metal or a metal oxide.

The invention of claim 3 forms a first image with a first toner containing a flat pigment formed of a metal or a metal oxide, and does not contain a flat pigment formed of a metal or a metal oxide and the first toner. A second image is formed with a second toner containing a first pigment having a volume average particle size smaller than the volume average particle size of the flat pigment, and the flat pigment and the first pigment are not contained and the second toner is formed. A forming portion that forms a third image with a third toner containing a second pigment having a volume average particle size smaller than the volume average particle size of the first pigment, and the third image, the second image, and the first. An image forming apparatus including a transfer unit for transferring one image to a medium in this order.

The third aspect of the present invention is the third aspect of the present invention, wherein the forming portion forms the second image with the second toner containing a spherical pigment as the first pigment formed of a metal or a metal oxide. It is an image forming apparatus.

In the first aspect, the first image is formed with a first toner containing a flat pigment formed of a metal or a metal oxide, and the maximum of the first toner does not contain a flat pigment formed of a metal or a metal oxide. An image forming apparatus including a forming portion for forming a second image with a second toner having a maximum length smaller than the length, and a transfer portion for transferring the second image and the first image to a medium in this order.

A second aspect is the image forming apparatus according to the first aspect, wherein the forming portion forms the second image with the second toner containing a spherical pigment formed of a metal or a metal oxide.

In the third aspect, the forming portion forms a third image with a third toner that does not contain the flat pigment and the spherical pigment and has a maximum length smaller than the maximum length of the second toner, and the transfer portion forms the third image. The image forming apparatus according to a second aspect, in which the third image, the second image, and the first image are transferred to a medium in this order.

In the fourth aspect, the first image is formed with a first toner containing a flat pigment formed of a metal or a metal oxide, and the flat pigment of the first toner is not contained and the flat pigment is formed of a metal or a metal oxide. A forming portion that forms a second image with a second toner containing a pigment having a volume average particle diameter smaller than the volume average particle diameter of the pigment, and a transfer portion that transfers the second image and the first image to a medium in this order. An image forming apparatus comprising.

A fifth aspect is the image forming apparatus according to the fourth aspect, wherein the forming portion forms the second image with the second toner containing a spherical pigment as the pigment formed of a metal or a metal oxide.

A sixth aspect is a third toner in which the forming portion contains a pigment that does not contain the flat pigment and the spherical pigment and has a volume average particle diameter smaller than the volume average particle diameter of the spherical pigment of the second toner. The transfer unit is an image forming apparatus according to a fifth aspect, which forms an image and transfers the third image, the second image, and the first image to a medium in this order.

According to the configurations of claims 1 and 3 of the present invention, as compared with the case where the first image and the second image are transferred to the medium in this order, the transfer when the first image is transferred from the forming portion to the medium. The decrease in rate can be suppressed. Further, according to the configurations of claims 1 and 3, the second image is transferred from the forming portion to the medium as compared with the case where the second image is transferred to the medium before the third image. It is possible to suppress a decrease in the transcription rate of.

According to the configurations of claims 2 and 4 of the present invention, it is possible to form an image expressed by combining colors of a spherical pigment formed of a metal or a metal oxide, and to make a first image and a second image. Compared with the case of sequentially transferring to a medium, it is possible to suppress a decrease in the transfer rate when the first image is transferred from the forming portion to the medium.

It is the schematic which shows the image forming apparatus which concerns on this embodiment. It is a schematic diagram which shows the image formation unit which concerns on this embodiment. It is a top view and the side view of the flat pigment contained in silver toner. It is a top view and a side view of a silver toner. It is a top view and a side view of a spherical pigment contained in a white toner. It is a top view and a side view of a white toner. It is a top view and a side view of the pigment contained in a color toner. It is a top view and a side view of a color toner. It is a side view which shows the silver toner, the white toner and the color toner. It is a schematic diagram which shows the image forming apparatus which concerns on a comparative example. It is a side view which shows the behavior of a silver toner. It is a schematic diagram which shows the behavior of a silver toner at a primary transfer position. It is a figure for demonstrating the measurement of the transfer rate. It is a graph which shows the measurement result of the transfer rate. It is a table which shows the evaluation result. It is a schematic diagram which shows the image forming apparatus which concerns on the 1st modification which includes a rotary developing apparatus. It is the schematic which shows the image forming apparatus which concerns on the 2nd modification of a direct transfer type.

An example of the embodiment according to the present invention will be described below with reference to the drawings. The arrow H shown in each figure indicates the vertical direction, and the arrow W indicates the horizontal direction and the device width direction.

(Image forming apparatus 10)
First, the configuration of the image forming apparatus 10 will be described. FIG. 1 is a schematic view showing a configuration in which the image forming apparatus 10 is viewed from the front side.

The image forming apparatus 10 is an apparatus for forming an image on a recording medium P such as paper by an electrophotographic method, and is a tandem type image forming device. Specifically, as shown in FIG. 1, the image forming apparatus 10 records a toner image forming unit 12 (an example of forming unit) for forming a toner image and a toner image formed by the toner image forming unit 12. A transfer device 30 for transferring to the medium P is provided. Further, the image forming apparatus 10 includes a fixing device 40 that heats and pressurizes the toner image transferred to the recording medium P and fixes it on the recording medium P, and a conveying device 50 that conveys the recording medium P. Hereinafter, specific configurations of the transport device 50, the toner image forming unit 12, the transfer device 30, and the fixing device 40 will be described.

(Transport device 50)
As shown in FIG. 1, the transfer device 50 includes a container 51 in which the recording medium P is housed, and a plurality of transfer rolls 52 for transporting the recording medium P from the container 51 to the secondary transfer position NT. doing. Further, the transport device 50 includes a plurality of transport belts 58 for transporting the recording medium P from the secondary transfer position NT to the fixing device 40, and the recording medium P from the fixing device 40 toward the discharging unit (not shown) of the recording medium P. It has a transport belt 54 for transporting the above.

