Ink set, printing device and printing method

Abstract

This ink comprises a medium, a coloring agent, a fixing agent polymer, and one or more polymers other than the fixing agent polymer. The coloring agent is dissolved in the medium or dispersed in the medium. The fixing agent polymer has a glass transition temperature Tg that is higher than the room temperature, and is dispersed in the medium. The one or more polymers other than the fixing agent polymer have Tg that are higher than the room temperature, and are dissolved in the medium or dispersed in the medium. The Tg of the fixing agent polymer is higher than the Tg of 80% by mass or more of polymers among all polymers other than the fixing agent polymer contained in this ink, said polymers having Tg that are higher than the room temperature.

Description

[Technical Field]

[0001] The present disclosure relates to inks, ink sets, and printing devices. [Background technology]

[0002] Known inks include a polymer in addition to a medium (e.g., a solvent) and a colorant (see, for example, Patent Document 1 below). Patent Document 1 discloses an ink that includes a pigment dispersing polymer for dispersing the pigment and a fixing aid polymer for improving the scratch resistance of printed matter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 138436 Summary of the Invention

[0004] An ink according to one embodiment of the present disclosure includes a medium, a colorant, a fixer polymer, and one or more polymers other than the fixer polymer. The colorant is dissolved in the medium or dispersed in the medium. The fixer polymer has a glass transition temperature higher than room temperature and is dispersed in the medium. The one or more polymers have a glass transition temperature higher than room temperature and are dissolved in the medium or dispersed in the medium. The glass transition temperature of the fixer polymer is higher than the glass transition temperature of 80% or more by mass of all polymers other than the fixer polymer contained in the ink that have glass transition temperatures higher than room temperature.

[0005] An ink set according to one embodiment of the present disclosure includes two inks, each of which is the ink described above and which contain different colorants. At least one of the two inks contains an ultraviolet absorber different from the colorant. The two inks have different contents of the ultraviolet absorber.

[0006] A printing apparatus according to one aspect of the present disclosure includes an ink ejection device, a drying device, and a melting device. The ink ejection device applies the ink to a substrate. The drying device heats the substrate to promote evaporation of the medium. The melting device heats the ink applied to the substrate to melt the fixative polymer, thereby fixing the ink to the substrate. A printing method according to one aspect of the present disclosure includes an ink ejection step, a drying step, and a melting step. The ink ejection step deposits the ink on a substrate. The drying step heats the substrate to promote evaporation of the medium. The melting step heats the ink attached to the substrate to melt the fixative polymer, thereby fixing the ink to the substrate. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a side view of a printing device according to a first embodiment. [Figure 2] FIG. 2 is a plan view of the printing device of FIG. [Figure 3A] FIG. 2 is a perspective view of the inkjet head of the printing device of FIG. 1, seen from above. [Figure 3B] FIG. 3B is a perspective view of the inkjet head of FIG. 3A as seen from below. [Figure 3C] FIG. 3B is a perspective view of a part (head main body) of the inkjet head of FIG. 3A as viewed from above. [Figure 3D] FIG. 3D is an enlarged view of region IIId in FIG. 3C. [Figure 4] 2 is a block diagram showing the configuration of a signal processing system of the printing device of FIG. 1. FIG. [Figure 5] FIG. 2 is a conceptual diagram illustrating a method for fixing ink in the printing apparatus of FIG. [Figure 6] FIG. 10 is a diagram showing the results of calculations of the time required for the ink medium to evaporate. [Figure 7] FIG. 2 is a diagram showing the results of calculations of the temperature distribution of the printing medium in the printing device of FIG. [Figure 8A] FIG. 10 is a diagram illustrating the results of calculations of temperature changes in resin heated by UV rays. [Figure 8B] FIG. 8B is a diagram illustrating the results of calculations of the temperature change of the water containing the resin of FIG. 8A. [Figure 9] FIG. 10 is a side view of a printing apparatus according to a second embodiment. [Figure 10] FIG. 10 is a side view of a printing device according to a third embodiment. [Figure 11] FIG. 10 is a side view of a printing device according to a fourth embodiment. [Figure 12A] FIG. 2 is a schematic diagram showing an example of light absorption characteristics of inks of different colors. [Figure 12B] 10A and 10B are schematic diagrams illustrating ink sets according to modified examples. [Figure 13A] FIG. 2 is a schematic diagram showing an example of light absorption characteristics of a UV absorbent. [Figure 13B] 10A and 10B are schematic diagrams illustrating an example of light absorption characteristics of ink according to a modified example. [Figure 14] 1A to 1C are diagrams illustrating a method for producing a polymer contained in the ink according to an embodiment. [Figure 15] 1A to 1C are diagrams illustrating a method for producing a dispersion system contained in the ink according to the embodiment. [Figure 16] 1A to 1C are diagrams illustrating a method for producing ink according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the drawings are schematic. Therefore, details may be omitted. Furthermore, the dimensional ratios do not necessarily correspond to the actual ones. The dimensional ratios between the drawings do not necessarily correspond to each other. Certain dimensions may be shown larger than they actually are, and certain shapes may be exaggerated.

[0009] In the explanations of the second and subsequent embodiments, differences from the previously described embodiments will be described. Matters not specifically mentioned may be considered to be the same as or may be inferred from the previously described embodiments. Furthermore, among multiple embodiments, corresponding configurations may be assigned the same reference numerals even if the details are different.

[0010] The "medium" may be, for example, a "solvent" (or "solvent") that dissolves other substances (solutes), or a "dispersion medium" that disperses other substances (dispersoids). The term "dispersion medium" is generally used in the narrow sense to refer to a medium in which particles (dispersoids) having a certain size (for example, particle size of 1 nm or more) are dispersed, or in the broad sense to include solvents in addition to the dispersion medium in the narrow sense. In the present disclosure, the term is used in the narrow sense.

[0011] As is well known, "particles" as dispersoids are not limited to solids and may be liquids or gases. However, in this disclosure, when simply referring to "particles," unless otherwise specified, it refers to solid particles, not particles as dispersoids.

[0012] The term "glass" is generally used in a narrow sense to refer to, for example, a substance primarily composed of silicate, or in a broad sense to refer to a substance that becomes an amorphous solid exhibiting a glass transition phenomenon upon heating. In the present disclosure, the term is used in the broad sense. Therefore, when referring to glass or glass component in the present disclosure, these are not limited to those primarily composed of silicate, but may also be, for example, those primarily composed of a polymer.

[0013] As is well known, the "glass transition temperature" (glass transition point) is the temperature at which a glass transition occurs. Hereinafter, the glass transition temperature may be abbreviated as "Tg." Tg may be measured in accordance with standards such as JIS (Japanese Industrial Standards) K7121. When more strictness is required, Tg may be, for example, the midpoint glass transition temperature among the extrapolated glass transition onset temperature, midpoint glass transition temperature, and extrapolated glass transition end temperature defined in the above standards. However, when a state below Tg is maintained, the extrapolated glass transition onset temperature may be referenced, and when a state above Tg is maintained, the extrapolated glass transition end temperature may be referenced.

[0014] "Color difference" is defined in "7.1.1 L" of JIS Z8730 (now abolished). * a * b *It may be calculated using the formula specified in "Color Differences According to Color Spaces."

[0015] "Normal temperature" (room temperature) may be, for example, 20±15°C as specified in JIS Z8703. When more strictness is required, normal temperature may be, for example, 20°C.

[0016] First Embodiment (Overall configuration of the printing device) Fig. 1 is a side view of a printing apparatus 1 according to a first embodiment of the present disclosure, and Fig. 2 is a plan view of the printing apparatus 1.

[0017] For convenience, these figures are shown with a Cartesian coordinate system D1-D2-D3 fixed in space. The printing device 1 can be configured so that any direction is the vertical direction, but for convenience, the +D3 side is considered to be vertically upward. Unless otherwise specified, the terms planar view and planar perspective refer to a view along the D3 axis.

[0018] The printing device 1, for example, transports the printing substrate 101 from a supply roller 3A to a collection roller 3B. The supply roller 3A, the collection roller 3B, and various other rollers described below constitute a transport device 5 that transports the printing substrate 101. The printing device 1 has various devices along the transport path of the printing substrate 101. For example, the printing device 1 has an ink discharge device 7 that discharges ink droplets toward the printing substrate 101, and multiple devices (e.g., 9, 11, and 13) that promote the fixation of ink discharged by the ink discharge device 7 and landing on the printing substrate 101 to the printing substrate 101. The printing device 1 also has a control device 15 (FIG. 1) that controls the various devices described above.

[0019] The printing device 1 may have a configuration other than that described above. For example, the printing device 1 may have an applicator (not shown) that uniformly applies a coating agent (described later) to the printing substrate 101 between the supply roller 3A and the ink ejection device 7. Furthermore, for example, the printing device 1 may have a cleaning unit that cleans the head 21 (described later) of the ink ejection device 7.

[0020] (Printing material) The printing substrate 101 is, for example, long and sheet-like. Before printing, the printing substrate 101 is wound around the supply roller 3A. The printing substrate 101 is fed from the supply roller 3A, passes below the ink ejection device 7, and is wound around the recovery roller 3B and recovered. The dimensions of the printing substrate 101, such as its material, width, length, and thickness, may be set as appropriate. For example, the material of the printing substrate 101 may be paper, resin, or cloth. The thickness of the resin (e.g., PET: polyethylene terephthalate) film serving as the printing substrate 101 may be set as appropriate. An example of the thickness range is 5 μm or more and 20 μm or less. In the following description, the surface of the printing substrate 101 to which ink is applied may be referred to as the front surface, and the opposite surface may be referred to as the back surface.

[0021] (ink) Before being ejected by the ink ejection device 7, the ink contains, for example, a medium (solvent and / or dispersion medium), a colorant, and multiple types of polymers. The multiple types of polymers include at least a fixer polymer. After the ink is ejected and lands on the printing substrate 101, the medium in the ink evaporates. Furthermore, the fixer polymer melts (for example, becomes glassy) when heated, and then solidifies. Through these actions, the colorant is fixed to the printing substrate 101.

[0022] As can be understood from the above description, the ink of this embodiment is not, for example, a UV-curable ink. UV-curable ink contains a synthetic resin (i.e., a UV-curable resin) that chemically changes from a liquid to a solid in response to ultraviolet energy, and is fixed to the printing substrate 101 by the curing action of the UV-curable resin. The ink of this embodiment does not substantially contain such a UV-curable resin (polymer). However, the ink of this embodiment may contain a quantity of UV-curable resin that does not qualify as UV-curable ink.

[0023] The medium is, for example, the component with the highest mass % of the components contained in the ink (before ejection). The mass % of the ink that the medium accounts for may be set appropriately and may be less than 50 mass % or greater than 50 mass %, for example, 50 mass % to 90 mass %. The medium may be water or an aqueous solvent, an organic substance (e.g., an organic solvent), or a mixture of the former and the latter. In the description of this embodiment, a case where the medium contains water and an organic solvent (organic solvent) may be taken as an example. When the medium contains at least water, the mass % of the ink that water accounts for may be less than 50 mass % or greater than 50 mass %, for example, 50 mass % to 70 mass %.

[0024] When describing the components of the completed ink, the mass % refers to the state before ejection (before the medium and the like evaporates) unless otherwise specified.

[0025] When the medium contains water and an organic solvent, the components and functions of the organic solvent may be appropriately set. For example, the organic solvent may contain an alcohol (e.g., glycerin or glycol) and / or an ether (e.g., glycol ether). The alcohol functions, for example, as a humectant that reduces drying of the ink before ejection. The ether contributes, for example, to adjusting the surface tension, viscosity, and / or drying speed of the ink. The mass ratio of water to the organic solvent may be appropriately set, and one mass % may be greater than the other mass %. For example, the mass % of water may be greater than the mass % of the organic solvent. More specifically, the mass % of water in the medium may be 60 mass % or more and 70 mass % or less.

[0026] The colorant may be a pigment that is insoluble in the medium, a dye that is soluble in the medium (solvent), or a combination of both. Various known pigments and dyes, as well as applications thereof, may be used. For example, the pigment may be surface-coated to prevent aggregation (so-called self-dispersing pigments), or may not be coated. The mass percentage of the colorant in the ink before ejection (before ejection) may be set appropriately. An example of the mass percentage range is 1 mass% to 10 mass%.

[0027] The multiple polymers may include, for example, two or more polymers having a glass transition temperature (Tg) higher than room temperature. These two or more polymers include the fixing agent polymer described above. The ink may or may not include a polymer having a Tg lower than room temperature.

[0028] (fixing agent polymer) As described above, the fixer polymer is melted by heating. In other words, the fixer polymer exists as particles (solid) in the ink before heating (e.g., before the ink is ejected). Therefore, the fixer polymer does not dissolve in the medium (e.g., water solubility) but is dispersed in the medium, and has a glass transition temperature (Tg) higher than the temperature of the ink before heating (e.g., room temperature and / or the temperature of the ink before ejection). Furthermore, the fixer polymer has the property of remaining as a solid component to fix the colorant even after the ink is heated. Note that the fixer polymer may perform functions other than fixing the colorant.

[0029] The Tg of the fixer polymer may be set relatively high compared to the Tg of other polymers in the ink. For example, the Tg of the fixer polymer may be higher than the Tg of most (or all) of all polymers contained in the ink that have a Tg higher than room temperature, other than the fixer polymer. The above "most (or all)" may be, for example, 80% by mass or more, 90% by mass or more, or 95% by mass or more, or may be 100% by mass. In the case of 100% by mass, from another perspective, the Tg of the fixer polymer is higher than the Tg of all polymers contained in the ink other than the fixer polymer. The above "most (or all) polymers" may include only one type of polymer, or may include two or more types of polymers.

[0030] The specific value of the Tg of the fixing agent polymer may be set as appropriate. An example of the range of the Tg of the fixing agent polymer is 70°C or higher and 120°C or lower (or 110°C or lower). An example of the range of the difference between the Tg of the fixing agent polymer and the Tg of the "majority (or all) of the polymer" is 40°C or higher and 60°C or lower.

[0031] For example, suppose it is stated that the Tg of a fixative polymer is higher than the Tg of 80% or more by weight of all polymers other than the fixative polymer that have a Tg higher than room temperature, and then, based on this premise, it is stated that the difference between the Tg of the fixative polymer and the Tg of the 80% or more by weight of the polymers is 40°C or more and 60°C or less. In this case, the specific value of the former 80% or more by weight may be different from the specific value of the latter 80% or more by weight. For example, if the Tg of the fixative polymer is higher than the Tg of 90% by weight of all polymers other than the fixative polymer that have a Tg higher than room temperature, only a portion of the 90% by weight of the polymers may have a difference of 40°C or more and 60°C or less from the Tg of the fixative polymer (for example, only 80% by weight of all polymers other than the fixative polymer that have a Tg higher than room temperature). The same applies when other conditions are added to the 80% by weight or more (or other value by weight %) of the polymers.

[0032] The mass % of the fixer polymer in the ink may be set as appropriate. For example, with respect to the mass % of the ink, the mass % of the fixer polymer may be smaller, equal to, or larger than the mass % of any type of polymer, the total mass % of all polymers other than the fixer polymer that have a Tg higher than room temperature, or the total mass % of all polymers other than the fixer polymer. For example, the mass % of the fixer polymer may be 0.1 times or more, 0.3 times or more, or 0.5 times or more the total mass % of all polymers other than the fixer polymer that have a Tg higher than room temperature. An example of the mass % range of the fixer polymer is 1% by mass or more and 40% by mass or less.

[0033] The specific composition and / or components of the fixative polymer may be selected as appropriate. For example, the fixative polymer may be a condensation polymer (e.g., a polyurethane polymer or a polyester polymer), an acrylic polymer, a styrene polymer, a styrene-acrylic polymer, a butadiene polymer, a styrene-butadiene polymer, a vinyl chloride polymer, or a methacrylic acid polymer. Some of the above may be considered vinyl polymers. The Tg of these polymers may be, for example, in the above-mentioned range of 70°C or higher and 120°C or lower.

[0034] The fixative polymer may be produced by combining two or more monomers from among the monomers that form the main components of the various polymers described above (for example, styrene is the main component monomer of a styrene-based polymer). In other words, the fixative polymer may be produced by combining monomers that form polymers with different Tg's. In this case, the Tg of the fixative polymer can be increased by relatively increasing the mass % of the monomer that forms a polymer with a relatively high Tg. Conversely, the Tg of the fixative polymer can be decreased by relatively increasing the mass % of the monomer that forms a polymer with a relatively low Tg. In other words, the Tg of the fixative polymer can be adjusted as desired.

[0035] (other polymers) The properties and roles of other polymers contained in the ink other than the fixative polymer may be appropriate. For example, the other polymer may or may not have the property of being soluble in a medium (solvent) (e.g., water-soluble), regardless of whether its Tg is higher than room temperature. Furthermore, the other polymer may be liquid or solid before heating (e.g., before ejection of the ink). Furthermore, the other polymer may be a dispersant polymer for dispersing the pigment (or, from another perspective, suppressing aggregation), or may be an abrasion-resistant polymer for improving the abrasion resistance of the ink.

[0036] The mass % of the other polymer in the ink may be set as appropriate. The relationship between the mass % of the other polymer and the mass % of the fixer polymer has already been described. An example of the mass % range of all polymers other than the fixer polymer, or all polymers other than the fixer polymer that have a Tg higher than room temperature, is 1 mass % or more and 40 mass % or less.

