Recording method and recording device

Abstract

This recording method includes: discharging of one or more kinds of ink toward a recording medium; and irradiation of ultraviolet rays onto the one or more kinds of ink on the recording medium. The one or more kinds of ink include a first ink that contains an ultraviolet absorber. In the discharging of the ink, according to the content of an image, the amount of each kind of ink corresponding to one dot is changed within a range not exceeding a predetermined upper limit value. The first ink, in a state of being discharged at the upper limit value and positioned on the recording medium and immediately before being irradiated with ultraviolet rays, has a transmittance of ultraviolet rays in the thickness direction of 1.0% or more. Alternatively, the first ink has a concentration of the ultraviolet absorber at the time of discharge of 1.6 mass % or less.

Description

Recording method and recording device

[0001] The present disclosure relates to a recording method and a recording apparatus for depositing ink onto a recording medium.

[0002] In inkjet printing, in which ink is propelled toward a recording medium (e.g., paper) to perform printing, various techniques have been proposed for drying ink that has landed on the recording medium (e.g., Patent Document 1 below). In Patent Document 1, a drying device and a melting device are arranged in sequence along a path along which the recording medium is transported. The drying device heats the recording medium to promote evaporation of the ink medium. The melting device irradiates the ink with ultraviolet light (hereinafter sometimes abbreviated as "UV"), thereby raising the temperature of the polymer in the ink and melting the polymer. The polymer then solidifies and adheres to the recording medium. Patent Document 1 also discloses including an ultraviolet absorber (hereinafter sometimes abbreviated as "UV absorber") in the ink. The contents of Patent Document 1 may be incorporated by reference in this application.

[0003] International Publication No. 2022 / 004486

[0004] A recording method according to one aspect of the present disclosure includes ejecting one or more types of ink onto a recording medium and irradiating the one or more types of ink on the recording medium with ultraviolet light. The one or more types of ink include a first ink containing an ultraviolet absorber. During the ejection of the ink, the amount of each type of ink corresponding to one dot is changed within a range not exceeding a predetermined upper limit value depending on the content of the image. The first ink has an ultraviolet light transmittance of 1.0% or more in the thickness direction when ejected at the upper limit value and positioned on the recording medium and immediately before being irradiated with ultraviolet light.

[0005] A recording method according to one aspect of the present disclosure includes ejecting ink containing an ultraviolet absorber onto a recording medium, and irradiating the ink on the recording medium with ultraviolet light, wherein the ink has a concentration of the ultraviolet absorber of 1.6% by mass or less when ejected.

[0006] A recording apparatus according to one aspect of the present disclosure includes an ejection device that ejects ink containing an ultraviolet absorber onto a recording medium, and an irradiation device that irradiates the ink on the recording medium with ultraviolet light. The ejection device changes the amount of ink corresponding to one dot within a range equal to or less than a predetermined upper limit value depending on the content of an image. In the ejection device, the upper limit value is set so that the ultraviolet light transmittance in the thickness direction of the ink when ejected at the upper limit value and positioned on the recording medium immediately before being irradiated with the ultraviolet light is 1.0% or more.

[0007] A recording apparatus according to one aspect of the present disclosure includes a discharge device that discharges ink containing an ultraviolet absorbent onto a recording medium, and an irradiation device that irradiates the ink on the recording medium with ultraviolet light. The discharge device discharges the ink having a concentration of the ultraviolet absorbent of 1.6% by mass or less.

[0008] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

[0009] (Overview of the embodiment) FIG. 1 is a schematic cross-sectional view of a printer 1 (an example of a recording device) according to an embodiment. For convenience, FIG. 1 includes a Cartesian coordinate system D1D2D3. The recording device according to the embodiment may be used in any orientation. However, for convenience, unless otherwise specified, an example in which the +D3 side is upward will be used, and expressions based on this assumption will be used. The cross-section shown in FIG. 1 spans, for example, the entire width (length in the D2 direction) of a medium 101 (an example of a recording medium), which will be described later.

[0010] The printer 1 is configured as a color inkjet printer that prints on a medium 101 such as paper. More specifically, in the illustrated example, the medium 101 is roll paper, which is transported from right to left in the figure. Then, printing is performed by ejecting ink of multiple colors from an ejection device 3 onto a front surface 101a of the medium 101. Thereafter, the medium 101 (more specifically, in the illustrated example, the printed area of ​​the medium 101) is transported to a drying device 5, where the ink of multiple colors is dried.

[0011] Unless otherwise specified or inconsistent, the matters described below will be explained using one of the multiple colors of ink (an example of the first ink) as an example. Therefore, terms such as "multiple colors" or "one color" will be omitted as appropriate. Unless otherwise specified or inconsistent, the explanation of one color of ink may (but does not have to) be applied to other colors of ink included in the multiple colors of ink.

[0012] The drying device 5 has one or more drying mechanisms 7 (ten in the illustrated example). Each of the one or more drying mechanisms 7 has at least one irradiation unit 7A. The irradiation unit 7A irradiates the ink with UV light. The ink contains a UV absorbent. The UV absorbent (and other components) absorbs the UV light, causing the temperature of the ink to rise. This promotes drying of the ink.

[0013] In this embodiment, one or both of the following two measures are taken to improve the fixation of the ink to the medium 101. Measure 1: The UV transmittance of the ink on the medium 101 is set to 1.0% or more. Measure 2: The concentration of the UV absorber contained in the ink is set to 1.6% by mass or less.

[0014] When ink fixation to the media 101 is poor, it is usually suspected that the ink has not been heated sufficiently. Therefore, one possible solution is to increase the concentration of the UV absorbent (the opposite of Solution 2) to improve the effect of UV heating. However, after extensive research, the inventors of the present application have found that lowering the concentration of the UV absorbent actually improves fixation. The principle behind this is similar to Solution 1. Specifically, it is as follows.

[0015] 2 is a schematic cross-sectional view showing an enlarged view of the front surface 101a of the medium 101 and the vicinity thereof. For convenience, the cross section is not hatched. This figure shows a state in which ink 103 is adhered to the front surface 101a with a uniform thickness b.

[0016] As shown by the open arrow, UV has an intensity P ０The UV light is incident on the upper surface of the ink 103 at an intensity P. Then, the UV light travels toward the lower surface of the ink 103 while its energy is absorbed by the ink 103 (while its intensity is reduced). Then, assuming that the medium 101 does not exist, the UV light exits from the lower surface of the ink 103 at an intensity P. The intensity P of the incident light ０ and the intensity P of the emitted light, P / P ０ × 100 is the transmittance T (%). In the following, P / P is not multiplied by 100. ０ The symbol T is sometimes used.

[0017] Here, if the UV intensity (see intensity P) in the lower surface portion of the ink 103 is too low, heat generation in the lower surface portion may be insufficient, potentially reducing the fixability of the ink 103 to the medium 101. Therefore, increasing the concentration of the UV absorber because of low fixability will actually result in a decrease in fixability.

