Inkjet printing apparatus and method for manufacturing printed materials

Abstract

The present invention provides an inkjet printing apparatus and a method for manufacturing printed materials that can print with high image quality and high productivity on non-absorbent or low-absorbent printing media using inks containing organic solvents that are not highly volatile. [Solution] The inkjet head 41 ejects ink to adhere it to a non-absorbent or low-absorbent printing medium P. The ink contains water and an organic solvent S. The amount of water is 3.0 to 10.0% by mass of the total amount of ink, and the organic solvent S contains an organic solvent A with a boiling point of 150°C or higher and less than 200°C. The heater 5 heats the printing medium P so that the surface temperature of the printing medium P is 40 to 43°C in order to dry the ink that has adhered to the printing medium P. The blower mechanism 9 blows air with a wind speed of 0.2 to 1.5 m / sec onto the printing medium P in order to dry the ink that has adhered to the printing medium P.

Description

[Technical Field]

[0001] This invention relates to an inkjet printing apparatus and a method for manufacturing printed materials. [Background technology]

[0002] When printing on non-absorbent or low-absorbent media using an inkjet printer, inks containing highly volatile organic solvents are often used to prevent image bleeding and subsequent degradation of image quality.

[0003] Furthermore, in inkjet printing devices, in order to suppress the deterioration of image quality due to image blurring and to achieve high productivity, the printing medium from which the ink has been ejected is heated and dried using a heater or the like (see Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7428043 [Patent Document 2] Patent No. 4429923 [Overview of the project] [Problems that the invention aims to solve]

[0005] When using inks containing highly volatile organic solvents as described above, the evaporation of the organic solvent may cause nozzle clogging or ink buildup near the nozzles of the inkjet head. This may result in poor ink ejection and a decrease in print quality. Furthermore, inks containing highly volatile organic solvents may worsen the working environment during printing due to the evaporation of the organic solvent. For this reason, it is desirable to use inks containing organic solvents that are not highly volatile and are safe.

[0006] Therefore, when printing on non-absorbent or low-absorbent media with an inkjet printer, inks containing organic solvents that are highly volatile, have high drying properties, can suppress image bleeding, and are not highly volatile are sometimes used.

[0007] However, even when using such inks, if the printing medium is heated and dried as described above, the heating of the printing medium may cause nozzle clogging or ink to solidify near the nozzles, potentially leading to poor ink ejection and a decrease in print quality.

[0008] Furthermore, when using a large amount of organic solvent with low volatility and a higher boiling point (for example, a boiling point of 200°C or higher), it was necessary to dry the material at an even higher temperature, which presented the challenge of damaging the printing medium due to the high temperature.

[0009] Therefore, there was a need for a technology that could print with high image quality and high productivity on non-absorbent or low-absorbent printing media using inks containing organic solvents that are not highly volatile.

[0010] The present invention has been made in view of the above, and aims to provide an inkjet printing apparatus and a method for manufacturing printed materials that can print with high image quality and high productivity on non-absorbent or low-absorbent printing media using an ink containing an organic solvent that is not highly volatile. [Means for solving the problem]

[0011] According to one aspect of the present invention, an inkjet printing apparatus is provided comprising: an inkjet head that ejects ink and adheres the ink to a non-absorbent or low-absorbent printing medium; a heating unit that heats the printing medium to dry the ink adhered to the printing medium; and a blowing unit that blows air onto the printing medium to dry the ink adhered to the printing medium, wherein the ink contains water and an organic solvent S, the amount of water is 3.0 to 10.0% by mass of the total amount of ink, the organic solvent S contains an organic solvent A having a boiling point of 150°C or more and less than 200°C, the heating unit heats the printing medium so that the surface temperature of the printing medium is 40 to 43°C, and the blowing unit blows air with a wind speed of 0.2 to 1.5 m / sec onto the printing medium.

[0012] According to another aspect of the present invention, a method for manufacturing a printed material is provided, comprising the steps of: attaching ink to a non-absorbent or low-absorbent printing medium; heating the printing medium to dry the ink attached to the printing medium; and blowing air over the printing medium to dry the ink attached to the printing medium, wherein the ink comprises water and an organic solvent S, the amount of water being 3.0 to 10.0% by mass of the total amount of ink, and the organic solvent S comprising an organic solvent A having a boiling point of 150°C or higher and less than 200°C, wherein in the step of heating the printing medium, the printing medium is heated so that the surface temperature of the printing medium is 40 to 43°C, and in the step of blowing air over the printing medium, air with a wind velocity of 0.2 to 1.5 m / sec is blown over the printing medium. [Effects of the Invention]

[0013] According to the present invention, it is possible to print with high image quality and high productivity on non-absorbent or low-absorbent printing media using an ink containing an organic solvent that is not highly volatile. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram of the inkjet printing apparatus according to the first embodiment. [Figure 2]It is a plan view of the main part of the inkjet printing apparatus shown in FIG. 1. [Figure 3] It is a control block diagram of the inkjet printing apparatus shown in FIG. 1. [Figure 4] It is a diagram showing the measurement result of the OD value of the black image in the printed matter of Example 2. [Figure 5] It is a diagram showing the measurement result of the OD value of the cyan image in the printed matter of Example 2. [Figure 6] It is a diagram showing the measurement result of the OD value of the magenta image in the printed matter of Example 2. [Figure 7] It is a diagram showing the measurement result of the OD value of the yellow image in the printed matter of Example 2. [Embodiments for Carrying Out the Invention]

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are denoted by the same or equivalent reference numerals throughout the drawings.

[0016] The embodiments shown below exemplify devices and the like for embodying the technical idea of this invention. The technical idea of this invention does not specify the materials, shapes, structures, arrangements, etc. of each component part as the following. The technical idea of this invention can be variously modified within the scope of the claims.

[0017] [First Embodiment] FIG. 1 is a schematic configuration diagram of an inkjet printing apparatus according to the first embodiment of the present invention. FIG. 2 is a plan view of the main part of the inkjet printing apparatus shown in FIG. 1. FIG. 3 is a control block diagram of the inkjet printing apparatus shown in FIG. 1. In the following description, the up-down, front-back directions indicated by the arrows in FIG. 1 are taken as the up-down, front-back directions of the inkjet printing apparatus. Also, the left-right directions seen from the front side are taken as the left-right directions of the inkjet printing apparatus.

[0018] As shown in Figures 1 to 3, the inkjet printing apparatus 1 according to the first embodiment includes a transport unit 2, a platen 3, a fan 4, a heater (corresponding to a heating unit) 5, a main scanning drive guide 6, a main scanning drive motor 7, a head unit 8, a blower mechanism (corresponding to an air blowing unit) 9, a control unit 10, and an outer cover 11 that covers the head unit 8 and the like.

[0019] The transport unit 2 transports the strip-shaped printing medium P. In the inkjet printing apparatus 1, the printing medium P is a non-absorbent printing medium that does not absorb ink, or a low-absorbent printing medium that does not easily absorb ink.

[0020] Non-absorbent printing media are not particularly limited, but examples include sheets, films, and textile products containing non-absorbent materials. Furthermore, non-absorbent printing media may have a layer containing a non-absorbent material (hereinafter also referred to as a "low-absorbent layer") on the surface of a substrate (e.g., paper, textiles, leather, plastic, glass, ceramics, metal, etc.). Non-absorbent materials are not particularly limited, but examples include olefin resins, ester resins, urethane resins, acrylic resins, and vinyl chloride resins.

[0021] Furthermore, there are no particular limitations on non-absorbent printing media, but examples include films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, and polyethylene terephthalate (PET), plates of metals such as iron, silver, copper, and aluminum, or metal plates and plastic films manufactured by vapor deposition of these metals, and plates of alloys such as stainless steel and brass.

[0022] Examples of low-absorption printing media include art paper, coated paper, and cast paper, which are commonly used in offset printing and have relatively low ink permeability. These are also called coated papers, and consist of a coating layer with relatively low ink permeability applied to a substrate such as paper. The coating layer is a layer made of resin, inorganic compounds, etc., which have low water absorption and are a layer with low ink absorption.

[0023] As shown in Figures 1 to 3, the transport unit 2 comprises a supply drive motor 21, a transport roller 22, two pinch rollers 23, a transport drive motor 24, a winding shaft 25, a winding drive motor 26, and print media guides 27 and 28.

[0024] The supply drive motor 21 rotates the core 31 of the printing medium roll 32, which is a roll of printing medium P wound around the core 31. The printing medium roll 32 is located below the rear side of the platen 3.

[0025] The transport roller 22 nips the printing medium P between itself and the pinch roller 23, transporting the printing medium P unwound from the printing medium roll 32 toward the platen 3. The transport roller 22 is positioned near the rear of the platen 3.

