Image forming device and image forming method

Abstract

To enable an image to be formed that exhibits photoluminescence while retaining the hue of a color image.SOLUTION: When printing data received from a host device 100 contains photoluminescent superposition part, an image forming device 1 refers to photoluminescent superposition information and changes a print pattern N of a silver toner image PS in the photoluminescent superposition part before printing to a medium MD. In this case, the image forming device 1 increases the image density of the superposing silver toner image PS to be relatively large when the chroma saturation in single color is relatively low, and reduces the image density of the superposing silver toner image PS to be relatively small when the chroma saturation in single color is relatively high, and further changes to a print pattern N that corresponds to a silver dot count d. Thus, it is possible for the image forming device 1 to bring both of an FI value and a C* retention ratio to relatively close values between mutually different colors, and obtain a good image exhibiting uniform glossiness while keeping the hue of the original image intact as a whole.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus and an image forming method, and is suitably applied to, for example, a printing process in which brilliant colors having brilliance and normal colors are printed in an overlapping manner. [Background technology]

[0002] Conventionally, when performing color printing, image forming devices that combine normal color toners such as black, magenta, cyan, and yellow (hereinafter referred to as color toners) to form (i.e., print) color images using the normal colors on a medium such as paper have been widely used.

[0003] Some image forming devices can form a glossy image on paper by using a glossy toner (hereinafter referred to as a glossy toner) such as silver or gold (hereinafter referred to as glossy colors) in addition to these normal colors. In this image forming device, for example, fine powder of a metal such as aluminum is used as a pigment for the glossy toner, thereby making it possible to present a high glossiness in the printed image (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-113783 A (Fig. 2, etc.) Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in an image forming device capable of using glossy toner as described above, a variety of glossy colors known as metallic colors can be produced by printing an image of glossy toner over an image of color toner (color image).

[0006] However, it is known that when a color toner is overlaid with a glitter toner, the saturation generally changes (decreases) slightly, and the degree of the change in saturation differs depending on the color. For this reason, for example, when a glitter toner image of uniform density is overlaid on a color toner image having parts of various colors, the degree of the change in saturation differs depending on the color of each part, and a user who sees this may feel unevenness or dullness.

[0007] In other words, when an image forming device prints an image by overlaying glossy toner on top of color toner, glossiness is added, but there is a problem in that the color tones of each part are different, which may give a user who sees the image an impression that is different from the original color image or give the user a sense of discomfort.

[0008] The present invention has been made in consideration of the above points, and aims to propose an image forming apparatus and an image forming method capable of forming an image exhibiting brilliance while maintaining the color tone of a color image. [Means for solving the problem]

[0009] In order to solve such problems, the image forming apparatus of the present invention is provided with a glossy image forming unit capable of forming a glossy image on a medium using a glossy developer, a non-glossy image forming unit capable of forming a non-glossy image on a medium using a non-glossy developer, and a control unit that controls the operation of the glossy image forming unit and the non-glossy image forming unit, and when a glossy image with an image density of 100[%] is superimposed on a non-glossy image to be formed on a medium, the control unit controls the glossy image forming unit and the non-glossy image forming unit so that if the non-glossy image has a first saturation, a glossy image with the first image density is formed, and if the non-glossy image has a second saturation greater than the first saturation, a glossy image with a second image density smaller than the first image density is formed.

[0010] Furthermore, the image forming method of the present invention includes a control step of receiving print data by a control unit and performing control based on the print data, and an image forming step of forming a glossy image using a glossy developer and a non-glossy image using a non-glossy developer on a medium by the glossy image forming unit and non-glossy image forming unit controlled by the control unit, respectively. In the control step, when a glossy image is superimposed on a non-glossy image to be formed on the medium, the glossy image forming unit and the non-glossy image forming unit are controlled so that if the non-glossy image has a first saturation, a glossy image of a first image density is formed, and if the non-glossy image has a second saturation higher than the first saturation, a glossy image of a second image density lower than the first image density is formed.

[0011] Furthermore, the image forming apparatus of the present invention is provided with a glossy image forming section capable of forming a glossy image on a medium using a glossy developer, a non-glossy image forming section capable of forming a non-glossy image on a medium using a non-glossy developer, and a control section which controls the operation of the glossy image forming section and the non-glossy image forming section, and when a glossy image with an image density of 100[%] is superimposed on a non-glossy image to be formed on a medium, the control section controls the glossy image forming section and the non-glossy image forming section so that if the non-glossy developer has a first saturation, a glossy image with a first image density is formed, and if the non-glossy developer has a second saturation greater than the first saturation, a glossy image with a second image density smaller than the first image density is formed.

[0012] The present invention superimposes a glossy image of a first image density on a non-glossy image of a first saturation, and superimposes a glossy image of a second image density lower than the first image density on a non-glossy image of a second saturation higher than the first saturation. This makes it possible to make the image density of the glossy image to be superimposed different between the first saturation portion and the second saturation portion of the non-glossy image, and to appropriately maintain the balance of glossiness and saturation before and after superimposition. Effect of the Invention

[0013] According to the present invention, it is possible to form an image that exhibits brilliance while maintaining the color tone of the color image. Image forming apparatus and image forming method This can be achieved. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus. [Diagram 2] FIG. 2 is a schematic diagram illustrating a configuration of an image forming unit. [Diagram 3] FIG. 2 is a schematic block diagram illustrating a circuit configuration of the image forming apparatus. [Figure 4] 4 is a schematic diagram showing an image formation area on a medium. FIG. [Diagram 5] 11 is a table showing the measurement results of glitter superimposed images of each color. [Figure 6] 11 is a graph showing the relationship between the image density and C* retention rate of silver toner in a glitter superimposed image of each color. [Figure 7] 1 is a graph showing the relationship between image density and FI value and C* retention rate of a silver toner for magenta. [Figure 8] 1 is a table showing the C* and various calculated values ​​for each color. [Figure 9] FIG. 13 is a schematic diagram showing a printing pattern for cyan. [Figure 10] 11A and 11B are schematic diagrams illustrating print patterns for magenta and yellow. [Figure 11] 11 is a table showing the correspondence between the dot count of silver and the print pattern of each color. [Figure 12] 1 is a table showing the FI value and C* value of each color according to the silver dot count in an evaluation test. [Figure 13] 1 is a table showing the average C* retention as a function of silver dot count for each example. [Figure 14] 13 is a flowchart showing a glitter superimposition printing process. [Figure 15] 11 is a schematic diagram illustrating a state in which a silver toner image is printed on the surface of a medium. [Figure 16] 11 is a schematic diagram showing a state in which a glitter superimposed image is fixed onto a medium. FIG. [Figure 17] 1 is a table showing the color gamut of each color of toner in a powder state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0016] [1. Configuration of image forming device] 1, the image forming apparatus 1 according to the present embodiment is an electrophotographic color printer that can form (i.e., print) a color image on a medium MD such as paper. Incidentally, the image forming apparatus 1 does not have an image scanner function for reading a document or a communication function using a telephone line, and is a single-function SFP (Single Function Printer) that has only a printer function.

[0017] Various parts are arranged inside a housing 2 formed in a substantially box shape in the image forming apparatus 1. In the following description, the right end portion in Fig. 1 is regarded as the front of the image forming apparatus 1, and the up-down direction, left-right direction, and front-rear direction are defined when viewed from the front.

[0018] The image forming apparatus 1 is controlled by the control unit 3. As described below, the control unit 3 executes various processes by reading and executing a predetermined program. The control unit 3 is also connected to a higher-level device 100 (FIG. 3) such as a computer device by wireless or wired connection, and when image data representing an image to be printed is provided from the higher-level device and printing of the image data is instructed, the control unit 3 executes a print process to form a print image on the surface of the medium MD. The display unit 4 is a display device such as a liquid crystal panel, and is disposed on the front side of the upper surface of the housing 2. The display unit 4 displays various information under the control of the control unit 3.

[0019] Five image forming units 10K, 10C, 10M, 10Y, and 10S are arranged in this order from the front to the rear on the upper side inside the housing 2. The image forming units 10K, 10C, 10M, 10Y, and 10S correspond to the colors black (K), cyan (C), magenta (M), yellow (Y), and spot color (S), respectively, but only the colors differ and all are configured similarly.

[0020] Black (K), cyan (C), magenta (M) and yellow (Y) are all colors used in general color printers (hereinafter, these are referred to as normal colors or non-glossy colors). On the other hand, the special color (S) is a special color (hereinafter, also referred to as a glossy color) that exhibits metallic luster, such as gold or silver. This special color may be used alone or may be used over a normal color. In this embodiment, a case where silver is used as a special color will be described as an example. For convenience of explanation, the image forming units 10K, 10C, 10M, 10Y and 10S will be collectively referred to as the image forming units 10 below. In addition, the image forming units 10K, 10C, 10M and 10Y will be referred to as non-glossy image forming units, and the image forming unit 10S will be referred to as a glossy image forming unit below.

[0021] 2, the image forming unit 10 is roughly composed of an image forming main body 11, a toner container 12, a toner supply unit 13, and an LED (Light Emitting Diode) head 14. The toner container 12 contains toner T (also called a developer) therein, and is configured to be detachable from the image forming unit 10. When the toner container 12 is mounted on the image forming unit 10, it is attached to the image forming main body 11 via the toner supply unit 13. Incidentally, the toner container 12 may also be called a toner cartridge or a developer container.

[0022] As described later, a toner containing a glitter pigment is used as the silver toner T. For convenience of explanation, the glitter color silver toner T will be referred to as silver toner TS, glitter toner, or glitter developer hereinafter. The toner container 12 that contains the silver toner TS will also be referred to as a glitter developer container.

[0023] On the other hand, yellow, magenta, cyan and black toners T are made of toners containing organic pigments, such as pigment yellow, pigment cyan, pigment magenta and carbon black, etc. For convenience of explanation, hereinafter, yellow, magenta, cyan and black (i.e. non-glossy color) toners T are also referred to as color toners TL, non-glossy toners or non-glossy developers.

[0024] The image forming main body 11 (FIG. 2) incorporates an image forming housing 20, a toner storage space 21, a first supply roller 22, a second supply roller 23, a developing roller 24, a developing blade 25, a photosensitive drum 26, a charging roller 27, and a cleaning blade 28. Among these, the first supply roller 22, the second supply roller 23, the developing roller 24, the photosensitive drum 26, and the charging roller 27 are each configured in a cylindrical shape with their central axes aligned in the left-right direction, and are each rotatably supported by the image forming housing 20.

[0025] The toner storage space 21 stores the toner T supplied from the toner storage container 12 via the toner supply unit 13. The first supply roller 22 and the second supply roller 23 each have an elastic layer formed of a conductive urethane rubber foam or the like on their circumferential side. The developing roller 24 has an elastic layer having elasticity and a surface layer having conductivity formed on their circumferential side. The developing blade 25 is made of, for example, a stainless steel plate of a predetermined thickness, and a part of it is in contact with the circumferential side of the developing roller 24 in a state where it is slightly elastically deformed.

[0026] The photoconductor drum 26, which serves as an image carrier, has a thin-film charge generating layer and a charge transport layer formed in that order on its peripheral surface so that it can be charged. The charging roller 27 has a conductive elastic body coated on its peripheral surface, which is brought into contact with the peripheral surface of the photoconductor drum 26. The cleaning blade 28 is made of, for example, a thin resin plate, and a part of it is brought into contact with the peripheral surface of the photoconductor drum 26 while being slightly elastically deformed.

[0027] The LED head 14 as an exposure unit is located above the photoconductor drum 26 in the image forming main body 11. This LED head 14 has multiple light-emitting element chips arranged linearly in the left-right direction, and causes each light-emitting element to emit light in a light emission pattern based on image data signals supplied from the control unit 3 (FIG. 1).

[0028] The image forming main body 11 rotates the first supply roller 22, the second supply roller 23, the developing roller 24, and the charging roller 27 in the direction of the arrow R1 (clockwise in the figure) and rotates the photosensitive drum 26 in the direction of the arrow R2 (counterclockwise in the figure) by receiving a driving force from a motor (not shown). Furthermore, under the control of the control unit 3, the image forming main body 11 applies a predetermined bias voltage to the first supply roller 22, the second supply roller 23, the developing roller 24, the developing blade 25, and the charging roller 27, thereby charging them.

[0029] The first supply roller 22 and the second supply roller 23 are charged to cause the toner T in the toner storage space 21 to adhere to their circumferential sides, and then rotate to cause the toner T to adhere to the circumferential side of the developing roller 24. The developing roller 24 has excess toner T removed from the circumferential side by the developing blade 25, and with the toner T adhered in a thin film form, the circumferential side is brought into contact with the circumferential side of the photosensitive drum 26.

[0030] Meanwhile, the charging roller 27, in a charged state, comes into contact with the photoconductor drum 26, thereby uniformly charging the circumferential side surface of the photoconductor drum 26. The LED head 14 sequentially exposes the photoconductor drum 26 by performing an exposure process in which it emits light at predetermined time intervals in a light emission pattern based on an image data signal supplied from the control unit 3 (FIG. 1). As a result, electrostatic latent images are sequentially formed on the circumferential side surface of the photoconductor drum 26 near its upper end.

