Image forming apparatus and image forming method

Abstract

To satisfactorily achieve both photoluminescent properties and color reproducibility when superimposing a photoluminescent toner on a plurality of color toners.SOLUTION: An image forming apparatus 1 changes, when a photoluminescent superimposition target portion is included in print data received from a host device 100, printing patterns N of a silver toner image PS and a color toner image PL in respective colors in the photoluminescent superimposition target portion and prints resulting images on a medium MD. The image forming apparatus 1 sets a photoluminescent area and a non-photoluminescent area, while setting the image density of the silver toner image PS in the photoluminescent superimposition target portion to 50%, reduces the image density within a range of 100% to 0% in the photoluminescent area, while maintaining the image density at 200% in the non-photoluminescent area, and prevents color toners TL from overlapping each other. Consequently, the image forming apparatus 1 can obtain sufficient photoluminescent properties in the images printed on the medium MD, and can sufficiently expand the color gamut of the images.SELECTED DRAWING: Figure 10

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 images with brilliance on paper by using toner (hereinafter referred to as brilliance toner) with brilliance such as silver or gold (hereinafter referred to as brilliance 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 brilliance toner, so that the printed image can have high brilliance.

[0004] In such an image forming apparatus, a variety of colors having a brilliance called metallic colors can be expressed by overlaying an image of a glitter toner (glossy image) on an image of a color toner (color image), but there is a risk of a decrease in color reproducibility and saturation compared to a color image. Therefore, an image forming apparatus has been proposed that satisfactorily achieves both brilliance and color reproducibility by appropriately defining the relationship between the amount of adhesion of a single color toner and a glitter toner to a medium (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-181025 A (Fig. 4, etc.) Summary of the Invention [Problem to be solved by the invention]

[0006] In the image forming apparatus, multiple color toners (hereinafter referred to as mixed color toners) may be superimposed on a medium. When the image forming apparatus prints an image using multiple color toners on a medium, the amount of toner attached to the medium increases compared to when a single color toner (hereinafter referred to as single color toner) is used.

[0007] For this reason, when an image forming device prints by overlaying a glossy toner on multiple color toners, there is a problem in that it is difficult to achieve both glossiness and color reproducibility, even if the adhesion amount of each toner is specified in the same way as when printing by overlaying a glossy toner on a single color toner.

[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 that can achieve both good glossiness and color reproducibility when a glossy toner is superimposed on multiple color toners. [Means for solving the problem]

[0009] In order to solve the above problems, the image forming apparatus of the present invention includes a glossy image forming unit capable of forming a glossy image made of a glossy developer in a glossy region on a medium, a first non-glossy image forming unit capable of forming a first non-glossy image made of a first non-glossy developer in a first region on the medium, a second non-glossy image forming unit capable of forming a second non-glossy image made of a second non-glossy developer in a second region on the medium, and a control unit that controls the glossy image forming unit, the first non-glossy image forming unit, and the second non-glossy image forming unit, and the control unit The glossy image forming unit, the first non-glossy image forming unit and the second non-glossy image forming unit are controlled so that in a non-glossy region where the glossy developer is not superimposed on the first non-glossy image and the second non-glossy image, the second non-glossy image is superimposed on the first non-glossy image at a first ratio, and in a glossy region where the glossy developer is superimposed on the first non-glossy image and the second non-glossy image, the second non-glossy image is superimposed on the first non-glossy image at a second ratio smaller than the first ratio.

[0010] The image forming method of the present invention also includes a control step of controlling image formation by a control unit so as to set a non-glossy region to be formed on the medium without superimposing a glittering image made of a glittering developer and a non-glossy image made of a first non-glossy developer and a second non-glossy developer, and a glittering region to be formed on the medium by superimposing a glittering image and a non-glossy image, respectively; and an image forming step of forming a non-glossy image on the medium using the developer, and the image formation control includes forming a first non-glossy developer in a first region on the medium and forming a second non-glossy developer in a second region on the medium that at least partially overlaps with the first region, forming a non-glossy image in the non-glossy region where the ratio of the second region overlapping the first region is a first ratio, and forming a non-glossy image in the glossy region where the ratio of the second region overlapping the first region is a second ratio that is smaller than the first ratio.

[0011] Furthermore, the image forming apparatus of the present invention is provided with a glossy image forming unit capable of forming a glossy image made of a glossy developer on a medium, a first non-glossy image forming unit capable of forming a first non-glossy image made of a first non-glossy developer in a first region on the medium, a second non-glossy image forming unit capable of forming a second non-glossy image made of a second non-glossy developer in a second region on the medium, and a control unit that controls the glossy image forming unit, the first non-glossy image forming unit, and the second non-glossy image forming unit, and the control unit controls the glossy image forming unit, the first non-glossy image forming unit, and the second non-glossy image forming unit, respectively, to form glossy regions in which the glossy developer is superimposed on the first non-glossy image and the second non-glossy image, and to form non-glossy regions in which the glossy developer is not superimposed on the first non-glossy image and the second non-glossy image.

[0012] Furthermore, in the image forming method of the present invention, in an image processing method for processing image data including a glittering superimposition target portion in which a glittering image is to be superimposed on a non-glossy image including a first non-glossy image and a second non-glossy image, the method includes the steps of setting glittering areas in the glittering superimposition target portion in which the glittering image is to be superimposed on the non-glossy image and non-glossy areas in which the glittering image is not to be superimposed on the non-glossy image, and the steps of superimposing the second non-glossy image on the first non-glossy image at a first ratio in the non-glossy areas, and superimposing the second non-glossy image on the first non-glossy image at a second ratio smaller than the first ratio in the glittering areas.

[0013] The present invention forms a first non-glossy image, a second non-glossy image, and a glossy image such that a second ratio of the second region overlapping the first region in a glossy region on the medium is smaller than a first ratio of the second region overlapping the first region in a non-glossy region. Therefore, the present invention can reduce the amounts of the first non-glossy developer and the second non-glossy developer constituting the first non-glossy image and the second non-glossy image overlapping the glossy image in the glossy region on the medium to be less than the amount of glossy developer constituting the non-glossy image in the non-glossy region, and as a result, the color gamut in the glossy region can be expanded. Effect of the Invention

[0014] According to the present invention, it is possible to realize an image forming apparatus and an image forming method that can satisfactorily achieve both glossiness and color reproducibility when glossy toner is superimposed on a plurality of color toners. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram illustrating an overall 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 diagram illustrating a circuit configuration of the image forming apparatus. [Figure 4] 1 is a table showing the powder hue values ​​for each color. [Diagram 5] 4 is a schematic diagram showing a print range on a medium. [Figure 6] 1 is a table showing the relationship between image density and FI value and C* value for silver toner. [Figure 7] 11 is a schematic diagram showing a print pattern when a silver toner image is superimposed on a color toner image. [Figure 8] 11 is a schematic plan view showing the configuration of a silver toner image and color toner images of each color in a print pattern N10. FIG. [Figure 9] 11 is a schematic side view showing the configuration of a silver toner image and color toner images of each color in a print pattern N10. FIG. [Figure 10] 11 is a schematic plan view showing the configuration of a silver toner image and color toner images of each color in a print pattern N11. FIG. [Figure 11] 13 is a schematic plan view showing the configuration of a silver toner image and color toner images of each color in a print pattern N12. FIG. [Figure 12] 11 is a schematic plan view showing the configuration of a silver toner image and color toner images of each color in a print pattern N13. FIG. [Figure 13] 11 is a schematic plan view showing the configuration of a silver toner image and color toner images of each color in a print pattern N14. FIG. [Figure 14]1 is a table showing FI values ​​and C* values ​​and their respective evaluation results in examples and comparative examples according to the first embodiment. [Figure 15] 13 is a flowchart showing a glitter superimposition printing process. [Figure 16] 13 is a schematic plan view showing the configuration of a silver toner image and color toner images of each color in a print pattern N21. FIG. [Figure 17] 13 is a table showing FI values ​​and C* values ​​and their respective evaluation results in examples and comparative examples according to the second embodiment. [Figure 18] 13 is a schematic plan view showing a configuration of a silver toner image and color toner images of each color in a print pattern according to another embodiment. FIG. [Figure 19] 13 is a schematic plan view showing a configuration of a silver toner image and color toner images of each color in a print pattern according to another embodiment. FIG. [Figure 20] 13 is a schematic plan view showing a configuration of a silver toner image and color toner images of each color in a print pattern according to another embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0017] 1. First embodiment [1-1. Configuration of image forming device] 1, the image forming apparatus 1 according to the first 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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, an example in which silver is used as a special color will be described. 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.