[0037] As described above, the Tg of at least one of the other polymers is higher than room temperature and lower than the Tg of the fixative polymer. For example, the Tg of the dispersant polymer and / or the abrasion-resistant polymer may be higher than room temperature and lower than the Tg of the fixative polymer. In this case, the proportion of the dispersant polymer or the abrasion-resistant polymer in all polymers other than the fixative polymer that have a Tg higher than room temperature may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, or may be less than the above. The specific value of the Tg of the polymer that has a Tg higher than room temperature and lower than the Tg of the fixative polymer may be any appropriate value. An example of such a range is 50°C or higher and lower than 70°C.

[0038] The specific composition and / or material of the other polymer may be set as appropriate. For example, the specific composition and / or material of the other polymer (e.g., dispersant polymer and / or scratch-resistant polymer) may be any of the various examples of the specific composition and / or material of the fixing agent polymer (e.g., styrene-based polymer, etc.). However, in this case, the mass ratio of the monomers in the manufacturing process of the other polymer and the fixing agent polymer is different. The Tg of the other polymer, like the Tg of the fixing agent polymer, can be set arbitrarily by setting the mass % of the various monomers contained in the other polymer.

[0039] The dispersant polymer may have any suitable structure, including known structures. For example, the dispersant polymer is a string-like polymer. However, the dispersant polymer may also be particulate. Furthermore, for example, the dispersant polymer has a portion that adsorbs to the pigment and a portion that exhibits dispersibility. Dispersibility is exhibited, for example, by steric hindrance, electrostatic repulsion, and / or conduction inhibition. A dispersant polymer is generally not required when the pigment is self-dispersible, but it may be added to an ink containing a self-dispersible pigment. For example, the dispersant polymer may contain styrene and butyl acrylate in a 70:30 ratio. In this case, the Tg of the dispersant polymer may be in the aforementioned range of 50°C or higher and lower than 70°C.

[0040] The abrasion-resistant polymer may be any suitable polymer, including those known in the art. For example, the abrasion-resistant polymer may be a polyester resin. In this case, the Tg of the abrasion-resistant polymer may be in the range of 50°C or higher and lower than 70°C.

[0041] The ink may contain other appropriate components in addition to the polymers described above. For example, the ink may contain surfactants (excluding dispersant polymers), humectants, surface tension adjusters, pH adjusters, and / or gloss-imparting agents. These additives may be composed of polymers or may constitute part of the medium (organic solvent).

[0042] (Transportation device) The conveying device 5 has, for example, a plurality of rollers (e.g., 3A, 3B, 17A, 17B, 19A to 19D) along the conveying path of the printing substrate 101. Each roller is a cylindrical or columnar member, and is arranged so that its axial direction is perpendicular to the conveying direction of the printing substrate 101, and its outer circumferential surface abuts against the front or back surface of the printing substrate 101 over the entire width of the printing substrate 101. At least one roller, including the recovery roller 3B, is rotated around its axis by a motor, thereby conveying the printing substrate 101. Note that, although the present embodiment takes as an example a mode in which the rollers are rotated by a motor, the rollers may also be rotated by another drive source or by human power.

[0043] The number of rollers, their positions relative to the conveying path, their diameters, etc. may be set as appropriate. In the illustrated example, the conveying device 5 has, in addition to the supply roller 3A and the recovery roller 3B, a first tension roller 19A, a second tension roller 19B, a first heating roller 17A, a second heating roller 17B, a third tension roller 19C, and a fourth tension roller 19D, in that order from the supply roller 3A side to the recovery roller 3B side. Each roller except the recovery roller 3B may be driven to rotate by a motor or the like, or may simply rotate passively due to frictional force from the printing substrate 101.

[0044] The first heating roller 17A and the second heating roller 17B are also used as a device that promotes the fixation of ink to the printing substrate 101, which will be described in detail later, and have the function of heating the printing substrate 101. The first tension roller 19A to the fourth tension roller 19D contribute to applying tension to the printing substrate 101. In the example shown, the first tension roller 19A to the fourth tension roller 19D also contribute to improving heating efficiency by bringing the printing substrate 101 into close contact with the first heating roller 17A and the second heating roller 17B.

[0045] More specifically, for example, the first heating roller 17A is in contact with the back surface of the printing substrate 101 upstream of the ink discharge device 7. The second tension roller 19B is located upstream of the first heating roller 17A without any other rollers interposed between them, and is in contact with the front surface of the printing substrate 101 (in other words, the surface opposite to the surface with which the first heating roller 17A is in contact). The first tension roller 19A is located upstream of the second tension roller 19B without any other rollers interposed between them, and is in contact with the back surface of the printing substrate 101 (in other words, the surface opposite to the surface with which the second tension roller 19B is in contact). At least one of the first tension roller 19A and the second tension roller 19B is biased toward the printing substrate 101 by a biasing unit (e.g., a spring and / or an actuator) not shown. As a result, tension is applied to the printing material 101, and the printing material 101 is brought into close contact with the first heating roller 17A.

[0046] Also, for example, the second heating roller 17B contacts the back surface of the printing substrate 101 downstream of the ink discharge device 7. The third tension roller 19C is located downstream of the second heating roller 17B without any other rollers interposed between them, and contacts the front surface of the printing substrate 101 (in other words, the surface opposite to the surface with which the second heating roller 17B contacts). The fourth tension roller 19D is located downstream of the third tension roller 19C without any other rollers interposed between them, and contacts the back surface of the printing substrate 101 (in other words, the surface opposite to the surface with which the third tension roller 19C contacts). At least one of the third tension roller 19C and the fourth tension roller 19D is biased toward the printing substrate 101 by a biasing unit (e.g., a spring and / or an actuator), not shown. As a result, tension is applied to the printing material 101, and the printing material 101 is brought into close contact with the second heating roller 17B.

[0047] For example, the diameter of the first heating roller 17A and / or the second heating roller 17B is relatively large. This increases the contact area of ​​these heating rollers with the printing substrate 101, improving heating efficiency. For example, the diameter of the first heating roller 17A is larger than the diameter of the first tension roller 19A and / or the diameter of the second tension roller 19B. Similarly, the diameter of the second heating roller 17B is larger than the diameter of the third tension roller 19C and / or the diameter of the fourth tension roller 19D. The diameter of the first heating roller 17A and / or the diameter of the second heating roller 17B may be larger than the diameter of all other rollers included in the conveying device 5.

[0048] In a side view, the line formed by the printing substrate 101 between the second tension roller 19B and the first heating roller 17A may be inclined with respect to the line formed by the printing substrate 101 between the first heating roller 17A and the next roller (the second heating roller 17B in the illustrated example). In this case, the angle of inclination may be relatively large. This increases the angular range around the axis of the first heating roller 17A over which the printing substrate 101 comes into close contact with the first heating roller 17A. For example, the angle of inclination may be 45° or more, 70° or more, or 90° or more. The same applies to the relationship between the line formed by the printing substrate 101 between the third tension roller 19C and the second heating roller 17B and the line formed by the printing substrate 101 between the second heating roller 17B and the roller immediately preceding it (the first heating roller 17A in the illustrated example).

[0049] Various arrangements of the rollers are possible other than those described above. For example, the surface of the printing substrate 101 that the first heating roller 17A, first tension roller 19A, and second tension roller 19B contact may be reversed from the illustrated example. The first tension roller 19A may be omitted, and the second tension roller 19B may be provided. The fourth tension roller 19D may be omitted, and the third tension roller 19C may be provided. The first tension roller 19A to the fourth tension roller 19D may be omitted. Rollers other than those illustrated in the example may be provided. For example, multiple rollers may be provided between the first heating roller 17A and the second heating roller 17B, arranged on a curve with the upper side convex in side view, and contacting the back surface of the printing substrate 101.

[0050] The manner in which the printing substrate 101 is moved may be set as appropriate depending on the manner of the ink ejection device 7, etc. For example, the transport device 5 may move the printing substrate 101 continuously, or may move the printing substrate 101 intermittently. Furthermore, when the printing substrate 101 moves continuously, the transport speed of the printing substrate 101 may be constant or may change. Note that, from another perspective, intermittent movement is movement accompanied by a change in speed. A specific value for the transport speed of the printing substrate 101 may be set as appropriate. Examples of ranges for the transport speed (for example, average speed when the speed changes) include 50 m / min or more and 300 m / min or less, or 100 m / min or more and 200 m / min or less.

[0051] (ink ejection device) The ink ejection device 7 has at least one head 21 (20 in the illustrated example) that faces the printing material 101 and is directly responsible for ejecting ink.

[0052] In addition, in the description of the position of the ink ejection device 7 in this disclosure, reference may be made to, for example, the position of the head 21, the position of the ejection surface 21a described below, or the position of an arrangement area of ​​the plurality of nozzles 21b described below. In other words, in the description of the position of the ink ejection device 7, the term ink ejection device 7 may be appropriately replaced with the term head 21, the ejection surface 21a, or the arrangement area of ​​the plurality of nozzles 21b.

[0053] In this embodiment, the head 21 is basically fixed in a direction intersecting the transport direction of the printing substrate 101, and the printing device 1 is a so-called line printer. However, the printing device may be a so-called serial printer that alternates between ejecting droplets while moving the head 21 in a direction intersecting the transport direction of the printing substrate 101 (for example, a direction substantially perpendicular to the direction of transport).

[0054] The head 21 is held by a member (not shown) so that the ejection surface 21a (the lower surface in the illustrated example) from which ink is ejected faces the printing substrate 101 in approximately parallel relation. The distance between the ejection surface 21a and the printing substrate 101 may be set as appropriate. For example, the distance is 0.5 mm to 20 mm, or 0.5 mm to 2 mm. The shape of the head 21 in a plan view (the shape of the ejection surface 21a) may be an appropriate shape, for example, an elongated shape (more specifically, a roughly rectangular shape) that is long in a direction intersecting the transport direction of the printing substrate 101. The direction intersecting the transport direction is, for example, a direction approximately perpendicular to the transport direction, and may also be referred to as the width direction of the printing substrate 101 (the same applies hereinafter).

[0055] 2, the multiple heads 21 are arranged to form at least one head group 23 (four in the illustrated example). Each head group 23 includes multiple heads 21 (five in the illustrated example). The multiple heads 21 included in each head group 23 are arranged so that the printable ranges of the heads 21 are connected to each other in the width direction of the printing substrate 101, or so that their edges overlap. This makes it possible to print without gaps in the width direction of the printing substrate 101.

[0056] In the illustrated example, more specifically, in each head group 23, three of the five heads 21 are aligned in the width direction of the printing substrate 101. The remaining two heads 21 are aligned in the width direction of the printing substrate 101 at positions shifted in the transport direction from the above three heads 21, and are positioned between the above three heads 21 in the width direction of the printing substrate 101. In other words, in each head group 23, the multiple heads 21 are arranged in a staggered pattern.

[0057] The four head groups 23 are arranged along the transport direction of the printing substrate 101. Ink is supplied to each head 21 from an ink tank 25 (FIG. 1). The heads 21 belonging to one head group 23 are supplied with ink of the same color, and the four head groups 23 can print with ink of four colors. The colors of ink ejected from each head group 23 are, for example, magenta (M), yellow (Y), cyan (C), and black (K). A color image can be printed by impacting such ink on the printing substrate 101.

[0058] The number of heads 21 mounted on the printing device 1 may be one, as long as printing is performed in a single color within the range printable by one head 21. The number of heads 21 included in a head group 23 and the number of head groups 23 can be changed as appropriate depending on the type of the printing substrate 101 and the printing conditions. For example, the number of head groups 23 may be increased to print in more colors. Furthermore, by arranging multiple head groups 23 that print in the same color and printing alternately in the transport direction, the transport speed can be increased even if heads 21 with the same performance are used. This allows the printing area per unit time to be increased. Furthermore, multiple head groups 23 that print in the same color may be prepared and arranged staggered in a direction intersecting the transport direction to increase the resolution in the width direction of the printing substrate 101.

[0059] Furthermore, in addition to printing colored inks, a liquid such as a coating agent may be printed uniformly or in a pattern using the head 21 to treat the surface of the printing substrate 101. For example, when the printing substrate 101 is one that is difficult for the liquid to penetrate, a coating agent that forms a liquid-receiving layer to facilitate ink fixation can be used. Alternatively, when the printing substrate 101 is one that is easy for the liquid to penetrate, a coating agent that forms a liquid-penetration suppressing layer to prevent excessive bleeding of the liquid or excessive mixing with other liquids that land adjacently can be used. The coating agent may be applied by the aforementioned applicator (not shown) instead of or in addition to printing using the head 21.

[0060] Although not specifically shown, the multiple heads 21 may be housed in a head chamber. The head chamber is, for example, basically configured as a space isolated from the outside. The head chamber also has an entrance that allows the printing substrate 101 being transported by the transport device 5 to enter the chamber, and an exit that allows the printing substrate 101 being transported by the transport device 5 to exit the chamber. Ink is then applied to the printing substrate 101 by the head 21 within the head chamber. In the head chamber, it is easier to reduce fluctuations in factors that affect ink application compared to the outside. Such factors include, for example, temperature, humidity, and air pressure. At least one of the various factors described above within the head chamber may be actively controlled by appropriate means.

[0061] The head 21 may eject ink droplets in any suitable manner. For example, the head 21 may be of a piezoelectric type that ejects droplets by applying pressure to the ink in the head 21 using a piezoelectric actuator. Alternatively, the head 21 may be of a thermal type that heats the ink to generate bubbles, and ejects droplets using the pressure generated by the generated bubbles.

[0062] (Device that promotes ink fixation to the printed material) As described above, the printing device 1 has a plurality of devices that promote the fixation of ink, which has been ejected by the ink ejection device 7 and landed on the printing substrate 101, to the printing substrate 101. The plurality of devices includes, for example, a drying device 9, a melting device 11, and an auxiliary melting device 13. Generally speaking, these devices promote the fixation of ink by heating the ink. However, these devices differ from each other in their specific configurations, heating amounts, and / or positions. Consequently, these devices exert different effects on the ink and / or interact with each other in terms of their respective effects.

[0063] (drying equipment) The drying device 9 promotes evaporation of the ink medium, for example, by heating the printing substrate 101. Heating of the printing substrate 101 by the drying device 9 may be performed before or after the ink is applied to the printing substrate 101, or may be performed both before and after the ink is applied. When heating the printing substrate 101 after the ink is applied, the drying device 9 may heat the printing substrate 101 from the back side (without directly heating the ink), may heat the printing substrate 101 from the front side (the ink may be directly heated together with the printing substrate 101), or may heat the printing substrate 101 from both the back side and the front side.

[0064] From another perspective, the drying device 9 may have a portion located upstream of the ink discharge device 7 in the transport direction of the printing substrate 101, a portion located at the same position as the ink discharge device 7, a portion located downstream of the ink discharge device 7, or portions located integrally or dispersedly at two or more of the above three positions. Furthermore, the drying device 9 may have a portion located on the front side of the printing substrate 101, a portion located on the back side, or both of the above. For example, the drying device 9 may not be located at the same position as the ink discharge device 7, but may have a portion located upstream of the ink discharge device 7. In this case, for example, the printing substrate 101 and the ink can be heated while suppressing the occurrence of turbulence in the space at the same position as the ink discharge device 7, which would reduce the ink discharge stability.

[0065] Note that in the description of the position of the drying device 9 in this disclosure, reference may be made to, for example, the position of a part of the drying device 9 that directly contributes to heating the printing substrate 101 (for example, the outer circumferential surface of the heating roller or the air outlet that blows out hot air), or the position of a part of the printing substrate 101 that is heated by the drying device 9 (for example, the part that the roller contacts or the part that hot air is blown onto). In other words, in the description of the position of the drying device 9, the term drying device 9 may be appropriately replaced with the term for the part that directly contributes to heating or the part of the printing substrate 101 that is heated.

[0066] The drying device 9 heats the printing substrate 101 generally uniformly in the width direction of the printing substrate 101 (the amount of heat is constant in the width direction). Consequently, the temperature distribution in the width direction of the printing substrate 101 is generally uniform. However, the drying device 9 may heat the printing substrate 101 at different amounts in the width direction. For example, the amount of heat may be relatively large on both sides in the width direction where heat is easily dissipated. In the transport direction of the printing substrate 101, the length that the drying device 9 can simultaneously heat may be set arbitrarily.

[0067] Various configurations are possible for the drying device 9. In this embodiment, the drying device 9 has a first heating roller 17A. As described above, the first heating roller 17A abuts against the back surface of the printing substrate 101 on the upstream side of the ink ejection device 7.

[0068] More specifically, the first heating roller 17A has only a portion of its outer circumferential surface around its axis in contact with the printing substrate 101. Furthermore, the first heating roller 17A does not, for example, basically slide against the printing substrate 101, but actively or passively rotates in accordance with the movement of the printing substrate 101. Therefore, the first heating roller 17A can be considered to have a first portion 17a and a second portion 17b that heat the printing substrate 101 at different positions around its axis, and the first portion 17a and the second portion 17b are alternately in contact with the printing substrate 101.

[0069] The specific configuration of the first heating roller 17A may be various, for example, a known configuration or a configuration based on a known configuration. For example, although not specifically shown, the first heating roller 17A may have an internal heating wire that generates heat according to Joule's law when an electric current flows through the heating wire. Alternatively, the first heating roller 17A may have an internal induction coil that generates heat through induction heating. Alternatively, the first heating roller 17A may have a flow path through which a heated heating medium is supplied from the outside. The cylindrical or columnar base of the first heating roller 17A may be made of an appropriate material such as ceramic and / or metal.

[0070] (Melting equipment) The melting device 11 heats the ink attached to the printing substrate 101, for example, by irradiating it with UV light. As described above, this heating melts the fixative polymer (or, from another perspective, the glass component) in the ink. The molten fixative polymer then solidifies, causing the colorant in the ink to be fixed to the printing substrate 101. Note that UV may be irradiated onto the printing substrate 101 at a non-ink placement position, or may be partially transmitted through the ink and irradiated onto the printing substrate 101. The printing substrate 101 may be made of a material that substantially transmits UV light, or may be made of a material that absorbs at least a portion of the UV light and generates heat.