[0026] The pinch rollers 23 press against the transport roller 22 via the printing medium P and rotate driven by the transport roller 22. Two pinch rollers 23 are positioned above the transport roller 22, spaced apart from each other in the left-right direction. The left pinch roller 23 nips the left end of the printing medium P between itself and the transport roller 22, and the right pinch roller 23 nips the right end of the printing medium P between itself and the transport roller 22. The two pinch rollers 23 are each configured to be movable in the left-right direction by motors or the like (not shown). This allows the positions of the two pinch rollers 23 to be adjusted according to the width of the printing medium P.

[0027] The transport drive motor 24 rotates the transport roller 22.

[0028] The winding shaft 25 winds up the printing medium P that is unwound from the printing medium roll 32 and transported via the platen 3. The winding shaft 25 is located below the front of the platen 3.

[0029] The winding drive motor 26 rotates the winding shaft 25.

[0030] The printing medium guide 27 guides the printing medium P between the printing medium roll 32 and the transport roller 22. The printing medium guide 28 guides the printing medium P between the platen 3 and the winding shaft 25.

[0031] The platen 3 supports the printing medium P. The platen 3 is formed in an elongated shape that extends in the left-right direction. Multiple air intake holes are formed in the platen 3.

[0032] The fan 4 draws air through the suction holes of the platen 3, generating suction force at the suction holes and causing the printing medium P to adhere to the platen 3.

[0033] The heater 5 heats the printing medium P via the platen 3 in order to dry the ink ejected from the inkjet head 41 (described later) and adhering to the printing medium P. The heater 5 is located on the underside of the platen 3.

[0034] The heater 5 heats the printing medium P via the platen 3 so that its surface temperature reaches 40-43°C. Heating the printing medium P to a surface temperature of 40°C or higher suppresses image blurring due to insufficient ink drying and reduces image quality degradation. Furthermore, heating the printing medium P to a surface temperature of 43°C or lower prevents nozzle clogging of the inkjet head 41 and ink adhesion near the nozzles due to the effects of heating the printing medium P. This reduces image quality degradation due to poor ink ejection.

[0035] The main scan drive guide 6 guides the head unit 8 to move in the left-right direction (main scan direction). The main scan drive guide 6 is formed in an elongated shape that extends in the left-right direction.

[0036] The main scanning drive motor 7 moves the head unit 8 in the left-right direction.

[0037] The head unit 8 moves left and right while ejecting ink onto the printing medium P to print an image. As shown in Figures 1 to 3, the head unit 8 comprises two inkjet heads 41 and a carriage 42.

[0038] The inkjet head 41 ejects ink to adhere it to the printing medium P. The two inkjet heads 41 are spaced apart from each other in the left-right direction and positioned at different locations in the front-back direction.

[0039] The inkjet head 41 is formed by multiple nozzles (not shown) arranged along the front-to-back direction, and has four rows of nozzles arranged in parallel in the left-to-right direction. Each nozzle in each row of the inkjet head 41 is formed on the nozzle surface 41a, which is the lower surface facing the platen 3. Each nozzle in each row of the inkjet head 41 ejects ink of a different color (for example, black (K), cyan (C), magenta (M), yellow (Y)) for each nozzle row. Details of the ink will be described later.

[0040] The ejection method of the inkjet head 41 is not particularly limited and may be any method such as a piezo method, electrostatic method, or thermal method.

[0041] The carriage 42 holds the inkjet head 41. The carriage 42 is formed in the shape of a hollow box. The carriage 42 holds the inkjet head 41 by inserting its lower end through an opening formed in its bottom plate.

[0042] The blower mechanism 9 blows air onto the printing medium P to dry the ink ejected from the inkjet head 41 and adhering to the printing medium P. The blower mechanism 9 is positioned behind the pinch rollers 23 at the same height as the pinch rollers 23 and blows air forward. The air from the blower mechanism 9 passes between the two pinch rollers 23 and hits the area of ​​the printing medium P where the image is formed by the ink ejected from the head unit 8.

[0043] The blower mechanism 9 blows air with a wind speed of 0.2 to 1.5 m / sec onto the printing medium P. A wind speed of 0.2 or higher suppresses image blurring caused by insufficient ink drying, thus preventing a decrease in image quality. A wind speed of 1.5 m / sec or lower suppresses the increase in ink mist caused by the wind. This prevents a decrease in image quality caused by mist stains that occur when ink mist adheres to the printing medium P.

[0044] The air temperature of the air blown onto the printing medium P by the blower mechanism 9 is preferably 35-40°C in an environment of 23°C and 50% RH. This reduces the likelihood of the surface temperature of the printing medium P falling outside the 40-43°C range. As a result, it is possible to further suppress the deterioration of image quality due to poor ink ejection and further suppress the deterioration of image quality due to blurring.

[0045] The control unit 10 controls the operation of the entire inkjet printing apparatus 1. The control unit 10 is composed of a CPU, RAM, ROM, hard disk, etc.

[0046] Next, we will explain the ink ejected by the inkjet head 41.

[0047] In this embodiment, the ink ejected by the inkjet head 41 contains water and an organic solvent S, wherein the amount of water is 3.0 to 10.0% by mass of the total amount of ink, and the organic solvent S is an inkjet ink containing an organic solvent A having a boiling point of 150°C or higher and less than 200°C.

[0048] For example, using a low-boiling point organic solvent to improve drying properties in order to reduce image blurring may result in poor ink ejection from the inkjet head 41.

[0049] The ink ejected by the inkjet head 41 in this embodiment contains an organic solvent S in the ink, which has an organic solvent A with a moderate boiling point of 150°C or more and less than 200°C. The ink also contains water, with the amount of water being 3.0 to 10.0% by mass of the total ink volume. It is presumed that the amount of water in the ink, which is 3.0% by mass or more of the total ink volume, can improve drying properties and contribute to reducing image blurring. This is thought to be due to the azeotropic phenomenon between water and the organic solvent. Furthermore, it is presumed that the amount of water being 10.0% by mass or less of the total ink volume can suppress an increase in ink viscosity and contribute to improving ink ejection performance.

[0050] Furthermore, the organic solvent S may contain organic solvent A, which has a boiling point of 150°C or higher and less than 200°C, in an amount of 90.0% by mass or more relative to the total amount of organic solvent S contained in the ink. This can further improve the drying properties of the ink. In addition, since a large amount of low-boiling-point organic solvent is not used, the occurrence of nozzle clogging and ejection failure due to ink solidification near the nozzle can be reduced. In this way, it is possible to form an image with better ink ejection performance while suppressing bleeding.

[0051] Furthermore, organic solvent A may contain water-soluble organic solvent B, which has a boiling point of 150°C or higher and less than 200°C, in an amount of 50.0% by mass or more relative to the total amount of organic solvent S in the ink. This makes it possible to incorporate water into the ink more stably and suppresses an increase in ink viscosity.

[0052] Ink may contain colorants. Ink may contain pigments, dyes, or a combination thereof as colorants.

[0053] As pigments, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and underglaze lake pigments, and inorganic pigments such as carbon black and metal oxides can be used. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metallic phthalocyanine pigments and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrrole (DPP). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black. Examples of metal oxides include titanium dioxide and zinc oxide. These pigments may be used individually or in combination of two or more types.

[0054] From the viewpoint of ejection stability and storage stability, the average particle size of pigment particles in the ink is preferably 1 μm or less, more preferably 500 nm or less, and even more preferably 300 nm or less, as the volume-based average value of the particle size distribution measured by dynamic light scattering.

[0055] Pigments may be incorporated into the ink as pigment dispersions. The pigment dispersions should be such that the pigment is dispersible in a solvent and the pigment is dispersed in the ink. For example, a dispersion in which the pigment is dispersed in a dispersion medium with a pigment dispersant, or a dispersion in which microencapsulated pigments coated with resin are dispersed in a dispersion medium can be used.

[0056] The dispersion form of the pigment may be a so-called encapsulated pigment in which the pigment is coated with a non-oil-soluble resin, or a dispersion in which colored resin particles are dispersed with a pigment dispersant, but it is preferable that the dispersion is in which the pigment dispersant is directly adsorbed onto the surface of the pigment and dispersed.

[0057] Any dye commonly used in the relevant art can be used. It is preferable to use an oil-soluble dye because it exhibits affinity for the non-aqueous solvent of the ink, resulting in better storage stability.

[0058] Examples of oil-soluble dyes include azo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes, xanthene dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, phthalocyanine dyes, and metal phthalocyanine dyes. These may be used individually or in combination.

[0059] From the viewpoint of print density and ink viscosity, the colorant content is preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass, and even more preferably 5 to 10% by mass, relative to the total amount of ink.

[0060] When an ink contains a pigment, a pigment dispersant can be used together with the pigment to stably disperse the pigment in the ink. The pigment dispersant is not particularly limited as long as it can stably disperse the pigment in the ink, but examples of preferred dispersants include hydroxyl group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, copolymers of vinylpyrrolidone and long-chain alkenes, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, polyoxyethylene alkyl phosphates, and polyester polyamines.

[0061] It is preferable to use a polymeric dispersant as the pigment dispersant. The polymeric dispersant may be synthesized or commercially available.