[0022] 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.

[0023] As described later, a toner containing a glittering pigment is used as the silver toner T. For convenience of explanation, the glittering color of silver toner T will be referred to as silver toner TS, glittering toner, or glittering developer hereinafter. The toner container 12 that contains the silver toner TS will also be referred to as a glittering developer container.

[0024] On the other hand, yellow, magenta, cyan and black toners T contain organic pigments such as pigment yellow, pigment cyan, pigment magenta and carbon black. For convenience of explanation, the yellow, magenta, cyan and black (i.e. non-glitter color) toners T (developers) are also referred to as color toners TL, non-glitter toners or non-glitter developers below. In addition, the magenta toner T is also referred to as the first non-glitter developer, and the cyan toner T is also referred to as the second non-glitter developer below.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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).

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The paper cassette 41 is configured in a hollow rectangular parallelepiped shape and is detachable from the housing 2. The paper cassette 41 stores media MD such as paper in a stacked state, i.e., accumulated state, with the paper surfaces facing up and down.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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 data conversion table 95. The data conversion table 95 stores information for forming the print data acquired from the higher-level device 100 into a print pattern of each color.

[0061] 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.

[0062] 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, thereby causing the display screen to be displayed on the display unit 4.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] [1-2. 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.

[0067] The powder hue of these toners in a powder state is expressed by the lightness L*, hue a*, and hue b* values ​​in the L*a*b* color system, i.e., L*, a*, and b*. In this L*a*b* color system, L* is a value that represents the lightness in the L* axis direction, a* is a value that represents the hue in the a* axis direction, i.e., the red-green direction, and b* is a value that represents the hue in the b* axis direction, i.e., the yellow-blue direction.

[0068] Specifically, the powder hue values ​​of each color in toner T were as shown in Table TBL1 in FIG. 4. However, in this evaluation test, the powder hue was measured using a spectrophotometer SE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), with a C light source, a field of view of 2°, and reflective settings. Specifically, for each toner color, 3.0 g of toner of each color was filled inside a cylindrical powder measurement cell (thickness 2 mm, diameter 30 mm) that is an accessory of the spectrophotometer, and the filling density was increased by vibrating the powder measurement cell against the direction of gravity (i.e., up and down) at a speed of 1 time / second for 30 seconds. Then, the powder hue (L*, a*, and b*) was measured.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Among these, the glittering pigment contains minute aluminum (Al) flakes, that is, small pieces having planar portions formed in a plate-like, flat or scaly shape. Hereinafter, this glittering pigment is also called an aluminum pigment or a metal pigment. The volume average particle size is also called a volume particle size, a volume median size or an average median size. In this embodiment, a glittering pigment having a volume average particle size of 5.4 [μm] is used, but this is not limiting, and a glittering pigment having a volume average particle size in the range of 5.3 to 5.7 [μm] may be used.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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].

[0079] [1-3. Evaluation of glitter superimposed images] Next, we will explain the case where the image forming device 1 prints an image on a medium MD by superimposing a color toner image PL using two normal color toners TL and a silver toner image PS using a brilliant color (i.e., silver) silver toner TS, i.e., a brilliant superimposed image PV (hereinafter also referred to as color metallic).

[0080] In the following, in the printing data supplied from the higher-level device 100, the portion of the entire image to be formed on the medium MD, 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), is also referred to as the glossy superimposition target portion.

[0081] As described above, when a glittering superimposed image PV (i.e., a color metallic image) is printed on the 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 any single color (magenta, yellow, cyan, and black), and also in mixed colors in which multiple colors are superimposed.

[0082] 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.

[0083] [1-3-1. Indicators used for evaluation] In this evaluation test, the amount of toner T (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 defined as 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[%].

[0084] For example, when printing solidly over the entire printable range of a given area (one rotation of the photosensitive drum 26 or one page of a print medium, etc.), printing with an area ratio of 100[%] is called a print image density of 100[%], and printing that corresponds to an area of ​​1[%] of this print image density of 100[%] is called a print image density of 1[%]. When the print image density DPD is expressed mathematically using the number of dots used Cm, the number of rotations Cd, and the total number of dots CO, it can be expressed as in the following formula (1).

[0085]

number

[0086] However, the number of dots used Cm is the number of dots actually used to form an image while the photoconductor drum 26 rotates Cd, and is the total number of dots exposed by the LED head 14 (FIG. 2) while forming the image. The total number of dots CO is the total number of dots per rotation of the photoconductor drum 26 (FIG. 2), that is, the total number of dots that can be potentially used when forming an image, regardless of whether or not the photoconductor drum 26 is exposed to light. In other words, the total number of dots CO is the total number of dots used when forming a solid image by transferring developer to all pixels. Therefore, the value (Cd×CO) represents the total number of dots that can potentially be used when forming an image while the photoconductor drum 26 rotates Cd.

[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 T is printed, 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 will be 50[%], and if the number of dots in the print pixels is 16 dots, the image density will be 25[%].

[0088] Furthermore, when multiple color toners TL are layered, the image density value may exceed 100[%]. In the following, a mixture of multiple color toners TL is also referred to as a mixed color toner. For example, in a mixed color toner in which cyan and magenta are layered to express blue, when cyan is 100[%] and magenta is also 100[%], the image density of the mixed blue is 200[%].

[0089] 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.

[0090] 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.).

[0091] 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.

[0092] In this evaluation test, the X-Rite eXact spectrophotometer (manufactured by X-Rite, Inc.) was used to measure the density and color gamut of cyan on paper. 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.

[0093] The color gamut is expressed using C*, which means saturation in color space, and C* is calculated according to the following formula (2) based on a* and b*, which can be measured using a spectrophotometer.

[0094]

number

[0095] For example, the C* (i.e., chroma) of 200% blue, which is a combination of 100% cyan and 100% magenta, was 55. In a color in which silver toner TS is overlaid on the 200% blue toner TL (hereinafter referred to as a metallic color), the C* value is lowered due to the influence of the silver toner TS. In this metallic color, the closer the C* value is to 55, which is the C* value for the normal color, the wider the color gamut is, and if it is 14 or higher, the visual perception of a vivid blue color is achieved.