[0071] The melting device 11 irradiates the ink with UV light, and is therefore located downstream of the ink ejection device 7 in the transport direction of the printing substrate 101, and is located on the surface side of the printing substrate 101, facing the surface. The relative positions (distance) between the ink ejection device 7 and the melting device 11 in the transport direction of the printing substrate 101 may be set appropriately. For example, the two may be arranged with a gap between them, or may be arranged adjacent to each other with (almost no) gap between them.

[0072] Note that in the description of the position of the melting device 11 in this disclosure, reference may be made to, for example, the position of the UV outlet (the frontmost part of the optical system) in the melting device 11, or the position of the area of ​​the printing substrate 101 that is irradiated with UV. In other words, in the description of the position of the melting device 11, the term melting device 11 may be appropriately replaced with the term UV outlet or the area of ​​the printing substrate 101 that is irradiated with UV.

[0073] UV irradiation by the melting device 11 may be started, for example, after heating of the printing substrate 101 by the drying device 9 is completed. From another perspective, melting of the fixative polymer in the ink may be started while the medium in the ink is evaporating or after evaporation of the medium is complete. Note that even if evaporation of the medium is completed, it does not matter in practice if a trace amount of medium remains. For example, evaporation of the medium can be considered complete even if the ink immediately before UV irradiation begins contains an amount of medium equivalent to 5% or less by mass of the ink before ejection.

[0074] From another perspective, the melting device 11 may be located downstream of the drying device 9 in the transport direction of the printing substrate 101. In this case, the relative positions (distance) between the drying device 9 and the melting device 11 in the transport direction of the printing substrate 101 may be set appropriately. For example, the two may be arranged with a gap between them, or may be arranged adjacent to each other with no gap between them.

[0075] The melting device 11 can irradiate UV light over the entire width of the area that can be printed by the ink ejection device 7, for example. For example, the melting device 11 has a length that spans the entire width of the printing substrate 101 or the entire width of the printable area, and irradiates UV light over the entire width. However, unlike the illustrated example, the melting device 11 may irradiate UV light over the entire width of the printable area by moving in the width direction of the printing substrate 101.

[0076] The melting device 11 irradiates the printing substrate 101 with UV light in a generally uniform manner in the width direction of the printing substrate 101. In other words, the energy of UV light irradiated onto the printing substrate 101 (and ink) per unit time is generally constant in the width direction of the printing substrate 101. The amount of UV light absorbed by the printing substrate 101 (and ink) is affected by the distribution of the ink in the width direction. Therefore, the amount of heat generated by UV light is not necessarily uniform in the width direction. Unlike the above, the melting device 11 may irradiate the printing substrate 101 with different amounts of UV light in the width direction.

[0077] The shape of the area on the printing substrate 101 that is irradiated with UV light is, for example, a rectangle with sides that are parallel to the transport direction of the printing substrate 101 and the width direction of the printing substrate 101. The area that is irradiated with UV light may have a shape other than a rectangle. As described above, the length of the area that is irradiated with UV light in the width direction of the printing substrate 101 is equal to or greater than the full width of the area that can be printed by the ink ejection device 7. Furthermore, the length of the area that is irradiated with UV light in the transport direction of the printing substrate 101 may be set as appropriate.

[0078] The specific configuration of the melting device 11 may be any appropriate one. For example, the melting device 11 has at least a light source 11a that generates UV light. In addition, the melting device 11 may have a reflector that reflects UV light leaking from the light source 11a to the side opposite the printing substrate 101, a diaphragm having an opening that adjusts the cross-sectional shape of the UV light from the light source 11a, and / or a lens that focuses the UV light. Even if such elements are provided, only the light source 11a may be defined as the melting device 11. The light source 11a may be composed of appropriate elements such as an LED (light emitting diode), an incandescent bulb, a fluorescent lamp, or a mercury lamp. The light source 11a may have only one of the above elements or may have a plurality of elements. A surface light source may be composed of a plurality of elements (e.g., LEDs).

[0079] As is well known, UV is light with a shorter wavelength than visible light, and its wavelength is, for example, 10 nm or more and 400 nm or less. The UV emitted by the melting device 11 may be near ultraviolet or far ultraviolet. Near ultraviolet may be any of so-called UV-A, UV-B, and UV-C. In other words, the wavelength of the UV emitted by the melting device 11 may be set appropriately. The UV emitted by the melting device 11 may have a narrow wavelength range in which energy is distributed, like laser light, or may have a wide wavelength range. In the description of wavelength in this disclosure, for example, the wavelength at which the energy peaks (the highest peak if there are multiple peaks) may be referenced.

[0080] The intensity of UV irradiated by the melting device 11 onto the printing substrate 101 (and ink) may be set as appropriate. In the present disclosure, the UV intensity refers to the energy per unit time of UV irradiated onto a unit area of ​​the printing substrate 101. The UV intensity may be set higher than the intensity of UV irradiated onto the printing substrate to cure UV-curable ink, for example. For example, the UV intensity for curing UV-curable ink is generally 10 W / cm 2 In contrast, the intensity of the UV from the melting device 11 is less than 10 W / cm 2 Above, 20W / cm 2or more than 30W / cm 2 However, unlike the above, the intensity of the UV from the melting device 11 may be lower than the intensity of the UV for curing UV-curable ink.

[0081] The cumulative amount of UV light irradiated by the melting device 11 onto the printing substrate 101 (and ink) may be set as appropriate. The cumulative amount of light is a value obtained by integrating the intensity described above over time. The cumulative amount of UV light may be set to be greater than the cumulative amount of UV light irradiated onto the printing substrate to cure UV-curable ink, for example. For example, the cumulative amount of UV light irradiated onto the printing substrate to cure UV-curable ink is generally 500 mJ / cm. 2 In contrast, the integrated amount of UV light irradiated onto the printing substrate 101 by the melting device 11 is less than 500 mJ / cm 2 2 More than 1000mJ / cm 2 More than 1500mJ / cm 2 More than 5000mJ / cm 2 or more than 10,000 mJ / cm 2 However, unlike the above, the cumulative amount of UV light irradiated by the melting device 11 onto the printing substrate 101 may be less than the cumulative amount of UV light irradiated onto the printing substrate to cure UV-curable ink.

[0082] (Auxiliary melting device) Auxiliary melting device 13 is located on the opposite side of substrate 101 from melting device 11, and assists in melting the fixer polymer by heating the back surface of substrate 101. Because auxiliary melting device 13 assists in melting the fixer polymer, the description of the position of melting device 11 may be applied to its position in the transport direction of substrate 101. For example, auxiliary melting device 13 may be located downstream of ink ejection device 7 and drying device 9.

[0083] As with the drying device 9, a description of the position of the auxiliary melting device 13 may refer to, for example, the position of a portion of the auxiliary melting device 13 that directly contributes to heating the substrate 101, or the position of a portion of the substrate 101 that is heated by the auxiliary melting device 13. In other words, in a description of the position of the auxiliary melting device 13, the term auxiliary melting device 13 may be appropriately replaced with the term portion that directly contributes to heating, or the portion of the substrate 101 that is heated.

[0084] In a planar perspective view of the printing substrate 101, at least a portion of the region of the printing substrate 101 that is heated by the auxiliary melting device 13 overlaps with at least a portion of the region of the printing substrate 101 that is irradiated with UV light by the melting device 11. The two regions may or may not generally coincide with each other. For example, the entire region that is irradiated with UV light may overlap with part or all of the region that is heated by the auxiliary melting device 13. In this case, as will be understood from the action described below, the UV energy can be efficiently used to melt the fixative polymer.

[0085] The auxiliary melting device 13 heats the printing substrate 101 almost uniformly in the width direction of the printing substrate 101 (the amount of heat is constant in the width direction). However, the auxiliary melting device 13 may heat the printing substrate 101 at different amounts in the width direction. For example, the amount of heat may be relatively large on both sides in the width direction where heat is easily dissipated. In the transport direction of the printing substrate 101, the length that the auxiliary melting device 13 can heat simultaneously may be set arbitrarily.

[0086] The auxiliary melting device 13 may have a variety of configurations. In this embodiment, the auxiliary melting device 13 has the second heating roller 17B described above. The configuration of the second heating roller 17B may be the same as or different from the configuration of the first heating roller 17A. In any case, the above-described explanation regarding the configuration of the first heating roller 17A (such as having a first portion and a second portion and having an electric heating wire, an induction coil, or a flow path) may be applied to the second heating roller 17B as appropriate.

[0087] (Ink ejection device head) The basic configuration of the head 21 of the ink ejection device 7 may be various, such as a known configuration or a configuration based on a known configuration. In this embodiment, the head 21 may also have a heater for heating the ink before ejection. By heating the ink before ejection, it is possible to reduce, for example, the time required for evaporation of the medium and / or melting of the fixative polymer in the ink after ejection. The configuration of the heater in the head 21 may be any appropriate configuration. Examples of heaters provided in the head 21 are shown below.

[0088] Fig. 3A is a perspective view of the head 21 as seen from above (the side opposite to the printing substrate 101). Fig. 3B is a perspective view of the head 21 as seen from below (the printing substrate 101 side). Fig. 3C is a perspective view of a part of the head 21 (head main body 27) as seen from above.

[0089] The head 21 has, for example, a head main body 27 and a back member 29 fixed above the head main body 27. The head main body 27 has an ejection surface 21a facing the printing substrate 101. A plurality of nozzles 21b that eject ink droplets are opened on the ejection surface 21a. In other words, the head main body 27 is a member that is directly involved in ejecting droplets. On the other hand, the back member 29 serves as an intermediary between the head main body 27 and other components (for example, the ink tank 25 and the control device 15). The head 21 may have other appropriate members (for example, a housing that covers the back member 29) in addition to the above.

[0090] The head body 27 has, for example, a plurality of individual flow paths that individually communicate with the plurality of nozzles 21b, and a common flow path that commonly communicates with the plurality of individual flow paths and extends along the ejection surface 21a, although not shown. One or more openings 27a that individually or commonly communicate with ends of one or more common flow paths are formed on the surface of the head body 27 opposite the ejection surface 21a. If the head 21 is a piezoelectric type, an actuator substrate 30 including a plurality of piezoelectric actuators that individually apply pressure to the plurality of individual flow paths may be provided on the surface of the head body 27 opposite the ejection surface 21a.

[0091] The back member 29 has, for example, one or more openings 29a communicating with the ink tank 25 via a tube or the like (not shown), and a flow path (not shown) connecting the opening 29a and the opening 27a of the head main body 27. Although not specifically shown, the back member 29 also houses a driver that supplies power to the head main body 27 (for example, the actuator board 30) and a circuit board on which the driver is mounted.

[0092] FIG. 3D is an enlarged view of region IIId in FIG. 3C.

[0093] The head main body 27 has a plurality of plates 31 stacked on top of each other. Nozzles 21b and flow paths leading to nozzles 21b are formed by forming through holes in the plurality of plates 31. The plates 31 are made of, for example, metal or resin.

[0094] In the head 21 configured as above, for example, as shown in FIG. 3A, a heater 33A may be provided on the upper surface of the back member 29. The heater 33A may be, for example, a sheet-like heater (film heater). The heater 33A is configured, for example, by sandwiching a heating wire that extends appropriately in a plane between sheet-like insulators. The planar shape and dimensions of the heater 33A may be set as appropriate.

[0095] 3D, a sheet-shaped heater 33B may be interposed between the plates 31 in addition to or instead of the heater 33A. Similar to the heater 33A, the heater 33B is configured, for example, by sandwiching a heating wire extending appropriately in a plane between sheet-shaped insulators. The planar shape and dimensions of the heater 33B may be set appropriately. For example, the heater 33B may have an area that covers all the nozzles 21b in a planar perspective view.

[0096] Although not specifically shown, in addition to or instead of the upper surface of the back surface member 29 and / or the inside of the head main body 27, a heater may be provided on the side of the head 21 (a surface intersecting the D1 direction or the D2 direction), inside the back surface member 29, and / or between the head main body 27 and the back surface member 29. The heater is not limited to being sheet-shaped, and may be, for example, one that is so thick that it cannot be considered sheet-shaped. Furthermore, in addition to or instead of the heater, the head 21 may have a flow path through which a heat medium flows.

[0097] (Control device) The control device 15 (FIG. 1) is configured to include, for example, a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an external storage device, although these are not specifically shown. In other words, the control device 15 is configured to include, for example, a computer. The CPU executes programs stored in the ROM and / or the external storage device to implement various functional units, which will be described later. The control device 15 may also include a logic circuit that performs only certain operations, or may be conceptualized to include drivers that supply power to various elements.

[0098] The control device 15 may be appropriately distributed in terms of hardware. For example, the control device 15 may be configured to include multiple lower-level control devices and one upper-level control device. The multiple lower-level control devices are provided individually for the conveying device 5, the ink discharge device 7, the drying device 9, the melting device 11, and the auxiliary melting device 13. The upper-level control device controls the multiple lower-level control devices (for example, synchronizes them) by sending and receiving signals to and from the multiple lower-level control devices.

[0099] (Configuration of signal processing system) FIG. 4 is a block diagram showing the configuration of a signal processing system of the printing device 1. As shown in FIG.

[0100] The control device 15 has various functional units (e.g., 35, 37, 39, 41, 43, and 45) constructed by the CPU executing a program, etc. The head control unit 35 controls the head 21. The conveying speed control unit 37 controls the conveying device 5. The first temperature control unit 39 controls the drying device 9 (in other words, the first heating roller 17A). The head temperature control unit 41 controls the head heater 33 (33A and / or 33B) of the head 21. The second temperature control unit 43 controls the auxiliary melting device 13 (in other words, the second heating roller 17B). The UV control unit 45 controls the melting device 11. More specifically, for example, they are as follows.

[0101] (Head control unit) The head control unit 35 generates information corresponding to the size of droplets to be ejected from each nozzle 21b at the ejection timings that occur at a predetermined cycle based on data including, for example, image information (text is also a type of image), and outputs the information to a driver (not shown) of the head 21. The driver (not shown) inputs a voltage corresponding to the input information to a drive element (e.g., a piezoelectric actuator) for each nozzle 21b. The head control unit 35 may be conceptually understood to include the driver. The ejection cycle may be a fixed value set by the manufacturer of the printing device 1, or may be a value set by the head control unit 35 based on predetermined information. The predetermined information may be, for example, the resolution in the transport direction of the printing substrate 101 set by the manufacturer or user, and / or the transport speed of the printing substrate 101 set by the manufacturer or user. For example, when printing on a printing substrate 101 transported at a speed of 100 m / min using a 1200 dpi head 21, the head 21 may be controlled to operate at a drive frequency of 78.74 kHz and eject ink.

[0102] (Transport speed control section) The conveying speed control unit 37 controls the conveying device 5 so that the conveying speed of the printing substrate 101 is maintained at a target value, for example. The target value is basically constant, for example, while the printing device 1 is in operation (or, from another perspective, while printing is in progress; the same applies below). The target value may be an unchanging value set by the manufacturer of the printing device 1, a value set by the user, or a value set by the conveying speed control unit 37 based on predetermined information. The above-mentioned predetermined information is, for example, the resolution in the conveying direction of the printing substrate 101 set by the manufacturer or user, and / or the droplet ejection cycle set by the manufacturer or user.

[0103] The conveying speed control unit 37 may, for example, perform feedback control based on the detection value of a speed sensor 47 that detects the speed of the printing substrate 101 (as shown in the example), or may perform open-loop control without feedback. The speed sensor 47 may detect the speed of the printing substrate 101 itself, or it may detect the speed of an element that drives the printing substrate 101. An example of the former is one that detects speed through image recognition, such as an optical mouse. An example of the latter is a sensor (for example, an encoder or resolver) that detects the rotation of the rollers of the conveying device 5 or the motor that drives the rollers. By using these, the speed of the printing substrate 101 and the timing of ejection from the head 21 can be synchronized.

[0104] The conveying speed control unit 37 supplies power to at least one motor that rotates at least one roller of the conveying device 5, for example, via a driver (not shown). The conveying speed control unit 37 may be conceptualized as including the driver. The driver may perform feedback control of the motor (feedback control that is lower than the feedback control described above), or may perform open-loop control of the motor.

[0105] (First temperature control unit) The first temperature control unit 39 controls the drying device 9 so that the temperature of a predetermined portion of the printing substrate 101 is maintained at a target value, for example. The predetermined portion is, for example, the temperature of an area of ​​the printing substrate 101 that is heated by the drying device 9. However, the predetermined portion may also be another area of ​​the printing substrate 101 where heating by the drying device 9 is dominant in temperature change. For example, the predetermined portion may be an area downstream of the area heated by the drying device 9 that is not heated by another device (for example, an area facing the ink ejection device 7 in the example of FIG. 1).

[0106] The target temperature value is, for example, essentially constant while the printing apparatus 1 is in operation. The target value may be an unchanging value set by the manufacturer of the printing apparatus 1, a value set by the user, or a value set by the first temperature control unit 39 based on predetermined information. The predetermined information is, for example, information about the ink input by the manufacturer or user (e.g., information that can identify the Tg of a predetermined polymer), the conveying speed of the printing substrate 101 set by the manufacturer or user, and / or the relative position (distance) between the drying apparatus 9 and other apparatuses (e.g., 7, 11, and / or 13) input by the manufacturer or user.

