JP5910135B2 - Printing apparatus and printing method - Google Patents

Description

  The present invention relates to a printing apparatus and a printing method.

  2. Related Art Inkjet printing apparatuses that print on a medium by discharging ink are known. Among such printing apparatuses, there is a printing apparatus that discharges ink (UV ink) that is cured by irradiation with light (for example, ultraviolet light (UV) or visible light). In this type of printing apparatus, UV ink is ejected from a nozzle onto a medium, and then light is irradiated to dots formed on the medium. As a result, the dots are cured and fixed on the medium (see, for example, Patent Document 1). For this reason, it is possible to form dots even on a medium that does not absorb ink (for example, a film).

JP 2008-265285 A

  In a printing apparatus that discharges UV ink, the UV ink may be irradiated with ultraviolet light in two stages. In the first stage, the UV ink on the medium is irradiated with ultraviolet light to control the wetting and spreading of the UV ink, or to further suppress bleeding with the UV ink discharged to the medium thereafter. In the second stage, the UV ink is completely cured by irradiating with ultraviolet light stronger than in the first stage. The first stage is sometimes called “temporary curing” or “pinning”, and the second stage is sometimes called “main curing”.

  Yellow UV ink absorbs ultraviolet light more easily than cyan or magenta UV ink. For this reason, at the time of temporary curing by irradiating relatively weak ultraviolet light, the ultraviolet light may be absorbed on the surface of the yellow ink, and the ultraviolet light may not reach the inside of the yellow ink. 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).

  An object of the present invention is to suppress the occurrence of wrinkles in yellow ink.

The main invention for achieving the above object, a first head to form a transport unit for transporting the medium in the conveying direction, ejecting magenta ink which is cured by irradiation with light, a magenta dot on the medium, the A first light source that is provided downstream of the first head in the transport direction and irradiates the magenta dots with the light, and discharges cyan ink that cures when irradiated with light, thereby forming cyan dots on the medium. A second head that is disposed downstream of the second head in the transport direction with respect to the second head, and discharges black ink that is cured when irradiated with light, a second light source that irradiates the cyan dots with the light, a third head for forming a black dot on the medium, provided downstream of the transport direction than the third head, and a third light source for emitting the light to the black dot, the second Discharge head, wherein the first light source, the second head, the second light source provided on the downstream side in the transport direction than the third head and the third light source, a yellow ink which is cured by irradiation with light And a fourth head for forming yellow dots on the medium, and the light emitted from the first light source, the second light source, and the third light source provided downstream of the fourth head in the transport direction. A fourth light source that emits stronger light, and a clear dot or a background color ink that is provided downstream of the fourth light source in the transport direction and that cures when irradiated with light. Alternatively, a fifth head that forms a background color dot and a lighter light than the fifth head, which is provided downstream of the fifth head in the transport direction, is stronger than the light emitted by the first light source, the second light source, and the third light source. Light That a fifth light source, wherein the first light source, the second light source and the third light source irradiates each of the magenta dots, the ultraviolet light intensity the cyan dots and the black dots are temporarily cured, the the fourth light source, the yellow dots irradiated with ultraviolet light with an intensity of the curing, the fifth light source, the clear dots or the background color dot is a printing device that be irradiated with ultraviolet light with an intensity of the curing .
Another main invention for achieving the above object is a transport unit that transports a medium in the transport direction, and a magenta head that ejects magenta ink that cures when irradiated with light and forms magenta dots on the medium. A magenta light source for irradiating the magenta dots with the light, a cyan head for discharging cyan ink which is cured when irradiated with light, and forming cyan dots on the medium; and irradiating the cyan dots with the light A cyan light source, a black head that discharges a black ink that is cured when irradiated with light and forms black dots on the medium, a black light source that irradiates the black dots with the light, and the magenta head, More than the light source for magenta, the cyan head, the light source for cyan, the black head, and the light source for black Provided on the downstream side in the feeding direction, ejecting yellow ink that is cured when irradiated with light, and forming a yellow dot on the medium, and provided on the downstream side in the transport direction from the yellow head, A yellow light source that emits light that is stronger than the light emitted by the magenta light source, the cyan light source, and the black light source, and a second yellow ink that has a higher light transmittance than the yellow ink. 2 yellow heads and provided downstream of the second yellow head in the transport direction, and emits light stronger than the light emitted from the magenta light source, the cyan light source, and the black light source. A second yellow light source, and applying the second yellow ink to a transparent medium to form a light yellow light-transmissive image. A printing apparatus for the.