[0096] Furthermore, in this evaluation test, the flop index value (hereinafter referred to as FI value) was used as an index value representing the metallic luster 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 the higher the value, the higher the brilliance. This FI value can be calculated using the following formula (3). In formula (3), when light is irradiated onto a paper surface at an angle of 45°, the intensities of reflected light received in directions of 0°, 30°, and -65° relative to the perpendicular direction of the paper surface are defined as reflected light intensities L*0, L*30, and L*-65, respectively.

[0098]

number

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

[0100] [1-3-2. 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. 5. 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 cyan image forming unit 10C and the magenta image forming unit 10M (Figure 1) in the image forming device 1, various bias voltages (developing voltage, etc.) were pre-adjusted for each unit so that when an image with an image density of 100% (a so-called solid image) was printed on the medium MD, 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 apparatus 1, data for converting image density (i.e., image area ratio) (described in detail later) was pre-stored in the data conversion table 95 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 bitmap data for printing based on the print data, separates this into separate bitmap data for each color (silver, cyan, magenta, 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 data conversion table 95 and performs a conversion process to convert the separate bitmap data for each color, thereby converting the image density to 50[%], 25[%], etc.

[0107] [1-3-3. Image density and pattern of silver toner in color metallic] Next, the image density of the silver toner image PS superimposed on the color toner image PL in this evaluation test will be described.

[0108] In a preparatory test conducted prior to this evaluation test, color metallic printing was performed in which a single-color cyan toner image PL (hereinafter also referred to as the cyan image) was superimposed with silver toner images PS having various image densities, and the FI value and C* (chroma) of each were measured.

[0109] Specifically, in this preparatory test, the image density of the silver toner image PS was set to four levels: 100[%], 75[%], 50[%], and 25[%]. As a result, the results shown in Table TBL2 in Figure 6 were obtained. From the values ​​in Table TBL2, it can be seen that in color metallic printing, when the image density of the silver toner image PS is reduced from 100[%], the FI value gradually decreases and the C* value gradually increases.

[0110] As for the FI value, as mentioned above, if the value is 10.0 or higher, that is, if the image density of the silver toner image PS is 50[%] or higher, the metallic luster can be perceived visually as being sufficiently strong. As for C*, the closer it is to the value of 55 for normal colors, that is, the lower the image density of the silver toner image PS, the wider the color gamut will be. Taking these factors into consideration, in this evaluation test, we decided to adopt 50[%] as the image density of the silver toner image PS in color metallic printing.

[0111] Next, the print pattern N of the silver toner image PS in this evaluation test will be described. In this evaluation test, the entire area to be printed with color metallic ink was divided into a lattice shape consisting of squares of 8 dots vertically and 8 dots horizontally, and the print pattern N (hereinafter also referred to as a unit pattern) was arranged in each of the areas divided into the lattice shape. The following description focuses on this print pattern N.

[0112] Figure 7(A) is a schematic plan view showing a printing pattern N1 of a glossy superimposed image PV in which a silver toner image PS having an image density of 50% is superimposed on a monochromatic cyan color toner image PL having an image density of 100%.

[0113] Incidentally, the image forming apparatus 1 controls each light emitting element chip of the LED head 14 (FIG. 2) to be 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 N can be printed on the medium MD.

[0114] In this printing pattern N1, the entire area of ​​the silver toner image PS, which is a square of 8 dots vertically and 8 dots horizontally, is divided vertically and horizontally into two, and divided into four small square areas of 4 dots vertically and 4 dots horizontally, and silver toner TS is placed in every other small area. With this printing pattern N1, a good C* was obtained.

[0115] 7B is a schematic plan view of a print pattern N2 of a glitter superimposed image PV, in which a silver toner image PS having the same pattern configuration as print pattern N1 is superimposed on a blue color toner image PL with an image density of 200% by color mixing, as seen from above. With this print pattern N2, the C* value is 9.9, which is significantly smaller than the value (55) when only the blue color toner image PL is printed without the silver toner image PS being superimposed, and it was found that the color gamut is extremely narrow.

[0116] 7C is a plan view showing a schematic view of a glittering superimposed image PV printed pattern N3, in which a silver toner image PS having a different pattern configuration from the printed pattern N1 is superimposed on a blue color toner image PL with an image density of 200% by color mixing. In this printed pattern N3, the entire area of ​​the silver toner image PS is divided into two in the horizontal direction only, into two rectangular small areas each having 8 dots vertically and 4 dots horizontally, and silver toner TS is placed only in one of the small areas. In other words, in printed pattern N3, the glittering image formed by silver toner TS is rectangular, occupying a part in the main scanning direction (left-right direction) and the whole part in the sub-scanning direction (front-back direction).

[0117] With this print pattern N3, the C* value was 14.4, which was smaller than the value (55) when only the blue color toner image PL was printed by mixing colors without superimposing the silver toner image PS, but was found to be a better value than print pattern N2. This is thought to be because print pattern N3 has enlarged small areas of each blue compared to print pattern N2, making the original blue color gamut easier to see.

[0118] Based on the above, in this evaluation test, for the silver toner image PS superimposed on the mixed blue color toner image PL, the entire area was divided horizontally only into two rectangular sub-areas each consisting of 8 dots vertically and 4 dots horizontally, similar to printing pattern N3, and silver toner TS was placed in only one of the sub-areas.

[0119] [1-3-4. 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 realizes a metallic color by superimposing silver on blue. Each print pattern N is a square with a side length of 8 dots, with the top row being a silver toner image PS, the middle row below that being a magenta color toner image PL, and the bottom row below that being a cyan color toner image PL.

[0120] For convenience of explanation, hereinafter, magenta (M) toner T is also referred to as magenta toner TM or first non-glossy developer, and cyan (C) toner T is also referred to as cyan toner TC or second non-glossy developer. Also, hereinafter, magenta (M) color toner image PL is also referred to as magenta toner image PM or first non-glossy image, and cyan (C) color toner image PL is also referred to as cyan toner image PC or second non-glossy image. Furthermore, hereinafter, magenta (M) image forming unit 10M is also referred to as first non-glossy image forming section, and cyan (C) image forming unit 10C is also referred to as second non-glossy image forming section.

[0121] 8(A), (B), and (C) are schematic diagrams of a medium MD on which a glitter superimposed image PV of a print pattern N10 is printed. FIG. 8(A) is a plan view showing the medium MD as viewed from above, showing a silver toner image PS superimposed on the topmost layer. FIG. 8(B) is a plan view showing a magenta toner image PM superimposed on the middle layer as viewed from above. FIG. 8(C) is a plan view showing a cyan toner image PC superimposed on the lower layer as viewed from above. FIG. 9 is a schematic side view of a medium MD on which a glitter superimposed image PV of a print pattern N10 is printed, as viewed from the side.

[0122] In print pattern N10, the image density is 100% for the silver toner image PS, magenta toner image PM, and cyan toner image PC, and toner is placed in the entire area of ​​print pattern N10, making it a so-called solid image. In other words, in print pattern N10, the entire range is a bright area where silver toner TS is superimposed, and in the color toner image PL composed of the magenta toner image PM and cyan toner image PC, the image density of the bright area is 200%.

[0123] 10A, 10B, and 10C correspond to FIGS. 8A, 8B, and 8C, respectively, and are schematic diagrams of a medium MD on which a glitter superimposed image PV of a print pattern N11 is printed. FIG. 10A shows a silver toner image PS superimposed on the top. In this silver toner image PS, the silver toner TS is not arranged in a small area in the right half (hereinafter referred to as a non-glitter area), and the silver toner TS is arranged only in a small area in the left half (hereinafter referred to as a glitter area). In other words, in this silver toner image PS, the ratio of the number of dots in which the silver toner TS is arranged to the total number of dots, that is, the ratio of the area of ​​the glitter area, is 50[%], and the ratio of the area of ​​the remaining non-glitter area is also 50[%], resulting in an overall image density of 50[%].