[0107] The first temperature control unit 39 may perform feedback control based on the detection value of a first temperature sensor 49 that detects the temperature of a predetermined portion of the printing substrate 101 (as shown in the example), or may perform open-loop control without feedback. The first temperature sensor 49 may detect the temperature of the printing substrate 101 itself, the air temperature near the printing substrate 101, or the temperature of an appropriate portion of the drying device 9 (e.g., the surface or interior of the first heating roller 17A). In either case, the first temperature sensor 49 may be a non-contact temperature sensor or a contact temperature sensor. Examples of non-contact temperature sensors include a radiation thermometer and a thermograph. Examples of contact temperature sensors include a thermocouple, a thermistor, and a resistance thermometer. The detected temperature may be compared directly with a target value, or may be compared with the target value after appropriate correction (e.g., conversion to a temperature at a position different from the sensor position) has been performed.

[0108] Specifically, the control of the drying device 9 is, for example, the control of power supplied to a heat-generating element (e.g., a heating wire or an induction coil) via a driver (not shown). More specifically, the voltage, current, and / or frequency (in the case of AC) may be controlled depending on the type of the heat-generating element. The first temperature control unit 39 may be conceptualized as including the driver. The control of the drying device 9 may also be other control than the above. For example, in a configuration in which a heat medium is supplied to the first heating roller 17A, the flow rate of the heat medium may be controlled.

[0109] (Head temperature control unit) The head temperature control unit 41 controls the head heater 33 so that the temperature of the ink held in a predetermined portion of the head 21 is maintained at a target value, for example. The predetermined portion may be, for example, either the head main body 27 or the back member 29, or any portion within these members (in other words, any flow path). However, if the predetermined portion is located within the nozzle 21b or close to the nozzle 21b, the accuracy of control of fixation of the ink 103 on the printing substrate 101 is improved.

[0110] The target temperature value is, for example, essentially constant while the printing device 1 is in operation. The target value may be an unchanging value set by the manufacturer of the printing device 1, a value set by the user, or a value set by the head temperature control unit 41 based on predetermined information. The predetermined information is, for example, information about the ink input by the manufacturer or user (for example, information that can identify the Tg of a predetermined polymer).

[0111] The head temperature control unit 41 may perform feedback control based on the detection value of the head temperature sensor 51 that detects the temperature of the ink (as shown in the example), or may perform open-loop control without feedback. The head temperature sensor 51 may be exposed in the flow path and detect the temperature of the ink itself, or it may detect the temperature of the head 21 without being exposed in the flow path. In the former case, for example, a contact-type temperature sensor can be used. In the latter case, for example, a contact-type or non-contact-type temperature sensor can be used. Specific examples of contact-type or non-contact-type temperature sensors are as described above. The detected temperature may be compared directly with a target value, or may be compared with the target value after appropriate correction (for example, conversion to a temperature at a position different from the sensor position) has been performed.

[0112] Specifically, the control of the head heater 33 is, for example, control of the power supplied to the head heater 33 via a driver (not shown). More specifically, the voltage, current, and / or frequency (in the case of AC) may be controlled according to the specific configuration of the head heater 33. The head temperature control unit 41 may be conceptualized as including the driver.

[0113] (Second temperature control unit) The second temperature control unit 43 controls the auxiliary melting device 13 so that the temperature of a predetermined portion of the printing substrate 101 is maintained at a target value. The predetermined portion is, for example, the temperature of an area of ​​the printing substrate 101 that is heated by the auxiliary melting device 13.

[0114] The target temperature value is, for example, essentially constant while the printing device 1 is in operation. The target value may be an unchanging value set by the manufacturer of the printing device 1, a value set by the user, or a value set by the second temperature control unit 43 based on predetermined information. The predetermined information is, for example, information about the ink input by the manufacturer or user (for example, information that can identify the Tg of a predetermined polymer).

[0115] The second temperature control unit 43 may perform feedback control based on the detection value of the second temperature sensor 53 that detects the temperature of a predetermined portion of the printing substrate 101 (as in the illustrated example), or may perform open-loop control without feedback. The second temperature sensor 53 may detect the temperature of the printing substrate 101 itself, may detect the air temperature near the printing substrate 101, or may detect the temperature of an appropriate portion of the auxiliary melting device 13 (for example, the surface or interior of the second heating roller 17B). In either case, the second temperature sensor 53 may be a non-contact temperature sensor or a contact temperature sensor. Specific examples of contact and non-contact temperature sensors are as described above. The detected temperature may be compared directly with a target value, or may be compared with the target value after appropriate correction (for example, conversion to a temperature at a position different from the sensor position) has been performed.

[0116] The auxiliary melter 13 may be designed to raise the temperature of the substrate 101 (and ink) to a predetermined temperature. The predetermined temperature may be, for example, a temperature equal to or higher than the Tg of most (or all) of all polymers contained in the ink that have a Tg higher than room temperature, excluding the fixer polymer, but lower than the Tg of the fixer polymer. The term "most (all)" is as described above. The melter 11 may be designed to raise the temperature of the ink to a temperature (e.g., a temperature equal to or higher than the Tg of the fixer polymer) higher than the predetermined temperature (the target temperature of the auxiliary melter 13) by irradiating UV light. If such an operation is intended and heating the ink by the melter 11 has a significant effect on the temperature of the substrate 101, the control of the auxiliary melter 13 may be, for example, feedback control that brings the detected temperature of an appropriate portion of the auxiliary melter 13 (including the temperature obtained by converting the detected temperature into the temperature of the substrate 101) closer to the target temperature, rather than the temperature of the substrate 101 itself.

[0117] Specifically, the control of auxiliary melting device 13 is, for example, the control of power supplied to a heat-generating element (e.g., a heating wire or an induction coil) via a driver (not shown). More specifically, the voltage, current, and / or frequency (in the case of AC) may be controlled depending on the type of heat-generating element. Note that second temperature control unit 43 may be conceptualized as including a driver. Furthermore, the control of auxiliary melting device 13 may be other control than the above. For example, in a configuration in which a heat medium is supplied to second heating roller 17B, the flow rate of the heat medium may be controlled.

[0118] (UV control unit) The UV control unit 45 controls the melting device 11 so that the intensity of the UV irradiated onto the printing substrate 101 is maintained at a target value when the distance (WD: working distance) from the melting device 11 to the printing substrate 101 is constant, for example.

[0119] The target intensity value is essentially constant during operation of the printing apparatus 1, for example. The target value may be a fixed value set by the manufacturer of the printing apparatus 1, a value set by the user, or a value set by the UV control unit 45 based on predetermined information. The predetermined information may be, for example, information about the ink input by the manufacturer or user (e.g., information that can identify the Tg of a predetermined polymer), and / or the temperature of the area of ​​the substrate 101 to be irradiated with UV light, assuming that UV light is not irradiated. The temperature assuming that UV light is not irradiated may be a value input by the manufacturer or user, or may be a value calculated by the UV control unit 45 based on predetermined information. The predetermined information may be, for example, the target temperature (or, in other words, the amount of heat) of the elements to be heated (9 (17A), 21 (33), and / or 13 (17B)) and the relative positions (distances) of these elements and the melting device 11.

[0120] The UV control unit 45 performs, for example, open-loop control without feedback of UV intensity. The UV control unit 45 also controls the power supplied to the light source 11a that generates UV via a driver (not shown). More specifically, the voltage, current, and / or frequency (in the case of AC) may be controlled depending on the state of the light source 11a. The driver may perform feedback control of the power. The UV control unit 45 may be conceptualized as including the driver.

[0121] (ink fixing effect) FIG. 5 is a conceptual diagram illustrating the fixing of ink onto the printing substrate 101 in the printing device 1. As shown in FIG.

[0122] The up, down, left, and right directions in FIG. 5 correspond to the up, down, left, and right directions in FIG. 1. FIG. 5 shows a cross section of a portion of the printing substrate 101. The printing substrate 101 is transported from the left side of the page to the right side of the page. An enlarged cross section of a portion of the head 21 is shown in the upper left of the page. When the ink 103 is ejected as droplets from the head 21 and adheres to the surface (top) of the printing substrate 101, it moves along with the printing substrate 101 while changing the ratio of its components and the state of its components (e.g., glassy state). FIG. 5 may be interpreted as a diagram showing the change in the state of the same droplet (ink 103) over time, or as a diagram showing multiple different droplets simultaneously. In the following description, the same reference symbol (103) is used for the ink 103 even if the ratio and state of its components change.

[0123] In FIG. 5, five states (component ratios and component states) of the ink 103 are conceptualized, from a first state S1 to a fifth state S5.

[0124] The first state S1 is the state of the ink 103 when it is held in the head 21 (in other words, before ejection). The ink 103 in the first state S1 contains, for example, a medium 105 (solvent and / or dispersion medium), a colorant 107, and two or more types of polymers (109 and 111). The two or more types of polymers include at least a fixer polymer 109 and a first polymer 111. The first polymer 111 is an example of a polymer having a Tg higher than room temperature and lower than the Tg of the fixer polymer 109. As described above, the ink may contain other components (including polymers) in addition to the above. However, for ease of illustration, the other components are omitted from FIG. 5.

[0125] The following description of the first polymer 111 may be applied to other polymers unless a contradiction arises. In the following description, the term "first polymer 111" may be replaced with the term "most (or all) of all polymers other than the fixer polymer 109 that are contained in the ink and have a Tg higher than room temperature and lower than the Tg of the fixer polymer 109," unless a contradiction arises. The term "most" has already been described.

[0126] For convenience of illustration, the colorant 107 is represented as particles (or, from another perspective, pigments) dispersed in the medium 105. Furthermore, the fixer polymer 109 exists in the form of particles (in other words, solids) in the first state S1. As described above, polymers other than the fixer polymer 109 may be solutes or dispersoids, and may also be liquids or solids in the first state S1. The illustrated first polymer 111 is represented as a string-like dispersant polymer. As described above, the drawings in this disclosure are schematic, and the diameters and densities of the particles in the ink 103 do not reflect actual values.

[0127] The second state S2 is the state of the ink 103 when it is flying from the head 21 toward the printing substrate 101 (in other words, after being ejected and before landing). The second state S2 (the ratio of the components and the state of the components) is basically the same as the first state S1.

[0128] The third state S3 is the state of the ink 103 after it is attached to the printing substrate 101 until a certain amount of time has passed. In this state, the medium 105 gradually evaporates. At this time, the ink 103 is heated in advance by the head heater 33, which promotes evaporation of the medium 105. In addition, the printing substrate 101 is heated by the drying device 9, and the heat is transferred to the ink 103, which promotes evaporation of the medium 105.

[0129] Although not specifically shown, polymers other than the fixer polymer 109 that were particles in the first states S1 and S2 may be partially or entirely in a glassy state in the third state S3. One or more of the other polymers may be decomposed by heat and evaporated. Additives other than the polymer contained in the ink may remain or may evaporate.

[0130] The fourth state S4 is the state of the ink 103 just before UV irradiation by the melting device 11. In this state, the evaporation of the medium 105 is more advanced than in the third state S3. For example, the evaporation of the medium 105 may be complete. As the medium 105 evaporates, the solutes dissolved in the medium 105 or the dispersoids dispersed therein (excluding those that evaporate as described above) remain aggregated. Figure 5 shows a state in which the colorant 107 and the fixer polymer 109 are aggregated.

[0131] Other polymers (e.g., first polymer 111) than the fixative polymer 109 may remain or may be decomposed and evaporated. If remaining, they may be in a glassy state or not. For example, all remaining polymers other than the fixative polymer 109 may be in a glassy state. Note that in FIG. 5, for ease of illustration, the first polymer 111 is omitted regardless of whether it is present or not for the ink 103 in the fourth state S4 and the fifth state S5.

[0132] The fifth state S5 is the state of the ink 103 when UV is irradiated by the melting device 11. In this state, the colorant 107 absorbs UV and generates heat, which melts the fixer polymer 109 (turning to a glassy state). Thereafter, although not shown, when the UV irradiation ends and the temperature of the ink 103 drops, the fixer polymer 109 solidifies, and the colorant 107 is fixed to the printing substrate 101. Although not shown, if the ink 103 contains another polymer (e.g., the first polymer 111) that remains after heating, the other polymer also solidifies (or remains in a solid state).

[0133] As described above, a part or all of the medium 105 may be evaporated before the fixative polymer 109 is melted. In this case, for example, it is possible to reduce the possibility that the fixative polymer 109 in a glassy state will form a film and inhibit evaporation of the medium 105. As a result, it is possible to efficiently evaporate the medium 105. The amount of evaporation of the medium 105 before the fixative polymer 109 is melted (or, from another perspective, immediately before heating with UV light) may be, for example, 30% by mass or more, 50% by mass or more, 70% by mass or more, or all (95% by mass or more or 100% by mass) of the medium 105 based on the first state S1.

[0134] By irradiating the ink 103 with UV light and heating it, for example, it is possible to raise the temperature of the ink 103 in a short time and melt the fixer polymer 109. However, heat generation occurs mainly in the colorant 107 and is therefore localized. As a result, if the ink 103 is heated only by UV, an excessive temperature rise occurs locally, which may degrade the quality of the ink 103 and / or the printed material 101. By heating the printed material 101 using the drying device 9 and / or auxiliary melting device 13, for example, it is possible to reduce the temperature rise time while mitigating localized heat generation.

[0135] Paradoxically, whether or not the fixer polymer 109 is a fixer polymer may be determined not by its composition and / or ingredients but by the presence or absence of the above-mentioned action. In other words, the fixer polymer 109 may be defined as a polymer, among two or more types of polymers contained in the ink 103, that exists in a solid (particle) state before heating by the melting device 11 (e.g., a device that irradiates UV light), melts (becomes glassy) due to the heating operation (e.g., UV irradiation) of the melting device 11, and then remains in the ink 103 as a solid component.

[0136] (head heater target temperature) The head 21 may have, for example, a head heater 33 that maintains the temperature of the ink 103 in the first state S1 at a predetermined target temperature, as described above. Furthermore, the first state S1 (component ratio and component state) may be basically the same as the state of the ink 103 at room temperature (except for viscosity, etc.). Therefore, for example, the target temperature of the head heater 33 may be set to a temperature lower than the Tg of any or all types of polymers that are not intended to be in a glassy state at room temperature. From the opposite perspective, the ink 103 may be configured so that the Tg of any or all types of polymers is higher than the target temperature of the head heater 33. Setting the target temperature and / or Tg as described above reduces the likelihood of the molten polymer adhering to the inner surface of the nozzle 21b, for example.

[0137] Furthermore, the target temperature of the head heater 33 may be set as high as possible within a range lower than the Tg of any or all of the polymers. Conversely, the ink 103 may be configured so that the Tg of any or all of the polymers is set as low as possible within a range higher than the target temperature of the head heater 33. Setting the target temperature and / or Tg in this manner can, for example, shorten the time it takes for the ink 103 to settle on the substrate 101 after landing on the substrate 101. Furthermore, for example, it can reduce the likelihood of unintended spreading of droplets after landing on the substrate 101 (improving shape retention). The inventors have found through experiments that keeping the temperature of the ink 103 high (for example, at 45° or higher) improves the shape retention of the ink 103.

[0138] Specific examples of the Tg of any or all of the above polymers and the target temperature of the head heater 33 are given below. The Tg of the polymer may be 50°C or higher. Meanwhile, the target temperature range of the head heater 33 may be 40°C or higher but lower than 50°C, or 40°C or higher but lower than 45°C. From another perspective, for example, the difference between the target temperature of the head 21 and the Tg of a specific type of polymer (e.g., a dispersant polymer or an abrasion-resistant polymer) contained in the ink 103 may be 1°C or higher but 10°C or lower, or 1°C or higher but 5°C, provided that the former is lower than the latter.

[0139] In the second state S2, the temperature of the ink 103 (droplets) decreases as they fly. This temperature change is linear with respect to the flight distance (over time). The amount of temperature decrease is relatively small. An example of a calculation is shown below. Assume that a 2 pL droplet flies a distance of 1 mm at an initial speed of 10 m / s in an atmosphere at 25°C. In this case, if the initial temperature of the droplet is 40°C, the temperature of the droplet decreases to 38.0°C. If the initial temperature of the droplet is 50°C, the temperature of the droplet decreases to 46.6°C. Assume that a 10 pL droplet flies a distance of 1 mm at an initial speed of 10 m / s in an atmosphere at 25°C. In this case, if the initial temperature of the droplet is 40.0°C, the temperature of the droplet decreases to 39.3°C. If the initial temperature of the droplet is 50°C, the temperature of the droplet decreases to 48.8°C. When setting the target temperature of the head heater 33 and / or the target temperature of the drying device 9 described below, this temperature difference may or may not be taken into consideration.

[0140] (Target temperature of the dryer) As described above, the drying device 9 may maintain the temperature of the substrate 101 at a target temperature. The temperature of the substrate 101 and the temperature of the ink 103 in the third state S3 may be considered to be approximately equal. The target temperature of the drying device 9 (or, from another perspective, the temperature of the ink 103 in the third state S3; the same applies in this and the next paragraphs) may be set lower than the Tg of the fixer polymer 109. Conversely, the ink 103 may be configured so that the Tg of the fixer polymer 109 is higher than the target temperature of the drying device 9. Setting the target temperature and / or Tg in this manner reduces the likelihood that evaporation of the medium 105 will be inhibited by a film of molten fixer polymer 109, as described above, for example.

[0141] The target temperature of the drying device 9 may be set as high as possible within a range lower than the Tg of the fixer polymer 109. For example, the target temperature of the drying device 9 may be set so that the temperature of the printing substrate 101 when the ink 103 lands on the printing substrate 101 is higher than the temperature of the ink 103. In this case, for example, the effect of promoting evaporation of the medium 105 is improved. From the opposite perspective, the ink 103 may be selected so that the Tg of the fixer polymer 109 is as low as possible within a range higher than the target temperature of the drying device 9. In this case, for example, the time required to melt the fixer polymer 109 can be shortened.

[0142] In setting the target temperature of the drying device 9, the time required for the medium 105 to evaporate may be taken into consideration.

