JP2013159101A - Golden color representing method and printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To represent a golden color without using a glittering ink.SOLUTION: A golden color representing method includes: a process of forming a light-transmissive light yellow image by applying a second yellow ink to a transparent medium by using a printing device which includes a first head discharging a first yellow ink for forming a color image and a second head discharging the second yellow ink having a light transmission rate higher than that of the first yellow ink: and a process of making the transparent medium having the light yellow image formed thereon come into close contact with a silver glossy surface.

Description

  The present invention relates to a gold color expression method and a printing apparatus.

  There is known a printing apparatus that prints an image having a metallic luster on a medium such as paper using a glitter ink called a glitter ink. Patent Document 1 proposes glitter ink used in an ink jet printing apparatus.

JP 2009-256565 A

Gold is a particularly demanding metallic luster color. For this reason, it is particularly desirable for the printing apparatus to be able to print gold.
However, if glitter ink is used to print gold, the printing cost is increased. Further, since the glitter ink contains silver particles, aluminum (flaky aluminum, scaly aluminum) or the like as metal particles, the metal particles are likely to precipitate. For this reason, when the glitter ink is mounted on the printing apparatus, a processing unit for stirring the glitter ink is necessary, and the printing apparatus itself is also expensive.

  An object of the present invention is to express gold without using glitter ink.

A main invention for achieving the above object is a first head for ejecting a first yellow ink for forming a color image, and a second head for ejecting a second yellow ink having a light transmittance higher than that of the first yellow ink. A step of applying a second yellow ink to a transparent medium to form a light-transparent light yellow image using a printing apparatus having two heads; and the transparent medium on which the light yellow image is formed. And a step of bringing it into close contact with a silver glossy surface.
Further, another main invention for achieving the above object includes a first head for ejecting a first yellow ink for forming a color image, and a second yellow ink having a light transmittance higher than that of the first yellow ink. And a second head that discharges light, and applying the second yellow ink to a transparent medium to form a light yellow light-transmissive image.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1A and 1B are explanatory diagrams of the outline of the present embodiment. FIG. 2 is a schematic side view of the printing apparatus 1. FIG. 3 is a block diagram of the printing apparatus 1. FIG. 4A is an explanatory diagram of a configuration of the black head unit 41K. FIG. 4B is an explanatory diagram of the configuration of the head assembly 411. FIG. 4C is an explanatory diagram of nozzle arrangement in the head 412. FIG. 5A is an explanatory diagram of an image (front printing image) formed by front printing. FIG. 5B is an explanatory diagram of an image (back printing image) formed by back printing. FIG. 6A is an explanatory diagram of a method for printing the label L in FIG. 1A. FIG. 6B is an explanatory diagram showing a state in which the label L is brought into close contact with an object having a metallic gloss surface. FIG. 7A is an explanatory diagram of a label L having a color image. FIG. 7B is an explanatory diagram of a method for printing the label L in FIG. 7A.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

Using a printing apparatus comprising a first head for ejecting a first yellow ink for forming a color image and a second head for ejecting a second yellow ink having a light transmittance higher than that of the first yellow ink, Applying the second yellow ink to a transparent medium to form a light yellow image with light transmission; and bringing the transparent medium on which the light yellow image is formed into close contact with a silver glossy surface. The golden expression method characterized by comprising is clarified.
According to such a gold color expression method, it is possible to express the gold color without using the glitter ink.

  A background image may be formed around the light yellow image by applying the background color ink around the light yellow image without applying a background color ink to a region where the light yellow image is formed. desirable. This makes it easier to visually recognize the golden image.

  It is desirable that the transparent medium is in close contact with the silver glossy surface so that the printing surface of the transparent medium is on the silver glossy surface side. As a result, the printed image is protected by the transparent medium and is not easily damaged.

  The average particle diameter of the pigment of the second yellow ink is preferably smaller than the average particle diameter of the pigment of the first yellow ink. Thereby, the light transmittance of the second yellow ink is increased.