[0031] Next, the photoconductor drum 26 rotates in the direction of arrow R2, thereby bringing the area where the electrostatic latent image is formed into contact with the developing roller 24. As a result, toner T adheres to the peripheral side surface of the photoconductor drum 26 based on the electrostatic latent image, and a toner image based on the image data is developed. The photoconductor drum 26 further rotates in the direction of arrow R2, thereby causing the toner image to reach the vicinity of the lower end of the photoconductor drum 26. For convenience of explanation, hereinafter, a toner image formed with silver toner TS having glitter properties is also referred to as a silver toner image PS or a glitter image, and a toner image formed with color toner TL, which is a normal color, is also referred to as a color toner image PL or a non-glitter image.

[0032] An intermediate transfer section 30 is disposed below each image forming unit 10 within the housing 2 (FIG. 1). The intermediate transfer section 30 includes a drive roller 31, a driven roller 32, a backup roller 33, an intermediate transfer belt 34, five primary transfer rollers 35, a secondary transfer roller 36, and a reverse bending roller 37. Of these, the drive roller 31, the driven roller 32, the backup roller 33, the primary transfer rollers 35, the secondary transfer roller 36, and the reverse bending roller 37 are all formed in a cylindrical shape with their central axes aligned in the left-right direction, and are rotatably supported by the housing 2.

[0033] The drive roller 31 is disposed below and rearward of the image forming unit 10S, and rotates in the direction of the arrow R1 when a driving force is supplied from a belt motor (not shown). The driven roller 32 is disposed below and frontward of the image forming unit 10K. The upper ends of the drive roller 31 and the driven roller 32 are positioned at the same level as or slightly below the lower ends of the photoconductor drums 26 (FIG. 2) in the respective image forming units 10. The backup roller 33 is disposed below and frontward of the drive roller 31 and below and rearward of the driven roller 32.

[0034] The intermediate transfer belt 34 is configured as an endless belt made of a high-resistance plastic film, and is stretched so as to go around the driving roller 31, the driven roller 32, and the backup roller 33. Furthermore, in the intermediate transfer section 30, five primary transfer rollers 35 are disposed below the portion of the intermediate transfer belt 34 stretched between the driving roller 31 and the driven roller 32, i.e., directly below each of the five image forming units 10, at positions facing each of the photoconductor drums 26 with the intermediate transfer belt 34 in between. A predetermined bias voltage is applied to the primary transfer rollers 35 under the control of the control section 3.

[0035] The secondary transfer roller 36 is located directly below the backup roller 33 and is biased toward the backup roller 33. That is, the intermediate transfer unit 30 has the intermediate transfer belt 34 sandwiched between the secondary transfer roller 36 and the backup roller 33. A predetermined bias voltage is applied to the secondary transfer roller 36. Hereinafter, the secondary transfer roller 36 and the backup roller 33 will be collectively referred to as the secondary transfer unit 39.

[0036] The reverse bending roller 37 is located at a position lower on the front side of the drive roller 31 and rearward on the upper side of the backup roller 33, and biases the intermediate transfer belt 34 in a front-upward direction. This prevents the intermediate transfer belt 34 from becoming loose, and tension acts between each roller. In addition, a reverse bending backup roller 38 is provided at a position above and in front of the reverse bending roller 37, sandwiching the intermediate transfer belt 34 therebetween.

[0037] The intermediate transfer section 30 rotates the drive roller 31 in the direction of the arrow R1 by the driving force supplied from a belt motor (not shown), thereby moving the intermediate transfer belt 34 in the direction along the arrow E1. In addition, each primary transfer roller 35 rotates in the direction of the arrow R1 with a predetermined bias voltage applied thereto. As a result, each image forming unit 10 transfers the toner image that has reached the vicinity of the lower end of the circumferential side surface of the photosensitive drum 26 (FIG. 2) to the intermediate transfer belt 34, and the toner images of each color are sequentially superimposed. At this time, the toner images of each color are sequentially superimposed on the surface of the intermediate transfer belt 34, starting from silver (S) on the upstream side. The intermediate transfer section 30 moves the intermediate transfer belt 34, thereby causing the toner images transferred from each image forming unit 10 to reach the vicinity of the backup roller 33.

[0038] Incidentally, inside the housing 2 (FIG. 1), a transport path W is formed, which is a path for transporting the medium MD. This transport path W heads from the front of the lower end inside the housing 2 toward the upper front direction, turns about halfway, and then proceeds rearward below the intermediate transfer unit 30. The transport path W then heads upward, travels upward along the rear side of the intermediate transfer unit 30 and the image forming unit 10S, and then heads forward. That is, the transport path W is formed as if it were drawing the capital letter "S" in FIG. 1. Inside the housing 2, various parts are arranged along the transport path W.

[0039] A first paper supply section 40 is disposed near the bottom end inside the housing 2 (FIG. 1). The first paper supply section 40 includes a paper cassette 41, a pickup roller 42, a feed roller 43, a retard roller 44, a transport guide 45, and transport roller pairs 46, 47, and 48. Incidentally, the pickup roller 42, the feed roller 43, the retard roller 44, and the transport roller pairs 46, 47, and 48 are all formed in a cylindrical shape with their central axes aligned in the left-right direction.

[0040] The paper cassette 41 is configured in a hollow rectangular parallelepiped shape and is detachable from the housing 2. The paper cassette 41 stores the medium MD in a stacked state with the paper surface facing up and down, i.e., in a stacked state. In this embodiment, the medium MD is a so-called OHP (Overhead projector) film, specifically, for example, CG3700 (manufactured by 3M Japan Ltd.). The medium MD has a sufficiently high transmittance of visible light and is a so-called transparent film-like medium.

[0041] The pickup roller 42 is in contact with the vicinity of the front end of the top surface of the medium MD stored in the paper cassette 41. The feed roller 43 is disposed slightly in front of the pickup roller 42. The retard roller 44 is located below the feed roller 43, and forms a gap between it and the feed roller 43 that corresponds to the thickness of one sheet of the medium MD.

[0042] When a driving force is supplied from a paper feed motor (not shown), the first paper feed section 40 rotates or stops the pickup roller 42, feed roller 43, and retard roller 44 as appropriate. As a result, the pickup roller 42 advances the topmost sheet or sheets of the media MD stored in the paper cassette 41. The feed roller 43 and retard roller 44 advance the topmost sheet of the media MD further forward, while blocking the second sheet and subsequent sheets. In this way, the first paper feed section 40 advances the media MD forward while separating them one by one.

[0043] The transport guide 45 is disposed in a front lower portion of the transport path W, and causes the medium MD to travel in a front-upper direction and then in a rear-upper direction along the transport path W. The transport roller pairs 46 and 47 are disposed near the center and near the upper end of the transport guide 45, respectively, and rotate in a predetermined direction by receiving a driving force from a paper feed motor (not shown). This causes the transport roller pairs 46 and 47 to transport the medium MD along the transport path W.

[0044] Further, a second paper feed section 50 is provided in front of the pair of transport rollers 47 in the housing 2. The second paper feed section 50 is provided with a paper tray 51, a pickup roller 52, a feed roller 53, a retard roller 54, etc. The paper tray 51 is formed in a thin plate shape in the vertical direction, and is configured to place the medium MD2 on its upper side. Incidentally, the medium MD2, which is different in size and paper quality from the medium MD stored in the paper cassette 41, for example, is placed on the paper tray 51.

[0045] The pickup roller 52, the feed roller 53, and the retard roller 54 are configured in the same manner as the pickup roller 42, the feed roller 43, and the retard roller 44 of the first paper feed section 40. When the second paper feed section 50 receives a driving force from a paper feed motor (not shown), it appropriately rotates or stops the pickup roller 52, the feed roller 53, and the retard roller 54 to feed the bottommost sheet of the medium MD2 on the paper tray 51 backward, while blocking the second and subsequent sheets. Thus, the second paper feed section 50 feeds the medium MD2 backward while separating them one by one. The fed medium MD2 is transported by the transport roller pair 57 along the transport path W in the same manner as the medium MD. For convenience of explanation, the medium MD2 will be simply referred to as the medium MD below without distinguishing it from the medium MD.

[0046] The rotation of the transport roller pair 47 is appropriately restricted, and a frictional force is applied to the medium MD to correct the inclination of the sides of the medium MD with respect to the direction of travel, i.e., to align the leading and trailing edges of the medium MD to the left and right, before sending the medium backward. The transport roller pair 48 is located a predetermined distance rearward from the transport roller pair 47, and rotates in the same manner as the transport roller pair 46, etc. to supply a driving force to the medium MD transported along the transport path W, causing the medium MD to travel further rearward along the transport path W.

[0047] The secondary transfer section 39 of the intermediate transfer section 30 described above, that is, the backup roller 33 and the secondary transfer roller 36, are disposed behind the pair of transport rollers 48. In the secondary transfer section 39, the toner image formed in the image forming unit 10 and transferred to the intermediate transfer belt 34 approaches the intermediate transfer belt 34 as the intermediate transfer belt 34 travels, and a predetermined bias voltage is applied to the secondary transfer roller 36. Therefore, the secondary transfer section 39 transfers the toner image onto the medium MD transported from the intermediate transfer belt 34 along the transport path W, and causes the medium MD to proceed further backward.

[0048] A fixing unit 60 is disposed behind the secondary transfer unit 39. The fixing unit 60 is composed of a heating unit 61 and a pressure unit 62 disposed to face each other across the transport path W. The heating unit 61 has a heater that generates heat, a plurality of rollers, and the like disposed inside a heating belt that is a hollow endless belt. The pressure unit 62 is formed as a cylindrical pressure roller with a central axis aligned in the left-right direction, and presses an upper surface against a lower surface of the heating unit 61 to form a nip portion.

[0049] Based on the control of the control unit 3, the fixing unit 60 heats the heater of the heating unit 61 to a predetermined temperature, rotates the roller appropriately to rotate the heating belt in the direction of the arrow R1, and rotates the pressure unit 62 in the direction of the arrow R2. After that, when the fixing unit 60 receives the medium MD onto which the toner image has been transferred by the secondary transfer unit 39, it sandwiches (i.e. nips) it between the heating unit 61 and the pressure unit 62, applies heat and pressure to fix the toner image to the medium MD, and sends it out backwards.

[0050] A pair of transport rollers 64 is disposed behind the fixing unit 60, and a switching unit 65 is disposed behind the pair of transport rollers 64. The switching unit 65 switches the traveling direction of the medium MD to the upward or downward direction according to the control of the control unit 3. A paper discharge unit 70 is provided above the switching unit 65. The paper discharge unit 70 is composed of a transport guide 71 that guides the medium MD upward along the transport path W, pairs of transport rollers 72, 73, 74, and 75 that face each other across the transport path W, and a discharge port 76.

[0051] Further, a re-conveying unit 66 is disposed below the switching unit 65, the fixing unit 60, the secondary transfer unit 39, etc. The re-conveying unit 66 has a conveying guide, a pair of conveying rollers (not shown), etc. that constitute a re-conveying path Z. The re-conveying path Z heads downward from below the switching unit 65, and then proceeds forward, and merges with the conveying path W downstream of the pair of conveying rollers 57.

[0052] When discharging the medium MD, the control unit 3 switches the traveling direction of the medium MD to the upper discharge unit 70 side by the switching unit 65. The discharge unit 70 transports the medium MD received from the switching unit 65 upward and discharges it from the discharge port 76 to the discharge tray 2T. When returning the medium MD upside down, the control unit 3 switches the traveling direction of the medium MD to the lower re-conveyance unit 66 side by the switching unit 65. The re-conveyance unit 66 transports the medium MD received from the switching unit 65 to the re-conveyance path Z, and eventually reaches the downstream side of the transport roller pair 57, causing the medium MD to be transported again along the transport path W. In this way, the image forming apparatus 1 can return the medium MD to the transport path W with the paper surface of the medium MD turned over, thereby performing so-called double-sided printing.

[0053] In this manner, in the image forming apparatus 1, a toner image is formed using toner T in the image forming unit 10 and transferred to the intermediate transfer belt 34, the toner image is transferred from the intermediate transfer belt 34 to the medium MD in the secondary transfer section 39, and then fixed in the fixing section 60, thereby printing an image on the medium MD, i.e., forming an image.

[0054] For example, in the image forming apparatus 1, when the image forming unit 10 sequentially transfers a silver toner image PS made of silver toner TS and a color toner image PL made of color toner TL onto the intermediate transfer belt 34, these images are transferred onto the medium MD at the secondary transfer section 39. As a result, the medium MD comes into a state in which the color toner image PL and the silver toner image PS are printed and superimposed on the surface thereof.

[0055] In the following, an image in which the silver toner image PS (i.e., the glossy image) is superimposed on the color toner image PL (i.e., the non-glossy image), i.e., a color metallic image, is referred to as a glossy superimposed image PV. In addition, in the following, the process of forming and fixing this glossy superimposed image PV on the medium MD, i.e., the process of printing, is also referred to as a glossy superimposed image printing process.

[0056] Incidentally, in the image forming apparatus 1, the absolute value of the bias voltage applied to each part under the control of the control unit 3 can be increased to increase the amount of toner T adhering to the toner image transferred to the medium MD, and the absolute value of the bias voltage can be decreased to decrease the amount of toner T adhering to the medium.