[0062] Examples of commercially available pigment dispersants include "Solspers J180," "Solspers J200," "Solspers 71000," "Solspers 74000," "Solspers 86000," "Solspers 87000," and "Solspers M387" from Lubrizol Japan Co., Ltd., and "BYKJET-9151," "BYKJET-9152," and "BYKJET-9170" from BYK Chemie Japan Co., Ltd. (all are product names). These may be used individually or in combination of two or more.

[0063] The pigment dispersant is preferably included in a mass ratio of 0.2 to 1.0 per unit of pigment. The pigment dispersant content in the total amount of ink is preferably 0.5 to 15% by mass, and more preferably 1 to 5% by mass.

[0064] The ink may contain a binder resin.

[0065] From the viewpoint of forming a uniform ink film and improving the adhesion of the image to the substrate, a resin that dissolves in the organic solvent S contained in the ink is preferred as the binder resin.

[0066] Examples of binder resins include (meth)acrylic resin, styrene-(meth)acrylic resin, styrene-maleic acid resin, ethylene-(meth)acrylic resin, urethane resin, vinyl chloride resin, vinyl chloride-vinyl acetate resin, polyester resin, polyvinyl alcohol resin, epoxy resin, and polyvinylpyrrolidone resin.

[0067] From the viewpoint of improving the adhesion of the image to the substrate, (meth)acrylic resin is preferred as the binder resin. More preferably, a (meth)acrylic resin that is soluble in the organic solvent S is preferred as the binder resin. When a (meth)acrylic resin is used, the adhesion of the image to plastic substrates such as olefin resins can be improved. In particular, olefin resins tend to have a low affinity for organic solvents in inks, and it can be difficult to obtain good image adhesion, but when a (meth)acrylic resin is used, it is easier to improve the adhesion of the image to the substrate.

[0068] The (meth)acrylic resin may be a resin comprising, for example, at least one unit selected from the group consisting of units derived from (meth)acrylic acid and units derived from (meth)acrylic acid esters.

[0069] In this disclosure, (meth)acrylic acid means acrylic acid and methacrylic acid collectively, (meth)acrylic acid ester means acrylic acid ester and methacrylic acid ester collectively, and (meth)acrylate means acrylate and methacrylate collectively.

[0070] Examples of (meth)acrylic acid esters include alkyl (meth)acrylates, benzyl (meth)acrylates, and hydroxyalkyl (meth)acrylates. Examples of alkyl (meth)acrylates include alkyl (meth)acrylates having an alkyl group with 1 to 8, 1 to 6, or 1 to 4 carbon atoms, specifically including methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0071] The (meth)acrylic resin may be, for example, a polymer of one or more monomers selected from the group consisting of (meth)acrylic acid and (meth)acrylic acid esters.

[0072] Examples of (meth)acrylic resins include poly(meth)acrylic acid, poly(meth)acrylic acid esters (e.g., methyl poly(meth)acrylate, ethyl poly(meth)acrylate, butyl poly(meth)acrylate, etc.), (meth)acrylic acid ester copolymer resins, (meth)acrylic acid-(meth)acrylic acid ester copolymer resins, etc.

[0073] The (meth)acrylic resin preferably contains units derived from, for example, alkyl (meth)acrylate. The units derived from alkyl (meth)acrylate may be, for example, 50.0% by mass or more, 70.0% by mass or more, or 90.0% by mass or more, relative to the total units of the (meth)acrylic resin.

[0074] Specific examples of (meth)acrylic resins include, for example, polymers of methyl (meth)acrylate, copolymers of methyl (meth)acrylate with at least one selected from the group consisting of (meth)acrylic acid, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and benzyl (meth)acrylate (for example, copolymers of 100 parts by mass of methyl methacrylate with 0.1 to 200 parts by mass, 1 to 180 parts by mass, or 10 to 150 parts by mass of at least one selected from the group consisting of methacrylic acid, butyl methacrylate, and benzyl methacrylate).

[0075] The glass transition temperature (Tg) of the (meth)acrylic resin may be, for example, 60°C or higher, preferably 80°C or higher, and more preferably 100°C or higher, from the viewpoint of improving the adhesion of the image to the substrate. The glass transition temperature of the (meth)acrylic resin may be, for example, 200°C or lower. The glass transition temperature of the (meth)acrylic resin may be, for example, 60-200°C, 80-200°C, or 100-200°C. In this disclosure, the glass transition temperature is an estimated value according to FOX's formula.

[0076] The weight-average molecular weight of the (meth)acrylic resin is preferably 5,000 to 150,000, and more preferably 10,000 to 100,000. From the viewpoint of water resistance and durability, the weight-average molecular weight of the (meth)acrylic resin is preferably 5,000 or more, and more preferably 10,000 or more. From the viewpoint of ink viscosity and discharge properties, the weight-average molecular weight of the (meth)acrylic resin is preferably 150,000 or less, and more preferably 100,000 or less. In this disclosure, the weight-average molecular weight is the value obtained by the GPC method on a standard polystyrene basis.

[0077] As the (meth)acrylic resin, a synthesized resin may be used, or a commercially available resin may be used.

[0078] The method for synthesizing (meth)acrylic resin is not particularly limited. (Meth)acrylic resin can be obtained, for example, by polymerizing one or more radical polymerizable monomers by solution polymerization or the like. For example, at least one monomer selected from the group consisting of (meth)acrylic acid and (meth)acrylic acid esters can be polymerized.

[0079] The polymerization solvent (reaction solvent) used in solution polymerization is not particularly limited, but it is preferable that it is capable of dissolving the (meth)acrylic resin obtained by polymerization. From the viewpoint of compatibility between the obtained (meth)acrylic resin and the organic solvent in the ink, and thereby preparing a low-viscosity ink, the polymerization solvent may be the organic solvent S or organic solvent A contained in the ink. For example, if the ink contains two or more organic solvents as organic solvent S or organic solvent A, only one of them may be used as the polymerization solvent.

[0080] Polymerization initiators, such as radical polymerization initiators, may be used during the polymerization reaction.

[0081] As radical polymerization initiators, known radical polymerization initiators such as azo compounds including 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4'-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate, and organic peroxides such as hydroperoxides, dialkylperoxides, peroxyesters, and diallylperoxides can be used. These may be used individually or in combination of two or more.

[0082] As the (meth)acrylic resin, from the viewpoint of good compatibility between the (meth)acrylic resin and the solvent, and thereby the preparation of a low-viscosity ink, an acrylic resin obtained by solution polymerization of a radically polymerizable monomer in an organic solvent S or organic solvent A used in the ink with a radical polymerization initiator is preferred. The (meth)acrylic resin may be, for example, a resin obtained by solution polymerization using only one of two or more organic solvents as the polymerization solvent when the ink contains two or more organic solvents as organic solvent S or organic solvent A.

[0083] Examples of commercially available (meth)acrylic resins include "Neocryl B-728" and "Neocryl B-801" from Covestro, and "Dianal BR-83," "Dianal BR-87," and "Dianal MB-7333" from Mitsubishi Chemical Corporation (all are product names).

[0084] The binder resin may be, for example, 1.0% by mass or more, or 3.0% by mass or more, relative to the total amount of ink. On the other hand, the binder resin may be, for example, 40.0% by mass or less, 30.0% by mass or less, or 20.0% by mass or less, relative to the total amount of ink. The binder resin may be, for example, 1.0 to 40.0% by mass, 1.0 to 30.0% by mass, or 3.0 to 20.0% by mass, relative to the total amount of ink.

[0085] Ink can contain water.

[0086] While there are no particular restrictions on the type of water used, it is preferable to use water that contains as few ionic components as possible. In particular, from the viewpoint of the storage stability of the ink, it is preferable to use water with a low content of polyvalent metal ions such as calcium. For example, deionized water, distilled water, or ultrapure water may be used.

[0087] From the viewpoint of reducing image blurring, the amount of water is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, and even more preferably 4.5% by mass or more, relative to the total amount of ink. When the amount of water is 3.0% by mass or more relative to the total amount of ink, the drying properties of the ink are improved, and for example, when printing on roll paper, image transfer during winding after printing can also be suppressed. On the other hand, from the viewpoint of improving ink ejection properties, the amount of water is preferably 10.0% by mass or less, more preferably 9.0% by mass or less, and even more preferably 8.0% by mass or less, relative to the total amount of ink. The amount of water is preferably 3.0 to 10.0% by mass, more preferably 4.0 to 9.0% by mass, and even more preferably 4.5 to 8.0% by mass, relative to the total amount of ink.

[0088] The amount of water in the ink may be the same as the amount of water actively added to the ink. On the other hand, when an organic solvent that has an affinity for water is added to the ink, such an organic solvent may absorb water vapor or other substances contained in the atmosphere, and in such cases, the amount of water added to the ink may not be the same as the amount of water in the ink.

[0089] The amount of water in the ink may be measured, for example, using the Karl Fischer method.