[0143] 6 is a diagram showing the results of calculations of the time required for evaporation of the medium 105. In this diagram, the horizontal axis represents the surface temperature T (°C) of the droplet of ink 103. The vertical axis represents the time t (s) until evaporation of the medium 105 of the ink 103 is complete.

[0144] In this calculation, we assumed a droplet of water, not a droplet of ink 103. Also, approximately 3.8 × 10 -10 m 2 It is assumed that a hemispherical water droplet with a surface area of ​​is exposed to an atmosphere at 25°C.

[0145] As shown in the figure, the time t rapidly decreases when the temperature T becomes higher than the ambient temperature, and then becomes roughly constant just before the boiling point (about 70°C). Although not shown in Figure 6, when the temperature T is the same as the ambient temperature (25°C), the time t is about 4000 s. From this result, the target temperature of the drying device 9 may be set to 70°C, for example.

[0146] Specific examples of the Tg of the fixer polymer 109 and the target temperature of the drying device 9 (or, from another perspective, the temperature of the ink 103 in the third state S3; the same applies throughout this paragraph) are given below. The Tg of the fixer polymer may be 70°C or higher and 120°C or lower. On the other hand, the target temperature of the drying device 9 may be 50°C or higher and lower than 120°C, 60°C or higher and lower than 120°C, or 70°C or higher and lower than 120°C, provided that the target temperature is lower than the Tg of the fixer polymer 109. Also, from another perspective, the difference between the Tg of the fixer polymer 109 and the target temperature of the drying device 9 may be 1°C or higher and lower than 50°C, 1°C or higher and lower than 30°C, or 1°C or higher and lower than 10°C, provided that the former is higher than the latter. These specific examples may be combined with the previously described specific examples of the Tg of polymers other than the fixer polymer 109 and the target temperature of the head heater 33, provided that no contradictions arise.

[0147] In this embodiment, the drying device 9 is realized by the first heating roller 17A. The temperature of the printing substrate 101 decreases with increasing distance from the position of the first heating roller 17A. In this embodiment, the above-mentioned target temperature may be, for example, a target value for the temperature at a predetermined position from the position of the first heating roller 17A to just before the position where the ink 103 lands (the position of the ink ejection device 7). For example, the predetermined position may be the position of the first heating roller 17A or a position just before the ink ejection device 7. The target value for the temperature at the predetermined position may be set so that the temperature of the printing substrate 101 falls within the above-mentioned target temperature range over the entire area from the position of the first heating roller 17A to the position just before the ink ejection device 7.

[0148] An example of the results of trial calculation of the temperature distribution of the printing substrate 101 is shown below.

[0149] The conditions (assumptions) for the calculations were as follows: Three cases were assumed for the temperature of the first heating roller 17A: 50°C, 60°C, and 70°C. The temperature of the second heating roller 17B was set to 70°C. The influence of the melting device 11 was not taken into consideration. The temperature of the atmosphere around the printing substrate 101 was set to 25°C. The conveying speed of the printing substrate 101 was set to 100 m / min. The printing substrate 101 was made of PET with a thickness of 12 μm.

[0150] Fig. 7 is a diagram showing the results of the trial calculation. In this diagram, the horizontal axis represents the position x (m) in the D1 direction. The vertical axis represents the temperature T (°C) of the printing substrate 101. Position x1 represents the position of the first heating roller 17A. Position x2 represents the position of the second heating roller 17B. Lines LT50, LT60, and LT70 represent the results of the trial calculation when the temperatures of the first heating roller 17A are 50°C, 60°C, and 70°C, respectively.

[0151] As shown in this figure, the temperature of the printing substrate 101 decreases approximately linearly. Therefore, for example, based on the temperature (or, from another perspective, the amount of heat) of the drying device 9 (first heating roller 17A in this embodiment), the relative position (distance) between the drying device 9 and another device (e.g., the ink discharge device 7 or the melting device 11), and the transport speed of the printing substrate 101, the temperature of the printing substrate 101 (ink 103) in the other device (7 or 11) can be easily estimated. Note that the distance and transport speed may also be considered as the transport time from the drying device 9 to the other device.

[0152] From another perspective, by setting the values ​​(target values) of the above parameters (heat amount, distance, transport speed, etc.), it is possible to realize any temperature at any position, thereby achieving the various effects described above. For example, the temperature of the portion of the printing substrate 101 immediately before it faces the ink ejection device 7 can be set to a temperature equal to or higher than the Tg of the first polymer 111 and lower than the Tg of the fixer polymer 109. In the region from immediately after the drying device 9 (first heating roller 17A in this embodiment) to immediately before it faces the melting device 11, the temperature of the printing substrate 101 can be set to a temperature equal to or higher than the Tg of the first polymer 111 and lower than the Tg of the fixer polymer 109. Furthermore, evaporation can be completed before the fixer polymer 109 is melted by the melting device 11.

[0153] 7 shows that when the temperature of the first heating roller 17A is set to 60°C or higher (even 70°C or higher), a temperature of approximately 40°C or higher is maintained even 1.5 m downstream. In other words, a relatively high temperature is maintained over a relatively long distance (or, from another perspective, time). This reduces the likelihood of a temperature drop occurring in the ink 103 that has landed on the printing substrate 101, for example, and ensures the shape retention of the ink 103. Alternatively, the temperature of the ink 103 can be raised to promote evaporation.

[0154] (Target temperature of auxiliary melting device) As described above, auxiliary melting device 13 may maintain the temperature of substrate 101 at a target temperature. Auxiliary melting device 13 may be intended to operate to raise the temperature of substrate 101 to a predetermined temperature below the Tg of fixative polymer 109. If the heating of melting device 11, which is performed in parallel with the heating of auxiliary melting device 13, has a significant effect on the temperature of substrate 101, the target temperature here may be a target value for the temperature of a predetermined location of auxiliary melting device 13, rather than the temperature of substrate 101 itself.

[0155] The target temperature of auxiliary melting device 13 may be determined based on the description of the target temperature of dryer 9, as appropriate. For example, the target temperature of auxiliary melting device 13 may be lower than the Tg of fixer polymer 109, or may be as high as possible within a range lower than the Tg of fixer polymer 109. Specific values ​​for the target temperature of auxiliary melting device 13 may be in the range of 50°C to less than 120°C, 60°C to less than 120°C, or 70°C to less than 120°C, provided that the target temperature is lower than the temperature of fixer polymer 109. From another perspective, the difference between the Tg of fixer polymer 109 and the target temperature of auxiliary melting device 13 may be in the range of 1°C to 50°C, 1°C to 30°C, or 1°C to 10°C, provided that the former is higher than the latter.

[0156] (UV irradiation by melting device) As described above, the temperature of the printing substrate 101 (or, from another perspective, the ink 103) when the printing substrate 101 arrives just before the melting device 11, and / or the temperature of the printing substrate 101 (or, from another perspective, the ink 103) heated by the auxiliary melting device 13 may be set appropriately. The intensity and irradiation time of the UV irradiated by the melting device 11 (or, from another perspective, the irradiation length in the D1 direction), etc. may be set appropriately so that the fixing agent polymer 109 reaches or exceeds its Tg.

[0157] Below is an example of the results of a trial calculation of temperature rise due to UV irradiation.

[0158] First, the temperature rise of a resin containing carbon black (pigment) as the colorant 107 was calculated. The calculation conditions (assumptions) were as follows: The particle shape of the colorant 107 was a cube of 70 nm; The density of the colorant 107 was 2200 kg / m 3 The specific heat of the colorant 107 was set to 691 J / kgK. 5200 particles of the colorant 107 were assumed to be present in 0.8 pL of resin. The density of the resin was 1060 kg / m 3 The specific heat of the resin was 1340J / kgK. The UV intensity was 352kW / m 2 It was assumed that 80% of this heat was converted into heat. It was also assumed that the heat would not escape to the outside of the resin. Two cases were assumed for the initial temperature before UV irradiation: 25°C and 50°C.

[0159] Figure 8A shows the temperature change of 0.8 pL of resin under the above conditions. The horizontal axis represents the UV irradiation time t (μs). The vertical axis represents the temperature T°C. The dashed line represents the case where the initial temperature is 25°C, and the solid line represents the case where the initial temperature is 50°C.

[0160] As shown in this figure, the temperature of the resin containing the colorant 107 rises in a relatively short time to a temperature equal to or higher than the Tg of the fixer polymer 109. Specifically, for example, the temperature of the resin rises from 50° C. to 120° C. in about 0.01 s.

[0161] Next, the temperature rise of water containing the above resin was calculated. The conditions (assumptions) for the calculation were as follows: the ink was composed of a mixture of 1.2 pL of water and 0.8 pL of the above resin (containing 5200 colorants 107). The density of water was 1000 kg / m 3 The specific heat of water was set to 4180 J / kgK. It was assumed that heat would not escape to the outside of the ink. Two cases were assumed for the initial temperature before UV irradiation: 25°C and 50°C.

[0162] Figure 8B shows the temperature change of the water (or, from another perspective, the entire ink) under the above conditions. The horizontal axis represents the UV irradiation time t (μs). The vertical axis represents the temperature T°C. The dashed line represents the case where the initial temperature is 25°C, and the solid line represents the case where the initial temperature is 50°C.

[0163] As shown in this figure, the temperature of the ink rises in a relatively short time to a temperature equal to or higher than the Tg of the fixer polymer 109. Specifically, for example, the temperature of the ink rises from 50° C. to 120° C. in about 0.05 s.

[0164] As described above, the ink temperature can be estimated from the UV intensity and irradiation time. Conversely, the UV intensity and irradiation time (irradiation length in the D1 direction) can be set to obtain a desired temperature and / or temperature change. The desired temperature change is, for example, an increase in the temperature of the ink 103 heated by the drying device 9 and / or auxiliary melting device 13 (e.g., a temperature below the Tg of the fixer polymer 109) to a desired temperature (e.g., a temperature equal to or higher than the Tg of the fixer polymer 109).

[0165] The above example calculation also shows that, for example, UV irradiation can raise the temperature of the ink 103 to an arbitrary temperature in a relatively short time (for example, 0.05 seconds or less).

[0166] In the above example calculation, it takes about 0.05 seconds for the ink 103 to reach 120°C, while it takes about 0.01 seconds for the resin containing the colorant 107 to reach 120°C. This shows that UV irradiation causes a local temperature rise. From another perspective, it shows that the local temperature rise can be alleviated by raising the temperature of the ink 103 not only by the melting device 11 but also by raising the temperature of the ink 103 by the drying device 9 and / or auxiliary melting device 13.

[0167] (Example of device dimensions) The various dimensions of the printing device 1, the various dimensions of the various devices inside it, and the relative positions (distances) between the devices may be set as appropriate. In this embodiment, the ink 103 is efficiently dried and fixed to the printing substrate 101, so it is easy to shorten the overall length of the printing substrate 101 (particularly the length from the ink discharge device 7 to the recovery roller 3B). Examples of dimensional ranges are shown below. The ranges shown below are merely examples, and the various dimensions may be outside the ranges shown below.

[0168] The overall length of the printing device 1 in the transport direction (D1 direction) of the printing substrate 101 may be 1 m or more and 5 m or less. The distance parallel to the D1 direction from the axis of the supply roller 3A to the axis of the first heating roller 17A may be 200 mm or more and 600 mm or less. The diameter of the first heating roller 17A (and the second heating roller 17B) may be 20 mm or more and 100 mm or less. The distance parallel to the D1 direction from the axis of the first heating roller 17A to the front end of the ink discharger 7 may be 200 mm or more and 600 mm or less. The length parallel to the D1 direction from the front end to the rear end of the ink discharger 7 may be 300 mm or more and 900 mm or less. The length parallel to the D1 direction from the rear end of the ink discharger 7 to the front end of the melting device 11 or the axis of the second heating roller 17B may be 200 mm or more and 600 mm or less. The length parallel to the D1 direction from the front end to the rear end of the melting device 11 may be 5 mm or more and 30 mm or less. The length parallel to the D1 direction from the rear end of the melting device 11 to the axis of the recovery roller 3B may be 300 mm or more and 900 mm or less when a cooling device (not shown) for cooling the printing substrate 101 (ink 103) is provided. The above dimensions may be combined with a conveying speed of the printing substrate 101 of 50 mm / min or more and 300 mm / min or less.

[0169] As described above, in this embodiment, the ink 103 includes the medium 105, the colorant 107, the fixer polymer 109, and one or more polymers other than the fixer polymer 109 (e.g., the first polymer 111). The colorant 107 is dissolved in the medium 105 or dispersed in the medium 105. The fixer polymer 109 has a glass transition temperature (Tg) higher than room temperature and is dispersed in the medium 105. The one or more polymers other than the fixer polymer 109 have a Tg higher than room temperature and are dissolved in the medium 105 or dispersed in the medium 105. The Tg of the fixer polymer 109 is higher than the Tg of 80% or more by mass of all polymers other than the fixer polymer 109 that are contained in the ink 103 and have a Tg higher than room temperature.

[0170] In this case, the Tg of the fixer polymer 109 can be said to be set relatively high. If the Tg of the fixer polymer 109 is low, for example, a coating may be formed by the molten fixer polymer 109, and this coating may prevent evaporation of the medium 105. However, if the Tg of the fixer polymer 109 is high, the likelihood that the coating will prevent evaporation of the medium 105 is reduced. As a result, for example, the time required for drying and fixing the ink 103 can be shortened.

[0171] The Tg of the fixer polymer 109 may be higher than the Tg of all the polymers contained in the ink 103 .

[0172] In this case, for example, the above-mentioned effect of reducing the probability that the coating of the fixative polymer 109 will prevent the medium 105 from evaporating is improved.

[0173] The medium 105 may include water and an organic solvent.

[0174] In this case, for example, since the medium 105 contains water, which generally evaporates more slowly than organic solvents, the effect of increasing the Tg of the fixative polymer and facilitating evaporation of the medium 105 is enhanced. Furthermore, the organic solvent can, for example, reduce the drying of the medium 105 before ejection and / or adjust the drying speed of the medium 105 after ejection. As a result, for example, evaporation of the medium 105 within the intended period of time is facilitated.

[0175] The difference between the Tg of the fixer polymer 109 and the Tg of 80% or more by mass of all polymers other than the fixer polymer 109 that have a Tg higher than room temperature and are contained in the ink 103 (Tg lower than the Tg of the fixer polymer 109) may be 40°C or more and 60°C or less.

[0176] If the difference in Tg is small, the fixer polymer 109 is likely to melt when the medium 105 is evaporated, increasing the likelihood that evaporation of the medium 105 will be hindered. This in turn increases the time required for evaporation of the medium 105. Furthermore, if the difference in Tg is large (if the Tg of the fixer polymer is too high), it will take longer for the temperature of the fixer polymer 109 to rise to its Tg, and it will also take longer for the molten fixer polymer 109 to cool and solidify. In other words, the drying and fixing time will be longer. However, if the difference in Tg is within the above range, the likelihood of such inconvenience occurring can be reduced.

[0177] In the ink 103, 80% by mass or more of all polymers contained in the ink 103 that have a Tg higher than room temperature, other than the fixer polymer 109, and that have a Tg lower than that of the fixer polymer 109, may include a dispersant polymer. Alternatively, the 80% by mass or more of the polymers may be accounted for by the dispersant polymer.

[0178] In this case, for example, the dispersant polymer is dispersed in the medium 105 before evaporation of the medium 105 is complete, and is therefore less likely to form a film. Therefore, for example, even if the temperature of the ink 103 is raised to a temperature higher than the Tg of the dispersant polymer, the likelihood of the film hindering evaporation of the medium 105 is lower than in an embodiment in which the temperature of the ink 103 is raised to a temperature higher than the Tg of the fixer polymer. As a result, for example, the effect of efficiently evaporating the medium 105 by relatively raising the temperature of the ink 103 before the film of the fixer polymer 109 is formed is improved.

[0179] The printing device 1 may have an ink ejection device 7, a drying device 9, and a melting device 11. The ink ejection device 7 may apply the ink 103 described above to the substrate 101. The drying device 9 may promote evaporation of the medium 105 by heating the substrate 101. The melting device 11 may heat the ink 103 applied to the substrate 101 to melt the fixer polymer 109, thereby fixing the ink 103 (colorant 107) to the substrate 101.

[0180] Therefore, for example, evaporation of the medium 105 and melting of the fixer polymer 109 can be performed in separate devices. As a result, for example, it is possible to speed up the fixing of the ink 103, improve the fixing efficiency of the ink 103, and / or improve the quality of the ink 103. Specifically, for example, the drying device 9 heats the printing substrate 101, and therefore can raise the temperature of the printing substrate 101 in advance before the ink 103 lands on the printing substrate 101. This allows the drying device 9 to immediately raise the temperature of the ink 103 after the ink 103 lands on the printing substrate 101, thereby starting evaporation of the medium 105. Furthermore, for example, the melting device 11 heats the ink, and therefore can heat the fixer polymer 109 before heat is released into the printing substrate 101. As a result, thermal efficiency is improved. Furthermore, for example, since the ink 103 is heated not only by the melting device 11 but also by the drying device 9 via the printing substrate 101, the likelihood of the quality of the ink 103 and / or the printing substrate 101 being degraded by localized excessive heating is reduced. For example, the likelihood of wrinkling and / or deformation occurring in the printing substrate 101 due to localized heating is reduced. The fact that localized heating can cause wrinkling and / or deformation is knowledge gained by the inventors through experiments.

[0181] The fuser 11 may be located downstream of the dryer 9 in the transport direction of the substrate 101. In another aspect, the fuser 11 may melt the fixer polymer 109 after the dryer 9 evaporates the medium 105.