(Toner image forming unit 12)
As shown in FIG. 1, the toner image forming unit 12 displays toner images of each color of yellow (Y), magenta (M), cyan (C), black (K), white (W), and silver (V). It has image forming units 20Y, 20M, 20C, 20K, 20W, and 20V (image forming unit) to be formed. The image forming units 20Y, 20M, 20C, 20K, 20W, and 20V (hereinafter referred to as 20Y to 20V) are arranged in this order from the upstream side to the downstream side of the transfer belt 31 described later in the transport direction. ..

(Y), (M), (C), (K), (W), and (V) shown in FIG. 1 indicate components corresponding to the above colors. In the description of the present specification, (Y), (M), (C), (K), (W), and (V) are added to the reference numerals when the colors are distinguished from each other. When adding (Y), (M), (C), (K), (W), (V) to the code, omit the parentheses and Y, M, C, K, W, V. May be described as. In the following, yellow (Y), magenta (M), cyan (C), and black (K) are collectively referred to as "color".

(Image forming unit 20)
The image forming unit 20 of each color is basically configured in the same manner except for the toner used. Specifically, as shown in FIG. 2, the image forming unit 20 of each color includes a photoconductor drum 21 that rotates in the clockwise direction in FIG. 2 and a charger 22 that charges the photoconductor drum 21. doing. Further, the image forming unit 20 of each color has an exposure device 23 that exposes the photoconductor drum 21 charged by the charger 22 to form an electrostatic latent image on the photoconductor drum 21, and a photoconductor drum 21 by the exposure device 23. It has a developing device 24 that develops an electrostatic latent image formed in the above to form a toner image.

Specifically, the exposure apparatus 36 irradiates the photoconductor drum 21 with exposure light modulated according to the image data to form an electrostatic latent image on the photoconductor drum 21. The electrostatic latent image is developed by the developing device 24 to form a toner image based on the image data. The image data includes, for example, image data generated by an external device (not shown) and acquired by the image forming device 10 from the external device.

Then, in the image forming unit 20V, a toner image (an example of the first image) is formed by using the silver toner 100 (see FIG. 4) as an example of the first toner. Hereinafter, for convenience of explanation, a toner image formed of silver toner is referred to as a “silver image”.

Further, in the image forming unit 20W, a toner image (an example of the second image) is formed by using the white toner 200 (see FIG. 6) as an example of the second toner. Hereinafter, for convenience of explanation, a toner image formed of white toner is referred to as a “white image”.

In the image forming units 20Y, 20M, 20C, and 20K (hereinafter referred to as 20Y to 20K), a color toner 300 (see FIG. 8) as an example of the third toner is used, and a toner image (an example of the third image) is used. To form. Hereinafter, for convenience of explanation, the toner image formed by the color color toner 300 will be referred to as a “color color image”. The specific configurations of the silver toner 100, the white toner 200, and the color toner 300 will be described later.

(Transfer device 30)
The transfer device 30 superimposes the toner image of the photoconductor drum 21 of each color on the transfer belt 31 (intermediate transfer body) for primary transfer, and transfers the superimposed toner image to the recording medium P at the secondary transfer position NT. It is designed to be transferred next. Specifically, as shown in FIG. 1, the transfer device 30 has a transfer belt 31 (an example of a medium) on which a toner image is transferred and the toner image is transferred to a recording medium P, and a primary transfer roll 33 (transfer unit). (Example)) and a secondary transfer roll 34.

(Transfer belt 31)
As shown in FIG. 1, the transfer belt 31 has an endless shape and is wound around a plurality of rolls 32 to determine its posture. In this embodiment, the transfer belt 31 has an inverted obtuse triangular posture that is long in the device width direction when viewed from the front. Of the plurality of rolls 32, the roll 32D shown in FIG. 1 functions as a drive roll that orbits the transfer belt 31 in the direction of arrow A by the power of a motor (not shown). The transfer belt 31 orbits in the direction of arrow A to convey the toner image of each color of the primary transfer from the primary transfer position T of each color to the secondary transfer position NT.

Further, among the plurality of rolls 32, the roll 32T shown in FIG. 1 functions as a tension applying roll that applies tension to the transfer belt 31. Of the plurality of rolls 32, the roll 32B shown in FIG. 1 functions as an opposing roll 32B of the secondary transfer roll 34. As described above, the opposite roll 32B is wound with the top portion of the transfer belt 31 having an obtuse-angled triangular posture on the lower end side. The transfer belt 31 is in contact with the photoconductor drum 21 of each color from below at the upper side portion extending in the device width direction in the above-mentioned posture.

(Primary transfer roll 33)
The primary transfer roll 33 is a roll that transfers the toner image of each photoconductor drum 21 to the transfer belt 31, and is arranged inside the transfer belt 31. Each primary transfer roll 33 is arranged to face the photoconductor drum 21 of the corresponding color with the transfer belt 31 interposed therebetween. Further, a primary transfer voltage (primary transfer current) having a polarity opposite to that of the toner polarity is applied to the primary transfer roll 33 by the feeding unit 37 (see FIG. 2). As a result, a transfer electric field is formed between the photoconductor drum 21 of the image forming unit 20 and the primary transfer roll 33, and an electrostatic force acts on the toner image formed on the photoconductor drum 21 to act on the toner image. Is transferred to the transfer belt 31 at the primary transfer position T.

In the present embodiment, the toner images of each color formed by the image forming units 20Y to 20V are transferred to the transfer belt 31 in the order of yellow, magenta, cyan, black, white, and silver by the primary transfer roll 33 of each color. Toner.