[0090] The ink may contain an organic solvent S. Examples of organic solvent S include organic solvents with a boiling point of 150°C or higher and less than 200°C (organic solvent A), and other organic solvents. Examples of other organic solvents include organic solvents with a boiling point of less than 150°C and organic solvents with a boiling point of 200°C or higher. Examples of organic solvents with a boiling point of less than 150°C include ethylene glycol monomethyl ether acetate. Examples of organic solvents with a boiling point of 200°C or higher include γ-butyrolactone and 2-pyrrolidone. The ink may contain one or more of these other organic solvents.

[0091] The organic solvent (organic solvent A) having a boiling point of 150°C or higher and less than 200°C may be any of the following: ketone-based organic solvents, alcohol-based organic solvents, glycol ether-based organic solvents, acetate-based organic solvents, etc. Organic solvent A may be used alone or in combination of two or more types.

[0092] From the viewpoint of reducing image blurring, the boiling point of organic solvent A is preferably less than 200°C, and more preferably 195°C or lower. On the other hand, from the viewpoint of improving ink ejection performance, the boiling point of organic solvent A is preferably 150°C or higher, more preferably 160°C or higher, and even more preferably 170°C or higher.

[0093] Organic solvent A may contain a water-soluble organic solvent (water-soluble organic solvent B) with a boiling point of 150°C or higher and less than 200°C, but may further contain a non-water-soluble organic solvent with a boiling point of 150°C or higher and less than 200°C.

[0094] Examples of water-soluble organic solvent B among organic solvent A include diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol dimethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, diethylene glycol monoethyl ether acetate, and 1,2-propanediol. These may be used individually or in combination of two or more.

[0095] Examples of non-water-soluble organic solvents among organic solvent A with a boiling point of 150°C or higher and less than 200°C include, for example, ethylene glycol monobutyl ether acetate, ethylene glycol diacetate, dipropylene glycol dimethyl ether, propylene glycol 1-monobutyl ether, butyl lactate, hexyl propionate, and ethyl 3-ethoxypropionate. Non-water-soluble organic solvents with a boiling point of 150°C or higher and less than 200°C may be used individually or in combination of two or more.

[0096] From the viewpoint of improving ink ejection and suppressing image bleeding, the amount of organic solvent A is preferably 90.0% by mass or more, more preferably 95.0% by mass or more, and even more preferably 99.0% by mass or more, relative to the total amount of organic solvent S in the ink. Organic solvent A may be 100% by mass relative to the total amount of organic solvent S in the ink. Organic solvent A may be, for example, 90.0 to 100% by mass, 95.0 to 100% by mass, or 99.0 to 100% by mass relative to the total amount of organic solvent S in the ink.

[0097] From the perspective of improving the ink ejection property, the water-soluble organic solvent B is preferably 50.0% by mass or more, more preferably 60.0% by mass or more, even more preferably 70.0% by mass or more, still more preferably 80.0% by mass or more, and even more preferably 90.0% by mass or more based on the total amount of the organic solvent S in the ink. The water-soluble organic solvent B may be, for example, 100% by mass based on the total amount of the organic solvent S in the ink. The water-soluble organic solvent B may be, for example, 50.0 to 100% by mass, 60.0 to 100% by mass, 70.0 to 100% by mass, 80.0 to 100% by mass, or 90.0 to 100% by mass based on the total amount of the organic solvent S in the ink.

[0098] From the perspective of stably presenting the binder resin in the ink, suppressing the increase in the viscosity of the ink, and further improving the ejection property, the water-soluble organic solvent B has a Hansen solubility parameter (HSP value) of 25.0 MPa 1 / 2 or less and preferably contains a water-soluble organic solvent Bx having a boiling point of 150°C or more and less than 200°C.

[0099] The HSP value of the water-soluble organic solvent Bx may be, for example, 23.0 MPa 1 / 2 or less. On the other hand, the HSP value of the water-soluble organic solvent Bx may be, for example, 10.0 MPa 1 / 2 or more or 15.0 MPa 1 / 2 or more. The HSP value of the water-soluble organic solvent Bx may be, for example, 10.0 to 25.0 MPa 1 / 2 or 15.0 to 23.0 MPa 1 / 2 and may be.

[0100] The Hansen solubility parameter was proposed by Hansen in 1967 and divides the solubility parameter introduced by Hildebrand into three components: a dispersion term δ D , a polar term δ P , and a hydrogen bond term δ H and represents it in three-dimensional space. The dispersion term represents the effect of dispersion force, the polar term represents the effect of dipole-dipole force, and the hydrogen bond term represents the effect of hydrogen bonding force.

[0101] For more details, see the POLYMER HANDBOOK.FOURTH EDITION. (Editors: J. BRANDRUP, EHIMMERGUT, and EAGRULKE), etc.

[0102] This disclosure uses values ​​calculated using the Hansen solubility parameter calculation software "HSPiP: Hansen Solubility Parameters in Practice" ver. 5.3 by Charles M. Hansen et al.

[0103] Examples of water-soluble organic solvents Bx include diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol dimethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, and diethylene glycol monoethyl ether acetate. These may be used individually or in combination of two or more.

[0104] From the viewpoint of further improving discharge performance, the amount of water-soluble organic solvent Bx is preferably 50.0% by mass or more, more preferably 75.0% by mass or more, even more preferably 80.0% by mass or more, and even more preferably 90.0% by mass or more, based on the total amount of water-soluble organic solvent B. On the other hand, the amount of water-soluble organic solvent Bx may be 100% by mass, based on the total amount of water-soluble organic solvent B. For example, the amount of water-soluble organic solvent Bx may be 50.0 to 100% by mass, 75.0 to 100% by mass, 80.0 to 100% by mass, or 90.0 to 100% by mass, based on the total amount of water-soluble organic solvent B.

[0105] Ink preferably contains a surfactant. For example, it is preferable for the ink to contain a surfactant in order to improve the wetting and spreading of the ink even on hydrophobic substrate surfaces, increase the drying speed, and form a good image. Examples of surfactants include silicone-based surfactants, fluorine-based surfactants, and nonionic surfactants such as polyoxyethylene derivatives.

[0106] Examples of silicone-based surfactants include polyester-modified silicones and polyether-modified silicones. Examples of commercially available silicone-based surfactants include "BYK-307," "BYK-313," "BYK-330," "BYK-333," "BYK-342," "BYK-370," "BYK-377," "BYK-378," "BYK-3550," "BYK-3750," "BYK-3761," "BYK-3762," "BYK-3764," and "BYK-SILCLEAN 3700" from BIC Chemie Japan Co., Ltd., and "Sylface SAG005," "Sylface SAG008," and "Sylface SAG503A" from Nisshin Chemical Industry Co., Ltd. (all are product names).

[0107] Examples of commercially available fluorine-based surfactants include "BYK-340" from BIC Chemie Japan Co., Ltd., and "Surflon S-241," "Surflon S-242," "Surflon S-242L," "Surflon S-243," "Surflon S-420," and "Surflon S-431" from AGC Inc. (all are product names).

[0108] As the polyoxyethylene derivative, it is preferable to use an acetylene glycol-based surfactant. Examples of commercially available acetylene glycol-based surfactants include, for example, "Surfinol 420," "Surfinol 440," "Surfinol 465," and "Surfinol 485" from Evonik Industries, and "Orfin E-1004" and "Orfin-1010" from Nisshin Chemical Industry Co., Ltd. (all are trade names).

[0109] From the standpoint of continuous ink ejection during printing and image color reproduction, it is preferable that the ink contains a silicone-based surfactant.

[0110] Surfactants may be used individually or in combination of two or more types.

[0111] The surfactant is preferably present in an amount of 0.05 to 2% by mass, and more preferably 0.1 to 1% by mass, relative to the total amount of ink.

[0112] Depending on the application, the ink may contain various additives. Examples of additives include UV absorbers, light stabilizers, antioxidants, and plasticizers.

[0113] The method for manufacturing ink is not particularly limited, but one method is to mix and stir each component together or separately to produce ink. Specifically, for example, all components can be put together or separately into a disperser such as a bead mill and dispersed, and if desired, the mixture can be passed through a filter such as a membrane filter to produce ink.

[0114] In the ink manufacturing method, for example, a pigment dispersion may be prepared by first mixing and stirring the pigment with a pigment dispersant and an organic solvent to disperse the pigment.

[0115] The viscosity of an inkjet ink varies depending on the nozzle diameter of the inkjet head 41 and the ejection environment, but generally, it is preferably 3 to 30 mPa·s at 23°C, more preferably 3 to 15 mPa·s, and even more preferably 4 to 10 mPa·s. In this disclosure, the ink viscosity is a value measured at 23°C. For example, a rheometer MCR302 manufactured by Anton Paar Japan Co., Ltd. can be used as a viscosity measuring device.

[0116] Next, the operation of the inkjet printing device 1 will be described.

[0117] When instructed to start printing, the control unit 10 starts driving the fan 4, heater 5, and blower mechanism 9.

[0118] Here, the control unit 10 controls the heater 5 so that the surface temperature of the printing medium P becomes 40 to 43°C.