[0124] 10B shows the magenta toner image PM superimposed in the middle. In the non-bright area of ​​the right half of this magenta toner image PM, magenta toner TM is placed over the entire area, forming a so-called solid image, with an image density of 100%.

[0125] On the other hand, the bright region of the left half of the magenta toner image PM is divided vertically and horizontally into two, resulting in four small rectangular regions of 4 dots vertically and 2 dots horizontally, with magenta toner TM disposed in two of these regions, the upper right and the lower left. That is, the image density in the bright region of the magenta toner image PM is 50[%].

[0126] 10C shows a cyan toner image PC superimposed on the lower part. In the non-bright area of ​​the right half of this cyan toner image PC, similar to the magenta toner image PM, cyan toner TC is arranged over the entire area, forming a so-called solid image, and the image density is 100[%].

[0127] Meanwhile, the bright region of the left half of the cyan toner image PC is divided vertically and horizontally into two parts, similar to the magenta toner image PM (FIG. 10(B)), into four small rectangular regions, each of which is 4 dots long and 2 dots wide. However, in the cyan toner image PC, cyan toner TC is disposed in two places, the upper left and lower right parts, of the four small regions, that is, in positions that do not overlap with the magenta toner TM in the magenta toner image PM and are complementary to the magenta toner TM. That is, in the bright region of the cyan toner image PC, the image density is 50% similar to that of the magenta toner image PM.

[0128] From another perspective, in print pattern N11, in the color toner image PL composed of the magenta toner image PM and the cyan toner image PC, the image density of the non-glossy area on the right side is 200[%]. On the other hand, in print pattern N11, the image density of the glittery area on the left side of the color toner image PL is 100[%], and the magenta toner TM and the cyan toner TC are arranged so as not to overlap each other.

[0129] For convenience of explanation, hereinafter, the region in the magenta toner image PM where the magenta toner TM is disposed is also referred to as the first region, and the region in the cyan toner image PC where the cyan toner TC is disposed is also referred to as the second region. In addition, hereinafter, the overlapping ratio of the first region and the second region in the non-glossy region is also referred to as the non-glossy overlapping ratio or the first ratio, and the overlapping ratio of the first region and the second region in the glossy region is also referred to as the glossy overlapping ratio or the second ratio.

[0130] In this case, in the print pattern N11, the non-overlapping ratio (first ratio), which is the ratio at which the first region and the second region overlap in the non-glossy region, is 100[%], while the overlapping ratio (second ratio), which is the ratio at which the first region and the second region overlap in the glittery region, is 0[%]. In other words, in the print pattern N11, the overlapping ratio (0[%]) is smaller than the non-overlapping ratio (100[%]).

[0131] Figures 11(A), (B), and (C) correspond to Figures 8(A), (B), and (C), respectively, and are schematic diagrams of a medium MD on which a glitter superimposed image PV of print pattern N12 is printed. Figure 11(A) shows a silver toner image PS superimposed on the top. As with print pattern N11 (Figure 10), this silver toner image PS has no silver toner TS arranged in the non-glitter area of ​​the right half, and silver toner TS arranged only in the glitter area of ​​the left half, resulting in an overall image density of 50[%].

[0132] 11B shows the magenta toner image PM superimposed in the middle. In the non-bright area in the right half of this magenta toner image PM, magenta toner TM is arranged over the entire area, forming a so-called solid image, similar to the print pattern N11 (FIG. 10), and the image density is 100[%].

[0133] On the other hand, in the bright region of the left half of the magenta toner image PM, magenta toner TM is arranged in the central two-dot region in the left-right direction of the four-dot region in the lower half in the vertical direction, that is, in a rectangular region of two dots horizontally and four dots vertically. Therefore, the image density in the bright region of the magenta toner image PM is 25%.

[0134] 11C shows a cyan toner image PC superimposed on the lower part. In the non-glossy region in the right half of this cyan toner image PC, cyan toner TC is arranged over the entire area, forming a so-called solid image, similar to print pattern N11 (FIG. 10), and the image density is 100[%].

[0135] On the other hand, in the bright region of the left half of the cyan toner image PC, the cyan toner TC is arranged in the central two-dot region in the left-right direction of the four-dot region that is the upper half in the vertical direction, that is, in a rectangular region of two dots horizontally and four dots vertically, that is, in a position that does not overlap with the magenta toner TM in the magenta toner image PM. Therefore, the image density in the bright region of the cyan toner image PC is 25%.

[0136] That is, in printing pattern N12, in a color toner image PL composed of a magenta toner image PM and a cyan toner image PC, the image density of the non-glowing area on the right side is 200% while the image density of the glowing area on the left side is 50%, and the magenta toner TM and cyan toner TC are arranged so that they do not overlap each other.

[0137] In other words, in print pattern N12, like print pattern N11, the non-overlapping ratio (first ratio), which is the ratio of overlap between the first region and the second region in the non-glossy region, is 100[%], while the overlapping ratio (second ratio), which is the ratio of overlap between the first region and the second region in the glittering region, is 0[%]. In other words, in print pattern N12, like print pattern N11, the overlapping ratio (0[%]) is smaller than the non-overlapping ratio (100[%]).

[0138] Figures 12(A), (B), and (C) correspond to Figures 8(A), (B), and (C), respectively, and are schematic diagrams of a medium MD on which a glitter superimposed image PV of print pattern N13 is printed. Figure 12(A) shows a silver toner image PS superimposed on the top. As with print pattern N11 (Figure 10), this silver toner image PS has no silver toner TS arranged in the non-glitter area of ​​the right half, and silver toner TS arranged only in the glitter area of ​​the left half, resulting in an overall image density of 50[%].

[0139] Fig. 12(B) shows the magenta toner image PM superimposed in the middle. In the non-bright areas of the right and left halves of this magenta toner image PM, magenta toner TM is placed over the entire area, so-called a solid image, similar to print pattern N11 (Fig. 10), and the like, and the image density is 100[%]. On the other hand, in the bright area of ​​the left half of the magenta toner image PM, magenta toner TM is not placed. Therefore, the image density in the bright area of ​​the magenta toner image PM is 0[%].

[0140] Fig. 12(C) shows a cyan toner image PC superimposed on the lower stage. In the non-bright areas of the right and left halves of this cyan toner image PC, cyan toner TC is arranged over the entire range, so-called a solid image, similar to print pattern N11 (Fig. 10), and the like, and the image density is 100[%]. On the other hand, in the bright area of ​​the left half of the cyan toner image PC, like the magenta toner image PM, cyan toner TC is not arranged. Therefore, the image density in the bright area of ​​the cyan toner image PC is 0[%]. From another perspective, it can also be considered that in this cyan toner image PC, cyan toner TC is arranged in a position that does not overlap with magenta toner TM.

[0141] That is, in printing pattern N13, in a color toner image PL composed of a magenta toner image PM and a cyan toner image PC, the image density of the non-glossy areas is 200% while the image density of the glossy areas is 0%, and the magenta toner TM and cyan toner TC are arranged so that they do not overlap each other.

[0142] In other words, in print pattern N13, like print patterns N11 and N12, the non-overlapping ratio (first ratio), which is the ratio at which the first region and the second region overlap in the non-glossy region, is 100[%], while the overlapping ratio (second ratio), which is the ratio at which the first region and the second region overlap in the glittery region, is 0[%]. In other words, in print pattern N13, like print patterns N11 and N12, the overlapping ratio (0[%]) is smaller than the non-overlapping ratio (100[%]).