A first head for discharging a first yellow ink for forming a color image; and a second head for discharging a second yellow ink having a light transmittance higher than that of the first yellow ink. The printing apparatus is characterized by applying a 2-yellow ink to form a light-transparent light yellow image.
According to such a printing apparatus, it is possible to express gold without using glitter ink.

  A background color head for discharging a background color ink for forming a background image is further provided, and the background color ink is not applied to a region where the light yellow image is formed, and the area around the light yellow image is formed. It is desirable to apply a background color ink to form the background image. This makes it easier to visually recognize the golden image.

  Preferably, the color image is formed on the transparent medium, and the background image is formed on the color image. As a result, the printed image is protected by the transparent medium and is not easily damaged.

=== Overview ===
1A and 1B are explanatory diagrams of the outline of the present embodiment. Here, a case will be described in which a label having a golden star is printed at the center of a white background image.

  As illustrated in FIG. 1A, the printing apparatus prints a label L on the transparent medium S. At this time, the printing apparatus applies white ink to the background area of the label. However, white ink is not applied to the star-marked area. A yellow ink having a high light transmittance (light-transmitting yellow ink, a second yellow ink described later) is applied to the star-marked region. At this stage, only a pale yellow star is printed on the transparent medium S.

  As shown in FIG. 1B, the label L printed as shown in FIG. 1A is used in close contact with (for example, wound around) an object having a metallic gloss surface (here, a metal can). The metallic gloss surface of an aluminum can or a steel can is silver, and when the label L is wound around such a silver metallic gloss surface, the star mark to which the light-transmitting yellow ink is applied appears gold.

  In addition, since a white background image is formed around the golden image, the contrast is clear inside and outside the golden image, and the golden image is easily visible.

  In this way, in this embodiment, it is possible to express gold without using the glitter ink.

=== This Embodiment ===
<Outline of printing device>
FIG. 2 is a schematic side view of the printing apparatus 1. FIG. 3 is a block diagram of the printing apparatus 1.

  The printing apparatus 1 includes a transport unit 10, a head unit 40, a detector group 50, a controller 60, a drive signal generation circuit 70, a temporary curing unit 80, and a main curing unit 90.

  The transport unit 10 has a function of transporting a medium. In the following description, the direction in which the medium is transported is referred to as the transport direction. The transport unit 10 includes a drum 11, a first roller 12, a second roller 12, and a third roller 13. The medium is supplied from a supply unit (not shown) on the upstream side of the transport unit 10 and taken up by a take-up roller (not shown) on the downstream side of the transport unit 10. The medium is stretched with a predetermined tension between the first roller 12 and the third roller 14, and is in close contact with the surface of the drum 11. Then, when the drum 11 rotates, the medium is conveyed. The medium may be paper, but it may be the transparent medium S as described above.

  The head unit 40 includes, in order from the upstream side in the transport direction, a first white head unit 41W, a magenta head unit 41M, a cyan head unit 41C, a black head unit 41K, a first yellow head unit 41Y, a second yellow head unit 42Y, and a second. It has a white head unit 42W. The head unit of each color ejects the ink of each color, whereby an image is printed on the medium. Each color head unit is provided along the surface of the drum 11. Each color head unit ejects UV ink. The UV ink is an ink having a property of curing when irradiated with ultraviolet light.

  A color image by the subtractive color method is printed by the magenta ink ejected by the magenta head unit 41M, the cyan ink ejected by the cyan head unit 41C, and the first yellow ink ejected by the first yellow head unit 41Y. Further, for printing a color image, black ink discharged from the black head unit 41K is also used. In the following description, magenta ink, cyan ink, first yellow ink, and black ink may be referred to as color ink.