[0119] Furthermore, the control unit 10 controls the blower mechanism 9 to blow air with a wind speed of 0.2 to 1.5 m / sec onto the printing medium P. Here, in an environment of 23°C and 50% RH, it is preferable that the temperature of the air blown onto the printing medium P by the blower mechanism 9 be 35 to 40°C.

[0120] Next, the control unit 10 controls the main scanning drive motor 7 to move the head unit 8, and while controlling the inkjet head 41 based on the image data to be printed, it ejects ink and applies the ink to the printing medium P, thereby performing the first pass of printing.

[0121] Once the first pass of printing is complete, the control unit 10 causes the transport unit 2 to transport the printing medium P forward by a predetermined amount of movement.

[0122] Next, the control unit 10 moves the head unit 8 in the opposite direction to the printing operation of the first pass, and controls the inkjet head 41 based on the image data to eject ink, thereby performing the printing of the second pass.

[0123] Once the printing operation of the second pass is completed, the control unit 10 causes the transport unit 2 to transport the printing medium P forward by a predetermined amount of movement.

[0124] Similarly thereafter, the control unit 10 performs printing on the printing medium P by alternately repeating the printing operation for one pass and the movement of the printing medium P.

[0125] Here, on the platen 3, the printing medium P is heated by the heater 5 via the platen 3, causing the organic solvent and water contained in the ink adhering to the printing medium P to evaporate. The evaporated organic solvent is removed from the vicinity of the surface of the printed area of ​​the printing medium P by the airflow from the blower mechanism 9. This prevents the concentration of organic solvent near the surface of the printed area of ​​the printing medium P from becoming saturated, and the ink dries. Also, as mentioned above, since the ink contains 3.0% by mass or more of water relative to the total amount of ink, the azeotropic phenomenon between water and organic solvent enhances the drying properties of the ink. The resin contained in the ink then concentrates, dries, and fixes to the printing medium P. In this way, the drying properties of the ink are maintained.

[0126] As mentioned above, the heating of the printing medium P by the heater 5 to a surface temperature of 40°C or higher, and the airflow velocity of the blower mechanism 9 being 0.2 or higher, suppresses image blurring due to insufficient ink drying and reduces the deterioration of image quality.

[0127] Furthermore, by heating the printing medium P so that its surface temperature is kept below 43°C, as mentioned above, nozzle clogging of the inkjet head 41 and ink adhesion near the nozzles due to the heating of the printing medium P are suppressed, thereby reducing the degradation of image quality due to poor ink ejection.

[0128] Furthermore, because the wind speed from the blower mechanism 9 is 1.5 m / sec or less, as mentioned above, the increase in ink mist due to the wind is suppressed, and the deterioration of image quality due to mist stains is suppressed.

[0129] The entire process ends when the final print pass is complete. In this way, the printed material is produced.

[0130] As described above, the inkjet printing apparatus 1 includes a heater 5 that heats the printing medium P via a platen 3 to dry the ink, and a blower mechanism 9 that blows air onto the printing medium P to dry the ink. The heater 5 heats the printing medium P so that its surface temperature reaches 40-43°C. This suppresses image quality degradation due to poor ink ejection and also suppresses image quality degradation due to blurring. The blower mechanism 9 blows air with a wind speed of 0.2-1.5 m / sec onto the printing medium P. This suppresses image quality degradation due to mist stains and also suppresses image quality degradation due to blurring.

[0131] Furthermore, the heater 5 and blower mechanism 9 dry the ink adhering to the printing medium P, enabling high-productivity printing.

[0132] Therefore, according to the inkjet printing apparatus 1, it is possible to print with high image quality and high productivity on non-absorbent or low-absorbent printing media P using an ink containing an organic solvent A that is not highly volatile.

[0133] Furthermore, by using the heater 5 and the blower mechanism 9, the ink can be dried in a short time even with relatively low heating temperatures of 40-43°C on the surface of the printing medium P. This minimizes damage to the printing medium P.

[0134] Furthermore, in an environment of 23°C and 50% RH, by setting the air temperature of the air blown by the blower mechanism 9 onto the printing medium P to 35-40°C, it is possible to reduce the likelihood of the surface temperature of the printing medium P falling outside the 40-43°C range, as mentioned above. Therefore, it is possible to further suppress the deterioration of image quality due to ink ejection failure, as well as the deterioration of image quality due to image blurring.

[0135] [Second Embodiment] Next, a second embodiment, which modifies part of the first embodiment described above, will be explained.

[0136] In the second embodiment, the control unit 10 sets the printing conditions during printing according to the printing width, which is the width of the printed image in the main scanning direction (left-right direction).

[0137] The printing conditions described above in the second embodiment include the amount of ink droplets ejected by the inkjet head 41, the correspondence between the input and output values ​​of the image data to be printed, and the maximum ink amount.

[0138] The ink droplet volume mentioned above is the size (amount of ink) of one ink droplet ejected from the nozzle of the inkjet head 41. For example, if the ejection method of the inkjet head 41 is a piezoelectric method, the ink droplet volume can be adjusted by controlling at least one of the drive waveform and drive voltage of the piezoelectric element.

[0139] The input values ​​described above represent the grayscale density in the image data. In this embodiment, the input values ​​are those after color adjustment using a color profile. The output values ​​are those obtained by adjusting the input values ​​according to the print width. Ink is ejected by the inkjet head 41 based on the output values.

[0140] For example, if the amount of cyan ink to be injected is to be the amount injected when the input value is 60%, then an adjustment is made to make the input value for cyan between 60% and 100% equal to the output value of 60%.

[0141] The maximum ink volume mentioned above is the maximum amount of ink that the inkjet head 41 ejects per unit area.

[0142] As mentioned above, the inkjet printer 1 performs printing on the printing medium P by alternately repeating a printing operation for one pass and the movement of the printing medium P in the direction from rear to front (sub-scanning direction).

[0143] In this process, during the printing operation of each pass, the inkjet head 41 moves (scans) by the print width in the main scanning direction while ejecting ink onto the printing medium P. Therefore, the inkjet head 41 reciprocates within the range of the print width in the main scanning direction.

[0144] Furthermore, the inkjet printing device 1 performs printing using a multi-pass method, in which the inkjet head 41 scans the same area multiple times to print on that area.

[0145] In other words, the control unit 10 alternately performs the operation of ejecting ink from the inkjet head 41 to the printing medium P while moving the inkjet head 41 by the printing width in the main scanning direction, and the operation of transporting the printing medium P in a sub-scanning direction perpendicular to the main scanning direction, thereby controlling the inkjet head 41, the main scanning drive motor 7 (corresponding to the drive unit), and the transport unit 2 to perform printing in a multi-pass manner.

[0146] As described above, in the inkjet printing apparatus 1 that performs printing using a multi-pass method by scanning the inkjet head 41 back and forth within the printing width range, the ink used has high drying properties, as previously mentioned. For this reason, under the same printing conditions, the image quality may change depending on the printing width. This is particularly noticeable in solid areas; for example, if the printing width is narrow, the solid areas may be filled with dots, but if the printing width is wide, the solid areas may not be sufficiently filled with dots, and sufficient density may not be obtained.

[0147] The reason why image quality changes with print width is that the amount of ink injected into the print area per unit time changes with print width. As described above, when printing using a multi-pass method by scanning the inkjet head 41 back and forth within the print width range, the wider the print width, the smaller the amount of ink injected into the print area per unit time.

[0148] Therefore, the wider the print width, the faster the ink applied to the printing medium P tends to dry. High-drying inks used in inkjet printers 1 are susceptible to this effect of print width. As a result, when the print width is wide, the dots become smaller, and as mentioned above, solid areas may not be adequately filled with dots.

[0149] Therefore, in the second embodiment, as described above, the control unit 10 sets the printing conditions according to the printing width.

[0150] The printing conditions corresponding to the print width are determined using the results of a test print. The test print is performed as preparation before the actual print is made using inkjet printer 1. The test print is performed at the same print resolution as the actual print.

[0151] The test printout may be performed with a different print width than the final printout. For example, if the final printout is relatively wide, the test printout may be performed with a narrower print width to reduce paper waste. Also, if the final printout is relatively narrow, and the text size or lines in the image to be printed are small, the image may be enlarged and the test printout may be performed with a wider print width than the final printout.

[0152] When performing a test print with a narrower print width than the final print, if the final print is performed using the same printing conditions that yielded good image quality in the test print, the solid areas may not be sufficiently filled with dots, resulting in a decrease in density. On the other hand, when performing a test print with a wider print width than the final print, if the final print is performed using the same printing conditions that yielded good image quality in the test print, bleeding may occur in the solid areas.

[0153] The reason for the decrease in image quality when performing the final print with a different print width than the test print, as described above, is that the amount of ink injected into the print area per unit time changes depending on the print width. As a result, the dot diameter in low-resolution areas, the degree of blurring at the boundaries between dots, and the maximum amount of ink that the printing medium P can tolerate differ depending on the print width. Consequently, even if good image quality was obtained with the print width used in the test print, changing the print width in the final print may result in a decrease in image quality.

