JP2013166306A - Printing device and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve scuff proof when a surface is made mat-like by a clear dot.SOLUTION: A printing device includes: a nozzle for discharging clear ink which is irradiated with light to be hardened and forming a clear dot on a medium; and a temporarily-hardening light source for irradiating the clear dot with the light. The nozzle can discharge a plurality kinds of clear ink droplets having different sizes. When the clear dot is uniformly formed on the medium, the smallest clear ink droplet is discharged from the nozzle and the clear dot formed by the smallest clear ink droplet is irradiated with the light.

Description

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

  2. Description of the Related Art Printing apparatuses that record images and characters by discharging liquid such as ink from nozzles and landing droplets (ink dots) on a medium are known. Some printing apparatuses eject ultraviolet curable ink (UV ink) that cures when irradiated with ultraviolet (UV) light.

  When recording an image using such UV ink, first, colored ink is ejected onto a medium to form an image, and then clear ink (transparent ink) is ejected to form a clear ink layer on the image. A method for coating an image is known. At this time, a method has been proposed in which fine ink is applied to the clear ink layer by adjusting the discharge amount of the clear ink to make the surface “matte (low glossiness)” (for example, Patent Document 1). ).

JP 2008-213152 A

  When making the surface matte (low glossiness) with clear dots, it has been considered effective to increase the unevenness of the clear ink layer while dispersing the clear dots so that they do not contact each other. For this reason, it has been considered effective to form clear dots with large dots.

  However, until now, no consideration has been given to abrasion resistance (wear resistance) when the surface is made to have a matte tone (low glossiness) with clear dots. The present inventor has found that when large dots are dispersed and formed, the abrasion resistance (friction resistance) decreases.

  An object of the present invention is to improve the abrasion resistance (wear resistance) when the surface is made to have a matte tone (low glossiness) by clear dots.

  The main invention for achieving the above object is to eject a clear ink that cures when irradiated with light, to form a clear dot on a medium, and a temporary curing light source that irradiates the light to the clear dot. The nozzle is capable of discharging a plurality of types of clear ink droplets having different sizes, and when forming the clear dots uniformly on the medium, the smallest clear ink droplet is discharged from the nozzle, The printing apparatus irradiates the light to the clear dots formed by the smallest clear ink droplets.

  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 the printing apparatus 1. FIG. 2 is a block diagram of the printing apparatus 1. FIG. 3 is an explanatory diagram of the peripheral structure of the nozzle. FIG. 4 is a diagram for describing an example of the drive signal COM generated by the drive signal generation circuit 70. 5A and 5B are explanatory diagrams of the relationship between the discharge amount of the clear ink and the glossiness. FIG. 6 is a table showing the measurement results of glossiness and abrasion resistance. FIG. 7 is an explanatory diagram of the printing method of the present embodiment.

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

A nozzle that discharges clear ink that cures when irradiated with light and forms clear dots on a medium; and a light source for temporary curing that irradiates the light to the clear dots, the nozzles having a plurality of different sizes The type of clear ink droplets can be ejected, and when the clear dots are uniformly formed on the medium, the smallest clear ink droplet is ejected from the nozzle, and the clear ink droplet is formed by the smallest clear ink droplet. A printing apparatus characterized by irradiating the light with dots is clarified.
According to such a printing apparatus, it is possible to improve the abrasion resistance (wear resistance).

  When the minimum clear ink droplet is ejected from the nozzle when the glossiness is set to a predetermined value or less, and the clear dots are uniformly formed on the medium so that the glossiness is higher than the predetermined value. It is desirable to discharge the largest clear ink droplet from the nozzle. Thereby, in both cases of high glossiness and low glossiness, it is possible to ensure abrasion resistance (wear resistance).

  When it is set to print in a matte tone, the smallest clear ink droplet is ejected from the nozzle, and when it is set to print in a glossy tone, the largest clear ink droplet is discharged from the nozzle. It is desirable to discharge. Thereby, in any case, abrasion resistance (wear resistance) can be ensured.