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

FIG. 1 is a schematic side view of a printing apparatus 1 according to the first embodiment. FIG. 2 is a block diagram of the printing apparatus 1. FIG. 3A is an explanatory diagram of a configuration of the black head unit 41K. FIG. 3B is an explanatory diagram of the configuration of the head assembly 411. FIG. 3C is an explanatory diagram of nozzle arrangement in the head 412. FIG. 4 is an explanatory diagram of the printing apparatus 1 of the comparative example. FIG. 5 is a schematic side view of the printing apparatus 1 according to the second embodiment. FIG. 6 is a schematic side view of the printing apparatus 1 according to the third embodiment. FIG. 7A is an explanatory diagram of an image (front printing image) formed by front printing. FIG. 7B is an explanatory diagram of an image (back printing image) formed by back printing. FIG. 8 is a schematic side view of the printing apparatus 1 according to the fourth embodiment. 9A and 9B are explanatory diagrams of the label L printing method. FIG. 9C is an explanatory diagram of the principle of gold expression.

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

A transport unit that transports the medium in the transport direction; a magenta head that discharges magenta ink that is cured when irradiated with light to form magenta dots on the medium; and a magenta light source that irradiates the magenta dots with the light. A cyan head that discharges cyan ink that is cured when irradiated with light and forms cyan dots on the medium; a cyan light source that irradiates the cyan dots with light; and a black that cures when irradiated with light. A black head for ejecting ink to form black dots on the medium; a black light source for irradiating the black dots with the light; the magenta head; the magenta light source; the cyan head; the cyan light source; It is provided downstream of the black head and the black light source in the transport direction, and is cured when irradiated with light. A yellow head that discharges yellow ink and forms yellow dots on the medium; and an irradiation of the magenta light source, the cyan light source, and the black light source provided downstream of the yellow head in the transport direction. And a yellow light source that emits light stronger than the light.
According to such a printing apparatus, the occurrence of wrinkles of yellow ink can be suppressed.

  It is desirable that the magenta head or the cyan head is disposed upstream of the black head in the transport direction. Even in such a case, since the yellow head is provided on the downstream side in the transport direction with respect to the head that discharges the other color ink, the occurrence of wrinkles of the yellow ink can be suppressed.

  The yellow light source is preferably a main curing light source. Thereby, since the yellow ink is fully cured without being temporarily cured, the ultraviolet rays reach the inside of the yellow dots, and the generation of wrinkles of the yellow dots can be suppressed.

  It further includes a clear head that discharges clear ink that is cured when irradiated with light, and the clear head is provided downstream of the yellow light source in the transport direction. Can be prevented from bleeding.

  It is preferable that a background head that discharges background ink that is cured when irradiated with light is further provided, and the background head is provided downstream of the yellow light source in the transport direction. Thereby, it is possible to suppress bleeding of the yellow ink and the background ink.

  A second yellow head that discharges yellow ink having a light transmittance higher than that of the yellow ink; and provided downstream of the second yellow head in the transport direction, the magenta light source, the cyan light source, A second yellow light source that emits light stronger than the light emitted by the black light source, and applying the second yellow ink to a transparent medium to form a light-transparent light yellow image. It is desirable to form. Thereby, if a printed matter is attached to a silver glossy surface, gold can be expressed.