[0018] Therefore, as in Measure 2, by limiting the concentration of the UV absorber to 1.6% by mass or less, it is possible to make it easier for UV to reach the lower surface portion of the ink 103. Ultimately, it is possible to improve fixability to some extent. The concentration of the UV absorber changes as the ink 103 dries, but, for example, the concentration at the time of ejection may be used as a reference. The concentration at the time of ejection can usually be considered to be the same as the concentration of the UV absorber in the ink in the head 15 or ink tank 17, which will be described later.

[0019] The threshold value of 1.6% by mass is a value found in the examples, as described below. However, the idea of ​​lowering the concentration rather than increasing the concentration to increase the UV-to-heat conversion efficiency in order to improve fixability is itself groundbreaking. Furthermore, for example, Patent Document 1 does not disclose the specific concentration of the UV absorber. Therefore, the threshold value of 1.6% by mass primarily serves as a guideline indicating the idea of ​​lowering the concentration. In other words, when 1.6% by mass is adopted, it is not necessary to achieve the same effect as in the examples. Furthermore, 1.6% by mass is not required to have a critical meaning. Consequently, the specific components of ink 103 and the specific conditions of UV irradiation (e.g., illuminance and irradiation time) are not limited to those in the examples.

[0020] Furthermore, as can be understood from the principle of the above-mentioned deterioration in fixability, it is also possible to directly stipulate that UV reaches the bottom surface of the ink 103, as in Measure 1. Specifically, the transmittance T may be set to 1.0% or more. This allows the bottom surface portion of the ink 103 to be heated by UV to some extent, thereby improving fixability.

[0021] The threshold value of 1.0% is a value found in the examples, as described below. However, the idea of ​​focusing on the transmittance T (in other words, the UV reaching the underside of the ink 103) to improve fixability has not existed in the past. Furthermore, from the perspective of improving the efficiency of UV-to-heat conversion, it is preferable that the UV does not penetrate the entire thickness of the ink 103 (it is preferable that all energy be consumed before reaching the underside of the ink 103). Therefore, the threshold value of 1.0% primarily serves as a guideline indicating the idea of ​​increasing the transmittance T above 0%. In other words, when 1.0% is adopted, it is not necessary to achieve the same effect as in the examples. Furthermore, 1.0% is not required to have a critical meaning. Furthermore, the specific components of the ink 103 and the specific conditions of UV irradiation (e.g., illuminance and irradiation time) are not limited to those in the examples.

[0022] The transmittance T is affected by the ink 103 components as well as the thickness b of the ink 103. Meanwhile, the amount of ink 103 ejected to form one dot on the medium 101 is controlled to vary within a range from 0 to a predetermined upper limit value depending on the content of the image. Consequently, the thickness b varies depending on the content of the image. Therefore, whether the transmittance T is 1.0% or greater may be determined based on the ink 103 on the medium 101 when the ink 103 is ejected at the above-mentioned upper limit value.

[0023] As will be described later, the ink 103 may be dried by a method other than UV between the time it lands on the medium 101 and the time it is irradiated with UV. In such a case, the transmittance T may be determined based on the ink 103 immediately before irradiation by the irradiation unit 7A begins. This is because the focus here is on whether the UV irradiated by the irradiation unit 7A reaches the bottom surface of the ink 103. However, if drying does not affect the transmittance T, the transmittance T may be determined at a time other than immediately before irradiation begins.

[0024] The transmittance T varies depending on the wavelength of the light (UV). However, due to the characteristics of the UV absorber and / or the characteristics of the light (UV) emitted by the irradiation unit 7A, the wavelength of UV that contributes to heating is limited. Therefore, it is more reasonable to refer to the transmittance T as a value that targets UV at an appropriately set reference wavelength or reference wavelength range, rather than a value that targets all light emitted by the irradiation unit 7A. Examples of the reference wavelength and reference wavelength range will be given later.

[0025] Another approach to UV heating the underside of the ink 103 is to use an incident light intensity P ０ (hereinafter referred to as Measure 3) ０ If the temperature is increased, excessive heat will be generated in the upper portion of the ink 103, forming a dry film on the surface, which may hinder evaporation of the solute (e.g., water) in the lower portion of the ink 103. However, by adopting Measure 2 instead of or in addition to Measure 3, the likelihood of such a problem occurring is reduced.

[0026] The printer 1 according to the embodiment does not necessarily have to achieve the fixability effect described above. Furthermore, a technology based on a different perspective from the above-described Measures 1 and 2 may be extracted from the embodiment. In this case, for example, the requirement that the transmittance T be 1.0% or more and / or the requirement that the concentration of the UV absorber be 1.6% by mass or less may not be satisfied.

[0027] The above is an overview of the embodiment. The following will be explained in the following order: 1. Printer 1 1.1. Printer in general 1.2. Discharge device 3 1.3. Drying device 5 2. Ink 103 2.1. Ink 103 in general 2.2. UV absorber 2.3. Transmittance and density 3. Examples and comparative examples (FIG. 3) 4. Summary of the embodiment

[0028] 1 includes, for example, a recording system 9 that ejects and dries ink, a transport device 11 that transports a medium 101, and a controller 13 that controls these. The recording system 9 includes an ejection device 3 and a drying device 5. In addition to these, the printer 1 may also include, for example, an operation unit (not shown) that receives user operations and inputs signals corresponding to the operations to the controller 13.

[0029] As described above, the printer 1 prints on roll paper as the medium 101. However, the medium 101 may also be sheet paper. The size of the medium 101 is also arbitrary. For example, the size of the medium 101 may be small, like a receipt, a size commonly used in offices, or large, like a poster.

[0030] As can be seen from the above, the transport device 11 may have any configuration, and the transport path may also be any form. Figure 1 illustrates a configuration in which a roller (reference numeral omitted) that contacts the media 101 rotates. Other configurations include, for example, a configuration in which a belt that adsorbs the media 101 is transported, or a configuration in which a drum around which the media 101 is wound is rotated. Furthermore, the transport path may extend generally straight (as in the illustrated example), or it may extend in a U-turn.

[0031] The controller 13 includes, for example, a computer, and controls the recording system 9 and the conveying device 11 based on print data including image data (which is a broad concept that includes text).

[0032] (1.2. Discharge Device) The discharge device 3 may be a device for color printing (as shown in the example) or a device for monochrome printing. In the description of the embodiment, the former will be taken as an example. For example, the discharge device 3 discharges ink of four colors to form a color image. The four colors are, for example, magenta (M), yellow (Y), cyan (C), and black (K).

[0033] The ejection device 3 has at least one head 15 (four in the illustrated example) that ejects ink toward the front surface 101a of the medium 101, and at least one ink tank 17 (four in the illustrated example) that supplies ink to the head 15. Depending on the configuration of the ejection device 3, the ink tank 17 may be replaceable, so the ink tank 17 may not be considered a component of the ejection device 3.