  A main curing light source that emits light stronger than the temporary curing light source, and when the smallest clear ink droplet is ejected from the nozzle, the temporary dot is formed on the clear dot formed by the smallest clear ink droplet; When the light is emitted from the curing light source and the light is emitted from the main curing light source and the largest clear ink droplet is ejected from the nozzle, the clear dot formed by the largest clear ink droplet is applied to the clear dot. It is desirable to irradiate the light from the light source for temporary curing without irradiating the light from the light source for temporary curing. Thereby, a low glossiness can be realized when the smallest clear ink droplet is ejected, and a high glossiness can be achieved when the largest clear ink droplet is ejected.

A printing method using a nozzle that discharges clear ink that is cured when irradiated with light and forms a clear dot on a medium, and a light source for temporary curing that irradiates the light to the clear dot. A step of ejecting a plurality of types of clear ink droplets of different sizes, ejecting the smallest clear ink droplets from the nozzles to uniformly form the clear dots on the medium, and the smallest clear ink And a step of irradiating the light to the clear dots formed by the droplets.
According to such a printing method, abrasion resistance (abrasion resistance) can be improved.

=== This Embodiment ===
<Outline of printing device>
FIG. 1 is a schematic side view of the printing apparatus 1. 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 first white head unit 41W, a magenta head unit 41M, a cyan head unit 41C, a yellow head unit 41Y, a black head unit 41K, a second white head unit 42W, and a clear head unit 41CL in order from the upstream side in the transport direction. Have In each head unit, a large number of nozzles are arranged at a predetermined nozzle pitch (for example, 1/360 inch) over the width direction of the medium. Each head unit ejects predetermined ink, whereby an image is printed on the medium. Each head unit is provided along the surface of the drum 11. Each head unit ejects UV ink. The UV ink is an ink having a property of curing when irradiated with ultraviolet light.

  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. 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.

  The first white head unit 41W and the second white head unit 42W discharge white white ink. White ink is background color ink that is used to form a background image that is the background of a color image. For example, when a color image alone is formed on a transparent medium, the visibility of the color image is not good. Therefore, by forming a background image together with the color image, the light shielding property (shielding property) of the color image is improved, Visibility is enhanced. However, the white ink may be discharged onto an opaque medium such as paper.

  The first white head unit 41W is used in surface printing that forms a background image before (under a color image) a color image. The second white head unit 42W is used in reverse printing for forming a background image after (on top of) a color image. When a color image is formed on a transparent medium by reverse printing, the color image is viewed from the transparent medium side (over the transparent medium).

  The clear head unit 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 (matte tone or gloss tone) 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. Clear ink is also composed of UV ink that cures when irradiated with ultraviolet light.

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

  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 yellow light source 81Y, a black light source 81K, a second white light source 82W, and a clear light source. 81CL. A light source for temporary curing is provided along the surface of the drum 11. Each light source is provided on the downstream side of the corresponding 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. An LED (light emitting diode) or the like is employed as the light source of the temporary curing unit 80.

  If only the glossy (high gloss) printing is performed using the clear ink, the clear light source 81CL may not be provided. However, in the present embodiment, when performing matte printing, it is necessary to temporarily cure the clear ink so as not to spread the dots, and thus the clear light source 81CL is necessary.

  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.

<Discharge of ink droplets>
FIG. 3 is an explanatory diagram of the peripheral structure of the nozzle. In the figure, a nozzle Nz, a piezo element PZT, an ink supply path 402, a nozzle communication path 404, and an elastic plate 406 are shown.

  Ink is supplied to the ink supply path 402 from an ink tank (not shown). These inks and the like are supplied to the nozzle communication path 404. A drive pulse of a drive signal described later is applied to the piezo element PZT. When the drive pulse is applied, the piezo element PZT expands and contracts according to the signal of the drive pulse and vibrates the elastic plate 406. An amount of ink droplets corresponding to the amplitude of the drive pulse is ejected from the nozzle Nz.

  FIG. 4 is a diagram for describing an example of the drive signal COM generated by the drive signal generation circuit 70. As shown in the figure, the drive signal COM is repeatedly generated every repetition period T.