A process of ejecting magenta ink that cures when irradiated with light while transporting the medium in the transport direction to form magenta dots on the medium, a process of irradiating the magenta dots with the light, and a light irradiation Then, a cyan ink to be cured is ejected to form cyan dots on the medium, a process to irradiate the cyan dots with the light, and a black ink to be cured when irradiated with light is ejected to the medium. A step of forming a black dot, a step of irradiating the light to the black dot, and a region where the magenta dot, the cyan dot and the black dot irradiated with the light are irradiated with light Discharging yellow ink to be cured and forming yellow dots on the medium; and after forming the yellow dots, the magenta dots Printing method for a step of irradiating the intense light than the light irradiated to the cyan dots and the black dots becomes apparent.
According to such a printing method, the occurrence of wrinkles of yellow ink can be suppressed.

=== First Embodiment ===
<Outline of printing device>
FIG. 1 is a schematic side view of a printing apparatus 1 according to the first embodiment. FIG. 2 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 a transparent medium S.

  The head unit 40 includes a magenta head unit 41M, a cyan head unit 41C, a black head unit 41K, and a yellow head unit 41Y in order from the upstream side in the transport direction. A color image is printed by the subtractive color method using the magenta ink ejected by the magenta head unit 41M, the cyan ink ejected by the cyan head unit 41C, and the yellow ink ejected by the 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, yellow ink, and black ink may be referred to as color ink.

  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.

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 will become clear from the description of the comparative example described later.

  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 a magenta light source 81M, a cyan light source 81C, and a black light source 81K in order from the upstream side in the transport direction. However, a yellow light source for temporary curing is not provided.

  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 light source for temporary curing irradiates relatively weak ultraviolet light (ultraviolet light weaker than the main curing light source 91) that does not completely cure the UV ink. This is because the UV ink has a property of repelling ink when completely solidified, and if the color ink is repelled, the image quality of the color image may be deteriorated.

  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. 3A 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. 3B 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. 3C 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.

<Printing method>
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 dots are irradiated with ultraviolet rays from the magenta light source 81M. Light is irradiated to temporarily cure the magenta dots.

  When the printing apparatus 1 continues to convey the medium, the portion where the magenta dots are formed (the region where the magenta image is formed) reaches the cyan head unit 41C. The printing apparatus 1 forms cyan dots on the medium by ejecting cyan ink from the cyan head unit 41C while conveying the medium. Since the magenta dots are already temporarily cured, the magenta dots and the cyan dots do not blur. The printing apparatus 1 irradiates ultraviolet light from the cyan light source 81C to temporarily cure the cyan dots.

  When the printing apparatus 1 further continues to convey the medium, a portion where magenta dots and cyan dots are formed (a region where a magenta image and a cyan image are formed) reaches the black head unit 41K. The printing apparatus 1 discharges black ink from the black head unit 41K while transporting the medium to form black dots on the medium. Since the magenta dots and the cyan dots are already temporarily cured, the black dots do not blur with other dots. The printing apparatus 1 irradiates ultraviolet light from the black light source 81K to temporarily cure the black dots.

  In the present embodiment, before yellow dots are formed, color dots of other colors (magenta, cyan, black) are formed, and these dots are temporarily cured. To this end, in the present embodiment, the yellow head unit 41Y is disposed downstream of the head unit that discharges color inks of other colors and the light source for temporary curing corresponding to the head unit in the transport direction. It has been done. This avoids that the light source for temporary curing of other colors irradiates the yellow ink with relatively weak ultraviolet light.

  When the printing apparatus 1 continues to convey the medium, a portion where magenta dots, cyan dots, and black dots are formed (a region where a magenta image, a cyan image, and a black image are formed) reaches the yellow head unit 41Y. The printing apparatus 1 forms yellow dots on the medium by ejecting yellow ink from the yellow head unit 41Y while transporting the medium. Since the color dots of the other colors are already temporarily cured, the yellow dots do not blur with the other dots.

  In the present embodiment, a yellow light source for temporary curing is not provided. For this reason, yellow dots are not temporarily cured. However, since the color dots of other colors are not formed after the yellow dots are formed, the yellow dots do not spread with other dots.

  Since the yellow dots are not irradiated with pre-cured ultraviolet rays (ultraviolet rays that are weaker than the main-cured ultraviolet rays), the occurrence of wrinkles on the surface of the yellow dots can be suppressed. If wrinkles occur on the surface of a bright color such as yellow, light and dark due to the wrinkles are easily perceived and image quality deteriorates. In the present embodiment, the occurrence of wrinkles of yellow dots can be suppressed, so that the image quality is improved.