[0182] In this case, for example, melting of the fixer polymer 109 by the melting device 11 starts after at least a portion of the medium 105 has evaporated. As a result, the effect of reducing the probability that a film formed by the melted fixer polymer 109 will hinder evaporation of the medium 105 is improved. Consequently, the ink 103 can be dried and fixed in a short time.

[0183] The amount of heating of the substrate 101 by the drying device 9 (or, in other words, the target temperature), the relative position (or, in other words, the distance) between the drying device 9 and the melting device 11, and the conveying speed of the substrate 101 may be determined so that evaporation of the medium 105 by the drying device 9 is completed before melting of the fixative polymer 109 by the melting device 11 begins.

[0184] In this case, for example, the effect of reducing the likelihood that the coating of the fixer polymer 109 described above will prevent evaporation of the medium 105 is improved. Also, for example, the likelihood that air bubbles will be generated in the fixer polymer 109 due to the evaporated medium 105 is reduced, improving the quality of the ink 103 after fixing. Specifically, for example, the reduction in gloss due to air bubbles is reduced.

[0185] The printing apparatus 1 may have an auxiliary melting device 13. The auxiliary melting device 13 is located on the opposite side of the substrate 101 from the melting device 11, and may heat the substrate 101 from the back side of the surface (front surface) of the substrate 101 on which the ink 103 is attached, thereby assisting in melting the fixer polymer 109.

[0186] In this case, for example, the ink on the front surface of the substrate 101 can be heated by the melting device 11 (for example, by UV irradiation) while the rear surface of the substrate 101 is heated by the auxiliary melting device 13. As a result, for example, the temperature of the substrate 101 can be raised in a short time. Also, for example, compared to an embodiment in which the fixer polymer 109 is melted only by UV irradiation (this embodiment may also be included in the technology according to the present disclosure), local excessive temperature rise within the ink 103 is suppressed, and the likelihood of deterioration in the quality of the ink 103 and / or the substrate 101 is reduced.

[0187] Auxiliary melting device 13 may have a heating surface (the outer peripheral surface of second heating roller 17B) that is controlled to maintain a predetermined temperature and that contacts the back surface of printing substrate 101. In other words, auxiliary melting device 13 may heat printing substrate 101 so that the temperature of printing substrate 101 reaches a predetermined temperature. Melting device 11 may heat the ink attached to printing substrate 101 to a temperature higher than the predetermined temperature.

[0188] In this case, for example, the temperature of the printing substrate 101 is set to a predetermined temperature by the auxiliary melting device 13, which makes it easier to achieve the effect of reducing the likelihood of the above-mentioned local excessive temperature rise. Furthermore, even if the temperature of the atmosphere around the printing substrate 101 fluctuates, the auxiliary melting device 13 adjusts the amount of heat in response to the fluctuation, so control in the melting device 11 (for example, adjustment of UV intensity or irradiation time) does not need to be performed. In other words, control in the melting device 11 is simplified.

[0189] The drying device 9 may alternately and repeatedly bring the first portion 17a and the second portion 17b, which heat the printing substrate 101, into contact with the printing substrate 101.

[0190] In this case, compared to, for example, an embodiment in which the heater is plate-shaped and slides against the substrate 101 (continuously abuts against the substrate 101) (this embodiment may also be included in the technology according to the present disclosure), the temperature of the first portion 17a or the second portion 17b, which has decreased due to abutment against the substrate 101, can be increased during the period when the heater is not abutting against the substrate 101. As a result, for example, the rate at which the substrate 101 is heated can be maintained while reducing the amount of heat generated per unit volume of a heat generating part such as a heating wire. Consequently, the burden on the heat generating part is reduced.

[0191] The drying device 9 may heat the substrate 101 to a temperature below the glass transition temperature (Tg) of the fixer polymer 109. The melting device 11 may heat the ink 103 deposited on the substrate 101 to a temperature above the Tg of the fixer polymer.

[0192] In this case, for example, the probability that the fixing agent polymer 109 will melt due to heating by the drying device 9 is low, or even if it does melt, the amount of melting will be small. On the other hand, the fixing agent polymer 109 can be reliably melted by the melting device 11. As a result, the effect of reducing the probability that the coating of the fixing agent polymer 109 described above will prevent the medium 105 from evaporating is improved.

[0193] The drying device 9 may heat the substrate 101 to a temperature equal to or higher than the Tg of 80% or more by mass of all polymers contained in the ink 103 other than the fixer polymer 109 that have a Tg higher than room temperature, but lower than the Tg of the fixer polymer 109.

[0194] In this case, for example, the ink 103 can be said to be heated by the dryer 9 to a relatively high temperature that is in a temperature range below the Tg of the fixer polymer 109. Therefore, for example, the dryer 9 is more effective in promoting evaporation of the medium 105 as described above.

[0195] The drying device 9 may include a first drying device (first heating roller 17A in this embodiment) located upstream of the ink discharge device 7 in the transport direction (direction D1) of the printing substrate 101. The amount of heat applied by the first drying device, the relative positions of the first drying device and the ink discharge device 7, and the transport speed of the printing substrate 101 may be determined by the manufacturer, the user, and / or the control device 15 so that the temperature of the portion of the printing substrate 101 immediately before facing the ink discharge device 7 is equal to or higher than the Tg of 80% by mass or more of all polymers contained in the ink 103 that have a Tg higher than room temperature, other than the fixer polymer 109, and lower than the Tg of the fixer polymer 109.

[0196] In this case, for example, because the temperature of the printing substrate 101 immediately before the ink ejection device 7 is lower than the Tg of the fixer polymer 109, the probability that the temperature of the ink 103 that lands thereafter will reach the Tg of the fixer polymer 109 is reduced. This in turn reduces the probability that the coating of the fixer polymer 109 described above will hinder the evaporation of the medium 105. On the other hand, because the temperature of the printing substrate 101 immediately before the ink ejection device 7 can be said to be relatively high, the temperature of the ink 103 that lands thereafter can be raised in a short period of time, thereby promoting the evaporation of the medium 105.

[0197] The drying device 9 may be located upstream of the melting device 11 in the transport direction of the substrate 101. The amount of heat generated by the drying device 9 (or the target temperature in another sense), the relative positions (or the distance in another sense) between the drying device 9 and the melting device 11, and the transport speed of the substrate 101 may be determined by the manufacturer, the user, and / or the control device 15 so that the temperature of the substrate 101 in the region immediately after the drying device 9 to immediately before the portion facing the melting device 11 is equal to or higher than the Tg of 80% by mass or more of all polymers contained in the ink 103 that have a Tg higher than room temperature, other than the fixer polymer 109, and lower than the Tg of the fixer polymer 109.

[0198] In this case, for example, since the temperature of the printing substrate 101 in the region from immediately after the drying device 9 to immediately before the melting device 11 is lower than the Tg of the fixative polymer 109, the likelihood of a coating of the fixative polymer 109 being formed in this region is reduced. This in turn reduces the likelihood that the coating will hinder evaporation of the medium 105. On the other hand, since the temperature of the printing substrate 101 in the region can be said to be relatively high, the effect of promoting evaporation of the medium 105 is improved.

[0199] The melting device 11 may heat the ink 103 attached to the printing substrate 101 by irradiating it with UV light.

[0200] In this case, UV irradiation raises the temperature of the colorant 107, which in turn heats the fixer polymer 109. Therefore, for example, the fixer polymer 109 can be heated before the heat is dissipated into the printing substrate 101, improving thermal efficiency. Also, for example, heating by UV irradiation heats the ink 103 locally, so the drying device 9 effectively reduces local heating.

[0201] Second Embodiment FIG. 9 is a side view showing the configuration of a printing device 201 according to the second embodiment, and corresponds to FIG. 1 of the first embodiment.

[0202] In the printing apparatus 201, the melting device 11 is located downstream of the second heating roller 17B in the transport direction of the printing substrate 101. In other words, the printing apparatus 201 does not have an auxiliary melting device 13 that faces the melting device 11 across the printing substrate 101. The second heating roller 17B, together with the first heating roller 17A, constitutes a drying device 209 that is located upstream of the melting device 11. In other words, it can be said that the drying device 209 has a first drying device constituted by the first heating roller 17A and a second drying device constituted by the second heating roller 17B.

[0203] Regarding the control and target temperature of the first heating roller 17A (first drying device), the description of the control and target temperature of the first heating roller 17A (drying device 9) in the first embodiment may be used unless a contradiction occurs. In this case, the term "drying device 9" may be replaced with the term "drying device 209" or the term "first drying device" unless a contradiction occurs.

[0204] Regarding the control and target temperature of second heating roller 17B (second drying device), the description of the control and target temperature of first heating roller 17A (drying device 9) in the first embodiment may be used unless a contradiction occurs. In this case, the term drying device 9 or the term first heating roller 17A may be replaced with the term second drying device or the term second heating roller 17B unless a contradiction occurs. And / or, the description of the control and target temperature of second heating roller 17B (auxiliary melting device 13) in the first embodiment may be used. In this case, the term auxiliary melting device 13 may be replaced with the term second drying device unless a contradiction occurs.

[0205] For example, the amount of heating of the substrate 101 by the drying device 209 or the second heating roller 17B (second drying device), the relative position of the drying device 209 or the second heating roller 17B and the melting device 11, and the conveying speed of the substrate 101 may be determined so that evaporation of the medium 105 by the drying device 209 or the second heating roller 17B is completed before melting of the fixative polymer 109 by the melting device 11 begins. The amount of heat generated by the drying device 209 or the second drying device, the relative positions of the second drying device and the melting device 11, and the conveying speed of the substrate 101 may be determined so that in the region from immediately after the drying device 209 (or from another perspective, immediately after the second drying device) to just before the part facing the melting device 11, the temperature of the substrate 101 is equal to or higher than the Tg of the first polymer 111 (or 80% or more by mass of all polymers other than the fixing agent polymer 109 that have a Tg higher than room temperature and are contained in the ink 103) and lower than the Tg of the fixing agent polymer 109.

[0206] As described above, in this embodiment as well, the printing device 1 has an ink ejection device 7, a drying device 209, and a melting device 11. The ink ejection device 7 applies ink 103 containing a medium 105 and a fixer polymer 109 to the substrate 101. The drying device 209 heats the substrate 101 to promote evaporation of the medium 105. The melting device 11 heats the ink 103 applied to the substrate 101 to melt the fixer polymer 109 and fix the ink 103 (colorant 107) to the substrate 101.

[0207] Therefore, for example, the same effects as those of the first embodiment can be achieved. Specifically, for example, evaporation of the medium 105 and melting of the fixer polymer 109 can be performed in separate devices. As a result, for example, it is possible to speed up the fixing of the ink 103, improve the fixing efficiency of the ink 103, and / or improve the quality of the ink 103, etc.

[0208] As in this embodiment, the drying device 209 may have a first drying device (first heating roller 17A) arranged upstream of the ink discharge device 7 in the transport direction of the printing substrate 101, and a second drying device (second heating roller 17B) arranged downstream of the ink discharge device 7. The melting device 11 may be located downstream of the second drying device.

[0209] In this case, for example, by raising the temperature of the printing substrate 101 in advance by the first heating roller 17A before the ink 103 lands, the temperature of the ink 103 can be raised quickly after it lands. Also, for example, by heating the ink 103 after it lands by the second heating roller 17B, the medium 105 can be evaporated quickly. This makes it easy to complete the evaporation of the medium 105 before UV irradiation by the melting device 11.

[0210] In the first embodiment, compared to the second embodiment, for example, the second heating roller 17B is more likely to contribute to raising the temperature of the fixer polymer 109 to or above its Tg, which in turn is more likely to reduce the load on the melting device 11. Also, for example, if the distance from the ink discharge device 7 to the axis of the second heating roller 17B is the same in the first and second embodiments due to constraints on mechanical design, the first embodiment makes it easier to shorten the overall length of the printing device 1.

[0211] Third Embodiment FIG. 10 is a side view showing the configuration of a printing device 301 according to the third embodiment, and corresponds to FIG. 1 of the first embodiment.

[0212] The printing apparatus 301 has multiple (three in the illustrated example) melting devices 11A, 11B, and 11C. Each of the melting devices 11A, 11B, and 11C is, for example, basically the same as the melting device 11 of the first embodiment (except for specific design matters such as dimensions). Hereinafter, the letters A to C may be omitted and the melting devices 11A to 11C may not be distinguished from one another. Note that these three melting devices 11 may be considered as one melting device.

[0213] The multiple melting devices 11 are, for example, located at different positions in the transport direction of the printing substrate 101. The areas of the printing substrate 101 that are irradiated with UV by the multiple melting devices 11 may be separated from each other in the transport direction, may be adjacent to each other with substantially no gaps, or may overlap each other.

[0214] The multiple melting devices 11 are arranged, for example, along the portion of the printing substrate 101 that is curved convexly toward the front side by the second heating roller 17B. Each melting device 11 generally irradiates the curved portion of the printing substrate 101 with UV light in the normal direction to that portion. In other words, the curved portion of the printing substrate 101 is irradiated with UV light from multiple normal directions. FIG. 10 shows an example in which three melting devices 11A, 11B, and 11C irradiate the curved portion of the printing substrate 101 with UV light. By further increasing the distance between each melting device 11 and the printing substrate 101, even more melting devices 11 may be arranged. This allows UV light from even more melting devices 11 to be irradiated onto the curved portion of the printing substrate 101. In this way, by irradiating UV light onto the convexly curved portion of the printing substrate 101, UV light from multiple melting devices 11 can be irradiated onto a specific area of ​​the printing substrate 101 at an angle close to perpendicular. As a result, the energy density of the irradiated UV light can be increased, and the fixative polymer 109 can be melted in a short time.

[0215] Unlike the illustrated example, the multiple melting devices 11 may be arranged along a linearly extending portion of the printing substrate 101, and UV may be irradiated onto the linearly extending portion. Furthermore, the portion of the printing substrate 101 that is curved so as to be convex toward the front side thereof and that is irradiated with UV may be formed by a roller other than the second heating roller 17B, or may be formed by two or more rollers.

[0216] Although not specifically shown, the curved portion of the printing substrate 101 may be irradiated with UV light from multiple normal directions by a method other than multiple melting devices 11. For example, one melting device 11 may be configured to fit along the curved portion of the printing substrate 101. Specifically, for example, multiple light sources 11a may be arranged along the curved portion of the printing substrate 101, and a reflector, aperture, and / or power supply circuit, etc., common to the multiple light sources 11a may be provided. The reflector and / or aperture may have a shape that fits along the curved portion of the printing substrate 101. However, in this embodiment, a melting device 11 may be defined for each light source 11a, and the reflector, aperture, and / or power supply circuit may be shared among the multiple melting devices 11. Furthermore, for example, a melting device 11 may be provided that has a curved surface light source (also an example of light source 11a) in which multiple LEDs (an example of light source 11a) are arranged along the curved portion of the printing substrate 101.

[0217] The multiple melting devices 11 may have the same or different conditions, such as the UV wavelength, UV intensity, and / or the length of the area of ​​the printing substrate 101 irradiated with UV in the conveying direction.

[0218] For example, the UV wavelengths of multiple (some or all) melting devices 11 may be the same. In this case, for example, the length of the area irradiated with UV in the conveyance direction of the printing substrate 101 can be made longer than the length of UV irradiation that one melting device 11 can achieve. As a result, for example, it is possible to increase the conveyance speed of the printing substrate 101 while ensuring the UV irradiation time required for melting the fixer polymer 109 for the same position on the printing substrate 101. From another perspective, this improves the degree of freedom in designing the melting devices 11 to ensure the irradiation distance (time) required for melting the fixer polymer 109.

[0219] Furthermore, for example, the UV wavelengths of the multiple (some or all) melting devices 11 may be different from each other. As will be explained later in the description of modified inks, the UV wavelength at which the amount of UV absorbed by the ink (the amount of heat generated by UV) is large varies depending on the color of the ink 103 (the type of colorant 107). Therefore, for example, if the printing device 1 is a color printer, by providing a melting device 11 for each color that irradiates UV with a wavelength that generates a large amount of heat, the inks 103 of multiple colors can be heated evenly.

[0220] Similar to the melting device that irradiates UV onto the curved portion of the printing substrate 101, multiple melting devices 11 (multiple light sources 11a from another perspective) that irradiate UV of different wavelengths from each other may share a reflecting mirror, aperture, and / or power supply circuit, and may be configured to be considered as a single melting device. Multiple LEDs (an example of light source 11a) that irradiate UV of different wavelengths from each other may be arranged in a jumbled state to form a single surface light source (also an example of light source 11a).

[0221] As described above, in this embodiment, the printing device 301 also has the ink ejection device 7, the drying device 9, and the melting device 11. Therefore, for example, the same effects as in the first embodiment can be achieved. Specifically, for example, evaporation of the medium 105 and melting of the fixer polymer 109 can be performed in separate devices. As a result, for example, it is possible to speed up the fixing of the ink 103, improve the fixing efficiency of the ink 103, and / or improve the quality of the ink 103, etc.

[0222] The printing device 301 may have a conveying device 5 that conveys the printing substrate 101 while curving at least a portion of the printing substrate 101 so that the surface on which the ink 103 is applied becomes convex. One or more melting devices 11 may irradiate UV light onto the portion of the printing substrate 101 that has been curved by the conveying device 5 (more specifically, the second heating roller 17B).

[0223] In this case, for example, because the outer periphery is wider than the inner periphery, the area in which one or more melting devices 11 are disposed can be made wider relative to the area of ​​the substrate 101 irradiated with UV. As a result, for example, UV can be irradiated from multiple normal directions onto a relatively narrow area of ​​the substrate 101, increasing the energy density and raising the temperature of the ink 103 in a short period of time. Also, for example, because the length of the area irradiated with UV can be secured in a direction other than direction D1, the printer 1 can be made shorter more easily.