[0143] 13(A), (B) and (C) correspond to Figs. 8(A), (B) and (C), respectively, and are schematic diagrams of a medium MD on which a glittering superimposed image PV of a print pattern N14 is printed. Fig. 13(A) shows a silver toner image PS superimposed on the top. This silver toner image PS is obtained by dividing the entire area into two parts vertically and horizontally into four square-shaped small areas each having four dots vertically and four dots horizontally, as in the above-mentioned print patterns N1 and N2 (Figs. 7(A) and (B)), and silver toner TS is placed in the small areas at the top left and bottom right. That is, in this print pattern N14, the small areas at the top left and bottom right are glittering areas, and the remaining small areas at the top right and bottom left are non-glittering areas.

[0144] Fig. 13B shows a magenta toner image PM superimposed in the middle row, and Fig. 13C shows a cyan toner image PC superimposed in the lower row. Both the magenta toner image PM and the cyan toner image PC have an image density of 100% and are so-called solid images in which toner T is placed in all areas within the print pattern N14.

[0145] That is, in the print pattern N14, the image density of the color toner image PL composed of the magenta toner image PM and the cyan toner image PC is 200% in both the bright and non-bright areas.

[0146] [1-3-5. Contents of Examples and Comparative Examples] Next, in this evaluation test, a plurality of examples X and a plurality of comparative examples Z were performed by printing a glitter superimposed image PV using the print pattern N (FIGS. 9 to 14) on a medium MD.

[0147] In this evaluation test, Examples X11, X12, and X13 were each performed. Specifically, in this evaluation test, pattern data corresponding to print patterns N11, N12, and N13 (FIGS. 10, 11, and 12) were stored in the data conversion table 95 provided in the memory unit 81 (FIG. 3) of the image forming apparatus 1. In addition, in this evaluation test, Comparative Examples Z11 and Z12 were each performed for comparison with each Example X. Specifically, in this evaluation test, pattern data corresponding to print patterns N10 and N14 (FIGS. 8 and 13) were stored in the data conversion table 95 (FIG. 3).

[0148] In the present evaluation test, each Example X and each Comparative Example Z were each carried out according to the following procedure. <Step 1> In the image forming apparatus 1, the glitter superimposed image PV of the print pattern N 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.

[0149] [1-3-6. Measurement results of Examples and Comparative Examples] Next, the measurement results of metallic luster (specifically, FI value) and color gamut (specifically, C*) for each of the examples and comparative examples in this evaluation test will be described.

[0150] Table TBL3 shown in Fig. 14 summarizes the measurement results of FI value and C* in Example X11, Example X12, and Example X13, and Comparative Example Z11 and Comparative Example Z12, and the respective judgment results. Among them, FI value is a value obtained by the above-mentioned measurement method. Also, C* is a value calculated by the above-mentioned method.

[0151] The FI value judgment result was expressed as good with a symbol "○" if it was 10 or more, and as poor with a symbol "×" if it was less than 10. The C* judgment result was expressed as excellent with a symbol "◎" if it was 18 or more, and as good with a symbol "○" if it was 14 or more but less than 18, and as poor with a symbol "×" if it was less than 14.

[0152] Focusing on the FI value in Table TBL3, the judgment results were good in all of Examples X11, X12, and X13. In other words, it was found that sufficient brilliance can be obtained even if the image density of the silver toner image PS in color metallic printing is reduced to 50%.

[0153] On the other hand, when focusing on the C* values ​​in Table TBL3, the judgment results were excellent in Examples X11 and X12, and good in Example X13, while the judgment results were poor in Comparative Examples Z11 and Z12. For this reason, in color metallic printing, if there are no non-glossy areas and only glossy areas as in Comparative Examples Z11 and Z12, a good color gamut cannot be obtained, and the colors appear dull.

[0154] On the other hand, in color metallic printing, if the image density of the color toner image PL in the shiny area where the silver toner TS is superimposed is within the range of 0[%] to 100[%] and the color toners TL are arranged so as not to overlap each other, at least a good color gamut can be obtained. Furthermore, in color metallic printing, an excellent color gamut can be obtained by setting the image density of the color toner image PL in the shiny area within the range of 50[%] to 100[%] and arranging the color toners TL so as not to overlap each other.

[0155] Based on such judgment results, in the image forming apparatus 1 according to the first embodiment, pattern data such as printing patterns N11, N12 and N13 (hereinafter referred to as image density reduction data) are pre-stored in the data conversion table 95 of the memory unit 81.

[0156] Specifically, in the image density reduction data, for the silver toner image PS, the entire range of the print pattern N is equally divided in the main scanning direction (left and right direction), and each is made into a shiny area and a non-shiny area, resulting in an image density of 50[%]. Also, in the image density reduction data, when two colors are used for the color toner image PL, the colors are arranged so that they do not overlap each other, and the image density is set within the range of 100[%] to 0[%]. Hereinafter, the image density of the silver toner image PS (i.e. the shiny image) is also referred to as the shiny image density, and the image density of the color toner image PL (i.e. the non-shiny image) is also referred to as the non-shiny image density.

[0157] [1-4. Brightness 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.

[0158] 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 two color toners are overlapped to create an image density of 200% and where a silver toner with an image density of 100% is overlapped to create a glitter superimposed image PV (i.e., a glitter superimposition target portion). If a positive result is obtained here, this indicates that in the glitter superimposition target portion, the silver toner image PS and each color toner image PL should be changed based on the image density reduction data. In this case, the control unit 3 proceeds to the next step SP3.

[0159] In step SP3, the control unit 3 refers to the data conversion table 95 (FIG. 3) in the storage unit 81, reads out the image density reduction data, and proceeds to the next step SP4. In step SP4, the control unit 3 changes the silver toner image PS and each color toner image PL of the glitter superimposition target portion from a solid image with an image density of 100[%] to an image based on the image density reduction data, as image formation control, and proceeds to the next step SP5. As a result, the control unit 3 sets a part of the glitter superimposition target portion as a glitter region, and sets the remaining part as a non-glitter region.

[0160] 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 glitter superimposition target portion, and therefore there is no need to change the print pattern. In this case, the control unit 3 proceeds to the next step SP5.

[0161] In step SP5, 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 images PL of each color, so as to be sequentially superimposed on the intermediate transfer belt 34 (FIGS. 1 and 2), and then proceeds to the next step SP6. If the toner images formed at this time include a glitter superimposition target portion, the silver toner image PS and the color toner images PL of each color in the glitter superimposition target portion are each changed to an image based on the image density reduction data.

[0162] In step SP6, the control unit 3 causes the secondary transfer unit 39 to transfer the toner image from the intermediate transfer belt 34 to the surface of the medium MD transported along the transport path W, and then proceeds to the next step SP7. In step SP7, the control unit 3 causes the fixing unit 60 to fix the toner image to the surface of the medium MD, and then causes the paper discharge unit 70 to transport the medium MD and discharge it onto the paper discharge tray 2T, and then proceeds to the next step SP8, where the glitter superimposition printing processing procedure RT1 is completed.

[0163] [1-5. Effects, etc.] In the above configuration, the image forming apparatus 1 according to the first embodiment stores image density reduction data in advance in the data conversion table 95 of the storage unit 81 (FIG. 3). If the print data received from the higher-level device 100 contains a glitter superimposition target portion in which a glitter color with an image density of 100% is superimposed on a mixed color with an image density of 200% obtained by superimposing two normal colors, the image forming apparatus 1 converts the data into an image based on the image density reduction data.