[0034] The four heads 15 and four ink tanks 17 correspond to the four colors described above. Note that the head 15, which is considered to be one unit in the description of the embodiment, may be a plurality of small heads arranged along the D1D2 plane.

[0035] The ejection device 3 is configured for use in a so-called line printer. That is, the head 15 spans almost the entire width (direction D2) of the medium 101. Then, as the medium 101 is transported, printing is performed in a band-shaped area extending in the direction D2, thereby forming a two-dimensional image.

[0036] However, the ejection device 3 may also be for a serial printer. In this case, for example, the operation of printing while moving the head in the D2 direction and the transport of the medium 101 are performed alternately. For convenience, in the explanation of the embodiments, a line printer may be used as an example unless otherwise specified.

[0037] The head 15 ejects ink droplets from, for example, nozzles (not shown) facing the medium 101. The configuration of the head 15 is arbitrary as long as it is capable of ejecting ink. For example, the actuator system that applies pressure to the ink for ejection may be a piezoelectric system that applies pressure to the ink by deforming a piezoelectric element, or a thermal system that applies pressure to the ink by heating the ink to generate bubbles.

[0038] (1.3. Drying Device) The drying device 5 may have any configuration as long as it has an irradiation unit 7A as the drying mechanism 7. In the illustrated example, the drying device 5 has a plurality of drying mechanisms 7 arranged along the transport path of the media 101 and a box 19 that houses the plurality of drying mechanisms 7.

[0039] In addition to the irradiation unit 7A, the multiple drying mechanisms 7 include, for example, an air supply unit 7B (a drying mechanism 7 indicated by an arrow pointing toward the media 101 in FIG. 1 ) and an air intake unit 7C (a drying mechanism 7 indicated by an arrow pointing away from the media 101 in FIG. 1 ). The air supply unit 7B supplies hot air (a broad concept including warm air) to the transport path of the media 101. The air intake unit 7C sucks gas (or moisture from another perspective) from the transport path. Examples of drying mechanisms 7 other than those shown in the figures include a heating roller that rotates in contact with the media 101 and a heating plate against which the media 101 slides. As can be understood from the above specific example, the drying mechanisms 7 other than the irradiation unit 7A may not contact the media 101, or may contact the media 101.

[0040] The drying device 5 may have only the irradiation unit 7A and may not have other drying mechanisms 7. The drying mechanisms 7 other than the irradiation unit 7A may be located on the front surface 101a side (ink side) of the media 101, or on the back surface 101b side. The drying device 5 may have drying mechanisms 7 (including the irradiation unit 7A) on both the front surface 101a side and the back surface 101b side (as shown in the example), or may have a drying mechanism 7 on only one side. The relative arrangement (order, etc.) of two or more types of drying mechanisms 7 including the irradiation unit 7A is arbitrary. The multiple drying mechanisms 7 may be adjacent to each other, as in the example shown, or may be separated from each other.

[0041] The box 19 may contribute to forming a space through which the media 101 passes. This space may be sealed except for the entrance and exit of the media 101. This reduces the likelihood of heat loss during drying. In the illustrated example, the drying mechanisms 7 are in contact with each other, and the surfaces of the drying mechanisms 7 facing the media 101 also form a space 19a through which the media 101 passes. The space 19a is sealed except for the entrance and exit of the media 101, the hot air outlet, and the gas inlet. Unlike the illustrated example, the drying device 5 does not necessarily have a box 19. The drying mechanism 7 may be held by an appropriate support member other than the box 19. The transport path for the media 101 does not necessarily have to be sealed.

[0042] The irradiation unit 7A is, for example, located on the front surface 101a side of the medium 101 and irradiates the front surface 101a with UV. However, in an aspect where the medium 101 is made of a material that transmits UV, the irradiation unit 7A may be located on the back surface 101b side of the medium 101 and irradiate the back surface 101b with UV. In this case, measures 1 and 2 make it easier for UV to reach the upper surface portion of the ink 103, for example. Note that in the description of the embodiment, an aspect where the irradiation unit 7A is located on the front surface 101a side will be taken as an example.

[0043] The irradiation unit 7A has a size that spans the entire width (length in the D2 direction) of the medium 101, for example, and simultaneously irradiates UV light across the entire width of the medium 101. The length in the D1 direction of the area on the medium 101 that is irradiated with UV light is, for example, constant in the D2 direction, and the specific value thereof is arbitrary. Note that the irradiation unit 7A may also be configured to move in the D2 direction like a serial head.

[0044] Any number of irradiation units 7A may be provided. In an embodiment in which multiple irradiation units 7A are provided, the description of T≧1.0% and other descriptions may apply to only one irradiation unit 7A, or may apply to each of two or more (some or all) irradiation units 7A. The multiple irradiation units 7A may have the same or different characteristics (e.g., peak wavelength and / or power spectrum) of the UV light they emit. The irradiation areas on the medium 101 by the multiple irradiation units 7A may or may not be arranged side by side with no gaps between them.

[0045] As is well known, UV light has a shorter wavelength than visible light, and its wavelength is, for example, 10 nm or more and 400 nm or less. The wavelength of the UV light emitted by the irradiation unit 7A is arbitrary. For example, the UV light may be near ultraviolet light or far ultraviolet light. The near ultraviolet light may be any of so-called UV-A, UV-B, and UV-C light. The UV light may have a narrow wavelength range in which the energy is distributed, such as laser light, or may have a wide wavelength range.

[0046] Factors that affect the fixation of ink by UV include, for example, wavelength and illuminance (e.g., intensity P ０ ) and irradiation time. The irradiation time can be obtained, for example, by dividing the length in the D1 direction of the area of ​​the medium 101 irradiated with UV by the transport speed of the medium 101. As described above, the wavelength is arbitrary. The illuminance and irradiation time are also arbitrary.

[0047] To give a specific example, the illuminance is 4000 mW / cm ２In this case, for example, it is possible to reduce the likelihood of an increase in heat generated when converting electricity into UV light. More specifically, for example, the irradiance may be 2000 mW / cm or less. ２ More than 3000mW / cm ２ With such an illuminance, ink at room temperature can be heated to about 100° C. with an irradiation time of 0.3 seconds or less, although this depends on the ink components, etc. Of course, the illuminance may be outside the above range.

[0048] Furthermore, for example, the irradiation time may be 6 ms or more and 300 ms or less, or 6 ms or more and 30 ms or more. As can be understood from the fact that the drying device 5 may have a drying mechanism 7 other than the irradiation unit 7A, the irradiation time may be short. For example, when raising the ink to a desired temperature (e.g., 100°C or more) using UV, the irradiation time can be shortened if another drying mechanism 7 preheats the ink before irradiation. Furthermore, if another drying mechanism 7 heats the ink after UV irradiation, the need to continue UV irradiation to maintain the desired temperature (e.g., 100°C or more) achieved by UV can be reduced, and the irradiation time can be shortened.