  When the printing apparatus 1 further continues to convey the medium, the portion where the color dots are formed (the region where the color image is formed) is irradiated with ultraviolet light from the main curing light source 91 of the main curing unit 90 and is finally cured. A color image composed of color dots is printed on the medium. The yellow dots that are not temporarily cured are cured by the ultraviolet light from the main curing light source 91. For this reason, the main curing light source 91 of the first embodiment functions as a yellow light source.

  In this embodiment, the yellow dots are not temporarily cured. However, since the yellow dots are completely cured immediately after the yellow dots are formed, the yellow dots do not spread out. Further, since the main curing light source 91 irradiates ultraviolet light stronger than the temporary curing light source, the ultraviolet light reaches the inside of the yellow dots during the main curing. For this reason, wrinkles do not occur in yellow dots.

<Contrast with comparative example>
FIG. 4 is an explanatory diagram of the printing apparatus 1 of the comparative example. The comparative example differs from the first embodiment in that the yellow head unit 41Y is provided upstream of the black head unit 41K in the transport direction, and a yellow light source 81Y for temporarily curing yellow dots is provided. .

  Also in the comparative example, the magenta head unit 41M is arranged on the upstream side in the transport direction with respect to the other color head units. When the magenta (or cyan) head unit which is the three primary colors of the subtractive color method is arranged on the most upstream side, the remaining two primary color head units (the cyan head unit 41C and the yellow head unit) are then used as in the comparative example. 41Y), and finally, a black head unit 41K that is not the three primary colors is considered.

  However, with this arrangement, black ink is ejected after the yellow head unit 41Y forms yellow dots. In order to prevent the yellow dots from bleeding with the black dots, it is necessary to provide a yellow light source 81Y for temporarily curing the yellow dots.

  The yellow light source 81Y for pre-curing irradiates ultraviolet light to the extent that yellow dots are not completely cured. This is because if the yellow light source 81Y irradiates ultraviolet light strong enough to completely cure the yellow dots, the black ink applied thereafter is repelled and the quality of the color image is degraded.

  However, when the yellow dots are irradiated with relatively weak ultraviolet light and temporarily cured, the ultraviolet light is absorbed on the surface of the yellow dots, and the ultraviolet light does not reach the inside of the yellow dots. In this case, only the surface of the yellow dot is cured, and the inside has a fluid state. When the main curing light source 91 radiates strong ultraviolet light to the yellow dots in this state and performs the main curing, the yellow ink inside the yellow dots is cured and contracted, so that the surface (the surface already cured) is obtained. I'm going to have it.

  When wrinkles occur on the surface of a bright color such as yellow, light and dark due to the wrinkles are easily visible. For this reason, in the configuration of the printing apparatus 1 as in the comparative example (particularly, the arrangement of the yellow head unit 41Y), the image quality is degraded.

  On the other hand, according to the printing apparatus 1 of the first embodiment shown in FIG. 1, the yellow head unit 41 </ b> Y ejects a color ink of another color, or a temporary curing light source corresponding to the head unit. It is arrange | positioned rather than the conveyance direction downstream. Thereby, since the yellow dots are not irradiated with the pre-curing ultraviolet rays (the weak ultraviolet rays compared with the main curing ultraviolet rays), it is possible to suppress the generation of wrinkles on the surface of the yellow dots. As a result, the image quality is improved.

=== Second Embodiment ===
FIG. 5 is a schematic side view of the printing apparatus 1 according to the second embodiment. The second embodiment is different from the first embodiment in that a yellow light source 81Y and a clear ink head 41CL are provided.

  The clear ink head 41CL discharges clear ink. The clear ink is a colorless and transparent ink that is applied to the surface of the color image in order to adjust the glossiness of the color image or to form a protective film on the surface of the color image. Note that the clear ink is colorless and transparent, and thus is different from the color ink used for printing a color image. The clear ink of this embodiment is also composed of UV ink that cures when irradiated with ultraviolet light. A light source for temporarily curing the clear ink may be provided on the downstream side in the transport direction of the clear ink head 41CL.