  A period T that is a repetition period corresponds to a period during which the medium S moves by one pixel in the transport direction. For example, when the print resolution is 360 dpi, the period T corresponds to a period for the medium S to move 1/360 inch relative to the nozzle. Then, based on the pixel data included in the print data, by selecting the drive pulses PS1 to PS4 in each section included in the period T and applying them to the piezo element PZT, ink droplets having different sizes in one pixel. Are ejected, and a plurality of gradations can be expressed.

  The drive signal COM includes a drive pulse PS1 generated in the section T1 in the repetition period T, a drive pulse PS2 generated in the section T2, a drive pulse PS3 generated in the section T3, and a drive pulse generated in the section T4. PS4.

  At the time of forming a small dot, the driving pulse PS4 is applied to the piezo element PZT. Further, when the medium dot is formed, the drive pulse PS1 is applied to the piezo element PZT. Further, when forming a large dot, the drive pulse PS3 is applied to the piezo element PZT. The drive pulse PS2 is a fine vibration pulse for finely vibrating the meniscus, and is applied to the piezo element PZT when there is no dot.

  In the present embodiment, when a small dot is formed, an ink droplet of 5 pl is ejected from the nozzle. When forming a medium dot, a 10 pl ink droplet is ejected from the nozzle. When forming a large dot, a 15 pl ink droplet is ejected.

<Glossiness adjustment>
5A and 5B are explanatory diagrams of the relationship between the discharge amount of the clear ink and the glossiness.

  As shown in FIG. 5A, when the clear dots are formed so as not to be in contact with each other, irregularities can be imparted to the surface of the clear ink layer. Thereby, the light incident on the surface of the clear dot is diffused and the glossiness is lowered, and as a result, it is visually recognized as a matte tone.

  As shown in FIG. 5B, when the clear ink is applied so as to fill the surface, the surface of the clear ink layer becomes smooth. As a result, the light incident on the clear ink layer is likely to be regularly reflected and the glossiness is increased, and as a result, it is visually recognized as a glossy tone.

  In this way, the glossiness can be adjusted by adjusting the number of clear dot formation pixels. When printing an image having a matte tone (low glossiness), it is preferable to form clear dots by setting a small number of pixels for forming clear dots and dispersing them so as not to contact each other. Further, when printing a glossy (high gloss) image, it is preferable to set a large number of pixels for forming clear dots and apply clear ink so as to fill the surface.

  By the way, when printing the matte tone (low glossiness) image shown in FIG. 5A, it is effective to form clear dots with large dots. This is because the use of large dots makes it possible to set a small number of pixels for forming clear dots and increase the unevenness of the clear ink layer. The measurement results to be described later also show that a matte tone (low glossiness) can be realized by clear dots of large dots. However, it has been found that when the matte tone is realized by the clear dots of large dots, the abrasion resistance (friction resistance) decreases as shown below.

<Measurement of glossiness and abrasion resistance>
The glossiness is an index representing the degree of glossiness, and can be measured using a glossometer. A general gloss meter emits light at a predetermined incident angle from a light source toward a measurement surface, and the reflected light from the measurement surface is detected by a light receiving unit installed in the regular reflection direction, thereby adjusting the gloss level. taking measurement.

  As the gloss meter, a gloss meter GM-60 manufactured by Konica Minolta is used. In addition, there is a method of measuring the light angle at 20 degrees, 45 degrees, 60 degrees, 75 degrees, and 85 degrees, but in this embodiment, the measurement is performed at an incident angle of 20 degrees. In addition, since glossiness shows a value proportional to the magnitude | size of an angle, even if it does not measure all the angles, it can grasp | ascertain the tendency of the glossiness of another angle by measuring about one angle.

  A test pattern to be measured for glossiness is printed on two types of media using the printing apparatus 1 described above. The test pattern is a pattern in which clear dots are uniformly formed on a plurality of color patch patterns having different densities. The color patch pattern is formed with medium dots (10 ng) of color dots, and the ratio of dot formation pixels (hereinafter referred to as “Duty”) varies by 10% between 0% and 100%. The clear dot is formed using a small dot (5 ng) or a large dot (15 ng) with a predetermined duty. Even for the same test pattern (even if the duty of the clear dot is the same), the glossiness varies depending on the density of the color patch pattern, so the average, maximum and minimum glossiness of the test pattern is measured. To do.