[0049] The time from when the ink lands on the medium 101 until the ink is irradiated with UV (more specifically, when irradiation begins) is arbitrary. From another perspective, the relationship between the distance between the head 15 and the irradiation unit 7A and the transport speed of the medium 101 is arbitrary. For example, the above time may be 1.0 second or less. This time indicates that the time from landing to irradiation is relatively short. For example, when the transport speed of the medium 101 is 100 m / min, the distance from the head 15 to the irradiation unit 7A is approximately 1.7 m or less. Note that the above time varies depending on the positions of the multiple nozzles. The requirement of 1.0 second or less may be met for some or all of the nozzles.

[0050] (2. Ink) (2.1. Ink in General) At least one of the multiple colors of ink (an example of a first ink) contains a UV absorber. Apart from this, the components of each of the multiple colors of ink may be various and may be publicly known. For example, each ink contains a medium (a solvent or dispersion medium, such as water or an organic solvent) and a colorant (a pigment or dye). The printer 1 then fixes the colorant to the medium 101 by drying the ink (evaporating the medium). In other words, the ink is not a UV-curable ink. Note that the ink may not contain a colorant (for example, an ink intended to impart gloss to the medium 101).

[0051] The specific manner in which the colorant is fixed to the medium 101 is arbitrary. For example, the fixation may be due to the colorant permeating the medium 101, due to the colorant accumulating on the medium 101 as the medium dries, due to the fixer polymer melting and solidifying to fix to the medium 101 together with the colorant, or a combination of these.

[0052] When a fixer polymer is used, for example, the temperature of the fixer polymer is raised to its glass transition temperature (hereinafter sometimes abbreviated as "Tg") by UV irradiation, thereby melting the fixer polymer. The specific value of Tg is arbitrary. For example, Tg may be 70°C or higher and 120°C or lower. Setting Tg at a high value in this manner reduces, for example, the likelihood of ink adhering to the head 15. Furthermore, the specific composition and / or components of the fixer polymer are arbitrary. For example, the fixer polymer may be an acrylic polymer, a styrene polymer, a vinyl chloride polymer, or a methacrylic acid polymer.

[0053] In addition to the components listed above, the ink 103 may contain other suitable components, such as a dispersant polymer for dispersing the pigment (or, from another perspective, suppressing aggregation), an abrasion-resistant polymer for improving the ink's resistance to abrasion, a surfactant (other than the dispersant polymer), a humectant, a surface tension adjuster, a pH adjuster, and / or a gloss-imparting agent.

[0054] The specific component ratios of the ink are also arbitrary. Examples of component ratios are given below using an ink containing a fixative polymer as an example. The medium (e.g., water or an aqueous solvent) may be 50% by mass or more and 70% by mass or less. The pigment may be 1.0% by mass or more and 10.0% by mass or less. The lower limit of the pigment may be 2.0%, 3.0%, or 4.0% by mass, which is greater than the 1.6% by mass of the UV absorber, instead of 1.0% by mass. The fixative polymer may be 1% by mass or more and 40% by mass or less (provided that the total with other components is 100% by mass).

[0055] (2.2. UV Absorber) For example, a UV absorber does not substantially function as a colorant. In other words, although a colorant can also absorb UV and contribute to heating of the ink, the UV absorber is contained in the ink as a component separate from the colorant. Therefore, even if the concentration of the UV absorber is changed, the color of the ink does not change significantly. A substance with such properties may be selected as the UV absorber.

[0056] However, in the embodiments, it is intended that the concentration of the UV absorber be low. At low concentrations, the UV absorber has a smaller effect on the color of the ink than at high concentrations. From another perspective, at high concentrations that exceed the range of UV absorber concentrations in the embodiments, the UV absorber may affect the color of the ink. Therefore, there is a high degree of freedom in the composition and / or components of the UV absorber.

[0057] The UV absorber exhibits, for example, a certain degree of extinction coefficient. For example, the following a' (1 / cm) may be used as the extinction coefficient: a' = -log １０ T' / b' where T' is the transmittance of the target component (light medium, e.g., UV absorber), and is not expressed as a percentage but as a ratio ranging from 0 to 1. Also, b' (cm) is the thickness of the target component. The larger the absorption coefficient a', the smaller the transmittance T'.

[0058] Furthermore, the following a (unit: 1 / cm or L / (cm·g)) may be used as the absorption coefficient: a=−log １０T / (bc) Here, we assume a situation in which only the target component (e.g., UV absorber) is mixed at a predetermined concentration c (mass % / 100 or g / L) in a film of thickness b (cm) made of a transparent medium such as water, as shown in Figure 2, and transmittance T (here, this is not expressed as a percentage but as a ratio in the range of 0 to 1) is obtained. The larger the extinction coefficient a, the smaller the transmittance T.

[0059] The specific value of the absorption coefficient of the UV absorber is arbitrary. For example, when focusing on ink of one color (an example of a first ink), the absorption coefficient a (or a'; the same applies hereinafter) of the UV absorber contained in that ink at a reference wavelength (described below) may be larger than, equal to, or smaller than the absorption coefficient a of the colorant contained in that ink. Furthermore, when focusing on ink of one color, the absorption coefficient a of the UV absorber contained in that ink at a reference wavelength may be 0.3 times or more, 0.5 times or more, 0.8 times or more, 1.0 times or more, 1.2 times or more, or 1.5 times or more the absorption coefficient a of the colorant contained in that ink. In any case, for example, as described above, the degree of UV absorption by the ink can be adjusted without changing the color of the ink.

[0060] Furthermore, for example, when focusing on inks of multiple colors (four colors in this embodiment), the absorption coefficient a of the UV absorber contained in one color of ink at the reference wavelength may be greater than the absorption coefficient a of the colorants of all colors, greater than the absorption coefficient a of the colorants of only some colors, or less than the absorption coefficient a of the colorants of all colors. For example, at the reference wavelength, the absorption coefficient a of the UV absorber contained in one color of ink may be less than the absorption coefficient a of the black colorant and greater than the absorption coefficient a of the colorants of the other three colors (or, from another perspective, all of the other colors), the other two colors, or one other color (or, from another perspective, some of the other colors). The various lower limit values ​​from 0.3 to 1.5 times described above may be used to refer to the relationship between the absorption coefficient a of the UV absorber contained in one color of ink and the largest or smallest value of the absorption coefficients a of the colorants of the multiple colors.

[0061] In addition, components other than the colorant and UV absorber are usually selected to have a configuration (composition and / or ingredients) with an extremely small visible light absorption coefficient a so as not to affect the color of the ink. As a result, the UV absorption coefficient a of the other components is likely to be extremely small compared to the UV absorption coefficient a of the colorant. In other words, the other components are usually not considered to fit the above definition of a UV absorber.

[0062] The UV absorber may have any configuration (composition and / or components). For example, the UV absorber may be one used in cosmetics. Examples of such UV absorbers include dihydroxybenzophenone-based compounds, benzotriazole-based compounds, hydroxyphenyltriazine-based compounds, and cyanoacrylate-based compounds.