[0057] Next, the circuit configuration of the image forming apparatus 1 will be described with reference to the block diagram of Fig. 3. The control unit 3 of the image forming apparatus 1 is configured mainly around a print control unit 80, to which a storage unit 81, an interface unit 82, a display control unit 83, a process control unit 84, a development voltage control unit 85, a supply voltage control unit 86, an exposure control unit 87, a transfer voltage control unit 88, and a motor control unit 89 are connected.

[0058] The printing control unit 80 has a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, and a RAM (Random Access Memory) 93 inside, and performs various processes by using the RAM 93 as a work area and executing various programs read from the ROM 92, the memory unit 81, etc. by the CPU 91.

[0059] The storage unit 81 is a non-volatile storage medium such as a hard disk drive (HDD) or a solid state drive (SSD), and stores various programs and information. The storage unit 81 is provided with a normal color data conversion table 95, a brilliant color data conversion table 96, and a status information table 97.

[0060] Among these, the normal color data conversion table 95 stores information for forming a print pattern of each color for the portion of the print data acquired from the higher-level device 100 that is represented by normal colors (black, cyan, magenta, and yellow). The glitter color data conversion table 96 stores information for forming a print pattern corresponding to the portion of the print data acquired from the higher-level device 100 that is represented by glitter color (silver).

[0061] Various pieces of information indicating various states of each part in the image forming apparatus 1 are stored in the status information table 97, and are updated as appropriate. For example, the number of rotations of the photoconductor drum 26 (FIG. 2) in the image forming unit 10 of each color is measured and stored in this status information table 97. Also, for example, for the toner container 12 of each color, the number of dots that have used (consumed) toner through printing since it was last replaced is tallied and stored in the status information table 97. Hereinafter, the number of dots tallied in this way is also referred to as the dot count.

[0062] The interface unit 82 functions as an interface for a wired LAN (Local Area Network) conforming to standards such as IEEE (Institute of Electrical and Electronics Engineers) 802.3u / ab / an / ae, or a wireless LAN conforming to standards such as IEEE 802.11a / b / g / n / ac / ax, etc. This interface unit 82 can transmit and receive various information to and from the higher-level device 100, a predetermined server device (not shown), etc.

[0063] Based on instructions from the print control unit 80, the display control unit 83 creates display screen data representing various display screens on which characters, figures, etc. are appropriately arranged, and sends the display screen data to the display unit 4 to cause the display screen to be displayed on the display unit 4.

[0064] The process control unit 84 controls the voltages of the various parts in the image forming units 10 for each color based on instructions from the print control unit 80. The development voltage control unit 85 controls the development voltage applied to the development roller 24 and the development blade 25 (FIG. 2) based on instructions from the print control unit 80. The supply voltage control unit 86 controls the supply voltage applied to the first supply roller 22 and the second supply roller 23 (FIG. 2) based on instructions from the print control unit 80.

[0065] The exposure control unit 87 controls the turning on and off of each light-emitting element chip provided in the LED head 14 based on instructions from the print control unit 80. The transfer voltage control unit 88 controls the transfer voltage applied to the primary transfer roller 35, the secondary transfer roller 36 (FIG. 2), etc. based on instructions from the print control unit 80. The motor control unit 89 controls the rotation of the photoconductor drum 26 (FIG. 2) and each roller, etc. based on instructions from the print control unit 80.

[0066] The higher-level device 100 is an information processing device such as a personal computer, and executes various application programs such as document creation, spreadsheets, and image editing based on user operations. A printer driver for printing documents, images, and the like in the image forming device 1 is pre-installed in the higher-level device 100. When the higher-level device 100 receives a print instruction for document data, image data, and the like from a user in an application program, the higher-level device 100 executes the printer driver to generate print data based on the document data, image data, and the like, and transmits the print data to the image forming device 1.

[0067] [2. Toner composition] Next, the toner (also called developer) stored in the toner container 12 of the image forming unit 10 (FIG. 2) will be described. For the standard colors of black (K), cyan (C), magenta (M) and yellow (Y), the toners of each color (black, cyan, magenta and yellow) commercially available for the C941dn manufactured by Oki Electric Industry Co., Ltd. were used.

[0068] For the special color (S) toner, i.e., the glitter toner, a silver toner (hereinafter also referred to as silver toner) was manufactured as described above and used. This silver toner was manufactured by the following method.

[0069] When manufacturing silver toner, in this embodiment, an aqueous medium in which an inorganic dispersant is dispersed is first produced. Specifically, 600 parts by weight of industrial trisodium phosphate dodecahydrate is mixed with 18,400 parts by weight of pure water, and dissolved at a liquid temperature of 60°C. Dilute nitric acid for adjusting pH (hydrogen ion exponent) is then added. A calcium chloride aqueous solution in which 300 parts by weight of industrial calcium chloride anhydride is dissolved in 2,600 parts by weight of pure water is added to this aqueous solution, and while maintaining the liquid temperature at 60°C, the mixture is stirred at high speed for 50 minutes at a rotation speed of 3,566 rpm using a line mill (PRIMIX Corporation). This prepares the aqueous phase, which is an aqueous medium in which a suspension stabilizer (inorganic dispersant) is dispersed.

[0070] In this embodiment, a material dispersion oil medium is prepared. Specifically, 470 parts by weight of a glittering pigment (volume median diameter 5.4 [μm]) containing aluminum powder and 23 parts by weight of a charge control agent (BONTRON E-84: manufactured by Orient Chemical Industry Co., Ltd.) are mixed with 7000 parts by weight of ethyl acetate, which is an organic solvent, to prepare a pigment dispersion liquid.

[0071] In this embodiment, the luster pigment used has a volume average particle size (also called the volume median diameter) of 5.4 μm, but is not limited to this. Specifically, the volume average particle size of the luster pigment is preferably 5 μm or more and 20 μm or less, and more preferably within the range of 5.3 to 5.7 μm.

[0072] Among these, the glittering pigment contains minute aluminum (Al) flakes, that is, small pieces having planar portions that are flat, flat, or scaly. Hereinafter, this glittering pigment is also called an aluminum pigment or a metal pigment. The volume average particle size is also called the volume particle size, the volume median size, or the average median size. In this embodiment, a glittering pigment with a volume average particle size of 5.4 [μm] is used, but this is not limiting, and a glittering pigment with a volume average particle size in the range of 5.3 to 5.7 [μm], for example, may be used.

[0073] Then, in this embodiment, while maintaining the liquid temperature of the pigment dispersion at 60°C, 175 parts by weight of ester wax (WE-4: manufactured by NOF Corp.) and 1670 parts by weight of polyester resin are added and stirred until no solid matter remains. This prepares an oil phase, which is a pigment dispersion oil-based medium.

[0074] Next, in this embodiment, the oil phase is added to the aqueous phase whose liquid temperature has been lowered to 55° C., and the oil phase is suspended by stirring at a rotation speed of 1000 rpm for 5 minutes to form particles in the suspension. The suspension is then distilled under reduced pressure to remove ethyl acetate, forming a slurry containing a toner. Nitric acid is then added to the slurry to adjust the pH to 1.6 or less, and the slurry is stirred to dissolve tricalcium phosphate, which is a suspension stabilizer, and the toner is formed by dehydrating the slurry. The dehydrated toner is then redispersed in pure water, stirred, and washed with water. After that, in this embodiment, a dehydration process, a drying process, and a classification process are performed to generate toner base particles.

[0075] In this embodiment, the toner base particles thus produced are mixed with 1.5% by weight of small silica (RY200: manufactured by Nippon Aerosil Co., Ltd.), 2.29% by weight of colloidal silica (X24-9163A: manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.37% by weight of melamine particles (EPOSTAR S: manufactured by Nippon Shokubai Co., Ltd.) as an external addition step. In this manner, in this embodiment, a silver toner having a lustrous appearance can be obtained.

[0076] Incidentally, as for the size of the aluminum flakes which are the luster pigment, as mentioned above, although it is regulated to some extent by the value of the volume average particle size, it is considered that the size is distributed centered on a certain range, for example according to a Gaussian distribution.

[0077] Therefore, it is considered that the size of the silver toner produced using this luster pigment also has a distribution centered on a certain range. In this embodiment, the volume average particle size (volume median diameter) of the silver toner produced was measured and found to be 15.01 [μm]. The volume median diameter of the silver toner is not limited to 15.01 [μm], and may be, for example, 10 to 20 [μm].

[0078] Meanwhile, in the image forming device 1 (FIG. 1), in the silver image forming unit 10 (i.e., image forming unit 10S), the silver toner is supplied to the first supply roller 22, etc. while being stirred by a stirring member or the like not shown inside the toner container 12 (FIG. 2) in which the silver toner is stored, inside the toner storage space 21, etc.

[0079] At this time, it was found that relatively small particles of silver toner tend to be used (consumed) preferentially in the image forming unit 10. That is, in the image forming device 1, the size of the silver toner is relatively small immediately after the silver toner container 12 is replaced, and as the silver toner is used (consumed), the size of the silver toner increases.

[0080] This is presumably due to the following reasons. That is, as described above, silver toner TS has a particle size distribution centered on the value of the volume average particle size. Also, the smaller the particle size of silver toner TS, the less the content of conductive glitter pigment and the higher the amount of charge, making it easier to develop. As a result, in the image forming unit 10, in the early stages of printing immediately after replacing the silver toner container 12, the glitter developer to be developed is preferentially used (consumed) in the order of size, starting from the small particle size silver toner TS that contains less glitter pigment and has low conductivity.

[0081] Accordingly, when the image forming device 1 prints an image using silver toner, the size of the silver toner contained in the image varies depending on the amount of silver toner consumed since the silver toner container 12 was replaced, and the impression given to a user who visually sees this may also vary.

[0082] Therefore, in this evaluation test, in the image forming apparatus 1, the consumption amount of the silver toner from the time when the silver toner container 12 was replaced was counted as a dot count d, and some of the processes were switched depending on this dot count d.

[0083] [3. Evaluation of glitter superimposed images] Next, we will explain the case where the image forming device 1 prints an image in which a color toner image PL made of color toner TL of normal colors (here, we focus on magenta, yellow, and cyan excluding black) and a silver toner image PS made of silver toner TS of a brilliant color (i.e., silver) are superimposed, that is, a brilliant superimposed image PV.

[0084] As described above, when a glittering superimposed image PV (i.e., a color metallic image) is printed on a medium MD, a phenomenon occurs in which the saturation is reduced (i.e., the color gamut is narrowed) in each part of the glittering superimposed image PV compared to a color toner image PL made only of color toner TL. This is because the superimposed silver toner TS is fixed in a state in which it covers the surface of the color toner TL. This phenomenon also occurs in all colors (magenta, yellow and cyan, as well as black).

[0085] Therefore, in this embodiment, various evaluation tests were carried out on the color gamut of the glitter superimposed image PV. These evaluation tests will be described below.

[0086] [3-1. Indicators used for evaluation] In this evaluation test, the amount of toner (color toner TL or silver toner TS) adhered per unit area to the medium MD is represented by image density [%]. This image density corresponds to the ratio of the area of ​​the printed portion (portion where an image is formed) on the medium MD to the total area of ​​the printable range (e.g., an area equivalent to one sheet of the medium MD) that can be printed by the image forming apparatus 1. Furthermore, this image density is set to 100[%] when an image with an area ratio of 100[%] is printed, as in so-called full-surface solid printing. For example, when an image is printed in an area equivalent to an area of ​​1[%] of the printable range of the medium MD, the image density is 1[%].

[0087] Furthermore, when a relatively small rectangular unit area is set and a print pattern N is specified that represents the arrangement of pixels (hereinafter referred to as print pixels) on which toner is printed, the image density represents the ratio of the number of dots in the print pixels to the total number of dots in the unit area. For example, if the unit area is a rectangle of 8 dots vertically and 8 dots horizontally and the total number of dots is 64 dots, if the number of dots in the print pixels is 32 dots, the image density is 50[%], and if the number of dots in the print pixels is 16 dots, the image density is 25[%].

[0088] The amount of toner (color toner TL or silver toner TS) adhered to the medium MD per unit area is sometimes called the print image density, print duty, or print rate in addition to the image density described above.

[0089] In this evaluation test, the luminous reflectance difference ΔY was measured as a measurement value showing the silvery hue of the glitter superimposed image PV on the paper surface, i.e., the degree of grayness. The luminous reflectance difference ΔY was measured using a spectrophotometer CM-2600d (manufactured by Konica Minolta Japan, Inc.).

[0090] The visual reflectance difference ΔY is calculated by subtracting the visual reflectance Y2 of the medium MD before printing from the visual reflectance Y1 on the image after the image is printed on the medium MD. The conditions for measurement using the spectrophotometer CM-2600d were as follows: the light source was auxiliary illuminant C (6774[K]) for color measurement, and SCE (specular reflected light excluded) was used for the specular reflected light. When measuring the visual reflectance Y, OS coated paper W without an image printed thereon was used as the underlay for the medium MD.

[0091] Furthermore, in this evaluation test, a spectrophotometer X-Rite eXact (manufactured by X-Rite, Inc.) was used to measure the density and color gamut of cyan on the paper surface. The measurement conditions for the X-Rite eXact spectrophotometer were a light source of D50, an angle of 2°, and ISO Status I density status.