[0154] Therefore, in the inkjet printer 1, when performing the actual print with a different print width than the test print, the actual print is set to different print conditions than those used to obtain good image quality in the test print.

[0155] In the conditional printing, printing is performed under multiple printing conditions, and the user checks the results of each print. Here, the user gives instructions to the inkjet printer 1 for conditional printing and for the actual print by operating an external terminal (not shown), such as a personal computer. In addition, during conditional printing and the actual print, the heater 5 and the blower mechanism 9 are driven in the same way as during printing in the first embodiment described above.

[0156] The user instructs the inkjet printer 1 via an external terminal to set the printing conditions that the user determined to have produced good image quality during the condition-setting print as the printing conditions for the print width used in the condition-setting print. As a result, the control unit 10 of the inkjet printer 1 sets the printing conditions that the user determined to have produced good image quality during the condition-setting print as the printing conditions corresponding to the print width used for the condition-setting print.

[0157] If the actual print width is the same as the print width used for testing, the control unit 10 of the inkjet printer 1 executes the actual print using the print conditions set as the print conditions corresponding to the print width used for testing. Here, as mentioned above, the actual print is performed at the same print resolution as the test print.

[0158] If the actual print width differs from the print width specified in the conditional settings, the control unit 10 sets the print conditions to be changed from the print conditions set as corresponding to the print width specified in the conditional settings and executes the actual print.

[0159] Specifically, if the actual print width is wider than the print width specified for testing, the control unit 10 performs at least one of the following actions: increase the ink droplet amount, change the correspondence between the input and output values ​​of the image data so that the output value is larger, or increase the maximum ink amount. This reduces the decrease in density of solid areas in the printed image.

[0160] Furthermore, if the actual print width is narrower than the print width specified for testing, the control unit 10 will perform at least one of the following actions: reduce the amount of ink droplets, change the correspondence between the input and output values ​​of the image data so that the output value becomes smaller, or reduce the maximum amount of ink. This reduces bleeding in the solid areas of the printed image.

[0161] As described above, when changing at least one of the following according to the print width—the amount of ink droplets, the correspondence between input and output values ​​of image data, and the maximum ink amount—the degree of each change is adjusted so that the amount of ink injected per unit time into the print area at the actual print width is equivalent to that when printing under the print conditions set as the print conditions corresponding to the print width used for condition testing.

[0162] Here, the more easily the printing medium absorbs ink, the faster the ink applied to the printing medium P dries, and the more likely the density of solid areas in the printed image is to decrease. For this reason, when printing on a different type of printing medium P in the actual print run than the one used for testing, the control unit 10 may further modify the printing conditions, which were changed according to the print width as described above, depending on the type of printing medium used in the actual print run. In other words, the control unit 10 sets the printing conditions according to the type of printing medium.

[0163] For example, if the type of printing medium used in the actual print is more ink-absorbent than the type of printing medium used in the conditional print, the control unit 10 will perform at least one of the following actions for the printing conditions changed according to the print width as described above: increase the amount of ink droplets, change the correspondence between the input and output values ​​of the image data so that the output value is larger, and increase the maximum amount of ink.

[0164] Furthermore, for example, if the type of printing medium used in the actual print is less ink-absorbing than the type of printing medium used in the conditional print, the control unit 10 will perform at least one of the following actions for the printing conditions changed according to the print width as described above: reduce the amount of ink droplets, change the correspondence between the input and output values ​​of the image data so that the output value becomes smaller, and reduce the maximum amount of ink.

[0165] As described above, when changing at least one of the following depending on the type of printing medium—the amount of ink droplets, the correspondence between input and output values ​​of image data, and the maximum amount of ink—the degree of each change is adjusted according to the ink absorbency of the type of printing medium.

[0166] As described above, in the second embodiment, the control unit 10 sets the printing conditions according to the printing width in the main scanning direction. This makes it possible to suppress changes in the amount of ink injected into the printing area per unit time due to differences in printing width. As a result, it is possible to reduce the deterioration of image quality.

[0167] Furthermore, the control unit 10 sets printing conditions according to the type of printing medium. This makes it possible to adjust the printing conditions according to the ink absorbency of the type of printing medium, thereby further reducing the degradation of image quality.

[0168] In the second embodiment, the printing conditions include the amount of ink droplets ejected by the inkjet head 41, the correspondence between the input and output values ​​of the image data, and the maximum ink amount. This allows the control unit 10 to adjust the amount of ink injected into the printing area per unit time with high precision.

[0169] As mentioned above, in the second embodiment, a test print is performed at the same print resolution as the actual print, and the print conditions are set according to the print width based on the results of the test print. The lower the print resolution, the faster the ink applied to the printing medium P dries. Therefore, even with the same print width, the print conditions that yield good image quality in the test print may differ depending on the print resolution. Thus, it can be said that the control unit 10 also sets the print conditions according to the print resolution. This makes it possible to further reduce the deterioration of image quality.

[0170] [Other embodiments] As described above, the present invention has been described by first and second embodiments, but the descriptions and drawings that constitute part of this disclosure should not be understood as limiting the invention. Various alternative embodiments, examples and operational techniques will become apparent to those skilled in the art from this disclosure.

[0171] In the first embodiment described above, the inkjet printing apparatus 1 was described as a serial type, but it may also be a line type.

[0172] In the second embodiment described above, a table associating print resolution, print medium type, print width, and print conditions may be stored in advance. In this case, when printing, the control unit 10 obtains print conditions by referring to the table based on the print resolution, print medium type, and print width, sets the obtained print conditions, and executes printing.

[0173] In the second embodiment described above, the user may input printing conditions according to the print width by operating an external terminal or the operation input unit (not shown) of the inkjet printer 1, and the control unit 10 may set the input printing conditions and execute printing.

[0174] In the second embodiment described above, printing conditions were set according to the type of printing medium and the printing resolution, in addition to the printing width. However, at least one of the type of printing medium and the printing resolution may be omitted as elements used to set the printing conditions.

[0175] In the second embodiment described above, the printing conditions used were the amount of ink droplets ejected by the inkjet head 41, the correspondence between the input and output values ​​of the image data, and the maximum ink amount. However, one or two of these may be omitted. Other elements may also be included in the printing conditions.

[0176] The present invention is not limited to the embodiments described above, and in the implementation stage, the components can be modified and implemented without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments.

[0177] [Note] This application discloses the following invention:

[0178] (Note 1) An inkjet head that ejects ink and deposits the ink onto a non-absorbent or low-absorbent printing medium, A heating unit for heating the printing medium in order to dry the ink adhering to the printing medium, The system includes a blower unit that blows air onto the printing medium to dry the ink adhering to the printing medium, The ink comprises water and an organic solvent S. The amount of water is 3.0 to 10.0% by mass relative to the total amount of ink. The aforementioned organic solvent S includes organic solvent A having a boiling point of 150°C or higher and less than 200°C. The heating unit heats the printing medium so that the surface temperature of the printing medium becomes 40 to 43°C. The aforementioned air blowing unit is characterized by blowing wind with a wind speed of 0.2 to 1.5 m / sec onto the printing medium.

[0179] (Note 2) The inkjet printing apparatus according to Appendix 1, characterized in that the blowing unit blows air with a temperature of 35-40°C onto the printing medium in an environment of 23°C and 50%RH.

[0180] (Note 3) A main scanning drive unit that moves the inkjet head in the main scanning direction, A transport unit that transports the printing medium in a sub-scanning direction perpendicular to the main scanning direction, The system further comprises a control unit that controls the inkjet head, the main scanning drive unit, and the transport unit to perform printing in a multi-pass manner by alternately performing the operation of ejecting ink from the inkjet head to the printing medium while moving the inkjet head by the printing width in the main scanning direction, and the operation of transporting the printing medium in the sub-scanning direction. The inkjet printing apparatus according to Appendix 1 or 2, characterized in that the control unit sets printing conditions according to the printing width.

[0181] (Note 4) The inkjet printing apparatus according to Appendix 3, characterized in that the control unit further sets the printing conditions according to at least one of the type of printing medium and the printing resolution.

[0182] (Note 5) The inkjet printing apparatus according to Appendix 3 or 4, characterized in that the printing conditions include at least one of the amount of ink droplets ejected by the inkjet head, the correspondence between input and output values ​​of image data to be printed, and the maximum amount of ink ejected per unit area by the inkjet head.

[0183] (Note 6) A process of applying ink to a non-absorbent or low-absorbent printing medium, A step of heating the printing medium in order to dry the ink adhering to the printing medium, The process includes a step of blowing air onto the printing medium to dry the ink adhering to the printing medium, The ink comprises water and an organic solvent S. The amount of water is 3.0 to 10.0% by mass relative to the total amount of ink. The aforementioned organic solvent S includes organic solvent A having a boiling point of 150°C or higher and less than 200°C. In the step of heating the printing medium, the printing medium is heated so that its surface temperature is 40 to 43°C. A method for manufacturing a printed material, characterized in that, in the step of applying air to the printing medium, an airflow with a wind speed of 0.2 to 1.5 m / sec is applied to the printing medium. [Examples]

[0184] The present invention will be described in detail below with reference to examples. The present invention is not limited to the following examples.