[0063] One color of ink may contain multiple types of UV absorbents. In this case, the above explanations of the absorption coefficient and the like may apply to the entire (average value) of the multiple UV absorbents. Similarly, for other explanations (for example, the explanation of the absorption peak wavelength, etc., described below), unless otherwise specified or unless a particular contradiction occurs, the UV absorbents contained in one color of ink may refer to the entire multiple types of UV absorbents. Of course, various explanations may be applied to each UV absorbent as long as a contradiction does not occur.

[0064] In an embodiment in which multiple ink colors contain a UV absorber, the types (compositions and / or components) of the UV absorbers may be the same or different from one another. In either case, the above explanation may be applied unless a contradiction arises. Furthermore, in multiple ink colors, the concentrations of the UV absorbers may be different from one another or the same from one another.

[0065] For example, an ink with a relatively high colorant extinction coefficient a or a' may have a lower concentration of UV absorber than other inks and / or may use a UV absorber with a lower extinction coefficient a than the UV absorbers in the other inks. Also, for example, an ink with a relatively high colorant extinction coefficient a or a' (e.g., black) may not contain a UV absorber.

[0066] (2.3. Transmittance and Density) As described above, the transmittance T may be referenced to a value at a reference wavelength. The reference wavelength may be, for example, the peak absorption wavelength of the UV absorbent contained in the ink. The peak absorption wavelength is, for example, a wavelength corresponding to a maximum value in a graph (not shown) with the UV wavelength on the horizontal axis and the absorption coefficient a or a' of the UV absorbent on the vertical axis. Note that if there are multiple maximum values, a rational decision may be made as to which maximum value is to be used as the peak absorption wavelength. For example, the wavelength closest to the peak wavelength of UV emitted by the irradiation unit 7A (peak emission wavelength, described below) may be selected as the peak absorption wavelength.

[0067] At the absorption peak wavelength, the effect of UV on heating the ink is large. Therefore, if T≧1.0% is satisfied at the absorption peak wavelength, there is a high probability that UV heating can occur in the lower surface portion of the ink 103. Furthermore, there is a high probability that the absorption peak wavelength is the wavelength at which the transmittance T is lowest. Therefore, it is difficult to satisfy T≧1.0%. In other words, by using the absorption peak wavelength as the reference wavelength, the requirements related to the ink are further limited so that the effects of the embodiment can be achieved.

[0068] Alternatively, the reference wavelength may be, for example, the wavelength at which the absorption coefficient a or a' of the UV absorbent is highest within a reference wavelength range including the wavelength of UV emitted by the irradiation unit 7A (for example, the peak emission wavelength described below) in the graph described above. In this case, the reference wavelength does not necessarily have to be a maximum value. The reference wavelength range may be, for example, the peak emission wavelength ±20 nm, 360 nm to 400 nm, or the UV-A wavelength range. With such a reference wavelength, it may be possible to expect the same effect as when the peak absorption wavelength is used as the reference wavelength.

[0069] Furthermore, for example, the reference wavelength may be the peak wavelength of UV light emitted by the irradiation unit 7 A (hereinafter referred to as the peak radiation wavelength). The peak radiation wavelength is, for example, a wavelength corresponding to the energy peak (maximum value) in the power spectrum of the UV light emitted by the irradiation unit 7 A. In this case, too, the value of transmittance T can be referenced, for example, at a wavelength at which the UV light has a large effect on heating the ink.

[0070] In practice, it is expected that the absorption peak wavelength and the emission peak wavelength will be close to each other, and therefore, regardless of which of the three reference wavelengths described above is selected, it is highly likely that the transmittance T will be substantially the same.

[0071] As described above, the requirement T≧1.0% may be determined for ink ejected at the upper limit when the amount of ink forming one dot on the medium 101 is changed depending on the image. More specifically, for example, when expressing the shading of an image, the amount of ink droplet forming one dot may be increased and / or the number of ink droplets forming one dot may be increased. In the latter case, the amount of ink forming one dot is the total amount of multiple ink droplets.

[0072] Typically, the above-mentioned upper limit value is set by the manufacturer of the discharge device 3. However, the user may be able to set the upper limit value by operating the discharge device 3. Alternatively, the controller 13 may set the upper limit value by performing a predetermined calculation based on predetermined information so that T≧1.0% (and / or other conditions) can be satisfied.

[0073] The upper limit value itself does not need to be specifically specified. When specifying the requirement T≧1.0%, it is sufficient to make it clear that the amount of ink is at the upper limit. Therefore, for example, whether the amount of ink is at the upper limit may be determined based on an electrical signal input to an actuator (e.g., a piezoelectric element or a heater) that applies pressure to the ink, and T that contributes to the success or failure of T≧1.0% may be specified based on this.

[0074] In cases where it is difficult to measure the transmittance T due to the small size of one dot, for example, a so-called solid image may be formed while setting the amount of ink to an upper limit value, and it may be determined whether T≧1.0% is satisfied for the ink in the solid image. A solid image used to measure the transmittance T is, for example, not simply one in which multiple dots are uniformly distributed on the medium 101, but one in which the ink is spread without gaps across multiple dot positions (positions where dots should be formed).

[0075] The amount of ink required to form a solid image without gaps can be easily calculated. For example, in the case of 1200 dpi (dots per inch), assuming that four dots form a square, the length of one side is approximately 21 μm (= 25.4 mm / 1200). For example, if the amount of ink droplets is 2 pL, the ink can fill the square with a thickness of approximately 5 μm. In other words, a solid image without gaps can be formed with an ink thickness of approximately 5 μm.

[0076] The transmittance T of a solid image may be measured for an area of ​​any size within the solid image. This is because a solid image is basically a solid image in which ink is distributed uniformly. However, the thickness of the ink may differ between adjacent dots. Therefore, for example, the transmittance T may be measured for an area including multiple dots (e.g., 100 or more).

[0077] In the above description, it is assumed that the upper limit of the ink amount is an amount that allows a solid image in which the ink spreads without gaps to be formed. However, unlike the description here, the upper limit does not have to be such an amount. Furthermore, in the description of the embodiment, the transmittance T when the ink amount is at the upper limit is taken up, but when determining whether T≧1.0% is satisfied for a solid image in which the ink spreads without gaps, the solid image may be formed with an amount of ink less than the upper limit. The mass of ink per unit area in a solid image before drying is arbitrary, and may be, for example, 2.0 g / m ２ That's all.

[0078] In a case where the ejection device 3 is configured to eject ink of multiple colors, as already mentioned, T≧1.0% may be satisfied for only one of the colors. Furthermore, for example, when the transmittance T of each color of ink is examined, T≧1.0% may be satisfied for only some of the multiple colors of ink (for example, only one, two, or three of four colors), or T≧1.0% may be satisfied for all colors.