  If the measurement result of glossiness is 40 or less, it is evaluated that it is matte (low glossiness). On the other hand, if the measurement result of glossiness is 80 or more, it is evaluated that it is glossy (high glossiness).

  Abrasion resistance (friction resistance) means the degree of resistance to scratching of the printing surface on the medium when a frictional force is applied. In the item of friction resistance of the JIS standard “K5701”, a method for examining the friction resistance by a Gakushin type friction tester is defined. Here, a Gakushin type friction fastness tester manufactured by Tester Sangyo Co., Ltd. is used.

  A test pattern to be measured for abrasion resistance is printed on two types of media using the printing apparatus 1 described above, and the abrasion resistance of the test pattern is determined. The test pattern is a pattern in which clear dots are uniformly formed on a color pattern having a predetermined density.

  In the abrasion resistance test, the object to be measured is set in a Gakushin friction fastness tester, high-quality paper (or white cloth) is used as the friction paper, the load is 200 g, and the number of friction between the measurement object and the friction paper is 100 reciprocations It is said. In the determination of the abrasion resistance, the change in the friction surface to be measured and the coloring state of the friction paper are evaluated in three stages. The evaluation index is as follows.

A: The friction surface is not scratched and the friction paper is not colored.
B: The friction surface is scratched, but the friction paper is not colored. Or there is no scratch on the friction surface, but there is coloring on the friction paper.
C: The friction surface is scratched and the friction paper is colored.

  FIG. 6 is a table showing the measurement results of glossiness and abrasion resistance. Those whose average glossiness measurement result is 40 or less are evaluated as matte (low glossiness), and the frame is indicated by a bold line. Further, the frame of A in the evaluation result of the abrasion resistance is indicated by a bold line.

  First, the measurement result when a large dot clear dot (clear ink weight: 15 ng) is formed will be examined.

  When a large dot is formed with a duty of 67% or more, it becomes glossy (glossiness of 80 or more). In addition, the glossiness becomes higher as the clear dot of a large dot is formed with a high duty. As shown in FIG. 5B, this is considered to be because the surface becomes smoother as large dots are formed with a high duty.

  When a glossy tone (high glossiness) is realized with a large dot, there is no problem in abrasion resistance (evaluation of abrasion resistance is A or B). In addition, as the large dots are formed with high duty, the abrasion resistance is improved. This is considered to be because the surface becomes smoother and the surface is more easily protected as shown in FIG.

  When a large clear dot is formed with a duty of 40% or less, it becomes a matte tone (glossiness of 40 or less). In addition, the glossiness becomes lower as a large dot is formed with a lower duty. This is because, as shown in FIG. 5A, when the number of pixels forming the clear dots is set to be small, the clear dots are dispersed to the extent that they do not contact each other, the light incident on the surface of the clear dots is diffused, and the glossiness is lowered. Because.

  However, when matte tone (low glossiness) is realized with large dots, there is a problem in abrasion resistance. In particular, the evaluation of scuff resistance is C for Duty (27% or less) in which both types of media have a matte tone. When the friction surface of the rubbing resistance test when the matte tone (low glossiness) is realized with the large dots, the large dots (and the color image) are peeled off from the surface. This is considered to be because when the large dots are formed with a low duty, the unevenness of the surface becomes large, and as a result, a large frictional force is applied to the surface.

  Next, a measurement result when a small dot clear dot (clear ink weight: 5 ng) is formed will be examined.

  If small dots are uniformly formed, a matte tone (glossiness of 40 or less) is obtained. Even if small dots of clear dots are formed with a high duty, a matte tone is obtained. This is because in the case of small dots, even if the duty is 100%, the surface is not filled with clear ink, there are gaps between the clear dots, and the surface is uneven. For this reason, the glossy tone cannot be realized in the case of small dots.

  When the matte tone (low glossiness) is realized with small dots, the evaluation of the abrasion resistance is improved as compared with the case where the matte tone is realized with large dots. In particular, when the duty of a small dot is 50% or more, a high abrasion resistance evaluation A is obtained. This is considered to be because when the matte tone is realized with small dots, the surface unevenness is smaller than that of the large dots, so that a large frictional force is not easily applied to the surface.