[0092] The color gamut is expressed using C*, which means saturation in color space, and C* is calculated according to the following formula (1) based on a* and b*, which can be measured using a spectrophotometer.

[0093]

number

[0094] When the image density of each of the normal colors (magenta, yellow, and cyan) is taken as 100%, the C* values ​​are 72, 93, and 60, respectively. In the color obtained by superimposing silver toner TS on the normal color toner TL (hereinafter referred to as metallic color), the closer the C* value of the metallic color is to the C* value of the normal color, the wider the color gamut is.

[0095] In addition, in this evaluation test, the "C* retention rate" calculated using C* was used as an index value. This C* retention rate is a percentage value that represents the proportion of the C* value of the color toner image PL that is retained after the silver toner image PS is superimposed. Specifically, the C* retention rate is calculated by dividing the C* value of the glitter superimposed image PV, in which the silver toner image PS is superimposed on the color toner image PL, by the C* value of the color toner image PL alone, and multiplying the result by the numerical value 100.

[0096] Furthermore, in this evaluation test, the flop index value (hereinafter referred to as FI value) was used as an index value representing the glossiness of the medium MD. The FI value was measured using a goniophotometer GC-5000L (manufactured by Nippon Denshoku Industries Co., Ltd.).

[0097] The FI value is a value that expresses the level of brilliance as a numerical value, and can be calculated by the following formula (2). In this formula (2), when light is irradiated onto the paper surface at an angle of 45°, the intensities of reflected light received in directions of 0°, 30°, and -65° with respect to the perpendicular direction of the paper surface are expressed as reflected light intensities L*0, L* 30 and L* -65 It states that:

[0098]

number

[0099] In this evaluation test, the FI values ​​obtained from various images printed on the medium MD were compared with the glossiness obtained by visual inspection of the images, and it was found that when the FI value was 10.0 or higher, the metallic gloss was perceived as being sufficiently strong.

[0100] [3-2. Evaluation test conditions] Next, we will explain various conditions, etc., used in this evaluation test when creating the evaluation medium MDE using the image forming device 1. In this evaluation test, a C941dn (manufactured by Oki Electric Industry Co., Ltd.) was used as the image forming device 1, and A4-sized OS coated paper W (manufactured by Fujifilm Business Innovation Co., Ltd.) was used as the medium MD.

[0101] In this evaluation test, the host device 100 (Fig. 3) created print data representing a glitter superimposed image PV in which a silver toner image PS was superimposed on a color toner image PL with an image density of 100% over the entire printable area of ​​an A4-sized medium MD, as shown in Fig. 4. Specifically, the medium MD had a long side length ML1 of 297 mm, a short side length ML2 of 210 mm, and a margin length ML3, which was the width of the margin formed between each side and the glitter superimposed image PV, of 5 mm.

[0102] Incidentally, in this evaluation test, the resolution of the image formed by the image forming apparatus 1 is set to 600 [dpi], and the length of a side of one dot (also called a picture element or pixel) is 0.042 [mm].

[0103] In addition, in this evaluation test, in the bright-colored (silver) image forming unit 10S (Figure 1) in the image forming device 1, when an image with an image density of 100% (a so-called solid image) was printed on the medium MD, various bias voltages (developing voltage, etc.) were adjusted in advance so that the visual reflectance difference ΔY would be a value of 33.

[0104] Furthermore, in this evaluation test, in the image forming unit 10M (Figure 1) of a normal color (magenta, etc.) in the image forming device 1, when an image with an image density of 100% (a so-called solid image) is printed on the medium MD, various bias voltages (developing voltage, etc.) were adjusted in advance so that the optical density OD would be 1.4.

[0105] Furthermore, in this evaluation test, in the control unit 3 (Figure 3) of the image forming device 1, a data conversion table for converting image density (i.e., image area ratio) was pre-stored in the normal color data conversion table 95 and the brilliant color data conversion table 96 of the memory unit 81.

[0106] When the control unit 3 of the image forming apparatus 1 receives print data from the higher-level device 100 (FIG. 3), it forms printing bitmap data based on the print data, generates separated bitmap data by separating the data into individual colors (silver, cyan, etc.), and supplies the generated exposure data through a predetermined conversion process to the exposure control unit 87. At this time, the control unit 3 refers to the bright color data conversion table 96 and performs a print pattern conversion process to convert the silver separated bitmap data into each print pattern N, thereby reducing the image density to 50[%], 25[%], etc.

[0107] [3-3. Determining the image density of silver toner for each color] Next, the results of various measurements and evaluations in this evaluation test will be explained. First, in this evaluation test, multiple glitter superimposed images PV were created by combining multiple types of color toner images PL and multiple types of silver toner images PS, and multiple types of evaluation media were created by printing each of them on media MD. Of these, the color toner images PL were the normal colors cyan, magenta, or yellow, and their image density was fixed at 100[%]. On the other hand, the silver toner images PS were set to three image densities: 100[%], 50[%], and 25[%].

[0108] Here, the image density values ​​of 100[%], 50[%], and 25[%] are 1 / 1, 1 / 2, and 1 / 4, respectively, expressed as fractions. In the image forming apparatus 1, the dots constituting the image to be printed are arranged in a grid pattern along the vertical and horizontal directions, so when the print pattern N is formed with a relatively small number of dots, the image density can be easily achieved if the fraction is relatively simple. For this reason, values ​​such as 100[%], 50[%], and 25[%] were adopted as the image density of the silver toner image PS in this evaluation test.

[0109] In this evaluation test, for each evaluation medium thus prepared, the FI value, which is an index representing glossiness, C*, which is an index representing saturation and color gamut, and the C* retention rate, which represents the degree to which saturation is retained after the silver toner image is superimposed, were measured and calculated. Table TBL1 shown in Figure 5 organizes the results of measurements and calculations obtained based on each evaluation medium in correspondence with the color of the color toner image PL and the image density of the silver toner image PS.

[0110] Furthermore, when the values ​​in Table TBL1 were plotted on a two-dimensional plane with the image density of the silver toner image PS and the C* retention rate as the coordinate axes, the graph shown in Figure 6 was obtained. Furthermore, simple linear approximation was performed based on the plots of cyan, magenta, and yellow, and characteristic curves QLC, QLM, and QLY were obtained. Specifically, the formulas expressing the characteristic curves QLC, QLM, and QLY are the following formulas (3C), (3M), and (3Y), where x is the variable expressing the image density of the silver toner image PS.

[0111]

number

[0112] 6, in order to maintain the hue of each color constant, for example, if the C* retention rate is 60%, the image densities of the silver toner images PS to be superimposed on cyan, magenta, and yellow are 58.9%, 28.5%, and 25.5%, respectively. These values ​​are relatively close to 50%, 25%, and 25%, respectively.

[0113] Next, in Table TBL1, assume that the image density of the silver toner image PS for cyan is reduced from 100%. The C* value increases and approaches 60, which is the C* value for single color cyan. Meanwhile, the FI value decreases and the metallic luster weakens. Therefore, in the following examples, the image density of the silver toner image PS superimposed on cyan is set to 50% (hereinafter referred to as cyan silver 50%]) to achieve a well-balanced and relatively high C* and FI values.

[0114] Next, we consider determining the optimal image density of the silver toner image PS to be superimposed on magenta and yellow when cyan silver is 50%. This is because if magenta and yellow can be matched to the same color tone as cyan, a print result with the same color gamut and brilliance as cyan can be obtained. In other words, by matching the color tone, when a silver toner image is superimposed while multiple color toners are used in one image, it is expected that a print result with the same color gamut and brilliance can be obtained for each color.

[0115] In this evaluation test, we focused on the FI value and C* retention as indicators for matching the color shades of each color. As described above, the C* retention is a value that represents the ratio of the C* value of the color toner image PL that is retained after the silver toner image PS is superimposed. In other words, the higher the C* retention, the closer the color gamut is to that of a single color toner.

[0116] Incidentally, a method of comparing the C* of each color may be considered as an index for matching the color shades of each color. However, this method may cause a problem that even if the C* value is the same for each color, the color shades may appear different. This is thought to occur because the C* value for a single color toner is different for each color, and the magnitude of the color shade difference value (hereinafter referred to as ΔC*) between the single color toner and the silver toner is also different. For this reason, in this evaluation test, the C* retention rate is used as an index, rather than the C* value itself.

[0117] Referring again to Table TBL1 (FIG. 5), the FI value of magenta is roughly constant (11.1-10.4) even when the image density of the silver toner image PS is changed between 100% and 25%, and is similar to the FI value (10.4) at 50% cyan silver. In addition, when the image density of the silver toner image PS superimposed on magenta is 25%, the C* retention value (68%) is closest to the C* retention value (58%) at 50% cyan silver.

[0118] Next, based on the values ​​in Table TBL1, we consider the range of image density of the silver toner image PS that can match the color tone of magenta to cyan. First, for the reference cyan silver 50[%], we investigated the range of fluctuations in the FI value and C* retention rate according to the dot count d after the toner container 12 was replaced. The FI value was in the range of 10.3 to 11.3, and the C* retention rate was 47 to 67[%].

[0119] Next, the FI value and C* retention rate value for magenta in Table TBL1 were examined. Figure 7(A) shows the relationship between the image density of the silver toner image PS and the FI value of magenta plotted on a graph, and an approximation curve ARF was created by approximating the relationship with a quadratic curve based on this blot. In this approximation curve ARF, the image density of the silver toner was determined so that the FI value was in the range of 10.3 to 11.3, similar to that of cyan silver 50[%], and the range of 17 to 100[%] was found to be appropriate as the first image density.

[0120] In Figure 7(B), the relationship between the image density of the silver toner image PS and the C* retention rate of magenta is plotted on a graph, and an approximation curve ARC is created using a quadratic curve based on this blot. In this approximation curve ARF, the image density of the silver toner that would result in a C* retention rate in the range of 47 to 67%, similar to that of cyan silver at 50%, was determined to be 23 to 44%.

[0121] In other words, the image density of the silver toner image PS that can match the color tone of magenta to cyan is appropriately within the range of 23 to 44% as the second image density. Therefore, in this evaluation test, 25% was adopted as the image density of the silver toner image PS superimposed on magenta, as it is a value within this range that can configure the print pattern N with a relatively small number of dots. Hereinafter, an image density of 25% of the silver toner image PS superimposed on magenta will be referred to as magenta silver 25%.

[0122] On the other hand, when focusing on yellow in Table TBL1, when the image density of the silver toner image PS was set to 100[%], 50[%] or 25[%], the FI value fell below the value of "10", making it difficult to achieve an FI value (10.4) at the same level as that of cyan silver 50[%].

[0123] However, when the image density of the silver toner image PS superimposed on yellow is set to 25% (hereinafter referred to as yellow silver 25%), the FI value (6.7) is lower than the FI value (10.4) of cyan silver 50% but the C* retention rate (67%) is similar to the C* retention rate (58%) of cyan silver 50%. Due to this relationship, in this evaluation test, the image density of the silver toner image PS superimposed on yellow is set to 25%, the same as that of magenta. Hereinafter, the image density of the silver toner image PS superimposed on yellow is set to 25% and is referred to as yellow silver 25%.

[0124] Here, the relationship between the saturation of each color and the image density of the superimposed silver toner image PS will be considered. First, the C* (corresponding to saturation) of the toner image printed (i.e. fixed on the medium MD) for each of cyan, magenta, yellow and silver was measured with an image density of 100[%], and the results were 60.0, 73.2, 93.6 and 1.9, respectively, as shown in Table TBL2 in FIG. 8. That is, the saturation of cyan (60.0) is smaller than the saturation of magenta and yellow (73.2 and 93.6). For convenience of explanation, the saturation of cyan will be referred to as the first saturation, and the saturation of magenta and yellow will be referred to as the second saturation.

[0125] In addition, if the difference value between C* for each color other than silver (i.e., normal colors) and C* for silver is defined as the color difference ΔC*, the values ​​of the color difference ΔC* for cyan, magenta, and yellow were 58.1, 71.3, and 91.7, respectively, as shown in Table TBL2.

[0126] Next, ΔE, which is the color tone including lightness (L*), was calculated for each of cyan, magenta, yellow and silver according to the following formula (4), resulting in values ​​of 81.3, 89.0, 128.9 and 73.4, respectively, as shown in Table TBL2. If the difference between ΔE for each color other than silver (i.e., normal colors) and ΔE for silver is taken as the color tone difference ΔE*, then the values ​​of the color tone difference ΔE* for cyan, magenta and yellow were 8.0, 15.6 and 55.5, respectively, as shown in Table TBL2.

[0127]

number

[0128] From this table TBL2, when a silver toner image PS is superimposed on a normal color toner image PL to print a glossy superimposed image PV, the image density of the silver toner image PS can be determined by reference to the image density of the silver toner image PS superimposed on cyan, magenta, and yellow.