(Secondary transfer roll 34)
The secondary transfer roll 34 is a roll that transfers the toner image superimposed on the transfer belt 31 to the recording medium P. As shown in FIG. 1, the secondary transfer roll 34 is arranged so as to sandwich the transfer belt 31 between the secondary transfer roll 32 and the counter roll 32B, and the secondary transfer roll 34 and the transfer belt 31 have a predetermined load. Are in contact with. The position between the secondary transfer roll 34 and the transfer belt 31 that are in contact with each other in this way is defined as the secondary transfer position NT. The recording medium P is timely supplied from the container 51 to the secondary transfer position NT. The secondary transfer roll 34 is rotationally driven in the clockwise direction in FIG.

Further, a negative voltage is applied to the counter roll 32B by the feeding unit 80 to the secondary transfer roll 34, and a potential difference is generated between the counter roll 32B and the secondary transfer roll 34. That is, when a negative voltage is applied to the counter roll 32B, a secondary transfer voltage (positive voltage) having a polarity opposite to the toner polarity is indirectly applied to the secondary transfer roll 34 forming the counter electrode of the counter roll 32B. Is applied to. As a result, a transfer electric field is formed between the counter roll 32B and the secondary transfer roll 34, an electrostatic force acts on the toner image of the transfer belt 31, and the recording medium P passes through the secondary transfer position NT. , The toner image is transferred from the transfer belt 31.

(Fixing device 40)
The fixing device 40 has a configuration in which the toner image is fixed to the recording medium P by pressurizing the toner image while heating it in the fixing nip NF formed by the fixing roll 41 and the pressing roll 42.

(Silver toner 100)
As shown in FIG. 9A, the silver toner 100 (flat toner) is composed of the flat pigment 110 and the binder resin 120. The flat pigment 110 is made of aluminum (an example of a metal). A known resin material is used for the binder resin 120, and the binder resin 120 has a lower conductivity than the flat pigment 110.

As shown in FIG. 3B, when the flat pigment 110 is viewed from the side in a state where the flat pigment 110 is placed on the flat surface 500, the flat pigment 110 has a dimension X1 in the left-right direction and a dimension Y1 in the vertical direction. The shape is longer than that of the other.

Further, when the flat pigment 110 shown in FIG. 3 (B) is viewed from above, the flat pigment 110 has a shape that is wider than the shape viewed from the side as shown in FIG. 3 (A) and is flat. The pigment 110 has a pair of reflecting surfaces 110A facing upward and downward when the flat pigment 110 is placed on a flat surface 500 (see FIG. 3B). As described above, the flat pigment 110 has a flat shape.

Since the flat pigment 110 has a flat shape, the silver toner 100 containing the flat pigment 110 also has a flat shape following the flat pigment 110. Therefore, when the silver toner 100 is viewed from the side with the silver toner 100 placed on the flat surface 500, the silver toner 100 has vertical dimensions (A1) up and down as shown in FIG. 4 (B). The shape is longer than the dimension (C1) in the direction.

Further, when the silver toner 100 shown in FIG. 4 (B) is viewed from above, the silver toner 100 has a shape that is wider than the shape viewed from the side as shown in FIG. 4 (A). It has a circular shape (approximately elliptical shape).

The maximum length A1 (longest diameter) when the silver toner 100 is viewed from above, the orthogonal length B1 orthogonal to the maximum length A1, and the thickness C1 (vertical dimension) when the silver toner 100 is viewed from above. The relationship is A1 ≧ B1> C1.

The maximum length A1 can be obtained by magnifying observation using a color laser microscope "VK-9700" (manufactured by KEYENCE CORPORATION) and calculating the maximum length of the toner plane with image processing software.

The maximum length of the silver toner 100 is, for example, 6 μm or more and 16 μm or less.

It is desirable that the value of "thickness C1 / orthogonal length B1" is in the range of 0.001 or more and 0.500 or less. When the value of "thickness C1 / orthogonal length B1" is 0.001 or more, the strength of the toner is ensured, breakage due to stress during image formation is suppressed, and charging due to exposure of the pigment is performed. It is reduced and the resulting fog is suppressed. On the other hand, when the value of "thickness C1 / orthogonal length B1" is 0.500 or less, an excellent metallic luster can be obtained.

(White Toner 200)
As shown in FIG. 9B, the white toner 200 is composed of a spherical pigment 210 and a binder resin 220. The spherical pigment 210 is made of titanium oxide (an example of a metal oxide). A known resin material is used for the binder resin 220, and the binder resin 220 has a lower conductivity than the spherical pigment 210.

When the spherical pigment 210 is placed on the flat surface 500, the spherical pigment 210 has the left-right dimension X2 and the front-rear dimension Z2 when viewed from above as shown in FIG. 5 (A), and FIG. 5 (B). The horizontal dimension X2 and the vertical dimension Y2 when viewed from the side shown in the above are equivalent.

Therefore, in the spherical pigment 210, the dimensional ratio between the horizontal dimension X2 and the vertical dimension Y2 when viewed from the side shown in FIG. 5B is smaller than the dimensional ratio in the flat pigment 110. There is. That is, the spherical pigment 210 has a shape closer to a spherical shape than the flat pigment 110.

The white toner 200 containing the spherical pigment 210 also has a spherical shape like the spherical pigment 210. Therefore, when the white toner 200 is placed on the flat surface 500, the white toner 200 has the left-right dimension A2 and the front-rear dimension B2 when viewed from above as shown in FIG. 6 (A), and FIG. 6 (A). The horizontal dimension A2 and the vertical dimension C2 when viewed from the side shown in B) are considered to be equivalent.

The maximum length of the white toner 200 is shorter than the maximum length A1 of the silver toner 100. The maximum length of the white toner 200 is such that the white toner 200 is regarded as a spherical shape and the volume average particle diameter of the white toner 200 is the maximum length.