[0224] The printing device 301 may have multiple light sources 11a that emit UV light of different wavelengths, forming one or more melting devices 11.

[0225] In this case, for example, as described above, if the printing device 1 is a color printer, the inks 103 of multiple colors can be heated evenly by providing a light source 11a that irradiates UV light of a wavelength that generates a large amount of heat for each color. As a result, for example, the likelihood of an excessive or insufficient amount of heat being generated in the ink 103 of a specific color is reduced. This in turn improves the quality of the ink 103 and / or the printing substrate 101. From another perspective, the dependency of the function of melting the fixative polymer 109 on the color of the ink 103 is reduced, thereby improving versatility for various printing devices, including monochrome printers and color printers.

[0226] <Fourth embodiment> FIG. 11 is a side view showing the configuration of a printing device 401 according to the fourth embodiment, and corresponds to FIG. 1 of the first embodiment.

[0227] Similar to the drying device 209 of the second embodiment, the drying device 409 of the printing device 401 has a first drying device (first heating roller 17A) located upstream of the ink discharge device 7, and a second drying device 410 located between the ink discharge device 7 and the melting device 11. However, the second drying device 410 has a different configuration from the second drying device (second heating roller 17B) of the second embodiment.

[0228] Specifically, the second drying device 410 may be a warm air dryer that blows warm air toward the printing substrate 101. In the example shown, the second drying device 410 has a front-side dryer 455A that blows warm air toward the front side of the printing substrate 101, and a back-side dryer 455B that blows warm air toward the back side of the printing substrate 101 (hereinafter, the two may be simply referred to as dryers 455 without distinguishing between them). Note that the second drying device 410 may have only one of the front-side dryer 455A and the back-side dryer 455B.

[0229] The dryer 455 has, for example, a heat source and a blower that blows gas around the heat source, although not specifically shown. The heat source may be, for example, the same as that exemplified for the first heating roller 17A (an electric heating wire, an induction coil, or a flow path through which a heat medium flows). The blower may have, for example, a fan and a motor that rotates the fan. The dryer 455 may have a duct that guides the gas blown out by the fan to the printing substrate 101. Gas from one heat source may be guided by a duct to both the front and back sides of the printing substrate 101. The gas blown out to the printing substrate 101 is, for example, air.

[0230] With regard to the control or target temperature of the drying device 409 or the second drying device 410, the explanation of the drying device 9 (first heating roller 17A) in the first embodiment and / or the second drying device (second heating roller 17B) in the second embodiment may be used, unless there is any contradiction.

[0231] For example, the amount of heating of the substrate 101 by the drying device 409 or the second drying device 410, the relative position of the drying device 409 or the second drying device 410 and the melting device 11, and the conveying speed of the substrate 101 may be determined so that evaporation of the medium 105 by the drying device 409 or the second drying device 410 is completed before melting of the fixative polymer 109 by the melting device 11 begins. The amount of heat applied by the drying device 409 or the second drying device 410, the relative positions of the second drying device 410 and the melting device 11, and the conveying speed of the substrate 101 may be determined so that in the region from immediately after the drying device 409 (or from another perspective, immediately after the second drying device 410) to just before the part facing the melting device 11, the temperature of the substrate 101 is equal to or higher than the Tg of the first polymer 111 (or 80% by mass or more of all polymers other than the fixing agent polymer 109 that have a Tg higher than room temperature and are contained in the ink 103) and lower than the Tg of the fixing agent polymer 109.

[0232] Also, for example, the control of the second drying device 410 may be open-loop control or feedback control, as with other drying devices. In the latter case, the temperature sensor that detects the temperature of the printing substrate 101 may detect the temperature of the printing substrate 101 itself, may detect the air temperature near the printing substrate 101, or may detect the temperature of an appropriate part of the second drying device 410. However, in the second drying device 410 configured as a warm air dryer, the temperature sensor may detect the temperature of the gas sent to the printing substrate 101.

[0233] Also, for example, the control of the second drying device 410 may be the control of the power to the heat source, as in the case of other drying devices. However, in the second drying device 410 configured as a hot air dryer, the amount of air blown may be controlled.

[0234] As described above, in this embodiment, the printing device 401 also has the ink ejection device 7, the drying device 409, and the melting device 11. Therefore, for example, the same effects as in the first embodiment can be achieved. Specifically, for example, evaporation of the medium 105 and melting of the fixer polymer 109 can be performed in separate devices. As a result, for example, it is possible to speed up the fixing of the ink 103, improve the fixing efficiency of the ink 103, and / or improve the quality of the ink 103, etc.

[0235] The drying device 409 (second drying device 410) may be configured to include a hot air dryer that blows out heated gas. In this case, the configuration of the second drying device is simpler than, for example, the second embodiment in which the second drying device is configured by the second heating roller 17B. Note that the second embodiment has higher energy efficiency than the present embodiment, for example, because heat is less likely to escape to the periphery of the printing substrate 101.

[0236] (Modification of ink set) The ink sets according to the modified examples described below are assumed to include inks 103 of different colors, and to be irradiated with UV light of the same wavelength (hereinafter sometimes referred to as "specific wavelength"). In other words, the ink sets according to the modified examples are assumed to be applied to color printers in which one or more melting devices 11 (or, from another perspective, one or more light sources 11a) emit UV light of the same wavelength. However, the ink sets according to the modified examples may also be applied to color printers that can emit UV light of different wavelengths.

[0237] 12A is a schematic diagram showing an example of the light absorption characteristics of inks 103 of different colors. The inks 103 in this diagram are, for example, the inks 103 according to the embodiment, and not the inks 103 according to the modified examples.

[0238] In this diagram, the horizontal axis represents wavelength λ (nm). The vertical axis represents absorbance Abs (a dimensionless quantity). Range RU represents the range of UV wavelengths. Range RV represents the range of visible light wavelengths. Range RI represents the range of infrared wavelengths. Line LY represents the characteristics of yellow ink 103. Line LM represents the characteristics of magenta ink 103. Line LC represents the characteristics of cyan ink 103. Line LK represents the characteristics of black ink 103. The optical path lengths are the same for all four colors.

[0239] The absorbance is, for example, the logarithm of incident light intensity / outgoing light intensity with the base 10. The absorbance may include the effects of reflection and scattering, or may be the absorbance excluding the effects of reflection and scattering. For convenience, the following description will ignore the effects of reflection and scattering on the absorbance.

[0240] As shown in this figure, the absorbance of the ink 103 varies depending on the wavelength of light. In other words, the amount of heat generated by the ink 103 when irradiated with light (e.g., UV) varies depending on the wavelength of the light. The manner of this change differs depending on the color of the ink 103. From another perspective, differences in the color of the ink 103 are due to differences in the material and / or content (mass%) of the colorant 107. Therefore, the amount of heat generated when irradiated with UV light of the same wavelength differs between inks 103 that differ in the material and / or content (mass%) of the colorant 107. In the example shown, the absorbance of UV light at the specific wavelength λ1 is highest for black, followed by cyan, and lowest for yellow and magenta. As a result, there is a possibility that black may be overheated or, conversely, yellow and magenta may not be heated enough.

[0241] Therefore, a UV absorber other than the colorant 107 may be added to at least one type of ink 103 in the ink set so that the amount of heat generated by UV (or, from another perspective, UV of a predetermined wavelength) from the melting device 11 is similar among the multiple types of ink 103 of different colors. For example, at least two types of ink in the multiple types of ink 103 may have different contents of the UV absorber other than the colorant 107 (one of the inks 103 may not contain a UV absorber). With this configuration, by adjusting the content of the UV absorber, it is possible to make the amount of heat generated by UV from the melting device 11 similar among the multiple types of ink 103.

[0242] Furthermore, among at least two types of ink 103, the colorant 107 contained in one ink 103 may have a lower absorbance of UV from the melting device 11 than the colorant 107 contained in the other ink 103. Additionally, the one ink 103 may have a higher content of UV absorber than the other ink 103. In this case, the other ink 103 may not contain a UV absorber. The specific wavelength λ1 used to compare UV absorbances may be the center wavelength of the UV wavelength range emitted by the melting device 11. The magnitude relationship between the absorbances of the colorants 107 may be determined based on the magnitude relationship between the molecular extinction coefficients (molar extinction coefficients) of the colorants 107. Furthermore, the magnitude relationship between the absorbances of the colorants 107 may be determined based on the magnitude relationship between the absorbances of solutions of the colorants 107 dispersed in a solvent (e.g., water) at similar concentrations. The molecular extinction coefficient is a value specific to the colorant 107, and the concentration of the colorant 107 in the ink 103 does not change significantly. Therefore, with this configuration, the amount of heat generated by UV from the melting device 11 can be made even closer among multiple types of ink 103.

[0243] Furthermore, among the multiple types of inks 103, the ink 103 with a lower absorption rate of the colorant for the UV from the melting device 11 may have a higher UV absorber content. In other words, when focusing on two types of inks 103, one ink 103 may have a lower absorption rate of the colorant 107 for the UV from the melting device 11 than the other ink 103. In addition, the one ink 103 may have a higher UV absorber content than the other ink 103. In this case, the other ink 103 may not contain any UV absorber at all. The specific wavelength λ1 used to compare absorbances may be the center wavelength of the wavelength range of UV emitted by the melting device 11. The absorbance may be, for example, absorbance or a value (absorption coefficient) obtained by dividing absorbance by the length of the sample (ink) on which the UV is incident. The "UV absorbance by the colorant 107 of the ink 103" may be, for example, the UV absorbance of a sample containing the colorant 107 at the same content as the colorant 107 in the ink 103, with the remainder (e.g., the medium 105) not substantially absorbing UV. Alternatively, the "UV absorbance by the colorant 107 of the ink 103" may be the UV absorbance of the ink 103 according to a modified example, in which the UV absorber is replaced with the same mass of the medium 105. The absorbance may be determined using measurements with a known spectrophotometer. With this configuration, the amounts of heat generated by UV from the melting device 11 can be made closer among the multiple types of inks 103.

[0244] FIG. 12B is a schematic diagram showing an ink set including ink 103 to which a UV absorber has been added as described above.

[0245] For ease of illustration, only the medium 105, colorant 107, and UV absorber 113 are shown among the components of the ink 103, and the fixative polymer 109 and other components are omitted. In the drawing, K, C, Y, and M correspond to black, cyan, yellow, and magenta.

[0246] The illustrated example assumes that UV of the specific wavelength λ1 in Figure 12A is used. The black ink 103, which generates the most heat at the specific wavelength λ1, does not contain a UV absorber 113. On the other hand, the cyan ink 103 contains a UV absorber 113. Furthermore, the yellow and magenta inks 103, which generate the least heat at the specific wavelength λ1, contain more UV absorber 113 than the cyan ink 103.

[0247] Fig. 13A is a schematic diagram showing an example of the light absorption characteristics of the UV absorber 113. The horizontal and vertical axes of this diagram are the same as those of Fig. 12A.

[0248] As shown in this figure, the UV absorber 113 has, for example, a peak where the absorbance increases. This peak is generally within the range UV. That is, the UV absorber 113 generates a large amount of heat due to UV, but has little effect on visible light (visibility of the ink 103). For example, the absorbance in the range RV is 10% or less or 5% or less of the peak of absorbance or the absorbance at the UV wavelength (specific wavelength λ1) of the melting device 11.

[0249] 13B is a schematic diagram showing an example of the light absorption characteristics of a modified ink 103 (ink 103 to which a UV absorber 113 has been added). The horizontal and vertical axes in this diagram are the same as those in FIG. 12A. The lines LY, LM, LC, and LK correspond to four colors, as in FIG. 12A.

[0250] In this figure, as explained with reference to FIG. 12B, by adding a UV absorber 113 having the characteristics shown in FIG. 13A, the absorbance (or, from another perspective, absorptance) at the UV wavelength (specific wavelength λ1) of the melting device 11 is made equal among multiple colors. For example, at the specific wavelength λ1, the difference in absorptance among all colors is 50% or less, 20% or less, or 10% or less of the highest absorptance. Note that, in the ink set according to the modified example, it is sufficient that the difference in absorptance at the specific wavelength λ1 between at least two colors of ink 103 is reduced to some extent by adding the UV absorber 113. In other words, it is not necessary for the absorptance at the specific wavelength λ1 of all colors to be equal, as in the example of FIG. 13B.

[0251] The color of the ink 103 differs before and after the UV absorber 113 is added to the ink 103. The color difference increases as the mass percentage of the UV absorber 113 in the ink 103 increases. Therefore, the mass percentage of the UV absorber 113 in each ink 103 may be set not only from the perspective of reducing the difference in UV absorption rate from other inks 103, but also from the perspective of keeping the color difference resulting from the addition of the UV absorber 113 below a predetermined threshold.

[0252] The threshold value is, for example, 10 or 5. This is because humans can generally recognize a color difference of 5 or more. The color difference may be measured, for example, using the color after printing as a reference. The color difference may be measured between an ink 103 containing a UV absorber 113 and an ink 103 having the same components as the ink 103 in the same ratios except for the UV absorber 113. The ratio here refers to the ratio of the masses of the components, not the percentage by mass that each component accounts for in the ink.

[0253] The inventors of the present application have confirmed through experiments that it is possible to make the UV absorption rates of inks 103 of different colors equal to each other while keeping the color difference caused by the UV absorber 113 at 10 or less. Specifically, this is as follows.

[0254] Black, cyan, yellow, and magenta inks 103 (without UV absorber 113 added) were prepared, each having approximately the same properties as those shown in Fig. 12A. For example, when the wavelength of this ink 103 was approximately 350 nm, the absorbance of black was approximately 0.8, the absorbance of cyan was approximately 0.4, and the absorbance of yellow and magenta was approximately 0.2.

[0255] Of the four ink colors 103, a UV absorber 113 was added to each of the three ink colors excluding black, which has the highest absorbance. The amount of UV absorber 113 added was 5% by mass (for convenience, referred to as 5% by mass; the same applies hereinafter) of the mass of the ink 103 before the UV absorber 113 was added. Dipropylene glycol was used as the UV absorber 113. Dipropylene glycol has a peak absorbance at a wavelength of approximately 350 nm.

[0256] The absorbance of the ink 103 was then measured after adding the UV absorber 113. At a wavelength of approximately 350 nm, the absorbance of cyan, yellow, and magenta was all higher than the absorbance of black (specifically, approximately 1 or higher). In other words, it was confirmed that the absorbance of the four colors could be made equivalent with an addition amount of 5% by mass or less.

[0257] Under the same conditions as above, ink 103 without UV absorber 113 added and ink 103 with UV absorber 113 added were prepared and the color difference between the two was measured. However, the amount of UV absorber 113 added was set to two levels: 2.5% by mass and 5% by mass relative to the mass of ink 103 before UV absorber 113 was added. The color difference was measured using ink 103 that had been applied to coated paper using a bar coater and had been sufficiently dried and fixed. The ink 103 was applied to a thickness such that the color of the coated paper would not affect the measurement.

[0258] Measurement results showed that when the amount added was 5% by mass, the color difference in all of cyan, yellow, and magenta was less than 10. Furthermore, when the amount added was 2.5% by mass, the color difference in yellow and magenta was less than 5. This confirmed that it is possible to keep the color difference due to addition to 10 or less at an amount that can make the absorbance equivalent.

[0259] The UV absorber 113 may have any suitable composition. For example, the UV absorber 113 may be one used to protect polymers or colorants, or one used in cosmetics. Examples of such UV absorbers include dihydroxybenzophenone-based compounds, benzotriazole-based compounds, hydroxyphenyltriazine-based compounds, dipropylene glycol-based compounds, and cyanoacrylate-based compounds.

[0260] In this modification, the ink 103 also includes a medium 105, a colorant 107, a fixer polymer 109, and other polymers (e.g., a first polymer 111). The Tg of the fixer polymer 109 is higher than the Tg of 80% or more by mass of all polymers contained in the ink 103 that have a Tg higher than room temperature, other than the fixer polymer 109. Therefore, the same effects as those of the embodiment are achieved. For example, the likelihood that a coating of the molten fixer polymer 109 will prevent the medium 105 from evaporating is reduced. As a result, for example, the time required for the ink 103 to dry and fix can be shortened.

[0261] The ink set may include two types of inks 103 that differ from each other in colorant 107. At least one of the two types of inks 103 may include a UV absorber 113 that is separate from the colorant 107. The two types of inks 103 may differ from each other in the content of the UV absorber 113.

[0262] In this case, for example, the amount of heat generated by UV does not depend only on the colorant 107, but is adjusted by the UV absorber 113. As a result, for example, as described above, it is easy to equalize the amount of heat applied to inks 103 of different colors. Alternatively, conversely to the above, it is also possible to increase the difference in the amount of heat applied to inks 103 of different colors, thereby prioritizing the drying of ink of a specific color.

[0263] Of the two types of ink 103, the colorant 107 contained in one ink (e.g., Y or M) may have a lower absorbance of UV at a specific wavelength λ1 compared to the colorant 107 contained in the other ink 103 (e.g., C or K). The one ink 103 may have a higher content of UV absorber 113 compared to the other ink.

[0264] And / or, among two types of ink 103, one ink 103 (e.g., Y or M) may have a lower absorption rate of UV at a specific wavelength λ1 by the colorant 107 compared to the other ink (e.g., C or K), and may have a higher content of a UV absorber 113 separate from the colorant 107.

[0265] In these cases, for example, when UV light of a predetermined specific wavelength λ1 is irradiated, the variation in the amount of heat generated per unit time between colors of ink 103 is reduced. This in turn reduces the likelihood of excessive or insufficient heating of a specific color of ink 103. As a result, for example, the ink 103 is stably fixed to the printing substrate 101 regardless of the content (color scheme) of the image on the printing substrate 101.