[0185] [Example of the First Embodiment] <Manufacturing of pigment dispersions> Each material listed in Table 1 was measured into a beaker in the proportions shown in Table 1, premixed, and then transferred to a plastic container with a lid. Zirconia beads with a diameter of 0.8 mm were added, and the mixture was dispersed for 60 minutes using a rocking mill RM-05 (manufactured by Seiwa Giken Co., Ltd.). The beads were then separated from the dispersion to produce pigment dispersions 1-4 with a pigment concentration of 20% by mass.

[0186] Details of the materials listed in Table 1 will be described later.

[0187] [Table 1]

[0188] <Synthesis of binder resin> The binder resin was manufactured as described below. In the following, the weight-average molecular weight of the manufactured binder resin was determined using the GPC method, converted to standard polystyrene equivalent. A GPC measuring instrument manufactured by Shimadzu Corporation was used for the measurement. The glass transition temperature (Tg) was calculated using the FOX formula.

[0189] (Synthesis of binder resin) In a 1 L flask, 317.8 g of diethylene glycol diethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), maintained at 90°C, was mixed with 340.0 g of methyl methacrylate, a radical polymerizable monomer, and 5.1 g of 2,2'-azobis(isobutyronitrile) (AIBN) (manufactured by Tokyo Chemical Industry Co., Ltd.), a polymerization initiator, dissolved in 85.0 g of diethylene glycol diethyl ether. This mixture was added dropwise over 2 hours. After the dropwise addition was complete, 1.1 g of AIBN was added at 30 minutes and 1 hour while maintaining the liquid temperature at 90°C. The reaction was further allowed to proceed at 90°C for 1 hour. The mixture was then diluted with diethylene glycol diethyl ether to obtain a binder resin solution with an active ingredient concentration of 40.0% by mass. The active ingredient concentration in the obtained binder resin solution was 40% by mass. The Tg of the binder resin was 105°C, and the weight-average molecular weight was 20,000.

[0190] <Ink Manufacturing> Each material listed in Table 2 was weighed out in the proportions shown in Table 2, mixed and stirred using a three-one motor, and then filtered through a 3 μm pore size membrane filter to obtain black ink, cyan ink, magenta ink, and yellow ink.

[0191] Details of the raw materials listed in Table 2 will be described later.

[0192] Table 2 also shows the amount of water in the ink, the amount of organic solvent S in the ink, the amount of organic solvent A with a boiling point between 150°C and 200°C in the ink, and the amount of water-soluble organic solvent B with a boiling point between 150°C and 200°C in the ink. These are shown as percentages (mass%) of the total ink volume. Furthermore, Table 2 shows the HSP value of water-soluble organic solvent B at 25.0 MPa. 1 / 2The following is a breakdown of the amount of water-soluble organic solvent Bx, which has a boiling point between 150°C and 200°C. This is expressed as a percentage (mass%) of the total amount of water-soluble organic solvent B.

[0193] The amount of water in the ink listed in Table 2 was measured using the Karl Fischer method. For the measurement, a KF-31 volumetric titration moisture meter manufactured by Nitto Seiko Analytech Co., Ltd. was used.

[0194] [Table 2]

[0195] Details of the materials listed in Tables 1 and 2 are shown below.

[0196] (Pigment) Pigment 1: Carbon black, "MOGUL L" (product name), manufactured by Cabot Corporation. Pigment 2: Copper phthalocyanine, "Fastogen Blue LAS5380" (product name), manufactured by DIC Corporation. Pigment 3: Magenta pigment, "Fastogen Super Magenta JM02" (product name), manufactured by DIC Corporation. Pigment 4: Yellow pigment, "Bayscript Yellow 4GF" (product name), manufactured by Lanxess Corporation. (Pigment dispersant) Polymeric dispersant: "Solspers J180" (product name), manufactured by Lubrizol Japan Co., Ltd., active ingredient 100% by mass (Pigment dispersion) Pigment dispersions 1-4: Prepared as described above, containing 20% ​​pigment by mass and 70% solvent (diethylene glycol diethyl ether) by mass. (Binder resin) Binder resin solution: Prepared as described above, active ingredient ((meth)acrylic resin) 40% by mass, solvent (diethylene glycol diethyl ether) 60% by mass, resin Tg 105℃, resin weight-average molecular weight 20,000 (Organic solvents) Water-soluble organic solvent: Diethylene glycol diethyl ether, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 188°C, HSP value 17.5 MPa 1 / 2 (Surfactants) Surfactant: Silicone-based surfactant, "BYK-333" (product name), manufactured by Bic Chemie Japan Co., Ltd. <Manufacturing of printed materials> Using the black ink, cyan ink, magenta ink, and yellow ink manufactured as described above, the printed materials of Examples 1-4 and Comparative Examples 1-6 were produced as follows.

[0197] Using a roll-type inkjet printer (DGI's "Perseus DP-194E" (product name)), an image was formed on the printing medium under conditions of 23°C and 50% RH, while simultaneously heating the printing medium with a heater and blowing air onto it with a fan.

[0198] For the printing medium, we used polypropylene synthetic paper with a whiteness of 96% (Yupo Corporation's "Yupo High Gloss GAR 110" (product name)).

[0199] The image consisted of monochrome black (K), cyan (C), magenta (M), and yellow (Y) print density patterns in 10% increments from 10% to 100%. The print resolution was 720 x 2400 dpi (dot density at 100% print density). The image width was 500 mm, and the print width was 1.5 m. 2 Printed at a productivity of / h.

[0200] The surface temperature, air velocity, and air temperature of the printing media in each of Examples 1-4 and Comparative Examples 1-6 are shown in Table 3.

[0201] The surface temperature of the printing medium was measured using a radiation thermometer (Shinwa Measuring Instruments Co., Ltd. "73010").

[0202] Wind speed and temperature were measured using an anemometer (Kanomax Japan Co., Ltd. "Climomaster Anemometer Model 6501-A0", probe "6541"). Wind speed and temperature were measured downstream from the inkjet head in the direction of transport of the printing medium, at the distance where the fan's airflow is most effective. Wind speed and temperature were measured at five equally spaced locations along the width of the printing medium, and the average value of the five measurements was used for both wind speed and temperature.

[0203] <Rating> The printed materials produced as described above were evaluated as follows.

[0204] (Image clarity) The images in the printed materials of Examples 1-4 and Comparative Examples 1-6 were visually observed, and the clarity of the images was evaluated according to the following evaluation criteria. ○: Printing is clean and free of smudging, blurring, or mist in any color or print density area. ×: There is at least one of the following: smudges, blurring, and mist in areas of at least one print density in at least one color. The evaluation results are shown in Table 3.

[0205] (Image density) The OD values ​​(including paper white) of each region of the image for each color in the printed material of Example 2 were measured using a spectrophotometer (X-Rite "i1 pro"). The measurement results of the OD values ​​of the black, cyan, magenta, and yellow images are shown in Figures 4 to 7, respectively. In Figures 4 to 7, the target density (OD value) for Japan Color is shown by a dashed line. The target densities for Japan Color are 1.70 for black, 1.55 for magenta and cyan, and 1.05 for yellow. The measurement conditions were: no UV cut filter, light source D50, viewing angle of 2 degrees, and density status T.

[0206] [Table 3]

[0207] As shown in Table 3, in Examples 1 to 4, where the surface temperature of the printing medium was 40 to 43°C, the wind speed hitting the printing medium was 0.2 to 1.5 m / sec, and the wind temperature was 35 to 40°C, good results were obtained in the evaluation of image clarity.

[0208] In other words, in Examples 1-4, the width was 500 mm and the length was 1.5 m. 2 High image quality was achieved while printing with high productivity at / h.

[0209] Furthermore, as shown in Figures 4-7, in Example 2, the area with 100% print coverage reached the target density of Japan Color for all ink colors, indicating that sufficient density was obtained.

[0210] On the other hand, comparative examples 1 to 6 did not yield satisfactory results in evaluating image clarity.

[0211] In Comparative Examples 1, 3, and 5, image blurring occurred. In Comparative Example 1, the surface temperature of the printing medium was less than 40°C, and in Comparative Example 3, the wind speed was less than 0.2 m / sec, so it is thought that the ink did not dry sufficiently, resulting in image blurring. In Comparative Example 5, the wind temperature was less than 35°C, which affected the surface temperature of the printing medium to be less than 40°C, and as a result, it is thought that the ink did not dry sufficiently, resulting in image blurring.