[0129] Specifically, for example, if the color difference ΔC* of the normal color is 58.1 or more and less than 71.3, and the color difference ΔE* is 8.0 or more and less than 15.6, the image density of the superimposed silver toner image PS can be set to 50[%], similar to cyan. Also, for example, if the color difference ΔC* of the normal color is 71.3 or more and less than 91.7, and the color difference ΔE* is 15.6 or more and less than 55.5, the image density of the superimposed silver toner image PS can be set to 25[%], similar to magenta and yellow. Hereinafter, the image density of cyan (50[%]) is also referred to as the first image density, and the image density of magenta and yellow (25[%]) is also referred to as the second image density.

[0130] [3-4. Print pattern composition] Next, in this evaluation test, multiple types of print patterns N, including ones for comparison, were prepared for the glitter superimposed image PV that realized 50% cyan silver, 25% magenta silver, and 25% yellow silver.

[0131] Incidentally, the image forming apparatus 1 controls each light emitting element chip of the LED head 14 (FIG. 2) to be turned on (lit) or off (unlit) by the exposure control unit 87 of the control unit 3 (FIG. 3). As a result, the image forming apparatus 1 develops toner and prints at the locations where each light emitting element chip of the LED head 14 is turned on, while not developing toner and not printing at the locations where it is turned off, so that an image based on the print pattern can be printed on the medium MD.

[0132] 9(A), (B), (C) and (D) are schematic diagrams of a medium MD on which a glitter superimposed image PV is printed, with the upper part being a plan view of the medium MD as seen from above, and the lower part being a side view of the medium MD as seen from the side. These Figs. 9(A) to (D) respectively show print patterns NC1, NC2, NC3 and NC4, each of which is a square with 8 dots on a side, with the lower layer being a color toner image PL and the upper layer being a silver toner image PS.

[0133] 9(A) to (D), in the print patterns NC1 to NC4, toner is used for all dots in the lower color toner image PL, and the image density is 100%. Note that the print patterns NC1 to NC4 all use cyan toner to form the color toner image PL. In the following, the print pattern N, which is a pattern in which dots (pixels) that use toner are arranged, is also referred to as the arrangement pattern.

[0134] In the print pattern NC1 (FIG. 9(A)), in the upper silver toner image PS, toner is used for all dots, just like in the lower color toner image PL, and the image density is 100%. In other words, the print pattern NC1 is configured by overlapping a silver solid image on a cyan solid image.

[0135] The print patterns NC2 to NC4 (FIGS. 9B to 9D) have different patterns formed by disposing the silver toner at different positions in the upper silver toner image PS while maintaining the image density at 50%. In other words, the print patterns NC2 to NC4 are all cyan silver 50%.

[0136] Specifically, in print pattern NC2, the entire area, which is a square of 8 dots vertically and 8 dots horizontally, is divided into multiple rectangular small areas, each of which is 4 dots vertically and 1 dot horizontally, and silver toner is placed in every other small area. In print pattern NC3, the entire area is divided into rectangular small areas, each of which is 4 dots vertically and 2 dots horizontally, and silver toner is placed in every other small area. In print pattern NC4, the entire area is divided into square small areas, each of which is 4 dots vertically and 4 dots horizontally, and silver toner is placed in every other small area. For convenience of explanation, in the following, for the entire area and small areas, the number of dots along the horizontal direction, which is the main scanning direction, is also referred to as the main scanning dot number, and the number of dots along the vertical direction, which is the sub-scanning direction, is also referred to as the sub-scanning dot number.

[0137] Next, Figures 10(A), (B), (C), (D), (E) and (F) are schematic diagrams of a medium MD on which a glitter superimposed image PV is printed, and are plan views showing the medium MD as viewed from above. Figures 10(A) to (F) show print patterns NM1, NM2, NM3, NM4, NM5 and NM6, respectively, and print patterns NM1 to NM6 have a lower layer of a color toner image PL and an upper layer of a silver toner image PS, similar to print pattern NC1 (Figure 9(A)) and the like.

[0138] Of these, print patterns NM1, NM2, and NM3 are all configured as squares with sides measuring 4 dots. Print pattern NM4 is configured as a square with sides measuring 6 dots. Print pattern NM5 is configured as a rectangle measuring 12 dots vertically and 16 dots horizontally. Print pattern NM6 is configured as a rectangle measuring 8 dots vertically and 24 dots horizontally.

[0139] Furthermore, each of the print patterns NM1 to NM6 uses, as the color toner image PL, an image made up only of magenta toner (that is, a solid magenta image) or an image made up only of yellow toner (that is, a solid yellow image).

[0140] In print pattern NM1 (FIG. 10A), like print pattern NC1 (FIG. 9A), toner is used for all dots in the upper silver toner image PS, as in the lower color toner image PL, resulting in an image density of 100%. In other words, print pattern NC1 is configured by overlaying a silver solid image on a magenta or yellow solid image.

[0141] In the print pattern NM2 (FIG. 10(B)), the entire area of ​​the upper silver toner image PS, which is a square shape of 4 dots vertically and 4 dots horizontally, is divided into multiple small square areas, each of which is 2 dots vertically and 2 dots horizontally, and silver toner is placed in every other small area. In other words, in the print pattern NM2, the image density of the silver toner image PS is set to 50[%].

[0142] In print pattern NM3 (Fig. 10(C)), the entire area of ​​the upper silver toner image PS, which is a square shape of 4 dots vertically and 4 dots horizontally, is divided into small square areas of 2 dots vertically and 2 dots horizontally, and silver toner is placed in only one of the four areas. In other words, in print pattern NM3, the image density of the silver toner image PS is 25[%], which corresponds to magenta silver 25[%] or yellow silver 25[%].

[0143] In print pattern NM4 (Fig. 10(D)), the entire area of ​​the upper silver toner image PS, which is a square of 6 dots vertically and 6 dots horizontally, is divided into multiple small square areas of 3 dots vertically and 3 dots horizontally, and silver toner is placed in only one of the total four areas. In other words, compared to print pattern NM3, print pattern NM4 has the same image density of the silver toner image PS at 25[%], which is also equivalent to magenta silver 25[%] or yellow silver 25[%], while each small area is expanded vertically and horizontally.

[0144] In print pattern NM5 (FIG. 10(E)), the entire area of ​​the upper silver toner image PS, which is a rectangle of 12 dots vertically and 16 dots horizontally, is divided into multiple rectangular small areas of 3 dots vertically and 4 dots horizontally, and silver toner is placed in 4 of the total 16 areas by drawing a diagonal line connecting the upper left and lower right parts of the entire area. In other words, compared to print pattern NM4, print pattern NM5 has the same image density of the silver toner image PS relative to the entire area of ​​25[%], which is also equivalent to magenta silver 25[%] or yellow silver 25[%], while each small area is expanded horizontally and the locations where silver toner is placed are arranged in a straight line or in a staircase shape along the inclined direction.

[0145] In the printing pattern NM6 (FIG. 10(F)), the entire area of ​​the upper silver toner image PS, which is a rectangle of 8 dots vertically and 24 dots horizontally, is divided into multiple rectangular small areas of 2 dots vertically and 6 dots horizontally, and silver toner is placed in 4 of the total 16 areas by drawing a diagonal line connecting the upper left part and the lower right part of the entire area. In other words, compared to printing pattern NM5, printing pattern NM6 has the same image density of the silver toner image PS relative to the entire area of ​​25[%], which is also equivalent to magenta silver 25[%] or yellow silver 25[%]. In addition, printing pattern NM6 shrinks each small area vertically while expanding it horizontally, and similarly arranges the areas where silver toner is placed in a straight line or a staircase shape along the inclined direction.

[0146] [3-5. Details of Examples and Comparative Examples] Next, in this evaluation test, a glitter superimposed image PV with appropriately different printing patterns N (Figures 9 and 10) was printed on a medium MD, and multiple examples X and multiple comparison examples Z were performed, centered on cyan silver 50[%], magenta silver 25[%], and yellow silver 25[%].

[0147] In this evaluation test, the dot count, which indicates the amount of toner used (consumed) from the time when the toner container 12 (FIG. 2) was replaced in the silver image forming unit 10S (FIG. 1), was tallied, and the printing pattern N in Example X and Comparative Example Z was appropriately switched according to this dot count d. The reason for switching the printing pattern N according to the silver dot count d will be described later. In the following, the dot count d is also referred to as the amount used after replacement.

[0148] First, in this evaluation test, Example X1C for cyan, Example X2M for magenta, and Example X3Y for yellow were performed. Specifically, in this evaluation test, the brilliant color data conversion table 96 provided in the memory unit 81 (FIG. 3) of the image forming device 1 was stored with the tables TBL3 and TBL4 shown in FIG. 11(A) and (B), and the printing pattern N was switched according to the dot count d.

[0149] In the cyan example X1C (Figure 11(A)), printing pattern NC2 (Figure 9(B)) was used when dot count d was in the range of 0 to less than 1661k, printing pattern NC3 (Figure 9(C)) was used when dot count d was in the range of 1661k or more and less than 3344k, and printing pattern NC4 (Figure 9(D)) was used when dot count d was in the range of 3344k or more.

[0150] That is, in Example X1C, cyan silver is 50% and, as the dot count d increases, the horizontal length of each small region (i.e., rectangle) constituting the silver toner image PS is sequentially extended while maintaining the vertical length, gradually increasing the horizontal width and area of ​​each small region.

[0151] Magenta Example X2M (FIG. 11B) uses print pattern NM3 (FIG. 10C) when dot count d is in the range from 0 to less than 1661k, and print pattern NM4 (FIG. 10D) when dot count d is in the range of 1661k or more and less than 3232k. Example X2M also uses print pattern NM5 (FIG. 10E) when dot count d is in the range of 3232k or more and less than 8564k, and print pattern NM6 (FIG. 10F) when dot count d is 8564k or more.

[0152] That is, in Example X2M, while the magenta silver is 25%, as the dot count d increases, each small area (i.e., rectangle) that makes up the silver toner image PS is expanded vertically and horizontally, and then changed to a stepped arrangement along a diagonal direction, and then the small area is compressed vertically while stretched horizontally.

[0153] The yellow embodiment X3Y (FIG. 11B) was partially similar to the magenta embodiment X2M. That is, the yellow embodiment X3Y used print pattern NM3 (FIG. 10C) when the dot count d was in the range from 0 to less than 1661k, and print pattern NM4 (FIG. 10D) when the dot count d was in the range of 1661k or more and less than 3232k. The embodiment X3Y also used print pattern NM5 (FIG. 10E) when the dot count d was in the range of 3232k or more and less than 6929k, and print pattern NM6 (FIG. 10F) when the dot count d was in the range of 6929k or more.

[0154] That is, in Example X3Y, while the yellow silver is 25%, as the dot count d increases, each small area (i.e., rectangle) constituting the silver toner image PS is expanded vertically and horizontally, then changed to a step-like arrangement along a diagonal direction, and then the small area is compressed vertically while being expanded horizontally. In other words, Example X3Y is similar to Example X2M in the range of dot count d less than 6929k and in the range of dot count d equal to or greater than 8564k, but differs from Example X2M in that only in the range of dot count d equal to or greater than 6929k and less than 8564k is the print pattern NM6.

[0155] In addition, in this evaluation test, comparative examples Z1C and Z2C for cyan, comparative examples Z3M and Z4M for magenta, and comparative examples Z5Y and Z6Y for yellow were performed for comparison with each Example X. Specifically, in this evaluation test, information on each Comparative Example Y was stored in tables TBL3 and TBL4 (FIGS. 11(A) and (B)) stored in the brilliant color data conversion table 96 (FIG. 3), similar to each Example X.

[0156] In the cyan comparative example Z1C (FIG. 11(A)), the print pattern was NC1 (FIG. 9(A)) regardless of the dot count d. That is, in the comparative example Z1C, both the cyan color toner image PL and the silver toner image PS were solid images. In other words, the comparative example Z1C has an image similar to a general cyan color metallic print. In the cyan comparative example Z2C (FIG. 11(A)), the print pattern was fixed to NC2 (FIG. 9(B)) regardless of the dot count d. That is, in the comparative example Z2C, while the cyan silver was 50[%], the size and arrangement of each small area (i.e., rectangle) that constitutes the silver toner image PS was constant regardless of the dot count d.

[0157] The magenta comparative example Z3M (FIG. 11(B)) had the print pattern NM1 (FIG. 10(A)) regardless of the dot count d. That is, in the comparative example Z3M, like the cyan comparative example Z1C, both the magenta color toner image PL and the silver toner image PS were solid images. In other words, the comparative example Z3M has an image similar to a general magenta color metallic print. The magenta comparative example Z4M (FIG. 11(B)) had the print pattern fixed to NM3 (FIG. 10(C)) regardless of the dot count d. That is, in the comparative example Z4M, although the magenta silver was 25[%], the size and arrangement of each small area (i.e., rectangle) constituting the silver toner image PS was constant regardless of the dot count d.

[0158] The yellow comparative example Z5Y (FIG. 11(B)) had a print pattern NM1 (FIG. 10(A)) regardless of the dot count d. That is, in the comparative example Z5Y, like the magenta comparative example Z3M, both the yellow color toner image PL and the silver toner image PS were solid images. In other words, the comparative example Z5Y has an image similar to a general yellow color metallic print. The yellow comparative example Z6M (FIG. 11(B)) had a fixed print pattern NM3 (FIG. 10(C)) regardless of the dot count d. That is, like the magenta comparative example Z4M, the comparative example Z6Y had a yellow silver of 25% but had a constant size and arrangement of each small area (i.e., rectangle) constituting the silver toner image PS regardless of the dot count d.