[0079] The upper limit values ​​of the ink amounts required to form one dot for the multiple colors of ink may be the same or different. In either case, when examining the transmittance T for each color of ink, the upper limit value for that ink may be used. As already mentioned, the types of UV absorbents contained in the multiple colors of ink may be the same or different. In either case, when using the absorption peak wavelength or the like for each color of ink, the absorption peak wavelength or the like of the UV absorbent of that ink may be used.

[0080] The inks of multiple colors may include inks that do not contain a UV absorbent (e.g., black). In this case, the absorption peak wavelength, etc., of ink of any other color may be used as the absorption peak wavelength, etc., when examining the transmittance T of the ink that does not contain a UV absorbent. In practice, since the absorption peak wavelength and the emission peak wavelength of ink of other colors are expected to be close values, even if the absorption peak wavelength of ink of other colors is used, the transmittance T can be examined at a wavelength that has a large effect on heating.

[0081] So far, we have discussed whether T≧1.0% is satisfied for each color of ink. However, when one dot (the same dot) is formed using two or more colors of ink, and each dot is a color different from the colors of the inks, T≧1.0% may be satisfied for all of the two or more colors of ink.

[0082] The maximum total amount of ink of two or more colors forming one dot may be smaller than, equal to, or larger than the upper limit when one dot is formed using only each ink. When the maximum amount is equal to or smaller than the upper limit, if T≧1.0% for each color, then T≧1.0% for the two or more ink colors as a whole is also usually the case.

[0083] If the maximum value of the above total is greater than the upper limit of each color, T≧1.0% may be satisfied for the two or more ink colors as a whole (not for each of the two or more ink colors individually) at that maximum value. Also, when a combination of ink colors (and its maximum value) that results in the smallest transmittance T is selected from multiple ink colors, T≧1.0% may be satisfied (but does not have to be satisfied).

[0084] Even when the transmittance T is checked for the entire ink of two or more colors, the transmittance T may be checked for the solid image described above, rather than for each dot.

[0085] The transmittance T may be set to a condition stricter than T≧1.0%. For example, the transmittance T may be set to 2.0% or more, 3.5% or more, or 5.0% or more. Furthermore, from the viewpoint of allowing UV to reach the lower surface portion of the ink, the upper limit of the transmittance T is not particularly limited. However, if the transmittance T is too high, this goes against the purpose of absorbing UV into the ink and increasing the ink temperature. Therefore, for example, the transmittance T may be set to 50% or less, 20% or less, 10% or less, or 5% or less. These upper limits and the lower limit of the transmittance T described above may be arbitrarily combined as long as no contradiction occurs.

[0086] The concentration c of the UV absorber may be set to a condition stricter than c≦1.6 mass%. For example, the concentration c may be set to 1.4 mass% or less, 0.8 mass% or less, or 0.5 mass% or less. Furthermore, from the viewpoint of allowing UV to reach the lower surface portion of the ink, the lower limit of the concentration c is not particularly limited. However, if the concentration c is too low, this goes against the purpose of absorbing UV into the ink and increasing the ink temperature. Therefore, for example, the concentration c may be set to 0.1 mass% or more, 0.3 mass% or more, or 0.5 mass% or more. These lower limit values ​​and the above-mentioned upper limit values ​​may be arbitrarily combined as long as no contradiction occurs.

[0087] As already mentioned, measures 1 and 2 may be combined. Furthermore, the lower limit value and / or the upper limit value of the transmittance T and the upper limit value and / or the lower limit value of the concentration c may be combined in any combination as long as no contradiction occurs.

[0088] (3. Examples and Comparative Examples) The inventors of the present application formed solid images using a plurality of inks with different UV absorber concentrations c, and examined the ink transmittance T, drying properties, and fixability. As a result, they found that the drying properties and fixability could be improved by setting the concentration c to 1.6% by mass or less and the transmittance T to 1.0% or more. Specifically, the findings are as follows.

[0089] The transmittance T was measured as follows. A solid image in which ink spread without gaps was formed on the front surface of a light-transmitting recording medium by inkjet printing. The solid image was irradiated with UV light by an irradiation unit arranged on the front surface side of the recording medium. The intensity of the UV light transmitted through the solid image (and the recording medium) was measured by a spectrophotometer arranged on the back side of the recording medium. The transmittance T was determined based on the measurement results.

[0090] The drying property was evaluated as follows: The dried solid image was manually rubbed against a piece of white paper. The white paper was then visually inspected to determine whether it fell into one of the following three categories: A: No color transfer at all; B: Light color transfer was observed; C: Dark color transfer was observed.

[0091] The fixation was evaluated as follows: A commercially available cellophane tape (25 mm wide) was attached to the dried solid image, pressed firmly, and then quickly peeled off by hand. At this time, the cellophane tape was pulled so that the peeled cellophane tape was perpendicular to the solid image. The solid image was then visually observed for peeling, and judged to fall into one of the following three categories: A: No image peeling at all; B: Slight image peeling observed; C: Image peeling observed.

[0092] The specific conditions for the experiment were as follows: Ink: Water-soluble ink containing pigment and fixative polymer; Pigment color: cyan; Tg of fixative polymer: 70°C to 120°C; UV absorber: Composition: Benzophenone-based compound; Absorption coefficient a: At the peak absorption wavelength and peak emission wavelength, lower than the absorption coefficient a of the black pigment and higher than the absorption coefficient a of the magenta, yellow, and cyan pigments; Peak absorption wavelength: 360 nm to 400 nm; Concentration c: 0.4% to 5.0% by mass; Ink thickness on recording medium: Approximately 5 μm (before UV irradiation); UV: Wavelength: UV-A wavelength (peak emission wavelength is 368 nm); Illuminance: 2000 mW / cm ２ ~3000mW / cm ２ Irradiation time: 0.3 seconds. Recording medium: Material: polyethylene terephthalate (PET). Thickness: 2 μm. Spectrophotometer: Light received through an aperture with a diameter of 10 mm (UV irradiation area is wider than this).

[0093] Figure 3 is a chart showing the experimental results. For reference, the chart also shows the results for ink that does not contain UV-absorbing additives (pigments and UV absorbers). As shown in the chart, when the concentration c of the UV absorber is 1.6% by mass or less, the transmittance T is 1.0% or more. Furthermore, both the drying speed and fixability are evaluated as A.

[0094] Here, attention is focused only on the upper limit of density c and / or the lower limit of transmittance T. However, if density c is too low (if transmittance T is too high), the ink will not be heated by UV, and both the drying property and the fixability will be evaluated as C. From this perspective, the lower limit of density c and / or the upper limit of transmittance T may be set from the value or range of density c or transmittance T that results in an evaluation of A in FIG. 3. For example, 0.4% by mass or 1.0% by mass may be selected as the lower limit of density c. Just to be clear, the lower limit of density c may be a value smaller than the value shown in FIG. 3 (for example, 0.3% by mass).