  By the way, magenta ink has a property that a color material for absorbing a predetermined wavelength and causing magenta to develop color is not easily broken by ultraviolet light. For this reason, in the present embodiment, the magenta head unit 41M is arranged on the upstream side in the transport direction from the head unit that discharges other color inks. When the magenta head unit that is the three primary colors of the subtractive color method is arranged on the most upstream side, normally, the remaining two primary color head units (cyan head unit 41C and yellow head unit 41Y) are arranged next. Finally, a black head unit 41K that is not the three primary colors is arranged. However, in this embodiment, although the magenta head unit 41M is arranged on the most upstream side, the yellow head unit 41Y is arranged on the downstream side in the transport direction from the black head unit 41K. The reason for this will be described later.

  The first white head unit 41W and the second white head unit 42W discharge white white ink. White ink is a background color ink used when forming a color image on a transparent medium. When a color image is formed alone on a transparent medium, the visibility of the color image is not good. Therefore, by forming a background image with white ink together with the color image, the light shielding property (shielding property) of the color image is improved. The visibility of the image is improved. For this reason, the white ink has a lower light transmittance than the color ink and has a high light shielding property. The average particle size of the white ink pigment is, for example, 300 nm to 400 nm, which is larger than the average particle size (about 200 nm) of the color ink pigment.

  Note that the first white head unit 41W is used in surface printing that forms a background image before (under a color image) a color image (described later). The second white head unit 42W is used in reverse printing that forms a background image after (on a color image) a color image (described later).

  The second yellow head unit 42Y discharges the second yellow ink. The second yellow ink is an ink having a higher light transmittance than the first yellow ink. The color ink (first yellow ink, cyan ink, and magenta ink) used for printing a color image may print a color image on a transparent medium. The second yellow ink is an ink having a high light transmittance because it is used for other purposes. The average particle size of the pigment of the second yellow ink is smaller (100 nm or less) than the average particle size (about 200 nm) of the pigment of the first yellow ink in order to increase the light transmittance.

  The detector group 50 represents various detectors that detect information of each unit of the printing apparatus 1. For example, the detector group 50 includes an encoder (not shown) that detects the rotation angle of the drum. The detector group 50 transmits a detection signal to the controller 60.

  The controller 60 is a control unit for controlling the printing apparatus 1. The controller 60 includes a CPU 61, a memory 62, and an interface unit 63. The CPU 61 is an arithmetic processing device for performing overall control of the printing apparatus 1. The memory 62 is a storage unit for securing a work area for the CPU 61, an area for storing a program, and the like. The CPU 61 controls each unit according to a program stored in the memory 62. The interface unit 63 transmits and receives data between the computer 110 that is an external device and the printing apparatus 1.

  The drive signal generation circuit 70 is a circuit that generates a drive signal for driving a drive element such as a piezo element included in the head unit 40. When the drive signal is applied to the drive element, the drive element is driven and ink droplets are ejected from the nozzles.

  The temporary curing unit 80 irradiates the UV light with such an intensity that the surface of the UV ink is cured (temporarily cured) so that the UV inks that have landed on the medium do not spread. The temporary curing unit 80 includes, in order from the upstream side in the transport direction, a first white light source 81W, a magenta light source 81M, a cyan light source 81C, a black light source 81K, a first yellow light source 81Y, a second yellow light source 82Y, and a first yellow light source 82Y. It has a 2 white light source 82W. A light source for each color for provisional curing is provided along the surface of the drum 11. Each color light source is provided on the downstream side of the corresponding color head unit. As a result, immediately after the UV ink has landed on the medium and dots have been formed, ultraviolet light is irradiated from the light source for temporary curing, and the dot surface of the UV ink is temporarily cured. As a light source of each color of the temporary curing unit 80, an LED (light emitting diode) or the like is employed.

  The main curing unit 90 irradiates UV light having an intensity capable of main curing (completely solidifying) the UV ink on the medium. The main curing unit 90 includes a main curing light source 91 for irradiating ultraviolet light stronger than the temporary curing light source. The main curing light source 91 is provided below the drum 11. Further, the main curing light source 91 irradiates the medium with ultraviolet light during the period from when the medium S leaves the drum 11 until it reaches the third roller 13. For example, a metal halide lamp or the like is employed as the main curing light source 91. The main curing unit 90 also includes a reflecting mirror that reflects the ultraviolet light of the main curing light source 91 toward the medium, fins for exhaust heat, a fan, a duct, and the like.