[0159] In the present evaluation test, each Example X and each Comparative Example Z were each carried out according to the following procedure.

[0160] <Step 1> In the image forming apparatus 1, the toner container 12 in the silver image forming unit 10S is replaced, and when the dot count d is at the value “0”, a glitter superimposed image PV of the printing pattern N corresponding to the dot count d is printed on the medium MD. <Step 2> The FI value and C* value of the medium MD (that is, the evaluation medium) on which the glitter superimposed image PV is printed are measured. <Step 3> In the image forming device 1, by repeating the process of printing an image on the medium MD with the image density of the silver toner TS set to 100%, the value of the dot count d is increased until it reaches the boundary value of the next dot count d in tables TBL3 and TBL4 (for example, 1661k or 1660k). <Step 4> A glitter superimposed image PV of the print pattern N according to the boundary value dot count d is printed on the medium MD. <Step 5> <Step 2> to <Step 4> are repeated until all the toner contained in the toner container 12 has been consumed, and the process ends when all the toner contained in the toner storage space 21 (Figure 2) of the image forming unit 10 has also been consumed.

[0161] In this evaluation test, the cyan toner was consumed when the dot count d reached 9,863k, and the magenta and yellow toners were consumed when the dot count d reached 11,771k.

[0162] [3-6. Measurement results of examples and comparative examples] Next, the measurement results of the glossiness (specifically, FI value) and color gamut (specifically, C*) for each of the examples and comparative examples obtained by this evaluation test will be described.

[0163] First, Table TBL5 shown in Fig. 12(A) summarizes the measurement results of the FI value in cyan Example X1C and Comparative Examples Z1C and Z2C in correspondence with the value of the dot count d. Table TBL6 shown in Fig. 12(B) summarizes the measurement results of the C* value in Example X1C and Comparative Examples Z1C and Z2C in correspondence with the value of the dot count d. Furthermore, Tables TBL5 and TBL6 calculate and list the standard deviation of the FI value and the standard deviation of C* for each Example X and Comparative Example Z.

[0164] Comparing Example X1C with Comparative Example Z1C in Table TBL5, Example X1C has a smaller standard deviation of the FI value. As described above, in Example X1C, the image density of the silver toner image PS is 50%. On the other hand, in Comparative Example Z2C, the image density of the silver toner image PS is 100%. That is, in Example X1C, by setting the image density of the silver toner image PS to 50%, the fluctuation range of the FI value is small and stable regardless of the increase in the dot count d, that is, the degree of glossiness is roughly constant.

[0165] Furthermore, comparing Example X1C with Comparative Example Z2C in Table TBL6, Example X1C has a smaller standard deviation of the C* value. As described above, in Example X1C, the printing pattern N is switched according to the dot count d. On the other hand, in Comparative Example Z2C, the printing pattern N is unchanged regardless of the dot count d. In other words, in Example X1C, by switching the printing pattern N according to the dot count d, the fluctuation range of the C* value becomes smaller regardless of an increase in the dot count d, and it can be seen that a large change in saturation can be suppressed.

[0166] Next, Table TBL7 shown in Figure 12(C) summarizes the measurement results of the FI values ​​in the magenta and yellow Examples X2M and X3Y and Comparative Examples Z3M, Z4M, Z5Y, and Z6Y in correspondence with the dot count d value. Table TBL8 shown in Figure 12(D) summarizes the measurement results of the C* values ​​in the Examples X2M and X3Y and Comparative Examples Z3M, Z4M, Z5Y, and Z6Y in correspondence with the dot count d value. Furthermore, Tables TBL7 and TBL8 calculate and list the standard deviations of the FI values ​​and the standard deviations of C* in each Example X and Comparative Example Z.

[0167] Comparing Example X2M of magenta with Comparative Example Z3M in Table TBL7, Example X2M has a smaller standard deviation of the FI value. As described above, in Example X2M, the image density of the silver toner image PS is 25%. On the other hand, in Comparative Example Z3M, the image density of the silver toner image PS is 100%. That is, in Example X2M, by setting the image density of the silver toner image PS to 25%, the fluctuation range of the FI value is small and stable regardless of the increase in the dot count d, that is, the degree of glossiness is roughly constant.

[0168] Also, comparing Example X2M of magenta with Comparative Example Z4M in Table TBL8, Example X2M has a smaller standard deviation of the C* value. As described above, in Example X2M, the printing pattern N is switched according to the dot count d. On the other hand, in Comparative Example Z4M, the printing pattern N is unchanged regardless of the dot count d. In other words, it can be seen that Example X2M switches the printing pattern N according to the dot count d, thereby reducing the fluctuation range of the C* value regardless of an increase in the dot count d, and thus preventing a large change in saturation.

[0169] Comparing Example X3Y and Comparative Example Z5Y for yellow in Table TBL7 again, Example X3Y has a smaller standard deviation of the FI value. As described above, in Example X3Y, the image density of the silver toner image PS is 25%. On the other hand, in Comparative Example Z3M, the image density of the silver toner image PS is 100%. That is, in Example X3Y, by setting the image density of the silver toner image PS to 25%, the fluctuation range of the FI value is small and stable regardless of the increase in the dot count d, that is, the degree of glossiness is roughly constant.

[0170] Also, comparing Example X3Y and Comparative Example Z6Y for yellow in Table TBL8, Example X3Y has a smaller standard deviation of the C* value. As described above, in Example X3Y, the printing pattern N is switched according to the dot count d. On the other hand, in Comparative Example Z6Y, the printing pattern N is unchanged regardless of the dot count d. In other words, it can be seen that, by switching the printing pattern N according to the dot count d, Example X3Y reduces the fluctuation range of the C* value regardless of an increase in the dot count d, and can prevent a large change in saturation.

[0171] Next, the relationship between the dot count d and the average value of the C* retention rate in Examples X1C, X2M, and X3Y was summarized, and the results are shown in Table TBL9 in Figure 13. From Table TBL9, it can be seen that in all of the Examples X, regardless of the dot count d, the fluctuation range of the C* retention rate is relatively small, and roughly the same value is maintained. In other words, in each Example X, a certain level of chroma can be well maintained even in the process where the dot count d increases.

[0172] Based on the results of the evaluation test described above, in the image forming apparatus 1 according to this embodiment, information corresponding to the cyan example X1C, the magenta example X2M, and the yellow example X3Y (hereinafter referred to as the brilliance superimposition information) is stored in advance in the brilliance color data conversion table 96 (FIG. 3) of the memory unit 81, and each printing pattern N is also stored in the memory unit 81.

[0173] [4. Bright overlay printing process procedure] Next, a description will be given of the glitter superimposition printing process when the glitter superimposition image PV is printed on the medium MD by the image forming device 1. When the control unit 3 (FIG. 3) of the image forming device 1 receives print data from the higher-level device 100 via the interface unit 82, the control unit 3 reads and executes the glitter superimposition printing program from the storage unit 81 by the print control unit 80, starts the glitter superimposition printing process procedure RT1 shown in FIG.

[0174] In step SP1, the control unit 3 analyzes the received print data and proceeds to the next step SP2. In step SP2, the control unit 3 determines whether the toner image to be generated based on the print data includes a portion where silver toner with an image density of 100% is superimposed on the color toner, that is, a portion to be the glitter superimposed image PV (hereinafter, this will be referred to as the glitter superimposed portion). If a positive result is obtained here, this indicates that the print pattern N should be changed in the glitter superimposed portion according to the color of the color toner image. In this case, the control unit 3 proceeds to the next step SP3.

[0175] In step SP3, the control unit 3 obtains the dot count d of the silver toner from the status information table 97 (FIG. 3) of the storage unit 81, and proceeds to the next step SP4. In step SP4, the control unit 3 refers to the glitter color data conversion table 96 (FIG. 3) of the storage unit 81, reads out the printing pattern N corresponding to the color and dot count d of the glitter superimposed portion, and proceeds to the next step SP5. In step SP5, the control unit 3 changes the silver toner image PS of the glitter superimposed portion from a solid image with an image density of 100[%] to an image of printing pattern N, and proceeds to the next step SP6.

[0176] On the other hand, if a negative result is obtained in step SP2, this indicates that the toner image to be generated based on the print data does not include a glittery overlapping portion, and therefore there is no need to change the print pattern. In this case, the control unit 3 proceeds to the next step SP6.

[0177] In step SP6, the control unit 3 causes the image forming units 10 of each color to form the toner images of each color, i.e., the silver toner image PS and the color toner image PL, on the intermediate transfer belt 34 (FIGS. 1 and 2) in a sequentially overlapping manner, and then proceeds to the next step SP7. If the toner image formed at this time contains a glittery overlapping portion, the glittery overlapping portion is changed to a printing pattern N corresponding to the color and dot count d of the color toner image PL.

[0178] In step SP7, the control unit 3 transfers the toner image from the intermediate transfer belt 34 to the surface of the medium MD transported along the transport path W in the secondary transfer unit 39, and then proceeds to the next step SP8. In step SP8, the control unit 3 fixes the toner image to the surface of the medium MD by the fixing unit 60, and further transports the medium MD by the paper discharge unit 70 and discharges it onto the paper discharge tray 2T, and then proceeds to the next step SP9, where the glitter superimposition printing processing procedure RT1 is completed.

[0179] [5. Effects, etc.] In the above configuration, the image forming apparatus 1 according to the present embodiment stores each print pattern N (FIGS. 9 and 10) in advance in the storage unit 81 (FIG. 3), and also stores in advance the glitter superimposition information corresponding to Examples X1C, X2M, and X3Y (FIG. 11) in the glitter color data conversion table 96. Then, when the print data received from the higher-level device 100 contains a glitter superimposition portion, the image forming apparatus 1 refers to the glitter superimposition information, changes the silver toner image PS of the glitter superimposition portion to a print pattern N corresponding to the silver dot count d and the color of the superimposed color toner image PL, and prints it on the medium MD.

[0180] At this time, the image forming apparatus 1 makes the image density of the glossy image (i.e., the silver toner image PS) to be superimposed relatively large for a color with a relatively low monochromatic saturation, and makes the image density of the glossy image to be superimposed relatively small for a color with a relatively high monochromatic saturation. Specifically, the image forming apparatus 1 sets the image density of the silver toner image PS to be superimposed to 50[%] for cyan, which has a relatively low monochromatic saturation, and sets the image density of the silver toner image PS to 25[%] for magenta and yellow, which have a relatively high monochromatic saturation.

[0181] Therefore, in the glitter superimposed portion of the image printed on the medium MD, the image forming apparatus 1 can roughly equalize the degree of glossiness by making the FI values ​​relatively close between portions of the color toner image PL having different colors, and can roughly equalize the saturation by making the C* retention rates relatively close. In other words, when the image forming apparatus 1 prints the glitter superimposed image PV based on the color toner image PL in which various colors are used for each portion, for example, the degree of glossiness and saturation are uniform between the portions of each color, and it is possible to obtain a good image that exhibits a uniform glossiness while maintaining the color tone of the original image as a whole.

[0182] However, when a silver toner image PS with the same image density is superimposed on multiple color toners with similar C* values, the degree of color change may differ for each color. This is presumably due to the difference in C* (i.e., color difference) between the original color and the superimposed color.

[0183] Therefore, in the image forming apparatus 1 according to the present embodiment, instead of the C* of each color, the C* retention rate is focused on, and the image density of the silver toner image PS to be superimposed on each is set. This C* retention rate represents the degree of smallness of change from the C* of a single color when the silver toner image PS is superimposed on the color toner image PL of each color. As a result, in the image forming apparatus 1, the degree of change in color caused by superimposing the silver toner image PS between different colors can be made uniform, and a large change in the impression of the image can be prevented.

[0184] As described above, the silver toner TS has a particle size distribution centered on the volume average particle size, and the charge amount varies depending on the particle size. For this reason, it is presumed that in the image forming unit 10, with regard to the glitter developer to be developed, small-particle-size silver toner TS that contains less glitter pigment and has low conductivity (high chargeability) is used (consumed) preferentially in the early stages of printing. It is also presumed that in the image forming unit 10, the silver toner TS remaining in the toner storage container 12 in the later stages of printing, i.e., small-particle-size silver toner TS that contains more glitter pigment and has high conductivity (low chargeability), is consumed in large amounts.

[0185] That is, when the silver dot count d is relatively small (early printing), the silver toner TS with relatively small particles is preferentially used, and as the dot count d increases, that is, in the later printing stage, the silver toner TS with larger particles tends to be used. As a result, even if a certain silver toner image PS is printed on the medium MD using this silver toner TS, the glossiness will differ depending on the silver dot count d, which may give a different impression to the user.

[0186] Therefore, in the image forming apparatus 1 according to the present embodiment, the fluctuation range of the FI value is suppressed by changing the print pattern N according to an increase in the silver dot count d in the glitter superimposition information (i.e., Examples X1C, X2M, and X3Y) stored in the glitter color data conversion table 96. Below, the reason why the FI value fluctuates according to the silver dot count d and the reason why this fluctuation can be suppressed by changing the print pattern N will be explained.