The volume average particle diameter is measured using, for example, a measuring instrument such as a Coulter counter TAII (manufactured by Nikkaki Co., Ltd.) or a multisizer II (manufactured by Nikkaki Co., Ltd.). Specifically, for the particle size range (channel) divided based on the particle size distribution measured by the measuring instrument, the cumulative distribution is drawn from the small diameter side on a volume basis, and the cumulative particle size (D50v) is 50%. Was defined as the volume average particle size. The following volume average particle diameters are also measured in the same manner.

The volume average particle size of the spherical pigment 210 is about 200 to 300 nm. This is larger than the pigment 310 in the color toner 300, but much smaller than the flat pigment 110 described above.
The volume average particle size of the white toner 200 is 4 μm or more and 14 μm or less, more preferably 5 μm or more and 12 μm or less, and further preferably 6 μm or more and 10 μm or less. If this volume average particle size exceeds 14 μm, good chargeability (charge amount and charge distribution) and its appropriate chargeability cannot be maintained for a long period of time, and fine dot reproducibility and gradation , The effect of improving graininess becomes poor. On the other hand, if the volume average particle size is less than 4 μm, not only the fluidity of the toner deteriorates, but also it becomes difficult to impart sufficient charging ability from the carrier, so that fog on the background portion occurs and the concentration reproducibility deteriorates. It may be easier.

The concentration (content) of the spherical pigment 210 with respect to the white toner 200 is, for example, 20% by mass or more and 50% by mass or less.

(Color Toner 300)
As shown in FIG. 9C, the color color toner 300 does not contain the flat pigment 110 and the spherical pigment 210, but contains a pigment 310 other than the flat pigment 110 and the spherical pigment 210 and a binder resin 320. ing. As the pigment 310, for example, a pigment that is a non-metal and a non-metal oxide (for example, an organic pigment) is used. That is, the color toner 300 has a pigment having a lower conductivity than the flat pigment 110 and the spherical pigment 210. A known resin material is used for the binding resin 320.

When the pigment 310 is placed on the flat surface 500, the pigment 310 has the left-right dimension X3 and the front-rear dimension Z3 when viewed from above shown in FIG. 7 (A), and is shown in FIG. 7 (B). The dimensions X3 in the left-right direction and the dimensions Y3 in the up-down direction when viewed from the side are equivalent.

Therefore, in the pigment 310, the dimensional ratio between the horizontal dimension X3 and the vertical dimensional Y3 when viewed from the side shown in FIG. 7B is smaller than the dimensional ratio in the flat pigment 110. .. That is, the pigment 310 has a shape closer to a sphere than the flat pigment 110.

The color toner 300 containing the pigment 310 also has a spherical shape like the pigment 310. Therefore, when the color toner 300 is placed on the flat surface 500, the color toner 300 has the left-right dimension A3 and the front-rear dimension B3 when viewed from above as shown in FIG. 8 (A). The horizontal dimension A3 and the vertical dimension C3 when viewed from the side shown in 8 (B) are equivalent.

The volume average particle size of the pigment 310 is about 50 to 150 nm, which is smaller than that of the flat pigment 110 and the spherical pigment 210 described above.
The maximum length of the color color toner 300 is shorter than the maximum length (volume average particle diameter) of the white toner 200. The maximum length of the color color toner 300 is such that the color color toner 300 is regarded as a spherical shape and the volume average particle diameter of the color color toner 300 is the maximum length. The method for measuring the volume average particle diameter is as described above.

The volume average particle diameter of the color color toner 300 is preferably 3 μm or more and 9 μm or less, and more preferably 3 μm or more and 8 μm or less. If the particle size is less than 3 μm, the chargeability may be insufficient and the developability may be lowered, and if it exceeds 9 μm, the resolution of the image may be lowered.
The concentration (content) of the pigment 310 with respect to the color toner 300 is, for example, 5% by mass or more and 20% by mass or less.

The color toner 300 may contain a compound composed of a divalent or higher metal element. The compound is added, for example, as an aggregating agent when the color color toner 300 is produced by the emulsion polymerization aggregation method. The content of the compound in the color color toner 300 is, for example, 0.05% by mass or more and 2% by mass or less.

As described above, the color toner 300 may contain a metal or a metal oxide, but its content (% by mass) is smaller than that of the silver toner 100 and the white toner 200, and the silver toner 100 and the white toner 200 It has lower conductivity as toner than.

The color color toner 300 may be a polymerized toner (chemical toner) obtained by a polymerization method such as an emulsion polymerization aggregation method, or may be a pulverized toner obtained by a pulverization method. Similarly, the silver toner 100 and the white toner 200 may be polymerized toner (chemical toner) or pulverized toner obtained by a pulverization method.

(Action according to this embodiment)
Next, the operation according to this embodiment will be described.

In the image forming apparatus according to the present embodiment, when an image in silver, white, and color is formed on the recording medium P, the image forming unit 20, the transfer device 30, and the fixing device 40 of each color are operated. As a result, a toner image is formed in the image forming unit 20 of each color. Specifically, in the image forming unit 20 of each color, a toner image is formed by the following image forming step (process).

That is, the photoconductor drum 21 of each color is charged by the charger 22 while being rotated. Further, each exposure device 23 emits each exposure light L according to the image data to expose each charged photoconductor drum 21. Then, an electrostatic latent image is formed on the surface of each photoconductor drum 21. The electrostatic latent image formed on each photoconductor drum 21 is developed by a developer supplied from the developing device 24. As a result, toner images of yellow (Y), magenta (M), cyan (C), black (K), white (W), and silver (V) are formed on the photoconductor drum 21 of each color.