  Since the clear ink is an ink applied on the color image, the clear ink head unit 41CL is provided on the downstream side in the transport direction from the head unit that discharges the color ink. For this reason, the clear ink head unit 41CL is provided on the downstream side in the transport direction from the yellow head unit 41Y.

  A yellow light source 81Y is provided on the downstream side in the transport direction of the yellow head unit 41Y. The yellow light source 81Y irradiates the yellow dots with ultraviolet light, thereby curing the yellow dots and preventing the clear ink and yellow dots applied thereafter from spreading.

  The yellow light source 81Y of the second embodiment irradiates with a temporary curing light source (magenta light source 81M, cyan light source 81C, black light source 81K) of another color so that the ultraviolet light reaches the inside of the yellow dots. Irradiate ultraviolet light stronger than ultraviolet light. Thereby, generation | occurrence | production of the wrinkle of a yellow dot can be suppressed.

  Since the yellow light source 81Y emits relatively strong ultraviolet light, the 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. The clear ink that is applied after the yellow dots are cured is a colorless and transparent ink, and is an ink that is uniformly applied to cover the surface of the color image. The impact on is small. For this reason, the yellow light source 81Y is allowed to emit relatively strong ultraviolet light.

  Also in the printing apparatus 1 of the second embodiment, the yellow head unit 41Y is disposed downstream in the transport direction from the head unit that discharges color inks of other colors and the temporary curing light source corresponding to the head unit. ing. Thereby, since the yellow dots are not irradiated with the pre-curing ultraviolet rays (the weak ultraviolet rays compared with the main curing ultraviolet rays), it is possible to suppress the generation of wrinkles on the surface of the yellow dots.

=== Third Embodiment ===
FIG. 6 is a schematic side view of the printing apparatus 1 according to the third embodiment. The third embodiment is different from the first embodiment in that a yellow light source 81Y, a first white ink head 41W, and a second white ink head 42W are provided.

  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.

  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.

  As a method of printing a background image together with a color image, there are surface printing and back printing described below.

  FIG. 7A 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. 7B 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. 7A and 7B, the background image layer and the color image layer are clearly separated, but in reality, the layers are not necessarily clearly separated. For example, if there is a gap between white dots constituting the background image of the front print image of FIG. 7A, some of the color dots constituting the color image may be formed on the transparent medium S.

  When reverse printing is performed, white dots are formed after yellow dots are formed on the medium. At this time, a yellow light source 81Y is provided in order to prevent bleeding of yellow dots and white dots. The yellow light source 81Y is provided on the downstream side in the transport direction of the yellow head unit 41Y.

  Similarly to the second embodiment, the yellow light source 81Y of the third embodiment also has other colors of temporary curing light sources (magenta light source 81M, cyan light source 81C, so that ultraviolet light can reach the inside of the yellow dots. Irradiate ultraviolet light stronger than the ultraviolet light irradiated by the black light source 81K). Thereby, generation | occurrence | production of the wrinkle of a yellow dot can be suppressed.

  Since the yellow light source 81Y emits relatively strong ultraviolet light, the 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. The white ink discharged from the second white head unit 42W after the yellow dots are cured is an ink that is uniformly applied so as to cover the surface of the color image in order to improve the light-shielding property of the color image. The impact on the quality of the color image is small even if it is played. For this reason, the yellow light source 81Y is allowed to emit relatively strong ultraviolet light.

  Also in the printing apparatus 1 of the third embodiment, the yellow head unit 41Y is disposed downstream in the transport direction from the head unit that discharges the color inks of other colors and the temporary curing light source corresponding to the head unit. ing. Thereby, since the yellow dots are not irradiated with the pre-curing ultraviolet rays (the weak ultraviolet rays compared with the main curing ultraviolet rays), it is possible to suppress the generation of wrinkles on the surface of the yellow dots.