[0095] The ink used in the experiment will not essentially be fixed to the recording medium unless its temperature is higher than the Tg of the fixative polymer. Furthermore, the Tg is set to 70°C or higher, which is relatively high. Therefore, compared to when other inks are used, the upper limit of density c and / or the lower limit of transmittance T described above can be considered to be stricter (narrowing the allowable range). In other words, the upper limit of density c and / or the lower limit of transmittance T described above may be applied to other inks.

[0096] Furthermore, as can be seen from the above, the ink used in the experiment does not essentially fix to the recording medium even when left at room temperature, so the influence of the work process from UV irradiation to the evaluation of drying and fixation properties on the evaluation is small.

[0097] The UV irradiation time in the experiment was calculated to be sufficient for the ink to be fixed to the recording medium, assuming that the entire thickness of the ink absorbs UV evenly and generates heat. Therefore, it can be considered that the influence of the irradiation time on the evaluation results was small. In other words, the upper limit value of the density c and / or the lower limit value of the transmittance T described above may be applied to various irradiation times.

[0098] (4. Summary of the embodiment) As described above, from the viewpoint of Measure 1, the printing method according to the embodiment includes ejecting one or more types of ink toward a medium 101 (an example of a printing medium) and irradiating the one or more types of ink on the medium 101 with UV light. The one or more types of ink include a first ink that contains a UV absorbent. When ejecting the ink, the amount of each type of ink corresponding to one dot is changed within a range equal to or less than a predetermined upper limit value depending on the content of the image. The first ink has a UV transmittance T of 1.0% or more in the thickness direction when ejected at the upper limit value and positioned on the medium 101 immediately before being irradiated with UV light.

[0099] Furthermore, from the perspective of Measure 1, the printer 1 (an example of a recording device) according to the embodiment includes a discharge device 3 and an irradiation unit 7A (an example of an irradiation device). The discharge device 3 discharges ink containing a UV absorbent toward a medium 101 (a recording medium). The irradiation unit 7A irradiates the ink on the medium 101 with UV. The discharge device 3 varies the amount of ink corresponding to one dot within a range equal to or less than a predetermined upper limit value, depending on the content of the image. In the discharge device 3, the upper limit value is set so that the UV transmittance T in the thickness direction of the ink when discharged at the upper limit value and positioned on the medium 101 immediately before being irradiated with UV is 1.0% or greater.

[0100] Therefore, as described in the overview of the embodiment, UV can reach the lower surface portion of the ink, and as a result, the lower surface portion can be directly heated by UV, thereby improving the fixability of the ink.

[0101] The one or more types of ink may include multiple types (e.g., multiple colors) of ink (other than the first ink, inks may not necessarily contain a UV absorbent.) Each of all types of ink may have a UV transmittance of 1.0% or more in the thickness direction when ejected at its upper limit and positioned on the medium 101 immediately before UV irradiation.

[0102] In this case, for example, even in dots (or areas) where inks of multiple colors overlap, UV can reach the underside of the ink, and as a result, the above-mentioned effects can also be achieved in color images.

[0103] The ink may be ejected in such a manner that the first ink can form a solid image that spreads without gaps on the medium 101. The solid image may have a UV transmittance of 1.0% or more in the thickness direction immediately before being irradiated with UV light.

[0104] In this case, for example, UV reaches the lower surface portion of the ink stably over a relatively wide area including a plurality of dots, thereby improving the above-mentioned effect.

[0105] The first ink may have a UV absorbent concentration of 1.6% by mass or less when ejected.

[0106] In this case, for example, it becomes easier to achieve T≧1.0%. From another perspective, the degree of freedom in setting the upper limit of the amount of ink increases.

[0107] From the viewpoint of Measure 2, the recording method according to the embodiment includes ejecting ink containing a UV absorbent onto a medium 101 (an example of a recording medium) and irradiating the ink on the medium 101 with UV rays. The ink has a UV absorbent concentration of 1.6% by mass or less when ejected.

[0108] Furthermore, from the viewpoint of Measure 2, the printer 1 (an example of a recording device) according to the embodiment includes a discharge device 3 and an irradiation unit 7A (an example of an irradiation device). The discharge device 3 discharges ink containing a UV absorbent toward a medium 101 (a recording medium). The discharge device 3 discharges ink having a UV absorbent concentration of 1.6% by mass or less.

[0109] Therefore, for example, the probability that T≧1.0% can be achieved increases, and the effect of T≧1.0% can be achieved. Even if T≧1.0% cannot be achieved, the probability that UV reaches the bottom surface of the ink or a position close to the bottom surface increases, reducing the probability that fixability will decrease.

[0110] When ejecting ink, the amount of ink corresponding to one dot may be changed within a range equal to or less than a predetermined upper limit depending on the content of the image. When a solid image is formed at the upper limit, the mass of ink per unit area on the medium 101 is calculated based on the density of the ink at the time of ejection and is 2.0 g / m. ２ It may be more than that.

[0111] In this case, for example, the mass of the ink per unit area is relatively large, and as a result, for example, the effect of setting the concentration of the UV absorber to 1.6 mass % or less can be easily achieved.

[0112] In the recording method, UV may be irradiated onto the ink before 1.0 second has elapsed since the ink landed on the medium 101 .

[0113] In this case, for example, UV heating can be started earlier. UV heating can raise the ink temperature in a shorter time than heating with hot air. Therefore, the time (or, from another perspective, the distance) it takes for the ink temperature to rise to the desired temperature after impact can be shortened. As a result, for example, the printer 1 can be made more compact.

[0114] The technology according to the present disclosure is not limited to the above-described embodiments and may be implemented in various forms.

[0115] For example, the recording device is not limited to those generally classified as printers. For example, the recording device may be a plotter. Furthermore, for example, the media is not limited to paper or film. For example, the media may be cut cloth, wood, or tiles transported by a transport device including a belt conveyor.