The toner images of each color formed on the photoconductor drum 21 of each color are sequentially transferred to the orbiting transfer belt 31 in the transfer electric field formed between the photoconductor drum 21 of each color and the primary transfer roll 33 of each color. .. As a result, a toner image on which the toner images of each color are superimposed is formed on the transfer belt 31. The superimposed toner image is conveyed to the secondary transfer position NT by the circulation of the transfer belt 31.

At this secondary transfer position NT, the toner image superimposed on the transfer belt 31 is transferred to the recording medium P conveyed from the container 51. The toner image transferred to the recording medium P is fixed to the recording medium P by the fixing device 40.

As described above, in the present embodiment, since the toner images of each color are transferred to the recording medium P, an image expressed by combining the colors of the silver toner 100, the white toner 200, and the color toner 300 is formed.

Here, positive electrode charges may be injected into the toner in the transfer electric field formed between the photoconductor drum 21 of each color and the primary transfer roll 33 of each color. When the toner is positively charged by being injected with the positive charge, it may be retransferred to the photoconductor drum 21 by receiving an electrostatic attraction. When the toner is re-transferred to the photoconductor drum 21, the transfer rate when the toner image is transferred from the photoconductor drum 21 to the transfer belt 31 decreases.

The retransfer here includes a case where the toner transferred from the photoconductor drum 21 to the transfer belt 31 is transferred again to the photoconductor drum 21 and a case where the toner is transferred to the photoconductor drum 21 on the downstream side. And are included.

Since the flat pigment 110 of the silver toner 100 is a metal, it has conductivity and has a flat shape. Since the flat pigment 110 has a flat shape in this way, by polarization, the silver toner 100 is in the longitudinal direction of the flat pigment 110 (longitudinal direction of the silver toner 100), as shown in FIG. 9A. ) Is likely to stand up along the direction orthogonal to the transfer belt 31 (hereinafter referred to as a hot standing state).

Since the flat pigment 110 exists in the silver toner 100 in a state where the longitudinal direction of the flat pigment 110 is aligned with the longitudinal direction of the silver toner 100, when the silver toner 100 is in a hot stand state, the photoconductor drum 21 and the transfer belt 31 A conductive path (see arrow E) is secured along the flat pigment 110 between the two. As a result, the silver toner 100 is more likely to be injected with positive charge than when it contains a spherical pigment.

On the other hand, the spherical pigment 210 of the white toner 200 has conductivity because it is a metal oxide, but has a spherical shape instead of a flat shape (see FIG. 9B). Therefore, unlike the flat pigment 110 in the silver toner 100, the spherical pigment 210 is uniformly dispersed in the white toner 200 and is difficult to be arranged in a specific direction. Therefore, a binder resin 220 having a lower conductivity than that of the spherical pigment 210 exists between the spherical pigments 210, and a conductive path (arrow E) between the photoconductor drum 21 and the transfer belt 31 as compared with the silver toner 100. See) is difficult to secure. As a result, the white toner 200 is less likely to be injected with positive charge than the silver toner 100.

Further, the pigment 310 of the color toner 300 has lower conductivity than the flat pigment 110 and the spherical pigment 210. Therefore, as compared with the silver toner 100 and the white toner 200, it is difficult to secure a conductive path (see arrow E) between the photoconductor drum 21 and the transfer belt 31 (see FIG. 9C). As a result, the color toner 300 is less likely to inject positive charge than the white toner 200.

Further, for example, in the comparative example shown in FIG. 10 in which the image forming units 20V, 20W, and 20Y to 20K are arranged in this order from the upstream side, the silver toner 100 of the silver image transferred from the image forming unit 20V to the transfer belt 31 is used. , The primary transfer positions T of the image forming unit 20W and the image forming units 20Y to 20K also pass through. As described above, the silver toner 100 is prone to charge injection, and therefore, when charge injection occurs in the transfer electric field at each primary transfer position T, the transfer rate is significantly reduced.

Further, in the above-mentioned comparative example, since the color color image and the white color image are superimposed on the silver color image transferred to the transfer belt 31, the white toner 200 and the color color toner 300 are as shown in FIG. 11 (A). Covers at least a portion of the silver toner 100. However, since the maximum length A of the silver toner 100 is longer than the maximum length (volume average particle diameter) of the white toner 200 and the maximum length (volume average particle diameter) of the color color toner 300, the covered silver toner 100 is covered. As described above, when the spikes are formed on the transfer belt 31, the upper part (two-point chain line) of the silver toner 100 is formed at the primary transfer positions TW, TY, TM, TC, and TK, as shown in FIG. 11 (B). (See part) is easily exposed. Therefore, as shown in FIG. 12, the silver toner 100 comes into contact with the photoconductor drum 21, and a conductive path (see arrow E) is secured between the photoconductor drum 21 and the transfer belt 31 along the flat pigment 110. Will be done. As a result, the silver toner 100 tends to have a positive charge injected, and the transfer rate tends to decrease.

Further, the volume average particle diameter of the flat pigment 110 contained in the silver toner 100 is larger than the volume average particle diameter of the spherical pigment 210 of the white toner 200 and the volume average particle diameter of the pigment 310 of the color color toner 300. Therefore, as compared with the white toner 200 and the color toner 300, the flat pigment 110 is more likely to be connected in the silver toner 100, and the conductive path (see arrow E) is transmitted between the photoconductor drum 21 and the transfer belt 31 along the flat pigment 110. ) Is easy to secure. From this point as well, the silver-colored toner 100 tends to have a positive transfer rate due to injection of positive charge.

Further, in the comparative example shown in FIG. 10, since the color color image is superimposed on the white image transferred to the transfer belt 31, the color color toner 300 covers at least a part of the white toner 200. However, since the maximum length (volume average particle diameter) of the white toner 200 is longer than the maximum length (volume average particle diameter) of the color color toner 300, the upper part of the covered white toner 200 is similar to the case of the silver toner 100. Is exposed. Therefore, at the primary transfer positions TY, TM, TC, and TK, the white toner 200 comes into contact with the photoconductor drum 21, and a conductive path is secured along the spherical pigment 210 between the photoconductor drum 21 and the transfer belt 31. Toner. As a result, the white toner 200 is more likely to have a positive charge injected than the color toner 300, and the transfer rate is likely to decrease.