<Configuration of head unit>
FIG. 4A is an explanatory diagram of a configuration of the black head unit 41K. Here, the black head unit 41K will be described, but the configurations of the head units of other colors are also the same.

  The black head unit 41 has six head assemblies 411. The six head assemblies 411 are arranged in a staggered pattern along the paper width direction. That is, the three head assemblies 411 on the upstream side in the transport direction and the three head assemblies 411 on the downstream side are alternately shifted in the paper width direction.

  FIG. 4B is an explanatory diagram of the configuration of the head assembly 411. The head assembly 411 has six heads 412. The six heads 412 are arranged in a staggered pattern along the paper width direction. That is, the three heads 412 on the upstream side in the transport direction and the three heads 412 on the downstream side are alternately shifted in the paper width direction.

  FIG. 4C is an explanatory diagram of nozzle arrangement in the head 412. The head 412 has 360 nozzles. The 360 nozzles are arranged in a line along the paper width direction to form a nozzle line. The 360 nozzles are arranged at intervals (nozzle pitch) of 1/360 inch.

  By configuring the black head unit 41K as described above, a large number of nozzles belonging to the black head unit 41K are arranged in the paper width direction substantially at intervals of 1/360 inch. As a result, the black head unit 41K can form dots on the medium at intervals of 1/360 inch (dot pitch). Instead of arranging the six head assemblies in a zigzag pattern, 36 heads 412 may be arranged in a zigzag pattern. In short, it is only necessary that a large number of nozzles are arranged in the paper width direction at a substantially predetermined nozzle pitch.

<Normal color image printing method>
When printing a color image on an opaque medium such as paper, the printing apparatus 1 prints a color image on the medium using the magenta head unit 41M, the cyan head unit 41C, the black head unit 41K, and the first yellow head unit 41Y. To do. First, the printing apparatus 1 transports the medium to the transport unit 10 and discharges magenta ink from the magenta head unit 41M while transporting the medium to form magenta dots on the medium, and the magenta light source 81M is formed on the magenta dots. Then, magenta dots are temporarily cured by irradiating with ultraviolet light. Thereafter, the printing apparatus 1 also forms dots on the medium for cyan, black, and yellow, as in the case of magenta, and irradiates ultraviolet light from a light source of each color for temporary curing to temporarily cure the dots. The temporarily cured color dots are irradiated with ultraviolet light from the main curing light source 91 of the main curing unit 90 to be main cured, and a color image composed of the color dots is printed on the medium.

  Normally, when printing a color image on an opaque medium, the first white head unit 41W and the second white head unit 42W are not used. However, white ink may be ejected from the first white head unit 41W or the second white head unit 42W onto the medium for the purpose of adjusting the color of the medium serving as the background of the color image. Note that the second yellow head unit 42Y is not used when printing a color image on an opaque medium.

  When printing a color image on a transparent medium, if the color image has a low light shielding property, the visibility of the color image is lowered. For this reason, in order to improve the light-shielding property of the color image, the background image is overlaid on the color image and printed. As a method for printing a background image together with a color image, there are surface printing and back printing.

  FIG. 5A is an explanatory diagram of an image (front printing image) formed by front printing. “Front-print printing” is printing for viewing a printed image from the printing surface side (front side) of a medium. Therefore, when a background image and a color image are formed by “front printing”, a color image is formed on the background image after the background image is formed on the medium.

  When performing surface printing, the printing apparatus 1 uses the first white head unit 41W to form a background image (white image) on the medium. That is, the printing apparatus 1 ejects white ink from the first white head unit 41W while transporting the medium, forms white dots on the medium, and irradiates the white dots with ultraviolet light from the first white light source 81W. Then, the white dots are temporarily cured to form a background image. Thereafter, a color image is formed on the background image after the temporary curing using the head unit on the downstream side in the transport direction from the first white head unit 41W. The main curing light source 91 irradiates the color image and the background image under the color image with ultraviolet light, and performs the main curing of the color image and the background image.