[0164] Specifically, similar to print pattern N11 (FIG. 10), image forming apparatus 1 sets the shiny and non-shiny regions with the image density of the silver toner image PS in the shiny superimposition target portion set to 50% and leaves the image density of the color toner image PL in the non-shiny region at 200%. On the other hand, image forming apparatus 1 reduces the image density of the color toner image PL in the shiny region where silver toner TS is superimposed to within the range of 100% to 0%, and prevents toners T of multiple colors from overlapping each other.

[0165] As a result, the image forming apparatus 1 can obtain sufficient brilliance in the brilliance superimposition target portion of the image printed on the medium MD, as in Examples X1 to X3, while making the color gamut sufficiently wide, so that the value is close to the color gamut in the portion containing only mixed colors without superimposing the brilliance color.

[0166] As a result, when the image forming device 1 superimposes a brilliant color only on a part of a mixed color formed by overlapping two normal colors in an image to create an image density of 200%, for example, the difference in color gamut between the part of the mixed color itself and the part where the brilliant color is superimposed can be kept extremely small, so that the overall impression of the image is not significantly changed.

[0167] In particular, in the image density reduction data, the image forming apparatus 1 sets the image density of the silver toner image PS to 50[%] like the print pattern N11 etc. (FIG. 10(A) etc.). Therefore, in comparison with the case where the image density of the silver toner image PS is set to 100[%], the image forming apparatus 1 can obtain sufficient brilliance although the FI value is somewhat lower, and by forming non-brilliant regions, the color toners are actively exposed and the color gamut can be expanded.

[0168] Furthermore, in the bright regions where the silver toner TS is superimposed in the print patterns N11, N12, and N13, the image density of the normal color is significantly reduced from 200% to within the range of 100% to 0% (FIGS. 10 to 12). Furthermore, the image forming apparatus 1 prevents the colors (cyan and magenta) from overlapping each other in the bright regions. This allows the image forming apparatus 1 to keep the layer thickness of the color toner TL formed below the silver toner TS in the bright regions on the printed medium MD relatively small (thin), and therefore suppresses the decrease in C*, thereby ensuring a sufficient color gamut.

[0169] Furthermore, in the printing patterns N11, N12, and N13, the image forming apparatus 1 divides the silver toner image PS into two in the left-right direction (i.e., the main scanning direction), and makes the non-glossy area and the glossy area into small rectangular areas with the longitudinal direction (i.e., the sub-scanning direction or the transport direction of the medium MD) as the longitudinal direction. In other words, the image forming apparatus 1 makes the silver toner image PS form vertical stripes along the sub-scanning direction (transport direction) on the medium MD printed based on the image density reduction data.

[0170] This is based on the fact that, through other experiments, the brilliance tends to decrease slightly when the silver toner image PS has horizontal stripes along the main scanning direction, but sufficient brilliance is obtained when the silver toner image PS has vertical stripes along the sub-scanning direction.The reason for this tendency is presumed to be related to the fact that, when heat and pressure are applied to the silver toner TS on the medium MD by the nip portion formed by the heating unit 61 and the pressure unit 62 in the fixing unit 60 of the image forming apparatus 1, the nip portion is formed along the main scanning direction, and the medium MD is transported along the transport direction (sub-scanning direction).

[0171] Based on this knowledge, in the image forming apparatus 1, the silver toner image PS forms vertical stripes along the sub-scanning direction (transport direction), thereby making it possible to reduce the area of ​​the shiny region to 50% of the total while still achieving sufficient shine.

[0172] 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 color toner image PL formed by superimposing two colors and the silver toner image PS superimposed thereon uniformly 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.

[0173] According to the above configuration, when the print data received from the upper device 100 includes a glitter superimposition target portion, the image forming device 1 according to the first embodiment changes the print pattern N of the silver toner image PS and the color toner image PL of each color in the glitter superimposition target portion and prints it on the medium MD. At this time, the image forming device 1 sets the glitter region and the non-glitter region with the image density of the silver toner image PS of the glitter superimposition target portion being 50[%], and while the image density in the non-glitter region is left at 200[%], the image density in the glitter region is reduced to within the range of 100[%] to 0[%], and the color toners TL are prevented from overlapping each other. As a result, the image forming device 1 can obtain sufficient glitteriness in the image printed on the medium MD and can sufficiently expand the color gamut.

[0174] 2. Second embodiment Image forming apparatus 201 (FIG. 1) according to the second embodiment differs from image forming apparatus 1 according to the first embodiment in that it has control unit 203 instead of control unit 3, but is otherwise configured similarly.

[0175] Control unit 203 differs from control unit 3 (FIG. 3) according to the first embodiment in that it has a storage unit 281 instead of storage unit 81, but is otherwise configured similarly. This storage unit 281 differs from storage unit 81 according to the first embodiment in that it has a data conversion table 295 instead of data conversion table 95, but is otherwise configured similarly.

[0176] In comparison with the data conversion table 95 according to the first embodiment, this data conversion table 295 stores in advance partially different pattern data (that is, image density reduction data).

[0177] In the second embodiment, an evaluation test different from that in the first embodiment was performed. Specifically, a print pattern N21 shown in Fig. 16 corresponding to Fig. 10 etc. was prepared. Figs. 16(A), (B) and (C) correspond to Figs. 10(A), (B) and (C) etc., respectively, and are schematic diagrams of a medium MD on which a glitter superimposed image PV of the print pattern N11 is printed.

[0178] 16A shows a silver toner image PS superimposed on the top row. As with print pattern N11 (FIG. 10), this silver toner image PS has no silver toner TS in the non-glossy area in the right half, and silver toner TS only in the glossy area in the left half, resulting in an overall image density of 50%.

[0179] Fig. 16B shows a magenta toner image PM superimposed in the middle section, and Fig. 16C shows a cyan toner image PC superimposed in the lower section. As in Figs. 8B and 8C, the magenta toner image PM and the cyan toner image PC both have an image density of 100% and are so-called solid images in which toner T is placed in all areas within the print pattern N21.

[0180] Next, in this evaluation test, Example X21 and Comparative Example Z21 were performed by printing a glitter superimposed image PV using the print pattern N (FIG. 16, etc.) on a medium MD. That is, in this evaluation test, as Example X21, pattern data corresponding to the print pattern N21 (FIG. 16) was stored in the data conversion table 295 provided in the storage unit 281 (FIG. 3) of the image forming device 201. In addition, in this evaluation test, Comparative Example Z11 similar to the first embodiment was performed for comparison with Example X21. Specifically, in this evaluation test, pattern data corresponding to the print pattern N10 (FIG. 8) was stored in the data conversion table 295 (FIG. 3).

[0181] Incidentally, in the second embodiment, Example X21 and Comparative Example Z11 were carried out according to Procedures 1 and 2 similar to those in the first embodiment.

[0182] Next, the measurement results of metallic luster (specifically, FI value) and color gamut (specifically, C*) for each of the examples and comparative examples in this evaluation test will be described.

[0183] Table TBL4 shown in FIG. 17 corresponding to FIG. 14 summarizes the measurement results of FI value and C* in Example X21 and Comparative Example Z11, and the respective judgment results. Among them, FI value is a value obtained by the measurement method described above. Also, C* is a value calculated by the above-mentioned technique. The judgment results of FI value and C* are based on the same judgment method as in the first embodiment.