Further, the volume average particle diameter of the spherical pigment 210 of the white toner 200 is larger than the volume average particle diameter of the pigment 310 of the color color toner 300. Therefore, as compared with the color toner 300, the spherical pigment 210 is more likely to be connected in the white toner 200, and a conductive path (see arrow E) is secured along the spherical pigment 210 between the photoconductor drum 21 and the transfer belt 31. Cheap. From this point as well, the white toner 200 is more likely to have a positive electrode charge injection than the color toner 300, and the transfer rate is likely to decrease.

On the other hand, in the present embodiment, the image forming unit 20V using the silver toner 100, which is most likely to cause positive charge injection among the silver toner 100, the white toner 200, and the color toner 300, is the image forming unit 20. It is located on the most downstream side of the.

Therefore, since the silver toner 100 does not pass through the primary transfer positions T of the image forming unit 20W and the image forming units 20Y to 20K, positive charge is injected into the silver toner 100 as compared with the comparative example shown in FIG. Hateful. Therefore, as compared with the comparative example shown in FIG. 10, a decrease in the transfer rate when the silver image formed by the silver toner 100 is transferred from the image forming unit 20V to the transfer belt 31 is suppressed.

Further, in the present embodiment, the image forming unit 20W using the white toner 200, which is the second most likely to cause positive charge injection among the silver toner 100, the white toner 200, and the color color toner 300, is the image forming unit 20V. Although it is on the upstream side, it is arranged on the downstream side of the image forming units 20Y to 20K.

Therefore, the white toner 200 passes through the primary transfer position T of the image forming unit 20V, but does not pass through the primary transfer position T of the image forming units 20Y to 20K. Therefore, as compared with the comparative example shown in FIG. 10, injection of positive charge into the white toner 200 is less likely to occur. Therefore, as compared with the comparative example shown in FIG. 10, a decrease in the transfer rate when the white image formed by the white toner 200 is transferred from the image forming unit 20W to the transfer belt 31 is suppressed.

(Measurement of transfer rate)
Here, in the six image forming units 20, each of the image forming units 20V, 20W, and 20C is located on the most upstream side (position of reference numeral 20 (1) in FIG. 13) and the most downstream side (reference numeral 20 (reference numeral 20) in FIG. The transfer rate of the image when placed at the position of 6)) was measured. In this measurement, a Color1000Press modified 6-color machine (manufactured by Fuji Xerox Co., Ltd.) was used as the image forming apparatus 10. The measurement was performed in an environment with a temperature of 10 ° C. and a humidity of 15%.

In the measurement of the transfer rate in the image forming unit 20 (1) arranged on the most upstream side, a solid image (patch) having a predetermined size is formed on the photoconductor drum 21 (1), and the solid image is transferred to the transfer belt. Transfer to 31. Then, in the image forming units 20 (2) and 20 (3) 20 (4) 20 (5) 20 (6) which are not the measurement targets, only the transfer operation by the primary transfer roll 33 was performed. The transfer rate is the transfer belt after passing through the six primary transfer positions T when the toner amount of the solid image on the photoconductor drum 21 (1) (toner amount at 90A in FIG. 13) is 100. It is obtained from the toner amount of the solid image on 31 (toner amount at 90B in FIG. 13). The amount of toner is determined, for example, by sucking the toner of the solid image of the photoconductor drum 21 (1) and the transfer belt 31 with a suction device and measuring the weight of the sucked toner with an electronic balance. The amount of toner in the solid image on the transfer belt 31 is based on the amount of toner at 90A in FIG. 13, after passing through each primary transfer position T, the photoconductor drums 21 (1), 21 (2), and 21 (3). ), 21 (4), 21 (5), 21 (6) may be subtracted from the total amount of toner (total amount of toner at 90C and 90E in FIG. 13).

In the measurement of the transfer rate in the image forming unit 20 (6) arranged on the most downstream side, a solid image (patch) having a predetermined size is formed on the photoconductor drum 21 (6), and the solid image is transferred to the transfer belt. Transfer to 31. The transfer rate is the toner amount of the solid image on the transfer belt 31 (FIG. 13) when the toner amount of the solid image on the photoconductor drum 21 (6) (toner amount at 90D in FIG. 13) is 100. It is obtained from the amount of toner at 90B in No. 13). The amount of toner is determined, for example, by sucking the toner of the solid image of the photoconductor drum 21 (6) and the transfer belt 31 with a suction device and measuring the weight of the sucked toner with an electronic balance. The amount of toner in the solid image on the transfer belt 31 is based on the amount of toner at 90D in FIG. 13 and the amount of toner adhering to the photoconductor drum 21 (6) after passing through the primary transfer position T (at 90E in FIG. 13). (Toner amount) may be subtracted.

A graph showing the results of the above measurements is shown in FIG. In FIG. 14, the transfer rate when arranged on the most upstream side (position of reference numeral 20 (1) in FIG. 13) is indicated by a bar with diagonal lines, and the position on the most downstream side (position of reference numeral 20 (6) in FIG. 13) is shown. ) Is shown by a white bar. As shown in the graph of FIG. 14, when the image forming unit 20V for forming a silver image is arranged on the most upstream side, the decrease in the transfer rate is the largest. The next largest decrease in transfer rate is when the image forming unit 20W that forms a white image is arranged on the most upstream side.