=== Fourth Embodiment ===
FIG. 8 is a schematic side view of the printing apparatus 1 according to the fourth embodiment. In the fourth embodiment, the second yellow head unit 42Y that discharges yellow ink (hereinafter referred to as second yellow ink) having a higher light transmittance than the above-described yellow ink (hereinafter referred to as first yellow ink), and the second yellow ink The third embodiment is different from the third embodiment in that a light source 82Y is provided.

  In the description of the fourth embodiment, the yellow head unit 41Y described above is referred to as a “first yellow head unit 41Y” in order to distinguish it from the second yellow head unit 42Y. Similarly, the yellow light source 81Y is referred to as a “first yellow light source 81Y”.

  The second yellow ink ejected by the second yellow head unit 42Y 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.

  In the fourth embodiment, a golden image can be expressed by attaching a transparent medium on which a light yellow image is formed with the second yellow ink to a metallic glossy surface. Thereby, the printing apparatus 1 of 4th Embodiment can express gold | metal | money, without using expensive glittering ink. Hereinafter, this point will be described.

  9A and 9B are explanatory diagrams of the label L printing method. Here, a case where a label L having a color and a gold star in a white background image is printed will be described.

  The label L can be divided into a golden region where a golden image (light yellow image) is formed and another region. A second yellow ink (a 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 and color ink (first yellow ink, cyan ink, and magenta ink) are 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). 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, forms white dots on the color image, and uses the second white for the white dots. A white image is temporarily cured by irradiating ultraviolet light from the 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.

FIG. 9C is an explanatory diagram of the principle of gold expression.
When the label L is brought into close contact with the metallic glossy surface, the metallic glossy surface is positioned immediately below the light yellow 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.

  In the fourth embodiment, the first yellow light source 81Y and the second yellow light source 82Y are more ultraviolet than the light sources for temporary curing of other colors (magenta light source 81M, cyan light source 81C, and black light source 81K). The amount of light irradiation is large. 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.

  Since the first yellow light source 81Y emits relatively strong ultraviolet light, the first yellow dots may have the 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.

  Since the second yellow light source 82Y emits relatively strong ultraviolet light, the second yellow dots may have the 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.

  Also in the printing apparatus 1 of the fourth embodiment, the first yellow head unit 41Y is located downstream in the transport direction from the head unit that discharges the color inks of other colors and the temporary curing light source corresponding to the head unit. Has been placed. As a result, the first yellow dots are not irradiated with pre-cured ultraviolet light (weak ultraviolet light as compared with the main-cured ultraviolet light), and thus the generation of wrinkles on the surface of the first yellow dots can be suppressed.

  Further, in the printing apparatus 1 of the fourth embodiment, the second yellow head unit 41Y is arranged on the downstream side in the transport direction from the head unit that discharges the color ink and the temporary curing light source corresponding to the head unit. Yes. As a result, the second yellow dot is not irradiated with pre-cured ultraviolet light (weak ultraviolet light compared to the main-cured ultraviolet light), so that the light-transparent light yellow image is suppressed from wrinkling and a high-quality gold color is expressed. It is possible.

=== 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.

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

Claims (5)