  From the above measurement results, it can be seen that the use of small dots of clear dots can improve the rub resistance while realizing a matte tone. Further, it can be seen that when a glossy tone is realized, even if a large dot is used, the abrasion resistance is high.

  When small dots of clear dots are used, the surface irregularities are reduced, and it is difficult for a large frictional force to be applied to the surface, thereby improving the abrasion resistance. Therefore, when clear ink droplets of a plurality of sizes can be ejected from the nozzle, it is desirable to eject the smallest ink droplet to form a clear dot.

<Printing method>
FIG. 7 is an explanatory diagram of the printing method of the present embodiment.

  A printer driver is installed in the computer 110 (see FIG. 2), which is an external device. The printer driver is a program that causes the computer 110 to generate print data for causing the printing apparatus 1 to perform a printing operation based on image data to be printed, and to send the print data to the computer 110.

  The printer driver checks whether the gloss level is set for the image data to be printed. If the gloss level is set, the printer driver checks whether the setting is matte or glossy. When the glossiness value is set, the matte tone is determined if the setting value is 40 or less, and the glossy tone is determined if the glossiness setting value is 80 or more.

  When the matte tone is set, the printer driver generates pixel data for controlling the clear head unit 41CL so that clear dots are uniformly formed with small dots. On the other hand, when the gloss tone is set, pixel data for controlling the clear head unit 41CL is generated so that clear dots are uniformly formed with large dots.

  The printer driver generates not only pixel data for controlling the clear head unit 41CL but also pixel data for controlling other head units. The printer driver also generates control data for controlling other units (such as the transport unit 10, the head unit 40, the temporary curing unit 80, and the main curing unit 90) other than the head unit.

  When forming clear dots with small dots (in the case of matte tone), the printer driver irradiates ultraviolet light from the clear light source 81CL of the temporary curing unit 80 and performs main curing of the main curing unit 90. Control data is generated so that ultraviolet light is emitted from the light source 91 for use. On the other hand, when forming clear dots with large dots (in the case of glossy tone), the printer driver does not irradiate ultraviolet light from the clear light source 81CL of the temporary curing unit 80, and the book of the main curing unit 90. Control data is generated so that ultraviolet light is irradiated from the curing light source 91. The reason for this will be described later.

  The printer driver transmits print data including pixel data and control data to the printing apparatus 1. The printing apparatus 1 that has received the print data controls each unit (the conveyance unit 10, the head unit 40, the temporary curing unit 80, the main curing unit 90, etc.) according to the print data. The printing apparatus 1 selects the drive pulses PS1 to PS4 of each section included in the period T according to the pixel data in the print data and applies them to the piezo element PZT, thereby causing inks having different sizes in one pixel. Discharge drops. The printing apparatus 1 causes the transport unit to transport the medium according to the control data in the print data, and irradiates the temporary curing unit 80 and the main curing unit 90 with ultraviolet light.

  In the present embodiment, when the image to be printed is matte, 5 ng of clear ink droplets are uniformly ejected from the clear head unit 41CL onto the medium. That is, when the clear dots are uniformly applied to the medium, the smallest clear ink droplet is ejected from the nozzle. As a result, a matte printed image having excellent abrasion resistance can be obtained.

  In addition, when realizing a matte tone, it is desirable that the surface is uneven. Therefore, when realizing the matte tone, after the clear ink droplets are uniformly applied to the medium, the printing apparatus irradiates ultraviolet light from the clear light source 81CL to temporarily cure the small dot clear dots. By temporary curing, the surface irregularities are maintained without spreading the small dots.

  In the present embodiment, when the image to be printed is glossy, 15 ng of clear ink droplets are uniformly ejected from the clear head unit 41CL onto the medium. That is, when the clear dots are uniformly applied to the medium, the largest clear ink droplet is ejected from the nozzle. In the case of a glossy tone, clear dots are formed with a high duty, so there is no problem of abrasion resistance (in the case of a glossy tone, use of a large dot is allowed).