Therefore, arranging the image forming unit 20V on the most downstream side has a high effect of suppressing a decrease in the transfer rate. Further, the image forming unit 20W is less effective in suppressing the decrease in the transfer rate than the case where the image forming unit 20V is arranged on the most downstream side, but is more effective than the case where the image forming units 20Y to 20K are arranged on the most downstream side. However, it is highly effective in suppressing the decrease in transcription rate. Therefore, it is considered that the arrangement of the image forming units 20Y to 20K, 20W, and 20V in this order from the upstream side as in the present embodiment is the optimum arrangement for suppressing the decrease in the transfer rate.

[Evaluation]
In this evaluation, the transfer rates of the silver image (silver toner 100), the white image (white toner 200), and the cyan toner image (cyan toner) in the image forming apparatus 10 of the present embodiment and the comparative example shown in FIG. 10 are determined. evaluated.

In this evaluation as well, as in the measurement of the transfer rate described above, a Color1000Press modified 6-color machine (manufactured by Fuji Xerox Co., Ltd.) was used. The evaluation was carried out in an environment of a temperature of 10 ° C. and a humidity of 15%.

The transfer rates of the embodiments and comparative examples were evaluated by A, B, and C as follows by observing the images visually.
A: Good transfer rate to the extent that almost no decrease in concentration is observed B: Good transferability to the extent that no obvious decrease in concentration is observed C: Poor transferability to the extent that a decrease in concentration can be confirmed

As a result of the evaluation, in the configuration of the present embodiment, as shown in FIG. 15, the transfer rate of the silver toner 100, the white toner 200 and the cyan toner was evaluated as A. In the comparative example, the transfer rates of the silver toner 100, the white toner 200, and the cyan toner were evaluated as C, B, and A, respectively. As described above, in the configuration of the present embodiment, the transfer rates of the silver toner 100 and the white toner 200 are superior to those of the configuration of the comparative example.

(First modification)
The image forming apparatus 10 according to the present embodiment is a tandem type image forming apparatus, but the present invention is not limited to this. For example, the image forming apparatus 600 shown in FIG. 16 equipped with a rotary developing apparatus may be used.

As shown in FIG. 16, the image forming apparatus 600 transfers the toner image forming unit 612 (an example of the forming unit) for forming the toner image and the toner image formed by the toner image forming unit 612 to the recording medium P. It is equipped with a transfer device 630.

The toner image forming unit 612 has a photoconductor drum 621 that rotates in the arrow-R direction and a charger 622 that charges the photoconductor drum 621. Further, the toner image forming unit 612 exposes the photoconductor drum 621 charged by the charger 622 to form an electrostatic latent image on the photoconductor drum 621, and the photofinishing device drum 621 by the exposure device 623. It has a rotary developing device 640 that develops the formed electrostatic latent image to form a toner image.

The transfer device 630 transfers the transfer belt 631 (an example of a medium) wound around a plurality of rolls 632 and the toner image of the photoconductor drum 621 to the transfer belt 631 at the primary transfer position T (transfer unit). (Example)) and a secondary transfer roll 634 that transfers the toner image superimposed on the transfer belt 631 to the recording medium P at the secondary transfer position NT.

The rotary developing device 640 has a rotating shaft 649 and yellow (Y), magenta (M), cyan (C), black (K), white (W), and silver (V) arranged around the rotating shaft 649. It is equipped with developers 64Y, 64M, 64C, 64K, 64W, 64V. The developing devices 64Y, 64M, 64C, 64K, 64W, and 64V contain toners of each color and have a developing roll 648 for adhering the toners to the photoconductor drum 621.

The rotary developer 640 is a developer 64Y, 64M, 64C, 64K, 64W, which performs development processing at a development position facing the outer peripheral surface of the photoconductor 62 by being rotated by 60 ° at a central angle in the arrow + R direction. 64V can be switched. In the image forming apparatus 600, the developing process is performed in the order of the developing devices 64Y, 64M, 64C, 64K, 64W, and 64V. Therefore, in the image forming apparatus 600, yellow (Y), magenta (M), cyan (C), black (K), white (W), and silver are obtained by performing the steps of charging, exposure, development, and primary transfer. Toner images are formed on the photoconductor drum 621 in the order of (V), and the toner images are sequentially transferred to the transfer belt 631.

In the image forming apparatus 600, the developing device 64V using the silver toner 100 finally performs the developing process. Therefore, since the silver toner 100 of the silver image passes through the primary transfer position T only once, the silver toner 100 has a positive electrode property to the silver toner 100 as compared with the case where the silver toner 100 passes through the primary transfer position T a plurality of times (comparative example). Charge injection is unlikely to occur. Therefore, a decrease in the transfer rate when the silver image formed by the silver toner 100 is transferred to the transfer belt 31 is suppressed.

Further, the developing device 64W using the white toner 200 performs the developing process after the developing devices 64Y, 64M, 64C, 64K and before the developing device 64V. As a result, the white toner 200 of the white image passes through the primary transfer position T twice, so that the white toner 200 has a positive electrode property to the white toner 200 as compared with the case where the white toner 200 passes through the primary transfer position T three times or more (comparative example). Charge injection is unlikely to occur. Therefore, a decrease in the transfer rate when the silver image formed of the white toner 200 is transferred to the transfer belt 631 is suppressed.

(Second modification)
The image forming apparatus 10 according to the present embodiment is a tandem type image forming apparatus, but the present invention is not limited to this, and for example, the direct transfer type image forming apparatus 700 shown in FIG. 17 may be used.

As shown in FIG. 17, the image forming apparatus 700 records a toner image forming unit 712 (an example of the forming unit) for forming a toner image and a toner image formed by the toner image forming unit 712 on a recording medium P (a medium). A transfer roll 733 (an example of a transfer unit) to be transferred to (one example) is provided.