[0212] Furthermore, blurring occurred in the images in Comparative Examples 2 and 6. In Comparative Example 2, the surface temperature of the printing medium exceeded 43°C, which is thought to have caused blurring due to nozzle clogging or ink adhesion near the nozzles resulting in poor ink ejection. In Comparative Example 6, the air temperature exceeded 40°C, which caused the surface temperature of the printing medium to exceed 43°C. As a result, blurring occurred in the images due to nozzle clogging or ink adhesion near the nozzles resulting in poor ink ejection.

[0213] Furthermore, mist staining occurred in Comparative Example 4. In Comparative Example 4, the wind speed exceeded 1.5 m / sec, which is thought to have increased the amount of ink mist and caused mist staining.

[0214] [Example of the second embodiment] <Manufacturing of printed materials> Using black ink, cyan ink, magenta ink, and yellow ink manufactured in the same manner as in the first embodiment described above, printed materials for Examples 5-8 and Comparative Examples 7 and 8 were manufactured as follows.

[0215] Using a roll-type inkjet printer (DGI's "Perseus DP-194E" (product name)), an image was formed on the printing medium under conditions of 23°C and 50% RH, while simultaneously heating the printing medium with a heater and blowing air onto it with a fan.

[0216] The surface temperature of the printing medium was set to 42°C. The surface temperature of the printing medium was measured using a radiation thermometer (Shinwa Measuring Instruments Co., Ltd. "73010").

[0217] The wind speed and temperature of the air blowing on the printing medium were set to 0.5 m / sec and 38°C, respectively. Wind speed and temperature were measured using an anemometer (Kanomax Japan Co., Ltd. "Climomaster Anemometer Model 6501-A0" and probe "6541"). Wind speed and temperature were measured at the distance from the inkjet head to the downstream side in the transport direction of the printing medium, where the fan's airflow was most effective. Wind speed and temperature were measured at five equally spaced locations along the width of the printing medium, and the average value of the five measurements was used for both wind speed and temperature.

[0218] For the printing medium, we used polypropylene synthetic paper with a whiteness of 96% (Yupo Corporation's "Yupo High Gloss GAR 110" (product name)).

[0219] The image was a solid color image containing solid areas of black (K), cyan (C), magenta (M), yellow (Y), red (R), green (G), and blue (B). The image also included white lines and text. The print resolution was set to 720 x 2400 dpi.

[0220] The print width, ink droplet volume, the relationship between input and output values ​​of image data, and the maximum ink volume for each of Examples 5-8 and Comparative Examples 7 and 8 are shown in Table 4.

[0221] In Table 4, "STD" indicates the conditions under which good image quality was obtained at the default print width. Here, a print width of 500 mm (Example 5) is the default print width.

[0222] Furthermore, in Table 4, "10% Up" in the correspondence between the input and output values ​​of the image data indicates that the output value was increased by 10% compared to the STD conditions. "15% Down" indicates that the output value was decreased by 15% compared to the STD conditions.

[0223] Furthermore, in Table 4, "20% increase" for maximum ink volume indicates that the maximum ink volume has been increased by 20% compared to the STD conditions. "10% decrease" indicates that the maximum ink volume has been decreased by 10% compared to the STD conditions.

[0224] <Rating> The images in the printed materials of Examples 5-8 and Comparative Examples 7 and 8 were visually observed, and the image quality was evaluated according to the following evaluation criteria. ○: There is no decrease in image density or blurring, and white lines and text are clearly visible without being distorted. △: The image exhibits at least one of the following: reduced image density, blurring, and loss of clarity in outlined lines and text. The evaluation results are shown in Table 4.

[0225] [Table 4]

[0226] Example 5 is an example in which good image quality was obtained by printing with a print width of 500 mm under specific conditions.

[0227] In Example 6, the printing width was increased to 1000 mm compared to Example 5, while the ink droplet volume was increased from 4 pl in Example 5 to 6 pl, resulting in good image quality.

[0228] In Example 7, the printing width was further widened to 1500 mm compared to Example 6, while the ink droplet size was increased from 4 pl in Example 5 to 6 pl, similar to Example 6. In Example 7, the correspondence between input and output values ​​was further modified so that the output value of the image data was 10% larger than in Example 5, and the maximum ink volume was increased by 20% compared to Example 5. As a result, good image quality was obtained in Example 7 as well.

[0229] In Example 8, the print width was narrowed to 100 mm compared to Example 5. Furthermore, the correspondence between input and output values ​​was modified so that the output image data value was 15% smaller than in Example 5. Additionally, the maximum ink volume was reduced by 10% compared to Example 5. As a result, good image quality was obtained in Example 8 as well.

[0230] In Comparative Example 7, printing was performed under the same printing conditions as in Example 5, but with a wider printing width of 1500 mm. In Comparative Example 7, the image density decreased. It is thought that widening the printing width under the same printing conditions as in Example 5 reduced the amount of ink deposited per unit time into the printing area, preventing the solid image from being sufficiently filled with dots, resulting in a decrease in density.

[0231] In Comparative Example 8, printing was performed under the same printing conditions as Example 5, but with a narrower printing width of 100 mm. In Comparative Example 8, image blurring and blurring of white lines and characters occurred. It is thought that narrowing the printing width under the same printing conditions as Example 5 increased the amount of ink injected into the printing area per unit time, resulting in image blurring and blurring of white lines and characters.

[0232] Furthermore, when the images in the printed materials of Examples 5-8 and Comparative Examples 7 and 8 were evaluated according to the image clarity evaluation criteria shown in the examples of the first embodiment described above, all received a "○" rating. In Examples 5-8 and Comparative Examples 7 and 8, as with Examples 1-4 of the first embodiment described above, the conditions of a surface temperature of 40-43°C, a wind speed of 0.2-1.5 m / sec, and a wind temperature of 35-40°C were met, resulting in good results in the evaluation of image clarity.

[0233] In other words, while good printing results were obtained in Comparative Examples 7 and 8 using the same printing conditions as Example 5, even better printing results were obtained by changing the printing conditions from those of Example 5 according to the printing width, as shown in Examples 6 to 8. [Explanation of Symbols]

[0234] 1. Inkjet printing device 2. Conveying section 3 Platen 4 Fans 5 Heater 6. Main scanning drive guide 7. Main scanning drive motor 8 head units 9. Blower mechanism 10 Control Unit 11 Exterior cover 21 Supply drive motor 22 Conveyor rollers 23 Pinch Roller 24. Transport drive motor 25 reel spindles 26 Winding drive motor 27,28 Print Media Guide 31 Core body 32 Print media rolls 41 Inkjet heads 42 Carriage

Claims

1. An inkjet head that ejects ink and deposits the ink onto a non-absorbent or low-absorbent printing medium, A heating unit for heating the printing medium in order to dry the ink adhering to the printing medium, The system includes a blower unit that blows air onto the printing medium to dry the ink adhering to the printing medium, The ink comprises water and an organic solvent S. The amount of water is 3.0 to 10.0% by mass relative to the total amount of ink. The aforementioned organic solvent S includes organic solvent A having a boiling point of 150°C or higher and less than 200°C. The heating unit heats the printing medium so that the surface temperature of the printing medium becomes 40 to 43°C. The aforementioned air blowing unit is characterized by blowing wind with a wind speed of 0.2 to 1.5 m / sec onto the printing medium.

2. The inkjet printing apparatus according to claim 1, characterized in that the blowing unit blows air with a temperature of 35 to 40 degrees Celsius onto the printing medium in an environment of 23 degrees Celsius and 50% RH.

3. A main scanning drive unit that moves the inkjet head in the main scanning direction, A transport unit that transports the printing medium in a sub-scanning direction perpendicular to the main scanning direction, The system further comprises a control unit that controls the inkjet head, the main scanning drive unit, and the transport unit to perform printing in a multi-pass manner by alternately performing the operation of ejecting ink from the inkjet head to the printing medium while moving the inkjet head by the printing width in the main scanning direction, and the operation of transporting the printing medium in the sub-scanning direction. The inkjet printing apparatus according to claim 1 or 2, characterized in that the control unit sets printing conditions according to the printing width.

4. The inkjet printing apparatus according to claim 3, characterized in that the control unit further sets the printing conditions according to at least one of the type of printing medium and the printing resolution.

5. The inkjet printing apparatus according to claim 3, characterized in that the printing conditions include at least one of the amount of ink droplets ejected by the inkjet head, the correspondence between input and output values ​​of image data to be printed, and the maximum amount of ink ejected per unit area by the inkjet head.

6. A process of applying ink to a non-absorbent or low-absorbent printing medium, A step of heating the printing medium in order to dry the ink adhering to the printing medium, The process includes a step of blowing air onto the printing medium to dry the ink adhering to the printing medium, The ink comprises water and an organic solvent S. The amount of water is 3.0 to 10.0% by mass relative to the total amount of ink. The aforementioned organic solvent S includes organic solvent A having a boiling point of 150°C or higher and less than 200°C. In the step of heating the printing medium, the printing medium is heated so that its surface temperature is 40 to 43°C. A method for manufacturing a printed material, characterized in that, in the step of applying air to the printing medium, air with a wind speed of 0.2 to 1.5 m / sec is applied to the printing medium.

Images