[0184] Focusing on the FI value in Table TBL4, the judgment result of Example X21 was good. That is, as in the first embodiment, although the image density of the silver toner image PS in the color metallic printing is reduced to 50[%], sufficient brilliance is obtained.

[0185] On the other hand, when focusing on the C* values ​​in Table TBL4, the judgment result was good in Example X21, and the judgment result was bad in Comparative Example Z11, similar to the first embodiment. This shows that in color metallic printing, even if the image density of the color toner image PL in the glittering area where the silver toner TS is superimposed is set to 200[%] and the color toners are superimposed on each other, a good color gamut can be obtained.

[0186] In the above configuration, the image forming apparatus 201 according to the second embodiment stores image density reduction data based on the print pattern N21 (FIG. 16) in advance in the data conversion table 295 of the storage unit 281 (FIG. 3). If the print data received from the higher-level device 100 contains a glitter superimposition target portion in which a glitter color with an image density of 100% is superimposed on a mixed color with an image density of 200% obtained by superimposing two normal colors, the image forming apparatus 201 converts the data into an image based on the image density reduction data.

[0187] Specifically, the image forming device 201 sets the glossy and non-glossy areas by setting the image density of the silver toner image PS in the glossy superimposition target portion to 50% as in printing pattern N21 (Figure 16), while leaving the image density of the color toner image PL at 200%.

[0188] Therefore, the image forming device 201 can obtain sufficient brilliance in the brilliance superimposition target portion of the image printed on the medium MD, as in Example X21, and can make the color gamut sufficiently wide, close to the color gamut in the portion containing only mixed colors without superimposing the brilliance color.

[0189] In other respects as well, the image forming apparatus 201 according to the second embodiment can achieve the same effects as the first embodiment.

[0190] 3. Other embodiments In the above-described first embodiment, the image density of the color toner image PL using two colors is set to 100[%], 50[%] or 0[%] as in the print patterns N11, N12 and N13 (FIGS. 10, 11 and 12) in the glitter region where the silver toner TS is superimposed among the glitter superimposition target portions. However, the present invention is not limited to this, and the image density of the color toner image PL may be set to any value within the range of 100[%] to 0[%]. Also, the image density of the glitter region may be different for each color in the color toner image PL of each color.

[0191] For example, in the print pattern N31 shown in FIG. 18, the silver toner image PS (A) is the same as the print pattern N11 (FIG. 10), and in the magenta toner image PM (B) and the cyan toner image PC (C), the right half of the non-glossy area is a solid image, while the image density of the left half of the glossy area is 37.5%. That is, in the print pattern N31, in the color toner image PL composed of the magenta toner image PM and the cyan toner image PC, the image density of the non-glossy area on the right side is 200% while the image density of the glossy area on the left side is 75%, and the magenta toner TM and the cyan toner TC are arranged so as not to overlap each other. In this way, when the image density of the color toner image PL in the glossy area with the silver toner image PS is set within the range of 100% to 50%, an excellent color gamut can be obtained as in the first and second embodiments (FIG. 14).

[0192] Also, for example, in the print pattern N32 shown in FIG. 19, the silver toner image PS (A) is the same as the print pattern N11 (FIG. 10), and in the magenta toner image PM (B) and the cyan toner image PC (C), the non-glossy area in the right half is a solid image, while the image density in the glossy area in the left half is 12.5%. That is, in the print pattern N32, in the color toner image PL composed of the magenta toner image PM and the cyan toner image PC, the image density in the non-glossy area in the right half is 200% while the image density in the glossy area in the left half is 25%, and the magenta toner TM and the cyan toner TC are arranged so as not to overlap each other. In this way, when the image density of the color toner image PL in the glossy area with the silver toner image PS is set within the range of 50% to 0%, a good color gamut can be obtained as in the third embodiment (FIG. 14).

[0193] Furthermore, for example, in the print pattern N33 shown in FIG. 20, the silver toner image PS in (A) and the magenta toner image PM in (B) are the same as those in the print pattern N11 (FIG. 10). That is, the image density of the bright region in the left half of the magenta toner image PM is 50%. On the other hand, in the cyan toner image PC in (C), the image density of the bright region in the left half is 25%. That is, in the print pattern N33, in the color toner image PL composed of the magenta toner image PM and the cyan toner image PC, the image density of the non-bright region on the right side is 200% while the image density of the bright region on the left side is 75% and the magenta toner TM and the cyan toner TC are arranged so as not to overlap each other. In this way, the image density of the bright region in the left half of the magenta toner image PM and the image density of the bright region in the left half of the cyan toner image PC may be made different from each other. Even in such a case, an excellent or good color gamut can be obtained by setting the image density of the bright area on the left side in the color toner image PL composed of the magenta toner image PM and the cyan toner image PC to be within the range of 100[%] to 50[%] or within the range of 50[%] to 0[%].

[0194] In the above-described first embodiment, in the glittering region where the silver toner TS is superimposed in the glittering superimposition target portion, two color toner images PL are arranged so as not to overlap each other, as in the print patterns N11, N12, and N13 (FIGS. 10, 11, and 12). However, the present invention is not limited to this, and for example, two color toner images PL may be superimposed on each other in a portion of the glittering region where the silver toner TS is superimposed. In this case, by setting the image density of the color toner image PL to a value smaller than 200[%], the color gamut can be expanded more than when the image density is 200[%].

[0195] Furthermore, in the above-mentioned first embodiment, the color toner image PL of the glitter superimposition target portion is configured with cyan and magenta. However, the present invention is not limited to this, and the color toner image PL may be configured with two colors of various combinations, such as cyan and yellow, or magenta and yellow. Furthermore, the color toner image PL may be configured with a combination of three or more colors. In addition, the image density of each color (cyan, magenta, and yellow) constituting the multiple color toner images PL is not limited to 100[%], and at least one color may be less than 100[%], for example. The same applies to the second embodiment. In addition, the order in which the color toner images PL of each color are superimposed is not particularly limited.

[0196] Furthermore, in the above-mentioned first embodiment, the image density of the silver toner image PS in the glitter superimposition target portion is changed from 100[%] to 50[%]. However, the present invention is not limited to this, and the image density of the silver toner image PS may be set to any value within the range of 25[%] to 75[%]. For example, when the image density is set to 25[%], as shown in FIG. 6, the glitteriness is slightly decreased compared to when the image density is set to 50[%], but the color gamut can be widened. On the other hand, when the image density is set to 75[%], as shown in FIG. 6, the color gamut is slightly narrowed compared to when the image density is set to 50[%], but the glitteriness can be increased. In other words, the image density of the silver toner image PS may be appropriately set within the range of 25[%] to 75[%], taking into consideration the balance between the glitteriness and the width of the color gamut. The same applies to the second embodiment.

[0197] Furthermore, in the above-mentioned first embodiment, a configuration has been described in which the silver toner image PS is divided into two in the left-right direction (main scanning direction) in the print pattern N11 (FIG. 10) and the non-glossy area and the shiny area are both rectangular small areas with their longitudinal direction in the vertical direction (sub-scanning direction or transport direction of the medium MD). However, the present invention is not limited to this, and for example, the silver toner image PS may be divided into two in the front-rear direction (sub-scanning direction or transport direction of the medium MD) and the non-glossy area and the shiny area may both be rectangular small areas with their longitudinal direction in the horizontal direction (main scanning direction). The same applies to the second embodiment.