[0266] The color difference between the printed color of the ink 103 containing the UV absorber 113 and the printed color of an ink having the same components as the ink 103 in the same proportions except for the UV absorber 113 may be 10 or less.

[0267] In this case, for example, it is possible to reduce the degradation of image quality caused by the addition of the UV absorber 113. As a result, for example, it is possible to shorten the time required for the ink 103 to fix while maintaining the image quality.

[0268] (Example) A specific example of a method for producing the ink 103 according to this embodiment will be described below.

[0269] Fig. 14 is a diagram for explaining Production Examples 1 and 6. Fig. 15 is a diagram for explaining Production Examples 2 to 5. Fig. 16 is a diagram for explaining Production Examples 7 to 10.

[0270] Production Example 1 is an example of a method for producing a dispersant polymer (an example of the first polymer 111). Production Examples 2 to 5 are examples of methods for producing an aqueous dispersion (a dispersion system mainly containing water as a medium; the same applies hereinafter) containing the dispersant polymer produced by Production Example 1 and a pigment as the colorant 107. Production Examples 2 to 5 are four production examples corresponding to four colors. Production Example 6 is an example of a method for producing an aqueous dispersion in which the fixer polymer 109 is dispersed. Production Examples 7 to 10 are examples of methods for producing an ink 103 containing the four color aqueous dispersions produced by Production Examples 2 to 5 and the aqueous dispersion of the fixer polymer 109 produced by Production Example 6. In the following, "parts" attached to numerical values ​​means "parts by mass" unless otherwise specified.

[0271] (Production Example 1: Synthesis of Dispersant Polymer) 115 parts of a monomer mixture liquid is prepared by mixing the multiple types of monomers shown in Fig. 14. Details of the monomers are as follows. Styrene: Wako Pure Chemical Industries, Ltd. Butyl acrylate: Wako Pure Chemical Industries, Ltd. Methacrylic acid: Wako Pure Chemical Industries, Ltd. Methoxypolyethylene glycol methacrylate: "Plenmer PME-200" (NOF Corporation)

[0272] A reaction vessel was charged with 10% (11.5 parts) of the monomer mixture, 18 parts of methyl ethyl ketone, and 0.03 parts of 2-mercaptoethanol (a chain transfer agent), followed by thorough nitrogen gas replacement. Meanwhile, a mixture of the remaining 90% (103.5 parts) of the monomer mixture, 0.27 parts of the chain transfer agent, 42 parts of methyl ethyl ketone, and 3 parts of 2,2-azobis(2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd.) (a polymerization initiator) was placed in a dropping funnel. The mixture in the reaction vessel was then heated to 75°C under a nitrogen atmosphere while being stirred, and the mixture in the dropping funnel was added dropwise to the reaction vessel over 3 hours.

[0273] After 2 hours at 75°C from the end of the dropwise addition, a solution of 3 parts of the polymerization initiator dissolved in 5 parts of methyl ethyl ketone is added to the reaction vessel. The mixture is further aged at 75°C for 2 hours and at 80°C for 2 hours, and then 50 parts of methyl ethyl ketone is added to the reaction vessel.

[0274] In this way, a solution of dispersant polymer is obtained. The weight average molecular weight of the dispersant polymer is about 50,000. The Tg of the dispersant polymer is about 60°C. The solid content concentration in the dispersant polymer solution is about 45% by mass.

[0275] (Production Example 2: Production of aqueous dispersion containing black pigment and dispersant polymer) 95.2 parts of the dispersant polymer solution obtained in Preparation Example 1 was dissolved in 53.9 parts of methyl ethyl ketone, and 15.0 parts of 5N aqueous sodium hydroxide and 0.5 parts of 25% aqueous ammonia were added as neutralizing agents, followed by 341.3 parts of ion-exchanged water. 100 parts of CI Pigment Black 7 (PB7, manufactured by Cabot Corporation) were then added as a carbon black pigment to obtain a pigment mixture. The degree of neutralization was approximately 79 mol%.

[0276] The pigment mixture is mixed for 1 hour using a disper blade at 7000 rpm and 20° C. The resulting dispersion is dispersed 15 times using a Microfluidizer "High-Pressure Homogenizer M-140K" (Microfluidics) at a pressure of 180 MPa.

[0277] Methyl ethyl ketone is removed from the resulting dispersion at 60°C under reduced pressure, and then water is removed. The dispersion is then centrifuged, and the liquid phase is filtered through a Mini Sart Syringe Filter (manufactured by Sartorius, pore size: 6 μm, material: cellulose acetate) to remove coarse particles, yielding an aqueous dispersion containing the black pigment and dispersant polymer.

[0278] To 100 parts of the obtained aqueous dispersion, 0.45 parts of an epoxy crosslinking agent (trimethylolpropane polyglycidyl ether manufactured by Nagase ChemteX Corporation, trade name: Denacol EX321L, epoxy equivalent 130) and 15.23 parts of ion-exchanged water are added, and the mixture is heated at 70°C for 3 hours while stirring.

[0279] After the heat treatment, the aqueous dispersion was cooled to room temperature, and the liquid layer was filtered through a "Mini Salt Syringe Filter" (manufactured by Saltous, pore size: 5 μm, material: cellulose acetate) to remove coarse particles, yielding an aqueous dispersion containing the black pigment and dispersant polymer. The solids concentration was approximately 22% by weight. The average particle size of the dispersant polymer was approximately 100 nm. Figure 15 shows the components and physical properties of the resulting aqueous dispersion.

[0280] (Production Examples 3 to 5: Production of aqueous dispersions containing pigments of other colors and dispersant polymers) Production Examples 3 to 5 were the same as Production Example 2, except that the type and amount of pigment, and the amount of Denacol EX321L added were changed. Details of the pigments shown in Figure 15 are as follows: Cyan: CI Pigment Blue 15:3 (manufactured by DIC Corporation) Magenta: CI Pigment Red 150 (Fuji Pigment Co., Ltd.) Yellow: CI Pigment Yellow 74 (Dainichiseika Color & Chemicals Mfg. Co., Ltd.)

[0281] (Production Example 6: Production of aqueous dispersion containing fixing agent polymer) 14 are mixed in a 1000 mL self-parable flask to prepare 200 parts of a monomer mixture. To this monomer mixture, 18.5 parts of Latemul E118B (emulsifier, Kao Corporation, active ingredient 26%), 96 parts of ion-exchanged water, and potassium persulfide (Wako Pure Chemical Industries, Ltd.) are added, and the mixture is stirred with a stirring blade (300 rpm) to obtain a monomer emulsion.

[0282] A reaction vessel was charged with 4.6 parts of Latemul E118B, 186 parts of ion-exchanged water, and 0.08 parts of potassium persulfide, and the atmosphere was replaced with nitrogen gas. Under a nitrogen atmosphere, the reaction vessel was heated to 80°C while stirring (200 rpm) with a stirring blade. The monomer emulsion was added dropwise to the reaction vessel using a dropping funnel over a period of 3 hours, and the reaction was allowed to proceed, yielding an aqueous dispersion containing fixing agent polymer 109.

[0283] In the aqueous dispersion containing the fixing aid polymer, the solid content is about 42% by weight, and the average particle size of the fixing aid polymer 109 is about 100 nm.

[0284] (Production Example 7: Production of black ink) 508.9 g of the aqueous dispersion containing the black pigment and dispersant polymer (22.0 wt.% solids) obtained in Production Example 2, 48.3 g of the aqueous dispersion containing the fixer polymer 109 (41.6 wt.% solids) obtained in Production Example 6, 44.0 g of diethylene glycol monoisobutyl ether (boiling point 230°C), 286.0 g of propylene glycol (boiling point 188°C), 5.5 g of a silicone surfactant (Shin-Etsu Chemical Co., Ltd., polyether-modified silicone, KF-6011, HLB 14.5), and 207.3 g of ion-exchanged water were mixed. The resulting mixture was filtered through a "Mini Sartus Syringe Filter" (Sartus, pore size: 5 μm, material: cellulose acetate) to obtain a black aqueous ink. Figure 16 shows the components and physical properties of the black ink.

[0285] (Production Examples 8-10: Production of inks of other colors) Production Examples 8 to 10 are basically the same as Production Example 7, except that the aqueous dispersions containing a black pigment were replaced with the aqueous dispersions obtained in Production Examples 3 to 5. Figure 16 shows the components and physical properties of the cyan, magenta, and yellow inks.

[0286] The technology according to the present disclosure is not limited to the above-described embodiment, and may be implemented in various forms.

[0287] The printing device to which the ink according to the present disclosure is applied may be any printing device and is not limited to the printing device according to the embodiment. For example, the printing device may be configured not to have a separate drying device that promotes evaporation of the medium and a melting device that melts the fixer polymer. Specifically, for example, a heating roller, a UV irradiation device, and / or a hot air dryer may be provided as a device that serves both as a drying device and a melting device. Even in this case, for example, the likelihood of a coating of the molten fixer polymer being formed prematurely is reduced, and the efficiency of evaporating the medium is likely to be improved.

[0288] From another perspective, the fixative polymer may be melted by, for example, a heated roller or a hot air dryer, rather than by UV irradiation. The fixative polymer may be melted by heat transferred from the substrate to the ink, rather than by directly heating the ink without the substrate being involved. The medium may be heated and evaporated by UV irradiation, rather than by a heated roller or a hot air dryer.

[0289] The printing substrate is not limited to a long object or to be conveyed by rollers. For example, the printing device may convey a conveyor belt, and the printing substrate may be placed on the conveyor belt and conveyed. In this case, the printing substrate may be, for example, a sheet of paper, a cut piece of cloth, wood, or a tile.

[0290] The printing apparatus is not limited to one having a transport device that moves the substrate. In other words, the concepts of "the transport direction of the substrate," "upstream in the transport direction," and "downstream in the transport direction" do not necessarily apply. For example, the printing apparatus may move various devices (drying device, ink ejection device, melting device, and / or auxiliary melting device) while the substrate is not moving. Specifically, printing may be performed while moving the ink ejection device along the surface of the substrate by a robot. Then, before bringing the ink ejection device close to the substrate or after the ink ejection device has retracted, the medium may be evaporated by a hot air dryer installed or transported by the robot. After the ink ejection device has retracted, the robot may bring the melting device close to the surface of the substrate to melt the fixative polymer. In this embodiment, not only two-dimensional printing but also three-dimensional printing may be performed by moving the ink ejection device along the surface of a three-dimensional substrate. Furthermore, the transportation of the substrate and the movement of various devices may be combined. Depending on the embodiment, the "transport direction of the substrate" may be replaced with the "direction of relative movement" between the substrate and various devices.

[0291] The drying device is not limited to a heating roller or a warm air dryer. For example, the drying device may heat the printing substrate by irradiating it with infrared rays. As mentioned in the description of the embodiment, the drying device is not limited to being located upstream or downstream of the ink ejection device in the conveyance direction of the printing substrate, but may be located at the same position as the ink ejection device. For example, the drying device may have a plate-shaped heater that faces the ink ejection device across the printing substrate and abuts against the back surface of the printing substrate. The melting device is not limited to one that irradiates UV. For example, a melting device that heats the ink directly without using the printing substrate may be one that blows warm air or irradiates infrared rays. [Explanation of symbols]

[0292] 1...printing device, 7...ink ejection device, 9...drying device, 11...melting device, 101...printing substrate, 103...ink, 105...medium, 109...fixing agent polymer.

Claims

1. It contains two types of ink, Each of the two types of ink is The medium and a colorant dissolved in or dispersed in the medium; an adhesion promoter polymer having a glass transition temperature greater than 20°C and dispersed in said medium; one or more polymers other than the adhesion promoter polymer, the polymers having a glass transition temperature greater than 20° C., dissolved in the medium or dispersed in the medium; It contains the glass transition temperature of the fixer polymer is higher than the glass transition temperature of 80% by mass or more of all polymers other than the fixer polymer that are contained in the ink and have a glass transition temperature higher than 20°C; The two types of inks have different colorants, At least one of the two types of ink contains an ultraviolet absorber separate from the colorant, Of the two types of inks, the colorant contained in one of the inks has a lower absorbance of ultraviolet light having a wavelength of 350 nm than the colorant contained in the other ink, and the one ink has a higher content of the ultraviolet absorber than the other ink. Ink set.

2. Of the two types of ink, one of the inks has a lower absorption rate of the colorant for ultraviolet light having a wavelength of 350 nm than the other ink, and has a higher content of the ultraviolet absorber than the other ink. The ink set according to claim 1 .

3. The color difference between the color of the one ink after printing and the color of an ink after printing that has the same components as the one ink in the same ratio except for the ultraviolet absorber is 10 or less. The ink set according to claim 1 or 2.

4. Ink and an ink ejection device that deposits the ink onto a substrate; a drying device that heats the printing material to promote evaporation of the medium contained in the ink; a melting device that heats the ink adhered to the substrate to melt a fixative polymer contained in the ink, thereby fixing the ink to the substrate; and The ink is the medium; a colorant dissolved in or dispersed in the medium; the adhesion promoter polymer having a glass transition temperature greater than 20°C and dispersed in the medium; one or more polymers other than the adhesion promoter polymer, the polymers having a glass transition temperature greater than 20° C., dissolved in the medium or dispersed in the medium; It contains the glass transition temperature of the fixer polymer is higher than the glass transition temperatures of 80% by mass or more of all polymers, other than the fixer polymer, that are contained in the ink and have a glass transition temperature higher than 20°C; The melting device irradiates the ink attached to the printing substrate with ultraviolet light to heat the ink. Printing device.

5. The melting device is located downstream of the drying device in the conveying direction of the printing material. The printing device according to claim 4 .

6. The fuser fuses the fixative polymer after the dryer evaporates the medium.

6. The printing device according to claim 4 or 5.

7. The amount of heating of the substrate by the drying device, the relative positions of the drying device and the fusing device, and the conveyance speed of the substrate are determined so that evaporation of the medium by the drying device is completed before melting of the fixative polymer by the fusing device begins. The printing device according to any one of claims 4 to 6.

8. the drying device heats the substrate to a temperature below the glass transition temperature of the fixative polymer; The melting device heats the ink on the substrate to a temperature above the glass transition temperature of the fixative polymer. The printing device according to any one of claims 4 to 7.

9. The drying device heats the printing substrate to a temperature equal to or higher than the glass transition temperature of the 80% or more by weight of the polymer and lower than the glass transition temperature of the fixer polymer. The printing device according to claim 8.

10. the drying device includes a first drying device located upstream of the ink ejection device in a transport direction of the printing medium, The amount of heat generated by the first drying device, the relative positions of the first drying device and the ink ejection device, and the conveyance speed of the printing substrate are determined so that the temperature of the portion of the printing substrate immediately before facing the ink ejection device is equal to or higher than the glass transition temperature of the 80% or more by mass polymer and lower than the glass transition temperature of the fixing agent polymer. The printing device according to claim 9.

11. the drying device is located upstream of the melting device in a conveying direction of the printing material, The amount of heat generated by the drying device, the relative positions of the drying device and the melting device, and the conveying speed of the printed material are determined so that the temperature of the printed material is equal to or higher than the glass transition temperature of the 80% or more by mass polymer and lower than the glass transition temperature of the fixing agent polymer in the region immediately after the drying device to just before the portion facing the melting device.

11. The printing device according to claim 9 or 10.

12. The difference between the glass transition temperature of the fixing agent polymer and the glass transition temperature of the polymer of 80% by mass or more is 40° C. or more and 60° C. or less. The printing device according to any one of claims 4 to 11.

13. the medium contains water that accounts for 50% by mass or more of the ink, The mass % of the fixer polymer in the ink is: 1% by mass or more, the total mass % of all polymers having a glass transition temperature higher than 20°C other than the fixer polymer is 0.5 times or more of the total mass % of the ink, The glass transition temperature of the fixing agent polymer is 70° C. or higher and 120° C. or lower. The printing device according to any one of claims 4 to 12.

14. an ink ejection step of depositing ink onto a substrate; a drying step in which the printing substrate is heated to promote evaporation of the medium contained in the ink; a melting step of heating the ink adhered to the substrate to melt a fixative polymer contained in the ink and fix the ink to the substrate; and The ink is the medium; a colorant dissolved in or dispersed in the medium; the adhesion promoter polymer having a glass transition temperature greater than 20°C and dispersed in the medium; one or more polymers other than the adhesion promoter polymer, the polymers having a glass transition temperature greater than 20° C., dissolved in the medium or dispersed in the medium; It contains the glass transition temperature of the fixer polymer is higher than the glass transition temperatures of 80% by mass or more of all polymers, other than the fixer polymer, that are contained in the ink and have a glass transition temperature higher than 20°C; The melting step involves irradiating the ink attached to the printing substrate with ultraviolet light to heat the ink. Printing method.

15. The melting step involves irradiating the ink adhered to the substrate with ultraviolet light to a temperature equal to or higher than the glass transition temperature of the fixative polymer. The printing method of claim 14.

16. The drying step heats the substrate to a temperature below the glass transition temperature of the fixative polymer before the fusing step.

16. The printing method according to claim 14 or 15.

17. The difference between the glass transition temperature of the fixing agent polymer and the glass transition temperature of the polymer of 80% by mass or more is 40° C. or more and 60° C. or less. The printing method according to any one of claims 14 to 16.

18. the medium contains water that accounts for 50% by mass or more of the ink, The mass % of the fixer polymer in the ink is: 1% by mass or more, the total mass % of all polymers having a glass transition temperature higher than 20°C other than the fixer polymer is 0.5 times or more of the total mass % of the ink, The glass transition temperature of the fixing agent polymer is 70° C. or higher and 120° C. or lower. The printing method according to any one of claims 14 to 17.

Images