[0187] In the glitter overlay information, when the silver dot count d is relatively small, as in print patterns NC2 (FIG. 9(B)) and NM3 (FIG. 10(C)), one area (hereinafter referred to as the silver toner area) is formed with a relatively small number of dots, such as 4 dots, in the silver toner image PS, and a relatively large number of such areas are arranged. In these print patterns N, there are a relatively large number of boundary portions that form the outer edge of the silver toner area.

[0188] 15A is a cross-sectional view showing a schematic diagram of a silver toner image PS printed on the surface of a medium MD. In this silver toner image PS, each silver toner area is relatively small, so that the silver toner TS contained in the silver toner area spreads relatively easily by fixing, and the orientation of the pigment becomes high, so that the FI value tends to be high.

[0189] That is, in the image forming apparatus 1, when the silver dot count d is relatively low, there is a risk that the FI value will decrease excessively because the particles of the silver toner TS are relatively small. However, by forming many boundary parts in the silver toner image PS and improving the orientation of the pigment, it is possible to suppress the decrease in the FI value and achieve a good value.

[0190] On the other hand, in the glitter overlay information, when the silver dot count d is relatively high, as in print patterns NC4 (FIG. 9D) and NM6 (FIG. 10F), each silver toner area is formed with a relatively large number of dots, for example 12 dots or 16 dots, in the silver toner image PS, and the areas are arranged in relatively small numbers. In these print patterns N, there are relatively few boundary portions that form the outer edges of the silver toner areas.

[0191] As shown in Figure 15(B) corresponding to Figure 15(A), in the silver toner image PS at this time, each silver toner area is relatively large, and therefore the orientation of the pigment in the silver toner TS contained in the silver toner area deteriorates, so that the FI value tends to decrease.

[0192] That is, in the image forming apparatus 1, when the silver dot count d is relatively high, there is a risk that the FI value will increase excessively because the particles of the silver toner TS are relatively large; however, by forming fewer boundary portions in the silver toner image PS and thereby worsening the orientation of the pigment, the increase in the FI value can be suppressed, and a good value can be obtained as a result.

[0193] Incidentally, in the fixing section 60 (FIG. 1) of the image forming apparatus 1, as a fixing process, heat and pressure are applied to the toner image transferred onto the surface of the medium MD by a heating section 61 and a pressure section 62. Furthermore, since the medium MD is generally made of paper and is constituted as an aggregate of fibers, when observed in detail, the surface is not necessarily flat, and some unevenness, gaps between fibers, etc. are formed.

[0194] 16A and 16B are schematic diagrams respectively showing the state of the fixing unit 60, the medium MD, the color toner TL, and the silver toner TS before and after the fixing process. As shown in FIG. 16A, the color toner TL and the silver toner TS are accumulated in a particulate state on the surface of the medium MD before the fixing process.

[0195] As shown in FIG. 16B, in the area of ​​the surface of the medium MD that is relatively far from the silver toner TS after the fixing process, the color toner TL spreads sufficiently, blends in with the unevenness of the medium MD, and is fixed well by penetrating into the gaps between the fibers. However, in the area of ​​the surface of the medium MD that is relatively close to the silver toner TS, a lot of heat is absorbed by the silver toner TS, so the color toner TL does not spread sufficiently, does not blend in with the unevenness of the medium MD, and is difficult to penetrate into the gaps between the fibers. As a result, exposed areas EP where the medium MD is exposed are formed near the silver toner TS on the surface of the medium MD. If the number of such exposed areas EP increases, the FI value of the medium MD as a whole will decrease.

[0196] Therefore, in the glitter superimposition information (i.e., Examples X1C, X2M and X3Y), when the silver dot count d in magenta exceeds 8589k, and when the silver dot count d in yellow exceeds 6929k, printing pattern NM5 (Figure 10(E)) is switched to printing pattern NM6 (Figure 10(F)).

[0197] Here, in print pattern NM5, each silver toner area is slightly short in the vertical direction and slightly long in the horizontal direction, and the ratio of the horizontal length to the vertical length (hereinafter referred to as the area aspect ratio) is approximately 1.33, which is slightly larger than the value "1." On the other hand, in print pattern NM6, each silver toner area is short in the vertical direction and sufficiently long in the horizontal direction, and the area aspect ratio is 3.00, which is sufficiently larger than the value "1" and is also sufficiently larger than the approximately 1.33 of print pattern NM5.

[0198] In comparison with the printing pattern NM5, the number of dots constituting each silver toner region in the printing pattern NM6 is the same at 12 dots, but the interval between the silver toner regions in the horizontal direction (main scanning direction) is expanded due to the increase in the region aspect ratio. As a result, in the medium MD on which the printing pattern NM6 is printed, the amount of color toner TL located near one silver toner region is increased compared to the medium MD on which the printing pattern NM5 is printed, and the proportion of the medium MD that is exposed increases, which may lead to a decrease in the FI value. On the other hand, as for the silver toner TS, as described above, the particles become relatively larger as the dot count d increases, and as a result, the FI value of the silver toner image PS may increase excessively.

[0199] In other words, in magenta and yellow, there is a risk that the FI value will increase excessively as the silver dot count d increases, but by switching printing pattern N from NM5 to NM6, the image forming apparatus 1 suppresses the increase in the FI value, thereby suppressing overall fluctuations in the FI value and maintaining a roughly constant glossiness.

[0200] In addition, in the image forming device 1, the fluctuation range of C* and C* retention rate can also be suppressed by changing the printing pattern N in accordance with an increase in the silver dot count d in the glitter superimposition information stored in the glitter color data conversion table 96 (i.e., Examples X1C, X2M, and X3Y).

[0201] That is, in the image forming apparatus 1, when the particle size of the silver toner TS increases with an increase in the silver dot count d, the area of ​​the color toner TL exposed on the surface of the medium MD decreases, causing a decrease in C*. Therefore, in the image forming apparatus 1, the printing pattern N is changed in stages with an increase in the dot count d, so that the number of dots constituting the silver toner area is gradually increased.

[0202] At this time, in the glitter superimposed image PV printed by the image forming apparatus 1, the number of dots in the range where color toners are adjacent to each other in each print pattern N also increases, so that the exposed portions of the color toners TL are enlarged, acting to increase C*. As a result, in the image forming apparatus 1, even if the silver dot count d increases, the fluctuations in C* and C* retention in the glitter superimposed image PV can be effectively suppressed, and good saturation can be maintained.

[0203] Incidentally, compared to magenta and yellow, cyan has a lower saturation as a single color (FIG. 8), and is considered to have a slightly closer hue than silver. In consideration of this relationship, in the image forming apparatus 1, in the printing patterns NC2 to NC4 (FIG. 9) when a silver toner image is superimposed on cyan, each silver toner area is made into a vertically long rectangular shape. This allows the image forming apparatus 1 to obtain sufficient brilliance and saturation on the medium MD on which the images of the printing patterns NC2 and the like are printed, without making the thin lines along the vertical direction of each silver toner area excessively noticeable.

[0204] In addition, in the glitter superimposition information (i.e., Examples X1C, X2M, and X3Y), in the printing patterns NM5 and NM6 when the silver toner image is superimposed on the magenta and yellow, the silver toner regions are arranged adjacent to each other in the diagonal direction, and are formed into a straight line along the diagonal direction as a whole. As a result, the image forming device 1 can slightly increase the distance between the silver toner regions on the medium MD on which the image of the printing pattern NM5 etc. is printed, compared to the case of cyan, and sufficient glitter and saturation can be obtained without excessive awareness of the thin lines along the diagonal direction of each silver toner region.

[0205] Moreover, when the image forming apparatus 1 prints the glitter superimposed image PV on the medium MD, the host device 100 simply has to specify the image density of the silver toner image PS to be superimposed on the color toner image PL to be uniformly set to 100% over the entire range. In other words, the image forming apparatus 1 does not require the user to perform the troublesome task of, for example, differentiating the image density of the silver toner image PS for each color portion.

[0206] According to the above configuration, when the print data received from the higher-level device 100 includes a glittery superimposed portion, the image forming device 1 according to the present embodiment changes the print pattern N of the silver toner image PS of the glittery superimposed portion and prints it on the medium MD. At this time, the image forming device 1 relatively increases the image density of the silver toner image PS to be superimposed if the color has a relatively low monochromatic saturation, and relatively decreases the image density of the silver toner image PS to be superimposed if the color has a relatively high monochromatic saturation, and further changes the print pattern N to one corresponding to the dot count d of silver. As a result, the image forming device 1 can make the FI value and C* retention rate relatively close between different colors, and can obtain a good image that exhibits a uniform glossiness while maintaining the color tone of the original image as a whole.

[0207] [6. Other embodiments] In the above-described embodiment, the printing pattern N in the glitter superimposed image PV is switched according to the silver dot count d, under the premise that the silver toner TS, which has relatively small particles, is used preferentially in the silver toner container 12 (FIGS. 9, 10, and 11). However, the present invention is not limited to this, and a constant printing pattern N may be used for each color regardless of the silver dot count d, for example, when the variation range of the particle size of the silver toner TS according to the dot count d is sufficiently small. Specifically, for example, regardless of the silver dot count d, printing pattern NC2 (FIG. 9(B)) may be used for cyan, and printing pattern NM3 (FIG. 10(C)) may be used for magenta and yellow.

[0208] In the above-described embodiment, for the magenta and yellow printing patterns NM3 to NM6 (FIG. 10) in the glitter superimposition information (i.e., Examples X1C, X2M, and X3Y), a form has been described in which the size of each printing pattern N (i.e., the number of dots constituting one printing pattern N) is increased as the silver dot count d increases (FIG. 11). However, the present invention is not limited to this, and for example, when the silver dot count d increases, the shape and arrangement of each silver toner area may be changed while maintaining the size of the printing pattern N.

[0209] Furthermore, in the above-mentioned embodiment, as the silver dot count d increases and the print patterns NC2, NC3, and NC4 are sequentially switched over to the cyan glitter superimposition information, the size of the entire region is maintained and the horizontal length of the small region is sequentially enlarged while maintaining the vertical length (FIGS. 9 and 11). However, the present invention is not limited to this, and for example, the horizontal length of the small region may be reduced while maintaining the vertical length, or the vertical length may be enlarged or reduced while maintaining the horizontal length, or both the vertical length and the horizontal length may be enlarged or reduced, or these may be appropriately combined. Alternatively, for example, at least one of the vertical length and the horizontal length of the entire region may be enlarged or reduced.

[0210] Furthermore, in the above-described embodiment, when switching from the print pattern NM5 to NM6 with an increase in the silver dot count d for the magenta and yellow glitter superimposition information, the entire region and the small region are both reduced in length in the vertical direction and expanded in length in the horizontal direction, and flattened to be horizontally long (FIGS. 10 and 11). However, the present invention is not limited to this, and for example, the entire region and the small region may be both reduced in length in the horizontal direction and expanded in length in the vertical direction, and flattened to be vertically long. Alternatively, for example, the size of the entire region may be maintained, and at least one of the vertical size or horizontal size of the small region may be expanded or reduced. Alternatively, for example, the size of the small region may be maintained, and at least one of the vertical size or horizontal size of the entire region may be expanded or reduced.

[0211] Furthermore, in the above-mentioned embodiment, in the cyan print patterns NC2 and NC3 (FIG. 9) in the glitter superimposition information, the entire area is divided into rectangular small areas that are long in the vertical direction (i.e., the sub-scanning direction), and silver toner is arranged in some of the small areas. However, the present invention is not limited to this, and for example, the entire area may be divided into rectangular small areas that are long in the horizontal direction (i.e., the main scanning direction), and silver toner may be arranged in some of the small areas. Alternatively, for example, as in the print patterns NM5 and NM6 (FIG. 10), the entire area may be divided into a lattice shape, and silver toner may be arranged so that the overall shape is linear along a diagonal direction. Alternatively, for example, the entire area may be divided into many relatively small lattices, and silver toner may be arranged to form halftone dots.

[0212] Furthermore, in the above-mentioned embodiment, in the magenta and yellow print patterns NM3 and NM4 (FIG. 10) in the glitter superimposition information, the entire area is divided vertically and horizontally into two to form four small areas, and silver toner is arranged in only one of the small areas. However, the present invention is not limited to this, and for example, as in the print patterns NM5 and NM6 (FIG. 10), the entire area may be divided into more grid-like small areas, and silver toner may be arranged so that the overall area is linearly aligned along an oblique direction, or silver toner may be arranged to form halftone dots.

[0213] Furthermore, in the above-mentioned embodiment, in the magenta and yellow print patterns NM5 and NM6 (FIG. 10) in the glitter superimposition information, the entire area is divided into a grid pattern, and silver toner is arranged in some of the small areas so that the entire area is linearly arranged along a diagonal direction. However, the present invention is not limited to this, and for example, as in the print patterns NC2 and NC3 (FIG. 9), the entire area may be divided into rectangular small areas that are long in the vertical direction (i.e., the sub-scanning direction), or the entire area may be divided into rectangular small areas that are long in the horizontal direction (i.e., the main scanning direction), and silver toner may be arranged in some of the small areas. Alternatively, for example, the entire area may be divided into a large number of relatively small grid patterns, and silver toner may be arranged to form halftone dots.