[0116] The following concepts can be extracted from the present disclosure. (Concept 1) A recording method comprising: ejecting one or more types of ink toward a recording medium; and irradiating the one or more types of ink on the recording medium with ultraviolet light, wherein the one or more types of ink include a first ink containing an ultraviolet absorber, and during the ejection of the ink, the amount of each type of ink corresponding to one dot is changed within a range not exceeding a predetermined upper limit value according to the content of the image, and the first ink has an ultraviolet light transmittance of 1.0% or more in the thickness direction when ejected at the upper limit value and positioned on the recording medium and immediately before being irradiated with ultraviolet light. (Concept 2) The one or more types of ink include a plurality of types of ink, and each of all types of ink has an ultraviolet light transmittance of 1.0% or more in the thickness direction when ejected at the upper limit value and positioned on the recording medium and immediately before being irradiated with ultraviolet light. The recording method according to Concept 1. (Concept 3) The recording method according to Concept 1 or 2, wherein the ejection of the inks enables the first ink to form a solid image that spreads without gaps on the recording medium, and the solid image has an ultraviolet transmittance of 1.0% or more in the thickness direction immediately before being irradiated with ultraviolet light. (Concept 4) The recording method according to any one of Concepts 1 to 3, wherein the first ink has an ultraviolet absorber concentration of 1.6% by mass or less at the time of ejection. (Concept 5) A recording method comprising: ejecting one or more types of ink toward a recording medium; and irradiating the one or more types of ink on the recording medium with ultraviolet light, wherein the one or more types of ink include a first ink that contains an ultraviolet absorber, and the first ink has an ultraviolet absorber concentration of 1.6% by mass or less at the time of ejection. (Concept 6) The one or more types of ink include multiple types of ink, and the ultraviolet absorber concentration of all of the inks at the time of ejection is 1.6% by mass or less (the inks other than the first ink may be 0% by mass).(Concept 7) When ejecting the ink, the amount of each type of ink corresponding to one dot is changed within a range equal to or less than a predetermined upper limit value depending on the content of the image, and when a solid image is formed at the upper limit value, the mass per unit area of ​​the first ink on the recording medium is 2.0 g / m, calculated using the density of the first ink at the time of ejection. ２The recording method according to any one of Concepts 1 to 6. (Concept 8) The recording method according to any one of Concepts 1 to 7, wherein the ultraviolet light is irradiated onto the ink before 1.0 second has elapsed since the ink landed on the recording medium. (Concept 9) A recording device comprising: a discharge device that discharges one or more types of ink including a first ink containing an ultraviolet absorber toward a recording medium; and an irradiation device that irradiates the one or more types of ink on the recording medium with ultraviolet light, wherein the discharge device changes the amount of each type of ink corresponding to one dot within a range equal to or less than a predetermined upper limit value according to image content, and the upper limit value in the discharge device is set so that the ultraviolet light transmittance in the thickness direction of the first ink in a state where the first ink is discharged at the upper limit value and positioned on the recording medium and immediately before being irradiated with the ultraviolet light is 1.0% or more. (Concept 10) The ejection device ejects a plurality of types of the ink, and in the ejection device, the upper limit values ​​for all types of the ink are set so that the ultraviolet transmittance in the thickness direction of each ink is 1.0% or more when the ink is ejected at the upper limit value and positioned on the recording medium and immediately before being irradiated with the ultraviolet rays. The recording device according to Concept 9. (Concept 11) The recording device according to Concept 9 or 10, wherein the ejection device is capable of forming a solid image in which the first ink spreads without gaps on the recording medium, and in a state immediately before being irradiated with the ultraviolet rays, the solid image having an ultraviolet transmittance of 1.0% or more in the thickness direction. (Concept 12) The recording device according to any one of Concepts 9 to 11, wherein the ejection device ejects the first ink having an ultraviolet absorber concentration of 1.6% by mass or less. (Concept 13) A recording apparatus comprising: a discharge device that discharges one or more types of ink, including a first ink containing an ultraviolet absorber, onto a recording medium; and an irradiation device that irradiates the one or more types of ink on the recording medium with ultraviolet light, wherein the discharge device discharges the first ink, the concentration of the ultraviolet absorber being 1.6% by mass or less. (Concept 14) The discharge device discharges multiple types of ink, the concentration of the ultraviolet absorber being 1.6% by mass or less when discharged (the inks other than the first ink may have a concentration of 0% by mass).) The recording device according to Concept 12 or 13. (Concept 15) The ejection device changes the amount of each type of ink corresponding to one dot within a range equal to or less than a predetermined upper limit value according to the content of an image, and in the ejection device, the upper limit value is set so that when a solid image is formed at the upper limit value, the mass per unit area of ​​the first ink on the recording medium is 2.0 g / m, calculated using the density of the first ink at the time of ejection. ２ The recording device according to any one of Concepts 9 to 14, wherein the irradiation device irradiates the ink with ultraviolet light before 1.0 second has elapsed since the ink landed on the recording medium. (Concept 16) The recording device according to any one of Concepts 9 to 15, wherein the irradiation device irradiates the ink with ultraviolet light before 1.0 second has elapsed since the ink landed on the recording medium.

[0117] 1... printer (recording device), 3... ejection device, 5... drying device, 7A... irradiation section (irradiation device), 101... medium (recording medium), 103... ink.

Claims

ejecting one or more inks onto a recording medium; and irradiating the one or more inks on the recording medium with ultraviolet light; Including, the one or more inks include a first ink containing an ultraviolet absorber; In the ejection of the ink, the amount of each type of ink corresponding to one dot is changed within a range not exceeding a predetermined upper limit value according to the content of the image, The first ink has a transmittance of 1.0% or more to ultraviolet light in a thickness direction when the first ink is ejected at the upper limit value and positioned on the recording medium and immediately before being irradiated with ultraviolet light. Recording method. 　 the one or more types of ink include a plurality of types of ink, Each of the inks of all types has a transmittance of ultraviolet light in the thickness direction of 1.0% or more when the ink is ejected at the upper limit value and positioned on the recording medium and immediately before being irradiated with ultraviolet light. The recording method according to claim 1 . 　 When the ink is ejected, the first ink can form a solid image that spreads without gaps on the recording medium, The solid image has an ultraviolet transmittance of 1.0% or more in the thickness direction immediately before being irradiated with ultraviolet rays.

3. The recording method according to claim 1 or 2. 　 The first ink has a concentration of the ultraviolet absorber of 1.6% by mass or less when ejected. The recording method according to any one of claims 1 to 3. 　 Discharging ink containing an ultraviolet absorber onto a recording medium; and Irradiating the ink on the recording medium with ultraviolet light; Including, The ink has a concentration of the ultraviolet absorber of 1.6% by mass or less when ejected. Recording method. 　 In the ejection of the ink, the amount of the ink corresponding to one dot is changed within a range equal to or less than a predetermined upper limit value according to the content of the image, When a solid image is formed at the upper limit value, the mass of the ink per unit area on the recording medium is 2.0 g / m, calculated based on the density of the ink at the time of ejection. ２ That's all The recording method according to any one of claims 1 to 5. 　 The ultraviolet light is irradiated onto the ink before 1.0 second has elapsed since the ink landed on the recording medium. 　 The recording method according to any one of claims 1 to 6. 　 a discharge device that discharges ink containing an ultraviolet absorbent toward a recording medium; an irradiation device that irradiates the ink on the recording medium with ultraviolet light; It has the ejection device varies the amount of ink corresponding to one dot within a range equal to or less than a predetermined upper limit value according to the content of the image; In the ejection device, the upper limit value is set so that the ultraviolet transmittance in the thickness direction of the ink in a state where the ink is ejected at the upper limit value and positioned on the recording medium and immediately before being irradiated with the ultraviolet rays is 1.0% or more. Recording device. 　 a discharge device that discharges ink containing an ultraviolet absorbent toward a recording medium; an irradiation device that irradiates the ink on the recording medium with ultraviolet light; It has The ejection device ejects the ink in which the concentration of the ultraviolet absorber is 1.6% by mass or less. Recording device.

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