[0198] Furthermore, in the above-mentioned first embodiment, the image density reduction data is stored in advance in the data conversion table 95 (FIG. 3) provided in the storage unit 81 of the image forming device 1, and in step SP4 of the glitter superimposition printing procedure RT1 (FIG. 14), each image of the glitter superimposition target portion is changed based on the image density reduction data. However, the present invention is not limited to this, and for example, the image density reduction data may be stored in the upper device 100 in advance, and the printer driver may refer to the image density reduction data to generate print data in which each image of the glitter superimposition target portion is changed, and the print data may be transmitted to the image forming device 1. In this case, the control unit 3 of the image forming device 1 may form and print each color toner image PL and silver toner image PS as they are, without changing each image of the glitter superimposition target portion. The same applies to the second embodiment.

[0199] Furthermore, in the above-mentioned first 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 (for example, CI Pigment Yellow 180, which is an organic pigment), a magenta pigment (for example, CI Pigment Red 122, which is an organic pigment), a red-orange fluorescent pigment (for example, 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. In addition, 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. The same applies to the second embodiment.

[0200] Furthermore, in the above-mentioned first 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. The same applies to the second embodiment.

[0201] Furthermore, in the above-mentioned first 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 the intermediate transfer belt 34, and the toner image is secondarily transferred from the intermediate transfer belt 34 to the 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 the medium MD. The same applies to the second embodiment.

[0202] Furthermore, in the above-mentioned first 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 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 glittering pigment, a binder resin, and an external additive, or a powdery material formed by the aggregation of these particles, are defined as glittering toner or glittering developer. The same applies to the second embodiment.

[0203] 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 an image forming apparatus having various other functions, such as an MFP (Multi Function Peripheral) having the functions of a copier or facsimile machine. The same applies to the second embodiment.

[0204] 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.

[0205] Furthermore, in the above-mentioned first embodiment, a description has been given of a form in which the image forming apparatus 1 is constituted by the image forming unit 10S as a glossy image forming section, the image forming units 10K, 10C, 10M and 10Y as non-glossy image forming sections, and the control section 3 as a control section. However, the present invention is not limited to this, and the image forming apparatus may be constituted by glossy image forming sections, non-glossy image forming sections and control sections having various other configurations. [Industrial Applicability]

[0206] 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]

[0207] 1, 201...image forming apparatus, 3, 203...control unit, 10, 10C, 10M, 10Y, 10K, 10S...image forming unit, 39...secondary transfer unit, 60...fixing unit, 80...print control unit, 81, 281...memory unit, 95, 295...data conversion table, 100...host device, MD...medium, N...printing pattern, PC...cyan toner image, PL...color toner image, PM...magenta toner image, PS...silver toner image, PV...glossy superimposed image, T...toner, TL...color toner, TS...silver toner.

Claims

1. a glitter image forming unit capable of forming a glitter image made of a glitter developer on a medium; a first non-glossy image forming unit capable of forming a first non-glossy image made of a first non-glossy developer in a first area on the medium; a second non-glossy image forming unit capable of forming a second non-glossy image made of a second non-glossy developer in a second area on the medium; a control unit that controls the glossy image forming unit, the first non-glossy image forming unit, and the second non-glossy image forming unit; Equipped with The control unit is forming a non-glossy image by superposing the second non-glossy image on the first non-glossy image at a first ratio in a non-glossy region where the glittering developer is not superposed on the first non-glossy image and the second non-glossy image; In a glittering region formed by superimposing the glittering developer on the first non-glitter image and the second non-glitter image, the second non-glitter image is superimposed on the first non-glitter image at a second ratio smaller than the first ratio, a first non-glossy image forming unit and a second non-glossy image forming unit; 1. An image forming apparatus comprising:

2. The control unit controls the non-glossy image forming unit so that the first region and the second region of the non-glossy image do not overlap each other in the glossy region.

2. The image forming apparatus according to claim 1,

3. The control unit controls the glossy image forming unit so that a non-glossy image density, which is a ratio of the combined area of ​​the first region and the second region in the non-glossy image to the area of ​​the glossy image in the glossy region, is 50% or more and 100% or less.

3. The image forming apparatus according to claim 2,

4. The control unit controls the glossy image forming unit so that a glossy image density, which represents a ratio of an area of ​​the glossy region to a total area of ​​the glossy region and the non-glossy region, is 25% or more and 75% or less.

2. The image forming apparatus according to claim 1,

5. The control unit is The length of the glossy image in a sub-scanning direction perpendicular to the main scanning direction is made longer than the length of the glossy image in the main scanning direction in the glossy image forming unit. Controlling the glitter image forming unit 5. The image forming apparatus according to claim 4.

6. The medium has rectangular unit patterns repeatedly arranged in a lattice pattern, The control unit controls the glossy image forming unit to form the glossy image in a rectangular shape that occupies a part of the unit pattern in the main scanning direction and an entire part of the unit pattern in the sub-scanning direction.

5. The image forming apparatus according to claim 4.

7. a control step of controlling image formation by a control unit to respectively set a non-glossy region formed on the medium without superimposing a glittering image made of the glittering developer and a non-glossy image made of the first non-glossy developer and a glittering region formed on the medium by superimposing the glittering image and the non-glossy image; an image forming step of forming the glitter image on the medium by a glitter image forming unit using the glitter developer, and forming the non-glitter image on the medium by a first non-glitter image forming unit and a second non-glitter image forming unit using the first non-glitter developer and the second non-glitter developer; having The image formation control includes: forming the first non-glossy developer in a first region on the medium and forming the second non-glossy developer in a second region on the medium that at least partially overlaps the first region, in the non-glossy image; forming the non-glossy image such that an overlap ratio of the second region to the first region in the non-glossy region is a first ratio; forming the non-glossy image in the glittering region such that the ratio of overlap of the second region with respect to the first region is a second ratio which is smaller than the first ratio.

1. An image forming method comprising:

8. a glitter image forming unit capable of forming a glitter image made of a glitter developer on a medium; a first non-glossy image forming unit capable of forming a first non-glossy image made of a first non-glossy developer in a first area on the medium; a second non-glossy image forming unit capable of forming a second non-glossy image made of a second non-glossy developer in a second area on the medium; a control unit that controls the glossy image forming unit, the first non-glossy image forming unit, and the second non-glossy image forming unit; Equipped with The control unit controls the glossy image forming unit, the first non-glossy image forming unit, and the second non-glossy image forming unit to form glossy areas in which the glossy developer is superimposed on the first non-glossy image and the second non-glossy image, and to form non-glossy areas in which the glossy developer is not superimposed on the first non-glossy image and the second non-glossy image, respectively.

1. An image forming apparatus comprising:

9. The control unit controls the glossy image forming unit so that a glossy image density, which represents a ratio of an area of ​​the glossy region to a total value of an area of ​​the non-glossy region and an area of ​​the non-glossy region, is 25% or more and 75% or less.

9. The image forming apparatus according to claim 8,

10. An image processing method for processing image data including a glitter superimposition target portion in which a glitter image is to be superimposed on a non-glitter image including a first non-glitter image and a second non-glitter image, A step of setting a glossy region in which the glossy image is superimposed on the non-glossy image and a non-glossy region in which the glossy image is not superimposed on the non-glossy image in the glossy superimposition target portion; a step of superimposing the second non-lustrous image on the first non-lustrous image at a first ratio in the non-lustrous region, and superimposing the second non-lustrous image on the first non-lustrous image at a second ratio smaller than the first ratio in the lustrous region; An image forming method comprising the steps of:

Images