  FIG. 5B is an explanatory diagram of an image (back printing image) formed by back printing. “Back printing” is printing for viewing a printed image through a transparent medium (from the back side of the printing surface of the medium). For this reason, when forming a background image and a color image by “back printing”, a color image is formed on a medium, and then a background image is formed on the color image.

  When performing reverse printing, the printing apparatus 1 uses the second white head unit 42W to form a background image (white image) on the medium. That is, the printing apparatus 1 forms a color image using the head unit upstream of the second white head unit 42W in the conveyance direction while conveying the medium, and the second white head is formed on the color image after temporary curing. White ink is ejected from the unit 42W to form white dots on the color image, and the white dots are irradiated with ultraviolet light from the second white light source 82W to form a background image. To do. The main curing light source 91 irradiates the color image and the background image on the color image with ultraviolet light, and performs the main curing of the color image and the background image.

  In FIGS. 5A and 5B, the background image layer and the color image layer are clearly separated, but in reality, the layers are not necessarily separated clearly. For example, if there is a gap between white dots constituting the background image of the front-printed image of FIG. 5A, some of the color dots constituting the color image may be formed on the transparent medium S.

  The explanatory diagrams of FIGS. 5A and 5B also show the order of the printing steps. For example, in the case of FIG. 5A, it is shown that white ink for forming a background image is first applied on the transparent medium S, and then color ink for forming a color image is applied. become.

<Golden image printing method (1)>
FIG. 6A is an explanatory diagram of a method for printing the label L in FIG. 1A. FIG. 6B is an explanatory diagram showing a state in which the label L is brought into close contact with an object having a metallic gloss surface. Here, a case where a label L having a gold star at the center of a white background image is printed will be described.

  The label L of this embodiment is formed by back printing. In the present embodiment, it is assumed that the label L is brought into close contact with a metallic glossy object (see FIG. 1B). If the label L is formed by back printing, the printed surface of the transparent medium faces the metallic glossy surface. Therefore, after the label L is attached to the metallic glossy surface, the label L is protected by the transparent medium.

  The label L has a gold region where a gold image (light yellow image) is formed and a background region outside the gold region. In other words, the label L can be divided into a golden region and other regions.

  A second yellow ink (a yellow ink having a high light transmittance) is applied to the gold region. That is, the printing apparatus 1 discharges the second yellow ink from the second yellow head unit 42Y while transporting the medium to form second yellow dots in the gold region (forms a light yellow image), and the first The two yellow dots are irradiated with ultraviolet light from the second yellow light source 82Y to temporarily cure the second yellow dots, thereby forming a golden image (light yellow image). Since the second yellow ink has a lower light shielding property than the first yellow ink, at this stage, a light yellow image (light yellow image) is printed in the gold region rather than a gold image. The printing apparatus 1 prints a light yellow image according to the image data of the golden image.

  White ink ejected from the second white head unit 42W is applied to the background area. That is, the printing apparatus 1 discharges white ink from the second white head unit 42W to form white dots, and irradiates the white dots with ultraviolet light from the second white light source 82W to temporarily cure the white dots. To form a background image. Since the label L is formed by reverse printing, the second white head unit 42W is used instead of the first white head unit 41W.

  The printing apparatus 1 further conveys the medium on which the golden image (light yellow image) and the background image are formed, and irradiates the golden image (light yellow image) and the background image with ultraviolet light from the light source 91 for main curing, The golden image (light yellow image) and the background image are fully cured.

  White ink is not applied to the golden area. For this reason, the background area is an area excluding the golden area. Thus, when the label L is brought into close contact with the metallic glossy surface, the metallic glossy surface is positioned immediately below the golden image. When the label L is wound around an aluminum can or a steel can, the label L comes into close contact with the silver metallic glossy surface.