  In addition, when realizing a glossy tone, it is desirable that the surface is as smooth as possible. Therefore, when realizing a glossy tone, after the clear ink droplets are uniformly applied to the medium, the printing apparatus does not irradiate the clear light source 81CL with ultraviolet light, and does not temporarily cure the clear ink. The clear ink is fully cured by using the light source 91. Thereby, the clear ink continues to have fluidity until immediately before the main curing, and the surface becomes smooth, and thereafter the clear ink can be cured.

=== 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>
The printing apparatus of the above-described embodiment is a so-called line-type printing apparatus (printing apparatus that forms an image by ejecting ink from a fixed head while transporting a medium). However, instead of the line-type printing apparatus, a so-called serial-type printing apparatus (a printing apparatus that alternately repeats an operation of conveying a medium and an operation of ejecting ink from a moving head to form dots) may be used.

  In the printing apparatus of the above-described embodiment, three types of ink droplets having different sizes can be ejected from the nozzle. However, the number of ink droplets is not limited to three, and any type of ink droplets may be ejected from the nozzle. When printing in a matte tone, it is preferable to uniformly form clear dots by ejecting the smallest ink droplet from among a plurality of types of ink droplets that can be ejected from a nozzle. Thereby, it is possible to improve the abrasion resistance while realizing a matte tone. When printing in a glossy tone, it is preferable to uniformly form clear dots by ejecting the largest ink droplets from the nozzles. Thereby, the surface is filled with clear ink, and the surface tends to be smooth.

<About temporary curing>
In the above-described embodiment, when the glossy tone is realized, the clear light source 81CL of the temporary curing unit 80 is not irradiated with ultraviolet light. However, it is not limited to this. When realizing the glossy tone, ultraviolet light may be irradiated from the clear light source 81CL of the temporary curing unit 80. Even in such a case, if the clear dots are formed with a high duty, the surface becomes smooth and a glossy tone can be realized.

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,
41C cyan head unit,
41M magenta head unit,
41Y yellow head unit,
41K black head unit,
41CL clear 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,
81C light source for cyan,
81M light source for magenta,
81Y yellow light source,
81K light source for black,
81CL clear light source,
82W light source for second white,
90 curing units, 91 curing light sources,
S medium (transparent medium)

Claims (5)

A nozzle that ejects clear ink that cures when irradiated with light and forms clear dots on the medium;
A light source for temporary curing that irradiates the light to the clear dots,
The nozzle is capable of discharging a plurality of types of clear ink droplets having different sizes,
When the clear dots are uniformly formed on the medium, a minimum clear ink droplet is ejected from the nozzle, and the light is irradiated to the clear dot formed by the minimum clear ink droplet. Printing device to do. The printing apparatus according to claim 1,
When making the gloss level equal to or less than a predetermined value, the smallest clear ink droplet is ejected from the nozzle,
When the clear dots are uniformly formed on the medium so that the glossiness is higher than the predetermined value, the largest clear ink droplet is ejected from the nozzle. The printing apparatus according to claim 1 or 2,
When it is set to print in a matte tone, the smallest clear ink droplet is ejected from the nozzle,
A printing apparatus that discharges the largest clear ink droplet from the nozzle when printing is set to glossy. The printing apparatus according to claim 2 or 3,
A light source for main curing that irradiates the light stronger than the light source for temporary curing;
When the smallest clear ink droplet is ejected from the nozzle, the clear dot formed by the smallest clear ink droplet is irradiated with the light from the temporary curing light source and the light from the main curing light source. And
When the largest clear ink droplet is ejected from the nozzle, the clear dot formed by the largest clear ink droplet is not irradiated with the light from the temporary curing light source, and the light is emitted from the main curing light source. Irradiating printing apparatus. A nozzle that ejects clear ink that cures when irradiated with light and forms clear dots on the medium;
A printing method using a light source for temporary curing that irradiates the light to the clear dots,
The nozzle is capable of discharging a plurality of types of clear ink droplets having different sizes,
Discharging the smallest clear ink droplets from the nozzle to uniformly form the clear dots on the medium;
Irradiating the clear dots formed by the smallest clear ink droplets with the light.

Images