[0214] Furthermore, in the above-described embodiment, when forming the glitter superimposed image PV, a form has been described in which the silver toner image PS is superimposed on the color toner image PL on the surface of the medium MD (FIG. 9). However, the present invention is not limited to this, and for example, the glitter superimposed image PV may be formed by superimposing the color toner image PL on the silver toner image PS on the surface of the medium MD, i.e., by reversing the stacking order of the color toner image PL and the silver toner image PS.

[0215] Furthermore, in the above-described embodiment, a form has been described in which, in a brilliance superimposition image PV in which a silver toner image PS is superimposed on a single color toner image PL of cyan, magenta or yellow, the image density is reduced by changing the silver toner image PS to a print pattern N corresponding to that color in accordance with the brilliance superimposition information. However, the present invention is not limited to this, and for example, if the color toner image PL has a red portion formed by mixing magenta and yellow, the print pattern N may be changed to the print pattern N corresponding to the predominant color of magenta or yellow that constitutes that portion.

[0216] Furthermore, in the above-described embodiment, the image density of the silver toner image PS (i.e., the glitter image) is changed according to the color gamut (C*) of the color toner TL (i.e., the color toner image PL) printed on the medium MD. However, the present invention is not limited to this, and the image density of the silver toner image PS may be changed according to the color gamut of the color toner TL in a powder state before printing. Note that, regarding the color toner TL used in the embodiment, the color gamut (L*, a*, b*, and C*) in a powder state before printing is, for example, a value shown in table TBL10 shown in FIG. 17. For this reason, for example, a glitter color data conversion table 96 (FIG. 3) created based on this table TBL10 may be stored in advance in the storage unit 81, and glitter superimposition printing processing may be performed in the same manner as in the embodiment.

[0217] The powder hues shown in Table TBL10 (FIG. 17) were measured using a spectrophotometer SE-2000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) with a C light source, a 2° field of view, and reflection settings. Specifically, 3.0 g of toner T of each color was filled into a cylindrical powder measurement cell (thickness 2 mm, diameter 30 mm) that is an accessory of the spectrophotometer, and the powder measurement cell was vibrated at a speed of 1 time / second against the direction of gravity for 30 seconds to make the filling degree dense, and the powder hues L*, a*, and b* in the powder state were measured. In addition, the color gamut (C*) of toner T was calculated by applying each measured powder hue value to the above-mentioned formula (1).

[0218] Furthermore, in the above-described embodiment, the glitter superimposition information is stored in advance in the glitter color data conversion table 96 (FIG. 3) provided in the storage unit 81 of the image forming apparatus 1, and the print pattern N of the glitter superimposition portion is changed in step SP5 of the glitter superimposition printing procedure RT1 (FIG. 14) executed by the control unit 3. However, the present invention is not limited to this, and for example, the glitter superimposition information may be stored in advance in the upper device 100, and the print data in which the print pattern N of the glitter superimposition portion is changed by referring to the glitter superimposition information by the printer driver may be generated, and the print data may be transmitted to the image forming apparatus 1. In this case, the control unit 3 of the image forming apparatus 1 may form and print the color toner image PL and the silver toner image PS as they are, without changing the print pattern of the glitter superimposition portion.

[0219] Furthermore, in the above-described embodiment, when a silver toner image PS with an image density of 100% is superimposed on a color toner image PL in print data received from the higher-level device 100, the control unit 3 of the image forming device 1 regards this as a glitter superimposed image PV and changes the print pattern N. However, the present invention is not limited to this. For example, when the print data is configured to superimpose silver toner images PS with various image densities on the color toner image PL, the control unit 3 may regard this as a glitter superimposed image PV and change the print pattern N. Alternatively, when an instruction to superimpose a silver toner image PS on a color toner image PL is written in various printing languages, for example, the control unit 3 may regard this as a glitter superimposed image PV and change the print pattern N.

[0220] Furthermore, in the above-mentioned embodiment, a silver toner T (silver toner TS) is used as the toner T having glittering properties. However, the present invention is not limited to this, and various colors of toner T having glittering properties, such as gold and copper, may be used. For example, gold toner T can be manufactured by partially modifying the manufacturing process of silver toner TS described in the embodiment. Specifically, when adding aluminum powder as the glittering pigment, a yellow pigment (e.g., CI Pigment Yellow 180, which is an organic pigment), a magenta pigment (e.g., CI Pigment Red 122, which is an organic pigment), a red-orange fluorescent pigment (e.g., FM-34N_Orange (manufactured by Shinroihi Co., Ltd.)), and a yellow fluorescent pigment (FM-35N_Yellow (manufactured by Shinroihi Co., Ltd.)) are added, respectively, to manufacture gold toner T. Furthermore, the glittering pigment is not limited to aluminum (Al), and various other pigments having glittering properties, such as pearl pigments (natural mica) and inorganic pigments made of titanium oxide, may be used.

[0221] Furthermore, in the above-described embodiment, the image forming apparatus 1 (FIG. 1) is described as being provided with five image forming units 10. However, the present invention is not limited to this, and the image forming apparatus 1 may be provided with four or less image forming units 10 or six or more image forming units 10.

[0222] Furthermore, in the above-described embodiment, the image forming apparatus (FIG. 1) is of a so-called intermediate transfer type, and a toner image formed in each image forming unit 10 is primarily transferred to intermediate transfer belt 34, and the toner image is secondarily transferred from intermediate transfer belt 34 to medium MD. However, the present invention is not limited to this, and for example, the image forming apparatus may be of a so-called direct transfer type, and the toner image formed in each image forming unit 10 may be directly transferred to medium MD.

[0223] Furthermore, in the above-described embodiment, the present invention has been described as being applied to an image forming apparatus 1 that forms an image using a developer used in a one-component development method. However, the present invention is not limited to this, and the present invention may also be applied to an image forming apparatus that forms an image using a developer used in a two-component development method in which a carrier and a toner are mixed and an appropriate amount of charge is imparted to the toner by utilizing friction between the carrier and the toner. When describing the two-component development method, particles containing a photoluminescent pigment, a binder resin, and an external additive, or a powdery material formed by the aggregation of these particles, are defined as photoluminescent toner or photoluminescent developer.

[0224] Furthermore, in the above-mentioned first embodiment, the present invention has been described as being applied to the image forming apparatus 1 which is a single-function printer. However, the present invention is not limited to this, and may be applied to image forming apparatuses having various other functions, such as an MFP (Multi Function Peripheral) having the functions of a copier or facsimile machine.

[0225] Furthermore, the present invention is not limited to the above-mentioned embodiments and other embodiments. That is, the scope of application of the present invention extends to embodiments in which the above-mentioned embodiments and the other embodiments are combined in part or in whole in any manner. The scope of application of the present invention also extends to embodiments in which a part of the configuration described in any of the above-mentioned embodiments and other embodiments is extracted and replaced or diverted with a part of the configuration of any of the above-mentioned embodiments and other embodiments, or an embodiment in which a part of the extracted configuration is added to any of the embodiments.

[0226] Furthermore, in the above-mentioned embodiment, the image forming apparatus 1 is configured by the image forming unit 10S as the glossy image forming unit, the image forming units 10C, 10M and 10Y as the non-glossy image forming units, and the controller 3 as the controller. However, the present invention is not limited to this, and the image forming apparatus may be configured by glossy image forming units, non-glossy image forming units and controllers having various other configurations. [Industrial Applicability]

[0227] The present invention can be used when forming an image on a medium by electrophotography using a non-photoluminescent developer and a photoluminescent developer. [Explanation of symbols]

[0228] 1...image forming apparatus, 3...control unit, 10...image forming unit, 12...toner container, 34...intermediate transfer belt, 60...fixing unit, 80...print control unit, 81...memory unit, 95...normal color data conversion table, 96...glitter color data conversion table, 97...status information table, 100...host device, D...image density, MD...medium, N, NC1, NC2, NC3, NC4, NM1, NM2, NM3, NM4, NM5, NM6...printing pattern, PL...color toner image, PS...silver toner image, PV...glitter superimposed image, T...toner, TL...color toner, TS...silver toner, d...dot count.

Claims

1. a glitter image forming unit capable of forming a glitter image on a medium using a glitter developer; a non-glossy image forming unit capable of forming a non-glossy image on the medium using a non-glossy developer; a control unit for controlling operations of the glossy image forming unit and the non-glossy image forming unit; Equipped with When the glossy image having an image density of 100% is formed on the medium by superimposing the non-glossy image, if the non-glossy image has a first saturation, the control unit controls the glossy image forming unit and the non-glossy image forming unit to form the glossy image having a first image density, and if the non-glossy image has a second saturation higher than the first saturation, to form the glossy image having a second image density lower than the first image density.

1. An image forming apparatus comprising:

2. a glitter developer container in which the glitter developer used for forming the glitter image is stored in advance and which is configured to be replaceable with respect to the glitter image forming unit; Further comprising: The control unit changes an arrangement pattern of dots in which the glitter developer is arranged in the glitter image according to a post-replacement usage amount, which is an amount of the glitter developer used after the glitter developer container is replaced in the glitter image forming unit.

2. The image forming apparatus according to claim 1,

3. The control unit expands a range of an area in which the glittering developer is arranged in the first image density portion of the glittering image in at least one of a main scanning direction in the glittering image forming unit and a sub-scanning direction perpendicular to the main scanning direction as the amount of usage after replacement increases.

3. The image forming apparatus according to claim 2,

4. The control unit repeatedly arranges small regions in a lattice pattern in the portion of the glossy image with the first image density, the small regions having dot counts in the main scanning direction and the sub-scanning direction, respectively, and increases at least one of the main scanning dot count and the sub-scanning dot count as the amount of use after replacement increases.

4. The image forming apparatus according to claim 3.

5. The control unit changes a ratio of the number of main scanning dots and the number of sub-scanning dots in the portion of the glossy image having the first image density in accordance with a change in the amount of usage after replacement.

5. The image forming apparatus according to claim 4.

6. The control unit arranges pixels that use the glitter developer in the small region along an inclined direction different from both the main scanning direction and the sub-scanning direction.

5. The image forming apparatus according to claim 4.

7. The control unit arranges dots using the glitter developer in a portion of the glitter image where the non-glitter image to be superimposed has the second saturation along an inclined direction different from both a main scanning direction and a sub-scanning direction perpendicular to the main scanning direction in the glitter image forming unit.

2. The image forming apparatus according to claim 1,

8. The control unit arranges dots using the glitter developer in a portion of the glitter image where the non-glitter image to be superimposed has the first saturation along a main scanning direction or a sub-scanning direction perpendicular to the main scanning direction in the glitter image forming unit.

2. The image forming apparatus according to claim 1,

9. A fixing section that fixes the glossy image and the non-glossy image formed on the medium to the medium. and The first saturation and the second saturation are values ​​measured in a state in which the non-glossy image and the glossy image are fixed to the medium by the fixing unit.

2. The image forming apparatus according to claim 1,

10. a glitter developer container in which the glitter developer used for forming the glitter image is stored in advance and which is configured to be replaceable with respect to the glitter image forming unit; Further comprising: The control unit is The second image density is set so that a difference in index value representing a degree of glitteriness between the non-glitter image of the first saturation on which the glitter image of the first image density is superimposed and the non-glitter image of the second saturation on which the glitter image of the second image density is superimposed is within a predetermined range, and a ratio of change in saturation in a case where a post-replacement usage amount, which is a usage amount of the glitter developer after the glitter developer container is replaced in the glitter image forming unit, is changed is within a predetermined range.

2. The image forming apparatus according to claim 1,

11. The second image density is equal to or greater than 23% and equal to or less than 44%.

11. The image forming apparatus according to claim 10.

12. a control step of receiving print data by a control unit and performing control based on the print data; an image forming step of forming a glossy image using a glossy developer and a non-glossy image using a non-glossy developer on a medium by a glossy image forming unit and a non-glossy image forming unit controlled by the control unit, respectively; having In the control step, when the glossy image is formed on the medium by superimposing the non-glossy image on the glossy image, if the non-glossy image has a first saturation, the glossy image is formed at a first image density, and if the non-glossy image has a second saturation higher than the first saturation, the glossy image is formed at a second image density lower than the first image density.

1. An image forming method comprising:

13. The image forming step includes: a glitter image forming step of forming the glitter image on the medium by the glitter image forming unit using the glitter developer; a non-glossy image forming step of forming the non-glossy image on the medium by the non-glossy image forming unit using the non-glossy developer; The image forming method according to claim 12, further comprising:

14. a glitter image forming unit capable of forming a glitter image on a medium using a glitter developer; a non-glossy image forming unit capable of forming a non-glossy image on the medium using a non-glossy developer; a control unit for controlling operations of the glossy image forming unit and the non-glossy image forming unit; Equipped with When the glossy image having an image density of 100% is formed on the medium by superimposing the non-glossy image, if the non-glossy developer has a first saturation, the control unit controls the glossy image forming unit and the non-glossy image forming unit to form the glossy image having a first image density, and if the non-glossy developer has a second saturation higher than the first saturation, to form the glossy image having a second image density lower than the first image density.

1. An image forming apparatus comprising:

Images