  Since the second yellow ink having a high light transmittance is applied to the gold region, the light from the outside is transmitted almost without being blocked, and is incident on the metallic glossy surface and reflected. However, since a light yellow image (light yellow image) is formed in the gold region, the predetermined wavelength is slightly absorbed in the gold region. As a result, when the label L is brought into close contact with the silver metallic glossy surface, the pale yellow image is visually recognized with a silver metallic gloss, and the golden region appears golden (see FIG. 6B).

  If the first yellow ink is applied to the gold region, the first yellow ink has a higher light shielding property than the second yellow ink, so that the color of the gold region is perceived as yellow rather than gold. For this reason, the printing apparatus 1 of the present embodiment has a yellow light transmittance higher than that of the yellow ink for printing a color image, separately from the head for ejecting yellow ink (first yellow ink) for printing a color image. A head for ejecting ink (second yellow ink) is prepared.

  It is also possible to print only a golden image on a transparent medium without providing a background area. However, in this case, since the contrast is small inside and outside the golden image, it is difficult to visually recognize the golden image. On the other hand, if a white background image is formed around the golden image as described above, the contrast is clear inside and outside the golden image, and the golden image is easily visible.

  It is also possible to form the label L by surface printing. However, when the label L (printed material) is brought into close contact with the object, the printed surface becomes the front side, so that the printed surface is not protected and easily damaged.

<Golden image printing method (2)>
FIG. 7A is an explanatory diagram of a label L having a color image. FIG. 7B is an explanatory diagram of a method for printing the label L in FIG. 7A.

  Even in a label L having a color image, it can be divided into a gold region where a gold image is formed and a region other than the gold region.

  As in the case described above, the second yellow ink (yellow ink having a high light transmittance) is applied to the gold region. Since the second yellow ink has a lower light shielding property than the first yellow ink, a light yellow image (light yellow image) is printed in the golden region at this stage. White ink is not applied to the golden region. In a region other than the gold region, a background image and a color image are formed according to reverse printing.

  The printing apparatus 1 forms a color image and forms a color image in the order of magenta, cyan, black, and first yellow while transporting the medium. Next, the printing apparatus 1 further conveys the medium, discharges the second yellow ink from the second yellow head unit 42Y, forms second yellow dots in the gold region (forms a light yellow image), and The second yellow dot is irradiated with ultraviolet light from the second yellow light source 82Y to temporarily cure the second yellow dot, thereby forming a golden image (light yellow image). Next, the printing apparatus 1 further conveys the medium, discharges white ink from the second white head unit 42W to an area other than the yellow area, and forms white dots on the color image. A white image is preliminarily cured by irradiating ultraviolet light from the 2-white light source 82W to form a background image. Finally, the printing apparatus 1 further conveys a medium on which a golden image (light yellow image), a color image, and a background image are formed, and irradiates ultraviolet light from the main curing light source 91 to obtain a golden image (light yellow image). The color image and the background image are fully cured.

  When the label L formed in this manner is brought into close contact with the metallic glossy surface, the metallic glossy surface is positioned immediately below the golden image. When the label L is wrapped around an aluminum can or a steel can, the label L comes into close contact with the silver metallic luster surface, and the light yellow image is visually recognized with a silver metallic luster, and the golden region becomes gold.

  A color image has a light-shielding property compared to a light yellow image, and is therefore hard to be visually recognized with a metallic luster. Further, since the background image is formed on the color image, even if the label L is wrapped around the silver metallic glossy surface and the color image is viewed through the medium, the external light is blocked by the background image. However, it has a metallic luster and is difficult to see. For this reason, even if the label L adheres to the silver metallic glossy surface, the color image is visually recognized in the same manner as in the case of normal back printing.