As described above, in the image forming apparatus 700, the recording medium P functions as an example of the medium. As described above, in the image forming apparatus 10 and 600, the transfer belts 31 and 631 function as an example of the medium. Therefore, the target to which the toner image formed by developing the latent image on the holding body (photoreceptor drums 21, 621) that holds the image is first transferred from the holding body is the medium in the present embodiment. Applicable.

In the image forming apparatus 700, the recording medium P is conveyed by the annular transfer belt 750. The transfer roll 733 is arranged on the inner peripheral side of the transport belt 750.

The toner image forming unit 712 forms image forming units 20Y and 20M for forming toner images of each color of yellow (Y), magenta (M), cyan (C), black (K), white (W), and silver (V). , 20C, 20K, 20W, 20V (image forming unit).

The image forming units 20Y, 20M, 20C, 20K, 20W, and 20V (hereinafter referred to as 20Y to 20V) are arranged in this order from the upstream side to the downstream side in the transport direction of the recording medium P. The configurations of the image forming units 20Y to 20V are as described above.

In the image forming apparatus 700, among the silver toner 100, the white toner 200, and the color toner 300, the image forming unit 20V using the silver toner 100, which is most likely to cause positive charge injection, is the most among the image forming units 20. It is located on the downstream side.

Therefore, since the silver toner 100 does not pass through the primary transfer positions T of the image forming unit 20W and the image forming units 20Y to 20K, positive charge is injected into the silver toner 100 as compared with the comparative example shown in FIG. Hateful. Therefore, as compared with the comparative example shown in FIG. 10, a decrease in the transfer rate when the silver image formed by the silver toner 100 is transferred from the image forming unit 20V to the recording medium P is suppressed.

Further, in the image forming apparatus 700, the image forming unit 20W using the white toner 200, which is the second most likely to cause positive charge injection among the silver toner 100, the white toner 200, and the color color toner 300, is the image forming unit 20V. Although it is on the upstream side of, it is arranged on the downstream side of the image forming units 20Y to 20K.

Therefore, the white toner 200 passes through the primary transfer position T of the image forming unit 20V, but does not pass through the primary transfer position T of the image forming units 20Y to 20K. Therefore, as compared with the comparative example shown in FIG. 10, injection of positive charge into the white toner 200 is less likely to occur. Therefore, as compared with the comparative example shown in FIG. 10, a decrease in the transfer rate when the white image formed by the white toner 200 is transferred from the image forming unit 20W to the recording medium P is suppressed.

(Other variants)
In the present embodiment, yellow (Y), magenta (M), cyan (C), and black (K) toners are used as the third toner, but the toner is not limited to this. As the third toner, a transparent toner or a toner having a color such as red, blue, green, orange, or violet may be used. As the transparent toner, a toner that does not contain a pigment may be used.

Further, in the present embodiment, the image forming unit 20V uses the silver toner 100, but the present invention is not limited to this, and for example, another metal color such as gold may be used.

Further, in the present embodiment, the silver toner 100 as an example of the first toner has a flat pigment 110 made of aluminum (an example of a metal), but the present invention is not limited to this. The first toner may have, for example, a flat pigment made of a metal such as brass, bronze, nickel, stainless steel, or zinc, or a flat pigment made of a metal oxide such as titanium oxide.

Further, in the present embodiment, the white toner 200 as an example of the second toner has a spherical pigment 210 composed of titanium oxide (an example of a metal oxide), but the present invention is not limited to this. The second toner may have, for example, a spherical pigment composed of a metal such as aluminum, brass, bronze, nickel, stainless steel, or zinc, or a spherical pigment formed of a metal oxide other than titanium oxide. ..

The present invention is not limited to the above embodiment, and various modifications, changes, and improvements can be made without departing from the gist thereof. For example, the above-mentioned modified examples may be configured by combining a plurality of them as appropriate.

10 Image forming device 12 Toner image forming part (example of forming part)
31 Transfer belt (example of medium)
33 Primary transfer roll (example of transfer unit)
100 silver toner (an example of the first toner)
110 Flat Pigment 200 White Toner (Example of Second Toner)
210 Spherical pigment (an example of the first pigment)
300 color toner (an example of third toner)
310 pigment (an example of the second pigment)
600 Image forming apparatus 612 Toner image forming part (example of forming part)
631 Transfer belt (example of medium)
633 Primary transfer roll (an example of transfer section)
700 Image forming device 712 Toner image forming part (example of forming part)
733 Transfer roll (an example of transfer unit)
P Recording medium (example of medium)

Claims (4)

The first image is formed with a first toner containing a flat pigment formed of a metal or a metal oxide, and the first image is formed without a flat pigment formed of a metal or a metal oxide and has a maximum length longer than the maximum length of the first toner. A forming portion that forms a second image with a second toner having a small size and forms a third image with a third toner that does not contain the flat pigment and has a maximum length smaller than the maximum length of the second toner.
The transfer unit that transfers the third image, the second image, and the first image to the medium in this order,
An image forming apparatus comprising. The image forming apparatus according to claim 1, wherein the forming portion forms the second image with the second toner containing a spherical pigment formed of a metal or a metal oxide. The first image is formed with a first toner containing a flat pigment formed of a metal or a metal oxide, and the volume average grain of the flat pigment of the first toner does not contain a flat pigment formed of a metal or a metal oxide. A second image is formed with a second toner containing a first pigment having a volume average particle size smaller than the diameter, and the volume of the first pigment of the second toner without containing the flat pigment and the first pigment. A forming portion that forms a third image with a third toner containing a second pigment having a volume average particle size smaller than the average particle size,
The transfer unit that transfers the third image, the second image, and the first image to the medium in this order,
An image forming apparatus comprising. The image forming apparatus according to claim 3, wherein the forming portion forms the second image with the second toner containing a spherical pigment as the first pigment formed of a metal or a metal oxide.