A transport unit for transporting the medium in the transport direction;
A first head that ejects magenta ink that is cured when irradiated with light and forms magenta dots on the medium;
A first light source provided downstream of the first head in the transport direction and irradiating the light to the magenta dots;
A second head that discharges cyan ink that is cured when irradiated with light and forms cyan dots on the medium;
A second light source provided downstream of the second head in the transport direction and irradiating the cyan dots with the light;
A third head that discharges black ink that is cured when irradiated with light and forms black dots on the medium;
A third light source provided downstream of the third head in the transport direction and irradiating the black dots with the light;
Yellow, which is provided downstream of the first head, the first light source, the second head, the second light source, the third head, and the third light source in the transport direction and cures when irradiated with light. A fourth head that ejects ink and forms yellow dots on the medium;
Wherein provided on the fourth downstream side of the transport direction of the head, and a fourth light source for irradiating the first light source, stronger light than the light irradiation of the second light source and the third light source,
A fifth head that is provided downstream of the fourth light source in the transport direction and discharges clear ink or background color ink that is cured when irradiated with light to form clear dots or background color dots on the medium;
A fifth light source that is provided downstream of the fifth head in the transport direction and that emits light stronger than the light emitted by the first light source, the second light source, and the third light source;
Equipped with a,
The first light source, the second light source, and the third light source irradiate ultraviolet light having an intensity at which the magenta dots, the cyan dots, and the black dots are temporarily cured, respectively.
The fourth light source irradiates ultraviolet light having an intensity at which the yellow dots are fully cured,
The fifth light source, the printing apparatus the clear dots or the background color dots you irradiated with ultraviolet light with an intensity of the curing. The printing apparatus according to claim 1,
The printing apparatus , wherein the yellow ink ejected from the fourth head is first irradiated with the light by the fourth light source . The printing apparatus according to claim 1 or 2,
The printing apparatus, wherein the first head or the second head is disposed upstream of the third head in the transport direction. A transport unit for transporting the medium in the transport direction;
A magenta head that ejects magenta ink that is cured when irradiated with light, and forms magenta dots on the medium;
A light source for magenta that irradiates the magenta dots with the light;
A cyan head that discharges a cyan ink that is cured when irradiated with light and forms cyan dots on the medium;
A cyan light source for irradiating the cyan dots with the light;
A black head that discharges a black ink that is cured when irradiated with light and forms black dots on the medium;
A light source for black that irradiates the light to the black dots;
Ejects yellow ink that is provided downstream of the magenta head, the magenta light source, the cyan head, the cyan light source, the black head, and the black light source in the transport direction and cures when irradiated with light. A yellow head for forming yellow dots on the medium;
A yellow light source that is provided downstream of the yellow head in the transport direction and that emits light stronger than the light emitted by the magenta light source, the cyan light source, and the black light source;
A second yellow head for ejecting a second yellow ink having a higher light transmittance than the yellow ink;
A second yellow light source that is provided downstream of the second yellow head in the transport direction and emits light stronger than the light emitted from the magenta light source, the cyan light source, and the black light source. When,
Bei to give a,
The second yellow ink was applied to the transparent medium, the printing apparatus, and forming a pale yellow images with optical transparency. While transporting the medium in the transport direction,
A first dot forming step of ejecting magenta ink that is cured when irradiated with light and forming magenta dots on the medium;
A first light irradiation step of irradiating the magenta dots with the light on the downstream side in the transport direction from the position of the first dot formation step ;
A second dot forming step of discharging cyan ink that is cured when irradiated with light and forming cyan dots on the medium;
A second light irradiation step of irradiating the cyan dots with the light on the downstream side in the transport direction from the position of the second dot formation step ;
A third dot forming step of discharging a black ink that is cured when irradiated with light and forming black dots on the medium;
A third light irradiation step of irradiating the black dots with the light on the downstream side in the transport direction from the position of the third dot formation step ;
Forming a fourth dot that discharges yellow ink that cures when irradiated with light to the area where the light-irradiated magenta dot, cyan dot, and black dot are formed, and forms a yellow dot on the medium Process,
After the yellow dots are formed , the first light irradiation step, the second light irradiation step, and the third light irradiation step are irradiated downstream of the position of the fourth dot formation step in the transport direction. A fourth light irradiation step of irradiating light stronger than light;
5th dot which discharges the clear ink or background color ink which hardens | cures when irradiated with light in the said conveyance direction downstream from the position of the said 4th light irradiation process, and forms a clear dot or a background color dot in the said medium Forming process;
Irradiate light stronger than the light emitted in the first light irradiation step, the second light irradiation step, and the third light irradiation step on the downstream side in the transport direction from the position of the fifth dot formation step. 5 light irradiation process,
As well as
In the first light irradiation step, the second light irradiation step, and the third light irradiation step, the magenta dots, the cyan dots, and the black dots are irradiated with ultraviolet light having an intensity that is temporarily cured,
In the fourth light irradiation step, the yellow dots are irradiated with ultraviolet light having a strength at which the yellow dots are fully cured,
The fifth light irradiation step is a printing method in which the clear dots or the background color dots are irradiated with ultraviolet light having a strength at which the clear dots or the background color dots are fully cured .

Images