<Reason for arranging the yellow head unit downstream in the transport direction>
Ultraviolet light is more easily absorbed by yellow than cyan and magenta. For this reason, when the yellow ink (the first yellow ink and the second yellow ink) is irradiated with relatively weak ultraviolet light and temporarily cured, the ultraviolet light is absorbed on the surface of the yellow ink, and the ultraviolet rays reach the inside of the yellow ink. The light may not reach. In this case, only the surface is cured, and the inside becomes fluid. When the yellow ink in this state is irradiated with strong ultraviolet light and is fully cured, the internal yellow ink is cured and contracted, thereby causing wrinkles on the surface (an already cured surface).

When wrinkles occur on the surface of a bright color such as yellow, the light and dark due to the wrinkles are easily perceived, and the image quality deteriorates. In addition, when the gold color is expressed by the light-transmitting light yellow image as in the present embodiment, the deterioration of the golden image quality is particularly significant when the brightness and darkness due to the wrinkles are perceived. Therefore, it is desirable to avoid irradiating yellow ink (particularly the second yellow ink) with relatively weak ultraviolet light.
For this reason, in this embodiment, yellow ink (first yellow ink and second ink) is applied to the medium after the temporary curing of the color inks of other colors (cyan ink, magenta ink, and black ink) is finished. Yellow ink) is being discharged. In other words, in the present embodiment, the first yellow head unit 41Y and the second yellow head unit 42Y are transported more than the head unit that discharges the color inks of other colors and the light source for temporary curing corresponding to the head unit. It is arranged downstream. This avoids that the light source for temporary curing of other colors irradiates the yellow ink with relatively weak ultraviolet light.

  In particular, in the present embodiment, the second yellow ink is ejected onto the medium after each temporary curing of the color ink has been completed. That is, in the present embodiment, the second yellow head unit 42Y is disposed downstream in the transport direction from the head unit that discharges color ink and the temporary curing light source corresponding to the head unit. As a result, the generation of wrinkles in the light-transmitting light yellow image is suppressed, and high-quality gold can be expressed.

  Further, in the present embodiment, the first yellow light source 81Y and the second yellow light source 82Y are more than the light sources for temporary curing of other colors (magenta light source 81M, cyan light source 81C, black light source 81K). Large amount of ultraviolet light irradiation. This avoids that the yellow ink is irradiated with relatively weak ultraviolet light, so that the ultraviolet light reaches the inside of the yellow ink at the stage of temporary curing.

By the way, UV ink has a property of repelling ink when it is completely solidified. For this reason, the magenta light source 81M, the cyan light source 81C, and the black light source 81K irradiate with relatively weak ultraviolet light (UV light weaker than the main curing light source 91) that does not completely cure the UV ink. The color ink applied thereafter is prevented from being repelled, and the color image quality is prevented from deteriorating.
On the other hand, since the first yellow light source 81Y emits relatively strong ultraviolet light, the first yellow dots may have a property of repelling ink. However, since all the color dots are formed at this stage (the color image is completed) and the color ink is not applied after that, there is a risk that the color ink will be repelled and the image quality will deteriorate. Absent. In addition, since the second yellow ink is applied only to the gold region, it is not applied to the region where the first yellow dot is formed, so there is no possibility that the second yellow ink will be repelled. For this reason, the first yellow light source 82Y is allowed to emit relatively strong ultraviolet light.
Similarly, since the second yellow light source 82Y also emits relatively strong ultraviolet light, the second yellow dots may have a property of repelling ink. However, since the color ink and the white ink are not subsequently applied to the golden region to which the second yellow ink is applied, it is not a problem that the second yellow dot has the property of repelling ink. For this reason, the second yellow light source 82Y is allowed to emit relatively strong ultraviolet light.

  The second yellow head unit 42Y may be provided on the downstream side in the transport direction from the second white head unit 42W and the second white light source 82W. Since the white ink is not applied to the area where the second yellow ink is applied, such an arrangement is also possible. In this case, the second yellow ink may be fully cured without being temporarily cured without providing the second yellow light source. Thereby, wrinkles can be prevented from occurring in the light-transmissive light yellow image.

=== Others ===
The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

<About printing devices>
In the above-described embodiment, the printing apparatus forms an image using UV ink. However, as long as an image can be formed on a transparent medium, the ink may not be UV ink. In this case, the temporary curing unit 80 and the main curing unit 90 of the above-described embodiment are not necessary. However, since a transparent medium such as a film hardly absorbs ink, it is desirable to use UV ink that can form an image by curing dots on the printing surface.

<About white ink>
The white ink described above is obtained by measuring the lightness (L *) and chromaticity (a *, b *) of white ink ejected on Epson genuine photographic paper <Glossy> (manufactured by Seiko Epson Corporation) at a duty of 100% or more. When measuring with the photometer Spectrolino (trade name: manufactured by GretagMacbeth) set as the measurement condition D50 light source, observation field 2 °, density DIN_NB, white reference Abs, filter No, measurement mode Reference In addition, the ink indicates a range of 70 ≦ L * ≦ 100, −4.5 ≦ a * ≦ 2, −6 ≦ b * ≦ 2.5.

  The aforementioned white ink contains a white pigment. Examples of the white pigment include metal oxide, barium sulfate, calcium carbonate, and the like. Examples of the metal oxide include titanium dioxide, zinc oxide, silica, alumina, magnesium oxide and the like. Among these, titanium dioxide is preferable from the viewpoint of excellent whiteness.

<About average particle size>
In this specification, the average particle diameter means a cumulative 50% particle diameter based on volume, and is measured by a light scattering method. The average particle diameter can be measured using, for example, Microtrac UPA150 (Microtrac Inc.).

<Silver glossy surface>
In the above-described embodiment, the label L is brought into close contact with a metal can having a silver metallic glossy surface. However, the object having a silver glossy surface is not limited to a metal, and may be another object.

1 printing device,
10 transport units, 11 drums,
12 1st roller, 13 2nd roller, 14 3rd roller,
40 head units,
41W 1st white head unit,
41M magenta head unit,
41C cyan head unit,
41K black head unit,
41Y 1st yellow head unit,
42Y second yellow head unit,
42W second white head unit,
50 detector groups, 60 controllers,
61 CPU, 62 memory, 63 interface part,
70 drive signal generation circuit,
80 temporary curing unit,
81W light source for first white,
81M light source for magenta,
81C light source for cyan,
81K light source for black,
81Y 1st yellow light source,
82Y light source for second yellow,
82W light source for second white,
90 curing units, 91 curing light sources,
S medium (transparent medium),
L label

Claims (7)

Using a printing apparatus comprising a first head for ejecting a first yellow ink for forming a color image and a second head for ejecting a second yellow ink having a light transmittance higher than that of the first yellow ink, Applying the second yellow ink to a transparent medium to form a light yellow image with light transmission;
A step of closely attaching the transparent medium on which the pale yellow image is formed to a silver glossy surface;
A golden expression method characterized by comprising: The gold color expression method according to claim 1,
Applying the background color ink around the light yellow image without applying a background color ink to the region where the light yellow image is formed, forming a background image around the light yellow image. Characteristic golden expression method. The golden expression method according to claim 1 or 2,
A gold color expression method, wherein the transparent medium is brought into close contact with the silver glossy surface so that a printing surface of the transparent medium is on the silver glossy surface side. It is the gold color expression method in any one of Claims 1-3,
The gold color expression method, wherein an average particle diameter of the pigment of the second yellow ink is smaller than an average particle diameter of the pigment of the first yellow ink. A first head that ejects a first yellow ink for forming a color image;
A second head that ejects a second yellow ink having a higher light transmittance than the first yellow ink;
A printing apparatus, wherein the second yellow ink is applied to a transparent medium to form a light yellow light-transmissive image. The printing apparatus according to claim 5,
A background color head for discharging a background color ink for forming a background image;
A printing apparatus that forms the background image by applying the background color ink around the light yellow image without applying the background color ink to a region where the light yellow image is formed. . The printing apparatus according to claim 5 or 6,
A printing apparatus that forms the color image on the transparent medium and forms the background image on the color image.

Images